NL2027083B1

NL2027083B1 - Process for deliming of hides, skins or pelts

Info

Publication number: NL2027083B1
Application number: NL2027083A
Authority: NL
Inventors: Gerardus Josephus Maria Van Der Ham Andreas
Original assignee: Stahl Int B V
Priority date: 2020-12-09
Filing date: 2020-12-09
Publication date: 2022-07-07
Also published as: EP4259832A1; WO2022124892A1

Abstract

The present invention relates to a novel process for deliming of skins, hides or pelts using aldaric acid or uronic acid e.g. meso-galactaric acid or D-galacturonic acid, as deliming auxiliary agent, preferably in combination With another type of deliming agent such as a cyclic ester of carbonic acid, and to the thus obtained delimed skins, hides or pelts.

Description

P128936NL00 Process for deliming of hides, skins or pelts The present invention relates to a novel process for deliming skins/hides/pelts to obtain delimed skins/hides/pelts of good quality.

It is well known that in the leather manufacturing process, pre- treatments for raw skins/hides/pelts shall be done before tanning and crusting. The leather manufacturing process generally consists of the following steps: soaking (dirt removal and re-hydration); dehairing (removal of hair, traditionally part of the liming process); liming (removal of hair and degradation of fats and proteins as well as swelling of the collagen structure, so called opening up); fleshing (removal of fatty tissue); splitting (horizontal cutting into grain split and flesh split); deliming (releasing lime, degraded proteins/fat and reducing pH); bating (removal of non-structural proteins, scut removal and fibre opening); pickling (lowering of pH value to around 3) and tanning (stabilization of the skin or hide matrix). Beamhouse processes in leathering manufacturing accounts for 80% of organic waste in effluent and sludges. Among these, around 70% comes from the liming process.

During the dehairing step the skins/hides/pelts are normally treated with an alkaline and a sulphide solution which aims at breaking the hair structure at its weakest point, the root of the hairs, by reduction of sulphur-sulphur bonds in the keratin. Lime is normally used as the vital alkaline agent to achieve graduate and controlled swelling effect. After liming, deliming is required to bring the pH value of pelt to a proper state of alkalinity. Deliming is about removing calcium hydroxide from the skins/hides/pelts, including surfaces and inner parts thereof, and lowering the pH value of skins/hides/pelts until around 8.5 to 7. A lower pH means the swelling is reduced, which causes the degraded protein/fat from inside the hide to flow into the float. To prevent grain damage and acid swelling, mild deliming should be carried out by applying satisfactory deliming agents which have good buffering capacity and are sufficient in lime removal.

Chapter 7 of text book Tanning Chemistry: The Science of Leather by Tony Covington, 2009, ISBN 9780854041701, pages 154-165 lists several types of deliming agents: washing with plenty of water; strong acids; weak acids; acidic salts; ammonium salts; magnesium sulphate; hydroxyl ‘sinks’ and carbon dioxide.

Conventional deliming agents used in leather industry are mainly based on ammonium salts, such as ammonium sulphate, ammonium chloride, etc.

US 2318454, which was granted in 1943, used ammonium salt as deliming component.

Ammonium salts have been widely accepted in leather industry due to the following characteristics: 1) cheap raw material prices compared with organic compounds; i1) buffering effect, which provides a narrow pH range in deliming float and prevents surface damage of the pelts and a mild removal of lime from the limed pelt.

Ammonium salts are known as good buffering agents in deliming recipes, that generate leather with a clean surface, even dying properties, and good handle feeling.

When ammonium salts are used for deliming purposes, they react with calcium hydroxide, which is physically and chemically bound to the lmed pelt.

For instance, the reactions between ammonium sulphate or ammonium chloride and calcium hydroxide are illustrated below: Ca(OH)2+ NH4Cl — CaCl: + NH3+ H20 Ca(OH)z + (NH4)2S04— CaSOs+ NHs + H20 Ammonium based deliming agents have two shortcomings, which limit their application in industry.

The ammonia that is released in this reaction results in undesired exposure to workers and in a necessity to remove ammonia from tannery effluent, which increases the costs and complexity/duration of wastewater treatment.

