JPH0832813B2 - Polyacetal resin composition - Google Patents

Description

TECHNICAL FIELD The present invention relates to a polyacetal resin composition having improved sliding properties.

More specifically, the present invention relates to a polyacetal resin composition which is obtained by blending a polyacetal resin with a cross-linked polymer of organopolysiloxane and silicone oil, has good processability, and has extremely excellent wear and wear characteristics in the short term and the long term.

[Conventional technology and its problems]

Since polyacetal resin has well-balanced physical properties and has excellent sliding characteristics as a resin,
Widely used as sliding parts for automobiles, electric / electronic products, office equipment, building materials, etc. However, with the expansion of its applications, the demands on the sliding characteristics also become more sophisticated, and there is a tendency that further improvement of the sliding characteristics and long-term sustainability thereof are required.

In order to meet such demands and improve sliding characteristics, there have been attempts to blend a lubricating oil into a polyacetal resin, and in particular, it has excellent weather resistance, low temperature characteristics, chemical and physical stability. Various studies have been made on the blending of silicone oil, which is an oil.

However, since lubricating oils such as silicone oils generally have extremely poor compatibility and affinity with polyacetal resins, it is extremely difficult to compound them, and even if such a composition can be prepared. When molding this, the oil easily seeps out on the resin surface, and the lubrication action causes slippage between the resin or between the resin and the screw, which results in poor biting into the molding machine, poor plasticization, etc. Raised, and in extreme cases, it becomes impossible to process. Further, the molded product thus obtained shows excellent properties in the initial stage of sliding, because most of the oil near the surface layer is exuded and consumed in a short time very easily. However, it is insufficient in terms of long-term slidability maintenance. In addition, since the oil easily exudes and sticks to the surface of the molded product, it has the drawback of reducing the commercial value.

Therefore, for the purpose of improving the above-mentioned drawbacks, a lubricating oil, particularly silicone oil, together with a third holding
Various additions of substances have been studied. For example, the inorganic holding material may be activated carbon, graphite or the like, and the organic polymer holding material may be high molecular weight polyethylene or the like. However, activated carbon, graphite, etc.
Since the ability to adsorb and hold silicone oil is small, and high molecular weight polyethylene and the like have a poor affinity with silicone oil, the holding ability of silicone oil is also small and a practically satisfactory effect cannot be obtained.

On the other hand, as a holding material having an excellent affinity with silicone oil, Japanese Patent Application Laid-Open No. 50-121344 discloses silicone rubber.

The silicone rubber shown here is a linear or partially branched polymer having a structure similar to that of silicone oil, and has only a slightly high degree of polymerization (or viscosity), and therefore has compatibility with silicone oil. Well, the workability in extrusion or molding is considerably improved.

However, such silicone rubber is still inadequate in terms of holding force of silicone oil under sliding, and has a drawback that sliding characteristics deteriorate with the passage of time during sliding. Further, since the silicone rubber itself, which is the holding material, is a substance having an ultra-highly viscous element, the sliding characteristics are not necessarily excellent, and the excellent sliding effect of silicone oil is reduced by half. Furthermore, since such silicone rubber exhibits fluidity when heated and has poor compatibility with the polyacetal resin as in the case of silicone oil, the rubber agglomerates on the resin surface layer of the molded product to form a thin film. This coating also has the drawback of being easily peeled off by external stress.

As described above, in the conventionally known method, it is not possible to obtain a polyacetal resin composition having good workability and excellent sliding properties in the short term and the long term, and further improvement is desired. It was

On the other hand, depending on the application of the sliding material, there are some cases where the exudation of oily substances is extremely disliked. For such applications, it has been common to mix solid lubricants such as Teflon and graphite conventionally. However, there is a drawback that slidability is gradually deteriorated due to abrasion powder due to abrasion, and there is a demand for improvement thereof.

Further, in recent years, the use of resins in special sliding fields has been increasing, and in this case, practical sliding characteristics suitable for the application are required. For example, tape running parts such as tape guides and guide rollers are required to have sliding characteristics suitable for running tapes, but no resin capable of meeting these requirements has been found and their development has been desired.

