JP3270503B2 - Heat shrinkable hard film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is mainly used for packaging materials and the like, and is particularly useful in impact resistance, stability over time (decrease in dimensions and physical resistance), mechanical strength, waist strength, transparency, shrinkage. The present invention relates to a hard heat-shrinkable film using a special vinyl aromatic copolymer composition having excellent properties.

[0002]

2. Description of the Related Art Conventionally, as a heat-shrinkable film for general packaging in the field of hard films, hard vinyl chloride (PVC) films, polyester (PET) films, styrene films and the like are generally known. Rigid PVC films have a problem of global environment due to a problem of pollution due to chlorine-based gas generated at the time of incineration, in addition to problems of hygiene and quality (whitening phenomenon in warm water, etc.) due to the use of a plasticizer. The solution is still not enough. Recently, PET films are hygienic, or cleanliness of the above problems at the time of incineration,
It has begun to be used due to its low heat of combustion, but amorphous copolymers are expensive and the technology for amorphizing crystalline resins is not sufficient. There is a problem with sex. Therefore, there is a problem that the delicate behavior characteristics required at the time of heat shrinkage fluctuate, and the heat shrinkable film for packaging lacks stability.

[0003] Stretched styrene films include polystyrene (GPPS) or polystyrene (H) containing a graft copolymer of styrene (S) and butadiene rubber (BR).
IPS), a block copolymer of a styrene block and a butadiene block (SBBC), a film composed of a blend composition containing at least one of these, and the like. First, GPPS film
Vicat softening point (AS called VSP)
(Measured at a load of 1 kg according to the TM-D1525 method at a heating rate of 20 ° C./min) is relatively high at 100 to 106 ° C., so that the heat shrinkage onset temperature becomes high, and the shrinkage at low temperatures is poor. It is brittle and easy to tear, and in applications where the film is folded and used, the bent part is cut off.
And other problems. Next, the HIPS film is G
Although the brittleness and low-temperature shrinkage of PPS have been improved, the quality is not yet sufficient due to poor transparency and a problem of spontaneous shrinkage of dimensions in addition to poor transparency (Japanese Unexamined Patent Publication No. Sho 60-4).
No. 8325). SB with improved transparency of the HIPS
BC also improves low-temperature shrinkage, but has the problem of gelling in rework during extrusion. In addition, the stiffness of the film is further weakened, and in addition, the natural shrinkage of the dimensions and the deterioration of physical properties are greatly increased. For these reasons, the mechanical suitability and mounting suitability during use are significantly deteriorated, and the performance as a hard shrinkable film Is not enough to satisfy SBBC and PS
Blend film with SBBC film
-30705 and JP-A-60-6414), the effect of improving waist is seen, but there remains a problem in that the low-temperature shrinkage, impact strength and transparency are reduced.

[0004] In order to improve these, proposals have been made for films such as a mixture composition of SBBC and a copolymer of vinyl aromatic hydrocarbon and an alkyl ester of an aliphatic unsaturated carboxylic acid (for example, butyl acrylate). There is (Tokuhei 3-
No. 12535, Japanese Patent Publication No. 3-18813). These films are generally superior to any of the above-mentioned films in terms of transparency, low-temperature shrinkage, stiffness, dimensional shrinkage, brittleness, etc. There is difficulty in sex . This is, for example, because the film may be cut off in such a way as to be used suddenly (pulling) by a machine, so that it is not at a practically complete level yet. In addition, since there is a problem that the elongation (tensile elongation) of the film decreases with time and a decrease in mechanical strength in a printing process, improvement of these qualities is required.

[0005]

As described above, the main problem is the occurrence of film breakage due to a tensile impact when the hard heat-shrinkable film is mounted on a packaging machine, followed by finishing in a shrink tunnel. Wrinkles, misalignment, tears, etc. The present invention has been intensively studied to solve the above-mentioned drawbacks, and as a result, to obtain a film which is firm and has excellent low-temperature shrinkage, impact resistance, and other properties (eg, mechanical strength, transparency, etc.). A specific styrene-based resin composition is developed, and the styrene-based resin composition is stretched and formed as appropriate to provide a film having a specific range of heat shrinkage.

[0006]

The gist of the requirements of the present invention is as follows.
The first is to use a mixed composition in which a specific copolymer (A) described later, the copolymer (B) and the polymer (C) are blended in a predetermined ratio, and the second is that the mixed This is to adjust the heat shrink force of the stretched film of the composition to a predetermined value. By satisfying these two requirements, the present invention having excellent shrink properties and quality stability has been completed.

That is, a vinyl aromatic hydrocarbon;
(A ₁ ) acrylic acid, (a ₂ ) alcohol having C _{1 to} C ₁₂ carbon atoms
(A ₃ ) methacrylate
Acrylic acid, (a ₄₎ alcohols and main carbon number C ₁ -C ₁₂
Ester derivative with tacrylic acid, (a ₅ ) α, β unsaturated
Sum dicarboxylic acid, or (a ₆ )
And at least one aliphatic unsaturated carboxylic acid derivative selected from the monomers are mono or diester derivatives <br/> of alcohols of C ₂ -C _12, in the copolymer, the Vicat softening point 105 5 to 95% by weight of the copolymer (A) not exceeding ℃, at least one polymer block mainly composed of vinyl aromatic hydrocarbon, and a polymer mainly composed of at least one conjugated diene derivative A mixed composition mainly comprising 5 to 95% by weight of a copolymer (B) composed of blocks, or alternatively, the copolymer (A) is used in the same amount in the mixed composition. Is a copolymer mainly composed of a polymer block obtained by hydrogenating at least a part of an unsaturated bond derived from a conjugated diene of the block copolymer (B), or 4 to 94% by weight of the block copolymer (B), or carboxylic acid-modified copolymer weight of polymer (B) Body, or the block copolymer of (B) 1
Part of the carboxylic acid-modified copolymer of the block copolymer (B) or a part of the carboxylic acid-modified copolymer of the block copolymer (B) hydrogenated, or methyl methacrylate- A film stretched at least uniaxially, comprising a mixed composition mainly composed of 1 to 30% by weight of at least one polymer (C) selected from a butadiene-styrene-based copolymer or a polyester-based polymer. A heat shrink force of at least 151 to 800 g / m in the main stretching direction
m ² , and the heat contraction force in the direction perpendicular to the above direction is 5 to 150.
g / mm ² , the main problem of the hard heat-shrinkable film is that the film breaks due to a tensile impact when mounted on a packaging machine, and the wrinkles and positions in the finished state in a shrink tunnel. It has been found that displacement, breakage and the like do not occur.

Hereinafter, the present invention will be described in detail. First, the resin and the mixed composition which are the first components of the present invention will be described. The copolymer (A) used in the present invention is:
A copolymer of a vinyl aromatic hydrocarbon and an aliphatic carboxylic acid alkyl ester or at least one aliphatic unsaturated carboxylic acid derivative selected from monomers in which a part thereof is a carboxylic acid; Softening point (hereinafter VSP
) Represents the copolymer component not exceeding 105 ° C. The copolymer is a component important for the present invention because the shrinkability temperature as a heat-shrinkable film can be arbitrarily controlled by appropriately adjusting the type of the monomer used for the copolymer and the copolymerization ratio. is there. Since the copolymer has a hard and brittle property contrary to this important property, a block polymer (B) described later is blended, or a polymer (C) described later is blended in addition thereto. Thereby, the excellent performance described later is exhibited. The blending ratio of the copolymer (A) is 5 to 95% by weight, preferably 20 to 80% by weight, and more preferably 30 to 70% by weight. If it is less than 5% by weight, the effect of addition is not exhibited, which is not preferable.
If it exceeds 5% by weight, the film becomes hard and brittle, which makes it practically difficult to use.

