DE3133091A1 - "SHRINK SHAPE SHORT LENGTH, LIKE SHRINK CAP, HOSE CUFF AND THE LIKE" - Google Patents

Description

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kabelmetal electro GmbH

E 1 1815

Aug 17, 1981

Short-length shrink molded part, such as shrink cap, tube, sleeve and derql. _i __ _a _

The present invention relates to a shrink molded part short length, such as shrink cap, tube, sleeve and Like. Made of extruded and crosslinked material.

Such shrink molded parts are usually produced by that a so-called preform injected or extruded, connect! networked and expanded in this networked state and duri Cooling this expanded molding whose expanded to stand by "freezing" is fixed.

It is already known (OE-PS 188.510), the extruded for the production of shrink tubing from thermoplastic materials or yerpritzteti small-diameter leeks, expand with compressed air and fix this changed state by subsequent cooling. The disadvantage here is However, that such heat-shrink tubing made of thermoplastics, both

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for example also made of polyvinyl chloride, for today's requirements are not sufficiently temperature-resistant and also do not have the desired "elastic shape memory", d. H. not in all details during the shrinking process take their original shape.

This is remedied by a technique, which is also known for the production of heat-shrinkable products sold under the trade name Thermofit, in which a high-density polyolefin material is used for injection molding of molded parts. These parts are then exposed to high-intensity electron radiation, so that a networked three-dimensional meshwork of the molecules is achieved. This results in a mechanically resistant shape α i 1, dar, Kr.i och foul i ... «; t, not tearing open and has an" elastic shape memory ". Will

z. B. a shrink tube processed in this way over the to be covered If the object is pulled, it shrinks when heated briefly above the crystallite melting point, in the known case above 135 °, it quickly returns to its original shape and dimensions, and a solid, resistant coating is created.

Any base polymers, including modified ones, can be used for the process described above, depending on the special requirements of use. However, the prerequisite is in any case the crosslinking by irradiation before the moldings are expanded or stretched in a heated state.

Another possibility is to use polymers as base materials for the shrink articles which, after grafting on crosslinking aids such as organosilanes, are crosslinked under the action of moisture before or during the shaping of the preform. It is also essential that the action of moisture is carried out either by means of a special device downstream of the production of the preform or by means of the polymers and additives provided at home. anhufl rncicm F ei i ti qke i I smcnigon in the form successcjon odoi Mi ¹ Ii I i ell I i ch also through οί | ΐΓ> κΊηϋ) Lücjorn

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can be achieved under environmental influence. This suggestion is based on the idea that in contrast to the long-known and z. B. used in cable technology peroxidic crosslinking under the action of heat through the grafting of reactive low molecular weight compounds z. B. of organosilanes, as crosslinking aids on the macromolecules of the base materials, which in turn in the course from secondary reactions to a polyfunctional chain linkage lead to form "bundle-like" crosslinking points, with several macromolecules via a crosslinking node are fixed to each other. This special chemical cross-linking mechanism leads to high binding forces in the molecular Area that is loosened when heated in the thermoplastic state and thus an expansion, for example, of the molding. after rewarming and rapid shrinkage, they return to their original shape.

Shrink articles made from such materials also have an "elastic shape memory", which is why they are suitable for be lovable. possible uses, e.g. B. as hoses and caps, for example for the pressure-tight and moisture-proof conclusion of the Ends of electrical cables or as sleeves, one or more parts, to protect connection or connection points of electrical Cable or tube bundle cable suitable - the properties compared to radiation-crosslinked shrink-fit articles not changed or only slightly changed, but the manufacturing process is significantly simplified.

Regardless of the type of base materials or the networking technology, including z. B. heard a chemical crosslinking by means of peroxides, but so far there are still difficulties in that z. B. in the production of shrink tubing, so shrink molded parts of short length, when expanding the blank, for example when inflating, a part of its "axial liümjo" is converted into "iridLüle Lüncj · '" ujt t. Ultimately, this has the consequence that such a tube is shortened by the stretching component which is axial during expansion during the shrinking process. A dimensional accuracy is therefore difficult to adhere to.

