JP3149151B2 - High slidability polyacetal resin composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-sliding polyacetal which is extremely excellent in friction and wear characteristics with respect to both resin and metal for a long period from the initial stage in point contact reciprocating sliding, and has less squeaking noise. It is intended to provide a resin composition.

[0002]

2. Description of the Related Art In general, polyacetal resin has excellent mechanical strength, fatigue resistance, electrical properties, etc., and is therefore widely used as an engineering resin in gears, bearings, other mechanical parts, automobiles, home electric appliances, and the like. ing. In addition, polyacetal resins are also extremely excellent in self-lubricating properties, and there are many uses where the characteristics are utilized.

[0003] However, in order to increase the functionality and diversification of polyacetal resin applications, the self-lubricating properties inherent in polyacetal resins and the lubricating properties of compositions obtained by simply adding a general lubricant to polyacetal resins alone are not enough. The required applications are not always sufficient and cannot be met. In particular, for electric parts and the like, materials capable of maintaining low friction and low wear characteristics for both resin and metal in point contact reciprocal sliding for a long period of time are desired.

[0004] As a prior art, Japanese Patent Publication No. 3-69378 discloses an improvement in frictional properties and abrasion in thrust contact sliding of a polyacetal resin comprising a composition of a silicone oil and an ester lubricant in a polyacetal resin. It has been known. However, with this composition, the point contact reciprocating slidability has not been able to obtain a sufficient value.

[0005] JP-A-4-234450 discloses a polyacetal resin composition containing a polyacetal resin, a silicone gum having a viscosity of 1 × 10 ⁶ CST or more, and a polytetrafluoroethylene resin, and a slide comprising the composition. It discloses that the member has excellent friction and wear resistance in surface contact thrust slidability under high speed and high load, and further has excellent moldability. However, there is still room for improvement in slidability in point contact reciprocal sliding. Further, the above publication does not disclose or suggest that a polyacetal resin homopolymer and a polyacetal resin copolymer in the present invention are used in combination and further a silicone oil is used in combination.

In Japanese Patent Publication No. 57-10144, a method of adding silicone oil and silicone gum to a polyacetal resin is disclosed in Japanese Patent Application Laid-Open No. 63-277263 [US Pat. No. 4,874,807 (corresponding Chinese Patent Application No. 88-026).
No. 19)] In the official gazette, 150,
Although a method of adding a silicone oil having a viscosity of 000 CST or more is disclosed, even in these methods, a polyacetal resin homopolymer and a polyacetal resin copolymer as in the present invention are used in combination, and further a silicone oil is combined. There is no description or suggestion about a technique that is excellent in point contact reciprocal sliding property.

[0007]

SUMMARY OF THE INVENTION According to the present invention, in the point contact reciprocating sliding test, low friction and low abrasion performance of both a resin and a metal are maintained for a long period of time. The present invention relates to a polyacetal resin composition provided with mobility. More specifically, in the reciprocating slidability by point contact, for both resin and metal,
An object of the present invention is to provide a polyacetal resin composition which exhibits an extremely low friction coefficient at an early stage, maintains the low friction coefficient for a long period of time, is excellent in abrasion characteristics, and is excellent in slidability with less generation of squeak noise.

[0008]

Means for Solving the Problems As a result of intensive studies on the above problems, the present inventors control the affinity between silicone oil and polyacetal resin by using a polyacetal resin homopolymer and a polyacetal resin copolymer in combination. It was found that the above problems could be solved, and the present invention was completed.

That is, the present invention comprises (A) a polyacetal resin homopolymer, (B) a polyacetal resin copolymer and (C) a silicone oil, and (A) and (B)
And (C) a polyacetal resin composition characterized in that X, Y, and Z are in the following ranges when the weight ratio (%) to the total amount of each component is X, Y, and Z, respectively.

[0010] Hereinafter, the polyacetal resin composition of the present invention will be described in detail. The (A) polyacetal resin homopolymer used in the composition of the present invention is produced from a formaldehyde monomer or a cyclic oligomer such as a trimer (trioxane) or tetramer (tetraoxane) thereof as a raw material. A polyoxymethylene resin consisting essentially of repeating oxymethylene units. Further, a preferred polyacetal resin homopolymer has a melt index (ASTM D1238-57TE, hereinafter abbreviated as MI) of 5 to 50 g / 10 minutes, and more preferably MI = 3.
0 to 40 g / 10 minutes.

The (B) polyacetal resin copolymer is a carbon number produced from the above raw materials and a cyclic ether such as ethylene oxide, propylene oxide, epichlorohydrin, 1,3-dioxolan, glycol formal and diglycol formal. It is a polyoxymethylene resin containing 0.1 to 4% by weight of 2 to 8 oxyalkylene units. Preferred polyacetal resin copolymers have an introduced amount of ethylene oxide of 1 to 4% by weight, more preferably 2 to 4% by weight.
３3% by weight. The MI is 5 to 50.
g / 10 minutes is preferable, and 7 to 15 g / 10 minutes is more preferable.

