JP2004323836A - Polybutylene terephthalate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide polybutylene terephthalate (PBT) excellent in a color tone, heat stability, transparency and extrusion moldability, decreased in generation of gas and foreign matter when molded, and capable of being suitably used for a film, monofilament, fiber, electrical and electronic part, automotive part, etc. <P>SOLUTION: This PBT contains titanium in an amount of ≤50 ppm as titanium atoms, has an intrinsic viscosity of 1.20-2.00 dL/g and has a carboxy end group concentration of ≥15 μeq/g. It is preferable that the PBT has a methoxycarbonyl end group concentration of ≤0.5 μeq/g, a temperature-descending crystallization point of 170-190°C which is measured at a temperature-descending rate of 20°C/min by a differential scanning calorimeter, a vinyl end group concentration of ≤0.5-12 μeq/g, and a solution haze of ≤10% which is measured by dissolving 2.7g of the PBT in 20 mL of a mixed solvent of phenol (3 pts.wt.) and tetrachloroethane (2 pts.wt.). <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to polybutylene terephthalate, in particular, color tone, thermal stability, transparency, extrudability is excellent, moreover, generated gas and foreign matter during molding is reduced, good appearance film, monofilament, fiber, The present invention relates to polybutylene terephthalate which can be suitably used for electric and electronic parts, automobile parts, and the like.

  Polybutylene terephthalate, a representative engineering plastic among thermoplastic polyester resins, is easy to mold, has mechanical properties, heat resistance, chemical resistance, fragrance retention, and other physical and chemical properties. Due to its excellent properties, it is widely used in injection molded products such as automotive parts, electric / electronic parts, precision equipment parts, etc. In recent years, taking advantage of its excellent properties, it has been widely used in the fields of films, sheets, monofilaments, coatings of various cables, bottles, tanks, and fibers.

  In particular, in the case of films, sheets, monofilaments, cable coatings, bottles and tanks, they are often manufactured by extrusion molding and blow molding, and require high molecular weight polybutylene terephthalate with a higher melt viscosity than injection molding. Have been.

  Further, in the above-mentioned applications, since the commercial value is largely influenced by foreign substances (the foreign substances in the film are sometimes called fish eyes), haze, coloring and the like, reduction and improvement of these are strongly demanded. It is considered that foreign matters and haze in polybutylene terephthalate are caused by degraded resins, generally called burns and tarnish, as well as deactivated substances and aggregates of metal compounds added as a catalyst.

  However, when 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 the catalyst. On the contrary, coloring tends to be promoted and foreign matter and haze tend to increase.

  In order to solve the above-mentioned problems, it has been widely practiced to once solidify polybutylene terephthalate obtained by melt polymerization and to carry out solid-phase polymerization at a temperature equal to or lower than its melting point to produce high-molecular-weight polybutylene terephthalate. (For example, see Patent Documents 1 and 2).

  However, performing solid-phase polymerization after melt polymerization means that an extra step is required, which leads to a problem that the equipment becomes excessively large and the operation becomes complicated. Further, obtaining high molecular weight polybutylene terephthalate by solid-state polymerization performed at a temperature lower than that of melt polycondensation means that the polymerization time is significantly increased, and there is a large problem in productivity. In addition, the film produced from polybutylene terephthalate obtained by solid-state polymerization is liable to produce fisheye, which is considered to be derived from fine powder generated during solid-state polymerization or a high molecular weight substance 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 equal to or higher than the melting point of polybutylene terephthalate, in conventional polybutylene terephthalate, even if the concentration of terminal carboxyl groups is reduced by solid-phase polymerization, the concentration of terminal carboxyl groups is reduced again by the heat applied during molding. There is a problem that rises. This increase in the terminal carboxyl group concentration is promoted by titanium contained in polybutylene terephthalate, but since it is inextricably linked to the reaction that generates butadiene and tetrahydrofuran, the problem of increased gas generation during molding is the result. (For example, see Non-Patent Document 1).

JP-A-9-316183 JP-A-57-2728 Handbook of saturated polyester resin (December 22, 1989, published by Nikkan Kogyo Shimbun, p. 304)

  The present invention has been made in view of the above circumstances, and has as its object to improve the color tone, heat stability, transparency, and extrudability, and to further reduce the generation of gas and foreign matter during molding, a film or a monofilament. It is an object of the present invention to provide polybutylene terephthalate which can be suitably used for fibers, electric and electronic parts, automobile parts and the like.

  The present inventors have conducted intensive studies to solve the above-mentioned problems, and as a result, if the esterification reaction is performed by supplying the titanium catalyst and the raw material in a specific mode, surprisingly, the utilization efficiency of the titanium catalyst Has been found, the amount of titanium catalyst used can be significantly 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. Thus, the present invention has been completed.

  The present invention has been completed based on the above findings, and the gist of the present invention is that it contains titanium, the amount of which is 50 ppm or less as a titanium atom, the intrinsic viscosity is 1.20 to 2.00, and the terminal carboxyl group. The polybutylene terephthalate having a concentration of 15 μeq / g or more.

