NL8502898A - EXTRUSION METHOD. - Google Patents

Description

VO 7445

Extrusion method.

The invention relates to an extrusion process and an apparatus for manufacturing a foam-coated wire, in which a plastic melt, mainly consisting of thermoplastics, cell binders and a natural propellant, as well as optionally dyes, is included together with the continuously fed extrusion tool. extrudes wire.

German Offenlegungsschrift 15 15 805 discloses a wire insulated with a foamed plastic. A disadvantage of this foam-plastic-coated wire is the fact that the bonding of the foam-sheath to the wire is unsatisfactory.

The object of the invention is therefore to provide a foam-plastic-coated wire, in which the foam-plastic jacket firmly encloses the wire.

This problem is solved according to the invention by using a wire cooled under ambient temperature, preferably under 0 ° C.

In the manufacture of such a wire provided according to the invention with a foam plastic jacket, one uses an apparatus, which is characterized according to the present invention, in that the extrusion tool is provided with a wire feed attachment, which extends into the extrusion tool without any contact, and the encloses the major part of the wire feed channel, which in turn extends cantilevered from the exit of the wire feed attachment into the mandrel, the wire feed channel in the wire feed attachment being surrounded by a cooling chamber, in order to feed the wire already cooled in the cooling device into the keep the extrusion tool cool until it comes into contact with the plastic melt.

The object of the invention is thus an extrusion process for making a foam-plastic-coated wire, in which a plastic melt consisting mainly of thermoplastics, cell binders and a natural propellant, as well as optionally dyes, is extruded together with the wire continuously fed into the extrusion tool. , and is characterized in that a wire cooled at ambient temperature is used.

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Furthermore, the subject of the present invention is the device described above for applying the method according to the invention, as well as the product, that is to say, the foam-plastic-coated wire and the use of this foamed wire 5 for tying up plant parts, such as trunks, stems, twigs, branches and the like. Moreover, according to the invention it is also possible to manufacture electrical conductors insulated with foam plastic sheaths.

The invention will be explained in more detail below with reference to Figs. 1 and 2, which represent a preferred embodiment, and the following description parts.

FIG. 1 is a cross-sectional view of the extruded tool with flanged wire feed attachment; Fig. 2 schematically shows an overall device according to the invention.

In the figures, the reference numbers have the following meanings: 1 extruder 2 extrusion tool 20 3 wire feed attachment 4 wire feed channel 5 outlet from the wire feed attachment (3) 6 doom tip 7 cooling chamber 25 8 through hole 9 spacer 10 extruder nozzle 11 nozzle outlet opening 12 nozzle of the pre-chamber 30 13 inlet 14 cooling unit 30 13 inlet 15 thread straightener 16 thread drum.

As shown in Fig. 1, the wire feed attachment 3 is flanged to the extruder 2. There is a spacer 9, preferably consisting of a thermally insulating material, between the wire feed attachment 3 and the extruder 2, so that the part of the wire feed attachment 3 extending into the extruder 2 does not come into contact with the extruder 2 coming. The free space between extrusion tool 2 and wire feed attachment 3 thus also serves the thermal insulation.

The wire feed channel 4 located in the wire feed attachment 3 is surrounded by the cooling jacket 7, through which the cooling liquid is passed. By means of this cooling liquid, not only the major part of the wire feed channel 4 is cooled, but also the parts of the wire feed attachment 3 extending into the extruder, namely by heat dissipation. In this way, the wire, already cooled before entering the wire feed attachment 3, retains its temperature, up to the mandrel 8, where it comes into contact with the hot plastic melt in the nozzle front space 12. Thereby quenching takes place of the plastic melt which comes into contact with the wire and the formation of a thin layer on the wire, which encloses it tightly. Because this layer can form by quenching on the wire, on the other hand it can be reheated, respectively. melting of the plastic layer formed on the thread during quenching is avoided, it is important that the path between mandrel opening 8 and nozzle outlet opening 11 is determined by the method determinations, respectively. the speed of the wire feed and the prevailing temperature ratios in the melt is adjusted.

The main cooling of the wire takes place - as already noted - before entering the wire feed attachment 3. This can be done in the manner shown in fig.

2 in that the wire is continuously pulled off from the wire drum 16 and, after passing the wire straightening device 15, it is passed through the cooling device 14, from which the wire, preferably directly, without coming into contact with the outside air, into the wire feed attachment 3 comes.

However, the entire wire drum can also be stored in a suitable deep-cooling cabinet, respectively. subcool a deep-cooling box and from there pass it through a special lock into a wire straightening device 15, preferably under vacuum and optionally also cooled, and then pass it directly into the wire feed attachment 3.

Thus, an essential feature of the invention is to be seen in the use of the cooled wire. Due to the preferably highly marked •. "" *. In the nozzle, that is to say in the nozzle pre-chamber 12, a quenching of the plastic melt to be foamed still takes place, which then separates as a thin non-foamed layer on the wire and thus makes the connection between wire and foam. If an uncooled wire is used, the foam jacket is non-tight against the wire. Even in this case, the wire has a certain amount of play in the foam jacket and can easily be moved back and forth.

