Method for dying a web of knitted fabric containing cellulose fibers

Abstract

A method for dyeing a web of knitted fabric containing cellulose fibers is described. In order to achieve the result of being able to continuously dye the knitted goods containing cellulose fibers in the spread-out state, using a pad, as well as dry it in-line, in a subsequent dyeing hotflue, and fix the color, the knitted fabric is first caught along the longitudinal edges in continuously transporting stentering chains, and then transverse strips of glue are applied to the longitudinal edges, reinforcing the longitudinal edge regions, adjacent to the stentering chains. The glue is dried and subsequently the web that has been released from the stentering chains is passed continuously through the dyeing pad and the dyeing hotflue, spread out, fundamentally like a woven web of fabric.

Description

The invention relates to a method for dyeing a web of knitted fabric containing cellulose fibers, whereby strips of glue are applied to the edge regions, adjacent to the longitudinal edges of the fabric web, before dyeing, and stiffened by means of drying, whereby the fabric web is dyed in a dyeing pad and then dried in a dyeing hotflue and the color is fixed.

Knitted fabric is generally produced as a tube. The fabric web is formed in that the tube is cut open parallel to its longitudinal axis, on as straight a line as possible. The cut edges that are formed in this connection tend to curl up. “Containing cellulose fibers” means that the knitted fabric consists entirely or in part of cellulose fibers.

When dyeing webs of woven fabric, the edges of which normally do not curl up on their own, continuous dyeing according to the so-called pad-dry principle is usual. Here, the fabric web is passed through a dyeing pad. Subsequently, in other words in line, continuously, the dyed fabric web is dried in a dyeing hotflue and the color is fixed. In a hotflue, the fabric web has no hold on the sides. Therefore, conventionally the pad-dry method can only be used for woven and similarly area-stable fabric webs.

Fabric webs consisting of knitted fabrics that contain cellulose fibers are, in contrast, treated according to the so-called drawing method, or according to the cold-pad batch principle, if dyeing is required. These methods operate discontinuously. They are therefore complicated and time-consuming.

Methods for continuous dyeing of knitted fabrics are known from DE 101 35 044 A1 and DE 101 31 000 A1, whereby either the entire area is (temporarily) stiffened, or so-called ancillary edges are applied onto the in the edge region and later removed again. In these references, it is stated that the goods must be stiffened “before” the dyeing process (over the entire area or at the edges). This pretreatment is therefore not carried out continuously, in one pass with the dyeing.

DE 32 38 378 A1 discloses various forms of edge glue strips and/or stiffening zones at the edge of a web of knitted fabric that tends to curl up. DE 195 22 124 A1 describes edge gluing on a stentering frame. In this connection, the information that the hot-melt glue is applied to the edges of the knitted fabric at the outlet of the stentering frame should be noted.

The invention is based on the task of creating a dyeing system for continuous dyeing of knitted fabric, which replaces the time-consuming methods according to the drawing method or according to the cold-pad batch principle, which have been usual up to now, in dyeing cellulose fibers. The primary concern is to continuously treat a web of knitted fabric that contains cellulose fibers, in one pass, from spreading the fabric web out to drying it and fixing the color.

The solution according to the invention is indicated in claim 1. It is preferably characterized, for the method stated initially, by a continuous run of the fabric web, with the following stages, i.e. steps:

• • a) Spreading out the fabric web, which tends to curl up at both longitudinal web edges;
  • b) Continuously stentering the fabric web, by means of attaching the two longitudinal edges to continuously transporting stentering chains;
  • c) Applying the glue strips in the form of transverse glue strips, whereby the width of the glue strip (measured proceeding from the edge of the fabric web crosswise to the running direction) is on the order of 1/25 of the axial distance between the upper and lower roller basket of the dyeing hotflue, but at least approximately 1 cm;
  • d) Releasing the fabric web from the stentering chains before it runs into the dyeing pad; and
  • e) Using a dyeing hotflue that is designed to guide the fabric web with a particularly uniform and extremely low longitudinal tension of the fabric, namely on the order of 10 newtons, with a maximal variation range of 5 newtons.

Preferably, a delivery of the dyed and dried fabric web that is free of longitudinal and transverse tension can follow. Some improvements and further embodiments of the invention are described in the dependent claims.

The state of the art described above, referring to DE 101 35 044 A1 and DE 101 31 000 A1, does disclose the stiffening of at least the edge regions of a web of knitted fabric, and the dyeing, drying, and color fixation of the dyed fabric web, which take place discontinuously, in a hotflue. However, the state of the art does not give any indications as to how stiffening of the edge zones is supposed to be continuously carried out ahead of the dyeing, drying, and color-fixing process. But this precisely is the concern of the present invention. It cannot have been made obvious by the state of the art, as a whole, because according to the knowledge of a person skilled in the art, introduction of the fabric web having edges that tend to curl up into a continuous work process presupposes an edge stiffening (that has already been produced).

