AND USE OF THE SAME

Field of the invention

The present invention relates to compositions and composite materials based on a mixture of polyethylenes: linear low-density polyethylene (LLDPE) and high-density polyethylene (HDPE). Preferred fields of application of such compositions are the manufacture of insulation and sheath of electrical and optical cables, tubular products, as well as insulation of steel pipelines.

Prior art

Polyethylene compositions used in modem pipe and cable industry must satisfy strict requirements; in particular, such compositions must possess a combination of specific, as rule, mutually exclusive properties. On the one hand, such compositions must provide the final product with good strength characteristics, a high heat resistance, and surface hardness. On the other hand, since the main product types made of such compositions are pipes and cables, equally important properties that allow the use of these articles under environmental conditions are flexibility and elasticity necessary for ease of transportation and installation, as well as resistance to temperature drop. Evidently, it is difficult to achieve all of the above properties in one composition.

Compositions based on bimodal and multimoldal HDPE demonstrate a balanced combination of thermal, mechanical, and technological properties, as disclosed in patents US7232866 and others. However, due to the crystalline nature of HDPE, the composite materials used according to these documents have a high hardness value (flexural modulus > 900 MPa), a low elasticity and a low impact resistance at low and ultralow temperatures.

One known approach to improve the properties of such compositions is the use of a combination of HDPE and LLDPE. Patent JP09241437 discloses compositions based on a mixture of polyethylenes (PEs) of different densities for insulation of steel pipes. In this document, the authors managed to achieve improvement in strength properties and heat resistance in combination with elasticity and impact resistance at low temperatures. However, a common drawback of such systems is a narrow tolerance interval for the HDPE/LLDPE ratio in the composition, due to limited compatibility of these polymers, causing a considerable deterioration of basic properties of such mixtures.

As known from the prior art, in particular from article “Nucleating and clarifying agents for polyolefins” Hoffmann, K., Huber, G., Mader, D. (Macromol. Symp. 2001, 176, 83-9), physico-mechanical properties of polymer compositions can be improved by addition nucleating agents. The addition of a nucleating agent causes crystallization of macromolecules on the surface of a formed phase and gives a polymer with a high crystallinity and small-sized crystallites similar in shape, which provides improved physical and other properties of the compositions. However, it should be noted that for such a very rapidly crystallizing polymer, such as polyethylene, especially HDPE, the use of inorganic and/or organic nucleating agents known in the art is either poorly effective or ineffective at all.

Nevertheless, there are a number of patent documents relating to HDPE-based polyethylene compositions containing inorganic (dispersed mineral fillers) and organic nucleating agents, the use of which makes it possible to solve certain technological problems, as well as to improve certain operating parameters of special-purpose HDPE products.

Thus, documents US7416686 and US2006275571 disclose the use of carbon black and inorganic dispersed mineral fillers in compositions of mono-, bi-, and multimodal HDPE for the manufacture of pressure pipes used to pump various substances. The use of carbon black is mainly limited to its function of photo- and thermal stabilization of the compositions, and mineral fillers, as additives, in an amount of from 1 to 10 wt.% are used to reduce sagging and deformation of the shape of a polyethylene (PE) tubular product during its extrusion, which in turn will not lead to the necessary balance of properties of a composition for a specific purpose.

Application W02008040504 (10.04.2008, BOREALIS TECH OY, FI) describes the use of organic nucleating agents of any nature, preferably organic pigments, for example, phthalocyanine blue, as well as polymers having a melting point of at least 200°C, for example polyvinylcyclohexane or poly-3 -methyl- 1 -butene, in bi- or multimodal HDPE compositions for the manufacture of pressure pipes with an increased flexibility. An increased flexibility of material is provided exclusively by the composition and microstructure of multimodal HDPE. The introduction of organic and polymeric nucleating agents solves the problem of reducing unwanted sagging of an extruded tube before cooling thereof, similar to previous patents.

It follows from the above that the use of nucleating agents of different nature in a polyethylene composition based on HDPE is known from the prior art to solve separate technical problems related firstly to rheological properties of HDPE. However, the unreasonable use of low-molecular weight organic and, in particular, inorganic nucleating agents enhances the negative consequences associated with increased strength and fragility of HDPE under impact conditions, especially at lower temperatures. The use of high-melting super-structural polymers, such as polyvinylcyclohexane, poly-3 -methyl-pentene-1, and others, for similar purposes is not very attractive due to their high price and low availability of such materials.

Thus, despite the efforts of the authors of the invention, further improvements in the field of producing polyethylene compositions characterized by an improved balance of physico-mechanical properties, such as flexibility, elasticity, and thermophysical properties, in particular frost resistance, allowing them to be used for the manufacture of cable and tubular products, which are known from the prior art, are of great importance.

Brief summary of the invention

The present invention is aimed at improving strength characteristics in combination with improving elasticity of LLDPE and HDPE polyethylene compositions for use in the cable and pipe industry by improving the morphology and uniform distribution of crystalline phase of polyethylene in these compositions.

The technical result of the present invention is an improvement of strength characteristics and elasticity of polyethylene compositions, in particular, an increase in the tensile strength up to 40 MPa and breaking elongation up to 850% by providing a new polymer composition according to the invention.

