JP3222343B2 - Polyoxymethylene resin composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel polyoxymethylene resin composition which does not degrade the slidability after moisture absorption. More specifically, the present invention provides that the polyoxymethylene resin composition placed in a high-temperature and high-humidity environment returns to a room-temperature low-humidity or low-temperature low-humidity environment,
It shows particularly excellent slidability even after the change that has been lowered. For example, it is suitable for use in precision equipment under high temperature and high humidity environment, OA equipment, sliding parts materials in the automotive field, etc., and excellent sliding property does not change even in equipment and parts exposed to bad environment of high temperature and high humidity. And a polyoxymethylene resin composition.

Hitherto, polyoxymethylene resins have 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 always sufficient as a sliding part only with its inherent wear resistance, and in particular, the friction coefficient increases when an environmental change occurs in which the ambient temperature changes to a low temperature or low temperature environment after high temperature and high humidity. As a result, there was a big problem that the original slidability could not be exhibited.

[0003] Specifically, when a polyacetal resin is used as an OA equipment component used in an adverse environment in which a high-temperature and high-humidity environment is repeated under a low-temperature or low-temperature environment, a malfunction may occur. At present, in most cases, grease is applied to a sliding portion to prevent this from occurring. However, this grease application
There are drawbacks such as a long work process and the application of grease using chlorofluorocarbon, which may lead to environmental destruction. Therefore, the development of a polyoxymethylene resin composition without grease application has been desired.

[0004]

2. Description of the Related Art A conventional technique for improving the slidability of a polyoxymethylene resin will be described 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)
JP-A-5-15616, a method of adding a borate ester of glycerin monofatty acid ester (Japanese Patent Publication No. 57-15616), and a method of adding a polyolefin having active hydrogen, polyethylene and isocyanate
JP-A-126758), a method of adding a copolymer of an α-olefin and an ethylene-vinyl monomer (JP-A-49-40346), and a method of further adding an ultra-high-molecular-weight polyethylene powder (JP-A-60-14435).
Although these methods improve the slidability at room temperature, the friction coefficient and the amount of wear caused by repeated environmental changes under normal temperature and low humidity or low temperature and low humidity after high temperature and high humidity are known in these methods. It had no effect on the increase.

Further, a method of adding an olefin-based graft copolymer and a lubricant (Japanese Patent Laid-Open No. 2-138357) and a method of adding an olefin-based graft copolymer (Japanese Patent Laid-Open No. 5-140342) are disclosed. It is disclosed that the slidability of the resin is improved. However, no remarkable effect can be expected from these methods.

[0006]

SUMMARY OF THE INVENTION Under such circumstances, the present invention provides a friction coefficient even after repeated environmental changes in which, after a high-temperature, high-humidity condition, a normal-temperature, low-humidity or low-temperature, low-humidity condition is repeated, especially in a point contact reciprocating sliding test. The object of the present invention is to provide a polyoxymethylene resin composition which exhibits no increase in friction and exhibits excellent friction and wear resistance.

[0007]

Means for Solving the Problems The present inventors have conducted intensive studies to achieve the above object, and as a result, (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 graft-modified with an aromatic vinyl monomer alone or an active hydrogen-containing vinyl monomer; 0.5 to 20% by weight And (E) an ester comprising a fatty acid and an aliphatic alcohol;
0.1 to 10% by weight of a polyoxymethylene resin composition is placed in a high-temperature and high-humidity environment, and the friction and wear characteristics are excellent even after returning to or lowering in a low-temperature or low-temperature environment at room temperature or lower than the environment. Have been found, and the present invention has been completed based on this finding.

Hereinafter, the present invention will be described in detail. The polyoxymethylene resin used as the component (A) in the present invention is obtained by polymerizing a cyclic oligomer such as a formaldehyde monomer or a trimer (trioxane) or tetramer (tetraoxane) thereof, and terminating both ends of the polymer with ether. , Including homopolymers blocked with an ester bond, etc., obtained by copolymerizing trioxane or tetraoxane with a cyclic ether such as ethylene oxide, propylene oxide, 1,3-dioxolan, glycol formal, or diglycol formal. 2 carbon atoms
Oxymethylene copolymers containing 0.1 to 20% by weight of oxyalkylene units and those having a branched molecular chain, and oxymethylene containing at least 50% by weight of a segment composed of oxymethylene units and at most 50% by weight of a heterogeneous component segment It is a methylene block copolymer.

