Polyethylene composition for cables and pipes

Abstract

The invention relates to polymer chemistry, and more particularly to performance-enhanced compositions based on low-density and high-density polyethylene, and can be used in the manufacture of cables and pipes. The present polyethylene composition comprises from 36.5 to 50.0 wt% low-density polyethylene (LDPE), from 41.5 to 55.0 wt% high-density polyethylene (HDPE), from 8.2 to 8.3 wt% UV stabilizer and from 0.2 to 0.3 wt% heat-stabilizing additive mixture, wherein the ratio of the complex viscosity values η of the polymers (ηLDPE:ηHDPE), measured at a frequency of 100 rad / s and 190°C, lies within a range of 1.0-1.5, and the ratio of the melt elasticity values G* / G** of the polymers (G* / G**LDPE:G* / G**HDPE), measured at a frequency of 0.1 rad / s and 190°C, is not more than 1.0, and the composition is characterized by a stress cracking resistance of not less than 2000 hours and a Shore D / 15 hardness of not less than 56 units. The technical result consists in achieving a balance between surface hardness, stress cracking resistance, thermal stability and manufacturability.

Description

[0001] POLYETHYLENE COMPOSITION FOR CABLE AND PIPE PRODUCTS WITH IMPROVED PERFORMANCE PROPERTIES

[0002] Field of technology to which the invention relates

[0003] The invention relates to polymer chemistry, in particular to compositions of composites based on low-density polyethylene and high-density polyethylene, and can be used in the production of cables and pipes.

[0004] State of the art

[0005] High demands are placed on the compositions intended for cable production; polyethylene-based materials used for the production of these compositions must have a number of properties, in particular, a combination of high strength characteristics, high surface hardness of the product, high resistance to cracking, high resistance to light and thermal-oxidative aging, while having good processability.

[0006] Despite the wide range of cable composites available on the market for use in various operating conditions, there remains a need to create a polymer composite with increased surface hardness while maintaining high crack resistance (preferably at least 2,000 hours) and high processability, which is determined by melt rheological properties such as viscosity and elasticity. The lower the viscosity, the better the processability and the higher the processing speed.

[0007] In particular, Russian industrial cable compositions based on LDPE (low density polyethylene), for example, grade 153-10K (manufactured according to GOST 16336), with a combination of high crack resistance (at least 1000 h) and good processability, exhibit low surface hardness and, conversely, compositions based on HDPE (high density polyethylene), with high surface hardness, exhibit lower processability and crack resistance than LDPE.

[0008] The prior art includes materials based on high-, medium-, and low-density polyethylenes, produced by various methods, including radical polymerization at high pressure and temperature (LDPE / LDPE) and catalytic polymerization at low pressure and temperature (HDPE / HDPE), and copolymers of ethylene with higher alpha-olefins, such as LLDPE (linear low-density PE) and MDPE (medium-density polyethylene). Also known are compositions based on these individual types of polyethylene, intended for use in various fields of technology, particularly the cable and pipe industries.

[0009] Patent CN106220940 (published December 14, 2016, Anhui Jisite Intelligent Equipment) discloses a composition with high resistance to stress cracking, comprising LDPE, terpene resin, methylphenyl silicone resin, acetyl tributyl citrate, TMC-201 binding agent, triphenyl phosphate, antioxidants, oils, cellulose, and a method for producing said composition. This composition exhibits relatively high strength properties and low-temperature resistance and can be used to manufacture the sheathing of construction optical cables. However, the use of a large number of complex components leads to increased costs for products manufactured using it, along with the complexity of the manufacturing process for such compositions.

[0010] A polyethylene composition EA041620 (published November 15, 2022, by PJSC SIBUR Holding) with improved strength properties is known for fiber optic cables and the outer insulation layer for steel pipelines. It contains LLDPE and HDPE, a nucleating agent (talc or carbon black), and an optional other additive or mixture thereof. The nucleating agent is added to the composition as a masterbatch in LLDPE when using carbon black or as a masterbatch in HDPE when using talc. A disadvantage of the claimed invention is the use of linear low-density metallocene polyethylene, which has poor processability and does not meet the composition's melt flow rate (MFR) requirements. In addition, the use of metallocene polyethylene leads to increased product costs.

