UD tape with improved processability and rough surface and method for manufacturing same

Abstract

The present invention relates to a method for producing a unidirectional tape having a surface polymer layer, the method comprising the steps of: a) providing an impregnation slurry containing polymer particles, water, optionally a surfactant, optionally an organic carrier medium, optionally an organic compound, and optionally a surface-active compound, and providing a press mold having a surface structure, wherein the surface structure has a surface roughness Ra of 1 to 20 μm, preferably 2 to 10 μm, more preferably 3 to 7 μm; b) impregnating a unidirectional fiber layer containing unidirectional fibers with the impregnation slurry to obtain an impregnated unidirectional fiber layer containing polymer particles; c) pressing the surface structure against the surface of the impregnated unidirectional fiber layer to form a surface polymer layer on the unidirectional fiber layer, so as to transfer at least a portion of the polymer particles in the impregnated unidirectional fiber layer onto the surface of the impregnated unidirectional fiber layer; and d) obtaining a unidirectional tape having a surface polymer layer.

Description

[Technical Field]

[0001] The present invention relates to a UD tape with improved processability and a rough surface, and a method for producing the same.

[0002] Unidirectional tape (UD tape) is a fiber-reinforced tape available in various widths and has been known for many years. It is typically impregnated with a thermoplastic polymer, with unidirectionally aligned reinforcing fibers, typically carbon or glass fiber. UD tape allows for the creation of structures that are not only lighter but also have advantageous structural properties, such as high stiffness and strength, compared to structures made from other conventional materials. As a result, UD tape is used for a variety of applications in a wide range of industries, including automotive, aerospace, and home appliances. Depending on the application, UD tape must meet a number of criteria, including mechanical properties such as strength and stiffness, size, and weight, as well as excellent processability and formability into complex shapes.

[0003] Subsequent processing of UD tapes typically involves melting the thermoplastic polymers present in the UD tape to form a coherent laminate or multi-layer laminate. These steps include tacking, tape placement, tape laying, solidification, and welding. Therefore, most processes require the melting and interdiffusion of the thermoplastic polymers present at the interfaces of adjacent UD tapes to form a fully consolidated laminate.

[0004] There is a need in the art for improved processability for UD tapes, meaning rapid adhesion, set characteristics, thermoforming behavior, and lateral flow for complex shapes, as well as a roughened surface for improved processing.

[0005] Therefore, there is a need in the art to provide a UD tape that has improved lateral flow and a roughened surface for improved processing.

[0006] There is also a need in the art to provide a method for producing UD tape that has improved lateral flow and a roughened surface for improved processing.

[0007] It is therefore an object of the present invention to provide a UD tape that has improved lateral flow and has a roughened surface for improved processing.

[0008] It is also an object of the present invention to provide a method for producing UD tape that has improved lateral flow and has a roughened surface for improved processing.

[0009] It has now been discovered that all of the above objectives can be achieved by a method for producing a UD tape having a polymer layer on the surface of a unidirectional fiber layer, by pressing the surface of the unidirectional fiber layer to form a roughened polymer layer on the unidirectional fiber layer, which provides improved lateral flow.

[0010] Accordingly, the present invention provides a method for producing a unidirectional tape having a surface polymer layer, the method comprising the steps of: a) providing an impregnation slurry containing polymer particles, water, optionally a surfactant, optionally an organic carrier medium, optionally an organic compound, and optionally a surface-active compound, and providing a press mold having a surface structure, wherein the surface structure has a surface roughness Ra of 1 to 20 μm, preferably 2 to 10 μm, more preferably 3 to 7 μm; b) impregnating a unidirectional fiber layer containing unidirectional fibers with the impregnation slurry to obtain an impregnated unidirectional fiber layer containing polymer particles; c) pressing the surface structure against a surface of the impregnated unidirectional fiber layer to form a surface polymer layer on the unidirectional fiber layer, so as to transfer at least a portion of the polymer particles in the unidirectional fiber layer onto the surface of the impregnated unidirectional fiber layer; and d) obtaining a unidirectional tape having a surface polymer layer.

