EP0268031B1 - Stuffer box and method for making crimped synthetic fibres - Google Patents

Description

The invention relates to a method for producing crimped synthetic fibers according to the upsetting method, in particular for acrylic fibers, and to a device for carrying out the method. In particular, the invention relates to a method for continuous compression crimping during a continuous fiber spinning and post-treatment process with high strip weights above 100,000 dtex and at production speeds above 200 m / min.

Methods and devices for crimping synthetic fibers are known. In the most preferred embodiment of the compression crimp, the fiber cable is fed through two guide rollers to a crimping chamber in which the cable accumulates and in which it is retained under pressure, the cable laying in small turns and forming the so-called crimp, see e.g. US-A-2 862 279. Three of the four walls of the crimping chamber are fixed, while the fourth is formed by a resilient plate which is resilient to pressure. When the internal pressure of the crimped cable has become equal to the pressure on the movable plate, it is pushed up and the compressed cable leaves the chamber through the slot thus formed.

It has now been shown that the previously known methods and devices of this type have the disadvantage, in particular when crimping acrylic fiber cables, that they can only crimp cables up to production speeds of approximately 150-200 m / min. At higher speeds, above approx. 200 m / min, caking of the acrylic fiber cables occurs. The reason for this is that at high speeds and large cable weights, such as those primarily used in continuously running spinning and aftertreatment processes, e.g. are described in EP-A-98 477, occur, large amounts of fiber accumulate in the stuffer box in the shortest possible time, the built-up kinetic energy of which must be dissipated in order to avoid caking. There was no lack of attempts, e.g. to take this into account by cooling the feed rollers, by special routing of the crimped cable (DE-A-1 435 438) or by wetting the fiber cable with moisture (US-A-3 041 705). However, cooling and special cable routing in the stuffer box alone do not allow high production speeds to be achieved, such as occur in continuous spinning and post-treatment processes. The crimping of moist acrylic fiber cables also has the disadvantage that the crimping is very unstable and often leads to so-called hacking points during crimping. Hack points are understood to mean crimping damage in the fiber cable, which lead to holes in the crimped filament structure and give rise to stack shortening and short fibers.

It was therefore an object of the present invention to provide a continuous crimping process, in particular for acrylic fiber cables of high strip weights, preferably above 100,000 dtex, for high production speeds, primarily greater than 200 m / min, and an apparatus for carrying out the process.

• a) Deckel und/oder Boden beweglich angeordnet sind und
• b) in Arbeitsstellung der Abstand zwischen Deckel und Boden bei der Eingangsöffnung kleiner als der Abstand zwischen Deckel und Boden bei der Ausgangsöffnung ist.

A method has now been found for crimping synthetic fibers with a stuffer box crimp, which comprises an inlet opening, a stuffer box with bottom, cover and side parts and an outlet opening, characterized in that a stuffer box is used in which

• a) lid and / or bottom are arranged movably and
• b) in the working position, the distance between the lid and bottom at the entrance opening is smaller than the distance between the lid and bottom at the exit opening.

The invention further relates to a device for stuffer box crimping of synthetic fibers with an inlet opening, a stuffer box with bottom, lid and side parts and an outlet opening, characterized in that the lid and / or bottom of the stuffer box are movably arranged and in the working position the distance between the lid and Bottom at the entrance opening is smaller than the distance between the lid and bottom at the exit opening.

In a preferred embodiment, the synthetic fibers to be crimped are attracted by a pair of squeeze rollers and pushed into the inlet opening.

In a further preferred embodiment, the cover and / or base are arranged such that they can move about a pivot point near the inlet opening, preferably about the axis of a nip roller of the pair of nip rollers.

In a further preferred embodiment, the side walls and cover of the stuffer box are fixed and the bottom is arranged to be movable about the axis of the nip roller.

• a) Die Fläche F₂ der Seitenteile von Stauchkammerteil 2 beträgt mindestens 85 % der Fläche F₁ der Seitenteile von Stauchkammerteil 1. Dieser mit V₁ bezeichnete prozentuale Anteil beträgt also mindestens 85 %.

