Country-level Life Cycle Assessment of Carbon Footprint in Processing of Bovine Upper Leather

by Mianhong Chen, Youdan Duan, Liming Dong, Min Chen and Haiming Cheng

Leather-making processes have achieved great improvements in reducing environmental pollution all over the world. In this study, we collected the data from the tanneries in five countries on the material flow to quantify and analyze the carbon footprint of leather-making process, based on the Life Cycle Assessment with two impact assessment methods that characterize the impact of climate change (IPCC 2013 GWP 100 years and GHG Protocol). To process 1000 kg of raw hides, tanneries in Chile, China, India, Italy, and Spain emitted 882, 1180, 1608, 1198, and 755 kg of carbon dioxide equivalent (CO2Eq), respectively. The carbon footprint of 1 kg of finished leather for shoe upper in five countries ranges from 3.41 to 6.30 kg CO2Eq. The average power consumption was the largest factor causing carbon emissions, followed by the consumption of acrylic resin, and chromium tanning agent. Carbon footprint analysis suggested that enzyme-assisted beamhouse and recycling of the liming float and the tanning float can effectively reduce carbon emissions during the leather-making process. This study will lay the foundation for the carbon footprint research of the downstream products of leather (shoes, apparel industry, etc.).

JALCA June 2019

Synthesis and Leather Application Properties of a Carboxylated Graphene Oxide Modified Waterborne Polyacrylate Leather Finishing Agent

by Shuangquan Lai, Yong Jin, Liangjie Shi and Weining Du

Carboxylated graphene oxide (GO-COOH), prepared by the reaction of bromoacetic acid with the hydroxyl and epoxy groups on the graphene oxide (GO) layers, was blended into a poly(ethyl acrylate) (PEA) emulsion and a PEA emulsion based polyacrylate leather finishing agent respectively, to prepare PEA/GO-COOH composite emulsions and GO-COOH modified waterborne polyacrylate leather finishing agents. The consequence of the amount of GO-COOH on the properties of the PEA film and related leather coatings were systematically investigated. The results indicate that stable GO-COOH dispersed composite emulsions were generated leading to homogeneously dispersed composite films. With an increase in the GO-COOH amount from 0 wt% to 0.5 wt%, the tensile strength increased by 106.2%. Additionally, TGA results demonstrated an improvement of the thermal stability of PEA film after modified with GO-COOH. Most importantly, the folding resistance and rubbing fastness properties of leather finished with GO-COOH modified polyacrylate leather finishing agents were improved proportionate to the GO-COOH amount. Therefore, the GO-COOH modified waterborne polyacrylate leather finishing agent possesses improved performances and likely offers beneficial leather finishing application properties.

JALCA June 2019

Graphene Oxide Grafted Maleic Anhydride Vinyl Acetate Co-polymer and its Enhancement of Flame Retardant and UV-resistance of Retanned Leather

by Yazhou He, Zhenyu Zhang, Haojun Fan, Yi Chen and Jun Yan

Maleic anhydride grafted graphene oxide (GOMA) monomer was prepared by modifying the graphene oxide (GO) with hexachlorocyclotriphosphazene (HCCP), ethylenediamine (ETA) and maleic anhydride (MA). Then a polymeric retanning agent, abbreviated as poly(GOMA-MA-VA) was synthesized from GOMA, MA and vinyl acetate (VA) by free radical polymerization. The structures of GOMA and poly(GOMA-MA-VA) were characterized by Fourier transform infrared (FTIR) spectroscopy, Raman and X-ray photoelectron spectroscopy (XPS), simultaneously, the flammability, UV-resistance as well as the thermal stability and mechanical properties of re-tanned leathers were also investigated. Results show that GO grafted by polymer presents well dispersing stability and can penetrate into collagen fibers to form strong combination with fibers. Furthermore, this novel multifunctional retanning agent can efficiently improve the flame retardance, ultraviolet (UV) resistance, thermal stability and mechanical properties of resultant leather.

