JPH09316182A - Production of polybutylene terephthalate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a process for producing polybutylene terephthalate having a low terminal carboxyl group content, an excellent hydrolysis resistance, and a good hue by maintaining the free specific surface area of a polycondensation reactor in a specified range. SOLUTION: In producing polybutylene terephthalate having an intrinsic vicosity of 0.5 or higher by melt polymn., a batch or continuous polycondensation reactor of which the free specific surface area Sv (cm<2> /cm<3> ) represented by formula I [wherein S is the total specific surface area (cm<2> ) of reactants in the reactor; and V is the total vol.(cm<3> ) of the reactants in the reactor] satisfies the relation represented by formula II wherein [η] is the intrinsic viscosity (dl/g, regarded as dimensionless) of a polymer at the outlet of the reactor; and [COOH] is the terminal carboxyl group content (eq/10<6> g, regarded as dimensionless) of the polymer at the outlet of the reactor} is used to produce polybutylene terephthalate having a carboxyl group content of 30eq/10<6> g or lower.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a batch type or a continuous type of polybutylene terephthalate (hereinafter sometimes abbreviated as “PBT”) having a low carboxyl terminal group concentration (hereinafter sometimes referred to as “acid value”). Regarding manufacturing technology.

[0002]

2. Description of the Related Art Thermoplastic polyester resins, especially PBT, are widely used as industrial resins because of their excellent chemical resistance and mechanical properties.

PBT is generally produced by a direct polymerization method or a transesterification method. The direct polymerization method is a method of producing PBT by forming a PBT precursor by a direct esterification reaction of terephthalic acid and 1,4-butanediol, and then polycondensing the PBT precursor under reduced pressure.
On the other hand, in the transesterification method, a lower alkyl ester of terephthalic acid and 1,4-butanediol are transesterified to form a PBT precursor, and then the PBT precursor is polycondensed under reduced pressure to produce PBT. Is the way to do it.

However, the PBT produced by either method
Both have a problem in hydrolysis resistance. For example, when used in a high temperature and high humidity atmosphere, durability is a problem, the application is often limited, and a PBT resin excellent in hydrolysis resistance is required. To improve this hydrolysis resistance,
It is effective to lower the carboxyl end group concentration (low carboxylation). Further, when the concentration of the carboxyl terminal group is low, the by-product of tetrahydrofuran in the polycondensation reaction is suppressed, which is advantageous from the viewpoint of loss of 1,4-butanediol and recovery of by-products.

As a method for lowering the concentration of carboxyl terminal groups, there is generally a solid phase polymerization method, and many methods for the solid phase polymerization method of PBT have been proposed. For example,
Japanese Examined Patent Publication (Kokoku) No. 57-2728 discloses that PBT is preliminarily heat-treated at a temperature below the solid-state polymerization temperature for 4 hours or more to obtain a crystallinity of 46%.
As mentioned above, the method of continuing solid-phase polymerization is disclosed. Further, Japanese Patent Laid-Open No. 6-172503 discloses a method in which melt polymerization is stopped at a stage of an intrinsic viscosity of 0.1 to 0.55 dl / g, and once solidified by cooling and solidification, Such a method is not preferable from an economical point of view, because a large amount of energy is required for solid phase polymerization and equipment costs are high.

Regarding the melt polymerization method, Japanese Patent Publication No. 50-1
Japanese Patent No. 4278 discloses that a reaction product is formed into a thin film on a twin screw or a twin roll surface having a thin film to facilitate diffusion and removal of 1,4-butanediol. Further, JP-A-3-239727 discloses that a continuous stirrer having a cocoon-shaped plate member is used to form a thin film for good surface renewal, but the carboxyl end group concentration and the production efficiency (polymerization reaction The correlation with speed) has not been examined at all.

[0007]

The present inventors have arrived at the present invention as a result of extensive studies to solve the problems of the prior art. That is, in producing a PBT polymer having excellent hydrolyzability, there is a close relationship between the free specific surface area Sv in the polycondensation reaction tank and the concentration of the carboxyl end group of the polymer, and the free specific surface area Sv is within a certain range. As a result, they have found that a PBT polymer having a low carboxyl terminal group concentration can be obtained, and completed the present invention.

