CS220942B1 - Polyethylene products or constructions mainly the cabling products with increased thermomechanic stability - Google Patents

Description

The invention relates to polyethylene articles or structures, in particular of the cable type, which have an improved thermochemical stability and are made wholly or with parts of a polymeric material cross-linked with peroxides.

• The screening number is to forgo polyethylene products with markedly improved iteirmomeichan properties made of chemically crosslinked polymer in such a way as to achieve savings on any component of the crosslinkable mixture, while at the same time only some, not solvable technical problems immediately related to such production.

By forming cross-links between the reusable polyethylene applied to the respective products, they are aspirated. its thermomeehanic properties. Organic peroxides are most commonly used as crosslinking agents for this purpose, which, by thermal decomposition, generate macro-radicals, which, by recombination, form cross-links. Thus, each transverse bond requires an equimolar amount of peroxide, which, in the eleidized structural conversion of the polymer, already constitutes, for the desired modification of its thermomechanical properties, endotration of the peroxide at levels which are significant both economically and technically. The necessary proportion of peroxide alone in such a mixture increases its material cost by more than 20%. With the need for crosslinking of polyethylene with a higher melt index, these costs not only rise to unbearable high, but also the necessary concentration of peroxide in the polymer increases to such a degree that it exceeds its solubility limit and consequently peroxide from the crosslinkable mixture. In cases where a particularly high resistance of the crosslinked polyethylene to hot defonation under mechanical stress is required, the method of crosslinking the polymer below its melting point by the peroxidic sorption additive is not even applicable at all to the relative relative effectiveness.

Partial improvement in this respect can be achieved in products where polyfunctional monomers, such as trialylcycyanate, trlalyl isocyanurate, trimeitylol propane trimehaacrylate and the like, are used simultaneously with the peroxide in the polymer blend to increase the crosslinking efficiency and thereby to reduce the crosslinking reaction. the amount of peroxide used. However, in view of the relatively high cost of such multifunctional monomers, the technological and other bones associated with their selection, storage and application in the desired process, this method is not sufficiently efficient and economical to produce conventional products. cannot be applied.

Disadvantages of the prior art are eliminated according to the invention by the solution which is characterized in that the polymeric material of the products is of cross-linked branched polyethylene with a melt flow rate of 0.2 to 210 g / 10 min containing, in proportion to 100 parts by weight of this basic polymer integrated blend of 5 to 40 parts by weight of higher molecular weight unsaturated or polyolefins of the type -CH 2 CH 2 CH-CH 2

CH-R wherein R is CHfCH 10 to 30 mole percent of groups -GH3 and 70 'to 90 mol perceinit hydrogen atoms, R' is CH-C-CH-CH or \ _/ S CH CH CH CH _t

CH in the CH-CH-CH-CH-CH comonomer which constitutes 0.15 to 10 mole percent of said polyolefine having a Mobhey plasticity value of 100 to 35 ML (1 + 4) at 100 ° C, wherein the icopoilymer optionally contains a polyfunctional monomer in 0.01 to about ^1, 5 parts by weight.

Preferably, the specified polyethylene is homogenized at a temperature of 100 to 200 ° C relative to 100 parts by weight of this with from 5 to 40 parts by weight of a modifying terpolymer of ethylene, propyl and di-cyclopehtadiene or ethyleneboronene containing 0, 5 to 10 mole percent of double bonds and a statement having a defined plasticity value. Thereafter, at a temperature of 100 to 135 ° C, a melt of said polymeric components is integrated, in proportion to 1 part by weight, of the content of the modifying terpolymer, opaque from 0.05 to 135 ° C.

0.4 parts by weight of peroxide, optionally together with a proportion of 0.01 to 0.5 parts by weight of the polyfunctional monomer, and subsequently the polymer material is thermoformed and crosslinked. Optionally, a peroxide-free polymer mixture is thermoformed to the desired profile, and a proportion of this component is applied to the surface of the already formed product in a limited proportion, and the polymer material is then crosslinked by creating the reaction conditions necessary for diffusion. and thermal decomposition of the applied peroxide.

