CHROME TANNING PROCESS

Description

FIELD OF THE INVENTION

[0001] The present invention relates to a chrome tanning process. More particularly, the present invention relates to carrying out the chrome tanning process without addition of water. The inherent water present in the pelt is utilized for chrome tanning. The process employs auxiliary chemicals such as fatliquors to enhance the distribution and exhaustion of chromium during tanning process. Moreover, the use of salt and the basification process are avoided in the new process. The organoleptic properties of the tanned leathers are on par with conventionally processed leathers. The strength characteristics of the crust leathers meet the standard norms, which ascertain the quality of the final leathers. This new invention makes an effort to attain sustainability with reduced pollution loads.

BACKGROUND OF THE INVENTION

[0002] 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. 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 seems logical.

[0003] Recycling of spent chromium liquor to tanning or pickle bath is one of the best methods of chrome management in overcoming the problem of chromium pollution (Sreeram et al., The Journal of the American Leather Chemists Association, 100, 233-242, Muralidharan and John, WO Patent 2012153203A1, 2012). However, regular control and monitoring of acidity and salt content of the liquor are necessary. The recovery/reuse methodology is a very simple and effective method for combating chrome pollution, which is gaining importance (Sreeram and Ramasami, Resources, Conservation and Recycling, 38, 185-212, 2003). The use of chrome exhaust aids, high exhaust chrome tanning salts and less chrome technologies have been developed (Ramamurthy et al., Clean Technologies and Environmental Policy, 16, 647-654, 2014; Van and Brendler, US Patent 7063728B2, 2014).

[0004] Pickle-basification free chrome tanning is another commercially feasible development, where the chromium tanning is carried out at higher pH around 5.0, 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, John and Muralidharan, WO Patent 2012153203A1, 2006). 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 the 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).

[0005] WO 2004/087967 discloses a pickle-free chromium tanning process which includes the preparation of solid or dissolved compositions of chromium sulphate, lactic or oxalic acid and formic acid with which delimed, bated and washed hides are treated.

[0006] 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. The prior art focused on technologies like pickle-less, alternate tanning system and use of alternative medium in chrome tanning. Recovery and recycling of spent liquor is also practised in some industries. However, generation of wastewater containing chromium is still a major challenge for leather makers. Further, the availability of quality water source for chrome tanning is also becoming scarce. Therefore, there exists a dire need to provide a zero water chrome tanning system.

OBJECTS OF THE INVENTION

[0007] The main objective of the present invention is to provide a zero water chrome tanning process, which obviates the limitations as stated above.

[0008] Another objective of the present invention is to utilize inherent water present in the pelt for chrome tanning.

[0009] Still another objective of the present invention is to use auxiliary chemicals like acid stable, cationic fatliquors during chrome tanning process.

[0010] Yet another objective of the present invention is to use organic acids to adjust the pH prior to chrome tanning.

[0011] Still another objective of the present invention is to improve the uptake of chromium.

[0012] Yet another objective of the present invention is to reduce pollution and toxic chemicals in the effluent.

[0013] Still another objective of the present invention is to provide physical strength characteristics to the leather similar to that of conventional chrome tanned leather.

[0014] Yet another objective of the present invention is to reduce processing time for chrome tanning in comparison to conventional processing.

[0015] Still another objective of the present invention is to eliminate basification processes in comparison to conventional processing.

SUMMARY OF THE INVENTION

[0016] Accordingly, the present invention provides a chrome tanning process, which comprises

i. treating delimed hide/skin with 0.5 to 1.5 wt% of organic acid in the presence of 40 to 60 wt% water to adjust the pH in the range of 4.8 to 5.8,

ii. draining the float and treating the hide/skin, as obtained in step (i), with 0.5 to 2.0 wt% conventional fatliquor for a period in the range of 20 to 60 min,

iii. treating hide/skin, as obtained in step(ii), with 5 to 8 wt% of conventional chrome tanning agent, added in one or more instalments, for a period in the range of 240 to 360 min to obtain chrome tanned leather.

[0017] The wt% are referred to the limed hides after fleshing

[0018] In an embodiment of the present invention, the organic acid used may be selected from formic acid, acetic acid, oxalic acid either individually or in different combinations.

[0019] 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.

DETAILED DESCRIPTION OF THE INVENTION

[0020] The invention is described below in detail.

