Title of the invention An improved dispersing agent composition for application in tanning and a process for the preparation thereof

Field of the Invention The present invention relates to an improved dispersing agent composition for application in tanning. More particularly, the present invention relates to a dispersing agent composition to facilitate tanning of hides/skins without adding external water. The invention also provides a process for the preparation of the said dispersing agent composition. The composition of the invention finds enormous application in leather processing industry as an important auxiliary for the purpose of tanning of hides and skins without adding external water to the tanning bath. Thus the composition provides an eco-benign solution for leather tanning without generating effluent.

Background and Prior art of the invention:

Leather making implicates use of large quantities of water, for conversion of raw hides and skins into finished leather. Typically in leather processing the preserved hides and skins are treated with water initially to rehydrate the skins. Subsequently they are treated with lime and sulfide or enzyme to facilitate removal of the hair and flesh adhering to the skins. The material at this stage is called limed pelt. These pelts are then processed in wooden drums using water as the medium of processing. The pelts are treated with acid salts to remove residual lime and short hairs present in an operation called deliming and bating. The operation employs about 2-3L of water per kilo of pelt. The medium is then discharged as effluent. Sometimes, degreasing for removal of excess fat is also carried out along with deliming and bating. Subsequently the pelts are treated with 1-2L of water per kilo of pelt along with salt and acid to condition to a pH of 2.5-2.8 from the pelt pH of about 8.0. This operation is called pickling. The used medium is again discharged as effluent rich in salinity. The pickled pelts are then treated with about 2-3L of water per kilo of material along with 8% chromium based tanning agent and mixture of alkalies in a process called chrome tanning. The material obtained at the end of chrome tanning is called "Wet blue leather". The pH of the leather will be in the range of 3.8-4.0 The pelts are sometimes treated with vegetable tannins instead of chromium. The leathers obtained through such process are called vegetable tanned leathers.

Essentially all these operations employ water as medium in drums to produce leathers of defined quality. Globally, this remains practice of leather making and for conversion of pelt to tanned leathers nearly 5-6L of water is employed which includes intermittent washing of leathers between the various operations.

While on one side need for water poses serious availability problem and since most of the water is discharged as effluent, treatment of the large quantity of effluent with all residual chemicals is another major environmental challenge. Nearly 30,000 Tonnes of hides and skins are processed per day globally leading to use of about 750-900 million liters of water on daily basis. The same quantity of water with high salinity, chromium residues and other unutilized chemicals need to be treated as effluent every day. Such practices have threatened the sustainability of leather making.

Efforts are being made to avoid use of water in leather processing. Our co-pending patent application (85/Del/2014) has provided a dispersing agent involving Basic Chromium Sulphate as one of the ingredients of the composition. The composition finds enormous application in water free pickle free tanning. However, the main limitation associated with this composition is that the presence of Basic Chromium Sulfate restricts its application to chrome tanning only, thereby, limiting the scope for its wider application in other areas, such as vegetable tanning.

This has prompted further research, whereby our another co-pending patent application 2104/del/2015 has provided a chrome free composition of a dispersing agent comprising polyalkalene polyhydric compound, carbonyl and/or hydroxyl compound and non-ionic surfactant. This dispersing agent composition finds application as an auxiliary in any type of tannage without addition of external water. However, the major limitation associated with this composition is that as a liquid product, it poses problem of uniformity and consistency in tanning when solid tanning agents are employed in large quantities.

Objective of the invention

The main objective of the present invention is to provide an improved dispersing agent composition for application in tanning, which obviates the limitations as stated above.

Another objective is to provide a dispersing agent composition to facilitate any tannage without addition of external water.

Yet another objective of the present invention is to provide a solution for the generation of effluent in leather tanning.

