Method for producing long-fiber thermoplastic resin materials

Abstract

A method for manufacturing long-fiber thermoplastic resin materials is provided. [Solution] A method for producing a long-fiber thermoplastic resin LFT extruded material, comprising the steps of preparing a thermoplastic resin supply material and a thermoplastic resin composite TPC supply material, wherein the TPC supply material comprises fragments, each fragment comprising both fibers and thermoplastic resin material, the method comprising an extrusion step carried out in an extrusion system (I), the extrusion system comprising an extruder 2 having an extrusion direction ED, the extruder comprising a barrel 3, a single-screw 4, a first inlet opening 6 and an outlet opening 5, the screw providing a flow path within the extruder, the extrusion step comprising supplying the thermoplastic resin supply material and the TPC supply material to the extruder, sending a mixture of the thermoplastic resin supply material and the TPC supply material to the outlet opening to obtain a mixed material C, and then extruding the mixed material C through the outlet opening to obtain an LFT extruded material D.

Description

Technical Field

[0001] The present invention relates to a method for producing a long fiber thermoplastic resin (LFT) extruded material. In a preferred embodiment, the method comprises the step of feeding a single feed stream comprising a mixture of a thermoplastic resin feed material and a TPC feed material into an extruder. Background Art

[0002] Introduction In one aspect, the present invention relates to a method for producing a long fibre thermoplastic (LFT) material, particularly to a method for producing an LFT extruded material (extruded article). LFT materials are sometimes also referred to as long fiber reinforced thermoplastic resin materials. LFT extruded materials can be used in the manufacture of a wide range of products comprising LFT materials, for example, automotive parts such as automotive door panels, instrument carriers, front ends, and also parts in other fields such as electronics. LFT extruded materials are used, for example, as raw materials for injection molding to form LFT products. LFT extruded materials are, for example, cut into pellets, and the pellets are used for injection molding. Injection molding of LFT materials is known as such, and LFT pellets are often used as the feed material. Such LFT pellets are, for example, 5 to 15 mm in length, preferably about 11 mm in length, and have a diameter of, for example, 1 to 10 mm, for example 1 to 5 mm. Each LFT pellet comprises fibers (e.g., carbon fibers, glass fibers or natural fibers) together with a thermoplastic polymer.

[0003] Current exemplary methods for producing LFT pellets are based on wire coating or thermoplastic pultrusion using dry continuous fibers. Here, "dry" indicates that the fibers have not yet been embedded in, for example, a thermoplastic material. For example, in some prior art methods for producing LFT pellets, dry fibers are wire-coated with a thermoplastic polymer. Wire coating and pultrusion yield coated or impregnated fiber strands, respectively, which are dimensionally (e.g., cut) to pellets of, for example, 11 mm in length. Longer pellets are difficult to process by injection molding. In strands obtained by wire coating and pultrusion, the fibers are continuous and aligned. In each pellet produced by cutting such a strand, the fibers are aligned parallel to each other and extend in a parallel arrangement along the length of the pellet. In typical manufacturing methods for producing LFT pellets currently available, the fiber length is the same as the length of the pellet. Long fibers are desirable because they contribute to the mechanical properties of injection-molded LFT parts. Extrusion, other than pultrusion, is generally not used to produce LFT strands or pellets. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] US 2002 / 0089082 [Patent Document 2] EP 1008435B1 [Overview of the project] [Problems that the invention aims to solve]

[0005] It is desirable to provide a method for producing LFT material, such as LFT pellets, wherein the produced LFT material is suitable for further manufacturing processes for producing LFT articles, such as LFT injection molding or further extrusion processes, and the method is more economical and / or yields an LFT material with improved properties.

[0006] US 2002 / 0089082 describes a method for producing a fiber-reinforced resin composition, wherein an apparatus equipped with a twin-screw plasticizing extruder is used, and the molten resin and fiber material are combined at the inlet opening of the plasticizing extruder.

[0007] EP 1008435B1 describes a method for producing fiber-reinforced resin ingots using a plasticizing extruder, wherein fibers and thermoplastic resin granules and / or long fiber-reinforced recycled chips are plasticized and then extracted as a processable plasticized material. Large long fiber-reinforced recycled chips, approximately 50 mm in diameter and up to 200 mm in length, are weighed and fed into a heated tube worm conveyor in dosed portions, and preheated and dried until just before they become sticky. The chips are then fed into a plasticizing extruder. [Means for solving the problem]

[0008] In a first embodiment, the present invention provides a method for producing a material, such as an extruded material, preferably a long-fiber thermoplastic (LFT) extruded material. - A process for preparing thermoplastic resin supply material and thermoplastic resin composite (TPC) supply material, wherein the TPC supply material includes, for example, flakes or chips, and the TPC supply material includes fragments, for example, flakes or chips, and the fragments each include both fibers and thermoplastic resin material; the method includes an extrusion process carried out in an extrusion system; the extrusion system comprises an extruder having an extrusion direction; the extruder comprises a barrel, a single-screw, a first inlet opening and an outlet opening, the screw providing a flow path within the extruder; the extrusion process is, - Supplying thermoplastic resin supply material and TPC supply material to the extruder; - A mixture of thermoplastic resin supply material and TPC supply material in the extruder is sent to the discharge port opening, thereby obtaining a mixed material; and - The present invention relates to a method comprising extruding a mixed material through an outlet opening to obtain LFT extruded material. Preferably, these feeding, conveying, and extrusion steps are carried out in the order described above.

