WO2000035661A1

WO2000035661A1 - Method for producing thermoretractable composite sheathing and composite sheathing produced according to said method

Info

Publication number: WO2000035661A1
Application number: PCT/DE1999/001590
Authority: WO
Inventors: Henry Mitschak; Jürgen Meyer
Original assignee: Cellpack Gmbh
Priority date: 1998-12-12
Filing date: 1999-05-29
Publication date: 2000-06-22
Also published as: DE19857437B4; DE19857437A1

Abstract

A method for producing thermoretractable composite sheathing by extruding a tubular synthetic thermoplasticformed body (1) consisting of at least two layers (3, 4) and provided with two spaced connecting web elements (2) that run in a longitudinal direction. Said body is cross-linked and subsequently heated beyond the melting point for crystallite, whereupon it is expanded in a heated state by homogeneous elongation of a larger partial area of the tubular profile, whereby said area is defined by the connecting web elements (2). When the formed body is expanded it is cooled by water under pressure, followed by airtight sealing so that the tubular profile can be divided up in a longitudinal manner along the thin-walled connecting web element which remains devoid of overlapping strips.

Description

Patent description

Process for producing a heat-shrinkable composite covering and composite covering produced according to this method

The invention relates to a method for producing a heat-shrinkable composite sheathing and a heat-shrinkable composite sheathing produced by this method, in particular for cable sleeves.

The method according to the invention serves for the production of long-known manned materials as a covering for cable connections. Such cable sleeves are supposed to be simple itiontiercar, and must meet high demands in terms of waterproofness and insulation properties.

The generic heat-shrinkable composite covering consists of a tubular, extruded, cross-linked, cross-linked, thermoplastic, multi-layer plastic that expands when exposed to heat by expansion, in which at least one overlap strip is connected to a connecting web. The connecting webs are pressed together by means of a rail which grips them when pushed on, and beforehand the overlap strip is inserted under the gap between the touching connecting webs.

Proceeding from the production method of a heat-shrinkable composite sheath for cable sleeves with a method for the production by extrusion of a tubular structure provided with two spaced slow-running connecting webs and consisting of a thermoplastic plastic and having at least two layers, which is cross-linked and then heated above the crystallite point, expanded and warmed in the heated state is cooled in the expanded state.

For this purpose, it is proposed that the tubular structure between co-extrusion and having at least two layers and two connecting webs between the two adjacent connecting webs has a smaller wall thickness than the web profile material on both sides of these webs, and that after crosslinking there is continuous heating in a heat transfer bath Widening by even stretching nes larger section of the tubular profile, delimited by the connecting webs, using a widening tool with an oval conical run-out area, followed by cooling of the tubular profile by means of pressurized water and then an airtight sealing in order to subsequently position the tubular profile along the thin-walled connecting web without overlap strips to enable.

In this procedure, the inner composite layer is either without any tear-resistant inserts, or such known embeddings can also be provided.

However, the invention also encompasses a heat-shrinkable covering which has a very improved and more effective tear-resistance than the prior art.

In a known composite covering according to EP 0 416 352 A2, the tear-resistant reinforcement layer consists of a large number of wound strands or windings or braids by means of thread, preferably in opposite directions, of essentially non-stretchable materials such as metal, glass, mineral, cotton, polyester or poly aramid or the like is formed.

The reinforcement of the film tube is necessary and very important in many applications because of the risk of tearing and tearing during stretching and especially during the shrinking process. This Verstär ^¬ effect is the well-known training ways to increase the tearing strength not sufficiently made possible because the materials used to form the reinforcing layer are not or only insufficiently stretching bar. In the known composite coverings of this type, the films are produced from a thermoplastic compound and crosslinked by means of a chemical or physical process. The film is then heated above its crystallite melting point in a heating zone and stretched or stretched in an expansion unit by means of excess pressure, vacuum or mechanical stress. In the above-mentioned composite wrapping, the reinforcing materials cannot participate in the stretching process because they should not be stretchable. This appears as a disadvantage of this method, because the stretched or stretched film or the film tube is cooled after reaching the desired size; after reheating, the film tube shrinks onto the Dimensions back before stretching or stretching. The processes are hampered by the non-stretchable structure.

A further disadvantage of the prior art appears that the overlap strip extending between two connecting webs in each case has the same material wall thickness with the full reinforcement layer as the actual tube wall outside of these webs. This full reinforcement layer is not required there; it can have a disadvantageous effect in manual assembly by inserting it under the edge area of the sleeve, because it is not flexible and flexible because of the full reinforcement layer and is therefore difficult to handle.

