TW202436443A - Improvements relating to the extrusion of polymeric material - Google Patents

Abstract

The invention relates to an extruded product, particularly an insulated conductor assembly, comprising a conductor wire, a first extruded layer and a second extruded layer. The first layer comprises a polymeric material (A) having a repeat unit of formula I wherein t1 and w1 independently represent 0 or 1 and v1 represents 0, 1 or 2. The second layer comprises a polymeric material (B) having a repeat unit of formula I

Description

Improvements related to extrusion of polymer materials

The present invention relates to an extruded product, a method for producing an extruded product and a use of a polymer material. Specifically, the present invention relates to an extruded insulating conductor assembly.

Elongated products (referred to herein as extruded products) having a specific cross-sectional profile, such as insulating conductors, films or tubes, can be formed using an extrusion process. A typical extrusion process involves forcing one or more flowable polymer materials through an extrusion die. Such a die includes an outlet for the polymer material, which is shaped to give the product the desired cross-sectional profile.

Some polymer materials have a tendency to adhere to the edges of the die exit and gradually form a large deposit at the die exit. Such deposits may be referred to as "die drool" (also known as "die build-up", "die drip", "die peel", "die bleed" or "plate out") and can adversely affect product quality and processing, for example by leaving marks on the surface of the extruded product or by cracking and contaminating the product at random intervals.

It is often difficult or impossible to manually remove mold deposits from the mold during the process without affecting the extruded product being formed. When such mold deposits form and begin to adversely affect the quality of the product, it may be necessary to stop the process and clean the extrusion equipment, especially the mold. This typically involves disassembling the extrusion equipment, causing significant downtime to the production process. For these reasons, polymer materials with a relatively high tendency to form mold deposits can only be used to produce extruded products in relatively short production cycles; this is inefficient and economically disadvantageous.

Mold deposits generally increase when the polymer material includes filler materials, such as particulate fillers, such as talc. As described in WO2022/175515, talc is known to be particularly beneficial for insulating conductors because it helps to improve the adhesion of the polymer to the conductor wires. Therefore, it would be desirable to reduce mold deposits when manufacturing such conductors, so that the efficiency of the process and the quality of the extruded product can be improved.

Mold deposits may also be exacerbated when the extrusion equipment is run at increased line speeds. Typically when line speeds are increased, the pressure in the mold increases due to the faster extrusion screw speed. This may cause the melt to expand more when leaving the mold, thereby increasing mold deposits. Therefore, it would be desirable to reduce mold deposits to allow faster line speeds in the production of extruded products.

One of the objects of the present invention is to provide an insulated conductor assembly and method or use that solves at least one disadvantage of the prior art (whether identified herein or elsewhere), or provides an alternative to existing extruded products, methods and uses. For example, an object of the present invention may be to provide an extruded insulated conductor that has a lower tendency to generate mold deposits during extrusion than comparable extruded products.

According to a first aspect of the present invention, an insulating conductor assembly is provided, comprising a conductive wire, a first extruded layer and a second extruded layer; the first layer comprises a polymer material (A), the polymer material (A) having a repeating unit of the following formula: (Formula I) wherein t1 and w1 independently represent 0 or 1, and v1 represents 0, 1 or 2; and the second layer comprises: a polymer material (B) having repeating units of Formula I (Formula I) wherein t1 and w1 independently represent 0 or 1, and v1 represents 0, 1 or 2; and a filler material, wherein the second layer is located between the wire and the first layer.

Preferably, the first layer comprises at least 50 wt%, more preferably at least 75 wt%, more preferably at least 85 wt%, most preferably more than 95 wt%, such as 99 wt% of the polymer material (A). Most preferably, the first layer consists essentially of or consists of the polymer material (A).

Preferably, the polymer material (A) comprises at least 40 wt%, preferably at least 70 wt%, preferably at least 80 wt% of PAEK polymer. In a preferred embodiment, the polymer material (A) is substantially at least 99 wt% PAEK.

Preferably, the second layer comprises at least 50 wt%, more preferably at least 75 wt%, more preferably at least 85 wt%, most preferably more than 95 wt%, such as 99 wt% of the polymer material (B). Most preferably, the second layer consists essentially of or consists of the polymer material (B).

The preferred polymer material (A) and/or (B) is polyetheretherketone (PEEK), wherein the repeating unit is t1=1, v1=0, and w1=0.

Alternatively, the polymer material may be a PAES polymer, such as polyphenylene sulfone (PPSU) or polysulfone sulfone (PSU).

In a preferred embodiment, the first layer consists essentially of PAEK, preferably PEEK, and the second layer consists essentially of a polymer material (B) being PAEK and a filler material, preferably PEEK and a filler material.

Unlike many known polymers, PAEK polymers or copolymers can be obtained in an amorphous or crystalline form as a direct result of the treated polymer. The glassy or amorphous state is achieved by rapidly quenching the polymer from the melt to below Tg, while slowly cooling the polymer from the melt will allow crystallinity to develop in the sample (melt crystallization). The crystalline form of a polymer can also be obtained from the polymer in its amorphous state, for example at room temperature by heating it to a temperature above Tg but below Tm before cooling back to room temperature (cold crystallization), or by holding the polymer at a constant temperature between Tg and Tm for a certain period of time before cooling back to room temperature (isothermal crystallization).

PAEK, including PEEK in particular, can be produced by nucleophilic polymerization of bisphenols with organic dihalide compounds in a suitable solvent in the presence of alkali metal carbonates and/or bicarbonates or alkali earth metal carbonates and/or bicarbonates. Such processes are described in, for example, EP0001879A, EP0182648A, EP0244167A and EP3049457A. PAEK can be produced according to WO2018055384, which is incorporated herein by reference. In one specific embodiment of the present invention, polymer material (A) and/or polymer material (B) can be PAEK produced according to EP3049457.

The or each polymer material (A) and/or polymer material (B) preferably has a degree of crystallinity of at least 10%, more preferably at least 20%, for example greater than 25%. However, for some applications, a lower degree of crystallinity (e.g. less than 25% or less than 22%) may be advantageous.

The degree of crystallinity is measured by DSC, with the onset of Tg being determined by the intersection of a line drawn along the pre-transition baseline with a line drawn along the maximum slope obtained during the transition. Tn is measured at the temperature at which the main peak of the cold crystallization exotherm reaches a maximum. Tm is the temperature at which the main peak of the melting endotherm reaches a maximum. The heat of fusion (ΔHm) during melting is obtained by connecting the two points at which the melting endotherm deviates from a relatively straight baseline. The integral area under the function of the endotherm value varying with time gives the enthalpy of the melting transition (mJ): the mass standard heat of fusion (J/g) is calculated by dividing the enthalpy by the mass of the sample. The degree of crystallinity (X%) is determined by dividing the heat of fusion of the sample by the heat of fusion of a completely crystalline polymer, which for polyetheretherketone is 130 J/g. ISO 11357-1 to ISO 11357-4 describe the test methodologies used to determine these measurements.

