JP5661437B2 - Polyacetal resin composition - Google Patents

Description

  The present invention relates to a polyacetal resin composition.

  Polyacetal resins have well-balanced mechanical properties and are excellent in friction / wear characteristics, chemical resistance, heat resistance, electrical characteristics, and the like. For this reason, polyacetal resins are widely used in the fields of automobiles, electrical / electronic parts, and the like, and the progress of utilization forms and processing techniques of polyacetal resins continues. Under such circumstances, the characteristics required for polyacetal resins tend to be sophisticated and specialized. As an example, polyacetal resin is required to improve sliding characteristics under high surface pressure and high load sliding conditions.

  In response to such a requirement, a method of adding a fluororesin or a polyolefin-based resin to the polyacetal resin is known in order to improve the sliding characteristics of the polyacetal resin. However, fluororesins and polyolefin resins are poorly compatible with polyacetal resins. For this reason, these resins may be separated from the polyacetal resin to cause peeling on the surface of the molded product, or may cause precipitates to be generated on the mold during molding of the molded product.

  In addition, in order to improve the sliding properties of the polyacetal resin, a method of adding a lubricating oil such as a fatty acid, a fatty acid ester, silicone oil, or various mineral oils to the polyacetal resin is known. However, when the molded product is molded, the polyacetal resin and the lubricating oil, etc. are separated, and the lubricating oil or the like is likely to ooze out. . Further, when the lubricating oil oozes out on the surface of the molded product, the appearance of the molded product may be impaired.

  In response to this problem, Patent Document 1 (Japanese Patent Laid-Open No. 2-138357) discloses a resin composition in which a specific graft copolymer is contained in a polyacetal resin, and a resin composition in which a lubricant is blended with the specific graft copolymer. Things are disclosed. However, in the composition of Patent Document 1, the surface hardness of the molded product may decrease, and due to local deformation under severe sliding conditions such as sliding under high surface pressure or sliding at high speed. It may cause deterioration of sliding characteristics and increase of wear.

  Patent Document 2 (Japanese Patent Laid-Open No. 3-111446) discloses a resin composition obtained by adding and blending a specific graft copolymer, a lubricant, and an inorganic powder having a specific particle diameter to a polyacetal resin. In the composition of patent document 2, the surface hardness which is the subject of patent document 1 is improved, and the sliding characteristic accompanying this is improved. However, the composition of Patent Document 2 may impair the surface smoothness and surface roughness of the molded article due to the blended inorganic powder, and may impair the friction characteristics and wear characteristics as compared with the method of Patent Document 1.

  Further, in Patent Document 3 (Japanese Patent Laid-Open No. 5-51514), a spindle calcium carbonate and a fatty acid ester having a specific particle diameter are blended with a polyacetal resin for use in a very special sliding application such as a felt clutch mechanism part. A resin composition is disclosed. In the composition of patent document 3, the fall of the moldability by the seepage of a fatty acid ester and the external appearance defect of the surface of a molded product may be caused. Further, Patent Document 3 assumes specific sliding called a felt clutch, and the effect described in Patent Document 3 cannot be considered as a general improvement in sliding performance.

  According to the compositions disclosed in these Patent Documents 1 to 3, it is possible to improve the slidability aimed by each document as compared with the prior art. However, even with these compositions, it is still difficult to satisfy the advanced sliding characteristics required in recent years and other well-balanced characteristics (surface properties (surface smoothness), mechanical properties).

JP 2-138357 JP-A-3-111446 JP-A-5-51514

  The present invention has been made in order to solve the above-mentioned problems, and its purpose is to provide excellent friction and wear characteristics under a wide range of sliding conditions including severe sliding conditions, and further to surface properties of molded products ( The object is to provide a polyacetal resin composition having good surface hardness, smoothness and the like, and excellent mechanical properties.

  As a result of intensive studies to solve the above problems, the present inventors have found that a polyacetal resin has a hindered phenol-based antioxidant, a specific nitrogen-containing compound, a specific graft copolymer, a fatty acid ester, and a spindle shape. It has been found that the selective combination of calcium carbonate is extremely effective in improving the sliding properties, and other properties can be improved or maintained in a well-balanced manner, and the present invention has been completed. More specifically, the present invention provides the following.

