JP6672727B2 - Ethylene-vinyl acetate copolymer resin composition, graft copolymer, polyacetal resin composition, and resin molded article - Google Patents

Description

  The present invention relates to an ethylene-vinyl acetate copolymer resin composition, a graft copolymer, a polyacetal resin composition, and a resin molded product.

  The polyacetal resin is excellent in slidability in addition to mechanical properties, electrical properties, moldability, and dimensional accuracy of a molded product. For this reason, polyacetal resins are used in a wide range of fields as sliding members such as bearings and gears.

  However, in recent years, with the development of the above-mentioned fields, higher requirements have been made for sliding members. In particular, sliding members are required to have further improved slidability such as a coefficient of friction, a wear amount, and a sliding noise (squeaking noise).

  Techniques for improving the sliding characteristics of polyacetal resin are disclosed in Patent Documents 1 and 2. In the techniques described in Patent Documents 1 and 2, the sliding characteristics of the polyacetal resin are improved by mixing an additive with the polyacetal resin.

  In the technique described in Patent Document 1, as an additive, a graft copolymer of polyethylene, an ethylene-glycidyl methacrylate copolymer, an acrylonitrile-styrene copolymer, and polystyrene is used. In the technique described in Patent Document 2, as an additive, a multiphase resin composed of an olefin-based copolymer and a vinyl-based copolymer is used.

JP-A-8-259766 JP-A-4-120159

  However, in the polyacetal resin composition obtained by mixing the above mixture with the polyacetal resin, although a sufficient sliding property is obtained in a sliding test using a mating material as a metal, a sufficient sliding property is obtained in a sliding test between the polyacetal resin compositions. Sliding property cannot be obtained. Further, with these polyacetal resin compositions, sufficient sliding properties cannot be obtained even in a sliding test under a high load.

  In view of the above circumstances, an object of the present invention is to provide a technique for improving the slidability of a polyacetal resin while maintaining mechanical properties.

In order to achieve the above object, an ethylene-vinyl acetate copolymer resin composition according to one embodiment of the present invention includes (A) an ethylene-vinyl acetate copolymer, (B) a vinyl copolymer, and (C) And an organic peroxide.
The (B) vinyl copolymer and the (C) organic peroxide are impregnated in the (A) ethylene-vinyl acetate copolymer.
The (A) ethylene-vinyl acetate copolymer contains 1 to 20% by weight of vinyl acetate.
(B) The vinyl copolymer is (b-1) styrene, (b-2) at least one of acrylonitrile and glycidyl methacrylate, (b-3) t-butyl peroxymethacryloyloxyethyl carbonate, b-4) a polymerization initiator.
Assuming that the content of the (A) ethylene-vinyl acetate copolymer is 100 parts by weight, the content of the (C) organic peroxide is 0.1 to 3 parts by weight.

  By adding the ethylene-vinyl acetate copolymer resin composition having this configuration to the polyacetal resin, a polyacetal resin composition having excellent mechanical properties and slidability can be obtained.

When the total content of the (A) ethylene-vinyl acetate copolymer, the (b-1) styrene, and the (b-2) acrylonitrile and at least one of glycidyl methacrylate is 100 parts by weight, The content of the ethylene-vinyl acetate copolymer (A) may be 50 to 90 parts by weight.
By using the ethylene-vinyl acetate copolymer resin composition having this configuration, a polyacetal resin composition having even better slidability can be obtained.

The (b-4) polymerization initiator may have a 10-hour half-life temperature of 50 to 75 ° C.
The (C) organic peroxide may have a 10-hour half-life temperature of 95 to 130 ° C.
In this configuration, the 10-hour half-life temperature of the organic peroxide (C) is higher than the 10-hour half-life temperature of the polymerization initiator (b-4). For this reason, the decomposition of the organic peroxide (C) hardly occurs during the polymerization reaction for obtaining the vinyl copolymer (B). Therefore, in the ethylene-vinyl acetate copolymer resin composition having this configuration, (C) the organic peroxide is difficult to decrease, and therefore the (A) crosslinking reaction of the ethylene-vinyl acetate copolymer is insufficient during melt kneading. Can be prevented.

The graft copolymer according to one embodiment of the present invention is obtained by melt-kneading the above-mentioned ethylene-vinyl acetate copolymer resin composition.
The main chain of the graft copolymer is composed of the (A) ethylene-vinyl acetate copolymer.
The side chain of the graft copolymer comprises a vinyl copolymer of (b-1) styrene and at least one of (b-2) acrylonitrile and glycidyl methacrylate.
By adding to the graft copolymer having this configuration, a polyacetal resin composition having excellent mechanical properties and slidability can be obtained.

The graft copolymer according to one embodiment of the present invention contains (X) a polyacetal resin and (Y) a graft copolymer.
When the content of the (X) polyacetal resin is 100 parts by weight, the content of the (Y) graft copolymer is 3 to 30 parts by weight.
With this configuration, it is possible to provide a polyacetal resin composition having more excellent mechanical properties and slidability.

