JP2008239771A - Method for continuously producing polyethylene terephthalate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for continuously producing a polyethylene terephthalate, further rapidly progressing an ester interchange reaction and also capable of inhibiting the formation of residual foreign materials caused by the residual ester interchange catalyst and thermal decomposition in producing the polyethylene terephthalate by using dimethyl terephthalate and ethylene glycol as main starting materials and a titanium compound which is not a heavy metal, as the ester interchange catalyst. <P>SOLUTION: This method for continuously producing the polyethylene terephthalate by passing through at least 2 stages of the ester-interchanging reaction and a polycondensation reaction in the presence of the titanium catalyst is provided by having the dimethyl terephthalate, ethylene glycol and an ethylene terephthalate oligomer having exchange reaction rate of ≥70% at the starting of the ester interchange reaction, having >0 and ≤50 ppm used amount of the titanium catalyst as the titanium metal atom based on the weight of the obtained polyethylene terephthalate, adding ≤20 mmol% alkali metal compound based on the dimethyl terephthalate in an optional stage until the completion of the ester-interchanging reaction and further performing the polycondensation reaction of the ethylene terephthalate oligomer obtained in the ester-interchanging reaction. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for producing polyethylene terephthalate. More specifically, when polyethylene terephthalate is produced in a continuous process using dimethyl terephthalate and ethylene glycol as the main starting materials in the presence of a titanium catalyst, the transesterification reactivity is improved and the heavy weight resulting from the residual catalyst is increased. The present invention relates to a continuous production method of polyethylene terephthalate capable of suppressing thermal decomposition in a condensation stage or a melt molding stage.

  Polyester is widely used in fibers, films and other molded articles because of its excellent mechanical, physical and chemical performance. In particular, polyethylene terephthalate is used in a very wide range of applications because of its characteristics and price. Traditionally, two methods are well known as industrial production methods for polyethylene terephthalate. One is a transesterification method using dimethyl terephthalate and ethylene glycol (hereinafter referred to as DMT method), and the other is a direct esterification method using terephthalic acid and ethylene glycol (hereinafter referred to as PTA method).

  In the DMT method, dimethyl terephthalate and ethylene glycol are charged into a reaction vessel, an appropriate transesterification catalyst is added, and methanol is distilled out of the reaction vessel to facilitate the reaction. Furthermore, the target polyethylene terephthalate can be obtained by subjecting the resulting oligomer of dimethyl terephthalate and ethylene glycol to a polycondensation reaction at high temperature and vacuum. As transesterification catalysts, calcium, magnesium, manganese, zinc, cadmium, cobalt, and the like are known (see, for example, Non-Patent Document 1).

  On the other hand, the PTA method does not require a catalyst in the first stage esterification reaction due to the autocatalytic action of terephthalic acid, and the esterification reaction proceeds by heating terephthalic acid and ethylene glycol and distilling off the generated water. . And the target polyethylene terephthalate is obtained by carrying out the polycondensation reaction of the obtained terephthalic acid and the oligomer of ethylene glycol by high temperature and vacuum (for example, refer nonpatent literature 1).

  Comparing these two methods, the PTA method can carry out the first stage reaction without catalyst and water is generated, whereas the DMT method requires a transesterification catalyst and generates methanol. . In the DMT method, the transesterification catalyst remaining in the obtained polymer is likely to cause thermal degradation during polycondensation reaction and molding, and alkaline earth metals such as calcium and magnesium are likely to be converted into foreign matter in the polymer. There are problems such as. Furthermore, recently, there is a worldwide movement to avoid the use of heavy metals as a catalyst for polyester, and although the use is not prohibited, the use of heavy metals such as manganese, zinc, cadmium and cobalt is not preferable. Considering these situations, it is expected that a titanium compound which is not a heavy metal and is in a polyester and which is less likely to become a foreign substance in the obtained polyethylene terephthalate is used as a transesterification catalyst.

  However, the catalytically active region of the titanium compound is relatively high compared to other metals, and requires a high temperature of at least 180 ° C. or more, preferably 200 ° C. or more in order to sufficiently proceed the reaction. Conventionally, the first stage transesterification by the DMT method generally starts at about 150 ° C., which is close to the melting point of dimethyl terephthalate, and increases the reaction rate and the reaction temperature. Therefore, since this general reaction condition is lower than the catalytically active region of the titanium compound, the reaction does not proceed sufficiently or a very long time is required for the reaction.

  In order to solve this problem, a method of increasing the amount of titanium catalyst added can be considered. However, although the reaction rate is improved, it is not preferable that the titanium catalyst is excessively present because the polymer is colored yellow or is likely to cause thermal deterioration during the polycondensation reaction or molding as described above.

In addition, it is described that a titanium compound is used as a transesterification catalyst, and that the reaction by the catalytic action of a titanium compound component is further accelerated when the transesterification reaction is performed under a pressure of 0.05 to 0.20 MPa. (For example, refer to Patent Document 1). Certainly, the initial speed of the reaction is accelerated by pressurization, but it is not sufficient. In addition, the pressurization requires a more robust reaction kettle and special specifications to prevent pressure leaks in mechanical seals. However, there is a problem that the equipment is expensive.
From the above, in the DMT method, when obtaining polyethylene terephthalate using a titanium catalyst, a method for proceeding the transesterification reaction more rapidly has been demanded.

Yuki Kazuo, Saturated Polyester Resin Handbook, Nikkan Kogyo Shimbun, 1989 JP 2004-285500 A

  The object of the present invention is to produce a polyethylene terephthalate using dimethyl terephthalate and ethylene glycol as main starting materials and a titanium compound that is not a heavy metal as a transesterification reaction catalyst. An object of the present invention is to provide a method for producing polyethylene terephthalate capable of suppressing the generation of residual foreign matters and thermal decomposition caused by a transesterification catalyst.

In view of the above prior art, the present inventors have intensively studied the DMT method, and as a result, have completed the present invention.
That is, the present invention is a method for producing polyethylene terephthalate, which includes at least two steps of a transesterification step and a polycondensation step in the presence of a titanium catalyst, and dimethyl terephthalate at the start of the transesterification step, Ethylene glycol and an ethylene terephthalate oligomer having a transesterification rate of 70% or more exist, and the amount of titanium catalyst used is an amount that is more than 0 ppm and less than 50 ppm as a titanium metal atom with respect to the weight of polyethylene terephthalate. Polyethylene terephthalate that further polycondenses the ethylene terephthalate oligomer obtained in the transesterification step by adding an alkali metal compound of 20 mmol% or less to dimethyl terephthalate at any stage until the reaction step is completed. It is an invention of a method for the continuous production over DOO, whereby the above problems can be solved.

  According to the present invention, polyethylene terephthalate using dimethyl terephthalate and ethylene glycol as main starting materials and a titanium compound that is not a heavy metal as a transesterification reaction catalyst, the transesterification reaction at the time of production thereof proceeds more rapidly. It is possible to provide a method for producing polyethylene terephthalate that can suppress the generation of residual foreign matters and thermal decomposition caused by the residual transesterification catalyst. Furthermore, since it is a continuous production method, it can be expected that production efficiency is good.

