Polyanionic bio-emulsifier: A heteropolysaccharide based bio-composite for leather post tanning process

by Sharmila Selvaraju, Sathya Ramalingam and Jonnalagadda Raghava Rao

Biopolymer-based composites are attracting significant interest in leather processing due to their incremental substitution of petrochemical products as raw materials in the retanning stage. Several polymeric bio-composites were developed and studied as alternatives to synthetic tanning agents (syntans). Bio-composite was prepared by simultaneously dispersing cellulose (acting as syntan) and emulsifying soybean oil with a bio-emulsifier termed Emulsan (acting as fatliquor). The resultant dual propertied of fullness and softness is endowed as a leather supplement to reduce the negative impact on the environment. Hence polymeric bio-composites were prepared through ultrasonication by blending different amounts of cellulose with soybean oil with an optimised Emulsan ratio. In order to enhance the biocompatibility of this bio-composite, the Emulsan surfactant we chose was extracted from Acinetobacter calcoaceticus. The poly-anionic nature of Emulsan serves as a stable surfactant to emulsify soybean oil into cellulose in the composite preparation. The resultant composites were characterised for functionality and physical properties by FTIR, DSC, TGA, and DLS. The value of an example composite in leathers’ post tanning processes was evaluated by utilising it as a retanning agent. Leather treated with a bio-polymeric composite showed improved strength and physical properties versus control leathers.

JALCA March 2019

Polyacrylate ester-based policarboxilate (PCE) as a new leather retanning agent

by Miquel Canudas, Nicola Menna, Antoni Torrelles, Joan De Pablo and Josep Maria Morera

Acrylic resins are extensively used as retanning products because of their affinity with chrome tanned leather. However, their anionicity changes the cationic leather surface becoming a problem for the subsequent uses of fatliquoring and dyeing agents. As a result of changing charges, a leather with lower color intensity and poorer structural properties is obtained.

This paper presents an initial study which analyses the use of polyacrylates esters based polycarboxylates (PCE) superplasticizers as a new retaining agent compared to traditional wet end acrylic resins. Properties of PCEs in leather were compared to acrylic resins. For the applying assays, PCEs with different molecular weight were synthetized and characterized using a gel permeation chromatography (GPC). Experimental results indicate that PCEs improve leather properties avoiding the dyeing and fatliquoring problems of the acrylic resins.

JALCA March 2019

Study on the microstructure of Crocodylus Niloticus skins during leather making process

by Qiang Tao-Tao and Han Mi-Mi

The variation on the microstructure of Crocodylus niloticus skins in the tanning process was observed and analyzed by using frozen section staining, which provide the reliable theoretical basis for Crocodylus niloticus leather production. The research on aldehyde fuchshin staining method showed that elastic fiber will receive a lot of damage in the bating and bleaching process. Through the observation of wet blue leather by scanning electron microscopy, the preparation work section and tanning process design are reasonable, also, inter-fibrillary substances had been well removed. The crosscut microstructure of Crocodylus niloticus hides before and after fatliquoring was observed by nile blue sulphate staining method, and the results showed that fatliquor could penetrate into the skin uniformly.

JALCA March 2019

Deciphering the role of individual retanning agents on physical properties of leathers

by Murali Sathish, Bhuvana Subramanian, Jonnalagadda Raghava Rao and Nishter Nishad Fathima

In post-tanning different types of retanning agents are used in combination to improve the functional properties of leather and therefore understanding the individual effect of each retanning agents on final properties is difficult. This work mainly focuses toward quantifying the individual effect of different weight percentages (4, 8 and 16%) of phenol-formaldehyde resin (PFR), melamine-formaldehyde resin (MFR), acrylic resin (AR) and biopolymers (BP) on physical properties of leather. It was found that the strength characteristics are greatly affected when the retanning agents offer increased above 8% where the effect of phenol-formaldehyde resin is higher than other re-tanning agents. Melamine-formaldehyde resin and biopolymer is predominantly affecting the belly region. It has also been observed that the phenol-formaldehyde resin improves the fullness whereas grain tightness and flatness are improved with increasing the percentages of melamine-formaldehyde resin offer. Biopolymer improves the grain smoothness and the ability of improving the roundness of leather is similar for all kind of retanning agents. A meaningful conclusion could not be drawn in the porosity results obtained due to the heterogeneous nature of leather matrix. Thus, a conventional triplicate method of measurement as done in this study would not suffice to provide a conclusive interpretation of results obtained using capillary flow porometry technique.

