JP4544228B2 - Method for producing polybutylene terephthalate - Google Patents

Description

  The present invention relates to a method for producing polybutylene terephthalate, and more specifically, to suppress color by-product while maintaining the color tone, hydrolysis resistance, thermal stability, transparency and moldability without sacrificing productivity. The present invention relates to a method for producing polybutylene terephthalate which is excellent and can be suitably used for films, monofilaments, fibers, electric and electronic parts, automobile parts and the like with reduced foreign matter.

  Polybutylene terephthalate, a representative engineering plastic among thermoplastic polyester resins, is excellent in molding process, mechanical properties, heat resistance, chemical resistance, aroma retention, and other physical and chemical properties. Therefore, 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 the fields of films, sheets, monofilaments, fibers, etc. In these fields, polybutylene terephthalate having a higher molecular weight than conventional injection molded products is used. It has been demanded.

  Polybutylene terephthalate has excellent properties as described above, but is not necessarily sufficiently resistant to hydrolysis. Particularly in use under wet heat, a decrease in mechanical properties accompanying a decrease in molecular weight has become a problem. Yes. In general, it is known that polybutylene terephthalate is deteriorated in hydrolysis resistance as the terminal carboxyl group concentration is high (see, for example, Patent Document 1), leading to a decrease in molecular weight due to hydrolysis, and a decrease in mechanical properties. Is a big problem.

  In order to solve the above problems, it is widely practiced to reduce the terminal carboxyl group concentration by solidifying the polybutylene terephthalate obtained by melt polymerization once and solid-phase polymerization at a temperature below its melting point ( For example, see Patent Document 1). However, this method has a problem that energy loss increases because it is necessary to raise the temperature of the polybutylene terephthalate once cooled and solidified. In addition, since ordinary melt molding is performed at a temperature higher than the melting point of polybutylene terephthalate, in conventional polybutylene terephthalate, even if the terminal carboxyl group concentration is reduced by solid phase polymerization, the terminal carboxyl group concentration rises again during molding. There is a problem. This increase in the terminal carboxyl group concentration is inextricably linked with the reaction for generating butadiene and tetrahydrofuran (see, for example, Non-Patent Document 1), and as a result, there is a problem that the generation of gas during molding increases.

  The rate of increase in the terminal carboxyl group concentration at the time of melting is considered to be promoted by the presence of the titanium compound added as a catalyst and remaining in the polybutylene terephthalate. If it is attempted to reduce the polymerization rate, the polymerization rate becomes slow, and when producing polybutylene terephthalate at a practical polymerization rate, the polymerization temperature must be increased. Therefore, as a result, the decomposition reaction in which the terminal carboxyl group concentration increases is promoted, and the terminal carboxyl group concentration does not decrease as intended. In addition, there is a problem that the reaction at a high temperature causes a deterioration of the color tone and decreases the commercial value.

  In order to solve the above problems, a method of setting a polymerization temperature low by using a specific molar ratio of a titanium compound and a specific metal compound as a catalyst (see, for example, Patent Document 2) or use of titanium in a specific state Has been proposed (see, for example, Patent Document 3). However, even with these methods, it cannot be said that the above-mentioned problem is sufficiently solved, and it cannot be said that the method is satisfactory as the quality requirements for polybutylene terephthalate increase.

  Generally known methods for producing polybutylene terephthalate include transesterification using dimethyl terephthalate and 1,4-butanediol as raw materials (DMT method) or direct polymerization using terephthalic acid and 1,4-butanediol. However, in the transesterification method, methanol is generated as a by-product of the reaction, and there is a problem of recovery treatment of by-product low molecular weight substances. Further, from the viewpoints of stability of product quality, miniaturization of production equipment, energy efficiency, and the like, a direct continuous polymerization method in which raw materials are continuously supplied and products are continuously obtained is attracting attention.

  However, the titanium catalyst used in the production of polybutylene terephthalate has a problem that a part thereof is deactivated during the production process of polybutylene terephthalate, and the deactivation uses terephthalic acid as a raw material. This is remarkable in the direct continuous polymerization method (see, for example, Patent Documents 4 and 5). The deactivation of the titanium catalyst literally has a serious problem of not only causing a deterioration in reactivity but also causing a haze deterioration and an increase in foreign matters.

  In order to solve these problems, a method of prescribing the amount of the organic titanium compound to be added in the production of polybutylene terephthalate and allowing the organic tin compound to coexist in the initial esterification reaction stage (see, for example, Patent Documents 4 and 6). Furthermore, the reaction of continuously esterifying terephthalic acid and 1,4-butanediol is divided into two stages. In the first stage esterification reaction, only an organotin compound is added, and in the second stage esterification reaction, A method of adding an organic titanium compound to reduce foreign matters and haze derived from a catalyst has been proposed (see, for example, Patent Document 7). However, these methods have a problem that not only the effect of reducing foreign matter and haze is limited, but also the color tone of polybutylene terephthalate is deteriorated due to the addition of a large amount of tin compound.

  Furthermore, in the direct continuous polymerization method of polybutylene terephthalate, tetrahydrofuran is produced as a by-product in the initial esterification reaction, and the basic unit of 1,4-butanediol as a raw material is deteriorated. In order to solve this problem, a method has been proposed in which the molar ratio of 1,4-butanediol to terephthalic acid during the esterification reaction is set to be relatively low and tin is allowed to coexist with titanium (for example, patents). The solution haze of the obtained polybutylene terephthalate is still high, and the problem of catalyst deactivation has not been solved at all. In addition, a method of performing esterification at a specific temperature and a specific pressure has been proposed (see, for example, Patent Document 8). However, even in this method, it was impossible to achieve both suppression of tetrahydrofuran by-product and prevention of catalyst deactivation.

Saturated polyester resin handbook (December 22, 1989, published by Nikkan Kogyo Shimbun, page 274) JP-A-9-316183 JP-A-8-20638 JP-A-8-41182 JP 2002-284868 A JP 2002-284870 A Japanese Patent Laid-Open No. 10-330469 Japanese Patent Laid-Open No. 10-330468 Japanese Patent Laid-Open No. 62-195017

  The present invention has been made in view of the above circumstances, and its purpose is to suppress color by-product, hydrolysis resistance, thermal stability, transparency, molding without sacrificing productivity while suppressing tetrahydrofuran by-product. Another object of the present invention is to provide a method for producing polybutylene terephthalate which is excellent in properties and can be suitably used for films, monofilaments, fibers, electrical and electronic parts, automobile parts and the like with reduced foreign matter.

