Production of an automotive part

Abstract

There is provided a method for production of an automotive part comprising the steps of: a. Providing a composition comprising 40-95 wt% by dry weight of a polymer and 5-60 wt% by dry weight of lignin; b. Supplying a physical blowing agent (PBA) to the composition to obtain a pressurized composition; c. Injection molding the pressurized composition to an automotive part.

Description

PRODUCTION OF AN AUTOMOTIVE PART TECHNICAL FIELD

[0001] The present disclosure relates to the field of injection moulding of plastics and in particular to production of an injection moulded automotive part.BACKGROUND

[0002] Injection moulding is a widely used manufacturing process designed to produce parts by injecting molten material into a mould. Injection moulding is typically used for plastics. The process begins with the preparation of raw material, usually in pellet form, which is fed into a hopper and melted inside a heated barrel. Once melted, the material is injected into a mould cavity under high pressure using a screw or plunger mechanism. The material then cools and solidifies inside the mould, conforming to its shape. After cooling, the solidified part is ejected from the mould, and the process is repeated for mass production.

[0003] In injection moulding applications, there is a desire to balance lightweighting of materials and production speed with reduced carbon emissions and desirable mechanical properties. Such applications include automotive parts being parts which are used in cars, motorcycles, trucks, buses or tractors.SUMMARY

[0004] According to a first aspect of the present disclosure there is provided a method for production of an automotive part comprising the steps of:a. Providing a composition comprising 40-95 wt% by dry weight of a polymer and 5-60 wt% by dry weight of lignin;b. Supplying a physical blowing agent (PBA) to the composition to obtain a pressurized composition;c. Injection moulding the pressurized composition to an automotive part.

[0005] The method provides production of automotive parts with a combination of lightweighting of materials, beneficial production speed, reduced carbon emissions compared with conventional plastics and desirable mechanical properties. Moreover, the surface finish of the parts has been found beneficially smooth.[ooo6] The PBA is typically a fluid, such as a gas. The fluid is typically selected from the group of: nitrogen (N2), carbon dioxide (CO2), air, hydrofluorocarbons (HFCs), hydrocarbons (HCs), hydrochlorofluorocarbons (HCFCs), helium (He), argon (Ar), methane (CH4), ethane (C2H6) or compositions thereof.

[0007] The polymer is typically a polyolefin or a copolymer comprising styrene and acrylonitrile or a polyamide or a polyester. The polyolefin is typically polypropylene (PP) or polyethylene (PE). The copolymer comprising styrene and acrylonitrile is acrylonitrile butadiene styrene (ABS) or acrylonitrile styrene acrylate (ASA) or styrene acrylonitrile (SAN).

[0008] The automotive part is a foamed automotive part. By addition of the PBA to the polymer and lignin, the composition foams and produces a porous, cellular structure. The cellular structure is made up of gas-filled cells or bubbles within a solid matrix comprising polymer and lignin.

[0009] The composition typically comprises 5-50 wt% lignin, such as 5-45 wt% lignin, such as 5-40 wt% lignin, such as 7-40 wt% lignin, such as 10-40 wt% lignin by dry weight of the composition.

[0010] The composition typically comprises 50-95 wt%, such as 55-95 wt%, such as 60-95 wt%, such as 60-93 wt%, such as 60-90 wt% polymer by dry weight of the composition.

[0011] The PBA is typically supplied to the composition in an injection moulding device comprising a hopper part, an extruder part and a mould part in that order. The PBA is in a preferred embodiment supplied to the hopper part, i.e. upstream of the extruder part.

[0012] The PBA may be supplied to the composition using a pressure of 5-30 bar. In such case, the PBA is typically supplied to the hopper part. Alternatively, the PBA is supplied to the composition using a pressure of 100-600 bar, such as 110-500 bar. In such case, the PBA is typically supplied to the extruder part.

[0013] According to a second aspect of the present disclosure, there is provided an automotive part produced by the method of the first aspect of the present disclosure.

