JP5079226B2 - Polybutylene terephthalate - Google Patents

Description

  The present invention relates to polybutylene terephthalate, and in particular, is excellent in productivity, color tone, hydrolysis resistance, thermal stability, transparency, moldability, and suitable for films, monofilaments, fibers, electrical and electronic parts, automobile parts, etc. It relates to polybutylene terephthalate which can be used.

  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 for 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, etc. In these fields, polybutylene terephthalate having a higher molecular weight than conventional injection molded products is used. It has been demanded.

  However, polybutylene terephthalate does not necessarily have sufficient hydrolysis resistance, and particularly when used under wet heat, there is a problem of a decrease in mechanical properties accompanying a decrease in molecular weight. In general, it is known that polybutylene terephthalate is deteriorated in hydrolysis resistance as the terminal carboxyl group concentration is high (for example, Patent Document 1), resulting in a decrease in molecular weight due to hydrolysis, and a decrease in mechanical properties. It is a big problem.

  In order to solve the above problem, it is widely practiced to reduce the terminal carboxyl group concentration by once solidifying polybutylene terephthalate obtained by melt polymerization 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 or above 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, the problem of increased gas generation during molding is also caused.

  The increase rate of the terminal carboxyl group concentration at the time of melting as described above 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 in the case of 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 the polymerization temperature low by using a titanium compound and a specific metal compound as a catalyst in a specific molar ratio (see, for example, Patent Document 2) or a titanium in a specific state Use is proposed (for example, refer patent document 3). However, these methods are not sufficient to solve the above problems.

  By the way, as a method for producing polybutylene terephthalate, generally, a transesterification method (DMT method) using dimethyl terephthalate and 1,4-butanediol as raw materials or a direct polymerization method using terephthalic acid and 1,4-butanediol are used. However, the transesterification method has problems in the recovery of by-product low molecular weight substances such as the generation of methanol as a by-product of the reaction. Direct polymerization methods are 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 case of the direct polymerization method (for example, Patent Documents 4 and 5). The deactivation of the titanium catalyst literally deteriorates the reactivity. In order to obtain polybutylene terephthalate having a desired molecular weight, it is necessary to add an extra catalyst or to react at a higher temperature.

  On the other hand, in applications such as films, sheets, monofilaments, and fibers, not only the color tone but also the haze and foreign matter (the foreign matter in the film is called fisheye) greatly affects the commercial value, so these must be significantly reduced. It has been.

  However, the addition of an excess catalyst increases the number of deactivated catalysts, leading to haze deterioration and increased foreign matter, while high reaction temperatures cause color deterioration, making it difficult to achieve both of these performances. is there.

  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.

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

  The present invention has been made in view of the above circumstances, and its purpose is excellent in productivity, color tone, hydrolysis resistance, thermal stability, transparency, moldability, film, monofilament, fiber, electrical and electronic component, An object of the present invention is to provide polybutylene terephthalate that can be suitably used for automobile parts and the like.

  As a result of intensive studies to solve the above problems, the present inventors have used a titanium compound and at least one metal compound selected from Groups 1 and 2 of the periodic table as a catalyst to achieve a specific mode. Surprisingly, when the polymerization reaction is carried out, the increase in the terminal carboxyl group due to the thermal decomposition reaction is suppressed, and a polybutylene terephthalate having a low terminal carboxyl group concentration is obtained. The increase in group concentration can also be suppressed, and in addition, the reaction during polycondensation is greatly promoted. As a result, the polymerization temperature is lowered, and the desired quality is prevented while preventing deterioration in color tone and thermal degradation. The knowledge that it is possible to produce polybutylene terephthalate having a molecular weight was obtained, and the present invention was completed.

  The present invention has been completed based on the above findings, the gist of which is obtained 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, The content of titanium per mol of terephthalic acid unit is 320 μmol or less as a titanium atom, the content of at least one metal selected from Groups 1 and 2 of the periodic table is 130 μmol or less as a metal atom, and the intrinsic viscosity is 1 The polybutylene terephthalate is characterized by being 10 or more.

