JP2006131752A - Method for producing polyester resin - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polyester resin excellent in curability as well as in hydrolyzability by lowering its water content by diminishing the amount of bubbles caught by the polyester resin. <P>SOLUTION: The method for producing the polyester resin is a method for producing a polyester resin comprising completing a polyester resin polymerization reaction in a vacuum, shifting the degree of vacuum of the reaction system to the side of normal pressure, and performing a depolymerization reaction or a modification reaction, wherein the reaction system is brought to a vacuum again after the depolymerization reaction or the modification reaction. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for producing a polyester resin. More specifically, the present invention relates to a method for providing a polyester resin having a low moisture content, excellent hydrolyzability and excellent curability.

  Copolymerized polyester resins are widely used in the fields of paints, adhesives, coating agents and the like because the glass transition temperature, melting point, and film properties can be controlled by the copolymerization components. Under the present circumstances, in order to obtain the polyester resin which has the characteristic according to the use, the molecular terminal of a polyester resin is often modified | denatured or depolymerized. For example, Patent Document 1 discloses a method for obtaining a polyester polycaprolactone block polymer by adding a polycaprolactone monomer in a molten state after production of a polyester resin as an adhesive for vibration-damping steel sheets. Patent Document 2 discloses a method of reacting phthalic anhydride, which is an acid anhydride compound, after a polyester resin polycondensation reaction. Furthermore, Patent Document 3 discloses a process of adding a trimellitic acid to a polyester resin and performing a depolymerization reaction after completion of the polyester resin polycondensation reaction.

  Usually, a high molecular weight polyester resin undergoes a polycondensation reaction at a high degree of vacuum. Therefore, an inert gas such as nitrogen or argon is used to add a raw material component for performing a modification reaction or a depolymerization reaction after the polyester polycondensation reaction. In many cases, a step of returning the pressure of the reaction system to near normal pressure is employed. Thereafter, a depolymerization reaction or a denaturation reaction is performed at around normal pressure. In order to make the reaction proceed uniformly and efficiently, it is essential to stir the reaction system with a stirrer.

  However, all of these steps are performed at around normal pressure, and coupled with the very high melt viscosity of the polyester resin, bubbles are caught in the polyester resin. The foam does not disappear no matter how much stirring is carried out, and is cooled and solidified in the subsequent dispensing process to produce foamed polyester resin pellets and the like. Normally, a large amount of water is used for cooling in the dispensing process, but in the case of foamed resin, water can be removed by a simple draining process that is usually performed, for example, water enters the foamed part and blows off with strong wind. It becomes a polyester resin with a high moisture content.

  Polyester resins copolymerized with aliphatic dicarboxylic acids and polyester resins with high acid values are known to be inferior in hydrolyzability compared to polyethylene terephthalate and polybutylene terephthalate that do not have a copolymer component. A polyester resin having a high moisture content tends to cause a hydrolysis reaction during storage, resulting in poor long-term storage stability. In addition, when using a copolyester resin as an adhesive, it is often dissolved in an organic solvent, mixed with a curing agent, applied, dried, and bonded. In many cases, the target adhesive strength cannot be obtained because the contained moisture inhibits the curing reaction. However, until now, no specific method for removing bubbles has been known in a polyester resin production method in which a depolymerization reaction or a modification reaction is performed, and an improvement has been demanded.

JP-A-1-198622 (Example) JP-A-5-70737 (Example) JP 2002-173582 A (Example)

  An object of the present invention is to provide a polyester resin having a low moisture content by reducing the amount of foam biting into the polyester resin, excellent hydrolyzability, and excellent curability.

The present inventors faced the above problems, and as a result of intensive studies, they have found a method capable of producing a modified or depolymerized polyester resin efficiently and inexpensively even at an industrial level. That is, the present invention provides a polyester resin production method in which a polyester resin polycondensation reaction is completed under reduced pressure, and the degree of reduced pressure of the reaction system is shifted to normal pressure to perform a depolymerization reaction or a modification reaction. A method for producing a polyester resin, wherein the pressure is reduced again later.
The polyester resin satisfies the conditions of an acid value of 50 to 5000 eq / t and 0.80 ≦ (specific gravity of the polyester resin / specific gravity after heat treatment of the polyester resin at 220 ° C. for 10 minutes) ≦ 1.00. .

