JP2007030411A - Heat-shrinkable laminated film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heat-shrinkable laminated film having excellently balanced properties, including stiffness suitable for shrink packaging, shrink bundling packaging and shrink labelling, good solvent resistance and good natural and low-temperature shrinkability. <P>SOLUTION: The heat-shrinkable laminated film consists of at least three layers including a front, a back and an intermediate layer made of a hydrogenated product of a block copolymer composed of a vinyl aromatic hydrocarbon and a conjugated diene type hydrocarbon. The front and back layers have a storage elastic modulus, E', at 25°C of ≥1.5×10<SP>9</SP>Pa and at least one peak temperature of the loss elastic modulus, E", between 50°C and 90°C, and the intermediate layer has a storage elastic modulus, E', at 25°C of ≤1.0×10<SP>9</SP>Pa and at least one peak temperature of the loss elastic modulus, E", between 10°C and -80°C. The heat shrinkage rate in the main shrinkage direction of the laminated film drawn at least uniaxially is ≥7% after 10-second immersion in hot water at 70°C, and the tensile elastic moduli measured in the main shrinkage direction and the right-angle direction are ≥1,200 MPa. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a heat-shrinkable laminated film excellent in balance of physical properties such as rigidity, solvent resistance, natural shrinkage, and low-temperature shrinkage suitable for shrink wrapping, shrink-bound wrapping and shrink labels.

A block copolymer composed of a vinyl aromatic hydrocarbon and a conjugated diene, which has a relatively high vinyl aromatic hydrocarbon content, is used for injection molding applications, sheets, films, etc. by utilizing characteristics such as transparency and impact resistance. It is used for extrusion molding applications. In particular, heat-shrinkable films using block copolymer resins composed of vinyl aromatic hydrocarbons and conjugated dienes are the residual monomers and plasticizers of vinyl chloride resins used in the past, and the generation of hydrogen chloride during incineration. Since there is no problem, it is used for food packaging, cap seals, labels, etc. The properties required for the heat shrinkable film include demands such as natural shrinkage, low temperature shrinkage, transparency, mechanical strength, and suitability for packaging machinery. So far, various studies have been made to improve these characteristics and obtain a good balance of physical properties.
For example, in Patent Document 1 below, in order to improve the natural shrinkability at room temperature, a composition of a block copolymer comprising a styrene hydrocarbon and a conjugated diene hydrocarbon and a random copolymer having a specific Tg containing a styrene hydrocarbon. A polystyrene-based heat-shrinkable film made of a product is disclosed. Patent Document 2 listed below discloses a vinyl aromatic hydrocarbon-aliphatic unsaturated carboxylic acid system in which the Vicat softening point does not exceed 105 ° C. in order to obtain a transparent heat-shrinkable film having excellent temporal stability and impact resistance of the film. A heat-shrinkable hard film characterized by a specific heat-shrinking force is disclosed, which is a composition of a derivative copolymer and a copolymer composed of a block of a vinyl aromatic hydrocarbon and a conjugated diene.

  In Patent Document 3 below, in order to obtain a composition that balances transparency, rigidity and low-temperature impact, a copolymer comprising a vinyl aromatic hydrocarbon having a specific structure and a molecular weight distribution and a block of a conjugated diene and a vinyl aroma A composition with a group hydrocarbon- (meth) acrylic ester copolymer resin is disclosed. Patent Document 4 listed below discloses a block copolymer having a vinyl aromatic hydrocarbon block vinyl aromatic hydrocarbon and a conjugated diene copolymer block having a specific structure in order to obtain a resin composition having excellent transparency and impact resistance. A transparent high-strength resin composition containing a copolymer of a vinyl aromatic hydrocarbon and a (meth) acrylic acid ester is disclosed. In Patent Document 5 below, in order to obtain a shrink film excellent in low-temperature shrinkage, optical properties, crack resistance properties, dimensional stability, etc., the vinyl aromatic hydrocarbon content is 95 to 20% by weight, and the Vicat softening point is 90. Multilayer low temperature shrinkage having at least one composition of vinyl aromatic hydrocarbon-aliphatic unsaturated carboxylic acid derivative copolymer not exceeding ℃ and copolymer comprising vinyl aromatic hydrocarbon and conjugated diene block A film is disclosed.

  In Patent Document 6 below, in order to obtain a shrink film excellent in natural shrinkage, strength, surface characteristics, rigidity, low temperature shrinkage, etc., both outer layers have a specific butadiene unit content styrene-butadiene-styrene type block copolymer and styrene. There is disclosed a multilayer polystyrene heat-shrink film of at least three layers comprising a mixture of butyl acrylate and an intermediate layer comprising a mixture of styrene-butadiene-styrene type block copolymer having a specific butadiene unit content and styrene-butyl acrylate. In Patent Document 7 listed below, in order to obtain a heat-shrinkable film excellent in any of the properties of natural shrinkage, heat-resistant fusion, transparency, and shrink finish, a vinyl aromatic hydrocarbon and a conjugated diene hydrocarbon are used. A block copolymer consisting of a vinyl aromatic hydrocarbon and a conjugated diene hydrocarbon, with a blend comprising a block copolymer, a copolymer of vinyl aromatic hydrocarbon and an aliphatic unsaturated carboxylic acid ester as an intermediate layer A heat-shrinkable polystyrene-based laminated film is disclosed in which a mixed polymer containing a coalescence as a main component is used as front and back layers.