[0021] Delimed hide/skin is treated with 0.5 to 1.5 wt% of organic acid in the presence of 40-60 wt% 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 hide/skin is treated with 0.5 to 2.0 wt% of conventional fatliquor. After a period of 20 to 60 min, the hide/skin is treated with 5 to 8 wt% of conventional chrome tanning agent, added in one or more instalments, for a period in the range of 240 to 360 min. The pH is checked to be in the range of 3.6 to 4.4 to obtain chrome tanned leather.

[0022] The inventive step of the present invention lies in utilizing the internal moisture content of raw material for chrome tanning 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.

Example 1

[0023] One delimed hide weighing 1.5 kg was treated with 7.5 g of formic acid diluted with 75 ml of water and drummed in the presence of 600 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 7.5 g of acid stable fatliquor. After a period of 20 min the hide was treated with 75 g of conventional chrome tanning agent (BCS) was added in 2 feeds with 30 min interval for a period of 240 min. The pH was checked to be 3.6 to obtain chrome tanned leather.

Example 2

[0024] Three delimed hides weighing 5 kg was treated with 50 g of acetic acid diluted with 500 ml of water and drummed in the presence of 2.5 L water. The pH of the pelt was checked to be 5.0. After attaining the pH, the float was drained and the hides were treated with 50 g of cationic fatliquor. After a period of 45 min the hides were treated with 350 g of conventional chrome tanning agent (BCS) was added in 3 feeds with 30 min interval for a period of 300 min. The pH was checked to be 3.8 to obtain chrome tanned leather.

Example 3

[0025] Two delimed hides weighing 3 kg was treated with 45 g of acetic acid diluted with 450 ml of water and drummed in the presence of 1.8 L water. The pH of the pelt was checked to be 5.8. After attaining the pH, the float was drained and the hides were treated with 60 g of universal fatliquor. After a period of 60 min the hides were treated with 240 g of conventional chrome tanning agent (BCS) was added in 4 feeds with 30 min interval for a period of 360 min. The pH was checked to be 4.4 to obtain chrome tanned leather.

Example 4

[0026] Four delimed hides weighing 10 kg was treated with 100 g of acetic acid diluted with 1 L of water and drummed in the presence of 6 L water. The pH of the pelt was checked to be 5.0. After attaining the pH, the float was drained and the hides were treated with 100 g of cationic fatliquor. After a period of 30 min the hides were treated with 600 g of conventional chrome tanning agent (BCS) was added in 2 feeds with 30 min interval for a period of 300 min. The pH was checked to be 4.0 to obtain chrome tanned leather.

Example 5

[0027] Two delimed hides weighing 6 kg was treated with 60 g of oxalic acid diluted with 600 ml of water and drummed in the presence of 3.6 L water. The pH of the pelt was checked to be 5.2. After attaining the pH, the float was drained and the hides were treated with 60 g of chrome stable fatliquor. After a period of 60 min the hides were treated with 360 g of conventional chrome tanning agent (BCS) was added in 3 feeds with 30 min interval for a period of 240 min. The pH was checked to be 4.4 to obtain chrome tanned leather.

Example 6

[0028] One delimed hide weighing 1 kg was treated with 10 g of oxalic acid diluted with 50 ml of water and drummed in the presence of 400 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 5 g of cationic fatliquor. After a period of 30 min the hide was treated with 60 g of conventional chrome tanning agent (BCS) added in 2 feeds with 30 min interval for a period of 240 min. The pH was checked to be 4.4 to obtain chrome tanned leather.

Example 7

[0029] Three delimed hides weighing 6 kg was treated with 30 g of acetic acid and 30 g of formic acid diluted with 900 ml of water and drummed in the presence of 3.6 L water. The pH of the pelt was checked to be 5.2. After attaining the pH, the float was drained and the hides were treated with 30 g of acid stable fatliquor and 30 g of chrome stable fatliquor. After a period of 60 min the hides were treated with 360 g of conventional chrome tanning agent (BCS) added in 2 feeds with 30 min interval for a period of 240 min. The pH was checked to be 4.2 to obtain chrome tanned leather.

