JPH0643543B2 - Antistatic polyoxymethylene resin composition - Google Patents

Description

TECHNICAL FIELD The present invention relates to a novel polyoxymethylene resin composition, and more specifically, it has excellent thermal stability, mechanical strength and lubricity as well as excellent antistatic properties. The present invention relates to a polyoxymethylene resin composition.

2. Description of the Related Art Polyoxymethylene resins are widely used in, for example, automobile parts, electronic / electric equipment parts, audio equipment parts, etc. because of their excellent mechanical strength, creep properties, lubrication properties, and electrical properties. However, when this is used as a sliding member, various problems in use are recognized due to the generation of static electricity due to friction, so it is often necessary to blend carbon black for the purpose of suppressing this. . However, the addition of carbon black to the polyoxymethylene resin causes undesirable problems such as a decrease in thermal stability, a decrease in fluidity, and a decrease in mechanical strength.

In order to avoid such deterioration of physical properties, low density polyethylene (Japanese Patent Laid-Open No. 53-1113) is used together with the conductive carbon black.
No. 48) or an ethylene oxide adduct of an amide compound (Japanese Patent Publication No. 61-31736) has been proposed, but low-density polyethylene cannot be sufficiently effective unless added in a large amount. It is unavoidable that the desirable physical properties of polyoxymethylene are impaired, and even if ethylene oxide adducts of amide compounds are used together, satisfactory improvement in physical properties is not observed.

On the other hand, it is known to use phosphates, polyphosphates, organic phosphates, organic phosphites, etc. as heat stabilizers for polyoxymethylene resins (Japanese Patent Publication No.
39-14519), these phosphorus compounds are effective when they are mixed alone, but hardly when they are mixed with a conductive carbon black.

Problems to be Solved by the Invention An object of the present invention is to have excellent antistatic properties and
It is to provide a novel polyoxymethylene resin composition having heat stability, mechanical strength, and lubricity superior to those of conventional ones.

Means for Solving the Problems The inventors of the present invention have conducted extensive studies in order to achieve the above-mentioned object, and as a result, together with a conductive carbon black, certain epoxy compounds, organic phosphorus compounds and long-chain alcohols or By blending the propylene oxide adduct with polyoxymethylene at a predetermined ratio, surprisingly, not only the antistatic property is improved, but also lubricity, thermal stability,
It has been found that the fluidity and mechanical strength are also improved, and the present invention has been completed based on this finding.

That is, the present invention is (A) polyoxymethylene resin, (B)
Dibutyl phthalate oil absorption 200ml / 100g or more conductive carbon black, (C) epoxy compound, (D) general formula (Wherein R, R ′ and R ″ are each a hydrogen atom, a methyl group or a methoxy group) and (E) a long-chain alcohol having 8 or more carbon atoms or a propylene oxide adduct thereof. And the content based on the total weight of the composition is (B) component 0.5 to
Antistatic polyoxymethylene resin in the range of 30% by weight, component (C) 0.05 to 10% by weight, component (D) 0.1 to 10% by weight, component (E) 0.5 to 10% by weight A composition is provided.

The polyoxymethylene resin used as the base component of the composition of the present invention can be arbitrarily selected from the commonly used polyoxymethylene and is not particularly limited.

Next, the conductive carbon black blended as the component (B) in the composition of the present invention preferably has a small particle size or a large surface area and a chain structure is developed, but dibutyl phthalate (hereinafter, DBP Oil absorption is 200 ml
/ 100g or more is required. This DBP
The oil absorption is a measure of the degree of development of the carbon black structure, and the DBP oil absorption increases and the conductivity increases as the structure develops. The DBP oil absorption (ml / 100g) is determined by using a certain amount of carbon black stirred by a kneader mixer using an automatic biuret.
It can be determined by titrating with. In this titration, the free-flowing powder at the time of DBP maximum absorption of carbon black (filling of voids) is converted into semi-plastic property and the kneader torque rapidly increases. The required DBP amount (ml) is the DBP oil absorption, which is recognized as the structure index of ASTM D2415-65T. Such DBP oil absorption is 200ml / 100g
With a carbon black of less than, the conductivity is too low and a large amount must be added to impart the desired antistatic performance, and the resulting composition has a mechanical property that the polyoxymethylene resin originally has. It brings about a remarkable decrease in physical properties.

