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Файл:Innovative Technologies for Manufacturing Leather and Fur Products. A Study Guide
.pdf
The Ministry of Science and Higher Education of the Russian Federation
Kazan National Research Technological University
A. Ostrovskaya, R. Shagivalieva, M. Suntsova
INNOVATIVE TECHNOLOGIES
FOR MANUFACTURING LEATHER
AND FUR PRODUCTS
A Study Guide
Kazan
KNRTU Press
2023
UDC 675.02:330.341(075)
Published by the decision of the Editorial Review Board
Ostrovskaya A.
Innovative Technologies for Manufacturing Leather and Fur Products :
A Study Guide / A. Ostrovskaya, R. Shagivalieva, M. Suntsova;
The Ministry of Education and Science of the Russian Federation, Kazan
National Research Technological University. – Kazan : KNRTU Press,
2023. – 96 p.
ISBN 978-5-7882-3320-8
ISBN 978-5-7882-3320-8
©
A. Ostrovskaya, R. Shagivalieva,
M. Suntsova, 2023
©
Kazan National Research Technological
University, 2023
UDC 675.02:330.341(075)
of the Kazan National Research Technological University
Reviewers:
PhD in Engineering N. Degtyarev
PhD in Engineering V. Abdullina
This study guide contains the characteristics of raw materials used in manufacturing leather and fur products and describes the techniques and methods of processing the same with inorganic substances, from preserving through tanning and
dressing.
It is intended for students pursuing a bachelor’s degree in Consumer Goods
Industry Technology and majoring in the Innovative Technologies for Manufacturing Leather and Fur Products.
It was developed at the Department of Plasma Technology and Nanotechnology of High Molecular Weight Materials.
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T A B L E O F C O N T E N T S
INTRODUCTION ................................................................................................... 4
1. RAW MATERIALS FOR LEATHER AND FUR PRODUCTION .................. 7
1.1. General Description of Hides and Skins ...................................................... 7
1.2. Primary Processes of Raw Materials ......................................................... 15
2. CLASSIFYING THE BASIC TYPES OF RAW HIDES AND FURS ............ 22
2.1. Types of Raw Hides and Furs .................................................................... 22
2.2. Rawhide Defects ........................................................................................ 35
2.3. Selecting Raw Materials for Stocks ........................................................... 38
2.4. Defining the Concepts of Leather and Fur. Principally Classifying
Leathers and Furs .............................................................................................. 40
3. PRIMARY PROCESSES AND OPERATIONS IN LEATHER
AND FUR PRODUCTION ................................................................................... 45
3.1. Basic Process Flow Parameters ................................................................. 46
3.2. Soaking of Raw Hides ............................................................................... 47
3.3. Mechanical Fur-Processing Operations at Preparatory Stages .................. 51
3.4. Degreasing ................................................................................................. 52
3.4.1. Degreasing Techniques
..................................................................... 53
3.4.2. Degreasing Practices ......................................................................... 55
3.5. Dehairing and Liming ................................................................................ 56
3.6. Mechanical Rawhide -
3.7. Re-Liming and Abating ............................................................................. 63
3.8. Pickling ...................................................................................................... 66
4. TANNAGE ........................................................................................................ 68
4.2. Neutralizing ............................................................................................... 81
4.3. Retannage .................................................................................................. 83
CONCLUSION...................................................................................................... 92
and Skin-Processing Operations ........................... 61
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I N T R O D U C T I O N
Discipline Consumer Goods Industry Technology is one of the basic
ones for students majoring in Innovative Technologies for Manufacturing
Leather and Fur Products. It is assumed to study the technology of manufacturing leather and fur items from raw materials through ready products.
Leather and fur products were known as early as in Ancient Egypt. Romans
borrowed the leather working art from Egyptians. Tanning was and is
the most important operation in manufacturing leather and fur products.
In ancient times, very different materials at hand were used for tanning, such
as bark of trees, nuts, acorns, acacia legumes, or sodium chloride. Hunter
used fats to liquor a skin procured and then crumpled it with his hands or
even with teeth, making the fat tannage.
