CURABLE COMPOSITION, ESPECIALLY FOR RUBBER TO SUBSTRATE BONDING

Abstract

The subject matter is a new curable composition comprising at least one hydroxyl-group containing resin, at least one nitroso-containing compound or at least one nitroso precursor compound, at least one hydrophopic silica and at least one blocked isocyanate, which provides excellent adhesion and steam resistance for rubber to substrate bonds, a process for bonding two substrates with this new curable composition and the corresponding article.

Claims

1. A curable composition comprising at least one hydroxyl-group containing resin, at least one nitroso-containing compound or at least one nitroso precursor compound, at least one hydrophopic silica and at least one blocked isocyanate.

2. The curable composition of claim 1, wherein the at least one hydroxyl group-containing resin is a non-halogenated hydroxyl group-containing resin, preferably selected from polyvinyl alcohol, polyvinyl butyral, polycellulose acetate butyrate, polyvinyl formal, polyamide, polyester, phenol resin, epoxy resin and phenoxy resin, preferably from epoxy resin and phenoxy resin.

3. The curable composition of claim 1, wherein the at least one hydroxyl group-containing resin is present in the composition in a range of from 1 to 20 wt %, preferably 2 to 15 wt %, more preferably 2,5 to 10 wt % of the total weight of the curable composition.

4. The curable composition of claim 1, wherein the hydroxy group-containing resin has a hydroxy content of from 1 to 35 wt % of the total weight of the hydroxy group-containing resin.

5. The curable composition of claim 1, wherein at least one nitroso-containing compound or at least one nitroso precursor compound is an aromatic nitroso-containing compound or an aromatic nitroso precursor compound, preferably an aromatic nitroso-containing compound.

6. The curable composition of claim 5, wherein the at least one aromatic nitroso compound or at least one aromatic nitroso precursor compound comprises at least one alkoxy silane moiety and at least one moiety selected from an aromatic nitroso or an aromatic nitroso precursor or combinations thereof.

7. The curable composition of claim 1, wherein the at least one nitroso-containing compound or at least one nitroso precursor compound is present in the composition in a range of from 1 to 30 wt %.

8. The curable composition of claim 1, wherein the hydrophopic silica is a hydrophopic fumed silica present in the composition in a range of from 2 to 25 wt % of the total weight of the curable composition.

9. The curable composition of claim 1, wherein the blocked isocyanate is present in the composition in a range of from 0.1 to 10 wt % of the total weight of the curable composition.

10. The curable composition of claim 1, wherein the curable composition further comprises a sulfur impregnated particulate solid.

11. The curable composition of claim 9, wherein the sulfur impregnated particulate solid is selected from the group consisting of: sulfur-impregnated clays, sulfur impregnated silicates, sulfur impregnated aluminates, sulfur impregnated charcoals and sulfur impregnated carbons such as sulfur impregnated carbon blacks, sulfur impregnated charcoals and combinations thereof.

12. The curable composition of claim 1, wherein the curable composition further comprises a carbon black.

13. The curable composition of claim 1, wherein the curable composition further comprises an organic solvent.

14. The curable composition of claim 1, wherein the curable composition is a one-component system.

15. A process for bonding a first substrate to a second substrate, comprising the steps of: providing a curable composition according to claim 1; applying the curable composition to at least one part of the surface of the first substrate; and contacting said surface of the first substrate with a surface of a second substrate, to which the curable composition is optionally also applied, under conditions of heat and pressure sufficient to create a cured bond between the two substrates.

16. A bonded assembly bonded together by the use of a curable composition according to claim 1.

17. A bonded assembly made by the process according to claim 14.

Description

EXAMPLES

[0216] To test the adhesion and the steam resistance buffers are prepared. Therefore, flat plate head screws (mild steel) are degreased with ethyl acetate, sandblasted and again cleaned with ethyl acetate. Afterwards for each example an adhesive having a composition according to the following tables is applied by spray application onto the screws and dried. The buffer is then produced with the rubber type Gumasol NR60 with an injection mold having a temperature of 160 C. To determine the adhesion the prepared buffer is tested in a tensile testing machine with a test speed of 100 mm/min. The results in MPa are listed for each adhesive in the following table.

[0217] For the initial value, the injection mold is directly closed and the rubber is vulcanized at 160 C. After vulcanization, the buffer is removed and stored for 24 hours at room temperature before testing.

[0218] For the prebake value, the screws are kept 5 minutes at 160 C. before injecting the rubber into the mold. Afterwards the rubber is again vulcanized at 160 C. And after vulcanization, the buffer is removed and stored for 24 hours at room temperature before testing.

[0219] For the combi value, the buffers prepared according to the prebake procedure are stored for 24 hours in a water steam chamber with a water steam temperature of 95 C. with an applied stress of 20% elongation. After removal from the water steam, the buffers are kept for 24 hours at room temperature without any stress before testing.

