DK148101B - PROCEDURE FOR THE PREPARATION OF CRUSHED OR LATENTLY CRUSHED FILAMENTS OR YARN OR THEREOF PRODUCED PRODUCTS OF SEMICRYSTALLINE POLYOLEFINES OR MIXTURES OF POLYOLEFINES AND OTHER MATERIALS - Google Patents

Description

148101

BACKGROUND OF THE INVENTION 1. Field of the Invention The invention relates to a process for the production of rippled or latently rippled filaments or yarns or processed products of semi-crystalline polyolefins or mixtures of polyolefins and other materials, in which the starting material is melt spun at a peel rate of 100 m / min. or less to form filaments which are asymmetrically cooled, heat treated and stretched, and optionally subjected to heat treatment to develop the latent ripple before or after further processing into yarn or fabric.

In the description of Danish Pat. 1730/74 discloses a method in which at least a portion of the filaments spun from a melt is rapidly and asymmetrically cooled, formed into one or more ropes and subjected to a heat treatment at least 100 ° C and then stretched, the extent of the heat treatment before applying stretching tension is sufficient to produce at least two ripples per cm. The temperature during the stretching step largely determines whether the ripple is instantaneous or remains latent until later developed by heat stimulation, with hot stretching leading to the greatest latency.

If the development of the ripple is suppressed until after the fabrication step (s), improved volume is achieved, partly because no ripple is lost during the fabrication step and partly because adjacent fibers affect each other during the ripple, so that not all fibers develop however, a further improvement in coverage is due to the displacement they obtain and which is produced by the fibers being rippled. Thus, the dual advantage is obtained that the largely uncrossed filaments are easier to handle during fabrication and that less ripple is lost during fabrication.

The present invention has for its object to provide a method of producing polyolefin filaments or yarns or processed products which have an even better ripple or which has such a better ripple incorporated therein as a latent ripple tendency any later point of manufacture or use may be triggered by an appropriate heat treatment of the filaments or the products in which they are contained.

This object is achieved by a method of the kind mentioned in the preamble, characterized in that the asymmetric cooling is carried out so rapidly that the neck area of the filaments is less than 50 times the full diameter of the filaments at the spinning plate that the filaments are joined to one or more ropes on which the heat treatment is carried out at at least 100 ° C and the stretching is carried out in more than one step, the last of which occurs at a temperature of at least 70 ° C, the heat treatment prior to the application of tensile stress being of such magnitude , that a subsequent heat treatment for the development of latent ripple produces at least two ripples per cm.

The ripple is a coil spring ripple and is defined as the number of whole rings per head. "cm tensioned spring", cf. page 5.

The first of the above-mentioned stretching steps is preferably carried out hot, e.g. at 120 ° C while the second or last stretching step is carried out at least 70 ° C, and preferably in the range 90 ° C and above. For financial reasons and for simplicity, it is preferable to perform the stretching in just two steps, but if desired, the stretching can be performed in more than two stages, in which case the last of the stretching steps must be performed at least 70 ° C.

Stretching, as is well known, leads to an irreversible molecular displacement, and in the process of the invention this occurs in at least two separate steps, which leads to the improved results described. Preferably, the two stretching steps occur directly in succession without any relaxation of the tension. If the voltage is lifted at the end of the first step, the ripple appears spontaneously, but disappears again by application of voltage in the next stretching step and then remains largely latent until later developed by heat treatment.

It has been found that by adjusting the stretch ratio of the two steps to each other in connection with the temperatures during the stretching stages, in particular the temperature of the second stretching stage, it is possible to control both the total ripple which may appear after the last heat treatment step, and also the part of the ripple which remains latent after the second stretching step. In general, it has been found that both the largest total ripple and the largest latent ripple are achieved when something less than half of the total stretch occurs in the first step.

Eg. for a first stretching temperature of 120 ° C and a second stretching temperature of 90 ° C, it has been found that if the total stretching ratio of both stages is 3: 1 and the two-stage proportions of this stretching ratio are varied, then both total ripple as the latent ripple when the first stage proportion of the total stretch grows from 0, and both of these properties then reach a maximum shortly after 148101 3 first step proportion of the total stretch ratio constitutes a quarter, i.e. when the first step stretch ratio is slightly greater than 1.5: 1. Then, both the total ripple and the latent ripple coincide in a substantially linear fashion as the first-stage proportion of the stretch ratio increases and the portion completed in the second step decreases toward 0.

