GB2090296A - Yarn Finishing - Google Patents

Abstract

A method and apparatus for making felt or felted yarn includes passing two or more yarns, preferably including keratinous fibres, through a flexible hollow tube while flexing the tube preferably in a travelling wave motion. The passage of two or more yarns substantially increases the felting action in comparison with the passage of a single yarn at the same speed. The tube is provided with an elliptical cross-section. <IMAGE>

Description

SPECIFICATION Yarn Finishing This invention relates to a method of finishing yarns. It represents an improvement in or modification of the invention described in our U.K. Patent Specification No. 1,505,162.

The method of Specification No. 1,505,1 62 is especially useful for higher count yarns such as carpet yarns. We have found however that in order to obtain adequate felting or bulking the throughput speed of yarn must be decreased with the count of yarn. Thus the weight of yarn treated per unit time drops markedly with count and for all practical purposes the process becomes too slow for commercial use on counts below 1000 tex.

The invention seeks to overcome the above disadvantage by providing a method of finishing relatively low count yarns at throughput speeds fast enough to be commercially acceptable.

According to the present invention there is provided a method of finishing yarns which comprises passing two or more yarns containing keratin fibres in the presence of moisture through a flexible tube and flexing the tube during the passage of the yarns.

The finishing effect is primarily that caused by entangling of the fibres in the yarn which, according to the conditions selected, can produce a dense, compact felted yarn or a yarn of increased bulk or loftiness. However the method may also be used for other finishing operations, e.g. scouring the yarns or application of dyestuffs or other chemical finishing agents. It will be appreciated that in order to obtain a felted effect yarns of, or containing a substantial amount of, keratinous fibres should be employed; but that where the apparatus is employed primarily for other finishing operations the yarns used may, in principle, be of any textile fibre. It is preferred to employ keratinous, especially wool, yarns; and in the following general description the use of wool or wool-rich yarns is to be assumed unless stated to the contrary.

We have surprisingly found that by passing two or more yarns through a single tube, the rate of treatment (in terms of weight per unit time) can be increased to commercially acceptable levels, but that the yarns although felted in themselves do not become inseparably entangled with one another.

The felting effect of the process of the invention can produce, inter alia, yarns in which the fibres are consolidated and which are therefore stronger and more stable than the untreated yarns. Thus it is possible by using the process of the invention to upgrade yarns to end uses for which they would not have been sufficiently strong. Conversely it is possible for a given end-use to use a yarn which has a lower twist factor than would otherwise be suitable. Since the twist factor ultimately determines the throughput speed of a spinning frame, saving in twist leads to greater throughput speed and therefore lower unit costs. When the large volumes of yarn produced are considered it will be seen that the savings here can be quite considerable.

The flexing or oscillation used in the method of the invention has a principal component transverse to the direction of motion of the yarn. A preferred form of the apparatus of the invention produces the requisite flexing of the guide tube in a manner similar to the operation of a peristaltic pump.

It will be appreciated that the yarn will need to be flexed sufficiently to produce the bulked effect.

Therefore, the specific number of flexions, i.e. the number of flexions per minute multiplied by the dwell time of the yarn in the tube (which depends on the tube length divided by the speed of throughput of the yarn) must be great enough.

It has been found, however, that the dwell time is longer than would be expected given the tube length and throughput speed of the yarn, so that the specific number of flexions is larger than would be expected from these two parameters. It is believed that the tube acts in some ways like a J-box allowing a reservoir of yarn to build up inside it before yarn emerges from it. This effect is greater as the tube cross-section/yarn count ratio increases. Thus, for a given yarn count and throughput speed, the dwell time will be greater for a larger diameter tube. In other words the specific number of flexions will increase with the tube diameter.

A specific number of flexions in excess of 300 is required to produce significant bulking and for best results this number should be in excess of 400 and preferably above 500. There is for each tube a rate of flexion above which an increase of the flexion rate does not greatly increase the bulking effect, and is therefore not preferred. For a silicone tube this maximum rate is about 1000, but for a polyurethane tube it is found to be 1 500 or more and for this reason a polyurethane tube is greatly preferred, permitting a substantially higher throughput of the apparatus.