The copolymer (A) is, for example, a styrene-butyl acrylate copolymer (referred to as SBA).
There is. Depending on the ratio of styrene and butyl acrylate, the copolymer can be obtained in a wide range of VSP from -55 ° C to 105 ° C. However, when emphasis is placed on shrinkage at low temperatures, for example, VSP 72 ° C (butyl acrylate (hereinafter referred to as BA)). ) Of about 18% by weight) is preferable, and when shrinkability at a relatively high temperature is required, for example, V
An SP of about 91 ° C. (BA content of about 10% by weight) is good, and in practice, it is preferable to select an optimum VSP according to use conditions. Generally, the VSP is preferably 105 ° C. or lower, more preferably 100 ° C. or lower, still more preferably 95 ° C. or lower, and most preferably 90 ° C. or lower. Here, the lower limit of the VSP is not shown because it differs depending on the type and the mixing amount of the other component (B). It becomes impractical due to dimensional changes and reduction in shrinkage during storage of the product at room temperature when used or when used in large quantities. VSP is preferably 40 ° C. or higher, more preferably 50 ° C. or higher (generally common). This applies when the amount of the polymer (A) is 40% by weight or more). When the amount of the copolymer is less than 40% by weight and not less than 5% by weight, the above-mentioned copolymer is not limited to the above-mentioned one, and the level of the plasticizer, that is, VSP is -55.
° C or more, preferably -30 ° C or more, more preferably -1
Those having a temperature of 0 ° C. or higher may be used.

In the copolymer, for example, a metal salt with acrylic acid or the like is used as a source of ionic crosslinking during polymerization in an amount of 0.01 to 5.0.
By adding in the range of weight%, the viscosity of the resin may be appropriately adjusted to improve the stretchability in film formation or the physical properties of the film. In this case, if the amount of the ionic crosslinking source exceeds 5.0% by weight, the fluidity of the resin is remarkably deteriorated, which is not preferable. Further, the copolymer may be ionomerized later, or may be ionized obliquely in the film surface layer or the thickness direction.

The preferred molecular weight of the copolymer is in the range of 50,000 to 600,000, more preferably 100,000 to 500,000, and still more preferably 200,000 to 450,000. When the molecular weight exceeds 600,000, a film with little deterioration in physical properties over time can be obtained, but the fluidity of the resin at the time of melting deteriorates and the compatibility with the other copolymer (A) shown in the present invention is deteriorated. It is not preferable because it lowers. On the other hand, if it is less than 50,000, the heat shrink force decreases with time, which is not preferable.

More specifically, the vinyl aromatic hydrocarbon used for the copolymer (A) in the film of the present invention mainly means a styrene monomer, specifically, styrene, α- Alkyl-substituted styrenes, for example, α-methylstyrenes, nucleated alkyl-substituted styrenes, nucleated halogen-substituted styrenes, etc., may be selected at least one suitable for the purpose.

The aliphatic unsaturated carboxylic acid derivative used for the copolymer (A) includes (a ₁ ) acrylic acid,
(A ₂ ) Alcohol having carbon number C _{1 to} C _12, preferably C _{2 to} C ₁₂ , such as methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, pentyl acrylate, hexyl acrylate, etc., and acrylic acid ester derivatives or, (a ₃₎ methacrylic acid or similarly,
(A ₄₎ the ester derivative of the number of C ₁ -C ₁₂ preferably carbon and C ₂ -C _12, more preferably alcohols and methacrylic acid C ₃ -C ₁₂ Further, (a ₅₎ α, β-unsaturated dicarboxylic acid , such as fumaric acid, itaconic acid, maleic acid, or <br/> others are those selected at least one mono or diester derivatives of the alcohols (a ₆₎ these dicarboxylic acids with C ₂ -C _12. These are generally those mainly composed of the esters, and the amount thereof is preferably at least 50 mol%, more preferably at least 70 mol%. Further, the type thereof is preferably those mainly composed of esters such as ethyl acrylate, propyl acrylate, butyl acrylate, hexyl acrylate and octyl acrylate. Further, a component containing at least one monomer having a glass transition point (Tg) of about 0 ° C. or lower, preferably −10 ° C. or lower in a single polymer of each of these esters, and a copolymer of styrene and Polymers are more preferred. Even when a styrene derivative component or a carboxylic acid derivative having a high Tg is used, as a result, two or three components in which the properties of another monomer having a low Tg of the copolymer are excellent. Above, 4 in some cases
If the alcohol of the ester is C ₁ (particularly methyl methacrylate), the mixed aliphatic unsaturated carboxylic acid derivative or the styrenic component may be copolymerized. multicomponent copolymers, including those of the same number of C ₂ or more carbon atoms at the same time is preferable. Further, a diene-based monomer may be further copolymerized thereto, or at least a part of a diene-based portion of these copolymers may be hydrogenated. Of various matrices in the form of a so-called graft copolymer using a polymer containing at least one part of a diene-based rubber (average diameter: 0.01 to 10 μm, including so-called matrix incorporation, salami structure, etc.) What is called transparent high impact (HI) containing is more preferable. These include, for example, a styrene-butyl acrylate-methyl methacrylate-diene-containing rubber-based polymer (including a graft portion), a copolymer, or a general HI formulation. In addition, a copolymer having at least one part of a part mainly composed of a styrene component and having at least one part of a part mainly composed of the unsaturated carboxylic acid component, or the other part is a styrene component or A copolymer of the above-mentioned free combination having a random portion with a carboxylic acid component may be used.

Alternatively, a random copolymer of the styrene-based component and the carboxylic acid-based component, or a block copolymer of both components, or one of which is random and the other is a block copolymer, or Such a block-like portion is a tapered polymer of both components, and the like, and further includes a free position of the free polymer main chain (at least one terminal portion, at least one terminal portion of the polymer or segment portion). Two central portions, etc.), a hydrocarbon group having ₁ to ₂₂ carbon atoms (for example, at least one hydrocarbon group such as an alkyl group or a cyclohexane structure).
Is preferable in terms of various strength characteristics. These may be obtained by adding a polymerization catalyst residue, a chain transfer agent residue, or a specific compound during polymerization. For the former, for example, a known peroxide catalyst is freely selected from monofunctional catalysts or at least one of more functional 2, 3, 4, 5,... Functional catalysts. Examples of polyfunctional compounds include those having a tetrafunctional ketol structure having a cyclohexane ring. Further, a chain transfer agent may be additionally used, such as n-butyl mercaptan or n-butyl mercaptan.
Dodecyl mercaptan and the like.

