RU2670101C1 - Polyethylene composition for outer cable sheath and outer insulation for steel pipes - Google Patents

Abstract

FIELD: chemistry.SUBSTANCE: invention relates to polymer composition for producing an insulating layer of pipes or a power cable. Composition comprises 80–95 % by weight of a mixture of ethylene (A) polymers and 5–20 % by weight of a mixture of ethylene polymers (B). Mixture (A) contains component (1), which is an ethylene homopolymer with a melt flow index (MFR) from 0.3 to 200 g/10 min, density from 0.955 to 0.970 g/cmand a crystallinity of 60–75 % and a component (2) which is a copolymer of ethylene and 1-hexene or a copolymer of ethylene and 1-butene with a melt flow index (MFR) from 0.01 to 0.3 g/10 min, density from 0.925 to 0.940 g/cmand with a crystallinity of 40–55 %, wherein the ratio of components (1) and (2), in weight %: is 30÷55:45÷70. Mixture (B) contains, as component (3), an ethylene/hexene-1 copolymer or an ethylene-butene-1 and hexene-1 copolymer having a melt flow index (MFR) from 0.3 to 5.0 g/10 min, a density of from 0.919 to 0.935 g/cmand a crystallinity of 20–50 %, component (4), which is an amorphous alpha-olefin elastomer having a melt flow index (MFR) from 3.7 to 5.0 g/10 min, a density of from 0.865 to 0.879 g/cmand a crystallinity of 2.5–16 %, and component (5), which is a technical carbon. And mass ratio of components (3):(4):(5) in mixture (B) is 0.01÷89.99:0.01÷89.99:10÷40.EFFECT: polymer composition of invention has good processability and electrical conductivity.1 cl, 5 tbl

Description

The invention relates to a polymer composition for producing an insulating layer of pipes or power cable. The invention also relates to mixtures of polyethylene with improved uniformity, in particular, to a mixture comprising several fractions of ethylene polymers with different molecular weights. Such mixtures are particularly suitable for the manufacture of films, pipes, upper layers of cable sheaths, insulation of metal pipes, molded products, wires and cables. However, not all known compositions have properties that allow them to be used simultaneously for several purposes. Another difficulty is the selection of the composition of polyethylene with good processability. High molecular weight polyethylenes have improved mechanical properties compared to their low molecular weight counterparts. However, as the molecular weight increases, the workability of the polymer usually decreases. By creating a mixture of high molecular weight and low molecular weight polymers, the properties inherent in the high molecular weight polymer can be maintained, and workability, in particular extrudability inherent in the low molecular weight component, can be improved.

Known polyethylene composition intended for the manufacture of molded products, films, pipes, wires and cables (RF patent No. 2540073, IPC C08L 23/04 (2006.01), C08L 23/08 (2006.01), C08J 5/00 (2006.01), publ. 01/27/2015), which has increased uniformity. The disadvantage is its limited use only for the manufacture of molded products, films, pipes, wires and cables, but not for insulation of pipes and the outer sheath of cables.

Also described is a molding polyethylene composition intended for pipes and the manufacture of wires and cables (RF patent No. 2536821, IPC C08L 23/04 (2006.01), C08L 23/08 (2006.01), publ. 27.12.2014). It is used to produce molded products and its disadvantage is low extrudability, which does not allow it to be used on high-speed equipment, which is now used in all large-capacity enterprises for applying the upper insulating layers to a pipe or cable.

Known polyethylene composition for electrical devices (RF patent No. 2614767, IPC C08L 23/02 (2006.01), C08L 23/04 (2006.01), publ. 03/29/2017), which is then subjected to stitching to impart the necessary properties. The polymer composition contains (a) polyethylene obtained in the presence of an olefin polymerization catalyst, (b) an unsaturated low density ethylene homopolymer (LDPE) or an unsaturated low density ethylene copolymer and (c) an anion exchange additive in an amount of from 0.000001 to less than 1 wt. % Moreover, the polyethylene (a) is selected from copolymers of ethylene of very low density, linear copolymers of low density polyethylene (LLDPE), copolymers of medium density ethylene (PESP) or homopolymers or copolymers of high density polyethylene (HDPE). The disadvantage is its limited scope - only for cable production.

