Die assembly for solid state extrusion of polyolefin material

Abstract

The invention relates to a mould assembly for solid extrusion of polyolefin material, where the mould assembly comprises a preferably circular, closed straight channel (1) comprising an inlet (2) and an outlet (3), interpreted that solid polyolefin material can be conveyed through the channel along a flow axis (4) from the inlet to the outlet, where the channel comprises an outer shell (5) to form an enclosure completely surrounding the channel; wherein the channel comprises a compression section having a first diameter D1 perpendicular to the flow axis towards the inlet side of the channel, and a second diameter D2 perpendicular to the flow axis towards the outlet side of the channel, where D1gt; d2 to form a tapered channel. Wherein the housing has an inner surface (6) forming an outer wall of the channel, where the inner surface (6) has a coefficient of friction such that the extrusion pressure can be maintained at a constant level during extrusion with an extrusion draw ratio of up to 25, preferably up to 50, where the extrusion draw ratio is the ratio of the area of the inlet to the area of the outlet. Such a mold assembly makes it possible to extrude a polyolefin material in a solid state without accumulation of excess pressure, resulting in an extrudate having desired material properties relating to melting temperature, crystallinity, and brittleness.

Description

[0001] The present invention relates to an extrusion die assembly for the solid state extrusion of polyolefin materials, in particular ultra-high molecular weight polyethylene materials. The present invention also relates to a method for extruding polyolefins in the solid state, in particular ultra-high molecular weight polyethylene.

[0002] In the processing of polyolefin materials, extrusion is a widely applied technique since it allows the manufacture of products of various desired shapes. The extrusion of polyolefin materials is typically carried out by heating the polyolefin material to a temperature above its melting point and then forcing the molten polyolefin through a die orifice of the desired shape, whereupon the extruded material is solidified by cooling (usually in water) to form a solid shape.

[0003] However, certain grades of polyolefins are not suitable for melting such that such a melt extrusion method can be applied to produce shapes of such materials. Specifically, polyolefin materials having a very high molecular weight are difficult or impossible to process via melt extrusion. Thus, if it is desired to produce shapes of such materials, alternative processing techniques are required such that polyolefins in the solid state can be processed.

[0004] A known technique for processing polyethylene that cannot be processed via melt processing methods is via solution processing. In such a method, polyethylene such as UHMWPE is dissolved in a solvent to form a dilute solution that typically has a gelled nature, and then it can be extruded or spun into shape. The method can be carried out at a temperature above the dissolution temperature of polyethylene in a particular solvent. By such a method, objects such as fibers comprising oriented polyethylene molecules can be formed. The object can be stretched to a high draw ratio, for example a draw ratio of more than 20. However, a disadvantage of such a method is that the steps of dissolving the polymer in a solvent and then removing the solvent are steps that significantly deteriorate the efficiency and economy of the method.

[0005] Accordingly, there is a desire for a viable solid state processing technique for polyolefins that does not exhibit such disadvantages.

[0006] Another processing technique provided in the art is to process polyolefin powder via calendering or double-belt pressing. In such a method, the powder is subjected to compression between two opposing steel belts to obtain a calendered sheet. Subsequently, the sheet can be stretched into a belt having a draw ratio of no more than, for example, 100 (compared to the initial sheet). However, a disadvantage of such a method is that the choice of shape design is rather limited; the product is a sheet in which only the width and thickness can be changed.

[0007] Accordingly, for alternative shapes, there is still a need to provide other solid state forming methods.

[0008] The present invention now provides a die assembly for a solid state forming method of polyolefin materials, in particular for the solid state forming of UHMWPE powder materials.

[0009] The die assembly of the present invention comprises a preferably circular, enclosed straight channel (1) which includes an inlet (2) and an outlet (3), and which is configured such that solid polyolefin material can be conveyed from the inlet to the outlet through the channel along a flow axis (4), wherein the channel includes a housing (5) to form a sheath completely surrounding the channel, wherein the housing has an inner surface (6) forming the outer wall of the channel, wherein the channel includes a compression section which has a first diameter D1 perpendicular to the flow axis at the inlet side of the channel and a second diameter D2 perpendicular to the flow axis at the outlet side of the channel, wherein D1 > D2 to form a tapered channel.

