JPH08127704A - Polyacetal resin composition - Google Patents

Abstract

PURPOSE: To obtain a polyacetal resin compsn. which has excellent friction and abrasion characteristics at working temps. of sliding parts. CONSTITUTION: 100 pts.wt. polyacetal resin is compounded with 0.5-20 pts.wt. polyethylene-polyolefin graft copolymer and 0.1-10 pts.wt. liq. ethylene-α-olefin random copolymer, giving a polyacetal resin compsn. having excellent friction and abrasion characteristics at an ambient temp. of 23-80 deg.C. Further addition of polyethylene (LDPE) gives the compsn. further improved friction and abrasion characteristics.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention is applicable to ambient temperature (23 ° C.).
˜80 ° C.) condition and relates to a polyacetal resin composition having excellent friction and wear properties.

[0002]

2. Description of the Related Art Polyacetal resins have well-balanced mechanical properties and excellent friction / wear properties, chemical resistance, heat resistance, electrical properties, etc., and are therefore widely used in parts such as automobiles, electricity and electronics. ing. However, the required properties in such fields are gradually becoming more sophisticated, and further improvement of sliding properties along with general physical properties is desired. The required sliding properties include not only a low friction coefficient at room temperature and a low specific wear amount, but also a low friction coefficient under a high temperature condition and a low specific wear amount have been taken up as important properties. Various methods have been tried so far in order to improve the sliding characteristics at room temperature.

For example, a graft copolymer of an olefin polymer and a vinyl polymer or an ether polymer on a polyacetal resin, a fatty acid having a total carbon number of 12 or more,
Method of adding alcohol and fatty acid ester (JP-A-2-138357), method of adding polyfunctional isocyanate compound and polyolefin and polyethylene having a functional group having active hydrogen (JP-A-4-126)
No. 758), a method of adding silane-modified polyethylene obtained by graft-polymerizing an ethylenically unsaturated silane compound to polyethylene (JP-A-5-247235), a copolymer of ethylene and α-olefin, or a modified polyethylene thereof. A method of adding wax (JP-A-6-49320) has been proposed.

In all of the prior arts, although the low friction coefficient at room temperature and the low specific wear amount are improved to some extent, the sliding characteristics under the highly demanded high temperature environment conditions have not been improved yet. Therefore, in the present situation, a lubricant such as grease is applied to the sliding portion to improve sliding characteristics.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a resin composition having improved lubricating properties by improving the problems of the conventional polyacetal resin material. That is, an object of the present invention is to provide a polyacetal resin composition having excellent friction and wear resistance and mechanical properties. This addresses the strong demand for non-greasing of sliding parts such as gears, bearings, cams and rollers.

[0006]

The inventors of the present invention have found that the room temperature (2
As a result of intensive research to develop a polyacetal resin composition having excellent friction and wear resistance under environmental conditions of 3 ° C to high temperature (80 ° C), a special olefin graft copolymer for polyacetal resin, Further, they have found that the above object can be achieved by adding a liquid olefin random copolymer, and have completed the present invention.

That is, the present invention provides (A) a polyacetal resin; (B) a graft copolymer of polyethylene and a polyolefin with respect to 100 parts by weight; 0.5 to 20% by weight, and (C) a liquid ethylene. An α-olefin random copolymer; 0.1 to 10% by weight of a polyacetal resin composition.

As the polyacetal resin used as the component (A) in the composition of the present invention, both a polyacetal homopolymer and a polyacetal copolymer in which most of the main chain is an oxymethylene chain can be used. In addition, a polyacetal modified by block, crosslinking or graft copolymerization by a known method can also be used as the base resin. The preferred polyacetal resin has an MI of 15 to 100 gr / 10 minutes, and particularly preferably has an MI of 30 to 80 gr / 10 minutes.

