JPH1030054A - Polyester resin composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyester resin composition which retains the excellent physical properties of polyethylene terephthalate resin with reduced content of corrosive volatile components, for example, tetrahydrofuran. SOLUTION: A polyester resin containing at least 90mol%, based on the whole acid components, of an aromatic dicarboxylic acid or its ester-forming derivative and at least 90mol%, based on the whole diol components, of 1,4- butanediole contains titanium in an amount of 15-300ppm calculated in its elementary form, phosphorus at a molar ratio of 0.5-1.5 to the titanium, an alkali metal at a molar ratio of 1.6-4.6 to the phosphorus or an alkaline earth metal at a molar ratio of 0.8-2.3 to the phosphorus element.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resin used for a compound molded product mainly used for electric parts and housings. More specifically, the present invention relates to a polyester resin composition which generates a small amount of gas from molded articles when used for housings for electric / electronic parts and lighting, and is highly effective in suppressing poor contact in electric parts and preventing fogging in lighting.

[0002]

2. Description of the Related Art Polyester resins, especially polybutylene terephthalate (hereinafter abbreviated as PBT) resins containing terephthalic acid and 1,4-butanediol as main components are crystalline resins. Because of its excellent mechanical strength, electrical properties, chemical properties, and physical properties as a plastic resin, it is used as an engineering plastic in a wide range of applications such as automobiles, electric and electronic parts. Also, it has excellent fragrance retention and gas barrier properties against water vapor and the like, and is used for containers, films and the like for foods and cosmetics.

[0003] However, PBT has a problem in the molding process that, when heated in a molten state, the resin is decomposed and gas or sublimate is generated, which causes voids in a molded product, May adhere to molds and molding machines and cause contamination and corrosion.

[0004] Further, even when PBT is used as a molded product in various applications, it generates gas such as tetrahydrofuran (hereinafter referred to as THF) in applications used in a high-temperature environment, so that PBT is used for relays, switches, connectors and the like. When used as electrical or electronic components, it may cause problems such as contaminating or corroding metal contacts, or causing fogging due to gas when used in lighting applications such as automotive headlight reflectors. It has been known.

Further, in the actual production process, the resin molding operation is not always performed in a place where the exhaust equipment is good, and the resin is melted by the intermittent molding operation into the molding machine for a long time. The generation of gas and sublimate generated due to time stagnation is serious, and improvement is desired.

In addition, containers for foods, beverages, cosmetics, etc.
When used for a packaging film or the like, the odor may be transferred to the contents, the taste may be impaired, and THF, which is a main component of gas, may have a bad effect on the human body.

As a countermeasure, a method of removing volatile components from a molded article by performing a heat treatment or a reduced pressure treatment after molding has been adopted. However, since the cost is increased due to an increase in the number of steps, the volatile component is reduced. A PBT resin composition has been desired.

The present inventors have previously proposed a method for improving the PBT resin in order to suppress the amount of gas containing THF as a main component by using a titanium compound and a tin compound together as a catalyst for polymerizing the polyester. Was found, and a patent application was filed earlier, but further research revealed a more effective resin composition and completed the present invention.

The present invention is directed to a PBT resin which maintains excellent physical properties of a PBT resin and has little corrosive volatile components such as THF even during or after molding.
It is intended to provide a resin.

[0010]

The present invention comprises an aromatic dicarboxylic acid or an ester-forming derivative thereof in an amount of at least 90 mol% of the acid component and 1,4-butanediol in an amount of at least 90 mol% of the diol component. In the polyester resin, titanium has an elemental amount of 150 to 300 ppm, phosphorus has a molar ratio to titanium of 0.4 to 1.5, and alkali metal has a molar ratio of 1.6 to 4.6 or alkaline earth metal. A polyester resin composition characterized by being contained in a molar ratio to phosphorus in the range of 0.8 to 2.3.

A feature of the present invention is that by adding titanium, phosphorus, and an alkali or alkaline earth metal to a resin composition for a molding material, mainly PBT, the corrosive property mainly composed of THF is obtained. It is a high quality resin that suppresses the generation of volatile gases and reduces the amount of THF generated during molding and in the environment in which the material is used.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION In the polyester resin composition of the present invention, at least 90 mol% of the acid component is composed of terephthalic acid or an ester-forming derivative thereof, and at least 90 mol% of the diol component is 1,4. A polyester resin composed of butanediol and containing a copolymer component in a range not exceeding 10 mol%.

