WO2004038086A1

WO2004038086A1 - Space-dyeing method and apparatus

Info

Publication number: WO2004038086A1
Application number: PCT/IB2002/004563
Authority: WO
Inventors: Luca Codeluppi
Original assignee: Tecnofil Srl
Priority date: 2002-10-25
Filing date: 2002-10-25
Publication date: 2004-05-06
Also published as: AU2002347417A1

Abstract

The method of producing a space-dyed yarn (YD) by an ink-jet applicator means (10) comprises the steps of (A) moving a continuous fiber structure (YR) through a path (P) between a source (12) of the continuous fiber structure and an uptake means (14) for the space-dyed yarn; the path (P) having at least one linear portion (PL) passing through a predetermined space-dyeing position (PD); (B) directing at least one sequence of controlled bursts (B) of a liquid ink composition onto the fiber structure (YR) when it passes the space-dyeing position (PD); and (C) directing the at least one sequence of controlled bursts (B) of ink along an axis (A) of burst application; wherein : (i) the axis of burst application forms an acute angle a with the straight line portion (PL) passing through the predetermined space-dyeing position (PD); and/or (ii) spreading the fiber structure while it passes through the space-dyeing position. The apparatus (1:3) for producing a space-dyed yam (YD) includes (a) a first means (13;33) for moving a continuous fiber structure (YR) from a source (12;32) of continuous fiber structure through a path (P) to an up-take means (14;34) for the space-dyed yam; (b) the path (P) having at least one linear portion (PL) passing through a predetermined space-dyeing position (PD); (c) a second means (10;30) for directing at least one sequence of controlled bursts (B) of a liquid ink composition onto the fiber structure when it passes the space-dyeing position (PD); (d) the second means (10;30) being arranged to direct the sequence of controlled bursts (B) of ink along an axis (A) of burst application; and wherein: (e) the axis (A) of burst application forms an acute angle (a) with the straight line portion (PL) passing through the predetermined space-dyeing position (PD) and/or (f) a third means is provided for maintaining the fiber structure in a spread state when passing through the predetermined space-dyeing position (PD).

Description

SPACE-DYEING METHOD AND APPARATUS

The invention relates to space-dyeing of fiber structures or yarns. "Space-dyeing" is a term used to refer to a prior art method of improving the ap- pearance of yarns, for example in patents US 6 019 779 and 5 594 968. and involves application of differently colored spots to a yarn (also termed "effect yarn" or "fancy yarn"). While various types of color applicators can be used, a preferred type of applicator is the so-called "ink-jet" or "nozzle jet" disclosed, for example, in US 3 653 596, US 4 150 794, US 4 215 350 and US 4 378 564. A main difference between these de- vices resides in the way of generating the pressure required for moving the ink through the jet onto the yarn, e.g. by piezoelectric or hydraulic means.

For the purposes of the present invention, ink applicator devices are preferred which comprise a tank for receiving and holding the ink of any given color and for pressurizing the ink by a compressed fluid, e.g. a gas, such as air. Application of the ink can be controlled both mechanically, e.g. by a high-speed solenoid valve, as well as hydrau- lically, i.e. by pressure changes. Shape and volume of the ink bursts are controlled and both regular as well as irregular patterns of ink can be applied depending upon control of the ink bursts. Examples of ink applicator preferred for the present invention are disclosed in US 5 085 402 and US 6 070 973 and the content of both patents is incorpo- rated herein by way of reference.

In conventional methods for space-dyeing of yarns by means of such devices, substantial amounts of ink leaving the jet are not taken up by the filaments but lost so as to add to the costs of the dye application, and ink permeation into the yarn tends to be deficient. Generally, a first drawback of prior art space-dyeing methods is insufficient control of ink application resulting in loss of ink and/or ink deposition in undesired areas of the yarn. Another disadvantage of such prior art methods results from low processing speeds typically in the range of not more than about 400 meters per minute (m min) and even then ink permeation may not be satisfactory.