Examples of the conductive carbon black that can be used in the composition of the present invention include Toka Black # 4500 [oil absorption; 230 ml / 100 g, manufactured by Tokai Carbon Co., Ltd.], # 3750 [oil absorption; 245 ml / 100 g, Mitsubishi Kasei Co., Ltd.], KETCHENBLACK EC [oil absorption; 350ml / 100g, manufactured by Lion-Akzo], KETCHENBLACK ECDJ-600 [[oil absorption; 480ml
/ 100g, Lion-Made by Akzo], Prinetex XE2
[Oil absorption amount: 370 ml / 100 g, manufactured by Degussa Co.] and the like can be mentioned, but the invention is not particularly limited thereto.

The blending amount of these conductive carbon blacks should be selected in the range of 0.5 to 30% by weight based on the weight of the composition. If this amount is less than 0.5% by weight, the antistatic property will be insufficient, and if it exceeds 30% by weight, the impact resistance will be significantly reduced. The preferred blending amount is in the range of 2 to 20% by weight.

In the composition of the present invention, the epoxy compound blended as the component (C) is preferably a mono- or polyfunctional glycidyl derivative. Examples thereof include 2-ethylhexyl glycidyl ether, 2-methyloctyl glycidyl ether, lauryl glycidyl ether, stearyl glycidyl ether, behenyl glycidyl ether, methylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether (ethylene oxide unit; 2 ~ 30), propylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether (unit of propylene oxide; 2-3)
0), neobentyl glycol diglycidyl ether,
1,6-hexanediol diglycidyl ether, glycerin diglycidyl ether, glycerin triglycidyl ether, trimethylolpropane diglycidyl ether, trimethylolpropane triglycidyl ether,
Bisphenol A diglycidyl ether, hydrogenated bisphenol A diglycidyl ether, sorbitan monoester diglycidyl ether, sorbitan monoester triglycidyl ether, pentaerythritol triglycidyl ether, pentaerythritol tetraglycidyl ether, diglycerin triglycidyl ether,
Examples thereof include diglycerin tetraglycidyl ether, a condensate of cresol novolac and epichlorohydrin (epoxy equivalent: 100 to 400, softening point: 20 ° C. to 150 ° C.), but are not particularly limited thereto.

These epoxy compounds may be used alone or in combination of two or more, and the compounding amount thereof is 0.05 to 10% by weight, preferably 0.1% by weight based on the weight of the composition. 5. It is selected in the range of ~ 7% by weight.
If this amount is less than 0.05% by weight, the effect as a heat stabilizer is hardly exerted, and if it exceeds 10% by weight, the mechanical strength is significantly reduced. The optimum blending amount is appropriately selected according to the type and the addition amount of the conductive carbon black to be used.

The organic phosphorus compound as the component (D) in the composition of the present invention is selected from the triphenylphosphines represented by the general formula (I), the methyl-substituted triphenylphosphines, and the methoxy-substituted triphenylphosphines. Examples of such a compound include triphenylphosphine and tri-m-
Trilyphosphine, tri-p-tolylphosphine, di-
m-tolylphenylphosphine, di-p-tolylphenylphenylphosphine, m-tolyldiphenylphosphine, p-
Examples thereof include trilyldiphenylphosphine, tri-p-methoxyphenylphosphine, di (p-methoxyphenyl) phenylphosphine, and (p-methoxyphenyl) diphenylphosphine.

These organic phosphorus compounds may be used alone or in combination of two or more. The blending amount is selected in the range of 0.1 to 10% by weight, preferably 0.5 to 7% by weight, based on the weight of the composition. If this amount is less than 0.1% by weight, the effect as a heat stabilizer is hardly exerted, while if it exceeds 10% by weight, the mechanical properties are significantly deteriorated. The optimum blending amount of the organophosphorus compound is appropriately selected depending on the kinds and addition amounts of the conductive carbon black and the epoxy compound used.

In the composition of the present invention, a long chain alcohol having 8 or more carbon atoms, preferably 8 to 50 carbon atoms, or a propylene oxide adduct thereof is used as the component (E). If the carbon number becomes too large, the lubricity of the obtained composition will be impaired. The long chain alcohol may be linear or branched, saturated or unsaturated. Examples of such products include octyl alcohol, capryl alcohol, nonyl alcohol, decyl alcohol, undecyl alcohol, lauryl alcohol, tridecyl alcohol, myristyl alcohol, pentadecyl alcohol, cetyl alcohol, heptadecyl alcohol, stearyl alcohol, oleyl alcohol. , Nonadecyl alcohol, eicosyl alcohol, behenyl alcohol, ceryl alcohol, melysyl alcohol, 2-hexyldecanol,
2-Isoheptylisoundecanol, 2-octyldodecanol, 2-decyltetradecanol, 2-cetylstearyl alcohol, Uniline alcohol # 425, Uniline alcohol # 550, Uniline alcohol # 770 (Uniline alcohol; Manufactured by Toyo Ink Co., Ltd., etc.