[0009] In a further embodiment, the present invention relates to a long-fiber thermoplastic (LFT) material obtained by this method. [Brief explanation of the drawing]

[0010] [Figure 1] This figure schematically shows the extrusion system of the first embodiment according to the present invention. [Figure 2A] Figure 2 schematically illustrates an exemplary method according to the present invention. In particular, Figure 2A shows an exemplary extrusion process and several other processes. [Figure 2B] Figure 2B shows some exemplary steps involved in bringing about TCP supplies. [Figure 2C] Figure 2C shows an embodiment that combines extrusion and injection molding. [Figure 3] This diagram schematically illustrates a comparative method for manufacturing LFT articles. [Figure 4] This figure shows the logarithmic scale of the fiber length distribution measured in a flake + MFI-50 injection molding bar. [Figure 5] This figure shows the flexural modulus, strength, and impact properties measured after processing the sample under the same conditions. [Figure 6] This diagram shows an example of an extruder layout. [Figure 7] This figure shows an example of calculating the D90 and D50 values ​​from a histogram. [Modes for carrying out the invention]

[0011] The figures are not intended to limit the present invention, but are merely illustrative.

[0012] Embodiments of the present invention are generally based on the reasonable insight that LFT materials, for example LFT pellets, which are suitable for producing LFT articles by for example LFT injection moulding and / or extrusion, extrusion moulding and / or compression moulding, can be advantageously produced by using an extrusion step carried out in an extruder provided with a screw, preferably a single-screw extruder, wherein both the thermoplastic resin material and the TPC feed material are fed into the extruder such that the TPC feed material is mixed with the thermoplastic resin material. It has surprisingly been found that this enables the reduction of fiber abrasion in the extrusion step.

[0013] As used herein, the abbreviation "TPC" stands for "thermoplastic composite".

[0014] The material fed to the extruder comprises a TPC feed material. The TPC feed material comprises, for example, TPC chips and / or TPC flakes. Other TPC feed materials may also be used. The TPC feed material comprises, for example, individual solid fragments of TPC material. The TPC feed material is provided, for example, as solid fragments of TPC material. Examples of the fragments include TPC chips and / or TPC flakes.

[0015] The abbreviation "LFT" means "long fibre thermoplastic". As used herein, long fibre thermoplastic material refers to a material comprising, consisting substantially of, or consisting essentially of a thermoplastic polymer and long fibres, wherein the polymer can be, for example, a neat polymer or a polymer mixed with additives. The long fibres have a representative length of 0.5 to 50 mm, more preferably 1 to 20 mm, most preferably 2 to 10 mm, and have a typical diameter of, for example, 1.0 to 100 μm, or 2 to 50 μm, most preferably 5 to 30 μm. In LFT materials, the long fibres are embedded in the thermoplastic polymer, for example, such as in the case of fibres impregnated with the thermoplastic polymer. In an exemplary embodiment, the TPC feedstock comprises an LFT material having fibres embedded in a thermoplastic polymer.

[0016] As used herein, thermoplastic composite (TPC) material refers to a material comprising, consisting substantially of, or consisting essentially of a thermoplastic polymer and fibres (dry fibres, impregnated short fibres, long fibres, and continuous fibres or mixtures thereof), wherein the polymer can be, for example, a neat polymer or a polymer mixed with additives, and the fibres are, for example, dry or impregnated, for example short fibres, long fibres, or continuous fibres or a mixture of any such fibres. As used herein, the TPC feedstock is, for example, an LFT feedstock. In some embodiments of the TPC feedstock, the fibres are embedded in the thermoplastic polymer, for example in the case of fibres impregnated with the thermoplastic polymer. The TPC feedstock, in particular fragments, comprises fibres having, for example, a length of long fibres, preferably at least 0.50 mm, at least 1.0 mm, or at least 2 mm, for example 0.5 to 50 mm, more preferably 1 to 20 mm, most preferably 2 to 10 mm, and optionally having a typical diameter of 1.0 to 100 μm, or 2 to 50 μm, most preferably 5 to 30 μm. Preferably, the TPC chips and / or TPC flakes fed to the extruder comprise fibres having such lengths.

[0017] The discrete solid pieces typically have at least one dimension that is at least 1.0 mm, and typically have at least two perpendicular dimensions that are at least 1.0 mm. The discrete solid pieces preferably individually comprise fibers and a thermoplastic resin material.

[0018] In an exemplary embodiment, the TPC feedstock may comprise flakes of TPC material having a thickness of at least 100 μm, typically less than 50 mm, and a minimum size in a direction perpendicular to the thickness direction of at least 1 mm, at least 10 mm, or at least 100 mm. Discrete pieces of the TPC feedstock generally have a size of less than 10 cm in at least one dimension. In particular, the discrete pieces have a size of less than 10 cm in three dimensions.

[0019] The TPC feedstock comprises, for example, TPC flakes and / or TPC chips. Such TPC flakes have, for example, a length of 2 mm to 40 mm, a width of 2 mm to 40 mm, and a thickness less than the length and / or less than 5.0 mm, for example a thickness of 0.1 mm to 4.0 mm. TPC chips have, for example, a length (L) of 2 mm to 50 mm, a width (W) of 2 mm to 50 mm, and a thickness (H) satisfying, for example, 0.1L < H < L. TPC flakes have an aspect ratio L / H of, for example, at least 10, such as at least 20. The TPC flakes have an end portion and two side surfaces, for example, at least 5 mm per each such side surface 2 or at least 10 mm 2 of surface area. TPC flakes having such dimensions are, for example, LFT flakes.

[0020] TPC flakes can be obtained, for example, by cutting or chopping the material from tape. TPC chips can be obtained, for example, by shredding CFRT (Continuous Fiber Reinforced Thermoplastic) material, such as by shredding laminates, or by shredding end-of-life portions of TPC material. TPC chips can be obtained, for example, as manufacturing waste from the CFRT sheet manufacturing process. TPC supply materials such as flakes and chips are typically abrasive due to their fiber content.

[0021] In some embodiments, the TPC supply material includes, for example, reduced-size (e.g., shredded) waste material, which contains or consists of TPC material. The TPC supply material is not limited to a specific thermoplastic polymer, nor is it limited to a specific fibrous material.

