JP2001040079A - Biodegradable resin and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an excellent biodegradable resin having high polymerization degree and improved resin properties and moldability and provide a process for easily producing the resin. SOLUTION: A mixture containing a hydroxycarboxylic acid, a polybasic carboxylic acid, a polyether and a monoorganotin derivative as a polymerization catalyst is subjected to condensation polymerization process by heating and stirring the mixture under reduced pressure or to an azeotropic dehydrative polymerization comprising the heating and stirring of the mixture in an organic solvent. The hydroxycarboxylic acid is lactic acid, glycolic acid or 3- hydroxybutyric acid and, when the acid contains asymmetric carbon atom, the acid is preferably D-isomer, L-isomer or racemic compound. The polybasic carboxylic acid is preferably the D-isomer, L-isomer or racemic compound of citric acid, tricarballylic acid, 2-methylpropanetricarboxylic acid, 1,2,4- butanetricarboxylic acid, 1,3,5-cyclohexanetricarboxylic acid or trimellitic acid.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a biodegradable resin which is excellent in molding processability and is easily decomposed by microorganisms, and a method for producing the same. An object of the present invention is to provide an excellent biodegradable resin having improved processability and a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, many types of plastic products, which are lightweight, have excellent workability, and are resistant to corrosion and decomposition, have been on the market, and are inexpensive and convenient. It has spread to every corner of the industry. On the other hand, in response to such a situation, the amount of waste of the plastic product after use tends to increase year by year, and furthermore, since it is a substance having characteristics that are difficult to corrode and decompose, this has become a major pollution problem. ing.

[0003] In response to this situation, naturally occurring organisms, especially microorganisms in soil and water, replace the above-mentioned corrosive and hard-to-degrade plastic products more easily and
Finally, various biodegradable plastics that are decomposed into water and carbon dioxide have been developed, and are attracting attention as environmental protection products. Examples of these biodegradable plastics include resins produced by microorganisms, natural polymers, and synthetic polymers.

As a resin produced by a microorganism, there is a hydroxybutyrate-based polyester produced by a certain kind of hydrogen bacteria. Examples of biodegradable natural polymers include plant-derived cellulose and starch, and animal-derived natural polymers such as chitin contained in shrimp and crab shells. In addition, synthetic polymers using the above natural polymers as raw materials, and polycaprolactone and pullulan, which are biodegradable synthetic polymers, and polymer alloys with other general-purpose plastics (non-biodegradable), etc. There is. Furthermore, examples of the biodegradable synthetic polymer include a biodegradable resin having a chemical structure and a functional group that can be used by microorganisms and recognized by an enzyme as a substrate, such as polylactic acid.

[0005] As another example of the biodegradable resin, there is a polyhydroxycarboxylic acid obtained by polymerizing a hydroxycarboxylic acid such as lactic acid, which has already been produced by the following methods. 1) Synthesis of an oligomer of hydroxycarboxylic acid such as lactic acid, lactide by depolymerization, purification by distillation,
A method of further performing ring-opening polymerization. 2) A method of synthesizing a lactic acid oligomer and then cross-linking between molecules using a compound having a functional group such as isocyanate.
3) A method of dehydrating a hydroxycarboxylic acid and then performing a dehydration condensation reaction using a molecular sieve in a reaction mixture containing an organic solvent such as anisole and diphenyl ether.

However, in the above-mentioned conventional method for producing a polylactic acid resin, in any case, if a catalyst is directly added to hydroxycarboxylic acid, it is deactivated. On the other hand, there is a problem in that the reaction route is lengthened, the reaction itself is complicated, a large number of steps are required for production equipment and separation and recovery of the organic solvent, and the cost is increased. The present inventors have previously disclosed in Japanese Patent Application Laid-Open No. 9-31182 a hydroxycarboxylic acid such as L-lactic acid containing water and a 1,3-substituted-1,1,3,3-tetraorganodista as a polymerization catalyst. A polyhydroxycarboxylic acid resin which can be easily produced in one pot by adding noxane and heating and stirring under reduced pressure or in an organic solvent is disclosed.