JALCA March 2019

Evaluation of Chemical Products in Leather Post-tanning Process and Their Influence in Presence of Neutral Salts in Raw Tannery Effluent

by M. V. Moreira, E. Hansen, G. Giacomolli, F.D.P. Morisso and P. M. Aquim

In the leather industry, several chemical products are used for the transformation of the raw hide into the demanded final product. The production flow and the post-tanning of wet-blue leathers may vary according to the available technologies and the type of final item produced. Previous operations and processes are also relevant, particularly the steps of unhairing-liming and tanning process. During the effluent treatment process, there is a great difficulty in removing soluble salts, such as sodium chloride and sodium sulfate in conventional effluent treatment stations. These salts might compromise the biological treatment of tannery wastewater and adversely impact the receiving water bodies, causing environmental pollution. Further, the presence of chlorides and sulfates might interfere in the implementation of the bath reuse system or in the recycling of the treated effluents in the post-tanning process. Therefore, this work aims to investigate the measures used to control the production of sodium neutral salts, such as the sodium chlorides and sulfates, contained in the chemical compounds uses in the industry that performs post-tanning in bovine wet-blue leather, mostly for automotive and furniture upholstery. The work was carried out following the production of the factory for six months, with approximately 1485 whole wet-blue leathers being processed per day, with an average production of 7500 m² of crust leathers per day. The work methodology was based on the diagnosis of the initial situation of the tannery, chemical analyses of the supplies employed and in proposals of action based on this initial profile. The work also involves the checking of the water consumption and the evaluation of the residual baths. The identification of the chemical products in the formulation that contribute directly to the presence of neutral salts in the gross effluent and their presence in the residual baths were among the main results observed in the present work. In order to determinate sodium, chlorides and sulfates, two methodologies were tested (ion chromatography, for chlorides and sulfates; and absorption spectroscopy, for sodium), showing similar results.

JALCA April 2019

Characterization of Halotolerant Bacillus Species Isolated from Salt Samples Collected from Leather Factories in Turkey

by E. Yilmaz and M. Birbir

Salt curing is the method most commonly utilized in the leather industry to prevent microbial growth on raw hides/skins. Despite this processing, a wide diversity of microorganisms belonging to Domains Bacteria and Archaea have nevertheless been observed on salted hides/skins. In order to understand whether halotolerant bacterial species in salt contaminate hides/skins during the curing process, 30 salt samples collected from 14 leather factories in Corlu and Tuzla (Turkey) were examined for halotolerant bacteria. Total counts of halotolerant bacterial numbers, pH values and moisture contents of the salt samples were respectively determined between 104 CFU/g and 106 CFU/g, 6.23 and 7.22, 0.90 and 5.02. All isolates were able to grow on both Nutrient Agar Medium without NaCl and Nutrient Agar Medium containing NaCl at concentrations ranging from 2 to 10%. The microorganisms isolated from the samples were identified using phenotypic characteristics and comparative partial 16S rRNA gene sequence analysis. The phylogenetic analysis, using more than 1300 base comparisons of 16S rRNA sequence data, revealed 83 halotolerant isolates that share highly similar identities (97.82-100%) with their closest phylogenetic relatives. These isolates were assigned to 12 different Bacillus species (B. amyloliquefaciens, B.atrophaeus, B.halotolerans, B.licheniformis, B.mojavensis, B.paralicheniformis, B.pumilus, B.safensis, B.siamensis, B.subtilis, B.tequilensis, B.velezensis). We detected catalase and protease activities, as well as production acid from fructose, in all Bacillus isolates. Fifty-five isolates demonstrated positive oxidase activities, and 50 isolates utilized citrate as a sole carbon source. While a fairly high percentage of the isolates produced acid from maltose, almost half of the isolates produced acid from myo-inositol. While 67% of the salt samples contained 1-2 different Bacillus species, 33% of the salt samples contained 3-4 different Bacillus species. Although B.amyloliquefaciens, B.atrophaeus, B.safensis, B.siamensis species were detected at a few salt samples, B.paralicheniformis and B.halotolerans species were detected at more than half of the salt samples. These results uphold the hypothesis that proteolytic halotolerant Bacillus species in the curing salts may contaminate hides/skins during curing process. Hence, we recommend sterilized salts be used in the preservation of the hides/skins to prevent economic losses in the leather industry.

