JPH0699409A - Manufacture of modified timber - Google Patents

Abstract

PURPOSE:To formalize even the inside of a thick timber, retain the woody feel of a natural wood and manufacture a modified timber of superior dimension stability by adjusting the water content to the fiber saturating point or lower, introducing gas and heating and formalizing plasma-emitted timber in the presence of an acid catalyst. CONSTITUTION:As the gas used at the time of plasma emission, H2, He, Ar, O2 or the like can be used. While at least one kind of the gases is flowed through a treatment tank 5, a timber 4 with water content of fiber saturating point or lower is plasma-emitted by applying high voltage electric field from a high frequency power source 7. The treated timber is heated and formalized in the fiber atmosphere in a formaldehyde derivative such as paraformaldehyde, trioxan or tetralin in the presence of an acid catalyst such as sulfur dioxide, chloride, sulfate or borate, and even the inside of the timber is activated by plasma emission, and even a thick timber can be formalized to the inside.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing modified wood used for housing equipment, building materials and the like.

[0002]

2. Description of the Related Art Formalization has long been known as a method for imparting dimensional stability to wood.

The treatment by formalization is a reaction in which formaldehyde crosslinks between the hydrophilic hydroxyl groups of wood components (cellulose, hemicellulose, lignin, etc.). The hydrophilicity of wood is reduced by such cross-linking, and for example, in the case of wood having a thickness of less than 3 mm, the anti-swelling ratio (ASE), which is a characteristic of dimensional stability even at a low weight gain rate of about 5 to 10%, is obtained. 50-
A value of 60% is shown.

In the above formalization, formaldehyde derivatives such as paraformaldehyde, trioxane and tetraoxane are used as a source of formaldehyde, and sulfur dioxide as a reaction catalyst for formalization and chlorination of hydrogen chloride, iron chloride, magnesium chloride, ammonium chloride and the like. The raw material wood was heated in a gas phase or liquid phase in a reaction vessel using a substance or a sulfate such as iron sulfate. In particular, when trioxane or tetraoxane is used as a formaldehyde supply source, sulfur dioxide is used as a reaction catalyst, and further, when gas phase treatment is performed using iron sulfate or the like as a promoter for promoting decomposition of trioxane or tetraoxane into formaldehyde,
It is known that discoloration and strength deterioration due to acid are small.

However, when the thickness of the wood is less than 3 mm, the formalization treatment is effective. When the wood becomes thicker, especially when the thickness becomes 5 mm or more, the conventional formalization treatment sufficiently forms the interior of the wood. As a result, the dimensional change becomes large and the wood texture as a natural wood is lost.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above facts, and an object thereof is to enable a formalization reaction to the inside of wood even if the raw wood is thick. Another object of the present invention is to provide a method for producing modified wood which retains the wood texture of natural wood and is excellent in dimensional stability.

[0007]

The method for producing modified wood according to the present invention is a method of introducing a gas into a wood whose moisture content is adjusted to a fiber saturation point or lower and subjecting the wood to plasma irradiation. The above wood is formalized by heating in the presence of an acid catalyst in a formaldehyde derivative vapor atmosphere.

[0008]

According to the present invention, when wood having a moisture content adjusted to a fiber saturation point or lower is subjected to plasma irradiation, radicals are generated in the wood by the plasma irradiation. The generated radicals excite other regions, and the inside of the wood is activated. During the formal treatment, formaldehyde is rapidly diffused into the wood by binding with the radicals imparted to the wood, and as a result, even thick wood can be formalized to the inside of the wood.

The present invention will be described in detail below. In the present invention, wood whose water content is adjusted to a fiber saturation point or lower is used. The shape of the wood is not particularly limited, and for example, log logs, lumber products, sliced veneer, plywood and the like are used. The tree species of the above-mentioned raw material wood is not limited at all.

The water content of the wood is below the fiber saturation point, and the wood may be in an absolutely dry state, or when the wood contains water, the water content is below the fiber saturation point. The fiber saturation point is a state in which free water does not exist and the cell membrane of wood is saturated with bound water. If the moisture content of the wood is above the fiber saturation point, the water in the wood is exposed on the surface of the wood and partially covers the fibers of the wood. Is less likely to occur, and also in the formalization treatment described later, if excess water is present, the formaldehyde monomer is polymerized with the water, so the effect on dimensional stability is reduced. Therefore, the water content is preferably 0 to 10 wt%.

In the present invention, a gas is introduced into the wood having the above moisture content adjusted to perform plasma irradiation. Examples of the gas include N ₂ , He, Ar, and O ₂ , and at least one of them is used to contribute to the generation of radicals in wood. The plasma irradiation may be performed by introducing the above gas after evacuating the vacuum, or may be performed in the atmosphere. In the case of performing in air, He or Ar among the above gases is introduced, and if necessary, He or Ar is mixed with N ₂ or O ₂ and then introduced.

