COMPOSITE MATERIAL FOR LOW-WEAR MECHANICAL COMPONENTS FOR POWER AND MOTION TRANSMISSION

Description

SUBJECT OF THE INVENTION

[0001] The invention relates to a composite material for mechanical components for force and motion transmission. The invention further relates to a mechanical component for force and motion transmission comprising the composite material according to the invention. The invention further relates to a gear pump comprising at least one gear comprising the composite material according to the invention. The invention also relates to the use of the composite material according to the invention for fluid-supported mechanical components in medical pump applications. BACKGROUND OF THE INVENTION

[0002] The present invention relates to the field of composite materials. Composite materials are used for mechanical components for transmitting force and motion. In particular, composite materials made of plastics and reinforcing materials are used to impart greater strength, greater wear resistance, lower weight, and other improved properties to the mechanical components produced therefrom. Force- and motion-transmitting mechanical components are used, for example, in gear pumps, particularly in the form of gears.

[0003] Gear pumps are used in medical technology, particularly in dialysis machines, to pump therapeutic fluids. These pumps are used to pump fluids used in dialysis therapy or to degas fluids used in dialysis.

[0004] A dialysis machine has a hydraulic circuit that essentially ensures the production, pumping, and supply of dialysis fluid. In certain applications, the dialysis fluid is produced in the dialysis machine from provided dialysis concentrates and ultrapure water. The ultrapure water is mixed with the dialysis concentrates in a mixing chamber and converted into ready-to-use dialysis fluid. To produce the dialysis fluid, it is necessary, among other things, to degas and pump the ultrapure water. This process is usually carried out using specially designed gear pumps. In addition, the dialysis machine also has pumping devices that pump the dialysis fluid to the dialysis filter and make it available for extracorporeal blood purification.In extracorporeal blood purification, the blood drawn from the patient is pumped via a tubing to the dialysis filter using blood pumps. There, the blood is brought into contact with the dialysis fluid, which is also pumped to the dialysis filter, via a semipermeable membrane, thus cleansing the blood. After completion of such a dialysis treatment, it is necessary for hygiene reasons to disinfect the hydraulic circuit of the dialysis machine. This involves flushing the hydraulic circuit with ultrapure water and disinfectant at elevated temperatures of approximately 85°C. Oxidizing agents are used primarily as disinfectants to decontaminate the hydraulic circuit.

[0005] The gear pumps used in the hydraulic circuit of a dialysis machine are therefore designed to pump dialysis fluids, ultrapure water, oxidizing disinfectants, and liquid-air mixtures, or even just air for degassing. The greatest pumping activity of these gear pumps is used for pumping dialysis fluids. Furthermore, such gear pumps are also designed to perform pumping processes that take place at elevated temperatures, e.g., during hot disinfection of the dialysis machine, e.g., at 85°C or higher, e.g., at up to 90°C or 95°C.

[0006] The gear pumps known and used in the production of dialysis fluids are designed in such a way that the gears float in the fluid being pumped during pumping operation. The gears are mounted, for example, in a stainless steel housing and can be driven via a rotating magnetic coupling. Gear pumps in dialysis machines typically use gears made of a composite material consisting of a polymeric carrier material and a reinforcement material. Gears for gear pumps are known to be made of a composite material consisting of polyetheretherketone (PEEK) and carbon fiber. Reinforcing PEEK with carbon fiber results in greater strength and lower thermal expansion of the composite material compared to pure PEEK.Reinforcing the support material with the reinforcement material is particularly necessary for pumps with floating gears, as the gears themselves bear the entire bearing load and are therefore subject to high mechanical stress. Therefore, the composite material requires high mechanical strength to be able to permanently build up the desired pressure in the fluid to be pumped.

[0007] For reasons of hygiene, ultrapure water with the highest possible degree of purity is used to produce dialysis fluid. Ultrapure water with an electrical conductivity of 10 -4 < S / m and less is preferably used for the production of dialysis fluid. A low electrical conductivity is regarded as a measure of high purity of the ultrapure water. However, the high purity of the ultrapure water has a disadvantageous effect on gear pumps which use the known composite materials. It has been shown that composite materials which contain reinforcing materials with a high electrical conductivity, such as carbon fibres, are subject to high levels of wear when in contact with ultrapure water due to the low electrical conductivity of the ultrapure water. The durability of the gears made from these composite materials is therefore significantly reduced during operation.In particular, contamination of the fluids by abraded particles is to be expected, which can lead to serious problems during dialysis therapy or during the hot cleaning process.

[0008] Reinforcing materials with low electrical conductivity based on inorganic materials are known. However, these inorganic materials exhibit comparatively high thermal expansion. High thermal expansion also leads to increased wear in mechanical components used for power and motion transmission. Corresponding composite materials consisting of a polymeric carrier material and an inorganic reinforcing material are therefore also unsuitable for applications at elevated temperatures. In particular, gears in gear pumps of dialysis machines made of such a composite material would not survive hot cleaning operations without significant material wear.

