JP4725027B2 - Polybutylene terephthalate - Google Patents

Description

  The present invention relates to polybutylene terephthalate, and more specifically, it is excellent in color tone, thermal stability, transparency, and extrusion moldability, and also has reduced appearance gas and foreign matter during molding, and has a good appearance, monofilament, fiber, The present invention relates to polybutylene terephthalate that can be suitably used for electrical and electronic parts, automobile parts and the like.

  Polybutylene terephthalate, a typical engineering plastics among thermoplastic polyester resins, is easy to mold, mechanical properties, heat resistance, chemical resistance, aroma retention, other physical and chemical properties Because of its excellent characteristics, it is widely used in injection molded products such as automobile parts, electrical / electronic parts, precision equipment parts. In recent years, taking advantage of its excellent properties, it has been widely used in fields such as films, sheets, monofilaments, various cable coatings, bottles, tanks, and fibers.

  In particular, films, sheets, monofilaments, cable coatings, bottles and tanks are often manufactured by extrusion molding and blow molding, and require high molecular weight polybutylene terephthalate having a higher melt viscosity than injection molding. Has been.

  Further, in the above applications, since the commercial value is greatly affected by foreign matters (the foreign matters in the film are sometimes called fish eyes), haze, coloring, and the like, there is a strong demand for reduction or improvement thereof. Foreign substances and haze in polybutylene terephthalate are considered to be caused by a deactivated substance or agglomerated substance of a metal compound added as a catalyst, in addition to a deteriorated resin generally referred to as burns or eyes.

  However, if polybutylene terephthalate having a high melt viscosity as described above is to be produced by melt polycondensation, it is necessary to lengthen the polymerization time, raise the polymerization temperature, or increase the amount of catalyst. On the contrary, coloring tends to be promoted, and foreign matter and haze tend to increase.

  In order to solve the above problems, it is widely practiced to produce polybutylene terephthalate having a high molecular weight by once solidifying polybutylene terephthalate obtained by melt polymerization and solid-phase polymerization at a temperature below its melting point. (For example, see Patent Documents 1 and 2).

  However, performing solid-phase polymerization after melt polymerization means that extra steps are added, which causes a problem that the facilities become excessive and the operation becomes complicated. In addition, obtaining high molecular weight polybutylene terephthalate by solid phase polymerization performed at a temperature lower than that of melt polycondensation means that the polymerization time is greatly increased, and there is a great problem in terms of productivity. In addition, the film produced from polybutylene terephthalate obtained by solid phase polymerization tends to produce fish eyes that are considered to be derived from fine powders or pellets formed during solid phase polymerization and from the skin layer of pellets, and has a commercial value. There is a problem of dropping.

  On the other hand, since ordinary melt molding is performed at a temperature higher than the melting point of polybutylene terephthalate, in the case of conventional polybutylene terephthalate, even if the terminal carboxyl group concentration is reduced by solid phase polymerization, the terminal carboxyl group concentration is increased again by the heat applied during molding. There is a problem of rising. This increase in the terminal carboxyl group concentration is facilitated by titanium contained in polybutylene terephthalate, but it is inextricably linked with the reaction of generating butadiene and tetrahydrofuran, resulting in a problem of increased gas generation during molding. (See, for example, Non-Patent Document 1).

JP-A-9-316183 Japanese Patent Publication No.57-2728 Saturated polyester resin handbook (December 22, 1989, published by Nikkan Kogyo Shimbun, page 304)

  The present invention has been made in view of the above circumstances, and the object thereof is a film, monofilament, which is excellent in color tone, thermal stability, transparency and extrusion moldability, and has reduced gas generation and foreign matter during molding. Another object of the present invention is to provide polybutylene terephthalate that can be suitably used for fibers, electrical and electronic parts, automobile parts and the like.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors have surprisingly found that if the titanium catalyst and the raw material are supplied in a specific manner to perform the esterification reaction, the utilization efficiency of the titanium catalyst As a result, the amount of titanium catalyst used can be remarkably reduced, and as a result, a novel polybutylene terephthalate having a significantly low content of titanium atoms can be obtained, thereby finding that the above problems can be easily solved. The present invention has been completed.

The present invention has been completed based on the above findings. The gist of the present invention is that it is produced by a direct polymerization method, contains titanium, and its amount is 50 ppm or less as titanium atoms, and has an intrinsic viscosity of 1.20 to 20. 2.00 dL / g , terminal carboxyl group concentration is 15 to 50 μeq / g, terminal methoxycarbonyl group concentration is 0.5 μeq / g or less, and terminal vinyl group concentration is 0.5 to 12 μeq / g. Polybutylene terephthalate (except for those having an intrinsic viscosity of 1.20 dL / g ).

  According to the present invention, it is excellent in color tone, thermal stability, transparency, extrusion moldability, and suitable for films, monofilaments, fibers, electrical and electronic parts, automobile parts, etc. with reduced gas and foreign matter during molding. Polybutylene terephthalate that can be used in the present invention is provided.

  Hereinafter, the present invention will be described in detail. The polybutylene terephthalate (hereinafter abbreviated as PBT) of the present invention has a structure in which a terephthalic acid unit and a 1,4-butanediol unit are ester-bonded, and 50 mol% or more of dicarboxylic acid units are composed of terephthalic acid units. It means a polymer in which 50 mol% or more of the diol component is composed of 1,4-butanediol units. The proportion of terephthalic acid units in all dicarboxylic acid units is preferably 70 mol% or more, more preferably 80 mol% or more, particularly preferably 95 mol% or more, and 1,4-butanediol unit in all diol units. The ratio is preferably 70 mol% or more, more preferably 80 mol% or more, and particularly preferably 95 mol% or more. When the amount of terephthalic acid units or 1,4-butanediol units is less than 50 mol%, the crystallization rate of PBT is lowered, and the moldability is deteriorated.

  In the present invention, the dicarboxylic acid component other than terephthalic acid is not particularly limited. For example, phthalic acid, isophthalic acid, 4,4′-diphenyldicarboxylic acid, 4,4′-diphenyletherdicarboxylic acid, 4,4′-benzophenone Aromatic dicarboxylic acids such as dicarboxylic acid, 4,4′-diphenoxyethanedicarboxylic acid, 4,4′-diphenylsulfone dicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 1,2-cyclohexanedicarboxylic acid, 1,3- Aliphatic dicarboxylic acids such as cyclohexanedicarboxylic acid and 1,4-cyclohexanedicarboxylic acid, aliphatic dicarboxylic acids such as malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid and sebacic acid I can list them. These dicarboxylic acid components can be introduced into the polymer skeleton as a dicarboxylic acid or using a dicarboxylic acid derivative such as a dicarboxylic acid ester or a dicarboxylic acid halide as a raw material.

  In the present invention, the diol component other than 1,4-butanediol is not particularly limited. For example, ethylene glycol, diethylene glycol, polyethylene glycol, 1,2-propanediol, 1,3-propanediol, polypropylene glycol, polytetra Methylene glycol, dibutylene glycol, 1,5-pentanediol, neopentyl glycol, 1,6-hexanediol, aliphatic diols such as 1,8-octanediol, 1,2-cyclohexanediol, 1,4-cyclohexanediol , 1,1-cyclohexanedimethylol, 1,4-cyclohexanedimethylol and other alicyclic diols, xylylene glycol, 4,4′-dihydroxybiphenyl, 2,2-bis (4-hydroxyphenyl) propane, bis ( 4- And aromatic diols such as hydroxyphenyl) sulfone.

