Polyethylene composition for making pressure pipes with improved flexibility

FIELD: chemistry.

SUBSTANCE: invention relates to a polyethylene composition for making pipes, which contains a polymer base comprising two polyethylene fractions with different molecular weight, to a pipe containing said composition and to use of said composition to make articles, preferably pipes. The polymer base accounts for not less than 90 wt % of the overall composition and has density of 932-938 kg/m3.The fraction of ethylene homo- or copolymer (A) has lower average molecular weight than the fraction of ethylene homo- or copolymer. The polyethylene composition has melt flow rate MFR5 between 0.1 and 0.6 g/10 min and shearing stress η2.7 kPa between 85 and 230 kPa. The polyethylene composition has improved combination of properties, particularly high flexibility, high mechanical strength and good long-term stability.

EFFECT: pipes obtained from the disclosed polyethylene composition have good operational characteristics, long-term stability and good resistance to rapid propagation of cracks, which facilitates their use in conveying liquids under pressure.

16 cl, 1 tbl, 3 ex

 

The present invention relates to a polyethylene composition for pipes, which contains a polymer base, including two fractions of polyethylene with different molecular weight. In addition, the present invention relates to a product, preferably to the tube containing the specified composition, and to use this composition for the manufacture of a product, preferably a pipe.

Plastic compositions containing two or more than two fractions of polyethylene with different molecular weight, often referred to as bimodal or multimodal polyethylene compositions. Such polyethylene compositions are often used, for example, for the manufacture of pipes due to their favorable physical and chemical properties, such as, for example, mechanical strength, corrosion resistance and long term stability. Given that liquid, such as water, or natural gas transported in the pipe, often under pressure and have varying temperatures, typically in the range from 0°C to 50°C, it is obvious that the polyethylene composition used for pipes shall meet the requirements. On the other hand, to facilitate the installation of pipes, for example, in the soil is desirable flexibility of the pipe.

In particular, the polyethylene composition used for pipes, must possess high is some mechanical strength, a good long-term stability, resistance to scratches/creep resistance and resistance to crack propagation, and at the same time high flexibility. However, at least some of these properties contradict each other, it is difficult to develop a composition for pipes, which outperforms the others in all of these properties simultaneously. For example, it is known that the rigidity, giving the pipe mechanical strength increases with increasing density, but, on the contrary, flexibility and resistance to scratches/creep resistance, as is well known, increases with decreasing density.

In addition, since the polymer tubes are usually produced by extrusion or, to a lesser extent, by injection molding, the polyethylene composition should also have good processing characteristics.

It is known that to comply with the opposite requirements for the pipe material can be applied bimodal polyethylene composition. Such compositions are described, for example, in documents EP 0739937 and WO 02/102891. Bimodal polyethylene compositions described in these documents usually contain two fractions of polyethylene, where one of these two factions has a lower molecular weight than the other faction, and preferably is a homopolymer, while another faction with more in the high molecular weight preferably is a copolymer of ethylene, containing one or more than one alpha-olefin of comonomer.

One significant drawback of such pipes for use in gas supply systems and cold water supply is insufficient flexibility of the pipe. These tubes are tough and durable. These mechanical properties are a result of the high requirements with respect to mechanical strength and long term stability.

In known ways of laying gas pipes or pipe cold water supply, for example when laying in open trenches or underground pipes, for example when laying with overlapping in place, frequent problems arise due to the stiffness of the pipe. It is often difficult to combine and perform fitting of the pipe in the trench. In addition, a frequent problem is the straightening of the tubes that store or transport into bays. A similar problem occurs if you have to pass the bends, which is especially important for pipes of small and medium size. Of course, all these problems are even more significant when the rigidity of the pipe is increased because of the reduced temperature, for example, when the weather is cold.

It is therefore particularly desirable to develop pipes with increased flexibility without loss of mechanical strength and long term stability.

Accordingly, the present invention is RA is the development of a polyethylene composition for pipes, with improved combination of properties, in particular having high flexibility, and at the same time, high mechanical strength and good long-term stability.

The present invention is based on the surprising discovery that the above objective can be achieved by means of a polyethylene composition comprising at least two polymer fractions with different molecular weights, with carefully chosen values of the density and velocity of the melt flow CTP5within small ranges, and a polyethylene composition having a shear stress in a specific range.

Accordingly, the present invention proposed a polyethylene composition comprising a polymer base, which includes

(a) a fraction (A) Homo - or copolymer of ethylene; and

(b) fraction (B) Homo - or copolymer of ethylene,

where

(i) a fraction (A) has a lower srednevekovoy molecular weight than fraction (B);

(ii) the polymer base has a density of from 932 to 938 kg/m3;

(iii) the polyethylene composition has a P5from 0.1 to 0.6 g/10 min; and

(iv) the polyethylene composition has a shear stress η2,CPAfrom 85 to 230 kPa.

Found that by using such plastic compositions, it is possible to produce pipes with enhanced flexibility. Therefore, the pipe, from otoplenie of a polyethylene composition according to the invention, it is much easier to straighten, align in the trenches and skip around corners. In addition, these pipes also have high mechanical strength, allowing, for example, to use this pipe for transporting fluids under pressure, excellent long-term stability and good resistance to rapid crack propagation. In addition, these plastic compositions also have good technical characteristics.

It should be noted that the composition of the present invention is characterized not only one of the above defined characteristics, but their combination. Thanks to this unique combination of characteristics it is possible to obtain tubes with superior performance properties, especially in terms of flexibility and rapid propagation of cracks (BRT) while maintaining the minimum long-term strength (TIR), technological characteristics, toughness and resistance to slow crack propagation.

Used here, the term "molecular weight" refers to srednevekovoy molecular mass Mw.

The term "polymer basis" means the polymer components in General in the polyethylene composition according to the invention typically comprise at least 90% wt./wt. the total composition. Preferably the polymer base consists of fractions (a) and (B), in the can, additionally it contains a fraction of the prepolymer in the amount of up to 20% wt./wt., preferably up to 10% mass/mass, more preferably up to 5% wt./wt. the total polymer base.