JALCA April 2019

Quantitative Analysis of FITC-trypsin Distribution in Goatskin Matrix

by Xuesong Li, Deyi Zhu, Jinzhi Song and Yanchun Li

The application of enzyme for leather making has attracted much attention in recent years. Therefore, the enzyme diffusion mechanism deserves to be investigated and it is helpful to enzyme application in leather industry. In this study, a novel method basing fluorescence detection technology was developed to achieve quantitative detection of trypsin distribution into goatskin matrix in the model of one-way and turbulent diffusion. In one-way diffusion, trypsin diffusion from the flesh side was faster than that from the grain side. As for turbulent diffusion assay, the trypsin diffusions in grain and flesh layer were directly influenced by the position of goatskin matrix such as back and belly, which could lead to different fluorescence intensity distribution. In addition, the modeling equations, which were fitted with fluorescence intensities, confirmed the quantitation feature in trypsin diffusion process. These results indicated that the method was competent for quantitative detection of enzyme spatial distribution in goatskin matrix. And it would provide the basis foundation for the development of researches in enzyme mass transfer kinetics.

JALCA April 2019

A Diverse Color-tunable Luminous Polyurethane Leather Coating Based on Long Persistent Phosphors and Photochromic Spiropyrans

by Saiqi Tian, Zhe Sun, Haojun Fan, Yi Chen and Jun Yan

A diverse color-tunable luminous polyurethane leather coating (CLPU) which can reversibly change color as well as fluorescent emission through the UV-vis or UV-darkness circle was prepared, via covalent incorporation of amino-functionalized phosphors and photochromic 1-(2-Hydroxyethyl)-3,3-Dimethylindolino-6’-nitrobenzopyrylospiran (SP). X-Ray Diffraction (XRD), X-ray photoelectron spectroscopy (XPS), UV-vis absorption spectra, reflectance spectra, fluorescent spectra as well as the migration percentage were measured to characterize the resultant samples structure and properties. In daylight, CLPU appears white before 365 UV irradiation and violet after UV irradiation, due to the transition of the spiro forms of spiropyran to merocyanine forms. In darkness, CLPU emits intense green light before UV irradiation, and the light changes to orange after UV irradiation, due to the phosphors showing pleasant diverse color-tunable luminous effect.

JALCA April 2019

Progress of certified reference materials in the leather field

by Zhiding Huang; Yang Zhao; Xinying Zhao; Wei Wang; Xugen Feng; Wenkai Chang

Certified reference materials in the leather industry are mainly used for testing of physical, mechanical and chemical safety properties of leather, footwear products and shoe materials. Certified reference materials are an important basis for ensuring the accuracy, reliability and traceability of the test results. In this paper, the progress of certified reference materials in leather industry at home and abroad was systematically reviewed, and the main research methods of certified reference materials in leather field are described. At the same time, the existing problems of the certified reference materials in leather industry were analysed. Finally, the prospects of the development and application of certified reference materials in leather industry were put forward.

JSLTC March/April 2019

Innovative application of dye ligand-attached nanoparticles for bating

by Açikel, Safiye Meriç; Aslan, Ahmet; Akgöl, Sinan

In the present work, poly (2-hydroxy ethyl methacrylate) nanoparticles (PHEMA-RR120) attached to Reactive Red 120 were synthesised as an adsorbent for use in the acidic bating process. PHEMA nanoparticles were first derived by emulsion polymerisation without the use of a surfactant. The dye ligand Reactive Red 120 was chemically attached to the PHEMA nanoparticles via a nucleophilic substitution reaction. The bating process of sheep leathers was then carried out separately with PHEMA-RR120 nanoparticles in place of an acidic protease at pH4.5 and pH6 and in place of an alkali protease at pH8 and pH6 to remove globular proteins from among the leather fibres. According to the results, at pH4.5 the COD, BOD, ammonia and nitrogen values of the acidic protease were respectively 9560mg/L, 4550mg/L, 69.1mg/L and 3.8mg/L, while the wastewater values of PHEMARR120 nanoparticles were respectively 9003mg/L, 4300mg/L, 66.8mg/L and 3.70mg/L. At pH8, the COD, BOD, ammonia and nitrogen values of alkaline protease were respectively 1543mg/L, 860mg/L, 95.3mg/L and 8.9mg/L, while the wastewater values of PHEMA-RR120 nanoparticles were respectively 1257mg/L, 666mg/L, 95.7mg/L and 7.9mg/L.

