JPH07133403A - Polyacetal resin composition - Google Patents

Abstract

PURPOSE:To obtain the composition having good friction and abrasion properties, a low initial sliding torque and a stable property in a intermittent sliding motion on a light load, by combining a specific olefinic polymer and a branched ester oil to a polyacetal resin. CONSTITUTION:To 100wt.pt. of a polyacetal resin (A), 0.5-40wt.pt. of a graft or a block copolymer (B) obtained from an olefinic polymer and at least one vinyl type polymer and 0.1-15wt.pt. of a branched ester oil (C) comprising a fatty acid having at least one branched chain and/or an alcohol, are combined. As the component (B), the copolymer obtained from a polymer selected from a polyethylene, a polypropylene and an ethylene propylene copolymer and a polymer selected from a polymethylmethacrylate and a copolymer of acrylonitrile-styrene, is used. The component (C) is an ester of a fatty acid with a carbon number of 16 or more having more than one branched chain, or an alcohol with a carbon number of 16 or more, or an ester of a similar branched fatty acid with a polyvalent alcohol.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyacetal resin composition having excellent friction and wear characteristics, low initial sliding torque, and stable characteristics during intermittent sliding under light load conditions. is there.

[0002]

BACKGROUND OF THE INVENTION Polyacetal resins have well-balanced mechanical properties.
It is widely used in the fields of automobiles, electric / electronic products, etc. due to its excellent friction / wear resistance, chemical resistance, heat resistance, and electrical characteristics. However, the required properties in such fields are becoming more sophisticated, and as an example, further improvement in sliding properties as well as general physical properties is desired. Such sliding characteristics include not only friction coefficient, specific wear amount and sliding noise (squeaking noise) but also low initial friction torque (initial friction coefficient) at the start of sliding. ing. The low initial friction torque is an important characteristic in practical parts that cause intermittent sliding.
It is required in a wide range of fields such as sliders, keyboards, VTRs (video tape recorders), and audio. For the purpose of improving such sliding properties, a fluororesin or a polyolefin resin is added to the polyacetal resin, and sliding modifiers such as fatty acids, fatty acid esters and various synthetic lubricating oils are added. However, the addition of a fluororesin or a polyolefin resin improves sliding properties including initial properties to some extent, but these resins have poor compatibility with polyacetal resin, and therefore peeling may occur on the surface of the molded product, or molding may occur. Precipitates are easily generated on the mold. Further, in order to sufficiently modify the surface of the polyacetal resin, it is necessary to add a large amount of such a resin, and in this case, the physical properties originally possessed by the polyacetal resin are significantly reduced. Also, the addition of lubricating oil alone has some effect in reducing the friction coefficient and the specific wear amount, but it is not sufficient in improving the initial friction torque. There are various difficulties such as seeping. In addition, the solid ester conventionally used as a lubricant for engineering plastics has a large change in initial sliding torque and stable running torque during sliding under a light load due to the melting phenomenon that accompanies the progress of sliding. May cause defects. Furthermore, the addition of a liquid synthetic lubricating oil that has been generally used conventionally cannot be used practically because of problems such as peeling of the resin skin layer and deterioration of moldability. As described above, in the conventional technology,
There is a demand for a material that cannot satisfy all of the initial sliding torque, sliding characteristics, molding processability, and other practicalities and has these properties in a well-balanced manner.

[0003]

Means for Solving the Problems The inventors of the present invention have conducted extensive studies on the development of a polyacetal resin composition having good general physical properties and particularly excellent sliding properties, and as a result, a specific olefin for the polyacetal resin has been obtained. The initial sliding torque is remarkably improved by blending the system copolymer and the specific branched ester oil, and the polyacetal resin has excellent friction / wear characteristics, sliding noise (squeaking noise), processability and other general physical properties. The inventors have found that a composition can be obtained and arrived at the present invention. That is, the present invention, (A) 100 parts by weight of a polyacetal resin (B) (b-1) olefin polymer, (b-2) at least one vinyl-based polymer obtained from a graft or block copolymer 0.5 To 40 parts by weight, and (C) 0.1 to 15 parts by weight of a branched ester oil obtained from a fatty acid having at least one branched chain and / or an alcohol having at least one branched chain, a polyacetal resin composition. It is provided.

