Molded article and method for producing molded article

Abstract

To provide a molded article of a wood flour-resin composite material having adequate thickness along with superior appearance, and a production method for the molded article.SOLUTION: A molded article contains wood flour and a resin, wherein an average wall thickness thereof is 5.0 mm or more, a content of the wood flour relative to a total amount of the molded article is 10 mass% or more, a total number of defective parts present on a surface and inside the molded article is two or less, and an area of each defective part on the surface and on any cross section is 0.50 mm2 or less.SELECTED DRAWING: Figure 3C

Description

[Technical Field]

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

[0002] The technology for combining wood flour and resin has a history of over 30 years, and with growing environmental awareness, there has been increasing attention in recent years on the development of molded wood flour resin composite products that have the desired appearance and physical properties achieved by applying this technology.

[0003] For example, Patent Document 1 discloses a method for producing wood resin molded products with excellent strength and moisture resistance, which includes the steps of: (1) extruding a molten wood flour-containing resin composition containing a thermoplastic resin and wood flour to produce a heated molded body; and (2) immersing the molded body in a solution containing a modifier and cooling it, with the aim of providing a method for producing wood resin molded products with excellent strength and moisture resistance. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-113364 Summary of the Invention [Problem to be solved by the invention]

[0005] However, it is difficult to say that sufficient development has been made into thick wood-based resin molded products. Through intensive research by the present inventors, it was found that conventional molded products using wood flour and resin tend to have air bubbles remaining inside the molded product when it becomes thick, which can particularly impair its appearance.

[0006] Therefore, the present invention has been made in consideration of the above problems, and an object of the present invention is to provide a molded product of a wood flour resin composite material that has sufficient thickness and excellent appearance, and a method for manufacturing such a molded product. [Means for solving the problem]

[0007] As a result of extensive research into achieving the above object, the present inventors have found that the above problems can be solved by the following configuration, and have thus completed the present invention.

[0008] That is, the present invention is as follows. [1] A molded article containing 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 product is two or less in total, The area of ​​the defect on the surface and in any cross section is 0.50 mm 2 Below is the Molded products. [2] further comprising a compatibilizer, [1] The molded product described in [1]. [3] The content of the wood flour is more than 50% by mass relative to the total amount of the molded product. [1] or [2]. [4] The resin includes a biodegradable resin. The molded article according to any one of [1] to [3]. [5] a mixing step of mixing wood flour and resin to obtain a wood flour resin composite; A molding step of molding the wood flour resin composite material, Manufacturing method of molded products. [6] The molding step includes a cooling step of cooling the wood flour resin composite, and the cooling time in the cooling step is 120 seconds or less. [5] A method for producing a molded article according to the present invention. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide a molded article of a wood flour resin composite material that has a sufficient thickness and an excellent appearance, and a method for manufacturing such a molded article. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a schematic diagram showing one embodiment of a molded article having a defect. [Figure 2] FIG. 1 is a schematic diagram showing one embodiment of a cross-sectional view of a molded product having a defect. [Figure 3A] 2 is a schematic diagram showing one aspect of a molding step in the method for manufacturing a molded product according to the present embodiment. FIG. [Figure 3B] 2 is a schematic diagram showing one aspect of a molding step in the method for manufacturing a molded product according to the present embodiment. FIG. [Figure 3C] FIG. 1 is a schematic diagram showing one aspect of a molded article of the present embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, a mode 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, but the present invention is not limited to the present embodiment. The present invention can be modified in various ways without departing from the gist of the present invention. In the drawings, 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 of the drawings are not limited to the ratios shown in the drawings.

[0012] 1. Molded products The molded product of this embodiment is a molded product containing wood flour and resin, and has an average thickness of 5.0 mm or more, a content of the wood flour of 10 mass % or more relative to the total amount of the molded product, and a total of two or less defects on the surface and inside the molded product, and the area of ​​each of the defects on the surface and in any cross section is 0.50 mm or less. 2 The following is the result.

