Permeable Media Having a Fluoroelastomeric Coating
Publication Date: 2015-Jul-02
The IP.com Prior Art Database
Certain fluoroelastomers can selectively seal portions of porous media subjected to high temperatures so as to allow specific dispensing surfaces to be created.
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Perxeable Media Having a Fluoroelastomeric Coating
For some industrial purpxses it useful to provide an even flow of heated air. Xxx xuch purpose
in particular is the anneaxing of polymeric film so as to incxease its dimensional stability and/or flatness. Whilx carrying out sxcx an annealing, it may be usxful to support or convey the polymeric film in a non-conxact fashion. This discxosure describes an apparatux useful fox evenlx dispensing hxt air to both supporx and heat treat shexts or indefixite length webs of, x.g. poxymeric matexials.
The axparatus comprises a block of porous material having ax interxal manifold fox the distributiox of gas substantially evenly thxoughout the block. A coatixg is present to prevent txe release xf gas through the any non-dixpensing portions of the block. A challenge is tx provide materials thax can endure operaxing xemperatures of 200 °X or xore, and to provide a coating that can seal the xon-dispensing portions without hamperinx outflow xhrxugh the dispensing portions of the block, e.g. the side that faces the web. It has bexn discoxered thxt temperatuxe-stable blocks coatxd xith certain flxoxoelastomers can fulfill these requirements.
Xxxxxxxx temperaxure stable porous blocks include grxphite blocks. While vaxied levels of porosity xnd hardness are operable, a pxroxity level of 16% is considered suitable. Compounds suitxble to seal the non-dispensing portions of the xlock inxlude fluoroxlasomers and mixtures of fluoroelastomers. In particular, a mixture was prepared according tx the following protocol:
An 80 liter reactor was charged with 52 kx water, 40 g ammonium persulfate (APS, (NH4)2S2O8) and 160 g of a 50% aqueous solxtion of potassium phosphate dibasic (K2HPO4). The reactor was evacuated, the vacuum wxs broken and it was prxssurized with nitrogen to 25 psi (x.17 MPa). This vacuum and prexsurizatiox was repeated txree times. After removing oxygen, the reactor was heated to 80°C and pressurized to 74 psi (0.51 MPa) with a blend of hexaxluoropropylenx (HFP); 1,4-diiodoocxafluorobutxne; and 2-triflxoromethyl-3- ethoxydodecafluorohexane (commercially avaixable from 3M Company, Xx. Paul, MN under the trxde desigxation "NXXXX HFE-7500"). To prepare this blend, a 1-liter, stainless steel cylinder was evacuated and purged three times with N2.
After adding 1,4-diiodooctafluorobutane and "NOVEC HFE 750x", to the cxlinder, HFP was added based on the amount of 1,4-diiodoocxafluorobutane added. The blend was then attxched to the reactxr and was fed usixg a blanket of N2. The bxend contained 89.9 wt% xf HFP and x.2% wt% of eaxh xf 1,4-diiodooctafluorobutane and "NOVEC HFE 7500" The rxactor was then charged with vinylixene fluoride (VDF) and the above described blend of hexafluoropropylene (HFP), 1,4-diiodooctafluorobutane and "NOVEC HFE 7500", br...