LEATHER PRODUCTION - FABRIC SOFTENING FULL
RAW LEATHER and FEATURES
Rawhide; It is the name given to the skin which has not been treated other than brine after being obtained by swimming from animals. The fact that the newly skinned skin contains 60-70% water and water-soluble, easily degradable protein creates a favorable environment for bacterial damage. To prevent bacterial damage and prevent skin deterioration, raw leather is either processed immediately or protected by brine. Brine process; may be in the form of drying, stock salting, brine brine or pickling. Raw hides of similar class and type, produced under conditions assumed to be an example, that have undergone the same protection processes, are called raw leather batch. The structure of the raw leather in order to understand the physical and chemical changes at different stages of the leather production of raw leather,
The structure of mammalian animal skins consists of three main layers in terms of their physiological and chemical properties.
The outermost layer of the upper skin (epidermis) contains hair, wool, nails and glands. It is the corium (dermis) layerthat is essential in leather production. The lowest layeris called the lower skin (hypodermis) . At the same time, while examining the textural structure of the skin, epidermal cells of the skin , glaze face , blood vessels of the skin, the nerves of the skin, the hair muscles of the skin should be examined.
The outermost layer, called the upper skin or epidermis, also contains hair, wool, nails and glands. Our epidermis constitutes 1-2% of the total skin thickness, and there are no blood vessels in this layer. Epidermic layer, hair and wool and nails are epidermal formations consisting of protein called keratin. The upper parts of the epidermis layer and the keratin, which forms the parts of the hair outside the skin, and the prececratin in the lower layers of the hair roots and epidermis layer are separated as structure. Due to the cysteine (Cystein) and sulfurhydrile (-SH) groups in the preecratin protein structure, it can easily swell and be affected by chemicals and enzymes.
The glands belong to the inner epithelial tissue and consist of cells. The sebaceous glands are larger in fine wool sheep and lamb leather than in thick wool goat and cattle skins. The oil and sweat glands are removed from the skin during liming and bating operations and their places remain as cavities.
The amount of fat that the skin contains and the composition of the oil differs in different regions of the skin according to the breed, age, climate and nutrition. The fat content in cowhide varies between 2-7% of the dry weight of the skin. High-fat fattening cattle leathers have high fat content and the skin has a loose structure. Fat in goatskin is 12-15%, and in sheep skins%30 ' up to rates. While there are not many fats containing cholestrin and phosphorus that cause oil vomiting in the corium layer in cattle skins, this ratio is high in sheep and goat skins; Fat vomiting problem may occur in the leathers obtained from sheep and goat leathers.
Coria layer composed of collagen fiber tissue constitutes 85% of the total skin thickness and constitutes the finished leather. There are cavities in the collagen fiber tissue with filling tissue. Although it consists of collagen in filling tissue, it does not swell with its acid and alkali effect. Due to this structure, collagen fiber tissue may swell not in accordance with its own structure, but in the way and direction allowed by the tissue structure. If the swelling effect exceeds the strength of the fibers, breaks occur in the fibers. The fiber texture, which is flexible in its normal structure, loses its flexibility with the breaking of the fibers and hardens.
Between the collagen fibers and the tissue water of the skin, there is a substance in the glue structure called inter fibrils substant. This substance holds the fibers together and also separates them. This substance moves away from the skin during lime and bating and enables the development of pellets in lime.
The tissue frequency and vertical binding frequency of the fibers differ in different parts of the skin. The frequency of vertical attachment decreases in the skin areas around the joints, the skin gains flexibility in these areas and does not interfere with movement. Fiber tissue is not tight in the groin and abdomen of the skin, vertical attachments are low. These regions have a flexible and loose structure. Fiber tissue density and vertical bonds are the highest in the dorsal (skin) part of the skin, and the strength is highest in this region. The tensile strength of the fibers in the directions they are directed too much is more than the direction perpendicular to this direction. Needle tear strength and flexing are less in this direction. The regions where the fibers are directed too much are primarily in the direction of hair growth. It has the highest tensile strength in the direction parallel to the ridge line in the head-tail direction,
In the vertical section of the corium layer, three separate layers, glazed, papillary layer and reticular layer, are seen. The glaze layer, which is 1-2 microns thick and consists of very tight collagen fiber texture, belongs to the papillary layer and has a special importance in terms of leather quality as it gives the appearance of the skin. Since the fibers in the layer of glazing are very thin, they have more surface; Dyeing, alkali and acid swelling, resistance to chemicals and enzymes are different from other layers of the skin. The glaze becomes brittle with the accumulation of excess sepsis material and tanning in a very bulging state. It takes a specific appearance due to the arrangement of the hairs on the skin according to the animal type. From this view, it is understood which type of animal the skin belongs to.
The papillary layer is located between the glaze and the reticular layer, and due to its tight relationship with the upper skin, it contains non-collagen tissues such as hair, hair sheath, hair muscle, sweat and sebaceous glands. Therefore, due to these tissues removed by liming processes, it has a loose and porous structure. If this layer is further weakened during leather production, its strength decreases very much, and the glaze cavity occurs due to the tissue loosening between the glaze and the reticular layer. When such leathers are bent with the layer of glaze inside, folds occur in the glaze. Since the papillary layer is prone to give glaze cavity, the gap between the papillary and reticular layer is improved by improving the connection between the glaze impregnation applied in the cabinet or finishing and the papillary and reticular layer. If the glaze cavity is observed on the skirts, this is called the skirt gap.
The fibers in the reticular layer are thicker and stronger than the papillary layer fibers. The reticular layer gives the skin tensile strength and durability. By splitting the skin and thinning it with excessive shaving, the strength of the skin decreases. In cases where high strength is required in the finished leather, it is important to choose raw leather that does not require splitting and shaving.
Collagen, the main protein of the skin layer of the skin, has negative and positively charged reactive groups at the ends of the polypeptide side chains. Positive and negative loads at the isoelectric point are at the maximum level, the molecule shows a minimal load against the outside due to the (+) and (-) load balancing within the molecule, the isoelectric point on the untreated skin is around pH 7. After the liming process, the isoelectric point of the tole shifts to pH 4.5-4.7, the skin reacts at the isoelectric point to a minimum level, as it moves away from the isoelectric point, it is loaded unilaterally (+ or -). The skin acts as a cation in an acidic environment, and as an anion in a basic environment. If the isoelectric point is at the acidic point, the acid character of the protein increases.