Accordingly, it is a main object of this invention to provide for improved method and apparatus means capable of substantially reducing ink losses in space- dyeing, notably when working at relatively high processing velocities, i.e. above 400 m/min while also improving ink permeation into the yarn. Thus, it is a primary object of the present invention to provide new method and apparatus means for space-dyeing of yarns with improved ink permeation and pattern control and/or substantially increased processing speeds, e.g. at least doubling the processing speed, so as to provide for space-dyeing speeds in the range of from about 1000 to 3000 meters per minute or even more without decreasing ink application quality.

According to the invention it has been found that a substantial reduction of ink losses in space-dyeing method as well as improved process control and dyeing intensity can be achieved by two relatively simple measures, namely selecting an acute angle of application of the dye by the ink jet combined with spreading the filaments at the point of ink application as will be explained in more detail below.

Surprisingly, it has now been found according to the present invention that an improved efficiency of space-dyeing of yarns by in-jet application can be achieved by applying the ink bursts at an acute angle and/or spreading the filaments.

Accordingly, the invention, in a first embodiment thereof, provides for a method of producing a space-dyed yarn by an ink-jet applicator comprising the steps of:

- moving a continuous fiber structure through a path between a source of the continuous fiber structure and an uptake means for the space-dyed yarn; the path has at least one linear portion passing through a predetermined space-dyeing position;

- directing at least one sequence of controlled bursts of a liquid ink composition onto the fiber structure when it passes the space-dyeing position; and

- directing the at least one sequence of controlled bursts of ink along an axis of burst application; wherein:

(i) the axis of said burst application forms an acute angle α with the straight line portion passing through said predetermined space-dyeing position; and/or (ii) maintaining the fiber structure in a spread state when it passes through the space- dyeing position.

In a preferred embodiment, both steps (i) and (ii) are applied in combination, i.e. the axis of burst application is arranged in an acute angle, and the fiber structure is maintained in a spread state when it passes the space-dyeing position and is impinged by the burst of ink.

The term "continuous fiber structure" as used herein is intended to include all types of fibers used in the production of yarns, both from synthetic as well as natural or semi-synthetic fibers. In other words, such fiber structures may be formed by a plurality or "strand" of practically endless filaments produced by spinning of a polymer from a melt, solution or gel of a synthetic polymer. Alternatively, a fiber structure suitable for space-dyeing according to the invention may be formed of spun staple fibers which may be of synthetic, semi-synthetic or natural origin.

The source of the fiber structure may be a production plant, a spinning machine, or a bobbin or any other means of generating a fast-moving fiber structure. By the same token, the uptake means can be any device for receiving and winding or otherwise processing the space-dyed yarn. The term "ink" is intended to include all compositions that can be applied to a yarn and retained on the yarn, with or without specific fixation treatments. Generally, suitable inks will be liquid, if viscous, compositions containing a coloring matter, such as a dye or pigment, a carrier and any other constituents contained in such inks. Suitable inks of any desired color and having the required physical properties for application by ink-jets are commercially available and do not require a detailed explanation.

The term "acute angle" refers to the angle between the incoming yarn, i.e. about to enter into the space-dyeing position where the ink bursts will impact on the yarn, and the axis of ink application, i.e. the direction in which the ink bursts move from the applicator onto the yarn. A suitable range of acute angles is between about 85° and about 5°. e.g. between about 70° and about 20° and, preferably between 60° and 30°. A generally preferred acute angle is one of about 45°.

On the other hand, the axis of burst application preferably is in a common plane which essentially passes through the axis of burst application and the linear path portion where the space-dyeing position is located. This plane, in turn, is essentially normal (at 90°) relative to a reference plane that passes through the space-dyeing position, or - in other words - the axis of ink burst application forms an angle (β) of 90° ± 10° with said reference plane.

