Volume 04 Issue 07-2024
13
International Journal of Advance Scientific Research
(ISSN
–
2750-1396)
VOLUME
04
ISSUE
07
Pages:
13-17
OCLC
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1368736135
\
A
BSTRACT
In this article, tannins are substances that, when exposed, change the physicochemical and mechanical
properties of leather and turn leather into leather. Vegetable tannins are commonly called tannins. Both
abroad and in our country, plant extracts are mainly used to soften thick leather on shoe soles, technical
leather, belt and seam leather, high boot leather and leather.
K
EYWORDS
Plants, chemical composition, tanning, plant bark, shoes, technical leather, belt, leather, ethics, leather.
I
NTRODUCTION
Tanned ones are formed as a result of plant
activity. A huge number of plants on the globe
contain tannins in different quantities. The plant
can contain tannins in its most diverse parts:
bark, wood [2]. At the same time, the chemical
composition of plants of one breed is not strictly
constant and varies depending on various factors:
geographical habitat, growing conditions, age of
plants, and sometimes the time of harvest.
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Research Article
STUDY OF THE COMPOSITION OF SOLUTIONS USED IN
LOCAL PLANT EXTRACTS AND TANNINS
Submission Date:
July 01,
2024,
Accepted Date:
July 06, 2024,
Published Date:
July 11, 2024
Crossref doi:
https://doi.org/10.37547/ijasr-04-07-03
A.O.Homidjonov
Namangan Institute of engineering and technology, Namangan, Uzbekistan
A.A.Urmanov
Namangan Institute of engineering and technology, Namangan, Uzbekistan
M.G.Nabijonov
Namangan Institute of engineering and technology, Namangan, Uzbekistan
Volume 04 Issue 07-2024
14
International Journal of Advance Scientific Research
(ISSN
–
2750-1396)
VOLUME
04
ISSUE
07
Pages:
13-17
OCLC
–
1368736135
Although the tannins produced in different plants
vary greatly in chemical structure, they all share
some common characteristics. In the molecules of
all vegetable tannins there are several benzene
rings, which necessarily contain a certain [1]
amount of hydroxyl groups as substituents. Thus,
all tannins are derivatives of polyhydric phenols.
That is, polyphenols. Concentrated tannin
extracts are called herbal tanning extracts.
Extraction and extraction of tannins from tanning
materials is carried out with hot water or aqueous
solutions of certain chemical reagents (for
example, salts of sulfurous acid) [3]. In this case,
in addition to tannins, other water-soluble
compounds that do not have tanning ability,
called nontannins, also pass into the solution. The
ratio of tannin content to total water-soluble
content, multiplied by 100%, is called good
quality. This indicator is important for
determining the quality of tanning raw materials
and tanning extracts [6].
Water extracts of vegetable tanned materials are
acidic in nature. Their acidity is due to the
phenolic hydroxyls of the tannide. Molecules and
eight free carboxyl groups of most hydrolyzable
tannins, as well as the presence of organic acids.
For different tanning materials, pH and acidity
values vary within the following limits: for
hydrolyzed tannins pH = 3-4, acidity 250-400
meq/l, for condensed tannins pH = 4-5, acidity 3-
100 mg l [7].
Tanning solutions have significant buffering
capacity, especially towards acids. Which
depends on the ratio of tannins and nontannides.
Typically, the buffer capacity of high quality
condensed tannin solutions is significantly lower
than that of low quality hydrolysable tannin
solutions. However, the buffering capacity is
influenced not only by the amount of nontannins,
but also by their different nature in individual
tannins, as well as the tannins themselves, and the
ability of various tannin extracts [4].
Tannides are substances with a wide range of
properties, depending on their nature and
partially modified as a result of certain
treatments, as well as conditions of use.
Although a characteristic feature of the use of
plant extracts is the availability of raw materials
for industrial production, tannins are widely used
throughout the world.
