Patent GB-1076909-A (GB)
Title: Process for the preparation of polyurethane resins
Inventor: KEBERLE WOLFGANG
IPC: C08G18/84
Filed: 1966-04-04
Abstract: Polyurethane resins are prepared by a process in which a predominantly linear polyurethane of M.W. 5000 to 2,000,000 prepared from one or more hydroxyl compounds having two or more reactive hydrogen atoms at least one of which is contained by a hydroxyl group and a M.W. of 300 to 10,000, one or more organic polyisocyanates and if desired one or more chain extending agents is reacted with an aliphatic or aromatic aldehyde and simultaneously or subsequently with a metal sulphite, metal hydrogen sulphite, metal aminocarboxylate, metal aminosulphonate, metal amidosulphonate or metal hydroxymethyl sulphoxylate at 0 DEG  to 150 DEG  C.  The process is effected in one of two ways, (a) by adding the aldehyde at an alkaline pH and then adding the reactive salt-type compound, or (b) by adding the aldehyde and salt-type compound simultaneously in which case an alkaline pH need not be established.  The predominantly linear polyurethanes may be prepared from (c) polyhydroxyl compounds which are polyesters, polyacetals, polyethers, polythioethers, polyamides or polyesteramides, (b) polyisocyanates which are aliphatic or aromatic diisocyanates, and which may be masked, 1,6-hexanediisocyanate being exemplified, and (c) chain extending agents which are glycols, diamines, aminoalcohols, dicarboxylic acids, aminocarboxylic acids and water.  Formaldehyde is the preferred aldehyde to react with the polyurethane but acetaldehyde, propionaldehyde, butyraldehyde, isobutyraldehyde, valeric aldehyde, benzaldehyde which may be substituted, salicylic aldehyde, vanillin and hexahydrobenzaldehyde may be used.  The lithium, sodium and potassium salts of the salt-type compounds are preferred, exemplified compounds being sodium sulphite, sodium hydrogen sulphite or laurine sodium.  Initially, the polyurethane may be prepared in the presence of an organic solvent which may subsequently be replaced or diluted with water or partly or completely replaced by water at the same time as or after the reaction of the polyurethane with the aldehyde and salt-type compound.  Suitable organic solvents are hydrocarbons which may be halogenated, ketones, alcohols, esters and nitriles.  The aqueous or aqueous-organic solutions or dispersions may also contain emulsifiers or dispersing agents or may be blended with solutions or dispersions of the same charge.  Cross-linking of the products of the process may also occur by reaction with e.g. sulphur, formaldehyde and formaldehyde donors, polyisocyanates, carbodiimides, polyamides, oxides, carbonates or hydroxides or polyvalent metals and peroxides.ALSO:Textiles, leather, paper, wood or metals may be coated with a polyurethane which has been prepared by reacting (I) a predominantly linear polyurethane of M.W. 5000 to 2,000,000 prepared from one or more hydroxyl compounds having two or more reactive hydrogen atoms at least one of which is contained by a hydroxyl group and a M.W. of 300 to 10,000 one or more organic polyisocyanates and if desired one or more chain lengthening agents with (II) an aliphatic or aromatic aldehyde and simultaneously or subsequently with a metal sulphite, metal hydrogen sulphite, metal aminocarboxylate metal aminosulphonate metal amidosulphonate or metal hydroxymethyl sulphoxylate at 0 to 150 DEG C.  The polyurethane (I) may be prepared from (a) polyhydroxyl compounds which are polyesters, polyacetals, polyethers, polythioethers, polyamides or polyesteramides (b) polyisocyanates which are aliphatic or aromatic and which may be masked and (c) chain lengthening agents which are glycols, diamines, aminoalcohols, dicarboxylic acids, aminocarboxylic acids and water.  Formaldehyde is the preferred aldehyde and sodium sulphite, sodium hydrogen sulphite or taurine sodium the preferred salt type compounds.  The reaction products are suitably coated onto the substrates in the form of an aqueous or aqueous-organic dispersion.