[0013] Generally, when molding resins, the temperature must be raised to a temperature at which the resin becomes fluid. Therefore, even when molding wood flour-resin composites, which are made by combining wood flour and resin, the temperature must be raised to a certain temperature. This can lead to the generation of bubbles, which can easily remain inside the molded product. The bubbles originate from water evaporation, pyrolysis gases from the resin, and wood gases from the wood flour. Wood gases, in particular, tend to be generated more frequently than pyrolysis gases from the resin. Furthermore, the thicker the molded product, the more likely it is that bubbles will accumulate inside the resin, especially near the surface of the molded product. This is because the surface of the molded product solidifies quickly during molding, making it difficult for the resin under pressure inside the mold to expel these bubbles. As a result, defects are likely to occur on the surface and / or inside the molded product. In particular, post-molding processes such as grinding or lacquering can easily damage the appearance of the molded product.

[0014] On the other hand, the molded article of this embodiment has the above-mentioned configuration, and therefore has a sufficient thickness and an excellent appearance.

[0015] 1.1. Wood flour The wood flour of this embodiment refers to wood flour obtained by pulverizing wood and subjecting it to a steaming treatment. The upper limit 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, even more preferably 700 μm or less, and even more preferably 500 μm or less. The lower limit of the particle size range is not particularly limited, but is preferably 10 μm or more, more preferably 50 μm or more, and even more preferably 100 μm or more. By limiting the particle size range of the wood flour to 1000 μm or less, compatibility with resins tends to be improved, and the strength and toughness of molded articles of wood flour resin composites tend to be improved. Furthermore, by limiting the particle size range of the wood flour to 10 μm or more, the moldability of wood flour resin composites tends to be improved. The particle size range described above 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, and wood flour with a particle size range of 40 μm to 60 μm can be obtained by passing wood flour through a filter with a mesh size of 60 μm and then capturing it with a filter with a mesh size of 40 μm.

[0016] The content of wood flour having a particle size range of 10 μm to 1000 μm is preferably 70% by mass or more, more preferably 80% by mass or more, even 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 wood flour. The upper limit is not particularly limited, but may be, for example, 100% by mass.

[0017] The wood can be crushed by any conventionally known method, and is not particularly limited. For example, crushing using a blade method or crushing using an impact crushing method can be used.

[0018] Wood refers to all plant-derived lignocellulose-based materials, i.e., lignocellulose-based materials containing lignin, hemicellulose, and cellulose. Examples of wood include, but are not limited to, zelkova, cacao, maple, white ash, cedar, paulownia, black pine, cypress, and beech. Among these, maple and white ash are preferred from the viewpoint of their high specific gravity and excellent compatibility with resins, and cacao is preferred from the viewpoint of excellent appearance of molded products. Furthermore, because cacao is a wood with a high oil content, molded products made using only cacao wood are prone to oil leaching when exposed to hot water, etc. To prevent this, it is preferred that the wood contain both cacao and other woods, such as zelkova. One type of wood may be used alone, or two or more types may be used in combination.

[0019] Steaming refers to a process in which wood flour is brought into contact with steam. Details of steaming are described below.

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

[0021] From the viewpoint of environmental friendliness, the wood flour content is preferably 20% by mass or more, more preferably 30% by mass or more, even more preferably 40% by mass or more, still more preferably 50% by mass or more, and particularly preferably 55% by mass or more, relative to the total amount of the molded product.

[0022] The upper limit of the wood flour content is preferably 80 mass %, but may also be 75 mass %, 70 mass %, 65 mass %, or 60 mass %, from the viewpoints of ease of molding and strength and toughness of the molded product.

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

[0024] Among these, 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, from the viewpoint of excellent environmental compatibility. Here, biomass resin refers to a resin produced using plant-derived raw materials. Biomass resins are not particularly limited, but examples of resins using plant-derived raw materials include biopolyethylene, biopolypropylene, biopolyester, biopolyurethane, and biophenolic resin. Furthermore, biodegradable resin refers to a resin that has the property of being decomposed by microorganisms present in nature. Biodegradable resins are not particularly limited, but examples 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, more preferably 150° C. or higher and 170° C. When the melting temperature of the resin is 180° C. or lower, after compounding with wood flour, the resin can be molded without causing thermal decomposition (discoloration) of the wood flour, and molded articles of wood flour resin composites tend to have excellent strength and toughness.