[0010] In an embodiment, the inner surface (6) has a coefficient of friction such that the extrusion pressure can be maintained at a constant level during extrusion with an extrusion draw ratio of at most 25, preferably at most 50, wherein the extrusion draw ratio is the ratio of the area of the inlet to the area of the outlet.

[0011] Figure 1 Examples of such dies are provided herein.

[0012] Such a die assembly enables the extrusion of polyolefin material in a solid state without the build-up of excessive pressure, producing an extrudate having desired material properties such as melt temperature, crystallinity, and brittleness.

[0013] In the die assembly according to the present invention, preferably the housing is capable of withstanding an extrusion pressure of up to 250 MPa, or up to 170 MPa, and is capable of operating at an operating temperature not higher than 180 °C, or not higher than 160 °C.

[0014] The inner surface of the housing may, for example, have a coefficient of friction lower than that of steel.

[0015] The inner surface of the housing may, for example, be made of a thermosetting material, preferably an epoxy resin, an unsaturated polyester resin, or a phenolic resin, particularly preferably an epoxy resin.

[0016] Particularly preferably, the housing is made of a thermosetting material, preferably an epoxy resin, an unsaturated polyester resin, or a phenolic resin. Alternatively, the housing may comprise an inner surface coating of a thermosetting material, preferably an epoxy resin, an unsaturated polyester resin, or a phenolic resin.

[0017] The thermosetting resin may, for example, be an epoxy resin produced by the curing of an epoxy reactant system comprising a certain amount of a compound of formula A and a certain amount of a compound of formula B:

[0018]

[0019] wherein R1 is a structural moiety containing 1 - 20 carbon atoms, preferably a hydrocarbon structural moiety, preferably a structural moiety of the following formula:

[0020]

[0021] wherein R3 is a structural moiety containing 1 to 8 carbon atoms, preferably -CH2- or -C(CH3)2- and

[0022] wherein R2 is a structural moiety containing 1 to 10 carbon atoms, preferably a hydrocarbon structural moiety, more preferably a linear alkyl structural moiety.

[0023] The compound of formula A can be, for example:

[0024]

[0025] The compound of formula B can be, for example:

[0026]

[0027] In one embodiment, the compound of formula A is:

[0028]

[0029] and the compound of formula B is:

[0030]

[0031] Curing can be carried out, for example, using a curing agent system comprising diethylmethylphenylenediamine, 1,2-diaminocyclohexane, bisphenol A, and p-toluenesulfonic acid.

[0032] In the mold assembly according to the present invention, the channel (1) can taper at an angle α, where α ≥ 1.0° and ≤ 60.0°, preferably ≥ 5.0° and ≤ 10.0°, more preferably ≥ 6.0° and ≤ 9.0°.

[0033] In an embodiment, the present invention also relates to a method for solid-state extrusion of a polyolefin material, wherein the polyolefin material is extruded by pressing it through the mold assembly according to the present invention at a temperature of ≤ 150 °C, preferably ≤ 140 °C, more preferably ≥ 90 °C and ≤ 130 °C, and at an applied pressure of ≤ 500 MPa, preferably ≤ 400 MPa, more preferably ≤ 300 MPa, still more preferably ≤ 150 MPa, yet still more preferably ≥ 50 and ≤ 150 MPa.

[0034] The polyolefin material can be provided to the extrusion assembly, for example, as a powder having a bulk density of ≥ 200 and ≤ 600 kg / m 3 , preferably ≥ 200 and ≤ 500 kg / m 3 and the bulk density is determined via ASTM D1895-96.

[0035] The polyolefin material can be, for example, a polyethylene or polypropylene homopolymer or copolymer. Preferably, the polyolefin material is an ultra-high molecular weight polyethylene (UHMWPE) material, preferably untangled UHMWPE.

