CHAPTER 5 CONCLUSIONS

Transcription

1 CHAPTER 5 CONCLUSIONS

2 /166/ 5.0 Summary The leather industry uses a quite number of chemicals during various steps involved in the conversion of raw hides and skins to finished leather. Surfactants are used in various stages during the leather manufacture. Fatliquoring is one the main step in leather processing where the surfactants play a key role. The fatliquor becomes a part of the composition of leather 218 and gives strength, suppleness, softy feel and stretch to the leather. Efforts have been continued to develop a new, more effective, efficient and mild class of surfactants with improved surface-active properties 219. As a part of the continual developments, the present research work was undertaken to synthesize new class of compounds as below: Synthesis, characterization of a new amphoteric surfactant, di ethylamino lauryl itaconate (DEALI) and its application on leather processing as a fatliquor. Synthesis, characterization of a new novel gemini surfactant, sulphonated dimeric malenised soya fatty acid (SDMS) and its application on leather processing as a fatliquor. The study on effect of the addition of phase transfer catalyst, nonionic wetting emulsifier, co-solvent on the degree of sulfonation during sulfosuccination and the effect of sulfonate content on leather processing as a fatliquor.

3 /167/ 5.1 Conclusions DEALI A New Amphoteric Surfactant An anionic polymerisable surfactant lauryl itaconate (LI) was synthesized. This was reacted with diethylamine to prepare a new amphoteric surfactant diethylamino-lauryl itaconate (DEALI). LI and DEALI were characterized by FT-IR and 1 H NMR spectra. The surface tension at different concentrations, critical micelle concentration, contact angle, surface energy, emulsification power, zeta potential and particle size properties of LI and DEALI were measured. Isoelectric point of DEALI was determined. LI and DEALI were formulated as fatliquors by blending a mixture of vegetable oil, mineral oil, chloroparaffin sulfonate and the synthesized surfactant. The composition was adjusted to 100 % using water. The prepared fatliquors were analysed for the parameters like colour, clarity, ph of 10% solution and hard water stability. The prepared fatliquors were applied 220 on full chrome wet blue cow leather. Fatliquor imparted properties on the leather were measured. Qualitative assessment of leathers showed an increase of 12.5% in softness and touch by the substitution of amphoteric surfactant. Quantitative assessment of Tensile strength showed an improvement of 33%.

4 /168/ Improvements were due the higher surfactant activity of the amphoteric surfactant. It yielded stable emulsion, good solubility and stability over the wide ph range. Dye brilliance and evenness was better due to the presence of cationic group through electrostatic coupling with the anionic dyestuffs SDMS - A New Gemini Surfactant Soya fatty acid having enriched in linoleic acid was reacted with maleic anhydride at higher temperatures to form malenised soya fatty acid (MS). Two moles of MS was reacted with 1,4-butane diol as a spacer, to form a dimeric gemini surfactant through esterification route. The gemini surfactant was sulphonated with sodium bisulfite to form sulphonated dimeric malenised soya fatty acid (SDMS). The compound was characterized by FT-IR, 1 H NMR and LCMS techniques. The surfactant activity was analysed using the measurement of surface properties such surface tension, critical micelle concentration, foam stability, contact angle, emulsification power, zeta potential and particle size were analysed. Surface activity of the gemini surfactant is far better than its conventional analogue.

5 /169/ Conventional surfactant in a fatliquor formulation was replaced by the new gemini surfactant with reduced dosage to different extents in a fatliquor formulation. The fatliquors were applied on full chrome wet blue cow leather. Leather properties were studied qualitatively and quantitatively, also through scanning electron microscopic studies. Surface energies of the fatliquors were calculated and proved the efficiency of the new compound. By the substitution of the gemini surfactant in place of conventional surfactant with the reduced dosage to the extent of 66%, leather performance was matched which leads to cost reduction and less environmental impact. The structure-property relationships were explained Sulfosuccinated surfactants Lauryl maleate monoester was sulfonated using sodium bisulfite of 20% solution at 70-75ºC for 3h as a control batch experiment. During the sulfosuccination, individual addition of 5% each of phase transfer catalyst (tetra butyl ammonium bromide), non-ionic wetting emulsifier (lauryl alcohol 8 moles ethoxylate) and co-solvent (isopropyl alcohol) found to improve the degree of sulfonation by 33%, 117% and 180% respectively. Sulfonate content had a direct effect on emulsification power, zeta potential and surface tension, whereas the additives phase transfer catalyst, non-ionic wetting agent and co-solvent played a role in deciding the particle size.

6 /170/ Fatliquors were prepared using sulfosuccinate having 5.2% and 14.6% sulfonate content and applied on full chrome wet blue cow leather. Leather properties were studied qualitatively and quantitatively. This was further confirmed by SEM studies. The fatliquor with the sulfosuccinate of 14.6% sulfonate content yielded better properties of softness, whiteness and surface touch, each to the extent of 11%. Tensile and grain crack strengths were improved by 21% and 11% respectively. The difference of degree of sulfonation of 2.17 times played the critical role in determining the improved performance. This present research forms the basis for the development of new fatliquoring agents for the leather industry. Judging from the conditions employed, this present study has great prospects for other industrial applications also with reduced cost and environmental friendly. 5.2 Suggestions for future work The synthesis of DEALI can be extended to other series of alcohols and also amines for further better functionalization. The synthesis of SDMS can be experimented with other alcohols as spacers in place of butane diol. The synthesized surfactants can be tried in other industrial applications.

7 /171/ 5.3 Future research in fatliquors Recently nano-scale materials have attracted great interest, both in industry and academically, because they often exhibit remarkable improvement in material properties when compared with conventional materials. Nanometre technology has been acknowledged generally as the most promising field of scientific research in the 21 st century 221. Surfactant treatment is the key of an organic/inorganic nano tanning agent 222. The development in the filed of micro-emulsified fatliquoring agents are expanding. A micro-emulsion is transparent, isotropic with stability in a thermodynamic system that is composed of surfactant, assisting surfactant, oil and water. The micro-emulsion particles range from 10nm-100nm in size 223. The droplet sizes of fatliquoring agents affect the fatliquor s effects greatly 224. Small, stable emulsion droplets give even and deep penetration of oil into the collagen fibre. In the case of the dispersion and uniformity of oil, the smaller the emulsion droplets are, the better are the effects.

8 /172/ In recent years, micro-emulsion technology (MET) has been applied in many fields including leather industry for fatliquoring. Liu Wanxing et al 225 used a non-ionic surfactant as the major emulsifier along with two anionic surfactants to prepare a micro-emulsified fatliquor. This was applied to goat garment leather. The resultant leather was soft, full waxy with a fine grain. Nano-scale materials research in the leather industry is going to be on the increase and the application fields of surface active agents in leather are expanding.