In the composition of the present invention, a graft copolymer of polyethylene and polyolefin is used as the component (B). As such a graft copolymer,
A conventional method for graft modification of polyolefins, for example, a method of utilizing a grafting reaction of a polymer having a side chain having a peroxide bond to a polyolefin ["Polymer Thesis Collection", Vol. 44, No. 2] , Pages 89 to 95 (1987)] and the like.

As the polyethylene used in this graft copolymer, polyethylene comprising 90% by weight or more of ethylene units and 10% by weight or less of vinyl monomer units such as butene-1 and propylene can be used. Among such polyethylene, the number average molecular weight is 2000 to 10
Those having a specific gravity of 0.91 to 0.98 and a melting point of 100 to 140 ° C. are preferable. Specifically, commercially available polyethylene wax, low density polyethylene (LDPE), linear low density polyethylene (LLDPE), high density polyethylene (HDPE), ultra high molecular weight polyethylene (UHPE), etc. may be mentioned.

Among these polyethylenes, LDP which is a homopolymer of ethylene having a number average molecular weight of 20,000 to 50,000.
HDPE, which is a homopolymer of E and ethylene having a number average molecular weight of 300,000 to 500,000, is preferable, and LDPE is particularly preferable. As the olefin monomer to be grafted on polyethylene, styrene, acrylonitrile, methyl acrylate, methacrylsanmethyl, cyclopentadiene, ethylidene norbornene, 1,4-hexadiene, acrylic acid, methacrylic acid, acrylamide,
Allylamine, acrylate, allyl alcohol, α.
Examples thereof include a hydroxyl group-containing ester of β-unsaturated carboxylic acid. α. A specific example of the hydroxyl group-containing ester of β-unsaturated carboxylic acid is a vinyl monomer represented by the following general formula (1).

[0012]

Embedded image

Specifically, for example, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, 2-hydroxyethyl acrylate, hydroxypropyl acrylate, 2-hydroxybutyl methacrylate, p-hydroxyphenyl methacrylate, p-hydroxybenzyl methacrylate, Examples thereof include 3-chloro-2-hydroxypropyl methacrylate, glycerin monomethacrylate, polyethylene glycol methacrylate and polypropylene glycol methacrylate.

Preferred vinyl monomers having a functional group having active hydrogen include α. Examples of the hydroxyl group-containing ester of β-unsaturated carboxylic acid include 2-hydroxyethyl methacrylate (HEMA), 2-hydroxypropyl methacrylate, 2-hydroxyethyl acrylate and hydroxypropyl acrylate.

The preferred combination among these vinyl monomers forming a grafted polyolefin is a vinyl monomer having a functional group having active hydrogen and propylene, styrene, butene-1, methyl methacrylate, methyl acrylate, acrylonitrile. , Vinyl acetate, cyclopentadiene, ethylidene norbornene and 1,4-hexadiene, and preferably a copolymer of vinyl monomer having a functional group having active hydrogen and styrene.

The vinyl monomer having a functional group having an active hydrogen of these vinyl copolymers is 0.5 to 10% by weight, and more preferably, 0.5 to 10% by weight based on the other vinyl monomers.
It is 2 to 5% by weight. The graft weight% of these polyolefins to polyethylene is usually selected from the range of 1 to 50% by weight, preferably 20 to 40% by weight from the viewpoint of abrasion resistance. In the present invention, the graft copolymer of polyethylene and polyolefin as the component (B) is 0.5 to 20% by weight, preferably 5 to 10% by weight based on 100 parts by weight of the polyacetal resin as the component (A). It is a ratio in the range of% by weight.

The liquid ethylene / α-olefin random copolymer as the component (C) in the composition of the present invention is a random copolymer of ethylene and an α-olefin having 3 to 20 carbon atoms. Examples of the α-olefin having 3 to 20 carbon atoms include propylene, butene-1, pentene-1, 4
-Methyl pentene-1, hexene-1, heptene-1,
Examples include octene-1, nonene-1, decene-1, undecene-1, dodecene-1, tridecene-1, tetradecene-1, pentadecene-1, ocotadecene-1, nonadecene-1, eicosene-1 and the like.
Of these, propylene is most preferable in terms of productivity.