[0011] Patent RU2756586 (published October 1, 2021, by Kazan Public Joint Stock Company "Organic Synthesis") discloses a thermoplastic composition intended for use in the cable industry, in the production of packaging material and other products, which contains LDPE, a phenolic or phosphite-type heat stabilizer and a UV light stabilizer. The phenolic heat stabilizer is an ester of 3,5-di-tert-butyl-4-hydroxyphenylpropionic acid and pentaerythritol, the phosphite-type heat stabilizer is a mixture of 3,5-di-tert-butyl-4-hydroxyphenylpropionic acid ester and pentaerythritol and tri- (2,4-di-tert-butylphenyl) phosphite in a 1:1 weight ratio, and a 30% concentrate of carbon black based on low-density polyethylene is used as a UV light stabilizer. The use of the mentioned heat stabilizers and UV light stabilizer ensures the necessary indicators in terms of surface hardness, heat stability and processability.However, the disadvantage of this composition is its low resistance to cracking.

[0012] The composition claimed in document WO0248258 (published June 20, 2002, Eastman Chemical), intended for the production of extrusion coating and films, consists of three components: LLDPE, HDPE and LDPE. This composition is characterized by the following parameters: tensile strength from 27,600 to 34,000 kPa, relative elongation of 839-927%, puncture resistance from 378 to 510 N / cm 2 and a melt strength of 10 cN. The disadvantage of this composition is its low crack resistance.

[0013] Patent JP09241437 (published September 16, 1997, Mitsubishi Chemical) discloses a composition for insulating steel pipes prepared from a blend of HDPE and LLDPE. The invention provides a good balance of low-temperature performance in the composition, resulting in an improvement in relative elongation at break at -45°C by up to 400%, and high-temperature performance; penetration resistance at 70°C. However, the relatively low HDPE content (10-40 wt.%) in the composition, as is obvious to those skilled in the art, reduces the potential for further improvement in the strength characteristics and heat resistance of such systems, thereby limiting the practical application of materials based on them.

[0014] RU2679135 (published February 6, 2019, Basell Polyolefine) discloses the composition of an ethylene polymer composite and its use in the production of products such as cable sheathing and plastic automotive parts. A disadvantage of this composite is the difficulty of its production, and the invention does not disclose key performance indicators such as crack resistance and Shore hardness.

[0015] The closest in technical essence (prototype) is the composition according to patent EA041625 (published on 15.11.2022, (PAO SIBUR Holding)), containing LDPE, LIN, HDPE, as well as nucleating agents that regulate the rate of crystallization of macromolecules. Inorganic compounds (preferably carbon black, talc) and organic compounds (preferably 3,4-dimethyldibenzylidene sorbitol, zinc stearate and calcium salt of 1,2-cyclohexanedicarboxylic acid) can be used as nucleating agents. The composition may contain other additives, such as antioxidants, heat stabilizers, light stabilizers or mixtures thereof. This composition has high strength and elastic characteristics, high resistance to stress cracking (at least 2000 hours), has a melt flow index from 0.24 to 1.10 g / 10 min and can be used for both film production and insulating coatings for electrical cables.The disadvantage of this composition is its multi-stage production and multi-component nature. The method for producing the composition involves the production of intermediate mixtures, their mixing with each other and other components of the composition during compounding in an extruder. Therefore, producing polyethylene using this method entails additional technological complexities, difficulty in selecting the right temperature regime for processing the composition, and the risk of insufficient uniformity of component distribution within it. Furthermore, the multi-stage and multi-component nature of the process leads to increased cost of the finished product.

[0016] It should be noted that the prior art does not disclose polyethylene compositions that simultaneously have good surface hardness, crack resistance, high processability and thermal stability, ensuring the successful use of such compositions in the manufacture of cable sheathing.

[0017] Thus, despite the efforts of previous researchers, there remains a need to develop polyethylene composites that are characterized by high strength properties, resistance to cracking, and, at the same time, have good processability and thermal stability, allowing them to be used for cable insulation and pipe manufacturing.

