JPH08174510A - Solution for modification of wood, and manufacture of modified wood using the solution - Google Patents

Abstract

PURPOSE: To obtain one-pack type wood-modifying solution wherein dimensional stability and weather resistance are given, manufacture of solution is simple, aging change is little, and a process of impregnating wood is simple by a method wherein phenolic monomer and hexamine of a specified mixed ratio are dissolved in alcohol-water mixed solvent. CONSTITUTION: For mixing ratio of phenolic monomer and hexamine in wood modifying solution, considering that 1mol of hexamine is decomposed by heating to generate 6mols of formaldehyde, it is used in (1/12-1/3)mol to 1mol of phenols monomer, 1:(1/8-1/2) in wt. ratio. Further, in order to give dimensional stability and weatherability to the wood, a phenolic resin content in the wood is set to be 15-50wt.%. Such a phenolic resin amount is controlled by varying a dissolved amount of phenolic monomer in the alcohol-water mixed solvent. 5-40 pts.wt. phenolic monomer is used to 100 pts.wt. of methanol-water solvent.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wood modifying solution suitable for improving the dimensional stability and weather resistance of wood materials such as veneer, plywood, timber, and laminated wood, and a solution for using the same. The present invention relates to a method for producing modified wood. More specifically, the present invention relates to a one-pack type wood modifying solution having a simple impregnation step and a modified wood manufacturing method using the same.

[0002]

2. Description of the Related Art Since wood is light and strong and easy to process, it has been used for a long time in building materials and furniture.
Although it is used in a wide range of other applications, it suffers from the drawback of large dimensional changes due to water absorption and moisture absorption. Further, when the wood is used for outdoor wall materials, eaves, shutters, etc., it is apt to deteriorate due to ultraviolet rays, moisture, oxygen, etc. in the sun's rays, and there is also a problem in weather resistance.

[0003] Conventionally, so-called wood-plastic composites in which wood is impregnated with a polymerizable substance such as phenol resin and the polymerizable substance is polymerized and hardened in the wood to impart wear resistance and excellent mechanical strength to the wood. Wood (WPC) is manufactured and used in large quantities in the field of floor boards and the like. However, the effect of improving the dimensional stability in such a WPC was insufficient. This is because the phenol resin having a large molecular weight cannot penetrate into the part in the cell wall necessary for modifying the dimensional change of wood. In addition, since WPC needs to be impregnated with a large amount of resin, it is expensive and the properties of wood itself are lost.

Further, as a method for improving the dimensional stability of wood by using a phenol resin, for example, (1) a method of impregnating a low molecular weight resol type phenol resin, or (2) a wood with (A) phenols Phenol resin in wood tissue by injecting either monomer (A) or aqueous solution (B) hexamethylenetetramine (hexamine) aqueous solution (A) or (B), then injecting the other solution and then heating In addition, a method of curing the phenol resin produced by further heating (Japanese Patent Application Laid-Open No. Hei 4-
No. 336203) and (3) a method of impregnating wood with a wood-modifying composition comprising a low molar ratio novolac type phenolic resin, hexamine and an aqueous solvent containing methanol, and heat curing (JP-A-6-47712). Have been proposed.

However, in the case of the method (1), since the low molecular weight resol type phenolic resin is rich in self-condensation, there is a problem that it cannot be stored for a long period of time due to a remarkable change with time. Further, there is a problem that such a resin has a small production amount and is expensive. In the case of the method (2), since both (A) and (B) have a small molecular weight, it easily penetrates into the cell wall of wood and has a large effect of improving the dimensional stability, but since it is used as a two-part solution. There is a problem that the impregnation process becomes complicated. Further, in the case of the method (3), it is said that a phenol monomer and hexamine form a complex to cause white precipitation and cannot be liquefied, so that once a low molecular weight novolac type phenol resin is generated, it is generated with formalin. Hexamethylenetetramine as an agent was added and dissolved, and the manufacturing process was extremely complicated.
In addition, since the molecular weight of novolac type phenolic resin was larger than that of phenolic monomer, it was difficult to penetrate into the cell wall of wood.

