The present invention relates lo a method for producing polymeric fal liquor for treating leather.
Background of the Invention
End use of leather determines the physical and aesthetic requirements of leather. For example, in one application, a piece of leather may be treated primarily to provide strength; its other aesthetic qualities being of much less importance for its intended application. In upper type of leather, both softness, light fastness and strength are required.
Many chemical and mechanical operations are involved in treating hides and skins to develop leather. One important chemical operation in the treatment of leather is fatliquoring. Fatliquoring is used to impart the desired strength and temper properties to tanned leather. Fat liquors lubricate the leather fibers so that after the leather is dried its fibers are capable of sliding over one another, !n addition to regulating the pliability of the leather, fatliquoring contributes greatly to the tensile and tearing strength of the leather.
The basic ingredients used in conventional fatliquoring operations are water insoluble oils and fatty substances such as raw oils and sulfated and sulfited oils.
Typically the weight percent of fatliquor oil on weight of leather ranges from 3 to 10 percent. The manner in which the oil is distributed throughout the leather affects the character of the leather and subsequent finishing operations. In order to obtain a uniform oil coating over a large surface of leather fibers it is typically necessary to dilute the oil with an organic solvent or preferably to disperse the oil in an aqueous system using emulsifiers.
The leathers processed with conventional fatliquors and syntan have been found to have a less Iightfastness.
The high performance/premium segment leathers demand higher Iightfastness characteristics without compromising softness and other properties obtained with conventional fatliquors and syntans.

The main objective of the present invention is to provide a polymer for fatliquoring and retanning which provides the treated leather with both the requisite strength and softness typically associated with the conventional fatliquors and also provides superior lightfastness. There will also be significant reduction in the usage of conventional syntans and fatliquors in processing upper type of leathers.
The polymeric fatliquor according to the present invention performs both as retanning and fatliquoring agent and provide the treated leather with a number of desirable properties including lightfastness, strength, body etc.
The objective of the present invention is to provide a process for preparing a novel polymeric fatliquor, which imparts better lightfastness characteristic to leather.
Detailed description of the invention
The object of the present invention is achieved by a method of producing a polymeric fatliquor, for treating leather comprising the step of preparing a copolymer by inversion emulsion wherein at least one copolymerisable hydrophilic monomer is dispersed in at least one surfmer such as an ester of itaconic acid. The copolymer is preferably an amphophilic copolymer.
Inverse emulsion is a method to produce a water-soluble polymer wherein a water-in-oil emulsion of the corresponding monomer/monomers of the polymer is prepared using an emulsifier and subjected to polymerization in the presence of an initiator such as pottassium persulphate to produce the desired homo/co-polymer in a water-in-oil emulsion.
The co-polymerisable hydrophilic monomer is dispersed in the sodium salt of the polymerisable surfactant and then polymerized. The reaction temperature is preferably raised upto 70 to 75 "C.
The polymeric fatliquor is substantially free from organic solvent, containing a dispersion of a selected amphophilic copolymer formed from a

predominant amount of at least one hydrophobic monomer and a minor amount of atlcast one co-polymerizable hydrophilic monomer. The treated leather has desirable strength and softness qualities and particularly better iightfastness characteristics.
The amphiphilic copolymers have been selected because of their ability to provide the leather with desirable strength and aesthetic softness characteristics and filling while reducing the total consumption of syntan and fatliquor in the recipe substantially.
II was found that dispersions of these amphiphilic copolymers, preferably in the form of aqueous emulsions, are substantive, or in other words they remain in the treated leather, and provide exceptionally good Iightfastness even under stringent conditions.
The selected amphiphilic copolymer has at least one hydrophobic monomer or surfmer. The term surfmer refers to polymerisable surfactant. Conventional surfactants are anchored on the polymer emulsion particle surface by physical forces alone and, hence their adsorption-desorption equilibrium has a crucial role in governing the stability and other characteristics of latexes prepared using them1. It is desirable therefore to have the surfactants covalently bound to the polymer latex for enhanced stability and performance. Therefore reactive surfactants, which become an integral part of the polymer during polymerization and would selectively reside on the surface of the latex providing it the requisite stability is used in the present invention.
The area of reactive surfactants has witnessed a surge of activity during the last decade, in part because of the combined efforts of many European laboratories2"4. Some very recent reviews provide a comprehensive summary of the current status of this field5'6. These polymerisable surfactants have extensive applications such as in synthetic rubbers, paints, adhesives, binders, additives in paper and textiles, impact modifiers, solid phase flocculants, rheologicai modifiers, solid phase supports in catalysis, diagnostic assays, cell separation, and drug delivery systems7"16. These classes of polymers have been used in leather treatment applications in the present invention.