The polyacetal resin composition according to one embodiment of the present invention further contains (Z-1) at least one selected from a fatty acid ester, a fatty acid amide, a polyethylene wax, and a paraffin wax as a lubricant.
When the content of the (X) polyacetal resin is 100 parts by weight, the content of the (Z-1) lubricant is 1 to 5 parts by weight.
With this configuration, it is possible to provide a polyacetal resin composition having more excellent mechanical properties and slidability.

The polyacetal resin composition according to one embodiment of the present invention further contains (Z-2) at least one selected from calcium carbonate and potassium titanate as an inorganic filler.
Assuming that the content of the (X) polyacetal resin is 100 parts by weight, the content of the (Z-2) inorganic filler is 3 to 8 parts by weight.
With this configuration, it is possible to provide a polyacetal resin composition having more excellent mechanical properties and slidability.

  A resin molded product according to one embodiment of the present invention is obtained by molding the above polyacetal resin composition.

  It is possible to provide a technique for improving slidability of a polyacetal resin while maintaining mechanical properties.

  Hereinafter, an embodiment of the present invention will be described.

<Overview>
In the present embodiment, the (Y) graft copolymer composed of a specific main chain and a side chain, and further having the main chain selectively crosslinked by an organic peroxide, is blended with the (X) polyacetal resin, whereby (Y) A polyacetal resin composition in which the graft copolymer is well dispersed in the (X) polyacetal resin is produced.

  In the polyacetal resin composition according to the present embodiment, excellent mechanical properties inherent in the polyacetal resin are maintained, and excellent slidability is obtained irrespective of the type of the counterpart material and the magnitude of the load. This polyacetal resin composition can be used in a wide range of fields such as electric parts, electronic parts, mechanical parts, precision equipment parts, and automobile parts.

  The (Y) graft copolymer according to this embodiment is obtained by melt-kneading an ethylene-vinyl acetate copolymer resin composition described below.

<Ethylene-vinyl acetate copolymer resin composition>
The ethylene-vinyl acetate copolymer resin composition according to this embodiment includes (A) an ethylene-vinyl acetate copolymer (EVA), (B) a vinyl copolymer, and (C) an organic peroxide. It contains. The (B) vinyl copolymer and the (C) organic peroxide are impregnated in the (A) ethylene-vinyl acetate copolymer.

[(A) Ethylene-vinyl acetate copolymer (EVA)]
The content of vinyl acetate in the structural unit of the ethylene-vinyl acetate copolymer (A) according to this embodiment is preferably 1 to 20% by weight, and more preferably 3 to 10% by weight.

  (A) In the ethylene-vinyl acetate copolymer, by keeping the content of vinyl acetate at 20% by weight or less, the slidability of the polyacetal resin composition is improved, and the content of vinyl acetate is reduced to 10% by weight or less. By fixing, the slidability of the polyacetal resin composition is further improved. Further, in these cases, the heat resistance of the (Y) graft polymer is improved.

  On the other hand, in the ethylene-vinyl acetate copolymer (A), by setting the content of vinyl acetate to 1% by weight or more, the cross-linking reaction with the organic peroxide (C) easily progresses, By setting the content of vinyl acetate in the ethylene-vinyl acetate copolymer to 3% by weight or more, the crosslinking reaction with the organic peroxide (C) is further facilitated.

  Further, as the (A) ethylene-vinyl acetate copolymer, any having any fluidity can be selected. However, the melt flow rate (MFR) of the ethylene-vinyl acetate copolymer (A) is preferably from 0.1 to 25 (g / 10 min) at 190 ° C. by a measuring method based on JIS K 7210. , 1.0 to 10 (g / 10 min).

  (A) In the ethylene-vinyl acetate copolymer, the slidability of the polyacetal resin composition is improved by keeping the MFR at 25 (g / 10 min) or less and further keeping the MFR at 10 (g / 10 min) or less. On the other hand, in the ethylene-vinyl acetate copolymer (A), the MFR is set to 0.1 (g / 10 min) or more, and further, the MFR is set to 1.0 (g / 10 min) or more, whereby the (Y) graft Workability in the polymer production process is improved.

[(B) vinyl copolymer]
The (B) vinyl copolymer according to this embodiment includes (b-1) styrene, (b-2) at least one of acrylonitrile and glycidyl methacrylate, and (b-3) t-butylperoxymethacryloyloxyethyl. It is composed of a vinyl monomer composition comprising carbonate and (b-4) a polymerization initiator.

  (B) The content of each of the monomers (b-1), (b-2), (b-3) and (b-4) in the vinyl copolymer can be determined as appropriate. However, when the total of the content of (b-1) styrene and the content of (b-2) at least one of acrylonitrile and glycidyl methacrylate is 100 parts by weight, the content of (b-1) styrene is It is preferably 50 to 99 parts by weight. Thereby, a polyacetal resin composition having particularly excellent slidability and mechanical properties can be obtained.