The use of natural tannins ensures the highest
quality leather processing. It should be noted that
this vegetable tanning is environmentally less
dangerous than tanning with mineral salts and
syntans; In addition, the use of plant extracts
allows the use of skin trimmings and shavings for
the production of gelatin[5]. Flora provides the
leather industry with a huge range of tanning
materials that have been used for several
millennia. The leather industry uses only wood
waste. According to available data, conventional
cutting, due to the state of oak plantations, can
provide an extract yield of 30-40% [8]. An
additional source of oak extract raw materials can
be waste from furniture and other wood
processing enterprises that produce products
from oak wood.
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International Journal of Advance Scientific Research
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VOLUME
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1368736135
Chestnut belongs to the same family as oak, but
grows faster and reaches maturity in 30-40 years.
Chestnut grows in the Caucasus, in the Black Sea
and Abkhazian forests.
The tannicity of chestnut wood reaches 10%
(with zero moisture content and good quality 75-
80%). Chestnut extract has good tanning
properties. Chestnut wood can be processed
either alone or in a mixture with oak wood,
increasing the tannin and good quality of the oak
extract.
In plants such as willow, spruce and larch, the
bulk of tannins accumulate mainly in the bark.
Willow grows in various places: in forests,
meadows, along the banks of rivers and lakes, and
often forms continuous thickets. There are more
than 200 species of willows and several hundred
varieties of their hybrids, differing from each
other in the appearance of bark, leaves, flowers,
fruits, etc.
Willow bark is collected by hand. Mechanization
of procurement has not yet been carried out and
is hardly possible.
The accumulation of tannins in the bark occurs as
the tree ages. Analyzes show that the cortical
layer, depending on the age of the tree, contains
3.5-7%, and the cortical layer 7-17% of tannins.
Therefore, until the tree is 60-80 years old, when
the cortical layer is still small, tannins and good
quality of the bark are maximum.
Volume 04 Issue 07-2024
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International Journal of Advance Scientific Research
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VOLUME
04
ISSUE
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Pages:
13-17
OCLC
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1368736135
Only in 2018, a group of scientists managed for
the first time to discover a plant organelle called
the tannosome, in which tannins are synthesized
- tannins. It is formed in chloroplasts and, after
polymerization of tannins, is isolated in a
membrane shell. Once formed, the tannosome
moves into the vacuole, where tannins then
remain.
The molecular weight of unassociated tannins
ranges from 1000 to 3000 atomic units, and in the
associated form reaches 18000. The isoelectric
point of most tannins is in the range pH = 2.5-3.5.
It is generally accepted that tannins in plants are
formed (synthesized) from sugars through a
series of intermediate products. First, phenolic
substances are formed that do not have tanning
properties, which, through a series of stages, are
converted into more complex compounds -
tannins. As a result, the tanning complex of plants
is a series of polyphenolic compounds, ranging
from free phenols and their simplest derivatives
to high-molecular compounds of the tannide type,
soluble and insoluble in water.
What is common to all catechins is their ability
when, when heated in dry form and in aqueous
solutions above 100°C, as well as when heated
with acids and under the action of enzymes, they
are converted first into amorphous, easily soluble
tannins in water, and then into water-insoluble
red phlobaphenes . It is assumed that the
formation of phlobaphenes should be attributed
to the pyran ring, since it has been proven that
phenolic hydroxyls do not participate in the
phlobaphenization process.
The vegetable tanning process consists of the
adsorption of tannins into the dermis, the
diffusion of tannins into the skin, and the binding
of the tannids. Tannids are present in the skin
both in free and bound states.
Depending on this, they behave differently in
relation to leaching with water and alkalis.
Production tests of ultrafiltration-refined leather
on the technological properties of the leather
gave positive results, a result based on which
Membrane technology is used for poor-quality
purification of extracts.
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Volume 04 Issue 07-2024
17
International Journal of Advance Scientific Research
(ISSN
–
2750-1396)
VOLUME
04
ISSUE
07
Pages:
13-17
OCLC
–
1368736135
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