  Advantageous Effects of Invention According to the present invention, it is suitable for films, monofilaments, fibers, electric and electronic parts, automobile parts, etc., which are excellent in color tone, heat stability, transparency, extrudability, and have reduced generated gas and foreign matter during molding. And a polybutylene terephthalate that can be used for

  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 terephthalic acid units and 1,4-butanediol units are ester-bonded, and 50 mol% or more of dicarboxylic acid units are converted from terephthalic acid units. And 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 at least 70 mol%, more preferably at least 80 mol%, particularly preferably at least 95 mol%, and 1,4-butanediol units in all diol units. Is preferably at least 70 mol%, more preferably at least 80 mol%, particularly preferably at least 95 mol%. When the amount of the terephthalic acid unit or the 1,4-butanediol unit is less than 50 mol%, the crystallization speed of PBT decreases, and the moldability deteriorates.

  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′-diphenylether dicarboxylic acid, 4,4′-benzophenone Aromatic dicarboxylic acids such as dicarboxylic acid, 4,4'-diphenoxyethane dicarboxylic 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, and aliphatic dicarboxylic acids such as malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, and sebacic acid. Can be mentioned. These dicarboxylic acid components can be introduced into the polymer skeleton as dicarboxylic acids or using dicarboxylic acid derivatives such as dicarboxylic acid esters and dicarboxylic acid halides as raw materials.

  In the present invention, diol components other than 1,4-butanediol are not particularly limited, and examples thereof include ethylene glycol, diethylene glycol, polyethylene glycol, 1,2-propanediol, 1,3-propanediol, polypropylene glycol, and polytetraol. Aliphatic diols such as methylene glycol, dibutylene glycol, 1,5-pentanediol, neopentyl glycol, 1,6-hexanediol, 1,8-octanediol, 1,2-cyclohexanediol, 1,4-cyclohexanediol Alicyclic diols such as 1,1,1-cyclohexane dimethylol and 1,4-cyclohexane dimethylol, 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, and p-β-hydroxyethoxybenzoic acid, and alkoxycarboxylic acids Monofunctional components such as acid, stearyl alcohol, benzyl alcohol, stearic acid, benzoic acid, t-butyl benzoic acid, benzoyl benzoic acid, tricarballylic acid, trimellitic acid, trimesic acid, pyromellitic acid, gallic acid, and trimethylolethane , Trimethylolpropane, glycerol, pentaerythritol, and other trifunctional or higher polyfunctional components can be used as the copolymer component.

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

  As the titanium catalyst, a titanium compound is usually used, and specific examples thereof include titanium oxide, inorganic titanium compounds such as titanium tetrachloride, tetramethyl titanate, tetraisopropyl titanate, titanium alcoholate such as tetrabutyl titanate, and tetraphenyl titanate. Titanium phenolate and the like can be mentioned. Of these, tetraalkyl titanates are preferred, and among them, tetrabutyl titanate is preferred.

  In addition to titanium, tin may be used as a catalyst. Tin is generally used as a tin compound, and specific examples thereof include dibutyltin oxide, methylphenyltin oxide, tetraethyltin, hexaethyldistin oxide, cyclohexahexyldistin oxide, didodecyltin oxide, and triethyltin hydroxide. , Triphenyltin hydroxide, triisobutyltin acetate, dibutyltin diacetate, diphenyltin dilaurate, monobutyltin trichloride, tributyltin chloride, dibutyltin sulfide, butylhydroxytin oxide, methylstannoic acid, ethylstannoic acid, butylstannoic acid, etc. Is mentioned.

  Also, in addition to titanium, magnesium acetate, magnesium hydroxide, magnesium carbonate, magnesium oxide, magnesium alkoxide, magnesium compounds such as magnesium hydrogen phosphate, calcium acetate, calcium hydroxide, calcium carbonate, calcium oxide, calcium alkoxide. , A calcium compound such as calcium hydrogen phosphate, an antimony compound such as antimony trioxide, a germanium compound such as germanium dioxide and germanium tetroxide, a manganese compound, a zinc compound, a zirconium compound, a cobalt compound, orthophosphoric acid, hypophosphorous acid, and hypochlorous acid. Phosphorus compounds such as phosphoric acid, polyphosphoric acid, esters and metal salts thereof, and reaction aids such as sodium hydroxide and sodium benzoate may be used.

  The PBT of the present invention is characterized by containing titanium and having an amount of 50 ppm or less as titanium atoms. The above values are 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, and 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, color tone, hydrolysis resistance, transparency, moldability and the like are deteriorated, and foreign matter tends to increase, and when less than 1 ppm, the polymerizability is deteriorated. is there.

  In the present invention, as described above, a tin catalyst can be used together with a titanium catalyst. In general, a tin catalyst has a lower catalytic activity than a titanium catalyst, and thus needs to be added in a larger amount than a titanium catalyst. However, when the amount of the tin catalyst used is too large, the color tone is deteriorated, and tin is toxic. Therefore, the amount of the 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 and the like can be measured using a method such as atomic luminescence, atomic absorption, and Inductively Coupled Plasma (ICP) after recovering the metal in the polymer by a method such as wet ashing.