In addition to the polymeric base in plastic compositions may be present additives commonly used for polyolefins, such as pigments, stabilizers (antioxidants), antacids and/or absorbers of UV radiation, antistatics and performance additives such as processing AIDS). Preferably the amount of these additives is 10% wt./wt. or lower, preferably 8% wt./wt. or lower, even more preferably 4% wt./wt. or below of the total composition.

Preferably the composition contains carbon black in the amount of 8% wt./wt. or below, preferably from 1 to 4% wt./wt. of the total composition.

In addition, preferably the amount of additives other than carbon black, 1.5% wt./wt. or less, more preferably 1.0% wt./wt. or less, most preferably of 0.5% wt./wt. or less.

Usually a plastic composition such as the composition of the present invention, containing at least two fractions of polyethylene obtained in different conditions of polymerization, resulting in different srednevekovym molecular mass fractions, Rel is referring to the "multimodal". The prefix "a lot" refers to the number of different polymer fractions that make up the composition. For example, a composition consisting only of the two factions, called "bimodal".

The shape of the curve of the molecular-mass distribution, i.e. the graph of the dependence of the mass fraction of the polymer from its molecular weight, such multimodal polyethylene has two or more than two maximum or at least distinctly broadened in comparison with the curves for the individual fractions.

For example, if the polymer is produced in a sequential multi-stage process, using reactors connected in series, and the different conditions in each reactor, each of the polymer fractions obtained in different reactors, must have its characteristic molecular weight distribution and srednevekovoi molecular weight. When constructing the curve of the molecular mass distribution of such polymer individual curves of these fractions are combined, forming the curve of the molecular-mass distribution for the total of the resulting polymer product, which usually yields a curve with two or more than two separate maxima.

The polyethylene composition preferably has a CTP5from 0.15 to 0.5 g/10 min, preferably from 0.2 to 0.45 g/10 minutes

The polymer base preferably which has a density of from 933 to 937 kg/m 3.

The shear stress η2,CPAthe polyethylene composition is preferably from 95 to 210 kPa and more preferably from 100 to 200 kPa.

In the preferred embodiment the polyethylene composition further comprises nuclearmoose agent. The number of such nuclearpower agent in the polyethylene composition is preferably from 0.01 to 0.5% wt./wt., more preferably from 0.05 to 0.25 wt.%./wt.

Nuclearmoose agent can be any compound or mixture of compounds capable of serving as a center of crystallization, for example, be a pigment having nuclearfusion effect, or additive used only for the purposes of okleinowania. Examples of such compounds are pigments phtalocyanine blue or green (for example, RU:1, RU:3, PG7), isoindoline and isoindoline pigments (for example, PY109, PY110, RO), benzimidazolone pigments (for example, RO, RO), chinaredorbit pigments (for example, PY19), benzimidazolone pigments (for example, PY180, PY181), chieftancy pigments (for example, PY138), chinaredorbit pigments (e.g., Pigment Violet PV19) and azaheterocycles pigments (for example, RO).

Nuclearmoose agent may also be a polymer additive, such as a polymer vinylcyclohexane or 3-methyl-1-butene. In this case, the polymer additive is which preferably has a melting point above 200°C. you can add to a bimodal polymer generally accepted methods in the extruder or pre polimerizuet on the catalyst, as described, for example, in document WO 99/24478.

Fraction (A) preferably has a P2from 10 to 400 g/10 min, more preferably from 20 to 200 g/10 min, even more preferably from 25 to 100 g/10 minutes

Fraction (A) preferably has a density of from 960 to 980 kg/m3.

The rate of decrease of viscosity with shear UVS is the ratio of the viscosities of the composition of polyethylene at various shear stresses. In the present invention are applied shear stress 2,7 kPa and 210 kPa to calculate the value of UVS(of 2.7/210)that can serve as a measure of the width of the molecular mass distribution.

The value of UVS polyethylene compositions of the present invention are relatively low. This is a sign of relatively narrow molecular mass distribution of polymer base. The value of hydrocarbon compositions of polyethylene according to the invention is preferably from 10 to 49, more preferably from 10 to 45 and more preferably from 15 to 35.

In addition, the fraction (A) preferably is a homopolymer of ethylene.

The modulus of elasticity in bending of the polyethylene composition is preferably from 300 to 700 MPa, more preferably from 400 to 700 MPa.

The ratio of the components of the polymer basics of fractions (a) and fraction (B) by weight is preferably (30-47):(70-53), more preferably (35-45):(65-55).

In addition, the polyethylene composition has good resistance to rapid crack propagation. Pipe made from the multimodal polyethylene composition of the present invention, preferably has a critical temperature of brittleness (TCrete)equal to -6°C or lower, more preferably -8°C or lower (value RCP-S4).

In addition, the polyethylene composition has a resistance to slow crack propagation at least 500 hours, more preferably at least 1000 hours, even more preferably at least 1500 hours and most preferably at least 2000 h at centrifugal tensile stress of 4.0 MPa, and the internal pressure of 8.0 bar at 80°C.

Pressure pipe made of the multimodal polymer composition of the present invention, preferably has a voltage rating corresponding to at least MRS 8,0.

Preferably the polyethylene compositions of the present invention without carbon black or fillers satisfy the following relations:

where FM denotes the modulus of elasticity in bending, as described above.

The numerator in prevedeno the above formula determines the flexibility of the material. However, if flexibility is too high, the material loses its ability to withstand pressure. The denominator determines the resistance of the material pressure. Therefore, the above ratio, how to find a plastic composition which fulfills the requirements of flexibility and resistance to pressure.

The polymer base of the polyethylene composition preferably contains at least 0.2 mol.%, more preferably at least 0.75 in mol.% and even more preferably at least 0,95 mol.% at least one alpha-olefin co monomer. The number of co monomer is preferably not more than 3.0 mol.%, more preferably not more than 2.5 mol.% and even more preferably not more than 2.0 mol.%.

