阅读说明：本技术 聚缩醛树脂组合物和滑动构件 (Polyacetal resin composition and sliding member ) 是由 服部和幸 门间智宏 于 2020-04-10 设计创作，主要内容包括：本发明目的在于,提供：保持成型品的外观、成型时的模具污染少、且具有摩擦/磨损特性优异的性能的聚缩醛树脂组合物和滑动构件。通过聚缩醛树脂组合物而实现,所述聚缩醛树脂组合物至少含有：(A)聚缩醛树脂100质量份、(B)受阻酚系抗氧化剂0.01质量份以上且1质量份以下、(C)硅油0.3质量份以上且5质量份以下、(D)碳酸钙0.1质量份以上且1.0质量份以下、和(E)脂肪酸0.02质量份以上且0.2质量份以下,前述(D)碳酸钙是平均粒径为1μm以下、且未经表面处理的轻质碳酸钙,前述(E)脂肪酸为碳数12以上且30以下的脂肪酸。(The object of the present invention is to provide: a polyacetal resin composition and a sliding member which maintain the appearance of a molded article, are reduced in mold contamination during molding, and have excellent friction/wear characteristics. The polyacetal resin composition comprises at least: (A) 100 parts by mass of a polyacetal resin, (B) 0.01 to 1 part by mass of a hindered phenol antioxidant, (C) 0.3 to 5 parts by mass of a silicone oil, (D) 0.1 to 1.0 part by mass of calcium carbonate, and (E) 0.02 to 0.2 part by mass of a fatty acid, wherein the calcium carbonate (D) is a light calcium carbonate having an average particle diameter of 1 μm or less and not subjected to surface treatment, and the fatty acid (E) is a fatty acid having 12 to 30 carbon atoms.)

1. A polyacetal resin composition comprising at least:

(A) 100 parts by mass of a polyacetal resin,

(B) 0.01 to 1 part by mass of a hindered phenol antioxidant,

(C) 0.3 to 5 parts by mass of silicone oil,

(D) 0.1 to 1.0 parts by mass of calcium carbonate, and

(E) 0.02 to 0.2 parts by mass of a fatty acid,

the calcium carbonate (D) is a light calcium carbonate having an average particle diameter of 1 μm or less and not subjected to surface treatment,

the fatty acid (E) is a fatty acid having 12 to 30 carbon atoms.

2. A sliding member comprising the polyacetal resin composition according to claim 1.

Technical Field

The present invention relates to a polyacetal resin composition and a sliding member.

Background

Polyacetal resins (also referred to as polyoxymethylene resins, abbreviated as POM resins) have well-balanced mechanical properties and are excellent in friction/wear resistance, chemical resistance, heat resistance, electrical characteristics, and the like, and thus are widely used in the fields of automobiles, electric/electronic products, and the like.

However, the required characteristics in the above-mentioned fields have been gradually advanced, and as one example, improvement of basic sliding characteristics such as a friction coefficient and a wear amount while maintaining excellent surface smoothness of the polyacetal resin has been strongly required.

In order to meet such a demand, a method of adding a fluororesin or a polyolefin resin to a polyacetal resin is known. However, the fluororesin and the polyolefin resin are poor in compatibility with the polyacetal resin. Therefore, there may be the following: these resins are separated from the polyacetal resin and are peeled off from the surface of the molded article, or precipitates are generated on the mold when the molded article is molded.

Further, a method of adding a lubricating oil such as a fatty acid, a fatty acid ester, a silicone oil, or various mineral oils to a polyacetal resin is known. However, there may be cases where: when a molded article is molded, the polyacetal resin is separated from the lubricating oil or the like, and the lubricating oil or the like is likely to bleed out, and the extrusion processability and molding processability are impaired by the bleeding lubricating oil or the like. Further, if the lubricating oil oozes out on the surface of the molded article, the appearance of the molded article may be impaired.

