JP5939843B2 - How to use polyacetal resin molded products - Google Patents

Description

  The present invention relates to a method of using a polyacetal resin molded article.

  The polyacetal resin has excellent characteristics in mechanical characteristics, thermal characteristics, electrical characteristics, slidability, moldability, and the like. For this reason, the polyacetal resin molded product manufactured using polyacetal resin is utilized in the wide field | area, for example, a mechanism component is mentioned.

  When a polyacetal resin molded product is used as a mechanical part, it may be used by applying grease to the polyacetal resin molded product in order to further improve sliding characteristics (see, for example, Patent Document 1).

  By the way, in order to stabilize the polyacetal resin, the polyacetal resin is often mixed with an antioxidant or other stabilizer. Known antioxidants blended in the polyacetal resin include sterically hindered phenolic compounds (hindered phenols), sterically hindered amine compounds (hindered amines), and the like. As other stabilizers, melamine, polyamide, alkali metal hydroxide, alkaline earth metal hydroxide, and the like are known. Antioxidants are often used in combination with other stabilizers (see, for example, Patent Document 2).

JP 2008-291073 A JP-A-10-273579

  Even when a polyacetal resin molded product is used as a mechanical component, it is naturally preferable that the physical properties of the polyacetal resin molded product are high. The object of the present invention is to improve the heat-resistant life of the polyacetal resin molded product to which the grease composition is applied. It is to provide the technology to make.

  The inventors of the present invention have made extensive studies to solve the above problems. As a result, when the grease composition comes into contact with a polyacetal resin molded article composed of a polyacetal resin composition obtained by blending a hindered phenolic antioxidant with a polyacetal resin, the hindered phenolic antioxidant has a grease composition. The polyacetal resin coated with a grease composition was found to affect the heat-resistant life of the polyacetal resin molded product coated with the product, and the amount of hindered phenolic antioxidant was less than usual. The inventors have found that the heat-resistant life of the molded product is long, and have completed the present invention. More specifically, the present invention provides the following.

  (1) (A) 0.10 to 0.25 parts by mass of a hindered phenolic antioxidant, 100 parts by mass of polyacetal resin, alkali metal fatty acid salt, alkali metal oxide, alkaline earth 0.01 to 0.10 parts by mass of at least one (C) metal compound selected from fatty acid salts of alkali metals and oxides of alkaline earth metals, and (D) 0.01 to 0 nitrogen-containing compounds. And a polyacetal resin molded article formed by molding a polyacetal resin composition containing 10 parts by mass with a grease composition containing an organic molybdenum compound.

  (2) The method according to (1), wherein the organic molybdenum compound is molybdenum dialkyldithiocarbamate.

  (3) The use method according to (1) or (2), wherein the grease composition contains melamine cyanurate.

  (4) At least one (E) mold release agent selected from fatty acid ester, fatty acid amide, polyoxyalkylene glycol, and silicone compound with respect to 100 parts by mass of the (A) polyacetal resin 0.01 to 1.00 The method according to any one of (1) to (3), further comprising parts by mass.

  According to the method of use of the present invention, the heat-resistant life of the polyacetal resin molded product to which the grease composition is applied can be extended.

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

  The method of using the polyacetal resin molded product of the present invention is a method of using a polyacetal resin molded product obtained by molding a specific polyacetal resin composition in contact with a specific grease composition.

<Polyacetal resin molded product>
The polyacetal resin composition constituting the polyacetal resin molded product used in the present invention comprises (A) a polyacetal resin, (B) a hindered phenol-based antioxidant, (C) a metal compound, and (D) a nitrogen-containing product. And a compound.

[(A) Polyacetal resin]
The type of the (A) polyacetal resin is not particularly limited as long as the object of the present invention is not impaired, and can be appropriately selected from conventionally known (A) polyacetal resins.

