US3052571A - Method of waterproofing leather - Google Patents

Description

-.without discoloring or darkening the leather.

United States Patent O 3,052,571 METHOD OF WATERPROOFING LEATHER Charles A. Fetscher, Short Hills, and Stanley Lipowski, Newark, N. J., assignors to Nopco Chemical Company, Harrison, NJ., a corporation of New Jersey No Drawing. Filed July 11, 1958, Ser. No. 747,818 9 Claims. (Cl. 117-142) This invention relates to a new and improved process for the waterproofing of leather. More particularly, the invention relates to a waterproofing process which is especially well suited for use in connection with the waterproofing of white leathers.

For obvious reasons, waterproofing is an extremely important step in the finishing of leather. However, it is of equal importance that the waterproofing of leather be accomplished without adversely aifecting the air permeability or water-vapor permeability of the leather and Many methods have been disclosed in the prior art as being .suitable for use in rendering leather waterproof. Some of these havebeen more satisfactory than others. In most cases the proposed methods have been successful in providing the leather with the. desired resistance to penetration by water or moisture. 'In many instances, however, this has been accomplished only-by sacrificing the permeability of the leather to air and water-vapor. In other instances, the desired waterproofing has been achieved but with a leather.

In all probability the most well known of the prior art leather waterproofing processes involves the drumming of emulsions of a wax or grease into the tanned skin prior to drying same. More recently, improved methods for the waterproofing of leather have been devised. These involve, for example, the treatment of leather with oil-in-water emulsions of various water-insoluble organic polymers.

In addition to the aforementioned methods, other waterproofing processes have been disclosed in the art. Thus, 40

for example, it is well known that penetration of waterproofing compounds into leather is facilitated when such compounds are added to the leather in the form of an organic solvent solution thereof. When such solutions are used, the waterproofing compounds appear to coat the surface of the fibers. The provision of such a coating is to be contrasted with the result obtained by certain of the previous mentioned methods wherein the waterproofing agent appears merely to be deposited in the spaces between the fibers. I

A fiow sheet representing in a schematic fashion the process of the invention is as follows:

discoloring or darkening of the' 3,052,571 Patented Sept. 4, I962 ice The object of invention is to provide a new and improved process for the waterproofing of leather.

A more particular object of the invention is to provide 7 will in part appear hereinafter.

It has been discovered that the objects of this invention can be accomplished :by treating leather which has been saturated thoroughly with an organic solvent solution of aluminum isopropoxide with an organic solvent solution of a soap-forming acid and subsequently washing and drying same.

The present invention contemplates the use and the treatment of tanned leather in ai-rdried condition. Preferably, our waterproofing process is carried out on the air-dried leather immediately after the fat-liquoring step. If desired, however, leather can be waterproofed by our method either prior to the fat-liquoring step or at any finishing step subsequent to fat-liquoring.

Furthermore, the process of the invention is such that it can be utilized in the treatment of leathers, without regard to the manner in which the leather has been tanned. Thus, for example, the invention can be practiced on leathers which have been subjected to chrome tannage, alum tannage, vegetable tannage, tannage and synthetic tannages, as well as on leathers which have been retanned.

-The process of the invention can be adapted readily for commercial use. This will be readily apparent from the description which follows hereinafter. -In carrying out the process, a dilute-organic solvent solution of aluminum isopropoxide is first prepared. In general, any organic solvent in which aluminum isopropoxide is soluble can be used in the preparation of this solution. In the preferred embodiment of the invention, however, are rna-tic hydrocarbon solvents, such as, benzene, toluene, xylene, etc. are employed. The concentration of the solution used may be varied over a relatively wide range. Preferably, a solution containing from about 3.0% to about 10.0% by weight of aluminum isopropoxide will be employed. It should be understood, however, that more dilute or more concentrated solutions can be employed in carrying out the process, if desired. However, it has been our experience, that by far the most satisfactory results are obtained when a solution containing not less than 3.0%, by weight, or more than 10.0%,. by weight,

of aluminum isopropoxide is used.

In the first step of the preferred procedure, the tanned leather is thoroughly impregnated or saturated with the organic solvent solution of aluminum isopropoxide thus prepared. In general, this can be accomplished in any convenient manner. For all practical purposes, however,

the complete saturation of the leather with the solution can be brought about most etiiciently by totally immersing the leather in the solution in a suitable vessel containing the solution, as, for example, in a drum or vat.

