Patent GB-1353388-A (GB)
Title: Process for impregnating foams
IPC: C08G/
Filed: 1971-07-29
Abstract: 1353388 Impregnated foams BAYER AG 29 July 1971 [29 July 1970] 35733/71 Heading C3R [Also in Division B2] Foams are impregnated by reacting at the phase-interface of a largely open-cell foam either alone or with a compound containing reactive hydrogen atoms an isocyanate comprising a non-distillable residual isocyanate of the kind obtained during the commercial production of an aliphatic, araliphatic, cycloaliphatic or aromatic polyisocyanate and/or an NCO groupcontaining addition product having an average molecular weight of up to 12,000 of the residual isocyanates with a compound containing reactive hydrogen atoms, at least 2% by weight of distillable monomeric mono- and/or polyisocyanates being present in the residual isocyanate and/or NCO group-containing addition product. The reaction may be carried out in the presence of a catalyst. Preferably the foam contains urethane and/or urea and/or isocyanurate groups. The volume of the foam can be increased through the addition of solvents with a swelling effect and can be irreversibly fixed by the solids formed. Examples of suitable residual isocyanates are (a) that obtained after distillation in the production of tolylene diisocyanates, having a monomer content of 8-30%, (b) that obtained after distillation during production of diphenyl methane diisocyanate, having a monomer content of 10-20%, (c) that obtained after distillation in the production of hexamethylene diisocyanate, m-, p-xylylene diisocyanate and/or isophorone diisocyanate, having a monomer content of 8-20%. The reaction may be carried out in the presence of an additional polyisocyanate, e.g. an aliphatic, araliphatic, cycloaliphatic or aromatic polyisocyanate containing biuret groups or a solution thereof in a liquid polyisocyanate free from diuret groups, a linear diisocyanate polyester, polyether, polythioether, polyacetal or polycarbonate having a molecular weight of 400-10,000 either individually or in admixture with another polyisocyanate. Examples of reagents are polyketimines and/or aldimines, a semi-acetal of formaldehyde, chloral, N-methylol caprolactam, a methylolated phenol, or a linear methoxymethyl urethane with an average mole weight of 400-10,000, gaseous ammonia. The reaction may also be carried out in the presence of a carbonyl compound, e.g. formaldehyde, chloral hydrate, acetaldehyde, isobutyraldehyde or crotonaldehyde, or a compound capable of aminoplast or phenoplast formation, e.g. urea, thiourea, methylene diurea, urotropin, dicyanodiamide or a methylolation product thereof. Pigments, fillers, herbicides, biocides, or plant-nutrient salts may also be present. The foam may be film, cellular moulding, foam particles, e.g. in a fluidized bed. The polyisocyanate may be sprayed on a loose foam matrix in a mould. The foam may be of polyurethane, polyamide, modified phenol/formaldehyde resins, aminoplast foams, polystyrene, ABS-polymers, polyvinyl chloride, polycarbonate, natural rubber, cellulose foams. The foams may be impregnated with, e.g. polyvinyl chloride, polyvinyl acetate, ethylene-vinyl chloride copolymers, polychlorobutadiene, anionic or cationic polyurethane dispersions, acrylonitrile-styrene-butadiene latices, natural rubber latex, tar and optionally fillers and pigments. The products range from elastic foams to hard products. The treatment may increase the thermal stability and non-flammability of the product. Uses mentioned are as filter materials, insulating materials for soundproofing and sound-damping.