Skin; It combines with freely available acidic and basic reagent groups to form acids and bases to form salt. As a result of the effects of acids and alkalis on polypeptide chains, polypeptide chains are partially broken down by hydrolysis, molecular lengths are shortened, new carboxyl and amine groups are released. Thus, by providing the development of pallet; In subsequent processes, the groups to which chemicals can be bound become free, and the desired properties in the finished skin become easier. The effect of acids and alkalies at high concentration and temperature, on the other hand, causes permanent damage by draining the skin, and this kind of long-term effect makes the skin unusable.
With the effect of acids and bases on the skin, an additional swelling occurs in water swelling. Swelling in alkaline environments does not depend on concentration; depends on the pH of the medium. Bases produce less swelling than mineral acids. Lime produces less swelling than swelling and sodium hydroxide. Acid swellings are not reversible and their negative effects are seen on the finished skin. alkali swellings are largely reversible and their effects are less noticeable on finished skin.
The lower skin (Hypodermis) connects the chorium and the meat layer with the help of muscle tissue. The lower skin, which is in the collagen fiber texture, is very loose as it contains a large amount of fat, muscle and blood vessels.
The longitudinal part from the tail to the first neck line, except for the skirts, covers the back and rump and is called croutons. The leather coat section does not differ much in thickness, it is more resistant to rupture and tearing than other parts of the skin. Neck and skirt parts are more relaxed than back. On average, the skin consists of 55% back and rump, that is, kropon, 23% neck and 22% skirts.
THE FIBER FIBROUS STRUCTURE
The most valuable part of the skin is the layer called corium or dermis. The so-called papillary and reticular layers of it are not separated from each other with strict boundaries. It is characterized by a complex knit appearance, with the fiber bundles extending randomly in various directions within the skin structure, being stuck overlapping and side by side. The characteristic structure of the skin can only be understood by examining these factors together, which are; leather fibers , bundles of fibers , and fibers from substances can be sorted.
LEATHER FIBERS
Although the fibers that make up the corium called the core of the skin are various, all of them are of protein origin. These are according to their characteristics; They form three separate fibers: collagen fibers, elastin fibers , reticular , and fibers.
COLLAGEN FIBERS
Collagen fibers are the most numerous. Collagen fibers contain collagen proteins, the most abundant protein in the body. Collagen is a very durable substance and collagen fibers give body structures great strength.
ELASTIN FIBERS
It is a type of protein that is elastin and albuminnoid. Among the various proteins in the body, elastin is the most resistant to heat and chemical effects. Elastic fibers exhibit a stretch ability of 100-150% against elongation and shrinkage. This feature decreases as you get older.
RETICULAR FIBERS
Reticular fibers are very fine fibers. They form a network that supports many tissues and organs.
FIBER Bundles
The most valuable part of the skin, the original skin layer called dermis or corium, is quite tight and has a complex structure like felt. Most of the fibrils in this structure, especially collagen fibrils, can show their main functions in bundles.
ARTICLE BETWEEN FIBER
The micro- and macro-spaces between the various fiber cells, fiber bundles and packages that make up the connective tissue of the skin are filled with a liquid substance in the consistency of pellets, consisting of high-molecular proteins and mucopolysaccharides and serve as a cement. This ensures that fiber bundles and packages cling to each other.
The glands of the skin are formations that develop from the epidermis and generally resemble bags, and they are poured into the base of the skin. The product composition of the products secreted in liquid form is different as well as their textural structure. These;
1. Oil glands
2. Sweat glands
3. Scent glands
4. Hair cover of the skin
1. Oil glands
2. Sweat glands
3. Scent glands
4. Hair cover of the skin
OIL CLOTHES
Sebum, which is the secretion of the sebaceous glands, empties on the hair. In this way, hair growth becomes easier. Sebum provides flexibility to growing hair.
Sweat Cloths
The sweat glands are long, curved, tubular glands found in other skin parts except the clitoris, penile head and lips.
ODOR CLOTHES
Like the sweat glands, they have excretory ducts. The secretory part consists of single prismatic cells. In these glands, the excretory duct does not join the cell ball.
SKIN CLOTH COVER
Bristles develop from hair follicles. Smooth muscle fibers, called the muscular erector pylorum, lie between the dermis and the lower part of the follicle. With the contraction of these muscles, the hairs erect, the skin surface is pulled inward, this situation is described as "I got goosebumps".
STRUCTURAL FEATURES OF VARIOUS LEATHER
Cattle Hides: Generally, there are similar sides in terms of many features of calf, cow and bull skins, but they also have privileged sides. Basically cattle hides show considerable structural changes according to the race, size, age and care conditions of the animal. and their weight is more. Therefore, bull skins are bigger and heavier.
BULLY LEATHER : The bull's floating skin is fresh about 25-30 kg even more and its thickness is 3.5-6 mm Although the ratios of the various tissues in the skin vary from animal to animal, it is possible to see all the previously mentioned tissues in this skin. In these leathers, the epidermis layer is quite thin and almost the same as the cow and calf leathers. The epidermis ratio in bull skins is only 1.0-1.7% of the entire skin. The papillar and reticular layers of the dermis, which constitute the main skin in these skins, together comprise approximately 94-97% of the total skin thickness. It is understood that the reticles of the skin occupy a very special place. The hypodermis or meat-fat layer, which forms the lowest layer of the skin, covers 2-5% of the total skin thickness. They consist of collagen and elastic fibers that hold the fat cells.
COWS: A normal sized cowhide, after swimming, is fresh, on average 15-25 kg thickness. 2.8-5.7 mm The rate of epidermis constitutes 0.6-1.8% of the entire skin thickness. The number of hairs is less in cow skins compared to calf skins. In general, the collagen fibers form a thin but tight net weave. creates.
LEATHER SKINS: Calf skins contain a large amount of water. At the same time, their areas are small and their weight is less. Epidermis makes up 1-2-3% of the thickness. Coria constitutes 95% of the skin thickness. The collagen fiber bundles in this skin are thin. The calf skin is softer. The hypodermis layer of the calf skin makes up 1-3% of the entire skin thickness. It consists of connective tissue fibers that hold fat cells.
SHEEP SKINS: In sheep skins, the epidermis covers 0.8-2.5% of the total skin thickness. It is observed that the papillar solid covering the upper part of the corium occupies a thicker place than various animal skins. This part constitutes approximately 45-75% of the thickness in sheep skins. Hypodermis shows connective tissue character. This layer consists of very loose collagen fiber bundles and fat cells packed between them. It is flexible. Sheep skins are divided into two types: wool-type sheep skins and hair-type sheep skins .
