JP2005263927A - Polyacetal resin composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the mold releasability during molding processing to an ultrahigh level without substantially deteriorating mechanical characteristics of a polyacetal resin at all. <P>SOLUTION: A polyacetal resin composition is obtained by adding (B) at least one kind of N,N'-ethylenebisfatty acid amide derived from a 12-22C higher fatty acid in an amount of 0.25-0.35 pt.wt. and (C) at least one kind of polyalkylene glycol having 3,000-20,000 number-average molecular weight in an amount of (1/4) to (1/2) that of pt.wt. of the component (B) to (A) 100 pts.wt. of the polyacetal resin. <P>COPYRIGHT: (C)2005,JPO&amp;NCIPI

Description

  The present invention improves the releasability at the time of molding processing to a very high degree without substantially damaging the excellent mechanical properties inherent in the polyacetal resin, and at the same time, provides long-term thermal stability such as heat aging resistance and water resistance. The present invention also relates to an excellent polyacetal resin composition and a precision mechanism component obtained using the same.

Polyacetal resins have well-balanced mechanical properties and excellent frictional wear resistance, and are used in a wide range of applications in various fields such as automobiles, electrical / electronic devices, and building materials.
In most cases, the molding is performed by injection molding. In the case of polyacetal resin, which is often used as mechanical parts and precision mechanism parts, the structures of these molded products are often complicated. As an example of a complicated structure, for example, there is a shape in which a thick part and a thin part, and furthermore, an ultra-thin part are intertwined in a single molded product, and further provided with a hollow cylindrical projection etc. They are also often small parts weighing from a few grams to a few tens of grams at most. In the case of such a molded product having a complicated shape, the molded product should be ejected and released as smoothly as possible after the molten resin is injected from the cylinder and cooled in the mold. This is because when a molded product with a complicated shape is ejected with an excessively strong force and released, the product is obtained in a damaged state, or when it is released with an excessive force until it does not break. When the product is subjected to excessive force, the molding distortion is stored inside the product, and when the product is used for a long period of time, the influence of the product will eventually be worsened, which is extremely undesirable in either case.

  Polyacetal resin is an extremely useful material that has most of the properties required for engineering plastics, so it is used in applications such as those described above. In addition to these properties, it has extremely superior fluidity. Therefore, it is inevitably used in products with complicated shapes, and it is theoretically desired that the product be obtained with as little release force as possible for the above-mentioned reasons.

The following various methods have been proposed as methods for improving the releasability.
For example, a method of adding a metal salt of dimer acid obtained by dimerizing linoleic acid to an acetal resin (see, for example, Patent Document 1), adding one or more higher fatty acids having 22 to 32 carbon atoms to the acetal resin 1 of polyhydric alcohol fatty acid ester derived from polyhydric alcohol having 2 to 10 carbon atoms and higher fatty acid having 22 to 32 carbon atoms with respect to 100 parts by weight of acetal resin 0.01 to 2.0 parts by weight of one or more species or one or more of 0.01 to 2.0 parts by weight of the polyhydric alcohol fatty acid ester and one or more higher fatty acid amides having a straight chain having 10 or more carbon atoms .01-2.0 parts by weight (for example, see Patent Document 3), terminal etherified polyalkylene glycol with respect to 100 parts by weight of acetal resin One or more kinds of polyhydric alcohol fatty acid esters derived from 0.01 to 5 parts by weight, a polyhydric alcohol having 2 to 10 carbon atoms and a higher fatty acid having 22 to 32 carbon atoms are added to 0.01 to 2 A method of blending parts by weight (for example, see Patent Document 4), a method of blending 0.1 to 5 parts by weight of alkylenebisstearylamide having an alkylene group having 4 or more carbon atoms with respect to 100 parts by weight of a polyacetal resin (for example, patents) Reference 5), to 100 parts by weight of polyoxymethylene resin, 0.01 to 20 parts by weight of a specific ether compound such as an alkylene oxide adduct to alcohol, and talc having a specific pH and particle size of 1 to 20 A method of adding and mixing 30 parts by weight (for example, see Patent Document 6), a specific alkyl-substituted diphenyl ether with respect to 100 parts by weight of a polyacetal resin A method of blending 0.1 to 5 parts by weight (for example, see Patent Document 7), a method of blending 0.2 to 25 parts by weight of a liquid modified ethylene / α-olefin polymer with respect to 100 parts by weight of a polyacetal resin (for example, , See Patent Document 8).

