Wax is a diverse class of organic compounds, pliable at ambient temperatures and melting into low-viscosity liquids. These substances are widely present in nature and produced through industrial processes. Waxes serve various purposes, from protective coatings to structural components, making them ubiquitous in many everyday items. Their unique physical properties allow for broad applications across many industries.
Natural Wax Production
Natural waxes originate from living organisms, with prominent examples including beeswax and plant-based varieties like carnauba and candelilla wax. Each natural wax undergoes specific collection and purification steps.
Beeswax is created by honeybees to construct their hives and store honey. Beekeepers collect beeswax primarily from the cappings that seal mature honeycombs during honey extraction. Raw beeswax contains impurities, which are removed through processing. This involves melting the wax, allowing it to separate from impurities due to density differences. The melted wax is then filtered and molded into blocks.
Plant-derived waxes also follow distinct extraction methods. Carnauba wax, sourced from the leaves of the carnauba palm in Brazil, is harvested during the dry season. Harvesters collect the palm leaves, which are then dried and beaten to separate the powdery wax from the leaf material. This raw powder is melted and refined through processes like filtration, centrifugation, and bleaching.
Candelilla wax, found on the stems of the candelilla plant in the Chihuahuan Desert, is traditionally extracted by boiling the plant in an acidic solution, which causes the wax to float to the surface as a foam. Modern methods often use citric acid as a safer alternative to sulfuric acid, improving both environmental impact and the quality of the extracted wax.
Jojoba oil, a liquid wax, is extracted from jojoba seeds primarily through cold pressing. The dried seeds are subjected to extreme pressure to squeeze out the oil without heat.
Petroleum Wax Manufacturing
Petroleum waxes, such as paraffin wax and microcrystalline wax, are byproducts of crude oil refining. Their production involves separation and purification steps from petroleum fractions.
The manufacturing process for paraffin wax begins with the distillation of crude oil. Crude oil is heated and separated into fractions based on their boiling points. Waxes are present in the heavier fractions, particularly those used for lubricating oils.
The next step, called dewaxing, separates the wax from the oil. This is often achieved through solvent dewaxing, where a solvent mixture (like toluene and methyl ethyl ketone) is added to the waxy oil and chilled. As the temperature drops, the wax crystallizes, while the oil remains liquid, forming a slurry. The crystallized wax is then filtered from the liquid oil. The resulting “slack wax” still contains some oil and undergoes further purification, known as deoiling, to reduce the oil content to desired levels.
Microcrystalline waxes are also derived from petroleum refining, specifically from the heavier distillates produced during lubricant oil manufacturing. These waxes differ from paraffin wax by containing a higher percentage of branched and naphthenic hydrocarbons, resulting in a finer crystal structure, greater viscosity, and increased elasticity. The production process involves de-oiling petrolatum, a byproduct from refining these heavy distillates. After de-oiling, microcrystalline wax may undergo additional processing, such as filtration or hydro-treating, to remove color and odor, depending on the final application. These purification steps contribute to the wax’s specific properties, making it suitable for applications requiring flexibility and higher melting points.
Engineered Wax Synthesis
Engineered waxes are created through controlled chemical synthesis, allowing for precise customization. Two prominent types are Fischer-Tropsch waxes and polyethylene waxes.
Fischer-Tropsch waxes are synthesized through the Fischer-Tropsch process, a chemical reaction that converts synthesis gas—a mixture of carbon monoxide and hydrogen—into various hydrocarbons, including waxes. This process occurs under elevated temperature and pressure conditions in the presence of metal catalysts. The reaction involves adsorption of carbon monoxide and hydrogen onto the catalyst surface, building hydrocarbon chains. Depending on conditions, the process can yield products from gases and liquids to high molecular weight paraffinic waxes.
Polyethylene waxes are low molecular weight polymers of ethylene, produced through various polymerization methods. One method involves direct polymerization of ethylene monomers under specific conditions to control molecular weight and branching. This can occur through high-temperature and high-pressure polymerization, or under low pressure.
Another approach involves thermal or mechanical degradation (cracking) of higher molecular weight polyethylene resins to produce lower molecular weight wax fractions. Polyethylene waxes can also be obtained as a byproduct during the synthesis of high-pressure polyethylene. These synthetic methods allow for precise control of properties like hardness, melting point, and viscosity.