JPH09208803A - Polyacetal resin composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyacetal resin composition which causes little mold deposit during molding and can therefore reduce the frequency of maintenance of a mold. SOLUTION: This composition is obtained by blending 100 pts.wt. polyacetal resin with 1-70 pts.wt. fibrous titanium oxide subjected to surface treatment, 0.01-5 pts.wt. of one or more compounds selected from nitrogenous compounds and metal-containing compounds comprising oxides, inorganic acid salts or carboxylic acid salts of an alkali metal or alkaline earth metal, 0.01-5 pts.wt. hindered phenol compound, and 0.01-5 pts.wt. fatty acid polyglyceride having high degree of conversion into a monoester and synthesized from a fatty acid or fatty acid glyceride and glycidol. The composition is molded to give a molded article used as a small or thin-wall precision part.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a composition in which a surface-treated fibrous titanium oxide is added to a polyacetal resin and a stabilizer in a specific combination, and a molded article made of such a composition. The polyacetal resin composition of the present invention is excellent in mechanical strength by blending fibrous titanium oxide, and the fibers are fine and there is little gate clogging, and the deposit on the mold by the combination with a specific stabilizer. Since it is very small, it is suitable for use in small or thin molded products.

[0002]

2. Description of the Related Art As is well known, acetal resin has been widely used in recent years as a representative engineering plastic having excellent physical properties such as mechanical properties and electrical properties, or chemical properties such as chemical resistance and heat resistance. It is used in the field. However, with the expansion of fields in which polyacetal resins are used, the properties of the materials are also required to be more specific.

For example, in the fields of wristwatch parts, small electric / electronic device products, etc., further miniaturization and thinning of parts are being studied, so that a material having higher strength and smaller filler size is required. Has been.

In order to meet this demand, conventionally known is a method of adding an inorganic filler such as glass fiber or potassium titanate fiber to a polyacetal resin.

[0005]

However, in general, glass fibers have an average fiber diameter of 6 to 13 μm and an average fiber length of 20 to 3
000 μm, wall thickness of several tens of μm such as watch gear
Is too large to be used for parts, and potassium titanate fibers have an average diameter of 0.2 to 2 μm and an average fiber length of 10 to 100.
Although it is μm and can be used, there are often problems with gate clogging, and it is hard to say that it is still sufficient.

On the other hand, recently, needle-shaped titanium oxide has been developed as a filler replacing the above-mentioned glass fiber and potassium titanate fiber, and a resin composition excellent in strength and surface gloss has been proposed by incorporating this into various plastics. (JP-A-1-113465).

However, according to the study by the present inventors, the polyacetal resin containing the acicular titanium oxide has a remarkably large amount of deposits on the mold at the time of molding, that is, the frequency of mold maintenance increases. It turns out that there is a problem. This problem is inherent in the molding of the polyacetal resin composition, and since maintenance is particularly time-consuming especially for small parts, it is a major obstacle to productivity improvement, and improvement is eagerly awaited. It was

[0008]

Means for Solving the Problems As a result of diligent studies to obtain a polyacetal resin composition in which these drawbacks have been solved, the present inventor has found that the polyacetal resin is treated with a specific combination of surface-treated fibrous titanium oxide. It has a good mechanical strength by blending a stabilizer, and because the fibers are fine, there is little gate clogging, and there is very little adhesion to the mold, so it is a resin composition suitable for small and thin molded products. It was found that a product was obtained, and the present invention was completed.

That is, the present invention relates to "(A) 100 parts by weight of polyacetal resin, (B) 1 to 70 parts by weight of surface-treated fibrous titanium oxide (C) nitrogen-containing compound, alkali metal or alkali 0.01 to 5 parts by weight of one or more compounds selected from metal-containing compounds consisting of oxides of earth metals, inorganic acid salts or carboxylates (D) 0.01 to hindered phenol compounds 5 parts by weight (E) Polyacetal resin composition obtained by blending 0.01 to 5 parts by weight of polyglycerin fatty acid ester having a high monoesterification rate synthesized from fatty acid or glycerin fatty acid ester and glycidol "and" from the same composition Is a molded product.