The structure of the present invention will be described in detail below. First, as the polyacetal resin (A) used in the present invention, both a polyacetal homopolymer and a polyacetal copolymer in which the main chain is mostly an oxymethylene chain can be used. Also, a polyacetal modified by crosslinking or graft copolymerization by a known method can be used as the base resin, and the degree of polymerization is not particularly limited as long as it can be molded.

Next, the graft or block copolymer used as the component (B) in the present invention is obtained from (b-1) an olefin polymer and (b-2) at least one vinyl polymer, Olefin-based polymer and vinyl-based polymer,
Branched or cross-linked A structurally chemically bonded graft or block copolymer. Here, as a specific example of the (b-1) olefin polymer constituting the main chain portion of the component (B),
Low density polyethylene, ultra low density polyethylene, linear low density polyethylene, medium density polyethylene, high density polyethylene, polypropylene, homopolymers of polyα-olefins such as polybutene, hydrogenated products of polybutadiene, and those containing these as the main components. A copolymer is mentioned. As the copolymer, ethylene / propylene copolymer, ethylene / 1-
Examples include butene copolymers. Of these, various polyethylenes, polypropylenes and ethylene-propylene copolymers can be particularly preferably used. Next, as the vinyl polymer (b-2) to be graft- or block-copolymerized with this olefin polymer (b-1), polymethyl methacrylate, polyethyl acrylate, polyacrylic acid ethyl, polyacrylic acid can be used. Examples thereof include butyl, poly (2-ethylhexyl acrylate), polystyrene, polyacrylonitrile, acrylonitrile-styrene copolymer, butyl acrylate / methyl methacrylate copolymer, butyl acrylate / styrene copolymer and the like. Particularly preferred are polymethylmethacrylate, acrylonitrile-styrene copolymer, polystyrene and the like. The graft or block copolymer (B), which is a feature of the present invention, includes the above-mentioned (b-1) olefin polymer constituting the main chain portion, and (b-2) vinyl polymer alone. It is not used but is a graft or block copolymer having a chain, branched or crosslinked structure in which a polymer of (b-1) and a polymer of (b-2) having different properties are chemically bonded at at least one point. By virtue of this feature, and by having such a graft or block structure as will be described later, a remarkable effect which cannot be obtained by simply blending (b-1) or (b-2) alone can be obtained. The method for preparing the graft or block copolymer comprising the (b-1) segment and the (b-2) segment is not particularly limited, but can be easily prepared by a well-known radical reaction. For example, polymers (b-1) and (b-2)
A method of melt kneading by adding a radical catalyst to, or free radicals are generated in the polymer (b-1) or (b-2) with a peroxide or the like, and this is melt-kneaded with other component polymers. It is prepared by a method or the like. Further, the graft or block copolymer (B) is also prepared by a method such as hydrogenation of styrene-butadiene rubber. Here, in order to form the graft or block copolymer of the component (B) (b-
The ratio of 1) to (b-2) is preferably 95: 5 to 40:60. 9
When the ratio of the component (b-1) is larger than that of the component (b-2) in excess of the ratio of 5: 5, the separation of the polyolefin component from the polyacetal becomes remarkable and the peeling and abrasion properties deteriorate. Also, 4
If the amount of the component (b-1) is less than the amount of the component (b-2) beyond the ratio of 0:60, the effect of modifying the surface of the polyacetal by the polyolefin component will be insufficient and the effect of improving the friction coefficient will not be exhibited. The above-mentioned (B) graft or block copolymer can be obtained from the market, for example, MODIPER A1400, A120 manufactured by NOF CORPORATION.
0, A1100 (trade name) and the like are commercially available. Also,
The component (B) is preferably added in an amount of 0.5 to 40 parts by weight, more preferably 1 to 30 parts by weight, based on 100 parts by weight of the component (A). If the amount of the component (B) is too small, the effects of improving the sliding characteristics and moldability that are the objectives of the present invention cannot be obtained, and if it is too large, surface peeling occurs and the appearance of the molded product deteriorates, which is not preferable.

