JP4823947B2 - Laminated film - Google Patents

Description

  The present invention relates to a laminated film having excellent gas permeability and water vapor permeability.

  In recent years, foods such as fruits and vegetables, fresh fish, fresh meat, side dishes are placed directly or on plastic trays, and these are stretch-wrapped with films. Instead of the film, a linear low-density polyethylene film (see, for example, Patent Document 1), or a three-layer film in which a linear low-density polyethylene is used as an intermediate layer, and an ethylene-vinyl acetate copolymer film is laminated on the front and back surfaces ( For example, see Patent Document 2 and Patent Document 3), ethylene such as a laminated film having a three-layer structure in which a high-pressure polyethylene film is used as an intermediate layer and a high-pressure low-density polyethylene film is laminated on the front and back surfaces (for example, see Patent Document 4). Packaging films based on a base resin have been put into practical use.

  These ethylene-based resin packaging films are widely used for packaging fruits and vegetables, meats, and sugar beets. However, in the case of side dishes such as dumplings and croquettes that package food while it is hot, or in the case of foods that are likely to release moisture when the outside air temperature is low, the film has low water vapor permeability. The water droplets caused problems such as dampening of the dumplings, whitening of the croquette, and the decay of food due to the growth of water-based spoilage bacteria and the contents not being clearly visible.

In order to improve these disadvantages, at least one side of a film made of a homopolymer or copolymer resin of ω-laurolactam having a flexural modulus of 10,000 kg / cm ² or less has (A ′) vinyl acetate content. 94 to 99.8% by weight of 5 to 25% by weight of ethylene-vinyl acetate copolymer resin or 1,2 polybutadiene resin and (B ′) sorbitan fatty acid ester and its ethylene oxide adduct, mono and polyglycerin fatty acid ester, There is described a laminated film for stretch wrapping in which a resin film containing 0.2 to 6% by weight of a sucrose fatty acid ester, glycerin ricinoleate and glyceryl acetyl ricinolate is laminated. (For example, see Patent Document 5)

  Further, a packaging film having a styrene-butadiene copolymer as a main component and having excellent freshness keeping performance, and a packaging film in which a styrene-butadiene block copolymer and an ethylene-vinyl acetate copolymer are laminated are described. (For example, see Patent Document 6 and Patent Document 7)

  However, the laminated film for stretch wrapping stretches unevenly when stretched at the time of packaging, and the portion where the thinned portion has a sharp corner in the packaged food or a tray on which the packaged food is placed. In the case where the corner is sharp, there is a defect that the contact portion is torn, and there is a problem that wrinkles are generated on the film due to non-uniform elongation and packaging with commercial value cannot be performed. Further, there is a problem that the intermediate layer resin is expensive.

Furthermore, laminated films for stretch packaging do not necessarily meet market demands in terms of deformation recovery, such as recovering without leaving wrinkles against deformation on the film surface during transport of packages and store displays. It was not clear.
JP-A 64-14018 Japanese Patent Publication No. 2-18953 JP-A-3-258542 JP-A-57-210853 Japanese Patent Publication No. 63-56065 JP-A-8-48371 JP-A-9-76427

  An object of this invention is to provide the laminated film which has transparency, moderate elasticity, is hard to tear, and has high oxygen permeability and water vapor permeability.

  As a result of intensive studies to solve the above problems, the present inventors have found that a styrene-based resin composition layer and a polyolefin-based resin layer containing a vinyl aromatic hydrocarbon-conjugated diene block copolymer having a specific structure. The present inventors have found that a laminated film made of can solve the above-mentioned problems and have completed the present invention.

That is, the present invention
[1] A styrene resin composition layer (A) containing at least one block copolymer (I) containing a vinyl aromatic hydrocarbon and a conjugated diene compound;
A layer (B) mainly composed of a polyolefin resin laminated on the styrene resin composition layer (A),
The block copolymer (I) is:
(1) The content of vinyl aromatic hydrocarbon is 60 to 95% by weight,
(2) A laminated film in which the proportion of the vinyl aromatic hydrocarbon polymer block is 50 to 95% by weight of the total vinyl aromatic hydrocarbon in the block copolymer (I),
[2] The styrenic resin composition layer (A) comprises the block copolymer (I) 10 to 99.
The laminated film according to the preceding item [1], which contains, by weight, 90% to 1% by weight of a thermoplastic resin,
[3] The preceding item, wherein the thermoplastic resin contains at least one resin selected from the group consisting of a vinyl aromatic hydrocarbon-aliphatic unsaturated carboxylic acid derivative copolymer (II) and a polystyrene resin (III). The laminated film according to [2],
[4] The laminated film according to any one of [1] to [3], wherein the polyolefin-based resin contains an ethylene-vinyl acetate copolymer,
[5] Any of [1] to [4] above, wherein the styrenic resin composition layer (A) contains at least one lubricant selected from the group consisting of fatty acid amides, paraffins, hydrocarbon resins, and fatty acids. The laminated film according to claim 1,
[6] The laminated film according to any one of [1] to [5], which is for food packaging,
I will provide a.

