elongated injection-molded component

Description

Technical field

[0001] The present invention relates to a component with an injection-molded base body and to a method for manufacturing the component. Furthermore, the present invention relates to a motor vehicle comprising the component. Background of the invention

[0002] Fiber-reinforced injection-molded components are used particularly in the automotive industry. The addition of reinforcing fibers increases the component's strength. However, glass fiber-reinforced components with long flow paths and wall thicknesses of less than 2 mm, for example, are currently only possible with compromised properties. For instance, thin-walled components with long flow paths often exhibit poor surface finish, reduced strength, and insufficient taper. Furthermore, shrinkage-related molding problems exist, such as sticking to the mold mandrel in the case of a tube component due to shrinkage during the cooling process.

[0003] Furthermore, in plastic injection molding, especially with added glass fibers, the fibers align themselves highly parallel along the flow path. This means that the fibers, which are actually used to improve strength, do not provide significantly higher strength when placed perpendicular to the flow path, as they are aligned parallel to the flow direction and glass fibers can only create a reinforcing effect along their longitudinal direction.

[0004] This is particularly evident in the rapidly decreasing strength values ​​when, during a tensile test, the tensile direction does not align with the fibers along the flow path. Investigations have shown that the resulting component failure often originates from a single point of failure (the weakest point of the bond in the load zone) and then propagates very rapidly through the component material by overloading neighboring structures.

[0005] US 2018 / 0215909 A1 discloses a fiber-reinforced component with a polymer matrix and a multitude of long reinforcing fibers. The polymer matrix constitutes 30 to 90 percent by weight of the component. Depending on the proportion of the polymer matrix, the fibers constitute 10 to 70 percent by weight of the component. The length of the reinforcing fibers can range, for example, from 1 mm to approximately 25 mm.

[0006] DE 100 09 559 A1 discloses a method for producing an expansion-molded object from fiber-reinforced thermoplastic resin. In particular, it is disclosed that a suction device is used to generate a vacuum in the injection mold.

[0007] EP 2 357 070 A1 discloses a method for injection molding condensation resins from the melt or suspension / solution, molded parts produced therewith, and an injection mold with which the method can be carried out. An injection mold is described that has gas outlet openings and / or walls made of porous materials, e.g., sintered metals.

[0008] WO 02 / 26482 A1 discloses an injection-molded component with reinforcing fibers. The component contains a plurality of fibers dispersed in a polymer matrix, wherein at least 10% of the total number of fibers have a length greater than 0.55 mm. The maximum thickness of the molded component is no longer between 1 mm and 2 mm. Furthermore, a foam material is used in which the void volume is at least approximately 5%. Description of the invention

[0009] It is an object of the present invention to provide a robust injection-molded component that can withstand stress in many directions.

[0010] This problem is solved by a component and a method for manufacturing the component according to the subject matter of the independent claims.

[0011] According to a first aspect of the present invention, a component comprising an injection-molded base body is described. The base body has a wall thickness of less than 1.9 mm. A plurality of gas bubbles and reinforcing fibers are embedded in the base body. The flow path length of the injection-molded base body is over 300 mm. The base body contains decomposition particles of a gas bubble-forming blowing agent, wherein the volume fraction of the decomposition particles of the blowing agent in the base body is 0.1% to 7%.

[0012] The base body forms a section of the component or the entire component. The base body can be a solid body made of a solid material. In this case, the wall thickness is defined by the material thickness or the diameter. Furthermore, the base body can be a hollow body, whereby the hollow body at least partially encloses an internal volume of the component. The base body can thus form a vessel with at least one open end. In particular, the base body forms an injection-molded tube. The wall thickness then defines the thickness of a wall that at least partially surrounds a cavity.

[0013] Specifically, the wall thickness is determined at the thickest part of the base body. In other words, the base body essentially has no area with a wall thickness greater than 1.9 mm (millimeters). This wall thickness refers only to the wall of the base body; therefore, additional functional components, such as fasteners, clamping ribs, retaining nipples, or similar elements that, for example, extend the geometric tubular shape and are manufactured in the same operation, do not define the wall thickness of the base body.

[0014] In particular, the base body is an injection-molded component. The starting material, plastic granules, is fed into an extruder where the plastic is liquefied. The liquefied plastic is then injected under pressure into an injection mold to form the base body. Reinforcing fibers are also added as filler in the extruder. Furthermore, a gas-forming medium, either gaseous or solid, is fed into the extruder. Specifically, a blowing agent is added as a solid before or within the extruder, which then forms the gas bubbles in the injection mold.

[0015] The maximum flow path in the mold body is the distance between the gate (i.e., the point on the injection mold where the molten material is introduced) and the last filled area (i.e., the end of the injection mold in the direction of the liquid material flow). On the mold body, the distance from the gate to the end of the flow path is measured. If the molten material flow in the injection mold splits into multiple flow paths, e.g., at openings, the longest possible flow path of the material in the injection mold is used to determine the length of each flow path.