[0009] WO 2015 / 019047 A1 discloses components consisting of a first part and a second part, wherein the first part comprises a first semi-crystalline polymer having phenylene, carbonyl, and ether units. The second part comprises a second semi-crystalline polymer which also comprises phenylene, carbonyl, and ether units. The second polymer has a melting temperature which is lower than the melting temperature of the first polymer. In one embodiment, the first polymer and the second polymer can be part of a first and second composition which comprise a filler, e.g. either glass fiber or carbon fiber. In a further embodiment, WO 2015 / 019047 A1 describes a gear which consists of two parts, wherein the second part defines a carrier and the first part comprises the teeth of the gear. The second part is reinforced by a fibrous material, e.g. in the form of a fabric.

[0010] US 4,837,251 describes a composition for a compression-molded core of a composite structure. The composition contains a thermoplastic resin selected from the group consisting of polyetheretherketones, polyetherketones, polyaryl sulfides, polyarylketones, polyarylsulfones, or polyarylethersulfones. In one embodiment, the composition comprises carbon fibers, glass fibers, and glass microspheres.

[0011] WO 02 / 10320 discloses plastic compositions for the production of plastic bearings. In one embodiment, the plastic composition consists of a polymeric matrix material selected from the group comprising polyamideimide, polyetherimide, polyimide, polyetheretherketone, polyphenylene sulfide, a liquid crystal polymer, or mixtures thereof. Furthermore, the plastic composition according to this embodiment contains carbon fibers and an additive selected from the group comprising boron nitride, carbon, graphite, molybdenum sulfide, talc, tetrafluoroethylene, and combinations thereof.

[0012] The composite materials disclosed in the prior art do not provide a satisfactory solution to the stated problems. In particular, the prior art does not disclose composite materials that exhibit low thermal expansion and favorable wear properties, making them suitable for mechanical components for power and motion transmission. OBJECT OF THE INVENTION

[0013] In a first aspect of the invention, the object was therefore to provide a composite material for mechanical components of force and motion transmission, which overcomes the aforementioned disadvantages of high wear in contact with ultrapure water and the high wear caused by thermal expansion.

[0014] In a further aspect of the invention, the object was to provide a mechanical component for the transmission of force and movement, in particular a gear, in which the wear properties are improved in contact with ultrapure water and in applications at elevated temperatures.

[0015] In a further aspect of the invention, the object was to provide a gear pump which has improved wear properties in pumping applications with ultrapure water and at elevated temperatures and thus has a longer service life and a lower susceptibility to failure. SUMMARY OF THE INVENTION

[0016] In a first aspect of the invention, the object is achieved by a composite material for mechanical components of force and motion transmission according to claim 1. Claims 2 to 12 represent preferred embodiments.

[0017] In a second aspect of the invention, the object is achieved by a mechanical component for force and movement transmission according to claim 13.

[0018] In a third aspect of the invention, the object is achieved by a gear pump according to claim 14.

[0019] In a fourth aspect of the invention, the object is achieved by the use of a composite material for fluid-supported mechanical components in medical pump applications according to claim 15. The invention is accordingly set out in the appended claims 1 to 15. CN 102 558 760 B discloses a composite material consisting of 10-30 wt.% polyetheretherketone, 10-15 wt.% PTFE, 4-14 wt.% polyethersulfone, 8-30 wt.% polyphenyl sulfide, 5-10 wt.% carbon fibers, and 15-18 wt.% glass fibers. JP 2006 226464 A discloses a composite material comprising (A) polyetheretherketone, (B) glass fibers or carbon fibers, and (C) polytetrafluoroethylene. US 7 575 800 B2 discloses a composite material comprising a fibrous filler and a matrix component, which may be polyetheretherketone, wherein the fibrous filler consists of carbon fiber. DETAILED DESCRIPTION OF THE INVENTION

[0020] In a first aspect, the invention relates to a composite material for mechanical components for force and motion transmission containing or consisting of at least three components (i) at least 45% by weight based on the total weight of the composite material of a carrier material consisting of polyetheretherketone, (ii) 3 to 20% by weight based on the total weight of the composite material of a first fibrous reinforcing material, and (iii) 10 to 45% by weight based on the total weight of the composite material of a second reinforcing material, wherein the first fibrous reinforcing material has a thermal expansion coefficient that is lower than that of the second reinforcing material and wherein the second reinforcing material has an electrical conductivity that is lower than that of the first reinforcing material, and wherein the weight proportions of the components contained in the composite material add up to 100% and wherein the first fibrous reinforcing material contains carbon fiber or consists of carbon fiber and the second reinforcing material contains glass fiber or consists of glass fiber.

[0021] As can be seen from the above, the composite material of the present invention may contain, in addition to the three components mentioned, other components that can be freely selected depending on the application and requirements. In any case, the proportions of the components present add up to 100 wt.%.

[0022] In a further embodiment according to the first aspect, the composite material is characterized in that the first fibrous reinforcing material has a thermal expansion of -0.15x10 -6< / K to 2x10 -6< / K parallel to the fiber direction and the second reinforcing material has an electrical conductivity of 10 -4< S / m or less.

