CS241570B1 - Crosslinkable polymer blend - Google Patents

Abstract

The invention relates to the field of electrical insulating materials for the cable industry. The invention addresses the production of insulating and semiconducting materials for high-voltage cables, capable of crosslinking at the melting temperature of the polymer. The essence of the invention is the application of peroxide with a half-life of 2 to 20 h. at a temperature of 100 °C, which, in the case of ethylene copolymers with a reduced melting temperature, allows for both safe preparation and processing of the crosslinkable mixture, and its crosslinking at temperatures of 80 to 100 °C, even in the case when these mixtures contain a hydrophilic filler.

Description

241570

BACKGROUND OF THE INVENTION The present invention relates to polymeric compositions crosslinkable below the melting point of the polymer by the use of peroxides as crosslinking agents in the water near its boiling point. The invention provides for the preparation of unfilled polymer blends as well as mixtures containing conductive carbon black, crosslinkable cost-free accessories. In the current production of power cables, cross-linked polyethylene is increasingly promoted as an insulating material because of its increased terrain-elasticity, which allows to increase the durable asphalt loadability of the insulation. In order to exploit the increased thermal resistance of such an isolation, the semiconducting materials for shielding the electroconductive core and the insulation, which must also be crosslinkable as an insulating material, are also enhanced. Since these semiconducting mixtures are included! A relatively large amount of carbon black with a distinctive stiffening effect, more preferred than polyethylene, has been used to make plasticized polymers, namely copolymer polyethylene with vinyl acetate, or ethyl acrylate with butyl acrylate. The cross-linking of the functional layers of the core cables takes place in a continuity of the process of extruding them continuously in a cross-linking tube of 100 m or more, whereby the decomposition of the peroxide and the desired material cross-linking occur at a temperature above 200 ° C. There must be an overpressure in the oven min. 0.5 MPa, thereby preventing the formation of cavities as a result of the vapor pressure of the decomposition compounds of peroxides formed at high temperatures. The industrial utilization of the crosslinking of thermo-mechanical properties of polyethylene thus requires considerable investment, as well as labor and energy-intensive process, which increases the cost of the product. Thus, the economic aspect is significantly influenced by the use of the advantageous properties of crosslinked polyethylene and its development. In order to simplify the process, the process of crosslinking polyethylene has been developed, based on the initiation of the decomposition of peroxide by the action of ultra-high frequency electro magnetic. The process takes place in a cross-section tube substantially shorter than in the previous case (about 40 m). Here, the inserted energy consumes more selectively to induce the decomposition of the peroxide, thus avoiding the heating of the polymer to a relatively high temperature and its subsequent cooling, and thus making the apparatus more economical. Another simplification of the polyethylene cross-linking technology is the method in which the cross-linking tube has been removed completely. The crosslinking is carried out by a discontinuous process by applying 80 to 100 ° C of hot water to the formed product. These are the so-called silane cross-linking in water, where vinylalkoxysilane is radically reacted to the polyethylene chains and siloxane crosslinks are formed in the presence of an organometallic catalyst and water. The advantage of this procedure is a significant reduction in investment and energy costs. Since water here does not only act as a heating medium, but also actively participates in the chemical reaction itself, the cross-linking time depends on the rapid diffusion of water into the polymer, i. E. j. largely from the netting ridge. Another drawback of this process, particularly in the cable industry, is the fact that it cannot be used for crosslinking semiconducting or other filled polymers. In the presence of filler, the silanol group no longer condenses, but preferably with surface moisture, respectively. with the hydroxyl groups of the filler, so that in this case no cross-linkages are formed, but between the polymer and the filler. For this reason, this method is known to be useful, for example, for the crosslinking of functional cores of high-voltage cables, whose construction includes carbon black filled semiconducting.

The disadvantages of the prior art have been eliminated by the solution according to the invention, in which, as a crosslinking agent for polymer blends filled or unfilled, containing ethylene copolymer with 5 - 30 wt. a polar monometer, a peroxide having a half-life of 2 to 20 hours at 100 ° C is used. This makes it possible to carry out the crosslinking of the polymer in the water bath below the melting point of the polymer, i.e. at 80 to 100 ° C. The cross-linking time under these conditions is 10 to 200 hours and depends only on the temperature and the ridge of the reticulated layer. The achieved cross-linking effect is not negatively affected by the presence of a hydrophilic filler.

In order to apply such a type of discontinuous networking technology to all functional layers of cores of all-plastic high-voltage cables, it is preferred to use copolymer ethylene with vinyl acetate or ethyl acrylate. butylacrylate, with a polar monomer content of 5 to 30% by weight, with an addition of 0.1 to 1.0% by weight. phenolic or amine antioxidants, such as 4,4'-thiobis (3-methyl-6-tert-butylphenol, or polymerized 2,2,4-trimethyl-1,2-dihydroquinoline, respectively). An optional amount of conductive carbon black with a specific surface area of 150-1,500 m 2 / g in a polymer is 10-50 weight percent, 1-di-tert-butylperoxy-3,3,5-trimethylcyclohexane being preferred for developing the crosslinking reaction 1 to 5 parts by weight per 100 parts by weight of the copolymer, optionally with the addition of 0.1 to 1.0% by weight of trialyl cyanurate, This polymer mixture is preferably crosslinked in a water bath at a temperature close to 100 ° C for The process safety of the mixture at 110 [deg.] C. given by the MoOH is at least 45 min.

