WO2008093353A1

WO2008093353A1 - An improved process for dehairing and fibre opening of hide/skin

Info

Publication number: WO2008093353A1
Application number: PCT/IN2007/000540
Authority: WO
Inventors: Thanikaivelan Palanisamy; Saravanabhavan Subramani; Raghava Rao Jonnalagadda; Chandrasekaran Bangaru; Unni Nair Balachandran; Ramasami Thirumalachari
Original assignee: Council Of Scientific & Industrial Research
Priority date: 2007-01-31
Filing date: 2007-11-14
Publication date: 2008-08-07
Also published as: DE112007001827T5; CN101484591A

Abstract

Global environmental regulations are changing, almost forcing all processing industries to adopt greener and cleaner manufacturing practices. Proteolytic and α-amylase enzymes have been found to be useful for dehairing and fibre opening process, respectively. However, this process is a two step method, in which dehairing is performed by the proteolytic enzyme followed by fibre opening through carbohydrolytic enzymes. The present invention integrates the two-step process into a single-step process, maintaining environmental sustainability. Various modes of application such as successive and simultaneous application of both the enzymes have been established. The extent of dehairing and fibre opening has been evaluated in comparison to the conventional or two-step enzyme based process derived skins/hides.

Description

"AN IMPROVED PROCESS FOR DEHAIRING AND FIBRE OPENING OF HIDE/SKIN"

Field of the invention

The present invention relates to an improved process for dehairing and fibre opening of hide/skin. More particularly, the present invention provides an improved process for making pelt (dehaired and fiber opened hide or skins) by dehairing and fibre opening employing enzymes in one process. The process has enormous potential application in tanning industry for processing hides/skins in an eco-benign way without adding to pollution load.

Background of the Invention

Conventional leather processing involves four important process steps, viz., pre- tanning, tanning, post tanning and finishing. It includes a combination of single and multi-step processes that employs as well as expels various biological, organic and inorganic materials as described by German (Science and Technology for Leather into the Next Millennium, Tata McGraw-Hill Publishing Company Ltd., New Delhi, p. 283, 1999). Liming and reliming processes (beam house or pre-tanning) employ lime and sodium sulfide and purifies the skin matrix by the removal of hair, flesh and other unwanted materials. Various application methods such as pit, paddle, drum and painting on flesh side have been employed depending on the skin type and tanners choice. After this stage, the hide/skin is termed as pelt. Deliming, bating and pickling processes prepare the skin for subsequent tanning using chromium salts or vegetable tannins. Tanned skin matrix is further retanned to gain substance, fatliquored to attain required softness and dyed to preferred shades.

Conventional liming-reliming process liquors contribute to nearly 50-70% of the total biochemical oxygen demand (BOD) and chemical oxygen demand (COD) load from a tannery wastewater and 15-20% in the case of total solids (TS) load as reported by Aloy ef a/ (Tannery and Pollution, Centre Technique Du Cuir: Lyon, France, 1976). Apart from this, a great deal of solid wastes containing lime sludge, fleshings, and hair are also generated.

Several lime and sulfide free liming methods have evolved during the past century. Bose and Dhar (Leather Science, 2, 140, 1955; 21 , 39, 1974) have reviewed the use of enzymes such as proteolytic, amylolytic, etc from various sources namely animal, mold, bacterial and plant for dehairing hides and skins. However, these methods include the use of lime, which results in the formation of lime sludge. Schlosser et al (Journal of the Society of Leather Technologists and Chemists, 70, 163, 1986) have reported the use of lacto-bacillus based enzymes at acidic conditions for dehairing. This method leads to the solubilisation of collagen at the experimental conditions. Various lime or sulfide free dehairing methods based on the use of chemicals such as chlorine dioxide, hydrogen peroxide, nickel carbonate and sodium hydroxide have been developed by Rosenbusch (Das Leder, 16, 237, 1965), Morera et al (Journal of the Society of Leather Technologists and Chemists, 81, 70, 1997), Sehgal et al (Journal of the Society of Leather Technologists and Chemists, 80, 91 , 1996) and Valeika et al (Journal of the Society of Leather Technologists and Chemists, 81 , 65, 1997; 82, 95, 1998), respectively. Commercial application of these methods is not popular in the global leather sector due to the possible damage of skin matrix by strong oxidising or reducing agents. However, enzyme-assisted lime-sulfide dehairing is being followed in some parts of the world. Thanikaivelan et al (Journal of the Society of Leather Technologists and Chemists 84, 276, 2000) have developed a lime free enzymatic dehairing process along with reduced amount of sodium sulfide, which ensures complete dehairing within 18 hrs. All these methods are applicable for only dehairing of skins/hides in leather processing. The dehaired pelts require fibre opening (reliming) for its future functions. Conventionally the fibre opening is obtained by treatment with lime through osmotic swelling.