  When the total content of (A) an ethylene-vinyl acetate copolymer, (b-1) styrene, and (b-2) at least one of acrylonitrile and glycidyl methacrylate is 100 parts by weight, A) The content of the ethylene-vinyl acetate copolymer is preferably 50 to 90 parts by weight. In this case, particularly good slidability in the polyacetal resin composition is obtained.

…（１） (B-3) t-butyl peroxymethacryloyloxyethyl carbonate in the (B) vinyl copolymer is a compound represented by the following chemical formula (1). When the ethylene-vinyl acetate copolymer resin composition according to the present embodiment is melt-kneaded, the peroxide bond of (b-3) t-butylperoxymethacryloyloxyethyl carbonate is thermally decomposed to generate radicals. (Y) A graft copolymer is obtained.

… (1)

  The polymerization initiator (b-4) in the (B) vinyl copolymer is not limited to a specific type, and known ones such as an organic peroxide and an azo initiator can be used. However, the (b-4) 10-hour half-life temperature of the polymerization initiator is preferably 50 to 75 ° C.

  Here, the 10-hour half-life temperature (hereinafter, also abbreviated as "T10") is defined as (b-4) the polymerization initiator concentration or the azo bond contained in the polymerization initiator or (C) the organic peroxide. When a solution dissolved in benzene is thermally decomposed so that the concentration becomes 0.1 mol / liter, the polymerization initiator (b-4) or the organic peroxide (C) has a half-life of 10 hours. This is the temperature at which you are greeted.

  By setting the (b-4) 10-hour half-life temperature of the polymerization initiator to 50 ° C. or higher, rapid decomposition of the (b-4) polymerization initiator is suppressed, and the polymerization temperature is easily controlled. On the other hand, by setting the (b-4) 10-hour half-life temperature of the polymerization initiator to 75 ° C. or lower, good decomposition of the (b-4) polymerization initiator is obtained, and the (Y) graft copolymer is obtained. (B-4) It becomes difficult for the polymerization initiator itself and other monomers to remain.

  In order to make it difficult for (A-4) the polymerization initiator itself and other monomers to remain in the (A) ethylene-vinyl acetate copolymer, the polymerization temperature for obtaining (B) the vinyl copolymer is adjusted. It is also conceivable to raise it.

  However, if the polymerization temperature is increased, the difference between the polymerization temperature and the 10-hour half-life temperature of the organic peroxide (C) becomes smaller, so that (C) the organic reaction (C) during the polymerization reaction to obtain the vinyl copolymer The peroxide is easily decomposed. Therefore, (C) the organic peroxide may be insufficient at the time of melt-kneading, and the (A) ethylene-vinyl acetate copolymer may not be able to perform a crosslinking reaction sufficiently. For this reason, it is not preferable to increase the polymerization temperature for obtaining the (B) vinyl copolymer.

(B-4) Examples of the organic peroxide that can be used as a polymerization initiator include the following. For each substance, the 10 hour half-life temperature is shown in parentheses.
t-butyl peroxy neoheptanoate (T10 = 51 ° C.)
t-hexyl peroxypivalate (T10 = 53 ° C.)
t-butyl peroxypivalate (T10 = 55 ° C.)
Di (3,5,5-trimethylhexanoyl) peroxide (T10 = 59 ° C.)
Dilauroyl peroxide (T10 = 62 ° C)
1,1,3,3-tetramethylbutylperoxy-2-ethylhexanoate (T10 = 65 ° C.)
2,5-dimethyl-2,5-di (2-ethylhexanoylperoxy) hexane (T10 = 66 ° C.)
t-hexylperoxy-2-ethylhexylhexanoate (T10 = 70 ° C.)
Di (4-methylbenzoyl) peroxide (T10 = 71 ° C.)
t-butyl peroxy-2-ethylhexanoate (T10 = 72 ° C.)
Dibenzoyl peroxide (T10 = 74 ° C)

(B-4) Examples of the azo compound that can be used as a polymerization initiator include the following. For each substance, the 10 hour half-life temperature is shown in parentheses.
2,2-azobis (2,4-dimethylvaleronitrile) (T10 = 51 ° C.)
2,2-azobis (isobutyronitrile) (T10 = 65 ° C)
2,2-azobis (2-methylbutyronitrile) (T10 = 67 ° C.)

[(C) Organic peroxide]
The (C) organic peroxide according to the present embodiment can crosslink the (A) ethylene-vinyl acetate copolymer by generating a radical by thermal decomposition during melt-kneading. (C) The organic peroxide is not limited to a specific type, and a known one can be used. However, the 10-hour half-life temperature of the organic peroxide (C) is preferably 95 to 130 ° C.