[0022] In a very preferred embodiment, the TPC supply material includes separated side edges (e.g., trims) of an impregnated fiber layer, such as an impregnated fiber tape or sheet. Such a tape is an intermediate step in a specific manufacturing method of a continuous fiber-reinforced material. The material may also be, for example, a CFRT material such as a CFRT sheet, or chips resulting from the shredding of a CFRT article such as a CFRT automotive part.

[0023] In some embodiments, the method for producing LFT extruded material according to the present invention results in the recycling of continuous fiber-reinforced thermoplastic (CFRT) waste. In some embodiments, the present invention relates to a method for producing LFT extruded material, comprising supplying such separated side ends as at least a portion of the feed stream.

[0024] Furthermore, in some embodiments, the TPC supply material is supplied at least partially by recycled streams from processes for manufacturing CFRT materials and CFRT components, elements, and articles, and / or recycled streams from used CFRT articles.

[0025] An advantage of this invention is that the TPC supply material used in this invention may be waste material. This results in the advantages of an environmentally friendly material processing method and economical TPC raw materials. This invention provides a method for recycling specific materials that have previously been considered waste material.

[0026] Furthermore, the method of the present invention provides a very efficient way to convert waste materials into high-quality recycled LFT materials, such as high-quality LFT pellets that can be used in LFT injection molding.

[0027] The thermoplastic resin supply material comprises a thermoplastic polymer, preferably one of the thermoplastic polymers discussed herein, preferably non-reinforced, and preferably containing less than 1.0% by mass of nonpolymer components. The thermoplastic resin supply material has, for example, an MFI of at least 50, measured according to ISO 1133-1. The thermoplastic resin supply material comprises, for example, a polyolefin having an MFI of at least 50, such as polypropylene. Lower viscosity may, advantageously, contribute to better mixing.

[0028] The method of the present invention includes the steps of supplying thermoplastic resin supply material and TPC supply material to an extruder, for example, supplying these materials to the extruder as a single combined flow after being preferably mixed. The method further includes the steps of sending the mixture of thermoplastic resin supply material and TPC supply material in the extruder, particularly in the flow path, toward the discharge opening to obtain a mixed material. The method further includes the steps of extruding the mixed material formed in the extruder through the discharge opening of the extruder to obtain LFT extruded material. In an integrated apparatus, the discharge opening may be the discharge opening of the extruder portion of the apparatus. The order of the steps indicates the position in a continuous process system.

[0029] In a first preferred method of the present invention, the thermoplastic resin feed material and the TPC feed material are supplied as a single flow of material in the extruder. In this preferred embodiment, the method of the present invention includes, for example, the step of supplying a single feed flow (Z) containing a mixture of the thermoplastic resin feed material and the TPC feed material to the extruder. The mixture contains, for example, at least 10% by mass of the thermoplastic resin feed material and at least 10% by mass of the TPC feed material, preferably, the total of the TPC feed material and the thermoplastic resin feed material constitutes at least 95% by mass or at least 99% by mass. The mass ratio of the TPC feed material to the thermoplastic resin feed material in the mixture can be adjusted so that a desired mass fraction of fibers is obtained in the product. Preferably, the mixture supplies at least 99% by mass of the total feed to the extruder, and preferably, is the sole feed to the extruder. In some embodiments, the mixture is supplied entirely to only one inlet opening of the extruder and not to two or more openings of the extruder. In some embodiments, one opening of the extruder receives at least 90% by mass of the total feed into the extruder, preferably the opening receives the feed as a single feed stream (Z).

[0030] In some embodiments, the single feed stream consists of TPC feed material, such as chips or tapes. Preferably, the feed stream supplies at least 99% by mass of the total feed to the extruder, and preferably, is the sole feed to the extruder. In some embodiments, the feed stream is supplied entirely to only one inlet opening of the extruder and not to two or more openings of the extruder. In some embodiments, one opening of the extruder receives at least 90% by mass of the total feed to the extruder, and preferably, this opening receives the feed as a single feed stream.

[0031] This single feed stream is supplied from the inlet opening to the flow path of the extruder. The method includes, for example, a step of mixing a thermoplastic resin feed material and a TPC feed material in a mixing unit to form a composite feed stream, and supplying this feed stream to the inlet opening of the extruder. The composite feed stream is granular, that is, composed of independent solid particles. The mixing unit may be integrated with the extrusion system or may be a separate unit. For example, the extrusion system includes a mixing unit.

[0032] Preferably, the feed flow is supplied to the extruder's sole inlet, or the upstream inlet of the extruder. Preferably, the extruder flow path immediately before receiving the feed flow from the mixing unit is empty, i.e., does not yet contain any material.

[0033] In this embodiment, the thermoplastic resin supply material is preferably a solid material and is fed into the extruder in the form of pellets. The thermoplastic resin supply material may include one or more thermoplastic polymers, i.e., unreinforced thermoplastic polymers which may be, for example, virgin polymers, recycled polymers, or combinations thereof.

[0034] TPC supply material generally includes, for example, flakes or chips of TPC material, or, for example, TPC pellets, preferably LFT material. The TPC supply material includes fragments of TPC material such as flakes or chips, preferably each fragment containing fibers and thermoplastic resin material. The flakes or chips are, for example, recycled materials. Optionally, the TPC supply material such as flakes or chips is converted into pellets.

[0035] As discussed herein, TPC feed material can be obtained from the manufacturing process of CFRT material, or CFRT articles or parts, or from used CFRT articles or parts. CFRT articles are, for example, woven, unwoven, or isotropic CFRT articles. TPC feed material can be obtained, for example, from LFT parts and articles in general. For example, from LFT injection molded parts and articles, and / or LFT extruded parts and articles, it can be obtained by shredding used LFT parts and articles, such as glass fiber mats or LFT direct molded parts. TPC feed material can be obtained as manufacturing waste from methods for producing LFT parts and articles. It is possible to obtain it.

[0036] The TPC supply material preferably includes fragments as an LFT supply material, each fragment consisting of, for example, at least a portion of impregnated fibers, which are partially or entirely impregnated with a thermoplastic polymer. The TPC supply material may also include other components such as dry fibers.

