Method for manufacturing a molded body, method for manufacturing wood plywood, and method for manufacturing a wooden straw

Abstract

The present invention aims to provide an adhesive for wood chips that has higher safety and higher water resistance. [Solution] The present invention provides an adhesive for wood chips comprising glucomannan and an alkali compound.

Description

Technical Field

[0001] The present invention relates to an adhesive for wood chips.

Background Art

[0002] Conventionally, a method of manufacturing a wood-based composite material by adhering wood chips such as wooden boards and wood powder together with an adhesive has been known (for example, Patent Documents 1 and 2).

[0003] Generally, synthetic resins are used as adhesives for adhering wood chips, and in the methods described in Patent Documents 1 and 2, synthetic resins such as phenolic resins, urea resins, polyethylene, polypropylene, and acrylic resins are mentioned as adhesives for adhering wood chips together.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, for wood products such as tableware, food containers, cooking utensils, and toys that may be put into a person's mouth or come into contact with food and beverages, high safety is required so that the adhesive components do not cause harm to health even if they dissolve into a person's saliva, food, and beverages. Furthermore, for adhesives used in wood products used in such applications, high water resistance is required so that the strength of the adhesive does not weaken due to moisture contained in saliva, food, and beverages, and as a result, the wood chips do not decompose.

[0006] Therefore, an object of the present invention is to provide an adhesive for wood chips having higher safety and higher water resistance. [Means for solving the problem]

[0007] As a result of diligent research by the inventor, it was discovered that glucomannan, a component of konjac, can effectively bond pieces of wood together, and furthermore, that when glucomannan is used in combination with an alkaline compound to bond pieces of wood together, the water resistance of the adhesive is enhanced. Based on these findings, the inventor completed the following invention.

[0008] In other words, the present invention provides the following inventions. [1] An adhesive for wood scraps containing glucomannan and an alkali compound. [2] Furthermore, the wood chip adhesive described in [1] contains water. [3] The wood chip adhesive according to [1] or [2], wherein the alkali compound is 0.2 to 50% by mass relative to the total amount of glucomannan. [4] The wood chip adhesive according to any one of [1] to [3], wherein the alkali compound is one or more selected from the group consisting of calcium hydroxide, potassium hydroxide, sodium hydroxide, calcium oxide, sodium carbonate, sodium bicarbonate, and ammonia. [5] A composition comprising an adhesive for wood chips as described in any of [1] to [4] and lignocellulose powder. [6] The composition according to [5], wherein the lignocellulose powder is one or more selected from the group consisting of woody biomass powder and herbaceous biomass powder. [7] The composition according to [5] or [6], wherein the lignocellulose powder is one or more selected from the group consisting of wood powder and bamboo powder. [8] A method for producing a molded article, comprising the steps of molding a composition described in any of [5] to [7], and drying the molded composition to obtain a molded article. [9] A method for producing a molded article, comprising the steps of: molding a composition containing glucomannan and lignocellulose powder; applying or impregnating the molded composition with an alkaline solution containing an alkaline compound; and drying the composition coated or impregnated with the alkaline solution to obtain a molded article.

[10] A plywood made by laminating multiple wood veneers using wood adhesive as described in any of [1] to [4].

[11] A method for manufacturing wood plywood, comprising the steps of: applying or impregnating a plurality of wood veneers with a solution containing glucomannan; bringing the plurality of wood veneers into contact with each other; and applying or impregnating the plurality of wood veneers that have come into contact with each other with an alkaline solution containing an alkaline compound.

[12] A method for manufacturing a molded body, comprising the step of forming the wood plywood described in

[10] or

[11] .

[13] A method for manufacturing a molded body, comprising the steps of: laminating multiple wood veneers to produce a wood plywood; molding the wood plywood; applying or impregnating the molded wood plywood with any of the wood chip adhesives described in [1] to [4]; and drying the wood plywood coated or impregnated with the wood chip adhesive to obtain a molded body.

[14] A method for manufacturing a molded body, comprising the steps of: applying or impregnating a plurality of wood veneers with a solution containing glucomannan; laminating the plurality of wood veneers to produce a wood plywood; molding the wood plywood; applying or impregnating the molded wood plywood with an alkaline solution containing an alkaline compound; and drying the wood plywood coated or impregnated with the alkaline solution to obtain a molded body.

[15] A method for manufacturing a molded article according to any one of [8], [9],

[12] to

[14] , wherein the molded article is tableware, food containers, cooking utensils, toys, stationery, furniture, ornaments, decorative members, automobile interior parts, home appliance parts, or building materials.

[16] The method for manufacturing a molded article according to

[15] , wherein the molded article is a straw.

[17] A method for manufacturing a wooden straw, comprising: a step of applying or impregnating a wooden thin plate with the adhesive for wood pieces according to any one of [1] to [4]; a step of forming the wooden thin plate impregnated or applied with the adhesive for wood pieces into the shape of a straw; and a step of drying the wooden thin plate formed into the shape of a straw to obtain a wooden straw.

[18] A method for manufacturing a wooden straw, comprising: a step of forming a wooden thin plate into the shape of a straw; a step of applying or impregnating the formed wooden thin plate with the adhesive for wood pieces according to any one of [1] to [4]; and a step of drying the wooden thin plate impregnated or applied with the adhesive for wood pieces to obtain a wooden straw.

[19] A method for manufacturing a wooden straw, comprising: a step of applying or impregnating a wooden thin plate with a glucomannan solution containing glucomannan; a step of forming the wooden thin plate impregnated or applied with the glucomannan solution into the shape of a straw; a step of applying or impregnating the formed wooden thin plate with an alkaline solution containing an alkaline compound; and a step of drying the wooden thin plate impregnated or applied with the alkaline solution to obtain a wooden straw.