[0220] By comparison of the results of the comparative examples with the inventive examples that the steam resistance could drastically be improved. The buffers of the comparative examples fall already apart during the storage in the steam so that a testing of the adhesion is not possible. Additionally, it can be recognized that the addition of a harder even improves the steam resistance.

TABLE-US-00001 Example Example Example Comp. 1 Comp. 2 Comp. 3 1 2 3 1-methoxy-2-propylacetate 68.58 47.55 63.79 63.79 Xylene 18.04 21.702 19.481 Ethylacetate 8 10.6 43.41 39.66 Cellulose acetate butyrate.sup.1 0.5 Phenoxy Resin.sup.2 10 4.85 5 5 Epoxy Resin.sup.3 5.98 6.5 Glymo.sup.4 0.9 0.87 0.9 0.9 0.77 0.9 BSU.sup.5 0.6 0.58 0.6 0.6 0.51 0.6 Nitrososilan.sup.6 8 7.8 19 19 16.23 19 Sulfur Release Agent.sup.7 2.5 2.43 2.5 2.5 2.13 2.5 Carbon Black.sup.8 Wollastonit 7.5 Hydrophobic Fumed Silica.sup.9 7.28 7.5 6.4 7.5 Blocked Isocyanate A.sup.10 1.42 0.71 0.71 3.28 Blocked Isocyanate B.sup.11 2.8 Blocked Isocyanate C.sup.12 Dicyandiamide 0.062 0.072 Dimethylphenylurea 0.006 0.007 Summe 100 100 100 100 100 100 Initial [MPa] 8.4 10.0 8.1 8.7 10.4 9.8 Prebake [MPa] 10.3 9.6 9.0 8.5 9.6 Combi [MPa] 5.5 6.1 7.4 Example 4 Example 5 Example 6 Example 7 Example 8 1-methoxy-2-propylacetate Xylene 23.18 22.476 22.476 24.38 24.1 Ethylacetate 47.49 53.445 53.445 45.62 45.4408 Cellulose acetate butyrate.sup.1 0.5 0.5 0.5 0.5 0.5 Phenoxy Resin.sup.2 Epoxy Resin.sup.3 6.5 3 3 3 3 Glymo.sup.4 0.9 0.9 0.9 0.9 1.13 BSU.sup.5 0.6 0.6 0.6 0.6 0.75 Nitrososilan.sup.6 8 8 8 12.5 12.2 Sulfur Release Agent.sup.7 2.5 2.5 Carbon Black.sup.6 4 4 Wollastonit.sup.9 Hydrophobic Fumed Silica.sup.10 7.5 7.5 10 7.5 7.8 Blocked Isocyanate A.sup.11 2.83 Blocked Isocyanate B.sup.12 1 1 Blocked Isocyanate C.sup.13 1 1 Dicyandiamide 0.072 0.072 0.072 Dimethylphenylurea 0.0070 0.0070 0.0072 Summe 100 100 100 100 100 Initial [MPa] 8.2 8.5 8.1 8.4 9.2 Prebake [MPa] 8.6 9.8 9.1 8.2 9.1 Combi [MPa] 3.2 9.4 7.5 1.8 8.4 .sup.1Cellulose ester with high butyryl content and high viscosity (butyryl content 37 wt %; acetyl content 13.5 wt %; hydroxyl content 1.8 wt %) .sup.2Phenoxy resin based on bisphenol A with epichlorohydrin; Mn 13,000 g/mol; Mw 52,000 g/mol; Tg 92 C. (DSC); .sup.3solid reaction product of bisphenol A and epichorohydrin; Epoxide Equivalent Weight 2500-4000 g/mol; Tg 152 C. .sup.4Glymo = 3-Glycidoxypropyltrimethoxysilane .sup.5BSU = N,N-bis(3-trimethoxysilylpropyl)urea .sup.6Nitrososilan: [00034]Carbon Black of Desorex: .sup.7Sulfur impregnated .sup.8Carbon Black; BET 80 m.sup.2/g (ASTM D6556) .sup.9Hydrophobic Fumed Silica with a BET of 200 m.sup.2/g and a C-content of 2.3 to 3.2% .sup.10HDI bluret blocked with dimethylpyrazole; equivalent weight (calculated) 410; NCO blocked 10.2%; 70% solids in methoxypropanol/ethyl acetate .sup.11HDI bluret blocked with diethyl malonate; equivalent weight (calculated) 477; NCO blocked 9.0%; 70% solids in methoxypropanol .sup.12Blocked isocyanate based on HDI; equivalent weight (calculated) 470; NCO blocked 8.9%; 70% solids in methoxypropylacetate