  Patent Document 8 listed below discloses a styrene having a specific Vicat softening point in order to obtain a heat-shrinkable film having no heat-shrinkability at low temperature, shrinkage finish, natural shrinkage, heat, and no blocking between films. -A multilayer heat-shrinkable polystyrene system having a specific heat shrinkage ratio mainly composed of a (meth) acrylic acid ester copolymer and the inner and outer layers of a styrene-conjugated diene block copolymer having a specific Vicat softening point. A film is disclosed. The following Patent Document 9 is characterized by a specific molecular weight distribution and a residual monomer amount in order to obtain a resin composition and film having a low processing property, storage stability, odor, and excellent rigidity and impact resistance, and a multilayer film. A copolymer resin composed of a styrene monomer and a (meth) acrylic acid ester monomer, a block copolymer resin composed of styrene and a conjugated diene, and a layer mainly composed of a high-impact polystyrene resin composition A (multilayer) heat shrinkable film is disclosed.

In Patent Document 10 below, two types of styrene-butadiene block copolymers were used for the intermediate layer and the front and back layers exhibiting specific viscoelastic behavior in order to obtain a heat-shrinkable film excellent in low-temperature shrinkage, rigidity, and natural shrinkage. A heat shrinkable laminated film is disclosed. In Patent Document 11 below, in order to obtain a hydrogenated copolymer which is rich in flexibility, excellent in resilience and scratch resistance, and good in handleability, the content of vinyl aromatic hydrocarbons, vinyl aromatic hydrocarbon heavy A hydrogenated copolymer in which the content of the combined block, the weight average molecular weight, and the hydrogenation rate of the double bond of the conjugated diene are in a specific range is disclosed. In Patent Document 12 below, in order to obtain a hydrogenated copolymer having excellent flexibility, tensile strength, abrasion resistance, dent resistance and good crosslinkability, the content of vinyl aromatic hydrocarbons, vinyl aromatic A hydrogenated copolymer in which the content of the hydrocarbon polymer block, the weight average molecular weight, the hydrogenation rate of the double bond of the conjugated diene, and the peak temperature of tan δ are in a specific range is disclosed.
However, these block copolymers consisting of vinyl aromatic hydrocarbons and conjugated dienes and their hydrogenated products are naturally shrinkable, low temperature shrinkable, rigid, transparent, impact and solvent resistant, rupture resistant, etc. The physical property balance is not sufficient, and these documents do not disclose methods for improving them.

JP-A-4-52129 JP-A-5-104630 JP-A-6-220278 JP 7-216187 A JP 61-41544 A JP 2000-185373 A JP 2000-6329 A JP 2002-46231 A JP 2002-201324 A JP 2004-74687 A WO03 / 035705 publication WO04 / 003027 Publication

  An object of the present invention is to provide a heat-shrinkable laminated film excellent in physical property balance such as rigidity, solvent resistance, rupture resistance, natural shrinkage and low-temperature shrinkage suitable for shrink wrapping, shrink-bound wrapping and shrinkage labels. To do.