The constituent components of the present invention will be described in detail below. Polyacetal resin (A) used in the present invention
As the above, any of polyoxymethylene homopolymer, polyoxymethylene copolymer in which most of the main chain is an oxymethylene chain, terpolymer and the like can be used. The degree of polymerization is not particularly limited, but it is generally desirable that the melt index is 7 g / 10 minutes or more, particularly when aiming at small-sized / thin-wall molded products.

In the present invention, the surface-treated fibrous titanium oxide (B) is blended with the polyacetal resin. When a fibrous titanium oxide that has not been surface-treated is blended, the polyacetal resin is not practical because it causes decomposition and foaming of the resin during compounding and during molding. The reinforcing effect of the fibrous titanium oxide blended here is greatly influenced by the aspect ratio of the fiber.
Below 10 the reinforcement effect is poor. Therefore, the aspect ratio of 10 or more is preferably used in the present invention.

It is preferable that the fibrous titanium oxide has an average fiber diameter of 0.02 to 0.6 μm and an average fiber length of 1 to 20 μm. The filling amount is 1 to 70 parts by weight with respect to 100 parts by weight of the polyacetal resin.

If it is less than 1 part by weight, the reinforcing effect is poor and it is not practical, and if it exceeds 70 parts by weight, the fluidity is remarkably lowered and the thermal stability of the composition is lowered, which is not preferable. Practically 10 to 50 parts by weight is preferable and 20 to
Most preferred is 40 parts by weight. The surface-treating agent applied to the fibrous titanium oxide in the present invention is not particularly limited in terms of chemical structure as long as it can substantially cover the fiber surface, and all known ones can be used. Examples include various coupling treatment agents such as titanate-based, aluminum-based, zirconate-based and the like.

Specifically, N- (2-aminoethyl)-
Examples thereof include 3-aminopropyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, isopropyltristearoyl titanate, diisopropoxyaluminum ethyl acetate, n-butyl zirconate. Granules of these fibrous titanium oxides are much more excellent in operability during compounding than non-granules, and are more preferable. However, if the focusing is too strong, the dispersion of the fibers may be poor, and the mechanical properties may deteriorate, so caution is required.

The component (C) used in the present invention is one or two selected from nitrogen-containing compounds, alkali metal or alkaline earth metal hydroxides, inorganic acid salts or metal carboxylate-containing compounds. The above compounds.
Here, the nitrogen-containing compound means nylon 12, nylon 61
Polyamides such as 0, nylon 6, and 66, homopolymers or copolymerized polyamides, substituted polyamides having a methylol group, nylon salts, polyesteramides synthesized from a combination with caprolactam, or a combination with caprolactone or caprolactam, polyaminotriazoles , Dicarboxylic acid dihydrazide, for example, oxalic acid hydrazide, adipic acid hydrazide, sebacic acid hydrazide, etc., heating condensate synthesized by heating from urea, nitrogen-containing condensation polymer synthesized with urea and diamines, heating urea Urea heating condensate, uracil, cyanoguanidine, dicyandiamide, synthesized by
Guanamine (2,4-diamino-sym-triazine), melamine (2,4,6-triamino-sym-triazine), N-butylmelamine, N-phenylmelamine, N, N-diphenylmelamine, N, N-diallyl Melamine, N, N ′, N ″ -triphenylmelamine,
N, N ′, N ″ -trimethylolmelamine, benzoguanamine (2,4-diamino-6-phenyl-sym-
Triazine), 2,4-diamino-6-methyl-sym
-Triazine, 2,4-diamino-6-butyl-sym
-Triazine, 2,4-diamino-6-benzyloxy-sym-triazine, 2,4-diamino-6-butoxy-sym-triazine, 2,4-diamino-6-cyclohexyl-sym-triazine, 2,4- Diamino-
6-chloro-sym-triazine, 2,4-diamino-
6-mercapto-sym-triazine, 2,4-dioxy-6-amino-sym-triazine (amelide),
2-oxy-4,6-diamino-sym-triazine (amerine), 2,4-diamino-6-methyl-sym
-Triazine, 2,4-diamino-6-methyl-sym
-Triazine, N, N ', N', N'-tetracyanoethyl benzoguanamine, a melamine-formaldehyde condensate, etc. are mentioned.