  Although the release force is considerably reduced by these methods, the mechanical properties which are the advantages of the polyacetal resin are often lowered. In recent years, more complex part shapes have been required than ever before, and such super-complex parts still require a high release force and may cause damage to the parts. In addition, polyacetal resins used in these ultra-complex parts are required to have higher mechanical properties than before, and higher molecular weight polyacetal resins, higher crystallinity, high melting point copolymers and homopolymers are available. Increasing use. When the molecular weight increases, the fluidity of the polyacetal resin decreases, and it is difficult to obtain a molded product having a target dimension. Further, when the degree of crystallinity increases, the molding shrinkage rate increases, and it becomes difficult to obtain a molded product having the same target size. If a molded product having a target dimension is not obtained, the release force is often extremely increased.

Further, in the case of continuous injection molding, depending on the mold shape, the release force may not be stable, and a phenomenon may occur in which the release force initially low gradually increases in proportion to the number of molding shots. As a general countermeasure against this, there is a method of applying a commercially available release agent to the mold before the release force exceeds the allowable limit, but not only is the operation complicated, but a commercially available release agent is Since it may be disliked as a contamination source when it adheres to the surface of a molded product and is a precise electronic / electrical device, it is preferable that injection molding can be stably performed over a long period of time without applying a release agent as much as possible.
Furthermore, because of the complexity of the shape of ultra-complex parts, distortion tends to remain in the molded product, and when these are used under harsh conditions such as high-temperature atmospheres or hot water atmospheres, cracks are left early in the strain-remaining parts. There is a case where a problem occurs that the parts are destroyed.

JP 59-4641 A JP-A-60-104151 JP-A 63-295661 Japanese Patent Laid-Open No. 4-100847 JP 7-18157 A Japanese Patent Laid-Open No. 7-228753 JP 7-278406 A JP 2000-129079 A

  The present invention reduces the mold release force at the time of injection molding without deteriorating the mechanical characteristics, and also exhibits the low mold release force in the stability at the time of long-term continuous injection molding, and at the same time, the obtained molded part It is an object of the present invention to provide a polyacetal resin composition that also improves the heat aging resistance and water resistance of water and a precision mechanism component obtained by molding the resin composition.

As a result of intensive studies to solve the above problems, the present inventors have found that polyacetal resin contains at least one N, N′-ethylenebisfatty acid amide derived from a higher fatty acid having 12 to 22 carbon atoms and at least one. The inventors have found that the purpose can be achieved by adding specific amounts of polyalkylene glycols having a number average molecular weight of 3000 to 20000, respectively, and based on this finding, the present invention has been made.
That is, the present invention
(1) (B) At least one kind of N, N′-ethylenebisfatty acid amide derived from a higher fatty acid having 12 to 22 carbon atoms is added to 0.25 to 0.35 with respect to 100 parts by weight of (A) polyacetal resin. A polyacetal resin composition comprising at least one part by weight of (C) a polyalkylene glycol having a number average molecular weight of 3000 to 20000 and 1/4 to 1/2 times by weight of the component (B),

(2) The polyacetal resin composition according to 1 above, wherein the component (B) is N, N′-ethylenebisstearylamide and the component (C) is polyethylene glycol.
(3) The polyacetal resin composition according to 1 or 2, wherein the component (C) is a polyethylene glycol having a number average molecular weight of 5000 to 10,000,
(4) The polyacetal resin according to any one of 1 to 3, which is a polyacetal resin obtained by adding a stabilizer to the component (A),
(5) Precision mechanism parts obtained by injection molding the polyacetal resin composition according to any one of (1) to (4),
(6) The precision mechanism part as described in 5 above, which is used for automobile parts,
About.