Due to the high NH: pollution induced by ammonium salts, three categories of acids have been explored as deliming agents in literature and patents: 1) inorganic acid, like boric acid; 11) small molecular organic acids,

including lactic acid, citric acid, succinic acid, or adipic acid; 111) macromolecules, such as polyimides, polysuccinimide and hydroxy polysuccinimide.

Sodium metabisulfite, NazS20s3, is often included in ammonium salt deliming, but its function is primarily to scavenge residual sulphide after lime/sulphide dehairing.

Boric acid has a very good buffering effect in deliming and is used as an alternative deliming agent, and enables even deliming across the thick pelts, thus generating leather with good quality. However, boric acid has reproductive toxicity and is listed in SVHC (substance of very high concern), according to REACH (Registration, evaluation, authorization and restriction of chemicals). A buffering system, which has low impact on workers' health and environment is currently lacking.

WO 2020126987 describes the use of pseudoalkali metal, alkali metal and/or alkaline earth metal salts of sugar acids in leather production, in particularly as swelling regulators during the liming step.

Yuhang Zeng et el, in JALCA, Vol 113, 2018 "A Cleaner Deliming Process Using Sodium Gluconate for Reduction in Nitrogen Pollution in Leather Manufacture” describes the use of sodium gluconate, citric acid and ammonium sulphate as a method to reduce the nitrogen effluent for the deliming step, but still an amount of ammonium sulphate is used, albeit a reduced amount.

EP 2956558 describes the use of methanesulfonic acid in leather manufacturing, including the deliming step.

EP 3456848 describes the use of certain phenolic compounds as deliming agent, with as advantage that the deliming agent contains no boric acid or ammonium salts, is quite environmentally friendly, meanwhile provides similar deliming effect as ammonium salts. The other advantage is that the deliming agent avoids dropping the pH value of the deliming solution to less than five even with overdosing of deliming agent, thus will not destroy the crust of the pelts and could provide soft handle feeling of the curst.

EP 3425068 describes the use of amino acids as deliming agents.

EP 3425069 describes the use of a deliming agent, which is free of ammonium and boric acid, comprising protein hydrolysate, which is produced according to a method comprising hydrolyzing hair, shavings, trimmings and/or feathers to generate amino acid and/or amino acid salt, then obtaining the protein hydrolysate.

CN 105177192 discloses a non-ammonium deliming agent comprising a component A, a component B and a component C.

The component A is one or more of sodium sulphate, potassium sulphate, calcium sulphate, sodium chloride, potassium chloride, and calcium chloride.

The component B is one or more of glycollic acid, acetic acid, citric acid, chloroacetic acid, and boric acid.

The component C is a molecular sieve.

WO 2013107233 describes the use of polysuccinimides selected from polysuccinimide and hydroxyl polysuccinimide as ammonium-free deliming agent.

Polyimides, polysuccinimides are polymers, which are slow in penetrating into thick limed pelts.

CN 102010917 describes the use of a mixture of 60 to 80 parts of organic acid A, 15 to 30 parts of organic acid B, 5 to 30 parts of inorganic salt, and 1 to 10 parts of additives, as a deliming agent.

The organic acid A 1s citric acid, succinic acid, glutaric acid, nylon acid or malonic acid; the organic acid B is gluconic acid or sulfosalicylic acid; the inorganic salt is sodium hydrogen sulphate, thiosulfate sodium sulphate or sodium sulphite; the additives are manganese sulphate, manganese acetate or manganese chloride.

KR 100947129 describes the use of a mixture of 88% to 90% of an organic acid selected from the group consisting of boric acid, lactic acid, or a mixture thereof, and 10% to 12% of a pH adjuster as a deliming agent.

DE 2113214 describes the deliming of lime-soaked unhaired hides with an aqueous solution of aminoacid(s) or aminoacid salt(s) followed by treating at 20-50 °C with a mixed enzyme of papaine and pancreatine until desired drenching effect is reached.

Since the use of ammonium salts, numerous trials have been done to seek for a safe, sufficient, and mild deliming agent, as described above.

