JP5026332B2 - Multilayer film - Google Patents

Description

  The present invention relates to a multilayer film obtained by stretching a laminate of a polylactic acid resin composition and a polypropylene resin.

  BACKGROUND ART Wrapping films for food packaging are used mainly for applications such as over a container such as a plate, directly wrapped food, stored in a refrigerator or freezer, or reheated in a microwave oven. For this reason, the wrap film is required to have basic performance such as transparency, heat resistance, cold resistance, adhesion between the wrap and the container, adhesion between the wraps, soft and moist touch and color, and drying of food. The water vapor barrier property for preventing the texture and maintaining the texture and taste, and the transparency for improving the visibility of the food and the cleanliness of the appearance are required.

On the other hand, due to increasing environmental awareness in recent years, aliphatic polyester-based resins derived from plant raw materials, such as polylactic acid, are attracting attention as resin materials, and various applications are being developed.
The same applies to wrap films, and Patent Documents 1 and 2 disclose a technique for a wrap film mainly composed of polylactic acid-based aliphatic polyester.
As a method for improving the water vapor barrier property, Patent Document 3 discloses a technique of blending a wax compound and flat particles.

Patent Document 4 discloses a technique for coating a polylactic acid film with a low molecular weight polyolefin on the surface thereof.
Patent Document 5 discloses a technique for producing a laminated film of a polyolefin-based resin and polylactic acid by an inflation method.
Furthermore, Patent Document 6 discloses a technique related to a laminated film in which polylactic acid and a polypropylene resin are combined.
Furthermore, Patent Document 7 discloses a technique for adhesively laminating a biaxially stretched polypropylene film to a polylactic acid biaxially stretched film, and Patent Document 8 discloses a technique for bonding polypropylene to a polylactic acid biaxially stretched film. A technique for extrusion lamination is disclosed, and Patent Document 9 discloses a technique for producing a heat-shrinkable film by laminating an olefin resin on the surface of polylactic acid and biaxially stretching.

JP 2000-26623 A Japanese Patent No. 3861488 JP 2007-16091 A JP 2003-276144 A Japanese Patent No. 3824846 JP 2007-90858 A JP 2001-58372 A JP 2005-119125 A JP 2007-283531 A

However, the films disclosed in Patent Documents 1 to 9 do not have sufficient characteristics as a multilayer wrap film, and further improvements have been desired.
The problem to be solved by the present invention is to provide a multilayer film excellent in heat resistance, adhesion, flexibility, water vapor barrier properties, and transparency.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors have found that the above-mentioned problems can be solved by making a multilayer film comprising a specific polylactic acid-based resin composition and a polypropylene-based resin. The present invention has been completed.

That is, the present invention is as follows.
[1]
A multilayer film having an inner layer and surface layers disposed on both front and back surfaces of the inner layer,
The surface layer is a layer containing a polylactic acid-based resin composition;
The polylactic acid-based resin composition is
100 parts by mass of a composition comprising 70 to 90% by mass of crystalline polylactic acid and 10 to 30% by mass of glycerol fatty acid ester and / or polyglycerol fatty acid ester,
As the flexible resin, 0.5 to 10 parts by mass of at least one flexible resin selected from the group consisting of the following (a) and (b), and / or 10 to 50 parts by mass of the flexible resin that is (c) below;
(A) a copolymer of an aliphatic hydroxycarboxylic acid, an aliphatic diol, and an aliphatic dicarboxylic acid,
(B) a copolymer of ethylene and vinyl acetate having a vinyl acetate content of 40 to 50% by mass;
(C) a copolymer of an aliphatic diol, an aliphatic dicarboxylic acid and an aromatic dicarboxylic acid,
Containing
The inner layer is a layer containing a polypropylene resin,
The polypropylene resin contains a propylene-α-olefin copolymer consisting of 65 to 90% by mass of propylene and 10 to 35% by mass of α-olefin,
The α-olefin is at least one selected from the group consisting of ethylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 1-heptene, 1-hexene, 1-octene and 1-nonene. There is a multilayer film.
[2]
The multilayer film according to [1], wherein a heat shrinkage rate at 100 ° C. is 35% or less.

  According to the present invention, the layer containing the polylactic acid-based resin composition is used as the surface layer, in particular, heat resistance and adhesion are expressed, and the layer including the propylene-based resin is used as the inner layer, in particular, water vapor. It is possible to obtain a multilayer film that exhibits barrier properties and is excellent in heat resistance, adhesion, flexibility, water vapor barrier properties, and transparency. The multilayer film of the present invention can be suitably used particularly as a multilayer wrap film.

  Hereinafter, the best mode for carrying out the present invention (hereinafter referred to as “the present embodiment”) will be described in detail. In addition, this invention is not limited to the following embodiment, It can implement by changing variously within the range of the summary.

The multilayer film of the present embodiment is a multilayer film having an inner layer and surface layers disposed on both front and back surfaces of the inner layer, and has a layer containing a polypropylene resin as the inner layer, and a polylactic acid resin composition as the surface layer It has a layer containing objects.
The polylactic acid-based resin composition is a resin composition containing crystalline polylactic acid, glycerin fatty acid ester and / or polyglycerin fatty acid ester, and a flexible resin.

(Polylactic acid resin composition)
The crystalline polylactic acid used in the present embodiment is a polymer mainly composed of L-lactic acid units or D-lactic acid units, or a copolymer thereof. The crystalline polylactic acid contains an L-lactic acid unit or a D-lactic acid unit as a main component and may be a copolymer with a comonomer other than lactic acid, but may be an L-lactic acid unit and / or a D-lactic acid unit. A polymer consisting of From the viewpoint of exhibiting heat resistance, the crystalline polylactic acid is preferably a polymer in which the optical purity of the L-lactic acid unit or D-lactic acid unit constituting the crystalline polylactic acid is 90% ee or more. Crystalline polylactic acid can be used alone or in combination.
The crystalline polylactic acid is not particularly limited, and specific examples include trade names “NatureWorks4042D” and “NatureWorks4032D” (manufactured by NatureWorks, USA, registered trademark, the same shall apply hereinafter).

  In the present embodiment, the weight average molecular weight (Mw) of the crystalline polylactic acid is preferably in the range of 80,000 to 400,000, more preferably 100,000 to 300,000, and further preferably 150,000 to 25. Ten thousand. If the weight average molecular weight of the polylactic acid polymer is 80,000 or more, a practical level of mechanical strength can be expressed, and if the weight average molecular weight is 400,000 or less, molding can be performed with an appropriate melt viscosity. it can.

