US1191527A - Tanning of hides and skins. - Google Patents

Description

ATENT on ERNEST WYNDHAM MERRY, 0F SHEFFIELD, ENGLAND, ASSIGNOR TO INTERNATIONAL IPYROTAN COMPANY, LIMITED, OF LONDON, ENGLAND.

TANNING 0F I-IIDES AND SKINS.-

Be it known that I, ERNEST WYNDIIIAM MERRY, subject of the King of Great Britain and Ireland, residing at 45 Cherry street,

Bramall Lane, Sheflield, in the county of York, England, have invented new and useful Improvements in the Tanning of 'Hides and Skins, of which the following is a specification.

This invention relates to the tanning of hides and skins by the action of the known mineral agents, alum and pyrophosphate of sodium and has for its object the carrying out of the tanning operation with hides or skins of any character or thickness with thoroughness and certainty in a simple and controllable manner.

I am aware that a process has been described in the specification of the United States Patent No. 1,039,150 in which the agents above referred to have been included in the ingredients of a tanning solution or solutions of definite strength which it is therein stated may be varied to suit the different classes and weights of hides being treated and specific proportions of the several ingredients are given as being effective for cow hides of a medium weight. I have discovered that the said process, however,

is only applicable to cow hides and other similar hides of a loose character and small thickness and that when thick hides or hides of a firm character such as ox hides are under treatment it is impossible to produce a satisfactory tannage even by increasing the strength of the tanning solution by 50%.

As the result of numerous experiments I believe that the permanent tanning action of a solution containing alumand sodium pyrophosphate is due to the interaction in the pores of the hide of the alum-andthe sodium pyrophosphate, whereby there results pyrophosphate of aluminium, which latter is insoluble in water and becomes fixed in the pores of the hide.

My present invention consists in the provision of a tanning solution or solutions of I such composition and concentration as are hereinafter set forth and within the limits defined. By observing these limits the tan- Specification of Letters Patent.

Patented July 18, 1916.

- Application filed January 12, 1916. Serial No. 71,652.

ning operation can be effected on any class I or thickness of hide with a celerity, certalnty and efliciency which is not at present attalnable by known means.

In describing how my present invention is carried into effect I shall define the proportlons employed as a percentage of the welght of hide to be treated. Sodium pyrophosphate as it is found in commerce contains a varying quantity of the pure anhydrous salt, say, from 45 to per cent. thereof, therefore in the percentages hereinafter given it must be understood that the same are based on the pure anhydrous salt Na P O According to my present invention; the alum (I refer to the crystallized salt with 24 molecules of water of crystallization) must exceed 5 and should not exceed 7 times the weight of sodium pyrophosphate, for example 10% of the former and 1.66% of the latter'and the Water must be between 20% and 40% of the weight of hide treated, for example 27%. While this latter concentration gives the greater penetrating effect any much higher concentration than this is not desirable owing to the risk of graining taking place due to the solution being too small in volume topermit of the uniformity of strength being maintained throughout the whole of the volume of solution, particullarily that portion between the layers of The composition'of the tanning bath is as follows: 10% ammonia alum, (NH ),SO,,Al (SO 24H O; 1.66% pyrophosphate of soda, Na P O 27% water, and say 5% of washed in the drum with warm water at 8090 F. The hides are then subjected to the action of a tanning bath containing alum, common salt or some similar substance to counteract the drawing effect of the alum, and sodium pyrophosphate in water at an initial temperature of 80"90 F. until the hide is completely penetrated. This bath is preferably prepared by dissolving the alum and common salt or its substitute in the desired quantity of hot water and dissolving the sodium pyrophosphate in a separate quantity of hot water and mixing the two solutions together. An alternative method which produces the same result is to thoroughly mix the substances mentioned in the dry state and dissolve this mixture in the requisite amount of hot Water. The tanning bath however prepared is then placed in the drum with the hides and drummed for 45 minutes or the tanning bath may be added by degrees to the drum if so desired. The mixture after drumming is then run off into another vessel and the hides transferred to such vessel and placed in the mixture therein or what is usually more convenient the hides and mixture are left in the drum, care being taken that no creasing or marking occurs. The tannage is allowed to progress for 34 hours or longer until the hides are tanned through. Alternate drumming and resting may be used to accelerate the process if close heavy hides are being treated. The tanned hides are then horsed up for 12 hours (usually overnight). The liquor in the drum is then mixed with the coloring bath which may be added direct to the drum. The coloring bath is obtained by dissolving each of the desired materials usually gambier and quebracho, in separate quantities of hot Water and finally mixing the solutions obtained in the usual manner. 3% gambier and'2% quebracho dissolved in as small a quantity of Water as possible will be found suitable but these quantities may be varied. The hides are rapidly replaced and drummed for 3 hours. A rather safer method is to drum the hides in the exhausted tanning bath liquor and then gradually add the prepared coloring bath during that process through the axle of the drum in Well known manner.

