roll # 24 leather industry

8/4/2019 Roll # 24 Leather Industry

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CHROME LEATHER

Leatheris a durable and flexible material created via the tanning of putrescible animal rawhide and skin,primarily cattle hide. It can be produced through different manufacturing processes, ranging from

cottage industry to heavy industry.

History of Leather:

From prehistoric times man has used the skins of animals to satisfy his basic needs. He has used hides to

make clothing, shelter, carpets and even decorative attire. To the Egyptian lady, a fur piece was highly

prized as her jewellery. From leather, manmade footwear, belts, clothing, containers for liquids, boats

and even armor. The principle protective armor of the Roman soldier was a heavy leather shirt.

In recorded history, pieces of leather dating from 1300 B.C. have been found in Egypt. Primitive societiesin Europe, Asia and North America all developed the technique of turning skins into leather goods

independently of one another. The Greeks were using leather garments in the age of the Homeric

heroes (about 1200 B.C. ), and the use of leather later spread throughout the Roman Empire. During the

middle Ages, the Chinese knew the art of making leather. The Indians of North America also had

developed great skills in leather work before the coming of the white man.

At some time, by accident or by trial and error, man discovered methods of preserving and softening

leather treating animal skins with such things as smoke, grease and bark extracts. The art of tanning

leather using the bark of trees probably originated among the Hebrews. In primitive societies, the art

was a closely guarded secret passed down from father to son. As civilization developed in Europe,

tanners and leather workers united in the trade guilds of the middle Ages, as did the craftsmen in otherfields. Royal charters or licenses were issued permitting people to practice leather tanning. In the

nineteenth century, vegetable tanning, i.e., tanning using the extracts from the bark of certain kinds of

trees, was supplemented by chrome tanning. This process uses chemicals and today accounts for about

eighty to ninety percent of all tanning done except for the leather used in the soles of shoes and tooling

leathers.


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Raw material:

The basic raw material for the tanning industry is a by-product of the meat processing industry i.e.

animal rawhide and skin (primary cattle hide). Approximately 25 million lambskins, 8 million sheepskins,

2.2 million cattle hides, 1.2 million calfskins, 200,000 goat skins and 400,000 deerskins are available for

processing into finished leather products in New Zealand tanning industry.

The tanning materials used in the conversion of skin to leather are mostly imported. They are of four

types:

1. Vegetable extracts from the bark and wood of trees (oak, wattle etc).2. Mineral- in the main, trivalent chromium sulfate. This is produced by the reduction of hexavalent

chromium in the form of sodium chromate or dichromate by organic or inorganic reducing agents.

3. Aldehydes- formaldehyde, glutaraldehyde or oxazolidine.We shall discuss only chrome tanning (mineral tanning) here

Sources of raw material in Pakistan:

Pakistan is fortunate that the raw material required by the industry is available in the country in

abundance. Local availability of raw materials and low wage cost gives the country a competitive edge in

the world market. The following are the types of basic raw materials which are being used by this

industry: - Cow hides - Buffalo hides - Goat skins - Sheep skins.

1) Buffalo

2) Cow

3) Goat

4) Sheep

1. Buffalo:

Buffalo is considered as the specialty of Pakistan in World, because of its ample availability in Pakistan

2. Cow:

The cow row material is considered a superior raw material upon buffalo because of its fine, tight and

comparatively uniform structure.

3. Goat:

It is good for making shoe upper leathers, garment and goods leather.

4. Sheep:

Leather made from sheep raw materials has a very good and softer touch and considered best for

leather garments.

The industry is meeting its 75% needs of raw hides from local resources while rest of the 25-30 per cent

is met through imports.

Pakistan imports leather from Saudi Arabia, Iran, and China, Dubai, Sudan, Kenya, Australia and Italy.


