JPH0698738B2 - Multilayer film for food packaging - Google Patents

Description

TECHNICAL FIELD The present invention relates to a multilayer film for food packaging.

More specifically, on the heat-sealing surface of the food packaging bag made of this film, the heat-sealing property is good even in the presence of impurities, and the heat-sealing surface has a high heat-sealing strength even when exposed to high temperatures. A multi-layer film for meat packing that can be kept.

[Prior Art] Conventionally, raw meat, processed meat, bone-in meat, fish, butter, cheese, etc. have irregular and non-uniform shapes, and their sizes are large and small, so they are finally adapted to these shapes. A heat-shrinkable packaging bag is widely used industrially for the purpose of reducing the oxygen in the packaging bag, extending the shelf life of food, and reducing the volume required for storage.
In addition, the packaging material constituting the heat-shrinkable packaging bag is required to have an oxygen barrier property in order to prevent the meat from spoiling due to contact with oxygen, and thus a base material having a low oxygen permeability is required. ing.

Furthermore, these base materials usually have poor heat-sealing properties, or even if heat-sealing can be performed, they must be at a relatively high temperature of 130 to 160 ° C., and at such a high temperature, the contents are altered, and The material film is partially distorted, loses commercial value or is partially thinned, heat seal strength is weakened, base material strength itself is weakened, and impact resistance strength is weakened, which is not desirable. Therefore, it is usually used as a multilayer film by providing a heat seal layer separately from these base material layers.

As the resin used for the heat-sealing layer, high-pressure low-density polyethylene, ethylene-vinyl acetate copolymer, ionomer, polypropylene, high-density polyethylene, ethylene-α-olefin copolymer and the like are used. High-pressure method low-density polyethylene has a heat-welding temperature of around 110 ° C and can be boiled with the contents still in it, and is excellent in terms of adhesive strength, stability, etc., but may have a slight odor. Alternatively, a large number of bends may cause pinholes in the bends, and air may flow in from the pinholes, causing the food in the contents to spoil.

The ethylene-vinyl acetate copolymer is excellent in low-temperature sealability, but in the case of high-temperature sterilization, odor increases, flex pinhole resistance, hot tack resistance, heat resistance, and heat seal strength at high temperatures are not sufficient. Absent. Ionomer is excellent in heat sealing strength and hot tack property, but its adhesive strength is slightly inferior, extrusion processability is also inferior, fish eyes and spots easily occur in the film, and when the film is laminated, the film is elastic. , It becomes a hard texture, and when the heavy goods such as chilled meat is vacuum-packed and moved, the hardness of the package is rubbed and pinholes are easily formed, which may cause a vacuum return. Further, the presence of water may cause hydrolysis, so that the water resistance is not sufficient. Furthermore, the eye and the eye adhere to the extrusion die during processing, which makes processing very difficult. Polypropylene has strong heat seal strength,
At the time of T-die processing, it is thermally decomposed and the molecular weight tends to decrease,
There is a processing defect such as a large neck-in, the heat sealing temperature is too high at 150 ° C, which makes it difficult to handle, and the cold resistance is poor, so the range of use is limited. Although high-density polyethylene has excellent heat-sealing strength, it has poor low-temperature heat-sealing properties, and has a large neck-in when T-die processing is performed, resulting in poor processability.

The ethylene-α-olefin copolymer has a heat seal temperature of 80 to 130 ° C, which can be selected in a considerably wide range depending on the grade, and has excellent heat seal strength and impact strength.
The heat-sealing strength at a high temperature required in a meat packaging bag and the heat-sealing strength when a fat content such as lard is present on the sealing surface are not sufficient. That is, the heat sealability of foreign matters is not sufficient. As described above, the materials used as the heat seal layer of the multilayer film for food packaging have advantages and disadvantages, and are not yet satisfactory.

[Problems to be Solved by the Invention] The present inventor has investigated the required performance as a material for a heat-sealing layer of a multilayer film for food packaging, and has found that the following performance is required, and a material satisfying this is found. ,
The present invention has been completed.

Low heat-sealing temperature Strong heat-sealing strength at high temperature Even if fats such as lard generated from meat are contaminated in the heat-sealing part, the heat-sealing strength is strong, odorless, and safe for food hygiene. The performance does not change due to bending No pinholes are generated due to bending Excellent low temperature impact resistance Excellent hot tacking [Means for solving the problem] As a result of earnest research, the present inventors have found that many polymers From among the above, select a polymer that satisfies the performance required as the heat seal layer of the above-mentioned multilayer film for food packaging,
As a result of conducting the experiment, a recently developed ethylene-butene-1-hexene-1 copolymer having a density of 0.910 g / ml or less is
The inventors have found that they have the corresponding performance and completed the present invention. That is, the present invention is that the heat-sealing layer comprising the ethylene-butene-1-hexene-1 copolymer having a density of 0.910 g / ml or less with or without an intermediate layer is laminated on the base material layer. It is a featured multilayer film for food packaging.

