DK157480B - PROCEDURE FOR THE MANUFACTURING OF CRIMINAL ARTICLES, SUCH AS CRIMPING HOSES, CRIME CRAFTS AND SHRINKPADS - Google Patents

Description

in

DK 157480 B

BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to a method of producing any wholly or partially foamed shrinkage articles, such as shrink tubing, shrink sleeves, and shrink sleeves, from a grafted, organosilane cross-linked, under the influence of moisture, cross-extrudable polymer, wherein the polymer is mixed with the silo and the graft. necessary peroxide and any foaming agent and the polymer is melted, the silane is applied to the polymer, condensation catalyst is added, an starting material is formed from the grafted material, the starting material is crosslinked and expanded in this crosslinked state, and the thus expanded starting material is cooled to fix its expanded state, workpiece may be coated internally with a hot melt adhesive.

From the specification of AT Patent No. 188,510, it is known in the manufacture of thermoplastic shrink tubing to extend a smaller diameter extruded or injection molded tube by compressed air, thereby pressing it against the interior wall of a duct which determines a larger diameter. In a subsequent cooling zone, the expanded hose is cooled to maintain the larger diameter. However, it is a disadvantage here that such shrink tubes of thermoplastic material, e.g. also of polyvinyl chloride, are not sufficiently temperature resistant to meet the requirements of today and furthermore do not possess the desired "elastic mold memory", i.e., in the shrinking process, they are unable to assume their original form in every detail.

These disadvantages are remedied by another known method of manufacturing heat-shrinkable products which are sold under the trade name THERMOFIT. In this known method, a high density polyolefin material is used for injection molding of mold parts. These parts are then subjected to high-intensity electron irradiation to obtain a cross-linked three-dimensional molecular network. Thereby, a mechanically resistant mold part which is creep-resistant, does not crack and has an "elastic mold memory". If a shrink tubing, e.g. is prepared in this way, drawn on the object to be coated and heated briefly to above the crystallite melting point, in the said case to above 135 ° C, it rapidly shrinks to its original

DK 157480 B

2 shape and dimensions and form a firm and resistant coating.

In the process just described, various base polymers, including modified ones, can be used depending on the purpose of the articles. However, it is a disadvantage that the cross-linking must be done by irradiation before expanding the starting items in the heated state. This requires great care (radiation protection) and requires the use of a large apparatus, which makes it difficult and therefore expensive to manufacture.

10

However, said prior art method also suffers from manufacturing technical disadvantages in that materials which are prone to adhesive can either not be used at all or can only be used if the friction between the surface of the hose and the inner wall of the duct 15 is reduced by means of abrasives or taken special measures which preclude contact between the duct and the hose. However, this is not possible due to the channel sizing and shaping function. However, if damage to the hose is avoided by this method, at least 20 surface roughnesses must be envisaged which, in addition to impairing the appearance of the hose, can form sites of corrosion attack, which are subsequently caused by external influences.

DE Publication No. 2,411,141 also discloses the manufacture of sheaths of moisture-resistant thermoplastic and silane peroxide crosslinking agent for electric cables, which sheaths are extruded but not expanded to obtain a shrinking article and which are not "frozen" ", i.e. fixed in such an extended state. In addition, the starting material of moisture-resistant thermoplastic and silane-peroxide cross-linking agent disclosed in this publication is first premixed at a temperature of 60-100 ° C, and only then the processed granules are extruded, ie. in another workflow.

DE Publication No. 2,649,874 relates to a mass comprising silane-grafted moisture-resistant polyolefin and / or copolymer of polyolefins and other monomers, which are intended for insulation of electrical cables, and a process for producing this mass. Essentially, this print can only be deduced

DK 157480 B

3 conditions that polymeric masses can be crosslinked by moisture action, even when containing a specified soda component. In the presentation change, on the other hand, there is no mention of the manufacture of shrink articles.

5

The object of the invention is therefore to provide a method for producing shrinkage articles having "elastic shape memory" having the same or at least comparable properties as the shrinking articles produced by the above known method, without the need to carry out the crosslinking by means of a relatively cumbersome radiation, and to simplify the manufacturing process and implement it in such a way that shrinkage articles of impeccable quality can be produced.

