UNDERCOAT COMPOSITION

PROBLEM TO BE SOLVED: To provide an undercoat compsn. which can form a uniformly foamed cell layer having a uniform surface skin and exhibiting enhanced impact absorption and soundproofness by using a polyvinyl chloride resin, a plasticizer, a calcium carbonate powder, a blowing agent, a blowing assistant, and a moisture absorbent as the essential ingredients and using urea or a urea compd. treated with a fatty acid as the blowing assistant. SOLUTION: A vinyl chloride-vinyl acetate copolymer. having a degree of polymn. of 1,500-2,100 and suitably having a vinyl acetate content of 4.0-10.0%, is used as the polyvinyl chloride resin. A combination of a phthalic ester plasticizer [e.g. di-n-butyl phthalate or di-2-ethylhexyl phthalate (DOP)] with at least one plasticizer selected from among polyester-, sulfonate-, and phosphate-based ones is used in an amt. of 35-60 wt.%. The average particle size of calcium carbonate used is pref. 0.03-0.07 μm. Both inorg. blowing agents (e.g. sodium bicarbonate) and org. blowing agents (e.g. azodicarbonamide) can be used. Urea. etc., coated with stearic acid, etc., is used as the blowing assistant.