EP3704275B1

EP3704275B1 - A composition useful for pre-treatment in waterless tanning and corresponding tanning process

Info

Publication number: EP3704275B1
Application number: EP18734308.2A
Authority: EP
Inventors: Palanisamy Thanikaivelan; Rathinam ARAVINDHAN; Balaraman Madhan; Palanivel SARAVANAN; Jonnalagadda Raghava Rao
Original assignee: Council of Scientific and Industrial Research CSIR
Current assignee: Council of Scientific and Industrial Research CSIR
Priority date: 2017-11-24
Filing date: 2018-05-30
Publication date: 2022-12-07
Anticipated expiration: 2038-05-30
Also published as: BR112020010308A2; CN111556901A; WO2019102487A1; CN111556901B; EP3704275A1

Description

FIELD OF THE INVENTION

The present invention relates to a composition useful for pre-treatment in waterless tanning. More particularly, the present invention relates to a composition that finds application in tanning, wherein the said composition uses the inherent water present in the substrate to be tanned, thereby eliminating the need of addition of external water. The developed composition is useful in leather processing industry for making chrome or vegetable tanned leather in an eco-benign way without adding to the environmental pollution.

BACKGROUND OF THE INVENTION

Huge volume of water is being utilized during leather processing, which leads to discharge of enormous quantity of wastewater (Rao et al., Journal of Cleaner Production, 11, 591-599, 2003). Researchers world over are involved in the development of technologies to minimize water utilization in leather processing. Chrome tanning is a widely practiced methodology to make leathers owing to its versatile properties. Vegetable tanning is also in vogue due to its eco-friendly nature compared to chromium, although less than 20% of world leather production follows this tanning procedure. Nevertheless, the use of partial-pickling process and water has been in practice during vegetable tanning. Use of water during chrome tanning is very important for attaining uniform diffusion, distribution and hydrolysis of chromium. The spent chrome liquor contains 1500-3500 ppm of chromium. The discharge of chromium is of major concern and 2 ppm as total chromium is the stipulated norm for the discharge of tannery effluent in inland water bodies (Suresh et al, Journal of Cleaner Production, 9, 483-491, 2001). Therefore, alternate technologies to reduce the chrome pollution or alternate tanning system are required to combat the present scenario. Owing to the non-availability of best-suited alternate tanning agent, it seems more appropriate to continue with the use of trivalent chromium as the main tanning material and chrome management through reduction of pollution at source or end-of pipe treatment.
Although the use of chrome exhaust aids, high exhaust chrome tanning salts and less chrome technologies have been developed ( WO 2014162059 A1 ), their commercial usage is lacking. The chrome recovery and reuse methodology is a very simple and effective method for combating chrome pollution, which is commercially practised in many countries including India (Rao et al., Journal of Cleaner Production, 11, 591-599, 2003). Pickle-basification free chrome tanning is another commercially feasible development, where the chromium tanning is carried out at elevated pH without the use of common salt. Also, the basification is not necessary in this process (Legesse et al, The Journal of the American Leather Chemists Association, 97, 475-486 2002; Rao et al, The Journal of the American Leather Chemists Association, 99, 82-94, 2004; WO 2012153203A1 ). Nevertheless, the disclosed process employs aqueous medium in significant quantity and discharge wastewater with fairly low pollution loads in comparison to the conventional pickle based chrome tanning system.
Further, the researchers are also looking at employing alternative medium to water during chrome tanning process. Silambarasan et al (RSC Advances, 5, 66815-66823, 2015) have shown that chrome tanning can be carried out in ethanol and its derivatives instead of water. Similarly, there are reports of using pressurized carbon dioxide as a medium for chrome tanning (Manfred et al., The Journal of Supercritical Fluids, 66, 291-296, 2012). A recent study demonstrates that a minimum of 55-65% internal moisture content within the collagen matrix is required for making chrome tanned leathers with comparable quality (Silambarasan et al., Journal of Cleaner Production, 87, 567-572, 2015).
A dispersing agent composition was developed for carrying out tanning without water or any other medium ( WO 2017009867 ). The dispersing agent essentially comprises polyalkylene polyhydric compound, an organic acid and a non-ionic surfactant. The major constituent of the said dispersing agent is polyalkylene polyhydric compound, which would increase the cost of the composition and would limit the commercial viability. Our co-pending Indian patent application No. 201611009091 provides a process for waterless chrome tanning that eliminates the use of water, salt, sulfuric acid and basification salts during the chrome tanning process. This process has been receiving more attention in global leather industries and several tanners in India have already adopted the process. However, use of more water and expensive organic acids for pre-treatment are posing problems for implementation in commercial environment. Hence, absorption of these new waterless chrome tanning technologies in worldwide leather industries has been slow thus threatening the sustainability of leather industries.
As can be seen in the prior art, the current knowledge on the cleaner chrome tanning processes as well as other chrome management options is well known. Not many cleaner technologies are developed for vegetable tanning. The prior art focused on technologies such as waterless chrome tanning process, dispersing agent for waterless tanning, etc. In short, it may be concluded that during the tanning process water is used in order to facilitate distribution and penetration of the tanning salts in the matrix and as per the literature available till date, the following drawbacks are associated with the prior art:

