JPH10168175A - Purification of aliphatic polyester - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for purifying an aliphatic polyester, by which the apliphatic polyester low in a catalyst content and low in contents of a low-molecular compound such as an unreacted monomer and a volatiel material, and excellent in thermal stability and weather stability is obtained in a good operability. SOLUTION: Aliphatic polyesters are brought into contact with an acidic material insoluble to the polyesters or a polyester solution while keeping the polyesters in a molten or dissolved state, or simultaneously treated with a solid carrier and separated, and thereafter, subjected to the separation of a low molecular compound, when purifying the aliphatic polyesters obtained by polymerizing at least one kind selected from a group of (1) an aliphatic hydroxycarboxylic acid, (2) cyclic esters thereof, (3) an aliphatic polyfunctional alcohol and an aliphatic polybasic acid, or (4) two or more kinds of monomers selected from the above components (1) to (3), and/or an oligomer and/or polymers obtained by polymerizing the monomers.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for purifying an aliphatic polyester useful as a biodegradable polymer as a substitute for a medical material or a general-purpose resin. More specifically, the present invention relates to a method for purifying an aliphatic polyester for obtaining an aliphatic polyester having almost no unreacted monomer or low-molecular-weight volatile component remaining.

[0002]

2. Description of the Related Art Among aliphatic polyesters, polylactic acid can be produced from a cyclic dimer of lactic acid, usually called lactide.
No. 970, U.S. Pat. No. 2,362,511 and U.S. Pat. No. 2,683,136. In addition, copolymers of lactic acid and other hydroxycarboxylic acids are usually produced from lactide, which is a cyclic dimer of lactic acid, and a cyclic ester intermediate of hydroxycarboxylic acid (glycolide, which is usually a dimer of glycolic acid). Regarding the production method, US Pat. No. 3,636,956 and US Pat.
No. 97,499.

When lactic acid or lactic acid and other hydroxycarboxylic acids are directly subjected to dehydration polycondensation, the starting lactic acid or lactic acid and other hydroxycarboxylic acids are preferably subjected to azeotropic dehydration condensation in the presence of a catalyst in an organic solvent in the presence of a catalyst. Then, by removing water from the solvent distilled off by azeotropic distillation, and returning the substantially anhydrous solvent to the reaction system, high-molecular-weight polylactic acid having practical strength and lactic acid and other hydroxycarboxylic acids are obtained. Copolymers with acids can be obtained (EP 0 567 267).
No. 5).

[0004] Among the aliphatic polyesters, with respect to a method for producing a polyester comprising an aliphatic polyhydric alcohol and an aliphatic polybasic acid, there is a method for obtaining a high-molecular weight aliphatic polyester having practical strength. And JP-A-4-189822 and JP-A-4-189823.

In these methods, after the melt polymerization, the obtained polymer is pelletized as it is, so that the used catalyst remains in the polymer, and even if the aliphatic polyester polymer is decomposed, the catalyst remains. There is a problem that depolymerization reaction of the polymer is easily caused by heating at the time of molding, and the molecular weight of the polymer is reduced to deteriorate physical properties. Further, in these methods, it is not possible to avoid that the monomer used as a raw material remains as an unreacted substance in the polymer at several percent. It is also known that impurities having a relatively low boiling point and low molecular weight volatiles such as chain or cyclic oligomers generated by side reactions during the polymerization remain in the polymer. Unreacted monomers and low-molecular-weight volatiles remaining in the polymer cause deterioration of the storage stability and processability of the polymer or the strength of the molded product.

Accordingly, in order to obtain an aliphatic polyester having a sufficiently high molecular weight and containing no catalyst, it is necessary to remove the catalyst by purification. Japanese Unexamined Patent Publication (Kokai) No. 7-228677 discloses a method of removing a low-molecular compound after inactivating a catalyst or insolubilizing a catalyst while maintaining an aliphatic polyester polymerized in the presence of a catalyst in a molten or solution state. A method for purifying an aliphatic polyester is disclosed. Among these, as a method of insolubilizing and separating a catalyst, a method of contacting the catalyst with an acidic substance such as phosphoric acids is also disclosed. Further, it is also disclosed that after the used acidic substance is neutralized with a neutralizing agent such as calcium carbonate, the insolubilized catalyst is separated. However, in this method, when an inorganic alkaline compound is used when neutralizing an excessive acidic substance, the aliphatic polyester may be hydrolyzed by water generated by the neutralization reaction and the molecular weight may be reduced depending on conditions. . Further, when an alkali carbonate compound is used, there is a possibility that a problem that the treatment liquid foams due to carbon dioxide gas generated by the neutralization may occur.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to remove low-molecular compounds such as catalysts and unreacted monomers and volatiles remaining in an aliphatic polyester obtained by a polycondensation reaction industrially at low cost and easily. It is another object of the present invention to provide a purification method with good operability to obtain an aliphatic polyester excellent in heat resistance and weather resistance, which has a low content of a catalyst, unreacted monomers and low molecular weight volatiles.

[0008]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the present inventors have found that an acidic substance insoluble in the polyester or the polyester solution while maintaining the aliphatic polyester in a molten or solution state. After contacting, or simultaneously treated with a solid support and separated,
Distillation or crystallization removes low molecular weight compounds contained in aliphatic polyesters, thereby obtaining aliphatic polyesters with low content of low molecular weight compounds, excellent heat resistance and excellent weather resistance, and completed the present invention. It was done.
That is, the present invention provides, in the presence of a catalyst, an aliphatic hydroxycarboxylic acid, a cyclic ester thereof, an aliphatic polyhydric alcohol and an aliphatic polybasic acid, or an aliphatic obtained from a mixture of two or more of the above. In purifying the polyesters, while keeping the aliphatic polyesters in a molten or solution state, after contacting the polyester or the polyester solution with an insoluble acidic substance, or simultaneously treating and separating with a solid carrier, This is a method for purifying aliphatic polyesters, which comprises removing low-molecular compounds. The present invention is specified by the following items [1] to [17].

[1] In the presence of a catalyst, (i) an aliphatic hydroxycarboxylic acid, (ii) a cyclic ester of an aliphatic hydroxycarboxylic acid, (iii) an aliphatic polyhydric alcohol and an aliphatic polybasic acid, (iv) at least one selected from the group consisting of two or more monomers selected from the group consisting of the above (i)-(iii) and / or oligomers and / or polymers obtained by polymerizing these monomers; In purifying the aliphatic polyester obtained by polymerization, while maintaining the aliphatic polyester in a molten or solution state, adding an acidic substance and a solid carrier that is insoluble in the polyester or the polyester solution. A method for purifying aliphatic polyesters, comprising separating a catalyst by adsorption treatment.