The invention is therefore based on the object of providing a possibility to find, especially heat shrink tubing or sleeves to produce that guarantee a dimensionally accurate fit, «1. H. in shrunken State no axial shortening.

This object is achieved according to the invention in that in the wall of the shrink molded part extending in the longitudinal direction and elements of increased tensile strength and distributed around the circumference low elongation are arranged. This has the consequence that a radial expansion, z. B. an inflation, as previously possible, the The conversion from "axial length" to "radial length" does not take place during the expansion and therefore does not occur during the shrinkage more comes into effect. The trained according to the invention Shrink molded parts are dimensionally accurate, a longitudinal shrinkage when There is no shrinking.

It is known per se, (DBP 2 344 577) the jacket electrical Reinforce cables with embedded tension elements. The goal here is the mechanical one for elongated goods of great length To increase strength in order to create so-called self-supporting aerial cables in this way. So when hanging the cable between The tensile forces occurring on the masts are taken over by the inserted endless tension elements, the ladder is relieved of tension.

On the other hand, the invention is based on the knowledge that the short-length preforms already embedded in the wall of the preform Elements for stabilizing the possibility of movement 5 of the shrinkable material in the axial direction during the expansion process care, while surprisingly the possibility of movement z. B. the polymer material in the radial direction can continue as before unhindered. Thus, the measure according to the invention additionally leads to an increase the longitudinal tensile strength of the end product, here the molded part, the flow of material in the desired direction when expanding

Direction and steered only in this.

In a further development of the invention, it is also advantageous if the tensile elements as fibers individually or in groups

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are collectively stored in the wall. This can e.g. be fiberglass-based or polyamide-based, as they are known, for example, under the trade name Kevlar. These elements, e.g. B. from solid profile strands 5 or bundles made from stranded or twisted single strands can also be coated with an adhesive and / or soaked. The mechanical connection to the polymer material can thereby be increased and further a sealing effect can be achieved in particular with bundled single strands. "

The wall of the shrink molded part can be made from individual layers, whereby these layers also consist of different ones Materials can exist. The elements of increased tensile strength are then in one of the layers or even between stored two layers at a time.

It has proven to be particularly advantageous in carrying out the invention However, the wall of the shrink molded part turned out to be a uniform material and a single-layer structure, with the elements of increased tensile strength in the polymer material are included. It has proven to be useful to put the elements of increased tensile strength in the outer phase of the To arrange wall. This applies to cases where material rounds odor due to de »jowoi! i.qcn intended use with an increased Leu notch effect must be expected.

In the known cables with so-called "undulating" strain relief elements In the outer jacket, the corrugation of these elements is intended to ensure the most intimate, non-positive connection possible between the strain relief elements and the jacket material to achieve (DDR-PS 124 162) to use the elements as pulling organs /.u.

DenujogcnUbor i .. ^c ; t. for di.i; Erf.indi.mcj essential that the axial i.üruit / ik-r F. Ic-tuon 1 c. i (jkoiL generally corresponds to the axial length of the shrink molded part before expansion. This ensures that with the short length of the shrink molded parts, the

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greater length is pulled out, but the holding elements actually do justice to their task of eliminating axial shrinkage. The well-known "curling" of the strain relief elements on the other hand, influences the "longitudinal stiffness" of the tension elements.

For the production of the shrink molded parts according to the invention yeht one, as far as those with two open ends, such as hoses, sleeves or the like. Concerned, expediently so that initially an endless tube or hose is extruded from the crosslinkable material and the elements during the extrusion increased tensile strength in concentric assignment to the pipe or hose wall are stored in this, and that of this endless tube or tube before or after the crosslinking, the shrink molded parts of the corresponding length are cut to length. This enables an efficient production of the preforms, whereby it is ensured that in the wall of each individual part the elements of increased tensile strength in the required axial Length are stored.

