JP2024002938A - Polybutylene terephthalate and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polybutylene terephthalate that has a favorable polymer hue, with less yellowness and bluishness, and causes less generation of acetic acid during heating, and a method for producing the same.

SOLUTION: A polybutylene terephthalate is provided, where the level of terminal acetyl groups is less than 0.1 equivalents per ton and the level of terminal butyl aldehyde groups is 0.05-0.13 equivalents per ton. In all the structural units derived from the diol component, the structural unit derived from 2-methyl-1,4-butanediol constitutes 0.020-0.080 mol%. A method for producing polybutylene terephthalate is also provided. This method produces the polybutylene terephthalate by reacting a terephthalic acid component with 1,4-butanediol. As the 1,4-butanediol, used is the type of 1,4-butanediol that contains 2-methyl-1,4-butanediol of 250-1000 mass ppm and 2-(4-hydroxybutyloxy) tetrahydrofuran of 10-1500 mass ppm.

SELECTED DRAWING: None

COPYRIGHT: (C)2024,JPO&INPIT

Description

The present invention relates to polybutylene terephthalate (hereinafter sometimes abbreviated as "PBT"), and specifically relates to PBT which has a preferable polymer color tone and generates less acetic acid when heated, and a method for producing the same.
The present invention also relates to a PBT composition using this PBT that can be suitably used for electrical and electronic parts, automobile parts, etc., a method for producing the same, and a molded article and a method for producing the same.

Terephthalic acid (hereinafter sometimes abbreviated as "TPA") is used as the main component of the dicarboxylic acid component, and 1,4-butanediol (hereinafter sometimes abbreviated as "BDO") is used as the main component of the diol component. PBT using PBT has excellent mechanical properties, heat resistance, moldability, and recyclability, and has high mechanical strength and excellent chemical resistance, so it is used in connectors, relays, and switches for automobiles and electrical/electronic equipment. It is widely used as a material for industrial molded products such as. Furthermore, it is widely used in films, sheets, fibers (filaments), etc., and as a result, high-quality PBT and its manufacturing method are required.

Methods for producing 1,4-butanediol, which is a raw material for PBT, include the butadiene method using butadiene as a raw material, and the Reppe method in which acetylene and formaldehyde are reacted.
However, BDO produced by either method contains impurities specific to each method, and these impurities cause problems such as deterioration of the color tone of the obtained PBT and corrosion of the equipment.

In particular, PBT using BDO produced by the butadiene method has a problem in that terminal acetyl groups remain, and acetic acid is generated due to the heat during kneading and molding due to the terminal acetyl groups. In addition, acetic acid causes problems in the recovery process of tetrahydrofuran (hereinafter sometimes abbreviated as "THF"), which is a by-product during the production of PBT. Here, the problem caused by acetic acid is the same as the problem caused by the terminal acetyl group caused by acetic acid mixed in terephthalic acid, which will be described later. Neutralization equipment may be required to neutralize acetic acid in wastewater after collection.

Although BDO by the Reppe method does not have this problem, it still has the problem of deterioration in the color tone of the PBT obtained due to specific impurities.
For example, Patent Document 1 describes that glycol whose main component is 1,4-butylene glycol (=BDO) containing 2-(4'-hydroxybutoxy)tetrahydrofuran and terephthalic acid (=TPA) containing acetic acid. Although a method for producing polybutylene terephthalate in which a dicarboxylic acid as a main component is esterified and polycondensed is disclosed, it does not disclose any characteristics or problems of the present invention.

Further, in PBT produced by the esterification reaction of terephthalic acid and BDO, a terminal acetyl group is formed due to acetic acid mixed in the terephthalic acid. This terminal group is hydrolyzed by heat during kneading or molding, for example, and generates acetic acid. The acetic acid generated causes deterioration of metal polymerization equipment, molding equipment, vacuum-related equipment, etc.
Similarly, when the terminal acetyl group of PBT is made into a molded product, acetic acid is generated by thermal decomposition and hydrolysis. For example, when used in electrical and electronic components, the generated acetic acid corrodes metal contact parts and causes malfunction.

For these reasons, a PBT with excellent color tone and suppressed generation of acetic acid is desired.

Japanese Patent Application Publication No. 2001-48968

The objects of the present invention are PBT which has a preferable color tone of the polymer, that is, has less yellowish or bluish tinge, and which generates less acetic acid upon heating, a method for producing the same, a PBT composition containing this PBT, a method for producing the same, and a PBT composition containing the PBT. The purpose of this invention is to provide a molded product using a molded product and a method for manufacturing the same.

As a result of intensive studies to solve the above problems, the present inventors found that terminal acetyl group and terminal butyraldehyde group, 2-methyl-1,4-butanediol (hereinafter abbreviated as "2Me1,4-BDO") The present inventors have discovered that these problems can be solved by using PBT having specific amounts of structural units derived from the following.), and have completed the present invention. This can be achieved to a higher degree by simultaneously using PBT having specific amounts of terminal benzaldehyde groups and terminal methylphenyl groups. This means that the diol raw materials for PBT include specific amounts of 2Me1,4-BDO and 1,4- 2-(4-hydroxybutyloxy)tetrahydrofuran (hereinafter sometimes abbreviated as "BGTF"). What can be achieved by using butanediol, and furthermore, specific amounts of 4-carboxybenzaldehyde (hereinafter sometimes abbreviated as "4CBA") and p-toluic acid (hereinafter "p-toluic acid") as dicarboxylic acid raw materials. It has been found that a higher degree of performance can be achieved by using terephthalic acid containing TA (sometimes abbreviated as "TA").
The present invention was completed based on these findings, and the gist thereof is as follows.

[1] The terminal acetyl group concentration is less than 0.1 equivalent/ton, the terminal butyraldehyde group concentration is 0.05 to 0.13 equivalent/ton,
The proportion of structural units derived from 2-methyl-1,4-butanediol in all structural units derived from diol components (hereinafter sometimes referred to as "2-methyl-1,4-butanediol") is Polybutylene terephthalate, characterized in that the content is 0.020 to 0.080 mol%.

[2] The method according to [1], characterized in that the terminal benzaldehyde group concentration is 0.03 to 0.07 equivalent/ton and the terminal methylphenyl group concentration is 0.3 to 0.8 equivalent/ton. Polybutylene terephthalate.

[3] In a method for producing polybutylene terephthalate by reacting a terephthalic acid component and 1,4-butanediol, as the 1,4-butanediol, 2-methyl-1,4-butanediol is used in an amount of 250 to 1000 The method for producing polybutylene terephthalate according to [1] or [2], characterized in that 1,4-butanediol containing 10 to 1500 ppm by weight of 2-(4-hydroxybutyloxy)tetrahydrofuran is used. .

[4] Producing polybutylene terephthalate with a consumption molar ratio of 1,4-butanediol and terephthalic acid components of 1.15 or more and less than 2.00 and containing 35 to 90 ppm of Ti [3] The method for producing polybutylene terephthalate described in .

[5] The method described in [3] or [4], characterized in that, as the terephthalic acid component, terephthalic acid having a 4-carboxybenzaldehyde content of 5 to 25 ppm and a p-toluic acid content of 85 to 185 ppm is used. A method for producing polybutylene terephthalate.

[6] A polybutylene terephthalate composition comprising the polybutylene terephthalate according to [1] or [2] and an additive.

[7] The method for producing a polybutylene terephthalate composition according to [6], characterized in that the polybutylene terephthalate and additives are kneaded using an extruder at a kneading resin temperature of 320° C. or lower.

[8] A molded article made of the polybutylene terephthalate composition according to [6].

[9] The method for producing a molded article according to [8], characterized in that the polybutylene terephthalate composition is molded using a molding machine at a molten resin temperature of 280° C. or lower.

The PBT of the present invention has a preferable color tone of the polymer, that is, it has less yellowish and blueish tinges, and generates less acetic acid when heated. Therefore, the compound and molded products obtained using the same have good color tone and commercial value. It has high corrosion resistance and generates less acetic acid, which corrodes metals. Therefore, the molded product obtained can be preferably used in various applications, such as electrical and electronic parts, automobile parts, films, sheets, and filaments.

