JP2006152252A - Polybutylene terephthalate and its production process - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polybutylene terephthalate (PBT) excellent in color tone, resistance to hydrolysis, transparency and moldability with reduced foreign matter, which is favorably applicable to films, monofilaments, fibers, electric electronic parts and car parts. <P>SOLUTION: PBT contains titanium (Ti) at 90 ppm or less as a Ti atom and at 90 ppm or less of a group 1 or 2 metal atom in the periodic table and 0.06-4 ppm of a cobalt (Co) as a Co atom. In a preferred embodiment, the concentration of manganese (Mn) is 0.06-4 ppm as a Mn atom and a content of an aldehyde group is 0.1 μeq/g or over. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to polybutylene terephthalate, and more specifically, a film, a monofilament, a fiber, an electric / electronic component, an automobile having excellent color tone, hydrolysis resistance, thermal stability, transparency, moldability, and reduced foreign matter. The present invention relates to polybutylene terephthalate that can be suitably used for parts and the like.

  Polybutylene terephthalate, a representative engineering plastic among thermoplastic polyester resins, is easy to process, mechanical properties, heat resistance, chemical resistance, fragrance retention, and other physical and chemical properties. Therefore, it is widely used in injection-molded products such as automobile parts, electrical / electronic parts, and 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 and the like.

  Production methods of polybutylene terephthalate are roughly classified into a transesterification method using dimethyl terephthalate as a terephthalic acid component as a raw material and a direct polymerization method using terephthalic acid as a raw material. However, the transesterification method generates methanol and tetrahydrofuran (THF) as by-products of the reaction, but these have a drawback that distillation separation after recovery is difficult due to their close boiling points. On the other hand, the direct polymerization method has been attracting attention recently because it does not generate methanol and the raw material unit is better than the transesterification method.

  However, the direct polymerization method has the following problems. That is, the raw material terephthalic acid contains cobalt as a catalyst residue and, in some cases, manganese. These deteriorate the color tone of polybutylene terephthalate produced by the direct polymerization method and reduce its commercial value. In order to solve such a problem, generally, high-purity terephthalic acid with enhanced purification and reduced cobalt or manganese content is used.

  However, in the above method, the production process of terephthalic acid becomes complicated and disadvantageous in terms of energy and cost. Therefore, even if medium purity terephthalic acid having a relatively large content of cobalt or manganese is used, There is a strong demand for a technique that does not deteriorate the color tone of polybutylene terephthalate.

  Furthermore, 4-carboxybenzaldehyde (4-CBA) by-produced in the production process of terephthalic acid also deteriorates the color tone of polybutylene terephthalate. Therefore, once obtained terephthalic acid with a high 4-CBA concentration is used as a transition metal catalyst. However, there is a problem that it is disadvantageous in terms of energy and cost as described above.

  In order to solve the above problem, for example, a method for defining a polycondensation temperature during the production of polybutylene terephthalate has also been proposed (see Patent Document 1). There is a strong demand for a technique that does not deteriorate the color tone of polybutylene terephthalate even when medium-purity terephthalic acid having a high content is used.

  Further, when a titanium catalyst is used in the direct polymerization method, there is a problem that a part of the added titanium catalyst is deactivated during the production process of polybutylene terephthalate. The deactivation of the catalyst not only literally deteriorates the reactivity, but also deteriorates the color tone and transparency, and increases the number of foreign matters. Especially in applications such as films, sheets, monofilaments, and fibers, the commercial value is greatly increased. Drop it.

  In order to solve the above problems, a method of prescribing the amount of the organic titanium compound to be added in the production of polybutylene terephthalate and coexisting the organic tin compound in the initial esterification reaction stage (see Patent Documents 2 and 3), Furthermore, the continuous esterification reaction of terephthalic acid and 1,4-butanediol is divided into two stages. In the first stage esterification reaction, only an organic tin compound is added, and in the second stage esterification reaction, an organic titanium compound is added. To reduce foreign matter and haze derived from the catalyst (see Patent Document 4), in the presence of a titanium compound and a tin compound, an alkaline metal compound is added at the time of polycondensation to reduce the concentration of terminal carboxyl groups and foreign matter. A reduction method (see Patent Document 5) has been proposed.

  However, in the above method, since the amount of titanium catalyst used is large, the color tone of the resulting polybutylene terephthalate is deteriorated, and the effect of reducing foreign matter and haze is not sufficient. Further, the use of a large amount of tin has an effect of improving reactivity and transparency, but also has a problem of causing deterioration in color tone. In order to solve such a problem, an operation for raising the reaction temperature is generally performed as an operation to compensate for the decreased reactivity due to the deactivation of the titanium catalyst without using a catalyst other than a titanium compound such as tin. However, such an operation further promotes the deterioration of the color tone of polybutylene terephthalate.

  On the other hand, if more titanium catalysts are used to compensate for the decreased activity due to the deactivation of the titanium catalyst, the absolute amount of the deactivated catalyst also increases, the color tone deteriorates, the transparency deteriorates, and the foreign matter increases. In particular, it is difficult to obtain polybutylene terephthalate having excellent quality by using terephthalic acid with low purity.

JP 51-47096 A Japanese Patent Laid-Open No. 10-330469 JP 2002-284868 A Japanese Patent Laid-Open No. 10-330468 JP 2001-114879 A

  The present invention has been made in view of the above circumstances, and its purpose is to use terephthalic acid having inferior purity, excellent color tone, hydrolysis resistance, thermal stability, transparency, moldability, and reduction of foreign matters. Another object of the present invention is to provide polybutylene terephthalate that can be suitably used for films, monofilaments, fibers, electrical and electronic parts, automobile parts and the like.

  As a result of intensive studies to solve the above problems, the present inventors have obtained the following knowledge. That is, the deterioration of the color tone caused by impurities in terephthalic acid appears when the amount of titanium catalyst used and the amount of deactivation are large. Therefore, even when terephthalic acid having inferior purity is used, deterioration in color tone can be suppressed if the amount of titanium catalyst used and the amount of deactivation can be reduced. In addition, if the esterification reaction is performed by supplying the titanium catalyst and the raw material in a specific manner, surprisingly, the deactivation amount of the titanium catalyst can be remarkably reduced, and the usage amount of the titanium catalyst can be reduced. At this time, if a periodic table Group 1 or Group 2 metal compound is used as a cocatalyst, a sufficient reaction rate can be maintained even if the amount of titanium catalyst used is reduced. The present invention has been completed based on these findings, and the gist thereof is as follows.

