JP2898790B2 - Molded product for felt clutch made of acetal resin - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a felt clutch molded article made of an acetal resin having excellent slidability with felt, and more particularly to a felt clutch mechanism component for VTR, 8 mm video and the like.

[0002]

2. Description of the Related Art Acetal resins have well-balanced mechanical properties, and are excellent in friction and wear resistance, chemical resistance, heat resistance, electrical properties, and the like. -Widely used in the field of sliding parts such as electronic parts. However, the required characteristics in such a field are gradually becoming more sophisticated, and with further improvement in sliding characteristics,
Its long-term sustainability is one of them. A typical example of a sliding component that requires such advanced sliding characteristics is a felt clutch mechanism component used in a tape running system such as a VTR, 8 mm video, and a typewriter. As the sliding characteristics required of the felt clutch mechanism parts, it is important to obtain a stable rotational torque in a short term and a long term with respect to the felt as well as the friction coefficient. Conventionally, acetal resin is mainly used as a material for felt clutch mechanism parts. However, recent trends include downsizing of felt clutch mechanism parts and speeding up of tape running, especially friction and wear characteristics with felt for long-term use, rotation torque stability, stick-slip phenomenon (torque stick), etc. Showed a tendency to worsen, and its improvement was desired.

[0003] In order to improve these problems, addition and mixing of an acetal resin with other resins such as a fluororesin, a polyolefin resin, a silicone resin, and a solid lubricant such as graphite, molybdenum disulfide, etc. Further, fatty acids, silicone oils, various mineral oils and the like are added. However, the addition of fluororesin or polyolefin resin improves the sliding properties to some extent, but these resins have poor compatibility with acetal resin, so they may cause peeling on the molded product surface or precipitate on the molding die. It is easy to generate things. In addition, addition of a solid lubricant such as graphite or molybdenum disulfide causes wear powder due to abrasion, so that an increase in rotational torque due to agglomeration and sticking to felt is observed. The addition of lubricating oils such as silicone oils and various mineral oils is effective in reducing the coefficient of friction and the specific wear, but is not yet sufficient in terms of slidability against felt and extrudability or formability. Is often a problem.

[0004] As described above, it is extremely difficult to obtain a molded product for a felt clutch which has good formability and exhibits excellent felt slidability both in a short term and a long term by a conventionally known method. Material development was eagerly awaited.

[0005]

Means for Solving the Problems The present inventors have conducted intensive studies to obtain an acetal resin material capable of meeting such a demand. As a result, by adding and using a specific fatty acid ester to the acetal resin, the VTR, 8 mm The inventors have found that extremely excellent performance can be obtained as a material for a felt clutch mechanism such as a video and a typewriter, and have reached the present invention. That is, the present invention comprises (A) 100 parts by weight of an acetal resin and (B) 1.0 to 10.0 parts by weight of at least one polyhydric alcohol fatty acid ester having a melting point of 40 ° C. or higher. The present invention relates to a molded article for an acetal resin felt clutch which is formed by molding a resin material having a Vicat softening point of 160 ° C. or higher as measured by a method similar thereto.

Hereinafter, the configuration of the present invention will be described in detail. First, the acetal resin (A), which is a base resin of the resin material of the present invention, is a formaldehyde monomer or its trimer (trioxane) or tetramer (tetraoxane)
Oxymethylene homopolymer substantially consisting of oxymethylene units produced from cyclic oligomers such as the above, and the above materials and ethylene oxide, propylene oxide, epichlorohydrin, 1,3-dioxolan,
Oxymethylene copolymers containing from 0.1 to 20% by weight of oxyalkylene units having 2 to 8 carbon atoms, prepared from cyclic ethers such as 1,3-dioxepane, glycol formal and diglycol formal,
Preferably, it is an oxymethylene homopolymer.

Next, the (B) polyhydric alcohol fatty acid ester used in the present invention is a fatty acid ester derived from a polyhydric alcohol such as glycerin or pentaerythritol and a fatty acid such as stearic acid or behenic acid. It has a melting point of 40 ° C. or higher, preferably 60 ° C. or higher. Here, the addition of an ester having a melting point of less than 40 ° C. is likely to exude in use at a high environmental temperature or in sliding with felt, or because the precipitate becomes a liquid and agglomerates abrasion powder due to abrasion, Problems such as an increase in rotational torque are likely to occur. Under these circumstances, preferred polyhydric alcohol fatty acid esters include stearic acid monoglyceride,
Stearic acid monodiglyceride, ethylene glycol distearate, polyethylene glycol monostearate, propylene glycol monostearate, sorbitan monostearate, behenic acid monoglyceride,
Examples thereof include propylene glycol monobehenate and sorbitan monobehenate. Particularly preferred are esters of stearic acid and / or behenic acid with a polyhydric alcohol selected from glycerin, ethylene glycol and polyethylene glycol, more preferably monoglyceride behenate. It is.

In the present invention, the amount of the fatty acid ester (B) to be added is 1.0 to 10.0 parts by weight based on 100 parts by weight of the acetal resin. If the amount is less than 1.0 part by weight, the effect of improving the slidability with felt cannot be expected, and if the amount is more than 10 parts by weight, the properties of the acetal resin as the base resin may be significantly impaired. Preferably, 1.0 to 5 parts by weight, particularly preferably 1.5 to 3 parts by weight, is blended.

