DEVELOPMENT OF NIGERIAN CALCINED KAOLIN AS POTENTIAL SUBSTITUTE TO TITANIUM DIOXIDE AND OTHER ADDITIVES IN EMULSION PAINT FORMULATION

Abstract

The Nigerian coating industry is import dependent as most raw materials are imported. To reduce the importation, this current study processed kaolin to calcined kaolin to replace the most expensive titanium dioxide as pigment and carboxymethylcellulose from unripe plantain peel, fruit stem and Mexican sunflower to replace conventional natrosol thickener base. Anacardic acid was isolated from cashew fruit juice to replace conventional formalin biocide and cashew nut shell liquid (CNSL) from nut shell to replace conventional Polydimethylsiloxane defoamer and calgon dispersant. Raw kaolin from four deposits; Alkaleri, Major Porter, Onibode and Ukpor was beneficiated, leached and thermally treated to obtain calcined kaolin. Mineralogical analysis indicated kaolinite as the major mineral in association with other impurities such as Zircon, Anatase and silica in the form of quartz. Chemical compositional analysis showed major chemical compounds varied at various processing stage. Alumina in raw kaolin ranged from 34.08, 32.89, 22.84 and 19.50% in Alkaleri, Onibode, Major Porter and Ukpor respectively and increased to 41.01, 39.20, 34.94 and 34.16% respectively after thermal treatment. Silica in the form of quartz in raw ranged from 45.05, 45.20, 55.53 and 56.05% varied to 45.35, 45.90, 50.25 and 53.60% respectively. Titanium dioxide in the form of titanifferous compound in the raw ranged from 2.62, 4.28, 4.04 and 5.28% and decreased to 1.03, 1.87, 2.75 and 0.14% respectively while Ferric oxide in the raw ranged from 1.90, 3.45, 2.13 and 5.20% and decreased to 0.57, 1.05, 0.82 and 0.80% respectively due to the effect of leaching. The yield of synthesized Carboxymethyl cellulose (CMC) from unripe plantain peel, fruit stem and Mexican ranged from 44.37%, 33.21% and 62.57%. The FTIR spectral showed the presence of strong absorption bands at 1597, 1588 and 1585 cm-1 that are indicative of the presence of strong carbonyl (C=O) group which also confirmed successful etherification process. The refractive index of 1.54 and specific gravity of 0.99 of extracted cashew nut shell liquid (CNSL) compared favourably with commercial defoamers, Polydimethylsiloxane and Linseed oil. The main constituents identified in the GC-MS are anacardic acid, cardanol and cardol. The FT-IR spectral of the freeze-dried cashew fruit juice (FCFJ) indicated the presence of O-H stretch and H- bonded for alcohols and phenols at 3272.6 and 69.019 cm-1 respectively. The FCFJ was screen against three bacteria strains, Klebsiella pneumonia, Streptococcus pyogenes and Staphylococcus aureus and three fungi strains, Trichoderma viride, Aspergillus niger and Candida albicans. The bacteria strains were susceptible to the FCFJ effect while the fungi strains were not susceptible. The control (formaldehyde) recorded the highest antimicrobial activity at 50 mg/L. The properties of the calcined kaolin substituted paint compared well with the laboratory standard formulated paint. Similarly, the properties of the processed raw materials formulated emulsion paint at 60% exhibited superior quality than that of the commercial (Fidelo).