JP2006063302A - Polylactic acid film and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polylactic acid film in which bleeding of a plasticizer to the film surface is suppressed, which is free from blocking phenomenon and which has good flexibility and transparency and to provide a method for producing the polylactic acid film. <P>SOLUTION: The polylactic acid film is obtained by molding, in the form of a film, a resin composition containing a polylactic acid-based resin composed of 50-100 mass% weakly crystalline or amorphous polylactic acid having 7-20% ratio of D-isomer and 0-50 mass% crystalline polylactic acid having 0-6% ratio of D-isomer and a plasticizer and applying crystallization treatment to the film. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a polylactic acid film and a method for producing the same.

In recent years, products that are rapidly decomposed after disposal and that do not accumulate in the natural environment have been desired, and products made of various biodegradable resins are commercially available. As biodegradable resins that can be formed into a film by a T-die extruder, aliphatic polyester resins such as polylactic acid are known. Polylactic acid is excellent in transparency but poor in flexibility. Therefore, attempts have been made to add flexibility to the film by blending a plasticizer.
However, when a plasticizer is blended with polylactic acid, the plasticizer bleeds out over the molded film surface over time, causing a bleed phenomenon that impairs the appearance of the film, and the films that have been formed and wound are in close contact with each other. There is a problem that a blocking phenomenon that does not peel off occurs.

Various proposals have been made for the purpose of solving such problems. As such a proposal, for example, a polylactic acid resin composition containing a crystallization accelerator (see, for example, Patent Document 1), a crystalline polylactic acid resin, a plasticizer, and a crystal nucleating agent are essential components. Related to highly crystalline polylactic acid resin composition (for example, see Patent Document 2), and related to L-lactic acid polymer composition in which SiO ₂ is contained in a mixture of a specific L-lactic acid polymer and a specific plasticizer (for example, , Patent Document 3), a lactic acid polyester molded product that crystallizes after molding a composition containing a specific lactic acid polyester and a plasticizer (see, for example, Patent Document 4), crystalline lactic acid resin and plastic And a biodegradable soft film in which the lactic acid resin component in the film has a specific heat of crystallization and heat of fusion (see, for example, Patent Document 5).

However, these proposals, in the plasticized soft polylactic acid film, from the viewpoint of effectively suppressing bleed to the film surface of the plasticizer and blocking between the films while maintaining transparency and flexibility, It was not always enough.
JP 2003-301097 A Japanese Patent No. 3410075 Japanese Patent No. 3472644 Japanese Patent Laid-Open No. 10-36651 JP 2003-12934 A

Accordingly, an object of the present invention is to provide a polylactic acid film having excellent flexibility and transparency, and a method for producing the same, in which bleeding of the plasticizer on the film surface is suppressed, blocking is not caused.
Another object of the present invention is to provide a polylactic acid film having further improved transparency and a production method for efficiently producing the polylactic acid film.

  As a result of intensive research, the inventors of the present invention formed a resin composition containing a weakly crystalline or amorphous polylactic acid having a D-form ratio in a specific range and a plasticizer into a film, It has been found that the above-mentioned problems can be solved by subjecting the film to a crystallization treatment, and the present invention has been completed.

That is, the polylactic acid film of the present invention is a crystal having a weak crystalline or amorphous polylactic acid of 50 to 100% by mass with a D-form ratio of 7 to 20% and a D-form ratio of 0 to 6%. A resin composition containing a polylactic acid-based resin composed of 0 to 50% by mass of polylactic acid and a plasticizer is molded and subjected to crystallization treatment.
The polylactic acid-based resin includes weakly crystalline or amorphous polylactic acid having a D-form ratio of 7 to 20% and crystalline polylactic acid having a D-form ratio of 0 to 6%. It is preferable that it consists of 5-50 mass%.

It is preferable to contain 15 to 50 parts by mass of a plasticizer per 100 parts by mass of the polylactic acid resin.
The plasticizer is preferably an acetylated monoglyceride plasticizer or a polyglycerol acetate plasticizer.
It is preferable to contain 0.01 to 2 parts by mass of a lubricant per 100 parts by mass of the polylactic acid resin.
The ratio of the D form of the crystalline polylactic acid is preferably 0 to 5%.
The heat of crystallization of the polylactic acid film of the present invention is preferably 0 to 2 J / g, and the heat of fusion is preferably 3 to 20 J / g.
The heat of fusion derived from weakly crystalline or amorphous polylactic acid having a D-form ratio of 7 to 20% is preferably 0.1 J / g or more.