  The first gist of the present invention includes titanium and Group 1 or Group 2 metal of the periodic table, the concentration of titanium is 90 ppm or less as a titanium atom, and the concentration of Group 1 or Group 2 metal of the periodic table is It exists in the polybutylene terephthalate characterized by being 90 ppm or less as a metal atom and having a cobalt concentration of 0.06 to 4 ppm as a cobalt atom.

  The second gist of the present invention includes titanium and a periodic table group 1 or group 2 metal, the concentration of titanium is 90 ppm or less as a titanium atom, and the concentration of the periodic table group 1 or group 2 metal is The polybutylene terephthalate is characterized by having a metal atom of 90 ppm or less and a manganese concentration of 0.06 to 4 ppm as a manganese atom.

  The third gist of the present invention contains titanium and a periodic table group 1 or group 2 metal, the concentration of titanium is 90 ppm or less as a titanium atom, and the concentration of the periodic table group 1 or group 2 metal is The polybutylene terephthalate is characterized by having a metal atom of 90 ppm or less and an aldehyde group content of 0.1 μeq / g or more.

  The fourth aspect of the present invention is to produce polybutylene terephthalate from terephthalic acid and 1,4-butanediol using a titanium catalyst and a co-catalyst composed of a group 1 or group 2 compound in the periodic table. A medium-purity terephthalic acid having a cobalt concentration of 0.08 to 5 ppm as a cobalt atom is used, and a considerable amount of titanium catalyst and a periodic table group 1 or a concentration in a polybutylene terephthalate to be produced is 90 ppm or less as a titanium atom. The present invention resides in a method for producing polybutylene terephthalate, wherein a substantial amount of a co-catalyst of 90 ppm or less is used as the Group 2 metal.

  The fifth aspect of the present invention is to produce polybutylene terephthalate from terephthalic acid and 1,4-butanediol using a titanium catalyst and a co-catalyst composed of a group 1 or group 2 compound in the periodic table. A medium-purity terephthalic acid having a manganese concentration of 0.08 to 5 ppm as a manganese atom is used, and a considerable amount of a titanium catalyst and a periodic table group 1 or a periodic table having a concentration of 90 ppm or less as a titanium atom in the resulting polybutylene terephthalate The present invention resides in a method for producing polybutylene terephthalate, wherein a substantial amount of a co-catalyst of 90 ppm or less is used as the Group 2 metal.

  The sixth aspect of the present invention is to produce polybutylene terephthalate from terephthalic acid and 1,4-butanediol using a titanium catalyst and a co-catalyst comprising a group 1 or group 2 compound in the periodic table. A medium purity terephthalic acid having a content of 4-carboxybenzaldehyde of 10 to 1000 ppm is used, and a considerable amount of titanium catalyst and a periodic table group 1 or group in which the concentration in the resulting polybutylene terephthalate is 90 ppm or less as titanium atoms. The present invention resides in a method for producing polybutylene terephthalate, wherein a substantial amount of a co-catalyst that is 90 ppm or less is used as the Group 2 metal.

  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 PBT that can be provided is provided.

  Hereinafter, the present invention will be described in detail. However, the description of the constituent elements described below is a representative example of embodiments of the present invention, and the present invention is not limited to these contents.

  The polybutylene terephthalate (hereinafter abbreviated as PBT) of the present invention has a structure in which a terephthalic acid unit and a 1,4-butanediol unit are ester-bonded, and 70 mol% or more of dicarboxylic acid units are formed from terephthalic acid units. It is a polymer in which 70 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 80 mol% or more, more preferably 90 mol% or more, particularly preferably 95 mol% or more, and 1,4-butanediol unit in all diol units. The ratio is preferably 80 mol% or more, more preferably 90 mol% or more, and particularly preferably 95 mol% or more. When the amount of terephthalic acid units or 1,4-butanediol units is less than 70 mol%, the crystallization rate of PBT is lowered, and 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.

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

  In the present invention, hydroxycarboxylic acids such as lactic acid, glycolic acid, m-hydroxybenzoic acid, p-hydroxybenzoic acid, 6-hydroxy-2-naphthalenecarboxylic acid, p-β-hydroxyethoxybenzoic acid, and alkoxycarboxylic acids. Monofunctional components such as acid, stearyl alcohol, benzyl alcohol, stearic acid, benzoic acid, t-butylbenzoic acid, benzoylbenzoic acid, tricarbaric acid, trimellitic acid, trimesic acid, pyromellitic acid, gallic acid, trimethylolethane Trifunctional or polyfunctional components such as trimethylolpropane, glycerol and pentaerythritol can be used as the copolymerization component.

  The PBT of the present invention is obtained using a titanium catalyst and a co-catalyst composed of a Group 1 or Group 2 compound in the periodic table.

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

  Specific examples of Group 1 metal compounds of the periodic table in the present invention include various compounds of lithium, sodium, potassium, rubidium, and cesium. Specific examples of Group 2 metal compounds of the periodic table include beryllium, magnesium, and calcium. , Strontium, barium, and the like. From the viewpoints of handling and availability, and the catalytic effect, lithium, sodium, potassium, magnesium or calcium compounds are preferable. Among them, lithium or magnesium compounds having excellent catalytic effect are preferable. A magnesium compound is particularly preferable. 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. In addition, 1 type of these periodic table group 1 or 2 metal compounds may be used, and 2 or more types can also be used together.

  In addition to the titanium compound and the periodic table Group 1 or Group 2 metal compound, 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 PBT, its addition amount is usually 200 ppm or less, preferably 100 ppm or less, more preferably 10 ppm or less, and preferably not added as tin atoms.

  Moreover, PBT of this invention is obtained through an esterification reaction, supplying a titanium catalyst and a raw material in a specific aspect so that it may mention later. Therefore, the deactivation amount of the titanium catalyst can be remarkably reduced, the usage amount of the titanium catalyst can be reduced, and the deterioration of the color tone due to the impurities in terephthalic acid is suppressed.

