Transparent pre-cure coating for rubbery polymers

DETAILED DESCRIPTION What is claimed is: 1.
A pre-cure paint comprising: a.
a rubbery diene polymer, b.
hydrated amorphous silica, c.
a zinc salt or zinc complex which is soluble in the rubbery diene polymer, and d.
a paint vehicle.
2.
The paint according to claim 1 wherein the zinc salt or zinc complex is formed in situ in the rubbery diene polymer from zinc oxide.
3.
The paint of claim 1 wherein contains sulfur.
4.
The paint of claim 3 wherein the zinc salt or complex is formed by a reaction between zinc oxide and a compound selected from the group consisting of ammonium sulfate, the tetrasodium salt of ethylene diamine tetra acetic acid, triethylene tetra amine, tetraethylene pentamine, sodium gluconate and sodium citrate.
5.
The paint according to claim 4 wherein the zinc oxide is reacted with ammonium sulfate.
6.
A process of preparing the unvulcanized rubbery surface of a product prior to vulcanization of the product, said surface containing light colored portions, comprising coating at least the light color portions of the surface with the precure paint of claim 1.
7.
The unvulcanized coated product of claim 6.
8.
A process comprising vulcanizing the coated unvulcanized product of claim 7.
9.
The vulcanized product of claim 8.
10.
The paint according to claim 1, wherein the polymer is in latex form and the vehicle is water.




Description:
This invention relates to transparent pre-cure paints and objects coated therewith.
Pre-cure paints are well known in the art (for example, see U.
S.
Pat.
No.
3,595,950).
They serve to form a coating on the unvulcanized surface of a product such as a pneumatic vehicle tire to act as a mold release and to permit flow of rubber at the surface of the product during vulcanization so as to avoid pock mark formation on the surface of the product.
Conventionally, such paints contain large amounts of carbon black (up to 800 parts by weight).
Normally, such paints have a non-aqueous solvent base.
Their use has been limited to dark stocks where the carbon black would have no adverse effect on color