[0007]

However, the above-mentioned polyhydroxycarboxylic acid resin (biodegradable resin) which can be easily produced in one pot has a problem to be solved, which is still insufficient in moldability. Was. Therefore, development of a biodegradable resin having good moldability has been strongly desired. Under such circumstances, an object of the present invention is to solve the above-mentioned problems recognized in conventional biodegradable resins, to facilitate and enable manufacturability, to achieve a high degree of polymerization,
An object of the present invention is to provide an excellent biodegradable resin having improved resin properties and moldability, and a method for producing the same.

[0008]

Means for Solving the Problems The present inventors have conducted various studies in response to such a current situation, and found that the above problems can be solved by using specific starting monomers, polymerization catalysts and polymerization methods. Was made. That is, the present invention is achieved by the following configurations. (1) Condensation polymerization in which a mixture containing a hydroxycarboxylic acid, a polycarboxylic acid and a polyether and a monoorganotin derivative as a polymerization catalyst is heated and stirred under reduced pressure, or azeotropic dehydration polymerization in which an organic solvent is heated and stirred. A biodegradable resin obtained by:

(2) The above (1), wherein the hydroxycarboxylic acid is lactic acid, glycolic acid or 3-hydroxybutyric acid, and when it has an asymmetric carbon, it is in D-form, L-form or racemic form. Biodegradable resin. (3) The polycarboxylic acid is citric acid, tricarballylic acid, 2-methylpropanetricarboxylic acid, 1,2,4-
The biodegradable resin according to the above (1), which is a D-form, an L-form or a racemic form of butanetricarboxylic acid, 1,3,5-cyclohexanetricarboxylic acid or trimellitic acid. (4) The biodegradable resin according to (1), wherein the polyether is polyethylene glycol, polypropylene glycol or polybutylene glycol.

(5) When the organo group bonded to the tin atom of the monoorganotin derivative used as a polymerization catalyst is methyl, ethyl, propyl, allyl, butyl, phenyl, benzyl, octyl or naphthyl The biodegradable resin according to the above (1), which is a base. (6) The biodegradable resin according to (1), wherein the substituent of the tin atom of the monoorganotin derivative used as the polymerization catalyst is a halogen, a thiocyan group, a hydroxyl group, a carboxylate or an alkoxy group. (7) The biodegradable resin according to (1), wherein the monoorganotin derivative used as the polymerization catalyst is a monoorganotin oxide.

(8) Condensation polymerization in which a mixture containing a hydroxycarboxylic acid, a polycarboxylic acid, and a polyether and a monoorganotin derivative as a polymerization catalyst is heated and stirred under reduced pressure, or azeotropically heated and stirred in an organic solvent. A method for producing a biodegradable resin, comprising performing dehydration polymerization. (9) The biodegradable resin according to the above (8), wherein the hydroxycarboxylic acid is lactic acid, glycolic acid or 3-hydroxybutyric acid, and when it has an asymmetric carbon, it is a D-form, an L-form or a racemic form. Manufacturing method.

(10) The polycarboxylic acid is citric acid, tricarballylic acid, 2-methylpropanetricarboxylic acid,
D of 1,2,4-butanetricarboxylic acid, 1,3,5-cyclohexanetricarboxylic acid or trimellitic acid
(8) The method for producing a biodegradable resin according to the above (8), which is in the form of an isomer, an L-isomer or a racemate. (11) The method for producing a biodegradable resin according to the above (8), wherein the polyether is polyethylene glycol, polypropylene glycol or polybutylene glycol.

