| abstract |
This invention provides organopolysiloxane materials having cone penetration between about 100 and about 350 (10-1 mm) and ultimate elongation of at least 100% and having reduced surface tack. This invention provides three methods of obtaining said materials with reduced surface tack. The first method comprises applying to the surface of such material an organic peroxide or a photoinitiator and irradiating the surface with ultraviolet light to further crosslink the surface to reduce or eliminate the tack of the surface. The second method comprises mixing a photoinitiator, such as benzophenone, in an organopolysiloxane fluid, thermally crosslinking the organopolysiloxane fluid to produce the material with the above cone penetration and ultimate elongation then irradiating the surface of the material with ultraviolet light to reduce or eliminate the tack of the surface. The third method comprises mixing a photoinitiator, such as benzophenone, in an organopolysiloxane fluid, crosslinking the fluid by irradiating a layer of the fluid with ultraviolet light to produce the above cone penetration and ultimate elongation properties then further irradiating the crosslinked material to reduce or eliminate the surface tack; this method can be carried out by simultaneous irradiation with ultraviolet light from two sides of a layer of the organopolysiloxane wherein one surface is irradiated at a higher intensity than the other surface. The materials produced by this invention are useful as tapes and sealants. |