The liquid ethylene / α-olefin random copolymer has an ethylene content of 20 to 80 mol%, preferably 30 to 70 mol%, and more preferably 40.
-60 mol%. The liquid ethylene / α-olefin random copolymer has a number average molecular weight of 500 to
The range is 10,000, preferably 600 to 8,000, and more preferably 700 to 5,000.

Liquid ethylene containing the above component (C)
The α-olefin random copolymer is, for example, Japanese Patent Publication No. 2
It can be produced by the method described in Japanese Patent Publication No. 1163. That is, in the presence of a Ziegler catalyst, hydrogen is used as a molecular weight regulator, and ethylene and C 3 -C 3
A liquid ethylene / α-olefin random copolymer can be obtained by randomly copolymerizing 20 α-olefins.

In the present invention, the liquid ethylene / α-olefin random copolymer as the component (C) is the above-mentioned (A).
With respect to 100 parts by weight of the component polyacetal resin, 0.
It is used in a proportion in the range of 1 to 10% by weight, preferably 0.2 to 8% by weight, more preferably 0.5 to 6% by weight. The composition of the present invention has good physical properties even when used as it is, and particularly has a remarkable effect on the sliding characteristics and the like, and in addition to the components (A) to (C), (D) )
Further effects can be obtained by using polyethylene together.

As the polyethylene (D), polyethylene having 90% by weight or more of ethylene units and 10% by weight or less of vinyl monomer units such as butene-1 and propylene can be used. Among such polyethylene, the number average molecular weight is 2000 to 1,000,000.
With a specific gravity of 0.91 to 0.98 and a melting point of 100 to
Those in the range of 140 ° C are preferable. In particular,
Polyethylene wax, low density polyethylene (LDPE), linear low density polyethylene (L
LDPE), high density polyethylene (HDPE), ultra high molecular weight polyethylene (UHPE) and the like.

Among these polyethylenes, LDP which is a homopolymer of ethylene having a number average molecular weight of 20,000 to 50,000.
HDPE, which is a homopolymer of E and ethylene having a number average molecular weight of 300,000 to 500,000, is preferable, and LDPE is particularly preferable. Further, the melt index (MI) of polyethylene is MI = 0.2 to 10 gr / 10 minutes,
Preferably, MI = 0.5 to 5 gr / 10 minutes. Regarding the method for producing the composition of the present invention, any method can be appropriately selected and used from known methods used for preparing a polyoxymethylene resin composition.

In the composition of the present invention, if desired, those conventionally used as plastic additives, such as antioxidants, light stabilizers, inorganic fillers, pigments, etc., within a range not impairing the object of the present invention. May be added. In addition, additional components usually used in polyoxymethylene resin, for example, polyamide, melamine, melamine derivatives,
You may mix dicyandiamide, fatty acid calcium, etc. According to the composition of the present invention, it was confirmed that a polyacetal resin composition having excellent sliding properties can be obtained under environmental conditions from room temperature (23 ° C) to high temperature (80 ° C).

[0024]

The present invention will be described in detail below with reference to examples and comparative examples, but the present invention is not limited thereto. (Examples 1 to 4) Polyacetal resin homopolymers obtained by adding 0.3 parts of "Irganox 245" (manufactured by Ciba-Gaggy Co., Ltd.) as an antioxidant to polyoxymethylene homopolymers having both ends acetylated, and The additives shown in Table 1 were blended in a nitrogen atmosphere, and a twin screw extrusion type with a vent having L / D = 25 set to 200 ° C. was used, and the screw rotation speed was 100 rpm and the discharge rate was 5 Kg / Hr. The resin composition having the composition shown in Table 1 was prepared by melt-kneading and further pelletized.

