JPH07196782A - Production of polyester having high polymerization degree and production of polyester molding having high polymerization degree - Google Patents

Abstract

PURPOSE:To obtain the subject polyester having relatively uniform distribution of molecular weight, being low in production cost and useful for fibers by melting and kneading a polyester having a low polymerization degree in the presence of a titanium alkoxide polymerization catalyst in a twin-screw extruder to carry out polycondensation reaction of the polyester. CONSTITUTION:(A) A polyester having a low polymerization degree and <=15X10<-6>eq/g terminal carboxyl group content is melted add kneaded in the presence of (B) a titanium alkoxide polycondensation catalyst in a twin-screw extruder in order to carry out polycondensation reaction to provide the objective polyester. Furthermore, intrinsic viscosities (measured at 35 deg.C in a mixed solvent in which a weight ratio of tetrachloroethane to phenol is 4:6) of the component A and the objective polyester are 0.3-0.8dl/g and >=1.2dl/g, respectively, and a volatile substance generated by the polycondensation reaction from a bent hole is preferably discharged. Furthermore, e.g. titanium methoxide, etc., is preferably used as the component B.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a high degree of polymerization polyester by melt-kneading a low degree of polymerization polyester and carrying out a polycondensation reaction, and a method for producing a molded product of the polyester.

[0002]

2. Description of the Related Art Polyesters, especially polyethylene terephthalate, polytetramethylene terephthalate, etc., have excellent mechanical properties and heat resistance,
Widely used as films and plastics. It is known that, among the physical properties of this polyester, the mechanical properties have a large proportion depending on the polymer polymerization degree, and the higher the polymerization degree, the higher the mechanical properties, especially the strength.

The polyester is usually produced by a melt polymerization method, but since this polymerization is a high temperature condensation reaction, a side reaction (for example, a thermal decomposition reaction) is likely to occur, and it takes a long time to produce a high polymer. In addition, when the degree of polymerization reaches a certain level, there is a problem that the degree of polymerization is decreased. Therefore, various methods for producing a polyester having a polymerization degree as high as possible have been studied and proposed. For example, a method called solid-phase polymerization is widely used in which polyester is once formed into granules and reacted at a temperature 10 to 60 ° C. lower than the melting point under vacuum or under N ₂ gas flow.

According to this solid-phase polymerization method, the attainable intrinsic viscosity can be increased to about 1.2 dl / g. Furthermore, the reaction rate can be increased by making the particle size very small in order to facilitate the distillation of the by-product to the outside of the system,
In the laboratory, it is possible to obtain an intrinsic viscosity of up to about 1.8 dl / g.

However, the polyester obtained by the solid-phase polymerization method generally has a non-uniform molecular weight distribution and lower productivity than the one obtained by the melt polymerization method, and therefore the production cost is high. Furthermore, in order to process it into a molded product, it is necessary to re-melt the solid polyester at a high temperature of 260 to 330 ° C., and in the process of this re-melting, the degree of polymerization is lowered and the ultimate viscosity of the final molded product is increased. Is at most 1.0 dl / g.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to produce a high degree of polymerization polyester having an intrinsic viscosity of 1.2 dl / g or more by a melt polymerization method which has advantages of relatively uniform molecular weight distribution and low production cost. It is to provide a possible method.

A further object of the present invention is to provide a method for producing a polyester having a high degree of polymerization, which enables the intrinsic viscosity of the polyester of the molded article after melt molding to be 1.2 dl / g or more.

[0008]

[Means for Solving the Problems] The inventors of the present invention have conducted extensive studies to achieve the above object, and as a result, a specific low-polymerization polyester having a low concentration of terminal carboxyl in the presence of titanium alkoxide as a polycondensation catalyst. Was melt-kneaded using a twin-screw extruder to cause polycondensation reaction, and then 1.2 dl /
It has been found that a high degree of polymerization polyester having an intrinsic viscosity of g or more can be easily obtained.