The polymer composition prepared according to the invention is preferably characterized also by:

- a tensile yield strength of not more than 21 MPa,

- a Vicat (10N) softening temperature of not more than 125°C,

- a Shore D hardness of from 58 to 70 c.u. at an exposure time of 1 sec,

- a melt flow rate, MFR _{190°C/2.16kg} of from 0.7 to 1.0 g/10 min,

- a flexural modulus (E-modulus) of from 380 to 750 MPa. This technical problem is solved and a desired technical result is achieved by using in the composition according to the invention two polyethylenes of different macrochain structures, determined by the methods of synthesis thereof, namely, linear low-density polyethylene (LLDPE) and high-density polyethylene (HDPE), as well by using in said composition additives, which are thermoplastic polymer compounds with a carbon-chain structure of macrochains close in their structure to PE. They include:

- isotactic homo- and copolymers of propylene, preferably semi-crystalline, and

- thermoplastic elastomers, which are preferably amorphous random copolymers of propylene with ethylene and/or butene- 1 (propylene based copolymers), or

- copolymers of ethylene with C ₄ -C ₈ a-olefin (ethylene based copolymers), or

- random copolymers of ethylene with acrylate ester comonomers.

The authors of the invention have unexpectedly found that in certain dosing intervals, all these polymers, when used in certain amounts in the above-described PE mixture, have a noticeable regulating effect on the process of crystallization of polyethylene macromolecules upon cooling of the melt of such compositions. Without wishing to be bound by a particular theory, the applicant assumes that this action can be characterized as a certain type of nucleating effect. As a result of this effect, not only the strength properties, which are characterized, in particular, by tensile strength, are significantly improved, but also the elasticity of the presented compositions, which are expressed by breaking elongation, simultaneously increases. In addition, when an elastomeric additive is used as a polymeric nucleating agent, the flexibility of the composition, which is expressed by flexural modulus, increases along with the strength and breaking elongation. These properties ease the difficult conditions of installation of cable and tubular products made of this composition.

On the other hand, the use of isotactic polypropylene as a nucleating additive allows further increase in the surface hardness of compositions to values that are not characteristic for polyethylene materials, providing improvement of the wear resistance of such products.

Brief description of drawings

Fig.l shows an effect of the addition of 5 wt.% of semi-crystalline isotactic homo- and copolymer of propylene on an increase in tensile strength of a mixture of HDPE 276-73 with LLDPE Daelim XP 9200.

Fig.2 shows an effect of the addition of 5 wt.% of elastomers on an increase in tensile strength of a mixture of HDPE 276-73 with LLDPE Daelim XP 9200.

Fig.3 shows an effect of the concentration of polymeric nucleating agent on an increase in tensile strength of a mixture of 40 wt.% of HDPE 276-73 and 60 wt.% of LLDPE Daelim XP 9200.

Detailed description of the invention

Herein, the following abbreviations are used:

LLDPE means a linear low-density polyethylene;

HDPE means a high-density polyethylene;

MFR means a melt flow index;

PE means polyethylene

PP means polypropylene;

MPa means megaPascal.

The composition according to the invention includes the following components:

A. from 28 to 67 wt.% of a linear low-density polyethylene (LLDPE);

B. from 32 to 55 wt.% of high-density polyethylene (HDPE);

C. from 1.0 to 12 wt.% of a polymer additive consisting of:

I. from 1.0 to 8 wt.% of semi-crystalline isotactic polypropylene, preferably semi-crystalline homo-polymer of propylene and/or random and/or block-copolymer of propylene with either ethylene or C ₄ -C ₈ a-olefin; or

II. from 1.0 to 10 wt.% of an elastomer, which is preferably an amorphous random copolymer of propylene with ethylene and/or butene- 1. Examples of copolymers are products produced by company Exxon Mobil under trade names Vistamax; or

III. from 1.0 to 12 wt.% of an elastomer, which is preferably an amorphous random copolymer of ethylene with C ₄ -C ₈ a-olefin. Examples of copolymers are products produced by companies Dow Chem., Exxon Mobil, LG Chem., and others under trade names Engage, Exact, Lucene and others; or

IV. from 1.0 to 8.0 wt.% of an elastomer, which is preferably an amorphous random copolymer of ethylene with acrylate comonomers, which in turn are unsaturated carboxylic acid esters with an ester comonomer content of from 5 to 40 wt.%. Examples of unsaturated carboxylic acid esters are alkyl acrylate and/or alkyl methacrylate, wherein the alkyl comprises up to 24 carbon atoms. Examples of alkyl acrylate and alkyl methacrylate are, in particular, methyl methacrylate, ethyl acrylate, n-butyl acrylate, iso-butyl acrylate, 2-ethylhexyl acrylate. Examples of copolymers are products produced by companies Du Pont, Exxon Mobil, Dow Chem. under trade names Elvaloy, Lotryl, and others.

D. from 0 to 5 wt.% another additive or a mixture of functional additives.

Hereinafter, a linear low-density polyethylene and a high-density polyethylene are indicated as LLDPE and HDPE, respectively.