In order to obtain the desired thickness of the foam jacket, it is necessary to select a predetermined ratio of the diameter of the wire exit opening and wire. This ratio is preferably 2.5 µl. In a preferred embodiment of the present invention, at this ratio of 2.5: 1 with a diameter of 1 mm, a foam jacket with a diameter of 10 mm is obtained. Naturally, the diameter of the foam jacket also depends on the composition of the plastic melt to be foamed.

Generally, the foamed plastic casing is obtained by extrusion using a screw extruder. As a rule, a chemical propellant, such as, for example, azodicarbon-20 amide and 4,4'-oxybis (benzolsulfonylhydrazide), or an inert gas, such as nitrogen, argon and carbon dioxide gas, or a gaseous or liquid hydrocarbon from the group methane, propane, butane, pentane and hexane or a gaseous or liquefied hydrofluorocarbon, such as, for example, trichloronofluoromethane, dichloride fluoromethane, trichlorotrifluoroethane and dichlorotetrafluoroethane. The plastics are generally polyolefin such as, for example, low density polyethylene, medium density polyethylene, high density polyethylene, polypropylene and a butyl rubber or a mixture of at least two of these materials. The most commonly used plastic materials are polyethylene and polypropylene.

According to a preferred embodiment of the invention, it is thus done that in order to obtain a foam density below 3. .

60 kg / cm and a rough surface of the plastic casing, wherein the ratio of wire diameter to diameter of the plastic casing 35 is at least 1: 8, -5- - ........__ ƒ (a) the natural propellant in an amount of 20 to 30%, based on the thermoplastics, dosing directly into the extruder in the melt; (b) used as low density 5 high pressure polyethylene thermoplastic; (c) leaving the mixture to be foamed with a temperature of 60 to 105 ° C out of the extruder nozzle together with the wire; (d) operates at an ejection velocity of at least 50 m / min; and 10 (e) uses as wire a soft iron wire of the quality class DIN 17140, which has a temperature of 10 ° C.

Obviously, in the method according to the invention, it is also possible to apply an adhesion promoter in the form of a very thin cover 15 before the introduction of the cooled wire into the plastic melt on the wire, so that in certain cases the adhesion of the foam plastic jacket to the wire can be improved further. In general, however, this is not necessary.

In the preferred embodiment described above, the distance between the nozzle opening 8 and the outlet opening 11 of the nozzle is preferably 18.5 cm.

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Claims (10)

1. Extrusion method for manufacturing a foam-plastic-coated wire, in which a plastic melt consisting mainly of thermoplates, cell binders and a natural propellant, as well as optional dyes, is extruded, together with the wire continuously fed into the extrusion tool, with the characterized in that a wire cooled under ambient temperature is used. Extrusion process according to claim 1, characterized in that 3 for obtaining a foam density below 60 kg / cm and a rough surface of the plastic casing, wherein the ratio of wire diameter to diameter of the plastic casing is at least 1: 8 (a) dosing the natural propellant in an amount of 20 to 30%, based on the thermoplastics, directly into the extruder in the melt; (B) used as high density low pressure polyethylene thermoplastics; (c) leaving the mixture to be foamed with a temperature of 60 to 105 ° C out of the extruder nozzle together with the wire; (d) operates at an ejection velocity of at least 50 m / min; and 20 (e) uses as wire a soft iron wire of the quality class DIN 17140, which has a temperature of 10 ° C. Extrusion process according to claims 1 and 2, characterized in that a subcooled wire is fed into the extruder, which is covered with an adhesion promoter. Device for applying the method according to claims 1-3, characterized in that the extrusion tool (2) is provided with a wire feed attachment (3), which extends into the extruder (2) without any contact and the encloses most of the wire feed channel (4), which in turn extends cantilevered from the outlet (5) from the wire feed attachment (3) into the mandrel (6), the wire feed channel (4) in the wire feed attachment (3 ) is surrounded by a cooling chamber (7) in order to keep the supplied wire, already sub-cooled in the cooling device (14), in the extruder (2) cool until it comes into contact with the plastic melt. , - »” 5, · Λ.-¾ Λ γ 0 -7- Device according to claim 4, characterized in that a thermal insulating material (9) is arranged between the wire feed attachment (3) and the extruder (2) in the flange region. Device according to claims 4 and 5, characterized in that the 5 mandrel is arranged in the extruder (2) in such a way that the mandrel (8) arranged in the spire (6) is so far from the outlet opening (11) of the nozzle is removed, on the one hand a homogeneous cooled layer is formed on the wire and, on the other hand, this formed layer does not melt again. Device according to claims 4-6, characterized in that the diameter of the nozzle outlet opening (11) is 2.5: 1 in relation to the diameter of the thread. 8. Device according to claims 4-7, characterized in that a separate cooling device (14) is provided in front of the extrusion tool (2) for continuously low-cooling the wire to be foamed. Foamed wire produced according to the method defined in claims 1-3. 10. Use of foamed wire according to claim 9 for tying up plant parts, such as trunks, stems, twigs, branches and the like. ------- "· ·