FI115571B - Cable having coextruded multi-layer construction - including barrier and protective layers with mechanical and barrier properties which can be controlled by changing orientation of fibrous reinforcement or lamella layers - Google Patents

Abstract

Multilayer, reinforced and stabilised cable construction has a core portion (1,11) and a non-metallic sheathing portion with barrier and protective layers and two or more reinforcement layers (12,13). The mechanical and barrier properties of the cable are controlled by orienting the barrier and protective layers or the reinforcement layers in a controlled manner at different angles by means of fibrous reinforcements or lamella barriers.

Description

115571

Multilayer reinforced and stabilized cable structure

The present invention relates to a multilayer reinforced and stabilized cable structure comprising a core member and a 5 metal free sheath member comprising barrier and shielding layers and two or more reinforcement layers.

Such cable structures are nowadays quite well known in connection with various types of cables, for example optical cables. Current metal-free optical cabinet-10 structures require many process steps, some of which may be very slow. Expensive reinforcements added alone may require the use of additives, for example to achieve adhesion or water tightness, which will further slow down the manufacturing process. In addition, to improve the thermal stability of the cable-15 structure, i.e. to reduce thermal compression, it is often necessary to use rod-like reinforcing elements, the use of which in itself brings certain, not always positive, properties to the cable such as bending stiffness, larger dimensions, 20 high prices, etc. is the so-called. middle tube structures; f. where they must be worn on the periphery of the heart and symmet- * I ·: v. in duplicate for at least two reasons.

If the cable is additionally required mechanical protection. 25 pts against rodents and termites, or oil and kernels -> «* * · ,, 'durability and / or barrier properties against moisture *' * and gases require expensive semi-preparations which have to be processed in separate, often cumbersome, steps , which further complicates the. · 30 structures and increases product costs.

It is an object of the invention to provide a cable structure which eliminates the drawbacks of the prior art described above. This is achieved by means of the cable structure according to the invention. The ka-j: 35 game structure according to the invention is, in particular, known for

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115571, to control the mechanical and barrier properties of the cable, the barrier and shielding layers and / or reinforcing layers are formed and oriented by extrusion so that the fiber reinforcements 5 or lamellar closures have a different orientation angle to the cable longitudinal axis.

The advantage of the invention over the prior art is, for example, that the mechanical and closing properties of the cable can be adjusted in a very advantageous manner according to the particular need. The advantage is due to the simplicity of the invention and the fact that the manufacturing can take place in a single extrusion step, whereby the costs are low.

It is a further advantage of the invention that it is possible with the invention to provide a fully meltable, reusable structure.

The invention will now be illustrated by the following detailed description of the accompanying drawings, in which: Fig. 1 is a schematic view of a prior art cable structure, and Fig. 2 is a plan view of a prior art cable sheath. Figures 3-6 illustrate examples of optical cable structures implemented in accordance with the invention, and Fig. 7 illustrates an example of a metal core cable implemented in accordance with the invention.

Figure 1 shows in principle a cable structure according to the prior art '·' *. In Figure 1, the core portion 30 is denoted by the reference numeral 1-2. The core portion may, for example, consist of optical fibers 1 and a secondary coating 2. In turn, are denoted by reference numerals 3 and 4. The rod-shaped reinforcing elements in turn are represented by reference numeral 5 '! * 35. Two rod-shaped reinforcing elements 5 are symmetrical: * * in the outer circumference of the cable as previously stated.

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The cable structure of Figure 1 is typically formed by extruding over the secondary coating 2 the functional layers described by reference numerals 3-4 in the example of Figure 1. The extrusion is typically made with a conventional cross-nozzle. A disadvantage of such a technique is e.g. joints formed in layers that adversely affect the properties of the cable. The drawbacks are due to the fact that the joint seams cause discontinuities in the layers 10, whereby the properties of the layers in the given layer are reduced. points are different than other layers of layers. Figure 2 is a cross-sectional view of a cable structure showing the above discontinuities. The discontinuities are indicated in Figure 2 by the N arrows.