The filler material may be a fiber filler material or a particulate filler material. The fiber filler material suitably has a longest dimension of 300 μm or less. Suitable fiber filler materials may be selected from inorganic fiber materials, organic fiber materials (such as polyarylamide fibers and carbon fibers). Preferably, the melting temperature of the fiber filler should be at least 450°C. Suitable fiber filler materials may be selected from glass fibers, carbon fibers, asbestos fibers, silica fibers, alumina fibers, zirconia fibers, boron nitride fibers, silicon nitride fibers, boron fibers, fluorocarbon fibers, and potassium titanium fibers or mixtures thereof. The preferred fiber fillers are glass fiber and carbon fiber.

In a preferred embodiment, the filler material is a filler material. Suitable particulate (or non-fibrous) filler materials can be selected from calcium sulfate, chromium oxide, glass fiber, iron oxide, magnesium carbonate, magnesium oxide, mica, silicon dioxide, silicon carbide, silicon dioxide (quartz), silicon nitride, sodium silicate, titanium dioxide, talc (e.g., Jetfine ^™ , including Jetfine 3CA), zinc oxide, zirconium oxide, barium sulfate and boron nitride.

The filler material may constitute at least 5 wt %, suitably at least 10 wt % or at least 15 wt % of the polymer material (B). The filler material may provide up to 50 wt %, up to 40 wt % or up to 30 wt % of the polymer material (B). Suitably, the filler material provides 5 to 50 wt % of the polymer material (B), 10 to 40 wt % or 15 to 35 wt % of the total composition of the polymer material (B). For example, 15 wt %, or 20 wt %, or 25 wt %, or 30 wt % of filler material, such as talc or zinc oxide, may be present in the polymer material (B). Optimally, the polymer material (B) comprises PEEK and talc or zinc oxide as the filler material preferably selected as appropriate.

Preferably, the filler material has a D50 between 0.001 and 50 µm, more preferably between 0.005 and 15 µm. Preferably, the filler material has a D50 of less than 10 µm. Preferably, the filler material has a D50 between 1 and 5 µm, for example between 3 and 5 µm. D50 is measured by laser Mastersizer, laser diffraction, Mie theory (ISO 13320-1).

The polymer material (B) containing the filler material can be prepared by any suitable method known in the art. For example, the material can be prepared by single-screw or twin-screw extrusion compounding, preferably by twin-screw extrusion compounding.

Suitably, the filler material provides improved properties, such as improved strength, ductility, heat resistance, chemical resistance. However, for insulating conductors, the filler material provides improved electrical resistance to the assembly. For example, the filler material may provide improved dielectric properties and/or electrical breakdown performance.

In the best arrangement, the first extrusion layer is positioned adjacent to the die of the extruder assembly. Advantageously, providing a first extrusion layer substantially free of filler material minimizes the risk of mold deposit formation at the die outlet. Thus, the first layer is used to provide a second layer cover or shield. The second layer is thus protected from the die when leaving the extrusion apparatus. Therefore, the insulating conductor of this first aspect suitably has fewer defects caused by mold deposits. In addition, the extrusion process is less prone to clogging and therefore less likely to require stopping the process for cleaning. This suitably provides a more efficient overall process. The process is equally applicable to the production of other extruded products, such as films, cable sheaths, filaments and tubes.

Preferably, the second layer is adjacent to the wire. Preferably, the second layer is deposited directly on the wire.

Preferably, the first layer is an outer layer. Preferably, the second layer is an inner layer closest to the wire. Preferably, the first extruded layer is positioned adjacent to the second layer.

In addition, the present invention provides for higher line speeds for producing extruded products. Increasing line speeds results in mold deposits, which makes increasing line speeds above a certain limit impractical. However, because the present invention reduces mold deposits, it is possible to achieve faster line speeds, increasing manufacturing throughput and efficiency. Typically, the insulation wire coating machine assembly operates at approximately 10 meters per minute. Advantageously, the present invention provides a line speed of approximately 50 meters per minute. The line speed may be greater than 50 meters per minute, such as up to 100 meters per minute, preferably between 30 and 80 meters per minute, and preferably between 40 and 60 meters per minute.

The present invention also allows a higher content of filler, such as greater than 20 wt%, preferably 25 wt%, 30 wt%, or 40 wt%, to be included in the polymer material of the inner layer of the extruded product, compared to the original situation where no filler would adversely affect the extrusion process. Such a higher content of filler may be desirable for improving the properties of the extruded product, such as resistance to corona discharge.

Such co-extrusion of unfilled PAEK material adjacent to filled PAEK material allows for the use of higher weight contents of filler and adds the possibility of running the co-extrusion line at higher line speeds, thereby achieving higher production rates.

If highly filled compounds can be coated on traces (without the process issues indicated above), it is believed that thinner coatings with higher levels of filler can achieve the same electrical performance as thicker coatings (where only lower levels of filler material were previously possible).

Reducing the overall thickness of the insulation around the conductors (while maintaining electrical and mechanical performance) will allow the design engineer to save space within the stator of the motor and/or increase the amount of conductors. Reduced coating thickness can also help dissipate heat from the motor.

The polymer material (A) in the first layer as an outer layer in the extruded product may also provide other advantages in terms of reducing other surface defects or strain related phenomena (which may occur when extruding some polymer materials, such as cracking of the surface of the extruded material). The polymer material (A) suitably has a much lower tendency to produce such defects.

The term "outer layer" is used herein to refer to one or more layers of the extruded product contacting the mold used to form the product when it leaves the mold. In some embodiments, the extruded product is formed by a process involving only one surface of the product contacting the mold when leaving. In such embodiments, the first layer is suitably the only outer layer of the extruded product, typically the outermost layer or surface of the extruded product. The second layer is typically an inner layer of the extruded product. In some embodiments, the extruded product is formed by a process in which two surfaces of the product contact the mold when leaving. In such embodiments, the extrusion product comprises a third layer, preferably the second layer is disposed between the first layer and the third layer. A plurality of material layers may be provided in a multi-coextrusion process.

The first and second layers of the extrudate may have a combined thickness of at least 100 μm, for example between 150 and 190 μm. The combined thickness may be up to 300 μm.

The thickness of the first layer is suitably less than the thickness of the second layer. The second layer may provide 50% to 95% of the combined thickness of the first layer and the second layer. The first layer suitably provides 5% to 50% of the combined thickness of the first layer and the second layer.