(12) The organo group bonded to the tin atom of the monoorganotin derivative used as a polymerization catalyst is a methyl group, an ethyl group, a propyl group, an allyl group, a butyl group,
(8) The method for producing a biodegradable resin according to the above (8), which is a phenyl group, a benzyl group, an octyl group, or a naphthyl group. (13) The substituent of the tin atom of the monoorganotin derivative used as the polymerization catalyst is a halogen, a thiocyan group,
The method for producing a biodegradable resin according to the above (8), which is a hydroxyl group, a carboxylate or an alkoxy group. (14) The method for producing a biodegradable resin according to the above (8), wherein the monoorganotin derivative used as the polymerization catalyst is a monoorganotin oxide.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.
The biodegradable resin of the present invention comprises at least one of a hydroxycarboxylic acid, a polycarboxylic acid and a polyether.
It is characterized by polymerizing a species and a monoorganotin derivative as a polymerization catalyst, and is obtained by subjecting these mixtures to condensation polymerization by heating and stirring under reduced pressure, or by azeotropic dehydration polymerization in an organic solvent. be able to.

The hydroxycarboxylic acid in the biodegradable resin of the present invention is not particularly limited, but is an aliphatic carboxylic acid having a hydroxyl group in the molecule, and in the case of having an asymmetric carbon, it is a D-form, an L-form or a racemic form. Is preferred. Specific examples of such hydroxycarboxylic acids include lactic acid,
Citric acid, malic acid, tartaric acid, glycolic acid, 3-hydroxybutyric acid, 4-hydroxybutyric acid, 3-
Examples include hydroxyvaleric acid, 5-hydroxyvaleric acid, and 6-hydroxycaproic acid. However, these do not limit the content of the present invention. Lactic acid, citric acid, glycolic acid, 3-hydroxybutyric acid, malic acid, tartaric acid and the like are preferably used alone or in combination from the viewpoint of availability. The amount of the hydroxycarboxylic acid added in the method for producing a biodegradable resin of the present invention is not particularly limited, but is 0.1 to 20 parts by weight, preferably 1.0 to 15 parts by weight, more preferably 1.0 to 15 parts by weight, based on the total amount of the raw material monomers. 2.5 to 10 parts by weight.

The polycarboxylic acid in the biodegradable resin of the present invention is not particularly limited as long as it has three or more carboxyl groups, and may be any of a linear compound, a heterocyclic compound and an aromatic compound. These anhydrides may be used, and any of D-form, L-form and racemic-form may be used. Specific examples of such polycarboxylic acids include citric acid, tricarballylic acid, 2-methylpropanetricarboxylic acid, 1,2,4-butanetricarboxylic acid, 1,3,3
Examples thereof include 5-cyclohexanetricarboxylic acid and trimellitic acid, and they are preferably used alone or in combination.
The amount of the polycarboxylic acid added in the method for producing a biodegradable resin of the present invention is not particularly limited, but is 0.1 to 60 parts by weight, preferably 1.0 to 5 parts by weight, based on the total amount of the raw material monomers.
0 parts by weight, more preferably 2.5 to 40 parts by weight.

The polyether in the biodegradable resin of the present invention may have any structure as long as both terminals of the molecular chain are hydroxyl groups. Specific examples of such polyethers include polyethylene glycol, polypropylene glycol, polybutylene glycol, and the like. Polyethylene glycol is preferable in consideration of affinity with water, and particularly, the weight average molecular weight is 100 to 3
000 range is more preferred. Weight average molecular weight of 3
If it is more than 000, the reaction mixture becomes soft without forming a resinous state. On the other hand, if it is less than 100, the crosslink density becomes too high, resulting in firm and brittle.

The amount of the polyether added is preferably such that the carboxyl group of the polycarboxylic acid and the hydroxyl group of the polyether are equimolar. When the addition amount of the polyether is small, the degree of crosslinking of the resin to be formed becomes insufficient, and good flexibility cannot be obtained.

In the method for producing a biodegradable resin of the present invention,
Monoorganotin derivatives used as polymerization catalysts,
Although not particularly limited, those represented by the following general formula (I) are preferred.

[0020]

Embedded image

In the general formula (I), Sn represents a tin atom, and R is a linear or cyclic organo group having 1 to 12 carbon atoms, preferably a methyl group, an ethyl group, a propyl group, an allyl group, Butyl group, phenyl group, benzyl group,
Any of an octyl group and a naphthyl group may be used. X, Y and Z are substituents, which may be the same or different from each other, and any of them may be used. However, halogens, thiocyan groups, hydroxyl groups, carboxylate salts or alkoxy groups are preferred for ease of synthesis. It is preferably any one of the groups.

