Thermoplastic resin composite containing natural materials with low water absorption

Abstract

To provide a new thermoplastic resin blended with a natural material which has a low water absorption rate, is excellent in mechanical strength and is useful as a building member.SOLUTION: There are provided a thermoplastic resin composite body which contains dust coal having an average particle diameter of 60 to 150 μm and a thermoplastic resin, wherein the dust coal is a heat treated object at 1,000 to 1,200°C of a chaff fired material; and a method for producing the same.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a thermoplastic resin composite suitable for use as a building material, and more specifically to a composite made of powdered coal derived from rice husks and a thermoplastic resin, which has low water absorption and excellent mechanical strength such as bending strength and tensile strength. [Background technology]

[0002] Thermoplastic resin composites made from thermoplastic resins such as polyethylene, polypropylene, polystyrene, and polyvinyl chloride and natural wood flour are molded into various shapes and have been widely used as building materials. Furthermore, a technology for blending plant-derived charcoal with thermoplastic resin has also been disclosed. For example, Patent Document 1 describes a building material with a specific surface area of ​​300 m2 that is designed to adsorb and remove odors such as formaldehyde and prevent the generation and buildup of static electricity. 2 A charcoal plastic member made of charcoal having a porosity of 1 / g or more and a thermoplastic resin has been proposed. Patent Document 2 also proposes a method for producing a thermoplastic resin molded article containing charcoal particles, aiming to provide a thermoplastic resin molded article that is lightweight, has low thermal conductivity, and is excellent in mechanical properties such as tensile strength. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-183658 [Patent Document 2] Japanese Patent Application Laid-Open No. 2014-185204 [Patent Document 3] Japanese Patent Application Publication No. 2018-86853 Summary of the Invention [Problem to be solved by the invention]

[0004] Thermoplastic resin composites containing the above-mentioned wood flour have problems such as dimensional changes due to the water absorption of the blended wood flour, and after construction, they can become dislodged from mounting hardware due to deformation or expansion, which places limitations on mounting design. A commonly known method for improving the water and moisture absorption properties of wood is a process (acetylation treatment) in which acetic acid is chemically bonded to hydrophilic hydroxyl groups contained in wood components (such as cellulose and lignin) to replace them with hydrophobic acetyl groups (see, for example, Patent Document 3). While it is possible to subject wood flour to acetylation treatment, the need for such chemical treatment in the production of wood flour as a filler is disadvantageous in terms of both equipment and cost.

[0005] The technologies disclosed in both D1 and D2 utilize the adsorption properties of charcoal. To utilize this adsorption property, the moisture adsorbed before blending with the thermoplastic resin must be desorbed (by drying the charcoal) during the process of producing a thermoplastic resin molded body. However, due to the adsorption properties of the charcoal, this process takes longer than general wood powder drying. Furthermore, if the charcoal is not dried sufficiently, air bubbles may form in the molded body. Furthermore, the manufacturing of the charcoal itself (carbonization process, pulverization process, etc.) has many economic disadvantages compared to wood flour manufacturing. For example, charcoal generally requires a high burning temperature of over 800°C, which requires costs for equipment and heat treatment. In addition, the charcoal must be pulverized before being mixed with resin, and because charcoal is black, cleaning the crushing equipment is time-consuming. Furthermore, when the blend weight of the charcoal component was 50% by weight or more, the mechanical strength (bending strength, tensile strength) was lower than that of a product blended with the same amount of wood flour, and the molded body could be damaged during processing such as planing.

[0006] In view of the above problems, the present invention provides a method for manufacturing a building material having low water absorption and excellent mechanical strength. The object of the present invention is to provide a novel thermoplastic resin containing natural materials. [Means for solving the problem]

[0007] As a result of extensive research into the above-mentioned problems, the inventors have newly discovered that a composite made of powdered coal derived from rice husks having an average particle size of 60 to 150 μm and a thermoplastic resin has low water absorption and excellent mechanical strength as a building material, and have thus completed the present invention.