Of course, when the part of the stretching relationship carried out in the second reaches 0, the method is as described in the description of the above-mentioned Danish Pat. 1730/74 and is not in accordance with the present invention. Almost similar results are obtained with a total stretch ratio of 2: 1, with the greatest values of both total ripple and latent ripple occurring just before the stretch ratio in the first step, reaching a value of 1.5: 1.

The heat treatment prior to application of the tensile stress is preferably done at low voltage, i.e. at a voltage just sufficient to prevent deflection of the filaments as they pass through the heat treatment zone. The required extent of this heat treatment can only be indicated by the result obtained, as it depends on a number of factors such as the type of polymer, the form and efficiency of the heating, the diameter of the filaments and the thickness of the rope or ropes.

Even with a very small amount of heat treatment, a lesser degree of ripple will eventually appear, but for practical reasons the least useful ripple is considered to be two ripples per minute. Therefore, sufficient heat treatment in the method according to the invention is therefore the heat treatment necessary to produce at least this degree of ripple.

The results described are obtained using a spin-pulling speed of 100 m / min or less. Such low spin-pulling speeds significantly simplify the overall process and facilitate the achievement of the important requirement for fast asymmetric cooling.

Low-speed spinning also allows groups of filaments to be fed directly to a twine head so that they can be wound onto a yarn laying unit at the same speed as they are produced, so as to produce textured yarn directly from the base polymer in a single production line .

Apart from the already mentioned two-stage stretch and the first heat treatment, the most critical of the second stages is the initial cooling, which, as already stated, must be rapid and asymmetric. In connection with the present invention, the cooling must be so rapid that the length of the neck area between the full diameter of each 4 UB1Q1 filament at the spinning plate and the reduced diameter resulting from the spinning pull is less than 50 times the full diameter of the filaments at the spinning plate. The faster the cooling occurs, the shorter the length of this neck portion and a neck length of less than 25 times, e.g. 5 times the full diameter gives very good results. The cooling must also be asymmetric, i.e. more powerful on one side of the filament than on the other. Compliance with both of these requirements leads to differences in properties between one side and the other side of each filament, and it is the difference between these properties that is basically responsible for the final production of the ripple.

Preferably, the rapid asymmetric cooling is carried out immediately after the filaments leave the splice nozzle plate, in which case it is most conveniently obtained by directing air towards the filaments as they leave the spinning nozzle plate. This cooling air, which is preferably at or below ambient temperature, can be directed obliquely against the spinning nozzle plate so that the filaments are cooled immediately as they emerge from the openings. The colder the air, the less velocity is required to achieve the same degree of cooling.

In a particularly advantageous method, the center of filaments, i.e. the transition point between the neck area of the filaments and the area of reduced diameter, cf. Fig. 3, within 0.5 cm of the spinning nozzle plate, and the frost line, i.e. the level at which solidification of the filaments is complete is about 1.5 cm away.

The asymmetric cooling does not necessarily have to be carried out by air. For example, the filaments may be passed over the surface of a roller which is cooled either by internal cooling or by allowing a thin layer of cold liquid such as water to flow over the surface in contact with the filaments. The sides of the filaments which abut against the roller are cooled faster than their opposite sides, leading to the differential effects already described.

The openings in the spinning nozzle plate may take the form of a length-to-width ratio of at least 3: 1, preferably at least 9: 1, with the cooling air directed at the filaments from the long side of the system. Usually there are two spinning nozzle plates and consequently two spaced systems for each extruder head. Air ducts are arranged at the long outside of each system so as to direct cooling air to the filaments. With such a form of cooling, most of the individual filaments are cooled more on the one hand than on the other to obtain the required asymmetric effect.

5 148101

The effect of the asymmetric cooling is most pronounced on the filaments closest to the airflow, and if air is supplied from both exterior sides of the systems, the filaments toward each of the outer edges of the system will have the greatest difference effect, while the filaments toward the inner edge of the system will only achieve a small difference effect, and can in some cases be cooled on both sides and will not develop ripple later. The proportion of non-rippled filaments that is acceptable under certain circumstances will depend on the particular properties required in the final product. In some cases, a very small percentage of wrinkled filaments will suffice, while a rather high proportion will be desirable in other cases.