As a result of intensive studies, the present inventors have found that the above object can be achieved by a specific block copolymer hydrogenated product, and have reached the present invention. That is, the present invention
[1] In a heat-shrinkable laminated film of at least three layers using a hydrogenated block copolymer comprising a vinyl aromatic hydrocarbon and a conjugated diene hydrocarbon for each of the front and back layers and the intermediate layer, at least uniaxial The laminated film stretched to a temperature of 70 ° C. in the main shrinkage direction has a heat shrinkage rate of 7% or more for 10 seconds and a tensile elastic modulus measured in a direction perpendicular to the main shrinkage direction is 1200 MPa or more. Heat shrinkable laminated film,
However, the front and back layers have at least one storage elastic modulus (E ′) at 25 ° C. of 1.5 × 10 ⁹ Pa or higher and a peak temperature of loss elastic modulus (E ″) of 50 ° C. or higher and 90 ° C. or lower. The hydrogenated block copolymer and the intermediate layer have a storage elastic modulus (E ′) at 25 ° C. of 1.0 × 10 ⁹ Pa or less and at least one peak temperature of loss elastic modulus (E ″). The hydrogenated block copolymer present at 10 ° C. or lower and −80 ° C. or higher.
[2] The hydrogenated block copolymer constituting the front and back layers and the intermediate layer is a mixture of the component (a) and the component (b), and the front and back layers have a component (a) of 70% by weight or more and an intermediate The layer contains the component (b) in an amount of 40% by weight or more and 60% by weight or less, the heat-shrinkable laminated film according to the above [1],
However, the component (a) has a vinyl aromatic hydrocarbon content of 80% by weight or more, a storage elastic modulus (E ′) at 25 ° C. of 2.0 × 10 ⁹ Pa or more, and a loss elastic modulus (E ″). A block copolymer hydrogenated product composed of a vinyl aromatic hydrocarbon and a conjugated diene hydrocarbon, each having a peak temperature of 55 ° C. or higher and 80 ° C. or lower.
Component (b) has a conjugated diene content of 20 to 50% by weight, a vinyl aromatic hydrocarbon and a conjugated diene system in which at least one peak temperature of loss modulus (E ″) is 10 ° C. or lower and −80 ° C. or higher. Hydrogenated block copolymer consisting of hydrocarbons.
[3] The above-mentioned [1], wherein the tensile elongation at 23 ° C. in the main shrinkage direction is 70% or more and the tensile elongation at 0 ° C. in the direction perpendicular to the main shrinkage direction is 100% or more. [2] The heat-shrinkable laminated film according to the above,
[4] The heat shrinkage according to any one of the above [1] to [3], wherein the shrinkage in the main shrinkage direction after storage for 30 days in a 30 ° C. environment is 1.5% or less. Laminated film,
It is.

Since this invention consists of the above structures, there exist the following effects.
The heat-shrinkable laminated film produced from the laminated film satisfying this rule has excellent physical property balance such as rigidity, solvent resistance, rupture resistance, natural shrinkage, low-temperature shrinkage and elongation.

Hereinafter, the present invention will be described in detail.
In the heat-shrinkable laminated film of the present invention, it is possible to achieve both fracture resistance and film rigidity by disposing a hydrogenated block copolymer having a high elastic modulus on the front and back layers. It has been found that when the rigidity of the film is maintained in the front and back layers as in the present invention, the proportion of the lamination ratio is smaller than that in the intermediate layer. Therefore, even when the intermediate layer for imparting fracture resistance is made thick, by providing a high-modulus block copolymer hydrogenated material on the front and back layers, it is possible to impart fracture resistance while maintaining the rigidity of the film. Is possible. The front and back layers imparting rigidity have a storage elastic modulus (E ′) at 25 ° C. of 1.5 × 10 ⁹ Pa or higher and a peak temperature of loss elastic modulus (E ″) of 50 ° C. or higher and 90 ° C. or lower. It is preferable that the film has rigidity at a storage elastic modulus (E ′) of 1.5 × 10 ⁹ Pa or higher at 25 ° C., and the peak temperature of the loss elastic modulus (E ″) is 50 ° C. or higher. When at least one is present at 90 ° C. or lower, rigidity at normal temperature, natural shrinkage, and shrinkage at low temperature can be exhibited.

On the other hand, since the intermediate layer plays a role of imparting fracture resistance, the storage elastic modulus (E) is 1.0 × 10 9 Pa or less and the peak temperature of the loss elastic modulus (E ″) is 10 ° C. or less, −80 It is necessary to use a hydrogenated block copolymer that exists at least at a temperature of at least 1 ° C. The film has a peak temperature of loss modulus (E ″) of 10 ° C. or lower and at least one of −80 ° C. or higher. It is possible to sufficiently impart the elongation characteristics.
The hydrogenated block copolymer constituting the front and back layers and the intermediate layer of the film of the present invention is a mixture of the component (a) and the component (b), and the front and back layers have a component (a) of 70% by weight or more, and The intermediate layer is preferably a heat-shrinkable laminated film in which the component (b) is contained in an amount of 40% by weight to 60% by weight.

However, the component (a) has a vinyl aromatic hydrocarbon content of 80% by weight or more, a storage elastic modulus (E ′) at 25 ° C. of 2.0 × 10 ⁹ Pa or more, and a loss elastic modulus (E ″). This is a hydrogenated block copolymer composed of a vinyl aromatic hydrocarbon and a conjugated diene hydrocarbon, each having a peak temperature of 55 ° C. or higher and 80 ° C. or lower. Component (b) has a conjugated diene content of 20 Hydrogenation of a block copolymer comprising a vinyl aromatic hydrocarbon and a conjugated diene hydrocarbon having a peak temperature of ˜50% by weight and a loss elastic modulus (E ″) of 10 ° C. or lower and −80 ° C. or higher. It is a thing.
The block copolymer hydrogenated component (a) of the present application is a block copolymer hydrogenated product mainly used for imparting rigidity, and the component (b) is a block copolymer water imparting fracture resistance. It is an accessory. Therefore, the present invention has been invented by mainly comprising (a) a hydrogenated block copolymer having a high elastic modulus in the front and back layers, and adding more (b) to the intermediate layer than the front and back layers to impart fracture resistance. A film can be created.