[20] A wooden straw composed of wooden thin plates adhered through an alkali-modified product of glucomannan.

[21] A wood molded body including a plurality of wood pieces adhered through an alkali-modified product of glucomannan.

[22] The molded body according to

[21] , wherein the wood molded body is a tableware, a food container, a cooking utensil, a toy, a stationery, a furniture, a figurine, a decorative member, an automotive interior part, a home appliance part, or a building material.

[23] The molded body according to

[21] or

[22] , which is a straw.

Advantages of the Invention

[0009] According to the present invention, an adhesive for wood pieces having higher safety and higher water resistance can be provided.

Embodiments for Carrying Out the Invention

[0010] <Adhesive for Wood Pieces> As one embodiment, the present invention provides an adhesive for wood pieces comprising glucomannan and an alkali compound. In this specification, "wood" refers to a woody material, and "woody material" refers to a material mainly composed of lignocellulose. "Wood piece" refers to a fragment formed from wood, and the size and shape of the wood piece are not limited. For example, the shape of the wood piece may be powdery, granular, sandy, spherical, plate-like, paper-like, chip-like, rod-like, cylindrical, or columnar, but is not limited to these. Specific examples of wood pieces include lignocellulose powder, wood veneer, and wood plywood. The adhesive of the present invention can firmly bond these wood pieces together.

[0011] (Glucomannan) The adhesive of the present invention uses glucomannan. Glucomannan is a water-soluble polysaccharide found abundantly in konjac potatoes, consisting of hexose glucose and mannose linked by β-1,4-glycosidic bonds in a ratio of approximately 2:3, and is the main component of konjac. Because the adhesive of the present invention uses glucomannan, a food component, it is safer than when synthetic resins are used as adhesive components, even if the adhesive components dissolve into human saliva, food, and beverages in wooden products such as tableware, food containers, cooking utensils, and toys. The adhesive of the present invention preferably contains 0.2 to 36% by mass of glucomannan, more preferably 1 to 23% by mass, and even more preferably 1 to 15% by mass, based on the total amount of adhesive. When glucomannan is included in the adhesive within the above range, wood pieces can be bonded together more strongly. Specifically, glucomannan can be used in the form of glucomannan powder, konjac powder (refined powder), etc.

[0012] (Alkali compounds) The adhesive of the present invention further comprises an alkali compound. In this specification, "alkali compound" means a compound that, when dissolved in water, produces hydroxide ions (OH -This results in the presence of an alkaline compound in addition to glucomannan in the adhesive of the present invention, which further improves the water resistance of the adhesive used to bond wood pieces together. Specifically, even when wood pieces bonded with the adhesive are immersed in water, the adhesive becomes less likely to dissolve in the water.

[0013] While not bound by theory, the inventors believe that the following chemical changes occur in the adhesive: The acetyl groups contained in glucomannan are removed by hydroxide ions of alkaline compounds, causing aggregation of the glucomannan molecular chains and forming a three-dimensional network structure (gel) while the glucomannan remains adhered to the wood pieces. In other words, the glucomannan contained in the adhesive undergoes alkali modification while adhering to the wood pieces, forming an irreversible gel. As a result, even when the wood pieces are immersed in water, they remain firmly bonded to each other and become difficult to dissolve in water.

[0014] The alkali compound can be any compound that dissolves in water to produce hydroxide ions and is not particularly limited, but examples include calcium hydroxide, potassium hydroxide, sodium hydroxide, calcium oxide, sodium carbonate, sodium bicarbonate, and ammonia. Among these, calcium hydroxide and sodium carbonate are preferred as alkali compounds because they provide higher water resistance to the adhesive when bonding wood pieces together and are highly safe when applied to wood products such as tableware.

[0015] In the adhesive of the present invention, the alkali compound is preferably present in an amount of 0.2 to 50% by mass relative to the total amount of glucomannan. When the alkali compound is present in the adhesive within the above range, the water resistance of the adhesive when wood pieces are bonded together can be further improved.

[0016] (water) The adhesive of the present invention preferably contains water in addition to glucomannan and an alkali compound. The inclusion of water in the adhesive prevents the glucomannan from being modified and hardened by the alkali compound before the adhesive is applied to the wood piece, thereby improving the handling properties of the adhesive. The amount of water is preferably 64 to 98% by mass of the total amount of the adhesive of the present invention. When the water content is within the above range, the handling properties of the adhesive are further improved.

[0017] (Additives) In addition to the materials described above, the adhesive of the present invention may contain additives as needed. Examples of such additives include colorants, pigments, pH adjusters, preservatives, antimicrobials, viscosity modifiers, surfactants, stabilizers, and antioxidants. To enhance the safety of the adhesive, it is preferable that these additives be made of highly safe ingredients that can also be used in food products. The content of additives can be 10% by mass or less of the total amount of adhesive.

[0018] (Method of manufacturing adhesives) The method for producing the adhesive of the present invention is not particularly limited, and it can be produced by mixing the materials described above.

[0019] (How to use adhesive) The method of using the adhesive of the present invention is not particularly limited, but examples include the following: The adhesive of the present invention is applied to or impregnated into the wood pieces to be bonded, the wood pieces to which the adhesive has been applied or impregnated are brought into contact with each other, and the wood pieces are dried while in contact with each other, thereby bonding them together.

[0020] (Application) The method of applying the adhesive to the wood pieces is not particularly limited and can be done by conventionally known methods, such as using a brush, roller, or coater. However, if the concentration of glucomannan in the adhesive is low, the viscosity of the adhesive will also be low, which may make it difficult to apply to the wood pieces. Therefore, from the viewpoint of improving handling, the adhesive may be heated during manufacturing or application.

