Moulding composition prepared from polyethylene with multimodal molecular weight distribution for making pipes with improved mechanical properties

FIELD: chemistry.

SUBSTANCE: invention relates to a moulding composition prepared from polyethylene with multimodal molecular weight distribution for making pipes, as well as a method of preparing said moulding composition via a multi-step sequence of reactions, comprising a sequence of polymerisation steps in the presence of a catalyst system, including a Ziegler catalyst and a cocatalyst. The composition contains 45-55 wt % ethylene homopolymer A with low molecular weight, 20-40 wt % high-molecular copolymer B consisting of ethylene and another olefin with 4-8 carbon atoms in amount of 1-8 wt % per weight of the high-molecular copolymer, and 15-30 wt % ethylene copolymer C with ultra-high molecular weight, containing 1-8 wt % of the weight of the ultra-high molecular weight copolymer C, ethylene and one or more olefins with 4-8 carbon atoms.

EFFECT: during storage, the composition has high processability as starting material for making pipes, has a good combination of properties, such as resistance to stress cracking caused by external conditions and mechanical strength, especially during a long period of time.

5 cl, 2 tbl, 2 ex

 

The present invention relates to molding compositions of polyethylene, which has a multimodal molecular weight distribution and is particularly suitable for receiving the pipe, as well as to a method for producing such a molding composition through multi-stage sequence of reactions consisting of successive stages of polymerization, in the presence of a catalytic system comprising a catalyst of Ziegler and socialization.

The expression "molding composition of polyethylene, which has a multimodal molecular weight distribution", or simply "polyethylene having a polymodal molecular weight distribution" refers to the injection of the composition, of polyethylene or polyethylene with a multimodal curve of the molecular mass distribution, i.e. polyethylene, includes many factions of the ethylene polymer, and each of them has a certain molecular weight. For example, according to a preferred variant implementation of the present invention the polyethylene with a multimodal molecular weight distribution can be obtained through multi-stage sequence of reactions consisting of successive stages of polymerization, carried out at predefined, different polymerization conditions in the respective R is the actors arranged in series so as to obtain the corresponding fractions of polyethylene with different molecular weights. A method of this type can be implemented in suspension medium: in this case, the monomers and the molecular weight regulator, preferably hydrogen, first polymerized in the first reactor under conditions for the first reaction in the presence of a suspension medium and a suitable catalyst, preferably a Ziegler catalyst, then transferred to the second reactor and polimerizuet further, when the conditions for the second reaction, and if the polyethylene, which should be readily available, has tramadolum molecular weight distribution, then transferred to the third reactor, and then polimerizuet when the conditions for the third reaction, and the conditions of the first reaction differ from the terms of the second and third reactions so to obtain three fractions of polyethylene with different molecular weights. This difference of molecular weight for different fractions of ethylene polymer are usually estimated using srednevekovoi molecular mass Mw.

Although the Ziegler catalysts are particularly suitable for the preferred applications of the present invention, it is also possible to use other catalysts, for example catalysts with similar catalytic center (or catalysts with single cent the om polymerization on the metal), for example metallocene catalysts.

Polyethylene is used in large quantities for the production of pipes that require a material with high mechanical strength, low tendency to undergo creep and high resistance to cracking under stress caused by external conditions. At the same time the material must be able to easily recycle and must be acceptable to the organoleptic level to use for the production of pipes for drinking water.

Molding compositions of polyethylene with a unimodal or modal molecular weight distribution, i.e. consisting of one faction of the ethylene polymer with predetermined molecular weight, have drawbacks either in respect of their ability to recycle or related to their resistance to cracking under stress caused by external conditions, or their mechanical strength.

Compared with them, molding compositions with a bimodal molecular weight distribution are technical step forward. They can be recycled more easily and, at the same time, at a density close to the density of the composition with modal molecular weight distribution, they have much better resistance to cracking under the action of the NAP is agenia, caused by external conditions, and higher mechanical strength.

Patent EP-A 739937 describes a pipe, consisting of such molding compositions based on polyethylene with a bimodal molecular weight distribution, which can be easily recycled and, nevertheless, possesses good mechanical properties.

The purpose of the present invention was to provide a molding composition based on polyethylene, which, while maintaining a good ability to recycle when it is used as a source material for pipes has the best combination of properties, associated with resistance to cracking under stress caused by external conditions, mechanical strength, particularly over a long period of time, as well as properties associated with its processing.

