EP0199239B1 - Method for the multistage post-treatment of continuously advancing fibre tows, and apparatuses required therefor - Google Patents

Description

Continuous threads (fiber cables) spun from solvent and joined to form ribbons of many individual filaments go through a series of post-treatment stages before they are passed on to the secondary spinning mill, that is to say in the yarn production.

The essential stages are washing to remove residual solvent, stretching, drying, crimping, crimp fixing and cooling.

While washing and drying to achieve optimal results, i.e. a high degree of washing or drying with the lowest possible washing water or heat consumption, the threads are run through the washing and drying units with the lowest possible occupancy density, ie as wide and thin a band as possible , it is advisable to carry out crimping, crimp fixing and cooling in as few devices as possible, which not only saves process and investment costs, but also leads to uniform product quality.

So far, for example, a sliver of a certain width has been divided into several narrow slivers after washing and drying and each crimped in its own crimping chamber, the crimping chamber not being arranged next to each other but staggered one behind the other for reasons of space, and also due to the different dwell time of the ribbons between Dryer and crimping unit, unevenly crimped sub-tapes are accepted, so it is now endeavored to use only a crimping apparatus for a certain cable thickness in the form of a wide ribbon in order to achieve an improvement in product quality, in particular a more uniform product quality in terms of crimping, lateral adhesion of the cable, achievable card speed, grip and dyeability, to name just a few essential parameters.

On the basis of this consideration, the task arises for economic reasons of coordinating the process steps and the necessary devices of the overall process in such a way that a product of higher quality and reduced damage is produced with a more economical driving style and reduced energy consumption.

DE-A 2 224 850 describes a device for sliver reduction in which, for reasons of the operability of the upper rollers 2 and 3 (see FIG. 1) Possibility of vertical band reduction is limited. It is therefore carried out in two stages between rolls 1 and 3 or 4 and 2. 4 rolls are required in each case for further belts to be installed, although for reasons of space it is not possible to shorten more than 3 belts. Two separate machine frames are required for the roller arrangements.

A solution to the problem according to the invention can be achieved, surprisingly, if the fiber cable is guided in compliance with certain process and device parameters, starting from the dryer outlet via a device for reducing the bandwidth, optionally a steaming unit, a stuffer box crimp, a cooling belt and optionally a cutting edge or a tearing machine.

The invention therefore relates to a process for the aftertreatment of washed and dried fiber cables with a minimum mass of 250 ktex by crimping, fixing, cooling (and optionally cutting or tearing), characterized in that the bandwidth of the cable running out of the dryer is covered with an occupancy density of at most 5 ktex / cm reduced by at least 50% of the original bandwidth with a corresponding increase in the packing density, in a stuffer box crimping device at a stuffer box pressure of 1.5 N / cm² to 6.0 N / cm² and a stuffer box temperature of 80 to 95 ° C curls, the curl fixed in or immediately after the stuffer box, the cable is placed on the surface of an air-permeable conveyor belt, where it blows or sucks air through the fiber package and conveyor belt (and then, if necessary, feeds the cable to a tear converter or a cutting machine).

The bandwidth of the cable can be reduced using inclined rods over which the sub-bands are guided. A new installation using rollers is preferably used.

The sliver to be reduced in width is removed from the take-off mechanism (a) in the form of at least two, preferably equally strong individual strips, the individual strips are guided over separate rollers (b 1), (b 2) etc. and one above the other on a roller (c) united a band of reduced width, the axis of the roller (a) with the axis of at least one of the rollers (b₁), (b₂) etc. includes an angle of 1.5 to 7 °.

Since the tapes always hit each roll vertically, the distance between the roll (a) on the one hand and the rolls (b₁), (b₂), etc., on the other hand, results from the aforementioned angle and the desired amount of tape laying.

The "laying" of the slivers on a common axis, which is also the central axis of the crimping rollers, is achieved by pivoting the rollers (rollers) b₁ and b₂, the effect being exploited that it is only a possible track axis for the sliver run there, namely the shortest distance from the deduction trio via role b₁ or b₂ to role c. Only this axis provides stable tracking, while all other tracks in the sliver have lateral forces that remain effective until the stable axis is reached again. If the rollers b 1 and b 2 are adjusted about their pivot point, the belt moves by the same angular amount in the corresponding direction. When adjusting the rollers against each other, it is thus possible to adjust the two belts exactly one above the other and on the central axis of the crimping device.

Preferably, the sliver is halved in width, that is divided into two sub-bands of the same width, which are guided over rollers (b₁) and (b₂) and combined on the roller (c), the axes of the rollers (b₁) and (b₂ ) with the axis of the roller (a) include an equally large but oppositely directed angle of 1.5 to 7 °, preferably 2 to 5 °.

At even smaller angles, the distance between the rollers (b₁) and (b₂) on the one hand and the roller (a) on the other hand would be uneconomically large, at larger angles a proper run of the slivers from the rollers would no longer be guaranteed with certainty.

Bezüglich α, V und L wird auf Fig. 1 verwiesen.