The invention thus relates to a cable structure by means of which the drawbacks of the prior art described above can be eliminated. According to the basic idea of the invention, in order to control the mechanical and barrier properties of the cable, the barrier and shielding layers and / or reinforcing layers are oriented by means of fibrous reinforcements or lamellar closures; way to different angles. The cable according to the invention is characterized by a tensile strength, a dimensional stability over a wide temperature range and a characteristic of non-metallic cables. 25 sudden temperature fluctuations as well as the firmness and flexibility of the structure. The invention is further characterized by the fact that the multilayer structure can be manufactured in a controlled manner in a single extrusion step.

The so-called cable core, or so-called. the cable structure stabilizing layer extruded on the secondary jacket 30 consists, for example, of a thermoplastic reinforced with solid reinforcing fibers such as glass, carbon, boron, aramid, polyolefin or the like, e.g. polyester, 35 polyamide or similar material. Alternatively, the reinforcing layer may be formed from a liquid crystalline polymer (LCP) thermotropic backbone polymer or a mixture of such and a conventional thermoplastic. In addition to conventional thermoplastics, particularly preferred thermoplastics are those which are easily orientable and / or crosslinkable during or after extrusion. These types of liquid crystal plastics are easily fluid in the molten state and can be processed like thermoplastics. Due to the inherent internal organization of the material, the molten solidifies to form a composite fibrous structure, in situ. Thus, defibration of the liquid crystal polymer occurs during the extrusion process. A particularly advantageous screw geometry for providing radial orientation during the process is disclosed in PCT / FI96 / 00261 and FI964988.

In the case of liquid crystal resins or mixtures thereof, it is preferable to aim for a high tensile ratio during processing, which results in a high degree of fiberization. It is then more advantageous to run the LCP reinforcing layers in as many thin layers as possible than one or two thicker layers, whereby the tensile ratio can be kept high and defibration occurs efficiently and throughout the layer.

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Part of the reinforcing layers can also be formed. the so-called. continuous fiber reinforced thermoplastic composites. In these »· * 25 applications, conventional thermoplastic or adhesive plastic is impregnated with fully continuous glass, aramid ♦

· '' Di- or other similar fibers. Oriented PE and PP

The v 'fibers have very good strength properties, but their use for this purpose has been hampered by comparatively low melting point of crystallite, which causes the high extrusion temperature required during processing to destroy the orientation and strength obtained on the fiber. Surprisingly, it has been found that even at relatively low irradiation levels, oriented PE fibers can be cross-linked so that the orientation remains more stable and thus significantly overcome the time the fiber can withstand without losing more than half its original strength. Alternatively, materials which have been first cross-linked and thus only orien-5 may be used as fibers may also be used. Chemically crosslinked polyethylenes are also contemplated. The use of oriented and crosslinked fiber structure provides one very significant mechanical advantage in addition to price. Namely, during the process, it has been surprisingly found that the fiber surface 10 partially softens and adheres to the surrounding matrix resin while maintaining a high level of mechanical strength. This good adhesion, which is very difficult to achieve with, for example, aramid fiber, guarantees e.g. good impact strength. In addition, the pure polyethylene structure guarantees good electrical properties. In the preferred cable structure of the invention, such a reinforcement layer can be fabricated integrally with the actual cable extrusion by impregnating the continuous fibers into the plastic matrix on-line. In fiber optic cable structures, the reinforcing layer described above may form a secondary shield to protect optical fibers.

As stated above, it is essential for the invention that the fibers of each reinforcing layer, protective layer t · · or barrier layer have a certain controlled own rotational orientation angle relative to the longitudinal axis of the cable. An exemplary embodiment of the invention is illustrated in principle in Figure 3. In Figure 3, the core member is designated by reference numerals 1 and 11. Layers with reinforcements over the core member are denoted by reference numeral 12. and 13. The surface layer of the jacket is designated by the number 15, 14, 14. The different orientation angles of the reinforcing fibers in the layers 12 and 13 are clearly visible in the pattern; you 3.