Conventional laminated films have mainly used a styrene-butyl acrylate copolymer as a raw material for maintaining the rigidity of the film and rubber dispersed polystyrene in which an acrylic resin is copolymerized in a continuous phase in order to maintain transparency. However, since these raw materials contain an acrylic component as a polymerization component, when arranged on the front and back layers, the film physical properties before printing show very good fracture resistance and film rigidity, but at the time of printing There was a drawback that the ink deteriorated. In addition, when a rubber-dispersed polystyrene-based resin is used, there is a drawback that whitening occurs. Therefore, it has been difficult to develop for applications that require printing and applications that require transparency.
On the other hand, if the raw material for imparting rigidity and solvent resistance is a hydrogenated block copolymer consisting of a vinyl aromatic hydrocarbon and a conjugated diene hydrocarbon, it may be arranged on the front and back layers and printed. In addition, significant solvent degradation does not occur as in the case of polymers in which acrylic is polymerized. Therefore, it is preferable to use a hydrogenated block copolymer comprising vinyl aromatic hydrocarbon and conjugated diene hydrocarbon as a raw material for imparting rigidity and solvent resistance.

Next, the hydrogenated block copolymer of each component (a) and (b) will be described.
The (a) block copolymer hydrogenated product for imparting rigidity has a vinyl aromatic hydrocarbon content of 80% by weight or more and a storage elastic modulus (E ′) at 25 ° C. of 2.0. Block copolymer water composed of a vinyl aromatic hydrocarbon and a conjugated diene hydrocarbon, each having a peak temperature of x10 ⁹ Pa or more and a loss modulus (E ″) of 55 ° C. or more and 80 ° C. or less An additive is preferable, and the front and back layers preferably contain 70% by weight or more.In the case of a block copolymer having a storage elastic modulus (E ′) of 2.0 × 10 ⁹ Pa or more, the rigidity of the film at room temperature. Since the front and back layers play a role of imparting the rigidity of the film, the (a) hydrogenated block copolymer is required to be 70% by weight or more, more preferably 80% by weight or more. Configure the front and back layers of the film (A) The block copolymer hydrogenated product may be a copolymer hydrogenated product composed of the above-mentioned vinyl aromatic hydrocarbon and conjugated diene hydrocarbon alone, or may be a combination of two or more types. When the loss elastic modulus (E ″) has a peak temperature of 55 ° C. or more and 80 ° C. or less, it is possible to exhibit the rigidity of the film at normal temperature, the natural shrinkage, and the shrinkage at low temperature. Therefore, a film having a loss elastic modulus (E ″) peak temperature in the range of 55 ° C. to 80 ° C., preferably 60 ° C. to 75 ° C., is used from the balance of film rigidity and low temperature shrinkage.

Next, the block copolymer hydrogenated product (b) imparting rupture resistance has a conjugated diene content of 20 to 50% by weight, and at least one peak temperature of loss elastic modulus (E ″) is 10 ° C. or less. It is preferably a hydrogenated block copolymer composed of a vinyl aromatic hydrocarbon and a conjugated diene hydrocarbon present at -80 ° C. or higher. The peak temperature of the loss modulus (E ″) is 10 ° C. or lower, − When at least one exists at 80 ° C. or higher, the elongation characteristics of the film can be sufficiently imparted. In addition, when the conjugated diene content is 20% by weight or more, it becomes possible to impart elongation characteristics, and when it is less than 60% by weight, it is possible to prevent a decrease in rigidity and a film appearance due to a gel due to crosslinking of the conjugated diene during processing. It becomes. Since the intermediate layer plays a role of imparting the fracture resistance of the film, it is more preferably contained in an amount of 40% by weight to 60% by weight. By including 40% by weight or more and 60% by weight or less, not only the fracture resistance of the film but also the elastic modulus of the intermediate layer can be imparted. The hydrogenated block copolymer consisting of a vinyl aromatic hydrocarbon and a conjugated diene hydrocarbon used in the present invention can be obtained by hydrogenating the block copolymer before hydrogenation. The polymer structure before hydrogenation of the block copolymer hydrogenated product is not particularly limited.
(AB) _n , A- (BA) _n , B- (AB) _{n + 1}
[(A−B) _k ] _{m + 1} −X, [(A−B) _k −A] _{m + 1} −X
[(BA) _k ] _{m + 1} -X, [(BA) _k -B] _{m + 1} -X

(In the above formula, segment A is a vinyl aromatic hydrocarbon homopolymer and / or a copolymer comprising vinyl aromatic hydrocarbon and conjugated diene, and segment B is a conjugated diene homopolymer and / or vinyl aromatic hydrocarbon. X is a copolymer of a conjugated diene, for example, X is a residue or polyvalent of a coupling agent such as silicon tetrachloride, tin tetrachloride, 1,3 bis (N, N-glycidylaminomethyl) cyclohexane, epoxidized soybean oil, etc. It represents a residue of an initiator such as a functional organolithium compound, where n, k, and m are integers of 1 or more, generally an integer of 1 to 5. In addition, the structure of a polymer chain that is bonded to X by a plurality May be the same or different.) A linear block copolymer hydrogenated product, a radial block copolymer hydrogenated product represented by the following formula, or any mixture of these polymer structures may be used.Further, in the hydrogenated radial block copolymer represented by the above general formula, at least one A and / or B may be bonded to X.

