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Session 3 (Wednesday)

Session chair: Ammenn, Jochen, Dr (Stahl, R&D Wet End and Production Support, Sandhausen, Germany); DEFEO, GUSTAVO, A., (ARS TINCTORIA SRL, SANTA CROCE SULL'ARNO, Italy)
Shortcut: S3
Date: Wednesday, 26 June, 2019, 3:50 PM – 5:05 PM
Room: Hall 1/2
Session type: Oral


Click on an contribution to preview the abstract content.

3:50 PM S3-01

Biopolymers for a more sustainable leather (#154)

L. Taddei1, F. Ugolini1, G. P. Bonino1, G. Giacomelli1, C. Franceschi2, M. Bertoldini3, R. Sole3, V. Beghetto3

3 University Ca’ Foscari of Venice, Department of Molecular Sciences and Nanosystems, VENICE, Italy

with the contribution of the LIFE Programme of the European Union


A novel class of bio-based polymers have been developed within the LIFE BIOPOL European project aiming to replace traditional re-tanning and fat-liquoring products reducing environmental impacts and increasing the safety of leather.

The purpose of the project is to enhance the recovery and reuse of different bio-derived by-products from leather and agro-industrial sector to produce eco-friendly and renewable bio-polymers with high re-tanning and fat-liquoring characteristics.

The LIFE BIOPOL project aims to make bio-based polymers in order to reduce the following parameters in re-tanning phase:

  • 20-30% COD,
  • 50-60% of inorganic salts (Sulphates and Chlorides),
  • 90% of Cr (III) salts,
  • 20% of water used in the leather process.

Other important goals of the project are:

  • reduction 70-90% of hazardous and environmental polluting substances normally found in conventional chemicals,
  • reactivity enhancement of 30-40% of the new biopolymers compared to the current leather application technology,
  • reduction of 70-80% of the Product Environmental Footprint of the new biopolymers related to the state of the art.

The vegetal biomasses and the tanned hides by-products were pretreated in order to obtain suitable building blocks for the production of bio-based polymers. Several protocols involving polymerization were used in order to achieve the synthesis of the biopolymers, which have been carried out at lab scale.

Macromolecular characterization of the biopolymers was performed in order to rationalize the synthetic strategy and practical application of the products giving important parameters such as molecular weight and chemical composition of the new biopolymers.

Performances of new bio-based polymers have been inspected and compared with traditional chemicals through application on different types of leather. The benefits of the new products within leather making process were evaluated through chemical analyses of re-tanning and fat-liquoring effluents.

The upgrade of the developed chemistry will be performed within a new devised prototype plant specifically designed and built-up for producing the bio-based polymers at industrial scale


Production of leather making biopolymers from biomasses and industrial by-products through Life Cycle Designed Processes

Logo of the LIFE BIOPOL project
Keywords: LIFE programme, Bio-based polymers, Biomass Recycle, Circular Economy
4:05 PM S3-02

Lignin-Modified Phenolic Syntan: A Contributor to Our Bio-Based Solutions (#129)

