JP2006219567A - Polyester resin composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a new polyester resin composition whose hydrolysis rate in a humid environment is remarkably improved. <P>SOLUTION: The polyester resin composition comprises, based on 100 pts.wt. of the polyester resin composition (A), 0.01-15 pts.wt. of at least one type of hydrolysis inhibitor (B) selected from a carbodiimides compound, an isocyanate compound, and an oxazoline compound, and 0.01-3 pts.wt. of the hydrolysis inhibitor (C) selected from magnesium oxide and calcium oxide; aluminum hydroxide; magnesium hydroxide and calcium hydroxide; magnesium carbonate and calcium carbonate; and hydrotalcite. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a polyester resin composition that is excellent in hydrolysis resistance and in which deterioration of resin properties with time is suppressed.

When a polymer material is used for food packaging, fibers, etc., long-term stability of the resin is required in order to prevent deterioration of the contents and maintain practical strength. However, for example, in the case of a polyester resin, there is a drawback that the molecular weight and strength are easily lowered by hydrolysis.
Therefore, studies have been made on additives in order to improve hydrolysis resistance.

For example, JP-A-46-5389 discloses a method of adding biscarbodiimide to polyester, and JP-B-38-15220 discloses a method of adding a carbodiimide compound containing three or more carbodiimide groups in the molecule. Although each has been proposed, the effect of improving hydrolysis resistance is low.
Japanese Patent Application Laid-Open No. 2003-192929 discloses a composition containing a biodegradable organic polymer compound, a flame retardant additive, and a hydrolysis inhibitor. However, there is no indication as to the influence of hydroxide compounds, phosphorus compounds, silica compounds, and the like exemplified as flame retardant additives on hydrolysis resistance.
Japanese Patent Laid-Open No. 46-5389 Japanese Examined Patent Publication No. 38-15220 JP 2003-192929 A

  An object of the present invention is to provide a novel polyester resin having a significantly improved hydrolysis rate in a humidity environment. Another object of the present invention is to provide a polyester resin composition that includes a hydrolysis inhibitor and a hydrolysis inhibition assistant, has hydrolysis resistance, and retains resin properties over a long period of time.

As a result of intensive studies in view of the above problems, the present inventors have found that a resin composition to which a hydrolysis inhibitor and a specific hydrolysis inhibition aid have been added can solve the above problems, thereby completing the present invention. . That is, the present invention
With respect to 100 parts by weight of the polyester resin (A), 0.01 to 15 parts by weight of at least one hydrolysis inhibitor (B) selected from carbodiimide compounds, isocyanate compounds, and oxazoline compounds, and hydrolysis suppression selected from the following: The present invention relates to a polyester resin composition comprising 0.01 to 3 parts by weight of auxiliary agent (C).
(C) Hydrolysis inhibitor: magnesium oxide, calcium oxide, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, magnesium carbonate, calcium carbonate, hydrotalcite.

Further, the present inventors have found that a resin composition to which a hydrolysis inhibitor and a specific hydrolysis inhibition aid are added is particularly suitable for solving the above-mentioned problems particularly with respect to an oxycarboxylic acid copolymerized polyester resin. Thus, the present invention has been completed.
That is, in the polyester resin composition of the present invention, when the polyester resin (A) has 100% by mole of all its structural units,
(1) 50 to 100 mol% of oxycarboxylic acid unit having 5 or less carbon atoms
(2) 25 to 0 mol% of dicarboxylic acid unit
(3) 25-0 mol% of diol units
It is preferable that it is each containing polyester.

  Furthermore, a carbodiimide compound is particularly suitable as the hydrolysis inhibitor (B) in order to solve the above problems.

According to the present invention, there is provided a polyester resin composition in which hydrolysis, which is a defect of a polyester resin, is remarkably suppressed. According to the present invention, since it is possible to suppress a decrease in physical properties of a polyester resin widely used in films, sheets, beverage containers and the like, it is extremely useful industrially.

In the present invention, 0.01 to 15 parts by weight of at least one hydrolysis inhibitor (B) selected from a carbodiimide compound, an isocyanate compound, and an oxazoline compound is selected from 100 parts by weight of the polyester resin (A) and the following: This is a polyester resin composition comprising 0.01 to 3 parts by weight of the hydrolysis inhibition aid (C).
(C) Hydrolysis inhibitor: magnesium oxide and calcium oxide, aluminum hydroxide, magnesium hydroxide and calcium hydroxide, magnesium carbonate and calcium carbonate, hydrotalcite.

