FIELD OF INVENTION

The invention relates to pipes comprising polypropylene resins; preferably pipes comprising a syndiotactic polypropylene resin.

BACKGROUND OF THE INVENTION

Polymer materials are frequently used for manufacturing pipes suitable for various purposes, such as fluid transport, i.e. transport of liquid or gas, e.g. water or natural gas, during which the fluid can be pressurized, and may have varying temperatures (up to 70 °C). These pipes are usually prepared from polyolefins, such as polyethylene and polypropylene. Because of the high temperatures involved, pipes made from polyolefins have special requirements.

The good thermal resistance of polypropylene compared with other polyolefins is particularly useful for applications such as pipes and pressure pipes. Pressure pipe resins require high stiffness (creep rupture strength), combined with a high resistance against slow crack growth as well as resistance to rapid crack propagation (impact toughness). All three main types of polypropylene, homopolymers, random copolymers and block copolymers have been used to produce pipes.

According to the standard DIN 8078, a pipe made of polypropylene must meet the requirement of at least 1000 hours before failure at 95 °C and 3.5 MPa pressure. One attempt to meet these requirements has been the increase of the rigidity of the polyolefin composition used for such pressure pipes. However, increasing the rigidity, sometimes results in reduction of the slow crack growth resistance (SCGR), resulting in earlier brittle failure and thus has a negative impact on the minimum required strength (MRS) rating as well. Doing so, the pressure pipe is also less and less flexible. Further properties which are desirable to improve or to maintain at a high level are processability, tensile modulus, short and long term pressure resistance, and impact properties of a pipe material.

Therefore, there remains a need to produce a polypropylene pipes "as flexible as possible" which can withstand high pressure for long times, while satisfying the criteria of processability, slow crack growth resistance and impact toughness of the existing standard. It is the object underlying the present invention to provide flexible pipes which can withstand high pressure for long times, while satisfying the criteria of processability, slow crack growth resistance and impact toughness of the existing standard.

SUMMARY OF THE INVENTION

The present inventors have now surprisingly found that one or more of the above objects can be achieved by using a syndiotactic polypropylene to manufacture pipes.

According to a first aspect, the present invention provides a pipe comprising a composition wherein said composition comprises a syndiotactic polypropylene, wherein said syndiotactic polypropylene has a syndiotactic index of at least 70 % as measured via ¹³ C-NMR spectroscopy; and wherein said syndiotactic polypropylene exhibits no melting temperature peak above 145 °C, as determined by differential scanning calorimetry. The ¹³ C-NMR analysis was performed as described herein below in the detailed description. The present inventors have shown that the claimed pipes, while being more flexible than current state-of-the art pipes, can withstand high stresses for long times, and at the same time, satisfying existing criteria of processing, slow crack growth resistance and impact resistance.

Preferably, the invention provides a pipe comprising a composition, said composition comprising at least one syndiotactic polypropylene, wherein said composition comprises at least 80 % by weight of said at least one syndiotactic polypropylene, based on the total weight of the composition; wherein said at least one syndiotactic polypropylene has a syndiotactic index of at least 70 % as measured using ¹³ C-NMR spectroscopy; and wherein said syndiotactic polypropylene exhibits no melting temperature peak above 145 °C, as determined by differential scanning calorimetry.

According to a second aspect, the present invention also encompasses a process for the manufacture of a pipe according to the first aspect, comprising the steps of:

(a) extruding the syndiotactic polypropylene resin into a pipe;

(b) cooling the pipe formed in step (a); and

(c) optionally heating/annealing the pipe formed in step (a).

Preferably, the present invention also encompasses a process for the manufacture of a pipe according to the first aspect, comprising the steps of:

(a) extruding a composition into a pipe; said composition comprising at least 50 % by weight of at least one syndiotactic polypropylene, based on the total weight of the composition; wherein said at least one syndiotactic polypropylene has a syndiotactic index of at least 70 % as measured using ¹³ C-NMR spectroscopy; and wherein said syndiotactic polypropylene exhibits no melting temperature peak above 145 °C, as determined by differential scanning calorimetry;

(b) cooling the pipe formed in step (a); and

(c) optionally heating/annealing the pipe formed in step (a).

According to a third aspect, the present invention provides the use of a pipe according to the first aspect, and/or produced according to the second aspect, for the transportation of fluids under pressure.

The present invention also encompasses the use of a pipe according to the first aspect, and/or produced according to the second aspect, for the manufacture of medical articles.

The present invention will now be further described. In the following passages, different aspects of the invention are defined in more detail. Each aspect so defined may be combined with any other aspect or aspects unless clearly indicated to the contrary. In particular, any feature indicated as being preferred or advantageous may be combined with any other feature or features indicated as being preferred or advantageous. BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a photograph of a water bath used to perform the creep experiments.

Figure 2 represents a graph plotting % of elongation as a function of time, of a tensile bar made of a syndiotactic polypropylene according to an embodiment of the invention.

Figure 3 represents a graph plotting % of elongation at inflection point, as a function of applied stress, of a tensile bar made of a syndiotactic polypropylene resin according to an embodiment of the invention.

Figure 4 represents a graph plotting the applied stress in function of inflection time, of tensile bar made of a syndiotactic polypropylene resin according to an embodiment of the invention versus a comparative example.

Figure 5 represents a photograph of the production of a pipe comprising syndiotactic polypropylene, according to an embodiment of the invention.

Figure 6 represents a graph showing the DSC profile of the exterior surface (OUT) and the DSC profile of the interior surface (IN) of a pipe comprising syndiotactic polypropylene, according to an embodiment of the invention.

Figure 7 represents a graph showing the DSC profiles of the interior surface of a pipe comprising syndiotactic polypropylene resin, according to an embodiment of the invention, at different times after heating/annealing of the pipe at 80 °C.

Figure 8 represents a graph showing the DSC profiles of the exterior surface of a pipe comprising syndiotactic polypropylene resin, according to an embodiment of the invention, at different times after heating/annealing of the pipe at 80 °C.

Figure 9 represents a graph showing the DSC profile of a pipe comprising syndiotactic polypropylene resin extruded at 160 °C, and annealed at 80 °C during 14 days, according to an embodiment of the invention.

Figure 10 represents a graph showing the DSC profile of a pipe comprising syndiotactic polypropylene resin extruded at 170 °C, and annealed at 80 °C during 14 days, according to an embodiment of the invention.

Figure 1 1 represents a graph showing the DSC profile of a pipe comprising syndiotactic polypropylene resin extruded at 220 °C, and annealed at 80 °C during 14 days, according to an embodiment of the invention.

Figure 12 represents a graph plotting the failure time in function of applied hoop stress, of 32 mm diameter pipes made of a syndiotactic polypropylene, according to an embodiment of the invention versus comparative examples, at a temperature of 20 °C.

DETAILED DESCRIPTION OF THE INVENTION

Before the present pipes, compositions, processes, articles, and uses of this invention are described, it is to be understood that this invention is not limited to particular pipes, compositions, processes, articles, and uses described, as such pipes, compositions, processes, articles, and uses may, of course, vary. It is also to be understood that the terminology used herein is not intended to be limiting, since the scope of the present invention will be limited only by the appended claims.

When describing the pipes and processes of the invention, the terms used are to be construed in accordance with the following definitions, unless a context dictates otherwise.

As used herein, the singular forms "a", "an", and "the" include both singular and plural referents unless the context clearly dictates otherwise.

The terms "comprising", "comprises" and "comprised of as used herein are synonymous with "including", "includes" or "containing", "contains", and are inclusive or open-ended and do not exclude additional, non-recited members, elements or method steps. The terms "comprising", "comprises" and "comprised of also include the term "consisting of.

The recitation of numerical ranges by endpoints includes all numbers and fractions subsumed within the respective ranges, as well as the recited endpoints.

Reference throughout this specification to "one embodiment" or "an embodiment" means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrases "in one embodiment" or "in an embodiment" in various places throughout this specification are not necessarily all referring to the same embodiment, but may. Furthermore, the particular features, structures or characteristics may be combined in any suitable manner, as would be apparent to a person skilled in the art from this disclosure, in one or more embodiments. Furthermore, while some embodiments described herein include some but not other features included in other embodiments, combinations of features of different embodiments are meant to be within the scope of the invention, and form different embodiments, as would be understood by those in the art. For example, in the following claims, any of the claimed embodiments can be used in any combination.

Unless otherwise defined, all terms used in disclosing the invention, including technical and scientific terms, have the meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. By means of further guidance, definitions for the terms used in the description are included to better appreciate the teaching of the present invention.

Preferred statements (features) and embodiments of the pipes, compositions, processes, articles, and uses of this invention are set herein below. Each statement and embodiment of the invention so defined may be combined with any other statement and/or embodiment, unless clearly indicated to the contrary. In particular, any feature indicated as being preferred or advantageous may be combined with any other features or statements indicated as being preferred or advantageous. Hereto, the present invention is in particular captured by any one or any combination of one or more of the below numbered aspects and embodiments 1 to 34, with any other statement and/or embodiment. A pipe comprising a composition, said composition comprising at least one syndiotactic polypropylene, wherein said at least one syndiotactic polypropylene has a syndiotactic index of at least 70 % as measured using ¹³ C-NMR spectroscopy; and wherein said syndiotactic polypropylene exhibits no melting temperature peak above 145 °C, as determined by differential scanning calorimetry.

A pipe comprising a composition, said composition comprising at least 50 % by weight of at least one syndiotactic polypropylene, based on the total weight of the composition; wherein said at least one syndiotactic polypropylene has a syndiotactic index of at least 70 % as measured using ¹³ C-NMR spectroscopy; and wherein said syndiotactic polypropylene exhibits no melting temperature peak above 145 °C, as determined by differential scanning calorimetry.

A pipe comprising at least one syndiotactic polypropylene, wherein said at least one syndiotactic polypropylene has a syndiotactic index of at least 70 % as measured using ¹³ C-NMR spectroscopy; and wherein said syndiotactic polypropylene exhibits no melting temperature peak above 145 °C, as determined by differential scanning calorimetry.

A pipe comprising at least one syndiotactic polypropylene, wherein said at least one syndiotactic polypropylene has a syndiotactic index of at least 70 % as measured using ¹³ C-NMR spectroscopy; wherein said pipe comprises at least 50 % by weight of said at least one syndiotactic polypropylene, based on the total weight of the pipe and wherein said syndiotactic polypropylene exhibits no melting temperature peak above 145 °C, as determined by differential scanning calorimetry.

The pipe according to any one of statements 1 to 4, wherein said syndiotactic polypropylene exhibits no melting temperature peak above 140 °C, preferably no melting temperature peak above 136 °C.

The pipe according to any one of statements 1 to 5, wherein said pipe exhibits no melting temperature peak above 145 °C, as determined by differential scanning calorimetry.

The pipe according to any one of statements 1 to 6, wherein the maximum melting temperature of said syndiotactic polypropylene, measured by differential scanning calorimetry, is at most 145 °C, preferably at most 140 °C.

The pipe according to any one of statements 1 to 7, having a flexural modulus of less than 1000 MPa as determined by ISO 178, preferably of less than 700 MPa, preferably of less than 500

MPa.

