Polyketone compound, process for its production and use, and molded bodies produced therefrom

Abstract

Aliphatic polyketone compound comprising 85.0 to 98.0 wt.% aliphatic polyketone and 2.0 to 15.0 wt.% ultra-high molecular weight polyethylene, characterized in that the D50 value of the polyethylene is below 75 µm.

Description

[0001] The invention relates to a polyketone compound based on aliphatic polyketones, in particular a polyketone compound with improved tribological properties. The invention further relates to a process for producing the polyketone compound, its use for manufacturing molded parts, in particular seals, and molded parts containing the polyketone compound. State of the art

[0002] Aliphatic polyketones are linear polymers produced from carbon monoxide and α-olefins, with the arrangement of the monomeric units in the polymer chain being strictly alternating.

[0003] This class of polymers was first mentioned in the work of Walter Reppe in 1940 and in the work of Merlin M. Brubaker, who in the 1950s at DuPont was involved in the interpolymerization of carbon monoxide into unsaturated substances such as aliphatic monoolefins and fluorinated ethylenes (e.g., US 2,495,286). The large-scale synthesis of aliphatic polyketones was developed, optimized, and patented by employees of the Shell Oil Company under the direction of Eit Drent in the last three decades of the 20th century (e.g., US 3,689,460; US 4,818,810; US 4,921,937). The polymerization can take place either in methanolic suspension or via gas-phase reaction with immobilized catalysts (see, among others, Drent, E.; Mul, WP; Smaardijk, AA (2001); “Polyketones”; Encyclopedia of Polymer Science and Technology and Bianchini, C.(2002); “Alternating copolymerization of carbon monoxide and olefins by single-site metal catalysts”; Coord. Chem. Rev. 225: 35–66). Palladium(II) complexes are mainly used as catalysts or their precursors (e.g., US 3,689,460; US 3,694,412; US 4,818,810; Sen, A.; Lai, TW (1982); “Novel palladium(II)-catalyzed copolymerization of carbon monoxide with olefins”; J. Am. Chem. Soc. 104 (12): 3520–3522; Drent, E.; Budzelaar, PHM (1996); “Palladium-Catalyzed Alternating Copolymerization of Alkenes and Carbon Monoxide”; Chem. Rev. 96 (2): 663–682). The mechanism for palladium catalysis in methanolic suspension was investigated by Maurice Brookhart (Rix, FC; Brookhart, M.; White, PS (1996) “Mechanistic Studies of the Palladium(II)-Catalyzed Copolymerisation of Ethylene with Carbon Monoxide”; J. Am. Chem. Soc. 118 (20): 4746-4764) using a palladium(II)phenanthroline catalyst as an example.

[0004] From 1996 onwards, aliphatic polyketones were first commercially available in larger quantities from Shell under the trade name Carilon. ® Available. In 2003, the South Korean company Hyosung began research on aliphatic polyketones (including US 7,803,897). Since 2015, Hyosung has been producing aliphatic polyketones under the trade name POKETON. ® on a semi-continuous plant with an annual capacity of 50,000 tonnes.

[0005] Hyosung now produces almost exclusively polyketone terpolymers instead of the classic polyketone copolymers ( Fig. ), which are produced only from carbon monoxide and ethylene. These polyketone terpolymers are produced from carbon monoxide, ethylene, and preferably small amounts of propylene.

[0006] In some cases, longer-chain α-olefins such as 1-butylene are also used as termonomers.

[0007] The reason for using terpolymers instead of copolymers lies in the significantly reduced brittleness of terpolymers. Due to their strictly alternating polymer chain structure with an extremely low defect rate (one defect per million monomer units; see Rix, FC; Brookhart, M.; White, PS (1996) “Mechanistic Studies of the Palladium(II)-Catalyzed Copolymerisation of Ethylene with Carbon Monoxide”; J. Am. Chem. Soc. 118 (20): 4746-4764) and the high number of polar keto groups, polyketone copolymers consisting of carbon monoxide and ethylene are highly crystalline, very hard, but also very brittle, which significantly limits their applications as polymeric materials.By adding small amounts of propylene (about 5%) during the synthesis, it was possible to disrupt the crystallinity in such a way that the melting point is reduced from 255 °C (copolymer of carbon monoxide and ethylene) to 220 °C (terpolymer), resulting in an extremely tough polymer instead of a brittle one.

[0008] Aliphatic polyketone terpolymers have a degree of crystallinity of approximately 30% and are characterized by good mechanical properties, which, unlike those of polyamides, for example, are largely unaffected by moisture. The tensile modulus of elasticity of unmodified polyketones, according to ISO 527-1 / 2, is approximately 1400 to 1500 MPa. Their elongation at yield, according to ISO 527-1 / 2, is approximately 25%, and compared to other engineering plastics, they can withstand a greater number of deformation cycles up to the yield strength without plastic deformation. Furthermore, they exhibit ductile behavior over a wide temperature range, with elongations at break exceeding 300%. The Charpy impact strength of an unfilled, unmodified polyketone terpolymer, according to ISO 179-1 / 1eU, is so high that no fracture occurs at either 23 °C or -30 °C.The Charpy impact strength according to the standard ISO 179-1 / 1eA is between 10 and 15 kJ / m, depending on the polymer chain length. 2 at a temperature of 23 °C and between 3.5 and 4.5 kJ / m² 2 at a temperature of -30 °C.

