WO2019168127A1 - Wood and method for producing wood - Google Patents

Abstract

The present invention removes lignin while maintaining the structure constituted of cellulose and hemicellulose. A raw wood material is immersed in a solution comprising an acid and an alcohol under the conditions of a temperature of 140-170°C and then immersed in a solution containing chlorous acid ions or hypochlorous acid ions.

Description

WOOD AND WOOD MANUFACTURING METHOD

The present invention relates to wood containing lignin and cellulose, wood obtained by treating a wood raw material, and a method for producing the same.

Timber is widely used as a raw material for building materials, furniture, acoustic materials and paper. Woody biomass is also used from the viewpoint of biorefinery such as bioethanol production. In particular, when wood is used from the viewpoint of biorefinery, lignin, which is a constituent component of wood, is removed, and cellulose and hemicellulose are taken out. In general, the treatment for removing lignin is called pretreatment. Various pretreatment techniques that destroy cells and wall layers have been reported so far.

Examples of pretreatment methods for removing lignin include physicochemical methods such as steam explosion treatment, acid treatment and alkali treatment, and biological methods utilizing lignin degrading enzymes or lignin degrading microorganisms. In addition to these, as a pretreatment method, for example, physical pulverization, steaming, ozone oxidation, γ-ray irradiation, and the like have been studied.

Also, high-temperature heat treatment using an organic solvent such as acetic acid, ethanol, high boiling alcohol, and phenol is called solvolysis and is known as an effective pretreatment method for removing lignin. Hallac et al. Ind Eng Chem Res, 49 (4), 1467-1472, 2010a has a weight percent of lignin of 1 by pulverizing a kind of cedar wood and treating it with a mixed solvent of ethanol and sulfuric acid at 195 ° C. for 1 hour. Find the condition to be a digit. Furthermore, Hallac et al. In Biotechnol Bioeng, 107, 795-801, 2010b, tissue observation of the sample after pretreatment revealed that lignin in the intercellular layer (layer between cells) was preferentially removed. I made it. From the above results, Hallac et al. Ind Eng Chem Res, 49 (4), 1467-1472, 2010a and Hallac et al. It has been concluded that the pretreatment method described in Biotechnol Bioeng, 107, 795-801, 2010b has a high pulping effect that removes lignin and at the same time promotes isolation between cells.

On the other hand, Japanese Patent Application Laid-Open No. 2006-001270 discloses that a lignin-removed wood chip is produced by immersing a cedar chip in a soap-soda ash mixed water and treating with a hydrogen peroxide solution. JP-A-2015-080759 discloses a method of separating lignocellulosic nomi-iomas into a liquid component containing lignin and a solid component containing cellulose by treating heat extraction and solid-liquid separation with an ethylene glycol solution in a single stage. Has been. JP 2012-1111849 discloses that wood powder obtained by pulverizing wood chips is degreased, delignified, demicellulose treated and bleached, then treated with cellulase enzymes, and then refined. A method for producing fine fibrous cellulose by performing is disclosed. In particular, as a delignification treatment, a Wise method using sodium chlorite and acetic acid is disclosed as an example. The Journal of the Wood Society of Japan vol. 50, no. 3, pl32-138 (2010) also discloses that delignification treatment is performed using a sodium chlorite solution adjusted to pH 3.8-4.0 by adding acetic acid.

As described above, there have been known methods for delignifying a lignocellulosic material such as wood by various methods. However, the above-described conventional method is a method for separating lignin from cellulose and hemicellulose, which destroys wood tissue and cells, and cannot maintain the shape before treatment. Although JP 2006-001270 A discloses a lignin removal method that maintains the honeycomb structure of wood chips, it is not a treatment that can maintain the shape of the wood chips themselves.

As described above, there has been no known technique for maintaining a structure composed of cellulose and hemicellulose while reliably removing lignin. Therefore, in view of the above-described circumstances, the present invention provides a method for removing lignin while maintaining a structure composed of wood, cellulose and hemicellulose with reduced lignin while maintaining the structure as wood, and the method. It aims at providing the manufacturing method of the timber which the lignin reduced by applying, and the said timber.

To achieve the above-described object, the present invention includes the following.
(1) Wood having a lignin content of less than 3% by weight and a cellulose content of 75% by weight or more.
(2) The wood according to (1), wherein the cellulose has a viscosity average degree of polymerization DPv of 300 or more.
(3) Wood as described in (1) or (2) whose hemicellulose content is 0.01 weight% or more and 15 weight% or less.
(4) A first step of immersing a wood raw material in a solution containing an acid and an alcohol under conditions of 140 ° C. or higher and 170 ° C. or lower, and then the wooden raw material is treated with chlorite ions or hypochlorite ions. The wood produced through the second step of immersing in the solution containing the lignin component is reduced.
(5) The wood according to (4), wherein the shape of the wood raw material is maintained.
(6) The wood according to (4) or (5), wherein the lignin component is reduced below the detection limit.
(7) The wood according to any one of (4) to (6), which is white.
(8) A first step of immersing the wood raw material in a solution containing an acid and an alcohol under conditions of 140 ° C. or higher and 170 ° C. or lower; The manufacturing method of the timber with which the lignin component was reduced including the 2nd process immersed in the solution to contain.
(9) The method for producing wood according to (8), wherein the alcohol is an alcohol having a boiling point of 150 ° C. or higher.
(10) The solution containing the acid and the alcohol is a solution containing sulfuric acid and ethylene glycol or a solution containing sulfuric acid and propylene glycol, according to (8) or (9) Wood manufacturing method.
(11) The solution containing an acid and an alcohol has an alcohol concentration of 90 to 99.5% by weight and an acid concentration of 0.05 to 10% by weight. (8) to (10) The method for producing wood according to any one of the above.
(12) The method according to any one of (8) to (11), wherein in the first step, the wood raw material is sealed in a state immersed in the solution, and the sealed space is deaerated. Wood manufacturing method.
(13) The solution containing the chlorite ion or hypochlorite ion is a sodium chlorite solution or a sodium hypochlorite solution, according to any one of (8) to (12), Wood manufacturing method.
(14) The solution containing chlorite ion or hypochlorite ion is a solution having a chlorite ion or hypochlorite ion concentration of 0.01 to 10% by weight (8 ) To (13).
(15) The method for producing wood according to any one of (8) to (14), wherein the second step is repeated a plurality of times.

It is the photograph which imaged the untreated wood raw material (A) used in Example 1, the wood raw material (B) after a 1st process, and the white wood (C) obtained after the process. The characteristic which shows the result of having analyzed the component by the infrared absorption spectrum about the untreated wood raw material (A) used in Example 1, the wood raw material (B) after a 1st process, and the white wood (C) obtained after a process. FIG. It is an X-ray image which shows the result of having image-analyzed by X-ray CT about the untreated wood raw material used in Example 1, and white wood. It is an image which shows the X-ray fiber figure obtained by X-ray diffraction about the untreated wood raw material used in Example 1, and white wood. It is the photograph which imaged the untreated wood raw material used in Example 2, and the white wood obtained after the process. It is a characteristic view which shows the result of having analyzed the component by the infrared absorption spectrum about the untreated wood raw material used in Example 2, and the white wood obtained after the process. It is an X-ray image which shows the result of having image-analyzed by X-ray CT about the untreated wood raw material used in Example 2, and white wood. It is the photograph which imaged the untreated wood raw material used in Example 3, and the white wood obtained after the process. It is a characteristic view which shows the result of having analyzed the component by the infrared absorption spectrum about the untreated wood raw material used in Example 3, and the white wood obtained after the process. It is the photograph which imaged the untreated wood raw material (A) used in Example 4, the wood raw material (B) after a 1st process, and the white wood (C) obtained after the process. It is a characteristic view which shows the result of having analyzed the component by the infrared absorption spectrum about the untreated wood raw material used in Example 4, and the white wood obtained after the process. It is the photograph which imaged the untreated wood raw material (A) used in Example 5, the wood raw material (B) after a 1st process, and the white wood (C) obtained after the process. It is a characteristic view which shows the result of having analyzed the component by the infrared absorption spectrum about the untreated wood raw material used in Example 5, the wood raw material after a 1st process, and the white wood obtained after the process. It is the photograph which imaged the white wood obtained after the process used in Example 6. FIG. It is a characteristic view which shows the result of having analyzed the component by the infrared absorption spectrum about the untreated wood raw material used in Example 6, the wood raw material after alkali treatment, the wood raw material after the first step, and the white wood obtained after the treatment. is there.