  The PBT of the present invention contains titanium and Group 1 or Group 2 metal of the periodic table, the concentration of titanium is 90 ppm or less as a titanium atom, and the concentration of Group 1 or Group 2 metal of the periodic table is as a metal atom. It is characterized by being 90 ppm or less. The titanium concentration and periodic table group 1 or group 2 metal values are the weight ratio of atoms to PBT. In the present invention, the lower limit of the titanium content is preferably 10 ppm, more preferably 20 ppm, particularly preferably 25 ppm, optimally 30 ppm, and the upper limit is preferably 70 ppm, more preferably 50 ppm, particularly preferably 40 ppm. is there. On the other hand, the lower limit of the content of Group 1 or Group 2 metal in the periodic table is preferably 3 ppm, more preferably 5 ppm, particularly preferably 8 ppm, optimally 10 ppm, and the upper limit is preferably 70 ppm, more preferably 40 ppm, particularly preferably 20 ppm, more preferably 15 ppm. When the content of titanium and Group 1 or Group 2 metal in the periodic table is too much above the above range, the color tone, hydrolysis resistance and the like are deteriorated, and when it is less than the above range, the polymerizability is deteriorated.

  The amount of the metal of the Group 1 or Group 2 metal in the periodic table is usually 0.1 to 2.5 times mol, preferably 0.2 to 1.0 times mol, of the amount of titanium.

  The PBT according to the first aspect of the present invention is characterized in that the concentration of cobalt is 0.06 to 4 ppm as cobalt atoms. If the cobalt content is too high, the color tone will deteriorate, and if it is attempted to reduce the content, it will be necessary to strengthen the purification of the raw material terephthalic acid, which complicates the process and is disadvantageous in terms of energy and cost. Become. And in a preferable aspect, the density | concentration of manganese is 0.06-4 ppm as a manganese atom, and content of an aldehyde group is 0.1 microeq / g or more. The above cobalt and manganese concentrations are the weight ratio of atoms to PBT.

  The PBT according to the second aspect of the present invention is characterized in that the concentration of manganese is 0.06 to 4 ppm as manganese atoms. If the manganese content is too high, the color tone will deteriorate, and if it is attempted to reduce it, it will be necessary to strengthen the purification of the raw material terephthalic acid, which complicates the process and is disadvantageous in terms of energy and cost. Become. And in a preferable aspect, content of an aldehyde group is 0.1 microeq / g or more. The concentration of manganese is the weight ratio of atoms to PBT.

  The PBT according to the third aspect of the present invention is characterized in that the content of aldehyde groups is 0.1 μeq / g or more. If the content of aldehyde groups is to be reduced, it is necessary to enhance the purification of terephthalic acid, which is a raw material, or to tighten the polymerization conditions, which complicates the process and is disadvantageous in terms of energy and cost. become.

  In the present invention, the lower limit of the cobalt content is preferably 0.08 ppm, more preferably 0.1 ppm, particularly preferably 0.12 ppm, and optimally 0.15 ppm. The upper limit is preferably 3 ppm, more preferably 2 ppm, particularly preferably 1 ppm, and optimally 0.5 ppm.

  In the present invention, the lower limit of the manganese content is preferably 0.08 ppm, more preferably 0.1 ppm, particularly preferably 0.12 ppm, and optimally 0.15 ppm. The upper limit is preferably 3 ppm, more preferably 2 ppm, particularly preferably 1 ppm, and optimally 0.5 ppm.

  In the present invention, the lower limit of the aldehyde group content is preferably 0.15 μeq / g, more preferably 0.2 μeq / g, and most preferably 0.3 μeq / g. The upper limit is preferably 1 μeq / g, more preferably 0.8 μeq / g, and particularly preferably 0.6 μeq / g. When there is too much content of an aldehyde group, color tone will deteriorate.

The metal atom content can be measured using a method such as atomic emission, atomic absorption, Inductively Coupled Plasma (ICP) after the metal in the polymer is recovered by a method such as dry ashing or wet ashing. I can do it. The content of the aldehyde group can be measured by a method such as ¹ H-NMR.

  The terminal carboxyl group concentration of the PBT of the present invention is usually 0.1 to 50 μeq / g, preferably 1 to 30 μeq / g, more preferably 1 to 20 μeq / g, and particularly preferably 1 to 15 μeq / g. When the terminal carboxyl group concentration is too high, the hydrolysis resistance of PBT is deteriorated.

  The terminal carboxyl group concentration is preferably lowered to a low molecular weight region that has a low molecular weight and is susceptible to a decrease in molecular weight due to hydrolysis. That is, it is recommended to satisfy the following formula (1-1). Preferably it is Formula (1-2), More preferably, it is (1-3), Most preferably, it is Formula (1-4).

  On the other hand, even if the terminal carboxyl group concentration of the PBT is lowered, if it is increased by heat during kneading or molding, not only the hydrolysis resistance of the product is deteriorated, but also gas such as THF is generated. Therefore, the increase in the terminal carboxyl group concentration excluding the increase in the terminal carboxyl group concentration due to the hydrolysis reaction when the PBT of the present invention is heat-treated at 245 ° C. for 40 minutes in an inert gas atmosphere is usually 20 μeq / g or less, preferably Is 15 μeq / g or less, more preferably 10 μeq / g or less, and particularly preferably 8 μeq / g or less.

  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 concentration of the titanium catalyst 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 increase rate of the terminal carboxyl group concentration is too small, and in the opposite case, it is too large and the evaluation becomes inaccurate. It is. 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 above heat treatment conditions, it is possible to ignore the decrease in the number average molecular weight due to reactions other than the hydrolysis reaction caused by the water contained in the PBT. Since the increase in the terminal glycol group concentration can be considered to be almost the same as the increase in the terminal glycol group concentration, the increase in the terminal carboxyl group concentration due to the thermal decomposition reaction other than the hydrolysis reaction, which is a problem during kneading or molding, is expressed by the following formula (2). Can be obtained.

From the viewpoint of the reliability of the thermal decomposition reaction evaluation, it is preferable that the hydrolysis reaction is less. Therefore, it is preferable that the PBT used for the evaluation is previously dried with a vacuum dryer or the like to have a water content of 100 ppm or less. The terminal glycol group concentration before and after the heat treatment can be quantified by ¹ H-NMR. At this time, a small amount of a basic component such as deuterated pyridine may be added to prevent overlap with the solvent signal.

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

  Further, the terminal vinyl group concentration of the PBT of the present invention is usually 15 μeq / g or less, preferably 10 μeq / g or less, more preferably 8 μeq / g or less. When the terminal vinyl group concentration is too high, color tone deterioration and solid-phase polymerizability deteriorate. When producing PBT with a large molecular weight or PBT with a low catalyst concentration without reducing productivity, it is generally required to increase the polymerization temperature or lengthen the reaction time. It tends to increase.

The terminal vinyl concentration can be quantified by dissolving PBT in a mixed solvent of deuterated chloroform / hexafluoroisopropanol = 7/3 (volume ratio) and measuring ¹ H-NMR.