[0023] The composite material is distinguished from prior art composite materials, which only comprise a reinforcing material with high electrical conductivity and low thermal expansion, such as carbon fiber, by significantly reduced wear. In addition, the thermal expansion coefficient of the composite material is low, so that the composite material is also suitable for the production of mechanical components for transmitting force and movement at elevated temperatures. Furthermore, the composite material according to the invention is distinguished from prior art composite materials, which only comprise a reinforcing material with low electrical conductivity but high thermal expansion, such as fiberglass, by significantly reduced wear.Furthermore, it was found that the composite material also has a high resistance to oxidative influences.

[0024] The thermal expansion of reinforcement materials is determined using well-known methods of thermomechanical analysis (TMA) in the technically relevant temperature range of 10 to 110°C. In particular, the DIN 51045-1:2005-8 standard for determining the thermal expansion of solid bodies is well known. The thermal expansion and electrical conductivity of reinforcement materials are also documented in the specialist literature.

[0025] The term " Composite material" is understood in the context of the present application as a cohesive mass of different materials that differ in terms of their material properties. The materials differ in terms of mechanical properties, such as tensile strength, thermal properties, such as thermal expansion, melting temperature or glass transition temperature, or chemical properties. In particular, in the context of the present application, the term "composite material" is understood as a mass consisting of a carrier material and reinforcing materials. As " Carrier material" is understood to mean a material that represents a continuous phase in the composite material. According to the present invention, a polymer is used as the carrier material. For the purposes of the present invention, polymers that have a high melting temperature and / or a high glass transition temperature are preferred, so that they remain dimensionally stable even at elevated temperatures. In addition, these polymers are also characterized by temperature-dependent softening behavior, so that these polymers can be processed in the melt above their melting temperature.

[0026] As " Reinforcing material" in the context of the present application is understood to mean a material which has a higher tensile strength and / or wear resistance than the carrier material. In particular, the reinforcing material in combination with the carrier material imparts a higher tensile strength to the composite material. According to the present invention, at least two reinforcing materials are provided. Reinforcing materials can be fibrous or non-fibrous, e.g. particulate or platelet-shaped. Known fibrous reinforcing materials are, for example, glass fiber, carbon fiber, asbestos fiber, silica fiber, aluminum oxide fiber, zirconium oxide fiber, boron nitride fiber or silicon nitride fiber. Known non-fibrous reinforcing materials are, for example, mica, silica, talc, aluminum oxide, kaolin, calcium sulfate, calcium carbonate, titanium dioxide, ferrite, clay, glass powder, zinc oxide, iron oxide, quartz powder, magnesium carbonate, graphite, carbon powder, e.g. also in the form of nanotubes.According to the present invention, the first reinforcing material of the composite material contains carbon fiber and the second reinforcing material contains glass fiber or first and second reinforcing materials consist thereof.

[0027] The composite material according to the present application, which contains or consists of at least three components, is preferably produced in a compounding process. The polymeric carrier material is mixed with the first fibrous reinforcing material and the second reinforcing material at an elevated temperature, which is preferably above the melting temperature of the polymeric carrier material. The elevated temperature is below the decomposition temperature of the polymeric carrier material. For the purposes of the present application, the " Melting point" of the polymeric carrier material is understood to mean the melting temperature determined by methods of Dynamic Differential Thermal Analysis (DSC). In particular, the standard DIN EN ISO 11357-3:2013-04 is known for determining the melting temperature of plastics. Advantageously, the molten polymeric carrier material can slightly wet the reinforcing materials so that the first fibrous reinforcing material and the second reinforcing material are evenly distributed and enclosed in the polymeric carrier material.

[0028] The polymeric carrier material and the first fibrous reinforcing material and the second reinforcing material can be constantly fed to a point in the compounding process where they are mixed, heated, and formed into the composite material by extrusion. In one example, a mass of fibrous reinforcing material can be passed through a melt of the polymeric carrier material. The mass can comprise a continuous length of fibrous filler or, more preferably, a plurality of continuous filaments that have been consolidated to at least some extent. The continuous fibrous mass can comprise, for example, a braid, woven fabric, or nonwoven fabric. The filaments comprising the fibrous mass can be substantially uniformly or stochastically distributed within the mass and, optionally, additionally can be oriented without any preferred direction.

[0029] Alternatively, the composite material may be produced in a process in which a predetermined amount of the first polymeric support material and a predetermined amount of the first fibrous reinforcing material and the second reinforcing material are obtained by melt mixing.

[0030] Preferably, the selected manufacturing method disperses the first fibrous reinforcing material and the second reinforcing material isotropically in the carrier material. Alternatively, the distribution of the first reinforcing material and the second reinforcing material in the carrier material may not be location-dependent, and the fiber orientation may not have a preferred direction. The material properties of the composite material are thus independent of any possible orientation of the first fibrous reinforcing material and the second reinforcing material in the carrier material. The mechanical properties of the composite material and of the mechanical components made from the composite material for force and motion transmission are therefore the same in all orientations, which represents an advantage.