A known polymer composition for an insulating layer, the composition of which contains as the only polymer components: a) a polyolefin selected from the group consisting of a low density ethylene homopolymer or a low density ethylene copolymer, a low pressure ethylene homopolymer or a low pressure ethylene copolymer comprising from 0.1 up to 15 mol. % C _3-20 alpha olefin comonomer, or low pressure polypropylene; and (b) optionally, a second polyolefin selected from the group consisting of a low density ethylene homopolymer or a low density ethylene copolymer, a low pressure ethylene homopolymer or a low pressure ethylene copolymer comprising from 0.1 to 15 mol. % C _3-20 alpha-olefin comonomer, or low pressure polypropylene, which is different from polyolefin (a). However, this polymer composition is used only for the insulating layer of the cable (RF patent No. 2579146, IPC C08L 23/02 (2006.01), C08L 23/04 (2006.01), publ. 04/10/2016), which is its disadvantage.

The invention is known according to the patent of the Russian Federation No. 2571663, IPC C08L 23/02 (2006.01), C08L 23/04 (2006.01), publ. 12/20/2015, which relates to a polymer composition with improved electrical properties at constant current, to the use of the composition to obtain a layer of power cable. At the same time, at least the insulating layer consists of a polymer composition, which includes (a) from 0.1 to 30 wt. % homopolymer of low pressure ethylene or copolymer of low pressure ethylene, comprising from 0.1 to 15 mol. % of one or more C _3-20 alpha-olefin comonomer (comonomers), and (b) from 99.9 to 70 wt. % homopolymer or copolymer of low density ethylene (LDPE). The resulting power cable has good mechanical properties and properties with respect to initiating thermal cracking, expressed as TSCR (thermal stress cracking), which are sufficient for applications in a DC cable. The disadvantage is the limitation of the scope of the composition only for cables, but not for the insulating layer of metal pipes.

Known composition for coatings by extrusion. The composition contains from 50 to 90 wt. % of the first polyethylene component, from 1 to 10 wt. % of the second polyethylene component and from 10 to 50 wt. % of the third polyethylene component. Moreover, in the composition, the first polyethylene component includes linear low-density polyethylene with a density in the range from 0.90 g / cm ³ to 0.96 g / cm ³ and a melt index (12) from 5 to 15 g / 10 min, the second polyethylene component includes high density low density polyethylene with a density in the range from 0.915 g / cm ³ to 0.930 g / cm ³ and a melt index (12) of 0.1 g / 10 min to 3 g / 10 min and the third polyethylene component comprises high density low density polyethylene pressure with a density in the range from 0.915 to 0.930 g / cm ³ and a melt index (12) from 5 to 15 g / 10 minutes ( RF patent No. 2619127, IPC C08L 23/08 (2006.01), C08L 23/06 (2006.01), C09D 123/06 (2006.01), publ. 12.05.2017). The disadvantage is a fairly narrow range of polyethylene grades used in this composition.

To improve the properties of electrical conductivity, carbon black is added to polyethylene compositions, which can be prepared in various ways, for example, as described in USSR AS No. 729223, IPC C09C 1/60, publ. 04/25/80.

An invention is known in which the cable has two layers, the carbon black being in the semiconducting layer and not in the insulating one (Eurasian patent No. 023152, IPC C08L 23/02 (2006.01), C08K 3/04 (2006.01), published on 04.29.2016. ), which of course affects the conductive properties of the insulating composition.

