Patent GB-683958-A (GB)
Title: Improved manufacture of protein plastics
IPC: C08L89/00
Filed: 1949-10-25
Abstract: In a process for producing a protein plastic from water-insoluble animal protein substances such as muscular flesh of fish, fish-wastes, milts, fish meal, and herring meal wherein the initial material is first treated with alkali with a subsequent precipitation by means of a mineral acid, the alkali is employed in a quantity by weight corresponding to a limit of 15 per cent based on the dry protein content of the raw material and in the form of a caustic soda lye of 0.5-1 per cent NaOH concentration, at a temperature of 40-60 DEG  C., the solution prior to its being precipitated being subjected to a hardening process at elevated temperature by means of formalin. The hardening process is preferably effected with 40 per cent formalin at a pH of 7-10 in quantities corresponding to 5-40 per cent of the weight of dry protein contained in the initial material.  The initial material prior to the alkali treatment may be pretreated with weak acids, e.g. acetic or sulphurous acid, thus 0.5 per cent aqueous acetic acid may be used in a proportion by weight of from 0.5 : 1 to 3 : 1 to the weight of dry animal protein in the initial material. The protein may be subjected to a bleaching treatment during and after the dissolving process with alkali but prior to the hardening process, thus bleaching may be carried out with 30 per cent HO2 in a quantity of 3-20 per cent by weight based on the weight of dry protein in the initial material. In addition to the bleaching and hardening treatments the protein may also be dyed in its dissolved state after the hardening process, suitable dyestuffs being completely absorbed by the protein so that the latter may be precipitated in a coloured form. The protein may also be condensed with carbamide resins or dicyandiamide resins, the resins being added in quantities of about 5-15 per cent relatively to the weight of dry protein in the raw material.  The final product prior to being moulded may be treated with alcohol to improve its transparency.  a -Naphthol may also be added to increase water resistance.  Fillers such as wood flour or plasticizing means such as monomeric sulphonamides may also be added to the precipitated protein prior to its being used for moulding.  In examples: (1) fish meal is dissolved in aqueous sodium hydroxide solution at 55-60 DEG  C. and after filtering from the bones sulphuric acid is added to reduce the pH to 9 and formalin then added, the hardening process being effected at 40-50 DEG  C.  The protein is then precipitated with a dilute mineral acid, e.g. sulphuric acid, the pH being thereby lowered to 4-5. The solution is then filtered off and the protein dried; (2) as in (1) except that during and after the dissolving process bleaching is effected with 30 per cent hydrogen peroxide; (3) fish meal is dissolved in caustic soda lye as in (1) and, after filtering, the pH is reduced to 7 by adding sulphuric acid.  Formalin is then added as well as a carbamide resin, the solution being then maintained at 40-50 DEG  C., followed by precipitation with sulphuric acid, filtration and drying; (4) fish meal is treated with 0.5 per cent acetic acid and the water content then increased and sodium hydroxide added.  The dissolution is effected at 50-60 DEG  C. and bleaching is effected during and after the dissolving process by means of 30 per cent hydrogen peroxide, the subsequent procedure being the same as in (1).  The Specification as open to inspection under Sect. 91 also includes a temperature of 50-70 DEG  C. for the alkali treatment and states that when the raw proteinaceous material is given a preliminary treatment with acetic acid prior to its dissolution with caustic soda lye that the treatment with formaldehyde may be dispensed with.  It is also stated that the hardening of the solution may be carried out with any aldehyde.  This subject-matter does not appear in the Specification as accepted.