JPH10204157A - Production of polyhydroxycarboxylic acid resin - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily produce a polyhydroxycarboxylic acid resin which can find utility in agricultural and horticultural materials, fishing materials, binders, etc., and, when discarded after being wasted, can be decomposed into carbon dioxide and water by hydrolysis and/or degradation by soil microbes or the like. SOLUTION: A mixture of a hydroxycarboxylic acid dimer (e.g. L-lactide) or a hydroxycarboxylic acid oligomer (e.g. lactic acid oligomer) with a saccharide (e.g. D-glucose or corn starch) is heated under agitation in vacuo or dehydratively polymerized in an organic solvent in the presence of a polymerization catalyst (desirably 1,3-substituted-1,1,3,3-tetraorganodistanoxane) to produce a polyhydroxycarboxylic acid resin.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a hydrolyzable and biodegradable polyhydroxycarboxylic acid 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. The present invention can be used for such agricultural and horticultural materials, fishery materials, binders, and the like, and is decomposed into carbon dioxide and water by hydrolysis and / or microorganisms in the soil even after disposal after use. It is an object of the present invention to provide a method for easily producing a polyhydroxycarboxylic acid resin.

[0003]

Means for Solving the Problems The present inventors have made intensive studies to achieve the above object, and as a result, added a polymerization catalyst to a mixture of a hydroxycarboxylic acid dimer or a hydroxycarboxylic acid oligomer and a saccharide. It has been found that a hydrolyzable and biodegradable polyhydroxycarboxylic acid resin can be produced by performing dehydration polymerization, and the present invention has been completed.

[0004]

DETAILED DESCRIPTION OF THE INVENTION The hydroxycarboxylic acid dimer or hydroxycarboxylic acid oligomer used in the present invention includes lactic acid, glycolic acid, tartaric acid, citric acid, malic acid, oxyvaleric acid, 2-hydroxystearic acid, salicylic acid. And dimers or oligomers such as o-oxycinnamic acid, or a mixture thereof. Preferred hydroxycarboxylic acid dimers are cyclic dimers, particularly preferably L-lactide. A preferred hydroxycarboxylic acid oligomer is a lactic acid oligomer.

The saccharides used in the present invention are preferably natural products, such as D-glucose, D-fructose,
Monosaccharides such as D-mannose and D-galactose; oligosaccharides (oligosaccharides) such as maltose and sugar (sucrose); starch;
In particular, polysaccharides such as corn starch, sweet potato starch, wheat starch and the like, and mixtures thereof can be mentioned.

[0006] In the present invention, the polymerization catalyst used for the polymerization reaction of a hydroxycarboxylic acid dimer or a hydroxycarboxylic acid oligomer with a saccharide is 1,3-substituted-
1,1,3,3-tetraorganodistanoxane can be mentioned. Here, the organo group bonded to the tin atom may be any of a methyl group, an ethyl group, a propyl group, a butyl group, an octyl group, an allyl group, a benzyl group, and a phenyl group. Is preferred. The substituent at the 1,3-position may be any of a halogen, a thiocyano group, a hydroxyl group, an alkoxy group, and a carboxyl group.

As the polymerization catalyst used in the present invention, any catalyst usually used for ester polymerization may be used. However, the 1,3-substituted catalyst has high catalytic activity and high hydrolysis resistance. -1,1,3,3-tetraol is preferably nodistanoxane.

The organic solvent used in the present invention may be any organic solvent as long as it has a higher boiling point than water and is not compatible with water. D-limonene, which has little adverse effect on the human body, is preferred. When a copolymer is synthesized using a cyclic dimer of hydroxycarboxylic acid and a saccharide as starting materials, it is only necessary to heat and stir under a nitrogen stream. When a copolymer is synthesized using a hydroxycarboxylic acid oligomer and a saccharide as starting materials, it is preferable to carry out a dehydration-condensation reaction with heating and stirring under reduced pressure or to carry out an azeotropic dehydration-condensation reaction in an organic solvent. When a copolymer is synthesized using hydroxycarboxylic acid and a saccharide as starting materials, a dehydration-condensation reaction with heating and stirring under reduced pressure or an azeotropic dehydration-condensation reaction in an organic solvent is preferably performed.

[0009]

According to the above-mentioned means, a hydrolyzable and biodegradable polyhydroxycarboxylic acid resin can be easily and efficiently produced in one pot. Even if these resins are discarded, they are hydrolyzed and / or decomposed into carbon dioxide and water by microorganisms in the soil with the passage of time.

