JP2008260895A - Polylactic acid-based resin film and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a film comprising a polylactic acid resin composition and having practical flexibility together with strengths, and a method for producing the same by an inflation method. <P>SOLUTION: The film comprises the polylactic acid resin composition comprising 100 pts.wt. polylactic acid resin, 10-30 pts.wt. benzyl alkyl glycol adipate and 1-5 pts.wt. hydrolysis inhibitor and having 1×10<SP>3</SP>-10×10<SP>3</SP>Pa s at 10 s<SP>-1</SP>shear rate at 180°C. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a film comprising a polylactic acid resin composition containing a biodegradable plasticizer, and a method for producing the film. More specifically, the present invention relates to a film made of a biodegradable polylactic acid resin composition containing a biodegradable plasticizer and having practical flexibility and strength, and a method for producing the film.

Examples of the resin film molding method include inflation molding, T-die film extrusion molding, and extrusion lamination molding. In particular, the inflation molding method can be performed with a compact apparatus, is superior in productivity for a small variety of products, and is low in cost as compared with other molding methods. Moreover, since the film shape obtained is a bag shape (seamless shape), it is suitable for manufacture of the bag for food packaging, a bag, etc.
Conventionally, as a resin used when manufacturing a film, resins such as polyethylene, polypropylene, soft polyvinyl chloride, and polyethylene terephthalate having both flexibility and strength are known, and these are garbage bags and packaging bags. Etc. are used. However, when these resins are disposed after use, they are hardly decomposed in the natural environment even if they are buried, so that they remain in the ground semipermanently and destroy the environment. In addition, the abandonment of the ocean destroys the living environment of marine life. Furthermore, the problem that the scenery is damaged by these discarded resins has occurred.

As a resin for solving such problems, polylactic acid, a copolymer of lactic acid and other aliphatic hydroxycarboxylic acid, an aliphatic polyhydric alcohol and an aliphatic polyvalent carboxylic acid, which are thermoplastic resins and biodegradable polymers. Polyesters derived from acids are known, and products for various uses have been developed.
Among these polymers, polylactic acid, in particular, biodegrades 100% within a few months to a year within the animal body, and begins to degrade in a few weeks in moist environments such as soil and seawater. It will disappear in 1 to several years. In addition, the decomposition product has characteristics that it is lactic acid, carbon dioxide, and water that are harmless to the human body.
In recent years, polylactic acid has been produced in a large amount and at low cost by the fermentation method of L-lactic acid as a raw material, and has a high decomposition rate in compost, resistance to mold, and odor resistance to foods. It has been expected to expand its application field by having excellent characteristics such as color resistance.
However, since polylactic acid has high rigidity, it is difficult to say that it is an appropriate resin for applications that require flexibility, such as agricultural multi-films, food packaging bags, garbage bags, and other films or packaging materials.

In general, as a technique for softening a resin, methods such as adding a plasticizer and blending soft polymers are known.
However, even if the method of adding a plasticizer can give sufficient flexibility to the resin composition, the melt viscosity of the resin composition decreases, and as a result, film production by inflation molding becomes difficult. In addition, the method of adding a plasticizer has a problem that the plasticizer bleeds out. Therefore, in order to put this method into practical use, several problems must be solved.

  On the other hand, in the method of blending soft polymers, considering the biodegradability, the resin to be blended is limited to a biodegradable resin having flexibility. Examples of such a resin include polybutylene succinate, polyethylene succinate, polycaprolactone, and the like. For example, Patent Document 1 and Patent Document 2 disclose resin compositions obtained by blending these soft polymers with polylactic acid. However, in this method, it is necessary to add a large amount of a soft polymer in order to impart sufficient flexibility (for example, an elastic modulus of 1000 MPa or less) to polylactic acid. For example, polybutylene succinate needs to be added in an amount of 60% by weight or more of the whole, and as a result, the above-mentioned features of polylactic acid are impaired.

For example, Patent Documents 3 to 5 disclose methods for forming a polylactic acid resin into a film by inflation molding. However, the methods described in these documents use an alloy of polylactic acid and other aliphatic esters, and are not formed into a film of a resin of polylactic acid alone, so that there is a problem that the characteristics of polylactic acid are impaired. .
Thus, at present, a method for producing a film having both practical strength and flexibility by inflation molding using only polylactic acid as a resin without using any other resin has been developed. Absent.

