Cyclic olefin homopolymers and copolymers are engineering thermoplastics derived from the ring-shaped norbornene molecule, which is made from dicyclopentadiene (DCPD) and ethylene.
New Cyclic Olefins Are Clearly Worth a Look
There is a growing family of polyolefins that are nothing like the polyethylenes and polypropylenes familiar to most processors. Cyclic olefin homopolymers and copolymers are engineering thermoplastics derived from the ring-shaped norbornene molecule, which is made from dicyclopentadiene (DCPD) and ethylene. These resins boast glass-like transparency, low dielectric loss, low moisture absorption, excellent dimensional stability, high heat resistance (212-374 F Tg), and high melt-flow rates that permit very precise molding. Cyclic olefins are also being investigated as a blending ingredient to stiffen polyolefin films.
Cyclic olefins are commercially available from a handful of pilot-scale plants around the world. Current world production of these resins is only about 20 million lb/yr from four suppliers. Three are in Japan (Nippon Zeon, Mitsui Chemical, and JSR Corp., formerly Japan Synthetic Rubber) and one is in Germany (Ticona). As applications multiply, several producers are increasing capacity. At mid-year, Ticona will start up the world’s first large-scale cyclic-olefin plant in Germany—66 million lb/yr.
Meanwhile, Bayer AG in Germany has applied for an international patent (No. WO98/33830, Jan. 1998) together with Teijin Ltd. of Japan for a new cyclo-olefin copolymer and the process to make it. This product has not been commercialized yet. Both Bayer and Teijin are also large producers of polycarbonate, which is expected to compete with cyclo-olefins in next-generation, higher-capacity DVDs.
Another producer of norbornene-based cyclic olefins is BFGoodrich Performance Materials in Charlotte, N.C. However, its resins are high-priced specialties (up to $3000/lb) that are non-melting and must be processed from solution. They can have very high heat resistance (Tg up to 700 F) and are aimed at microelectronic applications.
High moisture barrier
Although cyclic olefins are unfamiliar to U.S. processors, the ones they have heard the most about are the Topas family of amorphous copolymers developed by Ticona, whose U.S. office is in Summit, N.J. Until the commercial plant starts up, Topas is made in a 450,000-lb/yr pilot reactor in Germany, and larger quantities are being made by a toll supplier. Topas is already commercial on a small scale in a half-dozen grades used for medical films and bottles, injection molded medical devices, and lenses. Current truckload developmental pricing is $2.65/lb, which will drop somewhat when the new plant is fully on stream.
The first major commercial application is a five-layer laminated film, thermoformed into blister packs for Bayer Aspirin in Indonesia. The 12-mil film has a core of Topas 8007 with a thin skin of PP on either side. Topas is used as a moisture barrier to protect the aspirin from high humidity. Ticona in the U.S. is also developing five-layer coextruded films for extreme moisture barrier. One consists of 15 microns of PP on either side of 240 microns of Topas 8007, with tie layers in between. It’s said to be cost competitive with PVDC-coated PVC.
Topas is also used commercially in a number of optical and medical applications in Europe. Schott Pharmaceutical Packaging in Mainz, Germany (with U.S. offices in Cleona, Pa.), has developed a robotic clean-room process to injection mold and assemble Topas syringes.
In pharmaceutical bottles, Topas’s high moisture barrier could extend drug shelf life longer than plastics currently being used, Ticona says.
“We also think blends will be a major application for Topas,” says Donal McNally, Ticona’s U.S. marketing manager for the resin. Adding 10-20% Topas to a 3-mil polyethylene heat-seal layer in a packaging film makes it a great deal stiffer, he notes. “This is under evaluation now by a number of people in the food business for stand-up pouches.” At NPE in June, Macro Engineering of Mississauga, Ont., will run blown film of a Topas blend.