To reach this aim, using the molding composition of polyethylene with a multimodal molecular weight distribution, comprising from 45 to 55 weight % ethylene homopolymer And low (low) molecular weight, from 20 to 40 weight % high molecular weight copolymer containing ethylene and another olefin with the number of carbon atoms from 4 to 8, and from 15 to 30 percent by weight ethylene copolymer C is extremely high (high) molecular weight, where all percentage Pref is found relative to the total weight of the molding composition.

The expression "ethylene Homo-polymer And low molecular weight", "high molecular weight copolymer and the ethylene copolymer C, with an extremely high molecular weight" refers to the ethylene homopolymer And the ethylene copolymer and the ethylene copolymer With respectively differing increasing molecular mass.

The invention additionally relates to a method for producing such a molding composition during cascade suspension polymerization and pipes, consisting of such molding compositions, which has exceptional properties in respect of mechanical strength in combination with high rigidity.

Molding composition, of polyethylene according to this invention has a density at 23°C in the range from 0,945 to 0,957 g/cm3preferably from 0,945 to 0,955 g/cm3more preferably from 0,948 to 0,955 g/cm3and tri-modal molecular weight distribution. The copolymer with high molecular weight includes monomer units of additional olefin with the number of carbon atoms from 4 to 8 in number from 1 to 8 weight % relative to the weight of the high molecular weight copolymer Century Examples of such comonomers are 1-butene, 1-penten, 1-hexene, 1-octene and 4-methyl-1-penten. Ethylene copolymer With extremely you the Oka molecular weight also includes one or more of the above-mentioned comonomers in the number(s), reside(s) in the range from 1 to 8 weight % by weight of the ethylene copolymer With an extremely high molecular weight.

Such preferred amounts of the comonomers can achieve improved resistance to cracking under stress caused by external conditions. Within these preferred ranges molding composition from predominantly polyethylene has additionally improved combination of mechanical properties.

In addition, the molding composition according to this invention has a melt flow index according to ISO 1133, expressed by the value of the MFI190/5in the range from 0.1 to 0.8 DG/min, in particular from 0.1 to 0.5 DG/min, and the viscosity VNtotdetermined according to ISO/R 1191 in decaline at a temperature of 135°C, in the range from 200 to 600 cm3/g, in particular from 250 to 550 cm3/g, particularly preferably from 350 to 490 cm3/year

Trimodality as a quantitative indicator of the positions of the centers of gravity of three individual molecular-mass distributions can be described using the following viscosities VN according to ISO/R 1191 for polymers produced during the following one after the other stages of polymerization. This document should pay attention to the following characteristics of the polymers obtained in the course and the individual reaction stages:

Given viscosity VN1determined for the polymer after the first stage polymerization is identical to the viscosity VNApolyethylene And low molecular weight and is in accordance with this invention in the range from 50 to 120 cm3/g, in particular from 60 to 100 cm3/year

Given viscosity VN2determined for the polymer after the second stage polymerization, does not correspond to VNInpolyethylene with a relatively high molecular weight, produced during the second stage of polymerization, but, instead, represents the present, the viscosity of the mixture of polymer And polymer Century According to this invention VN2is in the range from 200 to 400 cm3/g, in particular from 250 to 350 cm3/year

Given viscosity VN3determined for the polymer after the third stage polymerization, does not correspond to VNWithcopolymer With an extremely high molecular weight, obtained during the third stage polymerization, which, moreover, can only be determined mathematically, but, instead, represents the present, the viscosity of the mixture of polymer And polymer and polymer C. According to this invention VN3is in the range from 200 to 600 cm3/g, in particular from 250 to 550 cm3/g, particularly preferably from 350 to 490 cm3 /year

The polyethylene can be obtained by polymerization of monomers in suspension at temperatures in the range from 70 to 100°C., preferably from 75 to 90°C., at a pressure in the range from 2 to 10 bar and in the presence of a highly active Ziegler catalyst, which consists of compounds of the transition metal and alyuminiiorganicheskikh connection. The polymerization can be carried out in three stages, that is, in three successive stages, and consequently the molecular weight at each stage of the regulate control of molecular weight, preferably using hydrogen.

