Abstract:
A process for leather tanning having the improvement of imparting waterproof properties to the leather by incorporating a sulfosuccinic monoester in the fatliquor.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to waterproofing leather by incorporating particular fatliquoring agents which import hydrophobic properties. The particular agents include sulfosuccinic acid monoester salts. 
     2. Statement of Related Art 
     Waterproof leather is produced by three basic methods, namely: 
     (1) impregnation by incorporation of water-insoluble substances, for example solid fats, waxes or particular polymers; 
     (2) impregnation by incorporation of water-swelling substances which, on taking up water, form highly viscous emulsions and block the fiber interstices of the leather, for example special emulsifiers of the water-in-oil (W/O) type; and 
     (3) treatment with hydrophobicizing substances, for example aluminium and chromium complexes, silicones or organic fluorine compounds. 
     These methods may be applied in the course of conventional fatliquoring using conventional fatliquoring agents, the impregnating and treatment agents mentioned being introduced into the fatliquoring bath. 
     A combination of methods (2) and (3) is often applied in practice, the drum or tumbler preferably being filled with aqueous liquor for economic and ecological reasons. The W/O emulsifiers are converted into hydrophobicizing metal salt complexes by fixing with chromium or aluminium salts. However, there are disadvantages to this process because, due to the instability of the fatliquoring emulsions normally used, impregnation has to be carried out at relatively high pH vaues (&gt;6) in order to avoid precipitation of the fatliquoring agents on the surface with resultant smearing. In addition, the fatliquoring bath generally has to have a high temperature of around 60° C. in this process which loosens the grain of the leather. Furthermore, penetrometer values obtained in practice frequently show considerable variations due to an uneven distribution of fat through the leather, so that the leather may have to be expensively aftertreated by spraying, casting or plush coating. 
     The fatliquoring bath is not stabilized with anionic and nonionic emulsifiers, such as alkylsulfates, alkylarylsulfonates or fatty alcohol ethoxylates, because of the increase in permeability to water vapor. 
     As used throughout this specification, the term &#34;leather&#34; is meant to include skins, hides, and similar materials of animal origin to which hydrophobic properties are to be imparted. 
     Other than in the operating examples, or where otherwise indicated, all numbers expressing quantities of ingredients, reaction conditions, or defining ingredient parameters used herein are to be understood as modified in all instances by the term &#34;about&#34;. 
     Published German patent application No. 16 69 347 describes the use of sulfosuccinic acid esters emulsifiable in water for the fatliquoring of leather. In this case, however, no waterproofing effect is obtained. 
     Published German patent application No. 34 19 405 relates to a process for the production of leather in which a combination of sulfosuccinic acid esters with certain anionic or nonionic emulsifiers is used as fatliquoring agent in the tranning liquor during chrome or aluminum tanning or retanning. Once again, no waterproofing effect is obtained. 
     DESCRIPTION OF THE INVENTION 
     It has now been found that leathers fatliquored with a composition containing known fatliquoring agents as well as at least one C 12-24 , preferably C 16-24 , or alternatively C 16-22  or C 16-18 , aliphatic sulfosuccinic acid monoester or its salt combines extreme softness with reduced permeability to water provided that, after acidification, the fatliquoring agent is fixed with chromium and/or aluminum salts. 
     In this way, it is possible, using sulfosuccinic acid monoesters in the impregnating and/or hydrophobicizing fatliquoring treatment, to improve the stability of the fatliquoring emulsions to such an extend that the previously described disadvantages of conventional processes do not arise. 
     Accordingly, the present invention relates to a process for the production of waterproof leathers using sulfosuccinic acid monoesters in combination with impregnating and/or hydrophobicizing fatliquoring compositions. In particular, after retanning, the leathers are treated in an aqueous bath with at least one impregnating and/or hydrophobicizing fatliquoring composition containing at least one sulfosuccinic acid monoester salt having a C 12-24  fatty residue and, after acidification, the fatliquoring composition is fixed by addition of a chromium and/or aluminum salt. 
