JP7499156B2 - Wood board and method for manufacturing wood board - Google Patents

Description

Embodiments of the present invention relate to wood boards and methods for manufacturing wood boards.

Amid growing concern about the environment, there is a demand for effective use of used tea leaves, which are an increasing amount of residue left over after tea beverage extraction. One known use for used tea leaves is wood boards that contain used tea leaves.

For example, Patent Document 1 discloses a method for producing tea leaves boards in which plant waste, the main component of which is tea leaves, is solubilized with an enzyme agent containing at least protease or pectinase, and the insoluble residue is dried and then heated and pressurized for molding. Patent Document 1 states that tea leaves need to be solubilized using an enzyme agent.

JP 2008-57089 A

An object of one embodiment of the present invention is to provide a wood board that can be manufactured by a simple method and has excellent strength.An object of another embodiment of the present invention is to provide a method for easily manufacturing a wood board that has excellent strength.

The present invention includes various embodiments. Examples of embodiments are listed below. The present invention is not limited to the following embodiments.

(1) A wood board comprising used tea leaves and wood material, wherein the mass ratio of leaves to stems in the used tea leaves is 6:4 to 9:1 (leaves:stems), and the saturation of the used tea leaves is 14.0 or more.
(2) The wood board described in (1) above, wherein the content of the used tea leaves is 2 to 30 mass%.
(3) A wood board according to (1) or (2) above, in which the pH of the wood board extract is 7.0 or less.

(4) A method for manufacturing a wood board, comprising: preparing used tea leaves having a mass ratio of leaves to stems of 6:4 to 9:1 and a saturation of 14.0 or higher, and wood material; preparing a slurry containing the used tea leaves, the wood material, and water; forming a wood mat using the slurry; and drying the wood mat.
(5) The manufacturing method described in (4) above, wherein the content of tea leaves in the wood board is 2 to 30 mass%.
(6) A manufacturing method described in (4) or (5) above, in which hydrated tea leaves containing the tea leaves and water are used to prepare a slurry, and the pH of the hydrated tea leaves is 6.0 or less.

According to an embodiment of the present invention, it is possible to provide a wood board that can be manufactured by a simple method and has excellent strength. According to another embodiment of the present invention, it is possible to provide a method for easily manufacturing a wood board that has excellent strength.

An embodiment of the present invention will be described. The present invention is not limited to the following embodiment.

<Wood board>
The wood board according to the embodiment of the present invention contains used tea leaves and wood material. The mass ratio of leaves to stems in the used tea leaves is 6:4 to 9:1, and the chroma of the used tea leaves is 14.0 or more. The wood board may contain optional components such as a sizing agent, a coloring agent, and a binder.

(Used tea leaves)
Used tea leaves are residues containing leaves and stems after tea components are extracted from raw tea with water. Used tea leaves include leaf residues and stem residues. In this specification, "raw tea" includes tea plant tissues containing active ingredients that can be extracted as tea, specifically leaves and stems. The raw tea may be any of non-fermented tea, semi-fermented tea, fermented tea, or a mixture thereof. An example of non-fermented tea is green tea, an example of semi-fermented tea is oolong tea, and an example of fermented tea is black tea. The raw tea is preferably green tea, and examples of green tea include steamed tea, sencha, gyokuro, bancha, gyokuryokucha, kettle tea, Chinese green tea, etc. The raw tea may be a raw tea consisting of only one type of raw tea, or a mixed raw tea containing two or more types of raw tea.

The used tea leaves contained in the wooden board contain leaves and stems in a mass ratio (mass ratio of dry solids) of leaves:stems = 6:4 to 9:1. The ratio of leaves and stems in the used tea leaves contained in the wooden board varies depending on the tea harvest season and harvest year, so in order to obtain a stable wooden board, the used tea leaves contained in the wooden board are preferably a mixture obtained by mixing separated leaves and stems to achieve the above mass ratio. The mass ratio of leaves and stems is preferably leaves:stems = 6.5:3.5 to 9:1, and more preferably 7:3 to 9:1. A mass ratio of leaves between 6 and 9 provides good strength.

