GB788009A - Improvements in and relating to adhesive compositions - Google Patents

Abstract

Adhesive compositions are made by blending 100 parts of a natural or synthetic vulcanizable rubbery diene polymer and 3 to 15 parts of an oil - soluble, heat advancing phenol - aldehyde resin compatible therewith, heating the blend without agitation until completion of the reaction and then masticating the mixture in the presence of admixed compatible tackifier resin until the mass is smoothly dispersible in heptane. Sulphur vulcanizing agents, e.g. dipentamethylene thiurum tetrasulphide may be included. The phenol-aldehyde resins specified are made by reacting formaldehyde with substituted phenols, e.g. p-tertiary-butyl phenol, p-tertiary amyl phenol or p-phenyl phenol. Activators such as zinc oxide or zinc resinates may be added to promote the curing reaction. In the examples: (1) a butadiene-styrene copolymer, zinc oxide, lecithin, "Pentalyn H" (the pentaerythritol ester of hydrogenated resin) and a phenol-aldehyde resin were admixed by warming the butadiene-styrene copolymer on a rubber mill, the other ingredients added, the mass cured by heating in an autoclave without agitation, milled, dispersed in a heptane - alcohol mixture, additional "Pentalyn" added and the resultant mixture coated on a paper backing; (2) and (3) rubber is warmed, zinc oxide, a tackifier resin (thermoplastic hydrocarbon terpene resin), dipentamethylene thiuram tetrasulphide and a phenol aldehyde resin added, the resultant mixture being heated in an autoclave and milled, further tackifier resin added, the mass dispersed in heptane containing alcohol and further tackifier resin added. The resultant adhesive compositions may be coated on paper, cloth, transparent cellulose films or flexible metal foils to form pressure-sensitive adhesive tapes. "Pentalyn" is a Registered Trade Mark.ALSO:Adhesive compositions are made by blending 100 parts of a synthetic or natural rubber and 3 to 15 parts of oil-soluble phenol-aldehyde resin compatible therewith, heating the blend without agitation, until completion of the reaction and then masticating the mixture in the presence of admixed compatible tackifier resin until the mass is smoothly dispensible in heptane. Sulphur vulcanizing agents, e.g. dipentamethylene thiuram tetrasulphide and activators, e.g., zinc oxide or zinc resinate, may be included. In examples (2) and (3), zinc oxide, a tackifier resin (a terpene resin), dipentamethylene thiuram tetrasulphide and a phenol-aldehyde resin are added to previously warmed smoked rubber sheets and milled, the resultant mixture being heated in an autoclave and remilled with further tackifier resin, the products being dispersed in an ethyl alcohol-heptane mixture containing further tackifier resin, coated on a backing and dried to form a pressure sensitive adhesive tape. Specified bases are paper, cloth, cellulosic films, fibrous webs or metal foils.