In addition, for example, a method of impregnating wood with an aqueous solution of polyethylene glycol, or a chemical substance such as an organic acid, an organic acid anhydride, an alkylene oxide or an isocyanate compound, which can react with a hydroxyl group in wood, is chemically bonded. In particular, acetylated wood obtained by chemically reacting acetic anhydride with hydroxyl groups in wood is currently industrially produced. However, in the former case, there is a problem that the effect is lacking in sustainability because polyethylene glycol easily dissolves in water, and in the latter case, it takes time to manufacture and side reaction products and unreacted products generated during the reaction. However, there is a problem that the cost becomes high because it is necessary to remove the wood from the wood.

[0007]

The problem to be solved by the present invention is to provide dimensional stability and weather resistance equivalent to or better than those of conventional modified wood, inexpensive, and
It is an object of the present invention to provide a one-pack type wood modifying solution which is easy to manufacture the solution itself, has little change over time, and has a simple process of impregnating wood, and a method for manufacturing modified wood using the same.

[0008]

According to the present invention, a wood modified by dissolving a phenolic monomer having a mixing ratio of 1/8 to 1/2 by weight and hexamine in an alcohol-water mixed solvent. A quality solution is provided, and the wood-modifying solution is further provided in which the alcohol-water mixed solvent is a methanol-water mixed solvent.
The wood-modifying solution is prepared by dissolving 5 to 40 parts by weight of a phenolic monomer in 100 parts by weight of a water mixed solvent, and further, the methanol content of the methanol-water mixed solvent is 10 to 40 wt%. A characteristic wood-modifying solution is provided.

Furthermore, according to the present invention, the above-mentioned wood-modifying solution is impregnated in wood to disperse and fix it in the wood structure, and then heated to form a phenol resin in the wood and polymerize and harden it. A method for producing modified wood and a method for producing modified wood characterized in that the heating temperature is 120 to 180 ° C.

That is, the present inventors have found that the phenolic monomer and hexamine have a small molecular weight and thus can easily penetrate into the cell wall of wood, and that even when the phenolic monomer and hexamine are mixed, the hexamine decomposes to formaldehyde. It is stable and does not change with time below the temperature at which it is generated (according to the results of thermogravimetric analysis, it starts to decompose at 120 ° C.), and when it exceeds the decomposition start temperature, they react to form a phenol resin and further cure. It was excellent that the phenolic monomer and hexamine could be uniformly dissolved in the alcohol-water mixed solvent under the specified conditions and the results of the intensive study, and that the obtained modified wood solution was impregnated and heated. It has been found that a modified wood having dimensional stability can be obtained, and the present invention has been completed.

The present invention will be described in detail below. Considering that 1 mol of hexamine decomposes by heating to generate 6 mol of formaldehyde, the mixing ratio of the phenolic monomer and hexamine in the wood modifying solution of the present invention is 1 with respect to 1 mol of the phenolic monomer. / 12
It is necessary to use in the range of ⅓ mol, and the weight ratio of ⅛ to ½. Even if hexamine is present in excess over this range, little improvement in dimensional stability and weather resistance of wood is seen, and if less than this range,
The phenolic resin does not cure sufficiently.

The phenolic monomer used in the present invention is not particularly limited as long as it is soluble in an alcohol-water mixed solvent, and examples thereof include phenol, cresol and xylenol. Further, the alcohol used in the alcohol-water mixed solvent (hereinafter referred to as alcohol water solvent) used in the present invention must be water-soluble and have a low boiling point (boiling point is 100 ° C. or lower). It can be used without particular limitation, for example, methanol, ethanol, etc. can be used. Among them, industrially mass-produced methanol can be preferably used in terms of economy.