In particular, a polyester resin,
[A1] When all the structural units are 100 mol%,
(1) 50 to 100 mol% of oxycarboxylic acid unit having 5 or less carbon atoms
(2) 25 to 0 mol% of dicarboxylic acid unit
(3) 25-0 mol% of diol units
Including each
[A2] With respect to 100 parts by weight of the polyester resin, 0.01 to 15 parts by weight of at least one hydrolysis inhibitor (B) selected from carbodiimide compounds, isocyanate compounds and oxazoline compounds, and hydrolysis selected from the following: A polyester resin composition comprising 0.01 to 3 parts by weight of the suppression aid (C) can be mentioned.
(C) Hydrolysis inhibitor: magnesium oxide and calcium oxide, aluminum hydroxide, magnesium hydroxide and calcium hydroxide, magnesium carbonate and calcium carbonate, hydrotalcite.

[Polyester resin]
The polyester resin used in the present invention is not particularly limited. Specific examples include at least one polyester selected from polyethylene terephthalate, polytrimethylene terephthalate, polybutylene terephthalate, polyethylene 2,6-naphthalate, polyglycolic acid, and a homopolymer or copolymer of polylactic acid.
Among them, a resin obtained by polymerizing an oxycarboxylic acid having 5 or less carbon atoms is preferable.

  Examples of the oxycarboxylic acid having 5 or less carbon atoms include glycolic acid, lactic acid, 4-hydroxy n-butyric acid, 2-hydroxyisobutyric acid, 5-hydroxy n-valeric acid, 3-hydroxypropionic acid, and the like. These may be used alone or in combination of two or more.

Among these oxycarboxylic acids, since a polyester resin having a high gas barrier property is obtained, glycolic acid, 3-hydroxycarboxylic acid, and the like are preferable. Especially in the case of polyglycolic acid that is easily hydrolyzed, a hydrolysis inhibitor (C ) Is more remarkable and preferable.
These oxycarboxylic acids are usually contained in an amount of 50 to 100 mol%, preferably 90 to 98 mol%, more preferably 95 to 97 mol%, when the total structural unit of the polyester resin is 100 mol%.

The dicarboxylic acid used in the present invention is not particularly limited.
Specific examples of dicarboxylic acid units that may be contained include aliphatic groups such as oxalic acid, malonic acid, succinic acid, fumaric acid, maleic acid, glutaric acid, adipic acid, sebacic acid, azelaic acid, and decanedicarboxylic acid. Examples thereof include alicyclic dicarboxylic acids such as dicarboxylic acid and cyclohexanedicarboxylic acid, and aromatic dicarboxylic acids having 8 to 12 carbon atoms such as isophthalic acid, terephthalic acid, phthalic acid, and 2,6-naphthalenedicarboxylic acid.
Among these, aromatic dicarboxylic acids are preferable in that polyesters excellent in gas barrier properties and mechanical properties can be obtained, and in particular, at least one selected from isophthalic acid, 2,6-naphthalenedicarboxylic acid, and terephthalic acid. preferable. In particular, it is preferable to use isophthalic acid.
These dicarboxylic acids may be used alone or in combination of two or more.

The diol unit used in the present invention is not particularly limited.
Specific examples of the diols that may be contained include aliphatic diols having 5 or more carbon atoms such as 1,6-hexanediol, neopentyl glycol, dodecamethylene glycol, triethylene glycol, tetraethylene glycol, and cyclohexane. Alicyclic diols such as dimethanol, 1,3-bis (2-hydroxyethoxy) benzene, 1,2-bis (2-hydroxyethoxy) benzene, 1,4-bis (2-hydroxyethoxy) benzene, bis [ Examples include diols containing aromatic groups such as 4- (2-hydroxyethoxy) phenyl] sulfone, 2,2-bis (4-β-hydroxyethoxyphenyl) propane, bisphenols, hydroquinone, and resorcin.

Preferably, an aliphatic diol having 4 or less carbon atoms is used.
Examples of the aliphatic diol unit having 4 or less carbon atoms include ethylene glycol, diethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, and the like. These aliphatic diols may be used alone or in combination of two or more. Among these, it is preferable to use ethylene glycol.