The direction of fiber twist in each or some of the layers may be in the same direction but with an orientation angle '| 35 different sizes. In this way, the tensile and bending properties of each layer can be controlled in a controlled manner. In the layer closest to the center of the cable, i.e. the first reinforcing layer, it is preferable to use fibers substantially parallel to the longitudinal axis of the cable, i.e. fibers having a small orientation angle. The twisting of the fibers is achieved, for example, by a twisting mandrel through which the fibers pass as disclosed in FI patent application 964989. A similar rotating mandrel can also be combined with the machine solution disclosed in PCT / FI96 / 00261 to provide a highly efficient helical molecular orientation in addition to continuous fibers. In this case, the fiber reinforcements will maximize the cable's tensile strength while their cable bending, stiffening effect will be minimized due to the short center distance.

Correspondingly, the orientation angles of the fibers of the outer reinforcing or shielding layers are preferably larger in order to have a smaller cable-lessening effect and, for example, a greater radial-compression strength-increasing effect of the cable. Such an arrangement is shown in Fig. 3. In addition, the dry layers of the outer layers; the greater orientation of the rods increases their protective * »· effect against rodents.

Different angularly oriented reinforcing fibrous layers, which are themselves transversely abrasive and of low tensile strength, reinforce one another, while supporting different directional fibers in different layers in transverse stress conditions.

The multilayer structure of lamellar structure of controlled oriented fibers thus provides a kind of mesh structure in which, by adjusting the orientation angles of the fibers in the various layers Λ and controlling the mechanical properties of the entire reinforcement.

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Cable core protection so-called. the barrier layer prevents moisture and possibly hydrogen from penetrating the cable core. Such a layer may preferably consist of a thermotropic main chain liquid crystal polymer (LCP), a polyolefin (mainly high density polyethylene, HDPE or polypropylene, PP), a cyclic olefin copolymer (COC) or the like. In the symmetrical joint 10 according to the invention, said the barrier properties are achieved by a very thin layer of the aforementioned plastics. Typically, the layer thickness can be from about 50 to 100 µιη depending on the material. The symmetrical homogeneous structure also guarantees even a thin layer is mechanically strong enough to remain intact and functional when the cable is subjected to mechanical stress. Particularly when using liquid crystal resin as a barrier material, the required reinforcing effect, i.e. tensile and compressive strength, can also be achieved in a single layer (lamellar structure). On the other hand, the use of liquid crystal and thermoplastic alloys as separate reinforcing layers so that the orientation directions of the LCP fibers or lamellas cross each other, provides not only excellent mechanical properties but also moisture protection. Such an embodiment is shown in Fig. 4. In Fig. 4, the core portion 25 is denoted by reference numeral 21. Laminates with LCP fibers or * * lamellas are denoted by reference numerals ·, ribs 22 and 23. The surface layer is denoted by reference t The transverse orientation directions of the lamellae are clearly • shown in Figure 4. Since the liquid crystal plastics involved are very aromatic in their chemical composition and form a solid state, they give a special * structure. good protection also against smaller gas molecules. A protective layer, particularly against hydrogen, is of paramount importance for optical fibers and, in non-metallic structures, it is provided by liquid crystal plastics.

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In a multi-layer structure consisting of several different thermoplastics, adhesion between functional layers, i.e. barrier layers, reinforcing layers, etc., is particularly important. In the structure of the invention, thin layers of adhesion can be run between thicker functional layers, if necessary. Because adhesive plastics are soft, it is important that their layer thicknesses are kept to a minimum. Particularly preferred adhesive layers are those which themselves have a functional side. For example, a semiconductor adhesive layer electrically shields the fiber optic cable inside. The symmetrical non-joint design allows for thin, even layers. In the cable structures according to the invention, the connections between the different reinforcing layers can be controlled by different thin layers of adhesive or buffer 15, whereby the interaction between the layers can be increased or decreased as necessary. The adhesive or elastic component components may also be mixed with the reinforcing layers themselves. It is also possible that in the same reinforcing layer 20, the fibrous segments alternate circumferentially with the more elastic polymer segments; h whereby a good balance is achieved between longitudinal reinforcement and bendability. Such an embodiment is illustrated in Fig. 5. In Fig. 5, the core member is denoted by reference numerals 1 and 31. The reference numeral 32 denotes a reinforcement layer divided into fibrous reinforcement blends * 32 * and more elastic padding members. Reference numeral 34b denotes a reinforced layer corresponding to layer 12 of the example shown in Figure 3. Reference numeral • j 30 33 denotes a cable surface layer. a portion or a separate buffer layer is formed by the foamed polymer in direct contact with the fiber reinforcements; to flex the cable bending and compression hall 35. Typically, such a layer consists of 115571 9 foamed polyolefins having a density of 50 to 200 kg / m 3.