In particular, it is preferable that the polymerization process was carried out using the highest hydrogen concentration specified in the first reactor. It is desirable that in the future, additional reactors, the hydrogen concentration is gradually lowered so that the concentration of hydrogen in the second reactor was lower than the hydrogen concentration in the second reactor. Preferably, in the second reactor and the third reactor used a pre-specified concentration of co monomer, preferably increasing when moving from the second reactor to the third reactor. As stated above, on stages, on which they receive a fraction of the copolymer, preferably in the second reactor and the third reactor, the monomer used, in affect, is, ethylene, as well as co monomer is preferable to use an olefin with the number of carbon atoms from 4 to 8.

Preferably, the molecular weight distribution of the molding composition, of polyethylene according to the present invention was tri-modal. Thus, it is possible to obtain the above-mentioned favorable combination of properties without undue complication of the manufacturing process through the use of three consecutive reactors, successfully keeping as a consequence, the size of the installation is somehow limited. Thus, to obtain a molding composition, of polyethylene with a tri-modal molecular weight distribution is desirable that the polymerization of ethylene was carried out during a continuous process, carried out in three series-connected reactors, where three reactors respectively specify different reaction conditions. Preferably, the polymerization was carried out in suspension: it is desirable that in the first reactor together with the suspension medium, socialization, ethylene and hydrogen were served a suitable catalyst such as a Ziegler catalyst.

It is advisable to comonomer not introduced into the first reactor. The suspension from the first reactor was then transferred to the second reactor, which is injected ethylene, hydrogen, and preferably also some pre for the data amount of the co monomer, for example 1-butene. Preferably, the amount of hydrogen supplied to the second reactor, reduced in comparison with the amount of hydrogen fed to the first reactor. The slurry from the second reactor is transferred into the third reactor. In the third reactor is injected ethylene, hydrogen and, preferably, a predefined number of co monomer, such as 1-butene, preferably in a quantity higher than the number of co monomer in the second reactor. The amount of hydrogen in the second reactor is reduced compared to the amount of hydrogen in the second reactor. From the suspension of the polymer, leaving the third reactor, separating the suspension medium and the resulting polymer powder is dried and, preferably, that it was then granulated.

The polyethylene produced by polymerization of monomers, for example, in suspension, preferably at temperatures in the range from 70 to 90°C., preferably from 80 to 90°C. the preferred pressure is in the range from 2 to 20 bar, preferably from 2 to 10 bar. Preferably, when the polymerization is carried out in the presence of a suitable catalyst such as a Ziegler catalyst, preferably sufficiently active to provide a pre-specified performance multistage process and preferably sensitive to hydrogen. Preferably, the Ziegler catalyst consisted of with the organisations of the transition metal and alyuminiiorganicheskikh connection.

Preferred trimodality, that is the preferred tri-modal shape of the curve of the molecular mass distribution can be described in terms of the positions of the centers of gravity of three individual molecular-mass distributions using the viscosities VN according to ISO/R 1191 for polymers obtained from each of the stages of the polymerization.

Preferably, the ethylene Homo-polymer And low molecular weight was gained during the first stage of polymerization: in this preferred embodiment, the above viscosity VN1determined for the polymer obtained from the first stage of polymerization is given by the viscosity of homopolymer And with low molecular weight, and preferably that it was in the range of from 50 to 150 cm3/g, more preferably from 60 to 120 cm3/g, in particular from 65 to 100 cm3/year

According to other variants of the implementation, during the first stage of polymerization can be obtained either high molecular weight ethylene copolymer, or a copolymer With an extremely high molecular weight.

Preferably, high molecular weight ethylene copolymer b received during the second stage polymerization.

According to a particularly preferred variant implementation, in which ethylenemethacrylic And low molecular weight gain during the first stage of polymerization, and high molecular weight ethylene copolymer obtained in the course of the second stage of polymerization, the viscosity VN2determined for the polymer obtained from the second stage of polymerization is given by the viscosity of the mixture of the ethylene homopolymer And with low molecular weight and high molecular weight ethylene copolymer Preferably Century, when VN2is in the range from 70 to 180 cm3/g, more preferably from 90 to 170 cm3/g, in particular from 100 to 160 cm3/year

In this preferred embodiment, on the basis of these specific values VN1and VN2given viscosity VNBhigh molecular weight ethylene copolymer can, for example, be calculated using the following empirical formula:

where w1represents the weight fraction of the ethylene homopolymer with low molecular weight, formed during the first stage of polymerization, as measured in weight percent of the total mass gained during the first two stages of polyethylene with a bimodal molecular weight distribution.