  In the polyacetal resin composition of the present invention, the releasability at the time of molding is extremely improved without substantially impairing the excellent mechanical properties inherent in the polyacetal resin. Therefore, it is suitable as a polyacetal resin for injection molding of precision mechanism parts having complicated shapes. In addition, since the polyacetal resin of the present invention is excellent in long-term thermal stability such as heat aging resistance and hot water resistance, parts related to automobiles such as fuel tank flanges, seats such as fuel tank flanges, and seats particularly required for these performances. It is particularly suitable for parts around a seat belt such as a belt winding mechanism.

Hereinafter, the present invention will be specifically described.
The polyacetal resin of component (A) used in the present invention is a substantially oxymethylene produced using a formaldehyde monomer or a cyclic oligomer such as a trimer (trioxane) or tetramer (tetraoxane) as a raw material. A polyoxymethylene homopolymer consisting of repeating units, or the above raw material and a cyclic ether such as ethylene oxide, propylene oxide, epichlorohydrin, 1,3-dioxolane, glycol formal, diglycol formal, etc. An oxymethylene copolymer containing 0.1 to 20% by weight, preferably 0.2 to 10% by weight of -8 oxyalkylene units, further having a crosslinked or branched molecular chain, oxymethylene units and oxyethylene units, Oxypropylene unit, methylene unit And polyoxymethylene block copolymers having repeating units different from oxymethylene units such as propylene units. Moreover, the mixture of various polyacetal resin mentioned above may be sufficient.

  The melt index (MI: g / 10 min) of the polyacetal resin composition of the present invention is not particularly limited, but the composition of the present invention is particularly effective for polyacetal resins that are difficult to be injection-molded. And a polyacetal resin having low fluidity, for example, MI of 5 g / 10 min or less. In addition, polyoxymethylene homopolymer has a very high crystallization rate and a high degree of crystallinity, resulting in a large shrinkage ratio after molding, which tends to cause dimensional defects in the molded product. In many cases, defective release occurs, but the composition of the present invention is very effective for improving the release of these homopolymers.

  As the higher fatty acid of N, N′-ethylenebisfatty acid amide derived from higher fatty acid having 12 to 22 carbon atoms which is component (B) of the present invention, those having a linear structure are preferred, lauric acid, myristic acid, Representative examples include saturated fatty acids such as palmitic acid, stearic acid, and behenic acid, and unsaturated fatty acids such as oleic acid and erucic acid. In order to express the effect of the present invention, N, N′-ethylenebisstearylamide is most preferable, and these (B) components can be used in combination of two or more. Moreover, (B) component is added 0.25-0.35 weight part with respect to 100 weight part of (A) polyacetal resin. If the amount is less than 0.25 parts by weight, the releasability is not sufficiently improved. When the amount is more than 0.35 parts by weight, the mechanical properties are deteriorated, and the heat aging resistance and the hot water resistance are also deteriorated. In order to exhibit the effects of the present invention, only addition within a very limited range of 0.25 to 0.35 parts by weight is effective.

  Typical examples of the polyalkylene glycol which is the component (C) of the present invention include polyethylene glycol and polypropylene glycol. In the present invention, polyethylene glycol is particularly preferable, and among these, a number average molecular weight of 3000 to 20000, particularly 5000 to 10,000 is preferable. If the number average molecular weight is too small or too large, the effect of improving the releasability is not sufficient. These (C) components can be used in combination of two or more. Moreover, it is necessary that the addition amount of the component (C) is 1/4 to 1/2 times by weight of the component (B). When the amount is less than 1/4 times by weight, the effect of improving the releasability, particularly the low releasability, cannot be expressed stably for a long time. On the other hand, when the amount is more than 1/2 times by weight, the mechanical properties are lowered, which is not preferable.

In the present invention, it is essential that the components (B) and (C) in a very limited range are simultaneously added to the polyacetal resin, thereby greatly reducing the initial release force. At the same time, the low release force can be stably expressed for a long time. Furthermore, heat aging resistance and hot water resistance are also improved without substantially reducing the mechanical properties. It has not been known so far and is novel because of the synergistic effect of component (B) and component (C) in a very limited range.
As the stabilizer used in the composition of the present invention, for example, a heat stabilizer, a weather resistance (light) stabilizer, or the like can be used alone or in combination. As heat stabilizers, antioxidants, formaldehyde and formic acid supplements and combinations thereof are effective.