A marked increase in the crosslinking effect is achieved in the applied material by the application of peroxides which are combined with a specific higher molecular weight polyolefin with built-in double bonds, either alone or together with a polyfunctional monomer, which then modifies the mixture at a lower degree of crosslinking. its network structure such that the resulting crosslinkable product achieves high thermomechanical resistance even at a relatively low peroxide content.

The practice of the present invention is simple. After the addition of peroxide and possibly also a polyfunctional monomer, the composition of the mixture is homogeneously mixed, the composition is shaped and intensified under peroxide disintegration conditions on application, or used for further post-hemogenization treatment without peroxide addition, which is then applied to the product surface after shaping. wherein the crosslinking reaction occurs only after the peroxide has diffused into the polymer and its subsequent thermal decomposition.

Achieving the necessary thermo-mechanical properties of the product is sufficient for the given solution! use of less than one patina of otherwise required amount of peroxide, if desired, when the polyethylene of lower molecular weight is fused, concentrations of peroxide well below the solubility limit of the polymer are sufficient. When soldering such additive polyethylene by the sorption additive of peroxide, deformed crosslinked polymer at 150 ° C and with a gentle load of 20 N / m ^{2, they do not} exceed 175%.

The solution according to the invention enables efficient and economical production of products with higher technical parameters. There are no material or technological complications associated with the implementation of the solution. Production is customary, including conventional methods of spraining materials by extrusion, absorption, or blow molding, as defined in the cable industry, but the defined changes in the composition of the mixture do not result in: negative but positive functional, technical, electrical, physical or mechanical properties.

Example 1

After melting 85 parts by weight of branched polyethylene with a melt index of 2 g / 10 ' min. In a screw mixer, at a temperature of 125 ° C, 15 parts by weight of ethylene copolymer containing 23 moles were added to the melt. % of methyl substituents and 3.8 mol. % dicyfclopentadiene and 0.8 parts by weight of dicumyl peiroxide. The mixture is stirred at the same temperature with the resin component, and 10 minutes another 3 peiroxidom iminúty, · then pressed out of it a writing tablet thickness 1 mm for Súča! · Depth of crosslinking of the polymer, i.e. 20 minutes at 170 'C ^Q Termomechainická resistance rated extension of the test specimen thus produced at ISO ° C and with a meirical load of N / cm ² , the IEC 6410 standard, reached 125%. To achieve this value for polyethylene of the same type, but without modification! Coagent according to the invention required up to 1.55 parts by weight of dicumyl peiroxide per 100 parts by weight of polymer.

Example 2

The same raw materials and the same procedure as in Example 1 were used except that the prepared mixture contained 25% by weight; % of the modifying unsaturated copolymer; and 0.45 parts by weight of peroxide. The elongation of this crosslinked mixture, measured as before, was 1:10 wash. In order to achieve analogous values for polyethylene products from the compositions without the solution according to the invention, a proportion of 1.7 parts by weight of dicumyl peroxide per 100 parts by weight of polymer would be required. .

Example 3

A crosslinkable polyethylene mixture was prepared in the same manner as in Example 1, but having the following composition: 85 parts by weight of polyethylene with a melt flow index of 2 g / l min, 15 parts by weight of ethylene copolymer containing 26 mol% of methyl subsituents;

5.5 mol. % of ethylidene boronorene, 0.3 parts by weight of trialyl camururate and 0.3 parts by weight of dicumyl peroxide. The thermomeehanic resistance of the crosslinked mixture exhibited an 80% elongation under the aforementioned measurement conditions, which normally requires the use of 1.85 parts by weight of dicumyl peroxide.

Example 1 4

85 parts by weight of branched polyethylene with a melt flow index of 20 g / .10 ' mime were used, to which 115 parts by weight of the modifying copolymer containing 5.5 moles was added in a screw mixer at 120 [deg.]. % ethylidene norbornene. After stirring for 10 minutes, a proportion of 0.5 parts by weight of trialyl isocyanurate and a proportion of 0.2 parts by weight were added. parts of bis-di-tert-butylperoxy-d1-isopropylbenzene, followed by further mixing of the components for three minutes. The cross-linked sample exhibited an 80% elongation at 150 µl and a 20 'N / c ² load, which is achieved by a proportion of 2.1 parts by weight of dicumyl peroxide in polyethylene of this type.