[0018] Disclosure of the Invention

[0019] The technical problem addressed by the claimed invention is the creation of a composite material with high strength characteristics, specifically, high crack resistance, good processability, and thermal stability. The technical result consists of achieving a balance between surface hardness, crack resistance, thermal stability, and processability.

[0020] The stated technical problem is solved, and the claimed technical result is achieved, through the use of a material consisting of a composite comprising polyethylenes with different macromolecular structures, namely low-density polyethylene (LDPE) and high-density polyethylene (HDPE). Furthermore, the composition contains carbon black as a UV stabilizer, and an effective mixture of phenolic and phosphite-type heat-stabilizing additives (primary and secondary antioxidants) is used as a heat stabilizer. HDPE, as the most highly crystalline component, enhances the strength properties of the composition, surface hardness, and heat resistance. LDPE also improves its elasticity.

[0021] The inventors unexpectedly discovered that, to achieve the desired set of properties, a key factor is the use of polymers with a specific ratio of rheological properties (complex viscosity and melt elasticity). These properties, being a function of the polymers' molecular structure, determine their behavior under dynamic melt mixing conditions. Without being limited by any specific theory, the authors propose that a specific ratio of the rheological properties of the blend components effectively homogenizes the melt and forms a supramolecular structure within the composition that ensures the desired combination of properties.

[0022] Furthermore, the required level of target characteristics is ensured by the use of an effective synergistic blend of primary and secondary antioxidants in the composition. Using only a primary or secondary antioxidant does not produce the desired result.

[0023] The composition has a MFI of 190 °C / 2, 16 kgf (hereinafter MFI) in the range of 0.30-0.45 g / 10 min, a Shore hardness D / 15 of at least 56 conventional units, thermal stability of at least 17 min, measured by the DSC method at 200 °C, rheological properties: melt elasticity at 190 °C in the range of 0.62-0.65, complex viscosity at 100 rad / sec in the range of 1100-1300 Pa-sec. In addition, the claimed composition has resistance to cracking under stress of at least 2000 hours, is characterized by a tensile yield strength from 14.1 to 14.5 MPa, tensile strength from 14.2 to 14.8 MPa, relative elongation at break from 690 to 720%. High resistance to cracking is one of the most important characteristics of cable and pipe products, determining their durability and resistance to aggressive fillers.

[0024] Low and thermal stability are necessary for the stability of polymer properties when exposed to high processing temperatures and operating conditions.

[0025] Increased surface hardness enhances the polymer material's protection from external mechanical stress, which can damage the coating's integrity. Processability is directly related to the melt's rheological properties. The higher the viscosity, the worse the processability, as the energy required to process the polymer increases. Therefore, it is important to optimize the processability when developing the composition. Reducing processing temperatures and increasing productivity result from improved processability.

[0026] Thus, the proposed composition's increased hardness, combined with high crack resistance, good processability, and thermal stability, represents a significant advantage. A polyethylene composition with these characteristics is suitable for the manufacture of medium-voltage cable sheaths and tubular products.

[0027] According to the present invention, there is provided a composition comprising:

[0028] - from 36.5 to 50.0% by weight of low-density polyethylene (LDPE);

[0029] - from 41.5 to 55.0% by weight of high-density polyethylene (HDPE);

[0030] - from 8.2 to 8.3% by weight of UV stabilizer;

[0031] - from 0.2 to 0.3% by weight. a mixture of heat-stabilizing additives, wherein the ratio of the values ​​of the complex viscosity of the polymers τ|, measured at a frequency of 100 rad / s and 190 °C, τ|PEVP / τ|PENP, is in the range of 1.0 - 1.5, and the ratio of the values ​​of the elasticity of the melt of the polymers G* / G**, measured at a frequency of 0.1 rad / s and 190 °C, G* / G**n3Bn / G* / G**n3Hn is not more than 1.0 and the composition is characterized by resistance to cracking under stress of at least 2000 hours and a hardness according to Shore D / 15 of at least 56 conventional units.

