Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From carboxylic acid or derivative thereof
Reexamination Certificate
1999-11-12
2001-07-24
Hampton-Hightower, P. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From carboxylic acid or derivative thereof
C528S312000, C528S322000, C528S323000, C528S326000, C528S422000, C524S495000, C524S496000, C524S606000, C524S847000, C523S223000
Reexamination Certificate
active
06265529
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to monomer cast nylon and, more particularly, to monomer cast nylon having improvement in the antistatic properties and physical properties and a method of producing thereof.
2. Description of the Related Art
Monomer cast nylon (hereinafter referred to as “MC nylon”), which has a molecular structure belonging to Nylon 6's or Nylon 12's, is quite different from general nylon in that it is prepared through anion polymerization in the presence of a base catalyst in a casting mold. Generally, MC nylon has very high crystallinity, which provides superiority in tensile strength and abrasion resistance to other nylons. With these properties, MC nylon has numerous applications in various fields.
Lacking a function of removing electrostaticity, MC nylon itself is of electrical insulation with a volume specific resistance from 10
14
&OHgr;·cm to 10
15
&OHgr;·cm. It is virtually impossible to use MC nylon for fly wheels, jigs and pallets, which are required in fabricating or assembling processes of the fine electronic articles, such as printed circuit boards, LCD's and the like.
Metal powder, carbon black and graphite have been suggested to be incorporated in MC nylon to improve electrical conductivity. These conductive materials are added to melt-casting material monomers before polymerization. Metal powder, however, is now found to be unsuitable because it is deposited after casting. Carbon black, when added, exists in a paste form due to its large in specific surface area to adsorb a large quantity of material monomers, which inhibits the polymerization reaction of the monomers. Graphite, which has a smaller specific surface area than the carbon black, is readily dispersed in the monomers without a bad influence on the polymerization.
U.S. Pat. No. 5,179,155 to Sano, et al. discloses that the addition of graphite at amounts of 5 and 10% by weight resulted in volume specific resistance of 5×10
8
&OHgr;·cm and 8×10
7
&OHgr;·cm, respectively. In Sano, et al., however, when incorporating 2.5 wt. % of graphite, the volume specific resistance of the resulting MC nylon is 1×10
11
&OHgr;·cm, which is too high to prevent static electricity. Sano, et al. note that the MC nylon has to incorporate at least 5 wt. % of graphite to have antistatic function. This requirement of at least 5 wt. % of graphite increases the production cost and may deteriorates intrinsic physical properties of MC nylon.
Moreover, Sano, et al. require that the graphite have a surface area of 10 m
2
/g or loss in order to prevent the adsorption of the graphite to the monomers. Also the graphite has to be in a particle size of 5-25 &mgr;m in order to prevent the agglomeration of graphite in the material monomer phase. The requirements for the surface area and the particle size are too limiting and may also increase the production cost.
There exist needs for development of MC nylon having an electrical conductivity level as that of a semiconductor (volume specific resistance of about 10
6
&OHgr;·cm) while its physical properties are not degraded.
SUMMARY OF THE INVENTION
One aspect of the present invention provides an antistatic monomer-cast nylon (MC nylon) polymer. The MC nylon polymer comprises graphite particles nonuniformly distributed in an MC nylon polymer structure. The graphite particles are partially agglomerated forming a micro-domain phase.
Another aspect of the present invention provides a method of producing antistatic MC nylon. The method comprises: preparing a mixture comprising a monomer of the nylon and graphite; casting the mixture in a mold; stirring the mixture in the mold with a stirrer; and subjecting the mixture to a polymerization reaction at from about 140° C. to about 200° C.
Still another aspect of the present invention provides an antistatic MC nylon polymer. The MC polymer comprises graphite particles in a polymer structure and produced according to the method as above.
REFERENCES:
patent: 4831098 (1989-05-01), Watanabe et al.
patent: 5084504 (1992-01-01), Sano et al.
patent: 5179155 (1993-01-01), Sano et al.
patent: 5744573 (1998-04-01), Brubaker
Merriam Webster's Collegiate Dictionary 10th Edition 1998, p. 508, Graplite.
Chung Dae-won
Kim Chang-Hoon
Hampton-Hightower P.
Knobbe Martens Olson & Bear LLP
Polypenco Korea Company Limited
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