JPH0820635A - Method for producing polyester - Google Patents

Abstract

(57) [Summary] [Structure] When a polyester having butylene terephthalate as a main repeating unit is produced, after the intrinsic viscosity of the polymer in the polycondensation reaction becomes 0.5 or more, 0.01% of the obtained polyester is obtained. A method for producing a polyester, which comprises adding 2% by weight of a release agent to a polycondensation reaction system. [Effect] Even after the polymerization, the polyester to which the releasing agent is added is not required to be melt-kneaded, and a polyester having excellent releasability and mechanical strength, particularly elongation at break and Izod impact strength, can be obtained.

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 polyester, and more particularly to a method for producing a polyester having butylene terephthalate as a main repeating unit, which is excellent in mold releasability and mechanical properties.

[0002]

2. Description of the Related Art Polybutylene terephthalate (hereinafter referred to as P
BT) is a resin with well-balanced physical properties such as mechanical properties, electrical properties, heat resistance, etc.
It is widely used as electric / electronic parts such as coil bobbins and automobile parts such as distributor caps. PBT is mainly injection-molded, and at that time, additives such as a release agent and a heat stabilizer are mixed.

On the other hand, materials for electric / electronic parts and automobile parts in which engineering plastics such as PBT and polyamide are used have become smaller and more complicated, and the mold releasability of molded pieces has become a particularly important characteristic. A releasing agent is usually added to impart releasability. As a method of adding the release agent, a method of melt-kneading these release agents together with PBT chips using a uniaxial or biaxial extruder is generally used.
However, heat deterioration may occur during melt-kneading, resulting in a decrease in mechanical strength and deterioration in color tone. Therefore, if a mold release agent is added during the polymerization of PBT and the melt kneading of the PBT containing the mold release agent can be omitted after the polymerization, the thermal deterioration can be prevented and the production can be simplified, that is, the cost can be reduced. You will be able to go down.

However, when a mold releasing agent is added at the time of polymerization, it is usually convenient in terms of the production process to add the mold releasing agent after the esterification or transesterification reaction and before the start of polycondensation. The effect of was not always sufficient. Therefore, there is a problem in that the polyester to which the release agent is added at the time of polymerization is inferior in releasability as compared with the polyester blended with the release agent and melt-kneaded by an extruder or the like.

[0005]

The object of the present invention is to produce a polyester having good releasability without the need for melt-kneading the polyester to which a release agent is added using an extruder or the like after polymerization. To provide a method.

[0006]

The present invention has been made to solve the above-mentioned problems, and its gist is to provide a polymer in a polycondensation reaction when producing a polyester containing butylene terephthalate as a main repeating unit. The method for producing a polyester is characterized in that 0.01 to 2% by weight of a releasing agent is added to the polycondensation reaction system with respect to the obtained polyester after the intrinsic viscosity becomes 0.5 or more. Hereinafter, the present invention will be described in detail.

The polyester containing butylene terephthalate as a main repeating unit in the present invention is a polyester containing terephthalic acid as a main acid component and 1,4BG as a main glycol component, and other acids can be used within a range not impairing the original properties. One or more components, glycol components and oxyacid components may be copolymerized. Other acid components include isophthalic acid, 2,6-naphthalenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid, 4,4-diphenyldicarboxylic acid, diphenoxyethane-4,4-
Examples of the dicarboxylic acid include diphenylsulfone-4,4-dicarboxylic acid, aromatic dicarboxylic acid such as diphenyl ether-4,4-dicarboxylic acid, and aliphatic dicarboxylic acid such as sebacic acid and adipic acid. Other glycol components include ethylene glycol, neopentyl glycol, trimethylene glycol, hexamethylene glycol, decamethylene glycol, cyclohexanedimethanol and the like. Examples of the oxyacid component include p-hydroxybenzoic acid, m-hydroxybenzoic acid, 6-hydroxy-2-naphthalenedicarboxylic acid and the like.

The method for producing the polyester in the present invention is carried out according to a conventional method by esterification or transesterification and further polycondensation. As the catalyst for the esterification or transesterification reaction, tin compounds and titanium compounds are preferable, and titanium compounds are most preferable. Examples of the titanium compound include titanium alcoholates and phenolates, but usually titanium alcoholates are used, and specific examples thereof include tetrabutyl titanate, tetraisopropyl titanate, and tetramethyl titanate.

In the polycondensation reaction, titanium compounds are preferable even though the same catalysts as those used in the above esterification or transesterification reaction are not used. If necessary, antimony or germanium oxide or the like may be added. Here, the esterification or transesterification reaction is usually conducted at 150 to 280 ° C., preferably 180 to 260 ° C.
The polycondensation reaction is carried out at 240 to 300 ° C. for 2 to 5 hours under reduced pressure of 3 torr or less. In the esterification or transesterification reaction, the amount of catalyst is 3 to 300 pp in terms of metal of titanium based on the polymer.
m, preferably 5 to 200 ppm, and the amount of catalyst further added in the polycondensation reaction is 0 to 300 ppm, preferably 5 to 20
It is 0 ppm.

