XXXV IULTCS CONGRESS 2019
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Speed Science

Session chair: V KANTH, SWARNA, Dr (CSIR-CENTRAL LEATHER RESEARCH INSTITUTE, CHORD, CHENNAI, India); Naffa, Rafea, Dr (New Zealand Leather and Shoe Research Association (LASRA), Palmerston NOrth, New Zealand)
 
Shortcut: SpSc3
Date: Thursday, 27 June, 2019, 2:55 PM – 3:20 PM
Room: Hall 1/2
Session type: Speed Science

Contents

Click on an contribution to preview the abstract content.

2:55 PM SpSc3-01

Study on the application of a new multi-epoxy reinforcement agent for sheep leather (#246)

X. Pang1, 2, N. Liu1, W. Ding1, 2, X. Liao2, Z. Ding1

1 China Leather and Footwear Research Institute Co. Ltd., Beijing, China
2 National Engineering Laboratory for Clean Technology of Leather Manufacture, Sichuan University, Chengdu, China

Content

Leather is a kind of natural biomass composite material which is made of animal skin as material by a series of chemical and physical processing. Its main structure is Collagen fibers of three-dimensional network structure. As we all know sheep leather always exist a common problem with low strength, while the strength of leather depended on the woven degree of collagen fibers. Through the past decades, many methods have been tried to improve the properties of sheep leather. The most commonly used methods are retanning. However, the strength enhancement of sheep leather is extremely limited by retanning, although the fullness and softness may be improved. In this study, a new type of multi-epoxy reinforcement agent (IGE) and IGE with the synergistic effect of polyamine (IGE-PA) were used to enhance the strength of sheep leather in tanning and fatliquoring process. Comparing with chromium tanned leather, it was found that under the optimized conditions (dosage: 10%, pH: 8, Temperature: 35℃ for penetration and 45℃ for fixation, tanning time: 10 h) with IGE as the main tanning agent, the tearing strength was increased 56.8%. While when the polyamine as the synergetic agent for IGE, the tearing strength was significantly increased 87.9%. While IGE and IGE-PA were used in fatliquoring process, it has significant reinforcement effect for tetrakis hydroxymethyl phosphonium (THP) salt tanned leather. It was found that under the optimized conditions (Dosage: 2.5%, pH: 7-8, Temperature: 50℃, Time: 2h) with IGE in fatliquoring process, the tear strength was increased 50.24%, while the IGE-PA was used, the tear strength was increased 64.3%. Furthermore, TGA results showed that decomposition temperatures of IGE and IGE-PA enhanced leather were all higher than traditional chromium tanned leather. In addition, SEM results showed that IGE and IGE-PA enhanced leather obtained better opened-up fiber structure.

Take-Away

1. A new type of multi-epoxy tanning agent (IGE) has reinforcement effect for sheep leather especially in tear strength.

2. IGE with the synergistic effect of polyamine (IGE-PA) were used in tanning process, which has a significant enhancement for the sheep leather.

3. IGE and IGE-PA can be also used in fatliquoring process to enhance the strength of sheep leather.

Keywords: multi-epoxy; reinforcement; Tanning; fatliquoring; tearing strength
2:58 PM SpSc3-02

A PRAGMATIC APPROACH TOWARDS THE MANUFACTURE OF WET-WHITE LEATHERS USING A BIO-POLYMERIC TANNING SYSTEM (#240)

P. N. Kariuki1, 2, 3, A. Yasothai3, 4, G. C. Jayakumar2, 3, S. V. Kanth2, 3

1 Dedan Kimathi University of Technology, Department of Chemistry, Nyeri, Kenya
2 Anna University, Department of Leather Technology, Chennai, India
3 CSIR-Central Leather Research Institute, Chennia, India
4 Anna University, Department of Chemistry, Chennai, India

Content

Different tanning materials endow leather with varying colors observable in undyed leathers. Periodate-oxidized starch tanned leathers have a yellow tinge or light brown color and get darker with age. The color change in situ is ascribable to iodate ions that are byproducts of periodate oxidation. Iodate ions undergo reduction to form iodine molecules that are yellow or brown in low or at higher concentrations. This study focuses on the removal of iodate ions from Dialdehyde Tapioca Starch (DTS) using a simple precipitation method. Preparation of DTS is by periodate oxidation and precipitation of iodate ions using an inorganic precipitant. The experiments for manufacturing wet-white leathers used pickled goatskins and DTS (unmodified and modified) tanning agents at various percentages based on pelt weight. Glutaraldehyde (GTA) tanning was the control. The percentage removal of iodate ions in modified DTS was 98%. Both unmodified and modified DTS had an aldehyde content of 70%. FT-IR and 1H-NMR confirmed the aldehyde groups. GTA, unmodified, and modified DTS tanned leathers had shrinkage temperatures of 80, 87, and 89°C, respectively. The physico-mechanical properties of the control and experimental leathers are comparable. GTA tanned leather had the typical brown color associated with GTA tannages. The ‘b’ color value of unmodified DTS tanned leather was high confirming yellowing of leathers upon ageing. Wet-white leather tanned with modified DTS had no discernible color change. Analysis of the spent tan liquor shows a reduction in the BOD, COD, TS, and TDS load when compared to GTA tanning system evincing the biodegradability of DTS. This study has overcome the drawback associated with periodate-oxidized starch tanning agents, viz. leather darkening over time, considering the chemical and physico-mechanical properties of the resultant leathers. The novel iodate free DTS can be scaled-up for commercial availability.