  According to the present invention, it is possible to obtain a modified or depolymerized polyester resin which is inexpensive and can be industrially implemented and has excellent quality. Since this polyester resin has excellent hydrolysis resistance, it can be used even after long-term storage, and the adhesive using the polyester resin is less susceptible to moisture content and exhibits stable adhesiveness. I can do it.

  The present invention relates to a polyester resin production method in which a polyester resin polycondensation reaction is completed under reduced pressure, the degree of reduced pressure of the reaction system is shifted to normal pressure, and a depolymerization reaction or a modification reaction is performed. A method for producing a polyester resin, wherein the pressure is reduced again.

  The polyester resin is usually polymerized under a high vacuum, but an operation of shifting the degree of pressure reduction to the normal pressure side is necessary in order to add the auxiliary material at the end of the polycondensation reaction of the polyester resin. At this time, it is preferable to introduce an inert gas such as nitrogen or argon into the reaction system.

  Subsequently, a step of adding an auxiliary material such as a polyvalent carboxylic acid to the molten polyester resin is required. At this time, the upper feed port of the reaction can is opened and charged, or the auxiliary material can be charged by a charging machine directly connected to the reaction can.

Thereafter, the polyester resin and the added auxiliary material are reacted. When performing the depolymerization reaction or the modification reaction, the pressure is preferably adjusted to a range of 1 × 10 ⁴ to 1 × 10 ⁶ Pa. Moreover, it is more preferable to adjust to the range of 5 * 10 < ⁴ > -5 * 10 < ⁵ > Pa. If the pressure is less than 1 × 10 ⁴ Pa, the reaction may proceed excessively to cause gelation of the polyester resin, or the secondary material may sublimate or evaporate, and normal reaction may not proceed. When the pressure exceeds 1 × 10 ⁶ Pa, the polyester resin may be decomposed. It is desirable to stir the reaction mixture in order to allow the depolymerization reaction and modification reaction to proceed efficiently and uniformly. However, when the stirring is performed, bubbles are caught in the polyester resin.

After completing the depolymerization reaction and the modification reaction, the pressure of the reaction system is reduced again. Here, it is preferable to stop stirring before decompression. The rate of pressure reduction is preferably in the range of 1 × 10 ⁵ to 1 × 10 ³ Pa / min. When the pressure is reduced at a rate exceeding 1 × 10 ³ Pa / min, foaming is intense and the liquid level rises, and the polyester resin may be distilled out of the system. If it is less than 1 × 10 ⁵ Pa, defoaming may not be sufficient. The final ultimate pressure reduction can be set by the amount of foam present and the melt viscosity of the polyester resin, but is preferably in the range of 5 × 10 ¹ Pa or more and less than 1 × 10 ⁴ Pa from the viewpoint of defoaming efficiency. . When the degree of vacuum is increased to less than 5 × 10 ¹ Pa, the polycondensation reaction further proceeds and a gel-like product may be partially generated. When it is 1 × 10 ⁴ Pa or more, it may not be sufficiently degassed.

  Examples of the polyvalent carboxylic acid component of the polyester resin used in the present invention include aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, orthophthalic acid, naphthalenedicarboxylic acid, succinic acid, glutaric acid, adipic acid, azelaic acid, sebacic acid, Aliphatic dicarboxylic acids such as dodecanedioic acid and dimer acids, (anhydrous) maleic acid, fumaric acid, unsaturated dicarboxylic acids such as terpene-maleic acid adducts, 1,4-cyclohexanedicarboxylic acid, tetrahydrophthalic acid, hexahydroisophthalate Acid, alicyclic dicarboxylic acid such as 1,2-cyclohexene dicarboxylic acid, trihydric or higher carboxylic acid such as (anhydrous) trimellitic acid, (anhydrous) pyromellitic acid, methylcyclohexenic carboxylic acid, etc. 1 type or 2 types or more can be selected and used.

