WO2018104968A1

WO2018104968A1 - Tanning agent composition, its use and process for preparation thereof

Info

Publication number: WO2018104968A1
Application number: PCT/IN2017/050582
Authority: WO
Inventors: Raja DAMODARAN; Sangavan CHELLAPANDIAN; Parameswaran ALAGAPPAN
Original assignee: Gg Organics (P) Ltd
Priority date: 2016-12-09
Filing date: 2017-12-08
Publication date: 2018-06-14

Abstract

The invention provides a novel tanning composition for tanning and pre-tanning of leather comprising one or more silicate, glutaraldehyde, a synthetic sulfone syntan and an aldehyde syntan and process of pre-tanning using the said composition. Preferably one or more silicate includes natural and /or synthetic silicate, aluminosilicate, complex magnesium silicate, china clay and kaolin. Preferably, sulfone syntan is 4,4' dihydroxy diphenyl sulfone. Preferably an aldehyde syntan is 2,2-Bis(hydroxymethyl)propionaldehyde. The process of tanning using novel composition according to the present invention provides a pre-tanned and tanned leather having high shrinkage temperature, suppleness and white in color to make white and light colored leathers with improved light fastness.

Description

Title: Tanning agent composition, its use and process for preparation thereof Field of invention

The present invention relates to making of a tanning agent composition comprising glutaraldehyde, natural and/or synthetic silicates, synthetic sulfone syntan and aldehyde syntan is of 2,2-Bis (hydroxymethyl) propionaldehyde and its use of said composition as a sole tanning and pre-tanning agent in leather industry. The present invention relates to process for preparation of said composition in powdered form.

Background of invention

Tanning is the process of treating skins and hides of animals with organic and inorganic chemical compositions to produce leather, which results in permanent preservation of hides and skins.

Tanning process involving basic chromium sulfate (BCS) results in residual BCS in the tanning effluent. The widely used chrome tanning process is declining due to stringent norms of presence or formation of Cr (VI) in the final leather, as it is an established carcinogen. Being an Inorganic tanning system the biodegradability of the finished is also a concern.

Polymer based tanning agents, silicate based tanning agents, vegetable based tanning agents, THPS based tanning agents and modified aldehydes such as dialdehydes are few chromium- free tanning compositions used in recent past. These organic tanning systems do not result in desired finished leather products like the chrome tanned leathers.

In search for tanning and pre-tanning and tanning systems that result in desired properties of finished leathers, the inventors of the present invention produced a novel tanning agent composition, which can be used as both as a solo tanning agent and a pre-tanning agent. This new tanning and pre-tanning agent improves the leather characteristics of finished leather. Summary of invention

In an aspect, the present invention provides a tanning agent composition, which is free of basic chromium sulfate (BCS) and the said compositions comprising natural and/or synthetic silicates, glutaraldehyde, synthetic sulfone syntan and aldehyde syntan. Preferably an aldehyde syntan is of 2,2- is (hydroxymethyl)propionaldehyde and preferably synthetic sulfone syntan is of 4,4' dihydroxy diphenyl sulfone.

In another aspect, the present invention provides tanning compositions that provide substantially white leather as semi-finished product with the said composition comprising glutaraldehyde, natural and/or synthetic silicates, synthetic sulfone syntans and an aldehyde syntan preferably is of 2,2- Bis(hydroxymethyl)propionaldehyde.

In yet another aspect, the present invention provides a process for production of the tanning agent compositions comprising glutaraldehyde, natural and/or synthetic silicates, synthetic sulfone syntans and an aldehyde syntan preferably is of 2,2- Bis(hydroxymethyl)propionaldehyde.

Detailed Description of the invention

Definitions

The present invention provides a novel composition which can be used for tanning or pre-tanning of leather. It can be used for both pre-tanning and tanning and any reference to pre-tanning also means tanning and any reference to tanning also means pre-tanning.

Syntan as used herein means Synthetic tanning agent or material. Accordingly, an aldehyde syntan means a synthetic tanning agent or material which is a condensation product of an aldehyde and sulfone syntan means a synthetic tanning agent or material which is a condensation product of a sulfone.

