JP3341409B2 - Polyester production method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing polyester. More specifically, the present invention relates to a method for producing a polyester containing naphthalenedicarboxylic acid as a main acid component and 1,4-butanediol as a main glycol component.

[0002]

2. Description of the Related Art Conventionally, polybutylene naphthalate (hereinafter abbreviated as PBN) is a plastic having various excellent mechanical properties and excellent moldability, like polybutylene terephthalate (hereinafter abbreviated as PBT). It is known to be useful as PBN is a resin that can be applied to a wider range of applications than PBT because it has a faster crystallization rate and a melting point of about 20 ° C. higher than PBT.

On the other hand, the use environment of electrical and electronic parts, such as connectors, and automotive parts materials using such engineering plastics has recently become increasingly severe such as high temperature and high humidity. Therefore, in these applications, PBN with improved hydrolysis resistance has been desired. In general, in the production or use of PBN, it is necessary to raise the polymerization temperature and the molding temperature as compared with the case of PBT. Was. For example, in the batch-type production of PBN, it takes about several tens of minutes to about one hour to withdraw the molten polymer after the polymerization is completed, and the amount of terminal carboxyl groups increases during the withdrawal. There was a drawback that the carboxyl group content was increased and the hydrolysis resistance was deteriorated. Therefore, from the viewpoint of improving the hydrolysis resistance of PBN, it has been desired to reduce the amount of increase in the number of terminal carboxyl groups in the heat-melted state at a high temperature.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for efficiently producing a polyester such as PBN which has a small increase in terminal carboxyl groups during heat retention at a high temperature and is excellent in heat resistance and hydrolysis resistance. To provide.

[0005]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problem, and its gist is to provide a dicarboxylic acid component containing naphthalenedicarboxylic acid and / or an ester-forming derivative thereof as a main component. A method for producing a polyester, comprising melt-polycondensing a glycol component containing 1,4-butanediol as a main component in the presence of an alkali metal salt of hypophosphorous acid.

Hereinafter, the present invention will be described in detail. The dicarboxylic acid component used in the present invention is a naphthalenedicarboxylic acid, for example, 2,6-naphthalenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid or an ester-forming derivative thereof, and a part thereof (based on the total acid component). Less than 20 mol%) with other dicarboxylic acids such as terephthalic acid, isophthalic acid, 4,4'-diphenyldicarboxylic acid, diphenoxyethane-4,4'-dicarboxylic acid,
It may be replaced with an aromatic dicarboxylic acid such as diphenylsulfone-4,4-dicarboxylic acid or diphenylether-4,4'-dicarboxylic acid, or an aliphatic dicarboxylic acid such as sebacic acid or adipic acid. In addition, examples of the ester-forming derivative of the acid component include lower alkyl esters, phenyl esters, and acid anhydrides.

As the glycol component, 1,4-butanediol is a main component, and a part (20 mol% or less of the total glycol) is replaced with another glycol such as ethylene glycol, neopentyl glycol, trimethylene glycol, or the like. It may be replaced with hexamethylene glycol, decamethylene glycol, cyclohexanedimethanol, or the like.

A dicarboxylic acid component mainly comprising naphthalenedicarboxylic acid or its ester-forming derivative and 1,4-
In conducting esterification or transesterification of a glycol component mainly containing butanediol, a titanium-based catalyst, for example, an alcoholate or phenolate of titanium is used as a catalyst. Usually, an alcoholate compound of titanium is used, specifically, tetrabutyl titanate,
Examples thereof include tetraisopropyl titanate and tetramethyl titanate.

As the catalyst in the melt polycondensation reaction, the same catalyst as in the above-mentioned esterification or transesterification reaction is used, and among them, a titanium compound is preferable. If necessary, an oxide of antimony or germanium may be added. Here, the esterification or transesterification reaction is 1
50 to 280 ° C, preferably 180 to 260 ° C for 2 to 4
The melt polycondensation reaction is carried out at 240 to 300 ° C. for 2 to 5 hours under a reduced pressure of 3 torr or less. The amount of the catalyst is 3 to 300 ppm, preferably 5 to 200 ppm, as a metal equivalent of titanium in the esterification or transesterification reaction, relative to the polymer, and the amount of the catalyst further added in the melt polycondensation reaction is 0 to 300 ppm, preferably 5 to 200 ppm.
It is.