[0010]

【Example】

(Example 1) 1 mol (144 g) of L-lactide, 14.4 g of corn starch and 1,3-dichloro-1,1,
0.2 mmol of 3,3-tetrabutyldistannoxane
(0.1 g) in a reactor and the atmosphere is replaced with nitrogen.
Stirred at 80 ° C. for 24 hours. The weight average molecular weight (Mw) of the obtained lactic acid-starch copolymer was 57,000.

The molecular weight of the obtained polyhydroxycarboxylic acid resin was measured by using GPC. The solvent used was chloroform, and the temperature was 40 ° C. and the flow rate was 1.0 ml / mi.
n. GPC equipment is manufactured by Japan Millipore Limited
High pressure pump (Model 510 for high-speed liquid chromatograph)
And Showa Denko's differential refractive index detector (Shodex)
RI-71) and column GPCK806M. The molecular weight is a value obtained by converting polystyrene as a standard sample.

Example 2 1 mol of 90% L-lactic acid (1 mol
00g), 10 g of corn starch and 0.1 m of 1,3-dichloro-1,1,3,3-tetrabutyldistannoxane
mol (50 mg) was placed in a reactor, and heated and stirred at 170 ° C. for 3 hours under reduced pressure. The weight average molecular weight of the obtained lactic acid oligomer was 1,200. 10 g of corn starch was put therein, and the mixture was heated and stirred at 170 ° C. for 17 hours. The weight average molecular weight (Mw) of the obtained lactic acid-starch copolymer was 28,000.

(Evaluation of Biodegradability by Hydrolysis Acceleration Test) In general, biodegradation of a biodegradable resin by a microorganism first occurs after hydrolysis and a decrease in the molecular weight of the resin occurs.
It is known that degradation by microorganisms occurs. Therefore, for the biodegradable resin, the evaluation of the hydrolyzability can be directly employed as one of the methods for evaluating the biodegradability. Then, in order to evaluate the hydrolyzability of the polyhydroxycarboxylic acid resin, a 2 mm sheet of a lactic acid homopolymer and a lactic acid-starch copolymer having a Mw of 12,000 was immersed in a 0.1 N NaOH aqueous solution, and 4 days after the immersion. The weight loss was measured. When the initial weight was 100, the lactic acid homopolymer was reduced to 91, whereas the lactic acid-starch copolymer was reduced to 75. From this, it was found that the polyhydroxycarboxylic acid resin obtained by the present invention has a higher biodegradation rate than the polyhydroxycarboxylic acid homopolymer.

[0014]

As described above, according to the present invention, a hydrolyzable and biodegradable polyhydroxycarboxylic acid resin can be easily and efficiently produced in one pot.
The obtained resin is used as a binder,
It can be used as horticultural material and fishery material,
Even if discarded, it is not a source of pollution because it is hydrolyzed over time or decomposed into carbon dioxide and water by microorganisms in the soil.

 ──────────────────────────────────────────────────の Continued on the front page (72) Inventor Nobuyuki Sakuta 2-2-8 Mishino-cho, Nishi-ku, Hiroshima-shi, Hiroshima Nishikawa Rubber Industries Co., Ltd.

Claims (6)

[Claims] 1. A method for producing a polyhydroxycarboxylic acid resin, comprising adding a polymerization catalyst to a mixture of a hydroxycarboxylic acid dimer or a hydroxycarboxylic acid oligomer and a saccharide and performing dehydration polymerization. 2. A method in which a polymerization catalyst is added to a mixture of a hydroxycarboxylic acid dimer or a hydroxycarboxylic acid oligomer and a saccharide, and the mixture is heated and stirred under reduced pressure or subjected to dehydration polymerization in an organic solvent. A method for producing a polyhydroxycarboxylic acid resin. 3. The method for producing a polyhydroxycarboxylic acid resin according to claim 1, wherein the hydroxycarboxylic acid dimer is L-lactide and the hydroxycarboxylic acid oligomer is a lactic acid oligomer. 4. The saccharides are monosaccharides such as D-glucose, D-fructose, D-mannose, D-galactose,
The polyhydroxycarboxylic acid according to any one of claims 1 to 3, which is a oligosaccharide (oligosaccharide) such as maltose or sugar (sucrose), a polysaccharide such as corn starch, sweet potato starch or wheat starch, or a mixture thereof. A method for producing an acid resin. 5. A polymerization catalyst comprising 1,3-substituted-1,1,3,3
The method for producing a polyhydroxycarboxylic acid resin according to any one of claims 1 to 4, wherein the resin is a tetraorganodistanoxane. 6. The method according to claim 2, wherein the organic solvent is D-limonene or decalin (decahydronaphthalene).
The method for producing a polyhydroxycarboxylic acid resin according to the above item.