Plastic and nonmetallic article shaping or treating: processes – Forming electrical articles by shaping electroconductive... – Conductive carbon containing
Patent
1996-10-19
1999-03-02
Fiorilla, Christopher A.
Plastic and nonmetallic article shaping or treating: processes
Forming electrical articles by shaping electroconductive...
Conductive carbon containing
26421123, C04B 3500
Patent
active
058766472
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a method for preparing a thermoplastic resin composition which comprises a thermoplastic resin and specific carbon black and which shows only a small variation in the conductivity, without accompanying any scattering of carbon black, in a high productivity rate; a method for preparing a conductive carbon black-containing conductive resin composition which shows stable conductivity even in a high resistance region (having a surface resistivity ranging from 10.sup.6 to 10.sup.16 .OMEGA.), wherein the control of the conductivity is difficult; and a method for preparing an electric conductor.
BACKGROUND OF THE INVENTION
The demand for thermoplastic resin products to which electric conductivity is imparted by incorporating carbon black into thermoplastic resins has recently been considerably increased in various fields, in particular, materials for electronic parts, computers and VTR, antistatic materials for household appliances and materials for electromagnetic shielding.
As methods for preparing such conductive thermoplastic resins, there have conventionally been used those in which a continuous twin-screw extruder is used. As methods for feeding ingredients to the extruder in the production method which makes use of such a continuous twin-screw extruder, there have in general been used a method in which carbon black and a resin are, in advance, blended in, for instance, a Henschel mixer or a tumbling mixer and then the resulting blend is fed to the extruder by a variety of feeders; and a method in which carbon black and a resin are separately and quantitatively fed to the extruder using counting feeders. If adopting either of these feeding methods, however, resins and carbon black differ from one another in true specific gravity, bulk density and shape and accordingly, they cause classification during blending or after being fed to the extruder to thus cause a difference in the concentration of carbon black in the composition. Therefore, the resulting resin cannot sometimes be practically used since these methods do not provide resins which do not have any variation in the conductivity and have stable conductivity.
The bulk density of carbon black used for imparting conductivity to resins is very low and accordingly the carbon black includes a large amount of air. Such a large amount of air is released when the carbon black is dispersed in resins using a twin-screw extruder and rises from the feed opening for the carbon black. The rise of the air leads to scattering of carbon black. As a result, there have been pointed out a variety of problems such that the scattering of carbon black leads to a difference in the carbon black concentration within the resin composition, that the scattering of carbon black also impairs the working environment, and that the suspended carbon black fine particles are adhered to the inner portions of precision machines to thus destroy the internal electronic parts thereof. The blowing up of carbon black is closely correlated to the feed rate thereof and accordingly, the feed rate should be reduced if carbon black causes scattering and this in turn results in a decrease of the productivity.
As a production method capable of being adopted when ingredients are fine particles, there has been proposed a production method in which an opening is positioned downstream of a feed opening for ingredients and the structure of the screw at the portion between the ingredient-feeding part and the opening is designed in such a manner that it does not compress the ingredients, but melts or knead the same (Japanese Un-Examined Patent Publication (hereinafter referred to as "J.P. KOKAI") No. Sho 58-29644). However, this method does not permit the improvement of the blend of a resin and carbon black in case of the conductive carbon black used in the present invention.
Alternatively, there has also been proposed a method which makes use of a resin master batch having a high carbon black content for the purpose of, in particular, preventing any scat
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Komatsu Hideo
Maeno Seiji
Makise Masayuki
Narita Michio
Fiorilla Christopher A.
Lion Corporation
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