[0021] (Impregnation) The method of impregnating the wood pieces with adhesive is not particularly limited, and impregnation can be carried out by conventionally known methods, such as immersing the wood pieces in adhesive. The wood pieces may also be heated together with the impregnation solution during the impregnation process. Heating can further improve water resistance.

[0022] Furthermore, when wood pieces are impregnated with adhesive, the adhesive is also applied to surfaces other than the bonding surface. In this case, after the wood pieces dry, a layer of alkali-modified glucomannan is formed on surfaces other than the bonding surface. This layer of alkali-modified glucomannan enhances the water resistance not only of the adhesive but also of the wood pieces themselves. When applying adhesive to wood pieces to enhance the water resistance of the wood pieces themselves, the adhesive may also be applied to surfaces other than the bonding surface.

[0023] (contact) The method for bringing together wood pieces to which adhesive has been applied or impregnated is not particularly limited as long as the surfaces to which the adhesive has been applied or impregnated come into contact. For example, if the wood pieces are wood powder, they can be mixed so that the wood powders come into contact with each other, or if the wood pieces are wood veneers, they can be laminated so that the wood veneers come into contact with each other. The wood pieces may be pressurized or heated when bringing them into contact.

[0024] (Drying) The drying method for wood chips is not particularly limited and can be carried out at room temperature or under heat, but heat drying is preferred. Heat drying allows for stronger adhesion between the wood chips. The heat drying temperature is preferably within a range that does not affect the color tone of the wood chips, for example, a range of 50°C to 120°C is preferred. Examples of heat drying methods include hot air drying, infrared drying, and hot plate drying.

[0025] It is preferable that the moisture content in the bonded wood pieces be 20% by mass or less, more preferably 10% by mass or less, and even more preferably 5% by mass or less, after drying. By removing water from the wood pieces through drying, the wood pieces and the adhesive can be firmly bonded together.

[0026] <Composition containing lignocellulose powder> In another embodiment, the present invention provides a composition comprising the wood chip adhesive described above and lignocellulose powder. From the composition of this embodiment, a molded article with excellent safety, water resistance, and moldability can be produced.

[0027] The composition contains the wood chip adhesive described above. The content of the wood chip adhesive in the composition is not particularly limited, but the amount of wood chip adhesive can be adjusted as appropriate from the viewpoint of improving the water resistance, handling properties, and moldability of the composition.

[0028] (Lignocellulose powder) Lignocellulose powder is a powder whose main component is lignocellulose. Lignocellulose is a material whose main components are cellulose, hemicellulose, and lignin.

[0029] Examples of lignocellulose powder include woody biomass powder and herbaceous biomass powder. Examples of woody biomass powder include wood powder and bamboo powder. Examples of wood include coniferous trees such as cedar, cypress, and pine, and broad-leaved trees such as beech, oak, and birch. Wood powder and bamboo powder may be produced by crushing raw wood, or by crushing waste wood. Examples of herbaceous biomass powder include powder made from crushed corn stalks, rice stalks, and rush stalks.

[0030] The particle size of the lignocellulose powder is not particularly limited, but the lower limit of the particle size can be 1 μm, 5 μm, 10 μm, or 15 μm. The upper limit of the particle size can be 1000 μm, 500 μm, 400 μm, 300 μm, or 200 μm.

[0031] The particle size can be defined as the D50 of the volume-based particle size distribution measured by a laser diffraction particle size analyzer.

[0032] The amount of lignocellulose powder in the composition is not particularly limited, but can be adjusted as appropriate from the viewpoint of improving the handling and moldability of the composition.

[0033] (Method for producing a composition containing lignocellulose powder) The method for producing the composition of this embodiment is not particularly limited, and it can be produced by mixing the lignocellulose powder described above with the wood chip adhesive.

[0034] (Method for manufacturing molded articles using lignocellulose powder) A method for manufacturing a molded article using the composition of this embodiment comprises the steps of molding the composition described above and drying the molded composition to obtain a molded article.

[0035] In the molding process, the molding method is not particularly limited; it may be molded by hand or by machine. When molded by hand, the composition can be easily obtained by deforming the mass into a desired shape by hand, dividing one mass into multiple pieces (e.g., tearing it), or combining multiple pieces into one.

[0036] When molding using machinery, the molded composition can be obtained using known methods such as extrusion molding, injection molding, and compression molding. For example, a straw or the like may be formed using tube molding as an extrusion molding method.

[0037] The resulting molded composition can be dried to obtain a dried molded body. The drying method is the same as that described above for the use of adhesive for wood chips.

[0038] It is preferable to remove the water content in the molded body by drying to 20% by mass or less, preferably 10% by mass or less, and more preferably 5% by mass or less. By removing water from the molded composition by drying, the lignocellulose powder and the adhesive are firmly bonded, resulting in a molded body with high water resistance and the desired shape.

[0039] (Another embodiment of the method for manufacturing a molded article using lignocellulose powder) As another embodiment of the method for producing a molded article using lignocellulose powder, the present invention provides a method for producing a molded article comprising the steps of: molding a composition containing glucomannan and lignocellulose powder; coating or impregnating the molded composition with an alkaline solution containing an alkaline compound; and drying the composition coated or impregnated with the alkaline solution to obtain a molded article.

[0040] In this embodiment, a molded composition is prepared by first molding a composition containing glucomannan and lignocellulose powder, and then an alkaline solution is applied or impregnated, and the molded composition is dried to obtain a highly water-resistant molded body in which the lignocellulose powder particles are bonded together by an alkali-modified glucomannan.

[0041] In this embodiment, the glucomannan, lignocellulose powder, and alkali compound can be used in the same manner as the materials described above.