If only a small proportion of non-crimped filaments are required, this can be achieved by mixing filaments that have been crimped according to the invention with non-crimped filaments. It is also possible to practice the method of the invention so that some of the filaments will develop little or no significant ripple. When the proportion of rippled filaments is rather high, a secondary effect occurs as all the filaments are later mixed with each other, and when the final ripple appears, filaments that have not been cooled differently may are forced into a wrinkled configuration by the shrinkage of the differently cooled filaments near them.

Due to the asymmetric cooling, the difference properties are already effectively locked into the filaments at the time they solidify, and the main effect of the heat treatment is to promote this difference. The temperature of this heat treatment should be at least 100 ° C, but the size at which it should be above 100 ° C and also the extent of the treatment depend on the factors mentioned above and also the degree of ripple required. In order to provide an accurate measure of the ripple obtained under certain operating conditions, a short piece of fiber, e.g. 15 cm, of the rippled tow after the ripple is developed and placed freely without tension on an object slide and allowed to assume its natural configuration - which is like a screw spring. The number of whole rings in this state is counted and from this the number of whole rings is calculated per "cm tensioned spring", ie. the number of spoke rings divided by the length of the spring in the unstressed state. The sample is repeated 100 times on different fibers taken over the entire tow and the mean is calculated.

Although, as already mentioned, the lower limit of the heating range is important, the upper limit is important only from a 6 US101 point of view to save time and space for the overall process. It is advisable to allow a reasonable margin above the minimum value, and when eg. If an air heater is used, a residence time of 1 minute has proved suitable for most working conditions.

In practice, the extent of the heat treatment can be very easily determined by removing a small cut piece from towet immediately when it emerges from the heat treatment zone. This of the cut piece is then hand-stretched in the cold state, ie. at ambient temperature.

If the heat treatment has been sufficient, spontaneous ripple will appear and this can be easily measured and will be an indication of the total ripple that can be expected after the development.

If you want a more accurate knowledge of the required heat treatment scope, the change in the fiber can easily be monitored by e.g. observing the change in the orientation of the filaments. The heat treatment step of the method according to the invention is in fact a cure or heat fixation step and, like all such steps, causes crystallite rearrangements where the orientation angle is a measure of the alignment of the crystals in relation to the fiber axis. The orientation angle is a convenient means of measuring this. Its measurement is described by Ingersol, Journal, and Applied Physics 17, 924 (1946). The heat treatment will produce a change in the measured angle and is complete when. further heating of the sample does not cause further change in the orientation angle. However, for practical purposes, the simple hand test described above is quite sufficient.

In general, the use of an air heater for the heat treatment as mentioned above is most appropriate, and to obtain maximum ripple no appreciable voltage is used. Applying voltage during this heat treatment step tends to reduce the overall ripple and can be used as a regulatory factor if desired. If the tension reaches the magnitude needed for stretching, the evolution of the ripple can in fact be completely suppressed, thus emphasizing the importance of regulating the extent of stress relapse resulting from the stretching operation, into the heating zone.

As an alternative to the use of an air furnace for the heat treatment, the filaments can be heated to a necessary extent in a radiator.

Another advantage of using a furnace for the heat treatment is that it is possible to carry out at least the first step of the section in the same furnace as the heat treatment by allowing the tow to make a number of passages through the furnace and by isolating the heating step from the first one. stretching at appropriate feeding means so that the heat treatment is of sufficient length before applying the tension. Eg. For example, one of the rollers around which the tow passes during its passage through the furnace may be positively driven to prevent stress relapse, and this roller is positioned in proportion to the number of passages to allow a heat treatment of sufficient duration before the stretch which will take place after the driven roller.

Another alternative is to heat the filaments by surface contact with a heated surface or surfaces. Eg. For example, the filaments can be brought into direct contact with a heated roller or rollers. Some kind of stress relapse means will generally be required to control the extent of the voltage running back from the stretching zone into the heating zone, regardless of the nature of the heating.

