JP4750367B2 - Heat shrinkable packaging - Google Patents

Description

  The present invention relates to shrink wrapping of articles, particularly foodstuffs such as chicken, cheese, partial or block meat, raw red meat and other processed meats, fruits, vegetables, bread and food. Shrink packaging refers to the use of a packaging film produced by a method that, when exposed to a predetermined amount of heat, preferably shrinks in both directions to reduce its overall surface area. This type of film wraps around the object, seals its edges, and when the package is passed through a heat shrink tunnel where it is exposed to high temperatures, the film reacts to heat and the object's Will shrink around. Depending on the respective application, the air trapped in the package can be evacuated prior to the final seal, or a small hole can be made in the film to allow air to escape during the heat shrink process. This method results in an attractive package that fits the article. There are many articles that are packaged using shrink wrap, which may include foods such as frozen pizza, cheese, chicken, raw red meat and processed meat products.

  Shrink packaging of foods such as chicken, cheese, raw red meat and processed meat products is used in making individual heat shrink packaging containers such as pouches and bags for packaging such foods This requires a suitable tough, fracture resistant and even flexible film material. In general, the shrink wrapping method for food is to place a predetermined food or article in an individual container, evacuate the container so that the container is deflated, remove the air, and heat seal over the opening or mouth of the container. Close the container and then expose the container to a heat source such as hot air flow, infrared, hot water, etc., thereby shrinking the container and bringing it into direct contact with the outer shape of the food or article. Is based. The packaging article produced by this packaging method has an attractive appearance that increases the commercial value of the packaged article, its contents are kept in a sanitary condition, and the shopper can It becomes possible to examine the quality of things. This type of packaging also extends the shelf life by removing air from the package.

  The present invention relates generally to packaging, and specifically to heat shrinkable packaging for foods that can be easily opened with hermetic heat sealability.

  Packaging articles such as food with thermoplastic films or laminates to protect the food to be packaged from misuse and external contamination, providing a convenient and durable package for transportation, and consumers Selling to is a common practice. Shrink wrapping of food has many of its advantageous properties that increase the commercial value of the packaged item, such as strength, compactness, content safety, purge resistance, attractive appearance of the packaged item, etc. Because of its widespread use.

  Shrink wrap is a packaging film that, when exposed to a certain amount of heat, shrinks in at least one direction, preferably in both directions, over its length or width, reducing its overall surface area. It is said to use what is manufactured by the method. When an article is packaged with this type of film, the air in the package is usually evacuated, and the package typically contains the object as the film reacts to the heat of the object. It is passed through a heat shrink tunnel that is exposed to high temperatures that shrink around. This method produces an attractive package that adheres to the object. There are a number of articles packaged using shrink wrapping, including food products such as frozen pizza, cheese, chicken, raw red meat and processed meat products, and non-food such as wooden blinds, CDs, etc. Food industry articles may be included.

  Many food products such as chicken, raw red meat, cheese and processed meat products are packaged in individual bags of pre-manufactured heat shrinkable films. Typically, an individual bag or pouch for packaging a food product will have one to three edges that are heat sealed by the bag manufacturer (one edge open and product insertion). And a final seal performed by the food processor. Such individual bags typically make a seamless tube of heat shrinkable film having the desired diameter from the shrink film, heat seal one end of the one tubular film, and Manufactured by cutting tube portions, including sealed portions, thereby forming individual bags. The resulting bag, when flattened, has a bottom edge formed by heat sealing, an opening on the opposite side of the sealed bottom, and the folding that occurs when the tube is flattened. With two seamless side edges formed by the eyes. An alternative method of forming the bag from the seamless tube involves creating a lateral seal spaced across the tube and cutting and opening the edges of the tube. If a flat sheet of film is used, the bag can be heat sealed at the three edges of the two overlaid film sheets or by folding the ends of the flat sheet and sealing the two edges. Then formed. US Patents that describe known heat shrinkable bags include US Pat. Nos. 6,511,688, 5,928,740 and 6,015,235. US patent application Ser. No. 10 / 371,950 filed Feb. 20, 2003 (Thomas Schell et al., Entitled “Heat-Shrinkable Packaging Receptacle”, see if desired) is preferably a continuous process for film Disclosed is an individual heat shrinkable bag formed from a sheet, wherein the opposite side edges of the sheet are sealed longitudinally to form a tube member, which is then sealed laterally and Cutting and closing the distal end of the tube member thereby forming a bag with a seam at the back.

  Known bags for heat shrink packaging include the last strong hermetic seal in the factory to prevent the heat sealed seam from being pulled away during heat shrink operations or during shipment and shipping of the packaged article. This strong heat seal provides protection against unwanted seal breakage, but such a seal also makes it difficult for the end consumer to open the package. Therefore, it includes a seal of sufficient seal strength to survive the heat shrink process and operation and withstand the natural opening due to the remaining shrink force, and without the need for the use of a knife or cutting instrument And the packaging material is torn or ruptured uncontrolled or randomly, for example separately from the sealing surface (this creates an opening in an undesired location or a sudden breakage of the package and There is a need for an improved heat shrinkable packaging container that includes at least one heat seal that can be easily opened by applying force without causing unintentional contamination or spillage of the contents of the item.

  Typically, an individual bag or pouch for packaging a food product will have one to three edges that are heat sealed by the manufacturer (one edge open to allow product insertion). Included). Such individual bags typically make a seamless tube of heat shrinkable film having the desired diameter from the shrink film, heat sealed one end of a tubular film, and this sealed Two seamless forms formed by a heat seal, an opening on the opposite side of the sealed bottom, and a crease that occurs when flattened when the tube portion including the portion is cut and thereby flattened Manufactured by forming a bag having side edges. An alternative method of forming a bag from a seamless tube involves making two lateral seals spaced across the tube and cutting that edge of the tube. If flat film sheets are used, the bag can be heat sealed at the three edges of the two overlaid film sheets, or by folding the ends of the flat sheets and sealing the two edges. Then formed.

Manufacturing a bag from a seamless tube requires that the tube be extruded to a specific width for the intended end use. Therefore, the production of small diameter tubes for small width bags is not economical because it does not use the full capacity of the film production equipment. The dimensions of the seamless tube are also limited by the manufacturing equipment that can make the width of the seamless tube small. The method of manufacturing an individual bag by superimposing two sheets and sealing about 3 edges treats the separate sheets, properly aligns the sheets, and around several edges. An expensive machine is required to provide the seal. In addition, having a third seal edge (four seal edges when closed) increases the risk of seal failure during the shrinkage process. Folding the film sheet and sealing the two edges results in a double thickness film at these seals, which undesirably protrudes from the side of the finished package.
US Pat. No. 6,511,688 U.S. Pat. No. 5,928,740 US Pat. No. 6,015,235 US patent application Ser. No. 10 / 371,950

  Thus, while known shrink bags meet many of the requirements for packaging applications, an improved heat-shrinkable bag structure that can be economically manufactured and sealed at the packaging site using standard bag sealing machinery. Further needs exist.

  In accordance with the present invention, there is provided an individual end-sealed packaging container such as a bag formed from a sheet of heat shrinkable film having a first edge and a second edge opposite the first edge. The packaging container has a first bag wall portion, a second bag wall portion, a first lay flat bag edge portion and a second lay flat bag edge portion, which are joined to each other by combining the first edge portion and the second edge portion. A first seal defining a tube member having a portion and an opening. The packaging container includes a second seal that extends laterally across the width of both the first and second wall portions through the first and second bag wall portions, thereby closing the end portions.

  The present invention also provides an easy-to-open heat shrinkable bag that contains a product disposed therein and is heat sealed in a sealed state to protect it. At least one heat seal is peelable and can be easily opened by applying force. The bag is formed from a sheet of film having a first side, a second side opposite thereto, an external surface, and an internal surface. The bag includes a first seal that causes the first side and the second side to adhere vertically in a longitudinal direction thereby defining a tube member. When the tube member is flattened, the first bag wall portion, the second bag wall portion, the first bag edge portion, the opposite second bag edge portion, the opening portion, and the end portion including. The bag includes a second seal that extends laterally near the distal end over the tube member, thereby sealing the first and second bag walls together and closing the distal end. . A product storage chamber is defined between the first and second bag walls, the second seal and the opening. Preferably, the first seal comprises a lap seal and this is at least one peelable heat seal.

  A preferred embodiment of the heat-shrinkable packaging container of the present invention is shown generally as bag 10 in FIGS. The bag 10 is formed from a sheet of heat-shrinkable film 11, which has a first edge 12, a second edge 14, a top surface 13 and a bottom surface 15. The bag 10 includes a first seal 16 that connects the first edge 12 and the second edge 14 from the top to the bottom of the bag in an overlapping arrangement, i.e., a lap seal. The tube member 18 shown in FIGS. 1 and 2 is formed in a partially lay-flat position, which includes a first bag wall portion 20, a second bag wall portion 22, and a first bag edge portion 24. And a second bag edge 26, an opening 28, and a bag end 30. In other words, the first bag edge 12 and the second bag edge 14 are located in an overlapping arrangement, and between the top surface 13 of the first edge 12 and the bottom surface 15 of the second edge 14. Is provided with a heat-seal-like seal so that the top surface 13 of the first edge 12 is sealed in face-to-face contact with the bottom surface 15 of the second edge. The bag 10 includes a second seal 32 that is provided via the first bag wall 20 and the second bag wall 22 and extends laterally from the first bag edge 24 to the second bag edge 26 across the bag 10. Thereby closing the bag end 30 and defining a product receiving chamber 34.

  Although the first seal 16 is illustrated as being located between and extending parallel to the first bag edge 24 and the second bag edge 26, those skilled in the art will appreciate this disclosure. In consideration of the above, when the bag 10 is in a lay-flat state, the first seal 16 is positioned from the first edge 24 to the second edge 26 in the first bag wall 20 or the second bag wall 22. It will be appreciated that it can be in any desired position and is located on either the first bag edge 24 or the second bag edge 26. Although the second seal 32 is illustrated as being straight and extending perpendicular to the first seal 16, those skilled in the art will recognize that the second seal 32 has the bag end 30 attached to the bag end 30. It will be appreciated that any shape can be taken as long as it is manipulated to close and thereby define the product storage chamber 34. For example, typical seal shapes include linear or linear seals that typically extend perpendicular to the bag edges 24 and 26 (the bag edges 24 and 26 generally extend parallel to each other), and For example, non-linear or curved edges such as those described in US Pat. No. 5,149,943. See the disclosure if desired. Both linear and non-linear seals can be made by any suitable sealing method known, including heated rods and impulse sealing methods.

  A second specific example of the heat-shrinkable packaging container of the present invention is generally illustrated as a bag 110 in FIGS. The bag 110 is formed from a sheet of heat-shrinkable film 111, which has a first edge 112, a second edge 114, a top surface 113, and a bottom surface 115. The bag 110 includes a first seal 116 that butt-connects the first edge 112 and the second edge 114, ie, a fin seal, thereby defining a tube member 118. To form the first seal 116, the first edge 112 and the second edge 114 are aligned with each other such that the bottom surfaces 115 of both the first edge 112 and the second edge 114 are in face-to-face contact. , And a seal like a heat seal is given between them. The tube member 118 is shown in FIGS. 3 and 4 in a partially lay-flat condition, which includes a first bag wall 120, a second bag wall 122, a first bag edge 124, and the like. A second bag edge 126, an opening 128, and a bag end 130. The bag 110 includes a second seal 132, which is provided via the first bag wall 120 and the second bag wall 122, and extends from the first bag edge 124 to the second bag edge over the bag 110. Extending laterally to the portion 126, thereby closing the bag end 130 and defining a product receiving chamber 134.

  Further, although the first seal 116 is illustrated as being located between the first bag edge 124 and the second bag edge 126, those skilled in the art will consider the present disclosure in view of this disclosure. 116 may be any desired position of either the first bag wall 120 or the second bag wall 122 from the first edge 124 to the second edge when the bag 110 is in a lay flat state. It will be appreciated that it is located on both the first edge 124 and the second edge 126. Since the first seal 116 forms a fin 117 that extends outwardly from the tube member 118, the first seal 116 preferably has a first bag edge and a second bag at or near the center of the bag wall. Located at a point between the edges. In this embodiment, the fin 117 is folded flat against the respective bag wall from which it extends, and the second seal 132 and the last hermetic seal (not shown) are finned in such a folded position. It will act to hold 117. This advantageously eliminates fin seals that are detrimental to undesirable aesthetics at the side edges of the packaged product. Similar to the second seal 32, the second seal 132 is illustrated as being straight and extending perpendicular to the first seal 116. Those skilled in the art will understand that the second seal 132 will act as described with respect to the second seal 132 so that the second seal 132 closes the bag end 130 and thereby defines the product receiving chamber 134. It will be appreciated that any shape can be taken, such as a curved shape.

  Another embodiment of the present invention is illustrated generally as a bag 210 in FIGS. The bag 210 is formed from a sheet of heat-shrinkable film 210, which has a first edge 212, a second edge 214, an inner surface 213, and an outer surface 215. The bag 210 includes a first seal 216 that directly connects the first edge 212 and the second edge 214 to each other and the surfaces of the first edge 212 and the second edge 214. Or it consists of the butt seal | sticker couple | bonded by the relationship adjacent to the vertical direction which is not couple | bonded directly. The first seal 216 preferably includes a butt seal tape 217, one side of which is sealed by the seal 216a to the outer surface 215 of the first edge 212, while the opposite side of the tape 217 is the second edge. And the seals 216a and 216b will be in a region adjacent to and along the first edge 212 and the second edge 214. The first seal 216 shown in FIGS. 5 and 6 in a partially lay-flat condition defines a tube member 218 that includes a first bag wall 220 and a second bag wall 222. A first bag edge 224, a second bag wall 226, an opening 228, and a bag end 230. The bag 210 includes a second seal 232, which is provided via the first bag wall 220 and the second bag wall 222 and spans the bag 210 from the first bag edge 224 to the second bag edge. Extending laterally to the portion 226, thereby defining a product storage chamber 234.