[2] In the presence of a catalyst, (i) an aliphatic hydroxycarboxylic acid, (ii) a cyclic ester of an aliphatic hydroxycarboxylic acid, (iii) an aliphatic polyhydric alcohol and an aliphatic polybasic acid, (iv) at least one selected from the group consisting of two or more monomers selected from the group consisting of the above (i)-(iii) and / or oligomers and / or polymers obtained by polymerizing these monomers; In purifying the aliphatic polyester obtained by polymerization, while maintaining the aliphatic polyester in a molten or solution state, adding an acidic substance and a solid carrier that is insoluble in the polyester or the polyester solution. A method for purifying aliphatic polyesters, comprising removing a low-molecular compound after separating the catalyst by adsorption treatment.

[3] "Addition of acidic substance and solid carrier"
The purification method according to [1] or [2], wherein a solid carrier is added after adding an insoluble acidic substance.

[4] “Addition of acidic substance and solid carrier”
The purification method according to [1] or [2], wherein the insoluble acidic substance and the solid carrier are added simultaneously.

[5] The purification method according to any one of [1] to [4], wherein the insoluble acidic substance is phosphoric acid or phosphorous acid.

[6] The purification method according to [5], wherein the phosphoric acid is phosphoric acid or pyrophosphoric acid.

[7] The purification method according to any one of [1] to [5], wherein the insoluble solid carrier is a mineral product.

[8] The purification method according to [7], wherein the mineral products are at least one selected from the group consisting of diatomaceous earth, kaolin, and activated clay.

[9] The purification method according to any one of [2] to [8], wherein the "removing low molecular compounds" method comprises removing low molecular compounds by distillation under reduced pressure.

[10] The purification method according to any one of [2] to [9], wherein the method of "removing low molecular weight compounds" comprises performing distillation under reduced pressure at 5 mmHg or less.

[11] The purification method according to [10], wherein the distillation is performed at a temperature in the range of 120 ° C to 250 ° C.

[12] The method of “removing a low molecular compound” is a method of removing a low molecular compound by crystallization.
The purification method according to any one of [2] to [8].

[13] The aliphatic polyester is a homopolymer of an aliphatic hydroxycarboxylic acid or a cyclic ester of an aliphatic hydroxycarboxylic acid [1] to [1].
2].

[14] The aliphatic polyester is a copolymer of an aliphatic hydroxycarboxylic acid or a cyclic ester of an aliphatic hydroxycarboxylic acid [1] to [12].
The purification method according to any one of the above.

[15] The purification method according to [14], wherein the aliphatic hydroxycarboxylic acid is at least one selected from the group consisting of lactic acid, glycolic acid, and 6-hydroxycaproic acid.

[16] The method according to any of [1] to [15], wherein the aliphatic polybasic acid is succinic acid and the aliphatic polyhydric alcohol is ethylene glycol and / or 1,4-butanediol. Purification method as described.

[17] An aliphatic polyester purified by the purification method according to any one of [1] to [16].

The present invention is specified by the items described in the above items [1] to [17], and further includes the following items [1] to [17].
It is specified by the items described in [10].

[1] Step 1 [dehydration condensation step]
In the presence of a catalyst, at least one monomer selected from the group consisting of an aliphatic hydroxycarboxylic acid, a cyclic ester of an aliphatic hydroxycarboxylic acid, and an aliphatic polyhydric alcohol and an aliphatic polybasic acid. A step of producing a reaction product containing an aliphatic polyester by dehydration-condensation polymerization. In step 2 [catalyst removal step], a reaction product containing the aliphatic polyester produced in step 1 (hereinafter, in this section, “ Step 1 product)) to maintain the aliphatic polyester in the Step 1 product in a molten state, or to dissolve the Step 1 product in the aliphatic polyester in the Step 1 product. By adding a certain solvent and keeping the aliphatic polyester in the product of Step 1 in a solution state, the aliphatic polyester in the product of Step 1 is converted into a liquid phase, At least one insoluble acidic substance selected from the group consisting of an acidic compound insoluble in the liquid phase, and a solid carrier (solid acidic compound such as a mineral product) insoluble in the liquid phase; And selectively adsorbing only the catalyst in the product of Step 1 to the acidic compound to separate and remove at least a part of the catalyst from the product of Step 1; Step 3 [purification step]; The reaction product obtained by separating and removing at least a part of the produced catalyst (hereinafter, referred to as “process 2 product” in this section) is subjected to vacuum distillation to obtain the monomer used in process 1 and / or the process A method of obtaining an aliphatic polyester by separating and removing at least a part of a low-molecular compound composed of an oligomer generated from the monomer used in 1 (hereinafter, referred to as “a vacuum distillation method” in this section), and Step 2 Crystallize the aliphatic polyester in the product,
A method for recovering an aliphatic polyester in a solid phase (hereinafter, referred to as
In this section, it is referred to as “crystallization method”. Step 2) Reprecipitating the aliphatic polyester in the product,
A method for recovering an aliphatic polyester in a solid phase (hereinafter, referred to as
In this section, this is referred to as the “reprecipitation method”. A) removing at least a portion of a substance other than the aliphatic polyester from the product in Step 2 by at least one method selected from the group consisting of:

[2] Step 1 [dehydration condensation step]
In the presence of a catalyst, at least one monomer selected from the group consisting of an aliphatic hydroxycarboxylic acid, a cyclic ester of an aliphatic hydroxycarboxylic acid, and an aliphatic polyhydric alcohol and an aliphatic polybasic acid. A step of producing a reaction product containing an aliphatic polyester by dehydration-condensation polymerization. In step 2 [catalyst removal step], a reaction product containing the aliphatic polyester produced in step 1 (hereinafter, in this section, “ Step 1 product)) to maintain the aliphatic polyester in the Step 1 product in a molten state, or to dissolve the Step 1 product in the aliphatic polyester in the Step 1 product. By adding a certain solvent and maintaining the aliphatic polyester in the product of Step 1 in a solution state, the aliphatic polyester in the product of Step 1 is converted into a liquid phase, Adding at least one insoluble acidic substance selected from the group consisting of an insoluble acidic compound and a solid carrier (a solid acidic compound such as a mineral product) that is insoluble in the liquid phase; A step of selectively adsorbing only the catalyst in one product to the acidic compound and separating and removing at least a part of the catalyst from the product in step 1; and step 3 [purification step]; The reaction product from which a part was separated and removed (hereinafter, referred to as “Step 2 product” in this section) was distilled under reduced pressure to obtain the monomer used in Step 1 and / or the monomer used in Step 1 A method of obtaining an aliphatic polyester from which at least a part of a low molecular compound composed of an oligomer formed from a body is separated and removed (hereinafter, referred to as “a vacuum distillation method” in this section); Crystallize ter,
A method for recovering an aliphatic polyester in a solid phase (hereinafter, referred to as
In this section, it is referred to as “crystallization method”. Step 2) reprecipitating the aliphatic polyester in the product,
A method for recovering an aliphatic polyester in a solid phase (hereinafter, referred to as
In this section, this is referred to as the “reprecipitation method”. A) removing at least a portion of a substance other than the aliphatic polyester from the product in Step 2 by at least one method selected from the group consisting of:

[3] The method according to [1] or [2], wherein the insoluble acidic substance contains at least one selected from the group consisting of phosphoric acid, pyrophosphoric acid, phosphorous acid, and derivatives of A method for purifying an aliphatic polyester.