This object is achieved by the process of the measures set forth at the outset when it is characterized by the fact that at least the condensation catalyst, the silane and the peroxide, before melting the polymer, are combined with it into a uniform mixture, the silane is applied at elevation of temperature and the grafted 20 polymer is then molded, the melting, grafting and shaping being carried out in one operation.

It is essential here that the moisture action is made by a particular device following the preparation of the starting material or can be obtained in the mold already by the amounts of moisture already present in the polymers and additives, or simply by storage under the influence of surroundings.

The invention is based on the recognition that, contrary to the well-known, e.g. used in the cable technique peroxidic crosslinking under heat effect, by grafting the base materials macromolecules with reactive low molecular weight compounds, e.g. organo-silanes as cross-linking aids, which again during the course of secondary reactions lead to a polyfunctional chain cross-linking, are formed in the form of bundled cross-linking sites where several macromolecules are fixed to one another over a cross-linking node.

This particular chemical cross-linking mechanism causes large bonding forces in the molecule area which, upon heating to

DK 157480 B

4 thermoplastic state is admittedly attenuated, thereby enabling an expansion, e.g. of the starting material, but after a reheat and a rapid shrinking, their original strength resumes.

Shrinkage articles made of such materials therefore have a "resilient shape memory" and are therefore suitable for versatile applications such as hoses and sheaths, e.g. for pressure-tight and moisture-tight termination of the ends of electrical cables or as single or multiple tea cuffs, for protection of the 10 connection or connection points by electrical cables or pipe bundle cables. The properties of the shrinkage articles made in accordance with the invention are not or only substantially altered in relation to the characteristics of shrinkage articles where the crosslinking has been done by irradiation, whereas the preparation itself is substantially simplified by the invention.

In carrying out the invention, it has been found advantageous to make the crosslinking of the starting material under the influence of moisture at elevated temperature of 80-200 °, preferably 140-180 °. The extension to the state in which the starting material is to be frozen takes place immediately adjacent to it, i.e. "On line" while the starting material is still hot. If the crosslinking reaction is provided by the molding or injection molding process in the actual preparation of the starting material, a separate moisture treatment below 25 can be omitted. The temperature increase prior to expansion can be carried out independently of the moisture treatment, e.g. by microwave-absorbent mixtures by means of UHF heating, thereby obtaining a further cost reduction of the preparation.

30

The crosslinking itself, as is already the case with moisture crosslinking in connection with cables, can be done in a kind of sauna, i.e. in a water vapor atmosphere with increased temperature. However, the cross-linking can also be done by using a heated glycerin-water mixture or an oil-water mixture which offers the advantage that uniform temperature conditions can be maintained without complicated control and partly that the components which are better compatible with shrinkage types are polymers, provide a quicker diffusion of the small amounts of water required for the crosslinking.

DK 157480 B

5

As a base material can be used all polymers with which incorporation of organo-silanes is possible by radical initiated grafting. According to the invention, it is particularly convenient for the sake of good processability to use polyethylene or ethylene blend polymers with vinyl acetate or acrylate comonomers as the base material. However, as a base material can also be used materials based on ethylene-propyl mono-rubber single or mixed with a polyolefin.

As condensation catalysts for use in the process of the invention, tin compounds such as e.g. tin-1 aurate and di butyl tindi1 aurate.

In order to obtain UV resistance and also to improve the mechanical and rheological properties of the mixture in the preparation of the starting materials, it has been found advantageous to add soot to the base material. Especially suitable are so-called acetyl one-soda types with non-hygroscopic properties. These soot types also have a high conductivity and, unlike other conventional soot types, small amounts of soot of 1.5-30, preferably 3.0-15 parts of soot per minute are sufficient. 100 parts polymer to give the shrinkage article antistatic properties or possibly conductivity by good mechanical and rheological properties. Furthermore, the use of non-hygroscopic acetylene sod is important because it does not interfere with the silane crosslinking.

An amount of 5-40, preferably 8-20 parts of non-hygroscopic soot per liter.

Therefore, 100 parts of polymer is considered most suitable for the shrinkage articles to be made according to the invention.

