WO2010103884A1 - Polyglycolic acid resin composition and molded object thereof - Google Patents

Abstract

A polyglycolic acid resin composition characterized by comprising a polyglycolic acid resin, a hindered phenol compound, and an acid phosphate compound; and a molded object of the resin composition.

Description

Polyglycolic acid resin composition and molded article thereof

The present invention relates to a polyglycolic acid resin composition, and more particularly to a polyglycolic resin composition that is excellent in water resistance and hardly undergoes coloration due to heat.

Polyglycolic acid-based resins are attracting attention as biodegradable polymer materials with a low environmental impact because they are excellent in microbial degradability and hydrolyzability. However, when this polyglycolic acid resin is heated for a long time at the time of melt kneading or melt molding, there is a problem that it is depolymerized by heat to generate glycolide and hydrolyze, or decomposes and colors by heat. . Therefore, in order to improve water resistance (hydrolysis resistance) and heat resistance (thermal stability), a heat stabilizer, an antioxidant and the like have been conventionally added to the polyglycolic acid resin.

For example, International Publication No. 2003/037956 (Patent Document 1) discloses a phosphorus compound having at least one hydroxyl group and at least one long-chain alkyl ester group represented by mono- or distearyl acid phosphate in polyglycolic acid. It is disclosed that the melt stability of polyglycolic acid is improved by adding a heat stabilizer such as.

International Publication No. 2006/095526 (Patent Document 2) discloses a long-chain alkyl ester of (sub-) phosphoric acid having a specific basicity such as monostearyl phosphate or distearyl phosphate in an aliphatic polyester resin. It is disclosed that the water resistance (hydrolysis resistance) of the aliphatic polyester resin composition is improved by adding a carboxylic acid, and further by adding a carboxyl group sealing agent such as a carbodiimide compound. It is also disclosed that the improvement is further improved. In addition, International Publication No. 2007/034805 (Patent Document 3) includes a polyglycolic acid resin and a long-chain alkyl ester of (sub-) phosphoric acid represented by an approximately equimolar mixture of mono- and distearyl acid phosphates. It is disclosed that the water resistance and thermal stability of a molded product obtained from the polyglycolic acid resin composition are improved by adding a carboxyl group-capping agent such as a heat stabilizer and / or a carbodiimide compound. . Further, JP-A-2007-126653 (Patent Document 4) discloses at least one hydroxyl group represented by a mixture of about 50 mol% monostearyl phosphate and about 50 mol% distearyl phosphate in an aliphatic polyester resin. The heat resistance of the aliphatic polyester resin composition is obtained by sequentially heating and melting and mixing a heat stabilizer such as an alkyl phosphite having at least one alkyl ester group and a carboxyl group sealing agent such as a carbodiimide compound. It is disclosed that coloration by heat and heat is improved.

JP 2007-23082 A (Patent Document 5) improves the hydrolysis resistance and stretchability of a polyglycolic acid resin composition by adding a predetermined amount of a phenolic resin to the polyglycolic acid resin. Thermal stabilizers such as phosphoric acid or alkyl esters of phosphorous acid are also disclosed.

However, in the resin compositions described in Patent Documents 1 to 3 and Patent Document 5, coloring due to heat is not sufficiently improved. In the resin composition described in Patent Document 4, a thermal stabilizer and a carboxyl group are not obtained. It was necessary to produce the sealing agent by a specific method such as heating and melting and mixing sequentially.

Japanese Patent Laid-Open No. 6-80872 (Patent Document 6) discloses a composition containing an aliphatic polyester, an antioxidant and an anti-coloring agent as an aliphatic polyester composition with little coloring. Phosphorus processing stabilizers such as hindered phenolic antioxidants and triphenyl phosphite are disclosed as inhibitors, and trialkyl phosphates typified by tributyl phosphate are disclosed as coloring inhibitors. JP-A-2003-313436 (Patent Document 7) discloses biodegradable plastics, carbodiimide compounds, and antioxidants as biodegradable plastic compositions that improve hydrolysis resistance and heat resistance and retain transparency. A composition containing an agent is disclosed. Patent Document 7 discloses a mixture of a hindered phenolic antioxidant and a phosphite antioxidant as a preferred antioxidant. Japanese Patent Application Laid-Open No. 2007-291336 (Patent Document 8) describes hydrolysis inhibition of polyester resins, carbodiimide compounds, etc. as a polyester resin composition that has hydrolysis resistance and preserves resin properties over a long period of time. A polyester resin composition containing an agent, a phosphorus stabilizer and a phenol stabilizer is disclosed. Phosphoric esters such as trioctyl phosphate and triphenyl phosphate are used as phosphorus stabilizers, and hinders are used as phenol stabilizers. Dophenol stabilizers are disclosed.

However, in the resin composition described in Patent Document 6, water resistance and suppression of coloring due to heat are not yet sufficient, and in the resin compositions described in Patent Documents 7 to 8, suppression of coloring due to heat is not sufficient. It was not enough yet.

International Publication No. 2003/037956 International Publication No. 2006/095526 International Publication No. 2007/034805 JP 2007-126653 A Japanese Patent Laid-Open No. 2007-23082 Japanese Patent Laid-Open No. 6-80872 JP 2003-31436 A JP 2007-291336 A

The present invention has been made in view of the above-described problems of the prior art, and an object of the present invention is to provide a polyglycolic acid resin composition that is excellent in water resistance and hardly colored by heat.

As a result of intensive studies to achieve the above object, the present inventors only improved the water resistance by adding a hindered phenol compound and an acid phosphate compound to the polyglycolic acid resin. Thus, the present inventors have found that coloring due to heat is suppressed and completed the present invention.

That is, the polyglycolic acid resin composition of the present invention contains a polyglycolic acid resin, a hindered phenol compound, and an acid phosphate compound.

As the acid phosphate compound, the following formula (1):

(In the formula (1), R represents a hydrocarbon group having 7 to 24 carbon atoms, and when a plurality of R are present, they may be the same or different, and m is 1 or 2. is there.)
And a compound in which R in the formula (1) is an alkyl group having 7 to 24 carbon atoms is more preferable. In addition, the content of the acid phosphate compound is preferably 0.003 to 3 parts by mass with respect to 100 parts by mass of the polyglycolic acid resin.

In the polyglycolic acid resin composition of the present invention, the hindered phenol compound is preferably a compound in which a tert-butyl group is introduced into at least one carbon atom of the ortho position of the phenol skeleton. The content of the hindered phenol compound in terms of phenolic hydroxyl group is preferably 0.3 to 30 μmol with respect to 1 g of the polyglycolic acid resin.

The molded article of the present invention is obtained from the polyglycolic acid resin composition of the present invention.

In addition, the water resistance of the polyglycolic acid resin composition is improved by using a hindered phenol compound and an acid phosphate compound together as in the present invention, and the reason why coloring due to heat is further suppressed is not always clear. However, the present inventors speculate as follows. That is, the catalyst used in the synthesis of the polyglycolic acid resin usually remains in the polyglycolic acid resin composition. When such a polyglycolic acid resin composition is heated, the polyglycolic acid resin is not only directly depolymerized and decomposed by heat, but also due to the action of the catalyst under heating, Depolymerize or decompose. When such depolymerization occurs, glycolide is generated, so that the water resistance of the composition is lowered, and when the decomposition occurs, the composition is colored.

In the polyglycolic acid resin composition of the present invention, since a hindered phenol compound and an acid phosphate compound exist, they interact with each other to directly depolymerize or thermally decompose as described above. In addition, it is presumed that depolymerization and decomposition due to catalytic action under heating are also suppressed, water resistance is improved, and coloring is less likely to occur. In particular, it is presumed that the acid phosphate compound suppresses depolymerization and decomposition due to catalytic action under heating by forming a chelate with the catalyst.

On the other hand, when only a hindered phenol compound is added, when a hindered phenol compound and a phosphite compound are added, when a hindered phenol compound and a trialkyl phosphate or triphenyl phosphate are added In this case, the direct depolymerization or decomposition of polyglycolic acid resin by heat and the depolymerization or decomposition by catalytic action under heating are not sufficiently suppressed. Inferred to occur. In particular, trialkyl phosphate and triphenyl phosphate do not form a chelate with a catalyst such as an acid phosphate compound, and it is presumed that depolymerization and decomposition due to catalytic action are not sufficiently suppressed.

In addition, when only the acid phosphate compound is added, both the direct depolymerization of polyglycolic acid resin by heat and the depolymerization by catalytic action under heating are suppressed, but direct decomposition by heat It is presumed that coloring occurs because the decomposition due to the catalytic action under heating is not sufficiently suppressed.

According to the present invention, it is possible to obtain a polyglycolic acid-based resin composition that is excellent in water resistance and difficult to be colored by heat.

Hereinafter, the present invention will be described in detail on the basis of preferred embodiments thereof.

First, the polyglycolic acid resin composition of the present invention will be described. The polyglycolic acid resin composition (hereinafter referred to as “PGA resin composition”) of the present invention comprises a polyglycolic acid resin (hereinafter referred to as “PGA resin”), a hindered phenol compound, and acid phosphate. Containing a fate compound.

<PGA resin>
As the PGA-based resin used in the present invention, the following formula (1):
— [O—CH ₂ —C (═O)] — (1)
A glycolic acid homopolymer consisting only of glycolic acid repeating units represented by the formula (hereinafter referred to as “PGA homopolymer”, including a ring-opened polymer of glycolide which is a bimolecular cyclic ester of glycolic acid). And a polyglycolic acid copolymer containing glycolic acid repeating units (hereinafter referred to as “PGA copolymer”). Such PGA-type resin may be used individually by 1 type, or may use 2 or more types together. From the viewpoint of heat resistance, gas barrier properties, and mechanical strength, the PGA resin is preferably crystalline.

The comonomers used together with the glycolic acid monomer in producing the PGA copolymer include ethylene oxalate (ie, 1,4-dioxane-2,3-dione), lactides, lactones (for example, β -Propiolactone, β-butyrolactone, β-pivalolactone, γ-butyrolactone, δ-valerolactone, β-methyl-δ-valerolactone, ε-caprolactone, etc.), carbonates (eg trimethylene carbonate, etc.), ethers (For example, 1,3-dioxane, etc.), cyclic monomers such as ether esters (eg, dioxanone), amides (ε-caprolactam, etc.); lactic acid, 3-hydroxypropanoic acid, 3-hydroxybutanoic acid, 4- Hydro, such as hydroxybutanoic acid and 6-hydroxycaproic acid Cicarboxylic acids or alkyl esters thereof; substantially equimolar mixtures of aliphatic diols (ethylene glycol, 1,4-butanediol, etc.) and aliphatic dicarboxylic acids (succinic acid, adipic acid, etc.) or alkyl esters thereof Can be mentioned. These comonomers may be used individually by 1 type, or may use 2 or more types together. Of these comonomers, hydroxycarboxylic acid is preferred from the viewpoint of heat resistance.

The catalyst used when the PGA resin is produced by ring-opening polymerization of glycolide includes tin compounds such as tin halide and tin organic carboxylate; titanium compounds such as alkoxy titanate; aluminum such as alkoxyaluminum. Known ring-opening polymerization catalysts such as zirconium compounds, zirconium compounds such as zirconium acetylacetone, and antimony compounds such as antimony halide and antimony oxide.

The PGA-based resin can be produced by a conventionally known polymerization method. The polymerization temperature is preferably 120 to 300 ° C., more preferably 130 to 250 ° C., particularly preferably 140 to 220 ° C., and 150 to 200. C is most preferred. When the polymerization temperature is less than the lower limit, the polymerization tends not to proceed sufficiently. On the other hand, when the polymerization temperature exceeds the upper limit, the produced resin tends to be thermally decomposed.

The polymerization time for the PGA resin is preferably 2 minutes to 50 hours, more preferably 3 minutes to 30 hours, and particularly preferably 5 minutes to 18 hours. When the polymerization time is less than the lower limit, the polymerization does not proceed sufficiently, whereas when the upper limit is exceeded, the generated resin tends to be colored.

In the PGA resin used in the present invention, the content of the glycolic acid repeating unit represented by the formula (1) is preferably 70% by mass or more, more preferably 80% by mass or more, and further preferably 90% by mass or more. 100 mass% is particularly preferable. When the content of the glycolic acid repeating unit is less than the lower limit, heat resistance and gas barrier properties tend to decrease.

The weight average molecular weight of the PGA resin is preferably 30,000 to 800,000, more preferably 50,000 to 500,000. When the weight average molecular weight of the PGA-based resin is less than the lower limit, the mechanical strength of the PGA-based resin molded product tends to be lowered. On the other hand, when it exceeds the upper limit, melt extrusion and molding tend to be difficult. The weight average molecular weight is a polymethylmethacrylate conversion value measured by gel permeation chromatography (GPC).

In addition, the melt viscosity (temperature: 240 ° C., shear rate: 100 sec ⁻¹ ) of the PGA-based resin is preferably 100 to 10,000 Pa · s, more preferably 300 to 8000 Pa · s, and particularly preferably 400 to 5000 Pa · s. . When the melt viscosity is less than the lower limit, the mechanical strength of the PGA-based resin composition tends to decrease. On the other hand, when the melt viscosity exceeds the upper limit, melt extrusion or molding tends to be difficult.

<Hindered phenolic compounds>
A conventionally well-known thing can be used as a hindered phenol type compound used for this invention. Here, the hindered phenol compound is a phenol compound in which a substituent is introduced into carbon atoms at both ortho positions of the phenol skeleton, and at least one of them is a substituent capable of becoming a steric hindrance. Examples of the substituent include alkyl groups such as a methyl group, an ethyl group, a propyl group, and a butyl group. Examples of the substituent that can cause steric hindrance include a bulky alkyl group such as a butyl group. A butyl group is preferred. Moreover, it is preferable that the substituent which may become a steric hindrance is introduced into carbon atoms at both ortho positions.

Such hindered phenol compounds include tetrakis [methylene-3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate] methane, n-octadecyl-3- (3,5-di- tert-butyl-4-hydroxyphenyl) propionate, 4,4′-methylene-bis (2,6-di-tert-butylphenol), pentaerythritol-tetrakis [3- (3,5-di-tert-butyl-4 -Hydroxyphenyl) propionate], triethylene glycol-bis [3- (3-tert-butyl-5-methyl-4-hydroxyphenyl) propionate], 1,6-hexanediol-bis [3- (3,5- Di-tert-butyl-4-hydroxyphenyl) propionate], 1,3,5-to Such as methyl-2,4,6-tris (3,5-di -tert- butyl-4-hydroxybenzyl) benzene. These hindered phenol compounds may be used alone or in combination of two or more.

In the PGA resin composition of the present invention, the content of the hindered phenol compound is preferably 0.3 to 30 μmol, more preferably 0.5 to 10 μmol, in terms of phenolic hydroxyl group, with respect to 1 g of PGA resin. 0.7 to 3 μmol is particularly preferable. When the content of the hindered phenol compound is less than the lower limit, the PGA resin composition tends to be colored. On the other hand, when the content exceeds the upper limit, the melt viscosity of the PGA resin composition is lowered, and the mechanical strength is decreased. It tends to decrease.

<Acid phosphate compound>
As the acid phosphate compound used in the present invention, the following formula (1):

The compound represented by these is mentioned. By adding such an acid phosphate compound to the PGA resin together with the hindered phenol compound, not only the water resistance of the PGA resin composition is improved, but also coloring due to heat can be suppressed. . In the present invention, the acid phosphate compound forms a chelate with the polymerization catalyst used in the synthesis of the PGA resin and suppresses the catalytic action of the polymerization catalyst, whereby the PGA due to the catalytic action under heating is used. It is presumed that depolymerization and decomposition of the resin are suppressed.

R in the formula (1) represents a hydrocarbon group having 7 to 24 carbon atoms (preferably 8 to 20 carbon atoms), preferably an alkyl group having 7 to 20 carbon atoms (more preferably 8 to 20 carbon atoms). Represents. m is 1 or 2. When a plurality of Rs in the formula (1) are present, they may be the same or different groups.

Examples of such acid phosphate compounds include mono (2-ethylhexyl) acid phosphate, monoisodecyl acid phosphate, monostearyl acid phosphate, monoalkyl acid phosphate such as monolauryl acid phosphate; monophenyl acid phosphate Monoaryl phosphates represented by: di (2-ethylhexyl) acid phosphates, diisodecyl acid phosphates, distearyl acid phosphates, dialkyl acid phosphates such as dilauryl acid phosphates; diaryls represented by diphenyl acid phosphates For example, phosphate. Of these, monostearyl acid phosphate and distearyl acid phosphate are preferable from the viewpoint of thermal stability at the melt kneading temperature. Moreover, these acid phosphate compounds may be used individually by 1 type, or may use 2 or more types together.

The content of the acid phosphate compound in the PGA resin composition of the present invention is preferably 0.003 to 3 parts by mass, more preferably 0.005 to 1 part by mass with respect to 100 parts by mass of the PGA resin. 0.01 to 0.5 parts by mass is particularly preferable. When the content of the acid phosphate compound is less than the lower limit, depolymerization and decomposition due to catalytic action are not sufficiently suppressed, and glycolide tends to increase. On the other hand, when the content exceeds the upper limit, the melt viscosity of the PGA resin composition is increased. Tends to decrease and the mechanical strength tends to decrease.

<Other additives>
In the PGA-based resin composition of the present invention, various additives such as a heat stabilizer, a terminal blocking agent, a plasticizer, a heat ray absorber, and an ultraviolet absorber, and other thermoplastics, as long as the effects of the present invention are not impaired. Resin can be added.

(PGA resin composition)
The PGA resin composition of the present invention contains the PGA resin, the hindered phenol compound, and the acid phosphate compound, and depolymerization of the PGA resin hardly occurs even under heating. Since the production of glycolide is suppressed, the water resistance is excellent. In addition, the PGA-based resin is not easily decomposed and is not easily colored during melt kneading. Furthermore, even if such a PGA-based resin composition is molded by a molding process involving heating such as an extrusion molding process, a molded body in which coloring is suppressed is obtained.

Such a PGA resin composition of the present invention can be produced by mixing the PGA resin, the hindered phenol compound, the acid phosphate compound, and other additives as necessary. it can. At this time, melt kneading is preferably performed using an extruder or the like. Thereby, it becomes possible to fully express the addition effect of additives, such as a hindered phenol type compound and an acid phosphate compound.

The temperature at the time of melt kneading is preferably 200 to 300 ° C., more preferably 230 to 280 ° C., and particularly preferably 240 to 270 ° C. When the melt kneading temperature is less than the lower limit, the effect of adding additives such as hindered phenolic compounds and acid phosphate compounds tends not to be sufficiently exhibited. On the other hand, when the upper limit is exceeded, the PGA resin composition is colored. It tends to be easy.

