Viscoelastic sound-absorbing polyurethane foam and preparation method thereof

A sound-absorbing viscoelastic polyurethane foam, characterized in that the foam is prepared from a reaction system comprising the following components:

• (a) a polyisocyanate composition comprising 0-5 wt % of toluene diisocyanate, based on the total weight of the polyisocyanate composition, wherein the number average functionality of isocyanate groups in the polyisocyanate composition is 2-2.4 and the NCO content is 20-35 wt %;
• (b) an isocyanate-reactive component consisting of:
• (bi) water, in an amount of 2-5 wt % of the weight of mixed polyethers;
• (bii) a copolyol of epoxypropane-epoxyethane or a conjugate thereof, wherein the content of oxy-ethylidene units is 5-35 wt % with an average functionality of 2-4 and an average hydroxyl value of 20-65 mgKOH/g, which is in an amount of 30-70 wt % of the weight of mixed polyethers;
• (biii) a copolyol of epoxypropane-epoxyethane or a conjugate thereof, wherein the content of oxy-ethylidene units is 75-80 wt % with an average functionality of 2.8-3.5 and an average hydroxyl value of 35-60 mgKOH/g, which is in an amount of 2-10 wt % of the weight of mixed polyethers;
• (biv) a polyether polyol of epoxypropane-epoxyethane or a conjugate thereof, wherein the content of oxy-ethylidene units is 0-20 wt % with an average functionality of 2-5 and an average hydroxyl value of 180-830 mgKOH/g, which is in an amount of 20-65 wt % the weight of mixed polyethers;
• (bv) a chain extender and/or a cross-linking agent, in an amount of 0-10 wt % of the weight of mixed polyethers;
• wherein the mixed polyethers are mixtures of component (bii), component (biii) and component (biv), and in the mixed polyethers, the sum of the weight percent of components (bii), component (biii) and component (biv) is 100 wt %;
• (c) a surfactant, in an amount of 0-1 wt % the weight of mixed polyethers;
• (d) a catalyst, in an amount of 0-3.5 wt % of the weight of mixed polyethers;
• and
• (e) an optional additive, comprising one or two or more of color pastes, internal mold release agents, flame retardants, fillers, antistatic agents, perfumes, antioxidants, light stabilizers, mineral oils and antimicrobial agents;
• wherein the reaction system has an isocyanate index of 0.6-0.8.