Leather Finishing Research Articles

Environmentally Friendly Polyurethane Composites: Preparation, Characterization and Mechanical Properties

The waterborne polyurethane (PU) prepolymer was prepared based on isophorone diisocyanate (IPDI), polyester polyol (N220), dimethylol propionic acid (DMPA) and hydroxyethyl methyl acrylate (HEMA). The modified waterborne polyurethane–acrylate (PUA) emulsions were obtained with different proportions of acrylate (butyl acrylate and methyl methacrylate) and initiating agent by in situ dispersion technique. The structures and thermal properties of prepared PU and PUA were analyzed and characterized with FT-IR, UV–Vis spectroscopy and DSC. The PUA hybrid samples had lower glass transition temperature of hard segment and higher decomposition temperatures than PU sample. Performances of the emulsion and film were studied by means of apparent viscidity, particle size and polydispersity, surface tension and mechanical properties. The results indicated that the particle sizes of the PUA dispersions were larger than those of the pure PU and the solvent resistance, mechanical properties of PUA films was improved compare with the unmodified polyurethane film. The film had the biggest hardness and the least water absorption when the BA/MMA mass ratio 5:5 modified PU. The obtained PUA have great potential application such as coatings, leather finishing, adhesives, sealants, plastic coatings and wood finishes.

Thermosensitive polyurethane film and finished leather with controllable water vapor permeability

AbstractThree types of water based polyurethane (PU), i.e. one ordinary elastomeric polyurethane (EPU) and two thermosensitive polyurethane (TSPU), were synthesized and applied in leather finishing. Differential scanning calorimetry, positron annihilation lifetimes (PAL), water swelling, and water vapor permeability (WVP) were measured to evaluate how the structure of the synthesized PU and the temperature influenced the WVP of the PU finished leather. In contrast to EPU, TSPU(b) with a glass transition reversible phase and TSPU(c) with a crystal transition reversible phase showed an obvious phase separation structure and a phase transition in the normal wearing temperature range. PAL study indicated that when the temperature was higher than the designed phase transition temperature, the ortho‐positronium lifetime (τ3) and the average radius (R) of free volume of TSPU showed dramatic changes, whereas τ3 and R of EPU remained unchanged. The water swelling and WVP of TSPU finished leather were found to depend on the structure of the polymer and the temperature, and they gave different responses to temperature variation. When the temperature was higher than the designed phase transition temperature, a significant WVP increase from 3800 g/(m2 24 h) to 7830 g/(m2 24 h) for TSPU(b) finished leather and from 4100 g/(m2 24 h) to 9450 g/(m2 24 h) for TSPU(c) finished leather were observed. Whereas EPU finished leather showed low WVP, and increased slightly as temperature increased. Phase transition accompanying a significant change in WVP can be used to develop “smart leather” with controllable water vapor permeability. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Preparation, Characterisation and Mechanical Properties of Environmentally Friendly Waterborne Polyurethane and Polyurethane-Acrylate

The waterborne polyurethane (PU) prepolymer was prepared based on the polyester polyol (N220), isophorone diisocyanate (IPDI), and dimethylol propionic acid (DMPA). The waterborne polyurethane-acrylate (PUA) dispersions were prepared with different proportions of acrylate by in situ dispersion technique. The structures and properties of prepared PU and PUA were analysed and characterised with FT-IR spectroscopy, etc. The results indicated that compared with PU, the PUA dispersions had larger particle diameters, narrower particle-size distribution, lower surface tension, high temperature stability and freeze-thaw stability. The PUA films showed better optical transparency, higher tensile strength and lower elongation at break. The prepared PUA have potential application such as coatings, leather finishing, adhesives, sealants, plastic coatings and wood finishes.

Electrocoagulation efficiency of the tannery effluent treatment using aluminium electrodes

An electro-coagulation laboratory scale system using aluminium plates electrodes was studied for the removal of organic and inorganic pollutants as a by-product from leather finishing industrial process. A fractional factorial 2(3) experimental design was applied in order to obtain optimal values of the system state variables. The electro-coagulation (EC) process efficiency was based on the chemical oxygen demand (COD), turbidity, total suspended solid, total fixed solid, total volatile solid, and chemical element concentration values. Analysis of variance (ANOVA) for final pH, total fixed solid (TFS), turbidity and Ca concentration have confirmed the predicted models by the experimental design within a 95% confidence level. The reactor working conditions close to real effluent pH (7.6) and electrolysis time in the range 30-45 min were enough to achieve the cost effective reduction factors of organic and inorganic pollutants' concentrations. An appreciable improvement in COD removal efficiency was obtained for electro-coagulation treatment. Finally, the technical-economical analysis results have clearly shown that the electro-coagulation method is very promising for industrial application.