  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, and alkoxycarboxylic acids. Monofunctional components such as acid, stearyl alcohol, benzyl alcohol, stearic acid, benzoic acid, t-butylbenzoic acid, benzoylbenzoic acid, tricarbaric acid, trimellitic acid, trimesic acid, pyromellitic acid, gallic acid, trimethylolethane Trifunctional or polyfunctional components such as trimethylolpropane, glycerol and pentaerythritol can be used as the copolymerization component.

  The PBT of the present invention is obtained by using a titanium catalyst in the esterification reaction (or transesterification reaction) between 1,4-butanediol and terephthalic acid (or dialkyl terephthalate).

  As the titanium catalyst, a titanium compound is usually used. Specific examples thereof include inorganic titanium compounds such as titanium oxide and titanium tetrachloride, titanium alcoholates such as tetramethyl titanate, tetraisopropyl titanate, and tetrabutyl titanate, and tetraphenyl titanate. Examples include titanium phenolate. Among these, tetraalkyl titanate is preferable, and among them, tetrabutyl titanate is preferable.

  In addition to titanium, tin may be used as a catalyst. Tin is usually used as a tin compound, and specific examples thereof include dibutyltin oxide, methylphenyltin oxide, tetraethyltin, hexaethylditin oxide, cyclohexahexylditin oxide, didodecyltin oxide, and triethyltin hydroxide. , Triphenyltin hydroxide, triisobutyltin acetate, dibutyltin diacetate, diphenyltin dilaurate, monobutyltin trichloride, tributyltin chloride, dibutyltin sulfide, butylhydroxytin oxide, methylstannic acid, ethylstannic acid, butylstannic acid Is mentioned.

  In addition to titanium, magnesium compounds such as magnesium acetate, magnesium hydroxide, magnesium carbonate, magnesium oxide, magnesium alkoxide, magnesium hydrogen phosphate, calcium acetate, calcium hydroxide, calcium carbonate, calcium oxide, calcium alkoxide In addition to calcium compounds such as calcium hydrogen phosphate, antimony compounds such as antimony trioxide, germanium compounds such as germanium dioxide and germanium tetroxide, manganese compounds, zinc compounds, zirconium compounds, cobalt compounds, orthophosphoric acid, phosphorous acid, hypochlorous acid Reaction aids such as phosphoric acid, polyphosphoric acid, phosphorus compounds such as esters and metal salts thereof, sodium hydroxide and sodium benzoate may be used.

  The PBT of the present invention is characterized in that it contains titanium and the amount thereof is 50 ppm or less as titanium atoms. The above value is the weight ratio of atoms to PBT.

  In the present invention, the lower limit of the titanium content is usually 1 ppm, preferably 3 ppm, more preferably 5 ppm, particularly preferably 8 ppm, more preferably 15 ppm. The upper limit of the titanium content is preferably 45 ppm, more preferably 40 ppm, and particularly preferably 33 ppm. When the content of titanium is more than 50 ppm, the color tone, hydrolysis resistance, transparency, moldability and the like deteriorate, and the foreign matter tends to increase. When the content is less than 1 ppm, the polymerizability may deteriorate. is there.

  In the present invention, as described above, a tin catalyst can be used together with a titanium catalyst. Generally, a tin catalyst has a lower catalytic ability than a titanium catalyst, so that it is necessary to increase the amount of addition compared to a titanium catalyst. However, when the amount of the tin catalyst used is too large, the color tone is deteriorated, and tin is also toxic. Therefore, the amount of tin catalyst used is usually 100 ppm or less, preferably 50 ppm or less, more preferably 20 ppm or less, and the most preferred embodiment is that no tin catalyst is used. The content of titanium atoms or the like can be measured using a method such as atomic emission, atomic absorption, Inductively Coupled Plasma (ICP) after recovering the metal in the polymer by a method such as wet ashing.

  The intrinsic viscosity of the PBT of the present invention is required to be 1.20 to 2.00 dL / g, preferably 1.20 to 1.60 dL / g, more preferably 1.30 to 1.50 dL / g, Especially preferably, it is 1.30-1.40. When the intrinsic viscosity is less than 1.20 dL / g, the extrusion moldability deteriorates, leading to resin drawdown and uneven molding, and when it exceeds 2.00 dL / g, the melt viscosity becomes high and the fluidity deteriorates. To do. The intrinsic viscosity is a value measured at 30 ° C. using a mixed solvent of phenol / tetrachloroethane (weight ratio 1/1).

  The terminal carboxyl group concentration of the PBT of the present invention needs to be 15 μeq / g or more, preferably 15 to 50 μeq / g, more preferably 20 to 40 μeq / g, and particularly preferably 20 to 30 μeq / g. When the terminal carboxyl group concentration is too high, the hydrolysis resistance and solid-phase polymerization property of PBT tend to deteriorate. On the other hand, when the terminal carboxyl group concentration is too low, the reactivity with a reactive additive such as an epoxy compound at the time of compounding tends to decrease, or the dyeability tends to deteriorate.

  By the way, even if the terminal carboxyl group concentration of PBT is lowered, if it is increased by heat at the time of kneading or molding, it not only deteriorates the hydrolysis resistance of the product, but also tetrahydrofuran (hereinafter abbreviated as THF), etc. Gas generation may be caused. Therefore, in the PBT of the present invention, the increase in the terminal carboxyl group concentration excluding the hydrolysis reaction upon heat treatment at 245 ° C. for 40 minutes in an inert gas atmosphere is usually 0.1 to 10 μeq / g, preferably 0.8. It is 5 to 5 μeq / g, more preferably 0.5 to 3 μeq / g, and particularly preferably 1 to 2 μeq / g.

  The hydrolysis reaction can be prevented by reducing the water content in the PBT, specifically if it is sufficiently dried, and it does not involve the generation of THF, which is a problem during molding. It is impossible to prevent an increase in the terminal carboxyl group concentration due to a decomposition reaction other than the above by a drying operation. In general, the lower the molecular weight and the higher the titanium concentration in PBT, the greater the increase in the terminal carboxyl group concentration due to thermal decomposition other than hydrolysis.

  In the above evaluation method, the temperature and time were specified because if the temperature is too low or the time is too short, the rate of increase of the terminal carboxyl group concentration is too small, and in the opposite case, it is too large and the evaluation becomes inaccurate. Because. Another reason is that when the evaluation is performed at an extremely high temperature, side reactions other than the generation of the terminal carboxyl group are accompanied and the evaluation becomes inaccurate. Under the heat treatment conditions, the decrease in the number average molecular weight due to reactions other than the hydrolysis reaction caused by the water contained in the PBT can be ignored, and the increase in the terminal carboxyl group concentration due to the hydrolysis reaction is the end before and after the heat treatment. Since the increase in glycol group concentration can be regarded as almost the same as the increase in glycol group concentration, the increase in the terminal carboxyl group concentration due to the thermal decomposition reaction other than the hydrolysis reaction, which is a problem during kneading or molding, is expressed by the following formula (1). You can ask.

