US2968580A

US2968580A - Process for increasing the waterresistance of leather

Info

Publication number: US2968580A
Application number: US744341A
Authority: US
Inventors: Plapper Jurgen; Heyden Rudi
Original assignee: Boehme Fettchemie GmbH
Current assignee: Boehme Fettchemie GmbH
Priority date: 1958-06-25
Filing date: 1958-06-25
Publication date: 1961-01-17
Anticipated expiration: 1978-01-17

Description

Unit

PROCESS FOR INCREASING THE WATER- RESISTANCE OF LEATHER No Drawing. Filed June 25, 1958, Ser. No. 744,341

14 Claims. (Cl. 117135.5)

This invention relates to an improved process for rendering leather both water-repellent and water-impermeable and more particularly to a method of rendering leather both water-proof and Water-resistant by a two step treatment of the leather with (1) aqueous solutions of salts of acid esters having at least two salt forming acyl groups and (2) aqueous alcohol solutions of organic metal complex compounds.

In our previous patent, Plapper et al., US. Patent No. 2,772,988, issued December 4, 1956, we disclose a process for impregnating leather with solutions which contain organic metal complex compounds which have been obtained by the reaction of basic polyvalent metal salts with acid phosphoric acid esters of high molecular weight hydroxyl compounds in the presence of low molecular weight monovalent alcohols. Especially suitable are organic complex compounds formed from basic aluminum or chromium salts, which are dissolved in methanol or ethanol, and acid monoor di-esters of phosphoric acid formed with high molecular weight hydroxyl compounds. These complex compounds produce water-repellent or water-proofing impregnations when leather is treated therewith.

An object of our invention is to still further improve the water-impermeability or water-resistance of leather.

A further object of our invention is to improve the penetration of the impregnation agents and give an easier, more rapid impregnation and uniform distribution of water-proofing agents even in thick leathers such as sole leathers.

We have found that the water-impermeability or waterresistance of leather treated in accordance with US. Patent No. 2,772,988 can be substantially improved if the leather is pretreated with water-soluble or water-dispersible complex-active organic compounds. Suitable complex-active compounds for this purpose are derivatives of di-basic or higher poly-basic inorganic or organic acids containing hydrophobic radicals or groups which have at least two salt-forming groups capable of forming complexes.

In tabular form our process for impregnating leather is as follows:

(1) Impregnating of leather with a water-miscible derivative of a polybasic acid, said derivative containing at least one hydrophobic radical and at least two saltforming radicals capable of forming complexes.

(2) Drying the impregnated leather.

'(3) Impregnating of the leather with a water-miscible, organic complex salt of a polyvalent metal containing a ratio of at least 2.5 mols of an alcohol-soluble, basic States atent C salt of a polyvalent metal with one mol of an acid ester of phosphoric acid esterified with an alcohol containing a hydrophobic radical, said alcohol having about 6 to about 18 carbon atoms, and having coordinated with said basic salt and said acid ester a lower molecular weight alcohol.

(4) Drying the impregnated leather.

(5) Further conventional treatment of finishing the leather.

The term hydrophobic group as used herein is well known in the chemical arts and has been defined by Schwartz and Perry in their publication 'Surface Active Agents, Interscience Publishers, Inc., New York (1949), on pages 17-19 as follows:

In View of these considerations it is important to examine some of the more usual types of hydrophobic groups and the ways in which they are obtained.

(1) The straight alkyl chains of eight to eighteen 01' more carbon atoms are derived from the natural fatty acids. These may be used as such or may be converted to acid chlorides for use in acylation reactions. The acids or their esters may also be reduced to the corresponding fatty alcohols or through the nitriles to the fatty amines. These in turn can be used as intermediates in a variety of reactions to introduce the long alkyl chain. The natural fatty acids are possibly the most important raw material for hydrophobic groups. A wider variety of detergents has been derived from them directly or indirectly, than from any other single source.

