JPH05117378A - Production of polyester having high degree of polymerization - Google Patents

Abstract

PURPOSE:To obtain a polybutylene terephthalate having high degree of polymerization in high efficiency by adding a specific amount of an aromatic sulfonic acid compound to terephthalic acid (caster) and 1,4-butanediol and subjecting the mixture to melt-polymerization and solid-phase polymerization. CONSTITUTION:A polybutylene terephthalate having high degree of polymerization is produced by carrying out melt-polymerization of (A) an acid component composed mainly of terephthalic acid (lower alcohol ester) and (B) a diol component composed mainly of 1,4-butanediol, temporarily solidifying the obtained polybutylene terephthalate and subjecting the solid polymer to solid-phase polymerization. In the above process, the reactional mixture is incorporated, prior to the solid-phase polymerization, with 0.005-2mol% (based on the total constituent acid component) of an aromatic sulfonic acid compound of formula (Ar is benzene ring or naphthalene ring; (n) is 1-10; R is 2-3C alkylene; M is alkali metal selected from lithium, sodium and potassium) at an arbitrary stage from the monomer compounding stage to the start of the solid-phase polymerization and subjected to solid-phase polymerization to obtain the objective polyester.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a process for producing a high-polymerization degree polyester having polybutylene terephthalate as a main component by solid-state polymerization, and particularly to obtain polybutylene terephthalate having a high degree of polymerization efficiently and economically. It provides a manufacturing method.

[0002]

2. Description of the Related Art Polybutylene terephthalate (hereinafter abbreviated as PBT) is excellent in molding processability and physical properties, and therefore it is used in industrial fields such as automobile parts, electric equipment parts and machine parts. It is widely used in the field of plastics for industrial use, but its mechanical properties are highly dependent on the degree of polymerization of the raw material polymer, which makes it suitable for molded products that require high mechanical properties, especially ductility and toughness. In order to use as a raw material polymer, it is an important technical subject to produce a polymer having a high degree of polymerization and to achieve this production economically. Here, there is a limit to the degree of polymerization that can be achieved in the melt polymerization due to the decomposition reaction no matter how long the polymerization is carried out.Also, there is a limit melt viscosity in the process of taking out from the polymerization vessel, and it is necessary to increase the degree of polymerization. There is a limit, and there is a limit melt viscosity in the process of taking out from the polymerization reactor, and there is a limit to increase the degree of polymerization. Therefore, as a method for producing a PBT having a high degree of polymerization, the latter half of the polycondensation reaction is generally solid phase. The method of processing is adopted. In general, this manufacturing method first polycondenses in a molten state by a conventional method,
Remove the melt prepolymer from the polycondensation vessel, then cool to solidify the melt, dry the granulated prepolymer for a considerable amount of time, crystallize, and then 5 to 60 ° C below its melting point. It is a method of producing a high-polymerization degree polymer by maintaining the temperature at 1. In this last stage of the production, the increase of the molecular weight proceeds in the solid state, and under the appropriate reaction conditions, the molecular weight can be made particularly high. Here, in the conventional solid-state polymerization method of PBT, it is important to perform crystallization treatment or the like as a pretreatment, and if such pretreatment is not performed, the particles will be fused to each other during the solid-state polymerization. As a result, even if such pretreatment is performed, polymerization in the solid phase proceeds only at an extremely slow rate, and it takes a long time to reach a predetermined degree of polymerization, and a short time is required. It has been desired to improve the degree of polymerization efficiently.

