JP3365436B2 - Polyester production method - Google Patents

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 containing butylene terephthalate as a main repeating unit, and more specifically, to heat resistance, moldability such as releasability and fluidity, and Izod impact value and elongation at break. The present invention relates to an inexpensive method for producing polyester having excellent mechanical strength.

[0002]

2. Description of the Related Art Polybutylene terephthalate (hereinafter referred to as P
BT) is a resin that has well-balanced physical properties such as mechanical properties, electrical properties, and heat resistance, and is widely used as electrical / electronic parts such as connectors and coil bobbins, and automobile parts such as distributor caps. .

In molding PBT, it is usually necessary to add additives such as a release agent and an antioxidant. Therefore, a method of kneading various compounding agents into PBT prior to molding has been usually practiced. However, there has been a problem that considerable heat deterioration occurs even when the additive is kneaded, resulting in a decrease in mechanical strength. Therefore, in order to omit the step of kneading these additives, it has been considered to add the additives during the polymerization of PBT.

However, when both the release agent and the antioxidant are added at the same time during the polymerization, the polymerization reaction is hindered due to the interaction of the additives, and the intended effect cannot be obtained, which is a problem in practice. It was Therefore, even when one of the release agent and the antioxidant is added during polymerization,
After all, the other additive had to be kneaded later.

[0005]

The object of the present invention is to prevent the polymerization reaction from being hindered by the addition of necessary additives including a mold release agent and an antioxidant during the polymerization. It is an object of the present invention to provide a method for producing a polyester containing butylene terephthalate as a main repeating unit, which does not require a step of kneading additives.

[0006]

The present invention has been made to solve the above-mentioned problems, and its gist is to provide a melt polycondensation reaction system in the production of a polyester having butylene terephthalate as a main repeating unit to a thioether system. A method for producing a polyester having butylene terephthalate as a main repeating unit, characterized in that an antioxidant, a hindered phenolic antioxidant and a polyethylene releasing agent having an average molecular weight of 500 to 2800 are present.

The present invention will be described in detail below. A polyester containing butylene terephthalate as a main repeating unit is usually obtained by subjecting an oligomer obtained by an esterification reaction or transesterification reaction of a terephthalic acid derivative such as terephthalic acid or dimethyl terephthalate and 1,4 butanediol to a polycondensation reaction. Manufactured by The polyester containing butylene terephthalate as the main repeating unit may contain other copolymerization components. These copolymer components include ethylene glycol, propylene glycol, hexamethylene glycol, bisphenol A, ethoxylated bisphenol A,
Or glycol component such as halide thereof, dicarboxylic acid such as isophthalic acid, naphthalenedicarboxylic acid, adipic acid, pentaerythritol, trimethylolpropane, trimellitic acid, oxybenzoic acid, oxynaphthalene acid, or halide thereof And the polyfunctional compound component, a polymer component having a functional group capable of reacting with polyester such as polyethylene glycol and polytetramethylene glycol to form a copolymer, and the like. The content of the copolymerization component in the polyester is usually 0 to
It is 25% by weight.

The method for producing the polyester in the present invention is carried out by an esterification reaction or transesterification reaction and then a melt polycondensation reaction according to a conventional method.
As the catalyst for the esterification or transesterification reaction, a titanium alcoholate compound is usually used, and specific examples thereof include tetrabutyl titanate, tetraisopropyl titanate, and tetramethyl titanate. As the catalyst in the melt polycondensation reaction, the catalyst used in the above-mentioned esterification or transesterification reaction is used as it is, and antimony or germanium oxide or the like may be added if necessary.

In addition, in the melt polycondensation reaction, a small amount of other known reaction aid other than the polycondensation reaction catalyst may be added to the reaction system. Other additives include, for example, phosphorus compounds such as phosphoric acid, phosphorous acid, hypophosphorous acid, metal salts thereof, and esters thereof. Here, the esterification or transesterification reaction is usually 120 to 250.
C., preferably 150 to 220.degree. C., and the melt polycondensation reaction is usually 200 to 300 at a reduced pressure of 3 torr or less.
It is performed at 2 ° C. for 2 to 4 hours.