In addition to or instead of the soot acting as filler, other non-hygroscopic fillers such as e.g. chalk, kaolin or talc. These fillers are advantageously used in amounts of 5-30, preferably 10-20 parts to 100 parts polymer. In this way, in addition to obtaining a lowering of the mixture and thus of the end product, an improvement in the hardness, heat resistance and compressive strength can also be obtained.

It is particularly advantageous, in combination with soot and other fillers, to add substances which, at higher temperatures, secrete water, which then provides a moisture content.

DK 157480 B

6 cross-linking in the tool itself. As such, in particular, partially hydrophobic silic acids or silicates or aluminum oxide hydrates are useful, respectively. The latter separates water at temperatures above 180 ° C according to formula 5

2A1 (OH) 3 - * A1203 + 3HzO

An alumina hydrate from the company Martinswerk, which is known by the trade name "Martinal A-S" or in silanized form under the trade name "Martinal A-S / 101", has proven to be particularly well suited for the practice of the invention. This filler has an average grain size of approx. 0.4 µm and in particular in the silanized form is well compatible with polyethylene.

By means of said soot, an additional advantage is obtained if the cross-linking occurs under the influence of humidity at room temperature or a temperature slightly higher than the room temperature, and the expansion of the starting material is subsequently heated by the injection molded part. In this case, the heating is very advantageous in the case of microwave irradiation, the soot chosen being particularly suitable for microwave absorption. The temperature obtainable here is dependent on the intensity of the UHF field and can be controlled as desired. A temperature of 102-170 ° C, preferably of 130-150 ° C, has been found to be appropriate.

25

Furthermore, it is essential for the desired moisture crosslinking and thus usefulness in grafting with crosslinking aids that these agents, e.g. organosil is present in a sufficient, but at the same time, relative to the peroxides metered amount to provide the molecular binding forces required for a shrinkage from the expanded state. The molar ratio of peroxides which provide radical sites to macromolecules and the amount of silanes added is therefore advantageously 1:10 according to the invention.

The expansion of the preformed output hose to its larger diameter to form the shrink tube can be repeated by repeatedly extending each end with a calibration of the output hose, the expansion being by means of negative pressure acting on the surface of the output hose between each calibration. This measure ensures

DK 157480B

7 high quality end products, both in terms of external appearance and partly in terms of shrink properties. The latter is especially the case if materials which can be cross-linked or are already cross-linked at the time of enlargement are used.

5

It has been found to be advantageous if the extension of the output hose to the final diameter occurs under a pressurized liquid bath. Hereby a particularly good surface quality is obtained in the te of the shrinkable final product. This is especially true if this liquid, e.g. water, while also serving as a lubricant or release agent during the calibration process. This simple possibility of an automated lubricant or release agent which is not to be looked after is not known in the prior art apparatus for expanding shrinkable products.

15

The expansion itself must be adapted to the polymeric material used, e.g. polyvinyl chloride, cross-linked or non-cross-linked polyethylene, etc. It has been found appropriate to allow the expansion to take place evenly, i.e. in uniform di ameter increasing steps. However, sometimes 20 may also be advantageous if the expansion is done in steps.

For the expansion of a hollow mold string, i.e. In order to obtain the increase in diameter, a prior heat treatment of the starting material in the cross-linked or non-cross-linked state is usually required. For this, e.g. a suitable temperable liquid bath is arranged in front of the extension apparatus. However, the heating can also be done by external heat radiation or by internal heating, e.g. over a high frequency 30 coil.

However, sometimes it may also be advantageous, especially if an increase to several times the original diameter is desired, to associate the increasing diameter increase of the output hose with a steadily increasing heating or through heating of the output hose.

According to the progressive expansion, an appropriate dosage of the heat quantity must then be made.

With an extension that corresponds to several times the original diameter

DK 157480 B

8 of the output hose (the output blank), it may sometimes also be advantageous if the internal surface of the output hose during expansion is subjected to a so-called support pressure during expansion by means of the negative surface acting. In this way, especially if the wall thickness is very small in relation to the full diameter, the starting material can be prevented from collapsing. In this connection it is possible, if desired, e.g. during the first steps of the expansion, to use the internal support pressure in the interior of the output hose to support the diameter increase 10 from the inside.