[0008] That is, the present invention covers the following [1] to

[14] . [1] A thermoplastic resin composite containing powdered coal having an average particle size of 60 to 150 μm and a thermoplastic resin, wherein the powdered coal is a rice husk burned material that has been heat-treated at 1000 to 1200 ° C. Thermoplastic composite. [2] The thermoplastic resin composite according to [1], wherein the powdered coal has an ignition residue of 85% or more after heating at 650°C for 4 hours in the atmosphere. [3] The thermoplastic resin composite according to [1], wherein the rice husk burned material is a rice husk burned material at 400 to 600°C. [4] The thermoplastic resin composite according to [1], wherein the powdered coal contains silicon (Si), potassium (K), and calcium (Ca), and contains potassium (K) in a mass ratio of 1 to 0.02 to 0.03. [5] The thermoplastic resin composite according to [1], wherein the thermoplastic resin composite has a water absorption rate of 1.0% or less after immersion in 35°C warm water for 96 hours. [6] The thermoplastic resin composite according to [1], wherein the thermoplastic resin composite has a bending strength of 30 MPa or more as measured in accordance with JIS K7171. [7] The thermoplastic resin composite according to [1], wherein the powdered coal is contained in an amount of 30 to 75 mass % relative to the total amount (100 mass %) of the powdered coal and the thermoplastic resin. [8] The thermoplastic resin composite according to [1], wherein the thermoplastic resin is polypropylene, polyethylene, polyethylene terephthalate or polyvinyl chloride. [9] The thermoplastic resin composite according to [1], wherein the thermoplastic resin composite is an extrusion molded product.

[10] A method for producing a thermoplastic resin composite containing powdered coal and a thermoplastic resin, A process of producing powdered coal with an average particle size of 60 to 150 μm through a heat treatment step of rice husks at a temperature of 1000 to 1200 °C. The step of mixing the obtained powdered coal with a thermoplastic resin is included. Manufacturing method.

[11] The manufacturing method according to

[10] , wherein the step of heat treating the rice husks is carried out in a self-combustion kiln.

[12] The manufacturing method according to

[10] , wherein the step of producing the powdered coal includes a step of burning rice husks at a temperature of 400 to 600°C, followed by a step of heat treating the rice husks at a temperature of 1000 to 1200°C.

[13]

[10] The method according to

[10] , further comprising a step of drying the powdered coal before the mixing step.

[14] The method according to

[10] , further comprising an extrusion molding step after the mixing step. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide a thermoplastic resin composite that has low water absorption and excellent mechanical strength and is useful as a building material. Furthermore, the powdered coal used in the thermoplastic resin composite of the present invention is made from rice husks, which are generated after harvesting rice, a useful part of a natural plant (rice), and leads to the effective use of industrial waste. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a diagram showing the cumulative distribution (volume basis) of the fine coal used in Example 1 (left axis: cumulative particle size distribution, right axis: frequency distribution). [Figure 2] FIG. 2 shows XRD charts of the powdered coal (FIG. 2(A)), the ignition residue of the powder (FIG. 2(B)), and the smoked rice husk charcoal (FIG. 2(C)) obtained in Production Example 1. [Figure 3] FIG. 3 is a scanning electron microscope image of the powdered coal obtained in Production Example 1. [Figure 4] Figure 4 shows the cumulative distribution (volume basis) of wood powder (▲), rice husk charcoal powder (▼), and binchotan charcoal powder (■) used in Comparative Examples 1 to 3 (Figure 4(A) cumulative particle size distribution, (B) frequency distribution). DETAILED DESCRIPTION OF THE INVENTION

[0011] [Thermoplastic resin composite] The present invention is a thermoplastic resin composite containing powdered coal having an average particle size of 60 to 150 μm and a thermoplastic resin. Hereinafter, the embodiments of the present invention will be described in detail, but the present invention can be implemented in many different forms and is not limited to the embodiments and examples shown below.

