The present invention relates to the use of certain polymers to manufacture polymer pipes. The invention is particularly relevant to the manufacture of thick walled pipes having particularly low levels of residual stress within their structure and at the same time a beneficially low variability in residual stress levels along the full length of the pipe. The invention further relates to a process for forming such high specification polymer pipes.

Pipes formed from thermoplastic polymers - for example a polyaryletherketone (PAEK) polymer such as polyetheretherketone (PEEK) may be of value in a range of industries, including the oil, gas and aerospace sectors for example. However, due to the often rapid crystallisation rates of PAEK polymers, extruded thick walled pipes may exhibit significant internal residual stresses that can adversely impact the operability of the pipe in use, causing fracture or failure of the pipe.

For example, when a pipe is cut to size, low residual stress in the pipe reduces the problem of the pipe shattering outwards, or cracking from the line of the intended cut. Furthermore, a pipe with lower residual stress will be less prone to failure through fatigue, slow crack propagation or physical impact and be more suitable for use in situations where the pipe carries high pressure fluid or is subject to high external forces. Achieving a low variability in residual stress levels all along the length of a pipe can provide a number of technical benefits. For example, it may avoid locally increased stresses which could act as initiation sites for failure. It may also minimise or completely avoid unwanted bends in different places along the length of the pipe. Furthermore, ensuring consistent properties may assist subsequent processing - for example a process to bond composite laminates onto the outer surface of the pipe. One of the aims of the present invention is to provide a pipe that exhibits good stability against exposure to certain types of chemicals. Such chemical-resistant and consistently low stress pipes may be attractive for use in the oil and gas industries, aerospace industry and other industrial sectors where high specification pipes are of particular value.

Crystallisation rates in polymers, in particular, in PAEK polymers, may be modelled using Avrami models as described in Seo et al. Jiho Seo, Anne M. Gohn, Richard P. Schaake, Daniele Parisi, Alicyn M. Rhoades, and Ralph H. Colby, Macromolecules 2020 53 (9), 3472-3481 , DOI: 10.1021/acs.macromol.9b02611.

WO2012/107753 A1 describes a process and apparatus for producing a polyetheretherketone (PEEK) pipe having a length greater than 250 metres and a residual stress of less than 5MPa. Example 1 of WO2012/107753 A1 reports an 8 inch pipe with a residual stress measurement of 1.64MPa. Accordingly, in one aspect of the invention provides a use of a polymer composition to manufacture of pipe having a length of at least 1 metre, wherein the polymeric composition comprises one or more polymeric materials each comprising:

(a) phenylene moieties;

(b) ether and/or thioether moieties; and optionally

(c) ketone and/or sulfone moieties; wherein the polymeric composition has a degree of crystallisation as determined by differential scanning calorimetry, DSC, wherein the variation of the degree of crystallisation with time of the polymeric composition fits a modified Avrami model wherein: the primary crystallisation rate constant, Ki, Log10(Ki) is equal to or less than -8, and at least or equal to -13; the primary Avrami number, , is at least 2.5 and less than or equal to 3.5; and the secondary Avrami number, n _å , is at least 1.4 and less than or equal to 2.6.

The dual Avrami model may be used to describe the degree of crystallisation as a function of time, wherein Ki, m, and n _å are the kinetic parameters. This dual Avrami model was derived by Seo et. al in Jiho Seo, Anne M. Gohn, Richard P. Schaake, Daniele Parisi, Alicyn M. Rhoades, and Ralph H. Colby, Macromolecules 202053 (9), 3472-3481 DOI: 10.1021/acs.macromol.9b02611.

By using the polymer composition according to the present invention, the overall residual stress of a long pipe is reduced across the entire length of the pipe while the crystallinity and therefore chemical resistance is maintained. Balancing good crystallinity and low residual stress is challenging, but is achieved by the present invention.

In one embodiment, Log10(Ki) is preferably less than or equal to - 9 and at least or more than - 12.

The polymeric composition may comprise a single polymeric material, or a mixture of two or more polymeric materials. The polymeric composition may be a copolymer or a blend of one or more polymers or copolymers.

In one embodiment, the polymeric composition comprises a first polyaryletherketone polymer (PAEK) and a second slower crystallising PAEK polymer, for example a PEEK-PEDEK copolymer, a copolymer containing -ether-phenyl-ether-phenyl-carbonyl-phenyl-(i.e. PEEK) and -ether-phenyl-phenyl-ether-phenyl-carbonyl-phenyl- (i.e. PEDEK) repeat units. The addition of the slower crystallising PAEK polymer, e.g. a PEEK-PEDEK copolymer to the PAEK polymer is that the polymeric composition has modified crystallisation kinetics.

