COATING AGENT FOR OIL SEAL

Abstract

A coating agent for oil seal comprising 10 to 90 parts by weight in total of fluororesin particles having a particle size of 2 μm or less and filler particles other than fluororesin particles having a particle size of 0.5 to 30 μm, and 10 to 40 parts by weight of a wax having a melting point of 40 to 160° C., based on 100 parts by weight of isocyanate group-containing 1,2-polybutadiene, and being prepared as an organic solvent solution, wherein the fluororesin particles are used at a ratio of 20 to 80 wt. % of the total filler amount. The coating agent for oil seal can improve abrasion resistance while maintaining the roughness of a coating surface to which the coating agent is applied.

Claims

1. A coating agent for oil seal comprising 10 to 90 parts by weight in total of fluororesin particles having a particle size of 2 μm or less and filler particles other than fluororesin particles having a particle size of 0.5 to 30 μm, and 10 to 40 parts by weight of a wax having a melting point of 40 to 160° C., based on 100 parts by weight of isocyanate group-containing 1,2-polybutadiene, and being prepared as an organic solvent solution, wherein the fluororesin particles are used at a ratio of 20 to 80 wt. % of the total filler amount.

2. The coating agent for oil seal according to claim 1, wherein fluororesin particles having a particle size of 0.5 μm or less are used.

3. The coating agent for oil seal according to claim 1, wherein filler particles other than fluororesin particles having a particle size of 1 to 20 μm are used.

4. The coating agent for oil seal according to claim 1, wherein all the fillers are used at a rate of 40 to 80 parts by weight.

5. The coating agent for oil seal according to claim 1, wherein the fluororesin particles are used at a rate of 30 to 70 wt. % of the total filler amount.

6. The coating agent for oil seal according to claim 1, wherein the wax is used at a rate of 10 to 30 parts by weight.

7. An oil seal, which is subjected to coating treatment using the coating agent according to claim 1.

8. The oil seal according to claim 7, wherein after coating treatment, heat treatment is performed at 150 to 250° C. for 10 minutes to 24 hours.

9. The oil seal according to claim 7, wherein a contact angle between an oil seal surface and engine oil is less than 35°.

10. The oil seal according to claim 8, wherein a contact angle between an oil seal surface and engine oil is less than 35°.

Description

EXAMPLES

[0036] The following describes the present invention with reference to Examples.

Example 1

[0037]

TABLE-US-00001 Isocyanate group-containing 1,2- 200 parts by weight  polybutadiene (TP1001, produced by Nippon Soda Co., (100 parts by weight)  Ltd.; containing 50 wt. % of butyl acetate) Polymethylsilsesquioxane particles 30 parts by weight (Tospearl 130, produced by Momentive; particle size: 3 μm) Polytetrafluoroethylene particles 30 parts by weight (Fluon 172J, produced by AGC Sei Chemical Co., Ltd.; particle size: 0.2 μm) Paraffin wax (melting point: 100° C.) 20 parts by weight Butyl acetate (remnant) parts by weight Total 2000 parts by weight 

[0038] Each of the above components was mixed, and a coating agent solution comprising the butyl acetate solution was sprayed to vulcanized rubber with a thickness of 2 mm, to a thickness of 10 to 30 μm. After heat treatment at 200° C. for 10 hours, the contact angle, dynamic friction coefficient in oil, and abrasion resistance were measured or evaluated. In addition, the dispersibility of the coating liquid was also evaluated. Each of the parts by weight is represented by a part by weight of the solution, and the net part by weight of each component is shown in parentheses (the same applies to the following Examples and Comparative Examples).

[0039] Dispersibility: After the coating liquid was prepared, the precipitation speed of the fluororesin particles was visually confirmed. When no precipitation was observed after 10 minutes, this case was evaluated as ◯, and when precipitation was observed within less than 10 minutes, this case was evaluated as X.

[0040] Contact angle: Using Drop Master 500 (produced by Kyowa Interface Science Co., Ltd.), the contact angle to Engine Oil OW-20 was measured. A contact angle of less than 35° was evaluated as ◯, and a contact angle of 35° or more was evaluated as X.

[0041] Dynamic friction coefficient in oil: Using a surface property tester (HEIDON TYPE14DR, produced by Shinto Scientific Co., Ltd.), reciprocation was carried out under the following conditions, and the dynamic friction coefficient on the forward side was measured. A dynamic friction coefficient of less than 0.2 was evaluated as ◯, and a dynamic friction coefficient of 0.2 or more was evaluated as X.

Load: 50 g

[0042] Rate: 50 mm/min
Reciprocation distance: 50 mm
Indenter: a steel ball having a diameter of 10 mm
Oil type: Engine Oil OW-20
Note: The dynamic friction coefficient in oil is an evaluation correlated with the real system evaluation of oil seal. When the dynamic friction coefficient in oil using the above test piece is low, the real system evaluation using oil seal is supposed to be excellent.

[0043] Abrasion resistance: Using Friction Player FPR-2000 (produced by Rhesca. Co., Ltd.), a SUS pin with a diameter of 0.4 mm was pressed against the surface of the coating film at 80° C. under a load of 300 g in a dry state, and rotated at a linear speed of 400 mm/sec. Then, the distance until the coating film was peeled off to expose the rubber was measured. A distance of 0.1 km or more was evaluated as ◯, and a distance of less than 0.1 km was evaluated as X.

Example 2

[0044] In Example 1, the same amount (30 parts by weight) of amorphous silicon dioxide particles (Silica 6B, produced by Chuo Silica Co., Ltd.; particle size: 7 μm) was used in place of polymethylsilsesquioxane particle.

Example 3

[0045] In Example 1, the amount of polymethylsilsesquioxane particles was changed to 56 parts by weight, and the amount of polytetrafluoroethylene particles was changed to 24 parts by weight, respectively.

Example 4

[0046] In Example 1, the amount of polymethylsilsesquioxane particles was changed to 24 parts by weight, and the amount of polytetrafluoroethylene particles was changed to 56 parts by weight, respectively.

Comparative Example 1

[0047] In Example 1, the amount of polymethylsilsesquioxane particles was changed to 40 parts by weight, and no polytetrafluoroethylene particles were used.

Comparative Example 2

[0048] In Example 1, the amount of polymethylsilsesquioxane particles was changed to 45 parts by weight, and the amount of polytetrafluoroethylene particles was changed to 5 parts by weight, respectively.

Comparative Example 3

[0049] In Example 1, the amount of polymethylsilsesquioxane particles was changed to 10 parts by weight, and the amount of polytetrafluoroethylene particles was changed to 55 parts by weight, respectively.

Comparative Example 4

[0050] In Example 1, no polymethylsilsesquioxane particles were used, and the amount of polytetrafluoroethylene particles was changed to 40 parts by weight.

Comparative Example 5

[0051] In Example 1, the amount of polymethylsilsesquioxane particles was changed to 50 parts by weight, and the amount of polytetrafluoroethylene particles was changed to 50 parts by weight, respectively.

Comparative Example 6

[0052] In Example 1, neither polymethylsilsesquioxane particles nor polytetrafluoroethylene particles were used.

Comparative Example 7

[0053] In Example 1, as the paraffin wax, the same amount (20 parts by weight) of paraffin wax having a melting point of 35° C. was used.

Comparative Example 8

[0054] In Example 1, as the paraffin wax, the same amount (20 parts by weight) of paraffin wax having a melting point of 170° C. was used.

Comparative Example 9

[0055] In Example 1, the amount of paraffin wax was changed to 50 parts by weight.

Comparative Example 10

[0056] In Example 1, the amount of paraffin wax was changed to 60 parts by weight.

Comparative Example 11

[0057] In Example 1, 30 parts by weight of Fluon 150J (particle size: 10 μm, produced by AGC Sei Chemical Co., Ltd.) was used as the polytetrafluoroethylene particles, and no paraffin wax was used.

[0058] The results obtained in the above Examples and Comparative Examples are shown in the following Tables 1 and 2.

TABLE-US-00002 TABLE 1 Measurement• Example evaluation item 1 2 3 4 Dispersibility of the ◯ ◯ ◯ ◯ fluororesin particles Contact angle (°) 21.3  10.8  19.4  20.8  ◯ ◯ ◯ ◯ Dynamic friction 0.18 0.15 0.18 0.19 coefficient in oil ◯ ◯ ◯ ◯ Abrasion resistance ◯ ◯ ◯ ◯

TABLE-US-00003 TABLE 2 Measurement•evaluation Comparative Example item 1 2 3 4 5 6 7 8 9 10 11 Dispersibility of the — ◯ ◯ ◯ ◯ — ◯ ◯ X ◯ X fluororesin particles Contact angle (°) 20.1 24.5 38.5 39.0 21.0 40.2 38.3 36.2 38.9 15.0 42.9 ◯ ◯ X X ◯ X X X X ◯ X Dynamic friction  0.18  0.15  0.25  0.32  0.30  0.23  0.18  0.30  0.23  0.40  0.31 coefficient in oil ◯ ◯ X X X X ◯ X X X X Abrasion resistance X X ◯ ◯ X X X ◯ X X ◯

[0059] The above results demonstrate the followings.

[0060] (1) The coating agent obtained in each Example achieves low torque characteristics while maintaining excellent abrasion resistance.

[0061] (2) If a sufficient amount of the fluororesin particles is not used, abrasion resistance is deteriorated (Comparative Examples 1 and 2).

[0062] (3) If the rate of the fluororesin particles is high, oil is repelled, and the contact angle and the friction coefficient in oil increase (Comparative Examples 3 and 4).

[0063] (4) If the total filler amount is large, the surface roughness of the coating film increases, causing the convex portion to run out of oil. If the total filler amount is small, the surface roughness decreases. In either case, the friction and abrasion resistance effect is reduced (Comparative Examples 5 and 6).

[0064] (5) If the melting point of the wax is too low, the wax is released during baking, and abrasion resistance is deteriorated (Comparative Example 7).

[0065] (6) If the melting point of the wax is too high, the wax is not melted during baking, and the friction coefficient in oil increases (Comparative Example 8).

[0066] (7) If the amount of the wax is small, the dispersibility of the fluororesin particles is not ensured, and the surface roughness gets too large (Comparative Example 9).

[0067] (8) If the amount of the wax is large, the coating film is softened, and the friction and abrasion resistance characteristics are deteriorated (Comparative Example 10).

INDUSTRIAL APPLICABILITY

[0068] The coating agent according to the present invention improves abrasion resistance and achieves low torque characteristics, while maintaining excellent seal performance inherent in oil seal; therefore, the coating agent according to the present invention can be effectively used not only for oil seal, but also for prevention of adhesion, reduction of friction, prevention of abrasion, etc., of rubber parts, such as rubber rolls for copiers, rubber belts for copiers, industrial rubber hoses, industrial rubber belts, wipers, automobile weather strips, glass runs, and the like.