GOAT LEATHER: The histological structure of goat skins has a textural feature between calf skins and sheep skins . Goat skins generally contain less fat than sheep skins. At the same time, since they are more homogeneous than them, their sole is smoother and more prominent. Epidermis layer is 1.0% of the total skin thickness.2.6mm The bristle cover of goat skins consists of coarse-long bristles and thin soft bottom bristles. The bundles of collagen fibers are thicker and contain many fibers. The hypodermis layer of the skin shows 1-2% thickness of the total skin thickness. It contains fat deposits that form loosely with connective tissue cells.
PIG SKINS: Pig skins have a durable fiber weave and a very hard grain structure. They have an oily structure. At the same time, the tight attachment of the hypodermis to the adherent connective tissue poses a different difficulty in the processes. The hair is thick and rough. In the hydrated environment, the fiber bundles of the corium begin to gelatine easily when the temperature starts to rise.
Wetting - Softening:
It can dissolve the water they lost during canning and storage, bringing the moisture and attitude that the skins have before conservation, cleaning the microorganisms on the raw skin from blood, dirt, salt, mud and urine, dissolving in the structure of the skin and dissolving in water-soluble albumin and neutral salts globulins. it is intended to remove proteins.
Soaking is the first stage of the leather process and soaking must be effective and sufficient for the subsequent processes to be performed effectively. The soaking error cannot be completely eliminated with subsequent processes and significantly reduces the finished leather quality. Leathers that are pickled with different techniques by wetting are brought to the skin that has just been skinned. The wetting process is adjusted according to the brine shape of the raw leather. This adjustment is done by applying wetting time, water temperature and mechanical processes in different ways. The most important purpose of wetting is to remove the dirt and blood residues of the skin in fresh leathers, to ensure that the water in the dry leathers is treated, and to remove the salt in a way that does not affect the following processes in addition to the two purposes specified in salted brine leathers. Water during wetting,
The enzyme, base, salt and other chemicals used in the wetting float remove unstructured proteins from the skin, which are insignificant in terms of water-soluble tanning and complicate further processing.
20-30 0 C water is used in soaking . In long soakes, water is used at low temperatures. Although the leather moistened at high temperatures is softer and draped, the leather wetted at 20 0 C shows a better attitude. During wetting, when cold and hot water are used, skin weight decreases. If hot and cold water are used first, an increase in weight occurs on the skin.
The transition of the salt in the skin to the wetting water is accelerated at the rate of the temparature of the wetting water and the length of the rotation time of the drum. The thicker and firmer the skin is, the more oily the lower skin layer is, the more time it takes for the skin to be fully wetted by the passage of salt in the skin to soaking water. In order to remove 80% of the salt in the well-pickled leathers, 2–3 wetting bath (flote) change is required. Well-wetted hides, like fresh hides, contain about 65% water. If the pre-and basic wetting is done with 150% flote of raw hides, the salt ratio drops to 3-4 Bé and this water can be used for liming .
It is understood that if there is a smell of stinking from the raw skin, if the hairs are separated from the skin with a slight pull and the skin is darkened, it is not made in brine under suitable conditions. As a result of advanced bacterial activity, adverse effects such as a dull and rough glaze structure, glaze cavity, peeling of glaze become completely unusable. Brine raw skin becomes degradable again with the effect of bacteria with wetting process. For this reason, pre-wetting (dirty wetting) should be kept as short as possible, water temparature should be suitable for wetting time and antibacterial and surfactants (surfactant, wetting aid) should be used when necessary. Thus, the latent period of bacteria is not reached; that is, the time and environment required for the bacteria to adapt to the new environmental conditions and become harmful will not be provided.
Enzymes, neutral salts, a small amount of alkali are used to increase the wetting time and shorten the wetting time, and temparature can be increased. Turning the skins in cabinets and propellers, applying the flesh to the raw leather, which is not damaged by mechanical processes during wetting, increases the wetting effectiveness and reduces the formation of veins.
Since basic substances used in wetting process in small amounts constitute leather oils and soap; When used with anionic and nonionic wetting agents, they facilitate wetting of the skin. Soluble proteins are better removed in alkaline medium. 0.1-0.3% wetting aid, 0.1-0.4% sodium hydroxide or 0.2-1.0% soda can be used for wetting in very oily cattle skins. PH should not exceed 10.5 in the wetting float with the addition of alkali. It creates swelling on both sides of the excess alkaline skin, making it difficult for limescale to penetrate into the skin, and a dull and nubuck-like glaze is formed in painting. . Strong alkali materials accelerate wetting but reduce strength and form a glaze cavity, the glaze has a matte appearance. If wetting is performed in an excessive alkaline environment or if it is worked in a weak alkaline environment at the beginning of liming; the bristles are firmly attached to the skin and cannot be completely removed from the skin by breaking down sufficiently in lime / lime. Sodium sulfide (Na 2 S - Zırnık) or Sodium tetra sulfide (Na 2 S 4) gives good results if used in small quantities. This effect is eliminated with the addition of 0.2-0.3% crumbs (100%). Sodium tetra sulfite, which is used at the rate of 0.3%, keeps the pH at 9.2 at the wetting float and the hair bottoms can be loosened better before skin swelling occurs. Soda buffering does not cause swelling in the glaze. It is safer than sodium hydroxide. If soda was used in the main soaking, a washing float should be taken before liming and the skins should be washed for 15 minutes.
In wetting, wetting, oil emulsifying and washing effects are provided by using anionic or nonionic surfactants for a better wetting, dirt dissolving and emulsifying oils; The wetting time is shortened by reducing the surface tension between the fibers adhered due to brine, allowing water to penetrate the skin section more quickly. Since some wetting aids contain antibacterial agents, it is not necessary to use antibacterial agents. Degreasing and wetting agents; Besides wetting and degreasing, wetting and liming auxiliary materials, solvent-free degreasing, complex active surfactant, wetting aids with emulsifying and washing effects, removing a significant part of the natural oils in the skin, homogeneous distribution of the remaining natural oils to the skin, It ensures the homogeneous distribution of chemicals in the skin section and metal soaps that can be formed are also removed from the skin. Nonionic emulsifiers; It can be used for wetting, liming, descaling and bating, pickling processes as well as for the removal of less natural oil and chromium soaps remaining on the surface of the skin before final tanning due to the fact that they are not bound to the skin, can be used in wide pH ranges besides high wetting and surface cleaning and washing properties. . When nonionic emulsifiers are used in the same bath with synthetic and natural tannins, they can cause precipitation depending on the amount of tannins. Due to its high wetting and surface cleaning and washing properties, it can be used in wetting, liming, descaling and bating, pickling processes, as well as the removal of less natural oil and chromium soaps remaining on the surface of the Wet-Blue skin prior to final tanning. When nonionic emulsifiers are used in the same bath with synthetic and natural tannins, they can cause precipitation depending on the amount of tannins. Due to its high wetting and surface cleaning and washing properties, it can be used in wetting, liming, descaling and bating, pickling processes, as well as the removal of less natural oil and chromium soaps remaining on the surface of the Wet-Blue skin prior to final tanning. When nonionic emulsifiers are used in the same bath with synthetic and natural tannins, they can cause precipitation depending on the amount of tannins.