For certain classes of leather such as sole leather and for close heavy hides it is sometimes found advisable to supplement the tanning process by the following treatment :Taking the hides out of the tanning bath and giving them a supplementary bath Which is added in two stages prior to the coloring bath. The first stage consists in the addition of a supplementary bath to the exhausted tanning bath liquor contained in the drum. The hides are then inserted and drummed for 45 minutes. The supplementary bath is prepared in a similar manner to the tanning bath described above. Its composition is :5% ammonia alum, 1.66% pyrophosphate of soda, 27% water, and say 5% common salt or its substitute.

The second stage consists in the further addition to the mixture in the drum of a solution of alum dissolved in as little hot water as possible; the quantity of alum being the same as that used in the supplementary bath. Drumming is now continued for a further 2 hours and the whole then allowed to stand 12-14 hours after adjusting the hides in the drum to prevent creasing. The hides are then colored by the addition of the coloring bath to the mixture in the drum using the same method as already described. The resulting colored hides whether prepared by the single or double bath process are finally horsed up for 12-14 hours and then rinsed through a bath which may con sist of water alone or a 5% solution of borax. After draining, the hides are then finished by one of the well known processes in the usual way.

I would have it clearly understood that any soluble aluminium salt may be substituted for the ammonia alum herein referred to such for example as soda alum Na S0,,Al (SO 24H O, potash alum K,SO,,A1 (809 2411 0, or aluminium sulfate .AI,,(SO 18H O.

In using these salts the relative proportions in the formulae given, must be modified so as to maintain the aluminium constituent at its proper value.

I claim 1. In a process of tanning by-means of alum and sodium pyrophosphate the treatment of the hides in a tanning solution in which the proportion of alum in terms of the crystallized salt with 24 molecules of water of crystallization to sodium pyrophosphate in terms of the pure anhydrous salt is in the ratio exceeding 5 up to 7 parts of alum to 1 part of sodium pyrophosphate.

2. In a process of tanning by means of alum and sodium pyrophosphatethe treatment of the hides in a tanning solution in which the proportion of alum in terms of the crystallized salt with 24: molecules of water of crystallization to sodium pyrophosphate in terms of the pure anhydrous salt is in the ratio exceeding 5 up to 7 parts of alum to 1 part of sodium pyrophosphate the proportion of the said alum being substantially th of the weight of hide treated.

3. In a process of tanning by means of alum and sodium pyrophosphate the treatment of the hides in a tanning solution in which the proportion of alum in terms of the crystallized salt with 24 molecules of water 27%, alum 10%, sodium pyrophosphate in terms of the pure anhydrous salt is in the ratio exceeding 5 up to 7 parts of alum to 1 part of sodium pyrophosphate the restriction of the quantity of the water in In testimony whereof I have signed my the tanning bath to from 20% to 40% of the name to this specification in the presence of 10 weight of hide trealted. f h f 11 two subscribing witnesses.

4. tanning so ution o .t e 0 owing 5 proportions on the weight of hide treated, ERNEST WYNDHAM MERRY water 27%, alum 10%, sodium pyrophos- Witnesses: phate 1.66% and, say, 5% of a pore opening Doms H. Hrroncocx, agent such as common salt. CHARLES J R. BULLOUGH.