JPH09328536A - Method for producing polyhydroxycarboxylic acid copolymer resin - Google Patents

Abstract

(57) [Abstract] [Problem] It can be used for agricultural and horticultural materials, fishery materials, binders, etc., and is hydrolyzed even if discarded after use, or carbon dioxide and water due to microorganisms in the soil. To provide a method for easily producing a polyhydroxycarboxylic acid copolymer resin that is decomposed into the like. SOLUTION: A polymerization catalyst such as 1,3-substituted-1,1,3,3-tetraorganodistannoxane is added to a mixture of hydroxycarboxylic acid such as L-lactic acid and metal oxide such as calcium hydroxide or phosphoric acid. Is added, and the mixture is heated and stirred under reduced pressure or in the presence of an organic solvent to obtain a copolymer resin. Or
The hydroxycarboxylic acid to which the polymerization catalyst has been added is dehydrated or made into an oligomer, then a metal oxide is added, and the mixture is heated and stirred under reduced pressure or in the presence of an organic solvent to obtain a copolymer resin.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing a hydrolyzable and biodegradable polyhydroxycarboxylic acid copolymer resin.

[0002]

2. Description of the Related Art
Various resin moldings are used as agricultural and horticultural materials (for example, polyvinyl chloride film) and fishing materials (for example, fishing nets made of polyethylene fibers), and these materials are eventually discarded. Therefore, there is a demand for a resin that does not become a pollution source even when discarded, and that is hydrolyzed over time or biodegraded by microorganisms in the soil. INDUSTRIAL APPLICABILITY The present invention can be utilized for such agricultural and horticultural materials, fishery materials, binders, etc., and even if it is discarded after use, it is decomposed into carbon dioxide and water by hydrolysis and microorganisms in the soil. It is an object of the present invention to provide a method for easily producing a hydroxycarboxylic acid copolymer resin.

[0003]

Means for Solving the Problems As a result of earnest studies to achieve the above object, the present inventor has found that a polymerization catalyst is added to a mixture of hydroxycarboxylic acid and a metal oxide, and the mixture is added under reduced pressure or in the presence of an organic solvent. To a copolymer resin by heating and stirring, or after dehydrating the hydroxycarboxylic acid to which a polymerization catalyst has been added or forming an oligomer, add a metal oxide, and heat and stir under reduced pressure or in the presence of an organic solvent. It was found that an easily hydrolyzable or biodegradable polyhydroxycarboxylic acid copolymer resin can be produced by using the copolymer resin as a copolymer resin to complete the present invention.

[0004]

BEST MODE FOR CARRYING OUT THE INVENTION The hydroxycarboxylic acid used in the present invention is preferably a hydroxycarboxylic acid of a fatty acid,
When it has asymmetric carbon, it may be any of D-form, L-form and racemic form. Moreover, you may use together 2 or more types of hydroxycarboxylic acid. Specific examples of such a hydroxycarboxylic acid include lactic acid, glycolic acid, tartaric acid, citric acid, malic acid, oxyvaleric acid and 2-hydroxystearic acid.

In the present invention, the polymerization catalyst used in the polymerization reaction of hydroxycarboxylic acid is preferably 1,3-substituted-1,1,3,3-tetraorganodistannoxane, which has a high catalytic activity. Here, the organo group bonded to the tin atom is a methyl group, an ethyl group, a propyl group, a butyl group,
It may be any of an octyl group, an allyl group, a benzyl group, a phenyl group and a naphthyl group, but a butyl group is preferable in view of solubility and cost. Further, the substituents at the 1 and 3 positions may be any of halogen, thiocyano group, hydroxyl group, alkoxy group and carboxyl group.

The metal oxide used in the present invention includes metal hydroxides such as aluminum hydroxide, calcium hydroxide, zinc hydroxide and barium hydroxide, and inorganic acids such as diphosphorus pentoxide and tetraphosphorus pentoxide. Are preferred, inorganic acids such as phosphoric acid and boric acid, calcium oxide, magnesium oxide, zinc oxide, etc., or a mixture thereof.

The organic solvent used in the present invention may be any one as long as it has a boiling point higher than that of water and is not compatibilized with water, but it is a natural product and even if it remains in the resin, it has no adverse effect on the environment or human body. Less D-limonene is preferred.

[0008]

The hydrolyzable or biodegradable polyhydroxycarboxylic acid copolymer resin can be easily and efficiently produced by the above-mentioned means. Even if these resins are discarded, they are hydrolyzed with the passage of time, and after their molecular weight is lowered, they are decomposed into carbon dioxide and water by the microorganisms in the soil.