Examples of the halogens include chlorine and bromine, and examples of the carboxylate include acetate, octate and laurate. Examples of the alkoxy group include those having 1 to 6 carbon atoms such as a methoxy group, an ethoxy group, a propoxy group, a butoxy group and a phenoxy group.

The monoorganotin derivatives represented by the above general formula (I) include monomethyl, monoethyl, monopropyl, monobutyl, monophenyl, monobenzyl,
Examples include oxides such as monooctyl and mononaphthyl, bromides, chlorides and fluorides. In addition, in addition to the monoorganotin derivative represented by the above general formula (I), some tin atoms form an oligomer with an oxygen atom interposed therebetween as in monoorganotannic acid in the present invention. It may be of a certain structure.

Specific examples of the monoorganotin derivative represented by the general formula (I) are shown below. However, these do not limit the content of the present invention. As oxides, monomethyltin oxide, monoethyltin oxide, monopropyltin oxide, monobutyltin oxide,
Monophenyltin oxide, monobenzyltin oxide, monooctyltin oxide, mononaphthyltin oxide. As bromides, monomethyltin tribromide, monoethyltin tribromide, monopropyltin tribromide, monobutyltin tribromide, monophenyltin tribromide, monobenzyltin tribromide, monooctyltin tribromide, mononaphthyltin tribromide .

The chlorinated products include monomethyltin trichloride, monoethyltin trichloride, monopropyltin trichloride, monobutyltin trichloride, monophenyltin trichloride, monobenzyltin trichloride, monooctyltin trichloride, mononaphthyl Tin trichloride. Examples of fluorinated compounds include monomethyltin trifluoride, monoethyltin trifluoride, monopropyltin trifluoride, monobutyltin trifluoride, monophenyltin trifluoride, monobenzyltin trifluoride, and monooctyltin trifluoride. ,
Mononaphthyltin trifluoride.

Examples of the alkoxy compound include monomethyltin trialkoxide, monoethyltin trialkoxide, monopropyltin trialkoxide, monobutyltin trialkoxide, monophenyltin trialkoxide, monobenzyltin trialkoxide, monooctyltin trialkoxide, and mononaphthyl. Tin trialkoxide (the alkoxy group referred to here is a methoxy group, an ethoxy group, a propoxy group, a butoxy group, a phenoxy group, or the like). Examples of the carboxy compound include monomethyltin tricarboxide, monoethyltin tricarboxide, monopropyltin tricarboxide, monobutyltin tricarboxide, monophenyltin tricarboxide, monobenzyltin tricarboxide, and monooctyltin tricarboxy. And mononaphthyltin tricarboxide (here, the carboxy group is an acetoxy group, a lacoxy group, a benzoxy group, an octoxy group, a lauroxy group, etc.).

In the method for producing a biodegradable resin of the present invention,
The amount of the monoorganotin derivative varies slightly depending on the type of hydroxycarboxylic acid. For example, in the case of lactic acid, the amount is preferably 0.0001 to 1% by weight. When the amount is less than 0.0001% by weight, remarkable catalytic activity cannot be obtained. When the amount is more than 1% by weight, the polymerization reaction is inhibited.

In the method for producing a biodegradable resin according to the present invention, in addition to the hydroxycarboxylic acid, polycarboxylic acid, polyether and monoorganotin derivative,
If necessary, a saccharide or a metal oxide may be added during the polymerization. As saccharides, starch, sucrose, glucose and the like can be preferably used. The amount of these saccharides added is 10 to 0.00 parts by weight per 100 parts by weight of hydroxycarboxylic acid.
A range of 1 part by weight is preferred. As the metal oxide, aluminum hydroxide, zinc hydroxide, magnesium hydroxide, calcium hydroxide, phosphoric acid and the like are preferable. The amount of addition of these metal oxides is
The range of 10 to 0.0001 parts by weight relative to parts by weight is preferred.