In order to solve these problems, a polyacetal resin composition obtained by adding a polyethylene wax, a polyethylene resin, and a silicone oil having a specific kinematic viscosity to a polyacetal resin has been proposed (for example, see patent document 1).

Documents of the prior art

Patent document

Patent document 1: japanese laid-open patent publication No. 2008-19430

Disclosure of Invention

Problems to be solved by the invention

However, even in the polyacetal resin composition described in patent document 1, there is still room for further improvement with respect to the deterioration of the appearance of the molded article such as bleeding of the lubricating oil or peeling of the surface of the molded piece, and the deposit on the mold during molding.

An object of the present invention is to provide: a polyacetal resin composition and a sliding member which maintain the appearance of a molded article, are reduced in mold contamination during molding, and have excellent friction/wear characteristics.

Means for solving the problems

The present inventors have conducted intensive studies to achieve the above object, and as a result, have found that: the present inventors have completed the present invention by finding that the above object can be achieved by using a polyacetal resin as a base and adding and mixing specific amounts of a hindered phenol antioxidant, a silicone oil, a light calcium carbonate having a specific particle diameter and not subjected to surface treatment, and a specific fatty acid.

1. A polyacetal resin composition comprising at least:

(A) 100 parts by mass of a polyacetal resin,

(B) 0.01 to 1 part by mass of a hindered phenol antioxidant,

(C) 0.3 to 5 parts by mass of silicone oil,

(D) 0.1 to 1.0 parts by mass of calcium carbonate, and

(E) 0.02 to 0.2 parts by mass of a fatty acid,

the calcium carbonate (D) is a light calcium carbonate having an average particle diameter of 1 μm or less and not subjected to surface treatment,

the fatty acid (E) is a fatty acid having 12 to 30 carbon atoms.

2. A sliding member comprising the polyacetal resin composition according to 1.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the present invention, there can be provided: the polyacetal resin composition is excellent in friction/wear characteristics, and further has good properties in appearance of molded articles and mold contamination during molding.

Detailed Description

The present invention is not limited to the following embodiments, and can be carried out with appropriate modifications within the scope of the object of the present invention.

< polyacetal resin composition >

The polyacetal resin composition of the present invention is characterized by containing at least: (A) a polyacetal resin, (B) a hindered phenol antioxidant, (C) a silicone oil, (D) light calcium carbonate, and (E) a fatty acid.

(A) polyacetal resin

As the polyacetal resin (a), any of a polyacetal homopolymer and a polyacetal copolymer having a main chain mostly composed of an oxymethylene chain can be used. The base resin may be a polyacetal modified by crosslinking or graft copolymerization by a known method, and the polymerization degree and the like are not particularly limited as long as the polyacetal can be molded.

Hindered phenol antioxidant (B)

