| 摘要 |
<p>Modifying polyvinyl alcohol comprises (a) spraying a PVA powder with an amt. of solvent contg. a free radical polymerisable monomer such that the solvent swells the PVA powder but does not form a slurry with the PVA powder and does not dissolve the powder; (b) allowing the sprayed powder to swell; (c) spraying a free radical source onto the swollen powder; (d) raising the temp. of the swollen powder to initiate a reaction between the PVA and the polymerisable monomer. Pref., the PVA powder is maintained under constant agitation. The PVA has a particle size of less than about 5mm. The polymerisable monomer is selected from vinyl sulphonic acid, allyl sulphonic acid, methallyl sulphonic acid, salts of these acids, acrylamide, N-methylol acrylamide, 2-acrylamido methyl-propane sulphonic acid, acrylonitrile, acrylic acid, methacrylic acid and mixts. thereof; pref., allyl sulphonic acid or a salt thereof. The PVA is 87-89 mole.% hydrolysed. The solvent is water. Glycerol monooleate is added to facilitate mixing. The polymerisable monomer and the free radical source are added in stages.</p> |