  According to the present invention, it is excellent in productivity, color tone, hydrolysis resistance, thermal stability, transparency, moldability, and can be suitably used for films, monofilaments, fibers, electrical and electronic parts, automobile parts and the like. Butylene terephthalate 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 50 mol% or more of dicarboxylic acid units are composed of terephthalic acid units. It means a polymer in which 50 mol% or more of the diol component is composed of 1,4-butanediol units. The proportion of terephthalic acid units in all dicarboxylic acid units is preferably 70 mol% or more, more preferably 80 mol% or more, particularly preferably 95 mol% or more, and 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.

  The PBT of the present invention comprises a titanium compound and a periodic table as a catalyst when polycondensing an oligomer obtained by an esterification reaction (or transesterification reaction) of 1,4-butanediol and terephthalic acid (or dialkyl terephthalate). It is obtained by using a compound of at least one metal selected from Group 1 and Group 2. These catalysts may be used in the esterification reaction (or transesterification reaction) and directly brought into the polycondensation reaction, not used in the esterification reaction (or transesterification reaction), or either one of them. Only the catalyst may be used and the other catalyst may be added in the polycondensation stage. Furthermore, in the esterification reaction (or transesterification reaction), a part of the catalyst amount finally used can be used, and can be added as the polycondensation reaction proceeds. In any case, in the present invention, the finally obtained PBT necessarily contains titanium and at least one metal selected from Groups 1 and 2 of the periodic table. It will be described later. In the following description, the titanium compound may be referred to as a titanium catalyst, the periodic table group 1 metal compound, and the group 2 metal compound as group 1 metal catalyst and group 2 metal catalyst, respectively.

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

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

  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 a tin atom, usually as a weight ratio to the finally obtained PBT. It is preferable.

  Specific examples of the periodic table group 1 metal compound in the present invention include various compounds of lithium, sodium, potassium, rubidium, and cesium. Specific examples of the periodic table group 2 metal compound include beryllium, magnesium, calcium, and strontium. And various compounds of barium, lithium, sodium, potassium, magnesium, and calcium compounds are preferable from the viewpoint of handling and availability, and catalytic effect. Among them, lithium or magnesium compound having excellent catalytic effect and color tone Is preferable, and 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 to the titanium catalyst, group 1 metal catalyst, and group 2 metal catalyst, antimony compounds such as antimony trioxide, germanium compounds such as germanium dioxide and germanium tetroxide, manganese compounds, zinc compounds, zirconium compounds and cobalt compounds Reaction aids such as orthophosphoric acid, phosphorous acid, hypophosphorous acid, polyphosphoric acid, phosphorus compounds such as esters and metal salts thereof may be used.

  The content of titanium in the PBT of the present invention is required to be 320 μmol or less, preferably 270 μmol or less, more preferably 230 μmol or less, and particularly preferably 190 μmol or less, per 1 mol of terephthalic acid unit. The lower limit of the titanium content is not particularly limited as long as titanium is contained, but is usually 45 μmol, preferably 90 μmol, and more preferably 130 μmol. When the content of titanium is too large, not only the color tone and hydrolysis resistance deteriorate, but also the solution haze and foreign matters increase due to the deactivation of the titanium catalyst, and when it is too small, the polymerizability deteriorates.

  The content of at least one metal selected from Groups 1 and 2 of the periodic table in the PBT of the present invention needs to be 130 μmol or less, preferably 120 μmol as a metal atom per 1 mol of terephthalic acid unit. Hereinafter, it is more preferably 110 μmol or less, particularly preferably 100 μmol or less. The lower limit of the content of at least one metal selected from Group 1 and Group 2 of the periodic table is not particularly limited as long as they are contained, but is usually 10 μmol, preferably 30 μmol, and more preferably 50 μmol.

  If the content of at least one metal selected from Group 1 and Group 2 of the Periodic Table is too large, the molecular weight will end at the end of the polycondensation and PBT with a predetermined molecular weight may not be obtained. In order to receive a lot of history, the color tone deteriorates and the hydrolysis resistance deteriorates. On the other hand, when the content is too small, the polycondensation rate becomes slow and the effect of the present invention cannot be seen.

  In the PBT of 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, Inductively Coupled Plasma (ICP) after recovering the metal in the polymer by a method such as wet ashing.