  Examples of the polyhydric alcohol component used in the polyester resin used in the present invention include ethylene glycol, propylene glycol (1,2-propanediol), 1,3-propanediol, 1,4-butanediol, and 1,2-butane. Diol, 1,3-butanediol, 2-methyl-1,3-propanediol, neopentyl glycol, 1,5-pentanediol, 1,6-hexanediol, 3-methyl-1,5-pentanediol, 2 -Ethyl-2-butyl-1,3-propanediol, 2,4-diethyl-1,5-pentanediol, 1-methyl-1,8-octanediol, 3-methyl-1,6-hexanediol, 4 -Methyl-1,7-heptanediol, 4-methyl-1,8-octanediol, 4-propyl-1,8-octane All, aliphatic glycols such as 1,9-nonanediol, diethylene glycol, triethylene glycol, polyethylene glycol, polypropylene glycol, ether glycols such as polytetramethylene glycol, 1,4-cyclohexanedimethanol, 1,3-cyclohexanedi Examples include alicyclic polyalcohols such as methanol, 1,2-cyclohexanedimethanol, tricyclodecane glycols, and hydrogenated bisphenols, and trihydric or higher polyalcohols such as trimethylolpropane, trimethylolethane, and pentaerythritol. One or more of these can be selected and used.

  After polycondensation of the polyester resin, a depolymerization reaction or a modification reaction is performed. In the depolymerization reaction, it is preferable to add a polyvalent carboxylic acid and / or a polyhydric alcohol to the molten polyester resin for reaction. As the auxiliary raw material component used here, for example, a polyvalent carboxylic acid or a polyhydric alcohol capable of constituting the above-described polyester resin can be used. At this time, for reasons such as easy reaction control and increased reactive end groups, terephthalic acid, isophthalic acid, trimellitic acid, pyromellitic acid, ethylene glycol, neopentyl glycol, trimethylolpropane, pentaerythritol, Glycerin and the like are preferably used. The reaction is preferably carried out in the range of 150 to 290 ° C. over a period of 1 to 300 minutes.

  Examples of the modification reaction include a ring-opening addition reaction of a lactone monomer to a polyester resin. This makes it possible to produce a block type polyester resin in which polycaprolactone is bonded to the end of the polyester resin. As a monomer to be used, ε-caprolactone is preferable. The reaction is preferably carried out in the range of 150 to 290 ° C. over a period of 1 to 300 minutes.

  Moreover, as a modification reaction, the ring-opening addition reaction of the lactide monomer of a polyester resin can be illustrated. This makes it possible to produce a block type polyester resin in which polylactic acid is bonded to the end of the polyester resin. As the monomer to be used, any of L-lactide, DL-lactide, and D-lactide can be used. The reaction is preferably carried out in the range of 150 to 290 ° C. over a period of 1 to 300 minutes.

  Examples of the modification reaction include addition reaction of a carboxylic acid anhydride to a polyester resin. By this method, a carboxyl group can be efficiently introduced into the end of the polyester molecule. As auxiliary materials to be used, phthalic anhydride, trimellitic anhydride, pyromellitic anhydride, 1,2,3,4-butanetetracarboxylic dianhydride, 1,2,3,4-pentanetetracarboxylic dianhydride 3,4,3 ′, 4′-benzophenonetetracarboxylic dianhydride, cyclopentanetetracarboxylic dianhydride, 2,3,6,7-naphthalenetetracarboxylic dianhydride, 1,2,5 , 6-Naphthalenetetracarboxylic dianhydride, ethylene glycol bistrimellitic dianhydride, 2,3,2 ′, 3′-diphenyltetracarboxylic dianhydride, thiophene-2,3,4,5-tetracarboxylic Acid dianhydride, ethylenetetracarboxylic dianhydride, 4,4′-oxydiphthalic dianhydride, 5- (2,5-dioxotetrahydro-3-furanyl) -3-methyl 3-cyclohexene-1,2-dicarboxylic anhydride, etc. There is, one out of these, or to select two or more can be used. Among these, phthalic anhydride, trimellitic anhydride, and ethylene glycol bistrimellitic dianhydride are preferable from the viewpoint of controlling the reaction and efficiently introducing a carboxyl group into the molecule. The reaction is preferably carried out in the range of 150 to 290 ° C. over a period of 1 to 300 minutes.