Next, the block copolymer (B) used in the present invention comprises a polymer block composed of at least one vinyl aromatic hydrocarbon and a block mainly composed of at least one conjugated diene derivative. Is a block copolymer. The block copolymer (B) can be arbitrarily controlled in flexibility, toughness, shrinking suitability temperature and the like as a heat-shrinkable film by appropriately adjusting the ratio or the same molecular weight of the blocks used in the copolymer. ,
It is an essential component of the present invention. The block copolymer has another important property that complements this important property and the brittle property of the copolymer (A). Since it has a property lacking in stiffness, excellent performance is exhibited by blending it with the above-mentioned copolymer (A) or further blending it with a polymer (C) described later. The blending ratio of the block copolymer (B) is 5 to 95% by weight when blended with the copolymer (A) (4 to 94% by weight when further blending the polymer (C)). )
Preferably from 20 to 80% by weight, more preferably from 30 to 7% by weight.
0% by weight is good. Less than 5% by weight (4% by weight in the case of a ternary composition of copolymer (A), copolymer (B) and weight (C)
) Is not preferable because the addition effect is not exhibited.
If it exceeds 5% by weight (94% by weight when the copolymer (A), the copolymer (B) and the weight (C) are blended), the film hardness (hip strength), low-temperature shrinkage, dimensions It is difficult to use in practice because it lacks stability.

The block copolymer (B) is, for example, a styrene-butadiene-block copolymer (SBB).
C). The vinyl aromatic hydrocarbon may be at least one selected from the same group as that used for the above-mentioned copolymer (A), and the main component is the conjugated diene as another component. Is the conjugate 2
Examples of olefins having a heavy bond include 1,3-butadiene, 2-methyl-1,3-butadiene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene,
1,3-hexadiene and the like may be used by selecting at least one appropriate one from these groups. 1,
Preferred examples include 3-butadiene, 2-methyl-1,3-butadiene, isoprene, chloroprene and the like. Further, if it does not matter, it may be further copolymerized with another monomer.

The SBBC used in the present invention has roughly three or more types of structures. For example, a perfect linear type (for example, BSBS, SBS, etc.) is one example.
In this case, B represents a butadiene-based block, and S represents a styrene-based block.) There are various types such as a branch type, a radial type, and other combination types, and any type of SBBC may be used. The total amount of diene in the SBBC is 5 to 90% by weight, preferably 10 to 80% by weight, more preferably 15% by weight.
The content is preferably from 70 to 70% by weight, more preferably from 30 to 50% by weight. If the total amount of diene is less than 5% by weight, the toughness of the film will be insufficient, and if it exceeds 90%, the film will not be rigid, which is not preferable. In addition, two or more of these having different amounts of diene may be blended. Either or both of the blocks may freely contain the other component in a random or tapered shape inside the block. S
The molecular weight of BBC is 10,000 to 10 in weight average molecular weight.
0,000, preferably 30,000-800,000, more preferably 10-
600,000 are suitable. These may contain at least one polymer having different molecular weights. If the molecular weight is less than 10,000, the mechanical strength of the film is insufficient, and if it exceeds 1,000,000, the dispersibility with the copolymer (B) of the present invention deteriorates and the extrudability deteriorates, resulting in a uniform film. Is difficult to obtain.

Next, the polymer (C) used in the present invention comprises at least one polymer block comprising a vinyl aromatic hydrocarbon and at least one unsaturated bond portion derived from a conjugated diene. At least one polymer selected from a copolymer mainly composed of a polymer block whose part has been hydrogenated, or a carboxylic acid-modified copolymer of the copolymer (B), or a block copolymer ( A carboxylic acid-modified copolymer of a block copolymer obtained by hydrogenating one part of B), or a copolymer obtained by hydrogenating one part of a carboxylic acid-modified copolymer of block copolymer (B), or It represents at least one polymer selected from methyl methacrylate-butadiene-styrene copolymer, polyester (especially low-crystalline or amorphous polyester copolymer), and the like. The polymer (C) is added to the blend of the copolymer (A) and the block copolymer (B) described above, whereby
Improving the compatibility of the two components, further improving the toughness, tensile elongation, and bending strength of the film, improving the strength particularly derived from the low orientation direction, and suppressing the deterioration over time of the physical properties. Since it has an effect, it is an important component for the present invention, and excellent performance is exhibited by its blending. The compounding ratio of the polymer (C) is 1 to 30% by weight, preferably 2 to 20% by weight, and more preferably 3 to 10% by weight. If it is less than 1% by weight, there is no effect of addition and 30
Exceeding the weight% is not preferred because the transparency of the film is reduced.

Examples of the polymer (C) include a saturated styrene-based thermoplastic elastomer (hereinafter referred to as TPS). The vinyl aromatic hydrocarbon may be at least one selected from the same group as that used for the copolymer (A) described above, and the other conjugated diene component is It means at least one selected from the same group as that of the conjugated diene component used in the copolymer (B). The hydrogenated polymer refers to a polymer obtained by reacting at least a part of the unsaturated bond derived from the conjugated diene with hydrogen or the like by a catalyst, and the like, and does not include a polymer having a reactive functional group. Or any of them. The hydrogenation ratio of the conjugated diene is 10% or more, preferably 40% or more, and more preferably 80% or more. When the hydrogenation ratio is less than 10%, there is no difference in performance with SBBC, and particularly, the effect of improving the bending strength of the film is not seen when a small amount is added, which is not preferable. The total amount of styrene in TPS is 70% by weight or less, preferably 60% by weight.
Below, more preferably 50% by weight or less is good. If the total amount of styrene exceeds 70% by weight, the film becomes hard and brittle, and the heat shrinkage characteristic shifts to the high temperature side, and the heat shrinkage becomes too high, so that it is extremely difficult to adjust the heat shrinkage of the film. It is not preferable because of problems such as These polymers can be used alone or in combination of at least two or more polymers. The carboxylic acid-modified copolymer refers to the above-mentioned SBBC or hydrogenated S
Acrylic acid, phthalic acid, fumaric acid, itaconic acid, maleic acid, methacrylic acid...
% By weight graft copolymer.

As described in detail above, the present invention also relates to at least two types of copolymer (A) and copolymer (B), or at least copolymer (A) and copolymer (B). The requirement is to use a composition in which the three kinds of components or the mixture of the coalesced (C) are mixed at a prescribed blending ratio, but the present invention is not limited to this. For example, a general additive used for a film (Plasticizers, petroleum resins, antistatic agents, lubricants, antifogging agents, inorganic fine powder, antioxidants, coloring agents, etc.) may be mixed.

In particular, as an antioxidant, a phenolic or phenolic acrylate [for example: 2-tert-butyl-6 (3'-tert-butyl-5'-methyl-2'-)
(Hydroxybenzyl) -4-methylphenyl acrylate and derivatives thereof]. More preferably, a phosphorus-based antioxidant (eg, tri (2,4-di-tert-butyl) -phenylphosphite, tri (4-nonyl) -phenylphosphite, etc.) is used in addition to the above compounds. good. In addition to the above two types, it is often preferable to add a sulfur-containing antioxidant. These may be used alone or in any combination. The amount of each of the antioxidants was 0.01 to 100 parts by weight of the mixed resin.
To 10.0 parts by weight, preferably 0.05 to 5.0 parts by weight, more preferably 0.10 to 4.0 parts by weight, even more preferably 0.15 to 3.0 parts by weight. If the amount is less than 0.01 part by weight, thermal deterioration of the resin (for example, crosslinking or molecular weight reduction).
When the amount exceeds 10.0 parts by weight, some problems (for example, poor dispersion, decrease in film strength, decrease in transparency, high cost, etc.) occur, which is not preferable.

Next, it is preferable to use an amine type or an amide type antistatic agent. For example, as the amine type, hydroxyethylalkylamine and its derivatives are used, and as the amide type, hydroxyethyl fatty acid amide and its derivatives are used. The amount of antistatic agent added is
0.1 to 10 parts by weight, preferably 0.2 to 5 parts by weight, more preferably 0.4 to 3.0 parts by weight per 100 parts by weight of the resin.
Parts by weight. If the amount is less than 0.1 part by weight, the antistatic effect is difficult to appear. If the amount exceeds 10 parts by weight, the gloss of the film surface is lost, the aesthetic appearance is deteriorated, and the printability of the film is unfavorably deteriorated. In addition, as a plasticizer, DOP,
Acid esters such as DOA, ATBC and DBS, and liquid paraffins such as MO may be added in an amount of 0.5 to 10% by weight, preferably 1 to 5% by weight.

Next, the heat shrinkage characteristic, which is the second component of the present invention, will be described. The heat shrinkage force of a stretched film made of the mixed composition of the present invention is measured according to ASTM-D2838, and the condition is a peak value which is expressed by immersion in a 100 ° C. silicone bath (the peak value is expressed). If not, the value is expressed in 30 seconds.) In order to give the shrink label or the like an optimal shrinkage as a heat shrinkable film for packaging, the heat shrinkage force in the main stretching direction is 151 to 800 g.
/ Mm ² , the heat shrink force in the direction perpendicular to the direction is 5 to 150 g / m 2
it is necessary that it is adjusted respectively to m ^2. These heat shrink forces, for example, by controlling the longitudinal direction and the lateral direction within the above range, the performance as a heat shrink film, for example, shrink finish, vertical cut resistance, etc. are significantly improved and satisfactory heat shrink film. Is obtained. To explain as an example, the heat shrinkage force in the main stretching direction, for example, the main shrinking direction as the horizontal direction is 151 to 800 g.
/ Mm ² , preferably 200 to 550 g / mm ² , more preferably 250 to 450 g / mm ² . 1
If it is less than 51 g / mm ² , there is a problem in practical use due to poor fit of the film to the package after heat shrinkage, and there is a practical problem.
If it exceeds 00 g / mm ² , another problem, for example, spontaneous shrinkage due to the aging of the film dimensions increases, giving rise to problems such as insufficient dimensions, poor flatness after aging of the rolls, etc. There is a problem that becomes difficult. The heat contraction force in the direction perpendicular to the direction is, for example, the heat contraction force in the vertical direction is 5
１５０150 g / mm ² , preferably 10-100 g / mm
² , more preferably 15 to 80 g / mm ² . If it is less than 5 g / mm ^2, strict requirements shrinkage balance of vertically and horizontally, preferably no, and 150 g / mm ² to more than the example shrink label because it may over time elongation decrease occurs that vertical cutting when the result packaging frequently In applications that are used, the finished dimension width is short, the end part is curled at the time of contraction, the film comes off from the packaged object,
Problems such as shrinking of a portion that the user does not want to shrink and bending of the film occur, which results in poor finish, which is not preferable. In this example, the direction in which the heat shrinking force is larger is described as the horizontal direction, but may be performed in the vertical direction. As described above, the present invention provides an optimal heat-shrinkable film by appropriately controlling the heat-shrinkage force of at least a uniaxially stretched film so that the other corresponds to one level in the main stretching direction and the direction perpendicular to the main stretching direction. It is an important requirement to satisfy both ranges of the heat shrinkage force in the two opposing directions.

As described in detail above, by satisfying the two requirements of the present invention, for example, by giving an example, that is, by defining the heat shrinkage force of the mixed composition and the film in the respective ranges, the problem has been solved so far. As a result, the heat-shrinkable film was not cut by the tensile impact of the packaging machine, and wrinkles, slippage, breakage, and the like were eliminated by the finish in the shrink tunnel.

The heat shrinkage of the film at 80 ° C. (the value after 10 seconds in a hot water bath) is as follows:
Preferably 15-75%, more preferably 25-70%
%, More preferably 30 to 65% or more, and 0 to 50%, preferably 0 to 35%, more preferably 0 to
~ 25%. The heat shrinkage at 100 ° C (100 ° C
Value after 10 seconds in an oil bath)
90%, preferably 20 to 80%, and the right angle direction is 0 to
It is 80%, preferably 1 to 70%.

Since the heat shrinkage rate directly affects the quality of the shrinkable film, the shrinkage of the warp and the width of the shrinkable film depends on the object to be shrinked or the shrinking conditions (eg, heat medium, temperature, time, heating method, etc.). Choose the balance appropriately. Therefore, the heat shrinkage rate is not generally determined, but if the level of the heat shrinkage rate which is inconvenient for the finish, for example, 80 ° C. and the main stretching direction is less than 10%, the problem of insufficient shrinkage will occur, and if it exceeds 85%, It is not preferable because the film is shifted due to excessive shrinkage. If the direction perpendicular to the direction at 80 ° C. exceeds 50%, for example, a shrink label shrinks greatly in the width direction, so that an unsuitable label comes up. The same can be said for the shrinkage in the main stretching direction at 100 ° C. and the direction perpendicular to the main stretching direction.

It is important for the film of the present invention to have a falling weight impact strength of at least 5 kg · cm, which is important for practical performance of the film, preferably 10 kg · cm or more, more preferably 20 kg · cm or more, and still more preferably. Is 3
0 kg · cm or more. If it is less than 5 kg · cm, the film will be cut when it is suddenly fed (pulled) by a packaging machine, resulting in poor productivity. Thus, the film breakage resistance represented by the falling weight impact strength was secured based on the present invention.

The modulus of elasticity in the main stretching direction of the film of the present invention is preferably at least 110 kg / mm ² , more preferably 140 kg / mm ² or more, even more preferably 175 kg / mm ² or more. The modulus of elasticity in the main stretching direction represents the stiffness of the film, and is a practically important characteristic such as, for example, improvement in mechanical suitability and smooth mounting on a package. The upper limit is not particularly limited as long as it is within the range of the resin composition of the present invention.
It is about 00 kg / mm ² . If it is less than 110 kg / mm ² , there is a problem that the film is insufficient in stiffness (hardness), so that the film is hardly applied to a packaging machine or the like, and a mounting failure or the like occurs to lower productivity. In some cases, the film thickness is increased in some parts, but this is not a cost-effective method.

The stretched film in the present invention is a film stretched uniaxially or biaxially, and is generally used equipment such as simultaneous biaxial or sequential biaxial, such as tenter stretching, bubble stretching, and roller stretching. Means a film stretched by a stretching film forming facility represented by a method or the like, and may be a film formed by any facility. The thickness of the film is
Although it depends on the use, it is usually 5 to 800 μm, preferably 10 to 500 μm, more preferably 20 to 300 μm. Although the stretching ratio of the film of the present invention is not limited, it is generally affected by the stretching temperature in order to appropriately adjust the heat shrink force, but it is generally 2.0 to 10.0 times, preferably 2 times in the main stretching direction. 0.5 to 8.0 times, and similarly in the direction perpendicular to the direction 1.1.
-2.5 times, preferably 1.2-2.0 times. The preferred ratio of the former and the latter is 1.8 to 9.1 in the former ratio,
More preferably, it is 2.0 to 6.7.

The stretching temperature is generally preferably from 70 to 12
It is appropriately determined by the VSP of the copolymers (A) and (B) in the range of 0 ° C. The film may be used as at least one layer of a multilayer film, in which case, the same type (combined with at least one of the same type of resin, that is, a styrene-based copolymer and an SBBC-based polymer), Alternatively, it may be used as at least one layer (surface layer, internal layer) of a heterogeneous (other than the above) multilayer film. In that case, there are other free combinations such as 2, 3, 4, 5, 6, and 7 layers.

[0031]

EXAMPLES The present invention will be described in detail below with reference to examples, but the present invention is not limited thereto. In the following Examples and Comparative Examples, the meaning and content of items used for various performance evaluations of films and the like are based on the following evaluation methods and evaluation scales. Unless otherwise specified, the film to be evaluated is one stored in an atmosphere of 23 ° C. for 1 to 3 days from the film formation. (1) Shrink finish: This is to judge the performance as a shrink label. There are two types of heat medium, steam and hot air, and it is best to finish both cleanly. Method a: A 1.5-liter PET bottle (filled with water at 30 ° C., maximum diameter 91 when the temperature in the tunnel is 87 ° C. and the passage time is 10 seconds in a steam shrink tunnel (total length 2 m))
The finished state of the shrink is determined for a tube in which a cylindrical film (folding width: 148 mm, height: 90 mm) set in a cylindrical kokeshi-shaped container having a height of 310 mm and a height of 310 mm is shrunk in a tunnel. Method b: A 1.5-liter PET bottle (filled with water at 30 ° C., having a maximum diameter of 91 mm and a height of 310 mm) in a hot-air shrink tunnel (total length 2 m) at a temperature of 135 ° C. and a passage time of 10 seconds. A cylindrical film (folding width 148 mm, height 90 mm)
Is set in a tunnel and shrinked, and the finished state of the shrink is determined. Judgment: ：: No wrinkles, no tears, no positional displacement (displaced from the predetermined position), good finish within 2% longitudinal shrinkage.

：: wrinkles are slightly observed, but otherwise the same level as ◎. The longitudinal shrinkage is within 5%, which is the lower limit of commercial value. Δ: Wrinkling and displacement were observed, and longitudinal shrinkage of 10% or more was observed. ×: The degree of wrinkles, tears, displacement, and longitudinal shrinkage was extremely poor.
No commercial value. (2) Fitability: It is to check whether the film shrinked by the method a and the method b fits into the bottle in the shrink state by the tunnel described in the preceding paragraph, and to judge the important performance of the shrink label similarly to the finish of the shrink. Shrink under the best conditions and lightly rotate the film set in the container in the circumferential direction with your fingertip to see the degree of its movement. (Evaluate each of the two methods in the previous section 10 by 10 and rank at least one of the following if there is one) ◎: No gap between the bottle and no rotation ○: Slight gap Yes, but does not rotate. △: Slightly rotates (within 2 mm). ×: Loose and ticks. 3 Drop weight impact strength: Rapid feeding (pulling) of film.
It is used to determine the degree of film breakage, and represents important characteristics indispensable for films. The higher the falling weight impact strength, the better the performance. At least 5 kg · cm is required, and it is indispensable to prevent frequent film breakage and maintain high productivity.

According to ASTM-D1709 (missile:
The drop weight impact strength D of the film is obtained by calculation with a diameter of 38 mm, its own weight of 32 g (weight addition / subtraction method in units of 20 g), and a drop height of 66 cm. (At least 3 per sample
Perform 0 drop tests. ：: 21 kg · cm or more ○: 5 to 20 kg · cm △: 3 to 4 kg · cm ×: 2 kg · cm or less 4 Waist strength (elastic modulus): Judge the waist (hardness) of the film The higher the value, the better it affects mechanical suitability and wearability.

The value in the main stretching direction is measured according to ASTM-D882. (N = decimal point in the average value of 5 rounding) ◎: 175kg / mm ² or more ^{○: 140~174kg / mm 2 △:} 110~139kg / mm 2 ×: 109kg / mm 2 or less 5 folding endurance: film Since it is folded and used in the form of a cylinder, it is determined whether or not it is difficult to cut the fold when it is bent. The one that has a large number of bends before breaking is excellent.

Load 2k in accordance with ASTM-D2176
In g, a value in a direction perpendicular to the main stretching direction (a state in which two sheets are folded and overlapped) is measured. (The average value of n = 5 is rounded off to the decimal point.): 101 times or more ：: 31 to 100 times ： １: 11 to 30 times ×: Less than 10 times 6 Tensile breaking strength: Determines the mechanical strength of the film Those with high breaking strength are excellent.

The value in the direction perpendicular to the main stretching direction is measured according to ASTM-D882. (Average of n = 5) ◎: 3.5kg / mm 2 or more ○: 3.0~3.5kg / mm lower than ² △: ^2.5~3.0kg / mm ² less ×: 2.5 kg / mm Less than ² 7 Tensile elongation: The elongation of the film was measured both 1 day after film formation and 30 days after film formation (stored at 30 ° C.). In addition, it is excellent because there is no deterioration in quality due to a solvent or heating in a printing process. The tensile elongation is preferably high.

The value in the direction perpendicular to the main stretching direction is measured according to ASTM-D882. (Average value of n = 5) a. Elongation: Measured on a film one day after film formation. ◎: 170 to 210% ：: 150 to less than 170% Δ: 120 to less than 150% ×: less than 120% b. Deterioration over time: The film is measured at 30 ° C. for 30 days after film formation, and the elongation reduction rate E of elongation is determined.

The reduction rate E (%) is calculated from the elongation E ₁ of the film 30 ° C. 30 days after oven storage for elongation E ₀ of the film after 1 day deposited by the following equation. E (%) = E ₁ × 100 / E ₀ ：: 95% or more ：: 85 to less than 95% Δ: 60 to less than 85% ×: less than 60% 8 Optical properties: The transparency and gloss of the film Significantly affects product value. Those that are transparent and have good gloss are excellent. The smaller the value of HAZE and the larger the value of GLOSS, the better. a. Transparency: HAZE according to ASTM-D1003
(%) Is measured. (Average value of n = 5): less than 1.8% ： １: 1.8 to less than 2.5% Δ: 2.5 to less than 5.0% ×: not less than 5.0% b. Gloss: Gloss value (%) is measured according to ASTM-D2457 (angle 45 °). (Average value of n = 5) ： １: 165% or more ：: 125 to less than 165% ：: 100 to less than 125% ×: Less than 100% 9-dimensional natural shrinkage ratio: for example, the storage state of a film during distribution (atmospheric temperature (Storage time), the dimensional change (shrinkage) of the film may cause troubles such as a decrease in size and difficulty in fitting into a container. Therefore, a small dimensional change rate is important for the quality of the film.

3 for the film length L _{0 in the} main stretching direction
The dimension L ₁ after storage in the oven at 0 ° C. for 30 days is calculated by the following equation, and the dimension shrinkage L is obtained. L (%) = (L ₀ −L ₁ ) × 100 / L ₀ ：: less than 1.5% ：: 1.5 to less than 3.0% Δ: 3.0 to less than 6.0% ×: 6. 0% or more 10 Comprehensive evaluation: The criteria for comprehensive judgment as a heat-shrinkable hard film based on the results of the above evaluations 1 to 9 are as follows.

Best level ：: 9 or more ◎, 1
And 2 and 3 do not have Δ and × Good level ○: ◎ or more, and 1 and 2 and 3 do not have Δ and × Fail level △: 4 or more, △ And the sum of × is less than or equal to 4. Rejection level ×: Not applicable to any of the above. In the comprehensive judgment, those having ranks of ◎ and ○ are practically acceptable levels, and ◎ is particularly excellent in quality.

[0041]

Examples 1 and 2 and Comparative Examples 1 and 2 SBA-1 (styrene-butyl acrylate copolymer, BA = 18% by weight) was used as copolymer (A) (hereinafter abbreviated as (A)) in the present invention. 0.1% by weight of zinc acrylate, polymerized ion-crosslinked resin, weight average molecular weight: 380,000, VSP = 72 ° C) 60% by weight in Example 1, 57% by weight in Example 2,
SBB as the copolymer (B) (hereinafter abbreviated as (B))
C-1 (BSBS type styrene-butadiene block copolymer: bound styrene content 70% by weight, molecular weight 20
10,000, VSP 82 ° C, MFI (JIS-K6870, 20
0 ° C. 5 kg) 5 g / 10 min) in Examples 1 and 2 was 40% by weight, and Example 2 was a polymer (C) (hereinafter referred to as (C)).
TPS-1 (hydrogenated styrene-butadiene copolymer: bound styrene amount 30% by weight, MFR (AS
TM-D1238, 230 ° C 2.16 kg) 3.4 g /
10 minutes) and 3% by weight, respectively, a total of 100% by weight were well blended in a blender. Before blending in a blender, the additive mixture (phenol acrylate-based antioxidant (2-tert-butyl-6 (3'-tert-butyl-5 ') was added to 100 parts by weight of the resin mixture. -Methyl-2'-hydroxybenzyl) -4-methylphenyl acrylate) and 0.5 parts by weight of a phosphorus-based antioxidant (tri (2,4-di-tert-butyl) -phenylphosphite). 2 parts by weight, 0.3 part by weight of another phosphorus-based antioxidant (tri (4-nonyl) -phenylphosphite), 0.7 part by weight of an amine-based antistatic agent (hydroxyethylalkylamine) including)
Was added.

The mixture was mixed and melted at a temperature of 190 ° C. in a 65 mmφ (L / D = 31) extruder and extruded from a T-die to form a uniform sheet. In Examples 1 and 2, the sheet was stretched 1.6 times in the MD direction at 92 ° C. with a roll stretching machine, and then stretched 6.0 times in the TD direction at an oven temperature of 87 ° C. with a tenter stretching apparatus to obtain a 50 μm sheet. A sequentially biaxially stretched film was obtained. In Example 1, the heat shrinkage values in the main stretching direction (TD) and the direction perpendicular to the direction (MD) of the film were 38, respectively.
5, 32 g / mm ² , and 380,
It was 30 g / mm ² . In Comparative Examples 1 and 2, films having different heat shrink forces were formed by using the same mixture as in Example 2 and changing only the MD stretching conditions in the same equipment. That is, in Comparative Examples 1 and 2, the TD stretching was the same as in Example 1 and the MD stretching was 93 ° C. and 1.05 times, and the MD stretching was 90 ° C. and 2.8 times. This is Comparative Example 2. The heat shrinkage values of these films in the main stretching direction (TD) and the direction perpendicular to the direction (MD) were 35 in Comparative Example 1, respectively.
0.3 g / mm ² , and in Comparative Example 2, 360, respectively.
It was 200 g / mm ² .

The films of Examples 1 and 2 and Comparative Examples 1 and 2 were evaluated for various properties including shrink finish. Table 1 shows the results. As shown in Table 1, the heat shrinkage value of the film-formed film of the mixed composition in the direction perpendicular to the main stretching direction is too small (Comparative Example 1) or too large (Comparative Example 2). Gets worse,
On the other hand, those having an appropriate heat shrinkage value (Examples 1 and 2)
It is clearly recognized that various excellent characteristics such as shrink finish are exhibited. In particular, if the heat shrinkage is small, tearing occurs due to tearing impact, and it is weak in bending, the deterioration over time in tensile elongation becomes large, and the quality that is important for practical use is reduced. It is clear that is lost.

[0044]

Example 3 and Comparative Examples 3 and 4
2 (styrene-butyl acrylate copolymer, BA = 1
(8% by weight, weight average molecular weight: 440,000, VSP = 72 ° C.) 57% by weight, (B) and (C) and additives
The same components as in Example 2 were used in the same amounts as in Example 2, and then blended in the same manner as in Example 2 to obtain a mixture. Example 3
A film obtained by sequentially biaxially processing the mixture under the same conditions as in Example 2 and having a heat shrinkage force of 400, 40 in the main stretching direction (TD) and the direction perpendicular to the direction (MD), respectively.
(G / mm ² ). In Comparative Examples 3 and 4, the mixture was used as it was, and films having different heat shrink forces were formed using the same equipment while mainly changing the TD stretching conditions. That is, in Comparative Examples 3 and 4, the MD stretching temperature was the same as in Example 2, and the MD stretching ratio was 1.7 times in Comparative Example 3 and 1.6 times in Comparative Example 4 (same as Example 2). Comparative Example 3 was set, and then the TD stretching conditions were increased by 1.05 times at 95 ° C.
Comparative Example 4 was 11.0 times at 87 ° C. In these films, the heat shrink force values in the main stretching direction (MD) and the direction perpendicular to the direction (TD) of Comparative Example 3 were 60 and 20 (g / g), respectively.
mm ² ), and the heat shrinkage values in the main stretching direction (TD) and the direction perpendicular to the direction (MD) in Comparative Example 4 were 900 and 3 respectively.
5 (g / mm ² ). In addition, the thickness of the obtained film is 50 μ in Comparative Example 3 and 40 μ in Comparative Example 4.

Table 2 shows the results of evaluating various properties of these films as heat-shrinkable hard films in the same manner as in Example 2. As can be seen from Table 2, if the heat shrinkage value in the main stretching direction of the film is too small (Comparative Example 3) or too large (Comparative Example 4), the shrink finish becomes poor. On the other hand, in the case of an appropriate heat shrink force value (Example 3)
It is clearly recognized that various characteristics such as shrink finish are excellent. Conversely, if the heat shrinkage is too small, it is difficult to produce a beautiful finish due to insufficient shrinkage, causing problems such as deterioration of physical properties over time and weak bending strength. However, there are problems such as misalignment, distortion in the finished state, breakage of the film during shrinking, and natural shrinkage of the dimensions of the film, which changes during the distribution stage. It is clear that this is undesirable.

[0046]

Examples 4 to 13 (A) 60% by weight of SBA-3 (styrene-butyl acrylate copolymer, BA = 10%, weight average molecular weight 450,000, VSP = 91 ° C.)
(B) SBBC-2 (SBS type styrene-butadiene block copolymer, bound styrene content 72% by weight, VSP 79 ° C, MFI (JIS-K6870, 20
0 ° C. 5 kg) 5.6 g / 10 min), 34% by weight, (C)
TPS-2 (hydrogenated styrene-butadiene copolymer: bound styrene amount 40% by weight, MFR (ASTM-D
1238, 230 ° C, 2.16 kg) 0.5 g / 10 min)
6% by weight, and a total of 100% by weight and an additive (same as in Example 1) were sufficiently blended with a blender to obtain a mixture of Example 4. As (A), the same SBA-3 as in the fourth embodiment is used.
SBBC-3 ((S-B)
nX type (radiation type) styrene-butadiene block copolymer, bound styrene content 75% by weight, VSP 93 ° C, MF
I (JIS-K6870, 200 ° C, 5kg) 6g / 10
Min.) As 40% by weight and (C) as TPS-3 (S-EB).
-S-type hydrogenated styrene-butadiene copolymer: bound styrene amount 30% by weight, MFR (ASTM-D1238, 23
(0 ° C 2.16 kg) 0.7 g / 10 min), 8 wt%, a total of 100 wt%, and additives (same as in Example 1) were thoroughly blended with a blender to obtain a mixture of Example 5. Also, as (A), SBA-4 (SBA-1 and SBA-2)
Is mixed at an equal weight ratio), 57% by weight, (B) is 40% by weight of SBBC-1, and (C) is TPS-1.
Was blended with a blender in an amount of 3% by weight, a total of 100% by weight, and an additive (same as in Example 1) to obtain a mixture of Example 6. Further, as (A), SBA-5 (styrene-butyl acrylate-methyl methacrylate-diene-containing graft rubber-based copolymer (so-called transparent high-impact formulation): weight ratio of styrene: butyl acrylate: methyl methacrylate: diene-containing rubber = 44: 31: 1
0:15, weight average molecular weight 400,000, VSP = 85 ° C.) 70% by weight, (B) 28% by weight of SBBC-1
2% by weight of TPS-1 as (C), total 100% by weight
And the additives (same as in Example 1) were blended well with a blender to obtain a mixture of Example 7. Further, as (A), SBA-6 (styrene-butyl acrylate-methyl methacrylate copolymer, weight ratio of styrene: butyl acrylate: methyl methacrylate = 47: 42:
11, weight average molecular weight 420,000, VSP = 89 ° C) to 70
%, The respective weights of (B) and (C) are as in Example 7.
And a total of 100% by weight and additives (same as in Example 1) were blended well with a blender to obtain a mixture of Example 8. The weights of (A) and (C) were the same as in Example 8, and (B) was SBBC-4 (SBB).
C-1 and SBBC-2 were mixed at an equal weight ratio of 28% by weight, and a total of 100% by weight and additives (same as in Example 1) were thoroughly blended with a blender to obtain a mixture of Example 9 and did. The weights of (A) and (C) were the same as in Example 8, and (B) was SBBC-5 (linear B-S-B-S type styrene-butadiene block copolymer elastomer, hard The polystyrene of the segment forms a domain to have a physical cross-linking function, the soft segment has a rubber function, and both segments have a microphase-separated structure to form a network.
2.16 kg) (2.6 g / 10 min) to 28% by weight,
A total of 100% by weight and the additives (as in Example 1) were blended well in a blender to give the mixture of Example 10.
Further, (A) is 53% by weight of SBA-2, (B) is 40% by weight of SBBC-1, and (C) is TPS-
4 (methyl methacrylate-butadiene-styrene copolymer, Jongbuk Chemical Co., Ltd., trade name: Kaneace B-31) was 7% by weight, and a total of 100% by weight and additives (same as in Example 1) were used. The mixture of Example 11 was well blended with a blender. (B) and the weight thereof were the same as those in Example 11, and (A) was 50% of SBA-2.
Wt-1 and PET-1 (copolyester resin, Eastman Chemical Co., trade name: Kodar)
PETG-6763) to 10% by weight, and a total of 100% by weight and additives (same as in Example 1) were blended well in a blender to give a mixture of Example 12. (B)
And the weight thereof are the same as those of the twelfth embodiment.
A-2 is 58% by weight, and (C) is TPS-5 (carboxylate-modified hydrogenated block copolymer, B-S-B-S-S type reactive saturated thermoplastic elastomer, double bond derived from butadiene Of MFR (ASTM-D1
238, 230 ° C. 2.16 kg) 2.2 g / 10 min) was 2% by weight, and a total of 100% by weight and additives (Example 1)
Was blended well in a blender to give a mixture of Example 13.

Each mixture shown in the above Examples 4 to 13
In the same equipment as in Example 1 and the respective stretching shown in Table 3.
Films were formed under the conditions described in Examples 4, 5, 6, 7,
60 in the order of 8, 9, 10, 11, 12, 13
μ, 100μ, 50μ, 50μ, 50μ, 50μ, 50
μ, 50 μ, 50 μ, and 50 μ were obtained. this
Direction perpendicular to the main stretching direction (TD) of these films (M
The heat shrink force value of D) was 500 and 80 in Example 4, respectively.
g / mm^TwoIn Example 5, 260, 100 g / mm
^Two390, 35 g / mm in Example 6^TwoAnd
Example 7 was 460, 79 g / mm^TwoExample 8
480,87g / mm^TwoExample 9 is 470, 8
3g / mm^TwoExample 10 was 360 and 40 g / m
m^TwoExample 11 was 500, 35 g / mm^TwoIn
Example 12 was 550, 36 g / mm^TwoAnd implemented
Example 13 was 400, 38 g / mm^TwoMet. These files
Various properties of film as heat-shrinkable hard film
Tables 3 and 4 show the results of evaluating the performance.

As can be seen from Tables 3 and 4, the type of the resin and the mixing composition ratio are appropriately selected within the scope of the present invention, and the heat shrinkage stress values in the main stretching direction and the direction perpendicular to the main stretching direction of the formed film are determined. Those falling within the scope of the present invention were excellent in various properties including shrink finish. In particular, in Examples 7 and 8, it can be understood that a remarkable effect is exhibited even with a copolymer containing methyl methacrylate or a diene-containing rubber in a styrene-butyl acrylate copolymer, and Examples 6 and 9 show that (A) and (B) as shown
It can be seen that the object of the present invention can be achieved even when different resins are used. Further, as shown in Example 12, it can be seen that in the case of using the copolyester resin in (C), a characteristic is seen in the improvement of the tensile strength at break. Also, as seen in the overall examples,
(C) A styrene-butadiene copolymer modified with a carboxylic acid-modified copolymer or a block copolymer obtained by hydrogenating a part of an unsaturated bond derived from a conjugated diene is used in an amount of 1 to 30% by weight. It can be seen from the results that, in addition to the excellent properties of the film, the improvement in the bending strength is remarkable.