Further, a propylene oxide adduct of a long-chain alcohol having 8 or more carbon atoms is added to the alcohol in an amount of 1 to 10 per 1 mol.
The one to which 0 mol of propylene oxide is added is preferable. Examples of such compounds include the general formula RO (C ₃ H ₆ O) _n H (II) (wherein RO is an alkoxy group having 8 or more carbon atoms, and n is 1 to 10).
A number of 0), in which R corresponds to the residues of various long-chain alcohols described above.

The above long-chain alcohols and propylene oxide adducts thereof may be used alone or in combination of two or more.

The long-chain alcohol or the propylene oxide adduct thereof as the component (E) in the composition of the present invention has an effect of improving the lubricity of the composition, and its compounding amount is 0 based on the weight of the composition. It is selected in the range of 0.5 to 10% by weight. If this amount is less than 0.5% by weight, the effect of improving the lubricity is hardly exhibited, while if it exceeds 10% by weight, the mechanical properties are significantly deteriorated. The optimum blending amount is appropriately selected in consideration of the desired balance of lubricity and mechanical properties.

Examples of the polyoxymethylene resin in the composition of the present invention include polyoxymethylene homopolymers and polyoxymethylene copolymers or terpolymers mainly composed of oxymethylene chains, such as formaldehyde or a cyclic oligomer of formaldehyde such as trioxane and tetraxane. Stabilized against decomposition from the end, obtained by polymerizing or copolymerizing a comonomer copolymerizable therewith or alone, usually with a stabilizer or an antioxidant added Is used.

The composition of the present invention is prepared by melt-kneading each of the components (A) to (E) by using a known device that is usually used for kneading a resin melt such as a kneader, a roll mill, and an extruder. be able to.

An extruder is most suitable as a melt-kneading device from the viewpoint of blocking oxygen and working environment. Types of this extruder include uniaxial, biaxial, vented, and no vent, and the composition of the present invention can be prepared by any extruder. The mixing temperature is not lower than the melting point of the polyoxymethylene resin used, and it can be sufficiently extruded at a temperature usually used in the range of 180 ° C to 230 ° C. The time required for kneading is almost the same as the time required for extruding the polyoxymethylene resin alone, and is sufficient.

Although the kneading conditions for preparing the composition of the present invention have been described above, the kneading method and conditions are not limited to the above, and there are known methods and conditions used for preparing a polyoxymethylene composition. Any one can be used from the inside.

In the composition of the present invention, if desired, various additives conventionally used in ordinary polyoxymethylene compositions, for example, pigments,
Fillers, lubricants, etc. can be added.

EFFECT OF THE INVENTION The composition of the polyoxymethylene resin of the present invention is prepared by blending a polyoxymethylene resin with an electrically conductive carbon black, an epoxy compound, an organic phosphorus compound and a long chain alcohol or a propylene oxide adduct thereof. , A composition that retains the antistatic property of the conductive carbon black as it is, greatly improves the thermal stability and lubricity deterioration of the polyoxymethylene resin due to the conductive carbon black, and retains the mechanical strength of the polyoxymethylene resin. is there.

The organophosphorus compound used in the composition of the present invention has a function as a catalyst for promoting the reaction between the epoxy compound and the surface of the conductive carbon black, mainly the carboxylic acid group, and the conductive carbon black and the epoxy compound. The effect of the present invention is not sufficiently exhibited by the combination of only the above, and the effect is hardly exhibited by the combination of only the conductive carbon black and the organic phosphorus compound. further,
The long-chain alcohol and the propylene oxide adduct of the long-chain alcohol serve as a particularly effective lubricant in the system of polyoxymethylene resin / conductive carbon black / epoxy compound / organophosphorus compound.

EXAMPLES Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

Each characteristic of the composition was obtained as follows.

(1) ST value Injection molding machine with a cylinder temperature of 230 ℃ [Arburg Allrounder
100; manufactured by Western Trading Co., Ltd.] When a resin composition is retained to form a molded piece of 12 × 3 × 120 mm, a silver streak occurs on 2/3 of the surface of the molded piece. (Min) was taken as the ST value.

