RU2768173C1 - Adhesive composition based on polyethylene with improved long-term stability, method for preparation and use thereof - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: present invention relates to a group of inventions: an adhesive composition based on polyethylene, a method of producing an adhesive composition, use of an adhesive composition and a pipe. This composition contains: A) from 50 to 80 wt. % of linear low-density polyethylene (LLDPE) obtained on catalytic systems Ziegler-Natta, having density from 0.915 to 0.925 g/cm³ and melt flow index (MFR_190/2.16) in range from 2.5 to 8.0 g/10 min; B) from 15 to 30 wt. % high-density polyethylene (HDPE) grafted with a functional monomer, having a density of not less than 0.955 g/cm³ and a melt flow index (MFR_190/2.16) in range of 1.5 to 2.5 g/10 min; and C) from 5 to 20 wt. % of elastomer. This method involves mixing the components taken in amounts relative to the total weight, and subsequent compounding of the obtained mixture in the melt. Polyethylene-based adhesive composition is used as an adhesive layer in multilayer coatings.

EFFECT: development of an adhesive composition based on polyethylene, which retains high adhesion strength in an aqueous environment for a long period of time, as well as resistance of the adhesive joint to cathode peeling; simple method of producing the composition by performing it in one step.

72 cl, 3 tbl, 6 ex

Description

FIELD OF TECHNOLOGY TO WHICH THE INVENTION RELATES

The invention relates to an adhesive composition based on polyethylene (PE), which is used to create an adhesive layer applied to various metal surfaces for the purpose of protection, including anti-corrosion, for a long time, as well as to a method for its preparation and application. In particular, the adhesive compositions of the present invention are used for pipe insulation, in the construction of gas and oil pipelines to maintain their continuous uninterrupted operation under changing climatic, mechanical, and electromagnetic environmental factors.

BACKGROUND OF THE INVENTION

From US patent 6855432, 08/03/1990, [1], compositions based on polyethylene are known, suitable for use as adhesive coatings for protecting metal pipes. In particular, the patent [1] discloses a composition used as an adhesive layer between the metal and the outer insulating material of the pipe, containing polyethylene or its copolymers with α-olefins. Known composition includes the following components: (A) from 20 to 60 wt. hours of polyethylene; (B) 10 to 30 wt. hours of polyethylene grafted with maleic anhydride; (C) 10 to 35 wt. including high-impact polystyrene; (D) 10 to 25 wt. including elastomer.

In the patent EA 007577, 29.12.2006, [2], a multi-component composition based on polyethylene is disclosed, suitable for various applications, in particular, the known composition is used to create an adhesive layer between the metal and the outer insulation of the pipe. The composition according to the invention [2] has the following composition: A) non-elastomeric polyethylene in an amount of from 40 to 97 wt.% of the total mass of the composition and B) an elastomer containing an elastomeric ethylene copolymer with polar comonomer groups, where component A) or components A) and C) grafted using a functional monomer (modifying agent).

Adhesive compositions used as coatings perform a protective function, they are subject to a number of requirements, first of all, the strongest adhesion of the composition to the surface of the protected material must be realized. Strong adhesion as a property can be characterized by adhesive strength, that is, peel strength to a particular material, in particular in the context of the present invention, to a clean or thermosetting resin-primed metal pipe surface.

The closest in technical essence to the present invention is US patent 8247053, 21.08.2012, [3], selected as a prototype, and revealing an adhesive composition based on polyethylene containing from 1 to 40 wt.% polyethylene or its copolymers with α-olefins (component A) grafted with a functional monomer, or a mixture of polyethylene (component A1) with a second polymer (component A2) other than Al, in which components A1 and A2 are jointly modified by grafting an unsaturated polar monomer selected from unsaturated carboxylic acids and their anhydrides. The content of unsaturated polar monomer is from 0 to 10,000 parts per million (ppm). Also, described in the prototype [3] composition contains from 25 to 98 wt.% ungrafted polyethylene (component B), obtained on metallocene catalytic systems, with a density of 0.910-0.930 g/cm ³ , from 1 to 35 wt.% elastomeric product (component C), which is either a copolymer of ethylene with α-olefins having a density of 0.860-0.900 g/cm ³ or copolymers of ethylene with alkyl methacrylate or terpolymers of ethylene, alkyl methacrylates and maleic anhydride, and a peroxide.

From [3] it is also known that in order to improve the processability of the adhesive composition based on polyethylene, sliding additives are used. As such additives mentioned are stearamides, oleamides, erucamides, calcium, zinc and aluminum stearates, as well as polyethylene waxes in an amount of from 0.01 to 1 wt.%.

The method for producing an adhesive composition according to the prototype US 8247053 is a two-stage process, including the stage of mixing and modifying one or more polyethylenes A, with further dilution of the resulting mixture with polymers B and component C. Mixing is carried out in a twin screw extruder. The known composition obtained in this way is used as an adhesive layer for protecting metal surfaces of a pipeline.

The disadvantage of the known invention [3] are the limitations in the method of obtaining ungrafted polyethylene (component B), in particular, its production using a metallocene catalyst system. There are also limitations in the method of obtaining the adhesive composition itself, in particular, there are no indications of the possibility and conditions for the use of maleized commercially available polyethylenes, which make it possible to simplify the technology by reducing the number of its stages. Also, in [3] there is no indication of conducting long-term tests of the specified composition with confirmation of its stability, and maintaining the adhesive strength values \u200b\u200bspecified in the well-known patent as a result of tests when exposed to water, temperature, cathodic polarization for a certain period of time. In all the above documents [1] - [3], the main task is to achieve the highest possible adhesive strength. The required values of this parameter are provided by a sufficient number of polar functional groups grafted to polyethylene in the course of its chemical modification, as mentioned earlier, with the help of maleic anhydride (MA).

Based on the need for long-term operation of pipelines, the quality of adhesive compositions designed to protect metal products should be assessed depending on such external factors as elevated temperature and humidity. Also, in addition to natural environmental factors, the stability of the adhesive strength of the adhesive joint in two- and three-layer pipe insulation is negatively affected by one of the methods widely used in modern designs of metal pipelines, the so-called "active" corrosion protection - cathodic protection system.

Thus, another important parameter for evaluating the quality of an adhesive coating is the retention of high values of adhesive strength and resistance to cathodic peeling, measured through the rate or magnitude of the peeling surface during cathodic polarization.

Document RU 2112004, 05/27/1998, [4], describes an insulating polymer coating, which was tested from the point of view of the stability of the adhesive strength in water by measuring the initial adhesive strength formed one day after applying the hot melt adhesive to the surface of the metal plate, and measuring the adhesive strength after 1000 hours of exposure to water at 20 ^o C. According to the test results according to [4], the decrease in adhesion strength in water at 20 ^o C is only 2%, and the peel rate measured under the same conditions at cathodic polarization is 3 cm ² / h . The results of the known technical solution according to RU 2112004 cannot solve the problems of the present invention, since the tests were carried out in "soft" conditions that do not correspond to the operating conditions of pipelines.