[0031] The first fibrous reinforcing material preferably has a coefficient of thermal expansion of -0.15x10 -6< / K to 2x10 -6< / K parallel to the fiber direction. The value of the coefficient of thermal expansion of the first fibrous reinforcing material is very low or negative compared to the polymeric carrier material. Typical thermal expansion coefficients of polymeric carrier materials suitable for the purposes of the present invention are between 30x10 -6< / K and 60x10 -6< / K. Fibrous reinforcing materials that have a negative coefficient of thermal expansion are preferred because they counteract the naturally high overall thermal expansion of the polymeric carrier material to a certain extent and are responsible for an overall low thermal expansion of the composite material.In preferred embodiments, the first fibrous reinforcing material has a thermal expansion coefficient of -0.12x10 -6< / K or more, in particular -0.1x10 -6< / K or more, in particular -0.8x10 -6< / K or more, in particular 0.5x10 -6< / K or more, in particular -0.02x10 -6< / K or more, but less than 1.8x10 -6< / K, in particular less than 1.5x10 -6< / K, in particular less than 1.2x10 -6< / K, in particular less than 1x10 -6< / K, in particular less than 0.8x10 -6< / K, in particular less than 0.5x10 -6< / K.

[0032] According to the invention, the second reinforcing material has an electrical conductivity of 10 -4 < S / m or less. The low conductivity of the second reinforcing material results in a reduced susceptibility to wear of the composite material. Surprisingly, it was found that the specific wear rate of the composite material according to the invention is unexpectedly lower than that of the carrier material alone or that of the composite material consisting solely of the polymeric carrier material and the first fibrous reinforcing material or that of the composite material consisting solely of the polymeric carrier material and the second reinforcing material.In preferred embodiments, the electrical conductivity of the second reinforcing material is 10 -5< S / m or less, in particular 10 -6< S / m or less, in particular 10 -7< S / m or less, in particular 10 -8< or less, in particular 10 -9< S / m or less, in particular 10 -10< S / m, or less, but at least more than 10 -15< S / m, in particular more than 10 -14< S / m, in particular more than 10 -13< S / m, in particular more than 10 -12< S / m, in particular more than 10 -11< S / m.

[0033] Fibrous reinforcing materials are preferred because they impart greater strength to the carrier material, particularly higher tensile strength and higher notched impact strength. Depending on the required strength of the composite material and the intended stress as a mechanical component in force and motion transmission, the use of the second reinforcing material in fibrous form may be advantageous.

[0034] In a further embodiment according to the first aspect, the invention is characterized in that the polymeric support material has a glass transition temperature of 120 to 200°C, preferably of 125°C to 190°C, more preferably of 130°C to 160°C. The glass transition temperatures can be determined, for example, using methods of differential scanning calorimetry (DSC). In particular, the standard DIN EN ISO 11357-2:2014-07 for determining the glass transition temperature is known. Above the glass transition temperature, the thermally induced softening of the polymeric support material, particularly under mechanical stress, increases with rising temperature. The glass transition temperature is therefore to be regarded as a measure of the thermal softening behavior of polymers.In particular, within the meaning of the present invention, polymers having a glass transition temperature of 120°C and above are to be regarded as hard and are therefore preferably suitable as polymeric carrier materials for a composite material according to the present invention.

[0035] In a further embodiment according to the first aspect, the invention is characterized in that the polymeric carrier material has a coefficient of friction of 0.13 to 0.21 µs and / or a specific wear rate of 2 to 6x10 -6< mm 3< / Nm, measured according to the "Block on the Ring Test." The "Block on the Ring Test" used for the investigation is based on the description of the ASTM G77-17 standard. The workpiece to be investigated is placed on a metal ring under load, and the ring is rotated. The coefficient of friction and the specific wear rate are determined according to this test setup.The use of a polymeric carrier material with a friction coefficient of 0.13 to 0.21 µs and / or a specific wear rate of 2 to 6x10 -6< mm 3< / Nm is advantageous for the production of the composite material together with the first fibrous reinforcing material and the second reinforcing material in order to set the advantageous low values ​​of the friction coefficient and the specific wear rate of the composite material.

[0036] In a further embodiment according to the first aspect, the invention is characterized in that the polymeric carrier material consists of polyetheretherketone (PEEK). This polymer is particularly suitable for the production of the composite material according to the invention due to its temperature resistance, mechanical properties, chemical inertness, and melt processability.

[0037] In a further embodiment according to the first aspect, the invention is characterized in that the first fibrous reinforcing material contains carbon fibers or consists of carbon fibers. For the purposes of the present application, the term " Carbon fiber " a fiber which is obtained from a plastic fiber through a pyrolysis process. Carbon fibers are characterized by high tensile strength and by a low, in particular negative, coefficient of thermal expansion parallel to the fiber direction. With an isotropic arrangement of the carbon fibers in the composite material according to the invention, the temperature-dependent expansion of the composite material can be kept low and thus the wear of mechanical components in the force and motion transmission, which are made from the composite material, can be kept low.

[0038] In a further embodiment according to the first aspect, the invention is characterized in that the second reinforcing material contains or consists of glass fibers. Glass fibers are characterized by high tensile strength and thus impart increased elongation at break to the composite material. Furthermore, glass is characterized by low electrical conductivity. This reduces wear on mechanical components in force and motion transmission systems made of the composite material and coming into contact with ultrapure water.

