JP5778518B2 - Polyacetal resin composition and sliding part - Google Patents

Description

  The present invention relates to a polyacetal resin composition that generates less formaldehyde and is excellent in slidability, and a sliding component formed by molding the polyacetal resin composition.

  Polyacetal resin has excellent properties in mechanical properties, thermal properties, electrical properties, slidability, moldability, etc., mainly as electrical materials, automotive parts, precision machine parts as structural materials and mechanical parts. Widely used in

  With the expansion of the field in which polyacetal resins are used, the required characteristics tend to become more sophisticated, complex and specialized. Among them, effective utilization of a cellulose-based material which is a renewable resource has attracted attention, and it has been studied to improve the properties as a polyacetal resin composition by blending it with a polyacetal resin.

  Patent Document 1 discloses a polyacetal resin composition in which pulp is blended with a polyacetal resin. Here, improvements such as mechanical strength, heat resistance, and flammability (resin dripping during combustion) are shown. However, in the method for preparing a polyacetal resin composition described in Patent Document 1, a pulp composition is easily agglomerated due to the aggregation of the pulp in the composition, and a resin composition that is less likely to generate formaldehyde and excellent in slidability. It is difficult to obtain and it is difficult to produce a practically excellent molded product.

  Patent Document 2 discloses a polyacetal resin composition in which a polyacetal resin and a fibrous cellulosic material having a specific bulk density are blended. Here, since the fibrous cellulosic material is used, the result that the aggregation of the fibrous cellulosic material is relatively suppressed is obtained. However, the method for preparing the resin composition described in Patent Document 2 is also difficult to obtain a resin composition that generates less formaldehyde and has excellent slidability, and produces a practically excellent molded product. Is difficult.

JP-A-3-217447 JP 2010-150313 A

  As described above, it is difficult to obtain a resin composition having a small amount of formaldehyde generated and excellent in slidability by a conventionally known technique. An object of the present invention is to solve these problems, and to provide a polyacetal resin composition having a small amount of formaldehyde generated and excellent in slidability, and a sliding part formed by molding the polyacetal resin composition. .

  As a result of intensive studies to solve the above problems, the present inventors have found that a specific (a) polyacetal resin, a specific (b) cellulose fiber powder, (c) a hindered phenol-based antioxidant, and a specific It has been found that a polyacetal resin composition capable of solving the above problems and achieving the object can be obtained by combining (d) a nitrogen-containing compound and a specific (e) long chain fatty acid derivative. It came to complete. More specifically, the present invention provides the following.

  (1) (b) cellulose having an aspect ratio of 1 to 20 and an α cellulose content of 98 to 100% with respect to 100 parts by weight of the polyacetal resin (a) having an unstable terminal group amount of 0.5% by weight or less 10 to 150 parts by weight of fiber powder, (c) 0.01 to 3 parts by weight of hindered phenolic antioxidant, at least one (d) nitrogen selected from aminotriazine compounds, guanamine compounds, hydrazide compounds and polyamides A polyacetal resin composition comprising 0.01 to 3 parts by weight of the containing compound and 0.01 to 3 parts by weight of (e) a long-chain fatty acid derivative having at least one hydroxyl group in the molecule.

  (2) The polyacetal resin composition according to (1), wherein the melt index (based on ASTM-D1238, 190 ° C., 2.16 kgf) of the (a) polyacetal resin is 10 to 50 g / 10 minutes.

(3) The polyacetal resin composition according to (1) or (2), wherein the amount of formaldehyde generated by the following measurement method is 100 ppm or less.
(Measuring method)
Resin pellets composed of 8 g of the polyacetal resin composition were filled into a metal cylinder adjusted to 200 ° C. and held for 5 minutes in a molten state. Subsequently, the formaldehyde gas generated from the molten resin was discharged together with the nitrogen stream while flowing nitrogen through the glass absorption bottle connected to the metal cylinder, thereby allowing the distilled water in the absorption bottle to absorb the formaldehyde gas. Formaldehyde absorbed in distilled water was quantified by a method based on JIS K0102, and calculated as a ratio to the evaluation sample (resin composition).