Pollutant removal from tannery effluent by electrocoagulation

An electrocoagulation laboratory scale system was studied for the removal of organic and inorganic pollutants from a wastewater of leather finishing industrial process. In order to obtain optimal values of the system state variables, a fractional factorial 2 3 experimental design was applied. The electrocoagulation process response was evaluated on the basis of chemical oxygen demand (COD), turbidity, total suspended solid, total volatile solid, and elements concentration values. The interactions between initial pH and electrolysis time, as well as between initial pH and current density were significant only for the total chromium removal. The reactor working conditions close to natural effluent pH and electrolysis time in the range of 30–45 min were enough to achieve the cost-effective reduction of COD, turbidity and chromium concentrations. The electrocoagulation method has shown similar pollutant removal efficiencies when compared with the conventional one and can be used successfully for industrial applications. Based on its low operational cost, the electrocoagulation method could be recommended instead of the conventional one.

Preparation and water resistance of crosslinked waterborne polyurethaneurea

Two series of cross-linked polyurethaneurea (PUU) aqueous dispersions with polyoxypropylene glycerol and pentaerythritol as internal cross-linking agents were prepared and characterised. The results revealed that in comparison with the uncross-linked one, the cross-linked PUU films exhibited excellent waterproof performance and mechanical properties. The amount of water absorption was as low as 2⋅5 wt-%, the contact angle of water on the surface of this kind of film was as high as 96°, and the tensile strength was as high as 42⋅8 MPa. The cross-linked PUU films with polyoxypropylene glycerol and pentaerythritol as cross-linked agents showed different properties at the same cross-linking agent content. The prepared triol-cross-linked or tetra-cross-linked PUUs had great potential application in meeting the highly diversified demands in modern technologies such as coatings, leather finishing, adhesives, sealants, plastic coatings and wood finishes, where high water resistance and durability were required.

Material flows in the life cycle of leather

This paper presents a study on the resource and environmental profile of leather for communicating to the consumers about the environmental burdens of leather products. The results indicate that significant environmental impacts were caused during the tanning and finishing of leather as well as the electricity production and transportation required in the life cycle. The use of fossil fuels in the production of energy has greater impact with increased emissions leading to about 15190 kg CO 2 equivalent of global warming and about 73 kg SO 2 equivalent of acidification while producing 100 m 2 of leather for shoe uppers. Further resource use of 174 kg of coal, 6.5 kg of fuel oil, 17.4 m 3 of water and 348 kg of chemicals of which about 204 kg are hazardous are consumed, and wastewater of about 17 m 3, BOD of 55 kg, COD of about 146 kg, TDS of 732 kg and solid waste of about 1445 kg are generated during the life cycle for the production of 100 m 2 of leather. The total solid waste generated is 1317 kg, out of which about 80% is biodegradable contributed by slaughtering, tanning and finishing stage, 14% is non-biodegradable contributed by tanning, finishing and electricity production stages and 6% is hazardous mainly from tanning and finishing stage of leather.

Styrene and butyl methacrylate copolymers and their application in leather finishing

AbstractHomopolymers and copolymers of styrene and butyl methacrylate were synthesized with different ratios by an emulsion polymerization technique with K2S2O8/NaHSO3 as the redox initiation system and sodium dodecyl sulfate as the emulsifier at 60°C for 3 h. The effects of different monomer ratios on the kinetics of emulsion polymerization and polymer viscosity were studied. These copolymers were applied to leather surfaces with a hand coater to a thickness of 18 μm. The effects of the coatings on the leather surfaces were evaluated through the measurement of physical and mechanical properties of coated and uncoated leather. IR spectra showed new bands characteristic of styrene and butyl methacrylate, which disappeared in the spectrum of uncoated leather. The physical and mechanical results showed that the water absorption content decreased with increasing styrene content, and the water vapor permeability of the coated leather was less than that of the uncoated leather; however, it was still in the acceptable range. The results indicated improvements in the tensile strength and elongation (%) for the coated leather with increases in the butyl methacrylate content. Thermogravimetric analysis showed characteristic improvements in the thermal stability of leather after the coating; its optimum stability was reached when the leather was coated with poly(styrene:butyl methacrylate) (1 : 1). Finally, scanning electron microscopy showed the full grain surface of the leather. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