  The film used to make the bag of the present invention can be a multilayer or single layer flexible heat shrinkable film made by any known method. For example, in commercial chicken packaging operations, monolayer films made from polyethylene and / or ethylene / vinyl acetate copolymers and multilayer films containing polyethylene and / or ethylene / vinyl acetate copolymers are widely used. . Similarly, when packaging raw red meat and processed meat products, a multilayer heat shrinkable film containing polyethylene and / or ethylene / vinyl acetate copolymer in one or more layers of the film Is commonly used. Preferred films also have one or more of the following characteristics, including high fracture resistance (eg, as measured by ram and / or hot water fracture tests), high shrinkage values, low haze and high seal strength. Or all advantageous combinations thereof. The film and / or bag can also include some sort of printing (eg, they can be printed). For example, a bag according to the present invention may preferably include a print indicating that the bag contains a product containing bone. For applications that print this film, it may be desirable to corona-treat the film surface to improve ink adhesion. Corona-treated surfaces are similar to untreated surfaces, but in most cases they are not heat sealed, so only those parts that do not form heat-sealed parts can be corona treated, or the film treatment area can be limited and later It may be desirable to minimize the adverse effects on the sealed area. For example, the central portion of the film can be corona treated, but the portions along each of the longitudinal edges of the film are not corona treated. In this embodiment, the respective longitudinal sections that are sealed together to form the first seal 16 or 116 as described above will not be corona treated and will have no adverse effect.

  Preferably, the film may have an unlimited shrinkage of at least 20% in at least one direction, more preferably an unlimited shrinkage of 35% or more in one direction or both the vertical and horizontal directions. Free shrinkage is measured by cutting square pieces for film measurement, each 10 cm in length and width. The film is immersed in water at 90 ° C. for 5 seconds. After removal from the water, the piece is measured and the difference from the original dimension is multiplied by 10 to obtain the percentage of shrinkage.

  The film used in the bag according to the invention can be a single layer or a multilayer film, but these bags preferably have two or more layers, more preferably 3-9 layers, even more preferably 3-7 layers. It is formed from the multilayer film which has. Since the bag of the present invention is primarily intended to hold food after evacuation and sealing, it is preferred to use a thermoplastic film that includes an oxygen and / or moisture barrier layer. The term “barrier” or “barrier layer” as used herein means a layer of a multilayer film that acts as a physical barrier to moisture or oxygen molecules. A barrier layer material and other film layer combination that is advantageous for packaging oxygen sensitive substances such as raw red meat is less than 70 cc / sq.m at 1 atmosphere at a temperature of 73 ° F (23 ° C) (preferably Will give oxygen gas permeability at 24 hours of 45 or less, more preferably 15 or less) and 0% relative humidity.

  The bags 10, 110 and 210 are preferably made continuously from a continuous sheet or roll. The wound material is slit to the desired width and sent to the bag making apparatus, the longitudinal edges of the film are aligned with each other, and the wrap seal (bag 10), fin seal (bag 110) or butt seal (bag 210) Either is sealed longitudinally to form a continuous single seam tube or tube member. A transverse seal is made over the tube, and the portion containing the transverse seal is cut from the continuous tube to form individual bags.

  The type of first seal 16, 116 or 216 that is incorporated into the bag of the present invention must be considered when selecting a suitable film. Generally, a heat seal is made by applying sufficient heat and pressure for a sufficient amount of time to produce a weld between the two polymer film surfaces. A common method of forming a heat seal is to use a heated rod sealing method in which adjacent polymer layers are held in face-to-face contact with opposing rods, at least one of which is heated, and adjacent polymer layers are relative to each other. Is held in face-to-face contact by a wire or ribbon that is energized for a very short time such that at least one of the rods generates sufficient heat to cause the film layer to fuse. Including the impulse sealing method. In general, the performance of the sealing layer of the film becomes even more important because less area is bonded by the impulse seal as compared to the heating rod seal. However, impulse seals generally look good because they use less area to form the bond. The first seal 16, or lap seal, requires that the top surface 13 and the bottom surface 15 can form a suitable heat seal therebetween. When the first seal 116, i.e. the fin seal, is to be formed, only the bottom surface 115 need be able to form a suitable heat seal. This is because an interlayer bond will be formed between the same surfaces or layers. If the first seal 216, a butt seal, is formed, then both the top and bottom surfaces must be able to form a suitable heat seal. Similarly, the butt seal tape 217 must be able to form a suitable heat seal with the top surface, or the tape can be taped depending on whether the tape 217 is located inside or outside the bag 110 using a suitable adhesive. 217 must be adhered to the top surface 13 or the bottom surface 15.

  A preferred multilayer barrier film structure for use in the present invention is shown generally as 40 in FIG. Where an oxygen barrier layer 42 is required, it is usually provided as a separate layer of a multilayer film, most commonly as a core layer sandwiched between the inner heat-sealable layer 44 and the outer layer 46, Various properties of the tie layer or adhesive layer as well as the desired film, such as heat sealability, toughness, abrasion resistance, tear resistance, heat shrinkability, delamination resistance, stiffness, moisture resistance, optical properties, printability, etc. Additional layers such as layers for adding or improving can also be included. Oxygen barrier materials that can be included in the films used for the bags of the present invention include ethylene vinyl alcohol copolymer (EVOH), polyacrylonitrile, polyamide and vinylidene chloride copolymer (PVDC). Preferred oxygen blocking polymers for use in the present invention are vinylidene chloride copolymers or copolymers of vinylidene chloride and various comonomers, such as copolymers of vinyl chloride (VC-VDC copolymer) or It is a copolymer (MA-VDC copolymer) with methyl acrylate and EVOH. Specifically, a preferred barrier layer is about 85% vinylidene chloride / methyl acrylate copolymer and about 15% vinylidene chloride / vinyl chloride, as described, for example, in U.S. Pat. No. 4,798,751 to Schuetz et al. It consists of a copolymer. Suitable and preferred EVOH copolymers are described in US Pat. No. 5,759,648. See these US patents if desired.

An inner heat-sealable layer 44 is generally provided on the side of the barrier layer 42, which barrier layer 42 becomes the inner surface 38 or bottom surfaces 15 and 115 of the bag 10, 110 or 210 shown in FIGS. . Optionally, other film layers can be incorporated between the barrier layer 42 and the inner heat sealable layer 44 as described above. A substantially linear copolymer of ethylene and at least one α-olefin and a copolymer of ethylene and an alkyl acrylate such as a vinyl ester or vinyl acetate are effective in one or more layers of the film. It can be used and constitutes single-layer and multi-layer thermoplastic films. Preferably, the inner heat-sealable layer comprises at least one ethylene / α-olefin copolymer (EAO) and ethylene vinyl acetate blend (EAO: EVA blend). Suitable α-olefins include C _{3 to} C ₁₀ α-olefins such as propene, 1-butene, 1-pentene, 1-hexene, 1-methylpentene, 1-octene, 1-decene and mixtures thereof. Is mentioned. The heat seal layer is optionally the thickest layer of the multilayer film and can contribute significantly to the fracture resistance of the film. Another desired property that affects this layer is the heat seal temperature range. The temperature range for heat sealing the film is preferably as wide as possible. This makes it possible to change the operation of the heat-sealing device more greatly compared to a film having a very narrow range. For example, it may be desirable to heat seal a suitable film over a wide temperature range that provides an opportunity for heat sealing above 80 ° F.

The outer layer 46 is provided on the side of the barrier layer opposite to the heat-sealable layer 44 and acts as the outer surface 39. In this case, when a wrap seal, such as the first seal 32 of the bag 10, is incorporated into the bag structure, the outer layer 46 must be a heat seal compatible with the inner heat sealable layer. Optionally, other polymer layers can be provided between the barrier layer and the outer layer as previously discussed. The outer layer can be composed of an ethylene / α-olefin copolymer (EAO), an ethylene vinyl acetate copolymer (EVA), or a blend thereof. EAO is primarily one or more suitable including C ₃ -C ₁₀ α-olefins such as propene, 1-butene, 1-pentene, 1-hexene, 1-methylpentene, 1-octene, 1-decene. And a copolymer containing an ethylene polymer unit copolymerized with 50% by weight or less of an α-olefin. Preferred α-olefins are 1-hexene and 1-octene. Recent progress to improve the properties of heat shrinkable films includes US Pat. No. 5,403,668, which is a multilayer heat where the outer layer of the film is a four component blend of VLDPE, LLDPE, EVA and plastomer. A shrinkable oxygen barrier film is disclosed. See this disclosure if desired. LLDPE, or linear low density polyethylene, is a class of ethylene / α-olefin copolymers having a density of 0.915 g / cm ³ or more. VLDPE, also called ultra low density polyethylene (ULDPE) is a class of ethylene · alpha-olefin copolymer having a density of 0.915 g / cm ³ or less, a density of up 0.900~0.915g / cm ³ Many commercial VLDPE resins are available. The plastomer is EAO which generally has a density of 0.900 g / cm ³ or less. U.S. Pat. No. 5,399,640 discloses a multilayer oxygen barrier film in which at least one outer film layer is a three component blend of VLDPE, EVA and plastomer. Alternatively, the outer layer may be, for example, a polyamide, a styrenic copolymer, such as a styrene / butadiene copolymer, a polypropylene, an ethylene / propylene copolymer, an ionomer or an α-olefin polymer and especially a linear low density polyethylene. (LLDPE), Very Low Density Polyethylene (VLDPE and ULDPE), High Density Polyethylene (HDPE), Low Density Polyethylene (LDPE), Member of Polyethylene Family such as Ethylene Vinyl Ester Copolymer or Ethylene Alkyl Acrylate Copolymer Or it can be formed from other thermoplastic materials such as various blends of two or more of these materials.

  In general, the single layer or multilayer film used in the heat shrinkable bag of the present invention has the desired properties for a particular packaging operation in which the film uses film, such as fracture resistance, modulus, seal strength, barrier. As long as it has a thickness and composition sufficient to provide properties, optical properties, etc., it can have any desired thickness. For material efficiency and protection, it is desirable to use the minimum film thickness to provide the necessary fracture resistance and other properties. Preferably, the film has an overall thickness of about 1.25 to about 8.0 mils, more preferably about 1.75 to about 3.0 mils.

  A film suitable for use in the present invention is disclosed in US Pat. No. 5,928,740. Refer to this if desired. This 5928740 patent describes a first polymer of ethylene and at least one α-olefin having a polymer melting point of 55 to 75 ° C, ethylene having a polymer melting point of 85 to 110 ° C and at least one α. A melting point of 115-130 ° C. selected from the group consisting of a second polymer of olefins, preferably an ethylene homopolymer such as HDPE and LDPE, and an ethylene copolymer of at least one α-olefin. A third thermoplastic polymer and optionally and preferably a fourth polymer such as a copolymer of ethylene and an alkyl acrylate or vinyl ester having a melting point of 80-105 ° C, preferably 90-100 ° C. A heat-sealable layer comprising a blend is disclosed. The 5928740 patent also discloses a specific example of a biaxially stretched heat-shrinkable three-layer barrier film that is preferred for use in the present invention. Specific examples of this three-layer barrier film are as described above, preferably combined with a barrier layer consisting of polyvinylidene chloride (PVDC) or vinylidene chloride-methyl acrylate copolymer (VDC-MA or MA-saran) or EVOH layer. Inner heat-sealable layer and an outer layer formed from at least 50%, preferably at least 70% by weight of a copolymer of ethylene and at least one α-olefin or at least one vinyl ester or blend thereof including. A preferred EVA will also have a vinyl acetate content of about 3% to about 18%.

  Preferred films for use in the present invention are disclosed in US patent application Ser. No. 09 / 401,692, filed Sep. 22, 1999. See if desired. This U.S. patent application Ser. No. 09 / 401,692 is a first polymer comprising a monolayer and (a) a copolymer of ethylene and 1-hexene having a melting point of 80-98 ° C., preferably 80-92 ° C., (B) a second polymer having a polymer melting point of 115 to 128 ° C. composed of a polymer of ethylene and at least one α-olefin, and (c) a copolymer of ethylene and alkyl acrylate or vinyl ester. A third polymer having a melting point of 60-110 ° C. and optionally (d) preferably an ethylene homopolymer such as HDPE and LDPE and an ethylene copolymer of at least one α-olefin. At least three polymer blends, optionally including a fourth polymer, and a selected fourth polymer having a melting point of 80-110 ° C (preferably 85-105 ° C). A multilayer film is disclosed having at least one layer made of a glass. It can be seen that the blends of this invention are useful as an internal heat-sealable layer in many multilayer embodiments. In preferred three-layer, four-layer or five-layer embodiments, the oxygen barrier layer of vinylidene chloride copolymer, polyamide or EVOH comprises at least 50 layers of the blend of this invention and EAO or at least one vinyl ester or blend thereof. Between the layer containing 1% by weight or another layer containing the blend of this invention.