JP-A-8-245866 JP-A-9-111107 WO 1999/45067 Japanese Patent No. 3510218 JP-A-11-116788

  An object of the present invention is to provide a film comprising a polylactic acid resin composition having practical flexibility and strength, and a production method thereof by an inflation method.

As a result of diligent studies to solve the above problems, the present inventors are a polylactic acid resin composition in which benzylalkyldiglycol adipate and a hydrolysis inhibitor are added to polylactic acid at a specific ratio, at a temperature of 180 ° C., A film having a melt viscosity of 1 × 10 ³ to 10 × 10 ³ Pa · s at a shear rate of 10 s ^-1 is suitable for inflation molding, and a film having practical flexibility and strength can be obtained by inflation molding. I found it.

This invention is completed based on the said knowledge, and provides the polylactic acid-type resin film of the following each item, and its manufacturing method.
Item 1. 100 parts by weight of polylactic acid resin, 10 to 30 parts by weight of benzyl alkyl diglycol adipate, and 1 to 5 parts by weight of hydrolysis inhibitor, melt viscosity at a temperature of 180 ° C. and a shear rate of 10 s ⁻¹ is 1 × 10 ³ A film comprising a polylactic acid resin composition of ˜10 × 10 ³ Pa · s.
Item 2. Item 2. The film according to Item 1, wherein the hydrolysis inhibitor is a carbodiimide compound.
Item 3. Item 3. The film according to Item 1 or 2, further comprising 0.3 to 1 part by weight of a crystal nucleating agent based on 100 parts by weight of the polylactic acid resin.
Item 4. Item 4. The film according to Item 3, wherein the crystal nucleating agent is a trimesic acid compound.
Item 5. Item 5. The film according to any one of Items 1 to 4, wherein the film has a tensile strength of 10 to 40 MPa, a tensile elastic modulus of 100 to 1000 MPa, and an elongation at break of 100 to 400%.

Item 6. Item 6. The film according to any one of Items 1 to 5, which is formed by inflation molding.
Item 7. 100 parts by weight of polylactic acid resin, 10 to 30 parts by weight of benzyl alkyl diglycol adipate, and 1 to 5 parts by weight of hydrolysis inhibitor, melt viscosity at a temperature of 180 ° C. and a shear rate of 10 s ⁻¹ is 1 × 10 ³ A method for producing a polylactic acid-based resin film, comprising molding a polylactic acid resin composition of ˜10 × 10 ³ Pa · s by an inflation method.
Item 8. Item 8. The method according to Item 7, wherein the hydrolysis inhibitor is a carbodiimide compound.
Item 9. Item 9. The method according to Item 7 or 8, wherein the polylactic acid composition further comprises 0.3 to 1 part by weight of a crystal nucleating agent with respect to 100 parts by weight of the polylactic acid resin.
Item 10. Item 10. The method according to Item 9, wherein the crystal nucleating agent is a trimesic acid compound.

The film of the present invention contains benzyl alkyl diglycol adipate and a hydrolysis inhibitor at a specific ratio, and has a melt viscosity of about 1 × 10 ³ to 10 × 10 ³ Pa · s at a temperature of 180 ° C. and a shear rate of 10 s ⁻¹ . As a result, while using polylactic acid as a base resin, it has both practically sufficient flexibility and strength. Moreover, it can manufacture easily by inflation molding.

Hereinafter, the present invention will be described in detail.
(I) Film The film of the present invention contains 100 parts by weight of a polylactic acid resin, about 10 to 30 parts by weight of benzyl alkyl diglycol adipate, and about 1 to 5 parts by weight of a hydrolysis inhibitor, at a temperature of 180 ° C., shear The film includes a polylactic acid resin composition having a melt viscosity of about 1 × 10 ³ to 10 × 10 ³ Pa · s at a speed of 10 s ⁻¹ .