[Means for solving the problem]

The present inventors have conducted extensive studies in order to obtain a polyacetal resin composition that can meet such demands, and as a result, a crosslinked polymer of organopolysiloxane that is a powder has excellent characteristics not found in conventional solid lubricants. It has a preferable sliding property when blended with a polyacetal resin, and when the crosslinked polymer of the organopolysiloxane and silicone oil are used in combination, the sliding property of the polyacetal resin is dramatically improved in the short term and the long term. The present invention has been achieved by finding that the workability is improved and the workability is hardly impaired.

That is, the present invention is a polyacetal resin with an average particle size of 0.1 ~ 1
Crosslinked polymer of organopolysiloxane which is a powder of 00 μm 0.05 to 25% by weight (in the composition), 500 to 300,000 cSt
The present invention relates to a polyacetal resin composition having improved slidability, which is obtained by blending 0.05 to 25% by weight (in the composition) of silicone oil having a viscosity of.

As the polyacetal resin in the present invention, both a polyacetal homopolymer and a polyacetal copolymer whose main chain is composed mainly of an oxymethylene chain can be used. Further, a product obtained by modifying polyacetal by crosslinking or graft copolymerization by a known method can also be used as the base resin, and the effect of the present invention is exhibited.

In the present invention, a crosslinked polymer of organopolysiloxane is blended with such a polyacetal resin. The crosslinked polymer of organopolysiloxane used here is not particularly limited, and any of those obtained by crosslinking organopolysiloxane by a known method can be used. For example, Such as a siloxane compound having two or more reactive groups, or one or more polysiloxanes, preferably in the presence of a catalyst, for dehydration condensation between silanols and dealcoholation of silanols and alkoxysiloxanes. Condensation, Dehydrogenative condensation between silane and silanol, or unsaturated group such as vinyl group Crosslinking is carried out by an addition reaction between and to obtain a crosslinked polymer. As the catalyst, an organic acid metal salt, an organic amine, a quaternary ammonium or phosphonium compound is generally used in the case of condensation reaction type crosslinking, and palladium, platinum or a compound thereof is used in the case of addition reaction type crosslinking.

In addition to this, in the presence of organic peroxide Various cross-linking forms such as cross-linking between groups are known. Further, a polysiloxane having a reactive group as described above and a reactive substance having no siloxane structure added thereto may be crosslinked.

The crosslinked polymer thus obtained generally has a structure as shown below as a main component, and has a structure different from that of a linear or partially or branched silicone rubber, and its properties are also completely different. It is a thing.

Here, R is mainly a methyl group, but part of it is hydrogen, an alkyl group other than a methyl group, an aryl group, a halogenated alkyl group, a halogenated aryl group, a vinyl group, an allyl group, a hydroxyl group, a fluoroester group, etc. It may be substituted with one kind or two or more kinds.

X is a cross-linking residue generated by the above-mentioned cross-linking reaction, which varies depending on the substance used in the reaction and is not particularly limited, but for example, —O—, —CH ₂ CH ₂ —, Etc.

In the present invention, among such crosslinked polymers, those having a siloxane unit in the crosslinked residue (-X-) are particularly preferable.

The crosslinked polymer of such an organopolysiloxane in the present invention has an average particle size of 0.
It is a granular material of 1 to 100 μm. Particularly preferably, the average particle size
It is 20 μm or less.

There is no particular limitation on the method for obtaining the powdery crosslinked polymer, for example, after mixing the raw materials to be subjected to the reaction, spraying in the air, reacting in the form of fine particles, and suspending in a solvent to finely react by stirring to react. Alternatively, it can be obtained by a method such as pulverizing a polymer obtained by crosslinking by a usual method.

In the present invention, the content of the powdery granular organopolysiloxane crosslinked polymer is 0.05 to 25% by weight (in the composition).
Is. If the amount is less than 0.05% by weight, the effect of improving slidability can hardly be expected, and the effect as a silicone oil retaining material becomes insufficient. On the other hand, if the amount is more than 25% by weight, the properties of the polyacetal resin as the substrate may be greatly impaired. The amount is preferably 0.2 to 20% by weight, particularly preferably 0.5 to 15% by weight.

In the present invention, the polyacetal resin is used together with the crosslinked polymer of the above-mentioned powdery particulate polyorganopolysiloxane in an amount of 500 to 3
Silicone oil with a viscosity of 00,000 cSt is 0.05-25
% By weight (in composition).