The hindered phenol antioxidant (B) that can be used in the present invention is not particularly limited, and examples thereof include: monocyclic hindered phenol compounds (e.g., 2, 6-di-t-butyl-p-cresol, etc.), polycyclic hindered phenol compounds linked by a hydrocarbon group or a sulfur atom-containing group (e.g., 2,2 '-methylenebis (4-methyl-6-t-butylphenol), 4' -methylenebis (2, 6-di-t-butylphenol), 1, 3-tris (2-methyl-4-hydroxy-5-t-butylphenyl) butane, 4 '-butylidenebis (3-methyl-6-t-butylphenol), 1,3, 5-trimethyl-2, 4, 6-tris (3, 5-di-t-butyl-4-hydroxybenzyl) benzene, 4' -thiobis (3-methyl-6-t-butylphenol), etc.), hindered phenol compounds having an ester group or an amide group (e.g., n-octadecyl-3- (4 '-hydroxy-3', 5 '-di-t-butylphenyl) propionate, n-octadecyl-2- (4' -hydroxy-3 ', 5' -di-t-butylphenyl) propionate, 1, 6-hexanediol-bis [3- (3, 5-di-t-butyl-4-hydroxyphenyl) propionate ], triethylene glycol-bis [3- (3-t-butyl-5-methyl-4-hydroxyphenyl) propionate ], pentaerythritol tetrakis [3- (3, 5-di-t-butyl-4-hydroxyphenyl) propionate ], 3, 9-bis {2- [3- (3-t-butyl-4-hydroxy-5-methylphenyl) propionyloxy ] -1, 9-bis 1-dimethylethyl } -2,4,8, 10-tetraoxaspiro [5.5] undecane, 2-tert-butyl-6- (3 ' -tert-butyl-5 ' -methyl-2 ' -hydroxybenzyl) -4-methylphenylacrylate, 2- [1- (2-hydroxy-3, 5-di-tert-pentylphenyl) ethyl ] -4, 6-di-tert-pentylphenylacrylate, bis-N-octadecyl-3, 5-di-tert-butyl-4-hydroxybenzylphosphonate, N ' -hexamethylenebis (3, 5-di-tert-butyl-4-hydroxy-dihydrocinnamamide, N ' -ethylenebis [3- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionamide ], their salts, N, N '-tetramethylenebis [3- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionamide ], N' -hexamethylenebis [3- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionamide ], N '-ethylenebis [3- (3-tert-butyl-5-methyl-4-hydroxyphenyl) propionamide ], N' -hexamethylenebis [3- (3-tert-butyl-5-methyl-4-hydroxyphenyl) propionamide ], N '-bis [3- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionyl ] hydrazine, N' -bis [3- (3-tert-butyl-5-methyl-4-hydroxyphenyl) propionyl ] hydrazine, N '-dimethylenebis [3- (3-tert-butyl-5-4-hydroxyphenyl) propionamide ], N' -hexamethylenebis [3- (3-methyl-4-hydroxyphenyl) propionamide, N '-propionamide, N' -bis [ 3-bis (5-tert-4-butyl-4-hydroxy-4-butyl-hydroxy-propionamide) and N, N '-bis (N, N' -bis (N, 1,3, 5-tris (3, 5-di-tert-butyl-4-hydroxybenzyl) isocyanurate, 1,3, 5-tris (4-tert-butyl-3-hydroxy-2, 6-dimethylbenzyl) isocyanurate, and the like.

In the present invention, at least one or two or more selected from these antioxidants may be used.

The content of the hindered phenol antioxidant (B) in the present invention is 0.01 to 1 part by mass, preferably 0.02 to 0.5 part by mass, based on 100 parts by mass of the polyacetal resin (a).

(B) When the amount of the antioxidant is small, the antioxidant property is not sufficient, and (a) the stability of the polyacetal resin tends to be insufficient against short-term oxidative deterioration at high temperature such as in molding or long-term oxidative deterioration at normal temperature, which is not preferable. Further, when the stability of the base polyacetal resin component (A) is insufficient and deterioration occurs, the sliding characteristics are adversely affected. On the other hand, when the amount of the antioxidant (B) is too large, the mechanical properties of the obtained resin composition may be impaired.

(C) Silicone oils

The type of silicone oil (C) is not particularly limited, and as an example, there are known: polydimethylsiloxane represented by the structure of the following formula (1), polymethylphenylsiloxane, and the like.

In the formula (1), R is substantially methyl, but a part thereof may be alkyl, phenyl, haloalkyl, halophenyl or the like.

In the present invention, two or more kinds of silicone oils having different structures or viscosities may be mixed and used, or a thickening material, a solvent, or the like may be added to the silicone oil to adjust the viscosity.

In the present invention, the amount of the silicone oil (C) is 0.3 to 5 parts by mass based on 100 parts by weight of the polyacetal resin (a). (C) When the amount of the silicone oil is small, the effect of improving the friction/wear characteristics, which is the object of the present invention, becomes insufficient, which is not preferable. On the other hand, if the amount of the silicone oil (C) is too large, mold contamination may occur during molding, and peeling may occur on the surface of the molded article in the sliding member, and the amount of abrasion of the material itself during sliding may increase, which is not preferable.