Hereinafter, the present invention will be described in detail. However, the explanation of the constituent elements described below is a representative example of the embodiment of the present invention, and the present invention is not limited to these contents.
In the present invention, the "main component" in the dicarboxylic acid component refers to a component contained in the component in an amount of 50 mol% or more. The same applies to the "main component" in the diol component.
In addition, the structural unit derived from 2-methyl-1,4-butanediol refers to the structural unit incorporated into PBT derived from 2-methyl-1,4-butanediol used as a raw material for producing PBT. As expected. Hereinafter, the "structural unit derived from 2-methyl-1,4-butanediol" may be simply referred to as "2-methyl-1,4-butanediol unit."
Moreover, "ppm" refers to "mass ppm".

<PBT>
(Dicarboxylic acid component, diol component, copolymerization component)
In the present invention, PBT has a structure in which a terephthalic acid component and a 1,4-butanediol (BDO) component are ester bonded, in which 50 mol% or more of the dicarboxylic acid component is composed of the terephthalic acid component, and 50 mol% of the dicarboxylic acid component is composed of the terephthalic acid component. Refers to a polymer in which mol% or more consists of BDO. The proportion of terephthalic acid component in all dicarboxylic acid components is preferably 70 mol% or more, more preferably 80 mol% or more, particularly preferably 95 mol% or more, and the proportion of BDO in all diol components is preferably It is 70 mol% or more, more preferably 80 mol% or more, even more preferably 95 mol% or more. When the terephthalic acid component or BDO is less than 50 mol%, the crystallization rate of PBT decreases, resulting in deterioration of moldability.

The PBT of the present invention further incorporates 2-methyl-1,4-butanediol as a copolymerization component with respect to such PBT, and contains 2-methyl-1,4-butanediol units in a predetermined ratio. It is something that

In the present invention, the dicarboxylic acids other than terephthalic acid are not particularly limited, and examples thereof include phthalic acid, isophthalic acid, 4,4'-diphenyldicarboxylic acid, 4,4'-diphenyl ether dicarboxylic acid, and 4,4'-benzophenone dicarboxylic acid. Aromatic dicarboxylic acids such as 4,4'-diphenoxyethanedicarboxylic acid, 4,4'-diphenylsulfonedicarboxylic acid, 2,6-naphthalene dicarboxylic acid, 1,2-cyclohexanedicarboxylic acid, 1,3-cyclohexane Dicarboxylic acids, alicyclic dicarboxylic acids such as 1,4-cyclohexanedicarboxylic acid, aliphatic dicarboxylic acids such as malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, etc. be able to. These dicarboxylic acid components other than the terephthalic acid component may be used alone or in combination of two or more.

In the present invention, there are no particular limitations on diol components other than BDO, such as ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,5-pentanediol, neopentyl glycol, 1,6 -Aliphatic diols such as hexanediol, 1,8-octanediol, dibutylene glycol, 1,2-cyclohexanediol, 1,4-cyclohexanediol, 1,1-cyclohexanedimethylol, 1,4-cyclohexanedimethylol, etc. Examples include aromatic diols such as alicyclic diols, xylylene glycol, 4,4'-dihydroxybiphenyl, 2,2-bis(4-hydroxyphenyl)propane, and bis(4-hydroxyphenyl)sulfone. .
Regarding these diol components other than BDO, only one type may be used, or two or more types may be mixed and used.

In the present invention, hydroxycarboxylic acids such as lactic acid, glycolic acid, m-hydroxybenzoic acid, p-hydroxybenzoic acid, 6-hydroxy-2-naphthalenecarboxylic acid, p-β-hydroxyethoxybenzoic acid, alkoxycarboxylic acids, etc. Acid, stearyl alcohol, benzyl alcohol, stearic acid, benzoic acid, t-butylbenzoic acid, monofunctional components such as benzoylbenzoic acid, tricarballylic acid, trimellitic acid, trimesic acid, pyromellitic acid, gallic acid, trimethylolethane , trimethylolpropane, glycerol, pentaerythritol, and other trifunctional or higher functional components can be used as a copolymerization component.

(Amount of copolymerization of copolymerization components)
The PBT of the present invention has a copolymerized amount of 2-methyl-1,4-butanediol, which is a ratio of 2-methyl-1,4-butanediol units to all structural units derived from the diol component, of 0.020 to 0. 080 mol%.
If the amount of 2-methyl-1,4-butanediol copolymerized exceeds the upper limit of the above range, the physical properties of PBT, such as melting point, color tone, solution haze, and fish eyes of the resulting molded product, are unfavorable, and the object of the present invention is adversely affected. cannot be achieved.
In order to reduce the amount of 2-methyl-1,4-butanediol copolymerized to less than 0.020 mol%, it is necessary to use BDO produced by the butadiene method, and the resulting PBT has residual terminal acetyl groups. However, as mentioned above, problems arise due to the production of acetic acid.

The copolymerized amount of 2-methyl-1,4-butanediol in the copolymerized PBT of the present invention is 0.020 mol% or more, preferably 0.030 mol% or more. The upper limit of the amount of 2-methyl-1,4-butanediol copolymerized is 0.080 mol% or less, preferably 0.070 mol% or less, more preferably 0.060 mol% or less, and even more preferably 0.050 mol% or less. It is less than mol%.

The amount of 2-methyl-1,4-butanediol copolymerized with PBT can be determined by the method described in the Examples section below.

(Terminal group of PBT)
The terminal acetyl group concentration of the PBT of the present invention is less than 0.1 equivalent/ton. If the terminal acetyl group concentration is less than 0.1 equivalent/ton, it is possible to suppress the generation of acetic acid during heating and prevent contact failures in electrical and electronic parts and the like.

The terminal butyraldehyde group concentration of PBT of the present invention is 0.13 equivalent/ton or less. If the terminal butyraldehyde group concentration is 0.13 equivalent/ton or less, the color tone of PBT will be good. The lower limit of the terminal butyraldehyde group concentration is usually 0.05 equivalent/ton, since it is an impurity that cannot be avoided due to the production method of the raw material BDO. Therefore, the terminal butyraldehyde group concentration of PBT of the present invention is 0.05 to 0.13 equivalent/ton, preferably 0.07 to 0.12 equivalent/ton, more preferably 0.08 to 0.11 equivalent/ton. /ton.

Note that the terminal acetyl group of PBT of the present invention is derived from 1-acetoxy-4-hydroxybutane (hereinafter sometimes abbreviated as "1,4-HAB") in the PBT raw material due to its manufacturing method. Although it is sometimes referred to as a group, it is specified by the measurement method described below, and is not limited to 1,4-HAB origin.
Further, the terminal butyraldehyde group of PBT of the present invention is sometimes referred to as the terminal aldehyde group derived from 4-hydroxybutanal in the PBT raw material due to its manufacturing method, but it was identified by the measurement method described below, and - Not limited to those derived from hydroxybutanal.

If a terminal benzaldehyde group, for example, a terminal benzaldehyde group derived from 4CBA derived from relatively inexpensive terephthalic acid, exists in PBT, the color tone of this PBT tends to worsen, that is, it tends to become more yellowish or blueish. The presence of a certain amount of phenyl groups, such as terminal methyl groups derived from p-toluic acid, tends to alleviate such color defects, although the reason for this is unclear. The presence of specific amounts of terminal benzaldehyde groups and terminal methylphenyl groups in PBT suppresses the development of yellowish and blueish colors, an effect that has not been previously known.

The terminal benzaldehyde group concentration of PBT of the present invention is preferably 0.03 to 0.07 equivalent/ton, more preferably 0.04 to 0.07 equivalent/ton, and still more preferably 0.05 to 0.06 equivalent/ton. preferable. Furthermore, the terminal methylphenyl group concentration of PBT of the present invention is preferably 0.3 to 0.8 equivalent/ton, more preferably 0.4 to 0.7 equivalent/ton, and 0.5 to 0.6 equivalent/ton. Tons are more preferred.