[0037] The TPC supply material comprises, for example, substantially only one type of thermoplastic polymer, and for example, at least 90% by mass of the thermoplastic portion of the TPC supply material is a single polymer. Preferably, the polymer or polymer blend of the TPC material is the same polymer or polymer blend used in the thermoplastic resin supply material.

[0038] Thermoplastic polymers are polymers selected from the group consisting of, for example, polyolefins, polyamides, polycarbonates, polyphenylene sulfides, polyaryl ether ketones, and polyethyleneimines. Examples of thermoplastic polymers include polyethylene or polypropylene.

[0039] As used herein, the term "thermoplastic polymer" includes, at a minimum, a plastic polymer that becomes flexible or moldable at a certain elevated temperature and solidifies upon cooling.

[0040] Without limiting the present invention, in some embodiments, the thermoplastic polymer is not crosslinked and is not cured.

[0041] The TPC supply material includes fibers, which are selected from the group consisting of, for example, glass fibers, carbon fibers, and natural fibers, and the natural fibers are selected from the group consisting of, for example, hemp, flax, jute, bamboo, and cellulose fibers. The TPC supply material may also include additional fibers. The TPC supply material includes, for example, at least 10% by mass of fibers, or at least 20% by mass of fibers, or at least 30% by mass of fibers, and typically less than 80% by mass of fibers.

[0042] Surprisingly, this method was found to result in less fiber abrasion than methods known in the art, as evidenced, for example, by the measured glass fiber lengths in Table 1 (Examples section) and other examples.

[0043] Figure 1 schematically shows an example of a first preferred method according to the present invention. This method is carried out in an apparatus comprising an extrusion system (1) comprising an extruder (2). The extruder (2) comprises a barrel (3) and a single-screw (4). The screw (4) is rotatable in the axial direction. The barrel is a hollow vessel, typically a cylindrical vessel having a length and diameter. The screw is located within the barrel, typically within the length of the barrel, and comprises a cylindrical shaft (11) and flights (12), typically one or more helical flights. The pitch of the flights is shown schematically only. The screw provides a flow path (8) within the extruder adapted to receive the material to be extruded. During operation, the material to be extruded is received into the flow path from the inlet and is fed to the discharge opening (5) by rotating the screw in the extrusion direction (ED). Due to the shear action between the screw and the barrel, at least a portion of the material melts in the flow path to form a molten material, which is extruded at a discharge opening, usually provided in the die, to become the extruded material.

[0044] In a first preferred method of the present invention, a thermoplastic resin supply material (A) is mixed with a TPC supply material (B) in a mixer (18) to obtain a mixed flow (Z), which is supplied to an extruder (2) and optionally sent to a first inlet opening (6) via a first supply device (16). The mixture is sent through the extruder in a flow path (8) to become a first mixed material (C). The term "first inlet opening" refers to the absence of an inlet opening upstream of the first inlet opening of the supply material. The resulting mixed material (C) is sent to a die (15), and the LFT extruded material (D) is received from the discharge opening (5).

[0045] Without limiting the present invention in any way, in a preferred embodiment, the TPC supply material is supplied as follows. B1) Prepare dry continuous fibers. B2) Impregnating fibers with thermoplastic resin to obtain a continuous sheet of impregnated fibers having ends. B3) Separating at least a portion of the edges from an impregnated fiber continuous sheet to obtain flakes that are separated edge fragments and each contain fibers, thermoplastic resin material, and trimmed continuous sheet. B4) Using the flakes as at least part of the TPC supply material; B5) Optionally, trimmed continuous sheets may be resized to form sheets or tapes, and optionally, laminates may be produced from the sheets or tapes. The sheets, tapes, or laminates may be placed in a mold and molded (e.g., by heat) to become molded CFRT articles.

[0046] Figure 2 schematically shows an example of a preferred method according to the present invention. In this preferred embodiment, which is merely illustrative, the method for producing LFT extruded material includes an extrusion step (205) to obtain LFT products such as extruded material strands using thermoplastic resin (TP) and TPC material, such as LFT material (e.g., flows A1, A2, A3, A4 shown in Figure 2B, and combinations thereof with each other and / or other flows), as shown in Figure 2A. The LFT products are further sized (206) (i.e., dimensionally adjusted, pelletized) to become LFT pellets. The LFT pellets are further optionally injection molded or extruded (207) to become LFT parts. These parts are, for example, LFT articles or LFT components.

[0047] In this preferred embodiment, the step of supplying the feed material includes a method for producing CFRT material (Figure 2B). This method includes, for example, steps B1 to B5 described above, and includes a step of impregnating (201) continuously dried fibers (e.g., glass fibers, natural fibers, or carbon fibers) with a thermoplastic polymer resin to obtain an impregnated continuous sheet or tape (single-layer sheet). The fibers are supplied, for example, as woven, unwoven, or isotropic tape. Sheets having low-quality edges are typically processed (202), for example, by trimming, to remove these edges. The removed edges are cut or slashed to reduce their size (202A) and recovered as LFT flakes (A1). In an exemplary embodiment, the TPC feed material is supplied by supplying such LFT flakes to an extrusion step. The sheets from which the edges have been removed are still continuous sheets and are laminated (203) to become CFRT material such as a CFRT laminate. The CFRT laminate is, for example, trimmed (204) to obtain a trimmed laminate ("blank") and trimming scraps. The trimming scraps are, for example, sized (e.g., shredded) to become LFT chips (A2) used, for example, as at least part of the TPC supply material.

[0048] CFRT material may be used for processing (208) to obtain CFRT articles. For example, processing (208) is the molding of material by placing solid CFRT material, such as a CFRT blank, into a mold, closing the mold, and molding the material using heat and / or pressure so that a molded CFRT article can be obtained. The molding step is usually carried out separately from the manufacture of CFRT sheets, for example, after the storage and transport of the CFRT material. Off-spec products from processing (208) can be resized (e.g., shredded) to make chips (A3) which can be optionally used as at least part of the TPC supply material. Furthermore, used CFRT articles (e.g., post-consumer articles) can be resized (209) (e.g., shredded) to make chips (A4) which can be optionally used as at least part of the TPC supply material. The illustrated TPC supply materials (A1, A2, A3 and A4) are for illustrative purposes only.