Preferred nitrogen-containing compounds are melamine, melamine derivatives and melamine-formaldehyde condensates.

Next, a metal-containing compound consisting of an alkali metal or alkaline earth metal hydroxide, inorganic acid salt or carboxylate will be described. Alkali metals include lithium, sodium and potassium, alkaline earth metals such as magnesium, calcium and barium, and inorganic acid salts such as carbonic acid, phosphoric acid and silicic acid, and carboxylate salts. Examples thereof include higher (C12-C32) fatty acids such as oxalic acid, malonic acid, succinic acid and stearic acid, and behenic acid, and salts of substituted higher fatty acids having a substituent such as a hydroxyl group.

Preferably, calcium, magnesium,
Lithium hydroxide, carbonate and carboxylate, and more preferably carboxylate.

Examples of particularly preferred metal-containing carboxylates include calcium stearate, calcium 12-hydroxystearate, calcium behenate and the like. These compounds (C) may be used alone or in combination of two or more kinds. The compounding amount of the compound (C) in the present invention is 0.01 to 5 parts by weight, preferably 0.03 to 2 parts by weight, and more preferably 0.05 to 100 parts by weight of the (A) polyacetal resin.
-1 part by weight is selected.

If the amount is less than 0.01 parts by weight, the effect of improving the thermal stability is not sufficiently exhibited, and if it exceeds 5 parts by weight, the compound itself tends to be deposited on the composition or the molding surface. Not preferable.

The component (C) is used in combination with a hindered phenolic compound (D) fatty acid or glycerin fatty acid ester and a polyglycerin fatty acid ester (E) synthesized from glycidol and having a high monoesterification rate to form a fibrous oxide. By being mixed with a polyacetal resin containing titanium (B), the decomposition of polyacetal is suppressed,
Further, since it has an effect of trapping formaldehyde generated by decomposition, it is presumed that generation of decomposition gas at the time of molding is suppressed as much as possible and almost no metal deposit is generated.

Next, as the hindered phenol compound (D) used in the present invention, 2,2-methylenebis (4-methyl-6-t-butylphenol), 1,2
6-hexanediol-bis [3- (3,5-di-t-
Butyl-4-hydroxyphenyl) propionate],
Pentaerythrityl tetrakis [3- (3,5-di-t
-Butyl-4-hydroxyphenyl) propionate], triethylene glycol-bis- [3- (3-t
-Butyl-5-methyl-4-hydroxyphenyl) propionate], 1,3,5-trimethyl-2,4,6-
Tris (3,5-di-t-butyl-4-hydroxy-benzyl) benzene, n-octadecyl-3- (4'-hydroxy-3 ', 5'-di-t-butylphenol) propionate], 4, 4'-butylidene-bis- (6
-T-butyl-3-methyl-phenol), distearyl-3,5-di-t-butyl-4-hydroxybenzylphosphonate 2-t-butyl-6- (3-t-butyl-
5-methyl-2-hydroxybenzyl) -4-methylphenyl acrylate, at least one of N, N'-hexamethylenebis (3,5-di-t-butyl-4-hydroxy-hydrocinnamamide) or 2 More than one species can be used.

Among these, 1,6-hexanediol-bis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate] and pentaerythrityl tetrakis [3- (3,5-di-] t-butyl-4-hydroxyphenyl) propionate], triethylene glycol-bis- [3- (3-t-butyl-5-methyl-4]
-Hydroxyphenyl) propionate], N, N'-
Hexamethylenebis (3,5-di-t-butyl-4-hydroxy-hydrocinnamide) is a particularly preferred substance.

The amount of the hindered phenol compound (D) added and blended in the present invention is 0.01 to 5 parts by weight, preferably 0.1 to 3 parts by weight, based on 100 parts by weight of the (A) polyacetal resin. It is a department. If the added amount of the component (D) is too small, a sufficient effect cannot be obtained, and if the added amount is too large, the effect of thermal stability reaches saturation, and rather leaching occurs, which is not preferable.

