JPH08134326A - Polyacetal sliding material composition - Google Patents

Abstract

PURPOSE: To obtain a composition capable of providing polyacetal sliding members having excellent sliding characteristics for cloud of dust and good performances in other various characteristics. CONSTITUTION: This polyacetal sliding material composition is obtained by blending (A) 100 pts.wt. polyacetal resin with (B) 3-25 pts.wt. polyolefin-based (co)polymer, selected from chlorinated polyolefins or block or graft copolymers of the polyolefin-based (co)polymers with vinylic (co)polymers and having <=3,000 kgf/cm<2> tensile elastic modulus and (C) 5-30 pts.wt. fibrous filler.

Description

Detailed Description of the Invention

[0001]

INDUSTRIAL APPLICABILITY The present invention has excellent friction and wear characteristics, does not generate a squeak noise even when sliding sand and sand dust in the sliding interface, and has excellent wear resistance. The present invention relates to a polyacetal sliding material composition.

[0002]

BACKGROUND OF THE INVENTION Polyacetal resins have well-balanced mechanical properties.
It is widely used in the fields of automobiles, electric / electronic parts, etc. due to its excellent friction and wear resistance, chemical resistance, heat resistance, and electrical characteristics. However, it has been confirmed that the excellent performance cannot be sufficiently exhibited with respect to the required characteristics in special applications. For example, bearings of roller skates, bearings of door cars such as windows of houses, sliding parts mainly used outdoors such as those suitably used for opening and closing mechanisms of doors of houses and automobiles are simple resins, In addition to sliding like resin to metal, dirt and dust are caught in the sliding interface, sliding against dust and sand occurs, and it does not exhibit the good sliding characteristics inherent to resin, It is common to make sliding noise worse. Further, such a phenomenon is not limited to a phenomenon outdoors, and can be seen in a case where a bearing such as a printer or a facsimile machine causes toner or paper dust to be caught in a sliding interface to generate an abnormal noise. Conventionally, such parts include
Grease-coated metal, ester lubricants and PTFE
Resin materials containing such substances have been used, but the grease itself aggregates and fixes dirt and dust, which not only worsens wear, but also causes unpleasant squeaking noise, which often causes problems. The wear resistance was not further improved by the system lubricant and PTFE, and a high sliding material has been earnestly desired.

[0003]

Means for Solving the Problems As a result of intensive investigations by the present inventors, the development of a polyacetal sliding member having excellent sliding characteristics against dust and excellent performance in other characteristics The inventors have found that a composition comprising a specific polyolefin (co) polymer and a fibrous filler mixed in specific amounts is effective in achieving such an object, and arrived at the present invention. That is, the present invention, (A) 100 parts by weight of the polyacetal resin, (B) chlorinated polyolefin, or a polyolefin-based (co) polymer and vinyl (co) is selected from block or graft copolymer of the polymer, A polyacetal sliding material composition comprising 3 to 25 parts by weight of a polyolefin (co) polymer having a tensile elastic modulus of 3,000 kgf / cm ² or less and (C) 5 to 30 parts by weight of a fibrous filler. is there.

The structure of the present invention will be described in detail below. First, as the polyacetal resin (A) used in the present invention, both a polyacetal homopolymer and a polyacetal copolymer in which the main chain is mostly an oxymethylene chain can be used. Also, a polyacetal modified by crosslinking or graft copolymerization by a known method can be used as the base resin, and the degree of polymerization is not particularly limited as long as it can be molded. Particularly, a polyoxymethylene copolymer containing 0.3 to 1% by weight of a comonomer unit typified by ethylene oxide unit in the polymer has high mechanical strength and good thermal stability, and is preferably used in practice. The invention exhibits performance regardless of the type of polyacetal polymer, and it is possible to use any polyacetal resin.

Next, the (B) component polyolefin-based (co)
The polymer is selected from a chlorinated polyolefin or a block or graft copolymer of a polyolefin-based (co) polymer and a vinyl-based (co) polymer and has a tensile modulus of 3,000 kgf / cm ² or less (copolymer ) A polymer. Examples of the chlorinated polyolefin containing chlorine as a functional group, which is one of the components (B), include chlorinated polyethylene and chlorinated polypropylene having a chlorine content of 10 to 40% by weight. Such a chlorinated polyolefin can be obtained from the market, and Erasulen (trade name) manufactured by Showa Denko KK can be used as a commercial product.

