JPWO2015072437A1 - Adhesive composition for woody materials - Google Patents

Abstract

It is a natural adhesive composition that can fully adhere wooden elements under the same conditions as conventional petroleum adhesives, and it can improve the problem of acid corrosion of manufacturing equipment and acidification of wooden materials It is an object to provide an agent composition. The present invention relates to an adhesive composition used for producing a wood material by bonding wood elements, (a) at least one sugar selected from monosaccharides and oligosaccharides, and (b) dihydrogen phosphate. It contains at least one phosphate selected from ammonium and diammonium hydrogen phosphate, and (c) calcium carbonate.

Description

  The present invention relates to an adhesive composition suitable for bonding wood. More specifically, the present invention relates to a natural adhesive composition that does not contain petroleum-derived substances or formaldehyde.

  In recent years, so-called natural resins produced from biological resources have been actively developed to prevent global warming and reduce consumption of petroleum resources. Recently, in order to suppress the burden on the human body and the environment as much as possible, chemical technology that refrains from the use of harmful substances has been emphasized. From this point of view, development of natural resins is desired.

  In particular, in the field of wood adhesives, adhesives that use formaldehyde as a raw material (urea resin, melamine resin, phenol resin, etc.) have been widely used, but these adhesives diffuse formaldehyde that causes sick house syndrome. Therefore, there is a possibility of harming human health. Therefore, development of a natural adhesive that does not contain formaldehyde is desired.

  So far, in the field of wood adhesives, various natural adhesives such as tannin adhesives and lignin adhesives have been developed and studied. Chemical modification with compounds and the use of harmful substances equivalent to poisonous and deleterious substances were essential. In addition, conventional natural adhesives often require higher temperatures and longer times for curing than petroleum-based adhesives, and the use of natural polymers has led to poor practicality. It was an obstacle. Therefore, development of an adhesive that does not depend on petroleum-derived substances or harmful substances, cures with low energy, and has excellent workability is desired.

  As an invention relating to a natural adhesive, Patent Document 1 discloses an adhesive composition containing a polyvalent carboxylic acid. Further, Patent Document 2 discloses that a solid ligno under heating and pressurization using “a sugar, starch, or a mixture thereof” and “a catalyst comprising an alkaline salt or a mixture of an alkaline substance and an acidic salt”. A method for bonding cellulosic materials is disclosed. Patent Document 3 discloses a binder containing an amine and a carbohydrate. Patent Document 4 discloses a binder solution obtained by dissolving reducing sugar, ammonium salt such as ammonium sulfate salt and ammonium phosphate salt, and optionally ammonia or the like in water. A binder solution prepared by dissolving glucose monohydrate, ammonium sulfate or phosphate, ammonium hydroxide and silane in water is disclosed.

  However, the adhesive of Patent Document 1 has a problem of low pH value because it contains a polyvalent carboxylic acid. For example, citric acid is classified as a weak acid with three carboxyl groups, but the pH value of an aqueous solution containing 2% citric acid is as low as about 2. Therefore, when a mixture of citric acid and a wood element such as wood particles or wood fibers is heated and pressed to produce a wood material (a product produced by bonding wood elements, such as a wood board), the mixture Since the pH value is low, there is a problem that the manufacturing apparatus is easily corroded. In addition, since the manufactured wooden board has a low pH value, it has disadvantages due to acidification (eg, nails driven into the wooden board are easily rusted).

In addition, when using natural adhesives instead of conventional petroleum adhesives, it is possible to use equipment that has been used in the past, and to manufacture under the same manufacturing conditions as before, for practical use. is important. In particular, when a wood element is bonded with an adhesive composition to produce a wood-based material, hot pressing is performed, but a higher temperature and longer time are required in the hot pressing process than before. However, there is a problem in that practical use does not progress because the energy used and cost greatly increase. More specifically, when manufacturing wood boards such as particle boards and fiber boards using petroleum-based adhesives, the temperature is about 160 ° C to 170 ° C and the time is about 60 seconds per 1mm of board thickness. In order to cure sufficiently, a natural adhesive having the same performance as this is desired.
However, there is a problem that it is difficult to develop a natural adhesive that does not depend on petroleum-derived substances or harmful substances, cures with the same low energy as in the past, and satisfies all the requirements of high safety.

  For example, the method of Patent Document 2 teaches the use of anhydrous aluminum chloride as a catalyst to reduce the press time and pressure in particle board production. Anhydrous aluminum chloride has the problem of corrosiveness to the eyes, skin, and respiratory tract, and the problem of reacting violently with water and moisture to generate hydrogen chloride. There is a problem that it cannot be used in this state.

  In Patent Document 3, an example of manufacturing a wood fiber board is disclosed in Example 13, but the curing condition for manufacturing a board having a thickness of about 0.4 inches (about 10 mm) is 350 ° F. (about 177 ° F.). Since it is 25-30 minutes at (° C.), there is a problem that high energy is required as compared with the conventional production method using a petroleum-based adhesive.

  Patent Document 4 also discloses that when a product to be manufactured is a wood board, a platen higher than 180 ° C. or 200 ° C. is used in a press (paragraph [0062]), so that a conventional petroleum-based product is used. Compared with the manufacturing method using an adhesive agent, there exists a problem that high energy is required.

WO 2012/133219 A1 US 4,183,997 B Special Publication 2009-503193 Publication Special Table 2010-535864 Publication

  Therefore, the present invention is an adhesive composition that does not use petroleum-derived substances or formaldehyde, is highly safe, and can sufficiently bond a wood element at a temperature of about 160 to 170 ° C. It is an object of the present invention to provide an adhesive composition capable of improving the problem of acid corrosion and the acidification of a wood material manufactured from a wood element.

