JP2002278460A - White film for heat shrinkable label and heat shrinkable label using the same as well as container - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a film for manufacturing a label which is thermally shrunk and attached to a container, such as a plastic bottle or glass bottle, has light blocking effect, is hardly elongatable, has hardness (stiffness) and has high tear strength as well, and a label formed with the same film and the container which is thermally shrunk and fitted with this label. SOLUTION: This white film for the heat shrinkable label includes a white thermoplastic resin layer containing white particulates. The thermal shrinkage rate in the main shrinking direction when the film is immersed in hot water of 80 deg.C for 10 seconds is <=15% and the average value of the total ray transmittance at a wavelength 400 to 700 nm when the film is shrunk 5% in the main shrinking direction is <=50%. In addition, the white film for the heat shrinkable label does not substantially include voids. This label is manufactured from the white film. Further, the container thermally shrunk and fitted with this label is provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a film for producing a heat-shrinkable label to be heat-shrink mounted on a container, a heat-shrinkable label produced from the film, and a container to which the label is heat-shrink-mounted. And, more specifically, a white film for producing a heat-shrinkable label for shielding a visible light, preventing deterioration and discoloration of a beverage or the like filled in a container, produced from the white film. The present invention relates to a heat-shrinkable label and a container to which the label is heat-shrinked.

[0002]

2. Description of the Related Art Generally, liquid products such as beverages are sold after being filled in plastic bottles such as paper boxes, metal cans, and PET bottles or glass bottles. However, a paper box or a metal can is inconvenient because, for example, it cannot be completely drunk once when the content is 500 ml or more, and when it is desired to reseal the cup, there is no reseal means. On the other hand, plastic bottles and glass bottles have resealing means called caps, so that they are convenient as containers for liquid products such as beverages having a large content. However, plastic bottles and glass bottles lack light-shielding properties like paper boxes and metal cans.For example, sake, beer, green tea, etc. Although used plastic bottles and glass bottles are used, these colored containers often cause problems during recycling.

[0003] Therefore, these problems can be solved all at once by using a heat-shrinkable label (hereinafter simply referred to as a label) almost completely over a colorless and transparent plastic bottle or glass bottle. it can. Labels having light shielding properties include those disclosed in JP-A-63-193822 and JP-A-5-111960. JP-A-63-193822 discloses that an unstretched film made of a mixture of a polyester-based resin and a polyolefin-based resin lacking in compatibility is obtained by stretching, or is extruded and stretched into a film by an inflation method. Thus, a label having a cavity therein and excellent in concealment degree obtained thereby is disclosed. Also, Japanese Patent Application Laid-Open No.
In 1960, there is disclosed a label having a cavity therein and excellent in cushioning property obtained by stretching an unstretched film made of a mixture of a polyester resin and a polystyrene resin lacking in compatibility.

[0004]

However, since these are labels (films) having a cavity inside, they are easy to stretch, lack hardness (waist), have low tear strength, and have the following problems. is there. That is, since the film is easily stretched, a pitch shift easily occurs during printing, and it is difficult to perform elaborate printing such as halftone printing. Due to insufficient hardness (waist), mounting errors are likely to occur when mounting the container on an automatic machine. Generally, the outer end of a film wound into a cylindrical shape by center sealing is likely to have fine cracks when passing through a guide roll in the next process. At the time of shrink mounting, the label is easily broken due to shrinkage stress.

It is an object of the present invention to provide a label which is heat shrunk to a container such as a plastic bottle or a glass bottle, has a light-shielding property, is hardly stretched, has hardness (waist), and has a high tear strength. An object of the present invention is to provide a film for producing a label. Another object of the present invention is to provide a label made from the film, and further to provide a container to which the label is attached by heat shrinkage.

[0006]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a white film for a heat-shrinkable label, comprising a white thermoplastic resin layer containing white fine particles, wherein the white film has a temperature of 80.degree.
The average thermal shrinkage in the main shrinkage direction when immersed in warm water for 10 seconds is 15% or more, and the average value of the total light transmittance at a wavelength of 400 to 700 nm when shrunk 5% in the main shrinkage direction is 50% or less. And a white film for a heat-shrinkable label substantially free of voids. Further, the present invention is characterized in that the label is a label made from the white film, and that the label is a container fitted with heat shrink.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The white fine particles of the present invention are not particularly limited. For example, titanium dioxide, calcium carbonate, magnesium carbonate, talc, kaolin, barium sulfate, zinc oxide, aluminum oxide, magnesium oxide, silica, etc. Or a mixture thereof. Among them, titanium dioxide, particularly rutile-type titanium dioxide, is preferable in terms of tinting strength (whiteness), weather resistance, heat resistance, sharpness, and the like.

The diameter (or major axis) of the white fine particles is preferably less than 5.0 μm, more preferably less than 1.0 μm, and still more preferably less than 0.5 μm. If the diameter (or long diameter) is 5.0 μm or more, cavities tend to be easily formed around the white fine particles even if surface treatment is performed on the white fine particles, for example, in order to make the particles easily compatible with the thermoplastic resin. The content of the white fine particles in the thermoplastic resin layer cannot be specified unconditionally because it depends on its light-shielding ability and the thickness of the thermoplastic resin layer, but the wavelength when the film is shrunk by 5% in the main shrinkage direction is 400 to 400 μm. It may be appropriately determined by preliminary experiments so that the average value of the total light transmittance at 700 nm is 50% or less.