[0009] Particularly preferred are polyoxymethylene homopolymers for the purposes of the present invention. In the present invention, the content of the polyoxymethylene resin as the component (A) needs to be in the range of 60 to 99.38% by weight. If the amount is less than 60% by weight or more than 99.38% by weight, the sliding properties under a high-temperature and high-humidity environment, that is, the sample is placed under a high-temperature and high-humidity environment and returns to a normal temperature low-humidity or low-temperature low-humidity environment. The friction and abrasion characteristics after the change, such as falling or falling, are deteriorated.

In the composition of the present invention, the polyamide used as the component (B) is a polymer having an amide group in the molecular chain and having a number average molecular weight of 1,000 or more. Specific compounds include Nylon 4-6, which produces a dicarboxylic acid and a diamine or an 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, described in JP-A-63-118328 and JP-A-3-234729. And / or a derivative thereof , or a primary amide content obtained by polymerizing acrylamide and a derivative thereof and another vinyl monomer in the presence of a metal alcoholate, having a primary amide content of 1.3 to 10 mmol / polymer 1 g poly β
And alanine copolymers. The average particle size of the preferred polyamide is 1 to 10 μm. Further preferred polyamides are described in JP-A-63-118328.
JP and primary amide content obtained by polymerizing in the presence of <br/> metal alcoholate acrylamide and derivatives thereof prepared by the method described in JP-A-3-234729 Patent Publication No. 1. 3 to 10 mmol / g of polymer,
The poly-β-alanine copolymer has an average particle size of 10 μm or less, more preferably 1 to 6 μm.

[0011] The polyamide in the present invention has a content of 0.01 to
5% by weight can be added. If the content is less than 0.01% by weight or more than 5% by weight, the slidability after the high temperature and high humidity environment intended in the present application is reduced. A preferable addition amount is 0.1.
1 to 0.5% by weight. The hindered phenol in the present invention is a compound having a structure that causes phenolic OH to cause steric hindrance by an alkyl group or the like. The preferred hindered phenol is a hindered phenol having a methyl group or a t-butyl group among the 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. More specific hindered phenols for the purpose of the present application are pentaerythrityl-tetrakis [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. If the content is less than 0.01% by weight or more than 5% by weight, the slidability after the high-temperature and high-humidity environment intended in the present application is reduced. A preferable addition amount is 0.1 to 0.5% by weight. Among the polyethylenes graft-modified with the aromatic vinyl monomer alone or the active hydrogen-containing vinyl monomer in the present invention, the aromatic vinyl monomer is a vinyl monomer containing a benzene ring. For example, alkyl group-substituted styrene such as styrene, methyl styrene, and ethyl styrene. Of these, styrene is preferred.

[0013] The active hydrogen-containing vinyl monomer specifically includes 2-hydroxyethyl methacrylate and 2-hydroxyethyl methacrylate.
Hydroxypropyl methacrylate, 2-hydroxyethyl acrylate, hydroxypropyl acrylate,
Hydroxyl-containing esters of α, β unsaturated carboxylic acids such as 2-hydroxybutyl methacrylate, p-hydroxyphenyl methacrylate, p-hydroxybenzyl methacrylate, glycerin monomethacrylate, polyethylene glycol methacrylate, polypropylene glycol methacrylate, acrylic acid, methacrylic acid, Acrylamide, allylamine, allyl alcohol and the like. Preferably, in order to solve the object of the present invention, a hydroxyl group-containing ester of an α, β unsaturated carboxylic acid, and more preferably 2-hydroxyethyl methacrylate.

The polyethylene constituting the graft-modified product is a polyethylene comprising at least 90% by weight of ethylene units and at most 10% by weight of vinyl monomer units such as butene-1 and propylene. Preferred molecular weight is 2,000-
It is in the range of 1,000,000 and the specific gravity is 0.91
Those having a melting point in the range of 100 to 140 ° C. and a melting point in the range of 100 to 140 ° C. are preferred. Specific examples include polyethylene wax, low-density polyethylene, linear low-density polyethylene, high-density polyethylene, ultra-high-molecular-weight polyethylene and the like, and low-density polyethylene which is a homopolymer of ethylene having a number average molecular weight of 20,000 to 50,000. Is preferred.

