JP3070439B2 - Shrink film and manufacturing method thereof - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention comprises an improved rubber-modified styrene resin as an essential component, and has excellent shrinkage characteristics such as shrinkage gradient, maximum shrinkage, shrinkage initiation temperature, etc. in the shrink wrapping and label fields, and at room temperature. Over time (hereinafter referred to as natural shrinkage) is improved, and furthermore, high transparency and high gloss,
The present invention relates to a shrink film having good mechanical strength and suitability for a packaging machine, and excellent in whitening of a bent portion during bending (hereinafter referred to as bending whitening).

[0002] In detail, transparency and resistance obtained by graft copolymerization of a styrene monomer and methyl (meth) acrylate in the presence of 1 to 20% by weight of a specific rubbery block copolymer. Graft polymerization of styrene monomer (b-2) and acrylic monomer (b-3) at a ratio of 30 to 90% by weight of resin (A) having excellent impact resistance and rubbery polymer (b-1). Single-layer shrink film mainly composed of a resin component containing the resin (B) obtained by the above method, and a rubber-modified copolymer resin (A ′) as an inner layer, and styrene- (meth) acrylic acid as a surface layer. A multi-layer shrink film in which a copolymer resin is laminated, and a mixed resin in which a block copolymer (C) of a styrene-based monomer and a diene-based monomer is used in combination with a rubber-modified copolymer resin (A '), Styrene-(meta Multilayer shrink film laminated acrylic acid copolymer resin, and, after melting a resin component of the resin (A) as an essential component kneading extruder, a method of manufacturing a shrink film which is stretched at a specific temperature condition.

[0003]

2. Description of the Related Art Conventionally, as a shrink film for shrink wrapping, a shrink film made of a polyvinyl chloride resin is frequently used because of its shrinkage, mechanical strength and transparency. Due to environmental problems caused by hydrogen chloride gas and corrosion problems of incinerators caused by chlorine gas,
The transition to styrene-butadiene copolymer shrink films is in progress. Thus, in recent years, with the advent of PET bottles, low-temperature shrinkage has been imparted, and as a shrink film having improved mechanical properties, a method of mixing a styrene-based resin with a styrene-butadiene block copolymer, and a styrene-butadiene block copolymer styrene Shrink films using block copolymers whose content and degree of polymerization have been adjusted have been developed.

[0004] For example, Japanese equity 2 -55 218 Publication,
A shrink film in which a specific low molecular weight polystyrene is blended with a block copolymer composed of a vinyl aromatic hydrocarbon and a conjugated diene is mentioned.
Japanese Patent No. 5544 discloses a shrink film in which styrene-butadiene copolymers having different butadiene contents are mixed.

[0005]

However, any of the above block copolymer-based shrink films has an extremely high rubber component in the film, so that the film is inferior in rigidity and transparency after stretched film formation and has low-temperature shrinkage to some extent. At present, it is possible to obtain only those which exhibit natural shrinkage.

An object of the present invention is to provide a shrink film having both rigidity and transparency, and having improved shrinkage characteristics, particularly low-temperature shrinkage, and improved natural shrinkage.

[0007]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems, and as a result, a specific amount of a rubbery polymer was used, and a styrene monomer and methyl (meth) acrylate were added thereto. By stretching a film containing a graft copolymer obtained by graft polymerization with
The inventors have found that a shrink film excellent in rigidity and transparency, and also excellent in shrinkage characteristics while improving natural shrinkage can be obtained, and completed the present invention.

That is, the present invention relates to a rubber-based polymer (a-1) , a styrene-based monomer (a-2) and methyl (meth) acrylate (a-3), wherein the block copolymer is used. (A-1)
(A) obtained by graft polymerization using a ratio of 1 to 20% by weight, a rubbery polymer (b-1), a styrene monomer (b-2), and an acrylic monomer (b-
3) that the rubbery polymer (b-1) is 30 to 90 weight
% Of the resin (B) obtained by graft polymerization using the resin (B) in an amount of 50% by weight or less with respect to the total weight of (A) and (B). A shrink film, wherein the inner layer is graft polymerized with a rubbery polymer (a-1), a styrene monomer (a-2) and methyl (meth) acrylate (a-3). (A ') obtained as a main component, and styrene- (meth)
A shrink film having an acrylic acid copolymer resin layer, a rubbery polymer (a-1), a styrene monomer (a-2), and methyl (meth) acrylate (a-
3) is melt-kneaded with a resin component having a resin (A) obtained by graft polymerization using the rubbery polymer (a-1) in an amount of 1 to 20% by weight, followed by extrusion,
In at least one direction, the glass transition point measured in accordance with JIS K-7198 is defined as Tg to (Tg + 30
C), a method for producing a shrink film, characterized in that the rubbery polymer (a-1), a styrene-based monomer (a-2), and methyl (meth) acrylate are used as an inner layer. (A-3) and a resin component having a resin (A ') as a main component obtained by graft polymerization, melt-kneaded, extruded, stretched in at least one direction, and provided on both surfaces with a styrene monomer and an acrylic monomer. And a method for producing a shrink film, characterized in that a surface layer mainly composed of a copolymer resin is formed.

The resin (A) used in the present invention comprises a rubbery polymer (a-1), a styrene monomer (a-2),
Methyl (meth) acrylate (a-3) is a resin obtained by graft copolymerization using the block copolymer (a-1) in a ratio of 1 to 20% by weight. When the amount of the polymer (a-1) is less than 1% by weight, it is difficult to stretch the unstretched sheet, and the impact resistance of the shrink film is reduced. Irregularities derived from rubber particles are likely to occur, irregular reflection on the film surface of visible light occurs and transparency decreases, and rigidity decreases with an increase in rubber component,
Makes natural shrinkage more likely to occur.

The rubbery polymer (a-1) used in the present invention
Is not particularly limited, and examples thereof include a rubber and a thermoplastic elastomer. Specifically, styrene butadiene rubber (S
A block copolymer of a styrene monomer and a diene monomer represented by BR), butadiene rubber (BR),
Natural rubber (NR), isoprene rubber (IR), chloroprene rubber (CR), isobutylene-isoprene rubber (I
IR), ethylene-propylene rubber (EPDM, EP
M), acrylic rubber (ACM, ANM), chlorinated polyethylene rubber (CSR), fluoro rubber (FKM), silicone rubber (Q), urethane rubber (AU, EU), polysulfide rubber (T), epichlorohydrin rubber (CO , EC
O), chlorosulfonated polyethylene (CSM), nobornene rubber, and vulcanized polymer materials thereof.

Among these, particularly, the balance between transparency and impact resistance, the improvement in bending whitening, and the styrene monomer (a-
2), a block copolymer of a styrene-based monomer and a diene-based monomer, butadiene rubber (BR), particularly a styrene-based monomer and a diene-based monomer in view of compatibility with methyl (meth) acrylate (a-3) Are preferred.

The block copolymer of the styrene-based monomer and the diene-based monomer is not particularly limited. However, the block copolymer having a styrene skeleton content of 30 to 55% by weight is required to have impact resistance and transparency. Is preferable from the viewpoint of improving That is, when the content is 30% by weight or more, the transparency and glossiness of the shrink film are remarkably excellent, and the rigidity is improved and the packaging machine is excellent in suitability, and the natural shrinkage can be improved. When the styrene skeleton content is 55% by weight or less, the impact strength of the shrink film is improved, and the whitening of the fold is reduced.

