CN109072317B

CN109072317B - Chrome tanning process

Info

Publication number: CN109072317B
Application number: CN201780018098.5A
Authority: CN
Inventors: 拉辛南·阿拉文丹; 帕拉尼萨米·塔尼凯维兰; 格莱斯顿·克里斯托弗·贾古马尔; 帕兰维尔·萨拉瓦南; 罗纳拉加达·拉加万·拉奥
Original assignee: Scientific And Industrial Research Council
Current assignee: Scientific And Industrial Research Council
Priority date: 2016-03-16
Filing date: 2017-01-11
Publication date: 2021-07-02
Anticipated expiration: 2037-01-11
Also published as: AR105795A1; ES2632994A1; ZA201608580B; BR112018068661A2; EP3430174B1; BR112018068661B1; TW201805434A; PT3430174T; WO2017158617A1; CN109072317A; EP3430174A1; MX2018011207A; ES2632994B1

Abstract

The present invention reveals that water must be used in the leather manufacturing process because it is important for the diffusion and distribution of chemicals in the leather matrix. Since a large amount of water is used in various unit processes, sewage discharge increases accordingly as pollutants increase. The invention relates to a chromium-free tanning process avoiding pickling-basification with water. Auxiliary chemicals such as fatliquoring agents are used to increase the chromium consumption during tanning. Furthermore, the new process avoids the use of salts and alkalization processes. The sensory and strength properties of tanned leather are comparable to conventionally processed leather. The new process is directed to tanning using the moisture carried in the leather itself, thus achieving sustainability with reduced pollution load.

Description

Chrome tanning process

Technical Field

The invention relates to an improved chrome tanning process. More particularly, the invention relates to performing a chrome tanning process without the addition of water. The moisture carried by the hide is used for chrome tanning. The process employs auxiliary chemicals such as fatliquoring agents to enhance the distribution and consumption of chromium during tanning. Furthermore, the new process avoids the use of salts and alkalization processes. The organoleptic properties of tanned leathers are comparable to conventionally processed leathers. The strength characteristics of the crust leather meet the standard specifications and determine the quality of the finished leather product. The new process is directed to the realization of sustainability development by reducing the pollution load.

Background

Leather processing uses large amounts of water, which results in the discharge of large amounts of waste water (lao et al, journal of clean production, 11, 591-. Researchers around the world have been involved in technological development to minimize the amount of water used in leather processing. Chrome tanning is a widely used leather manufacturing technique due to its versatile nature. The use of water in chrome tanning is important for uniform diffusion, distribution and hydrolysis of the chrome. The waste chromium solution contains 1500-3500ppm of chromium. Chromium emission is a major concern, and 2ppm total chromium is a regulated emission standard for tannery wastewater in inland waters (Sureshi et al, J. CLEAN. Productions, 9,483-491, 2001). Therefore, there is a need for alternative techniques for reducing chromium contamination or alternative tanning systems to alter the current situation. Without the most suitable alternative tanning agent, it seems more appropriate to continue to use trivalent chromium as the main tanning material, and chromium management with pollution reduction through source control or end treatment is also logical.

The recovery of spent chromium liquor for tanning or pickling is one of the best chromium management methods to solve the problem of chromium contamination (sllemm et al, journal of the american society of leather chemists, 100, 233-. However, the acidity and salinity of the liquid must be controlled and monitored periodically. The recovery/reuse method is a very simple and effective method for reducing chromium contamination and is increasingly important (sleim and lamassamia, resources, protection and recovery, 38, 185-212, 2003). The use of chromium stripping aids, high chromium stripping tanning salts and low chromium technologies (lamumuli et al, cleaning technology and environmental policy, 16, 647-.

