JP2000053671A - Cross-linking agent for thermoplastic polyester resin, and its use - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a cross-linking agent hardly causing a rapid change in viscosity and manifesting stable thickening activities when carrying out a foam molding of a thermoplastic polyester resin, and hardly causing discoloration of a molding product while operating a molding machine for a long time, and capable of providing the molding product having fine uniform bubble cells dispersed uniformly. SOLUTION: A (meth)acryloxy ester of trimellitic anhydride of general formula [1] (R1 and R2 are each H or methyl) as a cross-linking agent is compounded with a thermoplastic polyester resin, and the compounded product is subjected to a foam molding to provide a molding product.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a crosslinking agent suitable for a thermoplastic polyester resin comprising a trimellitic anhydride (meth) acryloxyalkyl ester compound and a method for crosslinking a thermoplastic polyester resin. The present invention relates to a thermoplastic polyester resin composition containing a (meth) acryloxyalkyl ester compound. Further, the present invention relates to a molded article of a thermoplastic polyester resin which is cross-linked by a trimellitic anhydride (meth) acryloxyalkyl ester compound and foamed.

[0002]

2. Description of the Related Art Thermoplastic polyester resins have excellent mechanical properties, heat resistance, chemical resistance, dimensional stability, transparency, weather resistance, insulation, etc. It is used for a wide range of applications, and various other applications are currently being developed. As one of the new uses, a foam molded article has been taken up, and attempts have been made to develop it into food containers, packaging materials, building materials, and the like.

[0003] In general, since the thermoplastic polyester resin has a low melt viscosity, foaming gas is released during foam molding, and it is difficult to produce a foam molded article in which fine bubbles are uniformly dispersed. Therefore, a thickening method for increasing the melt viscosity of the resin and enabling foam molding has been studied. As one of the methods, a crosslinking agent having an effect of crosslinking the polymer chain of the thermoplastic polyester resin and increasing the molecular weight of the polyester resin. Has been attempted.

For example, JP-A-53-24364 discloses a method using a polyvalent epoxide and a carboxylate or carbonate of an alkali metal or an alkaline earth metal, and a method using a polyvalent epoxide and a montan wax salt or a montan wax ester salt. Is proposed in Japanese Patent Laid-Open No. 54-50568. However, it has been pointed out that in these methods, although the viscosity increases rapidly with the progress of the crosslinking reaction, the viscosity tends to decrease rapidly thereafter, so that it is difficult to obtain the optimum viscosity.

A method using a diglycidyl ester is disclosed in JP-B-61-48409, and a method using a combination of a polyfunctional diglycidyl ester and a polyfunctional carboxylic anhydride is disclosed in JP-A-59-210955. Proposed. However, when the crosslinking treatment of the thermoplastic polyester resin and the molding operation are continued for a long time by these methods, a phenomenon in which the molded product is colored black is observed.

The present inventors have also tried a method using an epoxy resin as a thickener, but the crosslinking reaction is slow and the strand state during granulation changes with time, and the epoxide concentration changes with the progress of the crosslinking reaction. The epoxide itself has the property of reacting with each other due to the rapid change in viscosity, and it has been found that there is a problem in long-run property. The method using a polyvalent epoxide has not yielded satisfactory results.

[0007] In addition, use of a compound represented by pyromellitic anhydride having at least two acid anhydride groups in a molecule has been proposed in Japanese Patent Publication No. 5-15736. According to this method, a nucleophilic addition reaction to an acid anhydride group by a terminal hydroxyl group of a polymer chain of the thermoplastic polyester resin, or a transesterification reaction of an ester bond and an acid anhydride group in the polymer chain of the polyester resin proceeds, As a result, a crosslinking reaction occurs. However, even when all four carbonyl groups of the acid anhydride group form an ester bond with the thermoplastic polyester polymer chain, the four polymer chains are only crosslinked, so that it is necessary to obtain a sufficient melt viscosity. Need to be increased.

[0008]

SUMMARY OF THE INVENTION Accordingly, a first object of the present invention is to provide a crosslinking agent for a thermoplastic polyester resin having a different chemical structure from that of a conventionally known crosslinking agent. It is. The second purpose is that when it is applied to the crosslinking reaction of a thermoplastic polyester resin, it does not cause a sudden change in viscosity, coloring, and long run property disorder caused by the crosslinking agent reacting with each other. is there. The third purpose is to exhibit a stable thickening effect without a sudden change in viscosity when actually used for foam molding of a thermoplastic polyester resin, and that the state of a molded product surface does not change with time. In addition, it is possible to produce a molded article in which fine bubbles are uniformly dispersed without causing coloring of the molded article during a long operation.

