JP3375391B2 - Transparent heat shrinkable film - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-shrinkable film, and more specifically, it has a vertical and horizontal heat-shrinkage ratio suitable for a shrink film for packaging cylindrical objects such as bottles and is transparent. The present invention relates to a transparent heat-shrinkable film having excellent properties, low-temperature shrinkability, impact resistance, dimensional stability over time, waist strength, and flex and tear strength after printing.

[0002]

2. Description of the Related Art Recently, as a container for carbonated drinks, juice, beer, barley tea, sake, etc., a pre-labeled bottle in which a hollow bottle made of glass or PET is shrink-labeled is rapidly increasing. Conventionally, a large amount of polyvinyl chloride film, which has excellent heat shrinkability, strength, printability, and packaging finish, has been used as a material for pre-labels, but polyvinyl chloride film contains chlorine in the molecule. Since it contains it, it produces toxic gas when it is burned in an incinerator after use, which is an environmental problem. Therefore, environmentally friendly styrene resin films containing no chlorine in the molecule have begun to be used for this purpose. As the technology of the styrene resin film used for this purpose, for example, Japanese Patent Publication No. 61-25819 and Japanese Patent Publication No. 62-25701 disclose (1) vinyl aromatic carbonization having a Vicat softening temperature of 90 ° C. or less. A resin composition comprising a hydrogen-based copolymer and (2) a block copolymer comprising a vinyl aromatic hydrocarbon-based polymer block and a conjugated diene-based polymer block is 50 to 1
It is disclosed that the film has a stable stretching region in a wide temperature range of 10 ° C., and the film stretched is excellent in low-temperature shrinkability and transparency, and is suitable for this shrink label application. Further, in JP-A-5-104630, a hydrogenated block copolymer (3) obtained by hydrogenating the above block copolymer (2) as a third component in addition to the above (1) and (2). It is disclosed that a resin film obtained by stretching a resin composition comprising the above so as to have a specific heat shrinkage force is excellent in low-temperature shrinkability, transparency, impact resistance, and dimensional stability over time.

[0003]

As described above, a resin film formed by stretching a specific styrene resin composition by a conventional technique so as to have a specific heat shrinkage force has a low temperature shrinkability, transparency, It has been found that it has excellent impact resistance and dimensional stability over time, and is now beginning to be used for this application. On the other hand, in this application, in order to display the product name or to finish it beautifully as a product, it is often used as a product in which the back surface of the resin film is subjected to full-scale printing. Since the mechanical strength before and after printing is insufficient, cracks may occur from the bent part when it is folded and stored, or when it is transported or when it is mounted on a packaging machine. . The present invention, while maintaining low-temperature shrinkability, transparency, impact resistance, and dimensional stability over time, also maintains the initial mechanical strength at a practical level even after printing, crack defects from the bent portion. An object is to provide a transparent heat-shrinkable film that does not print.

[0004]

Means for Solving the Problems As a result of intensive studies made by the present inventors, a specific styrene resin, a specific non-crosslinking type thermoplastic rubber having good compatibility with the specific styrene resin, a specific particle size and a specific degree of crosslinking are selected. A resin film made of a styrene-based polymer containing a cross-linked graft rubber has a resin film stretched to have a specific heat shrinkage, and has excellent low-temperature shrinkability, transparency, impact resistance, and dimensional stability over time. In addition, the present invention was found to be a transparent heat-shrinkable film which has a high mechanical strength retention after printing and does not cause defective cracks from the bent portion.

That is, the present invention provides a resin composition comprising the following (A), (B) and (C), and (A) a copolymer of vinyl aromatic hydrocarbon and aliphatic unsaturated carboxylic acid ester: , Vicat softening temperature is 9
The temperature is 0 ° C or lower and the content of vinyl aromatic hydrocarbon is 95.
˜20 wt% copolymer 10-89.5 wt% (B) Block copolymer 89.5 comprising a vinyl aromatic hydrocarbon-based polymer block and a conjugated diene-based polymer block. 10% by weight (C) A rubber-modified styrene polymer containing a rubber-like polymer as dispersed particles, wherein the dispersed particles have a particle diameter of 2 to 10
0.5-30% by weight of a rubber-modified styrene-based polymer which is a cross-linked graft rubber having a cross-linking degree of 65% or more

Alternatively, a resin composition comprising the following (A), (B), (C) and (D), (A) a copolymer of a vinyl aromatic hydrocarbon and an aliphatic unsaturated carboxylic acid ester, Vicat softening temperature is 9
The temperature is 0 ° C or lower and the content of vinyl aromatic hydrocarbon is 95.
Copolymer consisting of 20 to 20% by weight 10 to 88.5% by weight (B) Block copolymer consisting of a polymer block mainly composed of vinyl aromatic hydrocarbon and a polymer block mainly composed of conjugated diene 88.5 10% by weight (C) A rubber-modified styrene polymer containing a rubber-like polymer as dispersed particles, wherein the dispersed particles have a particle diameter of 2 to 10
0.5-30% by weight of a rubber-modified styrenic polymer which is a cross-linked graft rubber having a cross-linking degree of 65% or more (D) A polymer block mainly composed of vinyl aromatic hydrocarbon and a conjugated diene A resin film comprising as an essential component 1 to 25% by weight of a hydrogenated block copolymer obtained by hydrogenating at least a part of an unsaturated bond structure derived from a conjugated diene of a block copolymer composed of a polymer block. Shrinkage rate is 8
50% in the main stretching direction when heated at 5 ° C for 10 seconds
As described above, the transparent heat-shrinkable film is characterized in that it is 20% or less in the direction perpendicular to the main stretching direction and has a total light transmittance of 70% or more when the thickness is 50 μm.