  The terminal carboxyl group concentration of the PBT of the present invention is usually 30 μeq / g, preferably 1 to 20 μeq / g, more preferably 1 to 10 μeq / g, and particularly preferably 1 to 7 μeq / g. 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 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 generation of gas such as tetrahydrofuran (THF) is generated. You may be invited. Therefore, in the PBT of the present invention, the increase in the terminal carboxyl group concentration excluding the hydrolysis reaction upon heat treatment at 245 ° C. for 40 minutes in an inert gas atmosphere is usually 0.1 to 20 μeq / g, preferably 0.8. 1-15 μeq / g, more preferably 0.1-10 μeq / g, particularly preferably 0.1-8 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 (1). You can ask.

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 of 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.

  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 high 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. Tend to rise.

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

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

  The intrinsic viscosity of the PBT of the present invention needs to be 1.10 dL / g. When the intrinsic viscosity is less than 1.10 dL / g, not only the mechanical strength of the molded product becomes insufficient, but also drawdown becomes large particularly when molding a film or a sheet, which adversely affects quality and productivity. coming out. The upper limit of the intrinsic viscosity is usually 1.60 dL / g, preferably 1.40 dL / g, more preferably 1.30 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-falling crystallization temperature of the PBT of the present invention is usually 160 to 200 ° C, preferably 170 to 195 ° C, 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 solution haze of the PBT of the present invention is not particularly limited, but is usually 10% or less as the solution haze when measured by dissolving 2.7 g of PBT in 20 mL of a phenol / tetrachloroethane mixed solvent (weight ratio 3/2). Is 5% or less, more preferably 3% or less, and particularly preferably 1% or less. When the solution haze is high, transparency tends to deteriorate and foreign matter tends to increase, so that the commercial value is remarkably reduced in applications requiring transparency, such as films, monofilaments, and fibers. The solution haze tends to increase when the deactivation of the titanium catalyst is large.

  The content of the cyclic dimer in the PBT of the present invention is usually 1500 ppm or less, preferably 1200 ppm or less, more preferably 1000 ppm or less, particularly preferably 800 ppm or less as a weight ratio with respect to PBT, and the lower limit is usually 10 ppm. is there. The content of the cyclic trimer is usually 1000 ppm or less, preferably 800 ppm or less, more preferably 600 ppm or less, particularly 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. .

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

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

  The Group 1 metal catalyst and / or the Group 2 metal catalyst can be supplied to the esterification reaction tank or the transesterification reaction tank, but the supply position is not particularly limited, and the reaction is carried out from the reaction gas phase portion of these reaction tanks. You may supply to a liquid upper surface, and you may supply directly to a reaction liquid phase part. 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 catalyst, it is independent of terephthalic acid or a titanium catalyst, and the reaction liquid gas phase. It is preferable to supply to the upper surface of the reaction liquid from the part.

  The group 2 metal catalyst is solid at room temperature and can be supplied as it is. However, in order to stabilize the supply amount and reduce adverse effects such as heat denaturation, water, 1,4-butanediol, etc. It is preferable to supply it by dissolving in a solvent. 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 metal catalyst with respect to the whole solution.

  Further, the group 1 metal catalyst and / or the group 2 metal catalyst can be added to a polycondensation reaction tank following the esterification reaction tank or the transesterification reaction tank, and an oligomer pipe attached thereto. In this case as well, in order to stabilize the supply amount and reduce adverse effects such as denaturation due to heat, it can be dissolved in a solvent such as water, 1,4-butanediol, or a copolymer component such as polytetramethylene ether glycol. It is preferable to supply. The concentration at this time is in the same range as described above.

  An example of a continuous esterification method employing a direct polymerization method is as follows. That is, the dicarboxylic acid component having terephthalic acid as a main component and the diol component having 1,4-butanediol as a main component are mixed in a raw material mixing tank to form a slurry, and in one or a plurality of esterification reaction tanks In the presence of a titanium catalyst and a Group 1 metal catalyst and / or a Group 2 metal catalyst, a temperature of usually 180 to 260 ° C., preferably 200 to 245 ° C., more preferably 210 to 235 ° C., and usually 10 To 133 kPa, preferably 13 to 101 kPa, more preferably 60 to 90 kPa (absolute pressure; hereinafter the same), usually 0.5 to 10 hours, preferably 1 to 6 hours, for continuous esterification reaction .