(A) used in the composition of the present invention
The blending amount of the polyacetal resin homopolymer and the copolymer (B) is such that the weight ratio (X) of the homopolymer to the total amount of the composition is 77.0 % by weight or more and less than 97.9% by weight, and the weight ratio (Y) of the copolymer is 2%. More than 0.0% by weight 2
0.0 % by weight or less , but polyacetal resin homopolymer
Less than 77.0% by weight of rimer or polyaceter
When the amount of the resin copolymer is 2.0% by weight or less, excellent long-term lubrication performance cannot be obtained in the point contact reciprocating sliding test of the present invention. Further, even when the blending amount of the polyacetal resin homopolymer is 97.9% by weight or more, the blending amount of the polyacetal resin copolymer exceeds 20.0 % by weight.
In the case of point contact reciprocating sliding high temperature test,
I can't see good.

Further, the compounding amount of the polyacetal resin copolymer is 2.0% from the viewpoints of long-term lubrication characteristics in a point contact reciprocating sliding test and generation of squeak noise in a point contact reciprocating sliding high temperature test. The content is preferably more than 20.0 % by weight and more preferably more than 40.0% by weight.

Next, (C) used in the composition of the present invention
Silicone oils are dimethylpolysiloxanes or those in which some of the methyl groups have been replaced by one or more of hydrogen, phenyl groups, halogenated phenyl groups, halogenated alkyl groups, and the like. It is a silicone having no structure. Two or more of these silicone oils may be used in combination. A preferred silicone oil is dimethylpolysiloxane or a copolymer of dimethylsiloxane and methylphenylsiloxane, both having a preferred average degree of polymerization of 1,000 to 1,000.
5,000. Further preferred average degree of polymerization,
3,000-5,000. Preferred copolymers are those having 1 to 20 mol% of methylphenylsiloxane units.

The amount of the silicone oil is 0.1 to 1 in weight ratio (Z) of the silicone oil to the total amount of the composition.
5% by weight. If the amount is less than 0.1% by weight,
The improvement of the long-term lubricating performance of the present invention is hardly observed. When the content exceeds 15% by weight, mechanical properties (particularly, bending strength or flexural modulus) are reduced, moldability is deteriorated, and peeling phenomenon occurs in a molded product. Becomes intense. The blending amount of the silicone oil is preferably from 1 to 10% by weight, and more preferably from 3 to 5% by weight.

The polyacetal resin composition of the present invention is substantially composed of three components, a polyacetal resin homopolymer, a polyacetal resin copolymer, and a silicone oil. In order to provide a known heat stabilizer, nucleating agent, release agent, antistatic agent, ultraviolet absorber, light stabilizers such as hindered amine compounds, antioxidants such as hindered phenol compounds, pigments of the present invention It can be added in a range that does not impair the purpose.

Next, the polyacetal resin composition of the present invention can be prepared at a temperature not lower than the melting point of the polyacetal resin by a known method, for example, a device usually used for kneading a resin melt such as a kneader, a roll mill or an extruder. It can be prepared by melt-kneading. Preferably, the silicone oil is fed and fed to the bottom of the extruder or to the vent port using a plunger pump, gear pump, snake pump, or the like. Further, when it is necessary to lower the viscosity in accordance with the capacity of the pump, it is preferable to use the pump and the feed tank by preheating and heating them.

The composition of the present invention is excellent in lubrication property of point contact reciprocating sliding and low squeal sound. The polyacetal resin fat composition of the present invention can be used for AV (Audio Visual), OA
(Office Automation) Used suitably for equipment parts.
Among them, it is suitable for cam gears, gears, bearings, levers, key stems, cams, ratchets, and rollers.

Particularly, it is suitable as a cam gear material used as a VTR (Video Tape Recorder) part.

[0020]

EXAMPLES The present invention will be further described below with reference to examples, but the present invention is not limited by these examples. The method for evaluating lubricity will be described. (1) The thrust type surface contact slidability was evaluated using a Suzuki type friction and wear tester (manufactured by Toyo Seiki Co., Ltd.). The measurement conditions and evaluation criteria are shown below.

(Measurement conditions) Load: 2 kgf / cm ² (contact area: 2 cm ² ), linear velocity: 6 cm / sec, environmental temperature: 23 ° C. Counter material: resin: polyacetal resin (Tenac (trademark) manufactured by Asahi Kasei Kogyo Co., Ltd.) Name) C4520), cylindrical wappa molded product (3oz molding machine: manufactured by Sumitomo Heavy Industries, Ltd.)
Nestal Promat 165 /
Molding was carried out at a mold temperature of 70.degree. ) Metal: SUS304 (cylindrical) Sample for evaluation: Cylindrical wappa molded product (molded at a mold temperature of 70 ° C. by the above 3 oz molding machine), after molding 23
The sample was left for 48 hours in an atmosphere at 50 ° C. and a humidity of 50%, and then used for measurement.