[0003]

Means for Solving the Problems As a result of intensive studies by the present inventors in order to solve the above problems, as a result, an acid component mainly composed of terephthalic acid or a lower alcohol ester thereof and 1,
In a method in which PBT obtained by melt polycondensation of a diol component mainly composed of 4-butanediol is first solidified and then solid-phase polymerized, a specific monofunctional sulfonate compound component is added prior to solid-phase polymerization. By doing so, it was found that the pretreatment step of solid-state polymerization can be omitted or greatly shortened, and that PBT having a high degree of polymerization can be efficiently prepared in a short time, and the present invention has been completed. That is,
In the present invention, polybutylene terephthalate obtained by melt polycondensation of an acid component mainly composed of terephthalic acid or its lower alcohol ester and a diol component mainly composed of 1,4-butanediol is first solidified and then solidified. In the method for producing a high-polymerization degree polybutylene terephthalate by heat-polymerizing with, in advance of solid phase polymerization, at any time from the step of preparing a monomer of melt polycondensation to the start of solid phase polymerization, all constituent acid components are added. TECHNICAL FIELD The present invention relates to a method for producing a high degree of polymerization polyester, which comprises adding 0.005 to 2 mol% of an aromatic sulfonic acid compound represented by the following general formula (I) and uniformly dispersing it, and then performing a solid phase polymerization reaction. It is a thing. HO (RO) _n -Ar-SO ₃ M (I) (wherein Ar is a benzene ring or a naphthalene ring. N is an integer of 1 to 10. R is selected from an alkylene group having 2 or 3 carbon atoms. R is the same or different when n is 2 or more. M is an alkali metal selected from lithium, sodium and potassium.) In the method for producing PBT of the present invention, first, terephthalic acid is used. Or the acid component mainly consisting of its lower alcohol ester and 1,4-
A diol component containing butanediol as a main component is melt-polycondensed to prepare a PBT homopolyester containing 1,4-butylene terephthalate as a main constituent repeating unit and a prepolymer of a copolyester mainly containing the PBT homopolyester.
Examples of the acid component mainly composed of a lower alcohol ester of terephthalic acid include terephthalic acid or its dimethyl ester. When preparing a copolyester, as the acid constituent comonomer, isophthalic acid, orthophthalic acid, 2,6-naphthalenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid, diphenic acid, 4,4'-diphenyldicarboxylic acid, It is possible to use one or more kinds of conventionally known bifunctional carboxylic acids such as adipic acid, sebacic acid, 1,4-cyclohexanedicarboxylic acid and their dimethyl esters, or lower alcohol esters thereof. The diol constituent comonomer is ethylene glycol, diethylene glycol, triethylene glycol, propanediol, 1,5-propanediol, 1,6-hexanediol, neopentyl glycol, 1,10-decanediol, 1,4-cyclohexane. Dimethanol, 1,4-cyclohexanediol, p-xylidene glycol, ethylene oxide adduct of hydroquinone, ethylene oxide adduct of 2,2-bis (4-hydroxyphenyl) propane, ethylene oxide adduct of bis (4-hydroxyphenyl) sulfone Body, 2,2-bis (3,5-dibromo-4-hydroxyphenyl) propane ethylene oxide adduct, 2,6-dihydroxynaphthalene ethylene oxide adduct, and the like, one or more known difunctional diols. To use Bets are possible. Further, halogen-substituted compounds of the above substances may be used as a comonomer to impart flame retardancy. The amount of these copolymerization components introduced is preferably 30 mol% or less, particularly preferably 20 mol% or less, based on the total repeating ester units. Further, trimesic acid, trimellitic acid and ester-forming compounds thereof, trifunctional or higher functional compounds such as trimethylolpropane and pentaerythritol, stearyl alcohol, monofunctional compounds such as methyl o-benzoylbenzoate, p-hydroxyl. It is also possible to use a small amount of a hydroxycarboxylic acid derivative such as methyl ethoxyphenylcarboxylate, a polypropylene glycol, a polyalkylene glycol such as polytetrahydrofuran, or a combination with the above-mentioned copolymerization component.