5 However, for many years, environmental friendly deliming agents which have a comparative deliming capacity, similar to ammonium salts and have a high penetration rate are still lacking and in mdustry the only ammonium-free methods in use employ boric acid, a combination of a weak acid and cyclic carboxylic ester, or a pressurized system with carbon dioxide gas for which special equipment is required. A major disadvantage of boric acid is that it has reproductive toxicity and is listed in SVHC (substance of very high concern), according to REACH (Registration, evaluation, authorization and restriction of chemicals) The object of the present invention is to provide a process for deliming skins/hides/pelt that provides skins/hides/pelts of good quality.

It is a further object of the present invention to provide deliming auxiliary agents for skins/hides/pelts to be used preferably in combination with another type of deliming agent, that have bio-based origin, that lead to less waste than the currently used deliming agents, that lead to less polluted wastewater, that lead to similar quality of crust and leather and yet are very effective deliming auxiliary agents. The term deliming auxiliary agent is used in the context of the present invention to refer to a compound having deliming capabilities but that operates best when used in combination with another type of deliming agent.

According to the present invention a process for deliming of hides, skins or pelts is provided, comprising treating the hides, skins or pelts with an aldaric and/or uronic acid as deliming auxiliary agent in an aqueous solution, preferably in combination with another type of deliming agent, in the deliming step resulting in a good quality of crust and good final leather, while the usage of such aldaric acids or uronic acid results in a lower COD (chemical oxygen demand) in the effluent. A further advantage of the use of an aldaric acid and/or an uronic acid, compared to industry-standard weak acids, is their biobased origin, because there is currently a big driving force for companies and the chemical industry in particular, for corporate responsibility and the use of sustainable or renewable sources of raw materials. Consumers are very interested in products that have been treated with "natural" materials that help to reduce fossil depletion, reduce our carbon dioxide footprint, and are derived from renewable materials.

While reacting with calcium ion from lime, the carboxylic groups from the aldaric and/or uronic acid forms soluble calcium salts, enabling the effective dissolution of lime and produce wet blue/ wet white hides/skins/pelts with clean surface.

Aldaric acids are characterised by the formula HOOC-(CHOH)n- COOH. Examples of aldaric acids are meso-alaric acid, meso-galactaric acid (also known as mucic acid), D-altralic acid, L-altralic acid, D-glucaric acid (also known as saccharic acid), L-glucaric acid, D-idaric acid, L-idaric acid, D-mannaric acid, L-mannaric acid, xylaric acid. A preferred aldaric acid for use in the present invention is meso-galactaric acid.

Uronic acids are characterized by the formula HOOC-(HC(OH))n- CHO. Examples of uronic acids are D-fructuronic acid, D-tagaturonic acid, D-glucuronic acid, D-galacturonic acid, D-mannuronic acid, L-iduronic acid and L-guluronic acid. A preferred uronic acid for use in the present invention is D-galacturonic acid.

At least one aldaric acid or at least one uronic acid is used as deliming auxiliary agent according to the present invention but also combinations of more than one aldaric acid or more than one uronic acid can be used; as well as combinations of aldaric acids and uronic acids.

The amount of deliming auxiliary agent for use in the present invention is strongly dependent on the thickness of the pelts (after fleshing and/or splitting) and the amount of lime used in the liming step (i.e. pH inside the pelt). The amount of deliming auxiliary agent and optional additional deliming agent is preferably chosen such that at least 90%

penetration of the leather is achieved, wherein penetration is meant to achieve a change of pH to below 8 inside at least 90% of the volume of the leather, which can be monitored by using pH-indicators, such as phenolphthalein. A preferred weight ratio of the amounts of deliming auxiliary agent and deliming agent is between 10/100 and 150/100, and more preferably between 20/100 and 120/100. The used amount of deliming agent will mostly be dependent on the thickness of the pelt and the used amount of deliming auxiliary agent will be dependent on the amount of lime, the resulting pH and also on the thickness of the pelt.

In a preferred embodiment, the deliming agent that is preferably used in combination with the deliming auxiliary agent of the present invention, is also free of ammonium and boric acid, and is most preferably a cyclic ester of carbonic acid. Examples of cyclic esters of carbonic acids are ethylene carbonate, propylene carbonate, trimethylene carbonate and glycerol carbonate. A preferred cyclic ester of carbonic acid for use in the present invention is glycerol carbonate.