  The intrinsic viscosity ([η]) of the PBT of the present invention is usually 0.60 to 2.00 dL / g, preferably 0.65 to 1.60 dL / g, more preferably 0.70 to 1.30 dL / g, Particularly preferred is 0.80 to 1.00 dL / g. When the intrinsic viscosity is less than 0.60 dL / g, the mechanical strength of the molded product becomes insufficient, and when it exceeds 2.00 dL / g, the melt viscosity becomes high, the fluidity deteriorates, and the moldability deteriorates. There is a tendency. The intrinsic viscosity is a value measured at 30 ° C. using a mixed solution of phenol / tetrachloroethane (weight ratio 1/1) as a solvent.

  The temperature-falling crystallization temperature of the PBT of the present invention is usually 170 to 190 ° C, preferably 172 to 185 ° C, more preferably 175 to 180 ° C. The temperature drop crystallization temperature in the present invention is the temperature of an exothermic peak due to crystallization that appears when the resin is melted using a differential scanning calorimeter at a temperature drop rate of 20 ° C./min. The temperature-falling crystallization temperature corresponds to the crystallization speed, and the higher the temperature-falling crystallization temperature, the faster the crystallization speed. Therefore, the cooling time can be shortened and the productivity can be increased during 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 solution haze of the PBT of the present invention is not particularly limited, but is usually 5% or less, preferably 5% 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). Is 3% or less, more 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. The production method of PBT using terephthalic acid as a raw material is roughly divided into a batch method and a continuous method depending on a raw material supply or a polymer discharge form. There are also methods in which the initial esterification reaction is performed in a continuous operation and the subsequent polycondensation is performed in a batch operation, or conversely, the initial esterification reaction is performed in a batch operation and the subsequent polycondensation is performed in a continuous operation. . In the present invention, from the viewpoint of productivity and product quality stability, and the improvement effect of the present invention, a method of continuously supplying raw materials and continuously performing an esterification reaction is preferable. A so-called continuous method in which the reaction is continuously carried out is preferred.

  The method for producing PBT according to the present invention comprises producing a polybutylene terephthalate using a predetermined medium-purity terephthalic acid when producing polybutylene terephthalate from terephthalic acid and 1,4-butanediol using a titanium catalyst. It is characterized by using a considerable amount of titanium catalyst whose concentration is 90 ppm or less as titanium atoms. And in the preferable aspect of this invention, the considerable amount of titanium catalyst from which the density | concentration in the polybutylene terephthalate to produce | generate becomes 70 ppm or less as a titanium atom is used.

  PBT which concerns on a 1st summary can be manufactured by the method of using the medium purity terephthalic acid whose density | concentration of cobalt is 0.08-5 ppm as a cobalt atom. If the cobalt content is too large, the color tone of PBT deteriorates, and if it is attempted to reduce the content, it is necessary to enhance the purification of terephthalic acid, which complicates the process and is disadvantageous in terms of energy and cost. In a preferred embodiment in this case, the concentration of manganese in medium-purity terephthalic acid is 0.08 to 5 ppm as a manganese atom, and the content of 4-carboxybenzaldehyde is 30 to 1000 ppm.

  The PBT according to the second aspect can be produced by a method using medium-purity terephthalic acid having a manganese concentration of 0.08 to 5 ppm as a manganese atom. If the manganese content is too large, the color tone of the PBT will deteriorate, and if it is attempted to reduce it, it will be necessary to enhance the purification of terephthalic acid, which will complicate the process and will be disadvantageous in terms of energy and cost. In a preferred embodiment in this case, the content of 4-carboxybenzaldehyde in medium purity terephthalic acid is 30 to 1000 ppm.

  The PBT according to the third aspect can be produced by a method using medium-purity terephthalic acid having a content of 4-carboxybenzaldehyde (4-CBA) of 30 to 1000 ppm. If the content of 4-CBA is too large, the color tone of PBT will deteriorate, and if it is attempted to reduce it, it will be necessary to enhance the purification of terephthalic acid, which will complicate the process and will be disadvantageous in terms of energy and cost. .

  In each of the above production methods, the concentration of cobalt is preferably 0.1 to 1 ppm, more preferably 0.15 to 1 ppm, particularly preferably 0.2 to 0.5 ppm, and the concentration of manganese is preferably 0. .1 to 2 ppm, more preferably 0.15 to 1 ppm, particularly preferably 0.2 to 0.5 ppm, and the concentration of 4-CBA is preferably 50 to 500 ppm, more preferably 100 to 400 ppm.

  Depending on the production method, terephthalic acid may contain acetic acid as an impurity. The content of acetic acid in the terephthalic acid used when producing the PBT of the present invention is usually 10 to 5000 ppm, preferably 100 to 3000 ppm, more preferably 500 to 2000 ppm. When the content of acetic acid is too high, the polymerization of PBT is inhibited, and as a result, the reaction at high temperature tends to deteriorate the color tone. Because it needs to be strengthened, it is disadvantageous in terms of energy and cost.

  In the present invention, in the esterification reaction tank, at least a portion of 1,4-butanediol is supplied to the esterification reaction tank independently of terephthalic acid in the presence of a titanium catalyst, while terephthalic acid and 1,4 are added. A step of continuously esterifying with butanediol is preferably employed. That is, in the present invention, haze and foreign matters derived from the catalyst are reduced, and the catalytic activity is not lowered. Therefore, in addition to 1,4-butanediol supplied together with terephthalic acid as a raw slurry or solution, Independent of the acid, 1,4-butanediol is fed to the esterification reactor. Hereinafter, the 1,4-butanediol may be referred to as “separately supplied 1,4-butanediol”.

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

  Moreover, 1,4-butanediol distilled from the esterification reaction tank usually contains components such as water, THF, dihydrofuran and alcohol in addition to the 1,4-butanediol component. Therefore, the 1,4-butanediol obtained by distilling the above is preferably separated and purified from components such as water and tetrahydrofuran after being collected by a condenser or the like, and returned to the reaction vessel. .

  In the present invention, it is preferable to return 10% by weight or more of “separately supplied 1,4-butanediol” directly to the reaction liquid phase part. Here, the reaction liquid phase part indicates the liquid phase side of the gas-liquid interface of the esterification reaction tank, and returning directly to the reaction liquid phase part means “separate supply 1, 4- This means that “butanediol” is supplied directly to the liquid phase part without going through the gas phase part. The ratio of returning directly to the liquid phase part of the reaction liquid is preferably 30% by weight or more, more preferably 50% by weight or more, particularly preferably 80% by weight or more, and most preferably 90% by weight or more. When the amount of “separately supplied 1,4-butanediol” returned directly to the reaction liquid phase is small, the titanium catalyst tends to be deactivated.