  As a result of repeated studies to solve the above-mentioned problems, the present inventors have found that an adhesive composition containing monosaccharide and / or oligosaccharide, ammonium dihydrogen phosphate and / or diammonium hydrogen phosphate is 160 to 160- It was found that a wood element with sufficient water resistance and high water resistance can be produced at a hot pressure temperature of 170 ° C. Further, as a result of further studies, the addition of calcium carbonate succeeded in bringing the pH value of the wood material closer to the original pH value of wood without impairing the water resistance of the wood material.

That is, the adhesive composition according to the present invention is
(a) at least one sugar selected from monosaccharides and oligosaccharides,
(b) at least one phosphate selected from ammonium dihydrogen phosphate and diammonium hydrogen phosphate, and
(c) It is characterized by containing calcium carbonate.

  In the adhesive composition, when the component (b) is ammonium dihydrogen phosphate, the weight ratio of the components (a) and (b) is preferably 90:10 to 60:40, and the component (b) Is a diammonium hydrogen phosphate, the weight ratio of components (a) and (b) is preferably 85:15 to 60:40.

  The component (b) is particularly preferably ammonium dihydrogen phosphate, and the weight ratio of the components (b) and (c) is preferably 1: 0.5 to 1: 1.5.

A preferred embodiment of the adhesive composition includes an adhesive composition containing components (a), (b) and (c) in an aqueous liquid.
As another preferred embodiment, there is provided an adhesive composition comprising an aqueous liquid containing components (a) and (b) and a powder of component (c), and containing the aqueous liquid and the powder in a separated state. Can be mentioned.

  The total weight of components (a), (b) and (c) preferably accounts for 90% by weight or more of the solid content weight (dry weight) of the adhesive composition.

  The adhesive composition according to the present invention is suitable for bonding wooden elements such as powders, fibers, small pieces and veneers of trees or herbaceous plants.

  The adhesive composition is brought into contact with the wood element, and after mixing, drying, molding and the like as necessary, the wood element is sufficiently bonded by hot pressing at a temperature of 140 ° C. or more and 200 ° C. or less. It is possible to produce a wood material excellent in water resistance.

  Moreover, the wood material manufactured by heat-pressing the wood element to which the adhesive composition is applied or sprayed exhibits excellent water resistance and a pH value comparable to that of wood.

  Since the adhesive composition of the present invention is a natural adhesive that does not contain formaldehyde, it is environmentally friendly. Furthermore, the adhesive composition of the present invention has a small load on the production apparatus, and the produced wood material exhibits a pH value close to the original pH value of wood. In addition, the adhesive composition of the present invention is cured at a temperature equivalent to the hot pressing temperature (about 160 ° C. to 170 ° C.) used during commercial production (mass production) of wood boards and the like.

FIG. 1 is a DSC curve showing the results of thermal analysis of a mixture of sucrose and ammonium dihydrogen phosphate. FIG. 2 is a DSC curve showing the results of thermal analysis of a mixture of sucrose and sodium dihydrogen phosphate.

The adhesive composition of the present invention is a natural adhesive and does not contain petroleum-derived compounds or formaldehyde. Typical examples of adhesives derived from petroleum include isocyanate adhesives, and examples of adhesives containing formaldehyde are made by polycondensation of formaldehyde and amino group-containing compounds or polycondensation of formaldehyde and phenols. Adhesives (urea resin, melamine resin, phenol resin, etc.) can be mentioned. In the present invention, the wood elements can be sufficiently bonded without using them.
In addition, the adhesive composition of the present invention includes isocyanate group-containing compounds, formaldehyde, silicon (Si) -containing compounds such as silane and silicone, aluminum chloride, organic acids (polyvalent carboxylic acids, etc.) or salts thereof (polyvalent carboxylic acids). Acidic ammonium salts, etc.), organic compounds containing nitrogen (amine compounds, etc.), condensed tannins, polysaccharides (starch, etc.), grain powders (wheat flour, etc.), liquefaction agents, additives such as ammonia and ammonium hydroxide Even if it does not do, the wooden material excellent in water resistance can be manufactured. Therefore, the adhesive composition of the present invention may not include the above-described components.
In addition, when the wood element is bonded by using the adhesive composition of the present invention to produce a wood material, a step of liquefying wood is unnecessary, and the wood element and the adhesive composition are brought into contact with each other. Accordingly, after performing mixing, drying, and molding treatment, it is possible to produce a wood material having excellent water resistance simply by hot pressing.

  The adhesive composition of the present invention contains at least one sugar (a) selected from the group consisting of monosaccharides and oligosaccharides as an essential component. Examples of monosaccharides include glucose, fructose, mannose, xylose, arabinose, galactose, rhamnose, xylulose, deoxyribose, and ribose. And trisaccharides such as raffinose. Of the oligosaccharides, disaccharides are more preferred. Particularly preferred sugars include sucrose, glucose, fructose, mannose, xylose, arabinose and galactose. A particularly preferred sugar is sucrose. The adhesive composition of the present invention may contain only one kind of the sugar or two or more kinds.

The adhesive composition of the present invention is at least selected from ammonium dihydrogen phosphate [(NH ₄ ) H ₂ PO ₄ ] and diammonium hydrogen phosphate [(NH ₄ ) ₂ HPO ₄ ] as an essential component. Contains a type of phosphate (b). The adhesive composition of the present invention may contain either or both of the above-mentioned phosphates, but it is particularly preferred that it contains only ammonium dihydrogen phosphate.
Further, the adhesive composition of the present invention is sufficient even if it does not contain a phosphate or ammonium salt other than the ammonium dihydrogen phosphate and diammonium hydrogen phosphate (particularly, an ammonium salt of a polyvalent carboxylic acid). Adhesive effect can be demonstrated. Therefore, the adhesive composition of the present invention may not contain any phosphate and / or ammonium salt other than component (b).