In another embodiment, the deliming auxiliary agent of the present invention is used in combination with an ammonium salt, wherein the ammonium salt functions as the deliming agent and wherein the use of the deliming auxiliary agent of the invention results in a reduction of the amount of ammonium salt that is needed to achieve satisfactory deliming meaning a penetration of the leather of at least 90 % is reached. A 30% to 60% reduction of the amount of ammonium salt needed can be achieved according to the present invention, while penetration of more than 90% can still be accomplished. Examples of suitable ammonium salts are ammonium sulphate and ammonium chloride.

Compared with purely ammonium salt based deliming agents in the deliming process, the deliming process of the present invention is more environmentally friendly. The deliming auxiliary agent of the present invention has the following features: 1) aldaric acids and uronic acids are safe compounds both to environment and workers; 2) aldaric acids and uronic acids will not introduce ammonia into the deliming effluent; 3) the deliming auxiliary agent can be obtained easily from sugar wastes, which decreases the cost of the deliming agent; 4) aldaric and uronic acids can be obtained from sugar wastes, which lowers the environmental footprint, such as the COD, of the deliming process; while the leather obtained is of similar quality. Beamhouse process Dehairing Dehairing is conventionally performed with sulphide and lime (calcium hydroxide). The dehairing treatment is generally carried out in connection with mechanical action, e.g using a paddle, drum, or mixer as mechanical agitation to accelerate the process. Liming The liming step is the conventional final dehairing step in the beamhouse process, which generally uses sulphide to reduce the disulphide bridges in the keratin molecules, and calcium hydroxide to loosen the collagen structure and to release interfibrillary non-collagenous proteins. The last remnants of hair are removed hereby. Deliming In the beamhouse process, deliming is performed after the liming process, to remove the liming agent from the pelts and to reduce the pH to

8.5 to 7. The reduction in pH causes the swelling to reverse, which causes an outflow of degraded protein/fat to the float. This is important to prepare the pelt for the remaining part of the beamhouse process. Pickling and Tanning These processes are the remaining steps in the beamhouse process and will not be affected by the modified procedures described above. Some beamhouse processes also include a bating step, which serves to remove additional proteins, this is however an optional step in the beamhouse process of the present invention. The skilled person in the art will know how to conduct these steps.

The deliming process of the present invention is exemplified below in detail and generally comprises the following steps, wherein the percentages are the weight percentages compared to the weight of the pelt (pelt being referred as the hides after fleshing and splitting): 1) Optionally, the limed skins/hides/pelts are washed in a drum with 50-200% of water together with 0.0-0.1% of a degreasing agent during 10 to 40 minutes, after which the liquid is drained from the drum.

11) The washed pelt is pre-delimed in a drum with a mixture of 20- 200% of water of moderate temperature and 0.0-0.1% of an optional degreasing agent. Next, 0.1-0.5% of the deliming auxiliary agent of the present invention and optionally 0.02-0.2% of sodium metabisulfite is added to initiate the deliming process. The mixture is run during 10 to 60 minutes and then the drum is drained.

(in) The pre-delimed pelt is delimed in a drum with a mixture of 10-60% of water of moderate temperature, 0.0-0.2% of an optional probiotic auxiliary, 0.0-0.1% of an optional degreasing agent and optionally 0.02-0.2% of sodium metabisulfite. The mixture is run during 5 to 20 minutes.

(iv) 0.1-0.5% of the deliming auxiliary agent is added and the mixture is run between 5 to 20 minutes. In this step the pH is decreased to about 8. In case esters of carbonic acid are used as deliming agent in step (v) it is beneficial to first decrease the pH to 8 to improve the efficiency of the deliming agent.

(v) Subsequently, 0.5-3% of a deliming agent is added and the mixture is run between 10 and 60 minutes.

(vi) In several consecutive additions, 0.1-0.5% of the deliming auxiliary agent is added per addition to the drum to maintain a pH of below 8 and to achieve a penetration of at least 90%. After the first additions, the mixture is run during 10 to 60 minutes, and after the last addition, the mixture is run between 60 and 180 minutes.