Note that the terminal benzaldehyde group of PBT of the present invention is sometimes referred to as the terminal aldehyde group derived from 4CBA in the PBT raw material due to its manufacturing method, but it is specified by the measurement method described below and is limited to that derived from 4CBA. It's not a thing. Similarly, the terminal methylphenyl group of PBT of the present invention is sometimes referred to as the terminal methyl group derived from p-toluic acid in the PBT raw material due to its manufacturing method, but it is identified by the measurement method described below, and is p-toluic acid. - Not limited to those derived from toluic acid.

The terminal carboxyl group concentration of PBT of the present invention is usually 0.1 to 50 equivalents/ton, preferably 1 to 40 equivalents/ton, more preferably 5 to 30 equivalents/ton, particularly preferably 7 to 25 equivalents/ton. most preferably from 10 to 19 equivalents/ton. If the terminal carboxyl group concentration is too high, hydrolysis resistance may deteriorate. In order to make this value less than 0.1 equivalent/ton, economically disadvantageous conditions such as, for example, a very small production scale must be adopted, which is not realistic.

The terminal hydroxyl group concentration of PBT of the present invention is usually 43 to 120 equivalents/ton, preferably 50 to 110 equivalents/ton, more preferably 55 to 100 equivalents/ton, particularly preferably 60 to 90 equivalents/ton. If the terminal hydroxyl group concentration is too high, a large amount of THF will be generated due to decomposition of the terminal hydroxyl groups during melting during molding or the like. For example, THF is generated during molding, and the molded product has appearance defects such as silver due to THF, which is undesirable. If the terminal hydroxyl group concentration is at least the above lower limit, PBT can be easily manufactured.

The terminal vinyl group concentration of PBT of the present invention is usually 0.1 to 13 equivalents/ton, preferably 0.5 to 12 equivalents/ton, and more preferably 1 to 11 equivalents/ton. If the terminal vinyl group concentration is too high, it causes deterioration in color tone. Since the terminal vinyl group concentration tends to further increase depending on the thermal history during molding, the deterioration in color tone becomes even more pronounced when the molding temperature is high or when the manufacturing method includes a recycling process. If the terminal vinyl group concentration is at least the above lower limit, PBT can be easily manufactured.

The terminal acetyl group concentration, terminal butyraldehyde group concentration, terminal benzaldehyde group concentration, terminal methylphenyl group concentration, terminal carboxyl group concentration, terminal hydroxyl group concentration, and terminal vinyl group concentration of PBT are described in the Examples section below. It can be determined using the method described.

(Cobalt/manganese content)
The PBT of the present invention may contain cobalt and manganese derived from the catalyst used in the production of terephthalic acid. The amounts of cobalt and manganese in the PBT of the present invention are each preferably at most 0.20 ppm, more preferably at most 0.15 ppm, from the viewpoint of color tone and thermal stability. This value is more preferably 0.10 ppm or less, particularly preferably 0.07 ppm or less, and most preferably 0.05 ppm or less. Note that even if cobalt and manganese are present at 0.01 ppm each, they do not substantially pose a problem.

<Production method of PBT>
In the method for producing PBT of the present invention, it is preferable to use 1,4-butanediol (BDO) described below as a diol component from the viewpoint of ease of obtaining the PBT of the present invention. For example, PBT is produced by mixing a dicarboxylic acid component whose main component is terephthalic acid and a diol component whose main component is BDO at a predetermined ratio with stirring to form a raw material slurry; A step of heating under pressure or reduced pressure to undergo an esterification reaction to obtain a PBT low polymer (oligomer), followed by a step of gradually reducing the pressure of the obtained oligomer and heating to perform a melt polycondensation reaction to obtain a PBT low polymer. Manufactured through a condensation process.

As an example of the process of forming oligomers, a single esterification reaction tank or a multi-stage reaction apparatus in which multiple esterification reaction tanks are connected in series is used to remove water and excess diol components produced in the reaction from the system. While removing the dicarboxylic acid component, the esterification reaction rate (proportion of esterification by reacting with the diol component) is carried out until the esterification reaction rate (the proportion of the carboxyl groups reacted with the diol component and esterified) of the raw dicarboxylic acid component reaches 90% or more, with or without using a catalyst. Another example is a method of performing an esterification reaction under normal pressure or reduced pressure to obtain an oligomer.

Generally, the temperature of the esterification reaction is preferably 212 to 233°C, more preferably 220 to 230°C, and even more preferably 223 to 228°C. If the esterification reaction temperature is low, the esterification reaction tends to be delayed, and if the esterification reaction temperature is high, THF tends to increase and the molar ratio of raw materials consumed tends to increase.
The pressure of the esterification reaction is preferably about 10 to 133 kPa, and the residence time is preferably about 1 to 4 hours.

As an example of the melt polycondensation process, a single melt polycondensation tank or a plurality of melt polycondensation tanks are connected in series, for example, the first stage is a complete mixing type reactor equipped with a stirring blade, and the Using a multi-stage reactor consisting of horizontal plug-flow type reactors with stirring blades in the second and third stages, the diol produced is distilled out of the system while heating under reduced pressure in the presence of a catalyst. One example is how to do it.

Usually, the temperature of the polycondensation reaction is 210 to 280°C, preferably about 220 to 250°C, and the pressure is 27 kPa or less, preferably 13 kPa or less. The reaction tank may be used alone or in multiple stages, but in order to suppress discoloration and deterioration, and to suppress the increase in end groups such as vinyl groups, at least one reaction tank has a high pressure of usually 1.3 kPa or less, preferably 0.3 kPa or less. It is best to do this under vacuum. In order to increase the reaction rate, conditions such as increasing the degree of pressure reduction, increasing the rate of temperature increase, and increasing the rate of renewal of the reaction liquid level may be adopted.

PBT obtained by the polycondensation reaction is usually extracted in the form of a strand or sheet from an outlet provided at the bottom of the polycondensation reaction tank, and then cut with a cutter while or after cooling with water to form pellets or sheets. It is made into a granular body such as a chip (for example, about 3 to 10 mm in length).

(Raw material 1,4-butanediol (BDO))
As BDO which is the main component of the diol component for producing PBT of the present invention, BDO obtained by the following Reppe method is preferably used.
Acetylene and formaldehyde are reacted to produce 1,4-butynediol, and then 1,4-butynediol is hydrogenated to produce 1,4-butenediol. Furthermore, the obtained 1,4-butenediol is hydrogenated to obtain BDO (BDO composition). This BDO composition can be purified to a high degree by further performing precision distillation in accordance with the required quality of BDO products in the purification process.

Regarding BDO used as a raw material for PBT of the present invention, the content of 2-methyl-1,4-butanediol and 2-(4-hydroxybutyloxy)tetrahydrofuran is adjusted by intensifying precision distillation or blending.

The content of 2-methyl-1,4-butanediol in the raw material BDO used for producing PBT of the present invention is usually 250 to 1000 mass ppm, preferably 300 to 800 mass ppm, and more preferably 350 to 700 mass ppm. preferable.
2Me1,4-BDO is partially reacted and incorporated into oligomers during the esterification reaction, and part is dehydrated and cyclized during the esterification reaction to form 3-methyltetrahydrofuran (hereinafter abbreviated as "3MTHF"). ) is distilled out of the system as an esterified distillate.
If the content of 2Me1,4-BDO in the raw material BDO exceeds the above upper limit, the amount copolymerized will increase, resulting in a decrease in the melting point of the resulting PBT, deterioration in the color tone b value, deterioration in solution haze, and deterioration of the resulting molded product. This is undesirable as it causes an increase in fish eyes. Furthermore, 2Me1,4-BDO is dehydrated and cyclized, resulting in an increase in 3MTHF distilled out in the esterification reaction, making it difficult to separate it from THF by distillation, which is not preferable for purifying and recovering THF.
On the other hand, BDO with a 2Me1,4-BDO content below the above lower limit is BDO produced by the butadiene method, and the resulting PBT has residual terminal acetyl groups, and as mentioned above, there is a problem due to the production of acetic acid. happen.