In other words: In order to achieve the result that a web of knitted fabric that contains cellulose fibers can be continuously dyed, in the spread-out state, using a pad, as well as dried in-line in a subsequent dyeing hotflue, and the color can be fixed, the knitted fabric is first caught along the longitudinal edges in continuously transporting stentering chains, and then glue that reinforces the longitudinal edge regions is applied to the longitudinal edges held in the stentering chains, adjacent to them, and subsequently (despite having been released from the stentering chains) the web is continuously, in other words in-line, passed through the dyeing pad and the dyeing hotflue, spread out, fundamentally like a woven web of fabric. Preferably, the upper and/or lower rollers of the hotflue should be driven.

In a hotflue used for color fixation and drying, for example according to DE 33 36 328 C2, the fabric web is passed up and down over guide rollers, in a meander shape, with a certain longitudinal tension. In the hotflue, there is a series of guide rollers that lie essentially parallel to one another, in the lower region and in the upper region, in each instance (so-called upper and lower rollers), approximately in a common plane, in each instance. Generally, heated air is blown into the loops of fabric web that are stretched between two upper or between two lower guide rollers, in each instance, from above or from below, respectively for drying and fixing.

Without a certain longitudinal tension, a fabric web cannot be moved through such a hotflue. In the case of webs of woven fabric, this generally does not cause a problem, but in the case of webs of knitted fabric (not having edge regions stabilized according to the invention) the longitudinal tension has the result that the fabric web does not remain spread out in the machine (as it runs over the guide rollers) but instead, the edges curl up more and more as it passes through the individual loops of the hotflue, and in an extreme case, the spread-out web turns into a skein. In the case of such a skein, the advantages of the hotflue do not have their effect, so that knitted fabric conventionally cannot be dried in a hotflue, and the color cannot be fixed.

According to the invention, it is proposed to stiffen merely the edge regions, which are narrow relative to the overall width of the fabric web, using transverse glue strips or similar stabilization means. Surprisingly, this stiffening of the narrow edge regions alone has the result that the web of knitted fabric does not run together into a skein in the hotflue, but instead passes through the hotflue spread out like a web of woven fabric. It is advantageous in this connection that the glue tracks at the two fabric web edges are not continuous but interrupted. For example, approximately two length units of a glue-free region are supposed to follow one length unit of a glued transverse strip (seen in the running direction of the fabric web). In practice, such a ratio on the order of 1:2 has proven itself.

The width of the glue track (measured transverse to the running direction, starting at the edge of the fabric web) depends, according to the invention, on the distance between the upper and the lower rollers of the dyeing hotflue. The greater the distance, the wider the glue strip has to be made, in order to exclude curling up or folding over of the stiffened edges on their path between two rollers, in each instance. It has turned out that this edge curl-up can be prevented if the width of the glue strips (that is the length of the glue strips), proceeding from the edge of the fabric web, is greater than approximately 1/25 of the axial distance between the upper and lower hotflue roller, according to the invention. The width of the glue strip should be at least approximately 1 cm.

The lower the longitudinal tensile force that acts on the fabric web, the easier it is to prevent turn-over or curl-up of the edges. Likewise, it is advantageous, within the scope of the invention, if the longitudinal tensile force that acts on the fabric web is approximately uniform everywhere in the hotflue, in other words in every fabric loop. In order to achieve this uniform, low longitudinal fabric tension throughout the entire dyeing hotflue, it is advantageous to drive the upper rollers not jointly by way of a chain drive, but rather to drive each individual upper roller, but at most two or three rollers together, in each instance (depending on the weight of the fabric), with a separate motor that has an adjustable drive moment.

Within the scope of the invention, the information “drying and color-fixing” means not only color-fixing during drying, but also drying and subsequent color-fixing. Once the fabric web has been dried and fixed, it can be delivered to a roll, or to a stack, by way of a lay-down device, without longitudinal or transverse tension, as is usual for woven fabric. Alternatively, the fabric web can first be treated in the hotflue, essentially for the purpose of fixation, and then be washed and dried in-line, with continuous further processing, as well as delivered essentially free of longitudinal and transverse tension.

Details of the invention will be explained using the attached representation of an exemplary embodiment of the system concept according to the invention, for continuous dyeing of a spread-out web of knitted fabric that consists at least in part of cellulose fibers. The figures show:

FIG. 1 a system in schematic, vertical cross-section; and

FIG. 2 a top view of a part of the system according to FIG. 1.