The temperature at which the method is carried out should exceed 300 C, but temperatures in excess of 650C do not give improved results, and can even lead to poorer results. Accordingly, the preferred temperature range is from 300C to 650 C, especially about 600 C.

As mentioned above, the process of the invention is especially applicable to spun yarns of keratinous fibres. Worsted, semi-worsted and woollen spun yarns may be bulked. While yarns of any count may be bulked (depending on the tube cross-section as explained more fully hereinafter) the process is particularly useful in relation to yarns, having counts below 1000 tex.

When passing two or more yarns through the tube, the ratio of tube cross-section to total yarn count should be greater than 5 mm2/k.tex, preferably greater than 20, and advantageously about 40.

Ratios in excess of 60 are too great in that the yarns can fold back on themselves and become tangled and irregular.

The method of the invention, using an oscillating guide tube a few decimeters long, can produce bulked yarns with an acceptable degree of bulking at a production rate which is comparable with that of conventional spinning processes.

If the oscillation motion is that of a transverse wave, then the yarn is subjected to forces which tend to transport the wool through the tube. Thus if there is no tension on the wool at either end of the tube, a direct relationship between the rate of transport and the frequency of the wave can be observed. This makes it possible to transport the wool without tension through the guide tubes, although it is preferred to take off the bulked yarn on driven rollers and utilise the transporting action only to draw the unbulked yarn into the tube. Further, it is preferred to control the input tension by providing a feed mechanism such as that described more fully hereinafter.

At its simplest, the apparatus of the invention may consist of a straight tube which is brought into a reciprocatory flexing motion through a crank, cam or similar mechanism.

The bulking process is accelerated markedly by the use of a flexible tube which is connected at only one or a few places to the remainder of the apparatus. A tube of elastic material, such as rubber, or a helical spring with a small pitch can be used to provide the flexible tube. As the recovery rate of the flexible tube is relatively low, a wave motion results, which appears to have a favourable effect on the bulking process. In the simplest case, a stationary wave motion will be generated. By a proper setting of the device which creates the motion, however, a travelling wave can be generated. In that case, besides the bulking action, the transporting action is also obtained.

As the felting/bulking effect obtainable by the method of the invention utilises the unique properties of keratinous fibres, and especially wool, it is preferred that the proportion of such fibres be as high as possible to produce the best results. However, blends of wool with other fibres may be employed provided that the proportion of wool is not too low for effective bulking to occur.

The bulking should take place in the presence of moisture; ideally an aqueous milling solution (e.g. an acid or alkaline solution containing soap or detergent) is passed through the tube with the yarn.

Ideally the preferred temperature of above 300C is maintained by heating a reservoir of milling liquid to the desired temperature by means of, for example, immersion heaters or steam pipes, and circulating this from the reservoir through the tube and back to the reservoir.

Speeds of up to 45 metres/min can be obtained, although for general purposes speeds of 10 to 30 metres/min are preferred.

In order to increase the ease of separation of the yarns after passage through the tubes it is preferred to employ tubes of oval cross-section. Since the tubes tend to flatten somewhat where they contact the rotors, the use of an oval tube results in a cross-section at the point of contact with the rotors which is an elongated flattened ellipse with substantially parallel flattened sides. This ensures that the yarns passing through lie side-by-side and do not cross one another and become entangled.

Accordingly the invention further provides an apparatus for finishing yarns comprising a flexible tube of elliptical cross-section defining a path for the yarns, means for supplying two or more moistened yarns to the tube and at least one member mounted for gyration in an orbit intersecting the path of the yarns whereby gyration of the member flexes the tube and the yarns therein.

For certain purposes the yarns treated need not be separated after emerging from the apparatus, but may be used as produced, lightly felted together. In particular a number of finer count yarns felted together in the apparatus may be used directly in the production of carpets, for example with gripper Axminster or tufting machinery. In this manner, fine count yarns may be used with relatively coarse gauge machinery to produce fine and coarse yarn effects in the finished carpet. Apart from the decorative effects possible, there are economic advantages in using coarse gauge machinery in this manner. The yarns treated according to the invention are sufficiently bound together to be processed by such machinery without problems of separation, but have the appearance of bundles of separate fine count yarns in the finished carpet.