The pipe according to any one of statements 1 to 8, said pipe having an extrapolated 50 °C / 50 years stress of at least 7.0 MPa.

The pipe according to any one of statements 1 to 9, wherein said composition comprises at least at least 60 % by weight, preferably at least 70 % by weight, preferably at least 80% by weight, preferably at least 90 % by weight, preferably at least 95 % by weight, yet more preferably at least 97 % by weight, yet even more preferably at least 98 % by weight of said at least one syndiotactic polypropylene, based on the total weight of the composition.

The pipe according to any one of statements 1 to 10, wherein said pipe comprises at least 60 % by weight, preferably at least 70 % by weight, preferably at least 80 % by weight, preferably at least 90 % by weight, preferably at least 95 % by weight of said at least one syndiotactic polypropylene, based on the total weight of the pipe.

The pipe according to any one of statements 1 to 1 1 , wherein said pipe is made of a composition comprising said at least one syndiotactic polypropylene, preferably wherein said composition comprises at least 80 % by weight, preferably at least 90 % by weight, preferably at least 95 % by weight of said at least one syndiotactic polypropylene, based on the total weight of the composition.

The pipe according to any one of statements 1 to 12, wherein said at least one syndiotactic polypropylene has a syndiotactic index of at least 73 %; more preferably of at least 75 %; preferably of at most 90 %, preferably of at most 85 %, most preferably of at most 80 % as determined using ¹³ C-NMR spectroscopy.

The pipe according to any one of statements 1 to 13, wherein said at least one syndiotactic polypropylene has a syndiotactic index of at most 90 % as determined using ¹³ C-NMR spectroscopy.

The pipe according to any one of statements 1 to 14, wherein said at least one syndiotactic polypropylene has a syndiotactic index of from about 74 % to 90 % as determined using ¹³ C-

NMR spectroscopy.

The pipe according to any one of statements 1 to 15, wherein said at least one syndiotactic polypropylene has a density of at most 0.900 g/cm ³ , as determined according to ASTM D-1505, at 23 °C for example of at least 0.800 g/cm ³ and of at most 0.900 g/cm ³ , preferably at least 0.820 g/cm ³ and at most 0.900 g/cm ³ , preferably at least 0.840 g/cm ³ and at most 0.9000 g/cm ³ , preferably at least 0.8605 g/cm ³ and at most 0.900 g/cm ³ , preferably at least 0.870 g/cm ³ and at most 0.900 g/cm ³ .

The pipe according to any one of statements 1 to 16, wherein said at least one syndiotactic polypropylene has a melt flow rate of at least 0.3 g/10 min, preferably at least 0.5 g/10 min, preferably at least 1.0 g/10 min, preferably at least 1.5 g/10 min, preferably at least 1.8 g/10 min as determined according to ASTM D-1238 condition L, at 230 °C under a load of 2.16 kg.

The pipe according to any one of statements 1 to 17, wherein said at least one syndiotactic polypropylene has a melt flow rate of at most 25.0 g/10 min, preferably at most 20.0 g/10 min, preferably at most 15.0 g/10 min, preferably at most 10.0 g/10 min as determined according to ASTM D-1238 condition L, at 230 °C under a load of 2.16 kg; preferably, the at least one syndiotactic polypropylene resin has a melt flow rate of at least 0.3 g/10 min and of at most 25.0 g/10 min; preferably a melt flow rate of at least 0.5 g/10 min and of at most 20.0 g/10 min; preferably a melt flow rate of at least 1.0 g/10 min and of at most 15.0 g/10 min; preferably a melt flow rate of at least 1 .0 g/10 min and of at most 10.0 g/10 min; most preferably a melt flow rate of at least 1.8 g/10 min and of at most 10.0 g/10 min, preferably of at least 1.8 g/10 min and of at most 9.0 g/10 min; preferably a melt flow rate of at least 1.9 g/10 min and of at most 8.0 g/10 min; preferably a melt flow rate of at least 1 .8 g/10 min and of at most 7.0 g/10 min; preferably a

MFR of at least 1.8 and of at most 6.0 g/10 min; preferably a melt flow rate of at least 1.8 g/10 min and of at most 5.0 g/10 min; more preferably a melt flow rate of at least 1 .8 g/10 min and of at most 4.0 g/10 min; most preferably a melt flow rate of at least 1.8 g/10 min and of at most 3.0 g/10 min.

19. The pipe according to any one of statements 1 to 18, wherein said at least one syndiotactic polypropylene is a syndiotactic polypropylene homopolymer having less than 0.7 % by weight of ethylene or other alpha-olefin comonomer (ethylene is preferred), preferably less than 0.5 % by weight of ethylene, preferably less than 0.4 % by weight of ethylene, preferably less than 0.1 % by weight of ethylene.

20. The pipe according to any one of statements 1 to 19, wherein said at least one syndiotactic polypropylene is a pure syndiotactic polypropylene homopolymer.

21. The pipe according to any one of statements 1 to 20, wherein said at least one syndiotactic polypropylene is a single-site catalyst catalyzed syndiotactic polypropylene, preferably a metallocene catalyzed syndiotactic polypropylene.

22. The pipe according to any one of statements 1 to 21 , having a flexural modulus of less than 1000 MPa as determined by ISO 178.

23. The pipe according to any one of statements 1 to 22, having an impact resistance of at least 40 kJ/m ² as determined by ISO 180- notched izod test at 23 °C.

24. Process for the manufacture of a pipe according to any one of statements 1 to 23, comprising the steps of:

(a) extruding a composition into a pipe; said composition comprising at least 50 % by weight of at least one syndiotactic polypropylene, based on the total weight of the composition; wherein said at least one syndiotactic polypropylene has a syndiotactic index of at least 70 % as measured using ¹³ C-NMR spectroscopy; and wherein said syndiotactic polypropylene exhibits no melting temperature peak above 145 °C, as determined by differential scanning calorimetry;

(b) cooling the pipe formed in step (a); and

(c) optionally heating/annealing the pipe formed in step (a).

25. Process for the manufacture of a pipe according to any of statements 1 to 23, comprising the steps of:

(a) extruding the at least one syndiotactic polypropylene into a pipe; wherein said at least one syndiotactic polypropylene has a syndiotactic index of at least 70 % as measured using ¹³ C- NMR spectroscopy; wherein said pipe comprises at least 50 % by weight of said at least one syndiotactic polypropylene, based on the total weight of the pipe and wherein said syndiotactic polypropylene exhibits no melting temperature peak above 145 °C, as determined by differential scanning calorimetry;

(b) cooling the pipe formed in step (a); and

(c) optionally heating/annealing the pipe formed in step (a).

26. Process for the manufacture of a pipe according to any of statements 1 to 23, comprising the steps of:

(a) extruding the at least one syndiotactic polypropylene into a pipe;

(b) cooling the pipe formed in step (a); and

(c) optionally heating/annealing the pipe formed in step (a).

27. The process of any one of statements 24 to 26, wherein step (c) is performed at a temperature of at least 60 °C.

28. The process of any one of statements 24 to 27, wherein step (c) is performed at a temperature of at most 120 °C.

29. The process of any one of statements 24 to 28, wherein step (c) is performed at a temperature of at least 70 °C to at most 120 °C.

30. The process of any one of statements 24 to 29, wherein step (c) is performed for at least 3 days.

31. The process of any one of statements 24 to 30, wherein step (c) is performed for at most 20 days.

32. The process of any one of statements 24 to 31 , wherein step (c) is performed for at least 3 days to at most 14 days.

33. The process of any one of statements 24 to 32, wherein step (c) is an annealing step.

34. Use of a pipe according to any of statements 1 to 23 and/or manufactured according to the process of any one of statements 24 to 33, for the transportation of fluids under pressure.

According to a first aspect, the invention encompasses a pipe comprising a composition, said composition comprising at least one syndiotactic polypropylene, wherein said at least one syndiotactic polypropylene has a syndiotactic index of at least 70 % as measured via ¹³ C-NMR spectroscopy; and wherein said syndiotactic polypropylene exhibits no melting temperature peak above 145 °C, as determined by differential scanning calorimetry. The invention also encompasses a pipe comprising at least one syndiotactic polypropylene, wherein said at least one syndiotactic polypropylene has a syndiotactic index of at least 70 % as measured via ¹³ C-NMR spectroscopy; and wherein said syndiotactic polypropylene exhibits no melting temperature peak above 145 °C, as determined by differential scanning calorimetry, as described in the example section.

Preferably, the invention provides a pipe comprising a composition, said composition comprising at least 50 % by weight of at least one syndiotactic polypropylene, based on the total weight of the composition; wherein said at least one syndiotactic polypropylene has a syndiotactic index of at least 70 % as measured using ¹³ C-NMR spectroscopy; and wherein said syndiotactic polypropylene exhibits no melting temperature peak above 145 °C, as determined by differential scanning calorimetry.

The invention also encompasses a pipe comprising at least one syndiotactic polypropylene, wherein said at least one syndiotactic polypropylene has a syndiotactic index of at least 70 % as measured using ¹³ C-NMR spectroscopy; wherein said pipe comprises at least 50 % by weight of said at least one syndiotactic polypropylene, based on the total weight of the pipe and wherein said syndiotactic polypropylene exhibits no melting temperature peak above 145 °C, as determined by differential scanning calorimetry.

The term "pipe" as used herein is meant to encompass pipes in the narrower sense, as well as all supplementary parts for pipes such as fittings, valves and all parts which are commonly necessary for a piping system (for example to transport gas, cold or hot water). Pipes according to the invention also encompass single and multilayer pipes, where for example one or more of the layers is a metal layer and which may include an adhesive layer. Other constructions of pipes, e. g. corrugated pipes, are possible as well.

The term "syndiotactic polypropylene" or "syndiotactic polypropylene resin" as used herein refers to syndiotactic polypropylene fluff or powder that is extruded, and/or melted and/or pelleted and can be produced through compounding and homogenizing of the syndiotactic polypropylene as taught herein, for instance, with mixing and/or extruder equipment. As used herein, the term "syndiotactic polypropylene", or "sPP" may be used as a short hand for "syndiotactic polypropylene resin".

The pipe according to the invention comprises syndiotactic polypropylene having a syndiotactic index of at least 70 % as measured via ¹³ C-NMR spectroscopy; preferably of at least 73 %; more preferably of at least 75 %; preferably of at most 90 %.