  The PBT of the present invention needs to have an intrinsic viscosity of 1.20 to 2.00 dL / g, preferably 1.20 to 1.60 dL / g, more preferably 1.30 to 1.50 dL / g, Particularly preferably, it is 1.30 to 1.40. If the intrinsic viscosity is less than 1.20 dL / g, the extrudability deteriorates, causing drawdown and uneven molding of the resin. If the intrinsic viscosity exceeds 2.00 dL / g, the melt viscosity increases and the fluidity deteriorates. I 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. If the terminal carboxyl group concentration is too high, the hydrolysis resistance and solid phase polymerization 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 raised by heat during kneading or molding, not only does the hydrolysis resistance of the product deteriorate, but also tetrahydrofuran (hereinafter abbreviated as THF) and the like. Gas generation may occur. Therefore, in the PBT of the present invention, the increase in the concentration of terminal carboxyl groups excluding the hydrolysis reaction when heat-treated at 245 ° C. for 40 minutes in an inert gas atmosphere is usually 0.1 to 10 μeq / g, preferably 0.1 to 10 μeq / g. It is 5-5 eq / g, more preferably 0.5-3 eq / g, and particularly preferably 1-2 eq / g.

  The hydrolysis reaction can be prevented by an operation of reducing the water content in the PBT, specifically, by performing drying sufficiently. The hydrolysis reaction does not involve the generation of THF which is a problem at the time of molding. An increase in the terminal carboxyl group concentration due to a decomposition reaction other than that described above cannot be prevented by the drying operation. In general, the lower the molecular weight, and the higher the titanium concentration in PBT, the greater the increase in terminal carboxyl group concentration due to thermal decomposition other than hydrolysis.

  In the above evaluation method, the temperature and the time are 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 if the temperature is too low, the evaluation is inaccurate because the rate is too large. That's why. Another reason is that when the evaluation is performed at an extremely high temperature, side reactions other than the generation of a terminal carboxyl group occur at the same time, and the evaluation becomes inaccurate. Under the heat treatment conditions, the decrease in the number average molecular weight due to a reaction other than the hydrolysis reaction caused by the moisture contained in the PBT can be ignored, and the increase in the terminal carboxyl group concentration due to the hydrolysis reaction is the difference between the terminal carboxyl groups before and after the heat treatment. Since the increase in the concentration of the glycol group can be considered to be substantially the same as the increase in the concentration of the glycol group, the increase in the concentration of the terminal carboxyl group due to a 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.

From the viewpoint of the reliability of the thermal decomposition reaction evaluation, it is preferable that the hydrolysis reaction is small. Therefore, the water content of PBT used for the heat treatment is generally 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 or the like and titrating the solution using an alkali solution such as a sodium hydroxide solution.

The terminal vinyl group concentration of the PBT of the present invention is usually 0.1 to 15 μeq / g, preferably 0.5 to 12 μeq / g, and more preferably 1 to 10 μeq / g. When the terminal vinyl group concentration is too high, it causes deterioration of color tone and solid state polymerization. When manufacturing PBT having a high molecular weight or PBT having a low catalyst concentration without lowering the productivity, it is generally required to raise the polymerization temperature or lengthen the reaction time. The base concentration tends to increase. The terminal vinyl group concentration can be determined by dissolving PBT in heavy chloroform / hexafluoroisopropanol = 7/3 (volume ratio) and measuring ¹ H-NMR.

  At the end of the PBT, a methoxycarbonyl group derived from a raw material may remain in addition to a hydroxyl group, a carboxyl group, and a vinyl group. Particularly, when dimethyl terephthalate is used as a raw material, a large amount may remain. . By the way, the methoxycarbonyl terminal generates methanol, formaldehyde, and formic acid by heat due to solid-state polymerization, kneading, molding, and the like, and particularly when used for food, the toxicity thereof becomes a problem. Formic acid also damages metal forming equipment and vacuum-related equipment. Therefore, the concentration of the terminal methoxycarbonyl group 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 of the above terminal group concentrations can be determined by dissolving PBT in a mixed solvent of chloroform / hexafluoroisopropanol = 7/3 (volume ratio) and measuring ¹ H-NMR. At this time, a very small amount of a basic component such as heavy pyridine may be added in order to prevent overlap with the solvent signal.

  The cooling crystallization temperature of the PBT of the present invention is usually 170 to 190 ° C, preferably 172 to 185 ° C, and more preferably 175 to 180 ° C. The cooling crystallization temperature in the present invention is a temperature of an exothermic peak due to crystallization that appears when the resin is cooled at a cooling rate of 20 ° C./min from a molten state using a differential scanning calorimeter. The cooling crystallization temperature corresponds to the crystallization speed, and the higher the cooling crystallization temperature, the faster the crystallization speed, so that the cooling time during molding can be shortened and the productivity can be increased. When the cooling crystallization temperature is low, crystallization takes a long time during molding, and the cooling time after molding has to be increased, and the molding cycle tends to be elongated and productivity tends to decrease.

  Although the solution haze of the PBT of the present invention is not particularly limited, it is usually 10% or less as a solution haze when 2.7 g of PBT is dissolved in 20 mL of a phenol / tetrachloroethane mixed solvent (3/2 by weight) and measured. Is at most 5%, more preferably at most 3%, particularly preferably at most 1%. If the solution haze is high, the transparency tends to deteriorate and the amount of foreign substances tends to increase. Therefore, the commercial value is significantly reduced particularly in applications requiring transparency, such as films, monofilaments and fibers. The solution haze tends to increase when the catalyst content is large or when the deactivation of the catalyst is large.

  Next, a method for manufacturing the PBT of the present invention will be described. Production methods of PBT are roughly classified into a so-called direct polymerization method using a dicarboxylic acid as a main material and a transesterification method using a dialkyl dicarboxylate as a main material from the viewpoint of raw materials. The former has a difference in that water is produced in the initial esterification reaction, and the latter has an alcohol produced in the initial transesterification reaction.