Summary of the invention

Accordingly, the present invention provides a dispersing agent composition for application in tanning, wherein the said composition comprises alkali metal salt of organic acid having 1-6 carbon atoms;

diatomaceous earth or its derivatives and

lyotropic agent optionally pre-treated with 50-100% w/w of reducing sugar,

wherein the ratio of (a):(b): (c) being in the range of 5:3:9 to 40: 1: 1 and 10% aqueous solution of the said composition exhibiting a pH in the range of 1.0 to 4.0.

In an embodiment of the present invention, the alkali metal salt is selected from the group consisting of sodium formate, sodium acetate and sodium citrate.

In another embodiment of the present invention, the acid used for pH adjustment is selected from the group consisting of sulfamic acid, citric acid, oxalic acid either individually or in any combination.

In yet another embodiment of the present invention, the lyotropic agent used is selected from either Calcium chloride or urea. In another embodiment of the present invention, the derivative of diatomaceous earth is silica. In another embodiment of the present invention, the reducing sugar used is selected from the group consisting of glucose, galactose and fructose

Further the present invention provides a process for preparation of the dispersing agent composition which comprises, optionally treating lyotropic agent with 50-100% w/w, of reducing sugar under stirring condition to obtain sugar pre-treated lyotropic agent, treating 2 to 9% w/w of lyotropic agent or sugar pre-treated lyotropic agent, as obtained in step (i), with alkali metal salt of organic acid, in presence of 1 to 3% w/w of diatomaceous earth or its derivative, added either simultaneously or in different succession, under continuous stirring, for a period of not less than 30 minutes and adjusting the pH of the dispersing agent composition in such a manner that the pH of 10% aqueous solution of the said composition is in the range of 1-4.

In an embodiment of the present invention, the alkali metal salt used in the process is selected from the group consisting of sodium formate, sodium acetate and sodium citrate. In another embodiment of the present invention, the lyotropic agent used in the process is selected from either calcium chloride or urea.

Further, the present invention provides a tanning process using the dispersing agent as claimed in Claim 1, which comprises treating delimed pelt with the dispersing agent and tanning agent in the ratio 1: 1 to 1:20 for a period of not less than 3 hours to obtain tanned leather.

Detailed description of the invention The process of the present invention is described below in detail.

Lyotropic agent is optionally treated with 50-100% w/w, of reducing sugar under stirring condition. 2 to 9% w/w of the resulting sugar pretreated lyotropic agent is added to the alkali metal salt of organic acid. The process involves an option of adding the said amount of lyotropic agent without subjecting the same to the pre-treatment of reducing sugar. 1 to 3% w/w of diatomaceous earth or its derivative is also added to the mixture. The additions take place either simultaneously or in different successions, under stirring conditions. After a period of not less than 30 minutes of treatment, the pH of the 10% aqueous solution of the resulting substrate is adjusted in the range of 1-4 to obtain the improved dispersing agent composition.

The improved dispersing agent composition of the invention exhibits the following composition

I

a) alkali metal salt of organic acid having carbon chain length in the range of one to three b) diatomaceous earth or its derivative c) lyotropic agent optionally pre-treated with 50-100% w/w,of reducing sugar, wherein(a):(b): (c) being in the range of 5 :3:9 to 40: 1: 1.

II pH of the 10% solution of the composition : 1 to 4

The improved dispersing agent is used for tanning in the following manner

Delimed pelt is treated with the improved dispersing agent and the tanning agent in the ratio of 1: 1 to 1:20 for a period not less than 3 hours to obtain tanned leather.

The inventive step of the present invention lies in the incorporation of lyotropic agent and diatomaceous earth to the alkali metal salt of organic acid to ensure effecting uniform spreading of tanning agent, thereby providing a solution to the lack of consistency in tanning, as encountered in the prior art. The following examples are given by way of illustration only and therefore should not be construed to limit the scope of the present invention. Example 1

150 gms of calcium chloride was mixed with 45 gms of silica for 15 minutes. The resulting product was added to 270 gms of sodium formate under stirring condition. After a period of 20 minutes, 270gms of citric acid was added to the above mixture with continuous stirring and the pH was adjusted to 2.8 to obtain the improved dispersing agent composition of the invention.