[4] The method for purifying an aliphatic polyester according to [2] or [3], wherein the distillation under reduced pressure is carried out at a pressure of 5 mmHg or less.

[5] The vacuum distillation method is performed at 120 ° C. to 250
The method for purifying an aliphatic polyester according to any one of [2] to [4], wherein the distillation is performed at a temperature in the range of ° C.

[6] In the step 1, the aliphatic hydroxycarboxylic acid is at least one selected from the group consisting of lactic acid, glycolic acid and 6-hydroxycaproic acid. [1] to [5] The method for purifying an aliphatic polyester according to any one of the above.

[7] In step 1, the aliphatic polybasic acid is succinic acid, and the aliphatic polyhydric alcohol is at least one diol selected from ethylene glycol and / or 1,4-butanediol. The method for purifying an aliphatic polyester according to any one of [1] to [6].

[8] In the step 1 [dehydration condensation step], the aliphatic hydroxycarboxylic acid and / or the cyclic ester of the aliphatic hydroxycarboxylic acid is subjected to dehydration condensation polymerization in the presence of a catalyst to form a homopolymer fat. [1] to [6], which are steps for producing a reaction product containing an aromatic polyester.
The method for purifying an aliphatic polyester according to any one of the above.

[9] In the step 1 [dehydration condensation step], the aliphatic hydroxycarboxylic acid and / or the cyclic ester of the aliphatic hydroxycarboxylic acid is subjected to dehydration condensation polymerization in the presence of a catalyst to form an aliphatic copolymer. The method for purifying an aliphatic polyester according to any one of [1] to [6], which is a step of producing a reaction product containing the polyester.

[10] An aliphatic polyester prepared by the purification method according to any one of [1] to [9].

[0037]

BEST MODE FOR CARRYING OUT THE INVENTION The aliphatic polyester used in the present invention includes a homopolymer or a copolymer thereof obtained from a hydroxycarboxylic acid or a cyclic ester thereof, or an aliphatic polyhydric alcohol and an aliphatic polybasic acid. It is a block copolymer obtained from the obtained polyester or a mixed material thereof.

Examples of the method for synthesizing these polymers include a method of directly dehydrating polycondensation from raw materials of hydroxycarboxylic acids, aliphatic polyhydric alcohols, and aliphatic polybasic acids, and an intermediate of a hydroxycarboxylic acid cyclic ester such as lactic acid. Ring opening in the presence of a catalyst using a copolymerizable monomer such as lactide, which is a cyclic dimer, glycolide, which is a dimer of glycolic acid, and ε-caprolactone, which is a cyclic ester of 6-hydroxycaproic acid, as appropriate. A method of polymerizing is used.

In the case of direct dehydration polycondensation, the starting hydroxycarboxylic acids, aliphatic polyhydric alcohols, and aliphatic polybasic acids are azeotropically dehydrated and condensed, preferably in an organic solvent and in the presence of a catalyst. A high-molecular-weight aliphatic polyester can be obtained by a method in which water is removed from the solvent that has flowed off by azeotropic distillation, and the substantially anhydrous solvent is returned to the reaction system.

The aliphatic polyester obtained by these methods has a weight-average molecular weight of 5 to have practical strength.
It is preferably at least 000. Such an aliphatic polyester has sufficient strength and toughness when processed into a film, a molded product or the like, and can be used as it is for a container or the like.

The starting hydroxycarboxylic acids or cyclic esters include lactic acid, glycolic acid, 3-hydroxybutyric acid, 4-hydroxybutyric acid, 4-hydroxyvaleric acid, 5-hydroxyvaleric acid, and 6-hydroxyvaleric acid. Examples include hydroxycaproic acid, lactide which is a cyclic dimer of lactic acid, glycolide which is a dimer of glycolic acid, and ε-caprolactone which is a cyclic ester of 6-hydroxycaproic acid. When the compound has an asymmetric carbon in the molecule, it may be a D-form or an L-form alone or a mixture of the D-form and the L-form, that is, a racemic form.

The polyhydric alcohols have an aliphatic hydroxyl group, and include trihydric or higher functional polyhydric alcohols. For example, ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, 1,3-butanediol, 1,4-butanediol, 3-methyl-1,5-pentanediol, 1,6-
Hexanediol, 1,9-nonanediol, neopentyl glycol, polytetramethylene glycol, 1,
4-cyclohexanedimethanol, 1,4-benzenedimethanol, glycerin, trimethylolpropane, pentaerythritol, mannitol, D-sorbitol, ribose, inositol, polyvinyl alcohol and the like, and also cellulose, cellulose nitrate, acetylcellulose, Methyl cellulose, ethyl cellulose, carboxymethyl cellulose, nitrocellulose;
Also included are regenerated cellulose such as cellophane, viscose rayon and cupra, hemicellulose, starch, amylopectin, dextrin, dextran, glycogen, pectin, chitin, chitosan or polysaccharides such as derivatives thereof. These can be used alone or in combination.

The polybasic acids include those having an aliphatic carboxyl group, and include polycarboxylic acids having a trifunctional or higher carboxyl group and / or acid anhydrides thereof. For example, succinic acid, oxalic acid, malonic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecandioic acid, dodecandioic acid,
1,4-phenylenediacetic acid, phenylsuccinic acid, polyacrylic acid, 1,2,3,4,5,6-cyclohexanehexacarboxylic acid, 1,2,3,4-cyclopentatetracarboxylic acid, tetrahydrofuran-2R , 3T, 4T,
5C-tetracarboxylic acid, 1,2,3,4-cyclobutanetetracarboxylic acid, 4-carboxy-1,1-cyclohexanediacetic acid, 1,3,5-cyclohexanetricarboxylic acid, 1,3,5-trimethyl-1 , 3,5 cyclohexanetricarboxylic acid, (1α, 3α, 5β) -1,
3,5-trimethyl-1,3,5-cyclohexanetricarboxylic acid, 2,3,4,5-furantetracarboxylic acid, 2-methyl-3,4,6-pyridinetricarboxylic acid, butane-1,2,3 , 4-tetracarboxylic acid, butane-1,2,3,4-tetracarboxylic anhydride, mes
o-butane-1,2,3,4-tetracarboxylic acid, 1,
3,5-pentanetricarboxylic acid, 2-methylpropanetricarboxylic acid, 1,2,3-propanetricarboxylic acid, 1,1,2-ethanetricarboxylic acid, 1,2,4-
Butanetricarboxylic acid and the like. Preferred combinations of polyhydric alcohols and polybasic acids are ethylene glycol and succinic acid, 1,4-butanediol and succinic acid,
The polymer obtained from 1,4-cyclohexanedimethanol and succinic acid has a melting point of 100 ° C. or higher. The polymer obtained from such a combination can be used for applications requiring heat resistance, such as for a microwave oven.