In the present invention, from the viewpoint of torque stability due to long-term sliding with the felt, the resin material comprising the above-mentioned components (A) and (B) has a Vicat softening measured by a method according to ASTM D-1525. It is important that the point show a temperature of 160 ° C or higher. If the softening point is lower than 160 ° C., problems such as an increase or fluctuation in rotational torque are likely to occur due to abrasion powder caused by the felt of the acetal resin in sliding against felt.

The stability of the resin material of the present invention can be further enhanced by adding various known stabilizers. Also,
In order to improve the physical properties according to the intended use, various known additives may be further compounded. Examples of additives include various colorants, lubricants, release agents, nucleating agents, antistatic agents,
Other surfactants, heterogeneous polymers, organic improvers and the like. In addition, as long as the performance of the resin material aimed at by the present invention is not significantly reduced, one or two kinds of fibrous or plate-like fillers such as inorganic, organic, and metal or other powdery fillers may be used. Seed mixtures can also be used.

Next, the resin material or molded article of the present invention is easily prepared by a known method generally used as a conventional resin material preparation method. For example, after mixing each component, it is kneaded and extruded with a single-screw or twin-screw extruder,
A method of preparing pellets and then molding, a method of once preparing pellets (master batch) having different compositions, mixing (diluting) the pellets in a predetermined amount and subjecting them to molding, and obtaining a molded article of a desired composition after molding. Etc. can be used.
In addition, in the preparation of such a resin material, pulverizing part or all of the acetal resin as a base, mixing this with other components, and then performing extrusion or the like is effective in improving the dispersibility of the additive. This is the preferred method.

[0012]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, but it should not be construed that the present invention is limited thereto.

The evaluation items and evaluation methods are as follows. 1) Vicat softening point Measured according to ASTM D-1525. 2) Friction coefficient: Pressurized 10 kg using a Suzuki type friction / wear tester
/ cm ² , linear velocity 30 cm / sec, contact area 2.0 cm ² , and dynamic friction coefficient was measured using metal (S55C) as a mating material. 3) Practical test: FIGS. 2 and 3 using the tester shown in FIG.
Acetal resin friction and abrasion test piece (φ30mm × φ
9.5mm x 1.5mm) and felt (φ22mm × φ16mm × 1mm; special hard No.5 made by Fujiko Ltd.) are slid at a contact load of 1.4kg at a rotation speed of 31.5rpm for 48 hours, and the fluctuation value of rotation torque ( The difference between the maximum torque and the minimum torque of the average rotation torque value) was measured using a load cell. The torque fluctuation width (difference between the maximum torque and the minimum torque) per rotation was evaluated as a torque stick (initial, 48 hours later).

Examples 1 to 6 and Comparative Examples 1 to 5 Various acetal resins and fatty acid esters shown in Table 1 were used in Table 1.
And then melt-kneaded with a twin-screw extruder to prepare a pellet-shaped composition. Next, a test piece was prepared from the pellet by injection molding and evaluated. For comparison, those containing no fatty acid ester, those containing a small amount (0.5% by weight) of a fatty acid ester, those containing a stearyl stearate not belonging to the requirements of the present invention as component (B), and those shown in Table 1 The acetal resin shown was evaluated by adding the component (B) of the present application. Table 1 shows the results.

[0015]

[Table 1]

[0016]

As is clear from the above description and Examples, the resin material of the present invention comprising a specific fatty acid ester mixed with an acetal resin has a remarkably improved sliding property against felt, and is suitable for use in felt clutches. It is preferable as a molded article. Therefore, the molded article of the present invention is suitable for applications requiring severe sliding characteristics, for example, felt clutch mechanism parts for VTR, 8 mm video, audio cassette and the like.

[Brief description of the drawings]

FIG. 1 is a diagram showing a torque measuring tester used in a practical test in an example.

FIG. 2 is a view showing the shape of an acetal resin friction and wear test piece used in a practical test in Examples.

FIG. 3 is a view showing a cut shape of an acetal resin friction and wear test piece used in a practical test in Examples.

[Explanation of symbols]

 1: Felt 2: Acetal resin friction and wear test piece

Claims (5)

(57) [Claims] Claims: 1. A blend of (A) 100 parts by weight of an acetal resin and 1.0 to 10.0 parts by weight of (B) at least one kind of a polyhydric alcohol fatty acid ester having a melting point of 40 ° C. or higher. A molded article for felt clutch made of acetal resin, which is formed by molding a resin material having a Vicat softening point of 160 ° C or higher as measured by a method according to the standard. 2. The acetal resin according to claim 1, wherein (B) the polyhydric alcohol fatty acid ester is an ester of stearic acid and / or behenic acid with a polyhydric alcohol selected from glycerin, ethylene glycol and polyethylene glycol. Molded product for felt clutch. 3. The molded article for an acetal resin felt clutch according to claim 1, wherein (B) the polyhydric alcohol fatty acid ester has a melting point of 60 ° C. or higher. 4. The molded article for an acetal resin felt clutch according to claim 1, wherein the (A) acetal resin is an oxymethylene homopolymer. 5. A molded article for an acetal resin felt clutch according to claim 1, which is a felt clutch mechanism part for a VTR, 8 mm video, audio cassette or typewriter.