Examples of copolymerizable acid components which can be used in an amount not exceeding 10 mol% include phthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid, adipic acid,
Sebacic acid, azelaic acid, succinic acid and their forming derivatives can be mentioned, and as the copolymerized diol component, ethylene glycol, propylene glycol, neopentyl glycol, 1,5-pentadiol, 1,6- Hexanediol, cyclohexanediol and the like can be mentioned. These copolymer components can be used alone or in combination of two or more.

The polyester resin composition of the present invention contains titanium in an elemental amount of 150 to 300 ppm. Titanium is generally used as a compound of titanium tetrabutoxide as a transesterification and polycondensation catalyst when obtaining PBT, but is not limited to titanium tetrabutoxide, but in the form of titanium oxide or other titanium compounds. ,
It may be contained as an additive other than the catalyst.

The amount of the titanium element in the resin is related to the amount of the phosphorus compound added at the same time.
If it does not exceed 300 ppm, the effect as a catalyst is small and an industrially sufficient reaction rate cannot be obtained.
In the case of exceeding, the effect as a catalyst is sufficiently exhibited, but the reddish brown coloring characteristic of a titanium catalyst is remarkable in the obtained polyester resin, and depending on polymerization conditions, the fluidity of the resin due to gelation is reduced, and Degradation due to thermal decomposition lowers the color tone, and in some cases, does not reach a predetermined degree of polymerization.

Further, the polyester resin composition of the present invention contains phosphorus. Its amount is from 0.4 to 1.5 as a molar ratio to titanium. If the molar ratio of phosphorus to titanium is less than 0.4, there is no substantial effect in suppressing the generation of gas containing THF as a main component.
If it exceeds 0, the catalytic activity of the titanium compound added as a catalyst is reduced, so that the reaction is suppressed and a predetermined degree of polymerization may not be obtained.

Phosphorus is a phosphate compound such as trimethyl phosphate, triphenyl phosphate or the like;
A high molecular weight compound having a melting point of 200 ° C. or higher is added in a polymerization step as a catalyst or in a compounding step as an additive. In particular, the amount of the phosphorus compound is an important factor because the phosphorus compound is effective in suppressing the generation of gas in the resin composition to be produced.

In the present invention, an alkali or alkaline earth metal is added to the polyester resin composition in addition to the titanium and phosphorus. It is considered that the addition of these metals exerts a synergistic effect with phosphorus to contribute to the prevention (suppression) of the generation of THF, and also has the effect of compensating the deactivation of the titanium catalyst, which is reduced by the addition of phosphorus. Conceivable.

When an alkali metal is used among the alkali or alkaline earth metals, the molar ratio to phosphorus is preferably in the range of 1.6 to 4.6. When an alkaline earth metal is used, the molar ratio to phosphorus is preferably in the range of 0.8 to 2.3. When two or more of these are used, an appropriate ratio according to the mixing ratio is used.

The molar ratio of alkali metal to phosphorus is 1.
If it is less than 6, there is no practical effect in terms of suppression of gas generation and reactivity, and if it exceeds 4.6, on the contrary, although the reactivity increases, it is not possible to obtain a good resin such as color tone. In some cases, thermal decomposition at the end of polycondensation is promoted to make it difficult to reach a predetermined degree of polymerization. Also, when an alkaline earth metal is used, the molar ratio to phosphorus is 0.8%.
Outside the range of ~ 2.3, the same problem as in the case of alkali metal occurs.

The polyester resin composition of the present invention comprises:
The amount of THF generated when treated at 50 ° C. for 120 hours is 100 ppm or less, the thermal discoloration (ΔE) is 20 or less,
It is preferable that the breaking strength retention after treatment in saturated steam at 2 ° C. and 2 atm for 72 hours is 40% or more.

In the polyester resin composition of the present invention having the above composition, the generation of THF is significantly suppressed. TH
The generation amount of F is 150 ° C.
Is preferably 100 ppm or less when treated for 120 hours. TH at 150 ° C for 120 hours
When the amount of F generation exceeds 100 ppm, when used as an application under relatively high temperature environment such as a headlight reflector of an automobile or an electric part such as a connector, a metal contact made of gas containing THF as a main component. Continuity failure, fogging of the lighting cover, etc., and the appropriate range for practical use tends to be extremely limited.