Instead of a positively driven roller as described in connection with a heating furnace, the anti-return means may be in the form of a pressure roller cooperating with another roller or alternatively a plurality of rollers or rods, e.g. three rollers or rods arranged in the corners of a triangle. When one or more heated rollers are used for the heat treatment, the reflux preventing means will be arranged so as to regulate the return of tension from the stretching zone to the heating zone. Another alternative for the anti-return means is to place a heated roller in the heating zone at a lower temperature than the previous roll (s).

The temperature during the last stretching stage is the most important, as it determines whether the ripple is largely latent or not and, as previously mentioned, a temperature in the last stretching step of at least 70 ° C and preferably 90 ° C or higher leads to the desired increase in latency. . A water bath at about 100 ° C seems to give better results than an oven at the same temperature. This may be due to better heat penetration. However, any suitable combination of heated surfaces, baths or ovens can be used, provided that the required heating requirements are met at each stage.

The steps described so far, i.e. The rapid and asymmetric cooling step, the heat treatment step and the stretching step can conveniently be carried out in continuous order on the same production line, the filaments passing directly from one step to the next. After this series of steps, the filaments can either pass directly to another fabrication step, such as stacking and carding, or they can be wound into units ready for further processing at a later date. The latent rippled filaments can be made easier to handle by applying mechanical ripple. This makes them more suitable for subsequent treatments, such as mapping.

It is also possible to interrupt the step sequence between the heat treatment and the stretching by recovering the filaments on laying units after the heat treatment. This completely avoids all problems caused by the return of voltage to the heat treatment stage.

To develop the latent ripple, the filaments must be subjected to heat treatment. To achieve maximum ripple, the temperature of this heat treatment is preferably of the same order of magnitude as the temperature of the heat treatment prior to stretching. This additional heat treatment is preferably dry, but wet treatment can be used if desired and can be used at any stage after the last stretching step. It may also be advantageous to add heat to the ripple development in more than one step, so that part of the ripple appears at one stage in the process and the remainder remains to be developed by further heat treatment in one or more subsequent steps.

For example, the filaments can be stapled and then spun to yarn, the heat treatment being carried out on the yarn formed. The treatment then induces the development of the ripple and including a relative movement of the fibers which tends to give the yarn more fullness.

Thus, if the yarn in question is used as a pile yarn in a blanket, the effect of the treatment is an increase in the yarn's coverability and that the rug itself becomes more full to allow a smaller yarn density to be used at the same equivalent coverability with consequent savings. The heat required for the treatment can e.g. result from the application of a backing to the carpet, or from a finishing process. The stacked filaments can be used either alone or mixed with other materials, e.g. 50% viscosity.

In practice, the degree of ripple can be determined at the filament making stage by taking cut pieces of the towel after the stretching step and heating them loosely in an oven for approx. \ minute. The temperature of the oven should correspond to the temperature of the final heat treatment just described and will generally be between 100 ° C and 130 ° C. The length change of the heated tow will provide a measure of the ripple ability. For example, a length reduction from 30 cm to 10 cm will constitute a satisfactory ripple.

The invention will now be explained in more detail with reference to the drawing, in which: fig. 1 is a plan view showing the plan of a production line as a whole; FIG. 2 is a perspective view of a single extrusion head and cooling arrangement; FIG. 3 is a detail view of a small section of spinning nozzle plate and cooling arrangement; and FIG. 4 and 5 are graphs showing the effect of the relative and total stretching ratios on the degree of latent and total ripple obtained.

In FIG. 1, three extruders are shown which, at 2, deliver filaments upwardly in the form of a rope which is passed around guide rollers 3, the single ropes being joined together to form a single combined rope 4, on which subsequent processing steps are carried out. Polymeric grains are supplied to the individual extruders 1 from a hopper 6 and the operation of the production line is controlled from a control panel 7.

The combined rope 4 is first introduced horizontally into a hot air oven 10, being guided by rollers 11 and 12 so as to carry out three passages through the furnace, the first two of which constitute the heat treatment and the third the first stretching step. In order to provide effective tensioning and prevent the tensile stress from returning to the heating zone, the roll 12 is positively driven, preferably at the same surface velocity as the rollers 3, so as to obtain minimal tension in the first two passages of the rope through the furnace, and thereby forms the heating zone. A temperature of at least 100 ° C is kept in the oven.

The rope then passes over rollers 14 and 15, which run about one and a half times as fast as rollers 3, 11 and 12, thus giving the rope the first stretch during its third passage through the furnace.