(vi) After deliming is complete, the liquid is drained and the optional bating is started.

In the above described process the delimining auxiliary agent is added in several stages to decrease the pH in small steps.

Thereafter, using conventional methods, crust is obtained after tanning (preferably Easywhite tanning, which is a tradename from Stahl Europe BV for chrome-free tanning), retanning, neutralization, dyeing and fatliquoring.

The crust or leather obtained by using the process of the present invention is of good quality. The feel of the leather is similar as when using a traditional deliming agent. These properties are visually and tactilely assessed.

The following examples serve to illustrate the invention, but they are not intended to limit it thereto: Example 1 — Comparative (reference; Decaltal Pic S) Dutch cattle hide that has been soaked, dehaired, limed and fleshed in conventional way was splitted at 4 mm and used for the application trial. Percentages are weight percentages compared to the weight of the pelt. The deliming process comprised the following steps: (1) Limed pelt was washed with a mixture of 120% of water of 30°C, 0.05% of a degreasing agent (Eusapon OC; obtainable from Stahl Europe BV), and 0.10% of sodium metabisulfite for 20 minutes and then the drum was drained.

(11) The washed pelt was pre-delimed in a drum with a mixture of 100% of water of 30°C combined with 0.05% of a degreasing agent (Eusapon OC: obtainable from Stahl Europe BV), 0.10% of sodium metabisulfite and

0.20% of acid (Decaltal Pic S; a mixture containing succinic acid, glutaric acid and adipic acid; obtainable from Stahl Europe BV), to start the deliming process. The mixture was ran for 20 minutes and then the drum was drained. Decaltal Pic S is known as a deliming auxiliary agent.

(iu) The pre-delimed pelt was delimed in a drum with a mixture of 20% of water of 30°C, 0.10% of a probiotic auxiliary (ProDegreaze; obtainable from Stahl Europe BV), 0.05% of a degreasing agent (Eusapon OC; obtainable from Stahl Europe BV) and 0.20% of sodium metabisulfite. The mixture was ran for 10 minutes.

(iv) 0.30% of acid (Decaltal Pic S; a mixture containing succinic acid, glutaric acid and adipic acid; obtainable from Stahl Europe BV) was added and the mixture was run for 10 minutes.

(v) Subsequently, 1.50% of a deliming agent (Decaltal ES-N liq; a mixture containing cyclic esters of alkyl carbonates; obtainable from Stahl Europe BV) was added and the mixture was run for 30 minutes.

(vi) In four additions, 0.20% of acid (Decaltal Pic S; a mixture containing succinic acid, glutaric acid and adipic acid; obtainable from Stahl Europe BV) was added per addition to the drum. After the first three additions, the mixture was run for 30 minutes, and after the last addition, the mixture was run for 90 minutes.

(vi) After deliming was complete, water was drained and bating was started by adding 60.0% of water of 35 °C, 0.50% of enzymes (Bemanol RS-305; obtainable from Stahl Europe BV) and 0.05% of a degreasing agent (Eusapon OC; obtainable from Stahl Europe BV). The drum was run for 40 minutes and then drained.

Thereafter, using conventional methods, crust was obtained after Easywhite tanning (a tradename from Stahl Europe BV for chrome-free tanning), retanning, neutralization, dyeing and fatliquoring.

Chemical Oxygen Demand (COD) was measured according to ISO

15705. A lower COD value, expressed in mg per kg of skin/pelt, is better. BOD; was measured according to EN 1899-1. The COD measured was 9748 mg Ov/keg.

Example 2 (galactaric acid instead of Decaltal Pic S) The process of Example 1 was followed, except that galactaric acid was used as deliming auxiliary agent instead of Decaltal Pic S, in the same amounts and with same timing.

The speed of the deliming step was monitored with a pH-indicator solution, and the colour change and the colour distribution among the thickness of the crust showed that the speed of deliming was similar as in Comparative Example 1.

Chemical Oxygen Demand (COD) was measured according to ISO

15705. A lower COD value, expressed in mg per kg of skin/pelt, is better. The COD measured was 8230 mg Og/kg. The COD of Example 2 was lower than that of Comparative Example 1.