Liming removes all the interfibrous materials especially proteoglycans and produces a system of fibres and fibrils of collagen which are clean as described by Campbell et al (Journal of American Leather Chemists Association, 68, 96, 1973). This is achieved by the alkali action as well as osmotic pressure built up in the skin matrix. Thanikaivelan et al (Environmental Science & Technology, 36, 4187, 2002) have successfully developed lime free fibre opening process employing α-amylase. This has been accomplished on a pelt that was treated with commercial protease and sodium sulfide for dehairing, which is a two-step process as also disclosed by Thanikaivelan et al (US Patent Number 6,708,531 , 2004). Recently, Saravanabhavan et al (US Patent Number 6,957,554, 2005) have successfully developed a process that completely eliminates the use of lime and sodium sulfide in leather processing. This process allows dehairing using commercial protease and silicate in the first step followed by fibre opening using silicate salt in the second step.

US 6,957,554 essentially discloses a process, which involves a step of dehairing using proteolytic enzymes optionally assisted with silicate salt, followed by a second step of fiber opening using silicate salt. The process does not provide any possibility of carrying out dehairing as well as fibre opening in the first step itself even if silicate is used there because of the adjustment of conditionalities therein. Moreover, silicate is associated with a limitation of exhibiting its activity when used in paste form.

While US 6,708,531 teaches an option to use hydrolytic enzyme for fibre opening, it is done on a skin having loosened hair, which facilitates enzyme activity. This does not teach us an option to carry out simultaneous hair loosening and fibre opening.

However, the present invention essentially provides an enzymatic option to replace silicate salt totally by using hydrolytic enzyme, which may be applied in conjunction with proteolytic enzyme, thereby ensuring both hair loosening and fibre opening simultaneously. This also provides an option to ensure chemical free leather processing in view of the environmental alertness in the present day scenario. Thus, the present invention is not envisaged to be obvious to a person reasonably skilled in the art so as to use hydrolytic enzyme and proteolytic enzyme simultaneously to carry out leather processing at the time of filing the application. The inventiveness lies in the simultaneous use of hydrolytic enzyme and proteolytic enzyme for simultaneous hair loosening and fibre opening.

The novelty and non-obviousness of the present invention lies in using proteolytic and carbohydrolytic enzymes simultaneously or successively to achieve dehairing and fibre opening in a single process, thereby providing an eco-benign bio-based based beam house process with reductions in labor and utilities.

Objects of the Invention

The main objective of the present invention is to provide an improved process for dehairing and fibre opening of hide/skin, which obviates the limitations as stated above.

Another objective of the present invention is to provide a process which uses proteolytic and carbohydrolytic enzymes simultaneously or successively to achieve dehairing and fibre opening in a single process, thereby providing an eco-benign bio- based beam house process with reductions in labor and utilities.

Still another objective of the present invention is to provide a bio-chemical based beam-house process that leads to significant reduction in chemical oxygen demand and total solids load.

Yet another objective of the present invention is to provide a lime free beam- house process that totally obviates the formation of lime sludge.

