Title of Invention

"POLYOLEFIN COATED STEEL PIPES"

Abstract Polyolefin coated steel pipes with high dynamic fracture toughness of the coating of the steel pipes during installation handling and in service, consisting of a steel pipe core, optionally an intermediate foamed plastic material, and a polyolefin coating, characterized in that the polyolefin coating consists of (3-nucleated propylene copolymers from 90.0 to 99.9 wt% of propylene and 0.1 to 10.0 wt% of a-olefins with 2 or 4 to 18 carbon atoms with melt indices of 0.1 to 8 g/10 min at 230 °C/2.16 kg, whereby a test polyolefin pipe fabricated from the ß-nucleated propylene copolymer has a critical pressure of >25 bars and a dynamic fracture toughness of >3.5 MNnr3/2.
Full Text The present invention relates to Polyolefin coated steel pipes Field of the invention
The. invention relates to polyolefin coated steel pipes with high dynamic fracture toughness of the coating of the steel pipes during installation handling and in service consisting of a steel pipe core, optionally an intermediate foamed, filled or solid plastic material, and a polyolefin coating, as well as a process for producing them.
Background of the invention
Polyolefin coated steel pipes with a polyolefin coating consisting of linear low density polyethylene (JP 08,300,561), blends of propylene polymers and α-olefin copolymer elastomers (JP 2000,44,909) or syndiotactic polypropylene (JP 08,300,562) are known. The disadvantage of these polyolefin steel coatings is the insufficient dynamic fracture toughness of test pipes fabricated from the coating material. A high dynamic fracture toughness is required for coated steel pipes in order to avoid cracking of the coating during installation handling and in service.
The term installation handling as used herein means any installation technique such as coiling and uncoiling of the ready made pipelines, welding and other jointing techniques and installation at the seabottom for off-shore intallations with specially designed ships, most often to a depth of several hundreds of meters, also to uncertain sea bottom conditions with risk of rock impingements etc. Installation handling of coated steel pipes, in particular for off-shore applications, involves tough conditions for the protective coating layer, including high stress, substantial elongation, surface damages, notches, impact events etc, both at low and high temperature conditions and also at high hydrostatic pressure. The coating layer is not only the layer protecting the pipeline as such from damages as mentioned, it is also doing so in a stage of high stress and/or at elevated temperatures and pressures, making the coating layer most sensitive for cracking, compare in particular the stresses induced during coiling and uncoiling. During the service life of the coated pipeline, the coating has to protect the pipeline from damages and

