JP2004237625A - Multi-layer film formed of biodegradable resin and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a biodegradable multi-layer film which is highly pliable and efficiently heat-sealable. <P>SOLUTION: This unoriented multi-layer film contains [1] not less than 50 wt.% of a lactic acid polymer (a) as a content ratio in the film and [2] comprises at least one layer (A) containing less than 40 to 10 wt.% or more of the lactic acid polymer (a) and 60 to 90 wt.% of a polyester (b) other than the lactic acid polymer (a)(provided (a)+(b)=100 wt.%) and [3] at least one layer (B) containing 60 to 80 wt.% of the lactic acid polymer (a) and 40 to 20 wt.% of the polyester (b) other than the lactic acid polymer (a) (provided (a)+(b)=100 wt.%). [4] At least either of the layer (A) or the layer (B) contains 0.05 to 10 wt.% of a lubricant and 0.05 to 10 wt.% of an anti-blocking agent to 100 wt.% of the total resin composition, in the resin composition constituting the layer. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

【００５２】
【表２】

【００５３】
【表３】

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an unstretched multilayer film made of a biodegradable resin composition having improved properties such as flexibility and transparency. More specifically, it relates to a biodegradable unstretched multilayer film having excellent flexibility and heat sealability.
[0002]
[Prior art]
Generally, shopping bags, garbage bags, packaging bags, sandbags, and agricultural multi-films are manufactured from general-purpose resins such as polyvinyl chloride, polyethylene, and polypropylene. These general-purpose resin films are inexpensive, strong, and long-lasting.However, they are hardly decomposed in the natural environment. Have problems such as causing environmental problems.
[0003]
On the other hand, as a thermoplastic resin having biodegradability, polyhydroxycarboxylic acids such as polylactic acid, and aliphatic polyesters derived from aliphatic polyhydric alcohols and aliphatic polycarboxylic acids have been developed. I have. These polymers are 100% biodegradable in the body of animals within months to a year, or, when placed in soil or seawater, begin to degrade in a few weeks in a humid environment, from about one year to several years. Disappears in the year. Furthermore, the decomposition product has the property of becoming lactic acid, carbon dioxide, and water that are harmless to the human body.
[0004]
In particular, polylactic acid has recently been produced in large quantities and inexpensively by fermentation of L-lactic acid as a raw material, has a high decomposition rate in compost (compost), has resistance to fungi, Due to its excellent characteristics, such as odor resistance and coloring resistance, it is expected that its field of use will be expanded.
However, since polylactic acid has high rigidity, it is hard to say that it is suitable for applications requiring flexibility such as films and packaging materials. In general, techniques for softening a resin include a method of adding a plasticizer and a method of blending a soft polymer.
[0005]
In the method of adding a plasticizer, a relatively small amount (approximately 10 to 20% by weight) can provide sufficient flexibility, but the glass transition temperature of polylactic acid is lowered, and the polylactic acid component can be added at a normal environmental temperature. Crystallization progresses, and as a result, it becomes hard, causing changes in physical properties such as changes in heat sealing temperature conditions, and problems such as bleeding of the plasticizer. There is.
[0006]
On the other hand, the method of blending a soft polymer is limited to soft polymers having biodegradability, for example, polyethylene succinate, polybutylene succinate, polybutylene succinate adipate, polyhydroxybutyric acid, polyhydroxyvaleric acid, polycaprolactone, polyethylene Examples thereof include carbonates, copolymers and mixtures thereof, and have already been disclosed in JP-A-8-245866, JP-A-9-111107, and JP-A-3182077. Furthermore, a method of mixing an aliphatic polyester and a plasticizer with polylactic acid is disclosed in Japanese Patent Publication No. WO99 / 45067 (Patent Documents 1 to 4).
