Composition and filament for carbon molded body for production of carbon molded body by three-dimensional printer molding and carbonization

Abstract

The present invention is a composition for a carbon molded body for production of a carbon molded body by three-dimensional printer molding and carbonization, the composition containing a pitch. The content ratio of the pitch is 10 mass % or more with respect to the mass of the composition.

Description

Carbon body composition and filament for producing carbon bodies by three-dimensional printer molding and carbonization

[0001] The present invention relates to a carbon compact composition, particularly a carbon compact composition that can be molded using a three-dimensional printer and maintains its shape during carbonization. The present invention also relates to a filament made of such a carbon compact composition.

[0002] A three-dimensional (3D) printer is a technology that calculates the shape of a thin cross section from three-dimensional data input by CAD or the like, and then builds up multiple layers of material based on the calculation results to create a three-dimensional object. Also known as additive manufacturing technology, 3D printers do not require the molds used in injection molding, and can create complex three-dimensional structures that cannot be molded by injection molding, making them a popular technology for high-mix, low-volume production.

[0003] Various materials have been developed for 3D printers (also known as additive manufacturing materials) depending on the type and application of the 3D printer, and the main materials used include photocurable resins, thermoplastic resins, metals, ceramics, wax, etc.

[0004] 3D printers are classified by the method used to create three-dimensional shapes from materials, including (1) binder spraying, (2) directed energy deposition, (3) material extrusion, (4) material spraying, (5) powder bed fusion, (6) sheet lamination, and (7) liquid vat photopolymerization. Among the above methods, 3D printers using the material extrusion method (also known as fused deposition modeling) are becoming increasingly affordable, and demand for them for home and office use is growing. Furthermore, 3D printers using powder bed fusion are attracting attention due to the development of systems that improve the recyclability of powder materials.

[0005] Fused deposition modeling (material extrusion) is a method of creating a shape by fluidizing thermoplastic resin in the form of threads called filaments using a heating means inside the extrusion head, then ejecting it from a nozzle onto a platform, and layering it little by little according to the cross-sectional shape of the desired object while cooling and solidifying it.

[0006] Various compositions have been disclosed as resin compositions for such fused deposition modeling three-dimensional printers.

[0007] Patent Document 1 discloses a resin composition that is a modeling material for three-dimensional printers, which contains inorganic fibers having an average fiber length of 1 μm to 300 μm and an average aspect ratio of 3 to 200, and a thermoplastic resin.

[0008] Patent Document 2 discloses a filament for a fused deposition model three-dimensional printer, which is formed from a functional resin composition containing a thermoplastic matrix resin and a functional nanofiller dispersed in the thermoplastic matrix resin.

[0009] International Publication No. 2018 / 043231 Japanese Patent Application Laid-Open No. 2016-28887

[0010] Conventional molded articles that can be molded using three-dimensional printers are resin-based molded articles.

[0011] In contrast to this, the present invention provides a composition that can be molded using a three-dimensional printer, and from which a carbon molded body can be obtained by carbonizing the obtained molded body.

[0012] After extensive research, the present inventors have found that the above-mentioned problems can be solved by the following means, and have thus completed the present invention. Specifically, the present invention is as follows: <Aspect 1> A carbon body composition for producing a carbon body by three-dimensional printer molding and carbonization, the carbon body composition containing pitch, the pitch content being 10 mass% or more relative to the mass of the carbon body composition. <Aspect 2> The carbon body composition according to Aspect 1, in which the pitch has a softening point of 50°C or more and 400°C or less. <Aspect 3> The carbon body composition according to Aspect 1 or 2, further containing a thermoplastic resin. <Aspect 4> The carbon body composition according to Aspect 3, in which the thermoplastic resin has a residual carbon percentage of 30% or less. <Aspect 5> The carbon body composition according to Aspect 3 or 4, in which the thermoplastic resin content is 10 mass% or more and 80 mass% or less relative to the mass of the carbon body composition. <Aspect 6> The composition for a carbon molded body according to any one of Aspects 1 to 5, further comprising a carbonaceous filler. <Aspect 7> The composition for a carbon molded body according to Aspect 6, wherein the carbonaceous filler is at least one selected from the group consisting of graphite and carbon fiber. <Aspect 8> The composition for a carbon molded body according to Aspect 6 or 7, wherein the content of the carbonaceous filler is 10% by mass or more and 80% by mass or less, relative to the mass of the composition for a carbon molded body. <Aspect 9> The composition for a carbon molded body according to any one of Aspects 1 to 8, wherein the overall carbon remaining rate of the composition for a carbon molded body is 15% by mass or more and 85% or less. <Aspect 10> A filament for producing a carbon molded body by three-dimensional printer molding and carbonization, comprising the carbon molded body composition according to any one of Aspects 1 to 9.