Additional preferred films for use in the present invention are disclosed in US patent application Ser. No. 09 / 611,192, filed Jul. 6, 2000. See if desired. This US patent application Ser. No. 09/611192 has a melting point of 55-98 ° C. comprising at least one copolymer of ethylene and at least one comonomer selected from the group consisting of 1-hexene and 1-octene. 45 to 85 wt% of the first polymer having 5 to 35 wt% of the second polymer having a melting point of 115 ° C. to 128 ° C. made of at least one copolymer of ethylene and at least one α-olefin. %, And 10 to 50 of a third polymer having a melting point of 60 to 110 ° C. comprising at least one unmodified or anhydride modified copolymer of ethylene and vinyl ester, acrylic acid, methacrylic acid or alkyl acrylate. Flexible thermoplastic biaxially oriented heat-shrinkable film having at least one layer comprising a blend of at least three copolymers containing wt% A multilayer barrier embodiment formed from is disclosed wherein the first and second polymers are at least 50% by weight based on the total weight of the first, second and third polymers. The bag film has a combined weight percent and a total energy absorption of at least 0.70 joules and a shrinkage value at 90 ° C. of at least 50% in at least one of the longitudinal and transverse directions. Any suitable oxygen barrier material or blend of these materials, such as ethylene-vinyl alcohol copolymer (EVOH) or vinylidene chloride (VDC) -vinyl chloride (VDC-VC) or VDC-methyl acrylate (VDC-MA) A barrier layer formed from a VDC copolymer such as Preferably, the barrier layer comprises a blend of 85 wt% VDC • MA and 15 wt% VDC • VC. The outer layer is preferably an EVA / VLDPE blend, more preferably an EVA / VLDPE / plastomer blend. U.S. patent application Ser. No. 09/611192 is (i) an ionomer polymer, such as an ethylene / methacrylic acid copolymer, wherein the acid group is partially or completely neutralized to form a salt, preferably zinc. Or 5-20% by weight of what forms the sodium salt, (ii) ethylene with a melting point of 55-95 ° C. and a M _w / M _n of 1.5-3.5 and at least one C ₆ -C ₈ 5 to 95% by weight of copolymer with α-olefin, (iii) 0 to 90 of copolymer of ethylene having a melting point of 100 to 125 ° C. and at least one C _{4 to} C ₈ α-olefin. (Iv) a copolymer of propylene and at least one monomer selected from the group consisting of ethylene and 1-butene, having a melting point of 105 to 145 ° C., 0 to 90% by weight, And (v) ethylene and 1-hexene A copolymer of at least one monomer selected from the group consisting of 1-octene and 1-decene, having a melting point of 125-135 ° C. Also disclosed is a film comprising a flexible thermoplastic film having at least one layer comprising a blend of polymers, wherein the polymers (ii), (iii), (iv) and (v) are: Having a combined weight percent of at least 80 weight percent based on the total weight of polymers (i), (ii), (iii), (iv) and (v), and the film comprises at least 1. Has a total energy absorption of 2 joules. Optionally, the same blend may be used as an internal heat-sealable layer for the bag film.

  Further preferred films for use in the present invention are described in US Pat. No. 5,302,402 (Dudenhoeeffer et al.), US Pat. No. 6,171,627 (Lustig et al.), US Pat. No. 4,863,769 and US Pat. ing. See these if desired.

In a preferred embodiment of the invention, the heat shrinkable bag is formed from a three layer film. This three-layer film is preferably a biaxially stretched film including a barrier layer disposed between the inner heat-sealable layer and the outer layer, as shown in FIG. The inner heat-sealable layer is approximately 37% ESCORENE LD701. Available from Exxon Chemical Company (Houston, Texas, USA). Ethylene-vinyl acetate (EVA) copolymer such as ID, approximately 24% VLDPE resin such as SCLAIR 10B (0.77 dg / min melt index and 0) available from Nova Chemicals (Calgary, Alberta, Canada) 911 g / cm ³ ), about 33% plastomer such as EXACT4053 available from Exxon Chemical Co. (Houston, Texas, USA), about 4% Spatech A27023 (lubricant / processing aid in VLDPE carrier resin) And about 2% of a blend of processing stabilizers such as Spatech A32434 (available from Spatec Polycom, Washington, PA, USA). The barrier layer comprises a blend of about 15% vinylidene chloride / vinyl chloride and about 85% vinylidene chloride / methacrylate, as further described in US Pat. No. 4,798,751. The outer layer is approximately 40% ESCORENE LD701. Ethylene-vinyl acetate (EVA) copolymer such as ID, about 33% plastomer such as EXACT4053, about 25% VLDPE resin such as SCLAIR 10B, and about 2% Ampacet 501236 (ampere in Tarrytown, NY, USA) VLDPE carrier concentrate blends of processing aids / lubricants (such as those available from Set). The inner layer, barrier layer and outer layer are about 57.7%, 17.7% and 25.1%, respectively, based on the total thickness of the three-layer film.

In another preferred embodiment of the present invention, the heat-shrinkable bag is another three-layer biaxially stretched shrinkage comprising a barrier layer disposed between the inner heat-sealable layer and the outer layer, as shown in FIG. Formed from film. The barrier layer preferably comprises a blend of about 15% vinylidene chloride / vinyl chloride and about 85% vinylidene chloride / methacrylate as further described in US Pat. No. 4,798,751. The barrier layer preferably accounts for approximately 16.5% of the thickness of the three-layer film. The inner heat-sealable layer preferably accounts for about 57.1% of the film thickness and is EXACT 9519 (0.895 g / cm ³ and 2.2 dg / min n melt index, from Exxon Chemical Company, Houston, TX, USA) About 35.1% by weight of an ethylene / 1-hexene copolymer such as ATTANE XU 61509.32 (available from Dow Chemical Company of Midland, Michigan, USA) and a density of about 0.912 g / cm ³ . About 36.5% of an ethylene 1-octene copolymer such as C ₂ C ₈ (<10 wt% C ₈ ) VLDPE) having a melt index of 5 dg / min, ESCORENE LD701. ID (ethylene / vinyl acetate copolymer available from Exxon Chemical Co., Houston, Texas, USA, 0.93 g / cm ³ density, 10.5 wt% vinyl acetate content, about 0.19 dg / min melt index) And 26.5% of ethylene-vinyl acetate (EVA) copolymers, such as those reported to have a melting point of about 97 ° C), Spatech A50050 (1.9% oleamide lubricant in VLDPE carrier resin and About 3% of lubricants / processing aids such as fluoroelastomers) and about 2% of processing stabilizers such as Spatech A32434 (10% DHT4A in VLDPE carrier resin available from Spatec Polycom, Washington, Pa., USA). % Blend. The outer layer preferably accounts for about 26.4% of the thickness of the film and about 35% by weight of an ethylene / 1-hexene copolymer such as EXACT9519, ethylene / 1-octene such as ATTANE XU61509.32. About 35% of the copolymer, ESCORENE LD701. About 27% of EVA copolymers such as ID and about 3% of lubricants / processing aids such as Spatech A50050 (available from Spatec Polycom, Washington, PA, USA).

In another preferred embodiment, the bag film comprises about 17 wt% ethylene / 1-octene copolymer, such as ATTANE XU 61509.32, about 18 wt% ESCORENE LD701. EVA such as ID, 58% EXACT 9110 (density of 0.898 g / cm ³ , melt index of 0.8 dg / min and melting point of 89 ° C.), 1-hexene copolymer, about 2% A biaxially oriented three-layer heat-shrinkable film with an internal heat-sealable layer made from a blend of processing stabilizers such as Spartech A32434 and a lubricant / processing aid blend such as about 5% Spartech A50050. The outer layer comprises about 19% by weight of ethylene / 1-octene copolymer such as ATTANE XU61509.32, 18% EVA (ESCORENE LD701.ID), 60% ethylene / 1-hexene copolymer such as EXACT9110. And processing aids such as 3% A50056. The barrier layer is 85% vinylidene chloride / methyl acrylate and about 15% vinylidene chloride / vinyl chloride. Preferably, the ratio of inner layer: barrier layer: outer layer thickness is about 62: 9: 29.

A preferred seven-layer film for use in making a bag according to the present invention is illustrated in FIG. The film 60 includes a first or internal heat sealable layer 61 that preferably accounts for about 10% of the total mass of the film 60. The inner heat-sealable layer 61 is preferably about 94% EXACT 3139 (ethylene / hexene copolymer having a reported melt index of 7.5 g / 10 min and a density of 0.900 g / cm ³ ), about Consists of a blend of 4% Spatech A27023 and about 2% Spatech A32434. The second layer 62 adjacent to the first layer 61 preferably accounts for about 42.2% of the total mass of the film and about 37% of the ESCORENE LD701. Consists of a blend of ID, about 33% EXACT4053, about 24% SCLAIR 10B, about 4% Spatech A27023, and about 2% Spatech A32434. The film 60 further includes a first tie layer 63 and a second tie layer 65, each of which preferably individually accounts for about 5% of the total mass of the film 60 and about 100% of VORIDIAN SP1330 (US Tennessee). And ethylene / methyl acrylate copolymer available from the Eastman Chemical Company's Bolidian Division of Kingsport, Oregon. The film 60 includes a blocking layer 64 between the first tie layer 63 and the second tie layer 65. The barrier layer 64 preferably comprises about 17.7% of the total weight of the film and comprises a blend of about 85% vinylidene chloride / methyl acrylate and about 15% vinylidene chloride / vinyl chloride. The film includes a third layer 66 that preferably accounts for about 15.1% of the total mass of the film 60. This third layer 66 is about 40% ESCORENE 701. Consists of a blend of ID, about 33% EXACT4053, about 25% SCLAIR10B and about 2% Spatech A27339. Film 60 preferably comprises a fourth or outer layer 67 comprising about 5% of the total mass of film 60 and comprising a blend of about 98% EXACT 3139 and about 2% Spatech A27339. The total thickness of film 60 is preferably about 2 mils or greater.

  Advantageously, it may be desirable to use a high melt flow index polymer in the sealant layer of the film to help seal laterally across the lap seal, butt seal or fin seal. This high melt flow index polymer has a melt flow index of about 5 dg / min or more. Higher melt flow index polymers are encountered when the second seal 32, 132 or 232 is in the region of the first seal 16, 116 and 216 between the first and second bag walls. Gaps such as gaps 9a (FIG. 2), 9b (FIG. 4) and 9c (FIG. 6) resulting from the difference are more easily filled than the lower melt flow index polymers. For example, other high melt index polymers such as EXACT 3040 having a reported melt index of 16.5 g / 10 min may be applied to inner layer 61 and outer layer 67 of film 60 for lower melt index ethylene / hexene copolymer. It may be used instead of coalescence.

  The film selected to make the container of the present invention is preferably biaxially stretched by well-known blown or double bubble techniques as described, for example, in US Pat. No. 3,456,044 by Pahlke. In this technique, the extruded first tube leaving the tube extrusion die is cooled and folded and then biaxially stretched, preferably by reheating and reexpansion, to form a second bubble. The film is preferably biaxially stretched, in which case transverse (TD) stretching is achieved by inflation so that the heated film is easily expanded. Stretching in the machine direction (MD) is preferably accomplished using nip rolls that rotate at different speeds to pull or draw the film tube in the machine direction.

  The stretch ratio of biaxial stretching to form the bag material is preferably sufficient to give the film a total thickness of about 1.5 to 3.5 mils. The MD stretch ratio is typically 3: 1 to 5: 1 and the TD stretch ratio is also typically 3: 1 to 5: 1.

  Referring now to FIG. 8, a double bubble or inflation process is shown. The polymer blends that make up several layers are coextruded by conveying separate melt streams 311 a, 311 b and 311 c to the die 330. These polymer melts adhere to each other and are coextruded from the annular die 330 as a multilayer tube 332 with relatively thick walls. This thick walled first tube 332 leaving the extrusion die is cooled and folded by a nip roller 331 which is stretched through the tube 332 by transport rollers 333a and 333b. The second bubble 334 is formed by being conveyed to a reheat zone that reheats below the melting point of the layer to be heated and expanded with a confined fluid, preferably a gas, more preferably air. The second bubble is formed by a fluid confined between a pair of first nip rollers at one end of the bubble and a second pair of nip rollers at the opposite end of the bubble. The Inflation that causes the film to expand in the radial direction provides transverse (TD) stretching. Stretching in the machine direction (MD) is accomplished by adjusting the relative speed and / or dimensions of the nip roller 336 and nip roller 337 to stretch (draw) the film in the machine direction. Roller 337 also collapses bubbles to form a lay-flat stretched film 338, which can be wound or slit on reel 339 to interrupt further processing.

  Biaxial stretching is preferably about 1.25 to about 8.0 mils, preferably 1.5 to 4 mils, more preferably 1.75 to 3.0 mils (44 to 76 μm), even more preferred for multilayer films. Is sufficient to give a total thickness of 2.5 mils.

  A preferred film for use in making a bag in accordance with the present invention and a method for producing a suitable film therefor are described in US patent application Ser. No. 09 / 401,692 (“Crush Resistant Heavy Duty”, filed September 22, 1999). Combined film, blend and manufacturing method "), filed on November 1, 1999, 09/431931 (" Fracture resistant high shrink film, blend and manufacturing method ") and filed July 6, 2000 No. 09/611192 (“Ionomer Fracture Resistant Thermoplastic Patch Bags, Films, Blends and Methods of Manufacturing),” see these teachings if desired.

  The method is the same for the single layer film, except that the first tube is manufactured using a single screw extruder (or a multi screw extruder through which the same polymer formulation is passed), and biaxially stretched. Is sufficient to provide a monolayer film having a total thickness of preferably 2-6 mils or more, typically about 3.5-4.5 mils, and generally MD and It is in the same range as the stretch ratio discussed above for both TDs, ie about 3: 1 to 5: 1.

  Although not required, it is preferred to irradiate the film with radiation to increase the range of heat sealing and / or improve the toughness of the inner and outer layers by radiation-induced crosslinking and / or splitting. This is preferably achieved by irradiation with an electron beam at a dose level of at least 2 megarads (MR), preferably in the range of 3-5 MR, but for thicker films, for example, higher doses may be used. Good. Irradiation is given to the first tube or after biaxial stretching. The latter, referred to as post-irradiation, is preferred and is described in US Pat. No. 4,737,391 to Lustig et al. See if desired.

  After stretching, the tubular film 338 is folded, slit longitudinally, flattened and wound on a reel 339 for use as a winder. One skilled in the art will be able to use the above method to form a film, that the film can be produced by a conventional single blown film method, and that stretched or unstretched sheets can be widened or widened to provide orientation. It will be appreciated that it can be produced by a slot cast sheet extrusion process without the use. Furthermore, those skilled in the art will recognize that the flat width of the folded tube determines the resulting sheet film width. Thus, the dimensions of the first tube and subsequent processing can be selected to give the maximum flat width and film thickness for the desired application, thereby advantageously maximizing the production capacity of the film production equipment. It can be made.