Use of water and generation of chrome containing wastewater during chrome tanning;
Reduced uptake of chrome tanning agent by the matrix;
Release of huge amounts of neutral salts owing to the pickling and basification process;
Partial pickling and use of water during vegetable tanning;

Thus, keeping in view the drawbacks of the hitherto reported prior art and problems associated with the available prior art technologies, the inventors of the present invention realized that there exists a dire need to provide a composition and process useful for pre-treatment during waterless chrome tanning process, which helps to eliminate water from tanning process thereby reducing the wastewater discharge. Elimination of mineral tanning salt and common salt will reduce the pollution load and chemical cost of the tanning process, thereby benefiting the industry.

OBJECTS OF THE INVENTION

The main objective of the present invention is therefore to provide a composition useful in pre-treatment in waterless tanning process, which obviates the limitations as stated above.
Another objective of the present invention is to avoid the use of water both during chrome and vegetable tanning and utilize inherent water present in the substrate.
Still another objective of the present invention is to use auxiliary chemicals like acid stable cationic fatliquors during the tanning process.
Yet another objective of the present invention is to improve the uptake of chromium and vegetable tannins during the process.
Still another objective of the present invention is to reduce the pollution load and toxic chemicals in the effluent.
Yet another objective of the present invention is to reduce processing time, water and cost for pre-treatment during waterless tanning in comparison to conventional processing.
Still another objective of the present invention is to eliminate the use of salt, sulfuric acid and basification process in comparison to conventional processing.

SUMMARY OF THE INVENTION

The present invention provides a composition useful in pre-treatment in waterless tanning process, wherein the said composition comprising:

i. 90 to 95% (v/v) of organic acid having carbon chain length in the range of C1 to C3;
ii. 3 to 8% (v/v) of primary alcohol having carbon chain length in the range of C1 to C3; and
iii. 2 to 5% (v/v) of a non-ionic surfactant.

The present invention provides a process for the preparation of the pre-treatment composition useful in waterless tanning, which comprises mixing 90 to 95% (v/v) of organic acid having carbon chain length in the range of C1 to C3, 3 to 8% (v/v) of primary alcohol having carbon chain length in the range of C1 to C3 and 2 to 5% (v/v) of a non-ionic surfactant for a period in the range of 5 to 30 min to obtain the composition. The said composition being water soluble, exhibiting a pH in the range of 1.8 to 2.6 as a 10% solution and characterized by transparent appearance.
In an embodiment, the present invention provides a waterless tanning process using the developed composition, wherein the steps comprising:

i. treating the delimed substrate to be tanned with 0.1 to 5% w/w of the developed composition in the presence of 10 to 60% water to adjust the pH in the range of 4.8 to 5.8 followed by draining the float to obtain pre-treated substrate,
ii. treating the pre-treated substrate as obtained in step (i) with 0.2 to 2.0% of a conventional fatliquor and 0.2 to 1.0% of an alkali metal salt of organic acid having carbon chain of length not more than two for a period in the range of 20 to 60 min,
iii. treating the substrate as obtained in step (ii) with 3 to 50% of conventional tanning agent, added in one or more instalments, for a period in the range of 90 to 600 min with simultaneous checking of pH in the range of 3.6 to 4.4 to obtain tanned substrate.