     The at least one sulfosuccinic acid monoester salt is preferably used in combination with impregnating fatliquoring agents, including in particular: oxidized or oxidized and partly sulfonated C 18-26  hydrocarbons or C 32-40  waxes; phosphoric acid mono-C 12-24  -alkyl esters; partial esters of polycarboxylic acids, such as citric acid mono-C 16-24  -alkyl esters; partial esters of polyalcohols, such as sorbitan-, glycerin- or pentaerythritol-C 16-24  -fatty acid esters; or any mixture thereof. 
     The at least one sulfosuccinic acid monoester salt makes up from 10 to 60%, preferably from 20 to 40%, by weight of the fatliquoring composition. Depending on the type of leather, the fatliquoring composition itself is used in a quantity of from 5 to 20% by weight, based on the pared weight of the leather. 
     The sulfosuccinic acid monoesters also may be used in combination with known fatliquoring ingredients including neutral oils, such as long chain hydrocarbons, chloroparaffin, animal and vegetable oils and fats or methylesters thereof and chlorinated fatty acid methylesters, in which instance the permeability of the leather to water is also reduced if, after fatliquoring, the fatliquoring solution is acidified and fixed with chromium and/aor aluminum salts. 
     The above monoesters may also be used for normal fatliquoring in conjunction with sulfated, sulfited and/or synthetic fatliquoring agents based on chloroparaffin sulfonates, more or less pronounced impermeability to water being obtained according to the percentage of impregnating and/or hydrophobicizing fatliquoring agent in the combination. 
     The sulfosuccinic acid monoester salts are produced in known manner by esterification of maleic acid anhydride with approximately one equivalent of the desired esterification component, followed by reaction with a sulfite or bisulfite in a quantity substantially equivalent to the maleic acid anhydride, such as in accordance with previously discussed published German patent application No. 16 69 347. Suitable esterification components are C 12-24  aliphatios (fatty residues) and compounds containing hydroxyl groups. The aliphatics may be saturated or unsaturated and may be derived from: fatty alcohols or fatty acid mono- or diglycerides, for example C 12-18  coconut oil fatty alcohol, C 12-18  tallow alcohol, C 16-18  tallow fatty acid monoglyceride; or from adducts of from 1 to 6 mols of alkylene oxide with the abovementioned fatty alcohols or fatty acid glycerides or with fatty acids, for example the adduct of from 2 to 3 mols of ethylene oxide with a C 16-18  tallow fatty alcohol or the adduct of from 4 to 6 mols of ethylene oxide with a C 16-24  fatty acid mixture of the adduct of  2 mols of ethylene oxide with a C 12-18  fatty acid mixture. The sulfosuccinic acid monoester salts are preferably prepared as sodium or ammonium salts, although other alkalis such as potassium or organic amines may be used as cations. 
     The sulfosuccinic acid monoester salts are fixed by water soluble chromium and/or aluminum salts. It is preferred to use basic chromium or aluminum salts or mixtures thereof, of the type also used for tanning leather. The water-soluble chromium and/or aluminum salts are used in the fatliquoring bath in a quantity effective to fix the monoesters, preferably from 1 to 10% by weight. 
     The claimed process is carried out by applying the sulfosuccinic acid monoester salts and, optionally, other fatliquoring agents as the fatliquor after retanning and, optionally, dyeing and after the subsequent removal of excess tanning agent by washing. High temperatures above 50° C. could be avoided. The aftertreatment is initially carried in the usual way by acidification, using any leather compatible acid in an acidifying effective amount, such as sulfuric, preferably formic acid, optionally preceded by a brief treatment with a polyacrylate tanning agent. This is followed by fixing with the chromium and/or aluminium salts at around pH 3.5. 
     The inventive fatliquoring agents are effectively taken up by the leather and are uniformly distributed throughout its entire cross-section. They show remarkable resistance to water and provide the leather with outstanding impermeability to water, particularly under dynamic stressing. 
     The leathers obtained are soft and first grained with a pleasant lardy feel and are particularly suitable for the production of shoe upper leather, garment quality suede and heavy suede. 
    