Suitably, at least one additional extrusion layer may be provided. Such a layer may comprise an enamel material or a release agent selected from metal stearates, erucamide, oleamide or a fluoropolymer.

Preferably, the or each additional layer may be located between the second layer and the wire. Preferably, the or each additional layer may comprise an additive to improve adhesion to the wire. The additive may for example be a copolymer of PAEK, such as PEEK/PEDEK as described in EP 3013888. Advantageously, providing such an additional layer offsets the need for pre-treatment of the wire. For example, the wire would typically require plasma pre-treatment.

In an alternative embodiment, the insulating conductor comprises a first outer layer of polymer material (A), an inner layer of part polymer material (B) as a second layer and another outer layer of part polymer material (A) as a third layer, wherein the second layer is arranged between the first layer and the third layer (in an A-B-A arrangement). Suitably, the first layer of polymer material (A), the third layer of polymer material (A) and the second layer of polymer material (B) are coaxially arranged to form a wire sheath. The wire sheath can be extruded directly onto the wire to form the insulating conductor assembly. Advantageously, due to the second layer comprising filler material, increased electrical insulation of the second layer and therefore of the entire assembly is achieved. The two outer layers of polymer material (A) suitably reduce or prevent mold deposits from forming on the upper and lower surfaces of the second (inner) layer of polymer material (B), which would otherwise form when the polymer material (B) leaves the extruder if the two outer layers of polymer material (A) were not present.

The conductor is preferably substantially copper or aluminum, but the present invention is applicable to a wide range of conductor materials. When the conductor is copper, it is preferably low-oxygen copper having an oxygen content of less than 30 ppm, more preferably less than 20 ppm.

According to another aspect of the present invention, an extrusion product assembly is provided, which comprises a core, a first extrusion layer and a second extrusion layer; the first layer comprises: a polymer material (A) having repeating units of formula I (Formula I) wherein t1 and w1 independently represent 0 or 1, and v1 represents 0, 1 or 2; and the second layer comprises: a polymer material (B) having repeating units of Formula I (Formula I) wherein t1 and w1 independently represent 0 or 1, and v1 represents 0, 1 or 2; and a filler material, wherein the second layer is located between the core and the first layer.

According to another aspect of the present invention, a method for producing an extrusion product assembly comprising a first layer and a second layer is provided, the method comprising the following steps: a) providing a source of a polymer material (A) having repeating units of formula I: (Formula I) wherein t1 and w1 independently represent 0 or 1, and v1 represents 0, 1 or 2; b) providing a source of a second polymer material (B) having repeating units of Formula I; (Formula I) wherein t1 and w1 independently represent 0 or 1, and v1 represents 0, 1 or 2; and a filler material; c) delivering the polymer material (A) and the second polymer material (B) to an extrusion table comprising a mold; d) extruding the polymer material (A) and the second polymer material (B) through the mold so that the polymer material (A) contacts the outlet of the mold during extrusion and the second polymer material (B) does not contact the mold during extrusion to form the extruded product assembly.

Optimally, the extruded product assembly is an insulating conductor assembly.

The steps of the method are suitably carried out in the order of steps a) and b) (suitably, simultaneously), followed by step c), followed by step d).

Suitably, the input and extrusion of the polymer material (A) and the second polymer material (B) are arranged so that at the outlet of the mould the second polymer material (B) is covered by the polymer material (A) so that the second polymer material does not contact the outlet of the mould. Suitably, the polymer material (A) forms an outer layer surrounding the second polymer material which forms an inner layer of the extruded product at the outlet of the mould or just before leaving the mould. Thus, the polymer material (A) prevents the second polymer material from contacting the surface of the mould at or near the outlet of the mould so as to provide a reduction in mould deposit as described herein.

The polymer material (A) may have any of the features and advantages described above with respect to any of the aforementioned aspects.

This aspect of the method suitably results in a reduction in the amount of mold deposit compared to comparable processes in which the second polymer material (B) is extruded through a mold in the absence of polymer material (A) and therefore in which the second polymer material contacts the mold, particularly the mold exit, during extrusion.

This method can be carried out on a suitable extrusion device, which includes a first supply device for feeding the polymer material (A) in a molten form to an extrusion die and a second supply device for feeding the second polymer material (B) in a molten form to the extrusion die, wherein the supply devices allow the second polymer material (B) to be extruded as an inner layer and the polymer material (A) to be extruded as an outer layer in the product (i.e., the first layer and the second layer described herein).

Step c) of the method suitably involves delivering the polymer material (A) to an extrusion stage comprising a die to provide a first outer layer of the product and a second outer layer of the product, the second polymer material (B) forming an inner layer disposed between the first outer layer and the second outer layer (i.e. the first layer, the second layer and the third layer as described herein). This suitably involves an extrusion apparatus comprising a third supply device for feeding a second stream of the polymer material (A) in molten form to the extrusion die to provide the second outer layer of the product.

Preferably, the first layer is introduced into the mold assembly at a first position, preferably, the first position is remote from the exit end of the mold. Preferably, the second layer is introduced into the mold assembly at a second position. Preferably, the second position is downstream of the first position. Preferably, the third layer is introduced into the mold assembly at a third position. Preferably, the third position is different from the first position or the second position. Preferably, the third position is downstream of the second position. Preferably, the third position is positioned toward the exit end of the mold. Preferably, each subsequent layer is introduced into the mold assembly at equally spaced positions.

Suitably, the process is carried out continuously for at least 1 hour, at least 5 hours, at least 10 hours, at least 15 hours or at least 24 hours. The reduction in mould deposit provided by the use of polymeric material (A) suitably allows the run time of the process for producing a product by extrusion to be increased compared to a similar process in which the polymeric material (A) is not used as a layer contacting the mould outlet.

According to another aspect of the present invention, there is provided a use of a polymer material (A) for reducing the formation of deposits on a die of an extrusion device during extrusion of at least a second polymer material (B); wherein the polymer material (A) has repeating units of the following formula: wherein t1 and w1 independently represent 0 or 1, and v1 represents 0, 1 or 2 (Formula I); and the second polymer material (B) has repeating units of Formula 1: wherein t1 and w1 independently represent 0 or 1, and v1 represents 0, 1 or 2; and filler material.

According to another aspect of the present invention, an insulating conductor assembly is provided, which comprises: a conductive wire; a first extruded layer and a second extruded layer; the first layer comprises a polymer material (D), the polymer material (D) having repeating units of the following formula: -O-Ph-O-Ph-CO-Ph- I and repeating units of the following formula: -O-Ph-Ph-O-Ph-CO-Ph- II wherein Ph represents a phenyl group; and the second layer comprises: a polymer material (B) having repeating units of formula I (Formula I) wherein t1 and w1 independently represent 0 or 1, and v1 represents 0, 1 or 2; and a filler material, wherein the second layer is located between the wire and the first layer.