The polyester taken out as a melt after the melt polycondensation reaction may be solidified by cooling and then comminuted, and the comminuted polyester may be solid-phase polymerized under reduced pressure or in an inert gas atmosphere. The present invention is characterized in that a specific release agent and two specific antioxidants are present in the melt polymerization reaction system.

The inventors of the present invention, in the case of combining these additives, do not inhibit the polymerization reaction and do not adversely affect each other, even if the additives are added during the polymerization, and It was found that the desired effect can be obtained in the finally obtained polyester. The release agent present in the melt polymerization reaction system is a polyethylene-based release agent having an average molecular weight of 500 to 2800. If the average molecular weight is 500 or less, the mold releasability is lowered and the molded piece is deformed. On the other hand, if the average molecular weight is 2800 or more, the mold releasability at the time of injection molding becomes unfavorable. A particularly preferable average molecular weight is 600 to 2500. The average molecular weight as referred to herein is Mv = 2.51 by measuring the intrinsic viscosity of the decalin solution of the polyethylene-based release agent at 135 ° C.
× 10 ⁴ [η] It is a value obtained by conversion by ^1.235 .
(However, in the above formula, Mv is the average molecular weight [η]
Means intrinsic viscosity. ) The amount of the polyethylene-based release agent used is 0.0 with respect to the polyester finally obtained.
It is 1 to 2% by weight, preferably 0.05 to 1.0% by weight, and most preferably 0.1 to 0.5% by weight. If this amount is too small, moldability and dimensional stability become poor,
On the other hand, if the amount is too large, the heat resistance or mechanical strength of the polyester itself is lowered, which is not preferable.

The antioxidants to be present in the melt polymerization reaction system are thioether type antioxidants and hindered phenol type antioxidants. The thioether-based antioxidant may be one having a thioether bond in the molecular structure, for example, dilauryl thiodipropionate,
Examples thereof include distearyl thiodipropionate and 3-dodecyl thiopropionic acid, and pentaerythritol tetrakis (β-lauryl thiopropionate) is particularly preferable.

The amount of the thioether-based antioxidant used is 0.01 to 2% by weight, preferably 0.05 to 1.0% by weight, and most preferably 0.1 to 2% by weight based on the finally obtained polyester. It is 0.6% by weight. If this amount is small, the effect as an oxidation stabilizer is insufficient, while if it is too large, the heat resistance or mechanical strength of the polyester itself is reduced, which is not preferable.

Examples of the hindered phenolic antioxidant include 2,4,6-tri-tert-butylphenol,
1,3,5-tris-methyl-2,4,6-tris (3,5-di-tert-butyl-4-hydroxy-benzyl) benzene and the like can be mentioned, but tetrakis [methylene-3 (3,5- Ditert-butyl-4-hydroxy-phenyl) propionate] methane is particularly preferred.

The amount of the hindered phenolic antioxidant used is 0.005 with respect to the polyester finally obtained.
% To 1% by weight, preferably 0.01 to 0.5% by weight, most preferably 0.02 to 0.3% by weight. If this amount is small, the effect as an antioxidant is insufficient, while if it is too large, the heat resistance or mechanical strength of the polyester itself is lowered, which is not preferable.

The release agent and antioxidant to be present in the melt polycondensation reaction system may be added during the esterification reaction or transesterification reaction, but are preferably added immediately before the polycondensation reaction. In addition, it is preferable that a releasing agent and an antioxidant be mixed at the time of addition, and the mixture be heated to a melting point or higher and added as a melt.