[0011] The present invention further provides a unidirectional tape having improved processability and a rough surface obtained by the method according to the present invention.

[0012] The present invention also has several surprising advantages. The formation of a surface polymer layer increases the polymer content present at the surface of the UD tape, resulting in improved lateral flow and reduced friction between the layers and between the mold and the composite laminate. Improved lateral flow and reduced friction improve the formability of the tape, allowing for faster forming and / or more complex shapes.

[0013] Tailoring the surface polymer layer by pressing with a surface topography further allows for the UD tape to have a predetermined surface roughness while maintaining a homogeneous UD tape material with few voids.

[0014] The method for producing a unidirectional tape (UD tape) according to the present invention will be described in more detail below.

[0015] The impregnation slurry used in the method of the present invention comprises polymer particles, water, optionally a surfactant, optionally an organic support medium, optionally an organic compound, and optionally a surface-active compound.

[0016] Preferably, the water is deionized water.

[0017] Preferably, the organic support medium comprises an alcohol.

[0018] Preferably, the organic compound comprises an antifoaming agent.

[0019] Preferably, the surface active compound comprises a surfactant.

[0020] Furthermore, there is provided a press mold having a surface structure. The surface structure has a surface roughness Ra of 1 to 20 μm, preferably 2 to 10 μm, and more preferably 3 to 7 μm. The press mold presses at least one surface of the unidirectional fiber layer, and preferably the press mold presses two surfaces of the unidirectional fiber layer, i.e., a first surface of the unidirectional fiber layer and a second surface opposite to the first surface.

[0021] When two surfaces of the unidirectional fiber layer are pressed with a press mold, the press mold includes a first press mold and a second press mold, where the first press mold presses the first surface of the unidirectional layer and the second press mold presses the second surface opposite to the first surface of the unidirectional fiber layer.

[0022] Preferably, the first press tool is identical to the second press tool.

[0023] In step b), the unidirectional fiber layer is impregnated with the impregnation slurry to obtain an impregnated unidirectional fiber layer containing polymer particles. The unidirectional fiber layer comprises a plurality of unidirectional fibers. These unidirectional fibers are generally aligned in one direction. That is, the plurality of fibers are generally aligned parallel to one another. Preferably, at least 75% of the plurality of fibers in the unidirectional fiber layer are aligned in one direction, more preferably at least 80%, even more preferably at least 90%, and most preferably at least 95%. The unidirectional fibers may comprise filaments or be composed solely of filaments. The number of filaments forming a fiber may vary. Typically, a single unidirectional fiber may be formed from 12,000 or 24,000 filaments. The diameter of the filaments is generally 5 to 7 μm.

[0024] The unidirectional fiber layer has two opposing surfaces, a first surface and a second surface.

[0025] In the impregnation step b), the polymer particles are attached or adhered between adjacent unidirectional fibers and / or between adjacent filaments of the unidirectional fibers, and further attached or adhered to the surface of the unidirectional fiber layer, preferably to both surfaces of the unidirectional fiber layer, i.e., the polymer particles can penetrate into the unidirectional fiber layer and adhere to the surface of the unidirectional fiber layer, preferably to both surfaces of the unidirectional fiber layer.

[0026] The polymer particles may generally have a particle size in the range of 10 μm to 500 μm, preferably 15 to 100 μm, and more preferably 20 to 25 μm. The particle size can be measured by laser diffraction analysis using, for example, a laser diffraction particle size distribution analyzer S3500 commercially available from Microtrac.

[0027] Preferably, step b) is carried out in an impregnation vessel, i.e., a vessel containing an impregnation slurry. The unidirectional fiber layer is impregnated with the impregnation slurry, preferably by moving the unidirectional fiber layer through the impregnation vessel. Preferably, the impregnation slurry is stirred during step b).