  In addition, PBT production methods are roughly classified into a batch method and a continuous method according to the form of raw material supply or polymer delivery. The initial esterification reaction or transesterification reaction is performed in a continuous operation and the subsequent polycondensation is performed in a batch operation, or conversely, the initial esterification reaction or transesterification reaction is performed in a batch operation and the subsequent polycondensation In a continuous operation.

  In the present invention, the direct polymerization method is preferred from the viewpoint of the availability of the raw materials, the ease of processing the distillate, the height of the raw material unit, and the improvement effect of the present invention. Further, in the present invention, from the viewpoint of productivity, stability of product quality, and the effect of improvement by the present invention, a method of continuously supplying a raw material and continuously performing an esterification reaction or a transesterification reaction is employed. In the present invention, a so-called continuous method in which a polycondensation reaction following an esterification reaction or a transesterification reaction is also continuously performed is preferable.

  In the present invention, in the esterification reaction tank, at least a portion of 1,4-butanediol is esterified independently from terephthalic acid (or dialkyl terephthalate) in the presence of a titanium catalyst. The step of continuously esterifying (or transesterifying) terephthalic acid (or dialkyl terephthalate) and 1,4-butanediol while supplying the mixture to the (tank) is preferably employed.

  That is, in the present invention, in order to reduce haze and foreign matter derived from the catalyst and not to lower the catalytic activity, apart from 1,4-butanediol supplied together with terephthalic acid or dialkyl terephthalate as a raw material slurry or solution, Further, 1,4-butanediol is supplied to the esterification reactor or the transesterification reactor independently of terephthalic acid or dialkyl terephthalate. Hereinafter, the 1,4-butanediol may be referred to as “separately supplied 1,4-butanediol”.

  The above-mentioned "separate feed 1,4-butanediol" can be applied to fresh 1,4-butanediol which is independent of the process. In addition, “separately supplied 1,4-butanediol” collects 1,4-butanediol distilled from an esterification reaction tank or a transesterification reaction tank with a condenser or the like and holds it as it is or in a temporary tank or the like. And refluxed to the reaction vessel, or impurities can be separated and purified and supplied as 1,4-butanediol with increased purity. Hereinafter, the “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”.

  Also, usually, 1,4-butanediol distilled from the esterification reactor or the transesterification reactor contains components such as water, alcohol, THF, dihydrofuran, etc. in addition to the 1,4-butanediol component. . Therefore, the 1,4-butanediol that has been distilled off should be separated and purified from components such as water, alcohol, and THF after or while being collected by a condenser or the like, and returned to the reaction tank. Is preferred.

  In the present invention, it is preferable that 10% by weight or more of the “separately supplied 1,4-butanediol” is directly returned to the liquid phase of the reaction liquid. Here, the liquid phase of the reaction liquid refers to the liquid phase side of the gas-liquid interface in the esterification reaction tank or transesterification reaction tank, and directly returning to the liquid phase of the reaction liquid means using a pipe or the like. This means that “separately supplied 1,4-butanediol” is directly supplied to the liquid phase portion without passing through the gas phase portion. The ratio of directly returning to the liquid phase 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 the amount of “separately supplied 1,4-butanediol” directly returned to the liquid phase of the reaction liquid is small, foreign substances tend to increase.

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

  Further, in the present invention, in order to reduce haze and foreign substances derived from the catalyst and not to decrease the catalytic activity, 10% by weight or more of the titanium catalyst used in the esterification reaction (or the transesterification reaction) is terephthalic acid. (Or dialkyl terephthalate) is preferably supplied directly to the reaction liquid phase. Here, the liquid phase of the reaction liquid indicates the liquid phase side of the gas-liquid interface in the esterification reaction tank or the transesterification reaction tank, and the supply directly to the liquid phase of the reaction liquid means using a pipe or the like. It means that the catalyst is supplied directly to the liquid phase portion without passing through the gas phase portion of the reactor. The proportion of the titanium catalyst added directly to the liquid phase of the reaction liquid is preferably at least 30% by weight, more preferably at least 50% by weight, particularly preferably at least 80% by weight, most preferably at least 90% by weight.

  The above titanium catalyst can be directly supplied to the liquid phase of the reaction liquid in the esterification reaction tank or the transesterification reaction tank with or without dissolving in a solvent or the like. In order to reduce adverse effects such as denaturation by heat from a heat medium jacket or the like, it is preferable to dilute with a solvent such as 1,4-butanediol. The concentration at this time is generally 0.01 to 20% by weight, preferably 0.05 to 10% by weight, and more preferably 0.08 to 8% by weight, as the concentration of the titanium catalyst based on the whole solution. From the viewpoint of reducing foreign substances, the water concentration in the solution is usually 0.05 to 1.0% by weight. The temperature at the time of solution preparation is usually 20 to 150 ° C, preferably 30 to 100 ° C, and more preferably 40 to 80 ° C, from the viewpoint of preventing deactivation and aggregation. Further, it is preferable that the catalyst solution is mixed with separately supplied 1,4-butanediol via a pipe or the like and supplied to the esterification reaction tank or the transesterification reaction tank from the viewpoint of preventing deterioration, preventing precipitation, and suppressing foreign substances.