The raw material monomer of the polylactic acid resin polylactic acid is not particularly limited, and examples thereof include known monomers such as L-lactic acid, D-lactic acid, DL-lactic acid, mixtures thereof, and lactide which is a cyclic dimer of lactic acid. . Polylactic acid may be obtained by polymerizing a plurality of types of monomers. Lactic acid is a useful raw material among biodegradable aliphatic polyester resins in that it can be obtained by fermenting renewable resources such as sugar and starch.
The weight average molecular weight of polylactic acid is preferably about 10,000 to 1,000,000, more preferably about 30,000 to 600,000, and still more preferably about 50,000 to 400,000. When the weight average molecular weight is in the above range, the mechanical strength is sufficient and the processability is excellent. In the present invention, the weight average molecular weight is a value measured by gel permeation chromatography. Specifically, the gel permeation chromatography uses HLC-8020 manufactured by Tosoh Corporation, the column uses KF803L × 1 and KF806L × 2 of the company connected in series, and the analysis is performed by AS-802 of the company. Was measured using a polystyrene with a known molecular weight as a standard sample.
Specific examples of such polylactic acid include “Lacia” series manufactured by Mitsui Chemicals, Inc., “Teramac” series manufactured by Unitika Ltd., and the like.

Benzyl alkyl diglycol adipate Benzyl alkyl diglycol adipate is effective as a plasticizer. The alkyl group of benzylalkyldiglycol adipate may be either linear or branched, but is preferably linear. Moreover, 1-20 are preferable, as for carbon number of an alkyl group, 1-8 are more preferable, and 1-4 are still more preferable. Particularly preferred are benzyl methyl diglycol adipate, benzyl ethyl diglycol adipate, benzyl n-propyl diglycol adipate, and benzyl n-butyl diglycol adipate having a linear alkyl group having 1 to 4 carbon atoms.
The content of benzyl alkyl diglycol adipate is preferably about 10 to 30 parts by weight, more preferably about 12 to 28 parts by weight, and still more preferably about 15 to 26 parts by weight with respect to 100 parts by weight of the polylactic acid resin. If it is the said range, the film which has a practically sufficient softness | flexibility will be obtained, and the resin composition of the intensity | strength suitable for inflation molding will be obtained.

As a hydrolysis inhibitor, a compound known as a hydrolysis inhibitor for polyester resins can be used without limitation. Examples of such hydrolysis inhibitors include carbodiimide compounds, oxozoline compounds, and isocyanate compounds. Of these, carbodiimide compounds are preferred.
The carbodiimide compound exhibits an effect of suppressing hydrolysis of the polylactic acid resin by performing a crosslinking reaction with the terminal carboxylic acid of the polylactic acid resin. The carbodiimide compound is not particularly limited as long as it has one or more carbodiimide groups in the molecule. For example, a carbodiimide compound synthesized by a decarboxylation reaction from an isocyanate compound according to a conventionally known method can be used. Moreover, you may use what is marketed.

Such a carbodiimide compound has a basic structure represented by the following general formula (1).
-(N = C = N-R-) n- (1)

(In the above formula (1), n represents an integer of 1 or more. R represents an organic bond unit selected from aliphatic, alicyclic, and aromatic.)

Monocarbodiimide compounds having one carbodiimide group in the molecule (compounds where n is 1 in the above formula (1)) include aliphatic or alicyclic monocarbodiimides such as diisopropylcarbodiimide, dicyclohexylcarbodiimide, dioctylcarbodiimide, and diphenylcarbodiimide. Aromatic monocarbodiimide and the like can be exemplified.
As an isocyanate compound (a compound in which n is 2 or more in the above formula (1)) in the synthesis of a polycarbodiimide having two or more carbodiimide groups in the molecule, 1,3-phenylene diisocyanate, 1,4- Phenylene diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, tetramethylxylylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 4,4'-diphenyldimethylmethane diisocyanate Aromatic diisocyanates such as narate; 1,4-cyclohexane diisocyanate, 1-methyl-2,4-cyclohexane diisocyanate, 1-methyl-2,6-cyclohexane diisocyanate, isophorone diisocyanate, 4, 4'-dicyclohexylmethane diisocyanate Aliphatic or alicyclic diisocyanates such as hexamethylene diisocyanate, and the like. Polycarbodiimide may have all or part of the isocyanate group remaining at the end sealed, and as such a sealing agent, monoisocyanate such as cyclohexyl isocyanate, phenyl isocyanate, tolyl isocyanate, etc. Compound: Compounds having active hydrogen such as hydroxyl group and amino group are exemplified.