  According to the present invention, it is possible to provide a packaging film having transparency, high oxygen permeability and water vapor permeability, and particularly excellent in keeping freshness when used for food packaging such as fruits and vegetables.

Hereinafter, the contents of the present invention will be described in detail.
The laminated film according to the present invention includes a styrene resin composition layer (A) containing at least one block copolymer (I) containing a vinyl aromatic hydrocarbon and a conjugated diene compound, and the styrene resin composition. And a layer (B) mainly composed of a polyolefin resin laminated on the layer (A).

Block copolymer (I) containing a vinyl aromatic hydrocarbon and a conjugated diene compound used in the styrene resin composition layer (A) of the present invention (hereinafter simply referred to as “vinyl aromatic hydrocarbon-conjugated diene block”) The content of the vinyl aromatic hydrocarbon constituting the copolymer (I) ”) is in the range of 60 to 95% by weight, preferably 65 to 90% by weight, more preferably 70 to 85% by weight. When the vinyl aromatic hydrocarbon content is in the range of 60 to 95% by weight, the laminated film is excellent in flexibility and transparency. The number average molecular weight by gel permeation chromatography (GPC) measurement of the block copolymer (I) used in the present invention is 30,000 to 500,000, preferably 50,000 to 300,000, more preferably 80,000 to 200,000. is there. When the number average molecular weight is in the range of 30,000 to 500,000, the moldability is excellent. The Vicat softening temperature of the block copolymer (I) used in the present invention is 70 to 90 ° C, preferably 70 to 85 ° C, more preferably 75 to 80 ° C. When the Vicat softening temperature is in the range of 70 to 90 ° C., the heat resistance is excellent.

  The block ratio of the vinyl aromatic hydrocarbon incorporated in the block copolymer (I) used in the present invention is 50 to 95% by weight, preferably 60 to 90% by weight. When the block ratio is in the range of 50 to 95% by weight, the flexibility of the laminated film according to the present invention is excellent. The block ratio of the vinyl aromatic hydrocarbon incorporated in the block copolymer (I) used in the present invention is determined by oxidative decomposition of the block copolymer with tertiary butyl hydroperoxide using osmium tetroxide as a catalyst. (Method described in I.M.KOLTHOFF, et al., J. Polym. ScI.1, 429 (1946)), and vinyl aromatic hydrocarbon polymer block component obtained by this method (however, average polymerization) This is a value obtained from the following equation using a vinyl aromatic hydrocarbon polymer component having a degree of about 30 or less.

The number average molecular weight Mn of the vinyl aromatic hydrocarbon polymer block of the block copolymer (I) used in the present invention is preferably 10,000 to 150,000, more preferably 20,000 to 120,000. When the number average molecular weight Mn of the vinyl aromatic hydrocarbon polymer block is 10,000 or more, it is preferable because of excellent rigidity, and when it is 150,000 or less, it is preferable because of excellent molding processability and transparency.

In the same manner as described above, the number average molecular weight of the block copolymer (I) used in the present invention is measured by a method of oxidatively decomposing the block copolymer with di-tertiary butyl hydroperoxide using osmium tetroxide as a catalyst [ I. M.M. KOLTHOFF, et al. , J .; Polym. Sci. 1,429 (1946)] can be obtained by gel permeation chromatography (GPC). The molecular weight is obtained by GPC measurement of monodisperse polystyrene for GPC, creating a calibration curve between the peak count number and the molecular weight of the monodisperse polystyrene, and calculating according to a conventional method (for example, “Gel Chromatography <Basics> Issued by Kodansha”). To do.

