GB2024096A - A spinning head for producing multicomponent filaments with matrix filament structure - Google Patents

Abstract

The spinning head comprises separate feed and distributing chambers (4, 3) for a least two synthetic polymer components each of differing properties and a die plate (2) with a plurality of spinning openings. Each spinning opening is immediately preceded by its own mixing system (7) for combining the polymer components to form the matrix-filament structure. The mixing systems each comprise a stack of metal foils. Each metal foil has a plurality of outer through flow openings at its periphery and/ or one or more inner through flow openings at its centre. Some of the foils are also provided with radially extending guide slots which communicate with the inner and/or outer through flow openings. The mixing systems allow the production of a stable filament cross-sectioned geometry with a controlled mutual association of their polymer components. <IMAGE>

Description

SPECIFICATION A spinning head for producing multicomponent filaments The present invention relates to a spinning head for producing multicomponent filaments with a matrix-filament structure comprising separate feed and distributing chambers for at least two synthetic polymer components differing from one another in their properties and a die plate with a plurality of spinning openings, each individual spinning opening being immediately preceded by its own mixing system for combining the polymer components to form a matrix-filament structure.

One such spinning head is known from British Patent No. 1,171,843 (Figs. 5 to 7 thereof). With this spinning head, it is possible to produce filaments having a matrixfilament structure in which a number of very fine microfilaments (segments) of component A is completely surrounded by and separated from a matrix component B. In this case, twocomponent structures having a core-jacket or side-by-side configuration are initially preformed and a plurality of these preformed structures is collected in a conically tapering chamber which terminates in a spinning opening and is extruded through the spinning openings.

In connection with the terminology of twocomponent filaments, reference is made P. A.

Kotch, Faserstoff-Tabellen "Bikomponenten- fasern" February 1 970 Edition, Chapter 1, according to which, in addition to filaments having a side-by-side structure (S/S type) or a core-jacket structure (C/C type) with a symmetrical or assymmetrical configuration, there are also filaments having a matrix/fibril structure (M/F type). Matrix-fibril structures are normally produced from a polymer mixture so that the fibrils present in the matrix of the drawn filament are only very short (staple fibre character, cf. Fig. 4 of British Patent No.

1,171,843). More recently, attempts have been made to produce filaments of particularly fine denier by dispersing one polymer component in another (the matrix component) in such a way that a plurality of very long microfilaments is present in the matrix during the spinning and drawing process and can be separated from the matrix either by mechanical after-treatment or by chemical aftertreatment. This is also the objective of British Patent No,1,171,843 (cf. Figs. 1 to 3 thereof).Although it is possible with the spinning head according to Figs. 5 to 7 of British Patent No. 1,171,843 to produce matrixfilament structures of this type (which is the term used for these structures in contrast to the matrix-fibril structures), the arrangement of the segments relative to one another in the cross-section of the filament and the separation of the segments by the matrix component are entirely random in-character. It is not possible to produce special cross-sectional geometries which embody a particular form of the individual segments. Neither does the principal on which the known spinning head is based allow a filament having a uniform cross section over its entire length to be produced, let alone allowing the same filament-cross sections to be reproducibly obtained from a plurality of spinning openings.

An object of the present invention is to redesign the mixing system immediately precending each individual spinning opening for combining the polymer components to form a matrix-filament structure in a spinning head of the type referred to at the beginning in such a way that it is possible to produced filaments in which the individual segments are present in a controlled arrangement and configuration in the filament cross-section which remains uniform along each filament and may be the same from one spinning opening to the next.

According to the invention there is provided a spinning head for producing multicomponent filaments with a matrix-filament structure comprising separate feed and distributing chambers for at least two synthetic polymer components the components having different proper ties from each other, a die plate with a plurality of spinning openings, each individual spinning opening being immediately preceded by a respective mixing system for combining the polymer components to form a matrixfilament structure, each of the mixing systems preceding the individual spinning openings comprising a plurality of metal foils stacked one on top of the other each metal foil comprising a plurality of outer throughflow openings at the periphery thereof and/or at least one inner throughflow opening substantially as the centre thereof, at least two of the metal foils being provided with radially extending guide slots which communicate with the inner and/or outer throughflow openings.

The mixing systems according to the invention with differently shaped metal foils achieve the controlled division of the polymer streams by virtue of the fact that, during their passage through these mixing systems, the polymer streams repeatedly have to make a perpendicular movement relative to the direction of flow by means of the radially extending guide slots. In this way, the individual components are divided up, repeatedly branched and delivered. This principal of division enables the branched component streams to be combined in a controlled and ordered manner.By virtue of the small dimensions of the metal foil pack (the diameter of a foil amounts to only 1 cm for a thickness of preferably less than 0.2 mm), the components are divided up and associated over a very short distance and the residence time of the melts in the mixing system is correspondingly short, so that temperature differences in the die construction can not adversely affect the individual flow rates. According to the invention, the dead flow spaces which are unavoidable in the known spinning head construction for collecting the individual two-component structures in front of the spinning jet no longer occur.In the spinning head according to the invention, the main pressure drop occur in the mixing systems, i.e. in the passages formed by the throughflow openings and in the guide slots, so that the spinning openings or the flow passages optionally preceding them merely serve the purpose of calibrating the filaments.