In the melt polycondensation reaction, a small amount of other additives may be present in addition to the catalyst. As other additives,
Phosphorus compounds such as phosphoric acid, phosphorous acid and esters thereof, thioether compounds such as dilauryl 3,3'-thio-dipropionate, pentaerythrityl-tetrakis (3-lauryl thiopropionate), and 2,6-
Hindered phenol compounds such as di-t-butyl-4-octylphenol and pentaerythrityl-tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate]. In addition, release agents such as polyethylene wax, polypropylene wax and montanic acid wax, and silicate compounds such as talc and kaolin.

The alkali metal salts of hypophosphorous acid in the present invention include lithium, potassium, and sodium salts of hypophosphorous acid, and may be added at any time before the completion of the melt polycondensation reaction. Although it may be at the time, it is advantageous from the viewpoint of the reaction operation, preferably after the esterification or transesterification reaction is performed and before the melt polycondensation reaction is started. The amount of the alkali metal hypophosphorous acid to be added is 10 to 1000 ppm, preferably 20 to 300 ppm, based on the produced polyester. If the addition amount is less than 10 ppm, the effect of improving hydrolysis resistance and thermal stability is not sufficiently exhibited, and even if added in excess of 1000 ppm, further effects cannot be obtained and the polycondensation reaction is inhibited. It will be easier.

As a method of adding the alkali metal salt of hypophosphorous acid, a method of adding as a powder or a method of adding as a solution or slurry of a suitable solvent such as 1,4-butanediol can be used. Assuming actual production, it is preferable to add an alkali metal salt of hypophosphorous acid as a solution or slurry using a solvent such as 1,4-butanediol. Among them, the addition as a slurry is particularly preferable since the decrease in the polymerization rate is small and the amount of reduction in the amount of carboxyl groups is almost the same as that in the solution addition.

According to the method of the present invention, the terminal carboxyl group of the polyester immediately after the completion of the polycondensation is reduced by causing the alkali metal salt of hypophosphorous acid to be present in the reaction system and performing the melt polycondensation. That is, the amount of terminal carboxyl groups is about 30 μeq / g to about 50 μeq / g in the system without addition of the alkali metal salt of hypophosphorous acid, whereas the amount in the addition system is about 10 μeq / g.
It can be set to about 25 μeq / g from μeq / g. Further, the amount of terminal carboxyl groups in the polyester obtained by causing the alkali metal salt of hypophosphorous acid to be present in the reaction system during heat retention can be reduced.

Generally, polyesters such as PBN are produced by a batch method. Polycondensation is performed in a vacuum, and when the viscosity reaches a predetermined value, the pressure is restored, and the resulting polymer is extracted as a strand, cooled, and formed into chips. At this time, it usually takes about one hour to extract the entire amount of the polymer from the reaction system. Therefore, the polymer in the final stage of withdrawal stays at 255 ° C., which is the withdrawal temperature (= polymerization temperature), for about 1 hour. During this time, the polymer undergoes heat history, so that the polymer terminal is decomposed and the terminal carboxyl group gradually increases. Usually, when an alkali metal salt of hypophosphorous acid is not added, the amount of increase in the terminal carboxyl group of the polyester due to heat retention at 255 ° C. for 1 hour is 35 to 50 μeq / g, By the presence of the alkali metal salt of phosphorous acid, the amount of increase of the terminal carboxyl group of the polyester when heated and held at a temperature of 255 ° C. for 1 hour can be reduced to about 15 to 30 μeq / g or less. Therefore, the average value of the terminal carboxyl groups of the total amount of the extracted polyester is 50 μeq / g to 75 μeq / g in the system without the addition of the alkali metal hypophosphite, whereas the average value of the alkali metal hypophosphite is 2 in the added system
From 0 μeq / g to 40 μeq / g. The thus obtained PBN obtained by adding an alkali metal salt of hypophosphorous acid at the time of polycondensation, has a [η] retention rate of a normal product even after being subjected to a hydrolysis treatment in saturated steam at 120 ° C. for 96 hours. Is 50 to 70%, while the [η] retention is 80% or more.

The polyester obtained by melt polycondensation may be further subjected to solid phase polycondensation. The solid-phase polycondensation is carried out at 3 torr or less or under the expected flow of inert gas such as nitrogen gas at a temperature below the melting point of polyester. When the amount of terminal carboxyl groups is small, the solid-state polymerization rate is high. Therefore, the polyester obtained in the method of the present invention is excellent in solid phase polymerizability.