The saturation of the tea leaves contained in the wood board is 14.0 or more. When the saturation is 14.0 or more, excellent strength can be obtained. The saturation is preferably 15.0 or more, and more preferably 116.5 or more. Since the saturation of tea leaves before heating or steamed tea leaves is 25, the saturation of the tea leaves may be 25 or less.

The chroma of used tea leaves is measured after removing the used tea leaves from the wooden board using tweezers or the like and crushing the removed tea leaves to a particle size of 1 mm or less. The chroma (C*) of used tea leaves can be calculated from the lightness L* and chromaticity a* and b* measured using a spectrophotometer.

The content of used tea leaves in the wooden board is preferably 2 to 30% by mass, based on the mass of the wooden board. When the content of used tea leaves is 2 to 30% by mass, a high strength improvement effect tends to be obtained. The content of used tea leaves is more preferably 2 to 25% by mass, and even more preferably 3 to 20% by mass.

(Wood materials)
The wood board contains wood material. The wood material may be contained in the wood board in the form of defibrated wood fibers or in the form of small chips. As the wood material, so-called wood, which is generally used as a building material, structural material, etc., can be used. Examples of tree species of wood material include coniferous trees such as cedar, cypress, Japanese cypress, larch, and pine; broad-leaved trees such as chestnut, birch, oak, chinquapin, poplar, and willow; and tropical wood such as lauan. It is also possible to use wood waste materials such as industrial waste materials and construction waste materials. It is also possible to use wood-derived raw materials such as paper pulp and waste paper. Only one type of wood material can be used, or two or more types can be mixed together.

The content of wood material in the wood board is preferably 70 to 98% by mass, based on the mass of the wood board. When the content of wood material is 70 to 98% by mass, the strength tends to improve when combined with used tea leaves. The content of wood material is preferably 75 to 98% by mass, based on the mass of the wood board, and more preferably 80 to 97% by mass.

(Optional Ingredients)
Depending on the desired characteristics, the wood board may contain optional components such as binders such as starch and PVC, other fiber reinforcements such as carbon fiber and ceramic fiber, and additives such as sizing agents and colorants. The binder is used to further improve the strength of the obtained wood board. The binder can be appropriately selected from those usually used in wood boards. On the other hand, if further improvement in strength is not required, the wood board may not contain a binder. The content of the binder in the wood board may be, for example, 0 to 20 mass%, 0 to 15 mass%, or 0 to 10 mass%, based on the total mass of tea leaves and wood material. The wood board according to the embodiment of the present invention has sufficient strength even without a binder by containing tea leaves.

(pH of wood board extract)
The pH of the wood board extract is preferably 7.0 or less from the viewpoint of obtaining good strength. The wood board extract is a liquid obtained by immersing the wood board in water for a predetermined time. Specifically, the pH of the wood board extract can be measured by the following method.
(1) Finely grind the wood board.
(2) Using a 100 mL beaker, 1 g of the ground material is immersed in 100 g of distilled water at 25° C. for 3 minutes. The pH of the distilled water before immersing the ground material is adjusted to 7.0.
(2) The liquid containing the ground material obtained after soaking is separated into liquid and solid by filtration. The liquid after separation is used as the wood board extract.
(3) The pH of the wood board extract at 25° C. is measured using a pH meter. The pH meter is calibrated at three points using pH buffer solutions (pH = 4.0, 7.0, and 9.0). The measurement is carried out five times, and the average of the five measurements is regarded as the pH of the water-absorbent paper extract.

The pH of the wood board extract is preferably 7.0 to 5.0, more preferably 7.0 to 5.2, and even more preferably 7.0 to 5.5. When a pH of 7.0 or less is obtained, it is believed that the tea leaves fibers are sufficiently defibrated within the wood board. When the pH is 5.0 or more, the tea leaves tend to further improve the strength of the wood board.

