Products used in hair-saving liming systems to prevent immuni- immuni-sation of hair roots and fixation of short hair

Mollescal HW Soaking auxiliary. Can be applied in hair-saving and hair-pulping processes. Prevents the hair roots from being immunized and enables hairs to be removed more easily.

Mollescal MF The liming auxiliary is added in hair-saving liming processes before the lime. It penetrates into the hair bulb and loosens the hair, which avoids the risk of immunisation of the roots.

Basozym L 10 Enzymatic liming auxiliary. Can be applied in hair-saving and hair-pulping processes on all types of raw stock. Loosens hair roots, helps to open up the skin and makes hair and melanin easier to remove.

Activity ca. 1000 LVU/g. Very effective in combina-tion with Mollescal LS, Mollescal MF or Mollescal AB.

Deliming

Purpose

Removal of mechanically deposited and chemically bound lime and of capillary lime by conversion into readily soluble salts.

BASF deliming agents

Decaltal A-N Nitrogen-free deliming agent that makes sulfi-des easier to remove by catalyzing their oxida-tion and contributes to increased safety. Pene-trates thick pelts quickly and assists in the

bating process on account of its weak hydrotro-pic action.

Decaltal ES-N Liquid For nitrogen-free deliming at pH > 8. Pelts are very clean and pale in colour. Has a weak degreasing action.

Decaltal N/ Deliming agents with a complexing action, Decaltal N Liquid based on non-swelling acids. Used to dissolve

lime deposits and to clean pelts. Can also be used in pickling.

Decaltal R Very high dissolving capacity for lime. Especially recommended for deliming unsplit hides quickly in short floats.

Bascal S Mixture of dicarboxylic acids. Promotes the action of other deliming agents. Can also be used without a float or in short floats.

Definition of deliming value, buffering capacity, lime dissolving value

Deliming value = amount of deliming agent in g necessary for neutralising 1 g calcium hydroxide.

Buffering capacity = titration according to deliming value with normal caustic soda solution from pH 8.5 to pH 10.5.

Difference = measure of buffering capacity.

Lime dissolving value = percentage of calcium hydroxide dissolved by the deliming agent according to the deliming value.

Deliming Buffering Lime dissolving

Product value capacityvalue

ca. ca. ca.

Decaltal A-N 3.6 26.5 54.5

Decaltal ES-N Liquid 1.6 – –

Decaltal N 1.7 15.5 28.0

Decaltal N Liquid 4.5 14.6 30.0

Decaltal R 1.7 18.3 62.5

Bascal S 1.8 0.2 100.0

Strength comparison of BASF deliming agents

1 part product Decal- Decal- Decal- Decal- Decal-

Bas-? tal tal tal tal tal cal

corresponds to A A-N ES-N N N R S

Liquid Liquid

Decaltal A-N – 1.0 0.6 1.5 0.6 1.0

Decaltal ES-N Liquid 1.0 – 0.6 1.6 0.6 1.0

Decaltal N 1.6 1.6 – 2.6 1.0 1.0

Decaltal N Liquid 1.5 1.5 0.4 – 0.4 0.4

Decaltal R 1.0 – 1.0 2.6 – 1.0

Bascal S 1.0 1.0 0.9 2.5 0.9 –

Amounts of deliming agent required for neutralizing 1 kg CaO 3.515 kg hydrochloric acid (37 %)

1.825 kg sulfuric acid (96 %) 1.930 kg formic acid (85 %) 4.280 kg acetic acid (50 %) 7.465 kg lactic acid (43 %) 2.210 kg boric acid (100 %)

3.710 kg sodium hydrogen sulfite (100 %) 1.910 kg ammonium chloride (100 %) 2.350 kg ammonium sulfate (100 %)

Other deliming agents

Product Effect Properties and use

Hydrochloric acid strong deliming acid Forms peptising CaCl₂. Danger of acid swelling.

Only for superficial deliming.

Sulfuric acid strong deliming acid Forms sparingly soluble CaSO₄. Risk of stain for-mation and acid swelling.

Only for superficial deli-ming.

Formic acid, strong deliming acids Deliming effect similar to

acetic acid that of mineral acids.

Less risk of acid swelling.

Salts formed have a slight buffering effect.

Lactic acid strong deliming acid Milder deliming effect due to the presence of anhydrides and lactates.

Finer grain.

Boric acid weak deliming acid Good penetration. Fixed lime is not completely removed. Fine grain.

Sodium hydrogen weak deliming acid Deliming and bleaching

sulfite effect at the same time.

Ammonium chloride weak deliming acid Conversion of Ca(OH)₂ into less plumping NH₄OH and formation of peptising CaCl₂.

Bating

Purpose

Further loosening and peptising of the fibre texture of the skin and elimination of alkali-swelling with the aid of specific enzymes.

Enzymes in bating agents

Enzymes are biological catalysts that accelerate the reactions without themselves being modified. Enzymes, which act specifically on proteins, are called proteases.

The following proteases are used as bating agents:

1. Pancreas proteases (trypsin) 2. Mould fungus proteases 3. Bacteria proteases

Bating agents with pancreas proteases (mainly used) develop their opti-mum effect in slightly alkaline pH range (8.0 – 8.5).

Composition:

Enzymes, wood flour as carrier substance, ammonium salts, neutral salts as buffering and deliming agents.

Bating agents with mould fungus proteases develop their best effect at pH 3.5 – 5.0, and bating agents with bacteria proteases at pH 6.0 – 7.2.

The buffering substances in these bating agents are among others sulfi-tes and bisulfisulfi-tes.

Commercial bating agents may contain a mixture of all three types of proteases.

Influencing the bating effect

Temperature: The rate of enzymatic reaction increases with rising temperature.

Bating temperature used in practice: 30 – 37 °C.

Higher temperatures cause damage to the skin material.

Neutral salt content: Higher concentrations may reduce or inactivate the bating effect.

Rating of bating agents

The enzyme value is the number of enzyme units in 1 g bating agent. One enzyme unit has the fermentative capacity to digest 1.725 mg casein.

Enzyme value = LVU

Enzyme unit = LVU x 1.725

The enzyme unit is determined according to Löhlein-Volhard by allowing the bating agent to act upon an alkaline casein solution. Undigested casein is precipitated with hydrochloric acid and sodium sulfate. The alkali consumption in re-titration is a direct measure of the enzymatic effectiveness of the bating agent.

This titration method was recently supplemented by a photometric method with trinitrobenzene sulfonic acid (Tegewa method). Almost all liberated amino groups are also detected after hydrolysis by proteolytic enzymes.

Pancreas-based bating agents mainly used in practice:

1. Weak bating agents = 500 – 1000 LVU

(technical leather, harness leather)

2. Medium strong bating agents = 1000 – 1500 LVU (upper leather, lining leather, fancy leather)

3. Strong bating agents = 1500 – 2000 LVU

(glove, clothing leather)

BASF bating agents

Basozym C 10 Bating agent based on pancreatic enzymes for use on all types of leather.

Activity ca. 1000 LVU/g.

Basozym CS 10 Special enzyme preparation for opening up small skins and fur skins in acid media.

Activity ca. 900 LVU/g.

Degreasing

Degreasing methods

1. Wet degreasing of pelts and moist leathers