JP2002069267A - Polyacetal resin composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyacetal resin composition which is excellent in sliding properties, generates reduced noise when sliding, and is excellent in long-term low noise characteristics and low frictional wear characteristics particularly in the sliding with glass. SOLUTION: The polyacetal resin composition comprises 100 pts.wt. of a polyacetal resin, 0.01-40 pts.wt. of mica with an average particle size of 40 μm or less and 0.05-10 pts.wt. of a sliding agent.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a polyacetal resin composition and a molded product obtained by molding the same, and more particularly, to a polyacetal resin composition for a sliding member and a molded product obtained by molding the same.

[0002]

2. Description of the Related Art Polyacetal resins have excellent mechanical strength, fatigue resistance, electrical properties, and the like, and are therefore widely used as engineering resins in mechanical parts, automobiles, home electric parts, and the like. In addition, polyacetal resins are also excellent in friction and wear characteristics, and there are many uses where the characteristics are utilized. Recently, due to its excellent friction and wear properties, it has been used as a guide component when glass is raised and lowered.

[0003] However, when the glass slides on the guide part at the portion where the glass slides, abrasion of the resin or frictional noise during sliding occurs, and the friction and wear characteristics inherent in polyacetal resin, fatty acid ester, silicone, The friction and wear characteristics of a resin composition to which only a solid lubricant such as polytetrafluoroethylene and molybdenum disulfide were added were insufficient for required applications.

A polyacetal resin composition used for such a sliding member is disclosed, for example, in JP-A-63-297.
No. 453 discloses a method of adding a high-viscosity silicone oil and a low-viscosity lubricant to a polyacetal resin, and JP-A-1-263145 discloses a method of adding a specific inorganic powder and a fatty acid ester to a polyacetal resin. And a polyacetal resin composition for a sliding member, which comprises: Japanese Patent Application Laid-Open No. 03-111446 discloses a polyacetal resin composition obtained by adding a specific graft copolymer, a lubricant and a specific inorganic powder to a polyacetal resin.

[0005] However, these polyacetal resin compositions do not sufficiently satisfy the friction and abrasion characteristics and the noise characteristics in parts in which glass slides and slides. Wear characteristics,
There is a problem that noise characteristics are reduced.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide an excellent sliding property, reduce the noise generated during sliding, and, especially in sliding with glass, have a long-term low noise characteristic and low friction wear characteristic. And to provide a polyacetal resin composition which is excellent in the above.

[0007]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problem, and its gist is that the average particle size is 40 μm per 100 parts by weight of polyacetal resin.
0.01 to 40 parts by weight of the following mica and 0.05 to 1 of the sliding agent
0 parts by weight of the polyacetal resin composition.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail. The polyacetal resin in the present invention is a polyacetal (polyoxymethylene) which is already commercially available.
And polyacetal copolymers. More specifically, an oxymethylene homopolymer having an oxymethylene unit structure, an oxymethylene copolymer having an oxyalkylene unit structure, an oxymethylene block copolymer, an oxymethylene graft polymer, and an oxymethylene copolymer having a crosslinked structure And the like.

An oxymethylene homopolymer having an oxymethylene unit structure is produced using formaldehyde, its trimer trioxane or its tetramer tetraoxane as a raw material. Oxymethylene copolymers having an oxyalkylene unit structure include formaldehyde, trioxane, tetraoxane and the like, ethylene oxide, epichlorohydrin, 1,3-dioxolan,
1,3,5-trioxepane, glycol former
And cyclic ethers having 2 to 8 carbon atoms, such as formal and diglycol. The oxymethylene copolymer having an oxyalkylene unit structure is preferably an oxymethylene copolymer containing 0.1 to 20% by weight of the oxyalkylene unit structure. Examples of the oxymethylene block copolymer include oxymethylene block copolymers having an oxymethylene homopolymer or oxymethylene copolymer as a main structure and having a block structure other than an oxymethylene unit structure or a terminal structure.

[0010] The polyacetal resin is generally selected from commercially available polyacetal resins in the form of powder, flakes or pellets in consideration of the intended use, and the object is achieved. be able to. Currently, commercially available polyacetals include oxygen,
One or two kinds of stabilizers or antioxidants such as melamine, cyanoguanidine, polyamide, and / or hindered phenol or hindered amine are used to suppress the decomposition by the action of heat, water, light and the like. It is often blended above. Additives such as stabilizers and antioxidants blended in such commercially available polyacetals generally normally effectively work to improve the thermal stability of the polyacetal resin composition of the present invention.