  When the (C) organic peroxide has a 10-hour half-life temperature of 95 ° C. or higher, the (C) organic peroxide is less likely to be decomposed during the polymerization reaction for obtaining the (B) vinyl copolymer. Therefore, it is difficult to reduce (C) the organic peroxide during the polymerization reaction for obtaining the (B) vinyl copolymer, and therefore the shortage of the (A) ethylene-vinyl acetate copolymer crosslinking reaction during melt kneading. Can be prevented.

  On the other hand, by setting the 10-hour half-life temperature of the organic peroxide (C) to 130 ° C. or lower, the organic peroxide (C) is decomposed favorably during melt kneading. Thereby, the cross-linking reaction of (A) the ethylene-vinyl acetate copolymer proceeds favorably.

Examples of the (C) organic peroxide that can be used in the present embodiment include the following. For each substance, the 10 hour half-life temperature is shown in parentheses.
t-hexylperoxyisopropyl monocarbonate (T10 = 95 ° C.)
t-butyl peroxy-3,5,5-trimethylhexanoate (T10 = 97 ° C.)
t-butyl peroxylaurate (T10 = 98 ° C.)
t-butyl peroxyisopropyl monocarbonate (T10 = 99 ° C.)
t-butyl peroxy-2-ethylhexyl monocarbonate (T10 = 99 ° C.)
t-hexyl peroxybenzoate (T10 = 99 ° C.)
2,5-dimethyl-2,5-di (benzoylperoxy) hexane (T10 = 100 ° C.)
t-butyl peroxyacetate (T10 = 102 ° C.)
2,2-di (t-butylperoxy) butane (T10 = 103 ° C.)
t-butyl peroxybenzoate (T10 = 104 ° C.)
n-butyl-4,4-di (t-butylperoxy) valerate (T10 = 105 ° C.)
Di (2-t-butylperoxyisopropyl) benzene (T10 = 119 ° C.)
Dicumyl peroxide (T10 = 116 ° C)
Di-t-hexyl peroxide (T10 = 116 ° C.)
2,5-dimethyl-2,5-di (t-butylperoxy) hexane (T10 = 118 ° C.)
t-butylcumyl peroxide (T10 = 120 ° C.)
Di-t-butyl peroxide (T10 = 124 ° C.)

  The content of the organic peroxide (C) according to the present embodiment is preferably 0.1 to 3 parts by weight, where the content of the ethylene-vinyl acetate copolymer (A) is 100 parts by weight. By making the content of (C) the organic peroxide 0.1 parts by weight or more, it is possible to prevent the crosslinking reaction of the (A) ethylene-vinyl acetate copolymer from being insufficient. On the other hand, by keeping the content of (C) the organic peroxide at 3 parts by weight or less, good fluidity can be obtained in the (Y) graft copolymer obtained by melt kneading.

<Polyacetal resin composition>
The polyacetal resin composition according to the present embodiment contains (X) a polyacetal resin and (Y) a graft copolymer.

[(X) polyacetal resin]
(X) The polyacetal resin can be produced by a known production method. (X) As the polyacetal resin, either a polyacetal homopolymer or a polyacetal copolymer may be used. As the base resin (X) of the polyacetal resin, a resin obtained by modifying a polyacetal by crosslinking or graft copolymerization by a known method can be used. (X) The degree of polymerization and the structure of the terminal group of the polyacetal resin are not limited to specific ones.

[(Y) graft copolymer]
The (Y) graft copolymer according to this embodiment is obtained by melt-kneading the above-mentioned ethylene-vinyl acetate copolymer resin composition. In the ethylene-vinyl acetate copolymer resin composition, (B) the vinyl copolymer and (C) the organic peroxide are impregnated in the (A) ethylene-vinyl acetate copolymer, so that a uniform graft copolymer is obtained. Is obtained.

  (Y) The main chain of the graft copolymer is composed of (A) an ethylene-vinyl acetate copolymer. The side chain of the (Y) graft copolymer comprises a vinyl copolymer of (b-1) styrene and (b-2) at least one of acrylonitrile and glycidyl methacrylate.

  The content of the (Y) graft copolymer is preferably 3 to 30 parts by weight, and more preferably 5 to 20 parts by weight, when the content of the (X) polyacetal resin is 100 parts by weight.

  By making the content of the (Y) graft copolymer 3 parts by weight or more, the slidability of the polyacetal resin composition is improved, and by making the content of the (Y) graft copolymer 5 parts by weight or more. The slidability of the polyacetal resin composition is further improved.

  On the other hand, by keeping the content of the (Y) graft copolymer at 30 parts by weight or less, the mechanical properties and appearance quality of the polyacetal resin composition are improved, and the content of the (Y) graft copolymer is reduced to 20 parts by weight. By keeping the number of parts or less, the mechanical properties and appearance quality of the polyacetal resin composition are further improved.

