US2964425A - Waterproofing of leathers - Google Patents

Description

Dec. 13, 1960 R. J. HOL'ZINGER ET AL 2,964,425 WATERPROOFING OF LEATHERS Filed April 29, 1958 54 R00 SINE DE RI VED COMPOUND INVEN TORS RUDOL PH J HOZZI/VGER L I A r TOR/VEY GEORGE M. WHEL/J/V JAM 1 A 0 N 6% M W m E 0 A N E l 9 w w m m G ART 7, SMW 0 L M L/ United States Patent WATERPROOFING OF LEATHERS Rudolph J. HolzingerfNorth Merrick, and George M. Whelan, New York, N.Y., assignors to Socony Mobil Oil Company, Inc., a corporation of New York Filed Apr. 29, 1958, Ser. No. 731,642

12 Claims. (Cl. 117-142) This invention relates to the treatment of leathers, particularly such leathers as upper leathers, to decrease their permeability to water without detrimental effect upon other desirable properties.

It is desirable, in the preparation of leathers designed for use in the uppers of shoes, particularly for armed services and heavy duty uses in working and field conditions, to have a high degree of waterproofness. At the same time, it is almost imperative to retainthe porosity and flexibility of the leather. Porosity not only permits breathing with consequent avoidance of the sweating and resultant foot troubles arising from con-' tinuous wearing of moisture vapor impermeable'footgear, but porosity contributes to some extent to'the'insulating capability of the leather. The problem is complicated by the fact that water may pass not only through such natural porosity as may exist, but also, due to the hydrophilic nature, of leather fibers, each fiber may become a duct for the passage of water.

The usual approach to this problem has been by stuffing theleather with oils, greases or waxy materials during preparation of the leather, by impregnating the leather during manufacture with plastic or rubber-like materials, or by applying a dubbing or other waterproofing material to the finished leather article. Not only do these treatments, if heavy enough to fill the pores, reduce the breathing capability of the leather, but in most cases they achieve no correction of the hydrophilic nature of the leather fibers themselves. Treatments applied to the finished articles are seldom thorough enough to stop even mechanical leakage. All fail to a great degree when the leather is subjected to the continuous flexure which occurs when the shoes are worn.

Anobject of the present invention is to provide a leather substantially waterproof under continuous flexure which still has a porosity suflicient to permit breathing.

Another object of this invention is to provide a leather in which the hydrophilic nature of the leather fibers is sufficiently suppressed to provide waterproofness without the sacrifice of porosity, which condition will permit breathing under use conditions in a leather that remains soft and flexible.

An important obiect is the provision of a waterproofing'treatment that may be applied without stuffing or, alternatively, may be applied as part of a stufling op? eration so conducted as to confer waterproofness, to give to the leather such desirable properties as may arise from the judicious controlled use of stufling compounds, and at the same time preserve the porosity, softness and flexibility of the leather under conditions of use.

-' All of these objects may be achieved by the use of certain sarcosine compounds which are more specifically described hereinafter, the compounds being generally aliphatic amino carboxylic acids having higher saturated or unsaturated aliphatic acid radicals directly attached to the nitrogen atom. The invention applies generally to chrome tanned and vegetable tanned leather but is found to be especially useful in the treatment of chrome retanned 2,964,425 Patented Dec. 13, 1960 ice leather. While the compounds of this invention can be used alone, they are generally mixed to some extent with a stufling grease and applied to the leather as a mixture by the standard stufling procedure well known to workers in this field. The quantity of the material to be used is usually calculated as a fixed percentage by weight of the leather to be treated. A leather stuffed with a mixture of 50 percent of the material of this invention and 50 percent stuffing grease would mean, therefore, that if the leather were, for example, 30 percent stuffed with the mixture, it would contain about 15 percent active Waterproofing agent. The optimum amount of the mixture used depends upon a balance of cost, waterproofing required and appearance of the finished leather desired.

The invention will be disclosed more fully in following detail description and in the attached figures.

Figure 1 shows a conventional stuffing drum in crosssection with a sample of leather being treated with the compound of this invention.

Figure 2 shows a portion of a treated leather strip in cross-section.

Referring to Figure l, the conventional stuffing drum is depicted. The cylindrical drum is mounted on its axis in a horizontal position and'the drum is rotated by suitable driving means such as an electrical motor through a conventional gear train. The leather and treating compound are introduced into the drum through the lid. The rotation of the drum causes the treating compound to be worked into the leather by carrying the hide up near the top, permitting it to fall back into'the pool of treating compound. After a suitable period of treatment, the

' treated leather is removed.

