JPH05247235A - Low-noise sliding material - Google Patents

Abstract

PURPOSE:To obtain the title material reduced in the production of a sliding noise otherwise produced when a sliding part made from an acetal resin slides by mixing an acetal resin with a specified silane-modified polyethylene resin in a specified ratio. CONSTITUTION:The title material is prepared by mixing 100 pts.wt. acetal resin (e.g. polyacetal) with 0.01-20 pts.wt. silane-modified PE resin prepared by grafting an ethylenically unsaturated silane compound (e.g. vinyltrimethoxysilane) onto a polyethylene resin.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a member that needs to reduce noise of an acetal resin product and has a high slidability, such as a roller for conveyance and a power transmission component such as a cam, a plunger, and a gear. Sliding sound (squeak noise,
The present invention relates to a low noise sliding material for the purpose of reducing gear meshing noise).

[0002]

2. Description of the Related Art Conventionally, in order to improve slidability of a resin molded product, a method of reducing frictional resistance of the material itself by adding oil, silicone resin, fluororesin, etc. to a base resin, There is a method of applying surface treatment such as grease application or fluorine coating. However, addition of oil, silicone resin, fluororesin, etc. often causes deterioration of the basic physical properties of the base resin, and if the addition amount is too small, the effect does not occur, and conversely if too much is added, interfacial peeling (below It may cause delamination). In addition, the surface treatment by applying grease or fluorine coating to the member itself causes a considerable increase in cost, the quality of the coating material deteriorates due to the operating environment, and scattering to other parts.
It may be difficult to maintain the effect for a long period of time and does not necessarily satisfy the required quality. Therefore, sliding members made of acetal resin have come to be used, but in this case, there is a problem that noise is generated during sliding. It is an object of the present invention to solve the above problems and provide a sliding material having high sliding performance and improved noise reduction performance.

[0003]

Means for Solving the Problems As a result of intensive investigations based on these circumstances, the inventors of the present invention have been able to maintain high sliding performance for a long period of time without affecting the molded product. The present invention has been completed by finding a low noise sliding material. That is, according to the present invention, a low noise sliding comprising 100 parts by weight of an acetal resin and 0.01 to 20 parts by weight of a silane-modified polyethylene resin obtained by graft-polymerizing polyethylene with an ethylenically unsaturated silane compound. Wood is provided.

The acetal resin used in the present invention includes not only a polymer having a polyoxymethylene structure formed by polymerization of formaldehyde but also a copolymer with ethylene oxide, and is usually commercially available. It can be appropriately selected and used from the available materials.

As the polyethylene used in the silane-modified polyethylene obtained by graft-polymerizing an ethylenically unsaturated silane compound onto polyethylene, a homopolymer of ethylene by a high, medium or low pressure method is used. It is also possible to use a copolymer of the above or a blended mixture thereof. Silane-modified polyethylene is obtained by graft-polymerizing an ethylenically unsaturated silane compound on these polyethylenes in the presence of a radical generator.

The ethylenically unsaturated silane compound used has a general formula: RSiR ' _n Y _3-n (wherein R is an ethylenically unsaturated hydrocarbon or oxyhydrocarbon group, R'is an aliphatic saturated hydrocarbon group). , Y is a hydrolyzable organic group,
n is 0, 1 or 2). Specifically, R is vinyl, acryl, isopropenyl, butenyl, cyclohexenyl, γ- (meth) acryloyloxypropyl, etc., R ′ is methyl, ethyl, propyl, decyl, phenyl, Y is methoxy, ethoxy. , Formyloxy, acetoxy, propionyloxy, alkyl or arylamino and the like, preferably a trialkylsilane in which R is vinyl or γ- (meth) acrylooxypropyl is used.

As the radical generator, any compound capable of generating a free radical site in the polyethylene 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, for example, in Japanese Examined Patent Publication (Kokoku) 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 of the silane compound to 100 parts by weight of the polyethylene.
Preferably about 0.5 to 10 parts by weight and about 0.01 to 5 parts by weight, preferably about 0.01 to 2 parts by weight of the radical generator are added, and the temperature at which the radical generator used is decomposed, generally 150. It can be performed by kneading at a temperature of from about 200 ° C. As a kneading method, a normal kneading machine such as a single-screw extruder, a twin-screw extruder, a Banbury mixer, a roll, a Brabender plastograph, a kneader can be used. The obtained silane-modified polyethylene is
Those having a density in the range of 0.945 to 0.965 g / cm ³ are preferable. If the density is less than 0.945 g / cm ³ , the heat resistance will be poor, and if it is more than 0.965 g / cm ³ , the slidability, which is one of the material characteristics, will be deteriorated.

The mixing ratio of the acetal resin and the silane-modified polyethylene resin is 0.01 to 20 parts by weight, preferably 0.05 to 10 parts by weight, more preferably 100 to 100 parts by weight of the acetal resin. Is in the range of 0.1 to 5 parts by weight. If the amount of the silane-modified polyethylene resin added is less than 0.01 parts by weight, the effect of the present invention is hardly exhibited, and if it is more than 20 parts by weight, terami may occur and rigidity may decrease.