Since it is preferable that the hydrolysis reaction is less from the viewpoint of reliability of the thermal decomposition reaction evaluation, the water content of PBT used for the heat treatment is usually recommended to be 300 ppm or less. The terminal glycol group concentration before and after the heat treatment can be quantified by ¹ H-NMR.

  The terminal carboxyl group concentration of PBT can be determined by dissolving PBT in an organic solvent and titrating the solution using an alkali solution such as a sodium hydroxide solution.

Moreover, the terminal vinyl group density | concentration of PBT of this invention is 0.1-15microeq / g normally, Preferably it is 0.5-12microeq / g, More preferably, it is 1-10microeq / g. When the terminal vinyl group concentration is too high, color tone deterioration and solid-phase polymerizability deteriorate. When producing PBT with a large molecular weight or PBT with a low catalyst concentration without reducing productivity, it is generally required to increase the polymerization temperature or lengthen the reaction time. The base concentration tends to increase. The terminal vinyl group concentration can be quantified by dissolving PBT in deuterated chloroform / hexafluoroisopropanol = 7/3 (volume ratio) and measuring ¹ H-NMR.

  In addition to the hydroxyl group, carboxyl group, and vinyl group, a methoxycarbonyl group derived from the raw material may remain at the end of the PBT, particularly when dimethyl terephthalate is used as the raw material. . By the way, the methoxycarbonyl terminal generates methanol, formaldehyde, and formic acid by heat due to solid phase polymerization, kneading, molding, and the like, and particularly when used for foods, these toxicities become a problem. Formic acid also hurts metal molding equipment and vacuum related equipment. Therefore, the terminal methoxycarbonyl group concentration in the present invention is usually 0.5 μeq / g or less, preferably 0.3 μeq / g or less, more preferably 0.2 μeq / g or less, particularly preferably 0.1 μeq / g or less. .

Each terminal group concentration can be quantified by dissolving ¹ PBT in a mixed solvent of deuterated chloroform / hexafluoroisopropanol = 7/3 (volume ratio) and measuring ¹ H-NMR. At this time, in order to prevent overlap with the solvent signal, a very small amount of a basic component such as heavy pyridine may be added.

  The temperature-falling crystallization temperature of the PBT of the present invention is usually 170 to 190 ° C, preferably 172 to 185 ° C, more preferably 175 to 180 ° C. The temperature drop crystallization temperature in the present invention is the temperature of an exothermic peak due to crystallization that appears when the resin is melted using a differential scanning calorimeter at a temperature drop rate of 20 ° C./min. The temperature-falling crystallization temperature corresponds to the crystallization speed, and the higher the temperature-falling crystallization temperature, the faster the crystallization speed. Therefore, the cooling time can be shortened and the productivity can be increased during molding. When the temperature-falling crystallization temperature is low, crystallization takes time during molding, and the cooling time after molding must be lengthened, and the molding cycle tends to be extended and productivity tends to decrease.

  The solution haze of the PBT of the present invention is not particularly limited, but is usually 10% or less as the solution haze when measured by dissolving 2.7 g of PBT in 20 mL of a phenol / tetrachloroethane mixed solvent (weight ratio 3/2). Is 5% or less, more preferably 3% or less, and particularly preferably 1% or less. When the solution haze is high, transparency tends to deteriorate and foreign matter tends to increase, so that the commercial value is remarkably reduced in applications requiring transparency, such as films, monofilaments, and fibers. The solution haze tends to increase when the catalyst content is high or the deactivation of the catalyst is large.

  Next, the manufacturing method of PBT of this invention is demonstrated. The production method of PBT is roughly divided into a so-called direct polymerization method using a dicarboxylic acid as a main raw material and a transesterification method using a dialkyl dicarboxylate as a main raw material. The former is different in that water is produced in the initial esterification reaction, and the latter is produced in the initial transesterification reaction.

  In addition, the production method of PBT is roughly divided into a batch method and a continuous method, depending on the raw material supply or polymer discharge form. The initial esterification reaction or transesterification reaction is carried out in a continuous operation, and the subsequent polycondensation is carried out in a batch operation. Conversely, the initial esterification reaction or transesterification reaction is carried out in a batch operation, followed by polycondensation. There is also a method of performing the above by continuous operation.

  In the present invention, the direct polymerization method is preferred from the viewpoints of raw material availability, ease of treatment of the distillate, the height of the raw material basic unit, and the improvement effect of the present invention. In the present invention, from the viewpoint of productivity, stability of product quality, and the improvement effect of the present invention, a method of continuously supplying raw materials and continuously performing an esterification reaction or a transesterification reaction is employed. In the present invention, a so-called continuous method is also preferred in which the polycondensation reaction subsequent to the esterification reaction or transesterification reaction is also carried out continuously.

  In the present invention, in the esterification reactor, in the presence of a titanium catalyst, at least a part of 1,4-butanediol is esterified independently of terephthalic acid (or dialkyl terephthalate) (or transesterification reaction). A step of continuously esterifying (or transesterifying) terephthalic acid (or dialkyl terephthalate) and 1,4-butanediol while being supplied to the tank is preferably employed.

  That is, in the present invention, haze and foreign matters derived from the catalyst are reduced and the catalytic activity is not lowered. Therefore, as raw material slurry or solution, separately from 1,4-butanediol supplied together with terephthalic acid or dialkyl terephthalate. In addition, 1,4-butanediol is supplied to the esterification reaction tank or transesterification reaction tank independently of terephthalic acid or dialkyl terephthalate. Hereinafter, the 1,4-butanediol may be referred to as “separately supplied 1,4-butanediol”.

  The “separately supplied 1,4-butanediol” can be applied with fresh 1,4-butanediol independent of the process. "Separately supplied 1,4-butanediol" collects 1,4-butanediol distilled from the esterification reaction tank or transesterification reaction tank with a condenser or the like and holds it as it is or in a temporary tank or the like Then, it can be refluxed to the reaction vessel, or can be supplied as 1,4-butanediol having a purity improved by separating and purifying impurities. Hereinafter, “separately supplied 1,4-butanediol” composed of 1,4-butanediol collected by a condenser or the like may be referred to as “recycled 1,4-butanediol”. From the viewpoint of effective utilization of resources and simplicity of equipment, it is preferable to apply “recycled 1,4-butanediol” to “separately supplied 1,4-butanediol”.

  In addition, 1,4-butanediol distilled from the esterification reaction tank or transesterification reaction tank usually contains components such as water, alcohol, THF, dihydrofuran in addition to the 1,4-butanediol component. . Therefore, after collecting 1,4-butanediol from the above-mentioned distillate with a condenser or the like, it is separated and purified from components such as water, alcohol and THF while being collected and returned to the reaction vessel. Is preferred.

