US2880053A - Process of tanning hides with polymethoxyaldehyde compounds and optionally vegetable tanning - Google Patents

Description

United States Patent r PROCESS OF TANNING HIDES WITH POLYMETH- OXYALDEHYDE COMPOUNDS .AND "OPTION- ALLY VEGETABLE TANNING Martin L. Fein, Riverside, N.'J.,-and Edward M. Filachione, Philadelphia, Pa., assignorsto-the United Statesof America as represented by the Secretary ofAgriculture No Drawing. Application January 3, "1956 'Serial No. 557,217

3 Claims. (Cl. 8-94.21

(Granted under Title 35, U. S. Code (1952), sec. 266) A non-exclusive, "irrevocable, royalty-free license in the invention herein described, throughout the world for all purposes of the United States Government, with power to grant sublic'enses forsuch purposes, is'hereby granted to the Government of the United States of America.

This invention relates to new reagents and newproces'ses fortanning'hide's.

From time immemorial, man has largely depended on natural vegetable tannins for converting animal hides into leather. However, the supply of such materials is constantly diminishing and "their cost increasing; consequently, great efforts have been made to develop suitable synthetic materials to replace the vegetable tannins. While many such synthetics have been used or suggested, none has been entirely satisfactory, either because of high cost or deficiencies in the properties of the leather produced thereby.

Accordingly, it is an object of this invention to provide new synthetic tanning agents that may be economically manufactured in any required amount and that react rapidly with hide substance to give a satisfactory tannage.

The process of the invention utilizes as tanning agents a class of long-chain aliphatic aldehydes called generically polymethoxyaldehydes and having the structure wherein n has an average value of 2 to 20. Such aldehydes are readily obtainable by the hydrolysis of the corresponding acetals, particularly the methyl acetals having the formula O OH: OCH:

These acetals may be obtained by the condensation of methyl vinyl ether and methanol by any known process, such as, for instance, those described in US. Patents 2,165,962 and 2,487,525. Because of the great reactivity and consequent instability of the free aldehydes, we generally prefer to store them in the form of the acetal. The free aldehyde is then generated just prior to its use or it may actually be generated in situ during the tanning process.

Since the polymethoxyaldehydes are polymeric in na- I 2,880,053 Patented Mar. 31, 1959 "the individual molecules of which wvillhave diflerent chain lengths and valuesof n. I

-In the interest of brevity and simphcity, 'the average value of n in particular lots of material will be des1gnated hereinafterfby the appropriate ,numeralsufiix; thus,

polymethoxyaldehyde i .re'fers ton material in which the average value of 'n is :4. flhiswe-abbreviate as PMA-4.

By the term hides": as used herein xwezmean any animal skin that is :commonly tanned, such as cowhide, horsehide, ca-lfskin, pigskin, sheepskin sand .goatskin, .as well as :any such hide that has :already been partially or completely tanned by a-conventional tanning process. Any hide, as :so defined, :can .be tanned by treatment with a polymethoxyaldehyde as shown hereinafter.

According to the invention, :liides are tanned :by immersion for :a suitable time fin a solution of polymethoxyaldehyde .in water or a :suitable organic .solvent. No

special preparation of the hide is necessary, the usual preparation for conventional Etannage being entirely 'sat- I isfactory. Likewise the :amount and concentration of tanning solution may be varied widely without detrimental aeifect. The affinity of the polymethoxyalde'hydes for the hide substance :is such :that dilute solutions are substantially exhausted by the hides, yet the use of a large excess of tanning agent results in no loss because the hide, when fully tanned, ceases to absorb the aldehyde.

The practice of the invention is illustrated by the following examples.

Preparation of polymethoxyaldehydes.-Polymethoxyacetals having average values of n in the above formulas of 4, 9 and 14 were hydrolyzed to the aldehyde by stirring at room temperature with several times their volume of 1% aqueous hydrochloric acid until substantially all the acetal dissolved in the water layer. The small amountof insoluble material could be brought into solution' by addition of a little alcohol or acetone, left in suspension or mechanically separated. The aqueoussolution of aldehyde was adjusted to they desired pH by addition of alkaline reagents and/or buffers. If desired, the aldehyde may be similarly prepared in a suitable organic solvent such as a lower aliphatic alcohol or ketone.