[0009]

Means for Solving the Problems In order to solve the above problems, the present inventors have searched for a compound suitable for a crosslinking agent, and have found a crosslinking agent according to the present invention. That is, the crosslinking agent for the thermoplastic polyester resin according to the present invention is a trimellitic anhydride (meth) anhydride represented by the following general formula [1].
It is an acryloxyalkyl ester compound.

Embedded image In the formula, R ¹ and R ² represent a hydrogen atom or a methyl group. In the present invention, a trimellitic acid group in which a trimellitic anhydride group is opened is also included.

[0010] The present invention also provides a method of crosslinking a thermoplastic polyester resin with a trimellitic anhydride (meth) acryloxyalkyl ester compound represented by the above general formula, and a composition comprising the compound and a thermoplastic polyester resin. Things.

Further, the present invention provides a thermoplastic polyester resin represented by polyethylene terephthalate, which is crosslinked by a trimellitic anhydride (meth) acryloxyalkyl ester compound represented by the above general formula [1], and is formed by foam molding. It is a formed polyester resin molded article.

[0012]

DETAILED DESCRIPTION OF THE INVENTION The crosslinking agent for a thermoplastic polyester resin according to the present invention, a method for crosslinking a thermoplastic polyester resin using the same, a resin composition, and a molded article using the same will be described in detail. I do.

The trimellitic anhydride compound The cross-linking agent according to the present invention is represented by the following general formula [1] and includes both acryloxyalkyl trimellitic anhydride compound and methacryloxyalkyl trimellitic anhydride compound. Is included.

Embedded image In the formula, R ¹ represents hydrogen or a methyl group, indicating that this compound is a derivative of acrylic acid or methacrylic acid. Further, the trimellitic anhydride group at the terminal of the general formula [1] may be opened to form a trimellitic acid group.

A specific example of the trimellitic anhydride (meth) acryloxyalkyl ester compound represented by the general formula [1] is shown in FIG. 1 below.

FIG.

In the compound shown in FIG. 1, (1) is 4-
(Acryloxyethyl) trimellitic anhydride, (2)
Is 4- (methacryloxyethyl) trimellitic anhydride, (3) is 4- (2-acryloxy-1-methylethyl) trimellitic anhydride, and (4) is 4- (2-methacryloxy-1-methyl) Ethyl) trimellitic anhydride, any of which can be used as a crosslinking agent for polyester resins. Among these, use of 4- (acryloxyethyl) trimellitic anhydride and 4- (2-acryloxy-1-methylethyl) trimellitic anhydride is particularly preferred.

The above compounds are 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 2
-Hydroxyethyl methacrylate or 2-hydroxypropyl methacrylate and trimellitic anhydride can be esterified by a method of reacting each in the coexistence of various dehydrating agents, and can be produced. Suitable dehydrating agents used in this dehydration reaction include 2-halopyridinium salt-amine, dicyclohexylcarbodiimide, N, N'-carbonyldiimidazole, trifluoroacetic anhydride and the like.

Further, it can also be produced by reacting a reactive derivative of trimellitic anhydride, for example, an acid halide or ester with the corresponding hydroxyacrylate or methacrylate compound. The acid halide of trimellitic anhydride can be synthesized, for example, by reacting trimellitic anhydride with various halogenating reagents such as thionyl chloride, phosphorus trichloride, and phosphorus tribromide.

In the reaction between hydroxyacrylate or methacrylate and trimellitic anhydride, or the reaction with a reactive derivative of trimellitic anhydride, the respective reaction reagents are usually supplied at a molar ratio of about 1: 1 and the solvent is dissolved in a solvent. At a temperature of 0 to 50 ° C. and a pressure of normal pressure to 10 atm.

The reaction solvent is selected from solvents such as halogenated hydrocarbons, aromatic hydrocarbons, esters, ethers, ketones, and nitriles according to the solubility of the raw materials and the reaction conditions. Can be obtained, for example, dichloromethane, chloroform, 1,2-dichloroethane,
Benzene, toluene, xylene, ethyl acetate, diethyl ether, tetrahydrofuran, 1,4-dioxane,
Acetone, acetonitrile and the like can be exemplified.

