JPH069854A - Polyacetal resin composition - Google Patents

Abstract

PURPOSE:To provide a palyacetal resin composition excellent in mechanical strength, causing few gate cloggings and developing little deposit on molds in its molding, suitable for esp. small-sized or light-gage molded products. CONSTITUTION:The composition can be obtained by incorporating (A) 100 pts.wt. of a polyacetal resin with (B) 1-70 pts.wt. of surface-treated fibrous titanium dioxide, (C) 0.01-5 pts.wt. of at least one kind compound selected from nitrogen-contg. compounds, alkali metal or alkaline earth metal hydroxides and metal-contg. compounds (i.e. inorganic acid metal salts or metal carboxylates), (D) 0.01-5 pts.wt. of a hindered phenolbased compound, and (E) 0.01-5 pts.wt. of an ester compound from a polyhydric alcohol and fatty acid.

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]

BACKGROUND OF THE INVENTION As is well known, acetal resins are representative of excellent physical properties such as mechanical properties and electrical properties, or chemical properties such as chemical resistance and heat resistance. In recent years, it has been used as an engineering plastic in a very wide range of fields. However, with the expansion of fields in which polyacetal resins are used, properties of the materials are required to be more specific. For example, in the field of wristwatch parts, small electric / electronic device products, etc., further miniaturization and thinning of parts are being studied, so materials with higher strength and smaller filler size are required. . 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. However, glass fibers usually have an average fiber diameter of 6 to 13 μm and an average fiber length of 20 to 3000 μm, and are too large to be used for parts with a wall thickness of several tens of μm, such as watch gears, and potassium titanate fibers are used. Has an average fiber diameter of 0.
Although it can be used because it has an average fiber length of 2 to 2 μm and an average fiber length of 10 to 100 μm, it is difficult to say that it is still sufficient because of the problem of gate clogging. On the other hand, recently, acicular titanium oxide has been developed as a filler to replace the above glass fiber and potassium titanate fiber, and a resin composition which is excellent in strength and surface gloss has been proposed by compounding this with 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 problem that the amount of the deposits on the mold at the time of molding is extremely large, that is, the frequency of mold maintenance becomes high. found. This problem is inherent in the molding of the polyacetal resin composition, and maintenance is particularly troublesome in the case of small parts, which is a major obstacle to productivity improvement and is eagerly awaited. It was

[0003]

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. By blending a stabilizer, it is possible to obtain a resin composition with good mechanical strength, little gate clogging, and very little adhesion to the mold, which is suitable for molding small and thin molded products. The present invention has been completed and the present invention has been completed. That is, the present invention, (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, water of alkali metal or alkaline earth metal One or more compounds selected from metal-containing compounds consisting of oxides, inorganic acid salts or carboxylates 0.01 to 5 parts by weight (D) Hindered phenolic compounds 0.01 to 5 parts by weight (E) Polyvalent Ester compounds from alcohols and fatty acids 0.01
The present invention relates to a polyacetal resin composition containing 5 to 5 parts by weight, and a molded article made of such a composition.

The constituent components of the present invention will be described in detail below. As the polyacetal resin (A) used in the present invention, any of polyoxymethylene homopolymers, polyoxymethylene copolymers in which the main chain is mostly oxymethylene chains, terpolymers and the like can be used. The degree of polymerization is not particularly limited, but it is particularly small and
When targeting thin molded products, MI is generally 7g / 10min
The above is desirable.

In the present invention, the surface-treated fibrous titanium oxide (B) is mixed 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, and when the aspect ratio is 10 or less, the reinforcing effect is poor. Therefore, in the present invention, the aspect ratio
Those of 10 or more are preferably used. The average fiber diameter of fibrous titanium oxide is 0.02 to 0.6 μm, and the average fiber length is 1 to 20.
It is preferably μm. The filling amount is 1 to 70 parts by weight with respect to 100 parts by weight of the polyacetal resin. 1
If it is less than part by weight, the reinforcing effect is poor and it is not practical.
If it exceeds the weight part, 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 40 parts by weight is most preferable. 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) -3-aminopropyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, isopropyltristearoyl titanate, diisopropoxyaluminum ethyl acetate, n-butyl zirconate and the like are available. Can be mentioned. still,
Granules of these fibrous titanium oxides are much more excellent in operability during compounding as compared with non-granules, and are more preferable. However, if the bundling is too strong, dispersion of the fibers may be caused and mechanical properties may be deteriorated.

