Patent ID: 6780455
Filing Date: 2004-08-24
Classification: B05C,B05D,G03C

Abstract:
A method of creating a material for use as a material to be coated by curtain coating and curtain coating the material comprising the step of:forming a freely falling curtain of a composite layer arranged to impinge against a continuously moving receiving surface of said material; creating a surface texture of said material such that h(&lgr;)&lE;Rz, h(&lgr;) being the height of the composite layer as a distance &lgr; from the point of impingement, in which &lgr; is the average periodicity of the surface texture and Rz (DIN4768) being the roughness of the material; and the material is coated with a freely falling curtain formed of a composite layer of one or more coating compositions that impinges at a point of impingement against a continuously moving receiving surface of said material having a roughness Rz (DIN4768) as stated above in which the coating composition forming the layer adjacent to said receiving surface has a viscosity, &eegr;, measured at a shear rate of 10,000 sâˆ’1 such that when combined with said roughness Rz, said curtain gives a value of a specifying parameter &phgr;0 that is greater than 1, where said specifying parameter &phgr;0 is defined by Ï†0=1818&it;â€ƒ&it;Ïƒ1/3&it;Rz&it;{10.0002&it;Î·&it;â€ƒ&it;U&it;â€ƒ&it;cos&it;â€ƒ&it;Î¸&af;(1+Î©&it;Ï &it;â€ƒ&it;Q20&it;â€ƒ&it;Î·)};in which &sgr; is the surface tension (Nmâˆ’1) of the layer adjacent to said receiving surface; &eegr; is the viscosity (Pas) measured at a shear rate of 10000 sâˆ’1 of the layer adjacent to said receiving surface; &thgr; is the angle formed between said curtain and a normal to said receiving surface at the point of impingement; &rgr; is the average density (Kg/m3) of said one or more coating compositions; Q is the total volumetric flow rate per unit width (m2/s) of said curtain; and &OHgr; is a Lorentzian factor which reduces the influence of momentum when flow rate is high or viscosity is low, &OHgr; being defined by Î©=2525+(Ï &it;â€ƒ&it;QÎ·-8)2.