JPH08199039A - Polyoxymethylene resin composition - Google Patents

Abstract

PURPOSE: To obtain a polyoxymethylene resin composition which can develop a low coefficient of friction even under adverse conditions in which it is first exposed to a high-temperature/high-humidity environment and then brought to an ordinary-temperature/low-humidity environment or to a still worse environment. CONSTITUTION: This composition comprises 60-99.38 wt.% polyoxymethylene resin, 0.01-5wt.% polyamide, 0.01-5wt.% hindered phenol, 0.5-20wt.% polyethylene onto which an aromatic vinyl monomer or both this monomer and an active hydrogen containing vinyl monomer are grafted and 0.1-10wt.% ester of a fatty acid with an aliphatic alcohol.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an excellent novel polyoxymethylene resin composition which does not deteriorate in sliding property after absorbing moisture. More specifically, the present invention is that the polyoxymethylene resin composition placed under a high temperature and high humidity environment is returned to a low temperature room temperature or low temperature low humidity environment rather than the environment,
It exhibits particularly excellent slidability even after a downward change. For example, it is suitable for use in precision equipment under high temperature and high humidity environment, office automation equipment, sliding parts materials in the field of automobiles, etc., and excellent slidability does not change even for equipment and parts exposed to adverse high temperature and high humidity environment. Another object of the present invention is to provide a polyoxymethylene resin composition.

Polyoxymethylene resins have hitherto been widely used as engineering plastics having well-balanced mechanical properties and excellent wear resistance in various mechanical parts, OA equipment and the like. However, this polyoxymethylene resin is not necessarily sufficient as a sliding part only by its inherent wear resistance, and in particular, when an environmental change occurs at room temperature and low humidity or low temperature and low humidity after high temperature and high humidity, the friction coefficient increases. However, there was a big problem that the original slidability could not be exhibited.

Specifically, when a polyacetal resin is used as an OA equipment part used in a bad environment in which high temperature and high humidity are followed by normal temperature and low humidity or low temperature and low humidity, malfunction may occur. At present, in most cases, the sliding part is coated with grease to prevent this. However, this grease application
Development of a polyoxymethylene resin composition that does not require application of grease has been desired because of the drawbacks such as a long working process and the application of grease using chlorofluorocarbon, which may lead to environmental damage.

[0004]

2. Description of the Related Art Now, a conventional technique for improving the slidability of a polyoxymethylene resin will be introduced below. First, a method of adding an ester of 1,4-butanediol and a fatty acid to a polyoxymethylene resin (Japanese Patent Publication No. 55-23304).
Gazette), then a method of adding a boric acid ester of glycerin monofatty acid ester (Japanese Patent Publication No. 57-16616), and a method of adding a polyolefin having active hydrogen, polyethylene and an isocyanate (Japanese Patent Application Laid-Open No. Hei 4).
-126758), a method of adding a copolymer of an α-olefin and an ethylene-vinyl monomer (JP-A-49-40346), and a method of adding ultra-high molecular weight polyethylene powder (JP-A-60-14435).
No. 1) is known, but in these methods, although the slidability at room temperature is improved, the friction coefficient and the wear amount of the friction coefficient and the wear amount caused by the environmental changes that are repeated at room temperature and low humidity or low temperature and low humidity environment after high temperature and high humidity. It had no effect on the increase.

Further, a method of adding an olefin-based graft copolymer and a lubricant (JP-A-2-138357) and a method of adding an olefin-based graft copolymer (JP-A-5-140342) are polyacetals. It is disclosed to improve the slidability of the resin. However, a remarkable effect cannot be expected from these methods.

[0006]

Under the above circumstances, the present invention has a friction coefficient even after use, especially in a point contact reciprocating sliding test, even after repeated environmental changes such as high temperature and high humidity and then normal temperature and low humidity or low temperature and low humidity. The purpose of the present invention is to provide a polyoxymethylene resin composition exhibiting excellent abrasion resistance and wear resistance, which does not increase.