[0017]

EXAMPLES The present invention will be described in more detail with reference to examples below, but the present invention is not limited to these examples as long as the gist thereof is not exceeded. The respective measuring methods carried out in the following examples and comparative examples are shown below. [[Η], (intrinsic viscosity of prepolymer and polyester)] 30 in a solvent of phenol: tetrachloroethane = 1: 1
It was measured at ° C.

[Elongation at Break] Measured according to ASTM D-638. [Izod impact value] Measured according to JIS-K-6719.

[Heat resistance] The polymer is heated in a gear oven in a chip state to 180 ° C. and air-dried for 24 hours, and the b value is increased and decreased before and after the treatment by Nippon Denshoku Industries Co., Ltd. “colorimetric color difference meter” It was measured at.

[Release Resistance Value] Cylinder temperature of 255 ° C.,
When releasing the molded piece from the mold by injection molding at a mold temperature of 80 ° C and releasing the molded piece from the mold with a cooling time of 10 seconds, using a pressure sensor attached to the central ejector pin. The pressure was measured.

Example 1 To 100 parts by weight of dimethyl terephthalate, 1.2 times mol of 1,4-butanediol was added, and 106 ppm of tetrabutyl titanate was added as a catalyst (based on the amount of dimethyl terephthalate as titanium metal). 150 ℃ ~
The transesterification reaction was carried out at 215 ° C. for 3.5 hours. To this reaction product, 0.01% by weight of sodium hypophosphite / monohydrate, based on the finally obtained polyester containing butylene terephthalate as a main repeating unit, a hindered phenolic antioxidant [Ciba Geigy] Manufactured by
Irganox 1010] 0.06% by weight, thioether-based antioxidant [Cypro Kasei Co., Ltd., Seenox
412S (pentaerythritol-tetrakis (β-lauryl thiopropionate))) was used as a mold release agent (high wax 100P, manufactured by Mitsui Petrochemical Co., Ltd.) containing 0.2 wt% of polyethylene wax having an average molecular weight of 900. In order to obtain a prepolymer, a melt polycondensation reaction was performed at 215 to 245 ° C. under reduced pressure of 3 torr or less. The polymerization time and [η] of the prepolymer at this time are shown in Table 1. The obtained prepolymer is 3 t
solid-state polymerization reaction at 195 ° C. under reduced pressure of orr,
A polyester having [η] = 1.04 was obtained. Table 1 shows the breaking elongation, Izod impact value, heat resistance, and release resistance of the obtained polyester.

Example 2 As a release agent in Example 1, 0.3 wt% of polyethylene wax having an average molecular weight of 900 was used instead of 0.3% by weight.
Example 1 except that 0.3% by weight of polyethylene wax No. 00 [high wax 200P manufactured by Mitsui Petrochemical Co., Ltd.] was used.
Polymerization was performed in exactly the same manner as in (1) to obtain a prepolymer and a polyester having [η] = 1.03 after solid phase polymerization. The results of measuring these physical properties are shown in Table 1.

Comparative Example 1 Instead of the thioether-based antioxidant in Example 1, a phosphite-based antioxidant [Adeka Stab 2112 (Tris (2,4-di-tert-butylphenyl) phos, manufactured by Asahi Denka Co., Ltd.] was used. [Fight)] Polymerization was carried out in the same manner as in Example 1 except that 0.2% by weight was used to obtain a prepolymer and a polyester having [η] = 1.05 after solid-phase polymerization. The results of measuring these physical properties are shown in Table 1.

Comparative Example 2 Instead of the thioether antioxidant in Example 1, a phosphite antioxidant [Adeka Stab TPP (triphenylphosphite), manufactured by Asahi Denka Co., Ltd.] 0.2
Polymerization was carried out in exactly the same manner as in Example 1 except that the amount was used in a weight ratio, but a sufficient polymerization rate could not be obtained. The polymerization results of the prepolymer are shown in Table-1.