[0039] In a further embodiment according to the first aspect, the invention is characterized in that the proportion of the first fibrous reinforcing material in the composite material is 3 wt.% or more, preferably 4 wt.% or more, further preferably 5 wt.% or more, further preferably 6 wt.% or more, further preferably 7 wt.% or more, and 20 wt.% or less, preferably 19 wt.% or less, further preferably 18 wt.% or less, further preferably 17 wt.% or less, further preferably 16 wt.% or less, further preferably 15 wt.% or less, in particular 3 wt.% to 18 wt.%, further preferably 5 wt.% to 18 wt.%, further preferably 5 wt.% to 15 wt.%, further preferably 7% to 15 wt.%, based on the total weight of the composite material. A proportion that is too high, more than 20 wt.%.A 3% weight ratio of the first fibrous reinforcement material, carbon fiber, based on the total weight of the composite material leads to unacceptably high levels of wear when used for mechanical components in force and motion transmission and in contact with ultrapure water. At a proportion of the first fibrous reinforcement material, carbon fiber, of less than 3% by weight, based on the total weight of the composite material, the high thermal expansion of the polymeric carrier material or the second reinforcement material, glass fiber, can no longer be adequately compensated. Accordingly, at elevated temperatures, the mechanical component can wear due to excessive thermal expansion in force or motion transmission applications.

[0040] In a further embodiment according to the first aspect, the invention is characterized in that the proportion of the second reinforcing material, glass fiber, in the composite material is 10 wt.% or more, preferably 12 wt.% or more, preferably 14 wt.% or more, more preferably 15 wt.% or more, more preferably 17 wt.% or more and not more than 45 wt.%, preferably not more than 42 wt.%, more preferably not more than 40 wt.%, more preferably not more than 38 wt.%, more preferably not more than 35 wt.%, more preferably not more than 33 wt.%, more preferably not more than 30 wt.%, particularly preferably 10 wt.% to 40 wt.%, more preferably 15 wt.% to 35 wt.%, more preferably 15 wt.% to 30 wt.%, based on the total weight of the composite material.

[0041] A proportion of the second reinforcing material, glass fiber, of more than 45 wt.%, based on the total weight of the composite material, can cause excessive thermal expansion of the composite material, which leads to unacceptable wear at elevated temperatures, particularly in mechanical components for force and motion transmission made from the composite material according to the invention. A proportion of the second reinforcing material, glass fiber, of less than 10 wt.%, based on the total weight of the composite material, must be compensated for by an additional reinforcing material, the first fibrous reinforcing material, so that the composite material has sufficient strength for mechanical components for force and motion transmission.Since these reinforcement materials are not inert to ultrapure water due to their higher electrical conductivity, unacceptable wear would be expected when using such mechanical components in contact with ultrapure water.

[0042] In a further embodiment according to the first aspect, the invention is characterized in that the proportion of the polymeric carrier material in the composite material is 45 wt.% or more, preferably 50 wt.% or more, more preferably 55 wt.% or more, more preferably 60 wt.% or more, based on the total weight of the composite material. A proportion of the polymeric carrier material of less than 45 wt.% can lead to the first fibrous reinforcing material and the second reinforcing material not being completely enclosed by the polymeric carrier material. The strength of the composite material can thereby be reduced, and increased wear can occur when the composite material is used for force- and motion-transmitting mechanical components.

[0043] In a further embodiment according to the first aspect, the invention is characterized in that the composite material comprises an antioxidant. The antioxidant prevents degradation of the carrier material and the first fibrous reinforcing material in the composite material caused by ion or radical formation.

[0044] In particular, charges are induced in composite materials used in components for force and motion transmission through frictional contact and the resulting triboelectric effect. In the case of the composite material defined according to the first aspect, the electrical charges are induced by homolytic and heterolytic covalent bond cleavage in the carrier material and / or the first fibrous reinforcement material, i.e., in particular, the carbon fiber material.

[0045] Heterogeneous bond cleavage generates an ion pair through the cleavage of covalent bonds, with the ionic sites being located at the molecular cleavage fragments of the carrier material or the fibrous reinforcement material. The ionic sites generated in this way in the carrier material or in the first fibrous reinforcement material are referred to as mechano-ions in the context of the present application, as they arise through mechanical frictional contact. The mechano-ions include cationic mechano-ions, i.e., positively charged molecular cleavage fragments, and anionic mechano-ions, i.e., negatively charged molecular cleavage fragments.

[0046] During homolytic bond cleavage, a radical pair is formed, with the radical sites located on the respective molecular cleavage fragments. Such radical sites are referred to as mechanoradicals in the context of this application, as they are generated by mechanical frictional contact.