[0012] <Powdered coal> The powdered coal according to the present invention is a heat-treated rice husk, more specifically, a rice husk burned product that has been heat-treated at 1000 to 1200°C. More specifically, it is a heat-treated product obtained by burning rice husks at 400 to 600°C and then heat-treating the burned rice husks at 1000 to 1200°C. The average particle size of the powdered coal is 60 to 150 μm, and can be, for example, 60 to 100 μm or 60 to 80 μm. The average particle size in the present invention can be the particle size that shows 50% of the cumulative particle size distribution (volume basis) from the fine particle side.

[0013] The pulverized coal used in the present invention can have an ignition residue (ignition residue) of 85% or more after heating at 650°C for 4 hours in air, and the upper limit of the ignition residue can be, for example, about 95%. In the present invention, ignition residue refers to ash content; that is, an ignition residue of 85% or more means that, out of 100% by mass of the weight of the pulverized coal (before heating), 85% by mass or more is ash content, with the remainder including carbon and the like. The ash content mainly contains silicon dioxide (silica: SiO2), and also contains potassium oxide (KO), calcium oxide (CaO), and the like. That is, the powdered coal of the present invention contains silicon (Si), potassium (K), and calcium (Ca) as elemental components, and can contain, for example, potassium (K) in a mass ratio of 0.01 to 0.06, or in a mass ratio of 0.02 to 0.04, or in a mass ratio of 0.02 to 0.03, per 1 part silicon (Si).

[0014] The powdered coal can be, for example, the one collected through a flue for exhausting smoke provided in a rice husk combustion device when rice husks are put into the device and burned. Any rice husks threshed after harvesting may be used, and there are no particular restrictions on the variety of rice (husks). For example, when rice husks are burned at a temperature of approximately 400 to 600°C in a spontaneous combustion kiln, burned rice husks (so-called rice husk charcoal) are produced in the kiln, and the combustion air current guides the fine powder of the burned rice husks (rice husk charcoal) along with the resulting volatile gases (carbon monoxide, etc.) into the kiln's flue. Because the combustion air current, which reaches approximately 1100°C, passes through the flue, the fine powder guided into the flue is subjected to a heat treatment at 1000 to 1200°C by this combustion air current, resulting in the production of the pulverized coal of the present invention. The fine powder (pulverized coal of the present invention) that has passed through the flue and been heat-treated by the combustion air current can be collected, for example, using a cyclone dust collector. The fine powder collected in the flue has previously been disposed of during the production of rice husk charcoal, which is used as a soil conditioner, etc., as described below. The inventors have newly discovered that by combining this fine heat-treated material with a thermoplastic resin, it is possible to impart low water absorption and good mechanical strength. Thus, the powdered coal of the present invention is not only useful as an additive that imparts excellent performance to resin moldings, but is also useful from the perspective of effective utilization of waste.

[0015] The spontaneous combustion kiln mentioned above refers to a kiln that uses a method (natural method) that utilizes the combustion heat of the material itself. Generally, carbonization methods for obtaining charcoal from natural combustible materials (wood, bamboo, rice husks, etc.) can be broadly divided into two methods: one in which the carbonaceous material that is the raw material for charcoal is directly ignited, and then carbonization is carried out while limiting the amount of combustion air relative to the carbonaceous material (hereinafter referred to as the ``spontaneous combustion method''); and one in which the carbonaceous material is placed in a container equipped with an exhaust port, the carbonaceous material is heated from outside the container, creating an oxygen-free environment inside the container, and carbonization is carried out under oxygen-free conditions (hereinafter referred to as the ``external heat method''). In the spontaneous combustion carbonization method, a portion of the carbonaceous material is ignited, and the carbonaceous material is carbonized by the heat generated by the spontaneous combustion of the carbonaceous material. When carbonizing carbonaceous material using a spontaneous combustion carbonization device, the carbonaceous material itself maintains an exothermic reaction while the carbonization proceeds, which has the advantage that the temperature of the carbonaceous material can be raised almost uniformly even in a large-scale carbonization device. In the external heat method, the temperature is controlled from outside the container, which makes it easy to control carbonization in small-scale devices. However, in large-scale carbonization devices, there are disadvantages such as variations in the temperature distribution within the container, variations in the condition of the carbonaceous material (shape, size, weight, moisture content, etc.), and variations in carbonization due to the need for external energy, which makes it less economical.

[0016] The ignition residue (atmospheric pressure / 650°C / 4 hours) (ash content) of the burned rice husks (rice husk charcoal) produced in a self-combustion kiln (inside the kiln) is said to be about 50% by mass, meaning that the carbon content (charcoal component) of the charcoal is thought to be about 50% by mass. Furthermore, rice husk charcoal has a structure with many fine holes after the gas components contained in the rice husks are burned, that is, it contains fine porous voids, so it is used as a soil conditioner and other material with water retention and breathability. On the other hand, the ignition residue (ash content) of the pulverized coal (pulverized coal according to the present invention) collected via a flue through which a combustion airflow of approximately 1100°C passes is approximately 85% by mass to 95% by mass, as mentioned above, and the remaining carbon content (charcoal components) is approximately 5 to 15% by mass, making it a material with an increased ash content (lower carbon content) compared to rice husk charcoal.

[0017] In general, mineral or synthetic silicon dioxide (silica), especially crystalline silica, is known to be used to reduce the water absorption rate of plastic materials such as thermoplastic resins and to improve their mechanical strength when blended with them. On the other hand, it is known that naturally occurring carbon components have a large specific surface area and are easily able to adsorb water molecules. As described above, the pulverized coal according to the present invention has a large amount of ignition residue (ash content) and a small amount of carbon content (charcoal component). It is a material that does not contain silicon dioxide (silica), and it can achieve the same amount of silicon dioxide (silica) as the rice husk charcoal obtained in a kiln, but in a smaller amount, and it is also possible to reduce the amount of charcoal components. Therefore, a resin composite containing the powdered coal of the present invention is expected to have the same mechanical strength despite the smaller amount of powdered coal added, and also to have a low water absorption rate.

[0018] <Thermoplastic resin> The thermoplastic resin used in the thermoplastic resin composite of the present invention may be an olefin such as polypropylene or polyethylene, or polyvinyl chloride, polyethylene terephthalate, etc. These thermoplastic resins may be made from virgin raw materials or may be made by blending recycled raw materials that have been used in the market, collected, and selected, in any ratio with the virgin raw materials.

[0019] <Thermoplastic resin composite> The blending ratio of the powdered coal and the thermoplastic resin is not particularly limited, and may be determined depending on the purpose, such as the use of the building material. As an example, the powdered coal can be 30 parts by mass or more and 75 parts by mass or less (30 to 75 mass%) with respect to a total mass of 100 parts by mass of the powdered coal and the thermoplastic resin (total amount 100 mass%). The above blending amount range is preferable from the viewpoint of use as a building material. In other words, by blending the powdered coal in an amount of 30 parts by mass or more, thermal expansion can be suppressed and shrinkage during molding can be suppressed, and by blending it in an amount of 75 parts by mass or less, the risk of molding defects can be prevented.

[0020] The thermoplastic resin composite of the present invention may also be in the form of an extrusion molded article.

[0021] If necessary, various additives commonly used in the art can be blended into the thermoplastic resin composite of the present invention. For example, ultraviolet absorbers, light stabilizers, and metal deactivators can be used to improve the weather resistance of thermoplastic resin composites. Also, antioxidants and anti-foaming agents can be used to stabilize the thermoplastic resin during molding, organic or inorganic colorants can be used to enhance design, and flame retardants, antibacterial agents, anti-algae and anti-fungal agents, anti-static agents, and other additives can be used to impart functionality. These additives are preferably water-insoluble or poorly water-soluble compounds.

