FI63046B - SAETT ATT TILLVERKA ETT FOEREMAOL AV TVAERBUNDEN POLYMER - Google Patents

Description

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jjäfg ^ <1) UTLÄCONI NOSSKIUFT 6 3 O 4 6 .¾ c (<s> 7; 1 1,33 ^ T ^ (51) K ».nu / int.a.3 C 08 J 3/24, C 08 K 5/00 752521 SUO MI - Fl N LAN D (21) Pmnttlh * lwmu · - Patmcanteknlnf (2J) HiknmhpUvi - An * 5knlnpd «j 08.09-75 (23) Alkuplivi — GiM | h« ts4a | 08.09 · 75 (41) ) Tullut lulklMkd - »llvlt affMtlif 10.03.76» plot, and the Registry Board (44) Nlht * vtolp «o« J. IcusMuUtoun date - 31.12.82

Patent, and registration 7 AmMun utlagd och «UkrtfMn pubUcorod (32) (33) (31) Requested« uoHMUt — Boflrd prlorltat 09 · 09 · 7 ^ 09.06.75 Swedish-Swedish (SE) 7 ^ 11327 ^ 5, 750653I- 8 (71) ASEA Aktiebolag, Västeras, Sweden-Sweden (SE) (72) Gunnar Jansson, Älvsjö, Sweden-Sweden (SE) (7 ^) Berggren Oy Ab (5 * 0 Method for making an article from a crosslinked polymer -Sätt att tillverka ett for the production of polymer

When making articles from a crosslinked polymer, the conditions of the crosslinking reaction, eso. temperature conditions and time to the degree of crosslinking achieved in the finished article. If a satisfactory degree of crosslinking is not achieved, this will normally result in the formed object having to be scrapped. It is important that the degree of crosslinking can be determined as early as possible in the manufacturing process, e.g. in the manufacture of insulated cable conductors, so that the manufacturing process can be interrupted or the manufacturing conditions adjusted if the degree of crosslinking proves to be too low. In this way, it is avoided as far as possible that the manufactured material has to be scrapped. Until now, time-consuming and material-destroying test methods have been forced to determine the degree of crosslinking. The extraction method is usually used. A sample of an object, e.g. an extruded insulating piece of a cable conductor, is then cooked in a solvent, followed by vacuum drying. The total processing time then moves in the order of one day. As the manufacture continues while the test is being carried out, there is a risk that the manufactured material will have to be scrapped, namely 2 63046 if the degree of crosslinking proves to be too low. If production were to be stopped pending the test result in order to avoid the production of scrap material, there would naturally be a reduction in production.

For the production of non-peroxide crosslinked plastics, namely epoxy, phenoxyepoxy and polyurethane resins, it is known to add Safranin B Extra dissolved in a solvent to a flowable resin used as a protective layer and as a binder. However, this has not been the case with production methods typical of peroxide-crosslinked polymers, such as extrusion. Safranin has also not been able to act as a color indicator because its color is not affected by the crosslinking reaction of peroxide crosslinked plastics.

According to the present invention, it has proved possible to determine the degree of crosslinking of an article composed of a peroxide crosslinked polymer in a very simple and fast manner. Determining the degree of crosslinking is normally possible without destroying the finished material. Due to the speed of the assay, the manufacturing conditions can be quickly adjusted, which means that the fabrication of an article, e.g., extruded cable insulation, can take place under optimal conditions, i.e. without large safety margins in time and temperature.