The block or graft copolymer, which is another type of the polyolefin-based copolymer as the component (B), is a component (b-1) mainly composed of polyolefin and a vinyl polymer other than the polyolefin. The main component (b-2) is a block or graft copolymerized copolymer. As the olefin (co) polymer constituting the component (b-1), low density polyethylene, ultra low density polyethylene,
One of α-olefin monomers such as ethylene, propylene, butene, hexene, octene, nonene, decene and dodecene represented by polyethylene such as medium density polyethylene, polypropylene, ethylene-propylene copolymer, poly-1 butene, or the like, or A polyolefin polymer or copolymer mainly composed of two or more kinds of monomer units,
And the above-mentioned olefin monomer units represented by ethylene ethyl acrylate copolymer, ethylene methyl methacrylate copolymer and the like, and ethylene-ethyl acrylic acid copolymer, ethylene-vinyl acetate copolymer, ethylene-glycidyl methacrylate. Examples thereof include random copolymers represented by copolymers and the like, and vinyl monomer units other than olefins. The vinyl-based (co) polymer constituting the component (b-2) is an aromatic vinyl compound such as styrene or α-methylstyrene, or acrylonitrile. Esters of α, β-unsaturated acids such as methyl acrylate, ethyl acrylate, methyl methacrylate, ethyl methacrylate,
Polymers composed of monomer units such as vinyl compounds such as vinyl acetate, vinyl chloride, vinyl methyl ether and derivatives of such compounds can be mentioned. The block or graft copolymer may be one or more olefinic copolymers (b-1 which are selected from ethylene / propylene copolymers, ethylene / acrylic acid ester copolymers and ethylene / methacrylic acid ester copolymers. And a block or graft copolymer obtained from one or more vinyl-based (co) polymers (b-2) selected from the group consisting of polymethylmethacrylate, acrylonitrile-styrene copolymer and polystyrene. To be done. Such a block or graft copolymer is an olefin-based (co)
Polymer (b-1) unit and at least one vinyl type (co)
The polymer (b-2) unit is a chemical bond in a branched or crosslinked structure. By having such a structure, simply (b
-1) or (b-2) has a remarkable effect which cannot be obtained by the single blending. Such (b-1) segment and (b-2)
The method for preparing the block or graft copolymer composed of segments is not particularly limited, but it can be easily prepared by a well-known radical reaction. For example, by grafting a polymer (b-1) and a radical catalyst such as a peroxide to any of (b-2) to generate free radicals, and melt-kneading the free radicals with other component polymers. A copolymer (B) is prepared. Further, the graft or block copolymer (B) is also prepared by a method such as hydrogenation of styrene-butadiene rubber. Here, the ratio of (b-1) and (b-2) to form the graft copolymer of component (B) is
80: 20-40: 60 is suitable. Beyond the ratio of 80:20 (b
If the amount of the component (-1) is larger than that of the component (b-2), squeaking noise will not occur, but the separation of the polyolefin component from the polyacetal will be remarkable, and the peeling and abrasion characteristics will be deteriorated. Again 4
If the component (b-1) is less than the component (b-2) in excess of the ratio of 0:60, the effect of modifying the surface of the polyacetal by the polyolefin component will be insufficient and the sliding noise represented by squeak noise will be improved. Not effective. As the block or graft copolymer as the component (B), those commercially available under the trade name of MODIPER A5400, A5200, A5100 manufactured by NOF CORPORATION can be used.

Here, the (B) polyolefin-based (co) polymer having a tensile elastic modulus of 3000 kgf / cm ² or less is used. When the tensile elastic modulus of the polyolefin-based (co) polymer exceeds 3000 kgf / cm ² , the squeaking noise when dust adheres is insufficiently improved, which is not preferable. More preferably
Those of 2000 kgf / cm ² or less are preferably used. Also,
The component (B) is preferably added in an amount of 3 to 25 parts by weight, more preferably 5 to 15 parts by weight, based on 100 parts by weight of the component (A). If the amount of the component (B) is too small, the sliding improvement performance aimed at by the present invention, particularly the suppression of sliding noise, becomes insufficient, and if it is too large, surface peeling and wear deteriorate, which is not preferable.

As the component (C) used in the present invention, any fibrous substance can be used, but a fibrous filler having a fiber diameter of 0.1 to 20 μm is preferably used. Particularly preferred is one or more fillers selected from the group consisting of glass fibers, carbon fibers and potassium titanate fibers. As the filler, a crushed product (milled fiber) can also be used. Such a filler exhibits the effect of dramatically improving wear resistance. The compounding amount of the (C) fibrous filler is 5 to 30 parts by weight, and more preferably 10 to 30 parts by weight, relative to 100 parts by weight of the component (A). If the amount is less than the above range, the effect of improving the wear resistance becomes insufficient, and if the amount exceeds the above range, sliding noise and molding workability are deteriorated, which is not preferable.

Component (B) or (C) used in the present invention
When each of the components is blended alone, sufficient effects cannot be obtained for suppressing sliding noise and improving wear resistance characteristics in the presence of dust. The combination of the component (B) and the component (C) improves the properties for the first time.

Further, the composition of the present invention may further contain various conventionally known additives in order to impart desired properties depending on its purpose. Examples of additives include various coloring agents, release agents, nucleating agents, antistatic agents, other surfactants,
For example, different polymers.

The preparation of the composition or molded article of the present invention is as follows.
It is easily prepared by a known method that is generally used as a conventional resin composition preparation method. For example, after mixing each component, pellets are prepared by kneading and extruding with a single-screw or twin-screw extruder, followed by a method of molding, once preparing pellets of different composition (masterbatch), Any method can be used, such as a method of mixing (diluting) a predetermined amount and subjecting to molding, and then obtaining a molded product of the target composition after molding.
Further, in the preparation of such a composition, it is preferable to pulverize a part or all of the polyacetal resin which is the substrate, mix this with other components, and then carry out extrusion or the like in order to improve the dispersibility of the additive. This is the preferred method. A sliding part formed by molding the polyacetal sliding material composition of the present invention is excellent in sliding against dust and is suitably used for parts such as bearings and sliders which particularly require such performance.