The present invention will be described in detail below.
The polyethylene terephthalate in the present invention is a polyester mainly composed of ethylene terephthalate units obtained by polycondensation reaction of dimethyl terephthalate and ethylene glycol. Here, “main” means that 70 mol% or more of all repeating units are ethylene terephthalate units. Components other than the dimethyl terephthalate component and the ethylene glycol component, for example, an aromatic dicarboxylic acid component, an aliphatic dicarboxylic acid component, an aliphatic / aromatic glycol component, or an oxycarboxylic acid component may be copolymerized. Aromatic dicarboxylic acid components include isophthalic acid components and naphthalenedicarboxylic acid components, aliphatic dicarboxylic acid components include adipic acid and sebacic acid, and glycol components include diethylene glycol, trimethylene glycol, tetramethylene glycol, and cyclohexane dicarboxylic acid. Preferred examples of the oxycarboxylic acid component include methanol, neopentyl glycol, hexanediol and the like, and paraoxybenzoic acid.

  The production method of the present invention is a continuous production method of polyethylene terephthalate that undergoes at least two steps of a transesterification step and a polycondensation step. The main reaction starting materials in the transesterification step are dimethyl terephthalate and ethylene glycol. And the transesterification process used as the 1st step needs to be implemented in presence of a titanium catalyst. When starting the transesterification reaction step, the reaction is started in the presence of an ethylene terephthalate oligomer having a transesterification reaction rate of 50% or more in the reaction tank in advance, and the resulting ethylene terephthalate oligomer is further polycondensed. It is necessary.

  The ethylene terephthalate oligomer previously present in the transesterification reaction tank needs to have a transesterification rate of 70% or more. When the transesterification reaction is continuously carried out at a transesterification rate of less than 70%, in other words, an ethylene terephthalate oligomer having a transesterification rate of less than 70% is sent to the next polycondensation reaction tank. When an ethylene terephthalate oligomer having a low transesterification reaction rate is used, the polycondensation reactivity is significantly lowered. If the transesterification rate is 70% or more, there is no problem, but it is preferably 80% or more, more preferably 90% or more.

  The above-mentioned “transesterification reaction rate” refers to the reaction rate when dimethyl terephthalate and ethylene glycol are transesterified. In the transesterification reaction, for example, when 1 mol of dimethyl terephthalate is subjected to the transesterification reaction, theoretically 2 mol of methanol is generated. The “transesterification rate” is determined by the amount of methanol generated, that is, 1 mol of dimethyl terephthalate is subjected to the transesterification reaction, and 1 mol of methanol is generated as “transesterification rate is 50%”. means. The ethylene terephthalate oligomer in this state is not necessarily a single component, and is a mixture of unreacted dimethyl terephthalate and a low polymerization degree ethylene terephthalate oligomer or a mixture of ethylene terephthalate oligomers having different transesterification rates. May be. When unreacted dimethyl terephthalate is mixed, it is considered that the dimethyl terephthalate has a transesterification rate of 0%, and the weight-average transesterification rate is 70% or more. Moreover, when mixing the ethylene terephthalate oligomer of multiple types of transesterification rate, the weight average transesterification rate should just be 70% or more.

  Addition of dimethyl terephthalate and ethylene glycol into the ethylene terephthalate oligomer can be carried out by any method, and the required amount can be added at once or several times, or in the ethylene terephthalate oligomer. You may supply continuously. However, since dimethyl terephthalate has high sublimation properties and is likely to precipitate in a methanol distillation pipe or the like at high temperatures, it is more preferable to supply dimethyl terephthalate in several degrees or continuously to prevent sublimation precipitation. Also, when adding dimethyl terephthalate to the ethylene terephthalate oligomer, do not drop it from the top of the ethylene terephthalate oligomer in a solid or melt state, but add it in a melt state from a pipe immersed in the ethylene terephthalate oligomer. Is preferred.

  In addition, the molar ratio of dimethyl terephthalate and ethylene glycol added to the ethylene terephthalate oligomer may be any molar ratio as long as the transesterification reaction proceeds, but the transesterification reaction rate should be increased more rapidly. The molar ratio of ethylene glycol / dimethyl terephthalate is preferably 1.4 or more.

  As described above, in the DMT method, the transesterification catalyst remaining in the polymer tends to cause thermal deterioration during polycondensation reaction or molding, and in particular, alkali such as calcium and magnesium generally used as a transesterification catalyst. Earth metals need to be added in a large amount because of their low catalytic activity per unit weight, and they tend to cause thermal degradation and are liable to become foreign substances in the polymer. In addition, heavy metals such as manganese, zinc, cadmium, and cobalt are also used as transesterification catalysts. Recently, there is a worldwide movement to avoid the use of heavy metals as a catalyst for polyesters. Because of these movements, the use of these heavy metals is not desirable, so use a titanium compound as a transesterification catalyst that is free of heavy metals, is unlikely to become a foreign substance in the polymer, and is unlikely to cause thermal degradation of the polymer if the amount added is small. As a result of intensive studies, the present invention has been found.

  The titanium catalyst used in the production method of the present invention includes (1) a titanium alkoxide compound represented by the following general formula (I), (2) a titanium alkoxide compound represented by the following general formula (I) and the following general formula: A product obtained by reacting the aromatic polyvalent carboxylic acid or acid anhydride represented by (II), or (3) a titanium alkoxide compound represented by the following general formula (I) and the following general formula (III) It is preferably at least one compound selected from the group consisting of products obtained by reacting the carboxylic acid represented. Accordingly, any one of these compounds or a mixture of two or more of them is preferable. The addition amount of these titanium catalysts needs to be more than 0 ppm and 50 ppm or less as titanium metal atoms with respect to the finally obtained weight of polyethylene terephthalate. Furthermore, it is preferable that it is 5-30 ppm. If the amount exceeds 50 ppm, the transesterification rate will be improved, but the polyester will be colored yellow, or heat degradation will easily occur during the polycondensation reaction or molding.

により表されるチタニウム化合物から選ばれることが好ましい。置換基Ｒ_１〜Ｒ_４は炭素数１〜１０個のアルキル基又は炭素数６〜１２個のアリール基であることが好ましく、炭素数１〜６個のアルキル基又は炭素数６〜１２個のアリール基であることがより好ましい。 In the production method of the present invention, the titanium alkoxide compound used for the titanium compound components (1), (2) and (3) constituting the titanium catalyst is represented by the following general formula (I):

It is preferable to be selected from titanium compounds represented by: The substituents R _{1 to} R ₄ are preferably an alkyl group having 1 to 10 carbon atoms or an aryl group having 6 to 12 carbon atoms, and an alkyl group having 1 to 6 carbon atoms or an alkyl group having 6 to 12 carbon atoms. More preferred is an aryl group.

  Examples of such titanium alkoxide compounds include tetraisopropoxy titanium, tetra-n-propoxy titanium, tetra-n-butoxy titanium, tetraethoxy titanium, tetraphenoxy titanium, hexabutyl dititanate, hexapropyl dititanate, hexaethyl dititanate. , Hexaphenyl dititanate, octabutyl trititanate, octapropyl trititanate, octaethyl trititanate, octaethyl trititanate or octaphenyl trititanate are preferably used.

の化合物から選ばれることが好ましい。このような芳香族多価カルボン酸又はその無水物としては、フタル酸、トリメリット酸、ヘミメリット酸、ピロメリット酸又はこれらの酸無水物から選ばれることがより好ましい。 In the method of the present invention, the aromatic polyvalent carboxylic acid used for the titanium compound component (2) constituting the catalyst is represented by the following general formula (II):

It is preferable to be selected from these compounds. Such an aromatic polyvalent carboxylic acid or anhydride thereof is more preferably selected from phthalic acid, trimellitic acid, hemimellitic acid, pyromellitic acid, or acid anhydrides thereof.