[0007]
However, in the method of mixing a biodegradable soft polymer, the effect of imparting flexibility to polylactic acid is not very effective, and a small amount (about 10 to 40% by weight) imparts sufficient flexibility. Can not. For example, it shows a soft physical property that stretches well at room temperature, but hardly stretches at low temperature, and has a problem such as tearing or tearing by a slight impact. It is conceivable to increase the amount of the soft polymer added and decrease the content of the lactic acid polymer.However, although flexibility is exhibited, the decomposition rate in the compost becomes extremely slow. There is a problem that the stirring device is entangled with the device and the handling becomes poor.
[0008]
In addition, in the method of mixing the biodegradable soft polymer and the plasticizer, sufficient flexibility can be imparted even when the polylactic acid component is 50% by weight or more, and the decomposition rate in the compost is high. Since bleeding or crystallization proceeds, problems such as a change in physical properties of the film and a change in heat sealability may occur.
[0009]
As described above, in a composition containing a large amount of polylactic acid, a general softening method (addition of a plasticizer or blending of a flexible polymer) requires sufficient flexibility, rapid decomposability in compost, and stable heat sealing. It is difficult to impart properties.
[0010]
[Patent Document 1] JP-A-8-245866
[Patent Document 2] JP-A-9-111107
[Patent Document 3] Japanese Patent Publication No. 3182077
[Patent Document 4] Published Patent Publication WO99 / 45067
[Problems to be solved by the invention]
The present invention addresses the above problems, and the present invention addresses some of the problems described above.
1, has a good decomposition rate in compost,
2. It has the flexibility to show elongation even at low temperature (-20 ° C),
3. An object of the present invention is to obtain a biodegradable film whose heat sealability does not change with time, and specifically to obtain a biodegradable multilayer film having excellent flexibility and heat sealability.
[0015]
[Means for Solving the Problems]
Means for Solving the Problems The present inventors have conducted intensive studies to achieve the above object, and as a result, have reached the present invention. That is, in the present invention, 1) the ratio of the lactic acid polymer (a) in the film is 50% by weight or more 2) At least one layer (A) is 10% by weight or more and less than 40% by weight of the lactic acid polymer (a) and other than the lactic acid polymer (a) 3) at least one layer (B) is 60 to 80% by weight of the lactic acid polymer (a), wherein the polyester (b) is 60 to 90% by weight (here, (a) + (b) = 100% by weight). 4) 20% by weight of polyester (b) other than lactic acid polymer (a) (here, (a) + (b) = 100% by weight) 4) Layer (A) / layer (B) thickness The ratio A / B is 0.2 to 0.8 / 0.8 to 0.2, and 5) at least one layer of the layer (A) or the layer (B) contains all resins in the resin composition constituting the layer. 0.05 to 10% by weight of a lubricant based on 100% by weight of the composition, anti-blocking Unstretched multilayer film characterized by containing 0.05 to 10% by weight. 1) The proportion of the lactic acid polymer (a) in the film is 50% by weight or more 2) The elongation percentage of the film at -20 ° C is 50% A multilayer film characterized by the above. And a method for producing a film.
[0016]
Lactic acid polymer (a)
As the lactic acid polymer (a) used in the present invention, L-lactic acid, D-lactic acid, DL-lactic acid or a mixture thereof, or lactide which is a cyclic dimer of lactic acid is used as a raw material, and dehydration polycondensation or ring-opening polymerization is performed. Is a polymer obtained by The D-lactic acid ratio is 1% or more, preferably 5% or more, more preferably 7% or more, and most preferably 10% or more. If the ratio of D-lactic acid is small, crystallization tends to proceed under environmental conditions, so that the film may be hard and brittle, or the heat sealability may change with time. Further, as a method for producing a lactic acid polymer, for example,
(1) Direct dehydration polycondensation method using lactic acid or a mixture of lactic acid and aliphatic hydroxycarboxylic acid as a raw material (for example, a production method described in US Pat. No. 5,310,865)
(2) Ring-opening polymerization method for melt-polymerizing a cyclic dimer of lactic acid (lactide) (for example, the production method disclosed in US Pat. No. 2,758,987)
(3) A ring-opening polymerization method in which a cyclic dimer of lactic acid and an aliphatic hydroxycarboxylic acid, for example, lactide or glycolide, and ε-caprolactone are melt-polymerized in the presence of a catalyst (for example, US Pat. No. 4,057,537). Disclosed manufacturing method)
(4) A method of directly dehydrating and polycondensing a mixture of lactic acid, an aliphatic dihydric alcohol and an aliphatic dibasic acid (for example, a production method disclosed in US Pat. No. 5,428,126).
