Papermakers fabric having diverse flat machine direction yarn surfaces

Abstract

A papermakers fabric having a stacked system of flat monofilament machine direction yarns (hereinafter MD yarns) which define the surface characteristics of the fabric. The system of MD yarns comprises upper and lower yarns which are vertically stacked. Preferably, the upper MD yarns define floats on the upper surface of the fabric and each upper MD yarn is paired in a vertically stacked orientation with a lower MD yarn. The upper MD yarns may be comprised of one type of material, such as nylon 6, 6 to define a hydrolysis resistance paper carrying surface with the lower MD yarns, which define the machine side surface, being made of a polyester (PET) yarns, which are lower in cost and are less hydrolysis resistant. Cross machine direction yarns (hereinafter CMD yarns) may be a third type of yarn, for example a relatively inert material such as Ryton.TM.. The CMD yarns are protected from abrasive wear by the upper and lower MD yarns. The stacked flat MD yarn construction permits a variety of other variations to provide different surface characteristics to the opposing sides of the fabric. Yarn dimensions may be varied to provide a wide range of permeability for fabrics using such a stacked MD yarn construction. Also float length can be varied between the upper and lower MD yarn weaves to impart different surface characteristics.