The method according to the invention is particularly advantageously carried out by means of an apparatus in which a so-called calibrator consisting of individual hollow discs arranged one after the other, whose bore diameters seen in the flow direction are increased evenly or stepwise, serves to expand the hollow output hose after or during warm up. Such calibrators are already known for producing plastic tubes of uniform outer dimensions and ensure a smooth guide over extremely small contact surfaces, thereby providing high-quality surfaces. The hollow discs are furthermore all summarized in a common bundle or in bundles which are placed in a separate possibly temperable liquid-carrying container which can be closed tightly. As a result, during the passage of the workpiece through the hollow slices a good guide with vanishingly small friction is obtained. The height of the liquid level, which can of course be adjusted, is suitably chosen in such a way that the hollow discs are completely covered, e.g. of water. Above this water level there are e.g. by appropriately adjusting the suction pumps, a negative pressure of up to 8 m VS is created, which ensures that the wall of the output hose is subjected to a suction influence between 30 every two consecutive hollow discs, that is, the output hose is expanded. The negative pressure also acts between the subsequent hollow discs, which have a larger bore diameter than the previous ones, so that after the expansion already made, a further expansion and so on.

Due to the even softer structure of the heat-treated output hose during its inlet into the hollow disc bundle, it has been found appropriate that the distance between the hollow discs, together with the increasing bore diameter, also be increased in the flow direction.

9

DK 157480 B

This eliminates the risk of the output hose being pushed into its hollow discs during its passage in its still soft state, which limits it, is torn or torn.

The properties of the products produced by the process according to the invention can be varied in that the limiting walls of these mold parts may consist wholly or partially of foamed material. In addition to significant material savings and thus also a reduction in weight, an additional advantage is obtained in the form of better heat insulation and the great mechanical stability obtained by the cross-linking compared to a conventional foam insulation. If the foamed portion of the shrink mold portion consists of an olefin polymer or olefin blend polymer, a shrink mold portion is obtained whose degree of crosslinking is between 30% and 80%. Thus, the product meets the requirements.

15

In addition to being dependent on the base polymer selected, the mechanical stability of the foamed insulation will depend in particular on the number, size and distribution of the pores formed during the foaming. The smaller these pores are, and the more uniformly they are distributed over the insulation cross-section, the better the stability, respectively, the tougher the melt during the foaming, the higher the foaming rates achieved by uniform pore structure. This is physicochemically justified, with the pore size and structure being crucial depending on the vapor pressure of the propellant and the surface tension of the melt.

25 However, the higher the surface tension, the higher the melting quality is. In practice, it has therefore been hitherto advanced in the way that a temperature reduction immediately before foaming was made to increase the viscosity of the melt. However, this possibility is rather complicated, requiring a special long-extruder method technique.

According to the invention, it is expedient to prepare an optionally wholly or partially foamed shrink article in that first an injection blank is extruded or extruded, the confining walls of which are wholly or partially foamed and crosslinked. Then, the starting blank in this foamed and crosslinked state is expanded, and upon cooling and freezing, this extended starting blank is fixed in its extended state. The crosslinking can be done below in any desired manner, e.g. by

DK 157480 B

10 the mold parts before, during or after foaming are subjected to an energy rich radiation. The temperature of the melt can hereby be optimally adjusted to the decomposition temperature of the propellant. In this way and conditional on the relatively high toughness of the melt during foaming, a fine cell uniform pore structure can be obtained over the full cross section.

For foaming the mixture which can be crosslinked in the presence of moisture, so-called chemical propellants can be used. However, if grafting and foaming are carried out in the same processing step, it must be ensured in the selection of these propellants that the by-products resulting from the splitting of the propellant do not interfere with the grafting process. To safely exclude this, instead of the chemical propellants, physical propellants, e.g. lower fluorinated chlorinated hydrocarbons, 15 or nitrogen respectively. These propellants also lead to high foaming rates, to the fine cell uniform pore structure and to good mechanical stability of the crosslinked product, without disturbing the grafting process.