[0032] In the context of the present invention, the low-density polyethylene (LDPE) used is polyethylene obtained by high-pressure polymerization of ethylene in tubular reactors using radical initiators using standard industrial technologies. This polyethylene is characterized by a MFI of i90°c / 2.i6 kgf from 0.21 to 0.39 g / 10 min, preferably from 0.30 to 0.39 g / 10 min, and a density of 0.919 g / cm 3 up to 0.922 g / cm 3 , preferably from 0.919 g / cm 3 up to 0.920 g / cm 3. It is preferable to use LDPE having a molecular weight of 200,000 to 300,000, preferably 220,000 to 250,000, and a polydispersity of 5 to 15, preferably 6 to 9. In this case, the molecular weight in the present invention is understood to mean the weight-average molecular weight, unless otherwise stated. Polyethylene is characterized by melt elasticity, measured at 190 °C and a frequency of 0.1 rad / sec in the range of 0.6 to 0.7, more preferably 0.685, and a complex viscosity at a frequency of 100 rad / sec in the range of 800-900 Pa-sec, more preferably 842 Pa-sec. As LDPE, LDPE grades 15313-003 or LDPE 15303-003 can be used, in accordance with GOST 16337, and other trade marks with similar properties.

[0033] High-density polyethylene (HDPE) is produced by low-pressure ionic coordination polymerization of ethylene on chromium catalysts using standard industrial technologies. This polyethylene is characterized by a MFI of 190°C / 5.0 kgf from 2.3 to 3.3 g / 10 min, preferably from 2.8 to 3.3 g / 10 min, and a density of 0.957 g / cm 3 up to 0.963 g / cm 3 , preferably from 0.960 g / cm 3 up to 0.963 g / cm 3. It is preferable to use HDPE having a molecular weight from 100,000 to 130,000 and a polydispersity from 4 to 6. In this case, the molecular weight in the present invention is understood to mean the weight-average molecular weight, unless otherwise stated. Polyethylene is characterized by melt elasticity, measured at 190 °C and a frequency of 0.1 rad / sec in the range from 0.5 to 0.6, more preferably 0.555 and a complex viscosity at a frequency of 100 rad / sec in the range of 1000-1200 Pa sec, more preferably 1176 Pa sec. As LDPE, HDPE of the HD07580 (SIBUR) brand and other brands with similar properties can be used.

[0034] Additionally, the composition according to the present invention may contain other additives such as antioxidants, heat stabilizers, light stabilizers or mixtures thereof, etc.

[0035] Phenolic and phosphite compounds are used as heat stabilizers, which are an effective synergistic mixture of the primary and secondary antioxidants Irgafos 168 and Irganox 1010, taken in a weight ratio of 1:1 to 1:4. In particular, Irganox B225 can be used, which is a synergistic mixture of the primary and secondary antioxidants Irgafos 168 and Irganox 1010, taken in a weight ratio of 1:1. Stabilization of polyethylene with mixed stabilizers of phenolic and phosphite types provides an additional improvement in the properties of materials by preventing thermo-oxidative and thermal destruction of the component molecules that make up the material.A phenolic or phosphite type heat stabilizer and a UV light stabilizer are used as stabilizers, wherein the phenolic type heat stabilizer is an ester of 3,5-di-tert-butyl-4-hydroxyphenylpropionic acid and pentaerythritol, the phosphite type heat stabilizer is a mixture of an ester of 3,5-di-tert-butyl-4-hydroxyphenylpropionic acid and pentaerythritol and tri-(2,4-di-tert-butylphenyl)phosphite, and a 30% concentrate of carbon black based on low density polyethylene is used as a UV light stabilizer.

[0036] To produce compositions resistant to photooxidative degradation, a UV light stabilizer—carbon black—is used. It is introduced as a 30% industrial concentrate based on LDPE (KTU). Carbon black is an effective light stabilizer for polymer compositions prone to cross-linking under the influence of UV rays, which leads to a decrease in such properties as tensile strength and elongation at break. All known UV stabilizers for polyethylene can also be used as light stabilizers: benzophenones, benzotriazoles, HALS amines, and ethers. The stated composition must primarily provide a combination of high crack resistance and high Shore hardness. These requirements are crucial for the reliable operation of cable and pipe products in harsh environmental conditions.Although these indicators exhibit an anti-crack relationship, the use of LDPE and HDPE with a specific ratio of rheological properties (viscosity and melt elasticity) ensures the formation of the required homogeneous structure in the composition, ultimately resulting in a composite with the desired properties. Achieving this combination of high crack resistance and high Shore hardness allows for reliable determination of the technical result achieved under the required operating conditions.

