Microcrystalline wax

Microcrystalline waxes are a type of wax produced by de-oiling petrolatum, as part of the petroleum refining process. In contrast to the more familiar paraffin wax which contains mostly unbranched alkanes, microcrystalline wax contains a higher percentage of isoparaffinic (branched) hydrocarbons and naphthenic hydrocarbons. It is characterized by the fineness of its crystals in contrast to the larger crystal of paraffin wax. It consists of high molecular weight saturated aliphatic hydrocarbons. It is generally darker, more viscous, denser, tackier and more elastic than paraffin waxes, and has a higher molecular weight and melting point. The elastic and adhesive characteristics of microcrystalline waxes are related to the non-straight chain components which they contain. Typical microcrystalline wax crystal structure is small and thin, making them more flexible than paraffin wax. It is commonly used in cosmetic formulations.

Microcrystalline waxes when produced by wax refiners are typically produced to meet a number of ASTM specifications. These include congeal point (ASTM D938), needle pentration (D1321), color (ASTM D6045), and viscosity (ASTM D445). Microcrystalline waxes can generally be put into two categories: "laminating" grades and "hardening" grades. The laminating grades typically have a melt point of 140-175 F and needle penetration of 25 or above. The hardening grades will range from about 175-200 F, and have a needle penetration of 25 or below. Color in both grades can range from brown to white, depending on the degree of processing done at the refinery level.

Production and Market Availability
Recent industry trends in the base lubricant market have reduced the total number of refineries producing purpose-made microcrystalline waxes. In North America, The International Group, Inc (IGI, http://www.igiwax.com) is one of the few remaining companies that have committed refining capacity dedicated to the long term supply of finished microcrystalline waxes. IGI's refineries in Farmer's Valley, PA, and Toronto, Ontario, Canada, both have capabilities for refining unfinished "slack wax" (the raw material) into a finished microcrystalline wax. Exxon-Mobil is also a major North American producer, with facilities in TX and LA. There are also existing companies that will purchase microcrystalline wax and use it internally for finished blends.

Industries and Applications
Microcrystalline wax is often used in industries such as the tire and rubber, candles, adhesives, corrugated board, cosmetics, castings, and a host of others. Refineries may also utlize blending facilities to combine paraffin and microcrystalline waxes. This type of activity is prevalent especially for industries such as tire and rubber.

Microcrystalline waxes are excellent materials to use when modifying the crystalline properties of paraffin wax. The microcrystalline wax has a significant effect on the branching of the carbon chains that are the backbone of paraffin wax. This is useful when some desired functional changes in the paraffin are needed, such as flexibility, higher melt point, and increased opacity.

Useful Links
 * microcrystallinewax.net: information on micro waxes
 * ASTM official website: wax tests
 * June '07 NCA technical presentation on microcrystalline wax