The glycerin fatty acid ester or polyglycerin fatty acid ester used in the present embodiment is an ester of glycerin and a fatty acid or an ester of polyglycerin and a fatty acid, and softens crystalline polylactic acid, and films, or ceramics or glass Has the effect of increasing the adhesion to the container.
The glycerin fatty acid ester or polyglycerin fatty acid ester used in the present embodiment is not particularly limited. For example, among the hydroxyl groups of glycerin or polyglycerin, a compound in which at least one hydroxyl group and a fatty acid are ester-bonded is used. is there.
Examples of the fatty acid include 2 to 2 carbon atoms such as caproic acid, caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, behenic acid, montanic acid, oleic acid, linoleic acid, and linolenic acid. 28 linear or branched saturated fatty acids or unsaturated fatty acids. As a fatty acid, a C6-C18 linear saturated fatty acid or unsaturated fatty acid is preferable. It may be an ester of one type of fatty acid or a mixed ester of two or more types of fatty acid.
Examples of the polyglycerin include polyglycerin such as diglycerin, triglycerin, and tetraglycerin.

  The glycerin fatty acid ester or polyglycerin fatty acid ester is not particularly limited. For example, glycerin tricaprate, glycerin tricaprylate, diglycerin oleate, diglycerin tetraacetate, polyglycerin monolaurate, and polyglycerin. Examples include monooleate.

In glycerin fatty acid ester or polyglycerin fatty acid ester, hydroxyl group derived from glycerin or polyglycerin that is not esterified with fatty acid prevents decomposition of crystalline polylactic acid, etc. by transesterification to ester bonds such as crystalline polylactic acid. For this purpose, it is preferably acetylated.
Such an acetylated compound is not particularly limited. For example, glycerol diacetomonocaprylate, glycerol diacetomonocaprate, glycerol diacetomonomyristate, glycerol diacetomonolaurate, glycerol diacetomono Examples include palmitate and glycerin diacetate monostearate.

The glycerin fatty acid ester or the polyglycerin fatty acid ester is not particularly limited, but specifically, the trade names “Liquemar PL004”, “Liquemar PL012”, “Liquemar PL019”, “Liquemar PL710”, “Poem G” -002 "," Poem G-038 "(manufactured by Riken Vitamin Co., registered trademark, the same shall apply hereinafter) and the like.
The glycerin fatty acid ester and / or the polyglycerin fatty acid ester can be used alone or in combination.

In this Embodiment, content of the said glycerol fatty acid ester and / or polyglycerol fatty acid ester in the composition which consists of crystalline polylactic acid and glycerol fatty acid ester and / or polyglycerol fatty acid ester is crystalline polylactic acid 70-90 mass. % To 10-30% by mass.
An appropriate plasticizing effect can be obtained by adding 10% by mass or more of the content of glycerin fatty acid ester and / or polyglycerin fatty acid ester, and the addition of 30% by mass or less provides sufficient strength as a multilayer film. It can be ensured, and problems such as bleeding out can be made difficult to occur.
In this Embodiment, it is preferable that a polylactic acid-type resin composition is a composition which consists of crystalline polylactic acid 75-85 mass%, fatty-acid glycerol ester, and / or polyglycerol fatty-acid ester 15-25 mass%.

In the present embodiment, the polylactic acid-based resin composition is a composition 100 composed of crystalline polylactic acid and glycerin or polyglycerin and an ester of fatty acid in order to enhance the adhesion between the food container and the multilayer film. It is necessary to add 0.5 to 10 parts by mass of at least one flexible resin selected from the following (a) and (b) and / or 10 to 50 parts by mass of the flexible resin (c) with respect to parts by mass. is there.
(A) Copolymer of aliphatic hydroxycarboxylic acid, aliphatic diol and aliphatic dicarboxylic acid (b) Copolymer of ethylene and vinyl acetate having a vinyl acetate content of 40 to 50% by mass (c) Copolymer of Aliphatic Diol, Aliphatic Dicarboxylic Acid and Aromatic Dicarboxylic Acid The above flexible resins can be used alone or in combination.

In (a) a copolymer of an aliphatic hydroxycarboxylic acid, an aliphatic diol, and an aliphatic dicarboxylic acid (hereinafter sometimes simply referred to as “copolymer (a)”) used in the present embodiment. The aliphatic hydroxycarboxylic acid is not particularly limited, and examples thereof include ω having 2 to 20 carbon atoms such as lactic acid, glycolic acid, 3-hydroxybutyric acid, 4-hydroxyvaleric acid, and 6-hydroxycaproic acid. -Hydroxy saturated aliphatic carboxylic acid etc. are mentioned. Aliphatic hydroxycarboxylic acids can be used alone or in combination.
The aliphatic hydroxycarboxylic acid is preferably lactic acid in order to enhance the compatibility with crystalline polylactic acid.
The aliphatic diol in the copolymer (a) is not particularly limited, and examples thereof include ethylene glycol, 1,3-propanediol, 1,4-butanediol, and 1,5-heptanediol. Examples thereof include saturated aliphatic diols having 2 to 20 carbon atoms. Aliphatic diols can be used alone or in combination.
The aliphatic dicarboxylic acid in the copolymer (a) is not particularly limited, and examples thereof include malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, and sebacic acid. And a saturated aliphatic dicarboxylic acid having 3 to 20 carbon atoms. Aliphatic dicarboxylic acids can be used alone or in combination.

As a method for copolymerizing the aliphatic hydroxycarboxylic acid, the aliphatic diol, and the aliphatic dicarboxylic acid, a block copolymerization method can be suitably used. As the copolymer (a) obtained by block copolymerization, for example, a copolymer having a block consisting of a repeating unit of an aliphatic hydroxycarboxylic acid and a block consisting of a repeating unit of an aliphatic diol and an aliphatic dicarboxylic acid A thing (a) etc. can be mentioned.
As a copolymerization ratio in the copolymer (a) obtained by the block copolymerization, the ratio of the polyester block of the aliphatic diol and the aliphatic dicarboxylic acid is preferably 20 to 80% by mass, and 40 to 60% by mass. It is more preferable that By containing 20 mass% or more of the polyester block of the aliphatic diol and the aliphatic dicarboxylic acid, the effect of improving the adhesion of the multilayer film is obtained, and if it is 80 mass% or less, the compatibility with polylactic acid is good. Can keep. The copolymer (a) can be used alone or in combination.
Such a copolymer (a) is not particularly limited, but specifically, trade names “Plamate PD150” and “Plamate PD350” (manufactured by Dainippon Ink Co., Ltd., registered trademark, the same shall apply hereinafter). ) And the like.