[0037] Thus, the use of LDPE and HDPE with a certain ratio of rheological characteristics (viscosity and elasticity of the melt) ensures the formation of the required homogeneous structure in the composition, which ultimately leads to obtaining a composition with the required properties.

[0038] Implementation of the Invention

[0039] The properties of the polymer composites were evaluated using standard methods: The melt flow index was determined at a temperature of 190 °C and a load of 2.16 N according to GOST 11645.

[0040] Determination of hardness according to Shore D / 15 is carried out according to GOST 24621.

[0041] The determination of resistance to stress cracking is carried out according to GOST 13518. The determination of physical and mechanical properties is carried out according to GOST 11262 on type I samples with a thickness of (2.0±0.2) mm at a speed of movement of the movable grip of the tensile testing machine of (100±10) mm / min.

[0042] Determination of thermal stability is carried out according to GOST R 56756.

[0043] The rheological properties of polymer melts are determined according to ISO 6721-1 and 6721-10. The measurements are carried out on a DHR-1 rotational rheometer equipped with a 25 mm parallel plate geometry under a nitrogen atmosphere on samples prepared by pressing. Oscillation tests are carried out at T=190 °C using frequencies in the range of (100-0.1) rad / sec. The results are expressed using the shear storage modulus G*, the shear loss modulus G**, the melt elasticity as the ratio G* / G**, and the complex shear viscosity g*. The values ​​of G*, G**, and g* are obtained as a function of frequency (cv). Thus, for example, rcoo is used as an abbreviation for the complex viscosity at a frequency of 100 rad / sec, and the melt elasticity is calculated using the values ​​of G* and G** at a frequency of 0.1 rad / sec.

[0044] The following were used as initial components to obtain the composition:

[0045] 1) LDPE - grade 15313-003 (GOST 16337-2022): y = 0.919-0.922 g / cm 3 , MFR19o / 2.16kg=0.21-0.39 g / 10 min, crack resistance 500 hours, Shore hardness D / 15=45. Melt elasticity measured at 190 °C and a frequency of 0.1 rad / sec is 0.685, and complex viscosity at a frequency of 100 rad / sec is 842 Pa-sec. manufactured by PJSC Kazanorgsintez, Russia;

[0046] 2) HDPE - grade HD07580SB (TU 20.16.10-250-00203335-2022): d=0, 957-0, 963g / cm 3 , MFR190 / 5.0KG=2, 3-3.3 g / 10 min, crack resistance 48 hours, Shore hardness D / 15=75. Melt elasticity measured at 190 °C and a frequency of 0.1 rad / sec is 0.555, and complex viscosity at a frequency of 100 rad / sec is 1176 Pa-sec manufactured by PJSC Kazanorgsintez, Russia; 3) HDPE2 (for a comparative example) - brand HD12443FE (TU 20.16.10-250-00203335-

[0047] 2022): d=0.943-0.949r / cM 3, PTR19O / 5.0 KG=0.4-0.7 G / 10 MIN, crack resistance 1000 hours, Shore hardness D / 15=77, melt elasticity measured at 190 °C and a frequency of 0.1 rad / sec=0.9, complex viscosity at a frequency of 100 rad / sec 2000 Pa-sec, manufactured by PJSC Kazanorgsintez, Russia;

[0048] 4) UV stabilizer - 30% carbon black concentrate (CBC) grade PELD-30MV based on LDPE grade 15313-003, carbon black grade OMCARB P72 manufactured by Omsk Carbon Group LLC, Russia, was used;

[0049] Heat-stabilizing additives: antioxidant: Irganox B225 - a synergistic mixture of antioxidants Irganox 1010 (pentaerythritol tetraoxy (3 - (3,5-di-tert-butyl-4-hydroxyphenyl) propionate) and Irganox 168 (tris (2,4-di-tert-butylphenyl) phosphite); antioxidant (for comparative example): Irganox 1010 (pentaerythritol tetraoxy (3 - (3, 5 -di-tert-butyl-4-hydroxyphenyl) propionate);

[0050] As a comparison sample, we used a low-density polyethylene composition of grade 153-UK - an industrial grade of black color, resistant to thermal-oxidative and photo-oxidative aging, intended for the application of insulation, sheaths, and protective coverings of cables by the extrusion method.