The first embodiment of the present invention is wood having a lignin content of less than 3% by weight and a cellulose content of 75% by weight or more. According to this embodiment, it becomes the wood which has cellulose as a main component and the lignin component is sufficiently reduced. Cellulose is a main component constituting the cell wall and plays an important role in ensuring the strength of the wood. On the other hand, lignin has been considered to play an important role in maintaining the structure of wood by playing a role of bonding between cells or between microfibrils in the cell wall. For this reason, it was very difficult to maintain the structure as wood while reducing lignin. However, according to the wood of this embodiment, the three-dimensional structure as a wood is maintained despite the lignin component being sufficiently reduced. Although the amount of lignin is reduced in this way, the detailed mechanism by which the three-dimensional structure is maintained is unknown, but for example, lignin is removed by manufacturing wood by the manufacturing method described later. It is considered that the shape as a three-dimensional structure is maintained by replacing water in the part and maintaining the cellulose structure (cellulose microfibrils, etc.) of the original wood without being destroyed. It is done. In addition, the said consideration does not restrict | limit the technical scope of this invention at all.

The wood of the present embodiment is white wood when viewed from the outside because the lignin component is sufficiently reduced. Therefore, it can be widely used as a new material.

Here, the term “wood” as used herein refers to a structure (tissue) in which cells are regularly arranged. Wood is clearly distinguished from pulp. It can be observed using an X-ray CT image or the like that the cells are regularly arranged and the tissue is formed as described in Examples below (for example, FIG. 3). As shown in FIG. 3, in wood, adjacent cells are arranged in order without dissociating from each other.

In this specification, “X to Y” indicating a range includes X and Y, and means “X or more and Y or less”. In this specification, unless otherwise specified, measurement of operation and physical properties is performed under conditions of room temperature (20 ° C. to 25 ° C.) / Relative humidity 45% RH to 55% RH.

Hereinafter, the first embodiment will be described in detail.

The lignin content in the wood is, in order of preference, less than 2% by weight, less than 1% by weight, less than 0.5% by weight, and less than 0.1% by weight. When the lignin content is in such a range, the whiteness is improved. The lower the lignin content, the better. The lower limit is 0% by weight. Here, 0% by weight indicates that the content of each of the following components is below the detection limit when measured by HPLC.

The content of cellulose in the wood is 75% by weight or more, and in a preferable order, it is 80% by weight, 85% by weight, 90% by weight, or 95% by weight or more. When the cellulose content is 75% by weight or more, the strength in the cellulose fiber direction in the wood structure is improved, and the whiteness is improved. In addition, the upper limit of the cellulose content is usually 99.9% by weight or less, preferably 99.5% or less in consideration of the production limit from the viewpoint of maintaining the wood structure.

The viscosity average polymerization degree DPv of cellulose contained in the wood is preferably 300 or more. It is preferable that the viscosity average degree of polymerization DPv of cellulose is 300 or more, since it becomes close to the cellulose fiber state of the original tree and the strength of the wood is improved. Usually, when some chemical treatment is performed, the viscosity average degree of polymerization of cellulose is remarkably reduced. For example, according to the production method described later, a significant decrease in the viscosity average degree of polymerization of cellulose is suppressed. The viscosity average polymerization degree DPv of cellulose is more preferably 500 or more, further preferably 800 or more, and particularly preferably 1,000 or more. In addition, the upper limit of the viscosity average degree of polymerization DPv of cellulose is preferably closer to the cellulose originally present in the tree, and from this viewpoint, it is usually 10,000 or less, preferably 5,000 or less, More preferably, it is 3,000 or less.

The viscosity average degree of polymerization of cellulose can be measured by the following measuring method.

<Measurement method of viscosity average degree of polymerization>
The Wise method using sodium chlorite and acetic acid is repeated on wood, followed by boiling with 5% aqueous sodium hydroxide to extract cellulose. After dissolving cellulose in copper ethylenediamine, the degree of polymerization is measured from the dropping speed with a Canon-Fenske viscometer. Specifically, it is measured as follows.

A 0.5 M copper ethylenediamine solution is prepared, and the viscosity η ₀ is measured using a Canon-Fenske viscometer. In addition, a solution in which cellulose is dissolved in a 0.5 M copper ethylenediamine solution (the cellulose concentration is c (g / dL)) is prepared, and the viscosity η is measured using a Canon-Fenske viscometer. The intrinsic viscosity (sometimes referred to as “ultimate viscosity”) [η] of the cellulose solution is determined by the following formula 1.

Intrinsic viscosity [η] = (η ₀ / η) / {c (1 + A × η / η ₀ )} Equation 1
In Equation 1, “A” indicates a unique value depending on the type of solution. In the case of a 0.5 M copper ethylenediamine solution, “A” is 0.28.

Next, the viscosity average polymerization degree DPv is obtained by the following formula 2 (Mark-Houwink-Sakurada formula).

Intrinsic viscosity [η] = K × DPv × a Equation 2
In Equation 2, “K” and “a” represent specific values depending on the type of polymer. In the case of cellulose, “K” is 0.57 × 10 ⁻³ and “a” is 1.

The content of hemicellulose in the wood is preferably 0.01% by weight or more, more preferably 0.1% by weight or more, further preferably 0.5% by weight or more, and 1% by weight. More preferably, it is more preferably 2% by weight or more. When the content of hemicellulose is equal to or more than the above lower limit, the amount becomes sufficient to bind cellulose, and the three-dimensional structure is easily maintained. Further, the upper limit of hemicellulose is not particularly limited, and since the cellulose content is 75% by weight or more, the wood raw material after the first step is 25% by weight or less, and 20% by weight or less. Is preferably 15% by weight or less, more preferably less than 10% by weight, and particularly preferably less than 5% by weight. In a preferred embodiment, the hemicellulose content is 0.01 wt% or more and 15 wt% or less.

The value measured according to the following measurement conditions is used for the content of each component.

<Measurement conditions>
Samples are treated with 72% sulfuric acid for 1 hour at room temperature. Thereafter, the sulfuric acid is diluted with water to about 3%. The diluted sulfuric acid is treated at 121 ° C. for 1 hour in an autoclave. The obtained sample is separated into solid and liquid fractions with a glass filter. For solids, the amount of lignin is determined by weight measurement. The liquid fraction is neutralized and then subjected to sugar analysis by HPLC. The HPLC conditions are as follows.

Equipment: Prominence UFLC (manufactured by Shimadzu Corporation)
Column: Asahipak NH2P-50 4E (4 mm × 250 mm, Lot: 080806, Shodex (registered trademark), manufactured by Showa Denko KK)
Precolumn: Asahipak NH2P-50G 4A / Opti-guard DVB (manufactured by Showa Denko)
solvent:
Mobile phase A: 0.3% phosphoric acid aqueous solution Mobile phase B: 0.3% phosphoric acid acetonitrile Reaction liquid: Boric acid-L arginine-potassium hydroxide aqueous solution Reactor temperature: 150 ° C.
Column temperature: 45 ° C
Detection condition: RF-AXL detector A value obtained by multiplying the glucose amount (% by weight) measured by the HPLC by 0.9 is defined as the cellulose amount. The amount of hemicellulose is calculated from the following formula;

The maximum load of the wood is preferably 0.1N or more, more preferably 1N or more, and further preferably 5N or more from the viewpoint of maintaining the crystal structure and ensuring the mechanical strength. Preferably, it is 10N or more and even more preferable. Moreover, the upper limit of the maximum load of the wood is not particularly limited, but is preferably 1,000 N or less, and more preferably 500 N or less. When the maximum load of the wood is not more than the above upper limit, the wood can easily take a porous structure.