[0014] According to a third aspect of the present disclosure, there is provided use of the part according to the second aspect in an automotive vehicle.BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Fig 1 shows an example of an injection moulding device.

[0016] Fig 2 shows an example of an injection moulding device.

[0017] Fig 3 shows maximum tensile strength of samples produced with PP as polymer.

[0018] Fig 4 shows strain at break of samples produced with PP as polymer.

[0019] Fig 5 shows maximum tensile strength of samples produced with ABS as polymer.

[0020] Fig 6 shows strain at break of samples produced with ABS as polymer. DETAILED DESCRIPTION

[0021] According to a first aspect of the present disclosure there is provided a method for production of an automotive part comprising the steps of:a. Providing a composition comprising 40-95 wt% by dry weight of a polymer and 5-60 wt% by dry weight of lignin;b. Supplying a physical blowing agent (PBA) to the composition to obtain a pressurized composition;c. Injection moulding the pressurized composition to an automotive part.

[0022] The method provides production of automotive parts with a combination of lightweighting of materials, beneficial production speed, reduced carbon emissions compared with conventional plastics, reduced energy consumption in manufacturing and desirable mechanical properties. Moreover, the surface finish of the parts has been found beneficially smooth.

[0023] The method can be conducted in an arrangement such as the one described in DE102014212048 Al. In such case, the injection moulding can be conducted in an injection moulding arrangement as the one described hereinafter. Such arrangement is also known as a Ku-Fizz arrangement.

[0024] The arrangement comprises an injection moulding device comprising a hopper part having an input chamber for feeding material to be injection moulded, a metering arrangement, a process fluid source for providing a process fluid in the formof a process gas, i.e. a PBA, and a material storage for storing or holding the material to be injection moulded, an extruder part and a mould part for moulding. In the hopper part, the material storage forms a first region, which has a first pressure level Pi. The first pressure level Pi is typically at ambient pressure (atmospheric pressure). The input chamber forms a second area, which is pressurized with the process fluid as a propellant or foaming gas, whereby the process fluid has a second pressure level P2 that is higher than the first pressure level Pi. The pressure at which the material is pressurized with at the second pressure level P2 is up to 200 bar, in particular up to 50 bar. The process fluid source, being part of a process fluid reservoir, may comprise, for example, a gas-filled pressure bottle and / or a gas-conveying pressure pump. The metering arrangement is set up for transferring desired quantities of the material to be injection moulded from the first area to the second area.

[0025] The metering arrangement comprises a material lock and a dosing device with a material inlet, which is connected to the first area or the material storage in order to receive material to be injection moulded from there, and a material outlet for dispensing the material to the material lock. The material lock has a linear and vertically extending lock passage formed in a pipe part and two valves each formed as a ball valve, which are integrated into the lock passage at a predetermined distance from each other, so that a lock chamber is formed in the distance between the two valves. Due to the integration of the two valves an entry passage is formed on a side of the upper first valve of the two valves facing away from the lock chamber from the lock passage and an exit passage is formed on a side of a lower second valve of the two valves facing away from the lock chamber from the lock passage. To the lock chamber as well as downstream of the lower valve, process fluid can be supplied to provide the pressure P2 to the material prior to being supplied downstream to the extruder part.

[0026] Alternatively, the method can be conducted in an arrangement such as the one being described in EP0952908 A2. In such case, the injection moulding can be conducted in an injection moulding arrangement as the one described hereinafter. Such arrangement is also known as a MuCell arrangement.

[0027] The arrangement comprises a hopper part, an extruder part and a moulding part. The extruder part is having an inlet designed to receive material fromthe hopper part, and an enclosed passageway, i.e. a barrel, connecting the inlet with a moulding part.

[0028] Along the barrel is at least one port in fluid communication with a source of an PBA. A pressure and metering device is typically provided between the PBA source and that at least one port. The device can be used to meter the PBA so as to control the amount of the PBA in the polymeric stream within the extruder to maintain the amount of PBA at a desired level. Within the extruder part, the polymeric material and PBA are advanced as a fluid stream in a downstream direction from the inlet end toward the moulding part.

