NL8203114A - SHAPED SHORT-LENGTH SHRINKAGE OBJECT, SUCH AS CRIMPING HOOD, CRIMPING HOSE, CRIMPING CUFF AND THE LIKE. - Google Patents

Description

* ^ i, N.O. 31,177 1

Short length molded shrink article such as shrink cap, shrink tubing, shrink sleeve and the like.

The invention relates to a short-length molded shrink article such as shrink cap, shrink tubing, shrink sleeve and the like of extruded and cross-linked material.

Such shaped shrink articles are generally manufactured, in that a so-called preformed object is sprayed or resp. extruded, then cross-linked, as well as dilated in this cross-linked state, and by cooling this flared shaped article, its removed state is fixed by "freezing".

It is already known from Austrian patent 188,510 to heat the extruded or injection-molded hose of small diameter for the production of heat-shrink tubing from thermoplastic masses, to widen it by means of air under pressure and to fix this changed condition by subsequent cooling. However, it is disadvantageous that such crimping hoses made of thermoplastics, for instance also of polyvinyl-chloride, are not sufficiently temperature resistant for the current requirements and moreover do not have the desired "elastic shape memory", that is to say in the crimping process no longer in all details. take their original form.

This is remedied by a likewise known method of manufacturing heat shrinkable products sold under the trade name "Thermofit", using a high density polyolefin material for spraying molded articles. These objects are then exposed to high-intensity electron irradiation, so that a cross-linked three-dimensional mesh of the molecules is achieved. A mechanically resistant molded article is hereby obtained, which is creep resistant, does not tear and has an "elastic shape memory". For example, if a shrink hose thus processed is pulled over the article to be coated, it shrinks upon brief heating above the crystallite melting point, the known case above 135 °, quickly returns to its original shape and size, and a tight resistive coating is produced.

For the above-described process, any base polymers, also modified, can be used, in each case according to the special requirements of the application. However, a prerequisite is in any case the cross-linking by irradiation before the shaped articles are dilated or expanded in the heated state.

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Another possibility is to use as base materials for the shrink article, polymers which are cross-linked under the influence of moisture after grafting of cross-linking aids such as organosilanes before or during the molding of the preformed article. In addition, it is essential that the action of moisture is carried out either by means of a special device arranged after the manufacture of the preformed article, or already by the amounts of moisture which adhere to the polymers and additives from home, form, or finally can also be achieved by simple storage under ambient influence. This proposal is based on the consideration that, in contrast to peroxidic cross-linking under the influence of heat, which has been known for a long time and has been used in cable manufacturing, for example, by grafting reactable low-molecular compounds, for example organo-silanes, as cross-linking aids on the macromolecules of the base materials which in turn lead to a polyfunctional chain crosslinking during the secondary reactions, "beam-shaped" crosslinking sites are formed, with several macromolecules fixed together via a crosslinking node. This particular chemical cross-linking mechanism 20 results in high bonding forces in the molecular region, which are loosened when heated in the thermoplastic state and thereby allow a widening of, for example, the molded article, after reheating and rapidly shrinking their original take shape.

Crimping articles made of such materials therefore also have an "elastic shape memory" and are therefore suitable for arbitrary application possibilities, for instance as hoses and caps, possibly for the pressure-tight and moisture-proof closure of the ultralands of electrical cables or as cuffs, either one-piece or more pieces-30, for the protection of connection or connection points of electrical cables, or also tube bundle cables. The properties with respect to radiation-cross-linked shrink articles have not changed, or only insignificantly, however, the manufacturing method is essentially simplified.

Regardless of the type of the base materials or of the cross-linking method, which also includes, for example, chemical cross-linking using peroxides, however, difficulties still arise so far, for example, in the production of crimp hoses, thus formed shrink articles of short length, when removing the starting articles, optionally when inflating, a portion of 8203114 * 3 * of its axial length is converted to "radial length". After all, this has the consequence that such a hose becomes shorter in the crimping process with the axial elongation portion that results when it is expanded. It is therefore difficult to maintain dimensional accuracy.

The object of the invention is to find a possibility, in particular, to produce shrink hoses or shrink sleeves, whereby dimensional accuracy is guaranteed, that is to say no axial shortening occurs in crimped condition.

According to the invention, this object is achieved in that longitudinally extending and circumferentially distributed elements with increased tensile strength and low elongation are arranged in the wall of the shaped shrink article. As a result, radial widening, for example inflation, as hitherto possible, avoids conversion from "axial length" to "radial length" during widening and therefore has no effect on shrinking. has more. The shaped shrink articles designed according to the invention are dimensionally accurate, while a longitudinal shrinkage is omitted when shrinking.

It is known per se from German Pat. No. 2,344,577 to reinforce the sheath of electrical cables through inlaid tensile elements. The object here is to increase the mechanical strength of elongated objects of a great length in order to provide so-called self-supporting air cables in this way. Thus, tensile forces which occur when the cable is suspended between the masts, are absorbed by the inlaid endless tension elements, so that the conductor is relieved in tension.

