PolyTHF: 25th anniversary of “Verbund” product, still going strong

* BASF successful in developing Spandex and Elastan fibers throughout global markets

Twenty-five years ago, in September 1983, BASF brought its first plant for the production of polytetrahydrofuran on line at its “Verbund” (integrated production) site in Ludwigshafen, Germany. The product is now marketed under the name PolyTHF® throughout the world. With a nameplate capacity of altogether 4,000 tons per year the first plant was the launch pad for a remarkable success story. Now with an aggregate capacity of 185,000 tons and a world-spanning network of production plants, BASF is globally the most important supplier of this multifaceted intermediate.

Driven by growing demand for PolyTHF, a second plant was built in Ludwigshafen and started operations in 1995. It had to be expanded in 2002. At the same time BASF was building added capacities close to Asian and NAFTA customers. Beginning in 1987 the company began supplying customers from a plant in Geismar in the U.S. state of Louisiana, while Asian customers started receiving PolyTHF from the Ulsan site in South Korea as of 1998. The newest chapter in the annals of success is the PolyTHF plant at the Caojing production base near Shanghai. Since becoming operational in early 2005 the plant has mainly supplied customers in Asia, now not only the largest PolyTHF market, but also the fastest growing.

“For us, PolyTHF is a core business. In keeping with our practice for the past 25 years, we will therefore continue to be a reliable partner in support of our worldwide PolyTHF customer base,” declared Dr. Beate Ehle, president of BASF’s Operating Division Intermediates. Not only are the world’s most important Spandex and Elastan fiber manufacturers customers, but also a constantly growing number of smaller producers in Asia. Ehle added: “Together with our customers we keep working on innovative fibers for the future.”


PolyTHF is a typical “Verbund” product

The success of PolyTHF is rooted in BASF’s integrated production concept, involving in this case natural gas, as the starting material, to produce acetylene which is converted in a reaction with formaldehyde to butindiol and, in turn, into butanediol from which by way of cyclization tetrahydrofuran (THF) is formed in the presence of a catalyst and then polymerized to PolyTHF, chemically speaking to polytetramethyl¬ene ether glycol (PTMEG).

PolyTHF provides lasting elasticity

The textile industry accounts for most of BASF’s PolyTHF output, roughly 70 percent. The industry recognizes the intermediate as an invaluable raw material for manufacturing elastic fibers. Known throughout the world either as Elastan or Spandex, the fibers are processed with nylon, cotton or polyester fibers into high-quality fabrics.

Because these fibers consist up to 80 percent of PolyTHF, their properties are largely determined by the BASF product. They will not only stretch up to 500 to 700 times of their original length, but also keep their form durably, meaning they retain their extreme elasticity without losing their shape. The fibers are also light in weight, smooth to the touch and can easily be dyed. They resist humidity and microbes in a wide temperature range and are permeable to steam. For that reason the fibers have demonstrated their value especially in direct contact with the body – for instance, in swimwear, underwear, socks, pantyhose and modern sportswear. Their use in diapers is relatively new. Featuring special flat fibers at the edges these diapers provide a reliable tight seal without the discomfort of cutting into the skin. It takes actually a small volume of fibers to make a woven fabric elastic and thus be more comfortable to wear. With merely three percent Spandex or Elastan woven into their fabric, stretch jeans live up to their name. In sportswear Spandex or Elastan may represent up to about five to ten percent, in swimwear it may range as high as 30 percent.

Fiber manufacturers appreciate particularly the high PolyTHF quality achieved by BASF thanks to a continuous production process. Use of the BASF intermediate enables producers to manufacture uniform homogenous fibers consistently, which, as a result, will not pose problems in further processing. At conventional operating speeds of 500 to 8000 meters per minute even these very thin fibers are not likely to break, preventing costly production stoppages.

PolyTHF is also an important intermediate in manufacturing thermoplastic polyurethane elastomers (TPU). These products are made into highly-abrasion resistant and flexible hoses, films and cable sheathing. Other applications include thermoplastic polyesters, polyetheramide and cast polyurethane elastomers, proven in their use for skateboard rollers and inline skates. Skaters appreciate the elastomers on which they roll because they make for a comfortable, cushioned ride. Yet the rollers are extremely tough, highly-resistant to wear and therefore long-lasting.

Comprehensive line of PolyTHF products offered

In addition to PolyTHF BASF supplies a broad palette of other raw materials for the production of Spandex and Elastan fibers and elastomers. The line includes isocyanates, chain extenders and stoppers, crosslinkers as well as a series of solvents.

BASF backs its products with a multitude of comprehensive services designed to make and keep its customers’ production increasingly efficient. In addition to start-up support and general technical consultations, the spectrum of services also aims to improve fiber properties, especially their functionality and thermal resistance. Furthermore special analyses are offered to determine the chemical composition, the morphology, the viscosity of the spinning solution, solvent recycling and support in attaining sustainability and providing Responsible Care.

This year the company will be opening a special PolyTHF application laboratory at the Shanghai-Pudong site. It will expand BASF’s technical customer service in Asia, in particular for the PolyTHF growth markets in Elastan and Spandex fibers as well as thermoplastic polyurethane and polyether ester elastomers (TPU, TPEE). The laboratory has access to modern polymer analytics and also will be equipped to perform various tests and syntheses. Due to its proximity to customers the laboratory will be positioned to develop new recipes and refine current formulations for them. It will also furnish adjustments of mechanical and thermal properties for PolyTHF derivatives.