ADVANTAGES OF THE PRESENT INVENTION

[0030] The main advantages of the present invention include:

1. Utilization of inherent moisture present in the delimed pet for tanning

2. Eliminating the use of process water during chrome tanning process

3. Reduction of pollution loads to the environment

4. Reduction of process time

5. A suitable process for all kinds of raw material

6. Production of soft and flexible leather

Claims

1. A chrome tanning process, which comprises:

i. treating delimed hide/skin with 0.5 to 1.5 wt% of organic acid in the presence of 40 to 60 wt% water to adjust the pH in the range of 4.8 to 5.8,

ii. draining the float and treating the hide/skin, as obtained in step (i), with 0.5 to 2.0 wt% conventional fatliquor for a period in the range of 20 to 60 min,

iii. treating hide/skin, as obtained in step (ii), with 5 to 8 wt% of conventional chrome tanning agent, added in one or more instalments, for a period in the range of 240 to 360 min to obtain chrome tanned leather
wherein the wt% are referred to the limed hides after fleshing.

2. The process as claimed in Claim 1, wherein the organic acid used is selected from formic acid, acetic acid and oxalic acid either individually or in different combinations.

3. The process as claimed in Claim 1, wherein the conventional fatliquor used is selected from cationic fatliquor, acid stable fatliquor, universal fatliquor and chrome stable fatliquor either individually or in different combinations.

Ansprüche

1. Ein Chromgerbverfahren, welches umfasst:

i) Behandeln von entkälktem Fell/entkälkter Haut mit 0,5 bis 1,5 Gew.-% einer organischen Säure in Gegenwart von 40 bis 60 Gew.-% Wasser, um den pH-Wert im Bereich von 4,8 bis 5,8 einzustellen,

ii) Entfernen der Flotte und Behandeln des/der Fells/Haut, wie in Schritt (i) erhalten, mit 0,5 bis 2,0 Gew.-% konventionellem Fettungsmittel für einen Zeitraum im Bereich von 20 bis 60 Minuten,

iii) Behandlung des/der in Schritt (ii) erhaltenen Fells/Haut mit 5 bis 8 Gew.-% eines herkömmlichen in einer oder mehreren Schritten zugegebenen Chromgerbstoffs über einen Zeitraum im Bereich von 240 bis 360 Minuten, um chromgegerbtes Leder zu erhalten,
wobei die Gew.-% bezogen sind auf die entkälkten Felle nach dem Entfleischen.

2. Das Verfahren wie in Anspruch 1 beansprucht, wobei die verwendete organische Säure entweder einzeln oder in verschiedenen Kombinationen ausgewählt ist aus Ameisensäure, Essigsäure und Oxalsäure.

3. Das Verfahren wie in Anspruch 1 beansprucht, wobei das verwendete konventionelle Fettungsmittel entweder einzeln oder in verschiedenen Kombinationen ausgewählt ist aus kationischem Fettungsmittel, säurestabilem Fettungsmittel, universellem Fettungsmittel und chromstabilem Fettungsmittel.

Revendications

1. Procédé de tannage au chrome, comprenant :

i. le traitement d'une peau déchaulée avec 0,5 à 1,5 % en poids d'un acide organique en présence de 40 à 60 % en poids d'eau pour ajuster le pH dans la plage allant de 4,8 à 5,8,

ii. l'évacuation du bain et le traitement de la peau, telle qu'obtenue dans l'étape (i), avec 0,5 à 2,0 % en poids d'une liqueur grasse conventionnelle pendant une période située dans la plage allant de 20 à 60 min,

iii. le traitement de la peau, telle qu'obtenue dans l'étape (ii), avec 5 à 8 % en poids d'un agent de tannage au chrome conventionnel, ajouté en une ou plusieurs fois, pendant une période située dans la plage allant de 240 à 360 min pour obtenir un cuir tanné au chrome
dans lequel les % en poids sont par rapport aux peaux chaulées après écharnage.

2. Procédé selon la revendication 1, dans lequel l'acide organique utilisé est sélectionné parmi l'acide formique, l'acide acétique et l'acide oxalique, soit individuellement, soit dans différentes combinaisons.

3. Procédé selon la revendication 1, dans lequel la liqueur grasse conventionnelle utilisée est sélectionnée parmi une liqueur grasse cationique, une liqueur grasse stable aux acides, une liqueur grasse universelle et une liqueur grasse stable au chrome, soit individuellement, soit dans différentes combinaisons.