Process for producing rigid open-cell foam

A process for producing a rigid open-cell foam, which comprises mixing and spraying onto a substrate, by a spraying method, a liquid component (X) which comprises a polyol (P), a blowing agent, a surfactant and a catalyst, and a liquid component (Y) which comprises a polyisocyanate compound, and subjecting the mixture on the substrate to foaming and a reaction for curing, wherein

• the polyol (P) comprises the following polyols (A), (B) and (C), and based on the entire amount of the polyol (P), the content of the polyol (A) is from 45 to 80 mass %, the content of the polyol (B) is from 10 to 40 mass %, the content of the polyol (C) is from 5 to 30 mass %, and the total content of the polyols (A), (B) and (C) is from 90 to 100 mass %, and
• the blowing agent comprises water,
• polyol (A):
• a polyol that has a hydroxy value of from 100 to 900 mgKOH/g, obtained by ring-opening addition of an alkylene oxide to an initiator (S1) that contains no nitrogen atom and has from 2 to 8 functionality, or a polyhydric alcohol that contains no nitrogen atom and has from 2 to 8 functionality and a hydroxy value of from 100 to 900 mgKOH/g,
• polyol (B):
• a polyol that has a hydroxy value of from 20 to 56 mgKOH/g and a terminal oxyethylene group content of from 5 to 15 mass %, obtained by ring-opening addition of an alkylene oxide other than ethylene oxide, to an initiator (S2) that contains no nitrogen atom and has from 2 to 8 functionality, followed by ring-opening addition of ethylene oxide,
• polyol (C):
• a polyol that has a hydroxy value of from 50 to 350 mgKOH/g, obtained by ring-opening addition of ethylene oxide and an alkylene oxide other than ethylene oxide, to an initiator (S3) that contains nitrogen atom(s) and has from 3 to 5 functionality, wherein the amount of ethylene oxide based on the entire amount of the alkylene oxide is from 30 to 80 mass %.