  (4) Based on the method A described in JIS K7218, a hollow cylindrical test piece formed by molding the polyacetal resin composition according to any one of (1) to (3) is formed, and the hollow cylindrical test piece And the carbon steel material (S45C) are slid for 24 hours under the conditions of 150 rpm and 20 kgf, the wear amount of the hollow cylindrical test piece is 20 mg or less, and the wear amount of the carbon steel material (S45C) is 0.1. The polyacetal resin composition according to any one of (1) to (3), having an abrasion characteristic of 2 mg or less.

  (5) Based on Method A described in JIS K7218, a hollow cylindrical test piece formed by molding the polyacetal resin composition according to any one of claims 1 to 4 is molded, and the hollow cylindrical test piece and carbon (1) From (1) which has the friction characteristic that the friction coefficient with respect to the said carbon steel material of the said hollow cylindrical test piece is 0.3 microseconds or less after sliding a steel material (S45C) on 150 rpm and 20 kgf conditions for 24 hours. 4) The polyacetal resin composition according to any one of the above.

  (6) A sliding part formed by molding the polyacetal resin composition according to any one of (1) to (5).

  The polyacetal resin composition of the present invention has a small amount of formaldehyde and is excellent in slidability. Therefore, the polyacetal resin composition of the present invention is suitable as a raw material for sliding parts.

  Hereinafter, embodiments of the present invention will be described. In addition, this invention is not limited to the following embodiment.

<(A) Polyacetal resin>
The polyacetal resin as component (a) is a polymer compound having an oxymethylene group (—OCH ₂ —) as a main constituent unit, and includes a polyacetal homopolymer substantially consisting only of repeating oxymethylene units, in addition to oxymethylene units. Polyacetal copolymers containing other comonomer units are representative resins. Further, polyacetal resins include copolymers in which a branched structure or a crosslinked structure is introduced by copolymerizing a branch-forming component or a crosslinking-forming component, polymer units composed of repeating oxymethylene groups, and other polymer units. Also included are block copolymers, graft copolymers and the like. These polyacetal resins can be used alone or in combination of two or more.

  In general, a polyacetal homopolymer is produced by polymerization of anhydrous formaldehyde or trioxane (a cyclic trimer of formaldehyde), and is usually stabilized against thermal decomposition by esterifying its terminal.

In contrast, the polyacetal copolymer is generally a formaldehyde or a cyclic oligomer of formaldehyde represented by the general formula (CH ₂ O) n [wherein n represents an integer of 3 or more] (for example, trioxane); It is produced by copolymerizing with a comonomer such as cyclic ether or cyclic formal, and is usually stabilized against thermal decomposition by removing terminal unstable parts by hydrolysis.

  Examples of the main raw material of the polyacetal copolymer include trioxane and tetraoxane, and trioxane is usually used.

  The comonomer includes a cyclic ether, a glycidyl ether compound, a cyclic formal, a cyclic ester (for example, β-propiolactone), a vinyl compound (for example, styrene, vinyl ether, etc.), and the like.

  Examples of the cyclic ether include ethylene oxide, propylene oxide, butylene oxide, cyclohexene oxide, epichlorohydrin, epibromohydrin, styrene oxide, oxetane, 3,3-bis (chloromethyl) oxetane, and tetrahydrofuran.

  Examples of the glycidyl ether compound include alkyl or aryl glycidyl ethers (for example, methyl glycidyl ether, ethyl glycidyl ether, phenyl glycidyl ether, naphthyl glycidyl ether), alkylene or polyalkylene glycol diglycidyl ether (for example, ethylene glycol diglycidyl ether). , Triethylene glycol diglycidyl ether, butanediol diglycidyl ether), alkyl or aryl glycidyl alcohol, and the like.

  Examples of the cyclic formal include 1,3-dioxolane, propylene glycol formal, diethylene glycol formal, triethylene glycol formal, 1,4-butanediol formal, 1,5-pentanediol formal, 1,6-hexanediol formal, and trioxepane. Etc.

  These comonomers can be used alone or in combination of two or more. Of these comonomers, cyclic ethers and / or cyclic formals are usually used, and cyclic ethers such as ethylene oxide, and cyclic formals such as 1,3-dioxolane, 1,4-butanediol formal, and diethylene glycol formal are preferred. .

