JP3796103B2 - Method for producing polybutylene terephthalate resin and polybutylene terephthalate resin obtained thereby - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing a polybutylene terephthalate resin and a polybutylene terephthalate resin obtained thereby, and more particularly, in a method for producing a polybutylene terephthalate resin in a continuous manner through a transesterification reaction. The present invention relates to a method for producing a small amount of polybutylene terephthalate resin, and a polybutylene terephthalate resin obtained thereby.
[0002]
[Prior art]
Polybutylene terephthalate resin has a higher crystallization speed and superior molding characteristics compared to polyethylene terephthalate resin, and also has excellent mechanical and electrical characteristics. Therefore, it has been widely used in the field of injection molding as an engineering plastic. In recent years, the polybutylene terephthalate resin has been recognized for its properties such as aroma retention and chemical resistance, and has attracted attention in the field of film forming.
[0003]
By the way, the manufacturing method of polybutylene terephthalate resin is a method (direct weight method) through an esterification reaction of a dicarboxylic acid component mainly composed of terephthalic acid and a diol component mainly composed of 1,4-butanediol. And a method (transesterification method) through a transesterification reaction between a dicarboxylic acid ester component mainly composed of a lower alkyl ester of terephthalic acid such as dimethyl terephthalate and a diol component mainly composed of 1,4-butanediol. Broadly divided.
[0004]
In the direct weight method, since terephthalic acid, which is a dicarboxylic acid component, acts as an acid catalyst, 1,4-butanediol undergoes a self-cyclization reaction during the esterification reaction, and a large amount of tetrahydrofuran is by-produced. Therefore, an excess amount of 1,4-butanediol is required as a raw material because the raw material 1,4-butanediol is consumed by tetrahydrofuran.
[0005]
In contrast, in the transesterification method, the by-product of tetrahydrofuran is very small, and the polybutylene terephthalate resin obtained by the batch process generally used is used not only in the field of injection molding but also in the field of film molding. ing.
On the other hand, a method for producing polybutylene terephthalate from a batch process to a continuous process has been attracting attention in order to reduce production costs and improve productivity.
[0006]
However, the polybutylene terephthalate resin produced by a transesterification reaction by a batch process can be used in the field of film molding, whereas the polybutylene terephthalate resin produced by a continuous process is a film molded product. In many cases, fish eyes are generated, and the problems such as deterioration of the appearance of the film and reduction of mechanical strength are inherent, which has been an obstacle to use in the field of film forming.
[0007]
[Problems to be solved by the invention]
The present invention has been made in view of the above-described prior art, and fish eyes generated when a polybutylene terephthalate resin produced by a continuous process is formed into a film have a larger number of reaction vessels than a batch process. In addition, since the reaction product flow path becomes longer, there are more places where the reaction product stays than in the batch process, so that the precipitate derived from the reaction catalyst and the carbide derived from the reaction product generated in such a stay part In the method for producing a polybutylene terephthalate resin in a continuous manner through the transesterification reaction in the presence of a transesterification reaction catalyst, the present invention has found out that it is the main factor that many occur. , Method for producing polybutylene terephthalate resin with less fish eye, and polybutylene terephthalate obtained thereby And to provide a tallates resin.
[0008]
[Means for Solving the Problems]
The present invention has been made to achieve the above object, that is, a dicarboxylic acid ester component mainly composed of a lower alkyl ester of terephthalic acid, and a diol component mainly composed of 1,4-butanediol. , In the presence or absence of a transesterification catalyst of 30 to 300 ppm of titanium compound as a titanium atom with respect to the theoretical yield of the resin in the transesterification reaction tank or tanks, and then the polycondensation reaction In the continuous production of polybutylene terephthalate resin by polycondensation reaction in the tank and then withdrawing from the polymer withdrawal die, the reaction between the first transesterification reaction outlet and the outlet of the polymer withdrawal die Polybutylene terephthal that installs a filter in the product flow path and passes the reaction product through the filter Production side of the over door-based resin Law Related.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
The method for producing a polybutylene terephthalate resin of the present invention comprises a dicarboxylic acid ester component having a lower alkyl ester of terephthalic acid as a main component and a diol component having 1,4-butanediol as a main component as a transesterification reaction catalyst. A polybutylene terephthalate resin is continuously produced by conducting a transesterification reaction in the presence, followed by a polycondensation reaction, and then extracting from the polymer extraction die.
