JP2005320389A - Polylactic acid film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polylactic acid film which has a high elongation at break and good impact resistance as well as a relatively high modulus of elasticity. <P>SOLUTION: The polylactic acid film is one having a high elongation at break and comprising 100 pts.wt. polylactic acid, 7 to 13 pts.wt. plasticizer, and 0.5 to 4 pts.wt. organically modified layered silicate. In one embodiment of the polylactic acid, the plasticizer is a mono- or poly-glycerol acetic ester plasticizer. In another embodiment, the organically modified layered silicate is a layered silicate between layers of which a primary to tertiary amine salt or a quaternary ammonium salt is ionically bonded. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a polylactic acid film having a high elongation at break.

In recent years, products that are rapidly decomposed after disposal and that do not accumulate in the natural environment have been desired, and various biodegradable resins are commercially available. As a biodegradable resin that can be formed into a film by a T-die extruder, an aliphatic polyester-based resin is known. For example, polylactic acid is excellent in transparency but lacks flexibility. For this reason, attempts have been made to blend a plasticizer to impart flexibility to the film.
When a plasticizer is added to polylactic acid, the elongation at break value can be increased, but the elastic modulus decreases in proportion thereto, and a result that satisfies the impact resistance cannot be obtained. Furthermore, when a large amount of plasticizer is added, obstacles such as bleeding of the additive on the surface also occur.

  On the other hand, for the purpose of improving the physical properties of a product made of a biodegradable resin containing polylactic acid, it has been proposed to blend a layered silicate organized into polylactic acid (see, for example, Patent Documents 1 and 2). . Patent Document 1 shows that there is an effect in improving rigidity and biodegradation speed, but no study has been made on film formation, and the invention disclosed in Patent Document 2 is a film tear. The purpose is to improve mechanical strength such as strength and Young's modulus and heat resistance, and no mention is made of improvement in elongation at break of a plasticized polylactic acid film.

JP 2001-89646 A JP 2003-82212 A

  The present invention has been made to solve the above-mentioned problems, and it has a high elongation at break and a good impact resistance while maintaining a high elastic modulus by keeping the blending amount of the plasticizer relatively small. The purpose is to provide a lactic acid film.

As a result of intensive studies, the present inventors solved the above problem by blending a specific amount of an organized layered silicate into a plasticized polylactic acid with a relatively small amount of plasticizer. The present invention has been completed by finding out what can be done.
That is, the gist of the present invention is a polylactic acid film having a high elongation at break containing 7 to 13 parts by weight of a plasticizer and 0.5 to 4 parts by weight of an organized layered silicate per 100 parts by weight of polylactic acid. is there.
The plasticizer is a mono- or polyglycerin acetate plasticizer, and the organically modified layered silicate is a layered silicate in which a primary to tertiary amine salt or a quaternary ammonium salt is ionically bonded between layers. desirable.

  The polylactic acid film of the present invention has a high elastic modulus since the blending amount of the plasticizer is relatively small, and has a high elongation at break and good impact resistance.

The polylactic acid used in the polylactic acid film of the present invention is a homopolymer or copolymer obtained by condensation polymerization or ring-opening polymerization using L-lactic acid or D-lactic acid or lactide which is a cyclic dimer thereof as a monomer. It is a coalescence.
The copolymerized polylactic acid includes not only a polymer composed only of lactic acid but also one obtained by blending lactic acid with a small amount of hydroxycarboxylic acid as a copolymerization component. Examples of such hydroxycarboxylic acids include glycolic acid, 3-hydroxybutyric acid, 4-hydroxyvaleric acid, 6-hydroxycaproic acid and the like.
The molecular weight of the polylactic acid used in the present invention is not particularly limited, but a weight average molecular weight of about 10,000 to 1,000,000 is suitable from the viewpoint of film strength and molding processability, and particularly 30,000 to About 500,000 is preferable.

The plasticizer to be mixed with polylactic acid in the present invention is not particularly limited as long as it is a plasticizer that can be suitably used for polylactic acid, and examples thereof include triethylene glycol and polyethylene glycol. Aliphatic alcohol plasticizers, aliphatic ester plasticizers such as tributyl acetyl citrate, glycerin monolauryl diacetate, and lactic acid esters, and epoxidized soybean oil, epoxidized linseed oil, etc. May include mono- or polyglycerol acetate plasticizers.
The amount of the plasticizer is 7 to 13 parts by weight, preferably 8 to 12 parts by weight per 100 parts by weight of polylactic acid. If the amount of the plasticizer is less than 7 parts by weight, the plasticizing effect is not sufficient, and the film Is not preferable because the tensile modulus of elasticity of the film is lowered.

  Examples of the layered silicate before the organic cation treatment of the organically layered layered silicate mixed in the polylactic acid include swelling layered clay minerals such as smectite and vermiculite, and swelling fluorine mica. Specific examples of smectite include montmorillonite, beidellite, hectorite, saponite and the like, and specific examples of swellable fluorine mica include Na type fluorine tetrasilicon mica, Na type teniolite, Li type teniolite and the like. In addition to the above, kanemite, macatite, magadiite, kenyaite and the like can also be used.

