Microfiber leather raw material leather soaking process

In Microfiber leather production, the raw hides used by Microfiber leather manufacturers must be effectively preserved to avoid bacterial attacks that may reduce their use value. The methods of preservative treatment of raw hides are different, but they all affect the moisture content, microstructure, and quality of the hides. Therefore, in the dipping operation, the specific traits of different hides should be treated differently, and the appropriate dipping process should be arranged to ensure the quality of rawhide dipping.

Light dry leather dipping

1.The properties of light dry skin

The drying method to preserve the rawhide's moisture content is about 15%. In this way, not only the adsorbed water and capillary water in the rawhide is removed, but more than two-thirds also deplete the combined water. It is more difficult to replenish this water when soaking and softening the lightly dried hides. During the preserving process of raw hides, as water is lost, the interfibrillar matrix in the dermis loses water. It solidifies, thus binding the collagen fibers together and shrinking and hardening the skin plate, preventing the penetration of water and chemicals.

Not only has the microstructure of lightly dried skin (especially the lightly dried skin that is overly sun-dried) changed, but also the microstructure of collagen has been profoundly changed. For example, many new hydrogen and salt bonds and cephaeline crosslinks are formed between collagen polypeptide chains, thus weakening hydration and reducing hydrophilic properties.

Moreover, the skid plate is under the high temperature of sunlight burns. The skin protein is denatured by heat, making the collagen gelatinized and reducing swelling. As a result, it is more complicated to make the light dry skin soak back to soft, affecting the degree of water filling. The water-filling degree of fresh skin is the largest. As the drying temperature increases, the degree of filling decreases. In sun-dried skin, the degree of water filling is the smallest.

2. The main points of the process of dipping lightly dried skins

According to the characteristics of light dry skin, when arranging the soaking and softening process, there should be targeted measures so that the light dry skin can be restored to the state close to the fresh skin as soon as possible. Because of the water loss and rawhide drying, collagen fibers stick to each other, or gelatinization occurs. In the condition of dry and hard skin plate, in the early stage of soaking, solid mechanical action should be avoided to prevent fiber breakage, so the initial stage should be arranged for static soaking, generally in the pool.

For light dry skin in the drying process of leather protein denaturation by heat, hydrophilic characteristics of reduced. Especially the drying temperature is high. The drying preservation time is long dry skin, skin protein denaturation by heat is more excellent, and almost wholly loses hydrophilic performance. In addition to the skin plate flesh surface is attached to grease, and meat film, so the bath is difficult to wet and penetrate the skin layer. In the arrangement of soaking back to smooth process, should consider the use of acid, alkali, enzymes, surfactants, and other soaking additives, to improve the wetting and penetration performance of the bath on the leather plate to accelerate the dry leather serving soft due to the dry leather board water loss shrinkage hardening, fiber close together, so that the leather soaking water back to soft obstruction. To make the dry skin filling water back to soft speed and make the rawhide filling water effect uniform, in addition to using chemical agents to help soften, there should also be timely arrangements for appropriate mechanical action, such as fleshing, scraping, fall soft and other processing. This not only accelerates the discharge of soluble proteins in the skin but also promotes the loosening of the skin fiber, thus accelerating the soaking water back to soft and making the rawhide reach the same soft and hard.

Because the light dry skin is filled with water slowly, the time to restore the fresh skin state is longer, coupled with the raw skin adhered to the mud, blood, feces, and other dirt and water immersion environmental conditions to the growth and reproduction of bacteria to create a suitable medium, bacteria will multiply and erode the raw skin. Therefore, the immersion process should be in the adjustment of water temperature and bath pH simultaneously, paying attention to the appropriate time to replace the immersion solution and adding the appropriate amount of preservatives to inhibit the role of bacteria to ensure that the skin from damage.

Salt dry skin and salt wet skin immersion

1. Properties of salt-dried skins and salt-wet skins

The raw material skins preserved by the salt-drying method have a moisture content of 15% to 20% by mass, which is more than that of lightly dried skins. And the combined water in the skin is only partly dissipated. In addition, in preserving rawhide with salt, some albumin and globulin in the skin dissolved in brine lost, then, after drying the salt-cured skin, so that the fiber bonding components are reduced. Therefore, salt-dried skin filled with water back to soft than light dry skin easy. Salt dry method preservative preservation of raw materials skin, in addition to collagen, contains many hydrophilic groups and has solid hydrophilic energy, constitute a neutral salt sodium chloride ions and sodium ions, hydration is more excellent and easy to combine with water, but also promote the immersion of water back to soft. As for the wet salt skin, its water content is more than light dry skin and dry salt skin; skin in the combined water is not dissipated. Moreover, in addition to the curing process has been dissolved to remove part of the ball protein, still in the skin of the ball protein also did not lose water bonding collagen fibers. Therefore, the skin plate can be more quickly filled with water back to soft.

2. The main points of dry salt skin and salt wet skin soaking process

The trait mentioned above characteristics of dry salt skin, it decided its water filling and softening is more accessible than the light dry skin, and the time required to restore the fresh skin state is also short. In soaking water softening, as long as the use of softening agents and appropriate to strengthen the mechanical effect, generally achieves satisfactory results. The trait characteristics of wet salt skin decided to fill the water softening easier. In the soaking process, applying appropriate mechanical treatment, such as fleshing, can accelerate the soaking process.

In the dry salt skin and wet salt skin soaking process, to ensure that the raw skin has sufficient water filling degree, the salt should be removed from the skin as completely as possible. However, it should be noted that the speed of salt removal should not be too fast. Too fast salt removal will make the non-collagen protein dissolve unevenly in the leather board, thus causing the leather board to be unevenly filled with water and softened and even making the leather empty and weak. Besides, we should focus on controlling the salt concentration in the dipping solution. The dehydration caused by high concentration will also affect the degree of water filling of the rawhide. In practice, you can use the drum equipment and the water change method to implement the water dipping.