Extruded layer means a layer having a cross-section which has been formed by an extrusion process, suitably by extrusion through a die which imparts a specific, preferably consistent, cross-sectional profile to the product.

The polymer material (D) is a polyaryletherketone (PAEK) polymer. More specifically, the polymer material (D) is a copolymer of poly(etheretherketone) (PEEK) and poly(etherdiphenyletherketone) (PEDEK), the repeating units of formula I (which may be referred to as EEK) providing the PEEK polymer component, and the repeating units of formula II (which may be referred to as EDEK) providing PEDEK. Therefore, the polymer material of formula (D) may be referred to as a PEEK/PEDEK copolymer. Suitable polymer materials of formula (D) (PEEK/PEDEK copolymers) are described in US4717761, WO2014/207458A1 and WO2015/124903A1, the contents of which are incorporated herein by reference.

WO 2014/207458 A1 discloses a PEEK/PEDEK copolymer having repeating units of formula I and II in a molar ratio of 55:45 to 95:5 and having a melt viscosity (MV) of at least 0.25 and less than 1.2 kNsm ^-2 measured at 340°C and a shear rate of 1000 s ^-1 .

WO 2015/124903 A1 discloses PEEK/PEDEK copolymers having repeating units of formula I and II in a molar ratio of 55:45 to 95:5 and a MV of at least 0.25 and less than 1.2 measured at 340° C. and a shear rate of 1000 s ⁻¹ .

FIG. 1 a shows a pressure extrusion die 100 for producing an extruded insulating conductor assembly 120 in a “pressure on” extrusion process. The extrusion die 100 includes a die body 1 and a die mandrel 2.

The die 100 includes a first channel 101 for delivering a first extrusion layer, a second channel 102 for delivering a second extrusion layer, a wire 103, a die outlet 110, and a die inlet 111. The first channel 101 is located at a first position 122 downstream of the die inlet 111. The first channel 101 is configured to deliver a first polymer material (A) in a molten form into the die 100 such that the polymer material (A) flows through the die in a direction substantially parallel to the direction of the wire 103 to provide an extruded first sheath 126 of the PAEK material. The second channel 102 is located at a second position 124 upstream of the first position 122 and closest to the die inlet 111. The second channel 102 is configured to deliver a molten second polymer material (B) into the die 100 such that the polymer material (B) flows through the die in a direction substantially parallel to the direction of the wire 103. In use, the second polymer (B) enters the mold and coats the wire 103, forming an extruded second sheath 128 of PAEK plus filler material. As best shown in FIG. 1 b , the extruded first sheath 126 is co-extruded over the second sheath 128 .

Since polymer material A is substantially free of filler material, polymer material A has a lower tendency to form such deposits than second polymer material B, and thus, the extruded insulated conductor assembly 120 is formed with a reduced amount of mold deposits (mold deposits) formed at the mold outlet 110. The first jacket 126 effectively insulates polymer material B from heat-exposed surfaces of the mold 100, particularly at the mold outlet 110, which would otherwise cause mold deposits to form on polymer material B. Thus, in this arrangement, the extrusion method and extruded product suitably provide an effective reduction in mold deposits compared to similar processes and products.

FIG. 2a shows an extrusion die 200 including a die body 1 and a die mandrel 2. The die 200 has a first channel 201, a second channel 202, a third channel 233 and a die outlet 210. The wire 203 is fed through the die 200 to form the core of the insulated conductor assembly. In this specific example, the third channel 233 is located between the first channel 201 and the second channel 202. The third channel 233 is configured to deliver an additional material into the die assembly. The third material is preferably a molten polymer material. Specifically, the first, second and third channels are used to supply molten polymer materials A, B and C, respectively. These polymer materials are fed under pressure through the die 200 to the die outlet 210 to continuously produce an extruded product comprising three extruded sheaths 228, 236, 226 coaxially arranged around the wire 3, as shown in FIG. 2b.

Molten polymer material A forms the outer layer of the extruded product and has the composition described above for polymer material (A), i.e. the first layer as described herein. Molten polymer material B forms the inner layer of the extruded product and is suitably polymer material (B) as described above for the second layer. Molten polymer material C forms the second inner layer of the extruded product and may be polymer material (B) as described above. Polymer material C suitably contains a filler that improves the electrical breakdown resistance of polymer material C and thus improves the electrical breakdown resistance of the wire or cable sheath. Suitably, polymer material B provides improved bonding between polymer material C and wire 203 compared to the bonding that would otherwise be obtained if polymer material C directly contacted wire 203.

Alternatively, channel 202 may deliver a material having adhesive properties that negate the need for pre-treating the wire. For example, channel 202 may deliver a copolymer of PAEK.

As described above with respect to FIG. 1a, the outer layer of A effectively insulates polymer materials B and C from heat-exposed surfaces of mold 200, particularly at mold outlet 210, which would otherwise cause mold deposits of polymer materials B or C. Thus, in this arrangement, the extrusion method and extruded product suitably provide an advantageous reduction in mold deposits compared to similar processes and products.

FIG. 3a shows a mold 300 formed by a mold body 1 and a mold mandrel 2. The mold 300 has a similar input arrangement to the mold 200, but is configured as a "tube-on" mold for coating, for example, wires 303. A first outer layer of polymer material A is introduced through a first channel 301 (i.e., the first layer), polymer material B is introduced through a second channel 302 (i.e., the second layer), and another outer layer comprising polymer material A is introduced through another channel 313 (i.e., the third layer). Coating the wire or cable 303 with a sheath occurs outside the mold body 300 after the sheath has left the mold through a mold outlet 310. Thus, in such a tube in process, the outermost and innermost surfaces of the jacket contact the heat-exposed surfaces of the mold 300 at the mold exit 310, and thus may present a risk of mold deposits. The wire or cable produced in this manner comprises three layers 311, 312 and 313 arranged coaxially around the wire 3 as shown in FIG. 3b, which layers correspond to the polymer materials supplied to the channels 301, 302 and 303, respectively. As shown, the formation of the jacket from polymer materials A and B occurs within the mold body, so that the first and second outer layers of A effectively insulate the polymer material B from the heat-exposed surfaces of the mold 300, as discussed above, to reduce or eliminate mold deposits when the jacket leaves the mold. As in the specific example described with respect to Figures 1 and 2, the molten polymer material A has the composition described above for polymer material (A). The molten polymer material B forms the inner layer of the extruded product and is suitably the polymer material (B) as described above. The polymer material B suitably contains a filler that imparts electrical breakdown resistance to the polymer material (B).