The value measured under the following measurement conditions is used for the maximum load.

Apparatus: AandD Fortester MCT-2150
Sample size: 1 cm ³ blocks Direction: Fiber direction (compressing the mouth end)
Since the wood of this embodiment has a reduced lignin amount, the appearance is white wood. By making the appearance white, it is possible to obtain a transparent molded product by impregnating the transparent resin, and coloring such as dyeing is also possible. The L * of the wood is preferably 88 or more, more preferably 90 or more, still more preferably 92 or more, and most preferably 93 or more. The a * of the wood is preferably 5 or less, more preferably 3 or less, most preferably 1 or less, further preferably −5 or more, more preferably −3 or more. And most preferably −1 or more. The b * of the wood is preferably 5 or less, more preferably 3 or less, and most preferably 2 or less. For the whiteness, an average value obtained by measuring five points on the wood surface using a color difference meter (SE-6000 manufactured by Nippon Denshoku Industries Co., Ltd.) is adopted.

In addition, the presence of cellulose and hemicellulose can be qualitatively confirmed by staining cellulose and hemicellulose by PAS staining (polysaccharide staining method). In addition, the amount of cellulose and hemicellulose can be quantified based on the dyeing area ratio or the like.
The measurement conditions are as follows.

<Measurement conditions>
The section is oxidized with an aqueous periodate solution and then reacted with a Schiff reagent. Wash with sulfite and then with distilled water. Prepare preparations, observe, and evaluate by colorimeter.

Such wood is obtained, for example, by the manufacturing method of the following third embodiment. The manufacturing conditions may be appropriately set depending on the size of the wood, the wood type, and the like, but can be controlled by the immersion time and number of times in the first step, the immersion time and number of times in the second step, and the like. In particular, by increasing the immersion time in the second step and increasing the number of times, it becomes easy to obtain wood with a reduced amount of lignin as described above.

In the wood of the first embodiment, it is preferable that a plurality of diffraction spots exist in concentric diffraction images in an X-ray fiber diagram obtained by X-ray diffraction. Such a diffraction spot can be visually recognized as a black point in the X-ray fiber diagram. The presence of a plurality of diffraction spots indicates that there is no disturbance in the orientation of cellulose microfibrils in the cell wall. Therefore, wood maintains the structure of cellulose microfibrils in the cell wall and is therefore excellent in strength. Here, the plural may be two or more. The number of X-ray diffraction spots is preferably the same as the number of spots observed on the same kind of raw material wood.

X-ray fiber diagram is measured as follows. First, a radiation slice is prepared, and a sample wound in a cylindrical shape with the L direction as an axis is set and measured. The measurement conditions are as follows.

Imaging plate single crystal structure analyzer: Rigaku Corporation R-AXIS RAPID
X-ray source: Cu target Further, in the crystal structure of cellulose, the full width at half maximum (FWHM) of X-ray diffraction (200 planes) is a viewpoint that the amount of lignin is reduced, the orientation of cellulose is improved, and the strength in the fiber direction is excellent. It is preferably 3 or less, more preferably 2.8 or less, and even more preferably 2.6 or less. Moreover, it is preferable that it is 1 or more from a viewpoint that a transparent molding can be obtained by impregnating a transparent resin, and coloring, such as dyeing | staining, also becomes possible, and it is 1.6 or more. It is preferably 2 or more and most preferably. It can be said that the crystal structure of natural cellulose is maintained when the full width at half maximum (FWHM) of X-ray diffraction (200 planes) of cellulose is in such a range. Therefore, wood is excellent in strength.

The crystal structure of cellulose is measured as follows.

X-ray apparatus: fully automatic horizontal multi-purpose X-ray diffraction apparatus (manufactured by Rigaku Corporation, SmartLab)
X-ray source: Cu target Although the raw material (origin) of wood is not particularly limited, it is preferably wood, and a suitable form is selected from the group consisting of conifers, hardwoods and bamboo. As described above, the definition of wood in the present specification is “it refers to a structure (tissue) in which cells are regularly arranged”, and therefore bamboo is also included in this specification as a raw material for wood. For this reason, in this specification, bamboo is included in wood.

Although it is not particularly limited as a conifer, Sugi, Scots pine, Larch, Black pine, Todomatsu, Himekomatsu, Yew, Ginkgo, Nezuko, Kaya, Harimomi, Iramimi, Inakiki, Fir, Sawara, Togasawara, Asunaro, Hiba, Tsuga, Komatsuki , Cypress, Sawara, Yew, Inugaya, Spruce, Yellow Cedar (Beihiba), Lawson Cypress (Beihi), Douglas Fir (Baymatsu), Sitka Spruce (Beisuhi), Radiata Pine, Eastern Spruce, Eastern White Pine, Western Larch, Western Fur , Western hemlock, tamarack and the like. Among these, the raw material for wood is preferably cedar, larch, or cypress.

Although it is not particularly limited as a broad-leaved tree, beech, china, birch, walnut, poplar, eucalyptus, acacia, asada, oak, itaya maple, wig, senoki, chestnut, elm, giraffe, honoki, willow, sen, ubatashi, konara, kunugi , Tochinoki, zelkova, boxwood, mizume, mizunara, dogwood, red oak, aodamo, balsa and aohada. Among them, the raw material for wood is preferably beech, balsa or elm, and is preferably either beech or elm.

Examples of bamboo include mushrooms, mosouchiku (Moso bamboo), and bees.

Therefore, in a preferred form of the present invention, the raw material (origin) is cedar, larch, cypress, beech, elm, balsa or bamboo, and more preferably cedar, larch, cypress, beech, elm or bamboo.

In the second embodiment of the present invention, a first step of immersing a wood raw material in a solution containing an acid and an alcohol under a condition of 140 ° C. or higher and 170 ° C. or lower; This wood is produced through the second step of immersing in a solution containing hypochlorite ions and has a reduced lignin component.

The wood according to the second embodiment includes a first step of immersing a wooden raw material in a solution containing an acid and an alcohol under a condition of 140 ° C. or higher and 170 ° C. or lower, and then converting the wooden raw material into chlorite ions or It is produced through a second step of immersing in a solution containing hypochlorite ions. That is, the present invention includes a first step of immersing a wooden raw material in a solution containing an acid and an alcohol under a condition of 140 ° C. or higher and 170 ° C. or lower, and then converting the wooden raw material into chlorite ions or hypochlorite. There is also provided a form of a method for producing wood having a reduced lignin component, comprising a second step of immersing in a solution containing acid ions. According to such a method, the lignin component contained in the wood raw material can be reduced while maintaining the structure composed of cellulose and hemicellulose. Therefore, the wood produced by the method has the characteristics that the structure made of the cellulose and the hemicellulose inherent in the wood raw material is maintained and the lignin component is reduced.

The reduced lignin component means that the lignin component in the wood is preferably less than 3% by weight, less than 2% by weight, less than 1% by weight, less than 0.5% by weight, and less than 0.1% by weight. .

Here, the wood raw material is a material having a predetermined shape using wood as a raw material. Although the tree used as a raw material is not particularly limited, it is preferably wood, and a suitable form is selected from the group consisting of softwood, hardwood and bamboo. In particular, conifers are preferred.

Although it is not particularly limited as a conifer, Sugi, Scots pine, Larch, Black pine, Todomatsu, Himekomatsu, Yew, Ginkgo, Nezuko, Kaya, Harimomi, Iramimi, Inakiki, Fir, Sawara, Togasawara, Asunaro, Hiba, Tsuga, Komatsuki , Cypress, Sawara, Yew, Inugaya, Spruce, Yellow Cedar (Beihiba), Lawson Cypress (Beihi), Douglas Fir (Baymatsu), Sitka Spruce (Beisuhi), Radiata Pine, Eastern Spruce, Eastern White Pine, Western Larch, Western Fur , Western hemlock, tamarack and the like.