In the method for producing a polylactic acid film of the present invention, a weakly crystalline or amorphous polylactic acid having a D-form ratio of 7 to 20% and a D-form ratio of 0 to 6% are included. Having a step of forming a resin composition containing 0 to 50% by mass of a crystalline polylactic acid and a plasticizer into a film, and a step of subjecting the film to a crystallization treatment. Features.
The polylactic acid-based resin includes weakly crystalline or amorphous polylactic acid having a D-form ratio of 7 to 20% and crystalline polylactic acid having a D-form ratio of 0 to 6%. It is preferable that it consists of 5-50 mass%.
The crystallization treatment is preferably a heat treatment at a temperature of 20 to 100 ° C.
The resin composition preferably contains a crystal nucleating agent.

In the polylactic acid film of the present invention, bleeding of the plasticizer on the film surface is suppressed, blocking does not occur, and flexibility and transparency are good.
Further, according to the method for producing a polylactic acid film of the present invention, a plasticizer bleed on the film surface can be suppressed, and a polylactic acid film having good flexibility and transparency can be obtained without blocking. .

  Further, the polylactic acid-based resin is a crystalline polycrystal having weak crystalline or amorphous polylactic acid 50 to 95% by mass with a D-form ratio of 7 to 20% and a D-form ratio of 0 to 6%. If it consists of 5-50 mass% of lactic acid, the polylactic acid film which further improved transparency can be manufactured efficiently.

<Polylactic acid resin>
The polylactic acid-based resin in the present invention is a crystalline having a weak crystalline or amorphous polylactic acid of 50 to 100% by mass with a D-form ratio of 7 to 20% and a D-form ratio of 0 to 6%. It consists of 0 to 50% by mass of polylactic acid, and the ratio of D-form is 7 to 20%. The weakly crystalline or amorphous polylactic acid is 50 to 95% by mass and the ratio of D-form is 0 to 6%. Those consisting of 5 to 50% by mass of crystalline polylactic acid are preferred.

(Weakly crystalline or amorphous polylactic acid)
The weakly crystalline or amorphous polylactic acid in the present invention uses L-lactic acid or a lactide that is a cyclic dimer thereof, and D-lactic acid or a lactide that is a cyclic dimer thereof as monomers. It is a copolymer obtained by condensation polymerization or ring-opening polymerization, and the ratio of D form (composition ratio of D-lactic acid units in the copolymer composed of L-lactic acid units and D-lactic acid units) is 7 to 20 %, Preferably 9 to 18%, more preferably 10 to 15%. The term “weakly crystalline or amorphous” in the present invention means that which does not show a melting point in a DSC curve obtained by measurement with a DSC (differential scanning calorimeter).

By setting the ratio of D-form in weakly crystalline or amorphous polylactic acid to 7% or more, the crystallinity of polylactic acid is sufficiently low, and bleeding of the plasticizer to the film surface is suppressed, No blocking between films. A weakly crystalline or amorphous polylactic acid having a D-form ratio exceeding 20% is not practical in view of availability.
When the ratio of D-form in polylactic acid is 7% or more, it usually does not show a clear melting point in the DSC curve, that is, it becomes amorphous. Note that even weak crystalline or amorphous polylactic acid having a D-form ratio of 7% or more can be crystallized by performing a crystallization treatment described later.

Weakly crystalline or amorphous polylactic acid may contain a small amount of units derived from hydroxycarboxylic acid. Examples of the hydroxycarboxylic acid include glycolic acid, 3-hydroxybutyric acid, 4-hydroxyvaleric acid, 6-hydroxycaproic acid and the like.
The weight average molecular weight of the weak crystalline or amorphous polylactic acid is suitably about 10,000 to 1,000,000, particularly preferably about 30,000 to 500,000 from the viewpoints of film strength, moldability, and the like.