In an embodiment of the present invention, the organic acid used may be selected from methanoic acid, ethanoic acid, propionic acid either individually or in different combinations.
In another embodiment of the present invention, the primary alcohol used may be selected from methanol, ethanol, propan-2-ol either individually or in different combinations.
In still another embodiment of the present invention, the non-ionic surfactant used may be selected from 2-[4-(2,4,4-trimethylpentan-2-yl)phenoxy]ethanol, polyoxyethylene (20) sorbitan monooleate, [2-[(2R,3S,4R)-3,4-dihydroxyoxolan-2-yl]-2-hydroxyethyl] octadecanoate either individually or in different combinations.
In another embodiment of the present invention, the conventional fatliquor used may be selected from cationic fatliquor, acid stable fatliquor, universal fatliquor, chrome stable fatliquor either individually or in different combinations.
In still another embodiment of the present invention, the alkali metal salt of organic acid used may be selected from sodium methanoate, sodium ethanoate either individually or in different combinations.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides a process for the preparation of composition, which comprising mixing 90 to 95% (v/v) of an organic acid having carbon chain length in the range of C1 to C3, 3 to 8% (v/v) of primary alcohol having carbon chain length in the range of C1 to C3 and 2 to 5% (v/v) of a non-ionic surfactant are mixed together for a period of 5 to 30 min to obtain a composition which is useful for pre-treatment in waterless tanning processes.
The prepared composition has the following characteristics:

pH of 10% solution: 1.8 to 2.6

Color: Transparent

Solubility in water: High
The composition is used for waterless tanning process as described below.
Delimed substrate is treated with 0.1 to 5% of the composition in the presence of 10-60% water. The pH of the pelt is adjusted in the range of 4.8 to 5.8. After attaining the pH, the float is drained and the substrate is treated with 0.2 to 2.0% of conventional fatliquor and 0.2 to 1.0% alkali metal salt of organic acid having carbon chain of length not more than two. After a period of 20 to 60 min, the substrate is treated with 3 to 50% of conventional tanning agent, added in one or more instalments, for a period in the range of 90 to 600 min. The pH is checked to be in the range of 3.6 to 4.4 to obtain tanned substrate.
The inventive step of the present invention lies in preparing the composition by prudent selection and combination of key chemicals such that the resultant composition can be easily used for pre-treatment in waterless tanning, which would help in carrying out the tanning more effectively and easily utilizing the internal moisture content of raw material to reduce the effluent discharge. Further, elimination of common salt and considerable reduction in water requirement, duration of the process and cost are achieved in the new invention.

EXAMPLES

The following examples are given by way of illustration only and therefore, should not be construed to limit the scope of the present invention in any manner.

Example 1

Composition was prepared by mixing of 45 ml of methanoic acid, 4 ml of methanol and 1 ml 2-[4-(2,4,4-trimethylpentan-2-yl)phenoxy]ethanol together for a period of 5 min. pH of 10% solution of the composition was 1.80. The colour of the composition was transparent and it had good solubility in water.
One delimed substrate (cow hide) to be tanned weighing 3 kg was treated with the above composition diluted with 500 ml of water and drummed in the presence of 1200 ml water. The pH of the pelt was checked to be 4.8. After attaining the pH, the float was drained and the hide was treated with 6 g of cationic fatliquor and 6 g of sodium methanoate. After a period of 20 min, 90 g of conventional chrome tanning agent (BCS) was added in 2 feeds with 30 min interval and drummed for a period of 90 min. The pH was checked to be 3.8 to obtain chrome tanned leather.

Example 2

Composition was prepared by mixing of 7 ml of ethanoic acid, 0.2 ml of ethanol and 0.15 ml Polyoxyethylene (20) sorbitan monooleate together for a period of 5 min. pH of 10% solution of the composition was 2.41. The color of the composition was transparent and it had good solubility in water.
Three delimed substrate (cow hide) to be tanned weighing 7.5 kg were treated with the above composition diluted with 75 ml of water and drummed in the presence of 3000 ml water. The pH of the pelt was checked to be 5.2. After attaining the pH, the float was drained and the hide was treated with 37.5 g of acid stable fatliquor and 15 g of sodium ethanoate. After a period of 30 min, 375 g of conventional chrome tanning agent (BCS) was added in 2 feeds with 30 min interval and drummed for a period of 180 min. The pH was checked to be 4.0 to obtain chrome tanned leather.

