JPH07268171A - Sliding resin composition - Google Patents

Abstract

PURPOSE:To provide a sliding resin composition containing a specific silane- modified polyethylene, a polytetrafluoroethylene, etc., having excellent slidability, low friction coefficient and high abrasion resistance and useful as a molding material for bearing, etc. CONSTITUTION:This sliding resin composition is composed of (A) 50-95wt.% of a silane-modified polyethylene graft-polymerized with (i) an ethylenic unsaturated silane compound, (B) 3-40wt.% of a powdery polytetrafluoroethylene (preferably having an average particle diameter of <=50mum) and (C) 2-30wt.% of potassium titanate whiskers and is produced by crosslinking the component A. Preferably, the crosslinked homopolymer of the component A has a gel fraction of >=30% measured by extracting with boiling xylene, the crosslinking is carried out in the presence of 0.1-10 pts.wt. (based on 100 pts.wt. of the component A) of a silanol condensation catalyst and the component A is produced by the graft polymerization of 0.01-15 pts.wt. of the component (i) to (ii) 100 pts.wt. of a polyethylene having a density of 0.93-0.965g/cm<3>.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a resin composition having excellent slidability. That is, the present invention relates to a slidable resin composition of silane-modified polyethylene which gives a molded article having a low friction coefficient and excellent wear resistance. This slidable resin composition is suitable as a molding material for sliding parts such as bearings, roller idlers and cable conduits.

[0002]

2. Description of the Related Art Recently, plastics for sliding members have been developed in various fields, and mainly polyacetal resin (PO
Resin materials having relatively excellent slidability such as M) and polyamide resins (PA6, 66, etc.) are used. However, while these materials have excellent wear resistance, they have the drawback of having a high friction coefficient. In order to improve these, it has been improved by filling the above resin material with a filler having excellent slidability such as molybdenum disulfide, graphite, and PTFE, but it is not always sufficient to meet the recent demand for higher performance. Was not. Although a method of reducing the friction coefficient by applying lubricating oil, grease or the like at the time of use is also performed, there is a problem that the cost is increased in the assembling process, and a sufficient solution has not been obtained.

[0003]

Accordingly, it is an object of the present invention to provide a resin composition which is excellent in slidability and abrasion resistance and which can be easily molded by extrusion, injection molding or the like.

[0004]

Means for Solving the Problems The inventors of the present invention have made extensive studies based on the above situation, and as a result, the composition of silane-modified polyethylene, polytetrafluoroethylene and potassium titanate whisker has excellent slidability. The inventors have found the present invention and have reached the present invention. That is, the present invention relates to A. Silane-modified polyethylene graft-polymerized with ethylenically unsaturated silane compound 50 to 95% by weight B.I. Polytetrafluoroethylene (PTFE) powder 3-40% by weight C.I. It is intended to provide a slidable resin composition composed of 2 to 30% by weight of potassium titanate whisker, which is obtained by crosslinking the component A and has excellent slidability. Furthermore, the present invention provides a sliding resin composition using, as the above-mentioned component A, a silane-modified polyethylene obtained by graft-polymerizing an ethylenically unsaturated silane compound having a gel fraction by xylene boiling point extraction of 30% by weight or more. To do.

The present invention will be described in more detail below. (Polyethylene) The polyethylene as the raw material of the silane-modified polyethylene used in the present invention has a density of 0.
930 to 0.965 g / cm ³ , preferably 94 to 0.955
g / cm ³ is used. These polyethylenes are
Usually, it is produced by a low pressure ionic polymerization method. Further, a copolymer of ethylene and an α-olefin such as propylene or butene-1 can also be used. In this case, the copolymerization component is preferably 20% by weight or less.