This is where the invention is based on specifying a method for creating a heat shrinkable composite sheathing that does not have these disadvantages, in order to make it possible to provide such a sheathing with the greatest possible effort with less technical manufacturing and handling effort The degree of tear prevention in the area of the finished cuff can be achieved. However, the invention also extends to provide a method for producing such a composite cover.

Based on the known manufacturing method described at the outset, it is proposed according to the invention that, by means of a partially limited, greater widening of the pipe profile geometry between the spaced connecting webs, the overlap strip formed by long separation has a smaller wall thickness than the wall thickness of the multilayer sleeve connecting the connecting webs contains a tear-resistant layer made of a polymer matrix with short sections made of tear-resistant fiber parts of organic or inorganic materials and / or of microspheres made of these substances.

This irregular storage of such sections of fiber parts, even from non-stretchable and hardly stretchable materials, eliminates the above-mentioned disadvantages and therefore enables the creation of an extremely effective tear-resistant and tear-resistant reinforcing layer without the stretching and stretching of the tubular orange film being impaired thereby.

This possibility was previously unknown in the prior art. To the disadvantages of the non-stretchable materials to form a reinforcement To avoid layer, EP-A2-0 471 892 proposes a procedure for such a reinforcement, in which several tear-resistant threads or fibers with carrier elements running in the shrinking direction - or transversely thereto - are incorporated into the wall and are structureless after stretching or shrinking be melted together and thereby form the reinforcement layer.

Furthermore, EP 0 416 352 A2, mentioned, for producing shrinkable sleeves with slow-speed connecting webs, proposes an extruded tubular structure made of polymeric material, in which at least one strand of polymeric material is wound in a spiral shape or a plurality of spiral-shaped strands are overlapped and overlapping, and at Another tube made of polymeric material is extruded onto it and the extruded tubes are then crosslinked and heated above the melting point, expanded in the heated state and cooled in the expanded state. The problems already described also occur here.

The proposal received in EP 0 423 549 A2 is also unable to solve the problem described. At least two, preferably three or more plastic components of the same or different degrees of crosslinking are proposed there, at least one of which should have the optimum mechanical strength. In this z. B. shrinkable polymer foam films, polyolefins, high or low density polyethylenes, copolymers or monomers and / or fillers such as carbon black or phenols or amines, and also non-shrinkable plastic components.

Furthermore, EP-A2-0 416 352 A2 for the production of shrinkable sleeves with slow-moving webs has disclosed a procedure according to which a tubular structure made of polymeric material is extruded and at least one strand of polymeric material is interwoven on it or several helical strands are overlapping are wound up, and in which a further tube of polymeric material is extruded and the extruded tubes are crosslinked thereon and heated above the crystallite melting point, expanded in the heated state and cooled in the expanded state.

In contrast, the above-mentioned method achieves the further object of the invention to provide a heat-shrinkable composite covering. to provide, which does not have the disadvantages described, the method specified for this requires a significantly lower technical outlay than in the prior art mentioned, and a considerably improved standard of tearing inhibition of the shrink sleeves produced thereby can be achieved.

The essential features of the invention are shown schematically in the drawing. Show it:

1 to 3, the tubular structure in the three essential manufacturing phases,

4 shows a schematic longitudinal section through the expanding tool,

5 shows a cross section A-A through the expanding tool,

6 shows a cross section B-B through the expanding tool,

7 shows the finished cuff before the long splitting,

Fig. 8 shows the finished cuff placed around a cable connection, not shown.

As can be seen from FIG. 1, the wall thickness d of the tubular structure 1 extruded in the co-extrusion process in the area between the spaced-apart adjacent connecting webs 2 is substantially less than the wall thickness D of the tubular profile material on both sides of these webs 2, and it can also be seen that that the tubular profile is formed from two layers 3 and 4. According to the teaching of the invention, the inner layer 3 can be designed as an anti-tear layer. FIG. 2 shows the tubular structure in front of the widening (extrusion) shown in FIG. 3, in which the longitudinal section (by means of a cutting device 5) can also be seen.