[0049] LFT flakes resulting from the edge removal process (202), for example, the edge trimming process, are considered waste in the prior art and, for example, are burned in an incinerator or crushed into dust in a crushing process in the prior art methods. In the present invention, not only LFT flakes but also other types of TPC materials can be used as part of the feed stream together with thermoplastic resin material as TPC feed material for the extrusion process (205) according to the present invention to produce LFT extruded material (extruded articles). The method of the present invention generally, more preferably, includes a step of pelletizing (206) the LFT extruded material from the extrusion process (205) to obtain LFT pellets. These pellets can optionally be stored and / or transported and optionally used further in, for example, LFT injection molding.

[0050] Each LFT pellet comprises a fiber and a thermoplastic resin material. The LFT pellets can be used, for example, in LFT injection molding (207). A comparative preparation method for producing LFT pellets is based on the steps of combining a continuous fiber and a thermoplastic resin (208) to obtain a continuous strand (the combining step being, for example, wire coating or pultrusion), and further steps of sizing the strand (209) to form an LFT pellet, as shown in the figure.

[0051] LFT pellets obtained by the method of the present invention are very suitable for LFT injection molding, extrusion, and / or compression molding. In such an LFT injection molding step (207), which is an optional further step of the method of the present invention, the LFT pellets are heated to melt the thermoplastic portion, and the fiber-containing molten material is injected into a mold. The mold is closed, and the material inside the mold solidifies to obtain an injection-molded LFT part, which is a molded article containing a thermoplastic polymer and fibers. The fibers preferably have a relatively long length within the molded article. The injection-molded LFT part is, for example, an automotive part.

[0052] In this preferred embodiment of the method of the present invention, TPC flakes and TPC chips, which are obtained as virtually waste materials in the conventional CFRT manufacturing process, are surprisingly and very advantageously recycled into high-value products. This embodiment of the method of the present invention is highly advantageous compared to currently used methods such as incinerating the flakes or chips, or crushing the flakes or chips into dust and using the dust as a low-cost filler.

[0053] Figure 2C shows an embodiment in which an integrated extrusion / injection molding apparatus 205A can be used. Such an apparatus comprises both a plasticizing unit and a molding unit. The plasticizing unit is located directly upstream of the molding unit and, together with a barrel and a single-screw, contains an inlet for the composite feed. In some embodiments, only one screw is used, which is simpler than an apparatus having two screws in series. In some embodiments, only one single-screw barrel is used, which is also simpler than an apparatus having two barrels in series. In embodiments, the method of the present invention has demonstrated remarkably good mechanical properties of the resulting material, even in such a simple unit having only one barrel and one screw.

[0054] Figure 3 schematically illustrates a comparative method for producing LFT articles, which is not according to the present invention. In this method, a thermoplastic resin and a continuously dried fiber are combined by a process such as pultrusion or wire coating (305) to obtain an LFT strand, which is then sized (e.g., cut) (306) to form pellets. These pellets can be used for LFT injection molding and / or LFT extrusion (307), and / or compression molding.

[0055] In a preferred embodiment, the TPC feed material comprises flakes, chips, shredded material from CFRT waste stream, or a combination thereof, and more preferably accounts for at least 90% or at least 95% by mass of the total feed stream. The flakes or chips preferably consist of TPC material and can be obtained from any suitable source.

[0056] Therefore, in one embodiment, the present invention relates to a method for producing long-fiber thermoplastic resin (LFT) extruded materials such as extruded strands or pellets.

[0057] In this preferred method, the thermoplastic resin supply material preferably does not contain fibers, and more preferably does not contain thermosetting polymer or nonpolymer fibers, or preferably contains less than 5.0% by mass or less than 1.0% by mass in total relative to the thermoplastic resin supply material.

[0058] The composite feed stream is preferably a solid material and is fed into the extruder in the form of pellets. The thermoplastic resin feed material preferably contains at least 80% by mass of an unreinforced thermoplastic polymer, which may be, for example, a virgin polymer, a recycled polymer, or a combination thereof.

[0059] As discussed herein, TPC feed material may be obtained from the manufacturing process of CFRT material, or CFRT articles or parts, or from used CFRT articles or parts. CFRT articles are, for example, woven, unwoven, or isotropic CFRT articles. TPC feed material can also be obtained, for example, from LFT parts and articles in general. It can also be obtained, for example, from LFT injection-molded parts and articles, and / or LFT extruded parts and articles, or by shredding used LFT parts and articles. TPC feed material may be obtained as manufacturing waste from methods for producing LFT parts and articles.

[0060] The TPC supply material preferably includes fragments as an LFT supply material, each fragment consisting of, for example, at least a portion of impregnated fibers, which are partially or entirely impregnated with a thermoplastic polymer. The TPC supply material may also include other components such as dry fibers.

[0061] The TPC supply material comprises, for example, substantially only one type of thermoplastic polymer, and for example, at least 90% by mass of the thermoplastic portion of the TPC supply material is a single polymer. Preferably, the polymer or polymer blend of the TPC material is the same polymer or polymer blend used in the thermoplastic resin supply material.

[0062] The thermoplastic polymer used in TCP supply materials and / or thermoplastic resin supply materials is, for example, a polymer selected from the group consisting of polyolefins, polyamides, polycarbonates, polyphenylene sulfides, polyaryl ether ketones, and polyethyleneimines.

[0063] As used herein, the term "thermoplastic polymer" includes, at a minimum, plastic polymers that become flexible or moldable at a certain elevated temperature and solidify upon cooling.

[0064] Without limiting the present invention, in some embodiments, the thermoplastic polymer is uncrosslinked and uncured.

