GOVERNMENT OF THE PEOPLE’S REPUBLIC OF BANGLADESH
BANGLADESH COLLEGE OF LEATHER ENGINEERING AND TECHNOLOGY
PURPOSE OF INDUSTRIAL TRAINING
In our institution we learn the theoretical aspect of leather production. Industrial training provides us a chance to compare our theoretical knowledge
with large commercial production of industry. The purpose of industrial training can be outlined under the following topics:
- To get an idea about the vast commercial production.
- To observe the management system of the industry.
- To observe the process of product development and quality control.
- To observe the plant layout of the industry.
- To observe the production of various leathers.
- To introduce with the factory environment.
DESCRIPTION OF THE INDUSTRY
1. Name of the Industry : Samina Tannery (Pvt.) Ltd.
2. Location : 36/1, Kalunagar, Hazaribagh,
Dhaka-1209.
Post:
1. Managing Director : Abdus Samad
2. General Manager : Moktar Hossain
3. Chief Leather Technologist : Mohiuddin Ahmed
4. Leather Technologist : a) Md. Fazlul Haque Tutul
b) Md. Rafiqul Islam
5. Wet Blue Tanner : Md. Siraj
6. Mechanical & Electrical Engineer : Eng. Salatun Nabi
Others:
1. Number of Foreman Instructor : 01
2. Number of Feeder Man : 02
3. Number of the workers
i) Wet Blue : 40
ii) Crust : 20
iii) Finish : 15
Administrative Management
Chairman/Managing Director
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General Manager
Production Manager
Leather Technologist
Mechanical & Electrical Engineer
Machine Operator
Labor
The tannery has following sections:
1. Wet blue.
2. Crust.
3. Finishing.
The Tannery has the following machineries:
Wet blue section:
Name: Number
- Drum : 20
- Fleshing machine : 01
Crust section:
Name: Number
- Drum : 08
- Shaving machine : 01
- Setting machine : 01
- Vacuum dryer : 01
- Toggle dryer : 01
- Vibration staking machine : 01
- Testing drum : 01
- Milling drum : 01
Finishing section:
Name: Number
- Auto spray : 01
- Hand spray : 01
- Polishing machine : 01
- Roto roller : 01
- Kiss plate machine : 01
- Buffing machine : 01
- Measuring machine : 02
- Hydraulic Press : 01
PRODUCT RANGE:
All kinds of drum dyed crust & finished leather such as:
1. Full chrome, semi chrome, full vegetable, natural & dyed crust.
2. Glazed shoe upper.
3. Softy shoe upper.
4. Garments leather
5. Nappa leather
6. Pull up, nubuck and burnished leather.
7. Brush off leather.
8. Lining leather.
9. Shrunken grain leather.
10. And also specific leather on customer’s choice.
Production Capacity:
Daily Production:
Wet Blue : 20,000 sq. ft
Crust : 20,000 sq. ft
Finish : 4,000 sq. ft
Annual Production Capacity:
Finish : 20%
Crust : 80%
Sister Organizations:
Contact:
Telephone : +88029663815, +88029660384
E-mail : samina1@dhaka.net
Fax : +88028614989
Responsible Technologists:
1.Md. Rafiqul Islam
COMMENT ON TANNERY
The main feature of Samina Tannery (Pvt.) Ltd. is that it is very well-managed, disciplined and its plant layout is quite reasonable. It provides worker
comfort and appraises customer satisfaction with great concern. They are very much devoted to quality improvement and quality maintaining. All the above
factors were instrumental for this zenith position of Samina Tannery (Pvt.) Ltd. This tannery plays pivotal role in our leather industry and one can take
Samina Tannery (Pvt.) Ltd. as a model of resurgent leather sector.
A BRIEF DESCRIPTION OF TANNERY WORK & OUR TRAINING
Day: 01
13.11.2010
Introduction:
Our training started on the 13th November 2010. We were five students in a group. On the very first day our guide teacher ABDULLAH-AL-MAHMUD
went to the tannery with us and introduces us with Mohiuddin Ahmed the senior technologist of SAMINA TANNERY LTD. We were also introduced with the
authority and other personnel concerned with production. I was trained at the Wet blue section from 13-11-2010 to 06-12-2010. Leather technologist Md.
