CN115666937A

CN115666937A - Heat-shrinkable multilayer film, heat-shrinkable label and beverage container

Info

Publication number: CN115666937A
Application number: CN202180037733.0A
Authority: CN
Inventors: 药野瞳; 吉田准; 泽里正
Original assignee: Denka Co Ltd
Current assignee: Denka Co Ltd
Priority date: 2020-05-25
Filing date: 2021-05-25
Publication date: 2023-01-31
Also published as: WO2021241562A1

Abstract

The object of the present embodiment is to provide a thermoplastic resin composition having excellent interlayer adhesion strength, heat shrinkability, transparency,A heat-shrinkable multilayer film having film formability and film appearance. The heat-shrinkable multilayer film of the present embodiment comprises at least a first layer comprising a first block copolymer containing a vinyl aromatic hydrocarbon and a conjugated diene, and a second layer comprising a polyester resin and a second block copolymer containing a vinyl aromatic hydrocarbon and a conjugated diene, wherein the first layer and the second layer are in direct contact with each other, the content of the second block copolymer in the second layer is 0.1 to 35 mass%, the mass ratio of the vinyl aromatic hydrocarbon and the conjugated diene in the second block copolymer is 65/35 to 85/15, and the number-average molecular weight of the second block copolymer is 5.0 × 10 ⁴ ～40.0×10 ⁴ 。

Description

Heat-shrinkable multilayer film, heat-shrinkable label and beverage container

Technical Field

The present embodiment relates to a heat-shrinkable multilayer film, a heat-shrinkable label using the same, or a beverage container having the heat-shrinkable label.

Background

A heat-shrinkable film using a block copolymer composed of a vinyl aromatic hydrocarbon and a conjugated diene is widely used as a shrink packaging product because it can be applied to various shapes and mounting modes of a packaged body. Further, it is excellent in that it does not cause environmental pollution such as polyvinyl chloride when discarded.

A heat-shrinkable film using a block copolymer has excellent heat shrinkability and low environmental load properties, but on the other hand, the film tends to shrink slightly (also referred to as natural shrinkability) if a long period of time passes even under a normal temperature environment. For example, there is a problem that a slight dimensional change occurs in a heat-shrinkable film stored in a warehouse, and a printing shift occurs in the production of a label. In order to solve such problems, a heat shrinkable film in which a layer of a block copolymer and a layer of a polyester resin are combined to form a multilayer to reduce natural shrinkability has been proposed.

In the case of obtaining a heat shrinkable film in which a layer of a block copolymer and a layer of a polyester resin are formed into a multilayer, a method of inserting an adhesive layer between the two layers may be selected, but at the same time, a problem arises in that new materials and equipment are required to provide an adhesive layer. Under such circumstances, studies have been made to solve the above problems. For example, patent document 1 discloses a shrinkable label comprising a base film (1), the base film (1) comprising an intermediate layer (A1) and outer surface layers (B1) laminated on both sides of the intermediate layer (A1), wherein the outer surface layers (B1) are composed of a polyester resin containing 1, 4-cyclohexanedimethanol as a diol component, the intermediate layer (A1) is composed of a composite resin of a styrene resin and the polyester resin, the styrene resin contains a resin containing butadiene, and the intermediate layer (A1) and the outer surface layers (B1) are directly bonded by fusion bonding. Patent document 2 discloses a heat-shrinkable laminated film composed of at least three layers including an intermediate layer and front and back layers laminated on both sides of the intermediate layer, the heat-shrinkable laminated film being uniaxially stretched at least, and having a heat shrinkage rate in the main shrinkage direction of 30% or more after immersion in hot water at 80 ℃ for 10 seconds, characterized in that the front and back layers contain at least one polyester resin, the intermediate layer contains at least one of block copolymers of a styrene-based hydrocarbon and a conjugated diene-based hydrocarbon, and the refractive index (n 1) of the block copolymers measured according to JIS K7142 is within the range of the refractive index (n 2) ± 0.02 of the polyester resin. Patent document 3 discloses a heat-shrinkable laminated film composed of at least three layers, i.e., an intermediate layer and front and back layers laminated on both sides of the intermediate layer, wherein the intermediate layer is composed mainly of a mixed resin of a copolymer (a) of an aromatic hydrocarbon and a conjugated diene hydrocarbon containing 50 mass% or more of an aromatic hydrocarbon and a copolymer (B) of an aromatic hydrocarbon and a conjugated diene hydrocarbon having 5 or less carbon atoms or a hydrogenated derivative thereof (B') in an amount of 1 to 30 parts by mass based on 100 parts by mass of the copolymer (a), and the front and back layers are composed of a polyester-based resin. Patent document 4 discloses a film comprising a laminate of two types of three layers, i.e., a skin layer/a core layer/a skin layer, each of which has a skin layer on both sides of a core layer, wherein the skin layer is a resin layer comprising 90 to 100 wt% of a polyester resin, and the core layer comprises at least 60 to 90 wt% of a styrene unit, 5 to 30 wt% of a conjugated diene unit, and 0.5 to 5 wt% of an oxazoline unit. Patent document 5 discloses a heat-shrinkable multilayer film in which a front layer containing a polystyrene resin and a polyester resin and a back layer containing a polystyrene resin and an intermediate layer containing a polystyrene resin are laminated, and the content of a polymer diol is 0.1 to 3.0 mol% based on 100 mol% of a diol component in the polyester resin. Patent document 6 discloses a resin composition which is a mixture of the resins specified in (a) and (B) and has an epoxy number concentration of 0.5 to 1.6% by mass as measured according to astm d 1652. Patent document 7 discloses a block copolymer resin composition containing 85 to 99.5 parts by mass of a resin component a and 0.5 to 15 parts by mass of a resin component B, the resin component a containing at least one vinyl aromatic hydrocarbon-conjugated diene block copolymer, the mass ratio of the vinyl aromatic hydrocarbon to the conjugated diene being 80/20 to 65/35, and the resin component B being a vinyl aromatic hydrocarbon-conjugated diene block copolymer or a conjugated diene polymer, wherein the mass ratio of the vinyl aromatic hydrocarbon to the conjugated diene is 30/70 to 0/100, and the number average molecular weight is 5,000 to 40,000.

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open publication No. 2004-170715

Patent document 2: japanese patent laid-open publication No. 2005-131824

Patent document 3: japanese patent laid-open publication No. 2006-159903

Patent document 4: japanese patent laid-open No. 2008-207487

Patent document 5: japanese patent laid-open No. 2012-210717

Patent document 6: japanese patent laid-open publication No. 2013-199616

Patent document 7: international publication No. 2016/117583

Disclosure of Invention

However, the multilayer film having the adhesive layer interposed therebetween requires a step of forming the adhesive layer, which increases the cost, and the adhesive layer may not be peeled off following the shrinkage of the film. On the other hand, a multilayer film without an adhesive layer interposed may have a certain degree of interlayer adhesive strength by selecting a specific resin or the like. However, a heat-shrinkable multilayer film is required to be excellent in heat shrinkability, transparency, film formability and film appearance in addition to interlayer adhesion strength, and development of a heat-shrinkable multilayer film having excellent properties is desired.

Accordingly, an object of the present embodiment is to provide a heat shrinkable multilayer film having good interlayer adhesion strength, heat shrinkability, transparency, film formability, and film appearance.

The embodiment can be described, for example, as follows.

(1) A heat-shrinkable multilayer film comprising at least a first layer comprising a first block copolymer containing a vinyl aromatic hydrocarbon and a conjugated diene, and a second layer comprising a polyester resin and a second block copolymer containing a vinyl aromatic hydrocarbon and a conjugated diene,

the first layer and the second layer are directly connected,

the content of the second block copolymer in the second layer is 0.1 to 35 mass%,

the mass ratio of the vinyl aromatic hydrocarbon to the conjugated diene in the second block copolymer is 65/35 to 85/15,

the number average molecular weight of the second block copolymer was 5.0X 10 ⁴ ～40.0×10 ⁴ 。

(2) The heat-shrinkable multilayer film according to the item (1), wherein the second block copolymer has a block portion composed of a vinyl aromatic hydrocarbon at least at one end portion.