The present invention will be described in more detail below. First, the resin, which is the first constituent requirement of the present invention, and the resin composition will be described. The copolymer (A) used in the present invention is a copolymer of vinyl aromatic hydrocarbon and a monomer mainly composed of an unsaturated unsaturated carboxylic acid ester, and has a Vicat softening temperature of 90 ° C. or lower. And the content of vinyl aromatic hydrocarbon is 95 to 20% by weight. Here, the vinyl aromatic hydrocarbon is mainly a styrene-based monomer, specifically, styrene, α
-Alkyl-substituted styrenes, nuclear halogen-substituted styrenes and the like can be mentioned, and at least one kind is selected according to the purpose. Further, the aliphatic unsaturated carboxylic acid ester is mainly a (meth) acrylic acid ester derivative, specifically, methyl (meth) acrylate, ethyl, propyl, butyl ...
And the like, esters with alkyl alcohol (C _{1 to} C ₁₂ ), esters with alkylene oxide, esters with alicyclic alcohol, and the like, and at least one of them In this case, it is necessary to satisfy that the Vicat softening temperature is 90 ° C. or lower when the copolymerization (A) with vinyl aromatic hydrocarbon is carried out. Other monomers, such as (meth) acrylic acid, α-β unsaturated dicarboxylic acid anhydride, α-β unsaturated dicarboxylic acid ester derivative, or any alkyl group, as long as these conditions are satisfied A vinyl ether derivative having (for example, C _{2 to} C ₁₂ ) or the like may be used as one component of the aliphatic unsaturated carboxylic acid ester. Specific examples thereof include mono- and diester derivatives of fumaric acid, maleic acid, itaconic acid and the like, or acid anhydrides thereof.

As the copolymer (A) used in the present invention, a copolymer of styrene and butyl acrylate, a copolymer of styrene, butyl acrylate and methyl methacrylate, or the like is used. The copolymer (A) is preferable for reasons such as easy availability of the body and superior cost. Further, as such a copolymer (A), for example, a copolymer obtained by polymerization with a general radical initiator can be used. The copolymers of the special difunctional radical initiators disclosed in JP-A-149211 and JP-A-4-149212 are more preferable because they have excellent compatibility with the block copolymer (B) and transparency.

The copolymer (A) is selected so that the Vicat softening temperature is 90 ° C. or lower, preferably 80 ° C. or lower, more preferably 75 ° C. or lower, and when it exceeds 90 ° C. Not only is it necessary to increase the heat shrinkage temperature, but it is not preferable because the stable stretching region temperature range is narrow to form a film having a predetermined heat shrinkage ratio,
Further, the lower limit is not particularly limited, but it is preferably 25 ° C. or higher because stickiness occurs when the temperature is lower than 25 ° C. The content of vinyl aromatic hydrocarbon in the copolymer (A) is 95 to 20% by weight, preferably 90 to 40% by weight, and more preferably 85 to 50% by weight. If it exceeds 95% by weight, the effect of copolymerizing the aliphatic unsaturated carboxylic acid ester is weak, while if it is less than 20% by weight, hardness and workability are deteriorated, which is not preferable.

In the present invention, the blending ratio of the copolymer (A) is 10 to 89.5% by weight, preferably 20 to 80% by weight, more preferably 30 to 70% by weight, and if less than 10% by weight, it is added. It is not preferable because the effect is not exhibited, and the film exceeding 89.5% by weight becomes brittle and practically difficult to use, which is not preferable. Examples of the block copolymer (B) used in the present invention include JP-B-62-25701, JP-A-5-104630, and JP-A-4-198.
It is described in detail in Japanese Patent No. 244, etc., and briefly described, a vinyl aromatic hydrocarbon monomer represented by styrene, P-methylstyrene or the like is used alone or as a main component. It is a block copolymer of a polymer block mainly composed of a conjugated diene represented by 1.3-butadiene, isoprene and 1.3-pentadiene. Here, the polymer block containing a conjugated diene as a main component means that the content of the conjugated diene is 40% by weight or more, preferably 50% by weight or more, more preferably 60% by weight or more, and the conjugated diene is a main component. The vinyl aromatic hydrocarbon copolymerized in the polymer block may be uniformly distributed in the polymer block or may be distributed in a taper shape. The weight ratio of vinyl aromatic hydrocarbon to conjugated diene in the block copolymer is 20:80 to 95: 5, preferably 60:40 to 90:10, and the content of vinyl aromatic hydrocarbon is 20 weight. If it is less than 0.1%, the compatibility with the copolymer (A) is insufficient and the transparency is lowered.
When it exceeds 5% by weight, the mechanical strength of the resin film is insufficient and the resin film is easily broken, which is not preferable. Further, as a method for producing the block copolymer (B), for example, Japanese Patent Publication No. Sho 3
6-19286, Japanese Patent Publication No. 43-14979, Japanese Patent Publication No. 48-2423, and Japanese Patent Publication No. 48-410.
The manufacturing techniques disclosed in Japanese Patent Publication No. 6 and Japanese Patent Publication No. 49-36957 can be used.