[0010]
Here, the lower alkyl group of the lower alkyl ester of terephthalic acid is an alkyl group having about 1 to 4 carbon atoms. Of these, dimethyl terephthalate is preferred as the lower alkyl ester of terephthalic acid, and the lower alkyl ester of terephthalic acid occupies 50 mol% of the total dicarboxylic acid ester component, and preferably occupies 80 mol% or more. And more preferably 95 mol% or more. Further, 1,4-butanediol as the diol component accounts for 50 mol% of the total diol component, preferably 80 mol% or more, and more preferably 95 mol% or more.
[0011]
Specific examples of the dicarboxylic acid ester component other than the lower alkyl ester of terephthalic acid include, for example, aromatic dicarboxylic acid esters such as dimethyl isophthalate and dimethyl 2,6-naphthalenedicarboxylate, dimethyl sebacate, and dimethyl adipate. And aliphatic dicarboxylic acid esters such as dimethyl succinate.
[0012]
Specific examples of the diol component other than 1,4-butanediol include aliphatic diols such as ethylene glycol, propylene glycol and hexamethylene glycol, 1,2-cyclohexanedimethanol, and 1,4-cyclohexane. Examples include alicyclic diols such as dimethanol, aromatic diols such as xylylene glycol 4,4-dihydroxybiphenyl, 2,2-bis (4′-hydroxyphenyl) propane, and bis (4-hydroxyphenyl) sulfone. .
[0013]
Furthermore, for example, hydroxycarboxylic acids and alkoxycarboxylic acids such as glycolic acid, m-hydroxybenzoic acid, p-hydroxybenzoic acid, 6-hydroxy-2-naphthalenedicarboxylic acid, and stearyl alcohol, benzyl alcohol, trimellitic acid, pyromellitic One or two or more multifunctional components such as acid, trimethylolethane, trimethylolpropane, glycerol, pentaerythritol and the like may be used as a copolymerization component.
[0014]
The method for producing a polybutylene terephthalate resin in the present invention is basically based on a method for producing a polybutylene terephthalate resin by a conventional continuous process. That is, the dicarboxylic acid ester component mainly composed of a lower alkyl ester of terephthalic acid and the diol component mainly composed of 1,4-butanediol are transesterified in one or a plurality of transesterification reaction tanks. In the presence of a catalyst, the ester exchange reaction was usually carried out at a pressure of 110 to 260 ° C., preferably 140 to 240 ° C., usually 10 to 200 kPa, preferably 20 to 170 kPa, with stirring for 2 to 5 hours. The oligomer as the transesterification reaction product is transferred to a polycondensation reaction tank, and is usually 210 to 280 ° C., preferably 220 to 265 ° C. in the presence of a polycondensation reaction catalyst in one or a plurality of polycondensation reaction tanks. Usually, the polycondensation reaction is performed for 2 to 5 hours under stirring under a reduced pressure of 30 kPa or less, preferably 20 kPa or less. It is polymerized. In addition, the resin obtained by the polycondensation reaction is usually transferred from the bottom of the polycondensation reaction tank to a polymer extraction die and extracted into a strand shape, and while being cooled with water or after being cooled with water, it is cut with a cutter and pelletized. , The granular material on the chip.
[0015]
Here, the transesterification catalyst in the present invention includes a titanium compound. Typical examples of titanium compounds include titanium alcoholates such as tetramethyl titanate, tetraisopropyl titanate, and tetrabutyl titanate, and titanium phenolates such as tetraphenyl titanate. The As a titanium atom for the theoretical yield of ribylene terephthalate resin 3 0 to 300 ppm, preferably 50 to 200 ppm.