  The proportion of these comonomer (for example, cyclic ether and / or cyclic formal) units is not particularly limited, but is generally in the range of 0.1 to 20% by weight with respect to the whole polyacetal resin, preferably 0.8. It is about 5 to 20% by weight, more preferably about 0.5 to 15% by weight (particularly 1 to 10% by weight).

  The polyacetal resin of component (a) used in the present invention must have an unstable end group amount of 0.5% by weight or less. Here, the unstable terminal group amount indicates the amount of a portion which is present at the terminal portion of the polyacetal copolymer and is unstable and easily decomposed with respect to heat or a base. The amount of such unstable end groups is as follows: 1 g of polyacetal copolymer is placed in a pressure-resistant sealed container with 100 ml of 50% (volume%) aqueous methanol solution containing 0.5% (volume%) ammonium hydroxide, and at 180 ° C. for 45 minutes. The amount of formaldehyde decomposed and dissolved in the solution obtained by cooling and opening after heat treatment was quantified, and expressed in weight% with respect to the polyacetal copolymer.

  When the polyacetal resin of component (a) does not have the above terminal properties and exceeds the upper limit value, it becomes difficult to obtain a polyacetal resin composition having a sufficiently low formaldehyde generation amount. From such a viewpoint, the polyacetal resin as component (a) has an unstable terminal group content of 0.5% by weight or less, preferably 0.3% by weight or less. On the other hand, the lower limit of the amount of unstable terminal groups is not particularly limited.

  The melt index of the polyacetal resin (a) is preferably in the range of 10 to 100 g / 10 minutes, and particularly preferably in the range of 10 to 50 g / 10 minutes. When the melt index is too small or too large, the effects of the present invention may not be sufficiently obtained. The melt index is a value measured under conditions of 190 ° C. and 2.16 kgf (21.2 N) according to ASTM-D1238.

<(B) Cellulose fiber powder>
(B) Cellulose fiber powder used in the present invention is made from a refined pulp as a raw material in a powder form, and its aspect ratio is 1 to 25. In particular, the preferred aspect ratio is 1.2-20. (B) When the aspect ratio of the cellulose fiber powder exceeds 25, the dispersibility of the cellulose fiber powder deteriorates, which is not preferable. The aspect ratio can be measured by observation with an SEM (scanning electron microscope) or an optical microscope. Moreover, when the cellulose fiber powder has a particle shape, the aspect ratio of the cellulose fiber powder can be calculated from the particle shape.

  Moreover, the preferable average fiber length of (b) cellulose fiber powder is 10-350 micrometers, and 20-320 micrometers is especially preferable. (B) When the average fiber length of the cellulose fiber powder is less than 10 μm, the improvement of the mechanical properties of the polyacetal resin composition is insufficient, and when it exceeds 350 μm, the dispersibility of the cellulose fiber powder is deteriorated, Moreover, since decomposition | disassembly of a polyacetal resin composition may advance, it is unpreferable. The average fiber length can be measured by observation with an SEM or an optical microscope. Moreover, the average fiber length of cellulose fiber powder can use the value of the particle diameter, when cellulose fiber powder is a particle shape.

  Moreover, the range of the (alpha) cellulose content rate of (b) cellulose fiber powder is 98 to 100% (weight%), and the range of 99 to 100% is especially preferable. When the α cellulose content is less than 98%, the polyacetal resin composition may be decomposed, which may be difficult to produce.

  (B) The compounding quantity of cellulose fiber powder is 10-150 weight part with respect to 100 weight part of (a) component polyacetal resin, Preferably it is 15-100 weight part. (B) When the blending amount of the cellulose fiber powder is less than 10 parts by weight, the improvement of the mechanical properties of the polyacetal resin composition is insufficient, and when it exceeds 150 parts by weight, the dispersibility of the cellulose fiber powder is deteriorated. Therefore, it is not preferable.