[0016] According to the invention, the component has a multitude of individual (spaced-apart) small gas bubbles, resulting in a very low gas bubble concentration. This improves strength because the gas bubbles in the injection mold push the reinforcing fibers away from their longitudinal alignment in the flow direction, thus causing the reinforcing fibers to align transversely, i.e., at an angle to the flow direction. As the gas bubbles expand, the fibers become less parallel (i.e., the fibers are pushed away from their parallel alignment by a small, adjacent gas bubble). Particularly with chemical blowing agents, the pressure and timing of gas bubble formation are easily controllable. This leads to a microscale bracing effect of the reinforcing fibers transversely to the flow direction. The gas bubbles thus disrupt the laminar flow, similar to a bridge pier in a stream carrying sediment.The fibers deviate from their homogeneous distribution, which in turn creates cross-bracing.

[0017] Furthermore, the gas bubbles introduce additional elasticity into the component. A so-called point of failure, at which the component breaks in a tensile test, becomes a larger zone instead of a single point in the fracture behavior. This larger zone, in turn, averages out the forces, meaning the weakest link fails later, as the elasticity distributes the forces more effectively to adjacent fiber composites (which are generally not the second weakest link).

[0018] Due to the increased strength of the component according to the invention, particularly against forces acting perpendicular to the flow direction, injection-molded components with an extremely thin wall thickness (1.9 mm) but with an extremely long flow path length of over 300 mm can be produced. Together with the reinforcing fibers and the introduced gas bubbles, this enables the production of an elongated injection-molded component (for example, a pipe) whose strength is significantly higher than that of injection-molded components without gas bubbles.

[0019] The minimal gas addition during injection molding according to the invention thus allows for design optimization compared to injection-molded components free of gas bubbles. With the same wall thickness as gas-molded components free of gas bubbles, the component according to the invention can have a lower weight, lower bending stiffness, and the same section modulus.

[0020] With the same bending stiffness compared to gas bubble-free injection molded components, the component according to the invention can have a slightly greater wall thickness but with a slightly reduced weight and increased section modulus.

[0021] With the same weight as gas bubble-free injection molded components, the component according to the invention can have a slightly greater wall thickness but with greater bending stiffness and a greater section modulus.

[0022] Introducing gas bubbles reduces the density and tensile modulus of the component. However, relative to its weight, the component's stiffness increases.

[0023] Furthermore, the component according to the invention exhibits a more uniform surface formation than a component without gas bubbles. This is due to the pressure distribution of the gas bubbles, which allows for a reduction in the holding pressure during injection molding. The use of gas bubbles according to the invention enables the internal pressure within the component to be maintained particularly well during the cooling phase. This cannot be achieved through additional holding pressure due to the long flow paths. The low viscosity and the resulting rapid filling of the cavities in the injection mold lead to no or minimal internal temperature gradients, thus preserving the homogeneity of the melt, especially with regard to the surface properties of the injection-molded component. Consequently, no streaking occurs on the surface, which contributes to surface defects, allowing for the injection molding of more complex components.

[0024] According to another exemplary embodiment, the flow path length is over 380 mm, in particular over 450 mm, and further, in particular, over 500 mm. With the admixture of gas bubbles and reinforcing fibers according to the invention, flow path lengths of over 380 mm and more are even possible, since sufficient strength cannot be achieved due to the fiber orientation of the reinforcing fibers not being parallel, i.e., at an angle to the flow direction.

[0025] According to another exemplary embodiment, the wall thickness can also be set below 1.8 mm, particularly below 1.7 mm, further particularly below 1.5 mm, and further particularly below 1.4 mm. Particularly good properties of the component compared to gas bubble-free injection-molded components have been achieved when the base body is significantly longer than the thinnest wall thickness. This is correspondingly possible with the admixture of gas bubbles and reinforcing fibers according to the invention, since sufficient strength cannot be achieved due to the fiber orientation of the reinforcing fibers not being parallel, i.e., at an angle to the flow direction.

[0026] According to a further exemplary embodiment, the fiber content of the reinforcing fibers in the base body is 5 wt.% to 60 wt.%, particularly 10 wt.% to 50 wt.%, and more particularly 20 wt.% to 40 wt.%. This addition of gas bubbles according to the invention increases the flowability (in the sense of a reduction in overall viscosity), which in turn makes it possible to achieve the same flow path lengths as without gas bubbles but at a lower dosing temperature. These effects were achieved with the fiber content of reinforcing fibers described above, ranging from 5% to 60%, preferably from 10% to 50%, and particularly preferably from 20% to 40%.