The invention, on the other hand, is based on the knowledge that the elements which have already been inserted into the wall of the preformed short-length article, during the widening operation, stabilize the possibility of movement of the shrinkable material in the direction of the centerline, while surprisingly, the possibility of movement of, for example, the polymer material in the radial direction further, as hitherto remains unimpeded. Thus, in addition to the increase in the longitudinal tensile strength of the end product, here of the molded shrink article, the measure according to the invention achieves, during widening, the material flowing in the desired direction and is controlled only in this direction.

In a further elaboration of the invention, it is advantageous if the tensile elements are inlaid into the wall as fibers, either separately or in groups. These elements may be 8203114 **

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4 are, for example, glass fiber-based elements, or also on polyamide base, as they are known, for example, under the trade name "Kevlar". These elements, for example, from solid profile strands or bundles made from stranded or strangled individual strands, can also be coated with an adhesive and / or glued therewith. The mechanical connection with the polymer material can thereby be increased and a sealing effect, in particular with bundled individual strands, can also be achieved.

The wall of the shaped shrink article can be made of separate layers 10, these layers also being able to consist of different materials. The elements with an increased tensile strength are then inserted in one of the layers, or also in between two layers.

However, it has been found particularly advantageous in the practice of the invention to build the wall of the molded shrink article from a homogeneous material and as a layer, the elements having increased tensile strength enclosed in the polymer material.

It has proved to be expedient to arrange the elements with increased tensile strength in the outer phase of the wall. This applies to cases in which, for material reasons or on the basis of the respective application purpose, an increased notch effect is to be expected.

In the known cables with so-called "corrugated" strain relief elements in the outer jacket, the corrugation of these elements must ensure the most intimate, positive connection between the strain relief elements and the jacket material (East German Patent 124 162), in order to provide the elements as use tensile members.

On the other hand, it is essential for the invention that the axial length of the elements with increased tensile strength mainly corresponds to the axial length of the shaped shrink article before widening. Namely, it is then ensured that, with the short length of the shaped shrink article, the length increased by the undulation is not pulled out, but the supporting elements can actually fulfill their function of switching off an axial shrinkage. The known "waves" of the strain relief elements, on the other hand, effect the "longitudinal stiffness" of the pull elements.

For the production of the shaped shrink articles according to the invention, as far as the articles with two open ends, such as hoses, cuffs or the like are concerned, it is preferred to proceed in such a way that first an endless tube or a hose is made from the cross-linkable material. Extruded and extruded the elements with 8203114

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5, the tensile strength in concentric relation to the pipe wall or hose wall is inlaid therein, and that the crimped articles of a suitable length are cut off from this endless pipe or hose before or after cross-linking. This allows rational manufacture of the preformed articles, ensuring that the elements of increased tensile strength are inserted into the required axial length in the wall of each individual article.

If, as is also contemplated according to a further inventive idea, the wall of the shaped shrink articles is composed of more layers, then preferably during an extrusion of the individual layers, the elements with increased tensile strength are preferably formed in the same processing step, inlaid in the last layer.

The cross-linking of the preformed articles, endless hose or tube, or also these in already cut form, can take place according to conventional methods. The chemical cross-linking, using suitable peroxides, is just as possible as the cross-linking by the application of high-energy rays.

Another possibility is the cross-linking by the action of moisture. For this it has proved advantageous to carry out the cross-linking of the preformed article during a moisture action at elevated temperatures between 80 ° C and 200 ° C, preferably 240 ° to 180 °. Removal to the state to be frozen then takes place immediately afterwards, that is to say "on line", with a still-heated preformed article. According to a further elaboration of the inventive idea, if the crosslinking reaction is caused by the molding or spraying operation during the production of the preformed article itself, then a separate moisture treatment at a higher temperature can be dispensed with.

The raising of the widening temperature can be carried out independently of the moisture treatment, for example in mixtures 30 which can absorb microwaves, by a UHF heating. The efficiency of the manufacturing process can thereby be further improved.

The cross-linking itself, as already used in the cross-linking by moisture of cables, can take place in a kind of sauna, ie in an atmosphere of water vapor with elevated temperatures. Advantageously, however, a heated mixture of glycerine and water, or oil and water can also be used in the practice of the invention for the same purpose, which is firstly accompanied by the advantage of uniform temperature conditions without special control equipment and some other. on the other hand, however, due to the components which the polymers of 8203114 6 * tolerate the shrink article formed better than water, the faster diffusion of the small amounts of water required for the cross-linking occurs. All polymers can be used as base materials, whereby attachment of organosilanes by radically-introduced grafting is possible.

Particularly advantageous, already for reasons of processability, for the purposes of the invention and irrespective of the crosslinking method chosen, the polyethylene, as well as ethylene mixed polymers with vinyl acetate or. acrylate comonomers. However, as base materials 10, materials based on ethylene-propylene rubber alone or cut with polypropylene can also be used.