Preferably, the ethylene copolymer With an extremely high molecular weight was obtained during the third stage of polymerization: in this preferred embodiment, and in the other the options of implementation, in which set the perfect order of polymerization, the viscosity VN3determined for the polymer produced in the third stage of polymerization, is a given viscosity of the mixture of ethylene homopolymer And with low molecular weight, high molecular weight ethylene copolymer and the ethylene copolymer With an extremely high molecular weight. It is desirable that the value VN3was within already defined above preferred boundaries, i.e. from 150 to 300 cm3/g, preferably from 150 to 280 cm3/g, more preferably in the range from 180 to 260 cm3/g, in particular in the range from 180 to 240 cm3/year

In this preferred embodiment, on the basis of these specific values VN2and VN3given viscosity VNWithcopolymer With an extremely high molecular weight, obtained during the third stage polymerization can be, for example, be calculated using the following empirical formula:

where w2represents the weight fraction of polyethylene with a bimodal molecular weight distribution formed in the course of the first two stages of polymerization, as measured in weight percent of the total mass of polyethylene with tramadolum molecular weight distribution obtained is during all three stages.

Although the method of calculation of viscosities for each fraction of the ethylene polymer molding compositions of polyethylene given in respect of the preferred case in which the ethylene Homo-polymer And low molecular weight, high molecular weight copolymer, and accordingly, the copolymer With an extremely high molecular weight get in the order described below, this method of calculation can also be applied to great orders of polymerization. In fact, in any case, regardless of the order received the three factions of the ethylene polymer shows the viscosity of the first fraction of the ethylene polymer is equal to the present viscosity VN1defined for the ethylene polymer obtained in the first stage polymerization, the viscosity of the second fraction of the ethylene polymer can be calculated based on the weights w1the first fraction of the ethylene polymer obtained in the first stage of polymerization, as measured in weight percent of the total weight of polyethylene with a bimodal molecular weight distribution obtained by the first two stages, and of the viscosities VN1and VN2determined for polymers obtained from the second and respectively third stage polymerization, then as the viscosity of the third faction of atilano the second polymer can be calculated by based on the weights w2polyethylene with a bimodal molecular weight distribution obtained during the first two stages, measured in weight percent of the total weight of polyethylene with a tri-modal molecular weight distribution obtained from all three stages, and of the viscosities VN2and VN3determined for polymers obtained from the second and respectively third stage polymerization.

Molding composition, of polyethylene according to the invention may, in addition to polyethylene optionally comprise additional additives. Such additives are, for example, stabilizers, antioxidants, compounds that absorb UV radiation, light stabilizers, metal deactivators, connections, destroying peroxides, basic co-stabilizers in amounts from 0 to 10 weight %, preferably from 0 to 5 weight %, and carbon black, fillers, pigments, preventing the ignition of the compounds or their combinations in total amounts of from 0 to 50 weight % of the total mass of the mixture.

Molding composition according to this invention is particularly suitable for the production of pipes.

To obtain a pipe molding composition according to this invention can be processed, in particular by extrusion process, and it has shock the strength to notches (ISO) in the range from 8 to 14 kJ/m 2and resistance to cracking under stress caused by external conditions (ESCR)>500 hours

Impact strength of a specimen with notchISOdetermined according to ISO 179-1/1eA/DIN 53453 at a temperature of -30°C. the sample Sizes are 10×4×80 mm made on sample V-shaped notch with an angle of 45°, a depth of 2 mm and a radius at the base of a cut equal to 0.25 mm

The resistance of the molding compositions according to this invention to cracking under stress caused by external conditions (ESCR) is determined by way of internal dimensions, and are in hours. This laboratory method is described by the author M. Fleiβner in Kunststoffe 77 (1987), p. 45 ff and complies with the ISO/CD 16770, which has since began to use. This publication shows that there is a correlation between the tendency of cracks to slow growth during creep testing for perifericheskie notched bars for testing and area light splitting with long-term testing at high pressure according to ISO 1167. Reducing the time to fracture achieve a reduction in time of crack initiation through the incision (1.6 mm, razor blade) in aqueous solution Alkopal with a concentration of 2%, is used as an environment conducive to cracking under stress caused by external conditions, at a temperature of 80 the C and the tensile strength of 4 MPa. Samples were obtained by cutting out three test specimens with a size of 10×10×90 mm from the pressed plate with a thickness of 10 mm samples for testing, make incisions peripheral way in the center with the help of razor blades in the apparatus for Ascania own production, designed for this purpose (see Fig. 5 publications). The depth of the cuts is 1.6 mm