The ¹³ C-NMR analysis was performed at an operative frequency of 125 MHz using a 500 MHz Bruker NMR spectrometer with a high temperature 10 mm cryoprobe under conditions such that the signal intensity in the spectrum is directly proportional to the total number of contributing carbon atoms in the sample. Such conditions are well known to the skilled person and include for example sufficient relaxation time, etc. In practice, the intensity of a signal is obtained from its integral, i.e. the corresponding area. The data were acquired using proton decoupling, 240 scans per spectrum, a pulse repetition delay of 1 1 seconds and a spectral width of 26000 Hz at a temperature of 130 °C. The sample was prepared by dissolving a sufficient amount of polymer in 1 ,2,4-trichlorobenzene (TCB, 99 %, spectroscopic grade) at 130 °C and occasional agitation to homogenize the sample, followed by the addition of hexadeuterobenzene (CeD ₆ , spectroscopic grade) and a minor amount of hexamethyldisiloxane (HMDS, 99.5+ %), with HMDS serving as internal standard. To give an example, about 200 mg of polymer were dissolved in 2.0 imL of TCB, followed by addition of 0.5 imL of C ₆ D ₆ and 2 to 3 drops of HMDS. Following data acquisition, the chemical shifts are referenced to the signal of the internal standard HMDS, which is assigned a value of δ 2.03 ppm. The syndiotacticity was determined by ¹³ C-NMR analysis on the total polymer. In the spectral region of the methyl groups, the signals corresponding to the pentads rrrr, mrrr, mrrm, mrmr, mmrm, rrmr and mmrr were assigned using published data. The syndiotactic index is calculated according to the following equation:

Syndiotactic index = rrrr + mrrr + mrrm + ½ ^* (mrmr + mmrm + rrmr + mmrr)

The ¹³ C-NMR detection limit in those conditions is about 0.6/10.000 C.

Syndiotactic polypropylene homopolymers are formed by the catalyzed polymerization of propylene monomer. In some embodiments, the syndiotactic polypropylene homopolymers suitable herein have a degree of syndiotacticity of from 70 % to 90 %. Preferably, the syndiotactic polypropylene homopolymers have a degree of syndiotacticity of from about 73 % to 90 %, preferably of from 75 % to 90 %.

The term "tacticity" refers to the arrangement of pendant groups in a polymer. For example, a polymer is "atactic" when its pendant groups are arranged in a random fashion on both sides of the chain of the polymer. In contrast, a polymer is "isotactic" when all of its pendant groups are arranged on the same side of the chain and "syndiotactic" when its pendant groups alternate on opposite sides of the chain. Syndiotactic polypropylene is thus, a polypropylene in which the pending methyl groups alternate in a regular fashion from one side of the chain to the other.

In a preferred embodiment, a suitable syndiotactic polypropylene is a homopolymer. As used herein syndiotactic polypropylene homopolymers include random copolymers of syndiotactic polypropylene having a very small amount of ethylene or other alpha olefin comonomer (ethylene is preferred), i.e., less than about 0.7 % by weight of the total polymer composition, preferably less than 0.5 % by weight, yet more preferably less than 0.1 % by weight of ethylene. Syndiotactic polypropylene copolymers having less than about 0.7 % by weight of ethylene, behave very much like 100 % by weight syndiotactic polypropylene homopolymers in regard to most physical properties. Unless noted to the contrary, the term syndiotactic polypropylene homopolymer will be understood to include both pure syndiotactic polypropylene homopolymers and syndiotactic polypropylene copolymers containing less than about 0.7 % by weight of various alpha olefins, preferably less than 0.7 % by weight of ethylene.

In some embodiments, said composition comprises at least 50 % by weight preferably at least 60 % by weight, preferably at least 70 % by weight, preferably at least 80% by weight, preferably at least 90 % by weight, preferably at least 95 % by weight, yet more preferably at least 97 % by weight, yet even more preferably at least 98 % by weight of said at least one syndiotactic polypropylene, based on the total weight of the composition. In some embodiments, said pipe comprises at least 50 % by weight preferably at least 60 % by weight, preferably at least 70 % by weight, preferably at least 80 % by weight, preferably at least 90 % by weight, preferably at least 95 % by weight of said at least one syndiotactic polypropylene, based on the total weight of the pipe. In some embodiments, the pipe according to the invention comprises at least one syndiotactic polypropylene having a density of at most 0.900 g/cm ³ as determined according to ASTM D-1505 at 23°C. In some preferred embodiments, the syndiotactic polypropylene has a density of at least 0.800 g/cm ³ and of at most 0.900 g/cm ³ ; preferably at least 0.820 g/cm ³ and at most 0.900 g/cm ³ , preferably at least 0.840 g/cm ³ and at most 0.900 g/cm ³ , preferably at least 0.8605 g/cm ³ and at most 0.9000 g/cm ³ , preferably at least 0.870 g/cm ³ and at most 0.900 g/cm ³ . The density of the syndiotactic polypropylene refers to the polymer density as such, not including additives such as for example pigments, for example black carbon, unless otherwise stated.

Examples of syndiotactic polypropylene suitable for use in the present pipes include without limitation FINAPLAS® 1251 , and FINAPLAS® 1471 syndiotactic polypropylenes, which are commercially available from Total Petrochemicals USA, Inc.

The syndiotactic polypropylene is desirably catalyzed using a metallocene catalyst system.

Preferably, the syndiotactic polypropylene suitable for the invention may be produced by polymerizing propylene and one or more optional co-monomers, optionally hydrogen in the presence of at least one single-site catalyst system, preferably a metallocene catalyst system.

As used herein, the term "catalyst" refers to a substance that causes a change in the rate of a polymerization reaction. In the present invention, it is especially applicable to catalysts suitable for the polymerization of propylene to syndiotactic polypropylene. The present invention especially relates to syndiotactic polypropylene prepared in the presence of single-site catalyst. Amongst these catalysts, metallocene catalysts are preferred. As used herein, the terms "metallocene-catalyzed syndiotactic polypropylene resin", and "metallocene-catalyzed syndiotactic polypropylene" are synonymous and used interchangeably and refer to a syndiotactic polypropylene prepared in the presence of a metallocene catalyst.

The term "metallocene catalyst" or "metallocene" for short is used herein to describe any transition metal complexes comprising metal atoms bonded to one or more ligands. The preferred metallocene catalysts are compounds of Group IV transition metals of the Periodic Table such as titanium, zirconium, hafnium, etc., and have a coordinated structure with a metal compound and ligands composed of one or two groups of cyclopentadienyl, indenyl, fluorenyl or their derivatives. The structure and geometry of the metallocene can be varied to adapt to the specific need of the producer depending on the desired polymer. Metallocenes typically comprise a single metal site, which allows for more control of branching and molecular weight distribution of the polymer. Monomers are inserted between the metal and the growing chain of polymer.

In some embodiments, the metallocene catalyst is a compound of formula (I):

R"(Ar) ₂ MQ _j (I),

wherein the metallocene according to formula (I) is a bridged metallocene;

wherein said metallocene according to formula (I) has two Ar bound to M which can be the same or different from each other; wherein j is an integer selected from 1 , 2, 3 and 4, and when j is 2 or more, the plurality of Q may be the same as or different from one another; preferably j is 2;

wherein Ar is an aromatic ring, group or moiety and wherein each Ar is independently selected from the group consisting of cyclopentadienyl, fluorenyl, indenyl (IND), and tetrahydroindenyl (THI), wherein each of said groups may be optionally substituted with one or more substituents each independently selected from the group consisting of hydrocarbyl having 1 to 20 carbon atoms, halogen, SiR'"3 wherein R'" is a hydrocarbyl having 1 to 20 carbon atoms, and wherein said hydrocarbyl optionally contains one or more atoms selected from the group comprising B, Si, S, O, F, CI, and P;

wherein M is a transition metal selected from the group consisting of titanium, zirconium, hafnium, and vanadium; and preferably is zirconium;

wherein each Q is independently selected from the group consisting of halogen, a hydrocarboxy having 1 to 20 carbon atoms, and a hydrocarbyl having 1 to 20 carbon atoms and wherein said hydrocarbyl optionally contains one or more atoms selected from the group comprising B, Si, S, O, F, CI, and P; and

wherein R" is a divalent group or moiety bridging the two Ar groups and selected from the group consisting of C1-C20 alkylene, germanium, silicon, siloxane, alkylphosphine, and an amine, and wherein said R" is optionally substituted with one or more substituents each independently selected from the group consisting of hydrocarbyl having 1 to 20 carbon atoms, halogen, S1R3 wherein R is a hydrocarbyl having 1 to 20 carbon atoms; and wherein said hydrocarbyl optionally contains one or more atoms selected from the group comprising B, Si, S, O, F, CI, Br, I and P.

Preferably, the metallocene comprises a bridged cyclopentadienyl-fluorenyl component. In some embodiments, the metallocene catalyst is a fluorenyl-type metallocene catalyst (FMC) of the following formula (II):

wherein M, Q and j are as defined herein above; and

wherein R ¹ , R ² , R ³ and R ⁴ are each independently selected from the group consisting of hydrogen, hydrocarbyl having 1 to 20 carbon atoms, halogen, SiR'"3 wherein R'" is a hydrocarbyl having 1 to 20 carbon atoms, and wherein said hydrocarbyl optionally contains one or more atoms selected from the group comprising B, Si, S, O, F, CI, Br, I and P; and wherein R ¹ and R ² are not bonded to each other to form a ring; and wherein R ³ and R ⁴ are not bonded to each other to form a ring;

R ⁵ and R ⁶ are each independently selected from the group consisting of hydrogen; hydrocarbyl having 1 to 20 carbon atoms, halogen, S1R3 wherein R is a hydrocarbyl having 1 to 20 carbon atoms; and wherein said hydrocarbyl optionally contains one or more atoms selected from the group comprising B, Si, S, O, F, CI, Br, I and P. Preferably, R ¹ and R ⁴ are the same. Preferably, R ² ; R ³ are the same. Preferably R ⁵ and R ⁶ are the same.

Examples of suitable hydrocarbyl group having 6 to 20 carbon atoms include: phenyl, o- chlorophenyl, m-chlorophenyl, p-chlorophenyl, bromoaryl groups such as o-bromophenyl, m- bromophenyl, p-bromophenyl, o-iodophenyl, m-iodophenyl, p-iodophenyl, naphthyl, chloronaphthyl, bromonaphthyl, iodonaphthyl, o-tolyl, m-tolyl, p-tolyl, bromomethylphenyl, dibromomethylphenyl, iodomethylphenyl, diiodomethylphenyl, ethylphenyl, n-propylphenyl, i-propylphenyl, n-butylphenyl, s- butylphenyl, t-butylphenyl, xylyl, benzyl, m-chlorobenzyl, p-chlorobenzyl, m-bromobenzyl, p- bromobenzyl, m-iodobenzyl, p-iodobenzyl, [alpha]-phenethyl, [beta]-phenethyl, diphenylmethyl, naphthylmethyl and neophyl.

In some embodiments, the metallocene catalyst is a FMC of formula (II), wherein R ¹ , R ² , R ³ and R ⁴ are each independently selected from the group consisting of hydrogen, hydrocarbyl having 1 to 20 carbon atoms, and SiR'"3 wherein R'" is a hydrocarbyl having 1 to 20 carbon atoms; and wherein R ¹ and R ² are not bonded to each other to form a ring; and wherein R ³ and R ⁴ are not bonded to each other to form a ring. More preferably, R ¹ and R ⁴ are the same; and R ² and R ³ are the same; and it is particularly preferable that R ² and R ³ are t-butyl groups.