The individual metal foils of a mixing system may differ widely in shape. By using modern techniques (stamping, photochemical processes), it is possible to incorporate throughflow openings and/or guide slots of any shape with minor tolerance fluctuations.

The most simple metal foils have only one inner throughflow opening and/or several (generally two, three or more) outer throughflow openings.

It is possible to use for each individual spinning opening a separate mixing system individually assembled for a certain filament cross-sectional geometry. The mixing systems are preferably identical in structure for all the spinning openings of a spinning head. In order to avoid errors in the structure of the individual mixing systems by confusion between individual metal foils, it is particularly advisable in this case to connect the corresponding metal foils of all the mixing systems of a spinning head to one another by webs.

Embodiments of the present invention are provided by way of example in the following description with reference to the accompanying drawings, wherein: Figure 1 is the spinning part of a spinning head according to the invention with flat metal foils inserted therein; Figure 2 is a mixing sytem with conically arched metal foils; Figure 3 is part of a spinning head similar to that used in Fig. 1 on a larger scale; Figure 4 is a spinning opening with the inner region of a preceding mixing system on a larger scale than that used in Fig. 3; lures 5 to 11 each show differently shaped metal foils; Figure 12 shows the separated metal foils of part of a complete mixing system;; Figure 13 shows a plurality of identical metal foils connected to one another by webs, and Figures 14 to 16 each show different crosssections of filaments produced with a spinning head according to the invention.

Fig. 1 diagrammatically illustrates the spinning part of a spinning head comprising a rear die plate 1 and front die plate 2. Situated between the two die plates is the distributing chamber 3 for component B. Component A is delivered through feed passages 4 in the rear die plate 1. The front die plate 2 comprises spinning openings 6, optionally preceded by flow passages 5. On the delivery side, the front die plate 2 comprises recesses 29 for accommodating mixing systems 7 which are pressed against the front die plate 2 by the rear plate 1 via feed elements 8 (with feed pipes 8a; 8bfor components A and B, respectively). In Figure 1, the mixing systems 7 comprise a plurality of flat metal foils stacked one on top of the other, as shown in more detail in Fig. 3.The individual metal foils are held in their relative positions to one another by centring pins 10 (Fig. 3).

Fig. 2 shows part of a spinning head similar to that illustrated in Fig. 1. The mixing system 9 comprises conically preformed metal foils (cf Fig. 9), the recess 30 and contact surface of the feed element 8' being designed accordingly.

The mixing system is described in the following with reference to Fig. 4 which shows part of a spinning head similar to that shown in Fig. 1 but on a larger scale. In this case, the mixing system is made up of three different types of metal foil 7.1; 7.2; 7.3 which are stacked in an alternating sequence. Details of the metal foils are shown in Figs. 5 to 7. All the metal foils 7.1; 7.2; 7.3 comprise central throughflow openings 18; 181, of which the diameter corresponds to that of the flow passage 5 preceding the spinning opening, and peripheral through flow openings 17; 17, which align with one another in the mixing system. The individual metal foils can be correctly and exactly associated with one another by means of centring recesses 26 at the circumstance of the metal foils.

In the metal foil 7.1 (Fig. 5), the throughflow openings 17, (for component B) communicate through radially extending guide slots 20 with the central throughflow opening 18,. Component B flows on the one hand through the guide slots 20 to the middle and, on the other hand, to the throughflow openings 1 7 in the metal foil 7.2 and the metal foil 7.3. Component A, which flows through the openings 17 in the metal foil 7.1, advances to the throughflow openings 1 7 in the metal foil 7.2 and to the throughflow openings 17, in the metal foil 7.3 where it then has the opportunity to flow through guide slots 20 to the central throughflow opening 18, (Fig. 7).

In Figs. 5 to 7 sections IV-IV relate to the section illustrated in Fig. 4. Component B Flows to the middle through the metal foil 7.1, whilst component A flows through the metal foil 7.3. In this way, a controlled mutual associated (layering) of the two components is developed in the passage formed by the central throughflow openings 18, 18,, enabling filament cross sections which are uniform, even from one spinning opening to the next, to be produced.

As shown in Fig. 4, a displacement body 11 may be provided in the passage formed by throughflow openings 18, 18,, providing for uniform rates of flow along the passage.

Fig. 8 shows a preferred embodiment of a metal foil corresponding to Fig. 5. This metal foil 7.4 is characterised in that the radially extending guide slots 21, which come from the peripheral throughflow openings 17,, open tangentially into the central throughflow opening 18,. By virtue of the fact that the components are tangentially fed into the central passage, the divided polymer streams are interlinked with one another in the filament cross-section.

The metal foil 1 2 shown in Fig. 9 comprises a missing segment 27. In this way, the metal foil can be preformed into a cone and inserted into recesses corresponding to Fig. 2.