Since ammonium dihydrogen phosphate is weakly acidic and diammonium hydrogen phosphate is weakly alkaline, when the adhesive composition of the present invention is a liquid composition containing water, the pH value of the composition is weakly acidic. ~ Weakly alkaline (usually about 4.5 to 8.5). Therefore, acid corrosion of the manufacturing apparatus is unlikely to occur. Further, by selecting these phosphates, the wood element can be sufficiently bonded at a low temperature (about 160 ° C. to 170 ° C.) similar to the case of using a petroleum adhesive.
Preferably, the liquid adhesive composition of the present invention contains ammonium dihydrogen phosphate and has an acidic pH value (particularly 4.0 or more and less than 7.0, more preferably 4.5 to 6.5).

The adhesive composition of the present invention contains calcium carbonate (c) as an essential component. When an adhesive composition containing only components (a) and (b) is used, the wood material produced is acidified, and the pH value of the water measured after immersing the wood material in 20 ° C. water for 24 hours is about 3 is shown. Even if sodium hydroxide or the like is added to increase the pH value of the adhesive composition, the pH value of the wood material does not increase, or the water resistance of the wood material significantly decreases. However, by adding calcium carbonate (CaCO ₃ ), while maintaining the water resistance of the wood material, the pH value measured under the above conditions is about 4 or more (preferably about 4.5 to 6.0, particularly preferably in the range of 5.0 to 6.0. ). Since calcium carbonate is hardly soluble in water, the pH value of the aqueous liquid does not fluctuate greatly even when added to the aqueous liquid. For example, when component (b) is weakly acidic ammonium dihydrogen phosphate, an aqueous liquid containing only components (a) and (b) shows acidity, but even if calcium carbonate (c) is added thereto, The aqueous liquid remains acidic (pH <7). Nevertheless, the wood material produced using the adhesive composition of the present invention comprising sugar (a), ammonium dihydrogen phosphate (b) and calcium carbonate (c) is an alkaline adhesive composition. It is less acidified than the woody material produced using and shows a higher pH value (see Tables 6 to 10).

  The weight ratio (a: b) between sugar (a) and phosphate (b) is preferably 90:10 to 60:40 when phosphate (b) is ammonium dihydrogen phosphate. 88:12 to 70:30, more preferably 87:13 to 75:25. When the phosphate (b) is diammonium hydrogen phosphate, a: b is preferably 85:15 to 60:40, more preferably 80:20 to 65:35, and 75: Particularly preferred is 25 to 67:33.

  The weight ratio (b: c) of phosphate (b) to calcium carbonate (c) is preferably 1: 0.5 to 1: 1.5 when component (b) is ammonium dihydrogen phosphate. 1: 0.60-1: 1.35, more preferably 1: 0.65-1: 1.3, and even more preferably 1: 0.8-1: 1.2. When component (b) is diammonium hydrogen phosphate, the weight ratio of components (b) and (c) is more preferably in the range of 1: 0.3 to 1: 0.7.

  A more preferable adhesive composition of the present invention contains only ammonium dihydrogen phosphate as the phosphate (b). Compared with diammonium hydrogen phosphate, ammonium dihydrogen phosphate exhibits high adhesive strength in a small amount, and can produce a woody material having excellent water resistance. Moreover, although the ammonium dihydrogen phosphate is weakly acidic and the diammonium hydrogen phosphate is weakly alkaline, the wood material produced using the adhesive composition containing the ammonium dihydrogen phosphate is better. There was a tendency to show a higher pH value (closer to a neutral pH value) than the wood material produced using the adhesive composition containing diammonium hydrogen phosphate.

  When the phosphate (b) is ammonium dihydrogen phosphate, the weight ratio of the component (a) to the solid content weight (dry weight) of the adhesive composition of the present invention is 55 to 87% by weight. Preferably, 63 to 82% by weight is more preferable, 68 to 80% by weight is particularly preferable, and the weight ratio of the component (b) is preferably 8 to 25% by weight, and more preferably 10 to 20% by weight. Preferably, it is particularly preferably 10 to 18% by weight, and the weight ratio of component (c) is preferably 5 to 20% by weight, more preferably 8 to 17% by weight, and 10 to 15% by weight. % Is particularly preferred.

  When the phosphate (b) is diammonium hydrogen phosphate, the weight ratio of the component (a) to the solid content weight of the adhesive composition of the present invention is preferably 50 to 70% by weight, The weight ratio of b) is preferably 20 to 35% by weight, and the weight ratio of component (c) is preferably 10 to 20% by weight.

  The solid content weight of the adhesive composition means a weight (dry weight) obtained by removing a solvent such as water from the adhesive composition of the present invention. That is, the solid content weight is the components (a) to (c) when the adhesive composition of the present invention comprises only components (a) to (c) or only components (a) to (c) and a solvent. When the adhesive composition of the present invention contains components (a) to (c) and other substances (other than the solvent), the components (a) to (c) and other substances are equal to the total weight of c) Equal to the total weight.

  The adhesive composition of the present invention is preferably a liquid adhesive composition containing water since it can be easily brought into uniform contact with the wood element. That is, at least one of the components (a) to (c) is dissolved or dispersed in water or a mixed liquid of water and a water-soluble solvent (hereinafter, water and the mixed liquid are collectively referred to as an aqueous liquid). preferable. In the present invention, the liquid adhesive composition is not only a composition in which all of the components (a) to (c) are present in the same aqueous liquid, but also the components (a) to (c). Means a composition in which each is present in a separate aqueous liquid, and furthermore, only a part of the components (a) to (c) is present in the aqueous liquid, and the rest is not added to the aqueous liquid but is a solid. It also means a composition that exists in the state. As a preferred example of the liquid adhesive composition, a composition containing all of the components (a) to (c) in the same aqueous liquid, or only the components (a) and (b) are dissolved in the aqueous liquid. Component (c) is a composition that exists separately from the aqueous liquid in a powder state.

  The aqueous liquid is particularly preferably composed only of water, but may contain a small amount of a water-soluble solvent. The amount of the water-soluble solvent is preferably 20% by weight or less, more preferably 10% by weight or less, and particularly preferably 5% by weight or less of the amount of water. The water-soluble solvent is preferably a solvent having a boiling point of 100 ° C. or lower. Particularly preferred adhesive compositions of the present invention contain only water as a solvent.

