JP3185665B2 - Method for producing modified wood - Google Patents

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 flame-retarded wood, and more particularly to a method for preventing metal oxides produced in wood from being eluted by the action of water and imparting flame retardancy to wood. The present invention relates to a method for producing semi-permanently modified wood.

[0002]

2. Description of the Related Art When wood is used, its characteristics such as "burning", "rotting" and "out-of-dimension" are disadvantageous, and the use is limited. Often. In particular, Heisei 2
The Building Standards Law was revised in June of the year, and wood can be used for the opening. However, it is necessary to clear the fireproof and flame-insulating standard of 60 minutes for Instep Type and 20 minutes for Type B. It is difficult to exceed this standard even if used as is.

The inventors of the present invention have made intensive studies on the development of wood that has improved these disadvantages. As a result, the wood is impregnated with silicon alkoxide, and silicon oxide is generated and fixed in the wood cell voids by hydrolysis and polycondensation. As a result, a modified wood having excellent flame retardancy, decay resistance, and dimensional stability was found [Journal of the Japan Wood Science Society 38 (11), 1043 (199).
2)]. This production method is based on a metal alkoxide sol-gel method. In a starting solution of a metal alkoxide-water-alcohol-catalyst, the metal alkoxide is converted into a metal oxide sol by hydrolysis and self-polycondensation. The solution is further reacted to form a gel. By performing this reaction in the wood cells, the inorganic composite of the wood with the metal oxide is realized.

However, recent studies have shown that the process of compounding wood with metal oxides depends greatly on the rate of hydrolysis of the metal alkoxide used, and that the distribution of the metal oxides in the wood cells varies greatly depending on the preparation conditions. It became clear. For example, in the mineralization of wood using a silicon alkoxide with a low hydrolysis rate, when the wood used is a humidity control specimen (all water contained in the wood is bound water and exists only in the cell wall), The hydrolysis / polycondensation reaction of the silicon alkoxide proceeds only in the cell wall where the bound water is present, and an inorganic composite wood having a cell cavity is obtained.
This composite wood maintains the light and strong heat-insulating properties of wood, and it maintains the porous properties of wood while providing dimensional stability, flame retardancy, and decay resistance. [Journal of the Japan Wood Science Society 39 (3), 301 (199)
3)]. However, when the wood used is a saturated specimen (water not only in the cell wall but also in the cell cavity),
It has been clarified that silicon-oxide is a mineral-composite wood made of silicon oxide in which not only the cell wall but also the lumen is filled with metal oxide [Journal of the Japan Wood Science Society 39 (3), 301 (1)
993)].

[0005] However, once the metal alkoxide used is changed, an inorganic composite wood having a completely different distribution can be obtained. For example, when a titanium alkoxide having a high hydrolysis rate is used, in a humidity-conditioned specimen, titanium oxide is produced only in the cell lumen, and in a saturated specimen, an oxide is produced only on the outer surface of the specimen. It has been found that the inside of the specimen cannot be complexed with a metal oxide [Journal of the Japan Wood Science Society 39 (3), 308 (1993)].

Further, based on these findings, the relationship between the intracellular distribution of the metal oxide and the function to be imparted is examined. As a result, by selectively complexing the metal oxide in the cell wall, It has been clarified that various functions can be effectively exhibited with a small amount of metal oxide. Examples of such composites include silicon alkoxides, boron alkoxides, and inorganic composite woods made of metal oxides from phosphorus alkoxides.In particular, the latter two are produced by treatment within a range in which the wood is not thermally decomposed. The metal oxide is easily eluted by water and is not stable.

[0007] The metal alkoxide itself has a high vapor pressure and is toxic, so that practical considerations are required.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method for producing modified wood which can prevent metal oxides from being eluted by the action of water and can stably exhibit flame retardancy over a long period of time. The purpose is to provide.

[0009]

Means for Solving the Problems and Embodiments of the Invention The present inventors have conducted intensive studies to achieve the above object, and as a result, a methylsiloxane oligomer containing phosphorus and / or boron in wood, specifically, Is represented by the following average composition formula (1) (CH ₃ SiO _1.5 ) _m (MO _1.5 ) _n (1) (wherein M represents one or more selected from P, PO and B; n is a positive number and m + n = 1, and m: n
Are in the range of 99: 1 to 50:50. )
, Impregnated with a methylsiloxane oligomer solution containing phosphorus and / or boron having a hydroxyl group and / or an alkoxy group having 1 to 4 carbon atoms at the end, followed by hydrolysis or thermal decomposition, and further polycondensation and curing It has been found that by forming a methylsilicone resin containing a nonflammable phosphor oxide and / or boron oxide in a cell wall, it is possible to obtain a modified wood having semi-permanent flame retardancy.

