Classifications

• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L23/00—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers
  • C08L23/02—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers not modified by chemical after-treatment
  • C08L23/04—Homopolymers or copolymers of ethene
  • C08L23/06—Polyethylene
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
  • C09D123/00—Coating compositions based on homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Coating compositions based on derivatives of such polymers
  • C09D123/02—Coating compositions based on homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Coating compositions based on derivatives of such polymers not modified by chemical after-treatment
  • C09D123/04—Homopolymers or copolymers of ethene
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L23/00—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers
  • C08L23/02—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers not modified by chemical after-treatment
  • C08L23/18—Homopolymers or copolymers of hydrocarbons having four or more carbon atoms
  • C08L23/20—Homopolymers or copolymers of hydrocarbons having four or more carbon atoms having four to nine carbon atoms
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
  • F16L—PIPES; JOINTS OR FITTINGS FOR PIPES; SUPPORTS FOR PIPES, CABLES OR PROTECTIVE TUBING; MEANS FOR THERMAL INSULATION IN GENERAL
  • F16L9/00—Rigid pipes
  • F16L9/12—Rigid pipes of plastics with or without reinforcement
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L2203/00—Applications
  • C08L2203/18—Applications used for pipes
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L2205/00—Polymer mixtures characterised by other features
  • C08L2205/02—Polymer mixtures characterised by other features containing two or more polymers of the same C08L -group
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/13—Hollow or container type article [e.g., tube, vase, etc.]
  • Y10T428/1352—Polymer or resin containing [i.e., natural or synthetic]
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/13—Hollow or container type article [e.g., tube, vase, etc.]
  • Y10T428/1352—Polymer or resin containing [i.e., natural or synthetic]
  • Y10T428/1397—Single layer [continuous layer]