[0007]

Means for Solving the Problems As a result of intensive studies to achieve the above object, the present inventors have found that (A) polyoxymethylene resin; 60 to 99.38% by weight and (B) polyamide; 0.01 to 5% by weight (C) hindered phenol; 0.01 to 5% by weight and (D) polyethylene modified by grafting with an aromatic vinyl monomer alone or an active hydrogen-containing vinyl monomer; 0.5 to 20% by weight And (E) an ester consisting of a fatty acid and an aliphatic alcohol;
A polyoxymethylene resin composition composed of 0.1 to 10% by weight is placed in a high temperature and high humidity environment, and has excellent friction and wear characteristics even after returning to or decreasing from the environment to a room temperature low humidity or low temperature low humidity environment. The present invention has been completed based on this finding.

The present invention will be described in detail below. The polyoxymethylene resin used as the component (A) in the present invention is obtained by polymerizing a formaldehyde monomer or a cyclic oligomer such as a trimer (trioxane) or a tetramer (tetraoxane) of the formaldehyde and ether at both ends of the polymer. , Including homopolymers blocked by ester bonds and the like, and obtained by copolymerizing the above trioxane or tetraoxane with a cyclic ether such as ethylene oxide, propylene oxide, 1,3-dioxolane, glycol formal, or diglycol formal. 2 to 2 carbon atoms
8 oxymethylene copolymer containing 0.1 to 20% by weight of oxyalkylene units and further having a branched molecular chain, and oxy containing 50% by weight or more of a segment composed of oxymethylene units and 50% by weight or less of a different component segment. It is a methylene block copolymer.

Particularly preferred are polyoxymethylene homopolymers for the purposes of the present invention. The content of the polyoxymethylene resin as the component (A) in the present invention needs to be in the range of 60 to 99.38% by weight. Even if this amount is less than 60% by weight or more than 99.38% by weight, the sliding characteristics after the high temperature and high humidity environment, that is, it is placed in the high temperature and high humidity environment and returned to the room temperature low humidity or low temperature low humidity environment The friction and wear characteristics deteriorate after the change.

The polyamide used as the component (B) in the composition of the present invention is a polymer having an amide group in the molecular chain and having a number average molecular weight of 1,000 or more. As a specific compound, nylon 4-6 which produces a dicarboxylic acid and a diamine or ω-aminocarboxylic acid by hydrolysis,
Polymers such as nylon 6, nylon 6-6, nylon 6-10, nylon 6-12 and nylon 12 and copolymers thereof are described in JP-A-63-118328 and JP-A-3-234729. Of acrylamide and its derivatives or acrylamide and its derivatives and other vinyl monomers produced by the method described above in the presence of a metal alcoholate, the primary amide content is 1.4 to 10 mmol / g of polymer. Examples thereof include poly β-alanine copolymer, which is a hit. A preferable average particle size of polyamide is 1 to 10 μm. A more preferable polyamide is JP-A-63-118.
The primary amide content obtained by polymerizing acrylamide and its derivative produced by the method described in JP-A No. 328 and JP-A-3-234729 in the presence of a metal alcoholate is 1.4 to 10. It is a poly-β-alanine copolymer having an average particle size of 10 μm or less, more preferably 1 to 6 μm, per millimole / g of polymer.

The polyamide in the present invention has a content of 0.01 to
5 wt% can be added. This is because if it is less than 0.01% by weight or more than 5% by weight, the slidability after the high temperature and high humidity environment, which is the object of the present application, is deteriorated. The preferable addition amount is 0.
It is 1 to 0.5% by weight. The hindered phenol in the present invention is a compound having a structure in which phenolic OH is sterically hindered by an alkyl group or the like. This preferred hindered phenol is a hindered phenol having a methyl group or a t-butyl group among alkyl groups as a hindered group. Specifically, octadecyl-3-
(3,5-di-t-butyl-4-hydroxyphenyl)
Propionate, 1,6-hexanediol-bis [3
-(3,5-di-t-butyl-4-hydroxyphenyl) propionate], pentaerythrityl-tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate] or triethylene glycol -Bis [3- (3-t-butyl-5-methyl-4-hydroxyphenyl) propionate] and the like. A more specific hindered phenol for achieving the object of the present application is pentaerythrityl-tetrakis [3- (3,3
5-di-t-butyl-4-hydroxyphenyl) propionate] or triethylene glycol-bis [3-
(3-t-butyl-5-methyl-4-hydroxyphenyl) propionate]. Most preferred is pentaerythrityl-tetrakis [3- (3,5-di-t-
Butyl-4-hydroxyphenyl) propionate].