The biodegradable resin of the present invention can be synthesized in principle by polymerizing the hydroxycarboxylic acid, polycarboxylic acid and polyether appropriately selected as described above using a monoorganotin derivative as a synthesis catalyst. Therefore, various modifications may be made within the scope of the present invention. For example, it can be obtained by a method of performing dehydration condensation in the presence of an organic solvent, a method of performing condensation polymerization in the absence of a solvent while heating and stirring under reduced pressure, and the like. In particular, the method of condensation polymerization in the absence of a solvent,
It is advantageous in terms of equipment and cost. In the case of the condensation polymerization, the reaction temperature is preferably from 150 to 200 ° C, more preferably from 170 to 190 ° C, in consideration of the production rate of the polymer and the thermal decomposition of the produced polymer.
The reaction time is also preferably 18 to 30 hours, more preferably 20 to 24 hours, in consideration of the rate of polymer production and thermal decomposition of the produced polymer.

The biodegradable resin thus obtained has a higher dissolution viscosity than a conventional lactic acid homopolymer or the like, and can be used as a resin for blow or foam formation.
Also, by mixing with other lactic acid-based polyesters, for example, the flexibility and biodegradability of the resin can be adjusted.

Furthermore, the biodegradable resin of the present invention can be further modified by adding a plasticizer or an additive as a secondary additive. As additives, for example, heat stabilizers,
Light stabilizers, antioxidants, UV absorbers, pigments, colorants,
Examples include various fillers, antistatic agents, release agents, fragrances, lubricants, flame retardants, foaming agents, fillers, antibacterial agents, and the like.

From the above, the biodegradable resin of the present invention is formed into sheets, films and the like, and used as various bags and packaging materials, and as a substitute for various soft vinyl chloride materials such as flexible tubes. But not limited to these.

[0033]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, but it should not be construed that the invention is limited thereto. Example 1 250% (2.5 mol) of 90% L-lactic acid, 6.3 g (2.5% by weight) of citric acid, 125 mg (0.05% by weight) of monobutyltin oxide, and a weight average molecular weight of 2
Then, 9.8 g (3.9% by weight) of polyethylene glycol was placed in a reactor having a capacity of 500 ml.
The reaction was continued while stirring under reduced pressure of a vacuum pump for hours. The glass transition point of the lactic acid-based polyester copolymer obtained by this reaction was 33.9 ° C., the melting point was 125.6 ° C., and the melt viscosity was 4.21 × 10 ³ poise. When this lactic acid-based polyester copolymer was measured with an A-type hardness meter (ASTM) and a D-type hardness meter (ASTM), each had a hardness of 1
00 and 81.

Example 2 250 g (2.5 mol) of 90% L-lactic acid, citric acid 1
2.5 g (5.0% by weight), 125 mg (0.05% by weight) of monobutyltin oxide, and 19.5 g (7.8% by weight) of polyethylene glycol having a weight-average molecular weight of 200 were placed in a 500-ml reactor. Put at 190 ° C for 2
The reaction was carried out for 0 hours while continuing to stir under reduced pressure of a vacuum pump. The glass transition point of the lactic acid-based polyester copolymer obtained by this reaction was 22.9 ° C, the melting point was 100.2 ° C,
The melt viscosity was 4.39 × 10 ³ poise. This lactic acid-based polyester copolymer was measured with an A-type hardness meter (ASTM)
The hardness was 100 and 66, respectively, as measured by a die hardness tester (ASTM).

Example 3 250 g (2.5 mol) of 90% L-lactic acid, citric acid 1
8.8 g (7.5% by weight), 125 mg (0.05% by weight) of monobutyltin oxide, and 29.3 g (11.7%) of polyethylene glycol having a weight average molecular weight of 200.
% By weight) was placed in a reactor having a capacity of 500 ml, and the reaction was carried out at 190 ° C. for 20 hours while continuing stirring under reduced pressure of a vacuum pump. The glass transition point of the lactic acid-based polyester copolymer obtained by this reaction was 16.1 ° C., the melting point was 87.4 ° C., and the melt viscosity was 3.43 × 10 ³ poise. When this lactic acid-based polyester copolymer was measured with an A-type hardness meter (ASTM) and a D-type hardness meter (ASTM), each had a hardness of 1
2 and 0.

