JP2004149809A - Biodegradable resin composition and producing method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a biodegradable resin composition which contains a polyhydroxycarboxylic acid resin which is increased in resin strengths and melt viscosity, can be used as a material for agriculture, horticulture, fishing, or the like, and when discarded after its use, is decomposed into carbon dioxide and water by hydrolysis and/or with soil microoganisms, or the like, and to provide a producing method for the composition. <P>SOLUTION: The biodegradable resin composition is prepared by mixing 100 pts.wt. polyhydroxycarboxylic acid resin with 1-300 pts.wt. fumed silica as a filler and foaming the mixture. The polyhydroxycarboxylic acid resin is produced by a method wherein a hydroxycarboxylic acid or a mixture of at least two hydroxycarboxylic acids; a mixture of a hydroxy carboxylic acid and saccharides; or a mixture of a hydroxy carboxylic acid and a metal hydroxide and/or an inorganic acid, is subjected in the presence of a polymerization catalyst to azeotropic dehydration polymerization in an organic solvent or to agitation under heating and under a reduced pressure. <P>COPYRIGHT: (C)2004,JPO

Description

  The present invention relates to a biodegradable resin composition and a method for producing the same.

  Conventionally, various resin moldings have been used as agricultural and horticultural materials (for example, polyvinyl chloride film) and fishing materials (for example, fishing nets made of polyethylene fiber), 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 is hydrolyzed over time or biodegraded by microorganisms in the soil. The present inventors have previously used such materials for agricultural and horticultural use, fishery materials, binders, etc., and even if they are discarded after use, carbon dioxide and water can be used due to hydrolysis and / or microorganisms in the soil. And invented a method for easily producing a polyhydroxycarboxylic acid resin which can be decomposed into a resin (see, for example, Patent Document 1).

JP-A-9-241357

  An object of the present invention is to provide a resin composition in which the resin strength and melt viscosity of the hydrolyzable and / or biodegradable polyhydroxycarboxylic acid resin are increased, and a method for producing the same.

  The present inventors have conducted intensive studies in order to achieve the above object, and as a result, by adding fumed silica as a filler to a polyhydroxycarboxylic acid resin which is a hydrolyzable and / or biodegradable resin, The inventors have found that the resin strength and the melt viscosity can be increased, and have completed the present invention.

  That is, the biodegradable resin composition of the present invention is characterized in that fumed silica is added to a polyhydroxycarboxylic acid resin as a filler and foamed, and the biodegradable resin composition of the present invention is also provided. Is a method of preparing a polymerization catalyst in a mixture of a hydroxycarboxylic acid or a mixture of two or more hydroxycarboxylic acids, a mixture of a hydroxycarboxylic acid and a saccharide, or a mixture of a hydroxycarboxylic acid and a metal hydroxide and / or an inorganic acid. Addition, azeotropic dehydration polymerization in an organic solvent or by heating and stirring under reduced pressure to synthesize a polyhydroxycarboxylic acid resin, adding fumed silica as a filler, and foaming. It is assumed that.

  As described above, according to the present invention, a polyhydroxycarboxylic acid resin composition to which a filler is added has a higher resin strength than a polyhydroxycarboxylic acid resin to which no filler is added, and has a melt viscosity. Because of its large size, it is easy to foam and, even when discarded, polyhydroxycarboxylic acid resin is decomposed into carbon dioxide and water by hydrolysis and microorganisms in the soil, etc. Because it is a substance that exists in large amounts in the soil, it is unlikely to have any adverse effect on the environment.

  The polyhydroxycarboxylic acid resin used in the present invention is an aliphatic carboxylic acid having a hydroxyl group. When the resin has an asymmetric carbon, any of D-, L- and racemic hydroxycarboxylic acids or two or more hydroxycarboxylic acids It is obtained by polymerizing a carboxylic acid. In place of the hydroxycarboxylic acid polymer, a copolymer may be synthesized from hydroxycarboxylic acid and starch, hydroxycarboxylic acid and metal hydroxide and / or inorganic acid, and used.

  As the filler used in the present invention, any of commonly used white carbons such as silica, aluminum hydroxide and titanium oxide may be used, but silica having a large reinforcing effect is preferred. Further, in consideration of mixing with the melted polyhydroxycarboxylic acid, fumed silica having a small water content in the silica and a small decrease in molecular weight due to hydrolysis is preferable. Specific examples of fumed silica include # 130, # 200, and R972 and R974 manufactured by Nippon Aerosil Co., Ltd., and MT-10 and MT-20 manufactured by Tokuyama Corporation.

  The addition amount of the filler is preferably 1 to 300 parts by weight based on 100 parts by weight of the polyhydroxycarboxylic acid resin. If the amount is less than 1 part by weight, the thickening effect cannot be obtained. For kneading the resin and the filler, any of an extruder, a kneader, a roll, various mixers and the like may be used.

  As the catalyst for polymerizing hydroxycarboxylic acid, any catalyst used for general ester polymerization may be used, but 1,3-substituted-1,1,3,3 having high catalytic activity and hydrolysis resistance is used. -Tetraorganodistanoxane is preferred. The organo group bonded to the tin atom of the 1,3-substituted-1,1,3,3-tetraorganodistanoxane is a methyl group, an ethyl group, a butyl group, an octyl group, an allyl group, a benzyl group, a phenyl group, It may be any of a naphthyl group and the like, and the substituent at the 1,3-position may be any of halogens, thiocyano group, hydroxyl group, alkoxy group and carboxyl group.

