HYDROGENATED NBR COMPOSITION

Abstract

A hydrogenated NBR composition comprising 30 to 200 parts by weight of titanium oxide and 1 to 8 parts by weight of magnesium oxide, based on 100 parts by weight of hydrogenated NBR. By forming a crosslinked rubber layer of the rubber composition on a metal plate, a gasket material with excellent blister resistance, whose roll kneadability is improved without reducing the rubber strength of hydrogenated NBR, is provided. Moreover, the rubber composition is effective as a rubber raw material for use in soft metal or a high hardness hydrogenated NBR material for which kneading processing is difficult.

Claims

1. A hydrogenated NBR composition comprising 30 to 200 parts by weight of titanium oxide and 1 to 8 parts by weight of magnesium oxide, based on 100 parts by weight of hydrogenated NBR.

2. The hydrogenated NBR composition according to claim 1, wherein the composition contains neither nylon fine particles nor a maleic anhydride group-containing ethylene-based copolymer.

3. A gasket material comprising a crosslinked rubber layer of the hydrogenated NBR composition according to claim 1 on a metal plate.

4. The gasket material according to claim 3, wherein a primer layer and a resin-based vulcanizing adhesive layer are interposed between the metal plate and the crosslinked rubber layer.

5. The gasket material according to claim 3, wherein the D hardness measured by JIS D durometer corresponding to ISO 7619-1 is 35 or more and 65 or less.

6. The gasket material according to claim 3, which is used as a cylinder head gasket.

7. The gasket material according to claim 5, which is used as a cylinder head gasket.

Description

EXAMPLES

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

Examples 1 to 8, Comparative Examples 1 to 4, and Reference Example

[0037] A Ti/Al-based primer (Ti compound: ORGATIX TC-100, produced by Matsumoto Fine Chemical Co. Ltd./Al compound: AS-520-A, produced by Nissan Chemical Corporation) was applied onto both surfaces of a degreased stainless steel plate (thickness: 0.2 mm), and baked at 200° C. for 10 minutes, thereby forming lower primer layers. An adhesive comprising an epoxy resin as a main component was applied onto the lower primer layers, and baked at 200° C. for 5 minutes to form cover coat layers. A rubber paste coating liquid was applied onto the cover coat layers, and vulcanized at 190° C. for 8 minutes to form rubber layers. A coating liquid in which wax and graphite were dispersed was applied onto the rubber layers, and baked at 200° C. for 5 minutes to form anti-adhesive layers, thereby producing a gasket material.

[0038] The rubber paste coating liquid had the following formation.

TABLE-US-00001 Hydrogenated NBR (Therban 3446, 100 parts by weight produced by Lanxess, Inc.) Carbon black (Seast G-S, produced by 80 parts by weight Tokai Carbon Co., Ltd.) Titanium oxide (Tipaque A100, produced by prescribed amount Ishihara Sangyo Kaisha, Ltd.) Magnesium oxide (Kyowamag 150, produced by prescribed amount Kyowa Chemical Industry Co., Ltd., D50 particle size: 4.2 μm) Stearic acid (DTST, produced by 1 part by weight Miyoshi Oil & Fat Co., Ltd.) Antioxidant (Nocrac ODA, produced by 2 parts by weight Ouchi Shinko Chemical Industrial Co., Ltd.) Crosslinking aid (Taic, produced by 2 parts by weight Hitachi Chemical Co., Ltd.) Organic peroxide (Perbutyl P, produced by 8 parts by weight NOF Corporation)
The above components were each kneaded with a kneader and an open roll, and the obtained kneaded material (composition) was dissolved and dispersed in methyl ethyl ketone, toluene, ethyl acetate, etc., thereby preparing a rubber paste coating liquid having a solid matters content of 20 wt. %.

[0039] The produced gasket material was evaluated and measured for the following items.

[0040] D hardness: A rubber sheet having a thickness of 2 mm obtained by vulcanizing the hydrogenated NBR composition at 170° C. for 20 minutes was measured by JIS D durometer corresponding to ISO 7619-1

[0041] Tensile strength: according to JIS K6251

[0042] Roll processability: [0043] ◯: Roll processability was excellent, and kneading was possible [0044] Δ: Roll processability was slightly poor, but working was possible [0045] X: Roll processability was poor, and working was difficult

[0046] Compression test evaluation: A donut-shaped convex mold was compressed at 250 MPa to a rubber laminate at 150° C. for 10 minutes, and then the state of the rubber layer was evaluated according to the following criteria (4 points or more were regarded as ◯) [0047] 5 points: No metal was exposed, and almost no rubber flow was observed [0048] 4 points: No metal was exposed, and rubber flow was small [0049] 3 points: Not a little rubber flow occurred, but metal exposure did not occur [0050] 2 points: Rubber flow was large, but metal exposure was less [0051] 1 points: Both rubber flow and metal exposure were large

[0052] The obtained results are shown in the following Tables 1 and 2. The particle size (D50 particle size) is a value measured using a Nikkiso particle size distribution analyzer “Microtrac MT3000 II” with MgO dispersed in a dispersion medium ethanol. Further, Comparative Example 1 (aliphatic C.sub.5 petroleum resin, WINGTAC 95, produced by Cray Valley) and Comparative Example 2 (coumarone resin, Nitto Resin G-90, produced by Nitto Chemical Co., Ltd.) are commonly used tackifiers, and hydrogenated NBR—TiO.sub.2 is added because the adhesion decreases and bagging occurs.

[0053] Magnesium oxide (Starmag U): produced by Konoshima Chemical Co., Ltd., D50 particle size: 12.4 μm

[0054] Fatty acid surface-treated magnesium oxide: Starmag CX150, produced by Konoshima Chemical Co., Ltd.,

TABLE-US-00002 TABLE 1 Example 1 2 3 4 5 6 7 8 [Additive components] TiO.sub.2 (Tipaque 100 100 30 100 200 100 100 100 A 100) MgO 1 3 5 5 5 8 (Kyowamag 150) MgO (Starmag 3 U) MgO (Starmag 3 CX150) [Measurement results] D hardness 57 59 52 60 65 61 58 96 Tensile 18.1 18.5 18.7 18.4 16.5 18.7 18.5 18.3 strength (Mpa) [Evaluation] Roll Δ ◯ ◯ ◯ ◯ Δ ◯ ◯ processability Bagging Adhesion Compression 5 5 4 5 5 5 5 5 test evaluation points points points points points points points points ◯ ◯ ◯ ◯ ◯ ◯ ◯ ◯

TABLE-US-00003 TABLE 2 Comp. Ex. 1 2 3 4 Ref. Ex. [Additive components] TiO.sub.2 100 100 100 100 100 (Tipaque A100) MgO 0.5 10 — (Kyowamag 150) Petroleum 5 resin Coumarone 5 resin [Measurement results] D hardness 55 54 57 63 57 Tensile 16.4 16.3 18.2 19.1 18.2 strength (MPa) [Evaluation] Roll ◯ ◯ X X X processability Bagging Adhesion Bagging Compression 3 points 3 points 5 points 5 points 5 points test evaluation X X ◯ ◯ ◯