<(C) Hindered phenolic antioxidant>
The polyacetal resin composition of the present invention can stably improve mechanical properties by using (c) a hindered phenol compound. (C) The hindered phenol compound is a monocyclic hindered phenol compound (for example, 2,6-di-t-butyl-p-cresol), a hydrocarbon group or a group containing a sulfur atom. Polycyclic hindered phenol compounds (for example, 2,2′-methylenebis (4-methyl-6-tert-butylphenol), 4,4′-methylenebis (2,6-di-tert-butylphenol), 1,1, 3-tris (2-methyl-4-hydroxy-5-t-butylphenyl) butane, 4,4′-butylidenebis (3-methyl-6-t-butylphenol), 1,3,5-trimethyl-2,4 , 6-tris (3,5-di-tert-butyl-4-hydroxybenzyl) benzene, 4,4′-thiobis (3-methyl-6-tert-butylphenol)), ester group or A hindered phenol compound having an amide group (for example, n-octadecyl-3- (4′-hydroxy-3 ′, 5′-di-t-butylphenyl) propionate, n-octadecyl-2- (4′-hydroxy-) 3 ′, 5′-di-t-butylphenyl) propionate, 1,6-hexanediol-bis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], triethylene glycol-bis [3- (3-tert-butyl-5-methyl-4-hydroxyphenyl) propionate], pentaerythritol tetrakis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], 3.9 -Bis {2- [3- (3-t-butyl-4-hydroxy-5-methylphenyl) propionyloxy] -1,1-dimethylethyl -2,4,8,10-tetraoxaspiro [5.5] undecane, 2-t-butyl-6- (3'-t-butyl-5'-methyl-2'-hydroxybenzyl) -4-methyl Phenyl acrylate, 2- [1- (2-hydroxy-3,5-di-t-pentylphenyl) ethyl] -4,6-di-t-pentylphenyl acrylate, di-n-octadecyl-3,5-di -T-butyl-4-hydroxybenzylphosphonate, N, N'-hexamethylenebis (3,5-di-t-butyl-4-hydroxy-dihydrocinnamamide, N, N'-ethylenebis [3- ( 3,5-di-t-butyl-4-hydroxyphenyl) propionamide], N, N′-tetramethylenebis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionamide], N N′-hexamethylenebis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionamide], N, N′-ethylenebis [3- (3-tert-butyl-5-methyl-) 4-hydroxyphenyl) propionamide], N, N′-hexamethylenebis [3- (3-tert-butyl-5-methyl-4-hydroxyphenyl) propionamide], N, N′-bis [3- ( 3,5-di-tert-butyl-4-hydroxyphenyl) propionyl] hydrazine, N, N′-bis [3- (3-tert-butyl-5-methyl-4-hydroxyphenyl) propionyl] hydrazine, 1, 3,5-tris (3,5-di-t-butyl-4-hydroxybenzyl) isocyanurate, 1,3,5-tris (4-t-butyl-3-hydroxy-2,6-dimethylbenzyl) i Cyanurate, etc.) and the like.

  In this invention, (c) hindered phenolic antioxidant can be used individually or in combination of 2 or more types. The blending ratio is 0.01 to 3 parts by weight, preferably 0.02 to 1 part by weight, based on 100 parts by weight of the polyacetal resin (a).

<(D) Nitrogen-containing compound>
The polyacetal resin composition of the present invention can be stably improved in mechanical properties by using at least one (d) nitrogen-containing compound selected from aminotriazine compounds, guanamine compounds, hydrazide compounds and polyamides, Melt stability is also improved.

  Examples of aminotriazine compounds include melamine or derivatives thereof [melamine, melamine condensates (melam, melem, melon, etc.)], guanamine or derivatives thereof, and aminotriazine resins [melamine co-condensation resins (melamine-formaldehyde resin, phenol-melamine). Resin, melamine-phenol-formaldehyde resin, benzoguanamine-melamine resin, aromatic polyamine-melamine resin, etc.), co-condensation resin of guanamine, etc.].

  Guanamine compounds include aliphatic guanamine compounds (monoguanamines, alkylenebisguanamines, etc.), alicyclic guanamine compounds (monoguanamines, etc.), aromatic guanamine compounds [monoguanamines (benzoguanamine and its functional group substitution) ), Α- or β-naphthoguanamine and their functional group-substituted derivatives, polyguanamines, aralkyl or aralkylenamines, etc.], heteroatom-containing guanamine compounds [acetal group-containing guanamines, tetraoxospiro ring-containing Guanamines (CTU-guanamine, CMTU-guanamine, etc.), isocyanuric ring-containing guanamines, imidazole ring-containing guanamines, etc.]. Moreover, the compound etc. which the alkoxymethyl group of said melamine, a melamine derivative, and a guanamine type compound substituted by the amino group are also contained.