As already stated above, the structure according to the invention can advantageously be produced in a single extrusion step, including intermediate steps, e.g. with the poles off the support. In addition, it is essential that the flow direction of the molten material is parallel to the cable core and that the molten mass flow is not distributed at any stage, thereby avoiding so-called. forming a joint seam. The Yt-10 seam is known to be a mechanically weak point in plastic products, where cracking often begins. The strength at the seam is significantly lower than elsewhere. Without the mass distribution, seamless homogeneous layers are obtained, which enables the desired properties to be achieved with layers thinner than normal. Lower material consumption is economically significant, since the polymers with the best properties, especially in reinforcement and barrier layers, are known to be quite expensive. Thus, according to the invention, multilayer cable structures 20, which are both technically and economically more advantageous than known structures, can be manufactured.

. The multilayer structures according to the invention can be made in principle with a conventional cross-head nozzle, * · \ with rotary nozzle tools. In practice, it is very difficult to produce a structure consisting of several layers using controlled techniques. The composite tower a multi-layer structures according to the invention are obtained by a so-called cone extruder, for example described in EP 0 422 042 B1.

; Although the invention has been described above primarily by means of various applications of optical cable, it should be noted that the invention can also be applied to cables having a core part formed by metal conductors.

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The following are some examples of solutions implemented in accordance with the invention for purposes of illustration. The examples are described as four-layered structures, but it is clear that depending on the construction of the 5 multilayer presses available, there may be more layers. The layers are listed from the inside to the outside.

A. Separate fiber optic core (PBT, optical fibers, gel) or metal conductor on which coextrusion 10 multi-layer structure (functional parts and outer sheath).

1. -adhesive plastic -LCP or LCP blend orientation + 45 ° (reinforcement) -LCP or LCP blend orientation -45 ° (reinforcement) 15 outer sheath (e.g. PE) the middle layers together form a barrier layer 2 .-adhesive resin -LCP, LCP blend or fiber composite, Orient. + 45 ° 20 LCP or LCP alloy, thin laminar (barrier) outer sheath (e.g. PE) first LCP or equivalent is the actual reinforcement.

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Special construction (fiber reinforced continuous, melt * t. 25 on-line regeneration).

• If required, a «· hot melt adhesive plastic can be applied to the PBT tube just before the coextrusion step.

30 1. -on-line impregnated continuous glass fiber, suitable:: at an angle around the PBT tube,, · as a matrix polyolefin (may include functionalized or nalized polyolefin, adhesion)> ·. -or matrix adhesive resin (good adhesion to both surfaces) 115571 11 -thin, smooth HDPE, COC, LCP or PO / LCP alloy (barrier) adhesive resin (eg PE) 5 2. ( -adhesive plastic) -Lim LCP or LCP (moisture barrier) -on-line impregnated continuous glass fiber, at a suitable angle around the PBT tube (polyolefin as a matrix) 10 (-adhesive plastic) outer sheath (polyolefin) B. Also do secondary coating in the same step 15 . -protective material LCP alloy or fiber composite (internal fiber, gel) 41 -also reinforcing structure (axial Orient.)-thin adhesive layer 42-actual reinforcement layer (LCP or fiber composite-20 ti), oblique orientation 43-outer sheath (e.g. PE) 44 This embodiment is illustrated in Figure 6. Numbers 41 -) 1 * ·, V. 44 refer to Figure 6.

