Water-soluble polymers prodn. - by suspension (co)polymerisation of N-vinyl-formamide or -acetamide, addn. of hydroxylamine to remove residual monomer, and acid hydrolysis

摘要

Prodn. of water soluble polymers (I) is by suspension polymerisation of N-vinyl amides of formula CH2=CH-NHCO-R (II), (R is H or Me), or a mixt. of (II) and other water soluble vinyl comonomer(s), followed by acid hydrolysis. (III) is added after polymerisation and before hydrolysis. Water-insol. hydrocarbon solvent is pref. used as dispersion medium (IV), in amts. of 0.5-10, pref. 1-5, times the wt. of the initial aq. monomer soln.; pref. solvent forms an azeotrope with water, esp. cyclohexane. Initial aq. monomer soln. has concn. 5-95 (pref. 20-80) wt.%. The system also contains acrylonitrile as comonomer, 0.01-5 (pref. 0.05-1) wt.% non-emulsifiable oil-soluble polymer or surfactant as dispersion stabiliser (w.r.t. amt. of IV) and 0.1-20 (pref. 1-15) wt.% polymerisation stabiliser, pref. NH4Cl or CaCl2, esp. pref. NH4Cl, (w.r.t. total monomers). (III) is added in the form of a salt of HCl, H2SO4 or HNO3. 90% or more (pref.95% or more) of the original monomer(s) is polymerised. (III) is added after polymerisation, pref. in amts. of 0.05-10 mols. per mol. residual monomer(s), and the mixt. is then stirred for 0.25-4 hrs. at a temp. between room temp. and polymerisation temp.. The mixt. is hydrolysed in the presence of HCl, pref. at 20-150 deg. C, and at least 60% of the amide gps. are hydrolysed. USE/ADVANTAGE - Esp. as flocculating agents and paper treatment additives. Addn. of (III) significantly reduces the amt. of residual (II) in the polymerised mixt.. This prevents the modified or hydrolysed prod. from gelling after acid hydrolysis and thus facilitates the prodn. of water-soluble (I) in the form of good quality powder.