Among the carbodiimide compounds, polycarbodiimide having two or more carbodiimide groups in the molecule is preferable from the viewpoint of improving hydrolysis resistance of a molded product molded from the obtained resin composition. From the viewpoint of the compatibility of the above and the hydrolysis resistance of the molded product molded from the resulting resin composition, an aliphatic or alicyclic carbodiimide, a polycarbodiimide obtained from an aliphatic or alicyclic diisocyanate is preferable. . A specific example of such a polycarbodiimide compound is Carbodilite LA-1 manufactured by Nisshinbo Industries, Ltd.
The hydrolysis inhibitor can be used alone or in combination of two or more.
The content of the hydrolysis inhibitor is preferably about 1 to 5 parts by weight, more preferably about 2 to 5 parts by weight, and still more preferably about 3 to 4 parts by weight with respect to 100 parts by weight of the polylactic acid resin. When the addition amount of the hydrolysis inhibitor is within the above range, a decrease in viscosity due to a decrease in molecular weight is prevented, and inflation molding can be performed smoothly. Further, an increase in viscosity due to an excessive crosslinking reaction is prevented, and inflation molding can be performed smoothly.

The crystal nucleating agent polylactic acid resin composition may further contain a crystal nucleating agent. As the crystal nucleating agent, a known compound can be used without limitation as a crystal nucleating agent added to the polylactic acid resin composition. A typical example of such a crystal nucleating agent is a trimesic acid triamide compound.
The trimesic acid triamide compound has the general formula (2)
R ^1- (CONHR ² ) ₃ (2)

(In the formula, R ¹ represents a residue obtained by removing all carboxyl groups from trimesic acid. Three R ^{2 s} are the same or different and are linear or branched having 1 to 4 carbon atoms. (It represents a cyclohexyl group optionally having 1 to 3 alkyl groups, or a linear or branched alkyl group having 1 to 4 carbon atoms.)
It is represented by

  The trimesic acid triamide compound may be produced by any method, for example, having trimesic acid or an acid chloride thereof and a linear or branched alkyl group having 1 to 4 carbon atoms. It can be obtained by amidating cyclohexylamine, which may be used, or a linear or branched alkylamine having 1 to 4 carbon atoms.

  Specific examples of the cyclohexylamine optionally having a linear or branched alkyl group having 1 to 4 carbon atoms include cyclohexylamine, 2-methylcyclohexylamine, 3-methylcyclohexylamine, 4-methyl. Cyclohexylamine, 2-ethylcyclohexylamine, 3-ethylcyclohexylamine, 4-ethylcyclohexylamine, 2-n-propylcyclohexylamine, 3-n-propylcyclohexylamine, 4-n-propylcyclohexylamine, 2-iso-propyl Cyclohexylamine, 3-iso-propylcyclohexylamine, 4-iso-propylcyclohexylamine, 2-n-butylcyclohexylamine, 3-n-butylcyclohexylamine, 4-n-butylcyclohexylamine, -Iso-butylcyclohexylamine, 3-iso-butylcyclohexylamine, 4-iso-butylcyclohexylamine, 2-sec-butylcyclohexylamine, 3-sec-butylcyclohexylamine, 4-sec-butylcyclohexylamine, 2-tert -Butylcyclohexylamine, 3-tert-butylcyclohexylamine, 4-tert-butylcyclohexylamine, 2,3-dimethylcyclohexylamine, 2,4-dimethylcyclohexylamine, 2,5-dimethylcyclohexylamine, 2,6-dimethyl Cyclohexylamine, 2,3,4-trimethylcyclohexylamine, 2,3,5-trimethylcyclohexylamine, 2,3,6-trimethylcyclohexylamine, 2,4,6-trimethyl Chill cyclohexylamine, 3,4,5-trimethyl cyclohexylamine, and the like. Specific examples of the linear or branched alkylamine having 1 to 4 carbon atoms include methylamine, ethylamine, n-propylamine, iso-propylamine, n-butylamine, iso-butylamine, sec-butylamine, tert -Butylamine is mentioned.