  In the liquid adhesive composition containing water, the components (a) to (c) may be dissolved or dispersed in water. Since sugar (a) and phosphate (b) are highly soluble in water, they usually dissolve in water and precipitate only when the saturation state is exceeded. Calcium carbonate (c) is hardly soluble in water. When there is an insoluble component in water, it may be used in a state in which the insoluble component is dispersed in water by performing a stirring process at the time of use.

  In addition, since calcium carbonate (c) is hardly soluble in water as described above, in the present invention, only sugar (a) and phosphate (b) are added to an aqueous liquid and used as a solution, and calcium carbonate (c) May be used as a solid without being added to the aqueous liquid. As such an example, an adhesive composition containing an aqueous solution containing sugar (a) and phosphate (b) and powdered calcium carbonate (c) in a separated state can be mentioned. For example, calcium carbonate (c) is added to the wood element in a powder state, and an aqueous solution containing sugar (a) and phosphate (b) can be sprayed onto the wood element using a spraying device such as a spray. it can. By setting it as such a structure, clogging of a spraying device can be prevented.

  When the adhesive composition of the present invention is liquid, it is usually contacted with a wood element and then subjected to a drying treatment and a hot pressing treatment as necessary. Therefore, the aqueous liquid (water or the like) contained in the liquid adhesive composition is vaporized at the time of drying or hot pressing. However, if the amount of the aqueous liquid is too small, the components cannot be sufficiently dissolved or dispersed in the aqueous liquid, and it is difficult to uniformly add the components to the wood element. On the other hand, if the amount of the aqueous liquid is too large, it is not preferable because it takes more energy and cost during drying or hot pressing. Therefore, in the liquid adhesive composition, the ratio of the aqueous liquid and the components [all or part of components (a) to (c)] contained in the aqueous liquid is 70:30 to 40:60 (weight). Ratio), more preferably 60:40 to 45:55.

  A particularly preferred adhesive composition of the present invention is an adhesive composition consisting essentially of the components (a) to (c) and water, and more preferred adhesive compositions are the components (a) to (c). And an adhesive composition consisting only of water. When the adhesive composition of the present invention contains other substances, the content of the other substances is the total weight of the adhesive composition (in the case of liquid, the amount including the solvent) or the solid content of the adhesive composition. It is preferably 15% by weight or less, more preferably 10% by weight or less, particularly preferably 5% by weight or less, and further preferably 3% by weight or less.

  The adhesive composition according to the present invention is suitable for bonding wood elements. In the present invention, the wood element means not only an element derived from a tree (wood chip, wood fiber, veneer, wood flour, etc.) but also an element derived from a herbaceous plant, and comprises lignocellulose, lignin and cellulose. At least one substance selected from the group. Further, the wood element may be lignocellulose, lignin or cellulose itself, or a mixture of two or more selected from these. The adhesive composition according to the present invention is particularly suitable for adhesion of wood elements containing lignocellulose. Moreover, recycled materials, such as a recycled chip, can also be used as a wood element.

When the adhesive composition according to the present invention is used for bonding a powdery, small piece, or fibrous wood element (for example, wood strand, wood chip, wood fiber or plant fiber), the water content is 10%. The total weight of the components (a) to (c) is 5 to 50 parts by weight (more preferably 10 to 40 parts by weight, particularly preferably 15 to 30 parts by weight) based on 100 parts by weight of the dried wood element. Thus, it is preferable to add an adhesive composition.
When the adhesive composition according to the present invention is used for bonding a single plate, the total weight of components (a) to (c) is 80 to 200 g / m ² (more preferably 100 to 150 g) per bonded surface. / m ² ) The adhesive composition may be applied to the surface of the single plate.

The adhesive composition of the present invention is useful as an adhesive for producing a wooden molded body, a wooden board such as particle board or fiber board, and plywood.
In the case of producing a wooden molded body, a powdery, small piece or fibrous wooden element is mixed with an adhesive composition, and if the adhesive composition contains water, it is dried, and then the mixture is placed in a mold. ^{, 5kgf / cm 2 ~70kgf / cm} 2 ( about 0.5MPa～7MPa), more preferably, it may Assure heat at a pressure of ^{30kgf / cm 2 ~50kgf / cm 2} ( about 3MPa~5MPa). As the wood element, wood powder that has passed a 60-mesh sieve is particularly preferable.

When manufacturing wood boards, such as a particle board and a fiber board, using the adhesive composition of this invention, it can manufacture in the same process as the method of using the conventional petroleum adhesive. For example, a method including a step of adding a liquid adhesive composition to a small piece or fibrous wood element, a step of mat forming, and a step of hot pressing can be mentioned. If necessary, a drying step may be performed before or after mat forming. As a suitable method of adding the liquid adhesive composition to the wood element, there is a method of spraying with a sprayer such as a spray.
In a particularly preferable example of producing a wood board, the component (c) is added to the wood element in a powder state, the components (a) and (b) are sprayed onto the wood element in an aqueous solution, and then a drying step is performed. Is desirable. By doing in this way, the clogging of a sprayer and the puncture by water vapor | steam can be prevented.

When manufacturing a wooden board, the hot pressing is generally performed by a vertical press using a hot plate (hot plate). The set pressure of the press machine may be equal to or higher than the pressure at which the wood mat containing the wood element and the adhesive composition is sufficiently compressed. Specifically, it may be at the same pressure as that of the production of the wood board by the conventional method (about 20 to 100 kgf / cm ² [about ² MPa to 10 MPa], particularly 30 to 70 kgf / cm ² [about 3 MPa to 7 MPa]). Similar to the method, it may be appropriately adjusted depending on the thickness of the board to be molded, the target density, and the like.