Y. Ma1, P. Berends1, M. Wijland1, R. Rumnit1, R. Pauli1, R. Meulenbroek1

1 Smit & zoon, R&D, Weesp, Netherlands


In order to contribute to a more sustainable leather manufacturing process and leather value chain, in 2016 Smit & zoon started its own designing process of new products through the Bio-Based innovation platform. As a logical first step, answers to several key questions have been looked for: What is Bio-Based? What is renewable? Which term and method do we use to define the Bio-Based content in the Bio-Based platform? What is biodegradable? How do our current products perform? What is our vision for future products? In the process of answering these questions and guided by the Cradle-to-Cradle (C2C) CertifiedTM program, Material Reutilization Score (MRS) was used to obtain deeper insights into the formulation and environmental performance of our leather chemicals and treated as the basis for the design of new generation bio-based chemicals. Three main focus areas are setting the tone of current activities in the Bio-based platform: 1. increasing the renewable contents of the existing product groups; 2. smart valorization of industrial side streams from biological origin and 3. improving the biodegradability of leather chemicals. While focusing on these topics, it is well-understood that a proper balance needs to be found between cost, sustainability and performance. In the meantime, leather’s end of life scenario plays a role and needs to be looked at again. One of the first results of this focused approach is our patent-pending polyphenolic syntan product, in which industrial lignins are used during the chemical conversion process to replace part of the phenol (40-50 w/w%) used in the production of otherwise 100% petro-based polyphenolic retanning chemicals. We have shown that our innovative technology is compatible with most of the industrial lignins (kraft, soda, organosolv, hydrolysis) from different origins (soft/hard wood, grass, straw). The obtained polyphenolic products have real tanning power and are suitable to be used as retanning agents for various types of leather rendering good organoleptic properties with additional added value of increased bio-based content, improved biodegradability thus a higher MRS. The improved biodegradability of these products can contribute to decrease the effluent treatment load. Moreover, these products can be tailor-made to meet low emission (low free phenol, low free formaldehyde) requirements as well. In addition to the lignin-based polymers, the quickly developing project portfolio within the bio-based platform manifests that Smit & zoon is making steady steps towards a largely sustainable leather value chain by 2025.


Bio-Based products contritbute to a sustainable leather manufacturing process and leather value chain.

Both the raw material renewability and product biodegradability are important parameters to evaluate the environmental impact of leather chemicals.

Smit & zoon has developed a patent-pending bio-based synthan product using industrial lignins to replace part of the petro-based phenols in the production process.


Keywords: lignin, syntan, bio-based, biodegradability
4:20 PM S3-03

Acrylic resins in wet white (#147)

O. Ballus1

1 CROMOGENIA UNITS, S.A., Leather application laboratory, Barcelona, Spain


The purpose of this paper is to study the influence of acrylic resins on the properties of the hide when added in the pickling-tanning stage of a wet white process.

Among retanning products, acrylic resins are very frequently used because they lend very good properties to the hide on account of their high affinity for chromium. When applied during chrome tanning, these resins provide the hides with high fullness, due to the strong interaction of the carboxylate groups with chromium.

Extensive bibliography is available on the application of acrylic resins in wet blue, where it is observed that the properties they provide to the hides depend basically on the type of monomers and molecular weight. However, less information is found when these products are applied in wet white tanning.

In this study, 9 resins with different molecular weights and different monomer compositions were selected (Table 1).

Resins were applied to pelt leathers of Spanish origin split at 3.5 mm. Hides were cut along the backbone. A standard process was applied to the left halves and the same process adding the resin was applied to the right halves. The resin was added after adjusting the salt of the bath and before adding the pickling acids.

The COD was measured before and after adding formic and sulfuric acid, and the shrinkage temperature and the degree of whiteness of the tanned hide were assessed. Hides were retanned and fatliquored with a standard process, and degree of softness, thickness, color intensity and organoleptic properties (fluffiness, compactness and grain tightness) were assessed. Leather shrinkage under temperature was also assessed, and images of leather sections were obtained by scanning electron microscopy (SEM).

While acrylic resins did not increase shrinkage temperature, they did fix and/or deposit themselves in the interfibrillary spaces of the hide; indeed, highly reduced COD values after acidification in the pickling stage were observed. This study shows that homopolymeric acrylic resins provided fuller and fluffier hides, while the rest of resins practically did not improve the physical and organoleptic properties of the hides.


Homopolymeric acrylic resins provided full er and fluffier hides, while the rest of resins practically did not improve the physical and organoleptic properties of the hides

Wet white tanning improvement

Table 1

Products, monomers and molecular weight

Keywords: tanning, retanning, wet white, acrylic resins
4:35 PM S3-04

Comparative Studies on Effect of cationic and anionic finishing agents on Surface Property of Finished Leather (#243)

M. W. Wajino1, A. D. Dhathathreyan2, S. V. K. V. Kanth3

1 leather industry developement institute of ethiopia , leather technology , Addis Ababa , Ethiopia
2 central leather research institute of india, CLRI, Chemical laboratory, Chennai, India
3 central leather research institute of india, CLRI, Center for human resource developement , Chennai, India