FIG. 4a shows an extrusion die 400 for forming a tube, the die being formed by a die body 1 and a die mandrel 2. The die 400 comprises a first channel 401, a second channel 402, a third channel 403, a fourth channel 404 and a die outlet 410. The first channel, the second channel and the third channel are used to supply molten polymer material under pressure, which is fed through the die 400 to the die outlet 410 to continuously produce an extruded tube product, which comprises three layers 411, 412 and 413 as shown in FIG. 4b, which correspond to the polymer materials supplied to the channels 401, 402 and 403, respectively. The fourth channel 404 comprises a pin 3 to produce a hollow center 414 of the tube. The molten polymer material supplied to the first channel 401 is the polymer material (A) as described above. The molten polymer material supplied to the second channel 402 is the second polymer material as described above, for example, the polymer material (B) as described above. The molten polymer material supplied to the third channel 403 is the polymer material (A) as described above. Thus, the mold 400 is used to produce an extruded product comprising an inner layer (i.e., the second layer) of the second polymer material disposed between two outer layers (i.e., the first layer and the third layer) of the polymer material (A). The formation of this extruded product is carried out with a reduced amount of mold deposits (mold fouling) formed at the mold outlet 410, because the polymer material (A) has a lower tendency to form such deposits than the second polymer material (which may contain filler material). The two outer layers of polymer material (A) effectively insulate the second polymer material from heat-exposed surfaces of the mold 400, particularly at the mold outlet 410, which would otherwise cause mold deposits of the second polymer material. Thus, in this arrangement, the extrusion method and extruded product suitably provide an advantageous reduction in mold deposits compared to similar methods and products.

FIG. 5a shows an extrusion apparatus 500 for producing an extruded film. The apparatus comprises a die body 1 and a co-extrusion feed block 2. The co-extrusion feed block 2 has a first channel 501, a second channel 502 and a third channel 503. The first and second channels are used to supply molten polymer material A and the third channel supplies polymer material B under pressure. These polymer materials are co-extruded through the co-extrusion feed block and are then delivered to the die 1 for molding into a film having a desired thickness. The molten polymer material A from channel 501 forms a first outer layer 511 of the film, the molten polymer material A from channel 502 forms a second outer layer 512 and the molten polymer material B from channel 503 forms an inner layer 513, as shown in FIG. 5b.

As in the specific example described above, only the outer layer of the polymer material A of the film contacts the co-extrusion feed block 1 and the mold 2, and therefore, mold deposit formation is reduced due to the reduced tendency of the polymer material (A) to generate mold deposits.

FIG6a shows a die 600 for producing a filament extrusion product. The die 600 is formed by a die body 1 and a die mandrel 2. The die 600 comprises a first channel 601, a second channel 602 and a die outlet 610. The first and second channels are used to supply molten polymer materials A and B under pressure. The molten polymer material A forms an outer layer 611 of a filament having a composition as described above for polymer material (A), and the molten polymer material B forms an inner layer or core 612 of the filament, as shown in FIG6b. The molten polymer material B is suitably a polymer material (B) as described above, and suitably comprises a filler material.

As in the specific example described above, only the outer layer of the polymer material A of the filament contacts the heat-exposed surface of the mold 600, and therefore, mold deposit formation is reduced due to the lower tendency of the polymer material (A ) to produce mold deposits than the polymer material (B) of the composition containing the filler material. The filament produced in this way can be suitable for use as a raw material material in multi-layer manufacturing.

The following extrudates were produced to demonstrate the mold deposit reduction that can be achieved according to the present invention.

The methods involve a process step of drying the polymer followed by extrusion into a solid form during which mold deposit generation is compared for various polymers and configurations. Examples of solid forms include polymer filaments, flat wires with polymer coatings, and coextruded round wires with multiple layers of polymer coatings. Polymer Drying

Prior to extrusion, the powder/pellets of each polymer material described below and used in the following methods are dried to less than 0.05% w/w moisture (dew point of -40°C) by placing the material in an air circulating oven at 150°C for a minimum of 3 hours or at 160°C for 2 hours. For PEEK/PEDEK copolymer materials (referred to herein as LMPAEK™ materials under the trademark), the optimal drying time is 2-3 hours at 120°C. To ensure that the material is sufficiently dry, the moisture content can be measured according to ISO 15512 method (B) according to ISO 1133. This drying is to prevent moisture from causing voids in the extrudate after extrusion due to the hygroscopicity of the polymer material in powder or pellet form.

It should be understood that references to unfilled PEEK (Victrex 381G) in any of the following embodiments include but are not limited to PEEK manufactured in accordance with WO2018055384. Example 1 - Filament

Filaments formed from polymeric materials are produced by continuously extruding molten polymeric materials in order to assess the relative rates at which these polymeric materials form mold deposits.

Example 1.1 - A PEEK polymer material designated 381TL30 manufactured by Victrex Manufacturing, Inc., as defined herein, comprising 30 wt% talc (JETFINE™ 3CA) filled material.

Example 1.2 - Unfilled PEEK material designated 381G manufactured by Victrex Manufacturing Co., Ltd.

Example 1.3 - PEEK/PEDEK copolymer as LMPAEK™ material manufactured by Victrex Manufacturing Co., Ltd. according to EP3013888. Method of producing filaments

The filaments are produced by introducing a pre-dried polymer material into a typical single screw extrusion line consisting of a heated extrusion barrel with a screw and the following multiple zones: a feed zone, a compression zone, a metering zone, and a die zone, each having a temperature between 300° C. and 390° C. (see Table 1). The polymer material is fed through the zones to produce molten filaments at the die zone outlet. The molten filaments are drawn from the die and cooled to below the melting point of the polymer material to freeze the filaments into their final form. Feeding area Compression area Measuring area Mold area LMPAEK materials 320 340 345 350 Unfilled PEEK 325 365 375 385 30% talc filled PEEK 325 365 375 385 Table 1: Zone temperature (℃)

The inner diameter of the extruder barrel is between 15 mm and 50 mm, with the length to diameter ratio (L/D) of the screw being between 16:1 and 28:1, and preferably between 18:1 and 24:1. The line speed is set at 8 to 8.5 m/min.

Typically, the screw speed is set between 15 and 25 rpm. The screw speed can vary from 3 to 50 rpm, preferably 4 to 30 rpm and optimally 5 to 30 rpm. The line speed can vary from 1 to 30 m/min, preferably 3 to 25 m/min and optimally 4 to 20 m/min.

The melt pressure during extrusion is measured with a pressure transducer, which can be placed at the end of the screw or in the die. The melt pressure can vary depending on the material type and speed, but is typically in the range of 2 bar to 500 bar.