In the present invention, the block copolymer (B)
The compounding ratio of 89.5 to 10% by weight, preferably 80 to
20% by weight, more preferably 70 to 30% by weight,
If it is less than 10% by weight, the film becomes brittle, which is not preferable.
On the other hand, if it exceeds 89.5% by weight, the dimensional stability of the film over time, gelation during extrusion, film elastic modulus, low-temperature shrinkability, etc. are insufficient, which is not preferable. The rubber-modified styrene-based polymer (C) used in the present invention is a rubber-modified styrene-based polymer having a rubber-like polymer as dispersed particles and a styrene-based polymer as a continuous phase structure. The styrene-based polymer to be used is styrene, P-methylstyrene,
Polymers obtained by polymerizing styrene monomers such as P-t-butylstyrene and α-methylstyrene alone or in a mixture, or monomers copolymerizable with styrene monomers, for example,
Acrylonitrile, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate,
It is a copolymer with butyl (meth) acrylate, (meth) acrylic acid, maleic anhydride and the like.

The dispersed particles have a glass transition temperature (T
g) is a rubber-like polymer having a temperature of -30 ° C or lower as a main component,
The glass transition temperature (Tg) is obtained by graft-polymerizing a polymer which is substantially the same as the above-mentioned styrene polymer.
Examples of the rubbery polymer having a temperature of −30 ° C. or lower include polybutadiene, styrene-butadiene random copolymer, styrene-butadiene block copolymer, ethylene-propylene copolymer, ethylene-propylene-nonconjugated diene terpolymer. One or more of polymers, isoprene polymers, styrene-isoprene copolymers, silicone rubbers and the like are used, but the molecular weight and degree of branching of the rubber-like polymer are not limited.

In the present invention, the particle diameter of the dispersed particles of the rubber-modified styrene polymer (C), which is an important requirement, is 2 to 1
It is in the range of 0 μ, preferably 2.5 to 8 μ, more preferably 3 to 7 μ, and when it is less than 2 μ, it is an object of the present invention when stretched to a resin film so as to have a predetermined heat shrinkage rate. The retention rate of mechanical strength after printing is insufficient, cracking from the bent portion cannot be sufficiently prevented, and when it exceeds 10 μ, the appearance of the resin film is deteriorated, which is not preferable. The method for measuring the particle size of the dispersed particles in the present invention is a known technique, for example, JP-A-4-35.
It can be determined by taking a transmission electron microscope photograph by a technique described in detail on page 8 of Japanese Patent No. 1652, that is, a resin ultrathin film slice method, and measuring a dispersed particle diameter in the photograph. .

In the present invention, the degree of crosslinking of the dispersed particles of the rubber-modified styrenic polymer (C), which is another important requirement, is 65% or more, preferably 75% or more, more preferably 80% or more. If it is less than 65%, the retention rate of mechanical strength after printing, which is the subject of the present invention, becomes insufficient, and the flexural tear strength after printing is insufficient, so cracking from the flexed part cannot be sufficiently prevented. It is not preferable. The method for measuring the degree of crosslinking of the dispersed particles in the present invention is to dissolve the rubber-modified styrenic polymer (C) in methyl ethyl ketone and then use a centrifuge at 20,000 rpm for 30
After treatment for 1 minute, the precipitate was separated, washed twice with methyl ethyl ketone, and dried in vacuum to obtain a sample.
The weight (W1) of the rubber-like polymer was determined from the infrared absorption spectrum of this sample, while the weight (W2) of the rubber-like polymer was determined from the infrared absorption spectrum of the rubber-modified styrene polymer (C). In the invention, the degree of crosslinking is
That is, the degree of crosslinking is calculated by the formula (1), which is a method utilizing the fact that the higher the degree of crosslinking, the more difficult it is to dissolve in methyl ethyl ketone.

[0015]

[Formula 1] Crosslinking degree = {(W1) / (W2)} × 10
0 (1) The content of the rubber-like substance in the rubber-modified styrene-based polymer (C) is not particularly limited, but is preferably 1 to 20% by weight because it can be produced by a usual production method. To obtain the rubber-modified styrenic polymer (C) of the present invention, a general production method is used, for example, a rubber-like substance is dissolved in a mixture of a styrenic monomer, a polymerization solvent and a polymerization initiator, and a stirrer is used. It is obtained by a method of performing polymerization by supplying to an attached reactor, the particle size control of dispersed particles can be easily controlled by changing the rotation speed of a stirring blade, etc. temperature,
It can be controlled by selecting the concentration of the initiator, the solvent and the like, and if necessary, a method of continuously or intermittently additionally adding a monomer or the like during the polymerization can also be used. In the present invention, the compounding ratio of the rubber-modified styrene polymer (C) is 0.5 to 3
It is 0% by weight, preferably 1 to 20% by weight, more preferably 2 to 15% by weight. If it is less than 0.5% by weight, the mechanical strength retention after printing is insufficient, and the flexing tear strength after printing is insufficient. Is not sufficient because cracking from the bent portion cannot be sufficiently prevented, and when it exceeds 30% by weight, the transparency of the film becomes insufficient, which is not preferable.