The conditions for generating plasma, that is, the frequency, power, etc., are appropriately set according to the desired degree of processing. The irradiation time is also the same.

A plasma irradiation processing apparatus will be described with reference to FIG. Parallel plate electrodes (1) and (2) are installed above and below the treatment tank (5),
A solid dielectric (3) is placed on the lower electrode (2). The solid dielectric (3) may be provided on the upper electrode (1) instead of the lower electrode (2), and the upper and lower electrodes (1) and (2) may be provided.
It may be provided on both sides. A wood (4) whose moisture content is adjusted to a fiber saturation point or lower is placed between the upper and lower electrodes (1) and (2), and the upper electrode (1) is higher than the high frequency power supply (7) while flowing gas. When an AC electric field of a voltage is applied, plasma is generated between the upper and lower electrodes (1) and (2), and the wood (4) receives the action of this plasma to generate radicals. This radical excites other regions and is activated even inside the wood (4). An insulator (6) is provided on the high voltage introducing part and the grounding extracting part of the processing tank (5). The frequency of the AC electric field to be applied is not particularly limited, but since the wood (4) is heated in a high frequency region, it is necessary to cool the wood (4) so as not to carbonize it or to shorten the irradiation time.

In the present invention, the above-mentioned plasma-irradiated wood is treated in a formaldehyde derivative vapor atmosphere,
Formalization is carried out by heating in the presence of an acid catalyst. Volume of wood to be processed formalization is not particularly limited with respect to the volume of the reaction vessel, 0.01~0.2m ³ / m ³ (volume of the reaction vessel) it is suitable.

The formaldehyde derivative is a compound which forms a formaldehyde monomer when thermally decomposed, and examples thereof include paraformaldehyde, trioxane and tetraoxane. These are 1 or 2
More than one species can be used. Of these, trioxane and tetraoxane are industrially effective because they are solid and have no formmarin odor, easily sublime, and thermally decompose to form formaldehyde monomer. The formaldehyde derivative is appropriately determined according to the amount of the acid catalyst and the degree of the formalization reaction, but the formaldehyde derivative is thermally decomposed to formaldehyde monomer in an amount of 30 to 300 mol / m ^3. (Capacity of reaction vessel) is appropriate.

The form of vapor permeation of the formaldehyde derivative is not particularly limited. For example, a solid formaldehyde derivative may be volatilized in a reaction vessel to permeate wood, or the formaldehyde derivative already vaporized may be used. Steam may be introduced into the reaction vessel to penetrate the wood.

An acid catalyst is used for the formalization in the present invention. The acid catalyst is not particularly limited,
For example, sulfur dioxide, hydrogen chloride, zinc chloride, iron chloride,
Examples thereof include chlorides such as magnesium chloride and ammonium chloride, sulfates such as iron sulfate, boric acid and salts thereof, and the like.
Of these acid catalysts, the use of sulfur dioxide is particularly effective in that the strength of wood is less likely to deteriorate. The concentration of the above-mentioned acid catalyst is not particularly limited, but a formaldehyde derivative is suitable in a molar ratio of 10 to 100 with respect to the acid catalyst. The acid catalyst is not limited to one type, and two or more types may be used if necessary.

In addition to the effect of promoting the formalization reaction of the hydrophilic hydroxyl groups in wood, the above-mentioned acid catalyst also has the effect of promoting the thermal decomposition of formaldehyde derivative into formaldehyde monomer. Therefore, if necessary,
When two or more kinds of acid catalysts are used and a part of them is used as a co-catalyst for promoting thermal decomposition to formaldehyde monomer, the reaction can be further promoted. For example, iron sulfate or the like is used as a co-catalyst that promotes thermal decomposition into formaldehyde monomers, and sulfur dioxide is used as an acid catalyst for the formalization reaction. As the co-catalyst, it is possible to use a catalyst other than the acid catalyst.

The method of permeating the acid catalyst is not particularly limited. For example, when the acid catalyst is a gas, it is introduced into a reaction vessel using a cylinder to permeate wood, and when the acid catalyst is liquid or solid. In some cases, it is gasified together with the wood in the reaction vessel and penetrated into the wood. When this formalization is carried out under reduced pressure or under pressure, it goes without saying that the reaction vessel must have pressure resistance.

