US1427221A - Tanning hides and skins - Google Patents

Description

No Drawing. Application filed February 11,

@Alfllllhllf ERNEST WYNDHAIVL MERRY, OF SHEFFIELD,

ENGLAND, ASfiIGNOR, BY MES'NE ASSIGN- MENTS, TD PYROTAN LEATHER OOR'PORATION, OF WILMINGTON, DELAWARE, A

CORPORATION OF DELAVIARE.

. TANNING HIDES AND SKINS.

Lei-27,221.

T 0 all whom it may concern lle it known th t l, EnNEs'r WYNDHAM ll lnnnr. a subject of Great Britian, residing at Sheflield, in the county of York, England, have invented certain new and useful improvements in Tanning Hides andSkins; and I do hereby declare the following to be a full, clear, and exact description of the invention, such as will enable others skilled in the art to which it appertains to make and use the same.

This invention relates to the tanning of hides and skins and has among other objects the improvement of the method of tanning with a solution of a soluble pyrophosphate and alum whereby a product of uniformly high quality is assured, and the process is maintained at a high standard efficiency.

Soluble pyrophosphates have been here-- tofore su gested as tanning agents in Letters Patent #1,039,150 and #l, l9l,527.wherein a process is described for the employment of solution of pyrophosphate of sodium with alum and salt. The hides are subjected to the action of such a solution after the usual preliminary cleansing and unhaii'in treatment. and under certain sneci fied conditions, to deposit aluminum pyrophosphate in the interstices of the hide substance. The process described has attained a wide commercial importance because of the high quality of the product, the

,inexpensivenessof the tanning agents and the relatively short time required to produce leather. The process described in said Letters Patent is particularly valuable in the production of fine'white leathers. Colored leathers are also produced advantageously through the operation of the process, which in fact is universally applicable to hides and skins of every character to produce leather of a uniform and distinctive duality.

I have discovered that the controlling factor in the production of a satisfactory product in accordance with the teaching of the Letters Patent hereinbefore referred to is the careful control of the temperature. Relatively slight variations in the tempera ture employed, particularly an increase in the temperature beyond a well defined maximum, results in deterioration in the quality of the product to a marked degree. The product where the temperature rises materiilpeeification of Letters Patent.

Patented Au 29, 11922.

ally above the maximum, hereinafter specified. lacks tensile strength, and becomes more or less brittle or "grain-cracky. By carefully limiting the temperature to a specified range, and particularly by positively preventing a rise in the temperature above a maximum 1 am enabled to produce leather of a uniform character and high quality from hides and skins of Widely varying origin and texture. Success in the commercial operation of the process of pyrophosphate tanning depends in fact upon such regulation of the temperature.

The range of temperature which I find to be best adapted for the practical operation of the process lies between approximately 90 F. and 107 F., the latter temperature marking the danger pointer extreme upper limit at which deterioration of the product commences, if the materials are permitted to attain such a temperature for any considerable period. Preferably, the range of temperature is maintained between 95 F. and 105 F, the product resulting from the process, when carried out within this range,

being markedly superior and of uniform quality, regardless of the texture and weight of the hides or skins which are subjected to the tanning operation.

in carrying out the process, in accordance with my invention, the hides are preferably subjected to the usual washing, liming, unhairing, and tleshing operations. The hides are then. preferably bated and finally washed in water or suitable cleaning solutions, until thoroughly clean and in suitable condition for the actual tanning operations. The details of the preliminary treat ment may be widely varied and may follow the established practice of tanyards or depart therefrom in various respects, the preliminary treatment forming no part of my present invention.

The thoroughly cleaned hides are then subjected in a suitable receptacle, for example, a pit, drum, wheel, or paddle, to the action of the tanning solution which includes a suitable proportion of a soluble pyrophosphate, a soluble aluminum. salt and a suitable material such as sodium chloride or common salt, for overcoming the astringent action of the aluminum salt upon the hide whereby it is maintained in porous condition v to assimilate the active tanning agents. Preferably, sodium pyrophosphate,

ammonia alum, and common salt are em ployed although other available soluble pyrophosphates may be substituted, and any soluble aluminum salt may be advan'tageously used. For example, soda alum, potash alum, aluininum'sulphate, or aluminum chloride-may be substituted for the-ammonia alum.