The thickness of the wood board is not particularly limited and may be an appropriate thickness depending on the application. The thickness of the wood board may be, for example, 0.5 to 50 mm.

Examples of wood boards include hardboard (HB, hard fiberboard), MDF (medium density fiberboard), and insulation board (IB, soft fiberboard). Wood boards manufactured by a wet process are preferred. Wood boards are preferably manufactured by the wood board manufacturing method described below. Wood boards can be preferably used for, for example, furniture; floors; interior walls; building underlays such as roofs; and fixtures such as doors and window frames. Wood boards may be surface-treated, such as with an anti-slip coating. However, if a surface treatment has been performed, the pH of the wood board extract is measured by crushing the wood board excluding the surface-treated portion.

<Wood board manufacturing method>
The method for manufacturing a wood board according to an embodiment of the present invention includes the steps of preparing used tea leaves having a mass ratio of leaves to stems of 6:4 to 9:1 and a chroma of 14.0 or more, and a wood material (hereinafter, sometimes referred to as a "preparation step"); preparing a slurry containing the used tea leaves, the wood material, water, and optional components such as a binder, if necessary (hereinafter, sometimes referred to as a "slurry preparation step"); forming a wood mat using the slurry (hereinafter, sometimes referred to as a "wood mat formation step"); and drying the wood mat (hereinafter, sometimes referred to as a "drying step"). The method for manufacturing a wood board may further include general steps performed for manufacturing a wood board, such as a step of crushing and fragmenting the wood material (fragmentation step) and a step of defibrating the wood material (defibration step). The "step" includes not only independent steps, but also steps that cannot be clearly distinguished from other steps, as long as the operation specified in the "step" is performed, even if the step cannot be clearly distinguished from other steps.

[Preparation process]
In the preparation step, at least used tea leaves and wood material are prepared. The used tea leaves may be dried or may be hydrated used tea leaves. From the viewpoint of obtaining a wood board with high strength, it is preferable to use hydrated used tea leaves.

(Water-containing used tea leaves)
The hydrated used tea leaves contain used tea leaves and water. The description of the used tea leaves in the above embodiment can be applied to the method of manufacturing a wooden board.

The moisture content of the hydrated tea leaves (i.e., the amount of water contained in the hydrated tea leaves) is preferably 65-95% by mass, more preferably 70-90% by mass, and even more preferably 70-85% by mass, based on the mass of the hydrated tea leaves. If the moisture content is 95% by mass or less, it tends to be easier to prevent differences in the moisture content of the hydrated tea leaves filled in the container due to separation of the tea leaves from the water. Differences in moisture content may affect the amount of tea leaves added when manufacturing wooden boards. Because hydrated tea leaves have good water retention, it is impossible to adjust the moisture content to less than 65% by mechanical dehydration, and drying using petroleum resources, etc. is required.

As the hydrated tea leaves, the water-containing residue obtained after extracting tea components from raw tea can be used as is. Further water can be added to the water-containing residue after extraction to adjust the moisture content. Alternatively, the water-containing residue can be dried to obtain dried tea leaves, and the dried tea leaves can be mixed with water and thoroughly mixed to obtain the hydrated tea leaves.

Extraction conditions can be set according to the type of tea leaves. The water used for extraction is, for example, tap water, natural water, distilled water, ion-exchanged water, etc. The temperature of the water is preferably 50 to 100°C, more preferably 60 to 95°C, and even more preferably 65 to 90°C. The extraction time is preferably 1 to 30 minutes, more preferably 2 to 20 minutes, and even more preferably 3 to 10 minutes. The amount of water used is preferably 0.1 to 10 L, more preferably 0.2 to 8 L, and even more preferably 0.3 to 5 L per 10 g of raw tea.

