Indian Patents. 251885:AN IMPROVED PROCESS FOR THE PREPARATION OF A TANNING AGENT

Title of Invention	AN IMPROVED PROCESS FOR THE PREPARATION OF A TANNING AGENT
Abstract	An improved process for the preparation of a tanning agent by dissolving gallic acid in 400-450% alkali (w/v) and adjusting the pH to7-8 by known method to get gallic acid solution, treating the gallic acid solution, with 10-20 % w/v of an organic crosslinker, preferably under agitation, for a period of not less than 60 minutes, to obtain a homogeneous solution of tanning agent.

Full Text	The present invention relates to an improved process for the preparation of a tanning agent. Field of the Invention More particularly the invention relates to a process for the preparation of a tanning agent from gallic acid. It has enormous potential application in leather processing industry for eco-benign tanning of leather. Background of the Invention The two major tanning systems adopted by the global leather industry are by using chromium salts and vegetable tanning materials. The tanned leathers are generally characterised by their ability to withstand thermo mechanical stress normally mentioned as shrinkage temperature. It is the temperature at which the leather fibres shrink in the length. The advantages of chrome tanning are ability to provide high strength characteristics, light weight, improved dyeing and fastness property apart from high hydro thermal stability in the range of 110-120°C to the leathers. But serious environmental concerns have emerged on waste streams emanating from industrial utilisation of chromium. Vegetable tanning methods are considered to be safe alternative. The tannins are extracted from natural materials such as root, leaves, bark, nuts etc.of certain tannin bearing trees and plants. The tannins obtained from different parts of the plants have different composition; structure and properties and leathers obtained from them also possess different properties. Though vegetable tanning imparts resistance to microbial attack and dimensional stability to the skins, the vegetable tanned leathers exhibit lower strength and fastness characteristics compared to chromium-tanned leathers. Extensive studies have been made on development of tanning materials combining the advantages of both the tanning materials viz., chromium and vegetable overcoming their inherent drawbacks. As reported by Dutta (Principles of leather manufacture, Indian Leather Technologists Association Publication 381 to 393, 1999 Edition) synthetic tannins which behave similar to vegetable tannin is prepared by condensing phenol or cresol sulphonic acid with formaldehyde. The limitation associated is that they are not capable of replacing the principal tanning materials in providing the necessary organoleptic properties like fullness, softness etc.. These synthetic tannins are characterised by treating the material with collageneous powder and after ascertaining the amount of material taken up by the collagen powder. This is normally termed as active matter As reported by Rajadurai and Kulasekaran (Acrylics and their uses in Leather Manufacture, CLRI Publication, 23, 1982) acrylic syntans can be used for tanning the leather. Acrylic syntans are prepared by using the monomers like methacrylic acid, acrylic acid etc. But the limitation of the syntan is that it will not give the shrinkage temperature of more than 70° C and the monomer is carcinogenic. Use of various combinations of metal tanning agents and synthetic tanning agents have been resorted to in the past but most of the materials, due to their inherent shortcomings, exhibited drawbacks which limited their wider adoption. The above limitations have prompted to look for a better option for the preparation of tanning material that is organic in nature and yet provide leathers like chromium tanned leathers. No prior art is available on preparation of organic tanning material from gallic acid. Objects of the Invention The main objective of the present invention is to provide an improved process for the preparation of a tanning agent, which obviates the limitations as stated above. Another objective of the present invention is to provide a process for the preparation of a tanning agent using gallic acid, which by itself is not a tanning agent. Summary of the Invention Accordingly the present invention provides an improved process for the preparation of a tanning agent, which comprises i) dissolving gallic acid in 400-450% alkali (w/v) and adjusting the