Acid wash-basification chrome-free tanning is another commercially viable development, where chrome tanning is carried out without the use of common salts and at higher pH of about 5.0. In addition, basification is not required in this process (Legassel et al, J.Amur. Chemicals, 97, 475-. However, compared to traditional acid wash based chrome tanning systems, the disclosed process uses large amounts of aqueous medium and discharges wastewater of considerably lower pollution load. In addition, researchers have also investigated alternative media for the use of water in chrome tanning processes. Broccombara et al (journal of the kingdom Imperial chemical society, 5, 66815-66823, 2015) have shown that chrome tanning can be carried out in ethanol and its derivatives, but not in water. Similarly, there are reports of the use of pressurized carbon dioxide as a medium for chrome tanning (menfrady et al, journal of supercritical fluids, 66, 291-. A recent study showed that the collagen matrix required at least 55-65% internal water for the manufacture of comparable quality chrome tanned leathers (broccoli et al, journal of clean production, 87, 567-.

As can be seen from the prior art, prior knowledge about cleaner chrome tanning processes and other chrome management measures is well known. The prior art has focused on techniques such as pickling-free, alternative tanning systems, and the use of alternative media in chrome tanning. Some industries also employ the recovery and reuse of waste streams. However, the production of chromium-containing wastewater remains a major challenge facing leather manufacturers. In addition, the available high quality water source for chrome tanning has become scarce. Therefore, there is an urgent need to provide a zero water chrome tanning system.

Object of the Invention

The main object of the present invention is to provide a zero water chrome tanning process which eliminates the above mentioned limitations.

Another object of the invention is to utilize the moisture carried by the hides itself for chrome tanning.

It is a further object of the present invention to use auxiliary chemicals such as acid stable fatliquor and cationic fatliquor during the chrome tanning process.

It is another object of the invention to use organic acids to adjust the pH prior to chrome tanning.

It is another object of the invention to improve the absorption of chromium.

It is another object of the present invention to reduce pollution and toxic chemicals in wastewater.

It is another object of the invention to provide leather with physical strength properties similar to those of conventional chrome tanned leather.

Another object of the invention is to reduce the processing time of chrome tanning compared to conventional processing.

Another object of the present invention is to eliminate the alkalization process compared to conventional processing.

Disclosure of Invention

Accordingly, the present invention provides an improved chrome tanning process comprising:

(1) treating the ashed hides/skins with 0.5-1.5% of an organic acid in 40-60% water to adjust the pH to 4.8-5.8;

(2) removing the floaters and treating the hides/skins obtained in step (1) with a conventional fatliquor at 0.5-2.0% for 20 to 60 minutes;

(3) the hides/skins obtained in step (2) are treated for 240 to 360 minutes by adding 5-8% of a conventional chrome tanning agent in one or more portions to obtain chrome tanned leathers.

In one embodiment of the invention, the organic acid used is selected from one or more of formic acid, acetic acid and oxalic acid in various combinations.

In another embodiment of the present invention, the conventional fatliquor employed is selected from one or more of a different combination of cationic fatliquor, acid-stable fatliquor, universal fatliquor and chromium-stable fatliquor.

Detailed Description

The present invention is described in detail below.

The deashed hides/skins are treated with 0.5-1.5% of an organic acid in 40-60% water. The pH of the hide is adjusted to be in the range of 4.8-5.8. After the pH requirement is reached, the floaters are drained off and the hides/skins are treated with 0.5-2.0% of conventional fatliquoring agents. After 20 to 60 minutes, the hides/skins are treated with one or more additions of 5-8% of conventional chrome tanning agents for 240 to 360 minutes. The pH is brought in the range of 3.6-4.4 to obtain chrome tanned leather.

The invention creatively utilizes the internal moisture of the raw materials to perform chrome tanning so as to reduce the discharge of waste water. In addition, the new process does not use common salts and significantly reduces water demand, process time and costs.

The following examples are presented by way of illustration only and therefore should not be construed to limit the scope of the present invention.

Example 1

A piece of ashed hide weighing 1.5kg was treated with 7.5g formic acid diluted with 75ml water and subjected to drum processing in 600ml water. The hide had a pH of 4.8. After the pH value requirement is met, floaters are drained, and the raw skin is treated by 7.5g of acid-stable fatliquor. After 20 minutes, the skins were treated with 75g of conventional chrome tanning agent (BCS) added twice at 30 minute intervals for 240 minutes. The pH was brought to 3.6 to obtain chrome tanned leather.