  Advantageously, the bag manufacturer adjusts the width of the sheet from various lengths and widths of the film roll (by slitting or cutting the roll to the desired width) and a specific bag or It can be manufactured by adjusting the distance between the lateral end seal and the bag mouth for a series of bags. This eliminates the costly need to produce specific width seamless tubes that have been widely used in recent years by butchers. The present invention also reduces costs and increases manufacturing efficiency by producing multiple width and length bags from a standard web that is manufactured using substantially 100% of the capacity of the film manufacturing equipment. Enable. This reduces the need for overstocking of any and all seamless tube windings with different widths. The bag manufacturer simply slits the film winder to the desired width and forms continuous tube members by longitudinally sealing the opposite side edges as described for bags 10, 110 and 210. It's okay. An adjustable length bag can be made by sealing the tube member laterally and cutting the tube member at a location spaced from the lateral seal. In addition, as described above, the film is formed such that a continuous tube member is formed by closely contacting the opposite side edges of the film in the vertical direction, the continuous tube member is folded, and the folded continuous tube member is used as a reel. It can also be made into a winding material for continuous tube members by winding. The continuous tube member roll is then provided to a food processor, at which time the food processor forms individual bags, such as bags 10, 110 and 210. Such a continuous tube member winding may have a fold diameter of up to 20 inches, preferably 20 inches or more, more preferably 22 inches or more.

  Preferably, the manufacture of the bag is a continuous process in which the film is directed to a bag manufacturing assembly (not shown) from which individual end seal bags are made. As described above, the web can be slit to the desired width, and the unused portion can be rewound for subsequent use. The bag continuously aligns the opposite side edges of the film with each other and forms a heat seal, such as a lap seal or fin seal, to form a continuous tube member, then at predetermined intervals across the width of the tube member. It is manufactured by heat sealing in the lateral direction and welding the first wall portion and the second wall portion of the tube member to each other. The tube member is preferably cut at the same time or in the same process as it is transversely heat sealed to form a bag as shown in FIG. Typically, when a transverse seal is made for a single bag, a transverse cut is being made that forms the mouth of the adjacent bag. This method is based on the bottom edge formed by lateral heat sealing, the opening formed by the cut edge, and the creases that occur when the tube member is flattened when flattened. A so-called “end seal” bag is formed having two side edges to be formed. A transverse heat seal should be applied over the entire tube member to ensure an airtight closure. Each bag being formed from one tube member is necessarily formed by at least two normally parallel spaced transverse cuts (resulting in a tube member segment), and Normally, a lateral seal adjacent to one of these cuts will define the bottom of the bag located opposite the bag opening formed by the remote cut. In a typical manufacturing method, the tube member is laterally sealed and adjacent lateral cuts are made as part of the same process, and the seal and adjacent cuts are in one bag. At the same time as forming the seal end for, the same cut also forms an opening for the adjacent bag, so that the adjacent bag can be referred to as the far cut. The spacing between the lateral seal and the cut point may vary and will determine the length of the bag formed. The length of the bag can be easily changed by changing the interval between the cut portions. The width of the bag can also be easily changed by changing the width of the film by slitting the standard winding material. In another embodiment of the present invention, the cuts and seals can be made alternately and spaced apart to form a double combined bag of saddleback type.

  The present invention advantageously provides a method of manufacturing a heat shrinkable bag that allows a bag manufacturer to manufacture multiple bag dimensions (different lengths and widths) from a single film stock size. Can advantageously maximize film production efficiency by eliminating the need to produce seamless tubes of different widths. In other words, the present invention allows a bag manufacturer to produce one standard width sheet film stock, such as 86, 94, 98, 104, 112, 126, 162 inches or more, depending on the capabilities of the film production equipment. Makes it possible to do. The standard sheet film stock can then be slit to the desired width to form a bag as described herein, and the remaining portion of the sheet film stock can be rewound for later use in another job. it can. Prior art bags reduce manufacturing efficiency by requiring the manufacturer to produce different seamless tube dimensions for each of the bag sizes produced.

Except as otherwise noted, the following physical properties are used to illustrate the films and seals of the present invention. These properties are measured by either the test procedure described below or a test similar to the following method.
Average gauge: ASTM D-2103
Tensile strength: ASTM D-882, Method A
1% secant modulus: ASTM D-882, Method A
Oxygen gas permeability (O ₂ GTR): ASTM D-3985-81
Elongation at break: ASTM D-882, Method A
Molecular weight distribution: Gel permeation chromatography Glossiness: ASTM D-2457, angle 45 °
Cloudiness: ASTM D-1003-52
Melt index: ASTM D-1238, Condition E (190 ° C.) (except for propene base (> 50% C ₃ content) polymer tested under Condition L (230 ° C.))
Melting point: ASTM D-3418, peak determined by DSC at a heating rate of 10 ° C./min m. p
Vicat softening point (Vsp): ASTM D-1525-82
Seal strength: ASTM F88-94.
All ASTM test methods described herein are included in this disclosure by reference.

Shrinkage value :
The shrinkage value is obtained by measuring the unlimited shrinkage of a 10 cm ² sample immersed in 90 ° C. (or indicated temperature if different) water for 10 seconds. Four specimens are cut from a given sample of film to be tested. The specimen is cut into a 10 cm long (MD) × 10 cm long (TD) square. Each specimen is completely immersed in a water bath at 90 ° C. (or indicated temperature if different) for 10 seconds. The specimen is then removed from the water bath and the spacing between the sides of the shrunken specimen is measured in both MD and TD directions. Multiply 10 by the difference between the measured interval for the shrunken specimen and the original 10 cm sides to obtain the shrinkage in each direction. Average the shrinkage of the four specimens and report their average MD and TD shrinkage values. The term “heat-shrinkable film at 90 ° C.” means a film having an unlimited shrinkage value of at least 10% in at least one direction.

Ten identical specimens of tensile seal strength (seal strength) test film are 1 inch (2.54 cm) wide and suitable length for test equipment, eg, about 5 inches (12.7 cm) long Cut to 1 inch and place a 1 inch (2.54 cm) wide seal in the center and sideways. Fix the opposing parts of the film sample to the opposing clamps of the universal tensile test instrument. The film is secured with a tensioned snug fit between the clamps without stretching before the start of the test. This test is performed at ambient or room temperature (RT) (about 23 ° C.) test temperature. Activating this instrument causes the film to break through a clamp that is transverse to the seal at a constant speed of 12.0 inches (30.48 cm) per minute (film or seal breaks or delamination and film Pull until integrity loss). Test temperature indicated and 1bs. Measure and record the breaking point force. This test is repeated for four additional samples and the average gram at the break is reported.

Ram Destruction Test The Ram Destruction Test is used to determine the maximum breaking load or breaking force and the maximum breaking stress of a flexible film when hit with a hemispherical or spherical shaped hammer. This test gives a quantitative measure of the fracture resistance of thin plastic films. This test is further described in US patent application Ser. No. 09 / 401,692.

  The following examples are given to illustrate the present invention and should not be construed as limiting the invention as set forth in the appended claims.

  In the following examples, film compositions are generally prepared using the apparatus and method described in US Pat. No. 3,456,044 (Pahlke) describing a coextrusion type inflation method and further according to the above detailed description. It was. All layers were extruded as a first tube, which was cooled at the same time as it exited the die, for example by jetting with tap water. This first tube is then concentrically around the moving first tube by a radiant heater (although other means well known to those skilled in the art such as conduction or convection heating can be used). Reheated with further heating to the stretching temperature for biaxial stretching achieved by the air cushion heated by itself in a transverse flow through the heated porous tube located in the shape. Cooling was achieved by means of a coaxial air ring. Stretch point temperature, bubble heating and cooling rates, and stretch ratio were generally adjusted to maximize bubble stability and throughput for the desired amount of stretching or stretching. All percentages are weight percent unless otherwise indicated.

Example 1
As generally illustrated in FIGS. 1 and 2, a puncture resistant bag according to the present invention has a coextruded three layer biaxial stretch shrinkage having (A) an inner heat-sealable layer, (B) a barrier layer and (C) an outer layer. It was produced from a film consisting of a film. The inner and outer layers are directly bonded to the opposing surface of the barrier layer. The three layers contained the following composition:
(A) 33% by weight EXACT4053, 37% ESCORENE LD701. ID, 24% SCLAIR 10B, 4% Spatech A27023 and 2% Spatech A32434,
(B) a blend of about 85% vinylidene chloride / vinyl chloride copolymer and about 15% vinylidene chloride / methacrylate copolymer, and (C) 33% by weight EXACT4053, 25% SCLAIR10B, 40% ESCORENE LD701. . ID and 2% Ampacet 501236.

  One extruder was used for each layer. Each extruder was connected to an annular coextrusion die in which the thermoplastic resin was coextruded while forming the first tube. The resin mixture for each layer was fed from a hopper to an attached single screw extruder where the mixture was thermoplasticized and extruded from a three layer coextrusion die into a first tube. The extruder barrel temperature for the barrier layer (B) is about 250-300 ° F (121-149 ° C), and for the inner layer (A) and outer layer (C) is about 290-330 ° F (143-143). 165 ° C.). The temperature distribution of the coextrusion die was set at about 320-350 ° F. (163-117 ° C.). The extruded multilayer first tube was cooled to 50-68 ° F. (about 10-20 ° C.) by spraying with cold tap water.

  A cooled first tube with a flat width of about 4 inches (10.16 cm) was made through a pair of nip rollers. The cooled flat first tube is expanded, reheated, biaxially stretched, and cooled again to produce a biaxially stretched film that is slit open and flattened to approximately 16 inches (40 inches). A sheet having a width of .64 cm) was formed and wound on a reel. The MD stretch ratio was about 5: 1 and the TD stretch ratio was about 4: 1. The stretching point or stretching temperature is below the main melting point for each stretched layer and above the main glass transition point of those layers, which appears to be about 68-85 ° C. The resulting biaxially stretched film had an average gauge of about 2.5 mils and had a stunning appearance.

  The film was irradiated at a dose level of about 5.0 MR. As described above, although not essential, it is preferable to irradiate the entire film to increase the range of heat sealing by irradiation-induced crosslinking and / or cutting and / or improve the toughness of the inner and outer layers. . Irradiation can be performed with the first tube or after biaxial stretching. The latter, referred to as post-irradiation, is preferred and is described in US Pat. No. 4,737,391 to Lustig et al. See if desired. The advantage of post-irradiation is that a relatively thin film is processed instead of the relatively thick first tube, thereby reducing the power required for a given processing level.

  The film was rewound and slit to a width of 13 inches (33.02 cm). Then, the film was sent to a bag manufacturing apparatus to form a tube member having a lap seal extending in a continuous longitudinal direction. A bag according to bag 10 shown in FIG. 1 was formed by sealing laterally across the tube member and simultaneously separating this sealed portion from the continuous tube structure.

  Various tests were performed on the film and / or the resulting inventive bag. The film thickness was confirmed to be an average of 2.1 mils. The lap seal was examined and had a very strong average seal strength of about 8000-10000 grams. The bag also had an average MD and TD heat shrinkage at 90 ° C. of 48 and 48, respectively. The result of ram destruction was equally great. The breaking resistance of the 2.1 mil thick film was measured and had a maximum breaking force of 86 Newton (N) and a total energy loss of 0.9 Joule (J). This preferred bag has a very good heat shrinkage and very good resistance to fracture, which is highly desirable for packaging raw red meat fillets. Thus, heat shrinkable bags were made that were economical to manufacture, had puncture resistance and strong seals, and had a unique combination of previously unknown features and commercial advantages.

  Advantageously, the bags 10 and 110 can be made economically from an approximate shape because these bags 10 and 110 are not formed from seamless tubes that must be made to the desired width. The only limitation on the size of the bag made is the size of the stock sheet film that is wide enough to meet the standard. Standard roll sheet films are available in widths greater than 100 inches (254 cm). The present invention allows bag manufacturers to produce bags of any size from flat sheets of any size of winder up to the size limit of the winder. For example, if the roll is 52 inches wide, a tube member having a fold diameter of approximately 26 inches can be made, excluding the overlap or contact amount of the first seal 16 or 116 used. If the manufacturer wants to make a bag with a fold diameter of 18 inches, then the manufacturer will add a standard winding to the appropriate width (plus an extra for the area of the first seal 16 or 116). Slit to approximately 36 inches). The unused portion of the slit forms a standard winder that is rewound for use in manufacturing bags of different dimensions. In this embodiment, the standard winding material film can be produced more economically. This is because the film production equipment can operate at or near the upper limit of film width production, so that almost all of the capabilities of this equipment can be used. Manufacturing bags from seamless tubes requires that the film device be operated with limited capacity to form tubes of different small widths. In addition, film manufacturing equipment requires costly equipment that significantly increases the cost of manufacturing seamless tubes and disruption between operations of different dimensions.

  A preferred embodiment of the heat shrinkable packaging of the present invention is made from a sheet 410 of heat shrinkable film 411, which comprises a first edge 412a and an opposite second edge 412b. These are connected by the third edge portion 412c and the fourth edge portion 412d. The first edge portion 412a and the second edge portion 412b are preferably parallel to each other when the film 411 is in a flat and flat state. The third edge 412c and the fourth edge 412d are preferably parallel to each other when the film 411 is in a lay-flat planar state. The first edge portion 412a and the second edge portion 412b are preferably perpendicular to the third edge portion 412c and the fourth edge portion 412d when the film 411 is in a lay-flat planar state. is there. The film 411 has four corners at the intersection of these four sides. These corners are a first corner 412ac determined by a contact between the first edge 412a and the third edge 412c, a second corner 412bc determined by a contact between the second edge 412b and the third edge 412c, A third corner 412ad determined by the contact point between the first edge portion 412a and the fourth edge portion 412d, and a fourth corner 412bd determined by the contact point between the second edge portion 412b and the fourth edge portion 412d. The film 411 has a top surface 413a surrounded by an outer periphery 414 formed by sides 412a, 412c, 412b and 412d, and an opposite bottom surface 413b surrounded by the outer periphery 414. FIG. 10 illustrates the corner 412ad of the film 411 turned up to reveal the bottom surface 413b.