Rafiqul Islam was our instructor. He was quite helpful to us. At this section we observed the following operations and mechanical process.
WET BLUE
Day: 02
14.11.2010
In wet-blue section, Technologist Md. Rafiqul Islam told us briefly about the tannery, its rules and regulation and different operations and functions of
cow wet-blue section. He also helped us to observe the wet-blue section. We saw that the tannery was arranged sequentially.
Day: 03
15.11.2010
In this section have about 40 workers. It has 20 industrial drums, and 1 fleshing machine. All the drums and machines are set-up sequentially. We saw large
amount of raw hide is processed here every day. Many people work there and the Technologist, Tanner and supervisors guide them. All people worked very
attentively and carefully. We also observed that a large number of Raw or wet-salted cow hides piles in raw storage and selection and cow wet-blue piles in
wet-blue storage section.
We are pleased and enjoyed to observe the leather manufacturing process in large production and acquired vast knowledge and idea and interested to do our
training regularly.
Day: 04
16.11.2010
Raw cow Hides Selection
Today we observed the selection of raw and wet salted cow hides. Main selector with workers was engaged for this purpose. He selects the hides with eye
observation and experience. He found out different defects from hides and made different lots of different grading. Grain damage, old ages, pin marks,
flaying cut, damage by insets and birds, pox, virus, small size, action of hot water, scratch marks etc. were mentionable defects found in raw hides. Then
we observed different machines.
Day: 05
17.11.2010
Trimming, curing, and weighing:
This is the first operation which is performed after the entry of raw H/S (cured) into the tannery. In case of fresh H/S curing is also done. Weight is
taken before starting chemical operation.
Day: 06
18.11.2010
Soaking Operation
Today we observed the soaking operation of cow hides. Soaking is the first tannery operation. During curing, hides and skins are large amount of its
physiological content of water and unless the former regains this water during soaking operation, good quality leather cannot be produced. It is best done
in two stages such as pre-soaking and main soaking. Pre-soaking which removes dirt, dung and curing salts from hides and skins. The main soaking rehydrates
the hides.
Presoaking:
In this process raw H/S are washed with water in drums or paddles.
Main soaking:
It is also washing of H/S with water and some chemicals which are wetting agents (LD-607), bactericide (Busan-40L), and soda ash etc. It is done in drums.
Objects of Soaking
- To remove the dirt, blood and dung from the hides and skins.
- To remove the curing salt in case of salted hide and skins.
- To rehydrate the skin protein.
- To open up the contracted fibrous structure of the skins
- To clean off surface filth.
- Softening the hides and skins.
Recipe for Soaking Operation
Presoaking:
200% Water
Run 60 min. Drain well.
Main soaking:
200% Water
0.25% Wetting agent (LD-607)
0.2% Bactericide (Busan-40L)
0.25% Soda ash
Run 30 min
Run 2 min each hour
Total time: 12-14hrs.
Day: 07
20.11.2010
Liming:
It is the treatment of H/S with milk of lime and sharpening agents. The intensity of liming is varied with the final product. Liming of cow hides and goat
skins are done in drums. Buffalo hides are limed in paddle. The chemicals used in liming are liming auxiliary (Busperse 7743L), sharpening agents (Na2S)
and lime (CaO).
Objectives of Liming
o To remove simply hair.
o To remove cementing substances.
o Splitting up of fiber bundles.
o To remove fat and grease.
Recipe for Liming Operation:
200% Water
0.5% Liming Auxiliary
0.25% Wetting Agent, Run 10 min.
+2.0% Na2S
2% Lime , Run 60 min.
+2% Na2S
2% Lime,
Run 30 min.
Total time: 16-18 hrs.
Day: 08
21.11.2010
Fleshing:
It is done by fleshing machine. After fleshing the pelts are weighed. This weight is known as pelt weight. Next all the percentages of chemicals used are
based on this weight.
Scudding:
This mechanical process is done to remove the hair roots. It is done with blunt knife.
Day: 09
22.11.2010
Weighing Operation
After fleshing the pelt, trimming was done and then took weight and send for the next operation. We observed the weighting process. We saw 50 kgs weights
were on one side of the balance and on the other side the pelt were measured.