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

  The above "1,4-butanediol supplied from the outside to the esterification reaction tank" means, in addition to 1,4-butanediol supplied together with terephthalic acid or terephthalic acid dialkyl ester as a raw slurry or solution. 1,4-butanediol (separately supplied 1,4-butanediol), 1,4-butanediol used as a solvent for the catalyst, and the like that enter the reaction tank from the outside of the reaction tank -Total of butanediol.

  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 THF are increased. 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.

  Moreover, an example of the continuous method which employ | adopted the transesterification method is as follows. That is, in the presence or absence of a titanium catalyst and a Group 1 metal catalyst and / or a Group 2 metal catalyst in one or a plurality of transesterification reaction tanks, it is usually 110 to 260 ° C, preferably 140 to 245 ° C, more preferably 180. The ester is continuously produced at a temperature of ˜220 ° C., usually 10 to 133 kPa, preferably 13 to 120 kPa, more preferably 60 to 101 kPa, usually 0.5 to 5 hours, preferably 1 to 3 hours. Exchange reaction.

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

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

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

  As the esterification reaction tank or the transesterification reaction tank, known ones can be used, and any type such as a vertical stirring complete mixing tank, a vertical heat convection mixing tank, a tower type continuous reaction tank, etc. Also, a single tank may be a plurality of tanks in which the same or different tanks are connected in series or in parallel. 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. 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.

  Next, the oligomer as the obtained esterification reaction product or transesterification reaction product is transferred to a polycondensation reaction tank. Under the present circumstances, the esterification rate of the oligomer prescribed | regulated by an Example is 90% or more normally, Preferably it is 95% or more, and a number average molecular weight is 300-3000 normally, Preferably it is 500-1500.

  The form of the polycondensation 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 these, at least one polycondensation reaction tank 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 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. 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. You may use the horizontal reactor which is excellent in the surface renewal and self-cleaning property which has a rotating shaft in a horizontal direction.

  The polycondensation reaction is usually performed at 210 to 280 ° C., preferably 220 to 250 ° C., more preferably 230 to 245 ° C., particularly preferably at least in the presence of a titanium catalyst and a Group 1 metal catalyst and / or a Group 2 metal catalyst. In one reactor, at a temperature of 230 to 240 ° C., preferably with stirring, usually 1 to 12 hours, preferably 3 to 10 hours, usually 27 kPa or less, preferably 20 kPa or less, particularly preferably 13 kPa or less. Perform under reduced pressure. 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, usually under a high vacuum of 1.3 kPa or less, preferably 0.5 kPa or less, more preferably 0.3 kPa or less. Good to do.

  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.

  Furthermore, the PBT polycondensation reaction step is to once 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.

  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 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.

  A flame retardant can be blended with the PBT of the present invention in order to impart flame retardancy. The flame retardant is not particularly limited, and examples thereof include organic halogen compounds, antimony compounds, phosphorus compounds, other organic flame retardants, and inorganic flame retardants. Examples of the organic halogen compound include brominated polycarbonate, brominated epoxy resin, brominated phenoxy resin, brominated polyphenylene ether resin, brominated polystyrene resin, brominated bisphenol A, polypentabromobenzyl acrylate and the like. Examples of the antimony compound include antimony trioxide, antimony pentoxide, sodium antimonate, and the like. As a phosphorus compound, phosphate ester, polyphosphoric acid, ammonium polyphosphate, red phosphorus etc. are mentioned, for example. Examples of other organic flame retardants include nitrogen compounds such as melamine and cyanuric acid. Examples of other inorganic flame retardants include aluminum hydroxide, magnesium hydroxide, silicon compound, and boron compound.

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

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

  The method of blending the various additives and resins is not particularly limited, but a method of using a single or twin screw 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 of oligomer:
It calculated from the acid value and the saponification value by the following 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) Weight ratio of terephthalic acid unit in oligomer mixture:
The oligomer obtained by the oligomer receiver described later contains PBT oligomer and unreacted 1,4-butanediol, which is referred to herein as an oligomer mixture and is distinguished from pure PBT oligomer. . 100 mg of the oligomer mixture was dissolved in 1 mL of a mixed solvent of deuterated chloroform / hexafluoroisopropanol = 7/3 (volume ratio), ¹ H-NMR was measured at room temperature, and 1,4-butane in the PBT oligomer molecule in the oligomer mixture The diol unit content, terephthalic acid unit content and unreacted 1,4-butanediol content were determined from these signal intensity ratios and calculated. “Α-400” or “AL-400” manufactured by JEOL Ltd. was used for the NMR apparatus.