  An example of the continuous method employing the direct polymerization method is as follows. That is, the dicarboxylic acid component containing terephthalic acid as a main component and the diol component containing 1,4-butanediol as a main component are mixed in a raw material mixing tank to form a slurry, and the slurry is mixed in one or more esterification reaction tanks. , In the presence of a titanium catalyst, usually at a temperature of 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 a pressure of usually 0.5 to 10 hours, preferably 1 to 6 hours, to continuously carry out an esterification reaction, and transfer the obtained oligomer as an esterification reaction product to a polycondensation reaction tank. Alternatively, in a plurality of polycondensation reaction tanks, preferably continuously, usually at 210 to 280 ° C, preferably 220 to 265 ° C in the presence of a polycondensation catalyst. 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, extracted in a strand shape, and cut with a cutter while cooling with water or after cooling with water, pelletized, chip-shaped. And the like.

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

  The above-mentioned "1,4-butanediol supplied from the outside to the esterification reaction tank" refers to 1,4-butanediol supplied together with terephthalic acid or dialkyl terephthalate as a raw material slurry or solution, and Is the total sum of 1,4-butanediol, such as 1,4-butanediol, which is independently supplied, and 1,4-butanediol used as a catalyst solvent, which enter the reaction tank from outside the reaction tank.

  When the value of BM / TM is smaller than 1.1, the conversion is lowered or the catalyst is deactivated. When the value is larger than 4.5, not only the thermal efficiency is reduced, but also by-products such as THF increase. 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 method employing the transesterification method is as follows. That is, in one or more transesterification reaction tanks, in the presence of a titanium catalyst, usually at a temperature of 110 to 260 ° C, preferably 140 to 245 ° C, more preferably 180 to 220 ° C, and usually 10 to 133 kPa, The transesterification reaction is carried out continuously under a pressure of preferably 13 to 120 kPa, more preferably 60 to 101 kPa, usually for 0.5 to 5 hours, preferably for 1 to 3 hours. Is transferred to a polycondensation reaction tank, and in the presence of a polycondensation reaction catalyst in one or more polycondensation reaction tanks, preferably continuously, usually at 210 to 280 ° C, preferably 220 to 265 ° C. The temperature is generally 27 kPa or less, preferably 20 kPa or less, more preferably 13 kPa or less, under reduced pressure, and is preferably 2 to 12 hours under stirring. Causes polycondensation reaction at 3-10 hours.

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

  When the value of BM / DM is smaller than 1.1, the conversion and the catalytic activity are reduced. When it is larger than 2.5, not only the thermal efficiency is reduced, but also by-products such as THF are generated. 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 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 thermal convection type mixing tank, and a tower-type continuous reaction tank may be used. Further, a single tank may be used, or a plurality of tanks of the same type or different types may be connected in series. Among them, a reaction vessel having a stirring device is preferable. As the stirring device, in addition to a normal type including a power unit, a bearing, a shaft, and a stirring blade, a turbine stator type high-speed rotary stirrer, a disk mill type stirrer, and a rotor mill type stirrer A type that rotates at high speed, such as the above, can also be used.

  The form of stirring is not particularly limited. In addition to the ordinary stirring method in which the reaction solution in the reaction tank is directly stirred from the upper, lower, and lateral portions of the reaction tank, a part of the reaction solution is piped to the reactor. It is also possible to adopt a method in which the reaction solution is taken out, stirred with a line mixer or the like, and the reaction solution is circulated.

  Known types of stirring blades can be selected, and specific examples include propeller blades, screw blades, turbine blades, fan turbine blades, disk turbine blades, faudler 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 are used, and the molecular weight is increased sequentially. Usually, a polycondensation reaction follows the initial esterification or transesterification reaction.

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

  The form of stirring is not particularly limited. In addition to the ordinary stirring method in which the reaction solution in the reaction tank is directly stirred from the upper, lower, and lateral portions of the reaction tank, a part of the reaction solution is piped to the reactor. It is also possible to adopt a method in which the reaction solution is taken out, stirred with a line mixer or the like, and the reaction solution is circulated. Above all, it is recommended that at least one of the polycondensation reaction tanks be a horizontal reactor having a horizontal axis of rotation and excellent in surface renewal and self-cleaning properties.

  In addition, in order to suppress coloring and deterioration and to suppress an increase in terminals such as vinyl groups, a high vacuum of usually 1.3 kPa or less, preferably 0.5 kPa or less, more preferably 0.3 kPa or less is used in at least one reaction tank. The temperature is usually 225 to 255 ° C, preferably 230 to 250 ° C, more preferably 233 to 245 ° C.

  Further, in the polycondensation reaction step of PBT, once a PBT having a relatively small molecular weight, for example, an intrinsic viscosity of about 0.1 to 1.0 is produced by melt polycondensation, and subsequently, a PBT having a temperature equal to or lower than the melting point of the PBT is produced. Although solid-phase polycondensation (solid-state polymerization) can be performed, solid-phase polymerization should not be performed in applications such as fish eyes and other films where appearance is important.

  In the PBT of the present invention, since the foreign matter derived from the catalyst is significantly reduced, the foreign matter does not need to be removed. However, by installing a filter in the flow path of the polymer precursor or the polymer, the PBT can be further improved in quality. Excellent polymer is obtained. In the present invention, for the above-described reason, when a filter having the same opening as that used in the conventional PBT manufacturing facility is used, it is possible to extend the life until the replacement. If the life until replacement is set to be the same, it is possible to install a filter with a smaller opening.