[0013] According to the present invention, it is possible to provide a composition that can be molded using a three-dimensional printer, and from which a carbon molded body can be obtained by carbonizing the obtained molded body.

[0014] <<Composition for Carbon Molded Body>> The composition for carbon molded body of the present invention is a composition for carbon molded body for producing a carbon molded body by three-dimensional printer molding and carbonization, and contains pitch, and the pitch content is 10 mass % or more relative to the mass of the composition.

[0015] That is, the present invention also relates to use of the above-mentioned composition for a carbon compact for producing a carbon compact by three-dimensional printer molding and carbonization.

[0016] The carbon molding composition of the present invention can be made into a filament form for producing a carbon molding by three-dimensional printer molding and carbonization, i.e., a filament form that can be fed into the extrusion head of a 3D printer and can maintain its shape by carbonization.

[0017] The inventors have found that by including pitch in the composition for carbon molding at the above content, it is possible to obtain a composition for carbon molding that can be molded using a three-dimensional printer and that can maintain its shape after carbonization. Without wishing to be bound by theory, this is thought to be because the pitch has both a high residual carbon fraction and fluidity at high temperatures.

[0018] The carbon remaining ratio of the composition for a carbon molded body of the present invention as a whole may be 15% by mass or more and 85% by mass or less. This carbon remaining ratio may be 15% by mass or more, 20% by mass or more, 25% by mass or more, 30% by mass or more, or 35% by mass or more, and may be 85% by mass or less, 80% by mass or less, 75% by mass or less, 70% by mass or less, 65% by mass or less, 60% by mass or less, or 55% by mass or less.

[0019] Here, in the present invention, the "residual carbon ratio" is a value measured as follows.

[0020] (Residual Carbon Ratio) Using a thermobalance, the temperature was raised from room temperature to 900°C at a rate of 20°C / min in a nitrogen atmosphere, and the temperature at 850°C was taken as the mass after firing, and the residual carbon ratio (mass%) was calculated using the following formula: Residual Carbon Ratio (%) = (Mass after firing (850°C) / Mass before firing) × 100

[0021] The carbon molding composition of the present invention may further contain an optional thermoplastic resin, particularly a thermoplastic resin having a residual carbon percentage of 30% or less. The presence of such a thermoplastic resin makes the carbon molding composition more susceptible to plastic deformation during molding with a 3D printer, thereby improving moldability with a 3D printer.

[0022] The carbon compact composition of the present invention may further contain an optional carbonaceous filler, which increases the overall carbon content of the carbon compact composition, thereby making it easier to maintain the shape before carbonization even after carbonization.

[0023] The carbon molding composition of the present invention can be obtained by kneading the constituent materials together with a solvent component and molding the mixture by known means such as extrusion molding. The solvent component can be, for example, an alcohol such as ethanol.

[0024] All mass contents referred to in this specification are based on the mass of solids, i.e., components other than the solvent component.

[0025] Each component of the present invention will be described below.

[0026] <Pitch> Pitch generally refers to a by-product of petroleum and coal tar that is solid at room temperature. Amorphous carbon can be produced by carbonizing pitch.

[0027] As the pitch, either mesophase pitch or isotropic pitch may be used.

[0028] Mesophase pitch refers to a pitch in which the constituent molecules are in a liquid crystal state and oriented, while isotropic pitch refers to a pitch in which the constituent molecules are randomly oriented and are optically isotropic.

[0029] As such pitch, commercially available pitch can be used.

[0030] The residual carbon ratio of the pitch may be 15% by mass or more and 85% by mass or less, and may be 15% by mass or more, 20% by mass or more, 25% by mass or more, 30% by mass or more, 35% by mass or more, 40% by mass or more, or 45% by mass or more, and may be 85% by mass or less, 80% by mass or less, 75% by mass or less, 70% by mass or less, 65% by mass or less, 60% by mass or less, or 55% by mass or less.