[0051] To illustrate the technical result achieved by implementing the proposed invention, examples are provided with the most representative ratios of the composition's components. The invention is illustrated by the following examples.

[0052] The compositions and results of studies of PE compositions, including examples 1-11, are given in Table 1.

[0053] These examples are given only to illustrate the present invention and do not limit it.

[0054] Table 1

[0055] Compositions and properties of the compositions according to examples 1-11

[0056] The test results for the polyethylene composites obtained in Examples 1-6 and Cf. 7-8, shown in Table 1, indicate that the ratio of low- and high-density polymers is a key indicator affecting the crack resistance of the composite. An LDPE content below 36.5% by weight or above 50.0% by weight, and an HDPE content below 41.5% by weight or above 55.0% by weight, lead to a decrease in crack resistance to an unacceptable level, despite the compliance of the rheological properties of the polymers included in the composite with the stated limits. Furthermore, as follows from Example Cf. 8, a discrepancy between the discussed indicator and the stated range may lead to a deterioration in Shore hardness.

[0057] The results of testing the composition obtained according to example cf. 10 demonstrate that the use of polymers in the composition, the ratio of the rheological characteristics of which does not correspond to the stated limitations, leads to a deterioration in all key indicators compared to the composition according to example 5, despite the high values ​​of crack resistance and Shore hardness of the HDPE brand used in the composition.

[0058] Comparative Example 9 demonstrates the importance of antioxidant selection for maintaining the composition's properties at the target level. Using Irganox 1010 antioxidant instead of Irganox B225 at the optimal polymer component ratio does not maintain the required level of crack resistance compared to the composition in Example 3, although parameters such as MFI and Shore hardness are at optimal levels.

[0059] It has also been shown that, in all characteristics, the compositions of the compositions according to examples 1-6 are superior to example 11, which is similar in composition to a well-known industrial analogue - a cable composition of low-density polyethylene grade 153-10K.

[0060] Thus, the best technical result is achieved when the polyethylene composition contains LDPE and HDPE with similar rheological properties, carbon black introduced into the composition as a concentrate in LDPE, and a synergistic mixture of primary and secondary antioxidants. LDPE is introduced into the composition in an amount of 36.5 to 50.0% by weight, and HDPE in an amount of 41.5 to 55.0% by weight. The composition according to the invention possesses a range of properties, such as increased surface hardness while maintaining high crack resistance, high processability, and thermal stability, which is essential for use in the cable and pipe industries for more efficient operation.

Claims

CLAUSES OF THE INVENTION 1. Polyethylene composition for the manufacture of cable and pipe products, including: - from 36.5 to 50.0% by weight of low-density polyethylene (LDPE); - from 41.5 to 55.0% by weight of high-density polyethylene (HDPE); - from 8.2 to 8.3% by weight of UV stabilizer; - from 0.2 to 0.3% by weight. a mixture of heat-stabilizing additives, wherein the ratio of the values ​​of the complex viscosity of the polymers τ|, measured at a frequency of 100 rad / s and 190 °C, τ|PEVP / τ|PENP is in the range of 1.0 - 1.5, and the ratio of the values ​​of the elasticity of the melt of the polymers G* / G**, measured at a frequency of 0.1 rad / s and 190 °C, G* / G**n3Bn / G* / G**n3Hn is not more than 1.0, and the composition is characterized by resistance to cracking under stress of at least 2000 hours and a hardness according to Shore D / 15 of at least 56 conventional units.

2. A polyethylene composition according to claim 1, characterized in that the composition preferably has a complex viscosity at 100 rad / sec of 1100 to 1300 Pa-sec.

3. A polyethylene composition according to claim 1, characterized in that it is characterized by melt elasticity at 0.1 rad / sec from 0.62 to 0.

65.