  (1) (A) 0.01-1 part by weight of a hindered phenol-based antioxidant, (C) 0.05-1 part by weight of a nitrogen-containing compound, and (D) with respect to 100 parts by weight of the polyacetal resin 2) 12 parts by weight of graft copolymer, 0.5-7 parts by weight of (E) fatty acid ester, and 2-18 parts by weight of spindle-shaped calcium carbonate (F) The nitrogen-containing compound is at least one selected from the group consisting of an aminotriazine compound, a guanamine compound, a hydrazide compound, and a polyamide compound, and the (D) graft copolymer has a main chain of (d1) an olefin polymer. And (d2) a vinyl polymer is included as a side chain, and the (E) fatty acid ester is composed of a fatty acid having 12 to 32 carbon atoms and a monovalent or polyhydric alcohol having 2 to 30 carbon atoms. Polyacetal resin composition.

  (2) The polyacetal resin composition according to (1), wherein the (d1) olefin polymer is composed of polyethylene, and the (d2) vinyl polymer is composed of acrylonitrile-styrene copolymer or polystyrene. .

  (3) The mass ratio (d1: d2) of (d1) olefin polymer and (d2) vinyl polymer in the (D) graft copolymer is 80:20 to 20:80 ( The polyacetal resin composition as described in 1) or (2).

  (4) The polyacetal resin composition according to any one of (1) to (3), wherein the spindle-shaped calcium carbonate (F) is surface-treated with aminosilane.

  (5) The (A) polyacetal resin is obtained by copolymerizing (a1) 99.9 to 90.0% by weight of trioxane and (a2) 0.1 to 10.0% by weight of a monofunctional cyclic ether compound. The total proportion of the alkoxy terminal group and the hydroxyalkoxy terminal group having at least 2 carbon atoms in the total terminal group of the (A) polyacetal resin is 70 to 99 mol%. The polyacetal resin composition according to any one of (1) to (4).

  According to the present invention, the friction and wear characteristics are excellent under a wide range of sliding conditions including severe sliding conditions, and the surface properties (surface hardness, smoothness, etc.) of the molded product are also good, and mechanical A polyacetal resin composition having excellent physical properties can be obtained.

  Hereinafter, embodiments of the present invention will be described in detail. The present invention is not limited to the following embodiments.

  The polyacetal resin composition of the present invention comprises (A) a polyacetal resin, (B) a hindered phenol-based antioxidant, (C) a nitrogen-containing compound, (D) a graft copolymer, and (E) a fatty acid ester. And (F) spindle-shaped calcium carbonate. Hereinafter, each component will be described.

[(A) Polyacetal resin]
The (A) polyacetal resin used in the present invention is a collective term for polymer compounds having a polymer skeleton composed of repeating oxymethylene groups, the oxymethylene group as a main structural unit, and substantially oxymethylene. Typical examples include polyacetal homopolymers composed only of a chain of groups, and polyacetal copolymers having a structure in which most of the main chain is composed of a chain of oxymethylene groups and a small amount of oxyalkylene units of about C2 to C6 are introduced. It is.

  In addition, the polyacetal resin (A) is a polyacetal copolymer having a branched or crosslinked structure obtained by adding a component capable of forming a branched or crosslinked structure and copolymerizing it, and other polymers during or after polymerization. Also included are modified polyacetal resins modified by graft copolymerization.

  In the present invention, any of these (A) polyacetal resins can be used, and the degree of polymerization thereof is not particularly limited as long as it can be molded.

The polyacetal resin (A) used in the present invention is obtained by copolymerizing 90.0 to 99.9% by weight of trioxane (a1) and 0.1 to 10.0% by weight of (a2) monofunctional cyclic ether compound. The resulting polyacetal copolymer is preferred.
(A2) Monofunctional cyclic ether compounds include monofunctional cyclic formal compounds. (A2) The monofunctional cyclic ether compound has a ring formed containing at least two adjacent carbon atoms, and (a1) is ring-opened by copolymerization with trioxane to form an oxyalkylene unit of about C2 to C6. It is necessary to be. Examples of such (a2) monofunctional cyclic ether compounds include ethylene oxide, propylene oxide, butylene oxide, 1,3-dioxolane, diethylene glycol formal, 1,4-butanediol formal, 1,6-hexanediol formal, diethylene glycol formal, and the like. Is mentioned.