In the melt-kneading, a stirrer or a continuous kneader can be used in addition to the extruder, but an extruder (from the viewpoint that a short time treatment is possible and a smooth transition to the subsequent cooling step is possible. In particular, a method using a twin screw kneading extruder) is preferable.

Among such melt-kneading methods, in order to efficiently obtain a PGA-based resin composition with little coloration, glycolide is subjected to ring-opening polymerization to synthesize a partial polymer. After continuously introducing into a shaft stirring device to obtain a partially pulverized partial polymer, solid pulverized product of this partial polymer is subjected to solid phase polymerization, and the resulting polymer is subjected to the hindered phenolic compound and the above-mentioned polymer. A method in which an additive such as an acid phosphate compound is added and melt-kneaded is preferred.

Hereinafter, the present invention will be described more specifically based on examples and comparative examples, but the present invention is not limited to the following examples. In addition, the measurement of glycolide content and the thermal stability test were implemented with the following method.

<Measurement of glycolide content>
To about 100 mg of PGA resin composition in pellet form, 2 ml of dimethyl sulfoxide containing 0.2 g / L of 4-chlorobenzophenone as an internal standard substance is added, and heated at 150 ° C. for about 10 minutes, the PGA resin composition The product was dissolved. After cooling the solution to room temperature and filtering, the amount of glycolide in the filtrate was measured by capillary gas chromatograph (“GC-2010” manufactured by Shimadzu Corporation, column: “TC-17” (0.25 mmφ × 30 mm), Detector: FID (hydrogen flame ionization detector)) was used under the following conditions to calculate the glycolide content in the PGA resin composition. A composition having a lower glycolide content is less likely to be hydrolyzed and has higher water resistance.

(GC analysis conditions)
Injection temperature: 180 ° C.
Column temperature: held at 150 ° C. for 5 minutes, heated to 270 ° C. at 20 ° C./min, and held at 270 ° C. for 3 minutes.
Detector temperature: 300 ° C.

<Thermal stability test>
3 g of PGA resin composition in the form of pellets was placed in a mold having a diameter of 25 mm and a thickness of 3 mm sandwiched between aluminum plates, heated for 1 minute on a heat press at 290 ° C., and then a pressure of 2 MPa was applied at this temperature. Hold for 30 minutes. Then, it cooled to room temperature and obtained the disk-shaped PGA resin molding. The yellowness (YI) of this molded product was measured by a reflected light measurement method using a spectrocolorimeter (“TC-1800” manufactured by Tokyo Denshoku Co., Ltd.) under the conditions of standard light C, 2 degree visual field and color system. It was measured.

(Synthesis example)
A SUS container (capacity: 56 L) having a steam jacket structure equipped with a stirrer was charged with 22500 g of glycolide and 0.68 g (30 mass ppm) of dichloride dihydrate, and the total proton concentration in the container was 0.13. Water 1.49g was added so that it might become mol%. Note that all protons in the container include protons of moisture (humidity) in the atmosphere in the container, and the amount of water added takes into account the amount of water (0.11 g) in the atmosphere in the container. Decided. Thereafter, the container was sealed, and steam was circulated through the jacket while stirring, and the mixture was heated until the temperature of the mixture in the container reached 100 ° C. to melt the mixture to obtain a uniform liquid mixture.

Next, a reactor comprising a main body provided with a jacket-structure reaction tube (made of SUS304, inner diameter 24 mm) and two jacket-structure metal plates (made of SUS304) was prepared. After attaching one of the metal plates (hereinafter referred to as “lower plate”) to the lower opening of the reaction tube, the temperature of the liquid mixture is maintained at 100 ° C. from the upper opening of the reaction tube. It was transferred as it was. Immediately after the transfer, the other metal plate (hereinafter referred to as “upper plate”) was attached and the reaction tube was sealed. Thereafter, a heat medium oil at 170 ° C. was circulated through the main body and a jacket of two metal plates and held for 7 hours to synthesize a polyglycolic acid resin (PGA resin).