The present invention is characterized by further using an aromatic sulfonic acid compound represented by the following general formula (I) as a raw material compound. HO (RO) _n -Ar-SO ₃ M (I) Here, Ar represents a benzene ring or a naphthalene ring having no other substituent other than that represented by the formula (I), and R is an alkylene having 2 or 3 carbon atoms. Represents a group, n is 1 to 10, preferably 1 to
3 and M is an alkali metal selected from lithium, sodium and potassium, preferably sodium. Specific examples of the compound of formula (I) include 4- (2-hydroxyethoxy) -sodium benzenesulfonate, 4- (2
-Hydroxypropoxy) -sodium benzenesulfonate, 4- (2-hydroxyethoxyethoxy) -sodium benzenesulfonate, lithium 4- (2-hydroxyethoxy) -benzenesulfonate, 4- (2-hydroxyethoxy) -benzenesulfone Potassium acid, 2-
(2-Hydroxyethoxy) -naphthalene-6-sulfonate sodium, 2- (2-hydroxypropoxy)-
Sodium naphthalene-6-sulfonate, 2-di (2-
Examples thereof include sodium hydroxyethoxy) -naphthalene-6-sulfonate and lithium 2- (2-hydroxyethoxy) -naphthalene-6-sulfonate. The addition amount of the compound represented by the general formula (I) is 0.005 with respect to all constituent acid components of the polyester alone or in combination of two or more kinds.
˜2 mol%, preferably 0.02 to 1.0 mol%. When the above-mentioned mole fraction is less than 0.005 mol%, the effect of improving the degree of polymerization during solid phase polymerization is small, and when it is more than 2 mol%, the attainable degree of polymerization of the polyester in melt polycondensation is low, and The solid-phase polymerizability is also lowered, rather it takes a long time, and it is difficult to obtain sufficient mechanical properties, which is not preferable.

These aromatic sulfonic acid compounds represented by the general formula (I) can be added at any time from the stage of preparing a monomer of melt polycondensation to the start of solid phase polymerization prior to the solid phase polymerization. is there. In particular, it is preferable to add it to the reaction system before the completion of the melt polymerization, and among them, in the first half of the melt polymerization, particularly during the preparation of the monomer (for example, added to 1,4-butanediol), the transesterification reaction or the ester. It is preferable to add before the end of the chemical reaction. It is also possible to add to the pellets that have undergone melt polymerization before solid phase polymerization and knead them with an extruder or the like to disperse them uniformly, but in this method, the steps of extrusion and kneading intervene, and generally The aromatic sulfonic acid compound represented by the formula (I) exists almost unreacted, and the effect of improving the degree of polymerization in the subsequent solid phase polymerization becomes insufficient, which is not preferable. Further, the aromatic sulfonic acid compound represented by the general formula (I) can be added at any stage in several divided steps as required.

With a lower alcohol ester of terephthalic acid
The transesterification reaction using 1,4-butanediol as the main raw material is carried out by using the lower alcohol ester of terephthalic acid and 1,4
-Butanediol is carried out under atmospheric pressure at a molar ratio of 1: 1 to 1: 2 at a temperature of 150 to 220 ° C while continuously removing methanol produced. Examples of the catalyst for obtaining a practical reaction rate include titanium compounds, lead oxide, lead acetate, zinc acetate, manganese acetate and the like. Among them, organic titanates, titanium tetrachloride, and their hydrolyzates or alcoholyses. The thing is suitable. Specifically, tetrabutyl titanate, tetrapropyl titanate, tetraethyl titanate, tetramethyl titanate and its hydrolyzate,
Hydrolyzates of titanium tetrachloride and titanium sulfate, inorganic titanium compounds such as potassium titanium fluoride, zinc zinc fluoride, and titanium fluoride, and titanium compounds known as polyester production catalysts such as titanium oxalate and titanium potassium oxalate can be mentioned. Particularly preferred are hydrolysates of tetrabutyl titanate, tetrapropyl titanate and titanium tetrachloride. The amount of these catalysts used is 10 to 10 as titanium.
1000 ppm (relative to polymer), preferably 30 to 800 ppm (relative to polymer). The addition of the catalyst can be divided into several times during the reaction if necessary. Also, terephthalic acid and 1,4-
The esterification reaction using butanediol as the main raw material is based on 1 mol of terephthalic acid and 1,4-butanediol
It is carried out at a temperature of 200 to 240 ° C. under atmospheric pressure or under pressure at a ratio of 5 mol while continuously removing water produced. Also in this case, it is preferable to carry out in the presence of the above-mentioned titanium compound or the like.