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

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

  On the other hand, the periodic table group 1 or group 2 metal compound (co-catalyst) may be supplied to the esterification reaction tank, and into the oligomer piping or polycondensation reaction tank to the polycondensation reaction tank following the esterification reaction tank. It can also be added. The supply position of the cocatalyst is not particularly limited, and may be supplied from the reaction liquid phase part of the reaction tank to the upper surface of the reaction liquid or directly to the reaction liquid phase part. Further, 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 the stability of the promoter, the reaction liquid is separated from the terephthalic acid or titanium catalyst. It is preferable to supply from the phase part to the upper surface of the reaction solution.

  Usually, the periodic table Group 1 or Group 2 metal compound is solid and can be supplied as it is, but in order to stabilize the supply amount and reduce the adverse effects such as denaturation by heat, 1,4-butane It is preferable to supply after diluting with a solvent such as diol. The concentration at this time is usually 0.01 to 20% by weight, preferably 0.05 to 15% by weight, more preferably 0.08 to 10% by weight, as the concentration of the cocatalyst with respect to the whole solution. Water may be added to this solution for the purpose of preventing precipitation and improving thermal stability, and the ratio is usually 0.01 to 25% by weight.

  An example of the continuous method of the present invention is as follows. That is, the dicarboxylic acid component having terephthalic acid as a main component and the diol component having 1,4-butanediol as a main component are mixed in a raw material mixing tank to form a slurry, and in one or a plurality of esterification reaction tanks In the presence of a titanium catalyst and a cocatalyst, the temperature is usually 180 to 260 ° C., preferably 200 to 245 ° C., more preferably 210 to 235 ° C., and usually 10 to 133 kPa (absolute pressure, the same applies hereinafter), preferably Oligomer as the esterification reaction product obtained by continuous esterification reaction under a pressure of 13 to 101 kPa, more preferably 60 to 90 kPa, usually for 0.5 to 10 hours, preferably 1 to 6 hours. In a polycondensation reaction tank and in the presence of a polycondensation catalyst, preferably continuously in the presence or absence of a polycondensation catalyst. 0 ° C., preferably 220 to 265 ° C., particularly preferably 230 to 245 ° C., usually 27 kPa or less, preferably 20 kPa or less, more preferably 13 kPa or less, with stirring, usually 2 to 15 hours, preferably Is polycondensed in 3 to 10 hours. At this time, a new catalyst may be added at the polycondensation stage, or the catalyst used in the esterification reaction may be used as it is as the polycondensation catalyst, and no new catalyst may be added. The polymer obtained by the polycondensation reaction is usually transferred from the bottom of the polycondensation reaction tank to a polymer extraction die and extracted in the form of a strand, and while being cooled with water or after being cooled with water, it is cut with a cutter to form pellets and chips. And so on.

  In the present invention, the molar ratio of terephthalic acid and 1,4-butanediol preferably satisfies the following formula (3).

  The above "1,4-butanediol supplied from the outside to the esterification reaction tank" refers to 1,4-butanediol supplied together with terephthalic acid as a raw slurry or solution, and independently supplied from these 1,4-butanediol, 1,4-butanediol used as a solvent for the catalyst, etc.

  When the above B / TPA value is smaller than 1.1, the conversion rate is reduced and the catalyst is deactivated. When the B / TPA value is larger than 5.0, not only the thermal efficiency is decreased, but also by-products such as tetrahydrofuran increase. Tend to. The value of B / TPA 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 reaction tank, known ones 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 reaction tank, 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 reaction tank having a stirring device is preferable, and as a stirring device, a turbine stator type high-speed rotating stirrer, a disk mill type stirrer, a rotor mill type stirrer in addition to a normal type including a power unit, a bearing, a shaft, and a stirring blade. A type that rotates at high speeds can also be used.

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

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

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

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

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

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

  Further, the PBT polycondensation reaction step is to produce a PBT having a relatively small molecular weight by melt polycondensation, for example, an intrinsic viscosity of about 0.1 to 1.0, and then at a temperature below the melting point of the PBT. Solid phase polycondensation (solid phase polymerization) can also be performed.

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

  If the filter is installed too far upstream of the manufacturing process, foreign matter generated downstream cannot be removed, and the pressure loss of the filter increases and the flow rate is maintained where the downstream viscosity is high. It is necessary to increase the opening of the filter, to increase the filter filtration area and piping, etc., and to receive high shear when passing through the fluid, so it is inevitable that PBT deteriorates due to shear heat generation. . Therefore, the filter installation position is selected so that the intrinsic viscosity of PBT or its precursor is usually 0.1 to 1.2, preferably 0.2 to 1.0, more preferably 0.5 to 0.9. Is done.

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

  The absolute filtration accuracy of the filter is not particularly limited, but is usually 0.5 to 200 μm, preferably 1 to 100 μm, more preferably 5 to 50 μm, and particularly preferably 10 to 30 μm. When the absolute filtration accuracy is too high, the effect of reducing foreign matters in the product is lost, and when it is too low, productivity is lowered and filter replacement frequency is increased. The absolute filtration accuracy indicates a minimum particle size when the filter is completely removed by filtration when a filtration test is performed using a standard particle size product such as glass beads having a known and uniform particle size.

  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, FIG. 2 is an explanatory diagram of an example of a polycondensation step employed in the present invention, and FIGS. 3 to 5 are polycondensations employed in the present invention. It is explanatory drawing of the other example of a process.

  In FIG. 1, terephthalic acid as a raw material is usually mixed with 1,4-butanediol in a raw material mixing tank (not shown), and supplied to the reaction tank (A) in the form of slurry from the raw material supply line (1). The On the other hand, the titanium catalyst is preferably supplied from a catalyst supply line (3) after being made into a solution of 1,4-butanediol in a catalyst adjustment tank (not shown). FIG. 1 shows a mode in which a catalyst supply line (3) is connected to a recycle line (2) for recycle 1,4-butanediol, and both are mixed and then supplied to the liquid phase part of the reaction tank (A). It was. The cocatalyst (group 1 or group 2 metal compound) is preferably made into a solution of 1,4-butanediol in a cocatalyst preparation tank (not shown), and then the cocatalyst supply line (15). Supplied from

  The gas distilled from the reaction tank (A) is separated into a high-boiling component and a low-boiling component in the rectification tower (C) through the distillation line (5). Usually, the main component of the high boiling point component is 1,4-butanediol, and the main components of the low boiling point component are water and THF.