induced stress and crack formations at conditions close to 0 °C, high hydrostatic pressures where a small damage or notch in the coating could propagate into a large crack putting the pipeline as such at risk. With a high dynamic fracture toughness of the coating material the material will not crack during installation handling and in service.
Object of the invention
It is the object of the present invention to provide polyolefin coated steel pipes with high dynamic fracture toughness of the coating of the steel pipes during installation handling and in service.
Brief description of the invention
According to the present invention, this object is achieved by polyolefin coated steel pipes with dynamic fracture toughness of the coating of the steel pipes during installation handling and in service, consisting of a steel pipe core, optionally an intermediate foamed plastic material, and a polyolefin coating, wherein the polyolefin coating consists of (3-nucleated propylene copolymers from 90.0 to 99.9 wt% of propylene and 0.1 to 10.0 wt% of a-olefins with 2 or 4 to 18 carbon atoms with melt indices of 0.1 to 8 g/10 min at 230 "C/2.16 kg, whereby a test polyolefin pipe fabricated from the B-nucleated propylene copolymer has a critical pressure of >25 bars and a dynamic fracture toughness of >3.5 MNrrf3/2 in the hydrostatic small scale steady state (hydrostatic 84) test at 3 "C.
Detailed description of the invention
The term installation handling as used herein means any installation technique such as
coiling, uncoiling, welding and other jointing techniques.
U-nucleated propylene polymers are isotactic propylene polymers composed of chains in a 3i helical conformation having an internal microstructure of U-form spherulites being composed of radial arrays of parallel stacked lamellae. This microstructure can be realized by the addition of β-nucleating agents to the melt and subsequent crystallization. The presence of the β-form can be detected through the use of wide angle X-ray diffraction
(Moore, J., Polypropylene Hand-book, p. 134-135, Manser Publishers Munich 1996).
According to an advantageous embodiment, the p-nucleated propylene copolymers of the polyolefin coating are p-nucleated propylene block copolymers having an IRr 2:0.97. More preferably, the p-nucleated propylene block copolymers have an IRi 2:0.98, a tensile modulus of 2:1100 MPa at +230C and a Charpy impact strength, notched, > 6 kJ/mz at -20°C. It is even more preferable for the p-nucleated propylene block copolymers to have an IRt of 20.985. The difference of 0.005 in IRt, IRt being a measure for isotacticity, encompasses a significant increase in mechanical polymer properties, especially in stiffness.
The IRt of the propylene polymers is measured and calculated as described in EP 0 277 514 A2 on page 5 (column 7, line 53 to column 8, line 11).
The propylene copolymers for use as coating for steel pipes according to the present invention have melt indices of 0.1 to 8g/10min at 230 "C/2.16 kg, preferably 0.2 to 5g/10minat230°C/2.16kg.
According to a further preferred embodiment the β-nucleated polypropylene block copolymers have a tensile modulus of preferably 2:1300 MPa and most preferably > 1500 MPa at +23 °C.
Charpy impact strength of the β-nucleated propylene copolymers is >6 kJ/m2 at -200C, preferably >9 kJ/m2 at -20°C, most preferably >10 kJ/m2 at -20°C. Charpy impact strength of up to at least 60 kJ/mz is possible for copolymers.
Dynamic fracture toughness calculated from the critical pressure in the hydrostatic small scale steady state (S4) test of test pressure pipes is an important safety parameter for steel pipe polyolefin coating materials with high dynamic fracture toughness of the polyolefin coating of the coating of the steel pipes during installation handling and in service.
The method of determining the dynamic fracture toughness is disclosed in Plastics, Rubber and Composites Processing and Applications, Vol. 26, No. 9, pp.387 ff.
The dynamic fracture toughness KD is calculated directly from the hydrostatic S4 test
critical pressure pc at 3 °C according to following equation:
wherein pc is the critical pressure, D is the diameter of the test pipe and D* is D/t and t is
the wall thickness of the test pipe.
Comparative values for critical pressure [bar] and dynamic fracture toughness [MNm"3/2] for common steel coating materials are approximately 7.44/bar1.5 MNm"3'2 for propylene-ethylene random copolymer. These materials are not suitable as polyolefin coating materials with high crack toughness of the coating of the steel pipes during coiling, uncoiling, installation handling and in service. For the propylene-ethylene random copolymers dynamic fracture toughness is insufficient for the proposed applications in steel pipe coatings.
According to a further embodiment, the li-nucleated propylene block copolymers of the polyolefin coating having an IR* of the propylene homopolymer block of £0.98 are propylene copolymers obtained by polymerization with a Ziegler-Natta catalyst system comprising titanium-containing solid components, an organoalumina, magnesium or titanium compound as cocatalyst and an external donor according to the formula
wherein R and R' are identical or different and are branched or cyclic aliphatic or aromatic hydrocarbon residues, and y and x independently from each other are 0 or 1, provided that x + y are 1 or 2.
A preferred external donor in the Ziegler-Natta catalyst system for producing the B-nucleated propylene block copolymers of the polyolefin coating of the steel pipes is dicyclopentyldimethoxysilane.
According to an advantageous embodiment the B-nucleated propylene copolymers of the polyolefin coating contain 0,0001 to 2,0 wt%, based on the propylene copolymers used,
dicarboxylic acid derivative type diamide compounds from C5-C8-cycioalkyl
monoamines or C6-C12-aromatic monoamines and C5-C8-aliphatic,
C5-C8-cycloaliphatic or C6-Ci2-aromatic dicarboxylic acids, and/or
diamine derivative type diamide compounds from Cj-Ca-cycloalkyl monocarboxylic
acids or C6-C12-aromatic monocarboxylic acids and C5-Cfl-cycloaliphatic or
Ce-Cij-aromatic diamines, and/or
amino acid derivative type diamide compounds from amidation reaction of
C5-C8-alkyl-, C5-C8-cycloalkyl- or C6-C12-arylamino acids, C5-C8-alkyl-,
C5-C8-cycloalkyl- or C6-C12-aromatic monocarboxylic acid chlorides and
C5-C8-alkyl-, C5-C8-cycloalkyl- or C6-C12-aromatic mono-amines, and/or
quinacridone derivative compounds of the type quinacridone compounds,
quinacridonequinone compounds, and/or dihydroquinacridone type compounds,
and/or
dicarboxylic acid salts of metals from group I la of periodic system and/or mixtures
of dicarboxylic acids and metals from group Ha of periodic system, and/or
salts of metals from group lla of periodic system and imido acids of the formula
wherein x = 1 to 4; R = H, -COOH, d-C12-alkyl, C5-C8-cycloalkyl or C6-C12-aryl, and Y = d-Ci2-alkyl, C5-C8-cycloalkyl or C6-Ci2-aryl - substituted bivalent C6-C12-aromatic residues, as ft-nucleating agent.
Examples of the dicarboxylic acid derivative type diamide compounds from C5-C8-cycloalkyl monoamines or C6-C12-aromatic monoamines and C5-C8-aliphatic, C5-C8-cycloaliphatic or CB-Ci2-aromatic dicarboxylic acids, optionally contained in the U-nucleated propylene copolymers of the polyolefin coating of the steel pipe, are - N.N'-di-Cs-Ce-cycloalkyl -2,6-naphthalene dicarboxamide compounds such as
N,N'-dicyclohexyl-2,6-naphthalene dicarboxamide and
N , N'-dicyclooctyl-2 , 6-naphthalene dicarboxamide,
N,N'-di-C5-C8-cycloalkyl-4,4-biphenyldicarboxamide compounds such as