の化合物から選ばれることが好ましい。このカルボン酸としては、酢酸、プロピオン酸、酪酸、安息香酸など用いられるが、なかでも酢酸がもっとも好ましく用いられる。 In the method of the present invention, the carboxylic acid used for the titanium compound component (3) constituting the catalyst is represented by the following general formula (III):

It is preferable to be selected from these compounds. As the carboxylic acid, acetic acid, propionic acid, butyric acid, benzoic acid and the like are used, and among them, acetic acid is most preferably used.

  In order to react the titanium alkoxide compound with an aromatic polyvalent carboxylic acid (or an anhydride thereof), the aromatic polyvalent carboxylic acid or an anhydride thereof is mixed with a solvent, and a part or all of the mixture is mixed in the solvent. The titanium alkoxide compound is dropped into this mixed solution and heated at a temperature of 0 ° C. to 200 ° C. for 30 minutes or longer, preferably at a temperature of 30 to 150 ° C. for 40 to 90 minutes. The reaction pressure at this time is not particularly limited, and normal pressure is sufficient. The solvent can be appropriately selected from those capable of dissolving a part or all of the aromatic polyvalent carboxylic acid or its anhydride, but preferably ethanol, ethylene glycol, trimethylene glycol, tetra It is selected from methylene glycol, benzene, xylene and the like.

  There is no limitation on the reaction molar ratio between the titanium alkoxide compound and the aromatic polyvalent carboxylic acid or its anhydride. However, if the proportion of the titanium alkoxide compound is too high, the hue of the resulting polyester may be deteriorated or the softening point may be lowered. Conversely, if the proportion of the titanium alkoxide compound is too low, the polycondensation reaction is difficult to proceed. May be. For this reason, it is preferable to control the reaction molar ratio group of a titanium alkoxide compound and aromatic polyhydric carboxylic acid or its anhydride within the range of 2/1-2/5.

  In the titanium catalyst used in the present invention, a phosphorus compound can be added as a stabilizer in addition to the titanium compound. In this case, the mixing ratio of the titanium compound component and the phosphorus compound component is such that the ratio mP / mTi of the titanium compound component molar amount (mTi) to the phosphorus compound component molar amount (mP) of the phosphorus compound component is 0.00. It is preferably 5 or more and 15 or less, and more preferably 1.0 or more and 10 or less. When the ratio of phosphorus is too large, the catalytic activity of the titanium compound is inhibited by the phosphorus compound. If the phosphorus ratio is too small, the effect as a stabilizer cannot be exhibited.

  As this phosphorus compound, any compound can be used. Specific examples thereof include monomethyl esters, monoethyl esters, monopropyl esters, monobutyl esters, monohexyl esters of phosphoric acid or phosphorous acid, Monophenyl esters, dimethyl esters, diethyl esters, dipropyl esters, dibutyl esters, dihexyl esters, diphenyl esters, trimethyl esters, triethyl esters, tripropyl esters, tributyl esters, trihexyl esters , Triphenyl esters; carbomethoxymethanephosphonic acid, carboethoxymethanephosphonic acid, carbopropoxymethanephosphonic acid, carboptoxymethanephosphonic acid, carbomethoxy-phosphono-phenylacetic acid, carbo Dimethyl esters, diethyl esters, dipropyl esters, dibutyl esters, dihexyl esters, diphenyl esters of toxi-phosphono-phenylacetic acid, carboprotoxy-phosphono-phenylacetic acid and carbobutoxy-phosphono-phenylacetic acid; phenyl Phosphonic acid, methylphosphonic acid, ethylphosphonic acid, propylphosphonic acid, isopropylphosphonic acid, butylphosphonic acid, tolylphosphonic acid, xylylphosphonic acid, biphenylphosphonic acid, naphthylphosphonic acid, anthrylphosphonic acid, 2-carboxyphenylphosphonic acid 3-carboxyphenylphosphonic acid, 4-carboxyphenylphosphonic acid, 2,3-dicarboxyphenylphosphonic acid, 2,4-dicarboxyphenylphosphonic acid, 2,5-dicarboxy Phenylphosphonic acid, 2,6-dicarboxyphenylphosphonic acid, 3,4-dicarboxyphenylphosphonic acid, 3,5-dicarboxyphenylphosphonic acid, 2,3,4-tricarboxyphenylphosphonic acid, 2,3,5 -Phosphonic acids such as tricarboxyphenylphosphonic acid, 2,3,6-tricarboxyphenylphosphonic acid, 2,4,5-tricarboxyphenylphosphonic acid, 2,4,6-tricarboxyphenylphosphonic acid, or these Monomethyl esters, monoethyl esters, monopropyl esters, monobutyl esters, monohexyl esters, monophenyl esters, dimethyl esters, diethyl esters, dipropyl esters, dibutyl esters, dihexyl esters, Diphenyl esters I can make it.

  Further, by adding an alkali metal compound of 20 mmol% or less to dimethyl terephthalate at an arbitrary stage until the transesterification reaction step is completed, a polyester having further excellent hue can be obtained. It is considered that the reason why a polyester having excellent hue is obtained is that the alkali metal compound suppresses the activity of the titanium catalyst for the decomposition reaction of the polyester. The larger the amount of the alkali metal compound added, the greater the effect. However, when the amount of the alkali metal compound added exceeds 20 mmol% with respect to dimethyl terephthalate, the alkali metal compound itself acts as a polyester decomposition catalyst. Therefore, it is not preferable. The addition amount of the alkali metal compound is more preferably 10 mmol% or less with respect to dimethyl terephthalate. On the other hand, even without an alkali metal compound, the object of the present invention can be achieved. Alkali metal compounds are lithium benzoate, sodium benzoate, potassium benzoate, lithium toluate, sodium toluate, potassium toluate, lithium acetate, sodium acetate, potassium acetate, lithium propionate, sodium propionate, potassium propionate. Alkali metal salt compounds of organic acids such as are preferred. Of these, potassium acetate or sodium acetate having high solubility in polyester is preferable.

  In the polyester production method of the present invention, ethylene glycol diester of terephthalic acid (or a low polymer (oligomer) thereof) may be obtained from dimethyl terephthalate and ethylene glycol in the transesterification step, and in the presence of the titanium catalyst. Polycondensation is performed in the polycondensation step. More specifically, it is preferably carried out by the following operation.

  In the transesterification reaction step, the inside of the reaction tank is at a temperature of 120 to 250 ° C., preferably there are a plurality of transesterification reaction tanks, and the conditions are such that the temperature increases as the reaction tank after the transesterification reaction proceeds. It is preferably carried out at normal pressure or under pressure. An ethylene terephthalate oligomer is retained and circulated in advance in each reaction tank, and a predetermined amount of dimethyl terephthalate, ethylene glycol, and titanium catalyst are charged into the transesterification reaction tank at the same time. The ethylene terephthalate oligomer having undergone the above is carried out while being extracted from another outlet. Among them, a method of performing the transesterification reaction under a pressure of 0.05 to 0.20 MPa is preferable. This is because when the pressure during the transesterification reaction is within this range, the promotion of the reaction by the catalytic action of the titanium compound is sufficiently advanced, the content of by-products such as diethylene glycol in the polymer is suppressed, and the resulting polyester The characteristics such as thermal stability of the resin are improved. Further, as described above, the transesterification rate of the transesterification can be calculated from the amount of methanol generated at this time.