Following the passage around rollers 14 and 15, rope 4 moves downwardly to a water bath 18, which contains an arrangement of three rollers 20 moving at the same speed as rollers 14 and 15. It then passes upwardly and out of the water bath 18 around a roller 21 having a cooperating roller 22 and then to a group of pre-rollers generally designated 24. It is these rollers 21-24 which apply the tension in the second stretching step, and the rope is thus stretched over the distance shown at 25 between the rollers 20 and 21. The group of rollers 20 withstands the tension applied by rollers 21, 22 and 24, thus separating the two stretching stages of the rope, although, of course, there is no tension between the steps.

After leaving the feed rollers 24, the rope 4 is fed to a mug chamber crusher 28 which applies a mechanical ripple and makes the rope more suitable for subsequent treatment. In a typical example, the clamping pressure at the feed rollers in the mug chamber 28 was 65 kg / kg. cm. It has been noted that excessive clamping pressure can reduce the total ripple that develops eventually. Finally, the rope is fed to a rewind head 30 which feeds it to a subsequent cylinder shown as 31. As each cylinder 31 is filled with rope, it is passed to the subsequent necessary treatment steps, as previously described.

The first of the necessary steps in the process of the invention consists in the rapid and asymmetric cooling of the filaments illustrated by FIG. 2 and 3. The individual filaments 35 are shown coming from a spinning nozzle plate 36, and an air nozzle 38 directs a flow of cooling air obliquely to the spinning nozzle plate 36 so as to strike the die plate itself approximately at the far side of the group of filaments as shown by the dotted line. 39 (Fig. 3). In a particular example, the diameter of the individual filaments is 1.0 mm, the distance denoted by A representing the vertical height of the die from the die plate is 12 mm, and the dimension B representing the horizontal distance from the die to the edge of the group of filaments, are 25 mm.

In this example, cooling air at ambient temperature is directed at the filaments at a rate of 40 m / sec, leading to a neck point (shown punctured) in the filaments at an average height C of approx. 2.5 mm above the surface of the spinning nozzle plate 36 and a frost line at a mean distance of approx. 1.5 cm and represented by the dotted line D. At the frost line, the filaments are completely solidified and are of 60 denier.

An example of the production of rippled filaments using the plant just described will now be described in more detail. The extruder used is commercially known as a "MACKIE CX" extruder and it is operated at box temperatures of 260 to 280 ° C. Each spinneret plate had the dimensions 400 x 30 mm, was kept at a temperature of 280 ° C, and had 5880 holes each with a diameter of 1.0 mm.

Polymer was pumped to the spinning nozzle plates at a rate which allowed a total production rate of 90 kg / h. The cooling arrangement was performed as already described in connection with Figures 2 and 3, and the air used for cooling had a temperature of 17 ° C. The air velocity measured at the exit from the gap in the nozzle, which was 0.5 cm wide, was 40 m / sec. Under these conditions for rapid and asymmetric cooling, the extruded filaments exhibited a neck point averaging about 2.5 mm from the die plate lying from 5 mm furthest away from the cooling nozzle to 1 mm closest to the nozzle. The peel rate of the filaments was 9.0 m / min.

Using the apparatus described and working conditions, the pigmented polypropylene having a melt flow index of 4.0 was extruded through 3 heads (2 spinning nozzle plates per head) into the extruder, yielding a total of 32,280 filaments assembled into a single rope. This was passed three times through the one shown in FIG. 1, which was maintained at a temperature of 120 ° C. The rope was introduced into the furnace at a speed of 9 m / min, and the roller 12 was also held at a surface speed of 9 m / min. The duration of the heat treatment, which was the first two passages of the rope through the furnace, was about 40 sec. The rope was then passed around the rollers 14 and 15, which had a surface velocity of 13.5 m / min, thus giving an initial stretch of 1.5: 1. From the rollers 14 and 15, the rope was introduced into the water bath 18 at 90 ° C and around the three rollers 20 having a surface velocity of 13.5 m / min, and then fed to the rollers 21-24 having a surface velocity of 27 m / min. and thus provided the second stretch step and completed the total stretch of 3: 1.