  Referring now to FIG. 11, a preferred embodiment of the present invention is shown generally as a bag 415 made from the film 411 of FIG. Bag 415 has first edge 412a overlapped with second edge 412b and is preferably sealed with heat to provide parallel spaced dotted lines 417a and 417b and third edge 412c and fourth. It is formed by creating a fused lap seal 416 that depends on the edge 412d. Although the wrap seal 416 is shown as a continuous elongated rectangle extending from side 412c to side 412d, the present invention allows the shape of this seal to be varied and can be, for example, wavy or zigzag shaped or otherwise Note that it is further intended that a shape of Also, the width of the seal can be changed as desired so as to be thicker or thinner. The seal can also optionally be made by alternative or additional means including, for example, by application of suitable heat tubes or adhesive materials known in the art for sealing the films together. The wrap seal 416 is shown as a continuous wrap seal 416 suitable for forming a hermetic package, but for some applications, such as certain industrial articles or stored goods, for example wavy or dotted lines. It is further contemplated that a discontinuous seal having the following appearance can be used. Examples of this intermittent seal are when it is undesirable to either apply a vacuum or seal with a trapped air or other gas bubble, or remove the air by other means. , Allowing air to escape from the sealed container during the packaging operation. Optionally, one skilled in the art will consider the teachings of the present application to change the strength of the seal to the shape, thickness, continuity or discontinuity of the seal, the type of seal material selection and the strength of different types of seals. By selection of the aforementioned parameters, such as well-known parameters, for example, it can be varied by adjusting the holding time or temperature for producing the heat seal. Such changes and adjustments can be made by those skilled in the art without undue experimentation.

  Referring again to FIG. 11, the wrap seal 416 is preferably a heat seal that forms a weld between the top surface 413a and the bottom surface 413b of the film 411. This overlap-sealed film 411 defines a tube member 418 where the top surface 413 a of the film 411 forms the inner film surface 419 of the tube member 418. The second seal 420 extends laterally across the tube member 418 adjacent to the third edge 412c of the film 411, thereby forming a sealed bag end 421. Various seals can be used. Preferably, the second seal 420 will be a heat seal that fuses the inner surface 419 of the bag film to itself. The second seal 420 near the sealed bag edge 421 forms both the first bag edge 422 and the opposite second bag edge 423 and the second seal extends across the tube member 418 to the first bag. Extending from the edge 422 to the second bag edge 423. In addition, as in the case of the lap seal 416 described above, various shapes, thicknesses, structures, and the like can be used for the second seal. The wrap seal need not be centrally located between the edges 422 and 423, but is preferably located somewhere in between.

  On the opposite side of the sealed bag edge 421, there is a bag frame formed based on the fourth edge 412d by a wrap-sealed film, through which the tube member 418, the sealed bag edge 421, and the bag mouth A product (not shown) can be placed in the product storage chamber 425 defined by the portion 424. The first bag edge 422 can be folded from the first bag end corner 426 so that the bag 415 can be folded into a lay-flat state having a first bag edge 422 and a second bag edge 423 on the opposite side. The first bag mouth point 427 can extend to the second bag edge 423 and the second bag mouth corner 428 can extend to the second bag mouth point 429. In a lay flat state or a state close to a lay flat as shown in FIG. 11, the bag end portion 421, the bag mouth portion 424, and the first bag edge portion 422 and the second bag edge portion 423 connected thereto are A first bag wall 430 and an opposite bag wall 431 connected thereto are defined. Tube member 418 has an inner surface 419 and an outer surface 433. The first bag wall portion 430 has a first bag wall portion first surface 430 a that is in the vicinity of the second edge portion 412 b and extends to the second bag edge portion 423. The first bag wall portion 430 also has a first bag wall seam surface 430b on the opposite side that is in the vicinity of the first edge portion 412a and extends to the first bag edge portion 422.

  Preferably, the second seal 420 is such that the first seal 416 is located within one of the first bag wall 430 and the second bag wall 431, thereby forming a “back seam” for the bag. Provided. This provides one seamless bag wall and two seamless bag edges that can contain printed graphics applied to the film before or after the bag is formed. Further, the second seal 420 can take any shape regardless of whether it is a straight line or a curved line as long as the second seal 420 acts to seal the end 421. At least one of the first seal 416 and the second seal 420 is a peelable seal. As used herein, a “peelable seal” (and similar terms) is an uncontrolled or uncontrolled packaging material that can cause premature destruction of the package and / or inadvertent contamination or spillage of the contents of the package. A seal, especially a heat seal, designed to be easily peelable without random tearing or rupture. A peelable seal is one that can be manually peeled off to open the package at its sealed portion without using a knife or other instrument to tear or rupture the package. In the present invention, the peelable seal must have sufficient seal strength to prevent the seal from breaking during the standard heat shrink process of the packaged article and also during standard shipping and shipping. . Also, the seal strength must be weak enough to allow the hand to open the seal. Preferably, seal parameters such as material and seal condition selection are used to adjust the seal strength to the desired level for a particular package and application.

Many different peelable seals are known in the art and are suitable for use in the present invention. The peelable seal is generally made from a thermoplastic film having a peelable system incorporated therein. Suitable strippable films and / or strippable systems are disclosed in U.S. Pat. Nos. 4,944,409 (Busche et al.), 4,875,587 (Lulham et al.), 3,655,503 (Stanley et al.), And 4,058632 (Evans et al.). No. 4,252,846 (Romesberg et al.), No. 4,615,926 (Hsu et al.), No. 4,666,778 (Hwo), No. 4,784,885 (Carespodi), No. 48882229 (Hwo), No. 6476137 (Longo). No. 5,997,968 (Dries et al.), No. 4,189,519 (Ticknor), No. 5,547,752 (Yanidis), No. 5,128,414 (Hwo), No. 5023121 (Pockat et al.), No. 4,937,139 (Genske). Other), same No. 916190 (Hwo) and ibid. No. 4,550,141 disclosed (Hoh). See these if desired. Preferred films for use in making bags according to the present invention can be selected from multilayer heat shrinkable films that can form peelable seals. Preferred films also include high fracture resistance (eg, as measured by ram and / or hot water fracture tests), high shrinkage value, low haze, high gloss, high seal strength and printability. One or more of these characteristics or all advantageous combinations thereof can also be provided. The bag of the present invention advantageously uses a thermoplastic film comprising an oxygen and / or moisture barrier layer since it can be used to hold oxygen or moisture sensitive articles such as food after bleed and seal. It is preferable to do. As used herein, the term “barrier” or “barrier layer” means a layer of a multilayer film that acts as a physical barrier to moisture or oxygen molecules. An advantageous barrier layer material and other film layer combination for packaging oxygen-sensitive products such as raw red meat is 70 cc / 24 hours at 73 ° F. (23 ° C.) at 1 atmosphere. It will give an oxygen gas permeability (O ₂ GTR) of less than square meters (preferably less than 45, more preferably less than 15) and 0% relative humidity.

In another embodiment, the gas permeability is controlled such that CO ₂ can escape to package respirable foods such as cheese, as described in US Pat. No. 6,511,688. Preferably, the film has an unlimited shrinkage of at least 20% (preferably at least 35%) at 90 ° C. in at least one direction, preferably both the machine direction (MD) and the cross direction (TD). Unrestricted (sometimes referred to as “free”) shrinkage is measured by cutting square film pieces measuring 10 cm in each of the longitudinal and transverse directions. The film is immersed in water at 90 ° C. for 5 seconds. After removal from the water, the pieces are measured and the difference from the original dimensions is multiplied by 10 respectively to obtain the shrinkage in each direction.

  Oxygen barrier materials that can be included in the films used for the bags of the present invention include ethylene vinyl alcohol copolymer (EVOH), polyacrylonitrile, polyamide, and vinylidene chloride copolymer (PVDC). For some applications, nylon provides useful oxygen barrier, particularly at low temperatures, such as used in frozen foods. Preferred oxygen blocking polymers for use in the present invention are vinylidene chloride copolymers or copolymers of vinylidene chloride and various comonomers, such as copolymers of vinyl chloride (VC / VDC copolymer) or acrylics. Copolymers with methyl acid (MA / VDC copolymer) and EVOH. A particularly preferred barrier layer comprises about 85% vinylidene chloride / methyl acrylate copolymer and about 15% vinylidene chloride / vinyl chloride copolymer, as described, for example, in U.S. Pat. No. 4,798,751 to Schuetz et al. . Suitable and preferred EVOH copolymers are described in US Pat. No. 5,759,648. Please refer to these patent specifications if desired.

  Various peelable films and peelable seal systems can be used in the present invention. In a preferred embodiment, at least three layers (one or more hybrids described below) having an outer layer, an inner heat seal layer, and a tie layer disposed between the outer layer and the inner heat seal layer. Films made of coextrudates (called three-layer strippable systems to distinguish from systems that use a sealing layer) are used. In this preferred three-layer system embodiment, these film layers are such that delamination occurs by breaking apart the tie layer and / or the bond between the tie layer and at least one of the outer layer and the inner layer. Selected. A durable bond, a peelable bond and a breakable bond are, for example, two adjacent first and second layers that have materials that are more compatible with each other than the second layer. And by providing an adjacent third layer that establishes a relatively durable bond between these layers when the two materials have a lower affinity for each other, can be incorporated into the coextrusion process. This three-layer structure is either between the first layer and the second layer (which have a higher affinity for each other than the second layer) or between the third layers with a lower affinity (in this case the second layer is A relatively durable bond is established in the tie layer or tie layer (common to both the first and third layers). Thus, the low affinity between the second and third layers for the first and second layers results in a relatively peelable bond between the second and third layers. The choice of various materials determines the nature of the bond, i.e. whether it is durable, peelable, breakable or a combination thereof.

Suitable polymers for use in the outer layer, tie layer and inner heat-sealable layer include both polytype materials such as ethylene homopolymers and copolymers and ionomer type materials. Examples of suitable polymers include ethylene vinyl acetate copolymer (EVA), ethylene α-olefin copolymer, linear low density polyethylene, low density polyethylene, very low density polyethylene (VLDPE), neutralized ethylene / acid. Copolymers, plastomers, ethylene acrylate copolymers, ethylene methyl acrylate copolymers and zinc or sodium salts of partially or fully neutralized ethylene / methacrylic acid copolymers. The inner heat seal layer advantageously uses a heat sealable material. The tie layer is selected to have a relatively low peel strength when bonded to be peelable to either one of the outer layer or the inner heat seal layer. The tie layer is typically about 5-30% polybutylene and another component, such as ethylene vinyl acetate copolymer, ethylene copolymer with C ₄ -C ₈ α-olefin, linear low density polyethylene. , Ionomers, neutralized ethylene / acid copolymers or unneutralized ethylene / acid copolymers and blends of two or more thereof. As used herein, the term “polybutylene” has polymer units derived from 1-butane as the major component (75% polymer units), preferably at least of the polymer units. 80% is derived from 1-butane. The preferred polybutylene reportedly has a density of 0.908 g / cm ³ , a melt index of 1.0 g / 10 min, and a melting point of 243 ° F., under the trade name PB8640, Basel Polyolefin Corporation (Nevada, The Netherlands). It is a random copolymer of 1-butene and ethylene available from a national corporation. In this preferred peelable embodiment, whether the heat seal formed between the inner heat seal layer and another layer to be heat sealed is part of another film or part of the same film Regardless, it should have a seal strength that is permanent, ie greater than the peelable bond between the tie layer and one of its adjacent layers. The preferred three-layer coextrusion peelable structure described above contemplates an optional additional layer for producing films of 4, 5, 6, 7, 8, 9, 10 or more layers. One or more additional layers can be coextruded with the above three layers or separately, and multilayer film structures can not only be formed by coextrusion, but are well known in the art such as coating lamination, adhesive lamination, or combinations thereof. It is further contemplated that it can be formed by other methods.

  It is also contemplated that one or more such additional layers can be adjacent to or between any of the three layers. In one embodiment of the present invention, a durable adhesive that may or may not be applied in the warmed or molten state, in the liquid state, or in other states can be used in place of the heat seal layer. However, it is preferred to use a heat sealable layer.

  It is also contemplated that peelable seals using one or more so-called “hybrid” surface layers can be used (in this case, delamination occurs at the seal layer interface 432 rather than the inner layer of the film 411). . This type of release system, for example, controls the diffusive properties that give high seal strength in the desired low form for release, as well as certain types that are packaged under conditions that can adversely affect seal integrity. The condition that the article of the product adheres particulates, starches, fats, greases or other components that may reduce the seal strength or impair the ability to provide a desired strength seal, such as a strong seal fusion by heat sealing Has the disadvantages associated with the problem of sealing below. Such a seal system is often referred to as a two-layer release system, but the film structure may include 3, 4, 5, 6, 7, 8, 9, 10 or more layers.

  A preferred peelable seal film and peelable seal system is disclosed in US Pat. No. 4,944,409 (Invention name “Easy Open Package”). See if desired.

A preferred multilayer barrier film structure for use in making a bag according to the present invention is illustrated in FIG. 12, which is an enlargement of the first seal 416 made from the sheet of heat shrinkable film 411 of FIG. An end view is shown. The thicknesses of the layers in FIG. 12 and the other figures shown here are not to scale, but are made to specific dimensions for ease of illustration. A preferred easily peelable heat shrinkable film 411 is a five layer coextrudate and includes from the inner surface 419 to the opposite outer surface 433 of the tube member 419 (see FIG. 11).
(A) The heat sealable layer 434 on the inner surface is preferably composed of a blend of ethylene vinyl acetate (EVA) and polyethylene,
(B) The blocking layer 435 is preferably made of a vinylidene chloride copolymer (PVDC),
(C) The core layer 436 is preferably composed of a blend of EVA and polyethylene;
(D) The tie layer 437 is preferably composed of a blend of polyethylene and polybutylene,
(E) The heat-sealable layer 438 on the outer surface is preferably made of polyethylene.