[0065] Preferably, the thermoplastic polymer supply contains at least 80% by mass of the same polymer or polymer blend used in at least 80% by mass of the TPC supply material, based on the total thermoplastic polymer supply.

[0066] The TPC supply material includes fibers, which are selected from the group consisting of, for example, glass fibers, carbon fibers, and natural fibers, and the natural fibers are selected from the group consisting of, for example, hemp, flax, jute, and cellulose fibers. The TPC supply material may also include additional fibers. The TPC supply material may include, for example, at least 10% by mass of fibers, or at least 20% by mass of fibers, or at least 30% by mass of fibers, and typically less than 80% by mass of fibers. The TPC supply material may include, for example, 30-70% by mass of fibers, or for example, 50-70% by mass of fibers. The method includes an extrusion step carried out in an extrusion system. The extrusion system includes an extruder having a barrel having a screw and an outlet opening inside. The outlet opening is provided in the die at the end downstream of the extruder. The extruder has an extrusion direction toward the outlet opening in the longitudinal direction of the screw. The extruder is a single-screw extruder, not a twin-screw extruder. Thus, the barrel contains one or fewer screws at each position in the length of the barrel. The barrel is heated to a temperature in the range of, for example, 230-280°C, for example, at least 150°C or at least 200°C, for example, for advantageous use in this embodiment. For example, extrusion is carried out at temperatures in this range.

[0067] The screw provides a flow path within the extruder. This flow path is an open space between the screw shaft, the flight, and the inner wall of the barrel. The barrel is, for example, a cylindrical container. During operation, the material is propelled through the flow path in the extrusion direction by the rotational action of the screw.

[0068] The extruder is provided with a first inlet opening for supplying thermoplastic resin feed material to the extruder. Optionally, TPC feed material is also supplied through the first inlet opening. The first inlet opening is provided with a first opening in the barrel for supplying thermoplastic resin feed material and, optionally, TPC feed material to the screw. In embodiments in which both thermoplastic resin feed material and TPC feed material are supplied through the first inlet opening, these feed materials are preferably supplied through the first inlet opening as a single feed stream (Z) containing a mixture of the thermoplastic resin feed material and the TPC feed material (typically as a mixture of particles of each feed material).

[0069] In the present invention, the extruder also typically includes a die. Therefore, the die is typically positioned parallel to the screw and on the screw projection in the extrusion direction. The die is typically mounted or attached to a barrel containing these feed ports.

[0070] This method optionally further includes a step of pelletizing LFT extruded material, particularly strands, to form LFT pellets. Preferably, the LFT pellets are suitable for LFT injection molding and / or LFT extrusion.

[0071] In some embodiments, an integrated extrusion / injection molding apparatus can be used, as illustrated in the examples.

[0072] Preferably, the LFT pellets have a length in the range of 2 to 25 mm, preferably 6 to 15 mm. Pellets of such length are particularly suitable for LFT injection molding. The method of the present invention may involve storage, packaging, and / or transportation of the LFT pellets between pelletization for forming the pellets and use of the pellets in, for example, injection molding.

[0073] In a further aspect, the present invention relates to LFT extruded materials obtained by this method, particularly LFT pellets. This method makes it possible to produce LFT extruded materials having relatively long fibers and a relatively high fiber fraction using discontinuous long fibers.

[0074] Preferably, in the material, preferably in the LFT pellets, the ratio of fiber length D90 to initial fiber length (I) is at least 30%, at least 40%, or at least 50%. Preferably, in the material, the ratio of fiber length D50 to initial fiber length (I) is at least 10%, at least 20%, and more preferably, in combination, the ratio of fiber length D90 to initial fiber length (I) is at least 30%, at least 40%, or at least 50%. Preferably, the material has a fiber content of at least 20% by mass, or at least 30% by mass, or at least 40% by mass, preferably in combination with the ratios described. Preferably, the fibers include glass fibers, carbon fibers, or natural fibers.

[0075] Here, D90 refers to the point in the frequency distribution of fiber length (histogram) where 90% or less of all fibers are contained. For example, if D90 is 11 mm, it means that 90% of the sample is 11 mm or smaller, as shown in Figure 7. Correspondingly, the D50 fiber length is calculated as the point in the frequency distribution of fiber length (histogram) where 50% or less of all fibers are contained, starting from 0 mm. D90 (D50) refers to the fiber length where 90% (50%) or less of all counted fibers are contained.

[0076] The fiber length of each fiber can be determined, for example, using optical image analysis. The D90 value of the material is important for the (mechanical) properties of LFT articles manufactured from LFT material, for example, by LFT injection molding.

[0077] The initial fiber length is the fiber length of the TCP material supplied to the extruder, preferably the D50 fiber length value of the TCP material supplied to the extruder. In a preferred embodiment, the initial fiber length is interpreted as being equal to the length (maximum dimension) of the TPC fragment (e.g., chips or flakes, or TPC pellets) supplied to the extruder, i.e., the input length for flakes. The TPC pellets consist of thermoplastic resin pellets having fibers with a maximum length within the size of the pellet.

[0078] In exemplary embodiments, the initial fiber length is interpreted as being equal to the length of the manufactured LFT pellet. Thus, in some embodiments, the ratio of D90 to the pellet length in the LFT pellet is at least 30%, at least 40%, or at least 50%.

[0079] The present invention also provides LFT pellets having lengths obtained, for example, by the method of the present invention, wherein the ratio of D90 to the pellet length is at least 30%, at least 40%, or at least 50%, and the pellet length is, for example, in the range of 10 to 20 mm, or for example, 12 to 16 mm. Preferably, the pellets comprise a thermoplastic resin material and fibers, as described in relation to the method. Preferably, the pellets have a fiber content of at least 20% by mass, at least 30% by mass, or at least 40% by mass.

[0080] As used herein, the verb "comprising" indicates that there may be additional elements (components, processes, features) other than those mentioned.

[0081] Figure 6 shows an example of an extruder layout.