  As a result of intensive studies to solve the above problems, the present inventors have used a titanium compound and a compound of at least one metal selected from Groups 1 and 2 of the periodic table as a catalyst in a specific mode. Surprisingly, if the esterification reaction and the polymerization reaction are performed, polybutylene terephthalate having a low terminal carboxyl group concentration is prevented while preventing the deactivation of the titanium catalyst and suppressing the increase of the terminal carboxyl group due to the thermal decomposition reaction. The polybutylene terephthalate is excellent in color and thermal stability because it can suppress the increase in terminal carboxyl group concentration during melt extrusion and molding, and the polycondensation reaction is greatly accelerated. As a result, the present invention has been completed.

  The gist of the present invention is that a titanium compound and a compound of at least one metal selected from Groups 1 and 2 of the periodic table are used as a catalyst, and polybutylene terephthalate is continuously produced from terephthalic acid and 1,4-butanediol. In producing the polybutylene terephthalate, the following conditions (a) to (c) are satisfied.

(A) An oligomer is obtained by continuously esterifying terephthalic acid and 1,4-butanediol in the presence of 460 μmol or less of titanium catalyst per 1 mol of terephthalic acid units as titanium atoms.

(B) The above oligomer is continuously subjected to a polycondensation reaction in the presence of at least one metal compound selected from metals of Group 1 and Group 2 of the periodic table of 450 μmol or less per 1 mol of terephthalic acid unit as a metal atom.

(C) The metal compound may be added as a metal atom in a range of 300 μmol or less per 1 mole of terephthalic acid unit before reaching an oligomer having an esterification rate of 90% or more, but the esterification rate is 90%. In the stage after reaching the above oligomer, 10 μmol or more per 1 mol of terephthalic acid unit is added as a metal atom.

  And the 2nd summary of this invention exists in the manufacturing method of the polybutylene terephthalate characterized by carrying out the solid phase polycondensation of the polybutylene terephthalate obtained by said manufacturing method at the temperature below melting | fusing point further.

  According to the present invention, it is suitable for use in films, monofilaments, fibers, electrical and electronic parts, automobile parts, etc. that are excellent in color tone, hydrolysis resistance, thermal stability, transparency, moldability, and reduced foreign matter. A process for producing polybutylene terephthalate that can be provided is provided.

  Hereinafter, the present invention will be described in detail. The polybutylene terephthalate (hereinafter sometimes abbreviated as PBT) in 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 terephthalic. It refers to a polymer composed of acid units, wherein 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 optimally 98% or more. The proportion of 1,4 butanediol units is preferably at least 70 mol%, more preferably at least 80 mol%, particularly preferably at least 95 mol%, and optimally at least 98%. 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.

  First, in the present invention, terephthalic acid and 1,4-butanediol are continuously esterified in the presence of 460 μmol or less of titanium catalyst per mol of terephthalic acid units as titanium atoms to obtain oligomers.

  Specific examples of the titanium catalyst include inorganic titanium compounds such as titanium oxide and titanium tetrachloride, titanium alcoholates such as tetramethyl titanate, tetraisopropyl titanate and tetrabutyl titanate, and titanium phenolates such as tetraphenyl titanate. Among these, tetraalkyl titanate is preferable, and among them, tetrabutyl titanate is preferable.

  The upper limit of the amount of titanium catalyst used is preferably 320 μmol, more preferably 230 μmol, and particularly preferably 190 μmol, as a value per 1 mol of terephthalic acid unit as a titanium atom. The lower limit of the amount of titanium catalyst used is not particularly limited, but is usually 45 μmol, preferably 90 μmol, and more preferably 130 μmol, as the same reference value as above. If the amount of titanium catalyst used is too large, the color tone, hydrolysis resistance, etc. tend to deteriorate, and foreign matter derived from the deactivated titanium catalyst tends to increase. If the amount of titanium catalyst used is too small, polymerization will occur. There is a tendency that the property deteriorates and the amount of THF produced as a by-product increases. In the present invention, when a plurality of esterification reactors are used and the esterification rate is gradually increased, it is not always necessary to add all of the necessary amount of the titanium catalyst in the first esterification reactor. In addition, it is possible not to perform the addition in the first-stage esterification reaction apparatus, and it is sufficient that a necessary amount is added by the end of the esterification reaction.

  In addition, the titanium catalyst can be directly supplied to the esterification reactor without being dissolved or diluted in a solvent or the like, but the supply amount is stabilized, and modification by heat from the heating medium jacket of the reactor, In order to reduce adverse effects such as generation of foreign matter due to deactivation, it is preferable to dilute with a solvent such as 1,4-butanediol. The concentration at this time is determined as appropriate, but generally the titanium catalyst concentration is usually 0.01 to 20% by weight, preferably 0.05 to 10% by weight, more preferably 0.08 to 8% by weight. is there.

  Among these, from the viewpoint of reducing foreign matters, the titanium catalyst is supplied as a 0.01 to 20% by weight (preferably 1 to 10% by weight) 1,4-butanediol solution, and the water concentration in the solution is 0.1. It is preferable that it is 05-1.0 weight%. Moreover, it is preferable to supply a titanium catalyst solution independently without mixing with a terephthalic acid before supplying to a reactor from the point of deterioration prevention, precipitation prevention, and foreign material control.

  Further, in the production method of the present invention, it is essential to perform an esterification reaction in the presence of a titanium catalyst, but it is also possible to further add a titanium catalyst after the esterification reaction or before the polycondensation reaction or during the polycondensation reaction. is there. Even in such a case, the upper limit of the content of the titanium catalyst in the finally obtained polybutylene terephthalate is preferably 460 μmol per 1 mole of terephthalic acid unit as a titanium atom, more preferably 320 μmol, particularly preferably 230 μmol, Most preferably, it is 190 μmol. When the content of the titanium catalyst exceeds the above upper limit, the color tone and hydrolysis resistance of the resulting polybutylene terephthalate tend to deteriorate, and foreign matters derived from the deactivated material of the titanium catalyst tend to increase.

  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, 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.

  Since tin deteriorates the color tone of polybutylene terephthalate, its addition amount is usually 200 ppm or less, preferably 100 ppm or less, more preferably 10 ppm or less, and most preferably not added as tin atoms.