In addition, 2-(4-hydroxybutyloxy)tetrahydrofuran (hereinafter sometimes abbreviated as "BGTF") in the raw material BDO is hydrolyzed to produce 2-hydroxytetrahydrofuran, which undergoes an acetal reaction during the ester reaction to produce 4- It becomes hydroxybutanal and is incorporated into PBT. If the BGTF content of the raw material BDO is too high, the amount of terminal butyraldehyde in the resulting PBT will increase, resulting in an unfavorable color tone. The upper limit of the BGTF content in the raw material BDO is 1500 mass ppm or less, preferably 1200 mass ppm or less, more preferably 950 mass ppm or less, and the lower limit is 10 mass ppm or more, preferably 100 mass ppm or more, more preferably is 150 mass ppm or more, more preferably 500 mass ppm or more.

(Raw material terephthalic acid (TPA))
The raw dicarboxylic acid component for obtaining the PBT of the present invention is not particularly limited, and commonly known terephthalic acid can be used. Preferably, terephthalic acid containing specific amounts of 4CBA and p-toluic acid is used. That is, terephthalic acid having a 4CBA content of 5 to 25 ppm, preferably 6 to 20 ppm, and a p-toluic acid content of 85 to 185 ppm, preferably 105 to 180 ppm, more preferably 142 to 175 ppm is used. When the contents of 4CBA and p-toluic acid are out of the above range, the resulting PBT tends to have a strong yellow tinge or a strong bluish tinge.

Further, the raw material terephthalic acid preferably has an acetic acid content of 200 ppm or less, more preferably 150 ppm or less, and even more preferably 130 ppm. When PBT is produced using terephthalic acid in which the acetic acid content is below the above upper limit, less acetic acid is generated from the produced PBT, which is preferable. The lower limit of the acetic acid content of the raw material terephthalic acid is generally preferably about less than 10 ppm.
Terephthalic acid having a content of 4CBA, p-toluic acid, and further acetic acid within the above range can be obtained by adjusting the purification conditions in the terephthalic acid manufacturing process.

The raw material terephthalic acid used in the production of PBT of the present invention may contain cobalt and manganese, which are residual catalysts from the production of terephthalic acid. The amounts of cobalt and manganese in the raw material terephthalic acid are each preferably 0.20 ppm or less, more preferably 0.15 ppm or less, and 0.10 ppm or less from the viewpoint of the color tone and thermal stability of the PBT obtained. It is more preferably at most 0.07 ppm, most preferably at most 0.07 ppm. Even if cobalt and manganese are present in terephthalic acid at 0.01 ppm each, they do not substantially pose a problem.

(polycondensation catalyst)
When polycondensing an oligomer obtained by an esterification reaction between a diol component and a dicarboxylic acid component, a titanium compound and preferably a metal compound of group 2A of the periodic table are usually used as a catalyst.
These catalyst components may be used in the esterification reaction and the polycondensation reaction may be carried out as is, or they may not be used in the esterification reaction, or only the titanium catalyst may be used and the remaining catalyst components may be used in the polycondensation reaction. You can add it in stages. Furthermore, in the esterification reaction, a part of the amount of catalyst finally used can be used and added as appropriate as the polycondensation reaction progresses. In any case, in the present invention, the PBT finally obtained necessarily contains titanium and preferably a metal from group 2A of the periodic table, the amount of which will be described later.

Specific examples of the titanium compound include inorganic titanium compounds such as titanium oxide and titanium tetrachloride, titanium alcoholates such as tetramethyl titanate, tetraisopropyl titanate, and tetrabutyl titanate, and titanium phenolates such as tetraphenyl titanate. These may be used alone or in combination of two or more.
Among these, tetraalkyl titanates are preferred, and among these, tetrabutyl titanate is preferred.

In order to adjust the terminal acetyl concentration, terminal butyraldehyde concentration, and 2-methyl-1,4-butanediol copolymerization amount of the obtained PBT to the specified ranges of the present invention, the content of the titanium (Ti) catalyst is The mass ratio of Ti) atoms to PBT is preferably 35 to 90 ppm. The Ti content of PBT is more preferably 45 to 69 ppm, still more preferably 52 to 68 ppm. If the Ti content is higher than this range, the amount of 2-methyl-1,4-butanediol and terminal butyraldehyde to be copolymerized will increase, resulting in a lower melting point and unfavorable color tone. Furthermore, if the Ti content is too high, the hydrolysis resistance of the obtained PBT and solution haze will deteriorate, and fish eyes will increase in the obtained molded product. On the other hand, when the Ti content is lower than the above range, the amount of copolymerized 2-methyl-1,4-butanediol and the amount of terminal butyraldehyde decrease, especially when the amount of 2-methyl-1,4-butanediol is copolymerized. As the amount of diol copolymerized decreases, the amount of 3MTHF that undergoes cyclodehydration and distillation in the esterification reaction increases. As a result, distillation separation from THF becomes difficult, which is not preferable for purifying and recovering THF. In addition, polymerizability deteriorates.

Specific examples of metal compounds of group 2A of the periodic table in the present invention include various compounds of beryllium, magnesium, calcium, strontium, and barium. Calcium compounds are preferred, and magnesium compounds, which have excellent catalytic effects, are particularly preferred. Specific examples of the magnesium compound include magnesium acetate, magnesium hydroxide, magnesium carbonate, magnesium oxide, magnesium alkoxide, magnesium hydrogen phosphate, and the like. Specific examples of calcium compounds include calcium acetate, calcium hydroxide, calcium carbonate, calcium oxide, calcium alkoxide, calcium hydrogen phosphate, and the like. These Group 2A metal compounds of the periodic table may be used alone or in combination of two or more.
Among these, magnesium acetate is preferred.

The content of the metal of group 2A of the periodic table in the PBT of the present invention is not particularly limited, but it is preferably 3 to 150 ppm in terms of mass ratio of metal atoms of group 2A of the periodic table to PBT. This amount is more preferably 5 ppm or more, and even more preferably 10 ppm or more. Moreover, this amount is more preferably 50 ppm or less, still more preferably 40 ppm or less, particularly preferably 30 ppm or less, and most preferably 15 ppm or less. If the content of the Group 2A metal in the periodic table is too high, color tone, hydrolysis resistance, etc. will deteriorate, and if it is too low, polymerizability will deteriorate. When using an acetate of a metal from Group 2A of the Periodic Table, the acetic acid source enters the reaction system, so the amount of metal from Group 2A of the Periodic Table of PBT is preferably 15 ppm or less.

The molar ratio of titanium atoms to periodic table 2A group metal atoms (periodic table 2A group metal/titanium) contained in the PBT of the present invention is usually 0.01 to 100, preferably 0.1 to 10, more preferably 0. 3 to 3, more preferably 0.3 to 1.5.

The content of metals such as titanium atoms in PBT can be measured using methods such as atomic luminescence, atomic absorption, and inductively coupled plasma (ICP) after recovering the metals in the polymer using methods such as wet ashing. Can be done.

In the production of PBT of the present invention, in addition to the titanium compounds and metal compounds of group 2A of the periodic table, antimony compounds such as antimony trioxide, germanium compounds such as germanium dioxide and germanium tetroxide, manganese compounds, zinc compounds, zirconium compounds, etc. You may also use reaction aids such as phosphorus compounds, cobalt compounds, orthophosphoric acid, phosphorous acid, hypophosphorous acid, polyphosphoric acid, esters and metal salts thereof, sodium hydroxide, sodium benzoate, and the like.