When the research was advanced based on the above findings,
When the free specific surface area Sv in the polycondensation reaction tank is reacted under predetermined conditions represented by the following formula (2), the acid value of PBT obtained by melt polymerization is 30 equivalents / 10 ⁶ g or less. Reproducibility I was able to confirm it well.

That is, in the present invention, terephthalic acid and / or a lower alcohol ester of terephthalic acid and 1,4-butanediol are esterified and / or transesterified to produce a PBT precursor and / or a PBT polymer. Then, when the PBT precursor and / or the PBT polymer are subjected to a polycondensation reaction under reduced pressure, by reacting the polycondensation reaction tank within a certain range of a free specific surface area Sv represented by the following formula, a carboxyl terminal is obtained. This is a method for producing a PBT polymer having a group concentration of 30 eq / 10 ⁶ g by melt polymerization.

[0010]

[Number 2] Sv = S / V (1) [(7.1 × [η] -3.1) / ([η] × [COOH])] 1 / 0. 49 ≦ Sv ≦ [(7.1 × [η] -3.1) / ( [η] × 0.7)] 1 / 0. 49 (2) [ wherein, S total free surface area of the reaction product of polycondensation reaction vessel (c
m ² ) and V represents the total volume (cm ³ ) occupied by the reactants in the polycondensation reaction tank. Further, [η] is the intrinsic viscosity of the polymer at the outlet of the polycondensation reaction tank (dl / g, but treated as dimensionless), and [COOH] is the carboxyl terminal group concentration of the polymer at the outlet of the reaction tank (eq / 10 ⁶ g , But treated as dimensionless). The present invention will be described in detail.

The operation of the present invention will be described. When the free specific surface area Sv in the polycondensation reaction tank is increased, the concentration of carboxyl end groups is exponentially decreased. Therefore, by increasing the free specific surface area Sv, a PBT polymer having a low concentration of carboxyl terminal groups and excellent hydrolysis resistance can be produced.

In the range where the free specific surface area Sv is smaller than the above equation, the concentration of carboxyl end groups is high and PBT having excellent hydrolysis resistance cannot be produced. Furthermore, the by-product of tetrahydrofuran is remarkable. Also, the free specific surface area S is
When v is large, the concentration of carboxyl end groups is low, but it is not suitable for actual production from the viewpoint of the size of the reaction tank.
Also, since the by-product of tetrahydrofuran is remarkable,
A large loss of 1,4-butanediol is not preferable.

The preferred range of the free specific surface area Sv is (3)
It is shown by the formula.

[0014]

Equation 3] 1.1 × [(7.1 × [η ] -3.1) / ([η] × [COOH]) 1 / 0. 49 ≦ Sv ≦ [(7.1 × [η] - 3.1) / (the ^{0.7 × [η]) 1 /} 0. 49 /2.0 (3) an intrinsic viscosity less than 0.5 PBT polymers, without producing in the method of the present invention, Generally, the concentration of carboxyl end groups is low and the hydrolysis resistance is good.

The reaction conditions in the polycondensation reaction tank of the present invention are preferably in the temperature range of 220 to 270 ° C. which is the usual PBT polycondensation condition. The degree of vacuum is not particularly limited, but 200 to 0.1 Torr is desirable. In the present invention, the number of polycondensation reaction tanks is not particularly limited, and a plurality of polycondensation reaction tanks may be connected for continuous production. Note that volatile substances such as 1,4-butanediol and tetrahydrofuran generated by the polycondensation reaction are discharged out of the system.

An inert gas can be continuously flowed into the polycondensation reaction tank of the present invention. The temperature of the inert gas is not particularly limited, but it is preferably 150 to 270 ° C. Moreover, the flow rate is not particularly limited. Furthermore, this inert gas can be recycled for economical reasons.

The intrinsic viscosity of the PBT precursor and PBT polymer supplied to the polycondensation reaction tank of the present invention is not particularly limited.

In the present invention, the PBT precursor and the polymer are produced in the presence or absence of a catalyst. When the reaction is carried out using a catalyst, any of the commonly used catalysts may be used. For example, titanium compounds, tin compounds, manganese acetate, lead acetate, etc. are exemplified, and among them, organic titanate compounds, titanium tetrachloride compounds and their hydrolyzed products or alcoholized products, organotin compounds and the like are preferable.