Formalization of the modified wood in the present invention is carried out as follows, as an example of using a solid formaldehyde derivative, a gaseous acid catalyst and a solid acid catalyst as a co-catalyst. First, a formaldehyde derivative and an acid catalyst which is a co-catalyst are put into a heated reaction container, and the reaction container is sealed. Next, the inside of the reaction vessel is depressurized using a vacuum pump. Decompression degree at this time is 3
It is preferably 00 torr or less. Then stop the vacuum pump,
A predetermined amount of gaseous acid catalyst is introduced into the reaction vessel, and the inside of the reaction vessel is heated and maintained at a predetermined temperature to form formal. The treatment temperature for formalization at this time is not particularly limited, but is preferably 90 to 120 ° C. The treatment time by formalization is not particularly limited, but when the formalization treatment is completed, the pressure in the formalization reaction container is 500 to
It is preferably 2000 torr. After performing formalization for a predetermined time, the residual gas in the reaction vessel is evacuated while heating. By sufficiently performing this exhaustion, most of unreacted formaldehyde and acid catalyst in the wood can be removed.

[0021]

EXAMPLES Examples and comparative examples of the present invention will be given below.

Example 1 As a raw material wood, a 5 mm thick cypress wood 100 × 100 m
m was dried at 105 ° C. for 8 hours. The moisture content of the wood was 0%. This wood was placed between the upper and lower electrodes (1) and (2) shown in FIG. 1, and plasma irradiation was performed under the following conditions.

Conditions of Plasma Irradiation: Interval of electrodes: 20 mm (used gas and flow rate): Inert gas: He: 5000 sscm Reactive gas: O _2: 100 sscm: sscm: 25 ° C., 1 atm Flow rate per minute (ml) (plasma conditions) ・ Frequency ───10 kHz ・ Treatment time ───1 minute ・ Power ───100 W ・ Treatment pressure ─760 mmHg Next, 10 pieces of the above wood that had been plasma-irradiated Then, the reaction mixture was placed in a reaction vessel of 5 liters which had been heated to 100 ° C. in advance, and further, in this reaction vessel, trioxane as the formaldehyde derivative was added in an amount of 150 mol / m ³ in terms of formaldehyde monomer, and an acid catalyst working as a co-catalyst was added. As ferric sulfate (Fe ₂ (SO ₄ ) ₃ )
Mol / m ^{3 was} added.

After that, the reaction vessel was sealed and the pressure was reduced to 50 torr with a vacuum pump. Next, 5.0 mol / m ^{3 of} sulfur dioxide (SO ₂ ) was introduced as an acid catalyst, and the mixture was held at 100 ° C. for 20 hours for formalization. At that time, the pressure in the final reaction vessel was 600 torr. The residual gas in the reaction vessel was sufficiently exhausted to obtain modified wood. The appearance of this modified wood retained the wood texture of natural wood.

The impregnation rate was measured as the degree of achievement of formalization of the obtained modified wood, and the anti-swelling rate (ASE) was measured as the dimensional stability of the modified wood.

The impregnation rate was determined according to the following formula. - impregnation rate _{(%) = {(W 2} -W 1) / W 1} ×
100 · W ₁ represents the absolute dry weight of the raw wood. · W ₂ represents the absolute dry weight of the resulting modified wood.

The anti-swelling ratio was determined according to the following formula. - anti-swelling rate _{(%) = {(S 1} -S 2) / S 1}
× 100 · S ₁ represents the swelling ratio of the raw wood. S ₁ is the dimension A of the raw wood after drying, and 72
The dimension B after immersion in time was measured and calculated based on the following formula. _{· S 1 (%) = {} (B-A) / A} × 100 · S 2 represents the swelling rates of the reforming timber. S ₂ is the dimension C of the modified wood after drying, and 72
The dimension D after immersion in time was measured and calculated based on the following formula. S ₂ (%) = {(D−C) / C} × 100 The results are shown in Table 2.

Examples 2 to 5 Woods subjected to plasma irradiation under the same conditions as in Example 1 were
Modified wood was obtained in the same manner as in Example 1 except that the trioxane concentration in the formalization treatment, the treatment temperature, and the treatment pressure in Example 1 were changed to those shown in Table 1 below. The appearance of this modified wood retained the wood texture of natural wood.

The impregnation rate and anti-swelling rate (A of the obtained modified wood)
SE) was measured as in Example 1. The results are shown in Table 2.

Comparative Example 1 As a raw material wood, a cypress material having a thickness of 5 mm 100 × 100 m
m was dried at 105 ° C. for 8 hours. This wood was not irradiated with plasma, and the above 10 woods were preheated to 100 ° C.
The mixture was placed in the same reaction vessel of 5 liters as in Example 1 heated to 1, and further, in this reaction vessel, as a formaldehyde derivative, trioxane was added at 150 mol / m ³ in terms of formaldehyde monomer to serve as a co-catalyst. As an acid catalyst, ferric sulfate (Fe ₂ (SO ₄ ) ₃ )
0.5 mol / m ^{3 was} added.