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

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

Among the graft-modified products in the present invention, a graft polymer of a hydroxyl group-containing ester copolymer of styrene-α, β-unsaturated carboxylic acid onto polyethylene is preferred. The polyethylene graft-modified with the aromatic vinyl monomer alone or with the active hydrogen-containing vinyl monomer in the present invention is 0.5 to 20 parts by weight based on the total weight of the composition.
% By weight. Less than 0.5% by weight 2
This is because even if the content exceeds 0% by weight, the slidability after a high-temperature and high-humidity environment is deteriorated. A preferable addition amount is 1 to 10% by weight, and more preferably 2 to 5% by weight, which provides a low coefficient of friction.

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 linear chain or has a branched structure, and is formed from a carboxylic acid or alcohol which may be a saturated hydrocarbon or an unsaturated hydrocarbon. The ester is preferably a saturated hydrocarbon based on heat discoloration resistance. More preferably, fatty acids having 12 to 16 carbon atoms and 12 to 1 carbon atoms
An ester comprising an aliphatic alcohol having 6 or more carbon atoms, more preferably an ester of a fatty acid having 14 or 15 carbon atoms, since a low coefficient of friction is obtained after a high-temperature and high-humidity environment.

Specifically, "lauric acid, tridecylic acid, myristic acid, pentadecylic acid, palmitic acid"
Esters of "lauryl alcohol, tridecyl alcohol, myristyl alcohol, pentadecyl alcohol, cetyl alcohol" are preferred. Furthermore, "myristic acid or pentadecylic acid" and "lauryl alcohol, tridecyl alcohol, myristyl alcohol,
Esters with pentadecyl alcohol, cetyl alcohol "are more preferred.

The ester comprising a fatty acid and an aliphatic alcohol in the present invention is used in an amount of 0.1 to 10 with respect to the total composition.
% By weight. Preferably, 0.5 to 5
% By weight, and more preferably 0.5 to 3% by weight. The composition of the present invention can be melt-kneaded and pelletized at a temperature equal to or higher 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, and in consideration of oxygen cutoff and working environment, the vent is depressurized and twin-screw (2 articles). Pelletizing with an extruder is preferred.

If desired, the composition of the present invention may be any of those conventionally used as plastic additives, for example, hindered amines, ultraviolet absorbers, inorganic fillers, pigments, carbon Black or the like may be added. The composition of the present invention can be used for various sliding members of OA equipment and automobiles, for example, gears, bearings, levers, key stems, cams, ratchets, rollers, 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, and the like.

[0022]

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

[0023]

Examples 1-27 U.S. Pat. No. 2,989,409
Intrinsic viscosity 1.2 (α-pinene 2% by weight)
For a solution of 0.1% by weight of polymer in p-chlorophenol containing
Melt index [ASTM D1238-57
(E)] A polyoxymethylene homopolymer powder acetylated at both ends at 9.0 g / 10 min was dried at 80 ° C. for 3 hours, and 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
Page (1987), a graft polymer ("Polymer A: a low-density polyethylene having Mn = 30,000") produced by using a method utilizing a grafting reaction of a polymer having a peroxide bond in a side chain to a polyolefin. And a styrene (28% by weight) -2-ethylhexyl methacrylate (2% by weight) copolymer "," Polymer B: Mn = 3
Graft polymer of low-density polyethylene and polystyrene (30% by weight) of 0000 "), and JP-A-63-118.
Primary amide content obtained by polymerizing acrylamide and methylenebisacrylamide (10 mol%) produced by the methods described in JP-A-328-328 and JP-A-3-234729 in the presence of a metal alcoholate Is 1.3 mmol / g of polymer, and
Poly β-alanine copolymer having an average particle size of 4 μm (polyamide A), crushed nylon 6,6 (average particle size of 4 μm)
m) and the esters described in Table 1 were blended under a nitrogen atmosphere, and a screw-rotation speed of 100 rpm was applied using a twin screw vent extruder with an L / D of 25 set at 200 ° C.
Discharge rate 3 kg / hour, maximum resin temperature 205-210 ° C,
Melt kneading under the conditions of kneading time (residence time) 0.5 to 0.7 minutes to prepare a resin composition having a composition shown in Tables 1 to 3,
It was further pelletized.