In the melt polycondensation reaction, the product obtained by the above-mentioned transesterification reaction or esterification reaction is added to 200-
In this step, the reaction system is depressurized at 260 ° C., and while 1,4-butanediol and by-products are continuously removed, melt polymerization is carried out until a desired degree of polymerization is obtained to obtain a prepolymer. As a catalyst for obtaining a practical reaction rate in the polycondensation reaction, a compound such as that used in the above transesterification reaction or esterification reaction can be used as it is, and in order to improve the rate of the polycondensation reaction, It is also possible to add one or more of these before the condensation reaction starts. It is also possible to add stabilizers such as sterically hindered phenols and phosphorus compounds at the monomer preparation stage or the polymerization stage. The aromatic sulfonic acid compound according to the present invention has almost no effect on the melt polycondensation reaction rate at the introduction amount specified in the present invention, and does not interfere with the melt polycondensation reaction.

The PBT prepolymer melt-polymerized under the above-mentioned conditions has an intrinsic viscosity of about 0.5 to 1.2 measured at 25 ° C. in orthochlorophenol, which is then solidified by cooling, pulverized or granulated. Then, the solid-state polymerization is started. The solidification by cooling is performed by a usual method. For example, the prepolymer discharged in a strand form or a sheet form from the melting reactor is introduced into an air stream or water to be cooled and solidified, and then ground or cut. At this time, it is advantageous to use particles (pellets) having a size as uniform as possible so that the increase of the molecular weight is uniformly carried out during the solid phase polymerization.

In the method of the present invention, the solid-state polymerization is immediately carried out in the solid-state polymerization reactor adjusted to an appropriate temperature. Here, the conventional solid-phase polymerization generally has the importance that crystallization and the like are essential as a pretreatment, and prior to the solid-phase polymerization, the solid-phase polymerization is performed at an appropriate temperature (120 to 180 ° C) for a long time (3 to 6).
Hold), requires pretreatment such as drying and crystallization,
If solid phase polymerization is not carried out thereafter, the polymer particles (pellets) will be fused to each other during solid phase polymerization to form a large lump, and the solid phase polymerization will proceed at an extremely slow speed.
Or, it hardly progressed and took a long time as a whole. On the other hand, in the present invention, there is no fusion of polymer particles even if the above pretreatment is omitted, the polymerization rate in solid phase polymerization is fast, and a polymer having a high degree of polymerization can be efficiently obtained, which simplifies the process. The productivity is improved by shortening the time, and the economic advantages are remarkable.

The solid phase polymerization in the present invention is carried out by a generally known method except that the above-mentioned pretreatment can be omitted. That is, the solidified and finely divided polymer particles (pellets) are kept at a temperature 5 to 60 ° C. lower than the melting point thereof, and transferred to a reactor having an appropriate gas inlet, exhaust port, vacuum connector, etc.,
Solid phase polymerization is carried out under an inert gas flow or in a vacuum. The reactor may be either a batch type or a continuous type, and the desired degree of polymerization can be appropriately adjusted by the residence time, the processing temperature and the like.

In the production of the polyester of the present invention, other thermoplastic resins, additives, organic fillers and inorganic fillers may be used alone or in combination of two or more, depending on the purpose, as long as the effects of the present invention are not impaired. It can also be supplementarily used during polymerization or kneading. Examples of the thermoplastic resin include polyolefin resin, polystyrene resin, polyamide resin, polycarbonate, polyacetal, polyarylene oxide, polyarylene sulfide, and fluororesin. Further, as additives, stabilizers such as conventionally known ultraviolet absorbers and antioxidants, antistatic agents, flame retardants, flame retardant aids, colorants such as dyes and pigments, lubricants, plasticizers, lubricants, Examples include release agents, crystal nucleating agents, and the like. In particular, the combined use of a crystal nucleating agent and the like is a preferable substance for further promoting the effects of the present invention. Further, as the inorganic filler, glass fiber, milled glass fiber, glass beads, silica,
Alumina fiber, zirconia fiber, potassium titanate fiber, carbon black, graphite, silica, calcium silicate, aluminum silicate, kaolin, talc, silicates such as clay, iron oxide, titanium oxide, zinc oxide, antimony oxide, alumina, etc. Metal oxides, carbonates and sulfates of metals such as calcium, magnesium and zinc, and further silicon carbide,
Silicon nitride, boron nitride and the like are exemplified, and examples of the organic filler include high melting point aromatic polyester fibers, liquid crystalline polyester fibers, aromatic polyamide fibers, polyimide fibers and the like.