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In the leather industry the raw materials are by-products of the meat industry, with the meat having

higher value than the skin. Taxidermy also makes use of the skin of animals, but generally the head and

part of the back are used. Hides and skins are also used in the manufacture of glue and gelatin.

Process description:

Chrome-tanned leather, invented in 1858, is tanned using chromium sulfate and other salts of

chromium. It is more supple and pliable than vegetable-tanned leather, and does not discolor or lose

shape as drastically in water as vegetable-tanned. Also known as wet-blue for its color derived from the

chromium. More esoteric colors are possible using chrome tanning.

When animal is alive, its skin is soft, flexible, very tough and hard wearing: it has ability to allow water

vapor to pass out, but it will not allow water in. when the skin dies it loses these characteristics: if it is

kept wet it rots, and if it is dried it goes hard and brittle. The process of tanning is to retain the skins

natural properties, to stabilize its structure and at the same time to chemically process it so it will no

longer be subject to putrefaction. Thus leather is animal skin that has been treated such that its natural

properties are retained

Chemistry of Skin:

Skin is made up of many bundles of interwoven protein fibers which are able to move in relation to one

another when the skin is alive. When the skin dies, these fibers tend to shrivel and stick together.

Essentially, the purpose of tanning is to permanently fix the fibers apart by chemical treatment, and to

lubricate them so they can move in relation to one another. Well tanned leather, therefore, retains the

properties of flexibility, toughness and wear. It also continues to 'breathe', allowing water vapor to pass

through but remaining reasonably Water-proof.

In addition, the process of tanning imparts the advantage of resistance to heat. This is an important

factor in many of the uses of leather. In conjunction with chemical processing, the tanner imparts color,

texture and finish to the leather, to enhance its appearance and suit it to today's fashion requirements.

The basic component of the skin is collagen, a fibrous protein. The latest research indicates that the

basic collagen structure consists of twined triple units of peptide chains of differing lengths. The amino

acid residues are joined together by peptide links. The peptide chains within the triple helices are held

together by hydrogen bonding (Figure 1).


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The main processing sequences of leather manufacture are shown in Figure 2. Where skins are

processed with the hair or wool on, the unhairing and liming processes are omitted and replaced by a

scouring (washing) of the wool or hair. The main chemical processes carried out by the tanner are the

unhairing, liming, tanning, neutralizing and dyeing.

Skin collagen is usually associated with keratin (the protein in hair, wool and nails). Most mammals have

an outer coat of hair, wool or fur, which acts as an insulating layer and keeps the animal warm. Keratin is

a fibrous protein and different from collagen in one very important aspect: the polypeptide chains are

linked together by cystine linkages.

The sulfur-sulfur linkage in cystine is susceptible to the action of alkali, and breaks down quite readily in

the presence of alkali and a reducing agent.

Animal skins are converted to leather in nineteen different stages discuss below:

1. Warehousing and sortingin the raw material area the skins are preserved in salt, stored in controlled cool rooms and before

processing, presorted for quality and weight.

2. Soakingthe skin is soaked to remove dirt and salt.

3. De-FleshingDuring this process tissue, flesh and fat remnants are removed by a roller mounted knife.

4. LimingBy adding lime and sulphur compound the hair is removed from the skin.

The process of liming is a combination of chemical and physical action on the skin structure.

The chemicals involved are similar to those in the unhairing operation. A solution of lime and sodium

sulfide is used and the skins are immersed in this solution for whatever time is necessary to produce the

desired effects. The process of unhairing is taken to completion during the liming process, and there is

appreciable modification of the collagen takes place due to the action of alkali.


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1) Hydrolysis of amide groups

2) Modification of guanide groups

Skin protein (collagen) 3) Hydrolysis of keto-imide links in protein chainsAlkali 4) Swelling

5) Removal of unwanted material

After the strong alkaline action, the skin structure is further opened up during the Deliming and bateing

process.