(BDO/TPA consumption molar ratio)
In order to adjust the amount of 2-methyl-1,4-butanediol copolymerized, terminal acetyl group concentration, and terminal butyraldehyde concentration of the obtained PBT to the specified range of the present invention, in the PBT manufacturing process, 2-methyl-1,4-butanediol in BDO is The content of methyl-1,4-butanediol and 2-(4-hydroxybutyloxy)tetrahydrofuran is set to a preferable range, and the molar ratio of consuming 1,4-butanediol and terephthalic acid ([BDO consumed (mol)] /[Consumed TPA (mol)], hereinafter sometimes referred to as "BDO/TPA consumption molar ratio") is preferably 1.15 or more and less than 2.00, and this molar ratio is 1.18 Above, 1.90 or less is more preferable, and 1.20 or more and 1.80 or less are still more preferable. When this molar ratio is less than 1.15, there is a tendency to reduce esterification reactivity and deactivate the catalyst, and when it is more than 2.00, thermal efficiency tends to decrease and by-products such as tetrahydrofuran increase. . This molar ratio can be controlled by the BDO/TPA molar ratio used in the esterification reaction, the amount of Ti catalyst, and the esterification reaction temperature. The BDO/TPA molar ratio used in the esterification reaction, the amount of Ti catalyst, and the esterification reaction temperature act in a complex manner on the consumed BDO/TPA molar ratio.
The above "BDO/TPA consumption molar ratio in the system during the esterification reaction" refers to BDO supplied together with terephthalic acid as a raw material slurry, BDO supplied independently, and BDO supplied as a catalyst solvent. This is the total amount of BDO used, etc., that enters the reaction tank from outside the reaction tank. Note that if the BDO/TPA consumption molar ratio is smaller than the BOD/TPA molar ratio added to the esterification reaction tank, excess BDO will be recycled and used.

<Physical properties of PBT>
(intrinsic viscosity)
When the PBT of the present invention is used for compounding or injection molding, it is preferable that the intrinsic viscosity of PBT is usually 0.6 to 1.3 dL/g. If the intrinsic viscosity is less than 0.6 dL/g, the mechanical strength of the molded product will be insufficient, and if it exceeds 1.3 dL/g, the melt viscosity will increase, fluidity will deteriorate, and moldability will deteriorate. There is a tendency. The intrinsic viscosity of the PBT of the present invention is more preferably 0.65 to 1.26 dL/g, and even more preferably 0.7 to 1.2 dL/g.

Furthermore, when the PBT pellets of the present invention are used for extrusion of films, sheets, or filaments, the intrinsic viscosity of PBT is usually 1.00 to 1.60 dL/g, preferably 1.03 to 1.50 dL/g, More preferably 1.05 to 1.45 dL/g, particularly preferably 1.10 to 1.40 dL/g, particularly preferably 1.15 to 1.35 dL/g. If the intrinsic viscosity is less than 1.00 dL/g, extrusion moldability will deteriorate, leading to resin drawdown and molding loss, resulting in insufficient mechanical strength of extruded products such as films, and melt viscosity. The fluidity becomes too high, resulting in poor extrusion moldability. On the other hand, when the intrinsic viscosity exceeds 1.60 dL/g, the melt viscosity increases, fluidity deteriorates, and extrusion moldability tends to deteriorate.

The intrinsic viscosity of PBT can be determined by the method described in the Examples section below.

(melting point)
The melting point of PBT of the present invention is usually 224.0 to 225.0°C. If the melting point is lower than this range, the heat resistance will be poor, which is not preferable. The higher the melting point, the higher the heat resistance, which is preferable.
The melting point of PBT can be determined by the method described in the Examples section below.

(cooling down crystallization temperature)
The cooling crystallization temperature of PBT of the present invention is usually 160 to 200°C, preferably 170 to 195°C, more preferably 175 to 190°C.
The cooling crystallization temperature in the present invention is the temperature of the exothermic peak due to crystallization that appears when the resin is cooled from a molten state at a cooling rate of 20° C./min using a differential scanning calorimeter. The cooling-down crystallization temperature corresponds to the crystallization rate, and the higher the cooling-down crystallization temperature, the faster the crystallization rate. Therefore, during injection molding, cooling time can be shortened and productivity can be increased. When the cooling-down crystallization temperature is low, it takes time for crystallization during injection molding, and the cooling time after injection molding has to be lengthened, which tends to lengthen the molding cycle and reduce productivity.
The cooling crystallization temperature of PBT can be determined by the method described in the Examples section below.

(solution haze)
The solution haze of PBT of the present invention is not particularly limited, but is usually 10% or less, preferably 5% or less, more preferably 3% or less, still more preferably 1% or less. When the solution haze is high, the amount of foreign matter tends to increase, which significantly reduces commercial value. Solution haze tends to increase when titanium catalyst deactivation is large.
The solution haze of PBT can be determined by the method described in the Examples section below.

<Compounding>
The PBT of the present invention can be made into a compound product by adding various additives or compounding materials as necessary at the PBT production stage or after PBT production.

For example, as an antioxidant, 2,6-di-t-butyl-4-octylphenol, pentaerythrityl-tetrakis [3-(3',5'-t-butyl-4'-hydroxyphenyl)propionate], etc. Phenol compounds, thioether compounds such as dilauryl-3,3'-thiodipropionate, pentaerythrityl-tetrakis (3-laurylthiodipropionate), triphenylphosphite, tris(nonylphenyl)phosphite, tris(2 , 4-di-t-butylphenyl) phosphite, paraffin wax, microcrystalline wax, polyethylene wax as a mold release agent, long-chain fatty acids and their esters such as montanic acid and montanic acid esters, and silicone. Oil etc. may be added.

Moreover, a reinforcing filler can be blended into the PBT of the present invention. Examples of reinforcing fillers include, but are not limited to, inorganic fibers such as glass fibers, carbon fibers, silica/alumina fibers, zirconia fibers, boron fibers, boron nitride fibers, silicon nitride potassium titanate fibers, metal fibers, and aromatic fibers. Examples include organic fibers such as polyamide fibers and fluororesin fibers. These reinforcing fillers can also be used in combination of two or more types. Among the above-mentioned reinforcing fillers, inorganic fillers, particularly glass fibers, are preferably used.

When the reinforcing filler is an inorganic fiber or an organic fiber, the average fiber diameter is not particularly limited, but is usually 1 to 100 μm, preferably 2 to 50 μm, more preferably 3 to 30 μm, particularly preferably 5 to 20 μm. . Further, the average fiber length is not particularly limited, but is usually 0.1 to 20 mm, preferably 1 to 10 mm.

In order to improve the interfacial adhesion with PBT, the reinforcing filler is preferably used after being surface treated with a binding agent or a surface treatment agent. Examples of the sizing agent or surface treatment agent include functional compounds such as epoxy compounds, acrylic compounds, isocyanate compounds, silane compounds, and titanate compounds. The reinforcing filler can be surface-treated in advance with a sizing agent or a surface treatment agent, or can be surface-treated by adding a sizing agent or a surface treatment agent during the preparation of the PBT composition. The amount of reinforcing filler added is usually 150 parts by mass or less, preferably 5 to 100 parts by mass, per 100 parts by mass of PBT.

The PBT of the present invention may contain other fillers together with the reinforcing filler. Other fillers to be mixed include, for example, plate-shaped inorganic fillers, ceramic beads, asbestos, wollastonite, talc, clay, mica, zeolite, kaolin, potassium titanate, barium sulfate, titanium oxide, silicon oxide, and oxide. Examples include aluminum and magnesium hydroxide. These can also be used in combination of two or more types. By blending the plate-like inorganic filler, it is possible to reduce the anisotropy and warpage of the resulting molded product. Examples of the plate-like inorganic filler include glass flakes, mica, and metal foil. Among these, glass flakes are preferably used.

Furthermore, a flame retardant can be added to the PBT of the present invention in order to impart flame retardancy. The flame retardant is not particularly limited, and examples thereof include organic halogen compounds, antimony compounds, phosphorus compounds, other organic flame retardants, and inorganic flame retardants. Examples of the organic halogen compound include brominated polycarbonate, brominated epoxy resin, brominated phenoxy resin, brominated polyphenylene ether resin, brominated polystyrene resin, brominated bisphenol A, polypentabromobenzyl acrylate, and the like. Examples of the antimony compound include antimony trioxide, antimony pentoxide, and sodium antimonate. Examples of the phosphorus compound include phosphoric acid ester, polyphosphoric acid, ammonium polyphosphate, red phosphorus, and the like. Examples of other organic flame retardants include nitrogen compounds such as melamine and cyanuric acid. Examples of other inorganic flame retardants include aluminum hydroxide, magnesium hydroxide, silicon compounds, and boron compounds. These can also be used in combination of two or more types.

