JP2970691B2 - 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 bearings, gears, cams, rollers, sliding plates, pulleys, levers for high quality required for electric / electronic equipment, office equipment, automobiles, industrial equipment, etc. The present invention relates to a polyacetal resin composition having excellent self-lubricating properties suitable as a material for sliding parts such as guides.

[0002]

2. Description of the Related Art Polyacetal is extremely useful as a material for sliding parts such as gears because of its good wear characteristics and light weight. In order to further improve the friction and wear properties of the conventional polyacetal, a method of impregnating and mixing oil into a polyacetal resin (for example, Japanese Patent Publication No. 46-5321, Japanese Patent Publication No.
No. 42217), a method of mixing polytetrafluoroethylene (for example, JP-B-46-30590), and a method of mixing high-density polyethylene (for example, JP-B-46-4145).
No. 6), and the like. However, the method of impregnating and mixing oil has a drawback that oil retention is poor and moldability is poor. The method of mixing polytetrafluoroethylene has the disadvantages that it is very expensive and that a mold deposit tends to be formed during molding. The method of mixing polyethylene is inferior in dispersibility of polyethylene in polyacetal, and has a problem of easily causing delamination.

Japanese Patent Publication No. 47-29374 discloses a method of mixing silicone oil and ultrahigh molecular weight polyethylene with a synthetic resin (which is considered to include polyacetal). And poor oil bleeding, resulting in poor moldability and poor molded product dimensional accuracy and surface appearance. Japanese Patent Publication No. 50-31887 discloses a method in which a lubricant is absorbed into an ethylene-vinyl acetate copolymer and mixed with a resin (which is considered to include polyacetal).
When the lubricant is silicone oil, it is also difficult to suppress bleeding from the surface of the molded product, and it is inferior in moldability. JP-B-52-28130 and JP-B-52-28131 disclose a composition in which polyacetal, a lubricant, and polyethylene having a molecular weight of 10,000 or more and less than 500,000 are added in a weight ratio of the lubricant to the polyethylene of 4 to 15. It is shown. As the lubricant, there is no description of using a silicone oil only with a hydrocarbon oil, but the silicone oil has a disadvantage that the affinity between polyethylene and the silicone oil is poor and the oil oozes out during molding.

In Japanese Patent Publication No. 62-253650,
A composition comprising 2 to 30% of a polyacetal and a polyethylene having a melt index of 10 or more has been proposed. Also in this case, the sliding characteristics and the noise during sliding are still insufficient, and furthermore, it is necessary to use a large amount of polyethylene.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to improve the disadvantages of the conventional polyacetal resin material and to provide a resin composition having excellent self-lubricating properties. That is, a first object of the present invention is to provide a polyacetal resin composition having excellent friction and wear resistance. A second object of the present invention is to provide a polyacetal resin composition having excellent practical moldability. Specifically, it provides a material that satisfies such properties as good penetration into screws during molding, low mold / deposit, good recyclability, and low oil bleeding from the molded product surface. It is in. A third object of the present invention is to provide a low-noise polyacetal resin composition. This is due to the recent strong demand for low noise of sliding parts such as gears, bearings, cams, rollers, etc. in the fields of electronic equipment, electric equipment, office equipment, industrial equipment, automobiles, etc. It is something to deal with.

[0006]

Means for Solving the Problems The present inventors have conducted various studies to solve the above-mentioned problems, and as a result, have found that a polyacetal resin composition having a specific composition can achieve the above object. Was completed. That is, the present invention provides 99.8 to 70 parts by weight (%) of polyacetal,
It is composed of a polyacetal resin composition containing 0.1 to 25 parts by weight (%) of polyethylene wax and 0.1 to 5 parts by weight (%) of silicone oil. The polyacetal used in the composition of the present invention is a homopolymer mainly composed of an oxymethylene chain obtained by a polymerization reaction using formaldehyde or trioxane as a main raw material, or a copolymer with a cyclic ether compound, and has a melting index (MI) [MI] [ ASTEM-D1238:
190 ° C. under a load of 2.16 kg] means 0.01 to 60. The polyacetal is usually subjected to a stabilization treatment against decomposition from a molecular end, and then added with a stabilizer, an antioxidant, and the like, and the shape thereof is powder, flake, pellet, or the like.