The combination of the above factors affecting the performance properties of the adhesive coating necessitated further research to improve the properties of the adhesive composition based on PE.

Thus, there is a need to create an adhesive composition based on polyethylene, which maintains high values of adhesive strength in an aqueous environment for a long period of time, as well as the resistance of the adhesive joint to cathodic peeling.

The objective of the present invention is to create an adhesive composition based on polyethylene, maintaining high values of adhesive strength in an aqueous environment for a long period of time, as well as the resistance of the adhesive to cathodic peeling.

The technical result of the present invention is to maintain the values of the adhesive strength of the composition based on polyethylene when holding the adhesive joint in an aqueous medium (for 1000 hours at 80 ° C) ^by at least 55% of the initial adhesive strength values. In addition, the claimed adhesive composition is characterized by the resistance of the adhesive to cathodic peeling, and the area of peeling at cathodic polarization for 30 days at 60 ^about C is not more than 13.5 cm ² . An additional technical result consists in reducing the concentration of polyethylene grafted with a functional monomer used in the composition. Another technical result is the simplification of the method for obtaining the composition by carrying it out in one stage.

At the same time, the value of the melt flow index of the composition (MFR _190/2.16 ) is at the level of at least 3-4 g/10 min, which is important for ensuring high manufacturability of products based on the polyethylene composition.

To achieve the desired technical result according to the present invention, it is essential to use in the composition a mixture of polyethylenes consisting of linear low density polyethylene (LLDPE) and high density polyethylene (HDPE), which differ significantly from each other in their density and values of the melt flow index, while essential is the use of polyethylene in the composition of the composition in the range of declared concentrations and characterized by certain values of density and MFR. As LLDPE according to the invention, polyethylene obtained using Ziegler-Natta catalytic systems is used.

DESCRIPTION OF THE INVENTION

According to the present invention, an adhesive composition based on polyethylene is claimed, containing, based on the total weight of the composition, the following components:

A) from 50 to 80 wt.% linear low density polyethylene (LLDPE) obtained on Ziegler-Natta catalytic systems, as well as having a density of 0.915 to 0.925 g/cm ³ and a melt flow index (MFR _190/2.16 ) in range from 2.5 to 8.0 g/10 min;

C) from 15 to 30 wt.% high-density polyethylene (HDPE), grafted with a functional monomer, having a density of not less than 0.955 g/cm ³ and a melt flow index (MFR _190/2.16 ) in the range from 1.5 to 2.5 g/10 min;

C) 5 to 20% by weight of elastomer.

The composition may also optionally include additional additives.

The indicated ratio of MFI _190/2.16 of linear low density polyethylene (LLDPE) used to HDPE grafted with a functional monomer is preferably in the range from 1:0.2 to 1:0.9, more preferably from 1:3 to 1: 0.7.

As linear low density polyethylene (LLDPE) according to the present invention, copolymers of ethylene with an α-olefin containing at least four carbon atoms are used. As the α-olefin, compounds selected from the group consisting of butene-1, hexene-1, octene-1 and the like α-olefins are used. The content of α-olefin comonomer in LLDPE is from 2.5 to 8 wt.%, preferably from 3 to 6 wt.%, most preferably from 3.5 to 5 wt.%

At the same time, to achieve a technical result, it is essential to use LLDPE obtained using Ziegler-Natta catalytic systems.

Said LLDPE has a density value in the range of 0.915 to 0.925 g/cm ³ , preferably 0.916 to 0.920 g/cm ³ . In this case, the melt flow index (MFR _190/2.16 ) is from 2.5 to 8 g/10 min, preferably from 3.0 to 6.0 g/10 min, most preferably from 3.0 to 4.5 g /10 min.

The content of LLDPE, based on the total weight of the composition, is from 50 to 80 wt.%, preferably from 60 to 80 wt.%, most preferably from 65 to 78 wt.%

High density polyethylene (HDPE) grafted with a functional monomer is an ethylene homopolymer with a functional monomer grafted onto its macromolecule. Examples of functional monomers are unsaturated carboxylic acids and their derivatives. Unsaturated carboxylic acids according to the invention include acids having from 2 to 20 carbon atoms, such as, for example, acrylic, methacrylic, maleic, fumaric and itaconic acids. Functional derivatives of these acids include, for example, esters and anhydrides of unsaturated carboxylic acids. Examples of esters of unsaturated carboxylic acids are alkyl(meth)acrylates, where alkyls contain up to 24 carbon atoms. Examples of suitable alkyl acrylate and alkyl methacrylate are, in particular, methyl methacrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, 2-ethylhexyl acrylate. Examples of unsaturated carboxylic acid anhydrides are, in particular, maleic anhydride, itaconic anhydride, citraconic anhydride, tetrahydrophthalic anhydride. The most preferred functional monomer of the present invention is maleic anhydride.

The amount of the functional monomer grafted onto the HDPE is at least 1% by weight, preferably from 1.0 to 1.5% by weight, based on the total weight of the HDPE grafted with the functional monomer.

As HDPE, polyethylene is used, obtained by the anionic-coordination polymerization of ethylene at low pressure on Ziegler-Natta catalytic systems or metallocene catalysts according to known technologies. The grafting of the functional monomer to the HDPE is carried out according to procedures well known to those skilled in the art, either batchwise or continuously using a melt agitator. In accordance with the present invention, grafting is carried out by reactive extrusion in the presence or absence of a radical initiator. Preferably, the grafting of the functional monomer is carried out in the presence of a radical initiator such as an organic peroxide. Examples of organic peroxide include, but are not limited to, the following products: tert-butyl hydroperoxide, cumene hydroperoxide, diisopropylbenzene hydroperoxide, di-tert-butyl peroxide, dicumyl peroxide, 1,3-1,4-bis-(tert-butylperoxyisopropyl)benzene, peroxide acetyl, benzoyl peroxide, isobutyryl peroxide, bis-3,5,5-trimethylhexanoyl peroxide, methyl ethyl ketone peroxide and other organic peroxides. Peroxides can be used both in pure form and applied to a mineral or polymer filler (peroxide concentrate). Examples of suitable peroxides are commercially available products known under trade names such as Trigonox 301, Luperox DCP, Luperox DC40, Luperox DC40KE, Luperox DC40MG, Luperox DC40P-SP2, Luperox DI, Luperox DTA, Luperox F, Luperox F40, Luperox F40MG , Luperox MIX, Luperox 101, Luperox 101SIL45, Luperox 130XL45, Luperox 801. The amount of said initiator in pure form added to the composition is preferably in the range from 0.01 to 0.4 wt.%, most preferably from 0.05 to 0.15% based on the total weight of the composition.