The step of saturating the leather with the solvent solution of aluminum isopropoxide can be, and is preferably, carried out at a temperature which is at or near ordinary room temperatures. However, the solvent solution can be heated to a temperature which is elevated somewhat above room temperatures, if .desired, prior to impregnating it into the leather which is to be waterproofed. It has been found that the use of a heated solvent solution during the step will facilitate, to some extent, the penetration of the aluminum isopropoxide solution into the leather. This means that, in such instances, complete saturation of the leather with the so lution can be accomplished in a shorter period of time. However, since even at room temperatures adequate sata ration can be achieved by immersing the leather in xylene, etc., are used mthe second and third steps. 1e solution for as short a period as fifteen minutes, from In the second step, solutions contammgfrom about 3.0% n economical standpoint there is no real advanta e in to 10.0% by weight the soap forrmng fatty acid are sing a heated solvent solution. In any event, seldom, preferably employed; However, more d lute or more 5 ever, will it serve any useful purpose to immerse the 5 concentrated solutions can be used, if desired. No par- :ather in a solution which has been heated to a temperat cular advantage -is ga ned, ow by t euse Of a so- 1re above about 50 C. lution which contains less than 3.0% weight or more The exact volume of the aluminunuisopropoxide soluthan 10.0% by weight of the soap-forming fatty acid. on which is employed in the practice of our invention is The precise volume of the fatty acid solutionused ot particularly critical. When the aluminum isopropoxm the practice of the invention is not particularly crmcal. le is introduced into the leather by an immersion proc- For maximum effectiveness, however, a suffcient quantity ss,.,the. bath used, however, should contain a quantity of fatty acid must be provided to react with all of the i f isopropoxidewhich is suflicient to impregaluminum isopropoxide present in the interstices of ate all of the interstices of the leather. Obviously, volthe leather. The use of a solvent solution containing me of the solution which must be used in any par-ticufrom about 3.0% to 10.0% by weight of fatty acid in uinstance will depend, at least in part, on the concena sufficiently large volume to permit the complete imration of the solution. A lesser voluine of a more highly mersion therein of the leather to be treated will provide oncentrated solution and a greater volume of a more the system with a quantity of fatty acid which is more ilu-te solution will be needed to supply a sufficient quanthan enough for our purposes. The use, or presence, ity of impregnant. As algenera-l rule, it has been found of an excess of acids in the bath is not economically hat the use of a solution containing from 3.0% to 10.0% disadvantageous since the bath can be used over and y weight of aluminum isopropoxide, in a sufficiently over again in subsequent runs, preferably after it has arge volume to permit the complete immersion therein been replenished by the addition of a quantity of fatty f the leather to be waterproofed, will insure the presence acid suflicient to return it to its original concentration. a quantity of aluminum isopropoxide which is more The treatment of the aluminum isopropoxide-saturated han enough for P p It may he noted in this leather with the solution of the soap-forming fatty acid egard that the use of a solution containing a greater can be, and is preferably, carried out at temperatures uantity of aluminum isopropoxide than is actually neceswhich are at or near ordinary room temperatures. Solary does not render the process n mi lly dlsadvanvent solutions of the fatty acid heated to temperatures ngeons- After the saEul'ated leather has been Withdrawn of up to about 50 C. can be used, however, if desired. 1'011 the bath, one'ean determine, y analytical methods, It has been observed that, when a heated solution of he q y of aluminum P P remaining in the fatty acid is used, the rate of ,the reaction of the fatty rath. The nused aluminum QP P Solution can acid with the aluminum isopropoxide is accelerated to veusedd e again, in q n ,P ?h Y some extent. Thus, for example, using an unheated tfter it has been repl ni y the addl-hon of a q ny solvent solution, the reaction will proceed to substantial f aluminum iSQPYOXide Sufheient to restore it to its 8- completion when the saturated leather is allowed to stand nal concentration. in contact with the fatty acid solution for a period of In t Second P of the P Procedure, h a111- about fifteen minutes. A ten minute immersion period ninn'm isopmpmide'sathmted leather is heated Wlth f will, on the other hand, often be suflicient when the fatty Solvent Solution 06 a P" fatty held- 40 acid solution is pre-heated to about C. Since, for