[0012]

As is apparent from the above description and Examples, according to the method of the present invention, in the solid-state polymerization of PBT,
Even if pretreatment such as crystallization process is omitted, polymer particles are not fused and a high degree of polymerization can be obtained efficiently, and productivity is improved by simplifying the process, shortening the time, etc. and the economical advantage is remarkable. Is. It is also possible to obtain a high degree of polymerization polymer that cannot be obtained by the conventional method.

[0013]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited thereto.

Examples 1-5, Comparative Examples 1-5 220.3 parts by weight of dimethyl terephthalate (DMT), 149.3 parts by weight of 1,4-butanediol, 4- (2-hydroxyethoxy) -benzene in the amounts shown in Table 1. Sodium sulfonate (I-a) and 0.1 parts by weight of titanium tetrabutoxide were charged into a reactor equipped with a stirrer and a distillation column, and after sufficiently replacing with nitrogen, the temperature was raised to 160 ° C under normal pressure and stirring was started. did. Furthermore, the temperature was gradually raised, the by-product methanol was distilled off, and an ester exchange reaction was carried out. When the amount of distillated methanol exceeded 90% by weight of the theoretical amount, the temperature of the reactant was raised to 210 ° C, which was then transferred to another reactor (melt polycondenser) and depressurized to 0.1 torr in 1 hour. At the same time, the temperature was raised to 250 ° C. Then at a pressure of 0.1 torr
After continuing stirring for 2.5 hours, the melt was extruded from the reactor as strands, the strands were cooled with water and passed through hot air to remove adhering water and cut into pellets of size 2 × 3 mm. The intrinsic viscosity of the obtained prepolymer was measured in orthochlorophenol at 25 ° C. Next, this pelletized prepolymer was fed through a preheater (residence 30 minutes) to a solid-state polymerization reactor equipped with a heating jacket (passing through a heating medium at 210 ° C) to an internal temperature of 205 ° C to 208 ° C. Solid-state polymerization was performed for a time. The intrinsic viscosity of the obtained polymer was measured in orthochlorophenol at 25 ° C. In addition, the fusion state of the polymer particles (pellets) was observed. The results are shown in Table 1. For comparison, when the aromatic sulfonic acid compound represented by the formula (I) is not used at all (Comparative Example 1) and when the amount of Ia added is outside the range of the present invention (Comparative Example 3,
5) was tested in the same manner. Further, for these comparative examples, a pretreatment (1
The test was also performed for the case (Comparative Examples 2 and 4) at 50 ° C. for 4 hours. The results are also shown in Table 1.

Examples 6 to 8 and Comparative Example 6 Instead of sodium 4- (2-hydroxyethoxy) -benzenesulfonate (Ia), sodium 4- (2-hydroxypropoxy) -benzenesulfonate (I-
b), 4- (2-hydroxyethoxyethoxy) -sodium benzenesulfonate (Ic) and 2- (2-hydroxyethoxy) -naphthalene-6-sodium sulfonate (Id) were used, respectively. Melt polymerization and subsequent solid phase polymerization were carried out in the same manner as in Example 3 to obtain a high degree of polymerization PBT. The results are shown in Table 2. For comparison, Table 2 also shows the results of the same test in the case of using 4-methylbenzenesulfonic acid (Ie) different from the formula (I) structure.