The flowability of each resin is not particularly limited, but it is preferable that the silane-modified polyethylene resin has better flowability than the acetal resin under the same temperature condition. The larger the difference in flowability between the two resins, the more preferable. Further, the compatibility of each resin is not required. On the contrary, the case where the compatibility is poor may produce better results, probably because the silane-modified polyethylene resin is likely to appear on the product surface.

The sliding material of the present invention essentially consists of the above-mentioned acetal resin and silane-modified polyethylene resin. Further, in the present invention, these two components are contained within the range that the effect of the invention is not significantly impaired. Other additional components can be added. As an additional component, various fillers,
For example, carbon black, calcium carbonate (heavy, light, colloidal), talc, mica, silica, alumina, aluminum hydroxide, magnesium hydroxide, barium sulfate,
Zinc oxide, zeolite, wollastonite, diatomaceous earth, glass fiber, glass beads, bentonite, montmorillonite, asbestos, hollow glass beads, graphite, molybdenum disulfide, titanium oxide, carbon fiber, aluminum fiber, stainless steel fiber, brass fiber , Aluminum powder, wood powder, rice husk and other fillers, as well as thermoplastic resins,
For example, polypropylene, polyethylene (high density, medium density, low density, linear low density), propylene ethylene block or random copolymer, rubber or latex component such as ethylene / propylene copolymer rubber, styrene / butadiene rubber, styrene. -Butadiene / styrene block copolymer or hydrogenated derivative thereof, polybutadiene, polyisobutylene; thermosetting resin such as epoxy resin, melamine resin, phenol resin, unsaturated polyester resin; antioxidant (phenolic, sulfur-based, etc.) ), Lubricants, various organic / inorganic pigments, UV absorbers,
Examples thereof include an antistatic agent, a dispersant, a neutralizing agent, a foaming agent, a plasticizer, a copper damage preventing agent, a flame retardant, a cross-linking agent, and a flowability improving agent.

The acetal resin and the silane-modified polyethylene resin may be added with an additional component, if desired, by using a conventional kneading machine such as a single-screw extruder, a twin-screw extruder, a Banbury mixer, a roll, a Brabender plastograph or a kneader. It can be mixed uniformly. Normally, each component is kneaded with an extruder or the like to form a pelletized compound, which is then subjected to molding processing.In a special case, each component is directly supplied to the molding machine and kneaded with the molding machine. It is also possible to mold while molding. The sliding material of the present invention can be molded by various molding methods such as injection molding, extrusion molding, and hollow molding.

The silane-modified polyethylene molded into a product is water-crosslinked in the presence of a silanol condensation catalyst. 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 catalyst,
Generally, there are carboxylates of metals such as tin, zinc, iron, lead and cobalt, organic bases, inorganic acids, and organic acids. Specifically, for example, dibutyltin dilaurate, dibutyltin diacetate, dibutyltin dioctoate. , Stannous acetate,
Carboxylates such as stannous caprylate, lead naphthenate, zinc caprylate and cobalt naphthenate, organic bases such as ethylamine, dibutylamine, hexylamine and pyridine, inorganic acids such as sulfuric acid and hydrochloric acid, toluenesulfonic acid, acetic acid , Organic acids such as 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 5 parts by weight, based on 100 parts by weight of the silane-modified polyethylene.

The method for allowing the silanol condensation catalyst to exist is as follows:
For example, the following method can be used. (1) A method of forming a master batch by kneading a silanol condensation catalyst with an extruder or the like to the same polyethylene as used for silane modification, and dry-blending the master batch with silane-modified polyethylene before molding the product. . (2) A method in which a product containing no silanol catalyst is immersed in an aqueous solution or emulsion of the silanol catalyst. A product in which a silanol condensation catalyst is introduced by these methods also undergoes water-crosslinking due to moisture in the atmosphere when left in the atmosphere, but the product is generally at room temperature to 200 ° C.
For about 10 seconds to 1 week, usually about 1 minute to 1 day, water may be contacted with water (liquid or vapor) at room temperature to about 100 ° C.

[0015]

INDUSTRIAL APPLICABILITY In the sliding material of the present invention, the polyethylene portion of the silane-modified polyethylene resin forms a skin layer at the time of molding, or partially projects on the surface, and after the molding of the product, it is water-crosslinked in the presence of a silanol condensation catalyst. As a result, good slidability is maintained and low noise is improved. In addition, since polyethylene is silane-modified, the silane group in the molecule reacts with the hydrophilic group on the other side, and the silane groups react with each other to form a network structure (crosslinking), and the acetal resin having a hydrophilic group and three-dimensional Probably because of forming the entangled structure, the above effect is maintained for a significantly long period of time.

[0016]

【Example】

Examples 1-5 and Comparative Examples 1-9 As described in Table-1 and Table-2, each component was supplied to the extruder at a predetermined ratio and kneaded to produce a molded product. The obtained molded products were evaluated using the following methods, and the results are shown in Table-1 and Table-2.