This can be aeeomphshed i y convenient F but all practical purposes this difference is not deemed' to P h fi p 18 cnmed out by mp s the be too highly significant, the reaction is preferably al- Jrated leather in a sell- 0f the fatty aeld- The l lowed to occur at ordinary room temperatures.

ment of the saturated leather with the solvent solution As indicated heretofore, the third step in our process If fatty acid results in formation, in F 9 F e involves washing the treated leather in a solvent, such Proofing "aluminum Salt of the fatty acld fivlthlh the as, an aromatic hydrocarbon, to remove any unreacted terstices of the leather. Isopropyl alcohol 1s also formed. ingredients present This step is carried out at room The formation of the water-insoluble aluminum salt 1n temperature f bl but, as was the case with the this unique manner greatly enhanee$ the Teslstahce preceding steps in the process, it too can be carried out leather to penetration by water and moisture. Inthe next 50 at elevated temperatures, that is, temperatures up to P, the fine-1 p of the Ph r the leather 1s Washed about 50 C., if desired. The washing operation can free of any unreacted aluminum ISOPI'OP and fatty be performed in any convenient manner but it is most acld present by m n of the use of a shltahle easily accomplished by immersing the treated leather solvent. After w s g, the waterproofed leather 15 P in a vat or drum of fresh solvent. Alternate methods mlfleq y at room temperature for accomplishing the desired result, however will be As mdle ted heretofore, the seeohd step 0f the Pl'ocess readily apparent to persons skilled in the art. Imcontem'p t the use Of a 015, W Ila-Sheen mersion of the treated leather in the solvent for not re to pfatty acld- BY we longer than about ten minutes, and generally for about mean that a solution of an aliphatic monocarboxylic acid, five minutes will be suflico either saturated, unsaturated or hydroxylated, which has 0 Finally, "when the i gg i g g g zzgt fi a cimhon length of from about 12 to about 24 leather is permitted to air dry. The waterproofed carbon atoms is employed. Thus, for example, soluleather ma be sub-acted thereafte a r to other conventi trons of soap-formlng fatty acids, such as lauric acid, processingyor finisllling steps. anal myristic acid, palm-itic acid, stearic acid, behen-ic acid, It should be understoud that th e se uenc d d a; gs 3 :5 or of 2 heretofore of treating the leather fir t with 5: :11- 0 are y or n e pm err minum iso propoxide solution and then with the fatt y acld m z g tg gg ggg sggf of laumc acid 01cm solution represents only the preferred method for prac- Any organic solvent in which the fatty acid is soluble ficing our fh' This sefluehc? is h critical insom; at s time, with 10 is: 2...: ii iil ltfif sza zrrltzrrss. use m eprecc mg stepo eprocesscan' u ire both in producing the fatty acid solution employed i h Thus, for example, the leather to be waterproofed could second step and in the washing operation of the third step. be saturated with the solvent solution of the fatty acid In the preferred practice of the invention, however, aroin the first step of the process and in the second step matic hydrocarbon solvents, such as, benzene, toluene, the saturated leather could be treated with the solvent solution of the aluminum isopropoxide. The various disclosures heretofore with respect to the practice of the invention by preferred method are applicable equally with respect to the practice of the invention by the alternate procedure. As in the preferred method, treatment by the alternate procedure results in the impregnation of the interstices of the leather with the desired waterproofing aluminum salt.

Many advantages accrue from the practice of our invention. First, by its leathers which are highly resistant to penetration by water and -moisture are obtained. Moreover, the process is economical and commercially feasible. It does not require the use of equipment not already in use in leather tanneries, and its practice does not necessitate a knowledge of special techniques. Furthermore, leather treated as disclosed herein is protected indefinitely. This is in contrast to leather which, in the prior art, has been surface treated with fats, waxes and preformed aluminum soaps. Such treatment affords temporary protection only. When the aluminum soap is formed in situ, by the two stage process described herein, it impregnates the leather. Permanent protection is thus provided since the impregnant cannot be abraded or washed away. Moreover, the process is noteworthy in that neither the air permeability nor the water-vapor permeability of the leather is adversely affected thereby. Finally, treatment by our process does not result in the discoloration or darkening of the leather. The latter feature will render the process invaluable for use in the waterproofing of light, and particularly white, leathers.