[0016]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist thereof. In addition, "part" in the examples
Certain parts represent "parts by weight", and the intrinsic viscosity [η] is 30 parts by weight in phenol / tetrachloroethane (1: 1 part by weight).
It is determined from the solution viscosity measured at ° C.

The amount of terminal carboxyl groups [COOH] is determined by dissolving the polymer in benzyl alcohol and adding 0.1N NaO
The value obtained by titration with H is the carboxyl group equivalent per 10 ⁶ g. After the polymerization, the heat resistance was measured under N ₂ at 255.
The entire amount of the molten polymer was extracted at 1 ° C. over 1 hour, and evaluated as a difference (increase) between the amount of terminal carboxyl groups at the initial stage of the extraction and the final stage of the extraction (after 1 hour).

[0018]

## EQU1 ## Δ [COOH] = [COOH] (after 1 hour) −
[COOH] (first extraction)

The hydrolysis resistance is as follows: The polymer chip in the middle of the extraction (after 0.5 hour) is heated at 120 ° C. in saturated steam at 9 ° C.
It was treated for 6 hours and evaluated by the retention of [η]. The retention is shown by the following equation.

[0020]

## EQU2 ## [η] retention rate = ([η] after processing / initial [η]) × 100 (%)

Example 1 244 parts of dimethyl-2,6-naphthalenedicarboxylate, 108 parts of 1,4-butanediol and 11 ppm of tetrabutyl titanate (in terms of titanium metal) with respect to the produced polybutylene naphthalate were used. In addition, a transesterification reaction was performed at 190 to 255 ° C. for 2.5 hours. Subsequently, 22 ppm (total 33 ppm) of tetrabutyl titanate and 60 ppm (in terms of sodium hypophosphite) of sodium hypophosphite / monohydrate are added to the produced polybutylene naphthalate, and the mixture is reduced at 255 ° C. under reduced pressure. A melt polycondensation reaction was performed. The decompression was performed gradually from normal pressure to 3 torr over 2 hours, and thereafter maintained at 3 torr. When the stirring torque increased to a predetermined value, the stirring was stopped, and the inside of the tank was restored and pressurized with N _{2 to} take out the polymer over 1 hour. The temperature of the molten polymer in the tank at that time was 255 ° C.
First, the terminal carboxyl groups were measured for the 0.5 hour and 1 hour withdrawn polymers. Also,
[Η] was measured for the polymer for 0.5 hour. The results are shown in Table 1.

Example 2 A polyester was obtained in the same manner as in Example 1 except that the amount of sodium hypophosphite / monohydrate added was 30 ppm and the polycondensation time was 2 hours and 55 minutes. Was. [Example 3] In Example 1, sodium hypophosphite
Polyester was obtained in exactly the same manner as in Example 1, except that 60 ppm of potassium hypophosphite was added instead of the monohydrate, and the polycondensation time was 3 hours and 5 minutes.

Example 4 In Example 1, the amount of tetrabutyl titanate before transesterification was 80 ppm, the amount of tetrabutyl titanate added in transesterification was 40 ppm, and the amount of sodium hypophosphite monohydrate was added. Was carried out in the same manner as in Example 1 except that the polycondensation time was set to 300 ppm and the polycondensation time was set to 3 hours and 20 minutes to obtain a polyester.

Comparative Example 1 The same procedure as in Example 1 was carried out except that sodium hypophosphite.monohydrate was not added, and the polycondensation time was 2 hours and 4 hours.
A polyester was obtained in exactly the same manner as in Example 1 except that the time was 5 minutes. The polyesters obtained in Examples 2 to 4 and Comparative Example 1 were evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0025]

[Table 1]

[0026]

According to the method of the present invention, a polyester having excellent hydrolysis resistance and heat resistance is produced by producing a polyester comprising naphthalenedicarboxylic acid as a main acid component and 1,4-butanediol as a main glycol component. Can be obtained.

Continuation of front page (58) Field surveyed (Int.Cl. ⁷ , DB name) C08G 63/00-63/91

Claims (2)

(57) [Claims] An alkali metal salt of hypophosphorous acid comprising a dicarboxylic acid component containing naphthalenedicarboxylic acid and / or an ester-forming derivative thereof as a main component and a glycol component containing 1,4-butanediol as a main component. A method for producing a polyester, comprising melt-polycondensation below. 2. The method for producing a polyester according to claim 1, wherein the alkali metal salt of hypophosphorous acid is added in an amount of 10 to 1000 ppm based on the produced polyester.