Said HDPE grafted with a functional monomer has a density value of at least 0.955 g/cm ³ , preferably at least 0.960 g/cm ³ . In this case, the melt flow index (MFR _190/2.16 ) of said HDPE is from 1.5 to 2.5 g/10 min., preferably from 2.0 to 2.5 g/10 min.

The content of functional monomer grafted HDPE in the adhesive composition of the invention is 15 to 30% by weight, preferably 15 to 25% by weight, most preferably 17 to 25% by weight, based on the total weight of the composition. The content of HDPE grafted with a functional monomer, less than 15 wt.% leads to a decrease in the concentration of functional polar groups in the interfacial zone near the protected material in contact with the adhesive composition and, as a result, to a decrease in adhesive strength. An increase in the content of HDPE grafted with a functional monomer, over 30 wt.%, leads to a significant deterioration in its compatibility with LLDPE due to the heterogeneity of their structures, which causes negative changes in the morphology of this mixture. Formed at a content of more than 30 wt.% HDPE grafted with a functional monomer, a coarse and inhomogeneous HDPE phase in the LLDPE matrix causes a deterioration in the structure and properties of the adhesive layer with a polar substrate (protected material), which entails a corresponding deterioration in adhesive strength.

In accordance with the present invention, as polyethylenes in the composition of the adhesive composition, LLDPE is used, which is characterized by a density in the range from 0.915 to 0.925 g/cm ³ , preferably from 0.916 to 0.920 g/cm ³ and HDPE grafted with a functional monomer, which is characterized by a density of not less than 0.955 g/cm ³ , preferably not less than 0.960 g/cm ³ . Otherwise, the convergence of density values for polyethylenes: less than 0.955 g/cm ³ for HDPE and more than 0.925 g/cm ³ for LLDPE, will lead to difficulty in diffusion of HDPE grafted with a functional monomer to the surface of the material with which the adhesive composition is in contact, which will lead to to deterioration of its adhesive strength.

The key to achieving the technical result of the present invention is also the use of polyethylenes in the composition, which are characterized by different values of the melt flow index (MFR _190/2.16 ). The melt flow index of HDPE grafted with a functional monomer is 1.5 to 2.7 g/10 min, preferably 1.5 to 2.5 g/10 min, preferably 2.0 to 2.5 g/10 min ., while LLDPE has a melt flow index in the range of 3.0 to 8.0 g/10 min, preferably 3.5 to 6.0 g/10 min. In this case, the ratio of MFI _190/2.16 of the polyethylenes used - LLDPE to HDPE grafted with a functional monomer should be in the range from 1:0.2 to 1:0.9, preferably from 1:0.3 to 1:0, 7. Without wishing to be bound by any theory, the present inventors believe that the above difference in MFI values is necessary to reduce the interfacial diffusion of the elastomer towards the layer in direct contact with the solid metal substrate and consisting of HDPE grafted with a functional monomer so as not to reduce its cohesive strength. , which decisively affects the adhesive strength of the adhesive joint as a whole.

The inventors of the present invention have unexpectedly found that the stability of the values of the adhesive strength index of the composition is significantly increased by LLDPE obtained using Ziegler-Natta catalyst systems.

Ziegler-Natta catalytic systems make it possible to obtain polymers of a certain tact (stereoregularity). Such catalytic systems are complexes formed by the interaction of transition metal compounds with alkyls and haloalkanes of metals of groups II-III. Highly active Ziegler-Natta catalytic systems in the form of supported titanium-magnesium complexes are most preferred.

These highly active supported titanium-magnesium complexes are titanium chlorides fixed on the surface of an “activated” magnesium-chlorine-containing support. Under polymerization conditions, in the presence of a trialkylaluminum activator (AlR ₃ ), titanium-magnesium complexes are activated and active centers are formed.

The synthesis of LLDPE on heterogeneous (supported) Ziegler-Natta catalytic systems, such as, for example, polynuclear titanium-magnesium systems, is accompanied by the growth of polyethylene macrochains simultaneously on several active centers located on the solid support surface. Thus, the use of Ziegler-Natta catalytic systems, which are characterized by a high density of active centers fixed on the support surface, to obtain linear low-density polyethylenes suitable as a component of the adhesive composition of the present invention, promotes the formation of a supramolecular structure of LLDPE with an increased density of the network of physical entanglements of macrochains. in the interfacial (intercrystalline) region, comprising up to 10 ¹² -10 ¹⁴ weaves per 1 mg of polymer. A dense network of physical interlacings makes it difficult for the elastomer to diffuse through such a medium, and, as a result, contributes to a better preservation of the structure and properties of the adhesive joint, which consists of three main layers: LLDPE, HDPE grafted with a functional monomer, and an elastomer located between them.

The use of LLDPE obtained on the indicated metallocene catalytic systems in the composition of the claimed composition leads to higher, but much less stable to the influence of unfavorable factors, adhesive strength values. Such a deterioration in the adhesive properties of the composition, according to the authors, occurs due to the lower barrier properties of such polyethylene compared to LLDPE of similar viscosity obtained using the Ziegler-Natta catalytic system. During prolonged exposure to high temperature, the most fusible part of the adhesive bond, the elastomer, will tend to diffuse into the LLDPE layer, which has a significantly lower density than HDPE grafted with a functional monomer. The degree of diffusion of the elastomer, and hence the weakening of the adhesive bond, will depend on the barrier properties of the LLDPE layer. The looser structure of metallocene LLDPE, compared to traditional LLDPE, will also contribute to more intensive diffusion of the elastomer coming from the interfacial layer into it.

In addition to LLDPE and HDPE grafted with a functional monomer, the composition also includes an elastomer in an amount of from 5 to 20 wt.%, preferably from 5 to 15 wt.%, most preferably from 5 to 10 wt.%, based on the total weight of the composition. In this case, the elastomer is used in a mass ratio to HDPE grafted with a functional monomer, equal to from 1:1 to 1:6, preferably from 1:2 to 1:3 m.h. The use of an elastomer in the composition of the claimed adhesive composition improves the compatibility of LLDPE and HDPE grafted with a functional monomer, and also increases the plasticity of the adhesive layer, which in turn increases its strength when subjected to external action.

As elastomers according to the invention, copolymers of ethylene with α-olefins containing from 4 to 8 carbon atoms (for example, Engage, Exact and the like) and/or copolymers of ethylene with esters of unsaturated carboxylic acids (for example, manufactured by DuPont, Exxon Mobil, Dow Chem under the brands Elvaloy, Lotryl and the like).