[(Z) Other additives]
The polyacetal resin composition according to the present embodiment may contain additives other than the above, if necessary. Examples of such additives include mineral oils, hydrocarbons, fatty acids, alcohols, fatty acid esters, fatty acid amides, metal soaps, natural waxes, lubricants such as silicones, magnesium hydroxide, inorganic flame retardants such as aluminum hydroxide, Organic or inorganic fillers such as halogen-based, phosphorus-based organic flame retardants, metal powder, talc, glass fiber, carbon fiber, wood powder, etc., antioxidants, UV inhibitors, lubricants, dispersants, coupling agents, Additives such as a foaming agent, a cross-linking agent, and a coloring agent, and other engineering plastics such as polyolefin resins, polyesters, polycarbonates, ABS resins, and polyphenylene ethers.

((Z-1) lubricant)
(Z-1) The lubricant preferably contains at least one selected from fatty acid esters, fatty acid amides, polyethylene waxes, and paraffin waxes. Thereby, the sliding property of the thermoplastic resin composition is further improved.

  Further, when the content of the (X) polyacetal resin is 100 parts by weight, the content of the (Z-1) lubricant is preferably 1 to 5 parts by weight. By setting the content of the (Z-1) lubricant to 1 part by weight or more, the slidability of the thermoplastic resin composition is further improved. By setting the content of the lubricant (Z-1) to 5 parts by weight or less, mechanical strength can be maintained.

((Z-2) inorganic filler)
(Z-2) The inorganic filler preferably contains at least one selected from calcium carbonate and potassium titanate. Thereby, the mechanical strength is further improved.

  Assuming that the content of the (X) polyacetal resin is 100 parts by weight, the content of the (Z-2) inorganic filler is 3 to 8 parts by weight. (Z-2) By setting the content of the inorganic filler to 3 parts by weight or more, the mechanical strength is improved. Further, when the content of the (Z-2) inorganic filler is 8 parts by weight or less, slidability can be maintained.

<Resin molded products>
Since the polyacetal resin composition according to the present embodiment is a thermoplastic resin, it can be easily formed into various shapes by injection molding, extrusion molding, or the like. The resin molded product obtained by molding the polyacetal resin composition according to the present embodiment is excellent in mechanical properties and slidability, so that it can be used in a wide range of fields such as electric parts, electronic parts, mechanical parts, precision equipment parts, and automobile parts. Can be used at

  Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples.

<Ethylene-vinyl acetate copolymer resin composition>
[Production of ethylene-vinyl acetate copolymer resin composition]
For Examples 1-1 to 1-13 and Comparative Examples 1-1 to 1-4, ethylene-vinyl acetate copolymer resin compositions having the compositions shown in Table 1 were produced. As one example, a process for producing the ethylene-vinyl acetate copolymer resin composition according to Example 1-1 is described below. In addition, the ethylene-vinyl acetate copolymer resin compositions according to other Examples and Comparative Examples were also manufactured by the same process as in Example 1-1.

[Production of ethylene-vinyl acetate copolymer resin composition according to Example 1-1]
2500 g of pure water was put into a 5 L stainless steel autoclave, and 2.5 g of polyvinyl alcohol was further dissolved as a suspending agent. 700 g of an ethylene-vinyl acetate copolymer (trade name “Ultracene 510”, manufactured by Tosoh Corporation, VAc content 6%, MFR = 2.5 g / 10 min) was added thereto, and the mixture was stirred and dispersed.

  Separately, 4.0 g of a radical polymerization initiator, 9.0 g of a radical (co) polymerizable organic peroxide, and 3.5 g of a crosslinking agent were combined with 210 g of styrene (St) and 90 g of glycidyl methacrylate. A solution dissolved in (GMA) was produced, and the solution was charged into an autoclave and stirred.

  As the radical polymerization initiator, di (3,5,5-trimethylhexanoyl) peroxide (trade name “Perloyl 355”, 10-hour half-life temperature = 59 ° C., manufactured by NOF CORPORATION) is used. As the polymerizable organic peroxide, t-butylperoxymethacryloyloxyethyl carbonate (MEC) was used, and as a crosslinking agent, 2,5-dimethyl-2,5-di (t-butylperoxy) hexane (trade name “ Perhexa 25B ", 10-hour half-life temperature = 118 ° C, manufactured by NOF CORPORATION).

  Then, the autoclave was heated to 60 to 65 ° C. and stirred for 3 hours to convert the monomer composition containing the radical polymerization initiator and the radical (co) polymerizable organic peroxide into an ethylene-vinyl acetate copolymer. Impregnated.

  Thereafter, the temperature of the autoclave was raised to 80 to 85 ° C., the temperature was maintained at that temperature for 7 hours, polymerization was carried out, and the polymer was washed with water and dried to obtain poly (St / GMA / MEC) copolymer which is a vinyl copolymer (B). (A) ethylene-impregnated with (A) ethylene-vinyl acetate copolymer, and (C) 2,5-dimethyl-2,5-di (t-butylperoxy) hexane, which is an organic peroxide, A vinyl acetate copolymer resin composition was obtained.