Although it is not particularly limited as a broad-leaved tree, beech, china, birch, walnut, poplar, eucalyptus, acacia, asada, oak, itaya maple, wig, senoki, chestnut, elm, giraffe, honoki, willow, sen, ubatashi, konara, kunugi , Tochinoki, zelkova, boxwood, mizume, mizunara, dogwood, red oak, aodamo, balsa and aohada.

Examples of bamboo include mushrooms, mosouchiku (Moso bamboo), and bees.

Therefore, in a preferred form of the present invention, the wood raw material is cedar, larch, cypress, beech, elm, balsa or bamboo, and more preferably cedar, larch, cypress, beech, elm or bamboo.

The woody raw material may be produced by performing a predetermined process on the raw material wood. Although it does not specifically limit as a process with respect to wood, Cutting process, grinding process, grinding | polishing process, a wrinkle process, a bending process etc. can be mentioned. According to these processes, the raw material wood can be processed into a desired shape, and a wood raw material having the shape can be obtained.

Further, the wood raw material may be composed of a single member or a plurality of members. For example, a wood raw material composed of a plurality of members can be produced by joining a plurality of members by a general method. Examples of a method for joining a plurality of members include a method using an adhesive, a method using a nail or a screw, a method using a metal fitting, and a method using a joint such as a mortise.

The shape of the wood raw material is not particularly limited, and examples thereof include a plate shape, a rod shape, a chip shape, a box shape, and a spherical shape. Regarding the shape of the wood raw material, it is preferable that the shape of the wood raw material sufficiently penetrates into the solution when immersed in the solution for a predetermined time in the first step and the second step described above. In other words, it is only necessary to adjust the dipping time of the wood raw material in the solution, and it can be understood that the wood raw material may have any shape.

Further, the size of the wood raw material is not particularly limited, but it can be a size that allows the solution to sufficiently penetrate into the solution when immersed in the solution in the first step and the second step described above. From this point of view, it can be seen that the preferred range of the size of the wood raw material varies depending on the immersion time in the solution and the type of wood used as the raw material, particularly the density of the wood. For example, when using cedar and the immersion time in the first step and the second step is 1 hour, the distance from the surface may be 10 cm or less at the position where the distance from the surface is the shortest in the wood raw material. Preferably, it is 5 cm or less, more preferably 3 cm or less, and most preferably 1 cm or less and 0.5 cm or less. From the viewpoint of ease of handling in production, it is preferably 0.05 cm or more, and more preferably 0.1 cm or more. Moreover, when using zelkova, elm, beech, oak (hardwood) instead of cedar (conifer), the same dimension when the immersion time in the first step and the second step is 1 hour is 5 cm or less. Preferably, it is 2.5 cm or less, more preferably 1.5 cm or less, and most preferably 0.5 cm or less. In addition, when bamboo is used instead of cedar (coniferous tree), the same dimension when the immersion time in the first step and the second step is 1 hour is preferably 10 cm or less, and 5 cm or less. Is more preferably 3 cm or less, and most preferably 1 cm or less.

In this embodiment, when it is difficult for the wood raw material to be whitened only by the above process, particularly when the wood raw material is bamboo, it is preferable to perform an alkali treatment before the first step described below. Such pretreatment is preferable because the lignin component can be efficiently removed.

In the alkali treatment, the alkali used for preparing the alkaline solution is not particularly limited, and is sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, calcium hydroxide, sodium bicarbonate, potassium bicarbonate, hydroxide. Examples include lithium and ammonia. Of these, sodium hydroxide, potassium hydroxide, sodium carbonate, and calcium hydroxide are preferable, sodium hydroxide, sodium carbonate, and calcium hydroxide are more preferable, and sodium hydroxide is particularly preferable. In addition, the said alkali may be used individually by 1 type, and may be used together 2 or more types.

The solvent for dissolving the alkali is not particularly limited, but is preferably water. That is, the alkaline solution is preferably an aqueous sodium hydroxide solution.

The alkali treatment is performed by immersing the wood raw material in the alkali solution. In this case, the immersion time can be appropriately set according to the shape and size of the wood raw material, the moisture content of the wood raw material, etc., and is, for example, 10 minutes to 5 hours, and 30 minutes to 2 hours. The immersion temperature is not particularly limited, but is preferably 135 ° C. or lower, and more preferably 115 ° C. or lower. The immersion temperature is preferably 55 ° C. or higher, and more preferably 75 ° C. or higher. If the temperature condition is too high, the wood will peel, and if it is too low, delignification in the subsequent process becomes difficult.

In the wood manufacturing method according to the present embodiment, first, the above-described wood raw material is immersed in a solution containing an acid and an alcohol under a condition of 140 ° C. or higher and 170 ° C. or lower (first step). Prior to this step, the wood raw material may be dried. For example, when a wood raw material is produced using a desiccant having a moisture content of about 20% or less, a drying step may be unnecessary. However, when a wood raw material is produced with a material having a moisture content exceeding 20%, Is preferably dried so as to be 20% or less.

The wood raw material is immersed in a solution containing acid and alcohol under conditions of 140 ° C. or higher and 170 ° C. or lower. Here, the condition of 140 ° C. or more and 170 ° C. or less means that the atmospheric temperature in the immersion environment is 140 ° C. or more and 170 ° C. or less. The temperature condition is preferably 140 ° C. or higher, more preferably 145 ° C. or higher, from the viewpoint of efficiently promoting delignification. From the viewpoint of suppressing a decrease in the molecular weight of cellulose, it is preferably 170 ° C. or lower, more preferably 165 ° C. or lower, and even more preferably 160 ° C. or lower.

In the first step, an amount of solution sufficient to immerse the entire wood raw material is prepared according to the shape and dimensions of the wood raw material. The solution used in the first step is a solution containing an acid and an alcohol. Here, although it does not specifically limit as an acid, Acids, such as a sulfuric acid, hydrochloric acid, nitric acid, and an acetic acid, can be mentioned. Of these, sulfuric acid is preferably used because of its low volatility as an acid. The alcohol is not particularly limited, but it is preferable to use, for example, a high-boiling point alcohol because the solvent is likely to remain even when heated. High boiling alcohol means, for example, an alcohol having a boiling point of 150 ° C. or higher, preferably 160 ° C. or higher, more preferably 170 ° C. or higher, and still more preferably 180 ° C. or higher. Examples of the alcohol that can be used in the first step include 1,2-ethanediol (ethylene glycol, boiling point: 197.2 ° C.), diethylene glycol (boiling point: 244.3 ° C.), and triethylene glycol (boiling point: 287.4). ° C), propylene glycol (boiling point: 187.4 ° C), 1,3-butanediol (boiling point: 207.5 ° C), 1,4-butanediol (boiling point: 228 ° C), 2-ethyl-1-hexanol ( Boiling point: 184.7 ° C.), benzyl alcohol (boiling point: 205.45 ° C.) and the like can be used. Among these, as the alcohol, it is preferable to use ethylene glycol or propylene glycol, and it is more preferable to use ethylene glycol. Propylene glycol is a material that can be used as a food additive, a material that can be used for food packaging materials, and the like, which is preferable in terms of safety. It is a preferable example that the material remaining for obtaining this wood is a food additive, and it is the most preferable example that all the materials used in the reaction are food additives.

In a preferred embodiment of the present invention, the solution containing an acid and an alcohol is a solution containing sulfuric acid and ethylene glycol or a solution containing sulfuric acid and propylene glycol. The suitable form of this invention is a solution in which the solution containing an acid and alcohol contains a sulfuric acid and ethylene glycol.

From the viewpoint that the lignin component of the wood raw material can be sufficiently reduced in the solution used in the first step, the acid concentration is 0.05% by weight or more, 0.1% by weight or more, and 0.3% by weight in order of preference. From the viewpoint of easily maintaining the structure consisting of cellulose and hemicellulose and maintaining the molecular weight of cellulose, the acid concentration is preferably 10% by weight or less and 5% by weight in order of preference. Hereinafter, it is 3 weight% or less. In a preferred form, the solution containing an acid and an alcohol has an acid concentration of 0.05 to 10% by weight.