  As the antioxidant, a hindered phenol antioxidant is preferable. For example, n-octadecyl-3- (3′5′-di-t-butyl-4′-hydroxyphenyl) -propionate, n-octadecyl-3- (3′-methyl-5′-t-butyl-4′- Hydroxyphenyl) -propionate, n-tetradecyl-3- (3'5'-di-t-hydroxyphenyl) -propionate, 1,6-hexanediol-bis- (3- (3,5-di-t-butyl) -4-hydroxyphenyl) -propionate, 1,4-butanediol-bis- (3- (3,5-di-t-butyl-4-hydroxyphenyl) -propionate, triethylene glycol-bis- (3- ( 3-t-butyl-5-methyl-4-hydroxyphenyl) -propionate).

  Tetrakis- (methylene-3- (3′5′-di-t-butyl-4′-hydroxyphenyl) -propionate methane, 3,9-bis (2- (3- (3-t-butyl) -4-hydroxy-5-methylphenyl) propionyloxy) 1,1-dimethylethyl) 2,4,8,10-tetraoxaspiro (5,5 ') undecane, N, N'-bis-3- (3 '5'-di-t-butyl-4-hydroxyphenol) priionyl hexamethylenediamine, N, N'-tetramethylenebis-3- (3'-methyl-5'-t-butyl-4-hydroxy Phenol) pripionyldiamine, N, N′-bis-3- (3 ′, 5′-di-t-butyl-4-hydroxyphenol) prepionyl) hydrazine, N-salicyloyl-N′-salicylidenehydrazine, 3- (N-salicyloyl) amine-1,2,4-triazole, N, N′-bis- (2- (3- (3,5-di-butyl-4-hydroxyphenyl) propionyloxy) ethyl) oxyamide and the like is there.

Among these hindered phenolic antioxidants, triethylene glycol-bis- (3- (3-tert-butyl-5-methyl-4-hydroxyphenyl) -propionate), tetrakis- (methylene-3- (3 '5'-di-t-butyl-4'-hydroxyphenyl) -propionate methane. These antioxidants are 0.01 to 3 parts by weight, preferably 0, based on 100 parts by weight of the polyacetal resin. 0.05 to 2 parts by weight, more preferably 0.1 to 1 part by weight.
Examples of formaldehyde and formic acid scavengers include (a) compounds and polymers containing formaldehyde-reactive nitrogen, and (b) alkali metal or alkaline earth metal hydroxides, inorganic acid salts, and carboxylate salts.

  (I) Formaldehyde-reactive nitrogen-containing compounds and polymers include dicyanamide, melamine, melamine and formaldehyde compounds, polyamide resins (for example, nylon 46, 6, 66, 610, 612, 12, 66-6, 66 -66-10, 66-12, etc.), poly-β-alanine, polyacrylamide and the like. Among these, a cocondensate of melamine and formaldehyde, a polyamide resin, poly-β-alanine, and polyacrylamide are preferable, and a polyamide resin and poly-β-alanine are more preferable. These are 0.001-5 weight part with respect to 100 weight part of polyacetal resin, Preferably it is 0.005-3 weight part, More preferably, it is 0.01-2 weight part.

  (B) Examples of alkali metal or alkaline earth metal hydroxides, inorganic acid salts and carboxylate salts include hydroxides such as sodium, potassium, magnesium, calcium or barium, carbonates of the above metals, and phosphoric acid. Examples include salts, silicates, and borates. Specifically, calcium salts are most preferred, and are calcium hydroxide, calcium carbonate, calcium phosphate, calcium silicate, calcium borate, and fatty acid calcium (calcium stearate, calcium myristate, etc.), and these fatty acids are substituted with hydroxyl groups. It may be. Of these, fatty acid calcium salts (calcium stearate, calcium myristate) are preferred. These alkali metal or alkaline earth metal hydroxides, inorganic acid salts and carboxylates are used in an amount of 0.01 to 3 parts by weight, preferably 0.03 to 1 part by weight, more preferably 100 parts by weight of the polyacetal resin. Is 0.03 to 0.5 parts by weight.