  If the installation position of the filter is too upstream of the manufacturing process, foreign substances generated on the downstream side cannot be removed, and the pressure loss of the filter will increase in places where the viscosity on the downstream side is high, and in order to maintain the flow rate, It is necessary to enlarge the size of the filter, to increase the filtration area of the filter and the facilities such as piping, and to receive high shear when the fluid passes, so that the degradation of PBT due to shear heat generation is inevitable. . Therefore, as for the installation position of the filter, the position where 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 selected. Is done.

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

  Although the absolute filtration accuracy of the filter is not particularly limited, it is generally 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 substances in the product will be lost, and if it is too small, productivity will decrease and the frequency of filter replacement will increase.

  Hereinafter, a preferred embodiment of a method for manufacturing a PBT will be described with reference to the accompanying drawings. FIG. 1 is an explanatory view of an example of an esterification reaction step or a transesterification reaction step adopted in the present invention, and FIGS. 2 and 3 show other examples of the esterification reaction step or the transesterification reaction step adopted in the present invention. FIG. 4 is an explanatory view of an example of the polycondensation step employed in the present invention, and FIGS. 5 to 7 are explanatory views 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 a slurry from a raw material supply line (1). You. On the other hand, when the raw material is dialkyl terephthalate, it is usually supplied to the reaction tank (A) as a molten liquid independently of 1,4-butanediol. 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 an embodiment in which a catalyst supply line (3) is connected to a recirculation line (2) for recirculating 1,4-butanediol, and the two are mixed and then supplied to the liquid phase portion of the reaction tank (A). Was.

  The gas distilled from the reaction tank (A) is separated into a high-boiling component and a low-boiling component in the rectification column (C) via the distilling line (5). Usually, the main component of the high-boiling component is 1,4-butanediol, and the main components of the low-boiling component are water and THF for the direct polymerization method, and alcohol, THF, and water for 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). And a part is returned to the rectification column (C) from the circulation line (7). 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 stored in the tank (F) via the condensate line (10). Can be stored. 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 a line (13). The condenser (G) is connected to an exhaust device (not shown) via a vent line (14). The oligomer generated in the reaction tank (A) is withdrawn through a withdrawal pump (B) and a withdrawal line (4).

  In the step shown in FIG. 1, the catalyst supply line (3) is connected to the recirculation line (2), but both may be independent. Further, the raw material supply line (1) may be connected to a liquid phase portion of the reaction tank (A).

  The process shown in FIG. 2 is different from the process shown in FIG. 1 in that the rectification column (C) is equipped with a reboiler (H), and the recovery line (15) for supplying liquid from the outside to the rectification column (C). ) Is provided. The installation of the reboiler (H) facilitates the operation control of the rectification column (C).

  The process shown in FIG. 3 is different 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 of the reaction tank (A). Therefore, in the case of the step shown in FIG. 3, a part of the recirculated 1,4-butanediol returns to the reaction solution via the gas phase of the reaction tank (A).

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

  The process shown in FIG. 5 is different 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 is different from the process shown in FIG. 4 in that a 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 including a plurality of stirring blade blocks and having a biaxial self-cleaning type stirring blade. The polymer introduced from the second polycondensation reaction tank (d) to the third polycondensation reaction tank (k) through the extraction line (L3) is further subjected to polycondensation here, and then the extraction gear pump (m ) And a drawing line (L5), and is drawn out from the die head (g) in the form of a molten strand, cooled with water or the like, and then cut by a rotary cutter (h) to form pellets. The symbol (L6) is a vent line of the third polycondensation reaction tank (k).

  The process shown in FIG. 7 is different from the process shown in FIG. 6 in that a filter (L3) is provided in the middle of the extraction line (L3) between the second polycondensation reaction tank (d) and the third polycondensation reaction tank (k). f) is provided.

  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, thioether compounds such as dilauryl-3,3'-thiodipropionate, pentaerythrityl-tetrakis (3-laurylthiodipropionate), triphenyl phosphite, tris (nonylphenyl) phosphite, tris (2 , 4-di-t-butylphenyl) phosphite and other antioxidants, paraffin wax, microcrystalline wax, polyethylene wax, long-chain fatty acids represented by montanic acid and montanic acid esters and esters thereof, silicone A release agent such as oil may be added.

  The PBT of the present invention may contain a reinforcing filler. The reinforcing filler is not particularly limited, but includes, for example, inorganic fibers such as glass fiber, carbon fiber, silica / alumina fiber, zirconia fiber, boron fiber, boron nitride fiber, potassium silicon nitride titanate fiber, and metal fiber, and aromatic fibers. Organic fibers such as polyamide fibers and fluororesin fibers are exemplified. 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.

  The reinforcing filler is preferably used after being surface-treated with a sizing agent or a surface treating agent in order to improve the interfacial adhesion with PBT. Examples of the sizing agent or the surface treatment agent include functional compounds such as an epoxy compound, an acrylic compound, an isocyanate compound, a silane compound, and a titanate compound. 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 preparation of the PBT composition. The amount of the reinforcing filler added is usually 150 parts by weight or less, preferably 5 to 100 parts by weight, based on 100 parts by weight of the PBT resin.