(Silane-modified polyethylene) The silane-modified polyethylene used as the component A in the present invention is obtained by graft-polymerizing the above-mentioned polyethylene with an ethylenically unsaturated silane compound in the presence of a radical generator. The ethylenically unsaturated silane compound used has a general formula; RSiR'nY _3- n (wherein R is an ethylenically unsaturated hydrocarbon or oxyhydrocarbon, R'is an aliphatic saturated hydrocarbon group, and Y is hydrolyzable. Organic groups, n is 0, 1
Or 2). Specifically, R is vinyl, acryl, isopropenyl, butenyl, cyclohexenyl, γ-methacryloyloxypropyl, etc., R ′ is methyl, ethyl, decyl, phenyl, Y is methoxy, ethoxy, formyloxy, acetoxypropionyl. Oxy, alkyl or allylamino, etc., preferably R is vinyl or γ- (meth)
Tolylalkoxysilane, which is acrylooxypropyl, is used.

As the radical generator, any compound capable of generating a free radical site in the polyolefin under the graft reaction condition and having a sufficiently short half-life at the graft reaction temperature can be used. These radical generators are described in, for example, Japanese Examined Patent Publication No. 48-1711, and typical radical generators include organic peroxides such as dicumyl peroxide, t-butylperoxyoctate, and benzoyl peroxide. And azo compounds such as azoisobutyronitrile and methylazoisobutyrate.

The graft reaction of the ethylenically unsaturated silane compound onto polyethylene is carried out by adding 0.01 to 15 parts by weight, preferably 0.5 to 10 parts by weight, of the silane compound to 100 parts by weight of the polyethylene, and the radical. It is carried out by adding 0.01 to 5 parts by weight, preferably 0.01 to 2 parts by weight, of a generator and kneading at a temperature at which the radical generator used is decomposed, generally at a temperature of about 150 to 200 ° C. You can As the kneading method, a normal kneading machine such as a single-screw or multi-screw kneading extruder, a Banbury mixer, a roll, a Brabender plastograph, a kneader and the like can be used.

(PTFE powder) PTF used in the present invention
As the E powder, for example, a homopolymer obtained by suspension polymerization or emulsion polymerization of tetrafluoroethylene (TFE) and pulverized and classified can be used. The average particle size of the powder is
It is 50 μm or less (desirably 10 μm or less), and if it is larger than this, the effect of the present invention cannot be obtained. The compounding amount of the PTFE powder is 3 to 40% by weight (desirably 5 to 30% by weight). If the blending amount is less than 3% by weight, the effect of the invention cannot be obtained, and if the blending amount is more than 40% by weight, not only the slidability (particularly abrasion resistance) is lowered but also the fluidity is remarkably impaired.

(Potassium titanate whiskers) The potassium titanate whiskers used in the present invention include, for example, 4-potassium titanate whiskers, 6-potassium titanate whiskers,
Single crystal fibers such as potassium 8-titanate whiskers can be used. These are obtained, for example, by firing a mixture of a titanium raw material compound and a potassium raw material compound. The whisker has an average fiber diameter of 5 μm or less (preferably 2 μm or less) and a fiber length of 500 μm or less (preferably 10 to 20).
0 μm) is desirable. The compounding amount is 2 to 30% by weight, preferably 5 to 20% by weight, more preferably 5 to 15% by weight.
Is. If it is less than 2% by weight, the coefficient of friction increases,
If it exceeds 5% by weight, the wear resistance is significantly reduced.

(Additional component) The slidable resin composition of the present invention essentially consists of a composition of A component, B component and C component. Further, in the present invention, the effect of the invention is remarkably impaired. In addition to these components, additional components can be added in an amount of 300 parts by weight or less based on 100 parts by weight of the composition, as long as the amount is not included. For example, carbon fibers, aramid fibers, various whiskers excluding potassium titanate whiskers (alumina boron, whiskers such as silicon carbide), other powdered carbides, calcium carbonate, talc, mica, silica, alumina, aluminum hydroxide, magnesium hydroxide, Barium sulfate, zinc oxide, zeolite, wollastonite, diatomaceous earth, glass beads, bentonite, montmorillonite, asbestos, hollow glass beads, graphite,
Fillers such as molybdenum disulfide may be mentioned. In addition, various resins such as polyolefin resins (polypropylene, copolymers of ethylene and vinyl acetate, acrylic acid ester, etc.) other than polyethylene, in a range not exceeding 40% by weight of the silane-modified polyethylene as the component A,
Various acrylate resins (PMMA, etc.), polystyrene,
ABS resin, PA resin (6, 66, 11, 12, etc.), modified polyphenylene ether, polycarbonate, polyethylene terephthalate, polybutylene terephthalate,
It may be replaced with polyphenylene sulfide, liquid crystalline polyester, various elastomers (olefin type, amide type, etc.).