Next, after drying the pellets at 80 ° C. for 3 hours, the mold temperature was set to 70 ° C. using a 1 oz. Molding machine (TI30G made by Toyo Machine Metal) set at a cylinder temperature of 200 ° C.
Under a condition of 10 ° C. and a cooling time of 10 seconds, a molded piece of 2 × 12 × 0.3 cm was formed to obtain a test piece. This test piece was heated at 60 ° C.
It was placed in a 90% humidity environment for 48 hours. It was taken out and placed in an environment of 23 ° C. and 50% humidity for 5 minutes. For this test piece, the point-contact reciprocating slidability was evaluated by a reciprocating friction and wear tester (AFT-15MS, manufactured by Tosoh Seimitsu Co., Ltd., load 2 kg, linear velocity 10 mm / sec, reciprocating distance 20 mm, mating material: 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 Comparative Examples 1 to 15 were carried out in the same manner as in Example 1 with the compositions shown in Tables 4 and 5. Table 4 shows the results.
It is shown in FIG.

[0027]

Example 28 An intrinsic viscosity of 1.1 and a melt index of 10 were obtained by the method described in U.S. Patent Application No. 3027352.
Except that a polyoxymethylene copolymer containing 2.8% by weight of oxyethylene groups per g / 10 minutes was used as the polyoxymethylene resin, the components and addition amounts shown in Example 17 were the same, and sliding was performed in the same manner. The test was performed.

As a result, the coefficient of friction after one round trip: 0.1
5, the coefficient of friction after 1000 reciprocations: 0.15.

[0029]

[Table 1]

[0030]

[Table 2]

[0031]

[Table 3]

[0032]

[Table 4]

[0033]

[Table 5]

[0034]

According to the present invention, in addition to a combination of a conventionally known graft-modified product and an ester-based lubricant, a hindered phenol and a polyamide, which have been conventionally considered as a stabilizer, are used in combination. It was considered difficult, "The deterioration of slidability that occurs in a bad environment, such as returning to normal temperature or low temperature and low humidity after exposure to high temperature and high humidity, or dropping."
Can be improved.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI C08L 77:00) C08L 77:00)

Claims (10)

(57) [Claims] (A) a polyoxymethylene resin;
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: a graft-modified polyethylene; 0.5 to 20% by weight and (E) an ester comprising 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 as the component (B) is a poly-β-alanine copolymer. 3. The polyoxymethylene resin composition according to claim 1, wherein the polyoxymethylene resin as the component (A) is a polyoxymethylene homopolymer. 4. The polyamide of component (B) is obtained by polymerizing acrylamide or a derivative thereof in the presence of a metal alcoholate, and has a primary amide content of 1.3 to 10 mmol / g of polymer, and Average particle size is 1-6μ
4. The polyoxymethylene resin composition according to claim 1, wherein the content of the polyβ-alanine copolymer is 0.1 to 0.5% by weight. 5. The hindered phenol of the component (C),
Pentaerythrityl-tetrakis [3- (3,5-di-
(t-butyl-4-hydroxyphenyl) propionate] is 0.1 to 0.5% by weight of the polyoxymethylene resin composition according to claim 1, 2, 3 or 4. 6. The hindered phenol of the component (C),
5. The polyoxy according to claim 1, wherein the amount of triethylene glycol-bis [3- (3-t-butyl-5-methyl-4-hydroxyphenyl) propionate] is 0.1 to 0.5% by weight. Methylene resin composition. 7. The graft-modified polyethylene as the component (D) has a number average molecular weight of 2 to 2 which is produced by a method utilizing a grafting reaction of a polymer having a peroxide chain in a side chain to a polyolefin. Graft polymer of 50,000 ethylene homopolymer and styrene homopolymer 2
The polyoxymethylene resin composition according to claim 1, wherein the content is 5% by weight. 8. The styrene-α, β-free polyethylene produced by the method using a graft reaction of a polymer having a side chain with a peroxide bond to a polyolefin, wherein the graft-modified polyethylene of the component (D) is used. The graft polymer of a hydroxyl group-containing ester copolymer of a saturated carboxylic acid and a homopolymer of ethylene having a number average molecular weight of 20,000 to 50,000 is 2 to 5% by weight. Polyoxymethylene resin composition. 9. An ester comprising a fatty acid and an aliphatic alcohol as the component (E) is an ester of a fatty acid having 14 or 15 carbon atoms in an amount of 0.5 to 3% by weight.
The polyoxymethylene resin composition according to 3, 4, 5, 6, 7, or 8. 10. The polyoxymethylene resin composition according to claim 1, wherein the ester comprising a fatty acid and an aliphatic alcohol as the component (E) is cetyl myristate. .