A polyethylene, which is used as LLDPE, is prepared by a method of anion coordination copolymerization of ethylene with higher C3-C10 a-olefins under reduced pressure on Ziegler-Natta catalysts according to standard industrial techniques. The LLDPE used in the composition is characterized by an MFR _{190°C/2.16kg} of from 0.1 to 2 g/10 min, preferably from 0.3 to 1 g/10 min, more preferably from 0.5 to 1 g/10 min, and has a density of from 0.910 to 0.930 g/cm ³ , preferably from 0.915 to 0.930 g/cm ³ , more preferably from 0.918 to 0.925 g/cm ³ .

It is preferable to use LLDPE having a molecular weight of from 50000 to 400000 g/mol, more preferably from 70000 to 250000 g/mol, most preferably from 80000 to 150000 g/mol. The molecular weight, as used herein, means a weight-average molecular weight, if otherwise is not specified.

The content of LLDPE in the composition is from 28 to 67 wt.%, preferably from 33 to 63 wt.%, more preferably from 35 to 55 wt.%.

LLDPEs of the known trade names or mixtures thereof can also be used as the LLDPE, for example, Daelim XP 9200, XP 9100, SABIC LLDPE 6118, SABIC LLDPE 118 and other trade names with similar properties.

A polyethylene used as HDPE is prepared by a method of anionic-coordination copolymerization of ethylene with higher C3-C10 a-olefins under low pressure on Ziegler-Natta catalysts according to standard industrial techniques. The HDPE used in the composition is characterized by an MFR _{190°C/2.16kg} of from 0.1 to 2 g/10 min, preferably from 0.5 to 1 g/10 min, and has a density of from 0.945 to 0.970 g/cm ³ , preferably from 0.955 to 0.965 g/cm ³ . In addition, only monomodal homo- and copolymers of ethylene with higher C3- C10 a-olefins with an average molecular weight of from 80000 to 200000 g/mol, preferably from 100000 to 150000 g/mol are used as the HDPE.

HDPEs of the known trade names or mixtures thereof can also be used as the HDPE, for example, LPPE-276-73, LPPE-273-83, LPPE PE 2260, SABIC HDPE 5429, SABIC HDPE 5933, SABIC HDPE BM 6246 LS, SABIC HDPE F 04660 and other trade names with similar properties.

The content of HDPE used in the composition is from 32 to 55 wt.%, preferably from 35 to 45 wt.%. The lower limit of the HDPE content in the composition is determined by the requirements to the surface hardness of an outer polyethylene cover layer (Shore D hardness must be not less than 58-60 c.u. at 15 sec). In addition, the HDPE content lower than 32 wt.% or higher than 55 wt.% results in a significant deterioration of strength characteristics of the composition (Fig.1 and Fig.2). A possible reason for the observed strength drop in a certain range of the HDPE content may be structural differences between HDPE and LLDPE macromolecules, which lead to a decrease in the compatibility of these phases, depending on their ratio to each other, emerged when the melt of mixtures is cooled during the process of crystallization of HDPE macromolecules. In addition, with an increase in the HDPE concentration in the composition, the possibility of controlling the crystallization of its macromolecules is significantly reduced due to a significant increase in the rate of the crystallization process.

An effect of an increase in strength characteristics of compositions based on HDPE and LLDPE in the above-mentioned range of the HDPE content occurs only in the presence of nucleating agents, which are polymers having the structure as described above. According to the present invention, the content of polymer nucleating agents in the composition is from 1 to 12 wt.%, preferably from 3 to 8 wt.%. A putative mechanism of the nucleating action of these polymers is based on the assumption that the process of crystallization of PE macromolecules is regulated by said polymers by the formation of a fine dispersion (emulsion) by particles of these polymers upon cooling the melt of the polyethylene composition. These particles do become centers of crystallization of PE macromolecules. The morphology and homogeneity of the structure of the crystalline phase of the final PE composition depend on the shape, average size and volume concentration of these centers. The morphology of the particles of the dispersed phase, in turn, is determined by its thermodynamic compatibility with the basic PE and molecular-mass characteristics of polymeric nucleating agents. The experimentally observed picture of the effect of polymeric nucleating agents on tensile strength of PE compositions is shown in Figs. 1-3. There are significant differences in strength characteristics, depending on the nature of polymers shown in the figures. The greatest increase in the strength indexes of PE compositions is observed in the presence of 5 wt.% of semi-crystalline isotactic polypropylene PPH030GP produced by Tomskneftekhim OOO (Fig.1). Its more high-flowable analogs, as well as the grades of random and block copolymer of propylene with ethylene, are somewhat inferior to the PPH030GP sample in this action. Known grades of thermoplastic elastomers provided in the present invention are also less effective than PPH030GP (Fig. 2). However, the concentration range for the nucleating action of elastomeric additives is noticeably larger than that of semi-crystalline PPs, which is apparently due to their better compatibility with PE (Fig.3). This makes it possible to vary the indexes of fluidity, elasticity and flexibility of the presented PE compositions in a wider range.

Thus, Fig. 1 shows that isotactic homopolymer PPH030GP has the greatest effect on increasing the tensile strength of the compositions. Its analogues are high- flowable PP homopolymers PPH270 and PPH450, and the grades of random and block copolymers of propylene with ethylene have a less pronounced nucleating effect on the PE mixture in a range of HDPE concentrations of from 32 to 55 wt.%.