Examples 9 to 11 At the time of transition from the transesterification reactor to the melt polycondensation reactor, the addition timing of 4- (2-hydroxyethoxy) -sodium benzenesulfonate (Ia) in the melt polymerization was changed. That is, the same tests were performed after the transesterification reaction, before the polycondensation reaction, at the end of the melt polycondensation reaction, and when the prepolymer pellets prepared in Comparative Example 1 were added and melt-kneaded with an extruder. The results are shown in Table 3.

[0017]

[Table 1]

[0018]

[Table 2]

[0019]

[Table 3]

Example 12, Comparative Example 7 192.8 parts by weight of dimethyl terephthalate (DMT), 27.5 parts by weight of dimethyl isophthalate (DMI) (12.5 mol% based on all acid components), 1,4-butanediol 149.3 parts by weight, 0.1 mol% of (Ia) compound with respect to the total acid component, and 0.1 parts by weight of titanium tetrabutoxide were charged in a reactor equipped with a stirrer and a distillation column, and the atmosphere was sufficiently replaced with nitrogen. The temperature was raised to 160 ° C and the stirring was started.
Further, the temperature was gradually raised and the by-product methanol was distilled off. When the amount of distillated methanol exceeded 90% by weight of the theoretical amount, the temperature of the reactant was raised to 210 ° C, which was then transferred to another reactor (polycondensation reactor) and depressurized to 0.1 torr in 1 hour. At the same time, the reaction temperature was raised to a temperature of 240 ° C.
After stirring for 3 hours at a pressure of 0.1 torr, the melt was extruded from the reactor as strands, the strands were cooled with water, passed through hot air to remove adhering water and cut to 2x.
The prepolymer pellets were 3 mm in size. The resulting prepolymer had an inherent viscosity of 0.72 in orthochlorophenol at 25 ° C. Next, this granular prepolymer was passed through a preheater (residence for 30 minutes) and then equipped with a heating jacket (185
Pass the heat medium at ℃) and supply it to the solid-phase reactor at 181 ℃ to 182 ℃ for 8 hours.
Solid-state polymerization was performed for a time. The resulting polymer has an intrinsic viscosity of 1.11 (difference 0.39) at 25 ° C in orthochlorophenol,
Almost no fusion of polymer particles (pellets) was observed.

For comparison, melt polymerization was carried out in the same manner as in Example 12 except that the compound of formula (I) was not used to obtain a prepolymer (the obtained frepolymer was in orthochlorophenol).
Although it had an intrinsic viscosity of 0.70 at 25 ° C), partial fusion of polymer particles (pellets) was already observed before the solid phase polymerization, and the subsequent solid phase polymerization was impossible.

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[Submission date] January 20, 1993

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[0002]

2. Description of the Related Art Polybutylene terephthalate (hereinafter abbreviated as PBT) is excellent in molding processability and physical properties, and therefore it is used in industrial fields such as automobile parts, electric equipment parts and machine parts. It is widely used in the field of plastics for industrial use, but its mechanical properties are highly dependent on the degree of polymerization of the raw material polymer, which makes it suitable for molded products that require high mechanical properties, especially ductility and toughness. In order to use as a raw material polymer, it is an important technical subject to produce a polymer having a high degree of polymerization and to achieve this production economically. Here, in the melt polymerization, there is a limit to the degree of polymerization that can be achieved because the decomposition reaction accompanies no matter how long the polymerization is carried out, and further, there is a limit melt viscosity in the process of taking out from the polymerization vessel and there is a limit to achieving a high degree of polymerization. Therefore, as a method for producing PBT having a high degree of polymerization, a method of treating the latter half of the polycondensation reaction with a solid phase is generally used. In general, this production method is such that polycondensation is first performed in a molten state by a conventional method, a melt prepolymer is taken out from a polycondensation container, then the melt is solidified by cooling, and the granulated prepolymer is taken for a considerable time. It is a method for producing a high degree of polymerization polymer by drying and crystallizing and then maintaining the temperature at 5 to 60 ° C. lower than its melting point. In this last stage of the production, the increase of the molecular weight proceeds in the solid state, and under the appropriate reaction conditions, the molecular weight can be made particularly high. Here, in the conventional solid-state polymerization method of PBT, crystallization treatment and the like have an important importance as a pretreatment,
Also, if such pretreatment is not carried out, the particles will be fused to each other during solid phase polymerization to form a large lump, and even if such pretreatment is carried out, the polymerization in the solid phase will proceed at an extremely slow rate. , It takes a long time to reach the predetermined degree of polymerization,
It has been desired to efficiently improve the degree of polymerization in a short time.