  In the present invention, the vinyl aromatic hydrocarbon in the copolymer of vinyl aromatic hydrocarbon and conjugated diene in segment A and segment B may be distributed uniformly or in a tapered (gradual decrease) form. Good. In the hydrogenated product of the copolymer, a plurality of portions where vinyl aromatic hydrocarbons are uniformly distributed and / or portions where tapes are distributed may coexist in the segment. Vinyl aromatic hydrocarbon content in segment A ({vinyl aromatic hydrocarbon in segment A / (vinyl aromatic hydrocarbon in segment A + conjugated diene)} × 100) and vinyl aromatic carbon in segment B The relationship between the hydrogen content ({vinyl aromatic hydrocarbon in segment B / (vinyl aromatic hydrocarbon in segment B + conjugated diene)} × 100) is greater with the vinyl aromatic hydrocarbon content in segment A. , Greater than the vinyl aromatic hydrocarbon content in segment B. The difference in the preferred vinyl aromatic hydrocarbon content between segment A and segment B is preferably 5% by weight or more.

In the hydrogenated block copolymer used in the present invention, the hydrogenation rate (hydrogenation rate) of the unsaturated double bond based on the conjugated diene is 60% of the unsaturated double bond based on the conjugated diene compound in the polymer. % Or more, preferably 75% or more, more preferably 85% or more, particularly preferably 90% or more. When the hydrogenation rate is 60% or more, the solvent resistance is excellent. The hydrogenation rate of the aromatic double bond based on the vinyl aromatic hydrocarbon in the copolymer is not particularly limited, but the hydrogenation rate is 50% or less, preferably 30% or less, more preferably 20%. The following is preferable. The hydrogenation rate can be known by a nuclear magnetic resonance apparatus (NMR).
The block copolymer before hydrogenation can be obtained, for example, by polymerizing a vinyl aromatic hydrocarbon and a conjugated diene using an initiator such as an organic alkali metal compound in a hydrocarbon solvent.

Examples of the hydrocarbon solvent include aliphatic hydrocarbons such as n-butane, isobutane, n-pentane, n-hexane, n-heptane, and n-octane, cyclopentane, methylcyclopentane, cyclohexane, methylcyclohexane, and cycloheptane. In addition, alicyclic hydrocarbons such as methylcycloheptane, and aromatic hydrocarbons such as benzene, toluene, xylene, and ethylbenzene can be used. These may be used alone or in combination of two or more.
As the polymerization initiator, aliphatic hydrocarbon alkali metal compounds, aromatic hydrocarbon alkali metal compounds, organic amino alkali metal, which are generally known to have anionic polymerization activity for conjugated dienes and vinyl aromatic compounds. A compound or the like can be used. Examples of the alkali metal include lithium, sodium, potassium, and the like. Suitable organic alkali metal compounds include aliphatic and aromatic hydrocarbon lithium compounds having 1 to 20 carbon atoms,
Examples thereof include a compound containing one lithium in one molecule, a dilithium compound containing a plurality of lithium in one molecule, a trilithium compound, and a tetralithium compound.

  Specifically, n-propyl lithium, n-butyl lithium, sec-butyl lithium, tert-butyl lithium, hexamethylene dilithium, butadienyl dilithium, isoprenyl dilithium, diisopropenylbenzene and sec-butyl lithium Examples of the reaction product include a reaction product of divinylbenzene, sec-butyllithium and a small amount of 1,3-butadiene. Furthermore, organic alkali metal compounds disclosed in US Pat. No. 5,708,092, British Patent 2,241,239, US Pat. No. 5,527,753, etc. are also used. be able to. These may be used alone or in combination of two or more.

Examples of vinyl aromatic hydrocarbons include styrene, o-methylstyrene, p-methylstyrene, p-tert-butylstyrene, 1,3-dimethylstyrene, α-methylstyrene, vinylnaphthalene, vinylanthracene, and 1,1-diphenylethylene. , N, N-dimethyl-p-aminoethyl styrene, N, N-diethyl-p-aminoethyl styrene, etc., and particularly common is styrene. These may be used alone or in combination of two or more.
The conjugated diene is a diolefin having a pair of conjugated double bonds, such as 1,3-butadiene, 2-methyl-1,3-butadiene (isoprene), 2,3-dimethyl-1,3-butadiene. 1,3-pentadiene, 1,3-hexadiene, etc., and particularly common examples include 1,3-butadiene and isoprene. These may be used alone or in combination of two or more.

