Pressure sensitive adhesive consisting of copolymers of alkyl esters of acrylic or methacrylic acid, and N-alkyl-substituted amides of ethylenically unsaturated carboxylic acids and, optionally, a copolymerizable therewith, ethylenically unsaturated compound.

摘要

A pressure-sensitive adhesive comprises an adhesive polymer containing units of (A) at least one monomer having the formula FORM:1072331/C3/1 and (B) at least one monomer having the formula FORM:1072331/C3/2 in which formulae, (i) R and R1 are hydrogen or methyl; (ii) X is -OH, -OR4 or FORM:1072331/C3/3 ; (iii) R1 represents alkyl groups containing up to 28 carbon atoms with an average no greater than 24; (iv) R2 represents alkyl groups containing up to 14 carbon atoms, at least 50% of the ester molecules having the R2 groups attached at non-tertiary carbon atoms to the indicated oxygen atom; (v) R3 represents hydrogen or alkyl groups containing up to 10 carbon atoms; and (vi) R4 represents alkyl groups containing up to 18 carbon atoms; the proportion by weight of (A) to (B) being from 1:19 to 3:1 but not exceeding a mol ratio of 1:1. The polymer may additionally contain up to 50% by weight of (A) and (B) of units of other monomers, e.g. acrylic and methacrylic acids and their nitriles, unsubstituted amides and esters, monoethylenically unsaturated dicarboxylic acids and their anhydrides, unsubstituted imide and amide derivatives and esters, vinyl esters (e.g. acetate, propionate and hexanoate) and ethers, vinyl and vinylidene chlorides, and unsaturated hydrocarbons such as styrene. The polymer may also comprise a small amount of a cross-linking monomer, e.g. ethylene glycol diacrylate or dimethacrylate, allyl acrylate or methacrylate, divinyl benzene, ethylene glycol dimaleate, dicitraconate, or di-itaconate, and the diamic derivatives of ethylene diamine and maleic, citraconic or itaconic acid. The polymers may alternatively be crosslinked simply by heating alone or in the presence of organic peroxides, epoxy compounds (e.g. a dicylic diepoxy carboxylate), formaldehyde resins, polyvalent metal compounds (e.g. of Zn, Ca or Cu) or polyamino, polyhydroxy or polyisocyanate compounds; cross-linking may also be effected with U.V. or electron beam irradiation. The adhesive polymers may be prepared by polymerizing the appropriate monomers (or the corresponding anhydride instead of monomer A with subsequent amidation) in solution in an inert solvent or in aqueous emulsion, preferably the latter employing a redox catalyst. Suitable catalysts include barium peroxide, hydrogen peroxide, dicumyl peroxide, di-t.-butyl peroxide, cumyl hydroperoxide, diacetyl peroxide, dibenzoyl peroxide, ammonium, sodium or potassium persulphate and potassium percarbonate with or without reducing agents such as ferrous salts, cuprous salts, bisulphites, thiosulphates, hydrosulphites, tetrathionates, dimethylaniline, triethanolamine and alkylene polyamines; polymerization may also be initiated with U.V. light in the presence of organic peroxides or photosensitizers such as benzophenone. Conventional ionic or nonionic emulsifiers can be used and, if desired, thickening agents such as polyvinyl alcohol, polyacrylates and cellulose derivatives; emulsifiers disclosed are sodium lauryl sulphate, ammonium laurate, polyalkylene glycol ethers and polyethoxylated isooctyl- and nonyl-phenols. The polymeric adhesive may contain additional components, e.g. tackifier resins, condensation resins, plasticizers such as glycerol, phthalate, phosphate and adipate esters, sebacic acid-propylene glycol polycondensates, sucrose esters, chlorinated biphenyl, liquid alkyl amic acids and diphenyl ether, and polymers such as polyvinyl methyl ether, polyvinyl ethyl ether and SBR rubbers. For application to a backing in preparing tapes, the adhesive may be dissolved in a solvent, e.g. methyl ethyl ketone or toluene.ALSO:Pressure-sensitive adhesive tapes are preprepared by coating an adhesive polymer, from an aqueous emulsion or a solution in methyl ethyl ketone or toluene, on a polyethylene terephthalate or paper backing. The adhesive polymer (see Division C3) comprises as essential components (A) one or more alkyl-substituted derivatives of acrylamide, methacrylamide, or mono-or di-amides, ester-amides or cyclic imides of certain unsaturated dicarboxylic acids (e.g. maleic, citraconic or itaconic), wherein said alkyl groups may contain up to 28 carbon atoms and (B) one or more alkyl acrylates or methacrylates containing up to 14 carbon atoms in the alkyl groups. The adhesives may additionally contain thickeners, tackifier resins, condensation resins, other addition polymers and plasticisers.