  Moreover, as (A) polyacetal resin used in this invention, what has the ratio of 70-99 mol% of all the terminal groups combining the alkoxy terminal group and the hydroxy alkoxy terminal group having at least 2 carbon atoms is preferable. . Examples of other end groups include hemiacetal groups and formyl groups. These end groups can be measured using a known method, for example, a method described in JP-A-5-98028, JP-A-2001-11143, or the like.

  As described above, the (A) polyacetal resin used in the present invention has two preferable conditions. By satisfying at least one of these conditions, the basic stability of the resin is excellent, and even if a component for improving slidability is added, the stability of the resin and the machine of the resin composition It is preferable because the effect of improving the slidability can be exhibited without any loss of physical properties.

[(B) hindered phenolic antioxidant]
It does not specifically limit as (B) hindered phenolic antioxidant which can be used by this invention, For example, the following compounds can be used.
Monocyclic hindered phenol compounds (for example, 2,6-di-t-butyl-p-cresol etc.), polycyclic hindered phenol compounds linked by a group containing a hydrocarbon group or a sulfur atom (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-tert-butylphenyl) butane, 4,4'-butylidenebis (3-methyl-6-tert-butylphenol), 1,3,5-trimethyl-2,4,6-tris (3,5-di-) t-butyl-4-hydroxybenzyl) benzene, 4,4′-thiobis (3-methyl-6-tert-butylphenol), etc.), hindered phenol compounds having an ester group or 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-t-butyl- 5-methyl-4-hydroxyphenyl) propionate], pentaerythritol tetrakis [3- (3,5-di-t-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-methylphenyl 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′-hexa Methylenebis (3,5-di-tert-butyl-4-hydroxy-dihydrocinnamamide, N, N′-ethylenebis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionamide ], N, N'-tetramethylenebis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionamide], N, N'-hexamethylenebis [3- (3,5-di -T- Til-4-hydroxyphenyl) propionamide], N, N′-ethylenebis [3- (3-tert-butyl-5-methyl-4-hydroxyphenyl) propionamide], N, N′-hexamethylenebis [ 3- (3-t-butyl-5-methyl-4-hydroxyphenyl) propionamide], N, N′-bis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionyl] hydrazine , N, N′-bis [3- (3-t-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) isocyanurate, etc.).

  In this invention, (B) hindered phenolic antioxidant can be used individually or in combination of 2 or more types. (B) The compounding quantity of a component is 0.01-1 weight part with respect to 100 weight part of (A) polyacetal resin, Preferably it is 0.02-0.5 weight part. When the blending amount of component (B) is less than 0.02 parts by weight, (A) polyacetal resin against short-term oxidative degradation at high temperatures such as during molding and oxidative degradation under long-term use at room temperature It tends to be insufficient in stability. Furthermore, such a lack of stability of the component (A) tends to unfavorably affect the sliding characteristics under severe conditions. Moreover, when the compounding quantity of (B) component is 1 weight part or more, not only is it uneconomical, but excessive addition may become a factor which impairs the mechanical physical property of the resin composition obtained.

[(C) Nitrogen-containing compound]
The polyacetal resin composition of the present invention contains (C) a nitrogen-containing compound selected from an aminotriazine compound, a guanamine compound, a hydrazide compound, and a polyamide compound.

  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 functional group substitution thereof) ), Α- or β-naphthoguanamine and their functional group-substituted derivatives, polyguanamines, aralkyl or aralkylenguanamines, 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 to the amino group are also contained.

  Examples of the hydrazide compound 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, etc.), 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 the polyamide 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. Further, 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.