The branched ester oil used as the component (C) in the present invention means a fatty acid ester obtained from a fatty acid having at least one branched chain and / or an alcohol having at least one branched chain in its molecule. Is. Typical examples of the branched chain fatty acid which constitutes the branched ester oil include isoacid and anteisoic acid, but not limited thereto, any branched fatty acid can be used as a constituent component of the ester oil. . Examples of such branched fatty acids preferably have 16 or more carbon atoms, and specific examples thereof include isostearic acid and isopalmitic acid. The branched alcohol preferably has 16 or more carbon atoms, and specific examples include isotridecyl alcohol, hexyldecyl alcohol, octyldodecyl alcohol, and isostearyl alcohol. None, any branched or unsaturated alcohol can be used as a constituent of the ester oil. Examples of the alcohol that forms a branched ester oil by combining with the branched chain fatty acid include straight chain aliphatic alcohols such as myristyl alcohol, cetyl alcohol, stearyl alcohol, and behenyl alcohol, ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol. Examples thereof include polyhydric alcohols such as neopentyl glycol, propylene glycol, glycerin, diglycerin, sorbitan, trimethylolpropane, pentaerythritol, and dipentaerythritol, and alcohols having the above branched chains. Further, as the fatty acid constituting the branched ester oil by combining with the alcohol having a branched chain, myristic acid, palmitic acid, stearic acid, linear fatty acids such as pehenic acid, citric acid, phthalic acid, adipic acid, Examples include dibasic acids such as trimellitic acid, and the above-mentioned branched chain fatty acids. By blending such branched ester oil, good sliding characteristics can be obtained in any case, but the melting point is 40
It is preferable to use an oil having a temperature of lower than 0 ° C, and particularly preferable to use a liquid ester oil having a melting point of 25 ° C or lower. Further, from the viewpoints of long-term sliding stability, extrudability, processability such as moldability, etc., the branched ester oil is preferably an ester composed of a branched saturated fatty acid and a polyhydric alcohol, and particularly preferably. Partial ester of isostearic acid and one or more polyhydric alcohols selected from the group of ethylene glycol, polyethylene glycol, propylene glycol, glycerin, diglycerin, trimethylolpropane and pentaerythritol (unreacted OH in the molecule)
With one or more groups) are particularly preferred. The branched ester oil (C) is based on 100 parts by weight of the component (A),
It contains 0.1 to 15 parts by weight, and exhibits good properties. Compounding amount
If it is less than 0.1 part by weight, the effect of improving the sliding characteristics is insufficient, and if it exceeds 15 parts by weight, the abrasion characteristics and the surface appearance are extremely deteriorated, which is not preferable. More preferably
It is in the range of 0.5 to 10 parts by weight.

The blending ratio of the olefin copolymer as the component (B) and the branched ester oil as the component (C) is not particularly limited.
The range of / (C) = 1 to 50 is preferable. Conventionally, when ester oil is blended, the problem that the sliding characteristics do not last due to the ease of spotting, and that the ester itself volatilizes and dissipates in the high temperature environment during extrusion and molding processing, and is not sufficiently blended was there. In the present invention, an olefin-based copolymer
This problem was solved by simultaneously blending (B) and the branched ester oil (C). Furthermore, the use of a special olefin-based copolymer has led to the invention of a polyacetal resin composition having good friction and wear characteristics, which does not cause the exfoliation of the polyolefin component by the branched ester oil and the deterioration of wear.

The composition of the present invention can be further reinforced by adding various known stabilizers. Further, various known additives may be further added in order to improve the physical properties depending on the intended use within a range that does not affect the effects of the present invention. Examples of additives include various coloring agents, release agents (other than the above lubricants), nucleating agents, antistatic agents,
Other surfactants, different polymers and the like. In addition, as long as it does not significantly reduce the performance of the composition of the present invention, fibrous inorganic, organic, metal, etc., powder,
It is also possible to use one kind or a mixture of two kinds of plate-like fillers. Next, the composition of the present invention is easily prepared by a known method generally used as a conventional resin composition preparation method. For example, after mixing each component, a method of preparing pellets by kneading and extruding with a single-screw or twin-screw extruder, once preparing pellets (masterbatch) having different compositions, and mixing a predetermined amount of the pellets (dilution) How to do
Either can be used. Further, in the preparation of such a composition, it is possible to improve the dispersibility of the additive by crushing a part or all of the base polyacetal resin (A), mixing this with other components, and then performing extrusion or the like. This is the preferred method for achieving this. The resin composition of the present invention is injection molded according to the purpose,
By extrusion molding and cutting these, various molded products, especially various sliding parts having excellent sliding characteristics can be obtained.