Fig. 1

zeigt eine Seitenskizze der Vorrichtung zur Verlegung der Faserbänder. Dabei sind (X) und (Y) die zu verlegenden Bänder, die das in seiner Breite reduzierte Band (3) ergeben. Auf den Rollen (a) liegen die Bänder (X) und (Y) nebeneinander. Die Rollen sind als b₁ und b₂ bzw. als Rolle c dargestellt.

Fig. 2

zeigt eine Draufsicht auf die Kabelverlegung mit den Einzelbändern (X) und (Y) und dem resultierenden Band (3), aus der α, L und V hervorgehen.

Fig. 3

zeigt eine Skizze der nachstehend beschriebenen Abzugsregelung des Kräuselkuchens vom Förderband. Das aufgetäfelte gekräuselte Faserband (4) wird auf dem Förderband (5) am Punkt (6) zu einem Faserband aufgezogen, das über die Zugmeßdose (7) und eine weitere Umlenkung (8) der Schneidevorrichtung (nicht gezeigt) zugeführt wird. Das Faserband wird durch Unterdruck, der durch den Ventilator (9) erzeugt wird, auf dem Förderband, das über die Rolle (10) und eine entsprechende, nicht gezeigte Rolle endlos umläuft, mit einer bestimmten Kraft festgehalten, deren Änderung über die Länge des gestreckten Faserbandes in der Fig. skizziert ist.

The device used in the process from a roller (a), at least two rollers (b₁), (b₂) etc. and a roller (c) and corresponding connecting parts which carry the rollers is characterized in that the axis of the roller (a ) with the axis at least one of the Rollers (b1), (b₂) etc. include an angle α of 1.5 to 7 °, preferably 2 to 5 ° and laying dimension V, distance L of the roller (a) from the rollers (b₁), (b₂) etc. and the angle α are linked by the following equation:

$\text{V = L · tan α}$

With regard to α, V and L, reference is made to FIG. 1.

Fig. 1

shows a side sketch of the device for laying the slivers. (X) and (Y) are the tapes to be laid, which result in the tape (3) being reduced in width. The belts (X) and (Y) lie side by side on the rollers (a). The roles are shown as b₁ and b₂ or as role c.

Fig. 2

shows a plan view of the cable laying with the individual tapes (X) and (Y) and the resulting tape (3), from which α, L and V emerge.

Fig. 3

shows a sketch of the deduction control of the crimp cake from the conveyor belt described below. The paneled crimped sliver (4) is drawn up on the conveyor belt (5) at point (6) to form a sliver, which is fed to the cutting device (not shown) via the tensile load cell (7) and a further deflection (8). The sliver is through Vacuum, which is generated by the fan (9), held on the conveyor belt, which rotates endlessly over the roller (10) and a corresponding roller, not shown, with a certain force, the change over the length of the stretched sliver in the Fig is outlined.

In order to fix and cool the crimped cable, horizontally running perforated band and metal fabric band coolers are used in particular, the circulation speed of which is 5 to 40 m / min. The sliver is in particular folded and placed on the cooling belt.

The slivers to be cooled are paneled on the conveyor belt with an occupancy of 10-15 kg / m².

The cooling capacity of a 10 m long and 40 cm wide cooling belt is up to 4,000 kg / h of fiber material.

The air which is sucked or blown through the fiber package expediently has a temperature which is as low as possible, in any case a temperature which is below that of the fiber sliver to be cooled. The air is preferably at ambient temperature.

The cooled cable is preferably fed to a cutting edge of a suitable design. When feeding the cable to the cutting edge, it is necessary for the thread cable to be transported with as constant a tension as possible. The cutting edge is preferably a rotor cutting edge.

It has been found that keeping the thread tension of a thread cable made of crimped threads constant, starting from a paneled fiber package, can be achieved if the fiber package is transported on a rotating, air-permeable conveyor belt, subjected to a vacuum on the conveyor belt and then pulled off by a drive, whereby it first runs through a tensile load cell and possibly further deflection elements, the tensile load cell comparing the actual thread tension with a predetermined setpoint value, braking the drive when the setpoint value is exceeded and accelerating when the value is undershot.

• a) ein luftdurchlässiges Förderband (5) mit Antrieb (10) und Ventilator (9)
• b) eine Zugmeßdose (7) und
• c) ein Abzugsorgan mit einem Antrieb (nicht auf Zeichnung dargestellt),

wobei Zugmeßdose und Antrieb so miteinander gekoppelt sind, daß die Zugmeßdose den Antrieb regelt und wobei der durch den Ventilator erzeugte Unterdruck auf das aufgelöste Faserband eine Reibkraft ausübt.The device used in the method according to the invention for keeping the thread tension of thread cables constant, starting from a paneled fiber package (4), contains

• a) an air-permeable conveyor belt (5) with drive (10) and fan (9)
• b) a load cell (7) and
• c) a trigger element with a drive (not shown in the drawing),

wherein the load cell and drive are coupled to one another in such a way that the load cell controls the drive and the vacuum generated by the fan exerts a frictional force on the loosened fiber sliver.