The mass ratio of leaves to stems (mass ratio of dry solids) is 6:4 to 9:1 as described above. The residue obtained after extracting the raw tea with a leaf:stem ratio of 6:4 to 9:1 may be used with the leaf:stem ratio unchanged. A stem sorter may be used to separate the leaves and stems. After separating the residue into leaves and stems, the mixture may be mixed to satisfy the leaf:stem ratio of 6:4 to 9:1.

As mentioned above, the saturation of tea leaves is 14.0 or more. The saturation of tea leaves tends to decrease the stronger the heating conditions applied to the raw tea before extraction. For example, if the heating temperature is high and/or the heating time is long, the saturation of tea leaves will decrease. On the other hand, if the heating temperature is low and/or the heating time is short, the saturation of tea leaves will increase.

The saturation of the used tea leaves can be measured after they have been dried. Drying is carried out under conditions that minimize the effect on the saturation of the used tea leaves while still allowing for sufficient drying. The drying temperature is, for example, preferably 70 to 105°C, more preferably 90 to 105°C, and even more preferably 90 to 100°C. The drying time is, for example, preferably 3 to 24 hours, more preferably 3 to 12 hours, and even more preferably 3 to 8 hours.

The particle size of the hydrated used tea leaves is preferably 0.3 mm or more and less than 10 mm. The particle size of the hydrated used tea leaves is more preferably 0.3 mm or more and less than 5 mm, and even more preferably 0.3 mm or more and less than 1 mm. When the particle size is 0.3 mm or more, it tends to be easier to prevent the tea leaves from detaching from the wooden board. When the particle size is less than 10 mm, the wood material and the tea leaves fibers tend to be entangled in the wooden board, improving its strength. The particle size of the hydrated used tea leaves can be adjusted, for example, by adding water to the residue obtained after extraction and wet grinding. A mixer, mill, refiner, pulper, mortar, etc. can be used for wet grinding. Also, tea leaves may be added to the process of defibrating the wood material and ground together. The particle size of the hydrated used tea leaves can be measured by a sieving method.

The pH of the hydrated tea leaves used to prepare the mixture slurry described below is preferably 6.0 or less, more preferably 6.0 to 3.0, and even more preferably 6.0 to 4.0. When the pH is 6.0 or less, it is considered that the fibers of the tea leaves are sufficiently defibrated in the mixture slurry. When the pH is 3 or more, destruction of the fibers of the tea leaves is prevented, and a wood board with sufficient strength tends to be obtained. The pH of the hydrated tea leaves may be adjusted using a pH adjuster. Examples of pH adjusters include acids such as hydrochloric acid, sulfuric acid, and acetic acid, and bases such as sodium hydroxide, potassium hydroxide, and ammonia. In addition, the pH of the hydrated tea leaves used to prepare the mixture slurry may be adjusted to a range of 6.0 to 3.0 by first lowering the pH of the hydrated tea leaves using a pH adjuster and then raising it further using a pH adjuster.

From the viewpoint of improving the strength of the wood board, it is preferable that the pH of the hydrated tea leaves is maintained at 6.0 or less for at least a predetermined time before the hydrated tea leaves are mixed with the pulp. The predetermined time is a time during which the tea leaves do not decay. The predetermined time is, for example, 6 hours to 60 days, preferably 12 hours to 45 days, and more preferably 24 hours to 30 days. The pH is more preferably 6.0 to 3.0. The pH adjusters described above can be used to adjust the pH.

(Wood materials)
The description of the wood material in the above embodiment can be applied to the wood material used in the manufacturing method of the wood board. The wood material may be in the form of a slurry in which wood fibers are suspended in water (hereinafter, sometimes referred to as "wood fiber slurry"). Examples of a method for obtaining wood fibers by defibrating wood material include a method using a defibrator, a hammer mill, a ring breaker, etc. Defibrators are preferably used from the viewpoint of obtaining fine and homogeneous fibers. The moisture content of the wood fiber slurry (the content of water in the slurry) is preferably 90 to 99.5% by mass, more preferably 93 to 99% by mass, and even more preferably 95 to 98% by mass, based on the mass of the wood fiber slurry.