Accordingly, the present invention provides the above-mentioned average composition formula (1)
And a method for producing modified wood characterized by impregnating and curing an oligomer represented by the formula:

That is, in the present invention, the water repellency of the methyl silicone resin prevents the phosphate oxide and / or the boron oxide from being eluted into water, thereby maintaining flame retardancy. Since wood is treated with the oligomer of the above formula (1), it is possible to provide a highly safe and practical wood modification method.

Hereinafter, the present invention will be described in more detail. In the method for producing modified wood according to the present invention, wood is impregnated with a specific methylsiloxane oligomer and cured.

The raw wood used in the present invention is not particularly limited, and includes, for example, raw logs, sawn timber, sliced veneers, plywood, and the like, and the tree species is not limited.

The methylsiloxane oligomer used in the present invention is represented by the following average composition formula (1): (CH ₃ SiO _1.5 ) _m (MO _1.5 ) _n (1)

In the formula (1), M represents one or more selected from P, PO and B. m and n are positive numbers (m + n = 1). In this case, m: n is an average molar ratio of 99: 1 to 50:50, more preferably 95: 5.
７０70: 30. When the molar ratio of m is less than 50 mol, the water repellency of the methyl silicone resin is not sufficient, and a sufficient elution preventing effect cannot be obtained.

The average degree of polymerization of the methylsiloxane oligomer is preferably 2 to 50, particularly preferably 2 to 20. If the average degree of polymerization is less than 2, the vapor pressure of the oligomer becomes high, which may cause a problem in safety. If it exceeds 50, it takes time to impregnate the wood.

The oligomer has a terminal group of a hydroxyl group and / or an alkoxyl group having 1 to 4 carbon atoms.

The above-mentioned phosphorus- and / or boron-containing methylsiloxane oligomer of the formula (1) comprises methyltrialkoxysilane or a partial hydrolyzate thereof, and phosphoric acid, phosphorous acid, trialkyl phosphite, boric acid, boric acid. It can be obtained by a common method of co-hydrolyzing one or more compounds selected from trialkyl acid and the like.

When the above-mentioned methylsiloxane oligomer is impregnated into wood, the wood may be impregnated with the methylsiloxane oligomer as it is, and alcohols such as methyl alcohol and ethyl alcohol, ketones such as acetone and methyl isobutyl ketone may be used. , May be diluted with another solvent for impregnation.

The above-mentioned methylsiloxane oligomer is mixed with a precursor of another metal oxide, for example, tetramethoxysilane, tetraethoxysilane, methylpolysilicate or ethylpolysilicate in order to further enhance the flame retardant effect of wood. May be added. In this case, these precursors may be subjected to co-hydrolysis in addition to methyl trialkoxysilane or a partial hydrolyzate thereof when obtaining the methylsiloxane oligomer. Further, in order to impart more water repellency, a long-chain alkyl trialkoxy silane, perfluoroalkyl trialkoxy silane, or the like may be added by co-hydrolyzing or mixing as described above.

When impregnating wood with the above-mentioned methylsiloxane oligomer solution, it is preferable that the wood is preliminarily conditioned and immersed in the oligomer solution, or a vacuum or pressure injection method is used. However, the wood does not necessarily have to be in a moisture-conditioned state, and the impregnation may be performed in a saturated state, and there is no particular limitation.

Next, the wood impregnated with the methylsiloxane oligomer is dried in a range where the wood is not thermally decomposed, preferably at 50 to 110 ° C. In this process, the oligomer is hydrolyzed, followed by polycondensation and hardens, transforming into a methylsilicone resin containing phosphorus oxides and / or boron oxides. In the hydrolysis step, an acidic catalyst or an alkaline catalyst can be used.

[0023]

EXAMPLES Next, the contents of the present invention will be described in detail with reference to examples and comparative examples, but the present invention is not limited to the following examples.