  The thickness of each layer based on the total thickness of the film 411 is typically <50% for the inner surface heat-sealable layer 434, <20% for the barrier layer 435, and <28% for the core layer 436. The tie layer 437 can be <15% and the outer heat sealable layer 438 can be <15%. The first seal 416 heat seals the inner film surface 419 of the film 411 longitudinally along their respective lengths to the outer film surface 433 so that the inner film surface 419 and the outer film surface 433 overlap. Made by. In this embodiment, fusion occurs between the inner surface heat sealable layer 434 and the outer surface heat sealable layer 438. The peelable bond of this system is provided by a tie layer 437 and there, for example, at the tie layer interface with the outer surface heat sealable layer 438 and / or at the tie layer interface with the core layer 436 and / or. Alternatively, peeling occurs between the outer layer 438 and the core layer 436. Thus, referring to FIGS. 11 and 12, the peelable portion of the film is outside the tube member 418, which is preferred. This is because the first seal 416 is peelable, while the second seal 420 and the last hermetic seal (not shown) are strong between the inner surface heat sealable layers 434 of the respective bag walls 430 and 431. Will ensure a good melt seal.

  Referring to FIG. 13, a partial cross-sectional view taken along line BB in FIG. 11 illustrates how the preferred embodiment of the present invention allows a wrap seal to function as an easy-open peel seal while at the same time providing a strong end seal. It is illustrated how it functions to generate. In FIG. 13, the film 411 has an outer surface 433 along with an outer surface layer 438, a tie layer 437, a core layer 436, a barrier layer 435 and an inner heat sealable layer 434 which are continuous layers therefrom. Referring to FIG. 11, a second seal 420 is provided over the tube member 418 and its surface 419 is collapsed on its own. Referring again to FIG. 13, this seal has the inner surface heat sealable layer 434 in intimate contact with itself with the peelable tie layer 437 positioned far from the end seal interface 439. The preferred embodiments of the present invention shown in FIGS. 11-13 include: (a) an end seal that bonds similar materials with strong sealing properties together while holding a tie layer 437 that can be easily peeled away; (B) Combining a lap seal having a peelable tie layer 437 near the outer surface heat sealable layer 438 and lap seal interface 432, thereby easily peeling to a bag or packaging material made using the above configuration Gives an opening that can.

  Film 411 is designed to control film breakage when peeled off by hand. Due to the composition of the peelable tie layer 437, its location near the lap seal interface 432, and in the case of a preferred three layer peelable system, the thinness and composition of the outer surface heat sealable layer 438, the second edge When the portion 417b is then manually pulled over the lap seal 416, an initial tear or tear begins. This tear spreads from the heat seal at the edge 417 b of the lap seal interface 432 to its outer heat sealable layer 438. If the peelable bond is designed to occur at the tie layer 437, the continuous application of the opening force is applied until the tear reaches the opposite edge 417a of the heat seal 416 / Causing delamination or failure of the adhesive layer along the interface of the heat-sealable layer 438 or along the interface of the tie layer 437 / core layer 436, and / or causing damage to the tie layer 437, or These occur together, where the tear extends across the outer layer 438 to either the edge 412a or the back, thereby opening the bag.

  In general, the film used in the heat shrinkable bag of the present invention has properties that are desirable for the particular packaging operation in which the film is used, such as peelable seal, fracture resistance, modulus, seal strength, barrier properties. As long as it has a thickness and composition sufficient to provide optical properties, etc., it can have any desired thickness. For material efficiency and protection, it is desirable to use the maximum film thickness to provide the necessary fracture resistance and other properties. Preferably, the film has a total thickness of about 1.25 to about 8.0 mils, more preferably about 1.75 to about 3.0 mils.

  Another embodiment of the present invention is illustrated generally in FIGS. 14 and 15 as bag 415a. The same reference numerals found in bag 415 are used for bag 415a. The bag 415a further includes a tensile flap 440. This tension flap 440 provides additional overlap by moving the first edge 412a and the second edge 412b further apart, and also on the second side of the first bag wall outside the product storage chamber 425. The first wrap seal 416 is positioned so that a portion of the first side 430a of the first bag wall portion overlapping the 430b is not sealed to the second side 430b. This tension flap 440 can be easily grasped and pulled by the end user without taking the means of a cutting instrument as often required when opening packaging materials that do not have a peelable system. The product can be opened easily. Although shown to expand the overall length of the bag 415a, those skilled in the art will be able to cut the tension flap 440 into the desired shape, or any other known that is known to assist in the initiation of peeling. You will recognize that you can adopt this mechanism. Also preferred for use in the bag 415a are the preferred films illustrated in FIGS. 10, 12 and 13 described above.

  14 and 15 has the positions of the bag mouth portion 424 and the second seal 420 of FIG. 11 reversed, which is indicated as the bag mouth portion 424a and the second seal 420a in FIG. It is represented.

  Referring to FIG. 16, an example of the second seal 420 a shown in a cross-sectional view is that the first bag wall is sealed from the first bag edge 422 to the second bag wall 431 of the second bag wall 423, and It shows that the first lap seal located between the first edge 412a and the second edge 412b is sealed. In known heat sealing methods, layers of film are pressed together with opposing sealing rods or wires for a time sufficient to cause fusion between the layers at elevated temperatures and pressures. These heat seal bars can be rigid and / or flexible, but in general this is not soft or soft enough to seal the film. As shown in FIG. 16, the second seal 420a has a seal boundary surface 439a, and the boundary surface 439a has a seal pressure close to the first edge portion 412a and the second edge portion 412b. It has two possible points that can be reduced during operation. That is, the seal pressure may decrease at a point 441 below the edge 412b of the second seal interface 439a, and the seal pressure may also decrease at a point 442 adjacent to the first edge 412a. For example, it is assumed that a void (gap) may exist at the point 442. In particular, seal parameters such as pressure, temperature, hold time and heat sealable layer composition as desired to produce the desired strong seal at points 411 and 422 and all along the second seal interface 439a. Can be adjusted to. In particular, it has been found advantageous to use a high melt flow index polymer component in the heat seal layer to satisfy potential voids. It may also be advantageous to taper one or both of the edges 412a and 412b to increase the contact surface and / or pressure between overlapping films, particularly at points 441 and 442 and adjacent areas.

  Another embodiment of the present invention is illustrated generally in FIG. 17 as a bag 415b. Similar elements also include similar reference numerals. The bag 415b includes a first fin seal 516. The first fin seal 516 contacts the first side 430a and the second side 430b of the bag wall portion 430 with the inner film surface 419 on each side facing each other. The seal interface 517 is coupled. One or both of the first edge 412a and the second edge 412b may extend outward beyond the first fin seal interface 517 so that a tensile flap (not shown) is provided. Bag 415a (FIG. 14) is preferred over bag 415b. This is because the plane of the first seal 416 is parallel to the plane of contraction force encountered during the heat shrink process. The first fin seal 516 of the bag 415b has its heat seal plane positioned perpendicular to the contraction force (as indicated by arrows Z ′ and Z ″ in FIG. 19), which is the heat shrinkage. Increase the risk of seal breakage (early delamination) during the process. Furthermore, since the container of the present invention is advantageously made from a single film sheet or web, the arrangement of fin seals such as the first seal 516 at this time is such that each seal of the container is a peelable seal. Need to be. Also, the second seal 420 and the last hermetic seal (not shown) are always peelable. This is because the first bag wall portion 430a and the second bag wall portion 430b are sealed in a state where the films are in the same contact relationship. For example, FIG. 19 is an enlarged view of the first fin seal 516 shown in cross-section showing the individual layers of the preferred film discussed above with respect to the bags 415 and 415a. Each wall 450 and 452 of seal 516 includes a three-layer peelable system (tie layer 437) that is equidistant from and close to the seal interface of sealant layer 438. Thus, this not only can not be pre-determined that a failure of peeling will occur at the wall 450 or 452, but will further reduce the ability of all seals to be easily peeled and the direction of the shrinkage force to create a strong seal. It cannot be determined in advance. Because of all these disadvantages, this embodiment is less preferred.

  Another embodiment of the present invention is illustrated generally in FIGS. 20 and 21 as a bag 415c. Again, like elements contain like reference numerals. The bag 415c includes a first seal 616 that includes a butt seal tape 641 comprising a butt seal film 611 having a first frame 607, a second frame 609, a seal surface 615, and an outer surface 614. . The first seal 616 includes a first heat seal 618 that has the first side 430a of the bag wall portion 430 butted against the first frame portion 607 of the seal tape 641 in the vertical direction and The two heat seal 619 has the second side 430b of the bag wall portion 430 abutted against the second frame portion 609 of the seal tape 641 in the vertical direction. Thus, the first side 430a and the second side 430b are joined in the relationship of adjacent edges, thereby forming a bag wall 430 without direct heat sealing therebetween. Preferably, the butt seal film 611 is made of the same film as described above and illustrated for the bags 415, 415a and 415b illustrated in FIGS. 10-19, and the outer heat sealable layer 438 (FIG. 11) is the inner surface. 615. Accordingly, the bag 415c can be manufactured from a film that does not include a peelable system therein, but can be peeled off by means of a strippable system included in the butt seal tape 641 used to form the first seal 616. Is included. Conversely, film 411 preferably includes a peelable system but does not include a butt seal tape, or both film 411 and butt seal film 611 may be compatible with others. A stripping system may be included. The butt seal film 611 is preferably heat shrinkable but is not essential. A tension flap 440 may be provided on the butt seal tape 641 to provide an area for the consumer to grip and pull to easily open the bag 415. If the butt seal tape 641 is sealed to the inner surface 419 of the film 411, then a portion of the first side 430a or the second side 430b extends outward beyond the first heat seal 618 or the second heat seal 619. A tensioning flap may be provided for the consumer to grip. The second seal 420 is preferably a durable seal made between the inner surface 419 of the first bag wall 430a and the second bag wall 430b.

  Although shown in FIG. 20 as being sealed to the outer surface 433 of the first side 430a and the second side 430b, those skilled in the art will recognize that the butt seal tape 641 forming the first seal 616 is the bag 410c. It will be appreciated that the sealing surface 615 is heat sealed to the inner surface 419 of the first side 430a and the second side 430b, thereby being located inside (not shown). In this case, preferably, at least one of the first side 430a and the second side 430b includes a portion extending outwardly with respect to the butt seal tape 641 beyond the heat seal. Thus, a tension flap is provided for the consumer to grasp.

  A further embodiment of the present invention is illustrated generally in FIG. 22 and 23 as 415d. Similar elements described above with respect to bags 415, 415a, 415b and 415c are given the same reference numerals in bag 415d. The bag 415d includes a first seal 716, which is composed of a seal strip 741 made of a strip film 711 having an inner surface 714 and an outer surface 715. The seal strip 741 includes a first edge 718 that is heat-sealed by the first heat seal 720 such that the outer surface 715 is heat sealed to the inner surface 419 of the film 411 in face-to-face contact. 430a is heat-sealed in the vertical direction. Seal strip 741 includes a second edge 719 that is secondly sealed by second heat seal 721 such that inner surface 714 is sealed in face-to-face contact with outer surface 433 of second side 430b. The side 430b is heat sealed in the vertical direction. A tensile flap 440 is provided by including a portion of the strip film 711 that extends outward beyond the second heat seal 721 joining the second edge 719 and the second side 430b. Alternatively, the first side 430a may include a portion that extends outward beyond the second heat seal 420.

  Preferably, the strip film 711 comprises a strippable system and comprises the same film as described above and illustrated for the bags 415, 415a and 415b illustrated in FIGS. 10-21, and its external heat sealability Layer 438 (FIGS. 12-13) forms an inner surface 714. In this embodiment, the heat seal 721 must be peelable and the film 411 must not include a peelable system. Alternatively, the outer heat sealable layer may include an outer surface 715 so that the heat seal 720 can be peeled off. In this case, the film 411 needs not to include a peelable system, and the second seal 420 can be made durable. In a manner similar to that described for bag 415c, strip film 711 may not include a strippable system and film 411 does not include a strippable system, or both film 411 and strip film 711 may be A compatible strippable system may be included. The strip film 711 is preferably heat shrinkable but is not essential.

  The bag according to the present invention is preferably as described in Gregory Robert Pockat et al. US patent application Ser. No. 10 / 371,950 filed Feb. 20, 2003 (invention name “Heat-Shrinkable Packaging Receptacle”). It is made continuously from a continuous sheet or roll. This roll is slit to the desired width and fed to a bag making machine where the longitudinal edges of the film are aligned with each other and either a lap seal (bags 415 and 415a) or a fin seal (bag 415b) And are sealed longitudinally to form a continuous single seam tube or tube member. A transverse seal is created over the tube member and the portion containing the transverse seal is cut from the continuous tube to form individual bags. In general, a heat seal is made by applying sufficient heat and pressure between the surfaces of two polymer film layers for a time sufficient to cause fusion between the polymer film layers. As a general method of forming a heat seal, there is a heating rod sealing method in which adjacent polymer layers are held in a face-to-face contact with opposed rods, at least one of which is heated, adjacent polymer layers Are held in face-to-face contact by means of opposing rods, one of which includes a wire or ribbon through which a current is passed for a short period of time such that sufficient heat is generated to cause the film layer to fuse. An impulse sealing method is exemplified. In general, the performance of the sealing layer of the film becomes even more important because less area is bonded to the heating rod seal with an impulse seal. However, impulse seals are generally more aesthetic because they use less area to form a bond.

  The film selected to make the container of the present invention is preferably biaxially stretched by well-known inflation or double bubble techniques as described, for example, in US Pat. Nos. 3,456,044 and 6,511,688. See these if desired. In this technique, the extruded first tube leaving the tube extrusion die is allowed to cool, fold, then stretched, preferably by reheating, reinflated to form a second bubble, and allowed to cool again. The film is preferably biaxially stretched, where transverse (TD) stretching is achieved by inflation to radially expand the heated film. Stretching in the machine direction (MD) is preferably accomplished by drawing or drawing the film tube in the machine direction using nip rolls rotating at different speeds. The stretch ratio of biaxial stretching to form the bag material is preferably sufficient to give the film a total thickness of about 1-8 mils. The MD stretch ratio is typically 3: 1 to 5: 1 and the TD stretch ratio is also typically 3: 1 to 5: 1.