  The hydrogenation catalyst for the block copolymer is not particularly limited, and is conventionally known (1) A support in which a metal such as Ni, Pt, Pd, or Ru is supported on carbon, silica, alumina, diatomaceous earth, or the like. Type heterogeneous hydrogenation catalyst, (2) so-called Ziegler type hydrogenation catalyst using an organic acid salt such as Ni, Co, Fe, Cr or a transition metal salt such as acetylacetone salt and a reducing agent such as organic aluminum, 3) A homogeneous hydrogenation catalyst such as a so-called organometallic complex such as an organometallic compound such as Ti, Ru, Rh, or Zr is used. Specific examples of the hydrogenation catalyst include Japanese Patent Publication No. 42-8704, Japanese Patent Publication No. 43-6636, Japanese Patent Publication No. 63-4841, Japanese Patent Publication No. 1-337970, Japanese Patent Publication No. 1-53851, The hydrogenation catalyst described in Japanese Utility Model Publication No. 2-9041 can be used. A preferred hydrogenation catalyst is a mixture with a titanocene compound and / or a reducing organometallic compound.

  As the titanocene compound, compounds described in JP-A-8-109219 can be used. Specific examples thereof include (substitution) such as biscyclopentadienyl titanium dichloride and monopentamethylcyclopentadienyl titanium trichloride. Examples thereof include compounds having at least one ligand having a cyclopentadienyl skeleton, an indenyl skeleton, or a fluorenyl skeleton. Examples of the reducing organometallic compound include organic alkali metal compounds such as organolithium, organomagnesium compounds, organoaluminum compounds, organoboron compounds, and organozinc compounds.

  The hydrogenation reaction is generally carried out in a temperature range of 0 to 200 ° C, more preferably 30 to 150 ° C. The pressure of hydrogen used for the hydrogenation reaction is 0.1 to 15 MPa, preferably 0.2 to 10 MPa, and more preferably 0.3 to 7 MPa. The hydrogenation reaction time is usually 3 minutes to 10 hours, preferably 10 minutes to 5 hours. The hydrogenation reaction can be any of a batch process, a continuous process, or a combination thereof. In the present invention, the polymerization temperature for producing the block copolymer before hydrogenation is generally -10 ° C to 150 ° C, preferably 40 ° C to 120 ° C. The time required for the polymerization varies depending on the conditions, but is usually within 10 hours, particularly preferably 0.5 to 5 hours. The polymerization atmosphere is preferably replaced with an inert gas such as nitrogen gas. The polymerization pressure is not particularly limited as long as it is carried out within a range of pressure sufficient to maintain the monomer and solvent in the liquid layer within the above polymerization temperature range. Furthermore, care must be taken not to mix impurities, such as water, oxygen, carbon dioxide, etc., that inactivate the catalyst and living polymer into the polymerization system.

  About the heat-shrinkable laminated film of the present invention comprising the block copolymer hydrogenated composition, it is necessary that the heat shrinkage rate for 10 seconds in 70 ° C. warm water in the main shrinkage direction is 7% or more. . When the shrinkage rate is 7% or more, the low temperature shrinkage can be satisfied. In terms of reducing the natural shrinkage rate, the shrinkage rate in the main shrinkage direction after storage for 30 days in a 30 ° C. environment is preferably 1.5% or less. Further, the tensile elongation at 23 ° C. in the main shrinkage direction is preferably 70% or more, and the tensile elongation at 0 ° C. in the direction perpendicular to the main shrinkage direction is preferably 100% or more. When the elongation rate in the main shrinkage direction of the film is low, it becomes easy to break the label at the perforation provided on the label of the bottle, and when it is remarkably low, the tearing force at the crease during the sleeve processing If it is added, it will break and become a hole. If the elongation at low temperature in the direction perpendicular to the main shrinkage direction (MD direction) is low, the film breaks when a tension is applied in the film flow direction such as printing and sleeve processing in a low temperature environment, and troubles are likely to occur. Therefore, in order to be able to be used without the above trouble, a film having an elongation at 23 ° C. in the main shrinkage direction of 70% or more and an elongation at 0 ° C. in the direction perpendicular to the main shrinkage direction is preferably 100% or more.

  Furthermore, the heat-shrinkable laminated film of the present invention comprising the block copolymer hydrogenated composition needs to have a tensile elastic modulus of 1200 MPa or more measured in a direction perpendicular to the main shrinkage direction. The rigidity of the film can contribute to improving the shrink finish. This is because when the shrink film is printed and made into a bag, it is pushed in mechanically when it is put on the bottle from the top of the bottle. This is because it causes wrinkles. Therefore, when the tensile elastic modulus specified in the present invention is 1200 MPa or more, the above-described film breakage hardly occurs and the appearance after shrinkage can be improved.