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[0003]

Means for Solving the Problems As a result of intensive studies by the present inventors in order to solve the above problems, as a result, an acid component mainly composed of terephthalic acid or a lower alcohol ester thereof and 1,
In a method in which PBT obtained by melt polycondensation of a diol component mainly composed of 4-butanediol is first solidified and then solid-phase polymerized, a specific monofunctional sulfonate compound component is added prior to solid-phase polymerization. By doing so, it was found that the pretreatment step of solid-state polymerization can be omitted or greatly shortened, and that PBT having a high degree of polymerization can be efficiently prepared in a short time, and the present invention has been completed. That is,
In the present invention, polybutylene terephthalate obtained by melt polycondensation of an acid component mainly composed of terephthalic acid or its lower alcohol ester and a diol component mainly composed of 1,4-butanediol is first solidified and then solidified. In the method for producing a high-polymerization degree polybutylene terephthalate by heat-polymerizing with, in advance of solid phase polymerization, at any time from the step of preparing a monomer of melt polycondensation to the start of solid phase polymerization, all constituent acid components are added. TECHNICAL FIELD The present invention relates to a method for producing a high degree of polymerization polyester, which comprises adding 0.005 to 2 mol% of an aromatic sulfonic acid compound represented by the following general formula (I) and uniformly dispersing it, and then performing a solid phase polymerization reaction. It is a thing. HO (RO) _n -Ar-SO ₃ M (I) (wherein Ar is a benzene ring or a naphthalene ring having no substituent other than those represented by the formula (I). N is an integer of 1 to 10. R is a group selected from alkylene groups having 2 or 3 carbon atoms, and when n is 2 or more, R may be the same or different, and M is an alkali metal selected from lithium, sodium and potassium. In the method for producing PBT of the present invention, first, an acid component mainly containing terephthalic acid or its lower alcohol ester and 1,4-
A diol component containing butanediol as a main component is melt-polycondensed to prepare a PBT homopolyester containing 1,4-butylene terephthalate as a main constituent repeating unit and a prepolymer of a copolyester mainly containing the PBT homopolyester.
Examples of the acid component mainly composed of a lower alcohol ester of terephthalic acid include terephthalic acid or its dimethyl ester. When preparing a copolyester, as the acid constituent comonomer, isophthalic acid, orthophthalic acid, 2,6-naphthalenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid, diphenic acid, 4,4'-diphenyldicarboxylic acid, It is possible to use one or more kinds of conventionally known bifunctional carboxylic acids such as adipic acid, sebacic acid, 1,4-cyclohexanedicarboxylic acid and their dimethyl esters, or lower alcohol esters thereof. The diol constituent comonomer is ethylene glycol, diethylene glycol, triethylene glycol, propanediol, 1,5-pentanediol, 1,6-hexanediol, neopentyl glycol, 1,10-decanediol, 1,4-cyclohexane. Dimethanol, 1,4-cyclohexanediol, p-xylidene glycol, ethylene oxide adduct of hydroquinone, ethylene oxide adduct of 2,2-bis (4-hydroxyphenyl) propane, ethylene oxide adduct of bis (4-hydroxyphenyl) sulfone Body, 2,2-bis (3,5-dibromo-4-hydroxyphenyl) propane ethylene oxide adduct, 2,6-dihydroxynaphthalene ethylene oxide adduct, and the like, one or more known difunctional diols. To use Bets are possible. Further, halogen-substituted compounds of the above substances may be used as a comonomer to impart flame retardancy. The amount of these copolymerization components introduced is preferably 30 mol% or less, particularly preferably 20 mol% or less, based on the total repeating ester units. Further, trimesic acid, trimellitic acid and ester-forming compounds thereof, trifunctional or higher functional compounds such as trimethylolpropane and pentaerythritol, stearyl alcohol, monofunctional compounds such as methyl o-benzoylbenzoate, p-hydroxyl. It is also possible to use a small amount of a hydroxycarboxylic acid derivative such as methyl ethoxyphenylcarboxylate, a polypropylene glycol, a polyalkylene glycol such as polytetrahydrofuran, or a combination with the above-mentioned copolymerization component.

