Polymer-graphite nanocomposites
Process for producing a polymer-graphite nanocomposite, which comprises the steps a) oxidation of graphite to graphite oxide, b) conversion of the graphite oxide into an aqueous dispersion, c) mixing of the aqueous dispersion comprising graphite oxide or, if appropriate, reduced graphite oxide which is obtained from b) with an aqueous polymer dispersion comprising at least one polymer and d) separating off the polymer-graphite mixture from the aqueous phase, wherein the graphite oxide which has been oxidized in step a) is reduced to graphite between step b) and c) or between step c) and d).
1. A process for producing a polymer-graphite nanocomposite, which comprises the steps
a) oxidizing graphite to graphite oxide,
b) converting the graphite oxide into an aqueous dispersion,
c) mixing the aqueous dispersion comprising graphite oxide or, if appropriate, reduced graphite oxide which is obtained from b) with an aqueous polymer dispersion comprising at least one polymer and
d) separating off the polymer-graphite mixture from the aqueous phase,
wherein the graphite oxide which has been oxidized in step a) is reduced to graphite between step b) and c) or between step c) and d); and
wherein the polymer particles in the aqueous polymer dispersion have a particle diameter of from 0.01 micron to 3000 microns.
2. The process according to claim 1 , wherein the polymer-graphite nanocomposite comprises from 5 to 99% by weight of at least one polymer and from 1 to 95% by weight of reduced graphite oxide, based on the total weight of the graphite nanocomposite.
3. The process according to claim 1 , wherein the graphite oxide is chemically reduced to graphite by addition of a reducing agent between step b) and c) or between step c) and d).
4. The process according to claim 1 , wherein the reducing agent is selected from the group consisting of NaBH 4 , diisobutylaluminum hydride, Zn/HCl, hydrazine, hydrazine substituted by organic radicals, hydroquinone, N,N-diethylhydroxylamine, sodium thiosulfate, sodium sulfite, dithionite, formaldehyde/sodium hydroxide, vitamin C, derivatives of vitamin C and mixtures thereof.
5. The process according to claim 1 , wherein the aqueous polymer dispersion comprises at least 2% by weight of one or more polymers, based on the total weight of the aqueous polymer dispersion.
6. The process according to claim 1 , wherein a primary dispersion, a secondary dispersion or a mixture of the two is used as aqueous polymer dispersion.
7. The process according to claim 1 , wherein the polymer dispersion comprises at least one thermoplastically processable polymer.
8. The process according to claim 1 , wherein the polymer dispersion comprises at least one polymer selected from the group consisting of polystyrene, polyolefins, poly(meth)acrylates, polyamides, polycarbonate, polyalkylene terephthalates, polyvinyl chloride, polyvinylidene fluoride, polytetrafluoroethylene, polyacrylonitrile, polyoxymethylene, polyimides, polycaprolactam, polyacetate and copolymers thereof, styrene-acrylonitrile copolymers, acrylonitrile-butadiene-styrene copolymers, butadiene-styrene copolymers, high-impact polystyrenes, styrene-maleic anhydride copolymers, acrylonitrile-styrene-acrylamide copolymers, styrene-(meth)acrylate copolymers, styrene-maleimide copolymers and thermoplastic polyurethanes.
9. The process according to claim 1 , wherein the polymer dispersion comprises at least one polymer selected from the group consisting of SAN, polystyrene, polyolefins, poly(meth)acrylates, acrylonitrile-butadiene-styrene copolymers and butadiene-styrene copolymers.
10. A process for producing moldings, semifinished parts, films, fibers and foams comprising a polymer-graphite nanocomposite, which comprises
i) producing the polymer-graphite nanocomposite by the process according to claim 1 ;
ii) optionally mixing the polymer-graphite nanocomposite with at least one polymer; and
iii) shaping the polymer-graphite nanocomposite which has optionally been mixed with at least one polymer to produce moldings, semifinished parts, films, fibers and foams.
11. The process according to claim 4 , wherein the organic radicals are selected from the group consisting of methylhydrazine, dimethylhydrazine, phenylhydrazine and mixtures thereof.