As the hydrogenated block copolymer (D) used in the present invention, at least a part of the polymer block mainly containing vinyl aromatic hydrocarbon and the polymer block mainly containing conjugated diene derivative is hydrogenated. A hydrogenated block copolymer consisting of a treated polymer block, wherein:
The vinyl aromatic hydrocarbon may be at least one selected from the same group as that used in the block copolymer (B), and the conjugated diene derivative may also have the same block copolymerization. At least one selected from the same group as that used in the combination (B) may be used. The hydrogenated polymer block is obtained by reacting at least a part of the unsaturated bond derived from the conjugated diene derivative with hydrogen in the presence of a catalyst, and the hydrogenation ratio is 10%. Or more, preferably 40
% Or more, more preferably 80% or more, and if the hydrogenation ratio is less than 10%, it is not preferable because the effect of improving impact resistance is insufficient, and in the hydrogenated block copolymer (D). The total amount of vinyl aromatic hydrocarbons is 70% by weight
Or less, preferably 60% by weight or less, more preferably 40% by weight or less.
It is less than or equal to weight%. The total amount of vinyl aromatic hydrocarbons is 70
If it exceeds 5% by weight, the heat shrinkage characteristics of the resin film may be shifted to the high temperature side, or it may be difficult to balance the heat shrinkage ratio and the heat shrinkage force, which is not preferable.

These hydrogenated block copolymers (D) can be used alone or in combination of two or more. In addition, (meth) acrylic acid, phthalic acid, fumaric acid,
Those obtained by modifying the hydrogenated block copolymer with itaconic acid, maleic anhydride or the like are also the hydrogenated block copolymer (D) of the present invention.
It is preferable that the amount of these modifiers is in the range of 0.5 to 10% by weight. As a modification method, an extruder is used to modify the modifier, a small amount of peroxide,
It can be obtained by a method such as melt-kneading it and the hydrogenated block copolymer at the same time. In the present invention, the addition of the hydrogenated block copolymer (D) is recognized to further improve the quality, and heat shrinkability, impact resistance, dimensional stability with time,
Good balance of practical physical properties such as mechanical strength and flexural strength after printing. At that time, the blending ratio of the hydrogenated block copolymer (D) is 1 to 25% by weight, preferably 2 to 15% by weight,
More preferably, it is 3 to 10% by weight, and if it is less than 1% by weight, the effect of addition is small, and if it exceeds 25% by weight, the transparency of the film becomes insufficient, which is not preferable.

The resin composition of the present invention contains general additives (plasticizers, petroleum resins, terpene resins, hydrogenated terpene resins, antistatic agents, lubricants, antifogging agents, inorganic fine powders, antioxidants). Agent, secondary antioxidant, colorant, etc.) may be mixed, and in particular, since the block copolymer (B) is a polymer that is relatively easy to gel, it is reported that this copolymer is effective. It is preferable to add a known stabilizer (for example, described in Japanese Patent Application No. 3-337479), and as disclosed in Japanese Patent Application Laid-Open No. 5-51503, hydrogenated terpene compounds are used. When 0.5 to 20% by weight of the resin is added, not only the film property anisotropy in the direction perpendicular to the main stretching direction but also the thermal stability is improved, and therefore addition of these is also preferable in the present invention. That is.

Next, the heat shrinkage characteristic which is the second constituent requirement of the present invention will be described. In order to provide the shrinkable label with optimum shrinkability as a heat-shrinkable film for packaging, the heat shrinkage in the main stretching direction is adjusted to 50% or more and the heat shrinkage in the orthogonal direction is adjusted to 20% or less. It is necessary to control the heat shrinkage ratios in the machine direction and the transverse direction within the range so that the performance as a heat shrinkable film (e.g., good shrink finish, no wrinkles, no printing) can be obtained. Characters will not be distorted, and will not shrink more than necessary in the vertical direction, resulting in poor appearance, etc.). In the present invention, the heat shrinkage ratio of the film in the main stretching direction is 50% or more, preferably 55% or more, more preferably 65% or more. If it is less than 50%, the fit of the film to the packaged object after heat shrinkage is insufficient, which is a problem in practice. Also, the heat shrinkage in the direction perpendicular to the direction is 20%
Or less, preferably 15% or less, more preferably 1
If it is less than 0, and if it exceeds 20%, curling of the edges at the time of shrinkage may cause the printed characters to be bent, and variations in finished dimensions may become large, causing defects. As described above, the present invention is an optimal heat-shrinkable film completed by using an anisotropically stretched resin film having a heat-shrinkability limited in the machine direction and the transverse direction. It is an important requirement to specify the heat shrinkage rate in two opposite directions.

