Removable pressure-sensitive adhesives for recyclable substrates

A pressure-sensitive adhesive composition which comprises:

• a) an inherently tacky, pressure-sensitive adhesive polymer formed by emulsion polymerization, which polymer comprises, on a polymerized basis and based on the total weight of the monomers:
• (i) at least one alkyl acrylate containing from about 4 to about 8 carbon atoms in the alkyl group, the total amount of alkyl acrylate present being from about 35 to 60 percent by weight;
• (ii) at least one vinyl ester containing from about 2 to about 16 carbon atoms in the alkyl group of the acid, the total amount of the vinyl ester present being from 15 to about 35 percent by weight;
• (iii) at least one diester of a dicarboxylic acid in which each alkyl group of the diester independently contains from about 6 to about 12 carbon atoms, the total of the diesters present being in amount from about 20 to about 40 percent by weight;
• and
• (iv) at least one unsaturated carboxylic acid containing from about 3 to about 5 carbon atoms, the total of the unsaturated carboxylic acid being present in a positive amount up to about 5 percent by weight, said polymer having a glass transition temperature of less than about -30.degree. C. and a gel content of from about 50 to about 70 percent by weight of the polymer, said formed emulsion polymer being combined with:
• b) for each 100 parts by weight of said formed emulsion polymer;
• (i) from about 3 to about 20 parts by weight of a rosin acid tackifer and,
• (ii) from about 1 to about 10 parts by weight of a rosin based surfactant,
• said pressure sensitive adhesive composition when applied to a paper backing being capable of self-separation from nonpaper surfaces of a polar or nonpolar substrate in hot water or alkali in less than about 5 minutes.

A pressure-sensitive adhesive composition which comprises:

• (a) an inherently tacky, pressure-sensitive adhesive polymer formed by emulsion polymerization, which polymer comprises, on a polymerized basis and based on the total weight of the monomers:
• (i) at least one alkyl acrylate including 2-ethylhexyl acrylate, isooctyl acrylate and mixtures thereof and having from about 4 to about 8 carbon atoms in the alkyl group, the total amount of alkyl acrylate present being from about 40 to about 50 percent by weight;
• (ii) vinyl acetate in an amount of from 15 to about 35 percent by weight;
• (iii) at least one diester of a dicarboxylic acid selected from di-2-ethylhexyl maleate and di-2-ethylhexyl fumarate and mixtures thereof present in an amount from about 20 to about 40 percent by weight;
• and
• (iv) an unsaturated carboxylic acid selected from the group consisting of acrylic acid, methacrylic acid and mixtures thereof present in an amount of from about 1 to about 3 percent by weight, said polymer having a glass transition temperature of less than about -30.degree. C. and a gel content of from about 50 to about 70 percent by weight of the polymer said formed emulsion polymer being combined with:
• b) for each 100 parts by weight of said formed emulsion polymer:
• (i) from about 3 to about 20 parts by weight of a rosin acid tackifier having an acid number greater than about 50 and less than 210;
• (ii) from about 1 to about 10 parts by weight of a rosin based surfactant;
• said pressure sensitive adhesive composition when applied to a paper backing being removable from a nonpaper surface of a polar or nonpolar substrate in hot water or alkali in less than 5 minutes.