    
     EXAMPLE 1 
     Hide upper: 
     Wet-blue hides chrome tanned in the usual way, but without any addition of anionic surfactants (pH 3.8, pared thickness 1.8 mm), are further processed as follows: 
     
         ______________________________________Procedure Amount (%) Ingredient    Time (min.)______________________________________Washing   200        water 40° C.                              20                drain off liquorNeutralization:     200        water 45° C.                              30     and 1.5    neutral auxiliary                tanning agent                based on a phenol/                napthalene con-                densate, pH leather                cross-section 4.8Dyeing:   1          acid dye      20Retanning:     3          synthetic tanning                              30                agent based on a                phenol condensate     and 3      vegetable tanning                agent     0.5        formic acid   30                pH˜3.8                drain off liquorWashing:  300        water 45° C.                              15                drain off liquorFatliquoring:     200        water 50° C.                              45(INVENTIVE     and        AS C.sub.16-18 sulfo-AGENTS)   (A) 6      succinic acid                monoester, Na salt     (B) 4      AS C.sub.16-18 sulfo-                              45                succinic acid                monoester, Na salt     and 2      C.sub.16-18 fatty acid                methyl ester,                chlorinated     (C) 2.5    AS sulfosuccinic                              45                acid monoester                (alcohol component:                C.sub.16-22 fatty acid-                1 P.O.-adduct),                NH.sub.4 salt     and 2.5    AS phosphoric acid                mono-C.sub.12-18 -alkyl-                ester, NH.sub.4 salt     and 1.5    AS C.sub.16-18 fatty                acid triglyceride     3          polyacrylate  30                tanning agentAcidification:     0.3        formic acid   30Fixing:   2          chrome tanning                              30                agent, 33% basic     2          aluminium tanning                              30                agent, 25% basic                pH about 3.5, then                drain off liquor______________________________________ 
    
     After adequate washing, the leather was blocked and finished as usual. Soft, firm-grained leathers having a pleasant feel were obtained. Penetrometer testing produced the following results (compression 10%): 
     
         ______________________________________         A      B         C______________________________________Water penetration after           25 mins. 90 mins.  &gt;480 mins.Water uptake after 1 hour           ca. 70%  ca. 34%   --Water uptake after 6 hours           --       --        &lt;20%______________________________________ 
    
     EXAMPLE 2 
     Hide upper, waterproof: 
     Starting material: wet-blue hides chrome-tanned in the usual way, but without surfactants; pared thickness 2.2 mm. 
     
         ______________________________________Procedure Amount (%) Ingredient    Time (min.)______________________________________Washing   300        water 45° C.                              15                drain off liquorNeutralization:     200        water 40° C.                              60     and 2      neutral auxiliary                tanning agent                based on a phenol/                napthalene con-                densateRetanning:     21         vegetable tanning                              12 (hours)                agent     2          aluminium tanning                              30                agent, 25% basic     then       drain off liquor                wash                pH 4.2 in the                leatherDyeing:   200        water 55° C.                              20     and 1      anionic dyeFatliquoring:     4          AS sulfoxidized                              45(INVENTIVE           slack paraffinAGENTS)              wax     and 2      AS phosphoric acid                mono-C.sub.16-18 alkyl                ester     and 1      AS sulfosuccinic                              45                acid mono-C.sub.16-24 -                alkyl ester,                Na salt     3          polyacrylate  30                tanning agentAcidification:     1          formic acid   30                drain off liquorFixing:   200        water 40° C.                              30     and 2      chrome tanning                agent 33% basic     2          aluminium tanning                              30                agent, 25% basic                pH about 3.5, then                drain off liquor,                wash______________________________________ 
    
     Leather to block and finish as usual. 
     Soft, firm-grain leathers thoroughly fatliquored throughout were obtained. Penetrometer testing produced the following results (compression 7.5%): 
     Water penetration after &gt;480 minutes 
     Water uptake after 6 hours &lt;20% 
     EXAMPLE 3 
     Soft hide upper, fashion-quality: 
     Starting material: wet-blue hides chrome tanned in the usual way, but without surfactants, pared thickness 2.0 mm. 
     