  In the present invention, (C) nitrogen-containing compounds selected from aminotriazine compounds, guanamine compounds, hydrazide compounds and polyamides can be used alone or in combination of two or more. (C) The compounding quantity of a component is 0.05-1 weight part with respect to 100 weight part of (A) polyacetal resin, Preferably it is 0.1-0.7 weight part. When the blending amount of the component (C) is less than 0.05 part by weight, sufficient heat stability cannot be imparted to the polyacetal resin, formaldehyde is generated due to decomposition of the resin during processing, and mold during molding It causes generation of deposits, deterioration of mechanical properties of the resin composition, and deterioration of sliding characteristics due to foaming. On the contrary, when the blending amount of the component (C) exceeds 1 part by weight, the resulting resin composition may cause discoloration, decrease in mechanical properties, or the like.

[(D) Graft copolymer]
The (D) graft copolymer used in the present invention is a graft copolymer of (d1) an olefin polymer and (d2) a vinyl polymer.

  (D) The olefin polymer constituting the main chain component of the graft copolymer includes homopolymers such as polyethylene, polypropylene and polybutene, and copolymers having these as main components. Examples of the copolymer include ethylene / propylene copolymer, ethylene / 1-butene copolymer and ethylene / α / β-unsaturated glycidyl ester (for example, glycidyl acrylate, glycidyl methacrylate, glycidyl ethacrylate). Etc.). Of these, polyethylene is most preferably used.

  This (d1) polymer to be graft copolymerized with the olefin polymer is (d2) a vinyl polymer, for example, polymethyl methacrylate, polyethyl acrylate, polybutyl acrylate, poly-2-ethylhexyl acrylate, polystyrene , Polyacrylonitrile, acrylonitrile-styrene copolymer, butyl acrylate and methyl methacrylate copolymer, butyl acrylate and styrene copolymer, and the like.

  In the present invention, among the graft copolymers exemplified above, a graft copolymer of (d1) an olefin polymer made of polyethylene and (d2) a vinyl polymer made of acrylonitrile-styrene copolymer or polystyrene. Is particularly preferred.

  The method for preparing the graft copolymer is not particularly limited, but can be easily prepared by a known radical reaction. For example, a monomer constituting the component (d1) and a method of adding a radical catalyst to the monomer constituting the component (d2) and kneading and grafting, or a peroxide on either the component (d1) or the component (d2) (D) Graft copolymer is prepared by adding a radical catalyst such as the above to produce free radicals, and then melt-kneading them with the polymer of the other component for grafting.

  (D) The ratio of (d1) olefin polymer and (d2) vinyl polymer constituting the graft copolymer is preferably d1: d2 = 80: 20 to 20:80 (weight ratio), particularly preferably. d1: d2 = 60: 40 to 40:60.

  In the present invention, the blending amount of the (D) graft copolymer is 2 to 12 parts by weight with respect to 100 parts by weight of the (A) polyacetal resin. When the blending amount of the component (D) is less than 2 parts by weight, the effect of improving the sliding characteristics aimed at by the present invention is insufficient. Further, when the blending amount of the component (D) exceeds 12 parts by weight, it is not preferable because mechanical properties such as rigidity are inhibited.

[(E) Fatty acid ester]
The (E) fatty acid ester used in the present invention is a fatty acid ester of a fatty acid having 12 to 32 carbon atoms and a monovalent or polyhydric alcohol having 2 to 30 carbon atoms.

  (E) Fatty acids constituting the fatty acid ester include saturated fatty acids such as lauric acid, myristic acid, palmitic acid, stearic acid, behenic acid, lignoceric acid, serotic acid, montanic acid, melicic acid, oleic acid, elaidic acid, Examples thereof include unsaturated fatty acids such as linoleic acid, linolenic acid, arachidonic acid, erucic acid, and ricinoleic acid.

  (E) The alcohol constituting the fatty acid ester includes monohydric alcohols such as propyl, isopropyl, butyl, octyl, capryl, lauryl, myristyl, stearyl, and behenyl, and ethylene glycol, propylene glycol, butanediol, glycerin, pentaerythritol. And polyhydric alcohols such as sorbitan.

  (E) The fatty acid ester is preferably a fatty acid selected from lauric acid, palmitic acid, stearic acid, and behenic acid, a monohydric alcohol selected from stearyl alcohol and behenyl alcohol, or ethylene glycol, propylene glycol, glycerin, pentaerythritol, An ester with a polyhydric alcohol selected from sorbitan, and specific examples include stearyl stearate, behenyl behenate, ethylene glycol monostearate, ethylene glycol distearate, glycerol monostearate, glycerol distearate, glycerol Examples include tristearate, glycerin monobehenate, sorbitan monostearate, sorbitan distearate, sorbitan monobehenate, and the like.

