EP0268031B2 - Stuffer box and method for making crimped synthetic fibres - Google Patents

Description

The invention relates to a process for the production of crimped synthetic fibers by the upsetting process, in particular for acrylic fibers, and to a device for carrying out the process. In particular, the invention relates to a method for continuous compression crimping during a continuous fiber spinning and aftertreatment 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, the plate 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, in particular when crimping acrylic fiber cables, have the disadvantage 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 continuous spinning and post-treatment processes, such as e.g. are described in EP-A-98 477, occur, accumulate large amounts of fibers 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 guidance 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 wet 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 crimp damage in the fiber cable, which lead to holes in the crimped filament structure and give rise to shortening of the stack 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 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. The solution is indicated by the features of the characterizing part of claim 1.

The invention further relates to a device for crimping synthetic fibers with the further features of the preamble of patent claim 5
Starting from this device, the features are specified in the characterizing part of claim 5 to achieve the object.

In a particularly preferred embodiment, the stuffer box is dimensioned such that that the area F₂ of the side parts of stuffer box part 2 is at least 85% of the area F₁ of the side parts of stuffer box part 1.

• 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.
  Hierfür gilt die Beziehung:
  
     Dieses Verhältnis V₂ stellt einen sogenannten Beschleunigungsfaktor dar und macht eine Aussage über die Kräuselbarkeit von Acrylfasern Bei Produktionsgeschwindigkeiten oberhalb 200 m/min und Kabelstärken größer 100'000 dtex sollte V₂ vorzugsweise kleiner 100 m/min . sec⁻¹ sein. Ist V₂ größer 100, dann kann die Kräuselkammer zu klein sein und das Material verbacken. Unter Verbacknung werden ineinader verflochtene und verklebt Kapillaren verstanden, die sich auch nach dem Schneiden und Auflösen bei der Weiterverarbeitung, z.B. über Krempeln und Karden, nicht mehr einwandfrei trennen lassen und zu Borsten und unsauberen Garnen führen.
• 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 δ 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.

   Die Dichte δ, worunter defintionsgemäß nicht die eigentliche Stoffdichte von Acrylfasern, sondern die Materialdichte des Faserkabels in der Stauchkammer verstanden wird, sagt ebenfalls etwas über den Kräuselzustand des Acrylfaserkabels in der Stauchkammer aus. Beträgt die Dichte δ weniger als 0,2 g/cm³, so liegen in der Regel nur schwach gekräuselte, nahezu glatte Faserkabel vor.In addition to V₁, the introduction of the following additional product and process-specific sizes has proven useful for describing the complex crimping processes for upsetting acrylic fibers:

• b) The ratio V₂ of belt speed v in (m / min) of the fiber cable fed to the stuffer box to the residence time t (in seconds) of the fiber cable in the stuffer box.
  The relationship applies here:
  
  This ratio V₂ 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, V₂ should preferably be less than 100 m / min. be sec⁻¹. If V₂ is greater than 100, the crimping chamber can be too small and the material baked. Baking is understood to mean interwoven and glued capillaries, which 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 V₃ of flow rate m (measured in g / seconds) of fiber cable through the stuffer box to the residence time t (measured in seconds). V₃ is preferably less than 50 g / sec². 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 δ of the acrylic fiber cables in the stuffer box. The density δ (measured in g / cm³) can be calculated from the ratio of the crimp chamber content in grams to the crimp chamber volume in cm³.

The density δ, which by definition is not to be understood as the actual material density of acrylic fibers, but rather 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 δ is less than 0.2 g / cm³, 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 spinning material is first collected in so-called spinning cans and then washed., Stretched approx. 1: 4 times, dried 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. Only with the advent of continuous spinning and post-treatment processes for dry-spun acrylic fiber cables was there a need to 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 chamber part works identically. However, the downstream second stuffer box part 2 is larger in the outlet opening between the bottom and the lid than the entry 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. Another 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. It is preferred in any case that the area ratio of F₂: F₁ = at least 85% defined in the ratio V₁ and the other specified boundary conditions V₂ = less than 100, V₃ less than 50 and the material density δ greater than 0.2 are observed.