  In the polylactic acid-based resin composition in the present embodiment, the addition amount of the copolymer (a) with respect to 100 parts by mass of the composition comprising crystalline polylactic acid and glycerin fatty acid ester and / or polyglycerin fatty acid ester It is 0.5-10 mass parts, and it is preferable that it is 2-8 mass parts. By adding 0.5 parts by mass or more, it is possible to obtain an adhesion assisting effect on the surface of the multilayer film by a flexible component composed of a repeating unit of an aliphatic diol and an aliphatic dicarboxylic acid, and by adding at 10 parts by mass or less, A multilayer film having suitable adhesion can be obtained.

A copolymer of ethylene and vinyl acetate (hereinafter referred to simply as “copolymer (b)” in which the content of (b) vinyl acetate used in the present embodiment is 40 to 50% by mass. ) Has a role to increase the flexibility of the polylactic acid-based resin composition, but in order to make it compatible with the crystalline polylactic acid, the vinyl acetate unit is 40 to 50% by mass in the copolymer (b). When the content of vinyl acetate units is 40% by mass or more, highly flexible vinyl acetate units are likely to be present on the surface of the multilayer film, and adhesion on the surface can be obtained. When the content is 50% by mass or less, good mechanical strength and heat resistance of the multilayer film can be maintained.The copolymer (b) whose vinyl acetate units are 40 to 50% by mass in the copolymer (b). )If, It can be used in Germany, it may be used in combination.
Although it does not specifically limit as such a copolymer (b), Specifically, brand name "Evaflex EV45LX", "Evaflex EV40LX" (the Mitsui DuPont polychemical company make, registered trademark) The same shall apply hereinafter).

  In the polylactic acid-based resin composition in the present embodiment, the addition amount of the copolymer (b) with respect to 100 parts by mass of the composition comprising crystalline polylactic acid and glycerin fatty acid ester and / or polyglycerin fatty acid ester It is 0.5-10 mass parts, it is preferable that it is 1-7 mass parts, and it is more preferable that it is 2-5 mass parts. By adding 0.5 parts by mass or more, an adhesion auxiliary effect on the surface of the multilayer film can be obtained, and by adding 10 parts by mass or less, a multilayer film having a suitable adhesion can be obtained.

  Copolymers of (c) aliphatic diols, aliphatic dicarboxylic acids and aromatic dicarboxylic acids used in the present embodiment (hereinafter sometimes simply referred to as “copolymer (c)”). Can be suitably used to control the flexibility of the polylactic acid resin composition.

The aliphatic diol in the copolymer (c) is not particularly limited, and examples thereof include ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-heptanediol, and 1 And saturated aliphatic diols having 2 to 20 carbon atoms such as 6-hexanediol. The aliphatic diol may be used alone, or a plurality of aliphatic diols may be used in combination.
The aliphatic dicarboxylic acid in the copolymer (c) is not particularly limited, and examples thereof include malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, and sebacic acid. And a saturated aliphatic dicarboxylic acid having 3 to 20 carbon atoms. Aliphatic dicarboxylic acids can be used alone or in combination.
The aromatic dicarboxylic acid in the copolymer (c) is not particularly limited, and examples thereof include phthalic acid, isophthalic acid, and terephthalic acid. Aromatic dicarboxylic acids can be used alone or in combination.
The copolymer (c) can be used alone or in combination.
The copolymer (c) is not particularly limited, and specific examples include trade name “Ecoflex” (manufactured by BASF).

  In the polylactic acid-based resin composition in the present embodiment, the addition amount of the copolymer (c) with respect to 100 parts by mass of the composition comprising crystalline polylactic acid and glycerin fatty acid ester and / or polyglycerin fatty acid ester It is 10-50 mass parts, and it is preferable that it is 20-40 mass parts. By adding 10 parts by mass or more, an effect of assisting adhesion of the multilayer film surface can be obtained, and by adding 50 parts by mass or less, a multilayer film having a suitable adhesion can be obtained.

  In this embodiment, the mechanism in which the flexible resin assists the adhesion of the multilayer film is that the repeating unit of aliphatic dicarboxylic acid and aliphatic diol or the repeating unit of vinyl acetate and ethylene in each copolymer is a multilayer film. It is considered that adhesion is enhanced by forming a domain having a glass transition temperature lower than room temperature locally on the surface.

In this embodiment, in order to adjust the tactile sensation and color tone of the multilayer film surface, it is not particularly limited as long as the target physical properties of this embodiment are not impaired. For example, epoxidized vegetable oil is added. be able to. Examples of the epoxidized vegetable oil include epoxidized soybean oil, epoxidized linseed oil, epoxidized tung oil, epoxidized castor oil, and epoxidized safflower oil. These epoxidized vegetable oils may be used alone or in combination of two or more according to the purpose.
In the polylactic acid-based resin composition in the present embodiment, as an addition amount of the epoxidized vegetable oil with respect to 100 parts by mass of a composition comprising crystalline polylactic acid and glycerin fatty acid ester and / or polyglycerin fatty acid ester, 0.1 to 5 parts by mass is preferable, and 0.5 to 4 parts by mass is more preferable. By adding in the range of 0.1 to 5 parts by mass, tactile sensation and color tone can be adjusted, and a multilayer film having suitable tactile sensation and color tone can be obtained.

  In the present embodiment, in order to adjust flexibility and melt viscosity, the polylactic acid resin composition includes at least one alcohol component selected from aliphatic monoalcohols, aliphatic diols and polycondensates thereof, and fat. Plasticizers such as esters with at least one carboxylic acid selected from aliphatic carboxylic acids and aliphatic dicarboxylic acids, and epoxidized products thereof can be added. More specifically, acetylated tributyl citrate, dibutyl sebacate, dioctyl adipate, isobutyl stearate, diisononyl adipate, poly (propylene glycol, adipic acid, lauric acid) ester, epoxidized stearic acid (2-ethylhexyl) Etc.

  In the present embodiment, known heat stabilizers, light stabilizers, lubricants, and the like can be added to the polylactic acid-based resin composition as long as the target physical properties of the present embodiment are not impaired.