Fraction (B) of the polyethylene composition preferably contains at least 0.4 mol.%, more preferably at least 0.6 mol.% and even more preferably at least 0.8 mol.% at least one alpha-olefin co monomer. The number of co monomer is preferably not more than 6.0 mol.%, more preferably not more than 5.0 mol.% and even more preferably not more than 4.0 mol.%.

As co monomer alpha-olefin is preferably used alpha-olefin having from 4 to 8 carbon atoms. Even more preferably, use alpha-olefin selected from 1-butene, 1-GE is sung, 4-methyl-1-pentene and 1-octene.

Here, if the characteristics of fractions (a) and/or (B) the composition of the present invention, these values are usually valid for cases in which they can be directly measured for the respective fractions, for example, when the fraction obtained separately or obtained in the first stage of the multistage process.

However, a polymer base also possible and preferably get in a multistage process, where, for example, fraction (a) and (B) get in successive stages. In this case, any of the characteristics of the fractions obtained at the second and third stage (or later stages) multi-stage process can be derived from polymers, which are obtained separately on a separate stage, employing the same conditions of polymerization (for example, an identical temperature, partial pressure of reagents/solvents, suspension medium, reaction time), and for stage multistage process in which this fraction, and using a catalyst that does not have any pre-obtained polymer. Alternative properties of the fractions obtained at a later stage of the multistage process, it is also possible to calculate, for example, in accordance with the publication .Hagström, Conference on Polymer Processing The Polymer Processing Society), Extended Abstracts and Final Programme, Gothenburg, August 19 to 21, 199, 4:13.

Thus, the characteristics of the fractions, although not directly measured in products multistage processes obtained in the later stages of this multi-stage process, it is possible to determine, using any or both of the above-mentioned method. Experts in the art should be able to choose the appropriate method.

A polyethylene composition according to the invention preferably receives such a way that at least one of the fractions (a) and (B), preferably (B)is obtained in gas-phase reactions.

In addition, it is preferable that one of the fractions (a) and (B) a polyethylene composition, preferably fraction (A), was obtained a suspension of the reaction, preferably in a circulation reactor, and one of the fractions (a) and (B), preferably fraction (B)was obtained in the gas-phase reactions.

In addition, plastic polymer base preferably get in a multistage process. Polymer compositions obtained in this process, also defined as a mixture of "in situ".

Multistage process is defined as the process of polymerization, which receive the polymer containing two or more than two fractions, by obtaining each fraction or at least two fractions of the polymer on the individual stages of the reaction, typically at different reaction conditions at each stage, presets is under the reaction product of the previous stage, which includes a polymerization catalyst.

Accordingly, preferably, fraction (a) and (B) polyethylene compositions were obtained at different stages of the multistage process.

Preferably the multi-stage process includes at least one gas-phase stage, which preferably receive a fraction (B).

In addition, the fraction (B) preferably receive, at a subsequent stage in the presence of fraction (A), which is obtained at the previous step.

Previously known to produce multimodal, in particular bimodal polymers of olefins, such as multimodal polyethylene, multistage process involving two or more than two reactors connected in series. As an example of this prototype, the preferred multistage process of obtaining a polyethylene composition according to the invention, mention can be made of the publication EP 517868, which is incorporated herein by reference in their entirety, including all preferred embodiments described therein.

Preferably the main stage of the multistage polymerization process such as described in EP 517868, i.e. obtaining fractions (a) and (B) carry out as a combination of suspension polymerization for the fraction (a) and gas-phase polymerization for the fraction (B). Suspension polymerization is preferably carried out in the so-called irculation reactor. In addition, slurry phase polymerization is preferably preceded by a gas-phase stage.

Possible and preferably the main stages of polymerization can be preceded by pre-polymerisation, which receive up to 20% wt./wt., preferably from 1 to 10% wt./wt., more preferably from 1 to 5% wt./wt. the total polymer base. The prepolymer preferably is a homopolymer of ethylene (HDPE). When the preliminary polymerization is preferably the entire catalyst is loaded into the circulation reactor, and preliminary polymerization carried out as suspension polymerization. Such pre-polymerization results in less of the fine particles in the subsequent reactors, and more homogeneous product, obtained as a result.

Polymerization catalysts include coordination catalysts of transition metals, such as catalysts of the Ziegler-Natta (TSN), metallocene, demetallized, Cr-containing catalysts, etc. of the Catalyst may be applied, for example, on conventional substrates, including silicon dioxide, Al-containing substrate and the substrate on the basis of magnesium dichloride. Preferably the catalyst is a catalyst of CR, more preferably the catalyst is a catalyst of CR deposited on the substrate, predstavlayu is not silicon dioxide, and most preferably the catalyst TSN on the basis of MgCl2.

The catalyst of the Ziegler-Natta preferably further includes a metal connection 4 groups (numbering according to the new IUPAC system), preferably compounds of titanium, aluminum and magnesium dichloride.

The catalyst may be commercially available or can be obtained according to or analogously to the methods described in the literature. The link to receive the preferred catalyst, applicable in the invention, made on documents WO 2004055068 and WO 2004055069 Borealis and EP 0810235. The contents of these documents in full incorporated herein by reference, in particular with respect to the principal and all preferred embodiments of the catalysts described therein, and methods of making catalysts. Particularly preferred catalysts of the Ziegler-Natta described in the publication EP 0810235.

The resulting end product consists of a homogeneous mixture of polymer from the reactor, and the various curves of the molecular weight distribution of these polymers together form the curve of the molecular mass distribution with a broad peak or several peaks, i.e. the final product is a multimodal polymer mixture.