The hindered phenol in the present invention is
0.01 to 5% by weight can be added. This is because if it is less than 0.01% by weight or more than 5% by weight, the slidability after the high temperature and high humidity environment, which is the object of the present invention, is deteriorated. The preferable addition amount is 0.1 to 0.5% by weight. Among the polyethylenes graft-modified with the aromatic vinyl monomer alone or with the active hydrogen-containing vinyl monomer in the present invention, the aromatic vinyl monomer is a vinyl monomer containing a benzene ring. For example, styrene, methylstyrene, ethylstyrene, and other alkyl group-substituted styrenes. Of these, styrene is preferable.

Further, the active hydrogen-containing vinyl monomer specifically includes 2-hydroxyethyl methacrylate and 2-hydroxyethyl methacrylate.
Hydroxypropyl methacrylate, 2-hydroxyethyl acrylate, hydroxypropyl acrylate,
2-hydroxybutyl methacrylate, p-hydroxyphenyl methacrylate, p-hydroxybenzyl methacrylate, glycerin monomethacrylate, polyethylene glycol methacrylate, polypropylene glycol methacrylate, and other hydroxyl group-containing esters of α, β unsaturated carboxylic acids, acrylic acid, methacrylic acid, Examples include acrylamide, allylamine, and allyl alcohol. From the viewpoint of solving the problems of the object of the present application, a hydroxyl group-containing ester of α, β unsaturated carboxylic acid and further 2-hydroxyethyl methacrylate are preferable.

The polyethylene constituting the graft modified product is a 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. Preferred molecular weight is 2,000-
In the range of 1,000,000 and a specific gravity of 0.91
Those having a melting point of ˜0.98 and a melting point of 100 to 140 ° C. are preferable. Specific examples thereof include polyethylene wax, low-density polyethylene, linear low-density polyethylene, high-density polyethylene, and ultra-high-molecular-weight polyethylene. Low-density polyethylene that is a homopolymer of ethylene having a number average molecular weight of 20,000. Is preferred.

The method for producing polyethylene graft-modified with an aromatic vinyl monomer alone or with an active hydrogen-containing vinyl monomer in the present invention is a method of grafting a vinyl monomer onto polyethylene in the presence of a radical initiator, or a method prepared in advance. There is a method of producing by grafting a polymer. Preferably, "Polymer Thesis Collection", Vol. 44, No. 2, pp. 89-95 (198)
7 years) and a method of utilizing a grafting reaction of a polymer having a peroxide bond in a side chain onto a polyolefin.

The content of the aromatic vinyl monomer in the modified graft product of the present invention is 20 to the total amount of the graft product.
It is preferable to contain 40% by weight. More preferably, 2
It is 5 to 35% by weight. The amount of the active hydrogen-containing vinyl monomer based on the total amount of the graft product is preferably 0.1 to 3% by weight. More preferably, it is 0.3 to 1.5% by weight.

Among the graft modified products of the present invention, preferred is a graft polymer of a styrene-α, β unsaturated carboxylic acid hydroxyl group-containing ester copolymer onto polyethylene. The polyethylene graft-modified with the aromatic vinyl monomer alone or the active hydrogen-containing vinyl monomer in the present invention is 0.5 to 20 with respect to the total weight of the composition.
% By weight can be added. 2 even if less than 0.5% by weight
Even if it exceeds 0% by weight, the slidability after high temperature and high humidity environment deteriorates. The preferable addition amount is 1 to 10% by weight, and more preferably 2 to 5% by weight, which can obtain a low friction coefficient.