(Polypropylene resin)
The polypropylene resin as the inner layer used in the present embodiment includes a propylene-α-olefin copolymer containing 65 to 90% by mass of propylene and 10 to 35% by mass of an α-olefin other than propylene as a comonomer.
By containing α-olefin as a comonomer in an amount of 10 to 35% by mass, it is possible to produce a multilayer film by simultaneously stretching the surface layer polylactic acid resin composition in a temperature range suitable for stretching the surface layer. In addition, even when a wrap film having a sticky surface is manufactured, a multilayer wrap film that is not affected by peeling or wrinkles between layers can be manufactured. Further, the co-extrusion and co-stretching processes enable continuous production with high productivity.
The α-olefin in the present embodiment is selected from the group consisting of ethylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 1-heptene, 1-hexene, 1-octene and 1-nonene. Is at least one. The α-olefin used as the comonomer may be one kind or plural kinds, but ethylene and 1-butene are preferably used.

  The propylene repeating unit in the polypropylene resin preferably has an isotactic or syndiotactic structure in order to ensure crystallinity. By setting the comonomer content to 10% by mass or more, the crystallinity of the polypropylene resin is partially impaired, and the melting point is lowered, so that the polylactic acid resin composition can be stretched in the stretching temperature range. Moreover, the intensity | strength of a multilayer film can be hold | maintained by moderate crystallization degree of polypropylene resin by making content of a comonomer 35 mass% or less.

As a copolymerization method of the propylene-α-olefin copolymer, any method such as block copolymerization, random copolymerization, graft polymerization, or a combination thereof can be used.
The melting point of the propylene-α-olefin copolymer is preferably 50 to 100 ° C, and more preferably 60 to 90 ° C. If the melting point is 50 ° C. or more, there is no change in physical properties at practical temperatures such as transportation and storage, and if the melting point is 100 ° C. or less, it is preferable because the simultaneous drawing processability with the polylactic acid resin composition is excellent.

The weight average molecular weight (Mw) of the propylene-α-olefin copolymer in the present embodiment is preferably in the range of 50,000 to 400,000. When the weight average molecular weight is 50,000 or more, a practical level of mechanical strength can be expressed, and when the weight average molecular weight is 400,000 or less, molding can be performed with an appropriate melt viscosity. Propylene-α-olefin copolymers can be used alone or in combination.
Although it does not specifically limit as a polypropylene resin, Specifically, brand name "Versify 2300", "Versify 2400", "Versify 3300", "Versify 3401.01" (US Dow Chemicals company make, registered trademark, the same below) ) And trade names “Tuffmer XM7070”, “Toughmer XM7080” (registered trademark, manufactured by Mitsui Chemicals, the same shall apply hereinafter), and the like.
In the present embodiment, when the inner layer is produced using a polypropylene resin, a known heat stabilizer, light stabilizer, lubricant, plasticizer, etc., as long as the target physical properties of the present embodiment are not impaired. Can be produced. For example, aliphatic hydrocarbon compounds such as liquid paraffin and synthetic paraffin can be used for the purpose of controlling the viscosity at the time of melting and the stretch processing characteristics.

(Multilayer film)
The multilayer film of the present embodiment is a multilayer film having an inner layer and surface layers disposed on both front and back surfaces of the inner layer, the surface layer is a layer containing the polylactic acid resin composition, and the inner layer is And a layer containing the polypropylene resin.

In the present embodiment, regarding the arrangement of the surface layer and the inner layer, the surface layer needs to be arranged on the surface corresponding to the front and back of the inner layer. That is, it is necessary to form a multilayer film having a laminated arrangement of surface layer / inner layer / surface layer.
As thickness of the multilayer film which combined the surface layer with the front and back of the inner layer, it is preferable that it is 5-15 micrometers or less, and it is more preferable that it is 7-13 micrometers. When the thickness of the multilayer film is 5 μm or more, the operation of the unwound film is easy and the multilayer films are not easily entangled with each other. If it is 15 micrometers or less, the touch of a multilayer film will not become hard too much, and the operation | work which adheres to the surface of a foodstuff or a food container can be performed easily.

The thickness of each layer can be adjusted within a preferable range of the thickness of the multilayer film.
The thickness of the surface layer is preferably 1 to 6 μm, more preferably 2 to 5 μm, for each front and back layer.
If the thickness of the surface layer is 1 μm or more, sufficient heat resistance can be obtained, and if it is 6 μm or less, the operation of wrapping food or a container with moderate rigidity becomes easier when used as a multilayer film, and the handling property is excellent. .
The thickness of the inner layer is preferably 2 to 13 μm or less, and more preferably 2.5 to 11 μm or less. If the thickness of the inner layer is 2 μm or more, good water vapor barrier properties can be ensured, and if it is 13 μm or less, the cut property of the multilayer film is not impaired.

  In the present embodiment, an intermediate layer may be provided as a surface layer and an inner layer auxiliary adhesion layer as long as the object of the present embodiment is not impaired. As a multilayer film provided with an intermediate layer, a layer structure such as surface layer / intermediate layer / inner layer / intermediate layer / inner layer can be exemplified.

As the intermediate layer in the present embodiment, it is preferable to use a material having affinity for both a lactic acid-based resin composition containing crystalline polylactic acid or the like or a polypropylene-based resin, and is not particularly limited. And a copolymer of an α-olefin and a polar vinyl compound.
Although it does not specifically limit as said alpha olefin, For example, ethylene, propylene, 1-butene etc. are mentioned.
The polar vinyl compound is not particularly limited, and examples thereof include acrylic compounds such as acrylic acid, methyl acrylate, ethyl acrylate, butyl acrylate, and methyl methacrylate, and epoxy compounds such as glycidyl methacrylate and glycidyl acrylate. And maleic acid, maleic anhydride, vinyl acetate, vinyl caproate, vinyl caprylate, vinyl caprate, vinyl laurate, vinyl myristate, vinyl palmitate, and vinyl stearate. These polar vinyl compounds may be used alone as a comonomer or may be copolymerized in combination.
As content of a polar vinyl compound, it is preferable that it is 30-60 mass% in the copolymer of the said alpha olefin and a polar vinyl compound, and it is more preferable that it is 40-50 mass%. The melt flow rate of the copolymer of the α-olefin and the polar vinyl compound measured by a load of 190 ° C. and 2.16 kg based on JIS-K7210 is preferably 1 to 300, and preferably 2 to 200. It is more preferable that
Examples of such a copolymer of an α-olefin and a polar vinyl compound are not particularly limited, but specifically, trade names “Evaflex EV45LX”, “Evaflex EV40LX”, “Evaflex” EV45X "," Evaflex EV40W "(manufactured by Mitsui DuPont Polychemical Co., Ltd.) and the like.

  As the intermediate layer, in addition to the copolymer of α-olefin and polar vinyl compound as described above, for example, a mixture of the respective compositions used for the surface layer and the inner layer can be used as the recycled resin.