(3) The heat-shrinkable multilayer film according to (1) or (2), wherein the mass ratio of the vinyl aromatic hydrocarbon and the conjugated diene in the first block copolymer is 65/35 to 85/15.

(4) The heat-shrinkable multilayer film according to any one of (1) to (3), wherein the content of the first block copolymer in the first layer is 50% by mass or more.

(5) The heat-shrinkable multilayer film according to any one of (1) to (4), wherein the content of the polyester-based resin in the second layer is 60% by mass or more and 99% by mass or less.

(6) The heat-shrinkable multilayer film according to any one of (1) to (5), wherein the polyester-based resin comprises a polyethylene terephthalate glycol modified with a diol containing terephthalic acid, ethylene glycol, and at least one member selected from the group consisting of 1, 4-cyclohexanedimethanol and neopentyl glycol as a polycondensation component.

(7) The heat shrinkable multilayer film according to (6), wherein the glycol-modified polyethylene terephthalate does not contain a polyol having a molecular weight of 400 or more.

(8) The heat-shrinkable multilayer film according to (6) or (7), wherein the glass transition temperature (Tg) of the glycol-modified polyethylene terephthalate is 60 ℃ or more and 120 ℃ or less.

(9) The heat-shrinkable multilayer film according to any one of (1) to (8), wherein the second layer is disposed on both of a first surface of the first layer and a second surface opposite to the first surface.

(10) A heat-shrinkable label comprising the heat-shrinkable multilayer film according to any one of (1) to (9).

(11) A beverage container having the heat shrinkable label of (10).

The present specification includes the disclosure of japanese patent application No. 2020-090542, which is the basis of the priority of the present application.

According to the present embodiment, a heat shrinkable multilayer film having good interlayer adhesion strength, heat shrinkability, transparency, film formability, and film appearance can be provided.

Detailed Description

The present embodiment is a heat-shrinkable multilayer film comprising at least a first layer comprising a first block copolymer containing a vinyl aromatic hydrocarbon and a conjugated diene, and a second layer comprising a polyester resin and a second block copolymer containing a vinyl aromatic hydrocarbon and a conjugated diene, wherein the first layer and the second layer are in direct contact, the content of the second block copolymer in the second layer is 0.1 to 35 mass%, the mass ratio of the vinyl aromatic hydrocarbon and the conjugated diene in the second block copolymer is 65/35 to 85/15, and the number-average molecular weight of the second block copolymer is 5.0 × 10 ⁴ ～40.0×10 ⁴ 。

The present embodiment will be described in detail below.

[ Heat-shrinkable multilayer film ]

The heat shrinkable multilayer film of the present embodiment includes at least a first layer and a second layer, and the first layer and the second layer are directly connected to each other. That is, the first layer and the second layer of the heat-shrinkable multilayer film of the present embodiment do not have an adhesive layer therebetween for securing interlayer adhesive strength therebetween. Therefore, a step of forming an adhesive layer is not required, and the production can be completed at a low cost, and there is no problem that the adhesive layer cannot follow the shrinkage of the film and is peeled off.

The heat-shrinkable multilayer film of the present embodiment is not particularly limited in form, and is, for example, a two-layer film composed of a first layer and a second layer, or a three-layer film in which the second layer is disposed on both a first surface (front surface) of the first layer and a second surface (back surface) opposite to the first surface.

The film thickness of the heat-shrinkable multilayer film of the present embodiment is not particularly limited, but is, for example, 15 μm or more and 500 μm or less, preferably 30 μm or more and 400 μm or less, or 50 μm or more and 300 μm or less.

(second layer)

The second layer contains a polyester resin and a second block copolymer containing a vinyl aromatic hydrocarbon and a conjugated diene.

The polyester-based resin is not particularly limited, and examples thereof include polycondensates of polycarboxylic acids and polyhydric alcohols. Specifically, examples of the polyester-based resin include 1:1 in the form of a polycondensate. The polyester resin may be used alone or in combination of two or more. Examples of the polycarboxylic acid include: terephthalic acid, isophthalic acid, succinic acid, glutaric acid, or the like. One of the polycarboxylic acids may be used alone, or two or more of them may be used in combination. Examples of the polyhydric alcohol include: ethylene glycol, 1, 2-propylene glycol, 1, 4-butanediol, neopentyl glycol, diethylene glycol, polyethylene glycol, butanediol or 1, 4-cyclohexanedimethanol, and the like. One kind of the polyhydric alcohol may be used alone, or two or more kinds may be used in combination. The polycarboxylic acid is preferably terephthalic acid, and the polyol is preferably ethylene glycol, diethylene glycol, neopentyl glycol or 1, 4-cyclohexanedimethanol.

The polyester-based resin is preferably polyethylene terephthalate glycol-modified. The glycol-modified polyethylene terephthalate is a polyethylene terephthalate (polycondensate) containing, as polycondensation components, terephthalic acid, ethylene glycol, and at least one selected from 1, 4-cyclohexanedimethanol and neopentyl glycol. Polyethylene terephthalate using only ethylene glycol as a polyol crystallizes due to changes over time and the like, and the polyethylene terephthalate glycol-modified with glycol is an amorphous resin, and therefore, the transparency and heat shrinkability of the film are good. In the polyethylene terephthalate glycol-modified, it is preferable that the main component of the polycarboxylic acid is terephthalic acid and the main component of the polyhydric alcohol is ethylene glycol. The polycarboxylic acid component contains terephthalic acid as a main component, meaning that the polycarboxylic acid component contains terephthalic acid in a maximum amount. Similarly, the main component of the polyol being ethylene glycol means that the content of ethylene glycol in the polyol component is the largest.

The glycol-modified polyethylene terephthalate may contain, as a polycondensation component, ethylene glycol, 1, 4-cyclohexanedimethanol, and a polyol other than neopentyl glycol (also referred to as another polyol). However, the molecular weight of the other polyol is preferably less than 400, preferably less than 350, preferably less than 300, preferably less than 250, from the viewpoint of film processability and molding processability. That is, it is preferable that the glycol-modified polyethylene terephthalate does not contain a polyol having a molecular weight of 400 or more as a polycondensation component.

Examples of other polyols include: diethylene glycol, trans-tetramethyl-1, 3-cyclobutanediol, 2, 4-tetramethyl-1, 3-cyclobutanediol, 1, 4-butanediol, 1, 3-cyclohexanedimethanol, 1, 4-cyclohexanediol, 1, 3-cyclohexanediol, spiroglycol, polytetramethylene glycol, or mixtures thereof. In particular, it is preferable to use at least one diol component having an alicyclic structure selected from the group consisting of trans-tetramethyl-1, 3-cyclobutanediol, 2, 4-tetramethyl-1, 3-cyclobutanediol, 1, 3-cyclohexanedimethanol, 1, 4-cyclohexanediol, 1, 3-cyclohexanediol, and spiroglycol. The other polyhydric alcohols may be used singly or in combination of two or more.

Examples of polycarboxylic acids other than terephthalic acid include: aromatic dicarboxylic acids derived from isophthalic acid, 2-chloroterephthalic acid, 2, 5-dichloroterephthalic acid, 2-methylterephthalic acid, 4-diphenylethylene dicarboxylic acid, 4-biphenyldicarboxylic acid, phthalic acid, 2, 6-naphthalenedicarboxylic acid, 2, 7-naphthalenedicarboxylic acid, bisbenzoic acid, bis (p-carboxyphenyl) methane, anthracene dicarboxylic acid, 4-diphenylether dicarboxylic acid, 4-diphenoxyethanedicarboxylic acid, 5-Na sulfoisophthalic acid, ethylene terephthalic acid, etc., and aliphatic dicarboxylic acids derived from adipic acid, sebacic acid, azelaic acid, dodecanedioic acid, 1, 3-cyclohexanedicarboxylic acid, 1, 4-cyclohexanedicarboxylic acid, etc. Among them, aromatic dicarboxylic acids such as isophthalic acid and 2, 6-naphthalenedicarboxylic acid are preferable. One or more polycarboxylic acids other than terephthalic acid may be used alone, or two or more of them may be used in combination.