The invention will be described further, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a diagrammatic side view of an apparatus constructed according to the invention; Figure 2 is a front view of the apparatus of Figure 1; and Figure 3 is a diagrammatic view of a yarn tensioning and feeding device for the apparatus.

As shown in the drawings, a shaft 10 carries a pair of end-plates 12 attached to which are six equally spaced rotor members 14. The rotor members 14 comprise rollers 16 of smooth plastics material mounted on axles 18 carried between the end plates 12 and a number of supporting discs 20.

The shaft 10 is mounted on bearings 22 carried in the frame of the apparatus and is rotated by means of a belt drive to a pulley 24. Flexible guide tubes 26 made from urethane rubber and elliptical in crosssection are fixed in bosses 28, 30 in the top of the apparatus. The tension of the guide tubes 26 is such that during rotation of the assembly of shafts and rotor members contact is maintained between the tube 26 and the rollers 1 6, and flattening of the tube to a flattened elongated ellipse takes place. The inlet bosses 28 each carry a short metal tube 32 which projects into a header tank 34 (omitted from Figure 2 for clarity) filled with milling solution 36. An immersion heater (not shown) maintains the temperature at 600 C. Ingoing yarns 38 are wetted by this solution 36 and carry a portion of it through the guide tubes 26.The exit bosses 30 each have a longer guide tube 40 projecting above the liquid surface. Holes 42 in the tube 40 allow the bulk of the solution carried through the guide tubes 26 to return to the tank 34 without interfering with the egress of bulked yarns 44. Supporting rollers 46 are provided to steady both the ingoing yarns 38 and the resultant bulked yarns 44.

As can be seen from Figure 1 , the guide tubes 26 bend where they are in contact with the rollers 16 and are straight in between. Thus when the shaft is driven, the bends in the tubes 26 move with the rollers 1 6 and the parts of the tubes between the rollers show an amplitude of displacement towards the central shaft 10. The result appears as a travelling transverse wave motion of the guide tubes 26.

The yarns 38 are bulked by this wave motion to bulked yarns 44 which are led off for storage or further use. Separation of the yarns may be aided by cutters positioned near the exits of the felting tubes.

Despite the fact that the rollers 1 6 are free to rotate about their axes 1 8 it has been found that at operating speeds a great deal of slippage takes place between the rollers 1 6 and the tubes 26. It is therefore beneficial to provide lubrication. Water or excess milling solution accomplishes this lubrication and greatly reduces wear on the tubes 26. The yarns may be removed by means of driven take-off rollers at the desired throughput speed. Typical shaft speeds lie in the range 400--1500 rpm with speeds of 900 to 1200 rpm giving good results.

The degree of bulking is usually sufficient for normal applications of wool yarns at throughput speeds of about 20 m/min. If, however, a higher degree of bulking is required, for instance when the yarns only partly consist of wool, the throughput speed can be decreased and/or the rotor speed increased i.e. the specific number of flexions increased. Alternatively, longer tubes can be employed, or two or more devices in series.

In order to protect the tubes and to prolong the time they can be used, a belt can be placed between the rollers and the tube. This belt is fixed to the frame of the machine and consists of a material which is flexible but cannot be stretched, for example reinforced rubber.

As the movement of the end of the tubes may be large, which could weaken and eventually damage the tubes, a buffer of elastic material may be mounted on the frame to restrain the oscillating movement of the tube near the bosses 30. Such a buffer can for instance be made from foam rubber.

Other ways of reducing this oscillation include providing the bosses 30 with a flexible downwardly tapering connected to the tubes 26, or increasing the distance of the bosses 30 from the rotor assembly. The provisions of a polyurethane conical boss 31 moulded on to the polyurethane tube 26 is preferred.

The yarns may be fed into the apparatus of the invention either in the direction of, or counter to, the rotation of the members although the former is preferred.

Figure 3 illustrates a feed device for the apparatus. The yarns 38 (one only shown in Figure 3 for clarity) are fed over a shaft 60, carrying a series of spaced discs 62, between two adjacent discs 62.

From the shaft 60, the yarns pass round a driven roller 64 and back over the shaft 60 between the next pair of discs 62 and so into the tubes 26 of the apparatus. The driven roller 64 adjusts the yarn tension to a desired value, or supplies a positive drive to the yarns if required, and the discs 62 ensure proper spacing and separation of adjacent yarns 38 which is essential if good results are to be obtained from the apparatus.