N,N'-dicyclohexyl-4,4-biphenyldicarboxamideand N, N'-dicyclopentyl-4,4-biphenyldicarboxamide,
- N.N'-di-Cs-Cg-cycloalkyl-terephthalamide compounds such as
N,N'-dicyclohexylterephthalamideand
N.N'-dicyclopentylterephthalamide,
- N,N'-di-C5-C8-cycloalkyl-1,4-cyclohexanedicarboxamide compounds such as
N,N'-dicyclohexyl-1,4-cyclohexanedicarboxamide and
N,N'-dicyclohexyl-1,4-cyclopentanedicarboxamide.
Examples of the diamine derivative type diamide compounds from C5-C8-cycloalkyl monocarboxylic acids or Ce-C^-aromatic monocarboxylic acids and C5-C8-cycloaliphatic or C6-Ci2-aromatic diamines, optionally contained in the B-nucleated propylene copolymers of the polyolefin coating of the steel pipe, are
N,N'-C6~C12-arylene-bis-benzamide compounds such as
N,N'-p-phenylene-bis-benzamide and
N,N'-1,5-naphthalene-bis-benzamide,
- N,N'-C5-Ce-cycloalkyl-bis-benzamide compounds such as
N,N'-1,4-cyclopentane-bis-benzamide and
N,N'-1,4-cyciohexane-bis-benzamide.
- N,N'-p-C6-Ci2-arylene-bis-C5-C8-cycloalkylcarboxamide compounds such as
N,N'-1,5-naphthalene-bis-cyclohexanecarboxamide and
N,N'-1,4-phenylene-bis-cyclohexanecarboxamide.
- N,N'-C6-C8-cycloalkyl-bis-cyclohexanecarboxamide compounds such as
N,N'-1,4-cyclopentane-bis-cyclohexanecarboxamide and
N,N'-1,4-cyclohexane-bis-cyclohexanecarboxamide.
Examples of the aminoacid derivative type diamide compounds, optionally contained in the B-nucleated propylene copolymers of the polyolefin coating of the steel pipe, are N-phenyl-5-(N-benzoylamino)-pentaneamide and/or N-cyclohexyl-4-(N-cyclohexylcarbonylamino)-benzamide.
Examples of the quinacridone type compounds, optionally contained in the B-nucleated propylene copolymers of the polyolefin coating of the steel pipe, are quinacridone,
dimethylquinacridone and/or dimethoxyquinacridone.
Examples of the quinacridonequinone type compounds, optionally contained in the (l-nucleated propylene copolymers of the polyolefin coating of the steel pipe, are quinacridonequinone, a mixed crystal of 5,12-dihydro(2,3b)acridine-7,14-dione with quino(2,3b)acridine-6,7,13,14-(5H,12H)-tetrone as disclosed in EP-B 0 177 961 and/or dimethoxyquinacridonequinone.
Examples of the dihydroquinacridone type compounds, optionally contained in the li-nucleated propylene copolymers of the polyolefin coating of the steel pipe, are dihydroquinacridone, dimethoxydihydroquinacridone and/or dibenzodihydroquinacridone.
Examples of the dicarboxylic acid salts of metals from group Ha of periodic system, optionally contained in the li-nucleated propylene copolymers of the polyolefin coating of the steel pipe, are pimelic acid calcium salt and/or suberic acid calcium salt.
Examples of salts of metals from group Ha of periodic system and imido acids of the formula
optionally contained in the B-nucleated propylene copolymers of the polyolefin coating of the steel pipe, are the calcium salts of phthaloylglycine, hexahydrophthaloylglycine, N-phthaloylalanine and/or N-4-methylphthaloylglycine.
According to an advantageous feature of the present invention, the intermediate foamed plastic material, being optionally interposed between the steel pipe and the polyolefin coating, is a foamed propylene copolymer having strain hardening behaviour and a melt index of 1.5 to 10 g/10 min at 230 "C/2.16 kg.
The propylene copolymer of the intermediate foamed plastic material, being optionally interposed between the steel pipe and the polyolefin coating, having a strain hardening
behaviour can be produced by any number of processes, e.g. by treatment of propylene copolymers with thermal decomposing radical-forming agents and/or by treatment with ionizing radiation, where both treatments may optionally be accompanied or followed by a treatment with bi- or multifunctionally unsaturated monomers, e.g. butadiene, isoprene, dimethylbutadiene or divinylbenzene. Further processes may be suitable for the production of the propylene copolymers having a strain hardening behaviour, provided that the resulting propylene copolymers meet the characteristics of strain hardening behaviour.
Examples of said propylene copolymers of the intermediate foamed plastic material, being optionally interposed between the steel pipe and the polyolefin coating, having a strain hardening behaviour are, in particular:
polypropylenes modified by the reaction of polypropylenes with bismaleimido-compounds
in the melt (EP-A-0 574 801; EP-A-0 574 804),
polypropylenes modified by the treatment of polypropylenes with ionizing radiation in the
solid phase (EP-A-0 190 889; EP-A-0 634 454),
polypropylenes modified by the treatment of polypropylenes with peroxides in the solid
phase (EP-A-0-384 431) or in the melt (EP-A-0-142724),
polypropylenes modified by the treatment of polypropylenes with multifunctional,
ethylenically unsaturated monomers under the action of ionizing radiation (EP-A-0 678
527)
polypropylenes modified by the treatment of polypropylenes with multifunctional,
ethylenically unsaturated monomers in the presence of peroxides in the melt (EP-A-0 688
817; EP-A-0 450 342)
The strain hardening behaviour as used herein is defined according to Fig. 1 and 2.
Fig. 1 shows a schematic representation of the experimental procedure which is used to
determine strain hardening.
The strain hardening behaviour of polymers is analyzed by Rheotens apparatus 1 (product
of Gottfert, Siemensstr. 2, 74711 Buchen, Germany) in which a melt strand 2 is elongated
by drawing down with a defined acceleration. The haul-off force F in dependence of drawn
down velocity v is recorded.
The Rheotens apparatus 1 is combined with an extruder/melt pump 3 for continuous
feeding of the melt strand 2. The extrusion temperature is 200 °C; a capillary die with a
diameter of 2 mm and a length of 6 mm is used and the acceleration of the melt strand 2
drawn down is 120 mm/sec2.
The schematic diagram in Figure 1 shows in an exemplary fashion the measured increase
in haul-off force F (i.e. "melt strength") vs. the increase in draw-down velocity v (i.e.
"drawability").
Figure 2 shows the recorded curves of Rheotens measurements of polymer samples with and without strain hardening behaviour. The maximum points (Fmax; vmax) at failure of the strand are characteristic for the strength and the drawability of the melt. The common propylene polymers 4, 5, 6 with melt indices of 0.3, 2.0 and 3.0 g/10 min at 230 "C/2.16 kg show a very low melt strength and low drawability. They have no strain hardening and therefore a problematic processability into extrusion foams. Modified propylene polymers 7 (melt index of the sample in the diagram is 2 to 3 g/10 min at 230 "C/2.16 kg) or unmodified common LDPE 8 (melt index of the sample in the diagram is 0.7 g/10 min at 190 °C/2.16 kg) show a completely different drawability vs. melt strength behaviour. With increasing the draw down velocity v the haul-off force F increases to a much higher level, compared to the unmodified common propylene polymers 4, 5, 6. The curve shape is characteristic for strain hardening.