  The PBT of the present invention may contain other fillers together with the reinforcing filler. As other fillers to be blended, for example, plate-like inorganic fillers, ceramic beads, asbestos, wollastonite, talc, clay, mica, zeolite, kaolin, potassium titanate, barium sulfate, titanium oxide, silicon oxide, oxide Aluminum and magnesium hydroxide are exemplified. 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 flake, mica, and metal foil. Among these, glass flake is preferably used.

  The PBT of the present invention may contain a flame retardant for imparting flame retardancy. The flame retardant is not particularly restricted but includes, for example, organic halogen compounds, antimony compounds, phosphorus compounds, other organic flame retardants, inorganic flame retardants and the like. 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, and polypentabromobenzyl acrylate. Examples of the antimony compound include antimony trioxide, antimony pentoxide, sodium antimonate and the like. Examples of the phosphorus compound include a phosphoric ester, polyphosphoric acid, ammonium polyphosphate, red phosphorus and the like. Other organic flame retardants include, for example, nitrogen compounds such as melamine and cyanuric acid. Other inorganic flame retardants include, for example, aluminum hydroxide, magnesium hydroxide, silicon compounds, boron compounds and the like.

  The PBT of the present invention may contain conventional additives and the like, if necessary. Such additives are not particularly limited, and include, for example, antioxidants, stabilizers such as heat stabilizers, lubricants, release agents, catalyst deactivators, crystal nucleating agents, crystallization accelerators, and the like. Can be These additives can be added during or after the polymerization. Furthermore, in order to impart desired performance to the PBT, a UV absorber, a stabilizer such as a weather resistance stabilizer, a coloring agent such as a dye / pigment, an antistatic agent, a foaming agent, a plasticizer, and an impact resistance improver are compounded. You can do it.

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

  The method of compounding the various additives and resins is not particularly limited, but a method using a single-screw or twin-screw extruder having equipment capable of devolatilizing from a vent port is preferable. Each component, including additional components, can be supplied to the kneader at once, or can be supplied sequentially. In addition, two or more components selected from each component, including additional components, can be mixed in advance.

  The method for molding the PBT 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. .

  Since the PBT of the present invention is excellent in color tone, hydrolysis resistance, thermal stability, transparency, and moldability, it is suitable as an injection-molded part for electric, electronic, and automotive parts. And has excellent transparency and thermal stability, so that the improvement effect is remarkable in applications such as films, monofilaments, and fibers.

  Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited to the following examples at all unless it exceeds the gist. The methods of measuring physical properties and evaluation items adopted in the following examples are as follows.

(1) Esterification rate:
It was calculated from the acid value and saponification value according to the following formula (4). The acid value was determined by dissolving the oligomer in dimethylformamide and titrating with a 0.1 N 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:
0.5 g of PBT or oligomer was dissolved in 25 mL of benzyl alcohol, and titrated using a 0.01 mol / L benzyl alcohol solution of sodium hydroxide.

(3) Intrinsic viscosity (IV):
It was determined as follows using an Ubbelohde viscometer. That is, using a mixed solvent of phenol / tetrachloroethane (weight ratio: 1/1), the falling seconds of only the polymer solution having a concentration of 1.0 g / dL and the solvent were measured at 30 ° C., and the following formula (5) was obtained. 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 (Inductively 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 heavy chloroform / hexafluoroisopropanol = 7/3 (volume ratio), 36 μL of heavy pyridine was added, and ¹ H-NMR was measured at 50 ° C. to determine. "Α-400" or "AL-400" manufactured by JEOL Ltd. was used for the NMR apparatus.

(6) Number of fish eyes:
A film having a thickness of 50 μm was formed using a Film Quality Testing System [Model FS-5 of Optical Control Systems Co., Ltd.], 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 lowering rate of 20 ° C./min. The temperature was taken as the cooling crystallization temperature. The higher the Tc, the faster the crystallization rate and the shorter the molding cycle.

(8) Solution haze:
2.70 g of PBT was dissolved in 20 mL of a mixed solvent of phenol / tetrachloroethane = 3/2 (weight ratio) at 110 ° C. for 30 minutes, then 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 densitometer (NDH-300A). The lower the value, the better the transparency.

(9) Pellet color tone:
Using a color difference meter (model Z-300A) manufactured by Nippon Denshoku Co., Ltd., the b value in the L, a, b color system was calculated and evaluated. The lower the value, the less yellowish and the better the color tone.

(10) Increase in terminal carboxyl group concentration due to a reaction other than the hydrolysis reaction (ΔAV (d)):
PBT pellets were crushed, dried, filled in a capillary having an inner diameter of 5 mm, filled and replaced with nitrogen, immersed in an oil bath controlled at 245 ° C. under nitrogen, taken out 40 minutes later, and quenched with liquid nitrogen. After the temperature of the contents was sufficiently lowered, the contents were taken out, and the terminal carboxyl group concentration and the terminal hydroxyl group concentration were measured, and were obtained from the above-mentioned 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 slurry at 60 ° C. mixed at a ratio of 1.80 mol of 1,4-butanediol to 1.00 mol of terephthalic acid was passed through a raw material supply line (1) from a slurry preparation tank in advance to obtain an esterification rate of 99%. % Of the PBT oligomer was continuously fed to the reaction vessel (A) for esterification having a screw-type stirrer at a rate of 28.5 kg / h. At the same time, the bottom component of the rectification column (C) at 185 ° C. is supplied at 12.0 kg / h from the recirculation line (2), and tetrabutyl titanate at 65 ° C. is used as a catalyst from the catalyst supply line (3). A 0 wt% 1,4-butanediol solution was fed at 69 g / h (30 ppm based on 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 generated water, THF and excess 1,4-butanediol are distilled out from the distillation line (5), and the rectification column (C) To separate into high boiling components and low boiling components. After the system is stabilized, 98% by weight or more of the high-boiling component at the bottom of the column is 1,4-butanediol, and the extraction line (8) is used so that the liquid level of the rectification column (C) is constant. Part of it was extracted to the outside. On the other hand, low-boiling components were withdrawn in the form of gas from the top of the column, condensed in a condenser (G), and withdrawn from the withdrawal line (13) so that the liquid level in the tank (F) was constant.