In the solution used in the first step, the alcohol concentration can be 90 to 99.5% by weight, preferably 95 to 99.5% by weight, and preferably 97 to 99% by weight. More preferred is 98 to 99% by weight. When the concentration of the alcohol in the solution is within this range, the lignin component of the wood raw material can be sufficiently reduced. Moreover, when the concentration of alcohol in the solution is within this range, the lignin component of the wood raw material can be sufficiently reduced, and a structure composed of cellulose and hemicellulose can be easily maintained.

The solution used in the first step is preferably an aqueous solution. By being an aqueous solution, water in the solvent enters the structure, and it becomes easy to maintain the three-dimensional structure of wood. As used herein, “aqueous solution” means that 100% by weight of the solvent is not limited to water, and a water-soluble organic solvent (eg, alcohol) is used in an amount of 0 to 30% by weight, preferably 0 to 5% by weight. In the present invention, these are treated as aqueous solutions. In the most preferred form, 100% by weight of the solvent is water.

In the first step, the wood raw material is immersed in the above solution and heated under a temperature condition of 140 ° C. or higher and 170 ° C. or lower. By heating in such a temperature range, the solution easily penetrates into the wood raw material. At this time, the temperature condition is not particularly limited as long as it is within the above range, but it is preferably a temperature lower than the boiling point of the alcohol to be used, more preferably 10 ° C. lower than the boiling point of the alcohol to be used. Preferably, the temperature is 20 ° C. or more lower than the boiling point of the alcohol used. In addition, the immersion time in the first step is not particularly limited, but it is preferable that the solution is sufficiently penetrated into the wood raw material. For this reason, the immersion time in a 1st process can be suitably set according to the shape and dimension of a wooden raw material, the kind of wood used as the raw material of a wooden raw material, the moisture content of a wooden raw material, etc. When using a solvent having a boiling point below the heating temperature condition, the reaction is preferably performed under pressure from the viewpoint of reducing the solvent volatilization amount, and the use of a pressure resistant vessel is also a preferred example.

Also, in the first step, it is preferable to carry out a process of replacing air or water contained in the wood raw material with the solution in a state where the wood raw material is immersed in the solution. By performing such treatment, the solution easily penetrates into the wood raw material. As the said process, the said wooden raw material is sealed in the state immersed in the said solution, and the process which deaerates the inside of sealed space is mentioned. For example, a process in which a wooden raw material is immersed in a solution in a container, the container is stored in a vacuum chamber, and the vacuum chamber is depressurized. In addition, air and water contained in the wood raw material can be replaced with the above solution by a process such as microwave irradiation (heating with a microwave oven) or ultrasonic irradiation.

When the treatment for replacing the air contained in the woody raw material with the solution is performed, the immersion time in the first step can be shortened compared to the case where the treatment is not performed. For example, if the wood raw material of 1 cm square made of cedar (water content: about 15%), when the treatment is performed, the immersion time in the first step can be 30 minutes or more, 45 minutes It is preferable to set it as above, and it is more preferable to set it as 1 hour or more. According to this example, the immersion time can be appropriately set according to the shape and size of the wood raw material, the type of wood used as the raw material of the wood raw material, and the moisture content of the wood raw material.

In the first step, since the temperature condition is set to 140 to 170 ° C. using a solution containing an acid and an alcohol, the structure composed of cellulose and hemicellulose is destroyed while removing the lignin component contained in the wood raw material. It can be maintained without any problems. Note that the first step may be performed once or a plurality of times.

After the first step, the obtained wood raw material may be washed. Here, water, alcohol, etc. are mentioned as a liquid used for washing | cleaning. A mixture of water and alcohol may be used. Examples of the alcohol include methanol and ethanol which are easy to handle in the subsequent steps. The washing may be performed a plurality of times, and the liquid type used in each time may be different.

Next, in the wood manufacturing method according to the third embodiment, the second step of immersing the wood raw material after the first step in a solution containing chlorite ions or hypochlorite ions is performed. In the second step, as in the first step, an amount of solution sufficient to immerse the entire wood raw material is prepared according to the shape and dimensions of the wood raw material. The solution used in the second step is a solution containing at least chlorite ions or hypochlorite ions. A solution containing chlorite ions is preferred. The solution containing chlorite ions or hypochlorite ions can be referred to as a chlorite or hypochlorite solution (preferably an aqueous solution). Although it does not specifically limit as a chlorite, Sodium chlorite, calcium chlorite, etc. can be mentioned. Especially, since removal of lignin is performed more effectively, it is preferable to use a sodium chlorite solution as the solution containing chlorite ions. Although it does not specifically limit as a hypochlorite, Sodium hypochlorite, a calcium hypochlorite, etc. can be mentioned. Especially, as a solution containing hypochlorite ion, since removal of lignin is performed more effectively, it is preferable to use a sodium hypochlorite solution.

Moreover, the solution used in the second step contains a weak acid such as acetic acid so that delignification is promoted by generating chlorine dioxide having strong oxidizing power in addition to chlorite ion or hypochlorite ion. It is preferable to do. Examples of the weak acid component that can be used in the second step include acetic acid, carbonic acid, and boric acid, and it is most preferable to use acetic acid. The pH of the solution used in the second step is preferably less than 11, more preferably 9 or less, and even more preferably 8 or less. On the other hand, from the viewpoint of maintaining the wood structure and maintaining the molecular weight of cellulose, the pH of the solution used in the second step is preferably 1 or more, more preferably 3 or more, and most preferably 4 or more.

In the solution used in the second step, the concentration of chlorite ions or hypochlorite ions is preferably 0.01 to 10% by weight, more preferably 0.05 to 5% by weight. 1 to 5% by weight is more preferred, 0.5 to 5% by weight is even more preferred, and 0.5 to 2% by weight is particularly preferred. When the concentration of chlorite ion or hypochlorite ion in the solution is within this range, the lignin component of the wood raw material can be sufficiently reduced. If the concentration of chlorite ion or hypochlorite ion in the solution is within this range, the lignin component of the wood raw material can be sufficiently reduced, and a structure composed of cellulose and hemicellulose can be easily maintained. In addition, it is preferable that the density | concentration of the said chlorite ion or a hypochlorite ion is the said range at the time of the first addition. Moreover, since the reactivity of a chlorite ion or a hypochlorite ion is high and unstable, the said density | concentration is not necessarily maintained during reaction.

In the solution used in the second step, the concentration of the weak acid can be 0.005 to 2.0% by weight, 0.01 to 1.0% by weight, 0.05% Is preferably 0.8 to 0.8% by weight, more preferably 0.1 to 0.6% by weight, and still more preferably 0.5% by weight. When the concentration of the weak acid in the solution is within this range, the lignin component of the wood raw material can be sufficiently reduced. If the concentration of the weak acid in the solution is within this range, the lignin component of the wood raw material can be sufficiently reduced, and a structure composed of cellulose and hemicellulose can be easily maintained.

The solution used in the second step is preferably an aqueous solution. By being an aqueous solution, water in the solvent enters the structure, and it becomes easy to maintain the three-dimensional structure. As used herein, “aqueous solution” means that 100% by weight of the solvent is not limited to water, and a water-soluble organic solvent (eg, alcohol) is used in an amount of 0 to 30% by weight, preferably 0 to 5% by weight. In the present invention, these are treated as aqueous solutions. In the most preferred form, 100% by weight of the solvent is water.

In the second step, the wooden raw material after the first step is immersed in the above solution. At this time, it is preferable to wash the wood raw material after the first step with ethanol or water. In particular, when the wood raw material after the first step is washed with ethanol, the acid component and the lignin component used in the first step can be removed.