In one embodiment the slower crystallising PAEK is selected from the following:

In one embodiment, the polymeric composition may include a first polymeric material having a high molecular weight Mw, and a second polymeric material having a low molecular weight Mw. In one example, the weight ratio of the first polymeric material and the second polymeric material is 70:30 to 97:3.

In another embodiment, the polymeric composition may include a first polymeric material is a PEEK polymer, and a second polymeric material is a PPSU polymer. In one example, the weight ratio of the first polymeric material and the second polymeric material is 70:30 to 99:1 , and more preferably, the weight ratio of the first polymeric material and the second polymeric material is 90:10 to 99:1.

In another embodiment, the polymeric composition may include a first polymeric material is a semi crystalline PAEK, and a second polymeric material is an amorphous PAEK. In one example, the weight ratio of the first polymeric material and the second polymeric material is 70:30 to 99:1 , and more preferably, the weight ratio of the first polymeric material and the second polymeric material is 90:10 to 99:1. In one embodiment, the polymeric composition comprises a blend of a first polyetheretherketone - a polymer containing -ether-phenyl-ether-phenyl-carbonyl-phenyl-(i.e. PEEK) and a PEEK- PEDEK copolymer, a copolymer containing -ether-phenyl-ether-phenyl-carbonyl-phenyl-(i.e. PEEK) and -ether-phenyl-phenyl-ether-phenyl-carbonyl-phenyl- (i.e. PEDEK) repeat units.

As explained hereinafter, the composition may include one or more fillers and/or colouring materials etc. The elongate opening of the calibrator device preferably includes a tapered mouth at the end of the elongate opening where the hot extruded pipe is received. The use of a mould- release agent [mold-release agent (in USA-English)] on the calibrator device in the area where a hot extruded pipe is received may be beneficial.

According to a further aspect of the invention, there is provided a method of manufacturing a polymer pipe from a polymer composition to manufacture of pipe having a length of at least 1 metre, wherein the polymeric composition comprises one or more polymeric materials each comprising:

(a) phenylene moieties;

(b) ether and/or thioether moieties; and optionally

(c) ketone and/or sulfone moieties; wherein the polymeric composition has a degree of crystallisation as determined by differential scanning calorimetry, DSC, wherein the degree of crystallisation fits a modified Avrami model wherein: the primary crystallisation rate constant, Ki, Log10(Ki) is equal to or less than -8, and at least or equal to -13; the primary Avrami number, , is at least 2.5 and less than or equal to 3.5; and the secondary Avrami number, n _å , is at least 1.4 and less than or equal to 2.6; the method comprising the steps of by extruding the polymeric composition through a suitably shaped die and using a calibrator device to controllably cool the pipe.

A further aspect of the invention provides a process for making a pipe (for example a pipe as described herein), the process comprising:

(i) using a calibrator device which includes an elongate opening for receiving a hot extruded pipe, wherein the elongate opening includes a vacuum applying region arranged to apply a vacuum to the outer surface of the pipe within the elongate opening, said device further comprises two or more temperature-controlled regions spaced apart along the length of the calibrator, said temperature controlled regions being arranged to apply a cooling effect to the pipe as it passes through the elongate opening, said calibrator device being in contact with one or more heat transfer fluids so as to assist said cooling effect on the pipe in each of the two or more temperature- controlled regions;

(ii) introducing a hot extruded pipe into the elongate opening of the calibrator and conveying the pipe through the elongate opening; while

(iii) applying a vacuum to the outer surface of the pipe as it passes through the calibrator; wherein

(iv) the temperature of the heat-transfer fluid used for the first temperature-controlled region to come into contact with the hot extruded pipe is 60°C or lower;

(v) the temperature of heat-transfer fluid used for the subsequent temperature- controlled region(s) is/are in the range of 80°C to 150°C; and wherein

(vi) the pipe has a polymer composition comprising one or more polymeric materials each comprising:

(a) phenylene moieties;

(b) ether and/or thioether moieties; and optionally

(c) ketone and/or sulfone moieties, wherein, the polymeric composition has a degree of crystallisation as determined by differential scanning calorimetry, DSC, wherein the variation of the degree of crystallisation with time fits a modified Avrami model wherein: the primary crystallisation rate constant, Ki, Log10(Ki) is equal to or less than -8, and at least or equal to -13; the primary Avrami number, , is at least 2.5 and less than or equal to 3.5; and the secondary Avrami number, n _å , is at least 1.4 and less than or equal to 2.6. In one embodiment any polymeric material has a repeat unit of formula (I): and/or a repeat unit of formula (II): and/or a repeat unit of formula (III): wherein: m, r, s, t, v, w and z each independently represent zero or a positive integer;