Light calcium carbonate (D)

The polyacetal resin composition of the present invention contains (D) precipitated calcium carbonate. In order to improve the surface hardness and the machinability, it is known to blend an inorganic powder with a polyacetal resin. As the inorganic powder, in addition to calcium carbonate, there are known: magnesium carbonate, talc, silica, clay, kaolin, diatomaceous earth, perlite, bentonite, feldspar, carbon, white carbon, and the like, but in the present invention, light calcium carbonate is used as the inorganic powder in consideration of slidability and hardness with the target material as the sliding member.

(D) The light calcium carbonate may be produced by chemical synthesis, and the particle shape and the like are not particularly limited. One kind may be used alone, or two or more kinds may be used in combination.

(D) The average particle diameter of the light calcium carbonate is 1 μm or less, preferably 500nm or less, and more preferably 200nm or less. When the average particle diameter is too large, the surface of the molded article becomes uneven, and the material to be slid may be damaged due to the increase in surface roughness, which is not preferable.

In the present specification, the particle size means: the arithmetic mean values of the major and minor diameters of the target particles were measured by observing at a magnification of 30000 times using a scanning electron microscope S3000H manufactured by Hitachi High-Technologies Corporation. In the present specification, the average particle size refers to an arithmetic average of particle sizes of 100 samples.

The lower limit of the average particle diameter is not particularly limited, and the average particle diameter of (D) precipitated calcium carbonate is preferably 50nm or more in order to prevent secondary aggregation of the polyacetal resin composition.

In the present invention, the amount of the precipitated calcium carbonate (D) is 0.1 to 1.0 parts by mass based on 100 parts by mass of the polyacetal resin (a). (D) When the amount of light calcium carbonate having an average particle diameter of 1 μm or less is small, the effect of improving the friction/wear characteristics, which is the object of the present invention, may become insufficient, which is not preferable. On the other hand, if the amount of the light calcium carbonate (D) having an average particle diameter of 1 μm or less is too large, the amount of abrasion of the material itself increases, which is not preferable. Further, it is not preferable that the surface of the molded article has irregularities, and the material to be slid may be damaged due to the increase in surface roughness.

The light calcium carbonate (D) that can be used in the present invention is not subjected to "surface treatment" in which various coupling agents such as silane coupling agents, fatty acids, and the like are reacted with the particle surface to modify the particle surface in order to impart functionality to the particles.

(D) When the light calcium carbonate is surface-treated, an increase in bulk density is seen after the surface treatment, and therefore, it is assumed that the particles are further aggregated by the surface treatment. Therefore, when melt kneading is performed with a resin, the dispersion of the precipitated calcium carbonate particles in the resin is deteriorated, and the frictional wear characteristics and the appearance are deteriorated, which is not preferable, as compared with the case where the surface treatment is not performed.

(E) fatty acids

The fatty acid (E) used in the present invention has a structure in which a carboxyl group is bonded to one end of an aliphatic hydrocarbon group, and is a higher fatty acid having 12 to 30 carbon atoms in total. The aliphatic hydrocarbon group constituting the fatty acid may be linear or branched, and may be saturated or unsaturated.

These fatty acids may be used alone in 1 kind or in combination of 2 or more kinds. Examples of the (E) fatty acid include lauric acid, myristic acid, pentadecanoic acid, palmitic acid, margaric acid, stearic acid, nonadecanoic acid, arachidic acid, behenic acid, lignoceric acid, cerotic acid, montanic acid, melissic acid, oleic acid, elaidic acid, cetoleic acid, erucic acid, brassidic acid, linoleic acid, linolenic acid, arachidonic acid, and stearylic acid.

(E) The aliphatic hydrocarbon group of the fatty acid may be substituted with a functional group such as a hydroxyl group.

