Improving Leather Quality In Retanning And Dyeing

Retanning is known as "golden touch" in leather making, leather. Whole style Basically, I is formed here. I. Based on the reasons of economy, safety and environmental protection in modern leather making, many tanning workers suggest that they should use the same process as far as possible in the production section with the same style of leather production, but only when they are retanning do they start sorting processing to get different styles of leather. In this regard, some useful explorations have been made and II has been obtained. It can be seen that retanning plays a decisive role in the final characteristics and final quality of leather.

　　 Retanning The purpose is to meet the requirements of full, solid and elastic leather body, and selective filling can reduce the difference of leather parts. Therefore, the retanning agent has higher requirements. The retanning agent should be permeable moderately and completely accumulate in the sensitive zone between the granular layer and the reticulate layer, so as to enhance the dense, meticulous and fullness of the granules. At the same time, retanning agent can not enhance the plastic feeling of leather, and reduce the leather's real skin feeling. Moreover, retanning agents need to entrust leather with solid grain and bone, because in the latter process, leather has to undergo mechanical operations such as pressing, polishing, soften, soften, stretching and so on. Leather is prone to mechanical loosening. All this needs to be solved by retanning. It is impossible to solve many problems mentioned above by simple one or several retanning agents. It is necessary to use a variety of good reagents with good properties to achieve the purpose. These retanning agents can include acrylic, polyurethane, melamine, protein, aldehydes, naphthalene sulfonic acid synthetic tanning agent, phenol sulfonic acid synthetic tanning agent, tannin extract and so on.

Recently, due to the requirements of foreign markets, people have turned their attention to the dyeing of high quality leather. Great changes have taken place in garment leather and furniture leather in recent years. These leather are different from the upper leather, which require the whole leather incision to be dyed. Even high quality shoe upper leather requires 121 of the whole leather cut. It is more difficult to dye the suede leather surface and incisions with basically the same color, which poses great challenges to dyes, dyeing auxiliaries and dyeing technology.

At the same time Soft leather Many other requirements have been put forward, such as good grain size, excellent light resistance, tensile strength, good coating adhesion and resistance to wiping, as well as rich and colorful finishing effect. This paper only discusses the problems of Retanning and dyeing.

The production process of modern soft leather has been perfected. Some people think that it is carried out in the traditional way from immersion to chrome tanning, and the special properties of leather are formed in retanning. Therefore, a more high-quality leather retanning agent can be developed in the chemical industry to meet the modern requirements.

However, it is impossible to achieve the same requirement by using ordinary phenol sulfonic acid and naphthalene sulfonic acid to synthesize tanning agent and a single acrylic synthetic tanning agent. Because this kind of synthetic tanning agent has good filling performance, the leather obtained is coarse and plastic. Therefore, it is necessary to develop new tanning agents that can ensure leather to achieve the desired properties. Fortunately, we have found a new type of polymer tanning agent that can be applied in the leather industry. The tanning agent is different from the synthetic tanning agent in the structure. It is a long chain chain aliphatic or aromatic compound made up of hydroxyl, carboxyl, aldehyde or other functional groups.

Leather is made from synthetic polymer tanning agent, which is made of leather with more fullness and fine grain. It has the same light fastness and selective filling property as chrome tanned leather. Most of the synthetic tanning agents do not have tanning properties. They are made of good combination of leather with chromium salts. In the application of synthetic tanning agent, the pH value of leather cut should be between 4.5 and 5. Under the combined action of main tanning agent, synthetic tanning agent and auxiliary tanning agent, the fullness and granularity of leather can be improved to a great extent. The main tanning agent will make the grain rough, so there will be a lot to do in the design of the process. Experienced tanning engineers will pre treat the raw leather with synthetic tanning agents or oils before tanning tanning agents. Taking the production of upper leather as an example, its process is listed in Table L. According to the weight of half finished leather, the amount of material is calculated and the thickness of the finished leather is 1.6mill.