Then, the reaction vessel was sealed and the pressure was reduced to 50 torr by a vacuum pump. Next, 5.0 mol / m ^{3 of} sulfur dioxide (SO ₂ ) was introduced as an acid catalyst, and the mixture was held at 100 ° C. for 20 hours for formalization. At that time, the pressure in the final reaction vessel was 600 torr. The residual gas in the reaction vessel was sufficiently exhausted to obtain modified wood.

The impregnation rate and anti-swelling rate (A of the obtained modified wood)
SE) was measured as in Example 1. The results are shown in Table 2.

COMPARATIVE EXAMPLE 2 The same wood as in Comparative Example 1 was subjected to no plasma irradiation,
Modified wood was obtained by performing formalization under the same conditions as in Example 2.

The impregnation rate and anti-swelling rate (A) of the obtained modified wood
SE) was measured as in Example 1. The results are shown in Table 2.

[0035]

[Table 1]

[0036]

[Table 2]

In Example 1 and Comparative Example 1, and in Example 2 and Comparative Example 2, the anti-swelling ratio (A
SE) was good.

[0038]

According to the production method of the present invention, by converting the wood in which radicals are generated by plasma irradiation into formal, the formalization treatment is efficiently performed, the wood texture of natural wood is maintained, and the dimensional stability is improved. Good modified wood is obtained.

[Brief description of drawings]

FIG. 1 is a schematic view of a plasma irradiation processing apparatus used in the present invention.

[Explanation of symbols]

 1 Upper Electrode 2 Lower Electrode 3 Solid Dielectric 4 Wood 5 Processing Tank 6 Insulator 7 High Frequency Power Supply

─────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] November 12, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] 0023

[Correction method] Change

[Correction content]

Conditions for plasma irradiation: Distance between electrodes: 20 mm (used gas and flow rate): Inert gas He: 5000 sccm Reactive gas O _2: 100 sccm Note that sscm is 25 ° C. Flow rate per 1 minute at 1 atm (ml) (plasma condition) ・ Frequency ───10 kHz ・ Treatment time ───1 minute ・ Power ───100 W ・ Treatment pressure ─760 mmHg The above-mentioned wood 10 subjected to plasma irradiation The sheet is placed in a reaction vessel of 5 liters which has been heated to 100 ° C. in advance, and further, in this reaction vessel, as a formaldehyde derivative, trioxane of 150 mol / m ³ in terms of formaldehyde monomer is added to serve as a co-catalyst. As an acid catalyst, ferric sulfate (Fe ₂ (SO ₄ ) ₃ ) 0.5
Mol / m ^{3 was} added.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Satoru Konishi 1048, Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Works Co., Ltd. (72) Kenji Ohnishi, 1048, Kadoma, Kadoma City, Osaka Prefecture 72) Inventor Ryusuke Honda 1048 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Works Co., Ltd.

Claims (8)

[Claims] 1. A wood having a moisture content adjusted to a fiber saturation point or lower is subjected to a plasma irradiation by introducing a gas, and the plasma-irradiated wood is exposed to an acid catalyst in a vapor atmosphere of a formaldehyde derivative. A method for producing modified wood, which comprises heating under a temperature to form a formal. 2. The gas is N ₂ , He, Ar or O.
_2. The method for producing a modified wood according to claim 1, wherein at least one of the _two is used. 3. The method for producing modified wood according to claim 1, wherein at least one of paraformaldehyde, trioxane and tetraoxane is used as the formaldehyde derivative. 4. The method for producing a modified wood according to claim 1, wherein the acid catalyst is at least one selected from the group consisting of sulfur dioxide, chloride, sulfate and borate. 5. The concentration of the formaldehyde derivative is ³⁰ to 300 mol / m ³ in terms of formaldehyde monomer relative to the volume of the reaction vessel, and the molar ratio to the acid catalyst is 10 to 100. The method for producing the modified wood according to any one of claims 1 to 4. 6. When the formalization treatment is completed,
The pressure inside the formalization reactor is 500-2000 torr
The method for producing a modified wood according to any one of claims 1 to 5, wherein 7. A relative volumes of the reaction vessel of wood processing the formalization of any one of claims 1 to 6, characterized in that a 0.01~0.2m ³ / m ³ modified timber Manufacturing method. 8. The processing temperature by the formalization is 90.
It is -120 degreeC, The manufacturing method of the modified wood in any one of Claim 1 thru | or 7 characterized by the above-mentioned.