Further, if necessary, an antioxidant, a nucleating agent,
Flame retardants and their dispersants may be included in the composition in an amount of 0.05 to 5% by weight. Further, various lubricating oils (mineral oil, animal and vegetable oils, ester oils, silicone oils, etc.) may be impregnated in order to further improve the slidability. The above-mentioned fillers described in the potassium titanate whiskers, PTFE powder and other additional components in the present invention can be subjected to various surface modifications in order to enhance the affinity with the silane-modified polyethylene. For example, silane coupling agent, titanium coupling agent, higher fatty acid such as stearic acid and oleic acid, higher fatty acid glycerin ester,
Amides, higher fatty acid metal salts, higher alcohols, various waxes, polar polyolefins (maleic anhydride modified polyolefin, oxidized polyolefin, etc.) can be used.

(Manufacturing Method and Molding Method of Kneading Composition) The composition of the present invention can be manufactured by using a conventional kneading machine such as a single-screw extruder, a twin-screw extruder, a Banbury mixer, a roll, a Brabender, and a kneader. it can. Usually, the above-mentioned essential components and, if desired, an additional component, a cross-linking catalyst, etc. are kneaded into pellets by an extruder or the like, and then subjected to processing, but each component is directly supplied to a molding machine to form a composition in the molding machine. It can also be molded while kneading. It is also possible to knead component B or component C in high concentration in advance to form a masterbatch, which can be blended or directly molded while being diluted with another component such as component A. The composition of the present invention can be molded by a usual molding machine for thermoplastic resins. That is, it can be applied to injection molding, extrusion molding, press molding, etc. after mixing a crosslinking catalyst with the composition as necessary. Of these, injection molding is preferable because it has excellent productivity.

(Silane Crosslinking) As described above, the A component: the silane-modified polyethylene is kneaded together with the B component: PTFE particles and the C component: potassium titanate whiskers in a predetermined compounding amount to form pellets, and then molded. Alternatively, it may be molded following kneading. Silane cross-linking is carried out in the presence of water, and there are methods that do not use a catalyst and that cross-link by heat and moisture in the atmosphere during kneading or molding, or cross-linking in the presence of a silanol condensation catalyst. In terms of the degree of progress and the degree of progress, it is advantageous to carry out the crosslinking reaction in the presence of a silanol condensation catalyst to promote the crosslinking reaction significantly. As the silanol condensation catalyst used here, a compound used as a catalyst for promoting dehydration condensation between silanols of silicone is used. Such silanol condensation catalysts generally include metal carboxylates such as tin, zinc, iron, lead and cobalt, organic bases, inorganic acids and organic acids, and specific examples include dibutyltin laurate and dibutyltin. Carboxylates such as octoate, dibutyltin acetate, lead naphthenate, cobalt naphthenate, ethylamine, dibutylamine, hexylamine,
Examples thereof include organic bases such as pyridine, inorganic acids such as sulfuric acid and hydrochloric acid, and organic acids such as toluenesulfonic acid, acetic acid, stearic acid and maleic acid. The amount of the silanol condensation catalyst used is in the range of about 0.001 to 10 parts by weight, preferably 0.01 to 3 parts by weight, based on the silane-modified polyethylene (component A) in the resin composition of the present invention. .