Further, the immersion time in the second step is not particularly limited, but it is preferable that the solution sufficiently penetrates into the wood raw material and removes the remaining lignin component as in the first step. For this reason, the immersion time in the second step is set as appropriate according to the shape and size of the wood raw material, the type of wood used as the raw material of the wood raw material, the moisture content of the wood raw material, and the like, as in the first step. be able to. However, in the second step, since the reactivity of chlorite ions or hypochlorite ions in the solution is high and unstable, the concentration of chlorite ions or hypochlorite ions described above can be maintained. Thus, it is preferable to add chlorite or hypochlorite to the solution when a predetermined time has passed. Alternatively, it is preferable to repeat the second step a plurality of times. By repeating the second step a plurality of times, a solution containing chlorite ions or hypochlorite ions sufficiently permeates into the wood raw material, and the remaining lignin component can be removed. Here, “multiple times” refers to 2 times or more, preferably 4 times or more, more preferably 6 times or more, and particularly preferably 8 times or more. Thus, the lignin component remaining in the wood raw material can be removed by performing the second step a plurality of times. In addition, the upper limit of the number of repetitions of the second step is not particularly limited, but considering productivity, it is preferably 20 times or less, more preferably 15 times or less, and 10 times or less. It is particularly preferred. In addition, as multiple times, it is also a preferable example including continuous dripping and dropping while controlling the pH in the solution.

For example, if it is a 1 cm square rectangular raw material made of cedar, the immersion time in the second step can be made 5 hours or more by adding hypochlorite every hour, and it is 6 hours or more. Preferably, it is more preferably 7 hours or longer. The upper limit of the immersion time is not particularly limited, but it is preferably 10 hours or less in view of the saturation of the effect and the productivity. However, the immersion time in the second step is set as appropriate according to the shape and dimensions of the wood raw material, the type of wood used as the raw material for the wood raw material, and the moisture content of the wooden raw material, as in the first step. be able to.

The temperature condition in the second step is not particularly limited, but can be, for example, 50 to 90 ° C., preferably 60 to 80 ° C., and more preferably 65 to 75 ° C. By setting the temperature condition of the second step within this range, the lignin component remaining after the first step can be sufficiently removed.

In the second step, since a solution containing chlorite ions or hypochlorite ions or a solution containing chlorite ions or hypochlorite ions and a weak acid is used, the wood remaining in the first step is used. While reliably removing the lignin component contained in the raw material, the structure composed of cellulose and hemicellulose can be maintained without destruction. That is, in the method for producing wood according to the present invention, the lignin component originally contained in the wood raw material can be greatly reduced by passing through the second step.

It is preferable to wash the wood obtained in the second step with water or alcohol. Washing may be a mixture of water and alcohol. Examples of the alcohol include methanol and ethanol which are easy to handle in the subsequent steps. By performing the washing treatment, the lignin component and the extra raw material / reaction component in the second step can be removed, and a wood having a maintained structure is easily obtained, which is preferable.

In addition, it is preferable to perform freeze-drying when drying after washing.

According to the method for producing wood according to the third embodiment, 80% by weight or more, preferably 90% by weight or more, more preferably 95% by weight or more, still more preferably 98% by weight of the lignin component originally contained in the wood raw material. % Or more, most preferably 99% by weight or more can be reduced. In other words, the wood according to the present invention is 80% by weight or more of the lignin component originally contained in the wood raw material, preferably 90% by weight or more, more preferably 95% by weight or more, still more preferably 98% by weight or more. It can be said that the wood is preferably reduced by 99% by weight or more.

In particular, in the wood manufacturing method according to the third embodiment, the first step and the second step according to the shape and size of the wood raw material, the type of wood used as the raw material of the wood raw material, the moisture content of the wood raw material, and the like. By adjusting the process conditions, almost all lignin components contained in the wood raw material can be removed. The removal of almost all lignin components contained in the wood raw material means that when the lignin component contained in the wood raw material is measured by a method for quantitatively measuring lignin in the wood, it is below the detection limit. means.

Moreover, according to the method for producing wood according to the present invention, the lignin component contained in the wood raw material can be reduced within the above-mentioned range, so that the wood raw material before treatment is whitened. The whitening of the wood raw material means that it approaches white according to the degree of reduction of the lignin component, and means that the higher the reduction ratio of the lignin component, the closer the color to white. For example, when the lignin component of the wood obtained by the wood production method according to the present invention is measured and is below the detection limit, the wood is white. Thus, according to the wood manufacturing method of the present invention, “white wood” can be manufactured.

Furthermore, according to the wood manufacturing method according to the third embodiment, the lignin component contained in the wood raw material can be reduced as described above, and a structure composed of cellulose and hemicellulose can be maintained. Here, maintaining the structure composed of cellulose and hemicellulose means that the cell wall structure inherent to the wood used as the raw material for the wood raw material is maintained, and as a result, the outer shape of the wood raw material before processing. It means that the shape and dimensions are maintained. Maintaining the external shape and dimensions of the wood raw material before the treatment means that when the dimensions of the wood raw material before and after the treatment are measured, the amount of change is 5% or less, preferably 3% or less, more preferably 2% or less, Preferably it means 1% or less.

As described above, according to the wood manufacturing method according to the third embodiment, the lignin component contained in the wood raw material before treatment can be significantly reduced, and the wood shape and dimensions of the wood raw material before treatment can be maintained. Can be manufactured. The wood according to the first embodiment or the wood according to the second embodiment (hereinafter “white wood”) is not particularly limited as a new material that has not been conventionally used, and can be applied to various fields. The preferred form of the present invention is wood that maintains the shape of the wood raw material.

Focusing on the fact that the original structure and cellular structure of the original tree is maintained as a characteristic of white wood, white wood can be used as the basis for material development using the optimal frame structure created by the tree. . In a harsh natural environment, the survival of a huge body of more than 100 meters is guaranteed for more than 1000 years. This is a hierarchical structure made of woody macromolecules whose trees are precisely controlled.

Conventionally, in the production of microfibrils, microfibrils are extracted after being processed into a pulp-like structure, so that only microfibrils having no orientation can be obtained regardless of the hierarchical structure that trees have. Absent. In addition, a technique for uniaxially orienting microfibrils having no orientation has not been established. However, since white wood maintains this hierarchical structure, microfibrils can be utilized while maintaining the orientation in white wood.

That is, by compressing in the tangential direction and the grain direction of the obtained white wood, it is possible to develop a paper or film in which cellulose microfibrils are oriented. Also, white wood having various organizational structures can be obtained depending on the type of tree used as a raw material. For this reason, paper / film using white wood can also take advantage of such characteristics of the structure and can be used as a material according to the purpose. In addition, naturally the cellulose microfibril contained in the obtained white wood can be utilized also for the use for which the cellulose microfibril, the cellulose nanofibre, etc. were utilized conventionally. For example, cellulose microfibrils derived from white wood are used for car bodies, tires, window glass, displays, battery materials, beakers, diapers, thickeners, food packaging materials, artificial blood vessels, artificial cartilage, food additives, etc. Can be used.

On the other hand, focusing on the fact that the shape and dimensions of the wood raw material (woody raw material) are maintained as a characteristic of white wood, white wood can be used as a light and strong structural material. For example, white wood can be used as a building material in place of the conventionally used wood. In addition, when used for the field | area where intensity | strength is requested | required of building materials etc., matrix components, such as resin, can also be absorbed with respect to white wood. That is, white wood can be used as a new three-dimensional composite resin material according to the required strength.

In addition, as a characteristic of white wood, focusing on maintaining the structure consisting of cellulose and hemicellulose constituting the wood raw material, in addition to the micrometer-order pores created by the cell lumen, the nano-order between the polysaccharides White wood can be used as a porous material in which micropores are formed. A material in which nano-order micropores are formed is called a mesoporous material (a porous material having a pore diameter of several nanometers to several tens of nanometers), but white wood can be used as a mesoporous material.

Examples of the use as a mesoporous material include a gas adsorbent, a heat insulating material, a gas separator, and a microorganism culture medium.

Also, The Murata Science Foundation Annual Report No. As described in 30 2016 page 151-153, a technique for producing a high dielectric material from silver nanowires and nanopaper made of cellulose fibers is known. Since cellulose microfibrils are oriented as a characteristic of white wood, a high dielectric material that maintains the characteristics of uniaxially oriented nanopaper can be produced. In addition, a conductive material can be produced by stretching silver nanowires over white wood. Thus, white wood can be used as a material for electronic components.