The molten polymer material flows through an extrusion line through a die having a circular opening of approximately 4 mm in diameter. The molten material is drawn from the die and cooled in air at ambient temperature until it is below the melting point of the material. A haul-off is used to draw the frozen filaments to the desired thickness. Filaments of approximately 1.5 to 2 mm, typically 1.7 mm, are produced by this process.

The size and shape of the die opening can vary, for example the opening can be 0.2 mm to 8 mm in diameter and can have a square, rectangular or leaf-shaped profile depending on the desired cross-sectional shape of the extruded product. The length of the die opening is suitably in the range of 0.1 to 6 times the diameter of the extruded filament, with the lead-in section preferably being smooth with a uniform diameter change, although stepped diameter changes are also possible.

The filament is extruded through the extrusion line until mold deposits are visible around the mold opening and begin to adversely affect the quality of the extruded product. Such adverse effects on the quality of the extruded product include visible marks and defects in the surface of the extruded product. Thinning of the diameter of the extrudate material and a reduction in diameter or thickness typically greater than 15% are detrimental to product quality. Amounts less than 15% should be understood to be acceptable to those with ordinary knowledge in the art. In addition, carbon-containing mold deposits that separate from the mold and attach to the extrudate may have an adverse effect on the quality of the final product. For different polymer materials, the time elapsed from the start of extrusion until the moment of adverse mold deposit formation is detailed in Table 2. Embodiment Polymer Materials Time until mold deposit is formed (minutes) 1.1 Filled PEEK (30 wt% talc) (Victrex 381TL30) 5 1.2 Unfilled PEEK (Victrex 381G) 60 1.3 Unfilled PEEK/PEDEK copolymer (Victrex LMPAEK™) 240 Table 2

The results in Table 2 show a significant difference in the generation of mold deposits between filled PEEK (Example 1.1) and unfilled PEEK or PEEK/PEDEK materials. Compared to using unfilled PEEK materials, there is a significant improvement in the time that elapses before mold deposits form, which can result in visible defects along the length of the extrudate. As a result, the extrusion process of the present invention can be run for a long time before the process must be stopped and the extrusion equipment cleaned. Advantageously, the process results in a more efficient production process and subsequently longer product lengths. Example 2 - Single-layer insulated wire

Coated wires suitable for use as insulated conductor wires were formed by extruding the polymer materials described in Table 2 above as a single layer onto copper wire. In addition, the process used continuous extrusion of molten polymer material onto the wire to evaluate the relative rate of mold deposit formation of the polymer material.

The coated wire was extruded through a clean extrusion die until significant mold deposits were visible around the die opening and the mold deposits began to adversely affect the quality of the extruded product. Such adverse effects on the quality of the extruded product included visible marks and defects in the surface of the extruded product. The time elapsed from the start of extrusion until the time of mold deposit formation was recorded and is provided in Table 3 for different polymer materials. The coated wire was produced using the method and apparatus described below. Method - Insulated Conductor Assembly Wire

Coated wire suitable for use as an insulated conductor wire is produced using an extrusion line having a barrel diameter ratio and line speed as described above for Example 1. Typically, the screw speed is set between 2 and 10 rpm. To produce the coated wire, the extrusion line is configured with a crosshead die into which molten polymer material enters from one side of the line. This type of configuration allows the polymer material to contact the wire within the die and form a sheath thereon. This type of extrusion process may be referred to as a "pressing" or "pressure die" system. In this embodiment, the wire is a copper wire having a rectangular cross-section. The wire is continuously fed through the extrusion line and the polymer material is extruded onto the wire in a continuous process. The line speed was set at 8 to 8.5 m/min.

The cross-sectional shape of the wire can vary, for example, square or rectangular. Rectangular wires can have an aspect ratio of up to 4:1.

The gap between the uncoated wire and the mold opening is typically between 50 and 300 microns. The final coated wire has a thickness between 100 and 200 microns. Table 3 below shows the results of the time to mold deposit formation. Embodiment Polymer coating Time until mold deposit is formed (minutes) Filled PEEK (30wt% talc) (Victrex 381TL30) 10 Unfilled PEEK (Victrex 381G) 35 Unfilled PEEK/PEDEK copolymer (Victrex LMPAEK™) 116 Table 3

The results in Table 3 show that unfilled PEEK on the wire is more resistant to mold deposit formation than filled PEEK. As a single polymer layer on the wire, the PEEK/PEDEK material in contact with the extrusion die during the extrusion process extends the time until significant mold deposits occur and begin to adversely affect the quality of the extruded product. In contrast, filled PEEK materials exhibit faster mold deposit formation. Therefore, the use of unfilled PEEK or PEEK/PEDEK allows the extrusion process to continue for a longer period of time before the extrusion equipment needs to be stopped and cleaned. This can provide a more efficient production process and longer extruded products.

There is a drive to use filled (e.g. talc filled) PAEK solutions in the field of insulating conductors in order to achieve, for example, a desired breakdown voltage. Therefore, the following example shows a specific example of the present invention that addresses mold deposits in the field of high voltage wire applications while also taking into account the need for filled PAEK materials. Example 3 - Insulating Wire Multilayer

Example 3 is an example of an extruded wire suitable for use as an insulated conductor assembly according to the present invention. Specifically, such wire is particularly advantageous in high voltage applications. Such wire is particularly advantageous in motor type applications.

Wires having inner and outer coatings of polymer materials as shown in Figures 1a and 1b were formed by extruding the polymer materials indicated in Table 4 below as outer and inner layers onto copper wires. The process used continuous extrusion of molten polymer materials onto the wires to evaluate the relative rates of mold deposit formation of these polymer materials. Embodiment Outer layer Inner layer 5.1 Filled PEEK (30wt% talc) (Victrex 381TL30) Filled PEEK (30% talc) (Victrex 381TL30) 5.2 Unfilled PEEK (Victrex 381G) Filled PEEK (30% talc) (Victrex 381TL30) 5.3 Unfilled PEEK/PEDEK copolymer (Victrex LMPAEK™) Filled PEEK (30% talc) (Victrex 381TL30) Table 4

As described above with respect to Figures 1a and 1b, the coated wire was extruded through a clean extrusion die until mold deposits were visible around the die opening and began to adversely affect the quality of the extruded product. Such adverse effects on the quality of the extruded product included visible marks and defects in the surface of the extruded product. The time elapsed from the start of extrusion until the moment when mold deposits formed that caused quality defects as described above was recorded and provided in Table 5 for different polymer materials. The coated wire was produced using the method and apparatus described below.