  In this invention, the compounding quantity of this (E) fatty acid ester is 0.5-7 weight part with respect to 100 weight part of (A) polyacetal resin. If the amount of the component (E) is less than 0.5 parts by weight, a sufficient slidability improvement effect cannot be expected, and if the amount of the component (E) is more than 7 parts by weight, the polyacetal resin is a base resin. The properties of may be impaired.

[Spindle-like calcium carbonate (F)]
In the present invention, (A) spindle-shaped calcium carbonate blended with (A) polyacetal resin is a particle belonging to light calcium carbonate and having a spindle shape. The spindle shape refers to a shape similar to a spindle used for picking up a yarn, that is, a columnar shape with a thick central portion and gradually narrowing at both ends. The (F) spindle shape used in the present invention. Any calcium carbonate may be used as long as it has a generally similar shape. The average particle diameter is preferably 0.1 to 1 μm, the average particle length is 0.5 to 10 μm, and the average particle length / particle diameter is preferably 2 to 10. Here, the particle diameter refers to the diameter of the maximum diameter portion of the spindle-shaped particle (usually approximately the center in the length direction), the particle length refers to the length of the spindle-shaped particle, and the average particle diameter and average particle length are This is a value measured by a method in which spindle-shaped calcium carbonate is photographed with an electron microscope, the particle diameter and particle length of 50 particles randomly selected from a photograph are read, and the average value is obtained.

  Examples of such specific (F) spindle-shaped calcium carbonate include Silver W, PC, PCX, and Callite SA manufactured by Shiraishi Kogyo Co., Ltd. The (F) spindle-shaped calcium carbonate used in the present invention is preferably surface-treated with a surface treatment agent, and particularly preferably surface-treated with aminosilane. Examples of such surface-treated (F) spindle-shaped calcium carbonate include SL-101 manufactured by Shiraishi Kogyo Co., Ltd. By performing the surface treatment, the adhesion between the resin and calcium carbonate is improved, and the dynamic frictional resistance is improved.

  In this invention, the compounding quantity of (F) spindle-shaped calcium carbonate is 2-18 weight part with respect to 100 weight part of (A) polyacetal resin, Preferably it is 3-15 weight part. When the blending amount of the component (F) is less than 2 parts by weight, excellent friction / wear characteristics under a wide range of sliding conditions including severe sliding conditions cannot be achieved. It cannot be expected to improve rigidity and surface hardness. When the blending amount of the component (F) exceeds 18 parts by weight, the smoothness of the surface of the molded product is insufficient, and the wear amount is increased and the friction coefficient is easily increased (deteriorated).

[Polyacetal resin composition]
The present invention is characterized by selectively combining the components (A) to (F) and adjusting the blending amount thereof. This achieves the main object of the present invention of improving the sliding characteristics under a wide range of sliding conditions, and maintains or improves other characteristics (mechanical properties, stability, etc.), and further improves the composition. It was made in consideration of processability in preparation and moldability at the time of molding.

  In other words, components for improving slidability or combinations of multiple components, and the blending amount of each component may be a factor that impairs mechanical properties and resin stability, or a factor that breaks the balance of sliding properties themselves. In some cases, the blending of a stabilizer component for stabilization against oxidative degradation or thermal degradation may adversely affect the sliding characteristics. In addition, these compounding components or a combination of them, the operability of the extruder in the preparation of the composition (resin slip on the screw of the extruder, surging phenomenon, vent up, etc.), moldability in the molding machine (poor bite, It is also a factor that has an important influence on plasticization defects).

  In the present invention, the selective combination of the above-described blending components and the blending amount of each component are based on a delicate balance based on such characteristics and circumstances. Can be obtained.

  In the polyacetal resin composition of the present invention, various known stabilizers and additives can be further blended as long as the objects and effects of the present invention are not significantly impaired. For example, various colorants, mold release agents (other than the above lubricants), nucleating agents, antistatic agents, other surfactants, heterogeneous polymers (other than the above graft copolymers), fibrous, plate-like, powder Examples thereof include granular inorganic or organic fillers.

