Tuesday, July 27, 2010

Method of Producing Carbon Nanomaterials And Centrifugal Melt Spinning Apparatus

National University Corporation Gunma University (Gunma, JP) earned U.S. Patent 7,763,353 for a method of producing a carbon nanomaterial and to a centrifugal melt spinning apparatus. More specifically it relates to a method of producing a carbon nanomaterial that is suitable for production of carbon nanomaterials such as carbon nanotubes and carbon nanofibers, and a centrifugal melt spinning apparatus that is directly used in the carbon nanomaterial production method, according to inventors  Asao Oya and Terukazu Sando.

A carbon nanomaterial is produced by: performing centrifugal melt spinning of core-shell particles that are prepared by using fine particles containing a carbon precursor polymer and a thermally decomposable polymer that disappears as a result of heat treatment, wherein the core-shell particles are heated up to a temperature at which phase separation thereof is not caused, and pressed against a plate-like heater having a large number of pores that penetrate therethrough in a thickness direction of the plate-like heater using centrifugal force; making the fiber obtained by the centrifugal melt spinning infusible; and performing carbonization thereof. According to this method, a carbon nanomaterial such as a carbon nanotube or a carbon nanofiber can be produced with high efficiency.

Conventionally, as a method of producing carbon nanotubes, a polymer blend spinning technique is used.  Specifically, in this method, a thermally decomposable polymer that disappears as a result of heat treatment and a carbon precursor polymer that leaves carbon after heat treatment are used as starting materials to prepare a polymer blend, and the polymer blend is stretched by melt-spinning, then the carbon precursor polymer is made infusible, and thereafter carbonized to produce carbon nanotubes. This method, by which high purity carbon nanotubes can be obtained, is far superior as a mass-production technique to currently used gas phase methods.

In the process of spinning the polymer blend according to this method a continuous melt spinning technique is generally applied in which spinning is performed by heating a spinning machine that houses a polymer blend to about 300.degree. C. in an electric furnace, supplying argon gas or nitrogen gas to the spinning machine and discharging the molten polymer blend from the spinning machine through a nozzle of the spinning machine, and winding the fiber discharged through the nozzle around a bobbin rotated by a motor.

In the continuous melt spinning technique, however, there is a problem that phase separation of the polymer blend in the spinning machine kept at a high temperature is caused due to melting, which is attributed to the long time period of spinning, and thus the desired carbon nanotubes cannot be efficiently obtained. The above-mentioned Patent Document suggests that a spinning method in which fibers are extracted using centrifugal force may be applied, but no specific centrifugal melt spinning method is disclosed therein. 

The Gunma University invention was made to solve the above problems, and an object of the invention is to provide a method of producing a carbon nanomaterial that can efficiently produce a carbon nanomaterial, and more specifically to provide a method of producing a carbon nanomaterial that can efficiently produce a carbon nanomaterial such as carbon nanotubes and carbon nanofibers by performing centrifugal melt spinning under a temperature condition at which phase separation of core-shell particles, that are formed in a polymer blend containing a carbon precursor polymer as a starting material for a carbon nanomaterial, is not caused. It is a further object of the invention to provide a centrifugal melt spinning apparatus that is suitable for direct use in the method of producing a carbon nanomaterial with high efficiency. 

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