[0027] According to another exemplary embodiment, the base body has at least one tube-like section. In particular, the entire base body can be designed as a tube. Especially with a tube-like design of the base body, where long flow paths occur compared to thin wall thicknesses, a significant improvement in quality is achieved due to the desired reinforcing fibers. In the injection molding of a tube, the viscous injection molding material is forced between an outer wall of the injection mold and an inner mandrel. The wall friction at the inner mandrel and the outer wall generally leads to a strong parallel alignment of the reinforcing fibers along the flow direction. The expansion of the gas bubbles, however, leads to a deflection of the reinforcing fibers away from the parallel direction to the flow direction, so that the bracing of the reinforcing fibers is achieved and higher strength is generated in the transverse direction of the tube.

[0028] According to another exemplary embodiment, the base body is designed such that it withstands a temperature shock test in a temperature range between -30 °C and +90 °C, particularly between -40 °C and 120 °C. In this test, the component is subjected to a negative extreme temperature and a positive extreme temperature within short time intervals, for example, less than 10 seconds, particularly less than 5 seconds, in order to test its temperature resistance. The component according to the invention, with the gas bubbles and reinforcing fibers, can even withstand a shock wave test in the range of -40 °C to 120 °C if cooling rates during the injection molding process are adjusted accordingly and / or the holding pressure is further adjusted.

[0029] According to another exemplary embodiment, the base body exhibits a processing shrinkage of 0.03% to 1.5%, particularly 0.05% to 0.5%, with respect to length or diameter after a 2-day storage period at room temperature following injection molding. For the 2-day storage period, the room temperature is specifically assumed to be 20 °C at 45% relative humidity and a constant air pressure of approximately 1013.25 hPa.

[0030] Due to cooling and outgassing of the component during or after the injection molding process, shrinkage begins. Shrinkage also occurs throughout the component's life cycle due to external physical influences. Shrinkage means that the component decreases in its geometric dimensions. Processing shrinkage is defined as shrinkage occurring immediately during injection molding and afterward until cooling to room temperature. From approximately two weeks after injection molding, further shrinkage is referred to as post-shrinkage.

[0031] The smaller processing shrinkage of the component according to the invention compared to an injection-molded component without gas bubbles is due to the fact that, in particular, the gas bubbles, especially due to the blowing agent, continue to expand during the cooling process of the component and thus counteract the shrinkage.

[0032] According to another exemplary embodiment, the base body exhibits a post-shrinkage of 0.01% with respect to length or diameter over a period of 5 days. The post-shrinkage occurs after, for example, 2 weeks. The post-shrinkage process takes correspondingly longer, although the change is smaller. In particular, shrinkage reduction tests on components with high holding pressure and no gas bubble content have shown that this leads to poorer surface quality and greater shrinkage compared to the component according to the invention. This results in a reduction in the shrinkage of the component according to the invention between injection (i.e., the injection of the molding compound into the mold) and demolding by more than 1 / 100 mm, more than 3 / 100 mm, and in particular more than 5 / 100 mm, compared to a component produced with the same mold without gas bubbles.This also allows for easy demolding of the injection-molded component, as there is hardly any orange peel effect on the surface, which tends to adhere to certain parts of the injection mold, e.g., to internal mandrels of the injection mold.

[0033] The reduction in shrinkage of the component according to the invention, caused by the gas bubbles, results in a more homogeneous surface and prevents microscale orange peel. In particular, the chemical generation of gas bubbles creates the same surface quality at the ends of the flow paths as in the injection point region (gate). This can be explained by the fact that the gas bubbles generate an inherent pressure during the cooling process along the entire length of the flow path, which has a positive effect on both the surface quality and the shrinkage of the component. Thus, a high-gloss finish can also be achieved on the inside of a tubular or pipe-shaped component (especially in products that are telescoping tubes), which, due to the reduced shrinkage, exhibits no tendency to scratch the surface, particularly during forming.In particular, the surface quality of the component according to the invention is equal to one quarter of the flow path length from the end of the flow path as one quarter of the flow path from the beginning of the flow path (i.e. at the gate).

[0034] According to another exemplary embodiment, the base body has a volume fraction of gas bubbles between 0.3% and 8%, particularly between 0.6% and 5%, and more specifically between 1.5% and 3%. The described volume fraction refers to the volume percentage relative to the total volume of the base body. With too few gas bubbles, there is no or insufficient deflection of the reinforcing fibers; with too many gas bubbles, the strength collapses. With the gas bubble fraction described above, particularly good results are possible in reducing the density of the injection-molded part due to gas bubbles.

[0035] According to another exemplary embodiment, at least 80% or at least 60% of the gas bubbles have a diameter between 1 micrometer and 100 micrometers, particularly between 2 micrometers and 50 micrometers, and in particular between 2 micrometers and 10 micrometers. With the gas bubble diameters described above, particularly good results are possible in reducing the density of the injection-molded part due to the gas bubbles. The size of the gas bubbles can be adjusted, for example, by selecting the blowing agent, the temperature of the material during injection molding, and the cooling rate.

