JP4110461B2 - Heat-shrinkable polyester resin film and label using the same - Google Patents

Description

【００３０】
【発明の効果】
本発明の熱収縮性ラベル及びこれをなすフィルムは実用上充分な熱収縮率を有し、熱収縮させ、被覆用途または結束用途に用いたとき、収縮工程での温度のゆらぎや不均一にかかわりなく均等な収縮結果を与え、カット性に優れるため、特に胴ラベルのような軽収縮ラベル分野において被装着物とラベルの分離が容易であり、そのリサイクル適性が発揮される。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a polyester film suitable as a packaging material used for coating, binding, exterior, and the like. Particularly suitable for container body labeling because it has excellent shrinkage with excellent heat resistance, has a beautifully finished appearance, and has excellent tearability and perforation cutability during light shrinkage. Used for
[0002]
[Prior art]
Since heat-shrinkable film has a function of shrinkability, it does not use fixing means such as adhesives and fasteners for the object to be applied, and it is laminated and integrated with the object by the shrinkage force and shapeability generated from the film. I can do it. For example, a design that takes advantage of the shape of the bottle can be applied by processing the film into a tube shape, covering the bottle, and allowing the film to pass through a heat-shrinkable tunnel for shrinkage and adhesion. Therefore, it has not only mechanical protection of the object by laminating or coating, but also functions such as binding and sealing. Further, when the shrink film itself has a special function, the special function can be freely added to the target object after the lamination by laminating. This property is effectively used in the packaging field where the main purposes are content preservation, protection and display during distribution, and design.
For example, various types of containers such as bottles (including glass and plastic bottles) and cans, and long objects (pipes, rods, wood, various rods, etc.) or sheet-like bodies for covering, binding, exterior Or used for sealing. Specifically, it is used for applications that cover part or all of the cap part, shoulder part, and body part of the bottle for the purpose of improving the commercial value by displaying, protecting, binding, and functionalizing.
Furthermore, it is also used for applications such as stacking and packaging a plurality of boxes, bottles, plates, sticks, notebooks, etc., and packaging (skin package) with a film in close contact with an object to be packaged. At this time, when the film is preliminarily displayed and shaped for the purpose of design, the product is a shrinkable label.
[0003]
As the material for the film, polyvinyl chloride, atactic polystyrene, polyester, polyamide, aliphatic polyolefin, derivatives thereof, hydrochloric acid rubber, and the like are used. Usually, these films are formed into a tube shape and, for example, covered with bottles or pipes are collected, and then packaged or bound by heat shrinking. As a result of using materials with various properties in this way, there is a common or unique advantage for each material. If you enumerate,
All of the above conventional films have poor heat resistance and cannot withstand high temperature boil processing and retort processing. Therefore, when applied to foods, sanitary goods, and pharmaceutical applications, there is a disadvantage that high temperature sterilization processing cannot be performed. . For example, when a retort process is performed, the conventional film is easily damaged during the process.
[0004]
When referring to the polyvinyl chloride film, this film has very good heat shrinkage properties, but it has poor adhesion to ink during printing, and it is easy to form a gel-like additive that is characteristic of the resin. , Pinholes are likely to occur on the printing surface of the film. Furthermore, there is a problem of environmental pollution when discarded and incinerated.
[0005]
Polystyrene film has a low density and is advantageous for separation in the recycling process, but has poor heat resistance. In addition, since it shrinks with time after manufacturing, a change in printing pitch due to shrinkage occurs, and high-precision printing cannot be performed. Further, it was partially dissolved or swollen in the solvent contained in the printing ink, and good printing was difficult.
[0006]
The polyester film is excellent in heat resistance, dimensional stability, solvent resistance, and the like. However, in order to achieve desirable shrinkage characteristics, adhesion, etc., precise manufacturing condition control technology is required. In addition, it is said that general heat-shrinkable polyester film is inferior to tear openability at the time of distribution and perforation cut necessary for label peeling process in recycling process after being heat-shrinked as a packaging bag or label. Depending on the situation, not only the cutting direction but also the tearing may occur in the orthogonal direction.
[0007]
[Problems to be solved by the invention]
The present invention solves the problems of conventional heat-shrinkable polyester films and labels, and the object of the present invention is that the heat shrinkage rate is sufficiently large and the film has uneven shrinkage when heat-shrinked. It does not occur, has a beautiful appearance, stably maintains its appearance even under high temperature conditions as experienced later, and after heat-shrinking as a packaging bag or label, tear and openability during distribution and use, An object of the present invention is to provide a heat-shrinkable polyester film and a label excellent in perforation cutability necessary for a label peeling process in a recycling process.