Day: 10
23.11.2010
Deliming:
In this process lime used in liming is removed by washing with water and deliming agents. This process is also done in drums. In deliming mainly ammonium
sulphate (NH4)2S04, sodium metabisulphite, ammonium chloride (NH4C1).
Objectives of Deliming
- To remove most of the lime and alkaline materials from the pelt.
- To reduce the swelling of the pelts.
- Solubilization of Ca-soaps.
- To remove flesh, scud etd.
- To prepare for different Tannages.
Recipe for Deliming Operation
50% Water
2% (NH4)2S04
0.5% Na-meta bisulphate
0.5% SNA Liquid, Run 45 min
Check Cross section, with phenolphthalein
Check PH: 8.3-8.2
Day: 11
24.11.2010
Bating:
It is a treatment of delimed pelt with enzyme and other chemicals to make the final leather soft, pliable and stretchy. Temperature is an important factor
for this operation. It is done in drums. The chemicals used in this operation are alkaline bate (Oropon-G) and acid bate (Oropon BRS).
Objectives of Bating
- To make the grain surface of the finished leather clean, smooth and fine.
- To remove some of the non-leather forming proteins materials like albumins, globulins.
- The scud of dirt, short hairs, greases and lime soaps, dark colored pigments and traces of epidermis are all loosened and are easily to make the final
leather soft, pliable and stretchy. - To allow the splitting up of collagen fibers.
Recipe for Bating Operation
0.8% Bating agent
0.5% Alkaline bate (Oropon-G), Run 60m
+0.5% Acid bate (Oropon-BRS), Run 30-45 min
+1.0% Degreasing agent (FA- 607), Run 15 min
Day: 12
25.11.2010
Pickling:
It is the treatment of the bated pelt with acid and salt. This process makes the leather suitable for chrome tanning. Concentration of salt and acid is an
important factor for this operation. P is another factor in this operation. It is done in drums.
Objectives of Pickling
- To bring the delimed or bated pelts to a require degree of acidity before chrome tannage, even vegetable tannage.
- To reduce the pH.
- To modify the fiber structure.
- To reduce the astringency of chrome tanning agents,
- To preserve the leathers and to achieve the special effect.
Recipe for Pickling Operation
80% Water
8% Salt, Run 10 min, Check Bo: 6-7
+ 0.25%Impropal CO, Run 10
+ 0.25%Formic acid, Run 15 min
+ 1.2%Sulphuric acid, Run 120 min
+ 0.25 Hypo, Run 20 min, Check PH: 2.6-2.8
Day: 13-14
27-28.11.2010
TANNING OPERATION
In leather manufacture the most outstanding process is Tanning. The process of converting putrescible hides and skins into un-putrescble leather is called
Tanning. The materials which are used for tanning are called tannins. There is various process of tanning such as chrome tanning, semi-chrome tanning,
Vegetable tanning, Aldehyde tanning, Oil tanning, Zr-Tanning, Alum-Tanning, Wet-white Tanning etc.
Objectives of Tanning
- To convert the putrescible hides and skins into un-putrescible leather.
- To raise the shrinkage temperature and to increase the resistance to hot water of the leather.
- To reduce the ability to swell when wet back.
- To increase the strength properties of leather.
- To stabilize the leather against enzymatic degrading.
Chrome tanning:
It is the treatment of leather with chrome powder and then with basifying agent to fix the chrome. It is done in drums.
Recipe for Chrome tanning:
Drain half of the pickle bath
+ 1.0% Ingrasente 99E, Run 20 min
+ 4.0% Chrome, Run 1 hour
+ 4.0% Chrome Run 1 hour
+0.5% SF Liquid, Run (0+10+10+40) min
+0 .25% Busan 30 L, Run 15 min
+1.0% NaHCO3, Run 2 hours
+0.5%NaHCO3, Run 1 hour
Check PH: 3.6-3.7, Unload and Pile up
Day: 15
29.11.2010
Name of some wet-blue chemicals used in Samina Tannery (Pvt.) Ltd. :
- LD 600 (ACI)
· Busan 40L (Buckman)
· Busan 30L (Buckman)
- Soda Ash
· Formic Acid (BASF)
· Basic Chromium Sulfate (LANXESS)
Day: 16-20
30.11- 05.12.2010
Wet-Blue Leather Selection
Today we observed the wet-blue leathers. After pre-tanning with Basic chrome powder the hides and skins are called wet-blue leather, as the color of the
leathers is Bluish-Green. We saw many piles of wet-blue leathers in the tannery. It is necessary to age the wet-blue leathers for few days for better
chrome fixation.