  Further, in the production method using an ester-forming derivative of an aromatic dicarboxylic acid such as dimethyl terephthalate as a starting material as in the present invention, the amount of the titanium compound as a catalyst can be reduced. In the production method of the present invention, in the transesterification reaction, one part or all of the titanium compound is added to the transesterification tank before the transesterification reaction, and the remaining part is the reaction of the transesterification reaction. It may be added to the transesterification tank halfway and after completion of the reaction, and at least one stage before and during the polycondensation reaction. The alkali metal compound can be added as described above at any stage until the transesterification step is completed. As a result, an ethylene terephthalate oligomer can be obtained. The produced ethylene terephthalate oligomer is then sent to the polycondensation step.

  Next, in the polyester production method of the present invention, a polymerization starting material composed of ethylene glycol diester of dimethyl terephthalate (or a low polymer (oligomer thereof)) is polycondensed in the presence of the catalyst. In general, the polycondensation reaction is performed at a temperature of 230 to 320 ° C. under normal pressure or reduced pressure, preferably 0.05 Pa to 0.20 MPa, or a combination of these conditions for 15 to 300 minutes. Is preferred. In particular, the polycondensation is performed by heating under a reduced pressure to a temperature higher than the melting point of polyethylene terephthalate (usually 260 ° C. or higher). This polycondensation reaction is desirably carried out while distilling off unreacted ethylene glycol and ethylene glycol generated by polycondensation outside the reaction vessel.

  In that case, you may use as compounds other than the said titanium compound, for example, polycondensation catalysts, such as a germanium catalyst and an antimony catalyst. However, as described above, since it is desired not to use heavy metals in recent years, it is preferable to use the titanium compound or germanium compound of the present invention instead of the antimony compound generally used as a polycondensation catalyst.

  The polycondensation reaction may be performed in one tank or may be performed in a plurality of tanks. For example, when the polycondensation reaction is performed in two stages, the polycondensation reaction in the first tank has a reaction temperature of 245 to 290 ° C., preferably 260 to 280 ° C., and a pressure of 100 to 1 kPa, preferably 50 to The polycondensation reaction is carried out under the condition of 2 kPa, and the polycondensation reaction in the final second tank is a reaction temperature of 265 to 300 ° C., preferably 270 to 290 ° C., and a reaction pressure of usually 1000 to 10 Pa, preferably 500 to 30 Pa. Done under.

  When the polycondensation reaction is completed, the polyethylene terephthalate chip is discharged by discharging the melted polyethylene terephthalate from the discharge port installed at one end of the polycondensation reaction tank, cooling it with water, etc., and cutting it into a predetermined shape. Can be obtained.

  The polyethylene terephthalate of the present invention may contain an antioxidant, an ultraviolet absorber, a flame retardant, a fluorescent whitening agent, a matting agent, a color modifier, an antifoaming agent, or the like, in addition to the above phosphorus compound, if necessary. One or more of these additives may be blended.

  As for the antioxidant, the polyethylene terephthalate produced in the present invention may contain an antioxidant containing at least one hindered phenol compound. The content is preferably 1% by mass or less based on the mass of the polyester. When the content exceeds 1% by mass, there may be a disadvantage that the quality of the obtained product is deteriorated due to thermal deterioration of the antioxidant itself. The hindered phenol compound is pentaerythritol-tetra extract [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], 3,9-bis {2- [3- (3-tert- Butyl-4-hydroxy-5-methylphenyl) propionyloxy] -1,1-dimethylethyl} -2,4,8,10-tetraoxaspiro [5,5] undecane, 1,1,3-tris (2 -Methyl-4-hydroxy-5-tert-butylphenyl) butane, 1,3,5-trimethyl-2,4,6-tris (3,5-di-tert-butyl-4-hydroxybenzyl) benzene, 1 , 3,5-tris (4-tert-butyl-3-hydroxy-2,6-dimethylbenzene) isophthalic acid, triethylglycol-bis [3- (3- ert-butyl-5-methyl-4-hydroxyphenyl) propionate], 1,6-hexanediol-bis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], 2,2- Thio-diethylene-bis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], octadecyl] [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate] You can choose from. It is also preferable to use these hindered phenol antioxidants and thioether secondary antioxidants in combination.

  Although there is no restriction | limiting in particular in the addition method to the polyester of the said hindered phenol antioxidant, Preferably it adds in the arbitrary steps after completion | finish of a polycondensation reaction after completion | finish of transesterification.

  Moreover, about the color adjusting agent, 0.1-10 mass ppm of color adjusting agents may be contained in the polyethylene terephthalate obtained by the manufacturing method of this invention on the basis of the total mass. The color adjusting agent represents an organic polyaromatic ring dye or pigment, and is preferably an anthraquinone dye, specifically, a blue color adjusting dye, a purple color adjusting dye, a red color adjusting dye. Examples thereof include color dyes and orange color adjusting dyes. These may be used singly or in combination of a plurality of types, but a blue color adjusting dye and a purple color adjusting dye may be used in a mass ratio of 90:10 to 40:60. preferable. Here, the blue color-modifying dye is generally indicated as “Blue” among commercially available color-adjusting dyes, and specifically, the maximum absorption in the visible light absorption spectrum in the solution. The wavelength is about 580 to 620 nm. Similarly, the purple color-modifying dye is the one described as “Violet” among commercially available color-adjusting dyes, and specifically has a maximum absorption wavelength in a visible light absorption spectrum in a solution. The thing in about 560-580 nm is shown. As these color adjusting pigments, oil-soluble dyes are particularly preferable. Specific examples of blue color adjusting pigments include C.I. I. Solvent Blue 11, C.I. I. Solvent Blue 25, C.I. I. Solvent Blue 35, C.I. I. Solvent Blue 36, C.I. I. Solvent Blue 45 (Polysynthren Blue), C.I. I. Solvent Blue 55, C.I. I. Solvent Blue 63, C.I. I. Solvent Blue 78, C.I. I. Solvent Blue 83, C.I. I. Solvent Blue 87, C.I. I. Solvent Blue 94 and the like. Examples of purple color adjusting pigments include C.I. I. Solvent Violet 8, C.I. I. Solvent Violet 13, C.I. I. Solvent Violet 14, C.I. I. Solvent Violet 21, C.I. I. Solvent Violet 27, C.I. I. Solvent Violet 28, C.I. I. Solvent Violet 36 etc. are mentioned.

Here, when the blue color adjusting dye and the purple color adjusting dye are used in combination, when the mass ratio of the blue color adjusting dye is larger than the mass ratio of 90:10, the color a of the obtained polyester composition ^{* If the} value is small and green, and the mass ratio of the blue color-changing dye is smaller than 40:60, the color a ^* value becomes large and red is not preferable. The color adjusting dye is more preferably a blue color adjusting dye and a purple color adjusting dye used in a mass ratio of 80:20 to 50:50.

The color adjusting agent used in the present invention is selected from color adjusting dyes having a mass decrease starting temperature of 250 ° C. or higher when measured with a thermobalance in a nitrogen atmosphere at a temperature rising rate of 10 ° C./min. It is preferable. Here, the mass decrease start temperature when measured with a thermobalance is the mass decrease start temperature (T ₁ ) described in JIS K-7120, and is a heat resistance index possessed by the color adjuster. Become. When the mass decrease starting temperature is less than 250 ° C., the heat resistance of the color adjusting agent is insufficient, which is not preferable because it causes coloring of the finally obtained polyester composition. The mass decrease starting temperature is more preferably 300 ° C. or higher. It is further preferable that the aromatic polyester does not decompose at a temperature at which it is in a molten state.

  Although there is no restriction | limiting in the intrinsic viscosity of polyester in this invention, It is preferable to exist in the range of 0.50-1.00 dL / g. When the intrinsic viscosity is within this range, melt molding is easy and the strength of the molded product obtained therefrom is high. A more preferable range of the intrinsic viscosity is 0.52 to 0.90 dL / g, and particularly preferably 0.05 to 0.80 dL / g.

