various investigators have suggested adding chromium salts to the syntans. chromium salts To increase the temperature of gelatinization of syntan leather.leather produced by the use of such syntans has exhibited a very poor temperature of gelatinization value usually running in the order of about 60 C.Leather properly tanned with chromium salts can usually be kept in boiling water for 5 minutes or longer without showing any signs of curling.the temperature of gelatinization is a relative measure of the reaction of the tanning agent upon the skin protein causing the latter to withstand or tolerate various degrees of temperature without harm.temperature of 40 gelatinization is used herein to connote that temperature at which the tanned leather shrinks or shrivels when subjected to elevated temperatures.chrome tanned leathers the individual fibers are usuallythin as in dried, raw skin, but in vege- 0 table tanned leathers, the fibers are much larger and in most cases they almost completely fill the interfibrillary spaces, thus giving a very desirable.chrome tannage will not produce the degree of plumpness and fullness which the trade demands. Chrome tanning processes take much less time than vegetable tanning processes, and at the present time most of the worlds supply of light leathers is tanned by means of chromium salts.In some cases,'such as in the tanning of sole leather, months are required to complete the process. At regular intervals the hides are moved into stronger and fresher tanning liquors until they are completely tanned. By such a process they treat the skins first with a tan liquor which has already been used to tan a large number of skins and in which, consequently, the ratio of nontannin to tannin is very great. tanners In order to overcome such difiiculties, tanners have found it necessary to adopt a stepwise process when tanning with vegetable tannins.the rate of combination of the tannin with the skin protein is very likely to be abnormally great compared to the rate of diffusion of the tannin into the interior of the skin consequently the outer layers of the hide are drawn or contracted to a greater extent than the inner layers whereby distortion of the outer layers with 25 respect to the inner layers is efi'ected, thus greatly detracting from the appearance and value of the leather.One method that has been proposed involves the use of concentrated tanning liquors.the vegetable taming process is used principally in the production of heavy leathers such as sole leather.leather is in the majority of cases, tanned by either a vegetable tanning process or a chrome tanning process depending upon the type of leather to be produced.This invention relates in general to the tanning of leather and more particularly to new synthetic tanning agents and to an improved process 1 of tanning leather.C14C3/00- Tanning Compositions for tanning.TANNING, IMPREGNATING, FINISHING APPARATUS THEREFOR COMPOSITIONS FOR TANNING C14C- CHEMICAL TREATMENT OF HIDES, SKINS OR LEATHER, e.g.Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.) Filing date Publication date Application filed by National Oil Products Co filed Critical National Oil Products Co Priority to US419944A priority Critical patent/US2401373A/en Priority to US608607A priority patent/US2437044A/en Priority to US608608A priority patent/US2401508A/en Application granted granted Critical Publication of US2401373A publication Critical patent/US2401373A/en Anticipated expiration legal-status Critical Status Expired - Lifetime legal-status Critical Current Links Original Assignee National Oil Products Co Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.) Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.) Expired - Lifetime Application number US419944A Inventor Edwin A Robinson Ralph M Beach Current Assignee (The listed assignees may be inaccurate. Google Patents US2401373A - Tanning of leatherÄownload PDF Info Publication number US2401373A US2401373A US419944A US41994441A US2401373A US 2401373 A US2401373 A US 2401373A US 419944 A US419944 A US 419944A US 41994441 A US41994441 A US 41994441A US 2401373 A US2401373 A US 2401373A Authority US United States Prior art keywords leather tanning vegetable chromium liquors Prior art date Legal status (The legal status is an assumption and is not a legal conclusion.
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