The fabric web 1 runs in the transport direction 2 (longitudinal direction of the fabric web) from the roller 3 through a spreading device 4 into a type of stentering frame 5, which is also shown in FIG. 2, in the top view, in principle. The stentering frame 5 possesses two stentering chains 6 and 7, which are equipped with needles 8 (alternatively, tenterhooks are also possible) for needling the edge regions 9 onto the longitudinal edges 10 of the fabric web 1. Each of the stentering chains runs, in endless manner, over chain wheels 11 (having a horizontal or vertical wheel axle 12). When the fabric web 1, i.e. its edge regions 9 are fixed in the chain 6, 7, in each instance, transverse glue strips are applied to the edge regions 9 in a gluing station 13. The length b of the transverse glue strips (seen crosswise to the transport direction 2) is supposed to be small relative to the total width B of the fabric web 1, and made to be approximately equal to 1/25 of the distance between the upper and lower rollers of the hotflue described below. The glue applied is stiffened in an edge drying station 14 that follows in the transport direction 2. As a result, the edge regions 9 lose their flexibility, which is typical for knitted fabric, so that the edges no longer curl up after the textile web 1 has been released at the exit 15 of the stentering frame 5.

The fabric web 1 is subsequently brought into a dyeing pad 17 having an immersion roller 18 and subsequent pair 19 of squeezing rollers, by way of a guide roller 16, to the inlet slit 20 of a dyeing hotflue designated as a whole as 21. In the hotflue 21, the fabric web 1 runs over a deflection roller 22 as well as in meander shape downward and upward over two series 23 and 24 of guide rollers, each of which consists of a plurality of guide rollers, namely lower rollers 25 and upper rollers 26. Within the hotflue 21, heated air is applied to the loops 27 of fabric web stretched between two guide rollers 25, 26 or a roller series 23, 24, in each instance, from blowing nozzles 28. At the end of the fabric web run in the hotflue 21, the fabric web 1 reaches a run-out region 31, e.g. having a support strip 32, by way of a deflection roller 29 and an outlet slit 30, for delivery of the fabric web 1 onto a roller 33, free of longitudinal and transverse tension.

REFERENCE SYMBOL LIST

• 1=fabric web
• 2=transport direction
• 3=roller
• 4=spreading device
• 5=stentering frame
• 6, 7=stentering chains
• 8=needles
• 9=edge region
• 10=longitudinal edges
• 11=chain wheel
• 12=wheel axle
• 13=gluing station
• 14=drying station
• 15=exit (5)
• 16=guide roller
• 17=dyeing pad
• 18=immersion roller
• 19=squeegee
• 20=inlet slit
• 21=dyeing hotflue
• 22=deflection wheel
• 23, 24=series of guide rollers
• 25=lower roller
• 26=upper roller
• 27=fabric web loop
• 28=blowing nozzle
• 29=deflection roller
• 30=outlet slit
• 31=run-out region
• 32=support strip
• 33=roller

Claims

1. Method for dyeing a web of knitted fabric (1) containing cellulose fibers, whereby strips of glue are applied to the edge regions (9), adjacent to the longitudinal edges (10) of the fabric web, before dyeing, and stiffened by means of drying, whereby the fabric web is dyed in a dyeing pad (17) and then dried in a dyeing hotflue (21) and the color is fixed, comprising the following stages, i.e. steps:

a) Spreading out the fabric web (1), which tends to curl up at both longitudinal web edges (10);

b) Continuously stentering the fabric web (1), by means of attaching the two longitudinal edges (10) to continuously transporting stentering chains (6, 7);

c) Applying glue strips in the fabric web running direction (2), in the form of transverse glue strips interrupted by glue-free regions, whereby the length of the glue strips (measured proceeding from the edge of the fabric web crosswise to the running direction) is on the order of 1/25 of the axial distance between the upper and lower rollers (25, 26) of the dyeing hotflue (21), but at least approximately 1 cm;

d) Releasing the fabric web (1) from the stentering chains (6, 7) before it runs into the dyeing pad (17); and

e) Designing the dyeing hotflue (21) to guide the fabric web (1) with a uniform longitudinal tension of the fabric on the order of 10 newtons±5 newtons.

2. Method according to claim 1, wherein a dyeing hotflue (21) having lower and/or upper rollers (24, 25) that are driven individually or in groups is used.

3. Method according to claim 1, wherein the transverse glue strips, seen in the web running direction (2), are made to be on the order of twice as wide as the regions free of glue.