(2) The lower alkyl groups of three to eight carbon atoms are frequently attached to aromatic nuclei such as benzene or naphthalene, the combination forming a useful type of hydrophobic group. The sources of lower alkyl groups are usually the alcohols. The lower alkyl groups are sometimes used by themselves as hydrophobic groups, as in the case of the dialkyl sulfosuccinates:

(3) Certain types of petroleum yield naphthenic acids in the normal course of refining. These are surface ac tive in themselves and have also been used as a source of hydrophobic groups in derived surface active agents. In the refining of petroleum oils by washing with sulfuric acid the surface active petroleum sulfonates are obtained.

In general, organic compounds which we have found to be suitable for this purpose are derivatives of dibasic or higher polybasic inorganic or organic acids which contain hydrophobic radicals and at least two free, salt-forming groups capable of combining with the mineral-tanning agent to form an organotnetallic complex grouping. Such polybasic acid derivatives have acid characteristics and are preferably used for the purpose set forth in the form of their water-soluble salts, especially those formed by neutralization with organic bases, their ammonium salts and alkali metal salts.

Examples of suitable inorganic polybasic acids upon which the above derivatives are based are boric acid, phosphoric acid, arsenic acid and the like. Similarly suitable organic polybasic acids are, among others, citric acid, trimesitinic acid, trimellitic 'acid, mellitic acid, diadipic acid, ethane-tetra-acetic acid, sulfophthalic acids, oxyphthalic acids, pyrogallic acid, pyrogallol carboxylic acid, and the like. Other suitable organic acids are those which contain hydrophobic radicals and may, for example, be obtained by subjecting high molecular weight 1111- .the process according to the invention.

3 saturated fatty acids, fatty alcohols or olefins to a condensation reaction with maleic acid, such as the condensation products of oleic acid, linseed oil fatty acid, soybean oil fatty acid, and the like, with one or several mols of maleic acid. Similarly condensation products such as alkylated malonic acids are suitable.

While the last mentioned high molecular Weight dior higher polybasic carboxylic acids may be used as such, the first mentioned trior higher polybasic inorganic acids or the low molecular weight trior higher polybasic organic carboxylic acids must be transformed .into complexactive compounds .by a partial esterification ,or-a partial amidation with high .molecular weight alcohols or amines which contain hydrophobic radicals, and these complex active compounds may then be used in These products are known materials and are readily obtainable according to simple procedures. In place of these compounds,

.however, any other .desired compounds which comprise at least two complex active salt-forming groups in addition to one hydrophobic radical may also be used.

Examples of some specific complex active compounds "which may be used for the purpose according to the invention are the following: acid dodecyl phosphate, acid octadeccnyl phosphate, hexadecyl borate, octadecenyl arsenate, acid hexadecyl citrate, acid dodecylsulfo- 'phthalate, citric "acid'mono-octadecyl amide, citric acid mononaphthenyl amide, andthe like, which may be employed as-suchorin the form of their salts.

The hydrophobic radicals of .these compounds may be of an aliphatic, cycloaliphatic, aliphatic-aromatic orali- -''phatic-cycloaliphatic nature, and may be interrupted by oxygen, sulfur and'nitrogen orcarry constituent radicals containing oxygen, sulfur or nitrogen atoms. Of particular interest, for example, are the esters of trior 'higher-polybasic organic or inorganic acids formed with "high molecular weight ethoxylated fatty alcohols containing from 1 to mols, preferably from 1 to 3 mols, of ethylene-oxide'per mol of high molecular weight fatty alcohol.

The treatment of leather with aqueous solutions or dis- In general, from 1 to 10%, but preferably from 2 in the solution or by brushing or otherwise applying the solution onto the leather.

-After this pro-treatment the leather is impregnated according to-theprocedure-described in U.S. Patent No. 'An alcohol solution of an organometallic complex isdiluted-with'water or anorganic solvent to the desired concentration andthe leather is'then impregnated with this solution by any ofthe customary methods.

The impregnating agents are solutions of organometallic complex compounds which have been obtained byreact- "ing basic polyvalent'metal-saitswith acid phosphoric acid esters formed with high molecular weight hydroxyl compounds in the presence of low-molecular weight monovalent alcohols.