{Circle around (5)} A method of condensing a polymer of polylactic acid, an aliphatic dihydric alcohol and an aliphatic dibasic acid in the presence of an organic solvent (for example, a production method disclosed in European Patent Publication 0712880 A2)
(6) In producing a polyester polymer by performing a dehydration polycondensation reaction of lactic acid in the presence of a catalyst, a method of performing solid phase polymerization in at least a part of the steps can be mentioned. Is not particularly limited. In addition, a small amount of trimethylolpropane, an aliphatic polyhydric alcohol such as glycerin, an aliphatic polybasic acid such as butanetetracarboxylic acid, and a polyhydric alcohol such as a polysaccharide may coexist and be copolymerized. Alternatively, the molecular weight may be increased by using a binder (polymer chain extender) such as a diisocyanate compound.
[0017]
Polyester other than (a) (b)
Examples of the polyester (b) include a biodegradable aliphatic polyester which can be produced by variously combining an aromatic dibasic acid, an aliphatic hydroxycarboxylic acid, an aliphatic dihydric alcohol and an aliphatic dibasic acid, which will be described later. Aromatic polyesters (eg, modified polybutylene terephthalate, modified polyethylene terephthalate), other soft biodegradable resins (eg, polyethylene carbonate), or mixtures thereof. The elastic modulus measured by the test method of JIS K7126 Is not more than 1000 Mpa, there is no limitation. The elastic modulus is preferably 1 to 750 Mpa, more preferably 1 to 500 Mpa, and most preferably 1 to 300 Mpa. If the elastic modulus is larger than 1000 MPa, the softening effect when added to polylactic acid may be small.
[0018]
Preferred polyesters (b) include, for example, polycaprolactone, polybutylene terephthalate adipate, polyethylene terephthalate adipate, polybutylene succinate, polybutylene succinate adipate, polyethylene succinate and the like. .
These polyesters may have a polymer chain extended by a binder such as diisocyanate, a small amount of an aliphatic polyhydric alcohol such as trimethylolpropane or glycerin, or a fatty acid such as butanetetracarboxylic acid. It may be copolymerized with polyhydric alcohols such as aromatic polybasic acids and polysaccharides.
[0019]
As a method for producing the polyester (b), a method similar to the method for producing polyethylene terephthalate, polybutylene terephthalate, or polylactic acid can be used, and the method is not limited.
In the present invention, in particular, polybutylene terephthalate adipate (Ecoflex, trade name, manufactured by BASF) and polybutylene succinate adipate (Bionole, trade name, manufactured by Showa High Polymer Co., Ltd.) are already commercially available and inexpensive. It is easily available and has a high effect of imparting flexibility to the lactic acid polymer.
[0020]
Specific examples of the aromatic dibasic acid shown in the present invention include terephthalic acid and isophthalic acid. These can be used alone or in combination of two or more.
[0021]
Specific examples of the aliphatic hydroxycarboxylic acid shown in the present invention include glycolic acid, lactic acid, 3-hydroxybutyric acid, 4-hydroxybutyric acid, 3-hydroxyvaleric acid, 4-hydroxyvaleric acid, 6-hydroxycaproic acid and the like. And cyclic esters of aliphatic hydroxycarboxylic acids, such as glycolide, which is a dimer of glycolic acid, and ε-caprolactone, which is a cyclic ester of 6-hydroxycaproic acid. These can be used alone or in combination of two or more.
[0022]
Specific examples of the aliphatic dihydric alcohol shown in the present invention include, for example, ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, 1,3-butanediol, 1,4-butanediol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, 1,9-nonanediol, neopentyl glycol, polytetramethylene glycol, 1,4-cyclohexanedimethanol, 1,4-benzene Dimethanol and the like. These can be used alone or in combination of two or more.
