FABRIC PREPARATION PROCESSES : YARN PREPARATION EQUIPMENT

Various types of equipment can be used for preparing fabric. The ultimate goal of any preparation process is to produce fabric that is clean and rid of all impurities that interfere with dyeing and finishing. The preparation steps can be carried out as either batch or continuous processes. The fabric may be transported as a rope or as an open sheet through the equipment. The choice is often predicated on the dyehouse itself. The distinguishing feature of batch equipment is that all of the fabric is simultaneously submerged in the liquor. The fabric is agitated by moving it through the
liquor. In continuous processes, the fabric passes non-stop through compartments and/or stages so that the fabric is incrementally subjected to the action of the chemicals. The equipment used for dyeing fabrics is also suitable for preparing fabric. In this section, the equipment used to perform fabric preparation will be described.

I. YARN PREPARATION EQUIPMENT

Slashing is the process where Size is applied to warp yarns for weaving. The purpose of size is to protect the yarn from the abrasive action of the loom. The process is carried out on a Slasher and the application procedure is called Sizing or Slashing. While technically this process is not considered as a step in preparing fabric, the materials used in this operation, to a large measure, account for the bulk
of what must be removed. Because the desizing step is highly dependant on what size was used, it is deemed instructive to discuss the slashing process as well as discuss the nature of the sizing materials.

Figure 1 shows a schematic diagram of a slasher. In slashing, section beams are combined to create a loom beam and at the same time apply the appropriate size to the warp yarns. The section marked (1) is the let-off station where one or more section beams are combined and fed through the rest of the range. The warp yarns are let-off as a flat sheet and then pass through a size applicator (2) consisting of a trough containing the size formulation and squeeze rolls. The yarns pass over heated cans (3) to dry. Located at the exit end of the slasher is an arrangement of bust bars which separate each warp end from its neighbor. The individual warp ends passthrough a reed which guides the yarn onto the take-up beam. Associated with the slasher is a cooking station, where the sizing material (starch or polyvinyl alcohol) is dissolved and stored. The solution is metered to the applicator as needed to
replenish what has been taken up by the warp sheet. The chemical nature of the size will be discussed in a later section along with the conditions needed to effectively remove the size.