Patent GB-945250-A (GB)
Title: Non-porous asbestos-reinforced plastic articles
IPC: F16L9/08
Filed: 1960-10-19
Abstract: A moulded fibre-reinforced plastic article such as a pipe or pipe fitting and which is non-porous, is made from asbestos fibre paper sheets or shreds fixed in a matrix of a cured thermosetting material the latter constituting between about 40% to 65% by weight of the article, the remainder being said asbestos paper, the asbestos paper comprising, by weight, about 90 to 99% of reinforcing fibres and about 1% to 10% of non-fibrous binder material, the reinforcing fibres comprising essentially asbestos fibres.  The thermosetting material may be derived from an epoxy, unsaturated polyester or phenolic resin, and the non-fibrous binder material may be a water insoluble acrylic ester polymer. In making the article a composition comprising the asbestos fibre paper impregnated with a thermosetting resin partially cured to a B-stage is formed to the desired shape, and then subjected to heat and pressure to mould the composition to the final shape and to cure the resin to the thermoset stage.  In particular examples:  (a) a paper of chrysolite asbestos fibres, 97% by weight, and a non-fibrous binder of polyalkyl acrylate emulsion, 3% by weight, is impregnated with a thermosetting epoxy resin, 59.5% by weight, comprising predominately the polyglycidyl ether of 4, 41-dihydroxy diphenyl dimethyl methane, the resin being cured to the B-stage with the aid of a catalyst of m-phenylene diamine the content of which is 10.5% by weight; the solvent, methyl ethyl ketone, content of the resin is 27% by weight and 3% by weight of carbon black is added,  (b) the paper as in (a) is impregnated with a thermosetting phenolic resin comprising predominately the condensation product of phenol and formaldehyde and including therein a suitable catalyst, e.g. hexamethylene tetramine, to effect cure; the resin has a content of 60% by weight and includes a solvent, ethanol, the content of which is 39% by weight,  (c) paper comprising asbestos fibre, cellulosic fibre (kraft paper) and a non-fibrous binder of polyalkyl acrylate emulsion respectively of 78, 19 and 3% by weight content, is impregnated with a thermosetting phenolic resin of 60% by weight content and comprising predominately the condensation product of phenol and formaldehyde and including therein a catalyst, e.g. hexamethylene tetramine a solvent (ethanol) of content 39% by weight and a dye of 1% by weight content, and  (d) the paper as in (c) is impregnated with a thermosetting epoxy resin of 59.5% by weight content and comprising predominately the polyglycidyl ether of 4, 41- dihydroxy diphenyl dimethyl methane, the impregnating solution including a solvent (methyl ethyl ketone), a catalyst (m-phenylene diamine) and carbon black respectively of 27,10.5 and 3% content.  The paper, including an acrylic resin binder (3% by weight content) may be impregnated with a high-temperature phenol-formaldehyde resin dissolved in methyl isobutyl ketone in the proportions 70 to 30% by weight, and paper of other types of asbestos fibre, e.g. Cape Blue, are impregnated with both epoxy and phenolic resins.  The paper may be of chrysolite asbestos fibre and impregnated with a thermosetting unsaturated polyester comprising diallyl phthalate and styrene in the ratio of about 80:20, and the resin is cured with the aid of a catalyst mixture comprising equal parts of benzoyl peroxide, and methyl ethyl ketone peroxide.  The paper is passed through a tank containing the resin and then through squeeze rollers to control the amount of liquid saturating material remaining in the paper; the latter is then passed through an oven maintained under controlled conditions to evaporate volatile components from the paper and to partially cure the resin to a B-stage. The paper comprises an asbestos fibre content of 99% by weight and a non-fibrous binder of polyalkyl acrylate emulsion of 1% by weight and the resin and catalyst contents are 99% and 1% by weight respectively.ALSO:A moulded fibre-reinforced plastic article such as a pipe or pipe fitting and which is non-porous, is made from asbestos fibre paper sheets or shreds fixed in a matrix of a cured thermosetting material the latter constituting between about 40% to 65% by weight of the article, the remainder being said asbestos paper, the asbestos paper comprising, by weight, about 90 to 99% of reinforcing fibres and about 1% to 10% of non-fibrous binder material, the reinforcing fibres comprising essentially asbestos fibres.  The thermosetting material may be derived from an epoxy, unsaturated polyester or phenolic resin, and the non-fibrous binder material may be a water insoluble acrylic ester polymer. In making the article a composition comprising the asbestos fibre paper impregnated with a thermosetting resin partially cured to a B-stage is formed to the desired shape, and then subjected to heat and pressure to mould the composition to the final shape and to cure the resin to the thermoset stage.