4 shows a schematic longitudinal section through an expanding tool 10 with the section information AA and BB: The tubular structure 1 with the two connecting webs 2 is conveyed through the expanding tool 10 by means of the two endless tapes 6, 7 guided over the rollers 8 and 9. The expansion is carried out by applying compressed air to the interior R through a liquid pressure medium with a pressure of up to about 2 bar.

In addition, the inlets and outlets indicated at 11 and 12 serve for the pressurized supply of the cooling liquid for cooling the area between the adjacent connecting webs 2. FIGS. 5 and 6 each show a sectional view AA and BB through the expanding tool 10 in FIG. 5 Connecting webs 2 can be seen, between which the wall thickness d is substantially less than the wall thickness D of the rest of the tubular profile. Furthermore, the two endless belts 6 and 7 can be recognized by the expanding tool 10 to demand the tubular profile. 7 and 8 show the finished composite sheathing before the implementation of the longitudinal cut by means of the indicated cutting tool and the finished sleeve 13 with the overlap strip 14 in a mounting state for covering a cable connection, not shown.

There are great advantages in the manufacturing process of the composite covering in the stretching and expanding phases if, according to the teaching of the invention, the inner layer is designed as a tear-resistant layer with a multi-layer design. In order to increase the rice strength, the multi-layer coating is produced in co-extrusion processes. According to the invention, one of the layers, but also a plurality of layers, preferably the middle layer, can be designed such that it has an anti-tear effect. The aforementioned randomly branched incorporation of tear-resistant fiber pieces made of organic or inorganic materials, preferably glass, plastic or natural fibers, but also microspheres, in the carrier material of the layer prevents a crack which is formed from spreading in a straight line. The intimate bond between the fiber pieces or microspheres with the carrier material and the individual layers with each other achieves an anti-tear effect during stretching and especially when shrinking.

As described, the invention combines a number of advantages in the field of process engineering, so that the finished sleeves produced represent an optimal combination of reliability and safety compared to the prior art.

The manufacturing method according to the invention is characterized by the following advantageous steps:

1. Continuous heating of the cross-linked tube profile in a heating Carrier bath to a material temperature 5 - 20% above the crystallite point of the material layer with the highest crystallite point.

2. Continuous application of internal pressure from the inlet or outlet side.

3. Sealing the inlet and outlet sides of the heat transfer bath with sealing elements that are recreated with the tubular profile, preferably made of non-ferrous metals, graphite or plastic.

4. To increase the sealing effect, the heat carrier is fed into the space between the sealing elements.

5. After leaving the hot carrier bath, it is passed on directly to the expansion tool.

6. The expansion tool is designed in such a way that a targeted expansion of a section of the pipe profile by means of the overpressure introduced takes place over an oval conical inlet area which is modeled on the pipe profile, up to the desired dimension of the expanded pipe profile (expandate).

7. The expansion tool is supported by one or more belt drives, supported by pressurized devices

Lubricant in the cold area of the expansion tool.

8. Following the expansion tool, the pipe profile is cooled in a calibration tool, which represents the nominal mass of the stretched pipe profile, by means of pressurized water, and thus the stresses are frozen.

9. The stretched and cooled tubular profile (expandate) is sealed airtight using suitable squeezing elements.

10. This is followed by a continuous or discontinuous longitudinal division along the area of the webs, as shown in FIG. 3.

11. A shrink sleeve is thus produced using a suitable closure rail.

Claims

claims

1. A process for producing a heat-shrinkable composite covering by extruding a tubular structure provided with two spaced, slow-moving connecting webs and consisting of a thermoplastic, at least two layers, which is crosslinked and then heated above the crystalline melting point, expanded in a heated state and cooled in the expanded state ,

characterized by

that the tubular structure produced by co-extrusion and having at least two layers and two connecting webs between the two adjacent connecting webs has a smaller wall thickness compared to the tubular profile material on both sides of these webs, and that after crosslinking, continuous heating in a heat transfer bath thereupon widening by evenly stretching one Larger section of the pipe profile delimited by the connecting webs by means of a widening tool with an oval conical accumulation area and then cooling of the pipe profile by means of pressurized water and then an airtight sealing, in order to subsequently elongate the pipe profile along the thin-walled connecting web without overlaps to enable.