Next, the heat medium oil circulating in the jacket was cooled to cool the reaction apparatus to near room temperature. Thereafter, the lower plate was removed, and the PGA resin mass was taken out from the lower opening of the reaction tube. In addition, when a PGA resin is synthesized by this method, the yield is almost 100%. The obtained PGA resin block was pulverized by a pulverizer. The weight average molecular weight (in terms of polymethyl methacrylate) in the GPC measurement of the obtained PGA resin was 225000.

(Example 1)
In 100 parts by mass of the PGA resin obtained in the above synthesis example, 0.030 parts by mass of a substantially equimolar mixture of mono- and distearyl acid phosphates (“ADEKA STAB AX-71” manufactured by ADEKA) and a hinder 1,3,5-trimethyl-2,4,6-tris (3,5-di-tert-butyl-4-hydroxybenzyl) benzene (“ADEKA STAB AO-330” manufactured by ADEKA Corporation) as a dophenol compound 0.030 part by mass was added. A twin-screw kneading extruder (“LT” manufactured by Toyo Seiki Seisakusho Co., Ltd.) in which the temperature of four sections provided between the supply section and the discharge section was set to 220 ° C., 230 ° C., 250 ° C., and 230 ° C. in this order. -20 ") and melt-kneading extrusion was performed to obtain a pellet-like PGA resin composition. Table 1 shows the measurement results of the glycolide content of this PGA resin composition and the results of the thermal stability test.

(Example 2)
A pellet-like PGA resin composition was obtained in the same manner as in Example 1 except that 0.030 parts by mass of diisodecyl acid phosphate (“DP-10R” manufactured by Daihachi Chemical Co., Ltd.) was added as the acid phosphate compound. . Table 1 shows the measurement results of the glycolide content of this PGA resin composition and the results of the thermal stability test.

Example 3
Pellet PGA as in Example 1 except that 0.017 parts by mass of bis (2-ethylhexyl) acid phosphate (“DP-8R” manufactured by Daihachi Chemical Industry Co., Ltd.) was added as the acid phosphate compound. A resin composition was obtained. Table 1 shows the measurement results of the glycolide content of this PGA resin composition and the results of the thermal stability test.

(Example 4)
Addition of 0.050 parts by mass of n-octadecyl-3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate (“ADEKA STAB AO-50” manufactured by ADEKA Corporation) as a hindered phenol compound A pellet-like PGA resin composition was obtained in the same manner as in Example 1 except that. Table 1 shows the measurement results of the glycolide content of this PGA resin composition and the results of the thermal stability test.

(Example 5)
Add 0.050 parts by mass of triethylene glycol-bis [3- (3-tert-butyl-5-methyl-4-hydroxyphenyl) propionate] (“Irganox245” manufactured by Ciba Japan Co., Ltd.) as a hindered phenol compound A pellet-like PGA resin composition was obtained in the same manner as in Example 1 except that. Table 1 shows the measurement results of the glycolide content of this PGA resin composition and the results of the thermal stability test.

(Example 6)
The amount of hindered phenolic compound 1,3,5-trimethyl-2,4,6-tris (3,5-di-tert-butyl-4-hydroxybenzyl) benzene added was changed to 0.010 parts by mass. A pellet-like PGA resin composition was obtained in the same manner as in Example 1 except that. Table 1 shows the measurement results of the glycolide content of this PGA resin composition and the results of the thermal stability test.

(Comparative Example 1)
A pellet-like PGA resin composition was obtained in the same manner as in Example 1 except that the hindered phenol compound was not added. Table 1 shows the measurement results of the glycolide content of this PGA resin composition and the results of the thermal stability test.

(Comparative Example 2)
A pellet-like PGA resin composition was obtained in the same manner as in Example 1 except that the acid phosphate compound was not added. Table 1 shows the measurement results of the glycolide content of this PGA resin composition and the results of the thermal stability test.