Examples of the method for allowing the silanol condensation catalyst to exist include the following methods. (1) A method of forming a masterbatch containing a silanol condensation catalyst using a composition not modified with silane, and adding the composition at the time of kneading the components of the present invention, or dry-blending before molding to perform molding. (2) A method of immersing a molded product containing no silanol catalyst in an aqueous solution or emulsion of the silanol catalyst. Molded articles with silanol catalyst introduced by these methods,
Although water crosslinking also progresses due to moisture in the atmosphere when left in the atmosphere, generally molded articles are at room temperature to 200 ° C, usually at room temperature to 100 ° C in water (liquid or vapor) and 10 seconds to 1 The contact may be performed for about a week, usually for about 1 minute to 1 day. In the present invention, the gel fraction after cross-linking the silane-modified polyethylene by the above method is 30% by weight or more, preferably 50% by weight or more, and when the gel fraction is less than 30% by weight, slidability, especially Abrasion resistance is significantly reduced.

In the present invention, the gel fraction is determined by using a crosslinked sample of the component A and using xylene as a solvent.
Extraction was carried out for 10 hours at the boiling temperature using a Soxhlet type extractor, and the weight of the extraction residue was expressed as a percentage according to the following formula. Gel fraction (%) = residual extraction weight (g) / sample weight before extraction
(g) x 100

[0017]

The present invention will be described in detail with reference to the following examples. The components used are as follows. Silane-modified polyethylene (I) With respect to 100 parts by weight of high-density polyethylene having a density of 0.952 g / cm ³ (“Mitsubishi Polyethylene” manufactured by Diapolymer Co., Ltd.),
1.5 parts by weight of vinylmethoxysilane and 0.03 parts by weight of dicumyl peroxide were blended and kneaded and extruded at 180 ° C. to obtain a grafted silane-modified product. (MFR
0.8g / 10min gel fraction 65%)

Silane-modified polyethylene (II ) 100 parts by weight of high-density polyethylene (“Mitsubishi Polyethylene” manufactured by Diapolymer Co., Ltd. ) having a density of 0.965 g / cm ³
2.0 parts by weight of vinyl methoxysilane and 0.015 parts by weight of di-t-butyl peroxide were blended, and a grafted silane-modified product was obtained by kneading and extruding at 180 ° C.
(MFR 16g / 10min, gel fraction 62%)

Silane-modified polyethylene (III) High-density polyethylene 200 having a density of 0.952 g / cm ³ with respect to 100 parts by weight of the silane-modified polyethylene (I).
Parts by weight were mixed and used. (Gel fraction 25%)

Silane-modified polypropylene As a polypropylene used for comparison, 100 parts by weight of "Mitsubishi Polypro" manufactured by Dia Polymer Co., Ltd. was used.
0 parts by weight of vinyl methoxysilane and 0.7 parts by weight of benzoyl peroxide were blended and kneaded at 220 ° C. to obtain a grafted silane-modified product by extrusion. (density
0.910 g / cm ³ MFR 11 g / 10 min, gel fraction 63
%)

PTFE I PTFE powder made by Kitamura Co., Ltd. KTL610 (average particle size 10 μm) PTFE II PTFE powder made by Kitamura Co., Ltd. KTL400H (average particle size 60 μm) Potassium titanate whisker Otsuka Chemical Co., Ltd. “Tismo "D101" Graphite "Natural graphite CP / B" manufactured by Nippon Graphite Co., Ltd. Molybdenum disulfide "Morifine powder Y" manufactured by Japan Inorganic Chemical Co., Ltd. Carbon fiber "A-6003" manufactured by Asahi Carbon Fiber Co., Ltd. Polyacetal (POM) BASF Corporation "Ultraform N2320" Nylon 66 (PA66) BASF Corporation "Ultramid A3K"

(Mixing, molding, silane cross-linking)
The components were mixed at the mixing ratios shown in Table 1 and Table 2 and kneaded at 160 ° C. using a twin-screw kneading extruder to obtain pelletized compositions. 5 parts by weight of the master batch of the following silanol condensation catalyst was mixed with 100 parts by weight of the silane-modified polyethylene or silane-modified polypropylene as the component A, and the pellets were molded at a molding temperature of 180 ° C. using an injection molding machine.
A plate having a length of 100 mm × a width of 100 mm × a thickness of 2 mm was formed at a mold temperature of 40 ° C. and divided into test pieces having a length of 30 mm × a width of 30 mm. The masterbatch of the silanol condensation catalyst used was 100 parts by weight of the same polyethylene or polypropylene as those used in the production of the above-mentioned silane-modified polyethylenes (I) to (III) and silane-modified polypropylene, and 1 part by weight of dibutyltin laurate. Was blended and kneaded at 180 ° C. Then, the test piece was immersed in hot water at 100 ° C. for 1 hour to perform silane crosslinking. On the other hand, a molded body was made to have the same size as the test piece using only the component A, and the molded body was ground with a file to obtain a sample for gel fraction measurement. This sample is subjected to boiling point extraction with xylene,
The gel fraction of component A was determined.