Preferred melt flow rate (JISK-) of the block copolymer (I) used in the present invention
Measurement according to 6870. Conditions are G condition, temperature 200 ° C., load 5 kg) from the viewpoint of molding processability, 0.01-100 g / 10 min, preferably 0.05-50 g / 10 min, more preferably 0.5-30 g / 10 min. . The number average molecular weight and melt flow rate (hereinafter sometimes abbreviated as MFR) can be arbitrarily adjusted by the amount of catalyst used for polymerization.

The vinyl aromatic hydrocarbon-conjugated diene block copolymer (I) used in the present invention is a vinyl aromatic hydrocarbon homopolymer and / or a copolymer composed of a vinyl aromatic hydrocarbon and a conjugated diene compound. It has at least one segment composed and at least one segment composed of a conjugated diene compound homopolymer and / or a copolymer composed of a vinyl aromatic hydrocarbon and a conjugated diene compound. The polymer structure 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
[(B−A) k] m + 1−X, [(B−A) k−B] m + 1−X
(In the above formula, segment A is a vinyl aromatic hydrocarbon homopolymer and / or a copolymer comprising a vinyl aromatic hydrocarbon and a conjugated diene compound, and segment B is a conjugated diene compound homopolymer and / or vinyl aroma. X is a copolymer made of, for example, silicon tetrachloride, tin tetrachloride, 1,3 bis (N, N-glycidylaminomethyl) cyclohexane, epoxidized soybean oil, etc. It represents a residue of a ring agent or a residue of an initiator such as a polyfunctional organolithium compound, etc. n, k and m are integers of 1 or more, generally an integer of 1 to 5. Multiple bonds to X The structure of the polymer chain may be the same or different.) A linear block copolymer or a radial block copolymer represented by (2), or any mixture of these polymer structures There can be used. In the 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 the vinyl aromatic hydrocarbon and the conjugated diene compound in segment A and segment B is uniformly distributed, but is distributed in a tapered shape (gradual decrease). May be. In 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 compound)} × 100) and vinyl aroma in segment B The relationship with the aromatic hydrocarbon content ({vinyl aromatic hydrocarbon in segment B / (vinyl aromatic hydrocarbon in segment B + conjugated diene compound)} × 100) The content is 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 present invention, the vinyl aromatic hydrocarbon-conjugated diene block copolymer (I) is obtained by polymerizing a vinyl aromatic hydrocarbon and a conjugated diene compound using an organic lithium compound as an initiator in a hydrocarbon solvent. Can be obtained. Examples of the vinyl aromatic hydrocarbon used in the present invention include styrene, o-methylstyrene, p-methylstyrene, p-tert-butylstyrene, 1,3-dimethylstyrene, α-methylstyrene, vinylnaphthalene, vinylanthracene, 1, Examples include 1-diphenylethylene, N, N-dimethyl-p-aminoethylstyrene, N, N-diethyl-p-aminoethylstyrene, and styrene is particularly common. These may be used alone or in combination of two or more.

  The conjugated diene compound used in the present invention 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 and the like, and particularly common examples include 1,3-butadiene and isoprene. These may be used alone or in combination of two or more.

In the vinyl aromatic hydrocarbon-conjugated diene block copolymer (I) used in the present invention, (i) a copolymer block comprising isoprene and 1,3-butadiene, (ii) isoprene and vinyl aromatic hydrocarbon And (iii) at least one polymer block selected from the group (i) to (iii) of a copolymer block consisting of isoprene, 1,3-butadiene and vinyl aromatic hydrocarbon, The weight ratio of butadiene to isoprene is 3/97 to 90/10, preferably 5/95 to 85/15, and more preferably 10/90 to 80/20. There is little gel formation in etc.

The vinyl aromatic hydrocarbon-conjugated diene block copolymer (I) used in the present invention can be obtained, for example, by anion living polymerization 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. And alicyclic hydrocarbons such as methylcycloheptane; aromatic hydrocarbons such as benzene, toluene, xylene, and ethylbenzene. These may be used alone or in combination of two or more.

  In addition, as a polymerization initiator, an aliphatic hydrocarbon alkali metal compound, an aromatic hydrocarbon alkali metal compound, an organic compound which are generally known to have anionic polymerization activity with respect to a conjugated diene compound and a vinyl aromatic compound are used. An amino alkali metal compound or the like can be used. Examples of the alkali metal include lithium, sodium, potassium, and the like, and preferable organic alkali metal compounds are aliphatic or aromatic hydrocarbon lithium compounds having 1 to 20 carbon atoms, one per molecule. Examples thereof include compounds containing lithium, dilithium compounds containing a plurality of lithium atoms in one molecule, trilithium compounds, and tetralithium compounds. 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.