[0042] In a composition containing glucomannan and lignocellulose powder, the amount of glucomannan is not particularly limited, but can be adjusted as appropriate from the viewpoint of improving the water resistance, handling properties, and moldability of the composition. The mass ratio of lignocellulose powder to glucomannan in the composition can be 95:5 to 50:50.

[0043] The composition containing glucomannan and lignocellulose powder preferably further contains water from the viewpoint of improving handling and moldability. The amount of water can be appropriately adjusted within a range that has a viscosity suitable for molding.

[0044] The method for molding the composition can be the same as that described above.

[0045] Next, the resulting molded composition is coated or impregnated with an alkaline solution containing an alkaline compound. The amount of alkaline compound contained in the alkaline solution is not particularly limited, but it is preferably 0.2 to 50% by mass relative to the total amount of glucomannan in the molded composition. The alkaline solution may be a saturated aqueous solution such as a saturated calcium hydroxide aqueous solution.

[0046] The method for applying or impregnating the molding composition with an alkaline solution is the same as that described in the method for using the wood chip adhesive above. Alternatively, the molding composition may be immersed in an aqueous calcium hydroxide solution (e.g., a saturated aqueous solution) at 60-100°C for about 1-60 minutes.

[0047] A molded body can be obtained by drying a molded composition coated or impregnated with an alkaline solution. The drying method is the same as that described above for the use of adhesive for wood chips.

[0048] <Wood plywood> In another embodiment, the present invention provides a wood plywood in which multiple wood veneers are laminated via the wood chip adhesive described above.

[0049] The wood veneers constituting the above-mentioned plywood are not particularly limited as long as they are boards formed from wood-based materials. For example, they may be solid wood boards, particleboards formed from small pieces of wood-based materials, or lignocellulose powder compressed into a board. Such wood-based materials can be obtained from coniferous trees such as cedar, cypress, and pine, broad-leaved trees such as beech, oak, and birch, and bamboo. The lignocellulose powder can be used in the same way as described above.

[0050] The thickness of the wood veneers constituting the above-mentioned plywood is not particularly limited, but can be, for example, 0.1 to 5 mm. Furthermore, the number of wood veneers to be laminated is not particularly limited; it must be two or more, and there is no particular upper limit, but can be, for example, 100.

[0051] (Method of manufacturing wood plywood) The above-mentioned wood plywood can be manufactured by applying or impregnating multiple wood veneers with the aforementioned wood adhesive, bringing the wood veneers into contact with each other, and drying the wood veneers while they are in contact. To improve the strength of the wood plywood, the wood veneers may be pressed after contacting each other before drying. The pressure applied during pressing can be, for example, 2 to 5 MPa. Pressing may be performed at room temperature or under heating. If heating is used, the temperature can be 100 to 150°C.

[0052] (Another embodiment of the method for manufacturing wood plywood) As another embodiment of the method for manufacturing wood plywood, the present invention also allows for the manufacture of the above-mentioned wood plywood by a method comprising the steps of: applying or impregnating a plurality of wood veneers with a solution containing glucomannan; bringing the plurality of wood veneers into contact with each other; and applying or impregnating the contacted plurality of wood veneers with an alkaline solution containing an alkaline compound. In this method, by bringing the wood veneers that have been previously coated or impregnated with the glucomannan solution into contact with each other, and then applying or impregnating them with an alkaline solution, a highly water-resistant wood plywood is obtained in which the wood veneers are bonded together with an alkali-modified glucomannan.

[0053] The concentrations of the alkaline compound and alkaline solution are not particularly limited, as described above, but can be set to 0.2 to 50% by mass relative to the total amount of glucomannan used. The concentration of the glucomannan solution is not particularly limited, but can be adjusted as appropriate from the viewpoint of improving the handling of the glucomannan solution and the water resistance of the resulting wood plywood.

[0054] In the above method, the step of applying or impregnating with an alkaline solution may be followed by a step of drying the multiple wood veneers to which the alkaline solution has been applied or impregnated. When manufacturing a molded body from plywood, following the step of applying or impregnating with an alkaline solution, the multiple wood veneers to which the alkaline solution has been applied or impregnated may be molded to produce molded wood plywood, and then the molded wood plywood may be dried.

[0055] (Method of manufacturing a molded body using wood plywood) A molded body can be obtained by molding the manufactured wood plywood. The method of molding the wood plywood is not particularly limited, and known molding methods can be used. For example, the plywood can be set in a concave mold, and then a convex mold can be pressed to mold it to the shape. The pressure applied during pressing can be, for example, 2 to 5 MPa. Pressing may be performed at room temperature or under heating. If heating is used, the temperature can be 100 to 150°C.

[0056] (Another embodiment of a method for manufacturing a molded body using wood plywood) As another embodiment of the method for manufacturing a molded body using wood plywood, the present invention provides a method for manufacturing a molded body comprising the steps of: laminating a plurality of wood veneers to produce wood plywood; molding the wood plywood; applying or impregnating the molded wood plywood with the above-mentioned adhesive for wood chips; and drying the wood plywood to which the adhesive for wood chips has been applied or impregnated to obtain a molded body. In this method, wood plywood is produced by lamination without using adhesive for wood chips or glucomannan solution, molded, and then adhesive for wood chips is used after molding.

[0057] In the steps of molding the manufactured plywood, applying or impregnating the molded plywood with adhesive for wood chips, and drying the plywood coated or impregnated with adhesive for wood chips to obtain a molded body, the molding method, application or impregnation method, and drying method described above can be used, respectively.

[0058] The resulting molded product has excellent strength and water resistance because the wood veneer adhesive for wood chips penetrates between the wood veneers that form the plywood.

