Classifications

• • C—CHEMISTRY; METALLURGY
  • C14—SKINS; HIDES; PELTS; LEATHER
  • C14C—CHEMICAL TREATMENT OF HIDES, SKINS OR LEATHER, e.g. TANNING, IMPREGNATING, FINISHING; APPARATUS THEREFOR; COMPOSITIONS FOR TANNING
  • C14C3/00—Tanning; Compositions for tanning
  • C14C3/02—Chemical tanning
  • C14C3/28—Multi-step processes

Definitions

• This invention relates to a process of making white washable leather which has superior properties, as compared with the best white leathers heretofore on the market.
• White leather made according to prior processes has been made white by the use of white filling p'gments. This has been necessary, because of the fact that the leather itself did not have suflicient whiteness to be usedalone. These previously known white leathers were not white entirely through their thickness but only to a depth to which the white filling pigment had penetrated. As a result, upon repeated cleaning, the whiting material wore off and the natural color of the leather appeared.
• white leather may be made which is white entirely through its thickness and which does not require the use of white filling pigments.
• the leather can be cleaned by wiping with a cloth dampened with soap and water or with naphtha or carbon tetrachloride or other cleaning agent and does not require the use of white shoe. polishes.
• the leather has certain very valuable physical and chemical properties which make its use advantageous and distinguish it from prior known white leather.”
• White calf leather made according to the process hereafter described in detail has a long silky fiber "and a tensile strength of at least 3900 lbs. per scguareinch. It has a tearing resistance of at least 6 lbs. and relative porosity of at least 1,000. It can be stretched at least 40% before the grain cracks and has a water absorption when immersed in water at F. for 30 minutes of not over 125%. l
• Sample A is one of the best white calf leathers on the market in which the whiteness was produced by filling with titanium oxide.
• Samples B. C and D are three white calf leathers made according to my preferred process:
• the leather be porous, so as to allow free circulation of air, provided that the leather has suflicient tensile strength, tearing resistance and wear resistance. It is also desirable that the amount of water absorption be not too great, as otherwise the leather may become too wet in cleaning or in use, when exposed to water. It is also desirable that the amount of water absorption be not too great, as otherwise the leather may become too wet in cleaning or in use, when exposed to water. It is also desirable that the amount of water absorption be not too great, as otherwise the leather may become too wet in cleaning or in use, when exposed to water. It
• my leather has a combination leather in accordance with the present inven-' tion is as follows:
• Bleaching The bleaching operation has been found to improve the appearance of the grain; particularly for full grain leather, by freeng the grain from impurities that would otherwise discolor it.
• the stock is taken directly from the bate and the quantities given. below are per lb. bated weight. Put pack into drum; start running and add 7.5 lb.. salt and 1 lb. sulfuric acid in 10 gal. water at 60 F. Run 10 minutes and add 0.5 lb';
• the stock is then given aformalin pretanning treatment.
• Formalz'n pretanning This operation is used chiefly for white leather, in order to make it fuller and softer.
• the quantlties given below are per one hundred pounds bated weight.
• Run 30 minutes longer when the pH value of the liquor should be about 8.5; if below 8.5, add enough more bicarbonate to bring it to this value.
• Run 90 minutes longer drain and wash in running water at 60 F. for 30 minutes. the temperature of the liquor to rise above 90 F.
• the running times may be correspondingly shortened.
• Graham-s salt which consists principally of hexametaphosphate, is a glassy material which is assumed to be a complex of the general formula Na2(Na4PsO1a) although some authorities believe that salts of the formula Na5(NaPsO1s) and NadNazPsOm) may also be present.
• Sodium metaphosp ate tanning Put pack into drum, start running and add 3 lb. Grahams salt, 2.5 lb. sulphonated cocoanut oil and 1.25 lb. phosphated cocoanut oil in 10 gal. water at 60 F. Run 15 minutes andadd slowly, over a period of 30 minutes, 1.5 lb. sulfuric acid in 2 gal. water. Run 15 minutes and measure the pH value of the liquor. If it is above 2.2, add enough more sulfuric acid to lower it to 2.2. The pH value should be kept between 2.0 and 2.4 during the entire period of the tannage. Be careful not to let the temperature rise above F. If the temperature of the liquor rises above this point, stop the drum, open the door and allow to cool. Run until the stock is completely tanned.
• Another method, particularly useful for thin stock where it is not easy to see a very thin, translucent layer, is to place a drop of pH indicator on a freshly-cut edge and note the uniformity of color throughout the entire thickness of the stock. If this color shows a pH value below 2.5 uniformly through the thickness of a cutting from the heaviest portion of the stock, the stock may be considered as fully tanned.
• Alum retanm'ng The stock for this retannage is taken immediately after the metaphosphate tanning. The quantities given below are per 100 lb. bated weight of stock. Put. pack into drum and wash in running water, at 60 F. for from 30 to 60 minutes, depending upon the thickness of the hides or skins. Drain and add 12 lbs. aluminum sulfate and 3 lb. salt in 12 gal. water at 60 F. Run
• the time required f9r complete tannage will be from one to two hours less than for calf.
• sheepskins are generally purchased after dewooling and pickling, no bated weight is available. It is customary to decrease and press the stock before tanning. In these methods, the hide-substance content of the pressed weight is taken as 20% and adjustments should be made for known deviations from this. Proceed exactly as for goatskins, but use quantities given as per lbs. pressed weight instead of as per 100 lbs. bated weight. Omit the operation of formalin pretanning entirely. After hanging to dry, instead of dampening and staking,

Landscapes

• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• General Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Treatment And Processing Of Natural Fur Or Leather (AREA)

Priority Applications (2)

Applications Claiming Priority (1)

Publications (1)

Family

ID=22903254

Family Applications (1)

Country Status (2)

Cited By (5)

• 1938
  • 1938-11-09 US US239679A patent/US2172233A/en not_active Expired - Lifetime
• 1939
  • 1939-11-02 DE DEC55474D patent/DE740267C/de not_active Expired

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