As the weathering (light) stabilizer, (i) a benzotriazole-based material, (b) an oxalic acid anilide-based material, and (c) a hindered amine-based material are preferable.
(I) Examples of the benzotriazole-based substance include 2- (2′-hydroxy-5′-methylphenyl) triazole, 2- (2′-hydroxy-3,5′-di-t-butylphenyl) benzotriazole, 2- (2′-hydroxy-3,5′-di-isoamylphenyl) benzotriazole, 2- [2′-hydroxy-3,5-bis- (α, α′-dimethylbenzyl) phenyl] -2H-benzo Examples include triazole and 2- (2′-hydroxy-4′-octoxyphenyl) benzotriazole. Preferably 2- [2′-hydroxy-3,5-bis- (α, α′-dimethylbenzyl) phenyl] -2H-benzotriazole, 2- (2′-hydroxy-3,5′-di-t- Butylphenyl) benzotriazole.

(B) Examples of the oxalic acid anilide-based substance include 2-ethoxy-2′-ethyloxalic acid bisanilide, 2-ethoxy-5-butyl-2′-ethyl-ethyloxalic acid bisanilide, 2- Examples include ethoxy-3'-dodecylethyl oxalic acid bisanilide. These substances are used alone or in combination.
(C) Examples of hindered amine substances include 4-acetoxy-2,2,6,6-tetramethylpiperidine, 4-steroyloxy-2,2,6,6-tetramethylpiperidine, and 4-acro-steroloid. Luoxy-2,2,6,6-tetramethylpiperidine, 4- (phenylacetoxy) -2,2,6,6-tetramethylpiperidine 4-benzoyloxy-2,2,6,6-tetramethylpiperidine 4-methoxy-2,2,6,6-tetramethylpiperidine, 4-stearyloxy-2,2,6,6-tetramethylpiperidine, 4-cyclohexyloxy-2,2,6,6-tetramethylpiperidine 4-benzyloxy-2,2,6,6-tetramethylpiperidine, 4-phenoxy-2,2,6,6-tetramethylpiperidine, 4- (ethyl carbonate) (Vamoyloxy) -2,2,6,6-tetramethylpiperidine, 4- (cyclohexylcarbamoyloxy) -2,2,6,6-tetramethylpiperidine, 4- (phenylcarbamoyloxy) -2,2,6,6 -Tetramethylpiperidine.

  Also, bis (2,2,6,6-tetramethyl-4-piperidine) -carbonate, bis (2,2,6,6-tetramethyl-4-piperidyl) -oxalate, bis (2,2,6, 6-tetramethyl-4-piperidyl) -malonate, bis (2,2,6,6-tetramethyl-4-piperidyl) -sebacate, bis (2,2,6,6-tetramethyl-4-piperidyl)- Adipate, bis (2,2,6,6-tetramethyl-4-piperidyl) -terephthalate, 1,2-bis (2,2,6,6-tetramethyl-4-piperidyloxy) -p-xylene It is done.

  Also, bis (2,2,6,6-tetramethyl-4-piperidyl) tolylene-2,4-dicarbamate, tris (2,2,6,6-tetramethyl-4-piperidyl) -hexamethylene 1,6 Dicarbamate, tris (2,2,6,6-tetramethyl-4-piperidyl) -benzene-1,3,5-tricarboxylate, tris (2,2,6,6-tetramethyl-4-piperidyl ) -Benzene-1,3,4-tricarboxylate and the like. The above hindered amine materials may be used alone or in combination. The combination of the benzotriazole-based material, oxalic acid anilide-based material and hindered amine-based material is the best. These are used in an amount of 0.01 to 3 parts by weight, preferably 0.05 to 2 parts by weight, and more preferably 0.1 to 2 parts by weight with respect to 100 parts by weight of the polyacetal resin.