  Examples of hydrazide compounds include aliphatic carboxylic acid hydrazide compounds (such as stearic acid hydrazide, 12-hydroxystearic acid hydrazide, sebacic acid dihydrazide, dodecanedioic acid dihydrazide, and eicosanedioic acid dihydrazide), alicyclic carboxylic acid hydrazide compounds (1 , 3-bis (hydrazinocarbonoethyl) -5-isopropylhydantoin), aromatic carboxylic acid hydrazide compounds (4-hydroxy-3,5-di-t-butylphenylbenzoic acid hydrazide, 1-naphthoic acid hydrazide) 2-naphthoic acid hydrazide, isophthalic acid dihydrazide, 2,6-naphthalenedicarboxylic acid dihydrazide, etc.), heteroatom-containing carboxylic acid hydrazide compounds, polymer-type carboxylic acid hydrazide compounds, and the like.

  As the polyamide, a polyamide derived from a diamine and a dicarboxylic acid; an aminocarboxylic acid, a polyamide obtained by using a diamine and / or a dicarboxylic acid in combination; a lactam; and a diamine and / or a dicarboxylic acid as needed Polyamide derived by the combined use of Also included are copolyamides formed from two or more different polyamide-forming components.

  Specific examples of polyamides include polyamide 3, polyamide 4, polyamide 46, polyamide 6, polyamide 66, polyamide 610, polyamide 612, polyamide 11, polyamide 12, and other aliphatic polyamides, aromatic dicarboxylic acids (for example, terephthalic acid). And / or polyamides obtained from isophthalic acid) and aliphatic diamines (eg hexamethylenediamine), polyamides obtained from aliphatic dicarboxylic acids (eg adipic acid) and aromatic diamines (eg metaxylylenediamine) And polyamides obtained from aromatic and aliphatic dicarboxylic acids (for example, terephthalic acid and adipic acid) and aliphatic diamines (for example, hexamethylenediamine), and copolymers thereof. It is also possible to use a polyamide block copolymer in which a polyamide hard segment and another soft segment such as a polyether component are combined.

  (D) Nitrogen-containing compounds selected from aminotriazine compounds, guanamine compounds, hydrazide compounds and polyamides can be used alone or in combination of two or more. The blending ratio is 0.01 to 3 parts by weight, preferably 0.02 to 1 part by weight, based on 100 parts by weight of the polyacetal resin (a).

<(E) Long chain fatty acid derivative>
The polyacetal resin composition of the present invention is a resin having a low formaldehyde generation amount and an excellent reduction in wear amount and friction coefficient by using at least one kind of (e) a long-chain fatty acid derivative having at least one hydroxyl group in the molecule. The composition can be obtained stably, and the melt processability of the resin composition is also improved.

  Examples of the (e) long-chain fatty acid derivative having at least one hydroxyl group in the molecule include ester compounds of long-chain fatty acids and alcohols.

  Examples of long chain fatty acids include monovalent or divalent fatty acids having 10 or more carbon atoms, monovalent unsaturated fatty acids having 10 or more carbon atoms, and divalent fatty acids (dibasic fatty acids) having 10 or more carbon atoms. Further, those in which some of the hydrogen atoms are substituted with other substituents can also be used.

  Specific examples of the (e) long chain fatty acid derivative having at least one hydroxyl group in the molecule used in the polyacetal resin composition of the present invention include ethylene glycol monopalmitate, ethylene glycol monodistearate, ethylene glycol mono Behenic acid ester, ethylene glycol monodimantanoic acid ester, glycerin mono- or dipalmitic acid ester, glycerin mono- or distearic acid ester, glycerin mono- or dibehenic acid ester, glycerin mono- or dimontanic acid ester, trimethylolpropane mono- or dipalmitic acid ester , Trimethylolpropane mono- or distearic acid ester, trimethylolpropane mono- or dibehenic acid ester, trimethylolpropane mono- or dimontanic acid ester Pentaerythritol mono to tripalmitate, pentaerythritol mono to tristearate, pentaerythritol mono to tribehenate, pentaerythritol mono to trimontanate, polyglycerol mono to tripalmitate, polyglycerol mono to tristearate Ester, polyglycerin mono to tribehenate, polyglycerin mono to trimontanate, sorbitol mono to tripalmitate, sorbitol mono to tristearate, sorbitol mono to tribehenate, sorbitol mono to tribetanate, Pal of polyalkylene glycol (polyethylene glycol, polypropylene glycol, etc.) Chin esters, stearic acid esters, behenic acid esters, and the like montanic acid ester.