The mica in the present invention is an alumina silicate which is a rock-forming mineral and forms a plate-like crystal. For example, muscovite, phlogopite, a wet-ground product, a dry-ground product and the like can be used. The average particle size of the mica is 40 μm or less. If the average particle diameter of mica exceeds 40 μm, sliding noise is high, frictional force is large, and abrasion is increased. The average particle size of the mica is preferably 0.5 to 40 μm, more preferably 1 to 40 μm.
30 μm. The average aspect ratio of mica is preferably 10 or more, more preferably 10 to 60.
If the aspect ratio is too small, the effect of suppressing vibration is insufficient, and if the aspect ratio is too large, the surface of the molded article tends to be non-smooth and slidability tends to be insufficient. The measurement of the average particle diameter and the average aspect ratio of mica includes, for example, a method of measuring the particle diameter and the thickness with an electron microscope.

[0012] A common phlogopite is a silicate mineral represented by the following formula (1).
It has a three-layer structure containing 1 and K.

[0013]

Embedded image K ₂ Al ₄ (Si ₆ .Al ₂ ) O ₂₀ (OH) ₄ (1)

Although such mica can be used as it is, it has been previously surface-treated with a surface treating agent, a coupling agent or the like, for example, a functional compound such as an epoxy compound, a silane compound, an isocyanate compound or a titanate compound. Mica can also be used.

The amount of mica having an average particle size of 40 μm or less is as follows:
It is 0.01 to 40 parts by weight based on 100 parts by weight of polyacetal. When the amount is less than 0.01 part by weight, the low noise effect is insufficient, and when the amount is more than 40 parts by weight, the wear resistance and the thermal stability are liable to decrease. The amount of mica having an average particle size of 40 μm or less is preferably 0.02 to 30 parts by weight, more preferably 0.05 to 25 parts by weight, based on 100 parts by weight of the polyacetal.

The sliding agent in the present invention is an auxiliary agent for reducing the sliding resistance and abrasion of the polyacetal resin. The sliding agent preferably includes paraffin wax, polyethylene wax, silicone oil, fatty acid ester, fatty acid and fatty acid metal salt. As the sliding agent, one kind may be blended, or two or more kinds may be blended.

Examples of the paraffin wax include known higher paraffinic hydrocarbons such as paraffin wax. Preferred paraffin wax is a paraffin wax having a melt viscosity at 100 ° C of 0.1 poise or less and a melting point of 50 to 70 ° C. As polyethylene wax,
Low-molecular-weight polyethylene, low-molecular-weight polyethylene copolymer, and modified polyethylene wax into which a polar group is introduced by oxidizing or acid-modifying these are exemplified. The number average molecular weight of the polyethylene wax is preferably from 500 to 15,000, more preferably 1,000.
〜１０10000.

Polyethylene waxes such as low molecular weight polyethylene and low molecular weight polyethylene copolymer can be obtained by a method of directly polymerizing ethylene or ethylene and an α-olefin with a Ziegler catalyst or the like, or by-products during the production of high molecular weight polyethylene or copolymer And a method of thermally decomposing a high molecular weight polyethylene or a copolymer. As such polyethylene wax, 50 to 99 mol% of ethylene and α-olefin 1 to 1
A copolymer type polyethylene wax with 50 mol% is preferred, and particularly preferred is a case where the α-olefin is polypropylene.

The oxidized polyethylene wax is obtained by treating a polyethylene wax with a peroxide or oxygen to introduce a polar group such as a carboxyl group or a hydroxyl group. Acid-modified polyethylene wax is one in which a polar group such as a carboxyl group or a sulfonic acid group is introduced by treating with an inorganic acid, an organic acid or an unsaturated carboxylic acid in the presence of peroxide or oxygen, if necessary. It is. These polyethylene waxes include general type high density polyethylene wax, general type low density polyethylene wax,
It is commercially available under the name of low oxidation type polyethylene wax, high oxidation type polyethylene wax, acid-modified type polyethylene wax or special monomer-modified type, and can be easily obtained.

