| 摘要 |
<p>The invention concerns wood glue powders which are re-dispersible in water, form solid blocks, have a minimum filming temperature of 0-5 ·C and contain: (a) 70-90 wt % one or more vinyl ester homopolymers or vinyl ester copolymers of vinyl esters of unbranched or branched alkyl carboxylic acids with 1-18 carbons; and (b) 10-30 wt % one or more fully saponified vinyl alcohol homopolymers or vinyl alcohol copolymers with a degree of hydrolysis of 96-100 mol % and a Hoeppler viscosity of 2-15 mPa/s, measured in a 4 % aqueous solution, the proportions in each case being expressed in terms of the total weight of polymer components (a) and (b). The proposed wood glue powders can be obtained by mixing aqueous dispersions of the vinyl ester polymers (a) produced by the emulsion polymerisation process with the vinyl alcohol polymers (b) and optionally other additives, followed by spray drying of the mixture. The wood glue powder is suitable for use in aqueous adhesive dispersions, the re-dispersible powder simply being dispersed in the appropriate quantity of water.</p> |
