GB439046A - A method for making moulded articles from impregnated fibrous materials - Google Patents

Abstract

Moulded articles are produced by aggregating fibres into ductile structures such as sheets &c. by felting or similar operations and impregnating the ductile structures in a dry state with a solution or emulsion of a binding medium so that the binder is incorporated in the individual fibres, the impregnated structures being subsequently dried and moulded between dies with relative displacement of the constituent fibres. The fibres may be of animal, vegetable, or mineral origin, preferably ligno or pecto cellulose with an admixture of asbestos fibre if desired. Before, during, or after the felting operation the fibres are treated to remove oils &c. and uncover the fibre skeleton. The treatment may be a mechanical one, such as is used for textile fibres, or a chemical one with oxidizing or reducing agents &c. After the fibres have been felted and dried, small pieces are punched out of the sheet &c. These are impregnated with a binder such as natural or artificial resin, oil, bitumen, glue, gelatine, cellulose derivatives, rubber &c., in a hot or cold condition, by dipping, spraying, &c. The binding medium may give off gases during the moulding operation or substances may be added which generate gas, such as ammonium carbonate. Alternatively, gas-adsorbing substances such as lime or ferrous oxide may be added. Fillers, such as china clay, talc, wood flour, &c. may be added to the fibrous material and colours may be included in the binder. The impregnated material is dried and then moulded, preferably with the application of heat. The pressing operation may be carried out in stages and metal reinforcements may be embedded in the article. One or more pieces of impregnated material may be used which are smaller than the base of the article to be produced. As an example, 1 part of cotton is mixed with 30 parts of water, to which 10 per cent of soda ash may be added, and the whole is treated for 4-5 hours at a temperature of 50 DEG C. The fibrous material is rinsed and felted and then impregnated with synthetic resin and moulded as previously described. Hemp may be pretreated with a soap solution containing 100 parts by weight of rosin and 25 parts of sodium hydroxide in 1000 parts of water.