[0028] The method of the present invention further includes a step c) of pressing the surface of the unidirectional fiber layer with a surface structure to migrate at least some of the polymer particles in the unidirectional fiber layer onto the surface, thereby forming a surface polymer layer on the unidirectional fiber layer. The surface structure of the press mold is pressed against the impregnated unidirectional fiber layer containing the polymer particles. The pressing does not change the unidirectional arrangement of the fibers in the impregnated unidirectional fiber layer, but it does force at least some of the polymer particles located in the impregnated unidirectional fiber layer onto one or preferably both surfaces of the impregnated unidirectional fiber layer. Thus, these polymer particles migrated onto one or both surfaces of the impregnated unidirectional fiber layer form a surface polymer layer on the surface of the impregnated unidirectional fiber layer, preferably on both surfaces of the impregnated unidirectional fiber layer. Preferably, the surface polymer layer comprises a polymer, and preferably consists solely of a polymer.

[0029] Preferably, step c) comprises pressing the surface structure against both surfaces of the impregnated unidirectional fibrous layer, preferably simultaneously, to transfer at least a portion of the polymer particles in the impregnated unidirectional fibrous layer to both surfaces, to form surface polymer layers on both surfaces of the impregnated unidirectional fibrous layer.

[0030] Preferably, the pressing step c) is carried out while the temperature T of the impregnated unidirectional fiber layer is in the range (Tc-150°C)≦T≦(Tc+150°C), where Tc is the crystallization temperature of the polymer. More preferably, the temperature is in the range (Tc-50°C)≦T≦(Tc+50°C), more preferably (Tc-25°C)≦T≦(Tc+25°C), and most preferably (Tc-10°C)≦T≦(Tc+10°C). The temperature T of the impregnated unidirectional fiber layer and the crystallization temperature Tc of the polymer are expressed in °C. After pressing, in step d), a unidirectional tape with a surface polymer layer is obtained.

[0031] The thickness of the surface polymer layer is preferably 1 to 15 μm, more preferably 2 to 10 μm, and most preferably 4 to 6 μm.

[0032] Preferably, the polymer is a thermoplastic polymer.

[0033] Preferably, the thermoplastic polymer comprises or consists solely of a polyaryletherketone (PAEK)-based polymer material, polyphenylene sulfide (PPS), polyetherimide (PEI), polyethersulfone (PESU, PES), or polysulfone (PSU). More preferably, the thermoplastic polymer comprises or consists solely of a polyaryletherketone (PAEK)-based polymer material or polyphenylene sulfide (PPS).

[0034] Preferably, the polyaryletherketone (PAEK) polymer material is selected from the group consisting of polyetherketone (poly-ether-ketone: PEK), polyetheretherketone (polyether-ether-ketone: PEEK), polyetheretherketoneketone (poly-ether-ether-ketone-ketone: PEEKK), polyetheretherketoneketone (poly-ether-ether-ketone-ketone: PEKK), polyetherketoneetherketoneketone (poly-ether-ketone-ether-ketone-ketone: PEKEKK), and polyetherether The polymeric material is preferably selected from the group consisting of polyetheretherketone-etherketone (PEEKEK), polyetheretheretherketone (PEEEK), polyetherdiphenyletherketone (PEDEK), meta-polyetheretherketone (PEmEK), polyaryletherketone (PAEK)-based polymeric materials having reactive (end) groups, copolymers thereof, and blends thereof. More preferably, the polyaryletherketone (PAEK)-based polymeric material is selected from the group consisting of polyetherdiphenyletherketone (PEDEK), polyetheretherketone (PEEK), copolymers thereof, and most preferably copolymers of polyetherdiphenyletherketone (PEDEK) and polyetheretherketone (PEEK).

[0035] Preferably, the unidirectional fibers are carbon fibers and / or glass fibers and / or quartz, more preferably carbon fibers. Suitable carbon fibers include, for example, Torayca T700G and Torayca T800G, both of which are commercially available from Toray. Preferably, the unidirectional fibers are continuous fibers, more preferably continuous carbon fibers.

