Aqueous polyvinyl ester dispersion, process for its manufacture, and its use
AssigneeHoechst Aktiengesellschaft
InventorsWerner Ehmann, Alfons Homanner, Helmut Rinno
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Abstract
An aqueous polyvinyl ester dispersion having a solids content of 35 to 65 weight % and containing 3 to 12 weight % (relative to the total amount of dispersed particles) of polyvinyl alcohol and 2 to 70 weight % (relative to the total amount of dispersed particles) of a natural starch has excellent adhesive properties. It is manufactured by emulsion polymerization of a vinyl ester optionally together with comonomers, and by subsequent distribution of the starch in the dispersion obtained by the emulsion polymerization. The dispersion is especially suitable for the manufacture of adhesives for porous substrates.
Claims13
An aqueous polyvinyl ester dispersion having a solid content of from 35 to 65 weight %,
- from 3 to 60 weight % of dispersed particles of which has a diameter of below 1 .mu.m and consists of from 95 to 100 weight % of polyvinyl acetate or a vinyl acetate copolymer and from 0 to 5 weight % of native starch,
- from 40 to 97 weight % of dispersed particles of which has a diameter of from 1 to 40 .mu.m and consists of from 20 to 95 weight % of polyvinyl acetate or a vinyl acetate copolymer and from 5 to 80 weight % of native starch, and
- the dispersion contains from 3 to 12 weight %, relative to the total amount of dispersed particles, of polyvinyl alcohol.
A process for the manufacture of an aqueous polyvinyl ester dispersion, having a solids content of from 35 to 65 weight % and dispersed particles of native starch, by free-radical-initiated polymerization of vinyl acetate, optionally together with up to about 10 weight %, relative to total polymer, of copolymerizable compounds, in an aqueous emulsion in the presence of polyvinyl alcohol,
- which comprises carrying out the polymerization in the presence of from 3 to 15 weight %, relative to the vinyl ester to be polymerized, of polyvinyl alcohol, having an ester number of from 60 to 210 and a viscosity (as a 4% aqueous solution) of from 4 to 60 mPa.s (measured at 20.degree. C.), and subsequently distributing the native starch homogeneously in the obtained dispersion.
A process for increasing the setting speed of adhesive comprising a polyvinyl acetate dispersion which comprises incorporating into the dispersion an amount of native starch particles sufficient to reduce the setting time without significantly reducing bonding strength.
Dependencies are inferred from the claim text.