In a particularly preferred embodiment, the stuffer box is dimensioned such that when the lid and base are placed in parallel, a stuffer box part 2 adjoining the inlet opening is formed, in which the distance from the lid to the bottom increases in the direction of the outlet opening. Here is preferably the lid of stuffer box part 1 in Angle to the cover of stuffer box part 2, while the bottom is formed in both parts by a single flat surface. In a very particularly preferred embodiment, the following applies:

• a) The area F _{2 of} the side parts of stuffer box part 2 is at least 85% of the area F _{1 of} the side parts of stuffer box part 1. This percentage, denoted by V ₁ , is therefore at least 85%.

• b) Das Verhältnis V₂ von Bandgeschwindigkeit v in (m/min) des der Stauchkammer zugeführten Faserkabels zur Verweilzeit t (in Sekunden) des Faserkabels in der Stauchkammer.

In addition to V _1, the introduction of the following additional product- and process-specific sizes has proven useful for describing the complex crimping processes during upsetting crimping of acrylic fibers:

• b) The ratio V ₂ of the belt speed v in (m / min) of the fiber cable fed to the stuffer box to the dwell time t (in seconds) of the fiber cable in the stuffer box.

The relationship applies here:

• c) Das Verhältnis V₃ von Durchsatzmenge m (gemessen in g/Sekunden) an Faserkabel durch die Stauchkammer zur Verweilzeit t (gemessen in Sekunden). V₃ ist vorzugsweise kleiner 50 g/sec². Bei Überschreitung des angegebenen Grenzwertes infolge zu hohen Durchsatzes oder zu geringer Verweilzeit werden wiederum verbackene Acrylfaserkabel beobachtet.
  

• d) Die Dichte a der Acrylfaserkabel in der Stauchkammer. Die Dichte δ (gemessen in g/cm³) läßt sich aus dem Verhältnis des Kräuselkammerinhaltes in Gramm zum Kräuselkammervolumen in cm³ berechnen.
  

This ratio V ₂ represents a so-called acceleration factor and makes a statement about the crimpability of acrylic fibers. At production speeds above 200 m / min and cable thicknesses greater than 100,000 dtex, V _{2 should} preferably be less than 100 m / min. sec - be ¹ . If V _{2 is} greater than 100, the crimping chamber can be too small and the material baked. Baking is understood to mean interwoven and glued capillaries that can no longer be separated properly even after cutting and dissolving during further processing, for example using cards and cards, and lead to bristles and unclean yarns.

• c) The ratio V ₃ of throughput quantity m (measured in g / seconds) of fiber cable through the stuffer box to the residence time t (measured in seconds). V ₃ is preferably less than 50 g / sec ² . If the specified limit value is exceeded due to too high throughput or too short a dwell time, baked acrylic fiber cables are observed.
  

• d) The density a of the acrylic fiber cables in the stuffer box. The density δ (measured in g / cm ³ ) can be calculated from the ratio of the crimp chamber content in grams to the crimp chamber volume in cm ³ .
  

The density 0, which by definition does not mean the actual material density of acrylic fibers, but the material density of the fiber cable in the stuffer box, also says something about the state of crimp of the acrylic fiber cable in the stuffer box. If the density 0 is less than 0.2 g / cm ³ , there are usually only slightly crimped, almost smooth fiber cables.

In the previously known manufacturing processes of acrylic fibers, crimping speeds above 200 m / min are not known. While in wet spinning the spinning speed in the precipitation bath is a maximum of approx. 15 m / min and after a 1: 6 to 1:10 stretching production speeds of maximum 150 m / min are reached, the speed ratios in dry spinning are similar. Here is spun from ring nozzles with a much smaller number of holes compared to wet spinning in shafts with higher spinning take-offs of approx. 200 - 300 m / min, but the spun material is first collected in so-called spinning cans and then washed., Stretched approx and curled. Here speeds of maximum 150 - approx. 200 m / min are also achieved. Higher speeds are inefficient because the time-determining factor is the solvent removal when washing the spinning material. The need only existed with the advent of continuous spinning and post-treatment processes of dry-spun acrylic fiber cables ability to adapt the crimping speed to the high production speeds as described, for example, in EP-A-98 477. The crimping method described according to the invention is therefore preferably suitable for continuously dry-spun acrylic fiber cables with high strip weights above 100,000 dtex and for production speeds of up to approximately 1,500 m / min, preferably 500-1,200 m / min.