  In the present invention, it is preferable to return 10% by weight or more of “separately supplied 1,4-butanediol” directly to the reaction liquid phase part. Here, the reaction liquid phase part refers to the liquid phase side of the gas-liquid interface in the esterification reaction tank or transesterification reaction tank. To return directly to the reaction liquid phase part, use piping or the like. "Separately supplied 1,4-butanediol" indicates that it is directly supplied to the liquid phase part without going through the gas phase part. The ratio of returning directly to the liquid phase part of the reaction liquid is preferably 30% by weight or more, more preferably 50% by weight or more, particularly preferably 80% by weight or more, and most preferably 90% by weight or more. When there is little "separately supplied 1,4-butanediol" returned directly to the reaction liquid phase part, foreign matter tends to increase.

  The temperature of “separately supplied 1,4-butanediol” when returning to the reactor is usually 50 to 220 ° C., preferably 100 to 200 ° C., more preferably 150 to 190 ° C. When the temperature of “separately supplied 1,4-butanediol” is too high, the amount of THF by-product tends to increase, and when it is too low, the heat load tends to increase, leading to energy loss.

  Further, in the present invention, haze and foreign matters derived from the catalyst are reduced, and the catalytic activity is not lowered. Therefore, 10% by weight or more of the titanium catalyst used in the esterification reaction (or transesterification reaction) is terephthalic acid. (Or dialkyl terephthalate) is preferably supplied directly to the liquid phase part of the reaction liquid independently. Here, the reaction liquid phase part indicates the liquid phase side of the gas-liquid interface in the esterification reaction tank or transesterification reaction tank, and the direct supply to the reaction liquid phase part uses a pipe, etc. This means that the catalyst is supplied directly to the liquid phase part without going through the gas phase part of the reactor. The proportion of the titanium catalyst added directly to the reaction liquid phase is preferably 30% by weight or more, more preferably 50% by weight or more, particularly preferably 80% by weight or more, and most preferably 90% by weight or more.

  The above titanium catalyst can be directly supplied to the reaction liquid phase part of the esterification reaction tank or transesterification reaction tank with or without being dissolved in a solvent or the like. In order to reduce adverse effects such as heat denaturation from the heat medium jacket, it is preferable to dilute with a solvent such as 1,4-butanediol. The concentration at this time is usually 0.01 to 20% by weight, preferably 0.05 to 10% by weight, more preferably 0.08 to 8% by weight, as the concentration of the titanium catalyst with respect to the whole solution. From the viewpoint of reducing foreign matter, the water concentration in the solution is usually 0.05 to 1.0% by weight. The temperature for preparing the solution is usually 20 to 150 ° C., preferably 30 to 100 ° C., more preferably 40 to 80 ° C. from the viewpoint of preventing deactivation and aggregation. Moreover, it is preferable to mix a catalyst solution with an additional supply 1, 4- butanediol and piping etc., and to supply to an esterification reaction tank or a transesterification reaction tank from a point of deterioration prevention, precipitation prevention, and foreign material control.

  An example of a continuous method employing a direct polymerization method is as follows. That is, the dicarboxylic acid component having terephthalic acid as a main component and the diol component having 1,4-butanediol as a main component are mixed in a raw material mixing tank to form a slurry, and in one or a plurality of esterification reaction tanks In the presence of a titanium catalyst, the temperature is usually 180 to 260 ° C., preferably 200 to 245 ° C., more preferably 210 to 235 ° C., and usually 10 to 133 kPa, preferably 13 to 101 kPa, more preferably 60 to 90 kPa. Under the pressure of, usually 0.5 to 10 hours, preferably 1 to 6 hours, and the esterification reaction product is continuously transferred to the polycondensation reaction tank. Or in a plurality of polycondensation reaction tanks in the presence of a polycondensation catalyst, preferably continuously, usually 210-280 ° C, preferably 220-265 ° C. Temperature, usually less than 27 kPa, preferably 20kPa or less, more preferably in the following reduced pressure 13 kPa, under agitation, usually 2 to 10 hours, preferably for polycondensation reaction at 2-5 hours. The polymer obtained by the polycondensation reaction is usually transferred from the bottom of the polycondensation reaction tank to a polymer extraction die and extracted in the form of a strand, and while being cooled with water or after being cooled with water, it is cut with a cutter to form pellets and chips. And so on.

  In the case of the direct polymerization method, the molar ratio of terephthalic acid and 1,4-butanediol preferably satisfies the following formula (2).

  The above "1,4-butanediol supplied from the outside to the esterification reaction tank" means, as raw material slurry or solution, in addition to 1,4-butanediol supplied together with terephthalic acid or dialkyl terephthalate. Is the total of 1,4-butanediol entering the reaction vessel from outside the reaction vessel, such as 1,4-butanediol supplied independently, 1,4-butanediol used as a solvent for the catalyst.

  When the above BM / TM value is smaller than 1.1, the conversion rate is lowered and the catalyst is deactivated. When it is larger than 4.5, not only the thermal efficiency is lowered but also by-products such as THF are increased. Tend to. The value of BM / TM is preferably 1.5 to 4.0, more preferably 2.0 to 3.8, and particularly preferably 2.5 to 3.5.

  An example of a continuous process employing the transesterification process is as follows. That is, in the transesterification reaction tank or tanks, in the presence of a titanium catalyst, usually 110 to 260 ° C, preferably 140 to 245 ° C, more preferably 180 to 220 ° C, and usually 10 to 133 kPa, Preferably, the transesterification reaction is carried out continuously under a pressure of 13 to 120 kPa, more preferably 60 to 101 kPa, usually for 0.5 to 5 hours, preferably 1 to 3 hours. In the presence or absence of a polycondensation reaction catalyst, preferably continuously in the presence or absence of a polycondensation reaction catalyst, usually 210-280 ° C, preferably 220-265 ° C. Temperature, usually not more than 27 kPa, preferably not more than 20 kPa, more preferably not more than 13 kPa, with stirring, usually for 2 to 12 hours. Causes polycondensation reaction at 3-10 hours.

  In the case of the transesterification method, the molar ratio of dialkyl terephthalate to 1,4-butanediol preferably satisfies the following formula (3).

  When the above BM / DM value is smaller than 1.1, the conversion rate and the catalytic activity are decreased. When the BM / DM value is larger than 2.5, not only the thermal efficiency is lowered but also by-products such as THF are reduced. It tends to increase. The value of BM / DM is preferably 1.1 to 1.8, more preferably 1.2 to 1.5.

  In the present invention, the esterification reaction or transesterification reaction is preferably performed at a temperature equal to or higher than the boiling point of 1,4-butanediol in order to shorten the reaction time. The boiling point of 1,4-butanediol depends on the reaction pressure, but is 230 ° C. at 101.1 kPa (atmospheric pressure) and 205 ° C. at 50 kPa.

  As the esterification reaction tank or the transesterification reaction tank, known ones can be used, and any type such as a vertical stirring complete mixing tank, a vertical heat convection mixing tank, a tower type continuous reaction tank, etc. Also, a single tank may be a plurality of tanks in which the same kind or different kinds of tanks are connected in series. Among them, a reaction tank having a stirring device is preferable, and as a stirring device, a turbine stator type high-speed rotating stirrer, a disk mill type stirrer, a rotor mill type stirrer in addition to a normal type including a power unit, a bearing, a shaft, and a stirring blade. A type that rotates at high speeds can also be used.