The copolymers of ethylene with esters of unsaturated carboxylic acids used as elastomers are random copolymers with an ester comonomer content of 5 to 40% by weight. Examples of esters of unsaturated carboxylic acids are alkyl acrylate and/or alkyl methacrylate, where alkyl contains up to 24 carbon atoms. Examples of alkyl acrylate and alkyl methacrylate are, in particular, methyl methacrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, 2-ethylhexyl acrylate.

The claimed composition may also optionally include various additives, such as antioxidants, UV absorbers, antistatic agents, crystallizing agents, fillers, slip additives, flame retardants and other additives in an amount of from 0 to 1 wt.%, preferably from 0.1 to 0, 5 wt%.

Examples of suitable antioxidants include 2,6-di-tert-butyl-p-cresol, tetrakis-[methylene-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate]methane, p-naphthylamine, and paraphenylenediamine derivatives. .

Examples of UV absorbers include 2,4-dihydroxybenzophenone, 2-(2'-hydroxy-3'5'-di-t-butylphenyl)-5-chlorobenzotriazole, 2-(2-hydroxy-3-t-butyl-5- methylphenyl)-5-chlorobenzotriazole; and bis-(2,2΄,6,6΄-tetramethyl-4-piperidine) sebacate.

Examples of antistatic agents include lauryl diethanolamine, palmityl, diethanolamine, stearyl diethanolamine, oleyl diethanolamine, behenyl diethanolamine, polyoxyethylene alkylamines, stearyl monoglycerides, and 2-hydroxy-4-n-octoxybenzophenone.

Examples of crystallizing agents include aluminum p-tert-butyl benzoate, dibenzylidene sorbitol, and aluminum hydroxy di-p-t-butyl benzoate.

Fillers that can be used in the composition are, for example, glass fiber, carbon fiber, talc, clay, silica, calcium carbonate, barium sulfate, magnesium hydroxide, calcium hydroxide and calcium oxide.

Glidants are used to facilitate the manufacture of the composition, in particular its extrusion. Examples of lubricants include, in particular, stearamides, oleamides, erucamides, calcium stearate, zinc stearate, aluminum stearate, magnesium stearate, polyethylene wax, liquid paraffin.

Examples of flame retardants are metal hydroxides, halogenating agents, antimony oxide, decabrombiphenyl ether and bis(3,5-dibromo-4-bromopropyloxyphenyl)sulfone.

The adhesive composition of the present invention is obtained by mixing all components using known methods of mixing thermoplastic materials, such as extrusion, or mixing in mixers of various designs. Closed mixers with paddles or rotors, single screw extruders, extruders with two co-rotating or counter-rotating screws can be used. In accordance with the present invention, the adhesive composition is obtained by mixing the components and then melt compounding the resulting mixture using equipment known in the art, for example, mixing equipment such as Banbury mixers, Brabender mixers, single screw extruder, twin screw extruder and the like mixers. . Preferably, mixing is carried out in a mixing equipment, and further compounding of the resulting mixture is carried out in an extruder. At the same time, compounding in the present invention is understood as a technological process of mixing polymers and additives in a melt in order to obtain a composition with homogeneously mixed components.

The present invention also relates to a method for obtaining the above adhesive compositions based on polyethylene, which includes mixing components A)-C), taken in the following amounts, based on the total weight of the composition:

A) from 50 to 80 wt.% linear low density polyethylene (LLDPE) obtained on Ziegler-Natta catalytic systems, as well as having a density of 0.915 to 0.925 g/cm ³ and a melt flow index (MFR _190/2.16 ) in range from 2.5 to 8.0 g/10 min;

C) from 15 to 30 wt.% high-density polyethylene (HDPE), grafted with a functional monomer, having a density of not less than 0.955 g/cm ³ and a melt flow index (MFR _190/2.16 ) in the range from 1.5 to 2.5 g/10 min;

C) from 5 to 20% by weight of an elastomer, and

subsequent compounding of the resulting mixture in the melt.

In accordance with the present invention, the composition is obtained in a one-step process by mixing components (A), (B) and (C) and optional additives, and then compounding the resulting mixture in the melt, for example, as described below.

Component (B), taken in an amount of 15 to 30 wt.% with respect to the total weight of the composition, is mixed with component (A), taken in an amount of 50 to 80 wt., based on the total weight of the composition, and component (C ), taken in an amount of from 5 to 20 wt.%, based on the total weight of the composition. Also, optional additives are introduced into the composition, taken in an amount of from 0 to 1 wt.%, preferably from 0.1 to 0.5 wt.%, based on the total weight of the composition. The mixing is carried out for a period of 1 to 20 minutes, preferably 2 to 10 minutes at a temperature of 10 to 100°C, preferably 10 to 50°C, more preferably 20 to 50°C, even more preferably 20 to 40°C. The resulting mixture is then melt compounded in a twin screw extruder at a temperature in the range from 190°C to 240°C, preferably from 220°C to 230°C, most preferably at a maximum barrel temperature of approximately 210°C and a screw speed of approximately 250 min ^-1 . The adhesive composition thus obtained is granulated and then used for its intended purpose.

The use of the adhesive composition based on polyethylene, obtained in accordance with the present invention, provides for its use as a co-extruded adhesive layer in multilayer coatings, preferably in insulation to protect, in particular, pipes intended for the construction of gas and oil pipelines.

The present invention also relates to an article that includes an adhesive layer containing the adhesive composition described above. Such products, for example, include pipes, cables, films, products made with the application of an adhesive composition in an extrusion process. The present invention particularly relates to a multilayer pipe, i.e. a pipe comprising a multilayer insulation with two, three, four, five or more layers, which includes a polyolefin layer and an adhesive layer adjacent to the polyolefin layer, which contains the adhesive composition described above. The invention will be further explained by examples, which are given to illustrate the present invention and are not intended to limit its scope.

EXAMPLES OF CARRYING OUT THE INVENTION

The polyethylenes shown in Table 1 were used as LLDPE.

Table 1. Characteristics of the polyethylenes used in the examples of the invention

brand Manufacturer Catalyst. system Density, g/cm ³ PTR _190/
2.16 Melting temperature, °С The degree of crystal personality,% Comonomer Additives Yield strength
MD/TD, MPa Tensile strength Rel. extension at break
MD/TD, % PE XP 9400 Daelim Metallocene. 0.917 3.7-3.0 114 hexene JSC 44/36 470/650 Sabic 318B Sabic C-Natta 0.918 2.8-3.2 122 41.6 butene 13/10 30/18.5 470/610 5118Q NKNKH C-Natta 0.916-0.920 2.5-3.5 122 44.6 butene+
hexene AO, TS, PPA 53/30 500/900 DOWLEX 5066 DOW Chem. C-Natta 0.934 1.7-2.0 125 52.2 octene JSC 14/17 21/23 590/620

Additives: AO (antioxidant), PPA (processing additive), TS (thermal stabilizer)

As HDPE grafted with a functional monomer, commercially produced polyethylenes are used, shown in table 2.

