JP2550372B2 - Oil-containing acetal resin composition - Google Patents

Description

TECHNICAL FIELD The present invention relates to an oil-containing acetal resin composition. More specifically, it relates to an oil-containing acetal resin composition having an improved elastic modulus.

[Conventional technology]

It is known that an oil-containing acetal resin obtained by impregnating an acetal resin with oil is generally excellent in sliding characteristics. The oil-containing acetal resin is a method of directly impregnating the acetal resin with oil, a method of impregnating a resin with good compatibility with oil once and blending it with an acetal resin as a masterbatch, or a large excess heated above the melting point of the acetal resin. It is manufactured by a method of mixing with an acetal resin in the oil, and then cooling and precipitating.

However, in the case of the method of adding the liquid oil to the resin, which is the most general method among these methods, when the mixture of the matrix resin and the liquid oil is kneaded using a screw extruder or the like, the resin adheres to the matrix resin. Due to the above oil, there is a problem that the oil does not slip into the extruder by slipping at the hopper opening of the extruder, and an oil-impregnated resin cannot be substantially obtained.

As a masterbatch method, a method is known in which a porous body produced by sintering ultrahigh molecular weight polyethylene having an average molecular weight of 500,000 or more and impregnated with lubricating oil is used (Japanese Patent Publication No. 47-29374). Gazette), the acetal resin has no affinity with oil. Therefore, when an oil-containing polyethylene sintered body is kneaded into the acetal resin at a temperature of 190 ° C or higher, the oil separated from the sintered body has an affinity with oil. It disperses in an acetal resin that does not have the above, and the desired sliding material cannot be obtained.

[Problems to be solved by the invention]

Therefore, the present applicant has previously proposed that the liquid oil be converted into porous styrene-
We have proposed an oil-containing resin adsorbed on a divinylbenzene copolymer, and have found that it can significantly improve the sliding characteristics of the added acetal resin, etc. without causing the above-mentioned drawbacks. (Japanese Patent Application No. 62-110,
No. 979).

However, since the oil-containing resin composition prepared here contains a large amount of liquid oil, it was subsequently found that the acetal resin becomes flexible depending on the type of oil, and as a result, the elastic modulus may decrease. . Such a decrease in the elastic modulus may cause a problem such as an increase in torque due to the deformation of the product during actual use and a change in the contact with the mating material under severe conditions.

When used as a bearing member, the friction coefficient of conventional bearings (Suzuki type, unlubricated, surface pressure 5 Kgf / cm ² , peripheral speed 0.2 m
/ Second, mating material S45C, mating material roughness 1.5S, time 24 hours) is 0.2
Although the material of 5 to 0.40 is used, it has recently been required to further lower the friction coefficient in order to improve the performance, and therefore the elastic modulus of the oil-impregnated acetal resin composition while satisfying the requirement for the friction coefficient. Is desired to be improved.

Therefore, as a result of next studying measures against this, by filling the composition with carbon powder,
It has been found that this problem can be effectively solved.

[Means for solving the problem]

Therefore, the present invention relates to an oil-containing acetal resin composition,
This oil-containing acetal resin composition comprises a porous styrene-divinylbenzene copolymer having liquid oil adsorbed thereon, and an oil-containing resin having a fluidity represented by an angle of repose of 45 ° or less of about 3 to 3.
It contains 30% by weight, about 3 to 40% by weight of carbon powder, and the rest is composed of acetal resin.

The porous styrene-divinylbenzene copolymer that adsorbs liquid oil is a resin in which the divinylbenzene portion acts as a cross-linking point of the styrene substrate, and there are those that apparently have pores and those that do not.

These resins are commercially available as Mitsubishi Kasei Industrial Products Diaion, but those with apparent pores (Diaion HP series) with a pore size of 16 to 8000Å and 0.1 ml / g.
It has pores with the above pore volume, and since the adsorptivity is strong, the pore volume is large, so if you drain the product sold with water completely in the pores, It is said that air will enter and will not come into contact with the liquid to be treated.

In the oil-containing resin used in the present invention, as a precursor of the microporous ion-exchange resin, a powder or granules of such a water-containing synthetic adsorbent having a function of adsorbing and removing impurities in an aqueous solution, and the like, About 3 to 1 at a temperature of 150 ℃
After being heated for 5 hours to be completely dried, a liquid oil having a viscosity of about 5 to 7,000 centistokes (40 ° C.) is adsorbed to the pores therein.

In order to complete the adsorption, liquid oil is first impregnated as an organic solvent solution, and the solution removes air in the pores of the porous styrene-divinylbenzene copolymer powder or granules as a dry synthetic adsorbent. Penetrate while expelling.

Further, even a copolymer resin having no apparent pores swells when immersed in an organic solvent such as toluene described below,
When the state was observed with an electron microscope, it was found that the pores opened. Therefore, such a copolymer resin can also be said to be a kind of porous body.