[0036] The polyolefin material has an intrinsic viscosity of ≥8.0, preferably ≥10.0, more preferably ≥20.0 dl / g, still more preferably ≥20.0 and ≤50.0 dl / g, as determined, for example, according to ASTM D4020 (2011) for the determination of dilute solutions of polyolefins in decalin at a temperature of 135 °C.

[0037] In one embodiment, it is further preferred that the polyolefin material has a melting temperature T of ≥135 °C, preferably ≥140 °C, as determined by DSC measurement in the first run. m 。

[0038] It is also preferred that the polyolefin material has a crystallinity X of ≥70%, preferably ≥75%, as determined by DSC measurement in the first run. c 。

[0039] The present invention further relates to an extruded article obtained by the method according to the present invention, preferably wherein the article is a belt, fiber, rod, sheet, tube or pipe.

[0040] In the context of the present invention, ultra-high molecular weight polyethylene, also referred to as UHMWPE, is understood to be a polyethylene material having a viscosity-average molecular weight (M v ) of more than 750 kg / mol. Even more preferably, the UHMWPE material can have an M v of more than 1,000 kg / mol. M v can be not more than 10,000 kg / mol. Particularly preferably, the UHMWPE material used in the context of the present invention has an M v of ≥1,000 kg / mol and ≤8,000 kg / mol.

[0041] The viscosity-average molecular weight of UHMWPE can be calculated using the Mark-Houwink equation from the intrinsic viscosity of the polymer:

[0042]

[0043] where IV is the intrinsic viscosity determined according to ASTM D4020 (2011) in units of dl / g; for polyethylene, K is a constant with a value of 6.20·10 -4 when measuring IV in decalin at 135 °C; and α is a constant with a value of 0.700, which also applies to polyethylene when measuring IV in decalin at 135 °C. Then M vis the calculated viscosity-average molecular weight, in g / mol. Thus, for the application of polyethylene according to the present invention, the Mark-Houwink equation that can be used is:

[0044]

[0045] which is converted to:

[0046]

[0047] The UHWMPE material can for example have an intrinsic viscosity IV of ≥ 8.0 dl / g, preferably ≥ 10.0 dl / g, more preferably ≥ 15.0 dl / g, still more preferably ≥ 20.0 dl / g. The UHMWPE material can have an IV of ≤ 60.0 dl / g, preferably ≤ 50.0 dl / g. The UHMWPE material can have an IV of ≥ 8.0 and ≤ 60.0 dl / g, preferably ≥ 10.0 and ≤ 60.0 dl / g, more preferably ≥ 15.0 and ≤ 60.0 dl / g, still more preferably ≥ 15.0 and ≤ 50.0 dl / g, yet still more preferably ≥ 20.0 and ≤ 50.0 dl / g.

[0048] The UHMWPE can for example have ≥ 200 kg / m 3 , preferably ≥ 200 and ≤ 700 kg / m 3 , more preferably ≥ 200 and ≤ 500 kg / m 3 of bulk density. The bulk density of UHMWPE can be measured according to the method of ASTM D1895 / A(2010). Such a bulk density ensures easy processing of the powder in the extrusion process and helps in the easy handling and storage of the polymer powder.

[0049] The UHMWPE can for example have an average particle size (D 50 ) in the range of 10.0 to 250.0 μm, preferably 50.0 to 250.0 μm, more preferably 60.0 to 200.0 μm, measured according to ISO-13320(2009).

[0050] In certain embodiments, the UHMWPE can be a copolymer comprising at least 95.0 wt%, preferably at least 98 wt%, more preferably at least 99.0 wt% of structural moieties derived from ethylene, based on the total weight of the UHMWPE.

[0051] In certain embodiments, the UHMWPE can be a copolymer that comprises a structural moiety derived from ethylene and a structural moiety derived from one or more α-olefins of up to 5.0 wt%, preferably up to 2.0 wt%, more preferably up to 1.0 wt% based on the total weight of the UHMWPE, wherein the α-olefin is selected from propylene, 1-butene, 4-methyl-1-pentene, 1-hexene, and 1-octene, preferably selected from propylene, 1-butene, 1-hexene, and 1-octene, and more preferably selected from 1-butene, 1-hexene, and 1-octene.