JALCA June 2019

Investigation of the Synthesis of a Novel Glycidyl Ether-amine Epoxy Tanning Agents and their Tanning Performance

by Xiaoyan Pang, Zhiwen Ding, Wei Ding, Xiao Xiao, Xuepin Liao and Bi Shi

Isophorone diamine (IPDA) and epichlorohydrin (ECH) were used to fabricate the epoxy tanning agents, and polyalcohol compounds (glycerol, polyethylene glycol, ethylene glycol) were employed to introduce the ether bonds into the epoxy tanning agents to improve their compatibility with water. The prepared epoxy tanning agents were named IGE, IPE and IEE for the introduction of glycerol, polyethylene glycol and ethylene glycol, respectively. FT-IR and 1H NMR analysis indicated that epoxy groups, ether bonds and hexatomic rings were successfully introduced into IGE, IPE and IEE. The tanning performances of the epoxy tanning agents were further evaluated in water, ethanol-50 (50% of ethanol in water) and ethanol-95 (95% of ethanol in water) medium, which suggested that ethanol-50 was the most favorable one for the epoxy tanning agents. The IGE tanned leather exhibited the highest shrinkage temperature of 83ºC in ethanol-50 due to its low viscosity, high epoxy value and wide molecular dispersion. Morphology observation indicated that the IGE tanned leather exhibited better dispersion of fiber network than that of IPE and IEE tanned leathers. These results illustrated that IGE was an appropriate tanning agent in water-ethanol medium, which could be considered as a candidate for the organic tanning agents.

JALCA June 2019

Feasibility study of a functional modification for porcine acellular dermal matrix

by Chen Yining; Dan Nianhua; Zheng Xin; Huang Yanping; Dan Weihua

In this paper, the porcine acellular dermal matrix (pADM) was used as a mimetic of collagen fibres, and chemical modification by an epoxy silicone modifier (3-(2,3 epoxypropoxy)propyltrimethylsilane, E3) was carried out to improve its physicochemical properties. The modification interaction between pADM and E3 was investigated, and the various properties of the pADM after modification by E3 (E3- pADM) were further evaluated. Fourier transform infrared (FTIR) spectroscopy indicated that E3 was successfully introduced into pADM. After the E3 treatment, X-ray diffraction (XRD) and FTIR analysis showed that the micro-structural integrity of pADM was still maintained and scanning electronic microscopy (SEM) observation showed that the surface topography and pore structure were maintained. The differential scanning calorimetry measurement (DSC) demonstrated that the thermal stability was enhanced due to the improved structural stability after modification. Further, E3-pADM was functionalized with hydrophobic properties compared with native pADM due to the silane sidechain. Enzymatic degradation study indicated that the resistance to enzymatic degradation of E3- pADM increased, which may benefit from hydrophobic chemical modification. In addition, the MTT assay and SEM observation illustrated that E3-pADM was favorable for the cellís adhesion, growth and proliferation. Taken as a whole, the results demonstrated that E3 could serve as a functional modifier for the chemical modification of pADM to improve the physicochemical and functional properties. Therefore, the prospect of E3 in the preparation of hydrophobic leather and acellular dermal matrix in future production and practice is brilliant.

JSLTC May/June 2019

Structural and performance characteristics of pigskin leather with different tanning methods

by Pervaia, Nataliia

This article studies the influence of mineral and organic tanning methods on a set of physicomechanical, thermophysical and hygienic properties of pigskin. The dialdehyde method of tanning
with subsequent anionic polymer filling provides the formation of a homogeneous porous structure of leather in various topographical areas with the necessary set of structural and performance characteristics. The described tanning technologies provide the formation of leather with appropriate hydrothermal resistance and adequate elastic-plastic properties. It meets the standard requirements for garment leather DSTU 3115-95. The resulting leather can be recommended for the manufacture of wide range goods, including chrome tanned for spring-summer goods and the dialdehyde tanned for autumn-winter goods.

JSLTC May/June 2019

Evaluation of collagen hydrolysate on the performance properties of different wet-white tanned leathers

by Dilek, Yusef; Basaran, Bahri; Sancakli, Aykut; Bitlisli, Behzat Oral; Yorganciouglu, Ali

Tanning with basic chromium sulphate is the most commercially favoured process in the manufacture of a variety of high quality leathers. Environmental restrictions to the disposal of chromium containing solids and effluents, as well as speculations concerning the presence of toxic and carcinogenic chromium(VI) traces in leather products, have already directed the industry towards using alternatives. Wet-white tannages which consist of zirconium (IV) and aluminium (III) salts with high durability and resistance and organic alternatives which use phosphonium, aldehydes and some syntans both types with more eco friendly and biodegradable characteristics seem to be the main options for industry. However, properties like high hydrothermal stability, tensile strength, and thickness cannot be achieved by any alternative single tanning method. In this study, collagen hydrolysates derived from gelatin manufacture were used to improve wet-white leather performance properties through combination with tanning agents comprising zirconium and aluminium salts, phosphonium salts and aldehydes. The result shows that the apparent density, shrinkage temperature, denaturation temperature and strength properties of differently tanned leathers increased with the addition of collagen hydrolysates. SEM analyses show that collagen fibres are dispersed after tanning. Besides, collagen hydrolysates make the fibres loosen and the fullness of leather is increased.