（式中、Ｒ^１は、一般式（２）におけると同義である。Ｒ^８は、炭素数１〜４の直鎖状若しくは分岐鎖状のアルキル基を表す。ｋは０又は１〜３の整数を表す。）
で表されるシクロヘキサン環を有するトリアミド化合物が好ましい。 Among the above trimesic acid triamide compounds, the compound represented by the general formula (3) is particularly excellent in improving the crystallization speed of the polylactic acid resin.

(In the formula, R ¹ has the same meaning as in General Formula (2). R ⁸ represents a linear or branched alkyl group having 1 to 4 carbon atoms. K is 0 or 1 to 3. Represents an integer.)
The triamide compound which has a cyclohexane ring represented by these is preferable.

  Among these, in particular, trimesic acid tricyclohexylamide, trimesic acid tri (2-methylcyclohexylamide), trimesic acid tri (3-methylcyclohexylamide), trimesic acid tri (4-methylcyclohexylamide), trimesic acid tri (2,3 -Dimethylcyclohexylamide) is preferable, and trimesic acid tricyclohexylamide and trimesic acid tri (2-methylcyclohexylamide) are particularly preferable.

As a specific example of the crystal nucleating agent comprising such a trimesic acid triamide compound, there is a nucleating agent NJESTER TF-1 manufactured by Shin Nippon Rika Co., Ltd.
A crystal nucleating agent can be used individually by 1 type or in mixture of 2 or more types.
The content of the crystal nucleating agent is preferably about 0.3 to 1 part by weight, more preferably about 0.5 to 0.8 part by weight, and still more preferably about 0.6 to 0.7 part by weight with respect to 100 parts by weight of the polylactic acid resin. If the amount of the crystal nucleating agent is within the above range, the film is sufficiently crystallized at the time of molding, so that sufficient film strength can be obtained. Also, a film having good transparency and excellent flexibility can be obtained.

Other additives Other components that are usually added to the biodegradable resin composition can be added to the polylactic acid composition as necessary, as long as the effects of the present invention are not impaired. Examples of such components include modifiers, fragrances, antibacterial agents, pigments, dyes, heat resistance agents, antioxidants, weathering agents, lubricants, antistatic agents, stabilizers, fillers, reinforcing agents, antiblocking agents, Examples include flame retardants, wood flour, and starch.

The melt viscosity of the polylactic acid composition is about 1 × 10 ³ to 10 × 10 ³ Pa · s, preferably about 1 × 10 ^{3 to} 5 × 10 ³ Pa · s, 1.5 × 10 ³ to 4 × About 10 ³ Pa · s is more preferable.
In the present invention, the melt viscosity is a melt viscosity at a temperature of 180 ° C. and a shear rate of 10 s ⁻¹ , and was measured by the method described in the examples using a parallel plate rheometer (MCR300 manufactured by Paar Physica). Value.
If the melt viscosity is in the above range, the inflation moldability will be good. In addition, a polylactic acid composition having an excessively high melt viscosity cannot be obtained unless the molecular weight of the polylactic acid is increased. However, since it is difficult to produce such a polylactic acid having a large molecular weight, the upper limit of the melt viscosity is also limited. .
The film having the above melt viscosity can be obtained by selecting the kind of the component of the resin composition and the blending ratio thereof from the above-described range and selecting the kneading conditions of the resin composition during film production from the range described below.

Film characteristics
<Tensile strength>
The tensile strength of the film of the present invention is preferably about 10 to 40 MPa, more preferably about 15 to 35 MPa, and even more preferably about 18 to 27 MPa.
In the present invention, the tensile strength of the film was measured based on the JIS standard (JIS K 7127) by using a universal testing machine (Autograph; AL-B manufactured by Minebea Co., Ltd.) at a tensile rate of 10 mm / min. Value.
If it is the range of said tensile strength, it will be hard to cut | disconnect or torn and it will become a flexible film.
A film having the tensile strength can be obtained by selecting the types of the components of the resin composition and the mixing ratio thereof from the above-described range.