  The polyester obtained by solid phase polycondensation is often used for general bottles and the like, and is therefore contained in the polyester and has an intrinsic viscosity of 0.70 to 0.90 dL / g. The cyclic trimer content of the ester of aromatic dicarboxylic acid and ethylene glycol is preferably 0.5 wt% or less, and the acetaldehyde content is preferably 5 ppm or less.

  Further, when the polyethylene terephthalate obtained by the production method of the present invention is used for each molded product such as a film, fiber, bottle, etc., according to the requirements, an antioxidant, a heat stabilizer, a viscosity modifier, a plasticizer, a hue Various functional agents such as an improving agent, a nucleating agent, and an ultraviolet absorber may be contained. For example, when used for forming into a film, in order to improve the handleability, inactive particles having an average particle diameter of 0.05 to 5.0 μm are used as a lubricant, and 0.05 to 5.0 weight with respect to the weight of polyethylene terephthalate. About% may be contained. At this time, as a feature of the polyethylene terephthalate obtained by the production method of the present invention, in order to maintain high transparency, the particle diameter of the added inert particles is preferably as small as possible, and the addition amount thereof should be as small as possible. Is preferred. Inert particles used as solvents include colloidal silica, porous silica, titanium oxide, calcium carbonate, calcium phosphate, barium sulfate, alumina, zirconia, kaolin, composite oxide particles, crosslinked polystyrene, acrylic crosslinked particles, methacrylic particles Crosslinked particles, silicone particles, and the like can be given.

  According to the production method of the present invention, a polyethylene terephthalate using a titanium compound that is not a heavy metal as a transesterification reaction catalyst, the transesterification reaction during the production can be advanced more rapidly, and a residual transesterification catalyst Polyethylene terephthalate capable of suppressing the generation of residual foreign matters and thermal decomposition due to the above can be obtained.

The invention is further illustrated by the following examples.
In the following Examples and Comparative Examples, the following tests were conducted on the manufactured polyethylene terephthalate (chip), plate, or film.

(1) Intrinsic viscosity:
0.6 g of polyester was dissolved by heating in 50 ml of orthochlorophenol, then cooled to room temperature, and the viscosity of the obtained polyester solution was measured at 35 ° C. using an Ostwald viscosity tube. The intrinsic viscosity (IV) of the polyester was calculated from the obtained solution viscosity data.

(2) Polymer color tone (color L value and color b value):
A polymer sample was melted at 290 ° C. under vacuum for 10 minutes, formed into a plate having a thickness of 3.0 ± 1.0 mm on an aluminum plate, and immediately cooled in ice water. The plate was cooled at 160 ° C. for 1 hour. Dry crystallization treatment was performed. Then, this was set | placed on the white standard plate for color difference adjustment, and the color L value and b value of the surface of a test plate were measured using Minolta Hunter type color difference meter CR-200. The L value indicates the lightness, and the larger the value, the higher the lightness. The b value indicates the greater the yellowness, the greater the value.

(3) Metal content concentration analysis:
When the sample form is a catalyst solution, the titanium atom concentration and the phosphorus atom concentration in the catalyst are filled in the liquid cell as they are, and when the sample form is a solid polyester resin, the granular polyester sample is placed on the aluminum plate. After being melted by heating, it was measured by molding into a compact having a flat surface with a compression press. Each sample was subjected to quantitative analysis by subjecting each sample to a fluorescent X-ray apparatus (type 3270E, manufactured by Rigaku Corporation). However, regarding the titanium atom concentration in the polymer to which titanium oxide was added as a matting agent, the sample was dissolved in hexafluoroisopropanol, the titanium oxide particles were precipitated from the hexafluoroisopropanol solution with a centrifuge, and the supernatant liquid was obtained by the gradient method. Only the sample was collected and the sample was prepared by evaporating the solvent. The sample was measured.

(4) Diethylene glycol (DEG) content:
The polymer was decomposed using hydrazine hydrate, and the content of diethylene glycol in the decomposition product was measured using gas chromatography (“263-70 type” manufactured by Hitachi, Ltd.).

(5) Thermal stability (unstretched film):
A granular polymer sample is heat-treated and dried at 150 ° C. for 6 hours in a dryer, and then heated and melted to 290 ° C. in a melt extruder, which is extruded into a sheet on a rotary cooling drum, rapidly cooled and solidified, and thickened. A 500 μm unstretched film (sheet) was produced. The value (A) of the intrinsic viscosity of the unstretched film and the value (B) of the intrinsic viscosity of the polymer used for the production of the unstretched film were determined, and from the difference value of (B)-(A), The thermal stability of the test unstretched film was determined according to the criteria.
Special grade: 0 to 0.05 dL / g: (The thermal stability is particularly excellent.)
First grade: more than 0.05 dL / g to 0.10 dL / g: (excellent thermal stability)
2nd grade: over 0.10 dL / g to 0.15 dL / g: (having thermal stability)
Third grade: Over 0.15 dL / g: (Inferior in thermal stability)

(6) Foreign matter in polymer:
One gram of a granular polymer sample was collected, the surface was washed away with acetone, dissolved in 20 ml of a hexafluoroisopropanol / chloroform 1/1 (v / v) mixture, and the solution was filtered with a membrane filter having an opening of 3 μm. . The foreign matters collected on the filter were observed with a microscope, the number of the foreign matters was visually counted, and the amount of foreign matters in the polymer was determined according to the following criteria.
Special grade: Less than 50 / g: (Few foreign matter)
First grade: 50 / g or more and less than 100 / g: (Relatively few foreign substances)
Second grade: 100 / g or more and less than 300 / g: (relatively many foreign substances)
Third grade: 300 units / g or more: (There are many foreign substances)

[Production Example 1] Titanium acetate synthesis method 6.3 parts by weight of tetrabutoxy titanium (0.9 parts by weight as a titanium metal component) in an ethylene glycol solution in which 4.5 parts by weight of acetic acid is mixed with 79 parts by weight of ethylene glycol The mixture was added and allowed to react in air at 60 ° C. under normal pressure for 30 minutes, and then cooled to room temperature to prepare the target titanium compound.

[Production Example 2] Method for synthesizing titanium trimellitic acid In an ethylene glycol solution obtained by mixing 2 parts by mass of trimellitic anhydride with 98 parts by mass of ethylene glycol, 1.77 parts by weight of tetrabutoxy titanium (0.25% as a titanium metal component). The molar ratio of 0.5 parts by weight to trimellitic anhydride was added, and the mixture was allowed to react at 80 ° C. under normal pressure in air for 60 minutes, and then cooled to room temperature to prepare the target titanium compound.

[Example 1]
(Production of ethylene terephthalate oligomer)
In a mixture of 194 parts by mass of dimethyl terephthalate and 112 parts by mass of ethylene glycol, 0.192 parts by weight of titanium acetate prepared in Production Example 1 (10 ppm as titanium metal with respect to the obtained polyethylene terephthalate), 0.0098 parts by mass of potassium acetate (10 mmol% with respect to dimethyl terephthalate) is charged into a stainless steel container (transesterification reaction tank) capable of pressure reaction, pressurized to 0.07 MPa, and gradually heated from 140 ° C to 240 ° C. The transesterification was carried out while distilling out the methanol produced as a result of the reaction out of the reaction vessel. At that time, when the distillation of methanol reached 57.6 parts by weight, the reaction was terminated to prepare an ethylene terephthalate oligomer having a transesterification reaction rate of 90%.