Preparation of Acrylic Resin/Nano-SiO2 for Leather Finishing Agent

Acrylic resin/nano-SiO2 (AR/nano-SiO2) composite was prepared by physical blends of acrylic resin (AR) and nano-SiO2, which was synthesized via the sol–gel way of tetraethoxysilane (TEOS) catalyzed with ammonia. The synthetic conditions of nano-SiO2 sol in the homogeneous experiment on nanocomposite' property were studied in detail. Transmission Electron Microscopy (TEM) indicated the diameter of nano-SiO2 kept 10 nm. Differential Scanning Calorimetry (DSC) confirmed the addition of nano-SiO2 influenced the glass temperature of AR. Moreover, in contrast to acrylic resin, the applied properties of the leather finished by the AR/nano-SiO2 were measured: air permeability increased by 7.33%, water vapor permeability improved by 9.15% as well as water resistance of light leather by 14.02%, and adhesive of finish by 10.35%.

Use of mixed rare earth oxides as environmentally benign pigments

A new class of environmentally benign brown rare earth colorants as alternatives to toxic inorganic colorants is presented. These colorants are based on mixed rare earth oxides. Unique feature of these colorants is the utilization of mixed rare earth oxides after the removal of radioactive thorium from monazite sand. The utility of mixed rare earth oxides for general exterior coating applications has been evaluated through mass tone/hiding power evaluations and the product has been fine tuned with respect to particle size, combination with hydrophilic agents, binders etc. to achieve good hydrophobicity and covering on porous surfaces like leather. The pigment was compatible with various auxiliaries employed in leather finishing and meets the current requirements for pigments like upgrading of finished leather through excellent covering of surface and improved levelness, no overloading of grain, excellent physical properties, ageing resistance and miscibility with water.

Aqueous dispersions of polyurethane–polyvinyl pyridine cationomers and their application as binder in base coat for leather finishing

This article deals with synthesis of poly(urethane-co-vinylpyridine) block copolymer dispersions and their application as binder in leather finishing. Polyurethanes (PUs) with built in iniferter fragments were used to synthesize block copolymers with controlled incorporation of vinyl pyridine (VPy) units. Cationomers of the block copolymers were prepared by quaternising the polyvinyl pyridine groups and the ionomers were subsequently dispersed in water. FT-IR and FT-NMR studies were used to confirm the structure of the block copolymers. Increase in the ionic content and incorporation of vinyl pyridine groups led to an increase in thermal stability as revealed by thermogravimetric analysis. DSC results indicated that the phase separation increased when the block copolymers were converted to ionomer. Poly(urethane-co-vinylpyridine) block copolymeric dispersions were used as binder in leather finishing. The performance of the dispersions as binder was assessed by standard testing procedures and found to be comparable with commercial products with decided advantage over cost.

Rheology Aspects of Leather Finishing Formulations

ABSTRACT The rheological properties of leather finishing formulations were investigated. The rheological analysis was performed in a Ford cup number 4, a Brookfield viscometer, and a rheometer. The effects of the formulation parameters on the viscosity behavior showed similar trends for each technique. The tests in the rheometer showed that soft acrylic resins produced shear thinning formulations, similar to the effect of the finishing pigments. Furthermore, samples containing soft resins and polymeric pigments produced formulations with elastic properties. Finally, the Ford viscosity does not change significantly with the formulation parameters as the Brookfield viscosity does (type of pigment, resin, or resin-pigment ratio). Thus, the non-Newtonian behavior shown by the finishing samples analyzed suggests avoiding the use of the Ford cup when assessing leather finishing formulations. The Brookfield viscometer, however, would provide more reliable viscosity values when a rheometer is not at hand.

Mortality among chrome leather tannery workers: an update.

Employees engaged in the tanning and finishing of leather are potentially exposed to numerous carcinogens. A previous mortality study among 9,352 workers from two chrome tanneries has been updated with the addition of 11 years of vital status and work history follow-up and 1,153 new deaths. Ninety-two different causes of death were analyzed using a modified life-table approach. Death rates from both the United States and the states in which the tanneries were located were used as the comparison populations in calculating cause-specific standardized mortality ratios (SMRs). The mortality risks from all causes and from all cancers were lower than the expected for the combined cohort. Analyzing the two tanneries separately, no a priori cause of death (i.e., cancer of the lung, pancreas, bladder, kidney, testes, nasal cavity, lymphoma, or soft-tissue sarcoma) was shown to be significantly elevated. An exception was lung cancer at one tannery when state death rates were used (SMR=130, P<0.01). Analyzing by duration of employment, no significant trend in any cause of death at either tannery was revealed. Some studies have shown elevated risks for various site-specific causes of cancer; however, sites in excess are not consistent between studies. The differences may have been due to distinct processes used by the tanneries resulting in varying levels, as well as different types, of exposures.