These salts are water-miscible, -cationic-active, organic, complex salts of a polyvalent metal containing aratio of at least 2.5 mols of an alcohol-soluble, basic salt of "a polyvalent metal selected from-the group consisting of aluminum, chromium, iron, mercury, tin, titanium and zirconium, for every one mol of an acidester of phos phoric acid esterified with an alcohol selected from the group consisting-of alkanols, alkenols, cycloalkanols, al-

kylphenols and alkylcycloalkanols, said alcohol having about 6 to about 18 carbon atoms in the molecule, and having coordinated with said basic salt and said acid ester a lower alcohol selected from the group consisting of lower alkanols, tetrahydrofurfuryl alcohol and 1,2 pro- -pylene glycol.

acid ester complexes are formed thereby whichhave a cationic character. Such products are also obtained when .berentirely or partially omitted, depending upon the amount ofqcomplex componnds,used. vFor the process 4 the process according to the present application is the subject matter of the copending patent application Serial No. 621,008, filed November 8, 1956, now U.S. Patent No. 2,885,417, in the name of one of us. The starting materials for the production of these organic complex salts are basic salts of polyvalent metals formed with inorganic or organic acids; for example, basic chromium chloride, basic aluminum nitrate, basic titanium chloride, etc. Suitable phosphoric acid esters are monoand diesters of ortho-phosphoric acid; for example, monoor dioctyl phosphoric acid ester, monoor didodecyl phosphoric acid ester, monoor dioleyl phosphoric acid ester, or esters of other aliphatic, cycloaliphatic, aliphatic-aromatic or cycloaliphatic-aromatic hydroxyl compounds. The starting material may also be an acid ester mixture, such as is. obtained by a rection of phosphorus pentoxide with high molecular weight hydroxyl compounds. Suitable low molecular .weight monovalent alcohols are primarily methanol and ethanol. The solutions obtainedin this manner are solutions of metal complex compounds in the low molecular weight monovalent alcohols, which may be'diluted to anydesired extent with water .and are then used in this form for the impregnation of the leather. These complex metal compounds are produced by the reaction under anhydrous conditions at reflux temperatures in theratio of at least 2.5 mols of an alcohol-soluble,

basic .salt of a polyvalent metal selected from the group sisting of alkanols, alkenols, cycloalkanols, alkylphenols and alkylcycloalkanols, said alcohol having about,6v to about 18 carbon atoms in the molecule. In the produc .tionof the above metal complex compounds it isnot absolutely, necessary to usethe above-mentionedprocess; instead, vother methods of producing these compounds may beused, provided that soluble metal alkylphosphoric basic metal salts are reacted with acid alkyl phosphates in,the molten state.

Thetreatment of the leather with these solutions proceedsin customary fashion, such as by immersion, rolling, brushing .or plush-wheeling; or, for example, in

lustering of suede leather, by spraying with the aid of spray guns. Since the complex compounds also possess fattingproperties, the customary fat-liquoring agents may according tothe invention about 1,to 10%, andpreferably betweeno and 8% by weight of thecomplex compounds, based upon the shaved weight of the leather,';is

required. Porbrushingor spraying it is advantageous to use 5 to 15%.,solutions. In place of the aqueous-solutions, solutions inorganic solvents, such as trichloroethylene, isopropyl alcohol, ,benzene, and the like may be used.

The, present process may be used for impregnating mineral-tanned, vegetable-tanned, synthetic-tanned, resintanned, formaldehyde-tanned and combination-tanned leathers,

The advantages of the present process reside inthat the two-step impregnation according to ,the invention produces leather'with especially valuable properties, be cause the pretreatment effects an improvement in the water-impermeability, whereas the subsequent treatment renders the individual leather fibers water-repellent, so that the fibers retain a very low water-absorbing capability. Furthermore, the process produces substantially easier and more rapid impregnation, even in thick leather, with substantially lower requirements of impregnating agents. 1 The advantages "of the process according to the invention make themselves felt especially with combina tion-tanned leather, such as with flexible combination tanned sole leather. The quality and value of such leather depends substantially upon the water-impermeability under conditions of ordinary usethat is, under pressurewhich is considerably improved by the present combined treatment.