[0036] Preferably, the pressing tool and / or the surface features of the pressing tool are made from a metal or metal alloy, such as iron or steel.

[0037] Preferably, the press mold is a pressure roller. Preferably, the impregnated unidirectional fiber layer containing the polymer particles is pressed by passing, more preferably continuously, the unidirectional fiber layer through the pressure roll and the flat support substrate.

[0038] When two surfaces of the unidirectional fiber layer are pressed with a press mold, the pressing rollers include a first pressing roller and a second pressing roller. Preferably, the impregnated unidirectional fiber layer containing polymer particles is pressed by passing through the first pressing roller and the second pressing roller, more preferably by passing through them consecutively. Preferably, the first pressing roller is the same as the second pressing roller. Preferably, the surface shape structure of the first pressing roller is the same as the surface shape structure of the second pressing roller.

[0039] The press mould has a surface texture, which means that the surface of the press mould used to press the impregnated unidirectional fibre layer is not perfectly flat.

[0040] Preferably, the surface shaped structure includes a protrusion for pressing the impregnated unidirectional fiber layer and a recess for receiving the polymer extruded from the impregnated unidirectional fiber layer. The protrusion of the surface shaped structure of the press mold presses against the impregnated unidirectional fiber layer made of polymer particles. The pressing does not change the unidirectional arrangement of the fibers in the impregnated unidirectional fiber layer, but it forcibly moves the polymer particles located in the impregnated unidirectional fiber layer to one or preferably both surfaces of the impregnated unidirectional fiber layer. Thus, these particles moved to one or both surfaces of the impregnated unidirectional fiber layer form a surface polymer layer on the surface of the impregnated unidirectional fiber layer.

[0041] Preferably, the protrusions and recesses are arranged in a predetermined pattern, and the pattern is preferably a regular or random pattern, more preferably a regular pattern. A regular pattern is, for example, a row of multiple protrusions with equal spacing between adjacent protrusions. A random pattern is, for example, a case where the protrusions are arranged randomly, i.e., the distance between adjacent protrusions is not equal, or at least not always equal.

[0042] The rough surface structure of the press mold in step c) gives the formed surface polymer layer a surface roughness. Preferably, the surface polymer layer has a surface roughness Ra of 1 to 20 μm, preferably 2 to 10 μm, more preferably 3 to 7 μm, measured in accordance with ISO 4287.

[0043] Preferably, the obtaining step d) comprises drying the unidirectional fibrous layer.

[0044] Preferably, the method further comprises the step of e) drying the unidirectional fiber layer between the impregnation step b) and the pressing step c).

[0045] Preferably, the method further comprises the step of: f) cooling the unidirectional fiber layer before or during the pressing step c), Preferably, the cooling in step f) is carried out through a press mold, more preferably by a pressing roller.

[0046] Preferably, the method according to the present invention further comprises step g) of electrostatically depositing secondary particles onto the surface polymer layer, or preferably onto both surface polymer layers. This allows for the formation of additional surface polymer layers containing or consisting solely of secondary particles on one or both surface polymer layers of the unidirectional tape. This means that a unidirectional tape with one or two additional surface polymer layers can be obtained. The one or two additional surface layers are preferably the outermost layers of the unidirectional tape. This allows for the surface properties of the UD tape to be adapted and fine-tuned, particularly for specific applications.

[0047] Preferably, electrostatic deposition is performed by electrospraying, which is preferably performed using one or more spray guns.

[0048] Step g) is preferably carried out after step c) and before step d), or after step d), more preferably after step d). Preferably, after step d), the unidirectional tape with one or two additional surface polymer layers is dried or solidified.

[0049] The secondary particles consist of a second polymer, preferably consisting solely of the second polymer. Preferably, the second polymer is a thermoplastic polymer. The thermoplastic polymer is the same as that described herein above for the polymer used in step a). Preferably, the second polymer is a polymer of the same class or subclass as the polymer of step a), or the second polymer is a polymer of a class or subclass other than the polymer of step a).

[0050] The secondary particles preferably have a particle size of 10 μm to 500 μm, more preferably 15 μm to 250 μm, and most preferably 20 μm to 200 μm. The size of the secondary particles must be such that they can be electrostatically attached, more preferably by electrospray. The particle size can be measured by laser diffraction analysis as described above.

[0051] The invention also relates to a unidirectional tape obtained by the method according to the invention. All embodiments of the method according to the invention described above are also preferred embodiments of the unidirectional tape obtained by the method according to the invention.

[0052] Thus, the present invention provides a unidirectional tape comprising a unidirectional fiber layer and a surface polymer layer, preferably two surface polymer layers, wherein the unidirectional fiber layer comprises unidirectional fibers and polymer particles, and the surface polymer layer comprises polymer particles, the surface polymer layer having a surface roughness Ra of 1 to 20 μm measured in accordance with ISO 4287 and a thickness of less than 15 μm, preferably less than 10 μm.

[0053] Preferably, the unidirectional tape further comprises a transition region located between the unidirectional fiber layer and the surface polymer layer, the transition region having a thickness of 2 to 15 μm, where the transition occurs from the surface polymer layer containing pure polymer to the unidirectional layer containing both unidirectional fiber and polymer.

[0054] The surface polymer layer has a thickness. This thickness does not have to be constant throughout the surface polymer layer, and may vary to some extent. Preferably, the variation in the thickness of the surface polymer layer is 0 to 75% of the average surface polymer layer thickness, preferably less than 30%, more preferably less than 10%.

[0055] The transition zone and thickness change were measured as follows: The resulting unidirectional tape was sliced ​​into several pieces. The cross sections of these pieces of tape were analyzed using an optical microscope. The thickness of the surface polymer layer was measured at least twice on at least five different slices. The average surface polymer thickness was calculated as the arithmetic mean. The thickness change was calculated from the surface polymer layer thickness and the average surface polymer thickness.

[0056] The thickness of the transition region is also calculated by optical microscopic analysis of the cross sections of these slices of tape as described above.

[0057] Preferably, the surface polymer layer contains voids, and the amount of voids in the surface polymer layer is 1 to 10 vol%, preferably less than 5 vol%, more preferably less than 2 vol%, based on the total volume of the surface polymer layer.

[0058] The amount of voids was also calculated by analyzing the cross-sections of these slices of tape with an optical microscope as described above. From the thickness of the surface polymer layer, the void volume and the width of the tape slice, the amount of voids expressed in vol% as well as the volume of the surface polymer layer was calculated.

[0059] Preferably, the polymer is a thermoplastic polymer and the unidirectional fibres are carbon fibres. The drawings show: [Brief explanation of the drawings]

[0060] [Figure 1] Figure 1a is a schematic diagram of the friction test, and Figure 1b is a schematic diagram of the friction test specimen. [Figure 2] Figure 2 shows the measurement results of shear stress. [Figure 3] FIG. 3 is a micrograph of a comparative example. [Figure 4] FIG. 4 is a micrograph of an embodiment of the present invention.

[0061] The present invention is further illustrated by the following non-limiting examples. [Example]

[0062] Material and sample preparation The material tested was a 145 gsm UD tape of carbon fiber reinforced PAEK-based polymer. In addition to the reference UD tape, two additional tapes were prepared. The comparative tape was prepared by pressing smooth surfaces together as usual, while the inventive tape was prepared by pressing rough surfaces together in accordance with the present invention.