The silicone oil can be arbitrarily selected from commonly known silicone oils. Examples of the silicone oil include a silicone oil composed of polydimethylsiloxane, a silicone oil in which a part of methyl groups of polydimethylsiloxane is substituted with phenyl groups, and a part of methyl groups of polydimethylsiloxane in which hydrogen or carbon number is 2 or more. A silicone oil in which a part of the methyl group of polydimethylsiloxane is substituted by a halogenated phenyl group, and a silicone oil in which a part of the methyl group of polydimethylsiloxane is substituted by a fluoroester group Epoxy-modified silicone oils such as polydimethylsiloxane having epoxy groups, amino-modified silicone oils such as polydimethylsiloxane having amino groups, and alkyl aralkyl silicones such as dimethylsiloxane and phenylmethylsiloxane. Oil, polyether-modified silicone oil such as polydimethylsiloxane having a structure in which some of the methyl groups of the dimethylsiloxane unit are substituted with polyether, and dimethyl in which some of the methyl groups of the dimethylsiloxane unit are substituted with polyether Alkyl aralkyl polyether-modified silicone oils such as a polymer of siloxane and phenylmethyl siloxane are exemplified.

The viscosity of the silicone oil at 25 ° C. is preferably at least 150,000 cst, more preferably at least 500,000 cst. Viscosity 1
If it is less than 50,000 cst, peeling tends to occur on the surface of the molded product.

The fatty acid esters include those having 5 to 32 carbon atoms.
And fatty acid esters of a monohydric or polyhydric alcohol having 2 to 30 carbon atoms. As fatty acids,
Caproic acid, caprylic acid, undecylic acid, lauric acid,
Tridecylic acid, myristic acid, palmitic acid, stearic acid, behenic acid, lignoceric acid, serotinic acid, montanic acid, saturated fatty acids such as melicic acid, or oleic acid, elaidic acid, linoleic acid, linolenic acid, arachidonic acid, pracidic acid, And unsaturated fatty acids such as erucic acid and ricinoleic acid. Alcohols include propyl, isopropyl, butyl, octyl, capryl,
Examples include monohydric alcohols such as lauryl, myristyl, stearyl, and behenyl, and polyhydric alcohols such as ethylene glycol, propylene glycol, butanediol, glycerin, pentaerythritol, and sorbitan. The fatty acid ester preferably has 12 carbon atoms.
And fatty acid esters of a C.sub.-22 fatty acid and a C.sub.2-22 monohydric or polyhydric alcohol.

The fatty acid includes a saturated or unsaturated fatty acid having 12 or more carbon atoms. Examples of fatty acids include lauric acid, tridecylic acid, myristic acid, pentadecylic acid, palmitic acid, heptadecylic acid, stearic acid, nonadecanoic acid, arachinic acid, behenic acid, lignoceric acid,
Cerotic acid, heptacosanoic acid, montanic acid, melicic acid, lacceric acid, oleic acid, elaidic acid, linoleic acid, linolenic acid, arachidonic acid, cetreic acid, erucic acid and the like. The fatty acid is preferably a saturated fatty acid having 12 to 22 carbon atoms.

The fatty acid metal salt is a salt of a higher fatty acid and a metal. Examples of the higher fatty acid include stearic acid, oleic acid, octanoic acid, lauric acid, behenic acid, and ricinoleic acid. Metals include zinc, calcium,
Examples include magnesium, nickel, and copper. When a combination of two or more sliding agents is used, for example, a combination of a fatty acid ester and a fatty acid metal salt is preferable.

The compounding amount of the sliding agent is as follows.
It is 0.05 to 20 parts by weight with respect to 00 parts by weight. If the amount is too small, the sliding effect is insufficient. If the amount is too large, moldability is poor, bleed-out is likely to occur, and mold contamination and appearance deterioration are likely to occur. The compounding amount of the sliding agent is preferably 0.1 to 15 parts by weight, more preferably 0.2 to 10 parts by weight.

The mechanism by which the mica and the sliding agent are blended with the polyacetal resin to remarkably improve the silencing characteristics and the continuity of the silencing is based on the effect of the improvement of the surface hardness by the mica and the flake shape of the mica itself. It is presumed to be due to the vibration suppression effect peculiar to mica, the effect by the sliding agent, and the like.

