Patent GB-1231787-A (GB)
IPC: B32B27/00
Filed: 1967-06-29
Abstract: 1,231,787. Coated fibrous webs. DUNLOP CO. Ltd. 26 June, 1968 [29 June, 1967], No. 30063/67. Heading B2E. [Also in Division C3] A sheet material comprises a fibrous web impregnated or coated with a composition which comprises the reaction product of a polyfunctional polymer having terminal thiol groups and a potentially thermosetting aminoplast. Catalysts may be present to accelerate the reaction between the two polymers. Suitable catalysts are acid dibutyl phosphates and para-toluene sulphonic acid. The catalyst may be in the form of an acidic solution in amount from 0.1 to 3 parts by weight and 100 parts by weight of the aminoplast. Suitable polymers for the backbone of the polyfunctional polymer are polymers of alkylene oxides, including copolymers with substituted alkylene oxides, such as polymers of 1:2-propylene oxide or 1:3-propylene oxide or copolymers of these with epichlorohydrin. Other suitable polymers may be formed by the reaction of sodium polysulphides with polyfunctional aliphatic halogen compounds. Difunctional aliphatic halogen compounds may be used with minor amounts of trifunctional halogen compounds for the purpose of increasing the functionality of the resulting polymer by branching. Excess of 95 mole percent difunctional compound is used with less than 5 mole percent of trifunctional compound. Suitable compounds are bis(2-chlorethyl formal) and trichloropropane. Other suitable polymers are those having a high molecular weight and a number of thiol groups such as the Synergite and Thiokol (Reg. Trade Mark) resins. The polymer may have molecular weight of 250 to 10,000. The polymers may be used as liquids or as solutions in solvents such as hydrocarbons, e.g. benzene and toluene and chlorinated hydrocarbons, e.g. chlorobenzene and chloroform, and carbon tetrachloride. Up to 300 parts by weight of solvent per 100 parts by weight of the polymer can be used. The solutions may be dipped, painted, spread or sprayed on to fibrous web. Suitable thermo-setting aminoplasts are the condensation products of amino compounds and formaldehyde and copolymers of the amino compounds with epoxides. Typical amino compounds which may be used are urea, ethylene urea and amino triazines such as melamine and benzoguanamine. The amount of aminoplast may be from 1.0 parts to 5.0 parts per 1.0 part of the polymer. The impregnating composition may be present in the product by ratio of from 1.0:0.5 to 1.0:3.0 of the weight of the fibrous web. The fibrous web may be a single layer such as a paper web or a web of textile fibres in the form of a woven fabric or non-woven fabric, e.g. a felt, or it may be a multi-layer composite web. Suitable composite webs are formed from paper webs and textile fibres and a layer of non-fibrous material such as a strip of aluminium or other heat-resistant material may be included to confer heat-resistant properties. The several layers may be united together before the impregnating composition is applied or they may be united by the impregnating operation itself when the composition is crosslinked to form a flexible laminate. The impregnated webs may alternatively be superimposed prior to or subsequent to the curing of the composition. In the former case they may be mechanically locked together, for example, as by needling or they may be laminated by means of conventional laminating resins such as aminoplasts or phenolic resins. Impregnated fibrous web may be dried at 70-80C. and curing subsequently effected by heating at 140-200C. Reference has been directed by the Comptroller to Specification 1,148,652.