The polyester resin composition of the present invention preferably has a thermal discoloration (ΔE) of 20 or less. Δ
An increase in E means coloring in the process of obtaining a molded article from the resin composition, and the higher the value of ΔE, the stronger the coloring, and when a molded article is used, the appearance during use is impaired, and the commercial value is significantly reduced. Preferably it does not exceed at most 20.

Furthermore, the polyester resin composition of the present invention preferably has a breaking strength retention of 40% or more when treated in saturated steam at 120 ° C. and 2 atm for 72 hours. These evaluation conditions are indices of the strength retention performance of the molded article of the polyester resin composition of the present invention under the use environment. When the retention strength at break is less than 40%, the life as an electric component or a lighting component is remarkably increased. It tends to be restricted.

The polyester resin composition of the present invention comprises
If necessary, pigments such as titanium oxide, silica and kaolin, inorganic additives having a lubricating effect, and modifiers such as glass fiber and talc can be contained.

[0026]

The present invention will be described below with reference to examples. The physical properties listed in the table were evaluated by the following methods.

[Measurement of Generated Gas and Amount Generated] An ASTM No. 1 tensile test piece was prepared under a certain condition using an injection molding machine, and this was pulverized to a certain particle size to obtain a sample.
Take 5 g of sample, 150 ml in 20 ml headspace
After standing at 2 ° C. for 2 hours, the generated gas was measured by gas chromatography, and the weight of the generated gas was shown by ppm with respect to the weight of the sample.

[Thermal discoloration (ΔE)] 100
A mm square plate was prepared and measured by a method specified in JIS Z-8730.

[Strength Retention] An ASTM No. 1 tensile test piece was prepared under a certain condition using an injection molding machine, set in a pressure cooker, and treated at 120 ° C. in saturated steam at 2 atm for 72 hours. The breaking strength was measured, and the strength retention was calculated by the following equation. Strength retention (%) = (rupture strength after treatment / rupture strength before treatment) × 100

[Examples 1 to 9] and [Comparative Examples 1 to 6] A reaction vessel equipped with a stirrer and a distillation column was sufficiently purged with nitrogen, and then 246 parts by weight of dimethyl terephthalate and 1,4-butanediol 145 were obtained. Parts by weight and the amounts of titanium butoxide, trimethyl phosphate, and sodium acetate shown in Table 1,
Potassium acetate, magnesium acetate, and calcium acetate were charged, and the temperature was gradually raised to distill off methanol as a by-product.

When the distilled methanol exceeds 90% of the theoretical amount, the temperature of the reactants is raised to 200 ° C., and then the mixture is transferred to a polycondensation reaction vessel, and 0.5 Torr for 1 hour.
Then, the reaction temperature was raised to 250 ° C., and stirring was continued in this state until a predetermined degree of polymerization was obtained. Thereafter, the mixture was discharged into a sheet, cooled and cut to obtain pellets.

About the obtained polyester resin, THF
The gas generation amount, thermal discoloration (ΔE), and strength retention after the pressure cooker treatment were measured by the methods described above. The results are collectively shown in Table 1.

[0033]

The polyester resin composition of the present invention, electric parts, lighting, etc., have a relatively low temperature in use environments and a small amount of gas generated during molding, and have a practically good color tone and strength retention. It has extremely excellent performance and further expands the range of application of the polyester resin material.

[Table 1]

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yasunori Shirai 2-1-1, Ushikawa-dori, Toyohashi-shi, Aichi Pref.

Claims (1)

[Claims] 1. An aromatic dicarboxylic acid or an ester-forming derivative thereof comprising at least 90 mol% of an acid component,
Butanediol at least 90 mol% of the diol component
In the contained polyester resin, titanium is 15
0 to 300 ppm, phosphorus in a molar ratio of 0.1 to titanium.
4 to 1.5, the molar ratio of alkali metal to phosphorus is 1.
A polyester resin composition comprising 6 to 4.6 or an alkaline earth metal in a molar ratio to phosphorus in the range of 0.8 to 2.3.