[0023]
Specific examples of the aliphatic dibasic acid shown in the present invention include oxalic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecandioic acid, dodecandioic acid, and phenylsuccinic acid , 1,4-phenylenediacetic acid and the like. These can be used alone or in combination of two or more.
[0024]
The weight average molecular weight (Mw) and molecular weight distribution of the lactic acid polymer (a) and polyester (b) are not particularly limited as long as they can be substantially molded. The weight average molecular weights of the lactic acid polymer (a) and the polyester (b) used in the present invention are not particularly limited as long as they exhibit substantially sufficient mechanical properties, but generally, the weight average molecular weight (Mw) In this case, the amount is preferably from 6 to 1,000,000, more preferably from 80,000 to 500,000, and most preferably from 100,000 to 300,000. In general, when the weight average molecular weight (Mw) is smaller than 60,000, when the mechanical properties of a molded article obtained by molding a resin composition are not sufficient, or when the molecular weight exceeds 1,000,000, The melt viscosity at the time of molding may be extremely high, which may make handling difficult or uneconomical in production.
[0025]
Layer (A) in multilayer film
The layer (A) constituting the multilayer film is preferably 40% by weight￣10% by weight, preferably 35% by weight￣15% by weight, more preferably 30% by weight￣20% by weight of the lactic acid polymer (a). The polyester (b) other than a) (b) is preferably 60% by weight to 90% by weight, preferably 65% by weight to 85% by weight, and more preferably 70% by weight to 80% by weight.
When it is larger by 40% by weight, flexibility may not be exhibited, and in particular, the elongation at low temperature may not be exhibited. When it is smaller than 10% by weight, it may be peeled off from other phases.
[0026]
Layer (B) in multilayer film
The layer (B) constituting the multilayer film comprises 55 to 85% by weight of the lactic acid polymer (a), preferably 60 to 80% by weight, more preferably 65 to 75% by weight, and the polyester (b) 45 other than the lactic acid polymer (a). -15% by weight, preferably 40-20% by weight, more preferably 35-25% by weight.
1) The film according to the present invention, in which the ratio A / B of the thickness of the layer (A) / layer (B) is 0.2 to 0.8 / 0.8 to 0.2, has good blocking resistance and smoothness of the film. It is preferable to add a blocking resistant agent or a lubricant in order to impart the property.
[0027]
In the present invention, it is preferable to add a small amount of an inorganic compound to impart blocking resistance between the films, and the addition amount is 0.05 to 10% by weight, preferably 0.5 to 7% by weight, more preferably 1 to 5 parts by weight. The amount of addition is appropriately selected from the optimum amounts that provide good moldability during the desired T-die extrusion molding or inflation molding, good blocking resistance of the obtained film, and good lubricity of the film.
Examples of the anti-blocking agent according to the present invention include inorganic compounds such as SiO2, CaCO3, talc, clay, kaolin, kaolin clay, mica, and zinc oxide, and preferably SiO2 and CaCO3. These can be used alone or as a mixture of two or more.
[0028]
Further, the particle size is 0.05 μm to 20 μm, preferably 0.1 μm to 15 μm, more preferably 0.5 μm to 10 μm, and most preferably 1 μm to 5 μm. If the thickness is less than 0.05 μm, the anti-blocking effect may not be exhibited, and if it is more than 20 μm, the tensile strength of the film may decrease.
[0029]
The amount of the antiblocking agent to be added is 0.05 to 20 parts by weight, preferably 0.5 to 10 parts by weight, more preferably 1 to 5 parts by weight based on 100 parts by weight of the resin composition. The amount of addition is appropriately selected from the optimum amounts that provide good moldability during the desired T-die extrusion molding or inflation molding, good blocking resistance of the obtained film, and good lubricity of the film.
[0030]
In the present invention, it is preferable to add a lubricant in order to impart slipperiness between the films.