5. Bating:Bating is an enzyme digestion process which continues the cleaning up process begun by the alkaline

action. Bateing is carried out at pH 9-10. This is achieved by treatment with acid salts (ammonium

chloride or ammonium sulfate) or carbon dioxide until the desired pH is reached.

Hydrolysis is continued by the enzyme process and further dissolution of unwanted material occurs. The

main fibrous network is then cleaned up and the swelling is reduced.

6. Pickling:The main acidification process is that of pickling. The skins are agitated in a solution of salt and sulfuric

acid until they are at or near equilibrium at a pH value of 3.0 - 3.5.

7. Tanning:The main chrome tanning material is trivalent chromium sulfate. It is now widely used in all leathers

preparation where softness, stretch and suppleness are required.

After pickling, when the pH is low, chromium salts (Cr3+) are added. To fixate the chromium, the pH is

slowly increased through addition of a base. The process of chromium tanning is based on the cross-

linkage of chromium ions with free carboxyl groups in the collagen. It makes the hide resistant to

bacteria and high temperature. The chromium-tanned hide contains about 2-3 dry weight percent of

Cr3+.

The use of chromium in tanning:

Chromium, a transition element which forms co-ordination complexes by using 3d orbital to

accommodate extra electrons, has an unrivalled position as a tanning agent. The complex is basic by

nature and will contain hydroxyl groups associated with the chromium nuclei.

There are two main features of chromium chemistry which enable it to act as a tanning agent.

Firstly, the complexes formed are of intermediate stability, and thus exchange of co-coordinating ligands

can take place comparatively easily. Secondly, chromium has the ability to form polynuclear complexes

in which Cr-O-Cr bridges are involved. These come about as follows:


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The final process of oxolation is a slow one and is not readily reversed. In a similar manner, long chains

may be built up. By means of these polynuclear units the gaps between collagen chains in the skin

structure can be bridged, giving the tanning action.

Chromium shows a strong tendency to form coordination compounds with molecules containing

carboxyl groups. The order of stability of complex ions involving chromium with other differing ligands

is:

The chromium-collagen complex lies approximately between (1) and (2) in the range of stabilities, and

the order in the series has a number of practical and theoretical implications. Individually these two

properties are found in the chemistries of many other elements, and do not give any great tanning

ability. But the two properties together give great tanning potency. The process of chrome tanning is

now thought to involve the ligand present in the chromium complex being replaced by collagen. Overall

during this stage the skin fibers absorb the tanning agents. That's when the skin becomes leather.

8. SammingDuring this process water is removed.

9. SplittingIn order to achieve an even specified thickness the leather is reduced in substance. The resulting split-

leather can then be processed further as suede.10.Skivingthe grain leather is brought to an even thickness. Irregularities are removed from the reverse side and

the leather is separated into color-batches.

11.SortingThe leather is sorted into various quality grades.

12.NeutralizingAfter tannage, leather must be neutralizedto remove unwanted acids to prevent deterioration during

the drying process, and to prepare the leather for the next stages in processing: dyeing and fat liquoring.

Neutralizing is often carried out using mild alkalis which have some effect on the chromium complex

13.DyeingDyeing is done using a variety of dyestuff types. Commercial dyes are essentially mixtures of chemical

compounds which can be fixed (combined) to the material to be dyed and which have appreciable

resonance within the molecule giving color. A simple example is Orange II:


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Its color comes from the presence of the hydroxide group in conjunction with the azo group, allowing a

high degree of resonance. It can be fixed to the material to be dyed by means of the sulphonic acid

group.

In chrome tanned leathers the most reactive sites are the chromium nuclei, and these form the main

points of fixation for dyestuffs. As with other processes, the main factors controlling dyeing are the

physical one of locating the dye in the required position within the leather structure and the chemical

one of controlling the conditions so that reasonable penetration and fixation are achieved.