         ______________________________________Procedure Amount (%) Ingredient    Time (min.)______________________________________Washing   300        water 40° C.                              15                drain off liquorNeutralization:     150        water 40° C.                              20     and 1      Na formate     1.5        auxiliary     20                tanning agent                based on a phenol/                napthalene con-                densateDyeing:   1          anionic dye   15Retanning:     3          phenol condensate                              30     and 3      mimosa     0.5        formic acid   30                drain off liquor,                washFatliquoring:     100        water at 50° C.                              45(INVENTIVE       and 1.5  AS sulfatedAGENTS)              neat&#39;s foot oil       and 0.5  AS glycerin mono-                C.sub.16-18 alkylester     and 2      AS sulfosuccinic                acid mono-C.sub.16-18 -                alkylester, NH.sub.4 salt     and 2      AS phosphoric                acid mono-C.sub.16-18 -                alkyl-ester     3          polyacrylate  30                tanning agentAcidification:     0.5        formic acid pH                              30                about 3.7, then                drain off liquorFixing:   200        water 40° C.     and 2      chrome tanning                              30                agent, 33% basic     2          aluminium tanning                              30                agent, 25% basic,                drain off liquor,                then wash______________________________________ 
    
     Soft, firm-grained leathers having a pleasant feel were obtained after finishing in the usual way. Penetrometer testing produced the following results (compression 15%): 
     Water penetration after ca. 90 minutes 
     Water uptake after 1 hour ca. 35% 
     EXAMPLE 4 
     Suede, garment-quality 
     Starting material: sheepskins tanned in the usual way, pared thickness 0.7 mm. 
     
         ______________________________________Procedure Amount (%) Ingredient    Time (min.)______________________________________Washing:  300        water 40° C.                              20                drain off liquorNeutralization:     200        water 45° C.                              20     and 1      auxiliary tanning                agent based on a                phenolnapthalene                condensate pH                about 4.5 leather                cross-sectionRetanning:     3          resin tanning agent                              40Fatliquoring:     5          AS sulfated neat&#39;s                              40(INVENTIVE           foot oilAGENTS)   and 2      neat&#39;s foot oil     and 3      AS mixture of:                sulfosuccinic acid                mono C.sub.16-18 -alkyl                ester, Na salt,                and phos-                phoric acid mono-                C.sub.12-18 -alkylester,                NH.sub.4 salt                ratio of 3:2     0.8        formic acid   30                drain off liquor,                cold rinse,                leather to block,                slick, hang-dry,                stake, buff.Dyeing    (% based on dry weight)                          45     1000       water 45° C.     and 5      ammonia solution,                25%     and 5      anionic dye                pH˜8     5          formic acid   30                pH˜4     2          cationic resin                              20                tanning agent     2          anionic dye   30Acidification:     2          formic acid   30                pH˜3.8Fatliquoring:     10         AS mixture of 40(INVENTIVE           sulfosuccinic acidAGENTS)              mono-C.sub.16-18 -alkyl-                ester, Na salt                phosphoric acid                mono-C.sub.12-18 -alkyl-                ester, NH.sub.4 salt,                ratio of 3:2Fixing:   3          aluminium tanning                              30                agent, 25% basic                pH about 3.5, then                drain off liquor                rinse at 25° C., and                finish.______________________________________ 
    
     The leathers were soft and smooth with a good dye finish and showed a pronounced water-repellent effect. 
     EXAMPLE 5 
     Heavy suede 
     Starting material: air-dried sheepskins 
     The sheepskins were processed to the color of hair in the usual way by soaking, washing, pickling/tanning, retanning and fatliquoring. Impregnation was then carried out as follows in the suede dye: 
     
         ______________________________________Procedure    Amount g/l Ingredient    Time (min.)______________________________________Suede dyeing:       liquor ratio 1:20                             90               water 40° C.    and 2      NH.sub.3    and 1      dye    and 1      auxiliary tanning               agent    and 2      chloroparaffin               sulfonate    and 1      dyeing auxiliaryFatliquoring:    11         a mixture of: 45(INVENTIVE          sulfosuccinic acidAGENTS)             mono-C.sub.16-18 -fatty               acid-1 P.O.-ester,               NH.sub.4 /Na salt; phos-               phoric acid mono-               C.sub.12-18 -alkyl ester,               NH.sub.4 salt; and               neat&#39;s foot oil;               weight ratio. 2:2:1Acidification:    1.5        formic acid   30               added in 4 portions               drain off liquor,               rinseFixing:             water 30° C.                             10    0.5        formic acid    5          aluminium tanning                             60               agent,               25% basic______________________________________ 
    
     To block without rinsing, hang-dry. 
     Soft, fleecy suedes having a pronounced water repellent effect are obtained.