Example 1 a d 5

Polyethylene crosslinking was not carried out by a conventional process of heating a peroxide-containing polymer, but this process only occurred additionally in a molded plate after application of the peroxide to the surface and its diffusion into the polymer and subsequent thermal decomposition: To this end stir for 10 minutes at 180 ° C. The mixture was prepared containing 910 parts by weight of polyethylene having a melt flow index of 2 g / 10 min, 10 parts by weight in Example 1 of said copolymer with built-in dicyclpemtadiene and 1 part by weight of triialyl cyanurate. 1.2 mm depth test plates were pressed from mixture ¹ at 14 ° C to one side of which a layer was applied. benzoyl peroxide, a paste in sillicon oil, with both components in a ratio of 1 liter; in an amount such that the peroxide content is 5% by weight of the weight of the test plate. The samples thus prepared were heated for 9Ό minutes in a water bath at 100 ° C. By the above procedure, the sintered samples exhibited a maximum 60% elongation at the thermal and mechanical stresses specified in Example 1, while the reference bodies: sintered equally but not containing the additive modifying mixture all ruptured under the same thermomechanical resistance measurement conditions.

The spQsoib linked polyethylene the result of the same thermo-mechanical resistance, the 'reproduced on the vein Kalbiy wherein isa the following way: to, xtrúderi Reifeinhauser S 45, the temperature distribution of 155 to 175 ^1¾ the annealed aluminum cable cross section of 2.5 mih ² pushed out Given a given mixture of the above properties, an insulation thickness of 0.85 millimeters, which, after application of a 0.112 mm thick layer of benzoyl peroxide paste for two hours, was rolled off in boiling water.

Example 6

The same raw materials were used as in Example 5 as well as the same polyethylene crosslinking principle, except that the crosslinkable mixture contained 15% by weight of an unsaturated copolymer of the composition of Example 5 and 1 weight percent of itrialyl cyanurate and 1 was used for sorption additive peroxide. 5% by weight pereent 1,1,11-β-tert-butylpeiroxy-3,3 _> 5-trl ¹ methylhexane coated unilaterally: as a 50% solution on a surface of 1.1 mm thick plate molded at 140 ° C from a mixture of the three ztažiek. After tempering for 17 hours in a 10 ° C warm tube, 60% of the weight of the test specimen was measured at the specified heating and mechanical stresses, and samples without modifying agent were broken under these conditions.

Based on the results of a trial evaluation of the essence of the invention according to the individual examples 1 to 6 above, the particular application of the solution appears to be suitable for the needs of the electrical industry. The application is particularly advantageous in the field of production of electrical cables and insulated conductors of high-current, low-frequency and high-frequency notification and other types of cables and conductors, with the possibility of applying the solution in the respective products for insulation and sheathing. A further application is given in particular in the production of polyethylene pipes, cable ties, connecting and terminating sets, fittings, pirophiles, which are still made using the existing technological equipment and the usual extrusion and injection processes.

Claims (1)

SUBJECT INVENTION Polyethylene products or structures, in particular cable products with increased thermo-mechanical stability, made wholly or in part of a peroxide-crosslinked polymeric material, characterized in that the polymeric material of the products is of branched polyethylene with a melt flow index of 0.2 to 20 g / 10 min. comprising, in proportion to 100 parts by weight of this base polymer, an integrated blend of 5 to 410 parts by weight of a higher molecular weight unsaturated polyolefin of the type FROM CH, in comonomer \ / CH — CH CH CH 'CH - CH CH - CH _Z -CH = CH-✓ch / \ CH sputum wherein R is 10 to 30 mole percent of -CH group and 70 to 90 mint pereent hydrogen atoms, R' is a face that 0,> 5 up to 10 mole per cent of said polyolefin having a Mooney plasticity value of 1.00 ° C of 35 to 1210 ML (1 + 4), wherein the copolymer optionally also contains a polyfunctional monomer in an amount of 0.01 to 0.5 parts by weight. QHa-C = CH-CHa or Severography, n. p., plant 7, Most