Under given conditions, the degree of cross-linking, expressed by the deformation value, is obtained, 241370

With a temperature of 200 ° C and a mechanical pull of 20 N / cm 2 below 175%, and a resistance to thermo-oxidative destruction in which the change in difficulty after 7 days of aging at 150 ° C does not exceed the tolerance of + 25% of the pedestrian] 'values.

The crosslinkable compositions according to the invention can be applied either to the preparation of the semiconductive shielding of the high-voltage cable cores, the isolation of which consists of a silane-diethylated polyethylene and all the layers cross-link in one process in hot water or to cross-link all three puffed layers, ie, semiconductive core shielding and isolation, as well as isolation itself.

The following examples demonstrate the preparation of polymer blends and their characteristic parameters after crosslinking compared to the silaneized polyethylene blended equal conditions. EXAMPLE 1 0.35 weight percent 4,4'-thio-bis- (3-methyl-6-tert-butylphenol and 0.15 weight percent) were added to a molten ethylene-vinyl acetate co-polymer containing 7.5 wt. of polymerized 2,2,4-trimethyl-1,2-dihydroquinoline, the mixture is homogenized for 4 min at 105 to 110 ° C on a twin roll with a 1.25: 1 roller fraction and subsequently after the addition of 4 wt. The di-tert-butylperoxy-3,3,5-trimethylcyclohexane dissolved in the liquid phlegmatizing agent is stirred for an additional 3 minutes The Mooney value of the prepared mixture, expressing its processing safety at 110 ° C, is 49 min. up to 1 mm by successive pressing of the material at a temperature of 100 to 110 ° C to a maximum pressure of 20 MPa, after which the compact is immediately cooled, the cross-linking of the test specimens is carried out at a temperature of 98 ± 2 ° C for 70 hours. 20 N / cm 2 reached 145% at 200 ° C and the initial elongation of 517% was reduced to 505% in the hot air oven at 150 ° C after 7 days of aging. Example 2

Here, the same cross-linking components and the same procedure as in Example 1 were used, except that the antioxidant system contained 0.35 weight per cent of 4,4 ' -thio-bis-β-methyl-6 tert-butylphenol) and 0.2 weight percent of polymerized 2,2,4-trimethyl-1,2-dihydroquinoline, with 1,1-di-tert-butylperoxy-3,3,5-trimethylcyclohexane 3.5 weight per cent was added. Mooney safety at 110 ° Cbola for 47 min, its deformation in mechanical and thermal retraction after 45 hours of crosslinking in water at 98 ± 2 ° C 120% and heaviness-HOSf 515% increased after aging to 554%.

B P rin g and d 3

The difference compared to the previous example was only in the crosslinking system consisting of 2 weight percent of 1,1-di-tert-butylperoxy-3,3,5-trimethyl-cyclohexane and 0.3 weight percent of tri-allyl cyanurate anchored to 30 % by weight of the inert carrier added to the mixture in the peroxide dosing phase. The Mooney safety reached 56 min at 110 ° C, the deformation of the crosslinked mixture after 25 h for the same conditions as before was 110 ° C, and the ductility increased from the flood value of 457% to 476% after aging. The same degree of cross-linking was achieved here after 200 h of test specimens in water temperature 81 + 3 ° C. The independence of the crosslinking time from the ridge ridge results from the fact that after 25 h tempering at 98 + 2 ° C, the deformation of mechanical and thermal loading ranged from 105 to 117% even for ridge samples 5 and 8 mm, thus practically the same as for a sample having a thickness of 0.8 to 1.0 mm.

However, cross-linking of silanylized polyethylene-catalytic 0.05% by weight di-butyl tin dilaurate required 5 mm 35 µl and 8 mm to 80 h in the case of this temperature and the same test specimen.

By the same procedure of sample preparation and testing as in Example 1, a crosslinkable mixture was prepared which contained a co-polymer of ethylene with 7.5 weight per cent of vinyl acetate and subsequently functionally added: 0.35 weight percent 4,4'-thio -bis- (3-methyl-6-tert-butylphenol, 0.2 weight percent of polymerized 2,2,4-trimethyl-1,2-dihydroquinoline, 2.2 weight percent trialkyanurate. min safetyMooney at 110 ° C and after 24 h cross-linking in the hot water 98 + 2 ° C was the resistance of the blasting bodies to deformation at the mechanical and thermal load of 90% and their resistance to thermo-oxidative aging changes the ductility of The suitability of using this material as a high voltage insulation is characterized by the temperature dependence of the loss factor having the following passage: 0.0045 at —40 ° C, 0.0062 at 2020 ° C, 0.0035 at 0 ° C, 0.0015 at 23 ° C, 0.0003 at 50 ° C, 0.0001 at 70 ° C and 0.00001 at 90 ° C. Example 5