Further, in producing the PBT polymer of the present invention, alkali metal, alkaline earth metal hydroxide, inorganic acid salt, organic acid salt such as, for example, an alkali acid salt, an alkaline earth metal salt, etc.
At least one kind of acetate, carbonate or hydrate, complex salt, ammonium salt or the like can be used, and if desired, several kinds can be used in combination. Specific examples of the compound, lithium hydroxide, sodium hydroxide, potassium hydroxide, rubidium hydroxide, cesium hydroxide, francium hydroxide, beryllium hydroxide, magnesium hydroxide, strontium hydroxide, barium hydroxide, lithium acetate, acetic acid Sodium, potassium acetate,
Examples include magnesium acetate, calcium acetate, lithium carbonate, sodium carbonate, potassium carbonate and the like. Of these, alkali metal compounds are particularly preferable.

One or more kinds of thermoplastic resins other than the commonly used PBT, pigments, additives, inorganic fillers and organic fillers are used in the outlet side of the polycondensation reaction tank of the present invention. Can be directly kneaded with a kneader or the like. Examples of other thermoplastic resins include polyester resins, polyamide resins, polystyrene resins, polycarbonates, polyacetals, and the like. Further, as additives, known antioxidants, antistatic agents, brominated polycarbonates, flame retardants such as brominated epoxy compounds, antimony trioxide, flame retardant aids such as antimony pentoxide, plasticizers, lubricants, Examples include release agents, colorants, crystal nucleating agents and the like. As the inorganic filler, glass fibers, talc, mica, glass flakes, carbon fibers, silica, alumina fibers, milled glass fibers, clay, carbon black, kaolin, titanium oxide, iron oxide, antimony oxide, metals such as alumina. Examples thereof include compounds and alkali metal compounds such as potassium and sodium. Examples of the organic filler include aromatic polyester fibers and liquid crystalline polyester fibers.

[0021]

EXAMPLES Examples of the present invention are shown below, but the present invention is not limited thereto.

In the claims and the following examples, P
The intrinsic viscosity [η] of BT is 2 in orthochlorophenol.
It is a value calculated from the melt viscosity measured at 5 ° C.

Carboxyl end group concentration ([COOH])
Is the method of A. Conix {(M
akromol. Chem, 26 , 226 (195
8)} is the number of equivalents per 10 ⁶ g of polymer.

In the following Examples and Comparative Examples, parts are parts by weight.

Example 1 A batch reactor of a complete mixing tank type equipped with a stirrer was controlled so that the temperature of the reaction product was 245 ° C., and 100 parts of dimethyl terephthalate and 65 parts of 1,4-butanediol were separately added. Of titanium having an average degree of polymerization of 4 produced using 0.08 part of titanium tetrabutoxide
The BT oligomer was mixed under the conditions of Sv = 0.15 cm ² / cm ³ , vacuum degree 0.5 Torr and stirring rotation speed 20 rpm.
The reaction was allowed for 0 minutes. The PBT polymer was pressurized with nitrogen and discharged to form chips.

[Η] of the obtained PBT polymer was 0.73.
The carboxyl terminal group concentration was 11 equivalents / 10 ⁶ g, and the hue was also good.

Example 2 A scraping-type continuous horizontal reactor having a rotating shaft was kept at 246 ° C., and separately 100 parts of dimethyl terephthalate, 65 parts of 1,4-butanediol and 0.08 part of titanium tetrabutoxide were used. The PBT polymer having an average degree of polymerization of 41 obtained by using and was continuously supplied, and the degree of vacuum was 0.1 Torr and the stirring speed was 5 rpm.
The reaction was performed for 5 minutes. At this time, Sv in the reactor is 0.3
It was stable at cm ² / cm ³ . The PBT polymer was continuously taken out by a gear pump and made into chips.

[Η] of the obtained PBT polymer was 0.98.
The carboxyl terminal group concentration was 17 equivalents / 10 ⁶ g, and the hue was good.

Example 3 A continuous vertical reactor having a rotating shaft was kept at 245 ° C. and 100 parts of terephthalic acid and 1,
Using 100 parts of 4-butanediol and 0.05 parts of titanium tetrabutoxide, 0.003 parts of potassium hydroxide was added and a PBT polymer having an average degree of polymerization of 105 was continuously supplied, and the degree of vacuum was 0. .1 Torr, stirring speed 7
The reaction was allowed to proceed for 25 minutes under the condition of rpm. At this time, Sv in the reactor was stable at 1.7 cm ² / cm ³ . P
The BT polymer was continuously taken out by a gear pump and made into chips.

