JPH0380819B2 - - Google Patents

Description

[Detailed description of the invention]

Industrial Application Field The present invention provides novel polyoxymethylene compositions,
More specifically, along with excellent antistatic properties,
The present invention relates to a polyoxymethylene composition having excellent thermal stability, mechanical strength and lubricity. Conventional technology Polyoxymethylene has excellent mechanical strength,
Because it has creep properties, lubricating properties, and electrical properties, it is widely used in, for example, automobile parts, electronic/electrical equipment parts, and audio equipment parts. However, when this material is used as a sliding member, various problems occur due to the generation of static electricity due to friction, so it is often necessary to incorporate carbon black to suppress this problem. . However, when carbon black is added to polyoxymethylene, undesirable problems such as a decrease in thermal stability, a decrease in fluidity, and a decrease in mechanical strength occur. In order to avoid such deterioration of physical properties, low-density polyethylene (Japanese Unexamined Patent Publication No. 111348/1982) or ethylene oxide adducts of amide compounds (Japanese Patent Publication No. 31736/1983) may be added together with conductive carbon black. However, since sufficient effects cannot be obtained unless low-density polyethylene is added in large quantities, the desirable physical properties of polyoxymethylene are inevitably impaired, and the use of ethylene oxide adducts of amide compounds cannot be avoided. Even though
No satisfactory improvement in physical properties was observed. On the other hand, as a heat stabilizer for polyoxymethylene,
Phosphate, polyphosphate, organic phosphate ester,
It is known to use organic phosphorous esters (Japanese Patent Publication No. 39-14519), but these phosphorus compounds are effective when blended alone, but when blended with conductive carbon black. If you do, it will have little effect. Problems to be Solved by the Invention An object of the present invention is to provide a novel polyoxymethylene composition that has excellent antistatic properties and also has better thermal stability and mechanical strength than conventional compositions. It is. Means for Solving the Problems In order to achieve the above object, the present inventors
As a result of extensive research, we have surprisingly found that by blending certain epoxy compounds and organic phosphorous compounds into polyoxymethylene in a predetermined ratio along with conductive carbon black, it has been found that not only the antistatic properties are improved, but also the antistatic properties are improved. , thermal stability, mechanical strength, etc. were also found to be improved, and based on this knowledge, the present invention was accomplished. That is, the present invention comprises (A) a polyoxymethylene resin, (B) a conductive carbon black with an oil absorption of dibutyl phthalate of 200 ml/100 g or more, (C) an epoxy compound, and (D) a general formula (R, R' and R'' in the formula are hydrogen atoms,
The content of component (B) is 0.5 to 30% by weight based on the total weight of the composition, and (C)
The present invention provides an antistatic polyoxymethylene composition containing 0.05 to 10% by weight of component and 0.1 to 10% by weight of component (D). The polyoxymethylene used as the base component of the composition of the present invention can be arbitrarily selected from commonly used polyoxymethylenes, and is not particularly limited. Next, in the composition of the present invention, it is preferable that the conductive carbon black blended as component (B) has a small particle size or a large surface area and a developed chain structure.
(abbreviated as DBP) must have an oil absorption of 200ml/100g or more. This DBP oil absorption is a measure of the degree of development of the carbon black structure, and as the structure develops, the DBP oil absorption increases and the conductivity increases. The DBP oil absorption (ml/100g) can be determined by titrating a certain amount of carbon black stirred in a kneader mixer using DBP using an automatic brewet. In this titration, the freely flowing powder changes to semi-plastic properties when carbon black reaches its maximum DBP absorption (filling of voids), and the kneader torque increases rapidly. required
The DBP amount (ml) is the DBP oil absorption amount, and ASTM
Recognized as a structure index for D2415−65T. Such DBP oil absorption amount is 200ml/100
Carbon black of less than 1.5 g has too low an electrical conductivity and must be added in large quantities to impart the desired antistatic properties, and the resulting composition will not have the inherent mechanical properties of the polyoxymethylene resin. A significant decrease in physical properties is inevitable. In the composition of the present invention, examples of conductive carbon black that can be used include Toka Black #4500 (oil absorption: 230ml/100g, manufactured by Tokai Carbon Co., Ltd.)
], #3750 [Oil absorption: 245ml/100g, Mitsubishi Kasei Co., Ltd.]
[Manufactured], Ketsuchen Black EC [Oil absorption: 350ml/
100g, manufactured by Lion Akzo Co., Ltd.], Ketsuchen Black ECDJ-600 [oil absorption capacity; 480ml/100g, manufactured by Lion Akzo Co., Ltd.], Printex XE2 [oil absorption capacity;
370ml/100g, manufactured by Degutsusa), but is not particularly limited to these. The content of these conductive carbon blacks is
Based on the weight of the composition, it should be chosen in the range of 0.5-30% by weight. If this amount is less than 0.5% by weight, the antistatic ability will not be fully exhibited, and if this amount is less than 0.5% by weight,
If it exceeds this, the impact resistance will be significantly reduced. The preferred amount is in the range of 2 to 20% by weight. In the composition of the present invention, the epoxy compound blended as component (C) is preferably a mono- or polyfunctional glycidyl derivative. Examples of such substances include 2-ethylhexyl glycidyl ether, 2-ethylhexylglycidyl ether,
Methyl octyl glycidyl ether, lauryl glycidyl ether, stearyl glycidyl ether, behenyl glycidyl ether, ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether (units of ethylene oxide; 2 to 30), propylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether ( Units of propylene oxide; 2-30), neopentyl 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,