The thermoplastic resin constituting the white thermoplastic resin layer containing the white fine particles of the present invention is not particularly limited. For example, polystyrene resin, polyester resin, polypropylene resin, high density or medium density Examples thereof include a polyethylene resin, a cyclic olefin resin, and a polyvinyl chloride resin. Among these, a polystyrene resin, a polyester resin, a polypropylene resin, and a cyclic olefin resin are more preferable. The method for incorporating the white fine particles into the thermoplastic resin is not particularly limited, and any known method may be used. As a preferred method, thermoplastic resin and white fine particles,
If necessary, dry blend with a dispersant, antioxidant, etc. using a drum tumbler or Henschel mixer, etc.
Examples of the method include melt-kneading using a twin-screw kneading extruder, extruding the blend from a strand die into a strand, and cutting the pellet in the air or in water to form a pellet.
The pellets may be a master batch containing a high concentration of white fine particles. If the moisture content of the white fine particles is high, fine foaming may occur during extrusion. In this case, it is desirable to perform vacuum degassing in a twin-screw kneading extruder. In order to adjust the color tone, the color tone may be adjusted with a bluing agent or the like during dry blending.

The film of the present invention may be composed of only a white thermoplastic resin layer. However, a substantially transparent resin composed of a thermoplastic resin of the same type or different from the intermediate layer of the white thermoplastic resin layer is used as an intermediate layer. At least 3 layers with front and back layers
Layered films are more preferred. By providing the substantially transparent resin layer as the front and back layers, the glossiness of the surface is increased, so that the printed surface printed thereon is more beautiful. Also,
Stable processing can be performed during center seal processing.
Further, the absence of the front and back layers tends to cause the loss of the white fine particles, but the provision of the front and back layers has the advantage that the white particles can be prevented from being lost.

In a more preferred form of the film of the present invention, the intermediate layer is mainly composed of an impact-resistant polystyrene resin containing white fine particles and / or a graft-type impact-resistant polystyrene resin, and the front and back layers are made of a styrene-conjugated diene block. A film having at least three layers composed mainly of a copolymer can be used.

The impact-resistant polystyrene resin constituting the intermediate layer is a mixture of polystyrene and a synthetic rubber such as polybutadiene or polyisoprene, or polybutadiene,
It is obtained by graft-polymerizing a styrene monomer onto a synthetic rubber such as polyisoprene. The graft-type impact-resistant polystyrene has a structure in which particles of a rubber-like polymer in which polystyrene is included in a continuous phase of polystyrene and polystyrene is grafted to a rubber component such as polybutadiene are dispersed. Means what you do.

The intermediate layer may further comprise 2 to 50 parts by weight of a styrene-conjugated diene block elastomer and / or styrene-conjugated diene block per 100 parts by weight of the impact-resistant polystyrene resin and / or the graft-type impact-resistant polystyrene resin. More preferably, the layer contains 5 to 60 parts by weight of the copolymer. Styrene-conjugated diene block elastomer is a styrene block and butadiene,
A conjugated diene block such as isoprene or the like, a styrene content of 5 to 50% by weight, and a conjugated diene content of 95 to 50%.
Refers to weight percent of elastomer. The styrene-conjugated diene block copolymer refers to a copolymer containing a styrene block and a block of a conjugated diene such as butadiene or isoprene, and has a styrene content of 55 to 95% by weight and a conjugated diene content of 45 to 5% by weight. In addition, styrene-conjugated diene block copolymer containing other components was used.
Binary and quaternary copolymers are also included in the present invention. Other components include, for example, acrylic acid, methacrylic acid, and metal salts thereof (eg, Na, K, Li, Mg, Ca, Zn, F
e) and aliphatic carboxylic acids such as acrylic acid esters and methacrylic acid esters, and derivatives thereof. Further, a compound obtained by partially hydrogenating a double bond residue based on a conjugated diene can also be exemplified. In addition, known additives such as various additives such as an antistatic agent, a lubricant, a stabilizer, and an ultraviolet absorber, and other resins may be appropriately added to the intermediate layer.

The styrene-conjugated diene block copolymer constituting the front and back layers includes a styrene block and butadiene,
A conjugated diene block such as isoprene; a styrene content of 55 to 95% by weight; and a conjugated diene content of 45 to 5%.
% By weight refers to, for example, SJS or JS-
J or (SJ) _n -S or (JS) _n -J (S
Is a styrene block, J is a conjugated diene block, and n is 2
The above integer is represented). In addition, a styrene-butadiene block copolymer containing other components including ternary,
The original copolymer is also included in the present invention. Other components include, for example, acrylic acid, methacrylic acid, metal salts thereof (for example, metal salts such as Na, K, Li, Mg, Ca, Zn, and Fe), and fatty acids such as acrylates and methacrylates. Aromatic carboxylic acids and derivatives thereof can be exemplified. Further, a compound obtained by partially hydrogenating a double bond residue based on a conjugated diene can also be exemplified.

The styrene-conjugated diene block copolymer preferably has a Vicat softening point of 70 ° C. or higher. More preferably, it is 80 to 100 ° C. If the temperature is lower than 70 ° C., the film tends to be easily blocked when it is warm.
If it exceeds 100 ° C., the shrinkage rate in a low temperature range tends to be adversely affected. The styrene-conjugated diene block copolymer may be a mixture of two or more kinds having different Vicat softening points and molecular weights.