pH to 7-8 by known method to get gallic acid solution, ii) treating the gallic acid solution, as formed in step (i), with 10-20 % w/v, of an organic crosslinker, for a period of not less than 60 minutes, to obtain a homogeneous solution of tanning agent. In an embodiment of the present invention, the alkali used may be selected from sodium hydroxide, soda ash. In another embodiment of the present invention, the organic cross linker may be selected from oxazolidine, formaldehyde, glutaraldehyde. In yet another embodiment of the present invention, the treatment of gallic acid solution with organic crosslinker may be carried out preferably under agitation. Detailed description The process of the present invention is described below Gallic acid is dissolved in 400-450% w/v, of alkali and the pH of the resulting solution is adjusted to a range of 7-8 by known method to get gallic acid solution. This solution is treated with 10-20% w/v, of an organic crosslinker, preferably under agitation, for a period of not less than 60 minutes, to obtain a homogeneous solution of tanning agent. The inventive step of the present invention lies in the selection as well as treatment of organic cross linker with gallic acid to convert gallic acid, which is a non-tanning agent, into a tanning agent. The following examples are given by way of illustration and therefore should not be construed to limit the scope of the present invention. Example 1 Gallic acid weighing 50 gm was taken and dissolved in 200 gms sodium hydroxide (10% solution) for a period of 30 minutes. Then the pH of the dissolved solution has adjusted to 7 using the same alkali. Then the resulting solution was treated with 5gm oxazolidine in a shaker for a period of 60 minutes. The resulting solution of tanning agent was stored in a plastic container. 100gm of delimed pelt was treated with 30 gm of the tanning agent in a shaker for a period of 3 hours. The resulting leather exhibited shrinkage temperature of 90 °C. Example 2 Gallic acid weighing 30 gm was taken and dissolved in 135 gms sodium hydroxide (10% solution) for a period of 30 minutes. Then the pH of the dissolved solution has adjusted to 8 using the same alkali. Then the resulting solution was treated with 6gm formaldehyde in a shaker for a period of 70 minutes. The resulting solution of tanning agent was stored in a plastic container. 100gm of delimed pelt was treated with 30 gm of the tanning agent in a shaker for a period of 3 hours. The resulting leather exhibited shrinkage temperature of 88 °C. Example 3 Gallic acid weighing 40 gm was taken and dissolved in 160gms sodium hydroxide (10% solution) for a period of 30 minutes. Then the pH of the dissolved solution was adjusted to 7 using the same alkali. Then the resulting solution was treated with 6 gm glutaraldehyde in a shaker for a period of 80 minutes. The resulting solution of tanning agent was stored in a plastic container. 100gm of delimed pelt was treated with 30 gm of the tanning agent in a shaker for a period of 3 hours. The resulting leather exhibited shrinkage temperature of 90 °C. Advantages The main advantages of the present invention are the following. 1 The process of the present invention is very simple and involves no difficult parameter. 2.The process is very economical. 3.The novel-tanning agent prepared from gallic acid gives imparts softness and grain tightness to the leathers. 4. The novel-tanning agent prepared gives the shrinkage temperature of not less than 85 °C in the resulting leather. We claim: 1. An improved process for the preparation of a tanning agent, which comprises i) dissolving gallic acid in 400-450% alkali (w/v) and adjusting the pH to 7-8 by known method to get gallic acid solution, ii) treating the gallic acid solution, as formed in step (i), with 10-20 % w/v, of an organic crosslinker, preferably under agitation, for a period of not less than 60 minutes, to obtain a homogeneous solution of tanning agent. 2. An improved process, as claimed in Claim 1, wherein the alkali used is selected from sodium hydroxide, soda ash. 3. An improved process, as claimed in Claims land 2, wherein the organic cross linker is selected from oxazolidine, formaldehyde, glutaraldehyde 4. An improved process, as claimed in Claims 1 to 3, wherein the treatment of gallic acid solution with organic crosslinker is carried out preferably under agitation. 4.. An improved process for the preparation of a tanning agent, substantially as herein described with reference to the examples.