  The polyacetal resin composition of the present invention and a molded product comprising such a composition can be easily prepared by a method conventionally known and generally used as a method for preparing a resin composition. For example, after mixing the components constituting the composition, the mixture is melt-kneaded with a single-screw or twin-screw extruder, extruded, cut to prepare a pellet-like composition, and then molded, Any method can be used, such as preparing different pellets (master batch), mixing (diluting) a predetermined amount of the pellets for molding, and obtaining a molded product of the desired composition after molding.

  In preparing the resin composition, part or the front part of the (A) polyacetal resin as a substrate is pulverized, mixed with this and other components, and then extruded to improve the dispersibility of the additive. This is a preferable method.

  In addition, (E) a fatty acid ester is previously mixed with (D) a graft copolymer, impregnated, and then kneaded with (A) a polyacetal resin or the remaining components, followed by extrusion or the like. This is a preferable method from the viewpoints of improving processability and slidability.

  EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited by these Examples.

<Examples and Comparative Examples>
Details of each component used in the examples and comparative examples are as follows.
(A) Polyacetal resin: manufactured by Polyplastics Co., Ltd., Duracon (registered trademark) M90
(B) Hindered phenol antioxidant: BASF, Irganox (registered trademark) 1010
(C) Nitrogen-containing compound: Melamine (D-1) Graft copolymer: PE-g-AS (manufactured by NOF Corporation, Modiper (registered trademark) A1401)
(D-2) Graft copolymer: PE-g-PMMA (NOF Corporation, MODIPER (registered trademark) A1200)
(E) Fatty acid ester: glycerin monobehenate (Riken Vitamin Co., Ltd., Riquemar (registered trademark) B-100)
(F-1) Spindle-like calcium carbonate (aminosilane surface-treated product): SL-101, manufactured by Shiroishi Central Laboratory
(F-2) Spindle-like calcium carbonate (surface untreated product): manufactured by Shiroishi Central Laboratory, Callite (registered trademark) SA
(F ′) Non-spindle-like calcium carbonate (for comparative example): manufactured by Toyo Fine Chemical Co., Ltd., Whiten (registered trademark) P-30

  The components shown in Tables 1 and 2 were mixed at the ratios shown in Tables 1 and 2, and then melt-kneaded with a twin-screw extruder to prepare a pellet-shaped composition. Next, a test piece was prepared by injection molding using this pellet and evaluated. The results are shown in Tables 1 and 2.

  For comparison, (F) a compound not containing spindle-shaped calcium carbonate (Comparative Example 1), (D) a compound not containing a graft copolymer (Comparative Example 4), and one using non-spindle-shaped calcium carbonate ( Comparative examples 2) and (F) were prepared in the same manner as for the compound (Comparative Example 3) in which spindle-shaped calcium carbonate was added in excess, and test pieces were prepared and evaluated.

<Evaluation>
The surface property, tensile strength, tensile fracture strain, bending strength, flexural modulus, Charpy impact strength, dynamic friction coefficient, specific wear amount (own material, steel material), and squealing (squeaking noise) generation load were evaluated. Specifically, each evaluation was performed by the following methods.

[Surface property]
The surface property is an evaluation of the surface state of the test piece. A test specimen for evaluation (50 mm × 50 mm × 1 mm: center pin gate method) was molded under two types of molding conditions of a cylinder temperature of 190 ° C., an injection pressure of 75 MPa, and an injection speed of 1 m / min and 3 m / min. In particular, the peeling state in the vicinity of the gate) was evaluated in five stages. The evaluation results are shown in Tables 1 and 2.
5: No peeling 4: Little peeling 3: Peeling slightly 2: Peeling 1: Most peeled

[Tensile, bending, impact properties]
Test specimens for evaluation were molded by injection molding in accordance with ISO standards (tensile physical properties: ISO527-1, 2, bending physical properties: ISO178, impact physical properties: ISO179 / 1eA), and various physical properties were evaluated. Tables 1 and 2 show the results of tensile strength, tensile fracture strain, bending strength, flexural modulus, and Charpy impact strength.

