HK1087160A - Method for dyeing a web of knitted fabric containing cellulose fibers - Google Patents

Description

Method for dyeing a web of knitted fabric containing cellulose fibers

The invention relates to a method for dyeing a web of knitted fabric containing cellulose fibers, wherein a strip of adhesive is applied to the edge regions adjacent to the longitudinal edges of the web before dyeing and is reinforced by drying (stiffening), and the web is dyed in a dye pad and then dried and fixed in a dye-air dryer.

The knitted goods are generally made as hoses. The web (material web) is formed in such a way that the hose is cut parallel to its longitudinal axis into lines which are as straight as possible. The cutting edge formed in this case tends to curl up. By "comprising cellulose fibres" is meant that the knitted article is entirely or partly composed of cellulose fibres.

In the case of dyeing textile webs whose edges are usually not wound up individually, continuous dyeing is usually carried out according to the so-called Pad-Dry-printing principle. The web is guided through a dye pad. The dyed web is then dried in a hot-air dryer and fixed in color, i.e., on-line, continuously. In the hot air dryer the web is not laterally fixed. The pad-drying method is therefore usually only used for dimensionally stable webs of textile or the like.

The web of knitted goods containing cellulose fibres is then treated according to the so-called exhaust dyeing method or according to the Cold Pad-Batch-Prinzip (Cold-Pad-Batch-Prinzip) dyeing principle, which works intermittently if dyeing is required. They are rather time consuming.

DE 10135044 a1 and DE 10131000 a1 disclose methods for continuous dyeing of knitwear, in which either (temporary) strengthening treatment is carried out on the entire surface or a coating is applied to the so-called auxiliary edges in the edge region and subsequently removed again. In these documents it is stated that the articles need to be strengthened (stiffening finish) before the dyeing process (over the entire surface or at the edges). I.e. this pretreatment is not carried out continuously with the dyeing.

DE 3238378 a1 discloses different forms of applying edge strips or reinforced areas on the edges of knitwear items prone to rolling. DE 19522124 a1 describes edge gluing on a tenter frame. Care should be taken here to the extent that the glue melt smears over the edges of the knitted fabric when the tenter is removed.

The object of the invention is to provide a dyeing device for the continuous dyeing of knitwear, which replaces the time-consuming method according to the dip dyeing method or the cold pad-batch principle, which has been used up to now in the dyeing of cellulose fibers. In particular, a web of knitted fabric comprising cellulose fibers is continuously treated from the unwinding of the web until drying and dye fixing.

The solution according to the invention is given in claim 1. In the case of the method described at the beginning, it is characterized in particular by a continuous web run with the following phases or steps:

a) unwinding the web having a tendency to curl at the longitudinal edges of the two webs;

b) continuously stretching the material web by fixing the two longitudinal edges to a continuously conveyed tensioning chain;

c) applying a strip of adhesive in the form of a cross-cut (leimqurstrichen) wherein the width of the strip of adhesive (measured from the edge of the web perpendicular to the direction of travel) is approximately 1/25 of the axial spacing between the upper and lower roll stands of the dye-air dryer, but is at least about 1 cm;

d) unwinding the web from the tensioning chain prior to entering the dye pad;

e) a dyeing-hot air dryer is used, which is designed to guide the material web with a particularly uniform and minimal product longitudinal tension, i.e. approximately 10N, with a maximum fluctuation range of 5N.

The dyed and dried web is then discharged, preferably without tension in the machine direction and cross direction. Some modifications and other constructions of the invention are indicated in the dependent claims.

Although the prior art cited above with reference to DE 10135044 a1 and DE 10131000 a1 discloses at least the reinforcement of the edge regions of a knitted fabric web and the subsequent intermittent dyeing, the dyed web is dried and color-fixed in a hot-air dryer. The prior art does not teach how the edge zone should be continuously strengthened prior to dyeing, drying and dye fixing. And the present invention is directed to this aspect. The prior art is generally not able to inspire or elicit these problems, since, according to the knowledge of the person skilled in the art, the introduction of a web having a tendency to curl at the edges into a continuous process is premised on (previously created) edge strengthening.