Pure, clean, and clear
Nippon Zeon launched Zeonex, an amorphous norbornene homopolymer, in 1991 and Zeonor, an amorphous copolymer, in 1998. Zeon will double production of the two in Japan next month to about 15 million lb/yr. In the U.S., Zeon Chemicals LP, Louisville, Ky., sells five grades of Zeonex. They are priced in the $15-18/lb range and have Tg values of 280-284 F. “It’s the purest, cleanest polymer on the market in terms of contaminants and residual ions,” says Paula Phipps, senior manager of new product development at Zeon Chemicals. The U.S. firm also markets three grades of Zeonor, which cost $4.50-6.00/lb and have a Tg range of 230-288 F. It boasts much higher impact strength than Zeonex.
Zeonex 480 is a standard grade used in molded optical lenses and prisms for cameras and video cameras. Medical parts are another market. Zeonex E48R is a low-birefringence grade for laser-optic parts such as lenses for CD players and laser printers. And Zeonex 490K is an extrusion-grade optical resin that can be made into 5-10 mil cast film on conventional equipment, Zeon says. Zeonex films are also used for mirrors and reflectors. Sony Corp. in Tokyo is developing plastic computer hard disks using Zeonex. This resin’s low moisture absorption, low birefringence, and high transparency to blue-green laser light also make it a candidate for next-generation, higher-capacity DVDs.
What is probably the largest part yet molded of a cyclo-olefin is a Nissan auto headlamp reflector injection molded of Zeonor 1600R. It was displayed at the recent International Plastics Fair ’99 in Tokyo and is being considered for U.S. production. Zeon sources say the resin was chosen because it has high flow (which permitted molding thinner walls), 47° F higher heat resistance than polycarbonate, and a smoother surface than PBT/PET blends. Zeonor high-flow grades also target light-guide panels and laptop computer screens. In addition, Zeonor is used for contact lenses because of its great dimensional stability and excellent purity.
In Japan, JSR sells about 2 million lb/yr of norbornene homopolymers and copolymers, called Arton. These amorphous resins were commercialized in 1997. They are functionalized with an ester side chain to control Tg. JSR Microelectronics Inc. in Sunnyvale, Calif., imports small amounts of Arton to the U.S., but most is used in Asia. Prices run $10-20/lb. Some is exported to Europe for film.
Arton G extrusion grade is used for optical films. JSR also sells two grades of optical films made of Arton homopolymer with a Tg of 340 F for LCD screens and touchscreen displays. Arton F and FX grades are for injection molding optical disks (CD and DVD) and lenses for cameras and laser printers. Injection grades have Tg values of 287-329 F. JSR is also developing new Arton grades for very high-end optical parts, such as lenses, prisms, optical fibers, and light guides.
Three years ago, JSR also introduced Artopps, a blend of 60-90% PPS with 10-40% Arton. Artopps is available only in Japan, where it is used for connectors.
Mitsui Chemical Co. makes Apel, an amorphous cyclo-olefin copolymer, used for barrier sheet in medical applications as well as in packaging films, bottles, lenses, and industrial parts. It is not marketed in the U.S. Mitsui had teamed up with Hoechst AG (former parent of Ticona) in the early 1990s for early development of metallocene-catalyzed cyclic olefins. Since then, Mitsui and Ticona have separately pursued different manufacturing methods and material types. Apel is reportedly much more expensive than Topas.
Zeonex norbornene homopolymer from Zeon Chemicals is a high-clarity, heat-resistant material that is molded into optical components like these laser-printer parts.
The first big application for Ticona’s Topas copolymer is as a moisture barrier in five-layer film for aspirin blister packs like these in Southeast Asia.
COMPARISON OF SELECTED NORBORNENE POLYMERS
Producer JSR Zeon Ticona
Resin Arton Zeonex Zeonor Topas
Grade F5023 FX4718 FX4726 480 490K E48R 1020R 1420R 1600R 8007 6013 6015 6017
Specif. Grav. 1.08 1.08 1.08 1.01 1.01 1.01 1.01 1.01 1.01 1.02 1.02 1.02 1.02
H20 Abs., % 0.4 0.3 0.2 <0.01 <0.01 <0.01 <0.01 <0.01 <0.01 <0.01 <0.01 <0.01 <0.01
TG, F 329 304 286 280 284 282 221 277 327 180 285 320 360
MFR, g/10 min 8 37 60 21 16 25 20 20 20 4.5 16 16 12
Elong., % 25 10 10 40 90 10 100 60 20 10 4 4 4