Primary backing

Dyeing of Nylon Carpet with Disperse Dyes. The objective of the first trial in the pilot-scale experiments was to dye nylon carpet to the same shade five times with reuse of the dyebath [8). The carpet was tufted from Nylon 6 face yarn with a polypropylene primary backing. Both regular nylon and cationic-dyeable yarns were used in the carpet however, the two types of yarns dyed to essentially the same color with disperse dyes. The carpet surface contained both cut pile and loops. 

A latex adhesive is necessary to bond the tufts into the primary backing, adhere the individual fiber strands in the yarn tufts together so they don t separate and "piU at the carpet surface, and attach the secondary backing to this primary structure. This is accomplished almost exclusively by carboxylated styrene-butadiene latex containing 400 or more parts per hundred parts of rubber of a mineral filler. In addition to economics, this filler hel s provide density and stiffness to the carpet structure for the desired hand." Feld ar used to he the filler of choice, but less expensive calcium carbonate has replaced it in most instances. 

Carpet is a complex, multicomponent system. The tufted carpet, the most common type (90%) as shown in Figure 16.1, typically consists of two layers of backing (mostly polypropylene fabrics), joined by CaCOs-filled styrene-butadiene latex mbber (SBR), and face fibers (majority being nylon 6 and nylon 6,6 textured yams) tufted into the primary backing. The SBR adhesive is a thermoset material, which cannot be remelted or reshaped. The waste containing the SBR (postconsumer and some industrial waste) has not found suitable uses, and it forms the major part of the carpet waste going into the landfills. Figure 16.2 shows the typical masses for the various components [13]. 

Zegler and Weinle [69] developed a process to make the secondary backing for new carpet from the shredded carpet waste. The carpet waste could contain nylon 6, nylon 6,6, polyvinyl chloride, vinyl copolymer, polypropylene, and polyethylene. The content of nylon was about 15-50 wt%. The chopped carpet waste was extruded at a temperature of 215°C, then calendared and bonded to a primary backing of the new carpet through an adhesive coating. 

A recyclable carpet based on polypropylene fibers also has been developed [98, 99]. Unlike polyester fiber, polypropylene fiber is pigmented during the fiberforming stage. The tufted polypropylene fiber is manufactured by the use of a needle-bonding method to interlock the primary and secondary backings. The polypropylene face yams were tufted into the primary backing first. Then the... 

Carpet backing n. A primary backing through which the carpet tuffs are inserted is always required for tufted carpets. The backing is usually made of woven jute or non-woven manufactured fiber fabrics. A secondary backing, again made of jute or manufactured fibers, is normally added at... 

Dynapoint process n. A continuous computer-controlled process for manufacturing tufted carpets with intricate patterns from undyed yarn. The carpet is dyed as it is tufted and the colors and pattern are clearly visible through the primary backing of the carpet. 

Primary backing n. The material, usually woven or non-woven polypropylene or jute, into which a carpet is tufted. The primary backing allows the positioning of each tuft and holds the tufts in position during processing, after which a secondary backing (q.v.) is applied to provide dimensional stability. 

Carpet waste generated each year and accumulated in landfills represents a considerable potential resource, as it may be converted into various useful products The rate of carpet disposal is about 2-3 million tons per year in the US A, and about 4-6 million tons per year worldwide. A carpet typically consists of two layers of (i) backing (usually fabrics from polypropylene tape yams), joined by CaCOj filled styrene-butadiene latex rubber (SBR), and (ii) face fibers (the majority being nylon 6 and nylon 66 textured yams) tufted into the primary backing. To use post-consumer carpet (PCC) as concrete or soil reinforcement, the carpet is shredded to recover fibers. It is generally not necessary to disassemble yams in the carpet into individual fibers. The size-reduction process yields the following from PCC ... 

Carpet Recycling. By the beginning of the century, about 4.7 million tons of residential carpets were disposed of annually in the United States, with less than 5% being reused or recycled (56). Scrap carpet is bulky and difficult to collect. Efforts are underway in the United States to reduce landfilled carpets by 40% by 2012. Carpeting is a complex product consisting of 40-60 wt% of yarn from PA-6, PA-66, PET, and PP, 4-6% of primary backing made from woven PP, 38-52 wt% of adhesive made from styrene-butadiene latex with calcium carbonate as a filler. 

Today, more than 90% of tufted carpets use PP as the primary backing (mostly woven) while, in the case of secondary backing, jute is still the dominant material [711]. The synthetic fabrics offer a combination of strength, dimensional stability, and uniformity that makes them truly all-purpose carpet backing materials. 

In tufting, a woven or film primary backing material is passed under a... 

The needles, which number up to 2000 for very fine gauge machines, insert the yarn into a primary backing supplied from a roll of material located in front of the machine. Spiked roUs on the front of the tufting machines feed the backing through the machine. 

The force expressed in pounds required to remove a single tuft from its primary backing (ASTM D 1335)... 

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