The amount of the fatty acid (E) of the present invention is 0.02 to 0.2 parts by mass based on 100 parts by mass of the polyacetal resin (a). (E) When the amount of the fatty acid is small, peeling occurs on the surface of the molded article of the sliding member, which is not preferable. On the other hand, if the amount of the (E) fatty acid blended is too large, mold contamination during molding and peeling of the sliding member from the surface of the molded article may occur, which is not preferable.

Other ingredients

The polyacetal resin composition of the present invention may further contain other components as necessary. Examples of the stabilizer include: 1 or 2 or more of hydroxides, inorganic salts, carboxylates and the like of alkali metals or alkaline earth metals.

Further, as long as the object and effect of the present invention are not impaired, 1 or 2 or more kinds of general additives, for example, a coloring agent such as a dye or a pigment, a lubricant, a release agent, an antistatic agent, a surfactant, an organic polymer material, an inorganic or organic fibrous, powdery or plate-like filler, and the like may be added to the thermoplastic resin as necessary.

< method for producing polyacetal resin composition >

A melting and kneading apparatus is used for producing the polyacetal resin composition of the present invention. The melt-kneading apparatus is not particularly limited, and an apparatus having a function of melt-kneading the polyacetal resin and the other components, preferably an apparatus having a function of exhausting gas, may be exemplified by: single-screw or multi-screw continuous extrusion mixers, kneaders, etc. having at least 1 vent hole.

As the method for producing the resin composition, a known method generally used as a conventional method for producing a resin composition can be used. For example, the following method can be employed: (1) a method in which all the components constituting the composition are mixed and supplied to an extruder to be melt-kneaded, thereby obtaining a composition in the form of pellets; (2) a method in which a part of the components constituting the composition is fed from a main feed port of an extruder, and the remaining components are fed from a side feed port, and melt-kneaded to obtain a composition in the form of pellets; (3) a method of preparing pellets having different compositions temporarily by extrusion or the like, and mixing the pellets to adjust the composition to a predetermined composition.

In the present invention, the method (1) is preferred. For example, it is preferable to mix the constituent components of the composition in a batch mixer, then supply the mixed raw materials to an extruder, and melt-knead the raw materials.

The melt kneading treatment is preferably carried out at a temperature of 260 ℃ or higher than the melting point of the polyacetal resin. If the temperature is higher than 260 ℃, decomposition and deterioration of the polymer occur, which is not preferable.

< sliding Member >

The sliding member of the present invention is configured to include a resin molded body containing the polyacetal resin composition. The sliding member has not only good friction/wear characteristics but also good performance in the surface properties of molded sheets, and is therefore suitable for use in sliding parts such as AV and OA fields, measuring instrument fields, and conveying parts.

Examples

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

< examples and comparative examples >

< preparation of polyacetal resin composition >

The components shown in tables 1 and 2 were compounded in the proportions shown in tables 1 and 2, and melt-kneaded at 210 ℃ in a twin-screw extruder to obtain pellets of the polyacetal resin compositions of the examples and comparative examples.

The components used in the examples and comparative examples of the present invention shown in tables 1 and 2 are as follows.

(A) Polyacetal resin

(A-1) A polyacetal copolymer (melt index (measured at 190 ℃ C. under a load of 2160 g): 9g/10 min) obtained by copolymerizing 96.7 mass% of trioxane and 3.3 mass% of 1, 3-dioxolane

(B) Hindered phenol antioxidant

(B-1) Irganox245 (manufactured by BASF CORPORATION)

Triethylene glycol bis [3- (3-tert-butyl-5-methyl-4-hydroxyphenyl) propionate ]

(C) Silicone oil

(C-1) SH200-60000CS (manufactured by Dow Corning Toray Co., Ltd.)

Kinematic viscosity at 25 ℃ of 60000cSt (600 cm)²/s)

(D) Calcium carbonate

(D-1) Brilliant-1500 (manufactured by Baishi industries Co., Ltd.),

light calcium carbonate with average particle size of 150nm and without surface treatment

(D-2) Whiton P-30(Toyo Fine Chemical Co., Ltd.)