In some embodiments, the metallocene catalyst is a FMC of formula (II), wherein R ⁵ and R ⁶ are each independently selected from the group consisting of hydrogen; hydrocarbyl having 1 to 20 carbon atoms and S1R3 wherein R is a hydrocarbyl having 1 to 20 carbon atoms; and wherein said hydrocarbyl optionally contains one or more atoms selected from the group comprising F, CI, Br and I. More preferably R ⁵ and R ⁶ are the same and are hydrocarbyl groups having 6 to 20 carbon atoms. Preferably, R ¹ and R ⁴ are the same and R ² and R ³ are the same.

In some embodiments, the metallocene catalyst is a FMC of formula (II), wherein R ¹ and R ⁴ are each preferably a hydrogen atom or a hydrocarbyl group having 6 to 20 carbon atoms; more preferably a hydrogen atom or an aryl group having 6 to 10 carbon atoms; most preferably a hydrogen atom, phenyl, o-tolyl, m-tolyl, p-tolyl, o-chlorophenyl, m-chlorophenyl or p-chlorophenyl. Preferably, R ¹ and R ⁴ are the same, R ⁵ and R ⁶ are the same and R ² and R ³ are the same.

In some embodiments, the metallocene catalyst is a FMC of formula (II), wherein R ⁵ and R ⁶ may be the same as or different from one another, and are each preferably an aryl group having 6 to 10 carbon atoms or an arylalkyl group having 6 to 10 carbon atoms; preferably phenyl, benzyl, m- chlorophenyl, p-chlorophenyl, m-chlorobenzyl or p-chlorobenzyl. Preferably, R ¹ and R ⁴ are the same, R ⁵ and R ⁶ are the same and R ² and R ³ are the same. Illustrative examples of FMCs suitable for use in the preparation of syndiotactic polypropylene for use herein include dibenzylmethylene(cyclopentadienyl)(2,7-dimethyl-3,6-di-tert - butylfluorenyl)zirconium dichloride [also referred to as 1 ,3-diphenylisopropylidene (cyclopentadienyl)(2,7-dimethyl-3,6-di-tert-butylfluorenyl) zirconium dichloride; hereinafter, alias of each compound is omitted], dibenzylmethylene(cyclopentadienyl)(2,7-di(2,4,6-trimethylph enyl)-3,6- di-tert-butylfluorenyl)zirconium dichloride, dibenzylmethylene(cyclopentadienyl) (2,7-diphenyl-3,6-di- tert-butylfluorenyl) zirconium dichloride, dibenzylmethylene(cyclopentadienyl) (2,7-di(3,5- dimethylphenyl)-3,6-di-tert-butylfluorenyl)zirconium dichloride, dibenzylmethylene(cyclopentadienyl) (2,7-di(4-methylphenyl)-3,6-di-tert-butylfluorenyl)zirconium dichloride, dibenzylmethylene(cyclopentadienyl) (2,7-dinaphthyl-3,6-di-tert-butylfluorenyl) zirconium dichloride, dibenzylmethylene(cyclopentadienyl) (2,7-di(4-tert-butylphenyl)-3,6-di-tert-butylfluorenyl)zirco nium dichloride, diphenethylmethylene(cyclopentadienyl)(2,7-diphenyl-3,6-di-t ert-butylfluorenyl)zirconium dichloride, di(benzhydryl)methylene(cyclopentadienyl)(2,7-diphenyl-3,6-d tert- butylfluorenyl)zirconium dichloride, di(cumyl)methylene(cyclopentadienyl)(2,7-diphenyl-3,6-d tert- butylfluorenyl)zirconium dichloride, diphenylmethylene(cyclopentadienyl)(3,6-d tert- butylfluorenyl)zirconium dichloride, di-o-tolylmethylene(cyclopentadienyl)(3,6-d tert- butylfluorenyl)zirconium dichloride, di-m-tolylmethylene(cyclopentadienyl)(3,6-d tert- butylfluorenyl)zirconium dichloride, di-p-tolylmethylene(cyclopentadienyl)(3,6-d tert- butylfluorenyl)zirconium dichloride, di(o-chlorophenyl)methylene(cyclopentadienyl)(3,6-d tert- butylfluorenyl)zirconium dichloride, di(m-chlorophenyl)methylene(cyclopentadienyl)(3,6-d tert- butylfluorenyl)zirconium dichloride, di(p-chlorophenyl)methylene(cyclopentadienyl)(3,6-d tert- butylfluorenyl)zirconium dichloride, di(o-bromophenyl)methylene(cyclopentadienyl)(3,6-d tert- butylfluorenyl)zirconium dichloride, di(m-bromophenyl)methylene(cyclopentadienyl)(3,6-d tert- butylfluorenyl)zirconium dichloride, di(p-bromophenyl)methylene(cyclopentadienyl)(3,6-d tert- butylfluorenyl)zirconium dichloride, di(o-iodophenyl)methylene(cyclopentadienyl)(3,6-d tert- butylfluorenyl)zirconium dichloride, di(m-iodophenyl)methylene(cyclopentadienyl)(3,6-d tert- butylfluorenyl)zirconium dichloride, ddii((pp--iiooddoopphheennyyll))mmeetthhyylleennee((ccyyccll ooppeennttaaddiieennyyll))(3,6-d tert- butylfluorenyl)zirconium dichloride, di(o-trifluoromethylphenyl)methylene(cyclopentadienyl)(3,6-d i- tert-butylfluorenyl)zirconium dichloride, di(m-trifluoromethylphenyl)methylene(cyclopentadienyl)(3,6- di-tert-butylfluorenyl)zirconium dichloride, di(p- trifluoromethylphenyl)methylene(cyclopentadienyl)(3,6-di-ter t-butylfluorenyl)zirconium dichloride, di(2-naphthyl)methylene(cyclopentadienyl)(3,6-di-tert-butylf luorenyl)zirconium dichloride, dibenzylmethylene(cyclopentadienyl)(3,6-di-tert-butylfluoren yl)zirconium dichloride, di(o- chlorobenzyl)methylene(cyclopentadienyl)(3,6-di-tert-butylfl uorenyl)zirconium dichloride, di(m- chlorobenzyl)methylene(cyclopentadienyl)(3,6-di-tert-butylfl uorenyl)zirconium dichloride, di(p- chlorobenzyl)methylene(cyclopentadienyl)(3,6-di-tert-butylfl uorenyl)zirconium dichloride, di(o- bromobenzyl)methylene(cyclopentadienyl)(3,6-di-tert-butylflu orenyl)zirconium dichloride, di(m- bromobenzyl)methylene(cyclopentadienyl)(3,6-di-tert-butylflu orenyl)zirconium dichloride, di(p- bromobenzyl)methylene(cyclopentadienyl)(3,6-di-tert-butylflu orenyl)zirconium dichloride, di(o- iodobenzyl)methylene(cyclopentadienyl)(3,6-di-tert-butylfluo renyl)zirconium dichloride, di(m- iodobenzyl)methylene(cyclopentadienyl)(3,6-di-tert-butylfluo renyl)zirconium dichloride, di(p- iodobenzyl)methylene(cyclopentadienyl)(3,6-di-tert-butylfluo renyl)zirconium dichloride, di(o- methylbenzyl)methylene(cyclopentadienyl)(3,6-di-tert-butylfl uorenyl)zirconium dichloride, di(m- methylbenzyl)methylene(cyclopentadienyl)(3,6-di-tert-butylfl uorenyl)zirconium dichloride, di(p- methylbenzyl)methylene(cyclopentadienyl)(3,6-di-tert-butylfl uorenyl)zirconium dichloride, (benzyl)(phenyl)methylene(cyclopentadienyl)(3,6-di-tert-buty lfluorenyl)zirconium dichloride, (benzyl)(phenyl)methylene(cyclopentadienyl)(2,7-diphenyl-3,6 -di-tert-butylfluorenyl)zirconi^ dichloride, (benzyl)(phenyl)methylene(cyclopentadienyl)(2,7-di-o-tolyl-3 ,6-di-tert- butylfluorenyl)zirconium dichloride, (benzyl)(phenyl)methylene(cyclopentadienyl)(2,7-di-p- chlorophenyl-3,6-di-tert-butylfluorenyl)zirconium dichloride, (p- chlorobenzyl)(phenyl)methylene(cyclopentadienyl)(2,7-dipheny l-3,6-di-tert-butylfluorenyl)zircon dichloride, (p-chlorobenzyl)(phenyl)methylene(cyclopentadienyl)(2,7-di-o -tolyl-3,6-di-tert- butylfluorenyl)zirconium dichloride, (p-chlorobenzyl)(phenyl)methylene(cyclopentadienyl)(2,7-dip- chlorophenyl-3,6-di-tert-butylfluorenyl)zirconium dichloride, (benzyl)(p- chlorophenyl)methylene(cyclopentadienyl)(2,7-diphenyl-3,6-di -tert-butylfluorenyl)zirconium dichloride, (benzyl)(p-chlorophenyl)methylene(cyclopentadienyl)(2,7-di-o -tolyl-3,6-di-tert- butylfluorenyl)zirconiumdichloride, (benzyl)(p-chlorophenyl)methylene(cyclopentadienyl)(2,7-di-p - chlorophenyl-3,6-di-tert-butylfluorenyl)zirconium dichloride, diphenylmethylene(cyclopentadienyl)(2,7-di-o-tolyl-3,6-di-te rt-butylfluorenyl)zirconium dichloride, di- p-tolyl-methylene(cyclopentadienyl)(2,7-di-o-tolyl-3,6-di-te rt-butylfluorenyl)zirconium dichloride, di(p- chlorophenyl)methylene(cyclopentadienyl)(2,7-di-o-tolyl-3,6- di-tert-butylfluorenyl)zirconium dichloride, di(p-trifluoromethylphenyl)methylene(cyclopentadienyl)(2,7-d i-o-tolyl-3,6-di-tert- butylfluorenyl)zirconium dichloride, di(2-naphthyl)methylene(cyclopentadienyl)(2,7-di-o-tolyl-3,6 -di- tert-butylfluorenyl)zirconium dichloride, dibenzylmethylene(cyclopentadienyl)(2,7-di-o-tolyl-3,6-di-te rt- butylfluorenyl)zirconium dichloride, di(p-chlorobenzyl)methylene(cyclopentadienyl)(2,7-di-o-tolyl -3,6- di-tert-butylfluorenyl)zirconium dichloride, di(p-methylbenzyl)methylene(cyclopentadienyl)(2,7-di-o- tolyl-3,6-di-tert-butylfluorenyl)zirconium dichloride, dibenzylmethylene(cyclopentadienyl)(2,7-di-o- tolyl-fluorenyl)zirconium dichloride, dibenzylmethylene(cyclopentadienyl)[2,7-di-(o-ethylphenyl)-3 ,6- di-tert-butylfluorenyl]zirconium dichloride, dibenzylmethylene(cyclopentadienyl)[2,7-di-[o-(n- propyl)phenyl]-3,6-di-tert-butylfluorenyl]zirconium dichloride, dibenzylmethylene(cyclopentadienyl)[2,7-di-[o-(iso-propyl)ph enyl]-3,6-di-tert-butylfluorenyl]zirc^ dichloride, dibenzylmethylene(cyclopentadienyl)[2,7-di-[o-(n-butyl)pheny l]-3,6-di-tert- butylfluorenyl]zirconium dichloride, dibenzylmethylene(cyclopentadienyl)[2,7-di-[o-(iso-butyl)phe nyl]- 3,6-di-tert-butylfluorenyl]zirconium dichloride, dibenzylmethylene(cyclopentadienyl)[2,7-di-[o-(sec- butyl)phenyl]-3,6-di-tert-butylfluorenyl]zirconium dichloride, dibenzylmethylene(cyclopentadienyl)[2,7- di-[o-(tert-butyl)phenyl]-3,6-di-tert-butylfluorenyl]zirconi um dichloride, dibenzylmethylene(cyclopentadienyl)[2,7-di-[o-(n-^