[0047] Mechano-ions and mechano-radicals cause subsequent chemical reactions, which in turn cause new covalent bond cleavages and thus contribute to the degradation and loss of strength of the composite material. If the formation of such mechano-ions and mechano-radicals is counteracted, weakening of the composite material can be avoided. Ultrapure water with a conductivity of 10 -4 < S / m is particularly unsuitable for reacting sufficiently with mechano-ions and mechano-radicals, as it contains only a few ions that can react with the mechano-ions or mechano-radicals in the composite material. It therefore proves to be a problem that composite materials according to the first aspect of the invention, when used as force- or motion-transmitting components and in conjunction with ultrapure water, lose strength due to the tribological effect when subjected to excessive frictional stress.

[0048] The strength of the composite materials according to the first aspect of the invention can be further increased under conditions of high frictional stress and in contact with ultrapure water by a proportion of antioxidant in the composite material.

[0049] The production of a composite material containing antioxidants can be carried out by melt extrusion, by compounding the components of the carrier material, the first fibrous reinforcing material, carbon fiber, the second reinforcing material, glass fiber, and antioxidants to form the composite material. For the purposes of the present application, the term " Antioxidants " is to be understood as meaning one or more substances which are chemically reactive with respect to ions or radicals. In particular, according to the present application, antioxidants are used which are reactive with respect to mechano-ions and mechano-radicals formed in the composite material according to the first aspect of the invention.

[0050] In particular, compounds such as tocopherols, tocotrienols, resveratrols, flavonoids, H-donors such as aromatic amines and sterically hindered phenols, hydroperoxide decomposers such as phosphites, phosphonites, thiosynergists, alkyl radical scavengers such as sterically hindered amine stabilizers, hydroxylamines, benzofuranones, acryloyl-modified phenols, or multifunctional stabilizers of the aforementioned type, or mixtures of stabilizers of the aforementioned type can be used as antioxidants.

[0051] In a further embodiment according to the first aspect, the invention is characterized in that the antioxidant is a primary and / or secondary antioxidant. The primary antioxidants can be sterically hindered phenols or secondary aromatic amines. The term "steric" refers to molecular groups that are spatially demanding at the molecular level. A preferred primary antioxidant is the commercially available Evernox 1330, which comprises the compound 3,3',3',5,5',5'-hexa-tert-butyl-a,a',a'-(mesitylene-2,4,6-trityl)tri-p-cresol. The secondary antioxidants can be peroxides, organic hydroperoxides, phosphates, thioethers, or organic sulfides. A preferred secondary antioxidant is the commercially available Doverphos S-9228, which contains the compound bis(2,4-dicumylphenyl)pentaerythritol diphosphite.The use of primary antioxidants is preferred.

[0052] In a further embodiment according to the first aspect, the invention is characterized in that the proportion of antioxidant in the composite material is 0.001 wt.% to 2.5 wt.%, preferably 0.01 wt.% to 2.0 wt.%, more preferably 0.1 wt.% to 1 wt.%, based on the total weight of the composite material. In particular, the proportion of antioxidant in the specified range only insignificantly influences the material properties of the composite material with regard to electrical conductivity and thermal expansion, so that wear of the composite material in use as a mechanical component in force and motion transmission during contact with ultrapure water and thermal expansion is not significant.

[0053] Further in particular, the present composite material according to the first aspect of the invention can be characterized in that the proportions of the carrier material, the first fibrous reinforcing material and the second reinforcing material and the antioxidant together amount to 100 wt.%.

[0054] In a further embodiment according to the first aspect, the invention is characterized in that the weight ratio of the second reinforcing material to the fibrous first reinforcing material in the composite material is 3:1 to 1:1. It has been shown that the wear rate of the composite material in the use of force- and motion-transmitting mechanical components has the lowest values ​​in this range of weight ratios.

[0055] In a further embodiment according to the first aspect, the invention is characterized in that the fibers of the fibrous first reinforcing material and / or the fibers of the fibrous second reinforcing material have a fiber diameter transverse to the longitudinal extent of the fibers of 1 µm or more, preferably 2 µm or more, more preferably 3 µm or more and 10 µm or less, more preferably 9 µm or less, more preferably 8 µm or less, in particular 1 µm to 10 µm, 2 µm to 9 µm, more preferably 3 to 8 µm.

[0056] In a further embodiment according to the first aspect, the invention is characterized in that the fibers of the fibrous first reinforcing material and / or the fibers of the second fibrous reinforcing material have a length of 10 µm or more, preferably 15 µm or more, preferably 20 µm or more, preferably 25 µm or more, and 60 µm or less, preferably 55 µm or less, more preferably 50 µm or less, in particular from 10 µm to 60 µm, preferably from 15 µm to 55 µm, more preferably from 20 µm to 50 µm. At fiber lengths above 60 µm, an advantageously isotropic distribution of the fibers in the composite material can be prevented. Particularly in the case of small mechanical components, fiber lengths above 60 µm can lead to fiber alignment during component manufacture, which can have a negative impact on the strength of the components.If the fiber length is 10 µm or less, the cross-linking character of the fibrous first or second reinforcing material in the composite material may be lost and lead to reduced strength of the composite material.