The following examples will further illustrate the pres ent invention and will enable others skilled in the art to understand it more completely. It is not intended, however, to limit the invention to these particular examples.

Example I Vache leather or heavy sole leather, which had been pretanned with 0.5 to 1% chromium oxide and retanned with about 20% vegetable tanning agents, and which had a pH of about 3.8 to 4.2 at the leather edge, was sammed until it had a water content of about 50 to 60%, and was then treated with 1.5 to 3% of the ammonium salt of an acid phosphoric acid dodecyl ester and with to 30% water in a hot air chamber. The running time was 30 minutes to 1 hour at a hot air feed temperature of about 60 C. Subsequent to this treatment the leather edge had a pH value of 4.5 to 5.0 and toward the end of the treatment was adjusted with formic acid (about 0.5%) to a value of about 3.5. The leather was then removed from the bath and stored on the horse overnight. Thereafter the leather was treated in the drum without hot air feed at a temperature of 30 to 40 C. for about 1 hour in a bath containing to 30% water and 15 to 25% of a 30% chrome complex salt solution which was produced as follows:

257 parts by weight of a methanol solution containing 17.5 parts by weight of 33% basic chromium (III) chloride were admixed with a solution of 14.75 parts by weight of a technical grade alkylphosphoric acid ester mixture (alkyl radicals containing 12 to 18 carbon atoms) in 85 parts by weight methanol. The mixture was boiled for 5 hours under reflux and then a portion of the methanol was distilled off.

Subsequently the leather was bufiered in the same bath with 1.5 to 2.5% sodium bicarbonate (based on the weight of chrome complex salt). The leather was then rinsed for a short time in a drum. After storage on the horse overnight, friction glazing and drying at 25 to 30 C., the leather was worked up in customary fashion.-

It was advantageous to redry the leather for a short time at temperatures of 50 to 70 C. The impregnation efiect thereby achieved its maximum value. When the leather was not redried at the elevated temperature, this maximum value was not reached until the storage sea soning of the leather.

Example II Fat-liquored and retanned waterproof leather was treated with 1 to 4% of the ammonium salt of a monododecylcitric acid ester and with 10 to 30% water. The running time was from 30 minutes to 1 hour under hot air feed in a hot air drum. The leather treated in this manner was stored on the horse overnight. Thereafter the leather was stuffed, under the customary conditions in a hot air drum, with a waterproofing composition which contained of the complex salt solution according to Example 1.

Example III Chrome tanned and neutralized ASA leather was prefatted and then treated at suitable fat-liquoring temperatures with 0.5 to 4% based on the weight of the leathers of a fat-liquoring oil consisting of a mixture of 40% sulfonated shark oil, 10% mineral oil. 40% sperm oil and 10% of the ammonium salt of an alkyl malonic acid, the alkyl radical of which had a carbon chain of 12 to 18 carbon atoms, this amount of mixed oil was dispersed in about 100%, based on the weight of 1eather,'of water.

a esgm The running time was about 30 to 45 minutes. At the end of this period the leather was acidified to a pH of about 3.5 with formic acid. Thereafter the leather was placed on the horse, allowed to remain there overnight, and was then treated with 10%, based on the weight of the leather, of the about 30% chrome complex salt mentioned in Example I at about 40 0., this amount of chrome complex salt was dissolved in about 50 to of water, based on the weight of the leather. The running time was 30 minutes to 1 hour. The leather was then dried and further worked up in customary fashion.

While we have illustrated our invention with various specific embodiments, it will be obvious to persons skilled in the art that various changes and modifications may be made without departing from the spirit of the invention or the scope of the appended claims.