  A certain amount of the oligomer produced 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 pressure reducer (not shown). The withdrawn reaction liquid was continuously supplied to the second polycondensation reaction tank (d).

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

Example 2:
Example 1 was carried out in the same manner as in Example 1 except that the polycondensation step shown in FIG. 7 was employed. 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 further reduced fish eyes than in Example 1 was obtained. 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 tank (A) was changed to 5.6 kg / h, and the inside of the second polycondensation reaction tank was changed. Example 1 was repeated 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. A PBT with less 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 set to 240 ° C., and the third polycondensation reaction was performed. The procedure was performed in the same manner as in Example 1 except that the residence time in the reaction tank (k) was 90 minutes. Fish eyes increased and transparency worsened. The analytical values are summarized in Table 1.

Comparative Example 2:
In Example 1, the catalyst supply line (3) in the esterification step shown in FIG. 1 was connected to the raw material supply line (1), and the recirculation line (2) was located in the gas phase of the reaction tank (A). Then, the same as Example 1 except that the supply amount of the 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. I went to. As shown in the table, haze, color tone, and thermal stability deteriorated, and there were many fish eyes. The analytical values are summarized in Table 1.

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

  After transferring the oligomer obtained above to a stainless steel reactor having an inner volume of 200 L having a vent tube and a double helical stirring blade, the temperature was increased to 245 ° C. and a pressure of 100 Pa over 60 minutes. A condensation reaction was performed. The stirring power value, which is the IV index of the polymer in the reaction tank, reached a plateau after 150 minutes, and it was impossible to further increase the IV. Therefore, after 180 minutes, the polymer was extracted in a strand shape and cut into pellets. IV was as low as 1.25 dL / g, color tone and thermal stability were poor, Tc was low, and 0.8 μeq / g of terminal methoxycarbonyl group remained. 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, 272.9 mol of dimethyl terephthalate (DMT), 327.5 mol of 1,4-butanediol, and 0.101 mol of tetrabutyl titanate (theoretical yield as titanium amount) (80 ppm per polymer) and sufficiently substituted with nitrogen. Subsequently, the temperature of the system was raised, and after 60 minutes, transesterification was carried out for 2 hours at a temperature of 210 ° C. and atmospheric pressure under nitrogen while distilling out generated methanol, 1,4-butanediol and THF from the system. (The reaction start time was a point in time when a predetermined temperature and a predetermined pressure were reached).

  After transferring the oligomer obtained above to a stainless steel reactor having an inner volume of 200 L having a vent tube and a double helical stirring blade, the oligomer 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 the completion of the reaction, the polymer was drawn out into a strand and cut into pellets. The obtained polymer was charged in a double-cone type solid-phase polymerization apparatus having a jacket of 100 L in inner volume, and reduced pressure / nitrogen substitution was repeated three times. The next pressure was controlled at 130 Pa, and the temperature was raised to 195 ° C. Six hours after the internal temperature reached 195 ° C, the jacket heating medium was started to be cooled, and the content was taken out when the internal temperature became 40 ° C or less. The obtained PBT was inferior in color tone and heat stability, had low Tc, and had many fish eyes. In addition, 2.1 μeq / g of the terminal methoxycarbonyl group remained. The analytical values are summarized in Table 1.

Explanatory drawing of an example of an esterification reaction step or a 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 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 reference numerals

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 (9)

  A polybutylene terephthalate containing titanium and having an amount of 50 ppm or less as a titanium atom, an intrinsic viscosity of 1.20 to 2.00, and a terminal carboxyl group concentration of 15 μeq / g or more.   The polybutylene terephthalate according to claim 1, wherein the concentration of the terminal methoxycarbonyl group is 0.5 µeq / g or less.   The polybutylene terephthalate according to claim 1 or 2, wherein a temperature-reducing crystallization temperature measured by a differential scanning calorimeter at a temperature-lowering rate of 20 ° C / min is 170 to 190 ° C.   The polybutylene terephthalate according to claim 1, wherein the terminal vinyl group concentration is 0.5 to 12 μeq / g.   The polybutylene according to any one of claims 1 to 4, wherein a solution haze is 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). Terephthalate.   The polybutylene terephthalate according to any one of claims 1 to 5, wherein an increase in terminal carboxyl group concentration excluding a hydrolysis reaction when heat-treated 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 6, wherein the terminal carboxyl group concentration is 20 to 30 µeq / g.   The polybutylene terephthalate according to any one of claims 1 to 7, having an intrinsic viscosity of 1.30 to 1.50.   The polybutylene terephthalate according to any one of claims 1 to 8, which is obtained without performing solid-state polymerization.