  The (e) long-chain fatty acid derivative having at least one hydroxyl group in the molecule can be used alone or in combination of two or more. The blending ratio is 0.01 to 3 parts by weight, preferably 0.1 to 2.5 parts by weight, more preferably 0.2 to 2 parts by weight with respect to 100 parts by weight of the polyacetal resin as the component (e). It is. In particular, when the content of the component (e) is 0.2 to 2 parts by weight, the friction with the counterpart material becomes very small when the resin composition of the present invention is molded into a sliding part.

<Other ingredients>
The polyacetal resin composition of the present invention may contain a substance that improves the adhesion between (a) the polyacetal resin and (b) the cellulose fiber powder. Here, the substances for improving the adhesion include isocyanate compounds, isothiocyanate compounds, and their modified isocyanate compounds, thermoplastic polyurethane resins, and acid anhydrides of α, β-monoolefinic unsaturated carboxylic acids. Examples thereof include a polymer, a copolymer, and a boric acid compound.

  Furthermore, various known additives can be blended with the resin composition of the present invention in order to improve its physical properties according to the intended use. Examples of additives include various colorants, lubricants, nucleating agents, surfactants, heterogeneous polymers, organic polymer modifiers, and inorganic, organic, metal and other fibrous, powdered, and plate-like fillers. 1 type or 2 types or more can be mixed and used.

<Preparation method of polyacetal resin composition>
In this invention, the specific aspect of the preparation method of the said polyacetal resin composition is not specifically limited, Generally, it can prepare with a well-known equipment and method as a preparation method of a synthetic resin composition or its molded article. That is, necessary components can be mixed and kneaded using an extruder or other melt kneader to prepare pellets for molding. A plurality of extruders or other melt kneaders may be used. In particular, as an extruder used for the preparation of the resin composition of the present invention, it is preferable to use a twin screw extruder from the viewpoint of improving mechanical properties and dispersibility of cellulose fiber powder.

  The composition of the components constituting the polyacetal resin composition may be added to any stage, for example, once added to the polyacetal resin of component (a), or may be added during the preparation of the resin composition, and the final molded product may be added. It is possible to add and mix immediately before obtaining, but in particular, from the viewpoint of improving mechanical properties and dispersibility of cellulose fiber powder, (b) cellulose fiber powder is added from the side of the extruder to the other side. It is preferable to supply and mix independently from the raw material.

  The polyacetal resin composition of the present invention obtained as described above can reduce the amount of formaldehyde generated from a molten sample. A preferred polyacetal resin composition in the present invention has a formaldehyde generation amount from a molten sample of 100 ppm or less. Here, the amount of formaldehyde generated was held for 5 minutes in a state where 8 g of a pellet-shaped composition (sample) was filled in a metal cylinder adjusted to 200 ° C. and melted as described in detail in the Examples. After that, the amount generated from the discharged molten resin is quantified by a method based on JIS K0102.

<Method and application of polyacetal resin composition>
Conventionally known molding methods (for example, injection molding, extrusion molding, compression molding, blow molding, vacuum molding, foam molding, rotational molding, gas injection molding, etc.) are employed using the polyacetal resin composition of the present invention as a raw material. Thus, various molded products can be molded. In particular, it is suitable for injection molding.

  Moreover, the molded article formed by molding the polyacetal resin composition of the present invention obtained as described above is excellent in slidability. Specifically, when the resin composition of the present invention is used as a raw material, a hollow cylindrical test piece formed by molding a polyacetal resin composition is molded based on the method A described in JIS K7218. And carbon steel (S45C) are slid for 24 hours under the conditions of 150 rpm and 20 kgf, the wear amount of the hollow cylindrical specimen is 20 mg or less, and the wear amount of the carbon steel material (S45C) is 0.2 mg or less. It is possible to produce a molded article having wear characteristics.