  The form of stirring is not particularly limited, and in addition to the usual stirring method in which the reaction solution in the reaction tank is directly stirred from the top, bottom, side, etc. of the reaction tank, a part of the reaction solution is connected to the reactor by piping or the like. A method of circulating the reaction solution by taking it outside and stirring it with a line mixer or the like can also be employed.

  Known types of stirring blades can be selected, and specific examples include propeller blades, screw blades, turbine blades, fan turbine blades, disk turbine blades, fiddler blades, full zone blades, and Max blend blades.

  In the production of PBT, usually, a plurality of reaction vessels are used, preferably 2 to 5 reaction vessels, and the molecular weight is sequentially increased. Usually, a polycondensation reaction is performed following the initial esterification reaction or transesterification reaction.

  The polycondensation reaction step of PBT may use a single reaction tank or a plurality of reaction tanks, but preferably uses a plurality of reaction tanks and is performed in a plurality of stages. The form of the reaction tank may be any type such as a vertical stirring complete mixing tank, a vertical heat convection mixing tank, a tower type continuous reaction tank, or the like. Among them, a reaction tank having a stirring device is preferable, and as a stirring device, a turbine stator type high-speed rotating stirrer, a disk mill type stirrer, a rotor mill type stirrer in addition to a normal type including a power unit, a bearing, a shaft, and a stirring blade. A type that rotates at high speeds can also be used.

  The form of stirring is not particularly limited, and in addition to the usual stirring method in which the reaction solution in the reaction tank is directly stirred from the top, bottom, side, etc. of the reaction tank, a part of the reaction solution is connected to the reactor by piping or the like. A method of circulating the reaction solution by taking it outside and stirring it with a line mixer or the like can also be employed. In particular, it is recommended that at least one of the polycondensation reaction tanks use a horizontal reactor having a surface rotation axis in the horizontal direction and excellent self-cleaning properties.

  Further, in order to suppress coloring and deterioration and to suppress an increase in the end of vinyl group or the like, in at least one reaction tank, a high vacuum of usually 1.3 kPa or less, preferably 0.5 kPa or less, more preferably 0.3 kPa or less. The temperature is usually 225 to 255 ° C, preferably 230 to 250 ° C, more preferably 233 to 245 ° C.

  Further, the PBT polycondensation reaction step is to produce a PBT having a relatively small molecular weight by melt polycondensation, for example, an intrinsic viscosity of about 0.1 to 1.0, and then at a temperature below the melting point of the PBT. Solid phase polycondensation (solid phase polymerization) can also be carried out, but it is better not to carry out solid phase polymerization in applications such as fish eye and other films where appearance is important.

  In the PBT of the present invention, foreign matters derived from the catalyst are drastically reduced. Therefore, it is not necessary to remove the foreign matters. However, by installing a filter in the polymer precursor or the polymer flow path, the quality can be further improved. An excellent polymer is obtained. In the present invention, for the reasons described above, when a filter having the same opening as that used in a conventional PBT manufacturing facility is used, it is possible to extend the life until the replacement. Further, if the life until replacement is set to be the same, a filter with a smaller opening can be installed.

  If the filter is installed too far upstream of the manufacturing process, foreign matter generated downstream cannot be removed, and the pressure loss of the filter increases and the flow rate is maintained where the downstream viscosity is high. It is necessary to increase the opening of the filter, to increase the filter filtration area and piping, etc., and to receive high shear when passing through the fluid, so it is inevitable that PBT deteriorates due to shear heat generation. . Therefore, the filter installation position is selected so that the intrinsic viscosity of PBT or its precursor is usually 0.1 to 1.1, preferably 0.2 to 1.0, more preferably 0.5 to 0.9. Is done.

  The filter medium constituting the filter may be any of a metal wind, a laminated metal mesh, a metal nonwoven fabric, a porous metal plate, etc., but from the viewpoint of filtration accuracy, a laminated metal mesh or a metal nonwoven fabric is preferable, and in particular, the mesh opening is large. Those fixed by a sintering process are preferred. The shape of the filter may be any type such as basket type, disc type, leaf disc type, tube type, flat cylindrical type, pleated cylindrical type, and the like. In order not to affect the operation of the plant, it is preferable to install a plurality of filters and use them, or to install an auto screen changer or the like.

  The absolute filtration accuracy of the filter is not particularly limited, but is usually 0.5 to 200 μm, preferably 1 to 100 μm, more preferably 5 to 50 μm, and particularly preferably 10 to 30 μm. If the absolute filtration accuracy is too large, the effect of reducing foreign matters in the product is lost, and if it is too small, productivity is lowered and filter replacement frequency is increased.

  Hereinafter, preferred embodiments of a method for producing PBT will be described with reference to the accompanying drawings. FIG. 1 is an explanatory diagram of an example of an esterification reaction step or transesterification reaction step employed in the present invention, and FIGS. 2 and 3 are other views of the esterification reaction step or transesterification reaction step employed in the present invention. FIG. 4 is an explanatory diagram of an example of the polycondensation step employed in the present invention, and FIGS. 5 to 7 are explanatory diagrams of another example of the polycondensation step employed in the present invention.

  In FIG. 1, terephthalic acid as a raw material is usually mixed with 1,4-butanediol in a raw material mixing tank (not shown), and supplied to the reaction tank (A) in the form of slurry from the raw material supply line (1). The On the other hand, when the raw material is a dialkyl terephthalate, it is usually supplied to the reaction vessel (A) as a molten liquid independently of 1,4-butanediol. Further, the titanium catalyst is preferably supplied from a catalyst supply line (3) after being made into a solution of 1,4-butanediol in a catalyst adjustment tank (not shown). FIG. 1 shows a mode in which a catalyst supply line (3) is connected to a recycle line (2) for recycle 1,4-butanediol, and both are mixed and then supplied to the liquid phase part of the reaction tank (A). It was.

  The gas distilled from the reaction tank (A) is separated into a high-boiling component and a low-boiling component in the rectifying column (C) through the distillation line (5). Usually, the main component of the high boiling component is 1,4-butanediol, and the main component of the low boiling component is water and THF in the case of the direct polymerization method, and alcohol, THF, and water in the case of the transesterification method. .

  The high-boiling components separated in the rectification column (C) are extracted from the extraction line (6) and partly circulated from the recirculation line (2) to the reaction tank (A) via the pump (D). , Part is returned from the circulation line (7) to the rectification column (C). Further, the surplus is extracted outside from the extraction line (8). On the other hand, the light boiling components separated in the rectification column (C) are extracted from the gas extraction line (9), condensed in the condenser (G), and temporarily passed through the condensate line (10) to the tank (F). Can be stored. A part of the light boiling components collected in the tank (F) is returned to the rectification column (C) through the extraction line (11), the pump (E) and the circulation line (12), and the remainder is extracted. It is extracted outside through the line (13). The condenser (G) is connected to an exhaust device (not shown) via a vent line (14). The oligomer produced | generated within the reaction tank (A) is extracted through an extraction pump (B) and an extraction line (4).

  In the process shown in FIG. 1, the catalyst supply line (3) is connected to the recirculation line (2), but both may be independent. Moreover, the raw material supply line (1) may be connected to the liquid phase part of the reaction vessel (A).