[0020]Crosslinking agent, crosslinking method, resin composition  Trimellitic anhydride (meth) acryl described above
Roxyalkylester compound is a thermoplastic polyester
It can be suitably used as a resin crosslinking agent. here
The thermoplastic polyester resin is an aromatic dicarboxylic acid
Thermoplastic polyester obtained by polycondensation of
It is a ester.

Examples of the aromatic dicarboxylic acid include terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid, diphenyl ether dicarboxylic acid, diphenyl sulfone dicarboxylic acid, diphenoxyethane dicarboxylic acid, and the like. These dicarboxylic acids may be used alone or in combination. A combination of more than one species may be used.

The diol component includes ethylene glycol, propylene glycol, 1,4-butanediol,
Trimethylene glycol, tetramethylene glycol,
Neopentyl glycol, hexamethylene glycol,
Examples thereof include cyclohexane dimethanol, tricyclodecane dimethylol, 2,2-bis (4-β-hydroxyethoxyphenyl) propane, 4,4-bis (β-hydroxyethoxy) diphenyl sulfone, and diethylene glycol. May be used alone or in combination of two or more.

Preferred examples of the thermoplastic polyester resin include polyethylene terephthalate, polytetramethylene terephthalate, polyethylene-2,6-naphthalenedicarboxylate, polybutylene terephthalate, and polycyclohexane terephthalate. Further, a mixture of these polyester resins or a modified resin containing 50% by weight or more of these polyester resins may be used. Further, a recycled product of the polyester resin used once may be used.

The crosslinking can be carried out by mixing the thermoplastic polyester resin and trimellitic anhydride (meth) acryloxy ester under the melting conditions of the polyester resin. At the time of blending, trimellitic anhydride (meth) acryloxyester as a crosslinking agent is usually 0.001 to 20 parts by weight, preferably 0.01 to 10 parts by weight, based on 100 parts by weight of the thermoplastic polyester resin. More preferably, it is added in a ratio of 0.05 part by weight to 1 part by weight to form a resin composition. When the compounding ratio is within the range, the resin composition has an appropriate viscosity in the steps of crosslinking or foam molding described below, and is less likely to color the final molded article.

Further, in the present invention, when the thermoplastic polyester resin is crosslinked in the presence of trimellitic anhydride (meth) acryloxyester in the presence of a small amount of a radical initiator, the crosslinking reaction is more effectively performed. And such cross-linking methods are also within the scope of the present invention. The radical initiator is a thermoplastic polyester resin 1
It is used in an amount of usually 0.0001 to 1 part by weight, preferably 0.001 to 0.1 part by weight, based on 00 parts by weight.

The usable radical initiator is not particularly limited, and azo compounds, peroxides, hydroperoxides and the like can be used. Examples include azobisisobutyronitrile, benzoyl peroxide, tert-butyl hydroperoxide, di-tert-butyl peroxide, cumene hydroperoxide, α, α′-bis
(tert-butylperoxy) diisopropylbenzene, metachloroperbenzoic acid and the like.
These may be used alone or in combination of two or more, and if necessary, a metal such as iron which promotes decomposition of the radical initiator may be added.

As a method for preparing a compound by adding the crosslinking agent and, if necessary, a radical initiator to the thermoplastic polyester resin, a general dry blending method using a tumbler or a Henschel mixer is used. Can be.

In addition, in the blending operation with the thermoplastic polyester resin, a crosslinking agent and, if necessary, a radical initiator are dissolved in a solvent, mixed with the thermoplastic polyester resin, and then the solvent is distilled off under air drying or reduced pressure. Can also be mixed. The solvent at this time is not particularly limited as long as it does not cause decomposition or reaction of the thermoplastic polyester resin, the crosslinking agent and the radical initiator, and examples thereof include alcohols such as methanol, ethanol, and isopropyl alcohol, benzene, and toluene. And aromatic hydrocarbons such as xylene, halogenated hydrocarbons such as dichloromethane, ethyl acetate, diethyl ether and acetone, esters, ethers and ketones.

When the thermoplastic polyester resin is crosslinked with the trimellitic anhydride (meth) acryloxyalkyl ester compound, the crosslinking temperature is higher than the melting point of the thermoplastic polyester resin, that is, 100 to 350, for example. ° C, preferably 150-
It can be performed by mixing at a temperature of 300 ° C. The mixing operation is desirably performed under kneading conditions using a single-screw or twin-screw extruder. The trimellitic anhydride (meth) acryloxyalkyl ester compound may be used alone or in combination of two or more, or may be used in combination with another crosslinking agent. it can.