"Propylene copolymers which have strain hardening behaviour" as used herein have enhanced melt strength with haul-off forces Fmax >15cN and enhanced drawability velocities vmax >150 mm/s.
According to a further preferred embodiment of the invention the test polyolefin pipe fabricated from the G-nucleated propylene copolymer has a critical pressure of >30 bars and a dynamic fracture toughness of >6.0 MNm"3/2 in the hydrostatic small scale steady state (hydrostatic S4) test at 3 °C.
A further object of the present invention is a process for producing polyolefin coated steel pipes with high dynamic fracture toughness of the coating of the steel pipes during installation handling and in service, consisting of a steel pipe core, optionally an intermediate foamed plastic material, and a polyolefin coating fabricated by coating extruder/rotating steel pipe technology, ring-die pipe coating technology or injection
molding technology, characterized in that the polyolefin coating consists of IJ-nucleated propylene copolymers from 90.0 to 99.9 % by weight of propylene and 0.1 to 10.0 % by weight of a-olefins with 2 or 4 to 18 carbon atoms with melt indices of 0.1 to 8 g/10 min at 230 "C/2.16 kg, whereby a test polyolefin pipe fabricated from the IJ-nucleated propylene copolymer has a critical pressure of >25 bars and a dynamic fracture toughness of >3.5 MNm"3'2 in the hydrostatic small scale steady state (hydrostatic S4) test at 3 °C.
The inventive propylene block copolymers for the coating of steel pipes may contain usual auxiliary materials, such as 0.01 to 2.5 wt% stabilizers and/or 0.01 to 1 wt% processing aids, and/or 0.1 to 1 wt% antistatic agents and/or 0.2 to 3 wt% pigments, in each case based on the propylene copolymers used.
As stabilizers preferably mixtures of 0.01 to 0.6 wt% phenolic antioxidants, 0.01 to 0.6 wt% 3-arylbenzofuranones, 0.01 to 0.6 wt% processing stabilizers based on phosphites, 0.01 to 0.6 wt% high temperature stabilizers based on disulfides and thioethers and/or 0.01 to 0.8 wt% sterically hindered amines (HALS) are suitable.
For a good interlaminar adhesion between the steel pipe core, optionally the intermediate foamed plastic material, or the polyolefin coating it is advantageous to use epoxy resin coated steel pipes and to apply a compatibilizing layer between the epoxy resin coated steel pipe and the polyolefin layer, whereby the compatibilizing layer consists of propylene copolymers or propylene polymer graft copolymers both with chemical bound ethylenically unsaturated carbonic acids and/or carbonic acid anhydrides, particularly acrylic acid, methacrylic acid and/or maleic acid anhydride.
Conventional extruders for melting the propylene copolymers pursuant to the inventive
process.
Producing the polyolefin coated steel pipes by coating extruder/rotating steel pipe
technology, the preheated steel pipe, optionally coated with an epoxy resin, under rotation
successively is melt coated by independent coating extruders having flat film dies for the
unfoamed polyolefin cover layer and the optional layers of the compatibilizing agent and
the foaming plastic material.
Producing the polyolefin coated steel pipes by crosshead die pipe coating technology, preferably a crosshead fed by extruders, for the outer unfoamed polyolefin cover layer and optional for the compatibilizing agent and the foaming plastic material, is used. The steel pipe is preferably coated with an epoxy resin layer and a compatibilizing layer on the epoxy resin layer. Preferably the steel pipe is preheated to a temperature ranging from 170 to 230 °C, and the extruder feeding the ring shaped die of the crosshead in the polyolefin steel pipe coating line has a temperature profile ranging from 175 to 250 "C. The optional foamed melt is brought first on the pipe, followed by the unfoamed outer layer of the p-nucleated propylene copolymer, subsequently the coated pipe is calibrated in the calibrating sleeve and cooled. Preferred are steel pipe diameters ranging from 50 to 500 mm.
Injection molding technology for producing the polyolefin coated steel pipes is used at field joint. The field joint coating machine consists of two parts. The injection molding machine melts the fi-nucleated propylene copolymer in an extruder with adapter zones and then injects it into the mold, which is controlled by the mold locking part. In this second part the li-nucleated propylene copolymer is cooled down to solid state by oil or water. The preferred temperature profile of the extruder is from 200 to 250 °C and of the adapter zones from 230 to 240 °C. The preferred mold temperature is from 80 to 100 °C.
If optional an intermediate foamed plastic material is applied on the steel pipe, preferred polyolefin mixtures containing 1 to 12 wt%, based on the polyolefin mixture, of chemical blowing agents that split off gas, or hydrocarbons, halogenated hydrocarbons and/or gases as blowing agents are used, whereby the steel pipes are preheated to a temperature ranging from 170 to 230 °C and the foam coating extruder has a temperature profile ranging from 175 to 250 °C.
Examples of suitable chemical blowing agents, that emit a gas, are sodium hydrogencarbonate, azodicarbonamide and/or cyanuric trihydrazide. Suitable hydrocarbons as blowing agents are readily volatile hydrocarbons, such as pentane, isopentane, propane and/or isobutane. Examples of suitable halogenated hydrocarbons are monofluorotrichloromethane and/or difluoromonochloromethane. Suitable gases as blowing agents are nitrogen, argon and/or carbon dioxide.
According to a feature of the present invention in the ring-die pipe coating technology for producing the polyolefin coated steel pipes a cone extruder is used, whereby the temperature of the melt of the nucleated propylene copolymer at the ring die is from 195 to 240 °C and the temperature of the preheated steel pipe is from 160 to 200 °C.
Preferred applications of polyolefin coated steel pipes are the off-shore transport of crude oil or gas products or district heating applications.