The PBT of the present invention may contain conventional additives other than those mentioned above, if necessary. Such additives are not particularly limited, and include, for example, stabilizers such as antioxidants and heat-resistant stabilizers, as well as lubricants, mold release agents, catalyst deactivators, crystal nucleating agents, and crystallization promoters. It will be done. These additives can be added during or after polymerization. Furthermore, in order to impart desired performance to PBT, stabilizers such as ultraviolet absorbers and weathering stabilizers, colorants such as dyes and pigments, antistatic agents, foaming agents, plasticizers, impact resistance modifiers, etc. are added. can do.

The PBT of the present invention may optionally include thermoplastics such as polyethylene, polypropylene, polystyrene, polyacrylonitrile, polymethacrylic acid ester, ABS resin, polycarbonate, polyamide, polyphenylene sulfide, polyethylene terephthalate, liquid crystal polyester, polyacetal, polyphenylene oxide, etc. Thermosetting resins such as resins, phenolic resins, melamine resins, silicone resins, and epoxy resins can be blended. These thermoplastic resins and thermosetting resins can also be used in combination of two or more types.

The method of blending the various additives and additional components such as resins is not particularly limited, but a method of melting and kneading them into PBT pellets using a single-screw or twin-screw extruder equipped with equipment that can devolatilize from a vent port is possible. preferable. Each component, including additional components, can be fed to the kneader all at once or sequentially. Furthermore, two or more components selected from each component can be mixed in advance, including additional components.

When the PBT of the present invention is used as at least a part of the raw material and is melt-kneaded using an extruder as described above to produce a compound product, it is preferable that the kneading resin temperature in the extruder is 320° C. or lower. If the kneaded resin temperature is 320° C. or lower, thermal decomposition tends to be suppressed. From this point of view, the temperature of the kneaded resin in the extruder is more preferably 310°C or lower, and even more preferably 300°C or lower. On the other hand, from the viewpoint of ensuring uniform meltability, the temperature of the kneaded resin in the extruder is preferably 240°C or higher, particularly 250°C or higher.

<Molding method>
The method of molding the PBT of the present invention and the compound product containing the PBT of the present invention is not particularly limited, and may be a molding method generally used for thermoplastic resins, such as injection molding, blow molding, extrusion molding, press molding, etc. The following molding methods can be applied.
In any molding method, it is preferable that the temperature of the molten resin during molding is 280° C. or lower from the viewpoint of suppressing thermal decomposition of PBT, color tone, and other aspects.

(injection molding)
Among the above molding methods, when used for automobile parts and electrical/electronic parts, it is preferable to use an injection molding machine.
The temperature of the molten resin during injection molding is preferably 280° C. or lower. It is preferable that the temperature of this molten resin is 280° C. or lower, since thermal decomposition is suppressed. From this viewpoint, the temperature of the molten resin during injection molding is more preferably 275°C or lower, and even more preferably 270°C or lower. On the other hand, from the viewpoint of ensuring uniform meltability, the temperature of the molten resin during injection molding is preferably 240°C or higher, particularly 250°C or higher.

(extrusion molding)
The PBT of the present invention has particularly low coloration and excellent transparency when thin, so it has a remarkable improvement effect in applications such as extrusion molded sheets, films, and monofilaments (including fibers).

The molding temperature for films, sheets, and filaments using PBT of the present invention is not particularly limited, but if the molding temperature, that is, the molten resin temperature is high, the color tone will deteriorate, the terminal carboxyl group concentration will increase, and the hydrolysis resistance will deteriorate. Since this causes deterioration, the temperature is usually 280°C or lower, preferably 265°C or lower, and more preferably 260°C or lower. The molded products (films, sheets, filaments) using PBT of the present invention do not contain high viscosity substances that cause fish eyes in the raw PBT pellets, so even when molded at the low temperature mentioned above, The occurrence of fish eyes is small, and it is possible to both reduce fish eyes and prevent thermal deterioration during molding, which has been difficult until now.
However, from the viewpoint of ensuring uniform meltability, the temperature of the molten resin is preferably 240°C or higher, particularly 250°C or higher.

<Use of recycled materials>
When molding the PBT of the present invention or the above-mentioned compound product, recycled raw materials may be used as at least a portion of the molding material from the viewpoints of waste reduction, cost reduction, and improvement effects of the present invention. Even in this case, if the proportion of recycled raw materials used is below a predetermined value, the decline in physical properties is within an acceptable range, which is preferable.

Here, recycled raw materials include parts other than the molded product produced when the PBT pellets of the present invention are molded, parts with no commercial value produced during manufacturing, such as film edges or sheet edges, etc. These include raw materials and materials. In this case, the runners, spools, film edges, sheet edges, etc. may be recycled in their original shape, or if there is a problem with production, such as having a negative impact on the ability to penetrate into the raw material feeder or the screw of the molding machine. If this occurs, processing such as granulation, cutting, and pulverization may be performed.

It is preferable that the proportion of recycled raw materials in raw materials or materials satisfies the following formula (1), where A is the mass of all raw materials or all materials including recycled raw materials, and C is the mass of recycled raw materials. Among these, it is recommended that the following equation (2), especially the following equation (3), be satisfied.
0.01 ≦ C/A ≦ 0.5 (1)
0.05 ≦ C/A ≦ 0.4 (2)
0.10≦C/A≦0.3 (3)

If the ratio of recycled raw materials is high, this will lead to deterioration in color tone, increase in foreign matter, and increase in the concentration of terminal carboxyl groups, while if the ratio of recycled raw materials is low, sufficient effects such as waste reduction and cost reduction may not be achieved. do not have.

EXAMPLES Hereinafter, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited to the following Examples unless the gist thereof is exceeded.
The methods for measuring physical properties and evaluation items adopted in the following examples are as follows.

(1) Intrinsic viscosity (IV)
It was determined using an Ubbelohde viscometer as follows. That is, using a mixed solvent of phenol/tetrachloroethane (mass ratio 1/1), the number of seconds for a polymer solution with a concentration of 1.0 g/dL and only the solvent to fall was measured at 30°C, and was determined from the following formula. .
IV=((1+4K _H η _sp ) ^0.5 -1)/(2K _H・C)
(However, η _sp =η ₀ −1, η is the number of seconds the polymer solution falls, η ₀ is the number of seconds the solvent falls, C is the polymer solution concentration (g/dL), and K _H is Huggins' constant. , 0.33 was adopted.)

(2) Titanium concentration PBT was wet-decomposed using high-purity sulfuric acid and nitric acid for the electronic industry, and measured using a high-resolution ICP (Inductively Coupled Plasma)-MS (Mass Spectrometer) (manufactured by Thermoquest).

(3) 2Me1,4-BDO copolymerization amount, terminal acetyl group concentration, terminal butyraldehyde group concentration, terminal vinyl group concentration, terminal hydroxyl group concentration, terminal benzaldehyde group concentration, terminal methylphenyl group concentration Contains a trace amount of tetramethylsilane PBT was dissolved in a mixed solvent of deuterated chloroform/deuterated hexafluoroisopropanol/deuterated pyridine (21/9/1 volume ratio), and ^{a 1} H NMR spectrum was measured using an AVANCE NEO spectrometer (manufactured by Bruker). The standard for chemical shift was that the signal of tetramethylsilane was 0.00 ppm.

(4) Terminal carboxyl group concentration Determined by dissolving 0.5 g of PBT or oligomer in 25 mL of benzyl alcohol and titrating the solution using a 0.01 mol/L solution of sodium hydroxide in benzyl alcohol.

