PLASTICS?

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 [T.sub.g] 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 [T.sub.g] range of 230-288 F. It boasts much higher impact strength than Zeonex (see table).

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[degrees] F higher heat resistance than polycarbonate, and a smoother surface than PET/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.

More varieties

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 [T.sub.g]. 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 [T.sub.g] 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 [T.sub.g] 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.

                COMPARISON OF SELECTED NORBORNENE POLYMERS
Producer           JSR                 Zeon
Resin              Arton               Zeonex
Grade              F5023 FX4718 FX4726 480             490K
Specif. Grav.      1.08  1.08   1.08   1.01            1.01
[H.sub.2]0 Abs., % 0.4   0.3    0.2    [less than]0.01 [less than]0.01
[T.sub.G], F       329   304    286    280             284
MFR, g/10 min      8     37     60     21              16
Elong., %          25    10     10     40              90
Producer
Resin                              Zeonor
Grade              E48R            1020R           1420R
Specif. Grav.      1.01            1.01            1.01
[H.sub.2]0 Abs., % [less than]0.01 [less than]0.01 [less than]0.01
[T.sub.G], F       282             221             277
MFR, g/10 min      25              20              20
Elong., %          10              100             60
Producer                           Ticona
Resin                              Topas
Grade              1600R           8007            6013
Specif. Grav.      1.01            1.02            1.02
[H.sub.2]0 Abs., % [less than]0.01 [less than]0.01 [less than]0.01
[T.sub.G], F       327             180             285
MFR, g/10 min      20              4.5             16
Elong., %          20              10              4
Producer
Resin
Grade              6015            6017
Specif. Grav.      1.02            1.02
[H.sub.2]0 Abs., % [less than]0.01 [less than]0.01
[T.sub.G], F       320             360
MFR, g/10 min      16              12
Elong., %          4               4