A wide range of dyes are used in leather processing and some examples are:


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The growing awareness of the effects on health of prolonged exposure to certain industrial chemicals

has led to the prohibition of the use of certain dye stuffs - examples are direct dyestuffs based on

benzidiene. Consumer requirements for both wash and light fastness in leather goods has lead to a shift

away from the more level dyeing direct and acid dyes to the faster pre- metalized and reactive dyes.

Dyeing technology has had to keep up to improve the level dyeing properties of these dyes.

14.Greasing or Fat liquoringFat liquoring is the process in which 'tanned' fibers are treated with reactive oils, which attach

themselves to the fibrous structure, and lubricate them so that they can move readily in relation to one

another, producing a soft, supple leather.

15.DryingTwo methods are used to dry leather. The vacuum process during which moisture is removed by suction

and the hanging process, when leather is hung and taken through ovens.

The chemical condition is stabilized and the final properties of the leather are determined.

16.StakingFollowing drying the leather is mechanically staked in order to soften it. Further processes take place in

preparation for finishing.

17.FinishingHere the leather is given its final surface treatment and look. Through processes of base coat, coloring,

embossing, ironing the leather becomes, depending on the demands of fashion, matt or shiny, two-tone

or uni-coloured, smooth or grained by applying a surface coating - pigments or dyes bound in an organic

(acrylic, butadiene or polyurethane) or protein (casein) medium.. The art of finishing lies in working in

wafer-thin layers without disturbing the natural look of the leather and its characteristics such as

suppleness and breath ability

18.Quality ControlIn between every process quality is controlled. Final control checks to ensure each individual production

is to specification and sorting into various trades.

19.DispatchThe leather is measured electronically, wrapped and dispatched


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Status of Leather Industry in Pakistan:

The history of leather industry in Pakistan is as old as the country itself. At the time of

independence there were only a few tanneries producing sole leather and that too at a very

small scale. However, since then this industry has been flourishing and has never looked

back. During 1950s, some well-equipped tanneries were set up at Karachi and Lahore, while

during 60s and 70s more units were established at Hyderabad Kasur, Sialkot, Multan,

Sahiwal and Gujranwala. Starting with the production of picked and vegetable tanned hides

and skins, the tanneries, today, are producing not only wet blue and crust, but also fully

finished leather.

In the early days of independence some tanneries were established in Karachi. In 1950's

some were established in Lahore and adjoining areas.

The entire production of hides and skins were being exported in a raw form. Thereafter the

local tanning industry making at first semi-finished leather made rapid progress due to

favorable raw material situation, cheap labor and the existence of growing demand and

foreign market.

Production capacity of Leather Industry in Pakistan is as follow:

Particulars Production Capacity per anum

Tanned leather 90 million sq. meter

Leather garments 7 million

Leather gloves 10 million

Leather footwear 200 million

Source: Pakistan Tanneries Association

Presently, there are some 461 leather garments/apparels making units, which annually produce

some 5.0 million pieces against a capacity of producing 7.0 million pieces. The 524 footwear units in

the country are currently producing 100 million pairs against a capacity for producing 200 million

pairs, while 348 leather gloves units are producing 5.0 million pairs against a capacity of making 10

million pairs annually.

These statistics clearly show that the capacity of this sector remains highly under-

utilized and with a little extra effort Pakistan can substantially increase the production

and exports of its shoes and other leather products.

Problems faced by the industry

1. Quality:

Good quality leather is mostly exported and is not available for high value-added Leather Garments &

Leather Products.

Leather garments in Pakistan are made mostly from low grade & medium grade leather. Lack of proper

training and inadequacy of skills in slaughtering are among the most important factors leading raw hides

and skins towards lower grades or even to rejection. Furthermore, inadequate knowledge of

preservation techniques and lack of sufficiently designed collection and storage facilities may cause


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problems that are associated with the lowering of the quality and quantity of raw material. Hence, the

need for strengthening training facilities for manpower at all levels through hiring of experts.

