JP2006321933A - Polyethylene naphthalene resin composition and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polyethylene naphthalate resin composition efficiently exhibiting hydrolytic resistance with a carbodiimide compound and suppressing even degradation of the carbodiimide compound itself and to provide a method for producing the composition. <P>SOLUTION: The polyethylene naphthalate resin composition comprises 0.1-10 wt.% of the carbodiimide compound and 0.05-1 wt.% of at least one kind of antioxidant selected from the group consisting of a hindered phenolic compound and a thioethereal compound. The method for producing the resin composition comprises adding the carbodiimide compound to the polyethylene naphthalate resin composition comprising the antioxidant. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a polyethylene naphthalate resin composition excellent in hydrolysis resistance, heat resistance and mechanical performance, and a method for producing the same.

  Polyethylene naphthalate (hereinafter sometimes referred to as PEN) is mechanical properties such as tensile strength, elongation, Young's modulus, elastic recovery rate, physical properties such as heat resistance and dimensional stability, chemical resistance, and water resistance. It is well known that it has a great industrial value because it has excellent chemical properties and is inexpensive, and is widely used in, for example, fibers, tire cords, bottles, films and the like.

  However, PEN has insufficient hydrolysis resistance, and its use has been limited in fields where hydrolysis resistance is required, such as automobile parts, electronic parts, lighting plates, heat-resistant food containers and the like. In order to solve such problems, Patent Document 1, Patent Document 2 and Patent Document 3 propose to incorporate a carbodiimide compound into PEN so as to improve the hydrolysis resistance of polyester.

  Certainly, these methods improve the hydrolysis resistance, but promote the degradation and degradation of the carbodiimide compound when left for a long time at a high temperature, and raise the terminal carboxyl group of the polyester. It was.

Japanese Patent Laid-Open No. 11-5854 JP 2003-251695 A JP 2003-335872 A

  An object of the present invention is to provide a polyethylene naphthalate resin composition in which hydrolysis resistance due to carbodiimide is efficiently expressed and decomposition of carbodiimide itself is suppressed in view of the above-described problems of the prior art.

  As a result of intensive studies to achieve the above-mentioned object, the present inventors have found that when a carbodiimide compound is used in combination with a specific antioxidant, decomposition of carbodiimide can be suppressed, and further, hydrolysis resistance itself is improved. The invention has been reached.

  Thus, according to the present invention, an object of the present invention is to contain at least one antioxidant selected from the group consisting of a hindered phenol compound and a thioether compound, containing 0.1 to 10% by weight of a carbodiimide compound. This is achieved by a polyethylene naphthalate resin composition containing 0.05 to 1% by weight.

  According to the present invention, as a preferred embodiment of the present invention, the terminal carboxyl group amount is 10 to 40 eq / T based on the weight of the polyethylene naphthalate resin composition, and the carbodiimide compound has a molecular weight of 200 to 1000. The carbodiimide compound is at least one selected from the group consisting of N, N′-diphenylcarbodiimide and N, N′-diisopropylphenylcarbodiimide, and the antioxidant is pentaerythrityl tetrakis [3 -(3,5-di-t-butyl-4-hydroxyphenyl) propionate], and the increase in the terminal carboxyl group of polyethylene naphthalate at a temperature of 285 ° C. for 20 minutes is at most 16 eq / T. That is, the amount of change in the color b value when held at a temperature of 285 for 20 minutes is at most 3. Polyethylene naphthalate resin composition comprising at least one of that is also provided.

  Furthermore, according to the present invention, at least one kind of antioxidant selected from the group consisting of hindered phenolic compounds and thioether compounds is added in an amount of 0.05 to 1% by weight. In addition, a method for producing a polyethylene naphthalate resin composition in which 0.1 to 10% by weight of a carbodiimide compound is added based on the weight thereof is also provided. In particular, the timing of addition of the carbodiimide compound and the antioxidant depends on the transesterification reaction. Alternatively, there is also provided a method for producing a polyethylene naphthalate resin composition which is added after completion of the melt polycondensation reaction via the esterification reaction and kept under vacuum without degassing.

  According to the present invention, it is possible to provide a polyethylene naphthalate resin composition in which the hydrolysis resistance due to the carbodiimide compound is efficiently expressed and the decomposition of the carbodiimide compound itself is suppressed, and such a polyethylene naphthalate resin composition can be provided. Can be provided more easily, and its industrial value is extremely high.