  Next, in the present invention, the above oligomer continuous polycondensation reaction is carried out in the presence of at least one metal compound selected from metals of Group 1 and Group 2 of the periodic table of 450 μmol or less per 1 mol of terephthalic acid unit as a metal atom. Let The upper limit of the compound of at least one metal selected from the metals of Group 1 and Group 2 of the periodic table existing during the polycondensation reaction is preferably 300 μmol, more preferably 180 μmol, particularly preferably per 1 mol of terephthalic acid unit as a metal atom. 130 μmol, most preferably 100 μmol. When the compound of at least one metal selected from metals of Group 1 and Group 2 of the periodic table existing during the polycondensation reaction exceeds the above upper limit, the polycondensation reaction rate tends to decrease as the polycondensation reaction proceeds. The color tone and hydrolysis resistance of the polybutylene terephthalate obtained may deteriorate. In addition, said value points out the total amount, when multiple metal seed | species is contained.

  Specific examples of Group 1 metal compounds include lithium, sodium, potassium, rubidium, and cesium compounds. Specific examples of Group 2 metal compounds include beryllium, magnesium, calcium, strontium, Although various compounds of barium are mentioned, the compound of lithium, sodium, potassium, magnesium, and calcium is preferable from the point of handling and availability, and a catalyst effect, and especially magnesium or a lithium compound excellent in a catalyst effect is preferable. Is preferably a magnesium compound. Specific examples of the magnesium compound include magnesium acetate, magnesium hydroxide, magnesium carbonate, magnesium oxide, magnesium alkoxide, magnesium hydrogen phosphate, and the like. Among these, magnesium acetate is preferable.

  The metal compound may be added as a metal atom in the range of 300 μmol or less per mol of terephthalic acid unit in the stage before reaching an oligomer having an esterification rate of 90% or more. In the subsequent stage, 10 μmol or more per 1 mol of terephthalic acid unit is added as a metal atom.

  The esterification rate of the oligomer can be calculated from the acid value and the saponification value by the calculation formula (1). The acid value is obtained by dissolving the oligomer in dimethylformamide and titrating using a 0.1N KOH / methanol solution. The saponification value is obtained by hydrolyzing the oligomer with a 0.5N KOH / ethanol solution. It can be obtained by titration with hydrochloric acid.

  When the amount of the metal compound added in the stage before reaching the oligomer having an esterification rate of 90% or more exceeds the above range, the esterification reaction is inhibited, resulting in a deterioration in color tone and an increase in the amount of THF by-produced. The amount of the metal compound used at this stage is preferably 270 μmol or less, more preferably 130 μmol or less, particularly preferably 90 μmol, and most preferably 45 μmol as the same standard value as described above. Most preferably, is not added.

  As described above, the lower limit of the amount of the metal compound to be added in the stage after reaching the oligomer having an esterification rate of 90% or more is 10 μmol, preferably 45 μmol, and more preferably 80 μmol. On the other hand, the upper limit is usually 300 μmol or less, preferably 180 μmol or less, more preferably 130 μmol or less, and particularly preferably 100 μmol or less as the same reference value as described above. The compounds of Group 1 and Group 2 metals in the periodic table increase the initial polycondensation rate, and improve the color tone and hydrolysis resistance of the resulting PBT. However, when the amount used is too large, the late polycondensation rate is lowered, so that the above effect is not exhibited. When the amount is too small, the initial polycondensation rate is not improved.

  In the present invention, the molar ratio [(periodic group 1 group + group 2 metal) / titanium) of at least one metal selected from Group 1 and Group 2 of the periodic table to titanium atoms is usually 0.1 to 5, Preferably it is 0.1-2, More preferably, it is 0.3-1.0, Most preferably, it is 0.3-0.8.

  The metal content such as titanium atom can be measured using a method such as atomic emission, atomic absorption, or inductively coupled plasma (ICP) after recovering the metal in the polymer by a method such as wet ashing.

  The metal compound to be added in the stage after reaching the oligomer having an esterification rate of 90% or more is preferably added as follows. That is, the intrinsic viscosity at the outlet of the reactor is usually 0.50 dL / g or less, preferably 0.40 dL / g or less, more preferably 0.30 dL / g or less. The intrinsic viscosity is a value measured at 30 ° C. using a mixed solvent of phenol / tetrachloroethane (weight ratio 1/1).

  Examples of the addition method include a method of adding to the liquid phase part via the gas phase part of the polycondensation reactor, a method of adding directly to the liquid phase part, etc., but prevents entrainment, deactivation, precipitation and the like. In order to achieve this, a method for supplying the oligomer to the polycondensation process by adding it to the oligomer extraction line (piping the oligomer from the final reaction tank in the esterification process and supplying it to the first reaction tank in the polycondensation process) Is preferred.

  In addition, the metal compound can be added directly without dissolving or diluting in a solvent or the like. However, the supply amount is stabilized, and heat generation from a heat medium jacket, etc., denaturation due to deactivation. In order to reduce adverse effects such as these, it is preferable to add after diluting with a solvent such as diol or water. The upper limit value of the concentration at this time is usually 10% by weight, preferably 3% by weight, more preferably 1.5% by weight, and particularly preferably 0.5% by weight, as the metal compound concentration. The concentration of the metal compound is usually 0.01% by weight, preferably 0.05% by weight, and more preferably 0.1% by weight. If the concentration of the metal compound is too high, the dilution effect due to the solvent will be lost, and if it is too low, a large amount of the diluted solvent will be sent to the reactor, leading to a decrease in molecular weight, The load on the polycondensation equipment increases.

  As the at least one dilution solvent, 1,4-butanediol having a slight influence on the process is preferable, and the concentration thereof is usually 50% by weight when the total weight of the solution containing the metal compound is 100% by weight. Above, preferably 70% by weight or more, more preferably 80% by weight or more, and particularly preferably 90% by weight or more.

  Moreover, it is preferable to use water having an effect of stably dissolving the metal compound as at least one of the dilution solvents. The lower limit value of the water concentration at this time is usually 0.01% by weight, preferably 0.1% by weight, more preferably 0.00% as the value when the total weight of the solution containing the metal compound is 100% by weight. 3% by weight, particularly preferably 0.5% by weight. On the other hand, the upper limit of the water concentration is usually 30% by weight, preferably 10% by weight, more preferably 5% by weight, and particularly preferably 3% by weight. If the water concentration is too low, the solubility of the compounds of the periodic table group 1 and group 2 metals tends to decrease, and precipitation, clogging, deactivation, etc. tend to occur. It tends to cause hydrolysis of the water or increase the load on the decompression device.