[0057] In particular, a preferred range of diameter and length of the fibers of the fibrous first and fibrous second reinforcing material is selected such that a ratio of diameter to length of the fibers of the first fibrous reinforcing material and the fibers of the second fibrous reinforcing material is 1:2 to 1:20. At least 60%, preferably at least 70%, more preferably at least 80% of the fibers of the fibrous first and fibrous second reinforcing material have this preferred ratio.

[0058] A further embodiment of the first aspect of the invention is characterized in that the composite material comprises a further component for friction modification. The further component is, for example, boron nitride and / or Teflon. The proportion of the further component for friction modification is 15% by weight or less, preferably 10% by weight or less, more preferably 5% by weight or less, at least, if the component for friction modification is provided in the composite material, 0.2% by weight or at least 0.5% by weight, or at least 1% by weight, based on the total weight of the composite material.

[0059] In a further embodiment according to the first aspect, the invention is characterized in that the proportions of the polymeric carrier material, the first fibrous reinforcing material and the second reinforcing material together amount to 97% by weight or more, in particular 100% by weight.

[0060] In a second aspect, the invention relates to a mechanical component for force and motion transmission, comprising a composite material according to at least one embodiment of the first aspect of the invention. The mechanical component according to the invention is characterized by low wear. In particular, the mechanical component exhibits low wear even in contact with ultrapure water.

[0061] In one embodiment of the second aspect, the invention relates to a mechanical component, wherein the mechanical component is a gear.

[0062] In a third aspect, the invention relates to a gear pump, which is characterized in that the gear pump has at least one gear according to an embodiment according to the second aspect of the invention. Due to the design, the gears of the gear pump are mounted in the fluid to be pumped. The advantage of the gear pump according to the invention is that it has low wear compared to the pumping of ultrapure water, in particular even at elevated temperatures. Furthermore, it has been found that the gear pump is also low-wear when pumping oxidizing disinfectants, e.g. in the hot cleaning of medical devices. The gear pump according to the invention is therefore suitable for use in the medical technology field and in particular as a pumping device in dialysis machines. EXAMPLES Block on the Ring Test

[0063] The "Block on the Ring Test" was performed based on the description of ASTM G77-17. A specimen was made from the composite material under test, measuring 4 x 4 x 17 mm. The specimen was mounted on a test stand and placed on a ring. The ring was made of CrNiMo steel. The specimen was then subjected to a force of 2.5 MPa and pressed against the outer surface of the ring. The ring was rotated so that the specimen slid over the contact area of ​​the ring at a relative speed of 0.5 m / s. The test temperature of the ring and specimen was set to 23°C. The specimen and ring were rinsed with water during the test. A total relative sliding distance of 36,000 m was traversed. (1) Specific wear rate

[0064] To determine the specific wear rate, an electrical voltage of 2.5 V was applied between the specimen and the ring during the test. The applied voltage creates a surface charge on the specimen and ring, simulating the corrosion conditions under ultrapure water application of the composite material. Standard laboratory-standard demineralized water was used as a lubricant. The abrasion volume of the specimen generated during the sliding process was measured over time. The specific wear coefficient is determined from the slope of a detected linear curve between abrasion volume and time.

[0065] At the same time, the friction coefficient is determined via the torque of the driven ring body.

[0066] For comparative investigations on different composite materials, the same process conditions are preset in each case, so that the determined specific wear rate and the friction coefficient depend only on the composition of the composite materials investigated. Production of composite materials (1) Example 1 - PEEK / CF / GF - Composite material made of PEEK carbon fiber and glass fiber

[0067] A mass of Victrex polyetheretherketone, carbon fibers with a thermal expansion coefficient of -0.1x10 -6 K, and glass fibers with an electrical conductivity of 1x10 -9 S / m are compounded by melt extrusion to form a composite material and then processed into a specimen. Carbon fibers and glass fibers are used in equal weight proportions. The proportion of carbon fibers and glass fibers in the specimen is 15 wt.% each. The specific abrasion coefficient and the friction coefficient are determined using the block-on-the-ring test. Furthermore, the thermal expansion of the composite material is determined by thermomechanical analysis. The values ​​are shown in Table 1. (2) Example 2, PEEK / CF - Composite material made of PEEK and carbon fiber comparison example

[0068] A mass of Victrex polyetheretherketone and carbon fibers with a thermal expansion coefficient of -0.1x10 -6 / K is compounded by melt extrusion and processed into a specimen. The carbon fiber content in the specimen is 30 wt.%. The specific wear rate and the coefficient of friction are determined using the block-on-the-ring test. Furthermore, the thermal expansion of the composite material is determined by thermomechanical analysis. The values ​​are shown in Table 1. Example 3, PEEK / GF composite material made of PEEK and glass fiber comparison example

[0069] A mass of Victrex polyetheretherketone and glass fibers with an electrical conductivity of 1x10 -9 < S / m are compounded by melt extrusion and processed into a sample. The glass fiber content in each sample is 30 wt.%. The specific wear rate and the coefficient of friction are determined using the block-on-the-ring test. Furthermore, the thermal expansion of the composite material is determined by thermomechanical analysis. The values ​​are shown in Table 1. Example 4 - Comparison example