<Tensile modulus>
The tensile elastic modulus of the film of the present invention is preferably about 100 to 1000 MPa, more preferably about 100 to 800 MPa, and even more preferably about 110 to 650 MPa.
In the present invention, the tensile elastic modulus of the film is measured by pulling at a pulling speed of 10 mm / min using a universal testing machine (Autograph; AL-B manufactured by Minebea Co., Ltd.) based on JIS standard (JIS K 7127). It is the value.
If the tensile elastic modulus is in the above range, the position of the contents can be fixed when used as a bag because it does not stretch too much, and the contents are adversely affected by the unevenness of the lower surface of the bag. Never give. Moreover, if a tensile elasticity modulus is the said range, a film has sufficient softness | flexibility.
By selecting the type of the component of the resin composition and the blending ratio thereof from the above-described range, a film having the tensile elastic modulus can be obtained.

<Elongation at break>
The elongation at break of the film of the present invention is preferably about 100 to 400%, more preferably about 125 to 375%, and still more preferably about 150 to 350%.
In the present invention, the elongation at break of the film is measured by pulling at a pulling speed of 10 mm / min using a universal testing machine (Autograph; AL-B manufactured by Minebea Co., Ltd.) based on JIS standard (JIS K 7127). It is the value.
If it is the range of the said elongation at the time of a fracture | rupture, it will become a film which has practically sufficient freedom degree, and the shape stability of a practical film will be acquired.
The film of the present invention is characterized by having biodegradability, but when it has the above-described tensile strength, tensile elastic modulus, and elongation at break, it is further excellent in the balance of flexibility, strength, and elongation at break. It will be.

The thickness of the thick film varies depending on the application, but can usually be about 10 to 500 μm.

(II) Film Production Method The polylactic acid resin composition film production method of the present invention comprises 100 parts by weight of polylactic acid resin, 10 to 30 parts by weight of benzyl alkyl diglycol adipate, and 1 to 1 part of hydrolysis inhibitor. In this method, a polylactic acid resin composition containing 5 parts by weight, having a melt viscosity of 1 × 10 ³ to 10 × 10 ³ Pa · s at a temperature of 180 ° C. and a shear rate of 10 s ⁻¹ is molded by an inflation method.
According to the method of the present invention, a polylactic acid resin film having practical flexibility and strength can be obtained.
After mixing the above components, the resin composition used for inflation molding is about 150 to 250 ° C., preferably about 160 to 200 ° C., using a small twin screw extruder, and the discharge rate is about 1 to 20 kg / hour. The kneading is preferably performed at about 2 to 10 kg / hour.
The temperature of the polylactic acid resin composition at the time of inflation molding is not particularly limited as long as it is a temperature at which it melts. Usually, it may be about 140 to 200 ° C, and more preferably about 150 to 180 ° C.

  EXAMPLES Hereinafter, although an Example is shown and this invention is demonstrated in more detail, this invention is not limited to these.

(1) Materials <br/> Polylactic acid: Lacia H-400 manufactured by Mitsui Chemicals, Inc.
Plasticizer: benzyl methyl diglycol adipate
(SN0213 manufactured by Daihachi Chemical Industry Co., Ltd.)
Hydrolysis inhibitor: Carbodiimide modified isocyanate
(Nisshinbo Co., Ltd. Carbodilite LA-1)
Crystal nucleating agent: New Japan Rika Co., Ltd. nucleating agent NJester TF-1

(2) Film production method
Kneading method Each component was mixed with polylactic acid at the ratio shown in Table 1 below, and kneading was performed at a kneading temperature of 160 ° C. using a twin screw extruder. Here, in Examples 1 to 5 and Comparative Examples 3 to 6, each component was mixed in advance using a mixer at room temperature and then charged into a twin-screw extruder. In Comparative Example 2, each component was left as it was. It put into the twin screw extruder.

