Polymeric adhesion promoters for vulcanizable mixtures of elastomers and mineral fillers

DETAILED DESCRIPTION In the polybutadiene oils of this invention, X is a hydrolyzable function, preferably halogen or alkoxy, e.
g.
, chlorine, bromine, iodine and alkoxy of up to 8 carbon atoms, of which methoxy, ethoxy, propoxy and butoxy are preferred.
Y and Z can be the same as X or can be, independently, H, alkyl of 1-8 carbon atoms, cycloalkyl of 5-12 carbon atoms, e.
g.
, of 3-7 ring members, preferably 5 or 6, or aryl of up to 10 carbon atoms, e.
g.
, phenyl or phenyl substituted by one or more groups, e.
g.
, halogen, alkyl or alkoxy as defined above.
Preferred Y and Z are halogen, alkoxy of up to 4 carbon atoms, methyl, ethyl and phenyl.
Reactive silyl groups are introduced into the polybutadiene oil by a conventional hydrosilylation method, i.
e.
, thermal, photochemical, free radical, or metal-catalyzed processes.
Surprisingly, the polybutadiene oils of this invention, contrary to the teachings of U.
S.
Pat.
No.
3,759,869, are excellent adhesion promoters.
The number average molecular weights of the polybutadiene oils particularly suitable for this purpose are 400-6,000, preferably 600-2,000.
Preferably, the polybutadiene oils have 10-60% of vinyl, 25-85% of cis-vinylene and 1-15% of transvinylene double bonds, most preferably 30-50% of vinyl, 35-70% of cis-vinylene and 3-12% of trans-vinylene.
The polybutadiene oils contain 3-20% by weight of reactive silyl polymer units as defined above, more preferably 4-17% by weight thereof.
These correspond to 0.
4-3% by weight and 0.
6-2.
5% by weight of bound silicon, respectively.
Most preferably, the polybutadiene oils are of 600-2,000 molecular weight; contain 10-60% of vinyl, 25-85% of cis-vinylene and 1-15% of trans-vinylene double bonds and have 4-17% by weight of reactive silyl groups.
The particularly low viscosity of the polybutadiene oils used facilitates the hydrosilylation reaction, which can be effected without a solvent that would otherwise be necessary, as well as the work up procedure and subsequent handling of the resulting adhesion promoters