E and E' each independently represent -O-, -S- ora direct bond;

G represents -O-, -S-, a direct bond or-O-phenylene-O-; and

Ar is -phenylene-C(0)-phenylene-, -phenylene-C(CH3) ₂ -phenylene-, -phenylene-0-(1 ,4- phenylene)-0-phenylene-, -phenylene- or -phenylene-C(0)-phenylene-C(0)-phenylene-

In some embodiments the phenylene groups mentioned in this specification are 1,4-linked to adjacent groups.

In one embodiment where Ar is -phenylene-C(0)-phenylene-C(0)-phenylene- the central phenylene may be 1 ,3- or 1 ,4-substituted to the adjacent carbonyl groups.

In one embodiment where Ar is -phenylene-C(0)-phenylene-C(0)-phenylene- the central phenylene is 1 ,4-substituted to the adjacent carbonyl groups.

In one embodiment, the polymeric material may comprise a repeat unit of formula (I) and no other repeat units. In one embodiment the polymeric material may be polyphenylenesulphide.

In one embodiment, the polymeric material may include more than one different type of repeat unit of formula (I); and more than one different type of repeat unit of formula (II); and more than one different type of repeat unit of formula (III).

In one embodiment the polymeric material only includes repeat units of formula (I). In one embodiment the polymeric material only includes repeat units of formula (II).

In one embodiment the polymeric material only includes repeat units of formula (III).

In one embodiment the polymeric material has repeat units consisting essentially of repeat units of formula (I), (II) and/or (III).

In some embodiments the phenylene groups in units of formula (I), (II) and (III) are not additionally substituted. In some embodiments the phenylene groups in units of formula (I), (II) and (III) are not cross-linked. Where wand/or z is/are greater than zero, each phenylene may independently be 1 ,4- or 1 ,3-linked to adjacent atoms in the repeat units of formula (II) and/or (III). In some embodiments where w and/or z is/are greater than zero, each phenylene is 1 ,4-linked.

In one embodiment G represents -0-, a direct bond or a -O-phenylene-O- group.

In one embodiment G is a direct bond.

“a”, “b” and “c” can be defined to represent the mole% of units of formula (I), (II) and (III) respectively within the polymeric material.

In one embodiment each unit of formula (I) in said polymeric material is the same.

In one embodiment each unit of formula (II) in said polymeric material is the same.

In one embodiment each unit of formula (III) in said polymeric material is the same. In one embodiment a is 20 or less. In one embodiment a is 10 or less. In one embodiment a is 5 or less. In one embodiment a is in the range from 45 to 100. In one embodiment a is in the range from 45 to 55. In one embodiment a is in the range from 48 to 52. In one embodiment b+c is in the range from 0 to 55. In one embodiment b+c is in the range from 45 to 55. In one embodiment b+c is in the range from 48 to 52. In one embodiment a/(b+c) is in the range from 0.9 to 1.1. In one embodiment a/(b+c) is about 1. In one embodiment a+b+c is at least 90. In one embodiment a+b+c is at least 95. In one embodiment a+b+c is at least 99. In one embodiment a+b+c is about 100. In one embodiment b is at least 20. In one embodiment b is at least 40. In one embodiment b is at least 45.

In one embodiment the polymeric material comprises repeat units where at least 98% of said repeat units consist essentially of moieties (I), (II) and/or (III).

In one embodiment the polymeric material comprises a homopolymer having a repeat unit of general formula (IV): or a homopolymer having a repeat unit of general formula (V): or a random or block copolymer formed from at least two different units of (IV) and/or (V), wherein: A and B each represent 0 or 1 , wherein at least one of A and B is 1 ;

C and D each represent 0 or 1 , wherein at least one of C and D is 1 ; and E, E', G, Ar, m, r, s, t, v, w and z are each as defined according to any statement herein.