dichloride, dibenzylmethylene(cyclopentadienyl)[2,7-di-(o-cyclohexylphen yl)-3,6-di-tert- butylfluorenyl]zirconium dichloride, dibenzylmethylene(cyclopentadienyl)[2,7-di-(biphenyl-2-yl)-3 ,6-di- tert-butylfluorenyl]zirconium dichloride, dibenzylmethylene(cyclopentadienyl)[2,7-di-[o-(2- naphthyl)phenyl]-3,6-di-tert-butylfluorenyl]zirconium dichloride, dibenzylmethylene(cyclopentadienyl) [2,7-di-[o-(2-phenanthryl)phenyl]-3,6-di-tert-butylfluorenyl ]zirconium dichloride, dibenzylmethylene(cyclopentadienyl)[2,7-di-(o-trimethylsilyl phenyl)-3,6-di-tert- butylfluorenyl]zirconium dichloride, dibenzylmethylene(cyclopentadienyl)[2,7-di-(o- triphenylsilylphenyl)-3,6-di-tert-butylfluorenyl]zirconium dichloride, diphenylmethylene(cyclopentadienyl)(2,7-diphenyl-3,6-di-tert -butylfluorenyl)zirconium dichloride, dibenzylmethylene(cyclopentadienyl)(2,7-diphenyl-3,6-di-tert -butylfluorenyl)zirconium dichloride, diphenylmethylene(cyclopentadienyl)(2,7-di-p-chlorophenyl-3, 6-di-tert-butylfluorenyl)zirconi dichloride, di-p-tolyl-methylene(cyclopentadienyl)(2,7-di-p-chlorophenyl -3,6-di-tert- butylfluorenyl)zirconium dichloride, di(p-chlorophenyl)methylene(cyclopentadienyl)(2,7-di-p- chlorophenyl-3,6-di-tert-butylfluorenyl)zirconium dichloride, di(p- trifluoromethylphenyl)methylene(cyclopentadienyl)(2,7-di-p-c hlorophenyl-3,6-di-tert- butylfluorenyl)zirconium dichloride, di(2-naphthyl)methylene(cyclopentadienyl)(2,7-di-p-chlorophe nyl- 3,6-di-tert-butylfluorenyl)zirconium dichloride, dibenzylmethylene(cyclopentadienyl)(2,7-di-p- chlorophenyl-3,6-di-tert-butylfluorenyl)zirconium dichloride, di(p- chlorobenzyl)methylene(cyclopentadienyl)(2,7-di-p-chlorophen yl-3,6-di-tert-butylfluorenyl)zircon dichloride, di(p-methylbenzyl)methylene(cyclopentadienyl)(2,7-di-p-chlor ophenyl-3,6-di-tert- butylfluorenyl)zirconium dichloride, dibenzylmethylene(cyclopentadienyl)(2,7-di-p-chlorophenyl-3, 6- ditrimethylsilylfluorenyl)zirconium dichloride, dibenzylmethylene(cyclopentadienyl)(2,7-di-p- chlorophenyl-3,6-dicumylfluorenyl)zirconium dichloride, dibenzylmethylene(cyclopentadienyl)(2,7-di- p-chlorophenyl-3,6-adamantylfluorenyl)zirconium dichloride, dimethylmethylene(cyclopentadienyl)(2,7-di-p-trifluoromethyl phenyl-3,6-di-tert- butylfluorenyl)zirconium dichloride, diethylmethylene(cyclopentadienyl)(2,7-di-p- trifluoromethylphenyl-3,6-di-tert-butylfluorenyl)zirconium dichloride, di-n- propylmethylene(cyclopentadienyl)(2,7-di-p-trifluoromethylph enyl-3,6-di-tert-butylfluoren

dichloride, di-iso-propylmethylene(cyclopentadienyl)(2,7-di-p-trifluorom ethylphenyl-3,6-di-tert- butylfluorenyl)zirconium dichloride, di-n-butylmethylene(cyclopentadienyl)(2,7-di-p- trifluoromethylphenyl-3,6-di-tert-butylfluorenyl)zirconium dichloride, di-iso- butylmethylene(cyclopentadienyl)(2,7-di-p-trifluoromethylphe nyl-3,6-di-tert-butylfluoreny^

dichloride, di-sec-butylmethylene(cyclopentadienyl)(2,7-di-p-trifluorome thylphenyl-3,6-di-tert- butylfluorenyl)zirconium dichloride, di-tert-butylmethylene(cyclopentadienyl)(2,7-di-p- trifluoromethylphenyl-3,6-di-tert-butylfluorenyl)zirconium dichloride, di-n- octylmethylene(cyclopentadienyl)(2,7-di-p-trifluoromethylphe nyl-3,6-di-tert-butylfluoren

dichloride, di-n-triacontylmethylene(cyclopentadienyl)(2,7-di-p-trifluor omethylphenyl-3,6-di butylfluorenyl)zirconium dichloride, phenylmethylene(cyclopentadienyl)(2,7-di-p- trifluoromethylphenyl-3,6-di-tert-butylfluorenyl)zirconium dichloride, diphenylmethylene(cyclopentadienyl)(2,7-di-p-trifluoromethyl phenyl-3,6-di-tert- butylfluorenyl)zirconium dichloride, di-p-tolylmethylene(cyclopentadienyl)(2,7-di-p- trifluoromethylphenyl-3,6-di-tert-butylfluorenyl)zirconium dichloride, di(p- chlorophenyl)methylene(cyclopentadienyl)(2,7-di-p-trifluorom ethylphenyl-3,6-di-tert- butylfluorenyl)zirconium dichloride, di(p-trifluoromethylphenyl)methylene(cyclopentadienyl)(2,7-d i-p- trifluoromethylphenyl-3,6-di-tert-butylfluorenyl)zirconium dichloride, di(2- naphthyl)methylene(cyclopentadienyl)(2,7-di-p-trifluoromethy lphenyl-3,6-di-tert- butylfluorenyl)zirconium dichloride, dibenzylmethylene(cyclopentadienyl)(2,7-di-p- trifluoromethylphenyl-3,6-di-tert-butylfluorenyl)zirconium dichloride, di(p- chlorobenzyl)methylene(cyclopentadienyl)(2,7-di-p-trifluorom ethylphenyl-3,6-di-tert- butylfluorenyl)zirconium dichloride, di(p-methylbenzyl)methylene(cyclopentadienyl)(2,7-di-p- trifluoromethylphenyl-3,6-di-tert-butylfluorenyl)zirconium dichloride; compounds in which a zirconium atom of the above compounds is replaced with a hafnium atom or a titanium atom; compounds in which a chlorine atom of the above compounds is replaced with methyl group or benzyl group; and combinations thereof, without being limited thereto. Among a hafnium atom, a zirconium atom and a titanium atom, preferable is a zirconium atom. These compounds may be used singly, or two or more kinds may be used in combination.

As used herein, the term "hydrocarbyl having 1 to 20 carbon atoms" refers to a moiety selected from the group comprising a linear or branched C1-C20 alkyl; C ₃ -C ₂ o cycloalkyl; C ₆ -C ₂ o aryl; C ₇ -C ₂ o alkylaryl and C ₇ -C ₂ o arylalkyl, or any combinations thereof. Exemplary hydrocarbyl groups are methyl, ethyl, propyl, butyl, amyl, isoamyl, hexyl, isobutyl, heptyl, octyl, nonyl, decyl, cetyl, 2- ethylhexyl, and phenyl.

As used herein, the term "hydrocarboxy having 1 to 20 carbon atoms" refers to a moiety with the formula hydrocarbyl-O-, wherein the hydrocarbyl has 1 to 20 carbon atoms as described herein. Preferred hydrocarboxy groups are selected from the group comprising alkyloxy, alkenyloxy, cycloalkyloxy or aralkoxy groups.

As used herein, the term "alkyl", by itself or as part of another substituent, refers to straight or branched saturated hydrocarbon group joined by single carbon-carbon bonds having 1 or more carbon atom, for example 1 to 20 carbon atoms, for example 1 to 12 carbon atoms, for example 1 to 6 carbon atoms, for example 1 to 4 carbon atoms. When a subscript is used herein following a carbon atom, the subscript refers to the number of carbon atoms that the named group may contain. Thus, for example, Ci-i ₂ alkyl means an alkyl of 1 to 12 carbon atoms. Examples of alkyl groups are methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, fert-butyl, 2-methylbutyl, pentyl and its chain isomers, hexyl and its chain isomers, heptyl and its chain isomers, octyl and its chain isomers, nonyl and its chain isomers, decyl and its chain isomers, undecyl and its chain isomers, dodecyl and its chain isomers. Alkyl groups have the general formula C _n H _2n+ .

As used herein, the term "cycloalkyl", by itself or as part of another substituent, refers to a saturated or partially saturated cyclic alkyl radical. Cycloalkyl groups have the general formula C _n H _2n- . When a subscript is used herein following a carbon atom, the subscript refers to the number of carbon atoms that the named group may contain. Thus, examples of C3- ₆ cycloalkyl include cyclopropyl, cyclobutyl, cyclopentyl, or cyclohexyl.

As used herein, the term "aryl", by itself or as part of another substituent, refers to a radical derived from an aromatic ring, such as phenyl, naphthyl, indanyl, or 1 ,2,3,4-tetrahydro-naphthyl. When a subscript is used herein following a carbon atom, the subscript refers to the number of carbon atoms that the named group may contain.

As used herein, the term "alkylaryl", by itself or as part of another substituent, refers to an aryl group as defined herein, wherein a hydrogen atom is replaced by an alkyl as defined herein. When a subscript is used herein following a carbon atom, the subscript refers to the number of carbon atoms that the named group or subgroup may contain.

As used herein, the term "arylalkyl", by itself or as part of another substituent, refers to an alkyl group as defined herein, wherein a hydrogen atom is replaced by an aryl as defined herein. When a subscript is used herein following a carbon atom, the subscript refers to the number of carbon atoms that the named group may contain. Examples of C6-ioarylCi-6alkyl radicals include benzyl, phenethyl, dibenzylmethyl, methylphenylmethyl, 3-(2-naphthyl)-butyl, and the like.