(Comparative Example 3)
Add 0.030 parts by mass of bis- (2,6-di-tert-butyl-4-methylphenyl) pentaerythritol diphosphite (“ADEKA STAB PEP-36” manufactured by ADEKA) instead of the acid phosphate compound A pellet-like PGA resin composition was obtained in the same manner as in Example 1 except that. Table 1 shows the measurement results of the glycolide content of this PGA resin composition and the results of the thermal stability test.

(Comparative Example 4)
A pellet-like PGA resin composition was obtained in the same manner as in Example 1 except that 0.030 parts by mass of tributyl phosphate (manufactured by Tokyo Chemical Industry Co., Ltd.) was added instead of the acid phosphate compound. Table 1 shows the measurement results of the glycolide content of this PGA resin composition and the results of the thermal stability test.

(Comparative Example 5)
A pellet-like PGA resin composition was obtained in the same manner as in Example 1 except that 0.030 parts by mass of triphenyl phosphate (manufactured by Tokyo Chemical Industry Co., Ltd.) was added instead of the acid phosphate compound. Table 1 shows the measurement results of the glycolide content of this PGA resin composition and the results of the thermal stability test.

As is clear from the results shown in Table 1, when the hindered phenolic compound and the acid phosphate compound were used in combination (Examples 1 to 6) as in the present invention, the PGA resin composition was a glycol. It was confirmed that the content was low and the water resistance was excellent, and that coloring due to heat was small.

On the other hand, when the hindered phenol compound was not added (Comparative Example 1), the PGA resin composition had a low glycol content and was excellent in water resistance, but was colored by heat. In addition, in the case where no acid phosphate compound was added (Comparative Example 2) and in the case where a phosphite compound, trialkyl phosphate or triphenyl phosphate was added (Comparative Examples 3 to 5), the PGA resin composition Was colored by heat and had a high glycol content and poor water resistance.

As described above, according to the present invention, by using a hindered phenol compound and an acid phosphate compound in combination, the water resistance of the PGA resin composition is improved, and further, coloring due to heat can be suppressed. It becomes. In particular, the water resistance of the PGA-based resin composition can be improved without adding a water resistance improver such as a carboxyl group blocking agent.

Therefore, since the PGA resin composition of the present invention has excellent water resistance and is not easily colored by heat, the film is produced by a molding method involving heating or melting, such as stretch molding, extrusion molding, or injection molding. It is useful as a raw material for sheets, sheets, fibers, containers, and the like, and is particularly useful as a raw material for those requiring colorless transparency.

Claims (7)

A polyglycolic acid resin composition containing a polyglycolic acid resin, a hindered phenolic compound, and an acid phosphate compound. The acid phosphate compound has the following formula (1):

(In the formula (1), R represents a hydrocarbon group having 7 to 24 carbon atoms, and when a plurality of R are present, they may be the same or different, and m is 1 or 2. is there.)
The polyglycolic acid resin composition according to claim 1, which is a compound represented by the formula: The polyglycolic acid resin composition according to claim 2, wherein R in the formula (1) is an alkyl group having 7 to 24 carbon atoms. 2. The polyglycolic acid resin composition according to claim 1, wherein the hindered phenol compound is a compound in which a tert-butyl group is introduced into at least one carbon atom of the ortho position of the phenol skeleton. The polyglycolic acid resin composition according to claim 1, wherein the content of the acid phosphate compound is 0.003 to 3 parts by mass with respect to 100 parts by mass of the polyglycolic acid resin. 2. The polyglycolic acid resin composition according to claim 1, wherein the content of the hindered phenol compound in terms of phenolic hydroxyl group is 0.3 to 30 μmol with respect to 1 g of the polyglycolic acid resin. A molded product obtained from the polyglycolic acid resin composition according to claim 1.