Example 1

Polymerization of ethylene was conducted as part of the continuous process in three consecutive reactors. The Ziegler catalyst, which was obtained by the method described in WO 91/18934, example 2, and which possessed a working number 2.2 in the document WO, was introduced in the first reactor in the amount of 15.6 mmol/h together with adequate suspension medium (hexane), triethylaluminium as socializaton in the amount of 240 mmol/h, ethylene and hydrogen. The number of ethylene (= 68,9 kg/h) and the amount of hydrogen (= 62 g/h) was set so that in the space for the gas in the first reactor, the ethylene content was 24 %by volume, and the hydrogen content amounted to 66.5 %by volume, the remainder was a mixture of nitrogen and vapor suspension medium.

The polymerization in the first reactor was carried out at a temperature of 84°C.

Then the suspension from the first reactor was transferred into the second reactor, in which the content of hydrogen in space for gas omegalite of 0.7 % by volume and in which filed ethylene in amounts to 43.2 kg/h with 1-butene in the number 1470 g/H. Reduce the amount of hydrogen was achieved by using an intermediate vent hydrogen. 73,5 % by volume of ethylene, of 0.7 % by volume of hydrogen and 4.8 % by volume of 1-butene were dosed out in space for gas in the second reactor, the remainder was a mixture of nitrogen and vapor suspension medium.

The polymerization in the second reactor was carried out at a temperature of 85°C.

The slurry from the second reactor was transferred by means of additional intermediate discharge pressure of hydrogen in the third reactor, through which the amount of hydrogen in the space for the gas in the third reactor was set equal to 0 vol %.

Ethylene in the amount of 24.3 kg/h with 1-butene in the amount of 475 g/h was applied in the third reactor. 72 vol % of ethylene, 0 % by volume of hydrogen and 5.3 % by volume of 1-butene were dosed out in space for gas in the third reactor, the remainder was a mixture of nitrogen and vapor suspension medium.

The polymerization in the second reactor was carried out at a temperature of 84°C.

Long-term activity of the catalyst for polymerization required for the above-described sequential operation method, achieved with the help of specially obtained Ziegler catalyst with the composition specified in the first mentioned document WO. Measure the suitability of the catalyst for use is its extremely high off the to hydrogen and its high activity, which remains constant over a long period of time from 1 to 8 hours.

The suspension medium was separated from the suspension of the polymer, leaving the third reactor, the powder was dried and granulated.

Pipe with dimensions of 110×10 mm was obtained from a granular material on the machine for the extrusion of pipes from Battenfeld in the performance of 200 kg/h and the melting point of 212°C. the Tube obtained in this way had a completely smooth surfaces.

Given viscosity and share wA, wBand wCpolymer a, b and C for injection molding of the composition, of polyethylene, obtained as described in example 1 are shown in table 1 below.

Table 1
Example1
wA[weight %]50
wB[weight %]32
wC[weight %]18
VN1[cm3/g]80
VN2[cm3/g]305
VNtot[cm3/g]450
3100
MFR [g/10 min]0,32
Density [g/cm3]0,947
Creep testing in tension (5 MPas/23°C)elongation [%]1,72
AZN [kJ/m2]13,7

Abbreviations for physical properties in tables 1 and 2 have the following meanings:

- FNCT = resistance to cracking under stress caused by external conditions (full creep testing at the cuts), determined using the method of internal dimensions, described by the author M. Fleiβner in [h], conditions: 80°C, 2.5 MPa, water/Arkopal with a concentration of 2%.

- AZN = impact strength of a specimen with notchISOaccording to ISO 179-1/1eA/DIN 53453 at a temperature of -30°C, represented in units of kJ/m2.

- Creep testing in tension in accordance with DIN EN ISO 899 at 23°C and a voltage of tensile 5 MPa; the figure represents the elongation in % after 96 hours

Comparative example

Polymerization of ethylene was conducted as part of the continuous process in two consecutive reactors. In the first reactor was introduced the same cat is the lyst Ziegler, as in example 1, which was obtained by the method described in WO 91/18934, example 2, and which possessed a working number 2.2 in the document WO, in the amount of 15.6 mmol/h together with adequate suspension medium (hexane), triethylaluminium as socializaton in the amount of 240 mmol/h, ethylene and hydrogen. The number of ethylene (=68,9 kg/h) and the amount of hydrogen (=62 g/h) was set so that in the space for the gas in the first reactor, the ethylene content was 24 %by volume, and the hydrogen content amounted to 66.5 %by volume, the remainder was a mixture of nitrogen and vapor suspension medium.