In the present invention, as the optical characteristics of the resin film, the total light transmittance is 7 when the thickness is 50 μm.
It is necessary to be 0% or more, preferably 80% or more, more preferably 85% or more, and if less than 70%, the indication, characters, bar code, etc. printed on the back side due to lack of transparency may occur. It is not preferable because it is difficult to see effectively and the sharpness of printing is insufficient. Similarly, the thickness is 50
When h is, the haze is 20% or less, preferably 10% or less, more preferably 5% or less, and when the haze exceeds 20%, the backside printed indicia, characters or bar is displayed. It is not preferable because it is difficult to see the code effectively and the sharpness of printing is easily lost. The stretching in the present invention means uniaxial stretching or biaxial stretching, and equipment generally used for simultaneous biaxial or sequential biaxial, for example, tenter stretching method, bubble stretching method, roller. Stretching can be performed by using a stretch film forming equipment typified by a stretching method and the like, and film formation by any equipment is not limited to this. Further, the stretching temperature is generally 70 to 120 ° C., and may be appropriately selected depending on the resin composition. The resin film may be used as at least one layer of a multilayer film, In that case, it may be used as at least one layer of the same kind of multi-layer film or different kinds of multi-layer film, and in that case, 2, 3, 4, 5, 6, 7 layers and the like can be freely combined.

[0021]

EXAMPLES Next, the present invention will be described in more detail by way of examples, which should not be construed as limiting the invention thereto. In the following examples and comparative examples, various performance evaluations of films were carried out according to the following methods. Unless otherwise specified, the film is formed for 3 days at a temperature of 23 ° C. and a humidity of 50%.
Samples were left after being left in the atmosphere. (1) Shrink finish The performance as a shrink label is determined, and there are two methods of shrink as a heat medium, a steam method and a hot air method, and it was evaluated that the clean finish is the best in either method. Steam method: Using a steam-type shrink tunnel (total length 2m), the temperature inside the tunnel is 85 ° C, the transit time is 10 seconds,
A 1.5 liter PET bottle (a cylindrical kokeshi-shaped container having a maximum diameter of 91 mm and a height of 310 mm filled with water at 30 ° C.) formed into a tubular shape (folding width 148 mm,
The height of 90 mm) was set, and the finish of the shrinkability was judged for the one that passed through the tunnel and was shrunk. Hot-air method: Using a hot-air type shrink tunnel (total length 2 m), the temperature inside the tunnel was 125 ° C., the transit time was 10 seconds, and a 1.5-liter PET bottle (water filled at 30 ° C., maximum diameter 91 mm, A film (folding width 148 m) formed into a cylinder in a cylindrical kokeshi-shaped container with a height of 310 mm.
m, height 90 mm) was set, and the finish of the shrinkability was judged for those that passed through the tunnel and were shrunk. Judgment: ⊚: Good finish without wrinkles, tears, or positional displacement (shifting from a predetermined position). ◯: Slightly wrinkles were observed, and others were at the same level as ◎ above, and the product value was at the lower limit level. Δ: Occurrence of wrinkles and displacement were observed. X: The product has no commercial value because of poor wrinkles, tears, misalignment, vertical contraction, and distortion of printed characters.

(2) Fitting property Using the sample in the shrink test by the tunnel described in the preceding paragraph, the film set in the container is lightly rotated in the circumferential direction with the fingertip and the degree of the movement is observed. It is an important performance of the shrink label as well as the shrink finish. Judgment: ⊚: There is no space between the bottle and it does not rotate at all. ◯: Some are slightly spaced, but do not rotate. Δ: slightly rotated (within 2 mm) X: Loose and twirl. (3) The method for measuring the bending strength of the film was as follows: a film with a solid print on the back surface and a film without printing were used as samples, and the sheet was heat-sealed in a tubular shape with the back surface inside, in accordance with ASTM-D2176. Then, the bending strength in the direction perpendicular to the main stretching direction was measured with a load of 2 kg. (4) The falling weight impact strength of the film was measured according to ASTM-D1709. (5) The tensile elastic modulus of the film was measured according to ASTM-D882.

(6) Optical characteristics of film (total light transmittance, haze) The measuring method was based on ASTM-D1003. (7) Vicat softening temperature measurement method is based on ASTM-D1525, load 1
It was measured under the conditions of Kg / cm ² and temperature rising speed of 2 ° C./min. (8) Storage Shrinkage of Film The length L _{0 in} the main stretching direction and the length L ₁ in the main stretching direction after storage in an oven at 30 ° C. for 30 days were obtained, and the storage shrinkage of the film was calculated from this ratio. It was calculated and calculated by the formula (2).

[Formula 2] Storage shrinkage rate = {(L ₀ −L ₁ ) / L ₀ } ×
100 (2) (9) Comprehensive evaluation Based on the measurement and evaluation results of the above (1) to (8), comprehensive evaluation as a heat-shrinkable flume for shrink label was performed. The judgment criteria are as follows. Judgment: A: The best level. Especially excellent in quality. ◯: Practically good level. Δ: A level at which some problems occur in practical use. X: A level where practical problems remain.