  In general, it is known that a polyester resin copolymerized with an aliphatic dicarboxylic acid is inferior in hydrolyzability compared to a polyester resin obtained by polymerizing only an aromatic dicarboxylic acid. This is conspicuous in modified polyester resins subjected to addition reaction of carboxylic acid anhydride and polyester resins subjected to depolymerization reaction with polyvalent carboxylic acid. This is because these polyester resins have a high acid value of 50 to 5000 eq / t. Such a tendency is stronger when the acid value is higher. Therefore, in the present invention, the effect is more preferably 100 to 5000 eq / t because the effect is remarkable. At this time, it is desirable to adjust (specific gravity of the polyester resin / specific gravity after heat-treating the polyester resin at 220 ° C. for 10 minutes) in a range of 0.80 to 1.00. Note that the specific gravity of the polyester resin here means that 10 samples are randomly sampled from the polyester resin pellets or other forms, and the polyester is cut into 3 mm × 3 mm × 3 mm cubes (in the case of pellets) In a calcium chloride aqueous solution adjusted to 30 ° C. (when the specific gravity is lighter than 1, the polyester resin is not dissolved and a combination of a solvent having a specific gravity lower than 1 and another solvent, the same shall apply hereinafter) This is a value obtained by adjusting the concentration of calcium chloride so that the polyester resin remains in the middle from the liquid surface to the bottom surface of the aqueous solution, and then measuring the specific gravity of the aqueous calcium chloride solution with a hydrometer. The specific gravity after heat-treating the polyester resin at 220 ° C. for 10 minutes means that the sample measured above is heat-treated in a thermostatic oven or dryer at a temperature of 220 ° C. without removing the bubbles, and the foam is removed. It is a value obtained by measuring the specific gravity in the same manner again. A value of 1 (specific gravity of polyester resin / specific gravity after heat treatment of polyester resin at 220 ° C. for 10 minutes) means that the resin does not bite bubbles at all. If it is less than 0.80, the hydrolyzability is lowered, which may affect the storage stability and curability of the resin.

  The glass transition temperature of the polyester resin after the modification or depolymerization reaction is preferably -100 to 85 ° C. A preferred lower limit is −50 ° C., more preferably −20 ° C. On the other hand, the upper limit is preferably 75 ° C. or lower, and more preferably 70 ° C. or lower. In the case of a polyester resin having a glass transition temperature of less than −100 ° C., the melt viscosity of the polyester resin tends to be low. Therefore, the defoaming efficiency may be low when the method of the present invention is used. When it exceeds 85 ° C., the melt viscosity of the resin tends to be high, so that defoaming may be difficult. The glass transition temperature can be measured with a differential scanning calorimeter (DSC).

  The reduced viscosity of the polyester resin after the modification or depolymerization reaction is preferably 0.02 to 1.80 dl / g. A preferred lower limit is 0.05 dl / g, more preferably 0.10 dl / g. A preferred upper limit is 1.0 dl / g, more preferably 0.60 dl / g. When the reduced viscosity is less than 0.02 dl / g, the melt viscosity of the polyester resin tends to be low, and thus the defoaming efficiency may be low when the method of the present invention is used. When it exceeds 1.80 dl / g, since the melt viscosity of the resin tends to be high, defoaming may be difficult.

  Hereinafter, the present invention will be described in more detail with reference to examples. In addition, the physical-property value measurement of the polyester resin was performed with the following method.

Composition of polyester resin The polyester resin was determined from its integral ratio by performing ¹ H-NMR analysis using a nuclear magnetic resonance analyzer (NMR) Gemini-200 manufactured by Varian in a deuterated chloroform solvent.