Example 3 (galacturonic acid instead of Decaltal Pic S) The process of Example 1 was followed, except that galacturonic acid was used as deliming auxiliary agent instead of Decaltal Pic S, in the same amounts and with same timing.

The speed of the deliming step was monitored with a pH-indicator solution, and the colour change and the colour distribution among the thickness of the crust showed that the speed of deliming was somewhat slower than in Comparative Example 1.

Example 4 (Glycerol carbonate instead of Decaltal ES-N) The process of Example 1 was followed, except that glycerol carbonate was used as deliming agent instead of Decaltal ES-N, in the same amounts and with same timing.

Example 5 (Glycerol carbonate instead of Decaltal ES-N and galactaric acid instead of Decaltal Pic S) The process of Example 1 was followed, except that galactaric acid was used as deliming auxiliary agent instead of Decaltal Pic S, and glycerol carbonate was used as deliming agent instead of Decaltal ES-N, in the same amounts and with same timing.

Chemical Oxygen Demand (COD) was measured according to ISO

15705. A lower COD value, expressed in mg per kg of skin/pelt, is better.

The COD measured was 8415 mg O»>/kg. The COD of Example 5 was lower than that of Comparative Example 1.

Example 6 — Comparative (reference ammonium sulphate reduction trials) Dutch cattle hide that has been soaked, dehaired, limed and fleshed in conventional way was splitted at 4 mm and used for the application trial. Percentages are weight percentages compared to the weight of the pelt. The deliming process comprised the following steps: (1) Limed pelt was washed with a mixture of 120% of water of 30°C, 0.05% of a degreasing agent (Eusapon OC; obtainable from Stahl Europe BV), and 0.10% of sodium metabisulfite for 20 minutes and then the drum was drained.

(in) The washed pelt was pre-delimed in a drum with a mixture of 100% of water of 30°C combined, 0.05% of a degreasing agent (Eusapon OC; obtainable from Stahl Europe BV), 0.10% of sodium metabisulfite and 0.20% of ammonium sulphate, to start the deliming process. The mixture was ran for 20 minutes and then the drum was drained.

(iv) 0.50% of ammonium sulphate was added and the mixture was run for 10 minutes.

(v) In four additions, 0.20% of ammonium sulphate was added per addition to the drum. After the first three additions, the mixture was run for 30 minutes, and after the last addition, the mixture was run for 90 minutes.

A total amount of 1.3% of ammonium sulphate was used.

Example 7 (ammonium sulphate partly replaced by galactaric acid) Dutch cattle hide that has been soaked, dehaired, limed and fleshed in conventional way was splitted at 4 mm and used for the application trial. Percentages are weight percentages compared to the weight of the pelt. The deliming process comprised the following steps: (1) Limed pelt was washed with a mixture of 120% of water of 30°C and 0.05% of a degreasing agent (Eusapon OC; obtainable from Stahl Europe BV) for 20 minutes and then the drum was drained.

(11) The washed pelt was pre-delimed in a drum with a mixture of 100% of water of 30°C combined, 0.05% of a degreasing agent (Eusapon OC; obtainable from Stahl Europe BV), 0.10% of sodium metabisulfite and 0.20% of ammonium sulfate, to start the deliming process. The mixture was ran for 20 minutes and then the drum was drained.

(iu) The pre-delimed pelt was delimed in a drum with a mixture of 20% of water of 30°C, 0.10% of a probiotic auxiliary (ProDegreaze; obtainable from Stahl Europe BV), 0.05% of a degreasing agent (Eusapon

OC; obtainable from Stahl Europe BV) and 0.20% of sodium metabisulfite. The mixture was ran for 10 minutes.

(iv) 0.50% of ammonium sulfate was added and the mixture was run for 10 minutes.

(v) In four additions, 0.20% of galactaric acid was added per addition to the drum. After the first three additions, the mixture was run for 30 minutes, and after the last addition, the mixture was run for 90 minutes.

The speed of the deliming step was monitored with a pH-indicator solution, and the colour change and the colour distribution among the thickness of the crust showed that the speed of deliming was similar as in Comparative Example 6.

A total amount of 0.5% of ammonium sulphate was used.