Preferably, the multimodal polymer polyethylene composition for the image is the shadow was a bimodal polyethylene blend, consisting of fractions (a) and (B)may additionally contain a small fraction of the preliminary polymerization in the amount described above. Also preferably, this bimodal polymer blend was obtained by polymerization as described above, under different conditions of polymerization in two or more than two polymerization reactors connected in series. Because of the flexibility that can be used for the reaction conditions, it is most preferable that the polymerization was performed in combination of the circulation reactor and gas-phase reactor.

Preferably the conditions of polymerization in the preferred two-stage method is selected so that a relatively low molecular weight polymer that does not contain co monomer was obtained in one stage, preferably the first stage, due to the high content agent transfer chain (hydrogen gas), whereas the high molecular weight polymer containing comonomer get to another stage, preferably the second stage. However, the order of these stages may be reversed.

In the preferred embodiment of the polymerization in the circulation reactor, with subsequent gas-phase reactor, the polymerization temperature in the circulation reactor is preferably from 85 to 115°C, more preferably from 90 to 105°C. and the most preferred is compulsory from 92 to 100°C, and the temperature in the gas-phase reactor is preferably from 70 to 105°C., more preferably from 75 to 100°C. and most preferably from 82 to 97°C.

Agent transfer chain, preferably hydrogen, add as needed in the reactor, and preferably in a reactor add from 200 to 800 mol. H2/KMOL ethylene when receiving low-molecular (NM) fraction in the reactor, and gas-phase reactor type from 0 to 50 mol. H2/KMOL ethylene in obtaining high molecular weight (VM) fractions in the reactor.

If the composition according to the invention is produced in the process, including the stage of compounding polymeric bases, i.e. mixtures, which are usually obtained from the reactor in the form of a powder polymer base, it is preferably ekstragiruyut in the extruder and then granularit in the form of granules of the polymer by any method known in this technical field.

Perhaps, additives or other components of the polymer can be added to the composition at the stage of compounding in the amount described above. Preferably the composition according to the invention, obtained from the reactor, compounding in the extruder together with additives by any method known in this technical field.

The extruder may represent, for example, any conventional extruder used.

In addition, the present invention from OSISA to the product, preferably the tube containing polyethylene composition as described above, and to the use of such a polyethylene composition for the manufacture of a product, preferably a pipe.

Examples

1. Definitions and methods of measurement

a) Density

The density is measured according to the standard International Organization for Standardization ISO 1183-2. The sample preparation is carried out in accordance with ISO 1872-2B.

b) the Rate of melt flow/speed ratio of the melt flow

The rate of melt flow (P) is determined according to ISO 1133 and is indicated in g/10 min. P is a measure of the fluidity and, therefore, the processing characteristics of the polymer. The higher the melt flow index, the lower the viscosity of the polymer. P is determined at 190°C., and can be determined at different loadings such as 2,16 kg (P2), 5,00 kg (CTP5) or 21.6 kg (P21).

The value of FRR (the ratio of the velocities of the melt flow) is a measure of molecular mass distribution and denotes the ratio of flow rates at different loads. Thus, FRR21/5denotes a value of P21/P5.

C) Rheological parameters

Rheological parameters such as the rate of decrease of viscosity with shear UVS and viscosity, determined using a rheometer, predpochtitel what about the rheometer Physica MCR 300, supplied by the company Anton Paar GmbH. The definition and the measurement conditions are described in detail on p.8, line 29 to page 11, line 25 publication WO 00/22040.

d) Rapid crack propagation

Resistance to rapid crack propagation (BRT) pipe define a method called test S4 (small scale test in steady state), developed at Imperial College London and is described in ISO 13477:1997 (E).

According to the test RCP-S4 have the pipe, the axial length of which is not below 7 pipe diameters. The external diameter of the tube is approximately 110 mm or more, and its wall thickness is about 10 mm or more. When defining properties, BRT pipe in accordance with the present invention, the external diameter of the pipe and the wall thickness is selected as 110 mm and 10 mm, respectively.

While the external side of the pipe is at ambient pressure (atmospheric pressure), the pipe is subjected to internal pressure, and the positive internal pressure in the pipe to maintain a constant and equal to 0.5 MPa. The pipe and surrounding equipment thermostatic at a predetermined temperature. On the rod inside the tube set the number of disks to prevent the pressure change during the test. Retractable knife of some form is injected into the tube, close to its one end in the so-called zone of introduction, to cause if the tro propagating axial cracks. The area of introduction provide a focus to avoid unnecessary deformation of the pipe. Equipment for testing regulate so was the appearance of cracks in the material studied, and at different temperatures are conducting a series of tests. Each test measured the area determine the crack length along the axis, with a total length of 4.5 in diameter, and lay on the graph against the values of the test temperature. If the crack length exceeds 4 diameter, the crack is defined as spreading. If the pipe passes the test at a given temperature, the temperature is successively reduced until, until it reaches the temperature at which the pipe is no longer passes the test, but the propagation of cracks exceeds 4 times the pipe diameter. The critical temperature (TCrete), i.e. the transition temperature from brittle condition in plastically deformed, measured according to ISO 13477:1997 (E), is the lowest temperature at which the pipe passes the test. The lower critical temperature, the better, because this leads to the expansion of the conditions of use of the pipe.

d) Test incised sample

Resistance to the rapid spread of the crack are determined according to ISO 13479:1997 number of hours during which the pipe can withstand a certain pressure pereopredelennoi the temperature in the test of notched specimen before fracture. Apply pipe with a diameter of 110 mm Here to obtain the desired pressure 4.0 MPa applied pressure 8.0 bar and a temperature of 80°C. the Measurements are performed on the pipe 110 SDR 11.

e) Constant tensile load (REC)

Resistance to slow crack propagation is determined using this test according to ISO 6252:1992 (E) using tests of notched specimen according to ASTM 1473, as follows.

Test REC is an accelerated test on slow crack propagation, where the acceleration is supported due to elevated temperature is 60°C. the Test is performed in the solution of surface-active substances, and the use of cut reduces the time to failure and provides a planar strain state of the samples.