In Russia, reference to pelts or peltry (“hide”) dates to the times of
Princess Olga’s rule (946 AD). “Hide” actually means “pelt” or “peltry”.
In the Russian language, “hide” and “furriery” are cognates, as well as “furrier”/“skinner”. Furrier/skinner is a skilled craftsperson manufacturing fur
and leather products.
Furs used to be the key asset of Ancient Rus, being the primary source
of the country’s revenues in international trade. Furs were used both to man-
ufacture clothes and as money: Furs were used to pay fines, transportation,
or customs duties. A pelt was treated as a certain amount of money. Its separate parts were equal to smaller amounts. Some amounts of money are even
named based on the names of some pelt parts in Russian.
Our country was also renowned for its furriers. Foreign companies
sent their raw materials to Russia for processing and invited our masters
to Leipzig, the global center of furriery.
Saffian leather boots had been worn in Russia since the 11th century.
Leather was utilized to do over shields and to make belts, tambourines,
drums, bags, saddles, and bridles. Cross-belts with various decorations were
worn by princess and passed from fathers to their offspring.
Now, too, once we look about, we can see fur coats, caps, or jackets –
all are leather and fur products. They have some properties that can hardly
be reproduced in synthetic materials. These are their hygienic properties,
elasticity, and high strength, all ensuring their service characteristics.
Russian researcher Modest Ya. Kittary, a professor at Kazan University, started the systematic studies of leather and fur manufacturing practices
in Russia over 100 years ago. Other researchers, such as N. V. Chernov,
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I. P. Strakhov, K. M. Zurabyan, and others, worked successfully in this area
during the Soviet times.
Contemporary leather and fur manufacturing is notable for its relatively high level of labor saving, the availability of automated machinery,
the use of chemical materials, and the utilization of the methods of physical
and chemical processing of raw materials and semifinished products, which
methods enhance the leather/fur quality and considerably step up the production processes.
Thus, leather and fur production aims at obtaining leathers and furs
from hides to use the former ones for making consumer items. This aim is
attained by using technology. Technology is a sequence of processes and
operations leading to obtaining leather and furs from animal hides/skins.
Leather and fur production consists of many operations and includes
both fluid-based and mechanical treatments. Their essence is made of chemical, physicochemical, and mechanical processes, and they consume much
water. Another special aspect of leather and fur production is the large share
of raw material costs within the final product cost. Raw material costs may
range within 60–90 and even more percent.
The process of transforming a hide or skin into leather/fur is quite
complicated. Its complicacy consists in the fact that the initial raw materials,
i.e., native protein, is an animal-derived high molecular weight compound.
It is difficult to forecast its compositions or properties clearly, as they are
influenced by too many factors. These are housing conditions, feeding habits, natural and climatic conditions, and diseases.
Core trends in developing leather and fur technology:
– Sustainable use of raw materials, i.e., animal hides and skins;
– Intensification of liquid-based processes;
– Combination of several processes within one apparatus;
– Purification of spent solutions and reuse thereof;
– Establishing waste-free green production;
– Improving the working conditions of those involved in production; and
– Mechanization and automation of manufacturing procedures.
Working conditions in enterprises are still rather difficult. Especially challenging are beamhouses and tanning yards at tanneries, while
in fur production it is the formalin tannage yard where fur finished shearlings are corrected using formaldehyde. Currying shops are mechanized
to the largest extent.
In general, the procedures of manufacturing leather and furs includes
up to 60–80 workflows and operations. This study guide considers the issues
of the primary treatment of raw materials, preparatory processes/operations,
and tanning with inorganic compounds.