Next, the polyglycerin fatty acid ester compound (E) having a high monoesterification rate used in the present invention is a compound synthesized from a fatty acid or a glycerin fatty acid ester and glycerin, and has a monofatty acid ester content. It is a high mixture. The compounding amount of the compound (E) component in the polyacetal resin composition of the present invention is
(A) 0.0 to 100 parts by weight of the polyacetal resin
It is 1 to 5 parts by weight, preferably 0.1 to 2 parts by weight. If the addition amount is too small, the improvement effect is poor, and if it is too large, there is a large amount of stabilizer bleeding, which is not preferable.

As the method for producing the polyglycerin fatty acid ester as the component (E) in the polyacetal resin composition of the present invention, the conventional esterification reaction of (1) polyglycerin and fatty acids {JAOCS (Journal of American Oil
Chemists' Society) Vol. 58, pp. 878 (1981), JP-A-6-41007, etc.}, (2) Polygly
Transesterification of Serine with Fatty Acid Esters, (3)
Transesterification reaction of polyglycerin with fats and oils, (4) Addition polymerization reaction of glycidol with fatty acid monoglycerides {see USP 4,515,775}, (5) Addition polymerization reaction of glycidol with fatty acids 51-6
No. 5705), etc. are known. In the polyacetal resin composition of the present invention, the component (E) "polyglycerin fatty acid ester having a high monoesterification rate synthesized from fatty acid or glycerin fatty acid ester and glycidol" is produced by the method (5) above. It is a thing.

Examples of the starting fatty acid used include fatty acids having 7 to 22 carbon atoms. The fatty acid may be a saturated fatty acid or an unsaturated fatty acid, may be a linear fatty acid or a fatty acid having a side chain, and may be a substituted fatty acid having a carbon chain substituted with a hydroxyl group. Specific examples of these fatty acids include caproic acid, caprylic acid, 2-ethylhexanoic acid, capric acid, lauric acid, isotridecanoic acid, myristic acid, palmitic acid, palmitoleic acid, stearic acid, isostearic acid, oleic acid, linoleic acid, Examples thereof include behenic acid, erucic acid, ricinoleic acid, hydroxystearic acid and the like. These may be used alone or in any combination of two or more.

The molar ratio of glycidol to fatty acid in the addition polymerization reaction of glycidol and the above fatty acid is
1-100, preferably 1-50, more preferably 1
It is good to choose in the range of ~ 10.

If the molar ratio is less than 1, wettability with an aqueous solution cannot be imparted to the polyacetal resin, and conversely, if the molar ratio is 100 or more, in the polyglycerin fatty acid ester, the hydrophilic group to the hydrophobic group is changed to the hydrophilic group. The ratio becomes too high and the compatibility with the polyacetal resin decreases, which is not preferable.

The addition polymerization reaction of the above fatty acid and glycidol is preferably carried out in the presence of a phosphoric acid-based acidic catalyst and, if necessary, a solvent. The phosphoric acid-based acidic catalyst used here is phosphoric acid or phosphoric acid ester. Specifically, phosphoric acid, phosphoric anhydride, polyphosphoric acid, orthophosphoric acid, metaphosphoric acid, pyrophosphoric acid, phosphoric acid such as triphosphoric acid, tetraphosphoric acid, methyl acid phosphate, ethyl acid phosphate, isopropyl acid phosphate, butyl acid. Phosphate, 2-
Examples thereof include acidic phosphoric acid esters such as ethylhexyl acid phosphate. The acidic phosphoric acid ester may be a monoester body, a diester body or a mixture thereof. Among the catalysts listed above, phosphoric acid and acidic phosphoric acid esters are particularly preferable.