Enzymes; It dissolves the soluble proteins that are not in the collagen tissue, which are located between the fibers, by removing them from the skin, accelerate wetting by creating new hydrophilic groups in the skin fibers and loosen the epidermis layer and bristle bottoms, giving clean, light colored tola in the limestone, and also makes the finished leather softer. Effective enzyme preparations are available in a weak basic environment to facilitate wetting and liming pH transition. These enzymes are effective between pH 9-11 at 28-30 o C, soda or sodium hydroxide is used for pH adjustment. Using the enzyme, salted brine leathers can be soaked in 4 hours and dry leathers in 12-48 hours. The skins that require special care are wetted at 20-25 o C and the skins that need to be wetted at 25-30 o C.
As wetting aid, it is used in polyphosphates, neutral aromatic sulfonic acids, alkyl-ol amines and sulfur-containing organic compounds. Alkyl amines promote the penetration of softening water into the skin without significantly increasing the absorption of the finished leather. It ensures that the salted leathers are softened at 25-30 o C in a few hours without any danger and homogeneous in the section.
The processes that start with soaking and continue with hair removal (liming), descaling and bating are called liming processes. Liming is a sensitive process that is very effective on finished leather quality. Errors caused by improper lime methods cannot be completely compensated for subsequent operations. These errors are not simple errors, but are strong defects, veining, epidermis and hair residues that make subsequent procedures difficult and even evident in the finished skin.
Wet Raw Skin Weights:
a) Since the salty wet sheep skins are based on the weighted average of 3-5 kg / pcs:
-4 kg / piece of average weight of salted wet sheep skins,
- The average blocking weight of sheep skins is 2.6 kg / pc,
- The average yield of a sheep skin is considered to be 65 dm 2 manufactured leather.
b) Since the salty wet lamb skins are based on the weighted average of 1.5-2.5 kg / pcs:
The average weight of salt wet lamb skins is 2 kg / piece,
-The average blocking weight of lambskin is 1.3 kg / piece,
- The average yield of a lamb skin is considered to be 40 dm2 product, leather.
c) Since the saline wet goat leathers are weighted average of 3.2-5.2 kg / pcs:
The average weight of salted wet goat skins is 4.2 kg / pc,
- Average blocking weight of goat skins is 2,750 kg / pcs,
- The average yield of a goat skin is considered to be 60 dm 2 manufactured leather.
d) Since the salty wet kid skinned skins are based on weighted average of 1-3 kg / piece
-The average weight of salt kid's skin is 2kg / piece,
-The average blocking weight of crop skin is 1.2 kg / piece,
- The average yield of a kid's skin is considered to be 36 dm 2 manufactured leather.
e) Yield in pickled beef skins (1 kg For raw leather )
- Cattle Napada: 12-14 dm 2
-In the cattle face: 9-12 dm 2 is accepted.
Softening Effectiveness:
The most effective factor on the condition of the raw leather is the form of brine.
The leather, which is pickled with different techniques, is tried to be brought to the newly skinned skin attitude by wetting process. The most important purpose of wetting is to remove the dirt and blood wastes of the skin in fresh leathers, to treat the
water in dry leathers to the skin, to
remove the salt in a degree that does not affect the following processes in addition to the two purposes specified in salted brine leathers
and the effect of wetting on the skin impurities:
For salted brine leathers (cattle), the total wetting time is 6-24 hours in the cabinets and propellers, once or twice with 100-300% water at 20-28 degrees. With this washing, dirt and brine substances are removed from the skin significantly. Leathers that are dirty and have excess fertilizer can be removed by passing through the cavitation and fertilizer machines during wetting. If the leather is not soft enough, it will be damaged during this process. This process can be removed with 1-2 hours of pre-softening. In salted brine, salt facilitates the wetting process. Removal of salt from the skin during wetting depends on the ratio of the amount of water to the weight of the skin, the water temperature, the mechanical rotational motion, the water ratio of the skin.
The most effective factor on the condition of the raw leather is the form of brine.
The leather, which is pickled with different techniques, is tried to be brought to the newly skinned skin attitude by wetting process. The most important purpose of wetting is to remove the dirt and blood wastes of the skin in fresh leathers, to treat the
water in dry leathers to the skin, to
remove the salt in a degree that does not affect the following processes in addition to the two purposes specified in salted brine leathers
and the effect of wetting on the skin impurities:
For salted brine leathers (cattle), the total wetting time is 6-24 hours in the cabinets and propellers, once or twice with 100-300% water at 20-28 degrees. With this washing, dirt and brine substances are removed from the skin significantly. Leathers that are dirty and have excess fertilizer can be removed by passing through the cavitation and fertilizer machines during wetting. If the leather is not soft enough, it will be damaged during this process. This process can be removed with 1-2 hours of pre-softening. In salted brine, salt facilitates the wetting process. Removal of salt from the skin during wetting depends on the ratio of the amount of water to the weight of the skin, the water temperature, the mechanical rotational motion, the water ratio of the skin.
Removal of Soluble Proteins:
Salt acid and bases in soaking water
remove the water-soluble proteins.These proteins need
to be removed from the skin as they make subsequent processes difficult.If they are wetted without using auxiliary materials in fresh leathers, these proteins cannot be removed from the skin, so salt is used in fresh skin wetting
. Proteins soluble in 2% are removed from the skin.
The effect of wetting on the water ratio of the skin : The
water ratio of the skin in wetting should be brought to the ratio of the fresh skin. In this process, the time, brine shape, the feature of the wetting water, mechanical rotation movement machine operations and wetting agents are effective.