Further, the bonding form of the polybutadiene structural site in the block copolymer of the styrene-based monomer and the diene-based monomer is not particularly limited, but the unsaturated bond based on the diene-based monomer of the block copolymer is not limited. Of which, the ratio of 1,2-vinyl bonds is 14 to 25%, particularly 16 to
It is preferred that the content is 22%, and the remainder is cis and trans bonds, since the grafting ratio becomes appropriate and a shrink film having an excellent balance between transparency and impact resistance can be obtained.

The bonding mode of the block copolymer includes random bonding and block bonding, both of which can be used, but block bonding is preferred.

The average particle diameter of rubber of the rubbery polymer (a-1) is not particularly limited.
m, and preferably 0.1 to 0.4 μm in terms of excellent impact strength, glossiness, transparency, and bending whitening.

The styrene monomer constituting the block copolymer of the styrene monomer and the diene monomer includes styrene, α-methylstyrene, m-methylstyrene, p-methylstyrene, ethylstyrene, isobutylstyrene, and tertiary. Butylstyrene, o-bromostyrene, m-bromostyrene, p-bromostyrene,
Examples thereof include o-chlorostyrene, m-chlorostyrene, and p-chlorostyrene, and among them, styrene is preferred from the viewpoint of transparency.

On the other hand, the diene monomers of the block copolymer of styrene monomers and diene monomers include butadiene, chloroprene, isoprene, 1,3-
Examples thereof include pentadiene, and among them, butadiene is preferable from the viewpoint of impact resistance and transparency, natural shrinkage, and bending whitening.

The styrenic monomer (a-
As 2), the same ones as exemplified as the styrene-based monomer used in the block copolymer (a-1) can be used. For example, styrene, α-methylstyrene,
m-methylstyrene, p-methylstyrene, ethylstyrene, isobutylstyrene, tert-butylstyrene, o-bromostyrene, m-bromostyrene, p-bromostyrene, o-chlorostyrene, m-chlorostyrene, p-chlorostyrene And the like. Among them, styrene is preferred from the viewpoint of the transparency of the shrink film.

Methyl (meth) acrylate (a-3)
Although it is an essential component for imparting transparency to the shrink film, methyl methacrylate is preferred because it is particularly excellent in transparency.

In the resin (A), the above (a-
In addition to the components (1) to (a-3), by further using a (meth) acrylic acid alkyl ester (a-4) having 4 or more carbon atoms as a graft component, shrinkage properties, particularly low-temperature shrinkage, are improved. The resulting shrink film is extremely excellent in achieving both natural shrinkage.

That is, in recent years, there has been an increasing demand for shrink films for use in containers requiring low-temperature shrinkage, such as PET bottles having inferior heat resistance. Can't handle application. In the section of the prior art, a shrink obtained by blending a specific low molecular weight polystyrene with a block copolymer composed of a vinyl aromatic hydrocarbon and a conjugated diene, which is exemplified as a shrink film described in JP-B-5-55218. Although the film has improved low-temperature shrinkage, it still has problems such as spontaneous shrinkage due to low molecular weight components.

In the present invention, the fourth component has 4 carbon atoms.
The above alkyl (meth) acrylate (a-4)
By grafting, a shrink film having not only a low-temperature shrinkage property but also an extremely good natural shrinkage inhibition property can be obtained.

The alkyl (meth) acrylate having an alkyl group having 4 or more carbon atoms (a-4) is not particularly restricted but includes, for example, n-butyl acrylate,
Examples thereof include -iso-butyl acrylate and 2-ethylhexyl acrylate. Among them, acrylic acid-n- which achieves low-temperature shrinkage and simultaneously reduces the occurrence of natural shrinkage without impairing the transparency of the shrink film. Butyl is preferred.

The method for producing the resin (A) used in the present invention is not particularly limited, and may be any of bulk-suspension polymerization, solution polymerization and bulk polymerization. In a continuous bulk polymerization line incorporating a tubular reactor in which a plurality of mixing elements are fixed, a method of continuously performing bulk polymerization while performing static mixing by the tubular reactor makes the polymer composition uniform. From the viewpoint of improving the transparency and impact resistance of the sheet.

Here, the plurality of mixing elements fixed inside the tubular reactor include, for example, the division and the flow direction of the flow of the polymerization liquid flowing into the tube, and the division and the merge are repeated to repeat the division and the merge. Are mixed. As such a tubular reactor, for example,
SMX-type and SMR-type Sulzer-type tubular mixers, Kenix-type static mixers, Toray-type tubular mixers and the like can be mentioned.

Further, at the time of polymerization, the rubbery polymer (a
-1), a styrene monomer (a-2), and (meth)
The mixing ratio with the methyl acrylate (a-3) is not particularly limited, but the balance between the transparency and the impact strength of the resin is remarkably good, so that the weight ratio of (a-1)
/ [(A-2) + (a-3)] = 1/99 to 20/8
0, and (a-2) / (a-3) = 45 / 55-85 /
A ratio of 15 is preferred.

When an alkyl (meth) acrylate (a-4) having an alkyl group having 4 or more carbon atoms is used as the fourth component, methyl (meth) acrylate (a-3) and ( When the mixing ratio with the alkyl (meth) acrylate (a-4) is the former / the latter = 9 on a weight basis.
It is preferable that the ratio be 0/10 to 40/60, since the shrink film has extremely excellent low-temperature shrinkage and natural shrinkage inhibiting properties.

The shrink film of the present invention further comprises a rubbery polymer (b-1), a styrene monomer (b-2) and an acrylic monomer (b) in addition to the resin (A) described above.
-3) and a rubbery polymer (b-1)
(B) obtained by graft polymerization using the resin (B) at a ratio of 30 to 90% by weight in a ratio at which the resin (B) is 50% by weight or less with respect to the total weight of (A) and (B). Therefore, the effect of the present invention that impact resistance and bending whitening can be further improved without deteriorating rigidity, transparency and natural shrinkage can be exhibited.

In the resin (B), the rubbery polymer (b-
If 1) is less than 30% by weight, the expected effect of improving the impact resistance and the effect of suppressing bending whitening cannot be obtained, and if it exceeds 90% by weight, transparency is degraded. Above all, the rubbery polymer is preferably from 30 to 90% by weight, more preferably from 50 to 80% by weight, in view of the balance between impact resistance, transparency and natural shrinkage.

The rubbery polymer (b-1) is not particularly limited, and includes rubber or thermoplastic elastomer. Specifically, a block copolymer of a styrene monomer and a diene monomer represented by styrene butadiene rubber (SBR), butadiene rubber (BR), natural rubber (NR), isoprene rubber (IR), chloroprene rubber ( CR), isobutylene-isoprene rubber (IIR),
Ethylene-propylene rubber (EPDM, EPM), acrylic rubber (ACM, ANM), chlorinated polyethylene rubber (CSR), fluoro rubber (FKM), silicone rubber (Q), urethane rubber (AU, EU), polysulfide rubber ( T), epichlorohydrin rubber (CO, ECO), chlorosulfonated polyethylene (CSM), nobornene rubber, and vulcanized polymer materials thereof.

Among these, particularly, the resin (A) which is an essential component, has a balance between transparency and impact resistance, an improvement in bending whitening, and the like.
A block copolymer of a styrene monomer and a diene monomer, butadiene rubber (BR),
Among them, a block copolymer of a styrene monomer and a diene monomer is preferred.

As the styrene monomer (b-2),
Styrene, α-methylstyrene, m-methylstyrene,
Examples include p-methylstyrene, ethylstyrene, isobutylstyrene, tertiary butylstyrene, o-bromostyrene, m-bromostyrene, p-bromostyrene, o-chlorostyrene, m-chlorostyrene, p-chlorostyrene, and the like. Above all, transparency, gloss, resin (A)
Styrene is preferred from the viewpoint of compatibility with styrene. The styrene monomer (b-2) is preferably used in such a manner as to be copolymerized in the resin (B) in an amount of 1 to 90% by weight, preferably 5 to 60% by weight, from the viewpoint of transparency.