Thus, according to the present invention, firstly, a low-polymerization degree polyester having a terminal carboxyl group content of 15 × 10 ⁻⁶ eq / g or less is produced in a twin-screw extruder in the presence of a titanium alkoxide polycondensation catalyst. Provided is a method for producing a high-polymerization polyester, which comprises melt-kneading and performing a polycondensation reaction to obtain a high-polymerization polyester.

Further, according to the present invention, secondly, a low-polymerization degree polyester having a terminal carboxyl group content of 15 × 10 ^-6 eq / g or less is produced in a twin-screw extruder in the presence of a titanium alkoxide polycondensation catalyst. A high-polymerization polyester obtained by melt-kneading and performing a polycondensation reaction to obtain a molten high-polymerization polyester, and directly supplying the molten high-polymerization polyester to a molding device without solidifying to form a molded product. A method of manufacturing a molded article is provided.

The above-mentioned objects are achieved by the above two inventions. BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below, and other objects, configurations, advantages and effects of the present invention will be apparent from the description.

In the present invention, the concentration of terminal carboxyl groups contained in the low-polymerization degree polyester used as a starting material is 15 × 10 ^-6 eq / g or less, preferably 10 × 10 6.
^-6 eq / g or less. Further, the intrinsic viscosity of the low-polymerization degree polyester is preferably 0.3 to 0.8 dl / g,
More preferably, it is 0.3 to 0.6 dl / g.

When the content of the terminal carboxyl group and the intrinsic viscosity of the low degree of polymerization polyester are within the above ranges, it becomes possible to easily produce a high degree of polymerization polyester having an intrinsic viscosity of 1.2 dl / g or more.

The low-polymerization polyester having a low content of terminal carboxyl groups is a dicarboxylic acid or an ester-forming derivative thereof which forms an acid component and a glycol or an ester-forming derivative thereof which forms a glycol component, which will be described later. It can be obtained by appropriately carrying out an esterification reaction and / or a transesterification reaction with other components used.

For example, the intrinsic viscosity is as low as 0.3 to 0.8 dl / g and the degree of polymerization is low, and the terminal carboxyl group concentration is 15
285 for low-polymerization polyester of less than 10 ^-6 eq / g
It can be prepared by carrying out a polycondensation reaction at a temperature of ℃ or less.

In the present invention, the intrinsic viscosity [η] of polyester is 4: 6 of tetrachloroethane and phenol.
It is the value measured at 35 ° C. using the mixed solvent (weight ratio).

In the present invention, the concentration of the terminal carboxyl group can be determined by the method of A. Conix [Makromol.
m. 26, 226 (1985)], and measured and calculated as follows. That is, polyester was dissolved in a benzyl alcohol-chloroform mixed solution (weight ratio 1: 1), phenol red was used as an indicator, and titration was performed with a benzyl alcohol-based caustic soda. Calculate (eq / g).

The acid component constituting the low-polymerization degree polyester used in the present invention includes terephthalic acid, isophthalic acid,
Examples thereof include naphthalene dicarboxylic acid, diphenyl dicarboxylic acid, diphenyl sulfone dicarboxylic acid, diphenoxyethane dicarboxylic acid, diphenyl ether dicarboxylic acid, methyl terephthalic acid and methyl isophthalic acid. Of these, terephthalic acid is particularly preferable. Examples of the glycol component include ethylene glycol, trimethylene glycol, tetramethylene glycol, hexamethylene glycol, decamethylene glycol, cyclohexane dimethylol and the like. Of these, ethylene glycol is particularly preferable.

The low-polymerization degree polyester may contain other components as a copolymerization component. The components include, for example, diol components such as diethylene glycol, propylene glycol and polyalkylene glycol, dicarboxylic acid components such as adipic acid, sebacic acid and phthalic acid, polyfunctional carboxylic acid components such as trimellitic acid and pyromellitic acid, and benzoylbenzoic acid. And monofunctional carboxylic acid components such as diphenylcarboxylic acid.