The glass transition temperature (Tg) of the polyethylene terephthalate glycol is preferably 60 ℃ or higher and 120 ℃ or lower, and more preferably 60 ℃ or higher and 100 ℃ or lower. When the glass transition temperature (Tg) is in the above range, orientation relaxation during storage is less likely to occur, and natural shrinkage is less likely to occur, which is preferable.

Examples of the diol-modified polyethylene terephthalate include: "EastarCopolyester GN001" manufactured by Istman, and "SKYGREEN S2008" manufactured by SK chemical industry, and the like.

The polyester-based resin and the block copolymer are incompatible and may cause a decrease in transparency after mixing, but by reducing the difference in refractive index between them, the decrease in transparency of the film can be suppressed. The difference in refractive index between the polyester-based resin and the block copolymer is preferably 0.01 or less, and more preferably 0.005 or less.

The content of the polyester-based resin in the second layer is preferably 60 mass% or more, 65 mass% or more, 70 mass% or more, 75 mass% or more, or 80 mass% or more. When the content of the polyester-based resin is 60% by mass or more, a film having low haze can be obtained. The content of the polyester-based resin is preferably 99 mass% or less, 98 mass% or less, or 95 mass% or less. When the content of the polyester resin is 99% by mass or less, a film having high interlayer adhesion strength and high heat shrinkage can be obtained.

The second block copolymer includes a vinyl aromatic hydrocarbon and a conjugated diene. In the present specification, the terms "vinyl aromatic hydrocarbon" and "conjugated diene" and the names of the specific compounds thereof are terms indicating raw materials (monomers) in the polymerization of the block copolymer, and may indicate monomer units contained in the obtained block copolymer.

One kind of the second block copolymer may be used alone, or two or more kinds may be used in combination. When a mixture of a plurality of block copolymers is used, for example, a mixture obtained by mixing predetermined amounts of the respective components in a solution state and then removing the solvent may be used, or a mixture obtained by mixing predetermined amounts of the respective components in a solid state and then melt-kneading the mixture by an extruder may be used.

The vinyl aromatic hydrocarbon is not particularly limited, and examples thereof include: styrene, o-methylstyrene, p-tert-butylstyrene, 1, 3-dimethylstyrene, alpha-methylstyrene, vinylnaphthalene, or vinylanthracene, and the like. The vinyl aromatic hydrocarbon is preferably styrene. One kind of the vinyl aromatic hydrocarbon may be used alone, or two or more kinds may be used in combination.

The conjugated diene is not particularly limited, and examples thereof include: 1, 3-butadiene, 2-methyl-1, 3-butadiene (isoprene), 2, 3-dimethyl-1, 3-butadiene, 1, 3-pentadiene, 1, 3-hexadiene, and the like. The conjugated diene is preferably 1, 3-butadiene or isoprene. One kind of conjugated diene may be used alone, or two or more kinds may be used in combination.

In the second block copolymer, it is preferable that the vinyl aromatic hydrocarbon is styrene and the conjugated diene is 1, 3-butadiene.

In the present embodiment, the content of the second block copolymer in the second layer is 0.1 mass% or more and 35 mass% or less. When the content of the second block copolymer is 0.1% by mass or more, the interlayer adhesion strength can be effectively improved. When the content of the second block copolymer exceeds 35 mass%, the haze increases and the kneading failure portion increases, so that the film appearance deteriorates. The content of the second block copolymer in the second layer is preferably 1.0 mass% or more and 30 mass% or less, 5.0 mass% or more and 30 mass% or less, or 10 mass% or more and 25 mass% or less.

In the present embodiment, the mass ratio of the vinyl aromatic hydrocarbon and the conjugated diene in the second block copolymer is 65/35 to 85/15. When the mass ratio of the vinyl aromatic hydrocarbon to the conjugated diene is less than 65/35, haze increases and fish eyes increase, thereby deteriorating the appearance of the film. When the mass ratio of the vinyl aromatic hydrocarbon to the conjugated diene exceeds 85/15, sufficient interlayer adhesion strength cannot be obtained. The mass ratio of the vinyl aromatic hydrocarbon to the conjugated diene is preferably 70/40 to 80/20.

The content of the vinyl aromatic hydrocarbon and the conjugated diene in the second block copolymer is, for example, 80 mass% or more, preferably 90 mass% or more, 95 mass% or more, or 99 mass% or more. The second block copolymer may contain impurities.

In the case of producing a block copolymer by anion polymerization, the mass ratio of the vinyl aromatic hydrocarbon and the conjugated diene contained in the block copolymer can be calculated from the charged amounts (mass) of the respective monomers at the time of production.

The mass ratio of the conjugated diene content may be measured by a known halogen addition method. The mass ratio of the content of the conjugated diene measured by the halogen addition method is described below in a general measurement procedure. Specifically, a precisely weighed sample is dissolved in an organic solvent in which the sample can be completely dissolved to obtain a detection solution, and then an excessive amount of iodine monochloride/carbon tetrachloride solution is added to the detection solution to allow the solution to react sufficiently. Then, the amount of the double bonds in the sample was measured by back-titrating the unreacted iodine monochloride remaining in the solution with a sodium thiosulfate/ethanol solution, and the ratio of the conjugated diene was calculated. In general, since a part of the charged main raw material may be lost, it is preferable to determine the mass ratio of the conjugated diene by the halogen addition method and to use it as the mass ratio of the vinyl aromatic hydrocarbon.

In this embodiment, the number average molecular weight of the second block copolymer is 5.0X 10 ⁴ ～40.0×10 ⁴ . At the second placeThe number average molecular weight of the block copolymer is less than 5.0X 10 ⁴ In the case of (3), the melt viscosity becomes too low, so that the film formability is reduced and the heat shrinkage rate is also reduced. The number average molecular weight of the second block copolymer exceeds 40.0 x 10 ⁴ In the case of (3), the melt viscosity becomes too high, and therefore, the load on the extruder increases, and the film-forming property decreases. The number average molecular weight of the second block copolymer is preferably 7.5X 10 ⁴ ～35.0×10 ⁴ 、10.0×10 ⁴ ～30.0×10 ⁴ Or 12.5X 10 ⁴ ～25.0×10 ⁴ . The number average molecular weight of the second block copolymer can be controlled by, for example, the addition amount of the initiator relative to the total addition amount of the monomers.

Preferred examples of the second block copolymer include those having the following general formula.

(a)A-B

(b)A-B-C-A

(c)A-B-A

(d)A-C-A

(e)A-C-B

(f)A-C-B-A

(g)A-B-B

(h)A-B-B-A

Wherein in the above general formula, A represents a polymer chain of a vinyl aromatic hydrocarbon, B represents a copolymer chain of a vinyl aromatic hydrocarbon and a conjugated diene, C represents a polymer chain of a conjugated diene, and each formula represents an order of arrangement of these polymer chains. The second block copolymer may contain one of the structural polymers (a) to (h) alone or in combination of two or more. In addition, a plurality of A, B or C may be present in the general formula. When a plurality of a, B or C are present in the general formula, their molecular weights, the mass ratios of the vinyl aromatic hydrocarbon and the conjugated diene in the copolymerized chain B, the distribution states of the vinyl aromatic hydrocarbon and the conjugated diene in the copolymerized chain B, and the like are independent of each other. The molecular weight and composition distribution of the copolymerized chain B are mainly controlled by the addition amounts and addition methods of the vinyl aromatic hydrocarbon monomer and the conjugated diene monomer. For example, the copolymeric chain B is a random block of a vinyl aromatic hydrocarbon and a conjugated diene or a tapered block of a vinyl aromatic hydrocarbon and a conjugated diene.

The second block copolymer may terminate with a residue of a multifunctional coupling agent. Examples of polyfunctional coupling agents include: silicon tetrachloride, epoxidized soybean oil, and the like.

The second block copolymer preferably has a block portion composed of a vinyl aromatic hydrocarbon at one end.