(Crystalline polylactic acid)
The crystalline polylactic acid in the present invention is obtained by condensation polymerization or ring-opening polymerization using L-lactic acid or lactide which is a cyclic dimer thereof and D-lactic acid or lactide which is a cyclic dimer thereof as monomers. It is a copolymer, and the ratio of D-form (composition ratio of D-lactic acid unit in the copolymer composed of L-lactic acid units and D-lactic acid units) is 0 to 6%, preferably 0 to 5 %belongs to. “Crystallinity” in the present invention means a material having a melting point in a DSC curve obtained by measurement with DSC (differential scanning calorimeter).

Crystalline polylactic acid may contain a small amount of units derived from hydroxycarboxylic acid. Examples of the hydroxycarboxylic acid include glycolic acid, 3-hydroxybutyric acid, 4-hydroxyvaleric acid, 6-hydroxycaproic acid and the like.
The mass average molecular weight of the crystalline polylactic acid is suitably about 10,000 to 1,000,000, particularly preferably about 30,000 to 500,000 from the viewpoints of film strength, moldability and the like.

  By setting the content of crystalline polylactic acid in the polylactic acid resin (100% by mass) to 5% by mass or more, crystallization is promoted in the crystallization process described later, and the time for crystallization to reach saturation is shortened. As a result, the production efficiency of the film can be improved. Moreover, the fall of the transparency of the film by a crystallization process is suppressed. By setting the content of crystalline polylactic acid in the polylactic acid-based resin (100% by mass) to 50% by mass or less, the flexibility of the film due to the volatilization of the plasticizer even when left for a long time under high temperature conditions. Even if it uses as an application | coating material which can suppress a fall and is exposed to high temperature for a long time at the time of use, for example, agriculture, it does not become a problem.

<Plasticizer>
The plasticizer in the present invention is not particularly limited as long as it is a plasticizer that can be suitably used for polylactic acid. Examples of the plasticizer include aliphatic alcohol plasticizers such as triethylene glycol and polyethylene glycol; acetylated monoglyceride plasticizers such as glycerol diacetomonolaurate and glycerol diacetomonooleate; aliphatic ester plasticizers such as lactic acid esters. Agent: Polyglycerin polymerization degree of polyglycerol having a degree of polymerization of 2 to 4 and acetylation rate of 50 to 100%; adipic acid ester plasticizer; epoxidized soybean oil, epoxidized linseed oil, etc. An epoxy plasticizer is mentioned. Of these plasticizers, an acetylated monoglyceride plasticizer or a polyglycerin acetate plasticizer is preferred from the viewpoint of good compatibility with polylactic acid and good plasticizing effect.

  The blending amount of the plasticizer is preferably 15 to 50 parts by mass and particularly preferably 20 to 40 parts by mass per 100 parts by mass of the polylactic acid resin. By making the compounding amount of the plasticizer 15 parts by mass or more, the plasticizing effect is sufficient. By making the compounding quantity of a plasticizer 50 mass parts or less, the adhesiveness of a film is suppressed and workability becomes favorable.

<Crystal nucleating agent>
In order to promote crystallization of weakly crystalline or amorphous polylactic acid, the resin composition may contain a crystal nucleating agent. Crystal nucleating agents include silicate compounds such as talc, kaolinite and montmorillonite; metal oxides such as zinc oxide and magnesium oxide; various inorganic crystal nucleating agents such as calcium carbonate and barium sulfate; and other various organic crystal nucleating agents Is mentioned.
The compounding amount of the crystal nucleating agent is preferably 0.05 to 10 parts by mass, particularly preferably 0.1 to 5 parts by mass per 100 parts by mass of polylactic acid.

<Lubricant>
In order to improve the film separation from the roll during film formation, a lubricant may be added to the film. Examples of the lubricant include polyethylene wax, fatty acid amide, stearic acid and the like.
The blending amount of the lubricant is preferably 0.01 to 2 parts by mass, particularly preferably 0.1 to 1.5 parts by mass per 100 parts by mass of the polylactic acid.

<Inorganic compound fine particles>
In order to prevent the film from sticking to the metal roll or blocking the films during molding, the film may contain inorganic compound fine particles. Examples of the inorganic compound fine particles include feldspar, silica, talc, kaolin and the like. The average particle size of the inorganic compound fine particles is preferably 1 to 7 μm.