[0029] The PBA is in this arrangement introduced at a supercritical state into the polymeric melt in the extruder part, i.e. into a barrel of the extruder part, and allowing the polymeric melt to expand and fill the tool cavity, creating a cellular structure when formed in the moulding part.

[0030] Both these techniques serve as non-limiting examples of techniques and arrangements that can be used to conduct the method.

[0031] In a preferred embodiment, the PBA is supplied to the composition in an injection moulding device comprising a hopper part, an extruder part and a mould part in that order. As is clear to the skilled person, an extruder part is the part of the injection moulding device comprising a barrel encasing at least one screw, and the barrel has heating element(s) to heat material inside the barrel. The mould part is the part of the injection moulding device comprising a mould and hopper part is the part for provision of the polymeric composition to the extruder part, typically comprising a hopper. For the avoidance of doubt, the hopper part is arranged upstream of the extruder part and the extruder part is arranged upstream of the mould part. In a preferred embodiment, the PBA is supplied to the hopper part, i.e. upstream of the barrel of the extruder part. In such case, it is beneficially supplied at a pressure of 5-30 bar, typically supplied in a gaseous state. Alternatively, the PBA is supplied to the barrel of the extruder part. In such case, it is beneficially supplied at a pressure of 100-600 bar, such as 110-500 bar. In the latter case it is typically supplied at a supercritical state. Supplying the PBA to the hopper part is advantageous as a pressure of 5-30 bar can be used and such lower pressure is beneficial from a perspective of cost efficiency, it is more economically favourable to operate at a lower pressure, as well that the process is less complicated.

[0032] Accordingly, all steps a., b. and c. can be conducted in an injection moulding device. For example, the composition in step a. can be provided into the hopper followed by supplying the PBA in the hopper or extruder part, followed by injection moulding into the automotive part.

[0033] The automotive part is preferably a thermoplastic automotive part.Thermoplastic parts, as opposed to thermoset parts, are easier to recycle as they can be melted and reshaped multiple times, which is a key advantage in terms of sustainability and reducing waste.

[0034] Thermoplastics also have advantageous mechanical properties over thermosets. Thermoplastics are generally tougher and more flexible than thermosets. This makes them suitable for applications that require high durability, flexibility, and the ability to withstand deformation without breaking. Further, thermoplastics are also more impact-resistant because they are flexible and can absorb energy by deforming. This flexibility allows them to resist cracking or breaking under stress. Thermosets, on the other hand, are typically more rigid and can become brittle, making them more prone to cracking under impact. The lower flexibility is also a disadvantage, in particular in automotive applications where flexibility is desirable.

[0035] Thermosets are crosslinked materials that have been physically crosslinked by a crosslinker. An example of a crosslinker is a peroxide. Another example is a chain extender having at least two reactive groups capable of forming polymer-polymer or polyester-lignin chain bonds. Accordingly, the composition is preferably free of any crosslinkers, such as peroxides and said chain-extenders.

[0036] The addition of lignin provides an advantageously low cycle time when preparing specimens according to the method of the present disclosure. A reduction in cycle time is beneficial as it improves production efficiency as more parts can be produced in a certain amount of time as further explained in the EXAMPLES’ section. Moreover, as the part can be produced as a thermoplastic, this also improves cycle times over thermosets as there is no need to conduct any crosslinking reaction.

[0037] The process temperature can also be kept lower when preparing specimens according to the method of the present disclosure. Heating up equipment is energy demanding and to thereby making it possible to work at a lower temperature is advantageous.

[0038] As is further explained in the EXAMPLES’ section, the use of lignin together with polymers in the foamed materials is also advantageous with respect to mechanical properties.

[0039] Accordingly, a combination of faster production rate, lower specimen weights, decreased energy consumption in terms of lower processing temperatures and yet desirable mechanical properties are all advantages of the method of the present disclosure.