Furthermore, the color characteristics of white wood, that is, white is a characteristic that the refractive index of cellulose and hemicellulose components is different from the refractive index of air contained therein. Therefore, by impregnating, for example, an acrylic resin into white wood, the refractive index of cellulose and the hemicellulose component can be brought close to the internal refractive index, and the material becomes colorless and transparent. A colorless and transparent material in which an acrylic resin is impregnated in white wood can be applied to, for example, a display or a solar cell substrate.

Furthermore, white wood swells when immersed in, for example, an aqueous sodium hydroxide solution to become a wood gel material. This is because when white wood is immersed in an aqueous sodium hydroxide solution, sodium ions enter the inside of the cellulose crystals, spreading the molecules, partially dissolving in the aqueous sodium hydroxide solution, and washing with water forms a cross-linked structure between the celluloses. Thus, physical properties as a gel are expressed. Specific treatment conditions include a condition of immersing in an aqueous solution of 8 to 20% sodium hydroxide at room temperature, treating for 12 hours, and then washing with water. The wood gel material using white wood becomes, for example, a functional material having elasticity by gelation, and thus can be applied to a medical gel material such as a wound film material and a food gel.

Furthermore, focusing on the characteristic of white wood that is derived from trees and not chemically modified, it can be said that it is a low environmental load material that was a biodegradable material. That is, as described above, specific applications in a wide range of fields can be understood by paying attention to various features of white wood, but everything using white wood can be completely decomposed by cellulase. For example, when the mesoporous structure of white wood is used as an adsorbent, it is possible to concentrate the adsorbed substance from the environment, for example, by biodegrading the adsorbent. Further, white wood can be used as, for example, a biodegradable heat insulating material instead of conventional foamed polystyrene.

Hereinafter, the present invention will be described in more detail with reference to examples. However, the technical scope of the present invention is not limited to the following examples.

[Example 1]
In this example, a wood raw material (woody raw material) of a rectangular parallelepiped (each side 1 cm) made of cedar (coniferous tree) was prepared. First, a solution in which ethylene glycol and 50% by weight sulfuric acid were mixed at a ratio of 99: 1 (acid concentration in the solution: 0.5% by weight) was prepared. In the airtight container, the wood raw material was immersed in the solution and pumped to replace the air in the wood raw material with the solvent. Next, the wood raw material was transferred to the pressure tube together with the solution and treated at 150 ° C. (atmospheric temperature) for 1 hour (first step).

After the treatment, the wood raw material was taken out and washed repeatedly with ethanol. Moreover, the solution which consists of 0.08 ml of acetic acid, 0.4 g of sodium chlorite, and 60 ml of water was prepared. And the wood raw material after ethanol washing was immersed in the said solution. The temperature condition was 70 ° C., and the immersion time was 1 hour (second step). In this example, the second step was performed 7 times, that is, after 1 hour of immersion, the step of adding 0.08 ml of acetic acid and 0.4 g of sodium chlorite and further treating for 1 hour was performed 7 times. (Immersion time, 8 hours total).

Then, by taking out the completely bleached wood and washing it with water, it was possible to remove the lignin component and obtain white wood that maintained the structure composed of cellulose and hemicellulose (FIG. 1). FIG. 1 shows untreated wood raw material in (A), wood raw material after the first step treatment in (B), and white wood obtained in (C). The dimensions of these untreated wood raw materials (A) and white wood (C) were measured as follows (Table 1). From this result, it became clear that white wood maintains the external shape and dimensions of untreated woody raw materials.

Further, when the constituent components were analyzed for (A) to (C), the amount of lignin in the wood raw material of (B) was 13.81%. In contrast, in the white wood (C), the amount of lignin was less than 0.1% by weight. Specifically, the component analysis by HPLC was as follows.

Here, the amount of cellulose in the wood is 96.44 × 0.9 = 86.8% by weight obtained by multiplying the glucose content (% by weight) by 0.9. Moreover, the amount of hemicellulose is 1.21 * 0.88 + 0.01 * 0.88 + 0.99 * 0.9 + 0.23 * 0.9 = 2. From said xylose, arabinose, mannose, and galactose content (weight%). 16% by weight.

Moreover, the viscosity average polymerization degree of the cellulose of the white wood of Example 1 is 1115, the full width at half maximum (FWHM) of 200 planes by X-ray diffraction is 2.50 (untreated 3.18), and the maximum load is 27N. Met. Except for the dimensions of Example 1 being 1.2 cm × 1.2 cm × 1 cm, the whiteness of white wood that was subjected to the same operation as Example 1 was L *: 94.0, a *: −0.26, b *: 1.02 (untreated: L *: 80.11, a *: 3.39, b *: 17.7).

Further, the results of analyzing the components of (A) to (C) by the infrared absorption spectrum are shown in FIG. As shown in FIG. 2, in the white wood of (C), no band (1510 cm ⁻¹ ) attributed to lignin was observed.

Further, FIG. 3 shows the result of image analysis of untreated wood raw material and white wood by X-ray CT (microfocus X-ray CT system, inspexIOSMX-100CT, manufactured by Shimadzu Corporation). As shown in FIG. 3, it was found that the white wood produced in this example maintained the tissue and cell structure like the untreated wood raw material.

FIG. 4 is an image showing an X-ray fiber diagram obtained by X-ray diffraction of the untreated wood raw material used in Example 1 and white wood. In the X-ray fiber diagram of FIG. 4, a plurality of diffraction spots are observed on a concentric image. Therefore, it was found that the white wood produced in this example maintained the orientation of the microfibrils in the cell wall, as with the untreated wood raw material.

In the above various analyzes (other than dimension measurement), the following freeze-drying was performed as necessary. The same applies to the following embodiments. After immersing the sample in 50% ethanol aqueous solution, the sample is placed in order of 70% ethanol aqueous solution, 90% ethanol aqueous solution, 95% ethanol aqueous solution, 99.5% ethanol aqueous solution, and absolute ethanol (3 times) for about 10 to 15 minutes. Soaked. Thereafter, the sample was immersed in absolute ethanol: t-butyl alcohol = 1: 1 for about 15 to 30 minutes, and further immersed in t-butyl alcohol for 15 minutes or more. This operation was repeated three times. The solvent was lightly wiped from the sample, stored in a refrigerator for 15 minutes or longer, and lyophilized.

From the above results, in this example, the wood raw material using cedar as a raw material, the lignin component was almost completely removed, the structure composed of cellulose and hemicellulose was maintained, and the shape before processing was maintained. It became clear that wood could be manufactured.

[Example 2]
In this example, white wood was produced in the same manner as in Example 1 except that zelkova (hardwood) was used as a raw material and the conditions of the first step were treated at 150 ° C. for 6 hours.

Fig. 5 shows the wood raw material before treatment and the obtained white wood. Moreover, it was as follows when the dimension of the untreated wood raw material and white wood of a present Example was measured. From this result, it became clear that white wood maintains the external shape and dimensions of untreated woody raw materials.

Moreover, the result of having analyzed the component with the infrared absorption spectrum about the raw material of wood before a process and the obtained white wood was shown in FIG. As shown in FIG. 6, a band (1510 cm ⁻¹ ) attributed to lignin was not observed in white wood.

Furthermore, FIG. 7 shows the result of image analysis of untreated wood raw materials and white wood by X-ray CT. As shown in FIG. 7, it was found that the white wood produced in this example maintained the tissue and cell structure like the untreated wood raw material.

From the above results, in this example, the wood raw material using zelkova as a raw material, the lignin component was almost completely removed, the structure composed of cellulose and hemicellulose was maintained, and the shape before processing was maintained. It became clear that wood could be manufactured.

[Example 3]
In this example, white wood was produced in the same manner as in Example 1 except that propylene glycol was used instead of ethylene glycol in the first step.