The term "maintaining the fiber structure in a spread state" implies a that the fiber structure includes a plurality of continuous filaments, i.e. at least 3, preferably at least 10, and typically in the range of from about 40 - 2000, neither limit being critical. When in a "spread" condition, these filaments are arranged such that the "width" of the fiber structure exceeds its "thickness", e.g. by a factor of at least about two (width: thickness ration is at least about 2:1) and preferably at least about 5 (5:1) so that the width of the structure is at least twice or at least five times as wide as it is thick. The "thickness" parameter is that measured along the axis of burst application while the "width" parameter is the extension normal (at 90°) to the thickness. Another way of defining this ratio geometrically is in terms of what is called

"frontally exposed surface" (or FES for short) and "totally exposed surface" (or TES for short). More specifically, FES is the total peripheral surface extension of all filaments of the fiber structure accessible (e.g. for an ink burst) or visible from a given direction (i.e. when looking at the fiber structure while TES is the total peripheral surface extension of all filaments.

According to a most preferred embodiment of the invention, the ^FES/_TES ratio of the fiber structure when in a spread condition is between 0.250 and 0.500.

Melt-spun filaments formed of thermoplastic polymers are a preferred species of fibers for space-dyeing according to the method of the invention. The term "about" preceding a numeric value (or range of values) given herein is intended to include the cited value with a deviation of up to 10% above and below the cited value.

The term "polymer" is intended to refer to macromolecular organic substances which are capable of forming monofilaments by spinning, e.g. by melt-spinning, solu- tion-spinning or gel-spinning. Generally, such polymers are man-made and can be ho- mopolymers, co-polymers obtained by co-polymerization and/or grafting, and mixtures thereof. Specific examples are polyalkylenes, such as polyethylene and polypropylene, polyesters, polyamides, polyacrylates and other polymers conventionally employed for production of yarns for various textile uses including carpets, furniture covers, bed or table cloth, upholstery, garments or garment linings, and other products including textile materials used in the manufacture of shoes. Recycled polymers of the thermoplastic type, such as recycled polyethylene, polypropylene and polyester are a preferred material for production of pseudo space-dyed yarns according to the invention, notably when the yarn is to be used in the manufacture of carpets. The terms "up-stream" and "down-stream" as used herein are relative terms and refer to a position closer to, or more removed from, the space-dyeing position.

The invention, in a further embodiment, provides an apparatus for producing a space-dyed yarn including:

- a first means for moving a continuous fiber structure from a source through a path to an uptake means for said space-dyed yarn;

- the path having at least one linear portion passing through a predetermined space- dyeing position;

- a second means for directing at least one sequence of controlled bursts of a liquid ink composition onto the fiber structure when it passes the space-dyeing position;

- the second means is arranged to direct the sequence of controlled bursts of ink along an axis of burst application; and wherein: - the axis of burst application forms an acute angle with the straight line portion passing through the predetermined space-dyeing position; and/or

- a third means is provided for maintaining the fiber structure in a spread state when passing through the space-dyeing position.

Again, in a preferred apparatus, the axis of burst application is arranged at an acute angle and the apparatus includes the third or spreading means.

Preferably, the apparatus according to the invention comprises, as a yarn- moving means at least one pair off rollers for engaging the filaments and passing them through the space-dyeing position at a speed of above about 400 meters per minute, e.g. between 1000 and 3000 m/min.

Preferably, the moving means includes a sequence of from at least 2 to about 10 cylinders and wherein the means for directing the sequence of controlled bursts of liquid ink is positioned between two adjacent cylinders of the sequence. A preferred apparatus according to the invention comprises at least one texturiz- ing and/or entangling means positioned between the space-dyeing position and the uptake means for the yarn; the means for directing the sequence of ink bursts include at least one ink-jet per yarn and may include several such jets per yarn. Generally, a control device is provided for controlling time sequence and burst duration of each ink-jet. The invention will now be discussed with reference to the enclosed drawings in which: Figure la is a schematic view of a yarn moving from a yarn source through a space-dyeing position to a yarn uptake;

Figure lb is a schematic sectional view to show lateral orientation; Figures 2a - 2d are diagrammatic cross-sectional views of a strand or yarn in various stages of filament-spreading; and

Fig. 3 is a schematic view of an apparatus according to the invention.