Further, in order to impart dimensional stability and weather resistance to the wood, the content of the phenol resin in the wood is 15 to 5
It should be about 0% by weight. If the content is less than this, the effect of imparting dimensional stability is small, and even if the content exceeds this, it does not contribute to the performance improvement because it is already filled in the cell wall. Such a phenol resin content can be controlled by changing the amount of the phenolic monomer dissolved in the alcohol-water mixed solvent, and when the solvent is a methanol-water mixed solvent (hereinafter referred to as methanol-water solvent). Phenol monomer is added to 100 parts by weight of methanol / water solvent.
It is recommended to dissolve it in an amount of about 40 parts by weight.

As described above, it is said that the phenolic monomer and hexamine are difficult to dissolve in a methanol / water solvent (Japanese Patent Laid-Open No. 06-47712).
However, as a result of examination by the present inventors, it was found that under the following conditions, it was dissolved to obtain a uniform wood-modifying solution. The result is shown in FIG. In FIG. 1, first, methanol-water mixed solvents having various methanol concentrations were prepared, and then phenol was dissolved in each solvent to a predetermined concentration, and then hexamine was gradually added so that hexamine became insoluble. The results of measuring the concentration are graphed with the hexamine concentration on the vertical axis and the phenol concentration on the horizontal axis.

Further, in FIG. 1, a straight line (A) at which the compounding ratio of phenol: hexamine is 1: 1/2, which is the upper and lower limit of the preferable compounding ratio of the phenol monomer and hexamine, and 1: 1/8. The straight line (B) is also shown in the figure.

Therefore, in order to obtain the modified wood excellent in dimensional stability and weather resistance which is the object of the present invention, the wood modifying solution is below the line representing the methanol / water solvent of various methanol concentrations, Moreover, it is necessary to select from the composition of the region sandwiched by the straight line (A) and the straight line (B). Further, it is particularly preferable to select from a range in which 5 to 40 parts by weight of a phenolic monomer is dissolved in 100 parts by weight of a methanol / water solvent, that is, a region sandwiched by straight lines shown by (C) and (D) in FIG. .

Further, it can be seen from FIG. 1 that the methanol concentration of the methanol-water solvent used in the wood modifying solution is preferably 10 to 40 wt%. Methanol concentration is 10wt
If it is less than%, it is difficult to provide a uniform solution and the selectable range becomes extremely small, which is not preferable.
When the concentration is more than 0 wt%, there is no problem in solubility but it is not preferable in terms of economy and safety.

Further, in the wood-modifying solution of the present invention, ammonia is generated when hexamine is decomposed, so that it acts as a polymerization catalyst for the subsequent phenol resin. Therefore, in the present invention, the polymerization catalyst is particularly preferable. Although it is not necessary to use it, sodium hydroxide, calcium hydroxide, ammonium chloride,
Chemical substances commonly used as polymerization catalysts for phenolic resins, such as hydrochloric acid and oxalic acid, are converted into phenolic monomer 1
0.01 to 2 parts by weight, preferably about 0.05 to 1 part by weight, may be added to 100 parts by weight and used. When the amount of the polymerization catalyst is less than the above range, the curing time can hardly be shortened, and when the amount is extremely large, the curing speed becomes fast, but problems such as deterioration and discoloration of wood due to the residual catalyst occur.

The present invention can be applied without particular limitation as long as it is a wood-based material that retains the structural structure of wood.
For example, it is effective for improving the dimensional stability and weather resistance of plate-like wood materials such as plywood and veneer, columnar wood materials such as timber, and other block-like wood materials, but especially large plates and pillars. It exerts a remarkable effect when used for wood.

Next, a method for producing modified wood will be described step by step. First, wood is impregnated with the wood modifying solution of the present invention. At this time, the wood is generally preferably dry wood,
If the water content is 30% or less, drying or the like may not be performed. The method of impregnation is not particularly limited, but, for example, a method of immersing wood in the wood modifying solution, or a method of impregnating under reduced pressure, under pressure or under reduced pressure and pressure can be used.

