"A kind of leather without dipping acid tanning method" won the national invention patent

On February 11, 2022, the State Intellectual Property Office of the People's Republic of China announced that the technical team of Yang Junzi of Wuzhi County, Hebei Province, after years of research and development, "a leather tanning method without acid immersion" was granted a national invention patent (Authorization Notice No. CN 112522455 B). The patent mainly solves the technical problem of "bare leather-leather" tanning without adding salt materials and acid leaching during the tanning process of cowhide, sheepskin and pigskin after softening, and finds a way to solve the problem of difficult treatment of tanning wastewater containing chlorine ions.

In the traditional tanning process, the bare leather is tanned by adding salts and acids such as formic acid and sulfuric acid in the drum for a certain period of time, then adding chromium powder for a certain period of time, and then tanning by changing the PH from outside to inside to combine with alkali, and then warming up to become blue wet leather. In this process, the main function of adding salt material is to prevent the collagen fibers of bare leather from swelling in acid under the lower acidic condition and to inhibit the effect of damaging collagen fibers. After making blue leather, the salt material has no effect and may also cause salt frost on the finished leather, so it must be cleaned in the later process, which increases the processing steps and costs, and also causes difficulties in wastewater treatment.

The use of non-impregnated acid tanning process is bare leather by first adding high absorption chromium powder salt-based degree of 33% turn uniform, before no hydrolysis to add formic acid, sulfuric acid and other acid substances, so that the side of hydrolysis, while creating conditions to penetrate. As chrome powder tanning agent also has weak tanning performance at this time, and then add the right amount of buffer bare leather in weak acidic conditions to achieve the purpose of non-hydrolysis acid swelling, to tanning agent chrome powder completely penetrate evenly, and then by lifting alkali temperature rise production of blue wet leather is feasible. Compared with the traditional non-impregnated acid tanning process, it only needs 3-4 hours of extended processing to achieve the same quality as the blue wet leather produced by the traditional process. After many experiments and quality comparisons, there is no quality difference between the blue wet leather produced by the traditional process and the non-impregnated acid tanning process through testing.

If adopt the non-leaching acid tanning process, each cabinet of cowhide (22 tons of cowhide) can reduce the use of salt by about 2 tons, and the processing cost can be reduced by 2000 yuan. As the wastewater does not contain chlorine ions, the treatment difficulty is reduced and the treated water can be used for garden irrigation, road and site spraying, etc., improving the recycling rate of water resources.

The patent in the research and development process, got the Hebei leather industry association senior technical adviser, the former Wenzhou University leather research institute deputy director of Professor Yin Dehai's full support, it gave a full range of guidance and help, to ensure the smooth development of technology.

At present, Wuji County Economic Development Zone Management Committee together with Wuji County Enterprise Federation is organizing the tanning enterprises in the county to promote and apply the technology on a large scale. Once the technology is popularized, it will certainly trigger a new technological revolution and quality innovation in the field of tanning, especially it will have a positive and far-reaching impact on saving resources, protecting the environment and creating an ecological tanning and recycling industry.