  The polyethylene naphthalate resin in the present invention is a polyester resin having ethylene naphthalate as the main repeating unit, and the ethylene naphthalate as the main repeating unit here means that 80% of the ethylene naphthalate unit is the total repeating unit of the polyester. It means to occupy more than%. When the ratio of the ethylene naphthalate unit is less than 80 mol%, the high strength, high chemical resistance, and high barrier resistance, which are the advantages of polyethylene naphthalate, become inferior.

  In the present invention, the polyethylene naphthalate resin may be copolymerized or mixed with a third component known per se as long as the effects of the present invention are not impaired. Examples of the naphthalene dicarboxylic acid component constituting the ethylene naphthalate include 2,6-naphthalenedicarboxylic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 1,3-naphthalenedicarboxylic acid, and the like. In particular, 2,6-naphthalenedicarboxylic acid is preferred. These naphthalenedicarboxylic acid components are used as 2,6-naphthalenedicarboxylic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, and 1,3-naphthalenedicarboxylic acid when directly passing through an esterification reaction. When transesterification is used, for example, dimethyl 2,6-naphthalenedicarboxylate, diethyl 2,6-naphthalenedicarboxylate, dimethyl 1,4-naphthalenedicarboxylate, dimethyl 1,5-naphthalenedicarboxylate, etc. It is done.

  In the polyethylene naphthalate resin composition of the present invention, the carbodiimide compound is 0.1 to 10% by weight, preferably 0.3 to 7% by weight, more preferably 0.5 to 3%, based on the weight of the resin composition. It is necessary to contain by weight. When the content of the carbodiimide compound is less than the lower limit, sufficient hydrolysis resistance is not exhibited, and even if the content exceeds the upper limit, the effect is hardly exhibited.

  The carbodiimide compound referred to in the present invention is a compound having at least one carbodiimide group in the molecule. Specific examples of the carbodiimide compound include N, N′-diphenylcarbodiimide, N, N′-diisopropylphenylcarbodiimide, N, N′-dicyclohexylcarbodiimide, 1,3-diisopropylcarbodiimide, and 1- (3-dimethylaminopropyl). And monocarbodiimides such as -3-ethylcarbodiimide and polycarbodiimide compounds such as poly (1,3,5-triisopropylphenylene-2,4-carbodiimide). Among these, N, N′-diphenylcarbodiimide and N, N′-diisopropylphenylcarbodiimide are preferable, and N, N′-diphenylcarbodiimide is particularly preferable. Further, the carbodiimide compound is not limited to one type, and a plurality of carbodiimide compounds may be used in combination. Preferably, among all carbodiimide compounds, N, N′-diphenylcarbodiimide and N, N′-diisopropylphenylcarbodiimide are 50 to 50%. It is preferable that it is 100 mol%.

  Moreover, it is preferable that the molecular weight of a carbodiimide compound exists in the range of 200-1000, especially the range of 200-600. If the molecular weight exceeds the upper limit, the dispersibility in the resin composition tends to decrease, and if the molecular weight is less than the lower limit, scattering tends to occur.

  In addition to the carbodiimide compound, the polyethylene naphthalate resin composition of the present invention contains 0.05 to 1% by weight of at least one antioxidant selected from the group consisting of hindered phenolic compounds and thioester based compounds, It is necessary to contain 0.1 to 0.5 weight% preferably. If the content of the antioxidant is less than the lower limit, decomposition degradation of the carbodiimide cannot be suppressed, and sufficient hydrolysis resistance is not exhibited. On the other hand, if the content exceeds the upper limit, the color tone of the polymer may be impaired.

  The antioxidants used in the present invention are hindered phenol compounds and thioether compounds, preferably hindered phenol compounds. Specific antioxidants for hindered phenol compounds include triethylene glycol-bis [3- (3-t-butyl-5-methyl-4-hydroxyphenyl) propionate], 1,6-hexanediol-bis. [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], 2,4-bis- (n-octylthio) -6- (4-hydroxy-3,5-di-t-butylanilino ) -1,3,5-triazine, pentaerythrityl tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], 2,2-thio-diethylenebis [3- (3 , 5-di-t-butyl-4-hydroxyphenyl) propionate], octadecyl-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate, N, N′-hexamethylenebis (3, 5-di-t-butyl-4-hydroxy-hydrocinnamamide), 3,5-di-t-butyl-4-hydroxybenzylphosphonate-diethyl ester, 1,3,5-trimethyl-2,4 , 6 -Tris (3,5-di-t-butyl-4-hydroxybenzyl) benzene. Specific thioether compounds include thiodipropionic acid, 4,4-thiobis (6-tert-butyl-3-methylphenol), dilauryl thiodipropionate, distearyl thiodipropionate, dimyristyl. Thiodipropionate, ditridecylthiodipropionate, mixed esters of thiodipropionic acid (lauryl and stearyl), and pentaerythritol tetrakis (3- (didecylthio) propionate), pentaerythritol-tetrakis (β-dodecyl-thiopro) Pionate). Among these, 4,4-thiobis (6-t-butyl-3-methylphenol), pentaerythrityl tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], 3 , 5-di-t-butyl-4-hydroxybenzylphosphonate-diethyl ester is preferred.