(A) The polyacetal resin includes a polyacetal homopolymer having only an oxymethylene group (—CH ₂ O—) as a structural unit, and a polyacetal copolymer containing another comonomer unit as a structural unit in addition to the oxymethylene group. In the copolymer, the comonomer unit includes an oxy C 2-6 alkylene unit (for example, an oxy C _2-4 alkylene unit such as an oxyethylene group (—CH ₂ CH ₂ O—), an oxypropylene group, an oxytetramethylene group). . Although content of a comonomer unit is not specifically limited, For example, 0.01-30 mol% with respect to the whole structural unit of polyacetal resin, Preferably it is 0.03-20 mol%, More preferably, it is 0.03-15. It can be selected from a range of about mol%.

  (A) When the polyacetal resin is a polyacetal copolymer, it may be a copolymer composed of two components, a terpolymer composed of three components, or the like. The polyacetal copolymer may be a random copolymer, a block copolymer, a graft copolymer, or the like. The (A) polyacetal resin may have a branched structure as well as a linear structure, and may have a crosslinked structure. Furthermore, you may stabilize the terminal of (A) polyacetal resin by esterification with carboxylic acids, such as acetic acid and propionic acid, or those anhydrides, for example.

  (A) The melt index of the polyacetal resin is not particularly limited, but the melt index (measured at 190 ° C. under a load of 2.16 kg according to ASTM-D1238) is preferably 1 g / 10 min or more and 50 g / 10 min or less.

[(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-t-butylphenol)), 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-tert-butyl-4-hydroxy-5-methylphenyl) propionyloxy] -1,1-dimethylethyl} -2,4,8,10-tetraoxa Pyro [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′-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-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-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) isocyanurate) It is below.

  Particularly preferred hindered phenol antioxidants in the present invention are pentaerythritol tetrakis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], triethylene glycol-bis [3- (3- t-butyl-5-methyl-4-hydroxyphenyl) propionate].

  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 0.10-0.25 mass part with respect to 100 mass parts of (A) polyacetal resin. If it is this range, while the heat-resistant lifetime of the polyacetal resin molded product with which the grease composition was apply | coated will increase, the thermal stability of a polyacetal resin composition is high. The preferred content of the component (B) is 0.10 to 0.20 parts by mass, and if it is within this range, the heat-resistant life of the polyacetal resin molded product to which the grease composition is applied is remarkably increased.

[(C) Metal compound]
The (C) metal compound used in the present invention is at least one selected from alkali metal fatty acid salts, alkali metal oxides, alkaline earth metal fatty acid salts, and alkaline earth metal oxides.

  Examples of the alkali metal oxide include lithium oxide. Examples of the alkaline earth metal oxide include calcium oxide and magnesium oxide. In the present invention, the use of an alkaline earth metal oxide is preferred, and magnesium oxide is more preferred.

  Fatty acids contained in alkali metal fatty acid salts and alkaline earth metal fatty acid salts include saturated fatty acids such as lauric acid, myristic acid, palmitic acid, stearic acid, behenic acid, lignoceric acid, serotic acid, montanic acid, and melicic acid. And unsaturated fatty acids such as oleic acid, elaidic acid, linoleic acid, linolenic acid, arachidonic acid, erucic acid, and ricinoleic acid.

  In the present invention, it is preferable to use an alkaline earth metal fatty acid salt, particularly preferably a calcium fatty acid salt, and most preferably calcium stearate.

  In this invention, content of (C) metal compound is 0.01-0.10 mass part with respect to 100 mass parts of (A) polyacetal. (C) It is required that the content of the component is 0.01 parts by mass or more because it is easy to achieve the target heat resistant life of the polyacetal resin composition, and the content is 0.10 parts by mass or less. It is necessary for the reason of suppressing discoloration. A preferable range of the content is 0.02 parts by mass or more and 0.08 parts by mass or less.

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

  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 compound, 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 optionally a diamine and / or a dicarboxylic acid And polyamides derived from the combined use. Also included are copolyamides formed from two or more different polyamide-forming components.