Example 3

Composition was prepared by mixing of 41 ml of propionic acid, 2.3 ml of propan-2-ol and 2.25 ml [2-[(2R,3S,4R)-3,4-dihydroxyoxolan-2-yl]-2-hydroxyethyl] octadecanoate together for a period of 5 min. pH of 10% solution of the composition was 2.58. The color of the composition was transparent and it had good solubility in water.
Two delimed substrate (cow hide) to be tanned weighing 5 kg were treated with the above composition diluted with 900 ml of water and drummed in the presence of 2000 ml water. The pH of the pelt was checked to be 5.4. After attaining the pH, the float was drained and the hide was treated with 15 g of Universal fatliquor and 27.5 g of sodium methanoate. After a period of 40 min, 300 g of conventional chrome tanning agent (BCS) was added in 2 feeds with 30 min interval and drummed for a period of 180 min. The pH was checked to be 4.10 to obtain chrome tanned leather.

Example 4

Composition was prepared by mixing of 45 ml of methanoic acid, 45 ml of ethanoic acid, 2.5 ml of methanol, 2.5 ml of ethanol, 2 ml of 2-[4-(2,4,4-trimethylpentan-2-yl)phenoxy]ethanol, 2 ml of Polyoxyethylene (20) sorbitan monooleate and 1 ml of [2-[(2R,3S,4R)-3,4-dihydroxyoxolan-2-yl]-2-hydroxyethyl] octadecanoate together for a period of 5 min. pH of 10% solution of the composition was 2.10. The color of the composition was transparent and it had good solubility in water.
Five delimed substrate (cow hide) to be tanned weighing 10 kg were treated with the above composition diluted with 1000 ml of water and drummed in the presence of 4000 ml water. The pH of the pelt was checked to be 4.8. After attaining the pH, the float was drained and the hide was treated with 20 g of chrome stable fatliquor and 80 g of sodium methanoate. After a period of 20 min, 800 g of conventional chrome tanning agent (BCS) was added in 2 feeds with 30 min interval and drummed for a period of 420 min. The pH was checked to be 3.6 to obtain chrome tanned leather.

Example 5

Composition was prepared by mixing of 18 ml of methanoic acid, 18 ml of ethanoic acid, 18 ml of propionic acid, 2 ml of methanol, 2 ml of ethanol, 0.8 ml of propan-2-ol, 1 ml of Polyoxyethylene (20) sorbitan monooleate and 0.2 ml of [2-[(2R,3S,4R)-3,4-dihydroxyoxolan-2-yl]-2-hydroxyethyl] octadecanoate together for a period of 5 min. pH of 10% solution of the composition was 2.10. The color of the composition was transparent and it had good solubility in water.
Four delimed substrate (cow hide) to be tanned weighing 8 kg were treated with the above composition diluted with 3000 ml of water and drummed in the presence of 3200 ml water. The pH of the pelt was checked to be 4.8. After attaining the pH, the float was drained and the hide was treated with 8 g of acid stable fatliquor, 8 g of chrome stable fatliquor, 40 g of sodium methanoate and 40 g of sodium methanoate. After a period of 60 min, 240 g of conventional chrome tanning agent (BCS) was added in 2 feeds with 30 min interval and drummed for a period of 360 min. The pH was checked to be 3.8 to obtain chrome tanned leather.

Example 6

Composition was prepared by mixing of 30 ml of methanoic acid, 15 ml of ethanoic acid, 26 ml of propionic acid, 1 ml of methanol, 0.5 ml of propan-2-ol, 0.5 ml of 2-[4-(2,4,4-trimethylpentan-2-yl)phenoxy]ethanol, 0.75 ml of Polyoxyethylene (20) sorbitan monooleate and 1 ml of [2-[(2R,3S,4R)-3,4-dihydroxyoxolan-2-yl]-2-hydroxyethyl] octadecanoate together for a period of 5 min. pH of 10% solution of the composition was 2.25. The color of the composition was transparent and it had good solubility in water.
Five delimed substrate (cow hide) to be tanned weighing 10 kg were treated with the above composition diluted with 750 ml of water and drummed in the presence of 4000 ml water. The pH of the pelt was checked to be 5.0. After attaining the pH, the float was drained and the hide was treated with 10 g of acid stable fatliquor, 10 g of universal fatliquor and 50 g of sodium methanoate. After a period of 40 min, 800 g of conventional chrome tanning agent (BCS) was added in 2 feeds with 30 min interval and drummed for a period of 420 min. The pH was checked to be 3.9 to obtain chrome tanned leather.