[0049]

Comparative Examples 5 to 9 As (A), 2% by weight of SBA-2 was used.
93% by weight of SBBC-1 as (B) and 5% by weight of TPS-1 as (C), a total of 100% by weight and additives (same as in Example 1) were well blended with a blender to obtain a mixture of Comparative Example 5 A mixture was obtained. (A), (B) and (C)
The same components as in Comparative Example 5 were used, and their weight ratios were 96, 4, 0% by weight, respectively, and a total of 100% by weight and additives (same as in Example 1) were blended well in a blender. 6, and 95,
3,2% by weight, total 100% by weight and additives (Example 1
Was mixed well with a blender to obtain a mixture of Comparative Example 7. Further, SBA-5 was 3% by weight as (A), SBBC-1 was 96% by weight as (B), TPS-1 was 1% by weight as (C), and a total of 100% by weight and additives (Example 1) Was mixed well in a blender to obtain a mixture of Comparative Example 8. For (A), (B) and (C), the same ones as those of Comparative Example 8 were used, and their weight ratios were 50, 50, 0% by weight, respectively, and a total of 100%.
% By weight and additives (same as in Example 1) were blended well in a blender to give a mixture of Comparative Example 9.

Each of the mixtures shown in Comparative Examples 5 to 9 was used
Using the same equipment as in Example 1, films were formed under the respective stretching conditions shown in Table 4, and the thickness of each of Comparative Examples 5, 6, 7, 8, 9 was 60 μm, 40 μm, 45 μm, 60 μm, and 50 μm, respectively. Got something. The main stretching direction (T
D) and the heat shrink force in the direction perpendicular to the direction (MD) were 280 and 30 g / mm ² for Comparative Example 5, and 4 for Comparative Example 6.
50, 50 g / mm ² , and Comparative Example 7 was 440, 80
a g / mm ^2, Comparative Example 8 is 270,45g / mm ^2, Comparative Example 9 was 360,4g / mm ^2. Tables 5 and 6 show the results of evaluating various properties of these films as heat-shrinkable hard films.

As shown in Tables 5 and 6, when the type of the resin and the mixing composition ratio were out of the range of the present invention, each heat shrink force value in the direction perpendicular to the main stretching direction of the formed film was measured. However, even if is within the range of the present invention, important properties as a heat-shrinkable hard film will not be exhibited due to inadequate properties of the overall properties of the mixed composition. For example, wrinkles, misalignment, and tearing are observed in the particularly important shrink finish, tensile shock resistance, waist strength (elastic modulus), bending strength, tensile elongation and its deterioration with time and dimensions. Natural contraction of
Significant performance degradation occurs in any aspect, such as optical properties, resulting in many defects in practice. In other words, it is clear that a defective film results when the type of the resin used and the mixing composition ratio are not within the specified range of the present invention.

[0052]

[Table 1]

[0053]

[Table 2]

[0054]

[Table 3]

[0055]

[Table 4]

[0056]

[Table 5]

[0057]

[Table 6]

[0058]

As described in detail above, the heat-shrinkable hard film of the present invention comprises at least three types of copolymers (A), (B) and (C), and polymers. And a heat shrink force of a film formed with the mixed composition, at least a value in a main stretching direction and a direction perpendicular thereto is set to a specified value. The main problem with hard heat-shrinkable films is that the film breaks due to tensile impact when mounted on a packaging machine and / or wrinkles, misalignments, tears, etc. in the finished state in a shrink tunnel. This completely eliminates the need to provide an excellent film with greatly improved workability, productivity, and aesthetics of the product.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI // B29K 25:00 B29K 25:00 105: 02 105: 02 B29L 7:00 B29L 7:00 (58) Field surveyed (Int .Cl. ⁷ , DB name) B29C 61/00-61/10 B29C 55/00-55/30 C08J 5/18

Claims (4)

(57) [Claims] 1. A vinyl aromatic hydrocarbon, (a ₁₎ A
Crylic acid, (a ₂ ) an alcohol having ₁ to ₁₂ carbon atoms and an alcohol
Ester derivative with crylic acid, (a ₃ ) methacryl
Acids, (a ₄ ) alcohols having ₁ to ₁₂ carbon atoms and metaac
Ester derivative with lylic acid, (a ₅ ) α, β unsaturated dica
Rubonic acid, or (a ₆ ) these dicarboxylic acids and C ₂ to
And at least one aliphatic unsaturated carboxylic acid derivative selected from the monomers are mono- or diester derivatives of alcohols of C _12, in the copolymer, the Vicat softening point 1
5 to 95% by weight of the copolymer (A) not exceeding 05 ° C;
A copolymer (B) consisting mainly of at least one polymer block mainly composed of at least one vinyl aromatic hydrocarbon and at least one polymer block mainly composed of a conjugated diene derivative, and 5 to 95% by weight. A film stretched at least uniaxially, comprising a mixed composition having a heat shrink force of at least 151 to 800 g / mm ^{2 in the} main stretching direction.
And the heat shrinkage in the direction perpendicular to the above direction is 5 to 150 g /
heat shrinkable rigid film, which is a mm ^2. 2. A vinyl aromatic hydrocarbon comprising: (a ₁ )
Crylic acid, (a ₂ ) an alcohol having ₁ to ₁₂ carbon atoms and an alcohol
Ester derivative with crylic acid, (a ₃ ) methacryl
Acids, (a ₄ ) alcohols having ₁ to ₁₂ carbon atoms and metaac
Ester derivative with lylic acid, (a ₅ ) α, β unsaturated dica
Rubonic acid, or (a ₆ ) these dicarboxylic acids and C ₂ to
And at least one aliphatic unsaturated carboxylic acid derivative selected from the monomers are mono- or diester derivatives of alcohols of C _12, in the copolymer, the Vicat softening point 1
5 to 95% by weight of the copolymer (A) not exceeding 05 ° C;
A copolymer (B) composed of at least one polymer block mainly composed of a vinyl aromatic hydrocarbon and at least one polymer block mainly composed of a conjugated diene derivative, and 4 to 94% by weight of a copolymer (B); Block copolymer (B)
Or a carboxylic acid-modified copolymer of the block copolymer (B) , or a block copolymer (B) , mainly composed of a polymer block obtained by hydrogenating at least a part of an unsaturated bond portion derived from a conjugated diene. A carboxylic acid-modified copolymer of a block copolymer obtained by hydrogenating a part of the copolymer (B) or a copolymer obtained by hydrogenating a part of the carboxylic acid-modified copolymer of the block copolymer (B) Or methyl methacrylate-
At least one polymer (C) 1 selected from a butadiene-styrene-based copolymer or a polyester-based copolymer
At least a uniaxially stretched film composed of a mixed composition mainly composed of at least 30% by weight and having a heat shrinkage force of at least 151 to 800 g / mm ² in the main stretching direction and a heat in a direction perpendicular to the above-mentioned direction. heat shrinkable rigid film shrinkage force is characterized by a 5 to 150 g / mm ^2. 3. The falling weight impact strength is at least 5 kg · cm.
The film according to claim 1, wherein 4. The heat shrinkage at 80 ° C. in the main stretching direction is 10
~ 85%, elastic modulus in main stretching direction at least 110kg
/ Mm ^2. The film according to claim 1.