Various aldehyde syntans and sulfone syntans are available in the market and can be used to prepare compositions of the present invention. The most preferred aldehyde syntan is of 2,2-Bis(hydroxymethyl)propionaldehyde and the most preferred sulfone syntan is of 4,4' dihydroxy diphenyl sulfone. Leather manufacturing is a complex process. It involves series of processes to arrive at a leather having desirable characteristics. The processes involved are liming, deliming, bating, pickling, pre-tanning, tanning, dyeing and finishing. Each one of these processes is complicated and requires multiple steps. Thus, pre-tanning as well as tanning are two key steps which are of decisive importance for the properties and quality of the resulting leather. Amongst the various tanning processes known in the art, mineral, vegetable and synthetic, and chrome -based tanning are conventional and widely used tanning processes. They have been employed on most kinds of skins and hides at Industrial scale and have been found to impart desired properties to leather prepared therefrom. The key desired properties of leather include high shrinkage temperature, suppleness and suitability for subsequent processing such as neutralization, retanning, fat-liquoring, dyeing, finishing.

Numerous pre-tanning and tanning materials have been proposed such as organic or metal compound tanning agents. These tanning agents known for use in the leather industry include aluminum, zirconium, titanium metal oxides or THPS (Tetrakis hydroxy phosphonium sulfate), vegetable tanning agents, glutaraldehyde, modified glutaraldehyde, carboxyl-containing epoxy resin tanning agent. Such tanning agents used in tanning processes are having number of disadvantages in operation and the leather produced is characteristically colored.

Therefore, the problem particularly observed with chrome free tanning agent is that it does not have the finished leather product properties similar to that of chrome tanning agent. More so ever light-colored leather or white leather cannot be produced. Glutaraldehyde is commonly used in tanning industry as pre-tanning or tanning agent in liquid form resulting in 70 to 80°C shrinkage temperature resulting in yellow color in the final product. The composition of the present invention is used for pre-tanning and tanning skins and hides of cow, pig, goat, and sheep; exotic animals such as alligator, ostrich, and kangaroo. The compositions of the present invention overcome the disadvantages of prior at and provides product and process for pre-tanning and tanning process that is easy to handle. The product is a powder composition or a composition in powdered form resulting in high thermal stability along with white color to leather, commonly know as wet white.

The tanning and pre-tanning composition according to the present invention comprises glutaraldehyde, at least one silicate, aldehyde syntan and synthetic sulfone syntan.

In a first aspect, the present invention provides a tanning and pretanning agent composition, which is chrome free and therefore environmentally friendly with good thermal stability, which yields white leather

In a second aspect, the present invention provides pre-tanning and / or tanning composition comprising at least glutaraldehyde, silicate and at least one syntan. Preferably the composition of the present invention contains two syntans. Most preferred two syntans are aldehyde and sulfone syntans. Under this aspect, the composition comprises of following:

1. natural and/or synthetic silicates,

2. glutaraldehyde,

3. synthetic sulfone syntans and

4. an aldehyde syntan

Preferably an aldehyde syntan is of 2,2-Bis(hydroxymethyl)propionaldehyde. Preferably a synthetic sulfone syntan is of 4,4' dihydroxy diphenyl sulfone.

Under this aspect, the various ingredients used in the tanning composition of the present invention are as provided below:

The natural and/or synthetic silicate is selected from alumino silicates and others such as China clay or Zeolite or Sepiolite or Kaolin.

The preferred aldehyde syntan used is of 2,2-Bis(hydroxymethyl)propionaldehyde. The preferred synthetic sulfone syntan used is of 4,4' dihydroxy diphenyl sulfone. In a third aspect, the present invention provides tanning compositions in the form of a powder unlike conventional solution/suspension of tanning and pre-tanning agents. The present invention adopts a novel process to arrive at novel tanning and pre-tanning composition in powder form.

In a fourth aspect, the present invention provides novel product and process of tanning and pre-tanning using novel composition in powder form. The process is simple, economical, efficient and avoids the pickling treatment process. Under this aspect, pickling treatment which is a necessary step in conventional leather tanning process can be avoided. The pickling step requires use of high concentration of acid and hence tannery effluents commonly having acid and high salt concentration must be disposed of diligently. Also pickling process consumes considerable time during tanning process.

Hence, under present invention, pre-tanning involving the novel composition of present invention dispenses with the pickling process which saves considerable time and the effluent disposal is made easy.

The tanning process of the invention is carried out directly after deliming and bating processes and provides a simple, economical, efficient pickle free process for tanning and pre-tanning of hides and skins.

The tanned and pre-tanned leathers made from the present novel product will be further treated by conventional methods for storage and/or shipment. The final leather product has desired characteristics such as high shrinkage temperature, suppleness and suitability for subsequent processing such as neutralization, retanning, fat-liquoring, dyeing, finishing in comparison to chrome tanned leather. In an embodiment, the animal hide and skin is treated with tanning and pre-tanning composition of the present invention preferably 4% by its weight in comparison to 8-10% by weight of other tanning and pre-tanning agents. The present invention provides, a process for pre-tanning of animal skins or hides comprising pre-tanning the delimed hides or skins with tanning agent composition comprising glutaraldehyde, natural and/or synthetic silicates, synthetic sulfone syntan and aldehyde syntan. An aldehyde syntan is preferably of 2,2- Bis(hydroxymethyl)propionaldehyde.