Then we observed the selection of wet-blue leathers. Selector told about selection. He selected the leathers in accordance with grading. The leather of
Grading 1,2,3 are kept in one lot, Grading 4,5,6,7,8 are kept in another lot and the much defected leathers are included in grading 9 and 10. The crust and
finished leathers are manufactured from these wet-blue leathers according to customer’s demand.
Day: 21
06.12.2010
Drawing Plant Layout of wet-blue section of the Tannery:
That day we drew the plan layout of Wet-Blue section of Samina Tannery (Pvt.) Ltd.
FLOW CHART OF THE PRODUCTION OF WET BLUE LEATHER FROM RAW HIDE & SKIN
Raw Hides & Skins Selection
Trimming
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Weighing
Presoaking
Soaking
Unhairing
Liming
Deliming
Bating
Pickling
Chrome Tanning
Wet Blue
Crust section
Responsible Technologists:
1. Md. Fazlul Haque Tutul
2. Md. Rafiqul Islam
CRUST
I was trained in crust section from 07-12-2010 to 27-12-2010. Here we acquired detail knowledge of the following operations:
Day: 01
07.12.2010
Selection & Grading
Today we observed the selection of finished and crust leather. The selector selected the leather according to grading. Good quality leathers were kept in
grading1,2 & 3. Less defected leather in grading 7,8,9,10 or rejected according to the type of leather.
Day: 02
08.12.2010
Sammying to Shaving
Today we observed the sammying, splitting and shaving machines and their functions. In this section there are sammying machine, splitting machine and
shaving machine.
Objectives of Sammying machine
o To reduce water from the leather.
o To add the chemicals for next operation
Splitting
The band knife splitting machine split the leather into two of more pieces if the leather is too thick. The object is to get the require thickness.
Example: for shoe upper leather thickness = 1.3-1.4mm.
Shaving
The wet-blue leather are shaved to get require thickness. After shaving wet-blue Leathers are sent to crust section of Samina Tannery Ltd. for
manufacturing of crust and finished Leather.
Day: 03
09.12.2010
Trimming and Weighing
Day: 04
11.12.2010
Wet Back & Re-Chroming Operation
Before retanning it is necessary to wet back the shaved wet blue/wet white leathers. It is done with acid, wetting agent and water. Acid is used to boring
the leather of optimum pH for re-chroming. Re-chroming is done to increase the strength of leather, to fix more chrome into the leather, to increase the
hydrothermal stability and shrinkage temperature, to improve the softness, fineness of the grain etc.
1. Acid Wash:
This is the washing of wet blue/wet white leather with acid in drums.
2. Rechroming:
Here chrome tanned leather is again treated with chrome and chrome syntan in drums.
Day: 05
12.12.2010
3.Neutralization:
It is done to prepare the leather for succeeding operation i.e. dyeing and fat liquoring. P” of leather is strictly controlled in this operation. It is
done in drums.
Objectives of Neutralization
o To remove the neutral salts and uncombined chromium salts from the leather.
o Neutralization of free acid in leather formed by the hydrolysis of the chrome complex.
o To control the affinity of the leather for anionic materials, particularly dyestuff and anionic oil emulsions by regulation its electrostatic charge.
Day: 06
13.12.2010
4. Retanning:
This process is done to impart combination of leather tannage to the leather.
Objectives of Re-Tanning Operation
o To fill the loose and softer parts of the leathers to produce leathers of more unirorm physical properties.
o To allow for the production of unlined footwear.
o The retannage may improve the chemical stability of the leather, particularly its resistance of alkalis and perspiration.
Day: 07
14.12.2010
Dyeing:
Leather is treated with dye of required color. It is done in drums.
Day: 08
15.12.2010
Fat Liquoring:
6.Leather is treated with emulsion of fat, fish oil etc. for softness of leather. Temperature is an important factor for this operation.
Objectives of Fat Liquoring:
o To improve the softness of the leather.
o To improve the sliding properties of the leather.
o To improve the toughness, water-repellent properties of the leather.
