Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Patent
1997-06-12
1998-12-01
Cain, Edward J.
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
5253324, 5253327, 525375, C08F 834
Patent
active
058440496
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
This invention relates to rubber compositions having improved physical properties. more particularly, it relates to sulfur-vulcanized rubber compositions which are vulcanized in the presence of particular coagents with anti-reversion and/or accelerating activity. The invention also relates to a sulfur-vulcanization process which is carried out in the presence of particular coagents with anti-reversion and/or accelerating activity and the use of such coagents in the sulfur-vulcanization of rubber. Finally, the invention relates to rubber products comprising rubber vulcanized with sulfur in the presence of such coagents.
BACKGROUND OF THE ART
In the tire and belt industries, among others, better mechanical and heat resistance properties are being demanded. It has long been known that the mechanical properties of rubber can be improved by using a large amount of sulfur as a cross-linking agent to increase the cross-link density in vulcanized rubbers. However, the use of large amounts of sulfur suffers from the disadvantage that it produces reversion and leads to a marked decrease in heat resistance and resistance to flex cracking, among other properties, in the final product. The fact that reversion is a continuing problem can be seen from, "Rubber Microstructure and Reversion", Nordsiek, Dr. K. H., Rubber World, 197 (3), pp. 30-38, 1987, and "Physikalische and Chemische Aspekte der Reversion", Kautschuk+Gummi-Kunstoffe, 34, No. 9, 1981.
In order to eliminate the foregoing disadvantage, it has been proposed to add coagents to sulfur-vulcanization systems. One known type of coagent are the maleimides. Such vulcanization systems are disclosed in, "Vulcanization With Maleimides", Journal of Applied Polymer Science, Vol. 8, pp. 2281-2298 (1964).
U.S. Pat. No. 3,297,713 suggests the use of dithio-bis(N-phenylmaleirnides) as vulcanizing agents for rubber. However, this system does not employ sulfur as a vulcanization agent and thus suffers from several disadvantages which result from the absence of sulfur cross-links in the rubber product.
Japanese patent publication JP b1014-238 discloses sulfur-vutcanization systems wherein maleimides are used as coagents and which also contain either dibenzothiazyl disulfide or tetrarnethylthiuram disulfide. However, this solution is of limited application since only vulcanization accelerators having relatively short scorch times can be used with the bis-maleimides.
European patent application (EP-A-) 0191931 suggests that the use of a bismaleimide compound in combination with a sulfenamide and a dithiophosphoric acid leads to further improvements in the mechanical and anti-reversion properties of sulfur-vulcanized rubbers. The patent specification claims that these rubbers exhibit improved resistance to reversion, resistance to heat aging and resistance to flex cracking. However, this system is limited to vulcanization carried out in the presence of a sulfenamide accelerator in combination with a dithiophosphoric acid accelerator and is thus of limited utility in actual practice.
In the article, "Change in the Structure and Properties of Vulcanizates Based on Natural Rubber Under Prolonged Vulcanization in the Presence of Vulcanizing Systems Containing Sulfur and Bismaleimides", Chaychich, T. A., et al., Kauchuk i Rezina, vol. 4, pp. 20-3, 1981, there is disclosed that vulcanization of natural rubber tread stocks with sulfur in the presence of m-phenylene-bismaleinide at 143 .degree. C. over a 600-minute period gave vulcanizates with enhanced physiomechanical properties and resistance to reversion Other articles relating to the sulfur-vulcanization of rubbers using bismaleimides as coagents include, "Vulcanization of cis-1,4-isoprene rubber by derivatives of maleimide under the action of high temperatures and radiation," Kauchuk i Rezina, vol 3, pp. 10-12, 1974; "High-temperature Vulcanization of Unsaturated Rubbers by Thio Derivatives of Maleimide", Kauchuk i Rezina, vol. 3, pp. 16-19, 1975; and, "Influence of the Type and Concentration of Crosslinki
REFERENCES:
patent: 3297713 (1967-01-01), Ladd
patent: 4482741 (1984-11-01), Kurek
"Rubber microstructure and reversion", Nordsiek, Dr. K.H., Rubber World 197(3), pp. 30-38, 1987.
"Physikalische und chemische Aspekte der Reversion", Kautschuk + Gummi-Kunstoffe, 34, No. 9, 1981.
"Vulcanization with Maleimides", Journal of Applied Polymer Science, vol. 8, pp. 2281-2298 (1964).
"Vulcanisation of cis-1, 4-isoprene rubber by derivatives of maleimide under the action of high temperatures and radiation", Kauchuk i Rezina, No. 3, pp. 10-12, 1974.
"High-temperature vulcanisation of unsaturated rubbers by thio derivatives of malimide", Kauchuk i Rezina, No. 3, pp. 16-19, 1975.
"Influence of the type and concentration of crosslinking agent on the effectiveness of a combined system of bismaleimide and sulphur", Kauchuk i Rezina, No. 10, pp. 15-19, 1985.
Hofmann, Rubber Technololgy Handbook, chapter 4, Rubber Chemicals and Additives, pp. 217-353, Hanser Publishers, Munich 1989.
J6 1014-238-A (abstract), 1984.
J6 3321-333-A (abstract), 1987.
J6 3286-445-A (abstract), 1987.
Chemistry of Synthetic High Polymers, No. 16, 1987, Chemical Abstract 107: 134698v (1986).
"Change in the Structure and Properties of Vulcanizates Based on Natural Rubber Under Prolonged Vulcanization in the Presence of Vulcanizing Systems Containing Sulfur and Bismaleimides", Chavchich, T.A., et al., Kauchuk i Rezina, vol. 4, pp. 20-23, 1981.
"Advanced Organic Chemistry" by J. March, 4th ed., John Wiley & Sons (pp. 205, 1005 and 1008).
Datta Rabindra Nath
de Hoog Arie Jacob
Dijk Berend Jan
Steenbergen Andre
Talma Auke Gerardus
Akzo Nobel nv
Cain Edward J.
Mancini Ralph J.
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