Measurement of melt viscosity The resin composition kneaded by the kneading method was measured using a parallel plate rheometer (MCR300 manufactured by Paar Physica). Specifically, each resin composition is placed at the measurement position of a parallel plate rheometer, melted at 210 ° C., and then a parallel plate with a diameter of 25 mm is set so that the gap is 1 mm. The melt viscosity at a temperature of 180 ° C. and a shear rate of 10 s ⁻¹ was measured while lowering the temperature from 0 ° C. to 80 ° C. at a rate of 2 ° C./min.
(Average value measured 5 times in 0.5 seconds at 180 ° C)

Molding method Various molding materials prepared by the above method were molded into a film using an inflation molding machine (YEI-S45-60-R manufactured by Yoshii Tekko Co., Ltd.) at a barrel temperature of 170 ° C. .
Evaluation of Film Formability For inflation molding in each example, the state during molding was evaluated according to the following criteria.
○: Good moldability, that is, it was able to be molded neatly.
(Triangle | delta): It can shape | mold, ie, a film can be pulled out, but it became a distorted form because of poor flexibility.
X: Molding was impossible, that is, the film could not be pulled out.
Table 1 shows the blending ratio of components in each example, the melt viscosity, and the results of moldability evaluation.

In Examples 1 to 5 and Comparative Example 6, the melt viscosity was a value between 1 × 10 ^{3 and} 10 × 10 ³ MPa.
In Examples 1 to 5 and Comparative Examples 1 and 6, films having a thickness of 40 to 200 μm could be formed, and the moldability of Examples 1 to 5 was particularly good. On the other hand, Comparative Example 1 was barely moldable, and Comparative Examples 2 to 5 could not be film-formed.

Evaluation of Physical Properties of Film Next, the tensile strength, tensile elastic modulus, and elongation at break were evaluated for the films obtained in Examples 1 to 5 and Comparative Examples 1 and 6.
The tensile strength, tensile modulus, and elongation at break are dumbbells specified by JIS K 6781 according to JIS standard (JIS K 7127) using AL-B manufactured by Minebea Co., Ltd. as a universal testing machine (autograph). The mold specimen was pulled at a pulling speed of 10 mm / min for evaluation.
The results of physical property evaluation are shown in Table 2. In Table 2, MD represents the pulling direction of the inflation tube in the longitudinal direction, and TD represents the pulling direction of the inflation tube in the circumferential direction.

  The films obtained in Examples 1 to 4 have practical tensile strength (10 to 40 MPa) and elastic modulus (100 to 1000 MPa), and the elongation at break is about 20% in Comparative Examples 1 and 6. Compared to that, it has increased dramatically to over 100%.

  The film of the present invention can be easily produced by inflation molding and has practical flexibility and strength, and therefore can be suitably used as an agricultural multi-film, a food packaging bag, a garbage bag, and the like.

Claims (10)

100 parts by weight of polylactic acid resin, 10 to 30 parts by weight of benzyl alkyl diglycol adipate, and 1 to 5 parts by weight of hydrolysis inhibitor, melt viscosity at a temperature of 180 ° C. and a shear rate of 10 s ⁻¹ is 1 × 10 ³ A film comprising a polylactic acid resin composition of ˜10 × 10 ³ Pa · s.   The film according to claim 1, wherein the hydrolysis inhibitor is a carbodiimide compound.   Furthermore, the film of Claim 1 or 2 which contains 0.3-1 weight part of crystal nucleating agents with respect to 100 weight part of polylactic acid resin.   The film according to claim 3, wherein the crystal nucleating agent is a trimesic acid compound.   The film according to any one of claims 1 to 4, wherein the film has a tensile strength of 10 to 40 MPa, a tensile modulus of 100 to 1000 MPa, and an elongation at break of 100 to 400%.   The film according to any one of claims 1 to 5, which is formed by inflation molding. 100 parts by weight of polylactic acid resin, 10 to 30 parts by weight of benzyl alkyl diglycol adipate, and 1 to 5 parts by weight of hydrolysis inhibitor, melt viscosity at a temperature of 180 ° C. and a shear rate of 10 s ⁻¹ is 1 × 10 ³ A method for producing a polylactic acid-based resin film, comprising molding a polylactic acid resin composition of ˜10 × 10 ³ Pa · s by an inflation method.   The method according to claim 7, wherein the hydrolysis inhibitor is a carbodiimide compound.   The method according to claim 7 or 8, wherein the polylactic acid composition further comprises 0.3 to 1 part by weight of a crystal nucleating agent with respect to 100 parts by weight of the polylactic acid resin.   The method according to claim 9, wherein the crystal nucleating agent is a trimesic acid-based compound.