60-65% in fresh leathers, 40-50% in brine brine, 30-40% in salted brine, 10-20% in dry leathers.The contraindication of the wetting effectiveness is made with the balance of the wetted weight of the skin. Normally, the wetted weight should be 100-110% of the weight of my fresh face.one hundred' Stop. Properties of Wetting Water: The salts that give permanent hardness in the water are not harmful on wetting, and a small amount of carbonate hardness isoelectric point facilitates water intake by making weak acid effect on the skin between pH 7.0-7.8. makes it difficult to use, and in the subsequent processes, undesirably hardened water contains a considerable amount of alkali. 20-30 s water is used in wetting. In long soaking, water at low temperature is used at high temperature, leather that is wet at 20 s , although it is softer and draped. It shows a better attitude. Although the shrinkage temparature is 65 s., it cannot be exceeded to 40 s. Water binding of leather:
In the deep regions, the water ratio varies depending on thickness, hair length, structure and age. In the natural state of the skin, water is found in the skin as an element of a macro molecular structure . Not available as free water: Effect of Brine Shape on the Water Rate of the Skin in Soaking: Fresh leathers and leathers that are soaked for a short time do not undergo significant weight change in wetting because they maintain the natural water ratios. They contain salt. During wetting, salt passes into the wetting water of the skin. Since the epidermis layer cures the passage of salt in the skin into wetting water, the salt usually passes into the wetting water by the meat.
and the concentration of salt in the wetting water the same until a continued migration of the wetting water of the salt contained in the skin .ıslat Up The temperature of the height ratio of the shift to the steep water salts on the skin in proportion to the length of time for rotation of drawers of water of hızlanır.tuzl pickled leather dewatering according to the water content and wet weights farklıdır.tuzl of Soaking leather prolongs the wetting time at the rate of dryness. In dry leathers, wetting sticks from the outer layers into the skin that has a very tight structure. Therefore, wetting takes a long time. Mechanical movement is required to separate the fibers. Bacteria Effect in Soaking:
Despite the brine, a significant portion of the large number of bacteria contained in fresh skin remains in the skin.
There is approximately 10 million bacteria in 1gram of freshly skinned skin. It
decreases by 90% if the skin is washed twice with 100% water. Since the bacteria
that only break down protein are harmful, the type of bacteria is more important than the number of bacteria. The latent period is shortened at the rate of the water's temparature. By soaking the dana skin in 400% water, the latent periods
are as follows: 15 hours, 18 hours / 20 hours, 10 hours / 25 hours, 4 hours / 30 hours, 2 hours
The number of bacteria in the soaking water depends on the condition of the skin. Bacteria multiply faster in skins that are not fertilized properly with more fertilized blood. The amount of oxygen in the soaking water accelerates the growth of bacteria . During bacterial fortune, the skin should not be harmed. Pre-wetting should be kept short, and the water temperature should be suitable for wetting time and antibacterial substance should be used when necessary. FACTORS AFFECTING WET: Effect of Acids , Bases and Salts Effect of Acids:
Acids have a wetting effect on the skin. Strong acids cause acid swelling in the glaze. According to practical experience, all the acids used in wetting form a glaze in the skin. Therefore, acidic wetting is no longer used in practice. The use of acid with salt is very common in the fur process.
Effect of Bases.
Since they form soap with leather oils, they facilitate wetting of the skin. When used together with anionic and non ionic wetting agents, they have a good dirt removing effect. Soluble proteins are better removed in alkaline environment
. Sodium hydroxide, sodium sulfur and soda can be used as alkali in wetting .
Neutral Salt Effect:
Salt is used for wetting dry leathers and dry skins. Fresh leathers give harder skin than salted brine leathers. Therefore, salt is used to wet fresh leathers. This is called salt maturation. Another recommendation is to turn salted brine and dry skins, which give the gap to the back, at 50-60% float for 3-4 hours, then to start soaking. Another recommendation is to use 0.3% sodium tetra sulfide instead of whirling. Sodium tetra sulfide ensures dry skins get wet in 48 hours and loosen the bristle bottoms.
Effect of Surfactants:
Better wetting by using surfactants in wetting
dirt dissolving and emulsification of oils are ensured, soaking time is shortened. The auxiliary substances used in terms of leather quality should be weakly bound to the skin. Otherwise, it creates
glaze cavity. polyphosphates,
neutral aromatic sulfonic acids, alkyl olmines and sulfur-containing organic compounds should also be used Enzymatic wetting aids and antibacterial agents Enzymes: Enzymes used as wetting auxiliaries have a catalytic effect in the biochemical decomposition of skin proteins .
protein separation (proteases amidas) guruplarıdır.enzim soluble protein to be separated from the skin
of hydrophilic groups on fiber hızlandırır.der oluştururlar.epidermis layer and make the bottom of loosens
in salt brine skin by using ler.enzim 4 hours to dry skin in 12 to 48 hours ıslatılabilmektedir.özel care desired skin at 20 Enzymatic wetting is carried out in 25-30 s. Leather in which the skin is desired to be wetted at -25 s.
Antibacterial Substances: In
good conditions, not well-stocked and dry leathers not pickled.
antibacterial agents are used to reduce and stop bacterial activity in wetting. Antibacterial agents
should not be bound to the skin and should not cause environmental problems.
The effect of mechanical processes
Churning Effect: The
cabinets and propellers used in leather production
facilitate the processing of the materials into the leather by turning and shaking. The processing of the materials into the leather constitutes 90% of the processing time and the reactions constitute 10%. These rates
show the importance of the churning effect . In dry skins and salty dry skins
, the rotational speed should not exceed 5 cycles / min in wetting, as the excessive speed causes mechanical damage .
Skin Treatments:
These processes are removal of manure from the skin, pre-broaching, and burnishing.
By burnishing processing leather stretching is relaxed, the more edilir.ko skin wetting good wool yield and burnishing uygulanır.ö the fleshing dirty soak in bovine skin to gain more surface
after uygulanır.böyle is made by a better wetting, allow easier to liming
Wetting methods:
Fresh And Soaking
Leaved Leathers For A Short Time The benefits of fresh leather processing are avoided in the areas where slaughterhouses are close to the leather enterprises (USA, Argentina) , avoiding the costs of brine, not affecting capital during the brine, no brine errors, no environmental problems due to salt.
In fresh leather processing, quality depends on age, gender and nutritional conditions.
Soaking Methods for Salted Brine Leathers:
Salted brine leathers are wetted within a maximum of 12 hours by changing the wetting water for a period of 25 seconds
. gösterirler.ha say effect maximum solvent on -6 salinity skin proteins should be held for a long period, this critical salt concentration, otherwise the skin substantially is lost protein
long soaking:
soaking and liming is made within 24 hours of
the water temperature in the wetting gelmektedir.uz become standard practice It is below the degree of 25 s. 12 hours
It is not necessary to use wetting agent in wetting periods longer than 15 minutes.It is sufficient to move the cabinet at certain intervals. If the skin is beaten with salt, the salt rate decreases to 3-4 Be if pre-wetting with 150% float and the basic wetting is used. This water can be used for liming. It is safe to use 200% water in the pre-wetting and main wetting.If washing is done after pre-wetting or if fresh water is taken for liming, it can be worked in a short float. As a result of its use, it looks dull and nubuck in painting.