[0012]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited thereto. Examples 1 to 11 and Comparative Examples 1 to 13 As shown in Tables 1 and 2, as the component (A), polyacetal resin (manufactured by Polyplastics Co., Ltd., trade name DURACON),
Various polyolefin-based (co) polymers as the component (B),
Various fibrous fillers as the component (C) were mixed in the proportions shown in Table 1, and then melt-kneaded by a twin-screw extruder to prepare a pelletized composition. Then, a test piece was prepared by injection molding using this pellet and evaluated. The results are shown in Table 1.
Shown in

Similarly, a comparative example is shown in Table 2. For comparison, PTFE and ester lubricant (stearyl stearate) -containing polyacetal were also evaluated. -Polyolefin (co) polymer (B-1) Graft copolymer of ethylene-propylene rubber (50% by weight) and polymethylmethacrylate (50% by weight) (tensile modulus = 1,000 kgf / cm ² ) (B -2) Graft copolymer of ethylene-ethyl acrylate copolymer (50% by weight) and acrylonitrile-styrene copolymer (50% by weight) (tensile modulus = 380 kgf / cm ² ) (B-3) ethylene -Graft copolymer of ethyl acrylate copolymer (70 wt%) and acrylonitrile-styrene copolymer (30 wt%) (tensile modulus = 330 kgf / cm ² ) (B-4) Chlorine content 30 wt % Polyethylene (tensile modulus = 12 kgf / cm ² ) (B'-1) polypropylene (50 wt%) and acrylonitrile-styrene copolymer (50 wt%) graft copolymer (tensile modulus = 5, 300 kgf / ^cm 2) as a comparison, ethylene ethyl Accession Rate copolymer (Mitsui Petrochemical Co., Ltd. A702), using low density polyethylene (Nippon Petrochemicals Co., Ltd. L504). The evaluation items and evaluation methods are as follows. As test powder, Kanto loam soil (JIS Z8901 8 types: 11 types = 1: 1)
Was used.・ Friction and wear characteristics Using a thrust-type friction and wear tester (Suzuki-type tester), test powder is applied to the sliding interface between the thrust test piece (cylindrical: test sample) and the flat plate test piece (30 x 3t: GF30% nylon 66). Test with the following sliding conditions with the body interposed.
The coefficient of friction and the amount of wear after sliding for time were measured. (Sliding conditions) Tester: Thrust Type Friction Wear Tester (Orientec Co., EFM-III-EN) Load: 20 kg (surface pressure: 10 kgf / cm ²⁾ linear velocity: 30 cm / sec sliding Time: 12 hours ・ Sliding noise The generation of squeaking noise during the above friction and wear characteristics measurement was detected with a precision sound level meter (sound source-microphone distance 3 cm), and the noise level was measured (noise is corrected by characteristic A). (Background noise =
35dB)

[0014]

[Table 1]

[0015]

[Table 2]

[0016]

As is apparent from the above description and examples, the present invention does not generate sliding noise such as squeaking noise in the presence of dust and has dramatically improved friction and wear characteristics. It was possible to obtain a polyacetal sliding material composition which is preferably used for sliding parts mainly used outdoors, such as bearings for doors, door bearings for windows of houses, and opening / closing mechanisms for doors of houses and automobiles.

Claims (5)

[Claims] 1. A binder selected from (A) 100 parts by weight of a polyacetal resin, (B) a chlorinated polyolefin, or a block or graft copolymer of a polyolefin (co) polymer and a vinyl (co) polymer, Tensile modulus of 3,000
A polyacetal sliding material composition comprising 3 to 25 parts by weight of a polyolefin-based (co) polymer of 0 kgf / cm ² or less and (C) 5 to 30 parts by weight of a fibrous filler. 2. A polyolefin-based copolymer as component (B),
The polyacetal sliding material composition according to claim 1, which is a chlorinated polyethylene having a chlorine content of 10 to 40% by weight. 3. A polyolefin-based copolymer as component (B),
One or more olefin-based copolymers selected from ethylene / propylene copolymers, ethylene / acrylic acid ester copolymers and ethylene / methacrylic acid ester copolymers
A block or graft copolymer obtained from (b-1) and at least one vinyl (co) polymer (b-2) selected from the group consisting of polymethylmethacrylate, acrylonitrile-styrene copolymer and polystyrene. Claim 1 which is united
The polyacetal sliding material composition described. 4. The (C) component fibrous filler is glass fiber,
The polyacetal sliding material composition according to any one of claims 1 to 3, which is one or more fillers selected from the group consisting of carbon fibers and potassium titanate fibers. 5. A sliding part which is formed by molding the polyacetal sliding material composition according to any one of claims 1 to 4 and which is excellent in sliding against dust.