  In the present invention, for the purpose of adjusting the polymerization rate, changing the microstructure of the polymerized conjugated diene moiety (ratio of cis, trans, vinyl), adjusting the reaction ratio of the conjugated diene compound and vinyl aromatic hydrocarbon, etc. Compounds and randomizing agents can be used. Polar compounds and randomizing agents include ethers such as tetrahydrofuran, diethylene glycol dimethyl ether and diethylene glycol dibutyl ether; amines such as triethylamine and tetramethylethylenediamine; thioethers; phosphines; phosphoramides; alkylbenzene sulfonates; An alkoxide etc. are mentioned.

In the present invention, the polymerization temperature for producing the block copolymer (I) 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 that inactivate the catalyst and living polymer, such as water, oxygen, and carbon dioxide, into the polymerization system.

In the present invention, the microstructure (the ratio of cis, trans, vinyl) of the conjugated diene portion of the vinyl aromatic hydrocarbon-conjugated diene block copolymer (I) can be arbitrarily changed by using the above-mentioned polar compound or the like. There are no particular restrictions. In general, the vinyl bond amount can be set in the range of 5 to 90%, preferably 10 to 80%, more preferably 15 to 75%. In the present invention, the amount of vinyl bonds means the total amount of 1,2-vinyl bonds and 3,4-vinyl bonds (however, when 1,3-butadiene is used as the conjugated diene compound, -Vinyl bond amount). The amount of vinyl bonds can be grasped by a nuclear magnetic resonance apparatus (NMR).
The block copolymer (I) of the present invention may be a mixture of two or more types.

The styrenic resin composition used for the laminated film according to the present invention comprises a composition of a block copolymer (I) and a thermoplastic resin in order to improve heat resistance or processability while maintaining transparency and rigidity. You can also

  As thermoplastic resins, polyolefin resins such as polyethylene, polypropylene, polybutene, polystyrene, rubber-modified high impact polystyrene (HIPS), styrene-butyl acrylate copolymer, styrene-methyl methacrylate copolymer, styrene-acrylonitrile copolymer Polymer, styrene-maleic anhydride copolymer, acrylonitrile-butadiene-styrene copolymer (ABS), methacrylate ester-butadiene-styrene copolymer (MBS), polyvinyl chloride resin, polymethacrylate ester resin, Polyester resins such as polycarbonate resins, polyethylene terephthalate, polytrimethylene terephthalate, polybutylene terephthalate, polyamide resins, polyphenylene sulfide resins, polyether resins Teruketon resins, polysulfone resins, polyphenylene oxide resins, polyimide resins, polyetherimide resins, polyacetal resins, cyclic olefin resins, norbornene resins. Preferable thermoplastic resins include vinyl aromatic hydrocarbon-aliphatic unsaturated carboxylic acid derivative copolymers and polystyrene resins.

  The vinyl aromatic hydrocarbon used in the vinyl aromatic hydrocarbon-aliphatic unsaturated carboxylic acid derivative copolymer (II) of the present invention mainly refers to a styrene monomer, specifically, Styrene, α-alkyl-substituted styrenes such as α-methyl styrenes, nuclear alkyl-substituted styrenes, nuclear halogen-substituted styrenes, etc., and at least one suitable one may be selected depending on the purpose. In addition, the aliphatic unsaturated carboxylic acid derivative used for the vinyl aromatic hydrocarbon and the aliphatic unsaturated carboxylic acid derivative copolymer is acrylic acid, methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate. , Pentyl acrylate, hexyl acrylate, etc., C1-C12, preferably C2-C12 ester derivatives of alcohol and acrylic acid, or methacrylic acid, or likewise C1-C12, preferably C2-C12 More preferably, an ester derivative of a C3 to C12 alcohol and methacrylic acid, an α or β unsaturated dicarboxylic acid such as fumaric acid, itaconic acid, maleic acid, or the like, or these dicarboxylic acid and a C2 to C12 alcohol. At least one selected from mono- or diester derivatives of These are generally vinyl aromatic hydrocarbons, and the amount is preferably 50 mol% or more, more preferably 70 mol% or more.

