Patent GB-572038-A (GB)
Title: Improvements in and relating to the treatment of protein or albuminoid material
IPC: A23J3/32
Filed: 1943-07-16
Abstract: The partial hydrolytic breakdown of protein or albuminoid materials by acid dissolution into colloidal dispersions is effected by incorporating a proportion of the material in an aqueous solution of an acid of a concentration not exceeding 2N and, when the acid has no amphoteric properties, a pH not exceeding 2.8 initially, and using the resulting solution as a solvent for one or more further proportions.  Boric acid may be used, when the pH will exceed 2.8. Addition of hydrochloric acid to reduce the pH is optional. Vegetable tanned leather is first subjected to an aqueous extraction to remove tanning matters, non-tans, salts, and sugars while chrome-tanned leather is treated with brine to eliminate free and combined sulphate.  The protein material may also be pretreated with nitrous acid as in the deamination of collagen.  The acid dissolution may be effected with, for example, hydrochloric, lactic or boric acid of N\2 - 1.5 N concentration for leathers and casein, and not above 2N for difficulty soluble proteins such as albumen, the quantity of acid being from below 2 to 5 times that of the protein.  For practical purposes, sulphuric, nitric, chromic, and phosphoric acids are excluded.  A temperature of 95-100 DEG  C. is used.  Alkali is excluded owing to the destructive action on arginine and histidine except for neutralizing the acid or for facilitating dissolution as in the case of vegetable-tanned leather where the fixed tans are loosened with caustic soda only during the dissolution by boric acid. The leather dissolutions obtained may have 75-85 per cent of the total N precipitable with phosphotungstic acid.  The products are used for producing dyestuffs and colouring matters by the processes of Specifications 552,189 and 555,866, chrome tanning liquors by the process of Specification 555,003, [Group VIII], plastics by condensation with aldehydes as in Specification 569,353 and, generally, products capable of being moulded or spun into threads. In Examples: (1) chrome leather cuttings or shavings are boiled with 6 per cent brine using successive treatments with fresh or used brine as desired.  After rinsing and, if desired, drying, the leather is added to approximately 3 per cent hydrochloric acid in three equal parts with simmering for 30-40 mins., 60-70 mins., and, finally, 5-7 hrs. after the respective additions.  Water may be added to keep the content of hide substance from exceeding 30 per cent.  The solution is filtered and the filtrate used direct or after neutralizing to a pH of 3-3.2 and concentrating.  The residue may serve as a filler for plastics; (2) 50 per cent more acid is used and a time not exceeding 5 hrs.; (3) vegetable tanned leather cuttings are boiled with water, washed with methylated spirit, and dried.  The product is added in three equal parts to 3 per cent boric acid, boiling for 1, 1, and 2 hrs. after the respective additions with small additions of 17N NaOH. The filtered solution may be treated with toluol or dipentane to prevent mould development.  It can be coupled with diazotised amines as in Specification 552,189.  The concentration of the boric acid may be doubled; (4) casein powder is refluxed with 1.5N HCl for 70 mins., 1hr., and 5-6 hrs. respectively after separate additions of 70, 70, and 60g.  Higher concentrations of acid may be used with a shorter time; (5) 3 per cent boric acid is used with additions of caustic soda and a total heating time of 1 1/2 hrs.  The products are applicable for plastics and adhesives; (6) egg albumen is added in two stages to hydrochloric acid, the acid also being added in three stages during the first half of the heating period; (7) egg albumen is dissolved in boric acid as is casein in (5), the total time required, however, being 30 hrs. with additional alkali.ALSO:Vegetable tanned leather cuttings are boiled with water, washed with methylated spirit and dried.  The product is added in three equal parts to 3 per cent. boric acid, boiling for 1, 1 and 2 hours after the respective additions with small additions of 17N NaOH.  The filtered solution is treated with toluol or dipentane to prevent mould development.