To produce a plywood using the adhesive composition of the present invention, the adhesive composition is interposed between plywood veneers, and 5 kgf / cm ^{2 to} 50 kgf / cm ² (about 0.5 MPa to 5 MPa), more preferably, it Assure heat at a pressure of ^{10kgf / cm 2 ~30kgf / cm 2} ( about 1MPa~3MPa).

  The hot pressure temperature when the wood element is bonded using the adhesive composition of the present invention to produce the wood material is preferably 145 ° C. or higher. The reason why the temperature is 145 ° C. or higher is that when a mixture of sugar and ammonium dihydrogen phosphate is subjected to thermal analysis, a peak that is considered to be caused by a curing reaction is observed around 145 ° C. The higher the temperature, the more it will be cured in a shorter time, so a hot pressure temperature of 150 ° C. or higher is more preferable, and 155 ° C. or higher is particularly preferable. On the other hand, in order to suppress the cost, it is preferable that the hot press temperature is low, and therefore, it is preferably 200 ° C. or lower, more preferably 180 ° C. or lower. A particularly preferred hot pressing temperature is 160 ° C. to 180 ° C., and a more preferred hot pressing temperature is around 170 ° C. (165 ° C. to 175 ° C.).

Since the appropriate time varies depending on the amount of the composition, the amount of the adherend (woody element), the temperature / pressure, and the like, the hot pressing time may be appropriately adjusted in consideration of these. Generally, the adhesive composition is sufficiently cured by increasing the hot pressing time. Therefore, the hot pressing time is preferably 30 seconds or longer, more preferably 1 minute or longer, and particularly preferably 3 minutes or longer. On the other hand, if the hot-pressing time is too long, it is not desirable from the viewpoint of production cost and the like, and thus the hot-pressing time is generally within 15 minutes (or 10 minutes depending on the product).
When the wooden material to be manufactured is a molded body and a wooden board, it is appropriate to hot-press in a time of 30 seconds to 90 seconds / mm, more preferably 40 to 75 seconds / mm, depending on the thickness of the product.
The preferred hot pressing time is generally 3 to 10 minutes, more preferably 5 to 10 minutes.

  Regarding the components (a) to (c) and solvents such as water, in the preceding paragraph, specific types and compound names, wt%, weight ratios have been described, but the adhesive composition according to the present invention includes: Compositions obtained by appropriately combining these are included. In addition, a plurality of weight% ranges or weight ratio ranges have been described for each component, but these upper limit values and lower limit values can be appropriately combined.

[Test method]
In order to find an adhesive composition that can sufficiently bond wood, the test composition is mixed with water to prepare an adhesive composition, which is added to and mixed with an adherend (wood element) such as wood flour. The dried mixture was dried and hot pressed with a mold to produce a molded body (woody material), and its water resistance was evaluated.
Unless otherwise specified, the production of the molded body and the water resistance evaluation were performed according to the following procedures.
[Method for producing molded article]
(1) A test composition (sugar, phosphate, additive, etc.) is mixed with 30 g of distilled water to prepare an adhesive composition.
(2) The adhesive composition is added to and mixed with a predetermined amount of the adherend (wood flour or the like) in a dry state.
(3) The mixture is dried in an oven at 90 ° C. for 18 hours.
(4) Place the dried mixture in a cylindrical mold having an inner diameter of 7 cm preheated at a predetermined temperature.
(5) The pressing pressure is 4 MPa and hot pressing is performed at a predetermined temperature and time.
[Evaluation of water resistance of molded products]
(1) Immerse the molded body in boiling water for 4 hours.
(2) After boiling in (1), dry in an oven at 105 ° C for 15 hours.
(3) The weight reduction rate is calculated from the weight change before and after the treatment and used as an index of water resistance (the lower the weight reduction rate, the higher the water resistance).

[Test Example 1]
Using various adhesive compositions, molded articles were produced by the above method, and water resistance performance was evaluated.
First, an adhesive composition that exhibits a sufficient adhesive strength at a temperature of 180 ° C. and can produce a molded article excellent in water resistance was examined.
As a result of the test, when an aqueous solution containing a specific phosphoric acid compound and sugar was used, it was hot-pressed at 180 ° C. for 10 minutes to give a molded product having sufficient water resistance (weight reduction rate after boiling for 4 hours was 20 Less than%). The results are shown in Table 1. The ratio of sugar and phosphate shown in the table is a weight ratio.
On the other hand, when an aqueous solution of citric acid or itaconic acid, which is a polyvalent carboxylic acid, is used as the adhesive composition, a molded body having sufficient water resistance can be obtained at a heat pressure of 180 ° C. for 10 minutes. However, it was necessary to perform hot pressing for a longer time or to set the hot pressing temperature to 200 ° C.

[Test Example 2]
Next, with respect to the adhesive compositions in Table 1, molded articles were produced at a hot pressure temperature of 160 ° C., and the water resistance was examined. As a result, the adhesive composition containing ammonium dihydrogen phosphate or diammonium hydrogen phosphate could produce a molded article having sufficient water resistance even when hot pressed at 160 ° C. On the other hand, when a composition containing other phosphates such as sodium dihydrogen phosphate was hot-pressed at 160 ° C., a molded article having sufficient water resistance could not be produced.
Table 2 shows the results when changing the ratio of sucrose and ammonium dihydrogen phosphate and hot pressing at 160 ° C for 5 minutes.Table 3 shows the results when changing the ratio of sucrose and diammonium hydrogen phosphate at 160 ° C. The result when hot-pressing for 5 minutes is shown.

As can be seen from Table 2 and Table 3, when both phosphates are used in combination with sugar, the molded body can maintain its shape even when immersed in boiling water for 4 hours under the condition of 160 ° C for 5 minutes. Could be manufactured.
Moreover, when ammonium dihydrogen phosphate and diammonium hydrogen phosphate were compared, it was found that ammonium dihydrogen phosphate exhibited an excellent adhesion effect in a small amount.