Coated wires were produced using an extrusion line as described above with a second heated extruder barrel for a second polymer material. The extrusion die used was of the type shown in FIG. 1a, configured for a "pressed" extrusion process, wherein outer and inner layers of polymer material form a sheath over the wire within the die, wherein the outer layer contacts the die as the product exits and the inner layer contacts the wire in the product. The polymer materials indicated in Table 4 were extruded through a first channel 101 and a second channel 102 as previously described and shown in the drawings to form the outer and inner layers, respectively, over the wire. Embodiment Outer layer Inner layer Time until mold deposit is formed (minutes) 5.1 Filled PEEK (30 wt% talc) Filled PEEK (30 wt% talc) 9 5.2 Unfilled PEEK Filled PEEK (30 wt% talc) 92 5.3 Unfilled PEEK/PEDEK copolymer (Victrex LMPAEK™) Filled PEEK (30 wt% talc) 125 Table 5

Example 5.2, which has an outer layer of unfilled PEEK in contact with the mold and an inner layer of PEEK plus talc filled, shows a significant improvement in mold deposits when compared to Example 5.1, which has two layers of PEEK plus filler.

Compared to similar filled PEEK materials, Example 5.3 having an outer layer of PEEK/PEDEK copolymer that contacts the surface of the extrusion die upon exiting the extrusion die can significantly increase the time until mold deposits form and begin to adversely affect the quality of the extruded product. Compared to using a filled PEEK material as the outer layer, using a PEEK/PEDEK material as the outer layer provides approximately a 12-fold improvement in the time that elapses before significant mold deposits form.

Advantageously, an extrusion process for forming a product comprising an outer layer of unfilled PAEK or alternatively PEEK/PEDEK can be continued for a longer period of time before the process needs to be stopped and the extrusion equipment cleaned, which can provide a more efficient production process. In addition, the process can be run at higher outputs or line speeds that would normally exacerbate mold deposits. Thus, in addition to product quality, productivity is also improved. Such extruded products having an inner layer comprising a PEEK polymer and a filler material can thus be formed without the polymer and filler material forming excessive mold deposits that would adversely affect the process and product.

While several preferred embodiments have been shown and described, it will be appreciated by those skilled in the art that various changes and modifications may be made without departing from the scope of the invention, as defined in the appended claims.

Throughout this specification, the term "comprising" or "comprises" means including the specified components, but should not exclude the presence of other components. The term "consisting essentially of" or "consists essentially of" means including the specified components, but excluding other components, except for materials that appear as impurities, unavoidable materials that exist due to the process used to provide the components, and components added for purposes other than achieving the technical effects of the present invention. Typically, when referring to a composition, a composition consisting essentially of a group of components will contain less than 5% by weight, typically less than 3% by weight, and more typically less than 1% by weight of non-specified components. The term "consisting of" or "consists of" means including the specified components, but excluding the addition of other components. Where appropriate, the use of the term "comprises" or "comprising" may also be regarded as covering or including the meaning "consists essentially of" or "consisting essentially of", and may also be regarded as including the meaning "consists of" or "consisting of", as the case may be. For the avoidance of doubt, where the amount of a component in a composition is described in wt%, this means the weight percentage of the specified component relative to the entire composition referred to. For example, "polymer material (A) provides 70 to 100 wt% of the outer layer" means that 70 to 100 wt% of the outer layer is provided by polymer material (A). The optional features described herein may be used individually or in combination with each other when appropriate, and in particular in the combinations described in the accompanying claims. The optional features of each aspect or exemplary embodiment of the invention as described herein should also be understood to be applicable to any other aspect or exemplary embodiment of the invention when appropriate. In other words, a person with ordinary knowledge in the art to which this specification belongs should regard the optional features of each exemplary embodiment of the invention as interchangeable and combinable between different exemplary embodiments.

It should be noted that all texts and documents related to this application that were filed simultaneously with or before this specification and that are open to public inspection with this specification, and the contents of all such texts and documents are incorporated herein by reference.

All features disclosed in this specification (including any accompanying claims and drawings) and/or all steps of any method or process so disclosed may be combined in any combination, except combinations of at least some of such features and/or steps that are mutually exclusive.

Unless expressly stated otherwise, each feature disclosed in this specification (including any accompanying claims and drawings) may be replaced by alternative features that achieve the same, equivalent or similar purpose. Therefore, unless expressly stated otherwise, each feature disclosed is only one example of a generic series of equivalent or similar features.

The present invention is not limited to the details of the foregoing specific examples. The present invention extends to any novel feature or any novel combination of features disclosed in this specification (including any accompanying patent application scope and drawings), or to any novel step or any novel combination of steps of any method or process so disclosed.

1: Mold body 2: Mold mandrel 3: Wire/pin 100: Pressure extrusion mold 101: First channel 102: Second channel 103: Wire 110: Mold outlet 111: Mold inlet 120: Extruded insulating conductor assembly 122: First position 124: Second position 126: Extruded first sheath 128: Extruded second sheath 200: Extrusion mold 201: First channel 202: Second channel 203: Wire 210: Mold outlet 226: Extruded sheath 228: Extruded sheath 233: Third channel 236: Extruded sheath 300: Mold/mold body 301: First channel/first layer 302: Second channel/second layer 303: Wire/cable/channel 304: Channel 310: Mold outlet 311: First outer layer 312: Inner layer 313: Channel/third layer/second outer layer 400: Extrusion mold 401: First channel 402: Second channel 403: Third channel 404: Fourth channel 410: Mold outlet 411: First outer layer 412: Inner layer 413: Second outer layer 414: Hollow center/hollow inner layer 500: Extrusion equipment 501: First channel 502: Second channel 503: Third channel 510: Mold outlet 511: First outer layer 512: Second outer layer 513: Inner layer 600: Mold 601: First channel 602: Second channel 610: Mold outlet 611: Outer layer 612: Inner layer/core A: Polymer material/First outer layer/Second outer layer/First outer layer/Second outer layer/Outer layer B: Polymer material/Inner layer C: Polymer material

In order to better understand the present invention and to show how to implement the exemplary specific examples, reference will now be made to the accompanying drawings, in which: [Figure 1a] is a schematic diagram of an extrusion die, which is used to manufacture the insulating conductor assembly of the present invention; [Figure 1b] is a schematic cross-section of the insulating conductor assembly produced by the extrusion process of Figure 1a; [Figure 2a] is a schematic diagram of an alternative extrusion die, which is used to manufacture the insulating conductor assembly of the present invention; [Figure 2b] is a schematic cross-section of an alternative specific example of the insulating conductor assembly produced by the extrusion process of Figure 2a; [Figure 3a] is a schematic diagram of an extrusion die, which is used to manufacture the insulating conductor assembly of the present invention; [Figure 3b] is a schematic cross-section of an insulating conductor assembly produced by the extrusion process of Figure 3a; [Figure 4a] is a schematic diagram of an extrusion die, which is used to produce an extruded product of a specific embodiment of the present invention in the form of a tube using a method according to the second aspect of the present invention; [Figure 4b] is a cross-section of an extruded tube produced by the extrusion process of Figure 4a; [Figure 5a] is a schematic diagram of an extrusion die, which is used to produce an extruded product of an alternative aspect of the present invention in the form of a film using a method according to one aspect of the present invention; [Figure 5b] is a cross-section of an extruded film produced by the extrusion process of Figure 5a; [Figure 6a] is a schematic diagram of an extrusion die for producing an extruded product in the form of a filament according to one aspect of the present invention using a method according to one aspect of the present invention; and [Figure 6b] is a cross-section of an extruded filament produced by the extrusion process of Figure 6a.