[0009] Furthermore, aliphatic polyketones exhibit excellent chemical resistance, particularly to nonpolar solvents such as aliphatic or aromatic hydrocarbons. They also demonstrate very good resistance to water and dilute bases and acids. For example, storage tests in water at 80 °C for 25 days resulted in a weight increase of only 2.5 wt.% and an increase in tensile strength of 1.3 MPa. Storage in 1% hydrochloric acid or 1% sodium hydroxide solution at 80 °C for 25 days also showed no deterioration in mechanical properties. Only strong acids or bases can lead to the degradation of aliphatic polyketones over time.

[0010] Hyosung's aliphatic polyketones are further refined by various compounders and are sold under various trade names, such as AKROTEK. ®PK (AKRO-PLASTIC GmbH), school ketone ® (A. Schulman GmbH), WITCOM PK (Witcom Engineering Plastics BV) or SUSTAKON ® (Röchling Sustaplast SE & Co. KG) commercially available. Compounding with specific additives allows for further improvement or modification of selected properties of aliphatic polyketones. Examples include polymer stiffening with short-cut glass fibers (e.g., in the commercial products AKROTEK). ® PK-VM GF15, AKROTEK ® PK-VM GF30, AKROTEK ® PK-VM GF50, school acetone ® GF15, school aceton ® GF30, Ketoprix™ EKT33G2P, Ketoprix™ EKT33G2P, etc.) or short-cut carbon fiber (e.g., in the commercial products AKROTEK) ® PK-HM CF12 black, TECACOMP ® PK TRM CF20 black, etc.) as well as flame-retardant equipment (e.g. in the commercial products AKROTEK ® PK-VM GF20 FR black, school acetone ®HV 4DE, etc.) are called.

[0011] The tribological properties of aliphatic polyketones are also good, which makes them interesting for sealing applications, among other things. For example, tests conducted by the Lübeck University of Applied Sciences on a universal tribometer (pin-plate, plate: 100Cr6, load: 2.5 MPa, stroke: 1.8 mm, R) showed that a = 0.42, sliding motion: 46 Hz) for example, it has been shown that aliphatic polyketones with an MVR of 60 g / 10 min have a coefficient of friction of 0.33 and a specific wear rate of 0.8 *10 6 mm 3 / Nm. However, to meet the high demands on tribological properties, such as those required for certain seals, tribological additives are often necessary. These additives then form a separating film between the polymer and mating surfaces, capable of withstanding significant forces during rolling or sliding contact over extended periods. Commercial products almost exclusively use PTFE powder or PTFE powder / silicone oil combinations for this purpose: e.g., in Akrotek. ® PK-VM TM, AKROTEK ® PK-HM TM, TECACOMP ® PK TRM TF10, Witcom PK / 3L1 and Witcom PK-3L3.

[0012] Another major advantage of aliphatic polyketones (both copolymers and terpolymers) is that they can be processed thermoplastically.

[0013] Against this background, it would be desirable to use aliphatic polyketones for seals, as they possess a certain degree of elasticity despite their hardness and exhibit high extrusion resistance as well as good tribological properties. They would be particularly interesting for rotationally symmetrical elements such as rod seals, piston seals, and wipers, and especially as a potential replacement for rod and piston seals made of PTFE, PTFE bronze, and PTFE glass fibers, since the latter, as explained in more detail below, cannot be produced using injection molding. A material change from PTFE, PTFE bronze, or PTFE glass fibers to an injection-moldable aliphatic polyketone would offer a significant advantage in terms of manufacturing process, time, and cost. Rod seals are primarily used in pneumatic and hydraulic cylinders and serve to seal the extending and retracting cylinder rod.The aim is to prevent the pressurized operating medium from escaping the cylinder. At the same time, it must be protected from external contamination (scraper). Piston seals, on the other hand, have the task of sealing the piston against the cylinder bore and ensuring its efficient movement with minimal friction.

[0014] Currently, both rod and piston seals are frequently manufactured from PTFE, PTFE-bronze compounds, or PTFE-glass fiber compounds, as these materials generate low friction and enable stick-slip-free operation. However, due to their relatively high modulus of elasticity, PTFE seals can no longer be radially compressed as a single unit between the rod or piston surface and the groove base. Instead, their compression must first be achieved by expanding the seal and then further reinforced by an elastomer seal, usually an O-ring. The O-ring, often referred to as a clamping ring, compression element, or energizer, also acts as a secondary seal. Since a PTFE sealing ring has high extrusion resistance, it can also be used under high pressure without a backup ring.