The closest is the invention, which relates to a polyethylene composition highly suitable for extrusion of an insulating layer of a pipe or power cable containing a base resin comprising three ethylene homo- or copolymer fractions (A), (B) and (C) with different weighted average molecular weight Mw, where a) fraction (A) has an index of STR 21 equal to or less than 20 g / 10 min, b) fraction (B) has a lower average molecular weight than fraction (C), c) fraction (C) has a lower average molecular weight SSA than fraction (A) wherein fraction (B) which is an ethylene homopolymer is present in the base resin in an amount of from 20 to 60 wt. % by weight of the main resin, fraction (B), which is a copolymer of ethylene and one or more alpha-olefin comonomers, is present in the main resin in an amount of from 20 to 60 wt. % by weight of the base resin. Fraction (A) has a density of 900 to 980 kg / m ³ , preferably 915 to 965 kg / m ³ , fraction (B) has a density of 915 to 980 kg / m ³ , preferably 940 to 980 g / m ³ . The main resin has a density of from 915 to 970 kg / m ³ , preferably from 930 to 970 kg / m ³ , while the resulting polymer powder was sent to an extruder, where it was mixed with 2.5 wt. % carbon black (Eurasian patent No. 011511, IPC C08L 23/02 (2006.01), C08L 23/04 (2006.01), published on April 28, 2009). The disadvantage is the need to obtain all polyethylene components in the presence of a Ziegler-Natta catalyst, which narrows the raw material base to obtain the composition.

An object of the invention is the creation of a universal polyethylene composition, which can be applied by extrusion both in the manufacture of the outer sheath of the cable and the insulation of steel pipes with the properties of the insulating layers and improved uniformity.

The solution to the technical problem is to create a universal polyethylene composition for an insulating layer of pipes or power cable, which can be applied by extrusion, including a mixture of polymers (A) and (B), characterized in that the mixture (A) contains component (1), which is an ethylene homopolymer high density having a melt flow rate (MFR _{2.16 kg / 190 ° C} ) from 0.3 to 200 g / 10 min, a density of from 0.955 to 0.970 g / cm ³ and a crystallinity of 60-75% and component (2), representing a medium density polyethylene, namely, ethylene copolymer hexene-1 or butene-1 having a melt flow rate (MFR _{2,16kg / 190 ° C)} of from 0.01 to 0.3 g / 10 min, a density of from 0.925 to 0.940 g / cm ³ and a crystallinity of 40-55% while the ratio of components (1) :( 2), in wt. % is 30 ÷ 55: 45 ÷ 70, the mixture (B) contains component (3), which is a low density polyethylene or linear

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low density polyethylene, namely, a copolymer of ethylene and butene-1 or a copolymer of ethylene with butene-1 and hexene-1, having a melt flow rate (MFR _{2.16 kg / 190 ° C} ) from 0.3 to 5.0 g / 10 min, a density of from 0.919 to 0.935 g / cm ³ and crystallinity of 25-50%, component (4), which is an amorphous alpha-olefin elastomer having a melt flow rate (MFR of _{2.16 kg / 190 ° C} ) from 3.7 to 5.0 g / 10 min, density from 0.865 to 0.879 g / cm ³ and crystallinity 2.5-16%, and component (5) representing carbon black, which is introduced into components (3) and / or (4) before mixing all to mponentov in an extruder, wherein the percentage ratio by weight of (3) :( 4) :( 5) is 0.01 ÷ 89.99: 0.01 ÷ 89.99: 10 ÷ 40 in the composition at a content of 80 ÷ 95 wt. % of the mixture (A) and 5 ÷ 20 wt. % of the mixture (B), wherein the amorphous alpha olefin elastomer is selected from the group consisting of a copolymer of ethylene with butene-1, an elastomer of propylene with ethylene and ethylene-propylene rubber.

Distinctive features are: the composition and combination of components of the polyethylene composition.

A similar combination of features is not described in any similar technical solution, while achieving good processability of the mixture of polyethylene and dispersibility of carbon black in the mixture of (co) polymers, while the inventive composition has uniformity and the necessary set of universal properties that can be used for insulating layers of metal pipes, and for the outer sheath of all types of cables, while the necessary condition is that the components (A) and (B) of this composition are strictly defined the composition according to the properties of the applied (co) polymers and they are mixed in a predetermined ratio between each other and with soot, which gives good processability and uniformity of the claimed composition, which is necessary when applying an insulating coating by extrusion.

