The Preparation Of Hyperbranched Polymer With Terminal Carboxyl Groups-Al Complex And Its Tanning Properties

Chrome tanning methods were still very popular in leather industry worldwide. With the increasing concerns on environment and establishment of strategy of sustainable development, chromium is considered to be very harmful for humans and living cells, it would cause cancer and cell death. So the development of chrome-free tanning agent becomes the current research hot spot. Aluminum. tanning has a long history in leather industry. The finished leather shows pure white, great softness, elongation and fine grain. However, it was unsatisfactory as its low shrinkage temperature and poor tanning performance. Aluminum tanning is mainly used in combination tannage and pretannage, such as combines with inorganic tanning agent (such as chrome, zirconium and titanium) or organic tanning agent (such as vegetable tanning agent, glutaraldehyde and synthetic tanning agent), it would dramatically improve the shrinkage temperature.In this paper, a chrome-free tanning agent from hyperbranched polymer with terminal carboxyl groups and aluminum sulfate was synthesized. The molecular structure of HPC-Al was characterized and analyzed by IR, UV and XRD. Finally, the HPC-Al apply to tanning process, optimizing the best application condition, compared with two kinds of alunminium tanning agent and observe their effect of tanning.The single factor experimental results indicated:the reaction raw ratio was n(-COOH):n(Al3+)=1:1, pH was3, reaction temperature was30℃, and the time was3h. The shrinkage temperature of HPC-A1tanning leather is78.6℃, The molecular structure of HPC-A1was characterized and analyzed by IR, UV and XRD. The results showed that partial carboxyl groups in HPAE-C were complexed with Al3+, and the experiment obtained the anticipated product according to the anticipated route. The thermostability of HPAE-F was researched by comprehensive thermal analysis instrument. The research discovered that the thermal decomposition form of HPC-A1was single. It had good hot stability. Its weightlessness was72.58%from the decomposition to the conclusion.Application results show that:applied HPC-A1to tanning process, the dosage of HPC-A1was8wt.%, the initial pH between3.0～3.2, the finish pH between3.8～4.0, the temperature of tanning was40℃, and the time of tanning was20h. Under the some dosage, using the market alunminium tanning agent, aluminum sulfate and HPC-A1in tanning process, the Ts are78℃,68.7℃and78.6℃, tensile strength are19.06N·mm-2,14.53N·mm-2and21.21N·mm-2, tearing strength are21.90N·mm-2,20.01N·mm-2and24.68N·mm-2, thickening percentage are20.24%,12.35%and25.32%. After chromium retanning, the chromium content of waste liquid is0.88g/L and the absorption rate of chrome is86.99%. It means HPC-A1also has a great effect on high-absorbency of chrome-tanning, and it would be used in chrome tanning as a high exhaustion chrome tanning auxiliary to reduce the chromium pollution and realize clean production.