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

  In the process shown in FIG. 1, the catalyst supply line (3) is connected to the recirculation line (2), but both may be independent. Moreover, the raw material supply line (1) and the promoter supply line (15) may be connected to the liquid phase part of the reaction tank (A).

  In FIG. 2, the oligomer supplied from the above-described extraction line (4) shown in FIG. 1 is polycondensed under reduced pressure in the first polycondensation reaction tank (a) to become a prepolymer, and then extracted. It is supplied to the second polycondensation reaction tank (d) through the gear pump (c) and the extraction line (L1). In the second polycondensation reaction tank (d), polycondensation usually proceeds at a lower pressure than that of the first polycondensation reaction tank (a) to become a polymer. The obtained polymer is extracted in the form of a melted strand from the die head (g) through the extraction gear pump (e) and the extraction line (L3), cooled with water, and then rotated with a rotary cutter ( It is cut into a pellet in h). Reference numeral (L2) is a vent line of the first polycondensation reaction tank (a), and reference numeral (L4) is a vent line of the second polycondensation reaction tank (d).

  The process shown in FIG. 3 differs from the process shown in FIG. 2 in that a filter (f) is provided in the flow path of the extraction line (L3).

  The process shown in FIG. 4 differs from the process shown in FIG. 2 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 composed of a plurality of stirring blade blocks and equipped with a biaxial self-cleaning type stirring blade. The polymer introduced into the third polycondensation reaction tank (k) from the second polycondensation reaction tank (d) through the extraction line (L3) is further subjected to polycondensation here, and then the extraction gear pump (m ) And the extraction line (L5), and is extracted from the die head (g) in the form of a melted strand, cooled with water, and then cut with a rotary cutter (h) to form pellets. Symbol (L6) is a vent line of the third polycondensation reaction tank (k).

  Compared with the process shown in FIG. 4, the process shown in FIG. 5 has a filter (L3) in the middle of the extraction line (L3) between the second polycondensation reaction tank (d) and the third polycondensation reaction tank (k). The difference is that f) is equipped.

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

  A reinforcing filler can be blended in the PBT of the present invention. The reinforcing filler is not particularly limited, but examples thereof include glass fibers, carbon fibers, silica / alumina fibers, zirconia fibers, boron fibers, boron nitride fibers, silicon nitride potassium titanate fibers, metal fibers and other inorganic fibers, aromatics Examples thereof include organic fibers such as polyamide fibers and fluororesin fibers. These reinforcing fillers can be used in combination of two or more. Among the above reinforcing fillers, inorganic fillers, particularly glass fibers, are preferably used.

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

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

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

  A flame retardant can be blended with the PBT of the present invention in order to impart flame retardancy. The flame retardant is not particularly limited, and examples thereof include organic halogen compounds, antimony compounds, phosphorus compounds, other organic flame retardants, and inorganic flame retardants. Examples of the organic halogen compound include brominated polycarbonate, brominated epoxy resin, brominated phenoxy resin, brominated polyphenylene ether resin, brominated polystyrene resin, brominated bisphenol A, 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 of the present invention can be blended with conventional additives as required. Such additives are not particularly limited and include, for example, stabilizers such as antioxidants and heat stabilizers, lubricants, mold release agents, catalyst deactivators, crystal nucleating agents, crystallization accelerators, and the like. It is done. These additives can be added during or after the polymerization. In addition, in order to give PBT the desired performance, UV absorbers, stabilizers such as weather resistance stabilizers, colorants such as dyes and pigments, antistatic agents, foaming agents, plasticizers, impact resistance improvers, etc. I can do it.

  For the PBT of the present invention, thermoplastics such as polyethylene, polypropylene, polystyrene, polyacrylonitrile, polymethacrylic acid ester, ABS resin, polycarbonate, polyamide, polyphenylene sulfide, polyethylene terephthalate, liquid crystal polyester, polyacetal, polyphenylene oxide, etc. A thermosetting resin such as a resin, a phenol resin, a melamine resin, a silicone resin, or an epoxy resin can be blended. These thermoplastic resins and thermosetting resins can be used in combination of two or more.

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

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

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

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

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

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

(3) Intrinsic viscosity ([η]):
It calculated | required in the following way using the Ubbelohde type viscometer. That is, a mixed solution of phenol / tetrachloroethane (weight ratio 1/1) was used as a solvent, and at 30 ° C., the polymer solution having a concentration of 1.0 g / dL and the falling seconds of the solvent alone were measured, and the following formula ( Obtained from 5).

(4) Cobalt (Co) and manganese (Mn) content:
In a platinum crucible, 1.0 g of terephthalic acid or PBT sample was weighed, 5 mL of high-purity sulfuric acid for electronic industry was added, and then carbide was generated by heating. At this time, the addition of sulfuric acid was repeated until the carbide was completely formed. The produced carbide was incinerated at 800 ° C., and then diluted with 2 mL of high-purity nitric acid for electronics industry. The metal element in this solution was quantified with a graphite furnace atomic absorption spectrophotometer (“GF-AAS” manufactured by Varian Technologies Japan Limited) and converted to an amount (ppm) per terephthalic acid or PBT.

(5) Titanium (Ti) and periodic table Group 1 or Group 2 metal content:
Weigh 2.0 g of PBT into a Kjeldahl flask, add 12 mL of high-purity sulfuric acid for electronic industry and hydrogen peroxide (add hydrogen peroxide as appropriate), perform wet decomposition until completely dissolved, and then add ultrapure water. Diluted to a predetermined concentration. The metal element in this solution was quantified by ICP (“JY46P” manufactured by JOBIN YVON) and converted to an amount per ppm (ppm).

(6) 4-CBA content:
The sample was dissolved in 2N-ammonia aqueous solution, diluted with ultrapure water to a predetermined concentration, and then measured by high performance liquid chromatography equipped with an ODS column.

(7) Acetic acid content:
The sample was dissolved in 2N-potassium hydroxide aqueous solution, acidified with an aqueous phosphoric acid solution, filtered through a filter paper, and acetic acid contained in the filtrate was quantified using gas chromatography equipped with a DB-FFAP capillary column. A propionic acid aqueous solution was used as an internal standard substance.

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

(9) Aldehyde group content:
About 100 mg of PBT was dissolved in 1 mL of a mixed solution of deuterated chloroform / deuterated hexafluoroisopropanol = 7/3 (volume ratio), and ¹ H-NMR was measured and determined at 20 ° C. As the NMR apparatus, “Varian Unity Plus 400” manufactured by Varian Co., Ltd. was used.