For a fuller understanding of the nature and objects of this invention, reference may be had to the following examples which are given merely as further illustrations of the invention and are not to be construed in a limiting sense. All parts given in. the examples are parts by weight unless otherwise indicated.

Example I Samples of side leather were waterproofed by process of the invention. The leather employed was chrome tanned, syntan retanned and fat-liquored.

A solution comprising benzene having dissolved therein 3.0% by weight of aluminum isopropoxide was first prepared. This solution was divided into two parts. A sample of side leather designated, hereinafter as sample I, was immersed in one of the parts of the solution. It was retained therein for a period of about 30 minutes. The solution had a temperature of about 27 C. An

other sample of the same/side leather, designated hereinafter as sample IL/was immersed in the second part of the solution and {tamed therein for a period of about 15 minutes. The" solution used had a temperature of about 27 C.

Each sample of leather was removed from the solution at the end of the designated time. Sample I was immediately immersed in a solution comprising 3.0% by weight of oleic acid in benzene and it was retained therein for a period of about 30 minutes. This solution had a temperature of about 27 C. Sample II was immediately immersed in a 3.0% by weight solution of oleic acid in benzene and retained therein for a period of about 15 minutes. This solution had a temperature of about 27 C.

At the end of the designated period of time, each of the samples of leather were removed from the oleic acid solution. Each was thereafter washed free of unreacted materials by immersion in benzene for a period of about minutes. Each sample was thereafter removed and allowed to dry at room temperature. Each of the dry samples were tested for static water absorption by the American Leather Chemists Association Provisional Method, April 1953 (Test Method E 30). Static water absorption is defined therein as the amount of water absorbed by leather which is immersed withoutflexing in water for a specified period of time. The test method contemplates two immersion periods in water, namely,

30 minutes and minutes. The method gives an adequate indication of the percent of water absorbed by leather in the specified periods of time. The following are the results of the static water absorption tests.

The foregoing procedure was repeated in every detail except that where a 3.0% by weight aluminum isopropoxide solution was employed originally, a 5.0% by weight solution thereof was instead used, and where 3.0% by weight of oleic acid solution was originally used, a 5.0% by weight of the oleic acid solution was instead emplayed. The samples of leather thus treated were tested for static water absorption in the same manner as were samples I and II. In the table which follows hereinafter, the designation sample III refers to the product corresponding to previous sample I. The designation sample IV refers to the product corresponding to the previously mentioned sample II. The result sof the static water absorption test were as follows:

Percent Water Absorption Immersion Period 30 minutes 120 minutes The foregoing procedures were repeated in every detail once again except that, in this instance, 10.0% by weight solutions of aluminum isopropoxide in benzene and 10.0% by weight solutions of oleic acid in benzene were used instead of the 3.0% by weight and 5.0% by weight solutions previously employed. These samples were tested for static water absorption in the same manner as were samples I to IV, inclusive. In the table which follows hereinafter, the designation sample V refers to a product corresponding to previously mentioned samples I and III. The designations, sample VI refers to a product corresponding to the previous samples II and IV. The results of these tests were as follows:

Percent Water Absorption 30 minutes 120 minutes The foregoing results furnish conclusive evidence that excellent waterproofing can be achieved when leather is treated by the process of our invention. However, in order to demonstrate that the result obtained is attributable to a reaction between the aluminum isopropoxide and oleic acid, in situ, rather than merely to the deposition of a coating of water-insoluble fatty acid in or on the leather, the following experiments were carried out. A solution of 3.0% by weight of oleic acid dissolved in benzene and a solution of 5.0% by weight of oleic acid dissolved in benzene was first prepared. Into each of the two solutions a sample of chrome tanned, syntan retanned and fat-liquored side leather was immersed. In one case, the leather was allowed to stand in contact with the 3% oleic acid solution for 30 minutes. The leather thus treated will be referred to hereinafter as sample VII. The second sample of leather hereinafter, designated as Percent Water Absorption (Samples Treated With Fatty Acid Only) Immersion Period. 30 minutes 120 minutes Sample v11 -Q no 116 Sample VIII 95 97 Since it is well known in the art that the properties of aluminum isopropoxide are such, that it alone could not be used and would not function as a waterproofing agent and since the foregoing results demonstrate that oleic acid alone is ineffective, the results of the static water absorption tests reported herein conclusively prove that the present process provides a valuable method of waterproofin leather.