  The polyethylene naphthalate resin composition of the present invention contains not only the above-mentioned carbodiimide compound but also an antioxidant selected from the group consisting of the above-mentioned hindered phenol-based compounds and thioether-based compounds. Decomposition is suppressed and the hydrolysis resistance of the carbodiimide compound can be maximized. As a result, excellent hydrolysis resistance that cannot be achieved with conventional carbodiimide compounds alone or antioxidants alone is exhibited. From this point, the weight ratio obtained by dividing the antioxidant content by the carbodiimide compound content is preferably in the range of 0.1 to 1.0, more preferably 0.15 to 0.8. If the said weight ratio is less than a minimum, the effect which suppresses hydrolysis of carbodiimide will become inadequate, and even if it exists exceeding the upper limit on the other hand, the improvement of the effect which suppresses hydrolysis of carbodiimide will become scarce.

  Furthermore, the preferable aspect of the polyethylene naphthalate resin composition of this invention is demonstrated. The polyethylene naphthalate resin composition of the present invention preferably has an intrinsic viscosity in the range of 0.4 to 1.0 dl / g, particularly 0.5 to 0.8 dl / g. If the intrinsic viscosity is less than the lower limit, the mechanical properties of the resulting resin composition tend to be poor, and if it exceeds the upper limit, the viscosity is too high and the moldability tends to be inferior. Such intrinsic viscosity can be adjusted by the production conditions of the polymer.

  The polyethylene naphthalate resin composition of the present invention has a terminal carboxyl group ratio of 10 to 40 eq / T, further 10 to 30 eq / T, particularly 10 to 25 eq / T, based on the weight of the polyethylene naphthalate resin composition. Preferably there is. When the ratio of the terminal carboxyl group exceeds the upper limit, the hydrolysis resistance becomes inferior even when a carbodiimide compound is used, which is not preferable. From the viewpoint of productivity, the lower limit is usually preferably 10 eq / T. Such an amount of terminal carboxyl groups can be achieved by allowing carbodiimide to act without being decomposed or scattered. The polyethylene naphthalate resin composition of the present invention preferably has an increase in the terminal carboxyl group of polyethylene naphthalate of at most 16 eq / T, more preferably 13 eq / T or less when held at a temperature of 285 ° C. for 20 minutes. . When the increase amount of the terminal carboxyl group exceeds the upper limit, the effect of improving the hydrolysis resistance of the carbodiimide compound is poor, which is not preferable. Such an increased amount of terminal carboxyl groups can be achieved by controlling the melt polymerization temperature or using an antioxidant and a carbodiimide in combination at a specific ratio as described above.

The polyethylene naphthalate resin composition of the present invention has a melt viscosity of 200 to 4000 Pa · s, more preferably 400 to 1000 Pa · s when measured at a measurement temperature of 300 ° C. and a shear rate of 1000 s ^−1. preferable. If the melt viscosity is less than the lower limit, the mechanical properties of the resin composition tend to be poor, while if the melt viscosity exceeds the upper limit, the viscosity is too high and molding tends to be difficult.

  The polyethylene naphthalate resin composition of the present invention preferably has a change in color b value of at most 3 when held at a temperature of 285 ° C. for 20 minutes. When the amount of change in the color b value exceeds the upper limit, the change in color tone is large, and even if the hydrolysis resistance is excellent, the appearance is poor and the use for optical purposes is restricted. In order to suppress the amount of change in the color b value, it is possible to use an antioxidant and carbodiimide in combination at a specific ratio.