[0016]
or As the polycondensation reaction catalyst, the transesterification reaction catalyst added during the transesterification reaction may be used as a polycondensation reaction catalyst without the need to add a new catalyst. The same catalyst as the reaction catalyst may be further added. The amount used at that time is, for example, in the case of tetrabutyl titanate, usually 300 ppm or less, preferably 150 ppm or less as a titanium atom with respect to the theoretical yield of polybutylene terephthalate resin. In addition, for example, an antimony compound such as antimony trioxide or a germanium compound such as germanium dioxide or germanium tetroxide, which is different from the transesterification catalyst added during the transesterification reaction, may be newly added.
[0017]
In addition, in the transesterification reaction and / or polycondensation reaction, besides the catalyst, orthophosphoric acid, phosphorous acid, hypophosphorous acid, polyphosphoric acid, and phosphorous compounds such as esters and metal salts thereof, sodium hydroxide , Reaction aids such as alkali metal or alkaline earth metal compounds such as sodium benzoate, magnesium acetate and calcium acetate, 2,6-di-t-butyl-4-octylphenol, pentaerythrityl-tetrakis [3- (3 Phenol compounds such as', 5'-t-butyl-4'-hydroxyphenyl) propionate], dilauryl-3,3'-thiodipropionate, pentaerythrityl-tetrakis (3-laurylthiodipropionate), etc. Thioether compounds, triphenyl phosphite, tris (nonylphenyl) phosphite, tris (2,4-di- Anti-oxidants such as phosphorous compounds such as t-butylphenyl) phosphite, paraffin wax, microcrystalline wax, polyethylene wax, long chain fatty acids represented by montanic acid and montanic acid esters, and esters thereof, release from silicone oil, etc. Other additives such as an agent may be present. Further, the transesterification reaction tank may be of 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 different kinds of tanks are connected in series may be used. The polycondensation reaction tank may be any of a vertical stirring polymerization tank, a horizontal stirring polymerization tank, a thin film evaporation polymerization tank, and the like, or a single tank or the same or different tanks in series. A plurality of tanks may be used.
[0018]
In the present invention, in the above-described method for producing a polybutylene terephthalate resin, a reaction product is formed by installing a filter in the reaction product channel between the outlet of the first transesterification reaction tank and the outlet of the polymer extraction die. It is essential to pass objects through the filter.
Here, the filter refers to a fluid having a melt viscosity of several thousand poise that exits from the outlet of the polymer extraction die from a filter that can filter a fluid having a melt viscosity of several tens to 100 poise that exits from the outlet of the first transesterification reactor. Any known filter can be used as long as it can be filtered.
[0019]
As a filter medium, for example, several fine meshes that determine filtration accuracy, reinforcing meshes and protective meshes are stacked, laminated metal meshes that are completely integrated by sintering, and stainless steel metal fiber felts, A sintered metal nonwoven fabric and the like can be mentioned.
Examples of the shape of the filter include a basket type, a disk type, a leaf disk type, a tube type, a flat cylindrical type, and a pleated cylindrical type.
[0020]
These filters can be appropriately selected and used according to the conditions such as the viscosity, pressure and temperature of the fluid at the place of installation. Tube type or flat cylinder type is preferred, and when installing prepolymers or polymers with high melt viscosity at the location where the polymer is filtered, the leaf disk type or pleated cylinder is used in terms of pressure resistance and processing flow rate per unit area. Type is preferred.
[0021]
The absolute filtration accuracy of these filters is preferably in the range of 0.5 to 50 μm from the viewpoint of filtration efficiency and the like. In the case of oligomer filtration with a low melt viscosity, the range of 0.5 to 30 μm In the case of filtration of a prepolymer having a high melt viscosity or a polymer, it is more preferably in the range of 5 to 50 μm.