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The present invention is characterized by further using an aromatic sulfonic acid compound represented by the following general formula (I) as a raw material compound. HO (RO) _n -Ar-SO ₃ M (I) Here, Ar represents a benzene ring or a naphthalene ring having no substituent other than that represented by the formula (I), and R represents an alkylene group having 2 or 3 carbon atoms. In the formula, n is 1 to 10, preferably 1 to 3, and M is an alkali metal selected from lithium, sodium and potassium, preferably sodium. Specific examples of the formula (I) compound include sodium 4- (2-hydroxyethoxy) -benzenesulfonate, sodium 4- (2-hydroxypropoxy) -benzenesulfonate, and 4- (2-hydroxyethoxyethoxy) -benzene. Sodium sulfonate, 4- (2-hydroxyethoxy) -lithium benzenesulfonate, potassium 4- (2-hydroxyethoxy) -benzenesulfonate, 2-
(2-Hydroxyethoxy) -naphthalene-6-sulfonate sodium, 2- (2-hydroxypropoxy)-
Sodium naphthalene-6-sulfonate, 2-di (2-
Examples thereof include sodium hydroxyethoxy) -naphthalene-6-sulfonate and lithium 2- (2-hydroxyethoxy) -naphthalene-6-sulfonate. The addition amount of the compound represented by the general formula (I) is 0.005 with respect to all constituent acid components of the polyester alone or in combination of two or more kinds.
˜2 mol%, preferably 0.02 to 1.0 mol%. When the above-mentioned mole fraction is less than 0.005 mol%, the effect of improving the degree of polymerization during solid phase polymerization is small, and when it is more than 2 mol%, the attainable degree of polymerization of the polyester in melt polycondensation is low, and The solid-phase polymerizability is also lowered, rather it takes a long time, and it is difficult to obtain sufficient mechanical properties, which is not preferable.

Claims (3)

[Claims] 1. A polybutylene terephthalate obtained by melt polycondensation of an acid component mainly composed of terephthalic acid or its lower alcohol ester and a diol component mainly composed of 1,4-butanediol is first solidified and then solidified. In the method of producing a high-polymerization degree polybutylene terephthalate by polymerizing in a phase state, prior to solid phase polymerization, all constituent acid components can be added at any time from the melt polycondensation monomer preparation step to the initiation of solid phase polymerization. 0.005 to 2 mol% of the aromatic sulfonic acid compound represented by the following general formula (I) is added, and then a solid-phase polymerization reaction is carried out. HO (RO) _n -Ar-SO ₃ M (I) (wherein Ar is a benzene ring or a naphthalene ring. N is an integer of 1 to 10. R is selected from an alkylene group having 2 or 3 carbon atoms. And R is the same or different when n is 2 or more. M is an alkali metal selected from lithium, sodium and potassium.) 2. The high degree of polymerization polyester according to claim 1, wherein the melt polycondensation is carried out in the presence of the aromatic sulfonic acid compound represented by the general formula (I), and then the solid phase polymerization reaction is carried out. Manufacturing method. 3. A transesterification reaction or an esterification reaction in the presence of an aromatic sulfonic acid compound represented by the general formula (I), a polycondensation reaction, and then a solid phase polymerization reaction. The method for producing a high degree of polymerization polyester according to claim 1 or 2.