The component (C) used in the present invention is one or two selected from a nitrogen-containing compound, a metal-containing compound consisting of an alkali metal or alkaline earth metal hydroxide, an inorganic acid salt or a carboxylic acid salt. More than one compound.
Here, the nitrogen-containing compound means nylon 12, nylon 6.1
0, homologous or copolymerized polyamides such as nylon 6.66.610, substituted polyamides having a methylol group, etc., polyamides such as polyester amides synthesized from nylon salts, caprolactam, or in combination with caprolactone or caprolactam, Polyaminotriazole, dicarboxylic acid dihydrazide, for example, oxalic acid hydrazide, adipic acid hydrazide, sebacic acid hydrazide, etc., a heat condensation product synthesized by heating from urea, a nitrogen-containing condensation polymer synthesized from urea and diamines, urea Urea heat condensates synthesized by heating, uracils, cyanoguanidines, dicyandiamide, guanamine (2,4-diamino-sym-triazine), melamine (2,4,6-triamino-sym-triazine), N- Butyl melamine, N-phenyl melami N, N-diphenylmelamine, N, N-diallylmelamine, N, N ', N''-triphenylmelamine, N, N', N ''-trimethylolmelamine,
Benzoguanamine (2,4-diamino-6-phenyl-sy
m-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-sy
m-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), N, N ', N', N'-tetracyanoethylbenzoguanamine, melamine-formaldehyde condensate and the like can be mentioned. Preferred nitrogen-containing compounds are melamine or melamine derivatives, melamine-formaldehyde condensates and the like. Next, the metal-containing compound consisting of an alkali metal or alkaline earth metal hydroxide, inorganic acid salt or carboxylate will be described. The alkali metal is lithium, sodium, potassium, etc., the alkaline earth metal is magnesium, calcium, barium, etc., and the inorganic acid salt is carbonic acid,
Each of the salts such as phosphoric acid and silicic acid is a carboxylic acid salt having a higher substituent such as oxalic acid, malonic acid, succinic acid and stearic acid, and higher (C _{12 to} C ₃₂ ) fatty acids such as behenic acid and a hydroxyl group. Examples thereof include salts of fatty acids. Preferred are hydroxides, carbonates and carboxylates of calcium, magnesium and lithium, more preferably carboxylates. Examples of particularly preferable metal-containing carboxylic acid salts 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 (A) the polyacetal resin 10
0.01-5 parts by weight, preferably 0.03-2, relative to 0 parts by weight
Parts by weight, more preferably 0.05 to 1 parts by weight. 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 precipitate on the surface of the composition or the molded article, which is not preferable.

The component (C) is used in combination with a hindered phenol compound (D) and an ester compound (E) from a polyhydric alcohol and a fatty acid, and is blended with a polyacetal resin containing a fibrous titanium oxide (B). As a result, the decomposition of polyacetal is suppressed, and the formaldehyde decomposed and generated is captured, so that the generation of decomposition gas at the time of molding is suppressed as much as possible, and it is presumed that almost no mold deposits are generated. .

Next, as the hindered phenol compound (D) used in the present invention, 2,2'-methylenebis (4-methyl-6-t-butylphenol) and 1,6-hexanediol-bis [3 -(3,5-di-t-butyl-
4-hydroxyphenyl) propionate], pentaerythrityl tetrakis [3- (3,5-di-t-butyl-4]
-Hydroxyphenyl) propionate], triethyleneglycol-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'- The-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, N, N'-hexamethylene bis (3,5-di-t-butyl-4-hydroxy-hydrocinnamamide 1) or at least 2 kinds thereof can be used. Among these, 1,6-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], N,
N'-hexamethylenebis (3,5-di-t-butyl-4-
Hydroxy-hydrocinnamamide) is a particularly preferred substance. The amount of the hindered phenolic compound (D) added and blended in the present invention is (A) polyacetal resin 10
0.01-5 parts by weight, preferably 0.1-3, relative to 0 parts by weight
Parts by weight. If the amount of component (D) added is too small, no sufficient effect will be obtained, and if it is too large, the effect of thermal stability will reach saturation and rather leaching will occur, which is undesirable.