[0082] Figure 6A shows an example of an extruder configuration SF1 having granules (1), flakes / chips (2), a die (3), a cooling unit (4), and a pelletizer (5).

[0083] Figure 6B shows an example of an extruder configuration SF2 having granules (1), flakes / chips (2), a die (3), a cooling unit (4), and a pelletizer (5). The inlets for the granules and flakes / chips are located relatively downstream compared to SF-1.

[0084] Figure 7 shows an example of calculating the D90 and D50 values ​​from a histogram. [Examples]

[0085] The present invention will be described below with reference to the following examples, but these are merely illustrative and do not limit the scope of the present invention or the claims.

[0086] (Example 1) material Master spools made of polypropylene (PP) reinforced with approximately 70% by mass of continuous glass fiber (GF) (nominal thickness 0.25 mm, mass 600 mm) were used as the basis for the study. These spools were cut to form 12 mm wide isotropic tape rolls. These were then resized using a pelletizer modified to cut the tape rather than the strands, producing flakes 5 mm long (fiber direction) and 12 mm wide (transverse direction). Virgin homopolymers of PP with different melt flow indices were used for melt processing dilution, and a wide range of MFIs (Melt Flow Indexes) were investigated: 2, 50, and 80 g / 10 min (measured at 230°C, 2.16 kg - ISO 1133). MFI refers to the melt flow index.

[0087] The reference samples were Stamax® 40YM240 (functioning as Ref. 1) supplied by Sabic® and Celstran® PP-GF40-02 (Ref. 2) supplied by Celanese®. Both materials contained 40% by mass of glass fiber and were selected as reference samples for comparison after processing under the same conditions. Both materials were long glass fiber reinforced grade pellets with a size of approximately 11 mm in length.

[0088] method PP / GF composite materials were prepared by melt processing in an Engel Victory 50 injection molding machine, where the plasticizing unit consists of a barrel and a screw (single-screw: screw diameter 30 mm, L / D screw length 20.5 mm). Extrusion or melt processing was performed at 250°C and rpm 13. The barrel and mold were set to 250°C and 80°C, respectively. PP / GF flakes and virgin PP pellets were extruded or melt-mixed to form LFT extruded material with a final concentration of 40 mass%GF, and then injection-molded to produce ISO 527 standard tensile test specimens. The samples were labeled MFI-2, MFI-50, and MFI-80, referring to the MFI of the pellets used in their mixing.

[0089] Tensile and bending tests were performed using an Instron 5966 universal testing machine. Tensile tests were measured at 5 mm / min using a clip-on extensometer in accordance with ISO 527. Bending tests were performed at a crosshead speed of 10 mm / min in accordance with ISO 178. Impact strength characteristics were measured using an Izod device, and notches were made on all test specimens using a notching cutter before testing. Notted Izod impact tests were performed using a Zwick / Roell impact testing machine in accordance with ISO 180. For all tests, the average of five measurements was calculated, and the standard deviation was reported.

[0090] The glass fiber content after processing was measured and compared to the original content of each tape roll. The GF content of both types of materials was obtained after burning a known amount of flakes or the PP matrix of an injection-molded bar at 600°C for 60 minutes. The test was repeated at least twice.

[0091] After ashing the polymers, the remaining fiber density (GF) length was measured using an IST-AG scanner and software. The measurements were repeated according to ISO 9276-1 / 2. For each formulation, an average of 60,000 to 100,000 fibers were measured.

[0092] result Morphological characterization The master spool contained 65–72% by mass of glass fiber. For comparison and homogeneity, flakes obtained from one roll of tape were used, and the glass fiber content was measured to be 69.5 ± 0.1% by mass.

[0093] After injection molding, untested bars were characterized, and their glass fiber content and length were measured and compared with the reference material (see Table 1). The standard deviation of the glass fiber content in the recycled material was slightly higher than that of the reference material, although within the acceptable range (<2%). This difference can be easily explained by the differences in the bar manufacturing process. The recycled flakes were dry-blended with PP pellets before processing, while the continuously produced reference material was homogeneous and processed as received. As expected, the GF length after processing decreased significantly, but all were greater than 1 mm and therefore defined as LFT. The molded reference LFT bars showed a higher residual GF length with 40 mass% fiber after injection molding. The difference obtained was due to the initial size of the input material; as shown in Table 1, the fiber length of the recycled material was 5 mm, while the fiber length of the reference material was more than twice as long, i.e., approximately 11 mm. Figure 4 shows the particle size distribution measured after ashing of flakes and bars prepared with MFI-50. In this figure, q1 (left axis) shows the density distribution by length, and Q1 (right axis) shows the cumulative distribution by length (mm). As can be seen from the figure, the range of fiber lengths is quite wide, which is thought to be due to the calculation method (i.e., geodesic length).

[0094] [Table 1]

[0095] mechanical performance Figure 5 shows the mechanical properties obtained by processing recycled and commercial materials under identical conditions and conducting bending and impact tests. The elastic modulus measured for both recycled and virgin materials was approximately 9 GPa. In the elastic region, stiffness is known to depend heavily on fiber content, but fiber-matrix interactions are not expected to have a significant impact. The high standard deviation obtained using recycled materials may be related to the high standard deviation of glass fiber content measured and reported in Table 1. This behavior is thought to be related to the non-homogeneity of the dry blend supply compared to the reference pellets.

[0096] Using impregnated and oriented pellets of sample Ref. 2 resulted in a slightly higher flexural strength (approximately 215 MPa) compared to recycled materials and other reference materials (approximately 200 MPa), indicating greater resistance to deformation. This may be related to both the longer residual GF after processing and the good bonding between PP and glass fibers due to proper embedding of drawn fibers. For recycled materials processed with different MFIs, the use of low-viscosity PP:MFI-50 appears to optimize flexural strength. The use of MFI-2 resulted in decreased material strength, which may be related to improper mixing of this viscous phase or residual stress in the injection molding bar. Impact strength values ​​are related to many parameters, including fiber content, fiber length, and fiber / matrix interaction. All recycled materials and sample Ref. 1 were within the same range, while sample Ref. 2 showed a slightly higher value. This may be related to the longest glass fibers in material Ref. 2. All materials were approximately 20 kJ / m 2 This indicates the impact strength. MFI does not significantly affect this result.