  A poly (St / GMA / MEC) copolymer was extracted with ethyl acetate from the obtained ethylene-vinyl acetate copolymer resin composition. As a result of measurement by gel permeation chromatography (GPC), it was found that the weight average molecular weight of the poly (St / GMA / MEC) copolymer was 400,000.

[Description of Comparative Examples 1-1 to 1-4]
In the ethylene-vinyl acetate copolymer resin composition according to Comparative Example 1-1, unlike the above embodiment, (C) the organic peroxide is not included.

  In the ethylene-vinyl acetate copolymer resin composition according to Comparative Example 1-2, (A) the content of vinyl acetate in the ethylene-vinyl acetate copolymer is higher than in the above embodiment.

  In the ethylene-vinyl acetate copolymer resin composition according to Comparative Example 1-3, the content of the organic peroxide (C) is larger than that in the above embodiment.

  In the ethylene-vinyl acetate copolymer resin composition according to Comparative Examples 1-4, (A) low-density polyethylene is used instead of the ethylene-vinyl acetate copolymer.

The meaning of each abbreviation in Table 1 is as follows.
EVA: ethylene-vinyl acetate copolymer (In each of Examples and Comparative Examples, one of the following three types is appropriately used.)
(I) “Ultracene 510”, manufactured by Tosoh Corporation, VAc content 6%, MFR = 2.5 (g / 10 min)
(II) "Ultracene 537", manufactured by Tosoh Corporation, VAc content 15%, MFR = 3.0 (g / 10 min)
(III) “Ultracene 750”, manufactured by Tosoh Corporation, VAc content 32%, MFR = 30 (g / 10 min)
LDPE: low-density polyethylene (“Sumikacene G401” manufactured by Sumitomo Chemical Co., Ltd., density = 0.926 g / cm ³ )
St: Styrene GMA: Glycidyl methacrylate AN: Acrylonitrile MEC: t-butylperoxymethacryloyloxyethyl carbonate R355: Di (3,5,5-trimethylhexanoyl) peroxide BW: Benzoyl peroxide (“Niper BW”, 10) (Time half-life temperature = 74 ° C, manufactured by NOF Corporation)
25B: 2,5-dimethyl-2,5-di (t-butylperoxy) hexane BuE: t-butylperoxy-2-ethylhexyl monocarbonate (“perbutyl E”, 10-hour half-life temperature = 99 ° C., day) Oil Co., Ltd.)

<Graft copolymer>
[Production of graft copolymer]
In Examples 2-1 to 2-13 and Comparative Examples 2-1 to 2-4, as shown in Table 2, they relate to Examples 1-1 to 1-13 and Comparative Examples 1-1 to 1-4, respectively. A graft copolymer was produced using the ethylene-vinyl acetate copolymer resin composition. As one example, a production process of the graft copolymer according to Example 2-1 is shown below. In addition, the graft copolymers according to other Examples and Comparative Examples were produced by the same process as in Example 2-1.

[Production of graft copolymer according to Example 2-1]
First, the ethylene-vinyl acetate copolymer resin composition obtained in Example 1-1 was melt-kneaded at 200 ° C. with a Labo Plastomill single-screw extruder (manufactured by Toyo Seiki Seisaku-sho, Ltd.) to cause a grafting reaction. As a result, a graft copolymer having a main chain composed of an ethylene-vinyl acetate copolymer and a side chain composed of poly (St / GMA) was obtained.

  When the MFR (220 ° C./10 kgf) of the obtained graft copolymer was measured, it was 0.6 (g / 10 min). The grafting reaction and the crosslinking reaction of the ethylene-vinyl acetate copolymer were in progress. It was confirmed. When the obtained graft copolymer was observed with a scanning electron microscope (“JEOL JSM T300”, manufactured by JEOL Ltd.), the spherical resin having a particle size of 0.1 to 0.2 μm was uniformly dispersed. It was confirmed that.

<Polyacetal resin composition>
[Production of polyacetal resin composition]
About Examples 3-1 to 3-14 and Comparative Examples 3-1 to 3-5, with respect to the polyacetal resin (trade name “Duracon M90-44”, manufactured by Polyplastics Co., Ltd.) at the compounding ratio shown in Table 3. The above graft copolymer was appropriately dry-blended in a predetermined amount and melt-kneaded in a twin-screw extruder set at 190 ° C. to obtain a polyacetal resin composition. In Table 3, the polypolyacetal resin is indicated by an abbreviation of “POM”.

  About Examples 4-1 to 4-8, except that (Z-1) a lubricant or (Z-2) an inorganic filler is added at a compounding ratio shown in Table 4, a method similar to that of Example 3-1 is used. A polyacetal resin composition is produced.