However, the upsetting process according to the invention is not only limited to a continuous production process 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 stuffer box crimping at high production speeds, in particular according to the continuous methods known from, for example, EP-A-98 477.

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

example 1

A 100 m / min spinning take-off and prepared acrylic fiber cable with a total denier of 626,000 dtex is stretched 1: 6-fold over heating rollers at a belt temperature of 100 ° C 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 performed 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 enlarged 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 crimping chamber is 50 mm. The area of the unchanged crimp part F₁ is calculated to 116 cm² and the area of the modified crimp part F₂ is calculated to 99 cm². 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 60 mm long. The single fiber end titer is 2.2 dtex. The curl the fiber 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.

   Der Inhalt der Stauchkräuselkammer beträgt 820 g. Für ein Acrylfaserkabel von Bandgewicht 10,4 g/m ergibt sich bei einer Produktionsgeschwindigkeit von 600 m/min ein Durchsatz von 104 g Sekunde. Demnach beträgt die Verweilzeit in der Stauchkammer 820:104 = ca 7,9 Sekunden.The ratio V₁ 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 results at a production speed of 600 m / min. Accordingly, the dwell time in the stuffer box 820 is: 104 = approx. 7.9 seconds.

   Das Verhältnis V₃ errechnet sich zu:

   Die Materialdichte δ des Faserkabels in der Kräuselkammer beträgt:

The acceleration factor V₂ is accordingly.

The ratio V₃ is calculated as:

The material density δ 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 crimping parameters and the evaluation of the crimping 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 with an acceleration factor V₂ greater than 100 the material can bake.

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 crimp chamber part become too large and the material can become matted.

Example 5 shows that by increasing the proportion of area F₂ a perfect compression crimp can be carried out again.

In example 6 it is shown 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 V₂ and V₃ 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).

1g =

Länge des gestreckten, entkräuselten Zustandes

1z =

Länge des zusammengezogenen, gekräuselten Zustandes

   Für Polyacrylnitrilfasern vom Woll-Typ liegt die Einkräuselung normalerweise bei ca. 15 - 22 % (vergl.: Riggert Melliand Textilbereichte 4/1977, Tabelle 1, Seite 278).It means:

1g =

Length of the stretched, crimped state

1z =

Length of the contracted, curled condition

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 (7)

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 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, the synthetic fibres are pushed into the inlet opening by means of a pair of crushing rollers, the lid and/or base are movable about a pivot point in the vicinity of the inlet opening, 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, the lid of the stuffing box section 1 being arranged at an angle to the lid of the stuffing box section 2 and the base in both stuffing box sections being formed by an even surface, and the strip weight of the fibres when entering the stuffing crimping chamber exceeds 100,000 dtex with a fibre input velocity greater than or equal to 200 m/min.
2. 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.
3. A method according to claims 1 and 2, characterised in that

   a) the surface F₂ of the side portions of the stuffing box section 2 corresponds to at least 85% of the surface F₁ of the side portions of the stuffing box section 1,

   b) the acceleration faction 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) the material density is:

   

   > 0.2.
4. A method according to claims 1 to 3, 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.
5. A device for crimping synthetic fibres with a strip weight exceeding 100,000 dtex and an input velocity greater than or equal to 200 m/min, comprising an inlet opening, a stuffing box having a base, lid and side portions and an outlet opening, characterised in that 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, a pair of crushing rollers is arranged upstream of the inlet opening, the lid and/or base are movable about a pivot point in the vicinity of the inlet opening, 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, 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.
6. A device according to claim 5, characterised in that the side walls and lid of the stuffing box are immovably arranged and the base is movable.
7. A device according to claims 5 and 6, characterised in that the surface F₂ of the side portions of the stuffing box section 2 corresponds to at least 85% of the surface F₁ of the side portions of the stuffing box section 1.

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