In normal salted brine, maximum 0,2% sodium hydroxide and maximum 0,5% soda are used. If you need to use soda in very oily leathers, an application can be made as follows.
1-2% of the saline weight, soda is given at the pre-wetting lasting for 2 hours with the addition of 01-0.5% wetting agent in 100% float for 25-30 seconds. The skins are washed and the main wetting is performed. A typical long wetting is performed as follows. -300 water stops for 30
minutes at 22-25 degrees, rotates for 30 minutes , drains, flesh is done. Essential wetting: 150-300% water is rotated for 30 minutes at 22-25 degrees, 5-10 minutes per hour (automatically) 2-4 Be 'flote is partially filtered, the rest used in liming.
Short-Term Wetting:
Generally, wetting and liming are done in 24 hours. Maximum 24 hours can be reserved for wetting at 24 hours working pace. Standard short soaking in the cabinet: pre-wetting
100-200% water is rotated 30-60 minutes at 28-32 degrees. Total 1 hour stops 0-30 minutes, float is filtered, Fleshing is performed. Main wetting: 100-200% water 28-32 degrees + 0.1-%, 5 alkali (50% likNAOH or soda) + 0.1--0.2 emulsifier and / or 0.2-0.5 wetting agent15 ' 4-6h wetting15 '
dry skins wetting:
Dry skins get 20% less than saline brines. The thinner the skins are, the faster the wetting should not be moved until the soft enough softens. Acids accelerate wetting, but reduce strength and form glaze cavity, matte glaze gives good results if
sodium sulphide or sodium tetra sulfite is used. + 0.3% non ionic emulsifier 0.5% NAOH (50%) 2h 16h5 ' 15 ' Washing with 25 degrees of water 2nd wetting 800% water 25 degrees 0.5% wetting material 16-18h5 ' 15 ' Washing with 25 degree water is successfully applied on dry skin, and wetting time decreases 18-24 h.
Salt acid and bases in soaking water
remove the water-soluble proteins.These proteins need
to be removed from the skin as they make subsequent processes difficult.If they are wetted without using auxiliary materials in fresh leathers, these proteins cannot be removed from the skin, so salt is used in fresh skin wetting
. Proteins soluble in 2% are removed from the skin.
The effect of wetting on the water ratio of the skin : The
water ratio of the skin in wetting should be brought to the ratio of the fresh skin. In this process, the time, brine shape, the feature of the wetting water, mechanical rotation movement machine operations and wetting agents are effective.
60-65% in fresh leathers, 40-50% in brine brine, 30-40% in salted brine, 10-20% in dry leathers.The contraindication of the wetting effectiveness is made with the balance of the wetted weight of the skin. Normally, the wetted weight should be 100-110% of the weight of my fresh face.
In the deep regions, the water ratio varies depending on thickness, hair length, structure and age. In the natural state of the skin, water is found in the skin as an element of a macro molecular structure . Not available as free water: Effect of Brine Shape on the Water Rate of the Skin in Soaking: Fresh leathers and leathers that are soaked for a short time do not undergo significant weight change in wetting because they maintain the natural water ratios. They contain salt. During wetting, salt passes into the wetting water of the skin. Since the epidermis layer cures the passage of salt in the skin into wetting water, the salt usually passes into the wetting water by the meat.
and the concentration of salt in the wetting water the same until a continued migration of the wetting water of the salt contained in the skin .ıslat Up The temperature of the height ratio of the shift to the steep water salts on the skin in proportion to the length of time for rotation of drawers of water of hızlanır.tuzl pickled leather dewatering according to the water content and wet weights farklıdır.tuzl of Soaking leather prolongs the wetting time at the rate of dryness. In dry leathers, wetting sticks from the outer layers into the skin that has a very tight structure. Therefore, wetting takes a long time. Mechanical movement is required to separate the fibers. Bacteria Effect in Soaking:
Despite the brine, a significant portion of the large number of bacteria contained in fresh skin remains in the skin.
There is approximately 10 million bacteria in 1gram of freshly skinned skin. It
decreases by 90% if the skin is washed twice with 100% water. Since the bacteria
that only break down protein are harmful, the type of bacteria is more important than the number of bacteria. The latent period is shortened at the rate of the water's temparature. By soaking the dana skin in 400% water, the latent periods
are as follows: 15 hours, 18 hours / 20 hours, 10 hours / 25 hours, 4 hours / 30 hours, 2 hours
The number of bacteria in the soaking water depends on the condition of the skin. Bacteria multiply faster in skins that are not fertilized properly with more fertilized blood. The amount of oxygen in the soaking water accelerates the growth of bacteria . During bacterial fortune, the skin should not be harmed. Pre-wetting should be kept short, and the water temperature should be suitable for wetting time and antibacterial substance should be used when necessary. FACTORS AFFECTING WET: Effect of Acids , Bases and Salts Effect of Acids:
Acids have a wetting effect on the skin. Strong acids cause acid swelling in the glaze. According to practical experience, all the acids used in wetting form a glaze in the skin. Therefore, acidic wetting is no longer used in practice. The use of acid with salt is very common in the fur process.
Effect of Bases.
Since they form soap with leather oils, they facilitate wetting of the skin. When used together with anionic and non ionic wetting agents, they have a good dirt removing effect. Soluble proteins are better removed in alkaline environment
. Sodium hydroxide, sodium sulfur and soda can be used as alkali in wetting .
Neutral Salt Effect:
Salt is used for wetting dry leathers and dry skins. Fresh leathers give harder skin than salted brine leathers. Therefore, salt is used to wet fresh leathers. This is called salt maturation. Another recommendation is to turn salted brine and dry skins, which give the gap to the back, at 50-60% float for 3-4 hours, then to start soaking. Another recommendation is to use 0.3% sodium tetra sulfide instead of whirling. Sodium tetra sulfide ensures dry skins get wet in 48 hours and loosen the bristle bottoms.
Effect of Surfactants:
Better wetting by using surfactants in wetting
dirt dissolving and emulsification of oils are ensured, soaking time is shortened. The auxiliary substances used in terms of leather quality should be weakly bound to the skin. Otherwise, it creates
glaze cavity. polyphosphates,
neutral aromatic sulfonic acids, alkyl olmines and sulfur-containing organic compounds should also be used Enzymatic wetting aids and antibacterial agents Enzymes: Enzymes used as wetting auxiliaries have a catalytic effect in the biochemical decomposition of skin proteins .
protein separation (proteases amidas) guruplarıdır.enzim soluble protein to be separated from the skin
of hydrophilic groups on fiber hızlandırır.der oluştururlar.epidermis layer and make the bottom of loosens
in salt brine skin by using ler.enzim 4 hours to dry skin in 12 to 48 hours ıslatılabilmektedir.özel care desired skin at 20 Enzymatic wetting is carried out in 25-30 s. Leather in which the skin is desired to be wetted at -25 s.