The second block copolymer can be produced, for example, by polymerizing monomers of a vinyl aromatic hydrocarbon and a conjugated diene in an organic solvent using an organolithium compound as an initiator. Examples of the organic solvent include: aliphatic hydrocarbons such as butane, pentane, hexane, isopentane, heptane, octane, and isooctane, alicyclic hydrocarbons such as cyclopentane, methylcyclopentane, cyclohexane, methylcyclohexane, and ethylcyclohexane, and aromatic hydrocarbons such as ethylbenzene and xylene. The organic lithium compound is, for example, a compound having one or more lithium atoms bonded to a molecule, and examples thereof include: monofunctional organolithium compounds such as ethyllithium, n-propyllithium, isopropyllithium, n-butyllithium, sec-butyllithium or tert-butyllithium, and polyfunctional organolithium compounds such as hexamethylenedilithium, butadienyldilithium or isoprenedilithium. The vinyl aromatic hydrocarbon and the conjugated diene can be used as described above, and one or two or more species thereof can be selected for polymerization. In the living anionic polymerization using the organic lithium compound as an initiator, almost all of the vinyl aromatic hydrocarbon and the conjugated diene used in the polymerization reaction are converted into a polymer.

The second layer may contain other resins in addition to the polyester-based resin and the second block copolymer as necessary. Examples of the other resin include: polystyrene resin or styrene-methyl methacrylate copolymer. The content of the other resin in the second layer is preferably 10% by mass or less, 5.0% by mass or less, or 1.0% by mass or less.

(first layer)

The first layer includes a first block copolymer containing a vinyl aromatic hydrocarbon and a conjugated diene.

One of the first block copolymers may be used alone, or two or more of the first block copolymers may be used in combination. When a mixture of a plurality of block copolymers is used, for example, a mixture obtained by mixing predetermined amounts of the respective components in a solution state and then removing the solvent may be used, or a mixture obtained by mixing predetermined amounts of the respective components in a solid state and then melt-kneading the mixture by an extruder may be used.

The content of the first block copolymer in the first layer is preferably 50 mass% or more, 60 mass% or more, 70 mass% or more, 80 mass% or more, 90 mass% or more, 95 mass% or more, or 99 mass% or more. When the content of the first block copolymer is 50% by mass or more, a film having a high heat shrinkage ratio and a good appearance after shrinkage can be obtained.

The first block copolymer and the second block copolymer are independent of each other, and the first block copolymer can be, for example, the same kind of substance as the second block copolymer. That is, the kind of the vinyl aromatic hydrocarbon and the conjugated diene is not particularly limited, and for example, the contents described in the second block copolymer can be applied. The mass ratio of the vinyl aromatic hydrocarbon and the conjugated diene in the first block copolymer is not particularly limited, and for example, the contents described in the second block copolymer can be applied. The content of the vinyl aromatic hydrocarbon and the conjugated diene in the first block copolymer is not particularly limited, and for example, the contents described in the second block copolymer can be applied. The number average molecular weight of the first block copolymer is also not particularly limited, and for example, those described in the second block copolymer can be applied. The preferred general formula of the first block copolymer can also be applied to the description of the second block copolymer.

In one embodiment, the mass ratio of the vinyl aromatic hydrocarbon and the conjugated diene in the first block copolymer is 65/35 to 85/15. When the mass ratio of the vinyl aromatic hydrocarbon and the conjugated diene in the first block copolymer is in the above range, a film having high interlayer adhesion strength and heat shrinkage and low haze can be obtained.

The first layer may contain other resins in addition to the first block copolymer as needed. Examples of the other resins include: polyester resin, polystyrene resin or styrene-methyl methacrylate copolymer. The content of the other resin in the first layer is preferably 10% by mass or less, 5.0% by mass or less, or 1.0% by mass or less.

The first layer and/or the second layer may contain various additives as necessary. Examples of additives include: stabilizers, lubricants, processing aids, antiblocking agents, antistatic agents, antifogging agents, weather resistance improvers, softeners, plasticizers, pigments, or the like. One additive may be used alone, or two or more additives may be used in combination.

Examples of the stabilizer include: phenol antioxidants such as 2- [1- (2-hydroxy-3, 5-di-t-pentylphenyl) ethyl ] -4, 6-di-t-pentylphenyl acrylate, 2-t-butyl-6- (3-t-butyl-2-hydroxy-5-methylbenzyl) -4-methylphenyl acrylate, octadecyl-3- (3, 5-di-t-butyl-4-hydroxyphenyl) propionate, and 2, 6-di-t-butyl-4-methylphenol, and phosphorus antioxidants such as 2, 2-methylenebis (4, 6-di-t-butylphenyl) octyl phosphate, trisnonylphenyl phosphate, and bis (2, 6-di-t-butyl-4-methylphenyl) pentaerythritol diphosphate.

As the lubricant, for example: saturated fatty acids such as palmitic acid, stearic acid, and behenic acid; fatty acid esters such as octyl palmitate, octyl stearate, or pentaerythritol fatty acid; fatty acid amides such as erucamide, oleamide, stearamide, and ethylene bisstearamide; higher alcohols such as myristyl alcohol, cetyl alcohol, and stearyl alcohol.

The processing aid is usually liquid paraffin, for example, and an organic acid ester such as adipate ester may be used.

As the antiblocking agent, for example: organic fillers such as High Impact Polystyrene (HIPS) and crosslinked beads of vinyl aromatic hydrocarbon copolymers, silica beads, quartz beads, and the like.

As the antistatic agent, for example: surfactants such as nonionic surfactants, anionic surfactants, cationic surfactants, or zwitterionic surfactants.

As the antifogging agent, for example: glycerin fatty acid esters such as glycerin mono fatty acid ester and glycerin di fatty acid ester; sorbitan fatty acid esters such as sorbitan monopalmitate and sorbitan monostearate.

As the weather resistance improver, for example: ultraviolet absorbers such as 2- (2 '-hydroxy-3' -tert-butyl-5 '-methylphenyl) -5-chlorobenzotriazole, 2, 4-di-tert-butylphenyl-3', 5 '-di-tert-butyl-4' -hydroxybenzoate or 2-hydroxy-4-n-octyloxybenzophenone, and hindered amine type weather resistance improvers such as tetrakis (2, 6-tetramethyl-4-piperidyl) -1,2,3, 4-butanetetracarboxylate.

The content of the additive in the first layer or the second layer is usually 10% by mass or less, and preferably 5.0% by mass or less, 3.0% by mass or less, or 1.0% by mass or less. When the content of the additive is 10% by mass or less, the additive can be inhibited from floating to the surface of the layer to affect the appearance.

The heat-shrinkable multilayer film of the present embodiment is preferably 55% or more, 60% or more, or 70% or more in heat shrinkage in the stretching direction after being immersed in hot water at 100 ℃ for 10 seconds. When the heat shrinkage ratio is in the above range, the occurrence of mounting failure due to the shape of the packaged body can be suppressed, and this is preferable in terms of practical use. For the same reason, the heat-shrinkable multilayer film of the present embodiment is preferably 10% or more, 15% or more, or 20% or more in the stretching direction after being immersed in hot water at 70 ℃ for 10 seconds.

The haze of the heat shrinkable multilayer film of the present embodiment is preferably 12% or less, 10% or less, or 8% or less. Haze can be measured according to ASTM D1003.

The heat-shrinkable multilayer film of the present embodiment can be produced by a known method. The heat shrinkable multilayer film is preferably produced by stretching a multilayer sheet produced by multilayer extrusion molding. Further, the heat-shrinkable multilayer film can be produced by using the resin compositions of the respective layers to produce a single-layer unstretched sheet, and then laminating and stretching the single-layer unstretched sheet.

The heat-shrinkable multilayer film of the present embodiment has good interlayer adhesion strength, heat shrinkability, transparency, film formation properties, and film appearance. Therefore, the heat-shrinkable multilayer film of the present embodiment can be suitably used for a heat-shrinkable label for beverage containers and the like.

Examples

The present embodiment will be described in more detail below with reference to examples, but the present embodiment is not limited to these examples.