Example 7

Composition was prepared by mixing of 40 ml of methanoic acid, 15 ml of ethanoic acid, 50 ml of propionic acid, 4 ml of methanol, 2 ml of ethanol, 4 ml of propan-2-ol, and 2 ml of polyoxyethylene (20) sorbitan monooleate together for a period of 5 min. pH of 10% solution of the composition was 2.6. The color of the composition was transparent and it had good solubility in water.
One delimed substrate (cow hide) to be tanned weighing 2 kg was treated with the above composition diluted with 1000 ml of water and drummed in the presence of 800 ml water. The pH of the pelt was checked to be 5.8. After attaining the pH, the float was drained and the hide was treated with 20 g of cationic fatliquor, 20 g of chrome stable fatliquor and 6 g of sodium ethanoate. After a period of 60 min, 60 g of conventional chrome tanning agent (BCS) was added in 2 feeds with 30 min interval and drummed for a period of 120 min. The pH was checked to be 4.4 to obtain chrome tanned leather.

Example 8

Composition was prepared by mixing of 10 ml of methanoic acid, 90 ml of ethanoic acid, 5 ml of ethanol and 5 ml of 2-[4-(2,4,4-trimethylpentan-2-yl)phenoxy]ethanol together for a period of 5 min. pH of 10% solution of the composition was 2.20. The color of the composition was transparent and it had good solubility in water.
Five delimed substrate (cow hide) to be tanned weighing 10 kg were treated with the above composition diluted with 1000 ml of water and drummed in the presence of 4000 ml water. The pH of the pelt was checked to be 4.8. After attaining the pH, the float was drained and the hide was treated with 50 g of acid stable fatliquor and 50 g of sodium methanoate. After a period of 20 min, 600 g of conventional chrome tanning agent (BCS) was added in 2 feeds with 30 min interval and drummed for a period of 300 min. The pH was checked to be 4.1 to obtain chrome tanned leather.

Example 9

Composition was prepared by mixing of 25 ml of methanoic acid, 20 ml of propionic acid, 2.5 ml of ethanol, 2 ml of 2-[4-(2,4,4-trimethylpentan-2-yl)phenoxy]ethanol and 0.5 ml of Polyoxyethylene (20) sorbitan monooleate together for a period of 5 min. pH of 10% solution of the composition was 2.00. The color of the composition was transparent and it had good solubility in water.
Ten delimed substrate (cow hide) to be tanned weighing 20 kg were treated with the above composition diluted with 3000 ml of water and drummed in the presence of 8000 ml water. The pH of the pelt was checked to be 4.8. After attaining the pH, the float was drained and the hide was treated with 20 g of cationic fatliquor, 100 g of acid stable fatliquor, 25 g of universal fatliquor, 50 g of chrome stable fatliquor, 25 g of sodium methanoate and 25 g of sodium ethanoate. After a period of 20 min, 1600 g of conventional chrome tanning agent (BCS) was added in 2 feeds with 30 min interval and drummed for a period of 540 min. The pH was checked to be 3.7 to obtain chrome tanned leather.

Example 10

Composition was prepared by mixing of 41 ml of propionic acid, 2.3 ml of propan-2-ol and 2.25 ml [2-[(2R,3S,4R)-3,4-dihydroxyoxolan-2-yl]-2-hydroxyethyl] octadecanoate together for a period of 5 min. pH of 10% solution of the composition was 2.58. The color of the composition was transparent and it had good solubility in water.
Five delimed substrate (goat skins) to be tanned weighing 5 kg were treated with the above composition diluted with 900 ml of water and drummed in the presence of 2000 ml water. The pH of the pelt was checked to be 5.3. After attaining the pH, the float was drained and the skins were treated with 15 g of Universal fatliquor and 27.5 g of sodium methanoate. After a period of 30 min, 1 kg of wattle GS powder was added in 2 feeds with 45 min interval and drummed for a period of 240 min. The pH was checked to be 3.80 to obtain vegetable tanned leather.