(3) Terminal carboxyl group concentration of PBT:
0.5 g of PBT was dissolved in 25 mL of benzyl alcohol and titrated using a 0.01 mol / L benzyl alcohol solution of sodium hydroxide.

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

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

(6) Concentration of titanium, periodic table group 1 metal and group 2 metal in PBT:
PBT was wet-decomposed with high-purity sulfuric acid and nitric acid for electronic industry and measured using a high resolution ICP (Inductively Coupled Plasma) -MS (Mass Spectrometer) (manufactured by ThermoQuest).

(7) 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.

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

(9) Cyclic dimer and cyclic trimer content in PBT:
After dissolving 0.1 g of PBT in 3 mL of hexafluoroisopropanol / chloroform = 2/3 (volume ratio), 20 mL of chloroform and 10 mL of methanol are added to precipitate the polymer. Subsequently, the supernatant separated by filtration was dried and then dissolved in 2 mL of dimethylformamide, and a mixed solvent of 2% by weight of acetic acid water / acetonitrile was used as an eluent, and high performance liquid chromatography (column: “manufactured by Mitsubishi Chemical Corporation” MCI-GEL ODS-1LU "). The smaller the cyclic dimer or the cyclic trimer, the less the mold contamination during molding.

(10) 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.

(11) 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 above IV and IV ′ values according to the following equation (6). It shows that hydrolysis resistance is so favorable that IV retention is large.

  In the following examples, the continuous esterification apparatus shown in FIG. 1 was used. In FIG. 1, reference numeral (A) is a slurry preparation tank equipped with a stirrer, (B) is a pump for slurry supply, (C) is a flow meter, and (D) is an overflow system that can continuously acquire oligomers. (E) is an oligomer receiver maintained at the same pressure as the esterification reaction tank, (F) is a condenser, and (G) is a liquid-sealed distillate. (H) is a cold trap, (J) is an automatic nitrogen supply valve for keeping the internal pressure constant, and (K) is a vacuum pump.

Example 1:
(Continuous esterification process)
Using the continuous esterification apparatus shown in FIG. 1, PBT was produced in the following manner. First, a slurry of 50 ° C. mixed at a ratio of 3.5 mol of 1,4-butanediol with respect to 1.0 mol of terephthalic acid was previously prepared from a slurry preparation tank (A) with a PBT oligomer having an esterification rate of 99%. The esterification reaction tank (D) filled was continuously supplied at 4.8 kg / h, and the oligomer was discharged from the overflow line. The piping to the oligomer receiver (E) was kept at the same temperature as the ester tank so that the oligomer did not precipitate, and the oligomer receiver (E) was kept at room temperature. In the slurry, 184 μmol of tetrabutyl titanate was added as a 6 wt% solution of 1,4-butanediol with respect to 1 mol of terephthalic acid as a catalyst.

  The internal temperature of the reaction vessel (D) is 230 ° C., the pressure is 79 kPa, and water, THF and excess 1,4-butanediol produced are distilled from the distillation line, condensed in the condenser (F), Some non-condensed components were collected in a cold trap (H) cooled with dry ice. The residence time in terms of terephthalic acid unit in the esterification reaction tank (D) after the system was stabilized was 3 hours, and the esterification rate of the obtained oligomer was 98%.

(Polycondensation process)
After charging 150 g of the oligomer obtained by the above continuous esterification reaction into a glass polymerization tube equipped with a stirrer with a torque meter, the inside of the polymerization tube was sufficiently substituted with nitrogen, and terephthalic acid obtained in advance by ¹ H-NMR. A predetermined amount of magnesium acetate tetrahydrate per unit was added as a 2 wt% aqueous solution. This was immersed in an oil bath at 245 ° C. to melt the oligomer for 15 minutes. Stirring was started after 15 minutes, and further, after 15 minutes, an operation of reducing the pressure from atmospheric pressure to 1 torr over 85 minutes was performed using a programmable pressure control device, and then maintained at 1 torr. The time when depressurization is started is set as the polycondensation start time, and while monitoring the stirring torque, the time until reaching the stirring torque corresponding to IV = 0.85, which has been tested in advance, and the time until reaching IV = 1.20. Time was measured. When a torque corresponding to IV = 1.20 was reached, the polymer was extracted, and pellets were obtained after water cooling. The polycondensation rate did not reach the peak even in the high viscosity region, and the polycondensation time was short. Moreover, the terminal carboxyl group density | concentration of the obtained polymer was small, and it was excellent in color tone, transparency, and thermal stability. The analysis results of this polymer are summarized in Table 1.