The above catalysts may be used alone or in admixture of two or more. The amount of the catalyst used was 0.
It is preferable to select in the range of 01 to 10% by weight. If it is less than 0.01% by weight, the reaction rate is too slow, and if it exceeds 10% by weight, the effect is not reached even if a large amount of the catalyst is used, and an addition polymer of glycidol is by-produced. Absent. In the above range of the amount of catalyst used, 0.1-5
% By weight is particularly preferred. The addition polymerization reaction can be carried out without a solvent, but a solvent may be used. As the solvent that can be used, aromatic hydrocarbons having 6 to 9 carbon atoms, particularly halogenated toluene such as benzene, toluene and trifluorotoluene, aliphatic ketones having 3 to 9 carbon atoms, especially methyl isopropyl ketone , Methyl isobutyl ketone, diethyl ketone, di-isobutyl ketone, and the like. Besides, ethers such as diisopropyl ether are also suitable. These solvents may be used alone or as a mixture of two or more kinds. When a solvent is used, the amount used is preferably as small as possible from the viewpoint of recovery operation after completion of the reaction, and particularly preferably twice the total amount of the reaction raw materials.

The reaction temperature varies depending on the presence or absence of a solvent, the type and amount of the catalyst, and the like, but it is preferably selected in the range of 50 to 180 ° C. If the temperature is lower than 50 ° C, the reaction rate is too slow, and if it exceeds 180 ° C, not only the coloring of the product becomes severe, but also glycidol is decomposed to cause a side reaction, which is not preferable. In the above temperature range, 70 to 160 ° C is preferable, and 140 to 160 ° C is particularly preferable.

The addition polymerization reaction is preferably carried out by mixing the fatty acid, the solvent and the catalyst in a reaction vessel, heating the mixture to the reaction temperature, and then adding glycidol little by little with stirring. The reaction can be carried out continuously or batchwise. When a solvent is used and its boiling point is below the reaction temperature, it is advantageous to carry out under pressure. It is desirable to carry out the addition polymerization reaction in an inert gas atmosphere such as nitrogen gas.

By the above reaction, glycidol is addition-polymerized with the fatty acid to produce a polyglycerin fatty acid ester having a higher degree of polymerization. The product is a monofatty acid ester form,
The polyglycerin fatty acid ester is a mixture of di-fatty acid ester body and tri-fatty acid ester body, and according to the above reaction, one having a large content ratio of mono fatty acid ester body is obtained.

That is, the polyglycerin fatty acid ester used in the present invention has a content of 70% or more represented by the peak area ratio of the monofatty acid ester body detected by an ultraviolet absorption detector by a column chromatography analysis method. It is a thing.

If the added amount is less than 0.01% by weight, the effect of improving the printability is not exhibited, and if the added amount exceeds 0.4% by weight, the mechanical properties may be deteriorated and the melt viscosity may be decreased. The decrease in melt viscosity often narrows the range of conditions for extrusion molding, which leads to deterioration in extrusion property formation and is not preferable.

The above polyglycerol fatty acid ester is
Each may be used alone or in combination of two or more.

The polyglycerin fatty acid ester used in the present invention has a glycerin number of 2 or more.
8 is preferred. The fatty acid of the polyglycerin fatty acid ester having a high monoesterification rate used in the present invention may have a linear structure or a branched structure having a side chain. The fatty acid may be saturated fatty acid or unsaturated fatty acid. The fatty acid of the polyglycerin fatty acid ester preferably has 10 to 32 carbon atoms, and particularly preferably 18 to 26. The blending amount of the above polyglycerin fatty acid ester in the present invention is 0.0 based on 100 parts by weight of the polyacetal resin.
1 to 5 parts by weight, preferably 0.03 to 1 part by weight, and more preferably 0.05 to 0.18 part by weight. If the amount is less than 0.01 part by weight, sufficient printability cannot be obtained. On the other hand, if it exceeds 5 parts by weight, thermal stability is lowered, silver streaks (silver stripes) are generated by decomposition gas during molding, and the appearance of the molded product is remarkably deteriorated, which is not preferable.

Further, the polyacetal resin composition of the present invention is further provided with conventionally known additives such as a lubricant, a nucleating agent, and a releasing agent in order to impart desired properties according to the purpose.
An antistatic agent, other surfactant, or a pigment can be added. The polyacetal resin composition of the present invention is easily prepared by a conventional method of preparing a resin composition, which is a commonly used method.