[Preparation process]
In the preparation step, a slurry containing used tea leaves, wood, water, and optional components such as a binder, etc., is prepared (hereinafter, sometimes referred to as a "mixed slurry"). Preferred methods include a method of mixing wet used tea leaves, a slurry containing wood fibers, and water to obtain a slurry; a method of adding water to wet used tea leaves and grinding them, mixing a slurry containing wood fibers, and water to obtain a slurry; and a method of mixing wet used tea leaves, wood, and water, and then defibrating the wood to obtain a slurry. In the latter method, for example, wet used tea leaves are mixed with wood chips and defibrated together by a defibrator. When tea leaves and wood are mixed and then defibrated, the operation is simple and a homogeneous mixture tends to be obtained.

The content of tea leaves in the mixture slurry (mass % of dry solids) may be 2 mass % or more. The content of tea leaves is preferably 2 to 30 mass %, more preferably 2 to 25 mass %, and even more preferably 3 to 20 mass %, based on the mass of the mixture slurry (excluding the mass of water). The content of wood material in the mixture slurry (mass % of dry solids) is preferably 70 to 98 mass %, more preferably 75 to 98 mass %, and even more preferably 80 to 97%, based on the mass of the mixture slurry (excluding the mass of water).

[Molding process]
In the molding process, the mixture slurry is used to form a wood mat. For example, a method of forming a wood mat includes a method of draining water from the mixture slurry. Water can be drained from the mixture slurry by papermaking, that is, by supplying the mixture slurry onto a filtering member such as a mesh and filtering the water. The thickness of the wood mat can be adjusted by adjusting the ratio between the filtering area and the amount of the mixture slurry supplied.

[Drying process]
In the drying step, the wood mat is dried. Drying is preferably carried out under conditions that allow the wood mat to dry uniformly throughout and have a moisture content of 0 to 8% by mass immediately after drying. The drying temperature can be, for example, 90 to 200°C, preferably 100 to 180°C. The drying time can be, for example, 1 to 24 hours.

The embodiments of the present invention will be described in detail with reference to examples. The embodiments of the present invention are not limited to the following examples.

[Example 1]
(Preparation of hydrated used tea leaves)
Green tea (manufactured by Itoen Co., Ltd.) was separated into leaves and stems using a stem sorter (manufactured by Hattori Seisakusho Co., Ltd.), and the leaves and stems were mixed in the ratio shown in Table 1 to obtain raw tea. Tea components were extracted from the raw tea (10 g raw tea/1 L water, 80°C, 5 minutes) to obtain tea and residue. Water was added to the residue and crushed in a mixer (BL310AJP, manufactured by Grooseve Japan Co., Ltd.) to obtain hydrated tea leaves. The saturation of all tea leaves was in the range of 14 to 15. Samples for saturation measurement were prepared by heating and drying the hydrated tea leaves at 105°C for 5 hours, and then crushing them in a mixer to 1 mm or less. The saturation was measured using a spectrophotometer (SE6000, manufactured by Nippon Denshoku Kogyo Co., Ltd.).

(Production of wooden boards)
A commercially available insulation board (manufactured by Daiken Kogyo Co., Ltd.) was soaked in water for 5 minutes, then placed in a mixer ("BL310AJP" manufactured by Grooseve Japan Co., Ltd.) and stirred for 5 minutes to obtain a wood slurry with a moisture content of 92%. Hydrated tea leaves were added to the obtained wood slurry to prepare a mixture slurry. The mixture slurry was divided into small portions so that the dry solid mass was 4 g, and poured onto a wire with an opening of 180 μm (sieve area: 0.018 m ² ) to produce a wood mat of 16 cm x 11 cm. A pressure of about 120 g/cm ² was applied from above the wood mat to perform dehydration. The board was then dried at 105° C. for 24 hours to produce a wood board containing tea leaves (tea leaves content 10% by mass).