The production method of the polybutylene terephthalate resin of the present invention will be described in more detail based on the drawings. For example, FIG. 1 shows one embodiment of a production apparatus used for the production method of the polybutylene terephthalate resin of the present invention. FIG. 1 is a flow chart, wherein 1 is a dimethyl terephthalate storage tank, 1a is a dimethyl terephthalate supply port provided at the top of the dimethyl terephthalate storage tank 1, 2 is a first transesterification reaction tank, and 2a is a first transesterification. The vent port provided at the upper part of the reaction tank 2, 2 b is the 1,4-butanediol supply port provided at the upper part of the first transesterification reaction tank 2, and 2 c is provided at the upper part of the first transesterification reaction tank 2. 3 is a second transesterification reactor, 3a is a vent port provided at the top of the second transesterification reactor 3, and 4 is a first polycondensation. The reaction tank, 4a is a vent port provided in the upper part of the first polycondensation reaction tank 4, 5a is a vent port provided in the upper part of the second double condensation reaction tank 5, 6 is a polymer extraction die, and 7 is A pelletizer, 8 is a filter installed in a reaction product flow path between the first transesterification reaction tank 2 and the second transesterification reaction tank 3, and 9 is a second transesterification reaction tank 3 and a first polycondensation reaction tank 4. 10 is a filter installed in the reaction product flow path between the first polycondensation reaction tank 4 and the second double condensation reaction tank 5, and 11 is a second double filter. M1, M2, M3, M4, and M5 are stirring devices, and P1, P2, P3, and P4 are pumps. These filters are installed in the reaction product flow path between the condensation reaction tank 5 and the polymer extraction die 6. , L1, L2, L3, L4, and L5 are pipes.
[0022]
In FIG. 1, dimethyl terephthalate is supplied from a supply line 1a to a storage tank 1, heated and melted while being stirred by a stirring device M1, passed through a pipe L1, and supplied to a first transesterification reaction tank 2. 1,4-butanediol is supplied to the first transesterification reaction tank 2 from the supply line 2b.
The first transesterification reaction tank 2 is a vertical reaction tank provided with a stirrer M2 having a vertical rotation shaft, and in the reaction tank 2, a transesterification reaction catalyst is supplied from a catalyst supply port 2c. The transesterification is carried out at 260 ° C., preferably 140-240 ° C., usually 10-200 kPa, preferably 20-170 kPa, with stirring by the stirring device M2, and preferably has a transesterification rate of 50-90%. An oligomer is produced, and the oligomer is passed through the pipe L2 by the pump P1 and transferred to the second transesterification reaction tank 3. At that time, a filter 8 having an absolute filtration accuracy of 0.5 to 50 μm is installed in the middle of the pipe L2 which is a flow path for the reaction product, and the transferred oligomer is filtered through the filter 8. The On the other hand, methanol and tetrahydrofuran as by-products and unreacted 1,4-butanediol are extracted from the vent port 2a connected to a decompressor (not shown) and passed through a rectifying column (not shown). Then, unreacted 1,4-butanediol is returned to the first transesterification reaction tank 2, and methanol and tetrahydrofuran are discharged out of the system.
[0023]
The second transesterification reaction tank 3 is also a vertical reaction tank provided with a stirrer M3 having a vertical rotation axis. In the reaction tank 3, it is usually 110 to 260 ° C, preferably 140 to 240 ° C, usually 10 to 10 ° C. Under a pressure of 200 kPa, preferably 20 to 170 kPa, the ester exchange reaction is further proceeded with stirring by the stirring device M3, and an oligomer having a transesterification rate of preferably 90 to 99.9% is generated. It is passed through the pipe L3 by the pump P2 and transferred to the first polycondensation reaction tank 4. At that time, a filter 9 having an absolute filtration accuracy of 0.5 to 50 μm is installed in the middle of the pipe L3 which is a flow path of the reaction product, and the transferred oligomer is filtered through the filter 9. The On the other hand, methanol and tetrahydrofuran as by-products and unreacted 1,4-butanediol are extracted from a vent port 3a connected to a decompressor (not shown) and passed through a rectifying column (not shown). Then, unreacted 1,4-butanediol is returned to the second transesterification reaction tank 3, and methanol and tetrahydrofuran are discharged out of the system.