Definitions

• the present invention relates to a polyethylene molding compound with a bimodal molar mass distribution and a high-strength tube made from this molding compound.
• Polyethylene is used extensively for the production of pipes, for example for gas and water transport systems, because a material with particularly high mechanical strength, high corrosion resistance and absolutely reliable long-term durability is required for such pipes. Numerous publications describe materials with a wide variety of properties and processes for their manufacture.
• EP-A-603,935 already describes a molding compound based on polyethylene which has a bimodal molar mass distribution and which is said to be suitable, inter alia, for the production of pipes. Pipes made from the molding compositions according to this reference, however, still leave something to be desired in terms of their internal pressure resistance, their resistance to stress, their low-temperature impact strength and their resistance to rapid crack growth.
• the object of the present invention was to develop a polyethylene molding compound with which even better strength of the pipes produced therewith can be achieved compared to the known pipe material of the strength class PE 100 according to ISO / DIS 9080.
• the invention also relates to a pipe made of this molding composition with very outstanding mechanical properties and its use for the construction of gas and water pipes.
• the polyethylene molding compound according to the invention has a
• the polyethylene can be low Contain proportions of up to 5 wt .-% of further monomer units with 4 to 10 carbon atoms. Examples of such comonomers are 1-butene, 1-pentene, 1-hexene or 4-methylpentene-1.
• the bimodality can be described as a measure of the position of the centers of gravity of the two single molar mass distributions with the aid of the viscosity numbers (VZ) according to ISO / R 1191 of the polymers formed in two successive polymerization stages.
• VZi of the low molecular weight polyethylene formed in the first polymerization stage is 40 to 90 cm 3 / g, while the VZi as a whole is in the range from 300 to 450 cm 3 / g.
• VZ 2 of the high molecular weight polyethylene formed in the second polymerization stage can be calculated using the following mathematical formula:
• wi stands for the weight fraction of the low molecular weight polyethylene formed in the first stage, measured m% by weight, based on the total weight of the polyethylene formed in both stages with a bimodal molar mass distribution.
• the value calculated for VZ 2 is normally in the range
• the molding compound according to the invention has long-term properties which go beyond the requirement of the quality class PE 100 according to ISO / DIS 9080 of 10.0 MPa after 50 a as LCL (Lower critical confidence limit), determined according to the extrapolation method.
• LCL Lower critical confidence limit
• the polyethylene molding composition according to the invention achieves an extraordinarily high resistance to slow crack growth with the necessary higher rigidity and with higher yield stress. turn. This high resistance to stress cracking is evident from the fact that bursts could not be observed during the LTHS (Long Term Hydrostatic Strength) internal pressure test on pipes made from the molding material according to the invention within a time interval of 5 33,000 h at a temperature of 80 ° C.
• LTHS Long Term Hydrostatic Strength
• the polyethylene is obtained by polymerizing the monomers in suspension, in solution or in the gas phase at temperatures in the range from 20 to 120 ° C., a pressure in the range from 2 to 60 bar and in the presence of a Ziegler catalyst which consists of a transition metal compound and an organic aluminum compound is composed.
• the polymerization is carried out in two stages connected in series, the molar mass of the polyethylene in each stage being regulated with the aid of hydrogen.
• the polyethylene molding composition according to the invention can contain other additives in addition to the polyethylene.
• additives are, for example, heat stabilizers, antioxidants, UV absorbers, light stabilizers, metal deactivators, peroxide-destroying compounds, basic costabilizers in amounts of 0 to 10% by weight, preferably 0 to 5% by weight, but also fillers, reinforcing agents, Plasticizers, lubricants.
• the pipe according to the invention is produced by first plasticizing the polyethylene molding compound in an extruder at temperatures in the range from 200 to 250 ° C. and then pressing it out and cooling it through an annular die.
• Pipes of the type according to the invention are generally suitable for all pressure classes in accordance with DIN 8074.
• Both conventional single-screw extruders with a smooth feed zone and high-performance extruders with a finely grooved cylinder and effective feed can be used for processing into pipes.
• the decompression screws have a discharge zone in which temperature differences in the melt are compensated for and in which the relaxation stresses caused by shear are to be reduced.
• the melt coming from the extruder is first distributed to a ring cross section via conically arranged bores and then fed to the mandrel / mouthpiece combination via a spiral distributor or a sieve basket.
• retaining rings or other construction elements can be installed in front of the nozzle outlet to even out the melt flow if necessary.
• Pipe diameters expediently by vacuum calibration.
• the actual shape takes place with slotted Kalib ⁇ erhulsen, which are made of non-ferrous metal for better heat dissipation.
• the water film supplied in the inlet ensures that the water cools down quickly
• the total length L of the cooling section is measured on the assumption that a melt with a temperature of 220 ° C with the help of water with a
• Temperature of 15 to 20 ° C should be cooled down to such an extent that the temperature of the inner surface of the pipe is a maximum of 85 ° C.
• the stress crack resistance is a feature that is already known from EP-A 436 520.
• the process of slow crack growth can be significantly influenced by molecular structural parameters such as molecular weight and comonomer distribution become.
• the number of so-called composite molecules is initially determined by the chain length of the polymer.
• the morphology of partially crystalline polymers is additionally adjusted by incorporating comonomers, because the thickness of crystallite lamellae can be influenced by introducing short-chain branches. This means that the number of composite molecules, so-called "tie molecules”, is higher in copolymers than in homopolymers with a comparable chain length.
• a shortening of the time to failure is achieved by shortening the crack repair time due to the notch (1.6 mm / razor blade) of ethylene glycol as a medium requiring tension at a temperature of 80 ° C and a tensile stress of 5 MPa.