[0015] Although thermoplastics, PTFE and modified PTFE, due to their extremely high molecular weight and high melt viscosity, cannot be processed from the melt like other thermoplastics, but only using various pressing and sintering techniques. Seals made of PTFE or PTFE compounds are therefore manufactured using the following complex process. The powdered polymer is pressed at room temperature into a preform, also called a "green body." In this process, the loose powder bed is compacted and compressed with a specific pressing pressure. The maximum pressing pressure depends on the properties of the powder and can range from 150 bar for, for example, non-free-flowing S-PTFE types to 800 bar for PTFE compounds. The pressing process is usually carried out slowly, uniformly, and without interruption.Once maximum pressure is reached, it must be maintained for a specific period (pressure holding time) to allow particle flow and to relieve internal stress peaks or irregularities. After a slow release of pressure, the press link is ideally stored stress-free for a specific period to allow further venting and stress equalization. After pressing, the compacts are subjected to a defined sintering cycle. This involves a defined heating process, adapted to the compact, followed by time-controlled sintering at a maximum temperature of 370 to 380 °C in a controlled sintering furnace. After exceeding the crystallization melting point of approximately 342 °C, the PTFE transitions into an amorphous state, and the previously compacted powder particles sinter together to form a homogeneous structure.Especially with larger pressed parts, a slow approach through the melting temperature range is recommended, as the material expands disproportionately and potentially generates significant stresses. Despite reaching or exceeding the melting / gel point, the sintering of the pressed parts occurs "without a mold" because PTFE's high molecular weight results in very high gel stability.

[0016] From the preceding description of the production of seals made from PTFE or PTFE compounds such as PTFE bronze, it is evident that the manufacturing effort is very high and associated with high costs.

[0017] It would therefore be of great advantage if aliphatic polyketones could be used for rotationally symmetrical seals, especially for rod and piston seals, since these have excellent mechanical properties and – unlike the commonly used PTFE or PTFE compounds – can be processed using injection molding.

[0018] Practical tests have shown, however, that this is not so easily achieved. A key criterion for rotationally symmetrical seals is their weld line strength, as explained below. While rod and piston seals made from aliphatic polyketone / PTFE compounds exhibit comparable tribological properties and leakage rates to rod and piston seals made from PTFE, PTFE bronze, or PTFE glass fiber, their poor weld line strength makes them unsuitable for use as rod or piston seals or similar rotationally symmetrical seals.

[0019] Rotationally symmetrical seals are typically manufactured using plastic injection molding when employing thermoplastic materials. Several methods exist for filling such rotationally symmetrical cavities, e.g., A) ring gates or umbrella gates, B) point or tunnel gates, or C) hot runner systems.

[0020] Umbrella gates or ring gates (A) have the disadvantage that the gate geometries must be separated from the actual ring-shaped product by downstream processing steps, which incurs corresponding costs. Therefore, these gate variants are usually only used in exceptional cases for efficient production.

[0021] A more modern and cost-effective manufacturing method is the point or tunnel gate (B) (gate = sprue). Here, the plastic is injected into the cavity via a single injection point. Products manufactured in this way generally require no post-processing, as the product is separated from the gate geometry upon ejection from the injection molding machine (finished). The sprue essentially shears itself off.

[0022] However, such side-injected products usually have a so-called weld line on the opposite side of the injection point, i.e., a point where the melt fronts merge. This weld line can represent a weak point and lead to a point of failure in the plastic product. How well the product holds together at the weld line is determined by factors such as injection pressure, melt and mold temperature, but also by the material selection and the influence of additives.

[0023] Practical tests have found that commercially available PTFE-filled polyketone compounds, such as AKROTEK, ® PK-VM TM, TECACOMP ®The use of PKTRM TF10, Witcom PK / 3L1, and Witcom PK-3L3 in injection-molded gaskets leads to a significantly reduced weld line strength, causing the components to break at the weld line even under minimal force and thus making them less suitable for spot or tunnel gating. Furthermore, application tests showed that rod gaskets made from PTFE-filled polyketone compounds such as Akrotek ® PK-VM TM seals, which were injection molded, break at the weld seam when installed in the cylinder, because the stiff seals have to be strongly deformed using assembly pliers.

[0024] In rod seals made from commercial Tribo-PK compounds, this deformation leads to fractures at the weld seam. Description of the invention

[0025] The invention is therefore based on the objective of providing a polyketone compound that can be processed by injection molding and is characterized by high weld line strength. Furthermore, the polyketone compound should exhibit the good tribological properties and high extrusion resistance necessary for sealing applications.

[0026] This problem is solved by an aliphatic polyketone compound comprising 85.0 to 99.5 wt.% aliphatic polyketone and 0.5 to 15.0 wt.% ultra-high molecular weight polyethylene.

[0027] According to the invention, it has been found that by mixing 0.5 to 15 wt.% ultra-high molecular weight polyethylene into aliphatic polyketones, their tribological properties in terms of friction and wear can be improved to such an extent that they are comparable to those of commercially available friction-modified polyketone compounds, but at the same time exhibit significantly better weld line strength and high extrusion resistance.