The front and back layers preferably further contain polystyrene (GPPS) in addition to the styrene-conjugated diene block copolymer. When polystyrene is blended,
This is because it is effective for further reducing the natural shrinkage, further improving the anti-blocking property of the film, and the like. In addition, the front and back layers, antistatic agent, anti-blocking agent,
Known additives such as various additives such as a lubricant, a stabilizer, and an ultraviolet absorber, and other resins may be appropriately added.

The amount of the polystyrene is preferably 5 to 70 parts by weight, more preferably 10 to 40 parts by weight, based on 100 parts by weight of the styrene-conjugated diene block copolymer.
More preferably, it is 20 to 30 parts by weight. If the amount is less than 5 parts by weight, the above effect is small, and if it exceeds 70 parts by weight, the stretchability tends to deteriorate, and the low-temperature shrinkage tends to deteriorate. Although the blending amount may be changed between the surface layer and the back layer,
From the viewpoint of curling and the like, it is desirable that the amounts are the same.

As the intermediate layer, a styrene-acrylate copolymer and / or a styrene-methacrylate copolymer may be used instead of the impact polystyrene and / or the graft type impact polystyrene. The styrene-acrylate copolymer or styrene-methacrylate copolymer refers to a copolymer of a styrene monomer and an acrylate or methacrylate. Styrene monomer means styrene or α
-Styrene derivatives such as methylstyrene and p-methylstyrene. The acrylate or methacrylate is preferably an ester of acrylic acid or methacrylic acid with at least one aliphatic alcohol having 1 to 14 carbon atoms, more preferably at least one ester having 2 to 10 carbon atoms. An ester with an aliphatic alcohol. More preferred is butyl acrylate.

The styrene-acrylic acid ester copolymer or styrene-methacrylic acid ester copolymer preferably has a Vicat softening point of 80 ° C. or less. More preferably, it is 75 to 55 ° C. When the temperature exceeds 80 ° C., the heat shrinkage rate in a low temperature range decreases. On the other hand, when the temperature is lower than 55 ° C., the resin may be blocked in summer. The styrene-acrylic acid ester copolymer and / or the styrene-methacrylic acid ester copolymer may be a mixture of two or more kinds having different Vicat softening points and molecular weights.

In the intermediate layer, in addition to a styrene-acrylate copolymer and / or a styrene-methacrylate copolymer, a styrene-conjugated diene block copolymer, impact-resistant polystyrene (HIPS), and a graft type Various polystyrene resins such as impact polystyrene may be further blended. In particular, it is more desirable to blend a styrene-conjugated diene block copolymer. This is because the blending of the styrene-conjugated diene block copolymer improves the fragility, elongation, impact strength and the like of the film. The styrene-conjugated diene block copolymer is as described above.

The blending amount of the styrene-conjugated diene block copolymer is 100 parts by weight of the styrene-acrylate copolymer and / or the styrene-methacrylate copolymer.
The amount is preferably from 5 to 95 parts by weight, more preferably from 10 to 60 parts by weight, even more preferably from 20 to 40 parts by weight based on parts by weight. If the amount is less than 5 parts by weight, the above effect is small, and 9
If it exceeds 5 parts by weight, the natural shrinkage tends to increase. The styrene-conjugated diene block copolymer may be a mixture of two or more kinds having different styrene contents and molecular weights.

Although the total thickness of the film is not particularly limited, it is usually 20 to 150 μm, preferably 30 to 150 μm.
８０80 μm. The ratio of the thickness of the middle layer to the front and back layers is
It may be determined in consideration of the heat shrinkage characteristics, blocking resistance, natural shrinkage ratio, and the like of the film. Preferably surface layer / intermediate layer /
Back layer = 1/2/1 to 1/20/1, more preferably surface layer / intermediate layer / back layer = 1/5/1 to 1/12/1. When the thickness of the intermediate layer is smaller than 1/2/1, the heat shrinkage characteristics in the low temperature range tend to be insufficient, and
If it exceeds 30, the impact resistance, the blocking resistance, and the natural shrinkage tend to be unfavorable. The laminating method may be any known method such as dry lamination and extrusion lamination, but a co-extrusion method is simple and more preferred.