Examples of the lubricant shown in the present invention include liquid paraffin, hydrocarbons such as polyethylene wax, fatty acids such as stearic acid, oxyacids, aliphatic alcohol esters, aliphatic polyhydric alcohol esters, and aliphatic polyglycol esters. Metal soaps such as aliphatic (polyhydric) alcohols, polyglycols, and calcium stearate, and the right column on page 389 of “10889 Chemical Products (1989, Chemical Daily, Inc., Nihonbashi-Hamacho, Chuo-ku, Tokyo)” "Aliphatic amide" described in the left column of page 391, and the like.
[0031]
Specific examples of the aliphatic carboxylic acid amide include, for example, lauric acid amide, palmitic acid amide, oleic acid amide, stearic acid amide, erucic acid amide, behenic acid amide, ricinoleic acid amide, and hydroxystearic acid amide. Monocarboxylic acid amides; N-oleyl palmitic acid amide, N-oleyl oleic acid amide, N-oleyl stearic acid amide, N-stearyl oleic acid amide, N-stearyl stearic acid amide, N-stearyl erucic acid amide, methylol stearin N-substituted aliphatic monocarboxylic acid amides such as acid amide and methylolbehenic acid amide; methylenebisstearic acid amide, ethylenebislauric acid amide, ethylenebiscapric acid amide, ethylenebisoleic acid amide, ethylene Stearic acid amide, ethylene biserucic acid amide, ethylene bis behenic acid amide, ethylene bis isostearic acid amide, ethylene bishydroxystearic acid amide, butylene bis stearic acid amide, hexamethylene bis oleic acid amide, hexamethylene bis stearin Aliphatic biscarboxylic acid amides such as acid amide, hexamethylene bisbehenic acid amide, hexamethylene bishydroxystearic acid amide, m-xylylene bis-stearic acid amide, and m-xylylene bis-12-hydroxystearic acid amide N, N'-dioleyl sebacamide, N, N'-dioleyl adipamide, N, N-distearyl adipamide, N, N'-distearyl sebacamide, N, N'-di; Stearyl isophthal N-substituted aliphatic carboxylic acid bisamides such as amide, N, N'-distearyl terephthalic acid amide; N-butyl-N'-stearyl urea, N-propyl-N'-stearyl urea, N-stearyl N-substitutions such as -N'-stearyl urea, N-phenyl-N'-stearyl urea, xylylene bis stearyl urea, toluylene bis stearyl urea, hexamethylene bis stearyl urea, diphenyl methane bis stearyl urea, diphenyl methane bis lauryl urea Ureas are exemplified. These may be one kind or a mixture of two or more kinds.
[0032]
Among these, erucamide, ethylenebisstearic acid amide, ethylenebislauric amide, and ethylenebisoleic amide are particularly preferable because they are inexpensive, effective, and effective.
[0033]
The addition amount is 0.05 to 10% by weight, preferably 0.2 to 5 parts by weight, and more preferably 0.5 to 2 parts by weight. As for the amount of addition, the optimum amount for obtaining the desired moldability at the time of T-die extrusion molding or inflation molding, the blocking resistance of the obtained film, and the lubricity of the film is appropriately selected in the same manner as the antiblocking agent. You.
[0034]
The lactic acid polymer used in the present invention may contain various additives (plasticizer, oxidizer, etc.) depending on the purpose (for example, improvement in moldability, secondary processing, degradability, tensile strength, heat resistance, storage stability, weather resistance, etc.). Inhibitors, ultraviolet absorbers, heat stabilizers, flame retardants, internal mold release agents, inorganic additives, antistatic agents, surface wetting improvers, incineration aids, pigments, lubricants, natural products, etc. can be added. .
[0035]
Method for forming multilayer film The film shown in the present invention may be extruded by mixing pellets of lactic acid polymer (a) and polyester (b) or other additives, and may be extruded by uniaxial or biaxial extrusion in advance. It may be extruded after melt-kneading in a machine. As the extruder used in the present invention, a known extruder can be used, and the same applies to the type of screw. The use of a screw of a dull mage type or the like increases the kneading effect and allows the resins to be satisfactorily kneaded, so that the present invention can be more suitably used.