Upon having studied this study guide, the student will know about:
– Ways of improving the workflows in leather and fur production
to enhance the quality of the products, intensify the production process itself, improve the environmental situation, and improve working conditions
for employees;
– How the properties of hides and skins are affected by the factors,
such as animal housing conditions, feeding, diseases, etc.;
– How conservation methods affect the subsequent processing of raw
materials;
– Theory of engineering processes in manufacturing leather and furs;
and
– Sequence of workflows and operations in manufacturing leather
and furs;
Be able to:
– Evaluate the quality of semifinished products, raw materials, and
end products;
– Improve the workflows of manufacturing leather and furs in order
to enhance the quality of products manufactured;
– Consider the environmental aspects of leather and fur production;
and
– Perform engineering analyses; and
Have skills of:
– Performing workflows and operations in manufacturing leather and
furs; and
– Forming single and comprehensive quality indicators for leather and
furs within the technology cycle.
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1 . R A W M A T E R I A L S F O R L E A T H E R
A N D F U R P R O D U C T I O N
1 . 1 . G e n e r a l D e s c r i p t i o n o f H i d e s a n d S k i n s
In leather and fur production, raw materials are the hides and skins of
domestic and wild animals. These are products of animal husbandry, fur
breeding, and hunting.
In leather industry, hides and skins of almost all species of domestic
animals are processed. These are cattlehides, horsehides, mule/ass hides,
camel hides, sheep skins, goat skins, pig skins, and deerskins. Of wild animal
hides/skins, manufacturers use chamois, elk skins, hog skins, seal skins,
whale skins, fur seal, and walrus hides.
Hides and skins of furbearers, some domestic species, and sea animals
are processed in fur production.
Russia is one of the largest manufacturers and exporters of furs. Over
50 species inhabit our country, the hides/skins of which are used in fur production.
Raw hides and skins are undressed, i.e., taken off the carcass and usually conservated hides or skins of domestic or wild animals, suitable for manufacturing various fur and leather products, in terms of the quality of their
skin covers and hair.
Hide is the vestiture of an animal, serves as a protection for its body,
and is simultaneously involved in metabolic regulation, heat control, and perception of various excitors in the environment.
In a hide, the distinction is made between hair side and skin covering.
Skin covering consists of three basic layers: Epidermis, corium, and hypodermis (Fig. 1.1).
Corium is used in leather production, while hair side, epidermis, and
corium are used in manufacturing the furs. Therefore, the corium indicators
are the most important parameters of assessing a hide in producing leather,
while both hair side and corium are the most important in fur production.
Epidermis is the outer part of skin covering, located under the hair side
and built of the cells of epithelial (limiting) tissue. There are two basic layers
in epidermis: Horny (outer) layer and Malpighian, or mucous (inner), layer.
Depending on its development stage, epidermis can contain up to six layers:
Malpighian layer may consist of the basic, reticular, and granular layer,
while the horny one may include clear, properly horny, and exfoliative layer.
Fig. 1.1. Schematic structure of a hide: 1 – horny layer; 2 – Malpighian
layer; 3 – papillary layer; 4 – reticular layer; 5 – corium; 6 – hypodermis;
7 – depot fat; 8 – collagen fiber bundle; 9 – cross section of collagen
fibers; 10 – sweat gland; 11 – hair erector muscle; 12 – hair follicle;
13 – sebaceous gland; 14 – hair shaft
Epidermis thickness depends on the hair side development stage. Thus,
the epidermis thickness of cow- or horsehides is 1 % of the hide thickness, while
it is up to 5 % in pig skins. I.e., the less developed is the hair side, the thicker is
the epidermis. In average, the epidermis thickness is 3 % of the hide thickness.
The boundary between epidermis and corium is irregular. At some sites, epidermis protrudes deeply into corium, especially near hair follicles, while corium
penetrates epidermis with multiple papillae on its surface.
In manufacturing leather, epidermis is totally removed, together with
the hair side. Many “elevations” (papillae) and epidermis cavities remain on
the corium surface. These irregularities form a unique pattern on the leather
surface. This pattern is typical of each animal species and referred to as
the “grain pattern”.