  Specific examples of the polyamide compound include polyamide 3, polyamide 4, polyamide 46, polyamide 6, polyamide 66, polyamide 610, polyamide 612, polyamide 11, polyamide 12, and other aliphatic polyamides and aromatic dicarboxylic acids (for example, terephthalic acid). Acid and / or isophthalic acid) and an aliphatic diamine (eg, hexamethylenediamine), a polyamide, an aliphatic dicarboxylic acid (eg, adipic acid) and an aromatic diamine (eg, metaxylylenediamine) Examples thereof include polyamides obtained from polyamides, 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, the nitrogen-containing compound (C) selected from aminotriazine compounds, guanamine compounds, hydrazide compounds and polyamide compounds can be used alone or in combination of two or more. (C) The compounding quantity of component is 0.01-0.10 weight part with respect to 100 weight part of (A) polyacetal resin, Preferably it is 0.03-0.07 weight part. When the blending amount of the component (C) is less than 0.01 parts by weight, it is necessary for achieving the target heat resistant life of the polyacetal resin composition. On the contrary, when the blending amount of the component (C) exceeds 0.1 parts by weight, it may cause a bleeding of the obtained nitrogen-containing compound.

[(E) Release agent]
The polyacetal resin composition can preferably contain a release agent. In particular, at least one mold release agent selected from fatty acid esters, fatty acid amides, polyoxyalkylene glycols, and silicone compounds is preferably used.

  In this invention, it is preferable that content of (E) mold release agent is 0.01 mass part or more and 1.00 mass part or less with respect to 100 mass parts of (A) polyacetal resin. If the content is 0.01 parts by mass or more, it is preferable for the reason of improving the releasability, and if the content is 1.00 parts by mass or less, appearance deterioration due to exudation of the release agent and mechanical property deterioration avoidance are avoided. This is preferable.

[Other ingredients]
Various known stabilizers and additives can be further blended in the polyacetal resin composition as long as the object and effects of the present invention are not impaired. Examples thereof include various colorants, nucleating agents, antistatic agents, other surfactants, and different polymers.

  Although content of another component is not specifically limited, It is preferable that it is about 20 mass% or less in a polyacetal resin composition, More preferably, it is 10 mass% or less.

[Preparation of polyacetal resin composition]
The specific aspect of the preparation method of a polyacetal resin composition is not specifically limited, Generally a resin composition can be prepared with the well-known equipment and method as a preparation method of a resin composition. For example, necessary components can be mixed, and the mixture can be kneaded using a single or twin screw extruder or other melt-kneading apparatus to prepare pellets for molding. A plurality of extruders or other melt kneaders may be used. Moreover, all the components may be charged simultaneously from the hopper, or some components may be charged from the side feed port.

[Manufacture of polyacetal resin molded products]
The polyacetal resin molded product can be produced by an injection molding method using the polyacetal resin composition as a raw material. The molding conditions in the injection molding are not particularly limited, and preferable conditions can be adopted as appropriate. A molding method other than the injection molding method can also be employed.

<Grease composition>
The grease composition used in the present invention contains an organomolybdenum compound. Further, a normal grease composition usually includes a base oil and a thickener.

[Base oil]
The type of base oil contained in the grease composition is not particularly limited, and examples of the base oil include mineral oil, animal and vegetable oils, ester synthetic oils, synthetic hydrocarbon oils, phosphate ester oils, silicone oils, fluorine oils, and mixtures thereof. Oil etc. are used. Further, the content of the base oil in the grease composition is appropriately determined according to the use and the like.

[Thickener]
As the thickener, either soap-based or non-soap-based can be used. As a soap-type thickener, a metal soap-type thickener such as calcium soap, aluminum soap, sodium soap, lithium soap, etc., obtained by reaction of carboxylic acid (including glyceride) with metal hydroxide; calcium complex soap Examples include complex soap thickeners such as aluminum complex soap, sodium complex soap, and lithium complex soap. Non-soap-type thickeners include urea-type thickeners such as aromatic diurea, aliphatic diurea, alicyclic diurea, triurea, polyurea, etc .; Examples include thickeners; inorganic thickeners such as organic bentonite, graphite, and silica gel. Further, the content of the thickening agent in the grease composition is appropriately determined according to the use.