[0036] According to the invention, the base body comprises decomposition particles of a gas-bubble-forming propellant. These decomposition particles are present in the base body and form solid decomposition residues of the original propellant as a byproduct of gas formation. Metal oxides are a typical example of such a propellant byproduct.

[0037] According to the invention, the volume fraction of the decomposition particles of the propellant in the base body is between 0.1% and 7%, in particular between 0.3% and 4%, and further, in particular between 0.5% and 2%. The described volume fraction refers to the volume percentage relative to the total volume of the base body.

[0038] According to a further exemplary embodiment, the blowing agent is a chemical blowing agent which is in particular exothermically reactive, wherein in particular at least more than half, in particular more than 80% or all, of the decomposition particles of the blowing agent have a diameter between 0.1 micrometers and 50 micrometers, in particular between 1 micrometer and 3 micrometers.

[0039] Blowing agents can be either endothermic or exothermic. Exothermic blowing agents are particularly advantageous because the released energy results in a longer liquid phase in the injection molding material along longer flow paths within the mold. This is primarily due to the fact that the thermal effect remains geometrically limited in the immediate vicinity of the gas bubble. Furthermore, chemical blowing agents lead to a more homogeneous gas bubble distribution than, for example, physical blowing agents. Additionally, gas bubble formation is delayed in chemically generated gases compared to physically generated gases, allowing for later control of gas bubble formation within the mold.

[0040] According to another exemplary embodiment, the gas bubbles, in particular at least 80% of all gas bubbles, are spaced apart from one another in the base body. By adding gas bubbles according to the invention, they are present in the base body in such a quantity that they predominantly remain discreetly within the mass and do not develop a foamy character in which the gas bubbles touch each other. In particular, this desired discreteness of the bubbles according to the invention can be controlled by the fineness or distribution of the blowing agents.

[0041] According to a further exemplary embodiment, the base body comprises at least one material consisting of the group comprising polyamides, in particular PA 6, 6.6, 4.6, 2.4, 11, aromatic and semi-aromatic polyamides (PA), polysulfone (PSU), polyphenylene sulfide (PPS), polyetherketones (PEK and PEEK) and polyesters (PET, PBT).

[0042] According to a further exemplary embodiment, the ratio between the length (e.g., the greatest extent of the base body in a spatial direction) of the base body and the thinnest wall thickness of the base body is greater than 50:1, in particular greater than 100:1, and further, in particular greater than 200:1. This is correspondingly possible with the admixture of gas bubbles and reinforcing fibers according to the invention, since sufficient strength cannot be achieved due to the fiber orientation of the reinforcing fibers not being parallel, i.e., at an angle to the flow direction.

[0043] According to a further exemplary embodiment, the majority (e.g., more than 50%, in particular more than 80% or 90%) of the reinforcing fibers in the base body have a diameter between 2 micrometers and 100 micrometers, in particular between 5 micrometers and 24 micrometers, and / or wherein the majority (e.g., more than 50%, in particular more than 80% or 90%) of the reinforcing fibers in the base body have a length between 0.05 mm and 4 mm, in particular between 0.1 mm and 1 mm.

[0044] According to a further exemplary embodiment, the reinforcing fibers comprise at least one material consisting of the group consisting of mineral fibers, in particular silicates, glass, basalt, asbestos and wollastonite, carbon fibers, in particular carbon nanotubes, polymer fibers, in particular polyamide, polyimide, polyester, polyolefins, polyesteramides and aramids, and natural fibers, in particular cellulose, cotton, viscose, lyocell, wood, hemp and silk.

[0045] According to a further aspect of the present invention, a method for manufacturing the component described above is described. According to the method, a base body of the component is injection molded, wherein the base body has a wall thickness of less than 1.9 mm and wherein a plurality of gas bubbles and reinforcing fibers are embedded in the base body. The flow path length of the injection-molded base body is over 300 mm.

[0046] In summary, the chemically generated gas bubbles, in particular, lead to improved stability of elongated and thin-walled injection-molded components. This is due, among other things, to the nucleation mechanisms, which, for example, occur in stages. On the one hand, the end face of a fiber forms a nucleation core or zone due to its inherent activation; on the other hand, the solid decomposition particles of the chemical blowing agents form nano- or microscale centers or nucleation cores. These second nucleation cores, however, only form later in the injection molding process, once the chemical blowing agents have reacted or even fully reacted. In the manufacturing process according to the invention, this staggered approach also contributes to a longer-lasting viscosity support and thus to achieving improved flow properties.Particularly good properties were achieved when the majority of the fibers used were within an exemplary diameter and length range.

[0047] According to another exemplary embodiment, the melt flow rate (MFI) of a material during the injection molding of the base body is set above 200 g / 10 min, particularly above 250 g / 10 min, and further, particularly above 300 g / 10 min. Such a higher melt flow rate can be achieved, for example, by increasing the temperature of the injected material (e.g., plastic). While this places a high thermal load on the material, it allows for longer flow paths. For example, the MFI of high-speed polyamide is around 100 g / 10 min. By superheating it by 30 °C above the nominal temperature, an MFI of over 200 g / 10 min can be achieved.

