Investigation of Formation Process of the Chrome-free Passivation Film of Electrodeposited Zinc

The feasibility was investigated to substitute chrome-free passivation treatment of electrodeposited zinc in a titanium bath for chromate passivation treatment. The formation mechanism of the chrome-free passivation film was further analyzed. The surface mor- phologies and the elemental compositions of the treated samples with varied immersion times were observed by scanning electron mi- croscopy （SEM） and determined by energy dispersion spectrometry （EDS）, respectively. The electrode potential of the sample surface was recorded in the film formation process. The changes of the electrode potential are in accordance with that of SEM and EDS of the sample surface. The results of X-ray photoelectron spectroscopy （XPS） show the chrome-free passivation film composed ofZnO, SiO2, TiO2, Zn4Si207（OH）2, and SrF2. The anode zinc dissolution and the local pH value increase due to the cathode hydrogen ion reduction process result in the formation of the chrome-free passivation film. The macro-images of the chrome-free passivation films formed on electrodeposited zinc show that the color of the film changes from blue to iridescence with the increase of the immersion times.

Mechanism of Chrome-free Tanning with Tetra-hydroxymethyl Phosphonium Chloride

Tetra-hydroxymethyl phosphonium chloride （THPC） has been considered as an important chrome-free tanning agent. To understand the THPC tanning mechanism, the structure, charge distribution, activity and tanning ability of each phosphorous compound in THPC tanning system were studied, by ^31p NMR, FT-IR spectroscopy, differential scanning calorimetry （DSC） and computational chemistry method, etc. When pH raised to 6.0, the decomposition of THPC would take place, which results in a production of free formaldehyde, tri-hydroxymethyl phosphonium （TrHP） and tri-hydroxymethyl phosphine oxide （TrHPO）. At pH 9.0, THPC will be converted completely to TrHP and most TrHP is further oxidized into TrHPO. It is possible that, in reaction of phosphorous compounds and collagens, both P-C and C-O bonds would break simultaneously or individually. From molecular charge distribution and bond polar properties, it is deduced that, if P-C bonds break, the activity is in order of TrHPO 〉 THPC 〉 TrHE whereas if C--O bonds break, the order is TrHP 〉 THPC 〉 TrHPO. It is more possible that P--C bonds will break in reaction with collagen, and TrHPO may be more active in the THPC tanning system. The results of tanning and DSC also prove the above conclusion. Furthermore, the fact that the shrinkage temperature of THPC tanned leather was below 70℃ when basified to pH 5.0 or lower suggests that the hydroxymethyl groups of THPC and TrHP are less possible to combine directly with amino groups of collagen.

甲醛鞣制毛皮新工艺研究

本文通过对甲醛鞣毛皮优缺点的分析，鞣制机理和条件的分析论述，重点研究了胰酶助浸水，中性蛋白酶软化，亲水性物质分散胶原纤维，中性介质中鞣制的工艺条件，制定了新工艺，完成了产品试制。

猪皮反绒服装革制造Ⅱ——有机结合鞣小试工艺研究

讨论了利用有机结合鞣制造猪皮反绒服装革的鞣制及后整理过程。提出了满足再制品质量和加工的一些方法。由于在结合鞣制过程中鞣剂的渗透与结合同时进行,而且鞣剂不能很好地分散胶原纤维导致结合鞣存在严重的缺陷。文章最终推出了一个参考工艺方案。

制革生产中间污水处理技术

简要介绍了制革生产中脱脂、浸灰脱毛、铬鞣等工序的污水处理技术。制革生产中间污水易于单独收集处理,并可回收部分化工材料。

甲醛鞣毛皮新工艺初探

本文通过对甲醛鞣毛皮优缺点的分析，及其鞣制机理和条件的分析论述，初步提出了以胰酶助浸水，中性蛋白酶软化和亲水性物质分散胶原纤维并直接在中性介质中用甲醛鞣制的新工艺。最后在２００多张东沙狐皮的鞣制实践中，取得了良好效果。

人工养殖鲟鱼皮的有效利用与制革实验研究

从环境友好的角度出发，选择了无铬工艺，以人工养殖鲟鱼皮为原料，经脱脂、浸水、浸灰、脱灰、脱骨刺、浸酸和铝鞣过程制得了鲟鱼皮革．报道了鲟鱼皮的不均匀性，鲟鱼皮脂的含量在6．07％～18．49％．讨论了浸灰时间和鞣革时间对鲟鱼皮革质量的影响．

A Novel Approach to Clean Tanning Technology

Traditional chrome tanning technology is still widely used today. In this technology, chrome shaving as well as chrome contained effluent in tanning and retanning processes is a big issue in the industry. Wet white tanning technology has been gaining in importance in recent years, but in general, the comprehensive performance of chrome-free tanned leather is not comparable with that of chrome tanned leather. In the present work, chrome-free tanning and chrome tanning are combined in a reversed procedure, which produces leather with chrome tanned leather quality without chrome tanned leather waste problems. In this procedure, a special amphoteric organic compound, no pickle, no salt chrome-free tanning agent TWT was used to tan delimed hides （no pickle） making wet white with shrinking temperature at 80-85 ~C. Then, new method called reversed tanning further process the wet white into chrome-tanned crust. In this reversed method, retanning, fatliquoring and coloring processes were carried out before chrome tanning. This technology eliminates chrome waste issue in tanning, shaving, post tanning processes. The chrome contained effluent is only concentrated in the last chrome tanning process. The leather made with this technology has complete conventional chrome-tanned leather quality. In this way, chrome leather quality without chrome waste problems was achieved. So, it is a new clean tanning technology.

A chrome-free combination tanning strategy: based on silicic acid and plant tannin

Silicic acid,commonly derived from cheap and easily available sodium silicate,has recently received great attention for application in leather industry to produce ecological leather with a cleaner approach.However,leather tanned with silicic acid alone is poor in storage stability,which limits its practical application in leather production.In this work,a new environment-friendly combination tannage based on silicic acid and plant tannin was developed to address this issue along with improving the comprehensive performances of leather.The obtained leather was characterized by scanning electron microscopy,Fourier transform infrared spectroscopy,X-ray photoelectron spectroscopy and so on.The results showed that compared with leather tanned with silicic acid alone,the leather tanned with this combination method possessed improved thermal stability,enhanced mechanical properties,acceptable softness,appropriate hydrophilicity,and especially enhanced storage stability.More importantly,the combination tanned leather with 1:1 of the mass ratio of silicic acid to vegetable tannin(composed of valonea extract and mimosa extract with the same weight)had more prominent comprehensive performances.In addition,the results demonstrated that hydrogen bonding played an important role in the combination tanning process.Furthermore,the hydrogen bonds generated between phenolic hydroxyl groups of polyphenols with silicon hydroxyl groups of silicic acid molecules inhibited the excessive condensation of Si-OH groups between themselves.Subsequently,the assessment of environmental impact revealed the value of BOD 5/COD of the wastewater produced in this combination tanning process is more than 0.3,indicating the chrome-free combination tannage based on silicic acid and plant tannin was an environment-friendly tanning technology.These findings therefore indicated that a new chrome-free tanning method with silicon and biomass materials as main tanning agents has potential practical application prospect in leather production.