(10) Number of fisheye:
Using a “Film Quality Testing System” (model FS-5) manufactured by Optical Control Systems, a film having a thickness of 50 μm was formed, and the number of fish eyes of 25 μm or more per 1 m 2 was measured.

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

(12) Solution Haze:
After dissolving 2.70 g of PBT in 20 mL of a mixed solution of phenol / tetrachloroethane = 3/2 (weight ratio) at 110 ° C. for 30 minutes, the mixture was cooled in a constant temperature water bath at 30 ° C. for 15 minutes, and manufactured by Nippon Denshoku Co., Ltd. A turbidity measured with a cell length of 10 mm was used as a solution Haze using a densitometer (NDH-300A). It shows that transparency is so favorable that a value is low.

(13) Pellet color tone (b value):
A color difference meter (Z-300A type) manufactured by Nippon Denshoku Co., Ltd. was used to measure the color coordinate b value of Hunter's color difference formula in the Lab color system. A lower value indicates less yellowing and a better color tone.

(14) Increase in terminal group carboxyl group concentration by reaction excluding hydrolysis reaction (ΔCOOH):
Using a Capillograph manufactured by Toyo Seiki Co., Ltd., PBT with a moisture of 100 ppm or less was dried at 120 ° C for 12 hours in a cylinder with an inner diameter of 10 mm, melted and held at 245 ° C for 40 minutes, and then extruded with a piston. It was. The intrinsic viscosity, terminal carboxyl group concentration and hydroxyl group concentration of the extracted polymer were measured, and the increase in terminal carboxyl group excluding the hydrolysis reaction (ΔCOOH) was calculated from the above formula (2).

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. 1.80 mol of 1,4-butanediol per 1.00 mol of medium purity terephthalic acid (TPA) having a cobalt concentration of 0.31 ppm, a manganese concentration of 0.21 ppm, a 4-CBA concentration of 225 ppm, and an acetic acid content of 1010 ppm The slurry at 60 ° C. mixed at a rate passes through the raw material supply line (1) from the slurry preparation tank to the reaction tank (A) for esterification having a screw type stirrer filled with a PBT oligomer having an esterification rate of 99% in advance. , 41 kg / h continuously. At the same time, the bottom component (98% by weight or more of 1,4-butanediol) of the 185 ° C. rectification column (C) is supplied at 19 kg / h from the recirculation line (2), and from the catalyst supply line (3). A 6.0 wt% 1,4-butanediol solution of tetrabutyl titanate at 65 ° C. was fed as a catalyst at 114 g / h (35 ppm as Ti based on the theoretical polymer yield). The water content in this catalyst solution was 0.20% by weight. On the other hand, a 10.0 wt% 1,4-butanediol solution of magnesium acetate tetrahydrate at 65 ° C. was supplied at 24 g / h as a periodic table group 1 or group 2 metal compound from the line (15). (10 ppm as Mg relative to theoretical polymer yield). The water content in this solution was 10.0% by weight.

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

  The oligomer produced in the reaction tank (A) is quantified by using the pump (B) and withdrawing from the extraction line (4) so that the average residence time of the liquid in the reaction tank (A) is 3.2 hours. Control the surface. 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 97.0%.

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

  The internal temperature of the second polycondensation reaction tank (d) is 240 ° C., the pressure is 130 Pa, the liquid level is controlled so that the residence time is 80 minutes, and a vent line (L4) connected to a decompressor (not shown). ), Polycondensation reaction was further carried out while extracting water, THF and 1,4-butanediol. The obtained polymer was continuously extracted in a strand form from the die head (g) via the extraction line (L3) by the extraction gear pump (e), and was cut by the rotary cutter (h).

  The obtained polymer had an intrinsic viscosity of 0.85, a terminal carboxyl group concentration of 11.0 μeq / g, and a b value of −0.9. Other analytical values are summarized in Table 1. PBT with few foreign matters, excellent color tone, and good transparency was obtained.

Example 2:
In Example 1, it carried out like Example 1 except having employ | adopted the polycondensation process shown in FIG. As the filter (f) in the polycondensation process shown in FIG. 3, a pleated process type filter made of a metal nonwoven fabric and having an absolute filtration accuracy of 20 μm was used. A PBT in which foreign matter was further reduced than in Example 1 was obtained. The analytical values are summarized in Table 1.

Example 3:
Example 1 was carried out in the same manner as Example 1 except that medium purity terephthalic acid / high purity terephthalic acid was used at 3/7. High-purity terephthalic acid is terephthalic acid with a refinement process stronger than medium-purity terephthalic acid, with a cobalt concentration of 0.02 ppm, a manganese concentration of 0.02 ppm, a 4-CBA concentration of 4 ppm, and an acetic acid concentration of less than 10 ppm. It was. The analytical values are summarized in Table 1.

Example 4:
The same procedure as in Example 1 was performed except that the supply amount of magnesium acetate tetrahydrate was changed as shown in Table 1 and the internal temperature of the second polycondensation reaction tank (d) was changed to 239 ° C. It was. The analytical values are summarized in Table 1.

Example 5:
In Example 1, the supply amount of tetrabutyl titanate was changed as shown in Table 1, except that the internal temperature of the second polycondensation reaction tank (d) was 239 ° C. and the residence time was 65 minutes. The same was done. The analytical values are summarized in Table 1.

Example 6:
In Example 1, instead of magnesium acetate tetrahydrate, calcium acetate monohydrate was supplied in the amount shown in Table 1, and the residence time of the second polycondensation reaction tank (d) was 90 minutes. Except for this, the same procedure as in Example 1 was performed. The analytical values are summarized in Table 1.

Example 7:
In Example 1, the supply amount of tetrabutyl titanate was changed as shown in Table 1, and instead of magnesium acetate tetrahydrate, lithium acetate dihydrate was supplied to the amount shown in Table 1, The same operation as in Example 1 was conducted except that the internal temperature of the polycondensation reaction tank (d) was 239 ° C. The analytical values are summarized in Table 2.

Comparative Example 1:
The same operation as in Example 5 was conducted except that the internal temperature of the second polycondensation reaction tank (d) was 243 ° C., the residence time was 70 minutes, and magnesium acetate tetrahydrate was not used. The color tone of the pellet deteriorated and there were many foreign substances. The analytical values are summarized in Table 2.