Comparative Example 3 Polymerization was carried out in the same manner as in Example 1 except that the thioether type antioxidant was not added in Example 1 to obtain a prepolymer and a polyester of [η] = 1.03 after solid phase polymerization. It was The results of measuring these physical properties are shown in Table 1.

Comparative Example 4 Example 3 was repeated except that 0.3 wt% of paraffin wax having an average molecular weight of 450 (155 ° F wax, manufactured by Nippon Seiro Co., Ltd.) was used in place of the polyethylene wax having an average molecular weight of 900 in Example 1. Polymerization was performed in the same manner as in Example 1 to obtain a prepolymer and a polyester having [η] = 1.04 after solid phase polymerization. The results of measuring these physical properties are shown in Table 1.

Comparative Example 5 A polyethylene wax having an average molecular weight of 4000 was used instead of the polyethylene wax having an average molecular weight of 900 in Example 1 [Hiwax 400P manufactured by Mitsui Petrochemical Co., Ltd.].
Polymerization was performed in the same manner as in Example 1 except that 0.3% by weight was used to obtain a prepolymer and a polyester having [η] of 1.05 after solid-phase polymerization. The results of measuring these physical properties are shown in Table 1.

Comparative Example 6 A polypropylene wax having an average molecular weight of 3000 was used in place of the polyethylene wax having an average molecular weight of 900 in Example 1 [Viscole 660P manufactured by Mitsui Kasei Co., Ltd.] 0.3.
Polymerization was carried out in the same manner as in Example 1 except that the amount by weight was used to obtain a prepolymer and a polyester having [η] of 1.03 after solid-phase polymerization. The results of measuring these physical properties are shown in Table 1.

Comparative Example 7 Melt polymerization and solid phase polymerization were carried out in the same manner as in Example 1 except that the thioether antioxidant and the releasing agent were not used, and [η] = 1. To the polyester of No. 04, a thioether antioxidant [Seenox 412S] was added to the polyester in an amount of 0.2% by weight, and a releasing agent [HIWAX 100P] was added in an amount of 0.3% by weight, using a biaxial kneader. . Table 1 shows the results of measuring the physical properties of the compound product.

Comparative Example 8 [η] = 1 obtained by carrying out melt polymerization and solid phase polymerization in exactly the same manner as in Example 1 except that the thioether-based antioxidant and the release agent were not used. The physical properties of the polyester of 0.04 were measured. The results are shown in Table-1. Table-
It can be seen from 1 that when a thioether-based oxidation stabilizer, a hindered phenol-based antioxidant and a polyethylene wax having a specific molecular weight are used in combination, the polymer has good strength, heat resistance and releasability.

[0031]

[Table 1]

[0032]

Industrial Applicability According to the method of the present invention, the polymerization reaction is not hindered, and the kneading step of adding the antioxidant and the mold releasing agent can be omitted, and the polyester resulting from thermal deterioration during kneading is obtained. It is possible to avoid a decrease in the mechanical strength of the resin, particularly a decrease in the elongation at break and the Izod impact value. Further, by omitting the kneading step, a great saving of manufacturing cost can be achieved.

Claims (2)

(57) [Claims] 1. A thioether-based antioxidant, a hindered phenol-based antioxidant and an average molecular weight of 500 to 280 are used in a melt polycondensation reaction system in the production of a polyester containing butylene terephthalate as a main repeating unit.
A method for producing a polyester containing butylene terephthalate as a main repeating unit, characterized in that a polyethylene-based releasing agent of 0 is present. 2. A melt polycondensation reaction system in the production of a polyester containing butylene terephthalate as a main repeating unit, to the polyester finally obtained,
0.01 to 2% by weight of thioether antioxidant, 0.
01 to 1 wt% hindered phenolic antioxidant and 0.01 to 2 wt% average molecular weight 500 to 28
A method for producing a polyester having butylene terephthalate as a main repeating unit, characterized in that a polyethylene-based release agent of No. 00 is present.