  The polyacetal resin composition according to Comparative Example 3-1 was manufactured using only the polyacetal resin without using the graft copolymer. In Examples 3-1 to 3-14, the graft copolymers obtained in Examples 2-1 to 2-13 were respectively used, and in Comparative Examples 3-2 to 3-5, Comparative Examples 2-1 to 2--5 were respectively used. The graft copolymer according to No. 4 was used.

[Evaluation methods]
-Tensile strength A test speed was set to 50 mm / min in accordance with JIS K-7113.

-Flexural modulus The test was performed at a test speed of 2 mm / min in accordance with JIS K-7203.

・ Slidability evaluation 1 (Thrust friction and wear test)
Testing machine: Orientec Co., Ltd. friction and wear testing machine EFM-III-F
Evaluation material: cylindrical material having an inner diameter of 20 mm and an outer diameter of 25.6 mm Evaluation material: polyacetal resin composition having the composition shown in Table 3 Counterpart material: cylindrical material having an inner diameter of 20 mm and outer diameter of 25.6 mm Counterpart material: (1) carbon Steel (S45C), (2) Same material as evaluation material Test conditions (when partner material is (1)): load 50N, linear velocity 50cm / sec
Test conditions (when the mating material is (2)): load 20N, linear velocity 50cm / sec
Test time: 100 minutes In this test, the wear amount (mg) and the dynamic friction coefficient of each evaluation material were obtained for each of the mating material (1) and (2).

・ Slidability evaluation 2 (reciprocating sliding test)
Testing machine: Loving tester 1566-A manufactured by Imoto Seisakusho
Evaluation material: flat plate of 80 mm in length, 10 mm in width, and 4 mm in height Evaluation material: polyacetal resin composition having the composition shown in Tables 3 and 4 Mating material: cylindrical material having a diameter of 10 mm Mating material: Duracon M90-44 (polyplastic Supplier)
Test conditions: load 3 kgf, linear velocity 100 mm / sec, 5000 reciprocations In this test, the wear amount (mg) of each evaluation material was determined.

-Evaluation of squeak noise The obtained evaluation material is used as a plate (60 mm x 100 mm x 2 mm) for a squeak noise evaluation test, and a polyacetal resin (trade name "Duracon M90-44", manufactured by Polyplastics Co., Ltd.) is rubbed. After cutting and deburring as a material plate (50 mm × 25 mm × 2 mm), the condition was adjusted at a temperature of 25 ° C. and a humidity of 50% for 12 hours each.

A squeak sound when the plate for the squeak noise evaluation test and each plate as the mating material are fixed to a Ziegler stick-slip measuring device SSP-02 and rubbed under the conditions of load = 40N and speed = 1mm / sec. Risk values were measured. The squeak noise risk value indicates that the smaller the value, the lower the risk of squeak noise generation. The criteria for determining the squeak noise risk value are as follows.
Squeak noise risk values 1 to 3: Low risk of squeak noise generation Scream noise risk values 4 to 5: Slightly high risk of squeak noise generation Scream noise risk values 6 to 10: High risk of squeak noise generation In the comparative example, the target value of the squeak noise risk value was set to 3 or less.

[Production of evaluation material]
By molding the polyacetal resin compositions according to Examples 3-1 to 3-14, 4-1 to 4-8, and Comparative Examples 3-1 to 3-5 by using an injection molding machine, Examples 3-1 to 3-1. Evaluation materials according to 3-14, 4-1 to 4-8 and Comparative Examples 3-1 to 3-5 were produced. The injection molding conditions were a barrel temperature of 200 ° C. and a mold temperature of 90 ° C.

[Evaluation results]
Table 3 shows the evaluation results of the evaluation materials according to Examples 3-1 to 3-14 and Comparative Examples 3-1 to 3-5.
Table 4 shows the evaluation results of the evaluation materials according to Examples 4-1 to 4-8.

The meaning of each abbreviation in Table 4 is as follows.
SS: Stearyl stearate GMS: Glycerin monostearate SA: Stearamide amide PEWAX: Polyethylene wax PLWAX: Paraffin wax CaCO ₃ : Calcium carbonate (cubic, treated with fatty acid)
TiK: Potassium titanate

-Mechanical properties In the evaluation materials according to Examples 3-1 to 3-14 and Examples 4-1 to 4-8, a large value of 50 MPa or more was obtained as the tensile strength, and the bending elastic modulus was 1.5 GPa. The above high values were obtained. On the other hand, in the evaluation material according to Comparative Example 3-2 containing no (C) organic peroxide, the tensile strength was a small value of less than 50 MPa.

-Evaluation of slidability In the evaluation materials according to Examples 3-1 to 3-14 and Examples 4-1 to 4-8, the thrust type friction and wear test using (1) carbon steel (S45C) as the mating material was performed. In Example 2, a small value of 2.0 mg or less was obtained as the wear amount, and a low value of 0.25 or less was obtained as the dynamic friction coefficient.