The following are examples of the production of bulked yarns according to the invention: Examples 1 to 16 Using the above apparatus with a milling solution comprising 3 g/l So 13 (soap/phosphate buffer-Stevensons) maintained at 600C a 675 tex twofold wool yarn was treated as follows. The rotor speed was held at 1200 r.p.m. and the throughput speed at 8 m/min over a tube length of 41.5 cm.

Yarns are processed through tubes of 4 diameters as follows: Table 1 Linear density per unit x-section area Example No. Tube diameter {g/m/area) No. of ends 1 5 13.8 4 2 10.3 3 3 6.9 2 4 6 11.9 5 5 9.5 4 6 7.2 3 7 7 4.8 2 8 12.3 7 9 10.5 6 10 8.8 5 11 7.0 4 12 8 5.3 3 13 13.4 10 14 10.7 8 15 8.1 6 16 5.4 4 The properties of the treated yarns are given in Table 2 below.

Table 2 Throughput constrant at 8 m/min. 1200 rpm rotor speed 12 tubes Tube Production Packing Bulk Exemple diameter No. of Resultant Count (tex) % Mean Individual Rate Factor increase No. (mm) Ends Nominal Observed increase Count (tex) kg/hr (%) (%) 1 5 4 2700 2800 + 6.7% 720 16.6 6.62 8.1 2 3 2025 2345 + 15.8% 780 13.5 6.54 9.2 3 2 1350 1580 + 17.0% 790 9.1 4.91 31.8 4 6 5 3375 3540 + 4.9% 710 20.4 6.77 6.0 5 4 2700 3200 + 18.5% 800 18.4 5.95 17.4 6 3 2025 2575 + 27.0% 860 14.8 5.48 23.9 7 2 1350 1680 + 24.5% 840 9.7 4.68 35.0 8 7 7 4725 5310 + 12.4% 760 30.6 6.65 7.6 9 8 4050 4570 + 12.8% 760 26.3 5.97 17.1 10 5 3375 4185 + 24.0% 835 24.1 5.58 22.5 11 4 2700 3690 + 36.7% 920 21.3 5.33 26.0 12 3 2025 2500 + 23.5% 835 14.4 5.01 30.4 13 8 10 6750 7250 + 7.4% 725 41.8 6.23 13.5 14 8 5400 6285 + 16.4% 785 36.2 5.38 25.3 15 6 4050 5045 + 24.6% 840 29.1 5.12 28.9 16 4 2700 3230 + 19.6% 810 18.6 4.62 35.8 As can be seen from the Table above, for a given tube diameter the bulking effect varies inversely with the number of ends passed through the tube but, as might be expected, the production rate varies directly with number of ends. Since a production rate of 30 Kg/hour or above (for a 12-tube machine) is comparable with batch felting methods, the larger tubes with greater number of ends are to be preferred. For adequate felting effect (bulk increase over 10%) at these production rates it can be seen that the conditions of Examples 13 to 15 are optimum.

As already mentioned, considerable advantages result from the use of a flexible tube of polyurethane instead of a silicone rubber tube. These tubes are preferably as thin-walled as practicable and a wall-thickness of about 1 mm is preferred as balancing the advantage of thinness with ease of manufacture.

The present preferred polyurethane tubes are those sold by Dunlop Rubber Plastics Division (Wrexham, England) under the Trade Mark Prescollan PCE 1589. The material itself, Grade 23017, has a density of 1.17 Mg/m3, a Shore hardness (ASTM D2240) A:88 and B:37, a tensile strength (ASTM D41 2 DicD) of 45 MN/m2, an elongation at break (ASTM D412) of 610%, and a resilience (Dunlop Tripsometer BS903) of 49.

The conical boss, restraining oscillation of the tube, may be moulded directly on the ends of a tube of polyurethane using a urethane prepolymer moulding composition, such as that sold by Compounding Ingredients Ltd. under the name ClL-Monothane, which is a one-component polyesterbased polyurethane moulding composition.