Next, the wood impregnated with the wood-modifying solution obtained by the above method and the extra wood-modifying solution not impregnated into the wood are separated, and then the wood-modifying solution is impregnated. Put only the timber in a container and heat. The heating method is not particularly limited, and may be a method for heating the wood with the wood modifying solution, such as heating by a tank, external heating such as press heating, or internal heating by high frequency. Further, the heating reaction is preferably performed at 120 ° C to 180 ° C.
When the temperature is lower than 120 ° C, decomposition and polymerization of hexamine are unlikely to occur, or the reaction time is too long, which is not preferable. Further, heating at a temperature exceeding 180 ° C. is not preferable because discoloration or deterioration of wood occurs even in a short time. The heating time depends on the type of phenolic monomer, reaction temperature, shape and size of wood, etc.
Generally, it is 0.1 to 8 hours, preferably 0.5 to 3 hours. During this time, a phenol resin is formed inside the wood structure, and the phenol resin is cured to obtain the modified wood intended by the present invention.

The modified wood thus obtained can be used as a product as it is because water and alcohol in the wood are volatilized during heating, and it is not necessary to carry out washing and drying.

[0023]

EXAMPLES The present invention will be described in more detail with reference to Examples and Comparative Examples, but it goes without saying that the present invention is not limited thereto. Various characteristics were evaluated by the following methods.

<Weight increase rate> The total dry weight (a) of the test piece before the modification treatment and the total dry weight (b) of the test piece after the modification treatment were measured, and the weight increase rate was calculated by the following formula 1. It was It can be said that the larger this value is, the more phenolic resin is fixed in the wood.

[0025]

[Equation 1]

<ASE Value> First, a test piece made of untreated wood and a test piece made of modified wood were prepared, and the volume (c) when fully dried by a hot air dryer at 105 ° C. was prepared.
And soak it in distilled water and depressurize for 30 minutes (25 mmH
g) and leave for 1 hour, then depressurize (2
The volume (d) when the pressure is set to 0 mmHg) and left to stand for a while, and the volume swelling rate is calculated according to the following mathematical formula 2.
Then, the volume swelling ratio (e) of the untreated wood and the volume swelling ratio (f) of the modified wood obtained were substituted into the following formula 3 to obtain AS
The E value was determined. Generally, the closer this value is to 100, the better the dimensional stability.

[0027]

[Equation 2]

[0028]

(Equation 3)

<Change with Time of Wood-Modifying Solution> The wood-modifying solution was put in a container and stored, and after a predetermined period of time, precipitation of a solid content and generation of gel were visually observed.

Examples 1 to 7 and Comparative Example 1 A wood-modifying solution was prepared by uniformly dissolving a phenolic monomer in an alcoholic water solvent at the compounding ratio shown in Table 1 and then adding hexamine to obtain a homogeneous solution. Solution (A ~
G) was obtained. Table 1 also shows the results of observing the changes with time of the respective solutions and the changes with time of the low molecular weight resol type phenol resin solution having a molecular weight of 185 for comparison.

[0031]

[Table 1]

Example 8 A cypress dry wood having a tangential direction of 3 cm, a radial direction of 3 cm and a fiber direction of 0.5 cm was placed in a container, the inside of the container was depressurized at 20 mmHg for 30 minutes, and then the wood modified in Example 4 was used. Quality solution (D)
Was impregnated into the test piece and opened, and then left for 30 minutes to impregnate the wood with the wood modifying solution. Then, the wood impregnated with the wood-modifying solution was taken out from the container, and the temperature was 40 ° C.
After drying overnight with a dryer of No. 1, a heating reaction was performed at a temperature of 150 ° C. for 2 hours using a hot press. After the reaction, post-drying was performed using a dryer to obtain modified wood. Various physical properties are shown in Table 2.

Example 9 Modified wood was obtained in the same manner as in Example 8 except that the solution (E) produced in Example 5 was used as the wood modifying solution. Various physical properties are shown in Table 2.

Example 10 Modified wood was obtained in the same manner as in Example 8 except that the solution (F) produced in Example 6 was used as the wood modifying solution. Various physical properties are shown in Table 2.

Example 11 Modified wood was obtained in the same manner as in Example 8 except that the solution (G) produced in Example 7 was used as the wood modifying solution. Various physical properties are shown in Table 2.