In the crosslinking operation, a crosslinking agent and, if necessary, a radical initiator are used by using a part of the thermoplastic polyester resin to be used or by using another resin compatible with the thermoplastic polyester resin, for example, polyethylene. Can be mixed by the above-described method to prepare a master batch in advance. Thereafter, the mixture is mixed with the remaining thermoplastic polyester resin, and the crosslinking reaction may proceed at this stage. Alternatively, a method may be employed in which only a crosslinking agent is blended in the masterbatch production stage, and a radical initiator is added in the subsequent dilution and mixing stage.

It is presumed that the crosslinking reaction with the thermoplastic polyester resin by the trimellitic anhydride (meth) acryloxyalkyl ester compound proceeds by the following mechanism. That is, the trimellitic anhydride (meth) acryloxyalkyl ester compound has an acryloyl group or a methacryloyl group which is a polymerizable vinyl group in the molecule, and has a reactivity with a hydroxyl group at the polymer chain end of the thermoplastic polyester resin. With an acid anhydride group with Therefore, under heat kneading conditions of a trimellitic anhydride compound and a thermoplastic polyester resin,
Considering that the polymer chain of the thermoplastic polyester resin reacted with the acid anhydride group of this compound is linked by the polymer chain grown by polymerization of the acryloyl group or methacryloyl group of this compound, and the crosslinking reaction of the polyester resin proceeds. I have. From this, it is considered that the crosslinking agent according to the present invention can easily cause a crosslinking reaction with many thermoplastic polyester resins having a terminal hydroxyl group.

[0032]Polyester resin molding  The polyester resin molded article of the present invention is a thermoplastic polyester.
Termellic acid according to the present invention is a trimellitic anhydride (meth)
Crosslinked structure by acryloxyalkyl ester compound
And by foam molding with a foaming agent
Fine bubbles are evenly dispersed and shaped into the desired shape
ing.

The method for producing the molded article includes a step of preparing a composition by blending a crosslinking agent and, if necessary, a radical initiator with a thermoplastic polyester resin, a step of melt-kneading the composition, and a step of melt-kneading the composition. The process comprises foaming the mixture and shaping it into a desired shape. The steps up to preparing the molten mixture are as described above,
Some of the steps up to this point, and all of the steps, can be performed in one step together with the foam molding step using an extruder used in the foam molding step described below.

In the foam molding step, first, the molten mixture is supplied to an extrusion foam molding machine, and a liquid or gaseous foaming agent is pressed into the extruder, and both are sufficiently dissolved and mixed. And extruded into the atmosphere to produce a foam molded article. At this time, the foaming agent is usually press-fitted from a vent provided at the center of the cylinder of the extruder and is dissolved and mixed into the molten resin.

The foamed molded article of the thermoplastic polyester resin can be produced by another method. For example, a thermoplastic polyester resin and a foaming agent are supplied to a hopper of an extrusion foaming molding machine, while a crosslinking agent of the present invention and a radical initiator as necessary are supplied from a supply port provided in an extruder cylinder, and the molten polyester is supplied under melting. This is a method of extruding and foaming. Further, it is also possible to uniformly mix a thermoplastic polyester resin, a crosslinking agent, a foaming agent and, if necessary, a radical initiator, supply the mixture to an extruder, and perform foam molding in one step.

When the thermoplastic polyester resin and the cross-linking agent are melt-mixed, water causes hydrolysis of the thermoplastic polyester resin. It is necessary to keep the water content as low as possible.
It is desirable to suppress it to 0 ppm or less. For this purpose, a method is preferably employed in which the thermoplastic polyester resin to be used is previously dried by a dehumidifying dryer or the like under the conditions of 60 to 180 ° C and a dew point of -20 ° C or less.

The foaming agents used include inert gas,
Saturated aliphatic hydrocarbons, saturated alicyclic hydrocarbons, aromatic hydrocarbons, halogenated hydrocarbons, ethers, ketones, and the like can be used, and these can be used alone or in combination of two or more. Specifically, carbon dioxide, nitrogen,
Helium, methane, ethane, normal butane, isobutane, normal pentane, isopentan, normal hexane, 2-methylpentane, 3-methylpentane, 2,2
-Dimethylbutane, 2,3-dimethylbutane, methylcyclopropane, cyclopentane, 1,1-dimethylcyclopropane, cyclohexane, methylcyclopentane,
Ethylcyclobutane, 1,1,2-trimethylcyclopropane, benzene and the like can be mentioned.