In the application as polyolefin coated steel pipes for off-shore transport of crude oil from sea bottom to tankers, coated steel pipes with an intermediate foamed propylene copolymer material with foam densities of the foamed layer ranging from 600 to 800 kg/m3 are preferred. In order to be able to pump crude oil coming from deposit in cold sea regions, the fluid has to be held sufficiently warm. By utilising the inventive coated steel pipes with an intermediate foamed propylene copolymer based insulation layer, it is possible to avoid extensive heat losses to the surrounding water and also to eliminate costly additional oil heating units along the pipe line. At water depths of 200 to 300 m the pressure is substantial and requires high mechanical stability of the foamed insulation layer. The foam layers of propylene copolymers having strain hardening behaviour have the outstanding balance between heat insulation efficiency and compression strength.
Examples
The following tests were made using injection molded test specimen prepared according
to I SO 1873
Tensile modulus according to ISO 527 (cross head speed 1 mm/min) at +23 °C
Charpy impact strength, notched according to ISO 179/1eA
Rapid crack propagation test according to ISO 13477 performed under hydrostatic
conditions
Dynamic fracture toughness according to Plastics, Rubber and Composites Processing
and Applications, Vol. 26, No. 9, pp. 387 ff.
Compressive strength according to ASTM D 695-96, 5 % compression
Example 1
1.1 Preparation of the fi-nucleated propylene copolymer
A mixture of
90 wt% of a propylene block copolymer, obtained by combined bulk and gas phase
polymerization using a Ziegler-Natta catalyst system with dicyclopentyldimethoxysilane as
external donor, having an ethylene content of 8.3 wt%, an IRi of the propylene
homopolymer block of 0.985 and a melt index of 0.30 g/10 min at 230 °C/2.16 kg,
10 wt% of a master batch comprising 99 parts by weight of a propylene block copolymer
having an ethylene content of 8.3 % by weight, an IRi of the propylene homopolymer
block of 0.985 and a melt index of 0.30 g/10 min at 230 °C/2.16 kg, and 1 part by weight of
pimelic acid calcium salt , and 0.1 wt% calcium stearate, 0.1 wt%
tetrakis[methylene(3,5-di-t-butylhydroxyhydrocinnamate)]methane and 0.1 wt%
tris-(2,4-di-t-butylphenyl)phosphite, based on the sum of the propylene polymers used, is
melted in a twin screw extruder with a temperature profile of
100/145/185/210/220/225/225/225/220/200/185 °C, homogenized, discharged and
pelletized.
The resulting propylene copolymer has a melt index of 0.32 g/10 min at 230 "C/2.16 kg, a
tensile modulus of 1290 MPa and a Charpy impact strength, using notched test
specimens, of 39 kJ/nf at -20 °C.
1.2 Manufacture of the propylene copolymer test pipe
For producing the propylene copolymer test pipe, the B-nucleated propylene copolymer of 1.1 is introduced in a single screw extruder (L/D=30, D=70mm, temperature profile 200/210/220/220/220/220/200 °C, 40 rpm), melted, extruded through a ring shaped die with a diameter of 110 mm, taken off over a vacuum calibrating sleeve as a pipe of a diameter of 110 mm and a wall thickness of 10 mm, and cooled in a 6 m water bath at +20 °C, the taking off velocity being 0.3 m/min.
Rapid crack propagation test shows a critical pressure of 31 barand a dynamic fracture toughness of 19.60 MNrrf3'2.
1.3 Manufacture of the polyolefm coated steel pipe
The pilot steel pipe coating line consists of a preheating unit, crasshead with two
extruders, vacuum calibration sleeve, cooling unit and cutting unit.
For producing the intermediate foamed plastic layer, a propylene polymer compound
comprising
- 30 wt% of a propylene homopolymer modified with 0.12 % by weight of bound butadiene
as determined by IR-spectroscopy and having strain hardening behaviour, a melt index of
0.45 g/10 min at 230 °C/2,16 kg and a crystallization enthalpy of 91 J/g ,
- 70 wt% of a propyiene block copolymer having an ethylene content of 8.3 % by weight,
an IR.T of the propylene homopolymer block of 0.974, and a melt index of 0.30 g/10 min at
230 °C/2.16kg, and 0.1 wt% calcium stearate, 0.1 wt%
tetrakis[methylene(3,5-di-t-butylhydroxyhydrocinnamate)]methane and 0.1 wt%
tris-(2,4-di-t-butylphenyl)phosphite, based on the sum of the propylene polymers used, is
dry blended with 2.2 wt%, based on the propylene compound, of a mixture of blowing
agents based on bicarbonate and citric acid and supplied by means of a metering system
to the feeding funnel of the first single screw extruder with a screw diameter of 90 mm, an
L/D of 35 and a temperature profile of 200/230/240/230/230/230/230/230/230/230 °C.
Initially, the mixture is melted and homogenized and subsequently the split off blowing gas
is mixed intensively in the extruder and distributed homogeneously. After that, the melt is
transferred by a melt pump onto the ring-shaped crosshead having a die temperature of
205 °C.
The said crosshead is fed by a second single screw extruder with a screw diameter of 60 mm, a L/D of 35 and a temperature profile of 200/230/240/220/220/220/220/220/220/220 °C with the p-nucleated propylene copolymer of 1.1.
Inside of the crosshead a steel pipe (0 150 mm), coated with a 25 urn epoxy resin layer and a 30 urn compatibilizing layer of a maleic acid anhydride grafted propylene polymer (0.20 wt% maleic acid anhydride), being preheated to a temperature of 190 °C, is driven forward with a speed of 1.2 m/min. The crosshead is designed so that the foamed melt is added first onto the coated steel pipe, followed by the melt of the unfoamed propylene polymer for the outer layer, just before the pipe enters the vacuum calibration sleeve, which is cooled by water of +20 "C.
From the polyolefin coated steel pipe test specimens of a length of 254 mm are machine cut. The polyolefm foam layer has a thickness of 50 mm and a density of 720 kg/m3. The unfoamed cover layer has a thickness of 8 mm. The compressive strength of coated steel pipe test specimens (ASTM D 695-96, 5 % compression) being 19 MPa.
Example 2
2.1 Preparation of the IJ-nucleated propylene copolymer A mixture of
94 wt% of a propylene block copolymer, obtained by combined bulk and gas phase
polymerization using a Ziegler-Natta catalyst system with dicyclopentyldimethoxysilane as
external donor, having an ethylene content of 8.3 wt%, an IRt of the propylene
homopolymer block of 0.985, and a melt index of 0.30 g/10 min at 230 °C/2.16 kg,
6 wt% of a master batch comprising 99.8 parts by weight of a propylene block copolymer
having an ethylene content of 8.3 wt%, an IRr of the propylene homopolymer block of
0.985, and a melt index of 0.30 g/10 min at 230 "C/2.16 kg, and 0.2 parts by weight of a
mixed crystal of 5,12-dihydro(2,3b)acridine-7,14-dione with
quino(2,3b)acridine-6,7,13,14-(5H,12H)-tetrone, and 0.05 wt% calcium stearate, 0.1wt%
tetrakis[methylene(3,5-di-t-butylhydroxyhydrocinnamate)]methane and 0.1 wt%
