Chemicals Used in Leather Processing BY EGEMEN

Chemicals Used in Leather Processing

Useful Information

The following is a list of chemicals commonly used in leather making:

Beamhouse and Tanyard

Biocides 

Biocides prevent the growth of bacteria which can damage the hides or skins during the soaking process

Surfactants

Surfactants are used to help with the wetting back of the hides or skins

Degreasers

Degreasers help with the removal of natural fats and greases from the hides or skins

Swell regulating agents

Swell regulating agents help prevent uneven swelling of the hides or skins during liming

Lime

Lime is used to swell the hides or skins

Sodium sulphide

Sodium sulphide chemically destroys the hair on hides or skins

Sodium hydrosulphide

Sodium hydrosulphide chemically destroys the hair on hides or skins. It does not create as much swelling as sodium sulphide

Low sulphide unhairing agents

Low sulphide unhairing agents help to reduce the amount of sulphides used in a tannery thus reducing the environmental impact of tanneries

Caustic soda

Caustic soda is used during the liming process to help swell the hides or skins

Soda ash

Soda ash is used during the soaking or liming processes to help raise the pH of the hides or skins

Ammonium sulphate

Ammonium sulphate is used during the deliming process and helps remove lime from the hides or skins

Ammonium chloride

Ammonium chloride is used during the deliming process and helps remove lime from the hides or skins

Sodium metabisulphite

Sodium metabisulphite is used during the deliming process and helps prevent the formation of toxic hydrogen sulphide gas during deliming. It also acts as a bleaching agent

Formic acid

Formic acid is used during the pickling process to lower the pH of the hides or skins

Sulphuric acid

Sulphuric acid is used during the pickling process to lower the pH of the hides or skins

Salt

Salt is used during the pickling process to prevent acid swelling of the hides or skins

Sodium formate

Sodium formate is used during the tanning process to assist with the penetration of chromium tanning salts into the hides or skins

Chromium sulphate

Chromium sulphate is the tanning agent used to make wet blue

Aldehyde tanning agents

Aldehydes are tanning agents used to make wet white

Magnesium oxide

Magnesium oxide is used during basification and raises the pH of the hide or skin to allow the chromium or aldehyde to chemically bind to the skin protein

Fungicide

Fungicides are chemicals that are used to prevent the growth of moulds or fungi on tanned hides or skins

Dyehouse

Surfactants / Wetting agents

Surfactants help in the wetting back of the wet blue in the dyehouse

Degreasers

Degreasers help remove grease or fats that may be present on the wet blue as a result of the wet blue coming into contact with machinery

Sodium formate

Sodium formate helps raise the pH during the neutralization process

Sodium bicarbonate

Sodium bicarbonate helps raise the pH during the neutralization process

Formic acid

Formic acid reduces the pH for the rechroming process or helps with chemically fixing dyehouse chemicals to the leather at the end of the dyehouse processes

Chrome syntans

Chrome syntans are used during rechroming to improve the softness of the final leathet

Chromium sulphate

Chrmium sulphate is used during rechroming to improve the softness of the final leather

Syntans

Syntans are used to give properties such as softness, fullness, roundness to the leather

Resins

Resins are used to give fullness and a tight grain to the leather

Polymers

Polymers are used to give fullness and a tight grain to the leather

Dyes

Dyes are used to give the leather a colour desired by the customer

Dyeing auxiliaries

Dyeing auxiliaries help disperse the dyes evenly

Fatliquors

Fatliquors are oils that are added to leather to give softness to the final leather

Finishing

Acrylic resins

Acrylic resins give specific properties to the leather finish such as adhesion, water resistance

Butadiene resins

Butadiene resins give specific properties to the leather finish such as good coverage

Polyurethane resins

Polyurethane resins give specific properties to the leather finish such as good toughness and good lightfastness

Fillers

Fillers help fill small blemishes on the leather surface

Dullers

Dullers help reduce the gloss of the finish

Crosslinkers

Crosslinkers are used to toughen the leather finish and improve the water resistance properties of polyurethanes

Handle modifiers

Handle modifiers are used to give the leather surface a waxy or slippery feel

Nitrocellulose lacquers

Nitrocellulose lacquers are used in the top coat of a leather finish

Acrylic lacquers

Acrylic lacquers are used in the top coat of a leather finish

Polyurethane lacquers

Polyurethane lacquers are used in the top coat of a leather finish

Viscosity modifiers

Viscosity modifiers are used to increase the viscosity of a finish mixture

Pigments

Pigments are colouring agents that help hide defects on the leather surface

Dyes

Dyes are colouring agents that are used to slightly change the colour of the leather finish or to give the leather finish a more natural look

Defoamers

Defoamers are used to prevent bubbles from forming in the finish mixture