Patent GB-596714-A (GB)
Title: Improvements in the production of board or similar material
Filed: 1945-07-31
Abstract: In the manufacture of boards or the like of fibrous material (see Group VIII), an emulsion of bituminous material together with a polymerizable material which will cause hardening on stoving is added to a fibrous pulp or sheet, the bitumen is precipitated, and the product is hardened by heating.  The polymerizable material may be wool grease pitch, stearin pitch, bone tar pitch, or the like, residues from the distillation of oils, or a thermo-setting material such as artificial resin.  The bitumen and polymerizable material may be mixed and emulsified together, or separate emulsions may be prepared and mixed together according to examples, (a) vegetable oil residue, stearin pitch, or vegetable oil pitch is heated with zinc oxide to neutralize any fatty acid present, and is stirred into Trinidad asphalt or a petroleum bitumen, and the mixture is emulsified in water containing sodium metasilicate and potassium hydroxide; (b) coal tar pitch is fluxed with Trinidad asphalt and a soft vegetable pitch, sulphur is added, and the mix emulsified in water containing casein, bentonite, and caustic soda; (c) powdered phenol-formaldehyde resin is dissolved in petroleum bitumen, and the mix emulsified as in (b).  Specification 577,469 is referred to.ALSO:In the manufacture of boards or the like of fibrous material (see Group VIII) an emulsion of a bituminous material together with a polymerizable material which will cause hardening on stoving, e.g. a thermosetting artificial resin, is added to a fibrous pulp or sheet, the bitumen is precipitated and the product is hardened by heating. The fibrous material is preferably asbestos, but paper or other material may be employed provided the heating is effected at lower temperatures for a longer period. The bituminous and polymerizable materials may be mixed and emulsified together (see Group III), or separate emulsions may be prepared and mixed together or applied separately to the fibres. Sulphur and other accelerators may be included.  The emulsion is thoroughly beaten into a pulp of 5 per cent of asbestos fibre in water, the amount of asbestos and bituminous material being substantially equal, and the bituminous material is then precipitated with aluminium sulphate.  The mixture is then diluted so as to contain 0.5-1 per cent solids and is fed to the board machine.  Alternatively, the emulsion may be applied to the dry or semi-dry board.  According to an example, powdered phenol-formaldehyde resin is dissolved in a petroleum bitumen, and the mix is emulsified in water containing casein, bentonite and caustic soda.ALSO:Boards and the like of fibrous material on which a bituminous material has been precipitated are formed by adding to a fibrous pulp or sheet an emulsion of bituminous material together with a polymerizable material which will cause hardening on stoving, precipitating the bituminous material and hardening by heating. The fibrous material is preferably asbestos, but paper or other material may be employed provided the heating is effected at lower temperatures for a longer period.  The polymerizable material may be wool grease pitch, stearin pitch, bone tar pitch, or the like, residues from the distillation of oils, or a thermosetting material such as an artificial resin.  The bitumen and polymerizable material may be mixed and emulsified together, or separate emulsions may be prepared and mixed together or applied separately to the fibres. Sulphur and other accelerators may be included, and, in order to prevent the formed web from adhering to the machine rollers, the fatty acids in the polymerizable material may be wholly or partially converted into heavy metal or alkaline earth metal soaps before emulsification.  The emulsion is throughly beaten into a pulp of 5 per cent. of asbestos fibre in water, the amount of asbestos and bituminous material being substantially equal, and the bituminous material is then precipitated with aluminium sulphate.  The mix is then diluted so as to contain 0.5-1 per cent. solids and is fed to the board machine.  The product is dried slowly at a temperature not exceeding 90 DEG C. and is then stoved at 150-170 DEG C. for a number of hours.  The material may be shaped either immediately after formation on the board machine, after drying, or during or after stoving; alternatively, after drying, the material may be reeled and stored until required for moulding and stoving.  Instead of incorporating the emulsion in the pulp, it may be applied to the dry or semi-dry board.  Stoving enamels may be added during the stoving. According to examples (a) vegetable oil residue, stearin pitch, or vegetable oil pitch is heated with zinc oxide, and stirred into Trinidad asphalt or a petroleum bitumen, sulphur is then added if desired, and the mix emulsified in water containing sodium metasilicate and potassium hydroxide; (b) coal tar pitch is fluxed with Trinidad asphalt and a soft vegetable pitch, sulphur is added, and the mix emulsified in water containing casein, bentonite, and caustic soda; (c) powdered phenol-formaldehyde resin is dissolved in a petroleum bitumen, and the mix emulsified as in (b).  Specification 577,469, [Group III], is referred to.