We claim:

1. The method of water-proofing leather which coniprises impregnating tanned leather with a. water-miscible derivative selected from the group consisting of esters, amides and acids of a polybasic acid selected from the group consisting of dibasic and higher polybasic organic acids and tribasic and higher polybasic inorganic acids, said derivative containing at least one hydrophobic radical and at least two salt-forming radicals capable of forming complexes and thereafter impregnating said tanned leather with a water-miscible, cationic-active, organic, com plex salt of a polyvalent metal containing a ratio of at least 2.5 mols of an alcohol-soluble, basic salt of a polyvalent metal, with one mol of an acid ester of phosphoric acid esterified with an alcohol containing a hydrophobic radical, said alcohol having about 6 to about 18 carbon atoms, and having coordinated with said basic salt and said acid ester a lower molecular weight alcohol.

2. The method of water-proofing leather which comprises impregnating tanned leather with a water-miscible derivative selected from the group consisting of esters, amides and acids of a polybasic organic acid containing at least two acidic salt-forming groups, said derivative containing at least one hydrophobic radical and at least two salt-forming radicals capable of forming complexes and thereafter impregnating said tanned leather with a water-miscible, cationic-active, organic, complex salt of a polyvalent metal containing a ratio of at least 2.5 mols of an alcohol-soluble, basic salt of a polyvalent metal with one mol of an acid ester of phosphoric acid esterified with an alcohol containing a hydrophobic radi cal, said alcohol having about 6 to about 18 carbon atoms, and having coordinated with said basic salt and said acid ester a lower molecular weight alcohol.

3. The method of water-proofing leather which comprises impregnating tanned leather with a water-miscible ester of a polybasic inorganic acid containing at least two acidic salt-forming groups, said ester containing at least one hydrophobic ester radical and at least two saltforming radicals capable of forming complexes and there after impregnating said tanned leather with a water-miscible, cationic-active, organic, complex salt of a polyvalent metal containing a ratio of at least 2.5 mols of an alcohol-soluble, basic salt of a polyvalent metal with one mol of an acid ester of phosphoric acid esterified with an alcohol containing a hydrophobic radical, said alcohol having about 6 to about 18 carbon atoms, and having coordinated with said basic salt and said acid, ester a lower molecular weight alcohol.

4. The method of water-proofing leather which comprises impregnating tanned leather with a water-miscible. ester of a polybasic acid selected from the group consisting of dibasic and higher polybasic organic acids and tribasic and higher polybasic inorganic acids, said ester containing at least one hydrophobic ester radical and at, least two salt-forming radicals capable of forming complexes and thereafter impregnating said tanned leather with a water-miscible, cationic-active, organic, complex salt of a polyvalent metal containing a ratio of at least.

2 9 ct analwh lz qlu le, ba i sa tg a p lyva en me a .With one mol of'an a i est O p osp r c' c d esterified with anal'cohol containing a hydrophobic radia 15 lcqh having out o ab u v 8 a bQ atoms and'hav n coor na wit said asi al n said acid ester a lower molecular weight alcohol.

5. The method of water-proofingdeather which comprises impregnating tanned leather with a'water-rniscible mid o a po yba c a id sel ct d .f om the up co s st n o diba i d hig p lybas c Organic ci sa amide derivative containing .at least one hydrophobic amide radical and at least two salt-forming radicals capable of forming complexes and thereafter impregnatn 'sa n ed eath w t a tc kmi ble c t on active, organic, complex salt of a polyvalent metal containing a ratio of at least 12.5 mols of an alcohol-soluble, basic salt of a polyvalent metal with one mol of an acid ester of phosphoric acid esterified with an alcohol containing a hydrophobic radical, said alcohol having about 6 to about 18 carbon atoms, and having coordinated with said basic salt and said acid ester a lower molecular weight'alcohol.

