Sabic polyacetal plant plan makes headway

AL-KHOBAR – Saudi Basic Industries Corp. (Sabic) has invited bids for the construction of a 50,000 tons-per-year polyacetal (POM) facility at its affiliate Ibn Sina in Jubail, industry sources said recently.

National Methanol Co, better known as Ibn Sina, is 50-percent owned by Sabic while Celanese Corp and an affiliate of Duke Energy Corp each have a 25 percent stake.

Companies invited to submit bids by Oct. 24 are Spain’s Dragados, China National Chemical Engineering Co, Taiwan’s CTCI, South Korea’s Hyundai Engineering, Daelim Industrial, Hanwha Engineering and SK Engineering and Construction.

In 2010, when Sabic signed an agreement with Celanese to develop the project, it said the investment was expected to be nearly $400 million. It said then the plant would go online by 2013 with engineering and construction work starting by 2011. The facility will use methanol feedstock from Ibn Sina to make POM, largely used in the automotive industry.

The engineering polymer polyacetal (also known as polyoxymethylene) has a long history of clinical use including in the femoral component of the Freeman all-polymer knee replacement.

Polyacetals are typically strong and tough, resistant to fatigue, creep, organic chemicals (but not strong acids or bases), and have low coefficients of friction. Electrical properties are also good. Improved properties for particular applications may be attained by reinforcement with fibers of glass or polytetrafluoroethylene, and by incorporation of an elastomeric toughening phase. The combination of properties has led to many uses such as plumbing fittings, pump and valve components, bearings and gears, computer hardware, automobile body parts, and appliance housings.

The polymer is a promising material for novel applications including the femoral component of hip resurfacing prostheses.

A polyether derived from aldehydes (RCHO) or ketones (RRCO) and containing ORO groups in the main chain. Of the many possible polyacetals, the most common is a polymer or copolymer of formaldehyde, polyoxymethylene (OCH2)n. While the substance paraformaldehyde contains oligomers or low-molecular-weight polyoxymethylenes (n very small), high-molecular-weight, crystalline polyoxymethylenes constitute an important class of engineering plastics that, in commerce, is often simply referred to as polyacetal. Cellulose and its derivatives also have a polyacetal structure.

Formaldehyde can be readily polymerized by using anionic initiators such as triphenylphosphine and, somewhat less readily, by using cationic initiators such as protonic acids. Alternatively, a similar polymer can be obtained by the ring-opening polymerization of trioxane using, for example, a boron trifluoride complex as initiator. See also Polymerization.

At temperatures above -110°C (230°F; the ceiling temperature, above which depolymerization becomes favored over polymerization), the polymers degrade by an unzipping reaction to monomer. To prevent this, one of two approaches is commonly used: esterification of the hydroxyl end groups, or copolymerization with a small amount of a monomer such as ethylene oxide or 1,3-dioxolane. – SG/QJM