In the present invention, the base material layer is a material having a low oxygen permeability so that oxygen in the air mainly permeates into the packaging bag and does not cause rotting of meat, and heat resistance, tensile strength, impact resistance, and low temperature. A base layer composed of a single layer or multiple layers made of a material having excellent characteristics. The materials constituting these layers are polypropylene, polyvinyl chloride, polyvinylidene chloride, polyacrylonitrile, nylon 6, nylon 66, nylon. 7, Nylon 10, Nylon 11, Nylon 12, Nylon 61
0, polyethylene terephthalate, polyethylene terephthalate-isophthalate, polybutylene terephthalate, polyvinyl alcohol, ethylene-vinyl alcohol copolymer, polycarbonate and the like, especially polyamide, polyvinylidene chloride, ethylene-vinyl alcohol copolymer, polyvinyl alcohol, polyester Is preferred, and polyvinylidene chloride is most suitable.

When the base material layer is a multilayer, other resin layers that can be used in combination with the resin layer having low oxygen permeability include high-pressure low-density polyethylene, medium-density polyethylene, ultra-low-density polyethylene, high-density polyethylene, and ethylene. -A vinyl acetate copolymer, an ethylene-acrylic acid ester copolymer, an ionomer, polybutene-1, poly-4-methyl-pentene-1, etc. can be selected and used. Also,
If desired, paper, cellophane, metal foil, etc. may be added as a single-component layer.

In the present invention, the intermediate layer is a layer provided between the base material layer and the heat seal layer, and is provided mainly for promoting the adhesion between the base material layer and the heat seal layer. It is necessary to provide it if the adhesiveness is sufficient. There is no. As the intermediate layer, an adhesive resin such as an ethylene-acrylic acid ester copolymer, an ethylene-vinyl acetate copolymer, an ionomer, a low crystalline ethylene-α-olefin copolymer, a conjugated diene-aromatic vinyl copolymer , High-pressure method low-density polyethylene, medium-density polyethylene, linear ethylene-α-olefin copolymers, acid-modified products thereof or glycidyl- (meth) acryl-modified products, N-substituted maleimide-modified products and the like. It is a thing.

An ethylene-butene-1-hexene-1 copolymer having a density of 0.910 g / ml or less used in the present invention is a known method, that is, a transition metal compound (a compound such as titanium and vanadium) as a main catalyst, a cocatalyst. As ethylene metal, butene-1 and hexene-1 in the presence of a Ziegler catalyst composed of an organometallic compound (eg, organoaluminum), a carrier (eg, oxides of silicon, titanium, magnesium, etc.), a chromium-based catalyst, etc. It is obtained by polymerizing under pressure or low pressure.

The polymerization is carried out by various methods such as slurry polymerization, gas phase polymerization, high temperature solution polymerization and the like. A particularly preferable method is to use a linear ethylene-butene-1-hexene-1 copolymer in a fluidized bed reaction zone at a temperature of 10 ° to 80 ° C and a pressure of 7,000 KPa or less, (a) 0.35: 1 to 8.0 1 (total mole of butene-1 and hexene-1, provided that the molar ratio of butene-1 and hexene-1 is 0.
Ethylene, butene-1 in a molar ratio of 5: 1 to 2: 1) to ethylene.
And hexene-1 (b) a gas mixture containing at least 25 mol% of at least one diluent gas is represented by the formula: MgmTi (OR) nXp [ED] q [wherein R represents 1 to 14 carbon atoms. Is an aliphatic or aromatic hydrocarbon group having or COR ', wherein R'is an aliphatic or aromatic hydrocarbon group having 1 to 14 carbon atoms, X is Cl, Br, I and ED is an organic electron donor compound selected from the group consisting of alkyl esters of aliphatic or aromatic acids, aliphatic ethers, cyclic ethers and aliphatic ketones, and m is 0.5 to 56, n is 0.1 or 2, p is 2 to 116, and q is 2 to 85], and the precursor is continuously contacted with particles of a catalyst system, and the precursor is The composition is diluted with an inert carrier material and has the formula: Al (R ) DX'eHf [wherein, X 'is' a, R Cl or OR' and R "1
A saturated hydrocarbon group having 14 to 14 carbon atoms, e is 0 to 1.5, f is 0 or 1, and d + e + f = 3].
A method for continuous production of ethylene copolymers, characterized in that the activating compound is used in an amount such that the molar ratio of total aluminum to titanium in the reaction zone is 10: 1 to 400: 1. However, it can be manufactured by the method described in detail in JP-A-59-230011.