Next, the ester compound (E) used in the present invention means at least 1 having 12 to 32 carbon atoms.
It is derived from certain saturated or unsaturated fatty acids and polyhydric alcohols such as glycerol, diglycerol, pentaerythritol, sorbitan and ethylene glycol. Fatty acids used for preparing the fatty acid ester compound include lauric acid, tridecylic acid, myristic acid, pentadecyl acid, palmitic acid, stearic acid, nonadecyl acid, behenic acid and naturally occurring fatty acids containing these components or those. Is a mixture of. Of these fatty acid ester compounds, fatty acid esters derived from a fatty acid selected from palmitic acid, stearic acid and behenic acid and a polyhydric alcohol selected from glycerol or sorbitan are preferred. Examples of preferred fatty acid ester compounds include glycerin monostearate,
Examples thereof include glycerin distearate, glycerin monobehenate, sorbitan monostearate and sorbitan monobehenate. Compound (E) in the composition of the present invention
The compounding amount of 0.01 to 5 relative to (A) polyacetal resin
Parts by weight, preferably 0.1 to 2 parts by weight. If the addition amount is small, the improvement effect is poor, and if it is too large, the stabilizer leaching is large, which is not preferable.

Further, the composition of the present invention further has conventionally known additives such as lubricants, nucleating agents, release agents, antistatic agents and other surfactants for imparting desired properties depending on the purpose. Alternatively, a pigment or the like can be added. The composition of the present invention can be easily prepared by a known method generally used as a conventional resin composition preparation method. The resin composition of the present invention is processed into various molded articles by a general molding method such as injection molding. Particularly, it is suitably used for molded products, wristwatch parts, printer parts, desk-top computer parts and the like used as small or thin precision parts.

[0011]

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 provided with surface-treated fibrous titanium oxide and various additives in Table 1. Extrusion kneading was carried out at a compounding ratio as shown in 2 to prepare a pelletized composition. 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 a fibrous titanium oxide that has not been surface-treated,
And (C) nitrogen compound, (D) hindered phenol,
(E) A composition containing no fatty acid ester 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 test pieces are left for 48 hours under conditions of temperature 23 ° C and humidity 50%,
Under that atmosphere, using a tester (Tensilon manufactured by Orientec Co., Ltd.) and a specific jig, ASTM-D638 (tensile) and ASTM
-Measured according to D732-85. Amount of gas generated during melting 8g of the above pellets were placed in a melt indexer at 200 ° C.
After the resin was melted and retained for 5 minutes, it was allowed to flow under a load, and the generated formaldehyde was collected and quantified, and it was expressed as the weight (ppm) of the generated formaldehyde to the resin per unit weight. Continuous molding test injection molding machine; Toshiba IS30EPN (manufactured by Toshiba Machine Plastics Engineering Co., Ltd.) Cylinder temperature: 200 ° C Injection pressure: 750kg / cm ² Injection time: 4 seconds Cooling time: 3 seconds Mold temperature: 30 ° C Above molding conditions After continuous molding (24 hours) of a molded product having a specific shape, the amount of deposits on the surface of the mold was evaluated by visual observation on a five-grade scale. A: Almost no adhering matter is observed B: Slightly adhering matter is observed C: Little adhering matter is observed D: Many adhering matter is observed E: Very little adhering matter Recognized in large quantities

[0012]

[Table 1]

[0013]

[Table 2]

The symbols in the table indicate the following. B. Surface treatment agent B1: N- (2-aminoethyl) -3-aminopropyltrimethoxysilane B2: 3-glycidoxypropyltrimethoxysilane C. Component (C) C1: Melamine C2: Calcium stearate D. Hinder Dephenolic 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. Fatty acid ester compound E1: Glycerin monostearate E2: Sorbitan monostearate

Continuation of front page (51) Int.Cl. ⁵ Identification number Office reference number FI technical display area C08K 5/3477 7/08

Claims (5)

[Claims] 1. (A) 100 parts by weight of polyacetal resin, (B) 1-70 parts by weight of surface-treated fibrous titanium oxide (C) Nitrogen-containing compound, water of alkali metal or alkaline earth metal One or more compounds selected from metal-containing compounds consisting of oxides, inorganic acid salts or carboxylates 0.01 to 5 parts by weight (D) Hindered phenolic compounds 0.01 to 5 parts by weight (E) Polyvalent Ester compounds from alcohols and fatty acids 0.01
A polyacetal resin composition containing 5 to 5 parts by weight. 2. The fibrous titanium oxide (B) has an average fiber diameter of 0.
The polyacetal resin composition according to claim 1, which has an average fiber length of 02 to 0.6 µm, an average fiber length of 1 to 20 µm, and an aspect ratio of 10 or more. 3. The ester compound (E) is glycerin monostearate, glycerin distearate, glycerin monobehenate, sorbitan monostearate or sorbitan monobehenate.
Or the polyacetal resin composition according to item 2. 4. A molded product used as a small-sized or thin-walled precision component, which is obtained by molding the polyacetal resin composition according to claim 1. 5. The molded product according to claim 4, wherein the small or thin precision parts are wrist watch parts, printer parts, and desktop computer parts.