Example 2

Three sheets of 5kg weight delimed hides were treated with 50g of acetic acid diluted with 500ml of water and subjected to drum processing in 2.5L of water. The hide had a pH of 5.0. After the pH value requirement is met, floating objects are discharged, and the raw hide is treated by 50g of cationic fatliquor. After 45 minutes, the skins were treated with 350g of conventional chrome tanning agent (BCS) added three times at 30 minute intervals for 300 minutes. The pH was brought to 3.8 to obtain chrome tanned leather.

Example 3

Two pieces of ashed hides weighing 3kg were treated with 45g of acetic acid diluted with 450ml of water and subjected to drum processing in 1.8L of water. The hide had a pH of 5.8. After the pH value requirement is met, floating objects are discharged, and the raw skin is treated by 60g of general fatting agent. After 60 minutes, the skins were treated with 240g of conventional chrome tanning agent (BCS) in four portions at 30 minute intervals for 360 minutes. The pH was brought to 4.4 to obtain chrome tanned leather.

Example 4

Four sheets of deashed hides weighing 10kg were treated with 100g of acetic acid diluted in 1L of water and subjected to drum processing in 6L of water. The hide had a pH of 5.0. After the pH value requirement is met, floating objects are discharged, and the raw hide is treated by 100g of cation fatliquor. After 30 minutes, the skins were treated with 600g of conventional chrome tanning agent (BCS) added twice at 30 minute intervals for 300 minutes. The pH was brought to 4.0 to obtain chrome tanned leather.

Example 5

Two pieces of ashed hides weighing 6kg were treated with 60g oxalic acid diluted in 600ml water and subjected to drum processing in 3.6L water. The hide had a pH of 5.2. After the pH value requirement is met, floating objects are discharged, and the raw skin is treated by 60g of chromium-stabilized fatliquor. After 60 minutes, the skins were treated with 360g of conventional chrome tanning agent (BCS) added three times at 30 minute intervals for 240 minutes. The pH was brought to 4.4 to obtain chrome tanned leather.

Example 6

A piece of ashed hide weighing 1kg was treated with 10g oxalic acid diluted in 50ml water and subjected to drum processing in 400ml water. The pH of the skins was brought to 4.8. After the pH value requirement is met, floating objects are discharged, and the raw skin is treated by 5g of cationic fatliquor. After 30 minutes, the skins were treated with two additions of 60g of conventional chrome tanning agent (BCS) at 30 minute intervals for 240 minutes. The pH was brought to 4.4 to obtain chrome tanned leather.

Example 7

Three sheets of de-ashed hides weighing 6kg were treated with 30g acetic acid and 30g formic acid diluted in 900ml water and subjected to drum processing in 3.6L water. The hide had a pH of 5.2. After the pH value requirement is met, floating objects are discharged, and the raw skin is treated by 30g of the acid-stabilized fatliquor and 30g of the chromium-stabilized fatliquor. After 60 minutes, the skins were treated with 360g of conventional chrome tanning agent (BCS) added twice at 30 minute intervals for 240 minutes. The pH was brought to 4.2, giving a chrome tanned leather.

Advantages of the invention

The main advantages of the invention include:

1. tanning by using the moisture carried by the ash-removed leather;

2. the chrome tanning process does not use process water;

3. the pollution load to the environment is reduced;

4. the processing time is shortened;

5. is a process suitable for various raw materials;

6. soft and elastic leather is produced.

Claims

1. A chrome tanning process comprising:

(1) treating the delimed hide with 0.5-1.5 wt% of an organic acid in 40-60 wt% water to adjust the pH to 4.8-5.8;

(2) removing the floaters and treating the hides obtained in step (1) with a conventional fatliquor in an amount of 0.5-2.0% by weight for a period of 20 to 60 minutes;

(3) and (3) adding 5-8 wt% of a conventional chrome tanning agent once or in multiple times to treat the hide obtained in the step (2) for 240-360 minutes to obtain chrome tanned leather.

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

3. A process according to claim 1, wherein the conventional fatliquor employed is selected from one or more of a different combination of cationic fatliquor, acid-stabilized fatliquor and chromium-stabilized fatliquor.