Moreover, the polyester resin used for this invention may contain 0.001-2 mol% of monomer units of the functional number 3 or more which have ester formation ability as needed, More preferably, it is 0.01-0.4 mol. % May be contained.
Examples of the monomer unit having 3 or more functional groups include units derived from polyfunctional carboxylic acids having 3 or more carboxyl groups or polyfunctional alcohols having 3 or more hydroxyl groups, and those having 3 or more carboxyl groups and hydroxyl groups. Examples include units derived from functional hydroxy acids.

Among these, it is preferable to contain units derived from polyfunctional alcohols having 3 or more hydroxyl groups. Specifically, glycerin, diglycerin, (trishydroxymethyl) methane, 1,1,1- (trishydroxymethyl) ethane, 1,1,1- (trishydroxymethyl) propane, pentaerythritol, dipenta Units derived from erythritol, sugars such as sorbitol, glucose, lactose, galactose, fructose, saccharose, and nitrogen-containing polyhydric alcohols such as 1,3,5-trishydroxyethoxyisocyanurate.
Among these, it is more preferable to select from units derived from glycerin, 1,1,1 (trishydroxymethyl) ethane, 1,1,1 (trishydroxymethyl) propane, pentaerythritol, and dipentaerythritol.

  In the polyester resin of the present invention, a heat stabilizer, a weather stabilizer, an ultraviolet absorber, a nucleating agent, an inorganic filler, a lubricant, a slip agent, an anti-blocking agent, and a stabilizer, which are blended in the conventional polyester as necessary. In addition, an appropriate amount such as an antistatic agent, an antifogging agent, a pigment, an oxygen absorbent, or a terminal blocking agent may be blended.

[Hydrolysis inhibitor (B)]
The hydrolysis inhibitor (B) is selected from a carbodiimide compound, an isocyanate compound, and an oxazoline compound, and among them, the carbodiimide compound has an effect of suppressing hydrolysis more effectively, and is preferable.
It is preferable that 0.01-15 weight part is added with respect to a polyester resin (A), and it is more preferable that 0.5-5 weight part is added especially.
The hydrolysis inhibitor (B) is selected from the following carbodiimide compounds, isocyanate compounds and oxazoline compounds, and may be used alone or in combination of two or more.

The carbodiimide compound is a compound having one or more carbodiimide groups in the molecule, and includes a polycarbodiimide compound having two or more functions.
Examples of monocarbodiimide compounds include dicyclohexyl carbodiimide, diisopropyl carbodiimide, dimethyl carbodiimide, diisobutyl carbodiimide, dioctyl carbodiimide, diphenyl carbodiimide, naphthyl carbodiimide, and the like.

Examples of the isocyanate compound include 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, m-phenylene diisocyanate, p-phenylene diisocyanate, 4,4′-diphenylmethane diisocyanate, and 2,4′-diphenylmethane diisocyanate. 2,2′-diphenylmethane diisocyanate, 3,3′-dimethyl-4,4′-biphenylene diisocyanate, 3,3′-dimethoxy-4,4′-biphenylene diisocyanate, 3,3′-dichloro-4,4 ′ -Biphenylene diisocyanate, 1,5-naphthalene diisocyanate, 1,5-tetrahydronaphthalene diisocyanate, tetramethylene diisocyanate, 1,6-hexamethylene diisocyanate, dodecamethylene diisocyanate Trimethylhexamethylene diisocyanate, 1,3-cyclohexylene diisocyanate, 1,4-cyclohexylene diisocyanate, xylylene diisocyanate, tetramethylxylylene diisocyanate, hydrogenated xylylene diisocyanate, lysine diisocyanate, isophorone diisocyanate, 4,4'-dicyclohexylmethane Examples include diisocyanate or 3,3′-dimethyl-4,4′-dicyclohexylmethane diisocyanate.
The said isocyanate compound can be easily manufactured by a well-known method, and a commercial item can be used suitably.