In other words: in order to achieve continuous dyeing of the knitted fabric web containing cellulose fibres in the spread state by means of a pad-mangle and drying and dye fixing in a subsequent dye-air dryer on the production line, the knitted fabric is first clamped at the longitudinal edges in a continuously conveyed tensioning chain, then glue is applied to the region of the longitudinal edges fixed in the tensioning chain, and the knitted fabric web is spread continuously (although detached from the tensioning chain), i.e. guided on the production line through the dye pad-mangle and the dye-air dryer on the same principle as the textile web. The upper and/or lower rolls of the hot air dryer should preferably be driven.

In a hot air dryer for dye fixing and drying, for example according to DE 3336328C 2, the material web is guided with a certain longitudinal tension in a zigzag manner up and down by guide rollers. In the hot air dryer, a row of guide rollers (so-called upper and lower rollers) which are substantially parallel to one another and are each located approximately in a common plane is located in each case in the lower region and in the upper region. The web loop tensioned between the two upper rolls and the two lower guide rolls is blown from above and below with usually heated air for drying and fixing.

Without a certain longitudinal tension, the web cannot pass through such a hot air dryer. In the case of webs made of textile material, which are not generally problematic, the longitudinal tension in the case of webs made of knitted fabric (without the reinforcing edge regions according to the invention) may not cause the web to unwind at the openings (when running on guide rollers), but rather the edges roll up more and more as it passes through the individual loops of the hot-air dryer. In the extreme case from a stretched tape into a strip. For such strips, the advantages of the hot air dryer are no longer true, so that usually knitwear cannot be dried and fixed in the hot air dryer.

According to the invention, only the narrow edge regions of the web are reinforced with a reinforcement method, such as a transverse strip of glue. Only by this reinforcement of the narrow edge region is it surprisingly achieved that the knitted fabric web does not become striped in the hot air dryer, but rather is spread out through the hot air dryer like a fabric strip. It is advantageous here that the strip of glue is not continuous at the two web edges, but rather intermittent. For example, after one length unit of a transverse line of glue (viewed in the direction of web travel) substantially two length units of glue-free regions should be connected. In practice this ratio of approximately 1: 2 has proven to be suitable.

According to the invention, the width of the glue strip (measured perpendicularly to the direction of travel from the web edge) is dependent on the distance between the upper and lower rollers of the dyeing hot-air dryer. The greater the distance, the wider must be the strip width to prevent the reinforced edge from rolling or curling up on the path between the two rollers. It has been determined that if the width of the strip of glue (i.e., the length of the glue line) from the edge of the web is greater than about 1/25 of the axial spacing between the upper and lower rollers of the hot air dryer in accordance with the present invention, such edge curl-up is prevented. The strip width should be at least about 1 cm.

The smaller the longitudinal tension acting on the web, the easier it is to prevent edge curling or rolling. It is also advantageous within the scope of the invention if the longitudinal tension acting on the web in the hot air dryer is uniform throughout, i.e. in each loop. In order to achieve such a uniform and low longitudinal product tension in the entire dyeing hot-air dryer, the upper rollers are not driven jointly by a chain drive, but are driven individually per upper roller-or individually per two or three rollers (depending on the product mass) -by means of an electric motor, the drive torque of which is adjustable.

In the context of the present invention, the expression "drying and dye fixing" means both dye fixing on drying and subsequent fixing. If the web is dry and fixed, it can be discharged, as is customary for knitwear, in a longitudinally and transversely unstressed manner, for example by means of conveyor belts, wound onto rollers or stacked by a folding machine. Alternatively, the material web can first be treated in a hot air dryer primarily for fixing, and washed and dried with continuous transport on the production line, and fed out in the machine direction and cross direction, if necessary, without tension.

The details of the invention are illustrated by means of the drawing of an embodiment of the device according to the invention for the continuous dyeing of a spread knitted fabric web composed at least partially of cellulose fibers. The attached drawings show that:

FIG. 1 is a vertical longitudinal section of the apparatus; and

fig. 2 is a partial plan view of the device according to fig. 1.