25 2. -the protective material is thermoplastic (incl. Optical, gel) • "-ethylene / propylene copolymer (suitable gel) i» ·

v: This is PBT

-or: COC (same moisture barrier): 30-thin adhesive layer -the actual reinforcement layer (PO / fiber t. PO / LCP blend), oblique orientation »· outer sheath (eg PE) 35 * * t 4 115571 12 C. Plain multilayer shell structure, core either spiral space or stranded structure or metal conductor 1. adhesive plastic

5 intermediate diaper PE

-adhesive plastic outer sheath PA 12 (e.g. termite shield, abrasion resistance) 10 2. Fire-resistant sheath -adhesive plastic barrier layer (HDPE, COC, LCP t. PO / LCP mixture) and / or reinforcing layer (see above) -adhesive plastic (Not Required) 15-HFFR Mixture 3. Rodent Resistant Sheath Adhesive Plastic 52 Polyolefin / Fiberglass 53 20 Polyolefin / High Fiberglass (Staple Fiber, Online Impregn. Continuous Fiber) 54, Large transverse orientation angle.

S «thin HDPE t.PAl2 skin 55« Such an embodiment is shown in Fig. 7. Reference numeral 51 shows a core of metal conductors. Reference numerals 52-55 denote the layers listed above. Reference numerals 52-55 are also shown in the exemplary layered description of V.

The foregoing embodiments are by no means intended to limit the invention, but the invention may be modified freely within the scope of the claims. Thus, it is clear that the cable structure according to the invention or its details need not necessarily be exactly as shown in the figures, 35 but other solutions are possible.

Claims (17)

115571 A multilayer reinforced and stabilized cable structure comprising a core member (1, 11, 21, 31, 41, 5 51) and a metal-free jacket member comprising barrier and shielding layers and two or more reinforcing layers, characterized in that to control the sealing properties, the sealing and shielding layers and / or reinforcing layers (12, 13, 22, 23, 32, 10 53, 54) are formed and oriented by extrusion so that the fiber reinforcements or lamellar closures have a different orientation angle to the cable longitudinal axis. Cable structure according to Claim 1, characterized in that the reinforcing layers are formed from short or long fiber reinforced thermoplastics. Cable structure according to Claim 2, characterized in that the reinforcements are glass, carbon, boron or aramid fibers. Cable structure according to Claim 1, characterized in that the reinforcing layers are formed of a material which is at least in part made of a liquid crystal plastic. Cable structure according to claim 1 or 2, characterized in that the staple fibers or continuous fibers are oriented polyolefin which is cross-linked. Cured at a gel content of more than 5%. Cable structure according to Claim 5, characterized in that the fiber reinforcement is welded to the matrix such that the adhesion energy between the fiber and the matrix is greater than the strength of the matrix. Cable assembly according to one of the preceding claims 1 to 6, characterized in that at least one reinforcement is used to adjust the tensile strength and the bendability. the layer is divided into segmental portions, alternating; 35 rigid reinforcing members (32a) and more elastic filling members (32b). 115571 Cable structure according to one of Claims 1 to 8, characterized in that the elastic padding members or separate buffer layers are formed of a foamed polymer. Cable structure according to Claim 1, characterized in that the barrier layers are formed of a material which is at least in part made of a liquid crystal plastic. Cable structure according to one of the preceding claims 1 to 9, characterized in that adhesive layers (42) improving interlayer adhesion are provided between the layers. Cable structure according to claim 10, characterized in that the barrier and adhesion layers and the reinforcement layers are thin, symmetrical and non-bonded layers. Cable structure according to claim 1, characterized in that at least one reinforcing layer is formed of a continuous fiber reinforced composite having a conventional thermoplastic or adhesive plastic matrix. Cable structure according to one of Claims 1 to 12, characterized in that the reinforcing fibers in the layer (12) closest to the center of the cable are arranged substantially longitudinally in the cable and more oriented in the outer layers (13). Cable structure according to one of the preceding claims 1 to 13, characterized in that the core part (11, 21, 31) is a part formed by optical fibers. The cable structure according to claim 14; 30, characterized in that the optical fiber sealing layer * * · and the protective layer are arranged to form a first reinforcement and / or sealing layer. Cable structure according to one of the preceding claims 1 to 13, characterized in that the core part 35 (51) is a part formed by metal conductors. » A cable structure according to any one of the preceding claims, characterized in that at least a portion of the matrices or fibers are cross-linked. 115571