More specifically, the present invention relates to a process for making an article from a crosslinked polymer, wherein the starting material containing peroxide and a polymeric material capable of undergoing a crosslinking reaction in the presence of peroxide is formed into an article and crosslinked, and the crosslinking is performed in the presence of the agent. has the ability to undergo a color change in the crosslinking reaction of a polymeric material, wherein the material undergoes a color change, wherein the material having the ability to undergo a color change is an aromatic compound containing at least one halogen atom or at least one heterocyclic ring having at least one nitrogen atom not attached a hydrogen atom. According to the invention, the degree of crosslinking can be determined visually. For ease of reading of the present invention, a substance having the ability to undergo a color change in connection with a crosslinking reaction of a polymeric material is hereinafter referred to as an indicator of crosslinking. In an optimal use of the invention, the crosslinking indicator is present at all times during casting and crosslinking. For example, in continuous processes, it is of course conceivable to include the crosslinking indicator only temporarily, e.g. during the run-in period to check the use of the correct manufacturing conditions and otherwise perform the manufacturing without adding the indicator.

A probable explanation for the effect obtained according to the invention is that the crosslinking indicator interacts with the free radicals formed during the cleavage of the peroxide, while generating an intermediate radical starting from the crosslinking indicator residue with a color other than that of the indicator itself. radicals are consumed to smooth the polymer. Namely, the electrical and mechanical properties of the crosslinked polymer become at least as good as when “63046 when no crosslinking indicator is used. In some cases, instead, an improvement in these properties is achieved, indicating that the presence of the indicator accelerates the formation of crosslinks.

With curable mixtures in the form of epoxy, epoxyphenoxy and polyurethane systems and with oily copolymers of conjugated diolefins, e.g. butadiene and unsaturated monomers, e.g. styrene, as flowable and soluble solvents, it is known to control curing with substances which undergo a color change during the curing of the resins.

The change in color of the crosslinking indicator can be, among other things, a change in color from e.g. purple to colorless or a change in color intensity or hue, e.g. from strong purple to weaker purple.

When applying the method according to the invention, it is suitable to calibrate the change in color of the crosslinking indicator at different degrees of crosslinking, using as a reference the determinations of the degree of crosslinking according to previous methods used for such determinations, e.g.

According to one embodiment of the invention, the crosslinking indicator can be distributed substantially evenly in the starting material of the peroxide and the polymeric material before casting. The amount of crosslinking indicator can vary within wide limits depending on the type of polymeric material, the type and amount of peroxide, and above all, the type of crosslinking indicator. However, the amount remains in the range of 0.0005 to 5 parts by weight per 100 parts by weight of the polymeric material. The amount of the indicator increases to 0.005 to 0.5 parts by weight per 100 parts by weight of the polymer material.

According to another embodiment of the invention, the crosslinking indicator is applied to locally limited areas of the starting material in connection with the casting of the article, e.g. in the form of a strand, wire, strip or individual granules spaced apart from each other. It is convenient to combine the crosslinking indicator with a suitable polymeric material in the preformed product used in said casting. In the exemplary cases, the preformed product has the shape of a thread, wire, ribbon or granulate. The polymeric material in the preformed product may suitably be of the same type as the polymeric material in the article feedstock, e.g. polyethylene in both products, but need not be the same type. In the preformed product, the polymeric material may be formed, for example, by a copolymer of ethylene and propylene with dicyclopentadiene, while the polymeric material in the starting material of the article may be polyethylene. chlorosulphonated polyethylene or polypropylene. The preformed product may or may not be provided with peroxide. The concentration of the crosslinking indicator in the preformed product increases from 0.0005 to 5 parts by weight and preferably from 0.005 to 0.5 parts by weight per 100 parts by weight of the polymeric material in the preformed product.

According to another embodiment of the invention, in addition to the crosslinking indicator, a dye having no ability to undergo a color change during the crosslinking reaction of the polymeric material is fed to the starting material or the preformed product mentioned in the previous paragraph. For example, a crosslinking indicator which changes from red to colorless upon crosslinking may be added, together with a yellow dye which does not change color during said reaction. Before the crosslinking of the starting material in the process, the starting material and the preformed product, respectively, then have an orange color, while the color after crosslinking is yellow. The concentration of the dye which is unable to undergo the color change suitably increases to 0.0005 to 5 parts by weight, and preferably 0.005 to 0.5 parts by weight, per 100 parts by weight of the polymeric material in the starting material, if the dye is evenly distributed in the starting material, or 100 parts by weight. towards the polymeric material in the preformed product, which product is applied locally to limited areas of the starting material.