(5) Melting point (Tm) and cooling crystallization temperature Using a PerkinElmer differential scanning calorimeter "Model DSC7", the temperature was raised from room temperature to 300°C at a heating rate of 20°C/min, and then the temperature was lowered at a rate of 20°C. The temperature was lowered to 30° C./min, and the temperature of the exothermic peak was defined as the cooling crystallization temperature. The higher the cooling crystallization temperature, the faster the crystallization rate and the shorter the molding cycle.
Subsequently, the temperature was raised again from room temperature to 300°C at a heating rate of 20°C/min, and the temperature of the endothermic peak at the time of heating again was taken as the melting point.

(6) Color Tone Evaluation was made using the L, a, b color system using a color difference meter "Model Z-300A" manufactured by Nippon Denshoku Co., Ltd. The lower the b value, the less yellowish the color, which is preferable. However, when the b value is lower than -2.2, although the yellowness is less, the color tone becomes more bluish and unfavorable.
The b value is preferably in the range of -2.2 to 1.5, more preferably -2.1 to 1.3, even more preferably -2.0 to 1.2.

(7) Amount of acetic acid generated PBT pellets vacuum-dried at 120°C for 8 hours were filled into a melt indexer at 270°C, melted for 10 minutes, extruded, cooled, and immediately placed in an aluminum moisture-proof bag. The container was sealed to prevent the generated components from evaporating and escaping.
Acetic acid was measured in the following manner using a thermal desorption tube (manufactured by Gestel, TDU tube) and a transport adapter for TDU that had been dried in a dryer at 200° C. for 30 minutes in advance.
50 (±2) mg of the melt-heat treated sample was accurately weighed and inserted into the TDU tube. After introducing this TDU tube into a thermal desorption device ("TDU" manufactured by Gestel) at 40°C, the inside of the tube was replaced with helium and the temperature was increased at 12°C/sec. The temperature was raised to 250° C. at a rate of 250° C., and heat extraction was performed for 10 minutes. During this thermal extraction, volatile components generated from the sample were collected by cooling a GC inlet filled with quartz wool ("CIS4" manufactured by Gestel) to -150°C. Here, an empty TDU tube into which no sample had been inserted was treated in the same manner as a blank. The components cooled and collected at the GC injection port are vaporized by rapidly heating the collection part to 250°C and introduced into the GC column for GC/MS (Agilent's "7890GC"/Agilent's "5977MSD"). Measurement was performed to confirm the amount of acetic acid. The smaller the amount of acetic acid generated, the more preferable it is.

(8) Concentration of acetic acid in distilled waste water Dissolve 1 to 20 g of sample in water and titrate to the end point using an automatic titrator using 0.1N KOH solution as the titrant, and measure from the titration amount from the start of titration to the end point. Acetic acid in the liquid was calculated.

(9) Cobalt (Co) and manganese (Mn) content 1.0 g of terephthalic acid or PBT sample was weighed in a platinum crucible, and after adding 5 mL of high-purity sulfuric acid for the electronic industry, carbide was generated by heating. At this time, addition of sulfuric acid was repeated until the carbide was completely generated. After incinerating the generated char at 800° C., it was diluted with 2 mL of high-purity nitric acid for the electronic industry. The metal elements in this solution were quantified using a graphite furnace atomic absorption spectrophotometer (“GF-AAS” manufactured by Varian Technologies Japan Limited) and converted into the amount (ppm) per terephthalic acid or PBT.

(10) Content of 4CBA and p-TA in terephthalic acid A sample was dissolved in a 2N ammonia aqueous solution, diluted to a predetermined concentration with ultrapure water, and then measured using high performance liquid chromatography equipped with an ODS column.

(11) Acetic acid content in terephthalic acid A sample was dissolved in a 2N potassium hydroxide aqueous solution, acid-precipitated with a phosphoric acid aqueous solution, filtered through a filter paper, and the acetic acid contained in the filtrate was removed using a DB-FFAP capillary column. Quantification was performed using gas chromatography. An aqueous propionic acid solution was used as an internal standard substance.

(12) Content of 2Me1,4-BDO, 1,4HAB, and BGTF in 1,4-butanediol A polar column (“DB-WAX” manufactured by J&W Co., Ltd. ), and the content of each peak component contained in BDO was determined by the modified area percentage method calculated from the effective carbon coefficient. Details of the GC conditions are as follows.
Conditions (polar column)
・Analysis column: J&W DB-WAX, 60m x 0.320mmid, df=0.5μm
・Column flow rate: 1mL/min
・Split ratio: 1/90
・Oven temperature: 70℃ (15min) → 10℃/min → 170℃ (45min)
・Sample chamber, detector temperature: 240℃
・Injection volume: 1mL
・Carrier gas: Nitrogen

(13) 3M THF concentration of esterification distillate Correction calculated from the effective carbon coefficient using a non-polar column (“DB-1” manufactured by J&W) using a gas chromatography analyzer (GC-2025 type manufactured by Shimadzu Corporation) The content of each peak component contained in BDO was determined by the area percentage method.
Conditions (non-polar column)
・Column: J&WDB-1, 60m x 0.25mmid, df=1μm
・Column temperature: 50°C (7 min) → 10°C/min → 250°C (20 min)
・Split ratio: 1/100
・Sample chamber, detector temperature: 240℃
・Injection volume: 0.8μL
- Carrier gas: Nitrogen In addition, the moisture contained in the sample was measured by the following method, the moisture concentration was subtracted from 100%, and the remaining components were calculated by proportionally dividing them into the concentrations of each component calculated by gas chromatography.
That is,
Gas chromatograph component concentration + water concentration = 100% by mass
And so.
The 3MTHF concentration is preferably 500 ppm or less.

(14) Water concentration in esterification distillate It was measured by the Karl Fischer method using Dia Instruments Model CA-200. Aquamicron dehydrated solvent GEX and Aquamicron titrant SS-Z 3mg were used as moisture measurement reagents. 10 μL of the esterification distillate was injected into the device using a microsyringe, and the water concentration was measured.

(15) Concentration of acetic acid in distilled waste water Dissolve 1 to 20 g of sample in water and titrate to the end point using an automatic titrator using 0.1 NKOH solution as the titrant. of acetic acid was calculated.
The acetic acid concentration in the distillation wastewater is preferably 300 ppm or less from the viewpoint of neutralization and equipment corrosion.

(16) Solution haze (HAZE)
After dissolving 2.70 g of PBT in 20 mL of a mixed solvent of phenol/tetrachloroethane = 3/2 (mass ratio) at 110°C for 30 minutes, it was cooled in a constant temperature water bath at 30°C for 15 minutes, and then dissolved in Nippon Denshoku Co., Ltd. Measurement was performed using a thermometer "NDH-300A" with a cell length of 10 mm. The lower the value, the better the transparency.

(17) Measurement of fish eye number PBT was dried at 140°C for 4 hours in a nitrogen atmosphere, and a film was formed using a continuous extrusion film forming device ("ME-20/26V2 & CR-7 &FS-5" manufactured by OCS) under the following conditions. Molding was performed and the number of fish eyes (pieces/m ² ) was measured. The number of fisheyes was measured by automatically counting the number of fisheyes with a length of 16 μm or more present in an area of 1 m ² using a CCD camera attached to the apparatus while forming a film. The smaller this value is, the better the molded appearance is. It is preferable that the number of fish eyes is 1,000 pieces/m ² or less.
・Cylinder temperature (temperatures at four points between the nozzle and the bottom of the hopper):
250℃-250℃-250℃-250℃
・Screw rotation speed: 100rpm
・Resin pressure: 75MPa
・Chill roll temperature: 50℃
・Film thickness: 50μm

[Terephthalic acid]
Terephthalic acid (hereinafter abbreviated as "TPA") used as a raw material for producing PBT in the following examples and comparative examples oxidizes p-xylene in the presence of a catalyst containing cobalt and manganese in an acetic acid solvent. It is manufactured through a process of hydrogenation and further purification by hydrogenation, and during this process, certain amounts of cobalt, manganese, 4CBA, p-TA, and acetic acid may be contained. The content of these terephthalic acids varies depending on the manufacturing conditions, but in the present invention, these terephthalic acids were used alone or in a blend so as to have the values shown in Table 1.
The terephthalic acid used in the blend also includes terephthalic acid that has not undergone hydrogenation reaction.