Table 2. Characteristics of HDPE functionalized with maleic anhydride.

No. HDPE functionalized with maleic anhydride The content of grafted MA, wt.% PTR _190/2.16 , g/10 min M _W , g/mol Molecular weight distribution (MWD) Density, g/cm ³ one. Fusabond 100 1.0 2.0 59000 5.0 0.960 2. Bondyram 5108 1.0 8.0 31000 5.5 0.961 3. BYC Scona TSPE 2102 2.0 0.35 37000 6.4 0.950

The elastomers used are Elvaloy AC3427 (a copolymer of ethylene and 27 wt% butyl acrylate) and Engage 8452 (a copolymer of ethylene and octene-1).

Tests for maintaining the adhesive strength of the claimed composition is carried out in accordance with GOST R. 52568 App. BUT.

Tests for the resistance of adhesive joints to cathodic polarization are carried out in accordance with GOST R. 51164 App. IN.

Example 1

In a paddle mixer, a mixture is prepared containing 15 wt.% HDPE grafted with a functional monomer, Fusabond 100 brand (see table 2 for properties), 80 wt.% PE 5118Q LLDPE (see table 1 for properties), 5 wt. elastomer - a copolymer of ethylene and butyl acrylate brand Elvaloy AC3427, and mixing is carried out for 2-10 minutes at a temperature of 10-50°C. The resulting mixture of components is processed in a twin-screw extruder LTE-20-44 at a maximum temperature in the zones of the cylinder 210°C and the number of revolutions of the screws 250 min ^-1 .

The resulting composition is characterized by an adhesive strength with respect to steel of 30.5 N/mm at 23°C, retention of adhesive strength after soaking in water for 1000 hours at a temperature ^of 80°C at the level of 73.1%, and a cathodic flaking area ^of 12.4 cm2.

Example 2

Get the composition according to Example 1, except that instead of 5 wt.% enter 10 wt.% Elvaloy AC 3427 and instead of 80 wt.% metered 75 wt.% LLDPE brand PE 5118Q.

The resulting composition is characterized by an adhesive strength against steel of 35.2 N/mm at 23°C, retention of adhesive strength after soaking in water for 1000 hours at a temperature ^of 80°C at the level of 80.1%, and a cathode peel area of 11.2 cm ² .

Example 3

Get the composition according to Example 1, except that instead of 15 wt.% enter 20 wt.% Fusabond 100 and instead of 80 wt.% metered 75 wt.% LLDPE brand PE 5118Q.

The resulting composition is characterized by an adhesive strength against steel of 30.4 N/mm at 23°C, retention of adhesive strength after soaking in water for 1000 hours at a temperature ^of 80°C at the level of 61.5%, and a cathode flaking area of 12.2 cm ² .

Example 4

A composition is obtained according to Example 1, except that instead of 15 wt.%, 25 wt.% Fusabond 100 is introduced, instead of 5 wt.%, 10 wt.% Elvaloy AC 3427 is introduced, and instead of 80 wt.%, 65 wt.% LLDPE brand is dosed RE 5118Q.

The resulting composition is characterized by an adhesive strength against steel of 34.4 N/mm at 23°C, retention of adhesive strength after soaking in water for 1000 hours at a temperature ^of 80°C at the level of 83.7%, and a cathodic flaking area of 7.8 cm ² .

Example 5

Get the composition according to Example 1, except that instead of LLDPE brand PE 5118Q injected LLDPE brand Sabic 318B.

The resulting composition is characterized by adhesive strength with respect to steel 29.2 N/mm at 23°C, retention of adhesive strength after soaking in water for 1000 hours at a temperature of 80 ^about With 59.6% and the area of the cathodic flaking 11.8 cm ² .

Example 6 (comparative)

A composition is obtained according to Example 1, except that instead of 15 wt.%, 35 wt.% Fusabond 100 is introduced, instead of 5 wt.%, 10 wt.% Elvaloy AC 3427 is introduced, and instead of 80 wt.%, 55 wt.% LLDPE brand RE 5118Q.

The resulting composition is characterized by an adhesive strength against steel of 11.7 N/mm at 23°C, retention of 52.1% adhesive strength after soaking in water for 1000 hours at a temperature ^of 80°C, and a cathode exfoliation area of 16.3 cm ² .

Example 7 (comparative)

A composition is obtained according to Example 1, except that 15.7 wt.% Fusabond 100 is added instead of 15 wt.%, 5.3 wt.% Elvaloy AC 3427 is added instead of 5 wt.% and instead of 80 wt.% PE 5118Q is dosed 78.9 wt% Daelim XP 9400 LLDPE (see Table 1 for properties).

The resulting composition is characterized by an adhesive strength against steel of 44.6 N/mm at 23°C, retention of 18.4% adhesive strength after soaking in water for 1000 hours at a temperature ^of 80°C, and a cathode peel area of 15.0 cm ² .

Example 8

A composition is obtained according to Example 1, except that Engage 8452 elastomer is used instead of Elvaloy AC 3427 as an elastomer.

The resulting composition is characterized by adhesive strength with respect to steel 29.5 N/mm at 23°C, retention of adhesive strength after soaking in water for 1000 hours at a temperature of 80 ^about With 68.8% and the area of the cathodic flaking 11.5 cm ² .

Example 9 (comparative).

Compositions are obtained according to Example 1, except that instead of 15 wt.%, 20 wt.% Fusabond 100 is used and the elastomer is excluded from the composition of the composition.

The resulting composition is characterized by an adhesive strength against steel of 33.6 N/mm at 23°C, maintaining 40.1% adhesive strength after soaking in water for 1000 hours at a temperature of 80 ^about C with a cathodic peel area of 19.2 cm ² .

Example 10 (comparative)

A composition is obtained according to Example 1, except that instead of Fusabond 100, a brand of HDPE grafted with a functional monomer, Bondyram 5108, is used.

The resulting composition is characterized by an adhesive strength against steel of 19.2 N/mm at 23°C, retention of 39.6% adhesive strength after soaking in water for 1000 hours at a temperature ^of 80°C and a cathodic peel area of 19.8 cm ² .

Example 11 (comparative)

Get the composition according to Example 1, except that instead of Fusabond 100 use the HDPE brand, grafted with a functional monomer, BYC Scona.

The resulting composition is characterized by adhesive strength with respect to steel 12.0 N/mm at 23°C, retention of 30.1% adhesive strength after soaking in water for 1000 hours at a temperature of 80 ^about C cathodic flaking area of 21.4 cm ² .