In one embodiment m is an integer in the range from 0 to 3. In one embodiment m is 0, 1 or 2. In one embodiment m is 0 or 1. In one embodiment r is an integer in the range from 0 to 3. In one embodiment r is 0, 1 or 2. In one embodiment r is 0 or 1. In one embodiment t is an integer in the range from 0 to 3. In one embodiment t is 0, 1 or 2. In one embodiment t is 0 or 1. In one embodiment s is 0 or 1. In one embodiment v is 0 or 1. In one embodiment w is 0 or 1. In one embodiment z is 0 or 1. In one embodiment the polymeric material is a homopolymer having a repeat unit of general formula (IV). In one embodiment Ar is -(1 ,4-phenylene)-C(0)-(1 ,4-phenylene)-, -(1 ,4-phenylene)-0-(1 ,4- phenylene)-0-(1 ,4-phenylene)-, -(1 ,4-phenylene)-C(CH3)2-(1 ,4-phenylene)-

, -(1 ,4-phenylene)-C(0)-phenylene-C(0)-(1 ,4-phenylene)- or-(1 ,4-phenylene)-.

In one embodiment the middle phenylene group of -(1 ,4-phenylene)-C(0)-phenylene-C(0)-(1 ,4- phenylene)- may be 1 ,3- or 1 ,4-linked. In one embodiment it is 1 ,4-linked.

In one embodiment Ar is -phenylene-C(0)-phenylene-, -phenylene-, -phenylene-0-(1 ,4- phenylene)-0-phenyiene- or-phenylene-C(0)-phenylene-C(0)-phenylene-.

In one embodiment Ar is -phenylene-C(0)-phenylene-C(0)-phenylene·, -phenylene- or-phenylene-C(0)-phenylene-.

In one embodiment Ar is -(1 ,4-phenylene)-C(0)-phenylene-C(0)-(1 ,4-phenylene)-, -(1 ,4- phenylene)-C(0)-(1 ,4-phenylene)-, -(1 ,4-phenylene)-0-(1 ,4-phenylene)-0-(1 ,4-phenylene)- or-(1 ,4-phenylene)-. In one embodiment Ar is -(1 ,4-phenylene)-C(0)-phenylene-C(0)-(1 ,4-phenylene)-, -(1 ,4- phenylene)-C(0)-(1 ,4-phenylene)- or-(1 ,4-phenylene)-.

In one embodiment the polymeric material includes at least 60mole% of repeat units which do not include -S- or-SC>2- moieties. In one embodiment the polymeric material includes at least 70mole% of repeat units which do not include -S- or-SC>2- moieties. In one embodiment the polymeric material includes at least 80mole% of repeat units which do not include -S- or -SO2- moieties. In one embodiment the polymeric material includes at least 90mole% of repeat units which do not include -S- or -SO2- moieties.

In one embodiment the polymeric material comprises at least 60mole% of repeat units which consist essentially of phenylene moieties, ether moieties and ketone moieties. In one embodiment the polymeric material comprises at least 70mole% of repeat units which consist essentially of phenylene moieties, ether moieties and ketone moieties. In one embodiment the polymeric material comprises at least 80mole% of repeat units which consist essentially of phenylene moieties, ether moieties and ketone moieties. In one embodiment the polymeric material comprises at least 90mole% of repeat units which consist essentially of phenylene moieties, ether moieties and ketone moieties.

In one embodiment the polymeric materials) (potentially including co-polymers) comprises repeat units that consist essentially of phenylene moieties in conjunction with ketone and/or ether moieties.

In one embodiment the polymeric material does not include repeat units which include -S- or-SC>2- moieties nor aromatic groups other than phenylene.

In one embodiment the polymeric material has at least 98% of its repeat units consisting essentially of formula (IV) wherein Ar is -phenylene-, E and E' are each -0-, m = 0, w = 1 , G is a direct bond, s = 0, and A and B are each 1. (i.e. polyetheretherketone).

In one embodiment the polymeric material has at least 98% of its repeat units consisting essentially of formula (IV) wherein E is -0-, E' is a direct bond, Ar is -phenylene-C(0)-phenyiene-C(0)-phenylene-, m = 0, A = 1 and B = 0. (i.e. polyetherketone).

In one embodiment the polymeric material has at least 98% of its repeat units consisting essentially of formula (IV) wherein E is -0-, Ar is -phenylene-C(0)-phenyiene-C(0)-phenylene-, m = 0, E' is a direct bond, A = 1 and B = 0. (i.e. polyetherketoneketone).

In one embodiment the polymeric material has at least 98% of its repeat units consisting essentially of formula (IV) wherein Ar is -phenylene-C(0)-phenyiene-C(0)-phenylene-, E and E' are both -0-, G is a direct bond, m = 0, w = 1, r = 0, s = 1, and A and B are both 1. (i.e. polyetherketoneetherketoneketone).