Examples of suitable crosslinking indicators are aromatic compounds containing at least one halogen atom and / or at least one heterocyclic ring containing at least one nitrogen atom to which no hydrogen atom is attached. Such crosslinking indicators include the following which contain one benzene ring having at least one halogen atom directly attached to it and / or which contain one heterocyclic 5- or 6-ring containing at least one nitrogen atom to which no hydrogen atom is attached : (benzene rings marked) carbazolidioxioxin violet (purple, colorless in e.g. polyethylene 6 63046 and copolymer of ethylene, propylene and dicyclopentadiene).

Cl C ^ H5 ^ JL ^ n. jj ^ (e.g. under the trade name PV Fast Violet BL, '___J manufactured by Hoechst, Casella), thioindigo-Bordeaux (red, colorless, e.g. in polyethylene and copolymer of ethylene, propylene and dicyclopentadiene) ci n ci JL, CS (e.g. under the trade name Bordeaux RN Pig- / eiV ment Red 88, manufactured by Ciba-Geigy),

Cl S C1 compound of the following formula (red violet, colorless in e.g. polyethylene and copolymer of ethylene, propylene and dicyclopentadiene): f1 «S Cl rV ^ C \ / CV \ (e.g. under the trade name PV Red Violet MR, manufactured by Hoechst, Casella), a compound of the following formula (yellow, change to a weaker yellow, e.g. in polyethylene and a copolymer of ethylene, propylene and dicyclopentadiene): 9h3 Cl Cl 9H3 (e.g. under the trade name H c- (r ^ NH * CO »CN = N - (y /) - Ns'NC »CO'HN - ^ \ cH3 PV Gelb GR, prepared.

'I' - 'hJc Hoechst, Casella), CH3 3 compound of the following formula (red, yellow in e.g. polyethylene and copolymer of ethylene, propylene and dicyclopentadiene):

a \ / - ^ (e.g. under the trade name Permanentrot TG

a '(\] 01, manufactured by Hoechst, Casella), K> i o o a compound of the following formula (red, yellow in e.g. polyethylene and copolymer of ethylene, propylene and dicyclopentadiene): 63046

Vc (e.g. under the trade name PV-Echt-Orange KKX> GRL, manufactured by Hoechst, Casella), a compound of the following formula (reddish brown, light brown in e.g. polyethylene and copolymer of ethylene, propylene and dicyclopentadiene): HN-C = 0

Ci HO CO · HN - ^) - NH (e.g. under the trade name PV-Echt-Braun s-1) - (HPR, manufactured by Hoechst, Casella), a 9 '* 8 compound of the following formula (yellow, slightly yellow) , e.g. in polyethylene and a copolymer of ethylene, propylene and dicyclopentadiene): CH 3? CH 3 coh 9CH 3 (e.g. under the trade name Permanent- , Casella), ch3o ch3o compound of the following formula (yellow, slightly yellow change, e.g. in polyethylene and copolymer of ethylene, propylene and dicyclopentadiene): CH3 ch OCH3 £ 0H C1 C1 I ch3 ° (e.g. under the trade name PV-Gelb NH · 0C · 11-N = N - ^ ^ y »= Ng-CO.HN- (3 GG, manufactured by Hoechst, Casella), a compound of the following formula (yellow, change to a weaker yellow, e.g. in polyethylene and ethylene, propylene and in the dicyclopentadiene copolymer): 1

Br (e.g. under the trade name Hostaperm. Scharlach GO, manufactured by Hoechst,

Br Casella), 0 8 63046

Of the crosslinking indicators presented above, six of the former are especially recommended based on the very clear color changes they achieve. The first four, which contain a halogen atom, have a halogen atom and a chlorine atom.

Some of the crosslinking indicators exemplified above have been shown to significantly improve the electrical breakdown strength of a crosslinked cast product.