  The tensile elastic modulus of the multilayer film in the present embodiment is an index of flexibility, and the lower the numerical value, the softer the multilayer film. The tensile elastic modulus is preferably 400 to 1500 MPa, more preferably 500 to 1000 MPa. When it is 400 MPa or more, a multilayer film having moderate flexibility can be obtained, and the films are easily entangled with each other during handling, and when it is 1500 MPa or less, the multilayer is excellent in flexibility and adhesion for wrapping containers and foods. It can be a film.

  The heat shrinkage rate at 100 ° C. of the multilayer film in the present embodiment is an index of dimensional stability when the packaged food is heated, and is preferably 35% or less in order to prevent the packaged food from being compressed, It is more preferably 25% or less, and further preferably 20% or less.

  The adhesion work of the multilayer film in the present embodiment is an index of adhesion, and measures the force with which the films adhere to each other or to ceramics or glassware. The higher the work of adhesion, the higher the sticking power, but 0.5 to 2.5 mJ is preferable in terms of moderate adhesion and ease of use of the multilayer film, and 0.7 to 2 More preferably, it is 2 mJ.

The moisture permeability of the multilayer film in this embodiment is an indicator of water vapor barrier properties, and is preferably 300 g / m ² / day or less, and 150 g / m ² / day or less in order to retain the moisture of the packaged food. It is more preferable that

  The 140 ° C. heat resistance of the multilayer film in the present embodiment is an index of heat resistance. When a multilayer film wraps food and is heated in a microwave oven, the multilayer film is heated by water vapor generated from the food, so when removing it during heating in the microwave oven or after overheating, or when peeling the multilayer film , It is required not to cut.

  The haze value of the multilayer film in the present embodiment is an index of transparency, and a preferred range when used as a food packaging wrap film is preferably 5 or less, more preferably 3 or less. preferable.

  The pulling force of the multilayer film in the present embodiment is a load required when unwinding the film wound in a roll shape having a width of 30 cm. It is an index indicating the usability of the multilayer film. The lower the value, the more the film can be pulled out with a light force. The pulling power is preferably 5 to 100 cN, more preferably 10 to 80 cN, and still more preferably 15 to 60 cN. If the pulling power is 5 cN or more, the film does not unwind too much, and if it is 100 cN or less, excessive force is not applied when pulling out the film, which is convenient.

(Method for producing multilayer film)
The multilayer film of the present embodiment shares a polylactic acid-based resin composition and a polyolefin-based resin obtained by melt kneading (hereinafter, both may be collectively referred to as “resin composition”). After passing through the process of laminating by an extrusion method, it can be manufactured by passing through a process of re-heating and stretching in at least two directions after cooling and solidification. Moreover, it is preferable to heat-set in order to adjust the heat shrinkage rate of the film obtained.

  In the present embodiment, as the melt-kneading method for obtaining the resin composition, a same-direction rotating twin-screw extruder, a different-direction rotating twin-screw extruder, and a single-screw extruder can be used. From the point of view, it is preferable to use a twin-screw extruder rotating in the same direction.

In the present embodiment, co-extrusion is a method of laminating the resin composition obtained by melt-kneading into a film state in a molten state by a feed block method or a multi-manifold method, or a combination thereof, and cooling and solidifying. This is a lamination method.
In this embodiment, in order to obtain a film having a good appearance, the melt viscosity of the polylactic acid resin composition used as the surface layer at the time of lamination is lower than the melt viscosity of the polyolefin resin used as the inner layer. It is preferable. The appropriate viscosity region varies depending on the layer thickness configuration, but within the scope of the present embodiment, the amount of glycerin fatty acid ester and / or polyglycerin fatty acid ester of the polylactic acid resin composition is adjusted, or an extruder or The melt viscosity can be adjusted by changing the temperature of the feed block and die.

In this embodiment, when extruding a laminated film in a flat shape, it is solidified by a cooling roll, but the temperature of the cooling roll is Tg (I) when the glass transition temperature of the polylactic acid-based resin composition of the surface layer is Tg (I) It is preferable to set it as Tg (I) -10 degreeC-Tg (I) +10 degreeC. By making the temperature of the cooling roll Tg (I) -10 ° C. or higher, the extruded film can be brought into close contact with the cooling roll to obtain a good surface state, and by setting the temperature to Tg (I) + 10 ° C. or lower, extrusion The peeled film can be peeled off from the cooling roll satisfactorily.
In this embodiment, when extruding a laminated film in a tube shape, a method of cooling by water cooling or air cooling can be employed, but the temperature at the time of cooling is Tg (I) -10 ° C. to Tg (I) + 10 ° C. It is preferable to set it as Tg (I) -5 degreeC-Tg (I) +5 degreeC. By setting the temperature of the cooling water to Tg (I) -10 ° C. or higher, wrinkling and tearing due to vitrification of the film can be suppressed, and by setting the temperature to Tg (I) + 10 ° C. or lower, the film is fixed. It can be formed into a tube shape without any problems.
By adopting such a lamination and extrusion method, the adhesiveness at the interface of each layer is increased as compared with the lamination method and the coating method, and a film having a good appearance can be obtained.

  In the present embodiment, stretching is a step of orienting molecules by reheating and stretching to a temperature equal to or higher than the glass transition temperature of the compound in the resin composition constituting the laminated film obtained by coextrusion. If it is a flat film, you can adopt a flat stretching method that stretches it using a roll or restraint. If it is a tube-shaped film, you can hold the cooled and solidified tube between rolls and then inflate it with air pressure. A tubular stretching method for stretching the film can be employed.

  As a heating method at the time of stretching, roll heating, hot air heating, infrared heating, or the like can be preferably used, but hot air heating or infrared heating in which the film and the roll are not in direct contact with each other in a heated state is more preferably used. Stretching is preferably performed in the film flow direction (MD direction) and in a direction perpendicular to the film direction (TD direction). The stretching ratio is preferably 2 to 5 times or less in the MD and TD directions, that is, it is preferably stretched at an area magnification of 4 to 25 times, 2.5 to 4.5 times, that is, area. It is more preferable that the magnification is 6.25 to 20.25 times or less. When the draw ratio in each direction is 2 times or more, heat resistance by orientation crystallization is obtained, and when it is 5 times or less, breakage due to excessive crystallization hardly occurs. The stretching temperature is preferably 40 ° C to 90 ° C, and more preferably 45 ° C to 80 ° C. If it is 40 ° C or higher, both the surface layer and the inner layer can be stretched, and orientational crystallization of crystalline polylactic acid in the polylactic acid resin composition of the surface layer is likely to occur. Occasionally sagging or tearing of the film hardly occurs and the film can be stretched satisfactorily. Moreover, when it is set as a wrap film, in order to improve the usability as a wrap film, such as the cutting property with a saw blade attached to the storage box, it is preferable to have a molecular orientation state that is easier to tear in the TD direction than in the MD direction. . More specifically, when the tear strength in the MD direction is Xm and the tear strength in the TD direction is Xt, it is preferable that Xm> Xt. As a method for adjusting the molecular orientation, in the case of flat film stretching, it can be adjusted by the rotation speed of the roll and the width of the film restraint in the tenter. It can be adjusted by changing the film take-up speed before and after.