The organically modified layered silicate used in the present invention is obtained by treating the above layered silicate with an organic cation, and a layered silicate in which a primary to tertiary amine salt or a quaternary ammonium salt is ionically bonded between the layers. Is preferred. Examples of the organic cation include phosphonium salts in addition to the above amine salts and ammonium salts. Examples of the primary amine include octylamine, dodecylamine, and octadecylamine. Examples of the secondary amine include dioctylamine, methyloctadecylamine, and dioctadecylamine. Examples of the tertiary amine include trioctylamine, Examples thereof include dimethyldodecylamine and didodecylmonomethylamine, and examples of the quaternary ammonium ion include tetraethylammonium, octadecyltrimethylammonium, dihydroxyethylmethyloctadecylammonium and the like. Examples of the phosphonium ion include tetraethylphosphonium, tetrabutylphosphonium, hexadecyltributylphosphonium, tetrakis (hydroxymethyl) phosphonium, and 2-hydroxyethyltriphenylphosphonium. These compounds may be used alone or in combination of two or more.
The layered silicate used in the present invention cannot be expected to improve the elongation at break of the film obtained according to the present invention unless it is organicized by an organic cation treatment.

  As a method of treating the layered silicate with an organic cation, the layered silicate is dispersed in water or alcohol, and the salt of the organic cation is added and mixed to ion-exchange the inorganic ions of the layered silicate with the organic onium ion. A method is mentioned.

  The organic layered silicate is added in an amount of 0.5 to 4 parts by weight, preferably 1 to 3.5 parts by weight, per 100 parts by weight of polylactic acid. A high elongation at break cannot be obtained, and when the amount exceeds 4 parts by weight, the elongation at break of the film rapidly decreases.

  In the present invention, other components can be added in addition to the above components without departing from the spirit of the present invention. Examples of such additive components include lubricants, antioxidants, ultraviolet absorbers, hindered amine light stabilizers, antistatic agents, thermal stabilizers, nucleating agents, tackifiers, pigments and dyes. it can.

  The polylactic acid film produced by the production method of the present invention is a single layer or a laminated film of two or more layers, and the thickness of the whole film is usually in the range of 10 to 300 μm, preferably 20 to 200 μm.

In the method for producing a polylactic acid film of the present invention, the resin composition constituting the film is first kneaded, and the method is a commonly used kneading method. Specifically, pellets, powders, solid strips, etc. are dry-mixed with a Henschel mixer or ribbon mixer, and supplied to a melt kneader such as a single or twin screw extruder, Banbury mixer, kneader, or mixing roll. Can be melt-kneaded. For example, first, the resin composition is placed in a tumbler and stirred and mixed for 10 to 20 minutes. Next, it can be melt-kneaded at a temperature of 140 to 210 ° C. with a single screw or twin screw extruder or the like to form pellets of the resin composition.
Next, the resin composition pellets are supplied to an extruder and formed into a film by T-die extrusion molding or inflation molding.

  Examples of the present invention will be described below, but the present invention is not limited to the examples.

Examples 1-3, Comparative Examples 1-8
The following were prepared as a resin for film forming and a compounding agent.
Resin: Polylactic acid (containing 1% D-form, glass transition temperature 60 ° C, melting temperature 170 ° C)
Polyglycerin acetate plasticizer [made by Riken Vitamin Co., Ltd., trade name “Riquemar PL-710”]
Layered silicate: Montmorillonite (Kunimine Industries, trade name “Kunipia F”)
Organized layered silicate A: the above layered silicate organized with n-octadecylamine Organized layered silicate B: the above layered silicate organized with poly (ethylene glycol) stearylamine Lubricant : Elcaic acid amide Eleven types of resin compositions were prepared according to the blending compositions of the examples and comparative examples shown in Table 1 (numbers indicate the parts by weight of each blending component). In all 11 resin compositions, 0.5 parts by weight of a lubricant was blended per 100 parts by weight of polylactic acid.
Subsequently, each composition was supplied to the extruder, and was extruded from the T die into a film by extrusion molding under conditions of a cylinder temperature of 140 ° C. and a die temperature of 135 ° C. Next, the molten film extruded from the T-die was rapidly cooled with a cast roll set at a first roll temperature of 45 ° C. and a second roll temperature of 20 ° C. to obtain 11 types of films having a thickness of 100 μm.
About each obtained film, elongation at break and a tensile elasticity modulus were measured by a conventional method, and the result is shown in Table 1.

  As is clear from the test results shown in Table 1, each of the films of each example showed a tensile modulus higher than 2 GPa and an elongation at break higher than 200%, but in each comparative example, a high tensile modulus. It can be seen that the film having a low elongation at break has a low elongation at break, and the film having a large amount of plasticizer has an increased elongation at break, but the tensile modulus decreases.

The polylactic acid film of the present invention can be used for agricultural films, food packaging films, packaging bags, stretch films, protective films and the like.

Claims (3)

A polylactic acid film having a high elongation at break containing 7 to 13 parts by weight of a plasticizer and 0.5 to 4 parts by weight of an organically layered silicate per 100 parts by weight of polylactic acid.   The polylactic acid film according to claim 1, wherein the plasticizer is a mono- or polyglycerol acetate plasticizer.   2. The polylactic acid film according to claim 1, wherein the organized layered silicate is a layered silicate in which a primary to tertiary amine salt or a quaternary ammonium salt is ionically bonded between layers.