[0008]
[Means for Solving the Problems]
The above object can be achieved by the invention described in the claims. That is, the heat-shrinkable polyester resin film according to the present invention contains 2 to 20% by weight of either a polyamide resin or an ethylene-ethyl acrylate copolymer resin, and is uniaxially stretched, so that the maximum heat shrinkage rate is at least. It is 20% or more in one direction, has a haze value of 50% or more and less than 80%, and has a cutting property.
( Cutability here refers to tearing a perforation with a 4.72 mm gap between the films in a straight line in the direction perpendicular to the stretching direction, and using a projector (10x objective). Meaning that the value is 1 mm or less when the maximum width in the direction perpendicular to the tearing direction of the brightened portion in the field scale range is measured between the polarizing plates made of crossed Nicols so that it becomes a dark field. )
In the case of this, it is preferable that the polyamide resin is an aromatic polyamide resin.
Furthermore, in this case, a heat-shrinkable polyester-based label is suitable for the use of the heat-shrinkable polyester-based resin film.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
The film material used in the present invention is a polyester resin composition. As the polyester-based resin, a known (copolymerized) polyester obtained by polycondensation with a polyhydric alcohol component using one or more of aromatic dicarboxylic acids, their ester-forming derivatives, and aliphatic dicarboxylic acids as dicarboxylic acid components. Can be used. Examples of the aromatic dicarboxylic acid include terephthalic acid, isophthalic acid, naphthalene-1,4- or -2,6-dicarboxylic acid, and 5-sodium sulfoisophthalic acid. Examples of these ester derivatives include derivatives such as dialkyl esters and diaryl esters. Examples of the aliphatic dicarboxylic acid include dimer acid, glutaric acid, adipic acid, sebacic acid, azelaic acid, oxalic acid, and succinic acid. Further, an oxycarboxylic acid such as p-oxybenzoic acid, and a polyvalent carboxylic acid such as trimellitic anhydride and pyromellitic anhydride may be used in combination as necessary.
[0010]
Examples of the polyhydric alcohol component include ethylene glycol, diethylene glycol, dimer diol, propylene glycol, triethylene glycol, 1,4-butanediol, neopentyl glycol, 1,4-cyclohexanedimethanol, 1,6-hexanediol, 3- Alkylene glycols such as methyl 1,5-pentanediol, 2-methyl-1,5-pentanediol, 2,2-diethyl-1,3-propanediol, 1,9-nonanediol, 1,10-decanediol, Examples include alkylene oxide adducts of bisphenol compounds or derivatives thereof, trimethylolpropane, glycerin, pentaerythritol, polyoxytetramethylene glycol, polyethylene glycol and the like. Moreover, although it is not a polyhydric alcohol, (epsilon) -caprolactone can also be used.
[0011]
The polyester raw material which comprises a polyester-type heat-shrinkable film may be individual, and may mix and use 2 or more types. When used alone, homopolyesters other than polyethylene terephthalate such as polybutylene terephthalate, polycyclohexylene dimethyl terephthalate, and polyethylene naphthalate are preferable. This is because polyethylene terephthalate alone does not exhibit heat shrinkability.
[0012]
From the viewpoint of adjusting the heat shrinkage characteristics, specifically adjusting the heat shrink temperature range, adjusting the shrinkage speed and the shrinkage stress, it is preferable to use a blend of two or more polyesters having different Tg. In particular, it is preferable to use a mixture of polyethylene terephthalate and a copolyester (may be two or more types), but a combination of copolyesters may also be used. Moreover, polybutylene terephthalate, polycyclohexylene dimethyl terephthalate, and polyethylene naphthalate can be combined, or these can be used in combination with other copolyesters.
The most preferable heat shrinkage property is suitable for adjustment of crystallinity, glass transition point, etc., and is a copolymer composed of terephthalic acid and polyethylene terephthalate, polybutylene terephthalate, a mixed diol component of ethylene glycol and neopentyl glycol, and the like. Three types of blends with polyester.
[0013]
Polyesters can be produced by melt polymerization in the usual way, but the so-called direct polymerization method in which oligomers obtained by direct reaction of dicarboxylic acids and glycols are polycondensed, dimethyl ester of dicarboxylic acid and glycol are transesterified. Examples include a so-called transesterification method in which polycondensation is performed after the reaction, and any production method can be applied. Moreover, the polyester obtained by another polymerization method may be sufficient.
The degree of polymerization of the polyester is preferably an intrinsic viscosity of 0.3 to 1.3 dl / g from the viewpoint of mechanical properties and moldability.