  A preferred embodiment of the present invention is a method for preparing a solution using 1,4-butanediol and water as a solvent. As the concentration with respect to the total amount of the solution, the concentration of 1,4-butanediol is usually 50% by weight or more, preferably 60% by weight or more, more preferably 70% by weight or more, and the concentration of water is usually 1% by weight. Above, preferably 3% by weight or more, more preferably 5% by weight or more, and the concentration of the metal compound is usually 0.1% by weight or more, preferably 1% by weight or more, more preferably 3% by weight or more. . And after using a preparation tank etc. and preparing normally at 0-100 degreeC, Preferably 20-80 degreeC, after mixing a preparation liquid and 1, 4- butanediol with a pipe and further diluting, it is made into an oligomer pipe. Added.

  The concentration of the metal compound in the metal compound solution when finally added to the oligomer extraction line is usually 10% by weight or less, preferably 2% by weight, as described above, from the viewpoint of preventing troubles such as piping blockage. Hereinafter, it is more preferably 1% by weight or less, particularly preferably 0.5% by weight or less. In addition, the pipe speed of the metal compound solution when finally added to the oligomer pipe is usually 0.01 m / s or more, preferably 0.03 m / s or more, more preferably from the viewpoint of preventing the addition pipe from being blocked. Is 0.05 m / s or more, particularly preferably 0.1 m / s or more.

  The upper limit of the terminal carboxyl group concentration of the PBT obtained in the present invention is usually 30 μeq / g or less, preferably 25 μeq / g or less, more preferably 20 μeq / g or less, particularly preferably 15 μeq / g or less, most preferably 10 μeq / g. The lower limit is usually 1 μeq / g or more, preferably 3 μeq / g or more, more preferably 5 μeq / g or more. When the terminal carboxyl group concentration is too high, the hydrolysis resistance of PBT tends to deteriorate.

  By the way, even if the terminal carboxyl group concentration of the PBT is lowered, if it rises again due to heat during kneading or molding, it not only deteriorates the hydrolysis resistance of the product but also generates gas such as tetrahydrofuran (THF). May be invited. Therefore, in the PBT obtained by the present invention, the increase in the terminal carboxyl group concentration excluding the hydrolysis reaction when heat-treated at 245 ° C. for 40 minutes in an inert gas atmosphere is usually 0.1 to 20 μeq / g, preferably It is 0.1 to 15 μeq / g, more preferably 0.1 to 10 μeq / g, and particularly preferably 0.1 to 8 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 considered to be substantially the same, 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 (2). You can ask.

(In the formula (2), ΔAV (d) is a change amount of the terminal carboxyl group concentration due to a thermal decomposition reaction other than the hydrolysis reaction, ΔAV (t) is a total change amount of the terminal carboxyl group concentration before and after the heat treatment, and ΔAV (h) Is the amount of change in the terminal carboxyl group concentration due to the hydrolysis reaction, and ΔOH is the amount of change in the terminal glycol group concentration before and after the heat treatment.)

From the viewpoint of reliability of thermal decomposition reaction evaluation, since it is preferable that the hydrolysis reaction is small, the water content of PBT used for the heat treatment is usually recommended to be 200 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 the PBT obtained in the present invention can be determined by dissolving PBT in an organic solvent and titrating with an alkali solution such as a sodium hydroxide solution.

  The intrinsic viscosity of the PBT obtained in the present invention is not particularly limited, but if it is too low, the mechanical properties deteriorate, and if it is too high, the fluidity decreases and the moldability deteriorates. Therefore, the lower limit is usually 0.70 dL / g, preferably 0.80 dL / g, more preferably 0.90 dL / g, particularly preferably 1.00 dL / g, optimally 1.10 dL / g. The upper limit is usually 2.50 dL / g, preferably 1.50 dL / g, more preferably 1.40 dL / g, and particularly preferably 1.20 dL / g. The intrinsic viscosity is a value measured at 30 ° C. using a mixed solvent of phenol / tetrachloroethane (weight ratio 1/1).

  The temperature lowering crystallization temperature of PBT in the present invention is usually 160 to 200 ° C, preferably 170 to 195 ° C, and more preferably 175 to 190 ° 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 injection molding. When the temperature-falling crystallization temperature is low, crystallization takes time during injection molding, and the cooling time after injection molding has to be lengthened, and the molding cycle tends to increase and productivity tends to decrease.

  The content of the cyclic dimer of PBT in the present invention is usually 5000 ppm or less, preferably 4000 ppm or less, more preferably 2000 ppm or less, particularly preferably 1500 ppm or less, and most preferably 800 ppm or less as a weight ratio with respect to PBT. The lower limit is usually 10 ppm. The cyclic trimer content is usually 4000 ppm or less, preferably 3000 ppm or less, more preferably 1000 ppm or less, particularly preferably 800 ppm or less, most preferably 500 ppm or less, and its lower limit is usually 10 ppm. . When the content of the cyclic dimer and the cyclic trimer exceeds the above range, mold stains and roll stains are caused, bleed out on the film surface, and elution becomes a problem in uses such as food packaging. .

  The solution haze of PBT obtained in the present invention is not particularly limited, but 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 (weight ratio 3/2). , Preferably 5% or less, more preferably 3% or less, 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 deactivation of the titanium catalyst is large.

  Next, the manufacturing method of PBT of this invention is demonstrated in detail.

  First, in the present invention, in the esterification reactor, at least a part of 1,4-butanediol is supplied to the esterification reactor independently of terephthalic acid in the presence of the titanium catalyst, A step of continuously esterifying 1,4-butanediol is preferably employed. Hereinafter, 1,4-butanediol supplied to the esterification reactor independently of terephthalic acid may be referred to as “separately supplied 1,4-butanediol”.

  Usually, 1,4-butanediol distilled from the esterification reactor contains components such as water, THF, alcohol, and dihydrofuran in addition to the 1,4-butanediol component. Therefore, the components distilled from the esterification reactor are separated and purified from components such as water, alcohol, tetrahydrofuran and the like after being collected by a condenser or the like while being collected. It is preferable to return to.

  In the present invention, in order to prevent deactivation of the catalyst, it is preferable to supply 10% by weight or more of the titanium catalyst used in the esterification reaction directly to the reaction liquid phase part independently of terephthalic acid. . Here, the reaction liquid phase portion indicates the liquid phase side of the gas-liquid interface of the esterification reactor, and the direct supply to the reaction liquid phase portion uses piping or the like, and the titanium catalyst is the gas phase of the reactor. This means that it is directly supplied to the liquid phase part without going through the phase part. 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 titanium catalyst is diluted with a solvent such as 1,4-butanediol in order to stabilize the supply amount as described above and reduce adverse effects such as denaturation due to heat from the heat medium jacket of the reactor. It is preferable. 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 the separate supply 1, 4- butanediol and piping etc., and supply to an esterification reactor from the point of deterioration prevention, precipitation prevention, and deactivation prevention.

