| 摘要 |
<p>PURPOSE:To obtain the subject resin having excellent dispersibility of inorganic materials and organic materials, flexibility, etc., and giving an ink composition for erasable marking pen having high stability to keep excellent writing performance with the lapse of time by acetalizing a specific modified PVA under specific condition. CONSTITUTION:A modified PVA containing 0.01-5mol% of a unit containing a hydrophilic group selected from COOM, SO3M, OSO3M, PO(OM)2, group of formula I (R is alkyl; M is H, Li, etc.), tertiary amine group, quaternary ammonium salt group and betaine residue and having a polymerization degree of 200-3,500 and a saponification degree of 75-99.8mol% is acetalized with acetaldehyde and/or butyraldehyde under a condition satisfying the formula II [A is acetalization degree (%); B is butyralization degree (%); A>=0; B>=0]. The modified PVA is preferably produced by performing the addition polymerization of a monosubstituted ethylene having the above hydrophilic group in the polymerization of polyvinyl acetate and hydrolyzing the product.</p> |