Examples of suitable dyes which do not undergo a color change during the crosslinking reaction are titanium dioxide, aminoanthraquinone violet

• S

(e.g. under the trade name Chinacridon-Violet, manufactured by Ciba-Geigy)

0 H

and copper phthalocyanine

H H

H ~ jfH

H (e.g. under the trade name Kupferphtalocyanin, H manufactured by Ciba-Geigy),

TC-N

H 'cX ίν.f / ^ c «JLJ ^

H H

Examples of substances containing both a crosslinking indicator and a dye which do not have the ability to undergo a color change during the crosslinking reaction of a polymeric material are PZ 153 Orange 2k (manufactured by Bakelite Xylonite Limited, change from orange to yellow), PZ 157 Violite 29 (manufactured by Bakelite 29). , change from purple to off-white.

Examples of polymeric materials which may undergo crosslinking when using peroxide and which may be used in carrying out the process of the invention include polyethylene, a copolymer of ethylene and propylene, a copolymer of ethylene or propylene or ethylene and propylene 9,63046 with diene monomers such as 1,4-pentadiene, , 4-hexadiene, 5-alkenyl-2-norbornadiene, 2,5-norbornadiene, 1,5-cyclooctadiene and dicyclopentadiene, the copolymers of which, after polymerization, have double bonds from the diene monomer molecules, ethylene-propylene-terpene and a copolymer of vinyl acetate, a copolymer of ethylene and ethyl acrylate, chlorosulfonated polyethylene, chlorinated polyethylene, polysulfide, polyurethane, silicone rubber, butadiene-acrylonitrile rubber, bi-diene-styrene rubber, natural propylene rubber, isadiene rubber, butadiene rubber, butadiene rubber

As examples of useful peroxides, mention may be made of organic peroxides, such as di-d-cumyl peroxide, di-tert. -butyl-peroxy-di, di- (tert-butylperoxy-isopropyl) -benzene, di- (tert-butyl-peroxy) trimethylcyclohexane, dimethyl-di (tert-butylperoxy) -hexane, benzoyl peroxide, dimethyl-di ( peroxybenzoate), tert-butyl peracetate, N-butyl bis (tert-butyl peroxy) valerate, tert-butyl perbenzoate, dimethyl di (tert-butyl peroxy) hexene, dichlorobenzoyl peroxide, cumene hydroperoxide, tert-butyl peroxide. legal methyl peroxide, di-tert-butyl peroxide and butanoic acid n-butyl ester. The amount of peroxide suitably increases to 0.1 to 5 parts by weight per 100 parts by weight of the total polymeric material. The term whole polymeric material refers as well to the starting material as to any polymeric material present in the preform used.

The temperature and time of the crosslinking reaction will vary depending on the polymeric material in the starting mixture, the type and amount of peroxide, the size and shape of the article, and the method of heating the crosslinking reaction. In many applications, the temperature is between 150-200 ° C. The time at such a temperature strongly depends on the material thickness of the article. For example, with a material thickness of about 1-2 mm, the time can in many cases be between 1-30 minutes.

The starting materials may, as usual, but need not, contain a filler (suitably 1-400 parts by weight per 100 parts by weight of the total polymeric material), e.g. chalk, kaolin, plasticizer (suitably 1-75 parts by weight per 100 parts by weight). per whole polymer material), e.g. dioctyl phthalate, aromatic or paraffinic oils, activators for peroxides (suitably 63046 10 0.3 to 3 parts by weight per 100 parts by weight of total polymeric material)., e.g. triallyl cyanurate, ethylene glycol dimethacrylate and metal oxides such as lead oxide or magnesium oxide (suitably 1 to 50 parts by weight per 100 parts by weight of the total polymeric material), antioxidants (suitably 0.5 to 5 parts by weight per 100 parts by weight of the total polymeric material), e.g. polymerized trimethyldihydroquinone, aldol-α-naphthylamine, flame retardant (suitably 1 to 60 parts by weight per 100 parts by weight of the total polymeric material), e.g. antimony trioxide and halogenated hydrocarbons and other conventional additives.