Fig. 1 shows a device according to the invention with a pair of squeeze rollers with the rollers (1) and (2), an inlet opening (3), a stuffer box with bottom (4), lid (5) and side parts and an outlet opening (6) in the working position. The stuffer box basically consists of a pair of squeeze rolls with rolls (1) and (2) and a downstream chamber. The side walls of this chamber are fixed, as is the chamber cover (5). The "chamber floor" (4) is movably mounted. At the end of the chamber floor there is a pressure cylinder (7) which exerts an adjustable force on the movable plate of the chamber floor.

How it works:

In the normal state with the crimp working, the exit height of the crimp chamber is between 40 and 50 mm. The working thrust of the printing cylinder, which is attached to the end of the movable plate, is therefore approx. 10 mm.

In the working position in the conventional stuffer box crimping method, the distance between the lid and the bottom of the crimping chamber inlet opening is generally greater than the distance between the lid and the bottom of the outlet opening. In the present invention, the front crimp part operates identically. However, the downstream second stuffer box part 2 is larger in the outlet opening between the bottom and the lid than the inlet opening (cf. FIG. 1).

In other words:

In Fig. 1 the (fixed) cover is flattened in the second stuffer box part.

Likewise, for example, the bottom could be flattened with the movable plate instead of the fixed cover. A further possibility arises by applying an adjustable piston force to the beveled surface with a pivot point at the beginning of this surface, as a result of which the stuffer box crimping process can be varied within wide limits. In any case, it is preferred that the area ratio of F ₂ : Fi = defined in the ratio V _{1 is} at least 85%, the other specified boundary conditions V ₂ = less than 100, V ₃ less than 50 and the material density 0 greater than 0.2.

The compression crimping method according to the invention is, however, not only limited to a continuous production method of dry-spun acrylic fibers. Likewise, dry or wet-spun acrylic fiber cables, which have been washed and, if appropriate, drawn and dried and are present, for example, in spinning cans, can subsequently be crimped at speeds above 200 m / min using the apparatus described. Other synthetic fibers can also be crimped according to the invention, in particular polyester and polyamide fibers. The method according to the invention permits continuous crimping of the stuffer box at high production speeds, in particular according to the continuous methods known from EP-A-98 477, for example.

The following examples serve to explain the invention in greater detail, without restricting it itself.

example 1

A prepared with 100 m / min spin draw dry acrylic fiber cable with a total titer of 626,000 dtex is stretched 1: 6-fold over heating rollers at 100 ° C belt temperature and fed to a stuffer box, as shown in FIG. 1. The tape weight presented was 10.4 g / m and the crimping speed 600 m / min. Crimping was carried out with a force of 294 N (30 kp) on the movable plate and a force on the infeed rollers of 17640 N (1,800 kp). The cable was further subjected to 10 kg / h spray steam before entering the crimping chamber. The crimp chamber length was 510 mm, the crimp chamber width 75 mm and the crimp chamber height 40 mm. The expanded opening, the crimping chamber wall opposite the movable plate, begins after a chamber length of 290 mm (see Fig.). The clear opening at the end of the crimp chamber is 50 mm. The area of the unchanged crimp chamber part F _{1 is} calculated to 116 cm ² and the area of the modified crimp chamber part F _{2 is} calculated to 99 cm ² . The feed rollers of the stuffer box can be tempered with water. The roller temperature was 70 C. The crimped fiber cable is then damped without tension and cut into staple fibers of 60 mm length. The single fiber end titer is 2.2 dtex. The crimson The fiber development is 19.5%. The flake has an adhesive force of 68 centi Newton / Ktex. The processing speed on the high-performance card is 110 m / min.

The ratio V ₁ is:

The content of the compression crimp chamber is 820 g. For an acrylic fiber cable with a tape weight of 10.4 g / m, a throughput of 104 g / second results at a production speed of 600 m / min. Accordingly, the dwell time in the stuffer box 820 is: 104 = approx. 7.9 seconds.

The acceleration factor V ₂ is therefore:

The ratio V _{3 is} calculated as follows:

The material density 0 of the fiber cable in the crimping chamber is:

Examples 2-12

The following table shows further examples of the crimping of acrylic fiber cables with different sized crimping devices for different strip weights and crimping speeds up to 1,200 m / min. The values of the corresponding crimp parameters and the assessment of the crimp are also given.