The titanium polyalkoxide of the polycondensation catalyst used in the method of the present invention is generally Ti (OR).
₄ (where R is an alkyl group, preferably 1 to 6 carbon atoms)
Is an alkyl group. ) Is a compound represented by
For example, titanium methoxide, titanium ethoxide, titanium propoxide, titanium butoxide, etc. are typical. The titanium alkoxide is used in an amount of 0.0 with respect to the weight of the low-polymerization degree polyester from the viewpoint of accelerating the polycondensation reaction and suppressing the thermal decomposition reaction during melt-kneading.
It is preferably present in an amount of 1 to 1.0% by weight, particularly 0.02 to 0.5% by weight.

The above titanium alkoxide catalyst is often used as a catalyst for preparing a low-polymerization degree polyester used as a raw material, and if it is contained in the prepared low-polymerization degree polyester in an appropriate amount, it is melt-kneaded. Therefore, it is not necessary to add titanium alkoxide. When the low degree of polymerization polyester is prepared by using another catalyst, an appropriate amount of titanium alkoxide is added during melt kneading.

In the present invention, the low molecular weight polyester is melt-kneaded to carry out a polycondensation reaction. A twin-screw extruder is used as a device for melt-kneading. In a twin-screw extruder, a pair of screws rotate in the same direction or in different directions while meshing or not meshing to knead and extrude the polyester under melting.

FIG. 1 schematically shows a side cross section of an example of the twin-screw extruder used in the present invention. The low molecular weight polyester is supplied to the twin-screw extruder 1 through the supply line 3. The low molecular weight polyester is kneaded by a screw 2 (only one of a pair of existing screws is shown and the other screws are not shown) to carry out a polycondensation reaction. The twin-screw extruder is preferably provided with at least one, especially 1 to 5, vent ports 4. The polycondensation reaction is accelerated by degassing from the vent port 4 under reduced pressure and removing volatile substances such as ethylene glycols generated as the polycondensation reaction progresses from the polycondensation system. The polyester having a high degree of polymerization due to the polycondensation reaction is taken out from the discharge port 5.

When a polycondensation reaction is carried out by melt-kneading using such a twin-screw extruder, the rotation of a pair of screws causes the polyester to become a thin film and efficiently agitates, so that the polyester per unit volume The evaporation area of ethylene glycols increases, and the diffusion rate of ethylene glycols to the polyester surface increases. As a result, the polycondensation reaction rate is significantly accelerated, and the degree of polymerization of the polyester is sufficiently high even when the residence time (reaction time) of the polyester in the twin-screw extruder is short. Also, the decomposition reaction of polyester does not proceed so much with a short residence time. Further, the polycondensation reaction proceeds more uniformly as compared with the case of the solid phase method, so that the molecular weight distribution is more uniform.

The degree of pressure reduction at the vent port 4 of the twin-screw extruder is preferably 10 mmHg or less, more preferably 5 mmHg or less.

The polycondensation reaction temperature (melting resin temperature in the twin-screw extruder) is 320 ° C. from the melting point of the low polymerization polyester.
Is preferable, and a temperature range from the melting point to 300 ° C. is more preferable.

The residence time (polycondensation reaction time) of the polyester in the twin-screw extruder is preferably about 10 to 60 minutes, and particularly preferably 10 to 45 minutes.

The rotation speed of the screw of the twin-screw extruder is 20 to
500 rpm is preferable and 20-100 rpm is more preferable.

In the polycondensation reaction, various additives such as an ultraviolet absorber, a heat stabilizer, a flame retardant, a whitening agent,
Lubricants, nucleating agents, pigments and the like may be added.

FIG. 2 is a schematic diagram showing a flow for carrying out one embodiment of the present invention. In the esterification tank or transesterification tank 11, bishydroxyethyl terephthalate as a polymerization raw material and / or its low polymer is produced from terephthalic acid dialkyl ester such as terephthalic acid or dimethyl terephthalate and ethylene glycol.