The material web 1 is unwound from the reel 3 in the transport direction 2 (longitudinal direction of the material web) by an unwinding device 4 in the form of a tenter, which is schematically illustrated in a top view in fig. 2. Tenter frame 5 has two tensioning chains 6 and 7 equipped with needles 8 (or alternatively grippers) for threading into edge zone 9 at longitudinal edge 10 of web 1. Each tensioning chain is circulated by a sprocket 11 (with a horizontal or vertical axle 12). While the material web 1 or its edge regions 9 are fixed to the respective chains 6, 7, transverse glue lines are applied to the edge regions 9 in a glue application station 13. The length B of the transverse glue lines (viewed perpendicular to the transport direction 2) should be small relative to the total width B of the web 1 and approximately equal to 1/25 of the distance between the upper and lower rolls of the hot air dryer described below. The applied glue is hardened in an edge drying station 14 connected downstream in the transport direction 2. This imparts to the edge region 9 its flexibility that is typical for knitwear, so that the edge is not rolled up after the web 1 is unwound at the exit 15 of the tenter 5.

The web 1 is then guided by a guide roll 16 into a dye pad press 17 having a dip roll 18 and a subsequent press roll pair 19 which leads to an inlet gap 20 of a dye hot air dryer, indicated overall by 21. In the hot air dryer 21, the material web 1 is guided in an upward and downward zigzag manner by a deflecting roller 22 and by two guide roller sets 23 and 24, each consisting of a plurality of guide rollers, namely a lower roller 25 and an upper roller 26. In the hot air dryer 21, a web loop 27, which is tensioned between each two guide rollers 25, 26 of a roller group 23, 24, is blown with heated air by a blowing nozzle 28. At the end of the web path in the hot air dryer 21, the web 1 passes through a deflecting roller 29 and an outlet gap 30 into an outlet area 31, for example, with a support belt 32, in order to feed the web 1 longitudinally and transversely to a reel 33 without stress.

List of reference numerals

1 web 20 entrance gap

2 conveying direction 21 dyeing hot air drier

3 reel 22 steering wheel

4 spreading device 23, 24 guide roller set

5 tenter 25 lower roll

6, 7 tension chain 26 upper roller

8-needle 27-web loop

9 edge zone 28 blow nozzle

10 longitudinal edge 29 turning roll

11 sprocket 30 exit slot

12 hub 31 output area

13 gluing station 32 support belt

14 drying station 33 rolls

15 (5) outlet

16 guide roll

17 dyeing and padding machine

18 impregnating roll

19 Press roll

Claims (3)

1. Method for dyeing a web of knitted fabric (1) containing cellulose fibers, wherein a glue strip is applied to the edge region (9) adjacent to the web longitudinal edge (10) before dyeing and is intensified by drying, and the web is dyed in a dye pad (17) and then dried and fixed in a dye-and-hot-air dryer (21), characterized by the following stages or steps:

a) unrolling a web (1) having a tendency to curl up at two web longitudinal edges (10);

b) the material web (1) is continuously stretched by fixing the two longitudinal edges (10) to continuously conveyed tensioning chains (6, 7);

c) applying the strip of glue in the form of transverse glue lines interrupted by glue-free zones in the direction of travel (2) of the web, wherein the length of each transverse glue line (measured perpendicularly to the direction of travel from the edge of the web) is approximately 1/25 of the axial distance between the upper and lower rolls (25, 26) of the dyeing-hot-air dryer (21), but is at least approximately 1 cm;

d) loosening the material web (1) from the tensioning chains (6, 7) before entering the dyeing and padding machine (17);

e) the dyeing/hot air dryer (21) is designed to guide the material web (1) with a uniform longitudinal product tension of approximately 10 +/-5N.

2. A method according to claim 1, characterized by: a dyeing-hot air dryer (21) with individually or group-driven lower and/or upper rolls (24, 25) is used.

3. A method according to claim 1 or 2, characterized by: the cross glue lines are approximately twice as wide as the glue-free zones, viewed in the direction of travel (2) of the web.