It can sometimes be advantageous if the foaming propellants are used at the same time as a carrier for at least some of the moisture needed for the crosslinking. Thus, moist gases, e.g. also water vapor leading to a fast crosslinking is introduced into the mixture. The water storage time can thus be significantly reduced.

The propellants, whether serving as a moisture carrier or not, can be added to the mixture in the usual manner. However, it is particularly simple if the propellant is drummed in powdered state.

However, sometimes it may also be advantageous to mix the grafted olefin polymerate or olefin mixture polymerate with a propellant-containing polymer batch.

Furthermore, if the cross-linking of the foamed material, as already explained, occurs under the influence of moisture, it has been found to be advantageous to initiate the cross-linking process using water-separating propellants. In this way, e.g. progress in all cases where the amount of water that the insulation automatically absorbs during the cooling water flow is not

DK 157480 B

π sufficient for the crosslinking process.

A further possibility of applying additional amounts of water can be obtained by the addition of non-hygroscopic metal oxides such as tin or tin oxides to the olefin polymer juices or olefin mixture polymers. These materials, in connection with the so-called siloxane crosslinking, immediately after completion of the molding lead to crosslinking degrees of approx. 30%. Already this one, e.g. by the addition of zinc oxides, the cross-linking effect obtained 10 results in a clear increase in the viscosity of the melt, to which must be added the viscosity already obtained by grafting. Thereby, a particularly tough melt is obtained which results in a very advantageous pore structure of the foam. In this connection, it may sometimes be advantageous if the addition of the metal oxides occurs only after the inoculation. In this way, difficulties are prevented during extrusion, e.g. as a result of incipient cross-linking during grafting.

The zinc oxide used has additional advantages in addition to the aforementioned improvements. Thus, it is known that zinc oxide influences the kinetics of the conventional propellant decomposition process, i.e. in part, the cleavage temperatures are significantly lowered in the presence of such oxides. Thus, it is possible to allow the propellant cleavage to take place already at relatively low temperatures, which also has an advantageous effect on the foam structure. Further advantages are obtained with respect to the electrical properties of the material, with residuals of un-split propellants remaining in the material becoming virtually immaterial.

Conveniently, the grafting and foaming of the materials used may occur in the same operation. This results in an increased reliability and reduced tendency to disrupt the process.

However, the same possibility is also obtained if, according to the invention, layers of foamed material and solid material follow alternately one another in the shape of the shrinkage part.

The process of the present invention is illustrated with reference to the accompanying drawing, wherein 12

DK 1 57480 B

Figure 1 illustrates the process sequence of Example 1, Figure 2 shows the same embodiment as Figure 1, but with the change that a separate heating of the starting blank is performed, Figure 3 shows another embodiment of the process sequence of Example I, Figure 4 shows a view of Figure 5 shows the process of producing endless mold strands with shrinkage cap, Figure 6 shows an enlargement of the inlet to the calibrator shown in Figure 5, and Figure 7 shows another embodiment of the process of producing endless strands of shape with shrinkage capes.

20

The invention will then be further elucidated in the mixing examples given below. All parts are parts by weight.

A mixture of the following composition 25

Example I

Polyethylene homopolymer (PE) (density 3.94 g / cm, melt index 0.2-2.5) 100 parts vinyl trimethoxysilane 1.0-1.5 parts dicumyl peroxide 0.03-0.05 "catalyst (dibutyltin 1) aurate) (Naftovin® SN / L) 0.05 sod (acetylene black Y) 15 "35 is either in already mixed state or as shown in FIG. 1 in the form of individual components filled in the funnel 1 of an extruder 2. It is convenient if the base polymers and the filler - soot or chalk or both - are distributed homogeneously in a prior mixing process. In the extruder 2, homogenization is first effected by melting

DK 157480B

13 and in a subsequent zone of the same extruder, respectively, injection molding machine extrudes the PE molecules with silane at temperatures above 140 ° C, preferably between 160 ° and 200 ° C. If shrinkage articles are manufactured which can be with or without 5 passage nozzles, the graft material is transferred to the molding tool 3 through the spray channel 4. The material can be added here or in advance to foam inserts, e.g. in the form of moist gas. In the event that shrinkable hoses or cuffs are to be manufactured, it is advantageous to proceed in the same manner as in the continuous manufacture of elongated goods continuously extruded by means of an extruder with hose extrusion tool and subsequent vacuum calibration. hoses which are then inflated to the dimensions that the hoses or cuffs must have after completion of moisture cross-linking.

