Scorch retardants for rubber reinforced with siliceous pigment and mercapto-type coupling agent
AssigneePPG Industries, Inc.
InventorMiles Q. Fetterman
Life of this patent
Estimating the term…
Abstract
Rubber vulcanizates reinforced with siliceous pigment have desirable properties. The addition of a mercapto-type coupling agent hastens curing and strengthens adhesion between the rubber polymer and the silica, but tends to cause premature vulcanization or scorch. The further addition of a thiomorpholine compound such as 4,4'-dithiodimorpholine or 2-(4-morpholinothio)-benzothiazole retards scorch and improves stress/strain properties and abrasion resistance, but affects curing time only moderately.
Claims24
A sulfur vulcanizable rubber compound comprising rubber;
- 5 to 200 parts per 100 parts of rubber of finely divided siliceous pigment;
- 0.1 to 15 parts per 100 parts of rubber of a coupling agent represented by the general formula A-R-B, wherein A represents a functional group capable of bonding to the siliceous pigment, B represents a sulfur functional group selected from the group consisting of mercapto, halomercapto, thioepoxide, and disulfide groups, and R represents a stable group which connects A and B;
- 0.2 to 8 parts per 100 parts of rubber of sulfur curative;
- and 0.1 to 15 parts per hundred parts of rubber of a thiomorpholine scorch retardant represented by the formula:
- ##STR6## wherein R.sub.1 is an active group that will allow the thiomorpholine group to retard scorch, each R' independently is an inert substituent, and i, the number of inert substitutents, is 0, 1, 2, or 3.
A method for retarding scorch which comprises employing 0.1 to 15 parts per 100 parts of rubber of a thiomorpholine scorch retardant in a sulfur vulcanizable rubber compound comprising rubber;
- 5 to 200 parts per 100 parts of rubber of finely divided siliceous pigment;
- 0.1 to 15 parts per 100 parts of rubber of a coupling agent represented by the general formula A-R-B, wherein A represents a functional group capable of bonding to the siliceous pigment, B represents a sulfur functional group selected from the group consisting of mercapto, halomercapto, thioepoxide, and disulfide groups, and R represents a stable group which connects A and B;
- and 0.2 to 8 parts per 100 parts of rubber of sulfur curative;
- the thiomorpholine scorch retardant being represented by the formula:
- ##STR9## wherein R.sub.1 is an active group that will allow the thiomorpholine group to retard scorch, each R' independently is an inert substituent, and i, the number of inert substituents, is 0, 1, 2, or 3.
Dependencies are inferred from the claim text.