  Further, a compound of at least one metal selected from Group 1 and Group 2 metals may be supplied to the esterification reactor. In this case, the supply position is not limited, and it may be supplied from the reaction solution gas phase portion of these reactors to the upper surface of the reaction solution, or may be supplied directly to the reaction solution liquid phase portion. In this case, it may be supplied together with terephthalic acid or a titanium catalyst, or may be supplied independently. However, from the viewpoint of catalyst stability, the reaction liquid phase is independent of terephthalic acid or titanium catalyst. It is preferable to supply to the upper surface of the reaction liquid from the part.

  An example of a continuous esterification method is as follows. That is, the dicarboxylic acid component containing terephthalic acid as the main component and the diol component containing 1,4-butanediol as the main component are mixed in a raw material mixing tank to form a slurry, and the inside of the single or multi-stage esterification reactor In the present invention, the esterification reaction is continuously carried out in the presence of a titanium catalyst in the absence of metals of Group 1 and Group 2 of the periodic table. The reaction temperature is usually 180 to 260 ° C., preferably 200 to 245 ° C., more preferably 210 to 235 ° C., the reaction pressure is usually 20 to 133 kPa, preferably 30 to 101 kPa, more preferably 50 to 90 kPa, and the reaction time is Usually, 0.5 to 10 hours, preferably 1 to 6 hours.

  In the case of the direct polymerization method, the molar ratio of terephthalic acid and 1,4-butanediol preferably satisfies the following formula (3).

(In formula (3), BM is the number of moles of 1,4-butanediol supplied from the outside to the esterification reactor per unit time, and TM is terephthalate supplied from the outside to the esterification reactor per unit time. Represents the number of moles of acid.)

  The above "1,4-butanediol supplied from the outside to the esterification reactor" refers to 1,4-butanediol supplied together with terephthalic acid as a raw slurry or solution, and independently supplied from these 1,4-butanediol (separately supplied 1,4-butanediol), 1,4-butanediol used as a solvent for the titanium catalyst, and the like of 1,4-butanediol entering the reactor from the outside of the reactor It is the sum.

  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 5.0, not only the thermal efficiency is lowered, but also by-products such as tetrahydrofuran increase. Tend to. The value of BM / TM is preferably 1.5 to 4.5, more preferably 2.0 to 4.0, and particularly preferably 3.1 to 3.8.

  In the present invention, the esterification 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 reactor, a known one can be used, which may be any type such as a vertical stirring complete mixing tank, a vertical heat convection mixing tank, a tower type continuous reactor, etc. Alternatively, a plurality of tanks in which the same kind or different kinds of tanks are connected in series or in parallel may be used. Among them, a reactor having a stirrer is preferable. As a stirrer, a normal type including a power unit, a bearing, a shaft, and a stirring blade, a turbine stator type high-speed rotating stirrer, a disk mill type stirrer, a rotor mill type stirrer 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 liquid in the reactor is directly stirred from the top, bottom, side, etc. of the reactor, a part of the reaction liquid 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.

  Subsequently, the oligomer as the esterification reaction product or transesterification reaction product obtained above is transferred to a polycondensation reactor. In this case, the number average molecular weight of the oligomer is usually 300 to 3000, preferably 500 to 1500.

  In the production of the PBT of the present invention, usually, polycondensation reactors having different reaction conditions in a plurality of stages, preferably 2 to 5 stages, particularly preferably 2 to 3 stages, are used, and the molecular weight is sequentially increased. The form of the polycondensation reactor may be any type such as a vertical stirring complete mixing tank, a vertical heat convection mixing tank, a column type continuous reactor, and the like, and these may be combined. Among them, at least one polycondensation reactor is preferably of a type having a stirrer, and as the stirrer, a normal type consisting of a power unit, a bearing, a shaft, a stirring blade, and a turbine stator type high-speed rotation type A high-speed rotating type such as a stirrer, a disc mill type stirrer, or a rotor mill type stirrer can also be used.

  The form of stirring is not particularly limited, and in addition to the usual stirring method in which the reaction liquid in the reactor is directly stirred from the top, bottom, side, etc. of the reactor, a part of the reaction liquid 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. Among them, at least one of the polycondensation reactors is recommended to use a horizontal reactor having a surface of rotation in the horizontal direction and excellent surface renewal and self-cleaning properties.

  In the present invention, it is necessary to add at least one metal compound selected from Group 1 and Group 2 of the periodic table when the esterification rate is 90% or more. In particular, after obtaining an oligomer having an esterification rate of 90% or more in an esterification reactor, the above metal compound diluted with a solvent is added to a pipe for supplying the oligomer to a reactor for polycondensation reaction at an absolute pressure of less than 20 kPa. It is preferable to do.

  The polycondensation reaction is preferably carried out with stirring. The reaction temperature is usually 210 to 280 ° C, preferably 220 to 250 ° C, more preferably 230 to 245 ° C, and particularly preferably 230 to 240 ° C in at least one reactor. The reaction time is usually 1 to 12 hours, preferably 3 to 10 hours, and the reaction pressure is usually less than 20 kPa, preferably less than 10 kPa, particularly preferably 5 kPa or less. In order to suppress coloring and deterioration and suppress an increase in side reactions such as vinyl group generation, in at least one reactor, a high vacuum of usually 1.3 kPa or less, preferably 0.5 kPa or less, more preferably 0.3 kPa or less. Preferably it is carried out below.

  The polymer obtained by the polycondensation reaction is usually transferred from the bottom of the polycondensation reactor to a polymer extraction die and extracted in the form of a strand, which is cooled with water or after being cooled with water, and then cut with a cutter to form pellets and chips. And so on.

  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 0.9, and then at a temperature below the melting point of the PBT. Solid phase polycondensation (solid phase polymerization) can also be performed.

  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 employed in the present invention, and FIG. 2 is an explanatory diagram of an example of a 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 transferred from the raw material supply line (1) to the reactor (A) in the form of slurry or liquid. Supplied. Further, the titanium catalyst is preferably supplied from a titanium 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 reactor (A). It was.