  The polyethylene naphthalate resin composition of the present invention has an ethylene naphthalate 1 to 5 mer (hereinafter referred to as oligomer) content of 0.4 to 1.0% by weight, more preferably 0.5 to 0.9% by weight. It is preferable that If the oligomer content is less than the lower limit, the fluidity at the time of molding tends to be impaired, while if it exceeds the upper limit, mold contamination due to the oligomer tends to occur at the time of molding. Such an oligomer amount can be achieved by controlling the melt polymerization temperature or using an antioxidant and a carbodiimide in combination at a specific ratio as described above.

  The polyethylene naphthalate resin composition of the present invention is added to the polycondensation reaction by the conventional method of kneading the carbodiimide compound into the polyethylene naphthalate resin except that both the carbodiimide compound and the above-mentioned antioxidant are added. Can also be manufactured. In the case of kneading, it is preferable to add an antioxidant before adding the carbodiimide compound to the polyethylene naphthalate resin. From the viewpoint of kneading dispersion power, a biaxial kneading extruder, particularly a biaxial kneading with a vent. A machine or the like is preferably used.

  By the way, such a kneading method has been performed because the decomposition of the carbodiimide compound cannot be suppressed, but in the present invention, since the decomposition of the carbodiimide compound itself can be suppressed, such a kneading process is performed. The carbodiimide compound can be directly added to the polymerization reaction system. As a result, an extra kneading step can be omitted, and there is an advantage that the thermal decomposition of the polymer caused by the kneading step can be eliminated.

  There is no restriction | limiting in particular about the manufacturing method itself of a polyethylene naphthalate resin, A conventionally well-known method is applicable. Examples thereof include a melt polymerization method such as a transesterification method and a direct esterification method, or a solution polymerization method. In addition, transesterification catalysts, esterification catalysts, etherification inhibitors used in these reactions, polymerization catalysts used in polymerization, various stabilizers such as heat stabilizers and light stabilizers, polymerization regulators, and the like are conventionally known. Can be used. For example, compounds such as manganese, cobalt, zinc, titanium and calcium as transesterification catalysts, compounds such as manganese, cobalt, zinc, titanium and calcium as esterification catalysts, and amine compounds as etherification inhibitors, etc. Can be mentioned. On the other hand, examples of the polycondensation catalyst include compounds such as germanium, antimony, tin, and titanium. It is also effective to add various phosphorus compounds such as phosphoric acid, phosphorous acid, and phenylphosphonic acid as a heat stabilizer. Other light stabilizers, antistatic agents, lubricants, antioxidants, mold release agents and the like may be added.

  In the present invention, a preferable method for producing a polyethylene naphthalate resin composition is a method in which a carbodiimide compound and an antioxidant are directly added to a polymerization reaction system. About addition amount, it is the quantity which becomes the content demonstrated with the above-mentioned polyethylene naphthalate resin composition. Here, it is necessary to add both the carbodiimide compound and the antioxidant, and the antioxidant is added at the same time as the carbodiimide compound or before that, hydrolysis of the carbodiimide compound is suppressed and polymerization is performed. Even if it is added to the reaction system, it is preferable because sufficient hydrolysis resistance can be obtained.

  The stage of addition of the carbodiimide compound and the antioxidant is preferably the stage after the polycondensation reaction because the thermal history received by the carbodiimide compound and the antioxidant can be relaxed. In addition, since the scattering of the carbodiimide compound can be suppressed, the first step in which the polycondensation reaction is degassed to bring it closer to the vacuum, and the second step in which degassing is stopped and the deaeration that is held in a state close to the vacuum is not performed. Are provided in this order, and the carbodiimide compound is preferably added in the second step. By adopting such a method, for example, the evaporation of the carbodiimide compound in the kneading step or the polycondensation reaction step can be suppressed. As a result, it is not necessary to use a carbodiimide compound having a large molecular weight in order to suppress transpiration, and the use of a carbodiimide compound having a large molecular weight suppresses an increase in the effect of decomposition of the carbodiimide compound itself and a decrease in dispersion of the carbodiimide compound. it can. Further, it is not necessary to further increase the amount added due to the damage caused by steaming.

  The polyethylene naphthalate resin composition of the present invention thus obtained was an unstretched or low-magnification monolayer sheet or multilayer sheet obtained by injection molding, T-die method, coextrusion method, or the like, and they were stretched. It can be used as a film, a deep drawing container having a low draw ratio, and a direct blow molding and a stretch blow molded article that are not stretched after molding. Further, it may be molded as a master batch by mixing with another resin not containing carbodiimide, which is preferable because the number of types of polymers to be prepared can be reduced.

  Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to these examples. The measuring methods for various properties of the polyethylene naphthalate resin composition of the present invention are as follows.

(1) Intrinsic viscosity (IV)
The polyethylene naphthalate resin composition produced in each example was measured for intrinsic viscosity before heat treatment using an Ostwald viscometer at a constant temperature of 35 ° C. using phenol / trichloroethane = 6/4 (weight ratio) as a solvent. To do. In addition, in order to evaluate hydrolysis resistance, the polyethylene naphthalate resin composition produced in each example was heated in an autoclay part at 150 ° C. for 8 hours, and was the same as the above-described method for measuring intrinsic viscosity before heat treatment. Then, the intrinsic viscosity after the heat treatment is measured. The smaller the difference between the intrinsic viscosity before the heat treatment and the intrinsic viscosity after the heat treatment, the better the hydrolysis resistance.

(2) Content of Carbodiimide and Antioxidant Quantification of Carbodiimide and Antioxidant: 1 g of resin was charged with 10 ml of benzyl alcohol containing 0.01 mol / l NaOH, decomposed in an autoclave at 160 ° C. for 24 hours, diluted with chloroform, and GPC440 manufactured by Waters. Quantified by mold.

(3) Terminal carboxyl group content (eq / 10 ⁶ g)
The polyethylene naphthalate resin composition obtained in each example and the terminal carboxyl group of the polyethylene naphthalate resin composition when the composition was held at a temperature of 285 for 20 minutes are respectively A. Measured according to Conix's method (Makromol. Chem. 26, 226 (1958)). In addition, it means that it is excellent in heat resistance, so that the amount of terminal carboxyl groups after hold | maintaining at high temperature is so small that the amount of terminal carboxyl groups is near, and the amount of terminal carboxyl groups before holding | maintenance. And before processing of the amount of terminal carboxyl groups of the polyethylene naphthalate resin composition obtained in each example, and before processing of the amount of terminal carboxyl groups of the polyethylene naphthalate resin composition when held at a temperature of 285 for 20 minutes The amount of increase relative to the amount of terminal carboxyl groups was taken as the increase after treatment.

(4) Color tone (Col-b value) and change in color tone (ΔCol-b)
A sample in which the polyester composition of each example was formed into a plate was dried at 140 ° C. for 2 hours, and then placed on a white standard plate for color difference adjustment, and the Hunter b value on the plate surface was measured by CM manufactured by Color Machine Co., Ltd. -Measured using a 7500 type color machine. The Col-b value indicates that the greater the value, the greater the degree of yellowing.
In addition, the change in color tone was obtained by obtaining a resin composition plate in which the polyester composition obtained in each example was stirred and held in a molten state at 285 ° C. for 20 minutes for 20 minutes to promote thermal decomposition. The Col-b value was measured. Then, the difference between the two was defined as an increase (ΔCol−b) after the process of changing the color tone.

(5) Hydrolysis resistance The polyester composition of each example was melted at 300 ° C. and rapidly solidified on a casting drum maintained at a surface finish of 0.3 S and a surface temperature of 60 ° C. using a T-type extrusion die. Thus, an unstretched film made of a polyethylene-2,6-naphthalate resin composition was obtained.
This unstretched film is preheated to 120 ° C., further heated by an infrared heater with a surface temperature of 830 ° C. from above 14 mm between low-speed and high-speed rolls, stretched 3.0 times in the film forming direction, rapidly cooled, Subsequently, it was supplied to a stenter and stretched 3.5 times in a direction perpendicular to the film forming direction at 125 ° C. to prepare a biaxially oriented film having a thickness of 200 μm.
This sample was placed in an autoclave and treated in saturated water at 2 atm and 121 ° C. for 100 hours. The breaking strength in the film-forming direction of the biaxially oriented film before and after the treatment was measured using a tensile tester “Tensilon” manufactured by Toyo Baldwin Co., Ltd. at a temperature of 20 ° C., a humidity of 50%, a sample width of 10 mm, and a sample length of 15 cm. The distance between chucks was 100 mm, the tensile speed was 10 mm / min, and the chart speed was 500 mm / min. This measurement was repeated 5 times, and the average value thereof was taken as the breaking strength of the biaxially oriented film before and after the treatment. The higher the value (strength retention) obtained by dividing the breaking strength after treatment by the breaking strength before treatment, the better the hydrolysis resistance.