In the present invention, itaconate esters are used as surfmers. Itaconic acid (1A) and its derivatives, both monoester {or hemiester) and diesters have been extensively studied with regard to their polymerization kinetics, role of bulky substituents, chain stiffness, glass-transition temperatures, etc17"23 Itaconic acid has also been used directly in surfactant-free emulsion polymerizations to generate stable latexes 24-25
Different esters of itaconates with carbon number varying from C-12 to C-18 were prepared, it was found that copolymers based on lauryl itaconate were found to give better performance as compared to other esters.
The hydrophilic comonomer used in the present invention is preferably acrylic acid.
The copolymer according to the present invention contains up to 90% of the polymerisable surfactant or surfmer. Preferably, the copolymer has up to 80% solid content and can be diluted to 30% solid content.
Co-polymer treated leather of present invention is found to have better lightfastness.
This invention is further explained in more detail referring to Examples, which is not by way of limitation but by way of illustration.
Example 1:
Procedure:
Preparation of Polymeric fatliquor involves two stages
1. Preparation of Surfmer
2. Preparation of Copolymer
Preparation of Surfmer-Lauryl Itaconate
In a three-neck flask with an agitator, one mole (186g) of lauryl alcohol is added and heated to 90°C. One mole (I30g) of itaconic acid is added slowly and agitation is maintained throughout the reaction, p -Toluene sulphonic acid (PTSA) 1% (weight percent) of the total charge is added as an esterification catalyst. The temperature is raised to 120°C and the reaction is run for two

hours. The completion of reaction is checked by acid value. The surfmer is neutralized at 60°C with ] mole of 50% sodium hydroxide solution.
Preparation of copolymer based on laurvl itaconate and acrylic acid.
One mole of sodium salt of lauryl itaconate 354g, is added to a three neck flask with agitator. The temperature is raised to 70°C and allowed to run for 30 min. The flask is cooled to room temperature and 1.2 moles (87g) of acrylic acid is added to the flask and allowed to run under high speed stirring for 30 min. Acrylic acid gets well dispersed in the surfmer. The temperature is raised to 70°C and 5.5g of potassium persulphate in 40g of water is added to the flask and then allowed to run for 4 hrs. The final copolymer is checked for its total solid content.
The unreacted surfmer is determined by extraction with acetone. The copolymer after acetone extraction is soluble in chloroform and can be characterized by 'H NMR spectroscopy. More than 90% incorporation of surfmer in the copolymer was noted. This inverse emulsion process also helps in processing a copolymer with very high solid content. The final copolymer is diluted to 30% solids and used as a polymeric fatliquor and retanning agent in leather applications.
Example 2:
The evaluation of the selected polymeric fatliquors according to the present invention with less amount of syntans and other conventional fatliquors was compared to standard recipe of known percentages of conventional syntans and fatliquors to make upper type of leather. Procedure: Comparison No. 1
Trial-1
Leather: Wet blue Goat