15

Independent of the species, i.e. the outer shape of the shrinkage articles is advantageous if the obtained injection or injection molding temperature is used to effect an accelerated crosslinking in a humid atmosphere.

20

To this end, the schematically indicated water bath 5, which contains an oil-water emulsion or a water-glycerine mixture, serves in a simple manner to ensure a temperature constant as well as to accelerate the water diffusion of the starting material. After the cross-linking process, the starting material is expanded in its still hot state, e.g.

the expansion of the casing 6 over the mandrel 7 by means of which the casing 6 is inflated from the inside, and this is frozen in its expanded state upon cooling. The cross-linking at higher temperatures occurs directly in connection with the expansion to utilize the heat content.

30

Other processes can also be used. Thus, in order to provide the crosslinking and / or extension, a separate progressive heating of the starting blanks, e.g. as shown in FIG. 2, using a UHF radiation 8, i.e. microwave heating in connection with the injection molding made and removal of the mold part of the injection molding tool 3. However, the cross-linking can also be partially or wholly done in the mold cavity of the injection molding by means of the moisture contained in the polymers and additives, respectively, and then completed by means of a heating arm.

DK 157480 B

14

However, additives such as certain alumina hydrates or partially hydrophobic silicates, which secrete small amounts of H2 O at higher temperatures, may also be added. The H 2 O proportion of these additives released at spray temperature is sufficient for the crosslinking. The mold part then leaves the injection molding machine in a cross-linked state.

If it is not about the manufacture of sheaths, but for example. about continuous extrusion of hoses, it is convenient to proceed 10 as shown schematically in FIG. 3, wherein the hose made in the extruder head 10 of extruder 11 first runs through a vacuum calibrator 12 and then is introduced into a glycerin-water bath 13, where the necessary cross-linking is carried out at temperatures of approx. 130-180 ° C, preferably 160-180 ° C. The hose is then held in a manner known per se in the mold by means of an internal support pressure. In the cooling apparatus 14, cooling takes place before the output items, hoses or cuffs are cut off by means of a cutting or cutting device not shown and e.g. in the embodiment of FIG. 1 and 2 are indicated during heating before freezing of the expanded state is allowed to cool.

20

FIG. 4 shows in a diagram the particular advantage of using materials which can be crosslinked by moisture, compared to materials which can be crosslinked peroxidically, in which the molar ratio of silane to peroxide content is usually greater than 10: 1.

The temperature course (a) shows the conditions of moisture crosslinking, and the process (b) is the temporal course of peroxidic crosslinking. In moisture crosslinking, the PE mixture to be seeded, both by conductive heat transfer from the heated cylinder wall of the injection molding machine and by the dissipation energy provided by the auger (friction), is brought up to the temperature required for the grafting - no upper temperature limit - and reaches this temperature into the tool, where cooling begins immediately.

35 In the case of peroxidic crosslinking, the mass must not exceed 130 ° C before shaping. With this temperature, the pulp reaches into the tool and here must be brought up to the cross-linking temperature (200 ° C) and kept in the mold for a while before the tool is cooled so that the workpiece can be removed from the mold.

DK 157480 B

15

The energy consumption needed for cooling during the molding process to avoid higher temperatures than 130 ° C is higher than the energy consumption required by moisture crosslinking to reach a temperature of 200 ° C because of the energy provided by the auger (dissipation). can be utilized.