As used herein, the term "alkylene", by itself or as part of another substituent, refers to alkyl groups that are divalent, i.e., with two single bonds for attachment to two other groups. Alkylene groups may be linear or branched and may be substituted as indicated herein. Non-limiting examples of alkylene groups include methylene (-CH ₂ -), ethylene (-CH2-CH2-), methylmethylene (-CH(CH ₃ )-), 1-methyl- ethylene (-CH(CH ₃ )-CH ₂ -), n-propylene (-CH ₂ -CH ₂ -CH ₂ -), 2-methylpropylene (-CH ₂ -CH(CH ₃ )-CH ₂ -), 3-methylpropylene (-CH ₂ -CH ₂ -CH(CH ₃ )-), n-butylene (-CH ₂ -CH ₂ -CH ₂ -CH ₂ -), 2-methylbutylene (-CH ₂ - CH(CH ₃ )-CH ₂ -CH ₂ -), 4-methylbutylene (-CH ₂ -CH ₂ -CH ₂ -CH(CH ₃ )-), pentylene and its chain isomers, hexylene and its chain isomers, heptylene and its chain isomers, octylene and its chain isomers, nonylene and its chain isomers, decylene and its chain isomers, undecylene and its chain isomers, dodecylene and its chain isomers. When a subscript is used herein following a carbon atom, the subscript refers to the number of carbon atoms that the named group may contain. For example, Cr C ₂ o alkylene refers to an alkylene having between 1 and 20 carbon atoms.

Exemplary halogen atoms include chlorine, bromine, fluorine and iodine, wherein fluorine and chlorine are preferred.

Suitable metallocene catalysts used herein are preferably provided on a solid support. The support can be an inert organic or inorganic solid, which is chemically unreactive with any of the components of the conventional metallocene catalyst. Suitable support materials for the supported catalyst include solid inorganic oxides, such as silica, alumina, magnesium oxide, titanium oxide, boron trioxide, calcium oxide, zinc oxide, barium oxide, thorium oxide, as well as mixed oxides of silica and one or more Group 2 or 13 metal oxides, such as silica-magnesia and silica-alumina mixed oxides. Silica, alumina, and mixed oxides of silica and one or more Group 2 or 13 metal oxides are preferred support materials. Preferred examples of such mixed oxides are the silica-alumina. Most preferred is a silica compound. In a preferred embodiment, the metallocene catalyst is provided on a solid support, preferably a silica support. The silica may be in granular, agglomerated, fumed or other form.

The FMC may be used in conjunction with one or more co-catalysts to form a catalyst system. A "catalyst system" as used herein refers to one or more chemical agents, which operate in concert to increase the rate of a reaction. Catalyst systems comprising an FMC of the type disclosed herein may be used to catalyze the polymerization of propylene into syndiotactic polypropylene.

In some embodiments a catalyst system for the production of a syndiotactic polypropylene for use herein comprises a co-catalyst. In employing the catalyst components of the present disclosure (i.e. FMCs) in polymerization procedures, they may be used in conjunction with an activating co-catalyst. Suitable activating co-catalysts can be any co-catalyst known for this purpose such as an aluminium- containing co-catalyst, a boron-containing co-catalyst or a fluorinated catalyst. The aluminium- containing co-catalyst may comprise an alumoxane, an alkyl aluminium, a Lewis acid and/or a fluorinated catalytic support.

In some embodiments, alumoxane is used as an activating agent for the metallocene catalyst. As used herein, the term "alumoxane" and "aluminoxane" are used interchangeably, and refer to a substance, which is capable of activating the metallocene catalyst. In an embodiment, alumoxanes comprise oligomeric linear and/or cyclic alkyl alumoxanes. In a further embodiment, the alumoxane has formula (V) or (VI):

R ^a -(AI(R ^a )-0) _x -AIR ^a 2 (V) for oligomeric, linear alumoxanes; or

(-AI(R ^a )-0-)y (VI) for oligomeric, cyclic alumoxanes

wherein x is 1-40, and preferably 10-20;

wherein y is 3-40, and preferably 3-20; and

wherein each R ^a is independently selected from a C-i-Csalkyl, and preferably is methyl. In a preferred embodiment, the alumoxane is methylalumoxane (MAO).

In a preferred embodiment, the metallocene catalyst is a supported metallocene-alumoxane catalyst comprising a metallocene and an alumoxane which are bound on a porous silica support.

One or more aluminiumalkyl represented by the formula AIR ^b _x can be used as additional co-catalyst, wherein each R ^b is the same or different and is selected from halogens or from alkoxy or alkyl groups having from 1 to 12 carbon atoms and x is from 1 to 3. Non-limiting examples are Tri-Ethyl Aluminum (TEAL), Tri-lso-Butyl Aluminum (TIBAL), Tri-Methyl Aluminum (TMA), and Methyl-Methyl- Ethyl Aluminum (MMEAL). Especially suitable are trialkylaluminiums, the most preferred being triisobutylaluminium (TIBAL) and triethylaluminum (TEAL).

The alkyl alumoxane co-catalyst and FMC may be employed in any suitable amount to provide an olefin polymerization catalyst. Suitable aluminum:FMC mole ratios are within the range of 10:1 to 20,000:1 alternatively, within the range of 50:1 to 10,000:1 , alternatively, within the range of 100: 1 to 5,000:1. The polymerization of propylene to form syndiotactic polypropylene may be carried out using solution phase, gas phase, slurry phase, bulk phase, high pressure processes or combinations thereof, for example. One example of a gas phase polymerization process includes a continuous cycle system, wherein a cycling gas stream (otherwise known as a recycle stream or fluidizing medium) is heated in a reactor by heat of polymerization. The heat is removed from the cycling gas stream in another part of the cycle by a cooling system external to the reactor. The cycling gas stream containing one or more monomers may be continuously cycled through a fluidized bed in the presence of a catalyst under reactive conditions. The cycling gas stream is generally withdrawn from the fluidized bed and recycled back into the reactor. Simultaneously, polymer product may be withdrawn from the reactor and fresh monomer may be added to replace the polymerized monomer. The reactor temperature in a gas phase process may vary from -30 °C to 120 °C, or from 60 °C to 1 15 °C, or from 70 °C to 1 10 °C, or from 70 °C to 95 °C, for example.

Slurry phase processes generally include forming a suspension of solid, particulate polymer in a liquid polymerization medium, to which monomers and optionally hydrogen, along with catalyst, are added. The suspension (which may include diluents) may be intermittently or continuously removed from the reactor where the volatile components can be separated from the polymer and recycled, optionally after a distillation, to the reactor. The liquefied diluent employed in the polymerization medium may include a C3 _-7 alkane (e.g. hexane or isobutene), for example. The medium employed is generally liquid under the conditions of polymerization and relatively inert. A bulk phase process is similar to that of a slurry process. However, a process may be a bulk process, a slurry process or a bulk slurry process, for example.

Slurry polymerization is preferably used to prepare the syndiotactic polypropylene, preferably in a slurry loop reactor or a continuously stirred reactor. As used herein, the terms "loop reactor" and "slurry loop reactor" may be used interchangeably herein. The loop reactor may be maintained at a pressure of from 27 bar to 45 bar and a temperature of from 38 °C to 121 °C, for example.

Polymerization can be performed in one reactor or in a sequence of reactors. Blends of various syndiotactic polypropylenes are also suitable for the invention.

In some embodiments, the pipe is made of a composition comprising the syndiotactic polypropylene and which can further comprise at least one processing aid. Non-limiting examples of suitable processing aids for use in the present invention include fluorine- of silicon-based processing aid.

Preferred processing aids can be selected from fluoropolymers including fluoro elastomers and crystalline or semi-crystalline fluoroplastics or blends thereof. The fluoropolymer to be blended with the syndiotactic polypropylene may be any polymer containing fluorine. The fluoropolymers as a class can be crystalline or generally amorphous. Exemplary of commercially available processing aids suitable for use in the present invention include materials available under the following designations: DuPont's Viton Freeflow Z100, Viton Freeflow Z1 10, Viton Freeflow Z200, Viton Freeflow Z210, Viton Freeflow Z300, Viton Freeflow 10, Viton Freeflow RC; 3M's Dynamar FX 591 1 , Dynamar FX 5912, Dynamar FX 5920A, Dynamar FX 5926, Dynamar FX 5927, Dynamar FX 9613, Dynamar FX 9614, Daikin's DAI-EL DA-410, DAI-EL DA-910 and Solvay's Tecnoflon NM and SOLEF 1 1010. A suitable class of fluoropolymer for use in the present invention is a polymer derived from one or more of the following materials: vinylidene fluoride, hexafluoropropylene and tetrafluoroethylene.

The processing aid can be added in a masterbatch or neat, in any stage of the production (for example, during pelletizing, compounding or at the pipe production line), as is generally known in the art.

For example, the composition comprising the syndiotactic polypropylene can comprise at least 50 ppm of at least one processing aid, preferably at least 100 ppm, preferably at least 200 ppm of at least one processing aid, preferably a silicon- or fluorine-based processing aid, for example a fluoroelastomer.

The composition comprising the syndiotactic polypropylene may additionally include effective quantities of any conventional additive as known in the art such as, for example antioxidants, antiacids, wetting agents, nucleating agents and the Ike.

Preferred antioxidants may be found in Zweifel, Hans, ISBN 354061690X, Springer- Verlag 1998. Preferred antioxidants are Irganox 1010 and Irgafos 168, as shown below.

Ir anox 1010:

Calcium stearate may be added as a processing aid. The additives can be added as a masterbatch or neat, in any stage of the production (for example, during pelletizing, compounding or at the pipe production line), as is generally known in the art.

In some embodiments, the composition comprising the syndiotactic polypropylene used for pipes may contain other auxiliary materials, such as fillers and/or stabilizers and/or antistatic agents and/or pigments and/or reinforcing agents.

Blends of syndiotactic polypropylene with another polymer are also possible. In such case, the proportion of the other polymer must be lower than 30 % by weight, preferably lower than 10 % by weight, even more preferably lower than 2 % by weight. Amongst possible polymers, addition of a small polyethylene content (typically 1 % by weight) is preferred as polyethylene acts as a nucleating agent of syndiotactic polypropylene. Other nucleating agents could also be added to the syndiotactic polypropylene.

For the purposes of the present application a nucleating agent is defined as a chemical compound that raises the crystallization temperature of the polypropylene. Suitable nucleating agents for use in the present invention can be selected from any of the nucleating agents knownby the skilled person. In some embodiments, the nucleating agent is selected from the group comprising talc, carboxylate salts, sorbitol acetals, phosphate ester salts, substituted benzene tricarboxamides and polymeric nucleating agents, as well as blends thereof.