The thickness of the heat-shrinkable laminated film of the present invention is 10 to 300 μm, preferably 20 to 200 μm, and more preferably 30 to 100 μm. Furthermore, the lamination thickness ratio of the front and back layers and the intermediate layer is not particularly limited as long as the above-described film characteristics can be satisfied. Although the method of achieving both rigidity and break resistance varies greatly depending on the blend ratio of each layer, the intermediate layer imparting break resistance is preferably 50% or more, more preferably 60% or more. The film may have any number of layers between the intermediate layer and the front and back layers as long as it satisfies this rule. For example, 2 types, 3 layers, 3 types, 5 layers, etc. may be used.
The heat-shrinkable uniaxial or biaxially stretched film using the block copolymer hydrogenated product and the composition of the present invention is obtained by converting the block copolymer hydrogenated product from a normal T die or a circular die into a flat shape or a tube shape. Extrusion is performed at 150 to 250 ° C., preferably 170 to 220 ° C., and the obtained unstretched product is substantially uniaxially or biaxially stretched.

For example, in the case of uniaxial stretching, in the case of a film or sheet, it is stretched in the extrusion direction with a calendar roll or the like, or in a direction perpendicular to the extrusion direction with a tenter or the like, and in the case of a tube, in the extrusion direction or circumferential direction of the tube. Stretch. In the case of biaxial stretching, in the case of a film or sheet, the extruded film or sheet is stretched in the longitudinal direction with a metal roll or the like and then stretched in the transverse direction with a tenter or the like. The tubes are stretched simultaneously or separately in the circumferential direction of the tube, that is, in a direction perpendicular to the tube axis.
In the present invention, the stretching temperature is 60 to 160 ° C., preferably 80 to 155 ° C., more preferably 85 to 150 ° C., and the stretching ratio is 1.5 to 8 times in the machine direction and / or the transverse direction, preferably 2 to 2. It is preferable to stretch 6 times. The stretching temperature is 60 ° C. or higher from the viewpoint of breaking during stretching, and 110 ° C. or lower from the viewpoint of shrinkage characteristics. The draw ratio is 1.5 times or more from the viewpoint of heat shrinkage and 8 times or less from the viewpoint of stable production. In the case of biaxial stretching, the stretching ratios in the longitudinal direction and the transverse direction may be the same or different. The uniaxially stretched or biaxially stretched heat-shrinkable film is then subjected to heat treatment at 60 to 160 ° C., preferably 80 to 155 ° C. for a short time, for example, 3 to 60 seconds, preferably 10 to 40 seconds. It is also possible to implement means to prevent natural contraction below.

Examples of the present invention will be described below, but these do not limit the scope of the present invention. In addition, the measurement of the physical property shown in the Example was performed by the following method.
1) Storage elastic modulus and loss elastic modulus Using a rheology viscoelasticity measuring and analyzing apparatus DVE-V4, measured using a test piece having a thickness of 2 mm under a vibration frequency of 35 Hz and a heating rate of 3 ° C./min. did.
2) Shrinkage The 70 ° C. shrinkage was calculated from the following equation by immersing the stretched film in 70 ° C. warm water for 10 seconds.
Thermal contraction rate (%) = (L−L1) / L × 100,
L: Length before contraction, L1: Length after contraction.
3) Natural shrinkage rate This is a value calculated by the following formula after leaving a stretched film having a shrinkage rate of 40% measured at 80 ° C for 3 days at 35 ° C.
Natural shrinkage (%) = (L2−L3) / L2 × 100,
L2: length before being left, L3: length after being left.
4) Tensile elastic modulus Based on JIS K-6732, it measured about the extending | stretching (TD) direction of the film at the tensile speed of 100 mm / min. The test piece was 10 mm in width and 20 mm between the marked lines. The measurement temperature was 23 ° C.
5) Elongation Based on JIS K-6732, it measured about the extending | stretching (TD) direction and the (MD) direction orthogonal to an extending | stretching direction at the tensile speed of 100 mm / min. The test piece was 10 mm in width and 20 mm between the marked lines. The measurement temperature was 23 ° C. in the TD direction and 0 ° C. in the MD direction.
6) Solvent resistance A stretched film of 5 cm in the MD direction × 5 cm in the TD direction was immersed in a 23 ° C. solvent having a ratio of ethyl acetate to isopropyl alcohol of 40/60, and the time until the start of shrinkage was visually measured.