[0059] (Another embodiment of a method for manufacturing a molded body using wood plywood) As another embodiment of the method for manufacturing a molded body using wood plywood, the present invention provides a method for manufacturing a molded body comprising the steps of: applying or impregnating a plurality of wood veneers with a solution containing glucomannan; laminating the plurality of wood veneers to produce wood plywood; molding the wood plywood; applying or impregnating the molded wood plywood with an alkaline solution containing an alkaline compound; and drying the wood plywood coated or impregnated with the alkaline solution to obtain a molded body. This method involves laminating wood veneers that have been previously coated or impregnated with a glucomannan solution, molding them, then applying or impregnating them with an alkaline solution, and drying them to obtain a molded body with high strength and water resistance in which the wood veneers are bonded together with an alkali-modified glucomannan. The materials used and the methods of application, impregnation, compression, molding, and drying are the same as described above.

[0060] <Molded body> As described above, a wood molded body containing multiple wood pieces bonded together via an alkali-modified glucomannan can be obtained by the manufacturing method of each embodiment.

[0061] The wood molded articles of the present invention can be used for a variety of applications, including tableware, food containers, cooking utensils, toys, stationery, furniture, ornaments, decorative components, automotive interior parts, home appliance parts, and building materials.

[0062] The wooden molded body of the present invention can also be used as a straw. In recent years, with reports that plastic straws have adverse effects on the health of marine life, and the sale and provision of plastic straws in stores being reduced in various countries, wooden straws have high value as an alternative to plastic straws.

[0063] The straws formed from the wood molded body of the present invention have high water resistance because the wood pieces are firmly bonded together via an alkali-modified glucomannan, and they are also highly safe because they use food-grade ingredients. Therefore, the straws of the present invention, with their high water resistance and safety, are particularly effective in applications where straws are often permeated with saliva in the human mouth or immersed in beverages for extended periods.

[0064] <Straw manufacturing method> In another embodiment, the present invention provides a method for manufacturing a wooden straw. The method of this embodiment comprises the steps of: applying or impregnating a thin wooden board with the above-mentioned adhesive for wood pieces; shaping the thin wooden board coated or impregnated with the adhesive for wood pieces into the shape of a straw; and drying the thin wooden board shaped into the shape of a straw to obtain a wooden straw. While straws formed from molded wooden bodies are formed from multiple pieces of wood, the method of this embodiment allows for the manufacture of a wooden straw from even a single thin wooden board.

[0065] In this specification, "wooden sheet" refers to a thin sheet of wood, and its thickness is not particularly limited, but for example, it can be 1 mm or less. From the viewpoint of improving the strength after molding, it is preferable that the thickness of the wooden sheet is 0.1 mm or more.

[0066] In the process of applying or impregnating a wooden board with wood chip adhesive, the application and impregnation methods can be the same as those described above. In the process of shaping the wooden board into a straw, the shaping method is not particularly limited as long as it is shaped into a straw, but for example, the wooden board can be shaped into a straw as follows.

[0067] A long, narrow rectangular wooden sheet, coated or impregnated with wood glue, is wrapped spirally (diagonally) around a rod whose diameter is the same as the inner diameter of the straw, overlapping the joined parts so as not to leave any gaps. After wrapping the wooden sheet spirally (diagonally) until it reaches a suitable length, the wrapped wooden sheet is pulled off the rod to form a wooden sheet shaped like a straw. Alternatively, when wrapping the wooden sheet around the rod, the long side of the rectangular wooden sheet may be wrapped along the longitudinal direction of the rod, so that the long side of the wooden sheet and the longitudinal direction of the rod are parallel. After wrapping, the wrapped wooden sheet is pulled off the rod to form a wooden sheet shaped like a straw. A wooden straw can be obtained by drying the formed wooden sheet. The drying method can be the same as the method described above. The wooden sheet may be cut as appropriate to the desired straw length before or after drying.

[0068] (Another embodiment of the method for manufacturing wooden straws) As another embodiment of the method for manufacturing wooden straws, the present invention provides a method for manufacturing wooden straws comprising the steps of: forming a thin wooden sheet into the shape of a straw; applying or impregnating the formed thin wooden sheet with the above-mentioned adhesive for wood chips; and drying the thin wooden sheet that has been applied or impregnated with the adhesive for wood chips to obtain a wooden straw. In this embodiment, the thin wooden sheet is first formed into the shape of a straw, and then the adhesive for wood chips is applied or impregnated after forming. The method for forming the sheet into the shape of a straw is the same as the method described above, except that the thin wooden sheet is applied or impregnated with the adhesive for wood chips. The application or impregnation method and the drying method are the same as the method described above.

[0069] As yet another embodiment of the method for manufacturing wooden straws, the present invention provides a method for manufacturing wooden straws comprising the steps of: coating or impregnating a wooden sheet with a glucomannan solution containing glucomannan; shaping the wooden sheet coated or impregnated with the glucomannan solution into a straw shape; coating or impregnating the shaped wooden sheet with an alkaline solution containing an alkaline compound; and drying the wooden sheet coated or impregnated with the alkaline solution to obtain a wooden straw. In this embodiment, the wooden sheet that has been first coated or impregnated with the glucomannan solution is shaped into a straw shape, and then the alkaline solution is coated or impregnated after shaping. The coating or impregnation method, shaping method, and drying method are the same as in the method described above.

[0070] The wooden straws produced in the manner described above have high water resistance because the wooden sheets are firmly bonded together via an alkali-modified glucomannan, and they are also highly safe because they use food-grade ingredients. Therefore, even when soaked in saliva in the human mouth or immersed in beverages for extended periods, the straws of this invention are highly water-resistant and safe, allowing users to use them with confidence.