Comparative Example 2 A resol type phenolic resin solution shown in Comparative Example 1 was prepared by placing dry wood of a cypress having a tangential direction of 3 cm, a radial direction of 3 cm and a fiber direction of 0.5 cm in a container and depressurizing the container at 20 mmHg for 30 minutes. Was impregnated, the pressure was opened, and the mixture was left for 30 minutes. Then, the wood impregnated with the resole resin solution was taken out from the container, and the temperature was adjusted to 40
After drying overnight in a dryer at 0 ° C., a heating reaction was performed at a temperature of 150 ° C. for 2 hours using a hot press. After the reaction, post-drying was performed using a dryer to obtain modified wood. Table 2
Shown in

[0037]

[Table 2]

As is clear from Table 1, the wood-modifying solutions (A to G) of the present invention are stable with little change over time as compared with the resol type phenol resin solution.
Further, as is clear from Table 2, the modified woods of Examples 8 to 11 have higher ASE values than the modified woods of Comparative Example 2 treated with the low molecular weight resole type phenolic resin,
It can be seen that the dimensional stability is good.

In the modified wood thus obtained, the residual monomer was found to have a small value by analysis such as titration and gas chromatography.

[0040]

EFFECTS OF THE INVENTION Unlike the case of using a conventional low molecular weight resol type phenol resin, the wood-modifying solution of the present invention has no unreacted formaldehyde or highly reactive methylol group, and therefore does not change with time and has a long pot life. It is long and easy to use. Also, because it is used in the state of monomer,
It has good permeability to wood and does not require pre-condensation of phenolic resin in advance. Furthermore, since it is a one-liquid type, it has the characteristic that the step of impregnating wood can be done only once.

Further, the modified wood obtained by the production method of the present invention disperses and hardens uniformly in the wood earlier than when the low molecular weight resol type phenol resin is used. It has more dimensional stability and can prevent deterioration due to ultraviolet rays, moisture, oxygen, etc. in sunlight. Further, as a secondary effect, it can be expected to prevent or suppress wood decay and ant damage caused by various wood decay fungi and termites.

As described above, the modified wood obtained by the production method of the present invention having excellent characteristics is suitable for construction materials, furniture materials and many other fields.
Pillars, beams, bases, base materials, floors, eaves, shutters, outer wall materials, desks,
It is used for bookshelves.

[Brief description of drawings]

FIG. 1 is a graph showing the maximum amounts of phenolic monomers and hexamine dissolved in methanol aqueous solvents having various methanol concentrations.

[Explanation of symbols]

(A) A straight line showing the position where the weight ratio of the phenolic monomer and hexamine is 1: 1/2 (B) A straight line showing the position where the weight ratio of the phenolic monomer and hexamine is 1: 1/8 (C) Methanol A straight line showing the position where the phenolic monomer becomes 5 parts by weight with respect to 100 parts by weight of the water solvent (D) A straight line showing the position where the phenolic monomer becomes 40 parts by weight with respect to 100 parts by weight of the methanol water solvent

Claims (6)

[Claims] 1. A wood-modifying solution obtained by dissolving a phenolic monomer having a mixing ratio of 1/8 to 1/2 by weight and hexamine in an alcohol-water mixed solvent. 2. The wood-modifying solution according to claim 1, wherein the alcohol-water mixed solvent is a methanol-water mixed solvent. 3. The wood-modifying solution according to claim 2, wherein 5 to 40 parts by weight of a phenolic monomer is dissolved in 100 parts by weight of a methanol-water mixed solvent. 4. The wood-modifying solution according to claim 2, wherein the methanol-water mixed solvent has a methanol content of 10 to 40 wt%. 5. A wood modifying solution according to any one of claims 1 to 4 is impregnated into wood to disperse and fix it in the wood tissue, and then heated to form a phenol resin in the wood and A method for producing modified wood, which comprises polymerizing and curing the wood. 6. The method for producing modified wood according to claim 5, wherein the heating is performed at 120 to 180 ° C.