In one embodiment the polymeric material has at least 98% of its repeat units consisting essentially of formula (IV), wherein Ar is -phenylene-, E and E' are both -0-, G is a direct bond, m = 0, w = 0 and s, r, A and B are all 1. (i.e. polyetheretherketoneketone). In one embodiment the polymeric material has at least 98% of its repeat units consisting essentially of formula (IV), wherein Ar is -phenylene-, E and E’ are both -0-, m = 1 , w = 1 , A = 1 , B = 0, and G is a direct bond (i.e. polyetherdiphenyletherketone).

In one embodiment the main peak of the melting endotherm (Tm) for said polymeric material may be at least 300°C.

In one embodiment the polymeric material comprises a repeat unit of formula (XX): wherein t1 = 0 or 1 , w1 = 0 or 1 and v1 represents 0, 1 or 2.

In one embodiment the polymeric material has at least 98% of its repeat units consisting essentially of formula (XX).

In one embodiment the polymeric material has at least 98% of its repeat units consisting essentially of formula (XX) wherein t1 = 0 or 1 , w1 = 0 or 1 and v1 represents 0, 1 or 2.

In one embodiment the polymeric material comprises a repeat unit of formula (XX) wherein t1 =1 , v1=0 and w1=0.

In one embodiment the polymeric material has at least 98% of its repeat units consisting essentially of formula (XX) wherein t1 =1 , v1=0 and w1=0.

In one embodiment the polymeric material comprises a repeat unit of formula (XX) wherein t1=0, v1=0 and w1=0.

In one embodiment the polymeric material has at least 98% of its repeat units consisting essentially of formula (XX) wherein t1=0, v1=0 and w1=0.

In one embodiment the polymeric material comprises a repeat unit of formula (XX) wherein t1=0, w1=1 and v1=2.

In one embodiment the polymeric material has at least 98% of its repeat units consisting essentially of formula (XX) wherein t1=0, w1=1 and v1=2. In one embodiment the polymeric material comprises a repeat unit of formula (XX) wherein t1=0, v1=1 and w1=0.

In one embodiment the polymeric material has at least 98% of its repeat units consisting essentially of formula (XX) wherein t1=0, v1=1 and w1=0.

In one embodiment the polymeric material comprises a repeat unit of formula (XX) wherein t1 =1 , v1=0 and w1=0.

In one embodiment the polymeric material has at least 98% of its repeat units consisting essentially of formula (XX) wherein t1 =1 , v1=0 and w1=0.

In one embodiment the polymeric material comprises a repeat unit of formula (XX) wherein t1=0, v1=0 and w1=0.

In one embodiment the polymeric material has at least 98% of its repeat units consisting essentially of formula (XX) wherein t1=0, v1=0 and w1=0.

In one embodiment the polymeric material comprises a repeat unit of formula (XX) wherein t1 =1 , v1=0 and w1=0.

In one embodiment the polymeric material has at least 98% of its repeat units consisting essentially of formula (XX) wherein t1 =1 , v1=0 and w1=0.

In one embodiment the polymeric material comprises polyetheretherketone polyetherketone, polyetherketoneetherketoneketone, polyetherketoneketone or polyetherdiphenyletherketone

In one embodiment the polymeric material is selected from polyetheretherketone polyetherketone, polyetherketoneetherketoneketone, polyetherketoneketone and polyetherdiphenyletherketone.

In one embodiment the polymeric material comprises polyetherketone or polyetheretherketone. In one embodiment the polymeric material is polyetherketone or polyetheretherketone.

In one embodiment the polymeric material comprises polyetheretherketone.

In one embodiment the polymeric material is polyetheretherketone. In one embodiment the polymeric material has a repeat unit of formula -O-Ph-O-Ph-CO-Ph- I and a repeat unit of formula

-O-Ph-Ph-O-Ph-CO-Ph- II wherein Ph represents a phenylene moiety wherein the repeat units I and II are in the relative molar properties l:ll of from 65:35 to 95:5.

In one embodiment the pipe comprises a composition which includes said polymeric material and one or more fillers.

In one embodiment the pipe may consist essentially of a composition which consists essentially of said polymeric material and one or more fillers.

In one embodiment the polymeric material makes up at least 60wt% of the total thermoplastic polymeric material in the composition from which the pipe is made. In another embodiment the above-mentioned figure is at least 70wt%. In another embodiment the above-mentioned figure is at least 80wt%. In another embodiment the above-mentioned figure is at least 90wt%. In another embodiment the above-mentioned figure is at least 95wt%.