[0071] Furthermore, the surfaces of various wood products obtained as described above, such as wood chip adhesives, molded bodies of compositions containing lignocellulose powder (e.g., straws), wood plywood and its molded bodies, and thin-sheet straws, may be coated as needed to improve water resistance. Examples of coatings include shellac and waxes (e.g., carnauba wax, candela wax, rice wax, and beeswax). For example, in the case of straws, the coating may be applied only to the outer surface or only to the inner surface, but from the viewpoint of improving water resistance, it is preferable to coat both the outer and inner surfaces. [Examples]

[0072] (Example 1: Preparation of glucomannan solution) A glucomannan solution was prepared by mixing 100g of water at three different temperatures (25°C, 60°C, and 80°C) with 3g of glucomannan. In the following examples, all glucomannan solutions prepared with water at the three different temperatures were used at room temperature (25°C).

[0073] (Example 2: Preparation of alkaline solution) An alkaline solution (concentration 15 g / L) was prepared by mixing 1.5 g of calcium hydroxide with 100 g of water at room temperature (25°C).

[0074] (Example 1: Preparation of adhesive for wood chips) Wood chip adhesive was prepared by mixing 100g of water at three different temperatures (25°C, 60°C, and 80°C), 3g of glucomannan, and 0.3g of calcium hydroxide. In the following examples, all wood chip adhesives prepared with water at the three different temperatures were used at room temperature (25°C).

[0075] (Example 2: Preparation of adhesive for wood chips) 100g of water at two different temperatures (60°C and 80°C) was mixed with 3g of glucomannan. A calcium hydroxide aqueous solution with a concentration of 15g / L (7.5g calcium hydroxide / 500g water) was then added to this mixture to prepare an adhesive for wood chips.

[0076] (Example 3: Making a wooden straw using wood powder and wood chip adhesive) The cedar powder (particle size 20 μm) and the wood chip adhesive prepared in Example 1 were mixed in a BEGO Motova 300 mixer to obtain the composition. After filling the composition into an extruder, it was molded into the shape of a straw with a diameter of 6 mm and a length of 150 mm by extrusion molding. After molding, the molded composition was dried at 60°C for 3 hours to obtain wooden straws.

[0077] (Example 4: Preparation of plywood using wood chip adhesive) Fifteen sheets of cedar wood veneer (0.15 mm thick) were prepared, and the wood adhesive prepared in Example 1 was applied to one side of each veneer. The wood veneers with the adhesive applied were laminated together, and a plywood was obtained by pressing them in a press machine at 145°C and a pressure of 3.0 MPa for 15 minutes.

[0078] (Example 5: Preparation of wood plywood using wood chip adhesive) Thirteen cedar wood veneers (0.15 mm thick) impregnated with the wood adhesive prepared in Example 1 were prepared, and the wood veneers were laminated together. A wood plywood was obtained by pressing it in a press machine at 110°C and a pressure of 3.0 MPa for 15 minutes.

[0079] (Example 6: Preparation of wood plywood using glucomannan solution and alkaline solution) Ten sheets of cedar wood veneer (0.15 mm thick) were prepared, and the glucomannan solution prepared in Example 1 was applied to one side of each veneer. The wood veneers coated with glucomannan solution were laminated together and pressed in a press machine at 145°C and 4 MPa for 15 minutes. After pressing, the laminated wood veneers were heated while being impregnated with the alkaline solution prepared in Example 2. The laminated wood veneers were removed from the alkaline solution and dried at 70°C for 2 hours to obtain wood plywood.

[0080] (Example 7: Preparation of a molded body using wood chip adhesive) Thirteen sheets of cedar wood veneer (0.15 mm thick) were prepared, and the wood veneer adhesive prepared in Example 1 was applied to one side of each veneer. The veneers with the adhesive applied were laminated together, placed in a mold, and pressed in a press machine at 145°C and 2 MPa for 10 minutes to obtain a molded body.

[0081] (Example 8: Preparation of molded articles using glucomannan solution and alkaline solution) Ten sheets of cedar wood veneer (0.15 mm thick) were prepared, and the glucomannan solution prepared in Example 1 was applied to one side of each veneer. The wood veneers coated with glucomannan solution were laminated together, placed in a mold, and pressed in a press machine at 145°C and 4 MPa for 15 minutes. After pressing, the laminated wood veneers were heated while being impregnated in the alkaline solution prepared in Example 2. The laminated wood veneers were removed from the alkaline solution and dried at 70°C for 2 hours to obtain a molded body.

[0082] (Example 9: Fabrication of a straw using thin wooden sheet) One sheet of thin cedar strip (0.1-0.2 mm thick, 60 mm wide, 220 mm long) was prepared. This strip was impregnated with the wood chip adhesive prepared in Example 1. The strip was removed from the wood chip adhesive, and an aluminum rod (6 mm in diameter) was placed on the strip at an angle to one side of the strip. The strip was then wrapped around the rod from one corner to form a tube, thus shaping the strip into a straw. After shaping, the strip was dried at room temperature or at 60°C to 120°C to obtain a wooden straw.

[0083] (Example 10: Fabrication of a straw using thin wooden sheet) One sheet of thin cedar wood strip (0.1-0.2 mm thick, 60 mm wide, 220 mm long) was prepared. An aluminum rod (6 mm in diameter) was placed on the strip at an angle to one side of the strip, and the strip was wrapped around the rod from the corner of the strip to form a tube, thus shaping the strip into a straw. After shaping, the wood chip adhesive prepared in Example 1 was applied to the strip. After application, the strip was dried at room temperature or at 60°C to 120°C to obtain a wooden straw.