In a preferred embodiment the process for preparation of the tanning composition of the present invention involves mixing silicate such as silica with a high absorption capacity for example identified with brand name Sipernat 22 S, the sulfone syntan such as Orgtan LF, clay such as for example china clay and stirring the mixture for about 15-20 minutes. Then adding glutaraldehyde to the mixed solids by maintaining the exothermic reaction temperature. Then aldehyde syntan is of 2,2-Bis(hydroxymethyl)propionaldehyde is added to the mixture and the powder is mixed for about 15-20 minutes. The mixture in powdered form is collected / drained into a container and further vacuum dried and used for tanning of animal hide and skin. Such vacuum dried powder form is a free-flowing composition. The tanning is performed at temperature below 40°C, preferably at 30-40°C. The process of preparation of the composition is very simple and carried out in a relatively short time of around 5 hrs or less, preferably 2 hrs or less. In an embodiment, time required to prepare composition of the present invention is around 45 mins.

When delimed skin is pre-tanned, during the pre-tanning, the pH of reaction mixture gradually decreases and is in the range of from 1 to 7, particularly the pH ranges from 2 to 5. The pH of present tanning composition is in the range of from 3 to 4. In a process of tanning or pre-tanning according to the present invention, pickling is not necessary and thus omitted. Therefore, subject of the invention is a pre- tanning process as described above, wherein the delimed hide(s) or skin(s) or pelt(s) is subjected to pre-tanning with a tanning agent composition as described herein without previous pickling step. The animal skin and hides when subjected to pre-tanning process using the tanning composition of the present invention provides shrinking temperature of skin and hides in the range of 70 to 80°C. Thus, present invention provides adequate hydrothermal stability to the hides or skins. Although pickling is not essential before pre-tanning / tanning when the pre-tanning or tanning is done using composition of the present invention, the animal skin used may be pickled before subjecting to pre-tanning process to give further desired properties to leather. The tanning and / or pre-tanning compositions of the present invention are suitable for pre-tanning of both pickled or pickled free skins and hides.

After the tanning process, the exhausted tanning bath may be drained off and the tanned leather, skin or pelt may be rinsed or washed with water. The tanned and pre-tanned leathers, skins and pelts produced by the process of the present invention are suitable for further treatment in conventional way, mainly for tanning, retanning, fat-liquoring, dyeing and finishing.

The tanning and / or pre-tanning compositions of the present invention overcome the disadvantages of using Glutaraldehyde alone as sole tanning agent. The present invention has an additional advantage that treating animal skins or hide with the compositions of the present invention does not require to subject it (such treated animal skins or hides) to a pickling treatment process.

The advantages of the present invention are:

1. Treatment with compositions of the present invention provides improved characteristics to the leather such as adequately high shrinking temperature, softness and suitability for further treatment of leather to get desired finished leather.

2. The treatment with compositions of the present invention provides soft leathers which is white, and which does not turn yellow on ageing.

3. The present invention used chrome free synthetic tanning agents.

4. The compositions of the present invention are in a powder form and therefore they are easy to handle, easy to transport and easy to store. 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.

Examples

Example 1

Preparation of the tanning agent composition (Formulation 1)

In a stainless steel ribbon blender with jacketed facility for cooling, sipernat 22 S (300kg) was charged. Then Orgtan LF (70kg, the sulfone syntan) was added and the mixture was stirred for 15 minutes. China clay (100kg) was then added and the mixture was stirred for 15 minutes. To this mixture glutaraldehyde (430kg) was added very slowly by maintaining the exothermic reaction temperature below 40°C. Then an aldehyde syntan of 2,2-Bis(hydroxymethyl)propionaldehyde (100kg) was added to the mixture. After completion of addition, the powder was stirred for 15 minutes and collected / drained into a container and further vacuum dried to afford a tanning agent formulation (1000kg). This tanning formulation was used as a pre- tanning agent for picked pelt or delimed pelt with regular conventional method as example 5 described below.

The pH of tanning agent: 3.5 - 4.5

It provides Hydrothermal stability (Ts) of 70 to 80°C.

