JPH0826209B2 - 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 improved wear resistance under high load conditions.

[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, the acetal resin becomes flexible depending on the type of oil, and as a result, under low to medium load conditions (about 30 Kgf / cm ² while indicating the degree or less), the excellent sliding properties, it has been found then that the high loading conditions (about 30~200Kgf / cm ²⁾ wear increases.

Therefore, an object of the present invention is to provide an oil-containing acetal resin composition having improved wear resistance under high load conditions.

[Means for solving the problem]

The oil-containing acetal resin composition of the present invention aiming to solve such a problem has a fluidity shown by a repose angle of 45 ° or less, which is obtained by adsorbing a liquid oil on a porous styrene-divinylbenzene copolymer. It contains about 3 to 30% by weight of oil-containing resin and about 3 to 30% by weight of tetrafluoroethylene resin 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 adsorptive property is strong, the pore volume is large, so if you drain the product sold with the pores completely in water, 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 heating for 5 hours and completely drying, liquid oil having a viscosity of about 5 to 70,000 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 an organic solvent solution of liquid oil, for example, mineral oil or silicone oil dissolved in aromatic hydrocarbons such as benzene, toluene, xylene, ester oil dissolved in ketones such as acetone and methyl ethyl ketone, methanol, ethanol, etc. Polyglycol oil dissolved in ketones such as alcohols or acetone, mixed solvent of tolchlortrifluoroethane or methylene chloride with it, fluorine oil dissolved in halogenated hydrocarbons such as tetrachlorodifluoroethane, etc., Generally, it is used as a solution having a concentration of about 20% by weight or more.

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. That is, when the angle of repose is 45 ° or less, oil having a pore volume equal to or less than the pore volume of the porous body is adsorbed, and in this state, mixing and dispersion with the acetal resin powder or granules becomes easy.

As the tetrafluoroethylene resin powder, those having a particle size of 30 mesh pass are generally used.

These oil-containing resins and tetrafluoroethylene resin powders contain about 3 to 30% by weight, preferably about 10 to 20% by weight of the oil-containing resin in the composition composed of them and the acetal resin.
The proportion of the tetrafluoroethylene resin powder is about 3 to 30% by weight, preferably about 10 to 20% by weight. If the usage ratio of the tetrafluoroethylene resin powder is less than this, the effect aimed at by the present invention cannot be obtained. On the other hand, if the usage ratio is more than this, the wear resistance is improved, but the moldability becomes impaired. .

The composition is prepared by stirring and mixing with a mixer such as a ribbon-type mixer or a V-type mixer, and the kneading and pelletizing with a crew extruder may improve 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 a tetrafluoroethylene resin powder together at that time, it does not compensate for the deterioration of the wear resistance of the acetal resin that has become soft due to the mixing of the oil-containing resin, The present invention provides a material exhibiting excellent sliding characteristics even under a high load condition of about 30 to 200 Kgf / cm ² .

〔Example〕

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

Example 1 Oil-containing resin impregnated with 1.25 g of silicone oil (Toray Silicone product silicone oil SH-200, viscosity at 25 ° C. 50 cst) per 1 g of styrene-divinylbenzene copolymer (Mitsubishi Kasei Kogyo product Diaion MP-A). 10% by weight and 10% by weight of tetrafluoroethylene resin powder (NOK product PTFE A type, particle size 42 mesh all-pass), acetal resin (polyplastics product DURACON M90-00
Frakes) 80% by weight, after mixing in a mixer,
The pellets were pelletized by an extruder, and the pellets were injection-molded to form a predetermined sample.

Example 2 5% by weight of the oil-containing resin used in Example 1, 15% by weight of tetrafluoroethylene resin powder and 80% of acetal resin
Similar samples were injection molded from weight percent.

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

Comparative Example 2 In Comparative Example 1, an oil-containing resin impregnated with a mineral oil (Nisseki Super Oil A, viscosity at 40 ° C. of 30 cst) was used in place of the silicone oil.

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, unlubricated Surface pressure: 150kgf / cm ² Peripheral speed: 0.015m / sec Phase material: S45C Counterpart material roughness: 1.5S Time: 24 hours The measurement results are shown in the following table.

Table Example Wear coefficient (× 10 ^-6 cm · cm ² · sec / kgf · m · hr) Example 1 70 Example 2 70 Comparative Example 1 90 Comparative Example 1 120 From the above results, silicone oil was used instead of mineral oil. It can be seen that the wear coefficient of the acetal resin is improved by using the impregnated oil-containing resin, but it is possible to further improve the wear coefficient by compounding tetrafluoroethylene resin powder therewith. .

Claims (1)

[Claims] 1. A porous styrene-divinylbenzene copolymer having a liquid oil adsorbed thereon, and an oil-containing resin having a fluidity of 45 ° or less and an angle of repose of about 3 to 30% by weight, and a tetrafluoroethylene resin powder of about 3. An oil-containing acetal resin composition containing 3 to 30% by weight and the rest being acetal resin.