[0036]
Examples of the method of extrusion molding of the film include multilayer inflation molding and multilayer T-die molding.
Extrusion conditions at the time of extrusion molding include, for example, in inflation molding, a resin temperature is 160 to 230 ° C., a die hole is 0.5 to 3 mm, and a blow-up ratio (BR) is 1.5 to 5.0, preferably 1. 7.0 to 4.5, more preferably 2.0 to 4.0. If BR is less than 1.5, it may be inefficient and molding may not be stable, and if it is more than 5.0, bubbles may be difficult to stabilize during molding and molding may not be possible.
[0037]
Characteristics of the multilayer film As the layer structure of the multilayer film, for example, a two-layer structure of layer (A) / layer (B) and a three-layer structure of layer (B) / layer (A) / layer (B) Such a structure can be taken, and there is no limitation in the structure at all.
[0038]
In the case of a two-layer structure, the ratio A / B of the thickness of the layer (A) / layer (B) is 0.2 to 0.8 / 0.8 to 0.2, preferably 0.25 to 0.75 / It is 0.75-0.25, more preferably 0.3-0.7 / 0.7-0.3.
In the case of a three-layer structure, the thickness ratio B / A / B of the layer (B) / layer (A) / layer (B) is 0.2 to 0.6 / 0.2 to 0.6 / 0.2. -0.6, preferably 0.25-0.5 / 0.25-0.5 / 0.25-0.5. . More preferably, it is 0.3 to 0.4 / 0.3 to 0.4 / 0.3 to 0.4. If the ratio is outside the above range, it may become hard and brittle, or the elongation at low temperatures may not be exhibited.
[0039]
Also, for example, when the application is a food packaging bag or compost bag, when at least the layer containing a large amount of lactic acid polymer is used as the outer layer, the excellent characteristics of lactic acid polymer ((1) Degradability, (2) resistance to mold, hygiene such as odor resistance and coloring resistance to food, etc.), and it is particularly preferable.
[0040]
The thickness of the multilayer film is 10 to 500 μm, preferably 20 to 250 μm, more preferably 20 to 150 μm.
The film has an elongation at −20 ° C. of 50% or more, preferably 75% or more, more preferably 100% or more, and a tear strength of 800 N / cm or more, preferably 1000 N / cm or more, more preferably 1200 N / cm. That is all.
The heat sealing start temperature of the film is 130 ° C. or less. Here, the heat sealing start temperature is the lowest heat sealing temperature at which the heat sealing strength becomes 8.0 N / 15 mm or more.
Secondary workability The film / sheet shown in the present invention is also excellent in secondary workability such as stretching, blow processing, vacuum forming, vacuum pressure forming, etc., and can obtain molded articles such as containers and trays. it can.
[0041]
Applications The film formed by the above method has an excellent balance between transparency and rigidity, and has heat sealing properties, hot tack properties and heat resistance. The resin composition according to the present invention is excellent in melt fluidity, that is, excellent in moldability, and can provide a molded article such as a film excellent in flexibility and mechanical properties, particularly, tensile properties and tear strength.
[0042]
In addition, the resin composition of the present invention has excellent heat stability and high-speed moldability, and also has excellent low-temperature heat sealability and seal stability, as well as lubricity, blocking resistance, etc. Also, a film excellent in suitability for high-speed filling during automatic filling and packaging can be provided.
[0043]
Films comprising the resin composition according to the present invention are used for various types of packaging such as standard bags, heavy bags, wrap films, heat shrink films, raw laminating webs, sugar bags, oil packaging bags, water packaging bags, and food packaging. Suitable for films, infusion bags, agricultural materials and the like. Also, this film can be used as a multilayer film by bonding it to a substrate such as nylon, polyester, or aluminum.
[0044]
【Example】
Hereinafter, the present invention will be described specifically with reference to Examples, but the present invention is not limited thereto without departing from the technical scope of the present invention.
