Abstract: Release agents for pressure-sensitive adhesive tapes comprise poly(amide acids), e.g., poly(N-fatty alkyl amide-acids) of the following recurring formula: ##STR1## wherein A is a divalent organic radical containing from 2 to 15, preferably 2 to 6, carbon atoms, R is a tetravalent organic radical containing at least 4 carbon atoms, R.sub.1 is hydrogen or an alkyl radical containing about 1 to 30 carbon atoms and R.sub.2 is an alkyl radical containing about 12 to 30 carbon atoms. When R.sub.1 is hydrogen, also provided are the corresponding cyclized imide products and mixtures of the polyamides and polyimides. These poly(amide acids) are formed by the reaction of tetracarboxylic acid dianhydrides and fatty diamines.

Abstract: A copolymeric material is provided in accordance with this invention which is the reaction product of a di (omega-thio-organo) dimethyl siloxane oligomer having terminal active hydrogen groups and a difunctional organic compound having terminal isocyanate groups. The siloxane-thiourethane copolymer provides good release per se from tacky adhesive masses or when combined with other film formers.

Abstract: Release agents are provided which comprise the polymeric reaction product of a fatty diamine with a diisocyanate and, optionally, a diol. These polyurea and polycarbamate products have the following recurring formula: ##EQU1## WHEREIN A is an alkylene radical containing about 2 to 6 carbon atoms, B is an arylene radical containing about 6 to 16 carbon atoms, D is an aliphatic organic radical containing about 2 to 6 carbon atoms, R is an alkyl radical containing about 12 to 25 carbon atoms, R' is hydrogen or an alkyl radical containing about 1 to 25 carbon atoms, a and b represent the number of recurring units and the ratio of b/a varies from 0 to 2, and c is 0, 1 or 2. Also provided are pressure sensitive adhesive tapes and release liners utilizing these novel release agents.