[0097] This Example 1 compares the performance of injection-molded bars made from tape waste and commercially available LFT pellets. Tape containing a high concentration of glass fibers was diluted with virgin PP having different melt flow indices to achieve a final GF content of 40% by mass. The melt flow index significantly affected flexural strength and slightly affected elastic modulus and impact strength. These results correlated with the fiber content and fiber size of each material measured. This clearly demonstrates the high potential of using composite material waste in the production of LFT materials. The recycled materials exhibited competitive mechanical properties compared to commercially available reference samples.

[0098] (Example 2) Extrusion methods were tested for various samples to produce pellets, as shown in Table 2, using glass fiber (GF) or carbon fiber (CF)-containing tape and other thermoplastic composite (TPC) feed materials, with extruder configuration SF1 as illustrated in Figure 6A, or an alternative extruder configuration SF2 (sample #7) as illustrated in Figure 6B. Nozzle diameter refers to the die diameter. Feed length refers to the length of the chips / flakes fed into the extruder.

[0099] The supplied thermoplastic resin granules were the same type of thermoplastic polymer (PP or PA6) used in tape / TPC materials.

[0100] The fiber length in the product is expressed as a percentage of frequency (fiber shape-length distribution histogram; see Figure 4 for an example of the histogram) based on the maximum length possessed by 50% of the fibers (D50) or the maximum length possessed by 90% of the fibers (D90). In other words, 90% or 50% of the fibers have a length shorter than that.

[0101] Fiber length was determined by burning pellets and by optical image analysis using Fibreshape® software and a FibreShape M scanner. Tape starting material contains continuous fibers aligned in the tape direction. When the tape is cut into flakes, an initial fiber length equal to the flake length is obtained. The flake length is the input length. In contrast, when TPC starting material such as fiber mats, laminates, or woven components is cut, the initial fiber length is wider.

[0102] As shown in Table 2A (Table 3), which lists the ratio of D50 or D90 to input length (I), good retention of fiber length (low wear) was achieved. In reference extruder processes using various starting materials, the D90 / I ratio was typically between 17% and 32%.

[0103] [Table 2]

[0104] [Table 3]

[0105] (Example 3) In addition to Example 1, the extrusion method was tested with various samples (described in Example 1), direct injection molding (integrated injection molding apparatus, configuration SFd), and the indicated MFI. The results are shown in Table 3 (Table 4). Fiber length measurement was the same as in Example 2.

[0106] [Table 4] [Explanation of Symbols]

[0107] 1. Extrusion System 2 Extruder 3 barrels 4 Single-screw 5 Outlet opening 6 Inlet opening 8 channels 11 shafts 12 Flights 15 Dies 16 Feeding device 18 Mixer A Thermoplastic feed material B TPC supply material C Mixed material D LFT extruded material ED Extrusion Direction Z mixed flow

Claims

1. A method for producing long-fiber thermoplastic (LFT) extruded material, The method described above is - Thermoplastic feed materials; - A step of preparing thermoplastic resin composite (TPC) supply material, such as flakes or chips, The process includes a step in which the TPC supply material comprises fragments, each fragment individually comprising both fiber and thermoplastic resin material; The method includes an extrusion step carried out in the extrusion system (1); The extrusion system (1) comprises an extruder (2) having an extrusion direction (ED); The extruder (2) comprises a barrel (3), a single-screw (4), a first inlet opening (6), and an outlet opening (5), and the screw (4) provides a flow path (8) within the extruder (2); The extrusion process described above is - Supplying the thermoplastic resin supply material and the TPC supply material to the extruder (2); - A mixture of the thermoplastic resin supply material and the TPC supply material is sent to the outlet opening (5) to obtain a mixed material (C); - A method comprising extruding the mixed material (C) through the discharge opening (5) to obtain an LFT extruded material (D).

2. - A single feed stream (Z) containing a mixture of the thermoplastic resin feed material and the TPC feed material, A step of supplying the material to the flow path (8) in the extruder (2) through the first inlet opening (6); - The method according to claim 1, comprising the step of sending the mixture to the outlet opening (5) to obtain the mixed material (C).

3. The method according to claim 1 or 2, wherein the TPC supply material includes flakes or chips, or shredded material from a CFRT waste stream.

4. The above step of preparing thermoplastic resin composite (TPC) supply material is B1) Prepare dry continuous fibers. B2) Impregnate the fibers with a thermoplastic resin to obtain a continuous sheet of impregnated fibers having ends. B3) Separating at least a portion of the end from the impregnated fiber continuous sheet to obtain flakes which are separated end fragments and which each contain fibers, thermoplastic resin material, and trimmed continuous sheet. B4) The method according to any one of claims 1 to 3, comprising using the flakes as at least part of the thermoplastic resin composite (TPC) supply material.

5. The method according to any one of claims 1 to 4, wherein the long fiber-reinforced thermoplastic resin material obtained by the above method contains 10 to 75% by mass, preferably 30 to 60% by mass, of fibers relative to the total mass of the long fiber-reinforced thermoplastic resin material.

6. The method according to any one of claims 1 to 5, further comprising the step of pelletizing the LFT extruded material to make LFT pellets, wherein the pellets are suitable for LFT injection molding and / or LFT extrusion.

7. The method according to any one of claims 1 to 5, wherein the extrusion system (1) comprises an integrated injection molding unit and an extruder.

8. A long-fiber thermoplastic (LFT) material obtained by the method described in any one of claims 1 to 7.

9. The LFT material according to claim 8, wherein the ratio of the fiber length D90 to the initial fiber length (I) is at least 30%, preferably at least 50%.

Images