[0028] As explained above, the improved weld line strength of the polyketone compound according to the invention, compared to commercially available PTFE-friction-modified aliphatic polyketone compounds, is a significant advantage, as it makes it possible, for example, to produce seals using a modern and cost-effective variant of the injection molding process that uses only one injection point. The products obtained in this way are characterized by high extrusion resistance. This is particularly advantageous for dynamic sealing applications, since otherwise extrusion flash can form over the service life of the seals, potentially leading to leakage or premature seal failure.At the same time, the aliphatic polyketone compounds according to the invention possess sliding and friction properties that are approximately comparable to those of PTFE, PTFE / bronze compounds, or commercially available PTFE-friction-modified polyketone compounds. Surprisingly, it was found that 0.5 to 15 wt.%, more preferably 2.0 to 8.0 wt.%, and particularly 5.0 to 7.5 wt.% of ultra-high molecular weight polyethylene, each based on the total weight of the polyketone compound, is sufficient to match the sliding and friction properties of an aliphatic polyketone filled with 20 wt.% PTFE. Furthermore, it was surprising that the aliphatic polyketone compound according to the invention does not break under deformation stress, such as that which occurs, for example, when installing a rigid piston seal into a piston chamber using an assembly pliers, while identical seals made from a commercial material with a weight of 20 g / m² do break.In 75 to 90% of installation tests, the 20 wt.% PTFE-modified polyketone compound failed at the weld line. The improved weld line strength can presumably be explained by the 5 to 19.5 wt.%, preferably 12 to 18 wt.%, and particularly 12.5 to 15 wt.% lower proportion of tribiological additive. It is assumed that during injection molding of seals with only one injection point, the rather nonpolar tribiological additives migrate to the interface between the polar polyketone and the mold wall during the injection process. Therefore, a particularly high concentration of these additives is found in the weld line region where the two flow fronts meet. This leads to adhesion problems and thus to subsequent weld line failures in the commercially available 20 wt.% PTFE-modified polyketone compounds. The polyketone compounds according to the invention, which contain less than 15 wt.% ultra-high molecular weight polyethylene, do not exhibit this problem due to the lower additive content.

[0029] Therefore, in a preferred embodiment of the invention, the aliphatic polyketone according to the invention has a total proportion of tribological additives, i.e., ultra-high molecular weight polyethylene and any other tribological additives present, such as silicone oils, PTFE powder, graphite, molybdenum disulfide, boron nitride, of less than 20 wt.%, preferably less than 5 wt.%, and particularly less than 2.5 wt.%. Nevertheless, the aforementioned additives may be present, for example, in amounts from 0.1 wt.% to 19.5 wt.%.

[0030] According to the invention, ultra-high molecular weight polyethylene (UHMWPE), often abbreviated as UHMWPE, is defined as polyethylene with a molecular weight exceeding 1.0 million g / mol, preferably 3.0 to 7.0 million g / mol, and particularly 3.0 to 5.0 million g / mol, as measured by Ubbelohde viscometry (dilute solution in decahydronaphthalene at 140 °C). Ultra-high molecular weight polyethylene can be obtained from monomeric ethylene by metallocene-catalyzed synthesis, typically yielding polymeric chains consisting of 100,000 to 250,000 monomeric units. Therefore, according to the invention, ultra-high molecular weight polyethylene is preferred which has polymeric chains consisting of 100,000 to 250,000 monomeric units.

[0031] Preferably, the average particle size of the ultra-high molecular weight polyethylene is in the range of 10 µm to 300 µm, more preferably from 20 µm to 50 µm, and particularly at 38 µm. In a further preferred embodiment, the particles of the ultra-high molecular weight polyethylene are finer than 75 µm. Thus, the D50 value of the polyethylene is preferably below 75 µm and / or the D95 value is preferably below 75 µm. The specific density of the ultra-high molecular weight polyethylene is preferably 0.93 to 0.94 g / cm³. 3 The bulk density is preferably 0.3 to 0.6 g / cm³. 3 and even more preferably 0.32 to 0.5 g / cm² 3 The molecular weight is preferably 3.0 to 7.0 million g / mol and even more preferably 3.0 to 5.0 million g / mol.

[0032] According to the invention, aliphatic polyketone and ultra-high molecular weight polyethylene are the main components of the aliphatic polyketone compound. The proportion of aliphatic polyketone in the polyketone compound is, according to the invention, 85.0 to 99.5 wt.%, preferably 90.0 to 99.5 wt.%, more preferably 92.0 to 98.0 wt.%, and particularly 92.5 to 95.0 wt.%, in each case based on the total weight of the polyketone compound. Furthermore, the proportion of ultra-high molecular weight polyethylene in the polyketone compound is, according to the invention, 0.5 to 15 wt.%, preferably 0.5 to 10 wt.%, more preferably 2.0 to 8.0 wt.%, and particularly 5.0 to 7.5 wt.%, in each case based on the total weight of the polyketone compound.

[0033] In a preferred embodiment of the invention, the aliphatic polyketone comprises a proportion of further tribological additives, for example silicone oils, of 0.1 wt.% to 2.0 wt.%, in particular of 0.5 wt.% to 1.5 wt.%.

[0034] In a preferred embodiment of the invention, the aliphatic polyketone has a melting point, measured according to the method DIN EN 11357-1, of 210 to 230 °C, and particularly of 220 to 222 °C. The glass transition temperature is in the range of 5 °C to 20 °C, preferably of 10 °C to 15 °C, and particularly of 11 °C to 13 °C. The density of the aliphatic polyketone, measured according to the method ISO 1183, is preferably in the range of 1.1 to 1.3 g / cm³. 3 and especially at 1.24 g / cm³ 3The moisture absorption of the aliphatic polyketone, measured according to method ISO 1110, is from 0.3 to 1.2% and particularly from 0.8 to 0.9% at 70 °C and 62% RH. Its MVR, measured according to method ISO 1133, is preferably in the range of 2 to 80 cm. 3 / 10 min and especially in the range of 6 to 60 cm 3 / 10 min at 240 °C and 2.16 kg test weight.