6; The method of waterproofing leather which comprises impregnating tanned leather with 1% to 10% by weight, based on the shaved weight of the leather of a water-miscible derivative selected from the group consisting of esters, amides and acids of a polybasic acid selected from the group consisting of dibasic and higher polybasic organic acids and tribasic and higher polybasic inorganic acids, said derivative containing at least one hydrophobic radical and at least two salt-forming radicals capable of forming complexes and thereafter impregnating said tanned leather with 1% to 10% by weight, based on the shaved weight of the leather of 'a waterm iscible, cationic-active, organic, complex salt of a polyvalent metal containing a ratio of at least 2.5 mols of an alcohol-soluble, basic salt of a polyvalent metal with one mol of an acid ester of phosphoric acid esterified with an alcohol containing a hydrophobic radical, said alcohol having about 6 to about 18 carbon atoms, and having coordinated with said basic salt and said acid ester 21 lower molecular weight alcohol.

' 7. A process for rendering leather water-proof which comprises treating the tanned leather with an aqueous solution containing 1% to 10% by weight based on the shaved weight of the leather of a water-miscible derivative selected from the group consisting of esters, amides and acids of a polybasic acid selected from the group consisting of dibasic and higher polybasic organic acids and tribasic and higher polybasic inorganic acids, said derivative containing at least one hydrophobic radical and at least two salt-forming radicals capable of forming complexes for a time sufficient to impregnate the leather and thereafter treating the tanned impregnated leather with a solution containing 1% to 10% by weight based on the shaved weight of the leather of a water-miscible, cationic-active, organic, complex salt of a polyvalent metal containing a ratio of at least 2.5 mols of an alcoholsoluble, basic salt of a polyvalent metal with 'one mol of an acid ester of phosphoric acid esterifiedwith an alcohol containing a hydrophobic radical, said alcohol having about 6 to about 18 carbon atoms, and having coordinated with said basic salt and said acid ester a lower molecular weight alcohol, for a time sufficient to impregnate the leather and then drying the leather at elevated temperatures.

8. A process for rendering leather water-proof which comprises treating the tanned leather with an aqueous solution containing 1% to 10% by weight based on the shaved weight of the leather of a water-miscible derivative selected from the group consisting of esters, amides and acids of a polybasic organic acid containing at least two acidic salt-forming groups, said derivative containing at least one hydrophobic radical and at least two saltfgrrning radicals capable of forming complexes for a time sufiicientto impregnate the leather and thereafter treat-V salt of a polyvalent metal with one mol of an acid ester of phosphoric acid esterified with an alcohol containing a hydrophobic radical, said alcohol having about 6 to about 18 carbon atoms, and having coordinated with said basic salt and said acid ester a lower molecular weight alcohol, for a time sufiicient to impregnate the leather and then drying the leather at elevated temperatures.

9. A process for rendering leather water-proof which comprises treating the tanned leather with an aqueous solution containing 1% to 10% by weight based on the shaved weight of the leather of a water-miscible ester of a polybasic inorganic acid containing at least two acidic salt-forming groups, said ester containing at least one hydrophobic ester radical and at least two salt-form ing radicals capable of forming complexes for a time suificient to impregnate the leather and thereafter treating the tanned impregnated leather'with a solution containing 1% to 10% by weight based on the shaved weight of the leather of a water-miscible, cationic-active, organic complex salt of a polyvalent metal containing a ratio of at least 2.5 mols of an alcohol-soluble, basic salt of a polyvalent metal with one mol of an acid ester of phosphoric acid esterified with an alcohol containing a hydrophobic radical, said alcohol having about 6 to about 18 carbon atoms, and having coordinated with saidbasic salt and said acid ester a lower molecular weight alcohol, for a time sufficient to impregnate the leather and then drying the leather at elevated temperatures.