The releasing agent in the present invention is not particularly limited, but those having an essentially large effect of imparting releasability such that the releasability becomes good when melt-kneaded are preferable. Specific examples of the release agent include paraffin wax, microcrystalline wax, and a molecular weight of 500 to 4000.
Hydrocarbon waxes such as low molecular weight polyethylene, long-chain fatty acids represented by montanic acid and montanic acid esters, esters thereof, and other silicones. Among them, polyethylene wax having a molecular weight of 500 to 4000 is particularly preferable.

The amount of the release agent added is 0.01 to 2% by weight, preferably 0.05 to 1% by weight, based on the obtained polyester. If it is less than 0.01% by weight, sufficient releasability cannot be obtained, and if it exceeds 2% by weight, the releasability does not change but mechanical properties such as tensile elongation at break are deteriorated, which is not preferable. In the present invention, the release agent is most preferably after the intrinsic viscosity of the polymer, which is the polyester in the polycondensation reaction, becomes 0.5 or more, preferably 0.65 to 1.2. After the time of reaching 0.75 to 1.0, it is added to the polycondensation reaction system. The intrinsic viscosity of the polymer here is a value measured at 30 ° C. in a phenol / tetrachloroethane (= 1/1 weight ratio) solvent. Since the polycondensation reaction proceeds by being heated and stirred under reduced pressure in a molten state, it is usually preferable to add a release agent when the stirring power corresponding to a predetermined intrinsic viscosity is reached. When the release agent is added when the intrinsic viscosity of the polymer is less than 0.5, the release effect is small, and the release agent may be added to the polycondensation reaction system after the time when the intrinsic viscosity exceeds 1.2. The melt viscosity of the polymer is high, the releasing agent is not sufficiently dispersed in the polymer by stirring, the releasing effect is insufficient, and mechanical properties such as tensile breaking strength and elongation are likely to be deteriorated. In order to uniformly mix the release agent, the polycondensation system is stirred after adding the release agent to the polycondensation reaction system, and the stirring time is usually 5 minutes or more, preferably 5 to 3
It is 0 minutes, more preferably 10 to 20 minutes.

As described above, at the time of polycondensation, a mold releasing agent is added to the reaction system after a specific time point and stirred, so that after the polycondensation, the polyester to which the mold releasing agent is added is not melt-kneaded. Also, a polyester having good releasability can be obtained. Further, by omitting the step of melt-kneading, it is possible to prevent thermal deterioration and contamination of the polymer due to melt-kneading, and prevent deterioration of mechanical strength, particularly breaking elongation and impact strength.

The properties of the release agent at the time of addition are as follows: solid state such as powder or pellets, melt state heated above melting point,
It may be in a slurry state in which it is dispersed in an appropriate solvent such as 1,4BG. The method of adding the release agent is not particularly limited. As an example, when adding to a polymerization tank under reduced pressure, a method of adding from a closed container or an addition tank connected to the polymerization tank by a pressure equalizing tube, a method of adding a release agent using a gear pump, and the like can be mentioned.

In the esterification or transesterification reaction, the polycondensation reaction step and the final stage of the polycondensation reaction, a small amount of other additives may be present in addition to the catalyst and the mold releasing agent. Other additives include phosphoric acid, phosphorous compounds such as phosphorous acid and its esters and metal salts, and alkali or alkaline earth metals such as sodium hydroxide, potassium hydroxide, sodium hypophosphite and sodium benzoate. Compound, 2,6-di-t-butyl-4-octylphenol, pentaerythrityl-tetrakis [3- (3,5-di-t-butyl-
4-hydroxyphenyl) propionate] and the like, and thioether compounds such as dilauryl 3,3′-thio-dipropionate and pentaerythrityl-tetrakis (3-laurylthiopropionate). In addition, a small amount of a silicate compound such as talc or kaolin as a nucleating agent, a core-shell type rubber as a toughness improving agent, and calcium carbonate or glass fiber as a filler / reinforcing agent may be present.

The polyester obtained by melt polymerization may be further solid-phase polymerized. The solid phase polymerization is carried out under reduced pressure or under an inert gas such as nitrogen gas at a temperature not higher than the melting point of the polyester.
In addition, when performing under reduced pressure, the pressure is 5 to 20 torr.
Is preferred. If it is less than 5 torr, the release agent may volatilize, and if it exceeds 20 torr, the polymerization rate is extremely slow.