The presence of new features gives this technical solution "novelty", and the possibility of using a polyethylene composition in

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the quality of the effective insulating top layer of both cables and metal pipes, which has excellent characteristics of processability and electrical conductivity, indicates the "inventive step" of the claimed technical solution. "Industrial applicability" is confirmed by examples of specific performance.

The polyethylenes for fractions (A) and (B) used for mechanical mixing to obtain the final insulating composition are obtained separately using any conventional method of homopolymerization or copolymerization of ethylene, respectively, for example, in the gas, suspension or liquid phase (bulk polymerization) using conventional reactors, such as loop, gas phase, batch or batch, in the presence of an appropriate polymerization catalyst.

The mixing method by which the composition for the insulating layer of pipes or power cable based on the multimodal polyethylene composition according to the invention is obtained is not critical to the present invention.

Obtaining the inventive polyethylene composition, based on specially selected components and their ratio to each other, for use as the outer layer of the polyethylene coating is carried out in a known manner in three stages: obtaining a homogeneous mixture of all components, melting and mechanical mixing in an extruder, cooling the melt and granulation. The granules of the resulting composition are placed in an extruder and using certain devices receive an insulating layer, which is applied to the pipe or cable, as this is done in practice. In the manufacture of the claimed composition receive a homogeneous mixture of all components by mixing in any known mixing device. For example, the composition can be obtained by mechanically mixing fractions in the claimed

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the amount, for example, using conventional compounding or mixing equipment, such as a Banbury mixer, double roll rollers for elastomers, a Buss plasticizer or twin screw extruder, or other methods by which appropriate homogenization of various polymer fractions and soot is achieved.

To analyze the properties of the components and the resulting composition using standard methods. Density is determined using a gradient column at a temperature of 23 ° C according to ASTM D1505; melt flow rate (MFR) - according to ASTM D1238; strength at yield and rupture, elongation at break, including at minus 45 ° C, according to GOST 11262; crack resistance according to ASTM D1693; Vicat softening temperature according to ASTM D1525; crystallinity according to ISO 11357-3: 1999, to calculate the peak area, the type of the base line “Horizontal to the Right” was used (Wunderlich B. Macromolecule Physics: 3 vol. T.3 / B. Wunderlich. - M.: Mir, 1984. - 488 from.). The Mooney viscosity (ML _{1 + 4} 100 ° C) was determined according to GOST R 54552. The fragility temperature of GOST 16783 option "B" and the volumetric electrical resistivity were tested according to GOST 6433.2.

Tests of the sample of the outer shell of the polyethylene composition applied to the power cable were carried out in accordance with GOST IEC 60811 (tensile strength, elongation at break, shrinkage, burst resistance) and GOST 24621 (Shore hardness).

For polyethylene coatings deposited on a metal pipe, the strength of the coating upon impact was determined according to GOST R 51164, the period of induction of oxygen absorption according to ISO 11357-6: 2002, the resistance of the polyethylene coating layer to thermal aging, the resistance of the coating to thermal cycling and the shrinkage of the polyethylene coating layer according to STO Gazprom 2-2.3-130 and OTT-25.220.60-KTN-103-15.

Table 1 presents the component-wise 12 options (types 1-12) of the claimed composition and their properties.

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Table 2 presents the composition, ratio of components and properties of the resulting polyethylene compositions (types 1-12 of table 1) in accordance with GOST 16336-2013 "Polyethylene compositions for the cable industry" and in accordance with the requirements for the electrical insulation properties of polymeric materials.

Table 3 presents the results of type tests of a sample of the outer shell of a polyethylene composition (obtained according to example 1) applied to a power cable (based on the requirements of GOST R 55025).

Table 4 presents the composition, ratio of components and properties of the obtained polyethylene compositions in accordance with the requirements presented in table A.4 of Appendix A of STO Gazprom 2-2.3-130 “Technical requirements for external anticorrosive polyethylene coatings of factory-applied pipes for construction, reconstruction and capital repair of underground and offshore gas pipelines with operating temperatures up to + 80 ° С ”.