The quality of raw hides and skins generally depends upon the quality of livestock. The hides and skins

removed out of young and healthy cattle may be taken as the best in its quality provided the conditions

in which these are removed and also their collection, preservation and storage is satisfactory.

In fact, there are many factors which affect the quality of leather at pre-slaughtering, during

slaughtering and post-slaughtering stages. It is estimated that around 20-25 per cent of the hides and

skins are affected by pre-slaughtering damages, like skin-cuts, rashes, diseases, injuries etc.

2. Cost of production:

Cost of production is also very high in Pakistan as compared to our competitors like China and India.

The high cost of various inputs especially utilities and taxes make our products uncompetitive in

international markets.

3. The issue of chrome

Chromium III salts are used extensively in the tanning process. Approximately 90% of the leather

manufactured is tanned using chromium III. This is because chromium is the most efficient and versatile

tanning agent available and it is relatively cheap. It has been used in the leather industry for almost 100

years and when it was introduced as an alternative to vegetable tanning extracts from oak bark and

similar sources, it heralded a new era for the leather industry. It reduced the time taken within the

tanning process from months to days, and offered leathers with properties that were previously

unattainable. The leather industry only uses chromium in its safest and most stable form - chromium III.

However, due to misconceptions about chromium and a failure to recognize the distinctions between

chromium III and chromium VI, which is generally understood to be toxic, the tanning industry has often

been placed under unwarranted pressure by regulatory bodies with regard to both the use and disposal

of chromium and chromium-containing materials. Chromium VI compounds are not used by the tanning

industry

4. Energy Issues

Generally, a leather unit consumes over 0.97-1.87 MJ i.e. 270-300 KWh of energy to produce 100ft2 of

finished leather. The absence of energy efficient technologies and lack of proper maintenance of steam


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pipes, steam traps and insulation are causing wastage of significant amount of energy in most leather

processing units.

5.Environmental challenge

Leather tanneries in Pakistan produce all three categories of waste: wastewater, solid waste and air

emissions. However, wastewater is by far the most important environmental challenge being faced

by Pakistan's tanneries.

Wastewater: Although the exact quantity varies widely between tanneries, a normal requirement of

around 50-60 liters of water per kilogram of hide is suggested. ETPI's sample audits of tanneries in

Pakistan show that in some cases the consumption of water is as high as three times the suggested

requirement. The overall water discharge also demonstrates a high degree of seasonal and daily

fluctuation. For most part, the current practice is to discharge this water into the local environment

without any treatment.

Solid Waste: Two types of solid wastes (tanned and untanned) are generated from leather

production processes. Solid waste include dusted curing salts, raw trimmings, wet trimmings, dry

trimmings, wet shavings, dry shavings, buffing, and packaging material. It is estimated that for a

tannery averaging 10,000 kilograms of skins per day, a total of some 5,500 kilograms of solid waste

would be produced per day.

In general, it is found that solid wastes from tanneries (except for dusted salt) have secondary users in

the local market. Glue manufacturing and poultry feed makers are a major user group of this waste.

However, an important problem with this use is the presence of chromium in it. The use of chrome

contained solid waste for poultry feed preparation could cause serious health problems for poultryconsumers.

Air Emissions: There are two sources of air pollution from tanneries in Pakistan. The first relates to

emissions from generators (diesel-based and operated only during power breakdowns) and from boilers.

Emissions were found to be well below the NEQS level. Ammonia emission during processing and

washing of drums, though intermittent but important has adverse effects on workers health.

Hydrogen sulphide emission during mixing of acid and alkaline wastewater in drain is also a serious

health hazardous. Segregated discharge of acidic and alkaline effluent can help to avoid the hydrogen

sulphide gas emission.

Solid Waste

Two types of solid wastes are generated from leather production processes (i.e. tanned and un tanned).