  Hydroxycarboxylic acids that are synthetic raw materials for polyhydroxycarboxylic acid resins include lactic acid, glycolic acid, tartaric acid, citric acid, malic acid, oxyvaleric acid, 2-hydroxystearic acid, salicylic acid, o-oxycinnamic acid, or a mixture thereof. Mixtures can be mentioned, but lactic acid is particularly preferred. Further, a hydroxycarboxylic acid dimer or a hydroxycarboxylic acid oligomer may be used instead of the hydroxycarboxylic acid.

  As the saccharide to be copolymerized with the hydroxycarboxylic acid, a natural product is preferable, and monosaccharides such as D-glucose, D-fructose, D-mannose and D-galactose, and oligosaccharides such as maltose and sugar (sucrose) ( Oligosaccharides), starch, particularly polysaccharides such as corn starch, sweet potato starch and wheat starch, or mixtures thereof.

  As the metal hydroxide to be copolymerized with the hydroxycarboxylic acid, aluminum hydroxide, calcium hydroxide, zinc hydroxide, barium hydroxide, magnesium hydroxide, or a mixture thereof is used. As the inorganic acid, boric acid is used. , Silicic acid, phosphoric acid, or a mixture thereof is used.

  Examples of the polymerization catalyst used for the polymerization or copolymerization reaction of hydroxycarboxylic acid include 1,3-substituted-1,1,3,3-tetraorganodistanoxane. 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. Further, the substituent at the 1,3-position may be any of halogen, thiocyano group, hydroxyl group, alkoxy group and carboxyl group.

  As the organic solvent used in the reaction, any one may be used as long as it has a higher boiling point than water and is not compatible with water, but it is a natural product, and even if it remains in the resin, it has an adverse effect on the environment and the human body. Less D-limonene or decalin is preferred.

[Action]
The polyhydroxycarboxylic acid resin to which the filler is added according to the present invention has a higher melt viscosity than that of the polyhydroxycarboxylic acid resin to which no filler is added, so that a low boiling point solvent method, a gas injection method, a chemical foaming method, and the like. Foaming is easy.
Further, even if the composition according to the present invention is discarded, the polyhydroxycarboxylic acid resin is decomposed into carbon dioxide and water by hydrolysis and microorganisms in the soil, while the filler is a substance that is present in a large amount in the soil such as silicon dioxide. Therefore, it is difficult for the environment to be adversely affected.

  Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples.

(Example 1)
3 kg (30 mol) of 90% L-lactic acid and 1.5 g (3 mmol) of 1,3-dichloro-1,1,3,3-tetrabutyldistannoxane were put into a 5 liter planetary mixer, and the mixture was heated at 170 ° C. for 24 hours. Vacuum agitation was performed. Fumed silica (R-972 manufactured by Nippon Aerosil Co., Ltd.) whose surface was subjected to a hydrophobic treatment was added thereto in an amount of 10 parts by weight based on 100 parts by weight of the synthesized polymer. Mix for hours.
When the melt viscosity of the polymer at 105 ° C. before and after the addition of the filler was measured, it increased from 2.1 poise to 3.3 poise. For the measurement of the melt viscosity, a constant load extrusion type thin tube rheometer CFT-500C was used.

(Example 2)
3 kg (30 mol) of 90% L-lactic acid, 1.5 g (3 mmol) of 1,3-dichloro-1,1,3,3-tetrabutyldistannoxane and 0.3 kg of corn starch were placed in a 5 liter planetary mixer, Vacuum stirring was performed at 170 ° C. for 24 hours. To this, fumed silica (# 130 manufactured by Nippon Aerosil Co., Ltd., dried at 105 ° C. for 2 hours) was added in an amount of 10 parts by weight based on 100 parts by weight of the synthesized lactic acid-starch copolymer. And further mixed at 170 ° C. for 4 hours.
When the melt viscosity of the lactic acid-starch copolymer at 105 ° C. before and after the addition of the filler was measured, it increased from 1.1 poise to 2.5 poise.

  As described above, according to the present invention, a polyhydroxycarboxylic acid resin composition to which a filler is added has a higher resin strength than a polyhydroxycarboxylic acid resin to which no filler is added, and has a melt viscosity. Because of its large size, it is easy to foam and, even when discarded, polyhydroxycarboxylic acid resin is decomposed into carbon dioxide and water by hydrolysis and microorganisms in the soil, etc. Since it is a substance that exists in a large amount in the soil, it is unlikely to have any adverse effect on the environment, and therefore, there is a great possibility that the molded article can be used as agricultural / horticultural materials, fishing materials, and the like.

Claims (3)

  A biodegradable foamed resin composition, characterized in that 1 to 300 parts by weight of fumed silica is added to 100 parts by weight of a polyhydroxycarboxylic acid resin and foamed.   Adding a polymerization catalyst to a hydroxycarboxylic acid or a mixture of two or more hydroxycarboxylic acids, a mixture of a hydroxycarboxylic acid and a saccharide, or a mixture of a hydroxycarboxylic acid and a metal hydroxide and / or an inorganic acid; A biodegradable foamed resin characterized by synthesizing a polyhydroxycarboxylic acid resin by performing azeotropic dehydration polymerization in water or heating and stirring under reduced pressure, adding fumed silica to the resin, and foaming. A method for producing the composition.   1,3-substitution as a polymerization catalyst in a hydroxycarboxylic acid or a mixture of two or more hydroxycarboxylic acids, a mixture of a hydroxycarboxylic acid and a saccharide, or a mixture of a hydroxycarboxylic acid and a metal hydroxide and / or an inorganic acid −1,1,3,3-tetraorganodistanoxane is added, and an azeotropic dehydration polymerization is carried out in an organic solvent or a polyhydroxycarboxylic acid resin is synthesized by heating and stirring under reduced pressure, and then filled. A method for producing a biodegradable foamed resin composition, comprising adding an agent and foaming.