[Organic molybdenum compounds]
When the organomolybdenum compound is included, the amount of the (B) hindered phenolic antioxidant is adjusted to the above range, thereby increasing the heat-resistant life of the polyacetal resin molded product at the time of applying the grease, and the polyacetal resin composition. Thermal stability can be made sufficiently high.

  Among organic molybdenum compounds, when the grease composition contains an organic molybdenum compound used as an extreme pressure additive, the heat-resistant life of the polyacetal resin molded product is particularly likely to be lowered. Among these, when the grease composition contains a molybdenum dialkyldithiocarbamate, the heat-resistant life is particularly likely to be reduced. Among them, when the grease composition contains molybdenum dibutyldithiocarbamate, the heat-resistant life is most likely to be reduced. According to the present invention, even when the organomolybdenum compound is likely to reduce the heat-resistant life of the polyacetal resin molded product, by adjusting the amount of (B) hindered phenolic antioxidant used in the above range, The heat stability of the polyacetal resin molded product can be increased, and the thermal stability of the polyacetal resin composition can be made sufficiently high.

  The content of the organomolybdenum compound in the grease composition is also appropriately determined according to the use, but when the organomolybdenum compound is contained in an amount of 0.5% by mass or more, the heat-resistant life of the polyacetal resin molded product is likely to be reduced. A technique like the present invention is particularly necessary.

[Melamine cyanurate]
Melamine cyanurate is an organic salt composed of melamine and isocyanuric acid. Melamine cyanurate may be added to the grease composition as a solid lubricant. When the grease composition contains melamine cyanurate and an organomolybdenum compound (particularly, a dialkyldithiocarbamate molybdenum salt), the heat-resistant life of the polyacetal resin molded product is likely to be reduced. Even when the molybdenum compound is included in the grease composition, by adjusting the amount of (B) hindered phenol antioxidant used in the above range, while increasing the heat-resistant life of the polyacetal resin molded product, The thermal stability of the polyacetal resin composition can be made sufficiently high.

  In addition, when the grease composition contains melamine cyanurate, an organomolybdenum compound (especially molybdenum salt of dialkyldithiocarbamate) and polytetrafluoroethylene (PTFE), the heat-resistant life of the polyacetal resin molded product is likely to be reduced. According to the method of use of the present invention, it is possible to suppress the decrease in the heat resistant life.

  The total content of melamine cyanurate and PTFE in the grease composition (the content of melamine cyanurate when PTFE is not included) is also appropriately determined according to the use, but the total content is 10 mass. If it is at least%, the heat-resistant life of the polyacetal resin molded product is particularly likely to be lowered, and in such a case, the technique of the present invention is particularly necessary.

[Other ingredients]
In addition to the above-mentioned components, the grease composition includes an antioxidant, a rust inhibitor, a solid lubricant, a filler, an oil agent, and a metal inertness, as long as the object of the present invention is achieved. You may mix | blend additives, such as a chemical | medical agent, a water-resistant agent, an extreme pressure agent, an antiwear agent, a viscosity index improver, and a coloring agent.

<Polyacetal resin molded product with grease composition applied>
The polyacetal resin molded product to which the grease composition is applied 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.

  EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto.

<Material>
[(A) Polyacetal resin]
Polyacetal resin melt index = 9 g / 10 min was used. The polyacetal resin was prepared as follows.

  A biaxial paddle type continuous polymerization machine was continuously supplied with a mixture of 96.7% by mass of trioxane and 3.3% by mass of 1,3-dioxolane, and 15 ppm of boron trifluoride was added as a catalyst for polymerization. . The mixture of trioxane and 1,3-dioxolane used for polymerization contained 6 ppm water, 3.5 ppm methanol, and 5 ppm formic acid as impurities.

  The polymer discharged from the discharge port of the polymerizer is immediately added with an aqueous solution containing 1000 ppm of triethylamine and pulverized and stirred to deactivate the catalyst, and then centrifuged and dried to obtain a crude polyacetal resin. It was.