Examples include, but are not limited to, diglycentriglycidyl ether, diglycerin tetraglycidyl ether, and a condensate of cresol novolak and epichlorohydrin (epoxy equivalent: 100-400, softening point: 20-150°C). . Each of these epoxy compounds may be used alone or in combination of two or more, and the amount to be blended is determined based on the weight of the composition.
It is selected in the range of 0.05 to 10% by weight, preferably 0.5 to 7% by weight. If this amount is less than 0.05% by weight, the effect as a heat stabilizer will hardly be exhibited, and
If it exceeds 10% by weight, mechanical properties will be significantly reduced. The optimum blending amount is appropriately selected depending on the type and amount of conductive carbon black used. The organic phosphorus compound as component (D) in the composition of the present invention is selected from triphenylphosphine, methyl-substituted triphenylphosphine, and methoxy-substituted triphenylphosphine represented by the general formula (). Examples of such substances include triphenylphosphine, tri-m-tolylphosphine, tri-p-tolylphosphine, di-m-tolylphenylphosphine, di-p-tolylphenylphosphine, m -tolyldiphenylphosphine, p-tolyldiphenylphosphine, tri-p
-methoxyphenylphosphine, di(p-methoxyphenyl)phenylphosphine, (p-methoxyphenyl)diphenylphosphine, and the like. These organic phosphorus compounds may be used alone or in combination of two or more, and the blending amount is 0.1 based on the weight of the composition.
-10% by weight, preferably 0.5-7% by weight. If this amount is less than 0.1% by weight, it will hardly be effective as a heat stabilizer;
If it exceeds % by weight, the mechanical strength will be significantly reduced.
The optimum blending amount of the organic phosphorus compound is appropriately selected depending on the type and amount of the conductive carbon black and epoxy compound used. The base component polyoxymethylene in the composition of the present invention is usually a polyoxymethylene homopolymer or a polyoxymethylene copolymer or terpolymer consisting mostly of oxymethylene chains, and is formaldehyde or a cyclic oligomer of formaldehyde such as trioxane or tetraxane. It is a product obtained by polymerizing or copolymerizing these alone or with a comonomer that can be copolymerized with these, and is stabilized against decomposition from the terminal, and stabilizers and antioxidants are usually added. It is used in a closed state. The composition of the present invention can be prepared by combining each component with, for example, a kneader,
It can be adjusted by melt-kneading using a known device, such as a roll mill or an extruder, which is normally used for kneading resin melts. As a melt-kneading device, an extruder is most suitable from the viewpoints of blocking oxygen and working environment. Types of extruders include single-screw, twin-screw, vented, and non-vented extruders, and the composition of the present invention can be prepared using any of these extruders. The mixing temperature is higher than the melting point of the polyoxymethylene resin used, and extrusion is sufficiently possible at the commonly used temperature in the range of 180 to 230°C. The time required for kneading is approximately the same as the time required for extruding the polyoxymethylene resin alone. The kneading conditions for preparing the composition of the present invention have been shown above, but the kneading method and conditions are not limited to the above, and may be any known method or method used to prepare a polyoxymethylene composition. Any conditions can be used. The composition of the present invention may contain, if desired, various additives commonly used in ordinary polyoxymethylene compositions, such as pigments, fillers, lubricants, and the like. Effects of the Invention The polyoxymethylene resin composition of the present invention is made by blending an epoxy compound and a certain type of organic phosphorus compound with conductive carbon black into the polyoxymethylene resin. This is a composition that significantly improves the decrease in thermal stability of polyoxymethylene resin caused by conductive carbon black, and maintains the mechanical properties of polyoxymethylene resin. The organic phosphorus compound used in the composition of the present invention acts as a catalyst that promotes the reaction between the epoxy compound and the carboxylic acid groups mainly on the surface of the conductive carbon black, and the The effect of the present invention is not sufficiently exhibited by a combination of only conductive carbon black and an organic phosphorus compound, and the effect is hardly exhibited by a combination of only conductive carbon black and an organic phosphorus compound. Examples Next, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited to these Examples in any way. In addition, each characteristic of the composition was determined as follows. (1) ST value Injection molding machine with cylinder temperature of 230℃ [Arburg
Allrounder 100 (manufactured by Western Trading Co., Ltd.) was used to retain the resin composition in a 12×3×
When a 120 mm molded piece was molded, the critical residence time (minutes) at which silver streaks appeared on 2/3 of the surface of the molded piece was taken as the ST value. (2) Ra value The weight residual rate (%) when the composition was heated in air at 230°C for 120 minutes was defined as the Ra value. (3) Surface electrical resistance The composition was molded into a molded piece of 130 x 110 x 3 mm using the injection molding machine, and measured using the molded piece and an insulation resistance measurement sample box TR-42 (manufactured by Takeda Riken). Examples 1 to 12 Pulverized polyoxymethylene resin copolymer [Tenatsuku-C7510 (melt index 30 g/10 minutes); registered trademark of Asahi Kasei Corporation], conductive carbon black, epoxy compound, and organic phosphorus compound were
~ After mixing using a Henschel mixer at the compounding ratio shown in Table 3, the screw rotation speed was adjusted using a 30mmφ twin-screw extruder with the cylinder temperature set at 190℃.
The mixture was kneaded at 150 rpm to form pellets. The ST value and Ra value (described above) of this pellet were measured, and test pieces were molded using a molding machine and the flexural modulus and surface electrical resistance were measured. The results are shown in Tables 1-3.