[0052] Preferably, the UHMWPE is a copolymer that comprises a structural moiety derived from ethylene of at least 95.0 wt% and a structural moiety derived from 1-butene, 1-hexene, or 1-octene of up to 5.0 wt% based on the total weight of the UHMWPE, preferably comprises a structural moiety derived from ethylene of at least 98.0 wt% and a structural moiety derived from 1-butene, 1-hexene, or 1-octene of up to 2.0 wt%, and more preferably comprises a structural moiety derived from ethylene of at least 99.0 wt% and a structural moiety derived from 1-butene, 1-hexene, or 1-octene of up to 1.0 wt% based on the total weight of the UHMWPE.

[0053] The UHMWPE is produced via a slurry process or via a gas phase process. In a preferred embodiment, the UHMWPE is produced via a slurry process in the presence of an organic diluent such as hexane. The polymerization can be carried out via a batch process, a semi-batch process, or in a continuous mode. In some aspects of the present invention, the UHMWPE can be produced by the polymerization of ethylene, optionally copolymerized with one or more α-olefin comonomers, in the presence of a supported catalyst composition, optionally in the presence of hydrogen.

[0054] The polymerization can be carried out, for example, at a polymerization temperature of 0 °C to 140 °C, preferably 10 °C to 90 °C, more preferably 25 °C to 80 °C. The ethylene pressure can be, for example, in the range of 50 to 5000 kPa, preferably 100 to 5000 kPa, more preferably 100 to 2000 kPa, still more preferably 100 to 1000 kPa.

[0055] The supported catalyst composition can, for example, comprise a transition metal complex containing two phenoxyimine structural moieties. Preferably, the transition metal in the complex is selected from Ti, Hf, and Zr. For example, the transition metal complex can be a complex containing a metal dihalide, such as a metal dichloride.

[0056] The carrier can be particulate methylaluminoxane. Preferably, the particulate methylaluminoxane has an average particle size of ≥2.0 and ≤10.0 μm. The average particle size of the carrier can be measured, for example, using a Mastersizer 200 Hydro S from Malvern Instrument Ltd. The particulate methylaluminoxane can have, for example, an aluminum content of ≥25.0% by weight, preferably ≥25.0 and ≤60.0% by weight, more preferably ≥30.0 and ≤50.0% by weight, based on the total weight of the particulate methylaluminoxane.

[0057] The present invention will now be illustrated by the following non-limiting examples.

[0058] Extrusion experiments were carried out using a mold produced from the epoxy resin RenLam LY 5210 and a mold produced from DIN 1.2436 steel. RenLam LY 5210 is an epoxy resin with CAS reg.nr. 1247949-81-0, a polymer of N,N'-(methylenedi-4,1-phenylene)bis[N-(2-(oxiranylmethyl)-2-oxiranemethanamine] and 2,2'-[1,4-butanediol bis(glycidyl ether)]bis[oxirane].

[0059] The molds used in the examples had Figure 2 the geometry shown, where all dimensions are in mm. Both molds had a taper angle α of 9°. The molds were configured to have an extrusion draw ratio of 15.

[0060] In Example 10, an additional mold ("epoxy resin-2") was used. This mold was produced using an epoxy resin as described above, and was configured according to Figure 8 the geometry. The epoxy resin-2 mold had an extrusion draw ratio of 45.

[0061] In the experiments of the present invention, ultra-high molecular weight polyethylene materials UH1 and UH2 were used. UH2 is a material of grade GUR 4120 obtained from Celanese.

[0062] UH1 is a material produced according to the following synthesis scheme.

[0063] Ethylene polymerization was carried out using a bis-phenoxy-imine titanium complex ([3-t-Bu-2-O-C6H3CH=N(C6F5)]2TiCl2) (as a dispersed transition metal complex) with CAS reg.nr. 352033-76-2 obtained from MCAT GmbH:

[0064]

[0065] A transition metal complex is supported on particulate methylaluminoxane (MAO), where the MOA has an aluminum content of 38.8 wt% and a particle size of 5.5 μm. The MAO is obtained from Tosoh Fine Chem Corporation. Triisobutylaluminum (TIBAL) with CAS reg.nr. 100-99-2 obtained from Lanxess is used as a scavenger.