Another preferred embodiment of the film of the present invention is a film having at least three layers in which the intermediate layer is mainly composed of a polyester resin containing white fine particles and the front and back layers are mainly composed of the polyester resin. be able to. The polyester-based resin is preferably a resin mainly containing a resin generally called a copolymerized polyester resin. The acid component constituting the copolymerized polyester resin may be a known acid component, for example, terephthalic acid,
Isophthalic acid, phthalic acid, naphthalenedicarboxylic acids such as 2,6-naphthalenedicarboxylic acid, dicarboxybiphenyls such as 4,4′-dicarboxylic acid diphenyl;
Substituted phthalic acids such as 5-t-butylisophthalic acid, 2,
Substituted dicarboxylic biphenyls such as 2,6,6-tetramethylbiphenyl-4,4′-dicarboxylic acid;
1,3-trimethyl-3-phenylindene-4,5-
Aromatic dicarboxylic acids such as dicarboxylic acid and substituted products thereof, 1,2-diphenoxyethane-4,4′-dicarboxylic acid and substituted products thereof, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, and azelaic acid Aliphatic dicarboxylic acids such as sebacic acid, pimelic acid, stearic acid, undecanoic acid, dodecanedicarboxylic acid, brassic acid, tetradecanedicarboxylic acid, tabsic acid, nonadecanedicarboxylic acid, and docholinedicarboxylic acid; And alicyclic dicarboxylic acids such as 4,4'-dicarboxycyclohexane, and substituted products thereof. The diol component may be a known one such as ethylene glycol, triethylene glycol, propylene glycol, butanediol, 1,6-hexanediol, 1,10-decanediol, neopentyl glycol, or 2-methyl-2.
-Ethyl-1,3-propanediol, 2-diethyl-
Aliphatic diols such as 1,3-propanediol and 2-ethyl-2-n-butyl-1,3-propanediol;
Alicyclic diols such as 1,3-cyclohexanedimethanol and 1,4-cyclohexanedimethanol;
Bis (4′-β-hydroxyethoxydiphenyl) propane, bis (4′-β-hydroxyethoxyphenyl)
Examples include ethylene oxide adducts of bisphenol compounds such as sulfones, aromatic diols such as xylylene glycol, and diethylene glycol. One type of copolymerized polyester resin may be used, or a mixture of two or more types may be used. Further, a small amount of polyethylene terephthalate resin, polybutylene terephthalate resin, or the like may be mixed. The copolymerized polyester resins constituting the intermediate layer and the front and back layers may be of the same type or different types. The thickness ratio of the surface layer, the intermediate layer, and the back layer and the total thickness of the film are the same as those of the above-mentioned polystyrene-based multilayer film. To each layer, various additives such as an antistatic agent, an anti-blocking agent, a lubricant, a stabilizer, and an ultraviolet absorber, and other known resins such as other resins may be appropriately added.

In another preferred embodiment of the film of the present invention, the intermediate layer is made of propylene-containing white fine particles.
A film having at least a three-layer structure mainly composed of a resin composition containing an α-olefin random copolymer as a main component and a front and back layer containing 40 to 150 parts by weight of a linear low-density polyethylene in 100 parts by weight of a cyclic olefin-based resin. Can be mentioned.

The cyclic olefin-based resin is a general generic name. Specifically, (a) ring-opening (co)
(B) a cyclic olefin addition (co) polymer; (c) a random copolymer of a cyclic olefin and an α-olefin such as ethylene or propylene; Examples include graft-modified products obtained by modifying a) to (c) with an unsaturated carboxylic acid or a derivative thereof. The cyclic olefin is not particularly limited, and examples thereof include norbornene, tetracyclododecene, and derivatives thereof.

The glass transition temperature of the cyclic olefin resin is preferably 50 to 100 ° C., more preferably 60 to 100 ° C.
゜ 90 ° C. If the temperature is less than 50 ° C., the natural shrinkage tends to be too large, and if it exceeds 100 ° C., the heat shrinkage in the main shrinkage direction in a low temperature region tends to be too small.

The linear low density polyethylene contained in the front and back layers preferably has a density of 0.910 to 0.935 g / c.
m ³ , more preferably 0.912 to 0.930 g / cm
³ , more preferably 0.915 to 0.925 g / cm
³ . When the density is less than 0,910 g / cm ³ , the heat resistance of the film surface is reduced, and the surface becomes sticky when heated, and when used as a label, the containers are blocked on the mounting line. The phenomenon tends to occur easily. On the other hand, the density is 0.935 g / cm ³
When it exceeds, the heat resistance is improved, but at the time of stretching, the film cannot be stretched unless the temperature is high, and the whole film tends to be whitish and the haze is poor.

The melt flow rate (MFR) of linear low density polyethylene (190 ° C., 21.18 N)
Is preferably 0.2 to 30 g / 10 min, more preferably 0.5 to 25 g / 10 min, and still more preferably 1.0 to 20 g / 10 min. MFR 0.2g
If it is less than / 10 min, the kneading and dispersion with the cyclic olefin-based resin will be poor, and the film will tend to have a poor surface condition. On the other hand, when the MFR is more than 30 g / 10 min, the viscosity is greatly reduced, and necking at the time of dropping from the die becomes large, so that a predetermined raw material width may not be obtained, and the film strength is also reduced. There is a tendency.

As the α-olefin to be copolymerized with ethylene of the linear low-density polyethylene, those having 4 to 12 carbon atoms are preferable. Among them, a binary copolymer with 1-butene or 1-hexene, Or 1-butene and 1
-Terpolymers with hexene are more preferred. Among these, a binary copolymer with 1-butene is more preferred.

The amount of the linear low-density polyethylene to be blended with the cyclic olefin-based resin is as follows.
40 to 150 parts by weight, preferably 60 parts by weight per 0 parts by weight
To 120 parts by weight, more preferably 70 to 90 parts by weight. If the amount is less than 40 parts by weight, it tends to be difficult to maintain lubricity when performing corona discharge treatment. On the other hand, if it exceeds 150 parts by weight, the transparency and gloss are poor, and the center seal cannot be performed stably with an organic solvent. The resin composition of the surface layer and the back layer, that is, the type (including the difference in MFR) of the cyclic olefin-based resin and the linear low-density polyethylene may be the same or different. Further, two or more of them may be included. Also, the resin composition ratio may be the same or different.

It is desirable to further add a hydrocarbon resin to the front and back layers composed of a resin composition of a cyclic olefin resin and a linear low-density polyethylene. The effect of improving the glossiness of the film surface is obtained by adding the hydrocarbon resin. The amount of the hydrocarbon resin is preferably 2 to 2 parts by weight based on 100 parts by weight of the resin composition of the cyclic olefin resin and the linear low-density polyethylene.
0 parts by weight, more preferably 5 to 15 parts by weight. When the addition amount is less than 2 parts by weight, the effect of the addition is small,
When the amount exceeds 20 parts by weight, the film becomes hard, brittle, and easily tearable, and the film surface tends to be sticky and blocking.