【table】

【table】

【table】

【table】

[Table] Comparative Examples 1 to 9 Polyoxymethylene resin [Tenatsuku-C7510
(Copolymer, melt index 30g/10 minutes)
Or Tenatsuku 7010 (homopolymer, melt index 30g/10 minutes); Asahi Kasei Corporation registered trademark] crushed product,
Conductive carbon black, stearic acid diethanolamide, low density polyethylene, epoxy compound, and organic phosphorus compound were mixed using a Henschel mixer in the proportions shown in Tables 4 and 5, and the cylinder temperature was set at 190°C. The mixture was kneaded into pellets using a 30 mmφ twin-screw extruder with a screw rotation speed of 150 rpm. The ST value and Ra value (described above) of this pellet were measured, and test pieces were molded using a molding machine and the flexural modulus and surface electrical resistance were measured. The results are shown in Tables 4 and 5.

【table】

【table】

[Table] Examples 13 to 16 Polyoxymethylene resin homopolymer [Tenatsuku 7010 (melt index 30 g/10 minutes); Asahi Kasei
Co., Ltd. registered product] Pulverized product, conductive carbon black,
The epoxy compound and the organic phosphorus compound were mixed using a Henschel mixer in the proportions shown in Table 6, and then kneaded into pellets using a 30 mmφ twin-screw extruder at a screw speed of 150 rpm with the cylinder temperature set at 190°C. The ST value and Ra value (described above) of this pellet were measured, and test pieces were molded using a molding machine and the flexural modulus and surface electrical resistance were measured. The results are shown in Table 6.

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【table】

Claims (1)

[Claims] 1 (A) polyoxymethylene resin, (B) conductive carbon black with dibutyl phthalate oil absorption of 200ml/100g or more, (C) epoxy compound, and (D) general formula (R, R' and R'' in the formula are hydrogen atoms,
The content of component (B) is 0.5 to 30% by weight based on the total weight of the composition, and (C)
An antistatic polyoxymethylene composition containing 0.05 to 10% by weight of component and 0.1 to 10% by weight of component (D).