Example 2

Preparation of tanning agent composition (Formulation 2)

In a stainless- steel ribbon blender with jacketed facility for cooling, sipernat 22 S (200kg) was charged. Then Orgtan LF (200kg) was added and the mixture was stirred for 15 minutes. Zeolite (150 kg, technical grade) was added and the mixture was stirred for 15minutes. To this mixture Glutaraldehyde (400kg) was added very slowly by maintaining the exothermic reaction temperature below 40°C. Then aldehyde syntan of 2,2-Bis(hydroxymethyl)propionaldehyde (50 kg) was added slowly to the mixture. After completion of addition, the powder was stirred for 15 minutes and collected / drained into a container and further vacuum dried to afford a tanning agent formulation (1000kg). This tanning formulation is used as a pre-tanning agent for picked pelt or delimed pelt with regular conventional method as example 5 described below.

The pH of tanning agent: 3.5 - 4.5

It provides Hydrothermal stability (Ts) of 75 to 82°C.

Example 3

Preparation of the tanning agent composition (Formulation 3)

In a stainless- steel ribbon blender with jacketed facility for cooling, sipernat 22 S

(150kg) was charged. Then Orgtan LF (100kg) was added and the mixture was stirred for 15 minutes. Zeolite (150 kg, technical grade) and Kaolin (150 kg) were added and the mixture was stirred for 15minutes. To this mixture Glutaraldehyde (375kg) was added very slowly by maintaining the exothermic reaction temperature below 40°C. Then aldehyde syntan of 2,2-Bis(hydroxymethyl)propionaldehyde (75kg) was added slowly to the mixture. After completion of addition, the powder was stirred for 15 minutes and collected / drained into a container and further vacuum dried to afford a tanning agent formulation (1000kg). This tanning formulation is used as a pre-tanning agent for picked pelt or delimed pelt with regular conventional method as example 5 described below.

The pH of tanning agent: 3.5 - 4.5

It provides Hydrothermal stability (Ts) of 76 to 82°C.

Example 4

Preparation of the tanning agent composition (Formulation 4)

In a stainless- steel ribbon blender with jacketed facility for cooling, sipernat 22 S (200kg) was charged. Then Orgtan LF (50kg) was added and the mixture was stirred for 15 minutes. Zeolite (200kg, technical grade) and Sepiolite (150kg) were added and the mixture was stirred for 15minutes. To this mixture Glutaraldehyde (300kg) was added very slowly by maintaining the exothermic reaction temperature below 40°C. Then aldehyde syntan of 2,2-Bis(hydroxymethyl)propionaldehyde (100kg) was added slowly to the mixture. After completion of addition, the powder was stirred for 15 minutes and collected / drained into a container and further vacuum dried to afford a tanning agent formulation (1000kg). This tanning formulation is used as a pre-tanning agent for picked pelt or delimed pelt with regular conventional method described below. The pH of tanning agent: 3.5 - 4.5 It provides Hydrothermal stability (Ts) of Hydrothermal stability (Ts): 75 to 80°C.

Example 5: Process for tanning of animal skin without pickling process (Pickle free tanning)

Ammonium sulfate 1.0

Sodium bisulfite 0.2

Orgzyme AA 0.5 Run 90 min,

(Bating agent) Check pH : 8.0 - 8.5

Drain out

Tanning Water 100

Orgtan PFA 2.5 Run 45 min and check pH :

(solid Organic acids) 5.0-5.5

Orgtan XO (Synthetic 3.0 Run 180 min, Leave tanning agent-based on overnight (L/O)

Sulfone and

phenol)

Next day Run 20 min

Check Ts - 60+5°C

Formic acid 0.5 Run 30 min

Formic acid 0.5 Run 60 min

Check pH: pH 3.5

Tanning agent 4.0 Run 240 min

composition of the

present invention

Sodium formate 1.0 Run 30 min

Sodium bicarbonate 0.5 Run 90 min

Check pH and adjust to 4.3

Check Ts - 75°C

Drain out, Wash, pile Example 6: Process for tanning of pickled animal hide or skin (with pickling process)

Claims

We claim

A synthetic tanning composition comprising

a) natural and/or synthetic silicates;

b) glutaraldehyde;

c) synthetic sulfone syntan and;

d) an aldehyde syntan of 2,

2-Bis(hydroxymethyl)propionaldehyde

A synthetic tanning composition comprising

a) natural and/or synthetic silicates;

b) glutaraldehyde;

c) synthetic sulfone syntan of 4,4' dihydroxy diphenyl sulfone;

d) an aldehyde syntan.

3. A synthetic tanning composition comprising

a) natural and/or synthetic silicate which is a high absorption capacity / hydrophilic silica;

b) glutaraldehyde;

c) synthetic sulfone syntan;

d) an aldehyde syntan.