[ production of Block copolymer ]

The heat shrinkable laminated films shown in examples 1 to 9, 11 to 13 and comparative examples 1 to 9 are two kinds of heat shrinkable laminated films having a three-layer structure, and each of them is composed of an inner layer as a first layer located inside the heat shrinkable laminated film and a layer as a second layer (both layers are collectively referred to as a front layer and a back layer) having the same composition and in direct contact with each other with both surfaces sandwiching the inner layer therebetween. The heat shrinkable laminates shown in examples 10 and 10 are two kinds of heat shrinkable films having a two-layer structure. Next, the production methods of block copolymers of reference examples 1 to 10, which are the raw materials constituting the inner layer, the surface layer or the inner layer of examples 1 to 13 and comparative examples 1 to 10, will be described.

< reference example 1> production of Block copolymer (polymerization example 1)

(1) To the reaction vessel were added 500.0kg of cyclohexane and 75.0g of Tetrahydrofuran (THF).

(2) 2000mL of a 10 mass% cyclohexane solution of n-butyllithium as a polymerization initiator solution was added thereto while being maintained at 30 ℃.

(3) 12kg of styrene were added to polymerize the styrene anion. The internal temperature rose to 40 ℃.

(4) After the styrene was completely consumed, the internal temperature of the reaction system was raised to 80 ℃ and the internal temperature was maintained, while adding 92kg of styrene and 10kg of 1, 3-butadiene at rates of 92kg/h and 10kg/h, respectively.

(5) After styrene and 1, 3-butadiene were completely consumed, the internal temperature of the reaction system was lowered to 60 ℃ and 66kg of 1, 3-butadiene was added at a time to polymerize 1, 3-butadiene anion. The internal temperature rose to 86 ℃.

(6) After 1, 3-butadiene was completely consumed, the internal temperature of the reaction system was lowered to 70 ℃ and 20kg of styrene was added to anionically polymerize styrene. The reaction vessel was cooled to remove the heat of reaction while continuing the polymerization. The internal temperature rose to 85 ℃.

(7) After complete consumption of styrene, the polymerization active terminals were finally deactivated by water to give a polymerization solution containing a block copolymer having a polystyrene block, a random block of styrene and butadiene, a polybutadiene block and a polystyrene block.

(8) The polymerization solution was preconcentrated and then devolatilized and extruded by a twin-screw extruder equipped with a decompression vent to prepare pellets, thereby obtaining a block copolymer of polymerization example 1.

< reference example 2> production of Block copolymer (polymerization example 2)

(1) To the reaction vessel were added 500.0kg of cyclohexane, 75.0g of Tetrahydrofuran (THF).

(3) 60kg of styrene were added to polymerize the styrene anion. The internal temperature rose to 65 ℃.

(4) After complete consumption of styrene, the internal temperature of the reaction system was lowered to 40 ℃ and 116kg of styrene and 24kg of 1, 3-butadiene were added in one portion. The internal temperature rose to 122 ℃.

(5) After complete consumption of styrene and 1, 3-butadiene, the entire polymerization active terminals were finally deactivated with water to obtain a polymerization solution containing a block copolymer having a polystyrene block and tapered blocks of styrene and butadiene.

(6) The polymerization solution was preconcentrated and then devolatilized and extruded by a twin-screw extruder equipped with a decompression vent to obtain a block copolymer in the form of pellets (polymerization example 2).

< reference example 3> production of Block copolymer (polymerization example 3)

(2) 1500mL of a 10 mass% cyclohexane solution of n-butyllithium as a polymerization initiator solution was added thereto while being maintained at 30 ℃.

(3) 50kg of styrene were added to polymerize the styrene anion. The internal temperature rose to 60 ℃.

(4) After styrene was completely consumed, the internal temperature of the reaction system was lowered to 30 ℃ and 104kg of styrene and 46kg of 1, 3-butadiene were added in one portion. The internal temperature rose to 123 ℃.

(5) After the styrene and 1, 3-butadiene were completely consumed, the internal temperature of the reaction system was lowered to 75 ℃ and 1200g of "ADK CIZERO-130P" manufactured by ADEKA, product of epoxidized soybean oil Co., ltd., diluted 4 times with cyclohexane was added as a polyfunctional coupling agent to complete the polymerization.

(6) Finally, all the polymerization active terminals were deactivated with water to obtain a polymerization solution containing a block copolymer having a polystyrene block and tapered blocks of styrene and butadiene.

(7) The polymerization solution was preconcentrated and then devolatilized and extruded by a twin-screw extruder equipped with a decompression vent to obtain the objective block copolymer in pellet form (polymerization example 3).

< reference example 4> production of Block copolymer (polymerization example 4)

(2) 3000mL of a 10 mass% cyclohexane solution of n-butyllithium as a polymerization initiator solution was added thereto while maintaining it at 30 ℃.

(4) After styrene was completely consumed, the internal temperature of the reaction system was lowered to 30 ℃ and 104kg of styrene and 46kg of 1, 3-butadiene were added in one portion. The internal temperature rose to 122 ℃.

(5) After complete consumption of styrene and 1, 3-butadiene, the entire polymerization active end was finally deactivated with water to obtain a polymerization solution containing a block copolymer having a polystyrene block and tapered blocks of styrene and butadiene.

(6) The polymerization solution was preconcentrated and then devolatilized and extruded by a twin-screw extruder equipped with a decompression vent to obtain a block copolymer in the form of pellets (polymerization example 4).

< reference example 5> production of Block copolymer (polymerization example 5)

(2) 600mL of a 10 mass% cyclohexane solution of n-butyllithium was added thereto as a polymerization initiator solution, and kept at 30 ℃.

(4) After complete consumption of styrene, the internal temperature of the reaction system was raised to 80 ℃ and maintained, and 114kg of styrene and 8kg of 1, 3-butadiene were simultaneously added at rates of 114kg/h and 8kg/h, respectively.

(5) After styrene and 1, 3-butadiene were completely consumed, the internal temperature of the reaction system was lowered to 60 ℃ and 38kg of 1, 3-butadiene was added in one portion to polymerize 1, 3-butadiene anion. The internal temperature rose to 90 ℃.

(6) After 1, 3-butadiene was completely consumed, the internal temperature of the reaction system was lowered to 70 ℃ and 28kg of styrene was added to anionically polymerize styrene. The internal temperature rose to 85 ℃.

(8) The polymerization solution was preconcentrated and then devolatilized and extruded by a twin-screw extruder equipped with a decompression vent to obtain the objective block copolymer in pellet form (polymerization example 5).

< reference example 6> production of Block copolymer (polymerization example 6)

(2) 6000mL of a 10 mass% cyclohexane solution of n-butyllithium as a polymerization initiator solution was added thereto while being maintained at 30 ℃.

(6) The polymerization solution was preconcentrated and then devolatilized and extruded by a twin-screw extruder equipped with a decompression vent to obtain a block copolymer in the form of pellets (polymerization example 6).

< reference example 7> production of Block copolymer (polymerization example 7)

(2) 1800mL of a 10 mass% cyclohexane solution of n-butyllithium as a polymerization initiator solution was added thereto while being maintained at 30 ℃.

(3) 44kg of styrene were added to polymerize the styrene anion. The internal temperature rose to 55 ℃.

(4) After styrene was completely consumed, the internal temperature of the reaction system was lowered to 30 ℃ while 66kg of styrene and 90kg of 1, 3-butadiene were added in one portion. The internal temperature rose to 130 ℃.

(6) The polymerization solution was preconcentrated and then devolatilized and extruded by a twin-screw extruder equipped with a decompression vent to obtain the objective block copolymer in pellet form (polymerization example 7).

< reference example 8>

The block copolymer 42 parts by mass of polymerization example 1 and the block copolymer 58 parts by mass of polymerization example 2 were mixed to 100 parts by mass, and the mixture was used as the block copolymer of reference example 8.

< reference example 9>

The block copolymer 62 parts by mass of polymerization example 1 and the block copolymer 38 parts by mass of polymerization example 2 were mixed to make 100 parts by mass, and the mixture was used as the block copolymer of reference example 9.