The Concentration of the solution with reference to the several'salts may vary somewhat depending upon the particular character of the-hide treated; Preferably, the relative quantity of the pyrophosphat'eto the alum is maintained at the lowest ratio compatible with the successful accomplishment of thedesir'edobject.r Ihave discovered that. depending'upon the particular character of the hide treated, the ratio of pyrophosphate t'o thealum mayyary, from 1:4 to 1:10, the higher proportions of pyrophosphate being desirable where the hides are heavy and close in texture, and'the lower proportions being desirable in the treatment of skins andhides joffloose texture and relativelylight weight.

Forgeneral purposes, the range of relative proportions of pyrophosphate to alum may be limited so that; the alum exceeds 5 but doesnot exceed 7 times the'weight of the pyrophosphate. In calculating the relative quantities'oftherespective ingredients, I refer to thecrystallized alum containing 24 molecules of water of crystallization, and

substantially chemically pure anhydrous sodium 'pyrophosphate.

' The'hides are subjected in the receptacle,

as hereinbefore stated'fto a suitable quantity of the solution, the water content: of which may vary between 20 and/l0 per cent of the veiglit of the hide substance treated.

or wheel wh-ichpermits a close regulation of. tlre temperature and insures a thorough treatment. of the hides exposingevery portion thereofto the action of tllGSOlHtlOll. The initial temperature of, the solution is governed by thefnecessity of. dissolving-the respective constituents and is inthe neigh borhoodof flo During the tanning operation-[the temperature tends 'to rise and,

i f the, process is not carefully watched and the tendency QQYer ned ,by suitable control,

it will eventually rise to a point considerably above the maximum herein'before specified with attending disastrous results to th'eproduct. Iii'accordanc'e with my invention the temperature is undercontrolthroughout the operation, a suitably arranged thermometer giving a continuous indication of the term perature. hen the process is carried out'in a wheel or drum the temperature may be reduced'at intervals when necessary by stopping rotation of the wheel or drum and opening thedoor. or closure thereof. contents of "the drum or' wheel thus remain quiescent for a period'sufficient to reduce the temperature as deslred after whichthesprocess is continued with alternateexposure of the contents to reduce the temperature as may-be necessary to maintain it below the maximum of 107 F. Preferably, as hereinbefore stated the temperature ijsfniever allowed to rise above 105 F., the best results being obtained when the range Cramps-t.

tide is between 95 F. and 105 When the tanning operation is satisfactorily concludedthe liquor iswithdrawn and the hides are subjected'to any of the usual finishing operations. If colored leather is to be produced the hidesmay be subjected to the action of a solution containing a suitable coloring agent, preferably containing 'a tannin. I

My present invention is directed solely to the limitation of. the temperature substantially throughout the tanning operation, whereby the rise in temperature above 107FQ is positively prevented.- This Ihave found to result in the production "of leather of uniform quality, regardless of the varia tion of other factors affecting the process.

Such factors. may be widely varied in applying the process to hides and skins of different quality andcharacter to produce commercial leather, so long as thetempera tufre'is prevented from exceeding the"maXimum hereinbefore specified substantially hroughout the tanning operation.

Various changes may therefore'be'made in the ingredients; proportions, and method of,

applying tanning agents to the hides or skins, so long as the temperature is maintained and prevented from exceeding the range as specified in the auneiied claims.

lclaimr" i V 1. A. method of tanning hides and skins which includes drumming the hides in a solution containing asdluble aluminum salt and a soluble pyrop hosphate and stopping the drumming opera-tlon'atintervals whereby th t fatui eof the mass is limited not to exceed 107F. 1 i

2. A n'ieth'od oftanning hides andskins in a quiescen icon dition while still in con:

tact with the. soliiti oniiiitiltlie ten'iperature is reduced, and" thereby preventing the temperature from exceeding 107 Fahrenheit.

In testimony whereof I aflix my signature.

' ERNEST WV'Y-NDI-IAMi'MERRY