  The compounding amount of the inorganic compound fine particles is preferably 0.01 to 2 parts by mass, particularly preferably 0.1 to 1.5 parts by mass per 100 parts by mass of polylactic acid. By setting the blending amount of the inorganic compound fine particles to 0.01 parts by mass or more, adhesion of the molten film to the processing roll and blocking between the films can be sufficiently suppressed. By setting the blending amount of the inorganic compound fine particles to 2 parts by mass or less, the transparency of the film is not impaired.

<Other additive components>
Other additive components can be added to the film without departing from the spirit of the present invention. Examples of such additive components include antioxidants, ultraviolet absorbers, hindered amine light stabilizers, antistatic agents, thermal stabilizers, nucleating agents, tackifiers, pigments, and dyes. Further, a small amount of other polylactic acid, other biodegradable resin, and other synthetic resins that do not cause a problem may be blended.

<Film production method>
The method for producing a polylactic acid film of the present invention comprises a step of forming a resin composition containing a polylactic acid resin and a plasticizer to form a film (hereinafter also referred to as a forming step), and a crystallization treatment on the film. (Hereinafter, also referred to as a crystallization treatment step).

  Prior to the molding step, first, a resin composition is prepared. The preparation is usually performed by kneading. As a kneading method, raw materials such as pellets, powders, and solid strips are dry-mixed with a Henschel mixer or a ribbon mixer and supplied to a melt kneader such as a single or twin screw extruder, a Banbury mixer, a kneader, or a mixing roll. And melt kneading. Specifically, first, the raw materials are placed in a tumbler and mixed with stirring for 10 to 20 minutes. Next, melt kneading is performed at a temperature of 140 to 210 ° C. by a single screw or twin screw extruder to obtain pellets of the resin composition.

(Molding process)
Next, the resin composition pellets are supplied to an extruder and formed into a film by T-die extrusion molding, inflation molding, or the like.

(Crystallization process)
Next, the film is crystallized to crystallize the polylactic acid in the film. Examples of the crystallization treatment include heat treatment in which the film is placed at a high temperature for a certain time. Examples of the heating method include a method of placing in a high temperature room, a method of directly irradiating the film with microwaves, and the like.

The treatment temperature is usually not less than the glass transition temperature of the pre-treatment film and not more than the melting start temperature. As a processing temperature, about 20-100 degreeC is suitable.
The processing time varies depending on the processing temperature. For example, when the processing temperature is 60 ° C., the object of the present invention can be achieved by processing for about 6 hours. Even if 6 hours or more are spent, crystallization proceeds only gradually.

  By performing the crystallization treatment, it is possible to suppress the bleeding of the plasticizer on the film surface and the blocking between the films, and the effect of increasing elasticity in the viscoelasticity of the film after the treatment is recognized, and deformation due to stress occurs. But resilience is great. In addition, the polylactic acid-based resin is composed of 50 to 95% by weight of weakly crystalline or amorphous polylactic acid having a D-form ratio of 7 to 20% and crystallinity having a D-form ratio of 0 to 6%. If it consists of 5-50 mass% of polylactic acid, the transparency before a crystallization process will not be impaired. The reason why such an effect is exhibited is considered to be that as a result of the crystallization treatment, a small amount of fine crystals are uniformly generated inside the film, and the blended plasticizer and the like are trapped between the fine crystals.

The degree of crystallization progress and the degree of crystallization by the crystallization treatment can be discriminated by the amount of crystallization heat and heat of fusion measured by the test method described later.
The crystallization treatment of the polylactic acid film is preferably carried out under conditions such that the heat of crystallization of the crystallized polylactic acid film is 0 to 2 J / g, preferably 0 J / g. The heat of fusion of the crystallized polylactic acid film is preferably 3 to 20 J / g. Furthermore, it is preferable that the heat of fusion derived from weakly crystalline or amorphous polylactic acid appearing in a temperature range of less than 130 ° C. is 0.1 J / g or more.
By setting the amount of heat of crystallization and the amount of heat of fusion within the above ranges, the anti-blocking property, anti-bleeding property, transparency and flexibility of the polylactic acid film are improved.