[0040] In one preferred embodiment, the PBA is provided to the hopper part or the extruder part. The inventors have realized that by producing the part in an injection moulding device and provide the PBA to the hopper part or the extruder part, a thermoplastic foamed part combining advantageous mechanical properties with recyclability can efficiently be produced. Commonly, mixing lignin into plastics and PBA, if present, requires a pre-mixing step due to the difference in chemical nature of lignin and plastics for provision of a homogeneous material with the PBA. The inventors realized that both polymer and lignin are homogeneously mixed with the PBA providing a homogeneous material when the PBA is supplied to the injection moulding device, i.e. to the hopper part or the extruder part. That is, such pre-mixing step can be omitted. Yet another advantage of the realization of the inventors is that by mixing all components, including the PBA in the injection moulding device, production rate is efficiently improved over pre-mixing of components that thereafter are supplied to an injection moulding device. Finally, the ability to produce foamed thermoplastic parts is of great advantage.

[0041] The PBA is typically a fluid, such as a gas. The fluid is typically selected from the group of: nitrogen (N2), carbon dioxide (CO2), air, hydrofluorocarbons (HFCs), hydrocarbons (HCs), hydrochlorofluorocarbons (HCFCs), helium (He), argon (Ar), methane (CH4), ethane (C2H6) or compositions thereof, preferably N2, CO2, air or compositions thereof. Whether the PBA is supplied as a gas is dependent on the pressure at which the fluid is exerted to when supplied. The PBA may be supplied to a sufficiently high pressure so that the PBA is provided as a fluid not being a gas, typically a supercritical fluid, or at a pressure where the PBA is a fluid in gas form. In case the PBA is supplied as a supercritical fluid it is preferably N2, CO2 or a composition thereof. On the other hand, in case the PBA is supplied as a gas it is preferably N2, air or a composition thereof.

[0042] There is no limitation in the source of the lignin. The lignin may be hardwood lignin or softwood lignin. The lignin can also be retrieved from crops, grass, bagasse, bamboo, kenaf, flax, hemp, rice husks, cotton stalks, coconut coir or corn stover. In the case of hardwood lignin or softwood lignin, the lignin is typically obtained from pulping of wood. When wood is pulped, the lignin is separated from the pulp into a liquor. The exact composition of the liquor varies and depends on the cooking conditions in the production process and the feedstock. There are various techniques to separate the lignin from the black liquor including Lignoboost® lignin, LignoForce™ lignin, precipitated lignin, and filtrated lignin. Other types of lignin directly extracted from wood are also possible to use and those includes acetosolv lignin, lignin from soda pulping, organosolv lignin and lignin from biorefinery processes. For the avoidance of doubt, lignosulfonates are also lignin in the meaning of the present disclosure. The lignin can be either used as received, i.e. unmodified, or chemically modified. From a practical perspective it may be preferred to use an unmodified lignin as no intermediate step of modifying the lignin is needed.Alternatively, the lignin has been modified via for example ether or ester linkages. The composition typically comprises 5-50 wt% lignin, such as 5-45 wt% lignin, such as 5-40 wt% lignin, such as 7-40 wt% lignin, such as 10-40 wt% lignin by dry weight. It is beneficial from an environmental perspective to replace the polymer matrix with as much lignin as possible, while providing a combination of lightweighting of materials, beneficial production speed, reduced carbon emissions compared with conventional plastics, desirable mechanical properties and smooth surface finish. Accordingly, a higher lignin content and lower polymer matrix content is preferred.

