Vegetable Tanning Agents

The distribution and structure of hydrolyzed tannins, the separation of tanning agents and their quantitative determination, methods for preparing tanning extracts, methods for increasing the efficiency of extracting raw material, and the chemical processes during tanning of hides are discussed. The literature from 1950 to 1999 is reviewed     

Matrix effect in second-order data: determination of dyes in a tanning process using vegetable tanning agents

The aim of this paper is to determine the concentration of three dyes throughout the tanning process of leather using vegetable tanning agents with a sequential injection analyser with second-order data treatment. As the vegetable tanning agents used are highly absorbent species, we focus on three aspects: (i) difficulties with the resolution (ii) the reduction in the working concentration range; and (iii) matrix effects. Ideally, second-order instruments provide “second-order advantage”; i.e. calibration is possible in the presence of uncalibrated interfering species. However, if the interfering species change the instrumental response of the analyte (in scale or shape), standard additions must be used to ensure the accuracy of the estimated analyte concentration. Here we study the presence of matrix effects for three dyes in several samples in order to significantly improve the accuracy of predictions in the presence of such effects. We found that there were matrix effects in at least 80% of the samples with an alpha risk of 5%. We used this method to study the exhaustion of dyes in the dyeing process.     

翻白草中鞣质的微波提取工艺研究

采用微波辅助提取方法,以提取剂浓度、pH值、液固比、微波提取时间、温度等为考察因素,并以提取物中总鞣质的提取率为评价指标,使用磷钼钨酸-干酪素分光光度法为定量测定方法,在单因素实验的基础上,通过正交实验优化翻白草中鞣质的提取工艺.实验结果表明,最佳提取条件为:使用70%甲醇作为提取剂、液固比40∶1、提取液pH为8.0、提取温度为40℃、提取时间为10 min.还对翻白草不同部位(根、茎、叶)的鞣质含量进行分析,发现根部中鞣质的含量最大,其次为茎和叶.此外,采用高效液相色谱法对翻白草中鞣质的种类进行定性分析.     

The Interaction between Collagen and an Aluminum Tanning Agent

The interaction between collagen and organometallic aluminum complexes was studied. From the analysis of the IR and UV spectra, the viscosity of collagen, and the treated collagen, a possible interaction model of the collagen with the aluminum tanning agent has been found. It indicates that such an aluminum tanning agent could be used as a cleaner tanning agent in leather tanning.

Viscosity curves of the untreated collagen solution (a) and the collagen solution treated with aluminum tanning agent (b).     

Improvement of hydrothermal stability and chrome uptake of leather: Amino-terminated hyper-branched polymer as high exhausted tanning auxiliary

Carboxyl-terminated hyper-branched polyester is extensively used as high exhaustion chrome tanning auxiliary owing to its strong coordination ability with trivalent chrome. Owing to lower electronegativity of N than O, the coordination ability with trivalent chrome for hyper-branched polyamide is stronger than polyester. Herein, in this paper, an amino-terminated hyper-branched polyamide (HBPN) is synthesized and used as high exhaustion chrome in tanning of pickling pigskin (HBPN–Cr). The effects of utilization of HBPN in denaturation temperature, shrinkage temperature, chrome uptake, and microstructure structure of wet-blue leather are studied. Moreover, the anti-oxidation stability of wet-blue leather is preliminary studied by heat treatment. The results show that incorporation of 1% HBPN in pickling process can significantly improve chrome uptake to 83.32%. The hydrothermal stability of wet-blue leather is improved due to the formation of higher crosslinking degree of collagen fibers. In addition, for the wet-blue leather without unsaturated fatliquoring agent, through heat treatment, hexavalent chrome does not appear after 24 ​h heat treatment. On the contrary, the chrome complex changes from hydroxyl copolymerization to more stable oxygen copolymerization or chrome oxide for C–Cr and HBPN-Cr tanned leather, respectively. These results will build a data support for the further study of hyper-branched polymer chrome tanning auxiliaries.     

与铬鞣有关的胶原化学研究进展

本文在回顾与制革有关的生皮胶原结构的基础上, 概述了铬鞣过程胶原与铬(?) 之间的作用, 并对近年来利用胶原计算机模型探讨鞣制反应和以提高铬鞣有效性为目的的胶原修饰化学的研究状况及其发展前景作简要论述。     

丙烯酸铈(Ⅲ)-丙烯酸丁酯对明胶的接枝共聚鞣制

以（ＮＨ４）２Ｓ２Ｏ８－ＮａＨＳＯ３作引发剂,用丙烯酸丁酯和丙烯酸铈（Ⅲ）对明胶进行乳液接枝共聚鞣制。考察了乳化剂种类及用量、介质ＰＨ值,乳液固含量和离子浓度等因子对反应及乳液稳定性的影响,通过对合成聚合物与明胶结全形式的研究,探讨了接枝共聚鞣制的机理。     