Fig. la illustrates the elements of both method and apparatus according to the invention in a diagrammatic manner. Apparatus 1 includes a source 12 for a fiber struc- ture, such as a strand of monofilament produced by melt spinning and drawing, or a prepared yarn unwound from a bobbin. The fiber structure or yarn Y_R is moved along a path P to a uptake means 14, e.g. a winder. Movement is accomplished, for example, by driven rollers 181, 182.

Path P of yarn or strand Y_R includes at least one linear portion P which passes space-dyeing position P_D which is determined by the position of an ink applicator, e.g. an ink-jet 10 arranged such that axis A - defined by the direction in which applicator 10 delivers discrete burst B of ink onto the fiber structure Y_R when passing position P_D - includes an acute angle α with direction P_L. While P_L in Fig. 1 is shown in a horizontal direction it is to be noted that this is not critical but preferred for practical reasons. A device 15 may be provided at P_D SO as to maintain the fiber structure Y_R in a spread state so that the ^FES/_TES ratio is within the range of 0.250 - 0.500. However, spreading may also be achieved by leading the yarn structure in such a manner between roller 16 and rollers 181,182 so that the filaments are maintained in a flat array of mutually adjacent monofilaments. In special but less preferred applications, spreading may be omitted if axis A is at an acute angle. By the same token, the acute angular position of ink jet 10 my be omitted (e.g. held at 90°) if fiber structure is spread sufficiently, e.g. held within the range of 0.330 . 0500. However, for most purposes, the combined use of acute angular arrangement of the ink-jet and spreading of the fiber structure is preferred. While Fig. la would seem to indicate that the dyed yarn Y_D passes from rollers 181,182 directly to uptake means 14, this is merely for simplicity of the illustration. In practice, fiber structure YD may pass more than one roller and/or be subjected to further processing steps, e.g. texturizing, entangling, heat treatment, size application, and the like conventional operations used to prepare yarns.

Fig. lb shows the preferred arrangement of axis A of ink applicator 10 when viewed in a plane crossing yarn Y_R when passing dyeing position P_D. Preferably, axis A is at an angle γ of about 90° but may vary within an angle β of about ± 10°. Figs. 2a - 2d show cross-sectional views of a fiber structure or yarn 20. In Figs

2b - 2d a spreading device or plate supporting the array is also shown in a cross- sectional view. In Fig. 2a, the yarn is in its "normal" or "un-spread" state (^FES/_TES ratio less than 0.250). With a planar spreader 21 as shown in Fig. 2b, the fiber structure will be in, for example, in a two-layer state 22 but could as well be in a substantially mono- layer state. In both cases, the ^FES/_TES ratio would be between 0.250 and 0.500. Use of a concave spreader 23 is shown in Fig. 2c to produce a spread array 24 with a ^FES/TES ratio between 0.250 and 0.500. By the same token, an angular spreader 25 will again produce a spread array with an ^FES/_TES ratio between 0.250 and 0.500. Obviously, the shape of the spreader can be varied as long as a flat structure or array of mutually contacting monofilaments will be achieved and - as mentioned briefly above - the rollers arranged adjacently upstream and downstream of space-dyeing position P_Dmay be used to maintain the filaments in an essentially flat array with an ^FES/TES ratio in the range of from 0.250 - 0.500. As will be readily apparent to those experienced in the art of yarn processing, the length of a spreading device is not critical, and that tension of the filament structure when passing P_D will favor forming an essentially flat array, notably when the yarn is passed between adjacent rollers. Such tension can be adjusted by differential speeds of the rollers and optimum parameters can be established by means of a few simple tests. Generally, such tension will be dependent upon a number of factors, such as the dtex or denier count, the number filaments, operating speeds and the like. For many types of filaments, typical tensions, measured in grams (g), are in the range of from 100 - 2000 g.

Fig. 3 illustrates a plant 30 of the a type known per se in the art and disclosed, for example, in U.S. patent 5 076 773. Such plants are available commercially and can be used for carrying out the process according to the invention by retro-fitting with commercially available ink-jets of the type mentioned above.