(Evaluation criteria) Friction characteristics Under the above conditions, the friction coefficient immediately after the start of measurement (hereinafter referred to as
μ), and μ at 24 hours after the start of the measurement. The smaller the value of μ, the better the friction performance. Further, μ immediately after the start of the measurement is expressed as an initial value, and μ after 24 hours is expressed as a long-term friction performance.

(2) The point contact reciprocating slidability was evaluated using a reciprocating friction and wear tester (AFT-15MS type, manufactured by Tosoh Seimitsu Co., Ltd.). The measurement conditions and evaluation criteria are shown below. (Measurement conditions) Load: 2 kg, reciprocating speed: 10 mm / sec, reciprocating distance: 20 mm, ambient temperature: 23 to 80 ° C. Counter material: Resin: polyacetal resin (Tenak (trade name) C4520, manufactured by Asahi Kasei Kogyo Co., Ltd.) Molded product with 5φ × tip R = 2.5 (1 oz molding machine: molded with a mold temperature of 70 ° C. using TI-30G manufactured by Toyo Machine Metal Co., Ltd.) Metal: steel ball (SUS304) 5φ × tip R = 2.5 Evaluation sample: 70 mm × 50 mm × 3 mmt flat plate molded product (5 oz molding machine: IS 100E manufactured by Toshiba Machine Co., Ltd.)
-3A at a mold temperature of 70 ° C. ), Atmosphere after molding at 23 ° C and 50% humidity
The sample was left for 48 hours in an atmosphere and then used for measurement.

(Evaluation Criteria) Friction Characteristics Under the above conditions, the number of reciprocating movements was one, 1,000 times.
At 30,000 times. The smaller the value of μ, the better the friction performance. The evaluation result when the number of reciprocating motions is 1 is represented as initial friction performance, and the evaluation result when 30,000 times is performed is represented as long-term friction performance.

Under the above conditions, the maximum wear depth (μm) of the molded article when the number of reciprocations was 30,000 was measured with a surface roughness meter (Tokyo Seimitsu Surfcom 570-A-3D). The value was taken as the amount of wear. The smaller the wear amount (μm), the better the wear performance. The evaluation result when the number of reciprocating motions is 30,000 is expressed as long-term wear performance.

The point contact reciprocating sliding test is close to a form in which sliding parts such as cams, gears and levers actually rub against the mating material, and is more practical than the thrust type surface contact sliding test (1). It is a closer evaluation. (3) Kisimi sound When the point contact reciprocating sliding tester is operated reciprocally at a temperature of 23 ° C or 23 to 80 ° C, the squishy sound (squeak sound) is generated at a position 50 cm away from the operating place.
The temperature at which this occurred was heard with human ears.

[0027]

Examples 1-4, 9-19 The preparation of the composition was carried out using polyoxymethylene homopolymer powder having acetylated at both ends (MI = 35 g / 10 prepared by a known method described in U.S. Pat. No. 2,998,409). Powder) and a polyoxymethylene copolymer of 2.8% ethylene oxide (MI = 10 g / 10 min pellets prepared by known methods described in US Pat. No. 3,027,352).
100 parts blended with the composition of 2,2'-
Using a pellet prepared by adding 0.25 parts of methylene bis- (4-methyl-6-tert-butylphenol),
The silicone oil was granulated using a 30φ twin-screw extruder by feeding the silicone oil directly under the hopper of the extruder with a snake pump preheated and heated to 100 ° C.

The silicone oil used was a polydimethylpolysiloxane having an average degree of polymerization of 1,000 (hereinafter abbreviated as silicone oil (A)) and an average degree of polymerization of 2,000 (hereinafter silicone oil (B)). Abbreviation),
3,000 (hereinafter abbreviated as silicone oil (C)),
4,000 (hereinafter abbreviated as silicone oil (D)),
5,000 (hereinafter abbreviated as silicone oil (E)),
Alternatively, it is a copolymer of dimethylsiloxane and methylphenylsiloxane having an average degree of polymerization of 4,000 (hereinafter abbreviated as silicone oil (F)) having 2.5 mol% of methylphenyl units.

The structural formulas of the silicone oils (A), (B) and (C) are shown below.

[0030]

Embedded image

The structural formulas of the silicone oils (D), (E) and (F) are shown below.