As the acrylic monomer (b-3),
Although not particularly limited, alkyl esters such as methyl (meth) acrylate, ethyl (meth) acrylate, and butyl (meth) acrylate may be mentioned. Among them, methyl (meth) acrylate is transparent and glossy. It is preferable from the viewpoint of compatibility and compatibility with the resin (A). Further, the acrylic monomer (b-3) is a resin (B) from the viewpoint of shrinkage characteristics such as shrinkage onset temperature, natural shrinkage, transparency, and compatibility with the resin (A).
It is good to have 10 to 90% by weight, preferably 15 to 80% by weight copolymerized therein.

The resin (B) may be made of, for example, acrylic resin in order to further improve the impact resistance and whitening of the shrink film, or to keep the transparency excellent by making the refractive index close to that of the resin (A). Other copolymerizable monomers such as acids, methacrylic acid, unsaturated fatty acids such as maleic anhydride, acrylonitrile and methacrylonitrile (b-4)
It is preferable to copolymerize
More than one species can be used in combination.

Resin containing rubbery polymer (b-1), styrene monomer (b-2), acrylic monomer (b-3) and, if necessary, other monomer (b-4) as a raw material component (B) preferably has a refractive index of 1.520-1.
It is preferably adjusted to be 570, more preferably in the range of 1.535 to 1.555. Further, the average rubber primary particle diameter of the resin (B) is not particularly limited, but is preferably 0.05 to 0.8 μm and preferably 0.1 to 0.8 μm.
A thickness of 1 to 0.4 μm is preferred because transparency when mixed with the resin (A) is not impaired, and bending whitening and impact resistance are further improved.

Among these resins (B), a copolymer resin (MBS) obtained by graft copolymerizing styrene and methyl (meth) acrylate onto a styrene-butadiene copolymer rubber from the viewpoint of improving impact resistance and transparency. Also, a copolymer resin (ABS) obtained by graft copolymerizing styrene and acrylonitrile on a styrene-butadiene copolymer rubber is preferable.

The mixing ratio of the resin (A) and the resin (B) is as follows:
As described above , the total weight of the resin (A) and the resin (B)
On the other hand, the content of the resin (B) is not more than 50% by weight,
0% by weight may be used, but in addition to being excellent in transparency, bending whitening, and impact resistance, (A) / (B) = 95/5 to 55/45% by weight in consideration of both low-temperature shrinkage characteristics and natural shrinkage. Is more preferable. The mixing method is not particularly limited, but it is preferable that the resin (A) and the resin (A) are melt-kneaded before extrusion film formation by a continuous method using a single-screw or twin-screw extruder or a batch method using a Banbury mixer or the like. It is preferable to uniformly disperse the resin (B) in the melting temperature range of the resin (B).

Various plasticizers and lubricants can be added to such a resin component in an amount of 0.01 to 20 parts by weight, preferably 0.02 to 10 parts by weight, depending on the purpose.
It is more preferable to add in the range of 0.02 to 5 parts by weight from the viewpoint of inhibiting natural shrinkage.

As the plasticizer, any known plasticizers can be used. For example, succinic acid, glutaric acid, adipic acid,
Dibasic acids such as pimelic acid, suberic acid, azelaic acid and sebacic acid, and ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,2
-Butylene glycol, 1,3-butylene glycol,
1,4-butylene glycol, neopentyl glycol, 1,5-pentanediol, 2,2,4-trimethyl-1,3-pentanediol, 3-methyl-1,5
-A dihydric alcohol having a molecular weight of 200 or less, such as pentanediol or 1,6-hexanediol, and preferably a polyester system in which a terminal capping agent is a monohydric alcohol or a monobasic acid, dibutyl phthalate (DBP), dioctyl. Phthalate (DOP), diheptyl phthalate (DHP), butyl benzyl phthalate (BB
P), butyl phthalyl butyl glycolate (BP
Phthalic acid series such as BG), di-n-butyl adipate,
Adipic acid such as di- (2-ethylhexyl) adipate (DOA), citric acid such as acetyl tri-n-butyl citrate (ATBC), di-n-butyl sebacate (DBS), di- (2 -Ethylhexyl) sebacate (DOS) and other epoxidized soybean oils (E
SBO), epoxidized linseed oil (ELSO), and epoxidized fatty acid esters (EFAE). In particular, polyester-based and phthalic-based plasticizers have the advantage that the shrinkage onset temperature can be finely adjusted and the transparency is not reduced.

Examples of the lubricant include metal soaps, hydrocarbon liquid paraffins, polyethylene waxes, fatty acid-based higher fatty acids, oxy fatty acids, etc., fatty acid amide-based fatty acid amides, bis-fatty acid amides, etc., and ester-based lubricants. Glycerides, ester waxes, fatty acid ketones,
Aliphatic alcohol-based monohydric alcohols, polyhydric alcohols and the like, and partial esters of aliphatic and polyhydric alcohols and complex lubricants can be added. Particularly, liquid paraffin, paraffin such as paraffin wax and dimethylpolysiloxane, Organic polysiloxanes such as methylphenylpolysiloxane, bisfatty acid amides such as ethylene bisstearyl amide, and ester waxes such as alkyl phosphates are preferred from the viewpoint of transparency and surface smoothness.

The method of adding the plasticizer and the lubricant is not particularly limited, but may be added to the resin (A), the resin (B) or the resin (C) in advance, or may be added to the resin (A). The resin (B) or the resin (A) and the resin (C) may be added at the time of melt-kneading, or may be added by mixing a previously prepared master batch.

Further, in addition to the plasticizer and the lubricant, various additives may be added depending on the purpose in an amount of 0.01 to 20 parts by weight, preferably 0.02 to 10 parts by weight, more preferably 0.02 to 5 parts by weight.
It can be added in the range of parts by weight.

Examples of the additives that can be used include anti-blocking agents such as silicon oxide, silicone fine particles, nylon fine particles and high-density polyethylene fine particles, sucrose fatty acid esters, glycerin fatty acid esters, sorbitan fatty acid esters, polyglycerin fatty acid esters, and the like. Antistatic agents such as fatty acid type such as ethylene oxide adduct, fatty acid amide type, fatty acid ketone type, fatty acid ester type and cationic activator, anionic activator and amphoteric activator,
Phenols such as 2,6-di-t-butyl-p-cresol (BHT), phosphorus-based antioxidants such as triphenylphosphite and sulfur-based antioxidants such as dilaurylthiodipropionate, hydroxybenzophenone-based Examples include benzotriazole-based ultraviolet absorbers, which can be added alone or in combination, but are not limited thereto. Among them, silicon oxide and silicone fine particles are preferable as the anti-blocking agent, and sucrose fatty acid ester is preferable as the antistatic agent. Particularly, the antistatic agent is preferably a surface coating type.

These additives may be added in advance to the resin (A), the resin (B) or the resin (C) as in the case of the plasticizer and the lubricant, or may be added to the resin (A) and the resin (B). May be added at the time of melt-kneading the resin (A) and the resin (C), or may be added by mixing a master batch prepared in advance.

In the present invention, the inner layer comprises a block copolymer (a-1) of a styrene monomer and a diene monomer, a styrene monomer (a-2), and methyl (meth) acrylate ( a-3) as a main component, and a multilayer shrink film having a copolymer resin layer of a styrene monomer and an acrylic monomer as surface layers on both surfaces thereof. The transparency, gloss, rigidity and surface hardness can be further improved by adopting such a multilayer structure.