The polymerization in the first reactor was carried out at a temperature of 84°C.

Then the suspension from the first reactor was transferred into the second reactor, in which the content of hydrogen in the space for the gas reduced to 0.7 % by volume and in which filed ethylene in the number 76,1 kg/h with 1-butene in the number of 2300 g/h reduce the amount of hydrogen was achieved by using an intermediate vent hydrogen. 78 % by volume of ethylene, 0,7 vol % hydrogen and 6 % by volume of 1-butene were dosed out in space for gas in the second reactor, the remainder was a mixture of nitrogen and vapor suspension medium.

The polymerization in the second reactor was carried out at a temperature of 84°C.

Long-term activity of the polymerization catalyst required is Oh for the above-described sequential operation method, reached accordingly with the help of specially obtained Ziegler catalyst with the composition specified in the first mentioned document WO. Another advantage of this catalyst is its extremely high response to hydrogen and its high activity, which remains constant over a long period of time from 1 to 8 hours.

The suspension medium was separated from the suspension of the polymer, leaving the second reactor, the powder was dried and granulated.

Pipe with dimensions of 110×10 mm was obtained from a granular material on the machine for the extrusion of pipes from Battenfeld. The surface of the tubes were completely smooth.

Given viscosity and share wAand wBpolymer a and b for injection molding of the composition of polyethylene with a bimodal distribution of the comparative example are shown in table 2 below.

Table 2
Comparative example
wA[weight %]47,5
wB[weight %]52,5
VN1[cm3/g]80
VN2[cm3/g] 370
FNCT (4 MPa/80°C) [h]1270
Creep testing in tension (5 MPas/23°C)elongation [%]1,67
MFR (190/5) [g/10 min]0,32
TSA (-30°C) [kJ/m2]12,3
Density [g/cm3]0,948

Comparison with example 1 clearly shows that the polyethylene with a bimodal molecular weight distribution of the comparative example has a much worse mechanical properties, expressed in terms FNCT (= resistance to cracking under stress caused by external conditions) and ACN (= impact strength of a specimen with notch), despite using the same catalyst, in spite of a slightly higher density and despite the same value of MFR. This fact is very unusual, and it can reasonably be explained by the change of the microstructure of the polymer with a tri-modal molecular weight distribution in the source material according to this invention.

1. Molding composition, of polyethylene with multimodal molecular mass distribution to obtain the pipe, which is engages from 45 to 55 wt.% ethylene homopolymer And low molecular weight, from 20 to 40 wt.% high molecular weight copolymer consisting of ethylene and another olefin with the number of carbon atoms from 4 to 8 in number from 1 to 8 wt.% based on the high molecular weight copolymer, and from 15 to 30 wt.% ethylene copolymer With ultra-high molecular weight, containing from 1 to 8 wt.% from the mass of ultra-high molecular weight copolymer With ethylene and one or more olefins with the number of carbon atoms from 4 to 8, where all percentages are given relative to the total weight of the molding composition, and molding the composition, of polyethylene has a reduced viscosity VNtotmeasured in accordance with ISO/R 1191 in decaline at a temperature of 135°C, in the range from 350 to 600 cm3/g and a density at 23°C in the range from 0,945 to 0,957 g/cm3.

2. Molding composition, of polyethylene according to claim 1, which has a melt flow index according to ISO 1133, expressed through the values of MFI190/5in the range from 0.1 to 0.8 DG/min, preferably from 0.1 to 0.5 DG/min

3. Molding composition, of polyethylene according to claim 1, which has a given viscosity VNtotdetermined according to ISO/R 1191 in decaline at a temperature of 135°C, in the range from 200 to 600 cm3/g, preferably from 250 to 550 cm3/g, particularly preferably from 350 to 490 cm3/year

4. The way the floor is placed molding compositions of polyethylene on one or more of claims 1 to 3, which comprises carrying out the polymerization of the monomers in suspension at temperatures in the range from 70 to 100°C., preferably from 75 to 90°C., at a pressure in the range from 2 to 10 bar and in the presence of a highly active Ziegler catalyst, which consists of compounds of the transition metal and alyuminiiorganicheskikh connection and performing the polymerization in three stages in three reactors arranged in series, and the molecular weight polyethylene obtained at an appropriate stage, govern in each case hydrogen.