In this embodiment, when stretching using the tubular stretching method, it is necessary to sandwich the laminated film with a pinch roll after cooling and solidification in order to separate the step of cooling and solidifying the laminated film and the step of stretching with pressurized air. At this time, in order to prevent defects such as wrinkling and tearing of the film, when the temperature of the cooling water is Tg (I) and the glass transition temperature of the polylactic acid resin composition is Tg (I) −10 ° C. It is preferable to set it as -Tg (I) +10 degreeC, and it is more preferable to set it as Tg (I) -5 degreeC-Tg (I) +5 degreeC. By setting the temperature of the cooling water to Tg (I) -10 ° C. or higher, wrinkling and tearing due to vitrification of the film can be suppressed, and by setting the temperature to Tg (I) + 10 ° C. or lower, the film is fixed. It can be formed into a tube shape without any problems.
When cooled and solidified, blown with pressurized air and stretched, the surface has a surface layer made of a polylactic acid-based resin composition with adhesive properties. As a result, air may not enter between the films and stable stretching may not be possible. In order to prevent this, when the cooled and solidified film is sandwiched between rolls, it is effective to enclose and retain the anti-adhesive agent on the inside of the film sandwiched between the rolls. More specifically, as shown in FIG. 1, a film is extruded vertically downward from a cylindrical die, the film is led into water and cooled and solidified, and an anti-sticking agent is applied from above through a cavity provided in the center of the die. Can be introduced.

The anti-sticking agent in the present embodiment is not particularly limited. For example, hydrocarbons, oils and fats, polyhydric alcohols, aliphatic alcohols, aliphatic alcohols and aliphatic carboxylic acids and / or Compounds such as esters with aliphatic dicarboxylic acids and epoxidized products thereof can be preferably used.
The boiling point of the anti-sticking agent is preferably 120 ° C. or higher and more preferably 150 ° C. or higher so that the anti-sticking agent does not boil due to radiant heat from the die or heat transfer from the molten film immediately after extrusion. . Moreover, in order to remove from the surface of a film by heat processing, it is preferable that a boiling point is 400 degrees C or less. Moreover, in order to apply | coat uniformly in the liquid state on the surface of a polylactic acid-type resin composition, it is preferable that melting | fusing point of a sticking prevention agent is 25 degrees C or less.

  Such an anti-sticking agent is not particularly limited, and examples thereof include polyhydric alcohols such as glycerin, polyglycerin, ethylene glycol, propylene glycol, and dipropylene glycol, esters with fatty acids, and liquid paraffin. , Hydrocarbons such as petroleum jelly, ceresin, microcrystalline wax, and squalane, oils and fats such as soybean oil, linseed oil, tung oil, castor oil, avocado oil, and olive oil, and epoxidized products thereof, acetylated tributyl citrate, Fatty alcohols and fats such as dibutyl sebacate, dioctyl adipate, isobutyl stearate, diisononyl adipate, poly (propylene glycol, adipic acid, lauric acid) ester, and epoxidized stearic acid (2-ethylhexyl) Esters of group a carboxylic acid and / or aliphatic dicarboxylic acids, and the like epoxides thereof. These anti-sticking agents may be used alone or in combination.

In the present embodiment, since the anti-sticking agent is used as a processing aid, the amount applied to the film surface is preferably set to such an amount that the film does not stick and does not inhibit the surface adhesion. In order to control the coating amount on the film surface, if it is a water-soluble compound, a method using a diluted aqueous solution is used, and if it is water-insoluble, an anti-sticking agent is added after sealing the water in the tube. A method of floating as an oil film or an oil layer on the upper portion, or a method of emulsifying it can be preferably used. By controlling the coating amount by such a method, the coating amount of the anti-sticking agent is controlled, and the anti-sticking agent can be removed from the outermost surface of the film by soaking into the film and / or volatilization by heat treatment. it can.
The coating amount of the solid inhibitor is preferably 100 to 5000 ppm with respect to the total mass of the multilayer film, more preferably 300 to 3000 ppm, and even more preferably 500 to 1500 ppm. By applying at a rate of 100 ppm or more, film sticking is prevented, and by setting it to 5000 ppm or less, it is possible to remove the anti-sticking agent from the surface by migration into the film and volatilization by hot air treatment. There is no hindrance.

In the present embodiment, heat setting is a step of heating a film to a predetermined temperature or higher using a heating roll, hot air, infrared rays, or the like to remove excessive tension of molecular chains generated by stretching. Although the method of heating is not particularly limited, it is preferably higher than the glass transition temperature of the polylactic acid resin composition constituting the surface layer and lower than the melting point. More specifically, the temperature is preferably 70 to 120 ° C, more preferably 80 to 110 ° C. By heating at 70 ° C. or higher, excessive tension of molecular chains can be removed, and by setting it to 120 ° C. or lower, fusing of the film during heat setting can be prevented. The heat setting time under the above heating conditions is preferably 1 to 30 seconds, and more preferably 2 to 20 seconds. The thermal shrinkage of the film obtained by passing through such a process can be suppressed to less than 20%.
The heat setting is performed in a state where the film is constrained to a certain width by a roll, a restraining tool, or pressurized air, but it is preferable to heat the film while relaxing the restraint. For example, after stretching 4 times in the TD direction, the heat setting can be efficiently performed by loosening the magnification to 3.8 times while heat fixing. The relaxation ratio of the draw ratio is preferably 1 to 10% from the maximum draw ratio. By relaxing 1% or more, excessive tension can be easily removed, and by setting it to 10% or less, sagging of the film can be suppressed and the film can be manufactured satisfactorily.

Hereinafter, the present embodiment will be specifically described with reference to examples and comparative examples, but the present embodiment is not limited to only these examples.
Note that the evaluation method and measurement method used in this embodiment are as follows.

(1) Tensile modulus The tensile modulus was measured by a method based on JIS-K7127 and JIS-K7161. The dimension of the film piece is cut into a width of 10 mm and a length of 100 mm along the MD and TD directions to make a test piece, measured at a tensile rate of 5 mm / min, and an average value of five measurements is a measured value. It was. The trade name “AUTOGRAPH AG-IS” (manufactured by Shimadzu Corporation) was used for the measurement.