  Melt flow rate of vinyl aromatic hydrocarbon-aliphatic unsaturated carboxylic acid derivative copolymer (II) used in the present invention (hereinafter referred to as “MFR”) [in accordance with JISK-6870, G condition (temperature Measured at 200 ° C. and a load of 5 kg)] is 0.1 to 20 g / 10 min, preferably 1 to 15 g / 10 min from the viewpoint of molding.

  The preferred blending amount of the vinyl aromatic hydrocarbon-aliphatic unsaturated carboxylic acid derivative copolymer (II) used in the present invention is preferably 1 to 90% by mass, more preferably 20 to 80% by mass, and still more preferably. It is 20-70 mass%. A blending amount of 90% by mass or less is preferable because of excellent moldability and rigidity.

  The polystyrene resin (III) used in the present invention is obtained by polymerizing styrene or a monomer copolymerizable therewith (excluding the above-mentioned aliphatic unsaturated carboxylic acid derivatives). Examples of the monomer copolymerizable with styrene include α-methylstyrene, acrylonitrile, maleic anhydride and the like. Examples of the styrenic resin include polystyrene, styrene-α-methylstyrene copolymer, acrylonitrile-styrene copolymer, and styrene-maleic anhydride copolymer. Particularly preferred styrene polymer is polystyrene. be able to.

  As the polystyrene resin (III) used in the present invention, in particular, MFR ([measured in accordance with JISK-6870, G condition (temperature 200 ° C., load 5 kg)] is 0.1 to 0.1 from the point of molding processing. 100 g / 10 min, preferably 0.5 to 50 g / 10 min, more preferably 1 to 30 g / 10 min.

  The preferable compounding quantity of the polystyrene-type resin (III) used by this invention is 1-90 mass%, More preferably, it is 20-70 mass%. A blending amount of 90% by mass or less is preferable because of excellent moldability and rigidity.

  The Vicat softening temperature of the styrenic resin composition comprising component (I) / (II) or component (I) / component (III) of the present invention is in the range of 70 ° C to 105 ° C, preferably 75 ° C to 100 ° C. is there. When the Vicat softening temperature of the composition is in the range of 70 ° C. to 105 ° C., the heat resistance is excellent.

  The Vicat softening temperature of the styrene resin composition can be obtained by adjusting the Vicat softening temperature of Component (I), Component (II), and Component (III), or adjusting the component ratio.

  To the styrene resin composition layer (A) of the present invention, at least one selected from the group consisting of fatty acid amides, paraffins, hydrocarbon resins and fatty acids can be added as a lubricant. By adding 0.01 to 5 parts by weight, preferably 0.05 to 4 parts by weight, more preferably 0.1 to 3 parts by weight, based on 100 parts by weight of the styrene resin composition of the present invention, blocking resistance is improved. Becomes better.

  Examples of fatty acid amides used in the present invention include stearoamide, oleyl amide, erucyl amide, behen amide, mono- or bisamide of higher fatty acids, ethylene bis stearamide, stearyl oleylamide, N-stearyl erucamide, These can be used alone or in admixture of two or more. Examples of the paraffin and hydrocarbon resin used in the present invention include paraffin wax, microcrystalline wax, liquid paraffin, paraffin synthetic wax, polyethylene wax, composite wax, montan wax, hydrocarbon wax, silicone oil, and the like. These can be used alone or in admixture of two or more. Examples of fatty acids used in the present invention include saturated fatty acids and unsaturated fatty acids. That is, examples include saturated fatty acids such as lauric acid, palmitic acid, stearic acid, behenic acid, and hydroxystearic acid, and unsaturated fatty acids such as oleic acid, erucic acid, and ricinoleic acid. These may be used alone or in combination of two or more. Can be used.

  The styrene resin composition layer (A) of the present invention is selected from the group consisting of benzophenone UV absorbers, benzotriazole UV absorbers and hindered amine light stabilizers as UV absorbers and light stabilizers. 0.05 to 3 parts by weight, preferably 0.05 to 2.5 parts by weight, more preferably 0.1 to 2 parts by weight, based on 100 parts by weight of the composition of at least one ultraviolet absorber and light stabilizer By adding, light resistance improves.