[0035] In a preferred embodiment of the invention, the aliphatic polyketone is a terpolymer, preferably produced from ethylene, carbon monoxide, and an alkene with 3 to 5 carbon atoms, preferably propylene and / or butylene, in particular propylene. The arrangement of carbon monoxide and olefin in the polymer chain is preferably strictly alternating.

[0036] In a preferred embodiment of the invention, the aliphatic polyketone has a molar mass mean value M n(Numerical molar mass) between 60000 and 100000 and / or M w (Mean molar mass) between 132,000 and 320,000. The polydispersity index is preferably between 2.2 and 3.2.

[0037] The polyketone compound according to the invention can contain silicone oil and other liquid or solid lubricants. Furthermore, it can contain other common polymer additives such as, among others, antioxidants, fillers, flame retardants, and pigments, as well as other polymeric materials, to improve or otherwise modify the properties of the composition. The content of liquid lubricants, such as silicone oils, is preferably 0.0 to 2.0 wt.%, and particularly preferably 0.0 to 1.5 wt.%, and especially 0.0 to 1.0 wt.%.

[0038] In a preferred embodiment of the invention, the aliphatic polyketone compound has a coefficient of friction µ, measured on a Lewis test rig at a speed of v = 0.84 m / s, a pressure of p = 0.84 MPa, and in the unlubricated state, of 0.1 to 0.4, more preferably of 0.1 to 0.3, and particularly of 0.1 to 0.25. Furthermore, in a preferred embodiment of the invention, the aliphatic polyketone compound has an average wear coefficient, measured on a Lewis test rig at a speed of v = 0.84 m / s, a pressure of p = 0.84 MPa, and in the unlubricated state, of 1 * 10 -7 up to 1 *10 -4 mm 3 / Nm and even more preferably 1 *10 -7 up to 1 *10 -5 mm 3 / Nm on.

[0039] Furthermore, the aliphatic polyketone compound according to the invention preferably has a tensile modulus of elasticity, measured according to DIN EN ISO 527-2 / 1A / 50, of 1600 MPa to 1850 MPa, a tensile strength, measured according to DIN EN ISO 527-2 / 1A / 50, of 55 MPa to 65 MPa and / or an elongation at break, measured according to DIN EN ISO 527-2 / 1A / 50, of 20% to 40%.

[0040] Furthermore, the aliphatic polyketone compound according to the invention exhibits, in a tribological test as described in Example 2, preferably a coefficient of friction of µ = 0.38 to 0.42 over the entire duration of the test, a coefficient of friction of µ = 0.38 to 0.40 over the “steady state”, and a wear coefficient of 10 * 10 -6 up to 20 *10 -6 over the entire duration of the test and / or a wear coefficient of 2 *10 -6 up to 5 *10 -6 about the “steady state”.

[0041] A further object of the present invention is a process for producing the aliphatic polyketone compound, comprising mixing 99.5 to 85.0 wt.% aliphatic polyketone with 0.5 to 15 wt.% ultra-high molecular weight polyethylene, more preferably 98.0 to 92.0 wt.% aliphatic polyketone with 2.0 to 8.0 wt.% ultra-high molecular weight polyethylene, and particularly 95.0 to 92.5 wt.% aliphatic polyketone with 5.0 to 7.5 wt.% ultra-high molecular weight polyethylene. The weights given refer to the total weight of the aliphatic polyketone compound.

[0042] The components of the aliphatic polyketone compound are preferably blended using extrusion technology. Co-rotating twin-screw extruders are preferably used, but counter-rotating twin-screw extruders, planetary roller extruders, and co-kneaders are also suitable. Single-screw extruders are more suitable for conveying than for compounding and are therefore less suitable for the production of the aliphatic polyketone compound according to the invention. In one embodiment, aliphatic polyketone is pre-dried at 70 °C to 90 °C for a period of four hours and then metered into a twin-screw extruder by means of a feeder, preferably a gravimetric feeder. The temperature of the feed zone is preferably in the range of 50 °C to 100 °C, while the temperature of the extruder zones is preferably 225 °C to 254 °C.The ultra-high molecular weight polyethylene is preferably fed to the polymer melt via a further feeder, preferably a gravimetric feeder. After exiting the extruder die, the strand is preferably placed on a conveyor belt and cooled with water and / or air before being granulated in a downstream granulator. It is advantageous to dry the produced granules to remove the moisture introduced during the cooling process.

[0043] According to the invention, aliphatic polyketone and ultra-high molecular weight polyethylene are mixed with each other and with any other components present in such a proportion that they form the main components of the aliphatic polyketone compound. Preferably, the polyketone is added to the compound in an amount of 99.5 to 90.0 wt.%, more preferably in an amount of 98.0 to 92.0 wt.%, and particularly in an amount of 95.0 to 92.5 wt.%. Furthermore, the ultra-high molecular weight polyethylene is preferably added to the compound in an amount of 0.5 to 10.0 wt.%, more preferably in an amount of 2.0 to 8.0 wt.%, and particularly in an amount of 5.0 to 7.5 wt.%. Amounts below 10 wt.% of ultra-high molecular weight polyethylene are advantageous because they make it particularly easy to prevent clogging of the extruder dies.