Example 11

Composition was prepared by mixing of 40 ml of methanoic acid, 15 ml of ethanoic acid, 50 ml of propionic acid, 4 ml of methanol, 2 ml of ethanol, 4 ml of propan-2-ol, and 2 ml of polyoxyethylene (20) sorbitan monooleate together for a period of 5 min. pH of 10% solution of the composition was 2.6. The color of the composition was transparent and it had good solubility in water.
One delimed substrate (cow hide) to be tanned weighing 2 kg was treated with the above composition diluted with 1000 ml of water and drummed in the presence of 600 ml water. The pH of the pelt was checked to be 5.6. After attaining the pH, the float was drained and the hide was treated with 20 g of cationic fatliquor, 20 g of Universal fatliquor and 6 g of sodium ethanoate. After a period of 30 min, 1 kg of wattle GS powder was added in 4 feeds with 20 min interval and drummed for a period of 600 min. The pH was checked to be 3.6 to obtain vegetable tanned leather.

ADVANTAGES OF THE PRESENT INVENTION

➢ A versatile composition for facilitating waterless tanning.
➢ Utilization of inherent moisture present in the delimed pet for tanning.
➢ Reduces the use of water during pre-treatment step.
➢ Eliminates the use of process water during tanning process.
➢ Use of salt and the basification process are avoided.
➢ Reduction of pollution load to the environment.
➢ Reduction of process time.
➢ A suitable process for all kinds of raw materials.
➢ Production of soft and flexible leather.
➢ Strength characteristics of the crust leathers meet the standard norms.

Claims

A composition useful for pre-treatment in waterless tanning, wherein the said composition comprising:
a) 90 to 95% (v/v) of an organic acid having carbon chain length in the range of C1 to C3 with transparent appearance;

b) 3 to 8% (v/v) of a primary alcohol having carbon chain length in the range of C1 to C3; and

c) 2 to 5% (v/v) of a non-ionic surfactant.
The composition as claimed in claim 1, wherein the organic acid used is selected from methanoic acid, ethanoic acid, propionic acid either individually or in different combinations.
The composition as claimed in claim 1, wherein the primary alcohol used is selected from methanol, ethanol, propan-2-ol, either individually or in different combinations.
The composition as claimed in claim 1, wherein the non-ionic surfactant used is selected from 2-[4-(2,4,4-trimethylpentan-2-yl)phenoxy]ethanol, polyoxyethylene (20) sorbitan monooleate, [2- [(2R,3 S ,4R)-3 ,4-dihydroxyoxolan-2-yl] -2-hydroxyethyl] octadecanoate either individually or in different combinations.
A process for the preparation of the composition as claimed in claim 1, wherein the steps comprising mixing 90 to 95% (v/v) of organic acid having carbon chain length in the range of C1 to C3, 3 to 8% (v/v) of primary alcohol having carbon chain length in the range of C1 to C3 and 2 to 5% (v/v) of a non-ionic surfactant for a period in the range of 5 to 30 min to obtain the desired composition, wherein the said composition being water soluble, exhibiting a pH in the range of 1.8 to 2.6 as a 10% solution and characterized by transparent appearance.
A tanning process using the composition as claimed in claim 1, wherein the steps comprising:
a) treating delimed substrate to be tanned with 0.1 to 5% w/w of the composition as claimed in claim 1 in the presence of 10 to 60% water to adjust the pH in the range of 4.8 to 5.8 followed by draining the float to obtain pre-treated substrate;

b) treating the pre-treated substrate as obtained in step [a] with 0.2 to 2.0% of a conventional fatliquor and 0.2 to 1.0% of an alkali metal salt of organic acid having carbon chain of length not more than two for a period in the range of 20 to 60 min;

c) treating the substrate as obtained in step [b] with 3 to 50% of conventional tanning agent added in one or more instalments for a period in the range of 90 to 600 min with simultaneous checking of pH in the range of 3.6 to 4.4 to obtain tanned leather.
The process as claimed in claim 6, wherein the conventional fatliquor used is selected from cationic fatliquor, acid stable fatliquor, universal fatliquor, chrome stable fatliquor, either individually or in different combinations.
The process as claimed in claim 6, wherein the alkali metal salt of organic acid used is selected from sodium methanoate, sodium ethanoate, either individually or in different combinations.