Load in the samples was 5.0 MPa (actual load on the cut). Surfactant used in the test is a IGEPAL CO-730 at 60°C.

Samples are obtained by stamping plates with a total length of 125 to 130 mm and a width at the ends 21±0.5 mm Then the plate is cut to the exact dimensions of the clip on both sides, with the distance between the centers of both the holders of 90 mm and a hole diameter of 10 mm in the Central part of the plate has a length of 30±0.5 mm, a width of 9±0.5 mm and a thickness of 6±0,5 mm

Then the sample with the face of the second side put a cut depth of 2.5 mm with blade, installed in a machine for applying cuts (PENT-NOTCHER, Norman Brown engineering), speed of cut of 0.2 mm/min For the remaining two sides of the cut grooves of 0.8 mm, which must be in the same plane with the cut. After applying cuts the sample incubated at 23±1°C and 50% relative humidity for at least 48 hours Then the samples are installed in the test chamber, in which there is an active solution (10%aqueous solution of IGEPAL CO-730, chemical substance: 2-(4-nonyl-phenoxy)ethanol, C17H28O2). The samples put a constant load and at the moment of rupture automatic timer shut off.

g) a pressure Test and rated voltage

Evaluation of the rated voltage is a voltage on the surface of the pipe, which is calculated pipe must withstand for 50 years without failure, and it is performed for various temperatures based on the minimum long-term strength (TIR) according to ISO/TR 9080. Thus, the TIR of 8.0 means that the pipe is a tube that can withstand the centrifugal tensile stress value of 8.0 MPa for 50 years at 20°C, and, similarly, TIR 10,0 means that the pipe can withstand centrifugal tensile stress to a value of 10 MPa for 50 years at 20°C.

These values are calculated on the basis of the results is tested under pressure, performed according to ISO 1167. Pipe with a diameter of 32 mm test at different temperatures and internal pressure.

C) Modulus of elasticity in bending

The modulus of elasticity in bending was determined according to ISO 178. The dimensions of the test samples was 80×10×4.0 mm (length × width × thickness). The length of the span between supports was 64 mm, test speed was 2 mm/min and a sensor for measuring the load had a value of 100 N. Used the device Alwetron TCT 25.

2. Polyethylene compositions

Obtaining polymer base polyethylene compositions were carried out in a multistage reaction, including preliminary polymerization in suspension in water reactor with a volume of 50 DM3with the subsequent transfer of slurry in circulation reactor of 500 DM3, where he continued polymerization in suspension to obtain a component with a low molecular weight, and the second gas-phase polymerization reactor in the presence of the product from the second circulation reactor with obtaining the co monomer containing a component with high molecular weight. Comonomer all made compositions consisted of a 1-butene.

As the catalyst used Lynx 200, supplied by Engelhard Corporation, Pasadena, USA.

To obtain comparative examples used the catalyst CIG the EPA-Natta in accordance with Example 1 of EP 0688794.

Nuclearmoose agent used in the Examples was a pigment Chronically Blue 4GNP (phtalocyanine blue).

The applied polymerization conditions shown in the Table.

Examples 1 and 2, showing the compositions 1 and 2, respectively, are examples according to the invention. Example 3 is a comparative example, which represents the composition 3. This example is a polyethylene composition according to the prior art. In all three examples at the stage of preliminary polymerization was obtained homopolymers.

Table
Example123 (EUR.)
The preliminary polymerization
Temperature°C606060
Pressurebar626363
P5g/10 min57 0,5
The suspension polymerization in a loop reactor
Temperature°C859595
Pressurebar575858
The concentration of C2mol.%4,04,05,6
H2/C2mol/KMOL217,6277,0947
With4/S2mol/KMOL50,00,00,0
P2g/10 min5247442
Densitykg/m3962975975
Gas-phase on Ameritania
Temperature°C85,085,085,0
Pressurebar202020
H2/C2mol/KMOL282848
With4/S2mol/KMOL194171218
The extruder JSW CIM90P
The feed speedkg/h221221221
Specific energy consumptionkW·h/t329291280
Melting point°C217226 226
Properties of polymeric bases
Densitykg/m3933936941
The ratio of the components (tentatively.2:38:602:38:602:44:54
Polym./circul./gasoven.)
Properties of composition
CTP5g/10 min0,430,410,91
P21g/10 min8,48,125,2
Densitykg/m3935 939951
The content of the co monomer% wt./wt.3,753,112,85
The modulus of elasticity in bendingMPa614674880*
TCrete(RS-84)°C-10-8-4
UVS2,7/21024,923,433,1
η2,CPAkPa10611352
ηPAkPa160,3172,785,7
The pressure test (80°C to 4.6h>845>700>400
MPa)
Minimum long-term durabilityMPa≥8,0≥8,0a total of 8.74
(TIR)
Constant tensile loadh>1500>1500>5000
(REC)
Test incised sampleh>1000>1000>5000
Chronically blue 4GNP% wt./wt.0,10,10
Soot% wt./wt.002,3
* without soot

1. Polyethylene component is ice for pipes, containing a polymer base comprising at least 90% wt./wt. total composition and including
(a) a fraction (A) Homo - or copolymer of ethylene; and
(b) fraction (B) Homo - or copolymer of ethylene, where
(i) a fraction (A) has a lower srednevekovoy molecular weight than fraction (B);
(ii) the polymer base has a density of from 932 to 938 kg/m3;
(iii) the polyethylene composition has a flow rate of the melt P5determined at 190°C. and a load of 5 kg, of 0.1 to 0.6 g/10 min; and
(iv) the polyethylene composition has a shear stress η2,CPA(viscosity at a shear stress of 2.7 kPa at 190°C.) of from 85 to 230 kPa.