[0014]
In addition to polymerization catalysts such as antimony oxide, germanium oxide, and titanium compounds, polyesters such as Mg salt, Ca salt, Mn salt, Zn salt, Co salt, etc. are used to prevent problems such as coloring and gel generation. Metal salts may be added. Moreover, you may add phosphorus compounds, such as a phosphate ester derivative.
Further, if necessary, fine particles such as silica, titanium dioxide, kaolin, calcium carbonate may be added, and an antioxidant, an ultraviolet absorber, an antistatic agent, a colorant, an antibacterial agent, etc. may be added. it can.
[0015]
The heat-shrinkable polyester resin film and label in the present invention have a cut property.
The cutability here means that when tearing with a notch, it can be cut stably in the direction that you would most likely manually, and when you cut the perforation straight and tear it manually along the eyes Shows the property of being able to cut stably.
Examples of a method for imparting cutability to the heat-shrinkable polyester resin film and the label in the present invention include blending a cutability improving material with the raw material resin. As the cutting property improving material, polyamide resin, particularly MXD6, which is an aromatic ring-containing polyamide, and an ethylene-ethyl acrylate copolymer are suitable. A preferable addition amount is 2 to 20% by weight. By adding such a cutting property improving agent, a complete or quasi-complete phase separation structure is generated, and it is considered that the cutting property is expressed by concentration of stress at the time of cutting.
[0016]
The heat-shrinkable polyester resin film and label in the present invention must have a haze value of 50% or more and less than 80%. As a result, a semi-transparent texture can be obtained, and an optimum value can be adjusted in consideration of the cut property depending on the application. Specifically, for example, the addition of inorganic particles and organic particles can be performed in addition to the amount of the cutting property improving material.
[0017]
The polyester-based composition is formed into a film by a known method (for example, an extrusion method or a calendar method). The shape of the film is, for example, a flat shape or a tube shape, and is not particularly limited. A normal method is adopted as the stretching method. Examples thereof include a roll stretching method, a long gap stretching method, a tenter stretching method, and a tubular stretching method. In any of these methods, stretching is performed by sequential biaxial stretching, simultaneous biaxial stretching, uniaxial stretching, and combinations thereof. In the biaxial stretching, stretching in the vertical and horizontal directions may be performed at the same time, but sequential biaxial stretching in which one of the two is performed first is effective, and either of the longitudinal and horizontal orders may be first.
[0018]
The draw ratio is arbitrarily set in the range of 1.0 to 6.0 times, and the magnification in one predetermined direction and the magnification in the direction orthogonal to the direction may be the same or different. In the stretching step, preheating is preferably performed at a temperature not lower than the glass transition temperature of the polymer constituting the film, for example, not higher than Tg + 50 ° C. In the heat setting after stretching, for example, it is recommended to pass a heating zone of 30 ° C. to 150 ° C. for about 1 second to 30 seconds after stretching. Further, after the film is stretched and before or after heat setting, the relaxation treatment may be performed at a predetermined degree. Further, after the stretching, a step of cooling while applying a stress to the film while keeping the stretched or tensioned state, or a cooling step after releasing the tensioned state following the treatment may be added. The thickness of the film obtained is preferably in the range of 10-100 μm.
[0019]
The heat-shrinkable polyester resin film and label in the present invention must have a maximum heat shrinkage of at least 20% in one direction. This performance can be used for general barrel labels. If it is 50% or more, it can be attached to a general PET bottle. Furthermore, if it is 60% or more, even a container having a complicated shape can be mounted. If it is 70% or more, it is suitable as a full label for a container having a complicated shape.
[0020]
Examples of methods for improving the maximum heat shrinkage include increasing the draw ratio, reducing heat setting, and adjusting the compatibility state of the mixed resin.
[0021]
[Action]
The heat-shrinkable film and label thus obtained are finished with a beautiful appearance as compared with the case of using the conventionally proposed heat-shrinkable film. A tear-opening property that can be stably cut in the direction you want when you put it and tear it. In addition, when a label with a perforation is manually peeled off as part of the recycling process, it follows the perforation. It is suitable for strict fractional recycling because it has the perforation cutability that can be cut stably and stably.
[0022]
【Example】
EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited only to these examples.
The evaluation method of a film is shown below.
[0023]
1) Maximum heat shrinkage rate The film is cut out so that the length of the film is shrunk and the width is 15 mm. Marks are marked at intervals of 200 mm in the long side direction. This sample is suspended in a gear oven, heated by applying 100 ° C. hot air for 1 minute, and the amount of change in the distance between the marked lines is measured. The percentage of this change in the original length is defined as the heat shrinkage rate (%), and the temperature is increased by 5 ° C., and the measurement is performed up to 150 ° C. The maximum value of the heat shrinkage rate of these samples is adopted.