A single polymeric material (as described herein) is preferably substantially the only thermoplastic polymer in said composition. Suitably, a reference to a thermoplastic polymer refers to a polymer which is melted in the formation of said pipe.

A filler is suitably a material which is not melted during the manufacture of said pipe. Said filler suitably has a melting temperature greater than 350°C and preferably greater than 400°C.

Said filler may include a fibrous filler or a non-fibrous filler. Said filler may include both a fibrous filler and a non-fibrous filler. A said fibrous filler may be continuous or discontinuous. A said fibrous filler may be selected from inorganic fibrous materials, non-melting and high-melting organic fibrous materials, such as aramid fibres, and carbon fibre. A said fibrous filler may be selected from glass fibre, carbon fibre, asbestos fibre, silica fibre, alumina fibre, zirconia fibre, boron nitride fibre, silicon nitride fibre, boron fibre, fluorocarbon resin fibre and potassium titanate fibre. Preferred fibrous fillers are glass fibre and carbon fibre. A fibrous filler may comprise nanofibres.

However, such a filler (particularly a fibrous filler) could detrimentally increase the roughness on the inside of the pipe and therefore reduce fluid flow through the pipe in use. A said non-fibrous filler may be selected from mica, silica, talc, alumina, kaolin, calcium sulfate, calcium carbonate, titanium oxide, ferrite, clay, glass powder, zinc oxide, nickel carbonate, iron oxide, quartz powder, magnesium carbonate, fluorocarbon resin, graphite, polybenzimidazole (PBI), carbon powder, nanotubes and barium sulfate. The non-fibrous fillers may be introduced in the form of powder or flaky particles.

Preferably, said filler comprises one or more fillers selected from glass fibre, carbon fibre, carbon black and a fluorocarbon resin. More preferably, said filler comprises glass fibre or carbon, especially discontinuous, for example chopped, glass fibre or carbon fibre.

In one embodiment the composition includes 35-100wt% of said polymeric material.

In one embodiment the composition includes 50-100wt% of said polymeric material.

In one embodiment the composition includes 65-100wt% of said polymeric material.

In one embodiment the composition includes at least 90wt% of said polymeric material.

In one embodiment the composition includes at least 95wt% of said polymeric material.

In one embodiment the composition includes at least 98wt% of said polymeric material.

In one embodiment the composition does not include a reinforcing filler (e.g. carbon fibre) but may include a non-reinforcing filler (e.g. talc or carbon black). Such a non-reinforcing filler may be included to reduce costs and/or to colour the pipe.

In one embodiment the total amount of filler in the composition is 65wt% or less.

In one embodiment the total amount of filler in the composition is 50wt% or less.

In one embodiment the total amount of filler in the composition is 35wt% or less.

In one embodiment the total amount of filler in the composition is 10wt% or less.

In one embodiment the total amount of filler in the composition is 7.5wt% or less.

In one embodiment the total amount of filler in the composition is 5wt% or less.

In one embodiment the total amount of filler in the composition is 5wt% or less and includes carbon black.

In one embodiment the composition includes carbon black as a filler.

In one embodiment the total amount of filler in the composition is 2.5wt% or less.

In one embodiment the total amount of filler in the composition is 1 wt% or less.

In one embodiment the composition includes substantially no filler.

In one embodiment the composition includes at least 95%wt of said polymeric material and at least 0.1wt% of a non-fibrous filler that is carbon black.

In one embodiment the composition includes at least 98%wt of said polymeric material and at least 0.1wt% of a non-fibrous filler that is carbon black.

In one embodiment the pipe consists essentially of a polymeric material where at least 98% of its repeat units are of the formula (XX). In one embodiment the pipe has a composition that consists essentially of a polymeric material where at least 98% of its repeat units are of the formula (XX) together with one or more fillers where the total amount of filler in the composition is 5wt% or less.

The incorporation of carbon black into the composition provides a pipe that works particularly well in any subsequent process where other materials are laser-welded onto the outside surface of the pipe. Accordingly, in one embodiment the pipe has a composition where between 0.05wt% and 5wt% of the composition is a filler that is carbon black. In one embodiment this range is 0.05wt% to 2.5wt%. In another embodiment this range is 0.05wt% to 1 5wt%. In one embodiment this range is 0.05wt% to 1wt%.

In one embodiment the pipe consists essentially of a polymeric material which is polyetheretherketone together with one or more fillers where the total amount of filler in the composition is 5wt% or less.