Is, as also provided according to a further idea of the invention, the wall of the shrink molded parts built up in several layers, then it is expedient for an extrusion of the individual layers in the same operation the Elomontc increased tfugfout.icjkei t preferably stored in the last layer on the outside.

The networking of the preforms, endless hose or pipe or even this in pre-cut form, can be done by customary methods. Chemical crosslinking by means of Suitable peroxides are just as possible as crosslinking through the use of high-energy rays.

Another possibility is crosslinking through the action of moisture. To this end, it has been found to be in front of toi. ihaf L orwi> -st-m, the networking of the preform. ¹ .; during <.ii.nr: r Feuohi iuk'ilra'M nvffect at elevated temperature doors /.wiweh BO C and 200 C, preferably 140 to 180, before /. The Aufwoi. The state to be frozen then takes place immediately afterwards, ie "on line", with the preform still heated. Will, as in

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Continuation of the inventive concept further provided that Crosslinking reaction caused by the molding or injection molding process during the production of the preform itself can then occur a separate moisture treatment at higher temperatures can be dispensed with. The temperature increase before the expansion can be done independently of the moisture treatment, e.g. B. in microwave-absorbent mixtures durcl a UHF heating. The economics of the manufacturing process can thus be further improved.

The crosslinking itself can take place in a kind of sauna, as with the moisture crosslinking of cables already in use. d. H. in a steam atmosphere with elevated temperatures. In carrying out the invention, however, a heated glycerol-water or a heated glycerol can also be used for the same purpose Oil-water mixture can be used, which once has the advantage of uniform temperature conditions without special control involves effort, but also due to the fact that it is better compatible with the polymers of the shrink articles than water Components ensures a faster diffusion of the small amounts of water required for crosslinking. As a base material In general, all polymers can be used for which an addition of organosilanes by radical initiated grafting is possible.

As particularly useful, if only for reasons of processing, have for the purposes of the invention and regardless of the selected type of crosslinking the polyethylene and ethylene copolymers Proven with vinyl acetate or acrylate comonomers As base materials, however, those based on ethylene-propylene rubber alone or in a blend with polypropylene can also be used be used.

For UV resistance, but also to improve the mechanical and rheological properties of the mixture in the In the production of the preforms, it has proven to be advantageous the base material. To add soot. Particularly suitable for this purpose, so-called acetylene blacks with non-hygroscopic

Properties. These carbon blacks also have a high conductivity; even small amounts of z. B. 1 _# 5 to 3.0 parts per 100 parts of polymer to give the shrink article the necessary UV resistance. The use of non-hygroscopic acetylene blacks is particularly important when the preforms are crosslinked by the action of moisture after silanes have been grafted onto the base materials.

The possible types of crosslinking result in moisture crosslinking desired, then it is also essential that the crosslinking auxiliaries, z. B. Organosilanes are available in sufficient but balanced amounts with regard to the peroxides, in order to generate the molecular binding forces necessary for the shrinkage from an expanded state. The molar The ratio of free radical sites on the macromolecule-generating peroxides to the amount of added silanes is therefore advantageous about 1:10 when practicing the invention.

The invention will be explained in more detail with reference to the shrink tube shown in FIGS.

The made of crosslinked material, e.g. B. from an endless one cross-linked tube or tube cut to length preform is, as can be seen from FIG. 1, denoted by 1. In the pipe or Hose wall 2 are elements 3 of increased tensile strength and low elongation, in the illustrated embodiment these consist of bundled individual threads 4 on glass 5 fiber base. As the figure illustrates, the run Elements 3 are straight in the axial direction, so the axial lengths of preform 1 and elements 3 are essentially the same. The elements 3 are arranged distributed over the circumference of the hose or pipe, their number is four here, each according to the requirements placed on the finished product the number of tensile elements can of course also be increased.