[0048] According to a further exemplary embodiment, after injection molding of the base body and after forming the base body, in particular as a tube shape, less than 20 mm, in particular less than 10 mm, further in particular less than 5 mm, further in particular less than 2 mm, is cut off from a longitudinally formed end of the base body.

[0049] According to a further exemplary embodiment, the base body is formed during injection molding along a flow path of an injection mold, wherein a vacuum is applied within the injection mold via vents in an end zone of the flow path. The end zone comprises less than 30% of the total length, in particular less than 20% of the total length, and further, in particular less than 10% of the total length of the flow path of the injection mold.

[0050] This reduces the amount of waste, particularly in the case of a tubular base body, by eliminating defective or low-quality beginning and end sections that would otherwise need to be cut off. Thanks to the longer flow paths and improved properties according to the invention, the injection-molded component can be used in high quality even towards the end of the flow path. This allows the component to be produced with less offcut and therefore less waste in the corresponding injection molding process. For example, if the base body is a tube, homogeneous component properties are possible over a longer stretch of the flow path. The area of ​​increasing inhomogeneity at the tube end / beginning is cut off and becomes waste. With the solution according to the invention, less than 20 mm, preferably less than 10 mm, particularly preferably less than 5 mm, and especially preferably less than 2 mm, needs to be cut off and disposed of / recycled.In particular, venting or evacuating in the end zone (corresponding, so to speak, to the pipe end) of the flow path helps to reduce the amount of material that needs to be cut off.

[0051] According to another exemplary embodiment, the blowing agent is added to a material of the base body before injection molding, wherein the weight fraction of the blowing agent in the total material before injection molding is 1%.

[0052] According to a further exemplary embodiment, during injection molding the blowing agent reacts exothermically and generates the gas bubbles and decomposition particles in the base body, wherein the blowing agent is added before injection molding in such a way that after injection molding, in particular at least more than half of the decomposition particles of the blowing agent have a diameter between 0.1 micrometers and 50 micrometers, in particular between 1 micrometer and 3 micrometers.

[0053] In another aspect, a manufacturing device for producing the component described above is described. The manufacturing device includes an injection mold for injection molding the component's base body. The injection mold can be over-dimensioned compared to standard dimensions to achieve high dimensional stability. This exceptionally high mold stability allows for the minimization of surface defects (moulding) on ​​the mold's closing edges (e.g., on the contact areas of two mold halves, such as when each half represents a pipe half) to such an extent that no surface defects (mold edges, etc.) are present in the component or base body.

[0054] According to another exemplary embodiment of the manufacturing device, the injection mold has at least one vent in an end zone of a flow path of the injection mold, wherein the vent is configured to create a vacuum within the injection mold. The end zone comprises less than 30% of the total length, in particular less than 20% of the total length, and further, in particular less than 10% of the total length of the flow path of the injection mold. For example, a vacuum pump can be connected to the vent. The injection mold can thus be evacuated during injection. This leads to increased gas bubble formation and a higher material flow rate. This can be used to achieve even longer flow paths, higher production speeds, and / or improved end-product properties (strength, surface finish, shrinkage, or flow path length).The same effect can be achieved by using different heat zones in the injection mold.

[0055] According to a further aspect of the present invention, the component described above is used in a motor vehicle. A motor vehicle can be, for example, a truck, a passenger car, or an electric vehicle. Due to the high temperature fluctuations, particularly in the interior of a motor vehicle, the advantages of the component according to the invention are especially evident. For example, in nested tubular components, such as those used in the opening mechanism of a motor vehicle's tailgate, the components according to the invention can be used because they can withstand high lateral loads, thus reducing the risk of jamming between two nested tubes. In particular, the low thermal expansion of the component according to the invention makes it especially suitable for use in motor vehicles.

[0056] It should be noted that the embodiments described here represent only a limited selection of possible embodiments of the invention. The invention is described in the accompanying claims. Brief description of the drawings

[0057] For further explanation and better understanding of the present invention, exemplary embodiments are described in more detail below with reference to the accompanying drawings. These show: Fig. 1 shows a schematic representation of a tubular component according to an exemplary embodiment of the present invention. Fig. 2 Figure 1 shows a schematic representation of a component with the corresponding gas bubbles and reinforcing fibers according to an exemplary embodiment of the present invention. Fig. 3shows a schematic representation of a component which is present in an injection mold during injection closing according to an exemplary embodiment of the present invention. Fig. 4 shows a schematic representation of a manufacturing device according to an exemplary embodiment of the present invention. Detailed description of exemplary embodiments

[0058] Identical or similar components in different figures are identified by the same reference numbers. The representations in the figures are schematic.