Moreover, in the process of preparing a composition, industrial grades of semicrystalline propylene homopolymer and/or random and/or block copolymer of propylene with ethylene or with C ₄ -C ₈ a-olefin are used as a semi-crystalline isotactic polypropylene (I). It is preferable to use a semi-crystalline propylene homopolymer with a melt flow rate of from 2 to 5 g/ 10 min, preferably from 2.5 to 4 g/ 10 min. The content of the semi-crystalline isotactic polypropylene in the composition varies from 1.0 to 8 wt.%, preferably from 3 to 7 wt.%, most preferably from 4 to 6 wt.%.

Examples of the used polypropylenes can be products known under trade names PPH030 GP produced by Tomskneftekhim OOO, OOO Tobolsk-Polymer OOO, Poliom OOO, Neftekhimiya NPO, Balen 01030 produced by Ufaorgsintez OAO, PP 1500J produced by Nizhnekamskneftekhim OOO, and etc. Industrial grades of statistical copolymers of propylene with ethylene or ternary copolymers of propylene with ethylene and butene- 1 (propylene based copolymers) are used as an elastomer (II). Examples of the copolymers are products produced by company Exxon Mobil under Vistamax grades. A preferred copolymer is Vistamax 6102. The content of elastomer (II) is from 1.0 to 10.0 wt.%, preferably from 3.0 to 7.0 wt.% based on 100% of nucleating agent (the content in the composition is from 1.0 to 12 wt.%).

A copolymer of ethylene with a-olefin containing from 4 to 8 carbon atoms, prepared in the presence of metallocene catalytic systems is used as an elastomer (III). Ethylene-octene-1 copolymer is preferably used. Said elastomer is characterized by a density of from 0.855 to 0.890 g/cm ³ , preferably from 0.857 to 0.885 g/cm ³ , and by a melt flow rate (MFR _{190°C/2.16kg} ) of 1 to 30 g/10 min, preferably 3 to 13 g/10 min, more preferably 3 to 7 g/10 min.

Examples of the used elastomers (III) may be products known under trade names Engage 8452, Engage 8842, Engage 8137, Exact 8210, etc.

The content of the elastomer (III) is from 1.0 to 12.0 wt.%, preferably from 3.0 to 10.0 wt.%, most preferably from 3.0 to 8.0 wt.% based on 100% of nucleating agent (contained in the composition in an amount of from 1.0 to 12 wt.%).

Amorphous random copolymers of ethylene with acrylate comonomers, which are unsaturated carboxylic acid esters with an ester comonomer content of from 5 to 40 wt.%, are used as an elastomer (IV). Examples of unsaturated carboxylic acid esters are alkyl acrylate and/or alkyl methacrylate, wherein the alkyl comprises up to 24 carbon atoms. Examples of alkyl acrylate and alkyl methacrylate are, in particular, methyl methacrylate, ethyl acrylate, n-butyl acrylate, iso-butyl acrylate, 2-ethylhexyl acrylate. Examples of copolymers are products produced by companies Du Pont, Exxon Mobil, and others under trade names Elvaloy, Lotryl, and others.

The content of the elastomer (IV) is from 1.0 to 8.0 wt.%, preferably from 3.0 to 7.0 wt.%, most preferably from 4.0 to 6.0 wt.% based on 100% of nucleating agent (contained in the composition in an amount of from 1.0 to 12 wt.%).

Summarizing the aforesaid, as related to the elastomers used in the present invention, FIG. 2 clearly demonstrates the effect of the optimal dosage of various variants of thermoplastic elastomers on the tensile strength of a mixture of PE with different structural organization of macrochains: LLDPE and HDPE. It can be seen that they are somewhat inferior to isotactic semi-crystalline homopolymer PPH030GP in their action on the strength index of PE blend compositions, and their nucleating effect strongly depends on the grade of used elastomer. The highest effectiveness is observed in the following Engage grades: Engage 8200 ( MFR _{190°C/2.16kg} = 5.0 g/10 min) in comparison with Engage 8842 ( MFR _{190°C/2.16kg} = 1.0 g/10 min) and Engage 8137 ( MFR _{190°C/2.16kg} = 13.0 g/10 min).

The principal difference of elastomeric additives from highly crystalline homo- and copolymers of propylene is a wider dosing interval and their nucleating effect on the strength index of the polymer mixture. A possible reason is a better compatibility of these elastomers with PE. Melt flow rate (MFR) of polymers also has a significant effect on the efficiency of the nucleating effect of an additive. Semi-crystalline polymers with MFR _{230°C/2.16kg} of from 3 to 9 g/10 min and amorphous polymers with MFR _{190°C/2.16kg} of from 3 to 7 g/10 min demonstrate the best results.

Thus, such use of isotactic PP or elastomeric statistical copolymers of ethylene or propylene as nucleating additives for PE compositions, which is unknown from the prior art, ensures the formation of a more homogeneous crystalline phase of polyethylene in their composition, which ultimately leads to a noticeable improvement in strength characteristics, along with improving the elasticity and flexibility of PE compositions with different structural organization of macrochains.