  In the styrenic resin composition layer (A) of the present invention, 2- [1- (2-hydroxy-3,5-di-t-pentylphenyl) ethyl] -4,6-di-t- is used as a stabilizer. By adding 0.05 to 3 parts by weight, preferably 0.1 to 2 parts by weight of pentylphenyl acrylate with respect to 100 parts by weight of the composition, a gel suppressing effect can be obtained. If the stabilizer is less than 0.05 parts by weight, there is no effect of suppressing the gel, and even if added over 3 parts by weight, it does not contribute to the gel suppression effect of the present invention or more.

  Examples of the olefin resin constituting the olefin resin layer (B) used in the present invention include olefin homo- or copolymers. Examples of the olefin include ethylene, propylene, 1-butene, isobutene, 4-methyl-1-butene, 1-pentene, 3-methyl-1-pentene, 1-hexene, 1-octene, 1-nonene, 1- C2-C16 α-olefins such as decene, 1-undecene, 1-dodecene (preferably C2-C10 α-olefins, more preferably C2-C8 α-olefins, especially 2 carbons) ˜4 α-olefins) and the like. These olefins may be used alone or in combination of two or more. Of these olefins, ethylene, propylene, particularly at least propylene is preferably contained.

  The olefin resin used in the present invention may be a copolymer of an olefin and a copolymerizable monomer. Examples of the copolymerizable monomer include (meth) acrylic acid esters [for example, (meth) acrylic acid alkyl esters such as methyl (meth) acrylate and ethyl (meth) acrylate]; vinyl esters (for example, vinyl acetate). And vinyl propionate); cyclic olefins (norbornene, ethylidene norbornene, cyclopentadiene, etc.); dienes (butadiene, isoprene, etc.) and the like. A copolymerizable monomer can be used individually or in combination of 2 or more types. The usage-amount of a copolymerizable monomer can be selected from the range of about 0-100 weight part with respect to 100 weight part of olefins, Preferably it is 0-50 weight part, More preferably, it is about 0-25 weight part.

  Examples of the olefin resin include polyethylene resins [for example, low, medium or high density polyethylene, linear low density polyethylene, ethylene-propylene copolymer, ethylene-butene copolymer, ethylene-propylene-butene copolymer. Propylene-containing polymers such as polypropylene, propylene-ethylene copolymer, propylene-butene copolymer, propylene-ethylene-butene copolymer, etc. 80% by weight or more of propylene resin), poly (methylpentene) resin, and the like. Examples of the copolymer include ethylene-vinyl acetate copolymer, ethylene- (meth) acrylic acid copolymer or its ionomer, ethylene- (meth) acrylate copolymer such as ethylene-ethyl acrylate copolymer, Examples thereof include maleic anhydride grafted polypropylene.

  The copolymer (a copolymer of olefins and a copolymer of an olefin and a copolymerizable monomer) includes a random copolymer, a block copolymer, or a graft copolymer.

  Of these olefin resins, ethylene-vinyl acetate copolymers are preferred from the viewpoint of water vapor permeability. The ethylene-vinyl acetate copolymer is specifically an ethylene-vinyl acetate copolymer resin having a vinyl acetate content of 5 to 40% by weight and an ethylene content of 95 to 60% by weight, and the vinyl acetate content is preferably 5 ~ 25% by weight. When the vinyl acetate content is in the range of 5 to 40% by weight, it is preferable from the viewpoint of wrinkling and blocking resistance of the package.

  The MFR (JIS K-7210; 190 ° C., 2.16 kg load) of the ethylene-vinyl acetate copolymer resin is preferably from 0.1 to 10 g / 10 min in view of appearance and packaging suitability.

  For example, an aliphatic alcohol having 1 to 12 carbon atoms, preferably 1 to 6 carbon atoms in order to impart antifogging properties, moderate slipperiness, self-adhesiveness, and antistatic properties to the polyolefin resin layer (B). A fatty alcohol ester of a fatty acid having 10 to 22 carbon atoms, preferably 12 to 18 carbon atoms, specifically monoglycerin oleate, polyglycerin oleate, glycerin trilysinolate, glyceryl acetyl Ricinolate, polyglyceryl stearate, polyglycerin laurate, methyl acetyl ricinoleate, ethyl acetyl ricinoleate, butyl acetyl ricinoleate, propylene glycol oleate, propylene glycol laurate, pentaerythritol oleate, polyethylene glycol oleate, polypropylene Glycol oleate, sorbitan oleate, sorbitan laurate, polyethylene glycol sorbitan oleate, polyethylene glycol sorbitan laurate, etc., and polyalkylene ether polyols, specifically polyethylene glycol, polypropylene glycol, etc. At least one selected compound may be added in an amount of 0.1 to 10% by weight, preferably 1 to 5% by weight. Moreover, you may mix | blend 0.1-10 weight% of these additives also to a styrene-type resin composition layer (A).

