GB1102244A - Adhesive product - Google Patents

Abstract

Adhesive-carrying material comprises a substrate having a non-tacky exposed side and having on the other side a plurality of superposed coatings over at least a portion thereof, one of said coatings in contact with said substrate, being a tacky, pressure-sensitive adhesive, and another of said coatings, the outermost layer, being dry, solid and non-tacky but activatable to tacky adhesive form upon the application of heat or solvent, characterised in that the substrate, pressure-sensitive adhesive coatings and the dry, solid, non-tacky activatable coating are so selected and applied that the bond strength between the substrate and said tacky, pressure sensitive coating is greater than that between the latter coating and said dry, solid, non-tacky activatable coating whereby the substrate and pressure sensitive adhesive coating may be peeled as a unitary structure away from the non-tacky, activatable coating. The substrate may be any sheet material used in packaging, e.g. paper (including paper board), synthetic plastics films or moulded sheet forms, metal foil, cloth and combinations of these, and may form part or all of the entire packing. The pressure sensitive layer may comprise an elastomeric polymer, tackified with a tackifying resin and plasticisers and may be natural or synthetic. Polymers exemplified are: natural rubber, styrene-butadiene copolymers, butadiene-acrylonitrile copolymers, neoprene rubber, vinyl ethers such as polyvinyl isobutyl methyl ether and acrylic polymers. The tackifying resins may be the terpene resins, rosin esters such as the glycol esters of hydrogenated rosin, hydrocarbon resins and coumarone-indene resin. Heat-, or organic solvent-, activated polymers are listed, e.g. polyvinyl acetate; vinyl acetate-vinyl chloride copolymers; vinyl acetate-crotonic acid copolymers; vinyl acetate-ethylene copolymers; vinyl acetate-vinyl pyrollidone copolymers; polyvinyl butyral; polyvinylidene chloride; vinylidene chloride-vinyl chloride copolymers; ethyl cellulose; polyethylene; styrene-butadiene copolymers; waxes and wax polymer blends such as paraffin wax and ethylene-vinylacetate copolymer; nitrocellulose. Water-activated polymers mentioned are: vegetable glues like dextrines and starches; animal glues; polyvinyl alcohol; cellulose ethers; vinylacetate-crotonic acid copolymers; vinyl acetate-vinyl pyrollidone copolymers; vinyl methyl ether-maleic anhydride copolymers; salts of polyacrylic acid. The dry, non-tacky layer may be made up of two strata, the outer stratum being the primary, activatable adhesive for subsequent bonding and being of a material which may have too much affinity for the pressure-sensitive layer and the inner stratum being incompatible with the pressure-sensitive layer and serving as a barrier to insulate the latter layer from the outer stratum. The bond between the barrier layer and the outer stratum should be greater than between the pressure sensitive layer and the barrier layer. The barrier layer may be one of the systems mentioned as the dry, non-tacky layer or a system exhibiting no adhesive bonding such as wax or silicone. The pressure sensitive coating may be applied to the substrate by e.g. a reverse roll coater, trailing blade or knife over roll technique. The outer layer may be applied, e.g. by an air-knife coater; by extrusion; lamination; by a hot melt system; by spraying or dusting in the form of a liquid or powder. In the Examples, specific substrates are bonded to specific surfaces such as vinylidene chloride copolymer-coated cellophane (Cellophane is a Trade Mark), a polyethylene film, corrugated paper board, stainless steel. The adhesive-carrying material may take the form of sheet-packaging material, labels, headers, tapes, lids for lipped, open-top pans and trays, backs for "blister" type packages, or the "blister" itself, flaps on boxes, envelopes, pouches or other packages. Upon activation of the outermost layer and bonding of the substrate through the outermost layer to a surface, the substrate may ultimately be peeled away from the outermost layer, which adheres to the surface, thereby exposing the pressure-sensitive layer which selectively adheres to the substrate and is carried thereby. The resulting peeled-away substrate is now pressure-sensitive and can be re-applied, if desired, either to the same initial area, or to another area by finger pressure. Examples of the uses of the adhesive-carrying material are illustrated in the drawings (not shown) and include tape for p sealing the flaps of corrugated boxes, a bread wrapper label and sealer, sealing aluminium foil pan or tray, sealing a package of the type used for bacon.