  The polylactic acid film of the present invention thus obtained is a single layer film or a laminated film having two or more layers. The thickness of the whole film is usually 10 to 300 μm, preferably 20 to 200 μm.

Examples are shown below. In addition, this invention is not limited at all by this Example.
In the examples, the antiblocking property, antibleeding property, transparency, flexibility, progress of crystallization (crystallization heat amount) and crystallization degree (heat of fusion) of the crystallization treatment are determined by the following test methods. Measurement and evaluation.

(1) Anti-blocking property:
Two test pieces were placed in a perfect oven maintained at a temperature of 60 ° C. for two weeks with two test pieces having a length of 160 mm, a width of 25 mm, and a thickness of 0.1 mm and a load of 10 kg applied. Was peeled off and evaluated according to the following criteria.
○: It peels without resistance.
X: There is resistance when peeling.

(2) Bleed prevention:
A test piece having a length of 160 mm, a width of 25 mm, and a thickness of 0.1 mm was left in a room maintained at a temperature of 40 ° C. and a relative humidity of 90% for 3 days, and then visually evaluated according to the following criteria.
A: Almost no bleeding of additives such as plasticizers is observed.
Δ: Slight bleeding of additives such as plasticizer is observed.
X: Many bleeding of additives, such as a plasticizer, is recognized.

(3) Transparency:
Based on JIS K 7105, the total light transmittance and the diffuse transmittance were obtained, the haze of the film was calculated by the following formula, and evaluated according to the following criteria.
Haze (%) = (diffuse transmittance / total light transmittance) × 100
A: Less than 5% of haze.
○: Haze 5% or more and less than 10%.
X: Haze 10% or more.

(4-1) Flexibility (before heat treatment):
The Young's modulus of a test piece having a length of 160 mm, a width of 25 mm, and a thickness of 0.1 mm was measured and evaluated according to the following criteria.
○: Young's modulus less than 500 MPa.
X: Young's modulus 500 MPa or more.

(4-2) Flexibility (after heat treatment):
A test piece having a length of 160 mm, a width of 25 mm, and a thickness of 0.1 mm was left in a perfect oven maintained at a temperature of 80 ° C. for 3 days, and then the Young's modulus of the test piece was measured and evaluated according to the following criteria.
○: Young's modulus less than 500 MPa.
X: Young's modulus 500 MPa or more.

(5) Heat of crystallization and heat of fusion:
After the film was dried under reduced pressure at 30 ° C. for 12 hours, 4.0 mg was weighed to prepare a sample. Using a DSC7 differential scanning calorimeter manufactured by PerkinElmer, Inc., the temperature was raised from −50 ° C. to 200 ° C. at a temperature rising rate of 20 ° C./min under a nitrogen gas flow to obtain a DSC curve. From the area of the crystallization peak and melting peak appearing on the DSC curve chart, the amount of crystallization heat and the amount of heat of fusion (J / g) per gram of the sample were measured.

[Examples 1-6, Comparative Examples 1-11]
The ratio of D-form is 1%, 6%, 8% and 12% respectively, and four kinds of poly DL lactic acid and polyglycerin acetate ester plasticizers having a mass average molecular weight of about 190,000 ("Riquemar" manufactured by Riken Vitamin Co., Ltd.) PL-710 "), and a lubricant (erucic acid amide). Nine types of resin compositions were prepared according to the blending composition of each Example and each Comparative Example shown in Table 1. (The numbers indicate the number of parts by mass of each compounding component.) In all nine resin compositions, 0.5 parts by mass of a lubricant was compounded per 100 parts by mass of the polylactic acid resin.

Next, each resin composition was supplied to an extruder and subjected to inflation molding under the conditions of a cylinder temperature of 140 ° C. and a die temperature of 135 ° C. to obtain nine types of films having a thickness of 100 μm.
Of the obtained films, eight types of films except for one type were placed in a room maintained at a temperature of 60 ° C. for 6 hours, and the film was subjected to crystallization treatment to promote crystallization of polylactic acid. In the crystallization treatment, thin paper was sandwiched between the films so that the films did not contact each other. Each of the total of 17 types of 8 types of films (Examples 1 to 6, Comparative Examples 8 and 10) thus crystallized and 9 types of untreated films (Comparative Examples 1 to 7, 9 and 11). The film was measured for its heat of crystallization and heat of fusion, and subjected to each evaluation test of anti-blocking property, anti-bleeding property, transparency and flexibility before heat treatment. Table 1 shows the measured values and the evaluation results.