[0009]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited thereto. Examples 1 to 10 and Comparative Examples 1 to 8 As shown in Table 1, as the component (A), a polyacetal resin (manufactured by Polyplastics Co., Ltd., trade name DURACON),
Various olefinic copolymers as the component (B) and various branched esters as the component (C) were mixed at the ratios shown in Table 1, and then melt-kneaded by a twin-screw extruder to prepare a pelletized composition. Then, a test piece was prepared by injection molding using this pellet and evaluated. The results are shown in Table 1.
For comparison, when the component (B) or the component (C) is not blended, or when the component (B) and the component (C) are used in the blending amounts shown in Table 2, the component (C) other than those specified in the present invention is used. Similar evaluations were made for the case of using one. The results are shown in Table 2.

The evaluation items and evaluation methods are as follows.・ Molded product surface condition; test piece for evaluation (50 mm × 50 mm × 1 mm:
A center pin gate method) was molded, and the peeling condition of the surface was evaluated on a 5-point scale. - sliding properties; light load initial sliding properties Suzuki type friction and wear tester (contact area 2.0 cm ²⁾ using, under pressure (0.1 kg / cm ^2), sliding conditions of a linear velocity of 2 mm / sec, 5 minutes And polyacetal resin (Polyplastics Co., Ltd.)
Manufactured by DURACON M90-44) with maximum friction coefficient up to 10 seconds (μ1) and friction coefficient during 5 min running (μ)
2) was measured. The smaller the value of μ1-μ2, the smaller the initial friction torque, which is preferable. Long-term sliding stability (against polyacetal resin) Using a Suzuki type friction and wear tester (contact area 2.0 cm ² ) under pressure (0.6 kg / cm ² ), linear velocity 150 mm / sec, running condition for 24 hours, Coefficient of dynamic friction with polyacetal resin (manufactured by Polyplastics Co., Ltd., trade name DURACON M90-44),
The specific wear amount was measured.

The component (B) and its constituents (b-
The substances used as 1) and (b-2) are as follows.
-In Table 2, it is indicated by abbreviations. (b-1) PE: low-density polyethylene PP: polypropylene (b-2) PMMA: polymethylmethacrylate AN / S: acrylonitrile-styrene copolymer (B) PE-g-PMMA: PE (50) and polymethacryl Graft copolymer with methyl acid (50) PE-g-AN / S: Graft copolymer with PE (50) and acrylonitrile-styrene copolymer (50) PP-g-AN / S: PP (70 ) And an acrylonitrile-styrene copolymer (30) graft copolymer

[0012]

[Table 1]

[0013]

[Table 2]

[0014]

As is apparent from the above description and examples, the polyacetal of the present invention comprises a polyacetal resin (A) containing a specific polyolefin copolymer (B) and a branched ester oil (C). The resin composition has a dramatically improved sliding property, especially the initial operating torque (friction coefficient), as compared with the resin composition in which each copolymer is blended alone or the one in which a solid ester that has been used for the same purpose has been added. And is preferable as a sliding member. Further, the composition of the present invention has a reduced initial operating torque, exhibits stable sliding characteristics over a long period of time, has improved difficulties in extrusion and molding, and has a component separation, exudation and the like. The difficulty has also been improved. Since the resin composition of the present invention has excellent properties as a sliding material as described above, audio- and video-related parts such as VTR, 8 mm video gears, cams, lever guide rollers, guide poles, etc. It is suitable for the sliding member. Besides, it is preferably used for mechanical parts of various office automation equipment such as textile machines, cameras, radios, facsimiles and computers.

Claims (4)

[Claims] 1. A graft or block copolymer obtained from (A) 100 parts by weight of a polyacetal resin (B) (b-1) an olefin polymer and (b-2) at least one vinyl polymer. To 40 parts by weight, and (C) 0.1 to 15 parts by weight of a branched ester oil obtained from a fatty acid having at least one branched chain and / or an alcohol having at least one branched chain. 2. The (B) graft or block copolymer comprises: (b-1) one or more olefinic polymers selected from polyethylene, polypropylene and ethylene-propylene copolymers; and (b-2) a poly (olefin). The polyacetal resin composition according to claim 1, which is obtained from at least one vinyl polymer selected from the group consisting of methyl methacrylate, acrylonitrile-styrene copolymer and polystyrene. 3. (C) A branched ester oil is a fatty acid ester obtained from a fatty acid having at least one branched chain and having at least 16 carbon atoms and / or an alcohol having at least one branched chain and having at least 16 carbon atoms. The polyacetal resin composition according to claim 1. 4. The polyacetal resin composition according to claim 1, wherein the branched ester oil (C) is an ester of a branched fatty acid having at least one branched chain and having 16 or more carbon atoms and a polyhydric alcohol.