4. A polyethylene composition according to claim 1, characterized in that it is characterized by a MFR value of 190°C / 2.16 kgf from 0.30 to 0.45 g / 10 min.

5. A polyethylene composition according to I.1, characterized in that it is characterized by a tensile yield strength of 14.1 to 14.5 MPa, 6. A polyethylene composition according to claim 1, characterized in that the composition has a tensile strength of 14.2 to 14.8 MPa, 7. A polyethylene composition according to claim 1, characterized in that the composition has a relative elongation at break of 690 to 720%.

8. Polyethylene composition according to 1, characterized in that it is characterized by thermal stability at 200°C for at least 17 minutes.

9. The polyethylene composition according to claim 1, characterized in that it preferably contains LDPE from 39 to 48% by weight, most preferably from 41 to 47% by weight.

10. The polyethylene composition according to claim 1, characterized in that the LDPE is characterized by a MFI value of 190°C / 2.16 kgf from 0.21 to 0.39 g / 10 min, preferably from 0.30 to 0.39 g / 10 min.

11. A polyethylene composition according to claim 1, characterized in that the LDPE is characterized by a density of 0.919 to 0.922 g / cm 3 , preferably 0.919 to 0.920 g / cm 3 .

12. The polyethylene composition according to claim 1, characterized in that the LDPE is characterized by an average molecular weight Mw from 200,000 to 300,000, preferably 220,000 to 250,000.

13. The polyethylene composition according to claim 1, characterized in that the LDPE is characterized by a polydispersity of 5 to 15, preferably 6 to 9.

14. The polyethylene composition according to claim 1, characterized in that the LDPE is characterized by melt elasticity, measured at 190 °C and a frequency of 0.1 rad / sec, in the range from 0.6 to 0.7, more preferably 0.

685.

15. A polyethylene composition according to item 1, characterized in that the LDPE is characterized by a complex viscosity at a frequency of 100 rad / sec in the range of 800-900 Pa-sec, more preferably 842 Pa-sec.

16. A polyethylene composition according to item 1, characterized in that it preferably contains HDPE from 43.5 to 52.5% by weight, most preferably 44.5 to 50.5% by weight.

17. The polyethylene composition according to claim 1, characterized in that the HDPE is characterized by a MFR190°C / 5.0 kgf value of 2.3-3.3 g / 10 min, preferably from 2.8 to 3.3 g / 10 min.

18. A polyethylene composition according to claim 1, characterized in that the HDPE is characterized by a density of 0.957 to 0.963 g / cm 3 , preferably from 0.960 to 0.963 g / cm 3 .

19. The polyethylene composition according to claim 1, characterized in that the HDPE is characterized by an average molecular weight Mw from 100,000 to 130,000.

20. A polyethylene composition according to claim 1, characterized in that the HDPE is characterized by a polydispersity of 4 to 6.

21. The polyethylene composition according to item 1, characterized in that the HDPE is characterized by melt elasticity, measured at 190 °C and a frequency of 0.1 rad / sec, in the range from 0.5 to 0.6, more preferably 0.

555.

22. A polyethylene composition according to item 1, characterized in that the HDPE is characterized by a complex viscosity at a frequency of 100 rad / sec in the range of 1000-1200 Pa-sec, more preferably 1176 Pa-sec.

23. A polyethylene composition according to claim 1, characterized in that the UV stabilizer is carbon black, which is introduced into the composition in the form of a concentrate in low-density polyethylene.

24. A polyethylene composition according to item 23, characterized in that carbon black is introduced into the composition in the form of a 30% concentrate in low-density polyethylene.

25. A polyethylene composition according to claim 1, characterized in that the mixture of heat-stabilizing additives used is a mixture of antioxidants, which are a synergistic mixture of primary and secondary antioxidants of the phenolic type and phosphite type.

26. Use of a composition according to any of paragraphs 1-25 in the manufacture of products.

27. Use of a composition according to clause 26, characterized in that the product is the outer sheath of cables or the outer layer of insulation of pipelines.

28. An article made from a composition according to any of paragraphs 1-25.

29. The product according to Article 28, characterized in that the product is the outer sheath of electrical cables or the outer layer of pipeline insulation.

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