Fig. 3 shows a diagrammatic side view of a large and wide roller machine 3. From a spinning unit 30 two groups 301,302 of a multiplicity of filaments emanate, typically for production of 6 - 12 yarns from each filament group 301,302. Small feed rolls 311,312, e.g. with a typical diameter of about 180 mm, serve to keep the melt emanating from the spinning unit under tension during solidification. Typically, rollers 311,312 are operated at a speed of 300 m/min and filament groups are formed to constitute an array of strands, there being at least two optically differing groups of filaments

A trio of small-diameter rolls 320,321,322 is used to produce what is called "passive tension", i.e. the frictional resistance required for drawing. Rollers 323 and 324 are large-diameter rolls, typically with a diameter of about 500 mm, again operated at a relatively low speed for the frictional resistance required for drawing by means of large- diameter (typically about 500 mm) drawing rolls operated at incrementally increased peripheral speeds, say by increments of from about 50 to 100 m/min starting at 1000 - 1200 and ending at 1200-1400 m/min. As an example, roll 325 could be operated at a peripheral speed of 1000 m/min, with 1250 m min for roll 326 and 1300 m/min for roll 327. Preferably, all rolls 323, 324, 325 and 327 are heated as is conventional for filament production, e.g. to temperatures in the range of from about 80 to about 180°C . As will be apparent to those experienced in the art, roll speeds and roll temperatures depend upon the processed polymer and are well-known to those experienced in the art and the above values are given merely by way of illustration. Each filament strand is passed through a space-dyeing position 34a as explained for P_D in connection with Fig. 1. One ink-jet is provided per strand between rollers 326 and 327 or between roll 327 and upstream of texturizer 36 where the space-dyed strands are bulked.

A cooling roll 38 is provided for cooling the space-dyed strands to ambient tem- perature, and a take-off roller 313 serves to collect the strand into yarns which are then passed through an entangler or interlacer 36 and via a take-off roll assembly 37 to a winder 39 and storage 35. The following example is non-limiting.

EXAMPLE:

Space-dyed polyamide yarns of 1450 deniers were produced (80 filaments per yarn) on a machine as illustrated in Fig. 3 retro-fitted with commercial pneumatically operated ink-jets with the following settings:

This yarn was dyed by the device here described in position (34a) with the following parameters:

Test runs were made with various angles α of the ink-jet axes. Jet angles of between about 45° and about to 60° provided optimum results. Starting with an angle of 30°, a substantial reduction ( to about 1/10th) in dye spreading over the machine walls was noticed, and some lateral yarn motion (compared with the dye projection axis) was observed and believed to be due to ink pressure. The filaments of each strand were spread at space-dyeing position 34a essentially as a double or triple layer without using a spreader of the type illustrated in Fig. 2b - d, i.e. simply by means of the filament array formation on the rolls of machine 3. The ^FES/_TES ratio was between about 0.33 and 0.45. The reduction in sideway motion of the yarn appears to be about proportional to the sinus function of the angle α formed between dye projection and yarn moving direction. Thus if the angle α is too low (below about 30°) ink permeation may suffer.

Calculating the time during which the filaments stay in lateral displacements ink loss can be estimated as follows (i.e. without filament spreading): Loss of about 60 - 70 % at α = 90° (not an acute angle, not according to the invention) Loss of about 30 - 40 % at α = 60° Loss of about 10 - 20 % at α = 45° Loss of about 5 - 10 % at α = 30°

When the yarn is spread as an array of 2-3 filament layers in each strand, the effectiveness of ink coverage approaches 90-100% (i.e. loss of 0 - 10%). In other words, the invention provides for a substantially reduced loss of ink and a significantly improved dye permeation of the yarn due to the /_TES ratio in the range of from 0.250 - 0.500.

It will be understood that various modifications may be made within the general teaching of the invention provided that at least one and preferably both the acute angular arrangement of the ink- jet and the ^FES/TES ratio as disclosed above are maintained.