(Evaluation of Sliding Property) The sliding property of the test piece in the examples was evaluated by using an Ito type abrasion tester (manufactured by Tokyo Testing Machine Co., Ltd.). As a slidability test ring of a friction partner, S45 having the shape shown in FIGS. 1 and 2 is used.
The one made of C steel material was used. The test conditions are shown below. Contact area 0.216cm ² (0.072cm ² × 3) Test load 20Kg (Surface pressure 93Kg / cm ² ) Rotation speed 180RPM Speed 20.3cm / sec Test time 5 hours Distance 3650m Dynamic friction from load torque applied to ring during test The coefficient was calculated. Further, the wear amount of the sample during a certain test time was reduced, and the wear depth was measured by a surface roughness meter (manufactured by Tokyo Seimitsu Co., Ltd.). The wear depth was determined by measuring four points on the circumference of the wear scar per sample and calculating the average value. After the slidability test of the examples, there was no change in weight due to wear of the ring sliding surface, and there was almost no damage such as scratches on the ring sliding surface. The above results are summarized in Tables 1 and 2.

[0024]

[Table 1]

[0025]

[Table 2]

[0026]

As can be seen from the results of Tables 1 and 2, the resin composition of the present invention containing the specific amounts of the components A, B and C in the present invention has a low friction coefficient,
It has extremely excellent slidability such as excellent wear resistance, and it has been used as a sliding material in the past.
Excellent results were obtained over the OM and PA resins. In addition, it was revealed that damage to the mating material was extremely small due to suppression of heat generation on the sliding surface due to the low friction coefficient. Furthermore, a product obtained by silane-crosslinking this molded product is further excellent in the above-mentioned properties. These materials can be applied to sliding parts such as rollers and bearings, and particularly to parts with strict performance requirements that were impossible with conventional resin materials.

[Brief description of drawings]

FIG. 1 is a bottom view of a slidability test ring of an abrasion tester used in Examples.

FIG. 2 is a diagram in which the bottom surface of the slidability test ring is about to come into contact with the sheet sample.

[Explanation of symbols]

 1 ring 2 sliding surface 3 sheet sample

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor, Jichio Deguchi, Toho-cho, Yokkaichi-shi, Mie No. 1 Toho-cho, Mitsubishi Petrochemical Co., Ltd. Yokkaichi Research Institute

Claims (4)

[Claims] 1. A. Silane-modified polyethylene graft-polymerized with ethylenically unsaturated silane compound 50 to 95% by weight B.I. Polytetrafluoroethylene (PTFE) powder 3-40% by weight C.I. A slidable resin composition comprising 2 to 30% by weight of potassium titanate whisker, which is obtained by crosslinking A. 2. The slidable resin composition according to claim 1, wherein the component A has a gel fraction of 30% by weight or more when measured by xylene boiling point extraction when the component A alone is crosslinked. object. 3. The sliding property according to claim 2, wherein the silane crosslinking is carried out in the presence of 0.01 to 10 parts by weight of a silanol condensation catalyst with respect to 100 parts by weight of the silane-modified polyethylene as the component A. Resin composition. 4. The density of the component A is 0.93 to 0.965 g / cm ^3.
Is a silane-modified polyethylene in which 0.01 to 15 parts by weight of an ethylenically unsaturated silane compound is graft-polymerized with respect to 100 parts by weight of polyethylene, and the B component is a PTFE powder having an average particle size of 50 μm or less. The slidable resin composition according to any one of claims 1 to 3.