Examples of suitable carboxylate salts include organocarboxylic acid salts. Particular examples are sodium benzoate and lithium benzoate. The organocarboxylic acid salts may also be alicyclic organocarboxylic acid salts, such as bicyclic organodicarboxylic acid salts and in particular bicyclo[2.2.1]heptane dicarboxylic acid salt. A nucleating agent of this type is sold as HYPERFORM® HPN-68 by Milliken Chemical. Examples of suitable sorbitol acetals include dibenzylidene sorbitol (DBS), bis(p-methyl-dibenzylidene sorbitol) (MDBS), bis(p-ethyl-dibenzylidene sorbitol), bis(3,4-dimethyl-dibenzylidene sorbitol) (DMDBS), and bis(4-propylbenzylidene) propyl sorbitol. Bis(3,4-dimethyl-dibenzylidene sorbitol) (DMDBS) and bis(4-propylbenzyhdene) propyl sorbitol are preferred. These can for example be obtained from Milliken Chemical under the trade names of Millad 3905, Millad 3940, Millad 3988 and Millad NX8000. Examples of suitable phosphate ester salts include salts of 2,2'-methylene-bis-(4,6-di-tert-butylphenyl)phosphate. Such phosphate ester salts are for example available as NA-11 or NA-21 from Asahi Denka. Examples of suitable substituted tricarboxamides include compounds of general formula UN):

wherein, in compounds of formula (III), R1 , R2 and R3, independently of one another, are selected from C1-C20 alkyl, C5-C12 cycloalkyl, or phenyl, each of which may in turn be substituted with one or more C1-C20 alkyl, C5-C12 cycloalkyl, phenyl, hydroxyl, C1-C20 alkylamino or C1-C20 alkyloxy etc. Examples of C1-C20 alkyl include methyl, ethyl, n-propyl, n-butyl, iso-butyl, tert-butyl, n-pentyl, iso- pentyl, 1 ,1-dimethylpropyl, 1 ,2-dimethylpropyl, 3-methylbutyl, hexyl, heptyl, octyl or 1 , 1 ,3,3- tetramethylbutyl. Examples of C5-C12 cycloalkyl include cyclopentyl, cyclohexyl, cyclooctyl, cyclododecyl, adamantyl, 2-methylcyclohexyl, 3-methylcyclohexyl or 2,3-dimethylcyclohexyl. Such nucleating agents are disclosed in WO 03/102069 and by Blomenhofer et al. in Macromolecules 2005, 38, 3688-3695. Non-limiting examples of polymeric nucleating agents include polymeric nucleating agents containing vinyl compounds, such as for example those disclosed in EP-A1- 0152701 and EP-A2-0368577. Polymeric nucleating agents containing vinyl compounds can either be physically or chemically blended with the polypropylene. Suitable vinyl compounds include vinyl cycloalkanes or vinyl cycloalkenes having at least 6 carbon atoms, such as for example vinyl cyclopentane, vinyl-3-methyl cyclopentane, vinyl cyclohexane, vinyl-2-methyl cyclohexane, vinyl-3- methyl cyclohexane, vinyl norbornane, vinyl cyclopentene, vinyl cyclohexene, vinyl-2-methyl cyclohexene. Further examples of polymeric nucleating agents include poly-3-methyl-1-butene, polydimethylstyrene, polysilanes and polyalkylxylenes. These polymeric nucleating agents can be introduced into the polypropylene either by chemical or by physical blending.

Other nucleating agents useful in the embodiments disclosed herein may include various organic and inorganic nucleating agents, such as: the gamma-crystalline form of a quinacridone colorant Permanent Red E3B "Q-Dye;" the disodium salt of o-phthalic acid; the aluminum salt of 6-quinizarin sulfonic acid; isophthalic and terephthalic acids; N',N'-dicyclohexyl-2,6-naphthalene dicarboxamide, also known as NJStar NU-100, available from the New Japan Chemical Co.; nucleating agents based upon salts of rosin/ad iebetic acid; zinc (II) monoglycerolate; nucleating agents based upon diamide compounds as disclosed in U.S. Pat. No. 6,235,823, such as N-cyclohexyl-4-(N- cyclohexylcarbonylamino)benzamide and N,N'-1 ,4-cyclohexane-bis-benzamide, for example; nucleating agents based upon trimesic acid derivatives, such as disclosed in WO 02/46300, WO 03/102069, WO 2004/072168, including, for example, 1 ,3,5-benzenetricarboxylic acid tris(cyclopentylamide), 1 ,3,5-benzenetricarboxylic acid tris(cyclohexylamide), and 1 ,3,5- benzenetricarboxylic acid tris(tert-butyl)amide.

The nucleating agents may be used in the form of powders, pellets, liquids, other commonly available forms, or combinations thereof, for admixture (melt blending) with polypropylenes. In other embodiments, the nucleating agent may be compounded with a polypropylene to form a nucleating additive master batch for admixture (melt blending) with polypropylenes. Compositions including polypropylene(s) and nucleating agent(s) according to the embodiments disclosed herein may be prepared by mixing or kneading the respective components at a temperature around or above the melting point temperature of one or more of the blend components. Typical polymer mixing or kneading equipment that is capable of reaching the desired temperatures and melt plastifying the mixture may be employed. These include mills, kneaders, extruders (both single screw and twin- screw), BANBURY® mixers, calenders, and the like. The sequence of mixing and methods may depend on the final composition as well as the form of the starting components (powder, pellet, masterbatch, etc.).

In some preferred embodiments, the composition comprising the syndiotactic polypropylene can comprise pigments. The specific color of the pigment may depend on the fluid to be carried in the pipes (water or gas) and on the country (depending on the imposed legislation).

The composition comprising the syndiotactic polypropylene used for pipes according to the invention may contain for example up to 40 % by weight of fillers and/or 0.01 % to 2.5 % by weight of stabilizers and/or 0.1 % to 1 % by weight of antistatic agents and/or 0.2 % to 3 % by weight of pigments and/or 0.2 % to 3 % by weight of reinforcing agents, in each case based on the total weight of the syndiotactic polypropylene.

Pipes according to the invention can be produced according to methods known in the art. According to a second aspect, the present invention also encompasses a process for the manufacture of a pipe according to the first aspect, comprising the steps of:

(a) extruding a composition comprising the syndiotactic polypropylene into a pipe;

(b) cooling the pipe formed in step (a); and

(c) optionally heating/annealing the pipe formed in step (a).

The extrusion step (a) can be performed at a temperature of at least 150 °C. For example the extrusion step (a) can be performed at a temperature ranging from at least 150 °C to at most 250 °C, preferably from at least 160 °C to at most 230 °C. In some embodiments, step (a) comprises first plasticizing the syndiotactic polypropylene composition in an extruder, for example at temperatures from at least 150 °C to at most 250 °C, and then extruding it through an annular die to the desired internal diameter.

The extruders for producing the pipes according to the invention can be single screw extruders or twin screw extruders or extruder cascades of homogenizing extruders (single screw or twin screw). To produce pellets from the fluff (when homogenizing and introducing the additives), a single screw extruder can be used, preferably with an L/D of 20 to 40, or twin screw extruders, preferably with an L/D of 20 to 40, preferably an extruder cascade is used. In some embodiments, supercritical CO2 or water are used during extrusion to help homogenization. Variations could be considered like the use of supercritical CO2 to help homogenization, use of water during extrusion. Optionally, a melt pump and/or a static mixer can be used additionally between the extruder and the ring die head. Ring shaped dies with diameters ranging from approximately 16 to 2000 mm and even greater are possible.

The melt arriving from the extruder can be first distributed over an annular cross-section via conically arranged holes and then fed to the core/die combination via a coil distributor or screen. If necessary, restrictor rings or other structural elements for ensuring uniform melt flow may additionally be installed before the die outlet.

After leaving the annular die, the pipe can be taken off over a calibrating mandrel. Once the pipe has been formed to the desired diameter and thickness, step (b) cooling of the pipe, takes place. The cooling of the pipe may be performed by air cooling and/or by water cooling, optionally also with inner water cooling.

After cooling, the pipe can be optionally subjected to a heating/annealing step (c). Said heating/annealing step can be performed in an oven, or any other suitable device, for a determined length of time; said process is known in the art as thermal annealing. In some embodiments, the pipes are subjected to thermal annealing at a temperature of at least 60 °C. In some embodiments, the pipes are subjected to thermal annealing at a temperature of at least 60 °C to at most 120 °C; preferably at a temperature of at least 70 °C to at most 1 10 °C; more preferably at a temperature of at least 75 °C to at most 90 °C. In some embodiments, the pipes are subjected to thermal annealing for at least 3 days. In some embodiments, the pipes are subjected to thermal annealing for at least 3 days to at most 20 days, for example at most 14 days; preferably for at least 4 days to at most 12 days; more preferably for at least 5 days to at most 10 days; most preferably for at least 6 days to at most 8 days.

In some embodiments, the pipes are subjected to thermal annealing at a temperature of at least 70 °C to at most 120 °C, for at least 3 days to at most 14 days.

The pipes according to the present invention surprisingly display improved mechanical properties and/or strength. In some embodiments, the pipe according to the invention has an impact resistance of at least 20 kJ/m ² as determined by ISO 180- notched izod test at 23 °C; preferably of at least 30 kJ/m ² ; preferably of at least 35 kJ/m ² ; preferably of at least 38 kJ/m ² ; preferably of at least 40 kJ/m ² ; preferably of at most 45 kJ/m ² .

The pipes according to the present invention surprisingly show improved flexibility properties, as measured by its flexural modulus, according to ISO 178. In some embodiments, the pipe according to the invention has a flexural modulus of less than 1000 MPa; preferably of less than 900 MPa; preferably of less than 800 MPa; preferably of less than 700 MPa; preferably of less than 600 MPa; more preferably of less than 500 MPa.

In some embodiments, the pipe according to the invention generally have a creep resistance which is such that they can be assigned a minimum required strength (MRS) rating according to the ISO/TR 9080 standard of MRS 10 rating (for PE100 resins). This rating is determined according to a statistical method and the minimum required strength MRS is defined as a classified lower prediction limit (LPL) at a 97.5 % confidence interval.

In some embodiments, the pipes according to the invention generally have an extrapolated 50 °C / 50 years stress of at least 7.0 MPa.

The pipes according to the present invention have excellent tensile strength, modulus and impact resistance, are of exceptional clarity, and may be clear enough to use without adding a separate clarifying agent to the pipe.

According to a third aspect, the present invention provides the use of a pipe according to the first aspect, and/or produced according to the second aspect, for the transportation of fluids under pressure. The pipes according to the invention are very suitable for the transportation of fluids under pressure, such as water and gas. They can be used over very wide temperature ranges.

The pipes according to the invention are also suitable for the transportation of fluids in the pharmaceutical, chemical and food production industries.

The present invention also encompasses the use of a pipe according to the first aspect, and/or produced according to the second aspect, for the manufacture of medical articles. Preferred articles are those requiring a see-through capacity. The most preferred articles have a wall thickness of about 2 mm or less, such as blood collection tubes, centrifuge tubes, culture bottles, syringe stoppers and barrels and the like.

The invention is illustrated but not limited by the following examples.

EXAMPLES

Test methods:

Unless otherwise stated, the density was measured according to the method of standard ASTM D- 1505 at 23 °C.

Creep experiments were performed on two different creep-testing devices (Table 2). The syndiotactic polypropylene (sPP) was molded by compression into 2 mm thickness sheets and then IS0527 5A type tensile bars were sampled into the sheets. The sample was inserted in the grips of the creep machine at a constant temperature (achieved with a water bath or a chamber), and a load was applied to the sample. Time to failure (deformation or break) was recorded for each sample.