In addition, the composition according to the present invention can comprise other functional additives known in the field of application of the compositions according to the invention, such as antioxidants, heat stabilizers, light stabilizers or mixtures thereof, etc. Additives that can be used as such an additive are sulfur- containing antioxidants, phenolic or phosphite antioxidants, for example pentaerythritol ester of 3,5-di-tert-butyl-4-hydroxy-phenylpropionic acid (trade name Irganox 1010), tri(phenyl-2,4-di-tert-butyl)phosphite (trade name Irgafos 168), and/or similar heat stabilizers of other trade names, and amine type light stabilizers, as well as stabilizers of other types or synergistic mixtures of stabilizers of trade names, such as Irganox B225, Irganox B215, and others.

The content of these additives in the composition may range from 0 to 5 wt.%, preferably from 0.1 to 3 wt.%, most preferably from 0.1 to 1.5 wt.%. For example, FIG. 3 shows the dosage of all the presented polymer additives, which is optimal in their effect on the tensile strength of the PE compositions. For most additives, the maximum efficiency is observed at a dosage of 5 wt.%.

The composition according to the present invention can be prepared by any known method of mixing of thermoplastic polymers. Preferably, the composition is prepared by a one-step method comprising melt processing of a dry mixture of all ingredients of the composition, wherein the mixture was previously prepared by any method known from the art, in any suitable equipment, including single or twin screw extruders, closed rotary mixers, etc.

The temperature usedof mixing of the components is traditional for this field and is determined by the properties of a particular polyethylene. More particularly, the components are mixed at a temperature higher than the melting points of the polyethylenes constituting the composition and lower than their decomposition temperatures. The temperature of mixing of the components is preferably from 180 to 250°C, more preferably from 190 to 220°C.

Processing modes of the resulting composition do not differ from standard ones used in each particular case, depending on rheological characteristics of polyethylenes. The most preferable method of processing is melt extrusion.

The compositions obtained by the method according to the invention are suitable for use as high-grade raw materials for the manufacture of the sheath and/or insulation of electrical cables, the sheath of fiber-optic cables, various tubular products, and the outer layer of insulation of pipelines.

The following examples are given for illustrative purposes and are not intended to limit the scope of the present invention.

Embodiments of the invention

As a polymer base, the following compounds were used:

1) LLDPE - Daelim XP 9200: d = 0.918 g/cm ³ , MFR _{190°C/2.16kg} = 1.0 g/10 min, produced by Daelim Industrial Co., Ltd, Korea;

2) HDPE 276-73: d = 0.958-0.963 g/cm ³ , MFR _{190°C/2.16kg} = 0.7 g/10 min, produced by Kazannefteorgsintez PAO, Russia;

As polymeric nucleating agents, the following compounds were used: 1) PP, PPH030GP: MFR _{230°C/2.16kg} = 3.0 g/10 min, produced by Tomskneftekhim OOO;

PPH270GP: MFR _{230°C/2.16kg} = 27.0 g/10 min, produced by Tomskneftekhim

OOO;

PPH450GP: MFR _{230°C/2.16kg} = 45.0 g/10 min, produced by Tomskneftekhim

OOO.

Maleinized PP homo-polymer - Bondyram 1001 : [MA] = 1 wt.%, MFR _{230°C/2.16kg} = 150 g/10 min, produced by Polyram (Israel).

2) or copolymers of propylene with ethylene: random copolymer PPR015EX: MFR23o _° c/2.i6kg = 1.5 g/10 min; PPR090: MFR230/2.16 = 9.0 g/10 min, produced by Tomskneftekhim OOO; block copolymer of propylene with ethylene: PP8300G: MFR _{230°C/2.16kg} = 1.5 g/10 min, produced by Nizhnekamskneftekhim PAO.

3) or elastomers: ethylene-octene copolymers: Engage 8137: d = 0.864 g/cm ³ , MFR _{190°C/2.16kg} = 13 g/10 min; Engage 8200: d = 0.870 g/cm ³ , MFR _{190°C/2.16kg} = 5 g/10 min; Engage 8842: d = 0.857 g/cm ³ , MFR _{190°C/2.16kg} = 1.0 g/10 min, produced by Dow Chem.; Exact 8230: d = 0.882 g/cm ³ , MFR _{190°C/2.16kg} = 30.0 g/10 min, produced by Exxon Mobil. Amorphous copolymers of propylene with ethylene and butene-1: Vistamax 6102: d = 0.862 g/cm ³ , MFR _{190°C/2.16kg} = 1.3 g/10 min, Vistamax 6202: d = 0.861 g/cm ³ , MFR _{190°C/2.16kg} = 7.4 g/10 min, produced by Exxon Mobil. Random copolymers of ethylene with butyl acrylate: Elvaloy 3427: d = 0.926 g/cm ³ , MFR _{190°C/2.16kg} = 4.0 g/10 min, produced by Du Pont; Lotryl 35BA40: d = 0.930 g/cm ³ , MFR _{190°C/2.16kg} = 35 g/10 min, produced by Arkema group.

Borstar 6052 composition, which is an industrial grade of a composition based on bimodal medium-density polyethylene produced by Borstar’ s two-reactor technology of Borealis, was used as a comparison sample. This grade is used for the manufacture of the sheath of fiber optic cables.