[0084] (Example 11: Fabrication of a straw using thin wooden sheet) One thin strip of cedar wood (0.1-0.2 mm thick, 60 mm wide, 220 mm long) was prepared. This strip was impregnated with the glucomannan solution prepared in Example 1. The strip was removed from the glucomannan solution, and an aluminum rod (6 mm in diameter) was placed on the strip at an angle to one side of the strip. The strip was wrapped around the rod from the corner of the strip to form a tube, thus shaping it into a straw. The straw-shaped strip was heated while being impregnated with the alkaline solution prepared in Example 2. After impregnation and heating, the strip was dried at room temperature or at 60°C to 120°C to obtain a wooden straw.

[0085] (Comparative Example 1: Fabrication of a straw using thin wooden sheet) A wooden straw was obtained in the same manner as in Example 10, except that the glucomannan solution prepared in Preparation Example 1 was applied instead of the wood chip adhesive prepared in Example 1.

[0086] (Comparative Example 2: Fabrication of a straw using thin wooden sheet) A wooden straw was obtained using the same method as in Example 11, except that after shaping it into a straw form, it was dried without applying an alkaline solution.

[0087] (Water resistance test) The wooden straws obtained in Examples 9-11 and Comparative Examples 1 and 2 were immersed in water for 24 hours. After immersion, the wooden straws were removed and visually inspected to see if the adhesive portion of the wooden veneer had come off. If the adhesive portion of the wooden veneer had not come off, it was checked whether it could be peeled off by hand.

[0088] As a result, the wooden straws of Examples 9-11 did not lose their adhesive bond to the wooden veneer even after being immersed in water for 24 hours, and could not be peeled off by hand. On the other hand, the wooden straws of Comparative Examples 1 and 2 lost their adhesive bond to the wooden veneer after being immersed in water.

[0089] Therefore, it was shown that the alkali-modified glucomannan maintained a strong bond between the wood slabs even after they were immersed in water for a long time.

[0090] (Example 12: Preparation of a straw using konjac powder-containing adhesive and thin wooden sheet) A wooden straw was obtained in the same manner as in Example 9, except that an adhesive containing konjac powder was used instead of glucomannan (however, the glucomannan content in the adhesive was the same).

[0091] The following elution tests were performed on the wooden straws obtained in Example 9 and Example 12 (in both cases, the water temperature during adhesive preparation was 25°C). No arsenic, heavy metals, phenol, or formaldehyde were detected in any of the straws. Arsenic (as As2O3): Solvent (4V / V% acetic acid): Detection limit 0.05 μg / mL Heavy metal (as Pb): Solvent (4V / V% acetic acid): Detection limit 1 μg / mL Phenols (as phenol): Solvent (water): Detection limit 0.5 μg / mL Formaldehyde: Solvent (water): Detection limit 0.5 μg / mL

[0092] <Straws made from cedar powder, glucomannan powder, and calcium hydroxide> (Example A1) Japanese cedar powder (particle size 22 μm) and glucomannan powder were prepared as lignocellulose powders. 90 parts by mass of Japanese cedar powder, 10 parts by mass of glucomannan, and water were stirred at room temperature (25°C) using a BEGO Motova 300 stirrer to obtain a molding composition.

[0093] (molding) The obtained molding composition was extruded through a 25 mm x 10 mm hole in an extrusion molding machine to obtain a molded body. This molded body was able to maintain its shape after molding. Furthermore, the molding composition could also be molded by hand.

[0094] (Impregnation with alkaline solution) 3000cm at room temperature of 25℃ 3A saturated calcium hydroxide solution was prepared by dissolving 6 g of calcium hydroxide in water. The calcium hydroxide solution was then boiled and maintained at 90°C. A molded body was placed in the calcium hydroxide solution maintained at 90°C and left for 30 minutes to allow the calcium hydroxide to permeate the molded body.

[0095] (Drying) The molded body removed from the aqueous solution was air-dried at room temperature (24°C) for 2 days to obtain a dried molded body. The moisture content of the dried molded body was approximately 9.2%.

[0096] (Comparative Example A1) A dried molded article was obtained in the same manner as in Example A1, except that it was dried without impregnation with an aqueous calcium hydroxide solution.

[0097] (Example A2 and Comparative Example A2) Except for adding cedar powder (particle size 22 μm) and glucomannan powder in a ratio of 80 parts by mass and 20 parts by mass, respectively, and setting the temperature of the calcium hydroxide aqueous solution during impregnation to 100°C, dried molded articles were obtained in the same manner as in Example A1 and Comparative Example A1. The moisture content of the dried molded article of Example A1 was approximately 3.4%.

[0098] (Evaluation: 3-point bending strength test) A dry molded body was cut with a laser cutter to obtain test workpieces measuring 8.5 mm in height, 6 mm in depth, and 70 mm in length. Subsequently, a three-point bending test was performed on the workpieces using a universal testing machine, and the maximum stress was measured.

[0099] (Evaluation: Compression strength test) A dry molded body was cut with a laser cutter to obtain test workpieces measuring 10 mm in height, 10 mm in depth, and 10 mm in length. Subsequently, the workpieces were subjected to compression tests using a universal testing machine, and the maximum stress was measured.

[0100] (Evaluation: Hardness test) The hardness of the dried molded product was measured using a durometer hardness tester (Type D). The conditions and results are shown in Table 1.

[0101] [Table 1]

[0102] <Composition containing cedar powder, konjac powder, and calcium hydroxide> (Example B1) Japanese cedar powder (particle size 22 μm) and konjac powder were prepared as lignocellulose powders. 90 parts by mass of Japanese cedar powder and 10 parts by mass of konjac powder were mixed with water at room temperature (25°C) using a BEGO Motova 300 mixer to obtain a molding composition. Subsequently, molding and alkali impregnation were carried out in the same manner as in Example A1 to obtain a dried molded article. The moisture content of the dried molded article from Example B1 was approximately 8.4%.