Among the useful casting methods, mention may be made in particular of extrusion (extrusion) and further injection molding and compression molding.

The invention will be described in more detail with reference to embodiments with reference to the accompanying drawing, in which Fig. 1 schematically shows an apparatus for implementing the method according to the invention in insulated cable duct extrusion in injection molding, Fig. 4 schematically shows an apparatus for carrying out the method according to the invention in profile extrusion, Fig. 5 is a cross-section of a profile made in the apparatus of Fig. 4 and Fig. 6 is a cross-section of an insulated cable conductor other than Fig. 2.

Example 1

The following components are mixed to a homogeneous mass and granulated in an extrusion machine with a granulation nozzle: 100 parts by weight of LD polyethylene having a melt index of 0.2 to 20 parts by weight of di-α-cumyl peroxide (e.g. Di-Cup R, ready.

Hercules Powder, USA), 0.01 part by weight of carbazolidioxazine violet (crosslinking indicator, e.g. PV Past Violet BL, manufactured by Hoechst, Casella), 0.2 part by weight of polymerized trimethyldihydroquinoline (antioxidant, e.g. Flectol, prepared by .Freport, USA).

6 3046

Instead of adding the crosslinking indicator as it is, it can be e.g. to be added in the form of a concentrate in the form of granules consisting of 99% by weight of LD polyethylene and 1% by weight of crosslinking indicator. In this case, one part by weight of seal is added.

The manufacture of an insulated cable conductor using the mass described above, with reference to Fig. 1, can take place in the following manner. The conductor 10, which in the exemplary case consists of aluminum with a cross-sectional area of 120 mm, is wound from the drum 11 by means of a traction device 12 in the form of two endless conveyor belts and is then provided with a semiconducting layer 29 approximately 0.5 mm thick in a conventional manner (Fig. 2) on hardware not shown. The conductor then passes through the crosshead in the extruder 14. In this case, the conductor is surrounded by a 3.5 mm thick mass insulator 15 (Fig. 2). The pulp is fed in the form of granules to the filling hopper 16 of the extruder. The temperature in the extruder is suitably maintained at approximately 120 ° C. The insulation is crosslinked by heating the insulated conductor in water vapor at a temperature of 215 ° C in the tube 17 · The residence time of the insulated conductor as it passes through the tube 17 is approximately 5 ~ 10 minutes. The cable conduit insulated from the steam pipe passes through the swivel wheel 18 to the cooling pipe 19, where it is cooled under pressure with water at room temperature. The insulated conductor then passes alternately through the water trap 20 and the traction device 21 in the form of two endless conveyor belts before being wound on the drum 22. The traction devices 12 and 21 operate together so that the conductor remains tensioned during the process.

The degree of crosslinking of polyethylene can be determined and monitored visually or with a measuring device somewhere after passing through the water trap 20 by examining the color of the insulation and comparing it to the same crosslinking indicator scale in the same polymeric material and the same concentration as the pulp calibrated to known degree of crosslinking. For this crosslinking indicator used, such a scale passes from a slab of relatively strong purple color corresponding to the color of the pulp before crosslinking, through slabs of continuously decreasing purity in intensity, to a slab of colorless color corresponding to an increasing degree of crosslinking.

If the sheath is completely colorless, the degree of crosslinking is at least 75%, which 12 63046 is satisfactory. If the color corresponds to too low a degree of crosslinking, it can be increased by extending the residence time in the tube 17 and / or by raising the temperature therein. Such control of the conditions can advantageously take place by means of a measuring device which reads the color of the insulation somewhere after the passage of the water trap 20 and which then controls the temperature in the pipe 17 or the speed of the conductor 10.