[0016]

EXAMPLES The present invention will be described in more detail with reference to examples below, but the present invention is not limited to the following examples unless it exceeds the gist thereof. In addition, "part" in the examples
Means "part by weight", and the intrinsic viscosity [η] is 30 in phenol / tetrachloroethane (1: 1 weight ratio).
It is a value measured at ° C. Releasability is cylinder temperature 255
When the molded piece is injection-molded at a mold temperature of 80 ° C and the mold piece is released from the mold with a cooling time of 10 seconds, the mold piece is released from the mold by the pressure sensor attached to the central ejector pin. The pressure sometimes applied, that is, the release resistance value was measured. Tensile rupture elongation is based on ASTM piece cylinder temperature 255
Injection molding at ℃, mold temperature 80 ℃, ASTM D638
It was measured according to.

[Example 1] Production is carried out using a reaction tank with an addition tank. In advance, polyethylene wax [Mitsui Petrochemical's High Wax 100 was used as a release agent in the addition tank.
P] (melting point: 114 ° C., polyethylene wax having an average molecular weight of 900) is added in an amount of 0.3% by weight (relative to the polymer), and the mixture is heated and melted to prepare a melt at 120 ° C. The reaction tank and the addition tank have equal pressures in a pressure equalizing tube, and the mold release agent melt is added to the reaction tank from the addition tank by opening the valve.

Dimethyl terephthalate 19 was used in the reaction tank.
4 parts, 108 parts of 1,4-butanediol and 80 ppm of tetrabutyl titanate (in terms of titanium metal / polymer) were added, and transesterification was carried out at 150 to 210 ° C. for 2.5 hours. After completion of the transesterification reaction, after adding 40 ppm of tetrabutyl titanate further, 210
The polycondensation reaction was carried out under reduced pressure at ˜245 ° C. The pressure was gradually reduced from normal pressure to 0.5 torr over 2 hours, and then maintained at 0.5 torr. Stirring power is [η] 0.80
When the stirring power reached a considerable level, 0.3% by weight of the above polyethylene wax was added to the reaction tank from the additive tank while stirring at 0.5 torr. The stirring was further continued, and when the stirring power reached the stirring power equivalent to [η] 0.85, the pressure was restored and the polymer was extracted. The obtained polymer [η], releasability and tensile elongation at break were measured. The results are shown in Table 1.

Example 2 The procedure of Example 1 was repeated, except that the stirring power for adding the release agent in Example 1 was equivalent to [η] 0.60. Table of results
It is shown in FIG.

Example 3 The procedure of Example 1 was repeated, except that the stirring power for adding the release agent was the same as [η] 0.70. Table of results
It is shown in FIG.

Example 4 The procedure of Example 1 was repeated except that the amount of the release agent was 1.0% by weight. The results are shown in Table 1.

Comparative Example 1 The procedure of Example 1 was repeated except that the release agent was not added. The results are shown in Table 1.

Comparative Example 2 The procedure of Example 1 was repeated, except that 0.005% by weight of the release agent was added. The results are shown in Table 1.

Comparative Example 3 The procedure of Example 1 was repeated except that the release agent was added in an amount of 3.0% by weight. The results are shown in Table 1.

[Comparative Example 4] The same operation as in Example 1 was carried out except that the stirring power for adding the release agent in Example 1 was equivalent to [η] 0.30. Table of results
It is shown in FIG.

Comparative Example 5 The transesterification reaction was carried out in the same manner as in Example 1. After completion of the reaction, 0.3 wt% of polyethylene wax was added under normal pressure. ([Η] of the reaction product immediately after the end of the transesterification reaction is about 0.1) From normal pressure to 0.5 t
Reduce pressure gradually to orr over 2 hours, then 0.5t
Hold at orr. When the stirring power reached a value corresponding to [η] 0.85, the pressure was restored and the polymer was extracted. The results are shown in Table 1.

[0027]

[Table 1]

[0028]

EFFECTS OF THE INVENTION According to the method of the present invention, after the polymerization, even if the polyester to which the release agent is added is not melt-kneaded, the mold release property is excellent, and the mechanical strength, especially the elongation at break and Izod are excellent. Polyester with excellent impact strength can be obtained.

Claims (3)

[Claims] 1. When producing a polyester containing butylene terephthalate as a main repeating unit, 0.01 to 2% by weight based on the obtained polyester after the intrinsic viscosity of the polymer in the polycondensation reaction becomes 0.5 or more.
A method for producing a polyester, which comprises adding the release agent of 1. to a polycondensation reaction system. 2. The method for producing polyester according to claim 1, wherein the release agent is polyethylene wax having a molecular weight of 500 to 4000. 3. The method for producing a polyester according to claim 1, wherein the mold releasing agent is added to the polycondensation reaction system, and then the polycondensation reaction system is stirred for 5 minutes or more.