< reference example 10>

The block copolymer of reference example 10 was prepared by mixing 15 parts by mass of the block copolymer of polymerization example 1 and 85 parts by mass of the block copolymer of polymerization example 2 to 100 parts by mass.

The number average molecular weight of the block copolymers of reference examples 1 to 7 in terms of standard polystyrene was measured by the following GPC measurement apparatus and conditions. The mass ratios of the styrene-derived units and the butadiene-derived units contained in 100 parts by mass of the block copolymers of polymerization examples 1 to 7, and the analysis values of the number average molecular weights thereof are shown in Table 1.

Device name: HLC-8220GPC (manufactured by Tosoh corporation)

And (3) chromatographic column: shodexGPCKF-404 (Shorex electrician) 4 roots were connected in series.

Temperature: 40 deg.C

And (3) detection: ultraviolet visible spectrometry (254 nm)

Solvent: tetrahydrofuran (THF)

Concentration: 2% by mass

Standard curve: the polystyrene resin was produced using standard polystyrene (manufactured by VARIAN Co., ltd.).

[ Table 1]

The block copolymers of reference examples 8 to 10 were obtained by mixing the block copolymers of polymerization example 1 and polymerization example 2 at predetermined ratios, respectively, and the mass ratios of the styrene units and the butadiene units thereof were calculated from the mass units of the styrene units and the butadiene units contained in the block copolymers of polymerization example 1 and polymerization example 2 at the respective mixing ratios. The number average molecular weight is a value measured by the above method using pellets obtained by melt-extruding pellets dry-blended in a predetermined ratio in an extruder. These results are shown in Table 2.

[ Table 2]

[ example 1]

Next, a method for producing the heat shrinkable laminated film of example 1 will be described.

The heat shrinkable laminated film of example 1 was produced by the following method. For convenience of explanation, the second layer of the heat-shrinkable laminated film of the present embodiment is referred to as a front layer and a back layer, and the first layer is referred to as an inner layer, and the production steps of the heat-shrinkable laminated film are described as being divided into (1) extrusion of the front layer and the back layer, (2) extrusion of the inner layer, and (3) sheet stretching.

(1) Sheet extrusion of surface and lining layers

Using an extruder equipped with a multi-layer T die having a lip width of 300mm, which was capable of extruding two kinds of three-layer sheets, 20 parts by mass of the block copolymer of reference example 8, 80 parts by mass of a polyethylene terephthalate glycol (Easter coplymer GN001, manufactured by Isyman, abbreviated as PET-G in Table 3-1) as a polyester-based resin, and 2 parts by mass of a product name "NATURAL EPM-7Y029" (manufactured by SUMIKA COLOR) as an antiblocking agent were melt-mixed and sheet-extruded to obtain a surface layer and a back layer, in the mass ratios shown in Table 3-1. The extruder for melting and feeding the resin for the surface and inner layers to the multilayer die was a 40mm phi single screw extruder set at a temperature of 240 ℃. It is to be noted that, at the inlet of the extruder, the block copolymer of reference example 8 was in a state in which 42 parts by mass of the pellets of the block copolymer of reference example 1 and 58 parts by mass of the pellets of the block copolymer of reference example 2 were dry blended, and in the extruder, the two pellets were melt-mixed and fed to a multilayer die. The temperature of the multilayer T-die was set to 210 ℃. Note that the Easter copplymer GN001 is a polycondensate of terephthalic acid, ethylene glycol, diethylene glycol and 1, 4-cyclohexanedimethanol. Further, the glass transition temperature thereof was 73 ℃.

(2) Sheet extrusion of inner layer

The block copolymer of reference example 8 was used to co-extrude the inner layer simultaneously with the extrusion of the surface and inner layers as described in (1). The extruder for the resin of the inner layer was a 65mm phi single screw extruder, set at a temperature of 200 ℃. Using an extruder equipped with a multilayer T-die, the front and rear layers described in (1) and the inner layer described in (2) were discharged from the multilayer T-die as two types of three-layer laminated sheets that were in close contact with each other. The thickness of the resulting laminated sheet was 0.25mm, and the ratio of the thickness of the surface layer/the inner layer was 17/66/17.

(3) Stretching of laminated sheet

The resulting laminated sheet was stretched 1.2 times in the MD direction at 85 ℃ by a longitudinal stretcher having two rolls with different rotation speeds, and then used in a tenter type transverse stretcher, and stretched 5 times in the TD direction at 90 ℃, to finally obtain a 50 μm thick heat shrinkable laminated film of example 1.

[ example 2]

The heat shrinkable laminate film of example 2 was produced in the same manner as in example 1, except that the block copolymer of reference example 8 was changed to the block copolymer of reference example 10 as the block copolymer to be blended in the front and back layers. The thickness of the resulting laminated sheet was 0.25mm, and the ratio of the thickness of the surface layer/inner layer was 17/66/17.

[ example 3]

A heat shrinkable laminate film of example 3 was produced in the same manner as in example 1, except that the block copolymer of reference example 8 was changed to the block copolymer of reference example 9 as the block copolymer blended in the front and back layers. The thickness of the resulting laminated sheet was 0.25mm, and the ratio of the thickness of the surface layer/the inner layer was 17/66/17.

[ example 4]

The heat shrinkable laminate film of example 4 was produced in the same manner as in example 1, except that the block copolymer of reference example 8 was changed to the block copolymer of reference example 4 as the block copolymer to be blended in the front and back layers. The thickness of the resulting laminated sheet was 0.25mm, and the ratio of the thickness of the surface layer/inner layer was 17/66/17.

[ example 5]

A heat shrinkable laminate film of example 5 was produced in the same manner as in example 1, except that the block copolymer of reference example 8 was changed to the block copolymer of reference example 3 as the block copolymer blended in the front and back layers. The thickness of the resulting laminated sheet was 0.25mm, and the ratio of the thickness of the surface layer/the inner layer was 17/66/17.

[ example 6]

The mass ratio of the block copolymer, polyethylene terephthalate glycol and antiblocking agent of reference example 8 blended in the front and back layers was set to 5:95: except for this, the heat shrinkable laminate film of example 6 was produced in the same manner as in example 1. The thickness of the resulting laminated sheet was 0.25mm, and the ratio of the thickness of the surface layer/inner layer was 17/66/17.

[ example 7]

The mass ratio of the block copolymer, polyethylene terephthalate glycol and antiblocking agent of reference example 8 blended in the front and back layers was set to 35:65: except for this, a heat shrinkable laminate film of example 7 was produced in the same manner as in example 1. The thickness of the resulting laminated sheet was 0.25mm, and the ratio of the thickness of the surface layer/inner layer was 17/66/17.

[ example 8]

The heat shrinkable laminate film of example 8 was produced in the same manner as in example 1, except that the block copolymer of reference example 8 was changed to the block copolymer of reference example 10 as the type of the block copolymer blended in the inner layer. The thickness of the resulting laminated sheet was 0.25mm, and the ratio of the thickness of the surface layer/inner layer was 17/66/17.

[ example 9]

The heat shrinkable laminate film of example 9 was produced in the same manner as in example 1, except that the block copolymer of reference example 8 was changed to the block copolymer of reference example 9 as the type of the block copolymer blended in the inner layer. The thickness of the resulting laminated sheet was 0.25mm, and the ratio of the thickness of the surface layer/inner layer was 17/66/17.

[ example 10]

The heat-shrinkable laminate film of example 10 is a two-layer film, and for convenience, the first layer of the heat-shrinkable laminate film of the present embodiment is referred to as an inner layer, and the second layer is referred to as a skin layer, and the production steps of the heat-shrinkable laminate film are described as being divided into (1) extrusion of the skin layer, (2) extrusion of the inner layer, and (3) sheet stretching.

(1) Sheet extrusion of surface layers

Using an extruder equipped with a multi-layer T die having a lip width of 300mm, which was capable of extruding two kinds of two-layer sheets, sheet extrusion was carried out in the same composition as that of the front and back layers described in example 1 at the mass ratio shown in Table 3-1. The extruder that melted and fed the resin for the skin layer to the multilayer die was a 40mm phi single screw extruder set at 240 ℃. The temperature of the multilayer T-die was set to 210 ℃.