Day: 09
18.12.2010
Preparation of Production Recipe
Recipe for The Production of Black Shoe Upper:
Shaved at: 0.9-1.0mm (Finally 1.1-1.3)
Acid Wash:
Water : 250%
Degreasing Agent (Busperse 7738) : 0.2%
Acetic Acid : 0.2% Run 30min
Re-Chroming:
Water : 100% at 35°C
Formic Acid : 0.2% Run 10min
+Chrome Powder : 5.0%
Chrome Syntan (Retaral CRO) : 3.0%
Sodium Formate : 1.0%
Chrome Stable Fat (Atlasol 177C) : 1.0% Run 60min
+Polymeric Tanning Agent (ICATAN 204) : 2.0% Run30min
+Water : 50% at NT
Sodium Formate : 1.0% Run 15min
+Sodium Bicarbonate : 0.8% Run (10+10+40) min
Check ph: 3.7-3.8
Leave Over Night
Next Morning Run 15min, Drain & Wash
Neutralization:
Water : 100% at 35°C
Neutralizing Syntan (Tamol NA) : 2.5%
Sodium Formate : 1.0% Run 30min
+Sodium Bicarbonate : 0.5% Run (15+30)min
Check pH: 4.5-4.8
Drain & Wash
Re-Tanning & Fat Liquoring:
Water : 100% at 35°C
Acrylic Resin (AR) : 5.0% Run 30min
+Mimosa : 4.0%
Quebracho : 2.0%
Tanigan OS (Replacement Syntan) : 3.0%
Basyntan AN (Amphotaric) : 3.0%
Neosyn N (Naphthalene) : 1.0% Run 30min
+Dye Leveller : 0.6% Run 10min
Dye (Black 3 TN) : 2.5% Run 60min
Check: Ø Penetration
+Dicyandiamide (Syntan DF585) : 5.0% Run 60min
+Water : 100% at 60°C
Synthetic Fat (Synthol FL327) : 3.0%
Semi Synthetic Fat (Atlasol 23kpm) : 3.0%
Sulphite fish oil (Vreka 400R) : 1.0%
Lecithine (Provol BA) : 1.0%
Lanoline (Vreka GFN) : 1.0%
Neats Foot oil (Atlasol 30CT) : 1.0% Run 60min
+Styrene Maleic Resin (Raaral RST) : 4.0% Run 30min
+Formic Acid : 2.5% Run (10+10+30)min
Drain & Wash
Top Dyeing:
Water : 200% at 60°C
Basic Black LNI : 0.8%
Acetic Acid : 0.4% Run 15min
+Basic Dye (5TN) : 0.8% Run 15min
+Formic Acid : 0.8% Run 15min
+Black Dye (5TN) : 0.8% Run 15min
+Formic Acid : 1.5% Run (5+5+30)min
Drain & Wash
+Water : 200% at NT
Cationic Fat (Catalix GS) : 0.6%
Neats foot oil (30CT) : 0.4% Run 15min
Drain/Horse up O/N
Recipe for The Production of Shoe Lining:
Acid Wash
Same as Upper
Re-Chroming:
Same as Upper
Neutralization:
Water : 100% at 35°C
Neutralizing Syntan (Tamol NA) : 2.0%
Sodium Formate : 1.5% Run 15min
+Sodium Bicarbonate : 1.0% Run (15+15+45) min
Check pH: 5.2-5.5
Drain & Wash
Re-Tanning & Fat Liquoring:
Water : 100% at 35°C
Acrylic Resin (AR) : 3.0% Run 20min
+Fish Oil (400R) : 2.0% Run 10min
+Mimosa : 3.0%
Tanigan OS (Replacement Syntan) : 2.0%
Basyntan AN (Amphotaric) : 2.0%
Neosyn N (Naphthalene) : 1.0% Run 30min
+Dye : 0.6% Run 30min
+Dicyandiamide (Syntan DF585) : 3.0% Run 60min
+Water : 100% at 60°C
Synthetic Fat (Synthol FL327) : 4.0%
Semi Synthetic Fat (Atlasol 23kpm) : 3.0%
Sulphite fish oil (Vreka 400R) : 4.0%
Lecithine (Provol BA) : 4.0%
Neats Foot oil (Atlasol 30CT) : 1.0% Run 90min
+Styrene Maleic Resin (Raaral RST) : 2.0% Run 20min
+Formic Acid : 2.5% Run (10+10+30) min
Drain & Wash
Top Dyeing:
Water : 200% at 60°C