An alternative way to determine the degree of crosslinking in the device of Figure 1 is as follows. In the apparatus of Figure 1, a preformed product in the form of a polyethylene strip containing a crosslinking indicator can be fed along a conductor as it enters the extruder. This can be done by attaching the tape to the semiconducting layer with adhesive tape before the conductor enters the crosshead 13. The insulation starting material around the conductor then does not contain any crosslinking indicator, but otherwise has the same composition as the insulator shown in the introduction to Example 1. The tape has the same composition as the latter mass, but possibly without peroxide and antioxidant. The fabrication of the insulated conductor takes place in the same manner as previously described. To determine the degree of crosslinking in the finished insulated conductor, a slice is cut transversely as shown in Fig. 2, in which the strip containing the crosslinking indicator is denoted 23. The color of the crosslinking indicator is then compared to a calibrated scale and any steps required to control the crosslinking reaction.

Example 2

The following components are mixed and beaten or rolled together to a cohesive mass: 100 parts by weight of a copolymer of ethylene, propylene and dicyclopentadiene, the latter compound having double bonds (e.g. Vistalon 2504, manufactured by Esso Chemical, USA) 100 parts by weight of kaolin (filler) e.g., Translink 37, ready.

Freeport, USA) 100 parts by weight of chalk (filler, e.g. Vinnofil S, manufactured by ICI,

English) 45 parts by weight of a low aromatic paraffin-based oil (plasticizer, e.g. Sunpar 150, manufactured by Sunoco, USA) 13 6 3 0 4 6 5 parts by weight of zinc oxide 1 part by weight of polymerized trimethyldihydroquinoline (antioxidant, e.g. Flectol, manufactured by Freeport) 0.2 parts by weight of thioindigo-Bordeaux dye (crosslinking indicator, e.g. Bordeaux RN Pigment Red 88, manufactured by Ciba-Geigy).

When a homogeneous mass has been obtained from these components, the following components are mixed together by whipping or rolling: 2.8 parts by weight of di-α-cumyl peroxide (e.g. Di-Cup R, ready.

Hercules Powder) 0.8 parts by weight of triallyl cyanurate (e.g. Aktivator OC, ready.

Degussa, Germany).

The pulp is used in strip form. The insulation of the insulated cable conductor can take place with the apparatus shown in Fig. 1, in which, however, the filling funnel 16 has been replaced by a strip feeding device suitable for a rubber strip. The conductor 10 can then consist of tinned copper with a cross-sectional area of 2.5 mm2 and coated with an insulator 15 with a thickness of 0.8 mm. The temperature in the extruder 1¾ can be 90 ° C. The temperature in the steam pipe is, as before, 215 ° C and the throughput time of the conductor in the steam pipe is 0.2-1 minutes. Otherwise, the conditions may be the same as those set forth in the preparation of the insulated conductor of Example 1.

The change in the crosslinking indicator occurs from red violet through the continuously decreasing red violet to colorless with the ever-increasing degree of crosslinking. To determine the degree of crosslinking, the color is compared to a calibrated scale of the same crosslinking indicator in the same starting material, and then any necessary steps are taken to control the crosslinking reaction in the insulating coating of the conductor.

Example 5

The same starting material with which the extruder is fed in the case of Example 1 is used for the production of an injection molded part in the tool of Fig. 3. The tool, shown in cross-section, consists of an upper tool half 24 with guide pins 25, i and a lower tool half 26 which are held against each other during molding. The upper tool half is provided with a 1H 63046 injection channel 27 for injecting the starting material through an injection molding machine (not shown) into the cylindrical mold space 28. The crosslinking reaction is carried out at 200 ° C for 10 minutes at a pressure of 50 atm. As in previous cases, the degree of crosslinking is determined by comparison with the calibrated scale of the same crosslinking indicator, after which the manufacturing conditions may be adjusted so that the desired degree of crosslinking is achieved.