Example 4 250% (2.5 mol) of 90% L-lactic acid, 6.3 g (2.5% by weight) of citric acid, 125 mg (0.05% by weight) of monobutyltin oxide, and having a weight average molecular weight of 1
48.8 g of polyethylene glycol (19.5)
% By weight) was placed in a reactor having a capacity of 500 ml, and the reaction was carried out at 190 ° C. for 20 hours while continuing stirring under reduced pressure of a vacuum pump. The glass transition point of the lactic acid-based polyester copolymer obtained by this reaction is −17.5 ° C., and the melting point is 103.6.
C. and the melt viscosity was 3.20 × 10 ³ poise. A lactic acid-based polyester copolymer was measured with an A-type hardness meter (ASTM) and D
The hardness was 92 and 31, respectively, as measured by a die hardness tester (ASTM).

Comparative Example 1 250 g (corresponding to 2.5 mol) of 90% L-lactic acid and 125 mg (0.05% by weight) of monobutyltin oxide were added to 5
The mixture was placed in a reactor having a capacity of 00 ml, and stirring was continued at 190 ° C. for 24 hours under reduced pressure of a vacuum pump. The obtained lactic acid homopolymer has a glass transition point of 52.5 ° C. and a melting point of 157.3.
C., and the melt viscosity was 1.68 × 10 ³ poise. When the lactic acid homopolymer was measured with an A-type hardness meter (ASTM) and a D-type hardness meter (ASTM), the hardness was 100 and 84, respectively.

Comparative Example 2 250 g of 90% L-lactic acid (corresponding to 2.5 mol), 6.3 g of citric acid (2.5% by weight), and a weight average molecular weight of 200
Of 9.8 g (3.9% by weight) of polyethylene glycol was placed in a 500 ml reactor, and stirring was continued at 190 ° C. for 20 hours under reduced pressure of a vacuum pump. The obtained lactic acid-based polyester copolymer was in the form of syrup without cross-linking. Table 1 summarizes the results obtained in Examples 1 to 4 and Comparative Examples 1 and 2.

[0039]

[Table 1]

As shown in Table 1, it was shown that the glass transition point, the melting point, and the hardness of the lactic acid-based polyester copolymer can be controlled by changing the addition amount and the molecular weight of the polycarboxylic acid and the polyether.

Test Example 1 (Tensile test) The lactic acid-based polyester copolymer obtained in Example 4 and a lactic acid homopolymer having a weight average molecular weight of 210,000 were subjected to a tensile test to evaluate the flexibility of the resin. The elongation of the resin was compared. Tensile test, according to the method specified in JIS K 7113, the test piece, using an injection molding machine
A test piece shaped into the shape of a No. 1 test piece specified in JIS K 7113 was used. As shown in Table 2, in each of the test items, the numerical value of Example 4 was superior to that of the lactic acid homopolymer, indicating that the flexibility of the lactic acid-based polyester copolymer of the present invention was good.

[0042]

[Table 2]

Test Example 2 (Hydrolysis Test) The lactic acid-based polyester copolymer obtained in Example 4 and a lactic acid homopolymer having a weight-average molecular weight of 210,000 were evaluated for the hydrolyzability of the resin. In the test method, in order to promote the hydrolysis of the resin, the water temperature was maintained at 30 ° C., and the test pieces were respectively placed in aqueous sodium hydroxide solutions having different concentrations, and the weight loss rate of the test pieces after 50 hours was measured. The test piece was cut into a shape of No. 1 test piece specified in JIS K 7113 using an injection molding machine, and cut.
A test piece of 10 mm × 10 mm × 3 mm was prepared. Table 3 shows the results
Shown in

[0044]

[Table 3]

As is evident from the results in Table 3, the lactic acid-based polyester copolymer of the present invention is about 10 times more hydrolyzable than the control lactic acid homopolymer, and decomposes faster in nature. That was shown.