Figs. 10 and 11 shows two metal foils 13; 1 4 which may be inserted together, comprising peripheral throughflow openings 17, 17,.

The metal foil 1 3 comprises a central throughflow opening 18, from which radial guide slots 22 extend into the region of slotlike, circularly extending throughflow opeings 19, of the metal foil 14 which in turn communicate through radial guide slots 23 with the peripheral throughflow openings 17,.

Fig. 1 2 shows part of a complete mixing system 1 5 in which component A is delivered centrally into the throughflow opening 1 8 in the metal foil 15. 1, whilst component B is delivered from the periphery through guide slots 24 into the peripheral throughflow openings 17,. Throughflow openings 17 in the first foil are not yet in operation. The metal foil 1 5.2 guides component A outwards through guide slots 25 into the throughflow openings 171, whilst component B advances towards the spinning opening in the throughflow openings 17. The metal foil 1 5.3 again comprises guide slots 24 which extend from the periphery to the throughflow openings 17, and through which component B is mixed with component A.Component A advances in the central throughflow opening 18, whilst component B advances in the throughflow openings 1 7.

Since throughflow openings 1 7 are only present at the periphery of the metal foil 15.5, component A has to flow through the guide slots 25 to the peripheral throughflow openings 171 in the region of the metal foil 15.4. Since there is only one central throughflow opening 1 8 in the metal foil 15.7, the components again flow inwards through guide slots in the metal foils 1 5.6 et seq and outwards in the metal foils 15.8, etc.

In this way, the components can be very finely mixed without significantly affecting the reproducibility of the results.

In order to obtain mixing systems identical in structure from one spinning opening to the next, the recesses for accommodating the metal foils (for example, reference 29 in Fig.

1) may be connected to one another by grooves and, as shown in Fig. 13, the corresponding metal foils 1 6 by webs 28.

The number of peripheral throughflow openings and the number of metal foils per mixing system may be selected within wide limits, according to the number of polymer components and the required filament crosssection.

Figs. 14 to 1 6 show three filament cross sections produced with the spinning head according to the invention. The cross section Fig. 14 shows a matrix 29 comprising polyethylene terephthalate with peripheral segments 30 and a core segment 31 of polycaprolactam. In the cross-section shown in Fig.

15, the matrix 32 comprises polycaprolactam; segments 33 of polyethylene terephthalate project into it from the periphery. Fig. 1 6 shows a cross-section in which the segments 35 are heavily enmeshed with the matrix 34.

Mixing systems of the spinning heads according to the invention may be made up of a relatively small number of metal foils, for example of less than 20 and, in some cases even of less than 10 metal foils. Only a few types of metal foil are required, being stacked one on top of the other in a recurring sequence. The number of types of metal foil required may be further reduced by successfully using one and the same type of foil in normal inclined, mirror-image or rotated form.

In addition, the already mentioned minor tolerance fluctuations in the throughflow openings and/or guide slots in the metal foils are further reduced by stacking a plurality of metal foils one on top of the other because the tolerance fluctuations are averaged out in this way.

Claims (10)

1. A spinning head for producing multicomponent filaments with a matrix-filament structure comprising separate feed and distrubuting chambers for at least two synthetic polymer components the components having different properties from each other, a die plate with a plurality of spinning openings, each individual spinning opening being immediately preceded by a respective mixing system for combining the polymer components to form a matrix-filament structure each of the mixing systems preceding the individual spinning openings comprising a plurality of metal foils stacked one on top of the other each metal foil comprising a plurality of outer throughflow openings at the periphery thereof and/or at least one inner throughflow opening substantially at the centre thereof, at least two of the metal foils being provided with radially extending guide slots which communicate with the inner and/or outer throughflow openings.

2. A spinning head as claimed in Claim 1, wherein the inner throughflow openings are arranged at the centre of the metal foils and align with the spinning openings or with flow passages which precede the spinning openings.

3. A spinning head as claimed in Claim 2, wherein at least two of the outer throughflow openings in a metal foil communicate through radially extending guide slots with the inner throughflow opening.

4. A spinning head as claimed in Claim 1, wherein the inner throughflow openings are in the form of arcuately extending slots.

5. A spinning head as claimed in Claim 4, wherein at least two of the outer throughflow openings in a metal foil communicate through radially extending guide slots with the inner throughflow openings.

6. A spinning head as claimed in any of Claims 1 to 3 wherein the throughflow openings are circular and the radially extending guide slots tangentially therein.

7. A spinning head as claimed in any preceding Claim wherein at least two of the outer throughflow openings communicate through radially extending guide slots with the periphery of the metal foil.

8. A spinning head as claimed in any preceding Claim, wherein the mixing systems are identical in structure for all the spinning openings.

9. A spinning head as claimed in Claim 8, wherein the corresponding foils of all the mixing systems are connected to one another by webs.

10. A spinning head for producing multicomponent filaments with a matrix-filament structure substantially as herein described with reference to Fig. 1 2 with or without reference to any of Figs. 1 to 11 and 1 3.