Patent GB-665196-A (GB)
Title: Improvements in or relating to heatsealing adhesive sheets or tapes
IPC: C09J7/21
Filed: 1948-04-01
Abstract: A heat-sealing adhesive sheet or tape comprises a flexible backing and a plurality of superposed polymeric coatings of mutually compatible heat softenable material thereon, the material of the coating next to the backing having a softening point from 20 DEG  to 100 DEG  F. higher than that of the surface coating.  The preferred material for the surface coating is a maleic-modified soft vinyl chloride-acetate copolymer, having a relatively low-melting point and high degree of cold flow, consisting of a copolymer of more than 65 per cent by weight of vinyl chloride with less than 30 per cent of vinyl acetate, the maleic acid or anhydride modification being 0.5 to 5 per cent of maleic acid based on the weight of copolymer, but vinyl chloride-vinylidene chloride copolymers, polymethacrylates, or polystyrene may also be used.  The lower layer may consist of any polymer having a softening point from 20 DEG  to 100 DEG  F. higher than that of the surface layer, and compatible therewith, including viny lchloride-acetate copolymers, polyvinyl chloride, vinylidene chloride-vinyl chloride copolymers, butadiene-acrylonitrile copolymers having an excess by weight of butadiene, and mixtures of these.  Plasticizers may be added to obtain the desired softening point differential, dioctyl phthalate, triglycol di-2-ethyl hexoate, amyl phthalate, chlorinated diphenyl, butoxyglycol adipate, butyl phthalate, butyl sebacate, butyl stearate, butyl tartrate, ethoxy-glycol phthalate, ethoxydiglycol phthalate, ethyl hexyl phthalate, ethyl phthalate, triglycol di-2-ethylbutyrate, triglycol di-2-ethylbutyrate, triglycol chlorhydrin phthalate, ethyl o-benzoyl benzoate, diglycol dipropionate, methoxyglycol acetyl ricinoleate, butoxyglycol phthalate, tricresyl phosphate, methoxyglycol phthalate, sebacate or stearate, methyl phthalate, phenol-indenecoumarone oil, phenyl phthalate, diphenyl-o-xenyl phosphate, tri-(p-tertiary butyl-phenyl) phosphate, o- and p-toluene ethyl sulphonamides, o-cresyl-p-toluene sulphonate, ethyl phthalyl ethyl glycollate, butyl phthalyl butyl glycollate, methyl phthalyl methyl glycollate, di-(methylcyclohexyl) adipate, and tributyl citrate being listed. Fillers, such as zinc or lead oxides or titanium dioxide, clay, calcium or magnesium carbonates, may be added, and in the case of polyvinyl chloride vinylidene chloride copolymers, stabilizers such as lead oxide and hydroxide, condensation products of urea, the aliphatic esters of acetoxy chloro stearic acids, tertiary ethyl amyl or butyl urea, phthalimides, sulphonimides such as sodium and magnesium sulphonimides, calcium ethyl acetal acetate, lead stearate or oleate, diphenyl lead stearate or oleate, tribenzyl lead stearate, oleate or ricinoleate, diphenyl oxide, diphenyl lead oxide, triphenyl lead stearate, triphenyl basic tin stearate, ethyl benzidine and calcium stearate.  The lower coating may be prepared by mixing the ingredients in a rubber mill and applying the material to the backing by a calender, or it may be dissolved in a solvent and coated by means of a knife coater or a reverse roll coater.  The surface coating material may be dissolved in a solvent and applied in any suitable manner.