JSLTC March/April 2019

Effect of enzymatic soaking on properties of hide and the leather produced

by Valeika, V.; Beleska, K.; Biskausaite, R.; Valeikiene, V.

The use of enzymes for soaking has influences on rehydration levels of hide and the amount of collagenous and non-collagen proteins removed. The removal depends on the EP (enzyme product) used and on the amount. The increase of the amount of EP in a soaking solution affects faster rehydration, higher content of removed non-collagen proteins but, unfortunately, has an effect on the collagen of hide not only during the soaking but during subsequent liming as well, this can be the reason for defects in the finished leather. The duration of enzymatic soaking has an influence on chroming and chromed leather properties also: too short an enzymatic soak leads to weakened grain and to decreased relative elongation of the leather. A properly chosen EP preparation and its amount can result in higher rehydration and removal of non-collagen materials from the derma during soaking when compared with the treatment without enzyme. On the other hand, such a use of EP has not caused any observable influence on the exploitation properties of the finished leather.

JSLTC March/April 2019

Recovery of collagen hydrolysate from chrome leather shaving tannery waste through two-step hydrolysis using magnesium oxide and bating enzyme

by Sasia, Alvin Asava; Sang, Paul; Onyuka, Arthur

Chrome-tanned solid waste emanating from leather industry is usually disposed of to the environment through landfill which not only pollutes the environment but also wastes the protein resource contained in it. Protein recovery for re-use in secondary industrial processes presents the best strategy for its re-utilisation. Dechroming by hydrolysis is the most practiced method of protein and chromium recovery from tanned solid waste. The alkali-enzyme two step hydrolysis methods are commonly utilised for improved protein recovery efficiency. However, enzyme cost and temperature dependence of the heat stable alkali enzyme has made the process economics difficult and therefore unattractive. The objective of the present study was to explore a relatively inexpensive method of recovering collagen hydrolysate through a two-step hydrolysis incorporating conventional bating enzyme. The method of treatment involved a first-step denaturation and degradation with alkali followed by inoculation with bating enzyme. The ash content, total kjeldahl nitrogen, dry matter and chromium content of the collagen hydrolysates obtained are reported. Protein recovery at 58.20% and 50.76% efficiency were obtained for the separate alkali and enzyme hydrolysis respectively. A combined protein recovery rate of 79.45% efficiency was obtained for the two-step process. The results of this study indicate that hydrolysis dechroming employing the use of conventional bating enzyme could offer a low-cost alternative for the effective treatment and reuse of chrome-tanned shaving solid waste.

JSLTC March/April 2019

Elimination of antibiotic resistant enterobacteriaceae via combined application of direct electric current, alternating electric current and 2-thiocyanomethylthio benzothiazole

by Birbir, Meral; Yazici, Eda; Caglayan, Pinar; Birbir, Yasar; Goebel, Richard Alan

Multidrug-resistant Enterobacteriaceae originating from animalsʼ intestinal tracts may be found on salted and soaked hides/skins. The presence of proteolytic, lipolytic, multidrug-resistant Enterobacteriaceae on hides/skins and the resulting destructive processes results in economic losses to the leather industry and creates health hazards for workers. To minimise this destructive bacterial presence, the bactericidal effect of combined application of direct or alternating electric current and an antibacterial agent against multidrug-resistant Enterobacteriaceae were examined in this study. Multidrug-resistant Citrobacter freundii, Citrobacter koseri, Enterobacter cloacae, Serratia rubidaea, Serratia marcescens, Serratia plymuthica, Morganella morganii, Proteus mirabilis, Providencia rettgeri, isolated from soaked hides/skins, were used in the present study. Among the test isolates, Proteus mirabilis, Serratia marcescens, Serratia plymuthica, Serratia rubidaea, were protease and lipase producer strains. All test isolates were resistant to critically important antimicrobials which are used in both human and veterinary medicine. Bacterial effect of combined application of 508mA/cm2 direct electric current, 454mA/cm2 alternating electric current and an antibacterial agent (2- (thiocyanomethylthio) benzothiazole) against the mixed culture of these micro-organisms were investigated in nutrient broth containing 3% NaCl. After application of six cycles of the combined electric current treatment against the mixed culture of multidrug-resistant Enterobacteriaceae treated with (2-(thiocyanomethylthio) benzothiazole) was completely killed within five hours. The Log10 reduction of the mixed culture at the end of the experiment was 7.55. In conclusion, the combined application of direct electric current, alternating electric current and antibacterial agent may be used in soak liquors to eliminate proteolytic, lipolytic, multidrug-resistant Enterobacteriaceae in the leather industry.