Examples 1 and 2, Comparative Examples 1 and 2 As the copolymer (A), SBA-1 [styrene-butyl acrylate copolymer, styrene = 83% by weight, weight average molecular weight = 350,000, Vicat softening temperature = 75 ° C.] as block copolymer (B), SBBC-1 [B-S-B-S type styrene-butadiene block copolymer, molecular weight = 20]
10,000, styrene content = 70% by weight, MFI = 3 (200
C, 5 Kg), Vicat softening temperature = 82 ° C.] as a rubber-reinforced styrene polymer (C), HIPS-1 [styrene polymer, molecular weight = 250,000, rubber content = 9% by weight,
Rubber type = sterene-butadiene random copolymer (butadiene = 85%), average rubber particle size = 5.5 μ, crosslinking degree =
88%, MFI = 6 (210 ° C., 5 Kg), Vicat softening temperature = 94 ° C.] as a hydrogenated block copolymer (D), as HSB-1 [hydrogenated SBS type styrene-butadiene block copolymer]. Polymer, styrene content = 32% by weight, MFI = 8 (200 ° C., 5 Kg), specific gravity = 9.0]
In the mixed composition shown in Table 1, and the antioxidant [2-ter] was added to 100 parts by weight of the mixture.
-Butyl-6 (3-ter-butyl-2-hydroxy-
5-methylbenzyl) -4-methylphenylacryle
0.5 parts by weight of phosphorus, a phosphorus-based secondary antioxidant [tri (2.
4-di-ter-butyl) -phenylphosphite]
0.3 part by weight, an ultraviolet absorber [2- (2-hydroxy-3-ter-butyl-5-methylphenyl) -5-chlorobenzotriazole] in an amount of 0.25 part by weight, an antistatic agent [ Diglycerin monostearate] was added in an amount of 0.5 part by weight and blended well with a tumbler.

The mixture was melt-mixed with a 65 mmφ (L / D = 31) extruder at a temperature of 195 ° C. and extruded through a T die to form a uniform sheet. The sheet was stretched 1.15 times in the MD direction at a roll temperature of 95 ° C. using a roll stretching machine,
Using a tenter-stretching machine, the film was stretched 6.0 times in the TD direction at an oven temperature of 85 ° C. to obtain a 50 μm sequentially biaxially stretched film. An antistatic agent [SAT-5W: manufactured by Nippon Pure Chemical Co., Ltd.] was coated on the obtained film. The main stretching direction (TD) of the film obtained in Example 1 and the perpendicular direction (M
The heat shrinkage ratio of D) is TD direction = 75%, MD direction = 8%
And the optical characteristics of the film are: total light transmittance =
87% and haze = 1.2%. The main stretching direction (TD) of the film obtained in Example 2 and the perpendicular direction (MD)
Has a heat shrinkage of 71% in the TD and 6% in the MD, and the optical characteristics of the film are that the total light transmittance is 86%.
% And haze = 1.8%. Further, in Comparative Example 1, a sheet was obtained in the same manner as in Example 1, and this was MD-equipped with the same equipment.
After being stretched 2.1 times in the machine direction, it was stretched 6.0 times in the TD direction to obtain films having different heat shrinkages. The heat shrinkages of the obtained films were TD = 72% and MD = 24%. The optical characteristics of the film are: total light transmittance = 85
% And haze = 1.9%.

In Comparative Example 2, a sheet was obtained in the same manner as in Example 1, stretched 1.15 times in the MD direction and then stretched 3.5 times in the TD direction to obtain films having different heat shrinkage rates. The heat shrinkage of the obtained film was TD direction = 41%, MD direction = 7%, total light transmittance = 85%, haze = 2.
It was 0%. These Examples 1 and 2 and Comparative Examples 1 and 2
Various performances including shrink finish were evaluated for the film No. 1, and the results are summarized in Table 1. As shown in Table 1, the film on which the mixture was deposited had a too small heat shrinkage in the main stretching direction (Comparative Example 2), and a film having a too large heat shrinkage in the direction orthogonal to the main stretching direction ( In Comparative Example 1), the shrink finish was poor. On the other hand, those having an appropriate heat shrinkage (Example 1,
It was clearly recognized that 2) had various excellent properties including shrink finish. Further, as shown in Examples 1 and 2, when the hydrogenated block copolymer (D) is contained, it is recognized that the various properties of the film are excellent.

[0027]

[Table 1]

(Examples 3 to 7 and Comparative Examples 3 to 6) As (A), SBA-2 [styrene-butyl acrylate copolymer, styrene = 74% by weight, weight average molecular weight = 38
10,000, Vicat softening temperature = 61 ° C.], SBA-3 [styrene-butyl acrylate copolymer, styrene = 77 wt%, weight average molecular weight = 250,000, Vicat softening temperature = 68
C.], SBA-4 [styrene-ethyl acrylate copolymer, styrene = 80% by weight, weight average molecular weight = 21
10,000, Vicat softening temperature = 72 ° C.], SBA-5 [styrene-methyl acrylate copolymer, styrene = 87 wt%, weight average molecular weight = 320,000, Vicat softening temperature = 83
C.], SBA-6 [styrene-butyl acrylate copolymer, styrene = 96% by weight, weight average molecular weight = 32
Vicat softening temperature = 98 ° C.] as (B)
BBC-2 [B-S-B-S type styrene-butadiene block copolymer, molecular weight = 250,000, contained styrene amount = 8
0 wt%, MFI = 5 (200 ° C., 5 Kg), Vicat softening temperature = 85 ° C.], SBBC-3 [B—S—B—S type styrene-butadiene block copolymer, molecular weight = 28
10,000, styrene content = 85% by weight, MFI = 8 (200
℃, 5Kg), Vicat softening temperature = 89 ℃],