Take-Away

  • Removal of iodate ions from periodate-oxidized starch before its use as a tanning agent is imperative to avoid leather color change over time.
  • This study reports the successful removal of iodate ions from Dialdehyde Tapioca Starch (DTS).
  • Wet-white leather tanned with the modified DTS had no observable color change upon ageing.

 

Keywords: Dialdehyde Tapioca Starch (DTS), Periodate oxidation, Leather darkening, Iodate ions removal, Wet-white leather
3:01 PM SpSc3-03

Cleaner Chrome Tanning–Technology of low-chrome tanning without salt, pickling and short procedure (#146)

L. Jianxun1, F. Yanjuan1, M. Hewei1

1 Jiaxing University, Department of Light Chemistry Engineering, College of Material & Textile Engineering, Jiaxing, China

Content

Tannery effluent with high salinity and chromium have a serious environmental impact. The traditional chrome tannage that involved the use of sodium chloride, acid and chromium is one of the main origins of salt and chromium pollution. In this study, a non-pickling, low-chrome tanning technology was developed. The novel Chrome-free agent SL can be directly employed to tan bated cattle pelts and the wet white was obtained. Then the shaved wet white was pre-treated by Poly-carboxylate auxiliary agent and tanned by chrome powder. It was tested that the shrinkage temperature of the wet white, the initial pH of chrome tanning, the consumption of chrome powder, the shrinkage temperature of the chrome-tanned leather, the content of Cr2O3 in effluent, the absorption of chromium and the other properties of the chrome-tanned leather. It was found that the shrinkage temperature of the wet white tanned by SL reached over 80oC, the optimal consumption of Poly-carboxylate auxiliary agent was 2wt% based on the weight of the shaved wet white, the better low-chrome tanning conditions were that the wet white was tanned by 4wt% chromium powder for 150~180min at room temperature when the initial pH value was 3.5. The next processes were same as traditional chrome tannage. Meanwhile, the shrinkage temperature of the leather tanned by the low-chrome tannage reached more than 95oC, the absorption of chromium was 96%, the content of Cr2O3 in the effluent was under 200mg/L. For the low-chrome tanned leather, the absorption of dyestuff, fat-liquor reached 99.5%, 82.5% respectively. Compared with the traditional chrome tanned process, not only the conventional pickling process was eliminated, the process was been shorten and reduce the pollution of sodium chloride, but it can reduce 50% of the consumption of Chrome powder, improve the absorption of chromium and can reduce content of Cr2O3 in effluent.

Take-Away

1. LUO JIAN-XUN, LI JING, LIAO XUE-PIN,etc.Cleaner Chrome Tanning – A Non-Pickling Process Using an Aliphatic Aldehyde as Pre-tanning Agent. J. Soc. Leather. Technol.Chem. 2012,96 (1):21-26.

2.LUO JIAN-XUN,FENG YANJUAN.Cleaner Processing of Bovine Wet-white: Synthesis and Application of a Novel Chrome-free Tanning Agent Based on an Amphoteric Organic Compound. J. Soc. Leather. Technol.Chem. 2015,99 (4):190-195.

3.XU JIA-LI, LUO JIAN-XUN.Synthesis and application of a polycarboxylate auxiliary agent. China Leather.2017,46(3):35-41.

Keywords: Less-chrome tanning; non-pickle;Shrinkage temperature;short procedure; Content of Cr2O3 in effluent
3:04 PM SpSc3-04

Advanced diagnostics and innovative solutions for leather defects: the problem of yellowing (#78)

C. Florio1, R. Aveta1, G. Calvanese1, B. Naviglio1

1 Stazione Sperimentale Industria Pelli e Materie Concianti, Napoli, Italy

Content

Providing peculiar enhanced features to leather items is a factor of primary importance for the marketing of high-end articles; although the tanning production is oriented to satisfy a wide market range, it is mainly in the "high end" and "premium luxury" categories that the quality properties of the material are more expressed, indeed, and where the main current challenges have been focalized, in terms of technological innovation, sustainability and product quality.

The light-coloured leathers belongs to the category of materials designed especially for the luxury market. For this type of articles, the uniformity of the colour and the agreeableness of the overall surface appearance are crucial requirements for the most of international fashion and luxury brands.

One of the most common and undesirable defects of this type of article is the alteration of the color, with particular reference to the effects of yellowing of the surface of the material. There are several causes able to contribute to this type of defects, due to the complexity of the matrix and to the variability of traditional or innovative production processes used: from the fragility, photosensitivity and thermo-sensitivity of the finishing polymers, to the chemical instability of some finishing pigments, further than the presence of photosensitive additives, the migration of skin components or assembly components of the articles (fats, fillers, plasticizers, glues, etc.), up to the indirect contribution of environmental and thermo-climatic factors able to affect negatively the performance of the material.

SSIP, which has always been involved in research and consulting activities for the leather industry with regards to defect monitoring, through this work, would offer an overview of all the main tools for advanced diagnostics (with particular reference to Scanning Electronic Microscopy and to chromatographic and spectroscopic methods) aimed to the identification of the causes of yellowing, beside to explore innovative solutions for the development of strategies for the resolution and / or minimization of the problem of yellowing.

The technical solutions will include innovative tanning processes, innovative finishing methods, and leather surface treatments carried out in order to provide a sensible attenuation of surface absorption of IR (infrared) and UV (ultraviolet)-visible radiation.

Take-Away

 Advanced Diagnostics and innovative solutions for leather yellowing

Keywords: Leather defects, yellowing, diagnostic, instrumental analysis, innovative solutions