Fig. 8 shows the wood raw material before treatment and the obtained white wood. In FIG. 8, (A) shows an untreated wood raw material, and (B) shows white wood obtained. The dimensions of these untreated wood raw materials (A) and white wood (B) were measured as follows (Table 4). From this result, it became clear that white wood maintains the external shape and dimensions of untreated woody raw materials.

Moreover, the result of having analyzed the component by the infrared absorption spectrum about the raw material of wood before a process and the obtained white wood was shown in FIG. As shown in FIG. 9, no band (1510 cm ⁻¹ ) attributed to lignin was observed in white wood.

Furthermore, as a result of image analysis by X-ray CT for untreated wood raw material and white wood, the white wood produced in this example maintains the tissue and cell structure in the same manner as the untreated wood raw material. I found out.

From the above results, in this example, when propylene glycol was used as the alcohol in the first step, the lignin component was almost completely removed, and the structure composed of cellulose and hemicellulose was maintained. It became clear that it was possible to produce white wood that maintained its shape.

[Example 4]
In this example, white wood was produced in the same manner as in Example 1 except that Harunire (hardwood) was used as a raw material.

Fig. 10 shows the wood raw material before treatment and the obtained white wood. FIG. 10 shows an untreated wood raw material in (A), a wood raw material after the first step treatment in (B), and white wood obtained in (C). The dimensions of these untreated wood raw materials (A) and white wood (C) were measured as follows (Table 5). From this result, it became clear that white wood maintains the external shape and dimensions of untreated woody raw materials.

Moreover, the result of having analyzed the component with the infrared absorption spectrum about the raw material of wood before processing and the obtained white wood was shown in FIG. As shown in FIG. 11, no band (1510 cm ⁻¹ ) attributed to lignin was observed in white wood.

Furthermore, as a result of image analysis by X-ray CT for untreated wood raw material and white wood, the white wood produced in this example maintains the tissue and cell structure in the same manner as the untreated wood raw material. I found out.

From the above results, in this example, the wood raw material using Harunire as a raw material, the lignin component was almost completely removed, the structure composed of cellulose and hemicellulose was maintained, and the shape before processing was maintained. It became clear that wood could be manufactured.

[Example 5]
In this example, white wood was produced in the same manner as in Example 1 except that beech (hardwood) was used as a raw material.

Fig. 12 shows the wood raw material before treatment and the obtained white wood. FIG. 12 shows untreated wood raw material in (A), wood raw material after the first step treatment in (B), and white wood obtained in (C). The dimensions of these untreated wood raw materials (A) and white wood (C) were measured as follows (Table 6). Moreover, it was as follows when the dimension of the untreated wood raw material and white wood of a present Example was measured. From this result, it became clear that white wood maintains the external shape and dimensions of untreated woody raw materials.

Moreover, the result of having analyzed the component by the infrared absorption spectrum about the raw material of wood before a process and the obtained white wood was shown in FIG. As shown in FIG. 13, no band (1510 cm ⁻¹ ) attributed to lignin was observed in white wood.

Furthermore, as a result of image analysis by X-ray CT for untreated wood raw material and white wood, the white wood produced in this example maintains the tissue and cell structure in the same manner as the untreated wood raw material. I found out.

From the above results, in this example, the wood raw material using beech as a raw material, the lignin component was almost completely removed, the structure composed of cellulose and hemicellulose was maintained, and the shape before processing was maintained. It became clear that wood could be manufactured.

[Example 6]
In this example, it was carried out except that the alkali treatment was performed before the first step under the following conditions, that Moso bamboo was used as a raw material, and the first step was performed at 150 ° C. for 4 hours. White wood was produced as in Example 1.

The alkali treatment was performed by immersing the wood raw material in a 1% aqueous sodium hydroxide solution and performing heat treatment at 95 ° C. for 1 hour.

The obtained white wood is shown in FIG. Moreover, when the dimension of the untreated wood raw material and white wood of a present Example was measured, the white wood maintained the external shape and dimension of the untreated wood raw material.

Moreover, the result of having analyzed the component by the infrared absorption spectrum about the raw material of wood before a process and the obtained white wood was shown in FIG. As shown in FIG. 15, no band (1510 cm ⁻¹ ) attributed to lignin was observed in white wood. In FIG. 15, S1 to S4 are divided into four sections from the inner side to the epidermis (inner side S1 → skin side S4).

Furthermore, as a result of image analysis by X-ray CT for untreated wood raw material and white wood, the white wood produced in this example maintains the tissue and cell structure in the same manner as the untreated wood raw material. I found out.

Moreover, the viscosity average polymerization degree of the cellulose of the wood of Example 6 was 1473.

From the above results, in this example, the wood raw material using Moso bamboo as a raw material, the lignin component was almost completely removed, the structure consisting of cellulose and hemicellulose was maintained, and the shape before processing was maintained It became clear that wood could be manufactured.

[Example 7]
In this example, white wood was produced in the same manner as in Example 1 except that balsa (hardwood) was used as a raw material.

White wood whiteness (dimensions 5 cm × 5 cm × 0.5 cm) is L *: 93.1, a *: −0.28, b *: 1.36 (untreated: L *: 85.56, a * : 2.25, b *: 10.64).

Furthermore, as a result of image analysis by X-ray CT for untreated wood raw material and white wood, the white wood produced in this example maintains the tissue and cell structure in the same manner as the untreated wood raw material. I found out.

In each example, the lignin content was less than 3% by weight, the cellulose content was 75% by weight or more, and the hemicellulose content was 0.01% by weight or more and 15% by weight or less.

This application is based on Japanese Patent Application No. 2018-035653 filed on Feb. 28, 2018, the disclosure of which is incorporated by reference as a whole.

Claims (15)

1. Wood with a lignin content of less than 3% by weight and a cellulose content of 75% by weight or more.
2. The wood according to claim 1, wherein the cellulose has a viscosity average degree of polymerization DPv of 300 or more.
3. The wood according to claim 1 or 2, wherein the hemicellulose content is 0.01 wt% or more and 15 wt% or less.
4. A first step of immersing the wood raw material in a solution containing an acid and an alcohol under conditions of 140 ° C. or higher and 170 ° C. or lower; and thereafter, converting the wooden raw material into a solution containing chlorite ions or hypochlorite ions. Wood produced through the second step of dipping and having reduced lignin components.
5. The wood according to claim 4, wherein the shape of the wood raw material is maintained.
6. 6. The wood according to claim 4 or 5, wherein the lignin component is reduced below a detection limit.
7. The wood according to any one of claims 4 to 6, which is white.
8. A first step of immersing the wood raw material in a solution containing an acid and an alcohol under conditions of 140 ° C. or higher and 170 ° C. or lower; and thereafter, converting the wooden raw material into a solution containing chlorite ions or hypochlorite ions. The manufacturing method of the timber with which the lignin component was reduced including the 2nd process to immerse.
9. The method for producing wood according to claim 8, wherein the alcohol is an alcohol having a boiling point of 150 ° C or higher.
10. The method for producing wood according to claim 8 or 9, wherein the solution containing an acid and an alcohol is a solution containing sulfuric acid and ethylene glycol or a solution containing sulfuric acid and propylene glycol.
11. 11. The solution containing an acid and an alcohol has an alcohol concentration of 90 to 99.5% by weight and an acid concentration of 0.05 to 10% by weight. The manufacturing method of the timber described in 2.
12. The wood production according to any one of claims 8 to 11, wherein, in the first step, the wood raw material is sealed in a state of being immersed in the solution, and the sealed space is deaerated. Method.
13. The wood solution according to any one of claims 8 to 12, wherein the solution containing chlorite ions or hypochlorite ions is a sodium chlorite solution or a sodium hypochlorite solution. Production method.
14. The solution containing the chlorite ion or hypochlorite ion is a solution having a concentration of chlorite ion or hypochlorite ion of 0.01 to 10% by weight. The manufacturing method of the timber of any one of these.
15. The method for producing wood according to any one of claims 8 to 14, wherein the second step is repeated a plurality of times.

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