Claims

1. A method of producing a space-dyed yarn (YD) by an ink-jet applicator means (10) comprising the steps of: (A) moving a continuous fiber structure (Y_R) through a path (P) between a source (12) of said continuous fiber structure and an uptake means (14) for said space-dyed yarn; said path (P) having at least one linear portion (P_L) passing through a predetermined space-dyeing position (P_D); (B) directing at least one sequence of controlled bursts (B) of a liquid ink composition onto said fiber structure (Y_R) when said fiber structure (Y_R) passes said space-dyeing position (P_D); and

(C) directing said at least one sequence of controlled bursts (B) of said ink along an axis (A) of burst application; wherein: (i) said axis of said burst application forms an acute angle α with said straight line portion (P_L) passing through said predetermined space-dyeing position (PD); and/or

(ii) spreading said fiber structure while it passes through said space-dyeing position.

2. The method of claim 1 wherein said axis (A) of burst application forms an angle (α) with said straight line portion (P_L) of between about 80 and about 10°, preferably between about 70 and about 20°, and especially between about 60 and about 30°.

3. The method of claim 1 or 2 wherein fiber structure is spread to provide for a ^FES/_TES ratio of between 0.250 and 0.500.

4. The method of any of claims 1 - 3 wherein said axis (A) of burst application forms an angle (β) of 90° ± 10° with a reference plane passing through said space dye- ing position (P_D).

5. The method of any of claims 1 to 4 , wherein said continuous fiber structure(YR) is formed by a plurality of substantially endless filaments formed of a thermoplastic polymer, obtained, e.g. by melt-spinning.

6 . The method of any of claim 1 to 5, wherein said continuous fiber structure(Y_R) is formed by a yarn or yarn precursor consisting essentially of spun staple fibers.

7. The method of any of claims 1 to 6, wherein said continuous fiber structure (Y_R) is moved through said linear path portion (PL) path at a speed of at least about 400 meters per minute, preferably between about 1000 and 3000 m/min .

8. An apparatus (1 :3) for producing a space-dyed yarn (Y_D) including:

(a) a first means (13;33) for moving a continuous fiber structure (Y_R) from a source (12;32) of said continuous fiber structure through a path (P) to an up take means (14;34) for said space-dyed yarn;

(b) said path (P) having at least one linear portion (P_L) passing through a predetermined space-dyeing position (PD);

(c) a second means (10;30) for directing at least one sequence of controlled bursts (B) of a liquid ink composition onto said fiber structure when said fiber structure (Y_R) passes said space-dyeing position (PD);

(d) said second means (10;30) being arranged to direct said sequence of con trolled bursts (B) of said ink along an axis (A) of burst application; and wherein:

(e) said axis (A) of burst application forms an acute angle (α) with said straight line portion (P_L) passing through said predetermined space- dyeing position (P_D) . and/or

(f) a third means is provided for maintaining said fiber structure in a spread state when passing through said predetermined space-dyeing posi- tion (P_D).

9. The apparatus (1;3) of claim 8, comprising, as a yarn-moving means (13):

(a) at least one pair of rollers (131,132; 331,332) for engaging said filaments and passing them through said space-dyeing position at a speed of at least about 400 meters per minute.

10. The apparatus (1;3) of claim 9 , wherein said yarn moving means (13;33) includes a sequence of from at least 2 to about 10 cylinders and wherein said means (10;30) for directing said sequence of controlled bursts (B) of said liquid ink is positioned between two adjacent cylinders of said sequence.

11. The apparatus ( 1 ;3) of any of claims 8 - 10 comprising means for spreading said filament structure when passing said space-dyeing position so as to increase ink-uptake efficiency of said filament structure.

.

12 The apparatus (1;3) of any of claims 8 - 11 comprising at least one texturizing and/or entangling means positioned between said space dyeing position (P_D) and said uptake means (14;34) for said yarn.

13. The apparatus of any of claims 8 - 12 wherein said means (10;30) for directing said sequence of bursts (B) of a liquid ink composition includes at least one ink-jet (38) per yarn, and wherein a control device (39) is provided for controlling time sequence and burst duration of said at least one ink-jet.

14 . A space-dyed yarn obtained by the method of any of claims 1 - 5.