Basic Black LNI : 0.8%
Acetic Acid : 0.4% Run 15min
+Basic Dye (5TN) : 0.8% Run 15min
+Formic Acid : 0.8% Run 15min
+Black Dye (5TN) : 0.8% Run 15min
+Formic Acid : 1.5% Run (5+5+30)min
Drain & Wash
+Water : 200% at NT
Cationic Fat (Catalix GS) : 0.6%
Neats foot oil (30CT) : 0.4% Run 15min
Drain/Horse up O/N
Recipe for F/C Natural Leather:
Acid Wash:
Water : 250% at NT
Degreasing Agent (Busperse 7738) : 0.2%
Oxalic Acid : 0.6% Run 30min Drain, Wash
Re-Chroming:
Water : 100% at 35°C
Formic Acid : 0.1% Run 10min
+Chrome Powder : 5.0%
Chrome Syntan (Retaral CRO) : 3.0%
Sodium Formate : 1.0%
Chrome Stable Fat (Atlasol 177C) : 1.0% Run 60min
+Polymeric Tanning Agent (ICATAN 204) : 2.0% Run30min
+Water : 50% at NT
Sodium Formate : 1.0% Run 15min
+Sodium Bicarbonate : 0.8% Run (10+10+40) min
Check ph : 3.7-3.8
Leave Over Night
Next Morning Run 15min, Drain & Wash
Neutralization:
Same as Upper
Re-Tanning, Fat Liquoring & Dyeing:
Water : 100% at 35°C
Acrylic Resin (AR) : 5.0% Run 30min
+Bleaching Syntan (Syntan SA) : 5.0%
Bleaching Syntan (Basyntan DLF) : 3.0%
Tanigan OS (Replacement Syntan) : 5.0% Run 30min
+Dicyandiamide (Syntan DF585) : 5.0% Run 60min
+Water : 100% at 60°C
Synthetic Fat (Synthol FL327) : 4.0%
Semi Synthetic Fat (Atlasol 23kpm) : 4.0%
Neats Foot oil (Atlasol 30CT) : 1.0% Run 60min
+Styrene Maleic Resin (Raaral RST) : 5.0% Run 30min
+Syntan SA : 2.0% Run 20min
+Formic Acid : 2.0% Run (10+10+30) min
Drain & Wash
+Water : 200% at NT
Cationic Fat (Catalix GS) : 0.6%
Neats foot oil (30CT) : 0.4% Run 15min
Drain/Horse up O/N
Day: 10
19.12.2010
Name of some crust chemicals used in Samina Tannery (Pvt.) Ltd.:
- Busperse 7738 (Degreasing Agent)
- Chrome Syntan (Retaral CRO)
- Chrome Stable Fat (Atlasol 177C)
- Polymeric Tanning Agent (ICATAN 204)
- Neutralizing Syntan (Tamol NA)
- Acrylic Resin
- Mimosa
- Quebracho
- Tanigan OS (Replacement Syntan)
- Basyntan AN (Amphoteric)
- Neosyn N (Naphthalene)
- Black 3TN (Dye)
- Dicyandiamide (Syntan DF585)
- Synthetic Fat (Synthol FL327)
- Semi Synthetic Fat (Atlasol 23Kpm)
- Sulphite fish Oil (Vreka 400R)
- Lecithine (Provol BA)
- Lanoline (Vreka GFN)
- Neats Foot Oil (Atlasol 30CT)
- Synthetic Maleic Resin (Retaral RST)
- Cationic Fat (Catalix GS)
Day: 11
20.12.2010
Setting Operation:
Today we observed the setting operation. It is done to reduce water and crease from the leather. There is a setting machine here. We saw that the operator
and wprlers were busy for setting the Ecological tanned leathers, Black lining leathers, yellow lining leathers, black upper leathers in setting machine.
Two rollers in setting machine pressed the leather.
Objectives of Setting Operation:
o To reduce water from the leather.
o To increase the area of the leather.
o To remove the crease.
o To increase the compactness of the leather.