Example 8 (ammonium sulphate partly replaced by galacturonic acid) The process of Example 7 was followed, except that galacturonic acid was used instead of galactaric acid, in the same amounts and with same timing.

Example 9 - Comparative (ammonium chloride) The process of Example 6 was followed, except that ammonium chloride acid was used instead of ammonium sulphate, in the same amounts and with same timing.

A total amount of 1.3% of ammonium chloride was used.

Example 10 (ammonium chloride partly replaced by galactaric acid) The process of Example 7 was followed, except that ammonium chloride was used instead of ammonium sulphate, in the same amounts and with same timing.

The speed of the deliming step was monitored with a pH-indicator solution, and the colour change and the colour distribution among the thickness of the crust showed that the speed of deliming was similar as in Comparative Example 9.

A total amount of 0.5% of ammonium chloride was used.

Example 11 (ammonium chloride partly replaced by galacturonic acid) The process of Example 10 was followed, except that galacturonic acid was used instead of galactaric acid, in the same amounts and with same timing.

Example 12 — evaluation of leather Leather samples obtained from Examples 1 to 11 were compared with each other. All leather samples, those according to the invention and the comparative ones, were comparable in quality.

Claims

Conclusions

A process for descaling hides, pelts or pelts comprising treating the hides, pelts or pelts with a descaling acid and/or uronic acid as a descaling aid.

The process of claim 1, wherein the descaling aid is selected from the group consisting of mesoalaric acid, meso-galactaric acid (also known as mucinic acid), D-altraalic acid, L-altraalic acid, D-glucaric acid (also known as saccharic acid), L -glucaric acid, D-1daric acid, L-idataric acid, D-manneric acid, L-mannaric acid, xylaric acid, D-fructuronic acid, D-tagaturonic acid, D-glucuronic acid, D-galacturonic acid, D-mannuronic acid, L-iduronic acid or L-guluronic acid.

The process of claim 1 or 2, wherein the descaling aid is meso-galactaric acid (also known as mucinic acid) or D-galacturonic acid.

The process according to any one of claims 1 to 3, wherein there acid or uronic acid is used as a descaling aid in combination with another type of descaling agent.

The process of claim 4, wherein a cyclic ester of carbonic acid is used as the descaling agent.

The process according to any one of claims 4 or 5, wherein glycerol carbonate is used as the descaling agent.

The process according to any one of claims 4 to 6, wherein the weight ratio of the amounts of descaling aid and descaling agent is between 10/100 and 150/100, preferably between 20/100 and 120/100.

The process according to any one of claims 4 to 7, comprising the following steps wherein the percentages are percentages by weight compared to the weight of the pelts (wherein pelt refers to the pelts after defatting and splitting): 1) Optionally, the limed hides/pelts/furs in a drum washed with 50-200% water along with 0.00-0.1% of a degreasing agent for 10 to 40 minutes, after which the liquid is drained from the drum.

11) The washed coat is pre-descaled in a drum with a mixture of 20-200% water of moderate temperature and 0.00-0.1% of an optional degreasing agent, Optional 0.02-0.2% sodium metabisulfite and 0 .1-0.5% of the descaling aid, to start the descaling process. The mixture is rotated for 10 to 60 minutes and then the drum is emptied.

(111) The pre-descaled coat is descaled in a drum with a mixture of 10-60% water of moderate temperature, 0.0-0.2% of an optional probiotic aid, 0.00-0.1% of a optional degreaser and optional 0.02-0.2% sodium metabisulfite. The mixture is swirled for 5 to 20 minutes.

(iv) 0.1-0.5% of the descaling aid is added and the mixture is rotated between 5 and 20 minutes.

(v) Then 0.5-3% of a descaling agent is added and the mixture is rotated for between 10 to 60 minutes.

(v1) In several successive additions, 0.1-0.5% of the descaling aid is added to the drum per addition. After the first additions, the mixture is rotated for 10 to 60 minutes and after the last addition, the mixture is rotated for between 60 to 180 minutes.

(vi) After descaling is complete, the liquid is drained and optional softening is started.

9. Descaled hides, pelts or furs obtainable by the process as defined in any one of claims 1 to 8.