(Wood board evaluation)
The prepared wood board was cut into a size of 3 cm x 4 cm, and the tensile strength was measured using a digital force gauge (IMADA Co., Ltd. "DPX-5TR").

(Measurement of fiber content in used tea leaves)
The tea leaves after extraction were dried with hot air at 105°C and dry-ground, and the fiber content (mass%) based on the mass of the tea leaves was measured using a tea component analyzer (GTN-9, manufactured by Shizuoka Seiki Co., Ltd.). The measurement results are shown in Table 1.

As shown in Table 1, wood boards containing used tea leaves with a mass ratio of leaves to stems of 6:4 to 9:1 and a saturation of 14.0 or higher had high strength.

[Example 2]
(Preparation of hydrated used tea leaves)
Green tea (manufactured by ITO EN Co., Ltd.) with a mass ratio of leaves:stem = 7:3 was heated in a frying pan to prepare raw tea (green tea leaves) with different heating degrees. Tea components were extracted from the raw tea (10 g raw tea/1 L water, 80 ° C, 5 minutes) to obtain tea and residue. Water was added to the residue and it was pulverized in a mixer ("BL310AJP" manufactured by Grooseve Japan Co., Ltd.) to obtain hydrated tea leaves.

(Production of wooden boards)
Except for using the above-prepared hydrated tea leaves, a wooden board was produced in the same manner as in Example 1. The tensile strength of the wooden board was measured in the same manner as in Example 1. The results are shown in Table 2.

(Wood board evaluation)
The tensile strength of the wood was measured in the same manner as in Example 1. The results are shown in Table 2.

[Example 3]
(Preparation of hydrated used tea leaves)
Using the same method as in Example 1, green tea residue (Itoen Co., Ltd., green tea (leaves: stems = 6:4)) with a moisture content of 80% after extraction was obtained. The chroma of the used tea leaves was 14.4. The chroma was measured using the same method as in Example 1. The pH of the hydrated used tea leaves at 25°C was 6.5. The pH was measured using the method described above.

Next, a pH adjuster was added to the hydrated tea leaves and mixed to obtain hydrated tea leaves with the pH values shown in Table 3. The hydrated tea leaves before and after the pH adjustment were left to stand at room temperature for one day. Hydrochloric acid and aqueous sodium hydroxide solutions were used as pH adjusters.

(Production of wooden boards)
Except for using the above-prepared hydrated tea leaves, wooden boards were prepared in the same manner as in Example 1. The pH of each wooden board was measured according to the above-mentioned method. The results are shown in Table 3.

(Wood board evaluation)
The tensile strength of the wood was measured in the same manner as in Example 1. The results are shown in Table 3.

Claims (6)

Contains used tea leaves and wood material,
a mass ratio of leaves to stems in the used tea leaves is 6:4 to 9:1;
The saturation of the used tea leaves is 14.0 or more.
Wood board. The wood board according to claim 1, wherein the content of the used tea leaves is 2 to 30% by mass. The wood board according to claim 1 or 2, wherein the pH of the wood board extract is 7.0 or less. preparing used tea leaves having a mass ratio of leaves to stems of 6:4 to 9:1 and a saturation of 14.0 or more, and a wood material;
Preparing a slurry containing the tea leaves, the wood material, and water;
forming a wood mat using the slurry; and drying the wood mat.
A method for manufacturing a wood board comprising: The manufacturing method according to claim 4, wherein the content of tea leaves in the wood board is 2 to 30% by mass. The manufacturing method according to claim 4 or 5, in which hydrated tea leaves containing the tea leaves and water are used to prepare the slurry, and the pH of the hydrated tea leaves is 6.0 or less.