In the present invention, the thickness of the multilayer film is 20 to 100 µ, and 40 to 80 µ is preferable.

The thickness of the heat seal layer is required to be at least 5 μ. If it is less than 5 μm, the low temperature sealability is insufficient, and even if heat seal can be performed at low temperature, the adhesive strength is weak, and the heat seal immediately undergoes heat seal due to weak stress and impact. The surface peels off, which is not desirable.

In the present invention, the food is raw meat, processed meat, bone-in meat, fresh fish, fish fillet, shellfish, butter, cheese, vegetables, fruits, peanuts, tea, coffee, cocoa, ramen, potato chips, mushrooms, whip , Rakkyo, Umeboshi,
It means buckwheat, udon, konjac, tofu, jelly, popsicles, fruit juice, sugar and the like.

The multilayer film of the present invention is obtained by co-extruding the resin forming the base layer and the resin forming the heat-sealing layer, or by forming one resin in advance as a film and extruding another resin on the film, laminating and laminating it. It is made by stacking. When heat shrinkability is required, the multilayer film is heated to a temperature at which it can be stretched and stretched at least 1.5 times in both the longitudinal and transverse directions.

The stretching method may be either a tenter method or an inflation method, but the inflation method is preferable because it is easy for the inflation method to have the same heat shrinkability in the machine direction and the transverse direction.

The resin constituting the multilayer film of the present invention includes a heat stabilizer, an antioxidant, a colorant, a pigment, carbon black, a lubricant, a processability improving agent, an anti-eye agent, a slip agent, an antiblocking agent, an antifogging agent, Antistatic agents, nucleating agents and the like may be added depending on the purpose and application. Examples will be shown below, but improved examples utilizing the technical idea of the present invention are within the scope of the present invention.

[Examples] Example I As a resin for the base layer, a composition comprising 100 parts of vinylidene chloride-vinyl chloride copolymer (80% by weight of vinylidene chloride and 20% by weight of vinyl chloride) and 1 part of epoxidized soybean oil was prepared. Then, an ethylene-ethyl acrylate copolymer (80% by weight of ethylene, 20% by weight of ethyl acrylate) was prepared as a resin for the intermediate layer, and an ethylene-butene-1-hexene-1 copolymer (ethylene 70% by weight, butene-1 10% by weight, hexene-1 20% by weight)
Prepared.

An inflation film was produced by air cooling using these resins under the following apparatus and processing conditions.

(1) Extruder: Inflation film processing equipment manufactured by Placo Co., Ltd. Diameter 40 mm x 3 units L / D 28 (2) Annular three-layer die: φ150 mm Die gap: 1.0 mm (3) Cooling device: Single lip straight and conical color Appended (4) Discharge rate: 45 kg / hr (5) Die temperature: 180 ° C (6) Blow ratio: 2.5 Produced laminated film Base layer Thickness 10μ Intermediate layer Thickness 10μ Heat seal layer Thickness 10μ Heat shrinkable packaging bag Manufacturing method The laminated film was stretched 3 times in the longitudinal direction and 3 times in the transverse direction.

Evaluation of laminated film Tear strength of film: Tear strength in the longitudinal direction is 80 kg, and in the transverse direction is 230 kg, which is practical.

Haze: Measured according to JIS K-6714, the numerical value is 2.5, and it has sufficient practicality.

Puncture resistance: The crab legs were bundled and placed in a heat-shrinkable packaging bag (length 20 cm, width 15 cm) made of a laminated film and vacuum packed, but the film was not broken by the crab legs.

Low-frequency embrittlement: 1 kg of beef is placed in a heat-shrinkable packaging bag (length 20 cm, width 15 cm) made of laminated film, vacuum packed,
It was put in a refrigerator at -50 ° C for 30 minutes, taken out, and dropped from a height of 1 m, but it was not broken.

Foreign matter heat-sealing property: After heat-sealing by attaching lard to the heat-sealing surface of the laminated film, the heat-sealing strength was measured.

