XXXV IULTCS CONGRESS 2019
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Session 5 (Thursday)

Session chair: Fathima, Nishter, N., Dr (CSIR-Central Leather Research Institute, Inorganic and Physical Chemistry Laboratory, Chennai, India); Keyong, Tang, Professor (Zhengzhou University, Zhengzhou, China)
 
Shortcut: S5
Date: Thursday, 27 June, 2019, 11:05 AM – 12:05 PM
Room: Seminar 1
Session type: Oral

Contents

Click on an contribution to preview the abstract content.

11:05 AM S5-01

Traceability of hides and skins: from field to leather (#212)

T. Poncet1, C. Vigier1

1 CTC, LYON, France

Content

Quality of leather is deeply dependant on the origin of the livestock including breeding, transportation and slaughter. Ten years ago, the French leather industry have commissioned CTC, the French Leather, leather goods and footwear research centre to improve the quality of hides and skins. In order to improve raw material, a unitary link is required between the quality of leather and its origin that is to say the raw material. This was the beginning of a huge project: traceability of hides and skins through the supply chain, from breeding to wet-blue (and even leather).  Data is captured from the animal’s ear tag at the point of slaughter which is then transfer on to a paper bar code. Hides and skins traders will then transfer definitively the code from the paper tag to the hides or skins thanks to an automatic high-pressure CO2 marking device on the hair side of the fresh or salted hide in the neck region. That unitary traceability is resistant to water, acid, alcalis, grease, solvents but also mechanical impacts such as splitting, shaving and even buffing. It is visible throughout all the process and fast enough. Once the permanent number code has been added, it can be visually or automatically read throughout the subsequent tanning process steps.  The automatic code reader takes the algorithm of the number and the data is collected by mean of artificial intelligence. This technology has been implemented by several abattoirs, trader and tanners.

Traceability is the essential tool for quality management throughout the supply chain. It helps the identification of the origin of defects for improvement and provides the origin of grade 1 hides and skins.  
This realistic industrial solution is a major issue for the leather industry whether it is for the improvement of quality or mastery of the supply chain and sustainability.

Take-Away

. In order to improve the quality of raw material, a unitary link is required between the quality of leather and its origin that is to say the raw material. This is the objective of that project: traceability of hides and skins through the supply chain, from breeding to wet-blue (and even leather) thanks to CO2 laser marquing.  

Keywords: traceability, supply chain, identification, leather, tannery
11:20 AM S5-02

False Positives II – Chlorophenols identification towards HPLC-DAD-MS analysis compared with ISO 17070:2015 technique. (#236)

G. A. Defeo1, M. Borgheresi1, M. De Cicco1, B. Carpignani1

1 Ars Tinctoria SRL, Analytical laboratory, Santa Croce sull'Arno, Italy

Content

The restriction of certain dangerous substances according to REACH (Registration, Evaluation, Authorisation of Chemicals as well as the Restricted Substances Lists (RSL) requirements promoted by various renowned brands obliges tanneries to everyday more numerous analysis with undesired conflictual situations on false positive tests results. This situation is worsened by the voluntary reduction of requested detection limits far below the levels recommended by the accepted ISO methods.

On this context, ISO 17070:2015 was extended in its current version from the determination of pentachlorophenol to tetrachlorophenol, trichlorophenol, dichlorophenol and monochlorophenol isomers. Some brands also included under this technique the ortho phenyl phenol (OPP) analysis, requesting a quantification limit below 1 mg/kg for all analytes.

The present paper proposes a new HPLC-DAD-MS direct method for the verification of chlorophenols positive cases, and its extension to leather chemicals analysis, as well as the discrimination among false positive cases and real positive ones.

The paper also illustrates case studies reporting differences in the quantification of the said analytes and the chlorophenol scission in different analytical conditions.

Take-Away

False positives verification of the presence of chlorophenols.

Quicker method respect to the current ISO 17070:2015 standard.

Method reliable on Leather chemicls chlorophenos research.

Generation of chlorophenols from certain AOX substances.