The polyethylene wax used in the composition of the present invention means a low-molecular-weight polyethylene, a low-molecular-weight polyethylene copolymer, or a modified polyethylene wax of a type in which a polar group is introduced by oxidizing or acid-modifying them. . Its number average molecular weight is preferably from 500 to 15,000, more preferably 1 to 1.
000 to 10,000. Polyethylene wax of low molecular weight polyethylene and low molecular weight polyethylene copolymer, a method of directly polymerizing ethylene or ethylene and an α-olefin with a Ziegler catalyst or the like, a method of obtaining high molecular weight polyethylene or a by-product during the production of the copolymer, It can be produced by a method of thermally decomposing high molecular weight polyethylene or a copolymer. Among them, a copolymer type polyethylene wax of 50 to 99 mol% of ethylene and 1 to 50 mol% of α-olefin is preferable. Particularly preferably, the α-olefin is propylene. The modified polyethylene wax means the above-mentioned low-molecular-weight polyethylene, low-molecular-weight polyethylene copolymer, or a modified polyethylene wax obtained by oxidizing or acid-modifying them. The oxidative modification is carried out by treating the wax with a peroxide or oxygen to introduce a polar group such as a carboxyl group or a hydroxyl group. Also,
The acid conversion treatment is performed by introducing a polar group such as a carboxyl group or a sulfonic acid group by treating the wax with an inorganic acid, an organic acid or an unsaturated carboxylic acid in the presence of peroxide or oxygen, if necessary. Is done. These polyethylene waxes are commercially available under the names of general-type high-density polyethylene wax, general-type low-density type polyethylene wax, low-oxidation-type polyethylene wax, high-oxidation-type polyethylene wax, acid-modified polyethylene wax or special-monomer modified molding. , Can also be easily obtained.

[0008] The compounding amount of polyethylene wax is 0.1
-20% by weight, preferably 0.5-5% by weight. When the amount exceeds 20% by weight, the mechanical performance of the polyacetal resin decreases, and when the amount is less than 0.1% by weight, the intended effect of the present invention is small. Polyethylene wax may be used alone or in combination of two or more.

The silicone oil used in the present invention can be arbitrarily selected from commonly known ones. For example, silicone oil composed of polydimethylsiloxane, silicone oil in which a part of the methyl group of polydimethylsiloxane is substituted with a phenyl group, part of the methyl group of polydimethylsiloxane is substituted with hydrogen or an alkyl group having 2 or more carbon atoms Silicone oil in which some of the methyl groups of polydimethylsiloxane are substituted with halogenated phenyl groups, silicone oil in which some of the methyl groups of polydimethylsiloxane are substituted with fluoroester groups, and epoxy groups Epoxy-modified silicone oil such as polydimethylsiloxane, amino-modified silicone oil such as polydimethylsiloxane having an amino group, alcohol-modified silicone oil such as polydimethylsiloxane having an alcoholic hydroxyl group, dimethylsilo An alkylaralkyl silicone oil such as sun and phenylmethylsiloxane, a polyether-modified silicone oil such as polydimethylsiloxane having a structure in which a part of the methyl group of a dimethylsiloxane unit is substituted with a polyether, a methyl group of a dimethylsiloxane unit And alkyl aralkyl polyether-modified silicone oils such as a polymer of a siloxane having a structure in which a part thereof is substituted with a polyether and phenylmethylsiloxane. These silicone oils preferably have a viscosity at 25 ° C. of 0.1%.
65 million or more Stokes (stokes) or less, more preferably 10 to 100,000 stokes (stokes) below.

[0010] The silicone oil is used alone or in combination of two or more. The amount added is 0.1 to 5% by weight, preferably 0.2 to 2% by weight of the total composition weight. If the amount is less than 0.1% by weight, sufficient friction and wear resistance cannot be obtained. On the other hand, if it exceeds 5% by weight, the molding processability of the composition is inferior and the appearance is deteriorated. The weight ratio of silicone oil to polyethylene wax is preferably in the range of 0.01 to 4, more preferably in the range of 0.05 to 2.

The method of mixing with polyacetal, polyethylene wax and silicone oil is not particularly limited, and a known mixing or blending method can be employed. The thus obtained composition of the present invention may be mixed with a known thermoplastic polymer, an inorganic additive, a pigment, a filler, a glass fiber, a carbon fiber, a whisker, a slipping inhibitor and the like according to the intended use. it can.

Hereinafter, the present invention will be described in detail with reference to Examples and Comparative Examples, but the present invention is not limited thereto. In addition, the method of composition evaluation is as follows. Injection molding: cylindrical thrust test specimen, cylinder temperature 2
00 ° C, mold temperature 80 ° C, molding cycle 30 seconds. Dynamic friction coefficient: Using a thrust-type friction and wear tester manufactured by Orientec, the case where the counterpart material was a steel material (S45C) and the same material was measured. Noise during sliding: Using the same friction and wear tester as above, surface pressure 5
kg / cm ² , linear velocity 10 cm / sec, and noise were measured at a distance of 7 cm between the thrust test piece and the microphone, between the same materials, and in decibel “A”.

[0013]

EXAMPLES Example 1 Polyacetal [Mitsubishi Gas Chemical, Iupital F20-
01, MI 9 g / 10 min], 96 parts by weight, polyethylene wax (manufactured by Mitsui Petrochemical, High Wax MH8051)
E, molecular weight 6000, high acid value type, acid value 10, ethylene-
Propylene copolymer type] 3.0 parts by weight, and silicone oil [Shin-Etsu Silicone, polydimethylsiloxane,
KF-96-50000, viscosity 50000cs] 1.0
Parts by weight (see Table 1 ) were mixed and homogenously mixed using a super mixer (manufactured by Kawada Seisakusho), and then pelletized using a twin-screw extruder (PCM-30, manufactured by Ikegai Iron Works). Subsequently, a cylindrical thrust test piece was molded using an in-line screw type injection molding machine (manufactured by Nissei Plastics Industries, PS-40), and the dynamic friction coefficient and noise during sliding were measured. Table 2 shows the measurement results. From Table 2 , the synergistic effect of polyethylene wax and silicone oil
It is known that excellent self-lubricating properties were obtained.

Example 2 In Example 1, 94 parts by weight of polyacetal was used, and instead of polyethylene wax MH8051E, MH400P [manufactured by Mitsui Petrochemical, high wax, molecular weight 4000, general high density type, acid value 0] 5.0 Except for using parts by weight (see Table 1 ), all treatments were the same as in Example 1 to obtain the results shown in Table 2 .

Example 3 In Example 1, 94 parts by weight of polyacetal was used, and instead of polyethylene wax MH8051E, MH1100P [manufactured by Mitsui Petrochemical, high wax, molecular weight 11,000, high density type, acid value 0] 5.0 Except for using parts by weight (see Table 1 ), all treatments were the same as in Example 1 to obtain the results shown in Table 2 .

Example 4 In Example 1, the polyethylene wax MH805 was used.
Except for using MH4400G [manufactured by Mitsui Petrochemical, High Wax, molecular weight 4000, general high-density type, acid value 0] instead of 1E [see Table 1 ], all were treated in the same manner as in Example 1 to obtain Table 2 . The results shown were obtained.

Example 5 In Example 1, the polyethylene wax MH805 was used.
2. MH720P [manufactured by Mitsui Petrochemical, high wax, molecular weight 7400, general high density type, acid value 0] instead of 1E
5 parts by weight and silicone oil KF-96-5000
0 KF-96-12500 instead of using [Etsu Silicone Co., viscosity 12500cs] 0.5 part by weight Table
1 ), the results were as shown in Table 2 .

Example 6 In Example 5, 94 parts by weight of polyacetal was used, and instead of polyethylene wax MH720P, M was used.
Except that 5.5 parts by weight of H310MP (manufactured by Mitsui Petrochemical, High Wax, molecular weight 3000, low acid value type, acid value 1) was used [see Table 1 ], all treatments were performed in the same manner as in Example 1 to obtain a table.
The results shown in FIG.

Example 7 Example 1 was repeated except that 98 parts by weight of polyacetal was used and MH405MP [manufactured by Mitsui Petrochemical, high wax, molecular weight 4000, low acid value, acid value 1] was used instead of polyethylene wax MH8051E. Using 5 parts by weight, instead of silicone oil KF-96-50000, KF-96-3000 [manufactured by Shin-Etsu Silicone, viscosity 3
000 cs] except that 0.5 part by weight was used (see Table 1 ), and the same treatment as in Example 1 was carried out to obtain the results shown in Table 2 .

Example 8 In Example 7, 96 parts by weight of polyacetal and MH405 instead of polyethylene wax MH405MP were used.
1E [Mitsui Petrochemical, high wax, molecular weight 320
0, high acid value type, acid value 12] 3.5 parts by weight [ Table
1 ), the results were as shown in Table 2 .

Example 9 In Example 1, the polyethylene wax MH805 was used.
Instead of 1E, use MH420P (manufactured by Mitsui Petrochemical, High Wax, molecular weight 4000, general low density type, acid value 0), and use KF-96-12500 [manufactured by Shin-Etsu Silicone, instead of silicone oil KF-96-50000. Except for using [Viscosity 12,500 cs] [see Table 1 ], all treatments were the same as in Example 1 to obtain the results shown in Table 2 .

Example 10 In Example 9, the polyethylene wax MH420 was used.
Except for using MH2203A (manufactured by Mitsui Petrochemical, High Wax, molecular weight 2700, acid-modified type, acid value 30) instead of P (see Table 1 ), all treatments were carried out in the same manner as in Example 9 and shown in Table 2 . The result was obtained.

Example 11 In Example 1, a polyethylene wax MH805 was used.
Except for using HW190P [Hoechst, Hoechst wax, molecular weight 9000, general high-density type, acid value 0] instead of 1E [see Table 1 ], all were treated in the same manner as in Example 1 and the results shown in Table 2 were obtained. I got

Example 12 In Example 1, a polyethylene wax MH805 was used.
Except for using HW191E [manufactured by Hoechst, Hoechst wax, molecular weight 9000, high acid value, acid value 16] instead of 1E [see Table 1 ], all were treated in the same manner as in Example 1 and the results shown in Table 2 were obtained. I got

Example 13 In Example 1, the polyethylene wax MH805 was used.
Except for using HW136E [manufactured by Hoechst, Hoechst wax, molecular weight 3000, high acid value type, acid value 60] instead of 1E [see Table 1 ], all treatments were performed in the same manner as in Example 1 and the results shown in Table 2 were obtained. I got

Example 14 In Example 1, 95 parts by weight of polyacetal and HW522 instead of polyethylene wax MH8051E were used.
E [Hoechst, Hoechst wax, molecular weight 2000,
High acid value type, acid value 25] 3.0 parts by weight and silicone oil KF-96-30 instead of KF-96-50000
0000 [Made by Shin-Etsu Silicone, viscosity 300000 cs]
Except for using 2.0 parts by weight [see Table 1 ], all treatments were the same as in Example 1 to obtain the results shown in Table 2 .

[0027] Comparative Example 1 In Example 1, 99 parts by weight of polyacetal was used.
Use silicone oil KF-96-50000
All were the same as in Example 1 except that they were not performed (see Table 1).
Processing gave the results shown in Table 2.

[0028] In Comparative Example 2 Example 1, using the polyacetal 97 parts by weight, except were not using polyethylene wax MH8051E [see Table 1], shown in Table 2 was treated in the same manner as in Example 1 The result was obtained.

Comparative Example 3 In Example 1, the polyethylene wax MH805 was used.
1E and silicone oil KF-96-500
Except that 00 was not used (see Table 1 ), all treatments were the same as in Example 1 to obtain the results shown in Table 2 .

Comparative Example 4 In Example 1, the polyethylene wax MH805 was used.
Except for using high molecular weight polyethylene having a molecular weight of 100,000 [manufactured by Mitsui Petrochemical, Hyzex 2200J] in place of 1E [see Table 1 ], all treatments were performed in the same manner as in Example 1 to obtain a table.
The results shown in FIG.

[0031]

The self-lubricating polyacetal composition of the present invention is a mixture of polyacetal and polyethylene wax and silicone oil. The synergistic effects of these are extremely excellent in friction and wear properties, moldability and low processability. It has a noise characteristic and can be suitably used as a material for various sliding parts requiring high performance.

[0032]

[Table 1]

[0033]

[Table 2]

──────────────────────────────────────────────────続 き Continuing on the front page (72) Kazuaki Ochiai 5-6-1, Higashi-Hachiman, Hiratsuka-shi, Kanagawa Prefecture Inside the Plastics Center of Mitsubishi Gas Chemical Company (72) Inventor Akiyoshi Shibata 5-6-Higashi-Yawata, Hiratsuka-shi, Kanagawa Prefecture No. 2 Mitsubishi Plastics Corporation Plastics Center (72) Inventor Toshikatsu Kawada 5-6-1 Higashi-Hachiman, Hiratsuka-shi, Kanagawa Pref. Mitsubishi Gas Chemical Co., Ltd. Plastics Center Examiner Hatsuo Miyasaka (58) (Int.Cl. ⁶ , DB name) C08L 59/00-59/04 C08L 23/04-23/06 C08L 83/04

Claims (4)

(57) [Claims] (1) 99.8 to 80 parts by weight of a polyacetal,
A polyacetal resin composition comprising 0.1 to 20 parts by weight of a polyethylene wax and 0.1 to 5 parts by weight of a silicone oil. 2. A polyethylene wax having a number average molecular weight of 5
The polyacetal resin composition according to claim 1, which is a copolymer of 50 to 99 mol% of ethylene and 1 to 50 mol% of α-olefin. 3. A polyethylene wax having a number average molecular weight of 5
The polyacetal resin composition according to claim 1, wherein the polyacetal resin composition has a polar group introduced by oxidation modification or acid modification. 4. The polyacetal resin composition according to claim 1, wherein the weight ratio of the silicone oil to the polyethylene wax is from 0.01 to 4.