JSLTC May/June 2019

Synthesis, characterisation and application of novel valonia tannin based waterborne polyurethane with natural colour

by Yang Liu; Haihang Luo; Benyapathitiwong Ruj; Tao You; Youjie He

A novel natural coloured waterborne polyurethane (PU) based on valonia tannin was successfully synthesised and characterised. A structural study of the polymer by Fourier Transform Infra Red (FTIR) spectroscopy confirmed the incorporation of valonia tannin into the backbone of the PU. The dispersion of valonia tannin and homogeneity of surface of the PU samples were confirmed by scanning electron microscopic (SEM) analysis. Chromaticity and colour difference further verified the colour depth and uniformity of the cured films. Thermogravimetric analysis (TGA) results indicated that the synthesised PU samples exhibited an improved thermal decomposition temperature. Particle size analysis, mechanical testing and water absorption of the synthesised PU samples further showed the effect of the cross-linked structure in the molecular chain segment. Moreover, the colour fastness and folding [flexing] resistance of the leather coating finished with synthesised PU was better than that of valonia tannin blending.

JSLTC May/June 2019

Synthesis of orthanilic acid modified glyoxylated melamine resin with improved retanning and thermal properties

by Ashraf, Muhammad Naveed; Khan, Shahzad Mehmood; Munir, Shahid; Saleem, Rashid

Amino resins have found important uses in leather manufacturing due to their selective filling properties. Conventional amino resins are produced from formaldehyde and result in an increase of formaldehyde content in finished leather greater than the permitted limits. Due to strict legislations and restrictions regarding formaldehyde contents in leather goods there is a growing demand to produce formaldehyde-free leather. In this study formaldehyde-free resins with improved thermal stabilities were prepared using glyoxal as condensing agent and orthanilic acid (o amino-benzene sulphonic acid) as a sulfonating agent. The glyoxal to melamine ratio (G/M) was varied from 2-6 and orthanilic acid to melamine ratio (ONA/M) was varied from 0.5-3 to produce aqueous solutions of the melamine resins. The viscosity trend in the series of resins was observed by varying the degree of sulfonation and varying the glyoxal/melamine ratio. Progress of reaction was monitored by FTIR spectrum through functional group region. Newly synthesised melamine resins (MGONA) were comparatively applied on leather as a retanning agent against a conventional melamine-formaldehyde resin and further evaluated for tear strength, tensile strength and elongation at break. The leather retanned with the optimal resin was further assessed for organoleptic properties and SEM analysis. The thermal stability of the optimised resin was also evaluated comparatively against a conventional resin. The optimised polymeric resin was free from formaldehyde plus having better retanning properties and improved thermal stability.

JSLTC May/June 2019

Acquisition and observation methods of three dimensional leather structure based on micro-CT

by Huayong Zhang; Tianduo Li; Yuling Wei; Jinyong Cheng

Components and working principle, parameters and data acquisition steps of micro-CT are introduced in detail. Taking the chrome-tanned leather for example, the images of each stage of the
experiment are presented and the 3D digital models of leather structure with 1.5µm resolution have been obtained by micro-CT. It lays a good foundation for the study of leather structure by micro-CT.

JSLTC May/June 2019

Physical gelation of gelatin solutions: Effect of gelatin concentration, pH, ionic strength and solvents

by Guangfeng Feng; Congde Qiao; Jianlong Zhang; Xianguang Ma

The effect of gelation conditions on the gelation of gelatin solutions was studied by rheological measurements. It showed that the gelling temperature (Tgel) increased with the increasing of gelatin concentration. Tgel was also enhanced by the deviation of solution pH from the isoelectric point (IEP) of gelatin. On the contrary, Tgel was reduced by the increasing of ionic strength. In addition, the solvent has a notable influence on the gelation of gelatin. Unlike in urea solution where the formation of hydrogen bonds between gelatin chains was hindered, thereby leading to a decrease of Tgel, in methanol solution the hydrophobicity decreased, and the gelation was facilitated with a high Tgel. Our results demonstrate that polymer gelation depends on gelation conditions and it provides structural insight to improve the design of biopolymer-based gels.