[0031] The softening point of the pitch may be 50° C. or higher and 400° C. or lower. This softening point may be 50° C. or higher, 60° C. or higher, 70° C. or higher, 80° C. or higher, 90° C. or higher, 100° C. or higher, 110° C. or higher, 120° C. or higher, 130° C. or higher, 140° C. or higher, 150° C. or higher, 160° C. or higher, 170° C. or higher, 180° C. or higher, 190° C. or higher, 200° C. or higher, 210° C. or higher, 220° C. or higher, 230° C. or higher, or 240° C. or higher, or 400° C. or lower, 390° C. or lower, 380° C. or lower, 370° C. or lower, 360° C. or lower, 350° C. or lower, 340° C. or lower, 330° C. or lower, 320° C. or lower, 310° C. or lower, 300° C. or lower, 290° C. or lower, 280° C. or lower, 270° C. or lower, or 260° C. or lower. In particular, a softening point of 200° C. or higher is preferred from the viewpoint of increasing the physical strength of the resulting carbon molded article. Furthermore, pitches having a softening point of 350° C. or lower generally have low quinoline-insoluble and toluene-insoluble contents, which is preferred from the viewpoint of enabling more stable three-dimensional modeling.

[0032] The softening point was measured by the ring and ball method in accordance with JIS K2425. Specifically, a sample that passed through an 840 μm (20 mesh) sieve was first heated and melted at a temperature not exceeding 50°C above the estimated softening point, and poured into a φ16×H6.4 mm ring to solidify. The ring was then placed on a sample rack, and a steel ball with a diameter of 9.525 mm and a weight of 3.5 g was placed in the center of the ring. The rack was then immersed in glycerin, and the bath temperature was increased at a rate of 5°C / min. The softening point was determined as the temperature at which the sample softened and the steel ball reached the bottom plate 25.4 mm below the ring.

[0033] <Thermoplastic Resin> As the thermoplastic resin, for example, a thermoplastic resin having a carbon residue rate of less than 30% can be used. This carbon residue rate may be 25% or less, 20% or less, 15% or less, 10% or less, 5% or less, 3% or less, or 1% or less, or may be 0%, and a carbon residue rate of 10% or less is particularly preferable from the viewpoint of improving moldability using a 3D printer.

[0034] Examples of such thermoplastic resins that can be used include vinyl resins such as vinyl chloride resin and vinyl acetate resin, acrylic resins such as polymethyl methacrylate (PMMA), thermoplastic polyimide (TPI), styrene resin, polyolefin resin, and copolymers thereof. Commercially available thermoplastic resins can be used.

[0035] The content of the thermoplastic resin may be 10% by mass or more and 80% by mass or less, based on the mass of the carbon molding composition. From the viewpoint of obtaining a molded body after carbonization, this content is preferably 10% by mass or more, 15% by mass or more, 20% by mass or more, 25% by mass or more, 30% by mass or more, or 35% by mass or more. This content may be 80% by mass or less, 75% by mass or less, 70% by mass or less, 65% by mass or less, 60% by mass or less, 55% by mass or less, 50% by mass or less, or 45% by mass or less.

[0036] The melt mass flow rate of the thermoplastic resin according to JIS K7210-1, when measured under conditions of a temperature of 360°C and a load of 2.16 kgf, may be 0.1 g / 10 min or more and 2.5 g / 10 min or less, for example, 0.1 g / 10 min or more, 0.5 g / 10 min or more, or 1.0 g / 10 min or more, and may be 10.0 g / 10 min or less, 5.0 g / 10 min or less, 3.0 g / 10 min or less, or 2.5 g / 10 min or less.

[0037] The melting point of the thermoplastic resin may be 250°C or higher and 400°C or lower, for example, 250°C or higher, 260°C or higher, 270°C or higher, 280°C or higher, 290°C or higher, 300°C or higher, 310°C or higher, or 315°C or higher, or 400°C or lower, 390°C or lower, 380°C or lower, 370°C or lower, 360°C or lower, 350°C or lower, 340°C or lower, 330°C or lower, or 325°C or lower.

[0038] The thermal decomposition temperature of the thermoplastic resin may be 380°C or higher and 500°C or lower, for example, 380°C or higher, 390°C or higher, 400°C or higher, 410°C or higher, 420°C or higher, or 430°C or higher, and may be 500°C or lower, 490°C or lower, 480°C or lower, 470°C or lower, 460°C or lower, 450°C or lower, or 440°C or lower.

[0039] Here, in the present invention, the melting point and thermal decomposition temperature can be measured by differential thermal analysis-thermogravimetric analysis (TG-DTA) under conditions of a nitrogen atmosphere and a heating rate of 10 ° C. / min. Specifically, a sample is heated under a nitrogen atmosphere at a heating rate of 10 ° C. / min, and a curve (TG curve) with mass on the vertical axis and temperature on the horizontal axis and a curve (DTA curve) with temperature difference on the vertical axis and temperature on the horizontal axis are obtained by differential thermal analysis-thermogravimetric analysis (TG-DTA) in accordance with JIS K0129, whereby the melting point and thermal decomposition temperature can be obtained. More specifically, when an endothermic peak is observed in the DTA curve at a position where no mass loss is observed in the TG curve, the temperature at which this minimum value is obtained can be determined as the melting point. Furthermore, when a mass loss is observed in the TG curve, the temperature at which the mass loss begins can be determined as the thermal decomposition temperature.

[0040] <Carbonaceous Filler> The carbonaceous filler may be carbon fibers and / or carbon particles dispersed in the pitch. In the carbon molded body obtained after carbonization, this carbonaceous filler will be dispersed in amorphous carbon.

[0041] Examples of carbon fibers include, but are not limited to, milled fibers and chopped fibers, which may be used alone or in combination.

[0042] The average length of the carbon fibers may be 10 μm or more and 800 μm or less, for example, 10 μm or more, 15 μm or more, 20 μm or more, 25 μm or more, 30 μm or more, 35 μm or more, 40 μm or more, 45 μm or more, 50 μm or more, 55 μm or more, 60 μm or more, 65 μm or more, 70 μm or more, 75 μm or more, 80 μm or more, 85 μm or more, or 90 μm or more, and may be 800 μm or less, 700 μm or less, 600 μm or less, 500 μm or less, 400 μm or less, 300 μm or less, 200 μm or less, 180 μm or less, 150 μm or less, 120 μm or less, or 110 μm or less.

[0043] The average fiber diameter of the carbon fibers may be 1 μm or more and 20 μm or less, for example, 1 μm or more, 3 μm or more, 5 μm or more, or 7 μm or more, and may be 20 μm or less, 15 μm or less, 12 μm or less, or 10 μm or less. The average length of the carbon fibers can be determined by observing and measuring 50 or more fibers randomly selected using a scanning electron microscope (SEM) or the like, and calculating the number average.

[0044] Examples of carbon particles include graphene, carbon nanotubes, graphite, and carbon black, which may be used alone or in combination.

[0045] The shape of the carbon particles is not particularly limited, and may be, for example, flat, array-like, spherical, or the like.

[0046] The average particle size of the carbon particles may be 100 nm or more and 20 μm or less, for example, 100 nm or more, 200 nm or more, 300 nm or more, 500 nm or more, 700 nm or more, 1 μm or more, 2 μm or more, or 3 μm or more, and may be 20 μm or less, 15 μm or less, 10 μm or less, or 7 μm or less. Here, in this specification, the average particle size means the median diameter (D50) calculated on a volume basis by laser diffraction method.

[0047] The content of the carbonaceous filler in the composition for a carbon molded body may be 5% by mass or more and 85% by mass or less, and is preferably, for example, 5% by mass or more, 10% by mass or more, 15% by mass or more, 20% by mass or more, or 23% by mass or more, relative to the mass of the composition for a carbon molded body, from the viewpoint of maintaining the shape. This content may be 85% by mass or less, 80% by mass or less, 75% by mass or less, 70% by mass or less, 65% by mass or less, 60% by mass or less, 55% by mass or less, or 50% by mass or less.

[0048] <<Method for Producing a Carbon Molded Body>> The method of the present invention for producing a carbon molded body includes: three-dimensionally printing the composition described above to provide a precursor molded body; and heat-treating the precursor molded body in a non-oxidizing atmosphere to carbonize the precursor molded body, thereby providing a carbon molded body.

[0049] <Providing Precursor Molded Body> The precursor molded body is provided by three-dimensionally printing the above composition.

[0050] The three-dimensional printing method used in the present invention is not particularly limited, and may be, for example, a material extrusion method (fused deposition modeling) or the like.

[0051] <Providing a Carbon Molded Body> The carbon molded body is provided by carbonizing the precursor molded body by heat treating the precursor molded body in a non-oxidizing atmosphere, which converts the pitch, and in some cases the thermoplastic resin, into amorphous carbon.

[0052] The non-oxidizing atmosphere may be, for example, an inert gas atmosphere such as nitrogen gas, argon gas, or helium gas, or a reducing atmosphere such as hydrogen-containing nitrogen gas, and among these, a nitrogen gas atmosphere is preferably used from the viewpoints of ease of handling and low cost. Note that the non-oxidizing atmosphere may contain oxygen to the extent that complete combustion of the layers laminated by three-dimensional printing can be prevented and carbonization can be achieved, and may contain oxygen in a range of, for example, 5% by volume or less, 3% by volume or less, or 1% by volume or less, or may not contain oxygen at all.

[0053] The temperature of the heat treatment may be 600°C or higher and 1200°C or lower, for example, 600°C or higher, 650°C or higher, 700°C or higher, 750°C or higher, 800°C or higher, 850°C or higher, or 900°C or higher, and may be 1200°C or lower, 1150°C or lower, 1100°C or lower, 1050°C or lower, or 1000°C or lower.

[0054] The present invention will be specifically explained with reference to examples and comparative examples, but the present invention is not limited to these.

[0055] The materials shown in Table 1 were kneaded in the content ratios shown in Table 1 to obtain compositions of Examples 1 to 4 and Comparative Examples 1 and 2. The details of the materials shown in Table 1 are as follows: MFP-A: Mesophase pitch A (residual carbon rate 50% by mass, softening point 250°C) MFP-B: Mesophase pitch B (residual carbon rate 30% by mass, softening point 90°C) MFP-C: Mesophase pitch C (residual carbon rate 70% by mass, softening point 360°C) PVAc: Vinyl acetate resin EtOH: Ethanol

[0056] <Evaluation> <Three-dimensional moldability> Each of the obtained carbon molded body compositions was tried to be molded using a three-dimensional printer, and the obtained molded body was visually confirmed. The evaluation results are as follows: A: The input shape was output. B: The input shape was output almost exactly, although it was a little rough. C: The input shape could not be output.

[0057] <Shape retention after carbonization> Each of the obtained carbon molded body compositions was molded into a given block shape by extrusion molding to obtain a precursor molded body for evaluating the shape after carbonization. Next, the resin molded body was carbonized by heat treatment at 1000°C for 50 hours in a non-oxidizing atmosphere to obtain a carbon molded body. The shape of the obtained carbon molded body was visually confirmed. The evaluation criteria are as follows: A: A molded body with a shape almost similar to the shape before carbonization was obtained. B: A molded body with a shape almost similar to the shape before carbonization was obtained, although some details were slightly distorted. C: A molded body with a shape that was significantly different from the shape before carbonization was obtained, or no molded body was obtained.

[0058] Table 1 shows the configurations and evaluation results of the examples and comparative examples.

[0059]

[0060] It can be seen from Table 1 that the compositions of the examples, which contain pitch and in which the pitch content is 10 mass % or more relative to the mass of the composition, have good three-dimensional formability and can maintain their shape even after carbonization.

Claims

1. A composition for a carbon formed body for manufacturing a carbon formed body by three-dimensional printer forming and carbonization, which contains pitch, and the content rate of the pitch is 10% by mass or more with respect to the mass of the composition for a carbon formed body.

2. The composition for a carbon formed body according to claim 1, wherein the softening point of the pitch is 50°C or higher and 400°C or lower.

3. The composition for a carbon formed body according to claim 1 or 2, which further contains a thermoplastic resin.

4. The composition for a carbon formed body according to claim 3, wherein the char residue rate of the thermoplastic resin is 30% or less.

5. The composition for a carbon formed body according to claim 3 or 4, wherein the content rate of the thermoplastic resin is 10% by mass or more and 80% by mass or less with respect to the mass of the composition for a carbon formed body.

6. The composition for a carbon formed body according to any one of claims 1 to 5, which further contains a carbonaceous filler.

7. The composition for a carbon formed body according to claim 6, wherein the carbonaceous filler is at least one selected from the group consisting of graphite and carbon fiber.

8. The composition for a carbon formed body according to claim 6 or 7, wherein the content rate of the carbonaceous filler is 10% by mass or more and 80% by mass or less with respect to the mass of the composition for a carbon formed body.

9. The composition for a carbon formed body according to any one of claims 1 to 8, wherein the overall char residue rate of the composition for a carbon formed body is 15% or more and 85% or less.

10. A filament for manufacturing a carbon formed body by three-dimensional printer forming and carbonization, which is composed of the composition for a carbon formed body according to any one of claims 1 to 9.

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