A low polymerization polyester is produced from this polymerization raw material in the initial polymerization tank 12 and the intermediate polymerization tank 13 according to the conventional method. The intrinsic viscosity of the low-polymerization degree polyester at this stage is usually 0.3 to 0.8 dl / g, and the terminal carboxyl group concentration is 15 × 10 ⁻⁶ eq / g or less.

After that, the twin-screw extruder 1 is used as the final reaction tank to perform melt polycondensation to directly produce a polymer having an intrinsic viscosity of 1.2 or more. The polymer produced is solidified by cooling and then finely pulverized by a cutting machine 15 into an appropriate size for use in clothing, industrial fibers, films and the like. Further, fibers, films and the like can be produced by directly sending them to a molding device known per se such as a melt spinning device 14 and an extrusion molding device in a molten state without undergoing atomization. The latter case is a preferred method because a molded product having substantially the same degree of polymerization can be obtained from a polyester having a high degree of polymerization produced by a twin-screw extruder.

The method of the present invention described above can be preferably used for producing polyethylene terephthalate, polybutylene terephthalate, polyethylene-2,6-naphthalene dicarboxylate having a high degree of polymerization and molded articles thereof, and particularly high It can be preferably used for producing polyethylene terephthalate having a degree of polymerization and molded articles thereof.

[0034]

EXAMPLES The present invention will be described below based on examples. In addition, the part in an Example represents a weight part.

Example 1 Dimethyl terephthalate (DM
T) 100 parts / hr and ethylene glycol (EG) 6
0 parts / hr and manganese acetate 0.03 parts / hr were charged into the continuous transesterification tank 11 in FIG. 1, and the produced methanol was distilled out of the system to raise the temperature from 140 ° C. to 220 ° C. and transesterify. It was made to react. The average residence time was 3 hours. Then, to the obtained transesterification reaction product, 0.03 part / hr of a 56% aqueous solution of orthophosphoric acid was added as a stabilizer, and after 10 minutes, 0.04 part / hr of tetrabutyl titanate was added as a polycondensation catalyst. After that, the polymer was continuously fed into the initial polymerization tank 12 and reacted at 50 mmHg and 260 ° C. for 1 hour to obtain a polymer having an intrinsic viscosity of 0.15 dl / g. Furthermore,
This is reacted in the molten state in the medium-term polymerization tank 13 under a reduced pressure of 5 mmHg at 280 ° C. for 1 hour to give an intrinsic viscosity of 0.3 dl.
/ G, terminal carboxyl group concentration is 10 × 10 ^-6 eq / g
A low degree of polymerization polyester of was obtained. Next, this was continuously fed in a molten state to the twin-screw extruder of FIG. 1 (which has two vent ports), and the degree of pressure reduction at the vent port was 0.3 mmH.
g, temperature 300 ° C., screw rotation number 40 rpm, residence time 40 minutes to carry out polycondensation reaction. The intrinsic viscosity of the obtained polyester was 1.33 dl / g and the terminal carboxyl concentration was 21 × 10 ⁻⁶ eq / g.

(Example 2, Comparative Example 1) In the polycondensation reaction using the twin-screw extruder of Example 1, the intrinsic viscosity and terminal carboxyl group concentration of the low-polymerization degree polyester fed to the twin-screw extruder are shown in Table 1. The polycondensation reaction was repeated with the same changes as described in. The results are shown in Table 1.

(Example 3, Comparative Example 2) In the polycondensation reaction using the twin-screw extruder of Example 1, the type and amount of the polymerization catalyst used were changed as shown in Table 1 The polycondensation reaction of 1 was repeated. The results are shown in Table 1.