tris-(2,4-di-t-butyl-phenyl)-phosphite, based on the sum of the propylene polymers used, is melted in a twin screw extruder with a temperature profile of 100/145/190/215/225/230/230/215/205/190 °C, homogenized, discharged and palletized.
The resulting polypropylene polymer has a melt index of 0.3 g/10 min at 230 "C/2.16 kg, a tensile modulus of 1450 MPa and a Charpy impact strength using notched test specimens at-20 °C of 21 kJ/m2,
2.2 Manufacture of the propylene copolymer test pipe
For producing the propylene copolymer test pipe, the fi-nucleated propylene copolymer of 2.1 is introduced in a single screw extruder (L/D=30, D=70mm, temperature profile 200/210/225/ 225/225/225/205 °C, 40 rprn), melted, extruded through a ring shaped die with a diameter of 110 mm, taken off over a vacuum calibrating sleeve as a pipe of a diameter of 110 mm and a wall thickness of 10 mm, and cooled in a 6 m water bath at 20 °C, the taking off velocity being 0.35 m/min.
Rapid crack propagation test shows a critical pressure of 34 bar and a dynamic fracture toughness of 21.5 MNnY3'2.
2.3 Manufacture of the polyolefin coated steel pipe
The pilot steel pipe coating line consists of a preheating unit, crosshead with two
extruders, vacuum calibration sleeve, cooling unit and cutting unit.
For producing the intermediate foamed plastic layer, a propylene polymer compound
comprising
- 20 wt% of a polypropylene copolymer having an ethylene content of 4.3 wt%, modified
with 0.16% by weight of bound divinylbenzene, as determined by IR-spectroscopy, and
having strain hardening behaviour and a melt index of 0.48 g/10 min at 230 °C/2.16 kg,
- 80 wt% of a propylene block copolymer having an ethylene content of 8.3 wt%, an IRi of
0.974 of the propylene block, and a melt index of 0.30 g/10 min at 230 "C/2.16 kg, and 0.1
wt% calcium stearate, 0.1 wt%
tetrakis[methylene(3,5-di-t-butylhydroxyhydrocinnamate)]methane and 0.1 wt% tris-(2,4-di-t-butylphenyl)phosphite, based on the sum of the propylene polymers used, is dry blended with 2.2 wt%, based on the propylene compound, of a mixture of blowing agents based on bicarbonate and citric acid and supplied by means of a metering system to the feeding funnel of the first single screw extruder with a screw diameter of 90 mm, an L/D of 35 and a temperature profile of 200/230/240/230/230/230/230/230/230/230 °C.
Initially, the mixture is melted and homogenized and subsequently the split off blowing gas is mixed intensively in the extruder and distributed homogeneously. After that, the melt is transferred by a melt pump onto the ring-shaped crosshead having a die temperature of 205 °C.
The said crosshead is fed by a second single screw extruder with a screw diameter of 60mm, an LID of 35 and a temperature profile of 200/230/240/220/220/220/220/220/220/220 °C with the B-nucleated propylene copolymer of 2.1.
Inside of the crosshead a steel pipe (0 150 mm), coated with a 25 urn epoxy resin layer and a 30 urn compatibilizing layer of a maleic acid anhydride grafted propylene polymer (0.20 % by weight of maleic acid anhydride), being preheated to a temperature of 190 °C, is driven forward with a speed of 1.2 m/min. The crosshead is designed so that the foamed melt is added first onto the coated steel pipe, followed by the melt of the unfoamed propylene polymer for the outer layer, just before the pipe enters the vacuum calibration sleeve, which is cooled by water of +20 °C.
From the polyolefin coated steel pipe test specimens of a length of 254 mm are machine cut. The polyolefin foam layer has a thickness of 55 mm and a density of 700 kg/m3. The unfoamed cover layer has a thickness of 8 mm. The compressive strength of coated steel pipe test specimens (ASTM D 695-96, 5 % compression) being 17 MPa.
Example 3
3.1 Preparation of the li-nucleated propylene copolymer
A mixture of
75 wt% of a propylene block copolymer obtained by combined bulk and gas phase
polymerization using a Ziegler-Natta catalyst system with dicyclopentyldimethoxysilane as
external donor, having an ethylene content of 8.3 wt%, an IRt of the propylene
homopolymer block of 0.985, and a melt index of 0.30 g/10 min at 230 "C/2.16 kg,
25 wt% of a master batch comprising 99.5 parts by weight of a propylene block copolymer
having an ethylene content of 8.3 wt%, an IRr of the propylene homopolymer block of
0.985, and a melt index of 0.30 g/10 min at 230 "C/2.16 kg, and 0.5 parts by weight of
hexahydrophthaloylglycine calcium salt, and 0.1 wt% calcium stearate, 0.1 wt%
tetrakis[methylene(3,5-di-t-butylhydroxyhydrocinnamate)]methane and 0.1 wt%
tris-(2,4-di-t-butylphenyl)phosphite, based on the sum of the propylene copolymers used, is melted in a twin screw extruder with a temperature profile of 100/145/185/210/220/225/225/200/185 °C, homogenized, discharged and pelletized.
The resulting propylene copolymer has a melt index of 0.32 g/10 min at 230 °C/2.16 kg, a tensile modulus of 1310 MPa and a Charpy impact strength using notched test specimens at-20°Cof37kJ/m2.
3.2 Manufacture of the propylene copolymer test pipe
For producing the propylene copolymer test pipe, the li-nucleated propylene polymer of 3.1 is introduced in a single screw extruder (L/D = 30, D = 70mm, temperature profile 200/210/220/220/220/220/200 °C, 40 rpm), melted, extruded through a ring shaped die with a diameter of 110 mm, taken off over a vacuum calibrating sleeve as a pipe of a diameter of 110 mm and a wall thickness of 10 mm, and cooled in a 6 m water bath at +20 °C, the taking off velocity being 0.3 m/min.
Rapid crack propagation test shows a critical pressure of 31 bar and a dynamic fracture toughness of 19.60 MNrn"3'2.
3.3 Manufacture of the polyolefin coated steel pipe
The pilot steel pipe coating line consists of a preheating unit, crosshead with extruder, vacuum calibration sleeve, cooling unit and cutting unit.
The crosshead is fed by a single screw extruder with a screw diameter of 60 mm, an L/D of 35 and a temperature profile of 200/230/240/220/220/220/220/220/220/220 °C with the S-nucleated propylene copolymer of 3.1.
Inside of the crosshead a steel pipe (0 150 mm), coated with a 25 urn epoxy resin layer and a 30 urn compatibilizing layer of a maleic acid anhydride grafted propylene polymer (0,20 wt% maleic acid anhydride), being preheated to a temperature of 190 °C, is driven forward with a speed of 1.2 m/min. The crosshead is designed so that the melt of the B-nucleated propylene copolymer is added onto the coated steel pipe, just before the pipe enters the vacuum calibration sleeve, which is cooled by water of +20 °C. The polyolefin coating has a thickness of 7.5 mm.