(2) Ra Value The weight residual ratio (%) when the composition was heated in air at 230 ° C. for 120 minutes was taken as the Ra value.

(3) Surface electrical resistance The composition was molded into a molded piece of 130 × 110 × 3 mm by the injection molding machine, and the molded piece and an insulation resistance measurement sample box TR-42 (manufactured by Takeda Riken) were measured.

(4) Friction coefficient The composition was molded into a cylindrical molded piece having an inner diameter of 20 mm, an outer diameter of 25.7 mm and a depth of 17 mm with the above molding machine, and a mating material S45C was used with a thrust type friction wear tester (manufactured by Toyo Seiki Seisakusho). , Surface pressure 10
It was measured under the conditions of kg / cm ² and linear velocity of 12 cm / sec.

(5) Abrasion amount The composition is molded into a cylindrical molded piece having an inner diameter of 20 mm, an outer diameter of 25.7 mm, and a depth of 17 mm with the above molding machine, and a mating material S45C is applied by a thrust type friction wear tester (manufactured by Toyo Seiki Seisakusho). , Surface pressure 2kg
/ Cm ² and linear velocity 60 cm / sec.
The wear amount (mm) at 0 km was measured.

Examples 1 to 12 Polyoxymethylene resin copolymer [Tenatsk-C7510
(Melt index 30 g / 10 min); Asahi Kasei Co., Ltd.) crushed product, conductive carbon black, epoxy compound, organic phosphorus compound and long chain alcohol or propylene oxide adduct of long chain alcohol, After mixing with a Hensiel mixer in the mixing ratio shown in the table,
Pelletization was carried out by kneading at a rotation speed of 150 rpm with a 30 mmφ twin-screw extruder with the cylinder temperature set at 190 ° C. The ST value and Ra value (described above) of this pellet were measured, and the test piece was molded with a molding machine, and the flexural modulus, surface electrical resistance, friction coefficient, and wear amount were measured. The results are shown in Tables 1 to 3.

Comparative Examples 1 to 12 Polyoxymethylene resin [TENAKU-C7510 (copolymer, melt index 30 g / 10 minutes) or TENAKU
7010 (Homopolymer, melt index 30g / 10
Min); Asahi Kasei Co., Ltd.] crushed product, conductive carbon black, epoxy compound, organic phosphorus compound, ester lubricant, stearic acid diethanolamide, low density polyethylene, long chain alcohol, as shown in Tables 4 to 6. After mixing with a Hensiel mixer in the mixing ratio shown, the mixture was kneaded with a 30 mmφ twin-screw extruder having a cylinder temperature of 190 ° C. at a rotation speed of 150 rpm to form a pellet. The pellet ST value and Ra value (described above) were measured, and the test piece was molded with a molding machine, and the flexural modulus, surface electric resistance, friction coefficient, and wear amount were measured. The results are shown in Tables 4-6.

Examples 13 to 16 Polyoxymethylene resin homopolymer [TENAK 7010]
(Melt index 30 g / 10 min); Asahi Kasei Co., Ltd.) crushed product, conductive carbon black, epoxy compound, organic phosphorus compound and long chain alcohol, propylene oxide adduct of long chain alcohol are shown in Table 7. After mixing with a Hensiel mixer in the mixing ratio shown, the mixture was kneaded with a 30 mmφ twin-screw extruder having a cylinder temperature of 190 ° C. at a rotation speed of 150 rpm to form a pellet. The ST value and Ra value (described above) of this pellet were measured, and the test piece was molded with a molding machine, and the flexural modulus, surface electrical resistance, friction coefficient, and wear amount were measured. The results are shown in Table 7.

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Claims (1)

[Claims] 1. A polyoxymethylene resin (A), (B) dibutyl phthalate oil absorption 200 ml / 100 g or more conductive carbon black, (C) epoxy compound, (D) general formula (Wherein R, R ′ and R ″ are each a hydrogen atom, a methyl group or a methoxy group) and (E) a long-chain alcohol having 8 or more carbon atoms or a propylene oxide adduct thereof. And the content based on the total weight of the composition is (B) component 0.5 to
Antistatic polyoxymethylene resin in the range of 30% by weight, component (C) 0.05 to 10% by weight, component (D) 0.1 to 10% by weight, component (E) 0.5 to 10% by weight Composition.