Methods of studying compositions

The melt flow rate was determined at temperatures of 230°C and 190°C and a load of 2.16 N, according to National State Standard GOST 11645.

The tensile yield strength, tensile strength, and breaking elongation were determined according to National State Standard GOST 11262 at a testing rate of 50 mm/min. The flexural modulus was determined according to ASTMD 790; the type of testing was a three-point bend test at a testing rate of 1.3 mm/min.

The Shore D/1 hardness was determined according to National State Standard GOST 24621.

The Vicat (ION) softening temperature was determined according to ASTM

1525.

The cracking resistance was determined according to National State Standard GOST13518.

Examples

Preparation of the compositions:

It is preferable to prepare compositions on an extrusion line. First, a mechanical mixture of ingredients of a PE composition, the so-called charge, is prepared in the preliminary step of dry mixing in a standard mixing equipment under standard conditions at a temperature from 15 to 30°C.

In the main stage of compounding, the resulting mixture is loaded into a funnel or another dosing device of an extruder, preferably twin-screw extruder, and processed into the finished product - granules - by standard methods. The maximum meltprocessing temperature in the extrusion equipment is from 210 to 240°C.

Samples for physico-mechanical, thermophysical and other tests are prepared by a hot-pressing method under standard conditions at a temperature of 160 to 190°C.

The test results of the PE compositions are shown in Table 1 including Examples 1-29. These examples are given only as an illustration of the present invention and are not intended to limit the present invention.

Example 1 (comparative)

1) Preliminary step of dry mechanical mixing of ingredients

A mixture (charge) is prepared in a paddle mixer, the mixture comprises 70 wt.% of LLDPE Daelim XP 9200 and 30 wt.% of HDPE 276-73, and the mixing is carried out for 2-10 minutes at room temperature and at rated number of revolutions for this equipment.

2) Main step of mixing in a melt The dry mixture of components (charge) obtained in the first step is processed in a twin-screw extruder LTE-20-44 at the maximum temperature in the cylinder zones of 240°C and the number of revolutions of the screws of 250 min ^-1 .

The resulting composition is characterized by a tensile strength of 32.9 MPa, a breaking elongation of 700%, a flexural modulus of 540 MPa, a Shore D/1 hardness of 57 units, and a Vicat _10N softening temperature of 119°C.

Example 2 (comparative)

The process is carried out similarly to Example 1, except that 60 wt.% of LLDPE Daelim XP 9200 and 40 wt.% of HDPE 276-73 are used to prepare a charge.

The resulting composition is characterized by a tensile strength of 31.1 MPa, a breaking elongation of 710%, a flexural modulus of 620 MPa, a Shore D/1 hardness of 60 units, and a Vicat _10N softening temperature of 121°C.

Example 3 (comparative)

The process is carried out similarly to Example 1, except that 45 wt.% of LLDPE Daelim XP 9200 and 55 wt.% of HDPE 276-73 are used to prepare a charge.

The resulting composition is characterized by a tensile strength of 27.2 MPa, a breaking elongation of 740%, a flexural modulus of 720 MPa, a Shore D/1 hardness of 63 units, and a Vicat _10N softening temperature of 123°C.

Example 4

The process is carried out similarly to Example 1, except that 63 wt.% of LLDPE Daelim XP 9200, 32 wt.% of HDPE 276-73, and 5 wt.% of PPH030GP are used to prepare a charge.

The resulting composition is characterized by a tensile strength of 35.0 MPa, a breaking elongation of 780%, a flexural modulus of 560 MPa, a Shore D/1 hardness of 59 units, and a Vicat _10N softening temperature of 121°C.

Example 5

The process is carried out similarly to Example 1, except that 55 wt.% of LLDPE Daelim XP 9200, 40 wt.% of HDPE 276-73, and 5 wt.% of PPH030GP are used to prepare a charge.

The resulting composition is characterized by a tensile strength of 40.2 MPa, a breaking elongation of 820%, a flexural modulus of 630 MPa, a Shore D/1 hardness of 63 units, and a Vicat _10N softening temperature of 122°C. Example 6

The process is carried out similarly to Example 1, except that 38 wt.% of LLDPE Daelim XP 9200, 55 wt.% of HDPE 276-73, and 7 wt.% of PPH030GP are used to prepare a charge.

The resulting composition is characterized by a tensile strength of 31.6 MPa, a breaking elongation of 830%, a flexural modulus of 750 MPa, a Shore D/1 hardness of

70 units, and a Vicat _10N softening temperature of 125°C.

Example 7 (comparative)

The process is carried out similarly to Example 1, except that 65 wt.% of LLDPE Daelim XP 9200, 30 wt.% of HDPE 276-73, and 5 wt.% of PPH030GP are used to prepare a charge.

The resulting composition is characterized by a tensile strength of 33.1 MPa, a breaking elongation of 680%, a flexural modulus of 550 MPa, a Shore D/1 hardness of 58 units, and a Vicat _10N softening temperature of 1 19°C.

Example 8 (comparative)

The process is carried out similarly to Example 1, except that 35 wt.% of LLDPE Daelim XP 9200, 60 wt.% of HDPE 276-73, and 5 wt.% of PPH030GP are used to prepare a charge.

The resulting composition is characterized by a tensile strength of 26.5 MPa, a breaking elongation of 750%, a flexural modulus of 780 MPa, a Shore D/1 hardness of

71 units, and a Vicat _10N softening temperature of 127°C.

Example 9

The process is carried out similarly to Example 9, except that 5 wt.% of PPH270GP is used to prepare a charge.

The resulting composition is characterized by a tensile strength of 38.5 MPa, a breaking elongation of 800%, a flexural modulus of 620 MPa, a Shore D/1 hardness of 62 units, and a Vicat _10N softening temperature of 122°C.

Example 10

The process is carried out similarly to Example 5, except that 5 wt.% of PPH450GP is used to prepare a charge. The resulting composition is characterized by a tensile strength of 39.4 MPa, a breaking elongation of 789%, a flexural modulus of 610 MPa, a Shore D/1 hardness of 61 units, and a Vicat _10N softening temperature of 121°C.

Example 11

The process is carried out similarly to Example 5, except that 5 wt.% of PPR015EX is used to prepare a charge.

The resulting composition is characterized by a tensile strength of 34.2 MPa, a breaking elongation of 780%, a flexural modulus of 610 MPa, a Shore D/1 hardness of 60 units, and a Vicat _10N softening temperature of 121°C.

Example 12

The process is carried out similarly to Example 5, except that 5 wt.% of PPR090 is used to prepare a charge.

The resulting composition is characterized by a tensile strength of 37.9 MPa, a breaking elongation of 790%, a flexural modulus of 620 MPa, a Shore D/1 hardness of

60 units, and a Vicat _10N softening temperature of 120°C.

Example 13

The process is carried out similarly to Example 5, except that 5 wt.% of PP8300 G is used to prepare a charge.

The resulting composition is characterized by a tensile strength of 37.7 MPa, a breaking elongation of 790%, a flexural modulus of 630 MPa, a Shore D/1 hardness of

61 units, and a Vicat _10N softening temperature of 121°C.

Example 14

The process is carried out similarly to Example 5, except that 5 wt.% of Engage 8842 is used to prepare a charge.

The resulting composition is characterized by a tensile strength of 34.7 MPa, a breaking elongation of 750%, a flexural modulus of 460 MPa, a Shore D/1 hardness of 60 units, and a Vicat _10N softening temperature of 122°C.

Example 15

The process is carried out similarly to Example 5, except that 5 wt.% of Engage 8200 is used to prepare a charge. The resulting composition is characterized by a tensile strength of 38.5 MPa, a breaking elongation of 800%, a flexural modulus of 480 MPa, a Shore D/1 hardness of 60 units, and a Vicat _10N softening temperature of 122°C.

Example 16

The process is carried out similarly to Example 5, except that 5 wt.% of Engage 8137 is used to prepare a charge.

The resulting composition is characterized by a tensile strength of 36.0 MPa, a breaking elongation of 780%, a flexural modulus of 420 MPa, a Shore D/1 hardness of 60 units, and a Vicat _10N softening temperature of 122°C.

Example 17

The process is carried out similarly to Example 16, except that 50 wt.% of LLDPE Daelim XP 9200 and 10 wt.% of Engage 8137 are used to prepare a charge.

The resulting composition is characterized by a tensile strength of 34.9 MPa, a breaking elongation of 810%, a flexural modulus of 380 MPa, a Shore D/1 hardness of

59 units, and a Vicat _10N softening temperature of 118°C.

Example 18

The process is carried out similarly to Example 5, except that 5 wt.% of Exact 8230 is used to prepare a charge.

The resulting composition is characterized by a tensile strength of 37.3 MPa, a breaking elongation of 810%, a flexural modulus of 440 MPa, a Shore D/1 hardness of

60 units, and a Vicat _10N softening temperature of 119°C.

Example 19

The process is carried out similarly to Example 18, except that 50 wt.% of LLDPE Daelim XP 9200 and 10 wt.% of Exact 8230 are used to prepare a charge.

The resulting composition is characterized by a tensile strength of 37.1 MPa, a breaking elongation of 850%, a flexural modulus of 400 MPa, a Shore D/1 hardness of 60 units, and a Vicat _10N softening temperature of 119°C.

Example 20

The process is carried out similarly to Example 5, except that 5 wt.% of Vistamax 6102 is used to prepare a charge. The resulting composition is characterized by a tensile strength of 36.5 MPa, a breaking elongation of 780%, a flexural modulus of 460 MPa, a Shore D/1 hardness of 60 units, and a Vicat _10N softening temperature of 121°C.

Example 21

The process is carried out similarly to Example 5, except that 5 wt.% of Vistamax 6202 is used to prepare a charge.

The resulting composition is characterized by a tensile strength of 33.5 MPa, a breaking elongation of 790%, a flexural modulus of 450 MPa, a Shore D/1 hardness of 60 units, and a Vicat _10N softening temperature of 120°C.

Example 22

The process is carried out similarly to Example 21, except that 50 wt.% of LLDPE Daelim XP 9200 and 10 wt.% of Vistamax 6202 are used to prepare a charge.