For the UV resistance, but also for the improvement of the mechanical and rheological properties of the mixture in the manufacture of the preformed articles, it has proved advantageous to add carbon black to the base material. So-called acetylene carbon black with non-hygroscopic properties is particularly suitable for this. Moreover, this carbon black has a high conductivity and already small amounts of, for example, 1.5 to 3.0 parts per 100 parts of polymer are already sufficient to give the shrinkage article the necessary UV resistance. The use of non-hygroscopic acetylene carbon black is of particular importance when the preformed articles are cross-linked by the action of moisture after the grafting of silanes to the base materials.

If a cross-linking by moisture is desired from the possible cross-linking methods, it is further essential that the cross-linking auxiliaries, for example organosilane, be available in sufficient quantity, but with respect to the peroxide, in a balanced amount to shrinkage from a dilated state to generate necessary molecular binding forces. The molar ratio of radical sites of the macromolecule-generating peroxides to the amount of the added silane is therefore preferably about 1:10 when practicing the invention.

The invention will be explained in more detail with reference to the shrink hose shown in Figs. 1 and 2.

The preformed article made of cross-linked material and cut to length, for example, from an endless cross-linked tube or hose, is indicated by 1 as shown in Fig. 1. In the pipe wall resp. hose wall 2 are elements 3 with increased tensile strength and low elongation, which in the illustrated embodiment consist of bundled individual wires 4 on a glass fiber basis. As shown in FIG. 40, the elements 3 run in a straight line in the axis direction, thus the axial lengths of the preformed article 1 and the elements 3 are essentially the same. The elements 3 are incidentally arranged over the circumference of the hose or tube and their number here amounts to four, although the number of tensile resistant elements can of course also be increased in accordance with the requirements imposed on the finished product.

In deviation from the embodiment according to Fig. 1, Fig. 2 shows the preformed article 1 in the already dilated or inflated state, ie in the form of the ready-to-use shaped shrink article, the expanded state of which has been frozen . The bore 5 is increased relative to that of Fig. 1, while the thickness of the tube wall 2 is reduced in accordance with the diameter increase of the bore 5. The axial length is determined by the elements 3, but remains unaffected by the invention in the radial dilation process. As a result, the shrinking process also takes place only in the radial direction, while the axial length of the shaped shrinking article 1 remains unchanged. Good maintenance of the size is therefore guaranteed.

As can be seen from Fig. 2, the elements 3 have a cross-sectional shape which has changed from that of Fig. 1, which is determined by the occurrence of the fibers in more cores. This shows the forces acting during the removal operation, the result of which were hitherto high axial shrinkage values of the hoses and the like. These forces are now absorbed by the elements 3, which allow a material movement 25 in the radial direction, but, however, avoid a change in the axial length during the dilation process.

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Claims (13)

Short-length molded shrink article, such as shrink cap, shrink tubing, shrink sleeves, and the like, of extruded and cross-linked material, characterized in that in the wall (2) of the molded shrink article, it extends longitudinally and circumferentially elements (3) with increased tensile strength and low elongation are provided. Shaped shrink article according to claim 1, characterized in that the elements (3) are inserted in the wall (2) as fibers, either separately or in groups joined together. Shaped shrink article according to claim 1 or 2, characterized in that the wall (2) is made up of several layers. Molded shrink article according to claims 1 to 3, characterized in that the elements (3) are coated with an adhesive and / or are 15 Impregnated. Molded shrink article according to any one of claims 1 to 4, characterized in that the elements (3) with increased tensile strength and low elongation are preferably in the outer phase of the wall (2) of the molded shrink article (1) applied. Molded shrink article according to claim 1 or one of the following, characterized in that the axial length of the elements (3) mainly corresponds to the axial length of the molded shrink article (1) before widening. A method of manufacturing a molded shrink article 25 according to claim 1 or one of the following two open ends, such as hoses, cuffs or the like, characterized in that first an endless pipe or a hose from the cross-linked material is extruded and during extrusion the elements (3) with increased tensile strength and low elongation concentrically with respect to the center line of the tube 30 or hose are also introduced during the formation of the tube or hose wall (2) be inserted therein and that the shaped shrink article (1) of a suitable length is cut off from this endless tube or hose. 8. A method for manufacturing a molded shrinkage blank according to claim 1 or one of the following, having two open ends, such as multilayer hoses, cuffs or the like, characterized in that after extrusion of One or more layers in the outward direction last layer the elements (3) are inlaid Method according to claim 7 or 8, characterized in that the 40 endless preformed articles are cross-linked by energy-rich irradiation. 10. Method according to claim 7 or 8, characterized in that the endless preformed articles are cross-linked under the action of moisture at an elevated temperature between 80 ° and 200 ° C, preferably 140 ° to 180 ° C. and then, while the article is still heated, it is dilated until the condition to be frozen is effected. Method according to claim 7 or Sen of the following, characterized in that as tensile elements with low elongation materials based on glass fibers are used. Process according to Claim 7 or SSn of the following, characterized in that polyethenes or ethylene-mixed polymers are used as base materials for the shrink articles formed. 13. Process according to claim 7 or SSn of the following, characterized in that as base materials, materials based on ethylene-propylene rubber are used alone or as cut components with polyolefins, possibly polypropylenes. ssssaeae 8203114