Full Text

The present invention relates to an improved process for the preparation of a
tanning agent.
Field of the Invention
More particularly the invention relates to a process for the preparation of a
tanning agent from gallic acid. It has enormous potential application in leather
processing industry for eco-benign tanning of leather.
Background of the Invention
The two major tanning systems adopted by the global leather industry are by
using chromium salts and vegetable tanning materials. The tanned leathers are
generally characterised by their ability to withstand thermo mechanical stress
normally mentioned as shrinkage temperature. It is the temperature at which the
leather fibres shrink in the length. The advantages of chrome tanning are ability
to provide high strength characteristics, light weight, improved dyeing and
fastness property apart from high hydro thermal stability in the range of
110-120°C to the leathers. But serious environmental concerns have emerged on
waste streams emanating from industrial utilisation of chromium.
Vegetable tanning methods are considered to be safe alternative. The tannins are extracted from natural materials such as root, leaves, bark, nuts etc.of certain tannin bearing trees and plants. The tannins obtained from different parts of the plants have different composition; structure and properties and leathers obtained from them also possess different properties. Though vegetable tanning imparts resistance to microbial attack and dimensional stability to the skins, the vegetable
tanned leathers exhibit lower strength and fastness characteristics compared to chromium-tanned leathers. Extensive studies have been made on development of tanning materials combining the advantages of both the tanning materials viz., chromium and vegetable overcoming their inherent drawbacks.
As reported by Dutta (Principles of leather manufacture, Indian Leather Technologists Association Publication 381 to 393, 1999 Edition) synthetic tannins which behave similar to vegetable tannin is prepared by condensing phenol or cresol sulphonic acid with formaldehyde. The limitation associated is that they are not capable of replacing the principal tanning materials in providing the necessary organoleptic properties like fullness, softness etc..
These synthetic tannins are characterised by treating the material with collageneous powder and after ascertaining the amount of material taken up by the collagen powder. This is normally termed as active matter
As reported by Rajadurai and Kulasekaran (Acrylics and their uses in Leather Manufacture, CLRI Publication, 23, 1982) acrylic syntans can be used for tanning the leather. Acrylic syntans are prepared by using the monomers like methacrylic acid, acrylic acid etc. But the limitation of the syntan is that it will not give the shrinkage temperature of more than 70° C and the monomer is carcinogenic.
Use of various combinations of metal tanning agents and synthetic tanning agents have been resorted to in the past but most of the materials, due to their inherent shortcomings, exhibited drawbacks which limited their wider adoption. The above limitations have prompted to look for a better option for the preparation of tanning material that is organic in nature and yet provide leathers like chromium tanned leathers.
No prior art is available on preparation of organic tanning material from gallic
acid.
Objects of the Invention
The main objective of the present invention is to provide an improved process for the preparation of a tanning agent, which obviates the limitations as stated above.
Another objective of the present invention is to provide a process for the
preparation of a tanning agent using gallic acid, which by itself is not a tanning
agent.
Summary of the Invention
Accordingly the present invention provides an improved process for the
preparation of a tanning agent, which comprises
i) dissolving gallic acid in 400-450% alkali (w/v) and adjusting the pH to 7-8 by known method to get gallic acid solution,
ii) treating the gallic acid solution, as formed in step (i), with 10-20 % w/v, of an organic crosslinker, for a period of not less than 60 minutes, to obtain a homogeneous solution of tanning agent.
In an embodiment of the present invention, the alkali used may be selected
from sodium hydroxide, soda ash.
In another embodiment of the present invention, the organic cross linker may be
selected from oxazolidine, formaldehyde, glutaraldehyde.
In yet another embodiment of the present invention, the treatment of gallic acid
solution with organic crosslinker may be carried out preferably under agitation.
Detailed description
The process of the present invention is described below
Gallic acid is dissolved in 400-450% w/v, of alkali and the pH of the resulting solution is adjusted to a range of 7-8 by known method to get gallic acid solution. This solution is treated with 10-20% w/v, of an organic crosslinker, preferably under agitation, for a period of not less than 60 minutes, to obtain a homogeneous solution of tanning agent.
The inventive step of the present invention lies in the selection as well as treatment of organic cross linker with gallic acid to convert gallic acid, which is a non-tanning agent, into a tanning agent.
The following examples are given by way of illustration and therefore should not be construed to limit the scope of the present invention.
Example 1 Gallic acid weighing 50 gm was taken and dissolved in 200 gms sodium hydroxide (10% solution) for a period of 30 minutes. Then the pH of the dissolved solution has adjusted to 7 using the same alkali. Then the resulting solution was treated with 5gm oxazolidine in a shaker for a period of 60 minutes. The resulting solution of tanning agent was stored in a plastic container. 100gm of delimed pelt was treated with 30 gm of the tanning agent in a shaker for a period of 3 hours. The resulting leather exhibited shrinkage temperature of 90 °C.
Example 2 Gallic acid weighing 30 gm was taken and dissolved in 135 gms sodium hydroxide (10% solution) for a period of 30 minutes. Then the pH of the dissolved solution has adjusted to 8 using the same alkali. Then the resulting solution was treated with 6gm formaldehyde in a shaker for a period of 70 minutes. The resulting solution of tanning agent was stored in a plastic container. 100gm of delimed pelt was treated with 30 gm of the tanning agent in a shaker for a period of 3 hours. The resulting leather exhibited shrinkage temperature of 88 °C.
Example 3 Gallic acid weighing 40 gm was taken and dissolved in 160gms sodium hydroxide (10% solution) for a period of 30 minutes. Then the pH of the dissolved solution was adjusted to 7 using the same alkali. Then the resulting solution was
treated with 6 gm glutaraldehyde in a shaker for a period of 80 minutes. The resulting solution of tanning agent was stored in a plastic container.
100gm of delimed pelt was treated with 30 gm of the tanning agent in a shaker
for a period of 3 hours. The resulting leather exhibited shrinkage temperature of
90 °C.
Advantages
The main advantages of the present invention are the following.
1 The process of the present invention is very simple and involves no difficult
parameter.
2.The process is very economical.
3.The novel-tanning agent prepared from gallic acid gives imparts softness and
grain tightness to the leathers.
4. The novel-tanning agent prepared gives the shrinkage temperature of not less
than 85 °C in the resulting leather.