Keywords: ISO 17070:2015, false positive, chlorophenols, HPLC-DAD-MS
11:35 AM S5-03

Extraction of New Vegetable Tanning Agent from Coriaria nepalensis Bark and Its Application in Tanning (#145)

L. Guo1, T. Qiang1, Y. Ma2, X. Wang1

1 Shaanxi University of Science and Technology, College of Light Industry Science and Engineering, Xi'an, China
2 Shaanxi University of Science and Technology, College of Chemistry and Chemical Engineering, Xi'an, China

Content

    Traditional chromium tanning agents cannot conform to the requirement of sustainable and cleaner development under current leather producing. Compared with chromium tanning agents, vegetable tanning agents have been widely used in tanning process by the virtue of its non-toxicity, low pollution, biodegradability and regenerability. In this study, a novel vegetable tanning agent was extracted from the Coriaria nepalensis bark (CNB) by alkali solution. In order to optimize extraction conditions, the response surface Box-Behnken design was used in this experiment. The key factors including alkali concentration, extraction time, extraction temperature, liquid to solid ratio and extraction times. The experimental results showed that under the conditions of 0.22% sodium hydroxide concentration, 63 min extraction time, 83℃ extraction temperature and 24 liquid to solid ratio, the yield of tannins in CNB is 15%, tannins in extractives up to 50%. Afterwards, the composition and molecular mass were evaluated, we discovered that the extractives belong to hydrolyzable tannins and its molecular mass ranged from 599 to 1457 Da. Furthermore, the extractives were used in sheep garment tanning process. The results showed that the shrinking temperature of tanned leather can reach to 75 ℃. Applying the extractives to the retanning process, the shrinking temperature of retanned leather can reach to 130 ℃. Surprisingly, the color of tanned or retanned leather coincide with the requirement of light leather.

Take-Away

1 New vegetable tanning agent from Coriaria nepalensis bark.

2 The vegetable tanning agent belongs to hydrolyzable tannins and its molecular mass ranged from 599 to 1457 Da.

3 The shrinking temperature of tanned leather and retanned leather can reach to 75 ℃ and 130 ℃ respectively.

Graphic abstract
Show the research contents in a schematic diagram.
Keywords: Coriaria nepalensis bark, Optimization, Vegetable tanning agent, Hydrolyzable tannins, Tanning
11:50 AM S5-04

Modelling charge across pH and the iso-electric point of bovine collagen during leather manufacture (#256)

A. D. Ballantyne1, S. J. Davis1

1 The University of Northampton, Institute of Creative Leather Technology, Northampton, United Kingdom

Content

Many areas of leather production rely heavily on the manipulation of acidic and basic residues within the primary collagen structure to vary the overall charge of the substrate. For example, it is the basis which enables swelling during liming, deswelling during deliming, penetration of chromium after addition of chrome tanning salts and the fixing of chromium to carboxylate residues during basification.

Manipulation of the charge on collagen is readily achieved through the addition of acids or bases into the float which may react with these residues to alter the charge. It is well understood at high pH the overall charge is anionic as both acidic and basic residues are deprotonated and at low pH the leather charge is cationic as both the acid and amine residues are protonated.

Often, the increase in anionic charge and reduction in cationic charge with increasing pH are shown to happen concurrently and linearly with the iso-electric point (IEP) given as the point at which the positive and negative charges present on the collagen are equal. In actuality, the pH at which carboxylate / acid groups undergo protonation / deprotonation is significantly lower than that at which an amine / ammonium is protonated / deprotonated. The blue line in the figure below shows a simulated charge profile of a model protein containing a repeating backbone with both acidic and basic residues of equal concentration (Gly – Pro – Lys – Gly – Glu – Hyp)­n. It is observed that acidic groups become protonated / deprotonated at a range of pH’s between pH 3 – 6 whereas amine groups are protonated / deprotonated at pH’s from 9 – 12. In the range between pH 6 – 9 there is very little change in the charge of the collagen with an IEP of c.a. 7.4. However, a slight increase in the ratio of acidic to basic residues can cause large variations in the IEP as it will consequently occur at a pH where a mixture of acid and carboxylate functional groups are present.

Here we will model the charge of a collagen substrate based on the amino acid profile of bovine skin, considering their relative levels within the collagen and their concentration within a water / collagen matrix, representative for collagen saturated with water as would be present within a float. Models will be presented for raw, limed, chromium tanned, and glutaraldehyde tanned bovine hides. In addition, the results of laboratory experiments will used to discuss the merits and limitations of this theoretical model.

It is demonstrated that the link between isoelectric point and charge on collagen across pH is more complex that most models currently in use and this has important implications on multiple stages of leather manufacture.

Take-Away

It is demonstrated that the link between isoelectric point and charge on collagen across pH is more complex that most models currently in use and this has important implications on multiple stages of leather manufacture.

Here we provide a model for prediction of the charge of collagen at different stages of leather manufacture, including raw, limed, chrome-tanned and wet-white tanned bovine hides.

 

Charge on model peptide across pH where both acidic and basic residues are present.
Keywords: Collagen, Isoelectric point, Charge, Modelling