[Η] of the obtained PBT polymer was 1.1.
The carboxyl end group concentration was 19 equivalents / 10 ⁶ g, and the hue was good.

[Comparative Example 1] A scraping-type continuous horizontal reactor having a rotating shaft was kept at 246 ° C, and 100 parts of dimethyl terephthalate, 65 parts of 1,4-butanediol and 0.08 part of titanium tetrabutoxide were separately added. The PBT polymer having an average degree of polymerization of 41 obtained by using the above is continuously supplied, and the degree of vacuum is 0.1 Torr, and the stirring speed is 2 rpm.
The reaction was performed for 5 minutes. At this time, Sv in the reactor is 0.0
It was stable at 06 cm ² / cm ³ . The PBT polymer was continuously taken out by a gear pump and made into chips.

[Η] of the obtained PBT polymer was 0.85.
The carboxyl terminal group concentration was 36 equivalents / 10 ⁶ g, and the hue was slightly poor.

[Comparative Example 2] A batch reactor equipped with a stirrer was controlled so that the temperature of the reaction product was 245 ° C, and 100 parts of terephthalic acid and 80 parts of 1,4-butanediol were separately added. And titanium tetrabutoxide 0.
08 parts with 0.006 parts of potassium acetate to prepare a PBT polymer having an average degree of polymerization of 18 and Sv = 30 c.
The reaction was carried out for 25 minutes under the conditions of m ² / cm ³ and a vacuum degree of 0.1 Torr.

[Η] of the obtained PBT polymer was 0.83.
The carboxyl terminal group concentration was as low as 4 equivalents / 10 ⁶ g and the hue was good, but a stable reaction (operation) was not possible.

[0035]

According to the present invention, a PBT polymer having a low carboxyl terminal group concentration, excellent hydrolysis resistance, and a good hue can be obtained in a short reaction time. Further, since the amount of by-product of tetrahydrofuran is small, the loss of 1,4-butanediol is small, the by-products can be easily recovered, and the economical operation becomes possible.

Claims (8)

[Claims] 1. When producing polybutylene terephthalate having an intrinsic viscosity of at least 0.5 by a melt polymerization method, a free specific surface area Sv represented by the following formula (1):
A polybutylene terephthalate having a carboxyl end group concentration of 30 equivalents / 10 ⁶ g or less is produced by using a batch or continuous polycondensation reaction tank in which (cm ² / cm ³ ) satisfies the relationship of the following formula (2). how to. [Number 1] Sv = S / V (1) [(7.1 × [η] -3.1) / ([η] × [COOH])] 1 / 0. 49 ≦ Sv ≦ [(7.1 × [η] -3.1) / ( [η] × 0.7)] 1 / 0. 49 (2) [ wherein, S total free surface area of the reaction product of polycondensation reaction vessel (c
m ² ) and V represents the total volume (cm ³ ) occupied by the reactants in the polycondensation reaction tank. Further, [η] is the intrinsic viscosity of the polymer at the outlet of the polycondensation reaction tank (dl / g, but treated as dimensionless), and [COOH] is the carboxyl terminal group concentration of the polymer at the outlet of the reaction tank (eq / 10 ⁶ g , But treated as dimensionless). ] 2. The method for producing polybutylene terephthalate according to claim 1, wherein a polycondensation reaction tank equipped with a twin screw or a twin roll is used. 3. The method for producing polybutylene terephthalate according to claim 1, wherein a polycondensation reaction tank which is a free-flowing type thin film evaporator having a tray is used. 4. The method for producing polybutylene terephthalate according to claim 1, wherein a polycondensation reaction tank which is a tubular thin film evaporator is used. 5. The method for producing polybutylene terephthalate according to claim 1, 2, 3 or 4, wherein a thin film evaporator having a rotatable screw is used. 6. The method for producing polybutylene terephthalate according to claim 1, wherein a polycondensation reaction tank equipped with a rotating scraping blade is used. 7. The method for producing polybutylene terephthalate according to claim 1, wherein an inert gas is continuously or intermittently caused to flow in the polycondensation reaction tank. 8. A method for producing polybutylene terephthalate according to any one of Examples 1 to 3.