The effective diameter of the tube can be varied by fitting a restrictor of the desired internal diameter at the outlet end of the tube. This may enable a wider tube to be employed with given yarns than would otherwise be suitable. It is advantageous to employ driven withdrawal means to withdraw the yarns from the tube when the diameter of the tube is restricted in relation to the size of the yarns.

Examples 17-20 To illustrate the beneficial effect on yarn strength and tenacity of the process of the invention, yarns of comparable count but different twist factor were each processed according to the invention under identical conditions. The results are given in Table 3 below.

Table 3 Before Felting After Felting Breaking Breaking Example Twist Load Tenacity load Tenacity No. Yarn (tpm) (Kg) (g/tex) (Kg) (g/tex) 17 Singles 40 27.5 4.30 30.3 5.06 18 2 Fold 65 30.5 5.14 36.9 6.28 19 3 Fold 80 33.6 5.46 34.0 5.87 20 4 Fold 100 41.6 6.71 40.5 6.59 As can be seen from the Table, felting increases both the strength and tenacity of the yarns of lower twist, and does so by a proportionately greater extent with the yarns of lower twist. Thus, the treated yarn of Example 17 is as strong as the untreated yarn of Example 18; and the treated yarn of Example 18 is as strong as the untreated yarn of Example 1 9. Hence the process of the invention enables yarns of lower twist to be used in applications where hitherto they have not been satisfactory, with consequent spinning economies.

Example 21 All wool yarns containing 6% spinning oil were processed according to the invention as described in Example 1 using the standard soap milling liquor. The treated yarns are found to have an oil content of about 0. 1% spinning oil and had thus been effectively scoured.

Claims (22)

Claims

1. A method of finishing yarns which comprises passing two or more yarns in the presence of moisture through a flexible tube and flexing the tube during the passage of the yarns.

2. A method as claimed in claim 1 in which the yarns contain keratinous fibres.

3. A method as claimed in either of claims 1 or 2 in which the flexing or oscillation has a principal component transverse to the direction of motion of the yarn.

4. A method as claimed in any one of claims 1 to 3 in which the yarn is subjected to a specific number of flexions in excess of 300.

5. A method as claimed in claim 4 in which the specific numberofflexions is in excess of 400.

6. A method as claimed in claim 5 in which the specific number of flexions is above 500.

7. A method as claimed in any one of claims 1 to 6 in which the tube is a polyurethane tube.

8. A method as claimed in claim 7 in which the specific number of flexions is not more than, 1,500.

9. A method as claimed in any one of claims 1 to 8 in which the temperature exceeds 300 C.

10. A method as claimed in any one of claims 1 to 9 in which the temperature is not greater than 650C.

11. A method as claimed in any one of claims 1 to 10 in which worsted, semi-worsted or woollenspun yarn having counts below 1,000 tex are employed.

12. A method as claimed in any one of claims 1 to 11 in which the ratio of the tube cross-section to total yarn count is greater than 5mm2 per kilotex.

13. A method as claimed in claim 12 in which the ratio of tube cross-section to total yarn count is greater than 20mm2 per kilotex.

14. A method as claimed in claim 13 in which the ratio of the tube cross-section to total yarn count is greater than 40.

1 5. A method as claimed in any one of claims 1 to 14 in which the bulking takes place in the presence of aqueous milling solution.

16. A method as claimed in any one of claims 1 to 1 5 in which the yarn speed is in the range of 10 to 30 meters per minute.

1 7. An apparatus for finishing yarns comprising a flexible tube of elliptical cross-section defining a path for the yarns, means for supplying two or more moistened yarns to the tube and at least one member mounted for gyration in an orbit intersecting the path of the yarns whereby gyration of the member flexes the tube and the yarns therein.

18. An apparatus as claimed in claim 1 7 in which the means for flexing the tube comprise rollers mounted on a disc rotatable about its centre and the tube is stretched over the rollers.

1 9. An apparatus as claimed in claim 1 7 or 1 8 in which the tube is of a flexible plastics material.

20. An apparatus as claimed in claim 1 9 in which the tube is of a polyurethane plastics material.

21. A method of treating the yarn substantially as hereinbefore described with reference to and as illustrated in the foregoing examples.

22. An apparatus for finishing yarns substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.