Example 2 shows that even high strip weights of, for example, 25 g / m, corresponding to 250,000 dtex, can be crimped using the process according to the invention.

Example 3 shows that if the acceleration factor V _{2 is} greater than 100, the material can cake.

In example 4 it is shown that the area ratio V _{1 should} preferably be greater than 85%, because otherwise the pent-up kinetic energy in the unchanged crimping chamber part would become too large and the material could become matted.

Example 5 shows that by increasing the area fraction F ₂ a perfect compression crimp can be carried out again.

Example 6 shows that with low crimp chamber filling and thus low material density in the crimp chamber, under certain circumstances only smooth fibers are obtained.

Example 7 shows that if the limit values for the parameters V ₂ and V _{3 are} not adhered to, caking of the acrylic fiber cable can occur.

Examples 8-10 show that, by appropriately dimensioning the crimping chamber, even high strip weights at very high crimping speeds can be properly crimped according to the inventive method.

Finally, in Examples 11 and 12 it is shown that the compression crimping method according to the present invention is also successfully used for smaller strip weights below 100,000 dtex can be.

(vergl. Riggert: Kräuselung von Chemie-Schnittfasern und -Kabeln und ihre Bedeutung für die Weiterverarbeitung in Melliand Textilberichte 4/1977 Seite 274) bestimmt.In the examples, the crimping of the fiber cable was based on:

(cf. Riggert: Crimping of chemical cut fibers and cables and their importance for further processing in Melliand Textile Reports 4/1977 page 274).

• 1 g = Länge des gestreckten, entkräuselten Zustandes
• 1 z = Länge des zusammengezogenen, gekräuselten Zustandes

It means:

• 1 g = length of the stretched, uncrimped state
• 1 z = length of the contracted, crimped state

For wool-type polyacrylonitrile fibers, the crimp is normally around 15-22% (see: Riggert Melliand Textilbereichte 4/1977, Table 1, page 278).

The adhesive force (measured in cN / Ktex) and the processing speed of the crimped cut fibers on the high-performance card (measured in m / min) were used as further evaluation criteria.

Claims (9)

1. A method for crimping synthetic fibres using a device comprising an inlet opening, a stuffing box having a base, lid and side portions and an outlet opening, characterised in that a stuffing box is used in which

a) the lid and/or base are arranged so as to be displaceable and

b) in the operative position the distance between the lid and base is smaller in the case of the inlet opening than the distance between the lid and base in the case of the outlet opening.

2. A method according to claim 1, characterised in that the synthetic fibres are pushed into the inlet opening by means of a pair of crushing rollers.

3. A method according to claim 1, characterised in that the lid and/or base are movable about a pivot point in the vicinity of the inlet opening.

4. A method according to claim 1, characterised in that a stuffing box is used, whose side walls and lid are immovably arranged and whose base is movable.

5. A method according to claim 3, characterised in that with the parallel position of the lid and base in a stuffing box section 1 adjoining the inlet opening, an adjoining stuffing box section 2 is formed, in which the distance between lid and base increases in the direction of the outlet opening.

6. A method according to claim 5, characterised in that the lid of the stuffing box section 1 is arranged at an angle to the lid of the stuffing box section 2 and the base in both stuffing box sections is formed by an even surface.

7. A method according to claim 5, characterised in that

a) the surface F₂ of the side portions of the stuffing box section 2 corresponds to at least 86% of the surface F₁ of the side portions of the stuffing box section 1,

b) the acceleration factor V₂ from the ratio of strip velocity v(m/min) to dwell time t (sec) in the crimping chamber is less than 100,

c) the ratio V₃ of throughput quantity m (g/sec) to dwell time t (sec) is less than 50, d)

8. A method according to at least one of the preceding claims, characterised in that the synthetic cable is an acrylic fibre cable and is introduced into the stuffing box at a velocity of at least 500 m/min.

9. A device for crimping synthetic fibres comprising an inlet opening, a stuffing box having a base, lid and side portions and an outlet opening, characterised in that a stuffing box is used in which

a) the lid and/or base are arranged so as to be displaceable and

b) in the operative position the distance between the lid and base is smaller in the case of the inlet opening than the distance between the lid and base in the case of the outlet opening.

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