Flexible graphite article and method of manufacture

An apparatus for the continuous production of resin-impregnated flexible graphite sheet, the apparatus comprising:

• (i) a reactor vessel for containing as reactants graphite particles in mixture with a liquid intercalant solution to form intercalated graphite particles;
• (ii) an expansion chamber in operative connection with the reactor vessel, the expansion chamber at a temperature of at least about 700° C., such that passing intercalated graphite particles from the reactor vessel to the expansion chamber causes expansion of the intercalated graphite particles to form exfoliated graphite particles;
• (iii) a compression station positioned to receive exfoliated graphite particles for compressing such particles into a coherent self-supporting mat of flexible graphite;
• (iv) an impregnation chamber for contacting the flexible graphite mat of (iii) with liquid resin and impregnating the mat with liquid resin;
• (v) a calender mill disposed to receive the flexible graphite mat of (iv) for increasing the density of said flexible graphite mat to form a continuous flexible graphite sheet having a thickness of no more than about 1.0.

A system for the continuous production of surface patterned, resin-impregnated flexible graphite sheet containing resin and other additives which comprises:

• (i) a reactor vessel for containing as reactants raw natural graphite flake-like particles in mixture with sulfuric and nitric acids;
• (ii) an acid containing vessel communicating with said reactor vessel for the introduction of a mixture of sulfuric and nitric acid into said reactor vessel;
• (iii) a graphite particle containing vessel for the introduction of graphite particles into the reactor vessel;
• (iv) a first additive containing vessel communicating with said reactor vessel for the introduction of intercalation enhancing materials, acids or organic chemicals;
• (v) a wash vessel containing water communicating with the reactor vessel to receive reaction product in the form of acid intercalated graphite particles and remove acid from the surface of the acid intercalated graphite particles and a portion of the mineral impurities contained in the natural graphite particles introduced into the reactor vessel;
• (vi) a drying chamber for drying washed acid intercalated graphite particles;
• (vii) conduit means extending from said wash vessel to said drying chamber for passing washed acid intercalated graphite particles from the wash vessel to the drying chamber;
• (viii) a second additive containing vessel communicating with the conduit means of (vii) for adding pollution reducing chemicals to the washed, intercalated graphite particles to the washed acid intercalated graphite particles;
• (ix) a collecting vessel for collecting washed acid intercalated graphite particles admixed with pollution reducing chemicals;
• (x) conduit means extending from said drying chamber to said collecting vessel for passing acid intercalated graphite particles admixed with acid additives from said drying chamber to said collecting vessel;
• (xi) a third additive containing vessel communicating with said conduit of (x) for the introduction of ceramic fiber particles in the form of macerated quartz glass fibers, carbon and graphite fibers, zirconia, boron nitride, silicon carbide and magnesia fibers, naturally occurring mineral fibers such as calcium metasilicate fibers, calcium aluminum silicate fibers, aluminum oxide fibers and the like into said conduit and the admixing and entrainment thereof with acid intercalated graphite particles passing from the washing vessel to the drying chamber;
• (xii) an expansion chamber enclosing an open flame at a temperature of 800 to 1300° C.;
• (xiii) conduit means extending from said collecting vessel to said expansion chamber for passing dried acid intercalated graphite particles admixed with ceramic particles to said expansion chamber;
• (xiv) gas inlet means communicating with the conduit means of (xii) for entraining the acid intercalated graphite particles admixed with ceramic particles in a stream of non-reactive gas and passing the entrained acid intercalated graphite particles admixed with ceramic particles into the open flame enclosed in said expansion chamber to cause expansion of the acid intercalated graphite particles of at least about 80 times to form vermiform elongated graphite particles;
• (xv) a collecting hopper for receiving said vermiform elongated graphite particles admixed with ceramic particles;
• (xvi) a separator vessel interposed between the expansion chamber and the collecting hopper to collect by gravity separation heavy solid mineral impurity particles from the mixture of vermiform graphite particles with ceramic particles;
• (xvii) a gas scrubber communicating with said collecting hopper to collect gases generated in the expansion chamber;
• (xviii) a compression chamber positioned to receive vermiform graphite particles mixed with ceramic fiber particles for compressing said vermiform particles mixed with ceramic particles into a coherent self-supporting mat of flexible graphite from about 1 to 0.015 inches in thickness and having a density of from about 5 to 25 lbs./ft.3;
• (xix) an impregnation chamber for contacting the flexible graphite mat of (xviii) with liquid resin and impregnating said flexible graphite with liquid resin;
• (xx) a dryer disposed to receive the impregnated flexible graphite mat of (xix) and heat and dry said mat;
• (xxi) a calender mill disposed to receive the flexible graphite mat of (xix) for increasing the density of said flexible graphite mat to form a continuous flexible graphite sheet having a density of from about 5 to 80 lbs/ft3, a thickness of from about 0.5 to 0.005 inches and evenly spaced apart opposite surfaces;
• (xxii) a device for mechanically deforming a surface of the continuous flexible graphite sheet of (xxi) to provide a series of repeating patterns on said surface flexible graphite sheet or the removal of material from said flexible graphite sheet in a series of repeating patterns;
• and
• (xxiii) an oven for receiving the mat from the dryer of (xxii) to cure the resin the mat.

A method for the continuous production of resin-impregnated flexible graphite sheet, the method comprising:

• (i) reacting raw natural graphite flake-like particles with a liquid intercalant solution to form intercalated graphite particles;
• (ii) exposing the intercalated graphite particles to a temperature of at least about 700° C. to expand the intercalated graphite particles to form a stream of exfoliated graphite particles;
• (iii) continuously compressing the stream of exfoliated graphite particles into a continuous coherent self-supporting mat of flexible graphite;
• (iv) continuously contacting the flexible graphite mat with liquid resin and impregnating the mat with liquid resin;
• and
• (v) continuously calendering the flexible graphite mat to increase the density thereof to form a continuous flexible graphite sheet having a thickness of no more than about 1.0 inches.