Glass transition temperature and melting point of polyester resin 5 mg of a polyester resin sample was put in an aluminum sample pan, sealed, and heated to 200 ° C. using a differential scanning calorimeter (DSC) DSC-220 manufactured by Seiko Instruments Inc. Measured at a rate of 20 ° C / min, the glass transition temperature is determined by the temperature at the intersection of the baseline extension below the glass transition temperature and the tangent that indicates the maximum slope from the peak rise to the peak apex. It was. The melting point was determined from the peak of the endothermic peak.

Reduced viscosity of polyester resin 0.10 g of polyester resin was dissolved in 25 cm ³ of a mixed solvent of phenol / tetrachloroethane (mass ratio 6/4), and measured at 30 ° C. using an Ubbelohde viscosity tube.

The moisture content of the polyester resin was measured with a CA-07 type trace moisture measuring device (coulometric titration automatic moisture measuring device) equipped with a moisture vaporizer manufactured by Mitsubishi Chemical Corporation. Aquamicron AX and CXU (Mitsubishi Chemical Corporation) were used as measurement solutions.

Acid Value of Polyester Resin 0.2 g of polyester was dissolved in 20 cm ³ of chloroform and titrated with a 0.1N potassium hydroxide ethanol solution to obtain an equivalent (eq / t) per 10 ⁶ g of resin. Phenolphthalein was used as the indicator.

Specific gravity of polyester resin Ten samples of polyester extracted at random were cut into cubes of 3 mm × 3 mm × 3 mm and measured in an aqueous calcium chloride solution adjusted to 30 ° C. After adjusting the concentration of calcium chloride so that the polyester resin stays in the middle from the liquid level to the bottom of the aqueous solution, the specific gravity of the aqueous calcium chloride solution was measured with a hydrometer to obtain the specific gravity of the polyester resin.
Further, the polyester was heat-treated for 10 minutes in a hot air dryer at 220 ° C. without fusing, and then allowed to cool to room temperature, and the specific gravity was measured again by the same method. By calculating (specific gravity of the polyester resin / specific gravity after heat treatment of the polyester resin at 220 ° C. for 10 minutes), it was used as a measure of the foam content.

[Example 1]
In a 3 L stainless steel polymerization vessel equipped with a stirrer and a condenser for distillation, 166 parts by mass of terephthalic acid, 66.4 parts by mass of isophthalic acid, 121.2 parts by mass of sebacic acid, 136.4 parts by mass of ethylene glycol, neo 187.2 parts by mass of pentyl glycol was charged, the pressure was increased to 2.0 kgf / cm ³ , the temperature was raised to 235 ° C. over 3 hours, and water was distilled off to conduct an esterification reaction. After completion of the esterification reaction, 0.14 parts by mass of titanium tetrabutoxide was added and stirred for 10 minutes. Then, initial vacuum polymerization was carried out to 650 Pa over 30 minutes and the temperature was raised to 255 ° C. Polymerization was performed. After completion of the polymerization, the pressure was adjusted to 1.0 × 10 ⁵ Pa with nitrogen and the mixture was cooled to 200 ° C. Next, with stirring, 7.7 parts by mass of trimellitic anhydride was added and stirred at 200 ° C. for 30 minutes. When a very small amount of sampling was performed, the resin bites a large amount of bubbles.
Subsequently, the stirring was stopped, the pressure was reduced to 1.3 × 10 ³ Pa at a speed of 6.7 × 10 ³ Pa / min, and deaeration was performed by maintaining the pressure for 10 minutes. The pressure was changed to 1.0 × 10 ⁵ Pa with nitrogen, and the pressure was changed to discharge the modified polyester resin from the bottom of the polymerization kettle. At that time, it was cooled and solidified with a large amount of water, and the surface adhering water was removed by blowing air.
The obtained modified polyester resin had a glass transition temperature of 8 ° C. and a reduced viscosity of 0.55 dl / g. The resin composition was terephthalic acid / isophthalic acid / sebacic acid / trimellitic acid // ethylene glycol / neopentyl glycol = 50/19/29/2 // 41/59 (molar ratio). The acid value was 154 eq / t, and the resin moisture content was 0.11 wt%. Visual inspection did not show any bubble entrapment. (Specific gravity of polyester resin / specific gravity after heat treatment of polyester resin at 220 ° C. for 10 minutes) was 0.99.