  The gas distilled from the reactor (A) is separated into a high-boiling component and a low-boiling component in the rectification column (C) through the distillation 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.

  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 reactor (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 in the reactor (A) is withdrawn via a withdrawal pump (B) and an oligomer withdrawal 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 reactor (A).

  A compound of at least one metal selected from Group 1 and Group 2 of the periodic table is prepared to a predetermined concentration in a preparation tank (not shown), and then passes through line (L7) in FIG. After being further diluted with 1,4-butanediol, it is supplied to the oligomer extraction line (4) shown in FIG.

  Next, the oligomer supplied to the first polycondensation reactor (a) is polycondensed under reduced pressure to become a prepolymer, and then passes through the extraction gear pump (c) and the extraction line (L1). It feeds into a double condensation reactor (d). In the second polycondensation reactor (d), polycondensation usually proceeds at a lower pressure than that of the first polycondensation reactor (a) to become a polymer. The obtained polymer is supplied to the third polycondensation tank (k) through the extraction gear pump (e) and the extraction line (L3). The third polycondensation reactor (k) is a horizontal reactor comprising a plurality of stirring blade blocks and equipped with a biaxial self-cleaning type stirring blade. The polymer introduced from the second polycondensation reactor (d) to the third polycondensation reactor (k) 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. Reference numerals (L2), (L4), and (L6) denote vent lines of the first polycondensation reactor (a), the second polycondensation reactor (d), and the third polycondensation reactor (k), respectively. .

  In the production method of the present invention, it is possible not only to suppress the deterioration of color tone and increase in foreign matters due to the deactivation of the titanium catalyst, but also to reduce the amount of THF produced as a by-product in the esterification reaction, as well as the speed of the polycondensation reaction PBT obtained by the production method of the present invention is excellent in color tone, hydrolysis resistance, thermal stability, transparency, and moldability, so that it can be used in electrical, electronic parts, automotive parts, etc. Although it is suitable as an injection-molded part, it has a high utility value in applications such as films, monofilaments, and fibers because it has few foreign matters and is excellent in transparency.

  Examples of PBT in the present invention include 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 You may add release agents such as oil .

  A reinforcing filler can be blended with the PBT in 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 Organic fibers such as polyamide fiber, fluororesin fiber, plate-like inorganic fillers such as glass flakes, mica, metal foil, ceramic beads, asbestos, wollastonite, talc, clay, mica, zeolite, kaolin, potassium titanate, sulfuric acid Barium, titanium oxide, silicon oxide, aluminum oxide, magnesium hydroxide and the like can be mentioned. These reinforcing fillers can be used in combination of two or more.

  In the PBT in the present invention, a flame retardant can be blended 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, and polypentabromobenzyl acrylate. 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 according to 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.

  In the PBT according to 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, and the like are used. 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 method for molding PBT in 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 in the present invention is excellent in color tone, hydrolysis resistance, thermal stability, transparency and moldability, and is therefore suitable as an injection molded part such as an electric, electronic part or automobile part. 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 measurement method of the physical property and evaluation item which were employ | adopted in the following examples is as follows.

(I) 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.

(Ii) Concentrations of titanium, group 1 and group 2 metals in the 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).

(Iii) THF byproduct amount:
The THF concentration in the distillate was quantified by gas chromatography and determined by the following formula (5). The smaller the number, the less by-product.

(In formula (5), m represents the amount of THF distilled (mol) per unit time, and M represents terephthalic acid (mol) supplied per unit time.)

(Iv) 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 a polymer solution having a concentration of 1.0 g / dL and a solvent at 30 ° C., the following formula (6) I asked more.

(Where η _SP = η / η ₀ −1, η is the polymer solution falling seconds, η ₀ is the solvent dropping seconds, C is the polymer solution concentration (g / dL), and K _H is the Huggins constant. Yes, K _H is 0.33.)

(V) 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.

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

(Vii) Increase in terminal carboxyl group concentration by reaction other than hydrolysis reaction (ΔAV):
PBT pellets were pulverized into a capillary having an inner diameter of 5 mm, dried, 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 (2).

(Viii) 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.

(Ix) Number of fisheye:
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 200 μm or more per 1 m ² was measured.

(X) Hydrolysis resistance (IV retention after hydrolysis test):
PBT pellets are placed in a pressure vessel filled with pure water so that they do not come into direct contact with water, sealed, and then treated under pressurized saturated steam at 121 ° C. for 48 hours to measure intrinsic viscosity (IV ′). The IV retention is calculated from the values of (IV) and (IV ′) described above by the following equation (7). It shows that hydrolysis resistance is so favorable that IV retention is large.

Example 1:
Through the esterification step shown in FIG. 1 and the polycondensation step shown in FIG. 2, 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 reactor (A) for esterification having a screw type stirrer filled with PBT oligomer at a rate of 40 kg / h. At the same time, the bottom component of the rectification column (C) at 185 ° C. (98% by weight or more is 1,4-butanediol) is supplied at 18.4 kg / h from the recirculation line (2), and the titanium catalyst supply line ( From 3), a 6.0 wt% 1,4-butanediol solution of tetrabutyl titanate at 65 ° C. was fed as a catalyst at 127 g / h. The moisture in the catalyst solution was 0.2% by weight.

  The internal temperature of the reactor (A) is 230 ° C., the pressure is 78 kPa, and the produced water, tetrahydrofuran 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, a low boiling component mainly composed of water and THF is extracted in the form of gas from the top of the column, condensed by a condenser (G), and an extraction line (13) so that the liquid level of the tank (F) becomes constant. More extracted outside.

  A certain amount of the oligomer generated in the reactor (A) is extracted from the oligomer extraction line (4) using the pump (B), and the average residence time in terms of the terephthalic acid unit in the liquid in the reactor (A). The liquid level was controlled so that was 3 hours. The oligomer extracted from the extraction line 4 was continuously supplied to the first polycondensation reactor (a). After the system was stabilized, the esterification rate of the oligomer collected at the outlet of the reactor (A) was 97.3%.

  Magnesium acetate tetrahydrate is dissolved in pure water, 1,4-butanediol is added, and magnesium acetate tetrahydrate, pure water, and 1,4-butanediol are 5% by weight and 20% by weight, respectively. , 75% by weight in a preparation tank (not shown). The temperature at this time was 25 ° C. This solution was supplied to the 1,4-butanediol line (L8) through the supply line (L7), and a predetermined amount was supplied to the oligomer extraction line (4) as a solution having a lower concentration. The concentration as magnesium acetate tetrahydrate at the time of supply to the line (4) was 0.29 wt%, the linear velocity was 0.18 m / s, and the supply amount was stable for 24 hours or more.