[0024]
The first polycondensation reaction tank 4 is a vertical reaction tank provided with a stirrer M4 having a vertical rotation axis. In the reaction tank 4, a catalyst supply port (not shown) provided in the reaction tank 4 is used. In the presence of the supplied polycondensation reaction catalyst or in the presence of the transesterification reaction catalyst supplied from the catalyst supply port 2c of the first transesterification reaction tank 2, it is usually 210 to 280 ° C, preferably 220 to 265 ° C. The polycondensation reaction is usually performed under a reduced pressure of 0.5 to 30 kPa, preferably 1 to 20 kPa, with stirring by the stirring device M4, and a prepolymer having an intrinsic viscosity of preferably 0.1 to 0.5 dl / g is formed. Then, the prepolymer is passed through the pipe L4 by the pump P3 and transferred to the second double condensation reaction tank 5. At that time, a filter 10 having an absolute filtration accuracy of 5 to 50 μm is installed in the middle of the pipe L4 as a flow path for the reaction product, and the prepolymer to be transferred is filtered through the filter 10. . On the other hand, methanol and tetrahydrofuran as by-products and unreacted 1,4-butanediol are withdrawn from the vent port 4a connected to a decompressor (not shown), and the total condenser (not shown) is connected. After that, it is cooled and liquefied and discharged out of the system.
[0025]
The second double condensation reaction tank 5 is a horizontal reaction tank equipped with a stirrer M5 having a horizontal rotation axis. In the reaction tank 5, it is usually 235 to 280 ° C., preferably 235 to 265 ° C., usually 2 kPa or less, The polycondensation reaction is further advanced under a reduced pressure of preferably 1 kPa or less and with stirring by the stirring device M5, and a polymer having an intrinsic viscosity of preferably 0.6 to 1.3 dl / g is produced. Is passed through the pipe L5 and transferred to the polymer extraction die 6. At that time, a filter 11 having an absolute filtration accuracy of 10 to 50 μm is installed in the middle of the pipe L5 serving as a reaction product flow path, and the polymer to be transferred is filtered through the filter 11. On the other hand, methanol and tetrahydrofuran as by-products and unreacted 1,4-butanediol are withdrawn from the vent port 5a connected to a decompressor (not shown), and the total condenser (not shown) is connected. After that, it is cooled and liquefied and discharged out of the system.
[0026]
The resin transferred to the polymer extraction die 6 is extracted in the form of a strand, and subsequently cut by the pelletizer 7 to form a pellet.
In the above description, the second transesterification reaction tank 3 and the second transesterification reaction tank 3 are connected to the second transesterification reaction tank 2 and the second transesterification reaction tank 3 as a filter 8 in the middle of the pipe L2 as a reaction product flow path. As a filter 9 in the middle of a pipe L3 that is a reaction product flow path between the first polycondensation reaction tank 4 and a pipe L4 that is a reaction product flow path between the first polycondensation reaction tank 4 and the second double condensation reaction tank 5. In the middle of the process, an example was shown in which filters were installed at four locations as the filter 11 in the middle of the pipe L5 as the reaction product flow path between the second double condensation reaction tank 5 and the polymer extraction die 6 as the filter 10. In the present invention, the position is not limited to a plurality of places, and may be one place as long as it is between the outlet of the first transesterification reaction tank 2 that is the first transesterification reaction tank and the polymer extraction die. . Among them, the filter 10 between the first polycondensation reaction tank 4 and the second double condensation reaction tank 5 or the second double condensation reaction tank 5 and the polymer extraction die 6 in terms of filtration efficiency and the like. Between the outlet of the reaction tank immediately before the final polycondensation reaction tank and the inlet of the final polycondensation reaction tank, or from the outlet of the final polycondensation reaction tank, as in the filter 11 between It is preferable to install between.
[0027]
In addition, the filter installation position is the intermediate position of each pipe constituting the reaction product flow path in the above description, but the inlet or outlet of the transesterification reaction tank or polycondensation reaction tank, or the inlet of the polymer extraction die Alternatively, it may be in a die, or a plurality of filters may be provided at each installation position.