  Next, this crude polyacetal resin is supplied to a twin-screw extruder having a vent port, and the unstable end portion is decomposed by melt-kneading at a resin temperature of about 220 ° C., and volatile matter containing decomposition products is removed from the vent port. Was devolatilized under reduced pressure. The resin taken out from the die of the extruder was cooled and shredded to obtain a pellet-like polyacetal resin from which unstable terminal portions were removed.

  In addition, the said melt index is the value (g / 10min) calculated | required on the conditions of 190 degreeC and 2160g according to ASTM-D1238.

(B-1) Antioxidant: Triethylene glycol-bis [3- (3-tert-butyl-5-methyl-4-hydroxyphenyl) propionate] (trade name: IRGANOX 245)
(B-2) Antioxidant: Pentaerythritol tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate] (trade name: IRGANOX 1010)
(C-1) Alkaline earth metal oxide: Magnesium oxide (C-2) Alkaline earth metal fatty acid salt: Calcium stearate (D) Nitrogen-containing compound: Melamine (E) Mold release agent: N, N'- Ethylene bis (stearic amide)

<Evaluation of grease composition>
The following grease composition 1 to grease composition 6 were used.
Grease composition 1: Grease composition having a molybdenum dibutyldithiocarbamate content of 2.3% by mass and a total content of melamine cyanurate and PTFE of 13.7% by mass ("Molicoat YM102", Toray Dow Corning) Made)
Grease composition 2: Grease composition containing 2.6% by mass of molybdenum dibutyldithiocarbamate and 20.5% by mass of melamine cyanurate (without PTFE) ("Molicoat PG641", Toray Dow Corning)
Grease composition 3: Grease composition containing 0.9% by mass of molybdenum dibutyldithiocarbamate and 14.8% by mass of melamine cyanurate (without PTFE) (“Sancor FG-84M”) Manufactured by Sankei Chemical Co., Ltd.)
Grease composition 4: Grease composition containing 0.8% by mass of molybdenum dibutyldithiocarbamate and 29.8% by mass of melamine cyanurate (without PTFE) (“Suncor FG-87HSR”) Manufactured by Sankei Chemical Co., Ltd.)
Grease composition 5: Grease composition having a total content of melamine cyanurate and PTFE of 20.8% by mass (“Permalbu FIM-3”, manufactured by Kyodo Yushi Co., Ltd.)
Grease composition 6: Molybdenum dibutyldithiocarbamate content 3.0% by mass (excluding melamine cyanurate and PTFE) ("Moly White HD No. 1", manufactured by Sankei Chemical Co., Ltd.)

  The content of each component was analyzed by the following method. First, hexane insoluble matter (mass%) in the grease composition is collected, and then this hexane insoluble matter is separated into methanol-soluble matter, chloroform-soluble matter, methanol and chloroform-insoluble residue, and they are dried. Each solvent was removed and the weight was measured. After gravimetric measurement, the main component contained in each isolate was identified using infrared spectroscopy (IR), nuclear magnetic resonance spectroscopy (NMR), and pyrolysis gas chromatography / mass spectrometry (GS / MS).

[Effect of grease composition on heat-resistant life of polyacetal resin molded product]
A dumbbell test piece defined by ISO was manufactured using Duracon (registered trademark) M90S manufactured by Polyplastics. The tensile strength of this dumbbell test piece was measured according to the method of ISO 527-1 (the tensile strength obtained here is the initial tensile strength).

  A similar dumbbell test piece was produced, and the grease composition 1 was applied to the test piece. The test piece coated with the grease composition 1 was heated at 120 ° C. for 10 days. The tensile strength of the dumbbell test piece after heating was measured in accordance with the method of ISO 527-1 (the tensile strength obtained here was the tensile strength (after 10 days)). The tensile strength retention rate ((tensile strength (after 10 days) / initial tensile strength) × 100) was calculated from the tensile strength (after 10 days) and the initial tensile strength. The results are shown in Table 1.

  Tensile strength (after 20 days), tensile strength (after 30 days), and tensile strength (after 40 days) were measured in the same manner as above. Similarly, the tensile strength retention rate (%) was also calculated. The results are shown in Table 1.