  The internal temperature of the first polycondensation reactor (a) was 246 ° C., the pressure was 2.4 kPa, and the liquid level was controlled so that the residence time was 120 minutes. An initial polycondensation reaction was performed while extracting water, tetrahydrofuran, 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 reactor (d).

  The internal temperature of the second polycondensation reactor (d) is 239 ° C., the pressure is 150 Pa, the liquid level is controlled so that the residence time is 130 minutes, and a vent line (L4) connected to a decompressor (not shown). ), Polycondensation reaction was further carried out while extracting water, tetrahydrofuran and 1,4-butanediol. The obtained polymer was continuously supplied to the third polycondensation reactor (k) via the extraction line (L3) by the extraction gear pump (e). The internal temperature of the third polycondensation reactor (k) was 238 ° C., the pressure was 130 Pa, the residence time was 70 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). The obtained PBT had an intrinsic viscosity of 1.20 dL / g, a terminal carboxyl group concentration of 17 μeq / g, excellent color tone and transparency, little foreign matter, and a small increase in the terminal carboxyl group concentration during heat retention. The results are summarized in Table 1.

Example 2:
The esterification reaction was performed in the same manner as in Example 1 except that the amount of magnesium acetate tetrahydrate solution shown in Table 1 was supplied from the line (15). After the system was stabilized, the esterification rate of the oligomer collected at the outlet of the reactor (A) was 96.5%. On the other hand, the supply amount of magnesium acetate tetrahydrate to the oligomer extraction line (4) is as shown in Table 1, and the concentration as magnesium acetate tetrahydrate when supplying to the line (4) is 0.88 wt. %. The conditions for the first polycondensation reactor (a) were the same as in Example 1. The internal temperature of the second polycondensation reactor (d) was 240 ° C., the pressure was 160 Pa, the internal pressure of the third polycondensation reactor (k) was A polycondensation reaction was performed in the same manner as in Example 1 except that the temperature was 243 ° C. The analysis values of the obtained PBT are shown in Table 1. The color tone and transparency were excellent, there were few foreign matters, and the increase in the terminal carboxyl group concentration during heat retention was small.

Example 3:
The esterification reaction was performed in the same manner as in Example 1 except that the amount of magnesium acetate tetrahydrate solution shown in Table 1 was supplied from the line (15) and the average residence time was 3.4 hr. After the system was stabilized, the esterification rate of the oligomer collected at the outlet of the reactor (A) was 95.4%. On the other hand, the supply amount of magnesium acetate tetrahydrate to the oligomer extraction line (4) and the conditions of the first polycondensation reactor (a) were the same as in Example 1, and the second polycondensation reactor (d) A polycondensation reaction was performed in the same manner as in Example 1 except that the internal temperature was 241 ° C, the pressure was 160 Pa, and the internal temperature of the third polycondensation reactor (k) was 244 ° C. The analysis values of the obtained PBT are shown in Table 1. The color tone and transparency were excellent, there were few foreign matters, and the increase in the terminal carboxyl group concentration during heat retention was small.

Example 4:
The esterification reaction was carried out in the same manner as in Example 1. In place of magnesium acetate tetrahydrate, a preparation tank (lithium acetate dihydrate, pure water, 1,4-butanediol was adjusted to 2.5% by weight, 20% by weight, and 77.5% by weight, respectively. (Not shown), this solution is supplied to the 1,4-butanediol line (L8) through the supply line (L7), and is further supplied to the oligomer extraction line (4) as a low-concentration solution. A fixed amount was supplied. The concentration of lithium acetate dihydrate at the time of feeding to the line (4) was 0.08% by weight. The conditions for the first polycondensation reactor (a) were the same as in Example 1. The internal temperature of the second polycondensation reactor (d) was 241 ° C., and the internal temperature of the third polycondensation reactor (k) was 242. A polycondensation reaction was carried out in the same manner as in Example 1 except that the temperature was changed to ° C. The analysis values of the obtained PBT are shown in Table 1. The color tone and transparency were excellent, there were few foreign matters, and the increase in the terminal carboxyl group concentration during heat retention was small.

Example 5:
In Example 1, the esterification reaction was performed in the same manner as in Example 1 except that the amount of tetrabutyl titanate was changed to the amount shown in Table 1. After the system was stabilized, the esterification rate of the oligomer collected at the outlet of the reactor (A) was 97.4%. The conditions for supply of magnesium acetate tetrahydrate and polycondensation were the same as in Example 1. The analysis values of the obtained PBT are shown in Table 1.

Example 6:
The esterification reaction was carried out in the same manner as in Example 1. The supply amount of magnesium acetate tetrahydrate to the oligomer extraction line (4) is as shown in Table 1, and the concentration as magnesium acetate tetrahydrate at the time of supply to the line (4) is 0.58% by weight. did. The conditions for the first polycondensation reactor (a) were the same as in Example 1. The internal temperature of the second polycondensation reactor (d) was 240 ° C., and the internal temperature of the third polycondensation reactor (k) was 241. A polycondensation reaction was performed in the same manner as in Example 1 except that the temperature was changed to ° C. The analysis values of the obtained PBT are shown in Table 1. The color tone and transparency were excellent, there were few foreign matters, and the increase in the terminal carboxyl group concentration during heat retention was small.

Comparative Example 1:
The same procedure as in Example 1 was performed except that magnesium acetate tetrahydrate was not added. Compared with Example 1, the molecular weight of the obtained PBT was low, and the polymerizability deteriorated. In addition, the increase in the terminal carboxyl group concentration during heat retention was large. The results are shown in Table 1.

Comparative Example 2:
In Example 1, the supply amount of magnesium acetate tetrahydrate was as shown in Table 1, and the concentration as magnesium acetate tetrahydrate at the time of supply to the oligomer extraction line (4) was 1.76% by weight. Others were the same as in Example 1. Two hours after the start of the supply of magnesium acetate tetrahydrate, the supply amount became unstable and a tendency to block the piping was observed. Moreover, the polymerizability deteriorated as compared with Example 1. The results are shown in Table 1.

Comparative Example 3:
Example 1 was carried out in the same manner as Example 1 except that the amount of tetrabutyl titanate was changed to the amount shown in Table 1. The obtained PBT had a high terminal carboxyl group concentration, a poor color tone, and a large increase in the terminal carboxyl group concentration during heat retention. Moreover, the solution haze was high and the amount of foreign matter was large. The results are shown in Table 1.