Heavy calcium carbonate with average particle size of 4.4 mu m

(D-3) Vigot-15 (manufactured by Baishi industries Co., Ltd.)

Light calcium carbonate having an average particle diameter of 150nm and surface-treated with fatty acid

(E) Fatty acids

(E-1) stearic acid (carbon number: 18)

(E-2) oleic acid (carbon number: 18)

(E-3) lauric acid (carbon number: 12)

(E-4) Octanoic acid (carbon number: 8)

[ Table 1]

[ Table 2]

< evaluation >

In order to evaluate the pellet-shaped polyacetal resin compositions of the examples and comparative examples, the frictional wear characteristics, the appearance of the molded article, and the amount of mold deposit during molding were evaluated. The results are shown in tables 3 and 4.

Characteristics of Friction and wear

Using the pellets of the polyacetal resin compositions of the examples and comparative examples, cylindrical test pieces (outer diameter: 25.6mm, inner diameter: 20mm, height: 15mm) were molded under the following conditions.

Using the test piece, the frictional wear characteristics were evaluated under the following conditions, and the coefficient of dynamic friction and the wear amount ratio at the end of the test were measured. The test was carried out at 23 ℃ under an atmosphere of 50 RH%.

[ evaluation method ]

Test method Suzuki friction wear test

Test device EFM-3-EN (ORIENTEC CORPORATION)

Test conditions subject materials: the cylindrical test piece made of polyacetal resin

(product name: DURACON (registered trademark) M90-44, Polyplatics Co., manufactured by Ltd.)

Surface pressure: 0.06MPa

Speed: 15 cm/sec

Test time: 24 hours

[ test piece Molding conditions A ]

A forming machine: FANUC ROBOSHOT alpha-S50 iA (manufactured by FANUC Corporation)

Molding conditions are as follows: barrel temperature (. degree. C.) nozzle-C1-C2-C3

200℃- 200℃- 180℃-170℃

Injection pressure 60(MPa)

Injection speed 0.4 (m/min)

Mold temperature 80 (. degree. C.)

Appearance of molded article

Using the pellets of the polyacetal resin compositions of the examples and comparative examples, test pieces (80 mm. times.80 mm. times.1 mmt; side gate 2 mm. times.1 mm) were similarly molded under the above test piece molding conditions A.

[ evaluation method ]

The surface of the obtained 10 molded pieces was visually observed. The number of fluffs or peeled pieces observed on the surface of the molded piece was determined according to the following criteria.

0: in all molded pieces, no fuzz or peeling was observed on the surface.

1: in the two or less molded sheets, fuzzing and peeling were observed on the surface.

2: in the three or more molded sheets, fuzz or peeling was observed on the surface.

Contamination of mold during Molding

Using the pellets of the polyacetal resin compositions of the examples and comparative examples, mold deposit test pieces (33 mm. times.23 mm. times.1 mmt) were molded under the following condition B.

[ evaluation method ]

After 5000 shots of the molded article were continuously formed, the surface of the cavity in the mold was visually observed, and the amount of deposit was visually judged according to the following criteria.

0: the presence of adhered matter was not confirmed at all

1: slight confirmation of attachment

2: the deposit was confirmed in the whole.

[ test piece Molding conditions B ]

Spreading machine: FANUC ROBOSHOT S-2000i 50B (FANUC corporation)

The molding conditions are as follows: barrel temperature (. degree. C.) nozzle-C1-C2-C3

205℃ 215℃ 205℃ 185℃

Injection pressure 40(MPa)

Injection speed 1.5 (m/min)

Mold temperature 80 (. degree. C.)

The evaluation results are shown below.

[ Table 3]

[ Table 4]

As is apparent from the above description, the resin composition of the present invention has not only good friction/wear characteristics but also good properties in terms of the appearance of the molded article and mold staining during molding.