| 摘要 |
<p>1403154 Coating rice hulls COR TECH RESEARCH LTD 4 Dec 1973 [14 Dec 1972 (2)] 56028 73 Heading B2E [Also in Divisions B5 and C3] Rice hulls are at least partially coated with a caustic (i.e. alkali) free, thermosetting phenolformaldehyde resin which is of a type that, in its uncured state, has a viscosity of more than 100 Krebb units at 120‹F. The hulls may initially be cleaned by toppling, grinding or abrading in a fluid stream followed by sieving or air flotation to remove the "fines" or dust. The resin may be applied as a powder or as an emulsion by rubbing on with rollers or by spraying inside a rotating blender provided with baffles, usually at a temperature above 150‹F. A pH-reducing acid catalyst or chemical that will decompose to yield such acid catalyst may also be sprayed onto the hulls, either before, after or together with the resin. A composition comprising the resin-coated rice hulls optionally together with wood chips and flakes may be fabricated into a composite article, particularly a board, by curing. Layers of the composition may be laid up in a press and cured under heat and pressure to form the board. The hulls in the outer layers of the board may be coated with 10-12% resin while those of the core layer may be coated with only 8-10%, thus providing greater surface hardness, The outer layers may also contain more fines relative to the core and may contain very little or no catalyst while the core contains 5-10% catalyst to ensure uniform cure of the board.</p> |