Table 5 presents the properties of the polyethylene coating (compounding of example 1 from table 4) of pipes in accordance with the requirements presented in STO Gazprom 2-2.3-130 “Technical requirements for external anti-corrosion polyethylene coatings of factory-applied pipes for construction, reconstruction and overhaul of underground and offshore gas pipelines with operating temperatures up to + 80 ° С "and OTT-25.220.60-КТН-103-15" Main pipeline transport of oil and oil products. Factory polyethylene coating of pipes. General technical requirements. "

Example 1. To obtain the composition using components (A) and (B) in a mass ratio of 88.2: 11.8, while component (A) contains an ethylene homopolymer with the following characteristics: density 0.965 g / cm ³ , _{MF 2.16 kg / 190 ° C} equal to 120 g / 10 min and a crystallinity of 71% and medium density polyethylene (copolymer of ethylene with hexene-1) with the following characteristics: 0.935 g / cm ³ , _{MF 2.16 kg / 190 ° C} equal to 0.05 g / 10

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min and a crystallinity of 50% in a ratio of 47:53, component (B) contains linear low-density polyethylene (a copolymer of ethylene with butene-1 and hexene-1) with a density of 0.918g / cm ³ , _{MF 2.16kg / 190 ° C} equal to 2 5 g / 10 min and a crystallinity of 37%, an amorphous ethylene butene-1 copolymer with the following characteristics: a density of 0.865 g / cm ³ , a MFI of _{2.16 kg / 190 ° C} equal to 5.0 g / 10 min and a crystallinity of 16% and carbon black in a ratio of 40:40:20, respectively.

As carbon black, a highly dispersed carbon product is used, manufactured on an industrial scale in accordance with ASTM D 1765.

It should be noted that carbon black is preliminarily introduced into, either individually in each component of the mixture (B), or in a pre-prepared mixture of components (B).

The resulting mixture is poured into the hopper of the extruder. As an extruder using standard twin-screw mixing equipment with screws rotating in one direction. The mixture is melted and mechanically homogenized. The temperature regime of processing is 180 ÷ 250 ° C. The melt of the composition after the die is cooled in a bath of cold water and the resulting strands are passed through a granulator, where they are cut using a rotating knife.

The resulting composition has a PTR of _{2.16 kg / 190 ° C} equal to 0.38 g / 10 min, a density of 0.953 g / cm ³ , strength at yield strength and at break of 23.8 MPa (at a rate of at least 22.6 MPa for GOST 16336 and at least 18 MPa for STO Gazprom 2-2.3-130) and 26.1 MPa (at a rate of at least 21.6 MPa for GOST 16336), the elongation at break (+ 23 ° C) is 780% (at a rate of at least 700 MPa for GOST 16336), elongation at break at minus 45 ° C - 197% (at a rate of at least 100% for STO Gazprom 2-2.3-130), softening temperature according to Vika 115 ° C (at a rate of at least 105 ° C) and resistance to cracking of more than 5000 hours (at a rate of at least 1000 hours according to GOST 16336 and at least 5000 hours STO Gazprom 2-2.3-130).

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Examples 2-12 are carried out as described in example 1, but using components with different characteristics and in a different ratio. The data presented in the table do not limit the use of similar types of polyethylene obtained by various polymerization methods.

All compositions are shown in table 1.

Table 2 presents the compositions obtained in examples 1-4, the compositions, the ratio of components and properties of the obtained polyethylene compositions (types 1-12 of table 1), determined in accordance with GOST 16336-2013 "Compositions of polyethylene for the cable industry" and in accordance with requirements for the electrical insulation properties of polymeric materials used for the insulation layers of electrical cables.

Table 3 shows the results of type tests of a sample of the outer shell of a polyethylene composition (obtained according to example 1) applied to a power cable (based on the requirements of GOST R 55025).

