JPH10218977A - Production of polyhydroxycarboxylic acid resin - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a process for easily producing a hydrolyzable and/or biodegradable polyhydroxycarboxylic acid resin which can be used for agricultural and horticultural materials, fishery materials, medical tools, and medicinal materials and is decomposed into carbon dioxide and water by microorganisms in soil when disposed of after being used. SOLUTION: A mixture of a zinc compd. and at least one compd. selected from among hydroxycarboxylic acids (e.g. L-lactic acid or glycolic acid), hydroxycarboxylic acid dimers (e.g. D,L-lactide), and hydroxycarboxylic acid oligomers (e.g. a lactic acid oligomer) is subjected to a thermal polymn. in the presence of a polymn. catalyst (a 1,3-substd.-1,1,3,3-tetraorganodistanoxane) under stirring in a reduced pressure or under a nitrogen stream or is subjected to azeotropic dehydrating soln. polymn. in an org. solvent, thus giving 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, fishing materials, medical tools, medical materials, and the like, and is hydrolyzed to be decomposed into carbon dioxide and water by microorganisms in the soil even if discarded after use. It is an object of the present invention to provide a method for easily producing a water-soluble and / or biodegradable polyhydroxycarboxylic acid resin.

[0003]

Means for Solving the Problems The present inventors have made intensive studies to achieve the above object, and have found that at least one kind of hydroxycarboxylic acid, hydroxycarboxylic acid dimer or hydroxycarboxylic acid oligomer and zinc compound A polymerization catalyst is added to the mixture, and the mixture is heated and stirred under reduced pressure or under a nitrogen stream to carry out polymerization, or azeotropic dewatering polymerization is carried out in an organic solvent to form a hydrolyzable and biodegradable polyhydroxyl. They have found that a carboxylic acid resin can be produced, and have completed the present invention.

That is, when a copolymer is synthesized from a hydroxycarboxylic acid and a zinc compound or a hydroxycarboxylic acid oligomer and a zinc compound as starting materials, a polymerization catalyst is added to the raw materials, and the mixture is heated and stirred under reduced pressure to carry out dehydration polymerization. Or azeotropic dewatering polymerization in an organic solvent.

As the organic solvent used in the azeotropic dewatering polymerization, any organic solvent which does not mix with water may be used, but the boiling point is appropriate as the reaction temperature, and it is a natural product. D-limonene which does not adversely affect the environment and the human body even if it remains in the resin is preferable.

On the other hand, when a copolymer is synthesized using a hydroxycarboxylic acid dimer and a zinc compound as starting materials,
It is only necessary to add a polymerization catalyst to the raw materials and heat and stir the mixture under a nitrogen stream.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The hydroxycarboxylic acid used in the present invention includes lactic acid, glycolic acid, tartaric acid, citric acid, malic acid, oxyvaleric acid, 2-hydroxystearic acid, salicylic acid, o-oxycinnamic acid, or These mixtures can be mentioned. Preferred hydroxycarboxylic acids are lactic acid and glycolic acid from the viewpoint of availability.

The hydroxycarboxylic acid dimer or hydroxycarboxylic acid oligomer used in the present invention includes:
Examples thereof include dimers or oligomers of lactic acid, glycolic acid, tartaric acid, citric acid, malic acid, oxyvaleric acid, 2-hydroxystearic acid, salicylic acid, o-oxycinnamic acid, and mixtures thereof. Preferred hydroxycarboxylic acid dimers are cyclic dimers (particularly preferably D, L-lactide), and preferred hydroxycarboxylic acid oligomers are lactic acid oligomers and glycolic acid oligomers.

The zinc compound used in the present invention includes: zinc metal; zinc oxide; zinc organic acid salts such as zinc acetate and zinc lactate; zinc halides such as zinc chloride; alkoxy zincs such as zinc acetylacetonate; Any of organic zinc such as diethyl zinc may be used.

In the present invention, any commonly used esterification catalyst may be used as a polymerization catalyst used for the polymerization reaction of a hydroxycarboxylic acid, a hydroxycarboxylic acid dimer or a hydroxycarboxylic acid oligomer with a zinc compound. However, 1,3-substituted-1,1,3,3-tetraorganodistanoxane is preferred. 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. Also, 1,3
The substituent at the position may be any of halogen, thiocyano group, hydroxyl group, alkoxy group and carboxyl group.

[0011]

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.

[0012]

【Example】

Example 1 (Reaction between hydroxycarboxylic acid and zinc lactate) 1 mol (100 g) of 90% L-lactic acid and 10 m of zinc lactate
mol (2.4 g) and 1,3-dichloro-1,1,3,
0.1 mmol of 3-tetrabutyldistannoxane (50
mg) in a 500 ml reactor,
The mixture was heated and stirred under reduced pressure for a time. The weight average molecular weight (Mw) of the obtained lactic acid-zinc copolymer was 8,000.