  If the amount of phosphate is too small or too large relative to sugar, water resistance tends to deteriorate, so a molded product with high water resistance (weight reduction rate after boiling for 4 hours is 20% In order to obtain a molded product of less than, it is preferable to adjust the ratio of sugar and phosphate to an appropriate range. Specifically, when ammonium dihydrogen phosphate is used as the phosphate, the weight ratio of sugar to phosphate is preferably 90:10 to 60:40, and 88:12 to 70:30. More preferably. When diammonium hydrogen phosphate is used as the phosphate, the weight ratio of sugar to phosphate is preferably 85:15 to 60:40, and preferably 80:20 to 65:35. More preferred.

[Test Example 3]
With respect to the composition containing ammonium dihydrogen phosphate and sugar, a molded body was produced at a heat pressure temperature of 160 ° C. and a heat pressure time of 3, 5, and 10 minutes. The results are shown in Table 4.

  As shown in Table 4, when a composition containing ammonium dihydrogen phosphate and sugar is used, the longer the hot press time, the better the water resistance, but the hot press time is 3 minutes. It was possible to produce a molded body having the same. From this, it was found that by using a composition containing ammonium dihydrogen phosphate and a sugar, not only the reduction of the hot pressure temperature (160 ° C.) but also the reduction of the hot pressure time can be realized.

  On the other hand, when ammonium chloride is used even when it is an ammonium salt, or when sodium dihydrogen phosphate is used even when it is a phosphate, sufficient water resistance is obtained at a hot pressure temperature of 160 ° C. The formed product could not be produced. The results are shown in Table 5. When ammonium chloride was used (test numbers 17 to 19), the weight loss rate after boiling for 4 hours exceeded 20% even when the hot pressing time was 10 minutes. When sodium dihydrogen phosphate was used (test number 20), the compact collapsed during the boiling treatment even when the hot pressing time was 10 minutes.

  From this, it was found that ammonium dihydrogen phosphate and diammonium hydrogen phosphate exhibited a high adhesive effect at a low heat pressure temperature (160 ° C.) as compared with other phosphates and ammonium salts.

[Test Example 4]
Thermal analysis of a mixture of sucrose and ammonium dihydrogen phosphate was performed using a differential scanning calorimeter (DSC).
Specifically, 1.7 g of sucrose and 0.3 g of ammonium dihydrogen phosphate dissolved in water and dried at 90 ° C. for 18 hours were measured at 10 ° C./min in a nitrogen atmosphere. The obtained DSC curve is shown in FIG. As shown in FIG. 1, since a peak is observed at 144.91 ° C., it is presumed that a curing reaction occurs near this temperature. Therefore, it is considered that the adhesive composition containing sucrose and ammonium dihydrogen phosphate is cured and exerts an adhesive force when hot-pressed at a temperature of about 145 ° C. or higher.

For comparison, thermal analysis of a mixture of sucrose and sodium dihydrogen phosphate was performed.
Similarly to the above, 1.7 g of sucrose and 0.3 g of sodium dihydrogen phosphate were dissolved in water and dried at 90 ° C. for 18 hours, and measured at 10 ° C./min in a nitrogen atmosphere. The obtained DSC curve is shown in FIG. As shown in FIG. 2, two peaks are observed, and it is assumed that the curing reaction is completed at 185.61 ° C.

As a result of the above thermal analysis, when an adhesive composition containing sugar and ammonium dihydrogen phosphate is used, a molded article having excellent water resistance can be produced at 160 ° C. for 3 minutes (Test No. 14). As a result, when an adhesive composition containing sugar and sodium dihydrogen phosphate is used, only a molded article having very poor water resistance (disintegrated during boiling) can be obtained even when hot pressed at 160 ° C. for 10 minutes. (Test number 20).
Therefore, the results of thermal analysis also confirmed that the adhesive composition containing sugar and ammonium dihydrogen phosphate was sufficiently cured at 160 ° C.

[Test Example 5]
In this test example, the pH value of the adhesive composition and the pH value of the molded body were examined. The results are shown in Table 6.
As shown in Table 6, the adhesive composition containing ammonium dihydrogen phosphate (Test No. 21) has a pH value of about 4.5, and the adhesive composition containing diammonium hydrogen phosphate (Test Nos. 22 and 23). ) Had a pH value of about 8. In contrast, when 2 g of citric acid used in Patent Document 1 was dissolved in 30 g of water, the pH value of the aqueous solution was about 2. Therefore, it is considered that the adhesive composition of the present invention is less susceptible to acid corrosion of the production apparatus than the adhesive composition of Patent Document 1.

  Furthermore, in order to confirm whether or not the molded product as the final product also shows weak acidity to weak alkalinity, the molded product is immersed in about 200 ml of water at 20 ° C. (about 23 times the volume of the molded product) for 24 hours. The pH value of the water was measured (hereinafter, the pH value measured by the above method is referred to as the pH value of the molded product). For comparison, the pH value was also measured for a molded body (test number 24) manufactured using an aqueous citric acid solution as an adhesive composition and a molded body (test number 25) manufactured by hot-pressing only wood flour. It was measured. The molded body of Test No. 24 was produced by mixing an aqueous citric acid solution with wood flour, drying it at 90 ° C. for 18 hours, putting it into a mold and hot pressing it. The molded body of test number 25 was produced by putting wood powder into a mold and hot pressing. The results are shown in Table 6.

As shown in Table 6, the pH value of the molded body (test number 25) produced only from wood flour is about 5. In contrast, the pH value of the molded article (test number 24) produced using the citric acid aqueous solution (pH about 2) was 3. When a composition containing ammonium dihydrogen phosphate that is weaker than citric acid (pH about 4.5) or a composition containing diammonium hydrogen phosphate that is weakly alkaline (pH about 8) is used, The pH value was expected to be higher than 3, but in all cases lower than 3 (test numbers 21-23).
Therefore, even if the pH value of the adhesive composition containing the phosphate and saccharide is about 4.5 or about 8, the final product, the molded product, is produced using an aqueous citric acid solution (pH about 2). It was found that the acidity was comparable to that of the molded body.
If the pH value of the product is low, problems arise due to the strong acidity (for example, if the nail is driven into the product, the nail is likely to be oxidized). Moreover, since it is thought that pH value falls in the process of hot-pressing the wood element which added the adhesive composition, possibility that a manufacturing apparatus will be corroded by an acid remains.