As shown in Table 1, in each comparative example, those using polylactic acid having a D-form concentration of 7% or more and those not subjected to crystallization treatment are both poor in blocking prevention and bleeding prevention, When the D-form concentration was less than 7%, the bleed prevention property was not improved even after crystallization treatment, and the transparency and flexibility were lowered.
On the other hand, in each Example, the improvement effect of the blocking prevention property and bleed prevention property by the crystallization treatment was remarkable, and the transparency and flexibility were hardly deteriorated.

Next, with respect to Example 2 and Comparative Example 2, the presence or absence of a crystal melting peak and the heat of fusion per gram were measured as ΔH (J / g) by the test method. The chart of each DSC curve is shown in FIG. 1 and FIG.
In Example 2, a crystal melting peak was present at 98.5 ° C., ΔH was 17.2 J / g, and crystallization was confirmed. On the other hand, Comparative Example 2 had no crystal melting peak and was not crystallized.

  From the above results, the polylactic acid film of the present invention is crystallized by a small amount of fine crystals uniformly formed inside the film by crystallization treatment such as heat treatment, so that the elasticity is moderately increased and transparency before crystallization treatment is obtained. It is considered that there will be no damage. Moreover, it is thought that the antiblocking property and the anti-bleeding property are improved because the blended plasticizer and the like are trapped between fine crystals.

[Examples 7 to 12, Comparative Examples 12 to 17]
The ratios of D-forms are 1%, 6%, and 12%, respectively, and three types of poly-DL lactic acid and polyglycerin acetate plasticizers having a mass average molecular weight of about 190,000 ("Riquemar PL-710" manufactured by Riken Vitamin Co. )), And a lubricant (erucic acid amide). Eight types of resin compositions were prepared according to the composition of each example and each comparative example shown in Table 2. (The numbers indicate the parts by weight of each compounding component.) In all eight types of resin compositions, 25 parts by mass of a plasticizer and 0.5 parts by mass of a lubricant were blended per 100 parts by mass of a polylactic acid resin.

Next, each resin composition was supplied to an extruder and subjected to inflation molding under the conditions of a cylinder temperature of 140 ° C. and a die temperature of 135 ° C. to obtain eight types of films having a thickness of 100 μm.
Crystallization of polylactic acid was carried out by subjecting the films to crystallization treatment in the room where the obtained eight kinds of films were kept at a temperature of 60 ° C. for the time shown in each Example and each Comparative Example shown in Table 2. Promoted. In the crystallization treatment, thin paper was sandwiched between the films so that the films did not contact each other. Crystallization was performed on a total of 13 types of films, ie, 9 types of films crystallized in this way (Examples 7 to 12 and Comparative Examples 12 and 13) and 4 types of untreated films (Comparative Examples 14 to 17). While measuring calorie | heat amount and heat of fusion, each evaluation test of blocking prevention property, bleed prevention property, transparency, and the softness | flexibility before and behind heat processing was done. Table 2 shows the measured values and the evaluation results.
The heat of fusion a shown in Table 2 represents the heat value of the melting peak derived from weakly crystalline or amorphous polylactic acid appearing in the temperature region below 130 ° C. in the DSC curve chart. The quantity of heat b represents the value of the quantity of heat of the melting peak derived from crystalline polylactic acid that appears in a temperature range of 130 ° C. or higher.

  As shown in Table 2, in the films (Examples 11 and 12) in which the weak crystalline or amorphous polylactic acid occupies almost all, it is necessary to perform the crystallization treatment for a long time, and the crystallization treatment Transparency is slightly reduced. The crystalline polylactic acid having a D-form ratio of 0 to 6% exceeds 50% by mass (Comparative Examples 12 and 13) has poor bleed resistance and poor flexibility after high temperature treatment even after crystallization treatment. there were. The crystallization treatment time can be short, but conversely, even if it is longer than this, the above disadvantages are not improved. Moreover, even if it mix | blends 5-50 mass% of crystalline polylactic acid with the density | concentration of D body 0-6% of a density | concentration, all the things which are not crystallized (Comparative Examples 14-17) are blocking. The prevention and bleeding prevention properties were poor or insufficient.