In the synthesis of the polymer of the present invention, a catalyst is usually used in both the method of direct condensation and the method of ring-opening polymerization of a cyclic ester intermediate of hydroxycarboxylic acid. Commonly used catalysts include II, III, and I in the periodic table.
Group V and V metals, oxides and salts thereof, and the like. Specifically, metals such as zinc dust, tin dust, aluminum and magnesium, metal oxides such as antimony oxide, zinc oxide, tin oxide, aluminum oxide, magnesium oxide and titanium oxide, stannous chloride, stannic chloride Metal halides, such as stannous bromide, stannic bromide, antimony fluoride, zinc chloride, magnesium chloride, aluminum chloride,
Magnesium carbonate, carbonates such as zinc carbonate, tin acetate, tin octoate, tin lactate, zinc acetate, organic carboxylate such as aluminum acetate, tin trifluoromethanesulfonate, zinc trifluoromethanesulfonate, magnesium trifluoromethanesulfonate, Organic sulfonates such as tin methanesulfonate, tin p-toluenesulfonate, and the like. In addition, organic metal oxides of the above metals such as dibutyltin oxide, or metal alkoxides of the above metals such as titanium isopropoxide, or alkyl metals of the above metals such as diethylzinc, ion exchange such as Dowex and Amberlite Examples thereof include resins and the like, and protic acids such as sulfuric acid, methanesulfonic acid, and p-toluenesulfonic acid. In order to obtain a polymer having a high molecular weight, a metal or a metal compound is usually used as a catalyst. Preferably, a metal or metal compound of tin and zinc, which has a high polymerization rate and a high molecular weight polymer is obtained, more preferably, a metal tin or tin compound is used. The amount of use is about 0.0001 to 10% by weight, preferably 0.001
To 5% by weight.

The state of the reaction after the ring-opening polymerization of the hydroxycarboxylic acid cyclic ester usually does not use a solvent in the polymerization, and therefore the polymer exists in a molten state.

In the state after the reaction in the case of direct dehydration polycondensation, since a solvent is used, the polymer exists in a state of being dissolved in the solvent.

In the aliphatic polyester polymerized mass thus polymerized by a known method, several percent of unreacted substances and low molecular weight compounds such as linear or cyclic oligomers, the active catalyst used for the polymerization, and the polymerization method Some contain solvents.

In the method of the present invention, while maintaining the aliphatic polyester thus obtained in a molten or solution state, it is brought into contact with an acidic substance insoluble in the polyester or the polyester solution or simultaneously with a solid carrier. After treatment and separation, low molecular compounds are removed.

The low molecular compounds include oligomers having a molecular weight of 500 or less, unreacted raw materials, and the like. Above all, it is preferable to remove hydroxycarboxylic acid cyclic esters such as lactide, glycolide, and ε-caprolactone.

In the method of the present invention, in which a solvent is used for treating an aliphatic polyester in the method of separating it after contacting with an insoluble acidic substance or simultaneously with a solid carrier, the solvent may be an aliphatic polyester. Can be used as long as it dissolves and does not dissolve acidic substances. Examples thereof include hydrocarbon solvents such as benzene, toluene, and xylene, and halogenated hydrocarbon solvents such as methylene chloride, chloroform, 1,2-dichloroethane, and o-dichlorobenzene. And ether-based solvents such as diphenyl ether and anisole, or a mixture of various organic solvents. The concentration of the aliphatic polyester to be dissolved is usually 3 to 50% by weight, but the concentration is not particularly limited as long as the aliphatic polyester solution can be stirred. When using an organic solvent during the polymerization,
After the completion of the polymerization reaction, the polymerization solution can be used as it is.

Examples of the insoluble acidic substance of the present invention include inorganic acids such as phosphoric acids and phosphorous acid. Among the phosphoric acids, phosphoric acid, pyrophosphoric acid and polyphosphoric acid are preferred.

The amount of the acidic substance used is
It is 0.1 to 20% by weight, preferably 0.5 to 10.0% by weight. If the amount is less than the above range, the effect of removing the catalyst tends to decrease. If the amount is more than 10.0% by weight, problems such as deterioration of the polymer may occur.

The temperature for the treatment with an acidic substance is usually from 0 to 2
Perform in the range of 00 ° C. When a phosphoric acid compound such as phosphoric acid or pyrophosphoric acid is used, the temperature is 20 to 200 ° C, preferably 50 to 180 ° C. If the temperature is lower than the above-mentioned temperature range, the conversion rate with the acidic substance becomes slow, and if it is too high, the polymer is deteriorated.

The contact time of the acidic substance may be 0.1 to 24 hours, preferably 0.5 to 12 hours. If the time is less than 0.1 hour, the removal of the catalyst may be insufficient, and
If the time exceeds 24 hours, some compounds may deteriorate.

The contact method of the acidic substance may be any of a batch system, a semi-batch system and a continuous system.

In the method of the present invention, when the treatment is carried out by contacting with an insoluble acidic substance in this way, it is necessary to adsorb and separate on a solid carrier. The solid support used may be any one capable of adsorbing acidic substances such as mineral products, inorganic oxide compounds, and ion exchange resins.For example, diatomaceous earth, bentonite, activated clay, zinc oxide, oxide Aluminum, titanium oxide, magnesium silicate, calcium phosphate, silica gel, alumino silica gel, activated carbon, zeolite, starch, cellulose and the like. Preferably, mineral products such as diatomaceous earth, bentonite, and activated clay are used.

The amount of the solid carrier to be used is generally 0.5 to 100% by weight, preferably 1 to 30% by weight, based on the polymer.
Use by weight%. If the amount is too small, the acidic substance cannot be completely adsorbed, and the catalyst removal efficiency is deteriorated. On the other hand, if the amount is too large, a load is imposed on the separation operation of the solid support.

The adsorption time may be sufficient as long as the acidic substance and the solid carrier are in sufficient contact. Usually, the solid carrier is put into the aliphatic polyester solution for 10 minutes or more, preferably 30 minutes or more, followed by stirring.

The adsorption temperature on the solid support is not particularly limited, and is usually at the same temperature as the treatment temperature with the acidic substance. Further, the treatment may be carried out by simultaneously loading the acidic substance and the solid carrier within the above-mentioned usage amount, and there is an advantage that the contacting step of the acidic substance and the adsorption step to the solid carrier can be simultaneously performed. In addition, a treatment in which an acidic substance is adsorbed on a solid carrier in advance can be charged and treated in the same manner.

As described above, a method for isolating the aliphatic polyester by removing the low molecular weight compound from the aliphatic polyester separated by contacting with the insoluble acidic substance or simultaneously treating with the solid support and separating the aliphatic polyester is performed. Is a method in which an aliphatic polyester is brought into a solution state, and then cooled to crystallize and isolate the aliphatic polyester.A poor solvent is added to the aliphatic polyester in a solution state, and the aliphatic polyester is precipitated and crystallized and isolated. And a method of removing a solvent and a low molecular weight compound by distillation to isolate an aliphatic polyester. Preferably, the aliphatic polyester is removed by distillation.