Tanning with polymethoxyaldehydes.-The aldehyde solutions prepared as described above were adjusted to the desired concentration, usually in the range 5 to 25%, though higher or lower concentrations could be used without difliculty; the pH was adjusted by use of suitable bufiers; salts such as sodium chloride or sulfate were added if desired and the hide, previously adjusted to the isoelectric point, was immersed in the solution. After being left at room temperature for various times, with continuous agitation, samples of the hide were cut out, tested for shrink temperature (Ts) and examined for leatherlike properties. Although the elevation in Ts was only moderately high, the samples, after being washed and dried were light colored and showed excellent leatherlike properties. A summary of the results of some typical experiments is shown in Table I.

Table L-Tafining with polymethoxyaldehydes (PMA) Treatment Shrinkage Temp., C., after- Example Aldehyde Butler Salt pH 1 day 2 days 3 days 6 days Cowhide:

1 PMA-4.-- Lactic acld,5 NaCl, 5% 3.3 60 6O 60 60 NSHCO), 0.2 None.-- 7.1-7.0 74 77 77 70 7.1-7.5 74 77 77 11. 1-10. 9 73 74 74 g0, 1 NaCl, 3 a 10.6-10.4 72 75 77 7s Lactic acid, NaCl, 5% 3. 6-3.7 63 61 70 NaHCQ;, 0.2M-.- None 7.3-7.7 70 72 72 74 NaHCOfi 0.2M.-. NaCl,4% 7.1-7.4 68 70 72 g 1 0' N801, 3 10.2-10.1 68 e9 72 73 Lactic acid, 5%..- NaCl, 4', 3. 6-3. 7 60 60 60 NaHCO;, 0.2M.-. None 7.3-7.7 70 73 73 74 NaHCO;,0.2M ---NaCl,4 o 7. 2-7.6 68 70 71 J MgO, 1% NaCl,3 10.5-10.3 67 68 72 72 Lactic acid, 5% 3. 3 58 60 61 -NaHCO;, 0.2M.-- None 7.3-7.0 73 74 74 74 MgO, 0.47 10. 5-10. 7 69 71 SE00; 7. 3-8. 0 68 70 73 NaHGO; B. 0-8. 3 01 e9 71 73 1 Results similar to those shown in the table were ob- We claim: tained when other kinds of hide, such as horsehide, pig- 1. The process for tanning hides comprising impregskin, sheepskin, goatskin or fur skins were used, or when mating the hides with an alkaline solution of a polymeththe PMA was dissolved in alcohol, acetone or similar oxyaldehyde having the formula organic solvent instead of water. Likewise, PMA of OH:(CHCH,)..CHO h1gher or lower molecular weights, 1n the range of PMA-2 CH 1 to PMA-20 gave equally satisfactory results. There is some advantage in using the lower molecular weight where! has an average value 2 to 20 the 111d materials, such as PMA-2 to 10, in that they are more are tannedefiective, pound for pound, they penetrate the hide faster The P of dam! wherein the hlde 15 51's! and they are easier to prepare fmm the acetaL tanned with vegetablev tannin and subsequently tanned Combination vegetable-aldehyde tannage in which Wlth apolymethoxyaldeilyde- 1 vegetable tanned leather was retanned with PMA or in The Process of 51mm 1 whereln the hide, after b61118 which PMA tanned leather was .rctanned with vegetable tannins gave products superior to those obtained by either tannage alone. They had higher shrink temperatures, were fuller and firmer and had better appearance. Furthermore retannage of the PMA tanned leather with vegetable tannins resulted in a much-more rapid penetration by the latter agent.

tanned with a polymethoxyaldehyde, is subsequently tanned with vegetable tannin.

References Cited in the file of this patent UNITED STATES PATENTS

Claims (2)

1. THE PROCESS FOR TANNING HIDES COMPRISING IMPREGNATING THE HIDES WITH AN ALKALINE SOLUTION OF A POLYMETHOXYALDEHYDE HAVING THE FORMULA

2. THE PROCESS OF CLAIM 1 WHEREIN THE HIDE IS FIRST TANNED WITH VEGETABLE TANNIN AND SUBSEQUENTLY TANNED WITH A POLYMETHOXYALDEHYDE.