We claim:
1. An improved process for the preparation of a tanning agent, which comprises
i) dissolving gallic acid in 400-450% alkali (w/v) and adjusting the pH to
7-8 by known method to get gallic acid solution, ii) treating the gallic acid solution, as formed in step (i), with 10-20 % w/v,
of an organic crosslinker, preferably under agitation, for a period of
not less than 60 minutes, to obtain a homogeneous solution of tanning
agent.
2. An improved process, as claimed in Claim 1, wherein the alkali used is
selected from sodium hydroxide, soda ash.
3. An improved process, as claimed in Claims land 2, wherein the organic cross
linker is selected from oxazolidine, formaldehyde, glutaraldehyde
4. An improved process, as claimed in Claims 1 to 3, wherein the treatment of
gallic acid solution with organic crosslinker is carried out preferably under
agitation.
4.. An improved process for the preparation of a tanning agent, substantially as herein described with reference to the examples.

Documents:

319-DEL-2004-Abstract-(11-08-2011).pdf

319-del-2004-abstract.pdf

319-del-2004-claims.pdf

319-DEL-2004-Correspondence Others-(11-08-2011).pdf

319-del-2004-correspondence-others.pdf

319-del-2004-correspondence-po.pdf

319-del-2004-description (complete).pdf

319-del-2004-form-1.pdf

319-del-2004-form-18.pdf

319-del-2004-form-2.pdf

319-del-2004-form-3.pdf

319-del-2004-form-5.pdf

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Patent Number

251885

Indian Patent Application Number

319/DEL/2004

PG Journal Number

16/2012

Publication Date

20-Apr-2012

Grant Date

13-Apr-2012

Date of Filing

27-Feb-2004

Name of Patentee

COUNCIL OF SCIENTIFIC AND INDUSTRIAL RESEARCH

Applicant Address

RAFI MARG, NEW DELHI-110 001, INDIA

Inventors:

#	Inventor's Name	Inventor's Address
1	JAMES KANAGARAJ	CENTRAL LEATHER RESEARCH INSTITUTE, ADYAR, CHENNAI-600 020, INDIA
2	VICTOR JOHN SUNDAR	CENTRAL LEATHER RESEARCH INSTITUTE, ADYAR, CHENNAI-600 020, INDIA
3	CHELLAPPA MURALIDHARAN	CENTRAL LEATHER RESEARCH INSTITUTE, ADYAR, CHENNAI-600 020, INDIA
4	SAYEED SADULLA	CENTRAL LEATHER RESEARCH INSTITUTE, ADYAR, CHENNAI-600 020, INDIA

PCT International Classification Number

C14C 3/02

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA