Molded article, and method for manufacturing molded article

Abstract

To provide a molded article of a wood flour resin composite material having sufficient thickness and excellent appearance, and a method for manufacturing the molded article. 【Solution means】A molded article containing wood flour and resin, having an average wall thickness of 5.0 mm or more, the content of the wood flour being 10% by mass or more based on the total amount of the molded article, and the total number of defective parts on the surface and inside of the molded article being 2 or less, and the area of each of the defective parts on the surface and any cross section being 0.50 mm 2 or less, the molded article.

Description

Technical Field

[0001] The present invention relates to a molded article and a method for manufacturing the molded article.

Background Art

[0002] The technology of compounding wood powder and resin has a history of about 30 years or more. Due to the increasing environmental awareness, in recent years, the development of molded articles made of wood powder resin composites with desired appearance and physical properties by applying the technology of compounding wood powder and resin has attracted more and more attention.

[0003] For example, in Patent Document 1, for the purpose of providing a method for manufacturing a wood resin molded article excellent in strength and moisture resistance, (1) a step of extruding a molten wood powder-containing resin composition containing a thermoplastic resin and wood powder to produce a molded body in a heated state, and (2) a step of immersing the molded body in a solution containing a modifier and cooling it are included. A method for manufacturing a wood resin molded article is disclosed.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, regarding such wood resin molded articles, it is hard to say that the development of thick molded articles has been sufficient. As a result of the inventors' intensive research, it has been found that in conventional molded articles using wood powder and resin, when the thickness increases, air bubbles tend to remain inside the molded article, which particularly easily impairs its appearance.

[0006] Therefore, the present invention has been made in view of the above problems, and an object thereof is to provide a molded article made of a wood powder resin composite having a sufficient thickness and excellent appearance, and a method for manufacturing the molded article.

Means for Solving the Problems

[0007] As a result of intensive studies to achieve the above object, the present inventors have found that the above problems can be solved by the following configuration, and have completed the present invention.

[0008] That is, the present invention is as follows. [1] A molded article containing wood powder and a resin, having an average wall thickness of 5.0 mm or more, wherein the content of the wood powder is 10% by mass or more based on the total amount of the molded article, wherein the total number of defective portions on the surface and inside of the molded article is 2 or less, and the area of each of the defective portions on the surface and any cross section is 0.50 mm 2 or less. Molded article. [2] Further comprising a compatibilizer, The molded article according to [1]. [3] wherein the content of the wood powder is more than 50% by mass based on the total amount of the molded article, The molded article according to [1] or [2]. [4] wherein the resin contains a biodegradable resin, The molded article according to any one of [1] to [3]. [5] A mixing step of mixing wood powder and a resin to obtain a wood powder resin composite, and a molding step of molding the wood powder resin composite, A method for manufacturing a molded article. [6] wherein the molding step has a cooling step of cooling the wood powder resin composite, and the cooling time in the cooling step is 120 seconds or less, The method for manufacturing a molded article according to [5].

Advantages of the Invention

[0009] According to the present invention, it is possible to provide a molded article of a wood flour resin composite material having a sufficient thickness and excellent appearance, and a method for manufacturing the molded article.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Figure 3A

Figure 3B

Figure 3C

Embodiments for Carrying Out the Invention

[0011] Hereinafter, embodiments for carrying out the present invention (hereinafter simply referred to as "the present embodiment") will be described in detail with reference to the drawings as necessary. However, the present invention is not limited to the following present embodiment. The present invention can be variously modified without departing from the gist thereof. In the drawings, the positional relationships such as up, down, left, and right are based on the positional relationships shown in the drawings unless otherwise specified. Furthermore, the dimensional ratios in the drawings are not limited to the illustrated ratios.

[0012] 1. Molded Article The molded article of the present embodiment is a molded article containing wood flour and resin, having an average wall thickness of 5.0 mm or more, the content of the wood flour being 10% by mass or more based on the total amount of the molded article, and the total number of defective parts on the surface and inside of the molded article being 2 or less, and the area of each of the surface and any cross-section of the defective part being 0.50 mm 2 or less as follows.

[0013] Generally, when molding a resin, it is necessary to raise the temperature to the temperature at which the resin becomes fluid. Therefore, even when molding a wood flour resin composite material in which wood flour and resin are compounded, it is necessary to raise the temperature to a predetermined temperature. However, this causes bubbles to be generated, and it becomes easier for the bubbles to remain inside the molded product. The bubbles are derived from the evaporation of moisture, the thermal decomposition gas of the resin, and the wood gas from the wood flour. In particular, the wood gas tends to be generated in a larger amount than the thermal decomposition gas of the resin. And, the thicker the wall thickness of the molded product, the easier it is for the bubbles to accumulate inside the resin existing particularly near the surface of the molded product. This is because bubbles are likely to be generated inside the resin due to the rapid solidification of the vicinity of the surface of the molded product during the molding process. However, when the wall thickness of the molded product is thick, it becomes difficult for the resin pressurized inside the mold to extrude the bubbles to the outside of the mold. As a result, defective parts are likely to occur on the surface and / or inside of the molded product. In particular, when machining such as cutting or painting is performed after molding, the appearance of the molded product is likely to be impaired.

[0014] On the other hand, the molded product of the present embodiment has the above configuration, and thus has a sufficient thickness and excellent appearance.

[0015] 1.1. Wood Flour The wood flour of this embodiment is obtained by pulverizing wood into a powder form, and means wood flour that has undergone cooking treatment. The upper limit value of the particle size range of the wood flour of this embodiment is not particularly limited, but is preferably 1000 μm or less, more preferably 900 μm or less, still more preferably 700 μm or less, and even more preferably 500 μm or less. The lower limit value of the particle size range is not particularly limited, but is preferably 10 μm or more, more preferably 50 μm or more, and still more preferably 100 μm or more. When the upper limit value of the particle size range of the wood flour is 1000 μm or less, the compatibility with the resin is improved, and the strength and toughness of the molded product of the wood flour resin composite tend to be improved. Also, when the lower limit value of the particle size range of the wood flour is 10 μm or more, the moldability of the wood flour resin composite tends to be improved. The above particle size range is not particularly limited, but can be adjusted, for example, by a sieving method. Specifically, for example, wood flour with a particle size range of 1000 μm or less can be obtained by sieving using a filter with a mesh size of 1000 μm. Also, wood flour with a particle size range of 40 μm or more and 60 μm or less can be obtained by capturing the wood flour that has passed through a filter with a mesh size of 60 μm with a filter with a mesh size of 40 μm.

[0016] Also, the content of wood flour with a particle size range of 10 μm or more and 1000 μm or less is preferably 70% by mass or more, more preferably 80% by mass or more, still more preferably 90% by mass or more, particularly preferably 95% by mass or more, and extremely preferably 98% by mass or more, based on the total amount of the wood flour. The upper limit value is not particularly limited, and may be, for example, 100% by mass.

[0017] Regarding the method for pulverizing wood, a conventionally known method can be used and is not particularly limited. Examples include pulverization by a cutting tool method and pulverization by an impact pulverization method.

[0018] Wood refers to all plant-derived lignocellulosic materials, that is, lignocellulosic materials containing lignin, hemicellulose, and cellulose. Although not particularly limited, examples of wood include zelkova, cacao, maple, white ash, cedar, paulownia, black pine, hinoki, and beech. Among these, from the perspective of high specific gravity and excellent compatibility with resin, it is preferably one or more of maple and white ash, and from the perspective of excellent appearance of the molded product, it is preferably to contain cacao. In addition, since cacao is a wood with a high oil content, when a molded product is manufactured using only cacao as the wood, the oil content is likely to ooze out when it comes into contact with hot water or the like. From the perspective of suppressing this, it is preferable that the wood contains cacao and other woods, such as zelkova. The wood may be used alone or in combination of two or more.

[0019] Cooking means a process of bringing water vapor into contact with wood powder. Details of the cooking will be described later.

[0020] The content of the wood powder is 10% by mass or more based on the total amount of the molded product, and may be 10% by mass or more and 80% by mass or less, may be 20% by mass or more and 75% by mass or less, may be 30% by mass or more and 70% by mass or less, may be 40% by mass or more and 65% by mass or less, or may be 50% by mass or more and 60% by mass or less.

[0021] From the perspective of environmental compatibility, the content of the wood powder is preferably 20% by mass or more, more preferably 30% by mass or more, still more preferably 40% by mass or more, even more preferably 50% by mass or more, and particularly preferably 55% by mass or more based on the total amount of the molded product.

[0022] Also, the upper limit of the content of the wood powder is preferably 80% by mass, and may be 75% by mass, 70% by mass, 65% by mass, or 60% by mass from the perspectives of ease of molding and the strength and toughness of the molded product.

[0023] 1.2. Resin The resin of this embodiment is not particularly limited, but is preferably a thermoplastic resin, and conventionally known resins can be used. The resin is not particularly limited, and examples thereof include olefin resins such as polypropylene and polyethylene, polylactic acid, acrylic resins, polyester resins, and thermoplastic elastomers.

[0024] Among them, from the viewpoint of excellent environmental compatibility, the resin of this embodiment preferably contains at least one of a biodegradable resin and a biomass resin, and more preferably contains a biodegradable resin. Here, the biomass resin means a resin produced using a plant-derived raw material. The biomass resin is not particularly limited, and examples of the resin using a plant-derived raw material include bio-polyethylene, bio-polypropylene, bio-polyester, bio-polyurethane, and bio-phenol resin. In addition, the biodegradable resin means a resin having a property of being decomposed by microorganisms existing in nature. The biodegradable resin is not particularly limited, and examples thereof include polylactic acid, polyhydroxyalkanoic acid, and polybutylene succinate. These may be used alone or in combination of two or more.

[0025] The melting temperature of the resin is preferably 140°C or higher and 180°C or lower, and more preferably 150°C or higher and 170°C or lower. When the melting temperature of the resin is 180°C or lower, after being compounded with wood powder, it can be molded without causing thermal decomposition (burning) of the wood powder, and the molded product of the wood powder resin composite tends to be excellent in strength and toughness.

[0026] The resin of this embodiment preferably has a tensile strength measured under the following measurement condition A of 25 MPa or higher, more preferably 30 MPa or higher, and even more preferably 35 MPa or higher. When the tensile strength of the resin is 25 MPa or higher, the molded product tends to be even more excellent in strength. The upper limit of the tensile strength is not particularly limited. For example, the tensile strength may be 100 MPa or lower, or 80 MPa or lower.

[0027] <Measurement Condition A> Sample: dumbbell piece (total length: 170 mm, distance between tab parts: 105 mm, length of parallel part: 85 mm, width of end part: 20 mm, width of central parallel part: 10 mm, thickness: 4.0 mm Test room temperature: 23 ± 2 °C Test humidity: 50 ± 5% RH Conditioning: in the test room for 88 hours or more Testing machine: Autograph AG-100kNXPlus (manufactured by Shimadzu Corporation) Load cell capacity: 5 kN Extensometer: TRViewX500D (manufactured by Shimadzu Corporation) Gauge length: 75 mm Distance between grips: 115 mm Test speed: 50 mm / min

[0028] The resin of this embodiment preferably has a flexural strength of 30 MPa or more, more preferably 35 MPa or more, and even more preferably 40 MPa or more when measured under the following Measurement Condition B. When the flexural strength of the resin is 30 MPa or more, the strength of the molded product tends to be more excellent. The upper limit of the above flexural strength is not particularly limited. For example, the flexural strength may be 100 MPa or less, or may be 80 MPa or less.

[0029] <Measurement Condition B> Sample: dumbbell piece (total length: 170 mm, distance between tab parts: 105 mm, length of parallel part: 85 mm, width of end part: 20 mm, width of central parallel part: 10 mm, thickness: 4.0 mm Test room temperature: 23 ± 2 °C Test humidity: 50 ± 5% RH Conditioning: in the test room for 88 hours or more Testing machine: Autograph AG-10TD (manufactured by Shimadzu Corporation) Load cell capacity: 5 kN Span between supports: 64 mm Radius of support base: 5 mm Radius of indenter: 5 mm Test speed: 2 mm / min

[0030] The resin content is preferably 20% by mass or more and 80% by mass or less, more preferably 30% by mass or more and 70% by mass or less, and still more preferably 40% by mass or more and 60% by mass or less, based on the total amount of the molded product. When the resin content is 20% by mass or more, the strength and toughness of the molded product tend to be further excellent. When the resin content is 80% by mass or less, the environmental adaptability tends to be further excellent.

[0031] 1.3. Compatibilizer The molded product of this embodiment preferably further contains a compatibilizer. The compatibilizer is not particularly limited as long as it can improve the compatibility between the wood powder and the resin. Examples thereof include acrylic polymers and maleic anhydride-based polymers. The compatibilizer may be a reactive type, a non-reactive type, a random polymer type, or a block polymer type. From the viewpoint of further improving the environmental adaptability, the compatibilizer is preferably produced using plant-derived raw materials.

[0032] The weight average molecular weight of the compatibilizer is preferably 1.0×10 7 or more, and more preferably 1.0×10 8 or more. When the weight average molecular weight of the compatibilizer is 1.0×10 7 or more, the compatibilizing effect tends to be further achieved. The measurement method of the weight average molecular weight is not particularly limited. For example, it can be measured using gel permeation chromatography.

[0033] The content of the compatibilizer is preferably 0.1% by mass or more and 10% by mass or less, more preferably 0.5% by mass or more and 5.0% by mass or less, and still more preferably 1.0% by mass or more and 5.0% by mass or less, based on the total amount of the molded product. When the content of the compatibilizer is within the above range, the strength and toughness of the molded product tend to be further excellent.

[0034] 1.4. Other components The molded product of the present embodiment may contain other components as long as the effects of the present invention are not impaired. The other components are not particularly limited, and examples thereof include surfactants, antioxidants, weather resistance improvers, plasticizers, flame retardants, fillers, antistatic agents, and lubricants. These may be used alone or in combination of two or more.

[0035] 1.5. Defective part The defective part means a space where there is no wood powder resin composite material caused by air bubbles. However, in the present embodiment, when the respective areas on the surface and any cross-section are 0.15 mm 2 In the following cases, it shall not be regarded as a defective part.

[0036] The area on the surface of the defective part means the area of the opening part of the defective part when the defective part exists on the surface of the molded product and is open toward the outside of the molded product (in contact with the atmosphere, etc.). As an example of the area on the surface of the defective part, although not particularly limited, for example, FIG. 1 can be referred to, and the respective surface areas of d1, d2, and d3 in FIG. 1 correspond to the area on the surface of the defective part.

[0037] The area of any cross-section of the defective part means the area of any cross-section of the defective part when the defective part exists inside the molded product and is not open toward the outside of the molded product (not in contact with the atmosphere, etc.). As the area of any cross-section of the defective part, although not particularly limited, for example, FIG. 2 can be referred to. FIG. 2 shows a cross-sectional view of a molded product having a defective part, and the respective cross-sectional areas of d4 and d5 correspond to the area of any cross-section of the defective part.

[0038] The molded product of this embodiment has a total of 2 or less defective parts on the surface and inside of the molded product, preferably 1 or less, and more preferably 0. Since the total number of defective parts on the surface and inside of the molded product is 2 or less, the appearance of the molded product is excellent. The method for adjusting the number of defective parts on the surface and inside of the molded product is not particularly limited. For example, it can be adjusted by thinning the molded product within a range where its average wall thickness is 5.0 mm or more, adjusting the content of wood powder in the molded product, or providing a gas venting mechanism in the molding process.

[0039] The molded product of this embodiment has an area of each of the defective part's surface and any cross-section being 0.50 mm 2 or less, preferably 0.4 mm 2 or less, and more preferably 0.3 mm 2 or less. Since the area of each of the defective part's surface and any cross-section is 0.50 mm 2 or less, the appearance of the molded product is excellent. Note that the "area of the defective part's surface and any cross-section" refers to the area per defective part. The method for adjusting the area of the defective part's surface and any cross-section of the molded product is not particularly limited. For example, it can be adjusted by thinning the molded product within a range where its average wall thickness is 5.0 mm or more, adjusting the content of wood powder in the molded product, or providing a gas venting mechanism in the molding process.

[0040] The types of molded products obtained by the manufacturing method of the molded product of this embodiment are not particularly limited. For example, they include containers such as bowls, plates, cups, lunch boxes, chopstick holders, bottles, tumblers, pancake cases and bowls, and nested lunch boxes, strainers, and trays.

[0041] 1.6. Average wall thickness The average wall thickness of the molded product of this embodiment is 5.0 mm or more, and if it is more than that, a suitable range can be used depending on the application. The average wall thickness may be 5.5 mm or more, 6.0 mm or more, 7.0 mm or more, or 8.0 mm or more. Also, the average wall thickness may be 15 mm or less, 13 mm or less, 11 mm or less, or 10 mm or less. Here, the average wall thickness of the molded product means the arithmetic mean of the wall thickness of the thinnest part and the wall thickness of the thickest part. However, in the case where the edge part in the cross section has a tapered shape, the tapered shape part is excluded.

[0042] 3. Manufacturing method of the molded product The manufacturing method of the molded product of this embodiment includes a mixing step of mixing wood powder and resin to obtain a wood powder - resin composite material, and a molding step of molding the wood powder - resin composite material, and may include other steps as long as the effects of the present invention are not inhibited. The manufacturing method of the molded product of this embodiment preferably includes, as other steps, a steaming step of steaming the wood powder and a washing step of washing the wood powder after steaming.

[0043] 3.1. Steaming step The steaming step is a step of obtaining wood powder by steaming wood powder in the state before steaming (hereinafter also referred to as pre - treated wood powder). As the steaming method, a conventionally known method can be used and is not particularly limited. For example, it includes accommodating the pre - treated wood powder in a container through which steam can pass, and supplying steam from a supply source such as a boiler thereto.

[0044] The steam is not particularly limited, and examples include saturated steam and superheated steam. Among these, it is preferable to use superheated steam.

[0045] The steam temperature is preferably 160°C or higher and 240°C or lower, more preferably 170°C or higher and 220°C or lower, and even more preferably 190°C or higher and 210°C or lower. When the steam temperature is 160°C or higher, hemicellulose, lignin, etc. contained in the wood powder before treatment can be decomposed to a certain extent, and the moldability tends to be even better. Also, when the steam temperature is 240°C or lower, excessive thermal decomposition (burning) can be prevented, and the odor resistance tends to be even better.

[0046] Also, the time for performing the cooking treatment is not particularly limited, and for example, it may be 30 seconds or longer and 1 hour or shorter, 1 minute or longer and 30 minutes or shorter, or 5 minutes or longer and 20 minutes or shorter. Also, in order to enhance the contact between the wood powder before treatment and the steam and promote the reaction, the pressure of the steam may be increased above normal pressure.

[0047] 3.2. Washing step The washing step is a step of washing the wood powder with water after the cooking step. The washing method is not particularly limited, and examples include filling water in a container and putting the wood powder into the container and stirring it. The water used for washing is not particularly limited, and examples include pure water, deionized water, and distilled water. Also, the water used in the washing step may contain other components as long as the effects of the present invention are not inhibited.

[0048] In the washing step, the temperature of the water used for washing is preferably 0°C or higher and 60°C or lower, more preferably 5°C or higher and 40°C or lower, and even more preferably 10°C or higher and 20°C or lower. When the above temperature is 0°C or higher, the removal of odor components can be promoted, and the odor resistance tends to be excellent. Also, when the steam temperature is 60°C or lower, the components in the wood powder can be prevented from flowing out more than necessary, and the strength, toughness, and moldability of the molded product tend to be excellent.

[0049] The washing time is not particularly limited, and it may be 10 minutes or longer and within 6 hours, 20 minutes or longer and within 4 hours, or 30 minutes or longer and within 2 hours.

[0050] 3.3. Mixing Process The mixing process is a process of mixing wood powder and resin to obtain a wood powder - resin composite material. As the method, a conventionally known method can be used and is not particularly limited. For example, after melting the resin, it is mixed with wood powder, and using a conventionally known granulation extruder, the filamentous mixture extruded from the die holes is cooled in a water tank and cut by a pelletizer.

[0051] 3.4. Molding Process The molding process of the molded product in this embodiment is a process of molding the above - mentioned wood powder - resin composite material. As the molding process, a conventionally known method can be used and is not particularly limited. For example, extrusion molding, injection molding, and blow molding can be mentioned. Since the wood powder - resin composite material of this embodiment contains wood powder and has excellent moldability, injection molding is particularly suitable. As for injection molding, it is not particularly limited. For example, after melting the wood powder - resin composite material, using a conventionally known injection molding machine, the melted wood powder - resin composite material is poured into the mold via a screw and cooled.

[0052] The molding temperature in the molding process is preferably 160°C or higher and 180°C or lower, and more preferably 165°C or higher and 175°C or lower. When the molding temperature is 160°C or higher, the moldability tends to be further excellent. Also, when the molding temperature is 180°C or lower, thermal decomposition can be suppressed, and the odor resistance, as well as the strength and toughness of the molded product, tend to be further excellent. Note that the molding temperature in this embodiment means the temperature when heating the wood powder - resin composite material to a fluid state during molding.

[0053] Also, the mold temperature is preferably 60°C or higher and 85°C or lower, and more preferably 65°C or higher and 80°C or lower. When the mold temperature is 60°C or higher, the moldability tends to be further excellent, and when the mold temperature is 85°C or lower, the production efficiency tends to be further excellent. Note that the mold temperature means the temperature of the mold into which the fluid wood powder - resin composite material is poured.

[0054] In the molding process, from the viewpoint of removing air bubbles inside the molded product, it is preferable to use a gas venting mechanism. Although not particularly limited as the gas venting mechanism, preferably, at least one or more gas venting pins are provided, and more preferably, at least one or more gas venting pins and at least one or more protruding portions are provided. Further, it is also preferable to provide a mechanism for performing molding with the protruding portion provided and removing the protruding portion after molding. Thereby, air bubbles inside the molded product can be further removed, and the appearance of the molded product tends to be excellent. Here, the gas venting pin means a member for discharging gas from the mold to the outside of the mold through a gas venting groove. Further, the protruding portion means a portion of the protrusion provided on the surface of the wood flour resin composite formed by the mold that is removed after molding.

[0055] Furthermore, it is preferable that the mold is configured such that the parting line is formed at the connection portion between the flash and the portion constituting the molded product. Thereby, since the air bubbles generated during molding escape from the parting line or accumulate in the flash, it is possible to suppress the remaining of air bubbles in the molded product. Here, the parting line means a convex line generated when the resin hardens at the combined portion of a plurality of molds. Further, the flash means a portion of the portion removed from the molded product after molding, excluding the above-mentioned protruding portion.

[0056] The manufacturing method of the molded product of the present embodiment has a cooling step of cooling the above-mentioned wood powder resin composite material, and the cooling time in this cooling step may be adjusted according to the shape and wall thickness of the molded product and is not particularly limited. For example, the cooling time may be 10 seconds or more, may be 20 seconds or more, or may be 30 seconds or more. The cooling time may be, for example, 120 seconds or less, may be 100 seconds or less, or may be 80 seconds or less. Conventionally, since there are many bubbles inside the molded product, the cooling time is short, and when the molded product is taken out of the mold in a state where the molded product is not sufficiently solidified, the internal bubbles cannot be suppressed from expanding, resulting in a tendency for the surface of the molded product to bulge. On the other hand, in the present embodiment, the bubbles inside the molded product can be sufficiently reduced, and the bulge of the molded product caused by the above-mentioned bubbles can be suppressed, so the cooling time can be made shorter than before. As a result, the appearance of the molded product can be made even better. In addition, since the cooling time can be shortened as described above, the production efficiency of the molded product tends to be excellent. The cooling time means the time from when the heating of the wood powder resin composite material filled in the mold is stopped until the mold is removed and the molded product is taken out.

Example

[0057] Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited to these examples.

[0058] 1. Production of molded product (Example) First, wood (Japanese zelkova: mass ratio of cacao is 26:25) was pulverized by an impact pulverization method, and then made uniform in particle size through a filter. The obtained wood powder was subjected to a steaming treatment at a steaming temperature of 200 ° C for 15 minutes, and then washed by immersing the steamed wood powder in water at a water temperature of 15 ° C in a container for 60 minutes.

[0059] Figure 3A is a schematic diagram showing a mold for molding a wood powder resin composite used in the molding process. The mold A is composed of a female mold A1, a male mold A2, and a gate portion A7. The wood powder resin composite was poured into the void portion A0 formed by the mold A through the gate portion A7. At that time, a large amount of gas was initially extracted from the gas vent pin A5 located below the gate portion A7 through the void portion A0 that finally forms the molded product to the outside of the mold A. After the wood powder resin composite solidified, the mold A was removed to obtain a precursor of the molded product shown in Figure 3B. This precursor had a protruding portion A4 and a runner A6 together with the bowl-shaped main body portion A9 that finally becomes the molded product. Also, a parting line A8 was formed at the connection portion between the main body portion A9 and the runner A6. The gas (bubbles) generated during molding was extracted from the parting line A8 and accumulated inside the protruding portion A4 and the runner A6. Thereafter, by removing the protruding portion A4 and the runner A6, the bowl-shaped molded product A10 shown in Figure 3C was obtained.

[0060] As specific operations and conditions, first, the washed wood powder, the resin described later, and the compatibilizer were mixed so that the mass ratio of each was wood powder: resin: compatibilizer = 51:45:4 to obtain a wood powder resin composite. Thereafter, after adjusting the mold A incorporating the gas vent pin A5 shown in Figure 3A to a mold temperature of 70°C, the molten wood powder resin composite at a molding temperature of 170°C was poured from the gate portion A7 into the void portion A0, and then cooled for 120 seconds to solidify the wood powder resin composite. After cooling, the mold A was removed, and further, the protruding portion A4 and the runner A6 were removed to obtain a molded product. The thickness of the obtained molded product was 8.5 mm on average, 7 mm at the thinnest part, and 10 mm at the thickest part, and the total number of defective parts on the surface and inside of the molded product was 0. By manufacturing the molded product in this way, the bubbles that tend to gather in the protruding portion A4 and the runner A6 can be efficiently removed, and the bubbles can also be removed from the parting line A8.

[0061] Here, the resins and compatibilizers used in the examples and comparative examples are as follows. · Bio-PBS: bio-PBS, manufactured by Mitsubishi Chemical Corporation ·Compatibilizer: Alkyl methacrylate, weight average molecular weight 1.0×10 7 , manufactured by Mitsubishi Chemical Corporation

[0062] (Comparative Example) A molded product of the comparative example was obtained by the same operation as in the example except that the cooling time was set to 100 seconds and the gas vent pin A5 and the flash A6 were not provided. The thickness of the obtained molded product was the same as that in the example, and the total number of defective parts on the surface and inside of the molded product exceeded 2, and the area of each of the defective parts on the surface and any cross section was far more than 0.50 mm 2 .

[0063] 2. Evaluation The obtained molded product was shaved into a bowl shape, painted with lacquer, and then a sensory evaluation regarding the appearance was performed by visual inspection by a skilled person in the art. The evaluation criteria are as follows. [Evaluation Criteria] 〇: There are no appearance problems compared with commercially available wood processed products. ×: There are appearance problems compared with commercially available wood processed products.

[0064] As a result of the evaluation, the example was 〇 and the comparative example was ×.

Industrial Applicability

[0065] Since the present invention can be widely used for housings and the like, it has industrial applicability.

Explanation of Reference Numerals

[0066] d1, d2, d3, d4, d5... Defective parts, A... Mold, A0... Void part, A1... Female mold, A2... Male mold, A4... Protrusion part, A5... Gas vent pin, A6... Flash, A7... Gate part, A8... Parting line, A9... Main body part, A10... Molded product.

Claims

1. A molded article comprising wood flour and resin, The average thickness is 5.0 mm or more, The content of the wood flour is 10% by mass or more relative to the total amount of the molded product, The number of defects on the surface and inside of the molded article is two or less in total, The area of ​​each of the defect portions on the surface and any cross section is more than 0.15 mm 2 and less than 0.50 mm 2 2 Below is the Molded products.

2. Further comprising a compatibilizer, The molded article according to claim 1.

3. The content of the wood flour is more than 50% by mass based on the total amount of the molded product. The molded article according to claim 1 or 2.

4. The resin includes a biodegradable resin. The molded article according to claim 1 or 2.

5. A method for producing a molded article according to claim 1 or 2, comprising the steps of: A mixing step of mixing wood flour and resin to obtain a wood flour resin composite material; A molding step of molding the wood flour resin composite material. A method for producing the molded article.

6. The molding step includes a cooling step of cooling the wood powder resin composite material, and the cooling time in the cooling step is 120 seconds or less. A method for producing the molded article according to claim 5.

Images