The present invention relates to the papermaking arts including fabrics and belts used in the forming, pressing and drying sections of a paper machine, and to industrial process fabrics and belts, TAD fabrics, fabrics/belts used for textile finishing processes such as conveying, tannery belts, engineered fabrics and belts, along with corrugator belts generally.
The fabrics and belts referred to herein may include those also used in the production of, among other things, wetlaid products such as paper and paper board, and sanitary tissue and towel products made by through-air drying processes; corrugator belts used to manufacture corrugated paper board and engineered fabrics used in the production of wetlaid and drylaid pulp; in processes related to papermaking such as those using sludge filters and chemiwashers; and in the production of nonwovens produced by hydroentangling (wet process), meltblowing, spunbonding, airlaid or needle punching. Such fabrics and belts include, but are not limited to: embossing, conveying, and support fabrics and belts used in processes for producing nonwovens; and filtration fabrics and filtration cloths.
Such belts and fabrics are subject to a wide variety of conditions for which functional characteristics need to be accounted. For example, during the papermaking process, a cellulosic fibrous web is formed by depositing a fibrous slurry, that is, an aqueous dispersion of cellulose fibers, onto a moving forming fabric in the forming section of a paper machine. A large amount of water is drained from the slurry through the forming fabric, leaving the cellulosic fibrous web on the surface of the forming fabric.
Such fabric structures are typically constructed from synthetic fibers and monofilaments by conventional textile processing methods. It is often desirable to selectively tailor the surface, bulk or edges of a fabric structure to affect or enhance a performance characteristic important to, for example, the papermaker, such as fabric life, sheet formation, runnability or paper properties.
Heat is commonly applied to dry, melt, sinter or chemically react a material incorporated into the fabric to achieve such structural changes. Since the fibers and monofilaments are commonly high molecular weight polyester, polyamide or other thermoplastic material, heat can affect these materials in a variety of adverse ways. For example, heat can cause (a) flow above the glass transition point of a thermoplastic material which effects dimensional changes, or (b) melting above the melt transition point.
U.S. Pat. Nos. 5,334,289; 5,554,467 and 5,624,790 relate to a papermaking belt made by applying a coating of photosensitive resinous material to a reinforcing structure which has opaque portions and then exposing the photosensitive material to light of an activating wavelength through a mask which has transparent and opaque regions. The light also passes through the reinforcing structure.
U.S. Pat. No. 5,674,663 relates to a method for applying a curable resin, such as a photosensitive resin, to a substrate of a papermaker's fabric. A second material is also applied to the substrate. After the photosensitive resin is cured, the second material is removed, leaving a patterned portion of the cured resin.
U.S. Pat. Nos. 5,693,187; 5,837,103 and 5,871,887 relate to an apparatus for making paper which comprises a fabric and a pattern layer joined to the fabric. The fabric has a relatively high UV absorbance. This prevents actinic radiation applied to cure the pattern layer from scattering when the radiation penetrates the surface of the pattern layer. By limiting the scattering of radiation beneath the surface of the pattern layer, extraneous material is minimized in the regions of the fabric where it is desired not to have pattern layer material.
For fabrics such as those used for the forming of paper and tissue products, or for the production of tissue/towel or through-air-drying “TAD” fabrics, such fabrics are often times joined by a seam. In this instance, the fabric is usually flat woven. Each fabric edge has a “fringe” of machine direction (“MD”) yarns. This fringe is rewoven with cross machine direction (“CD”) yarns in the same basic pattern as the fabric body. This process of seaming to make endless is known to those skilled in the art. The seam area therefore contains MD yarn ends. The strength of the seam is dependent upon the MD yarn strength, the number of MD and CD yarns used, and the crimp in the MD yarns themselves that physically “lock” themselves around CD yarns to an extent. Those MD yarn ends, when the fabric is under operating tension on, for example, a papermaking or tissue/towel making machine, can literally slip past one another and pull out. The “ends” themselves then protrude above the fabric plane causing small holes in the paper/tissue product or can eventually slip enough so that ultimately, the fabric seam fails and the fabric pulls apart.
To minimize this, the yarns in the seam are usually sprayed or coated with an adhesive. Unfortunately, this can alter the fluid handling properties of the seam area, and the adhesive can also be abraded and wear off. In addition, the width of the seam area, as measured in the MD, formed using conventional techniques typically range, for example, anywhere between three and a half to twenty inches or even more. For many reasons, it is desirable to reduce the seam area.
While the application of heat to partially melt or fuse yarns to each other in the seam area has been contemplated, the use of heat generally may cause unacceptable change to the fluid handling properties of the seam area since all yarns are affected and the seam may, for example, have a resultant different air permeability than the fabric body.
The modification of synthetic material, particularly fibers/yarns or monofilaments to absorb short wavelength infrared energy to create the possibility of having both heat absorbing and non-absorbing fibers/yarns or monofilaments is different, however, in the present invention than that in the patents described above.
Accordingly, an alternative method to enhance the seam strength/resistance to yarn pull out is desired.