JSLTC May/June 2019

Extraction of oil from tannery fleshings for chamois leather tanning

by Wainaina, Peris N.; Tanui, Paul; Ongaroa, Benson

The process of leather manufacturing produces vast amounts of solid waste annually (8.5 million tons worldwide), and most of the solid waste (80%) is produced in pre-tanning operations. The fleshing operation to remove flesh, subcutaneous tissue and natural fat from the flesh side of hide/skin (fleshings) accounts for 50-60% of total solid waste. Attempts to extract oil from the fleshings have been made, however, the application of the oils from fleshings in tanning has not been explored. The oil tanning process takes about 12 days (compared to chrome tanning which takes approximately 6 hours), and this explains why the technology is not commonly used. The objective of the research was to discover whether the fleshing oil could be used for chamois leather tanning. The oil was extracted from goat fleshings and characterised using Soxhlet extraction and chemical methods. The fat content, iodine value, acid value, percentage free fatty acid and saponification value of green fleshings were 27.56 ± 0.40%, 73.79 ± 0.34, 7.38 ± 0.13mg/g, 3.71 ± 0.06 and 187.08 ± 0.22 mg/g respectively while that of limed fleshings was 17.48 ± 0.55%, 67.40 ± 0.35, 6.08 ± 0.02mg/g, 3.06 ± 0.06 and 184.66 ± 0.33mg/g respectively. The results of the study show that the physical and organoleptic properties of fleshing oil-tanned leather were similar to those of cod oil-tanned leather. Tensile strength, elongation, tear strength and water absorption of the chamois leather were 27.88 ± 0.07N/mm2, 55.75 ± 0.17%, 56.64 ± 0.29N/mm, 211% respectively. The physical and organoleptic properties of the leathers resulting from this study suited the requirements for chamois leather.

JSLTC May/June 2019

Recovery and utilization of collagen protein powder extracted from chromium leather scrap waste

by Dang, X., Yang, M., Zhang, B. et al.

In this work, we investigate collagen protein powder (CPP) extracted from chromium leather scrap waste (CLSW). The composition and molecular weight distribution of CPP were determined by elemental analysis and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), respectively. The microstructure and size distribution of CPP were then characterized by scanning electron microscopy (SEM) and nanometer analyzer instrument. Finally, CPP was treated with corn starch (CS), and the swelling behavior of the resulting CPP-CS blend was investigated in order to determine its range of applications. The experimental data showed that CPP contains 13 different amino-acids. CPP also displayed low mineral salt levels and a nitrogen content of 43.84%, indicating its potential use as an organic fertilizer. The molecular weight range of CPP is 6.5 to ~ 26.6 kDa. After the obtained CPP was blended with CS, the CPP-CS blend is endowed with optimal swelling properties and is able to overcome the solubility drawbacks of CPP alone. In addition, when the CPP was used as a natural fertilizer, the germination rate and height of kidney beans obviously increased.

Environmental Science and Pollution Research March 2019

Taking tanning to the next level with an improved pickle product

by Rabe, Volker; Aertse, Maurice; Schneider, Thomas

The dominant chrome tanning process currently used at present time is simple, fast, reliable and highly efficient. Over past decades there have been countless initiatives to find alternatives, however chrome tanning remains the primary method for over 85% of the leather produced today. This long and continuing success is due to many reasons, not only those mentioned above but also its high adaptability. Over time, the focus has been developed and enlarged significantly. Starting from a focus on producing the optimum quality of leather, it became more and more a holistic view, including the environmental aspects of production. Although state-of-the-art chrome tanning is already at a very high level of performance in this respect, research at Lanxess is being continued in order to further optimise it, which will make this tanning method attractive and reliable in the foreseeable future and beyond.

World Leather May/June 2019

Tannins: a sustainable solution

In the first of two articles, Italian chemicals manufacturer Silvateam offers insight into sources of sustainable tannins from areas of Italy and South America. The second article will contain information about its use of quebracho from Argentina and tara from Peru. This paper focuses on its efforts to source chestnut tannins from Italy in a manner that respects the environment while also supporting the economic growth.

World Leather May/June 2019