1: Mold body

2: Mold spindle

100: Pressure extrusion mold

101: First channel

102: Second channel

103: Wires

110: Mould export

111: Mold entrance

122: First position

124: Second position

126: Extruded first sheath

128: Extruded second sheath

A:Polymer materials

B: Polymer materials

Claims (26)

An insulating conductor assembly comprising a conductive wire, a first extruded layer and a second extruded layer; the first layer comprises: a polymer material (A) having repeating units of formula I (Formula I) wherein t1 and w1 independently represent 0 or 1, and v1 represents 0, 1 or 2; and the second layer comprises: a polymer material (B) having repeating units of Formula I (Formula I) wherein t1 and w1 independently represent 0 or 1, and v1 represents 0, 1 or 2; and a filler material, wherein the second layer is located between the wire and the first layer. The assembly of claim 1, wherein the polymer material (A) comprises at least 80 wt % PAEK polymer. The assembly of claim 2, wherein the polymer material (A) is substantially at least 99 wt% PAEK. The assembly of any of the preceding claims, wherein the second layer comprises at least 50 wt % of the polymeric material (B). An assembly as claimed in any of the preceding claims, wherein the polymer material (A) and/or (B) is polyetheretherketone (PEEK). An assembly as claimed in any preceding claim, wherein the first layer consists essentially of PEEK and the second layer consists essentially of a polymer material (B) being PEEK and a filler material. The assembly of any of the preceding claims, wherein the polymer material (A) and/or polymer material (B) has a crystallinity of at least 20%. An assembly as in any of the preceding claims, wherein the filler material is a particulate filler material. An assembly as claimed in claim 8, wherein the filler material is talc or zinc oxide. An assembly as claimed in any preceding claim, wherein the filler material comprises at least 15 wt % of polymer material (B). An assembly as claimed in any preceding claim, wherein the filler material has a D50 between 1 and 5 µm as measured by laser particle size analyzer, laser diffraction, Mie theory (ISO 13320-1). An assembly as claimed in any of the preceding claims, wherein the first extrusion layer is positioned adjacent to a die of the extruder assembly. An assembly as in any of the preceding claims, wherein the second layer is adjacent to the wire. An assembly as in any of the preceding claims, wherein the first extrusion layer is positioned adjacent to the second layer. An assembly as claimed in any of the preceding claims, wherein an additional layer is provided, the additional layer comprising an enamel layer and/or another polymer layer, such as a thermosetting polymer layer, such as a fluoropolymer or a polyimide layer. An assembly as claimed in any preceding claim, wherein the first layer and the second layer of the extruded product have a combined thickness of at most 300 µm. An extrusion product assembly comprising a core, a first extrusion layer and a second extrusion layer; the first layer comprising: a polymer material (A) having repeating units of formula I wherein t1 and w1 independently represent 0 or 1, and v1 represents 0, 1 or 2; and the second layer comprises: a polymer material (B) having repeating units of formula I wherein t1 and w1 independently represent 0 or 1, and v1 represents 0, 1 or 2; and a filler material, wherein the second layer is located between the core and the first layer. An insulating conductor assembly comprises a conductive wire, a first extruded layer and a second extruded layer; the first layer comprises: a polymer material (D), the polymer material (D) having repeating units of the following formula: -O-Ph-O-Ph-CO-Ph- I and repeating units of the following formula: -O-Ph-Ph-O-Ph-CO-Ph- II wherein Ph represents a phenylene moiety, and the second layer comprises: a polymer material (B) having repeating units of formula I (Formula I) wherein t1 and w1 independently represent 0 or 1, and v1 represents 0, 1 or 2; and a filler material, wherein the second layer is located between the wire and the first layer. A method of producing an extrusion product assembly comprising a first layer and a second layer, the method comprising the following steps: a) providing a source of a polymer material (A) having repeating units of formula I: wherein t1 and w1 independently represent 0 or 1, and v1 represents 0, 1 or 2; b) providing a source of a second polymer material (B) having repeating units of formula I; wherein t1 and w1 independently represent 0 or 1, and v1 represents 0, 1 or 2; and a filler material; c) delivering the polymer material (A) and the second polymer material (B) to an extrusion table comprising a mold; d) extruding the polymer material (A) and the second polymer material (B) through the mold so that the polymer material (A) contacts the outlet of the mold during extrusion and the second polymer material (B) does not contact the mold during extrusion to form the extruded product assembly. The method of claim 19, wherein the extruded product assembly is an insulating conductor assembly. A method as claimed in claim 19 or 20, wherein the input and extrusion of the polymer material (A) and the second polymer material (B) are arranged so that the second polymer material (B) is covered by the polymer material (A) at the outlet of the mold so that the second polymer material does not contact the outlet of the mold. A method as in any of claims 19 to 21, wherein the first layer is introduced into the mold assembly at a first position, the first position being distal from an exit end of the mold. A method as in any of claims 19 to 22, wherein the second layer is introduced at a second location, the second location being downstream from the first location. A use of a polymer material (A) or (D) for reducing the formation of deposits on a die of an extrusion apparatus during extrusion of at least a second polymer material (B); wherein the polymer material (A) has repeating units of formula I: wherein t1 and w1 independently represent 0 or 1, and v1 represents 0, 1 or 2; or the polymer material (D) has repeating units of the following formula: -O-Ph-O-Ph-CO-Ph- I and repeating units of the following formula: -O-Ph-Ph-O-Ph-CO-Ph- II wherein Ph represents a phenylene moiety; and the second polymer material (B) has repeating units of formula 1: wherein t1 and w1 independently represent 0 or 1, and v1 represents 0, 1 or 2; and filler material. An electrical device comprising an insulating conductor as described in any one of claims 1 to 18. A motor or stator coil having an insulating conductor as claimed in any one of claims 1 to 18.