5. Pipe made from molding compositions of polyethylene on one or more of claims 1 to 3, which is resistant to cracking under stress caused by external conditions, expressed by the magnitude of FNCT, more than 1500 hours, preferably more than 2500 hours, and has impact strength of the specimen with a notch according to DIN 53453 at a temperature of -30°C in excess of 12.5 kJ/m2.



 

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7 cl, 1 tbl, 2 ex

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

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: chemistry.

SUBSTANCE: invention relates to rubber composition based on a ethylene-propylene-diene-monomer (EPDM) containing finely dispersed accelerated quartz (deposited silicon dioxide) and a coloured extruded polymer profile containing said composition which is specifically meant for use in construction and automobile industry. The invention also relates to a method of obtaining the disclosed composition.

EFFECT: polymer profile with low cost and suitable mechanical properties.

14 cl, 9 tbl

FIELD: chemistry.

SUBSTANCE: composition contains from 30 wt % to less than 50 wt % propylene-alpha-olefin copolymer and from more than 50 wt % to 70 wt % styrene block-copolymer. The propylene-alpha-olefin copolymer has at least 70 wt % links formed from propylene, and from 10 to 25 wt % links formed from C2- or C4-C10-alpha-olefin and has heat of fusion less than 37 J/g and melt flow index from 0.1 to 100 g/10 min. The composition has modulus of elasticity in tension less than 20 MPa, ultimate tensile stress of at least 5 MPa and elongation at failure of at least 900% and low relative instantaneous shrinkage.

EFFECT: composition has good physical properties such as elasticity and flexibility, and can also be easily processed using traditional equipment for processing polyolefins.

21 cl, 8 dwg, 2 tbl

FIELD: metallurgy.

SUBSTANCE: composition consists of copolymer of propylene, of first copolymer of ethylene with at least one linear or branched alpha-olefine having 3-8 carbon atoms and of second copolymer of ethylene with at least one linear or branched alpha-olefine having 3-8 carbon atms. Copolymer of propylene has value of poly-dispersity index within ranges from 4.5 to 10 and contents of isotactic penthalogy above 97.5 mol %. Also, said copolymer contains at least 95 wt % (relative to copolymer) links derivative from propylene. The first copolymer - copolymer of ethylene contains from 25 to less, than 40 wt % relative to this copolymer) links derivative from ethylene and is soluble in xylol at 25°C within the ranges from over 85 to 95 wt %, while the second copolymer of ethylene contains from 50 to less 75 wt %relative to this copolymer) links derivative from ethylene and is soluble in xylol at 25°C within the ranges from over 50 to 85 wt %, and possesses characteristic viscosity of fraction soluble in xylol below 1.8 sh/g.

EFFECT: composition possesses good resistance to stress causing whitening, and lustre combined with good balance of mechanical properties.

8 cl, 3 tbl, 2 ex

FIELD: chemistry.

SUBSTANCE: invention relates to a method of nucleating polypropylene resins for enhancing their physical, mechanical and/or optical properties. Method involves mixing a molten polyolefin composition containing 95-99.9 wt % polypropylene resin with polydispersity index P.I. (1) and 0.1-5 wt % of at least one propylene polymer with polydispersity index P.I. (2) greater than or equal to 15, where values of P.I. (1) and P.I.(2) satisfy the inequality P.I.(2)-P.I.(1)≥10. The mixture is then cooled. Polypropylene polymers obtained using the said method can be easily used to produce articles through moulding and extrusion, particularly for making thin-walled articles such as articles made through thermoshaping, extrusion or blow moulding with extrusion.

EFFECT: method significantly lowers the cost of producing nucleated polypropylene resins compared to methods which employ conventional nucleating agents in usual amounts.

7 cl, 6 tbl, 8 ex

FIELD: chemistry.

SUBSTANCE: invention relates to production of elastomeric composite materials modified with variable valence metals. The disclosed method involves high-speed thermal decomposition of metal-containing compounds selected from acetates and formates of variable valence metals in a polymer. The polymer used is an ethylene propylene diene copolymer. The metal-containing compound is incorporated into a polymer matrix before the decomposition process which is carried out in a metal mould which limits access to atmospheric oxygen. The degree of filling the mould is equal to 80-90%.

