Soy wax is a vegetable-based material derived from soybean oil, offering a modern alternative to traditional waxes like paraffin. It is made by chemically altering the liquid oil, transforming it into a soft, solid substance suitable for various applications. Its popularity stems from its origin as a renewable, agricultural product. The process starts with the raw harvest and moves through chemical transformation before the final wax product is ready.
Extracting Soybean Oil
The journey begins with harvested soybeans, which must first undergo cleaning to remove debris and impurities. After cleaning, the soybeans are cracked and de-hulled, separating the hard outer shell from the oil-rich inner core. The remaining material is then rolled into thin flakes to increase the surface area necessary for efficient oil extraction.
Oil is separated from the flakes using one of two primary methods: mechanical pressing or solvent extraction. Solvent extraction is the more common industrial method, using a chemical solvent, typically hexane, to dissolve the oil. The crude oil is still a liquid at room temperature and must undergo further refining and bleaching to prepare it for the next step.
The Hydrogenation Process
The purified, liquid soybean oil must be chemically transformed into a semi-solid wax through hydrogenation. This process is necessary because soybean oil consists mainly of unsaturated fatty acids, which have a naturally low melting point. Hydrogenation works by adding hydrogen atoms to the fatty acids’ molecular structure, converting unsaturated bonds into saturated ones.
To initiate this transformation, the refined oil is heated to an elevated temperature, typically between 140°C and 225°C, inside a high-pressure reactor. A metallic catalyst, most often nickel, is then introduced to the mixture, which facilitates the reaction. Hydrogen gas is continuously bubbled through the heated oil while the mixture is vigorously stirred to ensure uniform distribution of the catalyst and the gas.
The extent of hydrogenation controls the final wax properties, such as hardness and melting point. Partially hydrogenated oil remains softer and is suitable for container candles. Fully hydrogenated oil results in a harder, higher-melting wax, necessary for pillar candles. By carefully controlling the temperature, pressure, and time, manufacturers can engineer a wax with a specific texture and thermal performance.
Post-Processing and Final Product
Once the hydrogenation process is complete, the newly formed wax is still mixed with the nickel catalyst. The first step in post-processing is removing this catalyst through a rigorous filtration process. This separation ensures the final product is clean and free of residual metals.
Following filtration, the wax often undergoes a deodorization step, typically achieved using steam stripping. This process removes any lingering volatile compounds that might impart an undesirable odor. Depending on the desired commercial application, performance enhancers or additives may be blended in. Stearic acid or other waxes might be added to improve the wax’s structural integrity or to raise its melting point for use in free-standing candles.
The finished, purified soy wax is then cooled, solidified, and prepared for shipping to manufacturers. It is generally packaged in a convenient commercial form, such as large blocks, pellets, or flakes, allowing candle makers and other users to easily melt and handle the material.