Comparative Example 2:
In Example 1, the supply amount of tetrabutyl titanate was changed as shown in Table 1, except that the internal temperature of the second polycondensation reaction tank (d) was 239 ° C. and the residence time was 65 minutes. The same was done. Terminal carboxyl group concentration increased, pellet color tone and solution haze deteriorated, and there were many foreign substances. The analytical values are summarized in Table 2.

Reference example 1:
In Example 1, it carried out like Example 1 except having used the high purity terephthalic acid used in Example 3 instead of medium purity terephthalic acid. Although PBT having a color tone superior to that of Example 1 was obtained, the purification process of terephthalic acid was complicated. The analytical values are summarized in Table 2.

Reference example 2:
In Comparative Example 2, the procedure was the same as Comparative Example 2, except that the high-purity terephthalic acid used in Example 3 was used instead of medium-purity terephthalic acid. Although PBT having a color tone superior to that of Example 1 was obtained, the purification process of terephthalic acid was complicated. The analytical values are summarized in Table 2.

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 Explanatory drawing of another example of the polycondensation step employed in the present invention Explanatory drawing of another example of the polycondensation step employed in the present invention Explanatory drawing of another example of the polycondensation step employed in the present invention

Explanation of symbols

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

Claims (21)

  Containing titanium and a Group 1 or Group 2 metal in the periodic table, the concentration of titanium being 90 ppm or less as a titanium atom, the concentration of a Group 1 or Group 2 metal in the periodic table being 90 ppm or less as a metal atom, and Polybutylene terephthalate, wherein the concentration of cobalt is 0.06 to 4 ppm as cobalt atoms.   The polybutylene terephthalate according to claim 1, wherein the concentration of manganese is 0.06 to 4 ppm as manganese atoms.   The polybutylene terephthalate according to claim 1 or 2, wherein the aldehyde group content is 0.1 µeq / g or more.   The polybutylene terephthalate according to any one of claims 1 to 3, wherein the cobalt concentration is 0.1 to 1 ppm as a cobalt atom.   Containing titanium and a Group 1 or Group 2 metal in the periodic table, the concentration of titanium being 90 ppm or less as a titanium atom, the concentration of a Group 1 or Group 2 metal in the periodic table being 90 ppm or less as a metal atom, and Polybutylene terephthalate, wherein the manganese concentration is 0.06 to 4 ppm as manganese atoms.   The polybutylene terephthalate according to claim 5, wherein the content of aldehyde groups is 0.1 µeq / g or more.   Containing titanium and a Group 1 or Group 2 metal in the periodic table, the concentration of titanium being 90 ppm or less as a titanium atom, the concentration of a Group 1 or Group 2 metal in the periodic table being 90 ppm or less as a metal atom, and Polybutylene terephthalate, characterized in that the content of aldehyde groups is 0.1 μeq / g or more.   The polybutylene terephthalate according to any one of claims 1 to 7, which contains titanium and a Group 1 or Group 2 metal in the periodic table, and each has a concentration of 70 ppm or less as a titanium atom or a metal atom.   The polybutylene terephthalate according to any one of claims 1 to 8, wherein the amount of Group 1 or Group 2 metal in the periodic table is 0.1 to 2.5 times moles of titanium.   The polybutylene terephthalate according to any one of claims 1 to 9, wherein the terminal carboxyl group concentration is 1 to 30 µeq / g.   The increase in terminal carboxyl group concentration excluding the increase in terminal carboxyl group concentration due to hydrolysis reaction when heat-treated at 245 ° C for 40 minutes in an inert gas atmosphere is 20 µeq / g or less. Polybutylene terephthalate.   12. The polybutylene according to claim 1, which has a solution haze of 5% or less when 2.7 g of polybutylene terephthalate is dissolved in 20 mL of a phenol / tetrachloroethane mixed solution (weight ratio 3/2). Terephthalate.   The polybutylene terephthalate according to any one of claims 1 to 12, comprising magnesium as a Group 2 metal of the periodic table.   In the production of polybutylene terephthalate from terephthalic acid and 1,4-butanediol using a titanium catalyst and a co-catalyst composed of a Group 1 or Group 2 compound in the periodic table, the concentration of cobalt is reduced to 0. Using medium purity terephthalic acid of 08 to 5 ppm, the concentration in the resulting polybutylene terephthalate is 90 ppm or less as titanium atoms and 90 ppm or less as periodic table group 1 or group 2 metal. A process for producing polybutylene terephthalate, characterized in that a substantial amount of a cocatalyst is used.   The manufacturing method of Claim 14 whose density | concentration of manganese in medium purity terephthalic acid is 0.08-5 ppm as a manganese atom.   The production method according to claim 14 or 15, wherein the content of 4-carboxybenzaldehyde in medium-purity terephthalic acid is 10 to 1000 ppm.   In the production of polybutylene terephthalate from terephthalic acid and 1,4-butanediol using a titanium catalyst and a co-catalyst composed of a Group 1 or Group 2 compound in the periodic table, the manganese concentration is set to 0. Using medium purity terephthalic acid of 08 to 5 ppm, the concentration in the resulting polybutylene terephthalate is 90 ppm or less as titanium atoms and 90 ppm or less as periodic table group 1 or group 2 metal. A process for producing polybutylene terephthalate, characterized in that a substantial amount of a cocatalyst is used.   The production method according to claim 17, wherein the content of 4-carboxybenzaldehyde in the medium purity terephthalic acid is 10 to 1000 ppm.   In the production of polybutylene terephthalate from terephthalic acid and 1,4-butanediol using a titanium catalyst and a co-catalyst comprising a Group 1 or Group 2 compound in the periodic table, the content of 4-carboxybenzaldehyde is 10 A medium-purity terephthalic acid of ˜1000 ppm is used, and the concentration in the resulting polybutylene terephthalate is 90 ppm or less as a titanium atom, and the equivalent of 90 ppm or less as a group 1 or group 2 metal in the periodic table. A process for producing polybutylene terephthalate, characterized in that an amount of cocatalyst is used.   20. A substantial amount of a titanium catalyst having a concentration in the produced polybutylene terephthalate of 70 ppm or less as a titanium atom and a substantial amount of a promoter having a concentration of 70 ppm or less as a Group 1 or Group 2 metal in the periodic table are used. The manufacturing method in any one of.   20. A substantial amount of a titanium catalyst having a concentration in a polybutylene terephthalate to be 40 ppm or less as a titanium atom and a substantial amount of a promoter having a concentration of 40 ppm or less as a Group 1 or Group 2 metal in the periodic table are used. The manufacturing method in any one of.

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