In the present invention, the distillation of a low-molecular compound includes, in addition to the distillation of a low-molecular compound dissolved in a solvent, the evaporation of a low-molecular compound contained in a polymer.

The conditions for isolating the aliphatic polyester by distillation depend on the apparatus for performing the distillation, but are usually carried out at 300 ° C. or lower. If the temperature is kept at an excessively high temperature for a long time, the decomposition of the aliphatic polyester is likely to occur. If the temperature is too low, the removal of the low-molecular compound by distillation takes a long time, so that the temperature is preferably 120 ° C. or higher. The pressure in the system depends on the operating temperature, but is usually 50 mmHg or less, preferably 10 mmHg or less, more preferably 5 mmHg.
It is as follows.

It is also possible to enhance the effect of removing low molecular compounds contained in the aliphatic polyester by passing an inert gas into the system during vacuum distillation. Examples of the inert gas include nitrogen, helium, neon, and argon. Preferably, nitrogen is used.

The time required to remove the low molecular weight compound by distillation varies depending on the type of aliphatic polyester, distillation temperature, degree of vacuum, distillation apparatus, and the like. Removal of low molecular weight compounds
In the case of performing at 180 to 200 ° C. and a degree of reduced pressure of 5 mmHg or less, about 5 to 6 hours is sufficient. Distillation temperature 250
If carried out at a temperature of not less than ° C., the effect of removing low molecular compounds is further improved, and the distillation time can be shortened. However, if the temperature is kept too high, decomposition of the polymer tends to occur, which is not preferable.
At a temperature of 120 ° C. or lower, it takes a long time to remove the low-molecular compound. By increasing the degree of vacuum and keeping the degree of vacuum high, the distillation time can be further reduced.

These methods can remove the catalyst to 100 ppm or less, more preferably 50 ppm or less,
And a heat resistance of 1% or less of the residual amount of the low molecular weight compound,
An aliphatic polyester having excellent weather resistance can be obtained.

[0066]

Next, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples.

The physical properties and the like in the examples were measured by the following methods. -Average molecular weight of polymer The average molecular weight (weight average molecular weight) of the polymer was measured by gel permeation chromatography (GPC) using polystyrene as a standard under the following conditions. Apparatus: Shimadzu LC-10AD Detector: Shimadzu RID-6A Column: Hitachi Chemical GL-S350DT-5 + GL-S3
70DT-5 Solvent: chloroform Concentration: 1% Injection volume: 20 μl Flow rate: 1.0 ml / min ・ Amount of low molecular weight compound Dissolve aliphatic polyester in chloroform, and perform flame flame ionization detector (FID) gas chromatography (column : Silicon OV-210: 2 m × 3 mmφ, column temperature: 140 ° C.). Hereinafter, the amount of the low-molecular compound is represented by weight%. -Content of catalyst contained It was measured by fluorescent X-ray analysis. Heat resistance test Using TG / DTA220 manufactured by Seiko Denshi Kogyo Co., Ltd., 5%-in dry Air under the condition of a temperature increase rate of 10 ° C./min.
The temperature at the time of weight loss was measured. A weather resistance test A press film (thickness: 100 μm) was prepared under the conditions of 180 ° C./100 kg / cm 2. The resulting film was converted to a Suga Standard Sunshine Weather Meter (W
E-SUN) using a carbon arc light source at 120
It was held for 400 hours under the condition of minutes (18 minutes shower). A tensile strength test was performed on the film before and after the test, and the strength retention was calculated.

Production Example 1 5 kg of L-lactide and 0.2% by weight of tin octoate
(10 g) and lauryl alcohol 2% by weight (100
g) was sealed in a thick cylindrical stainless steel polymerization vessel equipped with a stirrer, degassed under vacuum for 2 hours, and then replaced with nitrogen gas. The mixture was stirred at 180 ° C. under a nitrogen atmosphere.
For 3 hours. While maintaining the temperature as it was, the air was gradually degassed by a vacuum pump through an exhaust pipe and a glass receiver, and the pressure inside the reaction vessel was reduced to 3 mmHg. One hour after the start of degassing, the inside of the vessel was replaced with nitrogen, and the polymer was drawn out from the lower part of the vessel in a string form and pelletized to obtain poly L-lactic acid. The average molecular weight of this polymer was 110,000, the Sn content was 580 ppm, and the lactide content was 3.1%.

Production Example 2 5 kg of L-lactide, 4 kg of L-lactide and DL
-Pelletization was carried out in the same manner as in Production Example 1 except that lactide was changed to 1 kg to obtain poly-DL-lactic acid. The average molecular weight of this polymer was 100,000, the Sn content was 610 ppm, and the lactide content was 2.7%.

Production Example 3 Pellets were pelletized in the same manner as in Production Example 1 except that 5 kg of L-lactide was changed to 4 kg of L-lactide and 1 kg of glycolide to obtain a copolymer of L-lactide and glycolide. The average molecular weight of this polymer was 110,000, the Sn content was 600 ppm, the content of lactide was 2.4%, and the content of glycolide was 0.4%.

Production Example 4 5 kg of 90% by weight L-lactic acid was added at 140 ° C./100 mmHg
After distilling water while stirring for 3 hours, 28.5 g of stannous chloride (dihydrate) was added, and 140 ° C./100 mm
The mixture was stirred with Hg for another 2 hours to be oligomerized. 10.6 kg of o-dichlorobenzene was added to this oligomer, and 1
An azeotropic dehydration reaction was performed at 40 ° C./230 mmHg, and the distilled water and the solvent were separated by a water separator, and only the solvent was returned to the reactor. After 4 hours, 2.3 kg of organic solvent returned to the reactor
The solution was passed through a column packed with Molecular Sieve 3A, and returned to the reactor at 140 ° C./230 mmH.
The reaction was further carried out for 40 hours with g to obtain a polylactic acid solution having an average molecular weight of 140,000. The Sn content in this polymer solution was 8
30 ppm (about 3300 ppm based on polymer), 1.0% lactide in solution (about 4.0% based on polymer)
%)Met.

Production Example 5 2.5 kg of 90% by weight of L-lactic acid and 0.3 kg of 70% by weight of glycolic acid were distilled at a temperature of 140 ° C./50 mmHg for 3 hours to distill water. Japanese) 1
1.2 kg was added, and the mixture was stirred at 150 ° C./50 mmHg for further 3 hours to be oligomerized. 3.0 kg of diphenyl ether was added to this oligomer, and the solvent was returned to the reactor through a column filled with molecular sieve 3A, and refluxed at 140 ° C./25 mmHg for 40 hours to obtain a copolymer solution having an average molecular weight of 120,000. . The Sn content in this polymer solution was 1300 ppm (3300 ppm based on the copolymer, the lactide content in the solution was 1.2%
(About 3.0% based on the copolymer), and the amount of glycolide in the solution was 0.3% (about 0.8% based on the copolymer).