Next, after drying the pellets at 80 ° C. for 3 hours, the mold temperature was set to 80 ° C. with a 3 ounce molding machine (Sumitomo Nestal molding machine) set to a cylinder temperature of 200 ° C.
Outside diameter 26 mm, inside diameter 20 m under cooling time of 20 seconds
m and a depth of 17 mm were molded into a cylindrical shape to obtain a test piece.

Regarding this test piece, JIS K-721
Method 8 (thrust type friction and wear test method, surface pressure 2 Kg
/ Cm2, linear velocity 10cm / sec, mileage 100K
m, mating material: polyoxymethylene homopolymer before addition of additives), the environmental temperature was changed to 23 °, 60 °, and 80 °, and the friction coefficient and wear amount were measured and evaluated. The results of those measurements and evaluations are shown in Table 1.

The substances used as the constituents of the components (B) and (C) are as follows, and are listed in Tables 1 and 2
Are indicated by abbreviations. Component (B) Component PE-g-PS (70-30): Graft copolymer of polyethylene (70% by weight) and polystyrene (30% by weight) PE-g-PS (70-30) HEMA (1 ): Graft copolymer of polyethylene (70 wt%) and polystyrene (29 wt%)-HEMA (1 wt%) PE-g-PS (50-50): Polyethylene (50 wt%) and polystyrene Graft Copolymer with (50 wt%) PE-g-AS (70-30): Graft Copolymer of Polyethylene (70 wt%) and Acnylonitrile-Styrene Copolymer (30 wt%) (C ) Constituent components HC600: Mitsui Toatsu Co., Ltd., Lucant (trade name)

(Examples 5 to 6) In Examples 5 to 6, polyethylene (LDPE) was further added to the special olefin graft copolymer and the liquid olefin random copolymer, and the results were measured and evaluated. The results of those measurements and evaluations are shown in Table 1.

Comparative Examples 1 to 6 In Comparative Examples 1 to 4, only a special olefin graft copolymer was used, in Comparative Example 5, only a liquid olefin random copolymer was used.
In Comparative Example 6, only polyethylene (LDPE) was used, and evaluation was performed in the same manner as in Example 1. The results of those measurements and evaluations are shown in Table 2.

[0030]

[Table 1]

[0031]

[Table 2]

[0032]

INDUSTRIAL APPLICABILITY According to the present invention, by mixing a special olefin graft copolymer and a liquid olefin random copolymer with a polyacetal resin, excellent friction and wear characteristics can be obtained under an ambient temperature condition of 23 ° C to 80 ° C. Have, in addition,
By adding polyethylene (LDPE), a polyacetal resin composition having further improved friction and wear characteristics was obtained. This composition can be suitably used as a material for various sliding parts that are required to have high performance under high temperature environmental conditions.

Claims (6)

[Claims] 1. A graft copolymer comprising (A) 100 parts by weight of a polyacetal resin and (B) a polyethylene and a polyolefin; 0.5 to 20% by weight, and (C) a liquid ethylene / α-olefin random copolymer. Coalescence; 0.1
A polyacetal resin composition containing 10% by weight. 2. The polyacetal resin composition according to claim 1, wherein the polyolefin in the graft copolymer (B) comprises a vinyl monomer having a functional group having active hydrogen and another vinyl monomer. 3. The polyacetal resin composition according to claim 1, wherein the monomer having a functional group having active hydrogen in (B) has the following general formula (1). Embedded image 4. The average molecular weight of (C) is 500 to 1000.
The polyacetal resin composition according to claim 1, wherein the polyacetal resin composition has an ethylene content of 0 to 80 mol%. 5. A polyacetal resin composition, further comprising:
(D) Polyethylene: 0.2 to 10% by weight (100 parts by weight of polyacetal resin) is blended.
The polyacetal resin composition according to claim 1. 6. The polyethylene of (D) has MI = 0.2 to
The polyacetal resin composition according to claim 5, which has a viscosity of 10 gr / 10 minutes.