The synthetic tanning composition according to the claims 1 to 2 wherein natural or synthetic silicate is selected from one or more of alumino silicates, china clay, zeolite, sepiolite or kaolin.

The synthetic tanning composition comprising

a) from around 10 - 60 % of natural and/or synthetic silicates;

b) from around 10 - 60 % of glutaraldehyde;

c) from around 5 to 40 % of synthetic sulfone syntan and; d) from around 5 to 25 % of an aldehyde syntan;

wherein the composition is in powder form.

The synthetic tanning composition according to the claims 1 to 3 comprising

a) natural and/or synthetic silicate comprising hydrophilic / a high absorption capacity silica;

b) glutaraldehyde;

c) synthetic sulfone syntan of 4,4' dihydroxy diphenyl sulfone;

d) aldehyde syntan of 2,2-Bis(hydroxymethyl)propionaldehyde and; e) one or more of additional silicate, clay, china clay, kaolin.

A process for pre-tanning of animal skins or hides comprising tanning with a composition comprising

a) glutaraldehyde;

b) natural and/or synthetic silicates;

c) synthetic sulfone syntan and;

d) aldehyde syntan.

wherein the composition is in powder form.

a) glutaraldehyde;

b) natural and/or synthetic silicates;

c) synthetic sulfone syntan and;

d) aldehyde syntan;

wherein synthetic sulfone syntan is of 4,4' dihydroxy diphenyl sulfone.

a) glutaraldehyde; b) natural and/or synthetic silicates;

c) synthetic sulfone syntan and;

d) aldehyde syntan;

wherein aldehyde syntan is of 2,2-Bis(hydroxymethyl)propionaldehyde.

10. A process for pre-tanning of animal skins or hides comprising tanning with a composition comprising

a) glutaraldehyde;

b) natural and/or synthetic silicates;

c) synthetic sulfone syntan and;

d) aldehyde syntan;

wherein synthetic sulfone syntan is of 4,4' dihydroxy diphenyl sulfone and /or; wherein an aldehyde syntan is of 2,2- Bis(hydroxymethyl)propionaldehyde.

11. A process for pre-tanning of animal skins or hides comprising tanning with a composition comprising

a) from around 10 - 60 % of natural and/or synthetic silicates;

b) from around 10 - 60 % of glutaraldehyde;

c) from around 5 to 40 % of synthetic sulfone syntan and;

d) from around 5 to 25 % of an aldehyde syntan.

12. A process for preparation of a tanning agent composition comprising a) adding in a blender, a natural and/or a synthetic silicate;

b) adding a sulfone syntan and optionally blending;

c) adding one or more of silicate, china clay, kaolin and optionally blending;

d) adding glutaraldehyde and maintaining reaction temperature below 40°C;

e) adding aldehyde syntan of 2,2-Bis(hydroxymethyl)propionaldehyde and; f) blending to obtain a powder;

g) vacuum drying the powder.

13. A process for preparation of a tanning agent composition comprising

a) adding in a blender, a natural and/or synthetic silicate;

b) adding sulfone syntan and optionally blending;

c) adding one or more of a silicate, china clay, kaolin and optionally blending;

d) adding glutaraldehyde and maintaining reaction temperature below 40°C;

e) adding an aldehyde syntan and;

f) blending to obtain a powder;

g) vacuum drying the powder. wherein synthetic sulfone syntan is of 4,4' dihydroxy diphenyl sulfone or; wherein an aldehyde syntan is of 2,2-Bis(hydroxymethyl)propionaldehyde, or; wherein at least one silicate is a silica with a high absorption capacity / hydrophilic silica.

14. A pre-tanned and / or tanned leather having high shrinkage temperature and suppleness prepared by a process comprising treating animal skins or hides with a powder composition comprising

a) glutaraldehyde;

b) natural and/or synthetic silicates;

c) synthetic sulfone syntan and;

d) aldehyde syntan

wherein synthetic sulfone syntan is of 4,4' dihydroxy diphenyl sulfone or wherein an aldehyde syntan is of 2,2-Bis(hydroxymethyl)propionaldehyde or wherein at least one silicate is a silica with a high absorption capacity / hydrophilic silica.

15. A pre-tanned and / or tanned leather according to the claim 14 prepared by a process comprising treating animal skins or hides with a powder composition wherein the amount of powdered composition for treatment is around 4 % of the weight of the animal skins or hides.

16. A process of converting animal skins or hides into a final leather comprising using pre-tanning and / or tanning process using a powder composition comprising

a) glutaraldehyde;

b) natural and/or synthetic silicates;

c) synthetic sulfone syntan and;

d) aldehyde syntan

wherein the process of converting does not require pickling step / process.