Example 4

The following components are mixed and beaten or rolled together to a homogeneous mass: 78 parts by weight of chloroprene rubber (e.g. Neopren TW, manufactured by Du Pont, USA) 22 parts by weight of styrene-butadiene rubber (e.g. Solpren 1205, manufactured by

Phillips Petroleum, The Netherlands) 63 parts by weight of kaolin (filler such as M 100, manufactured in English)

China Clay, England) 4 parts by weight of magnesium oxide 22 parts by weight of butyl oleate (plasticizer, e.g. Butyloleat, manufactured by Unilever-Emaeiy, USA) 3 parts by weight of paraffin (lubricant) 5 parts by weight of stearin (lubricant) 1 part by weight octamine (antioxidant, e.g. Octamin, ready.

Rubber Regenerating, USA) 0.07 parts by weight of thioindigo-Bordeaux (crosslinking indicator, e.g.

Bordeaux RN Pigment Red 88, ready. Ciba-Geigy).

When a homogeneous mass is obtained from these components, the following components are mixed together by whipping or rolling: 8 parts by weight of lead oxide (lead flake) 1 part by weight of di-α-cumyl peroxide (e.g. Di-Cup R, ready-made).

Hercules Powder).

The obtained mass can be used e.g. profile extrusion with the equipment shown in Figure 4. The pulp 30, which is preferably in the form of a strip, is then fed to an extruder 31 provided with a suitable strip feeder and a mouthpiece 32 to provide the desired profile 33, the cross section of which is shown in Figure 5. The temperature in the extruder may be 90 ° C. The formed profile is crosslinked by heating in a vulcanizing device 3, e.g. in a microwave oven. Suitable conditions for the crosslinking reaction are 200 ° C for 20 minutes. After crosslinking, the product is cooled in a cooling device, e.g. a water bath. The finished crosslinked product is marked with the number 36.

In this case, the change in the crosslinking indicator takes place from red-red to dark brown through the tones between them, the degree of crosslinking increasing all the time. As in previous cases, the degree of crosslinking is determined by comparison with the calibrated scale of the same crosslinking indicator, after which it is possible to adjust the manufacturing conditions so that the desired degree of crosslinking is achieved. The manufactured profile can be e.g. use as a list.

Example 3

The following components are mixed to a homogeneous mass and granulated in an extruder with a granulation nozzle: 100 parts by weight of LD polyethylene having a melt index of 0.2 to 20 parts by weight of di-α-cumyl peroxide (e.g. Di-Cup R, ready.

Hercules Powder, USA) 0.005 parts by weight of crosslinking indicator (e.g. PV Red Violet MR, manufactured by Hoechst, Casella)

Cl 8 <f1 0.2 parts by weight of polymerized trimethyldihydroquinoline (antioxidant, e.g. Flectol, or. Freeport, USA).

Instead of adding the crosslinking indicator as it is, it can be added e.g. in the form of a concentrate in the form of granules consisting of 99% by weight of LD polyethylene and 1% by weight of crosslinking indicator. In this case, 0.5 part by weight of concentrate is added.

The production of an insulated cable conductor using the mass described above can take place in the apparatus according to Fig. 1 in the manner shown in Example 1. In this case, however, there is an aluminum conductor. O. . # cross-sectional area 2.5 mm and the conductor is directly surrounded (i.e. no semiconducting layer is used) by a 0.8 mm thick insulating compound 15 (Fig. 6). The insulation is crosslinked under the same conditions as in Example 1, however, the residence time in the passage of the tube 17 is approximately 0.5 minutes.

The degree of crosslinking of the polyethylene can be determined, monitored and adjusted as described in Example 1.

An alternative method for determining the degree of crosslinking in the apparatus of Figure 1 uses a preformed product in the form of a polyethylene tape containing a crosslinking indicator. The strip is fed along the conductor to the extruder as described in Example 1. The tape has the same composition as the mass from which the insulation is formed, possibly without peroxide and antioxidant. The fabrication of the insulated conductor takes place in the same manner as previously described. To determine the degree of crosslinking of the finished insulated conductor, a slice shown in Fig. 6 is cut transversely, in which the strip containing the crosslinking indicator is denoted by 23- The color of the crosslinking indicator is compared to a calibrated scale and any necessary steps are then taken to control the crosslinking reaction.