Comparative Example 4:
In Example 1, it carried out like Example 1 except having supplied magnesium acetate tetrahydrate by esterification as Table 1 and not having added magnesium acetate tetrahydrate to the oligomer. The amount of THF by-produced was large, and the polymerizability deteriorated. The results are shown in Table 1.

Example 7:
In Example 1, the third condensation reactor (k) was not used, the extraction line (L3) of the second condensation reactor (d) was directly connected to the die head (g), and the second polycondensation reactor was used. The polymer obtained from (d) was continuously extracted in the form of a strand from the die head (g) and cut with a rotary cutter (h). The obtained chip had an intrinsic viscosity of 0.85 dL / g. This chip was placed in a double corn type jacketed solid phase polymerization apparatus having an internal volume of 100 L, and the reduced pressure / nitrogen replacement was repeated three times. Next, the pressure was controlled at 130 Pa and the temperature was raised to 190 ° C. Seven hours after the internal temperature reached 190 ° C., the jacket heating medium started to cool, and when the internal temperature became 40 ° C. or lower, the contents were taken out. The analytical values are summarized in Table 1. PBT having few foreign matters, oligomers and terminal carboxyl groups, excellent color tone, good transparency and excellent hydrolysis resistance was obtained.

Example 8:
In Example 1, the third condensation reactor (k) was not used, the extraction line (L3) of the second condensation reactor (d) was directly connected to the die head (g), and the second polycondensation reactor was used. The polymer obtained from (d) was continuously extracted in the form of a strand from the die head (g) and cut with a rotary cutter (h). The obtained chip had an intrinsic viscosity of 0.85 dL / g. This chip was placed in a double corn type jacketed solid phase polymerization apparatus having an internal volume of 100 L, and the reduced pressure / nitrogen replacement was repeated three times. Subsequently, the pressure was controlled to 130 Pa and the temperature was raised to 205 ° C. Five hours after the internal temperature reached 205 ° C., the jacket heating medium started to cool, and the content was taken out when the internal temperature became 40 ° C. or lower. The analytical values are summarized in Table 1. PBT with few foreign matters, oligomers and terminal carboxyl groups, excellent color tone, good transparency and excellent hydrolysis resistance was obtained.

Explanatory drawing of an example of the esterification reaction process employ | adopted by this invention Explanatory drawing of an example of the polycondensation step employed in the present invention

Explanation of symbols

1: Raw material supply line 2: Recirculation line 3: Titanium catalyst supply line 4: Oligomer 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: Metal compound supply line A: Reactor B: Extraction pump C: Rectification tower D, E: Pump F: Tank G : Capacitors L1, L3: extraction lines L2, L4, L6: vent line L5: polymer extraction line L8: 1,4-butanediol supply line L7: metal compound supply line a: first polycondensation reactor d: first Double condensation reactor k: Third polycondensation reactor c, e, m: Gear pump for extraction g: Die head h: Rotary cutter

Claims (14)

In the continuous production of polybutylene terephthalate from terephthalic acid and 1,4-butanediol using a titanium compound and a compound of at least one metal selected from Groups 1 and 2 of the periodic table as a catalyst, A process for producing polybutylene terephthalate, which satisfies the following conditions (a) to (c):
(A) An oligomer is obtained by continuously esterifying terephthalic acid and 1,4-butanediol in the presence of 460 μmol or less of titanium catalyst per 1 mol of terephthalic acid units as titanium atoms.
(B) The above oligomer is continuously subjected to a polycondensation reaction in the presence of at least one metal compound selected from metals of Group 1 and Group 2 of the periodic table of 450 μmol or less per 1 mol of terephthalic acid unit as a metal atom.
(C) The metal compound may be added as a metal atom in a range of 300 μmol or less per 1 mole of terephthalic acid unit before reaching an oligomer having an esterification rate of 90% or more, but the esterification rate is 90%. In the stage after reaching the above oligomer, 10 μmol or more per 1 mol of terephthalic acid unit is added as a metal atom.   2. The production method according to claim 1, wherein the addition amount of at least one metal compound selected from metals of Group 1 and Group 2 of the periodic table is 45 μmol or more per 1 mol of terephthalic acid unit as a total of metal atoms.   The production method according to claim 1 or 2, wherein the addition amount of at least one metal compound selected from metals of Group 1 and Group 2 of the periodic table is 180 µmol or less per 1 mol of terephthalic acid unit as a total of metal atoms.   The manufacturing method in any one of Claims 1-3 which obtain the polybutylene terephthalate whose intrinsic viscosity is 1.10 dL / g or more.   The production method according to any one of claims 1 to 4, wherein a polybutylene terephthalate having an intrinsic viscosity of 1.10 dL / g or more is obtained by a polycondensation reaction at a temperature equal to or higher than the melting point of polybutylene terephthalate.   The production method according to claim 1, wherein the terminal carboxyl group concentration of polybutylene terephthalate is 30 μeq / g or less.   The manufacturing method according to any one of claims 1 to 6, wherein the compound of the metals of Groups 1 and 2 of the periodic table is an organic acid salt.   The manufacturing method according to claim 1, wherein the metal of Group 1 and Group 2 of the periodic table is magnesium.   A compound of at least one metal selected from Group 1 and 2 metals of the periodic table is diluted with a liquid containing 1,4-butanediol as a main component and added as a metal compound in a solution of 1.5% by weight or less. The manufacturing method according to any one of claims 1 to 8.   A compound of at least one metal selected from metals of Group 1 and Group 2 of the periodic table is added as a solution having a water concentration of 0.01 to 10% by weight and 1,4-butanediol of 50% by weight or more. Item 10. The manufacturing method according to Item 9.   The manufacturing method in any one of Claims 1-10 which adds the compound of the at least 1 sort (s) of metal chosen from the periodic table group 1 and group 2 metal to the extraction line of an oligomer.   The production method according to any one of claims 1 to 11, wherein a polybutylene terephthalate having a titanium compound content of 460 µmol or less as a titanium atom per mol of terephthalic acid unit is obtained.   The production method according to any one of claims 1 to 11, wherein a polybutylene terephthalate having a titanium compound content of 320 µmol or less as a titanium atom per 1 mol of a terephthalic acid unit is obtained.   A method for producing polybutylene terephthalate, comprising subjecting polybutylene terephthalate obtained by the production method according to claim 1 to solid-phase polycondensation at a temperature lower than the melting point.