(2) Sheet extrusion of inner layer

The inner layer was co-extruded simultaneously with the extrusion of the skin layer described in (1) using the block copolymer of reference example 8. The extruder for the resin of the inner layer was a 65mm phi single screw extruder, set at a temperature of 200 ℃. By using an extruder having a multilayer T die, the surface layer described in (1) and the inner layer described in (2) are discharged from the multilayer T die as two kinds of two-layered laminated sheets that are closely adhered to each other. The thickness of the resulting laminated sheet was 0.24mm, and the ratio of the thickness of the surface layer/the inner layer was 50/50.

(3) Sheet stretching

The sheet stretching was performed in the same manner as in example 1 to produce a heat shrinkable laminated film of example 10.

[ example 11]

The heat shrinkable laminated film of example 11 was produced in the same manner as in example 9, except that an amorphous polyethylene terephthalate (CB-602, manufactured by far east new century, abbreviated as a-PET in table 3-1) was used instead of the diol-modified polyethylene terephthalate (easter coplymer GN001, manufactured by eastman). The thickness of the resulting laminated sheet was 0.25mm, and the ratio of the thickness of the surface layer/inner layer was 17/66/17.

[ example 12]

A heat shrinkable laminate film of example 12 was produced in the same manner as in example 1, except that the block copolymer of reference example 8 was changed to the block copolymer of reference example 1 as the type of the block copolymer to be blended in the inner layer. The thickness of the resulting laminated sheet was 0.25mm, and the ratio of the thickness of the surface layer/inner layer was 17/66/17.

[ example 13]

The heat shrinkable laminate film of example 13 was produced in the same manner as in example 1, except that the block copolymer of reference example 8 was changed to the block copolymer of reference example 2 as the type of the block copolymer to be blended in the inner layer. The thickness of the resulting laminated sheet was 0.25mm, and the ratio of the thickness of the surface layer/inner layer was 17/66/17.

Comparative example 1

A heat shrinkable laminate film of comparative example 1 was produced in the same manner as in example 1, except that the block copolymer of reference example 8 was changed to the block copolymer of reference example 7 as the block copolymer blended in the front and back layers. The thickness of the resulting laminated sheet was 0.25mm, and the ratio of the thickness of the surface layer/the inner layer was 17/66/17.

Comparative example 2

A heat shrinkable laminate film of comparative example 2 was produced in the same manner as in example 1, except that the block copolymer of reference example 8 was changed to the block copolymer of reference example 2 as the block copolymer blended in the front and back layers. The thickness of the resulting laminated sheet was 0.25mm, and the ratio of the thickness of the surface layer/inner layer was 17/66/17.

Comparative example 3

A heat shrinkable laminate film of comparative example 3 was produced in the same manner as in example 1, except that the block copolymer of reference example 8 was changed to the block copolymer of reference example 5 as the block copolymers to be blended in the front and back layers. The thickness of the resulting laminated sheet was 0.25mm, and the ratio of the thickness of the surface layer/inner layer was 17/66/17.

Comparative example 4

A heat shrinkable laminate film of comparative example 4 was produced in the same manner as in example 1, except that the block copolymer of reference example 8 was changed to the block copolymer of reference example 6 as the block copolymer blended in the front and back layers. The thickness of the resulting laminated sheet was 0.25mm, and the ratio of the thickness of the surface layer/the inner layer was 17/66/17.

Comparative example 5

The block copolymer of reference example 8 was not added to the resin composition for the front and back layers, and the mixing ratio (mass ratio) of the polyester-based resin and the antiblocking agent was set to 100: except for this, a heat shrinkable laminate film of comparative example 5 was produced in the same manner as in example 1. The thickness of the resulting laminated sheet was 0.25mm, and the ratio of the thickness of the surface layer/inner layer was 17/66/17.

Comparative example 6

As the resin composition for the front and back layers, the mixing ratio (mass ratio) of the block copolymer, the polyester-based resin and the antiblocking agent of reference example 8 was set to 50:50: except for this, a heat shrinkable laminate film of comparative example 6 was produced in the same manner as in example 1. The thickness of the resulting laminated sheet was 0.25mm, and the ratio of the thickness of the surface layer/the inner layer was 17/66/17.

Comparative example 7

A heat shrinkable laminate film of comparative example 7 was produced in the same manner as in comparative example 5, except that the block copolymer of reference example 8 was changed to the block copolymer of reference example 1 as the type of block copolymer to be blended in the inner layer. The thickness of the resulting laminated sheet was 0.25mm, and the ratio of the thickness of the surface layer/the inner layer was 17/66/17.

Comparative example 8

A heat shrinkable laminate film of comparative example 8 was produced in the same manner as in comparative example 5, except that the block copolymer of reference example 8 was changed to the block copolymer of reference example 2 as the type of the block copolymer blended in the inner layer. The thickness of the resulting laminated sheet was 0.25mm, and the ratio of the thickness of the surface layer/inner layer was 17/66/17.

Comparative example 9

A heat shrinkable laminate film of comparative example 9 was produced in the same manner as in comparative example 5, except that an amorphous polyethylene terephthalate (CB-602, manufactured by far east new century corporation) was used instead of the polyethylene terephthalate glycol-modified (easter coplymer GN001, manufactured by eastman corporation) as the polyester-based resin to be blended in the front and back layers. The thickness of the resulting laminated sheet was 0.25mm, and the ratio of the thickness of the surface layer/the inner layer was 17/66/17.

Comparative example 10

The block copolymer of reference example 8 was not added to the resin composition for a skin layer, and the mixing ratio (mass ratio) of the polyester-based resin and the antiblocking agent was set to 100: except for this, a heat shrinkable laminate film of comparative example 10 was produced in the same manner as in example 10. The thickness of the resulting laminated sheet was 0.24mm, and the ratio of the thickness of the surface layer/the inner layer was 50/50.

[ evaluation ]

The film formability and physical properties of the obtained heat-shrinkable laminated films (examples 1 to 13 and comparative examples 1 to 10) were evaluated by the following methods. The results are shown in tables 3-1 to 3-5.

(adhesive Strength)

The interlayer adhesion strength of the heat shrinkable laminated films obtained in examples 1 to 13 and comparative examples 1 to 10 was measured by the following method. Note that the interlayer adhesion strength between the back layer and the inner layer was measured in the heat shrinkable laminated films obtained in examples 1 to 9, 11 to 13 and comparative examples 1 to 9, and the interlayer adhesion strength between the surface layer and the inner layer was measured in the heat shrinkable laminated films obtained in example 10 and comparative example 10.

(1) Test pieces having an MD width of 15mm and a TD width of 100mm were cut from the heat shrinkable laminated films of examples 1 to 13 and comparative examples 1 to 10, respectively. It should be noted that the MD width herein refers to the length of the test piece in the MD direction.

(2) The surface of the former test piece was peeled off by sticking "PYOLAN CLUTH coated health tape Y-09-GR" (SUS plate adhesive force: 12N/25 mm) manufactured by Diatex, thereby peeling it off in advance by 50mm from one end portion of the test piece in the TD direction, and this was used as a holding margin of the test piece. Note that, in two types of three-layer heat shrinkable laminated films other than example 10 and comparative example 10, one end portion in the TD direction was a state in which only the back layer was peeled from the inner layer, and the surface layer and the inner layer remained adhered. In example 10 and comparative example 10, one end portion in the TD direction was in a state where the surface layer was peeled off from the inner layer. Using these test pieces, the peeling test was performed by clamping the peeled portion of the test piece to a jig of a tensillon universal tester RTG-1210 manufactured by a & T, and measuring the T-type adhesive strength in the TD direction. The peeling conditions were set to an initial jig interval of 50mm and a drawing speed of 500mm/min. Then, the interlayer adhesion strength was determined from the average load at the jig interval of 20mm to 60 mm. The average of 7 tests was used as the measured value of the adhesive strength. The measurement conditions were in accordance with JIS K6854-3.