Hydrocarbon resins include aliphatic hydrocarbon resins, aromatic hydrocarbon resins, alicyclic hydrocarbon resins, and hydrogenated products thereof, such as those generally referred to as petroleum resins, rosin, Rosin esters, terpene resins and the like are mentioned, and hydrogenated products thereof are particularly preferable.

To the front and back layers, known ones such as an antistatic agent, an antiblocking agent, a lubricant, an ultraviolet absorber, a stabilizer, and other resins are added as appropriate within a range not to impair the essence of the present invention. You may.

The propylene-α-olefin random copolymer used in the intermediate layer contains propylene as a main component, and the α-olefin preferably has 2 to 12 carbon atoms (excluding 3). The polymer may contain two or more α-olefins. Also, a mixture of different types (including differences in MFR) of propylene-α-olefin random copolymers may be used. As the propylene-α-olefin random copolymer,
More preferably, it is a propylene-ethylene random copolymer. More preferably, it is a propylene-ethylene random copolymer having an ethylene content of 2 to 7 mol%.

It is desirable to further add a hydrocarbon resin to the intermediate layer. The effect of increasing the heat shrinkage can be obtained by adding the hydrocarbon resins. The amount of the hydrocarbon resin added is preferably 5 to 70 parts by weight, more preferably 35 to 55 parts by weight, based on 100 parts by weight of the propylene-α-olefin copolymer. If the amount is less than 5 parts by weight, the effect of the addition is small, and if it exceeds 70 parts by weight, the film becomes hard and brittle, resulting in a film having a small strength. It tends to be easy to wake up. The hydrocarbon resins are as described above.

It is desirable that a linear low-density polyethylene is further added to the intermediate layer. By adding the linear low-density polyethylene, the impact resistance of the film is improved, and when the film has a three-layer structure, the effect of improving the delamination strength in combination with the linear low-density polyethylene of the front and back layers is obtained. can get. The addition amount of the linear low-density polyethylene is preferably 2 to 30 parts by weight, more preferably 5 to 20 parts by weight, based on 100 parts by weight of the resin composition of the propylene-α-olefin random copolymer and the hydrocarbon resin. Parts by weight. When the amount is less than 2 parts by weight, the effect of the addition is small. When the amount is more than 30 parts by weight, the transparency of the film is reduced, and when the film is softened and used as a label, an automatic mounting machine is used. Trouble tends to occur. The linear low-density polyethylene is as described above.

It is desirable to further add a rubber component to the intermediate layer. The effect of improving the impact resistance of the film can be obtained by adding the rubber component. The amount of the rubber component is preferably 2 to 30 parts by weight, more preferably 5 to 2 parts by weight, based on 100 parts by weight of the resin composition of the propylene-α-olefin random copolymer and the hydrocarbon resin.
0 parts by weight. When the amount is less than 2 parts by weight, the effect of the addition is small, and when it exceeds 30 parts by weight, the transparency of the film tends to decrease. The rubber component is not particularly limited, and examples thereof include ethylene-propylene rubber, ethylene-propylene-diene rubber, and ethylene-butene rubber. Among them, ethylene-propylene rubber is more preferable.

A known material such as an antistatic agent, a lubricant, an ultraviolet absorber, a stabilizer, or another resin may be appropriately added to the intermediate layer as long as the essence of the present invention is not impaired. The thickness ratio of the surface layer, the intermediate layer, and the back layer and the total thickness of the film are the same as those of the above-mentioned polystyrene-based multilayer film.

The film of the present invention has a heat shrinkage in the main shrinkage direction of 15% or more when immersed in hot water of 80 ° C. for 10 seconds;
It is preferably at least 25%, more preferably at least 30%. If it is less than 15%, the label produced from the film of the present invention cannot be tightly shrink-fitted to a container. Here, the main shrinkage direction means a direction in which the shrinkage ratio is large in the longitudinal direction and the transverse direction of the film. The heat shrinkage rate under the above conditions in the direction orthogonal to the main shrinkage direction is preferably 10
%, More preferably 5% or less. In the present invention, the reason why the measurement of the heat shrinkage rate is determined to be the hot water without using the hot air is because the variation in the measured value is smaller in the hot water than in the hot air.

In the film of the present invention, the average value of the total light transmittance at a wavelength of 400 to 700 nm when contracted by 5% in the main contraction direction is 50% or less, preferably 4% or less.
0% or less, more preferably 35% or less. 5
If it exceeds 0%, the light-shielding property is poor, and the ability to prevent deterioration and discoloration of the contents becomes small, which is not preferable. Also,
As will be described later, if silver or black ink is solid printed on the back surface, the color of silver or black ink is seen through from the front side, which is not preferable. The reason for shrinking by 5% in the main shrinking direction is that a label having a margin of about 5% with respect to the diameter of the container is generally used. When contracted 5% in the main contraction direction,
The film of the present invention having an average value of the total light transmittance at a wavelength of 400 to 700 nm of 50% or less, preferably 40% or less, more preferably 35% or less, has a wavelength of 200 to 4%.
Since the maximum transmittance in the ultraviolet region of 00 nm is 15% or less, preferably 12% or less, and more preferably 10% or less, there is an advantage that even a product which is easily deteriorated or discolored by ultraviolet rays can be protected.

