Polycarbonate composition resistant to gamma radiation

Details Polycarbonate composition resistant to gamma radiation Polycarbonate composition resistant to gamma radiation

2000-04-03

2001-03-06

Sanders, Kriellion (Department: 1714)

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

Processes of preparing a desired or intentional composition...

C524S084000

Reexamination Certificate

active

06197854

ABSTRACT:

The invention is directed to thermoplastic molding compositions and more particularly to polycarbonate molding compositions having improved resistance to gamma radiation-induced yellowing.
SUMMARY OF THE INVENTION
A thermoplastic polycarbonate molding composition having improved resistance to yellowing that is induced upon exposure to gamma radiation is disclosed. Particularly suitable for the manufacture of devices geared for medical applications, the composition contains
(i) polycarbonate resin,
(ii) 0.01 to 1.0 percent of a first stabilizer, the molecular structure of which features at least one benzofuran-2-one group per molecular chain and
(iii) 0.01 to 1.0 percent of saccharine,
the percents being relative to the weight of the resin.
BACKGROUND OF THE INVENTION
Because of their physical and mechanical properties, polycarbonate resins were found to be eminently suitable for a variety of applications in the medical field. However, those applications which require sterilization by exposure to ionizing radiation present a problem since polycarbonate tends to yellow and show increased haze. The relevant art is noted to include U.S. Pat. Nos. 4,624,972; 5,187,211; 4,804,692; 4,963,598; 4,874,802; 5,006,572; 5,187,208; 5,274,009 and 5,214,078 all of which relate to polycarbonate compositions rendered resistant to gamma radiation by the incorporation of a stabilizing agent.
Also presently relevant is U.S. Pat. No. 4,325,863 which disclosed benzofuranone compound useful as stabilizer for organic materials. The organic polymeric materials stabilized by this compound are said to include polycarbonates and polyamides as well as copolymers of styrene and acrylonitrile. Also presently relevant is U.S. Pat. No. 4,338,244 which disclosed benzofuran(2)one to be a useful stabilizer for organic materials. Polycarbonates, polyamides and SAN copolymers are mentioned among the many resins said to be stabilized by the incorporation of this compound. Also relevant are U.S. Pat. Nos. 5,175,312 and 5,607,624 which disclosed 3-phenyl-3H-benzofuran-2-ones and 3-arylbenzofuranones respectively, said to be suitable as stabilizing agents for organic materials against oxidative, thermal or light induced degradation. Lastly, U.S. patent applications Ser. Nos. 09/268,115 and 09/270,860, assigned to Bayer Corporation.
Saccharine has been disclosed as a stabilizer of polycarbonate compositions in WO 98/58996 (PCT/EP98/03425).


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