Other mixtures which may advantageously be used in the manufacture of shrinkage articles according to the invention are the following:

Example II

polyethylene copolymer with 2-7 mol% vinyl acetate 100 parts calcined clay (hard kaolin M 100) 10 "sod 10 vinyl trimethoxysilane 2.0" peroxide .0.05-0.1 "catalyst (di butyl tindi 1 aurate (Naphthovine) ® SN / L) 0.05 0.05

Example III

polyethylene copolymer with 2-7 mol% 100 parts vinyl acetate 25 non-hygroscopic chalk (eg Millicarb / Omya) 15 "sod 5" vinyl trimethoxysilane 2.0 "peroxide 0.05-0.1" 30 catalyst (di butyl Ti ndi 1 aurate (Naftovin® SN / L)) 0.05 "

Example IV

Polyethylene homopolymer 3 (density 0.94 g / cm, melt index 0.2 - 2.5) 100 parts al alumina hydrate (eg Martinal A-s / 101) 2-10 "

DK 157480 B

16 soot 10 "vinyl trimethoxysilane 1.8-2.0" peroxide 0.05-0.1 "catalyst 0.05" 5 Partially hydrophobic silicic acids can also be used instead of alumina hydrate.

The mixture of Example I is particularly suitable for the manufacture of 10 shrink tubing, but also for the manufacture of sheaths and cuffs, while the mixture of Example IV can be used mainly for the production of sheaths which are already fully cross-linked after shaping.

If the mold parts consist of a foamed material, the aforementioned mixture Examples I-IV are changed as follows:

Example I-S

PE homopolymer 3 (density 0.94 g / cm, melt index 0.2 - 2.5) 100 parts azodicarbonamide as chemical propellant 0.5-1.5 "vinyl trimethoxysilane 1.0-1.5" dicumyl peroxide 0, 03-0.05 "catalyst (di butyltin didiurate (Naftovin® SN / L)) 0.5 sod (acetylene black Y) 2.5"

Example II-S

polyethylene copolymer with 2-7 mol% vinyl acetate 100 parts azodicarbonamide (propellant) 0.5 "sod (Ketjenblack EC) 3.0 vinyl trimethoxysilane 2.0" peroxide 0.05-0.1 "catalyst (di butyl tindi 1 aurate (Naftovin® SN / L)) 0.05

DK 157480 B

17

Example III-S

polyethylene copolymer with 2-7 mol% ethylene acrylate 100 parts 5 azodicarbonamide (propellant) 0.8 "sod (Ketjenblack EC) 5" vinyl trimethoxysilane 2.0 "peroxide 0.05-0.1" catalyst (dibutyltin 1 aurate 10 (naphthovine) ® SN / L) 0.05

Example IV-S

polyethylene homopolymer 3 (density 0.94 g / cm, melt index 0.2 - 2.5) 100 parts diphenolic oxide -4,4-disulfohydrazide (propellant) 0.8-1.2 "alumina hydrate (e.g. Marti -20 nal As / 101) 2 -10 sod (acetylene sod Noir Y 200) 10 "vinyl trimethoxysilane 1.8-0.1" peroxide 0.05-0.1 "catalyst (dibutyltin dilaurate (Naftovin® SN / L)) 0.05

Other mixing examples for molded wall foam components are:

Example V 30 Ethylene Propylene Rubber (e.g. Buna AP 407 K) 100 parts propyl an (e.g. Hostalen PPH 1050) 80 "sod (Ketjenblack EC) 5" 35 vinyl trimethoxysilane 1.5 "peroxide (Perkadox 14) 0 1 "catalyst (dibutyltin dilaurate (Naftovin® SN / L)) 0.05 azodicarbonamide (propellant) 0.5-1.5"

DK 157480 B

18

Example VI

polyethylene homopolymer set (melt index: 1.5-2.0) 100 parts 5 sod (Ketjenblack EC) 5 "physical propellant (eg trichlorofluoromethane or dichlorofluoromethane) 0.5-2.5" vinyl trimethoxysilane 1.5 "10 peroxide (Luperox 270) 0.25" catalyst (di butyltindiur aurate (Naftovin® SN / L)) 0.05 Instead of alumina hydrate, partially hydrophobic silicates can also be used.

The mixture of Examples I-S is particularly suitable for the production of shrink tubing, but also for sheaths and cuffs, while the mixture of Example IV-S can be used mainly in the manufacture of 20 sheaths which are already in completely cross-linked form after shaping.

Especially for the rational manufacture of shrink tubing, the manufacture of endless mold strands with shrink properties is essential. A method for this is detailed and detailed in FIG. 5 and 7.