The resin (A ') used here is a rubbery polymer (a-1) which is a raw material component of the resin (A), a styrene monomer (a-2), and methyl (meth) acrylate. (A-3) and obtained by graft polymerization. The content of the rubbery polymer (a-1) in the resin (A ′) is not particularly limited, and can be appropriately set according to the purpose of use. Here, as in the case of the resin (A), the rubbery polymer (a-1) is a styrene-based monomer and a diene-based monomer in view of the balance between transparency and impact resistance and the improvement in bending whitening. Block copolymers with monomers are preferred.
The block copolymer of the styrene-based monomer and the diene-based monomer is not particularly limited, but the styrene skeleton content of 30 to 55% by weight is sufficient for impact resistance and transparency. It is preferable from the viewpoint that it becomes good.

Further, the bonding form of the polybutadiene structural site in the block copolymer of the styrene monomer and the diene monomer is not particularly limited, but the unsaturated bond based on the diene monomer of the block copolymer is not limited. Of which, the ratio of 1,2-vinyl bonds is 14 to 25%, particularly 16 to
It is preferred that the content is 22%, and the remainder is cis and trans bonds, since the grafting ratio becomes appropriate and a shrink film having an excellent balance between transparency and impact resistance can be obtained.

The block copolymer may be bonded in any of a random bonding mode and a block bonding mode, both of which can be used, but the block bonding is preferred.

Similarly to the resin (A), the resin (A ′) is grafted with a (meth) acrylic acid alkyl ester (a-4) having 4 or more carbon atoms as the fourth component, so that the resin (A ′) has a low-temperature shrinkage property. Not only can be imparted, but also a shrink film having extremely good natural shrinkage inhibiting properties can be obtained.

The method of polymerizing the resin (A ') is not particularly limited, and may be any of bulk-suspension polymerization, solution polymerization and bulk polymerization, and is a preferred example of the polymerization method of the resin (A). In a continuous bulk polymerization line incorporating a stirred reactor and a tubular reactor in which a plurality of mixing elements without moving parts are fixed, static mixing is performed by the tubular reactor. However, a method of performing bulk polymerization continuously is preferable from the viewpoint that the polymer composition can be uniformly controlled and the transparency and impact resistance of the shrink film are improved.

Raw material component (a-1) in resin (A ')
The polymerization ratio of (a-3) is not particularly limited, but is not particularly limited as described above. However, since the balance between the transparency of the resin and the impact strength is significantly improved, the weight (A-1) / [(a-2) + (a-3)]
= 1 / 99-20 / 80, and (a-2) / (a-3)
= 45/55 to 85/15 is preferable.

When an alkyl (meth) acrylate (a-4) having an alkyl group having 4 or more carbon atoms is used as the fourth component, methyl (meth) acrylate (a-3) and ( When the mixing ratio with the alkyl (meth) acrylate (a-4) is the former / the latter = 9 on a weight basis.
It is preferable that the ratio be 0/10 to 40/60, since the shrink film has extremely excellent low-temperature shrinkage and natural shrinkage inhibiting properties.

When the block copolymer (a-1) as a raw material component is used at a ratio of 1 to 20% by weight as the resin (A '), as in the case of the single-layer shrink film, By using the previously described resin (B) together,
Impact resistance and bending whitening can be further improved without impairing transparency and rigidity.

The mixing ratio of the resin (A ′) and the resin (B) is not particularly limited, but the resin (A ′) and the resin (B)
50% by weight or less based on the total weight of
Is preferably 1 to 50% by weight, and (A ′) / (B) = 9 from the viewpoint of more excellent transparency and impact resistance.
More preferably, it is 5/5 to 55/45. Mixing method is not particularly limited, continuous by uniaxial or biaxial extruder or the like, or it is preferable to melt-kneading before Ri extrusion formed by batch by Banbury mixer or the like, resin (A ' ) And the resin (B) are preferably uniformly dispersed in the melting temperature range of the resin (B).

Further, the resin (A ′) constituting the inner layer of the multilayer shrink film is further provided with a purpose of further improving bending whitening without impairing transparency and rigidity of the shrink film, and further improving impact resistance. A block copolymer (C) of a specific styrene monomer and a diene monomer may be contained.

The block copolymer (C) of the styrene monomer and the diene monomer is not particularly limited, but the styrene monomer is 5 to 50% by weight and the diene monomer is 95 to 50% by weight. %, Preferably 10 to 40% by weight of the styrene-based monomer and 90 to 60% by weight of the diene-based monomer.

The styrene monomer constituting the block copolymer (C) of the styrene monomer and the diene monomer includes, for example, styrene, α-methylstyrene,
m-methylstyrene, p-methylstyrene, ethylstyrene, isobutylstyrene, tert-butylstyrene, o-bromostyrene, m-bromostyrene, p-bromostyrene, o-chlorostyrene, m-chlorostyrene, p-chlorostyrene And the like, among which styrene is preferred from the viewpoint of transparency and compatibility with the resin (A ′).

The diene monomer constituting the block copolymer (C) of the styrene monomer and the diene monomer includes, for example, butadiene, chloroprene, isoprene, 1,3-pentadiene and the like. Butadiene is preferred because of its transparency and compatibility with the resin (A ').

Although the structure of the block copolymer (C) of the styrene-based monomer and the diene-based monomer is not particularly limited, the general structural formulas (AB) n, ABA, B
-(AB) n, [(BA) n] -m + 2X, [(A-
B) n] -m + 2X, [(BA) n-B] -m + 2X, [(A
-B) n-A] -m + 2X is preferred.
(A: styrene block, B: diene block, X:
Shows the residue of the coupling agent or the residue of the initiator. n and m are integers of 1 or more. )

When the resin (A '), the block copolymer (C) of the styrene-based monomer and the diene-based monomer are blended, the blending ratio is not limited, but the impact resistance and the prevention of bending whitening are prevented. (A ') / Resin (C) = 99/1 to 60/40% by weight is preferable in view of the remarkable improvement effect, and particularly preferably 95/5 to 70/30% by weight. .

The method of blending the resin (A ') and the resin (C) is not particularly limited, and is the same as that for blending the resin (A') and the resin (B) with a single-screw or twin-screw extruder. It is preferable that the resin (C) is uniformly dispersed in a melting temperature range of the resin (A) and the resin (C) by a continuous method using a machine or a batch method using a Banbury mixer or the like before the extrusion film formation. Is preferred.

A resin component constituting such an inner layer, that is, a resin (A ′), a mixture of the resin (A ′) and the resin (B), or a mixture of the resin (A ′) and the resin (C) In addition,
By adding a plasticizer or a lubricant, the shrinkage starting temperature and shrinkage gradient of the shrink film can be adjusted.

Examples of such a plasticizer include dibasic acids such as succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, and ethylene glycol, 1,2-propylene glycol, 3-propylene glycol, 1,2-butylene glycol, 1,3
-Butylene glycol, 1,4-butylene glycol,
Neopentyl glycol, 1,5-pentanediol, 2,2,4-trimethyl-1,3-pentanediol, 3-methyl-1,5-pentanediol, 1,6
A dihydric alcohol comprising a dihydric alcohol having a molecular weight of 200 or less, such as hexanediol, and preferably having a terminal capping agent of a monohydric alcohol or a monobasic acid;
Phthalate (DBP), dioctyl phthalate (DO
P), phthalic acid such as diheptyl phthalate (DHP), butyl benzyl phthalate (BBP), butyl phthalyl butyl glycolate (BPBG);
n-butyl adipate, di- (2-ethylhexyl)
Adipic acid such as adipate (DOA), citric acid such as acetyl tri-n-butyl citrate (ATBC), di-n-butyl sebacate (DBS), di- (2
-Ethylhexyl) sebacate (DOS), epoxidized soybean oil (ESBO), epoxidized linseed oil (ELSO), epoxidized fatty acid ester (EFA)
E) and the like.