  Referring now to FIG. 24, the double bubble method (also known as the inflation method) is shown. The polymer blends that make up several layers are coextruded by conveying separate melt streams 611a, 611b and 611c to a die 630. These polymer melts are combined and coextruded from a circular die as a multilayer tube 632 with relatively thick walls. The thick walled first tube 632 leaving the extrusion die is cooled and folded by the nip roller 631, and then the folded first tube 632 is transported to the reheat zone by the transport rollers 633a and 633b, where The tube 632 is reheated below the melting point of these layers being stretched and inflated with a confined fluid, preferably gas, most preferably air, to form a second bubble 634 and cooled. . The second bubble 634 is formed by a fluid confined between a first pair of nip rollers 636 at one end of the bubble and a second pair of nip rollers 637 at the opposite end of the bubble. Inflation that causes the film to bulge radially provides transverse (TD) stretching and stretching. Stretching in the machine direction (TD) is accomplished by adjusting the relative speed and / or dimensions of the nip roller 636 and nip roller 637 to stretch (stretch) the film in the machine direction.

  Biaxial stretching is preferably 10 mils or less, typically about 1.25 to 8.0 mils, more preferably 5 mils or less, even more preferably 1.75 to 3.0 mils (44. It is sufficient to give a total thickness of 5 to 76 μm).

  After stretching, the tubular film 638 is preferably folded to a fold diameter of up to 80 inches, typically about 5-30 inches, cut longitudinally, flattened, and used as a winder. Is wound around a reel 639. Those skilled in the art can form films using the methods described above, while providing other conventional methods such as stretching, including single bubble blown film or slot cast sheet extrusion methods with subsequent stretching. It will be appreciated that a film can be made with a tenter for. Furthermore, those skilled in the art will recognize that the flat width of the folded tube determines the width of the resulting sheet film. Thus, the dimensions of the first tube and subsequent processing can be selected to give the maximum flat width and film thickness for the desired application, thereby advantageously maximizing the production capacity of the film production equipment. Can do.

  Advantageously, the bag manufacturer can place bags of various lengths and widths from a roll of film winder, the sheet width and lateral end seals and bag mouths for a particular bag or series of bags. Can be manufactured by adjusting the distance between. This advantageously eliminates the costly need to produce a specific width seamless tube that has been widely used by butchers in recent years and does not include a peelable seal. The present invention also allows cost savings and manufacturing efficiency by allowing bags of many widths and lengths to be manufactured from standard webs. The bag manufacturer simply forms the continuous tube member by slitting the film winder to the desired width and longitudinally sealing the opposite sides as described for bags 415, 415a and 415b. Good. An adjustable length bag can be made by sealing the tube member laterally and cutting the tube member at a distance from the lateral seal.

  Preferably, the manufacture of the bag is a continuous process illustrated in FIG. 25, in which the film is directed to a bag manufacturing assembly (not shown) from which individual end seal bags are made. The film 411 is continuously supplied from the reel 639 and is optionally slit to form a film 411a having a desired width and an unused film 411b. The film 411a is supplied to a bag manufacturing assembly (not shown). Unused film 411b can be wound on reel 639b for later use, or supplied to another bag manufacturing assembly. The first side 430a and the second side 430b of the film 411a are mated to each other and preferably sealed longitudinally with a first seal, for example an additional overlapping portion that functions as a tensile flap, and seamed to the back A continuous tube member 418 is formed. A second seal 420 is provided laterally at a desired location away from the opening 424 across the tube member 418. The tube member 418 is then cut (preferably simultaneously) to detach the portion containing the second seal from the continuous tube, thereby forming a bag 415. Typically, when a transverse seal is made on a single bag, a transverse cut is being made that forms the mouth of the adjacent bag. This process, when flattened, is due to the bottom edge formed by the lateral heat seal, the opening formed by the cut edge, and the creases that occur when the tube member is flattened. A so-called “end seal” bag is formed having two side edges to be formed.

  The transverse seal should extend across the tube member to ensure a hermetic seal (if such is desired). Each bag being formed from a single tube member is necessarily formed by at least two normally parallel spaced apart cuts that can be segments of the tube member, and usually these cuts One lateral seal adjacent to one of the parts will define a bag bottom located on the opposite side of the bag opening formed by the remote cut. This lateral seal-opening spacing (which can be varied) will determine the length of the bag to be formed. The length of the bag can be easily changed by changing the spacing between the lateral seal and the cut. The width of the bag can also be easily changed by changing the width of the film by slitting a standard winding material.

Unless otherwise noted, the following physical properties are used to describe the films and seals of the present invention. These properties are measured either by the test procedure described below or by a test method similar to the following method.
Average gauge: ASTM D-2103
Tensile strength: ASTM D-882, Method A
1% secant modulus: ASTM D-882, Method A
Oxygen gas permeability (O ₂ GTR): ASTM D-3985-81
Elongation at break: ASTM D-882, Method A
Molecular weight distribution: Gel permeation chromatography Glossiness: ASTM D-2457, angle 45 °
Cloudiness: ASTM D-1003-52
Melt index: ASTM D-1238, Condition E (190 ° C.) (except for propene base (> 50% C ₃ content) polymer tested under Condition L (230 ° C.))
Melting point: ASTM D-3418, peak determined by DSC at a heating rate of 10 ° C./min m. p.
Vicat softening point (Vsp): ASTM D-1525-82
Seal strength: ASTM F88-94 (standard test method for seal strength of flexible barrier materials).
All ASTM test methods described herein are included in this disclosure by reference.

Shrinkage value :
The shrinkage value is obtained by measuring the unlimited shrinkage of a 10 cm ² sample immersed in 90 ° C. (or indicated temperature if different) water for 10 seconds. Four specimens are cut from a given sample of film to be tested. The specimen is cut into a 10 cm long (MD) × 10 cm long (TD) square. Each specimen is completely immersed in a 90 ° C. (or indicated temperature if different) water bath for 5-10 seconds. The specimen is then removed from the water bath and the spacing between the ends of the shrunken specimen is measured in both MD and TD directions. Multiply 10 by the difference between the measured interval for the shrunken specimen and the original 10 cm sides to obtain the shrinkage in each direction. Average the shrinkage of the four specimens and report their average MD and TD shrinkage values. The term “heat-shrinkable film at 90 ° C.” means a film having an unlimited shrinkage value of at least 10% in at least one direction.

Ten identical specimens of tensile seal strength (seal strength) test film are 1 inch (2.54 cm) wide and suitable length for test equipment, eg, about 5 inches (12.7 cm) long Cut to 1 inch and place a 1 inch (2.54 cm) wide seal in the center and laterally. Fix the opposing parts of the film sample to the opposing clamps of the universal tensile test instrument. The film is secured with a tensioned snug fit between the clamps without stretching before the start of the test. This test is performed at ambient or room temperature (RT) (about 23 ° C.) test temperature. Activating this instrument causes the film to break through a clamp that is transverse to the seal at a constant speed of 12.0 inches (30.48 cm) per minute (film or seal breaks or delamination and film Pull until integrity loss). Test temperature indicated and 1bs. Measure and record the breaking point force. This test is repeated for four additional samples and the average gram at the break is reported.

Ram Destruction Test The Ram Destruction Test is used to determine the maximum breaking load or breaking force and the maximum breaking stress of a flexible film when hit with a hemispherical or spherical shaped hammer. This test gives a quantitative measure of the fracture resistance of thin plastic films. This test is further described in US patent application Ser. No. 09 / 401,692. See if desired.

  The following are examples and comparative examples given to illustrate the present invention.

  In all the following examples, unless otherwise noted, film compositions are generally described in US Pat. Nos. 3,456,044 (Pahlke) and 6,511,688 (Edwards et al.) Describing coextrusion type inflation methods. Were further prepared according to the detailed description above. In the following example, all layers are extruded as a first tube (coextruded in the multilayer example), which is cooled by exiting the die, for example by jetting with tap water. This first tube is then reheated, stretched, and cooled as taught in the above patent.

Example 2
A heat-shrinkable bag according to the present invention as generally illustrated in FIGS. 10 and 11 is (A) an internal heat-sealable layer, (B) a barrier layer, (C) a core layer, (D) Manufactured from a film consisting of a co-extruded 5-layer biaxially stretched shrink film having a tie layer and (E) an external heat sealable layer. The inner layer and the outer layer are directly bonded to opposite faces of the barrier layer. The five layers contained the following composition:
(A) 37% by weight VLDPE, 24% EVA, 33% plastomer (EXACT4053), 6% processing aid (B) about 85% vinylidene chloride-vinyl chloride copolymer and about 15% vinylidene chloride -Blend of methacrylate ester copolymer (C) 100 wt% EMA
(D) 20 wt% VLDPE, 33% plastomer (EXACT4053) and 20 wt% polybutylene, and (E) 40 wt% VLDPE, 33% plastomer (EXACT4053), 25% EVA, 2% processing Auxiliary agent.

  One extruder was used for each layer. Each extruder was connected to an annular coextrusion die in which the thermoplastic resin was coextruded while forming the first tube. The resin mixture for each layer is fed from the hopper to the attached single screw extruder, where the mixture is thermoplastic under conditions similar to those disclosed in copending US patent application Ser. No. 10 / 371,950. And extruded from a five-layer coextrusion die into a first tube.

  Although not essential, it is preferred to irradiate the entire film to expand the range of heat sealing and / or improve the toughness of the inner and outer layers by radiation-induced crosslinking and / or cutting. This is preferably done by irradiation with an electron beam at a dose level in the range of at least about 2 megarads (MR), preferably 3-5 MR, but higher doses, particularly for thicker films or It may be used when one tube is irradiated. Irradiation can be performed on the first tube or after biaxial stretching. The latter, referred to as post-irradiation, is preferred and is described in US Pat. No. 4,737,391 to Lustig et al. See if desired. The advantage of post-irradiation is that a relatively thin film is processed instead of the relatively thick first tube, thereby reducing the power required for a given processing level.

  The film is wrapped and slit to the desired width. Next, the film is supplied to a bag manufacturing apparatus to form a tube member having a continuous lap seal extending in the longitudinal direction. A bag according to the bag 415a shown in FIG. 14 can be formed by sealing laterally across the tube member and simultaneously separating this sealed portion from the continuous tube structure.

  Various tests can be performed on the bags of the present invention. The gauge thickness will typically be a film thickness of 10 mils or less, preferably 1.25 to 5.0 mils. Wrap seals should typically have an average seal strength of at least 2 Kg / inch. The end seals will typically have an average seal strength of at least 3 Kg. The bag will also have an average MD and TD heat shrinkage at 90 ° C. of at least 20%, preferably at least 40%, respectively in both directions. This preferred bag has a very good heat shrinkage rate, which is very desirable for wrapping raw red meat fillets, and also has a very good resistance to breakage, more advantageously, Incorporates a peelable seal not found in food packaging bags. Therefore, it is economical to manufacture, has a peelable seal, puncture resistance and strong end seal, yet has a unique combination of previously unknown features and commercial advantages A bag is provided.

  The present invention advantageously provides individual heat shrinkable bags having a seal that is easily peelable. Thus, the container or bag of the present invention can be easily opened without the means of knives or other cutting / opening devices, and this allows food manufacturers to provide desirable consumer-oriented packages. Make it possible.

  Another preferred embodiment of the present invention uses a seven layer heat shrinkable film to produce a back seam material. This 7-layer film has several advantages over 3 and 5 layers. When a polymer having a high melt index of 2.0 dg / 10 min or more is used for the sealant layer, for example, an ethylene α-olefin copolymer such as EXACT4053, sealing is assisted by folds and wrinkles in the seal. This is important. This is because overlapping areas create wrinkles in the seal.

Another advantage is that a strong adhesive polymer, such as Emact SP1330 (which has a density of 0.948 g / cm ³ , a melt index of 2.0 g / 10 min, a melting point of 93 ° C., a softening point of 49 ° C. and An ethylene methyl acrylate copolymer (EMA) such as having a methyl acrylate (MA) content of 22%) is used as a PVDC tie layer to provide improved adhesion. . This has been shown to give excellent adhesion. EMA gives the finished film an adhesion of over 100 g. A preferred seven-layer structure includes a first heat seal layer made of an ethylene α-olefin copolymer (EXACT 3139 manufactured by Exxon), an EVA (Exxon 701.ID), an ethylene / 1-butene copolymer (EXACT 4053 manufactured by Exxon), A second peelable tie layer made of a polymer blend having 15 to 35% each of an ethylene / 1-octene copolymer (VLDPE10B made by Nova) and a third tie layer made of, for example, EMA (Voridian SP1330) And, for example, a fourth barrier layer as described in Example 1, a fifth tie layer made of, for example, EMA, and EVA, an ethylene / 1-butene copolymer and an ethylene / 1-octene copolymer, 20 to A sixth intermediate layer composed of a blend having 45% and an ethylene / α-olefin copolymer, for example, EX manufactured by Exxon; And a seventh outer surface layer made of CT3139.

  The above films are preferably 2 mils thick overall, and the layer thickness ratios for the first through seventh layers are 10: 42: 5: 18: 5: 15: 5, respectively.

  Bags 415, 415a, 415b, 415c and 415d can be economically manufactured from almost any size. This is because these bags are not formed from seamless tubes that must be made to the desired width. The only limitation on the size of the bag made is the size of the web film. Standard roll films are available in widths greater than 100 inches. The present invention allows bag manufacturers to produce bags of any size from flat sheets of the same winding material up to the dimensional limits of the winding material. For example, if the roll is 52 inches wide, it has a fold diameter of approximately 26 inches, taking into account the amount of overlap, gaps or contact portions of the first seals 416, 516, 616 and 716 used. A tube member can be manufactured. For example, if the manufacturer wants to produce a wrap seal or fin seal bag having a 18 inch fold diameter, then the manufacturer will place the standard web with the appropriate width (in the area of the first seal 416 or 516). Slit to approximately 36 inches) plus a margin. The unused portion slit from the standard roll is rewinded for use in manufacturing bags of different dimensions. In this embodiment, the standard winding material film can be manufactured more economically. This is because film production equipment can operate at or near the upper limit of film width production, thereby using almost all of the capacity of the equipment. Making a bag from a seamless tube requires that the film production apparatus be operated with limited capacity to form tubes of different small widths. Furthermore, this film production equipment requires costly equipment that significantly increases the cost of producing seamless tubes and disruption between operations of different dimensions.

