Use of hydrolysis products of polythylene terephthalate scraps to produce alkyd based paint

Abstract

In modern world, plastics play a significant role in our daily life. However Sri Lankans' still have not introduced proper waste management system to daily increasing plastic garbage. Polyethylene terephthalate (PET) is one of the main plastic used in day today life as packaging material, soft drink and mineral water bottles. Sri Lankan peoples alone consumes 6.5 million PET bottles per month but only 1.5 million bottles collected for recycling. This gives clear indication about the role of PET in environmental pollution. This report present development of effective chemical recycling process to depolymerize PET waste into its initial monomers and use of de-polymerized products to synthesized alkyd resin which can be use in coating industry. Depolymerization of PET was done by hydrolysis method to extract terephthalic acid(TPA) . Here Na2CO3 was successfully used as hydrolysis agent instead of highly corrosive NaOH . This overcome the common disadvantages of NaOH . At 170 °C, 35 minutes and 1:4 PET: EG (ethylene glycol) mole ratio 78.89% PET was reacted with Na2CO3 without any catalyst. Recovered terephthalic acid was used to replace Phthalic anhydride in alkyd resin. Due to the inability of conventional alcoholysis method to making alkyd resin from TPA, a new methodology was developed. New Process was successfully incorporated to produce long oil alkyd resin with soya oil, glycerin, maleic anhydride and recovered TPA. Under this new method alkyd processing time was greatly reduced and minimum time achieved was 120 minutes at 280 °C. Practical application of this project to the local PET waste will help to reduce the plastic land fill in Sri Lanka and also provide more beneficial effects to the alkyd paint industry by reducing production time and raw material cost.