(Transesterification reaction process)
Acetic acid prepared in Production Example 1 with 65 parts by mass of dimethyl terephthalate and 37 parts by mass of ethylene glycol / 1 hour in a state where the oligomer obtained by the above operation is present in the transesterification reaction tank Titanium 0.064 parts by weight / hour (10 ppm as titanium metal with respect to the obtained polyethylene terephthalate), potassium acetate 0.0033 parts by weight / hour (10 mmol% with respect to dimethyl terephthalate) continuously transesterification reactor The methanol produced while controlling the internal temperature at 240 ° C. under atmospheric pressure was distilled out of the reaction vessel, and 85 parts by weight of ethylene terephthalate oligomer (dimethyl terephthalate added per hour, Ethylene terephthalate obtained with ethylene glycol and other catalysts While extracting the amount) corresponding to the oligomer was subjected to a continuous ester interchange reaction. That is, the transesterification reaction was substantially carried out for 3 hours. The ethylene terephthalate oligomer obtained at this time had a transesterification rate of 90%.

(Polycondensation process)
The extracted ethylene terephthalate oligomer is immediately transferred to a reaction vessel (polycondensation reaction tank) equipped with a stirrer, a nitrogen inlet, a vacuum port and a distillation device, and 0.015 part of triethylphosphonoacetate (based on dimethyl terephthalate). 20 mmol%), 0.012 part by weight of germanium dioxide, and 0.00004 and 0.00003 part by weight of Solvent Blue 45 and Solvent Violet 36 (1 ppm in total with respect to the obtained polyethylene terephthalate) were added at 285 ° C. and 30 Pa. The following polycondensation reaction is carried out under high vacuum, and the polyester composition has an intrinsic viscosity of 0.64 dL / g, a diethylene glycol content of 1.3% by mass, and a color L / b of 83.2 / 0.2. Got. In addition, the results of thermal stability evaluation and foreign matter evaluation measured by the unstretched film method were both special grades. The results are shown in Table 1.

[Example 2]
In Example 1, it carried out like Example 1 except not adding potassium acetate. The results are shown in Table 1.

[Example 3]
(Production of ethylene terephthalate oligomer)
To a mixture of 194 parts by mass of dimethyl terephthalate and 112 parts by mass of ethylene glycol, 0.768 parts by weight of titanium trimellitic acid prepared in Production Example 2 (10 ppm as titanium metal with respect to the obtained polyethylene terephthalate), 0.0098 potassium acetate A mass part (10 mmol% with respect to dimethyl terephthalate) is charged into a stainless steel container (transesterification reaction tank) capable of pressure reaction, pressurized to 0.07 MPa, and gradually heated from 140 ° C to 240 ° C. However, the transesterification reaction was carried out while distilling methanol produced as a result of the reaction out of the reaction vessel. At that time, when the distillation of methanol reached 57.6 parts by weight, the reaction was terminated to prepare an ethylene terephthalate oligomer having a transesterification reaction rate of 90%.

(Transesterification reaction process)
In the state where the oligomer obtained by the above operation is present in the transesterification reactor, dimethyl terephthalate 65 parts by mass / hour and ethylene glycol 37 parts by mass / hour, the triglyceride prepared in Production Example 2 Continuous transesterification of 0.256 parts by weight of titanium meritate per hour (10 ppm as titanium metal with respect to the obtained polyethylene terephthalate) and 0.0033 parts by weight of potassium acetate per hour (10 mmol% with respect to dimethyl terephthalate) Methanol produced while being added to the reaction vessel and controlling the internal temperature to 240 ° C. under normal pressure was distilled out of the reaction vessel, and 85 parts by weight of ethylene terephthalate oligomer (terephthalic acid added per hour) Ethylene terephthalate obtained with dimethyl, ethylene glycol and other catalysts Tallate amount corresponding to oligomer) was subjected to a continuous ester interchange reaction while extracting the, that is, it was carried out substantially 3 hours transesterification. The ethylene terephthalate oligomer obtained at this time had a transesterification rate of 91%.

(Polycondensation process)
The extracted ethylene terephthalate oligomer is immediately transferred to a reaction vessel (polycondensation reaction tank) equipped with a stirrer, a nitrogen inlet, a vacuum port and a distillation device, and 0.015 part of triethylphosphonoacetate (based on dimethyl terephthalate). 20 mmol%), 0.012 parts by weight of germanium dioxide, and 0.00004 and 0.00003 parts by weight of Solvent Blue 45 and Solvent Violet 36 (1 ppm in total with respect to the obtained polyethylene terephthalate), respectively, to 285 ° C. The polyester is heated and subjected to a polycondensation reaction at a high vacuum of 30 Pa or less, an intrinsic viscosity of 0.64 dL / g, a diethylene glycol content of 1.3% by mass, and a color L / b of 82.9 / 0.4 A composition was obtained. The results are shown in Table 1.

[Example 4]
(Production of ethylene terephthalate oligomer)
In a mixture of 194 parts by mass of dimethyl terephthalate and 112 parts by mass of ethylene glycol, 0.0138 parts by weight of tetrabutoxy titanium (10 ppm as titanium metal with respect to the obtained polyethylene terephthalate), 0.0098 parts by mass of potassium acetate (in dimethyl terephthalate) 10 mmol%) in a stainless steel container (transesterification reaction tank) capable of pressure reaction, pressurizing 0.07 MPa, and gradually raising the temperature from 140 ° C. to 240 ° C. while producing the result of the reaction The transesterification reaction was carried out while distilling methanol to be distilled out of the reaction vessel. At that time, when the distillation of methanol reached 57.6 parts by weight, the reaction was terminated to prepare an ethylene terephthalate oligomer having a transesterification reaction rate of 90%.

(Transesterification reaction process)
In the state where the oligomer obtained by the above operation is present in the transesterification reactor, dimethyl terephthalate 65 parts by mass / 1 hour and ethylene glycol 37 parts by mass / 1 hour, tetrabutoxy titanium 0.0046 Parts by weight / 1 hour (10 ppm as titanium metal with respect to the obtained polyethylene terephthalate) and 0.0033 parts by mass of potassium acetate (10 mmol% with respect to dimethyl terephthalate) were continuously added into the transesterification reaction tank, The methanol produced while controlling the internal temperature at 240 ° C. was distilled out of the reaction vessel, and 85 parts by weight of ethylene terephthalate oligomer per hour (with dimethyl terephthalate, ethylene glycol and other catalysts added per hour) Obtained ethylene terephthalate oligo It was subjected to a continuous ester interchange reaction while extracting the amount) corresponding to over. That is, the transesterification reaction was substantially carried out for 3 hours. The ethylene terephthalate oligomer obtained at this time had a transesterification rate of 89%.

(Polycondensation process)
The extracted ethylene terephthalate oligomer is immediately transferred to a reaction vessel (polycondensation reaction tank) equipped with a stirrer, a nitrogen inlet, a vacuum port and a distillation device, and 0.015 part of triethylphosphonoacetate (based on dimethyl terephthalate). 20 mmol%), 0.012 parts by weight of germanium dioxide, and 0.00004 and 0.00003 parts by weight of Solvent Blue 45 and Solvent Violet 36 (1 ppm in total with respect to the obtained polyethylene terephthalate) were added and the temperature was raised to 285 ° C. Polyester composition having an intrinsic viscosity of 0.64 dL / g, a diethylene glycol content of 1.3% by mass, and a color L / b of 82.5 / 0.7. I got a thing. The results are shown in Table 1.