Antibacterial Substances: In
good conditions, not well-stocked and dry leathers not pickled.
antibacterial agents are used to reduce and stop bacterial activity in wetting. Antibacterial agents
should not be bound to the skin and should not cause environmental problems.
The effect of mechanical processes
Churning Effect: The
cabinets and propellers used in leather production
facilitate the processing of the materials into the leather by turning and shaking. The processing of the materials into the leather constitutes 90% of the processing time and the reactions constitute 10%. These rates
show the importance of the churning effect . In dry skins and salty dry skins
, the rotational speed should not exceed 5 cycles / min in wetting, as the excessive speed causes mechanical damage .
Skin Treatments:
These processes are removal of manure from the skin, pre-broaching, and burnishing.
By burnishing processing leather stretching is relaxed, the more edilir.ko skin wetting good wool yield and burnishing uygulanır.ö the fleshing dirty soak in bovine skin to gain more surface
after uygulanır.böyle is made by a better wetting, allow easier to liming
Wetting methods:
Fresh And Soaking
Leaved Leathers For A Short Time The benefits of fresh leather processing are avoided in the areas where slaughterhouses are close to the leather enterprises (USA, Argentina) , avoiding the costs of brine, not affecting capital during the brine, no brine errors, no environmental problems due to salt.
In fresh leather processing, quality depends on age, gender and nutritional conditions.
Soaking Methods for Salted Brine Leathers:
Salted brine leathers are wetted within a maximum of 12 hours by changing the wetting water for a period of 25 seconds
. gösterirler.ha say effect maximum solvent on -6 salinity skin proteins should be held for a long period, this critical salt concentration, otherwise the skin substantially is lost protein
long soaking:
soaking and liming is made within 24 hours of
the water temperature in the wetting gelmektedir.uz become standard practice It is below the degree of 25 s. 12 hours
It is not necessary to use wetting agent in wetting periods longer than 15 minutes.It is sufficient to move the cabinet at certain intervals. If the skin is beaten with salt, the salt rate decreases to 3-4 Be if pre-wetting with 150% float and the basic wetting is used. This water can be used for liming. It is safe to use 200% water in the pre-wetting and main wetting.If washing is done after pre-wetting or if fresh water is taken for liming, it can be worked in a short float. As a result of its use, it looks dull and nubuck in painting.
In normal salted brine, maximum 0,2% sodium hydroxide and maximum 0,5% soda are used. If you need to use soda in very oily leathers, an application can be made as follows.
1-2% of the saline weight, soda is given at the pre-wetting lasting for 2 hours with the addition of 01-0.5% wetting agent in 100% float for 25-30 seconds. The skins are washed and the main wetting is performed. A typical long wetting is performed as follows. -300 water stops for 30
minutes at 22-25 degrees, rotates for 30 minutes , drains, flesh is done. Essential wetting: 150-300% water is rotated for 30 minutes at 22-25 degrees, 5-10 minutes per hour (automatically) 2-4 Be 'flote is partially filtered, the rest used in liming.
Short-Term Wetting:
Generally, wetting and liming are done in 24 hours. Maximum 24 hours can be reserved for wetting at 24 hours working pace. Standard short soaking in the cabinet: pre-wetting
100-200% water is rotated 30-60 minutes at 28-32 degrees. Total 1 hour stops 0-30 minutes, float is filtered, Fleshing is performed. Main wetting: 100-200% water 28-32 degrees + 0.1-%, 5 alkali (50% likNAOH or soda) + 0.1--0.2 emulsifier and / or 0.2-0.5 wetting agent
dry skins wetting:
Dry skins get 20% less than saline brines. The thinner the skins are, the faster the wetting should not be moved until the soft enough softens. Acids accelerate wetting, but reduce strength and form glaze cavity, matte glaze gives good results if
sodium sulphide or sodium tetra sulfite is used. + 0.3% non ionic emulsifier 0.5% NAOH (50%) 2h 16h
Conservation: It is a process performed to kill the rotting bacteria and mold fungi that can be degraded by microorganisms or to increase the durability of microorganisms by preventing their vital activities. For this purpose, the amount of water in the skin is reduced and microorganisms are prevented from developing. Air drying of skins is called air dry conservation. It is the oldest method used. No auxiliary substances are used. With a sufficient drying, the water that reproduces and destroys the skin and hides and causes the reproduction of bacteria, is removed from the skin.
Processing of leathers with salt is also called conservation with salt. Salted dry canned by sprinkling the skin with salt, and the skin is made in brine as a result of treatment with salt solutions. First of all, the water in the skin is removed. Both methods should have an effect that will precisely block the move. Pickle conservation: It is used for hairs with de-bristled skin. The main effect of pickle conservation is the very strong acidity of the peak, which prevents the growth of bacteria and fungi in the first place.
Conservation Errors in Raw Skin
Conservation: To increase the resistance of a substance that can be degraded by microorganisms by killing rotting bacteria and mold fungi and preventing the vital activities of microorganisms. is a process for.
Conservation errors: These are the errors that occur during the period until the tanning process comes to the tanning since the raw skin is floated.
Errors Caused by Microorganisms
There are two reasons for its formation:
Bad weather, inadequate conservation or too late conservation
Despite the salty conservation made properly, the discolorations that occur
Hamling Errors: Initially, conservation is good; however, bacteria that find a suitable environment with the humidity and warming of the skin until the leather is processed in tanneries, reproduce and cause the skin to become raw.
Slight pacing errors are not noticeable. Moderate leakage errors are manifested by smell.
The skin is slippery and shiny on salty canned leathers as a result of heavy blasting, the smell is evident, how far can the hair shedding progress.
Bugs Caused by Insects
Canned (especially dried and salted preserved) leathers
are bugs created by insects and their larvae (For example, in pork skin
like oil beetles). Insects and larvae nibble on the skin, making holes resembling a pipe
Form.
Errors Caused by Chemicals
Chemicals contained in the conservation salt during the conservation process,
the conservation salt is dirty or the added substances also cause stains on the skin.
it causes.
Salt Spots: These are spots of different sizes from yellow to light brown on the flesh of the skins treated with salt. Salt stains occur as a result of the crystallization of the white calcium phosphate salt. The reason for the yellow and brown spots is the mixture of iron compounds into the salt. These stains are removed from the skin during the fleshing process.
Salt Traces: They are formations with small fluffy appearance, from light green to light blue color. It is formed by magnesium dirt in the conservation salt and light drying.