In particular, polyester-based and phthalic-based plasticizers allow fine adjustment of the shrinkage initiation temperature, and have good compatibility with resin (A '), resin (B) and resin (C) and are transparent. This is advantageous because it has the advantage of not reducing the properties.

Examples of the lubricant include metal soaps, hydrocarbon liquid paraffins, polyethylene waxes, fatty acid-based higher fatty acids, oxy fatty acids, etc., fatty acid amide-based fatty amides, bis-fatty acid amides, and ester-based lubricants. Glycerides, ester waxes, fatty acid ketones,
Fatty alcohol-based monohydric alcohols, polyhydric alcohols and the like and partial esters of aliphatic and polyhydric alcohols, and complex lubricants can be added. Particularly, liquid paraffin, paraffin such as paraffin wax, dimethylpolysiloxane,
Organic polysiloxanes such as methylphenylpolysiloxane, bisfatty acid amides such as ethylene bisstearyl amide, and ester waxes such as alkyl phosphates are preferred from the viewpoint of transparency and surface smoothness.

The method of adding the plasticizer and the lubricant is not particularly limited, but may be added to the resin (A ′), the resin (B) or the resin (C) in advance, or may be added to the resin (A ′). ) And the resin (B), or the resin (A ′) and the resin (C) during the melt-kneading, or may be added by mixing a previously prepared master batch.

The amount of these additives is not particularly limited in accordance with the purpose, and may be 0.1 to 100 parts by weight of the resin composition.
It is possible to add from 0.01 to 20 parts by weight, preferably from 0.02 to 10 parts by weight.
More preferably, it is added in the range of 0.02 to 5 parts by weight.

Further, other additives may be added to the resin (A '), the composition of the resin (A') and the resin (B), or the composition of the resin (A ') and the resin (C). Is possible. Other additives, for example, silicon oxide and silicone fine particles, nylon fine particles, anti-blocking agents such as high-density polyethylene fine particles, sucrose fatty acid ester,
Charge of fatty acids such as glycerin fatty acid esters, sorbitan fatty acid esters, polyglycerin fatty acid esters, ethylene oxide adducts, fatty acid amides, fatty acid ketones, fatty acid esters and cationic activators, anionic activators, amphoteric activators, etc. Inhibitor, 2,6-di-t
Phenols such as -butyl-p-cresol (BHT), phosphorus-based antioxidants such as triphenylphosphite, and sulfur-based antioxidants such as dilaurylthiodipropionate, and ultraviolet absorption such as hydroxybenzophenone and hydroxybenzotriazole. And can be added alone or in combination.

The amount of these additives is not particularly limited either, but is generally 0.01 to 20 parts by weight, preferably 0.0 to 20 parts by weight, per 100 parts by weight of the resin composition.
The content is preferably 2 to 10 parts by weight, more preferably 0.02 to 5 parts by weight.

These additives may be added to the resin (A ′), the resin (B) or the resin (C) in advance, as in the case of the plasticizer and the lubricant, or may be added to the resin (A) and the resin (B). And
Alternatively, it may be added when the resin (A ′) and the resin (C) are melt-kneaded, or may be added by mixing a previously prepared master batch.

The copolymer resin of a styrene-based monomer and an acrylic-based monomer constituting both of the inner layers described above gives the shrink film high transparency, high gloss and high rigidity, and further improves the surface hardness. Things.

Examples of the styrene monomer constituting the copolymer resin include styrene, α-methylstyrene, m-methylstyrene, p-methylstyrene, ethylstyrene, isobutylstyrene, tert-butylstyrene, and o-bromostyrene. , M-bromostyrene, p
-Bromostyrene, o-chlorostyrene, m-chlorostyrene, p-chlorostyrene and the like. Among them, styrene is preferred from the viewpoint of high transparency, high gloss, and high rigidity of the shrink film.

Examples of the acrylic monomer include, but are not particularly limited to, alkyl esters such as (meth) acrylic acid, methyl (meth) acrylate, ethyl (meth) acrylate, and butyl (meth) acrylate. Methyl (meth) acrylate is preferred from the viewpoints of transparency, high gloss, and excellent surface hardness.

That is, a styrene-methyl (meth) acrylate resin is preferred because it is compatible with the resin (A ′) forming the inner layer, does not peel off from the lamination interface, and has excellent transparency and glossiness itself. Further, the viscosity characteristics of the surface resin are as follows:
Under extrusion processing conditions, those exhibiting flow characteristics that are equal to the viscosity of the resin (A ′) or a viscosity difference of about ± 10000 poise are preferred.

As in the case of the single-layer shrink film, a plasticizer or a lubricant is added to the copolymer resin of the styrene-based monomer and the acrylic-based monomer to form such a surface layer, whereby the shrinkage of the shrink film is reduced. The starting temperature and shrinkage gradient can be adjusted.

Examples of such a plasticizer include dibasic acids such as succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid and sebacic acid, ethylene glycol, 1,2-propylene glycol, 3-propylene glycol, 1,2-butylene glycol, 1,3
-Butylene glycol, 1,4-butylene glycol,
Neopentyl glycol, 1,5-pentanediol, 2,2,4-trimethyl-1,3-pentanediol, 3-methyl-1,5-pentanediol, 1,6
A dihydric alcohol comprising a dihydric alcohol having a molecular weight of 200 or less, such as hexanediol, and preferably having a terminal capping agent of a monohydric alcohol or a monobasic acid;
Phthalate (DBP), dioctyl phthalate (DO
P), phthalic acid such as diheptyl phthalate (DHP), butyl benzyl phthalate (BBP), butyl phthalyl butyl glycolate (BPBG);
n-butyl adipate, di- (2-ethylhexyl)
Adipic acid such as adipate (DOA), citric acid such as acetyl tri-n-butyl citrate (ATBC), di-n-butyl sebacate (DBS), di- (2
-Ethylhexyl) sebacate (DOS), epoxidized soybean oil (ESBO), epoxidized linseed oil (ELSO), epoxidized fatty acid ester (EFA)
E) and the like.

In particular, polyester-based and phthalic-based plasticizers allow fine adjustment of the shrinkage onset temperature and have good compatibility with a copolymer resin of a styrene monomer and a (meth) acrylic monomer. This is advantageous because it does not lower the transparency.

Examples of the lubricant include metal soaps, hydrocarbon liquid paraffins, polyethylene waxes, fatty acid-based higher fatty acids, oxy fatty acids, etc., fatty acid amide-based fatty acid amides, bis-fatty acid amides, etc., and ester-based lubricants. Glycerides, ester waxes, fatty acid ketones,
Fatty alcohol-based monohydric alcohols, polyhydric alcohols and the like and partial esters of aliphatic and polyhydric alcohols, and complex lubricants can be added. Particularly, liquid paraffin, paraffin such as paraffin wax, dimethylpolysiloxane,
Organic polysiloxanes such as methylphenylpolysiloxane, bisfatty acid amides such as ethylene bisstearyl amide, and ester waxes such as alkyl phosphates are preferred from the viewpoint of transparency and surface smoothness.

The method for adding the plasticizer and the lubricant is not particularly limited, and can be added by melt-kneading with the copolymer resin.