  Compared with the process shown in FIG. 1, the process shown in FIG. 2 is equipped with a reboiler (H) in the rectifying column (C) and further supplies a liquid to the rectifying tower (C) from the outside (15 ) Is different. Installation of the reboiler (H) facilitates operation control of the rectification tower (C).

  The process shown in FIG. 3 differs from the process shown in FIG. 1 in that a bypass line (16) branched from the circulation line (7) is connected to the gas phase portion of the reaction vessel (A). Therefore, in the case of the process shown in FIG. 3, a part of the recycled 1,4-butanediol returns to the reaction solution via the gas phase part of the reaction tank (A).

  In FIG. 4, the oligomer supplied from the extraction line (4) shown in FIGS. 1 to 3 is subjected to polycondensation under reduced pressure in the first polycondensation reaction tank (a) to become a prepolymer, It is supplied to the second polycondensation reaction tank (d) through the extraction gear pump (c) and the extraction line (L1). In the second polycondensation reaction tank (d), polycondensation usually proceeds at a lower pressure than that of the first polycondensation reaction tank (a) to become a polymer. The obtained polymer is extracted in the form of a melted strand from the die head (g) through the extraction gear pump (e) and the extraction line (L3), cooled with water, and then rotated with a rotary cutter ( It is cut into a pellet in h). Reference numeral (L2) is a vent line of the first polycondensation reaction tank (a), and reference numeral (L4) is a vent line of the second polycondensation reaction tank (d).

  The process shown in FIG. 5 differs from the process shown in FIG. 4 in that a filter (f) is provided in the flow path of the extraction line (L3).

The process shown in FIG. 6 differs from the process shown in FIG. 4 in that the third polycondensation reaction tank (k) is provided after the second polycondensation reaction tank (d). The third polycondensation reaction tank (k) is a horizontal reaction tank composed of a plurality of stirring blade blocks and equipped with a biaxial self-cleaning type stirring blade. The polymer introduced into the third polycondensation reaction tank (k) from the second polycondensation reaction tank (d) through the extraction line (L3) is further subjected to polycondensation here, and then the extraction gear pump (m ) And the extraction line (L5), and is extracted from the die head (g) in the form of a melted strand, cooled with water, and then cut with a rotary cutter (h) to form pellets. Symbol (L6) is a vent line of the third polycondensation reaction tank (k).

  Compared with the process shown in FIG. 6, the process shown in FIG. 7 includes a filter (L3) in the middle of the extraction line (L3) between the second polycondensation reaction tank (d) and the third polycondensation reaction tank (k). The difference is that f) is equipped.

  The PBT of the present invention includes 2,6-di-t-butyl-4-octylphenol, pentaerythrityl-tetrakis [3- (3 ′, 5′-t-butyl-4′-hydroxyphenyl) propionate] and the like. Phenol compounds, dilauryl-3,3′-thiodipropionate, thioether compounds such as pentaerythrityl-tetrakis (3-laurylthiodipropionate), triphenyl phosphite, tris (nonylphenyl) phosphite, tris (2 , 4-Di-t-butylphenyl) phosphite and other phosphorus compounds, paraffin wax, microcrystalline wax, polyethylene wax, long chain fatty acids represented by montanic acid and montanic acid ester, and esters thereof, silicone A mold release agent such as oil may be added.

  A reinforcing filler can be blended in the PBT of the present invention. The reinforcing filler is not particularly limited, but examples thereof include glass fibers, carbon fibers, silica / alumina fibers, zirconia fibers, boron fibers, boron nitride fibers, silicon nitride potassium titanate fibers, metal fibers and other inorganic fibers, aromatics Examples thereof include organic fibers such as polyamide fibers and fluororesin fibers. These reinforcing fillers can be used in combination of two or more. Among the above 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, and particularly preferably 5 to 20 μm. . 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 the PBT, the reinforcing filler is preferably used after being surface-treated with a sizing 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 with a sizing agent or a surface treatment agent in advance, or can be surface-treated by adding a sizing agent or a surface treatment agent during the preparation of the PBT composition. The addition amount of the reinforcing filler is usually 150 parts by weight or less, preferably 5 to 100 parts by weight with respect to 100 parts by weight of the PBT resin.

  Other fillers can be blended with the reinforcing filler in the PBT of the present invention. Other fillers to be blended include, for example, plate-like inorganic fillers, ceramic beads, asbestos, wollastonite, talc, clay, mica, zeolite, kaolin, potassium titanate, barium sulfate, titanium oxide, silicon oxide, oxidation Aluminum, magnesium hydroxide, etc. are mentioned. By blending the plate-like inorganic filler, the anisotropy and warpage of the molded product can be reduced. Examples of the plate-like inorganic filler include glass flakes, mica, and metal foil. Among these, glass flakes are preferably used.

  A flame retardant can be blended with 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, sodium antimonate, and the like. As a phosphorus compound, phosphate ester, polyphosphoric acid, ammonium polyphosphate, red phosphorus etc. are mentioned, for example. 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 compound, and boron compound.

  The PBT of the present invention can be blended with conventional additives as required. Such additives are not particularly limited and include, for example, stabilizers such as antioxidants and heat stabilizers, lubricants, mold release agents, catalyst deactivators, crystal nucleating agents, crystallization accelerators, and the like. It is done. These additives can be added during or after the polymerization. In addition, in order to give PBT the desired performance, UV absorbers, stabilizers such as weather resistance stabilizers, colorants such as dyes and pigments, antistatic agents, foaming agents, plasticizers, impact resistance improvers, etc. I can do it.

  For the PBT of the present invention, 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. A thermosetting resin such as a resin, a phenol resin, a melamine resin, a silicone resin, or an epoxy resin can be blended. These thermoplastic resins and thermosetting resins can be used in combination of two or more.

  The blending method of the various additives and resins is not particularly limited, but a method of using a uniaxial or biaxial extruder having equipment capable of devolatilization from the vent port as a kneader is preferable. Each component including an additional component can be supplied to the kneader in a lump or can be supplied sequentially. In addition, two or more kinds of components selected from each component including an additional component can be mixed in advance.

  The PBT molding method of the present invention is not particularly limited, and molding methods generally used for thermoplastic resins, that is, molding methods such as injection molding, hollow molding, extrusion molding, and press molding can be applied. .

  The PBT of the present invention is excellent in color tone, hydrolysis resistance, thermal stability, transparency, and moldability, and is therefore suitable as an injection molded part for electric, electronic parts, automotive parts, etc. Therefore, the improvement effect is remarkable in applications such as films, monofilaments, and fibers.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to a following example at all unless the summary is exceeded. In addition, the measuring method of the physical property and evaluation item employ | adopted in the following examples is as follows.

(1) Esterification rate:
It calculated from the acid value and the saponification value by the following calculation formula (4). The acid value was obtained by dissolving the oligomer in dimethylformamide and titrating with a 0.1N KOH / methanol solution. The saponification value was determined by hydrolyzing the oligomer with a 0.5N KOH / ethanol solution and titrating with 0.5N hydrochloric acid.