It is preferable that the mica and the sliding agent in the present invention are directly added to and mixed with the polyacetal resin, melt-kneaded, and uniformly dispersed in the polyacetal resin. The kneading method of the polyacetal resin composition of the present invention can be kneaded by various known methods. It is prepared by adding mica and a sliding agent to the polyacetal resin, further adding other auxiliaries if necessary, heating and melting and kneading.
For example, a polyacetal resin and necessary components are uniformly mixed in advance by a tumbler or a mixer such as a Henschel mixer, and then supplied to a single-screw extruder or a twin-screw extruder to be melt-kneaded to produce pellets. At this time, all components may be added simultaneously or separately.

The polyacetal resin composition of the present invention comprises
Known additives that impart desired properties according to the purpose,
For example, heat stabilizers, antioxidants, release agents, weathering agents, antistatic agents, conductive agents, nucleating agents, fillers, such as glass fibers, glass beads, glass flakes, talc, calcium carbonate, zeolites, carbon fibers And a pigment.

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist of the present invention. The raw materials used in each example and comparative example are as follows. (1) Polyacetal copolymer: manufactured by Mitsubishi Engineering-Plastics Corporation (Iupital F20-0)
1). (2) Polyacetal homopolymer: manufactured by Asahi Kasei Corporation (Tenac 4010). (3) Mica A: muscovite (average particle size 5.6 μm, particle shape: flake, aspect ratio 20). (4) Mica B: muscovite (average particle diameter 14.3 μm, particle shape: flake, aspect ratio 30). (5) Mica C: muscovite (average particle size 50 μm, particle shape:
Thin section, aspect ratio 30)

(6) Inorganic filler: glass fiber, average fiber length 9 to 13 μm. (7) Inorganic filler: potassium titanate whisker, average fiber length 0.3 to 0.6 μm. (8) Inorganic filler: calcium carbonate, average particle size 10μ
m. (9) Inorganic filler: talc, average particle size 5 μm. (10) Inorganic filler: silica, average particle diameter 4 μm. (11) Inorganic filler: carbon black, average particle size 3
0 mμ.

(12) Paraffin wax: manufactured by Nippon Seiro Co., Ltd. (trade name: 155) (13) Polyethylene wax: manufactured by Mitsui Chemicals, Inc. (trade name: high wax: brand 800P) (14) Silicone oil: organosiloxane Manufactured by Shin-Etsu Chemical Co., Ltd. (trade name: Shin-Etsu Silicone: Brand KF9)
(15) fatty acid ester: stearyl-stearate (16) fatty acid: stearic acid (17) fatty acid metal salt: calcium stearate.

The evaluation method in each example and comparative example is as follows. (18) Evaluation of Quietness and Evaluation of Friction and Wear Characteristics Tensile test piece (ASTM D-638, No. 1 tensile test piece,
A sliding glass piece is placed vertically on a tensile test piece on a total length of 165 mm, a total width of 19 mm, and a thickness of 3.2 mm), and a friction is made between the glass tip R = 12.5 mm portion by reciprocating motion and a sliding noise at that time. Was measured by a sound level meter (NA-29, manufactured by Rion Co., Ltd.) in dB (A) in a direction parallel to the reciprocating motion by 50 mm.
It measured with the microphone installed in the position of 30 mm in height. Further, the frictional force at the time of reciprocating sliding was measured by the installed load meter. After the test, dents formed by wear were measured with a surface roughness meter (Co., Ltd.)
It was measured by Surfcom 554A manufactured by Tokyo Seimitsu. Load 19.6N, stroke 100mm, speed 50mm
/ Sec, 10000 round trips. The sliding glass piece is made of hard glass for automobiles, length 30mm, width 25mm, thickness 5mm.
And the tip R is 12.5 mm, and the surface roughness Ra =
Polishing was performed to 2.0 to 5.0 μm and Rmax = 10 to 20 μm. (The shape of the test piece is shown in Fig. 1.)

The evaluation criteria are as follows. (A) The sliding sound (unit: dB (A)) was measured during continuous sliding and 10,000 times under the above conditions. In addition, the background noise in the state of standing still without reciprocating motion was 39.8 dB (A). (B) The frictional force (unit: N) during reciprocating sliding was measured during continuous sliding and at 10,000 times. (C) The amount of abrasion was determined by measuring the depth of abrasion grooves generated after 10,000 reciprocations with a surface roughness meter.