Production Example 6 To 1 kg of ethylene glycol and 1.9 kg of succinic acid were added 7.0 kg of diphenyl ether and 14.5 g of metal tin powder, and the mixture was heated and stirred at 130 ° C./140 mmHg for 7 hours while distilling water out of the system. After oligomerization, 140 ° C
The azeotropic dehydration was performed at / 30 mmHg for 8 hours. Further, a column packed with molecular sieve 3A was attached, and the distilled solvent was returned to the reactor through the column packed with molecular sieve 5A, and the solvent was distilled off at 130 ° C./17 mmHg.
After stirring for 0 hour, a copolymer solution having an average molecular weight of about 130,000 was obtained. This solution was filtered to remove insoluble metallic tin powder. The Sn content in this copolymer solution was 1000 ppm. Example 1 0.5 kg of poly-L-lactic acid obtained in Production Example 1 and 2.0 kg of o-dichlorobenzene were charged and dissolved at 110 ° C.
To this was added 18.8 g (3.8% by weight) of pyrophosphoric acid,
After stirring at 110 ° C for 2 hours, diatomaceous earth 10.6g
(2.1% by weight) and further stirred at 110 ° C. for 30 minutes. Next, this solution was filtered hot to remove the solid carrier. After o-dichlorobenzene as a solvent was distilled off from this polymer solution under reduced pressure, the inside of the system was finally heated to 180 ° C., 3 mm
The pressure was reduced to Hg to remove low molecular compounds. 1 in the system
After 5 hours while maintaining the temperature at 80 ° C./3 mmHg, the inside of the system was replaced with nitrogen, and the polymer was extracted in a string form and pelletized. The average molecular weight of the obtained polymer was unchanged at about 110,000.
The residual lactide amount was 0.04%, and the Sn content was 9 ppm. When a heat resistance test was performed on the obtained polymer, the 5% weight loss temperature was 330 ° C. Further, the tensile strength of the obtained press film before the weather resistance test was 680 kg / cm 2, the strength retention after 400 hours of the weather resistance test was 100%, and both heat resistance and weather resistance were good.

Example 2 0.5 kg of poly DL-lactic acid and 2.0 kg of o-dichlorobenzene obtained in Production Example 2 were charged and dissolved at 110 ° C., and 18.8 g of pyrophosphoric acid (3.8 wt. %) And stirred at 110 ° C. for 2 hours.
g (2.1% by weight) was added, and the mixture was further stirred at 110 ° C. for 30 minutes. Then, the solution was filtered hot to remove the solid carrier. After o-dichlorobenzene as a solvent was distilled off from this polymer solution under reduced pressure, the inside of the system was finally heated to 180 ° C., 3 mm
The pressure was reduced to Hg to remove low molecular compounds. 1 in the system
After keeping the temperature at 80 ° C./3 mmHg for 5 hours, the inside of the system was replaced with nitrogen, and the copolymer was extracted in a string form and pelletized. The average molecular weight of the obtained polymer was unchanged at about 100,000. Further, the residual lactide amount was 0.03% and the Sn content was 10 ppm. When a heat resistance test was performed on the obtained copolymer, the 5% weight loss temperature was 320 ° C. The tensile strength of the obtained press film before the weather resistance test was 650 kg / cm 2,
The strength retention after 0 hour was 100%, and both heat resistance and weather resistance were good.

Example 3 0.5 kg of the copolymer of L-lactide and glycolide obtained in Production Example 3 and 2.0 kg of o-dichlorobenzene
Was dissolved at 110 ° C., and pyrophosphoric acid was added thereto.
After adding 8 g (3.8% by weight) and stirring at 110 ° C. for 2 hours, 10.6 g (2.1% by weight) of diatomaceous earth was added and further stirred at 110 ° C. for 30 minutes. Next, this solution was filtered hot to remove the solid carrier. After o-dichlorobenzene as a solvent was distilled off under reduced pressure from the polymer solution, the pressure in the system was finally reduced to 180 ° C. and 3 mmHg to remove low molecular compounds. After keeping the inside of the system at 180 ° C./3 mmHg for 5 hours, the inside of the system was replaced with nitrogen, and the polymer was extracted in a string form and pelletized. The average molecular weight of the obtained polymer was unchanged at about 110,000. The amounts of residual lactide and glycolide were 0.03% and 0.03%, respectively.
The Sn content was 13 ppm. A heat resistance test of the obtained copolymer showed that the 5% weight loss temperature was 31.
It was 0 ° C. Further, the tensile strength of the obtained press film before the weather resistance test was 610 kg / cm 2, and the strength retention after 400 hours of the weather resistance test was 95%, and both heat resistance and weather resistance were good.

Example 4 1.3 kg of diphenyl ether was added to 2.0 kg of the poly L-lactic acid solution obtained in Production Example 4, and 24.8 pyrophosphoric acid was added.
g (5.0% by weight) and stirred at 110 ° C. for 2 hours, and then 55.7 g (11.1% by weight) of diatomaceous earth was added.
The mixture was further stirred at 110 ° C. for 30 minutes. Next, this solution was subjected to hot filtration to remove the solid carrier. From the polymer solution, diphenyl ether as a solvent was distilled off under reduced pressure, and the pressure in the system was finally reduced to 180 ° C. and 3 mmHg to remove low molecular compounds. After keeping the inside of the system at 180 ° C./3 mmHg for 5 hours, the inside of the system was replaced with nitrogen, and the polymer was extracted in a string form and pelletized. The average molecular weight of the obtained polymer was about 140,000 and remained unchanged. Further, the residual lactide amount was 0.02% and the Sn content was 10 ppm. When a heat resistance test was performed on the obtained polymer, the 5% weight loss temperature was 320 ° C. The tensile strength of the obtained press film before the weather resistance test was 690 kg / cm @ 2, and the strength retention after 400 hours of the weather resistance test was 100%.
And both heat resistance and weather resistance were good.

Example 5 3.0 kg of diphenyl ether was added to 2.0 kg of the poly-L-lactic acid solution obtained in Production Example 4, and pyrophosphoric acid was added to the solution.
After adding 7.5 g (7.5% by weight) and stirring at 130 ° C. for 2 hours, 21.1 g (4.2% by weight) of diatomaceous earth was added and further stirred at 110 ° C. for 30 minutes. Next, this solution was subjected to hot filtration to remove the solid carrier. Next, the solution was cooled to 40 ° C., and the polymer was crystallized. After the crystallized polymer was separated by filtration, the low molecular weight compound adhering to the polymer was further removed by washing with isopropyl alcohol, and dried under reduced pressure to obtain powdery poly-L-lactic acid. The average molecular weight of the obtained polymer was about 140,000 and remained unchanged. The residual lactide amount was 0.01%, and the Sn content was 15 ppm. When a heat resistance test was performed on the obtained polymer, the 5% weight loss temperature was 330 ° C. The tensile strength of the obtained press film before the weather resistance test was 680 kg / cm 2, and the weather resistance test was 400 kg / cm 2.
The strength retention after 100 hours was 100%, and both heat resistance and weather resistance were good.