[Example 2]
Into a 3L stainless steel polymerization kettle equipped with a stirrer and a condenser for distilling, 149 parts by mass of terephthalic acid, 183 parts by mass of isophthalic acid, 136.4 parts by mass of ethylene glycol, 187.2 parts by mass of neopentyl glycol, The pressure was increased to 2.0 kgf / cm ^3, the temperature was raised to 235 ° C. over 3 hours, and water was distilled off to conduct an esterification reaction. After completion of the esterification reaction, 0.14 parts by mass of titanium tetrabutoxide was added and stirred for 10 minutes. Then, initial vacuum polymerization was carried out to 650 Pa over 30 minutes and the temperature was raised to 255 ° C. Polymerization was performed. After completion of the polymerization, the pressure was adjusted to 1.0 × 10 ⁵ Pa with nitrogen and the mixture was cooled to 200 ° C. Next, with stirring, 228 parts by mass of ε-caprolactone was added and stirred at 200 ° C. for 60 minutes. When a very small amount of sampling was performed, the resin bites a large amount of bubbles.
Subsequently, the stirring was stopped, the pressure was reduced to 8.5 × 10 ² Pa at a speed of 8.3 × 10 ³ Pa / min, and deaeration was performed by maintaining the pressure for 10 minutes. The pressure was adjusted to 1.0 × 10 ⁵ Pa with nitrogen, and further the pressure was applied, and the modified polyester resin was discharged from the bottom of the polymerization kettle. At that time, it was cooled and solidified with a large amount of water, and the surface adhering water was removed by blowing air.
The obtained modified polyester resin had a glass transition temperature of −12 ° C. and a reduced viscosity of 0.98 dl / g. The resin composition was terephthalic acid / isophthalic acid // ethylene glycol / neopentyl glycol // caprolactone = 45/55 // 41/59 // 100 (molar ratio). The acid value was 21 eq / t, and the resin moisture content was 0.15 wt%. Visual inspection did not show any bubble entrapment. (Specific gravity of polyester resin / specific gravity after heat treatment of polyester resin at 220 ° C. for 10 minutes) was 0.98.

[Example 3]
In a 3 L stainless steel polymerization vessel equipped with a stirrer and a condenser for distillation, 133 parts by mass of terephthalic acid, 133 parts by mass of isophthalic acid, 81 parts of sebacic acid, 136.4 parts by mass of ethylene glycol, 1,9-nonanediol 288.0 parts by mass were charged, the pressure was increased to 2.0 kgf / cm ³ , the temperature was raised to 235 ° C. over 3 hours, and water was distilled off to conduct an esterification reaction. After completion of the esterification reaction, 0.14 parts by mass of titanium tetrabutoxide was added and stirred for 10 minutes. Then, initial vacuum polymerization was carried out to 650 Pa over 30 minutes and the temperature was raised to 255 ° C. Polymerization was performed. After completion of the polymerization, the pressure was adjusted to 1.0 × 10 ⁵ Pa with nitrogen and the mixture was cooled to 200 ° C. Next, 287 parts by mass of L-lactide and 0.08 parts by mass of tin octylate were added while stirring, and the mixture was stirred at 200 ° C. for 60 minutes. When a very small amount of sampling was performed, the resin bites a large amount of bubbles.
Subsequently, the stirring was stopped, the pressure was reduced to 8.5 × 10 ² Pa at a speed of 8.3 × 10 ³ Pa / min, and deaeration was performed by maintaining the pressure for 10 minutes. The pressure was adjusted to 1.0 × 10 ⁵ Pa with nitrogen, and further the pressure was applied, and the modified polyester resin was discharged from the bottom of the polymerization kettle. At that time, it was cooled and solidified with a large amount of water, and the surface adhering water was removed by blowing air.
The obtained modified polyester resin had a glass transition temperature of −18 ° C., a melting point of 146 ° C., and a reduced viscosity of 0.65 dl / g. The resin composition was terephthalic acid / isophthalic acid / sebacic acid // ethylene glycol / 1,9-nonanediol // lactide = 40/40/20 // 13/87 // 97 (molar ratio). The acid value was 31 eq / t, and the resin moisture content was 0.15 wt%. Visual inspection did not show any bubble entrapment. The specific gravity of the polyester resin / specific gravity after heat-treating the polyester resin at 220 ° C. for 10 minutes was 0.86.