(2) Thermal shrinkage rate The thermal shrinkage rate was measured by measuring the length of each side after cutting into a 100 mm vertical and horizontal square along the MD and TD directions of the film and holding it in an oven at 100 ° C for 1 minute. The average value of five measurements was taken as the measurement value.

(3) Work of adhesion Work of adhesion was measured by the following method. First, ^two cylindrical measuring jigs having a bottom area of 25 cm ² with filter paper attached to the entire bottom surface are prepared. The film was covered on the bottom so that no wrinkles could enter, and was fixed in a tension state. Next, the cylindrical measuring jigs were aligned vertically so that the film surfaces were in contact with each other, and a weight of 500 g was placed on the upper jig, and a load was applied to the film contact surface for 1 minute. Thereafter, the weight was gently removed, and the energy required for peeling the film in a direction perpendicular to the contact surface with a tensile tester at a tensile speed of 5 mm / min was defined as the work of adhesion. The measurement was performed at a constant temperature and humidity of 23 ° C. and 50%, and an average value of five measurements was taken as a measurement value.

(4) Moisture permeability Moisture permeability measurement is the amount of water vapor permeated through the film per fixed time after measuring the mass increase at constant time in a constant temperature and constant humidity state (40 ° C. 90% Rh), according to JIS-K7129. It was measured. For measurement, a trade name “L80-5000 type water vapor transmission meter” (manufactured by Lyssy) was used, and an average value of five measurements was taken as a measurement value.

(5) Heat resistance at 140 ° C. Heat resistance was measured by the following method based on Article 11 of the Tokyo Metropolitan Consumer Life Ordinance. That is, both ends of a sample having a length of 140 mm and a width of 30 mm cut out along the MD direction and the TD direction of the film were protected with a piece of paper having a length of 25 mm and a width of 30 mm. One of them was fixed and suspended in an oven heated to 140 ° C. with a load of 10 g applied to the other. Five pieces of samples were prepared in each direction, and one hour after the start of heating, a film in which none of the samples was cut by the load was accepted, and a piece that could cut even one piece was marked as x.

(6) Haze value Transparency was represented by the haze value measured based on JIS-K7136. For the measurement, a trade name “300A” (manufactured by Nippon Denshoku Industries Co., Ltd.) was used, and an average value of five measurements was taken as a measurement value.

(7) Pull output Pull output was measured by the following method. First, a film prepared with a width of 300 mm is wound around a paper tube having an outer diameter of 36 mm and an inner diameter of 34 mm, and an acrylic cylinder having an outer diameter of 33 mm / inner diameter of 27 mm and a steel rod having a diameter of 10 mm are connected via a bearing. The steel rod was fixed to a tensile tester, and the acrylic cylindrical portion and the paper tube wound film were allowed to freely rotate. The edge of the film was fixed to a plate having a width of 330 cm directly connected to the load cell of the tensile tester, and the average value of the load generated when the film was pulled out at a speed of 1000 mm / min was measured. The measurement was performed under constant temperature and humidity of 23 ° C. and 50% Rh, and an average value of five measurements was taken as a measurement value.

Each component used for the Example and the comparative example is as follows.
(Polylactic acid resin composition)
PLA: crystalline polylactic acid, optical purity 92% ee, trade name “4042D” (manufactured by NatureWorks)
p-1: Glycerin diacetate (caprylic acid, capric acid) ester “Riquemar PL019” (manufactured by Riken Vitamin Co., Ltd.)
p-2: Diglycerin tetraacetate trade name “Riquemar PL710” (manufactured by Riken Vitamin)
a: Copolymer of aliphatic hydroxycarboxylic acid, aliphatic diol, and aliphatic dicarboxylic acid Trade name “Plamate PD150” (Dainippon Ink Co., Ltd.)
b: Ethylene vinyl acetate copolymer (vinyl acetate content 40-50 mass%) Trade name “Evaflex EV45LX” (Mitsui / Dupont Polychemical Co., Ltd.)
c: Polybutylene adipate terephthalate Product name "Ecoflex" (manufactured by BASF)
b ': Ethylene vinyl acetate copolymer (vinyl acetate content 25% by mass) Trade name "Evaflex EV360"
Epoxidized vegetable oil: Epoxidized soybean oil Trade name "New Sizer 510R" (manufactured by NOF Corporation, registered trademark)
(Polypropylene resin)
II-1: Propylene-α-olefin copolymer (α-olefin content: 10 to 35% by mass, trade name “Toughmer XM7070” (manufactured by Mitsui Chemicals, Inc.)
II-2: Propylene-α-olefin copolymer (α-olefin content: 10 to 35% by mass) Trade name “Versify 3401.01” (manufactured by Dow Chemical Company)
II-3: Propylene-α-olefin copolymer (α-olefin content: 10 to 35% by mass) Trade name “Versify 3300” (manufactured by Dow Chemical Company)
II′-1: Propylene-α-olefin copolymer (α-olefin content less than 10% by mass) Trade name “Versify 3000” (manufactured by Dow Chemical Company)
II′-2: Polypropylene (α-olefin content less than 10% by mass) Trade name “Novatech MA3H” (manufactured by Nippon Polypro, registered trademark)
Plasticizer: Liquid paraffin Trade name “Smoyl p70s” (registered trademark, the same shall apply hereinafter)

<Example 1>
The composition of the surface layer and the inner layer shown in Table 1 is melt-kneaded at 200 ° C. by the same-direction twin screw extruder, led to a feed block through a polymer pipe and laminated, and the structure of the surface layer / inner layer / surface layer from the T-die. Was extruded into a film. After the extruded laminate was cooled and solidified with a cast roll at 25 ° C., the obtained film was reheated to 50 ° C. with a heating roll, and stretched 3 times in the film take-up direction (MD direction). Next, after the film stretched in the MD direction was cooled again, the film was introduced into a tenter furnace, heated to 65 ° C., and stretched 4.5 times in the TD direction perpendicular to the MD direction. Thereafter, the film was heat-fixed at 120 ° C. for 3 seconds and wound up while relaxing the stretching ratio to 4.3 times to obtain a multilayer wrap film.
About the obtained multilayer wrap film, it evaluated by the method shown above (Table 1).

<Examples 2 to 7>
A multilayer wrap film was produced and evaluated in the same manner as in Example 1 except that the surface layer and inner layer compositions shown in Table 1 were used (Table 1).