WE CLAIM:
1. Polyolefin coated steel pipes with high dynamic fracture toughness of the
coating of the steel pipes during installation handling and in service, consisting
of a steel pipe core, optionally an intermediate foamed plastic material, and a
polyolefin coating, characterized in that the polyolefin coating consists of ß-
nucleated propylene copolymers from 90.0 to 99.9 wt% of propylene and 0.1 to
10.0 wt% of a-olefins with 2 or 4 to 18 carbon atoms with melt indices of 0.1 to
8 g/10 min at 230 °C/2.16 kg, whereby a test polyolefin pipe fabricated from
the ß-nucleated propylene copolymer has a critical pressure of >25 bars and a
dynamic fracture toughness of >3.5 MNnr3/2.
2. Polyolefin coated steel pipes according to claim 1, wherein the ß-
nucleated propylene copolymers are ß-nucleated propylene block copolymers
having an IRτ of the propylene homopolymer block of >0.98, a tensile modulus
of >1100 MPa and a Charpy impact strength, using notched test specimens at -
20 °C of > 6 kJ/m2.
3. Polyolefin coated steel pipes according to claim 2, wherein the ß-
nucleated propylene block copolymers having an IRτ of the propylene
homopolymer block of ≥0.98 are propylene copolymers obtained by
polymerization with a Ziegler-Natta catalyst system comprising titanium-
containing solid components, an organoalumina, magnesium or titanium
compound as cocatalyst and an external donor according to the formula
RxR'ySi(MeO)4-x-y,
wherein R and R' are identical or different and are branched or cyclic aliphatic or aromatic hydrocarbon residues, and y and x independently from each other are for 1, provided that x + y are 1 or 2.
4. Polyolefin coated steel pipes as claimed in claim 3, wherein the external
donor is dicyclopentyldimethoxysilane.
5. Polyolefin coated steel pipes as claimed in any one of claims 1 to 4,
wherein the ß-nucleated propylene copolymers contain 0.0001 to 2.0 wt%,
based on the propylene copolymers used,
dicarboxylic acid derivative type diamide compounds from C5-C8-cycloalkyl monoamines or C6-C12-aromatic monoamines and C5-C8-aliphatic, C5-C8-cycloaliphatic or C6-C12-aromatic dicarboxylic acids, and/or
diamine derivative type diamide compounds from C5-C8-cycloalkyl monocarboxylic acids or C6-C12-aromatic monocarboxylic acids and C5-C8-cycloaliphatic or C6-C12-aromatic diamines, and/or amino acid derivative type diamide compounds from amidation reaction of C5-C8-alkyl-, C5-C8-cycloalkyl- or C6-C12-arylamino acids, C5-C8-alkyl-, C5-C8-cycloalkyl- or C6-C12-aromatic monocarboxylic acid chlorides and C5-C8-alkyl-, C5-C8-cycloalkyl- or C6-C12-aromatic monoamines, and/or quinacridone derivative compounds of the type quinacridone compounds, quinacridonequinone compounds, and/or dihydroquinacridone type compounds, and/or
dicarboxylic acid salts of metals from group IIa of periodic system and/or mixtures of dicarboxylic acids and metals from group la of periodic system, and/or
salts of metals from group la of periodic system and imido acids of the formula
(Formula Removed)
wherein x = 1 to 4; R = H, -COOH, C1-C12-alkyl, C5-C8-cycloalkyl or C6-C12-aryl, and Y = C1-C12-alkyl, C5-C8-cycloalkyl or C6-C12-aryl -substituted bivalent C6-C12-aromatic residues, as ß-nucleating agent.
6. Polyolefin coated steel pipes as claimed in any one of claims 1 to 5,
wherein the intermediate foamed plastic material is a foamed propylene
copolymer having strain hardening behaviour and a melt index of 1.5 to 10
g/10 min at 230 °C/2. 16 kg.
7. A process for producing polyolefin coated steel pipes with high dynamic
fracture toughness of the coating of the steel pipes during installation handling
and in service, consisting of a steel pipe core, optionally an intermediate
foamed plastic material, and a polyolefin coating fabricated by coating
extruder/rotating steel pipe technology, ring die pipe coating technology or
injection molding technology, characterized in that the polyolefin coating
consists of ß-nucleated propylene copolymers from 90.0 to 99.9 wt% of
propylene and 0.1 to 10.0 wt% of a-olefins with 2 or 4 to 18 carbon atoms with
melt indices of 0.1 to 8 g/10 min at 230 °C/12.16 kg, whereby a test polyolefin
pipe fabricated from the 3-nucleated propylene copolymer has a critical
pressure of >25 bars and a dynamic fracture toughness of >3.5 MNm-3/2.
8. A process for producing polyolefin coated steel pipes as claimed in claim
7, wherein in the ring die pipe coating technology a cone extruder is used,
whereby the temperature of the melt of the nucleated propylene copolymer at
the ring die is from 195 to 240°C and the temperature of the preheated steel
pipe is from 160 to 200°C.
9. The polyolefin coated steel pipes as claimed in any one of claims 1 to 5 as and when used for off-shore transport of crude oil or gas products or district heating applications.