[0043] The polymer matrix is either a polyolefin or a copolymer comprising styrene and acrylonitrile or a polyamide or a polyester. The IUPAC gold book, i.e. the Compendium of Chemical Terminology, is a book published by the International Union of Pure and Applied Chemistry (IUPAC) containing internationally accepted definitions for terms in chemistry. In accordance with the gold book a copolymer is a polymer derived from more than one species of monomer. Examples of copolymers are copolymers that are obtained by copolymerization of two monomer species sometimes termed bipolymers, copolymers obtained from three monomers sometimes termed terpolymers, and copolymers obtained from four monomers sometimes termed quaterpolymers. Hence, a copolymer comprising styrene and acrylonitrile is a copolymer at least comprising styrene and acrylonitrile asmonomeric units. Typically, the copolymer comprising styrene and acrylonitrile is acrylonitrile butadiene styrene (ABS) or acrylonitrile styrene acrylate (ASA) or styrene acrylonitrile (SAN). The polyester is typically a biodegradable or bio-derived polyester, such as polylactic acid (PLA) or polycaprolactone (PCL) or polybutylene adipate terephthalate (PBAT) or polybutylene succinate (PBS) or polyhydroxyalkanoate (PHA) or bio-derived polyethylene terephthalate (PET) or compositions thereof. The polyolefin is typically polypropylene (PP) or polyethylene (PE). Polyethylene (PE), is a plastic used in several applications, from packaging and containers to toys and furniture. There are different grades of PE including high-density polyethylene (HDPE), low-density polyethylene (LDPE) and low-density polyethylene (LLDPE). Likewise, there are different grades of PP. The PE and / or PP maybe virgin PE, i.e. made form non-recycled material, the PE and / or PP may also be recycled that has been reprocessed from post-consumer or post-industrial waste, turning it back into a usable material. Recycled PE / PP is beneficial as it reduces plastic waste, conserves resources, reduces energy consumption, and minimizes environmental impact. Often the lower degree of purity of recycled PE / PP is negative for the mechanical properties of material from it. However, the inventors have realized that with the process and compositions of the present disclosure this negative effect is reduced or even omitted. Thereby, products containing a high level of recycled PE / PP in combination with lignin can be provided.

[0044] The composition typically comprises 50-95 wt%, such as 55-95 wt%, such as 60-95 wt%, such as 60-93 wt%, such as 60-90 wt% polymer by dry weight of the composition.

[0045] Preferably, the composition contains a low amount of reinforcing agents other than lignin as those affects the combination of weight reduction and environmental impact negatively. Such reinforcing agents includes glass fibres, carbon fibres, aramid fibres, metal fibres, carbon nanotubes, graphene and natural fibres, such as cellulosic fibres, jute fibres, hemp fibres or flax fibres. Such low amount is preferably < 10 wt%, such as < 7 wt %, such as < 5 wt %, such as < 3 wt% based on dry weight of the composition, such as that the composition is substantially free of other reinforcing agents than lignin. Likewise, typically at least 90 wt% by dry weight of the composition, such as at least 95 wt% by dry weight of the composition,such as at least 97 wt% by dry weight of the composition consists of the lignin and the polymer matrix.

[0046] Typically, the density of the composition is reduced by at least 5%, such as at least 7 % when injection moulded to an automotive part. The density of the composition before injection moulding can suitably be measured according to ISO 1183-1:2019 on samples produced according to ISO 1872-2:1997. The density of the injection moulded part can suitably be measured according to ISO 845:2006.

[0047] As a second aspect of the present disclosure there is provided an automotive part produced by the method of the first aspect of the present disclosure.

[0048] Automotive parts are used in automotive applications, i.e. cars, trucks, motorcycles, busses and tractors. Non-limiting examples of automotive parts are those used in seats and cushions or headliners or door panels or carpet underlays or bumpers or energy absorbers or armrests or steering wheel padding or pillars or interior trims or insulation or soundproofing or headrests or cargo area liners or engine covers or sun visors.

[0049] For the avoidance of doubt, automotive parts are those parts having an intended use in automotive applications.

[0050] The examples and embodiments discussed above in connection to the first aspect apply to the second aspect mutatis mutandis.

[0051] As a third aspect of the present disclosure there is provided use of the part according to the second aspect of the present disclosure in an automotive vehicle.

[0052] The inventive concept will now be described more fully hereinafter with reference to the accompanying drawings, in which exemplifying embodiments are shown. The inventive concept may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided by way of example so that this disclosure will be thorough and complete, and will fully convey the scope of the inventive concept to those skilled in the art. Like numbers refer to like elements throughout the description.