The air-permeable conveyor belt can also serve as a cooling belt for the crimped fiber package coming from the crimping device.

By driving the take-off process, the fiber package is loosened and drawn into a strand of crimped threads at a certain point. The dissolved fiber cable is held within the suction path with a force proportional to the negative pressure, the fiber bandwidth and the fiber ribbon length of the dissolved fiber ribbon. If this force is equal to the setpoint specified in the tensile load cell, the drive of the puller pulls the fiber cable off at a uniform speed. If the force with which the differential pressure tries to hold the fiber cable on the conveyor belt falls below the specified target value, the strain gauge regulates the drive of the pull-off device in such a way that the thread cable is pulled off at an increased speed. This shifts the point at which the fiber bundle is released against the direction of the thread running on the conveyor belt. This increases the length of the sliver. The force with which the vacuum holds the sliver increases, exceeds the setpoint of the tensile load cell, which then brakes the drive of the take-off process. By braking the take-off member, the point at which the fiber package is broken down into a fiber sliver moves in the direction of the thread, which reduces the force exerted on the fiber sliver by the differential pressure, since the fiber sliver length becomes smaller.

With a suitable setting on the tensile load cell, it can be achieved that the point at which the fiber package is broken down into a fiber band comes to lie within a certain range, the point shifting only insignificantly during operation.

example

Two slivers of 200 ktex 3.3 dtex single titer made of polyacrylonitrile, each with a width of 350 mm, were subjected to the treatment steps of washing, stretching and drying next to each other and then pulled out of the dryer using a trio (a). Subsequently, a sliver was placed over the rollers (b₁) and (b₂) and thereby laid on the common axis of the roller (c). The two bands then wrapped around the roll (c) one above the other and were then fed to the crimping device.

The distance between the rollers (a) and (b) at the same height was 4.5 m. Roll (b₂) was placed 40 cm above the extension of the horizontal through (a) and (b₁) and above a point 40 cm away from (b₁). Roll (c) was placed 80 cm below a point on the horizontal extension through (a) and (b₁) which was 20 cm from (b₁). The angle α was 2.5 °.

This resulted in a laying factor V of 200 mm.

Before entering the stuffer box at 80 m / min, the slivers were heated to 90 - 95 ° C using saturated steam. The crimping roller pressure was 600 N / cm, the chamber width was 350 mm, and the stuffer box pressure was 5 N / cm². The crimped fiber tapes left the crimping device as an endless package ("cake") with a stuffer box width and approx Cooler and fuser supplied. The folding factor (quotient of tape entry speed into the crimp and tape exit speed from the crimp) of the cake was 1:10.

The "cake" was taken from the conveyor belt of the cooling and fixing apparatus, the belt speed being 12% greater than the speed of the crimp cake pushed out of the crimping machine. This improved the air permeability of the fiber package. With a dwell time of approx. 1 min, the fiber material reached ambient temperature (cooling air approx. 12,000 m³ / h) and was now drawn back onto the stretched strip length. During this process, a tensile force of 4 N / ktex built up in the belt, with which it was fed to a rotor cutting edge, which cut the material into stacks at a speed of approx. 68 m / min. The width of the throat of the knife ring was 80 mm, the cutting ring diameter approx. 1,200 mm. In further treatment steps, the cut material was steamed and then packed.

The application test of the fiber material gave the following results: Ripple: 10% Residual ripple: 6.5% Resistance: 42% Number of sheets: 34 per 10 cm Average stack length: 55 mm Yarn boiling shrink: 2% Adhesive force: 72 cN / ktex Max. Carding speed: 120 m / min

Claims (3)

1. A method whereby washed and dried fibre tows having a weight of at least 250 ktex are after-treated by crimping, fixing and cooling, characterised in that the width of the sliver of tow, which leaves the drier at a packing density of not more than 5 ktex/cm, is reduced by at least 50% of the original width with a corresponding increase in packing density, the tow is crimped in a compression chamber at a pressure of 1.5 to 6 N/cm² and a temperature of 80 to 95°C, the crimping is fixed in or immediately after the compression chamber, and the tow is placed on the surface of an air-cooled conveyor belt, where cooling air is blown or sucked through the belt and the stack of fibres.
2. A method according to claim 1 in which the sliver width is reduced as follows: the sliver to be reduced in width is drawn in the form of at least two individual slivers off the take-off unit (a), the individual slivers are guided over separate rollers (b₁, b₂, etc.), and are superposed and combined in a single sliver on an additional roller (c), and the axis of roller (a) includes an angle of 1.5 to 7° with the axis of at least one of the rollers (b₁, b₂) etc.
3. A method according to claim 1 in which the thread tow is supplied to a tearing converter or a cutter at a constant tension such that the stack of fibres is conveyed on an air-permeable conveyor belt, is subjected to a negative pressure on the belt and is then opened to form a drawn sliver, which is acted upon by a frictional force which is proportional to the drawn length in the negative-pressure region and generates a thread tension which is measure by a draft gauge and compared with a set value, and the drive is slowed down when the set value is exceeded and accelerated when the value falls below.

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