[Comparative Example 1]
In a 3 L stainless steel polymerization vessel equipped with a stirrer and a condenser for distillation, 166 parts by mass of terephthalic acid, 66.4 parts by mass of isophthalic acid, 121.2 parts by mass of sebacic acid, 136.4 parts by mass of ethylene glycol, neo 187.2 parts by mass of pentyl glycol was charged, the pressure was increased to 2.0 kgf / cm ³ , the temperature was raised to 235 ° C. over 3 hours, and water was distilled off to conduct an esterification reaction. After completion of the esterification reaction, 0.14 parts by mass of titanium tetrabutoxide was added and stirred for 10 minutes. Then, initial vacuum polymerization was carried out to 650 Pa over 30 minutes and the temperature was raised to 255 ° C. Polymerization was performed. After completion of the polymerization, the pressure was adjusted to 1.0 × 10 ⁵ Pa with nitrogen and the mixture was cooled to 200 ° C. Next, with stirring, 7.7 parts by mass of trimellitic anhydride was added and stirred at 200 ° C. for 30 minutes. Subsequently, the modified polyester resin was discharged from the bottom of the polymerization kettle under pressure with nitrogen. At that time, it was cooled and solidified with a large amount of water, and the surface adhering water was removed by blowing air.
The obtained modified polyester resin had a glass transition temperature of 8 ° C. and a reduced viscosity of 0.54 dl / g. The resin composition was terephthalic acid / isophthalic acid / sebacic acid / trimellitic acid // ethylene glycol / neopentyl glycol = 50/19/29/2 // 41/59 (molar ratio). The acid value was 155 eq / t, and the resin moisture content was 1.2 wt%. Visual inspection confirmed a large amount of air bubbles. (Specific gravity of polyester resin / specific gravity after heat treatment of polyester resin at 220 ° C. for 10 minutes) was 0.78.

[Comparative Example 2]
Into a 3L stainless steel polymerization kettle equipped with a stirrer and a condenser for distilling, 149 parts by mass of terephthalic acid, 183 parts by mass of isophthalic acid, 136.4 parts by mass of ethylene glycol, 187.2 parts by mass of neopentyl glycol, The pressure was increased to 2.0 kgf / cm ^3, the temperature was raised to 235 ° C. over 3 hours, and water was distilled off to conduct an esterification reaction. After completion of the esterification reaction, 0.14 parts by mass of titanium tetrabutoxide was added and stirred for 10 minutes. Then, initial vacuum polymerization was carried out to 650 Pa over 30 minutes and the temperature was raised to 255 ° C. Polymerization was performed. After completion of the polymerization, the pressure was adjusted to 1.0 × 10 ⁵ Pa with nitrogen and the mixture was cooled to 200 ° C. Next, with stirring, 228 parts by mass of ε-caprolactone was added and stirred at 200 ° C. for 60 minutes. Subsequently, the modified polyester resin was discharged from the bottom of the polymerization kettle under pressure with nitrogen. At that time, it was cooled and solidified with a large amount of water, and the surface adhering water was removed by blowing air.
The obtained modified polyester resin had a glass transition temperature of −12 ° C. and a reduced viscosity of 0.99 dl / g. The resin composition was terephthalic acid / isophthalic acid // ethylene glycol / neopentyl glycol // caprolactone = 45/55 // 41/59 // 100 (molar ratio). The acid value was 20 eq / t, and the resin moisture content was 0.95 wt%. Visual inspection confirmed a large amount of air bubbles. (Specific gravity of polyester resin / specific gravity after heat treatment of polyester resin at 220 ° C. for 10 minutes) was 0.76.