[0103] (Comparative Example B1) A dried molded article was obtained in the same manner as in Example B1, except that impregnation with an aqueous calcium hydroxide solution was omitted.

[0104] (Example B2, and Comparative Example B2) Except for using cedar powder (particle size 22 μm) and konjac powder in a ratio of 80 parts by mass and 20 parts by mass, respectively, and setting the temperature of the calcium hydroxide aqueous solution during impregnation to 100°C, the same procedure as in Example B1 and Comparative Example B1 was followed to obtain dried molded articles. The moisture content of the dried molded article of Example B2 was approximately 3.5%.

[0105] (Example B3, and Comparative Example B3) Except for the addition ratio of cedar powder (particle size 22 μm) and konjac powder being 70 parts by mass and 30 parts by mass, respectively, the same procedure as in Example B2 and Comparative Example B3 was followed to obtain dried molded articles. The moisture content of the dried molded article of Example B3 was approximately 2.1%.

[0106] The strength of the dried molded article was evaluated in the same manner as in Example A1. The results are shown in Table 2.

[0107] [Table 2]

[0108] <Composition containing cedar powder, konjac powder, and calcium hydroxide> (Example C1) Japanese cedar powder (particle size 177 μm) and konjac powder were prepared as lignocellulose powders. 90 parts by mass of Japanese cedar powder and 10 parts by mass of konjac powder were mixed with water at room temperature (25°C) using a BEGO Motova 300 mixer to obtain a molding composition. Subsequently, molding and alkali impregnation were carried out in the same manner as in Example A1 to obtain a dried molded article. The moisture content of the dried molded article was approximately 7.6%.

[0109] (Comparative Example C1) A dried molded article was obtained in the same manner as in Example C1, except that impregnation with an aqueous calcium hydroxide solution was omitted.

[0110] (Example C2, and Comparative Example C2) Except for adding cedar powder (particle size 177 μm) and konjac powder in a ratio of 80 parts by mass and 20 parts by mass, respectively, and setting the temperature of the calcium hydroxide aqueous solution during impregnation to 100°C, the same procedure as in Example C1 and Comparative Example C1 was followed to obtain dried molded articles. The moisture content of the dried molded article of Example C2 was approximately 8.2%.

[0111] (Example C3 and Comparative Example C3) Except for the addition ratio of cedar powder (particle size 177 μm) and konjac powder being 70 parts by mass and 30 parts by mass, respectively, the same procedure as in Example C2 and Comparative Example C2 was followed to obtain dried molded articles. The moisture content of the dried molded article of Example C3 was approximately 8.7%.

[0112] The strength of the dried molded article was evaluated in the same manner as in Example B1. The results are shown in Table 3.

[0113] [Table 3]

[0114] In the example where the material was impregnated with an alkaline aqueous solution, a significant improvement in strength was observed in at least one of the three strength tests compared to the comparative example where the material was not impregnated.

[0115] (Example 13: Preparation of wooden straws using wood powder and wood chip adhesive (containing glucomannan)) The molding composition prepared in Example A2 was filled into an extruder and then molded into a straw shape with a diameter of 6 mm and a length of 150 mm by extrusion molding. After molding, the straw was impregnated with an aqueous calcium hydroxide solution in the same manner as in Example A2, and then the molded composition was dried at 60°C for 3 hours. After drying, the molded straw was impregnated with a shellac solution and then dried, and the outer and inner surfaces of the molded straw were coated with shellac to obtain a wood flour-derived straw.

[0116] (Example 14: Making a wooden straw using wood powder and wood chip adhesive (containing konjac powder)) A wood flour-derived straw coated with shellac on both the outer and inner surfaces was obtained in the same manner as in Example 13, except that the molding composition of Example B3 was used.

[0117] The same elution tests as described above were performed on the straws of Example 13 and Example 14, but no arsenic, heavy metals, phenol, or formaldehyde were detected in any of the straws.

Claims

1. A method for producing a molded article, comprising the steps of: molding a composition containing glucomannan and lignocellulose powder; applying or impregnating the molded composition with an alkaline solution containing an alkaline compound; and drying the composition coated or impregnated with the alkaline solution to obtain a molded article.

2. A method for manufacturing wood plywood, comprising the steps of: applying or impregnating a plurality of wood veneers with a solution containing glucomannan; bringing the plurality of wood veneers into contact with each other; and applying or impregnating the plurality of wood veneers that have come into contact with each other with an alkaline solution containing an alkaline compound.

3. A method for manufacturing a molded body, comprising the step of forming a wood plywood as described in claim 2.

4. A method for manufacturing a molded body, comprising the steps of: applying or impregnating a plurality of wood veneers with a solution containing glucomannan; laminating the plurality of wood veneers to produce a wood plywood; molding the wood plywood; applying or impregnating the molded wood plywood with an alkaline solution containing an alkaline compound; and drying the wood plywood coated or impregnated with the alkaline solution to obtain a molded body.

5. A method for manufacturing a molded article according to any one of claims 1, 3 to 4, wherein the molded article is tableware, food containers, cooking utensils, toys, stationery, furniture, ornaments, decorative members, automobile interior parts, home appliance parts, or building materials.

6. The method for manufacturing a molded body according to claim 5, wherein the molded body is a straw.

7. A method for producing a wooden straw, comprising the steps of: applying or impregnating a wooden sheet with a glucomannan solution containing glucomannan; shaping the wooden sheet coated or impregnated with the glucomannan solution into the shape of a straw; applying or impregnating the shaped wooden sheet with an alkaline solution containing an alkaline compound; and drying the wooden sheet coated or impregnated with the alkaline solution to obtain a wooden straw.

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