2. The polyethylene composition according to claim 1, additionally containing nuclearly agent.

3. The polyethylene composition according to any one of claims 1 and 2, where the fraction (A) has a flow velocity of the melt P2determined at 190°C. and load of 2.16 kg, of from 10 to 400 g/10 minutes

4. The polyethylene composition according to claim 3, where the fraction (A) has the P2determined at 190°C. and load of 2.16 kg, of from 25 to 100 g/10 minutes

5. The polyethylene composition according to claim 1, where the fraction (A) has a density of from 960 to 980 kg/m3.

6. The polyethylene composition according to claim 1, where the rate of decrease of viscosity with shear UVS(2,7/210) (the ratio of the viscosity measured at 2.7 kPa and 210 kPa at 190°C.) of the polyethylene composition is from 10 to 49.

7. The polyethylene composition according to claim 1, where the modulus of elasticity in bending of the polyethylene composition is from 300 to 700 MPa.

8. The polyethylene composition according to claim 1, where the mass ratio between the fraction (a) and fraction (B) is (30-47):(70-53).

9. The polyethylene composition according to claim 1, where the polymer base contains from 0.2 to 3.0 mol.% at least one alpha-olefin co monomer.

10. The polyethylene composition according to claim 1, where component (B) contains from 0.4 to 6.0 mol.% at least one alpha-olefin co monomer.

11. Pipe made from polyethylene composition according to any one of claims 1 to 10.

12. Pipe of claim 11, which satisfies the requirement MRS 8,0 according to ISO 9080.

13. Pipe of claim 11, having a resistance to rapid crack propagation, measured in the test S4, such that TCretelower than -6°C.

14. Pipe of claim 11, having a resistance to slow crack propagation, measured according to the standard International Organization for Standardization ISO 13479:1997, which is more than 500 hours

15. The use of a polyethylene composition according to any one of claims 1 to 10 for the manufacture of the product.

16. The application indicated in paragraph 15, where the product represents the pipe.



 

Same patents:

FIELD: chemistry.

SUBSTANCE: invention relates to a polyolefin composition which is suitable for making pipes. The composition used to make pipes contains polyolefin (A), a compound (B) which is bis(2,4-dicumyphenyl)pentaerythritol diphosphate, and a phenol compound (C) of formula (I), where R denotes an unsubstituted or substituted aliphatic or aromatic hydrocarbon radical, which can contain heteroatoms, or R denotes a heteroatom; each X1-X5 denotes H, OH and/or R'; where R' denotes a hydrocarbon radical or a hydrogen atom, and n equals 1-4; and g) possibly a stabiliser against UV light (D).

EFFECT: composition has low tendency to migration of additives and their decay products, particularly phenol compounds and a light stabiliser, not more than 1,8 mcg/l with surface to volume ratio S/V between 11,70 and 12,30 dm-1, without loss of stability.

10 cl, 3 tbl, 5 ex

FIELD: chemistry.

SUBSTANCE: polymer base is not less than 90 wt % of the overall composition and has density of 940-947 kg/m3.The fraction of homo- or copolymer of ethylene (A) has lower average molecular weight than the fraction of homo- or copolymer of ethylene. The polyethylene composition has melt flow rate MFR5 of 0.1-0.5 g/10 min and viscosity reduction index during shear (2.7/210) of 10-49, has better combination of properties, in particular high flexibility and high mechanical strength and good long-term stability.

EFFECT: pipes made from the disclosed polyethylene composition have good performance properties, especially in terms of flexibility and rapid propagation of cracks while preserving minimal required strength, processing characteristics, impact viscosity and resistance to slow propagation of cracks.

14 cl, 1 tbl, 3 ex

FIELD: chemistry.

SUBSTANCE: addition of a stabilising amount of a mixture to high density polyethylene, where the said mixture contains 4,4'-bis(α,α-dimethylbenzyl)diphenylamine and sterically hindered phenol, enables to increase resistance to decomposition caused by chlorinated water.

EFFECT: pipes made from such a stabilising composition are suitable for conveying hot water, particularly chlorinated water.

6 cl, 3 ex

FIELD: machine building.

SUBSTANCE: cooling agent pipeline includes the following layers: outer layer from moulding compound on the basis of polyamide; inner layer having the thickness at least of 0.3 mm and containing polypropene, 0.02 wt % of heat stabiliser. Polypropene is hetero-phase copolymer on the basis of propene, which contains 0.5 wt % to 20 wt % of ethene.

EFFECT: increasing heat stability and mechanical pipeline strength.

10 cl, 1 tbl

FIELD: machine building.

SUBSTANCE: multi-layer pipe is made out of composite material corresponding to reinforced materials in form of alternate mono-layers with cross and lengthwise laying of reinforced material impregnated, for example with thermo-reactive binding. Binding consists of internal and external structure layers divided with a barrier layer. The barrier layer is made out of a layer of heat insulating foam applied on external surface of the internal structure layer and of an additional layer arranged between the layer of heat insulating foam and internal surface of the external structure layer. The latter corresponds to successively lain metal screens out of continuous bands divided with polymer material.

EFFECT: increased heat resistance of wall of multi-layer pipe.

5 cl, 1 dwg

Polyethylene tubes // 2394052

FIELD: chemistry.

SUBSTANCE: method involves preparation of a mixture containing 5-50 wt % filler and 95-50 wt % low density polyethylene and 0-3 wt % of one or more stabilisers.The obtained mixture and high density polyethylene containing at least one low-molecular component which is a copolymer of ethylene and C3-C10 α-olefin are mixed in a molten mass until the end product is obtained at drop point of 165-185°C. The obtained composition for making tubes contains 1-20 wt % filler in terms of mass of the composition.

EFFECT: composition has better balance of properties and can be extruded with sufficiently high efficiency at optimal low melt temperature.

19 cl, 3 tbl, 7 ex

FIELD: technological processes.

