Influence of a Catalyst in Obtaining a Post-Consumer Pet-Based Alkyd Resin That Meets Circular Economy Principles

Abstract

The paper studied the influence of a catalyst, comparing it with its traditional counterparts, in the process of obtaining a polyethylene terephthalate (PET)-based alkyd resin from post-consumer beverage bottles and how it consumes raw materials and generates waste. The resin was obtained in two phases: 1) glycerol and soybean oil alcoholysis reaction, a renewable material, for polyalcohol production, and 2) polyalcohol and polyacid esterification reaction to obtain the alkyd resin (reaction via solvent). A lithium octoate catalyst (OctLi) was used, not traditional in the alcoholysis reaction, and a fraction of the polyacid replaced by post-consumer PET at a proportion of up to 24% by weight in the esterification reaction. The OctLi catalyst caused a reaction in 30 min, compared to zinc acetate (120 min) and lithium hydroxide (LiOH, 60 min). Using post-consumer PET in obtaining the alkyd resin also decreased the esterification reaction time by 22% (8% PET), 67% (16% PET) and 72% (24% PET), compared to esterification without PET. The reaction time, considering alcoholysis with OctLi and partial esterification with PET (with 24% PET), was 180 min. Adding alcoholysis time with the LiOH catalyst and esterification without PET raises the reaction time to 600 min. Process water formed during the esterification stage declined by 15% (8% PET), 50% (16% PET) and 77% (24% PET), compared to the reaction without PET. The shorter reaction time resulted in less equipment use and consequent lower energy consumption. Another result was that the alkyd resin obtained with 8% PET was adequate for paint formulations.

Current State of Alkyd Resin Synthesis and Characterization, Extracted from Vegetable Oils

“…The various extraction techniques employed in this study as seen in Table 1 encompassed; Soxhlet extraction [27,[29][30][31]33,39,42,44,46,49,51,55,60,62,65,66,69,[72][73][74]77,79], hot water floatation [4], [82],Mechanical press [47,50], distillation [58] whilst, [22,26,28,32,34,35,43,64,76,83] had their vegetable oils purchased.…”

“…Hot water floatation method was adopted by [4,82] for sesame seed oil, Mechanical press method was adopted by [47,50] for Beniseed oil, Jatropha curcas Linneaus seed oil and Rapeseed oil respectively, on the other hand, distillation method of extraction was employed by [61] [47,50]. Only 1 Researcher employed the distillation method and hot water floatation methods for their extraction [61,82] whereas, 10 Researchers had their vegetable oils purchased [22,26,28,32,34,35,43,64,76,83] The wide use of Soxhlet extraction method could be attributed to its notable high extraction efficiency especially for extracting oil from solid materials such as seeds or plant materials as it allows for thorough and complete extraction of oil, resulting in a higher oil yield compared to other methods. It also allows for selective extraction of specific compounds, including oils, from the solid materials [27,33,72].…”

“…The fatty acid process of alkyd resin synthesis involves the reaction of fatty acids with a polyhydric alcohol, such as glycerol or pentaerythritol, in the presence of an organic acid catalyst [76,83]. This process is commonly used in the production of long oil alkyd resins.…”

“…These oils are subjected to a process called saponification, where the oil is heated with an alkali, such as sodium hydroxide, to break it down into its constituent fatty acids. The resulting fatty acids are then purified and separated [58,76,83].…”