<Example 8>
The composition of the surface layer and inner layer shown in Table 1 is melt-kneaded at 200 ° C. by a co-directional twin-screw extruder, led to a feed block through a polymer pipe and laminated, and the surface is formed from a cylindrical die 2 having a cavity in the center. The cylindrical laminated film 3 was extruded in the vertically downward direction in the configuration of layer / inner layer / inner layer. The obtained laminated film 3 was led into 25 ° C. cooling water 7 and rapidly cooled and solidified, and sandwiched between two pinch rolls 6 with a folding width of 130 mm. Here, in order to prevent the laminated films 3 from sticking to each other, as shown in FIG. 1, distilled water is contained in a cylindrical film sandwiched by pinch rolls 6 from a hollow 1 portion provided at the center of a cylindrical die. 300 cc of 5 was introduced, and 50 cc of liquid paraffin (trade name “Smoyl p70” manufactured by Matsumura Oil Co., Ltd.) was introduced as the anti-adhesive agent 4. The folding film 8 coated with the anti-sticking agent 4 on the surface was guided to a differential roll 9 that can adjust the take-up speed, and after passing through a process of heating to 60 ° C. with hot water, air was injected to stretch the tube. By adjusting the take-up speed after heating, the film is stretched 3 times in the flow direction of the film, that is, in the MD direction, and the tube diameter, that is, the stretching ratio in the TD direction is adjusted to 4 times by the air pressure. A stretched film of 520 mm was obtained. Next, both ends of the cylindrical stretched film are slit into two stretched films, each end is restrained by a restraining tool and guided to a heating furnace, and heat fixing is performed by blowing hot air at 100 ° C. A wrap film was obtained. The relaxation at the time of heat setting was adjusted to a relaxation rate of 10%. The obtained multilayer wrap film was evaluated by the method shown above (Table 1).

<Example 9>
A multilayer wrap film was produced and evaluated in the same manner as in Example 1 except that the composition of the surface layer and the inner layer shown in Table 1 was used and heat setting was not performed (Table 1).

<Comparative Examples 1 and 2>
A multilayer wrap film was produced and evaluated in the same manner as in Example 1 except that the surface layer and inner layer compositions shown in Table 1 were used (Table 1).

<Comparative Example 3>
A multilayer wrap film was produced and evaluated in the same manner as in Example 1 except that the inner layer was not laminated (Table 1).

<Comparative Examples 4 and 5>
In the composition of the surface layer and the inner layer shown in Table 1, an attempt was made to produce a multilayer wrap film in the same manner as in Example 1. However, since the copolymer content of the polypropylene resin in the inner layer was less than 10% by mass, It could not be stably produced between 40 ° C. and 90 ° C. which is the stretching temperature range of the layer (Table 1).

As is clear from the results in Table 1, the multilayer wrap films of Examples 1 to 9 are multilayer wrap films excellent in heat resistance, adhesion, flexibility, water vapor barrier properties, and transparency, and have a good balance of properties. I have.
Moreover, when compared with Comparative Example 1 containing more than 50 parts by mass of the copolymer (c) in the surface layer, the copolymer (c) in the surface layer is 10 in terms of heat resistance, adhesion, and transparency. The multilayer wrap films of Examples 6 and 7 contained in the range of ˜50 parts by mass were excellent.
Furthermore, when compared with Comparative Example 2 in which the vinyl acetate content of the copolymer (b) in the surface layer is less than 40% by mass, the vinyl acetate content is in the range of 40 to 50% by mass in terms of adhesion. Among them, the multilayer wrap films of Examples 4 and 5 were excellent. In contrast to Comparative Example 2 in which 25 parts by mass of liquid paraffin was added to draw a propylene-based resin having an α-olefin content of less than 10% by mass, a large amount of plasticity was obtained in terms of elastic modulus. The multilayer wrap films of Examples 1 to 9 that can be stretched without adding an agent were excellent. Furthermore, when compared with Comparative Example 2 containing less than 0.5 parts by mass of the copolymer (a) in the surface layer, the copolymer (a) in the surface layer is 0.5 to 10 masses in terms of adhesion. The multilayer wrap films of Examples 1, 2, 3, 7, 8, and 9 contained within the range of parts were excellent.
Furthermore, in the comparative example 3 which does not have an inner layer as a polypropylene resin, it is inferior in the point of a softness | flexibility, water vapor | steam barrier property, and transparency, and contains the alpha-olefin in less than 10 mass% propylene-alpha-. In Comparative Examples 5 and 6 in which the olefin copolymer was used as the inner layer, none of the multilayer wrap films could be produced stably.

  The present invention can provide a multilayer film having excellent heat resistance, adhesion, flexibility, water vapor barrier properties, and transparency. The multilayer film of the present invention has industrial applicability particularly as a wrap film for food packaging.

In Example 8, the schematic diagram of the process which cools and solidifies the film extruded from die | dye, and apply | coats an anti-adhesion agent to the film surface is shown.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Cavity provided in the center part of cylindrical die 2 Cylindrical die 3 Laminated film 4 Anti-sticking agent 5 Distilled water 6 Pinch roll 7 Cooling water 8 Folding film 9 Differential roll

Claims (2)

A multilayer film having an inner layer and surface layers disposed on both front and back surfaces of the inner layer,
The surface layer is a layer containing a polylactic acid-based resin composition;
The polylactic acid-based resin composition is
100 parts by mass of a composition comprising 70 to 90% by mass of crystalline polylactic acid and 10 to 30% by mass of glycerol fatty acid ester and / or polyglycerol fatty acid ester,
As the flexible resin, 0.5 to 10 parts by mass of at least one flexible resin selected from the group consisting of the following (a) and (b), and / or 10 to 50 parts by mass of the flexible resin that is (c) below;
(A) a copolymer of an aliphatic hydroxycarboxylic acid, an aliphatic diol, and an aliphatic dicarboxylic acid,
(B) a copolymer of ethylene and vinyl acetate having a vinyl acetate content of 40 to 50% by mass;
(C) a copolymer of an aliphatic diol, an aliphatic dicarboxylic acid and an aromatic dicarboxylic acid,
Containing
The inner layer is a layer containing a polypropylene resin,
The polypropylene resin contains a propylene-α-olefin copolymer consisting of 65 to 90% by mass of propylene and 10 to 35% by mass of α-olefin,
The α-olefin is at least one selected from the group consisting of ethylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 1-heptene, 1-hexene, 1-octene and 1-nonene. There is a multilayer film.   The multilayer film according to claim 1, wherein the heat shrinkage rate at 100 ° C. is 35% or less.

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