One from a store deducted e.g. The moisture cross-linked hollow mold strand 21 is therefore guided as shown in FIG. 5 first to a heater 22. This apparatus may e.g. consist of a vessel containing hot water, but a radiator can also be used.

The tube thus pretreated then runs into the e.g. vacuum calibrator 23. also filled with temperate water. The water tank 24 disposed in front of this, which can of course also be replaced by spray nozzles or other suitable means, serves to apply water as a lubricant or grease agent on the surface of the mold string 21 as it is introduced into the calibrator. 23. As a major component, the calibrator 23 contains the bundle 25 of consecutively arranged holes and bores for the continuous string of hollow discs 26, the spacing of which increases in the direction of passage. The calibrator is filled with water in the region 27 so as to hollow the discs

DK 157480 B

19 are covered. In the area 28, a vacuum of up to 8 m VS is prevailed above the water level. This vacuum interacts between the hollow discs on the outer wall of the molding, so that, in conjunction with a support pressure in the molding itself, an extension occurs during the continuous passage of the molding string between the hollow discs, while each subsequent hollow disc provides the calibration. The expanded tube or hose 29 is frozen in its expanded state after leaving the calibrator, e.g. by introducing it into a refrigerator 30. Then the product is rolled up or 10 immediately cut into ready-made lengths.

FIG. 6 shows the inlet to the calibrator 23 on a larger scale than in FIG. 5. On a base plate 31 with a central bore 32 to the inlet of the mold string 21, e.g. three uniformly distributed retaining bolts 33, which in turn serve to retain the hollow discs 26 as support members for the mold string. These hollow discs 26 are located at the entrance due to the yet easily deformable string 21 located adjacent to each other and are located at a greater distance from each other with progressive expansion.

20 At the same time, as the diameter of the die increases with increasing progress, the bore diameter of the discs also increases. The water, which completely surrounds the hollow discs, because of its tempering, supports the expansion process and furthermore, as a glue, constantly ensures that the continuous, continuous molding stream runs through the hollow discs and thus does not get stuck.

In FIG. 7 is a view from that of FIG. 5 differs from one embodiment in which the heating and calibration is carried out practically simultaneously in that with a temperable liquid, e.g. also filled with a glycerine-water mixing container 34. The portion 36 containing calibrating hollow discs 35 is placed here in the rear third of this container. The cooling of the mold string 37 to freeze the expanded state then takes place, as already explained, in a cooling vessel or cooling duct 38.

Claims (7)

A method of preparing any wholly or partially foamed shrinkage articles, such as shrink tubing, shrink sleeves and shrink sleeves, from a grafted with organosil, and under the influence of moisture, cross-extrudable, extrudable polymer, by which method the polymer is mixed with the silo and the graft. necessary peroxide and any foaming agent and the polymer is melted, the silane is applied to the polymer, condensation catalyst is added, an starting material is formed of the grafted material, the starting material is crosslinked and expanded in this crosslinked state, and the thus expanded starting material is cooled to fix its expanded state, blank is optionally coated internally with a hot melt adhesive, characterized in that at least the condensation catalyst, silane and peroxide prior to melting the polymer are joined together to form a uniform mixture, the silane is applied at elevation of temperature, and the grafted polymer then mgiving, the melting, grafting and shaping being carried out in one operation. 20 Process according to claim 1, characterized in that the polymer is polyethylene or ethylene blend polymerisates. Process according to claim 1 or 2, characterized in that the polymer is ethylene propylene rubber only or mixed with a polyolefin. Process according to any one of the preceding claims, characterized in that a non-hygroscopic soot is added to the base materials as filler 30 in an amount of 5-40, preferably 8-20 parts by weight. 100 parts by weight of polymer. Process according to any one of the preceding claims, characterized in that 35 inactive inorganic fillers are added to the base materials in an amount of 5-30, preferably 10-20 parts by weight per minute. 100 parts by weight of polymer. Process according to any one of the preceding claims, characterized in that the molar amount ratio of organosilane to peroxide is approx. 10: 1. A method according to any one of the preceding claims, wherein the expanded and cooled blank is coated internally with a melting adhesive, characterized in that the melting adhesive is on a polyamide or polyester basis. 10 15 20 25 30 35