In one embodiment the pipe has a composition consisting essentially of a polymeric material which is polyetheretherketone together with carbon black where the carbon black is between 0.05wt% and 5wt% of the composition. In one embodiment this range is 0.05wt% to 2.5wt%. In another embodiment this range is 0.05wt% to 1.5wt%. In one embodiment this range is 0.05wt% to 1wt%.

In this specification, when referring to a pipe or length of a pipe, this refers to a pipe that is extruded/extrudable in a single extrusion process, rather than the length being formed from two or more individual pipe sections that are joined together.

Accordingly, in any embodiment herein, the pipe comprises a single extrusion.

In a further embodiment the pipe comprises a single extrusion, has substantially constant cross- section along its entire length and has a length of at least 100m.

In one embodiment the pipe has a length of at least 5m.

In one embodiment the pipe has a length of at least 10m.

In one embodiment the pipe has a length of at least 50m.

In one embodiment the pipe has a length of at least 100m.

In one embodiment the pipe has a length of at least 500m.

In one embodiment the pipe has a length of at least 1km.

In one embodiment the pipe has a length of at least 1 5km.

In one embodiment the pipe has a length of at least 2km.

In one embodiment the pipe has a length of at least 2.5km. In one embodiment the pipe has a length of at least 3km.

In one embodiment the pipe has a length of at least 3.5km.

In one embodiment the pipe has a substantially constant cross-section along its entire length.

In one embodiment the pipe has an annular cross-section, for example a circular cross-section. In some embodiments the elongate opening of the calibrator device has an annual cross-section, for example a circular cross-section.

The pipe produced according to this invention may be used as one continuous length or may be cut into shorter lengths (for example 0.5m, 1 m, 5m) for technology applications that require such shorter lengths.

In some embodiments the pipe has an outside diameter of at least 0.6cm.

In some embodiments the pipe has an outside diameter of at least 2.5cm.

In some embodiments the pipe has an outside diameter of at least 7cm.

In some embodiments the pipe has an outside diameter of at least 10cm.

In some embodiments the pipe has an outside diameter of at least 15cm.

In some embodiments the pipe has an outside diameter of less than 50cm.

In some embodiments the pipe has an outside diameter of less than 40cm.

In some embodiments the pipe has an outside diameter of less than 30cm.

In some embodiments the pipe has an outside diameter in the range from 0.5cm to 35cm.

In some embodiment the pipe has an outside diameter in the range from 0.6cm to 31 cm.

The outside diameter of a pipe may be defined as “d” cm and the thickness of the pipe wall may be defined as “t” cm. Accordingly the diameter to thickness ratio (d/t) can be defined for a pipe. In some embodiments the diameter to thickness ratio of the pipe is at least 6.

In some embodiments the diameter to thickness ratio of the pipe is in the range from 6 to 40.

In some embodiments the diameter to thickness ratio of the pipe is in the range from 15 to 40.

In one aspect of the invention, the pipe (as described herein) is part of an assembly which comprises said pipe as an inner part and is surrounded by an outer part, said outer part being arranged around substantially all of the outer wall of the pipe and being arranged to reinforce the pipe. In a further embodiment of this assembly, the outer part of the assembly comprises a first material and a second material, the first material comprising a thermoplastic or thermosetting polymer and said second material comprising a fibrous material. In one embodiment the first material comprises a thermoplastic polymer. In one embodiment this thermoplastic polymer comprises a PAEK polymer. In one embodiment it comprises polyetheretherketone polymer. In some embodiments the second material comprises a fibrous material wherein the fibrous material is carbon fibre. In some embodiments of this aspect of the invention the outer part comprises greater than ten layers which are overlaying each other. In one aspect of the invention, the pipe (as described herein) is pulled through a heated or cooled die, post extrusion. The diameter of the die may be no less than 95% of the pipe outside diameter, for example, the diameter of the die may be from 95% the diameter of the pipe to 99.9% the diameter of the pipe. In one example, the die may be from 96% the diameter of the die to 98% the diameter of the die. It has been surprisingly found that a pipe being passed or pulled through a die post extrusion exhibits a significant reduction in residual stress.