The resulting composition is characterized by a tensile strength of 34.7 MPa, a breaking elongation of 820%, a flexural modulus of 420 MPa, a Shore D/1 hardness of

58 units, and a Vicat _10N softening temperature of 119°C.

Example 23

The process was carried out similarly to Example 5, except that 5 wt.% of Elvaloy 3427 is used to prepare a charge.

The resulting composition is characterized by a tensile strength of 34.9 MPa, a breaking elongation of 790%, a flexural modulus of 460 MPa, a Shore D/1 hardness of

59 units, and a Vicat _10N softening temperature of 121°C.

Example 24

The process is carried out similarly to Example 5, except that 5 wt.% of Lotryl 35BA40 is used to prepare a charge.

The resulting composition is characterized by a tensile strength of 32.5 MPa, a breaking elongation of 820%, a flexural modulus of 440 MPa, a Shore D/1 hardness of 58 units, and a Vicat _10N softening temperature of 115°C.

Example 25

The process is carried out similarly to Example 15, except that 48 wt.% of LLDPE Daelim XP 9200 and 12 wt.% of Engage 8200 are used to prepare a charge. The resulting composition is characterized by a tensile strength of 33.2 MPa, a breaking elongation of 820%, a flexural modulus of 460 MPa, a Shore D/1 hardness of

59 units, and a Vicat _10N softening temperature of 121°C.

Example 26

The process is carried out similarly to Example 6, except that 33 wt.% of LLDPE Daelim XP 9200 and 12 wt.% of Engage 8200 are used to prepare a charge.

The resulting composition is characterized by a tensile strength of 32.9 MPa, a breaking elongation of 830%, a flexural modulus of 490 MPa, a Shore D/1 hardness of 62 units, and a Vicat _10N softening temperature of 122°C.

Example 27 (comparative)

The process is carried out similarly to Example 25, except that 45 wt.% of LLDPE Daelim XP 9200 and 15 wt.% of Engage 8200 are used to prepare a charge.

The resulting composition is characterized by a tensile strength of 31.1 MPa, a breaking elongation of 810%, a flexural modulus of 440 MPa, a Shore D/1 hardness of 57 units, and a Vicat _10N softening temperature of 1 16°C.

Example 28 (comparative)

The process is carried out similarly to Example 5, except that 59.5 wt.% of LLDPE Daelim XP 9200 and 0.5 wt.% of PPH030GP are used to prepare a charge.

The resulting composition is characterized by a tensile strength of 31.8 MPa, a breaking elongation of 710%, a flexural modulus of 620 MPa, a Shore D/1 hardness of

60 units, and a Vicat _10N softening temperature of 122°C.

Example 29 (comparative)

The process is carried out similarly to Example 5, except that 5 wt.% of PP Bondyram 1001 is used to prepare a charge.

The resulting composition is characterized by a tensile strength of 28.7 MPa, a breaking elongation of 750%, a flexural modulus of 590 MPa, a Shore D/1 hardness of 59 units, and a Vicat _10N softening temperature of 117°C. Table 1 shows the PE compositions according to Examples and properties of the polyethylene compositions. Table 1. Compositions (wt.%) and properties of the compositions according to Examples 1 to 12

Continuation of Table 1.Compositions (wt.%) and properties of the compositions according to Examples 13-24

Continuation of Table 1. Compositions (wt.%) and properties of the compositions according to Examples 25-29

The test results of the polyethylene compositions obtained according to Examples 1-3 (comparative) demonstrate changes in the basic properties of PE compositions with an increase in the percentage of HDPE from 30 to 55 wt.%.

Subsequent Examples 4-6 show an effect of the addition of semi-crystalline isotactic PP PPH030GP on the simultaneous increase in the strength and breaking elongation of these compositions compared with the starting compositions. It should be also noted that positive changes in the surface hardness and heat resistance are observed in the PE compositions comprising a PP additive.

As can also be seen, for all characteristics, the compositions of Examples 5 and 6 are superior to the known commercial analogue of the bimodal polyethylene composition Borstar 6052 used for fiber-optic cables, which is also widely used in the production of pipes.

Examples 7 and 8 (comparative) demonstrate a weak effectiveness of the action of additive PPH030GP on the strength and breaking elongation of the PE compositions beyond the limits of the specified concentration range for the used HDPE.

Examples 9 to 26 demonstrate a positive effect on the balance between strength, elasticity and flexibility of the presented PE compositions comprising polymeric nucleating agents of different nature in the specified range of their dosing.

Examples 27 and 28 (comparative) demonstrate a negative response of the basic properties of the compositions beyond the specified limits for the dosing of polymeric nucleating additives Engage 8200 and PPH030 GP.

Example 29 (comparative) demonstrates an inefficient use of an additive, which is isotactic PP modified by grafting maleic anhydride (MA) and having a high MFR.

Thus, the best technical result is achieved in the case when the polyethylene composition contains LLDPE, monomodal HDPE, a nucleating agent, which is either semi-crystalline isotactic PP or elastomer of the nature described above. In this case, HDPE is introduced into the composition in an amount of from 32 to 55 wt.%, and the nucleating agent is introduced in an amount of from 1.0 to 12 wt.%, depending on its nature and purposes of the proposed composition.