[0026] The resin of this embodiment preferably has a tensile strength of 25 MPa or more, more preferably 30 MPa or more, and even more preferably 35 MPa or more, as measured under the following measurement condition A. When the resin has a tensile strength of 25 MPa or more, the strength of the molded article tends to be even better. There is no particular upper limit to the tensile strength, but the tensile strength may be, for example, 100 MPa or less, or 80 MPa or less.

[0027] <Measurement condition A> Sample: Dumbbell piece (total length: 170 mm, distance between tabs: 105 mm, length of parallel part: 85 mm, width of end: 20 mm, width of central parallel part: 10 mm, thickness: 4.0 mm) Test room temperature: 23±2℃ Test humidity: 50±5%RH Conditioning: 88+ hours in the laboratory Testing machine: Autograph AG-100kNXPlus (Shimadzu Corporation) Load cell capacity: 5kN Extensometer: TRViewX500D (Shimadzu Corporation) Distance between gauge lines: 75mm Grip distance: 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, as measured under the following measurement condition B. When the resin has a flexural strength of 30 MPa or more, the strength of the molded article tends to be even better. There is no particular upper limit to the flexural strength, but the flexural strength may be, for example, 100 MPa or less, or 80 MPa or less.

[0029] <Measurement condition B> Sample: Dumbbell piece (total length: 170 mm, distance between tabs: 105 mm, length of parallel part: 85 mm, width of end: 20 mm, width of central parallel part: 10 mm, thickness: 4.0 mm) Test room temperature: 23±2℃ Test humidity: 50±5%RH Conditioning: 88+ hours in the laboratory Testing machine: Autograph AG-10TD (Shimadzu Corporation) Load cell capacity: 5kN Distance between fulcrums: 64mm Support stand radius: 5mm Indenter radius: 5mm Test speed: 2mm / 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 even more preferably 40% by mass or more and 60% by mass or less, based on the total amount of the molded article. When the resin content is 20% by mass or more, the molded article tends to have better strength and toughness, and when the resin content is 80% by mass or less, the molded article tends to have better environmental compatibility.

[0031] 1.3. Compatibilizers The molded article of this embodiment preferably further contains a compatibilizer. The compatibilizer is not particularly limited as long as it improves the compatibility between the wood flour and the resin, and examples thereof include acrylic polymers and maleic anhydride polymers. The compatibilizer may be reactive, non-reactive, random polymer, or block polymer. From the viewpoint of further improving environmental friendliness, 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 More preferably, it is 1.0×10 8 The weight average molecular weight of the compatibilizer is 1.0 × 10 7 The weight-average molecular weight may be measured by any method, but may be measured by gel permeation chromatography, for example.

[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 even more preferably 1.0% by mass or more and 5.0% by mass or less, relative to the total amount of the molded article. When the content of the compatibilizer is within the above range, the strength and toughness of the molded article tend to be even better.

[0034] 1.4.Other Ingredients The molded article of the present embodiment may contain other components as long as the effects of the present invention are not impaired. Examples of other components include, but are not limited to, 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 defect refers to a space where no wood flour resin composite material is present, which is caused by air bubbles. In this embodiment, however, the surface area and any cross section area are 0.15 mm 2 The following cases are not considered to be defects:

[0036] The surface area of ​​a defect refers to the area of ​​the opening of the defect when the defect is present on the surface of the molded article and is open to the outside of the molded article (contacting the atmosphere, etc.) Examples of the surface area of ​​a defect include, but are not limited to, Figure 1, where the surface areas d1, d2, and d3 in Figure 1 correspond to the surface area of ​​the defect.

[0037] The area of ​​a defect in any cross section refers to the cross-sectional area of ​​the defect when the defect is present inside the molded article and is not open to the outside of the molded article (not in contact with the atmosphere, etc.). The cross-sectional area of ​​the defect is not particularly limited, but for example, refer to Figure 2, which shows a cross-sectional view of a molded article having a defect, and the cross-sectional areas d4 and d5 correspond to the area of ​​the defect in any cross section.

[0038] The molded article of this embodiment has a total of two or less defects on the surface and inside of the molded article, preferably one or less, and more preferably zero. Having a total of two or less defects on the surface and inside of the molded article results in excellent appearance of the molded article. There are no particular limitations on the method for adjusting the number of defects on the surface and inside of the molded article, but examples include adjusting the number by thinning the molded article so that the average thickness is 5.0 mm or more, adjusting the wood flour content in the molded article, or providing a degassing mechanism in the molding process.

[0039] In the molded product of this embodiment, the surface area of ​​the defect and the area of ​​any cross section are each 0.50 mm 2 less than 0.4 mm, preferably 2 or less, more preferably 0.3 mm 2 The surface area and any cross section of the defect are 0.50 mm or less. 2 The appearance of the molded article is excellent when the following is satisfied. Note that the "area of ​​the surface and any cross section of the defect" refers to the area of ​​one defect. There are no particular limitations on the method for adjusting the area of ​​the surface and any cross section of the defect of the molded article, but examples include adjusting the area by thinning the molded article within the range of an average thickness of 5.0 mm or more, adjusting the wood flour content in the molded article, or providing a degassing mechanism in the molding process.

[0040] The types of molded products obtainable by the molded product manufacturing method of this embodiment are not particularly limited, but include, for example, bowls, plates, cups, lunch boxes, chopstick holders, bottles, tumblers, bread cases, bowls, containers such as bento boxes, strainers, and trays.

[0041] 1.6.Average wall thickness The average wall thickness of the molded article of this embodiment is 5.0 mm or more, and any thickness greater than this can be used in a suitable range 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. The average wall thickness may also 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 article refers to the arithmetic mean of the wall thickness of the thinnest part and the wall thickness of the thickest part. However, if the edge portion in the cross section is tapered, this does not include the tapered portion.

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

[0043] 3.1. Steaming process The steaming process is a process in which wood flour in a state before steaming (hereinafter also referred to as pre-treated wood flour) is steamed to obtain wood flour. The steaming method can be a conventionally known method and is not particularly limited, but an example is placing the pre-treated wood flour in a container that is permeable to steam and supplying steam thereto from a supply source such as a boiler.

[0044] The water vapor is not particularly limited, but examples thereof include saturated steam and superheated steam, and 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. A steam temperature of 160°C or higher can decompose hemicellulose, lignin, and other components contained in the wood flour before treatment to a certain extent, which tends to improve moldability. Furthermore, a steam temperature of 240°C or lower can prevent excessive thermal decomposition (scorching), which tends to improve odor resistance.

[0046] The time for steaming is not particularly limited, but may be, for example, 30 seconds to 1 hour, 1 minute to 30 minutes, or 5 minutes to 20 minutes. The pressure of the steam may be higher than normal pressure to increase the contact between the wood flour and steam before treatment and promote the reaction.

[0047] 3.2.Cleaning process The washing step is a step of washing the wood flour with water after the steaming step. The washing method is not particularly limited, but for example, a method of filling a container with water, adding the wood flour to the container, and stirring the mixture can be used. The water used for washing is not particularly limited, but for example, pure water, deionized water, and distilled water can be used. The water used in the washing step may contain other components as long as they do not impair the effects of the present invention.

[0048] In the washing step, the temperature of the water used for washing is preferably from 0°C to 60°C, more preferably from 5°C to 40°C, and even more preferably from 10°C to 20°C. A temperature of 0°C or higher can facilitate the removal of odorous components, and odor resistance tends to be excellent. Furthermore, a steam temperature of 60°C or lower can prevent the components in the wood flour from leaking out more than necessary, which tends to result in the molded product having excellent strength, toughness, and moldability.

[0049] The washing time is not particularly limited, but may be from 10 minutes to 6 hours, from 20 minutes to 4 hours, or from 30 minutes to 2 hours.

[0050] 3.3.Mixing process The mixing step is a step of mixing wood flour and resin to obtain a wood flour-resin composite material. The method can be any conventionally known method, and is not particularly limited. For example, the resin is melted and mixed with wood flour, and the resulting fibrous mixture is extruded through holes in a die using a conventionally known granulating extruder. The extruded mixture is cooled in a water tank and cut using a pelletizer.

[0051] 3.4. Molding process The molding process for the molded product of this embodiment is a process of molding the wood flour resin composite. As the molding process, a conventionally known method can be used, and is not particularly limited, but examples thereof include extrusion molding, injection molding, and blow molding. Since the wood flour resin composite of this embodiment has excellent moldability despite containing wood flour, injection molding is particularly suitable. As an injection molding method, there is no particular limit, but an example thereof is to melt the wood flour resin composite, and then use a conventionally known injection molding machine to pour the molten wood flour resin composite into a mold via a screw and cool it.

[0052] The molding temperature in the molding step is preferably 160°C or higher and 180°C or lower, more preferably 165°C or higher and 175°C or lower. A molding temperature of 160°C or higher tends to result in better moldability. A molding temperature of 180°C or lower can suppress thermal decomposition, and the molded product tends to have better odor resistance, strength, and toughness. In this embodiment, the molding temperature refers to the temperature at which the wood flour resin composite is heated to a fluid state during molding.

[0053] The mold temperature is preferably 60° C. or higher and 85° C. or lower, more preferably 65° C. or higher and 80° C. A mold temperature of 60° C. or higher tends to result in better moldability, while a mold temperature of 85° C. or lower tends to result in better production efficiency. The mold temperature refers to the temperature of the mold into which the wood flour resin composite in a fluid state is poured.

[0054] In the molding process, a venting mechanism is preferably used to remove air bubbles from inside the molded product. The venting mechanism is not particularly limited, but preferably includes at least one vent pin, and more preferably includes at least one vent pin and at least one protrusion. It is also preferable to provide a mechanism for molding with a protrusion and then removing the protrusion after molding. This allows for more efficient removal of air bubbles from inside the molded product, which tends to improve the appearance of the molded product. Here, the venting pin refers to a component for discharging gas from the mold through the vent groove. The protrusion refers to a protrusion 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 be configured so that a parting line is formed at the connection between the dead wall and the part that constitutes the molded product. This allows air bubbles generated during molding to escape through the parting line or accumulate in the dead wall, thereby preventing air bubbles from remaining in the molded product. Here, the parting line refers to a convex line that appears when the resin solidifies at the mating part of multiple molds. Furthermore, the dead wall refers to the part that is removed from the molded product after molding, excluding the protruding part.

[0056] The method for producing a molded product according to this embodiment includes a cooling step for cooling the wood flour resin composite. The cooling time in this step is not particularly limited and can be adjusted depending on the shape and thickness of the molded product. For example, the cooling time may be 10 seconds or more, 20 seconds or more, or 30 seconds or more. The cooling time may be 120 seconds or less, 100 seconds or less, or 80 seconds or less. Conventionally, due to the presence of many air bubbles inside the molded product, the cooling time is short, and when the molded product is removed from the mold before it has fully solidified, the expansion of the internal air bubbles cannot be suppressed, resulting in a tendency for the surface of the molded product to bulge. In contrast, this embodiment can sufficiently reduce the number of air bubbles inside the molded product, thereby suppressing the bulging of the molded product caused by the air bubbles, thereby shortening the cooling time compared to conventional methods. As a result, the appearance of the molded product can be improved. Furthermore, the shortened cooling time as described above tends to improve the production efficiency of molded products. The cooling time means the time from when heating of the wood flour resin composite material filled in the mold is stopped to when the mold is removed and the molded product is taken out. [Example]

[0057] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0058] 1. Preparation of molded products (Example) First, wood (mass ratio of zelkova to cacao 26:25) was crushed using an impact crushing method, and then passed through a filter to make the particle size uniform. The obtained wood flour was steamed at 200°C for 15 minutes, and then the steamed wood flour was washed by immersing it in water at 15°C in a container for 60 minutes.

[0059] FIG. 3A is a schematic diagram showing the mold used in the molding process to mold the wood flour resin composite. Mold A is composed of a female mold A1, a male mold A2, and a gate A7. The wood flour resin composite was poured into the cavity A0 formed by mold A through gate A7. A large amount of gas was initially released from mold A through the cavity A0, which would ultimately form the molded product, via a gas vent pin A5 located below gate A7. After the wood flour resin composite solidified, mold A was removed to obtain a precursor to the molded product shown in FIG. 3B. This precursor had a bowl-shaped main body A9 that would eventually become the molded product, as well as a protruding portion A4 and a dead portion A6. A parting line A8 was also formed at the connection between main body A9 and dead portion A6. Gas (bubbles) generated during molding were released through the parting line A8 and accumulated inside the protruding portion A4 and dead portion A6. Thereafter, the protruding portion A4 and the excess portion A6 were removed to obtain a bowl-shaped molded product A10 shown in FIG. 3C.

[0060] Specifically, the wood flour resin composite was prepared by mixing the washed wood flour with the resin and compatibilizer (described below) in a mass ratio of 51:45:4 (wood flour:resin:compatibilizer). Then, a mold A incorporating a gas vent pin A5 (see Figure 3A) was adjusted to a mold temperature of 70°C. The molten wood flour resin composite was poured into the cavity A0 through the gate A7 at a molding temperature of 170°C and cooled for 120 seconds to solidify. After cooling, the mold A was removed, and the protrusions A4 and the waste material A6 were removed to obtain a molded product. The resulting molded product had an average thickness of 8.5 mm, a thinnest portion of 7 mm, and a thickest portion of 10 mm. There were zero defects on the surface or inside the molded product. This process efficiently removed air bubbles that tend to collect in the protrusions A4 and waste material A6, as well as from the parting line A8.

[0061] The resins and compatibilizers used in the examples and comparative examples are as follows. Bio-PBS: bio-PBS, manufactured by Mitsubishi Chemical Corporation Compatibilizer: methacrylic acid alkylate, weight average molecular weight 1.0 x 10 7 , manufactured by Mitsubishi Chemical Corporation

[0062] (Comparative Example) A comparative molded article was obtained by the same procedure as in Example, except that the cooling time was 100 seconds and the gas vent pin A5 and the excess part A6 were not provided. The thickness of the obtained molded article was the same as in Example, and the number of defects on the surface and inside of the molded article was more than two in total, and the area of ​​each of the defects on the surface and in any cross section was 0.50 mm 2 It was far more than that.

[0063] 2. Evaluation The resulting molded product was cut into a bowl shape, and then coated with lacquer. After that, a skilled artisan visually evaluated the appearance of the product using the following criteria: [Evaluation criteria] Good: There are no problems with appearance compared to commercially available wood processed products. ×: There is a problem with the appearance compared with commercially available wood processed products.

[0064] As the evaluation results, the example was rated as good, and the comparative example was rated as bad. [Industrial Applicability]

[0065] The present invention can be widely used for housings and the like, and therefore has industrial applicability. [Explanation of symbols]

[0066] d1, d2, d3, d4, d5...defective part, A...mold, A0...void part, A1...female mold, A2...male mold, A4...protruding part, A5...gas vent pin, A6...waste material, A7...gate part, A8...parting line, A9...main body part, A10...molded product.

Claims

1. A molded article containing 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 product is two or less in total, The area of ​​the defect on the surface and in any cross section is 0.50 mm 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 relative to 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 mixing step of mixing wood flour and resin to obtain a wood flour resin composite; A molding step of molding the wood flour resin composite material, Manufacturing method of molded products.

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

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