Example 12 (comparative)

A composition is obtained according to Example 1, except that 3.0 wt.% Elvaloy AC 3427 is used instead of 5 wt.%, and 82 wt.% LLDPE PE 5118Q is used instead of 80 wt.%.

The resulting composition is characterized by an adhesive strength with respect to steel 33.5 N/mm at 23^aboutC, retention of 38.2% adhesive strength after soaking in water for 1000 hours at a temperature of 80^aboutСi area of cathodic peeling 20.7 cm².

Example 13 (comparative)

Get the composition according to Example 1, except that instead of LLDPE brand PE 5118Q use brand DOWLEX 5066 (see table.1).

The resulting composition is characterized by an adhesive strength with respect to steel 21.2 N/mm at 23^aboutC, retention of adhesive strength after soaking in water for 1000 hours at a temperature of 80^aboutC at the level of 44.3% and the area of cathode exfoliation 18.9 cm².

Table 3 shows the compositions of compositions based on polyethylene (Examples 1-12) and the results of determining their adhesive strength during long-term tests and cathodic polarization.

Table 3. Compositions and properties of adhesive compositions of polyethylene according to examples 1-12.

Components Composition, wt.% Example 1 Example 2 Example 3 Example 4 Example 5 Example 6
(compar.) Example 7
(compar.) HDPE, grafted func. monomer Fusabond 100, MFR _190/2.16 = 2.0 g/10 min 15.0 15.0 20.0 25.0 15.0 35.0 15.7 Bondyram 5108, MFR _190/2.16 = 8.0 g/10 min BYC Scona, MFR _190/2.16 = 0.35 g/10 min LLDPE PE 5118Q, ZN, C ₄₊₆ , MFR=3.0 g/10 min 80.0 75.0 75.0 65.0 55.0 Sabic 318B, TsN, C ₄ , MFR= 2.8 g/10 min 80.0 Daelim XP 9400, MTs, C _6, MFR=3.5 g/10 min 78.9 ELASTOMER Elvaloy AC 3427, MFR _190/2.16 = 4.0 g/10 min 5.0 10.0 5.0 10.0 5.0 10.0 5.3 Engage 8452 MFR _190/2.16 = 3.0 g/10 min Composition properties: Adhesion strength to steel at 23 ºС, N/mm 30.5 35.2 30.4 34.4 29.2 11.7 44.6 Adhesion strength after 1000 hours exposure to water at +80 ^o C, N/mm 22.3 28.2 18.7 28.8 17.4 6.1 8.2 Retention of adhesive strength at 23°C after 1000 hours exposure ^to water at +80°C, % 73.1 80.1 61.5 83.7 59.6 52.1 18.4 Peeling area at cathodic polarization for 30 days at +60 ^o C, cm ² 12.4 11.2 12.2 7.8 11.8 16.3 15.0

Continuation of Table 3

Components Composition, wt.% Example 8 Example 9
(compar.) Example10
(compar.) Example11
(compar.) Example12
(compar.) Example13
(compar.) HDPE, grafted func. monomer Fusabond 100, MFR _190/2.16 = 2.0 g/10 min 15.0 20.0 15.0 15.0 Bondyram 5108, MFR _190/2.16 = 8.0 g/10 min 15.0 BYC Scona, MFR _190/2.16 = 0.35 g/10 min 15.0 LLDPE PE 5118Q, ZN, C ₄₊₆ , MFR=3.0 g/10 min 80.0 80.0 80.0 80.0 82.0 Sabic 318B, TsN, C ₄ , MFR= 2.8 g/10 min Daelim XP 9400, MTs, C _6, MFR=3.5 g/10 min LLDPE:d= ^0.934 g/cm3 DOWLEX 5066, ZN, C ₈ , MFR=1.7 g/10 min 80.0 ELASTOMER Elvaloy AC 3427, MFR _190/2.16 = 4.0 g/10 min - - 5.0 5.0 3.0 5.0 Engage 8452 MFR _190/2.16 = 3.0 g/10 min 5.0 - - - - Composition properties: Adhesion strength to steel at 23 ºС, N/mm 29.5 33.6 19.2 12.0 33.5 21.2 Adhesion strength after 1000 hours exposure to water at +80 ^o C, N/mm 20.3 13.5 7.6 3.6 12.8 9.4 Retention of adhesive strength at 23°C after 1000 hours exposure ^to water at +80°C, % 68.8 40.1 39.6 30.1 38.2 44.3 Peeling area at cathodic polarization for 30 days at +60 ^o C, cm ² 11.5 19.2 19.8 21.4 20.7 18.9

As can be seen from the presented experimental data, the claimed adhesive composition of polyethylene has a long-term stability of adhesive strength values when the adhesive joint is kept in an aqueous medium ^for 1000 hours at 80 ° C, while maintaining its initial values from 59.6% to 83.7%. At the same time, the values of the peeling area during cathodic polarization of the presented compositions based on polyethylene for 30 days at +60 ° C change in ^the allowable range from 12.4 cm ² to 7.8 cm ² .

The advantages of the presented composition are demonstrated by the examples shown in Table 3.

Examples 1-5 demonstrate the change in the properties of the claimed compositions with an acceptable change in the dosing interval and the choice of grades of the base components of the HDPE composition grafted with a functional monomer, LLDPE and elastomer.

The experimental results (Examples 1-5 and Example 8) fully confirm the technical result achieved in the present invention, subject to the following conditions:

1) the densities of the polyethylenes used differ significantly from each other; thus, the density of LLDPE is in the range from 0.915 to 0.925 g/cm ³ , preferably from 0.916 to 0.920 g/cm ³ , while the density of HDPE grafted with a functional monomer is at least 0.955 g/cm ³ , preferably at least 0.960 g/cm ³ ;

2) as part of the composition, polyethylenes are used, which are characterized by different values of the melt flow index (MFR _190/2.16 ). The melt flow index of functional monomer grafted HDPE is from 1.5 to 2.7 g/10 min, preferably from 2.0 to 2.5 g/10 min., LLDPE has a melt flow index in the range from 3.0 to 8.0 g/10 min, preferably 3.5 to 6.0 g/10 min;

3) the composition includes LLDPE obtained on Ziegler-Natta catalytic systems; And

4) the optimal ratio of starting components is from 50 to 80 wt.% LLDPE, most preferably from 56 to 75 wt.%, from 15 to 30 wt.%, HDPE grafted with a functional monomer, most preferably from 15 to 25 wt.% and from 5 to 20 wt.% elastomer, most preferably from 5 to 10 wt.%.