SUBSTANCE: inventions relate to pipe of flaky composite material and method of its manufacturing. Method for manufacturing of pipe includes winding of inner glass plastic layer onto mandrel, bonding of intermediate foam plastic layer and winding of ribs and outer layer of glass plastic. In intermediate foam plastic layer there are circular grooves arranged for location of ribs. Ribs and outer layer is wound in a single technological operation by bundle of cross threads. Bundles are equipped with longitudinal threads, using method of cross-fibred longitudinal-transverse winding. At the same time longitudinal threads are bent as bundle changes from winding of external layer to winding of ribs and back with filling of each groove by mentioned bundle till ribs are formed.

EFFECT: improved manufacturability and reliability of glass plastic pipes operation.

2 cl, 4 dwg

Pressed shell // 2387910

FIELD: machine building.

SUBSTANCE: invention refers to pipe fabrication. The pressed shell containing layers of roll woven cloth with binding is made with circular layers of woven material in form of separate strips of length not less, than length of shell and width equal to perimetre of the latter with overlap.

EFFECT: increased reliability and expanded process functionality of pressed shell.

2 cl, 2 dwg

FIELD: transport.

SUBSTANCE: meshed cover in the form of rotation body from composite materials includes spiral and circular ribs comprised of layers repeated throughout the cover wall thickness of the systems of crossing spiral and circular strips. Inclined strip passages between circular strips are equally offset relative to each other in circumferential and spiral directions and are made in the form of one family of congruent continuous circular zigzag-shaped spirals located along circular surfaces, which is common to circular surfaces of layers of the systems of crossing spiral and circular strips. Tops of zigzags are adjacent to circular strips of circular ribs crossing in the gap between them with spiral strips or spiral and circular strips of spiral and circular ribs correspondingly so that circular zigzag-shaped ribs are formed and mainly arranged on cover ends.

EFFECT: increasing rigidity, improving reliability and decreasing the weight of the design.

4 cl, 4 dwg

FIELD: construction.

SUBSTANCE: invention is related to method for manufacturing of pipeline. Method provides for filling of space between ends of pipe composite layers by winding of fibrous material impregnated with binder, and attachment of composite layers is provided via winding of additional layers of fibrous material impregnated with binder on them and onto fibrous material with further polymerisation.

EFFECT: expansion of assembly resources and improved reliability after welding of pipe polymer layers.

1 dwg

FIELD: chemistry.

SUBSTANCE: thermoplastic material, having a polyethylene matrix which contains 1-70 pts. wt polypropylene per 100 pts. wt polyethylene matrix, is used to make medical and hygienic films. After heating, said material is passed through a pressing zone between cooled rollers, where the initial film-type linen is heated to molten state of the material of the polyethylene matrix but not up to temperature of molten polypropylene.

EFFECT: inproved operational characteristics of film-type linen including for films with thickness equal to less than 20 mcm.

25 cl, 1 dwg, 6 tbl, 2 ex

FIELD: chemistry.

SUBSTANCE: invention relates to a polyethylene moulding composition for pressure casting finished parts, for example bottle tops and bottles, and to a method of preparing said moulding composition. The composition has polymodal molecular weight distribution and contains an ethylene homopolymer (A) with low molecular weight, an ethylene copolymer (B) with high molecular weight an ethylene copolymer (C) with ultrahigh molecular weight. At temperature 23°C, the moulding composition has density of 0.948-0.957 g/cm3, melt flow rate MFR (190°C/2.16 kg) of 1-2.7 dg/min and coefficient of viscosity VN3 of the mixture of ethylene homopolymer A, copolymer B and ethylene copolymer C, measured in accordance with ISO/R 1191 in decalin at temperature 135°C ranging from 150 to 240 cm3/g.

EFFECT: besides processability, the moulding composition has high mechanical strength and rigidity, excellent organoleptic properties and high cracking resistance under the effect of the surrounding medium.

12 cl, 2 tbl, 2 ex

FIELD: chemistry.

SUBSTANCE: polymer base is not less than 90 wt % of the overall composition and has density of 940-947 kg/m3.The fraction of homo- or copolymer of ethylene (A) has lower average molecular weight than the fraction of homo- or copolymer of ethylene. The polyethylene composition has melt flow rate MFR5 of 0.1-0.5 g/10 min and viscosity reduction index during shear (2.7/210) of 10-49, has better combination of properties, in particular high flexibility and high mechanical strength and good long-term stability.

EFFECT: pipes made from the disclosed polyethylene composition have good performance properties, especially in terms of flexibility and rapid propagation of cracks while preserving minimal required strength, processing characteristics, impact viscosity and resistance to slow propagation of cracks.

14 cl, 1 tbl, 3 ex

FIELD: chemistry.

SUBSTANCE: composition contains a mixture of a low molecular weight polyethylene component and a high molecular weight polyethylene component and a binding agent containing at least 0.0025 wt % polysulphonyl azide. The mixture has sine peak on the lamella thickness distribution (LTD) curve.

EFFECT: prolonged wear resistance of pipes under gas or water pressure, resistance to cracking under stress associated with environmental factors, resistance to slow formation of cracks, to fast crack propagation and to creep under internal stress.

64 cl, 3 dwg, 24 tbl, 6 ex

FIELD: chemistry.

SUBSTANCE: film is made from a composition having multi-modal molecular-weight distribution and density between 0.940 and 0.948 g/cm3. The composition contains 40-60 wt % of a first fraction of an ethylene polymer made from a homopolymer A, 25-45 wt % of a second fraction of ethylene polymer made from a first copolymer B of ethylene and at least one first comonomer from a group of olefins having 4-8 carbon atoms and 10-30 wt % of a third fraction of ethylene polymer made from a second copolymer C of ethylene and at least one second comonomer from a group of olefins having 4-8 carbon atoms. The first copolymer B of ethylene has molecular weight which is less than that of the second copolymer C of ethylene, but greater than that of homopolymer A.

EFFECT: disclosed thin films have improved mechanical properties, particularly impact resistance when testing the films using a falling pointed load, with high rate of collection without deterioration of stability of the molten bubble.

12 cl, 2 tbl, 3 ex

FIELD: chemistry.