Summary of the Invention

Accordingly, the present invention provides an improved process for dehairing and fibre opening of hide/skin, which comprises :

[a] treating soaked hide/skin with

- 0.5 to 1.5% w/w, of proteolytic enzyme, exhibiting optimum activity at pH 7.5 to 11.0 and temperature in the range of 25 to 40 degree C and

- 0.25 to 1.5% w/w, of carbohydrolytic enzyme exhibiting optimum activity at pH 7.5 to 10.0 and temperature in the range of 25 to 40 degree C, either simultaneously or in different succession in the presence of 5 to 150% w/w of water, preferably under stirring conditions, optionally in the presence of not more than 1.5%w/w of sulfide or silicate salt, for a period of not less than 3 hrs at a pH in the range of 8 to 10,

[b] removing the hair and flesh by known method to obtain dehaired hide/skin incorporated with fibre opening

In an embodiment of the present invention, the proteolytic enzyme used may be selected from bacterial protease, fungal protease, either individually or in any combination.

In another embodiment of the present invention, the carbohydrolytic enzyme used may be selected from α-amylase, β-amylase, zymase, maltase, pectinase, elastase, hyaluronidase, α-galactosidase, either individually or in any combination.

In yet another embodiment of the present invention, the sulfide salt used may be selected from sodium sulfide, sodium sulfhydride, either individually or in combination.

In still another embodiment of the present invention, the silicate salt used may be selected from sodium metasilicate, water glass, sodium orthosilicate, either individually or in combination. Description of the Invention

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

Soaked hide/skin is treated with 0.5-1.5% w/w, of proteolytic enzyme, exhibiting optimum activity at pH 7.5-11.0 and temperature 25-4O⁰C, and 0.25-1.5% w/w, of carbohydrolytic enzyme exhibiting optimum activity at pH 7.5-10.0 and temperature 25-4O⁰C either simultaneously or in different succession in the presence of 5-150% w/w, of water, preferably under stirring condition. The treatment is continued for a period of not less than 3 hrs at a pH in the range of 8-10 optionally in the presence of not more than λ .5%w/w, of sulfide or silicate salt. The treated hide/skin is subjected to removal of hair and flesh by known method to obtain dehaired hide/skin incorporated with fibre opening.

The invention is described in detail in the following examples, which are provided by way of illustration only and therefore should not be construed to limit the scope of the present invention.

Example 1

Three dry salted sheepskins, weighing 4.7 kg, were soaked in 14.1 lit water for 3 hrs in a pit. Then the skins were again soaked in 14.1 lit fresh water for 3 hrs. The soaked skins were drained to remove surface water and the weight was found to be 6 kg. 15 gms α-amylase was added along with 3000 ml water to the drum containing soaked skins. The drum was run for 3 hrs continuously. 60 gms alkaline bacterial protease and 30 gms alkaline bacterial protease were added along with 300 ml water. The drum was run for 20 min followed by rest for 40 min. The cycle was repeated for 3 hrs. The treated skins were left undisturbed for 12 hrs.

The skins were then dehaired using conventional beam and blunt knife technique and fleshed in a hydraulic fleshing machine. The extent of dehairing and fibre opening were comparable to a two step enzyme based dehairing and fibre opening process in terms of hair removal and swelling. The resultant pelts were taken for further processing. Example 2

Three wet salted goatskins, weighing 2.8 kg, were soaked in 8.4 lit water for 3 hrs in a pit. Then the skins were again soaked in 8.4 lit fresh water for 2 hrs. The soaked skins were drained to remove surface water and the weight was found to be 3 kg. 30 gms alkaline bacterial protease and 3 gms sodium sulfide along with 300 ml water were added to a drum containing the soaked skins. The drum was run for 20 min followed by rest for 40 min. The cycle was repeated for 3 hrs. 22.5 gms α-amylase was added along with 2250 ml water to the drum. The drum was run for 3 hrs continuously. The treated skins were left undisturbed for 12 hrs. The skins were then dehaired using conventional beam and blunt knife technique and fleshed in a hydraulic fleshing machine. The extent of dehairing and fibre opening were comparable to a two step enzyme based dehairing and fibre opening process in terms of hair removal and swelling. The resultant pelts were taken for further processing. Example 3