[1,4-butanediol]
BDO used as a raw material for producing PBT in the following Examples and Comparative Examples was produced as follows.
(1) Reppe method Acetylene and formaldehyde are reacted to produce 1,4-butynediol, and then 1,4-butynediol is hydrogenated to produce 1,4-butenediol. The obtained 1,4-butenediol was further hydrogenated to produce BDO, but in this process, 2-methyl-1,4-butanediol (2Me1,4-BDO), 2-(4-hydroxy A certain amount of butyloxy)tetrahydrofuran (BGTF) may be included. The content of these materials varies depending on the manufacturing conditions, but in the present invention, purification was enhanced by additional distillation to achieve the values shown in Table 1, or they were blended to achieve a predetermined content.

(2) Butadiene method Butadiene is acetoxylated to obtain 1,4-diacetoxybutene, further hydrogenated to obtain 1,4-diacetoxybutane, further hydrolyzed to obtain 1-acetoxy-4-hydroxybutane, and further In the BDO composition obtained by hydrolysis, the hydrolysis process of acetoxy compounds was adjusted. After that, high-boiling substances and light boiling substances are separated by distillation from the crude BDO, and further, 1-acetoxy-4-hydroxybutane (1,4-HAB) and 2-(4-hydroxybutyloxy)tetrahydrofuran ( Crude BDO containing 1,4-HAB and BGTF (BGTF) is distilled from the top of the column along with some BDO, and a BDO composition with adjusted 1,4-HAB and BGTF contents is distilled from the bottom of the column. Obtained. Even after this process, a certain amount of 1,4-HAB and BGTF may still be contained. The contents of 1,4-HAB and BGTF vary depending on the hydrolysis conditions and distillation conditions, but in the present invention, these BDOs were used alone or in a blend so as to have the values shown in Table 1.

[Example 1]
PBT was manufactured in the following manner.
1,4-HAB shown in Table 1 for 1.00 mol of TPA with 4-carboxybenzaldehyde (4CBA), p-toluic acid (p-TA), acetic acid, Co and Mn contents shown in Table 1. , BGTF, 2Me1,4-BDO A slurry containing 1.80 moles of BDO was mixed in an esterification reaction tank equipped with a screw type stirrer filled with PBT oligomer with an esterification rate of 99% (Table 1). (abbreviated as "Es") was continuously supplied to carry out an esterification reaction. A BDO solution containing a tetrabutyl titanate catalyst in an amount such that titanium was 55 ppm based on PBT was supplied to the esterification reaction tank. Additional BDO was supplied to the esterification tank so that the molar ratio of BDO to terephthalic acid was 2.6. The temperature of the reaction tank was 226° C., the pressure was 60 kPa, and the average residence time was 180 minutes.

Next, the PBT oligomer with an esterification rate of 96.5% was continuously transferred to the first polycondensation reaction tank. In the first polycondensation reaction tank, a polycondensation reaction was carried out continuously. The reaction temperature was 230°C, the pressure was 3.9 kPa, and the average residence time was 120 minutes. Next, this product was transferred to a second polycondensation reactor, and a polycondensation reaction was continuously performed. The reaction temperature was 240° C., the pressure was 130 Pa, and the average residence time was 80 minutes.

The obtained polymer is continuously extracted in the form of a strand from the die head through a filter through an extraction line by an extraction gear pump, and cut with a rotary cutter to form PBT pellets (longer diameter: about 3 mm, shorter axis: about 2 mm, A length of about 4 mm) was obtained.

The intrinsic viscosity (IV) of the obtained PBT was 0.85 dL/g. The terminal acetyl group concentration was less than 0.1 equivalent/ton, the terminal butyraldehyde group concentration was 0.06 equivalent/ton, and the amount of 2-methyl-1,4-butanediol copolymerized was 0.030 mol%.
The melting point of this PBT was 224.9°C. When the color tone (b value) of this PBT was measured, it was good at -0.8, and the amount of acetic acid generated after heat treatment at 270° C. for 10 minutes was small at less than 1 ppm.

Note that a distillation operation was performed in a distillation column in order to recover THF from the distillate from the esterification reaction tank. Analysis of the esterification distillate revealed that 3MTHF was 200 ppm. From the viewpoint of the size of an industrial distillation column, reflux ratio, and throughput, 3MTHF is preferable since it is contained as an impurity of 500 ppm or less.
A composition liquid containing THF as a main component was obtained on the low boiling point side (tower top) of the distillation column, and an acetic acid-containing composition liquid containing water as a main component was obtained on the high boiling point side (bottom). The acetic acid concentration in this mixed solution (this mixed solution is referred to as "distilled wastewater") was less than 10 ppm. The content is preferably 300 ppm or less from the viewpoint of corrosion of the material of the distillation column and waste treatment cost. The molar ratio of BDO and TPA consumed was 1.26.
The evaluation results of the obtained PBT are summarized in Table-2.

[Example 2]
In Example 1, PBT was obtained in the same manner as in Example 1 except that terephthalic acid and BDO shown in Table 1 were used, and the conditions shown in Table 1 were changed. Evaluation was performed in the same manner, and the results are shown in Table 2. Indicated. These were preferred as in Example 1.

[Comparative Examples 1 to 4]
In Example 1, PBT was obtained in the same manner as in Example 1 except that terephthalic acid and BDO shown in Table 1 were used, and the conditions shown in Table 1 were changed. Evaluation was performed in the same manner, and the results are shown in Table 2. Indicated.

As shown in Tables 1 and 2, the PBTs of Examples 1 and 2, which met the requirements of the present invention, had good color tone, generated a small amount of acetic acid, and were high quality PBTs.
On the other hand, the PBTs of Comparative Examples 1 to 4 that did not meet the requirements of the present invention were PBTs that were undesirable in any of the following ways, such as low melting point, poor color tone, high fisheye, and high solution haze.
In addition, some PBTs had a high content of 3M THF in the ester distillate (crude THF), making it difficult to recover THF by distillation.

Claims (9)

The terminal acetyl group concentration is less than 0.1 equivalent/ton, the terminal butyraldehyde group concentration is 0.05 to 0.13 equivalent/ton,
A polybutylene terephthalate characterized in that the proportion of structural units derived from 2-methyl-1,4-butanediol in all structural units derived from diol components is 0.020 to 0.080 mol%. The polybutylene terephthalate according to claim 1, characterized in that the terminal benzaldehyde group concentration is 0.03 to 0.07 equivalent/ton and the terminal methylphenyl group concentration is 0.3 to 0.8 equivalent/ton. . In a method for producing polybutylene terephthalate by reacting a terephthalic acid component and 1,4-butanediol,
As the 1,4-butanediol, 1,4-butanediol containing 250 to 1000 mass ppm of 2-methyl-1,4-butanediol and 10 to 1500 mass ppm of 2-(4-hydroxybutyloxy)tetrahydrofuran. The method for producing polybutylene terephthalate according to claim 1 or 2, characterized in that the method uses: The consumption molar ratio of 1,4-butanediol and terephthalic acid component is 1.15 or more and less than 2.00,
The method for producing polybutylene terephthalate according to claim 3, characterized in that polybutylene terephthalate containing 35 to 90 ppm of Ti is produced. The method for producing polybutylene terephthalate according to claim 3, characterized in that, as the terephthalic acid component, terephthalic acid having a 4-carboxybenzaldehyde content of 5 to 25 ppm and a p-toluic acid content of 85 to 185 ppm is used. . A polybutylene terephthalate composition comprising the polybutylene terephthalate according to claim 1 or 2 and an additive. 7. The method for producing a polybutylene terephthalate composition according to claim 6, characterized in that the polybutylene terephthalate and additives are kneaded using an extruder at a kneading resin temperature of 320° C. or lower. A molded article comprising the polybutylene terephthalate composition according to claim 6. 9. The method for producing a molded article according to claim 8, wherein the polybutylene terephthalate composition is molded using a molding machine at a molten resin temperature of 280° C. or lower.