Solid waste includes dusted curing salts, raw trimmings, wet-blue trimmings, dry trimmings, wet-blue

shavings, dry shavings, buffing, and packaging material etc. On an average a tannery processing 10,000

kilograms of raw material per day produces some 5,500 kilograms of solid waste daily. The solid wastes

do have secondary use in glue manufacturing and poultry feed making etc. However, the use of chrome-


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containing solid waste for poultry feed preparation can cause serious health problems for poultry

consumers.

Future of Leather Industry in Pakistan

Recommendations

1. Introducing Brand NamesLeather and Leather products from Pakistan have carved a respectable place in the world market.

Some of leather products from Pakistan especially leather jackets are much in demand but under

the foreign renowned brand names. Made-in-Pakistan label and brands born in Pakistan have yet to

come. Steps need to be taken by the industry in this regard. Renowned Pakistani firms need to

register trade marks with respect to the leather products they manufacture. In light of the

Agreement on trade related aspects of intellectual property rights (TRIPS) of WTO, Pakistan through

Trade Marks Ordinance, 2001, provides effective protection and rights to the owner of trade marks.

2. Focusing on Footwear SectorFootwear, the largest segment of the leather industry around the world has been surprisingly

neglected in Pakistan. Foreign franchised companies have become household names in Pakistan.

This is despite the fact that the entire stuff and skill they use belong to Pakistan.

Moreover, having a strong industrial base, Pakistan's leather industry looks treading without shoes.

This vacuum in leather industry calls for the attention of the industry leaders to bridge the gap to

give a comprehensive look to the leather and leather products industry in Pakistan. One of the

options to enter the field of footwear sector is to seek partnership with international brand

producers by offering them attractive incentives.

3. Tackling Environmental and Labor IssuesRegarding environmental concerns of WTO, the industry has made little progress in this regard.

Combined effluent treatment plants need to be built so that hazardous chemicals from the

tanneries do not affect the environment. Moreover, the industry needs to tackle all the labor issues

to which the consumers in the importing countries are sensitive to. It needs to be ensured that the

leather industry in Pakistan adheres to the working condition requirements that have been

developed by certain international bodies, particularly, the associations of leather industries in the

importing countries of the west. Under the WTO regime, member countries can impose penalties or

restrict imports from exporting countries whose industries do not observe environmental/labor

concerns or social compliance.

4. Control on Smuggling & Diseases of LivestockLeather manufacturing sector in Pakistan can also suffer because of massive smuggling of livestock

to other countries, shortage of raw material and absence of the organized dairy farming in the

country. Steps should be taken to overcome these problems

Moreover, diseases in the livestock in Pakistan can prove hurdle in the manufacturing and exports of

finished products of leather. Concrete measures need to be taken to overcome this threat to the


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livestock as a result the live animals are suffering from different diseases that damage the quality of

the leather and tarnish the image of products at international level.

5. Reduction of Duties on MachineryThe duties on the import of tanneries related machinery need to be further reduced. The machinery

made locally is technologically inferior which not only increases the cost of production but restrainsfrom developing at par with the international market.

REFRENCES

http://www.dailytimes.com.pk/default.asp?page=2009/12/03/story_3-12-2009_pg5_17 http://pisd-pak.org/leather.php http://jang.com.pk/thenews/jul2009-weekly/busrev-13-07-2009/p4.htm Lahore chambers of commerce and industries Pakistan tanneries association Trade Development Authority of Pakistan (TDAP) Furniture Today magazine, article published on September 16, 2001
http://www.dailytimes.com.pk/default.asp?page=2009/12/03/story_3-12-2009_pg5_17http://www.dailytimes.com.pk/default.asp?page=2009/12/03/story_3-12-2009_pg5_17http://pisd-pak.org/leather.phphttp://pisd-pak.org/leather.phphttp://pisd-pak.org/leather.phphttp://www.dailytimes.com.pk/default.asp?page=2009/12/03/story_3-12-2009_pg5_17

roll # 24 leather industry

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