GB1528612A - Polyurethane foams and foam composites - Google Patents

Abstract

1528612 Polyurethane foams and foam compositions IMPERIAL CHEMICAL INDUSTRIES Ltd 15 Jan 1976 [27 Jan 1975] 3365/75 Heading C3R Semi-rigid to rigid polyurethane foams are made by a process which comprises (a) preparing an NCO-ended quasi prepolymer from an excess of a mixture of methylene bridged polyphenyl polyisocyanates, (MDI), and a polyol, said prepolymer having admixed therein a non-ionic emulsifying agent devoid of hydroxy, amino and carboxylic acid groups, (b) mixing water with the said prepolymer to form a water in oil emulsion, there being used more than the theoretical amount of water required to react with each unreacted NCO group in the prepolymer, and (c) allowing the water in oil emulsion to foam and set. In an embodiment a polyurethane foam bonded aggregate is prepared by mixing together aggregate or filler material and the above water in oil emulsion and allowing the mixture to foam and set. Suitable polyols are linear or branched polyesters, polyesteramides and polyethers, or monomeric polyols, e.g. ethylene glycol, trimethylol propane or butane diol. Suitable emulsifying agents include condensates of alkyl phenols, long chain alcohols and amides with ethylene oxide, the end hydroxy group being etherified or esterified, but is preferably one of the formula where R is a C 1 -C 4 alkyl group, n is at least 5 and X is the residue of a di- or polyisocyanate and contains at least one free NCO group. X may be derived from MDI or NCO-ended prepolymers thereof. The emulsifying agent may also be one of the formula where X is the residue of an organic isocyanate, R<SP>1</SP> is a C 1 -C 4 alkyl radical, n+m is at least 10, and R which is only present when X represents the residue of a di- or higher functional isocyanate, is an isocyanate group or a group of the formula and may be prepared by reaction of an isocyanate with a bis-(alkoxypolyethenoxy) ester of malonic acid. The emulsifying agent may be added during or after the preparation of the prepolymer or it may be prepared in situ during step (a), for example, by reacting the mixture of methylene bridged polyphenyl polyisocyanate with a polyethenoxy alcohol of the formula RO(CH 2 CH 2 O) n H, before, after or simultaneously with the reaction with the polyol. The amount of emulsifying agent used is generally from 1-15 p.b.w. per 100 p.b.w. of MDI. The amount of water used in step (b) is generally from 0À5 to 6À0 molecules of H 2 O per NCO group in the prepolymer. A catalyst, preferably an imidazole may be used to increase the rate of foaming in step (c). An inert lowboiling solvent, e.g. trichlorofluoromethane, may be added to the prepolymer to reduce its viscosity. The water in step (b) may contain a protective colloid, e.g. a silica dispersion. The aggregate of filler may be expanded clay, expanded vermiculite, pumice, broken foamed concrete, foundry sand, hollow or expanded glass spheres, chopped rigid urethane or isocyanurate foam scrap, scrap polystyrene, wood chip, cork, saw dust, fibrous materials and powdered fillers. When the aggregate or filler is absorbent it may be prewetted prior to admixture with the emulsion. A thickening agent such as sodium alginate, sodium carboxymethylcellulose or polyacrylamide may be added to the water, when the filler used is porous. A fire-retardant, e.g. a chlorinated phosphate, urea, ammonium salts, phosphates, borates, sodium hexametaphosphate or sodium pentaborate, and additional surface active agents to make the product more hydrophilic, may be incorporated into the foam formulation. Thin slices of the foam may be crushed to produce non-woven fabric type materials. The foam composites can be used in the building industry. In Examples 1 and 2 a foam is prepared by reacting crude MDI oxypropylated glycerol (M.Wt. 1000) and a monomethyl ether of polyethylene glycol (M.Wt. 300) in the presence of either trichloroethyl phosphate (Example 1) or acetylacetone (Example 2), optionally diluting the resulting emulsifiable prepolymer with trichlorofluoromethane (Example 1), and then emulsifying with water containing sodium bicarbonate and a catalyst, e.g. 2-methyl-imidazole and allowing the mixture to foam. Thin slices of the foam of Example 2 were compressed to give hydrophilic compacted sheets. In Example 3 a foam composite is prepared by mixing expanded clay balls (diameters 4-30 mm.) with water thickened with polyacrylamide, and then adding a water in oil emulsion of a prepolymer prepared by reacting crude MDI, an oxypropylated glycerol and a monomethyl ether of polyethylene glycol, then adding water containing dimethylimidazole and an ethylene oxide tipped oxypropylated ethylene glycol surfactant, transferring the resulting mixture into a jigged panel cavity and allowing it to foam.