Iron Stains: It is in the form of rust-colored spots with small or large forms on the flesh of the skin.
Naphthalene Stains: They are formed as a result of using naphthalene in conservation. They are mostly seen in sheep skins.
STRUCTURE AND PROPERTIES OF WATER MOLECULE
Water is very important in leather industry. So it is necessary to know the structure of the water.
Water consists of the maximum overlap of the 1S orbitals of the two hydrogen atoms with the half-filled 2Px and 2Py orbitals of oxygen, according to the wave mechanics.
The water molecule is not symmetrical. Hydrogen ions from the oxygen nucleus0.96 A Away. Since the oxygen atom is very electronegative, it attracts the electrons of the hydrogen atom. Positive charges on two hydrogen nuclei create mutual thrust. This leads to an enlarged angle between hydrogen atoms. The bond between the atoms that make up the water molecule is polar and covalent. It is covalent because it is formed by the joint use of electrons of hydrogen and oxygen atoms. The reason for the formation of polarity is that these electrons preferably concentrate around oxygen.
So, in the water molecule, the center of gravity of the positive charges does not coincide with the center of gravity of the negative charges. As a result, the water molecule consists of a permanent dipole with a high dielectric moment.
Water, which is an oxide of hydrogen and represented by the formula H 2 O, is a chemical compound with very interesting physicochemical properties. There are three aggregate states: solid, liquid and gas. Indispensable for life, water determines not only the structure of bio macro molecules, but also their biological functions. This reluctance indicates the existence of a force that holds the water molecules together. This force comes from hydrogen bonds in water.
Apart from H 2 O molecules, it is a pure water polymer with no impurities.
Structurally, water shows different types.
a) Monomer
b) Small polymer water (H 2 O) n n = 2-4
c) N> 4 in large polymer water.
d) Ice water
e) Hydration water surrounding ions in aqueous solutions
f) Crystal water
g) Steamy water
h) Water in the structure of apolar molecules and surrounding the material in the form of a fence.
The polymer property of water has been known since the 19th century. A number of theories have been put forward as a mixture of water, monomers and small polymers. In general, there are two major theories, "mixture models" and "continuous models." But there is no clear distinction between them yet.
The fact that water is so convenient to use in industry comes from the dipole character. In addition, its solubility, polymerization ability is also important.
PHYSICAL PROPERTIES OF WATER
Pure water is flavorless, odorless and colorless. It looks bluish when in thick layers. Many physical constants have been identified according to water.
WATER DENSITY
+4 C the density of water was considered as 1 and the density of other substances were determined accordingly. That0 C As it freezes, its density decreases and its volume increases. This increase is about 10%. If this was not the case, cold water would go down to the bottom of the lakes and seas and become ice. Ice would not be defrosting because there was warmer water on the surface. As a result, most of the water on earth would turn into ice in a few years.4 C The volume increases as the density decreases below. Ice is collected by collecting and prevents water from cooling further.
REACTIONS OF WATER IN VARIOUS SUBSTANCES
It is examined in two categories.
1. Hydration : It consists of the combination of H2O molecules with metal cations with a large charge density.
The greater the density of the cation and the smaller the atomic diameter, the stronger the hydration. Because the power of the metal cation increases in proportion to the size of the charge and the atomic diameter, the force to push the proton and attract electrons increases.
2. Hydrolysis : The reactions that occur between some salt and other compounds and h2o molecules are called hydrolysis. As a result of the reaction of salt with H2O, the free acid, free base or basic salt that forms the salt is formed. Considering the balance that creates the hydrolysis, hydrolysis can be considered as the opposite of the neutralization event.
Salts are examined under four groups for their hydrolysis.
· Neutral salts are the salts formed from strong acids and strong bases.
· Basic salts include salts formed from weak acids and strong bases.
· The acidic salts include salts formed from weak bases and strong acids.
SOFTENING SOFT WATER
Softening the water means separating the hardening mineral substances from the water. Softening the water is important in the following respect.
· Less soap for washing the laundry is exerted.
· The minerals present in hard waters accumulate in the water pipes and cause clogging of the pipes.
· Some industry and manufacturing branches also require soft water. Soft water is also required in canning, textile, paper manufacturing, leatherworking and ice starch manufacturing. But very soft waters become corrosive. These are called corrosive water.
· It is important in aquaculture.
The most important components that play a role in water hardness are calcium and magnesium bicarbonate and sulfates. A small amount of calcium and magnesium chloride and nitrate are encountered.
The hardness of the waters from bicarbonates is partially removed by aeration. Also, water-insoluble carbonates are formed due to CO2.
The main methods used to soften the water are as follows.
· Soda-lime method
· Aluminum sulfate method
· Permutit procedure
· Trisodium phosphate method
· Ion exchangers
CHANGES IN THE LEATHER SQUARE DURING THE CONSERVATION
With the end of life, enzyme activity begins, which acts as the biological breakdown of tissues. Ferments, which are controlled in a living environment, accelerate the dissolution of the protein structure by the death of the animal and protein breakdown products occur. Proteins, which become soluble by the effects of enzymes and ferments, create a favorable growth environment for microorganisms. Bacteria adapt to the new living conditions in a certain period of time in this environment, they show a very rapid growth at the end of this period, in parallel, the development of enzymes is accelerated. This period, which is necessary for bacteria to multiply rapidly, is called latent period. Latent period is shortened with increasing temperature. In hot climates, the brine of the skin should be done before this period. Leathers cleaned by washing before or after cutting, It can be stored for 24 hours before pickling in non-hot weather. It is most convenient to make unleaned leather immediately in brine.
The fact that the newly skinned skin contains 60-70% water and water-soluble, easily degradable protein creates a favorable growth environment for bacteria.
The purpose of canning; for bacterial activities, as much as possible, is the preparation of the environment. The skin must contain at least 30-35% water for the bacteria to survive. Microorganisms grow in neutral and weak alkaline environment, they cannot grow in acidic environment.
The skins should be cooled very well after my face. Stinking begins within a few hours on uncooled leather. This stench occurs in the glaze layer, which is particularly sensitive. Storing the glazed skins by stacking them in a row causes a fast heat, gelatinization begins in the skin.
Effect of Leather on Water Rate in Soaking
Fresh leathers and brines made of brine for a short period of time do not undergo significant weight change in wetting as they maintain a great amount of natural water rates. 2030 C A little weight increase occurs after 2-4 hours of wetting. In dense and long-haired leathers, the wetted weight is slightly more than the water retention rate.
Depending on the water ratio of salted brine leathers, their water intake and wet weights are different. Salty brines, which have a low water content, take longer to get water during wetting.
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