[0059] Fig. 1Figure 1 shows a schematic representation of a tubular component 100 according to an exemplary embodiment of the present invention. The component 100 has an injection-molded base body 101, wherein the base body 101 has a wall thickness d of less than 1.9 mm and a plurality of gas bubbles 102 and reinforcing fibers 103 are embedded in the base body 101. A flow path length FI of the injection-molded base body 101 is over 300 mm. The base body 101 in Fig. 1 forms an injection-molded tube. The base body 101 has no area whose wall thickness d is greater than 1.9 mm.

[0060] The maximum flow path in the base body 101 is the distance between gate 402 (i.e. the location on the injection mold where the liquefied material is introduced into the injection mold, see Fig. 4) and the last filled area (i.e., the end of the injection mold in the flow direction Fr of the liquid material). On the base body 101, the distance from the gate to the end of the flow path is measured, i.e., in this case, from the beginning of the pipe to the end of the pipe of the base body 101.

[0061] The base body 101 contains a large number of individual (spaced-apart) small gas bubbles 102, resulting in a low gas bubble concentration. This improves strength because, in the injection mold, the gas bubbles 102 push the reinforcing fibers 103 away from their longitudinal orientation in the flow direction Fr, thus causing the reinforcing fibers 103 to align transversely, i.e., at an angle, to the flow direction Fr. Due to the increased strength of the component 100, particularly against forces acting perpendicular to the flow direction Fr or the longitudinal direction of the pipe, injection-molded components 100 with an extremely thin wall thickness d (1.9 mm) but an extremely long flow path length FL of over 300 mm can be produced.

[0062] The fiber content of the reinforcing fibers 103 in the base body 101 can, for example, be 5 wt.% to 60 wt.%. This addition of gas bubbles 102 according to the invention increases the flowability (in the sense of a reduction in overall viscosity), which in turn makes it possible to achieve the same flow path lengths FI as without gas bubbles 102 but with a lower dosing temperature.

[0063] Furthermore, component 100 exhibits low shrinkage. The reduction in shrinkage of component 100 according to the invention, caused by the gas bubbles 101, results in a more homogeneous surface and prevents microscale orange peel. Thus, a high-gloss finish can be achieved on both the inside and outside of the tubular or tubular base body 101, which, due to reduced shrinkage, shows no tendency to scratch the surface, particularly during forming.

[0064] The volume fraction of gas bubbles 102 in the base body 101 is, in particular, between 0.3% and 8%. The gas bubbles 102 have a diameter between 1 micrometer and 100 micrometers. The size of the gas bubbles 102 can be adjusted, for example, by the choice of blowing agent, the temperature of the material during injection molding, and the cooling rate.

[0065] The base body 101 further comprises decomposition particles 104 of a gas-bubble-forming propellant. The decomposition particles 104 are present in the base body 101 and form solid decomposition residues of the original propellant as a byproduct of gas formation. The volume fraction of the decomposition particles 104 of the propellant in the base body is between 0.1% and 7%. The propellant is, in particular, a chemical propellant, which is especially exothermic, wherein, in particular, at least more than half of the decomposition particles 104 of the propellant have a diameter between 0.1 micrometers and 50 micrometers in the base body 101.

[0066] The gas bubbles 102 are further spaced apart from one another in the base body 101. By adding gas bubbles 102 according to the invention, these are present in the base body in such a quantity that they predominantly remain discreetly within the mass and do not develop a foamy character in which the gas bubbles 102 touch each other.

[0067] A ratio between the length (e.g., the greatest extent of the base body 101 in a spatial direction) of the base body 101 and the thinnest wall thickness d of the base body 101 can be greater than 50:1. This is correspondingly possible with the admixture of gas bubbles 102 and reinforcing fibers 103 according to the invention, since sufficient strength cannot be achieved due to the fiber orientation of the reinforcing fibers 103 not being parallel, i.e., at an angle α to the flow direction Fr.

[0068] The majority of the reinforcing fibers 103 in the base body 101 have a diameter between 2 micrometers and 100 micrometers. The reinforcing fibers 103 in the base body 101 have a length between 0.05 mm and 4 mm.

[0069] Fig. 2 Figure 1 shows a schematic representation of a component 100 with the corresponding gas bubbles 102 and reinforcing fibers 103 according to an exemplary embodiment of the present invention. Fig. 3 a component 100, which is present in an injection mold during injection closing.

[0070] The base body 101 contains a multitude of individual (spaced-apart) small gas bubbles 102, resulting in a low gas bubble concentration. This improves strength because the gas bubbles 102 in the injection mold push the reinforcing fibers 103 away from their longitudinal orientation in the flow direction, thus causing the reinforcing fibers to align transversely, i.e., at an angle α, to the flow direction Fr. The 'expanding' of the gas bubbles causes the reinforcing fibers 103 to align less parallel (i.e., the reinforcing fibers 103 are pushed away from their parallel alignment by a small, adjacent gas bubble 102). Particularly with chemical blowing agents, the pressure and the timing of gas bubble formation are easily controllable.