The polyacetal resin composition of the present invention is processed into various molded articles by a general molding method such as injection molding. In particular, it is suitably used for molded products, wristwatch parts, printer parts, desk-top computer parts, etc. used as small or thin precision parts.

<Examples> The present invention will be described below with reference to examples, but the present invention is not limited to these examples.

Examples 1 to 9 and Comparative Examples 1 to 6 Polyacetal resin [manufactured by Polyplastics Co., Ltd., trade name “DURACON M270]” is surface-treated with fibrous titanium oxide and various additives. The agents were extrusion kneaded at the compounding ratios shown in Tables 1 and 2 to prepare pelletized compositions.

Then, a test piece was molded from the pelletized composition using an injection molding machine, and the strength shown below was measured. At this time, the presence or absence of foaming was evaluated from the state of the injected strand. In addition, the following evaluation was performed. For comparison, a composition using potassium titanate instead of titanium oxide, a composition containing fibrous titanium oxide not surface-treated, and (C) nitrogen compound, (D) hindered phenol, (E) fatty acid ester A composition not containing any of the above was prepared and evaluated.

The results are shown in Tables 1 and 2. The measurement / evaluation methods are as follows.

Tensile strength and shear strength Strength: The test piece was left under the condition of a temperature of 23 ° C. and a humidity of 50% for 48 hours, and in that atmosphere, a testing machine (Tensilon manufactured by Orientec Co., Ltd.) was used.
Was measured according to ASTM-D638 (tensile) and ASTM-D732-85 using a specific jig.

Amount of gas generated upon melting: 8 g of the above pellet
Is melt-retained in a melt indexer at 200 ° C. for 5 minutes, then is allowed to flow under a load, the formaldehyde generated is collected and quantified, and the weight of formaldehyde generated per unit weight of resin (ppm) Expressed as

Continuous molding test: Injection molding machine / Toshiba IS30EPN (manufactured by Toshiba Machine Plastic Engineering Co., Ltd.) Cylinder temperature / 200 ° C. Injection pressure / 750 kg / cm ² Injection time / 4 seconds Cooling time / 3 seconds Mold temperature / 30 ℃ Under the above molding conditions, the continuous molding of molded products with a specific shape (24
Time), visually check the amount of deposits on the surface of the mold.
The grade was evaluated.

A: Almost no deposit is observed.

B: A slight amount of deposit is observed. C: A small amount of deposit is recognized.

D: Many deposits are recognized.

E: An extremely large amount of deposit is recognized.

[Reference Example 1] 0.5 mol of stearic acid was added to a 4-liter flask with a capacity of 1 liter equipped with a stirrer, a thermometer, a temperature controller, a reflux condenser, a dropping cylinder, a nitrogen gas introducing tube and the like. 142.25g) and phosphoric acid (purity 85
% Product) 0.0622 g, and the internal temperature is 140 while stirring.
Heated to ° C. Then, while maintaining the internal temperature at this temperature and stirring, 3.0 mol (222.24 g) of glycidol was added dropwise over 5 hours, so that the oxirane concentration in the system was 0.1%.
The reaction was continued until:

Reference Example 2 5.0 mol of glycidol (3
The same as the example described in Example 1 except that 70.40 g) was used. (The following margins) Table 1 Example 1 2 3 4 5 Mixing ratio and type (A) 100 100 100 100 100 (B) Type Titanium oxide Average fiber diameter 0.1 0.2 0.1 0.1 0.1 (μm) Average fiber length 8 12 8 8 8 Surface treatment agent B1 B1 B2 B1 B1 (parts by weight) 25 25 25 45 25 (C) Symbol C1 C1 C1 C1 C2 (parts by weight) 0.2 0.2 0.2 0.2 0.2 (D) Symbol D1 D1 D1 D1 D1 (parts by weight) 0.4 0.4 0.4 0.4 0.4 (E) Symbol E1 E1 E1 E1 E1 (parts by weight) 0.3 0.3 0.3 0.3 0.3 Physical properties Tensile strength 830 880 820 1050 840 (kg / cm2) Shear strength 590 625 580 730 600 (kg / cm2) Formability Molding No foaming None None None None None Continuous molding test A A A B A Generated gas amount 100 70 105 120 95 (ppm) Example 6 7 8 9 Compounding ratio and type (A) 100 100 100 100 (B) Type Titanium oxide average Fiber diameter 0.1 0.2 0.1 0.1 (μm) Average fiber length 8 8 8 8 Surface treatment agent B1 B1 B1 B1 (part by weight) 25 25 25 25 (C) Symbol C1 C1 C1 C1 (part by weight) 0.2 0.2 0.4 0.2 (D) Symbol D2 D1 D1 D1 (weight part) 0.4 0.4 0.4 0.4 (E) Symbol E1 E2 E1 E1 (weight part) 0.3 0.3 0.3 0.6 Physical properties Tensile strength 830 825 820 820 (kg / cm2) Shear strength 595 590 580 590 (kg / cm2) Moldability Foaming during molding None None None None None Continuous molding test A A A A Amount of gas generated 95 120 60 70 (ppm) Comparative example 1 2 3 4 5 6 Mixing ratio and type (A) 100 100 100 100 100 100 (B) Type Potassium titanate Average fiber diameter 0.3 0.3 0.1 0.1 0.1 0.1 (μm) Average fiber length 15 15 8 8 8 8 Surface treatment agent B1 B1 B1 B1 B1 Untreated (weight part) 25 45 25 25 25 25 (C) Symbol C1 C1 − C1 C1 C1 (weight part) 0.2 0.2 − 0.2 0.2 0.2 (D) Symbol D1 D1 D1 − D1 D1 (weight part) 0.4 0.4 0.4 − 0.4 0.4 (E) Symbol E1 E1 E1 E1 − E1 (parts by weight) 0.3 0.3 0.3 0.3 − 0.3 Physical properties Tensile strength 900 1100 835 830 835 − (kg / cm2) Shear strength 590 630 590 570 580 − (kg / cm2) Moldability Foaming during molding None None None None None Foaming continuous molding test D E D D C Unmoldable amount of generated gas 280 510 200 175 180- (ppm) The symbols in the table indicate the following.

(A): Polyacetal resin (B): Whiskers (C): Nitrogen compound (D): Hindered phenol compound (E): Ester compound B. Surface treatment agent B1: N- (2-aminoethyl)- 3-Aminopropyltrimethoxysilane B2: 3-glycidoxypropyltrimethoxysilane C. Component (C) C1: Melamine C2: Calcium stearate D. Hindered phenol compound D1: Pentaerythrityl-tetrakis- [3- ( 3,5
-Di-t-butyl-4-hydroxyphenyl) propionate] D2: triethylene glycol-bis- [3- (3-t-
Butyl-5-methyl-4-hydroxyphenyl) propionate] E. Polyglycerin monofatty acid ester compound E1: Hexaglycerin monostearate (Reference Example 1) E2: Decaglycerin monostearate (Reference Example 2)
(Below margin)

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location C08K 5/3477 C08K 5/3477 7/08 7/08 C08L 61/28 LNP C08L 61/28 LNP

Claims (4)

[Claims] 1. (A) 1 to 70 parts by weight of surface-treated fibrous titanium oxide per 100 parts by weight of polyacetal resin (C) nitrogen-containing compound, oxide of alkali metal or earth metal , One or more compounds selected from metal-containing compounds consisting of an inorganic acid salt or a carboxylic acid salt.
01 to 5 parts by weight (D) 0.01 to 5 parts by weight of hindered phenolic compound (E) 0.01 to 5 parts by weight of polyglycerin fatty acid ester synthesized from fatty acid or glycerin fatty acid ester and glycidol and having high monoesterification rate A polyacetal resin composition containing 1 part by weight. 2. The fibrous titanium oxide (B) has an average fiber diameter of 0.02 to 0.6 μm, an average fiber length of 1 to 20 μm, and an aspect ratio of 10 or more. Polyacetal resin composition of. 3. A molded product used as a small-sized or thin-walled precision component, which is obtained by molding the polycetal resin composition according to any one of claims 1 to 3. 4. The molded article according to claim 4, wherein the small or thin precision parts are wrist watch parts, printer parts, and desktop computer parts.