(2) Terminal carboxyl group concentration:
PBT or oligomer 0.5g was melt | dissolved in benzyl alcohol 25mL, and it titrated using the 0.01 mol / L benzyl alcohol solution of sodium hydroxide.

(3) Intrinsic viscosity (IV):
It calculated | required in the following way using the Ubbelohde type viscometer. That is, using a mixed solvent of phenol / tetrachloroethane (weight ratio 1/1) and measuring the number of seconds of dropping only the polymer solution having a concentration of 1.0 g / dL and the solvent at 30 ° C., the following formula (5) I asked more.

(4) Titanium concentration in PBT:
PBT was wet-decomposed with high-purity sulfuric acid and nitric acid for electronic industry and measured using a high resolution ICP (Inductivery Coupled Plasma) -MS (Mass Spectrometer) (manufactured by ThermoQuest).

(5) Terminal methoxycarbonyl group concentration and terminal vinyl group concentration:
About 100 mg of PBT was dissolved in 1 mL of a mixed solvent of deuterated chloroform / hexafluoroisopropanol = 7/3 (volume ratio), 36 μL of deuterated pyridine was added, and ¹ H-NMR was measured and determined at 50 ° C. For the NMR apparatus, “α-400” or “AL-400” manufactured by JEOL Ltd. was used.

(6) Number of fish eyes:
Using a film quality testing system [Optical Control Systems, Inc., Type FS-5], a film having a thickness of 50 μm was formed, and the number of fish eyes of 25 μm or more per 1 m ² was measured.

(7) Temperature drop crystallization temperature (Tc):
Using a differential scanning calorimeter [Perkin Elmer, Model DSC7], the temperature was raised from room temperature to 300 ° C. at a temperature rising rate of 20 ° C./min, and then the temperature was lowered to 80 ° C. at a temperature falling rate of 20 ° C./min. The temperature was defined as the temperature-falling crystallization temperature. The higher the Tc, the faster the crystallization speed and the shorter the molding cycle.

(8) Solution haze:
After dissolving 2.70 g of PBT in 20 mL of a mixed solvent of phenol / tetrachloroethane = 3/2 (weight ratio) at 110 ° C. for 30 minutes, it was cooled in a constant temperature water bath at 30 ° C. for 15 minutes, and made by Nippon Denshoku Co., Ltd. The measurement was performed with a cell length of 10 mm using a dynamometer (NDH-300A). It shows that transparency is so favorable that a value is low.

(9) Pellet color tone:
A color difference meter (Z-300A type) manufactured by Nippon Denshoku Co., Ltd. was used, and b values in the L, a, and b color systems were calculated and evaluated. A lower value indicates less yellowing and a better color tone.

(10) Increase in terminal carboxyl group concentration by reaction other than hydrolysis reaction (ΔAV (d)):
PBT pellets were pulverized and filled in capillaries with an inner diameter of 5 mm, filled and purged with nitrogen, immersed in an oil bath controlled at 245 ° C. under nitrogen, taken out after 40 minutes, and rapidly cooled with liquid nitrogen. After the temperature of the contents was sufficiently lowered, the contents were taken out, the terminal carboxyl group concentration and the terminal hydroxyl group concentration were measured, and obtained from the above formula (1).

Example 1:
Through the esterification step shown in FIG. 1 and the polycondensation step shown in FIG. 6, PBT was produced in the following manner. First, a 60 ° C. slurry mixed at a ratio of 1.80 moles of 1,4-butanediol with respect to 1.00 moles of terephthalic acid is passed through a raw material supply line (1) from a slurry preparation tank in advance with an esterification rate of 99. % Was continuously fed to a reaction tank (A) for esterification having a screw type stirrer filled with PBT oligomer at 28.5 kg / h. At the same time, the bottom component of the rectification column (C) at 185 ° C. is fed from the recirculation line (2) at 12.0 kg / h, and 6. 5% of tetrabutyl titanate at 65 ° C. is used as the catalyst from the catalyst feed line (3). A 0 wt% 1,4-butanediol solution was fed at 69 g / h (30 ppm relative to the theoretical polymer yield). The water content in this solution was 0.20% by weight.

  The internal temperature of the reaction tank (A) is 230 ° C., the pressure is 78 kPa, and the produced water, THF and excess 1,4-butanediol are distilled from the distillation line (5), and the rectification column (C) It separated into a high boiling component and a low boiling component. The high-boiling component at the bottom of the column after the system has been stabilized is 98% by weight or more of 1,4-butanediol, and the extraction line (8) so that the liquid level of the rectifying column (C) is constant. A part of it was extracted outside. On the other hand, the low boiling component was extracted from the top of the column in the form of gas, condensed by the condenser (G), and extracted from the extraction line (13) to the outside so that the liquid level of the tank (F) was constant.

  A certain amount of the oligomer generated in the reaction tank (A) is extracted from the extraction line (4) using the pump (B) so that the average residence time of the liquid in the reaction tank (A) is 3.3 hr. The liquid level was controlled. The oligomer extracted from the extraction line 4 was continuously supplied to the first polycondensation reaction tank (a). After the system was stabilized, the esterification rate of the oligomer collected at the outlet of the reaction vessel (A) was 97.4%.

  The internal temperature of the first polycondensation reaction tank (a) was 240 ° C., the pressure was 2.1 kPa, and the liquid level was controlled so that the residence time was 120 minutes. An initial polycondensation reaction was performed while extracting water, THF, and 1,4-butanediol from a vent line (L2) connected to a decompressor (not shown). The extracted reaction liquid was continuously supplied to the second polycondensation reaction tank (d).

  The internal temperature of the second polycondensation reaction tank (d) is 241 ° C., the pressure is 130 Pa, the liquid level is controlled so that the residence time is 120 minutes, and a vent line (L4) connected to a decompressor (not shown). ), Polycondensation reaction was further carried out while extracting water, THF and 1,4-butanediol. The obtained polymer was continuously supplied to the third polycondensation reaction tank (k) via the extraction line (L3) by the extraction gear pump (e). The internal temperature of the third polycondensation reaction tank (k) was 238 ° C., the pressure was 140 Pa, the residence time was 120 minutes, and the polycondensation reaction was further advanced. The obtained polymer was continuously extracted in the form of a strand from the die head (g) and cut with a rotary cutter (h). A PBT with less fisheye, excellent color tone, good transparency and excellent thermal stability was obtained. The analytical values are summarized in Table 1.

Example 2:
In Example 1, it carried out like Example 1 except having employ | adopted the polycondensation process shown in FIG. As the filter (f) in the polycondensation step shown in FIG. 7, a pleated cylindrical filter made of a metal nonwoven fabric and having an absolute filtration accuracy of 20 μm was used. A PBT with a reduced fish eye was obtained as compared with Example 1. The analytical values are summarized in Table 1.

Example 3:
In Example 1, the flow rate of the bottom component of the rectification column (C) supplied from the recirculation line (2) to the reaction vessel (A) is changed to 5.6 kg / h, and the inside of the second polycondensation reaction vessel is changed. The same procedure as in Example 1 was conducted except that the temperature was 243 ° C., the internal temperature of the third polycondensation reaction tank (k) was 243 ° C., and the residence time was 150 minutes. PBT with few fish eyes, excellent color tone, good transparency and excellent thermal stability was obtained. The analytical values are summarized in Table 1.