The materials used in the above examples and comparative examples are as follows. 1. polyacetal (Mitsubishi Gas Chemical Co., Ltd., trade name "Iupital") 2. high density polyethylene having a density of 0.952g / cm ³ for the (Mitsubishi Petrochemical Co., Ltd. under the trade name "Mitsubishi polyethylene HD") 100 parts by weight, 1.5 parts by weight of vinyltrimethoxysilane and 0.
Blended with 03 parts by weight of dicumyl peroxide, 220 ° C
A silane-modified product grafted by kneading and extrusion at (density: 0.952 g / cm ³ , MFR: 0.2 g / 10 min). 3. A masterbatch containing 1% by weight of dibutyltin dilaurate for high density polyethylene (trade name "Mitsubishi Polyethylene HD" manufactured by Mitsubishi Petrochemical Co., Ltd.) having a density of 0.952 g / cm ³ . 4. 1.2 parts by weight of maleic anhydride and 100 parts by weight of high-density polyethylene (trade name “Mitsubishi Polyethylene HD” manufactured by Mitsubishi Oil Chemical Co., Ltd.) with a density of 0.965 g / cm ³ and lauroyl for maleic anhydride. A maleic anhydride-modified product (MFR: 2.3 g / 10 min) was prepared by mixing 0.8 mol of peroxide and graft-kneading at 200 ° C. for extrusion. 5. High density polyethylene with a density of 0.958 g / cm ³ (trade name “Mitsubishi Polyethylene HD” manufactured by Mitsubishi Yuka Co., Ltd.) (MFR: 21
g / 10 min). 6. Glass fiber with an average diameter of 13 μm and an average length of 3 mm.

Experiments and evaluation methods in Examples and Comparative Examples are as follows. 1. Test piece manufacturing method 1) Injection molding: Mold clamping force: 120ton mold, Clamping method: Toggle method, Injection capacity (PS): 273g Injection rate: 450cc / sec, Maximum injection pressure: 1820kg /
cm ² Using a molding machine having the above specifications, a 100 × 100 × 2 mm sheet, an ASTM bending test piece, and a spur gear (module 1; number of teeth 40; tooth width 5 mm) are molded, and then crosslinked. 2) Pipe molding: Screw diameter: 40φ, screw shape: full flight screw, L / D: 25 Using a molding machine with the above specifications, a pipe with an outer diameter of 21 mm and a wall thickness of 3.5 mm is molded and then subjected to a crosslinking treatment. . 2. Cross-linking method The test piece is cross-linked in hot water at 90 ° C for 3 hours.

3. Coefficient of friction Using an Ito-type instrumentation wear tester manufactured by Tokyo Testing Machine Co.,
Surface pressure P (1.5 kg / cm ² ) × peripheral speed V (18 m / min) = 27 (kg
/ Cm ² · m / min), using chromium-plated steel as the mating material, and measuring at a temperature of 23 ° C and a humidity of 50% 6
The friction coefficient (μ) at the time of running for 0 min (18 m / min × 60 min = 1080 m) was obtained. 4. Flexural modulus According to ASTM D790. 5. Cross-cut peeling test Using a single-edged razor, draw 11 parallel and 11 vertical and horizontal lines perpendicular to the sheet surface of 100 x 100 x 2 mmt at 2 mm intervals to make 100 cross-cuts. A cellophane adhesive tape (JISZ1522) was sufficiently pressure-bonded on it, and it was peeled off at a stroke while keeping it at about 45 degrees with respect to the surface. 6. Observation of Delamination Use a pipe with an outer diameter of 21 mm, a wall thickness of 3.5 mm, and a length of 500 mm, and observe the delamination state when one side is clamped and a load is applied to the other side at 90 degrees. 7. Noise test Measure the noise level when a gear made of this material is rotated in a silent box at a load torque of 5 kgcm and a rotation speed of 200 rpm.

[0020]

[Table 1]

The results shown in Table 1 are those obtained by adding the silane modified product to the polyacetal (Examples 1 and 2), the polyacetal alone (Comparative Example 1) and the polyacetal added with the maleic anhydride modified product (Comparative Example). Compared to 2), it shows that the friction coefficient is low and the noise reduction effect is extremely high.

[0022]

[Table 2]

The results shown in Table 2 are obtained by adding a silane-modified product to polyacetal (Examples 3 and 4) and adding high-density polyethylene to polyacetal (Comparative Example 3).
And 4) and polyacetal to which a maleic anhydride modified product was added (Comparative Examples 5 and 6), the coefficient of friction was low, and delamination of the product was not observed.

The samples of Example 2, Comparative Example 2 and Comparative Example 4 were subjected to a continuous test under the same conditions as described above, and the results of measuring the friction coefficient at each traveling distance are shown in the table.
3 shows. The sliding material of the present invention retains excellent slidability even during extremely long running.

[0025]

[Table 3]

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Claims (1)

[Claims] 1. A low noise sliding material comprising 100 parts by weight of an acetal resin and 0.01 to 20 parts by weight of a silane-modified polyethylene resin obtained by graft-polymerizing polyethylene with an ethylenically unsaturated silane compound.