• the sample is produced by saying three test specimens with the dimensions 10 x 10 x 90 mm from a 10 mm thick press plate. The test specimens are all around with a
• the notch depth is 1.6 mm.
• the fracture toughness of the pipe according to the invention is also determined using an internal measurement method on test specimens with the dimensions 10 ⁇ 10 ⁇ 80 mm, which were said from a 10 mm thick press plate. In the already notch device mentioned, six of these specimens are scored with the razor blade in the middle. The notch depth is 1.6 mm. Carrying out the measurement largely corresponds to the Charpy measurement procedure according to ISO 179 with modified test specimens and modified impact geometry (abutment spacing). All test specimens are heated to the measuring temperature of 0 ° C. over a period of 2 to 3 hours. A test specimen is then drafted onto the abutment of a pendulum impact tester in accordance with ISO 179. The abutment distance is 60 mm.
• the fall of the 2 J hammer is drawn, whereby the fall angle is set to 160 °, the pendulum length to 225 mm and the impact speed from 2.93 m / sec.
• the quotient of the impact energy used and the initial cross-sectional area at the notch a FM is calculated in mJ / mm 2 . Only values for complete breakage and hinge breakage can serve as the basis for a common mean (see ISO 179).
• the impact value IS0 is measured according to ISO 179.
• the dimension of the sample is 10 x 4 x 80 mm, whereby a V-notch is grooved with an angle of 45 °, a depth of 2 mm and a notch base radius of 0.25 mm.
• the bending creep modulus is measured as a one-minute value according to DIN 54852-Z4.
• the S4 test (Small Scale Steady State - Test) is used to determine the resistance of the pipe to rapid crack propagation and is carried out on pipes with the dimension PN 10 with a diameter of 110 mm. The exact procedure is described in ISO / DIS 13477. This method determines the critical pressure p c in bar, above which the pipe under this pressure p c is determined rips open along the entire length.
• Example 1 (according to the invention):
• a polyethylene molding compound was produced using a Ziegler catalyst and in accordance with the specification in WO 91/18934, while observing the operating conditions given in Table 1 below:
• the polyethylene molding compound produced in this way had one Melt flow index MFI 5 / i9 0 oc of 0.18 dg / mm, measured according to ISO 11 33, and a density d of 0.950 g / cm 3 .
• the polyethylene was subjected to a preparative TREF analysis (Temperature Rismg Elution Fractionation) for even better characterization. This method of analysis is a very useful tool for determining the comonomer distribution in partially crystalline polyethylene and was published by L. Wild and T. Ryle under the title: "Crystallyzation dist ⁇ bution in Polymers: A new analytical technique" in poly. Prep. Am Chem. Soc, Polym.
• GPC Gel Permeation Chromatography
• FIG. 1 shows the result of a combined TREF-GPC analysis with the polyethylene molding composition according to the invention.
• the polyethylene produced according to Example 1 as described above was first dissolved in p-xylene (boiling point: 138 ° C.) as indicated above and then deposited on a Chromosorb P carrier material by cooling. Then fractions were formed at temperatures of 60, 70, 78, 83, 86, 89, 93, 100 and 110 ° C by elution. Then the fraction was dissolved at 78 ° C ⁇ 3 K and the therein Polymer content performed a GPC analysis.
• Peak 1 shows the low molecular weight, highly crystalline PE fraction with a small thickness of the crystallite lamellae soluble at 78 ° C, while Peak 2 is caused by a portion with a larger molar mass, but at the same time a high portion of comonomer incorporation and thus also lower crystallinity.
• This product fraction falling under peak 2 is responsible for the high number of so-called “tie molecules” between the crystallite lamellae and thus for the extraordinarily high resistance to stress cracking of the tube produced from the molding composition according to the invention.
• the polyethylene produced according to Example 1 as described above was plasticized in an extruder with a diameter of 48 mm and a length corresponding to 24.4 times the diameter (117.12 cm) at a temperature of 227 ° C. and then through an annular Extruded nozzle with an outer diameter of 32.1 mm and a mandrel with a diameter of 26.5 mm to a tube with a diameter of 32.1 mm and a wall thickness of 3.08 mm with the aid of a vacuum calibration.
• the cooling took place in a cooling bath with a length of 3 m, which was kept at a temperature of 15.degree.
• Table 2 The properties measured on the finished pipe are given in Table 2 below.
• a pipe made of polyethylene was produced in accordance with the information from Example 1 of EP-A-739 937.
• the properties measured on the pipe are also summarized in Table 2 below.
• the abbreviations of the physical properties in Table 2 have the following meaning:
• BKM bending creep modulus, measured according to ISO 54852-Z4 in N / mm 2 as a one-minute value
• BZ fracture toughness measured according to the previously described internal measuring method at 0 ° C in mJ / mm 2 ,
• - KSZ IS0 impact strength, measured according to ISO 179 / DIN 53453 in mJ / mm 2 at -20 ° C and at +23 ° C,
• VBK processability, measured as extruder throughput for an extruder with a diameter D of 48 mm and a length L of 24.4 D at a constant screw speed of 80 revolutions per mm in kg / h,
• p c resistance to rapid crack growth, measured according to the S4 test in bar on pipes of pressure class PN 10 with a diameter of 110 mm.

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• Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Engineering & Computer Science (AREA)
• Medicinal Chemistry (AREA)
• General Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Health & Medical Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Life Sciences & Earth Sciences (AREA)
• Polymers & Plastics (AREA)
• Wood Science & Technology (AREA)
• Mechanical Engineering (AREA)
• Addition Polymer Or Copolymer, Post-Treatments, Or Chemical Modifications (AREA)
• Rigid Pipes And Flexible Pipes (AREA)
• Compositions Of Macromolecular Compounds (AREA)
• Manufacture Of Macromolecular Shaped Articles (AREA)
• Laminated Bodies (AREA)

Priority Applications (8)

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• 1999
  • 1999-06-30 DE DE19929812A patent/DE19929812A1/de not_active Withdrawn
• 2000
  • 2000-06-20 EP EP00945778A patent/EP1192216B1/de not_active Revoked
  • 2000-06-20 KR KR1020017016727A patent/KR100703580B1/ko not_active Expired - Fee Related
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  • 2000-06-20 AU AU59750/00A patent/AU768098B2/en not_active Ceased
  • 2000-06-20 WO PCT/EP2000/005651 patent/WO2001002480A1/de not_active Ceased
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• 2001
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• 2011
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