[Friction coefficient, specific wear amount]
Using a Suzuki friction / abrasion tester, the dynamic friction coefficient and specific wear amount were evaluated under pressure (0.98 MPa), linear velocity of 300 mm / sec, contact area of 2.0 cm ² and the counterpart material as steel (S55C). . The evaluation results are shown in Table 1.

[Sliding sound characteristics]
Using a Suzuki friction / wear tester, while keeping the speed constant (10 mm / sec) between the same materials with a contact area of 2.0 cm ² and increasing the surface pressure by 0.1 MPa every minute The occurrence of squeak noise was evaluated. The presence or absence of the occurrence of squeak noise was determined by a sensory test, and the load when it was determined that squeak noise was generated was defined as the squeak noise generation load.

  Examples 1-4 have excellent surface properties, sufficient mechanical strength (tensile strength, tensile fracture strain, bending strength, flexural modulus, Charpy impact strength), and sliding properties (friction coefficient, ratio) It was confirmed that the wear amount and the squeak noise were also good.

It was confirmed that in Comparative Example 1 containing no component (F), squealing is likely to occur and the surface condition is poor.
In Comparative Example 2 using calcium carbonate ((F ′) component) that is not spindle-shaped, it was confirmed that in addition to a large coefficient of dynamic friction and easy wear, the surface condition was also poor.
It was confirmed that Comparative Example 3 containing an excessive amount of component (F) has a large friction coefficient and is easily worn, and also has a poor surface condition and lower tensile fracture strain and Charpy impact strength.
It was confirmed that the comparative example 4 which does not contain (D) component has a bad surface state, and also Charpy impact strength becomes low.

  From the above, unless a specific component is added in a specific amount, good surface properties, excellent mechanical strength (tensile strength, tensile fracture strain, bending strength, bending elastic modulus, Charpy impact strength), good It was confirmed that not all of the sliding characteristics (friction coefficient, specific wear amount, squeak noise) were satisfied.

  In addition, when (E) fatty acid ester is not blended, it has the same mechanical properties as the corresponding examples, but the sliding properties (friction coefficient, specific wear amount, squeak noise) are extremely inferior, Is not listed.

Claims (5)

(A) For 100 parts by weight of polyacetal resin,
(B) 0.01-1 part by weight of a hindered phenolic antioxidant,
(C) 0.05 to 1 part by weight of a nitrogen-containing compound;
(D) 2 to 12 parts by weight of the graft copolymer;
(E) 0.5 to 7 parts by weight of a fatty acid ester;
(F) 2-18 parts by weight of spindle-shaped calcium carbonate, and
The (C) nitrogen-containing compound is at least one selected from the group consisting of an aminotriazine compound, a guanamine compound, a hydrazide compound, and a polyamide compound,
In the graft copolymer (D), the main chain is an (d1) olefin polymer, and the side chain includes (d2) a vinyl polymer.
The (E) fatty acid ester is a polyacetal resin composition composed of a fatty acid having 12 to 32 carbon atoms and a monovalent or polyhydric alcohol having 2 to 30 carbon atoms. The (d1) olefin polymer is composed of polyethylene,
The polyacetal resin composition according to claim 1, wherein the (d2) vinyl polymer is composed of an acrylonitrile-styrene copolymer or polystyrene.   The mass ratio (d1: d2) of (d1) olefin polymer and (d2) vinyl polymer in the (D) graft copolymer is 80:20 to 20:80. 2. The polyacetal resin composition according to 2.   (F) The polyacetal resin composition according to any one of claims 1 to 3, wherein the spindle-shaped calcium carbonate is surface-treated with aminosilane. The (A) polyacetal resin was obtained by copolymerizing (a1) 99.9 to 90.0% by weight of trioxane and (a2) 0.1 to 10.0% by weight of a monofunctional cyclic ether compound. Is,
The total ratio of the alkoxy terminal group and the hydroxyalkoxy terminal group having at least 2 carbon atoms in the total terminal group of the (A) polyacetal resin is a ratio of 70 to 99 mol%. The polyacetal resin composition according to any one of the above.