[0024]
2) Perforation cut ability (Ripple distance)
A line of perforations with an eye spacing of 4.72 mm is placed in a straight line on the film (created with every other piece of roulette teeth marked with CLOVER) and teared manually. Using a projector (Nikon's PROFILE PROJECTOR, V-12, objective lens magnification 10x) with transmitted light, the film was placed between the polarizing plates made of crossed Nicols so that it became a dark field, and it became bright within the visual field scale range. Measure the maximum width in the direction perpendicular to the tear direction of the part. A value of 1 mm or less was accepted.
[0025]
3) Use a tearable scissors to make a 5mm incision, determine the direction, and tear manually.
O: Can be stably cut in the desired direction Δ: Unable to determine the cutting direction ×: Unintentional cutting 4) Measured according to haze JIS K-7105.
4) Intrinsic viscosity Using a Ubbelohde-type viscosity tube, the sample was dissolved in a mixed solvent of phenol / tetrachloroethane in a weight ratio of 6/4 at a solution concentration of 0.4 g / dl, and the reduced viscosity was determined from the value measured at a temperature of 30 ° C. Was converted into an intrinsic viscosity.
[0026]
(Example 1)
PET resin (PEs-A: Intrinsic viscosity 0.75) and neopentyl glycol 30 mol% copolymerized PET resin (PEs-B: Intrinsic viscosity 0.725), PBT resin (PEs-C: NV5020 / Mitsubishi Rayon) 2) MXD6 (Toyobo's T-600) as a cutting property improving material was mixed in a 37:53:10 weight ratio, respectively, and a 30 mmφ twin screw extruder. Was melted at 275 ° C., extruded onto a cooling roll from a die, and adhered and cooled and solidified by an electrostatic application method to obtain an amorphous sheet having a thickness of about 160 μm.
The amorphous sheet was first preheated to 84 ° C. using a stenter-type lateral uniaxial stretching machine, and stretched in the transverse direction at a stretching temperature of 76 ° C. at a magnification of 4.0. Thereafter, a heat setting treatment was performed at 79 ° C. for 10 seconds, followed by rapid cooling to room temperature. The obtained film was used as a heat shrink label. The maximum heat shrinkage, haze, and MD direction tearability of this product were measured. The results are shown in Table 1.
[0027]
(Example 2)
In the same manner as in Example 1 except that ethylene-ethyl acrylate copolymer resin (EVAFLEX-EEA-A-701, manufactured by Mitsui / DuPont Chemical) was used instead of the cutting property improving material used in Example 1, A label was obtained and measured.
(Example 3)
In the same manner as in Example 1 except that ethylene-ethyl acrylate copolymer resin (EVAFLEX-EEA-A-709, manufactured by Mitsui / DuPont Chemical) was used instead of the cuttability improving material used in Example 1, A label was obtained and measured.
[0028]
(Comparative Example 1)
In Example 1, a film and a label were obtained and measured by the same method as in Example 1 except that the cut property improving material was not used.
(Comparative Example 2)
A film and a label were obtained and measured in the same manner as in Example 1 except that polymethyl methacrylate resin (PMMA) was used instead of the cutting property improving material used in Example 1.
[0029]
[Table 1]

[0030]
【The invention's effect】
The heat-shrinkable label of the present invention and the film forming the same have a heat shrinkage rate sufficient for practical use, and are related to temperature fluctuations and non-uniformity in the shrinking process when heat-shrinked and used for coating or binding. In particular, in the field of light shrinkage labels such as body labels, it is easy to separate the article to be attached and the label, and the recyclability is exhibited.

Claims (3)

It contains 2-20% by weight of either polyamide resin or ethylene-ethyl acrylate copolymer resin, is uniaxially stretched, has a maximum heat shrinkage of at least 20% in one direction, and a haze value of 50% A heat-shrinkable polyester resin film characterized by having a cutting property of less than 80%.
( Cutability here refers to tearing a perforation with a 4.72 mm gap between the films in a straight line in the direction perpendicular to the stretching direction, and using a projector (10x objective). Meaning that the value is 1 mm or less when the maximum width in the direction perpendicular to the tearing direction of the brightened portion in the field scale range is measured between the polarizing plates made of crossed Nicols so that it becomes a dark field. ) The heat-shrinkable polyester resin film, wherein the polyamide resin according to claim 1 is an aromatic polyamide resin. Heat-shrinkable polyester label characterized by using a heat-shrinkable polyester resin film according to claim 1 or 2 wherein.