Examples 2-6:
In Example 1, it carried out like Example 1 except having added the compound shown in Table 1 instead of the magnesium acetate tetrahydrate.

Comparative Example 1:
In Example 1, it carried out like Example 1 except not adding a magnesium acetate tetrahydrate. The polycondensation rate was inferior and the color tone deteriorated.

Comparative Example 2:
In Example 1, it carried out like Example 1 except having added 182 micromol of magnesium acetate tetrahydrate with respect to 1 mol of terephthalic acid units. The terminal polycondensation rate was inferior, and the terminal carboxyl group concentration increased and the color tone tended to deteriorate compared to Example 1.

Comparative Example 3:
In Example 1, it carried out like Example 1 except having added 370 micromol of tetrabutyl titanate with respect to 1 mol of terephthalic acid units. The terminal carboxyl group concentration increased and the color tone deteriorated. Moreover, the solution haze was also high and it was inferior to transparency.

Example 7:
In Example 1, when IV = 0.85 was reached, polycondensation was stopped, the polymer was extracted, and pellets were obtained after water cooling. 15 g of the pellets were dried at 120 ° C. for 4 hours, charged into a glass tube, sufficiently purged with nitrogen, held at 0.3 torr and 190 ° C., and subjected to solid phase polymerization. The pellet was taken out when the predetermined IV was reached. A polymer with low AV and low cyclic dimer and cyclic trimer concentrations was obtained.

Example 8:
In Example 1, when IV = 0.85 was reached, polycondensation was stopped, the polymer was extracted, and pellets were obtained after water cooling. 15 g of the pellets were dried at 120 ° C. for 4 hours, charged into a glass tube, sufficiently purged with nitrogen, held at 0.3 torr and 205 ° C., and subjected to solid phase polymerization. The pellet was taken out when the predetermined IV was reached. A polymer with low AV and low cyclic dimer and cyclic trimer concentrations was obtained.

Illustration of an example of this continuous esterification device

Explanation of symbols

A: slurry preparation tank B: slurry supply pump C: flow meter D: esterification reaction tank E: oligomer receiver F: condenser G: distillate receiver H: cold trap J: automatic valve K: vacuum pump

Claims (8)

The catalyst is obtained by using a titanium compound and at least one metal compound selected from Groups 1 and 2 of the periodic table as a catalyst, and the content of titanium is 45 μmol or more and 320 μmol or less as a titanium atom per 1 mol of terephthalic acid unit. A polybutylene terephthalate, wherein the content of at least one metal selected from Group 1 and Group 2 of the periodic table is 10 to 130 μmol as a metal atom, and the intrinsic viscosity is 1.10 or more.   The polybutylene terephthalate according to claim 1, wherein the terminal carboxyl group concentration is 0.1 to 10 µeq / g.   The polybutylene terephthalate according to claim 1 or 2, wherein the content of titanium is 190 µmol or less.   The polybutylene terephthalate according to any one of claims 1 to 3, wherein the content of at least one metal selected from Groups 1 and 2 of the periodic table is 100 µmol or less.   The polybutylene terephthalate according to any one of claims 1 to 4, wherein at least one metal selected from Groups 1 and 2 of the periodic table is magnesium.   The polybutylene terephthalate according to any one of claims 1 to 5, wherein the content of the cyclic dimer is 1500 ppm or less.   The polybutylene terephthalate according to any one of claims 1 to 5, wherein the content of the cyclic dimer is 1000 ppm or less. The polybutylene terephthalate according to any one of claims 1 to 7, wherein the polybutylene terephthalate is obtained by a direct polymerization method using terephthalic acid and 1,4-butanediol.

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