If the blending amount of the silicone oil is less than 0.05% by weight, it is not sufficient to obtain the effect of improving the sliding property by the combined use with the crosslinked organopolysiloxane polymer.
If the content exceeds 10% by weight, it becomes difficult to mix it with the polyacetal resin, and the physical properties of the resin are significantly impaired. A preferred blending amount is 0.2 to 20% by weight, particularly preferably 0.5 to 15
% By weight. In addition, considering polysiloxane cross-linked polymer from the viewpoint of silicone oil retention and slidability,
The silicone oil / crosslinked polymer ratio is preferably 10/1 to 1/5.

Silicone oil used for such a purpose is dimethylpolysiloxane or a part of its methyl group is hydrogen,
It is substituted with one kind or two or more kinds of phenyl group, halogenated phenyl group, halogenated alkyl group, fluoroester group and the like.

In the present invention, the viscosity of the silicone oil used is generally 500 to 500 when considering the slidability improving effect and its durability, the dispersibility of the oil in the resin, the workability during melt kneading and molding, and the like. It is preferably 300,000 cSt (25 ° C).

Further, in the present invention, two or more kinds of silicone oils having different structures or viscosities can be mixed and used, and the viscosity and the like can be adjusted by adding a thickener, a solvent and the like to the silicone oil. Is.

Although the mechanism of action for improving the sliding characteristics of such a polysiloxane crosslinked polymer in the present invention is not always clear, it is due to the appropriate fine unevenness formed on the surface of the polyacetal resin by the incorporation of the crosslinked polymer, particularly the powdery granular polymer. It is presumed that the effect of reducing the sliding contact area and the preferable sliding property of the polysiloxane crosslinked polymer itself are combined.

In addition to the above effects, the silicone oil is retained in the cross-linked polymer having a unique structure of cross-linking, in addition to the above-mentioned effects, by further blending it with silicone oil,
Silicone oil film that is not easily peeled off is formed on the surface of the molded product, or the exudation of silicone oil is controlled appropriately by the presence of a cross-linked polymer, so the silicone oil itself has excellent sliding properties. It is estimated that the characteristic improvement effect will continue for a long time.

In the composition of the present invention, solid lubricants such as graphite, molybdenum disulfide, metal soap, polyethylene resin, polytetrafluoroethylene resin, and the like can be imparted with good lubricity for the purpose of further improving sliding characteristics. A polymer or the like can also be blended. Further, according to the purpose, in order to improve the physical properties, various known additives may be further blended.

Examples of additives include antioxidants, weather and light resistance stabilizers, heat stabilizers, lubricants, release agents, nucleating agents, silicone oil dispersants, antistatic agents, flame retardants, colorants, and the like.

In addition, the composition of the present invention may be added with a fibrous, plate-like, or granular inorganic filler such as glass fiber depending on the purpose, and additionally, other resin or polymer substance may be supplementarily added and commonly used. Of course, it is also possible.

The composition of the present invention can be easily prepared by a known method generally used as a conventional resin composition preparation method. For example, after mixing each component, kneading and extruding with a single-screw or twin-screw extruder to prepare pellets, and then forming, pellets having different compositions are prepared once, and the pellets are mixed in a predetermined amount. Can be used for molding to obtain a molded product of the desired composition after molding, and a method of directly charging one or more of each component into a molding machine.

In the preparation of such a composition, it is preferable to grind a part or all of the base polyacetal resin, mix this with other components, and then carry out extrusion or the like in order to improve the dispersibility of the additive. Is the way.

Further, a method of mixing silicone oil with a polysiloxane cross-linked polymer in advance, impregnating it, then mixing with a polyacetal resin, and performing extrusion or the like is also a preferable method from the viewpoint of processability improvement.

〔Example〕

Hereinafter, the present invention will be described more specifically with reference to Examples.
The present invention is not limited to this.

Reference Examples 1 to 3 and Comparative Examples 1 to 4 Polyacetal resin [manufactured by Polyplastics Co., Ltd., trade name “DURACON M90”] was mixed with a crosslinked polymer of organopolysiloxane at a ratio shown in Table 1, and then biaxial The composition was melted and kneaded by an extruder to prepare a pelletized composition. Then, using the pellets, test pieces were prepared by injection molding and evaluated.