[0063] Preparation for interlaminar friction tests Interlaminar friction tests were performed using a benchmark friction tester, as shown in Figure 1a. As shown in Figure 1b, the test specimen consisted of two outer layers and one middle layer, with all fibers aligned longitudinally. Figure 1b shows a schematic of the specimen, with dimensions in millimeters. The specimen was mounted on a universal testing machine. The middle and outer layers could be moved relative to each other by controlling the speed V of the upper clamp. The resulting tensile force Fp was measured with a 1 kN load cell and used to calculate the shear stress:

[0064]

number

[0065] A is the area of ​​the heated pressure plate (50 × 50 mm 2 ) A normal force Fn was applied to the plate, which was measured using three load cells. The pressure area was kept constant by using an additional overlap of 15 mm, as shown in Figure 1a.

[0066] As can be seen from FIG. 2, in the example of the present invention (rough surface), a clear reduction in shear stress is observed not only in the plateau region of the graph but also in the peak value.

[0067] The lower the shear stress, the better the processing behavior.

[0068] Micrograph Photomicrographs of cross sections of both the comparative example with a smooth surface (Figure 3) and the example of the present invention with a rough surface (Figure 4) were taken using a microscope at 20x magnification. Figures 3 and 4 each show a polished surface perpendicular to the carbon fiber direction.

Claims

1. 1. A method for producing a unidirectional tape having a surface polymer layer, comprising: a) providing an impregnation slurry comprising polymer particles and water, and providing a press mold having a surface texture, the surface texture having a surface roughness Ra of 1 to 20 μm; b) impregnating a unidirectional fiber layer comprising unidirectional fibers with said impregnation slurry to obtain an impregnated unidirectional fiber layer comprising particles of said polymer; c) pressing a surface structure against the surface of the impregnated unidirectional fiber layer to move at least a portion of the polymer particles in the impregnated unidirectional fiber layer onto the surface of the impregnated unidirectional fiber layer to form a surface polymer layer on the unidirectional fiber layer; d) obtaining a unidirectional tape having a surface polymer layer; A method comprising:

2. The method of claim 1 , wherein the polymer is a thermoplastic polymer.

3. 3. The method of claim 2, wherein the thermoplastic polymer comprises or consists of a polyaryletherketone (PAEK) based polymer material, polyphenylene sulfide (PPS), polyetherimide (PEI), polyethersulfone (PESU, PES), or polysulfone (PSU).

4. The polyaryletherketone (PAEK) polymer materials include polyetherketone (poly-ether-ketone: PEK), polyetheretherketone (polyether-ether-ketone: PEEK), polyetheretherketoneketone (poly-ether-ether-ketone-ketone: PEEKK), polyetheretherketoneketone (poly-ether-ether-ketone-ketone: PEKK), and polyetherketoneetherketoneketone (poly-ether-ketone-ether-ketone-ketone: PEKEK).

4. The method of claim 3, wherein the polymerizable monomer is selected from the group consisting of polyetheretherketone etherketone (PEEKEK), polyetheretheretherketone (PEEEK), polyetherdiphenyletherketone (PEDEK), meta-polyetheretherketone (PEmEK), copolymers thereof, and mixtures thereof.

5. 5. The method according to claim 1, wherein the unidirectional fibers are carbon fibers and / or glass fibers and / or quartz.

6. 6. The method of claim 1, wherein the surface polymer layer has a surface roughness Ra of 1 to 20 μm.

7. 7. The method according to claim 1, further comprising the step of: e) drying the unidirectional fiber layer, said step e) occurring between said impregnation step b) and said pressing step c).

8. 8. The method of claim 1, further comprising the step of: f) cooling the unidirectional fiber layer before or during the pressing step c).

9. 9. The method according to claim 1, wherein the pressing step c) is carried out while the temperature T of the unidirectional fiber layer is in the range (Tc-150°C)≦T≦(Tc+150°C), where Tc is the crystallization temperature of the polymer.

10. 10. The method according to claim 1, wherein the surface structure includes a protrusion for pressing the impregnated unidirectional fiber layer and a recess for receiving the polymer extruded from the impregnated unidirectional fiber layer.

11. 11. The method of claim 1, further comprising the step g) of electrostatically depositing secondary particles onto the surface polymer layer.

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