The amount of these additives is not particularly limited either, but may be from 0.01 to 20 parts by weight, based on 100 parts by weight of the copolymer resin of the styrene monomer and the acrylic monomer, depending on the purpose. Preferably 0.02 to 10
Although it is possible to add by weight, it is more preferable to add in the range of 0.02 to 5 parts by weight from the viewpoint of natural shrinkage inhibiting properties.

Furthermore, in addition to the above-mentioned plasticizer and lubricant, other additives can be added to the copolymer resin of the styrene-based monomer and the acrylic-based monomer forming the surface layer.

Other additives include, for example, anti-blocking agents such as silicon oxide, silicone fine particles, nylon fine particles and high-density polyethylene fine particles, sucrose fatty acid esters, glycerin fatty acid esters, sorbitan fatty acid esters, polyglycerin fatty acid esters, and ethylene oxide. Antistatic agents such as fatty acids such as adducts, fatty acid amides, fatty acid ketones, fatty acid esters and cationic activators, anionic activators and amphoteric activators;
Phenol-based antioxidants such as di-t-butyl-p-cresol (BHT), phosphorus-based antioxidants such as triphenylphosphite, and sulfur-based antioxidants such as dilaurylthiodipropionate;
An ultraviolet absorber such as a hydroxybenzophenone type or a hydroxybenzotriazole type may be mentioned, and may be added alone or in combination.

The amount of these additives is not particularly limited, but is generally 0.01 to 20 parts by weight, preferably 0.0 to 20 parts by weight, based on 100 parts by weight of the copolymer resin.
The content is preferably 2 to 10 parts by weight, more preferably 0.02 to 5 parts by weight.

These additives can be added by melt-kneading with the copolymer resin as in the case of the plasticizer and the lubricant.

The layer structure of the multilayer shrink film is not particularly limited, but the thickness of the inner layer containing resin (A ') as a main component is from 8 to 250 μm, and styrene The thickness of the surface layer mainly composed of a copolymer resin of an acrylic monomer and an acrylic monomer is 2 to 50.
It is preferable that the particle size be μm because the rigidity, practical shrinkage and impact resistance of the inner layer and the gloss and surface hardness of the outer layer are well balanced, and the transparency as a whole is extremely good. In particular, when the inner layer is in the above range, it becomes easy to adjust the shrinkage characteristics such as the shrinkage start temperature and the shrinkage gradient, and there is also an effect of suppressing natural shrinkage.

Further, from the viewpoint that these characteristics become more remarkable, the thickness of the inner layer is in the range of 18 to 160 μm, more preferably 28 to 80 μm, and the thickness of the surface layer is 4 to 160 μm.
It is preferably in the range of 30 μm, more preferably 8 to 20 μm.

The method for producing the single-layer or multilayer shrink film described in detail above is not particularly limited, but the production method of the present invention described below is preferred. That is, the production method of the present invention provides a rubbery polymer (a-
1), a styrenic monomer (a-2), and (meth) a
Methyl acrylate (a-3) with the rubbery polymer (a
-1) is used in a ratio of 1 to 20% by weight to obtain a graft weight.
A resin component containing the resin (A) obtained as an essential component
Extrusion after melt kneading, in at least one direction, to JISK-7198
T when the glass transition point measured according to Tg
g to (Tg + 30 ° C)
It is to be a film . The resulting shuffle
The transparency of the link film can be significantly improved. That is, T
If it is less than g, the resin does not soften and stretching film formation is impossible,
Above (Tg + 30 ° C), rubber particles are formed on the film surface after stretching.
Irregularities originating from the child are generated, and visible light film surface
Irregular reflection occurs and the transparency is reduced. Said
When producing the shrink film of the present invention,
In addition to the fat (A), the resin (B) is an essential component, and in addition, a resin component in which the above components are blended is melt-kneaded, extruded, and stretched in at least one direction . In the case of a multi-layer shrink film, the resin component containing the above-mentioned resin (A ') as a main component and other components are extruded after melt-kneading and stretched in at least one direction. A method of forming a surface layer containing a copolymer resin of an acrylic monomer and an acrylic monomer as a main component is exemplified.

In the latter method for producing a multilayer shrink film, specifically, a method of co-extrusion and stretching, a method of thermally laminating a film formed in advance simultaneously with extrusion and then stretching, and a method of extruding and forming separately. A method of stretching a raw material obtained by laminating the film-formed sheets, or a method of laminating films obtained by extruding and stretching separately.

In the method (1), for example, there is a film forming method by a T-die method or an inflation method.
Lamination is carried out by a commonly used method such as a feed block method or a multi-manifold die method, but is not limited thereto. The extrusion temperature of the surface layer and the inner layer was 190 to 250 ° C., especially 20
0-230 ° C is preferred. Further, it is preferable to stretch immediately and continuously after the extrusion.

In the method of (1), for example, while extruding a sheet of the inner layer resin alone by the above-mentioned sheet forming method using a T-die or inflation, the surface resin alone previously formed in the same manner on both surfaces thereof is formed. A method of thermally laminating a film can be used.

In the method (1), for example, a method of separately forming a film of a surface layer and a resin of an inner layer resin separately by the above-described sheet film forming method by T-die or inflation, and then laminating using an adhesive or the like can be mentioned.

Of these, the co-extrusion method is preferred because the film production process is simple and the cost is advantageous.

In the production of the single-layer and multi-layer shrink films, the extrusion temperature at the time of producing the single-layer or multilayer shrink film from the raw material composition varies depending on the production method and is not particularly limited.
~ 250 ° C, especially preferably 200 ~ 230 ° C.

In the above method for producing a single-layer shrink film or a multilayer shrink film,
The stretching method is not particularly limited, and may be uniaxial or biaxial.
A method of stretching simultaneously or sequentially is preferred.

The stretching method will be described in detail. In the case of flat uniaxial stretching, the film is mainly stretched in the extrusion direction at a speed difference between heating rolls or in a direction perpendicular to the extrusion direction by a tenter or the like. In the case of (1), the film is longitudinally stretched in the extrusion direction at a speed difference between the heating rolls and then horizontally stretched by a tenter or the like, or simultaneously stretched vertically and horizontally in the tenter.

In the case of annular uniaxial stretching, the expansion of bubbles is suppressed and draft is suppressed in the extrusion direction, or the draft is suppressed and the bubbles are expanded to extend substantially in the circumferential direction. In the case of biaxial stretching, Air is injected into the bubble and stretched simultaneously or sequentially in the extrusion direction and the circumferential direction.

The unstretched sheet extruded from the T-die is an air knife, a vacuum knife, a touch roll,
It is cooled uniformly by electrostatic pinning or the like, but the cooling method is not limited to this.

In the production method of the present invention, the stretching ratio is
The stretching ratio in one direction in the stretching direction is specifically 2.0 to 6.0 times, preferably 2.5 to 5.5 times, and more preferably 3.0 to 4.5 times. Is preferred. When the stretching ratio is 2 times or more, a decrease in shrinkage during shrink wrapping, generation of wrinkles and looseness, poor finish, and the like can be prevented. Excellent film formability and improved productivity.

The stretching temperature is, as described above, JIS K-7198
The temperature range is from Tg to (Tg + 30 ° C.) where Tg is the glass transition point measured in accordance with Especially
The range of (Tg + 2 ° C) to (Tg + 15 ° C) is preferable.
Below (Tg), the resin does not soften and stretching film formation is impossible.
Above (Tg + 30 ° C.)
Irregularities due to the film particles occur, and the visible light film surface
Diffuse reflection occurs on the surface, resulting in reduced transparency.