The crosslinked organopolysiloxane polymer used here is
It was obtained by the following method.

Polymer A A powder-like crosslinked polymer having an average particle size of 8 μm obtained by reacting dimethylpolysiloxane having vinyl groups at both ends with dimethylpolysiloxane partially substituted with hydrogen using a platinum catalyst to crosslink.

Polymer B A powder-like crosslinked polymer having an average particle diameter of 3 μm obtained by reacting dimethylpolysiloxane having both ends blocked with hydroxyl groups and triethoxymethylsilane in the presence of dibutyltin dilaurate.

Further, for comparison, the same evaluation was performed for a polyacetal resin and a linear silicone rubber having no cross-linked structure, polytetrafluoroethylene or graphite blended therewith. The results are shown in Table 1.

 The evaluation items and evaluation methods are as follows.

Moldability: Using a screw type injection molding machine, the plasticization time was measured when the cylinder temperature was 190 ° C. and the screw rotation speed was 150 rpm, and it was expressed as a ratio to the plasticization time of the polyacetal resin. When this value is large, the pellets slip on the screw, the biting is poor, and the moldability is poor.

Appearance: The appearance of the pellets and molded products, especially the leaching state of liquid matter, and the stickiness were examined.

Friction coefficient: Pressurized 0.75kg / c using Suzuki friction and wear tester
m ² , linear velocity 180 mm / sec, contact area 2.0 cm ² , PB as mating material
Using T resin, the dynamic friction coefficient was measured immediately after the start of sliding and after sliding for a predetermined time.

Tape running property: The VTR tape was run by the method shown in FIG. 1 and the torque applied to the test piece was measured. The tape length is 50 cm, the tape running speed is 1.7 m / sec, and the tape tension is 110 g.
And 23 ° C. and 50% RH.

Examples 1 to 13 and Comparative Examples 5 to 14 A polyacetal resin [manufactured by Polyplastics Co., Ltd., trade name "DURACON M90"] is mixed with a crosslinked polymer of organopolysiloxane and various silicone oils in the proportions shown in Table 2. Then, the evaluation was performed in the same manner as in Examples 1 to 3.

For comparison, the same evaluation was performed for a polyacetal resin blended with only silicone oil, and a blended blend of a straight-chain silicone rubber having no cross-linked structure and silicone oil. The results are shown in Table 2.

[Effects of the Invention] As is clear from the above description and reference examples, the composition obtained by blending the polyacetal resin with the crosslinked polymer of powdered organopolysiloxane is preferable because it has excellent sliding stability. Is. Further, in the present invention, by additionally using silicone oil in the composition, the sliding property is dramatically improved and its long-term sustainability is further improved, which is more preferable. Also,
The coexistence of the crosslinked organopolysiloxane polymer suppresses the leaching of silicone oil, resulting in a decrease in processability due to leaching of silicone oil, which has been a problem in the past, and a poor appearance on the surface of molded products (stickiness). The problems such as) are remarkably improved.

As described above, the composition of the present invention obtained by mixing the polyacetal resin with the crosslinked polymer of polysiloxane and the silicone oil has excellent properties and is therefore preferably used as a sliding component in a very wide field. In addition, it can be sufficiently applied to applications where leaching of an oily substance is disliked.

Further, the composition of the present invention exhibits favorable properties even for contact running of a tape, which is a special type of sliding, and is preferably used for tape running system parts such as tape guides and guide rollers.

[Brief description of drawings]

FIG. 1 is a perspective view of an apparatus used for evaluation of tape running property. 1 …… Test piece 2 …… Tape 3 …… Torque arm 4 …… Torque detector 5 …… Rotary motor (built-in)

Claims (2)

[Claims] 1. A polyacetal resin having an average particle size of 0.1 to 100.
0.05 to 25% by weight (in the composition) of a crosslinked polymer of organopolysiloxane, which is a powder of μm, and 0.05 to 25% by weight (in the composition), a silicone oil having a viscosity of 500 to 300,000 cSt. A polyacetal resin composition having improved slidability. 2. A crosslinked polymer of an organopolysiloxane,
The polyacetal resin composition having improved sliding properties according to claim 1, which is crosslinked mainly through a residue having a siloxane unit.