Further, trichloromonofluoromethane, dichlorofluoromethane, monochlorodifluoromethane,
Examples thereof include trichlorotrifluoroethylene, dichlorotetrafluoroethylene, dimethyl ether, 2-ethoxyethanol, acetone, methyl ethyl ketone, and acetylacetone. Among these, in consideration of safety during molding, an inert gas such as carbon dioxide, nitrogen, and helium is preferable as the foaming agent.

The amount of the foaming agent to be added is 0.0 to the total amount of the molten mixture containing the thermoplastic polyester resin and the crosslinking agent.
It is 5 to 50% by weight, more preferably 1 to 40% by weight. When the amount of the foaming agent is in this range, a foam molded article having uniformly fine cells can be obtained.

In the foam molding, an antioxidant, a heat stabilizer, a weather stabilizer, a nucleating agent, a pigment, a flame retardant, an antistatic agent, a filler,
Other additives can be arbitrarily added and mixed.

In the extrusion foam molding, depending on the shape of a die attached to the tip of the extruder, a foam molded article having a sheet shape, a filament shape, an irregular shape, etc. can be obtained.
The expansion ratio can be arbitrarily changed by adjusting the amounts of the radical initiator and the foaming agent and adjusting the extrusion conditions. The expansion ratio varies depending on the application, but can usually be changed in the range of 2 to 8 times. The foamed molded article thus manufactured is flexible and has appropriate mechanical properties, and also has heat resistance and chemical resistance, so that it can be used for various applications such as packaging materials and building materials. can do.

[0042]

EXAMPLES The present invention will be specifically described below based on examples, but the present invention is not limited to these examples. <Examples 1 to 3> 25 mg of an acryloxyalkyl trimellitate anhydride compound or a methacryloxyalkyl trimellitate anhydride compound shown in FIGS. 1 (1) to 1 (3) was dissolved in 2 ml of acetone. It was placed in a test tube with a diameter of 18 mm and a capacity of 30 ml with a rim.
5 g of polyethylene terephthalate resin pellets were further added and mixed, and then acetone was distilled off under reduced pressure and dried to prepare a sample for evaluation.

The test tube containing the mixture of the polyethylene terephthalate resin and the trimellitic anhydride ester was tilted 5 degrees from the horizontal, and was placed under an argon atmosphere under an argon atmosphere.
It was kept at 0 ° C. and left still for 5 minutes. While keeping the temperature at 290 ° C., the mixture is melt-mixed by rotating the test tube at a speed of 10 times per minute for 15 minutes. Then, the rotation is stopped and the molten mixture moves a predetermined distance. Was measured. The results are shown in Table 1.
cm).

Further, the number average molecular weight (Mn) and the weight average molecular weight (Mw) of the polyethylene terephthalate resin obtained by this evaluation experiment were measured by gel permeation chromatography (GPC).
The results are shown in Table 1.

[0045]

[Table 1]

<Comparative Example 1> An evaluation sample was obtained by repeating the same operation as in Example 1 except that only 5 g of pelletized polyethylene terephthalate resin was used without adding trimellitic anhydride ester. And the embodiment
The same evaluation test as in Example 1 was performed, and the results are shown in Table 1.

Comparative Example 2 Pyromellitic anhydride 25 was used in place of the trimellitic anhydride ester used in Example 1.
The same operation as in Example 1 was repeated except that mg was used,
A sample for evaluation was obtained. The transfer time of the molten mixture was measured, and the results are shown in Table 1.

In Table 1, the numerical value indicated by the moving time of the molten PET resin means that the larger the value, the higher the melt viscosity. Table 1 shows the moving time when the type of the cross-linking agent was changed in comparison with the moving speed when no cross-linking agent was added. Means a high thickening effect. Further, it shows that a higher melt viscosity can be obtained as compared with the case where pyromellitic anhydride is used as a crosslinking agent.