Referring to Figure 2, it is seen that the collagen fibre bundles are separated from each other allowing the leather to breathe. 1 In untreated leather the porous collagen fibre bundles act as Wicks and cause water to penetrate into and through the leather by capillary action. The'waterproofing compound of this invention is shown on Figure 2 asa coating layer surrounding each collagen fibre bundle. It is seen that the coating material prevents the transfer of liquid water and blocks the Wick ing action. However, the pores of'the leather remain open, allowing the transfer of air and water vapor and hence normal breathing techniques.

An accepted method of test for the efliciency of waterproofing treatment of upper leathers and the like is the so-called Maeser Test, developed in the leather labora-. tory of the National Bureau of Standards to simulate conditions of natural use, and reported by Meith Maeser in the Journal of the American Leather Chemists Association, vol. XLII, page 401 et seq., August 1947. In short, it consists of mechanically flexing a sample ofleather, cons rained in the form of a trough, in contact upon one side with water, either for a preset number of flexes; and measuring the water that has penetrated through the leather, or more usually, noting the number of flexes required before water appears upon the dry side. An-

other test method, commonly referred to as the Dow Corna necessity of constant operator attention when testing high- 1y resistant leathers with the Maeser water pentration' machine, this method for automatic end point determination was developed. This method is similar to the Dow Corning Test in that it is based on the sudden change.

in the electrical resistance between the inside and the.

outside of the leather at the instant that some point is completely wet through. The method used is reported by Meith Maeser and Robert M. Lollar in the Journal of the American Leather Chemists Association, vol. LI, page 377 et seq., July 1956. This test was selected and the results reported hereinafter are test results obtained in accordance with this most recent test procedure. The test reports the percentage of water picked up after a fixed number of flexes as indicating waterproofing ability even though penetration has occurred.

The waterproofing compounds with which this invention is concerned are the free aliphatic acids of the folterial Sarkosyl-O, oleyl sarcosine;

wherein R is a radical of a higher aliphatic acid of from 12 carbon atoms to 22 carbon atoms, saturated or unsaturated. Of these materials, the unsaturated aliphatic acids of from 16 to 18 carbon atoms are preferred. A particularly preferred compound is the commercial material Sarkosyl-O, oleyl carcosine;

and the corresponding stearoyl sarcosine sold under the trade name Sarkosyl-S.

CnHas--N-CHz-C O OH (3H5 Examples illustrating the invention are as follows:

Example I A sample of retanned leather was treated with oleyl sarcosine in accordance with well known stulfing procedures, being stuffed to about 30 percent of the weight of the test leather specimen. Oleyl sarcosine is primarily an oleic sarcosine compound with a minor amount of closely related sarcosine compounds and other unsaturates. The molecular weight of oleyl sarcosine is 340-350, color (FAC) 10, setting point 0 C., specific gravity 0.948 and solubility is miscible with stoddard solvent at 25 C. The sample was then tested in accordance with the E-Z modified Maeser test procedure (Journal of the American Leather Chemists Association, July 1956) for 10,000 cycles without showing any sign of water emergence through the leather. The total water picked up by the test specimen was 3.1' percent of the weight of the leather specimen. When using this E-2 end point test procedure with clean leather not treated with the waterproofing material of this invention, water shows through the leather in about -20 flexes and at least by 100 flexes, the leather is completely saturated. It is clear, therefore, from these results, that oleyl sarcosine is an outstanding-compound for use in rendering leather waterproof.

Example II A sample of retanned leather was treated with cocoyl sarcosine (available under the trade name Sarkosyl LC). This material is approximately 2 percent capric, 55 percent lauric, 22 percent myristic and 21 percent stearic compounds, in other words, carbon chains of about C C The leather sample was stuffed to about 30 percent by weight and tested in accordance with the E-2 procedure. The sample showed water penetration at 495 flexes, 6.34 grams of water being absorbed by the test' sample at that point. The test was continued to 5,000 cycles and showed a water pick-up of about 23 percent of the weight of the leather sample.

Example III A sarcosine largely saturated C and C in approximately equal proportions was tested, using the same test procedure as used in Examples I and II. This test-sample showed water penetration at 101 flexes with a water absorption of 8.77 grams of water. The test was continued for 5,000 cycles and was then found to have picked up only about 33 percent water by weight of the leather sample. It is seen that the compounds of Examples II and III, while passing water to some extent at a rather low number of cycles, do have the capacity for substantially limiting the amount of water that is picked up by the leather.

Example IV A twelve carbon sarcosine, lauroyl sarcosine, being about percent lauric and the remainder myristic, palmitic and oleic sarcosine compounds, was tested according to the test procedure used for Examples I-III. This material is available under the trade name Sarkosyl L. This test sample showed water penetration after 175 flexes and absorbed 7.85 grams. At the end of 5,000 flexes the sample had picked up 30 percent water by weight of leather test sample.