[Example 5]
In Example 1, 0.0136 parts by weight of sodium acetate trihydrate (10 mmol% with respect to dimethyl terephthalate) instead of 0.0098 parts by weight of potassium acetate in the production process of ethylene terephthalate oligomer, continuous transesterification Example 1 except that 0.0045 parts by weight of sodium acetate trihydrate per hour (10 mmol% with respect to dimethyl terephthalate) was used instead of 0.0033 parts by weight of potassium acetate per hour during the reaction step The same was done. The results are shown in Table 1.

[Example 6]
(Production of ethylene terephthalate oligomer)
In a mixture of 194 parts by mass of dimethyl terephthalate and 112 parts by mass of ethylene glycol, 0.384 parts by weight of titanium acetate prepared in Production Example 1 (20 ppm as titanium metal with respect to the obtained polyethylene terephthalate), 0.0098 parts by mass of potassium acetate (10 mmol% with respect to dimethyl terephthalate) is charged into a stainless steel container (transesterification reaction tank) capable of pressure reaction, pressurized to 0.07 MPa, and gradually heated from 140 ° C to 240 ° C. The transesterification was carried out while distilling out the methanol produced as a result of the reaction out of the reaction vessel. At that time, when the distillation of methanol reached 57.6 parts by weight, the reaction was terminated to prepare an ethylene terephthalate oligomer having a transesterification reaction rate of 90%.

(Transesterification reaction process)
Acetic acid prepared in Production Example 1 with 65 parts by mass of dimethyl terephthalate and 37 parts by mass of ethylene glycol / 1 hour in a state where the oligomer obtained by the above operation is present in the transesterification reaction tank 0.128 parts by weight of titanium / 1 hour (20 ppm as titanium metal with respect to the obtained polyethylene terephthalate), 0.0033 parts by weight of potassium acetate / 1 hour (10 mmol% with respect to dimethyl terephthalate) continuously in a transesterification reactor The methanol produced while controlling the internal temperature at 240 ° C. under atmospheric pressure was distilled out of the reaction vessel, and 85 parts by weight of ethylene terephthalate oligomer (dimethyl terephthalate added per hour, Ethylene terephthalate obtained with ethylene glycol and other catalysts While extracting the amount) corresponding to the oligomer was subjected to a continuous ester interchange reaction. After the polycondensation step, the same procedure as in Example 1 was performed. The results are shown in Table 1.

[Example 7]
(Production of ethylene terephthalate oligomer)
In a mixture of 194 parts by mass of dimethyl terephthalate and 112 parts by mass of ethylene glycol, 0.768 parts by weight of titanium acetate prepared in Production Example 1 (40 ppm as titanium metal with respect to the obtained polyethylene terephthalate), 0.0098 parts by mass of potassium acetate (10 mmol% with respect to dimethyl terephthalate) is charged into a stainless steel container (transesterification reaction tank) capable of pressure reaction, pressurized to 0.07 MPa, and gradually heated from 140 ° C to 240 ° C. The transesterification was carried out while distilling out the methanol produced as a result of the reaction out of the reaction vessel. At that time, when the distillation of methanol reached 57.6 parts by weight, the reaction was terminated to prepare an ethylene terephthalate oligomer having a transesterification reaction rate of 90%.

(Transesterification reaction process)
Acetic acid prepared in Production Example 1 with 65 parts by mass of dimethyl terephthalate and 37 parts by mass of ethylene glycol / 1 hour in a state where the oligomer obtained by the above operation is present in the transesterification reaction tank Titanium 0.256 parts by weight / hour (40 ppm as titanium metal with respect to the obtained polyethylene terephthalate), potassium acetate 0.0033 parts by weight / hour (10 mmol% with respect to dimethyl terephthalate) continuously transesterification reactor The methanol produced while controlling the internal temperature at 240 ° C. under atmospheric pressure was distilled out of the reaction vessel, and 85 parts by weight of ethylene terephthalate oligomer (dimethyl terephthalate added per hour, Ethylene terephthalate obtained with ethylene glycol and other catalysts While extracting the amount) corresponding to the oligomer was subjected to a continuous ester interchange reaction. After the polycondensation step, the same procedure as in Example 1 was performed. The results are shown in Table 1.

[Example 8]
(Production of ethylene terephthalate oligomer)
In a mixture of 130 parts by mass of dimethyl terephthalate and 74 parts by mass of ethylene glycol, 0.128 parts by weight of titanium acetate prepared in Production Example 1 (10 ppm as titanium metal with respect to the obtained polyethylene terephthalate), 0.0066 parts by mass of potassium acetate (10 mmol% with respect to dimethyl terephthalate) is charged into a stainless steel container (transesterification reaction tank) capable of pressure reaction, pressurized to 0.07 MPa, and gradually heated from 140 ° C to 240 ° C. The transesterification was carried out while distilling out the methanol produced as a result of the reaction out of the reaction vessel. At that time, the reaction was terminated when the distillation of methanol reached 29.9 parts by weight to prepare an ethylene terephthalate oligomer having a transesterification rate of 70%.

(Transesterification reaction process)
Acetic acid prepared in Production Example 1 with 65 parts by mass of dimethyl terephthalate and 37 parts by mass of ethylene glycol / 1 hour in a state where the oligomer obtained by the above operation is present in the transesterification reaction tank Titanium 0.064 parts by weight / hour (10 ppm as titanium metal with respect to the obtained polyethylene terephthalate), potassium acetate 0.0033 parts by weight / hour (10 mmol% with respect to dimethyl terephthalate) continuously transesterification reactor The methanol produced while controlling the internal temperature at 240 ° C. under atmospheric pressure was distilled out of the reaction vessel, and 85 parts by weight of ethylene terephthalate oligomer (dimethyl terephthalate added per hour, Ethylene terephthalate obtained with ethylene glycol and other catalysts While extracting the amount) corresponding to the oligomer was subjected to a continuous ester interchange reaction. That is, the transesterification reaction was substantially carried out for 2 hours. The ethylene terephthalate oligomer obtained at this time had a transesterification rate of 80%.

(Polycondensation process)
The extracted ethylene terephthalate oligomer is immediately transferred to a reaction vessel (polycondensation reaction tank) equipped with a stirrer, a nitrogen inlet, a vacuum port and a distillation device, and 0.015 part of triethylphosphonoacetate (based on dimethyl terephthalate). 20 mmol%), 0.012 part by weight of germanium dioxide, and 0.00004 and 0.00003 part by weight of Solvent Blue 45 and Solvent Violet 36 (1 ppm in total with respect to the obtained polyethylene terephthalate) were added at 285 ° C. and 30 Pa. The following polycondensation reaction is carried out under a high vacuum, and the polyester composition has an intrinsic viscosity of 0.64 dL / g, a diethylene glycol content of 1.3% by mass, and a color L / b of 82.0 / 0.9. Got. The results are shown in Table 1.

[Comparative Example 1]
(Transesterification reaction process)
194 parts by weight of dimethyl terephthalate and 112 parts by weight of ethylene glycol, 0.192 parts by weight of titanium acetate prepared in Production Example 1 (10 ppm as titanium metal with respect to the obtained polyethylene terephthalate), 0.0098 parts by weight of potassium acetate (dimethyl terephthalate) 10 mmol%) to the outside of the reaction tank while the ethylene terephthalate oligomer is not present in the transesterification reaction tank at the start of the reaction and the internal temperature is controlled at 240 ° C. under normal pressure. The ester exchange reaction was carried out, and the reaction was completed when the distillation of methanol was completed. The reaction time was very long and required a reaction time of 490 minutes.