The polybutylene terephthalate resin obtained by the production method of the present invention has a reduced fish eye. For example, in a film having a thickness of 50 μm, the number of fish eyes having a nucleus having a size of 20 μm or more is 10/100 cm. ² It can be the following, and further 5 / 100cm ² It is also possible to:
[0028]
In addition, the resin granules after the polycondensation reaction obtained in the method for producing a polybutylene terephthalate resin of the present invention are subjected to an inert gas atmosphere or / and a reduced pressure of about 0.01 to 1.5 kPa. In general, the heat treatment is usually performed for about 5 to 20 hours at a temperature 5 to 50 ° C. lower than the melting point of the resin, preferably 10 to 40 ° C. lower than the melting point, while allowing the particles to flow so as not to stick to each other. By performing solid phase polycondensation, the degree of polymerization can be further increased, and the reaction by-products such as tetrahydrofuran and low-molecular oligomers can be reduced.
[0029]
【Example】
Hereinafter, although an example and a comparative example explain the present invention still in detail, the present invention is not limited to these examples.
Example 1
The same manufacturing apparatus as shown in FIG. 1 is used except that the filter installation flow path is a flow path described later. Dimethyl terephthalate is supplied from the supply line 1a to the storage tank 1, and is heated and melted while being stirred by the stirring device M1, 1,4-butanediol is supplied from the pipe L1 at a rate of 44.0 kg / hr and 26.5 kg / hr from the supply port 2b (BG / DMT molar ratio = 1.3), and tetrabutyl titanate is supplied to the catalyst as a catalyst. 2c to 0.035 kg / hr (100 ppm as titanium metal / polymer), supplied to the first transesterification reactor 2 adjusted to a temperature of 180 ° C. and a pressure of 105 kPa, and stirred for 1.5 hours with the stirring device M2. Transesterification was performed to obtain an oligomer having a transesterification rate of 82.5%.
[0030]
Subsequently, the oligomer is passed through the pipe L2 by the pump P1 and transferred to the second transesterification reaction tank 3 adjusted to a temperature of 195 ° C. and a pressure of 80 kPa, and the transesterification reaction is carried out for 1 hour with stirring by the stirring device M3. Further, an oligomer having a transesterification rate of 96.7% was obtained, and the oligomer was passed through the pipe L3 by the pump P2 and transferred to the first polycondensation reaction tank 4 adjusted to a temperature of 240 ° C. and a pressure of 4 kPa. In the presence of the titanium compound supplied from the catalyst supply port 2b of the first transesterification reaction tank 2, a polycondensation reaction is performed for 1 hour with stirring by the stirring device M4, and a prepolymer having an intrinsic viscosity of 0.21 dl / g is obtained. Obtained.
[0031]
Subsequently, the prepolymer was passed through the pipe L4 by the pump P3 and installed in the middle of the pipe L4 (corresponding to the installation flow path of the filter 10 in FIG. 1). A laminated metal mesh having an absolute filtration accuracy of 20 μm was used as a filter medium. After passing through the pleated cylindrical type filter, it is transferred to the second double condensation reaction tank 5 adjusted to a temperature of 245 ° C. and a pressure of 0.15 kPa, and is subjected to a polycondensation reaction for 2.5 hours with stirring by the stirring device M5. To obtain a polymer having an intrinsic viscosity of 0.86 dl / g, the polymer is passed through the pipe L5 by the pump P4, transferred to the polymer extraction die 6, extracted in the form of a strand, and cut by the pelletizer 7. In this way, polybutylene terephthalate resin pellets were produced.
[0032]
Next, the obtained polybutylene terephthalate resin pellets were supplied to a single screw extruder equipped with a T die and the cylinder temperature set at 270 ° C., melted and extruded into a film, and then maintained at a temperature of 58 to 62 ° C. By quenching with a metal cooling roll, it was formed into a film having a thickness of 50 μm, and the number of fish eyes was measured by the method shown below. ² Met.
[0033]
Here, the transesterification rate, the intrinsic viscosity (IV), and the number of fish eyes were measured by the following methods.
<Transesterification reaction rate>
The obtained oligomer was dissolved in a mixed solvent of hexafluoroisopropyl alcohol / chloroform-d (weight ratio 3/7). ¹ Measured by 1 H-NMR, the concentration of methyl groups derived from unreacted dimethyl terephthalate was measured, and the transesterification rate of the oligomer was determined.