The film of the present invention is white. For the purpose of differentiation from other products, improvement of the visibility of the products, precautionary notes, and the like, multicolor printing is usually performed on the film surface. If the film is provided with light-shielding properties by coloring, the solid white printing must be thickened to make the coloring invisible, but since the film of the present invention is white, there is no need for such . In some cases, white solid printing may be omitted. Further, in order to impart further light shielding properties, solid printing of white, silver, black ink or the like may be performed on the back surface of the film in some cases.

Further, the film of the present invention is a film substantially free of voids. The term “film substantially free of cavities” as used in the present invention means that most of the fine particles (70%
The above-mentioned fine particles) do not include voids around the cross-sectional area of the fine particles, preferably, most of the fine particles (70%
The above-mentioned fine particles) do not include cavities having a half or more of the cross-sectional area of the fine particles around the fine particles, and more preferably, those having almost no cavities. The magnification of the (electron) micrograph may be appropriately selected depending on the diameter (or long diameter) of the white fine particles. Usually, about 500 to 200,000 times is desirable. Further, if the film is composed of only a white thermoplastic resin layer, the apparent specific gravity of the film obtained by the measurement method described below is A, and the true specific gravity of the film raw material obtained by calculation from the raw material composition of the film is B, Equation 1 below
Is 0.88 or more, preferably 0.91
Above, more preferably 0.94 or more, further preferably 0.96 or more. X = A / B (Formula 1) Further, the film has at least a three-layer structure in which a white thermoplastic resin layer is used as an intermediate layer, and a substantially transparent resin layer made of the same or different thermoplastic resin is used as a front and back layer. In the case of a multilayer film, a film consisting of only a white thermoplastic resin layer may be produced under the same thickness and under the same production conditions as the multilayer film, and the X value thereof may be determined. X value is 0.8
When the film is less than 8, the film substantially contains voids, so that it is easy to stretch, the hardness (lumbar) is insufficient, the tear strength is weak, and the above-mentioned problem tends to occur, which is not preferable.

The film of the present invention can be produced by a known method such as a flat method and a tubular method. For example, in the case of the flat method, the resin is melted by using a plurality of extruders, (co) extruded from a T-die, taken up by a take-up roll, roll-stretched in a longitudinal direction, and tenter-stretched in a transverse direction, An example is a method of obtaining a film by annealing, cooling, performing corona discharge treatment on a surface to be printed if necessary, and winding the film with a winding machine. The stretching ratio is 2-1 in the direction corresponding to the main stretching direction (main shrinking direction).
2 times, preferably 3 to 8 times, the direction orthogonal to it is 1 to
It is desirable to select a magnification ratio of 3 times (1 means that the film is not stretched), preferably 1 to 2 times, substantially in the category of uniaxial stretching. This is because a film obtained with a normal biaxial stretching ratio has a large heat shrinkage in a direction orthogonal to the main stretching direction (main shrinking direction). Film (label)
This is because heat shrinkage causes a so-called vertical shrinkage phenomenon, which is not preferable.

An example of a method for producing a shrink label from the film thus obtained will be described. The surface of the film produced at a magnification ratio substantially in the category of uniaxial stretching is printed by an appropriate method such as gravure printing. At this time, it is general that the end of the film serving as a seal margin is a printed pattern that becomes a non-printed portion.

As one embodiment for obtaining a tube-shaped label from the printed flat heat-shrinkable film thus obtained, a center seal using an organic solvent is shown in FIG.
It will be described based on. FIG. 1 is a simplified view showing a typical center seal processing method. 1 is a flat film which is folded in an envelope shape at both ends so that a printed surface faces outward, and 2 is a tube formed by center sealing. 3, a center seal portion, 4 a seal margin, 5 a nozzle for applying an organic solvent, and 6 a nip roll. The film travels in the direction of the arrow in FIG. 1, an organic solvent is applied to the seal margin 4 from the nozzle 5, and is pressed by the nip roll 6 to produce a tubular film. Next, this is cut to an appropriate length to obtain a label.
The speed of the center seal is usually 80 to 170 m /
Min, preferably 120-150 m / min. The organic solvent used is not particularly limited as long as it dissolves or swells the front and back layers of the film.

The container in the present invention means a colorless and transparent container in which the film (label) of the present invention functions effectively.
For example, a plastic bottle such as a colorless plastic bottle or a colorless glass bottle can be exemplified. In addition, the content (content) is not particularly limited, but the film (label) of the present invention functions most effectively in beverages and the like which are liable to be degraded or discolored by visible light or ultraviolet light.

[0047]

EXAMPLES Next, typical examples of the present invention will be described.

The thermal shrinkage in the main shrinkage direction (main stretching direction) when the film is immersed in hot water at 80 ° C. for 10 seconds is measured by the following method. That is, length x width = 100.
Precisely cut out 10 samples of 0 mm × 100.0 mm. Then, place one of these samples in warm water at 80 ° C.
After being immersed for 0 second and immediately cooled with cold water, the length L (mm) in the longitudinal direction or the transverse direction (main shrinking direction, ie, direction corresponding to the main stretching direction) is measured. And 100-L
Is calculated. The same was repeated for the remaining nine samples, and the average value of a total of ten samples was defined as the heat shrinkage in the main shrinkage direction when immersed in 80 ° C. hot water for 10 seconds.

