Coating processes – Brush or absorbent applicator utilized
Reexamination Certificate
1999-07-23
2001-04-17
Parker, Fred J. (Department: 1762)
Coating processes
Brush or absorbent applicator utilized
C427S385500, C427S393600, C015S257060
Reexamination Certificate
active
06217946
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates generally to the ability to provide a uniform application of polymeric diphenylmethane diisocyanate (pMDI) onto gypsum boards, cellulose gypsum panels and other surfaces. More particularly, the present invention relates to the use of rotary cylinder brush technology to provide a uniform application of pMDI onto cellulose/gypsum based substrates.
Exterior wall cladding is used as a barrier to keep exterior air and moisture out of the wall cavity. If water and moisture penetrate the wall cladding surface damage will result to the cladding board itself. Prior art exterior wall cladding was made out of gypsum sheathing or water resistant gypsum board. It was found that the application of pMDI to gypsum board greatly increased the board's strength and water resistance; however, early attempts at applying pMDI to cellulose/gypsum based substrate membranes have met with little success. The prior art method of applying the pMDI was to use a spray apparatus which atomized the pMDI so it could be applied to gypsum board. The spray technique has several problems. First, the spraying of the pMDI results in a non-uniform application of the coating which prevents the achieving uniform water resistance across the gypsum board. Second, the atomization of pMDI creates a health concern by introducing small particles of pMDI into the air that can be inhaled by persons in the vicinity. The disclosed invention applies the pMDI with an apparatus that provides a uniform coating across the gypsum board which results in an increase in water resistance.
SUMMARY OF THE INVENTION
The disclosed invention consists of a means for conveying a gypsum board or panel to a rotary cylinder brush station where pMDI resin is delivered onto the rotary cylinder brush just as the panel passes under the brush. A resin distribution system is used to coat the rotary cylinder brush applicator with pMDI. Optionally, to assist in the spreading of the pMDI resin over the surface of the gypsum board to achieve complete coverage of the cellulose/gypsum based substrate, a second rotary cylinder brush can be included. The bristles of the second rotary cylinder brush may be finer than the bristles of the first rotary brush.
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ICI Polyurethanes, “The Nature of the MDI/Wood Bond” No. WD-516, 7/91, Ten Pages.
Forest Products Society 1994, Forest Prod. J. 44(3):34-40; “Effect of polyisocyanate level on strength properties of wood fiber composite materials” Bernard C.H. Sun, Robert N. Hawke, Margaret R. Gale, Mar. 1994.
Bolind Michael L.
Porter Michael J.
Scalf Mark B.
Calcagni Jennifer
Janci David
Lee Mann Smith McWilliams Sweeney & Ohlson
Lorenzen John M.
Parker Fred J.
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