Ethylene acrylate copolymer was used here

Claims (2)

241570 18 wt.% Acrylate copolymer, in which, in addition to the antioxidant and peroxide in a pre-process, 36 wt.% Conductive carbon black with a surface area of 200 m @ 2 / g were admixed at 120 DEG C. for 10 minutes after cooling the mixture to 105-110 ° C as in Example 1, 0.35 weight percent 4,4'-thio-bis- (3-methyl-6-tert-butylphenyl) and 2.3 weight percent 1,1-di-tert-butylperoxy-3 were added. , 3,5-trimethylcyclohexane. The test specimen preparation procedure, as well as their testing, was the same as in Example 1. The processing safety of the Mooney crosslinkable mixture was 66 minutes at 110 ° C. The samples were crosslinked for 48 hours in water at 98 ± 2 ° C. Celsius, after which they achieved a degree of crosslinking characterized by a mechanical and thermal deformation value of 77 ° / o, a specific internal resistance of 0.2 ohm.m at 23 ° C and a resistance to thermo-oxidative aging after 7 days at 150 ° C, characterized by a change in ductility from 186 ° to 215%. Example 6 In the preparation of the semiconductive crosslinkable mixture as well as its crosslinking and testing, the procedure described above was followed, except that the components of the mixture formed ethylene butyl acrylate copolymer containing 22% by weight of butyl acrylate, 24% by weight. percent conductive solids having a specific surface area of 430 m 2 / g, 0.35 wt.% of 4,4'-thio-bis- (3-methyl-6-tert-butylphenol) and 2.5 wt. The process safety of the Mooney at 110 ° C reached 62 minutes, the value of the deformation of the body weight of 35 hours in water at 98 ° C. ++ 2 ° C 85 ° / o, specific internal resistivity 0.3ohm.m at 23 ° C and change in ductility at tero-oxidative aging from 160 to 183%. Example 7! In the unchanged working process, the conductive mixture was ethylene vinyl acetate copolymer with 14 weight percent vinyl acetate, 15.5 weight percent conductive carbon black with a specific surface area of 1100 meters2 / g, 0.5 weight percent 4,4'- thio-bis (3-methyl-6-tert-butylphenol) and 2.4% by weight of 1,1-di-tert-butylperoxy-3,3,5-trimethylcyclohexane. Mooney crosslinkable safety for 56 minutes at 110 ° C for 50 h. Cross-linking in water at 98 + 2CD reached 60% deformation in mechanical and thermal retraction, 0.3 ohm. m specific resistivity at 23 ° C and ductile decrease from 306% to 264% after thermo-oxidative aging. EXAMPLE In applying the same unchanged process, the semiconducting mixture consisted of ethylene vinyl acetate copolymer 7.5 weight percent vinyl acetate, 17 weight percent conductive rate surface 1100 m2 / g, 0.5 weight percent 4,4'- thio-bis- (3-methyl-6-tert-butylphenol), 0.35 weight percent polymerized 2,2,4-trimethyl-1,2-dihydroquinoline and 2.7 weight percent 1.1 -di-tert-butylperoxy-3,3,5-trimethylcyclohexane.Mooney safety of the crosslinking mixture at 110 ° C was 68 minutes, and after 24 hours of grounding in water at 98 ± 2 ° C, it exhibited spinning characteristics: a mechanical and thermal load of 91%, a specific internal resistance of 0.2 ohm. m at 23 ° C and changing the ductility from 237% in the basin to 220% after thermo-oxidative aging. Test specimens prepared from silanylated polyethylene, to which 0.1% by weight of dibutyltin dilaurate were added, as well as the same amounts of carbon black mentioned therein and crosslinked under the conditions described above in water did not exhibit at 200 ° C. resistance to deformation at 20 N / cm 2. The solution according to the invention makes it possible, in a technically and economically very advantageous manner, to produce high-voltage cages with cross-linked functional layers. The use of the solution according to the invention is possible and feasible both for the producers of ethylene copolymers in their utilization by additive additives on the crosslinkable mixture as well as in the cable manufacturers for the crosslinking of the plastic layers of the formed veins. SUBSTITUTE A crosslinkable polymer blend comprising a copolymer of ethylene with 5 to 30% by weight of a polar monomer selected from the group consisting of vinyl acetate and alkyl esters of acrylic acids, such as ethyl acrylate and butyl acrylate, 1 to 5% by weight, based on polymer blend, peroxide and optionally and] inventing a conductive carbon black with a specific surface area of 150 to 1500 m 2 / g, in an amount of 10 to 50% by weight, based on the polymer composition, characterized in that it contains peroxide as a peroxide component with a half-life of 2 to 20 hours at 100 ° C, preferably 1,1-di-tert-butylperoxy-3,3,5-trimethylcyclohexane. Severografla, n. P., Závod 7, Most Price 2,40 Kčs