The selection of appropriate weave patterns for papermaking fabrics is dictated primarily by the intended end use of the textile. For example, forming fabrics, which are used to support and drain the nascent web in the forming section of a papermaking machine, can be constructed as a single layer of interwoven warp and weft yarns, or they may comprise two or more such layers, bound together to form a multilayer or composite fabric; other designs are known and used as appropriate. Fabric constructions including more than one layer of yarns allow the fabric designer to select a weave pattern for the paper side surface which meets the requirements for the sheet, while the machine side layer can be chosen to maximize the ability of the fabric to resist the abrasive and other destructive forces of contact between the fabric and the machine elements. However, there are numerous applications where, for various reasons, a single layer fabric is preferred over a multilayer construction.
Single layer fabrics are particularly appropriate for through-air drying (TAD) of tissue and towel products because the higher operating costs of TAD processes can be offset by a higher production speed and improved sheet quality in terms of bulk, absorbency and softness. The efficiency of the TAD process can be significantly enhanced by the use of single layer fabrics which have a high air permeability. A TAD fabric needs sufficient open area to allow air to pass though once it has passed through the paper web, so as to promote efficient drying. The fabric should also have a sufficiently high contact area on its paper side surface to ensure successful transfer of the sheet from the TAD to subsequent dryer elements, such as a Yankee cylinder. Fabrics intended for this purpose and which impart a machine direction (MD) oriented pattern in the sheet are generally preferred over those which impart a generally cross-machine direction (CD) oriented pattern because this provides the sheet with a smoother feel, which is desirable in consumer oriented products such as tissue, towel and similar absorbent products. An MD oriented pattern in the sheet will require longer MD oriented yarn “floats”, or areas in the fabric where the MD oriented yarns are not bound by the CD yarns. Fabric weave patterns which provide long MD oriented floats will generally also provide higher air permeabilities than patterns which do not.
However, the known single layer TAD fabrics have several significant disadvantages which reduce their applicability to certain TAD environments. Firstly, like all single layer fabrics, they present difficulties of ensuring sufficient seam strength to prevent catastrophic seam failure; the interwoven yarns in the seam region are frequently glued in place to prevent their slippage under tension and subsequent fabric failure. Second, single layer fabrics do not possess the mechanical stability of double or multiple layer fabrics and tend to be sleazy and prone to distortion and creasing, which is not desirable. Thirdly, the paper side surfaces of TAD fabrics frequently need to be sanded or otherwise pre-treated so as to render them monoplanar and maximize their contact surface area with the sheet to assure successful sheet transfer from the TAD section, as noted above.