Example 6 1.25 kg of diphenyl ether was added to 1.25 kg of the copolymer solution obtained in Production Example 5, and 18.8 g (3.8% by weight) of pyrophosphoric acid was added thereto. The mixture was stirred at 110 ° C. for 5 hours. And 21.1 g (4.2% by weight) of diatomaceous earth were added, and the mixture was further stirred for 30 minutes. Next, this solution was subjected to hot filtration to remove the solid carrier. From this copolymer solution,
Diphenyl ether as a solvent was distilled off under reduced pressure, and the pressure in the system was finally reduced to 180 ° C. and 3 mmHg to remove low molecular compounds. After keeping the inside of the system at 220 ° C./3 mmHg for 5 hours, the inside of the system was replaced with nitrogen, and the polymer was extracted in a string form and pelletized. The average molecular weight of the obtained copolymer is about 1
No change at 20,000. Further, the residual lactide amount and the glycolide amount were 0.08% and 0.05%, respectively, and the Sn content was 12 ppm. A heat resistance test of the obtained polymer showed that a 5% weight loss temperature was 310 ° C. Further, the tensile strength of the obtained press film before the weather resistance test was 610 kg / cm 2, and the strength retention after 400 hours of the weather resistance test was 95%, and both heat resistance and weather resistance were good.

Example 7 1.3 kg of diphenyl ether was added to 2.0 kg of the copolymer solution obtained in Production Example 6, and pyrophosphoric acid 2
After adding 4.8 g (5.0% by weight) and stirring at 130 ° C. for 2 hours, 24.8 g (5.0% by weight) of diatomaceous earth was added and further stirred at 130 ° C. for 1 hour. Next, this solution was subjected to hot filtration to remove the solid carrier. Diphenyl ether as a solvent was distilled off from the polymer solution under reduced pressure, and the pressure in the system was finally reduced to 180 ° C. and 3 mmHg, and low-molecular-weight compounds were distilled off under reduced pressure. 180 ° C, 3mmH
After 5 hours while maintaining the g, after the distillation of the low molecular weight compound disappeared, the inside of the system was replaced with nitrogen, and the polymer was extracted in a string form and pelletized. The average molecular weight of the copolymer obtained was unchanged at about 130,000. The Sn content was 10 ppm. When a heat resistance test of the obtained polymer was performed,
The 5% weight loss temperature was 310 ° C. The tensile strength of the obtained press film before the weather resistance test was 370 kg.
/ Cm 2, the strength retention after 400 hours of weathering test was 100%, and both heat resistance and weather resistance were good.

Example 8 0.5 kg of poly-L-lactic acid obtained in Production Example 1 and 2.0 kg of o-dichlorobenzene were charged and dissolved at 110 ° C.
To this, 18.8 g (3.8% by weight) of pyrophosphoric acid and 10.6 g (2.1% by weight) of diatomaceous earth were added.
Stirred for hours. Next, this solution was subjected to hot filtration to remove the solid carrier. After distilling off o-dichlorobenzene as a solvent from this polymer solution under reduced pressure, the system
C., the pressure was reduced to 3 mmHg to remove low molecular compounds. After keeping the inside of the system at 180 ° C./3 mmHg for 5 hours, the inside of the system was replaced with nitrogen, and the polymer was extracted in a string form and pelletized. The molecular weight of the obtained polymer was unchanged at about 110,000. The remaining lactide amount was 0.03%, and Sn
Content was 7 ppm. When a heat resistance test was performed on the obtained polymer, the 5% weight loss temperature was 330 ° C. Further, the tensile strength of the obtained press film before the weather resistance test was 680 kg / cm 2,
The strength retention after 0 hour was 100%, and both heat resistance and weather resistance were good.

COMPARATIVE EXAMPLE 1 Except for adding 0.5 g (0.1% by weight) of diatomaceous earth,
The same processing as in Example 1 was performed. The average molecular weight of the obtained poly L-lactic acid was about 110,000, which was not changed. In addition, poly L-
The residual lactide amount in lactic acid was 0.10%, and the Sn content was 1000 ppm. A heat resistance test of the obtained polymer showed that the 5% weight loss temperature was 280 ° C. The tensile strength of the obtained press film before the weather resistance test was 590 kg / cm @ 2.
The strength retention after the time decreased to 50%, and both heat resistance and weather resistance were inferior to Example 1.

Comparative Example 2 The same treatment as in Example 1 was performed except that the distillation temperature of the low molecular weight compound by distillation was kept at 260 ° C. Poly L obtained
-Lactic acid was colored dark brown, and the average molecular weight of poly L-lactic acid was reduced to 50,000.

Comparative Example 3 The removal of low molecular weight compounds by distillation was performed at 180 ° C. and a reduced pressure of 20 m.
The processing was performed in the same manner as in Example 1 except that the processing was performed at mHg. The average molecular weight of the obtained poly L-lactic acid was about 110,000, which was not changed, but the residual lactide amount was 0.8%. A heat resistance test of the obtained polymer showed that a 5% weight loss temperature was 310 ° C. The tensile strength of the obtained press film before the weather resistance test was 600 kg / cm 2, the strength retention after 400 hours of the weather resistance test was reduced to 70%, and both the heat resistance and the weather resistance were compared with those of Example 1. Was inferior.

Comparative Example 4 2 kg of the poly-L-lactic acid obtained in Production Example 1 was heated and melted at 180 ° C. under a nitrogen atmosphere, and gradually degassed by a vacuum pump through an exhaust pipe and a glass receiver. Finally 3m
The pressure was reduced to mHg, and the low-molecular compounds contained therein were distilled off. After 5 hours with the inside of the system at 3 mmHg, the inside of the container was replaced with nitrogen, and the poly-L-lactic acid was extracted in a string form and pelletized. The average molecular weight of the obtained poly L-lactic acid was about 110,000, which was not changed. Further, the amount of residual lactide in the poly-L-lactic acid was 1.0%, and the Sn content was 500 ppm. When a heat resistance test was performed on the obtained polymer, the 5% weight loss temperature was 300 ° C. The tensile strength of the obtained press film before the weather resistance test was 590 kg / cm 2, the strength retention after 400 hours of the weather resistance test was reduced to 50%, and both the heat resistance and the weather resistance were compared with those of Example 1. Was inferior.

Comparative Example 5 2 kg of the copolymer obtained in Production Example 2 was heated and melted at 180 ° C. under a nitrogen atmosphere, gradually degassed by a vacuum pump through an exhaust pipe and a glass receiver, and finally the system was finally degassed. 3mm
The pressure was reduced to Hg, and the low-molecular compounds contained therein were distilled off. After 5 hours with the inside of the system at 3 mmHg, the inside of the vessel was replaced with nitrogen, and the copolymer was extracted in a string form and pelletized. The average molecular weight of the resulting copolymer was unchanged at about 100,000. The amount of residual lactide in the copolymer is 0.8
%, Sn content was 540 ppm. When a heat resistance test was performed on the obtained copolymer, the 5% weight loss temperature was 280 ° C. The tensile strength of the obtained press film before the weather resistance test was 600 kg / cm 2,
The strength retention after 400 hours of the weather resistance test was reduced to 40%, and both heat resistance and weather resistance were inferior.