[0044] Ultra-high molecular weight polyethylene (UHMWPE) tends to agglomerate, accumulating in the extruder die area and clogging it. While the production of compounds with more than 10 wt% UHMWPE can still be carried out using the process described above, especially in small batches, the agglomeration of UHMWPE and the associated clogging of the extruder die make it advantageous to implement specific technical measures for continuous production.

[0045] The aliphatic polyketone compound according to the invention can be processed into various products by conventional shaping processes such as extrusion, compression molding and injection molding, which are particularly suitable for applications requiring good tribological properties.

[0046] Another object of the present invention is shaped bodies, preferably rotationally symmetrical shaped bodies, in particular seals such as rod and / or piston seals, structural parts (with and / or without sealing function), wiper elements, coupling elements, backing rings (anti-extrusion rings), wear strips and / or guides, which contain the polyketone compound according to the invention.

[0047] In a preferred embodiment, the molded body exhibits a weld line strength greater than 120 N in a bending test as described in Example 2. Furthermore, in a bending test at maximum crosshead travel (43.31 mm) as described in Example 2, the molded body preferably does not break at the weld line.

[0048] The aliphatic polyketone compound according to the invention is particularly suitable for molded parts produced by injection molding processes, in particular by injection molding processes that use only one injection point, for example point or tunnel gates.

[0049] Furthermore, the invention relates to the use of the aliphatic polyketone compound according to the invention for the production of molded bodies, preferably rotationally symmetrical molded bodies, in particular seals such as rod and / or piston seals, structural parts (with and / or without sealing function), wiper elements, coupling elements, gears, plain bearings, backing rings, in particular anti-extrusion rings, wear strips and / or guides.

[0050] The invention is explained in more detail below by means of examples. Example 1: Production of a polyketone compound according to the invention

[0051] The production of a tribologically modified polyketone compound according to the invention was carried out on a 27 mm twin-screw extruder from Leistritz, type ZSE 27 iMAXX (screw diameter: 28.3 mm, channel depth: 5.6 mm (without clearance)). a / D i = 1.66, maximum torque: 256 Nm, screw speed: 600-1200 rpm), equipped with a solid feeder from SCHOLZ Dosiertechnik GmbH type BASIC 401 for dosing the aliphatic polyketone, a solid feeder from SCHOLZ Dosiertechnik GmbH type BASIC 300 for dosing the ultra-high molecular weight polyethylene, a conveyor belt for strand depositing, a water cooling system for cooling the deposited polymer strand, and a downstream granulator from Maag Automatik GmbH type PRIMO 60E for comminuting the deposited strand.

[0052] AKROTEK was identified as an aliphatic polyketone. ® PK-VM natural (4774) from AKRO-PLASTIC GmbH is used. AKROTEK® PK-VM natural (4774) is an unreinforced polyketone type with high flowability. Its melting point, measured according to DIN EN 11357-1, is 220 °C, and its density, measured according to ISO 1183, is 1.24 g / cm³. 3 , their moisture absorption, measured according to the ISO 1110 method, is between 0.8 and 0.9% at 70 °C and 62% RH, and their MVR, measured according to the ISO 1133 method, is at 60 cm 3 / 10 min.

[0053] INHANCE UH-1700 ultra-high molecular weight polyethylene (UHMWPE) from Nordmann Rassmann was used. The average particle size of the UHMWPE particles is 38 µm, and all particles are finer than 75 µm. INHANCE UH-1700 is a UHMWPE grade with surface-treated particles to improve dispersibility and adhesion within the surrounding polymer. The material has a specific density of 0.93 to 0.94 g / cm³. 3 , a bulk density of 0.32 to 0.5 g / cm³3 and a molecular weight of 3.0 to 5.0 million g / mol.

[0054] The aliphatic polyketone was fed into the extruder's feed zone using a BASIC 401 solids feeder. The feed zone temperature was set to 50 °C. The extruder's twelve heating zones were set to temperatures ranging from 230 °C to 245 °C. The die temperature was 230 °C. The measured melt temperature of the polymer was 238 °C. The total material throughput was 19.97 kg / h. The throughput of Akrotek ® The PK-VM throughput was 18.97 kg / h, and the Inhance UH-1700 throughput was 1.0 kg / h. The finished compound was discharged onto the conveyor belt via a single-hole nozzle, cooled with water spray, and fed into the granulator. Since the granules still contained a significant amount of residual moisture after water cooling, they were dried at 80 °C for 30 to 45 minutes.

[0055] Before the compound was sprayed into test specimens, the granules were dried again for four hours at 80 °C. Example 2: Mechanical and tribological tests of the polyketone compound from Example 1

[0056] Test specimens for mechanical and tribological testing were manufactured on an Arburg GmbH & Co. KG 320C 600-100 Allrounder injection molding machine. An AIM™ Quick Change Mold from Axxicon Moulds was used as the injection mold. S1A tensile bars for mechanical testing and Lewis test specimens for tribological testing were produced.