[0066] Polymerization is carried out in a 10 L stirred autoclave using 5 L of purified hexane as a diluent. TIBAL (1 mmol) is added as a scavenger to the hexane, and the stirrer is set to 1000 rpm. The mixture is heated to a polymerization temperature of 30 °C and pressurized with ethylene to a pressure of 150 kPa.

[0067] In a separate glass container, a suspension containing a predetermined amount of the transition metal complex is premixed with a suspension containing a predetermined amount of MAO by manually shaking the resulting suspension for a period of 10 min under an inert atmosphere. The molar ratio of MAO to the transition metal complex in the suspension is 400.

[0068] Subsequently, the resulting suspension containing the supported catalyst is injected into the reactor via a pressure cell, rinsing the cell with hexane at this time. The amount of the suspension added to the reactor is such that the concentration of the transition metal complex in the reactor is 0.02 mmol / l. The temperature in the autoclave reactor is kept constant at 30 °C, and the pressure is kept constant by passing additional ethylene feed through a mass flow meter. The reaction is stopped after 48 min. The reaction is stopped by reducing the pressure and cooling the reactor, and reducing the stirrer speed. The reactor contents are passed through a filter. After that, the wet polymer powder is collected and dried at 50 °C in vacuo.

[0069] The bulk density of the polymer powder is determined according to ASTM D1895 / A (2010) to obtain a bulk density of 219 kg / m 3 The intrinsic viscosity (IV) is determined via the method of ASTM D4020 (2011), involving a dilute solution of polyethylene in decalin at a temperature of 135 °C, to obtain an IV of 36.4 dl / g. When applying the Mark-Houwink equation: IV = K·M v α, the applicable values K = 6.20·10 -4 and α = 0.700 for polyethylene in decalin at 135 °C are used to calculate a viscosity-average molecular weight M v of 5909 kg / mol.

[0070] UH1 is obtained via this protocol.

[0071] Solid state extrusion was carried out using a ram extrusion mechanism equipped with the die as described above. A Zwick Z020 static mechanical testing machine with a barrel diameter of 10 mm was used to prepare the ram mechanism. The UHMWPE powder as described above was introduced into the barrel and pre-compressed at room temperature by applying a force of 200 N for 30 s using an empty die. After pre-compression, the empty die was replaced with one of the steel or epoxy resin dies shown above. The mechanism was then heated to the operating temperature shown in Table 1 below.

[0072] The extrusion experiment was carried out by applying pressure to the ram in such a way as to ensure a defined and constant ram displacement. During extrusion, the extrusion pressure to be applied to the piston of the ram was continuously measured.

[0073] Table 1: Experimental conditions

[0074] Example Mold Temperature Plunger speed Material 1 Steel 120℃ 5mm / min UH1 2 Epoxy resin 120℃ 5mm / min UH1 3 Epoxy resin 120℃ 1mm / min UH1 4 Epoxy resin 120℃ 20mm / min UH1 5 Epoxy resin 120℃ 60mm / min UH1 6 Epoxy resin 100℃ 5mm / min UH1 7 Epoxy resin 110℃ 5mm / min UH1 8 Epoxy resin 130℃ 5mm / min UH1 9 Epoxy resin 120℃ 5mm / min UH2 10 Epoxy resin - 2 120℃ 5mm / min UH1

[0075] The measured extrusion pressures for each example as a function of piston displacement are shown in Figures 3 - 6 below. Figure 3 An extrusion experiment is shown where the use of a steel die versus an epoxy resin die was compared at a piston displacement speed of 5 mm / min at 120 °C. It can be observed that when using the steel die (Example 1), the pressure increased rapidly without significant displacement; it was not possible to extrude the UH1 material. However, when using the epoxy resin die (Example 2), under the same operating conditions, extrusion occurred in a predictable manner, where the extrusion pressure gradually increased to approximately 70 MPa during the first 30 mm of piston displacement and remained at approximately that level for the remainder of the piston displacement, i.e., up to 50 mm displacement.