2. A method for producing the heat-shrinkable composite covering by extruding a tubular structure provided with two spaced, slow-moving connecting webs and consisting of a thermoplastic and having at least two layers, which is crosslinked and then heated above the crystallite melting point, expanded in the heated state and cooled in the expanded state,

marked by

Co-extrusion of the tubular structure having at least two layers and two connecting webs, in which at least one of the layers is designed as a tear-resistant layer which is randomly and branched into dense packs of fiber pieces and / or fabric pieces and / or microfibers. contains crocodiles of inorganic and / or organic material embedded in the polymer matrix, and which has a much thinner wall thickness between the two adjacent connecting webs compared to that of the tubular profile material on both sides outside of these webs, and that after crosslinking, continuous heating in and on a heat transfer bath the widening by uniform stretching of the larger section of the tubular profile delimited by the connecting webs by means of an expanding tool with an oval conical inlet area and subsequent cooling of the tubular profile by means of pressurized water and subsequent airtight sealing of the tubular profile in order to free the subsequent long parts of the tubular profile along the overlap strip enable.

3. The method according to any one of claims 1 or 2, characterized in that the expansion of the tube profile takes place during the passage of the expanding tool caused by the funding, the inner region of which is recreated on the upstream side of the geometry of the extruded tubular profile and in which the inner region of the tool on the Final dimension enlarged, whereby in the expansion tool a partial expansion of the tube profile geometries takes place over the circumference of the tube profile, and that the partially expanded tube profile passes through the cold and warm areas maintained by physical separation in the expansion tool, and that after the longitudinal cutting of the partially stretched tube profile then with a joint an overlap strip is created, which enables an overlap when the tube profile is reclosed to form a sleeve.

4. The method according to claim 3, characterized in that one or more driven endless belts are used as the conveying means in the expanding tool.

5. The method according to claim 3, characterized in that the areas in the expanding tool for guiding the connecting webs and between the adjacent connecting webs is cooled.

6. The method according to claim 5, characterized in that in the on-tool the areas to be cooled are pressurized with a cooling liquid.

7. The method according to any one of claims 1 or 2, characterized in that that the heat transfer bath is provided with sealing elements which are shaped to the geometry of the tubular profile, and that the heat transfer elements are inserted between these sealing elements.

8. The method according to claim 7, characterized in that the sealing elements consist of plastic, graphite or non-ferrous metal.

9. The method according to claim 5, characterized in that the connecting webs and the area between the connecting webs consist of a different or more strongly cross-linked PE compound than the area on both sides outside of the connecting webs, and that this area is not shrinkable.

10. Heat-shrinkable composite sheathing, in particular for cable sleeves, manufactured according to claim 1, from a tubular extruded, cross-linked, cross-linked and stretched thermoplastic multilayered plastic when exposed to heat by expansion, in which an overlap strip adjoins at least one connecting web,

characterized,

that by means of an only partially circumferentially limited widening of the tubular profile geometry between the spaced connecting webs, the overlap strip formed by long separation has a smaller wall thickness than the wall thickness of the multi-layered sleeve connecting the connecting webs.

11. Heat-shrinkable composite sheath, in particular for cable sleeves, produced according to claim 2, from a tubular extruded, cross-linked and spaced longitudinal connecting webs, and thermoplastic multilayered plastic stretched when exposed to heat, with at least one tear-resistant layer, in which there is an overlap strip on a connecting web connects

characterized,

that by means of a partially circumferentially limited widening of the pipe profile geometry between the spaced connecting webs of the Overlap strips formed by long separation have a smaller wall thickness than the wall thickness of the multi-layered sleeve connecting the connecting webs, the tear-resistant layer of a polymer matrix with randomly embedded and branched short sections made of tear-resistant fiber parts of organic or inorganic materials and / or of Contains microspheres from these substances.

12. Composite covering according to claim 2, characterized in that the tear-resistant fiber pieces consist of glass, plastic or natural fibers.

13. composite covering according to claim 2, characterized in that the tear-resistant fiber pieces consist of PE / EVA, TRE or TPV or consist of carbon.

14. The composite covering according to claim 1, characterized in that the outer layer made of the thermoplastic material has a thickness between 0.2 mm and 4.0 mm and the inner composite layer has a thickness between 0.5 and 3.0 mm, and that the overlap strip has a thickness of 0.5 to 2.0 mm.

15. A composite covering according to claim 2, characterized in that the outer layer made of the thermoplastic material has a thickness between 0.2 mm and 4.0 mm and the inner tear-resistant composite layer with the fiber pieces and / or fabric pieces of the size between 10 and 1000 my a thickness between 0.5 and 3.0 mm, and that the overlap strip has a thickness of 0.5 to 2.0 mm.