[0045]
(1) Physical properties of film (elongation, elasticity)
The tensile test of the film was measured according to JIS K7126.
[0046]
{Circle over (2)} The heat sealability of the heat sealable film was evaluated according to JIS Z1707, and the seal strength at 130 ° C. was measured. Further, the seal strength at 130 ° C. of the film immediately after film formation and after storage at 23 ° C. for one month was compared to evaluate the stability of heat sealability.
[0047]
{Circle around (3)} Decomposability in compost A 10 cm * 10 cm film having a thickness of 30 μm was buried in a compost having a temperature of 58 ° C. and a water content of 60%, and changes with time were observed.
Evaluation method ◎: Elimination within 7 days ○: Elimination in 8-14 days Δ: Elimination in 15-25 days X: Elimination in 26-40 days
Embodiment 1
LACEA H-440 (trade name, manufactured by Mitsui Chemicals, Inc., D-lactic acid content: 4 wt%) as a lactic acid polymer and Ecoflex (trade name, manufactured by BASF) as a polyester (b) in a ratio of 30/70. After that, the mixture was melt-melted and kneaded at a resin temperature of 180 to 210 ° C. using a twin screw extruder to form pellets. The obtained pellet was dried at 60 ° C. for 5 hours. Hereinafter, it is referred to as pellet A.
[0049]
LACEA H-440 as a lactic acid polymer, Sylysia 530 (trade name, manufactured by Fuji Silysia K.K., average particle size 2.7 μm) as an Ecoflex AB agent as a polyester (b), and erucamide as a lubricant at a weight ratio of 70. The mixture was mixed at a ratio of / 26/3/1, and melt-kneaded and kneaded at a resin temperature of 180 to 210 ° C. with a twin-screw extruder to form pellets. The obtained pellet was dried at 60 ° C. for 5 hours. Hereinafter, it is referred to as pellet B. Pellet B / Pellet A / Pellet B are put into a surface layer / intermediate layer / surface layer hopper using a T-die three-layer extruder, and the thickness ratio becomes 1/1/1 at a resin temperature of 190 to 200 ° C. Extruded.
The thickness of the obtained film was 40 μm, and the results of evaluation of physical properties, sealability, and biodegradability are shown in Table 1.
[0050]
Examples 2 to 5 and Comparative Examples 1 to 4
The procedure was performed in the same manner as in Example 1 except that the types and amounts of the lactic acid polymer, polyester (b), AB agent and lubricant, and the blow-up ratio during inflation molding were changed. Tables 1 and 2 show physical properties (thickness, elongation at 23 ° C., elastic modulus, elongation at −20 ° C., heat seal strength immediately after film formation and one month after film formation) of the obtained film.
[0051]
[Table 1]

[0052]
[Table 2]

[0053]
[Table 3]

Claims (3)

1) The ratio of the lactic acid polymer (a) in the film is 50% by weight or more 2) At least one layer (A) is 10% by weight or more and less than 40% by weight of the lactic acid polymer (a) and a polyester (b) other than the lactic acid polymer (a) 3) at least one layer (B) comprises 60-80% by weight of a lactic acid polymer (a), and 60% by weight-90% by weight (here, (a) + (b) = 100% by weight). (a) + (b) = 100% by weight of polyester (b) other than a) (where (a) + (b) = 100% by weight) 4) Ratio A / B of layer (A) / layer (B) thickness Is 0.2 to 0.8 / 0.8 to 0.2, and 5) at least one layer of the layer (A) or the layer (B) contains 100% of the total resin composition in the resin composition constituting the layer. 0.05 to 10% by weight of lubricant and 0.05 to 1% of antiblocking agent Unstretched multilayer film which comprises by weight% 1) The proportion of the lactic acid polymer (a) in the film is 50% by weight or more 2) The unstretched multilayer film characterized in that the elongation percentage of the film at -20 ° C is 50% or more The method for producing an unstretched multilayer film according to claim 1.