The average value of the total light transmittance at a wavelength of 400 to 700 nm when the film is shrunk by 5% in the main shrinkage direction is determined by the following method. That is, a sample of main shrinkage direction × perpendicular direction = 150.0 mm × 100.0 mm is cut out from the film. Next, mark lines at intervals of 100.0 mm are accurately inserted into the sample so that the length in the main contraction direction can be determined. Next, mark lines were placed at both ends of the jig having a distance of 95.0 mm (that is, 5% of the sample was moved in the main shrinkage direction).
The sample is removed from the jig after the sample is immersed in hot water at 80 ° C. for 10 seconds and immediately cooled with cold water. Next, the part contracted by 5% is cut out, the front and back surfaces are washed with methanol, and air-dried. The sample obtained in this manner is used as a spectrophotometer (manufactured by Hitachi, Ltd.).
U-3410 spectrophotometer
r) and the average value of the total light transmittance continuously measured from 400 nm to 700 nm was determined (JIS).
K-7105). In the same manner, the measurement was repeated 10 times in total, and the average value of the average value of the total light transmittance was defined as the average value of the total light transmittance at a wavelength of 400 to 700 nm when contracted by 5% in the main contraction direction. In addition, the ultraviolet transmittance from 200 nm to 400 nm was also measured.

The glossiness of the front and back surfaces when the film is shrunk by 5% in the main shrinkage direction is measured by the following method.
That is, the front and back surfaces of the sample obtained in the same manner as described above were measured with a gloss meter (Glos, manufactured by Nippon Denshoku Industries Co., Ltd.
sMeter VG2000) and the glossiness of the front and back surfaces was measured (based on JIS Z-8741). Similarly, the measurement was repeated 10 times in total, and the average value was defined as the glossiness of the front and back surfaces when the film was shrunk by 5% in the main shrinkage direction.

Evaluation of cross section of film by electron micrograph
Is based on the following method. That is, OsO ₄For dyeing ultra-thin section method
The cross section of the film prepared by
50,000 times magnification using electronic JEM-1200EX)
And photographed to observe the presence or absence of cavities.

The X value is determined by the following method. That is,
Length x width = 100.0mm x 100.0mm from film
Cut out the sample exactly. Then increase the thickness to 100
The average value α (μm) of the thickness is obtained by performing point measurement. Then
The weight β (mg) is measured. And (β × 10
⁻³ ) / (10 × 10 × α × 10 ⁻⁴ ) is obtained by calculation, and is defined as the apparent specific gravity A ′ of the sample. Similarly, the apparent specific gravity A ′ of each sample obtained by repeating a total of 10 times
Is defined as the apparent specific gravity A of the film. On the other hand, B is the true specific gravity of the film raw material obtained by calculation from the film raw material composition. Then, the X value was obtained from the following equation 1. X = A / B (Equation 1)

Example 1 As an intermediate layer (B), 100 parts by weight of a graft-type impact-resistant polystyrene (SS-700 manufactured by A & M Styrene Co.) and 8 parts by weight of a styrene-butadiene block elastomer (Tuffrene 126 manufactured by Asahi Kasei Kogyo Co., Ltd.) Part and titanium dioxide masterbatch (base resin: SS-70 manufactured by A & M Styrene Co., Ltd.)
0 40% by weight, rutile type titanium dioxide (average particle size 2
20 nm) 60% by weight) and 20 parts by weight were melt-kneaded using an extruder, and further, using two extruders,
Polystyrene (GPPS) 2 as front and back layers (A) and (C)
Styrene-butadiene block copolymer containing 0% by weight (Clearen 200ZH manufactured by Denki Kagaku Kogyo Co., Ltd.) 1
00 parts by weight, 1.4 parts by weight of an antistatic agent masterbatch (Erestmaster SB-10 manufactured by Kao Corporation) and an antiblocking agent masterbatch (base resin: 90% by weight of Clearen 200ZH manufactured by Denki Kagaku Kogyo Co., Ltd., organic) An anti-blocking agent: a mixture of 0.8 parts by weight of Art Pearl F-5P (10% by weight, manufactured by Tohshin Chemical Co., Ltd.) is melt-kneaded, and the mixture is heated at 190 ° C. in the order of (A) / (B) / (C). And then extruded in a T-die, taken up using a take-up roll at 45 ° C.
Roll-stretched 1.4 times in the machine direction at 0 ° C.
After preheating for 20 seconds, the tenter was stretched 5.0 times in the transverse direction at 90 ° C., and annealed at a temperature of 85 ° C. in the vicinity of the exit of the tenter while relaxing 3.7% in the transverse direction over 17 seconds, at 40 ° C.
To obtain a heat-shrinkable white film for labels. The average thickness of the film was 5 μm for both the surface layer (A) and the back layer (C), 40 μm for the intermediate layer (B), and 50.0 μm in total. The heat shrinkage in the main shrinkage direction (lateral direction) when immersed in hot water at 80 ° C. for 10 seconds, and the wavelength when the film shrinks by 5% in the main shrinkage direction is 400 to 7
Table 1 shows the average value of the total light transmittance at 00 nm and the glossiness of the front and back surfaces when the film was shrunk by 5% in the main shrinkage direction. When a cross section of the film was taken with an electron microscope photograph and confirmed, no cavities were observed. In addition, 8 in the direction (vertical direction) orthogonal to the main contraction direction
The thermal shrinkage when immersed in 0 ° C warm water for 10 seconds is -1%,
The maximum transmittance in the ultraviolet region having a wavelength of 200 to 400 nm was 3% (at 400 nm) (see FIG. 2).