Anexamination of the leather after treatment by the method disclosed herein reveals that in each instance the sample was waterproofed without sacrificing the air and water vapor permeability thereof and without darkening or discol'oring the leather.

Example 11 In this example the procedure of Example I was repeated in every detail except that calfskin rather than side leather was employed in this example. The calfskin used was chrome tanned and syntan retanned but it had not been fat-liquored prior to waterproofing.

Calfskin (sample I) was treated at a temperature of 27 C. by immersing it first in a 3.0% by weight solution of aluminum isopropoxide in benzene for 30 minutes and thereafter in a 3.0% by weight solution of oleic acid in benzene for 30 minutes. benzene for minutes and finally air-dried.

Calfskin (sample II) was treated at a temperature of 27 C. by immersing it first in a 5.0% by weight solution of aluminum isopropoxide in benzene for 30 minutes and thereafter in a 5.0% by weight solution of oleic acid in benzene for 30 minutes. The leather sample was then washed in benzene for a period of about 5 minutes and finally air-dried.

Calfskin (sample III) was treated at a temperature of about 27 C. by immersing it first in a 10.0% by weight solution of aluminum isopropoxide in benzene for 30 minutes and thereafter in a 10.0% by weight solution of oleic acid in benzene for 30 minutes. The leather sampic was then washed in benzene for about 5 minutes and finally air-dried.

Calfskin (sample IV) was treated in the same manner as sample I except that it was immersed in the benzene solutions of aluminum isopropoxide and oleic acid for 15 minutes rather than 30 minutes.

Calfskin (sample V) was treated in the same manner as sample II except that it was immersed in the benzene solutions of aluminum isopropoxide and oleic acid for 15 minutes each rather than 30 minutes.

Calfskin (sample VI) was treated in the same manner as sample III except that it was immersed in the benzene solutions of aluminum isopropoxide and oleic acid for 15 minutes each rather than 30 minutes.

Calfskin (sample VII) was treated in the same manner as sample I except that the benzene solutions of aluminum isopropoxide and oleic acid were heated to a temperature of 50"v C. priorto immersing the leather therein and except that the leather was allowed to remain immersed in each of the solutions for 10 minutes rather than for 30 minutes.

The leather was then washed in Calfskin (sample VIII) was treated in the same manner as sample II except that the solutionsof aluminum isopropoxide and oleic acid used were heated to a temperature of 503C. prior to immersing the leather therein and except that the leather was allowed to remain immersed in each solution for 10 minutes rather than 30 minutes.

Calfskin (sample IX) was treated in the same manner as sample III except that the solutions'of aluminum isopropoxide and oleic acid were heated to a temperature of 50 'C; prior to immersing the leather therein and except that the leather was allowed to remain immersed in each solution for 10 minutes rather than 30 minutes.

For comparative purposes the basic procedure employed in treating each of samples I to III, inclusive, and VII through XI, inclusive, of this example was repeated in every detail except that the steps of immersing the leather in the solution of aluminum isopropoxide and the step of finally washing the treated leather in benzene were omitted. In the tables which follow hereinafter the samples corresponding to samples I, II, III, VII, VIII and IX are designated as samples X, XI, XII, XIH, XIV and XV respectively.

Each of the dry samples were tested for static water absorption by the Provisional Method of the American Leather Chemists Association, April 1953, referred to heretofore. The following are the results of those tests:

Percent Water Percent Water Absorption (Samples Treated With Fatty Acid Only) Immersion Period 30 minutes 120 minutes Sample X 110. 5 113 Sample XI. 107 108 Sample XII 116. 5 108 Sampl XIIL. 135 136 Sample XI 137 137 Sample XV 1Q 142 These results demonstrate the extent to which leather treated by our method was rendered water-repellant. It was further observed that this result was accomplished without darkening or discoloring and without adversely affecting the air or water permeability of the leather.

Example III In this example, samples of chrome tanned side leather were treated.

A solution of 3.0% by weight of aluminum isopropoxide was first prepared. This was divided into three parts. A separate sample of leather was immersed in each solution and retained therein for a period of about 30 minutes.