Example 6

The insulated cable conductor is prepared as described in Example 5, with the difference that instead of the crosslinking indicator shown therein, the same amount of the aforementioned compound having the trade name PV-Gelb GR, manufactured by the manufacturer, is used as the crosslinking indicator. Hoechst, Casella.

Example 7

The insulated cable conductor is prepared as described in Example 5, with the difference that instead of the crosslinking indicator shown therein, the same amount of the aforementioned compound having the trade name Permanentrot TG 01, manufactured by the manufacturer, is used as the crosslinking indicator. Hoechst, Casella.

Example 8

The insulated cable conductor is prepared as shown in Example 5

Claims (14)

63046 17 with the difference that instead of the crosslinking indicator shown therein, the same amount of the aforementioned compound having the trade name PV-Echt-Orange GRL manufactured by PV-Echt-Orange is prepared as the crosslinking indicator. Hoechst, Casella. The process according to the invention is suitable for use in the manufacture of all kinds of articles consisting of any peroxide-crosslinkable polymer. In addition to the pieces described, the insulation of the cable conductors and the strips, mention may be made of cable sheaths, pipes, e.g. HVAC pipes for high temperature applications, hoses, seals, etc. A method of making an article from a crosslinked polymer, wherein the starting material containing peroxide and a polymeric material capable of undergoing a crosslinking reaction in the presence of peroxide is formed into an article and crosslinked, characterized in that crosslinking is performed in the presence of the ability to undergo a color change in the crosslinking reaction of a polymeric material, wherein the material undergoes a color change, wherein the agent having the ability to undergo a color change is an aromatic compound containing at least one halogen atom or at least one heterocyclic ring having at least one nitrogen atom free of hydrogen. Process according to Claim 1, characterized in that the substance which has the ability to undergo a color change is distributed substantially evenly in the starting material before casting. A method according to claim 1, characterized in that the substance having the ability to undergo a color change is applied locally to limited areas in the starting material, e.g. in the form of a thread, wire or strip, during the casting of the article. uV 'Λ,) / 1 4. A method according to claims 1 to 3, characterized in that a substance having the ability to undergo a color change is fed to the starting material mixed with another substance, preferably a polymeric material and in particular a polymeric material of the same species as the starting material. 18 6 3046 Process according to one of Claims 1 to 4, characterized in that a substance which has the ability to undergo a color change is fed to the starting material together with a dye which does not have the ability to undergo a color change in connection with the crosslinking reaction of the polymeric material. Process according to Claim 1, characterized in that the aromatic compound contains a benzene ring having at least one halogen atom directly attached to it. Process according to Claim 1 or 6, characterized in that the halogen atom is a chlorine atom. Process according to Claim 1, 6 or 7, characterized in that a carbazolidioxioxin violet Cl C2H5 ΟΧίψΧώο c'h5 01 thioindigo-Bordeaux dye Cl 9 Cl Cl JJ Cl is used as the substance having the ability to undergo a color change. formula Cl Cl or a compound of formula? h3 Cl Cl p NH-C0 * $ - N = N -ό-ό- N = N-4-CO * HN - ^ ^ - CH5. CH3 h3c 19 63046 Process according to Claim 1, characterized in that the aromatic compound contains a heterocyclic 5- or 6-ring containing at least one nitrogen atom to which no hydrogen atom is attached. Process according to Claim 1 or 9, characterized in that a compound of the formula o o or a compound of the formula σΜο O is used as the substance having the ability to undergo a color change. Method according to one of Claims 1 to 10, characterized in that the polymeric material consists of polyethylene. Method according to one of Claims 1 to 11, characterized in that the casting of the object is carried out by extrusion (extrusion). Method according to one of Claims 1 to 11, characterized in that the casting of the article is carried out by injection molding or compression molding. Method according to Claim 12, characterized in that the starting material is cast as an insulator or cable sheath for the cable conductor. 63046 20