[0076] Additional experiments were carried out to evaluate the effect of the piston displacement speed, as reflected in Examples 3 - 5. In Figure 4 below, the effect of the change in displacement speed on the extrusion pressure is shown, showing that for each extrusion speed, the epoxy resin die can be used to extrude the material UH1 quite smoothly at an extrusion pressure not exceeding approximately 120 MPa.

[0077] The effect of temperature was studied in Examples 6 - 8. The results regarding extrusion pressure versus total displacement are shown in Figure 5 below, showing that for each extrusion temperature, the epoxy resin die can be used to extrude the material UH1 quite smoothly at an extrusion pressure not exceeding approximately 150 MPa.

[0078] To evaluate the suitability of the epoxy resin die for the extrusion of different UHMWPE materials, Example 9 was carried out using Celanese GUR4120 (UH2). The results regarding extrusion pressure versus total displacement are shown in Figure 6It is also shown that the extrusion of GUR 4120 using an epoxy resin mold is feasible, although the extrusion pressure experiences some fluctuations. Visual inspection of the extrudates of Example 2 (using UH1) and Example 9 (using GUR 4120) is as shown in Figure 7 As shown. It can be observed from this figure that the extrudate strands of UH1 are completely straight and regular in nature, while the extrudate strands of UH2 are very irregular and curly in shape. Additionally, it is observed that the extrudate of UH2 is very brittle in nature, while that of UH1 is not. The extrudate of UH1 is transparent, while that of UH2 is white.

[0079] Example 10 is included to illustrate the suitability of the mold according to the present invention for processing UHMWPE materials with a higher extrusion draw ratio. The UH1 material was extruded at a plunger displacement speed of 5 mm / min at 120 °C. From Figure 9 It can be observed that the extrusion of such a high extrusion draw ratio as 45 can be completed using the mold of the present invention.

[0080] The UH1 and UH2 samples were measured via DSC before extrusion, and the melting temperature and crystallinity of the extruded material obtained from Example 2 and Example 9 respectively. The results of these DSC measurements are shown in Table 2 below.

[0081] Table 2: DSC measurements

[0082] Material <![CDATA[T m,1 > <![CDATA[T m,2 > <![CDATA[X c,1 > <![CDATA[X c,2 > UH1 141 146 80 >90 UH2 141 141 65 65

[0083] Where T m,1 is the melting temperature of the material before extrusion (in °C), T m,2 is the melting temperature after extrusion (in °C), X c,1 is the crystallinity before extrusion (in %), and X c,2 is the crystallinity after extrusion (in %).

[0084] DSC analysis was performed by taking samples of 1.5 ± 0.2 mg for each analysis. During each analysis, nitrogen was continuously purged at 50 ml / min to prevent sample degradation. The thermal protocol applied during the measurement included: 1) a first heating run from -40 °C to 180 °C at 10 °C / min; 2) an annealing step at 180 °C for 5 mins to eliminate the thermal history of the powder; 3) a cooling run from 180 °C to -40 °C at 10 °C / min; and 4) a final heating run from -40 °C to 180 °C. The melting endotherm obtained from 1) was used to obtain the crystallization fraction X c by using the ratio between the enthalpy of polyethylene measured during the heating run and the equilibrium melting enthalpy (293 J / g). The melting temperature T m was taken at the maximum of the melting endotherm obtained in step 1) of this protocol.

[0085] It can be observed that for UH1, both the melt temperature and the crystallinity increase after extrusion, while this is not the case for UH2. This indicates that the extrusion of UH1 (unentangled UHMWPE) using a shrink die produces a product with high crystallinity and a high degree of orientation in the machine direction.

Claims

1. A die assembly for the solid-state extrusion of polyolefin materials, wherein the die assembly comprises a preferably circular, closed, straight channel (1) which includes an inlet (2) and an outlet (3), and which is configured such that solid polyolefin material can be conveyed from the inlet to the outlet through the channel along a flow axis (4), wherein the channel includes a housing (5) to form a sheath completely surrounding the channel, and wherein the housing has an inner surface (6) forming the outer wall of the channel; wherein the channel includes a compression section having a first diameter D1 perpendicular to the flow axis at the inlet side of the channel and a second diameter D2 perpendicular to the flow axis at the outlet side of the channel, wherein D1 > D2 to form a tapered channel.