Example 4 Polyethylene Terephthalate
(Mitsui Chemicals Co., Ltd., trade name J120, intrinsic viscosity 0.
73 (dl / g)) was dried at 160 ° C. for 4 hours, and 0.5 parts by weight of 4- (acryloxyethyl) trimellitic anhydride was added thereto, followed by di- (2-t-butylperoxy). Isopropenyl) benzene (trade name: Perbutyl P, manufactured by NOF Corporation) 0.01 part, and dehydrated acetone 1
0 parts by weight were mixed and then dried at room temperature under a nitrogen stream.

The obtained mixture was supplied to a hopper of a 45 mmφ twin-screw extruder, and subjected to extrusion foam molding under the following conditions while press-fitting carbon dioxide gas to form a foam sheet having a thickness of 3 mm. Foaming molding conditions: Set temperature of extruder die section; 270 ° C Screw rotation speed; 100 rpm Carbon dioxide injection pressure; 4 MPa Extrusion amount; 6 kg / hour As a result, the formed sheet has a very small foam cell diameter,
It was a foam in which the cells were uniformly dispersed.

[0051]

When the trimellitic anhydride (meth) acryloxyalkyl ester compound according to the present invention is mixed with a thermoplastic polyester resin in a molten state, it acts as a crosslinking agent for the polyester resin and increases the melt viscosity of the polyester resin. And improve the formability. On this occasion,
When used in combination with a radical initiator, the crosslinking reaction proceeds even at a low concentration, and there is no risk of coloring the polyester resin molded article.

When the trimellitic anhydride (meth) acryloxyalkyl ester compound according to the present invention is used as a cross-linking agent and applied to the pelletizing, extrusion and foaming of a thermoplastic polyester resin, the cross-linking agent increases the viscosity. Due to the effect, it is possible to avoid a sudden change in viscosity during molding of the polyester resin, and it is possible to continue the stable operation of the molding machine for a long time.

Further, the foamed molded article produced by extrusion foaming which has been continued for a long time is hardly colored, and is produced in a favorable state in which fine bubbles are uniformly dispersed. It can be suitably used in the field of materials and the like.

Continued on the front page F term (reference) 4C037 RA11 4F074 AA65 BA32 BB03 BB27 CA22 CC06X CC22X DA03 DA33 DA34 DA50 4J002 CF061 EH136 FD146 GG00 GL00 4J029 AA03 AB04 AB07 AC01 AC02 AD01 AE01 BA03 BA05 J06B06 J06B06

Claims (9)

[Claims] 1. A crosslinking agent for a thermoplastic polyester resin, which is a trimellitic anhydride (meth) acryloxyalkyl ester compound represented by the following general formula [1]. Embedded image In the formula, R ¹ and R ² represent a hydrogen atom or a methyl group. 2. The trimellitic anhydride group in the general formula [1] is a trimellitic acid group.
The crosslinking agent for the thermoplastic polyester resin according to the above. 3. The method according to claim 1, wherein the compound represented by the general formula [1] is 4-acryloxyethyl trimellitic anhydride or 4-acryloxyethyl trimellitic anhydride.
The crosslinking agent for a thermoplastic polyester resin according to claim 1, wherein the crosslinking agent is (2-acryloxy-1-methylethyl) trimellitic anhydride. 4. A polyester resin molding characterized in that a thermoplastic polyester resin is cross-linked by a trimellitic anhydride (meth) acryloxyalkyl ester compound represented by the following general formula [2] and foam-molded. body. Embedded image In the formula, R ¹ and R ² represent a hydrogen atom or a methyl group. 5. The polyester resin molded article according to claim 4, wherein the thermoplastic polyester resin is polyethylene terephthalate. 6. A thermoplastic polyester resin having the following general formula:
A method for crosslinking a polyester resin, comprising mixing a trimellitic anhydride (meth) acryloxyalkyl ester compound represented by the formula [3] and mixing the resulting mixture under the melting conditions of the polyester resin. Embedded image In the formula, R ¹ and R ² represent a hydrogen atom or a methyl group. 7. The polyester resin according to claim 6, wherein the trimellitic anhydride (meth) acryloxyalkyl ester compound is incorporated in an amount of 0.001 to 20 parts by weight per 100 parts by weight of the thermoplastic polyester resin. Crosslinking method. 8. The method for crosslinking a polyester resin according to claim 6, wherein the method is carried out in the presence of a radical initiator. 9. A thermoplastic polyester resin having the following general formula:
A polyester resin composition comprising the trimellitic anhydride (meth) acryloxyalkyl ester compound represented by [4]. Embedded image In the formula, R ¹ and R ² represent a hydrogen atom or a methyl group.