[Example 1]
100 mol (24.4 kg) of dimethyl 2,6-naphthalenedicarboxylate (hereinafter referred to as NDCM), 180 mol (11.2 kg) of ethylene glycol (hereinafter referred to as EG), and 0.03 mol of manganese acetate tetrahydrate per 100 mol of NDCM The Japanese product was heated to 240 ° C. in a nitrogen atmosphere to conduct a transesterification reaction. After the distillation amount of methanol reaches 90% or more of the theoretical amount, 0.02 mol of antimony (III) oxide and 0.04 mol of trimethyl phosphate (hereinafter referred to as “TMP”) are added to 100 mol of NDCM. And kept at 260 ° C. for 30 minutes. Thereafter, the temperature is increased and the pressure is gradually reduced. Finally, polymerization is performed at 0.1 kPa at 300 ° C. and 0.1 kPa or less, and when a predetermined viscosity is reached, Matsumoto Yushi Seiyaku Co., Ltd. (N , N′-diphenylcarbodiimide) and pentaerythrityl tetrakis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate] as an antioxidant are added in the amounts shown in Table 1. The mixture was stirred and held at 1 kPa for 10 minutes to obtain a copolymerized polyethylene naphthalate resin composition.
Table 1 shows the characteristics of the obtained copolymer polyethylene naphthalate resin composition.

[Examples 2 to 8 and Comparative Examples 1 to 4]
As shown in Table 1, the same operations as in Example 1 were repeated except that the intrinsic viscosity and the types and amounts of the carbodiimide compound and the antioxidant were changed.
Table 1 shows the characteristics of the obtained copolymer polyethylene naphthalate resin composition.

  In Table 1, carbodiimide compound A is N, N′-diphenylcarbodiimide, carbodiimide compound B is N, N′-dicyclohexylcarbodiimide (manufactured by Tama Chemical Co., Ltd.), and antioxidant C is pentaerythrityl tetrakis [ 3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], antioxidant D is 3,5-di-t-butyl-4-hydroxybenzylphosphonate-diethyl ester, antioxidant E is 4,4-thiobis (6-tert-butyl-3-methylphenol).

  The polyethylene naphthalate resin composition of the present invention retains the heat resistance, transparency, mechanical performance, and moldability of the polyethylene naphthalate resin, and has excellent hydrolysis resistance, so that it can be used for fibers, bottles, and films. In particular, it can be suitably used for fields requiring hydrolysis resistance, such as automobile parts, electronic parts, lighting plates, heat-resistant food containers, etc., and its industrial significance is great. And according to this invention, such a polyethylene naphthalate resin composition can be manufactured efficiently, and also it can manufacture by skipping the conventional kneading | mixing process, The industrial value is high.

Claims (9)

  It contains 0.1 to 10% by weight of a carbodiimide compound and 0.05 to 1% by weight of at least one antioxidant selected from the group consisting of hindered phenolic compounds and thioether compounds. A polyethylene naphthalate resin composition.   The polyethylene naphthalate resin composition according to claim 1, wherein the terminal carboxyl group amount is 10 to 40 eq / T based on the weight of the polyethylene naphthalate resin composition.   The polyethylene naphthalate resin composition according to claim 1, wherein the carbodiimide compound has a molecular weight of 200 to 1,000.   The polyethylene naphthalate resin composition according to claim 1, wherein the carbodiimide compound is at least one selected from the group consisting of N, N'-diphenylcarbodiimide and N, N'-diisopropylphenylcarbodiimide.   The polyethylene naphthalate resin composition according to claim 1, wherein the antioxidant is pentaerythrityl tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate].   2. The polyethylene naphthalate resin composition according to claim 1, wherein the amount of increase in the terminal carboxyl group of polyethylene naphthalate when held at a temperature of 285 ° C. for 20 minutes is at most 16 eq / T.   2. The polyethylene naphthalate resin composition according to claim 1, wherein the amount of change in the color b value is 3 at most when held at a temperature of 285 for 20 minutes.   A carbodiimide based on the weight of a polyester resin composition in which at least one antioxidant selected from the group consisting of a hindered phenol compound and a thioether compound is added in an amount of 0.05 to 1% by weight. A method for producing a polyethylene naphthalate resin composition, comprising adding 0.1 to 10% by weight of a compound.   9. The addition timing of the carbodiimide compound and the antioxidant is added after the end of the melt polycondensation reaction via the transesterification or esterification reaction and maintained under vacuum without degassing. The manufacturing method of the polyethylene naphthalate resin composition of description.