The adhesive strength of the heat-shrinkable laminated films of examples 1 to 13 and comparative examples 1 to 10 was rated according to the following criteria. The higher the adhesive strength, the more preferable it is, and the grade A to C is at a level at which there is no problem as a product, and it is judged to be good.

A: more than 1.5[ 2] N/15mm ];

b:1.5[ 2], [ N/15mm ] or less and more than 1.0[ N/15mm ];

c:1.0[ 2], [ N/15mm ] or less and more than 0.8[ N/15mm ];

d:0.8[ N/15mm ] or less.

(Heat shrinkage Rate)

The heat shrinkage was measured by the following method.

(1) A test piece having a MD width of 100mm and a TD width of 100mm was cut from the heat-shrinkable laminate film.

(2) The test piece was immersed in warm water at a predetermined temperature (70 ℃ C. Or 100 ℃ C.) for 10 seconds, taken out, and sufficiently wiped to remove water, thereby measuring the TD length L (mm).

(3) The heat shrinkage was calculated according to the following formula.

Heat shrinkage (%) = { (100-L)/100 } × 100

The heat shrinkage rates (100 ℃) of the heat-shrinkable laminated films of examples 1 to 13 and comparative examples 1 to 10 were classified according to the following criteria. In the case of grades A to C, the grade was judged to be good at a level at which no problem was found in the product.

Thermal shrinkage at 100 ℃

A: a heat shrinkage rate at 100 ℃ of 70% or more;

b: a heat shrinkage rate at 100 ℃ of less than 70% and 60% or more;

c: a heat shrinkage rate at 100 ℃ of less than 60% and 55% or more;

d: the heat shrinkage at 100 ℃ is less than 55%.

The results of the heat shrinkage ratios (70 ℃) of the heat-shrinkable laminated films of examples 1 to 13 and comparative examples 1 to 10 are also shown in the table as reference data. Note that the heat shrinkage at 70 ℃ was not classified.

(measurement of haze)

The haze of the heat shrinkable laminated films of examples 1 to 13 and comparative examples 1 to 10 was measured in accordance with ASTM D1003 using the following apparatus.

The device comprises the following steps: model NDH-1001DP haze Meter manufactured by Nippon Denshoku industries Ltd

The haze of the heat shrinkable laminate film was graded according to the following criteria. The smaller the haze value is, the more preferable the haze value is, and the A to C grades are at a level at which there is no problem as a product, and are judged to be good.

A: less than 8 percent;

b: more than 8% and 10% or less;

c: more than 10% and 12% or less;

d: over 12%.

(film Forming Property)

In the process for producing the heat-shrinkable laminated films of examples 1 to 13 and comparative examples 1 to 10, film formability was evaluated from the viewpoints of "film breakage is less likely to occur during stretching" and "natural variation in film thickness is small". The film formability of the heat shrinkable laminate film was evaluated according to the following criteria.

A: the film was not broken during transverse stretching, and the film thickness varied naturally within 10 μm.

B: the film was not broken during the transverse drawing, and the natural variation of the film thickness exceeded 10 μm.

C: the transverse stretching causes breakage.

D: the film was frequently broken during transverse stretching, and a long-term film formation could not be achieved.

(film appearance)

The film appearance of the sample other than film (D) could not be evaluated in the above evaluation of film formability. The film appearance of the heat shrinkable laminated film was graded according to the following criteria.

A: the film has no poor mixing part, and the number of fish eyes is less than 100;

b: the film has a small amount of poor mixing parts, and the number of fish eyes is less than 100;

c: the film has a small amount of poor mixing parts, and the number of fish eyes is more than 100 and less than 150;

d: the mixing defective part of the film is more than 10, or the fish eye is more than 150;

the kneading failure portion was an opaque portion of the film, and the number of kneading failure portions was measured in 3.3 square meters, which was visually observed. In addition, the number of fish eyes (foreign matter due to poor melting or the like) was obtained by counting the number in 3.3 square meters.

< production of Heat-shrinkable Label >

The heat-shrinkable laminated films obtained in examples 1 to 13 and comparative examples 1 to 10 were slit into a cylindrical shape having a diameter of 70mm such that the TD direction (main stretching axis direction) was set as the circumferential direction, and the film ends were fused by tetrahydrofuran to obtain a heat-shrinkable label for evaluating the shrinkage processability.

< evaluation of shrinkage processability >

The heat-shrinkable laminated films of examples 1 to 13 and comparative examples 1 to 10 were processed to obtain heat-shrinkable labels for evaluating the shrinkage processability. Next, the heat-shrinkable label for evaluating the shrinkage processability was placed on an aluminum bottle can (with a lid) having a cylindrical portion with a diameter of 66mm, and immersed in warm water at 90 ℃ for 10 seconds to thermally shrink the label, thereby producing a label-coated container. For each label after heat shrinkage, interlayer peeling from the fused portion was visually observed. Interlayer peeling occurred in the film having an adhesive strength of 0.8N/15mm or less.

The block copolymer resin composition of the present embodiment is suitably used for heat-shrinkable labels, heat-shrinkable cap seals, and packaging films for packaging various containers.

[ Table 3-1]

[ tables 3-2]

[ tables 3 to 3]

[ tables 3 to 4]

[ tables 3 to 5]

The upper limit and/or the lower limit of the numerical range described in the present specification can be arbitrarily combined to define a preferable range. For example, the upper limit and the lower limit of the numerical range may be arbitrarily combined to define a preferable range, the upper limit of the numerical range may be arbitrarily combined with each other to define a preferable range, and the lower limit of the numerical range may be arbitrarily combined with each other to define a preferable range.

While the present embodiment has been described in detail above, the specific configuration is not limited to these embodiments, and design changes within a range not departing from the gist of the present disclosure are also included in the present disclosure.

In this specification, unless otherwise specified, expressions in the singular form should be understood to include concepts in the plural form as well. Thus, articles in the singular (e.g., "a," "an," "the," etc. in the english language) should be understood to also include the concept in the plural as long as not specifically stated.

All publications, patents and patent applications cited in this specification are herein incorporated by reference as if fully set forth.

Claims

1. A heat-shrinkable multilayer film comprising at least a first layer comprising a first block copolymer containing a vinyl aromatic hydrocarbon and a conjugated diene, and a second layer comprising a polyester resin and a second block copolymer containing a vinyl aromatic hydrocarbon and a conjugated diene,

the first layer and the second layer are directly connected,

2. The heat shrinkable multilayer film according to claim 1, wherein the second block copolymer has a block portion composed of a vinyl aromatic hydrocarbon at least one end portion.

3. The heat-shrinkable multilayer film according to claim 1 or 2, wherein the mass ratio of the vinyl aromatic hydrocarbon and the conjugated diene in the first block copolymer is 65/35 to 85/15.

4. The heat shrinkable multilayer film according to any one of claims 1 to 3, wherein the content of the first block copolymer in the first layer is 50% by mass or more.

5. The heat-shrinkable multilayer film according to any one of claims 1 to 4, wherein a content of the polyester-based resin in the second layer is 60 mass% or more and 99 mass% or less.

6. The heat shrinkable multilayer film of any one of claims 1 to 5, wherein the polyester-based resin comprises a polyethylene terephthalate glycol modified with a diol containing terephthalic acid, ethylene glycol, and at least one selected from 1, 4-cyclohexanedimethanol and neopentyl glycol as a polycondensation component.

7. The heat shrinkable multilayer film of claim 6, wherein the glycol-modified polyethylene terephthalate does not contain a polyol having a molecular weight of 400 or more.

8. The heat shrinkable multilayer film according to claim 6 or 7, wherein the glass transition temperature Tg of the glycol-modified polyethylene terephthalate is 60 ℃ or more and 120 ℃ or less.

9. The heat shrinkable multilayer film according to any one of claims 1 to 8, wherein a second layer is disposed on both of a first surface of the first layer and a second surface opposite to the first surface.

10. A heat shrinkable label comprising the heat shrinkable multilayer film of any one of claims 1 to 9.

11. A beverage container having the heat shrinkable label of claim 10.