[0071] In Fig. 3The state at the end of the injection molding process, or at the beginning of cooling, is depicted. The gas bubbles 102 have expanded to their final size. It can be seen that the gas bubbles 102 have shifted the reinforcing fibers 103 in a somewhat more chaotic, i.e., transverse, orientation compared to a gas-free version of the component, resulting in higher strength due to improved interlocking. The internal pressure of the gas bubbles 102 also presses the outer zone against the injection mold wall during cooling, thus reducing shrinkage and improving surface quality. Furthermore, the gas bubbles 102 were able to take over the function of holding pressure, particularly at the end of the flow path FI (where the injection material is already somewhat stiffer than at the injection point (i.e., at the gate) and therefore the holding pressure on the injection side is less effective), thus enabling uniform outward shrinkage along the entire length of the component 100.

[0072] Furthermore, this addition of gas bubbles according to the invention increases the flowability (in the sense of a reduction in the overall viscosity), which in turn makes it possible to achieve the same flow path lengths FI as without gas bubbles but with a lower dosing temperature.

[0073] Fig. 4 Figure 400 shows a schematic representation of a manufacturing device according to an exemplary embodiment.

[0074] In the manufacturing device 400, a base body 101 of the component 100 is injection molded, wherein the base body 101 is produced with a wall thickness d of less than 1.9 mm and a plurality of gas bubbles 102 and reinforcing fibers 103 are embedded in the base body 101. A flow path length FI of the injection molded base body 101 is over 300 mm.

[0075] The manufacturing device 400 includes an injection mold 401 for injection molding the base body 101 of the component 100. The injection mold 401 can be over-dimensioned compared to conventional dimensions to achieve high dimensional stability. This particularly high stability of the tool allows for the minimization of surface defects (moulding) on ​​the closing edges of the injection mold 401 (i.e., on the contact areas of two mold halves of the injection mold 401, for example, if each mold half represents a pipe half-shell) to such an extent that no surface defects (mold edges, etc.) are present in the component 100 or in the base body 101.

[0076] As a starting material 405 for the base body 101, for example, plastic granules are fed into an extruder 404, in which the starting material 405 is liquefied. A chemical blowing agent is added to the starting material 405, whereby the gas production of the chemical component is activated later, for example, in the injection mold 401, by pressure and / or temperature. The liquefied starting material 405 is then injected under pressure into the injection mold 401 to form the base body 101. Reinforcing fibers 103 are also added as filler in the extruder 404. Furthermore, a physical blowing agent can be added as a solid via a blowing agent feeder 406 into the extruder 404, which then forms the gas bubbles 102 in the injection mold 401. The weight fraction of the blowing agent in the total material before injection molding is, for example, 1%.

[0077] In the injection molding of a pipe (tubular base body 101), the viscous injection molding material is forced between an outer wall of the injection mold 401 and an inner mandrel. As in Fig. 4As shown, the liquefied starting material 405 flows along the flow direction 403 in front of the injection mold 401 to the edge region of the injection mold 401. The gate 402 is located there, through which the liquefied starting material 405 is injected into the injection mold 401. The wall friction on the inner mandrel and the outer wall of the injection mold 401 generally leads to a strong parallel alignment of the reinforcing fibers 103 along the flow direction FI in the injection mold 401. The expansion of the gas bubbles 102, however, leads to a deflection effect of the reinforcing fibers 103 away from the parallel direction to the flow direction FI, so that the bracing of the reinforcing fibers 103 is achieved and higher strength is generated in the transverse direction of the pipe.

[0078] The melt flow rate (MFI) of a material (e.g., the liquefied starting material 405) during the injection molding of the base body 101 can be set above 200 g / 10 min. Such a higher melt flow rate can be achieved, for example, by increasing the temperature of the injected liquefied starting material 405 (e.g., a plastic).

[0079] After injection molding the base body 101, particularly in a tubular shape, ends in an end zone 407 can be cut off to remove defective end sections. For example, 2 mm to 5 mm can be cut off from a longitudinally shaped end of the base body 101. The end zone 407 comprises, for example, less than 30% of the total length of the flow path Fr of the injection mold 401. This reduces defective or low-quality start and end areas that need to be cut off, especially in the case of a tubular base body 101, and thus reduces the amount of waste.

[0080] In particular, during injection molding, the blowing agent reacts exothermically and generates gas bubbles 102 and decomposition particles 104 in the base body 101, wherein the blowing agent is added via a blowing agent supply 406 before injection molding in such a way that, after injection molding, at least more than half of the decomposition particles 104 of the blowing agent have a diameter between 0.1 micrometers and 50 micrometers.