The ester comprising a fatty acid and an aliphatic alcohol in the present invention has a structure in which carbon atoms are connected in a chain of one row or has a branched structure, and is composed of a carboxylic acid and an alcohol which may be a saturated hydrocarbon or an unsaturated hydrocarbon. In terms of the effect of heat discoloration resistance, a saturated hydrocarbon type ester is preferable. More preferably, a fatty acid having 12 to 16 carbon atoms and 12 to 1 carbon atoms
An ester of an aliphatic alcohol having a carbon number of 6, and more preferably, an ester of a fatty acid having a carbon number of 14 and 15 since a low friction coefficient is obtained after a high temperature and high humidity environment.

Specifically, "lauric acid, tridecyl acid, myristic acid, pentadecyl acid, palmitic acid"
And an ester of "lauryl alcohol, tridecyl alcohol, myristyl alcohol, pentadecyl alcohol, cetyl alcohol". Furthermore, "myristic acid or pentadecyl acid" and "lauryl alcohol, tridecyl alcohol, myristyl alcohol,
Esters with pentadecyl alcohol and cetyl alcohol "are more preferable.

The ester composed of fatty acid and fatty alcohol in the present invention is 0.1 to 10 relative to the total composition.
% By weight can be added. Preferably 0.5 to 5
Further, it is 0.5 to 3% by weight. The composition of the present invention can be melt-kneaded and pelletized at a temperature not lower than the melting point of the polyoxymethylene resin used by using a commonly used melt-kneader. Examples of the melt-kneader include a kneader, a roll mill, a single-screw extruder, a twin-screw extruder, and a multi-screw extruder. However, in consideration of oxygen blocking and work environment, the pressure of the vent is reduced by 2 screws (2 lines). Pelletizing with an extruder is preferred.

If desired, the composition of the present invention may be any one conventionally used as a plastic additive, for example, a hindered amine, an ultraviolet absorber, an inorganic filler, a pigment or a carbon as long as the object of the present invention is not impaired. You may add black etc. The composition of the present invention can be used for OA equipment, various sliding members for automobiles, such as gears, bearings, levers, key stems, cams, ratchets, rollers and VTs.
R guide roller, side plate, cam gear, copier gear, L
It can be used for BP paper feed drive parts, toner stirring gear trains, cartridge gears, CD-ROM sliding parts, etc.

[0022]

The present invention will be described in more detail by way of examples, which should not be construed as limiting the invention thereto.

[0023]

Examples 1-27 US Patent Specification No. 2998409
Intrinsic viscosity 1.2 (α-pinene 2% by weight
Value measured at 60 ° C. for a solution prepared by dissolving 0.1% by weight of a polymer in p-chlorophenol containing
Melt Index [ASTM D1238-57
(E)] A polyoxymethylene homopolymer powder having both ends acetylated at 9.0 g / 10 min was dried at 80 ° C. for 3 hours to give pentaerythrityl-tetrakis [3- (3,5- Di-t-butyl-4-
Hydroxyphenyl) propionate] (hindered phenol A), triethylene glycol-bis [3-
(3-t-butyl-5-methyl-4-hydroxyphenyl) propionate] (hindered phenol B), octadecyl-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate (hindered phenol) C) or 1,6-hexanediol-bis [3-
(3,5-di-t-butyl-4-hydroxyphenyl)
Propionate] (hindered phenol D)
And "Polymer Papers" Vol. 44, No. 2, 89-95.
A graft polymer ("Polymer A: low density polyethylene with Mn = 30000" produced by a method utilizing a grafting reaction of a polymer having a peroxide bond in a side chain onto a polyolefin described in page (1987). And styrene (28% by weight) -2-ethylhexyl methacrylate (2% by weight) copolymer "," Polymer B: Mn = 3
0000 graft polymer of low density polyethylene and polystyrene (30% by weight) ", and JP-A-63-118.
Primary amide content obtained by polymerizing acrylamide and methylenebisacrylamide (10 mol%) produced by the method described in JP-A No. 328 and JP-A-3-234729 in the presence of a metal alcoholate. Is 1.3 mmol / g of polymer, and
Poly β-alanine copolymer (polyamide A) having an average particle size of 4 μm, nylon 6,6 crushed product (average particle size of 4 μm
m) and the ester described in Table 1 were blended under a nitrogen atmosphere, and a twin-screw vent extruder with L / D25 set at 200 ° C. was used, and screw-rotation speed 100 rpm,
Discharge rate 3 kg / hour, maximum resin temperature 205-210 ° C,
Melt kneading is performed under the conditions of kneading time (residence time) of 0.5 to 0.7 minutes to prepare resin compositions having compositions shown in Tables 1 to 3,
Further pelletized.