The molecular weight of the obtained polyhydroxycarboxylic acid resin was measured by using a gel filtration chromatograph (GPC). The solvent used was chloroform and the temperature was 40
At 100C, the flow rate is 1.0 ml / min. The GPC apparatus is a high pressure pump (Model 510 for high performance liquid chromatography) manufactured by Nippon Millipore Limited, a differential refractive index detector (Showex RI-71) manufactured by Showa Denko KK, and a column G.
PCK806M. The molecular weight is a value obtained by converting polystyrene as a standard sample.

Example 2 (Reaction between hydroxycarboxylic acid and zinc lactate) 1 mol (90 g) of D, L-lactic acid, 10 mmol of zinc lactate
l (2.4 g) and 0.1 mmol of 1,3-dichloro-1,1,3,3-tetrabutyldistannoxane (50 m
g) and 100 ml of D-limonene into a 500 ml reactor, and a device (Dean-St) for discharging the produced water out of the system
ark trap) to conduct azeotropic dewatering polymerization for 24 hours.
Time went. The weight average molecular weight (Mw) of the obtained lactic acid-zinc copolymer was 16,000.

Example 3 (Reaction of cyclic dimer of hydroxycarboxylic acid with zinc lactate) 1 mol (144 g) of D, L lactide and 20 m of zinc lactate
mol (4.8 g) and 1,3-dichloro-1,1,3,
0.2 mmol of 3-tetrabutyldistannoxane (0.
1g) was placed in a 500-ml reactor, and the atmosphere in the reactor was replaced with nitrogen. The weight average molecular weight (Mw) of the obtained lactic acid-zinc copolymer was 27,000.

Example 4 (Reaction of hydroxycarboxylic acid oligomer with zinc lactate) 1 mol (100 g) of 90% L-lactic acid and 1,3-dichloro-1,1,3,3-tetrabutyldistanoxane 0.1 mol.
1 mmol (50 mg) was placed in a 500 ml reactor, and heated and stirred at 170 ° C. for 3 hours under reduced pressure. The weight average molecular weight (Mw) of the obtained lactic acid oligomer is 800
Met. 10 mmol of zinc lactate (2.4 g)
Was further added and stirred at 170 ° C. for 17 hours.
Weight average molecular weight (Mw) of the obtained lactic acid-zinc copolymer
Was 8,000.

(Evaluation of Biodegradability by Hydrolysis Acceleration Test) In general, biodegradation of a biodegradable resin by a microorganism first occurs after hydrolysis occurs, and the molecular weight of the resin decreases.
It is known that degradation by microorganisms occurs. Therefore, as for the biodegradable resin, the evaluation of the easily hydrolyzable property can be directly employed as one of the methods for evaluating the biodegradability. Therefore, in order to evaluate the hydrolyzability of the polyhydroxycarboxylic acid resin, a lactic acid homopolymer having a Mw of 12,000 and a lactic acid-
A 2 mm sheet of the zinc copolymer was immersed and the weight loss was measured 4 days later. When the initial weight was set to 100, the lactic acid homopolymer was reduced to 91, whereas the lactic acid-zinc copolymer was reduced to 65. From this, it was found that the polyhydroxycarboxylic acid resin obtained according to the present invention is easily decomposable.

[0018]

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 can be used as agricultural and horticultural materials, fishery materials, medical tools and medical materials.Even if it is discarded, it is hydrolyzed over time to carbon dioxide and water by microorganisms in the soil. It is decomposed and does not become a source of pollution.

Claims (6)

[Claims] 1. A polymerization catalyst is added to a mixture of a zinc compound and at least one of hydroxycarboxylic acid, hydroxycarboxylic acid dimer or hydroxycarboxylic acid oligomer, and the mixture is heated and stirred under reduced pressure or under a nitrogen stream. Or an azeotropic dewatering polymerization in an organic solvent. 2. The method of claim 2, wherein the hydroxycarboxylic acid is lactic acid, glycolic acid, tartaric acid, citric acid, malic acid, oxyvaleric acid,
The method for producing a polyhydroxycarboxylic acid resin according to claim 1, which is hydroxystearic acid, salicylic acid, o-oxycinnamic acid, or a mixture thereof. 3. The method for producing a polyhydroxycarboxylic acid resin according to claim 1, wherein the hydroxycarboxylic acid dimer is L-lactide, glycolide or a mixture thereof. 4. The method for producing a polyhydroxycarboxylic acid resin according to claim 1, wherein the hydroxycarboxylic acid oligomer is a lactic acid oligomer, a glycolic acid oligomer or a mixture thereof. 5. A zinc compound comprising metal zinc; zinc oxide; zinc organic acid salts such as zinc acetate and zinc lactate; zinc halides such as zinc chloride; alkoxy zincs such as zinc acetylacetonate; and organic compounds such as diethyl zinc. The method for producing a polyhydroxycarboxylic acid resin according to claim 1, which is a zinc; or a mixture thereof. 6. A polymerization catalyst comprising 1,3-substituted-1,1,3,3
The method for producing a polyhydroxycarboxylic acid resin according to claim 1, which is -tetraorganodistanoxane.