  Examples of the oxazoline compound include 2,2′-o-phenylenebis (2-oxazoline), 2,2′-m-phenylenebis (2-oxazoline), and 2,2′-p-phenylenebis. (2-oxazoline), 2,2′-p-phenylenebis (4-methyl-2-oxazoline), 2,2′-m-phenylenebis (4-methyl-2-oxazoline), 2,2′-p -Phenylenebis (4,4'-dimethyl-2-oxazoline), 2,2'-m-phenylenebis (4,4'-dimethyl-2-oxazoline), 2,2'-ethylenebis (2-oxazoline) 2,2′-tetramethylenebis (2-oxazoline), 2,2′-hexamethylenebis (2-oxazoline), 2,2′-octamethylenebis (2-oxazoline), 2,2′- Chirenbisu (4-methyl-2-oxazoline), or 2,2'- diphenylenebis (2-oxazoline).

[Hydrolysis inhibitor (C)]
The hydrolysis inhibitor (C) is selected from magnesium oxide and calcium oxide, aluminum hydroxide, magnesium hydroxide and calcium hydroxide, magnesium carbonate and calcium carbonate, and hydrotalcite. The hydrolysis inhibitor (C) is usually added in an amount of 0.01 to 3 parts by weight. However, if added in a large amount, it tends to crystallize at the time of molding and the transparency is impaired, so in applications where transparency is required. The added amount is preferably 0.01 to 2 parts by weight, more preferably 0.01 to 1 part by weight.
Since the compound has an effect of neutralizing an acid generated by hydrolysis of polyester, it is considered to have an effect of suppressing a decrease in molecular weight due to hydrolysis.

[Production method]
The manufacturing method of the composition which consists of a polyester resin, a hydrolysis inhibitor, and a hydrolysis inhibitory assistant is not specifically limited, A well-known method can be used. Preferably, a method of melt-kneading a hydrolysis inhibitor and a hydrolysis inhibition aid to a polyester resin can be used.
The order of addition in the case of melt kneading may be simultaneous or either one of them. Moreover, the composition obtained by melt-kneading either one in the polyester resin first may be further melted, and the remaining additives may be added and melt-kneaded.

  The present invention will be described more specifically with reference to the following examples, but the present invention is not limited to these examples. The physical properties of the resin of this example were measured and evaluated by the following methods.

(Reduced viscosity)
The reduced viscosity IV of the polyester resin was measured at 25 ° C. in a mixed solution of phenol and tetrachloroethane (weight ratio 1/1).
(transparency)
The transparency of the polyester resin was determined on a 300 μm thick press sheet using a haze meter (manufactured by Nippon Denshoku).
(Hydrolysis acceleration test)
A 300 μm-thick amorphous press sheet was hung in a constant temperature and humidity chamber (PR-1G type) manufactured by Tabai Co., Ltd. under an atmosphere set to 38 ° C. and relative humidity 85%, and the change in reduced viscosity (IV) with time was measured. followed.
In addition, the numerical value of the lower right of IV value represents the elapsed days from the start of a hydrolysis promotion test, respectively. Moreover, as an index indicating the maintenance ratio of the molecular weight after hydrolysis, the reduced viscosity (IV ₁₀ ) of the press sheet after being maintained for 10 days under the above-mentioned hydrolysis promotion condition, and the reduced viscosity of the press sheet before the hydrolysis promotion test ( The ratio of IV ₀ ) (IV ₁₀ / IV ₀ ) was used.

(Production Example 1)
Glycolic acid 304 g (4.0 mol), isophthalic acid 35.3 g (0.21 mol), and ethylene glycol 17.1 g (0.28 mol) were charged into a reaction vessel, and 150-180 while distilling off the generated water. The esterification reaction was performed at 7 ° C. for about 7 hours.
The obtained polyester oligomer was charged into a glass reactor equipped with a stirrer and a distillation pipe. The distilling pipe is connected to a vacuum device composed of a vacuum pump and a decompression regulator, and has a structure capable of distilling off the evaporated material. A germanium-based catalyst (germanium dioxide) was added thereto and first melted at 220 ° C. under a nitrogen stream, and then the pressure was reduced to about 1 torr over about 1 hour with stirring to maintain the conditions. The reaction was carried out for about 6 hours after reaching the condition of about 1 torr, and the produced ethylene glycol and oligomer were distilled out of the system. After this polycondensation reaction, the resin was extruded in a strand form from a nozzle and cut into pellets. The reduced viscosity IV of the obtained polyester resin was 0.720 dl / g.