Toxicity Review of Ethylene Glycol Monomethyl Ether and its Acetate Ester

Ethylene glycol monomethyl ether (EGME) and its acetate ester (EGMEA) are highly flammable, colorless, moderately volatile liquids with very good solubility properties. They are used in paints, lacquers, stains, inks and surface coatings, silk-screen printing, photographic and photo lithographic processes, for example, in the semiconductor industry, textile and leather finishing, production of food-contact plastics, and as an antiicing additive in hydraulic fluids and jet fuel.EGME and EGMEA are efficiently absorbed by inhalation as well as via dermal penetration. Dermal absorption may contribute substantially to the total uptake following skin contact with liquids or vapours containing EGME or EGMEA. EGMEA is rapidly converted to EGME in the body and the two substances are equally toxic in animals. Therefore, the two substances should be considered as equally hazardous to man.Effects on peripheral blood, testes, and sperm have been reported at occupational exposure levels ranging between 0.4 and 10 ppm EGME in air, and with additional, possibly substantial, dermal exposure. Severe malformations and disturbed hematopoiesis have been linked with exposure to EGME and EGMEA at unknown, probably high, levels. Embryonic deaths in monkeys and impaired spermatogenesis in rabbits have been reported after daily oral doses of 12 and 25 mg per kg body weight, respectively. In several studies, increased frequency of spontaneous abortions, disturbed menstrual cycle, and subfertility have been demonstrated in women working in the semiconductor industry. The contribution of EGME in relation to other exposure factors in the semiconductor industry is unclear.

皮革仕上工程自動化用ロボットシステム

To establish highly automated leather finishing process, it is necessary to develop the leather handling robot system which are provided with automatic aligned stacking and feeding functions of side-leather for loading and unloading to leather finishing machines. The robot system are composed of manipulation hand with vacuum pad and image processing system to recognize the shape patterns of side-leather for aligning functions. For the image processing, 2 types of sensors are applied. They are CCD camera for the recognition of shape patterns and other one is luster sensor to detect grain or flesh side. By applying the developed shape patterns recognition algorithms to the image processing system, side-leather discriminations of grain or flesh, head or tail, belly or back were carried out perfectly. As the result, the handling robot aligned side-leathers with following 2 stacking methods.1) Stacking with left and right side along the backbone (LR method).2) Stacking with grain to grain (GG method).Also, investigated on the robot hand to hold correctly each 1 leaf from stacked up side-leathers on the table.

Sizing particles used in the leather industry by light scattering

Three optical methods for sizing polymer particles are instrumented to be used in the leather industry. One method is based on the measurement of the light scattered intensity for several angles, and the other two are monochromatic or spectral extinction methods. Uniform latex particles and two commercial products used in leather finishing are measured. Advantages compared with electronic microscopy are discussed.

Performance evaluation of full scale wastewater treatment facility for finished leather industry

Abstract Medium strength finished leather wastewater has been successfully treated using anaerobic and aerobic systems in laboratory scale. Encouraged with the results, a full scale wastewater treatment facility was commissioned in one of the modern leather finishing industry in India. It has been possible to achieve an effluent BOD level of about 135 mg/L with an influent BOD of about 1260 mg/L. It is worthwhile to mention that wastewater contains some toxic materials which are very difficult to degrade. However, other parameters like phenol related compounds have been reduced to 0.3 mg/L in the effluent. Total dissolved solids could not be contained by biological methods. In addition a tannery equation has also been developed from an extensive survey carried out in India.

Characterization of organics in tannery effluents by liquid chromatography mass spectrometry

Combined high performance liquid chromatography mass spectrometry using a moving belt interface has been used to study extracts from five tannery and leather finishing industry discharges. Liquid chromatographic separation was performed with a Zorbax CN column using a normal phase solvent system of hexane + methylene chloride + methanol. Twenty different compounds were identified. Binaphthyl sulfone, which could not be gas chromatographed successfully, was one of the major components found in all five tannery extracts.

Measures taken against water pollution in tanneries and leather finishing plants.

This paper reviews the experience of several authors in the treatment of tannery effluents up to the present time. Special attention is paid to the mixing and equalization of tannery effluents, application of polycoagulants and thickening of the sludge.

The Colouring and Finishing of Leather

The Colouring and Finishing of Leather