  Further, when the resin composition of the present invention is used as a raw material, a hollow cylindrical test piece formed by molding a polyacetal resin composition is formed based on the method A described in JIS K7218, and the hollow cylindrical test piece and the carbon steel material are formed. It is possible to manufacture a molded article having a friction characteristic in which the coefficient of friction with respect to the carbon steel material of the hollow cylindrical test piece after sliding (S45C) for 24 hours under the conditions of 150 rpm and 20 kgf is 0.3 μs or less.

  Therefore, the molded product formed by molding the resin composition of the present invention can be used for various applications such as automobile parts, electrical / electronic parts, building materials, life-related parts, makeup-related parts, and medical-related parts. In particular, it can be suitably used for mechanical parts that require slidability, specifically, sliding parts such as gears, levers, cams, pulleys, and bearings.

  Hereinafter, the present invention will be described more specifically based on examples, but the present invention is not limited to these examples.

<Use ingredients>
Details of the components used are as follows.
(A) Polyacetal resin (a-1) Polyacetal resin obtained by copolymerizing 96.5% by weight of trioxane and 3.5% by weight of 1,3-dioxolane, 0.2% by weight of unstable terminal groups, melt index = 27 g / 10 min (manufactured by Polyplastics Co., Ltd.)
(B) Cellulose fiber powder (b-1) ARBOCEL BWW40, aspect ratio 10, average fiber length 200 μm, α-cellulose content of about 99.5% by weight (manufactured by Rettenmeier)
(B-2) KC Flock W-50GK Aspect ratio 1-2, α cellulose content 99% by weight or more (manufactured by Nippon Paper Chemicals)
(B-3) ARBOCEL ZZ 8-1, aspect ratio 24.4, average fiber length 1100 μm, α-cellulose content 75 to 85% by weight (manufactured by Rettenmeier)
(B ′) Other cellulosic substances (b′-4) Pulp, α-cellulose content of about 95% by weight (manufactured by Nippon Paper Group)
(C) Hindered phenol antioxidant (c-1) Pentaerythritol tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate]
(D) Nitrogen-containing compound (d-1) Melamine (e) Long chain fatty acid derivative having at least one hydroxyl group in the molecule (e-1) Glycerin monostearate (e ′) Other long chain fatty acid derivative (e '-2) Ethylenebisstearylamide (e'-3) Pentaerythritol stearic acid full ester (e'-4) Stearyl stearate

<Examples 1-5, Comparative Examples 1-7>
In the ratio shown in Table 1, (a) polyacetal resin, (b) cellulose fiber powder, (c) hindered phenol-based antioxidant, (d) nitrogen-containing compound, and at least one hydroxyl group in the molecule (e ) A long-chain fatty acid derivative was melt-kneaded with a twin-screw extruder to prepare a pellet-like polyacetal resin composition.

In addition, (b) cellulose fiber powder was supplied and mixed from the feeder independently from the side of the twin screw extruder. In Comparative Example 7, instead of (b) cellulose fiber powder, (b ′) other cellulosic material is used, and in Comparative Examples 2 to 5, 7 have at least one hydroxyl group in the molecule (e) length. Instead of the chain fatty acid derivative, (e ′) other long chain fatty acid derivatives were used. A predetermined test piece was molded by an injection molding machine using the obtained pellet, and the test evaluation was performed. The results are shown in Table 1.
[Extrusion conditions]
Extruder: TEX-30α (L / D = 38.5), Nippon Steel Works screw rotation: 129 rpm
Barrel temperature: C2 = 160 ° C., C3 to C11 · D = 200 ° C.
〔Molding condition〕
Molding machine: ROBOSHOT S2000i100B, screw diameter 28 mm, FANUC cylinder temperature: 200 ° C
Mold temperature: 90 ° C (water temperature control)

〔Test method〕
Details of the test method are as follows.