SUBSTANCE: invention relates to a polyethylene moulding composition having multi-modal molecular-weight distribution, especially suitable for films made via extrusion blowing, having thickness between 8 and 200 mcm. The polyethylene moulding composition has density between 0.953 and 0.960 g/cm3 and MFR190/5 of the end product after extrusion between 0.10 and 0.50 dg/min. The composition contains 42-52 wt % of a first fraction of ethylene polymer made from a homopolymer A, having a first molecular weight, 27-38 wt % of a second fraction of ethylene polymer made from another homopolymer or a first copolymer B of ethylene and at least one first comonomer from a group of olefins having 4-8 carbon atoms,whereby the first copolymer B has a second molecular weight greater than the said first molecular weight, and 15-25 wt % of a third fraction of ethylene polymer made from a second copolymer C having a third molecular weight greater than the second molecular weight.

EFFECT: disclosed polyethylene moulding composition enables to obtain thin films with improve processing properties without deterioration of mechanical properties.

12 cl, 2 tbl, 3 ex

Polyethylene tubes // 2394052

FIELD: chemistry.

SUBSTANCE: method involves preparation of a mixture containing 5-50 wt % filler and 95-50 wt % low density polyethylene and 0-3 wt % of one or more stabilisers.The obtained mixture and high density polyethylene containing at least one low-molecular component which is a copolymer of ethylene and C3-C10 α-olefin are mixed in a molten mass until the end product is obtained at drop point of 165-185°C. The obtained composition for making tubes contains 1-20 wt % filler in terms of mass of the composition.

EFFECT: composition has better balance of properties and can be extruded with sufficiently high efficiency at optimal low melt temperature.

19 cl, 3 tbl, 7 ex

FIELD: chemistry.

SUBSTANCE: present invention relates to a polyethylene composition with multimodal molecular weight distribution for blow moulding canisters with volume ranging from 2 to 20 dm3 and a method of preparing the said composition. The composition has density ranging from 0.950 to 0.958 g/cm3 at 23°C and melt flow rate (MFR190/5) from 0.30 to 0.50 dg/min. The composition also contains 40 to 50 wt % low molecular weight ethylene homopolymer A and 25 to less than 30 wt % high molecular weight copolymer B obtained from ethylene and another 1-olefin containing 4 to 8 carbon atoms, and 24 to 28 wt % ethylene copolymer C having ultra-high molecular weight.

EFFECT: obtained composition has good resistance to chemical effect, especially high mechanical strength, high corrosion resistance and is a naturally light material; high melt strength of the composition enables prolonged extrusion without breaking the workpiece, and an accurately selected swelling index of the composition enables optimisation of controlling thickness of the wall of the article.

10 cl, 1 tbl, 1 ex

FIELD: chemistry.

SUBSTANCE: polyethylene in form of ethylene homopolymers and copolymers of ethylene with α-olefins and having molecular weight distribution range Mw/Mn from 6 to 100, density from 0.89 to 0.97 g/cm3, weight-average molecular weight Mw from 5000 g/mol to 700000 g/mol and from 0.01 to 20 branches/1000 carbon atoms and at least 0.5 vinyl groups/1000 carbon atoms, where the fraction of polyethylene with molecular weight less than 10000 g/mol has degree of branching from 0 to 1.5 branches on the side chains, longer than CH3/1000 carbon atoms. The catalyst composition for synthesis of polyethylene in paragraph 1 consists of at least two different polymerisation catalysts, from which A) is at least one polymerisation catalyst based on monocyclopentadienyl complex of a group IV-VI metal, in which the cyclopentadienyl system is substituted by an uncharged donor (A1) of formula Cp-Zk-A-MA (II), where variables assume the following values: Cp-Zk-A is , MA is a metal which is selected from a group consisting of titanium (III), vanadium, chromium, molybdenum and tungsten, and k equals 0 or 1, or with hafnocene (A2), and B) is at least one polymerisation catalyst based on a ferrous component with a tridentate ligand containing at least two ortho-, ortho-disubstituted aryl radicals (B).

EFFECT: obtaining polyethylene with good mechanical properties, possibility for processing and high content of vinyl groups.

27 cl, 12 ex, 2 tbl, 5 dwg

FIELD: chemistry.

SUBSTANCE: invention relates to high-strength bimodal polyethylene compositions which are meant for preparing compositions for pipes, particularly high-strength compositions for pipes. The composition has density equal to or greater than 0.940 g/cm3, overall polydispersity index equal to or greater than 25 and contains a high-molecular polyethylene component and a low-molecular polyethylene component. The ratio of weight-average molecular weight of the high-molecular component to the weight-average molecular weight of the low-molecular component of the composition is equal to or greater than 30. The weight-average molecular weight of the low-molecular polyethylene component ranges from 5000 to 30000. The composition is classified as PE 100 material, has proper balance of properties such as strength and hardness, as well as good processing properties. A pipe made from the composition which has undergone internal strength tests has extrapolated stress equal to or greater than 10 MPa when the internal strength curve of the pipe is extrapolated to 50 or 100 years in accordance with ISO 9080:2003(E).

EFFECT: increased strength of products.

15 cl, 6 tbl, 10 ex

FIELD: rubber materials, polymers.

SUBSTANCE: invention relates to composition based on ethylene-propylene or ethylene-propylenediene rubber and copolymer of ethylene and octyne that is used as an inter-strand filling agent in cables. Method involves preparing the composition containing the following components, mas. p. p.: rubber, 100; copolymer of ethylene and octyne, 25-55; paraffin, 50-170; stearic acid, 4-30; dibutyl phthalate, 4-25; chalk, 500-1600. The composition can comprise aluminum trihydrate additionally, 180-270 mas. p. p. per 100 mas. p. p. of rubber. Invention provides enhancing electric, physical and technological indices of materials used for filling cable articles.

EFFECT: improved and valuable properties of composition.

1 ex

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