The dispersing agent was then analysed and the composition was found to be as follows : a) Sodium formate

b) Silica

c) Calcium chloride

wherein(a):(b): (c) being 6: 1:3.3

II pH of the 10% solution of the composition : 2.8

The improved dispersing agent composition was then used for chrome tanning in the following manner :

Ten Goat delimed pelts weighing lOkgweretreated with 300gms of above dispersing agent and 300 gms of Basic Chromium sulfate for a period of 3 hrs to obtain wet blue leather.

Example 2

2 kilos of calcium chloride was mixed with 4 kilos of silica for 30 minutes. The resulting product was added to 34 kilos of sodium formate under stirring condition. After a period of 30 minutes, 32 kilos of Sulfamic acid and8 kilos of citric acid was added to the above mixture with continuous stirring and the pH was adjusted to 2.5 to obtain the improved dispersing agent composition of the invention. The dispersing agent was then analysed and the composition was found to be as follows : I

a) Sodium formate

b) Silica

c) Calcium chloride

wherein(a):(b): (c) being 17:2: 1

II pH of the 10% solution of the composition : 2.5

Five cow limed pelts weighing 50kg was treated with 1250gms of dispersing agent and 3250 gms of Basic Chromium sulfate for 8 hrs to obtain wet blue leather, saving 200 L of water that would have been conventionally used.

Example 3 15 gms of urea was mixed 10 gms of glucose to obtain glucose treted urea which was mixed with 5 gms of silica for 20 minutes. The resulting product was added to 200 gms of sodium acetate under stirring condition. After a period of 20 minutes, 20 gms of Oxalic acid was added to the above mixture with continuous stirring and the pH was adjusted to 4.0 to obtain the improved dispersing agent composition of the invention.

The dispersing agent was then analysed and the composition was found to be as follows : I

a) Sodium acetate

b) Silica

c) Urea

wherein(a):(b): (c) being 40: 1:3

II pH of the 10% solution of the composition : 4.0 Ten sheep delimed pelts weighing 10kg was treated with 200gms of above dispersing agent and 1500 gms of wattle extract for 5 hrs to obtain vegetable tanned leather

Example 4 5 gms of urea was mixed with 2.5 gms of fructose for 15 minutes to obtain fructose treated urea which was then mixed with 5 gms of silica for 20 minutes. The resulting product was added to 50 gms of sodium citrate under stirring condition. After a period of 20 minutes, 30gms of citric acid was added to the above mixture with continuous stirring and the pH was adjusted to 1.0 to obtain the improved dispersing agent composition of the invention.

The dispersing agent was then analysed and the composition was found to be as follows : I

a) Sodium citrate

b) Silica

c) Urea

wherein(a):(b): (c) being 10: 1: 1

II pH of the 10% solution of the composition : 1.0 Ten Goat delimed pelts weighing 10kg was treated with 500gms of above dispersing agent and 600 gms of modified glutaraldehyde for 3 hrs to obtain aldehyde tanned leather.

The biological resource used in the invention are the delimed pelts obtained from the Supplier, Abdul kareem, Tanners, Traders of quality finished, Semi Finished Leathers and Hides & Skins, Chemicals and Tanning Materials, 57, Narayanan Street, Pudupet, Chennai - 600 002

Advantages of the present invention

The advantages of the present invention are the following:

^■ The dispersion agent composition is suitable for any type of tannage.

^■ The process for the preparation of the composition is very simple and cost effective.

^■ The application of the composition of the invention for leather tannage is suitable for all kinds of raw materials .

■ The application of the composition of the inventionfor leather tannageensures complete elimination of use of water and common salt for tanning, thereby avoiding generation of tanning effluents.

^■ The composition of the invention ensuresuniform and consistent results, when used for leather tannage.