Example 1
100 parts by weight of the polyester resin obtained in Production Example 1, sufficiently dried by a vacuum dryer, 3 parts by weight of polycarbodiimide (Carbodilite LA-1 manufactured by Nisshinbo Co., Ltd.), and hydrotalcite (Synthetic hydro manufactured by Kyowa Chemical Industry Co., Ltd.) 0.5 parts by weight of talcite DHT-4C) was melt-mixed for 3 minutes under the condition of a rotor rotational speed of 100 rpm in a lab plast mill (manufactured by Toyo Seiki Co., Ltd.) set at a temperature of 220 ° C.

Next, after the resulting resin composition was sufficiently dried with a vacuum dryer, a predetermined amount was sandwiched between the two brass plates, the aluminum plate and the release film, melted at 240 ° C. with a compression molding machine, and 30 at 10 MPa. Compressed for seconds. Then, it was compressed and cooled again at 10 MPa with a compression molding machine set at 0 ° C. to produce a press sheet having a thickness of about 300 μm. The reduced viscosity IV ₀ of the press sheet was 0.840 dl / g. The haze of the 300 μm thick press sheet was 5.0%. The obtained sheet was stored in a constant temperature and humidity chamber at 38 ° C. and a relative humidity of 85%, and a hydrolysis promotion test was performed.

(Comparative Example 1)
Using the resin obtained in Production Example 1, without adding a hydrolysis inhibitor / suppression aid, and giving no heat history by kneading, a press sheet is prepared as it is, and measurement of reduced viscosity IV ₀ and hydrolyzability Was evaluated.

(Comparative Examples 2 to 5)
Molding and evaluation were performed in the same manner as in Example 1 except that the formulation was changed as shown in Table 1.

Table 1 below shows the IV change over time of Example 1 and Comparative Examples 1 to 5, the IV retention rate after 10 days, and the initial haze value.
The carbodiimide and bisoxazoline used are Carbodilite HMV-8CA manufactured by Nisshinbo Co., Ltd. and 1,4-bis (4,5-dihydro-2-oxazolyl) benzene manufactured by Wako Pure Chemical Industries, Ltd.

  By simultaneously adding the hydrolysis inhibitor and the auxiliary agent (Example 1), the IV retention rate is higher than any of the additive-free (Comparative Example 1) and the hydrolysis inhibitor alone (Comparative Example 2). It is shown that. Moreover, it can be said that LA-1 is most effective in maintaining IV in the comparison between the hydrolysis inhibitors (Comparative Examples 2, 3, and 4). In addition, when only the hydrolysis inhibition aid is added (Comparative Example 5), the hydrolysis inhibition effect is not observed.

(Production Example 2)
After obtaining a polyester resin in the same manner as in Production Example 1, solid phase polymerization was performed. The reduced viscosity of the obtained polyester resin was 0.92 dl / g.

(Example 2)
30 parts by weight of polycarbodiimide (LA-1) and 0.125 parts by weight of hydrotalcite (DHT-4C) were dry blended with respect to the polyester resin of Production Example 2 sufficiently dried by a vacuum dryer, and 30 Kneading and granulation were performed under a condition of a cylinder temperature of 220 ° C. using a ~ 20 mm taper type twin screw extruder (manufactured by Harke). The obtained resin was formed into a press sheet in the same manner as in Example 1. The reduced viscosity IV ₀ of the press sheet was 0.859 dl / g. The haze of the 300 μm thick press sheet was 6.3%.

(Example 3)
Except for changing the additive composition as shown in Table 2, the mixture was kneaded with an extruder in the same manner as in Example 2 to perform molding and evaluation.

(Comparative Example 6)
Using the resin obtained in Production Example 2, molding and evaluation were carried out using an extruder without adding any additives.

(Comparative Examples 7 and 8)
Molding / evaluation was performed in the same manner as in Example 2 except that the formulation was changed as shown in Table 2.

  Table 2 below shows the IV change over time of Examples 2 and 3 and Comparative Examples 6 to 8, the IV retention rate after 10 days, and the initial haze value.

  In Examples 2 and 3, when nothing was added (Comparative Example 6) and when the hydrolysis inhibitor (C) was not added with the same amount of hydrolysis inhibitor (B) (Comparative Example) Compared to 7, 8), the IV maintenance rate is high.

(Production Example 3)
A polycondensation reaction was carried out in the same manner as in Production Example 1 except that 304 g (4.0 mol) of glycolic acid, 17.4 g (0.11 mol) of isophthalic acid, and 8.5 g (0.14 mol) of ethylene glycol were used. It was. Next, the obtained pellets were subjected to solid phase polymerization under a nitrogen stream. The resulting polyester resin had a reduced viscosity IV of 0.909 dl / g.