改性三聚氰胺树脂鞣剂合成

本文采用一种全新的乙醇胺醚化－－助剂体系改性三聚氰胺树脂鞣剂，并通过研究单体，醚化剂，助剂用量，浓度，pH变化等工艺条件，获得了稳定性，水溶性良好的鞣剂产品。     

Use of glyoxal in production of a composite chromium tanning agent

Conditions in which a composite chromium tanning agent can be obtained in the presence of glyoxal were studied. It was found that the expenditure of the aldehyde and sulfuric acid affects the reduction kinetics of hexavalent chromium. Spectrophotometry and conductometry were used to examine the composition of composite tanning agents. It was shown that chromaldehyde tanning agents can be applied in manufacture of leather and fur.     

Preparation and Application of a Nanocomposite (MPNS/SMA) in Leather Making

Environmental pollution is one of headache problems in leather tanning industry.Traditionally chrome tanning was the predominant technique used in leather making.However,chrome tanning is being substituted due to its pollution and scarcity of resource.The study of non-chrome tanning in leather shows more interests with the development of nanomaterial and nanotechnology.J.Z.Ma et al.have reported that organic–montmorillonite nanocomposite can raise the shrinkage temperature of pickled pigskin…     

Thermofraktographie zur Charakterisierung natürlicher Polyphenole,Gerbstoffdrogen und Leder

In this report the behaviour of a number of phenolic substances of natural and synthetic origin-e.g. monomeric phenols, defined tanning agents and their constitutional units (model substances), tanning drugs and leather-was investigated under the conditions of thermofractography (TFG), with linear increase of temperature in the range 50–450° C. The TLC conditions had to be optimized first in order to achieve the best possible identification of the phenols expected to originate during TFG. The TFG of the model substances showed varying fragmentations according to their constitutional units and their types of linkage. Regarding the thermal range of fragmentation and the phenols which appear in the thermofractograms (TFG), the assignment to the types of tanning agents in plant material has become possible. The same assignment can be made for the tanning agents which are bound in collagen (leather) by hydrogen bonds. Further, TFG gives hints about substances which have been used for finishing and dyeing leather. The figures of the thermofractograms of some natural and synthetic tanning agents are given and discussed.     

Interaction of Maleic Acid Copolymers with Collagen

One of the present trends to increase the efficiency of the chrome tanning process is the use of chemicals which change the affinity and induce a better binding of the chromium ions in the hides. Recently, some anionic polyelectrolytes based on poly(acrylic acid) or maleic acid copolymers were developed as additives in the chrome tanning. The effect of polyelectrolytes could be explained by their interaction with the collagen from hide. In our work four maleic acid copolymer/collagen systems were investigated by turbidimetric, conductometric and potentiometric titrations. The interaction between the two macromolecular compounds was clearly evidenced, and its dependence on the chemical structure of the maleic acid copolymer and on the amount of added chromium ions was studied. Homogeneous systems or turbid dispersions were observed depending on the hydrophilic or hydrophobic character of the maleic copolymer, on the [CH]/[MP] ratio, and on the concentration of the chromium ions.     

催化电位滴定法测定铬鞣剂中铬(Ⅲ)

报道了以氨三乙酸存在下锰(Ⅱ)催化KIO4氧化结晶紫的反应指示终点,结晶紫电极作指示电极用催化电位滴定法测定铬鞣剂中Cr(Ⅲ)的方法。该法终点灵敏、准确度高、重现性好,结果满意,用标准加入法测得的平均回收率为100.03%,RSD为0.24%。     

Obtaining Granules from Waste Tannery Shavings and Mineral Additives by Wet Pulp Granulation

This paper presents the results of research on the granulation process of leather industry waste, i.e., tanning shavings. It is economically justified to granulate this waste together with mineral additives that are useful in the processes of their further processing. Unfortunately, the granulation of raw, unsorted shavings does not obtain desired results due to their unusual properties. In this study, the possibilities of agglomeration of this waste were examined by a new method consisting of the production and then the granulation of wet pulp. During granulation, no additional binding liquid is added to the granulated bed. As part of this work, the specific surface of granulated shavings, the granulometric composition of the obtained agglomerates, and their strength parameters were determined. The use of a vibrating disc granulator, the addition of a water glass solution (in the pulp), dolomite, and gypsum made it possible to obtain durable, mechanically stable granules.     