Preferred combinations of stabilizers in the resin composition of the present application include hindered phenols (particularly triethylene glycol-bis- (3- (3-tert-butyl-5-methyl-4-hydroxyphenyl) -propionate), tetrakis- (Methylene-3- (3 ′, 5′-di-t-butyl-4′-hydroxyphenyl) propionate methane)), a polymer containing formaldehyde-reactive nitrogen (especially polyamide resin, poly-β-alanine) And alkaline earth metal fatty acid salts (particularly fatty acid calcium salts). The addition amount is 0.1 to 0.5% by weight relative to the polyacetal resin, 0.01 to 1.0% by weight of a polymer containing formaldehyde-reactive nitrogen, and an alkaline earth metal fatty acid salt (particularly a fatty acid). Calcium salt) 0.05 to 0.5% by weight.
The composition of the present invention includes known heat stabilizers, antioxidants, formic acid scavengers, weathering (light) stabilizers, and crystals of lubricants, talc, boron nitride, etc., as long as the effects of the present invention are not impaired. Nucleating agents, pigments, reinforcing materials, conductive materials, thermoplastic resins, thermoplastic elastomers and the like can be added.

  Although there is no restriction | limiting in particular in the method of manufacturing the polyacetal resin composition of this invention, The method of mixing each component and melt-kneading is common. As the polyacetal resin of component (A), both powder and pellets can be used, and together with component (B), component (C), and other additives as necessary, Henschel mixer, tumbler, V-shaped After mixing with a blender or the like, it is melt-kneaded with a single screw or twin screw extruder. At the time of mixing, a very small amount of an additive such as liquid paraffin or fatty acid ester may be used. Moreover, it is also possible to produce the polyacetal resin of the present invention by continuously feeding each component alone or several kinds at a time using a quantitative feeder or the like without continuous mixing and feeding them continuously to an extruder. Alternatively, a high-concentration masterbatch comprising the components (A), (B), and (C) is prepared in advance, and the composition of the present invention can be obtained by diluting with a polyacetal resin at the time of extrusion melt kneading or injection molding. it can.

  The polyacetal resin composition in the present invention is particularly suitable for precision mechanism parts having complicated shapes that require low mold release force during injection molding, but is also used for gas injection molding, extrusion molding, blow molding, compression molding, etc. it can. In addition, since the polyacetal resin of the present invention is excellent in mechanical properties and long-term thermal stability, automobile-related precision mechanism parts, particularly fuel-related parts such as fuel tank flanges, and seats such as seat belt winding mechanisms. It is particularly suitable for belt-around parts.

The present invention will be described based on examples and comparative examples.
First, the evaluation methods used in Examples and Comparative Examples are shown below.
(1) Melt index (MI: g / 10 min)
The measurement was performed under conditions of 190 ° C. and 2160 g using ASTM-D1238 using a MELTININDEXER manufactured by Toyo Seiki.
(2) Flexural modulus (GPa)
Using a SH-75 injection molding machine manufactured by Sumitomo Heavy Industries, Ltd., a test piece was prepared at a cylinder temperature of 210 ° C., an injection pressure of 80 MPa, an injection speed of 30%, an injection time of 25 seconds, a cooling time of 15 seconds, and a mold temperature of 70 ° C. And measured based on ASTM-D790.

(3) Tensile strength (MPa)
Test pieces were prepared under the same conditions as in (2) above and measured based on ASTM-D638.
(4) Release force (N)
Using a SH-75 injection molding machine manufactured by Sumitomo Heavy Industries, Ltd., cylinder temperature 220 ° C., injection pressure 30 MPa, injection speed 30%, injection time 25 seconds, cooling time 15 seconds, mold temperature 95 ° C., height 50 mm The bottomed cylindrical molded body having an outer diameter of 50 mm and a thickness of 2 mm is continuously formed, and the resistance force applied to the protruding pin when the molded body is released from the mold by protruding the protruding pin is measured by a load cell. It was set as a mold force. The lower the release force at the fifth shot after the start of molding, the better the initial release property, and the smaller the difference between the release forces at the fifth and 50th shots, the better the long-term stability of the release force.
For the method and apparatus for measuring the release force, Japanese Patent Application Laid-Open No. 11-12460 was referred to.