The temperature of the solution used in each instance was After 30 minutes each sample was removed from its fat-X t'y acid bath and washed free of unreacted materials by immersion in benzene for about minutes. Each sample was removed thereafter and allowed'to dry at room temperature.

For comparative purposes, the procedureused in waterproofing each of the samples I, II andlII'was repeated except that in each instance the steps of immersing the leather in the aluminum isopropoxide solution and 'of' washing the leather in benzene were omitted. In the tables which follow hereinafter, the comparative'samples which correspond to samples 1,11 and HI have been designated at samples. IV, V and VI respectively. a Each of these six samples of treated leather were tested for static water absorption by the Provisional Method of American 'Leather Chemists Association, April 1953', referred to in Example I. The results of the tests thus conducted were as follows:

Percent Water Absorption Immersion Period 30 minutes 120 minutes Percent Water sorption (Samples Treated Wlth Fatty Acid Only) Example IV In this example, chrome tanned, high grade sheepskin, a soft leather of the type used in the glove and garment industries, was employed. The leather was fat-liquored and air-dried prior to use.

A sample of this leather, hereinafter referred to as sample I, was immersed first in a solution of 3.0% by weight of aluminum isopropoxide in benzene and retained therein for 30 minutes. The solution used had a temperature of 27 C. After immersion in this solution, the leather sample was removed and it was immersed immediately in a solution of 3.0% by weight stearic acid in benzene and retained therein for a period of 30 minutes. The stearic acid solution used had a temperature of 27 C. At the end of the designated period of time the sample was removed from the stearic acid solution, immersed in benzene and retained therein for 5 minutes and thereafter air-dried.

The dynamic water resistance of the leather thus treated was tested by the American Leather Chemists Association Provisional Method, April 1953 (Test Method B 31). For comparative purposes, a sample of non-waterproofed sheepskin which was chrome tanned and fat-liquored was subjected to the same test method. This non-waterproofed leather sample will be referred to hereinafter as sample II. For further comparison, chrome tanned sheepskin, which after fat-liquoring and drying, was waterproofed using chromium couples was also subjected to the 70 dynamic water resistance test. This sample will be referred to as sample III. Finally, chrome tanned sheepskin which, after fat-liquoring and drying, had been waterproofed using chromium couples and which was further ple was alsotested for dynamic water absorption. This is sample IV.

The test for dynamic water absorption revealed that, of all the samples tested, sample I, that is, leather treated by the process of this. invention, was most resistant to the penetration of water. Initialtwater penetration of sample I occurred only after 7,500 cycles. The test proved sample IV to be secondbest, with water penetrating the leather only after 6,500 cycles, sample III was shown to be. thirdxbest, with water penetrating the leather only after 5,500 cycles. In thecase of sample II, water penetrated the leather almostinstantly.

: 'Ihe American Leather. Chemists Association Test for;

static water absorption was then carried out in connection withsamples I and III. 'It was found that'sample III which was waterproofed using only chromium couples took up as much as 107% water whereas sample I absorbed only 32% in the same period of time.

The foregoing results conclusively demonstrate that 80-. perior waterproofing of leather is provided by the process of the present invention. In addition, examination of leather which was subjected to the method disclosed herein revealed that the desired water repelling properties were achieved without darkening or discoloring of the leather. 4

Having described our invention what we claim as new and desire to secure by Letters Patent is:

l. A method of waterproofiing leather with an aluminum salt of an aliphatic monocarboxylic acid having a carbon chain length of from about 12 'to about 24 carbon atoms consisting essentially of impregnating tanned leather with a solution consisting of an aromatic hydrocarbon and aluminum isopropoxide', and with a solution consisting of an aromatic hydrocarbon and an aliphatic monocarboxylic acid having a carbon chain length of from about 12 to about 24 carbon atoms and subsequently washing the leather thus treated with an aromatic hydrocarbon solvent.

2. Tanned leather produced by the process of claim 1 characterized by its water repellency, the permanency of its water repellency, and its air permeability and water vapor permeability and further characterized in that it is not discolored or darkened as a result of that process.