  The laminated film according to the present invention uses a plurality of extruders to form a styrene-based resin composition layer (A) and a polyolefin-based resin layer (B). Can be laminated and formed by a known method such as co-extrusion method or extrusion lamination method.

  Among them, in order to obtain a laminated film in which mechanical strength such as tear strength in the vertical direction and horizontal direction is sufficiently balanced, a coextrusion method by inflation molding is preferable, and the blow ratio at that time is 2 to 20 times, preferably 2 ~ 15 times. The blow ratio here refers to the ratio of the circumferential length of the final blown film to the circumferential length of the die slit. Furthermore, the laminated film obtained as described above may be heated to a temperature lower than the crystallization temperature of the resin, and stretched 1.2 to 5 times in the longitudinal direction of the film using a difference in speed between nip rolls. Absent. The thickness of this laminated film is 10 to 500 μm as a whole.

  The laminated film according to the present invention can be used for various uses, for example, packaging of fruits and vegetables, fresh foods, confectionery, clothing, stationery, etc. by utilizing the characteristics. Particularly preferred applications include packaging films such as fruits and vegetables that are excellent in water vapor permeability and oxygen permeability and need to maintain the freshness of food.

Examples of the present invention will be described below, but these do not limit the scope of the present invention.
(Measurement and evaluation method)
The measurement and evaluation described in Examples and Comparative Examples were performed by the following methods.

(A) Evaluation (1) Block ratio and number average molecular weight of the vinyl aromatic hydrocarbon polymer block of the block copolymer (1) A block copolymer was formed with di-tertiary butyl hydroperoxide using osmium tetroxide as a catalyst. Method of oxidative decomposition [I. M.M. KOLTHOFF, et al. , J .; Polym. Sci. 1,429 (1946)] was quantified and determined from the following formula.

  Moreover, the number average molecular weight was obtained for the vinyl aromatic hydrocarbon polymer block component obtained by this method using GPC.

(2) Vinyl aromatic hydrocarbon content It measured using the ultraviolet spectrophotometer (Shimadzu Corporation UV-2450).

(3) Tensile elastic modulus MD and TD were measured at a test speed of 5 mm / min using a TG-5KN type tester manufactured by Minebea Co., Ltd. according to ASTM D638.

(4) Total light transmittance and haze Based on JIS K7105, the Nippon Denshoku Co., Ltd. haze meter (1001DP) was used. The measurement was performed by applying liquid paraffin.

(5) Water vapor permeability Measured according to JIS Z-0208.

(6) Carbon dioxide permeability Measured by a differential pressure method using a gas permeability measuring device manufactured by Toyo Seiki Seisakusho Co., Ltd.

(7) Oxygen permeability It measured by the isobaric method based on ASTM D-3985 using OX-TRAIN 100 type made by MODERN-CONTROLS.

(8) Preservability After placing a croquette with a surface temperature of 60 ° C. on a stretched polystyrene tray, it was stretch-wrapped with a laminated film, and the state of the croquette after 1 hour was observed with the naked eye. evaluated.
○: When there is no particular change ×: When the croquette is whitened by water droplets.

(9) Wrinkle generation situation A sphere having a diameter of 10 cm was packaged with a laminated film having a length and width of 25 cm, the film was removed after 1 hour, and the presence or absence of wrinkles on the film was visually observed.