(Polycondensation process)
Thereafter, the obtained oligomer was transferred to a reaction vessel (polycondensation reaction tank) equipped with a stirrer, a nitrogen inlet, a vacuum port and a distillation device, and 0.044 parts of triethylphosphonoacetate (based on dimethyl terephthalate). 20 mmol%), 0.037 parts by weight of germanium dioxide, and 0.00012 and 0.00008 parts by weight of Solvent Blue 45 and Solvent Violet 36 (1 ppm in total with respect to the obtained polyethylene terephthalate) were added, and the temperature was raised to 285 ° C. A yellow polyester having an intrinsic viscosity of 0.63 dL / g, a diethylene glycol content of 2.0 mass%, and a color L / b of 82.2 / 7.2. A composition was obtained. Moreover, the result of the thermal stability evaluation measured by the unstretched film method was the third grade, and the thermal deterioration was large. The results are shown in Table 1.

[Comparative Example 2]
(Production of ethylene terephthalate oligomer)
In a mixture of 65 parts by mass of dimethyl terephthalate and 37 parts by mass of ethylene glycol, 0.064 parts by weight of titanium acetate prepared in Production Example 1 (10 ppm as titanium metal with respect to the obtained polyethylene terephthalate), 0.0033 parts by mass of potassium acetate (10 mmol% with respect to dimethyl terephthalate) is charged into a stainless steel container (transesterification reaction tank) capable of pressure reaction, pressurized to 0.07 MPa, and gradually heated from 140 ° C to 240 ° C. The transesterification was carried out while distilling out the methanol produced as a result of the reaction out of the reaction vessel. At that time, the reaction was terminated when the distillation of methanol reached 12.8 parts by weight, and an ethylene terephthalate oligomer having a transesterification rate of 60% was prepared.

(Transesterification reaction process)
Acetic acid prepared in Production Example 1 with 65 parts by mass of dimethyl terephthalate and 37 parts by mass of ethylene glycol / 1 hour in a state where the oligomer obtained by the above operation is present in the transesterification reaction tank Titanium 0.064 parts by weight / hour (10 ppm as titanium metal with respect to the obtained polyethylene terephthalate), potassium acetate 0.0033 parts by weight / hour (10 mmol% with respect to dimethyl terephthalate) continuously transesterification reactor The methanol produced while controlling the internal temperature at 240 ° C. under atmospheric pressure was distilled out of the reaction vessel, and 85 parts by weight of ethylene terephthalate oligomer (dimethyl terephthalate added per hour, Ethylene terephthalate obtained with ethylene glycol and other catalysts While extracting the amount) corresponding to the oligomer was subjected to a continuous ester interchange reaction. That is, the transesterification reaction was substantially carried out for 1 hour. The ethylene terephthalate oligomer obtained at this time had a transesterification rate of 70%.

(Polycondensation process)
The extracted ethylene terephthalate oligomer is immediately transferred to a reaction vessel (polycondensation reaction tank) equipped with a stirrer, a nitrogen inlet, a vacuum port and a distillation device, and 0.015 part of triethylphosphonoacetate (based on dimethyl terephthalate). 20 mmol%), 0.012 part by weight of germanium dioxide, and 0.00004 and 0.00003 part by weight of Solvent Blue 45 and Solvent Violet 36 (1 ppm in total with respect to the obtained polyethylene terephthalate) were added at 285 ° C. and 30 Pa. The polycondensation reaction was continuously carried out at the following high vacuum, but the polymerization reaction did not proceed sufficiently and reached an intrinsic viscosity of only 0.58 dL / g, reaching a peak.

[Comparative Example 3]
In Example 1, potassium acetate in the production step of ethylene terephthalate oligomer and potassium acetate in the continuous transesterification step were 0.0245 parts by mass and 0.0082 parts by mass per hour, respectively (based on dimethyl terephthalate). In the same manner as in Example 1, except that each was 25 mmol%). The results are shown in Table 1.

[Comparative Example 4]
In Example 1, 1.056 parts by weight and 0.352 parts by weight / hour of titanium acetate in the production process of the ethylene terephthalate oligomer and titanium acetate in the continuous transesterification reaction process were obtained, respectively. In contrast to Example 1, except that the titanium metal was 55 ppm). The results are shown in Table 1.

[Comparative Example 5]
(Transesterification reaction process)
194 parts by weight of dimethyl terephthalate, 112 parts by weight of ethylene glycol, 0.122 parts by weight of calcium acetate monohydrate (69 mmol% with respect to dimethyl terephthalate), 0.0098 parts by weight of potassium acetate (10 mmol with respect to dimethyl terephthalate) %)), The ethylene terephthalate oligomer is not present in the transesterification reaction tank at the start of the reaction, and the methanol produced is distilled out of the reaction tank while controlling the internal temperature at 240 ° C. under normal pressure. The reaction was carried out, and the reaction was terminated when the distillation of methanol was completed. The reaction time took 240 minutes.

(Polycondensation process)
Thereafter, the obtained oligomer was taken out and transferred to a reaction vessel (polycondensation reaction vessel) equipped with a stirrer, a nitrogen inlet, a vacuum port and a distillation device, and 0.044 parts of triethylphosphonoacetate (diethyl terephthalate) 20 mmol%), 0.037 parts by weight of germanium dioxide, and 0.00012 and 0.00008 parts by weight of Solvent Blue 45 and Solvent Violet 36 (1 ppm in total with respect to the obtained polyethylene terephthalate) were added up to 285 ° C. Polyester having an intrinsic viscosity of 0.63 dL / g, a diethylene glycol content of 1.3% by mass, and a color L / b of 82.2 / 0.9 by performing a polycondensation reaction at a high vacuum of 30 Pa or less at an elevated temperature. A composition was obtained. Moreover, the result of the thermal stability evaluation measured by the unstretched film method was the third grade, and the thermal deterioration was large. The results are shown in Table 1.

  According to the present invention, dimethyl terephthalate and ethylene glycol are used as the main starting materials, a titanium compound that is not a heavy metal is used as a transesterification reaction catalyst, the transesterification reaction at the time of production is advanced more quickly, and the residual transesterification catalyst is used. It is possible to provide a method for producing polyethylene terephthalate in which generation of residual foreign matters and thermal decomposition are suppressed.

Claims (3)

  A method for producing polyethylene terephthalate that undergoes at least two steps of a transesterification step and a polycondensation step in the presence of a titanium catalyst, and dimethyl terephthalate, ethylene glycol, and transesterification at the start of the transesterification step An ethylene terephthalate oligomer having a reaction rate of 70% or more is present, and the amount of titanium catalyst used is an amount that is more than 0 ppm and less than 50 ppm as a titanium metal atom with respect to the weight of polyethylene terephthalate, and the transesterification reaction step is completed. Continuous production of polyethylene terephthalate in which an alkali metal compound of 20 mmol% or less is added to dimethyl terephthalate at any stage up to and further polycondensation of the ethylene terephthalate oligomer obtained in the transesterification step Law. The titanium catalyst is (1) a compound represented by the following general formula (I), (2) a compound represented by the following general formula (I) and an aromatic polyvalent carboxylic acid represented by the following general formula (II) Or a product obtained by reacting with an acid anhydride, or (3) a product obtained by reacting a compound represented by the following general formula (I) with a carboxylic acid represented by the following general formula (III) The continuous production method of polyethylene terephthalate according to claim 1, wherein the method is one kind or a mixture of two or more kinds.

  The continuous production method of polyethylene terephthalate according to claim 1 or 2, wherein the alkali metal compound is sodium acetate or potassium acetate.