Examples 1 to 15 Mica and a sliding agent were added to a polyacetal resin in the amounts shown in Table 1, mixed with a tumbler blender, and melt-kneaded with a 30 mmφ twin screw extruder to obtain resin pellets. . The obtained pellet was molded by an injection molding machine to obtain a molded product. Table-Evaluation results
1, Table-2 and Table-3.

[0035]

[Table 1]

[0036]

[Table 2]

[0037]

[Table 3]

Comparative Examples 1 to 16 Resin pellets and molded products having the compositions shown in Tables 4 to 6 were obtained in the same manner as in Example 1. The evaluation results are shown in Table-4, Table-5 and Table-6.

[0039]

[Table 4]

[0040]

[Table 5]

[0041]

[Table 6]

From Tables 1 to 4, the following becomes clear. (1) When mica and paraffin wax are added,
The sliding noise is small, the frictional force is small and the amount of wear is small.
(Examples 1 to 6) (2) When mica and any one of polyethylene wax, silicone oil, stearyl stearate, stearic acid and potassium stearate were added, the sliding noise was small, the frictional force was small, and the wear amount was small. small. (Examples 7 to 15)

(3) When mica and a sliding agent are not added, the sliding noise shows a high value, the frictional force is large, and the amount of wear is extremely large. (Comparative Example 1) (4) When glass fiber, potassium titanate whisker, calcium carbonate, talc, silica or carbon black and stearyl stearate were added, the sliding noise showed a high value, and the frictional force and abrasion loss were high. There are also many. (Comparative Example 2
(7) When mica having an average particle size of 50 μm and stearyl stearate are added, sliding noise is high, and frictional force and abrasion are extremely large. (Comparative Example 8) (6) When only mica is added, the sliding noise is small, but the frictional force is large and the amount of wear is extremely large. (Comparative Examples 9 and 10) (7) When only the sliding agent is added, the sliding noise increases as the number of reciprocations increases, and the abrasion is large. (Comparative Example 11
~ 16)

[0044]

According to the present invention, the polyacetal resin composition comprises:
Excellent noise and low-friction wear characteristics, and also excellent low-noise and low-friction wear characteristics over a long period of time. And is extremely useful as various industrial parts. The molded article of the present invention is silent as a sliding material,
It has excellent friction resistance and durability, and is suitable for, for example, a window glass ascending and descending guide.

[Brief description of the drawings]

FIG. 1 is an explanatory view of the shape of a glass test piece.

[Explanation of symbols]

 a: 25.0 mm b: 5.0 mm c: 30.0 mm R: 12.5 mm

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C08K 5/101 C08K 5/101 C08L 23/06 C08L 23/06 83/04 83/04 91/06 91 / 06 (72) Inventor Daisuke Sanada 5-6-1, Higashi-Hachiman, Hiratsuka-shi, Kanagawa Prefecture Inside the Technology Center of Mitsubishi Engineering-Plastics Co., Ltd. (72) Inventor Hiroaki Sato 5-6-1, Higashi-Hachiman, Hiratsuka-shi, Kanagawa Prefecture Mitsubishi F-term in Engineering Plastics Technology Center (reference) 4F071 AA14 AA15 AA40 AA67 AB30 AC09 AC10 AD05 AE11 AE17 AF28 AF50 AH12 AH17 BA01 BB05 4J002 AE042 BB032 BB052 BB152 BB252 CB001 CP032 EG037 EG037 EG037 EG037 EG037 EG037 EG037 EG037 GN00 GQ00

Claims (6)

[Claims] 1. A polyacetal resin composition obtained by mixing 0.01 to 40 parts by weight of mica having an average particle diameter of 40 μm or less and 0.05 to 10 parts by weight of a sliding agent with respect to 100 parts by weight of a polyacetal resin. 2. The polyacetal resin composition according to claim 1, wherein the mica has an aspect ratio of 10 or more. 3. A sliding agent comprising (A) paraffin wax,
(B) polyethylene wax, (C) silicone oil, (D) fatty acid ester, (E) fatty acid and (F)
3. The polyacetal resin composition according to claim 1, comprising at least one kind or two or more kinds of fatty acid metal salts. 4. The polyacetal resin composition according to claim 1, wherein the sliding agent is (D) a fatty acid ester and (F) a fatty acid metal salt. 5. A molded article obtained by molding the polyacetal resin composition according to claim 1. 6. A molded product according to claim 5, wherein the molded product is a member having a sliding portion with glass.