2. The die assembly according to claim 1, wherein the inner surface (6) has a coefficient of friction such that the extrusion pressure can be maintained at a constant level during extrusion with an extrusion draw ratio of at most 25, preferably at most 50, wherein the extrusion draw ratio is the ratio of the area of the inlet to the area of the outlet.

3. The die assembly according to any one of claims 1-2, wherein the housing is capable of withstanding an extrusion pressure of at most 250 MPa, or at most 170 MPa, and is capable of operating at an operating temperature of at most 180 °C, or at most 160 °C.

4. The die assembly according to any one of claims 1-3, wherein the inner surface of the housing is made of a thermosetting material, preferably epoxy resin, unsaturated polyester resin or phenolic resin.

5. The die assembly according to any one of claims 1-4, wherein the housing is made of a thermosetting material, preferably epoxy resin, unsaturated polyester resin or phenolic resin, or wherein the housing includes an inner surface coating of a thermosetting material, preferably epoxy resin, unsaturated polyester resin or phenolic resin.

6. The die assembly according to any one of claims 4-5, wherein the thermosetting resin is an epoxy resin cured via an epoxy reactant system which comprises a quantity of a compound of formula A and a quantity of a compound of formula B: wherein R1 is a structural moiety containing 1-20 carbon atoms, preferably a hydrocarbon structural moiety, preferably a structural moiety of the following formula: wherein R3 is a structural moiety containing 1-8 carbon atoms, preferably -CH2- or -C(CH3)2- and wherein R2 is a structural moiety containing 1-10 carbon atoms, preferably a hydrocarbon structural moiety, more preferably a linear alkyl structural moiety.

7. The die assembly according to any one of claims 1-6, wherein the channel (1) tapers at an angle α, wherein α ≥ 1.0° and ≤ 60.0°, preferably ≥ 5.0° and ≤ 10.0°, more preferably ≥ 6.0° and ≤ 9.0°.

8. A method for the solid-state extrusion of polyolefin materials, wherein the extrusion is carried out by extruding the polyolefin material through the die assembly according to any one of claims 1-7 at a temperature of ≤ 150 °C, preferably ≤ 140 °C, more preferably ≥ 90 °C and ≤ 130 °C, and at an applied pressure of ≤ 500 MPa, preferably ≤ 400 MPa, more preferably ≤ 300 MPa, still more preferably ≤ 150 MPa, yet still more preferably ≥ 50 and ≤ 150 MPa.

9. The method according to claim 8, wherein the polyolefin material is provided to the extrusion assembly as a powder having a bulk density of ≥ 200 and ≤ 600 kg / m 3 , and wherein the bulk density is determined via ASTM D1895-96.

10. The method according to any one of claims 8 - 9, wherein the polyolefin material is a polyethylene or polypropylene homopolymer or copolymer.

11. The method according to any one of claims 8 - 10, wherein the polyolefin material is an ultra - high molecular weight polyethylene (UHMWPE) material, preferably untangled UHMWPE.

12. The method according to any one of claims 8 - 11, wherein the polyolefin material has an intrinsic viscosity of ≥8.0, preferably ≥10.0, more preferably ≥20.0 dl / g, still more preferably ≥20.0 and ≤50.0 dl / g as determined according to ASTM D4020 (2011) for dilute solution determination of polyolefins in decalin at a temperature of 135°C.

13. The method according to any one of claims 8 - 12, wherein the polyolefin material has a melting temperature T of ≥ 135 °C, preferably ≥ 140 °C, as determined in the first run by DSC measurement m .

14. The method according to any one of claims 8 - 13, wherein the polyolefin material has a crystallinity X of ≥ 70%, preferably ≥ 75%, determined in the first run by DSC measurement c .

15. An extruded article obtained by the method according to any one of claims 8 - 14, preferably wherein the article is a belt, fiber, rod, sheet, tube or pipe.

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