JSLTC March/April 2019

Influence on Rex rabbit hair by low-temperature plasma in different gas media

by Zhang Meina; Liu Hongyan; Li Lixin; Zhang Zongcai

In order to find out changes of the Rex rabbit hair under different Low Temperature Plasma (LTP) treatments, Rex rabbit hair fibres which were modified by oxygen, nitrogen, and air plasma, were examined by XPS, ultraviolet-visible spectrophotometery, Lab-eye software, HP-386 multi-angle gloss meter, YM-06A electronic single fibre strength meter, as well as by a Y151 fibre friction coefficient tester. The results show that oxygen plasma, nitrogen plasma and air plasma can all dramatically enhance exhaustion and fixation rate of Rex rabbit hair during dyeing. Treatment with air plasma and nitrogen plasma introduced more -NH2 to the surface of Rex rabbit hair fibres, promoting the reaction between -NH2 and -SO3H of an anionic dyestuff in an acidic medium. Besides, the oxidation of oxygen plasma introduces polar functional groups such as hydroxyl or carbonyl, thus improving the hydrophilicity of Rex rabbit hair fibres. Compared with fibres without plasma treatment, the dyeing depth of fibres treated with oxygen, air, and nitrogen plasma has been significantly enhanced. In addition, the rupture strength and elongation as well as glossiness of fibres reduces to a slight extent after LTP treatment with oxygen, nitrogen, and air. Ultimately, after oxygen, air and nitrogen plasma, the gap between the friction coefficients of against and along scale is narrowed, which can enhance the ability of the anti-felting performance.

JSLTC March/April 2019

A new approach for bating: reactive red120 dye

by Açikel, Safiye Meriç; Aslan, Ahmet; Türker, Evren; Akgöl, Sinan

In the present work, Reactive Red 120-attached poly (2-hydroxy ethyl methacrylate) nanoparticles (PHEMA-RR120) were synthesized as an adsorbent for the removal of the proteins albumin and globulin. PHEMA nanoparticles were first prepared by surfactant-free emulsion polymerisation. The dye ligand Reactive Red 120 was chemically attached to the PHEMA nanoparticles via a nucleophilic substitution reaction. Characterisation of the PHEMA-RR120 nanoparticles was carried out by specific surface area, dry mass weight of the nanoparticle, SEM, FTIR and Zeta Size analysis. Albumin and globulin adsorption of PHEMA-RR120 nanoparticles was investigated with respect to process conditions (temperature, pH, time, initial concentration and ionic strength), and the re-usability of PHEMA-RR120 was also determined. The albumin and globulin protein adsorption of PHEMA-RR120 nanoparticles was found to be respectively 24.60g/g and 3.95g/g at 25°C, 12.58g/g and 3.86g/g at 37°C, 11.45g/g and 2.69g/g at 45°C. The results show that PHEMA-RR120 nanoparticles can be used for the effective, reusable removal of albumin and globulin due to their large surface area and high adsorption capacity.

JSLTC March/April 2019

The number of restricted substances listed in REACH has increased with an additional 33 highlighted in Annex XVII entry 72.

One of the most significant REACH updates in recent years will come into effect on 1st November 2020, when restrictions begin to apply for 33 substances listed in Commission Regulation (EU) 2018/1513. These restrictions are intended to be applicable for textiles, with clothing and footwear specifically mentioned. However, there are important exemptions that will be highlighted in this article.

Some of the 33 substances already have some restrictions for specific products – such as toys or certain materials that will be in contact with the skin – but those substance restrictions will broaden as a result of the latest additions. The objective of the regulation is to reduce consumers’ exposure to harmful chemicals. This article will discuss the legislation that is appropriate to footwear, while identifying the key substances on which SATRA members may need to take action in order to demonstrate compliance.