Experimental Details

Example 1 - polymeric material for pipe manufacture

A blend of Victrex 650G (PEEK polymer having a melt viscosity according to ISO 11443 of 475 Pa.s, available from Victrex manufacturing Limited, Hillhouse International, Thornton Cleveleys, Lancashire, UK) and PEEK-PEDEK copolymer made according to the following:

A 300 litre vessel fitted with a lid, stirrer/stirrer guide, nitrogen inlet and outlet was charged with diphenylsulphone (125.52kg) and heated to 150°C. Once fully melted 4,4'-diflurobenzophenone (44.82kg, 205.4mol), 1 ,4-dihydroxybenzene (16.518kg, 150mol) and 4,4'-dihydroxydiphenyl (9.311kg, 50mol) were charged to the vessel. The contents were then heated to 160°C. While maintaining a nitrogen blanket, dried sodium carbonate (21.368kg, 201.6mol) and potassium carbonate (1 106kg, 8mol), both sieved through a screen with a mesh of 500 micrometres, were added. The temperature was raised to 180°C at 1 °C/min and held for 100 minutes. The temperature was raised to 200°C at 1 °C/min and held for 20 minutes. The temperature was raised to 305°C at 1 °C/min and held until desired melt viscosity was reached, as determined by the torque rise of the stirrer. The required torque rise was determined from a calibration graph of torque rise versus MV. The reaction mixture was poured via a band caster into a water bath, allowed to cool, milled and washed with acetone and water. The resulting PEEK-PEDEK polymer powder was dried in a tumble dryer until the contents temperature measured 112°C.

The blend was formed by melt kneading 95% by weight 650G polymer and 5% by weight PEEK- PEDEK polymer above the melting temperature of the 650G polymer in a ZSK twin screw extruder through a die to form a lace and granulating the extruded lace into granules.

It should be noted that a mixture of granules or coarse powder of 650G and PEEK-PEDEK can be fed directly into the pipe extruder and this has the benefit of reducing the number of heating cycles that the polymer blend is subject to prior to making the pipe.

Comparative example Victrex 381 G was used as a comparative example. Victrex 381 G (PEEK polymer having a melt viscosity according to ISO 11443 of 300 Pa.s, available from Victrex manufacturing Limited, Hillhouse International, Thornton Cleveleys, Lancashire, UK) has typical PEEK-like crystallisation kinetics and is considered a fast crystallising polymeric material. Victrex 381 G is a recommended grade of PEEK polymer for general extrusion processes such as extruded pipes.

Method for determining kinetic parameters and crystallisation

Differential scanning calorimetry, DSC, measurements were performed on a TA instruments DSC2500 available from TA Instruments™. Samples of polymeric materials of Example 1 and the Comparative example were heated to 400°C, held for 5 minutes, cooled at 20°C/min to 320°C then held isothermally to allow crystallisation to proceed. The dual Avrami model was fitted to the isothermal data numerically, from the point at which crystallisation started (running integral exceeded 0.0001% or total).

After isothermal crystallisation at 320°C, the crystallisation X% of Example 1 and the Comparative example was determined using a reference value for 100% crystallinity of 130 J/g.

Results

The inventors have surprisingly found that a polymeric composition with modified crystallisation kinetic parameters improve the mechanical properties of the extruded pipe, while maintaining low levels of residual stress. By making a polymer blend comprising both fast crystallising PEEK and slower crystallising PEEK-PEDEK copolymer, the residual stresses formed on cooling the polymeric material through the pipe extrusion process are managed so that maximum crystallinity, mechanical strength and chemical resistance is retained in the pipe while minimal residual stresses develop. A further benefit of the invention is that the selection of the modified polymer to extrude the pipe reduces the requirement for controlled cooling of the pipe which is not always possible for thick walled or where large diameter pipes.

Table 1 - kinetic parameters

Without being bound by theory, it is believed that to achieve the optimum crystallisation properties of the polymeric composition, selecting polymeric materials that have good crystallisation properties, yet have modified rates of crystallisation. If the polymeric composition crystallises too quickly, it will have excellent chemical resistance, but the residual stress of the resultant extruded pipe will be very high resulting in poor pipe performance. If the polymeric composition crystallises too slowly, the residual stress in the resultant pipe will be low, but crystallinity of the pipe will also be low resulting in a pipe with poor mechanical and chemical resistance properties. Determining the variation of the degree of crystallisation with time in order to modify the polymer composition so that it falls within the ranges described, results in an extruded pipe having excellent mechanical and chemical resistance properties and low levels of residual stress.

Example 1 of the present invention has an excellent final crystallinity as shown in Table 2, and therefore a pipe manufactured using this polymeric composition exhibits excellent mechanical and chemical resistance properties while exhibiting very low residual stresses along the length of the pipe, even with thick walled pipes.

Table 2 - Crystallisation