The present work attempts to analyze the surface and physical properties of leathers finished with cationic and anionic finishing chemicals. The contact angles of liquid drops resting on the leather surface have been used to evaluate surface energy, acidity, basicity components of the surface energy, polarity and work of adhesion. Contact angle values have been measured for chrome tanned and conventionally retanned crust and finished leather made by varying pigment and binder combinations. The wettability of finished leather has been correlated with the contact angle values: the higher the contact angle value the lesser is the wetting observed. Complete wetting can be obtained when the contact angle value is zero i.e. the drop of liquid spreads spontaneously on the surface and partial wetting is obtained when the contact angle value is in between 0and 900. Acrylic binders with different film forming properties, protein, polyurethane and butadiene binders have been combined to prepare different finish formulations.The results have been correlated with wet and dry rub fastness, finish adhesion, vamp flexing value, water vapour permeability and water proofness. It has been observed that when the surface of leather is coated with acrylic binder the contact angle value due to polar solvents(water) , non polar solvents(hexadecane) and moderately polar( DMSO) and methyl iodide show that as the thickness of coating increases, the contact angle value decreases for the base coat and sharply increases when top coat is applied. Top coats have the ability to increase the contact angle and they improve the performance properties of leather such as water resistance, fastness, finish adhesion etc. Cationic and anionic finishing formulations have been compared to study their effect in modifying the surface of finished leather based on contact angle values, wet and dry fastness to circular rubbing and water resistance. It has been observed that leathers finished using anionic finishing technique shows better wet rub fastness and water resistance effect compared to cationic finishing technique.


1.The effect of number of top coats on water contact angle value were determined ,and the experiment showed that the value were decreased gradually at the beginning of the coat because the top coats are water based so during the coating process the hydrophobic nature of the surface of chrome tanned leather have decreased

The experimental result from contact angle value showed that coating with pigments and binders have increased the contact angle value compared to the control crust

It has been observed that leathers finished using anionic finishing technique shows better wet rub fastness and water resistance effect compared to cationic finishing technique.


Keywords: contact angle; surface energy; cationic finishing; anionic finishing; work of adhesion
4:50 PM S3-05

High Exhaustion Sytem (HES) for leather  process: Role of biocatalyst as an exhaustive aid for wet-end  (#235)

G. C. Jayakumar1, 4, V. Karthik2, 4, A. D. Asan Fathima3, 4, A. Tamil Selvi3, 4, C. Muralidharan2, 4, S. V Kanth3, 4

1 CSIR - Central Leather Research Institute, Centre for Academic and Research Excellence (CARE), Chennai, India
2 CSIR - Central Leather Research Institute, Leather Processing Technology Division (LPTD), Chennai, India
3 CSIR - Central Leather Research Institute, Centre for Human and Organizational Resources Development (CHORD), Chennai, India
4 Anna University, Department of Leather Technology, Chennai, India


Application of biocatalyst becomes an imperative due to their eco-friendly advantages.  Enzymes in pretanning for unhairing, fiber opening, defleshing and bating are well reported and practiced. However, the role of enzymes as a chemical aids is less explored and consider as a secondary applications. Leather enzymes are known for its hydrolytic behavior which makes it more suitable for pretanning operations. However, typical chemical exhaustive aids acts as a vehicle for the diffusion of chemicals, whereas enzymes aids in the splitting of fibers which facilitate the diffusion of chemicals and create more functional sites for the tanning and post tanning chemicals to interact. In this research, pickled pelts are treated with acid protease and subsequently tanned using chrome tanning agent. Enzymatic treated pelts resulted in better uptake of chromium as compared to conventionally processed leathers. Similarly, after neutralization, chrome tanned leathers are treated with alkaline protease to conventional post tanning has been carried out. Enzymatic treated wet blue leathers showed high uptake of post tanning chemical, uniform dyeing and reduction in the pollution load. From the preliminary research, an interesting finding has augmented that application of enzymes at an optimized concentration, temperature, pH and time would lead to better uptake of chrome which reduces the pollution and minimization pollution load in post tanning. This study, emphasize on the application of enzymes in tanning and post tanning for higher diffusion of chemicals.




1. Replacement of conventional exhaustive aids using biocatalyst

2. Higher exhaustion rate of tanning and post tanning chemicals

3. Futuristic technology for sustainable leather manufacture



Keywords: Biocatalyst, post-tanning, tanning, High-Exhaustion System