(A rope sample was taken before the roll 12 and the total ripple potential was examined by cold stretching by hand. It developed 8 ripples / cm and it was found that the orientation angle before the heat treatment was 24 ° and after the heat treatment 36 °).

The rope was brought to the ripple apparatus 28 and collected in containers 31. It was stacked to 15 cm, post-treated with an antistatic agent and the cardboard, prepared and spun to a 4.23 Nm yarn with a twist of 197 turns / m and 2-twisted with 118 turns / m. The yarn was woven into an Axminster blanket, which was coated with latex at the back and cured in an oven at 120 ° C. The latent ruffle of the pile yarn was developed, resulting in a blanket with an even greater covering capacity than that which appeared in it in the description to Danish Pat. No. 1730/74.

FIG. 4 and 5 are graphs showing how changing the first stretching ratio affects latency and total ripple extent. In graph 148101 12 4, the total distance (first plus second distance) is 3: 1. The percent ripple is plotted as ordinate against first stretch ratio such as abscissa, which ratio miles as the ratio of roller speeds, i.e. The roll 12 'temperature temperature is * 9 9 ° C and thus also gives a first stretch temperature of 120 ° C. The water bath temperature, i.e. the second stretching temperature is equal to 90 ° C.

Curve A shows total ripple after development at 122 ° C (i.e. the subsequent heat treatment). Curve B shows immediate ripple (spontaneous) developed under ambient conditions, and curve C is similar to curve B minus A and shows the latent ripple.

The graph 5 is produced in a similar manner, but in this case the total distance is 2: 1. It is seen that slightly higher ripple values are obtained at this lower total stretch.

The additional latency produced by the process provides an even greater volume of volume utilized in multiple stage development. Thus, the yarn may e.g. treated in boiling water to develop part of the ripple, and the remainder can then be developed by the latex curing of the rug.

Due to the bulkiness that occurs in the yarn before insertion as tufts in the rug and partly after insertion in the rug, a rug is produced which not only has maximum coverage, but also excellent tuft delimitation.

It should be noted that not only is the process of the invention advantageous in carpet fabrication Young, but also in many other textile processes, not least it is well-suited for the production of nonwoven fabrics, particularly in the spinning bonding process in which a large number of filaments are extruded onto a fabric. conveyor to which sufficient spacing is provided with sufficient heat to merge a number of the filaments so that the filaments are bonded together as a coherent, non-woven non-woven web during handling, and the effect of heat on latent filaments spiral ripple is that the filaments are literally twisted so that at intervals as they touch and intersect, they become intertwined, thereby providing a more solid consolidation of the web than would be the case alone of the fusion.

Claims (8)

148101 Patent Claims. A process for the production of rippled or latent rippled filaments or yarns or processed products of semi-crystalline polyolefins or mixtures of polyolefins and other materials, wherein the starting material is melt spun at a peel rate of 100 m / min. or less to form filaments which are asymmetrically cooled, heat treated and stretched, and optionally subjected to heat treatment to develop the latent ripple before or after further processing into yarn or fabric, characterized in that the asymmetric cooling is performed so rapidly that the filament neck area is obtained a length of less than 50 times the full diameter of the filaments at the spinning plate, that the filaments are assembled into one or more ropes on which the heat treatment is carried out at at least 100 ° C, and that the stretching is performed in more than one step, the last of which occurs at a temperature of at least 70 ° C, where the heat treatment prior to the application of tensile stress is such that a subsequent heat treatment for the development of latent ripple produces at least two ripples per cm as defined in the specification. Process according to claim 1, characterized in that the temperature of the last stretching step is in the range of about 90 ° C. Method according to claim 1 or 2, characterized in that there are two stretching steps. Method according to one of the preceding claims, characterized in that the temperature during the first stretching step is at least 100 ° C. Method according to one of the preceding claims, characterized in that the asymmetric cooling of the filaments is carried out by directing cooling air towards them at the point where they leave the spinning plate. Method according to claim 5, characterized in that the cooling air is directed obliquely to the spinning plate. Method according to claim 5 or 6, characterized in that the neck point of the filaments is kept on average within a distance (C) of 2.5 mm from the spinning plate and that the frost line is on average at a distance (D) of approx. 1.5 cm from the spinning plate. Method according to one of the preceding claims, characterized in that the pre-stretch heat treatment and the