Comparative Example 6 2 kg of the copolymer obtained in Production Example 3 was heated and melted at 180 ° C. in a nitrogen atmosphere, and was gradually degassed by a vacuum pump through an exhaust pipe and a glass receiver, and finally the system was finally degassed. 3mm
The pressure was reduced to Hg, and the low-molecular compounds contained therein were distilled off. After 5 hours with the inside of the system at 3 mmHg, the inside of the vessel was replaced with nitrogen, and the copolymer was extracted in a string form and pelletized. The average molecular weight of the resulting copolymer was unchanged at about 110,000. Further, the residual lactide amount and the residual glycolide amount in the copolymer were 0.8% and 0.3%, respectively, and the Sn content was 610 ppm. A heat resistance test of the resulting copolymer showed that the 5% weight loss temperature was 280 ° C.
Met. Further, the tensile strength of the obtained press film before the weather resistance test was 570 kg / cm 2, and the strength retention after 400 hours of the weather resistance test was reduced to 50%.
The weather resistance was also poor.

Comparative Example 7 4 kg of the poly-L-lactic acid solution obtained in Production Example 4 was heated to 180 ° C. under a nitrogen atmosphere, and gradually degassed by a vacuum pump through an exhaust pipe and a glass receiver. Finally 3mm
The pressure was reduced to Hg, and diphenyl ether and low molecular weight compounds as solvents were distilled off. After 5 hours at 3 mmHg, the inside of the system was replaced with nitrogen, and the polymer was extracted in a string form and pelletized. The average molecular weight of the obtained poly L-lactic acid is about 1
40,000 did not change, but the remaining lactide amount was 3.2%,
The Sn content was 2300 ppm. A heat resistance test was performed on the obtained polymer.
70 ° C. Further, the tensile strength of the obtained press film before the weather resistance test was 580 kg / cm 2, and after 400 hours of the weather resistance test, the film was cracked, the test was impossible, and the heat resistance and the weather resistance were poor.

Comparative Example 8 The same treatment as in Example 1 was carried out except that the distillation temperature of the low molecular weight compound by distillation was kept at 100 ° C. At 100 ° C., the poly-L-lactic acid was solidified. Therefore, the stirring was stopped, and the subsequent processing operation was carried out. The average molecular weight of the obtained poly-L-lactic acid was about 110,000, which was not changed, but the residual amount of lactide varied from 0.8 to 3.8% depending on the sample location.

[0089]

According to the method of the present invention, the use of a solid carrier simplifies the operation of removing the catalyst, and also reduces the content of the catalyst and the low molecular weight compound contained in the polymer, and provides heat resistance and weather resistance. An excellent aliphatic polyester can be obtained.

 ──────────────────────────────────────────────────の Continued on the front page (72) Inventor Masanobu Amioka 1190 Kasama-cho, Sakae-ku, Yokohama-shi, Kanagawa Prefecture Mitsui Toatsu Chemicals Co., Ltd.

Claims (17)

[Claims] (1) In the presence of a catalyst, (i) an aliphatic hydroxycarboxylic acid, (ii) a cyclic ester of an aliphatic hydroxycarboxylic acid, (iii) an aliphatic polyhydric alcohol and an aliphatic polybasic acid, iv) polymerizing at least one selected from the group consisting of two or more monomers selected from the group consisting of the above (i)-(iii) and / or oligomers and / or polymers obtained by polymerizing these monomers; When purifying the aliphatic polyesters obtained by adding the acidic substance and a solid carrier, which are insoluble in the polyester or the polyester solution, while maintaining the aliphatic polyesters in a molten or solution state, A method for purifying aliphatic polyesters, comprising separating a catalyst by adsorption treatment. (2) In the presence of a catalyst, (i) an aliphatic hydroxycarboxylic acid, (ii) a cyclic ester of an aliphatic hydroxycarboxylic acid, (iii) an aliphatic polyhydric alcohol and an aliphatic polybasic acid, iv) polymerizing at least one selected from the group consisting of two or more monomers selected from the group consisting of the above (i)-(iii) and / or oligomers and / or polymers obtained by polymerizing these monomers; When purifying the aliphatic polyesters obtained by adding the acidic substance and a solid carrier, which are insoluble in the polyester or the polyester solution, while maintaining the aliphatic polyesters in a molten or solution state, A method for purifying aliphatic polyesters, comprising removing low-molecular compounds after separating the catalyst by adsorption treatment. 3. The purification method according to claim 1, wherein the method of “adding an acidic substance and a solid carrier” comprises adding a solid carrier after adding an insoluble acidic substance. 4. The purification method according to claim 1, wherein the method of “adding an acidic substance and a solid carrier” comprises simultaneously adding an insoluble acidic substance and a solid carrier. 5. The purification method according to claim 1, wherein the insoluble acidic substance is a phosphoric acid or a phosphorous acid. 6. The purification method according to claim 5, wherein the phosphoric acid is phosphoric acid or pyrophosphoric acid. 7. The purification method according to claim 1, wherein the insoluble solid carrier is a mineral product. 8. The purification method according to claim 7, wherein the mineral products are at least one selected from the group consisting of diatomaceous earth, kaolin, and activated clay. 9. The purification method according to claim 2, wherein the method of “removing a low-molecular compound” comprises removing the low-molecular compound by distillation under reduced pressure. 10. The method of “removing a low molecular compound” comprises the steps of:
Distillation under reduced pressure is performed at 5 mmHg or less.
The purification method according to claim 2. 11. The purification method according to claim 10, wherein the distillation is performed at a temperature in the range of 120 ° C. to 250 ° C. 12. The method for “removing a low molecular compound” comprises the steps of:
The purification method according to any one of claims 2 to 8, wherein the low-molecular compound is removed by crystallization. 13. The purification method according to claim 1, wherein the aliphatic polyester is a homopolymer of an aliphatic hydroxycarboxylic acid or a cyclic ester of an aliphatic hydroxycarboxylic acid. 14. The purification method according to claim 1, wherein the aliphatic polyester is a copolymer of an aliphatic hydroxycarboxylic acid or a cyclic ester of an aliphatic hydroxycarboxylic acid. 15. The method according to claim 1, wherein the aliphatic hydroxycarboxylic acid is at least one selected from the group consisting of lactic acid, glycolic acid, and 6-hydroxycaproic acid.
4. The purification method described in 4. 16. The method according to claim 1, wherein the aliphatic polybasic acid is succinic acid and the aliphatic polyhydric alcohol is ethylene glycol and / or 1,4-butanediol.
The purification method according to any one of the above. 17. An aliphatic polyester refined by the purification method according to claim 1. Description: