COATING SOLUTION AND FLUORORUBBER METAL LAMINATED SHEET USING THE SAME

Abstract

A coating solution comprising an organic solvent solution containing polyol-crosslinkable fluororubber, a polyol vulcanizing agent, and N-phenyl-3-aminopropyltrialkoxysilane, preferably a coating solution further containing an epoxy resin in addition thereto, and a fluororubber metal laminated sheet formed by applying the above coating solution to a metal sheet, followed by vulcanization. The coating solution can not only impart stability over time to the fluororubber paste, but also improve the interlayer adhesion and abrasion resistance of the fluororubber metal laminated sheet. Therefore, when it is used as a cylinder head gasket, it is possible to cope with the reduction in rigidity due to the increase in combustion pressure of the engine, and with weight saving. As a result, it will greatly contribute to the improvement of fuel efficiency of automobiles.

Claims

1. A coating solution comprising an organic solvent solution containing polyol-crosslinkable fluororubber, a polyol vulcanizing agent, and N-phenyl-3-aminopropyltrialkoxysilane.

2. The coating solution according to claim 1, wherein the polyol vulcanizing agent is used at a ratio of 3 to 20 parts by weight and the N-phenyl-3-aminopropyltrialkoxysilane is used at a ratio of 1 to 15 parts by weight, based on 100 parts by weight of the polyol-crosslinkable fluororubber.

3. The coating solution according to claim 1, wherein 40 parts by weight or less of epoxy resin is further comprised.

4. The coating solution according to claim 1, wherein 50 parts by weight or less of silica resin is further comprised.

5. A method for producing the coating solution according to claim 3, the method comprising kneading components other than a vulcanization component and an epoxy resin, then dissolving the resultant in an organic solvent, dissolving the vulcanization component and the epoxy resin therein, and then compounding N-phenyl-3-aminopropyltrialkoxysilane.

6. The coating solution according to claim 1, which is applied onto a metal sheet.

7. A fluororubber metal laminated sheet comprising a metal sheet, on which a vulcanization coating layer formed from the coating solution according to claim 6 is laminated.

8. The fluororubber metal laminated sheet according to claim 7, which is used as a gasket.

9. The fluororubber metal laminated sheet according to claim 8, which is used as a cylinder head gasket.

Description

EXAMPLES

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

TABLE-US-00001 Example 1 Fluororubber (Viton A-200, produced by DuPont) 100 parts by weight MT Carbon black (THERMAX N990, 25 parts by weight produced by Cancarb Limited) Graphite (A-O, produced by East Japan Carbon 30 parts by weight Co., Ltd.) Silica (NIPSIL ER, produced by Tosoh Silica 10 parts by weight Corporation) Magnesium oxide (KYOWAMAG 150, produced 8 parts by weight by Kyowa Chemical Industry Co., Ltd.) Hydrotalcite (DHT-4A, produced by 3 parts by weight Kyowa Chemical Industry Co., Ltd.) Processing aid (VPA #2, produced by Du Pont) 2 parts by weight Vulcanizing agent (CURATIVE #30, produced 5 parts by weight by Du Pont) Vulcanization accelerator (CURATIVE #20, 9 parts by weight produced by Du Pont) Epoxy resin (EPICLON N695, produced by 25 parts by weight DIC Corporation)
Of the above components, those other than the vulcanizing agent, vulcanization accelerator and epoxy resin were kneaded with a pressure kneader or an open roll.

[0037] The obtained kneaded product was dissolved in an isophorone-methyl ethyl ketone-methanol (volume ratio=7:2:1) mixed solvent, and the vulcanizing agent, vulcanization accelerator and epoxy resin were dissolved therein so that the solid matters content was adjusted to about 35 to 40 wt. %. Finally, 3 parts by weight of N-phenyl-3-amnopropyltrimethoxysilane (KBM573, produced by Shin-Etsu Chemical Co., Ltd.), which was a silane coupling agent, was compounded to prepare a fluororubber paste.

[0038] The prepared fluororubber paste was applied to the surface of a stainless steel SUS301 sheet (thickness: 0.2 mm) so that the rubber thickness after vulcanization was 20 to 25 μm, followed by vulcanization in an oven at 230° C. for 15 minutes, thereby obtaining a fluororubber laminated metal sheet.

[0039] The fluororubber paste and the fluororubber laminated metal sheet were measured and evaluated by the methods described below.

[0040] Evaluation of Fluororubber Paste Stability:

[0041] The fluororubber paste was measured using a Brookfield B type viscometer (SB type viscometer, Annex 1 of JIS K7117) under the condition of #3 SB Spindle 12 rpm to measure the viscosity immediately after preparation and after 4 hours. When the viscosity change after 4 hours was within 20%, the stability was evaluated as ◯, and when the viscosity change exceeded 20%, the stability was evaluated as ×.

[0042] Adhesion Test:

[0043] The fluororubber laminated metal sheet was subjected to an adhesion test according to the drawing test method of JIS K6894 for two items, i.e., initial adhesiveness and heat-resistant adhesiveness after an aging test at 200° C. for 70 hours. If the adhesive strength was not sufficient, the coating film would peel off; thus, this was evaluated on a 5-point scale. When the score was 4 points or more, the adhesiveness was evaluated as ◯. [0044] 5 points: No peeling was observed. [0045] 4 points: Slight peeling was observed near the intersection of the drawn circles. [0046] 3 points: Slight peeling was observed around the drawn circles. [0047] 2 points: Peeling was observed around the drawn circles. [0048] 1 points: Peeling was observed in a wide range.

[0049] Abrasion test: The fluororubber laminated metal sheet was subjected to reciprocating motion using an abrasion tester (FPR-2100, produced by Rhesca Co., Ltd.) and an MS5-25 straight pin under the following conditions: load: 1 kg, linear velocity: 6.3 cm/sec, and temperature: 25° C., 80° C. and 150° C. The number of times when the metal sheet was exposed was defined as the number of abrasion times.

Example 2

[0050] In Example 1, the amount of N-phenyl-3-aminopropyltrimethoxysilane was changed to 5 parts by weight.

Example 3

[0051] In Example 1, the amount of N-phenyl-3-aminopropyltrimethoxysilane was changed to 10 parts by weight.

Comparative Example 1

[0052] In Example 1, as the silane coupling agent, the same amount (3 parts by weight) of 3-aminopropyltrimethoxysilane (KBM-903, produced by Shin-Etsu Chemical Co., Ltd.) was used.

Comparative Example 2

[0053] In Example 1, as the silane coupling agent, 5 parts by weight of 3-aminopropyltriethoxysilane (KBE-903, produced by Shin-Etsu Chemical Co., Ltd.) was used.

Comparative Example 3

[0054] In Example 1, as the silane coupling agent, 10 parts by weight of 3-amnopropyltriethoxysilane (KBE-903) was used.

Comparative Example 4

[0055] In Example 1, as the silane coupling agent, 5 parts by weight of 3-glycidoxypropyltrimethoxysilane (KBM-403, produced by Shin-Etsu Chemical Co., Ltd.) was used.

Comparative Example 5

[0056] In Example 1, as the silane coupling agent, 10 parts by weight of 3-glycidoxypropyltrimethoxysilane (KBM-403) was used.

Comparative Example 6

[0057] In Example 1, epoxy resin was not used.

[0058] The following table shows the measurement and evaluation results obtained in the above Examples and Comparative Examples.

TABLE-US-00002 TABLE Example Comparative Example Measurement•Evaluation 1 2 3 1 2 3 4 5 6 Rubber paste stability Immediately after 1910 1850 1810 2310   2300 2240   1940 1900   1500   preparation (mPa .Math. s) After 4 hours (mPa .Math. s) 2020 2010 1960 — 3480 — 2230 2210   1640   Evaluation ◯ ◯ ◯ X X X ◯ ◯ ◯ Adhesion test Initial Point 4 5 4 4 4 4 4 3 2 Evaluation ◯ ◯ ◯ ◯ ◯ ◯ ◯ X X After heat resistance test Point 4 4 4 4 4 4 3 3 2 Evaluation ◯ ◯ ◯ ◯ ◯ ◯ X X X Abrasion test  25° C. (number of times) 80 84 96 60  64 61  62 34  23   80° C. (number of times) 13 15 16 8 10 11  10 5 3 150° C. (number of times) 3 3 4 1 1 1 1 1 1 Note) “—” in the rubber paste stability (after 4 hours) indicates >10000, which was unmeasurable.

[0059] The above results reveal that those according to the present Examples have excellent rubber paste stability and abrasion resistance at each measurement temperature.

[0060] In contrast, it is revealed that those using 3-aminopropyltrimethoxysilane or 3-aminopropyltriethoxysilane lack rubber paste stability, and that those using 3-glycidoxypropyltrimethoxysilane and those using no epoxy resin lack interlayer adhesion in the rubber metal laminated sheets.