[0053] Fig. 1 shows an example of an injection moulding device 1 that the method of the first aspect can be used with. The injection moulding device comprises an extruder part 101, a mould part 102 and a hopper 103. The extruder part 101comprises a barrel 104, a screw 105, heating elements 106 and a nozzle 107. The mould part 102 comprises a mould 108. The polymeric composition is provided to the extruder part 101 through the hopper 103. The hopper 103 comprises an arrangement 109 for providing PBA to the polymeric composition not being melted and present in the hopper 103. The polymeric composition together with PBA is provided to the extruder part 101 entering the barrel 104 arranged downstream from the hopper 103 and transported forward in the barrel 104 by the screw 105. While being transported, the polymeric composition is melted by heat provided by the heating elements 106 so that when reaching the nozzle 107 the polymeric composition is melted. From the nozzle 107 the polymeric composition is provided to the mould part 102 comprising a mould 108. In the mould the polymeric composition is allowed to cool so that an automotive part is formed. The PBA is provided with a pressure of 5-30 bar. The injection moulding device in this example is a single-screw injection moulding device. However, it should be mentioned that that the injection moulding device could be a double screw injection moulding device.

[0054] Fig. 2 shown another example of an injection moulding device 2 that the method of the first aspect can be used with. The injection moulding device comprises an extruder part 101, a mould part 102 and a hopper 103. The extruder part 101 comprises a barrel 104, a screw 105, heating elements 106 and a nozzle 107. The mould part 102 comprises a mould 108. The polymeric composition is provided to the extruder part 101 through the hopper 103. The barrel 104 comprises an arrangement 209 for providing PBA to the at least partly melted polymeric composition present in the barrel 104. The PBA is provided with a pressure of 100-600 bar. The injection moulding device in this example is a single-screw injection moulding device.However, it should be mentioned that the injection moulding device could be a double screw injection moulding device.EXAMPLESPreparation of compositions

[0055] Different compositions were pre-mixed at room temperature using the following: polypropylene (PP) being either virgin PP (vPP) or recycled PP (rPP), acrylonitrile butadiene styrene (ABS), lignin, glass fibers (GF) and cellulosic fibers.The compositions of each composition are presented below in Table 1. All components are given in wt% on about the dry weight of the respective compositions.

[0056] All compositions were thermoplastic compositions.

[0057] The vPP was either Moplen EP300K (IE1-IE3) or Sabie 58NK10 (IE4-IE8). The rPP was supplied by Swerec. In case of PP with GF, the PP was PP Polyfill PPH GF5020PD being a GF-reinforced PP. PP reinforced with cellulose fibers was UPM Formi HP 30. The ABS was Cycolac MG47.Table 1. Compositions prepared.Preparation of specimens from the compositions

[0058] For each composition, there were 2 specimens prepared: one specimen using a conventional injection moulding technique and one specimen using the arrangement and method described in DE102014212048 Al, hereinafter referred to as “Microcellular”, as a foamed composition was produced as opposed to with the conventional injection moulding technique.

[0059] The arrangement for microcellular comprises an injection moulding device comprising an extruder part with a barrel equipped with heating elements. Inside of the barrel is a screw. Upstream of the extruder there is a hopper part comprising an input chamber for feeding material to be injection moulded, a metering arrangement, a process fluid source for providing a process fluid in the form of a process gas, i.e. a PBA, and a material storage for storing or holding the material to be injection moulded. The material storage forms a first region, which has a first pressure level Pi being ambient pressure. The input chamber forms a second area, which is pressurized with the PBA, whereby the PBA is supplied at a second pressure level P2 that is higher than the first pressure level Pi.

[0060] In the conventional injection moulding technique an after pressure, i.e. holding pressure, of 550 bar was applied and using the microcellular device and method a second pressure level P2 of 22-24 bar using nitrogen gas (N2) as PBA was applied to the compositions prior to being fed to the extruder part of the device.