(B) Raw material used 1) Block copolymer (a-1)
Using an autoclave with a stirrer, under a nitrogen gas atmosphere,
i) 0.080 parts by mass of n-butyllithium was added to a cyclohexane solution containing 25 parts by mass of styrene and polymerized at 80 ° C. for 20 minutes.
Next, ii) a cyclohexane solution containing 15 parts by mass of styrene and 24 parts by mass of 1,3-butadiene was continuously added for 60 minutes and polymerized at 80 ° C.
Subsequently, iii) A cyclohexane solution containing 36 parts by mass of styrene was continuously added for 25 minutes to polymerize at 80 ° C., and then kept at 80 ° C. for 10 minutes. Thereafter, the polymerization was stopped by adding methanol to the polymerization vessel at a 0.9-fold mole relative to n-butyllithium, and 2- [1- (2-hydroxy-3,5-di-t-pentylphenyl) was used as a stabilizer. ) Ethyl] -4,6-di-t-pentylphenyl acrylate is added to 0.5 part by mass with respect to 100 parts by mass of the block copolymer, and then the solvent is removed to obtain the block copolymer (a-1). Obtained. Block copolymer a-1 is polymer block A in which styrene / 1,3-butadiene = 100/0 mass ratio, and polymer in which styrene / 1,3-butadiene = 38.5 / 61.5 mass ratio. This is an ABA block polymer composed of polymer block A in which block B and styrene / 1,3-butadiene = 100/0 mass ratio. The obtained block copolymer a-1 has a number average molecular weight of 85,000, a styrene content of 77.5% by mass, a block rate of 79% by mass, and a melt flow rate of 7 g / 10 min (according to ASTM D1238). Compliance, 200 ° C., load 5 kg).

(2) Block copolymer (a-2 to a-4)
Using the same method as the block copolymer (a-1), the amount of styrene and 1,3-butadiene added in i), ii) and iii) of (a-1), and n-butyllithium The block copolymer (a-2 to a-4) was prepared by appropriately controlling the amount of addition (see Table 1).
In addition, when the addition amount of n-butyllithium is decreased, the molecular weight increases. When the amount of styrene added in ii) was increased with respect to the amount of styrene added in i) and iii), the styrene block rate decreased.

(3) Polystyrene Polystyrene 685 (manufactured by PS Japan Corporation) was used as polystyrene (b-1).

(4) Vinyl aromatic hydrocarbon-acrylic acid ester copolymer SC004 (manufactured by PS Japan Ltd.) was used (b-2).

(5) Polyethylene As polyethylene, Suntec M1920 (manufactured by Asahi Kasei Chemicals Corporation) was used (c-1).

(6) Ethylene-vinyl acetate copolymer A commercially available ethylene-vinyl acetate copolymer (vinyl acetate content: 15% by weight) was used (c-2).

[Examples 1-8, Comparative Examples 1-3]
A two-layer film having a thickness of 100 μm and a layer composition ratio of 50% / 50% was prepared using a multilayer film extruder in which a multilayer T-die and a single screw extruder were combined. The evaluation results of this film are shown in Table 2.

  From the results shown in Table 2, it can be seen that the laminated film according to the present invention is excellent in transparency, oxygen permeability, water vapor permeability and the like.

  The laminated film according to the present invention is excellent in transparency, oxygen permeability and water vapor permeability, and has a characteristic that it does not easily become cocoon when used as a packaging material. Therefore, foods such as fruits and vegetables, fresh fish, fresh meat, and side dishes are packaged. It can use suitably for the film to do.

Claims (6)

A styrenic resin composition layer (A) containing at least one block copolymer (I) containing a vinyl aromatic hydrocarbon and a conjugated diene compound;
A layer (B) mainly composed of a polyolefin resin laminated on the styrene resin composition layer (A),
The block copolymer (I) is:
(1) The content of vinyl aromatic hydrocarbon is 60 to 95% by weight,
(2) The laminated film in which the proportion of the vinyl aromatic hydrocarbon polymer block is 50 to 95% by weight of the total vinyl aromatic hydrocarbon in the block copolymer (I). The styrenic resin composition layer (A) is 10 to 99% by mass of the block copolymer (I).
The laminated film according to claim 1, further comprising 90 to 1% by mass of a thermoplastic resin.   The thermoplastic resin contains at least one resin selected from the group consisting of vinyl aromatic hydrocarbon-aliphatic unsaturated carboxylic acid derivative copolymer (II) and polystyrene resin (III). The laminated film as described.   The laminated film according to any one of claims 1 to 3, wherein the polyolefin resin contains an ethylene-vinyl acetate copolymer.   5. The styrene resin composition layer (A) according to claim 1, comprising at least one lubricant selected from the group consisting of fatty acid amides, paraffins, hydrocarbon resins, and fatty acids. Laminated film.   The laminated film according to any one of claims 1 to 5, which is for food packaging.