The flexion test used to characterize the pipe flexibility has been adapted from the ISO 178 three- point bending test. The sole difference was that the polymer sample has been replaced by a 40 cm pipe segment (diameter 32 mm - SDR 1 1 ). The pipe segment was introduced in the Zwick type 1445 machine, in the center of a three-point bending test (span = 200 mm). During the test, the force is applied at the center of the span, also corresponding to the center of the pipe segment. The specific conditions for the test are (if a parameter or condition test is not mentioned, this means that its value is the same as the one imposed for the measurement of the flexural modulus of a polymer sample based on the ISO 178 three-points bending test) :

- Radius of the loading edge: 10 mm

- Radius of the supports: 5 mm

- Pre-charge: 5 N

- Test speed: 1 mm/min

- Temperature: 23 °C

The force as a function of the elongation is recorded. The lower the force, the more flexible is the pipe.

Thermal properties of the polymer pellets or pipes were analyzed with Perkin-Elmer Pyris Diamond differential scanning calorimeter (DSC) calibrated with indium as standard. The specimens (a 2 mg to 10 mg sample extracted from the polymer pellets or from the pipe) were heated from -50 °C to 220 °C at a rate of 20 °C/min, followed by an isothermal for 3 min, and a subsequent cooling scan to -50 °C at a rate of -20 °C/min followed by an isothermal for 3 min, and then were reheated to 220 °C at 20 °C/min. Melting temperatures (Tm), corresponding to the temperature at the maximum of the peak, were measured during this second heating process.

Hoop stress tests were performed according to ISO 1 167: 1996(E).

Example 1 ISO 527 type 5A tensile bars were prepared by compression molding at 50 °C using Finaplas® 1251 (metallocene catalyzed syndiotactic polypropylene homopolymer, having a syndiotactic index of 75 % as measured using ¹³ C-NMR, commercially available from Total Petrochemicals USA, Inc. Properties shown on Table 1 ). These tensile bars were aged at 60 °C in a simple furnace during 3 days prior to performing the creep experiments.

Table 1

The creep experiments were performed in water baths illustrated in Figure 1 , and as listed in Table 2.

Table 2

The tests were run as follows: to the tensile bars, which were held at a constant temperature of 50 °C throughout the test, a steady tensile load was applied, the deformation of the sample (elongation) was measured though time, until failure of the sample occurred; the resulting data of time vs % elongation was plotted.

Figure 2 shows the creep curve obtained when applying a constant stress of 8.5 MPa. At the beginning of the test, deformation of the sample occurred sharply; however, the speed of deformation slowed progressively down until a constant deformation rate was reached (middle part of the curve), whereupon necking of the tensile bar occurred (inflection point of the curve), which means that the yield strength of the sample had been reached (the yield corresponds to the limit between the reversible elastic zone and the irreversible plastic zone of the polymer). The inflexion point of the creep curve was determined by mathematical fitting, using Matlab software, as described herein. The time-evolution of the deformation ε (between ε = 20 % and 50 %) were introduced as "data" in statistica. This dependence has been fitted using the following equation:

e(t) = x(1 ) ^* exp(x(2) ^* (t-x(3))) + x(4) ^* t + x(5) - x(6) ^* exp(-x(7) ^* (t - x(8))).

With x(i) height free-adjustable parameters. Intrinsically, this equation contains the Burger model plus an exponential term (imposed to describe the time-evolution at high deformation/time). In addition, it does not impose the (0,0) point (in fact, small fluctuations around the (0,0) coordinate allowed to take into account some experimental errors due to the way the stress was imposed). As soon as the x(i) parameters were determined, the inflection point was analytically calculated via annulations of the second derivative of the elongation function as a function of time.

In the particular case of Figure 2, the inflection point appeared 1047 h after the start of the test, and the recorded elongation was 35.5 %.

Table 3 shows the average inflection time and corresponding elongation obtained after mathematical fitting of the creep curves obtained.

Table 3

Figure 3 shows the elongation of the inflexion point of the creep experiment performed at 50 °C under various constant stresses.

Comparative example 1

ISO 527 type 5A tensile bars, prepared using Finathene®XT10N (polyethylene PE100, commercially available from Total Petrochemicals USA Inc, density 0.949 g/cm ³ ASTM D-792, melt index 7.5 g/10 min (21.6 kg-190 °C ASTM D-1238) and RA130E-8427 (polypropylene random copolymer, provided by Borealis A/S, density 0.905 g/cm ³ ISO 1 183, MI2 0.25 g/10 min (230 °C/2.16 kg ISO 1 133)) by compression molding at 50 °C were subjected to a creep test as described in Example 1.

Figure 4 shows the plot of the average inflection time against the applied stress for both the samples of Example 1 and for the Comparative example 1. From this plot it was possible to determine that the tensile bars made with syndiotactic polypropylene can withstand as much (or higher) stress as the tensile bars made with polyethylene (Finathene®XT10N). Figure 4 further shows the resulting regression curve (and equation) of the syndiotactic polypropylene tested in Example 1 (Finaplas® 1251 ); extrapolation to 50 years on this curve, gives a pressure resistance of about 8 MPa.

The flexural modulus and impact resistance of the tensile bars obtained in Example 1 and the Finathene®XT10N bars were measured. The impact resistance was measured using ISO 180- notched izod test at 23 °C. The results are shown in Table 5.

Table 5

Sample Flexural modulus Impact resistance

Example 2

Finaplas® 1251 (syndiotactic polypropylene, provided by Total Petrochemicals USA, Inc. Properties shown in Example 1 ) was extruded on a single-screw extruder (Reifenhauser) with a diameter of 70 mm and L/D = 25. The throughput was in the range 15-20 kg/h. A 25 mm die was used to conform the melted polymer to a final diameter of 32 mm. Then a 32 mm calibrator was used to produce the pipes (Figure 5 shows a picture of the melted polymer at the exit of the die and before the entrance in the calibrator). After cooling inside a water bath (10-15 °C), the pipes were subjected to slow drawing at a speed that allowed the final thickness wall of the pipe to be of ~2 mm. Table 6 shows the processing parameters used to produce the pipes. Pipe 1 was extruded from a dry-blend- mixture of Finaplas® 1251 and 1 % by weight of HD6081 (high density polyethylene, provided by TOTAL Petrochemicals), while pipes 2-6 were extruded from 100 % Finaplas® 1251. Pipe 1 was slightly whiter than the pipes produced from pure sPP. The pipes produced at higher melt temperatures had a smoother outer surface.

Table 6

The flexural modulus of the resulting pipes was measured according to ISO 178 and was surprisingly low for all pipes tested (-450 MPa).

The ageing conditions of sPP were evaluated.

Figure 6 shows the DSC thermograms of the interior surface and the exterior surface of the sPP pipe 2. The exterior surface, did not have time to crystallize (because of the quenching of the pipe), and therefore the DSC thermogram (labeled OUT") only exhibits one sharp melting peak around 125 °C. The interior surface had time to crystallize, and its DSC thermogram (labeled "IN") exhibits two distinct melting peaks (-1 13 °C and 125 °C). Therefore, the interior of the pipe has a more stable microcrystalline structure.

Table 7 shows the data from the DSC thermograms of the pipes produced at different extrusion temperatures. The data show that as the extrusion temperature increased, the cooling rate increased as well, and the sPP form appearing in between 1 10 °C and 120 °C had a gradual disappearance of the "low" melting peak (-1 10 °C). The pipe prepared with 1 % HD6081 (pipe 1 ), provided the thermogram with the largest low melting peak (~1 15 °C), showing the effect of HD6081 in aiding the crystallization of sPP.

Table 7

In another experiment, a piece of sPP pipe 2 was placed inside an oven set at a constant temperature of 80 °C. At regular intervals, a small part of the pipe was cut off in order to be analyzed by DSC. Figure 7 shows the recorded thermogram of the interior of the pipe, while Figure 8 shows the recorded thermogram of the exterior of the pipe. The relative intensity of the melting peaks allowed to determine that annealing at 80 °C during 3 days is useful to further stabilize the sPP microstructure in the pipe on both the internal and external surfaces.

Pipes 1 , 2 and 6 were placed in an oven at 80 °C during 14 days, after which time a DSC analysis was performed. Table 8 summarizes the percentage of partial area of the "low" temperature melting peak and the total melting enthalpy. The DSC thermograms of the sPP pipes produced at different extrusion temperatures, and then annealed at 80 °C during 14 days, are shown in Figures 9 to 1 1 . Figure 9 show the DSC thermogram obtained for pipe 1 (sPP + 1 % HD6081 at 160 °C), Figure 10 show the DSC thermogram obtained for pipe 2 (pure sPP at 170 °C) and Figure 1 1 show the DSC thermogram obtained for pipe 6 (pure sPP at 220 °C). For all samples, the total melting enthalpy was increased from to -29 J/g to -39 J/g. The thermogram of Pipe 1 (Figure 9) showed that the two melting peaks had almost the same relative intensity. Integration of the partial area was evaluated to be around 70 %. After the annealing step, the DSC thermograms of Pipes 2 (Figure 10) and 6 (Figure 1 1 ) were almost identical, indicating that their microstructures have evolved during annealing to yield a stable and equivalent crystalline state.

Table 8

Pipes 1 and 2 were subjected to an annealing step at 80 °C, for 7 days and then, hoop stress tests at a temperature of 20 °C were performed on the produced pipes. The results are shown in the Table 9. Table 9

Comparative example 2

Pipes having 32 mm diameter were produced using Finathene®XT10N (PE100, commercially available from Total Petrochemicals USA Inc, density 0.949 g/cm ³ ASTM D-792, melt index 7.5 g/10 min (21 .6 kg, 190 °C, ASTM D-1238). Pipes having 32 mm diameter were produced using RA130E- 8427 (polypropylene random copolymer, commercially available from Borealis A/S, density 0.905 g/cm ³ ISO 1 183, MI2 0.25 g/10 min (230 °C/2.16 kg ISO 1 133)). Pipes having 32 mm diameter were produced using MDPE 3802 (PE80 polyethylene, commercially available from TOTAL Refining & Chemicals, density 0.938 g/cm ³ ISO 1 183, MI2 20 g/10 min (230 "C/21.6 kg ISO 1 133- G)) The pipes were produced using a 45 mm die to conform the melted polymer to a final 32 mm diameter. The pipes were subjected to an annealing step at 80 °C, for 7 days.

The flexural modulus of the resulting pipes was measured according to ISO 178 (1 100-1300 MPa). The pipes comprising sPP were more flexible than the pipes comprising isotactic polypropylene.

Hoop stress tests at 20 °C were performed on the produced pipes. Figure 12 shows the plot of the failure time against the applied hoop stress for a pipe (Pipe 5) produced in Example 2 and for the pipes tested in the Comparative example 2. From this plot, it was possible to determine that at a temperature of 20 °C, the pipe made with syndiotactic polypropylene (Finaplas® 1251 ) can withstand as much (or higher) stress as the pipes made with polyethylene (Finathene®XT10N, MDPE 3802).