Three dried buffcalfs, weighing 18 kg, were soaked in 54 lit water for 3 hrs in a pit. Then the calfs were again soaked in 54 lit fresh water for 3 hrs with 9 gms wetting agent. The soaked calfs were drained to remove surface water and the weight was found to be 22 kg. 220 gms alkaline bacterial protease and 330 gms sodium sulfhydride along with 3300 ml water were added to a drum containing the soaked calfskins. The drum was run for 20 min followed by rest for 40 min. The cycle was repeated for 3 hrs. 150 gms α-amylase, 22 gms β-amylase, 22 gms elastase and 22 gms α-galactosidase were added along with 22000 ml water to the drum. The drum was run for 3 hrs continuously. The treated calfskins were left undisturbed for 12 hrs.

The calfskins were then dehaired using conventional beam and blunt knife technique and fleshed in a hydraulic fleshing machine. The extent of dehairing and fibre opening were comparable to a two step enzyme based dehairing and fibre opening process in terms of hair removal and swelling. The resultant pelts were taken for further processing. Example 4

Four green cow sides, weighing 23 kg, were soaked in 58 lit water for 2 hrs in a pit. The soaked sides were drained to remove surface water and the weight was found to be 24 kg. 120 gms alkaline bacterial protease,180 gms α-amylase, 60 gms zymase, 60 gms maltase, 30 gms pectinase, 30 gms hyaluronidase and 360 gms sodium metasilicate were added along with 36000 ml water to a drum containing the soaked sides. The drum was run for 30 min followed by rest for 30 min. The cycle was repeated for 3 hrs. Then the drum was run for 2 hrs continuously. The treated sides were left undisturbed for 12 hrs. The sides were then dehaired using conventional beam and blunt knife technique and fleshed in a hydraulic fleshing machine. The extent of dehairing and fibre opening were comparable to a two step enzyme based dehairing and fibre opening process in terms of hair removal and swelling. The resultant pelts were taken for further processing.

Advantages

1. This process does not require any complicated control measures.

2. The process leads to significant reduction in water, COD and TS by 26, 30 and 35%, respectively. 3. It completely eliminates the formation of dry sludge.

4. Provides reduction in total solids and chemical oxygen demand.

5. Suitable for all kinds of raw materials.

6. The product produces soft and supple leathers.

7. Cheaper and commercially available chemicals and enzymes are used for the process of the present invention.

Claims

CLAIMS:

1. An improved process for dehairing and fibre opening of hide/skin, which comprises : [a] treating soaked hide/skin with

- 0.5 to 1.5% w/w, of proteolytic enzyme, exhibiting optimum activity at pH in the range of 7.5 to 11.0 and temperature in the range of 25 to 40 degree C and

- 0.25 to 1.5% w/w, of carbohydrolytic enzyme exhibiting optimum activity at pH in the range of 7.5 to 10.0 and temperature in the range of 25 to 40 degree C, either simultaneously or in different succession in the presence of 5 to 150% w/w of water, preferably under stirring conditions, optionally in the presence of not more than 1.5%w/w of sulfide or silicate salt, for a period of not less than 3 hrs at a pH in the range of 8 to 10; and

[b] removing the hair and flesh by known method to obtain dehaired hide/skin incorporated with fibre opening.

2. A process according to claim 1 , wherein the proteolytic enzyme used is selected from the group consisting of bacterial protease, fungal protease, either individually or in any combination.

3. A process according to claim 1 , wherein the carbohydrolytic enzyme used is selected from the group consisting of α-amylase, β-amylase, zymase, maltase, pectinase, elastase, hyaluronidase, α-galactosidase, either individually or in any combination.

4. A process according to claim 1 , wherein the sulfide salt used is selected from the group consisting of sodium sulfide, sodium sulfhydride, either individually or in combination.

5. A process according to claim 1 , wherein the silicate salt used is selected from the group consisting of sodium metasilicate, water glass, sodium orthosilicate, either individually or in combination.