As (C), HIPS-2 [styrene-
Butyl acrylate copolymer, styrene = 95% by weight,
Molecular weight = 250,000, rubber content = 10% by weight, average rubber particle size = 3.8 μ, crosslinking degree = 90%, rubber type = sterene-butadiene random copolymer (butadiene = 90% by weight), MFI = 8 ( 210 ° C., 5 Kg), Vicat softening temperature = 96 ° C.], HIPS-3 [styrene-cyclohexyl acrylate copolymer, styrene = 95 wt%, molecular weight = 220,000, rubber content = 12 wt%, average rubber Particle size = 4.6 μ, degree of cross-linking = 88%, rubber type = sterene-butadiene block copolymer (butadiene = 70 wt%),
MFI = 5 (210 ° C., 5 Kg), Vicat softening temperature =
98 ° C.], HIPS-4 [styrene-methyl methacrylate copolymer, styrene = 92% by weight, molecular weight = 20
10,000, rubber content = 10% by weight, average rubber particle size = 6.0
μ, degree of crosslinking = 92%, rubber type = sterene-butadiene block copolymer (butadiene = 85% by weight), MFI =
4 (210 ° C, 5Kg), Vicat softening temperature = 98
C.], HIPS-5 [styrene-methyl acrylate copolymer, styrene = 92% by weight, molecular weight = 280,000, rubber content = 10% by weight, average rubber particle size = 4.5 .mu., Crosslinking degree = 96%, Rubber type = sterene-butadiene block copolymer (butadiene = 70% by weight), MFI = 7 (210
℃, 5Kg), Vicat softening temperature = 96 ℃], HIPS
-6 [styrene-butyl acrylate copolymer, styrene = 95% by weight, molecular weight = 250,000, rubber content = 10% by weight, average rubber particle size = 1.2 μ, crosslinking degree = 90%, rubber type = sterene -Butadiene random copolymer (butadiene = 90% by weight), MFI = 6 (210 ° C, 5 Kg),
Vicat softening temperature = 95 ° C.], HIPS-7 [styrene polymer, molecular weight = 220,000, rubber content = 10% by weight, average rubber particle size = 4.2 μ, crosslinking degree = 40%, rubber type = sterene-butadiene Random copolymer (butadiene = 90
% By weight, MFI = 8 (210 ° C., 5 Kg), Vicat softening temperature = 95 ° C.],

As (D), HSB-2 [hydrogenated S-
B-S type styrene-butadiene block copolymer, styrene content = 28% by weight, MFR = 7 (200 ° C., 5K
g), specific gravity = 9.2], HSB-3 [hydrogenated SB-
S-type styrene-butadiene block copolymer, styrene content = 40% by weight, MFR = 9 (200 ° C., 5K
g), specific gravity = 9.3], respectively, in the mixed composition shown in Table 2, and 100 parts by weight of the total of this resin mixture is mixed with 0% of an antioxidant [Sumilyzer-GS: Sumitomo Chemical Co., Ltd.]. 0.5 parts by weight, 0.2 parts by weight of a phosphorus-based secondary antioxidant [Ultranox 626], and a light stabilizer [SANOL LS77].
0] of 0.25 parts by weight and an antistatic agent [dihydroxyethylalkylamine] of 0.2 parts by weight were added and well blended with a tumbler.

The mixture was melt-mixed with a 65 mmφ (L / D = 31) extruder at a temperature of 200 ° C. and extruded from a T die to form a uniform sheet. The sheet was sequentially biaxially stretched to obtain a stretched film of 50 μm in the same manner as in Example 1. An antistatic agent [SAT-5W: manufactured by Nippon Pure Chemical Co., Ltd.] was coated on the obtained film. With respect to these films, various performances including shrink finish were evaluated. The results are summarized in Table-3. As shown in Table-2 and Table-3, the type of resin and the mixing composition ratio are appropriately selected within the range of the present invention, and the heat shrinkage rate of the film formed is within the range of the present invention. It was extremely excellent in properties. On the other hand, when the rubber-reinforced styrene-based polymer (C) was used in which the dispersed particles had a too small rubber particle diameter (Comparative Example 4), the bending resistance and falling weight impact strength of the film were weak. This causes cracks or tears in the bent portion in practical use, and particularly the printed film has further weaker bending resistance and is practically difficult to use. Further, when the dispersed particles having too small a rubber cross-linking degree were used (Comparative Example 5), the bending resistance and falling weight impact strength of the film were weak as in Comparative Example 4. Further, when a large amount of the rubber-reinforced styrene polymer (C) was used (Comparative Example 6),
The optical characteristics are poor and the back-printed display is difficult to see, resulting in poor appearance in practical use, and the printing surface is limited to the front side, making it unsuitable for the application.

[0032]

[Table 2]

[0033]

[Table 3]

(Examples 8 to 9 and Comparative Examples 7 to 10) The mixed compositions shown in Table 4 were used, and the antioxidant [2-ter-butyl-6 (was added to 100 parts by weight of this resin mixture in total. 3'-ter-butyl-5'-methyl-2'-hydroxybenzyl) -4-methylphenylacryle-
0.5 parts by weight of phosphorus, a phosphorus-based secondary antioxidant [tri (2.
4-di-ter-butyl) -phenylphosphite]
Was added in an amount of 0.3 parts by weight, and an antistatic agent [diglycerin monostearate] was added in an amount of 0.5 parts by weight, and the mixture was blended well with a tumbler. The mixture was melt-mixed with a 65 mmφ (L / D = 31) extruder at a temperature of 195 ° C. and extruded from a T die to form a uniform sheet. A 60 μ stretched film was obtained from the sheet in the same manner as in Example 1 by using a roll stretching machine.
With respect to these films, various performances including shrink finish were evaluated. The results are summarized in Table-5.
It was shown to. As shown in Table 4 and Table 5, the heat shrinkage ratio of the formed film in the direction perpendicular to the main stretching direction is within the range of the present invention, and the type of resin and the mixture composition ratio are within the range of the present invention. It is found that the effect of the present invention is remarkably exerted when it is within the range, while on the other hand, when the heat shrinkage ratio in the direction orthogonal to the main stretching direction is out of the range of the present invention, the type of resin and the mixed composition Even if the ratio is within the range of the present invention, it is clear that the heat shrinkable shrink film does not exhibit important properties due to the lack of heat shrinkage properties.

[0035]

[Table 4]

[0036]

[Table 5]

[0037]

As described in detail above, in the heat-shrinkable film of the present invention, the specific copolymer (A) (B) or (A) (B) (D) is limited to a specific composition ratio. In addition, since it contains a specific amount of specific crosslinkable rubber particles having a limited average particle diameter and a limited degree of crosslinking by blending (C) therein, the anisotropic stretched film has greatly different stretching ratios in the length and width directions. The tear strength in the low stretching direction which is likely to occur is improved, and a resin film having this composition having specific heat-shrinking properties and optical properties, workability as a shrink film for packaging, strength, storability, It was discovered that it has an excellent appearance, and it has been provided here.

Front page continuation (58) Fields surveyed (Int.Cl. ⁷ , DB name) C08J 5/00-5/24 C08L 1/00-101/16

Claims (2)

(57) [Claims] 1. A resin film containing a resin composition comprising the following (A), (B) and (C) as an essential component, which is mainly stretched under a heating condition having a heat shrinkage rate of 85 ° C. and 10 seconds. 50% or more in the direction and 20 in the direction perpendicular to the main stretching direction.
% Or less, total light transmittance is 70% when the thickness is 50μ
The transparent heat-shrinkable film characterized by the above. (A) A copolymer of vinyl aromatic hydrocarbon and aliphatic unsaturated carboxylic acid ester having a Vicat softening temperature of 9
The temperature is 0 ° C or lower and the content of vinyl aromatic hydrocarbon is 95.
˜20 wt% copolymer 10-89.5 wt% (B) Block copolymer 89.5 comprising a vinyl aromatic hydrocarbon-based polymer block and a conjugated diene-based polymer block. 10% by weight (C) A rubber-modified styrene polymer containing a rubber-like polymer as dispersed particles, wherein the dispersed particles have a particle diameter of 2 to 10
0.5-30% by weight of a rubber-modified styrene-based polymer which is a cross-linked graft rubber having a cross-linking degree of 65% or more 2. A resin film comprising a resin composition comprising the following (A), (B), (C) and (D) as an essential component, which has a thermal shrinkage of 85 ° C. and a heating condition of 10 seconds. And 50% or more in the main stretching direction, 20% or less in the direction orthogonal to the main stretching direction, and the total light transmittance is 70% or more when the thickness is 50 μm. . (A) A copolymer of vinyl aromatic hydrocarbon and aliphatic unsaturated carboxylic acid ester having a Vicat softening temperature of 9
The temperature is 0 ° C or lower and the content of vinyl aromatic hydrocarbon is 95.
Copolymer consisting of 20 to 20% by weight 10 to 88.5% by weight (B) Block copolymer consisting of a polymer block mainly composed of vinyl aromatic hydrocarbon and a polymer block mainly composed of conjugated diene 88.5 10% by weight (C) A rubber-modified styrene polymer containing a rubber-like polymer as dispersed particles, wherein the dispersed particles have a particle diameter of 2 to 10
0.5-30% by weight of a rubber-modified styrenic polymer which is a cross-linked graft rubber having a cross-linking degree of 65% or more (D) A polymer block mainly composed of vinyl aromatic hydrocarbon and a conjugated diene 1-25% by weight of a hydrogenated block copolymer obtained by hydrogenating at least a part of an unsaturated bond structure derived from a conjugated diene of a block copolymer composed of polymer blocks.