[Test Example 6]
In order to solve the above-mentioned problem of acidification of the product, an additive capable of bringing the pH value of the molded body closer to the pH value of the molded body containing only wood flour was investigated. Each adhesive composition was used to produce two molded bodies, one used for water resistance testing and the other used for pH testing. In the water resistance test, as described above, the weight reduction rate of the molded product after boiling for 4 hours was obtained, and in the pH test, as described above, the pH value of the water after immersing the molded product in 20 ° C. water for 24 hours. Asked. The results are shown in Tables 7-9. For the molded body that collapsed during boiling for 4 hours, the pH value of the molded body was not measured except for a part.

  As shown in Table 7, an attempt was made to increase the pH value of the molded article by adding sodium hydroxide or sodium carbonate to increase the pH value of the adhesive composition. However, even when sodium hydroxide was added to bring the pH value of the adhesive composition to about 7, the pH value of the molded article still remained at about 3, and the water resistance deteriorated significantly (Test No. 26). Further, when the amount of sodium hydroxide added was increased to make the adhesive composition alkaline, the water resistance of the molded article was extremely deteriorated and disintegrated during the boiling treatment (test numbers 27 and 28). In addition, when sodium carbonate was added, the water resistance of the molded product was extremely deteriorated (test numbers 29 and 30).

  Tables 8 and 9 show the results of using sodium hydrogen carbonate, sodium silicate, urea, magnesium oxide, disodium hydrogen phosphate, or sodium dihydrogen phosphate. When urea and sodium dihydrogen phosphate were added (test numbers 35, 36, 39, and 40), the pH value of the adhesive composition and the water resistance and pH value of the molded product were tested without adding these additives. The value was close to No. 21, and the effect of the additive could not be confirmed. When sodium bicarbonate, sodium silicate, and magnesium oxide were added (test numbers 31 to 34), the pH value of the adhesive composition increased to about 6 to 9, but the water resistance of the molded article was extremely poor. It collapsed during the boiling process. When disodium hydrogen phosphate was added, the pH value of the adhesive composition increased to about 6.5, but the water resistance deteriorated significantly during the boiling treatment (test number 38), or the water resistance of the molded body Even if the properties were good, the pH value of the molded body still remained at about 3 (Test No. 37).

[Example 1]
As a result of further experiments, by adding calcium carbonate, a molded article having good water resistance and a pH value of about 4 to 5.5 was successfully produced. The results are shown in Table 10.
Test numbers 41, 42 and 44 were tested using an adhesive composition prepared by adding and mixing calcium carbonate in distilled water (Method A), but calcium carbonate is completely insoluble in water. The adhesive composition became a cloudy solution. Therefore, the pH value of the adhesive composition shown in the table is a pH value (apparent pH) in a state where calcium carbonate is not completely dissolved.
The composition of the adhesive composition of Test No. 43 is the same as that of Test No. 42, but only sucrose and phosphate are dissolved in distilled water, and calcium carbonate is not added to distilled water, but is added to the wood flour in a powder state. (Method B). Therefore, the pH value of the adhesive composition of test number 43 is the pH value of an aqueous solution containing only sucrose and phosphate.
Details of Method A and Method B are shown below. The water resistance test and the measurement of the pH value of the molded body were performed by the methods described above.

Method A
(1) Sugar, phosphate and calcium carbonate are mixed with 30 g of distilled water to prepare an adhesive composition.
(2) The adhesive composition is added to and mixed with 8 g of a dry adherend (cedar wood flour).
(3) The mixture is dried in an oven at 90 ° C. for 18 hours.
(4) Place the dried mixture in a cylindrical mold with an inner diameter of 7 cm preheated to 160 ° C.
(5) Hot-press for 5 minutes at a pressure of 4MPa and a temperature of 160 ° C.

Method B
(1) Dissolve sugar and phosphate in 30 g of distilled water.
(2) Calcium carbonate powder is added to and mixed with 8 g of a dry adherend (cedar wood flour).
(3) Add the aqueous solution of (1) to the mixed powder of (2) and mix.
(4) The mixture of (3) is dried in an oven at 90 ° C. for 18 hours.
(5) Place the dried mixture in a cylindrical mold with an inner diameter of 7 cm preheated to 160 ° C.
(6) Hot press for 5 minutes at a pressure of 4MPa and temperature of 160 ℃.

When the phosphate is ammonium dihydrogen phosphate (test numbers 41-43), as shown in Table 10, by using the same amount of calcium carbonate as ammonium dihydrogen phosphate (test numbers 42 and 43) The water resistance of the molded body was good, and the pH value of the molded body was higher than the pH value (5.14) of the molded body containing only wood flour (test number 25). Comparing the results of Test Nos. 42 and 43, the molded product produced by Method A (Test No. 42) showed higher pH value and water resistance than the molded product produced by Method B.
Also, when calcium carbonate in an amount 2/3 that of ammonium dihydrogen phosphate was used (Test No. 41), a molded article having a pH value exceeding 4.5 and good water resistance could be obtained.
When the amount of calcium carbonate is too small, the pH value is unlikely to rise, and when the amount of calcium carbonate is too large, water resistance tends to deteriorate. Therefore, when the phosphate is ammonium dihydrogen phosphate, phosphate : The weight ratio of calcium carbonate is preferably in the range of 1: 0.5 to 1: 1.5, and more preferably in the range of 1: 0.60 to 1: 1.35.

  When the phosphate is diammonium hydrogen phosphate (Test No. 44), use a half amount of calcium carbonate to obtain a molded article with a pH value exceeding 4 and good water resistance. I was able to. From this, when the phosphate is diammonium hydrogen phosphate, the weight ratio of phosphate: calcium carbonate is preferably in the range of 1: 0.3 to 1: 0.7.