Experimental data show that when using polyethylenes (LLDPE and functional monomer grafted HDPE) whose density ratios are outside the density ranges of the claimed composition, there is a deterioration in adhesive strength retention values (see Comparative Example 13) Comparative Example 10 demonstrates the effect of using HDPE, grafted with a functional monomer, with an undesirably high melt yield strength (MFR _190/2.16 equal to 8.0 g/10 min) on the retention of adhesive strength, as well as the exfoliation area at cathodic polarization. Comparative Example 11 demonstrates the effect on adhesive strength of using HDPE with an undesirably low melt yield strength (MFR _{190/2.16 =} 0.35 g/10 min).

5) Comparative example 7 demonstrates that the use of PEs produced on catalytic systems other than Ziegler-Natta catalysts, in particular on metallocene catalysts, leads to a decrease in adhesive strength retention and a sharp increase in the peel area during cathodic polarization. Comparative examples 6, 9, 12 show a decrease in the retention of adhesive strength to the level of 52.1%-38.2% with an increase or decrease in the optimal ranges of the original components.

Thus, the examples presented above fully confirm the receipt of the claimed adhesive composition based on polyethylene, which retains high values of adhesive strength in an aqueous environment for a long period of time, as well as the resistance of the adhesive to cathodic peeling.

Claims (81)