Liquid oil can be impregnated into the copolymer resin by using such pores, but since the impregnation rate is slow as it is, the organic solvent is used as described above and the fine pores opened by swelling are used. A method of impregnating liquid oil as an organic solvent solution is preferably used.

As the organic solvent solution of liquid oil, for example, mineral oil or silicone oil dissolved in aromatic hydrocarbons such as benzene, toluene and xylene, ester oil dissolved in ketones such as acetone and methyl ethyl ketone, methanol, ethanol, etc. In general, polyglycol oil dissolved in alcohols or ketones such as acetone, trichlorotrifluoroethane or a mixed solvent of methylene chloride with it, and fluorine oil dissolved in halogenated hydrocarbons such as tetrachlorodifluoroethane are generally used. A concentration of about 20% by weight or more is used as a solution.

After impregnating the porous copolymer powder or granules in these organic solvent solutions by stirring, the organic solvent is evaporated and removed by heating and / or depressurizing the organic solvent to about 50 to 150 ° C. Oil having a pore volume equal to or less than that of the substance is adsorbed in the copolymer to obtain an oleoresin.

The oil-containing resin thus obtained has, for example, about 1.1 to
It shows a large oil content of 1.2 ml / g but does not adhere to each other and shows a free-flowing state, and it has a fluidity test method indicated by the angle of repose (using a Hosokawa Micron powder tester) of 45 ° or less. It is a resin with good flowability that exhibits an angle of repose. At a repose angle of 45 ° or less, oil having a pore volume of the porous body or less is adsorbed, and in this state, mixing and dispersion with the acetal resin powder or granules becomes easy.

As the carbon powder, those having a particle size of 80 mesh pass are generally used, and generally carbon fibers having a fiber diameter of about 20 μm or less and a fiber length of about 10 mm or less can also be used as the carbon powder.

The oil-containing resin and the carbon powder are contained in the composition composed of the acetal resin and the acetal resin in an amount of about 3 to 30% by weight, preferably about 10 to 20% by weight, and about 3 to 30% by weight of the carbon powder. -40% by weight, preferably about 10-30
Used in proportions of weight% respectively. If the use ratio of carbon powder is less than this, the effect aimed at by the present invention cannot be obtained, while if it is used at a ratio higher than this, although the elastic modulus is improved, it is required for a sliding member having a friction coefficient of 0.25 or less. The sliding characteristics will not be satisfied.

The composition is prepared by stirring and mixing with a mixer such as a ribbon-type mixer or a V-type mixer, and further kneading and pelletizing with a screw extruder may reduce its operability and moldability. It can be molded with an injection molding machine, a thermal compression molding machine, etc. without damaging it.

〔The invention's effect〕

Acetal resin is the most rigid resin and has the characteristics of long fatigue life, good resilience, low moisture sensitivity, good solvent resistance and chemical resistance, and excellent electrical insulation. Therefore, it is effectively used in applications such as bushes, ball seats, gears, etc., especially by mixing with the oil-containing resin used in the present invention,
It is possible to improve the sliding characteristics of the molded product, but by using carbon powder together at that time, the decrease in elastic modulus of the acetal resin softened by mixing the oil-containing resin is not compensated, and the sliding member The present invention provides a material that satisfies the above sliding characteristics in terms of friction coefficient.

〔Example〕

 Next, the present invention will be described with reference to examples.

Example 1 20% by weight of oil-containing resin and carbon impregnated with 1.25 g of mineral oil (NOK Kluber product, viscosity of 30 cst at 40 ° C.) per 1 g of styrene-divinylbenzene copolymer (Mitsubishi Kasei Kogyo product Diaion MP-A) Powder (Chuetsu Graphite Product CM
W-200, particle size 150 mesh pass 95.5% by weight or more) 30% by weight together with 50% by weight of acetal resin (Polyplastics product DURACON M90-00 Flakes) in a mixer and pelletized by an extruder. Was injection molded to form a predetermined sample.

Example 2 A similar sample was injection molded from 13 wt% of the oil-containing resin used in Example 1, 15 wt% of carbon powder and 72 wt% of acetal resin.

Comparative Example A similar sample was injection molded from 20% by weight of the oil-containing resin and 80% by weight of the acetal resin used in Example 1.

The samples obtained in the respective Examples and Comparative Examples above were subjected to a Suzuki type friction and wear test under the following test conditions.

Environment: Room temperature, no lubrication Surface pressure: 5kgf / cm ² Peripheral speed: 0.2m / sec Counterpart material: S45C Counterpart material roughness: 1.5S Time: 24 hours The measurement results are shown in the following table.

Claims (1)

(57) [Claims] 1. An oil-impregnated resin having a fluidity indicated by an angle of repose of 45 ° or less, which is obtained by adsorbing a liquid oil on a porous styrene-divinylbenzene copolymer, and a carbon powder of about 3-40. An oil-containing acetal resin composition containing wt% and the rest being acetal resin.