[0061] For the avoidance of doubt, the inventive examples (IE) refers to the inventive compositions as foamed materials. The same compositions, produced in a non-foamed way are not part of the invention and are therefore comparative examples (CE). Likewise, comparative compositions as foamed materials are comparative examples.Evaluation of cycle times of the process

[0062] The cycle times of injection mouldings in seconds were measured using either the conventional injection moulding or the microcellular process and time reduction using microcellular compared with conventional injection moulding was calculated. The results are presented in Table 2 below.Table 2. Cycle times.N.M.: Not Measured;a“Microcellular” is the inventive example

[0063] The addition of lignin provided a significant reduction in cycle times when using microcellular compared with the convention injection moulding technique. Moreover, the lower holding pressure is also beneficial, as it facilitates the process.Evaluation of process temperature

[0064] The process temperature of the different composition during microcellular injection moulding was measured as average temperature in the barrel and nozzle temperature. The results are presented in Table 3 below.

[0065] Table 3. Process temperatures.[oo66] The inventive examples containing PP (IE1-IE8) could be run with an average temperature of 170 °C and a nozzle temperature of 180 °C, whereas the comparative examples containing PP (CE1-CE2) needed an average temperature of 180 °C and a nozzle temperature of 190 °C to provide a desirable melt flow and filling behaviour. The comparative example (CE6) containing PP and glass fibres even required with an average temperature of 214 °C and a nozzle temperature of 225 °C.

[0067] Likewise, the inventive example containing ABS (IE9) could be run with an average temperature of 201 °C and a nozzle temperature of 215 °C, whereas for the comparative example containing ABS (CE5) it was required an average temperature of 217 °C and a nozzle temperature of 235 °C to provide a desirable melt flow and filling behaviour.

[0068] Hence, the lignin contributes with aiding in decreasing necessary temperatures in injection moulding, which is beneficial from an energy perspective.Evaluation of the specimens with respect to weight reduction

[0069] The test specimens were evaluated in terms of weight reduction when comparing the conventional injection moulding process with the microcellular process. The results are presented in Table 4 below.

[0070] Table 4. Weight reduction.a“Microcellular” is the inventive example

[0071] The specimens produced according to IE1-IE9 all displayed both a significant weight reduction and a low total weight by using microcellular compared with conventional. In addition, all inventive examples produced with PP as polymer using microcellular (IE1-IE8) provided a reduced sample weight compared with PP injection moulded with conventional injection moulding (CE4) and the inventive example (IE9) using ABS using microcellular provided a reduced sample weight compared with ABS injection moulded with conventional injection moulding (CE5).

[0072] Regarding CE3 no good foaming structure was obtained. Hence, as has been made clear from CE3 not all additives provides good foaming structures, and thereby a beneficially reduced weight. In CE4 and CE5 having no additives it was not possible to obtain a foaming structure and only conventional injection moulding could be used. Hence, leaving the plastic without any additives is not possible either for provision of a good foam structure. A good foam structure is important not only for lightweighting of a polymers, but also for taking advantage of reduced cycle times provided by the microcellular method compared with conventional injection moulding.Evaluation of the specimens with respect to mechanical properties Tensile properties in injection moulding direction

[0073] The specimens were evaluated by tensile testing in the injection moulding direction (“oo-direction”) by measuring maximum tensile strength as well as strain at break. The results are presented in Table 5 below. The results of tensile strength of IE4-IE8 and CE4 being PP as polymer are also presented in Figure 3 and the strain atbreak results in Figure 4. The results of tensile strength of IE9 and CE5 being ABS as polymer are also presented in Figure 5 and strain at break results in Figure 6.

[0074] In Figures 3-6 the filled circles represent conventional injection moulding and the hollow circles represent microcellular.Table 5. Results of tensile testing in the injection moulding direction, “oo-direction”.N.M. Not Measured;a“Microcellular” is the inventive example

[0075] As shown in Figures 3-6 as well as Table 5, inclusion of lignin in respective polymers and running the microcellular process provide comparable mechanical properties to those of the specimens produced by conventional injection moulding.