23 ℃: 2800g / 15mm 80 ℃: 2300g / 15mm 90 ℃: 2200g / 15mm The above values indicate that there is sufficient practicality, and particularly good results even at a high temperature of 90 ℃.

Pinhole resistance: Approximately 7 kg of chilled beef is placed in two cardboard cases that are vacuum-packaged, the package is dropped horizontally from a height of 60 cm three times, and then the bag's pinhole The presence / absence was confirmed, and the number of bags with pinholes in 50 bags was examined. 0, and the pinhole resistance is good.

Hot tacking property: Using the above-mentioned laminated film, using a vertical pillow type automatic bag making and filling machine (Kawashima Kikai Co., Ltd.), the size of one bag after bag making is 14 cm x 20 cm, bag making speed 90 bags / min. When 200 g of the sugar content was filled under the conditions, no peeling was observed in the heat-sealed part of any bag.

Heat-sealing strength at high temperature: The heat-sealing strength of the heat-sealed portion at 90 ° C was measured and found to be 3100 g / 15 mm, so there is sufficient practicality.

[Advantageous effects of the present invention] In the present invention, the specific ethylene-butene-1-hexene-1 copolymer is used as the material for the heat-sealing layer, so the multilayer film for food packaging made of this causes food to rot. Suppresses the permeation of enzymes, has excellent tear strength and impact strength, has good heat-sealability even if contaminants are present on the heat-seal surface, and maintains strong heat-seal strength even when the heat-seal surface is exposed to high temperatures. It is possible to solve the problems that cannot be solved by conventional packaging bags, and is particularly useful as a packaging bag for raw meat and fresh fish.

Claims (5)

[Claims] 1. An ethylene-butene-1-hexene-having a density of 0.910 g / ml or less with or without an intermediate layer in a base material layer.
1. A multilayer film for food packaging having a total thickness of 20 to 100 μm, characterized in that a heat-sealing layer made of 1 copolymer is laminated. 2. The layer constituting the substrate layer is composed of a single layer or multiple layers selected from polypropylene, polyvinyl chloride, polyvinylidene chloride, polyamide, polyester, polyvinyl alcohol and ethylene / vinyl alcohol copolymer. The multilayer film for food packaging according to claim 1. 3. The intermediate layer comprises a polymer layer selected from ethylene-acrylic acid ester copolymers, ethylene-vinyl acetate copolymers, ionomers, and low crystalline ethylene-α-olefin copolymers. Claim 1
The multilayer film for food packaging described. 4. Linear ethylene-butene-1-hexene-
1 copolymer was produced by a gas-phase low-pressure method using a catalyst, so-called Ziegler catalyst, which is produced by a combination of a transition metal compound of Group IV to VIII and an organic metal of Group I to III in the periodic table. The multilayer film for food packaging according to claim 1, which is a product. 5. Linear ethylene-butene-1-hexene-
1 copolymer at a temperature of 10 ° to 80 ° in the fluidized bed reaction zone and
At a pressure of 7,000 KPa or less, (a) 0.35: 1 to 8.0: 1 (the total moles of butene-1 and hexene-1, but the molar ratio of butene-1 and hexene-1 is 0.5: 1 to 2: 1). ) To ethylene in a molar ratio of ethylene, butene-1 and hexene-1 and (b) at least 25 mol% of at least one diluent gas, a gas mixture having the formula: MgmTi (OR) nXp [ED] q [ Wherein R is an aliphatic or aromatic hydrocarbon group having 1 to 14 carbon atoms or COR ', where R'is an aliphatic or aromatic hydrocarbon group having 1 to 14 carbon atoms. A hydrogen group, X is selected from the group consisting of Cl, Br, I and mixtures thereof, ED is selected from the group consisting of alkyl esters of aliphatic or aromatic acids, aliphatic ethers, cyclic ethers and aliphatic ketones. Is an organic electron-donating compound, m is 0.5 to 56, and n is 0.1 or 2. Wherein p is 2-116 and q is 2-85] and the precursor composition is diluted with an inert carrier material in continuous contact with particles of a catalyst system comprising the precursor composition. With the formula: Al (R ′) dX′eHf [where X ′ is Cl or OR ″, R ′ and R ″ are saturated hydrocarbon groups having 1 to 14 carbon atoms, and e is 0 ˜1.5, f is 0 or 1, and d + e + f = 3]],
A method for continuous production of ethylene copolymers, characterized in that the activating compound is used in an amount such that the molar ratio of total aluminum to titanium in the reaction zone is 10: 1 to 400: 1. The multilayer film for food packaging according to claim 1, which is a product.