Based on the above results, using an adhesive composition containing sugar and ammonium dihydrogen phosphate or diammonium hydrogen phosphate strengthens the wood at the curing temperature (about 160 ° C) when using petroleum-derived adhesives. It was found that a product with high water resistance can be produced. Further, it was found that addition of calcium carbonate to the adhesive composition can prevent acidification of the product without impairing the water resistance of the product.
In addition, it was found that a product having a pH value closer to neutrality can be produced by using ammonium dihydrogen phosphate than by using diammonium hydrogen phosphate. This was an unexpected result because the pH value of the adhesive composition containing ammonium dihydrogen phosphate was significantly lower than the pH value of the adhesive composition containing diammonium hydrogen phosphate.

[Example 2]
Comparative sugar, a particle board prepared by using the ammonium dihydrogen phosphate, and calcium carbonate (CaCO ₃ there), the physical properties of the particle board was prepared using only sugar and ammonium dihydrogen phosphate (without CaCO ₃₎ did. In addition, unlike sugar and ammonium dihydrogen phosphate, calcium carbonate is difficult to dissolve in water. Therefore, spraying a solution containing calcium carbonate in water with a sprayer may cause the sprayer to be clogged. Therefore, when using calcium carbonate, calcium carbonate was added in a powder state, and sugar and ammonium dihydrogen phosphate were added in an aqueous solution state. A specific method for manufacturing a particle board is shown below.

[Production method]
(1) Dry the recycled chips for particleboard in an oven at 80 ° C to a moisture content of about 3%.
(2) Dissolve sucrose and ammonium dihydrogen phosphate in water at a weight ratio of 80:20 to prepare a 50 wt% aqueous solution.
(3) Weigh dry chips so that board size is 300 × 300 × 9 mm and target density is 0.8 g / cm ³ .
(4) When adding calcium carbonate powder, about 67% of the weight of ammonium dihydrogen phosphate is added to the dry chips. The addition was performed by adding calcium carbonate powder to the dry chips charged in the blender.
(5) Spray the aqueous solution while the blender is operating. The amount of the aqueous solution sprayed is such that the solid weight of the aqueous solution (weight of sucrose and ammonium dihydrogen phosphate) is 20 parts by weight with respect to 100 parts by weight of the dry chip.
(6) The chip coated with the aqueous solution is dried in an oven at 90 ° C. for 18 hours.
(7) Create a mat using a 30 x 30 cm forming box and insert it into a hot press.
(8) Hot press at a sufficient pressure using a distance bar with a thickness of 9 mm at a hot pressing temperature of 170 ° C. and a hot pressing time of 9 minutes (1 min / mm).

[Board physical property test]
In order to investigate the physical properties of the manufactured particle board, a bending test, a peel test, and a water absorption thickness expansion coefficient test were performed in accordance with JIS A 5908. Moreover, in order to investigate the degree of acidification of the particle board, the pH value of water after the water absorption thickness expansion coefficient test was measured. The results are shown in Table 11.

  From the results in Table 11, it can be seen that the addition of calcium carbonate improves the physical properties of the particle board. Moreover, it was found from the pH value of the water after the water absorption thickness expansion test that the board becomes weaker acid by the addition of calcium carbonate.

  Since the adhesive composition of the present invention does not contain a petroleum-derived compound or a compound corresponding to a poisonous or deleterious substance, it is environmentally friendly and is suitable as an adhesive for producing a wooden material such as a wooden board. In addition, the adhesive composition of the present invention is inexpensive and can harden the wood element at the same temperature and time as petroleum-based adhesives. It is possible to mass produce wood materials. Furthermore, since the problem of acid corrosion of the manufacturing machine and acidification of the manufactured product can be improved, the practicality is very high.

Claims (11)

(a) at least one sugar selected from monosaccharides and oligosaccharides,
(b) at least one phosphate selected from ammonium dihydrogen phosphate and diammonium hydrogen phosphate, and
(c) An adhesive composition for a wood material, characterized by containing calcium carbonate.   Component (b) is ammonium dihydrogen phosphate and the weight ratio of components (a) and (b) is 90: 10-60: 40, or component (b) is diammonium hydrogen phosphate The adhesive composition according to claim 1, wherein the weight ratio of components (a) and (b) is 85:15 to 60:40.   The adhesive composition according to claim 1 or 2, wherein the component (b) is ammonium dihydrogen phosphate.   The adhesive composition according to claim 3, wherein the weight ratio of components (b) and (c) is 1: 0.5 to 1: 1.5.   The adhesive composition according to any one of claims 1 to 4, wherein the components (a), (b) and (c) are contained in an aqueous liquid.   It consists of the aqueous liquid containing a component (a) and (b), and the powder of a component (c), The said aqueous liquid and the said powder are included in the isolate | separated state, The any one of Claims 1-4 characterized by the above-mentioned. The adhesive composition according to item.   The total weight of components (a), (b) and (c) is 90% by weight or more of the solid content weight of the adhesive composition, according to any one of claims 1 to 6. Adhesive composition.   The adhesive composition according to any one of claims 1 to 7, wherein the adhesive composition is used for bonding a wood element selected from the group consisting of powders, fibers, small pieces and veneer of a tree or herbaceous plant. .   A step of bringing the adhesive composition according to any one of claims 1 to 8 into contact with a wooden element, and a step of hot pressing at a temperature of 140 ° C or higher and 200 ° C or lower. Bonding method.   A step of bringing the adhesive composition according to any one of claims 1 to 8 into contact with a wooden element, and a step of hot pressing at a temperature of 140 ° C or higher and 200 ° C or lower. Production method.   It is a woody material containing the adhesive composition of any one of Claims 1-8, Comprising: The woody material manufactured by heat-pressing the wood element in which the said adhesive composition was apply | coated or spread | dispersed.

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