[0046]

Industrial Applicability The biodegradable resin of the present invention has a higher melt viscosity and is more flexible and hydrolyzable than conventional lactic acid homopolymers and the like, so that it can be used for various packaging materials or materials for manufacturing flexible tubes. It can be used effectively. further,
Even in the disposal of various products made using this packaging material or soft tube into the environment after use, since they are highly hydrolyzable, they naturally collapse and greatly reduce environmental destruction. There are big things that contribute to conservation. The biodegradable resin of the present invention is particularly effective when used for various materials in the industrial field that require a large amount of cost for recovery.

Claims (14)

[Claims] 1. A condensation polymerization in which a mixture containing a hydroxycarboxylic acid, a polycarboxylic acid, and a polyether and a monoorganotin derivative as a polymerization catalyst is heated and stirred under reduced pressure, or an azeotrope is heated and stirred in an organic solvent. A biodegradable resin obtained by dehydration polymerization. 2. The method according to claim 1, wherein the hydroxycarboxylic acid is lactic acid, glycolic acid or 3-hydroxybutyric acid, and when it has an asymmetric carbon, it is D-form, L-form or racemic-form. Biodegradable resin. 3. The polycarboxylic acid is citric acid, tricarballylic acid, 2-methylpropanetricarboxylic acid,
D-form of 2,4-butanetricarboxylic acid, 1,3,5-cyclohexanetricarboxylic acid or trimellitic acid, L
The biodegradable resin according to claim 1, which is in a form or a racemic form. 4. The biodegradable resin according to claim 1, wherein the polyether is polyethylene glycol, polypropylene glycol or polybutylene glycol. 5. An organo group bonded to a tin atom of a monoorganotin derivative used as a polymerization catalyst, wherein the organo group is a methyl group, an ethyl group, a propyl group, an allyl group, a butyl group, a phenyl group, a benzyl group, an octyl group or a naphthyl group. The biodegradable resin according to claim 1, wherein: 6. The method according to claim 1, wherein the substituent of the tin atom of the monoorganotin derivative used as a polymerization catalyst is a halogen, a thiocyan group, a hydroxyl group, a carboxylate or an alkoxy group. Decomposition resin. 7. The biodegradable resin according to claim 1, wherein the monoorganotin derivative used as a polymerization catalyst is a monoorganotin oxide. 8. A condensation polymerization in which a mixture containing a hydroxycarboxylic acid, a polycarboxylic acid and a polyether and a monoorganotin derivative as a polymerization catalyst is heated and stirred under reduced pressure, or an azeotropic dehydration in which an organic solvent is heated and stirred. A method for producing a biodegradable resin, comprising performing polymerization. 9. The method according to claim 8, wherein the hydroxycarboxylic acid is lactic acid, glycolic acid or 3-hydroxybutyric acid, and when it has an asymmetric carbon, it is in D-form, L-form or racemic form. Production method of biodegradable resin. 10. The polycarboxylic acid is citric acid, tricarballylic acid, 2-methylpropanetricarboxylic acid,
D-form of 2,4-butanetricarboxylic acid, 1,3,5-cyclohexanetricarboxylic acid or trimellitic acid, L
9. The method for producing a biodegradable resin according to claim 8, wherein the biodegradable resin is in a solid or racemic form. 11. The method for producing a biodegradable resin according to claim 8, wherein the polyether is polyethylene glycol, polypropylene glycol or polybutylene glycol. 12. The monoorganotin derivative used as a polymerization catalyst, wherein the organo group bonded to the tin atom is a methyl group, an ethyl group, a propyl group, an allyl group, a butyl group, a phenyl group, a benzyl group, an octyl group or a naphthyl group. The method for producing a biodegradable resin according to claim 8, wherein 13. The method according to claim 8, wherein the substituent of the tin atom of the monoorganotin derivative used as the polymerization catalyst is a halogen, a thiocyan group, a hydroxyl group, a carboxylate or an alkoxy group. Production method of decomposed resin. 14. The method for producing a biodegradable resin according to claim 8, wherein the monoorganotin derivative used as the polymerization catalyst is a monoorganotin oxide.