[0076] Moreover, the use of glass fibres (CE7) decreased the strain at break of the PP (CE4) while the use of lignin even shown an increase in strain at break of the PP in most cases.Tensile properties in injection moulding cross direction

[0077] The tensile properties in cross direction, i.e. perpendicular to the flow of polymer melt into the mould in the finished specimen was also measured (“90-direction”). The results from the tensile measurements in the perpendicular, “90”, direction are presented in Table 6 below. The isotropy of the specimens was also evaluated by calculating the ratio of maximum tensile strength in “00” direction and “90” direction. A value being 1 or close to 1 means that the material is isotropic. A high or low value means, on the other hand, that the material is isotropic.Table 6. Results of tensile testing in the injection moulding cross direction, “90-direction”.N.M. Not Measured;a“Microcellular” is the inventive example

[0078] Just as for the tensile measurements in “00” direction, the use of glass fibres (CE7) significantly decreased the strain at break of the PP (CE4). The use of lignin, on the other hand, provided a higher strain at break than inclusion of glass fibres.

[0079] Regarding isotropic properties, the use of lignin provides a substantially isotropic material having a tensile ratio close to 1, whereas glass fibres, on the other hand, provides a heavily anisotropic material. It is generally considered advantageous to produce isotropic specimens as it is desirable to provide strength properties in all directions when in use as part of an automotive vehicle.

[0080] Accordingly, a combination of faster production rate, lower specimen weights, decreased energy consumption in terms of lower processing temperatures and yet comparable mechanical properties are obtained for the inventive examples compared to the comparative examples. In addition, beneficially isotropic mechanical properties are provided.

Claims

CLAIMS1. Method for production of an automotive part comprising the steps of:a. Providing a composition comprising 40-95 wt% by dry weight of a polymer and 5-60 wt% by dry weight of lignin;b. Supplying a physical blowing agent (PBA) to the composition to obtain a pressurized composition;c. Injection molding the pressurized composition to an automotive part.

2. The method of claim 1, wherein the PBA is a fluid or a gas.

3. The method of claim 2, wherein the gas is selected from the group of: nitrogen gas (N2), carbon dioxide (CO2), air, hydrofluorocarbons (HFCs), hydrocarbons (HCs), hydrochlorofluorocarbons (HCFCs), helium (He), argon (Ar), methane (CH4), ethane (C2H6) or compositions thereof.

4. The method according to any one of the preceding claims, wherein the polymer is a polyolefin or a copolymer comprising styrene and acrylonitrile or a polyamide or a polyester.

5. The method according to claim 4, wherein the polyolefin is polypropylene (PP) or polyethylene (PE).

6. The method according to claim 4 or 5, wherein the copolymer comprising styrene and acrylonitrile is acrylonitrile butadiene styrene (ABS) or acrylonitrile styrene acrylate (ASA) or styrene acrylonitrile (SAN).

7. The method according to any one of the preceding claims, wherein the composition comprises 5-50 wt% lignin, such as 5-45 wt% lignin, such as 5-40 wt% lignin, such as 7-40 wt% lignin, such as 10-40 wt% lignin by dry weight.

8. The method according to any one of the preceding claims, wherein the composition comprises 50-95 wt%, such as 55-95 wt%, such as 60-95 wt%, such as 60-93 wt%, such as 60-90 wt% polymer by dry weight of the composition.

9. The method according to any one of the preceding claims, wherein the PBA is supplied to the composition in an injection moulding device comprising a hopper part, an extruder part and a mould part in that order.

10. The method according to claim 9, wherein the PBA is supplied to the hopper part.

11. The method according to any one of the preceding claims, wherein the PBA is supplied to the composition using a pressure of 5-30 bar.

12. The method according to claim 9, wherein the PBA is supplied to the extruder part.

13. The method according to claim 12, wherein the PBA is supplied to the composition using a pressure of 100-600 bar, such as 110-500 bar.

14. The method according to any one of the preceding claims, wherein the automotive part is a thermoplastic automotive part.

15. An automotive part produced by the method according to any one of the preceding claims.

16. Use of the part of claim 15 in an automotive vehicle.

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