US Patent 7320767 Method of increasing dimensional stability of a mat

A dimensionally more stable mat is made from a less dimensionally stable mat by saturating the mat with a binder and passing and compressing the mat between a pair of squeeze rolls to remove binder from the mat. At least one of the rolls has a series of annular grooves therein spaced apart along the length of the roll and across the width of the mat whereby as the mat is passed between the rolls a first and a second series of longitudinally extending bands are formed in the mat having different average binder concentrations. The second series of bands, formed in the mat at the annular grooves of the roll, has an average binder concentration greater than that of the first series of bands.