[0032]

Embedded image

The evaluation results of the experiment are shown in Tables 1, 2, and 3. As a result, it can be seen that μ in the thrust type test shows a low value for resin and metal. Further, in the point contact reciprocating sliding test, μ from the initial stage to the long period for resin and metal is much lower. In addition, the amount of wear was extremely small, and in the point contact reciprocal sliding according to the present invention, a low μ was initially exhibited, the μ was maintained for a long period of time, and the wear characteristics were excellent. Furthermore, there was no problem with the moldability of the present composition, and during the evaluation of lubricity at 23 ° C., no squeaking noise or the like was generated.

In Examples 1 to 4 and 14 to 19, the generation of kissing noise was similarly evaluated under the conditions of 23 to 80 ° C.

In Example 19, instead of the silicone oil (E) used in Example 18, a silicone oil (F) having the same average degree of polymerization was blended to evaluate the lubricating performance. Silicone oil (F) showed better performance than silicone oil (E).

[0036]

Comparative Examples 1 to 11 The polyacetal resin homopolymer, copolymer and silicone oil used in the composition are the same as those described in Example 1. The production of the composition was adjusted in the same manner as in Example 1. The method of evaluating lubricity is the same as described in Example 1.

The evaluation results are shown in Tables 4 and 5. Comparative Examples 1 and 2 in which the polyacetal resin is only a homopolymer or a copolymer are thrust-type tests and point-contact reciprocal sliding tests, and μ for resin and metal shows an absolutely high value in the long term from the initial stage. The amount of wear in the point contact reciprocating sliding test is extremely large, and there is generation of a squeaking sound at the time of measurement at 23 to 80 ° C. In addition, in Comparative Examples 3 to 9, in which the polyacetal resin is a mixture of a homopolymer and a copolymer, and the ratio of both is out of the range of the present invention, the results of the thrust test show that the friction coefficient is higher than that of Examples. Although not so bad, the point contact reciprocal sliding test shows that the low friction and low wear properties over the initial to long term are still large and insufficient. In addition, polyacetal resin copolymers
Comparative Example 11 in which the blending amount was out of the range of the present invention was
The friction and wear properties are excellent in the test and the point contact reciprocating sliding test.
However, the improvement of the Kisimi sound is insufficient.

[0038]

Comparative Example 10 The polyacetal resin homopolymer and copolymer used in the composition are the same as those described in Example 1. Also, the production of the composition was adjusted by the same operation as in the examples. For evaluation of bending properties, see ASTM
It measured according to D-790. The composition of Example 12 was compared with the bending characteristics, and the evaluation results are shown in Table 6. It can be seen that both the bending strength and the elastic modulus of the composition of Comparative Example 10 were significantly reduced. Furthermore, in the molded product for bending measurement, peeling (roughening of the surface) near the gate portion was severe.
(Compared with Example 12)

[0039]

[Table 1]

[0040]

[Table 2]

[0041]

[Table 3]

[0042]

[Table 4]

[0043]

[Table 5]

[0044]

[Table 6]

[0045]

The composition of the present invention is excellent in point contact reciprocating sliding lubricating property and low squeaking sound property.
Visual) and OA (Office Automation) equipment parts. Among them, it is suitable for cam gears, gears, bearings, levers, key stems, cams, ratchets, and rollers. In particular, it is suitable as a cam gear material used as a VTR (Video Tape Recorder) part.

Claims (8)

(57) [Claims] 1. A method comprising: (A) a polyacetal resin homopolymer, (B) a polyacetal resin copolymer and (C) a silicone oil, wherein (A), (B) and (C)
The weight ratio (%) to the total weight of each component is represented by X and Y, respectively.
And X, wherein X, Y and Z are in the following ranges. Wherein (B) weight ratio of the polyacetal resin copolymer (Y) is, the polyacetal resin composition according to claim 1, wherein 4 to 10 wt%. (A) a polyacetal resin homopolymer having a melt index (ASTMD1238-57T);
3. The polyacetal resin composition according to claim 1, wherein the composition is 30 to 40 g / 10 minutes. 4. The polyacetal resin composition according to claim 1, wherein the polyacetal resin copolymer (B) has a melt index of 7 to 15 g / 10 minutes. 5. The silicone oil according to claim 1, wherein (C) the silicone oil is dimethylpolysiloxane or a copolymer of dimethylsiloxane and methylphenylsiloxane.
The polyacetal resin composition according to the above. 6. The polyacetal according to claim 1, wherein (C) the silicone oil is dimethylpolysiloxane having an average degree of polymerization of 3,000 to 5,000, or a copolymer of dimethylsiloxane and methylphenylsiloxane. Resin composition. 7. The polyacetal resin composition according to claim 1, wherein (C) the silicone oil is a polydimethylsiloxane containing 1 to 20 mol% of a methylphenylsiloxane unit. 8. The polyacetal resin composition according to claim 1, wherein the blending amount (weight ratio) of (C) silicone oil is 3 to 5% by weight.