[0057] Mechanical tests revealed a tensile modulus of elasticity of 1725 ± 10 MPa, a tensile strength of 58.7 ± 0.2 MPa, measured according to DIN EN ISO 527-2 / 1A / 50, and an elongation at break of 28.2 ± 7.1 %, measured according to DIN EN ISO 527-2 / 1A / 50.

[0058] The tribological tests were performed on a Lewis Research Inc. LRI-1a test rig. A D2 steel / 52100 with chemical composition 100Cr6 served as the mating surface. The test was conducted in the unlubricated condition. The speed was v = 0.84 m / s and the contact pressure p was 0.84 MPa. Both parameters were chosen to maintain a continuous operating temperature between 54 °C and 58 °C. Under these test conditions, the compound exhibited a coefficient of friction of µ = 0.275 over the entire duration of the test, a coefficient of friction of µ = 0.269 over the steady state, and a wear coefficient of 6.556 * 10 -6 over the entire duration of the test and a wear coefficient of 1.862 *10 -6 about the “steady state”. In comparison to the compound according to the invention, the PTFE-modified AKROTEK ® PK-VM TM and the unmodified AKROTEK ®PK-VM measured. The unmodified AKROTEK ® Under analogous test conditions, PK-VM showed a coefficient of friction of µ = 0.412 over the entire duration of the test, a coefficient of friction of µ = 0.390 over the “steady state”, and a wear coefficient of 15.641 *10 -6 over the entire duration of the test and a wear coefficient of 3.814 *10 -6 about the "steady state". The tribologically modified AKROTEK ® Under analogous test conditions, PK-VM TM showed a coefficient of friction of µ = 0.221 over the entire duration of the test, a coefficient of friction of µ = 0.214 over the “steady state”, and a wear coefficient of 2.087 *10 -6 over the entire duration of the test and a wear coefficient of 1.670 *10 -6 about the "steady state". It turns out that the PTFE-modified benchmark AKROTEK ®PK-VM TM - although it contains significantly more tribological additives (approximately 20 wt.% PTFE) than the compound according to the invention (5 wt.% tribological additive), performs only minimally better.

[0059] To assess the weld seam strength, five rod seals were produced from the compound manufactured in Example 1 according to the procedure described in Fig.The geometry shown in Example 1 (1: rod diameter of 50 mm) was produced using injection molding with only one injection point and subsequently subjected to a bending test. The seals were positioned in the test apparatus such that the weld line and the opposite injection point were horizontally aligned, and the pressure plate (diameter of the punch: 25 mm) pressed onto the seal at a 90° angle to the weld line and injection point. A single support point was used. The pressure plate was pre-loaded with a force of 5 N and then moved at 5 mm / minute. The maximum crosshead travel was 43.3 cm. The tribologically modified polyketone compound produced in Example 1 showed no weld line fracture in this test setup. For all five tested rod seals, the pressure plate was moved to the maximum crosshead travel without any seals breaking (see Table 1). Table 1: Results of the bending tests on rod seals made from the polyketone compound according to the invention as described in Example 1. Nr.: F1mm: F2mm: F3mm: F4mm: Fmax: Maximum distance: Remark: 1 12,31 N 19,12 N 25,25 N 30,65 N 124,8 N 42.97 mm Ring not broken 2 12,35 N 19,31 N 25,57 N 31,06 N 113,2 N 43.31 mm Ring not broken 3 12,45 N 19,37 N 25,59 N 31,03 N 121,7 N 43.30 mm Ring not broken 4 12,39 N 19,32 N 25,55 N 31,00 N 114,9 N 32.29 mm Ring not broken 5 12,29 N 19,20 N 25,41 N 30,87 N 113,3 N 43.29 mm Ring not broken

[0060] In comparison to the polyketone compound according to the invention, rod seals made from a commercially available, friction-modified polyketone compound containing approximately 20 wt.% PTFE were tested under analogous test conditions. Of the four rod seals tested, three broke after a crosshead travel of 32.3 to 35.4 mm and a compressive force of 96.7 to 105.4 N (see Table 2). Table 2: Results of the bending tests on rod seals made from a commercially available polyketone compound modified with approximately 20 wt.% AKROTEK® PK-VM TM. Nr.: F1mm: F2mm: F3mm: F4mm: Fmax: Maximum distance: Remark: 1 12,47 N 19,20 N 25,20 N 30,36 N 96,7 N 32.34 mm Ring broken 2 12,30 N 19,04 N 25,03 N 30,25 N 112,8 N 43.16 mm Ring not broken 3 12,42 N 19,21 N 25,22 N 30,45 N 105,4 N 35.36 mm Ring broken 4 9,60 N 16,74 N 23,13 N 28,71 N 103,3 N 34.20 mm Ring broken

[0061] Furthermore, the rod seals made from the compound according to the invention were repeatedly tested on a hydraulic test bench under near-application conditions against the current benchmark, a rod seal made from a PTFE / bronze compound. A diagram of the test bench is shown in Fig. 2 shown. The test rig has the following components: extrusion gap ( 1 ), test seal ( 2 ), Leadership ( 3 ), pressure chamber ( 4 ). The rod movement ( 5 ) runs horizontally. The test bench settings were as follows: Stroke 400 mm Speed ​​0.3 m / s Pressure 400 bar (40 MPa) Temperature 100 °C Test duration: 50,000 double strokes Shell Tellus 46 oil