(1) Formaldehyde generation amount 8 g of a pellet-shaped composition (sample) prepared in Examples and Comparative Examples was filled in a metal cylinder adjusted to 200 ° C., and the resin pellets were melted to 5 Hold for a minute. Here, the used metal cylinder is connected to a glass suction bottle containing distilled water.
Subsequently, the formaldehyde gas generated from the molten resin is discharged into the distilled water in the glass suction bottle together with the nitrogen stream while flowing nitrogen into the glass absorption bottle connected to the metal cylinder. Formaldehyde gas was absorbed in the distilled water inside. Formaldehyde absorbed in distilled water was quantified by a method based on JIS K0102, and calculated as a ratio to the evaluation sample (composition).

(2) Sliding property Using a rotary friction abrasion tester based on JIS K7218, a hollow cylindrical test piece designated by the same standard A method molded from the resin compositions of Examples and Comparative Examples was replaced with carbon steel (S45C). The material was slid for 24 hours under conditions of 150 rpm and 20 kgf, and the wear amount (mg) of the own material (resin composition) and the wear amount (mg) of S45C were measured. Moreover, the friction coefficient 24 hours after performing the sliding test on the same conditions was measured.

  From the comparison of the results in Table 1, it can be seen that the polyacetal resin compositions (Examples 1 to 5) that satisfy the requirements of the present invention exhibit a low formaldehyde generation amount and a low wear amount. In particular, in Examples 2-5, it turns out that a low friction coefficient is also shown. On the other hand, in the case of Comparative Examples 1 to 5 where (e) the long-chain fatty acid derivative does not satisfy the requirements of the present invention, it can be seen that the wear amount and the coefficient of friction are high.

  Furthermore, in Comparative Example 6 in which the cellulose fiber powder does not satisfy the requirements of the present invention, the extrudability is poor and cannot be evaluated. In Comparative Example 7, the amount of formaldehyde generated is high, and the wear amount and the coefficient of friction are high. I understand that.

Claims (6)

(A) 100 parts by weight of polyacetal resin having an unstable terminal group amount of 0.5% by weight or less,
10 to 150 parts by weight of (b) cellulose fiber powder having an aspect ratio of 1 to 20 and an α cellulose content of 99.5 to 100%,
(C) 0.01 to 3 parts by weight of a hindered phenol antioxidant,
0.01 to 3 parts by weight of at least one (d) nitrogen-containing compound selected from an aminotriazine compound, a guanamine compound, a hydrazide compound and a polyamide;
A polyacetal resin composition comprising 0.2 to 2 parts by weight of (e) a long-chain fatty acid derivative having at least one hydroxyl group in the molecule.   The polyacetal resin composition according to claim 1, wherein the melt index (based on ASTM-D1238, 190 ° C., 2.16 kgf) of the (a) polyacetal resin is 10 to 50 g / 10 minutes. The polyacetal resin composition according to claim 1 or 2, wherein the amount of formaldehyde generated by the following measurement method is 47 ppm or less.
(Measuring method)
Resin pellets composed of 8 g of the polyacetal resin composition were filled into a metal cylinder adjusted to 200 ° C. and held for 5 minutes in a molten state. Subsequently, the formaldehyde gas generated from the molten resin was discharged together with the nitrogen stream while flowing nitrogen through the glass absorption bottle connected to the metal cylinder, thereby allowing the distilled water in the absorption bottle to absorb the formaldehyde gas. Formaldehyde absorbed in distilled water was quantified by a method based on JIS K0102, and calculated as a ratio to the evaluation sample (resin composition). Based on the method A described in JIS K7218, a hollow cylindrical test piece formed by molding the polyacetal resin composition according to any one of claims 1 to 3 is molded, and the hollow cylindrical test piece and the carbon steel material (S45C ), The amount of wear of the hollow cylindrical specimen is 4.7 mg or less, and the amount of wear of the carbon steel (S45C) is 0.2 mg or less. The polyacetal resin composition according to any one of claims 1 to 3, wherein the polyacetal resin composition has wear characteristics.   Based on the method A described in JIS K7218, a hollow cylindrical test piece formed by molding the polyacetal resin composition according to any one of claims 1 to 4 is molded, and the hollow cylindrical test piece and the carbon steel material (S45C 5), the friction coefficient of the hollow cylindrical test piece with respect to the carbon steel material after sliding for 24 hours under the conditions of 150 rpm and 20 kgf is 0.3 μs or less. The polyacetal resin composition as described.   A sliding part formed by molding the polyacetal resin composition according to any one of claims 1 to 5.