On the other hand, in Examples 7-10, the improvement effect of blocking prevention property and bleed prevention property was remarkable by crystallization treatment for a short time, and transparency and flexibility were also good.
From the above test results, it was found that a great effect can be obtained by blending crystalline polylactic acid having a higher degree of crystallinity in terms of shortening the crystallization treatment time.

Moreover, the chart of the DSC curve of the film obtained in Example 8 is shown in FIG. 3, and the same chart for Comparative Example 15 is shown in FIG.
In the chart of FIG. 3, it can be seen that the crystallization peak does not appear and the crystallization is progressing, and the melting peak derived from weakly crystalline or amorphous polylactic acid is in a temperature region below 130 ° C. Appears and a melting peak derived from crystalline polylactic acid appears in a temperature region of 130 ° C. or higher. In the chart of FIG. 4, a crystallization peak is observed, indicating that crystallization is insufficient, and a melting peak derived from weakly crystalline or amorphous polylactic acid is not observed.

  The polylactic acid film of the present invention can be used for agricultural films, food packaging films, other packaging films, stretch films, protective films and the like. Furthermore, it can be used in combination with other films depending on the purpose of use.

6 is a chart showing a DSC curve of the film of Example 2. It is a chart which shows the DSC curve of the film of the comparative example 2. It is a chart which shows the DSC curve of the film of Example 8. 16 is a chart showing a DSC curve of the film of Comparative Example 15.

Claims (12)

  It consists of 50 to 100% by mass of weakly crystalline or amorphous polylactic acid having a D-form ratio of 7 to 20% and 0 to 50% by mass of crystalline polylactic acid having a D-form ratio of 0 to 6%. A polylactic acid film obtained by molding a resin composition containing a polylactic acid-based resin and a plasticizer and subjecting it to a crystallization treatment.   The polylactic acid-based resin comprises weakly crystalline or amorphous polylactic acid having a D-form ratio of 7 to 20% and crystalline polylactic acid having a D-form ratio of 0 to 6%. The polylactic acid film according to claim 1, comprising 5 to 50% by mass.   The polylactic acid film according to claim 1 or 2, comprising 15 to 50 parts by mass of a plasticizer per 100 parts by mass of the polylactic acid resin.   The polylactic acid film according to any one of claims 1 to 3, wherein the plasticizer is an acetylated monoglyceride plasticizer or a polyglycerol acetate plasticizer.   The polylactic acid film according to any one of claims 1 to 4, comprising 0.01 to 2 parts by mass of a lubricant per 100 parts by mass of the polylactic acid-based resin.   The polylactic acid film according to claim 2, wherein a ratio of the D form of the crystalline polylactic acid is 0 to 5%.   The polylactic acid film according to any one of claims 1 to 6, wherein the heat of crystallization is 0 to 2 J / g and the heat of fusion is 3 to 20 J / g.   The polylactic acid film according to claim 7, wherein the heat of fusion derived from weakly crystalline or amorphous polylactic acid having a D-form ratio of 7 to 20% is 0.1 J / g or more. It consists of 50 to 100% by mass of weakly crystalline or amorphous polylactic acid having a D-form ratio of 7 to 20% and 0 to 50% by mass of crystalline polylactic acid having a D-form ratio of 0 to 6%. Forming a resin composition containing a polylactic acid-based resin and a plasticizer into a film;
And a step of crystallizing the film. A method for producing a polylactic acid film.   The polylactic acid-based resin comprises weakly crystalline or amorphous polylactic acid having a D-form ratio of 7 to 20% and crystalline polylactic acid having a D-form ratio of 0 to 6%. The method for producing a polylactic acid film according to claim 9, comprising 5 to 50% by mass.   The method for producing a polylactic acid film according to claim 9 or 10, wherein the crystallization treatment is a heat treatment at a temperature of 20 to 100 ° C. The method for producing a polylactic acid film according to any one of claims 9 to 11, wherein the resin composition contains a crystal nucleating agent.

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