[0070] A PEEK specimen is prepared. The specific wear rate and coefficient of friction are determined using the block-on-the-ring test. Furthermore, the thermal expansion of the composite material is measured. The values ​​are shown in Table 1. Table 1 Example Coefficient of thermal expansion [10 -6 < / K] Friction coefficient [µs] specific wear rate [10 -6< mm 3< / Nm] (1) PEEK / CF / GF 7 0,14 0,9 (2) PEEK / CF 4 0,14 9 (3) PEEK / GF 16 0,22 8 (4) PEEK 47 0,17 4

[0071] The results show that the PEEK / CF / GF composite material according to the invention has a friction coefficient equivalent to that of the PEEK / CF composite material. The friction coefficient is lower than that of the PEEK / GF composite material. The thermal expansion coefficient of PEEK / CF / GF is lower than that of the PEEK / GF composite material, but is higher than that of the PEEK / CF composite material due to the glass fiber content. Unexpectedly, the specific wear rate of the PEEK / CF / GF composite material is significantly lower than that of the comparison composite materials PRRK / CF and PEEK / GF.

Claims

1. A composite material for mechanical components of force and motion transmission consisting of at least three constituents (i) at least 45% by weight of a substrate material in relation to the total weight of the composite material consisting of polyether ether ketone, (ii) 3 to 20% by weight of a first fibrous reinforcing material in relation to the total weight of the composite material, and (iii) 10 to 45% by weight of a second reinforcing material in relation to the total weight of the composite material, wherein the first fibrous reinforcing material has a lower thermal expansion coefficient than the second reinforcing material and wherein the second reinforcing material has a lower electrical conductivity than the first reinforcing material and wherein the parts by weight of the constituents contained in the composite material add up to 100%, and wherein the first fibrous reinforcing material contains or is carbon fiber, and wherein the second reinforcing material contains or is glass fiber.

2. The composite material according to claim 1, characterized in that the first fibrous reinforcing material exhibits a thermal expansion of from -0.15x10-6 / K to 2x10-6 / K parallel to the direction of the fibers and the second reinforcing material has an electrical conductivity of 10-4 S / m or less.

3. Verbundmaterial nach Anspruch 1 oder 2, dadurch gekennzeichnet, dass das erste Verstärkungsmaterial und das zweite Verstärkungsmaterial isotrop in dem Trägermaterial dispergiert sind.

4. The composite material according to at least one of the preceding claims, characterized in that the second reinforcing material is fibrous.

5. The composite material according to at least one of the preceding claims, characterized in that the amount of the first fibrous reinforcing material in the composite material is 3% to 18% by weight, preferentially 5% to 15% by weight, further preferentially 7% to 15% by weight relative to the total weight of the composite material, and / or characterized in that the amount of the second reinforcing material in the composite material is to 10% to 40% by weight, further preferentially 15% to 35% by weight, further preferentially 15% to 30% by weight relative to the total weight of the composite material.

6. The composite material according to at least one of the preceding claims, characterized in that the amount of the substrate material in the composite material is at least 50% by weight, further preferentially at least 55% by weight, further preferentially at least 60% by weight relative to the total weight of the composite material.

7. The composite material according to at least one of the preceding claims, characterized in that the weight ratio of the second reinforcing material to the fibrous first reinforcing material is 3:1 to 1:1, preferentially 2:1 to 1:1.

8. The composite material according to at least one of the preceding claims, characterized in that the composite material comprises an antioxidant, preferentially characterized in that the antioxidant is a primary and / or a secondary antioxidant9. The composite material according to at least one of the preceding claims, characterized in that the amount of the antioxidant in the composite material is 0.001% to 2.5% by weight, preferably 0.01% to 2.0% by weight, more preferably 0.1% to 1% by weight, based on the total weight of the composite material.

10. The composite material according to at least one of the preceding claims, characterized in that the fibers of the fibrous first reinforcing material and / or the fibers of the fibrous second reinforcing material have a fiber diameter of from 1 µm to 10 µm, preferentially 2 µm to 9 µm, further preferentially 3 µm to 8 µm and / or characterized in that the fibers of the fibrous first reinforcing material and / or the fibers of the second fibrous reinforcing material have a length of 10 µm to 60 µm, preferentially 15 µm to 55 µm, further preferentially 20 µm to 50 µm.

11. The composite material according to at least one of the preceding claims, characterized in that the ratio of diameter to length for the fibers of the first fibrous reinforcing material and the fibers of the second fibrous reinforcing material is greater than 1:2 to 1:20.

12. The composite material according to at least one of the preceding claims, characterized in that the amount of the substrate material, the first fibrous reinforcing material and the second reinforcing material and if applicable the antioxidant together add up to 100% by weight.

13. A mechanical component for force and motion transmissions comprising a composite material according to at least one of claims 1 to 12, characterized in that the component is a gear.

14. A gear pump comprising at least one gear according to claim 13.

15. Use of a composite material according to at least one of claims 1 to 12 for mechanical components suspended in liquid in medical pumping applications, preferably for mechanical components suspended in liquid in dialysis pumps or pumps for pumping ultrapure water.