Compounders ranging from feedstock suppliers to local independents are finding ways to develop the in-between potential of thermoplastic polyurethanes. As niche market leader BFGoodrich Co. says in a brochure, the polymers ``bridge the gap between rigid plastics and rubbery elastomers.'' TPUs can range from hard and stiff to soft and flexible, with applications including ski goggles, heart catheters and high-tech sailboat gear.
Units of Dow Chemical Co., BASF AG and Bayer AG supply resin feedstocks to manufacture TPUs and other urethanes, in addition to marketing TPU resins. Hybrid supplier BFGoodrich makes both feedstocks and a line of specialty compounds.
Custom compounders such as M.A. Hanna Co. of Cleveland, A. Schulman Inc. of Akron, Ohio, and Teknor Apex Co. of Pawtucket, R.I., buy feedstock and blend or alloy the TPU with compounding ingredients or other polymers.
The market seems unpredictable.
``Five years ago, TPUs were somewhat stagnant, mainly due to substitution by modified polyolefins,'' said Dan Cox, regional manager in Houston for Century Specialties. ``Things have leveled off now, but people wait longer for justification of an order, and the end uses are more specific.''
The firm, a unit of Century Inc. of Traverse City, Mich., makes twin-screw extruders and aftermarket replacement parts for specialized alloying, coloring and reinforcing applications.
``The critical nature of new formulations will require this type of sophistication,'' Cox said, ``plus urethanes are not that easy to process. They are shear-sensitive and don't like to get wet.''
The largest U.S. thermoplastic polyurethane compounder just got bigger.
``We increased the capacity of our state-of-the-art compounding capability, and more than doubled our fixed investment in the TPU business,'' said Michael Marasch, senior marketing manager with the Estane TPU division of BFGoodrich Co.'s specialty plastics group in Brecksville, Ohio.
One goal of the new capacity: Replace thermoset rubber.
BFGoodrich added flexibility.
``Now, we can make runs of 20 pounds to 2 million pounds through each step in the scale-up process, while growing a new application,'' Marasch said.
Recently, a major cellular telephone manufacturer tested that flexibility. A sales representative learned of the need for a TPU coil cord with the look and feel of thermoset rubber.
BFGoodrich developed a new formulation, conducted trials and obtained end-user approval within four months. Its Estane X-4787 matte-finish TPU expands on the company's capabilities for wire and cable applications.
``We incorporated compounding technology using proprietary additives to provide a dull or matte finish to the finished cord,'' said Marasch, claiming others have been unsuccessful in meeting the requirement for a consistent matte finish.
``We are different from other TPU manufacturers in that we are not backward-integrated to a large degree,'' Marasch said. ``We are willing and able to tweak compounds as well as the resin backbone to make TPU systems for specialty applications.''
Regarding TPU's inconsistent past, ``The material was probably ahead of its time,'' said Mark Remmert, Pellethane senior product market manager for Dow Plastics in Midland, Mich.
``Engineering techniques did not take full advantage of the materials,'' Remmert said. ``Now, with better design and fabrication technology, we have the ability to custom-tailor products for individual applications. That's where the growth is coming from.''
Dow projects 10 percent annual TPU industry growth through the year 2000.
``We have seen interest in softer TPU products for soft touch and grips, but film and sheet is another development area,'' Remmert said. ``We've developed softer materials in the 60-65A range for waterproof fabric laminations as well as breathable apparel.''
Also, Dow sees interest in TPU for automotive lumbar bags, foam seating and dead-feel material that mimics rubber.
In Anderson, S.C., Ryobi Motor Products Corp. developed a deep-down carpet and upholstery cleaning machine that, on opposite sides of a flexible, 2-gallon Pellethane TPU bladder, stores fresh solution and recovered dirty fluid.
A project collaborator, Ameri-can Components Inc. of Dand-ridge, Tenn., suggested the use of Pellethane after the material met long-term durability requirements for automotive lumbar supports.
Martin Sixsmith, business manager of Bayer's Texin and Desmo-pan thermoplastic polyurethanes, projects industry growth of about 9 percent in 1997, ``and Bayer is growing faster than the industry.''
A shortage of key feedstocks in 1995 led to some hoarding, and could account in part for a slower first-quarter pace as companies trimmed inventories, he said.
In the first quarter, Bayer acquired a plant in Cuddalore, India, to complement its U.S. production in New Martinsville, W.Va., and European operations.
Bayer subsidiary Deerfield Urethane in South Deerfield, Mass., uses aliphatic TPU to make a new type of greenhouse film that is undergoing U.S. site tests.
``Significant volumes are anticipated in 1997,'' Sixsmith said, particularly if marketers can ``convince industry that it is worth paying more money up front in return for longevity.''
Bayer expects a Big Three automaker to use its aliphatic TPU in a yet-to-be-revealed application that will appear in showrooms beginning in August 1997.
While most urethane manufacturers are large chemical companies and produce only clear resins, Thermedics Inc. is an exception.
``We make the resin and can put in any additives before we polymerize,'' said Daniel Brown, vice president of polymer products for the Woburn, Mass., firm. ``That saves heat history.''
Medical compounders add barium sulfate, bismuth compounds or tungsten powder into TPU so catheters of the material will appear on X-rays. Thermedics' color additives for medical product identification use reactive dyes and food-grade pigments.
``We disperse into a liquid rather than a solid,'' Brown said, ``and sell colored pellets ready for extrusion or injection molding.''
In 1983, instrumentation firm Thermo Electron Corp. spun out Thermedics into a publicly traded subsidiary. Thermedics had profit of $15.1 million on 1995 sales of $175.8 million.
``About 2 million to 3 million pounds of TPU are used for medical applications,'' said Curtis Smith, director of research and development for New England Urethane Inc. of North Haven, Conn.
Formed in 1989, the firm ships TPU to Irish manufacturing facilities of U.S. firms and other customers in Europe and Asia, ``but not 1 pound in Connecticut yet,'' Smith said.
He described medical uses as including arterial and vascular tubing, diagnostic and balloon catheters, artificial heart chambers, heart-assist devices and pacemaker lead insulation.
In the capital equipment arena, Werner & Pfleiderer Corp. in Ramsey, N.J., has ``sold a handful of small TPU machines in the North American market in the past five years,'' said Daniel Mielcarek, manager of process applications.
The firm's 30- and 40-millimeter-diameter twin-screw extruders sell for $100,000-$250,000, but ``it costs three times that amount by the time you install it,'' Mielcarek said.
The larger, 92mm model can process 1,000-1,500 pounds of compound per hour.
Mielcarek estimated that Werner & Pfleiderer customers have ``20 machines doing polymer reactions and maybe 20 doing compounding of urethanes'' in North America.
Machine maker B&P Process Equipment and Systems LLC has customers that compound materials for abrasion-resistant and strong-impact applications, said Peter Giles, sales manager.
Located in Saginaw, Mich., B&P manufactures Baker Perkins twin-screw extruders with 19-160mm barrel diameters and length-to-diameter ratios as great as 50:1. Four sizes in the 40-80mm range are most popular with TPU extruders.
The U.S. market consumed 70 million pounds of TPU in 1991 and 94 million pounds in 1994, according to end-use market surveys by the Society of the Plastics Industry Inc.'s polyurethane division in New York.