[0022] The thermoplastic resin composite of the present invention can have a water absorption rate of 1.0% or less after immersion for 96 hours in warm water at 35° C., and can have a water absorption rate of 5% or less after immersion for 96 hours in warm water at 60° C. The water absorption rate can be evaluated by immersing the thermoplastic resin composite in water under specified conditions and measuring the change in mass of the composite before and after immersion. The thermoplastic resin composite of the present invention may have a bending strength of 30 MPa or more as measured in accordance with JIS K7171, for example.

[0023] <Method of manufacturing thermoplastic resin composite> A method for producing a thermoplastic resin composite containing the above-mentioned powdered coal and thermoplastic resin can include, for example, the following steps. (1) A process of producing powdered coal with an average particle size of 60 to 150 μm through a heat treatment step of rice husks at a temperature of 1000 to 1200 °C; (2) A step of mixing the obtained powdered coal with a thermoplastic resin.

[0024] In a preferred embodiment, the step of heat-treating the rice husks in (1) above can be carried out in a spontaneous combustion kiln. The process for producing powdered coal can include a step of burning the rice husks at a temperature of 400 to 600°C, followed by a step of heat-treating the rice husks at a temperature of 1000 to 1200°C. The step of heat treating at a temperature of 1000 to 1200°C can actually be carried out, for example, in the flue of the spontaneous combustion calciner. Therefore, in a preferred embodiment, the pulverized coal can be produced in an apparatus equipped with a spontaneous combustion calciner (a spontaneous combustion calciner and a flue equipped in the calciner).

[0025] The step (2) of mixing the powdered coal with the thermoplastic resin can be carried out by, for example, melt kneading. The melt-mixing method and device are not particularly limited, but for example, powdered coal can be placed in a chamber equipped with blades rotating at high speed, and the temperature of the powdered coal can be raised to 150°C or higher by the shear heat generated by stirring.After that, thermoplastic resin can be added and the blades can be rotated at an even higher speed, thereby melting and mixing the powdered coal and thermoplastic resin. The powdered coal used in the present invention has a low moisture content, but if necessary, a step of drying the powdered coal may be provided before the mixing step (2) to remove moisture from the powdered coal.

[0026] The mixing step (2) can be followed by a molding step such as extrusion. For example, the mixture obtained by melt mixing can be loaded directly into a molding machine and molded into various components, or the mixture can be first pelletized using a pelletizer, and the pellets can be loaded into a molding machine and molded into various components. The molding method for molding the member is not particularly limited, and any molding machine used for molding ordinary thermoplastic resins may be used, and extrusion molding, injection molding, blow molding, etc. may be employed. Among these, extrusion molding using an extruder having one or two screws can be preferably used. [Example]

[0027] The following examples illustrate the present invention in detail, but are not intended to limit the scope of the present invention.

[0028] (Production Example 1: Production of powdered coal) The rice husks were placed into the furnace body of the spontaneous combustion furnace, which then ignited them and began the burning process. The spontaneous combustion (using the heat of combustion of the material itself) continued inside the furnace at approximately 500°C, during which time the temperature of the combustion airflow passing through the flue of the burning furnace reached approximately 1100°C. The ash (pulverized coal) emitted from the flue was collected by a dust collector. The collected pulverized coal is a heat-treated product of secondary burning of fine particles from the rice husk burned at approximately 500°C in a combustion airflow at approximately 1100°C. [Average particle size] The cumulative distribution (volume basis) of the above powdered coal is shown in Figure 1 (left axis: cumulative particle size distribution, right axis: frequency distribution, measurement results of N=3 are shown). The average particle size D50 of the powdered coal was 70 μm. [Ignition residue] The ignition residue of the above powdered coal after heating at 650°C for 4 hours in air was 91% (N=3). [XRD measurement] XRD measurements were performed on the above powdered coal, the ignition residue of the powdered coal (650°C / 4 hours), and the rice husk burned material burned at 500°C (collected from the furnace body of the spontaneous combustion furnace in Production Example 1; hereafter referred to as rice husk charcoal). Figure 2 shows the XRD charts of (A) powdered coal, (B) powdered coal (ignition residue), and (C) smoked rice husk charcoal. As shown in Figure 2, the charts of (A) powdered coal and (B) powdered coal (ignition residue) clearly show a peak at around 2θ = 22° due to crystalline silica (cristobalite). At the stage of (C) smoked rice husk charcoal, a broad diffraction pattern believed to be derived from amorphous matter was observed, and the results indicated that crystallization had progressed in (A) powdered coal and (B) powdered coal (ignition residue). [SEM-EDX measurement] Surface image observation and elemental analysis of the above powdered coal were carried out using SEM / EDX (scanning electron microscope with X-ray analyzer). <Equipment / conditions> Equipment: SU8000 (SEM) manufactured by Hitachi High-Tech Corporation XMAX(EDX) Horiba Ltd. Measurement conditions: accelerating voltage 15 kV Figure 3 shows SEM images of two randomly selected locations (Figures 3(A) and (B)). The black areas in Figure 3 indicate the conductive (carbon) tape used as the measurement substrate. As shown in Figure 3, the porous shape and numerous streaks characteristic of plant origin were confirmed, confirming that the powder had a complex shape. X-ray analysis also confirmed the presence of at least carbon (C), oxygen (O), silicon (Si), potassium (K), calcium (Ca), and manganese (Mg). Semi-quantitative analysis confirmed that the ratio of potassium (K) to silicon (Si) was 0.026 (Figure 3(A)) and 0.024 (Figure 3(B)).

[0029] (Reference production example 1) The temperature of the combustion furnace was set to (a) less than 400°C (350°C) or (b) more than 600°C (650°C), and the rice husks used as raw materials in Production Example 1 were placed into the furnace to burn the rice husks. (a) When firing was carried out at 350°C, which is lower than 400°C, not all of the rice husks in the furnace were carbonized (they did not become rice husk charcoal), and more hydrocarbon components remained than in rice husk charcoal. Furthermore, (b) when firing was carried out at 650°C, which is above 600°C, the rice husks in the furnace were carbonized, but the ignition residue did not reach 85% (the rice husks remained as charcoal), and since the particle size of the fired product was large, when it was mixed with thermoplastic resins, etc., processes such as crushing and classification would be necessary, which was expected to be economically disadvantageous.

[0030] (Reference production example 2) In Production Example 1, the equipment near the flue was cooled / heated so that the temperature of the combustion airflow passing through the flue of the firing furnace was (a) less than 1000°C (950°C) or (b) more than 1200°C (1250°C), and secondary firing was carried out at that temperature. (a) When secondary firing was performed at 950°C, which is lower than 1000°C, the ignition residue of the resulting heat-treated product was approximately 60-70%, and a large amount of carbon remained, making the heat-treated product prone to water absorption. Furthermore, (b) when the secondary firing is performed at 1250°C, which is higher than 1200°C, the amount of energy consumed for firing increases, and an increase in production costs is expected.

[0031] Example 1 The powdered coal obtained in Production Example 1 (54% by mass of the total composite) was placed in a mixer and rotated with blades having a diameter of 750 mm at a peripheral tip speed of approximately 1,750 m / min. The internal temperature was raised to 175°C by the rotation of the blades, and the powdered coal was dried until no more steam was emitted. Table 2 shows the time from when the temperature was raised to 175°C until no more steam was emitted (until steam could no longer be visually confirmed). Then, while continuing to rotate, polypropylene (44% by mass) and various additives (2% by mass) were added to the mixer. Because the torque increased and the motor load increased, the peripheral speed was reduced to approximately 580 m / min. The materials in the mixer were melted and kneaded to obtain a thermoplastic resin composite. The composite was then pelletized using a pelletizer, and the pellets were fed into a single-screw extruder so that the resin temperature reached 175°C, producing a molded product.

[0032] (Comparative Example 1) A thermoplastic resin composite and a molded body were obtained in the same manner as in Example, except that wood powder was used instead of powdered charcoal. (Comparative Example 2) A thermoplastic resin composite and a molded body were obtained in the same manner as in the examples, except that the powdered coal was changed to rice husk charcoal powder (the burned material (rice husk charcoal) recovered from the furnace body of the self-combustion combustion furnace in Manufacturing Example 1). (Comparative Example 3) The thermoplastic resin composite and the thermoplastic resin composite were prepared in the same manner as in the examples, except that the powdered coal was replaced with Binchotan powder. A molded body was obtained.

[0033] The cumulative distributions (volume basis) of the various fillers (wood powder, rice husk charcoal powder, and binchotan charcoal powder) used in Comparative Examples 1 to 3 are shown in Figure 4 ((A) cumulative particle size distribution, (B) frequency distribution), and the average particle sizes D50 are shown in Table 1 (in Figure 4, wood powder is indicated by ▲, rice husk charcoal powder by ▼, and binchotan charcoal powder by ■). As shown in Figure 4(B), the binchotan charcoal powder of Comparative Example 3 had peaks near 60 μm and 10 μm, which could be said to be a mixture of two types of fillers with different particle sizes. Table 1 also shows the results of the ignition residues of the various fillers used in Comparative Examples 1 to 3 after heating in air at 650° C. for 4 hours. [Table 1]

[0034] In addition, the average particle size D 50 The production of thermoplastic resin composites and molded articles was investigated using wood powder having an average particle size D50 of 50 μm and, as Reference Comparative Example 2, wood powder having an average particle size D50 of 200 μm. In Reference Comparative Example 1, when polypropylene was introduced into the mixer, the torque increased significantly, causing a situation in which stirring stopped during melt-kneading. In addition, in Reference Comparative Example 2, a thermoplastic resin composite was obtained by melt kneading, and granules (pellets) were obtained using a pelletizer. However, when this was fed into a single-screw extruder to perform (melt) extrusion molding, the viscosity of the molten material was low, and sufficient pressure could not be applied in the feeder of the extruder, causing the molten material to backflow, and extrusion was not possible.

[0035] <Performance evaluation> The molded articles obtained in Example 1 and Comparative Examples 1 to 3 were processed into plates measuring 100 mm in length, 10 mm in width, and 4 mm in thickness to prepare performance evaluation samples, which were subjected to the evaluation of (1) water absorption and (2) strength described below.

[0036] (1) Water absorption rate The performance evaluation samples were pre-dried at 120°C for 24 hours, and then immersed in 35°C hot water for 96 hours (4 days) or 60°C hot water for 96 hours (4 days). The mass and thickness of the samples were measured before and after immersion, and the change in mass (%) and thickness (%) after immersion were calculated. The results are shown in Table 2.

[0037] (2) Strength The bending strength and tensile strength of the above performance samples were measured in accordance with JIS K7171. The results are shown in Table 2.

[0038] [Table 2]

[0039] Conventionally, artificial wood made from thermoplastic resin materials containing wood powder, etc. has often been used outdoors, and water adheres to the surface due to rainwater, frost, and dew, causing it to absorb water. In this test, the time until the water absorption rate reaches saturation was measured in an accelerated test, and the results were compared with other materials. As shown in Table 2, Example 1, which contains powdered charcoal derived from rice husks, showed a significant improvement (reduction) in water absorption compared to Comparative Example 1, which contains wood powder, and also showed improved water absorption compared to smoked rice husk charcoal (Comparative Example 2) and binchotan powder (Comparative Example 3). Generally, water absorption tests for wood are conducted by immersing the wood in water at 25±1°C for 24 hours, and a water absorption rate of about 1% under these conditions is considered sufficient for evaluation as a product. In this test, water absorption was evaluated under harsher environments, such as immersion in 35°C hot water for 96 hours and then in 60°C hot water for 96 hours. The water absorption test results, which showed a water absorption rate of only about 1% even under such harsh conditions, highlight the low water absorption rate of the thermoplastic resin composite (artificial wood) of the present invention. Furthermore, although the mechanical strength of Example 1, which contained powdered charcoal derived from rice husks, was inferior to that of Comparative Example 1, which contained wood powder, it was equal to or better than that of the rice husk charcoal mixture (Comparative Example 2) and better than that of the binchotan powder mixture (Comparative Example 3). Furthermore, the rice husk-derived powdered charcoal used in Example 1 did not produce any visible steam after heating to 175°C (0 minutes), and it was confirmed that the material adsorbs less moisture than wood powder (20 minutes), smoked rice husk charcoal (80 minutes), and binchotan charcoal powder (250 minutes). In other words, the present invention makes it virtually unnecessary to dry the powdered charcoal before mixing with the thermoplastic resin, and it is also possible to reduce the cost and time required for such drying. [Industrial Applicability]

[0040] The present invention is a thermoplastic resin composite containing powdered rice husk charcoal made from rice husks, a natural resource that is also an industrial waste, and a thermoplastic resin. This composite can be extruded to form solid boards, hollow boards, hollow square timber, etc., and can be widely used as artificial wood in building materials.

Claims

1. A thermoplastic resin composite comprising powdered coal having an average particle size of 60 to 150 μm and a thermoplastic resin, wherein the powdered coal is a product of rice husk burned material, which is a product of rice husks burned in a spontaneous combustion furnace at 400 to 600 ° C., and heat-treated at 1000 to 1200 ° C. in the flue of the spontaneous combustion furnace; The powdered coal is contained in a ratio of 30 to 75% by mass with respect to the total amount (100% by mass) of the powdered coal and the thermoplastic resin, Thermoplastic composite.

2. 2. The thermoplastic resin composite according to claim 1, wherein the powdered coal has an ignition residue of 85% or more after heating at 650°C for 4 hours in air.

3. The powdered coal contains silicon (Si), potassium (K), and calcium (Ca), and contains potassium (K) in a mass ratio of 0.02 to 0.03 relative to silicon (Si). The thermoplastic resin composite according to claim 1.

4. 2. The thermoplastic resin composite according to claim 1, wherein the thermoplastic resin composite has a water absorption rate of 1.0% or less after immersion in 35°C warm water for 96 hours.

5. The thermoplastic resin composite according to claim 1, wherein the thermoplastic resin composite has a flexural strength of 30 MPa or more as measured in accordance with JIS K7171.

6. The thermoplastic resin composite according to claim 1 , wherein the thermoplastic resin is polypropylene, polyethylene, polyethylene terephthalate, or polyvinyl chloride.

7. The thermoplastic resin composite according to claim 1 , wherein the thermoplastic resin composite is an extrusion molded article.

8. A method for producing a thermoplastic resin composite containing powdered coal and a thermoplastic resin, In a self-combustion type calcination furnace, the rice husk is calcined at a temperature of 400 to 600 ° C, followed by the self-combustion type calcination furnace. a step of producing pulverized coal having an average particle size of 60 to 150 μm through a heat treatment step at a temperature of 1000 to 1200 ° C. in the flue of Mixing the obtained powdered coal with a thermoplastic resin, The powdered coal is contained in a ratio of 30 to 75% by mass relative to the total amount (100% by mass) of the powdered coal and the thermoplastic resin, Method for manufacturing thermoplastic resin composites.

9. The step of drying the powdered coal before the mixing step is included. The method of claim 8.

10. After the mixing step, an extrusion molding step is further included. The method of claim 8.

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