Corium, i.e., skin proper, is the basic hide layer used in leather industry. It is located directly under epidermis and formed by a compound weave
of collagen and elastin fibers. Corium is basically composed of collagen fibers. Collagen is a helical protein. Its name comes from the Greek
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κόλλα (kólla), meaning “glue” and suffix -γέν, -gen, denoting “producing”.
Collagen makes about 30 % of all the proteins found in an animal body and
forms its frame. It is characterized by high physical and mechanical resistance. When heated in water, collagen comes into gelatin or glue.
The basic structural unit of collagen is polypeptide chain:
Here, * means amino acid residues
...
C N CH
2
C N
...
O O
Collagen is composed by up to 18 different amino acids, including:
Glycine (glycocoll) – CH2NH2COOH,
Alanine (amino propionic acid) – СН3CH2NH2COOH,
Proline
NH
H
2
C
C
CH
CH
2
COOH
H
2
Oxyproline
NH
H
2
C
CH
CH
CH
2
COOH
HO
Aspartic acid
CH
2
COOH
H
2
NCHCOOH
Glutamic acid
CH2CH2COOH
H2NCHCOOH
Collagen fibers are conglomerated in bundles. Interlacing, they
form fine knits. Knit type determines the corium tightness. There are lozenge-shaped, diagonal, looped, and horizontal knits. Lozenge knits are
the toughest.
Elastin fibers make 1–5 % of the content. They consist of the protein
named elastin and form a fine mesh that is a frame of the structural elements
of corium. They are in the upper part of corium, especially around hair follicles and blood vessels.
Corium consists of two layers: Upper (papillary) dermis and lower (reticular) dermis.
Papillary dermis is also called thermostatic layer because it is involved
in the body heat exchange. Papillary layer is adjacent to epidermis, coming
into it with papillae at some sites, hence the name. This is where hair follicles, sweat and fat glands, nerves, muscles, and pigment cells are located.
Thickness of papillary dermis is determined by the depth of hair follicles.
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There is a very small layer of superfine, tightly woven fibers in the upper
part of the papillary dermis, at the border of epidermis, also called “grain
layer” or “grain membrane”. The finished leather value depends on the integrity and beauty of the grain layer, while its quality, i.e., density, grain pattern sharpness, and elasticity, mainly depends on the papillary dermis structure. Collagen fibers of this layer have a well-developed active surface,
which determines their high reactivity to chemicals and water.
Sweat gland appears as a tube wound into a ball. Excretory duct of
the gland comes into the upper end of a hair follicle. Number of sweat glands
is different in different animals. Sheep have many of them, therefore, sheep
skin is loose. There are many of them in horsehides, too. There are fewer of
them in cowhides or pig skins, while there are very few in goat or deer skins.
Fat glands are located near hair follicles and appear as uniquely shaped
sacs. Excretory ducts of the glands are connected to the hair channel. Sebaceous secretion excreted by the glands lubricates the surface of hair and epidermis. Overflow of fat and sweat gland secretions in sheep forms a paste
named suint that impregnates the sheep hair. In fine-wool sheep, suint makes
30–40 % of the entire wool weight.
Sweat and sebaceous glands are removed in preparatory processes of
the industry.
Reticular dermis of a hide consists of evenly interlaced collagen fibers,
more powerful than those in the papillary dermis. Reticular dermis is
the most solid and dense layer. This layer determines the solidity of a hide
and of the leather/fur made of it. This layer becomes thicker with the age.
In furbearers, this layer of corium is not very thick.
Subcutaneous adipose tissue (hypodermis tissue, superficial fascia)
consists of collagen and elastin fibers packed loosely and horizontally. It is
run through by blood vessels and has many fat deposits.
Hide/skin topography. Hide/skin has different structures at different
sites. Hide/skin parts that are relevant to certain parts of an animal body and
characterized by a combination of certain properties, such as thickness, density, and hair cover features, are called topographic (Fig. 1.2).
Basic topographic terms.
Backbone is a conventional line going along the vertebral column
from the head through the tailhead.
Hide/skin configuration is the contour of the hide/skin upon skinning
an animal.
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