  For the grease compositions 2 to 6, similarly, the tensile strength was measured and the tensile strength retention rate was calculated. These results are shown in Table 1. For the grease compositions 2 to 6, the tensile strength (after 20 days), the tensile strength (after 30 days), the tensile strength (after 40 days), and the tensile strength (after 60 days) were measured, and the tensile strength retention rate for these was measured. Calculated.

＊：ダンベル試験片の劣化が著しく正確な測定が困難

*: Accurate measurement is difficult due to significant deterioration of dumbbell specimens

  From the results of Table 1 above, it was confirmed that when the grease composition 1 containing an organomolybdenum compound, melamine cyanurate, and PTFE was used, the heat-resistant life of the polyacetal resin molded product was particularly likely to decrease. In addition, when a grease composition containing an organic molybdenum compound and melamine cyanurate is used, the polyacetal resin molded article is compared with a grease composition containing an organic molybdenum compound and not containing melamine cyanurate. It was confirmed that the heat-resistant life tends to decrease. Further, it was confirmed that when the grease composition containing no organic molybdenum compound was used, the heat-resistant life of the polyacetal resin molded product was hardly lowered.

<Preparation of polyacetal resin composition>
The components shown in Table 2 were supplied to the extruder at the ratio shown in Table 2 to produce polyacetal resin pellets of Examples and Comparative Examples.

[Evaluation of thermal stability]
Thermal stability was evaluated from the weight reduction rate when 5 g of the pellets after extrusion was used as a test piece and the test piece was heated in air at 230 ° C. for 45 minutes. The results are shown in Table 2.

<Manufacture of polyacetal resin molded products>
Using the polyacetal resin compositions prepared in the examples and comparative examples, ISO dumbbell test pieces were molded by an injection molding method.

  The tensile strength of the dumbbell test piece was measured according to a method based on ISO 527-1 (initial tensile strength).

  A similar dumbbell test piece was produced, and the grease composition 1 was applied to the test piece. The test piece coated with the grease composition 1 was heated at 120 ° C. for 40 days. The tensile strength of the dumbbell test piece after heating was measured according to the method of ISO 527-1 (the tensile strength obtained here was the tensile strength (after 40 days)). The tensile strength retention ((tensile strength (after 40 days) / initial tensile strength) × 100) was calculated from the tensile strength (after 40 days) and the initial tensile strength. The results are shown in Table 2.

  As is clear from the results in Table 2, it was confirmed that in Comparative Examples 3 and 4 where the content of the hindered phenol antioxidant was large, the heat-resistant life of the polyacetal resin molded product was greatly reduced. On the other hand, in Comparative Examples 1 and 2 where the content of the hindered phenol-based antioxidant is small, the heat resistance life of the polyacetal resin molded product is high, but the thermal stability of the polyacetal resin composition is low. In contrast to these comparative examples, it was confirmed that the polyacetal resin molded products of the examples had a high heat-resistant life and that the thermal stability of the polyacetal resin composition was sufficient.

Claims (3)

(A) For 100 parts by mass of polyacetal resin,
(B) 0.10 to 0.25 parts by mass of a hindered phenol antioxidant,
0.02 to 0.08 parts by mass of at least one (C) metal compound selected from an alkali metal fatty acid salt, an alkali metal oxide, an alkaline earth metal fatty acid salt, and an alkaline earth metal oxide When,
(D) A grease containing a melamine cyanurate, an organomolybdenum compound, and polytetrafluoroethylene as a polyacetal resin molded product obtained by molding a polyacetal resin composition containing 0.01 to 0.07 parts by mass of a nitrogen-containing compound. A method for using a molded article of polyacetal resin used in contact with a composition.   The method according to claim 1, wherein the organic molybdenum compound is molybdenum dialkyldithiocarbamate. 0.01 to 1.00 parts by mass of (E) a release agent selected from fatty acid esters, fatty acid amides, polyoxyalkylene glycols, and silicone compounds with respect to 100 parts by mass of (A) polyacetal resin. Furthermore, the usage method of Claim 1 or 2 containing.