(5) Heat aging resistance (90% tensile strength retention days)
The test piece prepared in the above (2) was left in a gear oven at 120 ° C. or 140 ° C., and the number of days until the tensile strength was reduced to 90% of the initial strength was determined and used as the retention day of 90% tensile strength. The longer the 90% tensile strength retention days, the better the heat aging resistance.
(6) Hot water resistance (Tensile strength 80% retention days)
The test piece prepared in the above (2) was immersed in hot water at 100 ° C. or 120 ° C., and the number of days until the tensile strength was reduced to 80% of the initial strength was determined and was defined as the retention strength of 80%. The longer the number of days the tensile strength is 80%, the better the hot water resistance.

[Example 1, Comparative Examples 1-7]
As polyacetal resin of component (A), polyacetal homopolymer powder of MI = 2 g / 10 min (manufactured by a known method described in Patent Document 10) with respect to 100 parts by weight, N, N′— as component (B) Ethylene bisstearylamide, polyethylene glycol having a number average molecular weight of 6000 as component (C) is added in the amount shown in Table 1, and 0.2 parts by weight of poly-β-alanine copolymer as a heat stabilizer, antioxidant. 0.15 parts by weight of ethylenebis (oxyethylene) bis [3- (5-tert-butyl-4-hydroxy-m-tolyl) propionate] as a mixture and mixing with a Henschel mixer, L / D = 30 The pellets were melt-kneaded with a vented 30mm twin-screw extruder under the conditions of a set temperature of 200 ° C, a screw speed of 100 revolutions, and a discharge rate of 4 kg / hour. It was. The pellet was dried at 80 ° C. for 3 hours and then used for each evaluation. The evaluation results are summarized in Table 1. The heat aging evaluation was performed at 120 ° C., and the hot water evaluation was performed at 100 ° C.

[Example 2, comparative example 8]
As the polyacetal resin of component (A), nylon 6-6 is 0.1% by weight as a heat stabilizer, and ethylene bis (oxyethylene) bis [3- (5-tert-butyl-4-hydroxy-m) as an antioxidant. -Tolyl) propionate] was added to the polyacetal copolymer pellets with MI = 3 g / 10 min obtained by copolymerizing 0.045 mol of 1,3-dioxolane as a comonomer with respect to 1 mol of trioxane. (Manufactured by a known method described in Patent Document 11) 100 parts by weight of N, N′-ethylenebisstearylamide as component (B) and polyethylene glycol having a number average molecular weight of 6000 as component (C) After mixing with the Henschel mixer, the set temperature is set with a 30 mm twin-screw extruder with a vent of L / D = 30. The mixture was melt-kneaded under the conditions of a temperature of 200 ° C., a screw rotation speed of 100 rotations, and a discharge rate of 4 kg / hour to obtain pellets. The pellet was dried at 80 ° C. for 3 hours and then used for each evaluation. The evaluation results are summarized in Table 2. The heat aging evaluation was performed at 140 ° C. and the hot water evaluation was performed at 120 ° C.

  The polyacetal resin composition of the present invention is suitable as a polyacetal resin for injection molding of precision mechanism parts having complicated shapes. Particularly, it is suitable for fuel-related parts such as a fuel tank flange and parts for automobile-related precision mechanisms such as seat-belt parts such as a seat belt retracting mechanism.

Claims (6)

(A) With respect to 100 parts by weight of the polyacetal resin, (B) 0.25 to 0.35 parts by weight of at least one of N, N′-ethylenebisfatty acid amide derived from a higher fatty acid having 12 to 22 carbon atoms and (C) A polyacetal resin composition comprising at least one polyalkylene glycol having a number average molecular weight of 3000 to 20000 added by 1/4 to 1/2 times by weight of the component (B). The polyacetal resin composition according to claim 1, wherein the component (B) is N, N'-ethylenebisstearylamide and the component (C) is polyethylene glycol. The polyacetal resin composition according to claim 1 or 2, wherein the component (C) is polyethylene glycol having a number average molecular weight of 5,000 to 10,000. The polyacetal resin according to any one of claims 1 to 3, which is a polyacetal resin in which a stabilizer is added to the component (A). The precision mechanism component obtained by injection-molding the polyacetal resin composition in any one of Claims 1-4. The precision mechanism part according to claim 5, which is used for an automobile part.