[0034]
<Intrinsic viscosity (IV)>
The viscosity of a solution obtained by dissolving the obtained polymer in a mixed solvent of phenol / tetrachloroethane (weight ratio 1/1) at a concentration of 1.0 g / dl is determined by measuring at 30 ° C. using an Ubbelohde viscometer. It was.
<Number of fish eyes>
About the obtained film, 10cm square (100cm ² ) Was observed with a stereomicroscope with a magnification of 50 times, the number of fish eyes having nuclei having a size of 20 μm or more at each location was counted, and the average value was calculated.
[0035]
Example 2
A pleated cylindrical filter using a metal nonwoven fabric having an absolute filtration accuracy of 30 μm as a filter medium was used, and the filter was installed in the middle of a pipe L5 between the second double condensation reaction tank 5 and the polymer extraction die 6. The polybutylene terephthalate resin pellets were manufactured in the same manner as in Example 1 except that (corresponding to the installation flow path of the filter 11 in FIG. 1). At that time, the transesterification rate of the oligomer at the outlet of the first transesterification reactor 2 is 83.1%, the transesterification rate of the oligomer at the outlet of the second transesterification reactor 3 is 96.9%, The intrinsic viscosity of the prepolymer at the outlet of the polycondensation reaction tank 4 is 0.22, the intrinsic viscosity of the finally obtained polymer is 0.85 dl / g, and the number of fish eyes in the film is 2.9 / 100cm ² Met.
[0036]
Comparative Example 1
Polybutylene terephthalate resin pellets were produced in the same manner as in Example 1 except that no filter was used. At that time, the transesterification rate of the oligomer at the outlet of the first transesterification reactor 2 is 83.0%, the transesterification rate of the oligomer at the outlet of the second transesterification reactor 3 is 96.7%, the first The intrinsic viscosity of the prepolymer at the outlet of the polycondensation reaction tank 4 is 0.22, the intrinsic viscosity of the finally obtained polymer is 0.87 dl / g, and the number of fish eyes in the film is 13.1 / 100cm ² Met.
[0037]
【The invention's effect】
According to the present invention, in the continuous production of a polybutylene terephthalate resin through a transesterification reaction in the presence of a transesterification reaction catalyst, a method for producing a polybutylene terephthalate resin with less fisheye, and thereby The resulting polybutylene terephthalate resin can be provided.
[Brief description of the drawings]
FIG. 1 is a flow chart showing an embodiment of a production apparatus used in the method for producing a polybutylene terephthalate resin of the present invention.
[Explanation of symbols]
1: Dimethyl terephthalate storage tank
1a: Dimethyl terephthalate supply port
2: First transesterification reactor
2a: Vent port
2b: 1,4-butanediol supply port
2c: catalyst supply port
3: Second transesterification reactor
3a: Vent port
4: First polycondensation reaction tank
4a: Vent port
5: Second double condensation reactor
5a: Vent port
6: Polymer extraction die
7: Pelletizer
8, 9, 10, 11: Filter
M1, M2, M3, M4, M5: Stirring device
P1, P2, P3, P4: Pump
L1, L2, L3, L4, L5: Piping

Claims (3)

  A dicarboxylic acid ester component mainly composed of a lower alkyl ester of terephthalic acid and a diol component mainly composed of 1,4-butanediol are compared with the theoretical yield of the resin in one or more transesterification reactors. By transesterification in the presence of a 30-300 ppm titanium compound transesterification catalyst as a titanium atom, followed by polycondensation reaction in one or more polycondensation reaction tanks, and then withdrawing from the polymer extraction die In the continuous production of polybutylene terephthalate resin, a filter is installed in the reaction product channel between the outlet of the first transesterification reaction tank and the outlet of the polymer extraction die, and the reaction product passes through the filter. A process for producing a polybutylene terephthalate-based resin, characterized by comprising:   The method for producing a polybutylene terephthalate resin according to claim 1, wherein the filter is installed between the outlet of the reaction tank immediately before the final polycondensation reaction tank and the inlet of the final polycondensation reaction tank.   The method for producing a polybutylene terephthalate resin according to claim 1 or 2, wherein the flow path for the filter is between the outlet of the final polycondensation reaction tank and the outlet of the polymer extraction die.

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