Example 2 Five-color printing was performed on the back surface (C) of this film using a gravure printing machine. The printed design was three in the width direction of the film, and each end was used as a non-printed part. Next, three slits were made with a slitter. Then, using a mixed solvent of n-hexane / tetrahydrofuran = 100/20 (weight ratio) as an organic solvent, the center was sealed at a processing speed of 130 m / min with the apparatus shown in FIG. The folding diameter was 113 mm, and the seal margin was 4 mm. Next, this tube was cut into a label having a length of 183 mm to form a label. The tube was covered with a plastic bottle having a content of 500 ml, and a wet heat shrink tunnel (length 5 m, temperature 80 ° C-85 ° C-
(3 zones at 93 ° C.) for 8 seconds.
The label was attached to the bottle tightly and was beautiful without wrinkles, avatars, etc.

(Example 3) Graft type impact-resistant polystyrene (SS-700 manufactured by A & M Styrene Co., Ltd.)
100 parts by weight of true specific gravity: 1.08) and 8 parts by weight of styrene-butadiene block elastomer (TAFPRENE 126 manufactured by Asahi Kasei Kogyo Co., Ltd.) and titanium dioxide masterbatch (base resin: A & M Styrene Co., Ltd. SS-) A mixture of 40% by weight of 700 and 20 parts by weight of rutile-type titanium dioxide (average particle diameter: 220 nm, true specific gravity: 4.10) 60% by weight was melt-kneaded using an extruder, and the thickness was adjusted in the same manner as in Example 1. A 50.0 μm monolayer film was obtained. Heat shrinkage in the main shrinkage direction (lateral direction) when immersed in 80 ° C. hot water for 10 seconds, average value of total light transmittance at a wavelength of 400 to 700 nm when the film is shrunk by 5% in the main shrinkage direction, and Table 1 shows the glossiness of the front and back surfaces when the film was shrunk by 5% in the main shrinkage direction. The X value of this film was 0.972. In addition, 80 in the direction (vertical direction) orthogonal to the main contraction direction
The heat shrinkage when immersed in hot water for 10 seconds is -2%, and the maximum transmittance in the ultraviolet region having a wavelength of 200 to 400 nm is 2
% (At 400 nm) (see FIG. 3). Next, a label was produced using this film in the same manner as in Example 2, and was attached to a PET bottle by heat shrinking. The label was attached to the bottle tightly and was beautiful without wrinkles, avatars, etc.

[0056]

[0057]

Since the present invention has the above-described configuration, the following effects can be obtained.

The film of the present invention is less likely to elongate, has higher hardness (rigidity), and is superior in tear strength as compared with a film containing a cavity, so that an excellent label can be produced. In addition, because of its excellent light-shielding properties, the colorless and transparent container to which the label produced from the film of the present invention is heat-shrink-fitted has the function of protecting the inner products that are susceptible to deterioration or discoloration by visible light or ultraviolet light. . Further, since the container is colorless and transparent, there is no problem during recycling.

[Brief description of the drawings]

FIG. 1 is a simplified diagram showing a center sealing method using an organic solvent.

FIG. 2 shows that the film obtained in Example 1 has a wavelength of 200 to 80.
It is a measurement chart figure of the light transmittance in 0 nm.

FIG. 3 shows that the film obtained in Example 3 has a wavelength of 200 to 80.
It is a measurement chart figure of the light transmittance in 0 nm.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Flat film 2 Tubular film 3 Center seal part 4 Seal margin 5 Nozzle for applying organic solvent 6 Nip roll

[Procedure amendment]

[Submission date] May 22, 2001 (2001.5.2)
2)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0056

[Correction method] Change

[Correction contents]

[0056]

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0058

[Correction method] Change

[Correction contents]

The film of the present invention is less likely to elongate, has higher hardness (rigidity), and is superior in tear strength as compared with a film containing a cavity, so that an excellent label can be produced. In addition, because of its excellent light-shielding properties, the colorless and transparent container to which the label produced from the film of the present invention is heat-shrink-fitted has the function of protecting the inner products that are susceptible to deterioration or discoloration by visible light or ultraviolet light. . In addition, since it is white, a colorless and transparent container to which a label produced from the film of the present invention is heat-shrink-mounted is rich in cleanliness. Further, since the container is colorless and transparent, there is no problem during recycling. Two

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C08K 3/00 C08K 3/00 C08L 101/00 C08L 101/00 // B29K 101: 12 B29K 101: 12 105 B02L 7:00 B29L 7:00 F term (reference) AG01 AG03 RA03 RC02 RG02 RG04 RG09 RG43 4J002 AA011 BB031 BB121 BC031 BD031 BK001 CF001 DE076 DE106 DE136 DE236 DG046 DJ016 DJ036 DJ046 FD016 FD096 GG01 GG02

Claims (3)

[Claims] 1. A white film for a heat-shrinkable label comprising a white thermoplastic resin layer containing white fine particles, wherein the white film is 80 ° C.
The average thermal shrinkage in the main shrinkage direction when immersed in warm water for 10 seconds is 15% or more, and the average value of the total light transmittance at a wavelength of 400 to 700 nm when shrunk 5% in the main shrinkage direction is 50% or less. And a white film for a heat-shrinkable label substantially free of cavities. 2. A heat-shrinkable label produced from the white film for heat-shrinkable labels according to claim 1. 3. A container to which the heat shrinkable label according to claim 2 is heat shrunk.