[0062] Leakage and extrusion stability were evaluated under continuous use. The results showed that the PTFE / bronze compound is damaged after approximately 40,000 cycles due to gap extrusion, and consequently, the leakage more than quadruples from 20 drops to 90 drops by the end of the service life after 50,000 cycles. The seals made from the polyketone compound according to the invention, produced as described in Example 1, remain extrusion-stable over the entire service life of 50,000 cycles (leakage of approximately 20 drops by the end). QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] US 2495286

[0003] US 3689460

[0003] US 4818810

[0003] US 4921937

[0003] US 3694412

[0003] US 7803897

[0004] Zitierte Nicht-Patentliteratur

[0000] Drent, E.; Mul, W. P.; Smaardijk, A. A. (2001)

[0003] Sen, A.; Lai, T. W. (1982); „Novel palladium(II)-catalyzed copolymerization of carbon monoxide with olefins“; J. Am. Chem. Soc. 104 (12): 3520-3522

[0003] Drent, E.; Budzelaar, P. H. M. (1996); „Palladium-Catalyzed Alternating Copolymerization of Alkenes and Carbon Monoxide“; Chem. Rev. 96 (2): 663-682)

[0003] Rix, F. C.; Brookhart, M.; White, P. S. (1996) „Mechanistic Studies of the Palladium(II)-Catalyzed Copolymerisation of Ethylene with Carbon Monoxide“

[0003] Rix, F. C.; Brookhart, M.; White, P. S. (1996)

[0007] ISO 527-1 / 2

[0008] DIN EN 11357-1

[0034] ISO 1133

[0034] DIN EN ISO 527-2 / 1A / 50 [0039, 0057]

Claims

[1] Aliphatic polyketone compound comprising 85.0 to 99.5 wt.% aliphatic polyketone and 0.5 to 15.0 wt.% ultra-high molecular weight polyethylene. [2] Aliphatic polyketone compound according to claim 1, characterized by , that the proportion of ultra-high molecular weight polyethylene is 2.0 to 8.0 wt.% and in particular 5.0 to 7.5 wt.%. [3] Aliphatic polyketone compound according to claim 1 or 2, characterized by that the ultra-high molecular weight polyethylene has a molecular weight of over 1.0 million g / mol, preferably of 3.0 to 7.0 million g / mol. [4] Aliphatic polyketone compound according to one or more of the preceding claims, characterized by , that the ultra-high molecular weight polyethylene has an average particle size in the range of 10 µm to 300 µm. [5] Aliphatic polyketone compound according to one or more of the preceding claims, characterized by, that the aliphatic polyketone has a melting point, measured according to the method DIN EN 11357-1, of 210 to 230 °C and / or a glass transition point in the range of 5 °C to 20 °C and / or a density in the range of 1.1 to 1.3 g / cm³ 3 and especially at 1.24 g / cm³ 3 and / or a moisture absorption of 0.3 to 1.2% and / or an MVR in the range of 2 to 80 cm 3 / 10 min. [6] Aliphatic polyketone compound according to one or more of the preceding claims, characterized by that the aliphatic polyketone is a terpolymer. [7] Aliphatic polyketone compound according to one or more of the preceding claims, characterized by , that the aliphatic polyketone is produced from ethylene, carbon monoxide and an alkene with 3 to 5 carbon atoms, preferably propylene. [8] Aliphatic polyketone compound according to one or more of the preceding claims, characterized by, that during its production the arrangement of carbon monoxide and olefin in the polymer chain is strictly alternating. [9] Aliphatic polyketone compound according to one or more of the preceding claims, characterized by that the aliphatic polyketone has a molar mass mean value M n (Numerical molar mass) between 60000 and 100000 and / or M w (average molar mass) between 132000 and 320000, wherein the polydispersity index is preferably between 2.2 and 3.

2. [10] Method for producing an aliphatic polyketone compound comprising mixing 99.5 to 85.0 wt.% aliphatic polyketone with 0.5 to 15 wt.% ultra-high molecular weight polyethylene. [11] Molded parts, in particular seals, wiper elements, coupling elements, backing rings (anti-extrusion rings), wear strips, guides and structural parts, characterized bythat the molded bodies contain an aliphatic polyketone compound according to one or more of the preceding claims. [12] Molded body according to claim 11, characterized by that the shaped body is a rotationally symmetric shaped body. [13] Molded body according to claim 11 or 12, characterized by that the molded part was manufactured using injection molding processes, in particular injection molding processes that use only one injection point. [14] Use of an aliphatic polyketone compound according to one or more of claims 1 to 9 for the production of molded parts, preferably rotationally symmetrical molded parts, in particular seals such as rod and / or piston seals, structural parts (with and / or without sealing function), wiper elements, coupling elements, gears, plain bearings, backing rings, in particular anti-extrusion rings, wear strips and / or guides. [15] Use according to claim 14, characterized bythat a molded body is manufactured using injection molding processes, in particular using injection molding processes that only use one injection point.

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