  Various evaluations were performed below using the polyester resin obtained as described above. The evaluation methods are summarized below, and the evaluation results are summarized in Table 1.

[Storage stability of polyester resin]
The polyester resin cut into a size of 3 mm × 3 mm × 3 mm was stored at 30 ° C. × 85% RH for 30 days. The reduced viscosity after that was measured and it was judged how much hydrolysis progressed.

[Curability of polyester resin]
Cyclohexanone 78, 1.2 parts by mass of benzophenone tetracarboxylic acid, 3.6 parts by mass of Epototo YD8125 (manufactured by Tohto Kasei Co., Ltd.), 0.01 parts by mass of Irganox 1010 from Ciba Specialty Chemicals as a stabilizer In addition to 6 parts by mass and 100 parts by mass of Solvesso, mixing was performed by stirring at 70 ° C. for 1 hour. After cooling to room temperature, 0.8 parts by mass of triphenylphosphine was added to the mixed varnish, and the mixture was further stirred, and applied to the corona-treated surface of the biaxially stretched polyethylene terephthalate film so that the dry film thickness was 30 μm. The curing reaction was carried out for 3 minutes. After 3 minutes, the film was taken out, cooled to room temperature, cut into a size of 3 cm × 4 cm, and the mass was measured. Subsequently, it was immersed in methyl ethyl ketone / toluene = 1/1 (mass ratio) for 1 hour, air-dried at room temperature, and the mass was measured again. The gel fraction was calculated based on the mass of a biaxially stretched polyethylene terephthalate film of the same area that had been measured in advance. The larger the numerical value of the gel fraction, the better the curability.

  According to the present invention, it is possible to obtain a modified or depolymerized polyester resin which is inexpensive and can be industrially implemented and has excellent quality. Since this polyester resin has excellent hydrolysis resistance, it can be used even after long-term storage, and the adhesive using the polyester resin is less susceptible to moisture content and exhibits stable adhesiveness. I can do it.

Claims (9)

  In the polyester resin production method in which the polyester resin polycondensation reaction under reduced pressure is completed and the degree of pressure reduction of the reaction system is shifted to the normal pressure side to perform the depolymerization reaction or modification reaction, the pressure is reduced again after the depolymerization reaction or modification reaction. A method for producing a polyester resin.   The method for producing a polyester resin according to claim 1, wherein the depolymerization reaction is a reaction of a polyvalent carboxylic acid and / or a polyhydric alcohol with the polyester resin.   The method for producing a polyester resin according to claim 1, wherein the modification reaction is a ring-opening addition reaction of a caprolactone monomer with the polyester resin.   The method for producing a polyester resin according to claim 1, wherein the modification reaction is an addition reaction of the carboxylic acid anhydride compound with the polyester resin.   The method for producing a polyester resin according to claim 1, wherein the modification reaction is an addition reaction of lactide with the polyester resin. The method for producing a polyester resin according to claim 1, wherein the depolymerization reaction or the modification reaction is performed at 1 × 10 ⁴ to 1 × 10 ⁶ Pa. The method for producing a polyester resin according to any one of claims 1 to 6, wherein the pressure when the pressure is reduced again after the depolymerization reaction or the modification reaction is 5 x 10 ¹ Pa or more and less than 1 x 10 ⁴ Pa.   The method for producing a polyester resin according to any one of claims 1 to 7, wherein the stirring is stopped before the pressure is reduced again after the depolymerization reaction or the modification reaction.   A polyester resin having an acid value of 50 to 5000 eq / t and satisfying a condition of 0.80 ≦ (specific gravity of polyester resin / specific gravity after heat treatment of polyester resin at 220 ° C. for 10 minutes) ≦ 1.00.