  Although the end-sealed bag having a seamless side portion of the heat-shrinkable film that can be easily peeled has been described above, in consideration of this disclosure, the side-sealed heat-shrinkable bag and pouch made from a plurality of films are also included in the present invention. It will be apparent that a heat shrinkable container can be provided that conforms to and is easy to peel open. The present invention can be used in the heat-shrinkable state formed in pouches as described in US Pat. Nos. 6,015,235 (Kraimer et al.) And 6,206,569 (Kraimer et al.). See these if desired.

  While the invention has been described in terms of certain specific embodiments, those skilled in the art will recognize that many modifications can be made without departing from the scope and spirit of the invention, and that such modifications are You will recognize that you are within the scope of

FIG. 3 is a schematic view illustrating an end-sealed shrink bag having a wrap seal according to the present invention, slightly opened from a lay flat state. It is a cross-sectional view of the bag illustrated in FIG. 1 obtained by cutting along line 2-2 in FIG. It is the schematic which illustrated the end seal shrink bag which has a fin seal according to this invention in the state opened slightly from the state of the lay flat. FIG. 4 is a cross-sectional view of the bag illustrated in FIG. 3 obtained by cutting along line 4-4 in FIG. 3. It is the schematic of the end seal shrink bag illustrated in the state which opened the end seal shrink bag which has a butt seal according to this invention from the state of a lay flat slightly. 6 is a cross-sectional view of the bag illustrated in FIG. 5 obtained by cutting along line 6-6 in FIG. FIG. 3 illustrates a preferred three-layer film structure for forming a bag according to the present invention. 1 is a schematic representation of a preferred method for producing a film for use in the present invention. FIG. 6 illustrates a preferred seven-layer film structure for forming a bag according to the present invention. 1 is a schematic view of a heat shrink bag sealed for peel according to the present invention. FIG. It is the schematic which illustrated the preferable specific example of the heat-shrinkable bag according to this invention in the state of a lay flat substantially. Line AA in FIG. 11 shows an enlarged view (not to scale) of a preferred film lap seal portion for use in making the bags illustrated in FIGS. It is the fragmentary sectional view obtained by cut | disconnecting along. FIG. 12 is a partial cross-sectional view taken along line BB in FIG. 11, showing the end seal portion of the preferred film enlarged (not to scale). FIG. 4 is a schematic view of another preferred embodiment of a heat shrinkable bag according to the present invention having a tensile flap. FIG. 15 is a cross-sectional view of the bag illustrated in FIG. 14 obtained by cutting along line CC in FIG. 14. It is sectional drawing obtained by cut | disconnecting along the line DD of FIG. 15 which shows an end seal. FIG. 6 illustrates yet another bag in accordance with the present invention having a fin seal back seam. It is sectional drawing of the bag illustrated by FIG. 17 obtained by cut | disconnecting along line EE. FIG. 19 is a partial enlarged cross-sectional view of the seal portion of FIG. 18 showing a preferred film structure in detail. FIG. 6 illustrates a specific example of another bag according to the present invention having a butt seal back seam. It is sectional drawing of the bag illustrated by FIG. 20 obtained by cut | disconnecting along line FF. Fig. 4 illustrates another bag according to the present invention having a release strip. It is sectional drawing of the bag illustrated by FIG. 22 obtained by cut | disconnecting along line GG. 1 is a schematic representation of a preferred method for producing a film for use in the present invention. 1 is a schematic illustration of a preferred method of manufacturing a bag according to the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Bag 11 Heat-shrinkable film 12 1st edge 13 Top surface 14 2nd edge 15 Bottom surface 16 1st seal 18 Tube member 20 1st bag wall 20
22 Second bag wall portion 28 Opening portion 30 Bag end portion 32 Second seal 34 Product storage chamber 42 Barrier layer 44 Internal heat-sealable layer 46 External layer 60 Film 61 Internal layer 67 External layer 110 Bag 116 First seal 117 Fin 118 Tube member 132 Second seal 210 Bag 213 Internal surface 215 External surface 216 First seal 232 Second seal 311a Melt flow 311b Melt flow 311c Melt flow 330 Die 331 Nip roller 332 First tube 333a Transport roller 333b Transport roller 338 Stretched film 339 Reel 411 Heat shrinkable film 412a 1st edge part 412b 2nd edge part 413c 3rd edge part 413d 4th edge part 416 Lap seal 418 Tube member 419 Inner surface 420 2nd seal 421 Sealing Edge 422 First bag edge 423 Second bag edge 424 Bag mouth 425 Product storage chamber 433 External surface 434 Heat seal layer 435 Barrier layer 436 Core layer 437 Tie layer 438 Heat seal layer 440 Tensile flap 516 First Fin seal 607 First frame portion 609 Second frame portion 611 Seal film 615 Seal surface 616 First seal 618 First heat seal 619 Second heat seal 641 Butt seal tape 711 Strip film 714 Inner surface 715 Outer surface 716 First seal 718 First edge 719 Second edge 720 First heat seal 741 Seal strip

Claims (48)

An end-sealed packaging container formed from a sheet of heat shrinkable film having a first side, an opposite second side, an inner surface and an outer surface, wherein the container comprises the first side In close contact with the second side and having a first container wall, a second container wall, opposing first and second container edges, an end and an opening on the opposite side of the end A first seal defining a tube member;
A second seal provided via the first container wall and the second container wall, wherein the second seal is transverse in a position close to the end across the width of both the first container wall and the second container wall; An empty product storage chamber defined by the first container wall, the second container wall, the second seal and the opening, wherein the first seal is peelable consists sex seal and lap seal, a butt seal or sealing strip, sheet of the heat shrinkable film is a biaxially oriented film having a shrinkage value of at least 20% shrinkage in at least one direction at 90 ° C., moreover An end-sealed packaging container, wherein the sheet of heat-shrinkable film comprises a multilayer film comprising a peelable system configured to peel at an inner layer of the film. The first seal includes a butt seal tape having a first frame portion and a second frame portion, a first heat seal that closely contacts the first frame portion with the first side portion, and the second frame portion as the second frame. The container according to claim 1, comprising a butt seal including a second heat seal closely attached to the side portion. The container of claim 2 wherein the butt seal tape comprises a tensile flap. The container according to claim 2 or 3 , wherein the first frame part is heat-sealed to the inner surface of the first side part, and the second frame part is heat-sealed to the inner surface of the second side part. The container according to any one of claims 2 to 4 , wherein a tensile flap is formed by extending at least one of the first side portion and the second side portion outward. The butt seal tape comprises a butt seal film comprising a strippable system.
The container in any one of 2-5 . The container according to any one of claims 2 to 6 , wherein the first heat seal and the second heat seal are peelable. A first seal comprising a seal strip comprising a strip film having a first edge, a second edge, an inner surface and an outer surface, and the outer surface of the first edge closely contacting the inner surface of the first side The container of Claim 1 containing the 1st heat seal to make and the 2nd heat seal which adheres this inner surface of this strip film to the outer surface of the said 2nd side part. The container of claim 8 , wherein the second heat seal is a peelable seal. The container according to claim 8 or 9 , wherein the first heat seal is a peelable seal. A container according to any one of claims 8 to 10 , wherein the strip film comprises a strippable system. 12. A container according to any one of claims 8 to 11 wherein the strip film comprises a tensile flap. The container according to any one of claims 1 to 12 , wherein the multilayer film comprises a multilayer barrier film. Multi-layer barrier film
(A) inner heat-sealable layer,
(B) a barrier layer;
(C) a core layer,
14. The container of claim 13 , comprising (d) a tie layer, and (e) an outer heat sealable layer. 15. A container according to claim 14 , wherein the outer heat sealable layer forms the outer surface of the container. A container according to claim 14 or 15 tie layer is attached so that it can be peeled off the outer side heat-sealable layer. The container according to any one of claims 14 to 16 , wherein the tie layer comprises a blend of polybutylene and at least one other component. 18. A container according to claim 17 , wherein the at least one other component comprises polyethylene. The container according to any one of claims 14 to 18 , wherein the outer heat-sealable layer is made of polyethylene or ionomer . The container according to any one of claims 14 to 19 , wherein the core layer comprises a blend of polyethylene and an ethylene / vinyl acetate copolymer. The container according to any one of claims 14 to 20 , wherein the barrier layer is selected from the group consisting of a vinylidene chloride copolymer, an ethylene / vinyl alcohol copolymer, polyacrylonitrile, and polyamide. The container according to claim 21 , wherein the barrier layer comprises a vinylidene chloride copolymer. The container according to any one of claims 14 to 22 , wherein the inner heat-sealable layer comprises an ionomer or a blend of polyethylene and ethylene / vinyl acetate copolymer. The tie layer is made of a blend of polybutylene and at least one other component, the outer heat-sealable layer is made of polyethylene or ionomer , the core layer is made of a blend of polyethylene and ethylene / vinyl acetate copolymer, and the barrier layer 24. Container according to any of claims 14 to 23 , characterized in that is made of a vinylidene chloride copolymer and the inner heat-sealable layer is made of an ionomer or a blend of polyethylene and ethylene / vinyl acetate copolymer. . Consists of at least one other component is polyethylene, moreover blocking layer is characterized by comprising a blend of vinylidene chloride with methyl vinylidene chloride-acrylic acid copolymer, vinyl chloride copolymer, according to claim 24 Container. Based on the total thickness of the film, the inner heat-sealable layer occupies 0-50%, the barrier layer occupies 0-20%, the core layer occupies 0-28%, and the tie layer 26. Container according to any of claims 14 to 25 , characterized in that it occupies 15% and the outer heat-sealable layer occupies 0-15%. A container according to any one of claims 1 to 26 Chapter 1 seal having a seal strength of less 2 kg for strips 1 inch (2.54 cm). 28. A container according to any of claims 1 to 27 , wherein the first seal has a seal strength of no more than 1.5 kilograms for a 1 inch (2.54 cm) strip. 27. A container according to any preceding claim, wherein the first seal has a seal strength of greater than 3 kilograms per inch. 30. A container according to any of claims 1 to 26 or 29, wherein the first seal has a seal strength of greater than 6 kilograms per inch (2.54 cm). A container according to any one of claims 1 to 30 and the second seal is a peelable. The container according to any one of claims 1 to 30 , wherein the second seal cannot be peeled off. 1. Sheet of heat shrinkable film 25 mil to 8 . 33. A container according to any one of claims 1 to 32 having a thickness of 0 mil. 1. Sheet of heat shrinkable film 75 mils- 3 . 34. A container according to any one of claims 1 to 33 having a thickness of 0 mil. A container according to any one of claims 1 to 34 wherein the shrinkage value is the vertical direction. The container according to any one of claims 1 to 34, wherein the shrinkage value is a lateral direction. The container according to any one of claims 1 to 34, wherein the shrinkage values are both in the vertical direction and the horizontal direction. The container according to any of claims 14 to 37 , wherein the first seal comprises a lap seal and the inner heat-sealable layer forms the inner surface of the container. The first seal is made of lap seal, yet the first side includes a portion which is not sealed and extending outwardly beyond the first seal, container of any of claims 1-38. 40. A container according to any of claims 1 to 39, wherein the second seal has a seal strength of greater than 3 kilograms per inch (2.54 cm). 41. A container according to any of claims 1 to 40 , wherein the containers are individual containers. The container is a bag, the first container wall and the second container wall are a first bag wall and a second bag wall, and the first container edge and the second container edge are a first bag. The container according to any one of claims 1 to 41 , which is an edge and a second bag edge. 43. A container according to any of claims 1 to 42, wherein the first seal joins the first side to the second side along its entire length and is continuous. Next step:
(A) preparing a sheet of heat shrinkable thermoplastic film having a first side and a second side opposite to the first side;
(B) providing a first seal between the first side and the second side to form a tube member having a first container wall, a second container wall, a bottom, and an opening; ,
(C) providing the first container wall and the second container wall with a second seal extending laterally across the tube member at a location close to the bottom, wherein the first seal is from a peelable seal. It becomes, and lap seal, a butt seal or sealing strip, sheet of the heat shrinkable film is a biaxially oriented film having a shrinkage value to shrink at least 20% in at least one direction at 90 ° C., moreover, heat At least one peelable seal from a flat sheet of film, characterized in that the sheet of shrinkable film consists of a multilayer film with a peelable system configured to peel at an inner layer of the film A method of forming an end-sealed heat-shrinkable packaging container.

45. The method of claim 44 , wherein the sheet of heat shrinkable thermoplastic film is slit to a desired width prior to mating the first side and the second side. The sheet of heat-shrinkable thermoplastic film comprises a continuous roll of film sheet, and (d) the tube member has a cut portion extending laterally across at least the widths of both the first container wall and the second container wall. 46. A method according to claim 44 or 45 , further comprising providing a lateral direction, thereby detaching a portion of the tube member including the second seal from the tube member. The heat-shrinkable thermoplastic film is coextruded with the first film tube, the first film tube is allowed to cool, the first film tube is folded, the first film tube is inflated, and the inflated first Reheat the film tube, biaxially stretch the first film tube, allow the first film tube to cool and fold again, slit the first film tube longitudinally, and the slit first tube 47. A method according to any of claims 44 to 46 , wherein the method is formed by opening a biaxially stretched film flat sheet. The container is a bag, the first container wall and the second container wall are a first bag wall and a second bag wall, and the first container edge and the second container edge are a first bag. 48. A method according to any of claims 44 to 47 , wherein the edge and the second bag edge.

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