<Criteria> ◎ 10 seconds or more, ○ 5 seconds or more and less than 10 seconds, × 5 seconds or less [Example 1]
Block copolymer hydrogenated product (I) (styrene / butadiene = 91/9, E ′ = 2.5 × 10 ⁹ Pa, E ″ peak temperature 63 ° C.) 50% by weight, block copolymer hydrogenated product (II ) (Styrene / butadiene = 70/30, E ′ = 3.2 × 10 ⁸ Pa, E ″ peak temperature−25 ° C./103° C.) 50% by weight of the mixed resin was mixed with the intermediate layer resin (E ′ = 1.6 × 10 ⁹ Pa, E ″ peak temperature −24 / 68 ° C.), mixed resin of 80% by weight of block copolymer hydrogenated product (I) and 20% by weight of block copolymer hydrogenated product (II) (E ′ = 2.3 × 10 ⁹ Pa, E ″ peak temperature−24 / 64 ° C.) The respective raw materials are melt-extruded by separate extruders, merged in a die, and three layers having a thickness of 300 μm. Molded into a sheet. This sheet was stretched uniaxially 5 times in the perpendicular direction (TD) by a tenter to produce a heat shrink film having a thickness of about 60 μm (lamination ratio 10/80/10). However, the stretching temperature was set so that the heat shrinkage rate was 20%. The characteristic data of the obtained film is shown in Table 1.

[Comparative Example 1]
A mixed resin of 80% by weight of block copolymer hydrogenated product (I) and 20% by weight of block copolymer hydrogenated product (II) was used as an intermediate layer resin, and 50% by weight of block copolymer hydrogenated product (I), A film was produced in the same manner as in Example 1 except that 50% by weight of the block copolymer hydrogenated product (II) was used as the front and back layer resin. The results are shown in Table 1.

[Comparative Example 2]
Polymer (III) (styrene / butyl acrylate = 84/16, E ′ = 2.2 × 10 ⁹ Pa, E ″ peak temperature 76 ° C.) 50% by weight, block copolymer hydrogenated product (II) 50% by weight In the same manner as in Example 1, except that the mixed resin is an intermediate layer resin, and the mixed resin of 80% by weight of the polymer (III) and 20% by weight of the hydrogenated block copolymer (II) is the front and back layer resin. Table 1 shows the results.

[Comparative Example 3]
A film was prepared in the same manner as in Example 1 except that the mixed resin of 80% by weight of the block copolymer hydrogenated product (I) and 20% by weight of the block copolymer hydrogenated product (II) was used as an intermediate layer and front and back layers. Produced. The results are shown in Table 1.

  The heat-shrinkable laminated film obtained by stretching the composition of the hydrogenated block copolymer of the present invention is excellent in the balance of physical properties such as rigidity, solvent resistance, natural shrinkage, low-temperature shrinkage and elongation. Breaking resistance and rigidity can be achieved at the same time, and it can be used favorably for beverage container packaging and cap seals.

Claims (4)

In a heat-shrinkable laminated film of at least 3 layers, a hydrogenated block copolymer composed of a vinyl aromatic hydrocarbon and a conjugated diene hydrocarbon was used for each of the front and back layers and the intermediate layer, and the film was stretched at least uniaxially. Heat shrinkage of the laminated film at 70 ° C. in the main shrinkage direction at 10 ° C. for 10 seconds and a tensile elastic modulus measured in a direction perpendicular to the main shrinkage direction is 1200 MPa or more Laminated film.
However, the front and back layers have at least one storage elastic modulus (E ′) at 25 ° C. of 1.5 × 10 ⁹ Pa or higher and a peak temperature of loss elastic modulus (E ″) of 50 ° C. or higher and 90 ° C. or lower. The hydrogenated block copolymer and the intermediate layer have a storage elastic modulus (E ′) at 25 ° C. of 1.0 × 10 ⁹ Pa or less and at least one peak temperature of loss elastic modulus (E ″). The hydrogenated block copolymer present at 10 ° C. or lower and −80 ° C. or higher. The hydrogenated block copolymer constituting the front and back layers and the intermediate layer is a mixture of the component (a) and the component (b), the front and back layers are the component (a) of 70% by weight or more, and the intermediate layer is the component The heat-shrinkable laminated film according to claim 1, wherein (b) is contained in an amount of 40 wt% to 60 wt%.
However, the component (a) has a vinyl aromatic hydrocarbon content of 80% by weight or more, a storage elastic modulus (E ′) at 25 ° C. of 2.0 × 10 ⁹ Pa or more, and a loss elastic modulus (E ″). A block copolymer hydrogenated product comprising a vinyl aromatic hydrocarbon and a conjugated diene hydrocarbon, each having a peak temperature of 55 ° C. or higher and 80 ° C. or lower.
Component (b) has a conjugated diene content of 20 to 50% by weight, a vinyl aromatic hydrocarbon and a conjugated diene system in which at least one peak temperature of loss modulus (E ″) is 10 ° C. or lower and −80 ° C. or higher. Hydrogenated block copolymer consisting of hydrocarbons.   The tensile elongation at 23 ° C in the main shrinkage direction is 70% or more, and the tensile elongation at 0 ° C in the direction perpendicular to the main shrinkage direction is 100% or more. Heat shrinkable laminated film.   The heat-shrinkable laminated film according to any one of claims 1 to 3, wherein the shrinkage rate in the main shrinkage direction after storage for 30 days in a 30 ° C environment is 1.5% or less.