In the production method of the present invention, it is possible to stretch at a relatively low temperature, whereby high rigidity,
At the same time as high transparency can be achieved, both low-temperature shrinkage and natural shrinkage suppression are achieved, and the coating finish (practical shrinkage) on the object to be coated becomes extremely good. Here, Tg is defined as JIS K- using a stretched film of the raw material composition, a raw material of a non-stretched sheet or a sheet formed by pressing.
It is a glass transition point (Tg) measured in accordance with 7198, and is a peak value of a loss tangent (tan δ) represented by a ratio of a storage elastic modulus and a loss elastic modulus, which are dynamic viscoelastic characteristic values.

The thickness of the obtained shrink film is not particularly limited, but is preferably from 10 to 250 μm. That is, when the thickness is 10 μm or more, the impact resistance becomes good, and it becomes easy to adjust the shrinkage characteristics such as the shrinkage starting temperature and the shrinkage gradient. On the other hand, 250μ
By setting m or less, transparency becomes remarkable.

When the single-layer or multi-layer shrink film described in detail above is used as a heat-shrinkable packaging material or a heat-shrinkable label material, the maximum shrinkage in the stretching direction is 30 to 50%.
95%, preferably 50-90%, more preferably 60%
Preferably it is ~ 85%. That is, the maximum shrinkage is 3
When it is 0% or more, uniform shrink wrapping can be performed without wrinkles or relaxation phenomenon, and practical shrinkage becomes good. On the other hand, when it is 90% or less, it is possible to stably form a stretched film.

Here, the shrinkage rate was 3 in a silicone oil bath.
The amount of shrinkage of the original dimension when heat-treated for 0 seconds is expressed as a percentage (%) obtained by dividing the amount of shrinkage by the original dimension. The maximum shrinkage rate is the equilibrium at which the shrinkage rate of the film does not change even when the temperature rises. Represents the contraction rate at the time.

The shrinkage gradient also affects the productivity at the time of shrink-wrapping, the finish after shrink-wrapping, the quality of the contents, and the like. In the present invention, the maximum shrinkage gradient is in the range of 0.5 to 10% / ° C. Is preferable, and in particular, the range of 2 to 5% / ° C. is preferable. When it is 0.5% / ° C. or more, the shrinkage response becomes good, the heating time is shortened, and the productivity is improved. In addition, as the heating time is shortened, it is possible to prevent deformation of the packaged object due to exposure in a high-temperature atmosphere. Also, 1
At 0% / ° C or more, the optimal shrinkage temperature range is narrow, so that shrinkage spots and wrinkles are easily generated, and the appearance after shrinkage packaging is deteriorated.
C. or lower is preferred.

[0105]

EXAMPLES The present invention will be described below in detail with reference to examples, but the content of the present invention is not limited to these examples.

Examples 1 to 8 As the resin (A), a styrene-butadiene block copolymer (styrene / butadiene weight ratio: 37.5 / 6)
2.5), styrene, methyl methacrylate, and n-butyl acrylate were used in the proportions shown in Tables 1 and 2, respectively, and a stirring reactor and a plurality of mixing elements without moving parts were fixed inside. In the continuous bulk polymerization line incorporating the tubular reactor, the bulk polymerization was continuously performed while performing static mixing by the tubular reactor.

Next, a 50 mm extruder (L / D = 24) was prepared using the obtained resin according to the composition shown in Tables 1 and 2.
After melt-kneading at, a non-stretched sheet is formed with a T-die, and continuously stretched and formed with a horizontal stretching machine (tenter) to a thickness of 50 μm.
m shrink film was obtained. Table 3 shows the stretching conditions.

In Tables 1 and 2, "DB
“P” and “DOP” are plasticizers, which represent dibutyl phthalate (DBP) and dioctyl phthalate (DOP), respectively, and are kneaded in advance with a part of the resin obtained in the example by a small twin-screw kneader. It was used in The same applies to the following Tables 7, 8 and 11.

In Tables 1 to 16 below, "parts" indicate "parts by weight" and "%" indicates "% by weight".

[0110]

[Table 1]

[0111]

[Table 2]

[0112]

[Table 3] Table 4 shows various properties of the shrink film thus obtained. In addition, each measurement was performed based on the following 1. to 10. 1. Haze: JIS K7105 2. Hikarizawa: JIS K7105 3. Impact: Compliant with JIS P8134 (Film Impact) 4. Modulus: Compliant with JIS K7127 5. Bending whitening: Bending the film 180 degrees, made of isoprene Observe the degree of whitening after passing through the nip roll.

◎: Completely no whitening ・ ・ ・: Very slight whitening, but hardly discernable by visual inspection ・ ・ ・: Craze occurred, slightly whitened visually ×: Crack Equal occurrence and complete whitening 6. Shrinkage onset temperature: The film was immersed in a silicone oil bath for 30 seconds at a temperature in the range of 30 to 160 ° C., and a percentage (%) was calculated from a value obtained by dividing a contracted length by an original dimension. . This percentage is defined as a shrinkage ratio, and a shrinkage curve is obtained from the shrinkage ratio and the temperature.
The temperature at which% shrinkage occurs is defined as the shrinkage start temperature. 7.Maximum shrinkage: Shrinkage reaches equilibrium in the above shrinkage curve,
Shrinkage when no longer changing. 8. Maximum shrinkage gradient: The gradient with the largest shrinkage rate with respect to temperature in the above shrinkage curve. 9. Practical shrinkage: 1.5 liter cylindrical PET bottle (maximum circumference of the body 300 mm) or glass bottle (maximum circumference of the body 250 mm), processed into a cylindrical shape with a margin of + 5% The bottle was covered with a film and covered with a shrink tunnel.

The observation items were the presence or absence of wrinkles after shrinkage coating and the adhesion. The adhesion was determined by comparing the small diameter of the upper part of the PET bottle (circumferential 210 mm) and the small diameter of the upper part of the glass bottle (circle 1).
30 mm) and the film circumference after shrink coating at each small diameter portion.

The setting condition of the shrink tunnel is P
ET bottle at tunnel temperature 100 ° C, transit time 5 seconds,
The glass bottle was kept at 150 ° C. for 5 seconds.

Evaluation Criteria: No wrinkles ○ Present ×: Adhesion: 100% ；: 102% ○: ~ 110% △: 110% or more × Comprehensive evaluation ◎: Completely tight body and upper part The small diameter part is covered without wrinkles and warps. ○ ・ ・ ・ Slightly small diameter part has insufficient shrinkage, but practically acceptable. △ ・ ・ ・ Small diameter part has insufficient shrinkage × ・ ・ ・ Complete Those which cannot be coated on the surface 10. Natural shrinkage: Shrinkage after leaving for 1 week in a constant temperature room at 45 ° C.

In Examples 1 to 8 above, shrink films excellent in practical use were obtained, satisfying the contradictory performances of transparency and impact resistance, and free of natural shrinkage, which is shrinkage at room temperature. In addition, it has high rigidity and excellent suitability for packaging machines.

[0118]

[Table 4]

Examples 9 to 11 The resin compositions obtained in Examples 2, 4 and 6 were used as a central layer.
Both surface layers were laminated by a co-extrusion feed block method using a styrene-methyl methacrylate (MMA content 50%) resin, and subjected to a stretching process with a horizontal stretching machine.
A shrink film of 40/5 μm having two types and three layers was obtained. In Example 11, 5 parts of a plasticizer (DOP) was added in advance to the surface layer in order to adjust the fluidity at the time of lamination and to make the shrinkage characteristics coincide with those of the central layer. . Tables 5 and 6 show the stretching conditions and various physical properties.