新型阻燃性氨基树脂鞣剂的合成

现有的阻燃剂产品多数分解温度低,难溶于水,不易渗透皮革纤维。本文合成的季戊四醇二氢酯羟甲基化三聚氰胺树脂具有高效的阻燃作用,又具有三聚氰胺树脂鞣剂独特的鞣革作用。本文考察其合成工艺条件及其对产品性能的影响因素。     

Investigations on geometrical features in induced ordering of collagen by small molecules

Binding energies of the interaction of collagen like triple helical peptides with a series of polyphenols, viz. gallic acid, catechin, epigallocatechingallate and pentagalloylglucose have been computed using molecular modelling approaches. A correlation of calculated binding energies with the interfacial molecular volumes involved in the interaction is observed. Calculated interface surface areas for the binding of polyphenols with collagen-like triple helical peptides vary in the range of 60–210 ?² and hydrogen bond lengths vary in the range of 2.7–3.4 ?. Interfacial molecular volumes can be calculated from the solvent inaccessible surface areas and hydrogen bond lengths involved in the binding of polyphenols to collagen. Molecular aggregation of collagen in the presence of some polyphenols and chromium (III) salts has been probed experimentally in monolayer systems. The monolayer arrangement of collagen seems to be influenced by the presence of small molecules like formaldehyde, gluteraldehyde, tannic acid and chromium (III) salts. A fractal structure is observed on account of two-dimensional aggregation of collagen induced by tanning species. Atomic force microscopy has been employed to probe the topographic images of two-dimensional aggregation of collagen induced by chromium (III) salts. A case is made that long-range ordering of collagen by molecular species involved in its stabilisation is influenced by molecular geometries involved in its interaction with small molecules. Dedicated to Professor C N R Rao on his 70th birthday     

Study of the influence of NaOH treatment on the pyrolysis of different leather tanned using thermogravimetric analysis and Py/GC-MS system

This paper presents a study of the influence of a NaOH treatment on leather samples tanned using different tanning agents. Thermogravimetric analysis (TG/DTG) and flash pyrolysis (Py/GC-MS) was carried out on treated samples, and the results were compared with those obtained with the untreated samples. Treatment with sodium hydroxide seemed to decrease the temperature of maximum leather decomposition rate between 4 and 27 °C, depending on the tanning agent, and increased the range of temperatures where leather degradation occurs. From flash pyrolysis experiments, it was found that the volatile products obtained from NaOH-treated samples contain higher amounts of nitrogen compounds than those obtained from untreated samples. The results of a multivariate analysis applied to pyrolytic products obtained in the flash pyrolysis of samples showed greater similarity between the results obtained in all treated samples than between treated and untreated samples produced with the same tanning process.     

Synthesis of Citric Acrylate Oligomer and Its In-Situ Reaction with Chrome Tanned Collagen (Hide Powder)

Summary: The purpose of this study was to formulate the new combined system of acrylic and citric acids, which was prepared by free radical polymerization and esterification reaction at the same time to form citric-acrylate CAC oligomer. The presumable chemical structure of this oligomer and the reaction mechanism were investigated by different spectroscopic tools (¹H,¹³C-NMR and ATR-IR), GPC and TGA/DTA. The effect as masking agent of the eco-friendly oligomer (CAC) in the chrome tanning of the collagen and the pickling of the hide was approached by the study of the hydrothermal and mechanical properties of in-situ treated/grafted chrome tanned collagen (hide powder) and pickled hide, respectively. The use of citric acrylate CAC oligomer instead of the traditional strong acids resulted in significant improvement in chrome exhaustion and physical properties of the leather.     

Analysis of commercial vegetable tanning agents by reversed-phase liquid chromatography-electrospray ionization-tandem mass spectrometry and its application to wastewater

Commercial vegetable tanning agents that are derived from plants and consist of condensed or hydrolyzable tannins were analyzed by electrospray ionization–tandem mass spectrometry (ESI–MS/MS) to identify their major constituents and to study their collision-induced dissociation. In the condensed tannin wattle a series of proanthocyanidin dimers to tetramers was identified together with the flavonoid monomers catechin and gallocatechin. The composition of the hydrolyzable tannin chestnut was more heterogenous. Besides the monomers ellagic and gallic acid a variety of gallotannins were detected, namely mono-, di- and trigalloylglucose, and a variety of ellagitannins. Reversed-phase HPLC–ESI–MS/MS methods were developed to detect condensed and hydrolyzable tannins in tannery wastewaters by multiple reaction monitoring (MRM). The methods proved suitable even for highly loaded wastewaters. However, the detected amount of wattle tanning agent in spent retanning baths was about two orders of magnitude below the amount used for the retanning. This suggests that the condensed tannins of polyphenolic structure are rapidly transformed during the tanning process to yet unknown products.