EFFECT: invention simplifies the technology of producing heat resistant elastomeric articles.

2 dwg,1 tbl, 4 ex

FIELD: chemistry.

SUBSTANCE: rubber antiageing agent and modifier based on ethylene propylene diene rubber is a product of reaction of epoxy diene resin ED-20, epichlorohydrin and aniline in weight ratio 4:1:2.5, respectively, at 150°C.

EFFECT: improved physical-mechanical and adhesion properties of vulcanisates based on ethylene propylene diene rubber.

4 tbl, 1 ex

FIELD: chemistry.

SUBSTANCE: rubber mixture based on ethylene propylene diene rubber SKEPT-40 contains the following, pts. wt: SKEPT-40 100, sulphur 2, zinc oxide 5, stearic acid 1, technical carbon P-234 100, tetramethylthiuram disulphide 1.5, mercaptobenzthiazole 0.5, modifier 2. The modifier is preferably obtained from reacting epoxy diane resin ED-20, epichlorohydrin and aniline in weight ratio 4:1:2.5, respectively, at temperature 150°C.

EFFECT: invention increases rubber adhesion when gluing with chloroprene adhesives 88CA and 88H, improved physical and mechanical properties.

3 tbl, 1 ex

FIELD: chemistry.

SUBSTANCE: composition contains crystalline propyelen polymer, elastomeric copolymer of ethylene and propylene and polyethylene. When combined with components with certain values of polydispersity index and characteristic viscosity in given ratios, the composition exhibits high hardness, impact resistance and resistance to bleaching under loading. The composition has flexural modulus higher than 1300 MPa, resistance to bleaching during impact corresponding to diametre of the bleaching area not greater than 1.7 cm, caused by a die falling from a height of 76 cm and diametre of the bleaching area not greater than 1.2 cm, caused by a die falling from a height of 20 cm, and Izod impact resistance at 23°C greater than 14 kJ/m2 and at least equal to 6.5 kJ/m2 at -20°C.

EFFECT: composition has good balance of mechanical properties, is suitable for making articles through pressure casting, such as casings of batteries and consumer goods, and during hot shaping processes.

2 cl, 4 tbl, 3 ex

FIELD: textile, paper.

SUBSTANCE: heat-shielding material is made of a shaped layer of aramid fibre of non-woven structure with diametre of fibre from 1 to 10 nm, laid between two layers of rubber mix on the basis of ethylene-propylene rubber with further curing in item composition.

EFFECT: invention makes it possible through usage of new nanofibre filler to solve the problem of its recycling on completion of item life cycle.

1 dwg, 1 tbl

FIELD: chemistry.

SUBSTANCE: invention can be particularly used in the cable industry when making electrical cable shielding used in explosive environments, in electrical engineering when making working sheath of earthing electrodes in general-purpose protective earthing systems, protection from static electricity and electrochemical protection from corrosion in the ground, fresh and sea water etc. The rubber mixture contains the following in pts. wt: synthetic ethylenepropylene diene rubber 90-100, technical sulphur 0.3-0.5, paraffin-naphthalene oil 10-15, bis-tertbutylperoxyisopropyl benzene 5.0-6.5, zinc oxide 5-8, electroconductive technical carbon 80-100, carbon-fibre material made from hydrocellulose fibre 15-25. The electrical current conductor comprises at least one conductor which has a shielding or working sheath made from the said rubber mixture.

EFFECT: improved operational characteristics of the electroconductive rubber mixture and electrical current conductors made from the said mixture.

4 cl, 2 tbl, 3 ex

FIELD: chemistry.

SUBSTANCE: composition contains basic polyethylene resin making up at least 90 wt % of all the composition and having time to failure equal to at least 250 hours measured according to ISO 1167 at 95°C and 4.3 MPa. The basic resin contains a copolymer of ethylene with alpha-olefin, containing 4-20 carbon atoms, as fraction (A) and a homopolymer of ethylene or copolymer of ethylene with alpha-olefin, containing 4-20 carbon atoms, as fraction (B). Fraction (A) has lower molecular weight than fraction (B). Density of the basic resin is lower than 940 kg/cm3, and melt flow rate (MFR5) at 190°C/5.00 kg is equal to at least 0.20 g/10 min.

EFFECT: higher pressure resistance at high temperature, as well as improved flexibility of the tube.

12 cl, 1 tbl, 2 ex

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