3. A method of waterproofing leather with an aluminum salt of an aliphatic monocarboxylic acid having a carbon chain length of from about 12 to about 24 carbon atoms consisting essentially of immersing tanned leather in a solution consisting of an aromatic hydrocarbon and from about 3.0% to about 10.0% by weight of aluminum isopropoxide for a period of time sufiicient to saturate said leather with said solution, immersing said leather in a solution consisting of an aromatic hydrocarbon and'from about 3.0% to about 10.0% by weight of an aliphatic monocarboxylic acid having a carbon chain length of from about 12 to about 24 carbon atoms and subsequently washing the leather thus treated by immersing it in an aromatic hydrocarbon solvent.

4. A method of waterproofing leather with an aluminum salt of an aliphatic monocarboxylic acid having a carbon chain length of from about 12 to about 24 carbon 0 atoms consisting essentially of immersing tanned leather in a solution consisting of an aromatic hydrocarbon and from about 3.0% to about 10.0% by weight of an aliphatic monocarboxylie acid having a carbon chain length of from about 12 to about 24 carbon atoms for a period of time sutricient to saturate said leather with said solution, immersing said leather in a solution consisting of an aromatic hydrocarbon and aluminum isopropoxide and subsequently washing the leather thus treated byimmersing it in an aromatic hydrocarbon solvent.

5. A method of waterproofing leather with an aluminum salt of an aliphatic monocarboxylic acid having a carbon chain length of from about 12 to about 24 carbon atoms consisting essentially of immersing tanned leather in a solution consisting of about 3.0% to about 10.0% by subjected to the treatmentgiven to sample I of this examweight of aluminum isopropox-ide and an aromatic hydro- 1 1 arbon solvent selected from the group consisting of ben- :ene, toluene and xylene for a period of time suflicient to aturate said leather with said solution, immersing said eather in a solution consisting of 3.0% to about 10.071: y weight of an aliphatic monocarboxylic acid having a :arbon chain length of from about 12 to about 24 carbon ltoms in an aromatic solvent selected from the group conisting of benzene, toluene and xylene and subsequently vashing the leather. thus treated by immersing it in an tromatic hydrocarbon solvent selected from the group mnsisting of benzene, tolueneand xylene.

6. A method of water-proofing leather with an alumilum salt of a fatty acid selected fromthe group consisting f lauric acid, stearic acid and oleic acid consisting essenially of immersing tanned leather in a solution consisting )f from about 3.0% to about 10.0% by weight of alu-- ninum isopropoxide and the remainder being an aromatic lydrocarbon selected from the group consisting of benene, toluene and xylene for a period of time suflicient to aturate said leather with said solution, immersing said eather in a solution consisting of from about 3.0% to lbOllt 10.0% by weight of an aliphatic monocarboxylic lcid selected from the group consisting of lauric acid, itearic acid and oleic acid and the remainder being an I carboxylic acid employed is lauric acid.

8. The process of claim 6 wherein the aliphatic monocatboxylic acid employed is stearic acid. 7

9. The process of claim 6 wherein the aliphatic monocarboxylic acid employed is'oleic acid.

References Cited in the file of this patent UNITED STATES PATENTS 1,242,327 Cuthbertson Oct. 9, 1917 2,182,045 Bell Dec. 5, 1939 2,323,387 Edelstein July 6, 1943 2,603,576 Cook et al. July 16, 1952 2,670,303 Mailander Feb. 23, 1954 FOREIGN PATENTS 609,002 Great Britain Sept. 23, 1948 767,585 Great gritain Feb. 6, 1957

Claims (1)

1. A METHOD OF WATERPROOFING LEATHER WITH AN ALUMINUM SALT OF AN ALIPHATIC MONOCARBOXYLIC ACID HAVING A CARBON CHAIN LENGTH OF FROM ABOUT 12 TO ABOUT 24 CARBON ATOMS CONSISTING ESSENTIALLY OF IMPREGNATING TANNED LEATHER WITH A SOLUTION CONSISTING OF AN AROAMTIC HYDROCARBON AND ALUMINUM ISOPROPOXIDE, AND WITH A SOLUTION CONSISTING OF AN AROMATIC HYDROCARBON AND AN ALIPHATIC MONOCARBOXYLIC ACID HAVING A CARBON CHAIN LENGTH OF FROM ABOUT 12 TO 24 CARBON ATOMS AND SUBSEQUENTLY WASHING THE LEATHER THUS TREATED WIHT AN AROMATIC HYDROCARBON SOLVENT.