Next, after drying the pellets at 80 ° C. for 3 hours, a mold temperature of 70 was obtained with a 1 ounce molding machine (TI30G made by Toyo Kikai Kinzoku Co., Ltd.) set at a cylinder temperature of 200 ° C.
A test piece was obtained by molding into a molded piece of 2 × 12 × 0.3 cm under the conditions of a temperature of 10 ° C. and a cooling time of 10 seconds. This test piece at 60 ° C,
It was placed in an environment of 90% humidity for 48 hours. It was taken out and placed in an environment of 23 ° C. and a humidity of 50% for 5 minutes. Regarding this test piece, the point contact reciprocating slidability was measured by a reciprocating friction wear tester (AFT-15MS type manufactured by Tohsei Precision Co., Ltd., load 2 kg, linear velocity 10 mm / sec, reciprocating distance 20 mm, mating member; tip R
= 2.5, SUS material, environment 23 ° C, humidity 50%), and the friction coefficient after 1 and 1000 reciprocations was measured.

The results are shown in Tables 1 to 3.

[0026]

Comparative Examples 1 to 15 In Comparative Examples 1 to 15, the same composition as shown in Tables 4 and 5 was carried out in the same manner as in Example 1. The results are shown in Table 4,
5 shows.

[0027]

Example 28 Intrinsic viscosity 1.1, melt index 10 by the method described in US Pat.
Sliding in the same manner, except that the polyoxymethylene copolymer containing 2.8% by weight of oxyethylene groups in g / 10 min was used as the polyoxymethylene resin, except that the components and the addition amounts shown in Example 17 were the same. The test was conducted.

As a result, the coefficient of friction after one reciprocation; 0.1
The coefficient of friction after 5 and 1000 reciprocations was 0.15.

[0029]

[Table 1]

[0030]

[Table 2]

[0031]

[Table 3]

[0032]

[Table 4]

[0033]

[Table 5]

[0034]

INDUSTRIAL APPLICABILITY In addition to the conventionally known combination of the graft modified product and the ester-based lubricant, the present invention uses a hindered phenol and a polyamide, which are conventionally considered to be stabilizers, in combination with the conventional composition. It has been considered difficult to "deteriorate slidability that occurs in adverse environments, such as after being exposed to high temperature and high humidity, then returning to room temperature low humidity or low temperature low humidity, and lowering."
Can be improved.

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Claims (2)

[Claims] 1. A polyoxymethylene resin (A); 60-
99.38% by weight, (B) polyamide; 0.01 to 5% by weight, (C) hindered phenol; 0.01 to 5% by weight, (D) aromatic vinyl monomer alone or active hydrogen-containing vinyl monomer A polyoxymethylene resin composition comprising: graft-modified polyethylene; 0.5 to 20% by weight; and (E) an ester consisting of a fatty acid and an aliphatic alcohol; 0.1 to 10% by weight. 2. The polyoxymethylene resin composition according to claim 1, wherein the polyamide is a poly β-alanine copolymer.