Deviating from don AuiitiirhuiHj.slK-ir.pi <· I according to tlor PU). 1 xejcjl. FIG. 2 shows the preform 1 in the already expanded or

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inflated state, d. H. in the form of the ready-to-use shrink molded part, its expanded state frozen is. The bore 5 is enlarged compared to that according to FIG. 1, the thickness of the pipe wall 2 corresponding to the increase in diameter the hole 5 is reduced. The axial length is determined by the elements 3, it remains on due to the invention Expansion process in the radial direction not involved. As a result, the shrinking process is also exclusive takes place in the radial direction, while the axial length 10 'of the shrink molded part 1 remains unchanged. A high level of dimensional accuracy is thus guaranteed.

As can be seen from dor Fig. 2, the elements 3 show a Gegei Above Fig. 1 due to the multicore structure of the fibers changed cross-sectional shape. It illustrates this during the expansion process acting forces, the consequence of which so far were high axial shrinkage values of the hoses and the like. Diose Forces are now absorbed by the elements 3, which allow material migration in the radial direction, a change but prevent the axial length during the expansion process.

Claims (1)

kabelmetal electro GmbH E 1 1815 Aug 17, 1981 Claims 1. Shrink molding short length, such as shrink cap, tube, sleeve and the like. Made of extruded and crosslinked material, characterized in that in the wall (2) of the shrink molding in the longitudinal direction and distributed on the circumference elements (3) increased tensile strength and lower Stretching are arranged. 2. Shrink molded part according to claim 1, characterized in that the elements (3) are incorporated as fibers individually or combined in groups in the wall (2). 3. Shrink molding according to claim 1 or 2, characterized in that the wall (2) is constructed in several layers. 4. Schrumpfformtet 1 nuch claim 1 to 3, characterized in that the Kiemente (3) coated with a pressure sensitive adhesive and / or impregnated. 5. Shrink molding according to one of several of the claims 1 to 4, characterized in that the elements (3) of increased tensile strength and low elongation are preferably arranged in the outer phase of the wall (2) of the shrink molded part (1). 6. Shrink molding according to claim 1 or one of the following. characterized in that the axial length of the elements (3 essentially corresponds to the axial length of the shrink-fitting part (1) before the expansion. 7. A method for producing a shrink molded part according to claim 1 or one of the following with two open ends, such as hoses, sleeves or the like., Characterized qekenn _r is characterized in that first an endless tube or hose is extruded from the crosslinked material and during the extrusion the Elements (3) of increased tensile strength and low elongation in concentric assignment to the pipe or hose axis are also introduced and stored in this when the pipe or hose wall (2) is formed, and that the shrink molded parts (1) of the corresponding length are cut to length from this endless pipe or hose . 8. A method for producing a shrink molded part according to claim 1 or one of the following, with two open ends, such as hoses, sleeves or the like., Which are multilayered, characterized in that "after extrusion 5 one or more layers in the last outward Layer dio elements (3) are stored. '). Method according to Claim 7 or 8, characterized in that the endless preforms are crosslinked by high-energy radiation. JO. The method of claim 7 or 8, characterized in that the end lots preforms are crosslinked during a Peuchtigkeitseinwirkunq at Incr Lon temperatures between 80 ° and 200 ⁰ C, preferably 140 to 180 C and ₇ anschließei • · ft when the preform is still heated, the expansion on the to be frozen State takes place. 11. The method according to claim 7 or one of the following, characterized in that those based on glass fiber are used as tensile elements with low elongation. 12. The method according to claim 7 or one of the following, characterized in that the base materials used for the shrink molded parts are polyethylene or ethylene copolymers. 13. The method according to claim 7 or one of the following, characterized in that those based on ethylene-propylene rubber alone or as a blend component with polyolefins, such as polypropylene, are used as base materials. IAD ORIGINAL