1. Adhesive composition based on polyethylene, containing, based on the total weight of the composition, the following components: A) from 50 to 80 wt.% linear low density polyethylene (LLDPE) obtained on Ziegler-Natta catalytic systems and having a density of from 0.915 to 0.925 g/cm ³ and a melt flow index (MFR _190/2.16 ) in the range from 2.5 to 8.0 g/10 min; C) from 15 to 30 wt.% high-density polyethylene (HDPE) grafted with a functional monomer and having a density of not less than 0.955 g/cm ³ and a melt flow index (MFR _190/2.16 ) in the range from 1.5 to 2 .5 g/10 min; And C) 5 to 20% by weight of elastomer. 2. The adhesive composition according to claim 1, wherein the content of LLDPE, based on the total weight of the composition, is from 60 to 80% by weight. 3. Adhesive composition according to claim 2, wherein the content of LLDPE, based on the total weight of the composition, is from 65 to 78 wt%. 4. Adhesive composition according to claim 1, wherein the content of HDPE grafted with a functional monomer, based on the total weight of the composition, is from 15 to 25 wt.%. 5. Adhesive composition according to claim. 4, where the content of HDPE grafted with a functional monomer, based on the total weight of the composition, is from 17 to 25 wt.%. 6. The adhesive composition according to claim 1, wherein the elastomer content, based on the total weight of the composition, is from 5 to 15 wt.%. 7. The adhesive composition according to claim 6, wherein the elastomer content, based on the total weight of the composition, is between 5 and 10% by weight. 8. Adhesive composition according to claim 1, where the mass ratio of elastomer and HDPE grafted with a functional monomer is from 1:1 to 1:6. 9. Adhesive composition according to claim 8, wherein the weight ratio of elastomer and HDPE grafted with functional monomer is from 1:2 to 1:3. 10. Adhesive composition according to claim 1, wherein the density of the LLDPE is from 0.916 to 0.920 g/cm ³ . 11. The adhesive composition according to claim 10, wherein the density of the HDPE grafted with the functional monomer is at least 0.960 g/cm ³ . 12. Adhesive composition according to claim 1, wherein the MFR _190/2.16 for LLDPE is in the range of 3.0 to 6 g/10 min. 13. Adhesive composition according to claim 1, wherein the MFR _190/2.16 for functional monomer grafted HDPE is in the range of 2.0 to 2.5 g/10 min. 14. Adhesive composition according to claim 1, where the ratio of MFR _190/2.16 LLDPE to HDPE grafted with a functional monomer is in the range from 1:0.2 to 1:0.9. 15. Adhesive composition according to claim 1, where the ratio of MFR _190/2.16 LLDPE to HDPE grafted with a functional monomer is in the range from 1:0.3 to 1:0.7. 16. The adhesive composition according to claim 1, wherein the LLDPE is a copolymer of ethylene with an alpha-olefin containing at least four carbon atoms. 17. Adhesive composition according to claim 16, wherein the content of alpha-olefin comonomer in LLDPE is from 2.5 to 8 wt.%. 18. Adhesive composition according to claim 17, wherein the content of alpha-olefin comonomer in LLDPE is from 3 to 6 wt.%. 19. Adhesive composition according to claim 18, wherein the content of alpha-olefin comonomer in LLDPE is from 3.5 to 5 wt.%. 20. The adhesive composition according to claim 1, wherein the HDPE grafted with a functional monomer is an ethylene homopolymer with a functional monomer grafted to the macromolecule. 21. Adhesive composition according to claim 1, where the functional monomer is selected from unsaturated carboxylic acids and their derivatives. 22. Adhesive composition according to claim 21, where unsaturated carboxylic acids are acids containing from 2 to 20 carbon atoms. 23. The adhesive composition of claim 21, wherein the unsaturated carboxylic acid derivatives include ester derivatives and anhydrides of unsaturated carboxylic acids. 24. Adhesive composition according to claim 23, where ester derivatives of unsaturated carboxylic acids include, in particular, alkyl (meth) acrylate, where alkyl contains up to 24 carbon atoms. 25. The adhesive composition of claim 23, wherein the unsaturated carboxylic acid anhydrides include maleic anhydride, itaconic anhydride, citraconic anhydride, tetrahydrophthalic anhydride. 26. The adhesive composition according to claim 1, wherein the functional monomer is maleic anhydride. 27. The adhesive composition according to claim 1, wherein the amount of functional monomer grafted onto the HDPE is at least 1% by weight relative to the total weight of the HDPE grafted with the functional monomer. 28. The adhesive composition according to claim 27, wherein the amount of functional monomer grafted onto the HDPE is 1.0 to 1.5 wt % relative to the total weight of the functional monomer grafted HDPE. 29. The adhesive composition according to claim 1, where the Ziegler-Natta catalytic system is a complex obtained by reacting transition metal compounds with alkyls and haloalkanes of metals of groups II-III. 30. The adhesive composition of claim 1, wherein the Ziegler-Natta catalyst system is selected from supported titanium-magnesium catalyst systems. 31. Adhesive composition according to claim 1, where LLDPE is a polyethylene with an increased density of the network of physical entanglements of macrochains, up to 10 ¹² -10 ¹⁴ entanglements per 1 mg of polymer. 32. Adhesive composition according to claim 1, where the composition includes optional additives. 33. The adhesive composition according to claim 32, wherein the optional additives are used in an amount of 0 to 1% by weight, preferably 0.1 to 0.5% by weight. 34. The adhesive composition of claim 32, wherein the optional additives include antioxidants, UV absorbers, antistatic agents, crystallizing agents, fillers, lubricants, flame retardants. 35. A method for producing an adhesive composition based on polyethylene, including: mixing the following components, taken in quantities in relation to the total mass: A) from 50 to 80 wt.% linear low density polyethylene (LLDPE) obtained on Ziegler-Natta catalytic systems, having a density of from 0.915 to 0.925 g/cm ³ and a melt flow index (MFR _190/2.16 ) in the range from 2.5 to 8.0 g/10 min; C) from 15 to 30 wt.% high-density polyethylene (HDPE), grafted with a functional monomer, having a density of not less than 0.955 g/cm ³ and a melt flow index (MFR _190/2.16 ) in the range from 1.5 to 2.5 g/10 min; C) from 5 to 20 wt.% elastomer, And subsequent compounding of the resulting mixture in the melt. 36. The method of obtaining an adhesive composition according to p. 35, where the content of LLDPE in relation to the total mass of the composition is from 60 to 80 wt.%. 37. The method of obtaining an adhesive composition according to p. 36, where the content of LLDPE in relation to the total mass of the composition is from 65 to 78 wt.%. 38. The method for producing an adhesive composition according to claim 35, where the content of HDPE grafted with a functional monomer, relative to the total mass of the composition, is from 15 to 25 wt.%. 39. The method for producing an adhesive composition according to claim 38, where the content of HDPE grafted with a functional monomer, relative to the total weight of the composition, is from 17 to 25 wt.%. 40. The method for producing an adhesive composition according to claim 35, where the content of elastomer in relation to the total mass of the composition is from 5 to 15 wt.%. 41. The method of obtaining an adhesive composition according to p. 40, where the content of elastomer in relation to the total mass of the composition is from 5 to 10 wt.%. 42. The method of obtaining an adhesive composition according to claim 35, where the elastomer is used in a mass ratio to HDPE grafted with a functional monomer, equal to from 1:1 to 1:6. 43. The method of obtaining an adhesive composition according to claim 42, where the elastomer is used in a mass ratio to HDPE grafted with a functional monomer, equal to from 1:2 to 1:3. 44. The method of obtaining an adhesive composition according to claim 35, where the density of LLDPE is from 0.916 to 0.920 g/cm ³ . 45. The method of obtaining an adhesive composition according to p. 44, where the density of HDPE grafted with a functional monomer is not less than 0.960 g/cm ³ . 46. The method of obtaining an adhesive composition according to claim 35, where the MFR _190/2.16 for LLDPE is in the range from 3.0 to 6 g/10 min. 47. A process for preparing an adhesive composition according to claim 35, wherein the MFI of _190/2.16 for functional monomer grafted HDPE is in the range of 2.0 to 2.5 g/10 min. 48. A method for producing an adhesive composition according to claim 35, where copolymers of ethylene with an alpha-olefin containing at least four carbon atoms are used as LLDPE. 49. The method of obtaining an adhesive composition according to p. 48, where the content of alpha-olefin comonomer in LLDPE is from 2.5 to 8 wt.%. 50. The method of obtaining an adhesive composition according to p. 49, where the content of alpha-olefin comonomer in LLDPE is from 3 to 6 wt.%. 51. The method for producing an adhesive composition according to claim 50, where the content of alpha-olefin comonomer in LLDPE is from 3.5 to 5 wt.%. 52. The method for producing an adhesive composition according to claim 35, where the HDPE grafted with a functional monomer is an ethylene homopolymer, to the macromolecule of which a functional monomer is grafted. 53. A method for producing an adhesive composition according to claim 35, where the functional monomer is unsaturated carboxylic acids and their derivatives. 54. The method of obtaining an adhesive composition according to p. 53, where unsaturated carboxylic acids are acids containing from 2 to 20 carbon atoms. 55. The method for producing an adhesive composition according to claim 53, where derivatives of unsaturated carboxylic acids include ester derivatives and anhydrides of unsaturated carboxylic acids. 56. The method for producing an adhesive composition according to claim 55, where ester derivatives of unsaturated carboxylic acids include, in particular, alkyl (meth) acrylate, where alkyl contains up to 24 carbon atoms. 57. The method for producing an adhesive composition according to claim 55, where the anhydrides of unsaturated carboxylic acids include maleic anhydride, itaconic anhydride, citraconic anhydride, tetrahydrophthalic anhydride. 58. The method for producing an adhesive composition according to claim 35, where the functional monomer is maleic anhydride. 59. The method of obtaining an adhesive composition according to claim 35, where the amount of functional monomer grafted onto HDPE is at least 1 wt.% in relation to the total mass of HDPE grafted with functional monomer. 60. The method for producing an adhesive composition according to claim 59, wherein the amount of functional monomer grafted onto HDPE is from 1.0 to 1.5 wt.% relative to the total weight of HDPE grafted with functional monomer. 61. A method for producing an adhesive composition according to claim 35, where complexes formed during the interaction of transition metal compounds with alkyls and haloalkanes of metals of groups II-III are used as Ziegler-Natta catalytic systems. 62. The method of obtaining an adhesive composition according to p. 35, where the Ziegler-Natta catalyst system is selected from supported titanium-magnesium catalyst systems. 63. A method for producing an adhesive composition according to claim 35, where polyethylene with an increased network density of physical macrochain entanglements is used as LLDPE, up to 10 ¹² -10 ¹⁴ entanglements per 1 mg of polymer. 64. The method of obtaining an adhesive composition according to p. 35, where the composition includes optional additives. 65. The method of obtaining an adhesive composition according to p. 64, where optional additives are used in an amount of from 0 to 1 wt.%, preferably from 0.1 to 0.5 wt.% 66. The method of preparing an adhesive composition according to claim 64, wherein the optional additives include antioxidants, UV absorbers, antistatic agents, crystallizing agents, fillers, lubricants, flame retardants. 67. A method for preparing a composition according to claim 35, comprising the step of mixing HDPE grafted with a functional monomer with LLDPE and an elastomer for a period of time from 1 to 20 minutes, preferably from 2 to 10 minutes at a temperature of from 10 to 100 ° C, preferably from 20 to 50°C. 68. The method of obtaining a composition according to p. 35, where the compounding in the melt is carried out at a temperature of from 190 to 240°C, preferably from 220 to 230°C. 69. The method of obtaining a composition according to p. 35, where mixing and compounding in the melt is carried out using mixing equipment and an extruder. 70. The use of a polyethylene-based adhesive composition according to any one of claims 1 to 34 as an adhesive layer in multilayer coatings. 71. Application according to clause 70, where the coating is a multilayer insulation, in particular, pipes intended for the construction of gas and oil pipelines. 72. A pipe provided with a multilayer insulation containing an adhesive layer comprising an adhesive composition based on polyethylene according to any one of paragraphs. 1-34.