[0009]

EXAMPLES The present invention will be described in more detail with reference to Examples and Comparative Examples. (Example 1) In a reactor capable of heating and depressurizing 5 l, L-
20 mol of lactic acid and 0.2 mol of aluminum hydroxide and 1
-Chloro-3-hydroxy-1,1,3,3-tetrabutyl distannoxane (2 mmol) was added, and the mixture was stirred at 170 ° C for 30 minutes.
The mixture was heated and stirred for 24 hours under reduced pressure of mmHg or less. The weight average molecular weight of the obtained resin was measured and found to be 15,000.
It was 0. As a GPC device for measuring the molecular weight, a liquid chromatography pump ShodexDS
-4, differential refractive index detector Shodex RI-71 and column GPC806M (manufactured by Showa Denko) were used.

(Example 2) 0.2 m of aluminum hydroxide
Polymerization was performed in the same manner as in Example 1 except that 0.2 mol of magnesium hydroxide was used instead of ol. The weight average molecular weight of the obtained resin was 11,000.

(Example 3) Aluminum hydroxide 0.2 m
Polymerization was performed in the same manner as in Example 1 except that 0.2 mol of calcium hydroxide was used instead of ol. The weight average molecular weight of the obtained resin was 10,000.

(Example 4) Example 1 using 20 mol of L-lactic acid, 1 mol of phosphoric acid and 2 mmol of 1,3-dichloro-1,1,3,3-tetrabutyl distanoxane.
Polymerization was carried out under the same conditions as in. The weight average molecular weight of the obtained resin was 29,000.

Example 5 Example 1 was prepared using 20 mol of L-lactic acid, 1 mol of boric acid and 2 mmol of 1,3-dichloro-1,1,3,3-tetrabutyldistannoxane.
Polymerization was carried out under the same conditions as in. The weight average molecular weight of the obtained resin was 14,000.

Comparative Example The same polymerization as in Example 1 was carried out except that aluminum hydroxide was not added. The weight average molecular weight of the obtained resin was 25,000.

(Hydrolysis Experiment) The copolymer resins and homopolymers obtained in Examples 1 to 5 and Comparative Example were made to have a thickness of 2
When the sheet was molded into a sheet of 0.1 mm and immersed in a 0.1 N aqueous solution of sodium hydroxide at 30 ° C. for 48 hours, only the surface of the sheet of Comparative Example was whitened. Became brittle and collapsed.

[0016]

As described above, according to the present invention, a hydrolyzable or biodegradable polyhydroxycarboxylic acid copolymer resin can be easily and efficiently produced in one pot, and the obtained resin is a viscous resin. The molded product can be used as a binder and as an agricultural / horticultural material and a fishery material, and even if it is discarded, it is hydrolyzed over time (it is more easily hydrolyzed than lactic acid homopolymer),
Alternatively, it does not become a pollution source because it is decomposed into carbon dioxide and water by microorganisms in the soil. Further, it has an effect that it has a high melt viscosity and is easy to process.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical indication C08L 67/04 KJR C08L 67/04 KJR

Claims (6)

[Claims] 1. A polyhydroxycarboxylic acid copolymerization characterized by adding a polymerization catalyst to a mixture of a hydroxycarboxylic acid and a metal oxide, and heating and stirring under reduced pressure or in the presence of an organic solvent to obtain a copolymer resin. Resin manufacturing method. 2. A hydroxycarboxylic acid to which a polymerization catalyst has been added is dehydrated or made into an oligomer, and then a metal oxide is added and heated and stirred under reduced pressure or in the presence of an organic solvent to obtain a copolymer resin. And a method for producing a polyhydroxycarboxylic acid copolymer resin. 3. The hydroxycarboxylic acid is lactic acid, glycolic acid, tartaric acid, citric acid, malic acid, oxyvaleric acid, 2-
3. The method for producing a polyhydroxycarboxylic acid copolymer resin according to claim 1, which is hydroxystearic acid, salicylic acid, o-oxycinnamic acid, or a mixture thereof. 4. The polymerization catalyst is 1,3-substituted-1,1,3,3
-The method for producing a polyhydroxycarboxylic acid copolymer resin according to any one of claims 1 to 3, which is tetraorganodistannoxane. 5. The metal oxide is a metal hydroxide such as aluminum hydroxide, calcium hydroxide, zinc hydroxide or barium hydroxide, or an anhydride of an inorganic acid such as diphosphorus pentoxide or tetraphosphorus pentoxide. At least one metal compound selected from the group consisting of inorganic acids such as phosphoric acid and boric acid, and metal oxides in a narrow sense such as calcium oxide, magnesium oxide, and zinc oxide. A method for producing the polyhydroxycarboxylic acid copolymer resin according to any one of 1. 6. The method for producing a polyhydroxycarboxylic acid copolymer resin according to any one of claims 1 to 5, wherein the organic solvent is D-limonene.