Table 4 shows the composition, ratio of components and properties of the polyethylene composition (obtained according to example 1) in accordance with STO Gazprom 2-2.3-130 “Technical requirements for external anti-corrosion polyethylene coatings of factory applied pipes for the construction, reconstruction and overhaul of underground and offshore gas pipelines with operating temperatures up to + 80 ° С ”.

Table 5 presents the properties of the polyethylene coating of pipes obtained according to example 1, presented in table 4, determined in accordance with STO Gazprom 2-2.3-130 “Technical requirements for external anti-corrosion polyethylene coatings of factory-applied pipes for construction, reconstruction and overhaul of underground and gas pipelines with operating temperatures up to + 80 ° С ”and in accordance with the requirements of OTT-25.220.60-KTN-103-15“ Main pipeline transport of oil and oil products. Factory polyethylene coating of pipes. General technical requirements. "

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Thus, the use of a new combination of polyethylene and other components in the claimed composition, intended for applying an insulating coating to the surface of metal pipes or cables, allows you to expand the range of materials used and the raw material base for insulating coatings, with the possibility of use for both pipes and cables, since the claimed according to the invention, the compositions have the necessary inherent properties for such an application, while maintaining both processability and economic efficiency ivnost as implied use of known and available on the components market, which has not previously been used for the inventive purposes.

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* - Characteristics for HDPE from GOST 16336-2013; ** - Requirements for STO Gazprom 2-2.3-130 coatings

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* "Technical requirements for external anticorrosive polyethylene coatings of factory applied pipes for the construction, reconstruction and overhaul of underground and offshore gas pipelines with operating temperatures up to + 80 ° C", Appendix A Table A.4.

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* “Technical requirements for external anticorrosive polyethylene coatings of factory applied pipes for the construction, reconstruction and overhaul of underground and offshore gas pipelines with operating temperatures up to + 80 ° C” (table 2).

** “The main pipeline transport of oil and oil products. Factory polyethylene coating of pipes. General technical requirements ”(table 6.1).

Claims (1)

A polyethylene composition for an insulating layer of pipes or power cable, comprising a mixture of polymers (A) and (B), characterized in that the mixture (A) contains component (1), which is a high density ethylene homopolymer having a melt flow index (MFR _{2, 16kg / 190 ° C} ) from 0.3 to 200 g / 10 min, density from 0.955 to 0.970 g / cm ³ and crystallinity 60-75%, and component (2), which is medium density polyethylene, namely, ethylene copolymer with hexene-1 or butene-1 having a melt flow rate (MFR of _{2.16 kg / 190 ° C} ) from 0.01 to 0.3 g / 10 min, density from 0.925 to 0.940 g / cm ³ and crystallinity 40-55%, while the ratio of components (1) :( 2), in wt. % is 30 ÷ 55: 45 ÷ 70, mixture (B) contains component (3), which is a low density polyethylene or linear low density polyethylene, namely, a copolymer of ethylene and butene-1 or a copolymer of ethylene with butene-1 and hexene- 1, having a melt flow index (MFR of _{2.16 kg / 190 ° C} ) from 0.3 to 5.0 g / 10 min, a density of from 0.919 to 0.935 g / cm ³ and crystallinity of 25-50%, component (4), representing an amorphous alpha olefin elastomer having a melt flow rate (MFR _{2.16 kg / 190 ° C} ) from 3.7 to 5.0 g / 10 min, a density of from 0.865 to 0.879 g / cm ³ and a crystallinity of 2.5- 16%, and component (5), representing carbon black, which is introduced into components (3) and / or (4) before mixing all the components in the extruder, while the percentage mass ratio of components (3) :( 4) :( 5) is 0, 01 ÷ 89.99: 0.01 ÷ 89.99: 10 ÷ 40 when the content in the composition is 80 ÷ 95 wt. % of the mixture (A) and 5 ÷ 20 wt. % of the mixture (B), wherein the amorphous alpha olefin elastomer is selected from the group consisting of a copolymer of ethylene with butene-1, an elastomer of propylene with ethylene and ethylene-propylene rubber.