The examples given hereinabove demonstrate the efficacy of the indicated compounds when applied alone as a waterproofing agent.

It is also to be noted that these compounds are competent waterproofing agents when applied with, or as part of, more conventional treatments, such as in stufling or fat liquoring.

For example, a quite conventional stuffing grease may be made up of equal parts of beef tallow and a paraffin wax of -127 F. melting point, as is well known in the art. The waterproofing agents herein disclosed may be admixed with this stuffing grease, to the extent of from about 10 percent to about 75 percent of the mixture, usually preference being had for waterproofing agent concentrations ranging from about 25 percent to about 50 percent by weight of the stuffing mixture. Application of such stufling mixtures not only achieves a satisfactory degree of waterproofing, but also gives those desirable features arising from the use of the conventional agents, both in the process and in the finished leather.

Example V The oleyl sarcosine, previously described with respect to Example I, was mixed in equal parts with a stufiing grease and the leather sample was stuffed to about 30 percent of the weight of the leather. The sample was then tested in accordance with the E-2 test procedure. The sample showed water penetration at 108,840 flexes, 4.71 grams of water being absorbed by the sample at that time. At 110,000 flexes the leather had picked up only 13 percent water by weight of the leather, demonstrating the outstanding waterproofing ability of this compound.

Example VI The oleyl sarcosine was mixed with stufling grease in the proportion of 25 percent sarcosine compound to 75 percent stuffing grease. The leather sample was stuffed to about 30 percent of the weight of the leather and tested in accordance with the 13-2 test procedure described hereinabove. The. sample showed water penetration after 51,360 flexes, 7.49 grams of water being absorbed. At 100,000 flexes the leather sample had picked up only 25 percent water by weight of the leather.

The examples given hereinabove are not to be considered limiting, but are supplied merely to illustrate the invention. The invention is to be construed broadly, the limitations intended being those of the attachedclaims.

We claim:

1. The method of making leather resistant to water penetration which comprises introducing into the leather a compound ofthe formula wherein R is an aliphatic acyl radical of 16 to 22 carbon atoms, 1

2. The method of making leather resistant to water penetration which comprises introducing into the leather a compound of the formula R-rf-om-o 0 on wherein R is an aliphatic acyl radical of 16 to 18 carbon atoms.

3. The method of making leather resistant to water penetration which comprises introducing into the leather a compound of the formula R-N-CHr-COOH wherein R is an unsaturated aliphatic acyl radical of 16 to 22 carbon atoms.

4. The method of making leather resistant to water penetration which comprises introducing into the leather a compound of the formula wherein R is a saturated aliphatic acyl radical of 16 to 18 carbon atoms.

5. The method of making leather resistant to water penetration which comprises introducing into the leather a compound of the formula GnHu-f'l-N-CH,-CO0H 6. The method of making leather resistant to water penetration which comprises introducing into the leather a compound of the formula 7. As an article of manufacture a leather impregnated with a relatively small amount, sufiicient to impart water resistance to the leather, of a compound of the formula R-N-CHa-COOH wherein R is an aliphatic acyl radical of 16 to 22 carbon atoms.

9. The claim 7 further characterized in that the radical R is ll (Jr-(Harc- 10. The claim 8 further characterized in that the radical R is 11. The claim 7 further characterized in that the radical R is 12. The claim 8 further characterized in that the radical R is ll CnHu-C References Cited in the file of this patent UNITED STATES PATENTS 2,047,066 Gleitenberg July 7, 1936 2,047,069 Hentn'ch et a1 July 7, 1936 2,293,844 Maxwell Aug. 25, 1942 2,689,170 King Sept. 14, 1954 2,700,625 Morris et al. Jan. 25, 1955 2,825,660 Roux Mar. 4, 1958 2,830,064 Monick Apr. 8, 1958 2,841,573 Ahlbrecht et a1. July 1, 1958 UNITED STATES PATENT OFFICE CERTIFICATION OF CORRECTION Patent No., 2,964,425 December 13, 1960 Rudolph J. Holzinger et alo It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below Column 3, line 13 for vterial Sarkosyl-O, oleyl sarcosiner" read lowing general configuratlonr, llne 22, for "carcosine" read sarcosine Signed and sealed this 13th day of June 19610 (SEA L) Attest: ERNEST W. SWIDER DAVID L. LADD Attesting Officer Commissioner of Patents

Claims (1)

1. THE METHOD OF MAKING LEATHER RESISTANT TO WATER PENETRATION WHICH COMPRISES INTRODUCING INTO THE LEATHER A COMPOUND OF THE FORMULA

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