| KEMIRA TANFORTM T (T) is a new inorganic-organic composite tanning agent for wet-white, and the active ingredient of T is the condensation of aluminium-silicon compounds and special organic acids. However, the shrinkage temperature (Ts) of leather tanned by T is lower than that of leather tanned by chrome, and the tanning mechanism of T is still not clear. Therefore, in order to further promote the application of T, it is necessary to study on its tanning mechanism and combination tanning properties with other tanning agent.The test methods of carbonization, ashing, ED AX, XRD and FT-IR were adopted to analyze the chemical composition of T and the results showed that T mainly contained aluminum and silicon elements, existing as the form of coordination complex of silicate and organic acid. In addition, hydroxyl and sulfate radical were also found.The best tanning process conditions in experiment of pickled sheepskins tanned by KEMIRA TANFORTM T-A(T-A) were optimized by single factor experiment method in which the Ts was used as index.The results showed that the initial liquid ratio of tanning bath was 100%, the initial pH of tanning bath was 2.5, the dosage of T-A was 5%, the permeation time was 180min, the end pH of basifying was 4.5 by sodium bicarbonate within 120min, the liquid ratio was 200%after adding hot water(40℃), then the temperature kept 40℃, and finally the turning time was 240 min, stopping drum for the night, the next day turning for 30 min, and finally the wet-white with Ts of 73～74℃was gained.In the research on mechanism of T-A, firstly, polyamide (PA) and polyvinyl alcohol (PVA) reacting with T-A were used to simulate amide and hydroxyl groups of collagen, respectively, and the method of weight analysis was adopted to examine the degree of combination of T-A. The results showed that T-A on PA and PVA were the low binding amounts of 0.42% and 0.48% respectively, which indicated that there were some chemical reaction of hydrogen bonds.The gelatin reacting with T-A was used to simulate the interaction of T-A and collagen in which the method of FT-IR was adopted. The result showed that hydrogen bonding and coordination bond generated between T-A and gelatin, in which aluminum and silicon elements of T-A were involved.The hide powder was applied in simulation experiment reacting with T-A, and best dosage of T-A was 6%. Then under the best dosage, T-A reacted with modified (decarboxylation, deamination, deguanidino) hide powder, and weight analysis and DSC analysis were adopted to examine the way and degree of the combination between the active group and T-A, as well as the change of kinetic parameters in the tanned hide powder. The results showed that T-A mainly reacted with carboxyl, followed by amino, and then guanidine. DSC analysis showed that the distribution of collagen fibers on the tanned hide powder was more non-uniform, but the thermal stability was improved. The improvement of the thermal denaturation temperature (ΔTP) of the (unmodified, decarboxylation, deamination, deguanidino) hide powder were 19℃,8℃,13.8℃ and 18.5℃, which signified that the binding of T-A and carboxyl of collagen had great contribution to ΔTP, and the binding of T-A and amino of collagen had lower contribution to ΔTP. Amino acid analysis showed that the types of amino acids and their contents in both hide powder and tanned hide powder had no significant change, indicating that the chemical bonds of T-A and hide powder were non-resistant to strong acid medium, and were the reversible binding.T-A reacted with all kinds of sheepskins (unmodified, decarboxylation, deamination, deguanidino), and the Ts of the tanned leather were 73.7℃,64.7℃, 68.4℃ and 71.9℃, respectively, which indicated that T-A mainly reacted with carboxyl, followed by amino, and then guanidine. After unmodified leather washed by the different ways(water, acetone, sodium carbonate aqueous solution), the corresponding drop values of Ts were 1℃,2.3 ℃ and 4.5 ℃, which indicated that T-A mainly reacted with collagen by coordinative bonds, followed by electrovalent bonds and hydrogen bonds. The XRDs showed that, compared with corresponding non-tanned leather pieces, the drop values of crystallinity were 11.8%,7.1%,9.6% and 10.2%, which signified that T-A permeated into the collagen fibers and then formed multi-chemical combinations with the active groups on the peptide chain. But the tanning binding of modified leather fiber and T-A had different degrees of decline, in which the combination of decarboxylation leather and T-A weakened the most, which further indicated that the carboxyl group in the leather fibers played a dominant role in combining with T-A.Bated sheepskins were pretanned by Granofin(?) Easy F-90 (F-90), pickled without salt to pH 2.3-2.7, then tanned by T-A. The results showed that the pretanned crust was not swelling when the dosage of F-90 was 4% or higher; when the combination tannage was carried out with 4% F-90, Ts of the pretanned crust was 70-72 ℃ stably, the Ts of the combination tanned crust gradually increased with the increase of dosage of T-A and when the dosage of T-A was more than 4%, the increasing trend was not obvious and the Ts was about 82.3 ℃; compared with F-90 and T-A tanning respectively, the combination tanned leather achieved good comprehensive properties with higher hydrothermal stability, better resistance to mediums and larger fiber dispersion degree. The combination tanning technology of non-salt pickling T-A based on F-90 pretanning was a kind of clean production method of wet-white leather, which not only can realize T-A tanning with non-salt pickling, but also can have a good reference to salt-free pickling chrome tanning embodiment. |
PDF Full Text Request