10. A process for rendering leather water-proof which comprises treating the tanned leather with an aqueous solution containing 1% to 10% by weight based on the shaved weight of the leather of a water-miscible ester of a polybasic acid selected from the group consistingof dibasic and higher polybasic organic acids and tribasic and higher polybasic inorganic acids, said ester contain ing at least one hydrophobic ester radical and at least two salt-forming radicals capable of form-ing complexes for a time sufiicient to impregnate the leather and thereafter treating the tanned impregnated leather with a solution containing 1% to 10% by weight based on the shaved weight of the leather of a water-miscible, cationicactive, organic, complex salt of a polyvalent metal containing a ratio of at least 2.5 mols of an alcohol-soluble, basic salt of a polyvalent metal with one mol of an acid ester of phosphoric acid esterified with an alcohol containing a hydrophobic radical, said alcohol having about 6 to about 18 carbon atoms, and having coordinated with said basic salt and said acid ester a lower molecular weight alcohol, for a time sufiicient to impregnate the leather and then drying the leather at elevated temperatures.

11. A process for rendering leather Water-proof which comprises treating the tanned leather with an aqueous solution containing 1% to 10% by weight based on the shaved weight of the leather of a Water-miscible amide of a polybasic acid selected from the group consisting of dibasic and higher polybasic organic'acids, said amide containing at least one hydrophobic amide radical and at least two salt-forming radicals'capable of forming complexes for a time sufficient to impregnate the leather and thereafter treating the tanned impregnated leather with a solution containing 1% to 10% by Weight based on the shaved weight of the leather of a water-miscible, cationic-active, organic, complex salt of a polyvalent metal containing a ratio of at least 2.5 mols of an alcoholsoluble, basic salt of a polyvalent metal with one mol of an acid ester of phosphoric acid esterified with an alcohol containing a hydrophobic radical, said alcohol having from about 6 to about 18 carbon atoms, and having coordinated with said basic salt and said acid ester a lower molecular weight alcohol, for a time sufiicient to impregnate the leather and then drying the leather at elevated temperatures.

12. The process of claim 10 wherein said water-miscible ester of a polybasic acid is an ammonium salt of an acid phosphoric acid monododecyl ester.

13. The process of claim 10 wherein said water-miscible ester of a polybasic acid is an ammonium salt of the monododecyl citric acid ester.

14. The process of claim 8 wherein said water-miscible derivative selected from the group consisting of 10 esters, amides and acids of a polybasic organic acid is an ammonium salt of an alkyl-malonic acid, said alkyl radical containing 12 to 18 carbon atoms.

References Cited in the file of this patent UNITED STATES PATENTS 2,372,985 Roth Apr. 3, 1945 2,693,996 Von Fuchs Nov. 9, 1954 2,772,988 Plapper et a1 Dec. 4, 1956 FOREIGN PATENTS 541,861 Canada June 4, 1957

Claims

1. THE METHOD OF WATER-PROOFING LEATHER WHICH COMPRISES IMPREGNATING TANNED LEATHER WITH A WATER-MISCIBLE DERIVATIVE SELECTED FROM THE GROUP CONSISTING OF ESTERS, AMIDES AND ACIDS OF A POLYBASIC ACID SELECTED FROM THE GROUP CONSISTING OF DIBASIC AND HIGHER POLYBASIC ORGANIC ACIDS AND TRIBASIC AND HIGHER POLYBASIC INORGANIC ACIDS, SAID DERIVATIVE CONTAINING AT LEAST ONE HYDROPHOBIC RADICAL AND AT LEAST TWO SALT-FORMING RADICALS CAPABLE OF FORMING COMPLEXES AND THEREAFTER IMPREGNATING SAID TANNED LEATHER WITH A WATER-MISCIBLE, CATIONIC-ACTIVE, ORGANIC, COMPLEX SALT OF A POLYVALENT METAL CONTAINING A RATIO OF AT LEAST 2.5 MOLS OF AN ALCOHOL-SOLUBLE, BASIC SALT OF A POLYVALENT METAL, WITH ONE MOL OF AN ACID ESTER OF PHOSPHORIC ACID ESTERIFIED WITH AN ALCOHOL CONTAINING A HYDROPHOBIC RADICAL, SAID ALCOHOL HAVING ABOUT 6 TO ABOUT 18 CARBON ATOMS, AND HAVING COORDINATED WITH SAID BASIC SALT AND SAID ACID ESTER A LOWER MOLECULAR WEIGHT ALCOHOL.