Comparative Example 3 In the polycondensation reaction using the twin-screw extruder of Example 1, a vent-type single-screw extruder (provided with two vent ports) was used instead of the twin-screw extruder, and the vent port was used. Degas (under reduced pressure of 0.3 mmHg), temperature 300
A polycondensation reaction was carried out at a temperature of 60 ° C., a screw rotation speed of 60 rpm, and a residence time of 80 minutes. The obtained polyester had an intrinsic viscosity of 0.78 dl / g and a terminal carboxyl concentration of 38 × 10.
^-6 eq / g.

(Comparative Example 4) In the polycondensation reaction using the twin-screw extruder of Example 1, a non-screw cage type reactor was used in place of the twin-screw extruder, and a temperature of 300 mmHg was applied under a reduced pressure of 0.3 mmHg.
The reaction was carried out at a temperature of 20 ° C., a stirring blade rotation speed of 20 rpm, and a residence time of 120 minutes. The obtained polyester has an intrinsic viscosity of 0.80.
dl / g, terminal carboxyl group concentration is 35 × 10 ^-6 eq
/ G.

(Comparative Example 5) In Comparative Example 2, Comparative Example 2 was repeated except that the intrinsic viscosity and the terminal carboxyl group concentration of the low-polymerization degree polyester fed to the twin-screw extruder were changed as shown in Table 1. . The results are shown in Table 1.

(Comparative Example 6) In Comparative Example 5, a vent type uniaxial extruder was used instead of the twin screw extruder.
Provided), degassed from the vent port (under reduced pressure of 0.3 mmHg), temperature 300 ° C., screw rotation speed 60 rpm,
The reaction was carried out with a residence time of 80 minutes. The polymer obtained had an intrinsic viscosity of 0.72 dl / g and a terminal carboxyl group concentration of 3
It was 3 × 10 ⁻⁶ eq / g.

[0042]

[Table 1]

[0043]

According to the method of the present invention, a high degree of polymerization polyester having an intrinsic viscosity of 1.2 dl / g or more can be obtained by using a twin screw extruder in the melt polymerization method of polyester. Furthermore, by directly molding the molten high-polymerization degree polyester obtained by the method of the present invention without solidifying, it is possible to obtain a molded article made of the high-polymerization degree polyester having an intrinsic viscosity of 1.2 dl / g or more. .

[Brief description of drawings]

FIG. 1 is a view schematically showing a side cross section of an example of a twin-screw extruder used in the present invention.

FIG. 2 is a schematic diagram showing one embodiment of a flow for carrying out the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Twin screw extruder 2 Screw 3 Supply line 4 Vent port 5 Discharge port 11 Esterification tank or transesterification tank 12 Initial polymerization tank 13 Mid-term polymerization tank 14 Melt spinning device 15 Cutting machine

Claims (4)

[Claims] 1. The content of terminal carboxyl groups is 15 × 10 ^−6.
A low polymerization degree polyester having a high polymerization degree of eq / g or less is melt-kneaded in a twin-screw extruder in the presence of a titanium alkoxide polycondensation catalyst to carry out a polycondensation reaction to obtain a high polymerization degree polyester. Production method. 2. The intrinsic viscosities of the low-polymerization polyester and the high-polymerization polyester (measured at 35 ° C. in a mixed solvent of tetrachloroethane and phenol at a weight ratio of 4: 6) are 0.3 to 0.8 dl /, respectively. g and 1.2 dl / g or more. The method for producing a high degree of polymerization polyester according to claim 1. 3. The method for producing a high degree of polymerization polyester according to claim 1, wherein the twin-screw extruder has a vent port, and the volatile matter generated by the polycondensation reaction is discharged from the vent port under reduced pressure. 4. The terminal carboxyl group content is 15 × 10 ^−6.
A low-polymerization degree polyester having an eq / g or less is melt-kneaded in a twin-screw extruder in the presence of a titanium alkoxide polycondensation catalyst to carry out a polycondensation reaction to obtain a high-polymerization degree polyester melted. A method for producing a high-polymerization polyester molded product, which comprises directly molding the product into a molding device to solidify the molded product.