US1941485A - Manufacture of leather - Google Patents

Description

Patented Jan; 2, 1934 v 1,94 1,4s MANUFACTURE or LEATHER Richard Pasternack, Brooklyn, and Gordon 0. Cragwall, Queens Village, N.- Y., assignors to Charles Pfizer & Company, Brooklyn, N. Y., a

. 12 Clai s.

This invention relates to the tanning of hides, kips, skins and other organic substances containing collagen and has for its object to produce white or bright colored leathers which are flex- 5 ible, durable and resistant to the action of water as well as other causes of decay.

It is well known that aluminum compounds may be used in tanning leather, but the product has always been considered inferior to that produced by other tanning methods because of the supposed low affinity of collagen for aluminum, and instability of the combination produced by known methods of alum tanning. This situation is recognized in Vol. II of The Chemistry of Leather Manufacture, by J. A. Wilson, page 698 if, where attention is called to the fact that processing with aluminum compounds is commonly referred to as tawing to distinguish it i from true or permanent tanning.

We have found, however, that the defects of previous alum tanning processes were due to the use of unsuitable aluminum preparations. We have discovered that by treating hides, etc., with a composition of aluminum and gluconic acid containing 10-24% A1203, and here referred to as aluminum gluconate; either with or without pretreatment with formaldehyde, a leather is obtained which is light colored, flexible and durable, and resistant to the action of water at a temperature as high as 88 C. In permanence ofcharacteristics it is comparable to the best of chrome tanned leathers, while its white color is highly advantageous for many purposes.

Many of the aldehydes have been used previously for tanning purposes. They can be used alone to produce a white leather, but such processes requireafter-treatment with soap or a mild alkali, and the leather producedis not of satisfactory durability. i

It is also recognized that the use of formaldehyde as a pre-treatment in vegetable tanning processes facilitates the absorption of the tanning agents, and a leather of satisfactory. durability may be prepared by such a combination process, but it is necessarily of a brownish color due to the action of the second tanning agent.

By the use of formaldehyde or other aliphatic aldehyde suitable for tanning purposes, followed by treatment with aluminum gluconate, we overcome the above and other defects of previous processes and obtain a white product which is also especially suited to dyeing in light or pastel colors. I

In the application of our process we do not limit ourselves to the use of any particular apparatus, but can use any equipment suitable for tanning according to previously known processes. Our process is also applicable to leathers which are to undergo subsequent treatment by 0 other tanning processes.

corporation of New Jersey No Drawing. Application July 29, 1931 Serial No. 553,884

The following examples aregiven as specific illustrations of our process:

Example I Add 100 pounds of skins, previously unhaired, bated, and pickled, to a bath composed of:

. Pounds Water 250 Salt 12 Sodium bicarbonate 3 Formaldehyde, 36% soln 10 Th'is'bath is preferably maintained at a temperature of 40-45 C. and is agitated by suitable means for four hours. At the end of this time the skins are removed and washed with cold Aluminum gluconate, containing 18-19% This bath is agitated by suitable means for four hours at an initial temperature of 40-45" 0., after which the tanned skins are removed and washed thoroughly with water at 30-40 C. The.

redrying, being very similar to chrome-tanned leather in this respect.

; In place of formaldehyde, chemically equivalent quantities of other aliphatic aldehydes may be used. If the color of the finished product is not important, other tanning agents such as tannin, syn-tan, etc., may be employed.

Example II Add 100 pounds of skins, previously unhaired, bated and pickled, to a bath composed of Pounds Water 250 Aluminum gluconate, containing 18-19% 'Salt 2 12 This bath is agitated by suitable means for twentyfour hours, after which the process is completed as in Example I.

Example III- A tanning bath is prepared from 225 lb. gluconic fermentation liquor, containing about 45.2 lb. gluconic acid. To this is added 4.5 lb. aluminum, previously cut up into smallpieces, washed with 10% caustic, rinsed with cold water, and superficially amalgamated by treatment with a suitable mercury salt, as mercuric gluconate. Upon heating to -60 C., the aluminum dissolves, leaving a finely divided precipitate of mercury which is removed by filtration.

To this are added 100 lb. hides, previously unhaired, bated and pickled, and pretreated with formaldehyde as in Example I. The process is completed as in Example I.

In each example, in place of aluminum gluconate, the molecular equivalents of an aluminum salt, such as the sulphate, chloride, etc., and gluconic acid may be used. These solutions should be neutralized to a pH of 4-6 with soda. Instead of aluminum salt, a soluble aluminate may be used with gluconic acid, adjusted to a pH of 4-6 as before.

The invention claimed is:

1. The step in theprocess of tanning hides and the like which consists in subjecting same to the action of a bath containing in solution aluminum and gluconic acid.

2. The step in the process of tanning hides and the like which consists in subjecting same to the action of a bath containing aluminum gluconate.

3. The step in the process of taming hides and the like which consists in subjecting same to the action of a bath containing an aluminum salt and gluconic acid. v

4. The step in the process of tanning hides and the like which consists in subjecting same to the action of a bath containing a water-soluble composition of aluminum and gluconic acid whose A1203 content is between 10% and 24%.

5. The step in the process of tanning hides and the like which consists in subjecting same to the action of a bath containing a soluble aluminate and gluconic acid, and adjusted to pH 46.

.6. The process of tanning hides and the like which comprises subjecting the hides to the action of an aliphatic aldehyde and then subjecting them to the action of a bath containing in solution aluminum and gluconic acid.

7. The process of tanning hides and the like which comprises subjecting the hides to the action of formaldehyde and then subjecting them to the action of a bath containing in solution aluminum and gluconic acid.

8. The process of tanning hides and thelike which comprises subjecting the hides to the action of formaldehyde and then subjecting them to the action of a bath containing aluminum gluconate.

'9. As a new product, leather tanned by the action of a water-soluble composition of aluminum and gluconic acid.

10. As a new product of manufacture, white flexible and durable leather tanned and made resistant to the action of water up to 88 C. by the action of aluminum gluconate.

11. As a new product of manufacture, a composition containing the residues of the action of formaldehyde, followed by a water-soluble composition of aluminum and gluconic acid upon hide proteins.

12. The step in the process of tanning hides and the like which consists in subjecting same to the action of a bath containing in solution an aluminum compound and gluconic acid, neutralized to pH 4-6.

RICHARD PASTERNACK. GORDON O. CRAGWALL.