Comparative Example 1:
In Example 1, the supply amount of tetrabutyl titanate was adjusted so that the Ti content in the polymer was as shown in Table 1, the internal temperature of the second polycondensation reaction tank (d) was 240 ° C., and the third polycondensation. The same operation as in Example 1 was conducted except that the residence time in the reaction vessel (k) was 90 minutes. Fish eyes increased and transparency deteriorated. The analytical values are summarized in Table 1.

Comparative Example 2:
In Example 1, the catalyst supply line (3) of the esterification step shown in FIG. 1 is connected to the raw material supply line (1), the recirculation line (2) is positioned in the gas phase part of the reaction vessel (A), Then, the same as Example 1 except that the supply amount of 1,4-butanediol solution of tetrabutyl titanate was 340 g / h, the pressure of the third polycondensation reaction tank (k) was 150 Pa, and the residence time was 100 minutes. Went to. As shown in the table, haze, color tone, thermal stability deteriorated, and there were many fish eyes. The analytical values are summarized in Table 1.

Comparative Example 3:
In a 200 L stainless steel reaction vessel equipped with a turbine type stirring blade, dimethyl terephthalate (DMT) 272.9 mol, 1,4-butanediol 327.5 mol, tetrabutyl titanate 0.189 mol (theoretical yield as titanium amount) 150 ppm per polymer) was charged and sufficiently substituted with nitrogen. Subsequently, the temperature of the system was raised, and after 60 minutes, at a temperature of 210 ° C. and atmospheric pressure under nitrogen, a transesterification reaction was performed for 2 hours while distilling methanol, 1,4-butanediol, and THF generated out of the system. (The reaction start time was the time when a predetermined temperature and a predetermined pressure were reached).

  After the oligomer obtained above was transferred to a stainless steel reactor having an internal volume of 200 L having a vent pipe and a double helical stirring blade, it was allowed to reach a temperature of 245 ° C. and a pressure of 100 Pa over 60 minutes. A condensation reaction was performed. The stirring power value, which is an IV index of the polymer in the reaction vessel, reached a peak after 150 minutes, and no further increase in IV was expected. Therefore, after 180 minutes, the polymer was extracted into a strand and cut into a pellet. IV was as low as 1.25 dL / g, inferior in color tone and thermal stability, Tc was low, and a terminal methoxycarbonyl group remained at 0.8 μeq / g. The analytical values are summarized in Table 1.

Comparative Example 4:
In a 200 L stainless steel reaction vessel equipped with a turbine-type stirring blade, dimethyl terephthalate (DMT) 272.9 mol, 1,4-butanediol 327.5 mol, tetrabutyl titanate 0.101 mol (theoretical yield as titanium amount) 80 ppm per polymer) was charged and sufficiently substituted with nitrogen. Subsequently, the temperature of the system was raised, and after 60 minutes, at a temperature of 210 ° C. and atmospheric pressure under nitrogen, a transesterification reaction was performed for 2 hours while distilling methanol, 1,4-butanediol, and THF generated out of the system. (The reaction start time was the time when a predetermined temperature and a predetermined pressure were reached).

  After transferring the oligomer obtained above to a stainless steel reactor having an internal volume of 200 L having a vent pipe and a double helical stirring blade, it was allowed to reach a temperature of 245 ° C. and a pressure of 100 Pa over 60 minutes. A time polycondensation reaction was performed. After completion of the reaction, the polymer was extracted into a strand shape and cut into a pellet shape. The obtained polymer was charged in a double cone type jacketed solid phase polymerization apparatus having an internal volume of 100 L, and the reduced pressure / nitrogen replacement was repeated three times. The next pressure was controlled to 130 Pa and the temperature was raised to 195 ° C. Six hours after the internal temperature reached 195 ° C., the jacket heating medium started to cool, and the content was taken out when the internal temperature became 40 ° C. or lower. The obtained PBT was inferior in color tone and thermal stability, had a low Tc, and had many fish eyes. Further, 2.1 μeq / g of terminal methoxycarbonyl group remained. The analytical values are summarized in Table 1.

Explanatory drawing of an example of the esterification reaction process or transesterification reaction process employed in the present invention Explanatory drawing of another example of the esterification reaction step or transesterification reaction step employed in the present invention Explanatory drawing of another example of the esterification reaction step or transesterification reaction step employed in the present invention Explanatory drawing of an example of the polycondensation step employed in the present invention Explanatory drawing of another example of the polycondensation step employed in the present invention Explanatory drawing of another example of the polycondensation step employed in the present invention Explanatory drawing of another example of the polycondensation step employed in the present invention

Explanation of symbols

1: Raw material supply line 2: Recirculation line 3: Catalyst supply line 4: Extraction line 5: Distillation line 6: Extraction line 7: Circulation line 8: Extraction line 9: Gas extraction line 10: Condensate line 11: Extraction line 12: Circulation line 13: Extraction line 14: Vent line
15: Recovery line 16: Bypass line A: Reaction tank B: Extraction pump C: Rectification tower D, E: Pump F: Tank G: Condenser H: Reboiler L1: Extraction line L3, L5: Extraction line L2, L4, L6: Vent line a: first polycondensation reaction tank d: second polycondensation reaction tank k: third polycondensation reaction tank c, e, m: extraction gear pump f: filter g: dice head h: rotation Type cutter

Claims (6)

Manufactured by a direct polymerization method, containing titanium and having an amount of 50 ppm or less as titanium atoms, intrinsic viscosity of 1.20 to 2.00 dL / g , terminal carboxyl group concentration of 15 to 50 μeq / g, terminal methoxy Polybutylene terephthalate having a carbonyl group concentration of 0.5 μeq / g or less and a terminal vinyl group concentration of 0.5 to 12 μeq / g (excluding those having an intrinsic viscosity of 1.20 dL / g ) ). Decreasing crystallization temperature measured with a differential scanning calorimeter at a temperature decreasing rate of 20 ° C./min (using a differential scanning calorimeter, increasing the temperature from room temperature to 300 ° C. at a temperature increasing rate of 20 ° C./min, then decreasing the temperature at 20 ° C. 2. The polybutylene terephthalate according to claim 1, wherein the temperature of the exothermic peak when the temperature is lowered to 80 ° C. at / min) is 175 to 180 ° C. 3.   The polybutylene terephthalate according to claim 1 or 2, which has a solution haze of 10% or less when 2.7 g of polybutylene terephthalate is dissolved in 20 mL of a phenol / tetrachloroethane mixed solvent (weight ratio 3/2).   The polybutylene terephthalate according to any one of claims 1 to 3, wherein the increase in the terminal carboxyl group concentration excluding the hydrolysis reaction upon heat treatment at 245 ° C for 40 minutes in an inert atmosphere is 0.1 to 10 µeq / g. . The polybutylene terephthalate according to any one of claims 1 to 4, which has an intrinsic viscosity of 1.30 to 1.50 dL / g .   The polybutylene terephthalate according to any one of claims 1 to 5, obtained without performing solid phase polymerization.