  Further, in each of the evaluation materials according to Examples 3-1 to 3-14 and Examples 4-1 to 4-8, the partner material is the same as (2) the evaluation material, that is, the evaluation materials are used. Also in the thrust type friction and wear test, a small value of 2.0 mg or less was obtained as the amount of wear, and a low value of 0.25 or less was obtained as the dynamic friction coefficient.

  Furthermore, in the evaluation materials according to Examples 3-1 to 3-14 and Examples 4-1 to 4-8, a small value of 10.0 mg or less was obtained as the amount of wear in the reciprocating sliding test.

  On the other hand, in all the evaluation materials according to Comparative Examples 3-1 to 3-5, the wear amount was larger than 2.0 mg in the thrust type friction wear test in which the counterpart material was (1) carbon steel (S45C). Met. In addition, the evaluation material according to Comparative Example 3-1 containing no (Y) graft copolymer had a dynamic friction coefficient higher than 0.25.

  In all of the evaluation materials according to Comparative Examples 3-1 to 3-5, the mating material is the same as the evaluation material (2), that is, in the thrust-type friction and wear test between the evaluation materials, the amount of wear is also large. Was greater than 2.0 mg. In addition, in the evaluation material according to Comparative Example 3-1 containing no (Y) graft copolymer, the dynamic friction coefficient was a value higher than 0.25.

  Furthermore, in the evaluation materials according to Comparative Examples 3-1 to 3-5, the wear amount was a value larger than 10.0 mg in the reciprocating sliding test.

・ Evaluation of squeak noise risk In the evaluation materials according to Examples 3-1 to 3-14 and Examples 4-1 to 4-8, the squeak noise risk value was a small value of 3 or less. On the other hand, in the evaluation materials according to Comparative Examples 3-1 to 3-5, the squeak noise risk exceeded 3.

  Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and it is needless to say that various changes can be made without departing from the spirit of the present invention.

Claims (7)

(A) an ethylene-vinyl acetate copolymer, (B) a vinyl copolymer, and (C) an organic peroxide,
The (B) vinyl copolymer and the (C) organic peroxide are impregnated in the (A) ethylene-vinyl acetate copolymer,
(A) the ethylene-vinyl acetate copolymer contains 1 to 20% by weight of vinyl acetate,
(B) the vinyl copolymer is (b-1) styrene, (b-2) at least one of acrylonitrile and glycidyl methacrylate, (b-3) t-butyl peroxymethacryloyloxyethyl carbonate, b-4) a polymerization initiator;
(A) the ethylene - When the content of the vinyl acetate copolymer is 100 parts by weight, Ri content 0.1 to 3 parts by weight der of the (C) an organic peroxide,
(B-4) a 10-hour half-life temperature of the polymerization initiator of 50 to 75 ° C,
(C) An ethylene-vinyl acetate copolymer resin composition wherein the organic peroxide has a 10-hour half-life temperature of 95 to 130 ° C. An ethylene-vinyl acetate copolymer resin composition according to claim 1,
Assuming that the total content of the (A) ethylene-vinyl acetate copolymer, the (b-1) styrene, and the (b-2) acrylonitrile and at least one of glycidyl methacrylate is 100 parts by weight, The ethylene-vinyl acetate copolymer resin composition wherein the content of the (A) ethylene-vinyl acetate copolymer is 50 to 90 parts by weight. Obtained by melt-kneading the ethylene-vinyl acetate copolymer resin composition according to claim 1 or 2 ,
The main chain comprises the (A) ethylene-vinyl acetate copolymer,
A graft copolymer having a side chain comprising a vinyl copolymer of (b-1) styrene and (b-2) at least one of acrylonitrile and glycidyl methacrylate. (X) a polyacetal resin, and (Y) the graft copolymer according to claim 3 ,
Wherein the content of (X) polyacetal resin is 100 parts by weight, the (Y) polyacetal resin composition content of the graft copolymer according to claim 3 is 3 to 30 parts by weight. It is a polyacetal resin composition according to claim 4 ,
(Z-1) If the lubricant further contains at least one selected from fatty acid esters, fatty acid amides, polyethylene waxes, and paraffin waxes and the content of (X) the polyacetal resin is 100 parts by weight, the above-mentioned (Z-1) ) A polyacetal resin composition having a lubricant content of 1 to 5 parts by weight. It is a polyacetal resin composition according to claim 4 or 5 ,
(Z-2) Assuming that the content of the polyacetal resin (X-2) is 100 parts by weight, the inorganic filler (Z-2) contains at least one selected from calcium carbonate and potassium titanate as an inorganic filler. A polyacetal resin composition having an agent content of 3 to 8 parts by weight. A resin molded article obtained by molding the polyacetal resin composition according to any one of claims 4 to 6 .