+BaIsynBB17 3.0
(Melamine replacement syntan)
+Balsyn DR 5.0
(Replacement syntan)
GS Powder 3.0
(Vegetable syntan)
+BaImol RNF 0.75 20'
Balmol SXE 1.0
(Synthetic fatliquor)
+Balsyn DNP 2.0 30'
(Amphoteric replacement syntan)
+Black Dye 2.0 60'
(Anionic dye)
+BalfillPL 3.0 30'
(Organic filler)
+BalmolRNF 1.75 45'
Balmol SXE 2.0
(Synthetic Fatliquor)
+Formicacid 2.0 3*10+30' Drain the exhaust bath
Wash and Pile the leather
COMPARISON NO 2
Tria)-1
Leather: Wet blue Goat
Wet Blue was cut into two pieces along the backbone and named as left hand side and right hand side. % Based on Shaved weight
Left hand side (LHS)
(Processed according to the present invention)
Process % Used Duration Remarks
+Wash 10'
Drain the bath

Process % Used Durationdn Minutes) Remarks
+Wash 10'
Drain the bath
+Water 100 30"
Formic acid 0.5 Check pH of the leather
3.0/3.2, Drain the bath
+Water 100 40'
Basic Chrome Sulphate 4.0
Balsyn CR 4.0
(Chrome syntan)
+Balmol SAR 2.0 30'
(Soft Acrylic Syntan)
+Sodium formate 1.0 30'
Sodium Bicarbonate 0.8 2*10'+30' pH of the leather
should be 3.8/4.0 Drain the bath ,Wash the leather and Drain the bath
+Water 200 45'
Balsyn NS 1.5 pH of the leather should
(Neutralizing syntan) be 5.0/5.2, Drain the
bath and Wash the
+Water 200 30'
Balsyn MAR 2.0
(Acrylic syntan)
+Balsyn RBI 7 3.0 60'
(Melamine replacement syntan)
Balsyn DR 5.0
(Replacement syntan)
GS Powder 3.0
(Vegetable syntan)
+Ba]mo)RNF 0.75 20'
BalmolSXE 1.0
(Synthetic fatliquor)
+Balsyn DNP 2.0 30'
(Amphoteric syntan)
+Black Dye 2.0 60'
(Anionic dye)
+Balfill PL 3.0 30'
(Organic Filler)
+Balmol RNF 1,25 40'

Balmol SXF 2.0
(Fatliquors)
+Formic acid 2.0 3*10+30' Drain the exhaust bath,
Wash and Pile the
Result:
As can be noted from the Table 1, the leather treated by the polymeric fatliquor according to the present invention is superior to the leather treated by the conventional methods in respect of the physical properties as shown.

References
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WE CLAIM:
1. A method of producing a polymeric fatliquor, for treating leather comprising the step of preparing a copolymer by inversion emulsion wherein at least one copolymerisable hydrophilic monomer is dispersed in at least one surfmer such as an ester of itaconic acid.
2. The method as claimed in claim 1, wherein the co-polymerisable hydrophilic monomer is dispersed in the sodium salt of the surfmer and then polymerized.
3. The method as claimed in claim I, wherein the surfmer is lauryl itaconate.
4. The method as claimed in claim 1, wherein the hydrophilic monomer is acrylic acid.
5. The method as claimed in claim 1, wherein the reaction temperature is preferably raised upto 70 to 75°C.
6. The method as claimed in claim 1, wherein the copolymer contains up to 90% of the surfmer.
7. The method as claimed in claim 6, wherein the copolymer has up to 80% solid content.
8. The method as claimed in claim 1, wherein the fatliquor is substantially free from organic solvent.

Q A polymeric fat-liquor, which comprises a copolymer containing a) a
suiTmer and b) a hydrophilic monomer as produced by the method as claimed in any of claims I to 8.
10. A method for treating leather which imparts light fastness characteristic
to leather, comprising the step of fatliquoring leather which has been
tanned and not previously subjected to a fatliquor, with a polymeric
fat liquor obtained by the method as claimed in any one of claims 1 to 9.
11. The method as claimed in claim 10, wherein the copolymer when used as fatliquoring retanning agent imparl considerable amount of softness and filling and the product shows reduction in consumption of syntan and other fatliquors used in leather processing.
12. Leather produced by the method as claimed in claims 10 tol 1.