[0120]

[Table 5]

[0121]

[Table 6]

Examples 12 to 16 As the resin (A), the polymers obtained in Examples 2, 4 and 8 were used, and as the resin (B), a styrene-butadiene block copolymer, styrene, Using an MBS resin (/ = (60-80) / (20-40) / (30-10) in weight ratio) obtained from methyl (meth) acrylate, it is necessary to prepare two axes in advance according to the formulation in Table-7. After kneading with an extruder, an extruded film was formed with a 50 mm extruder (L / D = 24),
After stretching with a horizontal stretching machine, a shrink film having a thickness of 50 μm was obtained. The stretching processing conditions are shown in Table-9. Table 10 shows these physical properties.

Examples 17 to 19 Examples 2 to 4, and 8 were used as the resin (A ').
The polymer obtained in Example 12 and the resin (B)
As the inner layer, a resin component obtained by mixing the MBS resin used in No. 16 was used as the inner layer.
Using the styrene-methyl methacrylate resin used in No. 11, according to the formulation in Table-8, a laminated shrink film of two and three layers was obtained in the same manner as in Example 9. Table 9 shows the stretching conditions. Table 10 shows these physical properties.

[0124]

[Table 7]

[0125]

[Table 8]

[0126]

[Table 9]

[0127]

[Table 10]

Examples 20 to 22 As the resin (A '), the polymers obtained in Examples 2 and 4 were used, and as the resin (C), the MFR (190.degree.
16 kg) A triblock-type styrene-butadiene block copolymer having 6.1 g / 10 min and a styrene content of 35% was used as a resin component for the inner layer, and styrene used in Examples 9, 10 and 11 was used as a surface resin. -Using a methyl methacrylate resin and following the formulation in Table 11, a laminated shrink film having two and three layers was obtained in the same manner as in Example 9. Table 12 shows the stretching conditions. Table 13 shows these physical properties.

[0129]

[Table 11]

[0130]

[Table 12]

[0131]

[Table 13]

Comparative Examples 1 to 3 In Comparative Examples 1 and 2, a resin component mainly composed of a styrene-butadiene block copolymer shown in Table 14 was used, and a film was formed by stretching under the stretching conditions shown in Table 15. A 50 μm shrink film was obtained. In Comparative Example 3, the performance of a commercially available 60 μm PET bottle shrink film for labeling was examined. Table 16 shows these physical properties.

[0133]

[Table 14]

[0134]

[Table 15]

[0135]

[Table 16]

[0136]

According to the present invention, a shrink film having both rigidity and transparency and excellent impact resistance can be provided. In addition, a natural shrinkage inhibiting property becomes good while further providing low-temperature shrinkage property, and a shrink film having good practical shrinkage property can be obtained.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI B32B 27/18 B32B 27/18 Z 27/30 27/30 Z B65B 53/00 B65B 53/00 NB65D 65/40 B65D 65 / 40D C08F 279/02 C08F 279/02 287/00 287/00 // B29K 96:02 B29L 7:00 (56) References JP-A-7-82387 (JP, A) JP-A 5-271503 (JP JP-A-1-207347 (JP, A) JP-A-50-66589 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C08J 5/18 CA (STN)

Claims (14)

(57) [Claims] 1. A rubbery polymer (a-1), a styrene monomer (a-2) and methyl (meth) acrylate (a-
3) and a resin (A) obtained by graft polymerization using the rubbery polymer (a-1) in a ratio of 1 to 20% by weight, a rubbery polymer (b-1) and styrene. Resin (B) obtained by graft-polymerizing the rubber-based polymer (b-1) with the monomer (b-2) and the acrylic monomer (b-3) at a ratio of 30 to 90% by weight. ) And
A shrink film comprising the resin (B) in a proportion of 50% by weight or less based on the total weight of (A) and (B). 2. The shrink film according to claim 1, wherein the rubbery polymer (a-1) is a block copolymer of a styrene monomer and a diene monomer. 3. The shrink film according to claim 2, wherein the rubbery polymer (a-1) has a styrene content of 30 to 55% by weight. 4. The resin (A) further comprises, as a monomer component, an alkyl (meth) acrylate (a-4) having an alkyl group having 4 or more carbon atoms in an amount of 1 to 30% by weight of the raw material monomer component. 4. The shrink film according to claim 1, wherein the shrink film is obtained by graft polymerization using the following range. 5. The shrink film according to claim 1, further comprising a plasticizer or a lubricant. 6. The resin (A ′) whose inner layer is obtained by graft polymerization of a rubbery polymer (a-1), a styrene monomer (a-2) and methyl (meth) acrylate (a-3). )
A shrink film characterized by having a resin layer mainly composed of a copolymer resin of a styrene monomer and an acrylic monomer as a surface layer on both surfaces thereof. 7. The shrink film according to claim 6 , wherein the thickness of the inner layer is from 8 to 250 μm, and the total thickness of the surface layer is from 2 to 50 μm. 8. The rubbery polymer (a-1), wherein the inner layer comprises a rubbery polymer (a-1), a styrene monomer (a-2) and methyl (meth) acrylate (a-3). ) Is 1-2
A resin (A ') obtained by graft polymerization using a ratio of 0% by weight, a rubbery polymer (b-1), a styrene monomer (b-2), and an acrylic monomer (b-3). (B) obtained by graft polymerization using the above rubbery polymer (b-1) in a ratio of 30 to 90% by weight.
The shrink film according to claim 7, which comprises: 9. An inner layer comprising a rubbery polymer (a-1), a styrenic monomer (a-2) and methyl (meth) acrylate (a-3), wherein said block copolymer (a-1) ) Is 1
A resin (A ') obtained by graft polymerization using a proportion of -20% by weight and a block copolymer (C) of a styrene-based monomer and a diene-based monomer (C). Shrink film as described. 10. A rubbery polymer (a-1), a styrene-based monomer (a-2) and methyl (meth) acrylate (a-3), Is 1-2
The resin component containing resin (A) obtained by graft polymerization using a ratio of 0% by weight is melt-kneaded and then extruded, and glass transition measured in at least one direction according to JIS K-7198. Tg to (Tg +
(30 ° C.). 11. A rubbery polymer (a-1), a styrenic monomer (a-2) and methyl (meth) acrylate (a-
3) and a resin (A) obtained by graft polymerization using the rubbery polymer (a-1) in a ratio of 1 to 20% by weight, a rubbery polymer (b-1) and styrene. Resin (B) obtained by graft-polymerizing the rubber-based polymer (b-1) with the monomer (b-2) and the acrylic monomer (b-3) at a ratio of 30 to 90% by weight. ) And
The production method according to claim 10, wherein the resin component containing the resin (B) in a ratio of 50% by weight or less based on the total weight of (A) and (B) is melt-kneaded, extruded, and stretched in at least one direction. 12. The rubbery polymer (a-1) as an inner layer
And a resin component containing a resin (A ′) obtained by graft polymerization of a styrene-based monomer (a-2) and methyl (meth) acrylate (a-3) as a main component, extruding after melt-kneading. A method for producing a shrink film, comprising: stretching in one direction, and forming a surface layer mainly composed of a copolymer resin of a styrene monomer and an acrylic monomer on both surfaces thereof. 13. The production method according to claim 10, wherein the stretching ratio at the time of stretching is 2 to 6 times. 14. The resin (A) or the resin (A ′)
Further, a (meth) acrylic acid alkyl ester having an alkyl group having 4 or more carbon atoms as a monomer component (a-
The method according to any one of claims 10 to 13, wherein graft polymerization is performed using 4) in an amount of 1 to 30% by weight.