[0081] Furthermore, the injection mold 401 of the manufacturing device 400 has at least one vent in the end zone 407 of a flow path of the injection mold 401, wherein the vent is designed to create a vacuum within the injection mold 401. For example, a vacuum pump 408 can be connected to the end zone 407. The injection mold 401 can thus be evacuated during injection molding. This leads to increased formation of gas bubbles 102 and a higher flow rate of the starting material 405. The same effect can be achieved by different temperature zones in the injection mold 401. It should also be noted that "comprehensive" does not exclude any other elements or steps, and "one" or "a" does not exclude a plurality.

[0082] Reference numerals in the claims are not to be regarded as limitations. Reference symbol list:

[0083] 100 Component 101 Base body 102 Gas bubble 103 Reinforcing fiber 104 Decomposition particle 400 Manufacturing device 401 Injection mold 402 Gate 403 Flow direction before the injection mold 404 Extruder 405 Starting material 406 Blowing agent feed 407 End zone 408 Vacuum pump dWall thickness FIFlow path length FrFlow direction αAngle

Claims

1. A component (100), comprising an injection-molded base body (101), wherein the base body (101) has a wall thickness (d) of less than 1.9 mm, wherein a plurality of gas bubbles (102) and reinforcing fibers (103) are embedded in the base body (101), wherein a flow path length (Fl) of the injection-molded base body (101) is over 300 mm, characterized in that the base body (101) comprises decomposition particles (104) of a gas bubble-forming blowing agent, wherein a volume fraction of the decomposition particles (104) of the blowing agent in the base body (101) is 0.1% to 7%.

2. The component (100) according to claim 1, wherein the flow path length (FI) is over 380 mm, in particular over 450 mm, further in particular over 500 mm.

3. The component (100) according to claim 1 or 2, wherein the wall thickness (d) is below 1.8 mm, in particular below 1.7 mm, further in particular below 1.5 mm, further in particular below 1.4 mm.

4. The component (100) according to any one of claims 1 to 3, wherein the fiber content of the reinforcing fibers (103) in the base body (101) comprises 5 wt.% to 60 wt.%, in particular 10 wt.% to 50 wt.%, further in particular 20 wt.% to 40 wt.%.

5. The component (100) according to any one of claims 1 to 4, wherein the component comprises at least one of the following features: wherein the base body (101) comprises at least one tubular section, wherein the base body (101) is in particular formed as a tube, wherein the base body (101) is formed such that the base body (101) withstands a temperature shock cycle test in a temperature range between -30 °C and +90 °C, in particular between -40 °C and 120 °C.

6. The component (100) according to any one of claims 1 to 5, wherein the gas bubbles (102) have a diameter between 1 micrometer to 100 micrometers, in particular 2 micrometers to 50 micrometers, further in particular 2 micrometers to 10 micrometers.

7. The component (100) according to any one of claims 1 to 6, wherein the base body (101) comprises a volume fraction of gas bubbles (102) between 0.3% to 8%.

8. The component (100) according to any one of claims 1 to 7, wherein in particular a volume fraction of the decomposition particles (104) of the blowing agent in the base body (101) is between 0.3% to 4%, in particular between 0.5% to 2%, wherein the blowing agent is in particular a chemical blowing agent which is in particular exothermically reactive, wherein in particular at least more than half of the decomposition particles (104) of the blowing agent have a diameter between 0.1 micrometer to 50 micrometers, in particular between 1 micrometer to 3 micrometers.

9. The component (100) according to any one of claims 1 to 8, wherein the gas bubbles (102), in particular at least 80% of all gas bubbles (102), are present spaced apart from one another in the base body (101).

10. The component (100) according to any one of claims 1 to 9, wherein a ratio between the length of the base body (101) and the thinnest wall thickness (d) of the base body (101) is greater than 50:1, in particular greater than 100: 1, further in particular greater than 200:1, wherein the plurality of reinforcing fibers (103) in the base body (101) in particular comprise a diameter between 2 micrometers and 100 micrometers, in particular between 5 micrometers to 24 micrometers, and / or wherein the plurality of reinforcing fibers (103) in the base body (101) comprise a length between 0.05 mm and 4 mm, in particular between 0.1 mm and 1 mm.

11. A method for manufacturing a component (100) according to any one of claims 1 to 10, the method comprising injection molding a base body (101) of the component (100), wherein the base body (101) has a wall thickness (d) of less than 1.9 mm, wherein a plurality of gas bubbles (102) and reinforcing fibers (103) are embedded in the base body (101), and wherein a flow path length (FI) of the injection-molded base body (101) is over 300 mm, wherein the base body (101) is formed along a flow path of an injection mold (401) during the injection molding, characterized in that negative pressure is applied within the injection mold (401) in an end zone (407) of the flow path of the injection mold (401) via vents in the injection mold, and in that the end zone (407) forms less than 30% of the total length of the flow path of the injection mold (401).

12. Use of the component (100) according to any one of claims 1 to 10 in a motor vehicle.