Example 4
Except that the polyester of Production Example 3 was used as a raw material, 3 parts by weight of polycarbodiimide (LA-1) and 0.125 parts by weight of hydrotalcite (DHT-4C) were kneaded in the same manner as in Example 1, Press sheet. The reduced viscosity IV ₀ of the press sheet was 1.053 dl / g. The haze value of the 300 μm thick press sheet was 6.2%.

(Examples 5 to 7), (Comparative Example 9)
Except for changing the composition of the additive as shown in Table 3, the mixture was kneaded in the same manner as in Example 4, and then molded and evaluated.

(Comparative Example 10)
The resin obtained in Production Example 3 was molded and evaluated as it was without adding a hydrolysis inhibitor / auxiliary agent and without adding a heat history due to kneading.

  Table 3 below shows the IV change over time of Examples 4 to 7 and Comparative Examples 9 and 10, the IV retention after 10 days, and the initial haze value.

  In all the examples, the IV maintenance rate is higher than that in the case where the hydrolysis inhibition aid (C) was not added (Comparative Example 9).

(Example 8)
Except that 3 parts by weight of polycarbodiimide (LA-1) and 0.5 parts by weight of magnesium hydroxide (manufactured by Wako Pure Chemical Industries, Ltd.) were used as additives for the polymer obtained in Production Example 3. In the same manner as in Example 1, the mixture was kneaded and formed into a press sheet. The reduced viscosity (IV ₀ ) of the press sheet was 1.049 dl / g.
Subsequently, a hydrolysis acceleration test was performed, and the change with time of the reduced viscosity (IV) was measured.

(Examples 9 to 12), (Comparative Examples 11 and 12)
Except for changing the formulation of the additive as shown in Table 4, the mixture was kneaded in the same manner as in Example 8, and molding and evaluation were performed.

In addition, the following commercially available reagents were used for each additive.
Magnesium hydroxide (Wako Pure Chemical Industries, Ltd.), Aluminum hydroxide (Wako Pure Chemical Industries, Ltd.), Calcium hydroxide (Wako Pure Chemical Industries, reagent grade), Calcium carbonate (99.9%) ( Wako Pure Chemical Industries, Ltd.), magnesium oxide (heavy) (special grade reagent manufactured by Wako Pure Chemical Industries, Ltd.), calcium stearate (manufactured by Sansha Gosei Co., Ltd.), magnesium stearate (plant-derived) (Wako Pure Chemical) First grade reagent manufactured by Kogyo Co., Ltd.
Table 4 below shows the time course of IV change in Examples 8 to 12 and Comparative Examples 9 to 12, and the IV maintenance rate after 10 days.

From Table 4, the metal hydroxide used in Examples 8 to 10, the metal carbonate used in Example 11, and the metal oxide used in Example 12 all have IV retention rates higher than those of Comparative Examples 9 and 10. The effect as a hydrolysis inhibiting aid (C) was high.
However, since the stearic acid metal salts shown in Comparative Examples 11 and 12 have a low IV retention rate after 10 days and are inferior to the blank (Comparative Example 9) to which the inhibitor (C) is not added, the hydrolysis of the present invention. The effect is insufficient as compared with the suppression aid (C).

Claims (3)

With respect to 100 parts by weight of the polyester resin (A), 0.01 to 15 parts by weight of at least one hydrolysis inhibitor (B) selected from carbodiimide compounds, isocyanate compounds, and oxazoline compounds, and hydrolysis suppression selected from the following: A polyester resin composition comprising 0.01 to 3 parts by weight of the auxiliary agent (C);
(C) Hydrolysis inhibitor: magnesium oxide, calcium oxide, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, magnesium carbonate, calcium carbonate, hydrotalcite. It is a polyester resin composition of Claim 1, Comprising: When the said polyester resin (A) makes the whole structural unit 100 mol%,
(1) 50 to 100 mol% of oxycarboxylic acid unit having 5 or less carbon atoms
(2) 25 to 0 mol% of dicarboxylic acid unit
(3) 25-0 mol% of diol units
A polyester resin composition comprising each of them. The polyester resin composition according to claim 1 or 2, wherein the hydrolysis inhibitor (B) is a carbodiimide compound.