Documents:

1968-DELNP-2003-Abstract-(08-06-2009).pdf

1968-delnp-2003-abstract.pdf

1968-DELNP-2003-Claims-(08-06-2009).pdf

1968-delnp-2003-claims.pdf

1968-DELNP-2003-Correspondence-Others-(08-06-2009).pdf

1968-DELNP-2003-Correspondence-Others-(29-03-2010).pdf

1968-delnp-2003-correspondence-others.pdf

1968-DELNP-2003-Description (Complete)-(08-06-2009).pdf

1968-delnp-2003-description (complete).pdf

1968-DELNP-2003-Drawings-(08-06-2009).pdf

1968-delnp-2003-drawings.pdf

1968-DELNP-2003-Form-1-(08-06-2009).pdf

1968-delnp-2003-form-1.pdf

1968-delnp-2003-form-13-(08-06-2009).pdf

1968-delnp-2003-form-18.pdf

1968-delnp-2003-form-2.pdf

1968-DELNP-2003-Form-3-(08-06-2009).pdf

1968-delnp-2003-form-3.pdf

1968-DELNP-2003-Form-5-(08-06-2009).pdf

1968-DELNP-2003-GPA-(08-06-2009).pdf

1968-delnp-2003-gpa.pdf

1968-delnp-2003-pct-210.pdf

1968-delnp-2003-pct-409.pdf

1968-DELNP-2003-Petition-137-(09-06-2009).pdf

abstract.jpg


Patent Number 239275
Indian Patent Application Number 01968/DELNP/2003
PG Journal Number 12/2010
Publication Date 19-Mar-2010
Grant Date 15-Mar-2010
Date of Filing 20-Nov-2003
Name of Patentee BOREALIS TECHNOLOGY OY
Applicant Address P.O.BOX 330, FI-06201 PORVOO, FINLAND.
Inventors:
# Inventor's Name Inventor's Address
1 JAMES MCGOLDRICK PAUL-HAHN-STRASSE 49, A-4614 MARCHTRENK, AUSTRIA.
2 TONY LINDSTROEM BLEKETV. 5, SE-471 96 BLEKET, SWEDEN
3 SIEGFRIED LIEDAUER FASANENGASSE 4, A-4073 WILHERING, AUSTRIA
4 CECILIA RYDIN KRUKMAKAREV 2, SE-444 95 OEDSMAL, SWEDEN.
PCT International Classification Number C08K 5/00
PCT International Application Number PCT/EP02/05547
PCT International Filing date 2002-05-21
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 PCT/EP02/05547 2002-05-21 PCT