Day: 12
21.12.2010
Vacuum Dryer:
In order to dry the leather, Vacuum dryer is used where leather is dried under certain temperature and pressure. There is a vacuum dryer in this section.
Four operators are engaged in these purposes and the workers helped them. They worked very rapidly. After every 30 seconds the platform of vacuum dryer
pressed the leather and thus dried it. The pressure was 5 bars and temperature was 60°c. After vacuum, the leather was partially dried and produced smooth
grain.
Day: 13
22.12.2010
Staking Operation
Today we observed the staking operation. Staking is done to make the leather soft and smooth. There is a vibration staking machine in this tannery. Four
operators were engaged for this purpose and four workers helped them.
Day: 14
23.12.2010
Toggle Drying:
After staking, the leathers were sent to toggle dryer for drying. There was a continuous toggle dryer here. The object of toggling is to dry the leather by
passing hot air into the toggle dryer and to stretch the leather i.e. to increase the area of the leather. Eight people were engaged for this purpose and
six people helped them. They worked so fast with experience.
Day: 15
26.12.2010
Trimming:
It was done to give the leather a suitable shape and to cut out the defected area of the leather.
Kiss-Plate:
This machine has another name hydraulic press machine. This machine applies heavy weight with plane plate on the leather. As a result, Smooth and glossy
grain surface is appeared on the leather. There is an only hydraulic press in this tannery. By changing the plate of different design, the appearance of
that plate produced on the leather.
Day: 16
27.12.2010
Observation of Leather Machines:
Today chief mechanical engineer helped us to observed different machines present in this tannery and shortly described their functions.
Drawing Plant Layout of Crust section of the Tannery:
That day we drew the plan layout of Crust section of Samina Tannery (Pvt.) Ltd.
FLOW CHART OF THE PRODUCTION OF CRUST LEATHER FROM WET BLUE/WET WHITE
Acid Wash
Rechroming
Neutralization
Retanning
Dyeing
Fatliquoring
Setting
Vacuum
Hang Drying
Staking
Toggling
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Trimming
Plating
Crust Leather
NEXT MORNING:
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Vacuum Drying at 60oC 1 min
Hang Dry (1 day)
Staking (2/3 pressure)
Toggle
Trimming
Plating
Crust Leather
Responsible Technologists:
1.Mohiuddin Ahmed
2.Md. Fazlul Haque Tutul
3.Md. Rafiqul Islam
FINISHING
From 29-12-2010 to 05-01-2010 I was trained in finishing section. He has given us a good overview of the finishing process.
Day: 01
16.12.2010
Study on Finishing
Definition of Finishing
The last & most important operation in a tannery today is finishing where the Leather surface is coated with nice looking, colored or colorless,
flexible, stretchy, durable film of some film forming materials. Finishes on Leather also serve as a protective coating.
Purpose of Finishing
(1) Levelness of color on the Leather.
(2) Uniformity of shape from Leather to Leather.
(3) Changing the color to that which is required.
(4) Giving a surface to the Leather varying from Matt to gloss.
(5) Adding a transparent film through which the natural appearance of the Leather may be viewed.
(6) Render the Leather fast to acids, alkalis & perspiration.
(7) Render the Leather resistant to repeated flexing.
Different types of Leather Finishes:
There are three different types of Leather Finishes, which are commonly used by Leather Finishes—
(1) Water type Finishes: –These may be based on pigments protein binders, such as casein, shellac, gelatin, egg & blood albumin, waxes &
mucilaginous substances.
(2) Solvent type Finishes: — In contrast to water type Finishes solvent based Finishes contain as a binder either polyurethane or collodion cotton. These
Finishes are dissolved in organic solvents such as butyl acetate, cyclohexanone etc.
(3) Emulsion type Finishes: — Emulsion type Finishes consists of emulsions of mtrocellulose’s or resins.
Preparation of the Finishes:
Finishes should be prepared in the following order of additions: —
(a) Pigment pastes & aniline dyes.
(b) Plasticizers of the soluble oil type.
(c) Protein binder thoroughly mixed with wax emulsion when desired
(d) Mucilage’s, thickeners.
(e) Water for dilution
(f) Resin dispersion bin