Example 1 Methyltrimethoxysilane 1
23 g (0.9 mol) and 3.1 g (0.05 mol) of boric acid are placed in a 1-liter flask, and 16 g of a 30% phosphoric acid aqueous solution (0.05 mol as phosphoric acid) are dropped and mixed at 30 ° C. And reacted. After aging at 60 ° C. for 1 hour, a 65% methanol solution of the oligomer was obtained. The solution was further diluted by adding methanol, and 10
% Methanol solution was prepared for the experiment. The average composition formula of this oligomer is (CH ₃ SiO _1.5 ) _0.9 (OPO _1.5 ) _0.05 (BO _1.5 )
_{It was 0.05} , the average degree of polymerization was about 4, and the terminal groups were a methoxy group and a hydroxyl group.

Next, acetone and water were used to prepare 24
Soxhlet extraction for 50 hours, moisture content adjusted to 25% 50
A veneer sample of a hemlock sapwood of mm × 100 mm × 1 mm was impregnated with a methanol solution of the oligomer at room temperature under reduced pressure for 3 days. Thereafter, the specimen was placed at 65 ° C. for 24 hours,
Heat treatment was performed at 5 ° C. for 24 hours for curing to obtain modified wood. The weight increase rate of this modified wood by a silicone resin containing an oxide of phosphorus and boron was 11.3%. Next, 250 ml of distilled water was put into a 300 ml beaker, stirred at 160 ± 3 rpm, and the prepared specimen was put into the beaker and stirred for 4 hours. 7.5% eluted. As a result of measurement using this sample by a thermogravimeter, the residual weight after flaming combustion was 65%, but was 66% in another sample not subjected to the dissolution test. Also,
Untreated wood was 27%.

The physical properties of the modified wood were measured by the following methods. (1) Weight increase rate (WPG) The absolute dry weight (Wu) of an untreated specimen that had been subjected to Soxhlet extraction with acetone and water for 24 hours was determined. next,
After the specimen is made into an inorganic composite, it is dried at 105 ° C. for 24 hours to determine the absolute dry weight (Wt) of the modified wood, and the weight increase rate (WPG) of the modified wood is calculated from the following equation. . WPG (%) = [(Wt−Wu) / Wu] × 100
(%) (2) Elution rate of silicone resin (%) In a 300 ml beaker, add 250 ml of deionized water (water temperature: 20 to 24 ° C), and stir with a magnetic stirrer (160 ± 3 times / min). The modified wood specimen is put therein, and after stirring for 4 hours, the dried specimen is taken out and the absolute dry weight (Wt ′) after drying is determined. Assuming that the weight increase rate of the modified wood after 4 hours of the dissolution test is (WPG '), the dissolution rate of the silicone resin can be calculated from the following equation. Elution rate (%) = [(WPG-WPG ′) / WPG] × 1
00 (%) (3) Residual rate by thermogravimetry (%) Using a thermogravimeter, a TG curve of weight change in the process of raising the temperature of the modified wood is obtained. Here, the weight at 170 ° C. is 100
% And the change in weight is indicated. For example, in untreated wood, flaming combustion corresponds to a sharp weight loss around 350 ° C., and surface burning occurs in the region of 370-550 ° C. The residual rate (%) by thermogravimetry is calculated corresponding to that at the end of flaming combustion.

Example 2 Methyltrimethoxysilane 1
23 g (0.9 mol), 10.4 g of trimethyl borate
(0.1 mol) in a 1 liter flask and 15 g of water
Was added dropwise while stirring at 30 ° C. to cause a reaction. 60
Aging was conducted at 1 ° C. for 1 hour to obtain a 65% methanol solution of the oligomer. Methanol was further added to this solution to dilute it, and a 10% methanol solution of the oligomer was prepared for the experiment. The average composition formula of this oligomer was (CH ₃ SiO _1.5 ) _0.9 (BO _1.5 ) _0.1 , the average degree of polymerization was about 6, and the terminal groups were a methoxy group and a hydroxyl group.

Next, using this oligomer solution, modified wood was obtained in the same manner as in Example 1. Its weight increase was 10.8%. In the dissolution test, 6.8%
Of silicone resin was eluted. As a result of the thermogravimetry test, the residual weight after flaming and burning after the dissolution test was 64%, and even when the dissolution test was not performed, it was 64%.

Example 3 Methyltrimethoxysilane 1
02 g (0.75 mol) and 21 g (0.25 mol) of phosphorous acid are placed in a 1 liter flask and placed in a nitrogen atmosphere at 30 ° C.
And stirred for 5 hours to obtain an 80% methanol solution of the oligomer. Methanol was further added to this solution to dilute it, and a 10% methanol solution of the oligomer was prepared for the experiment. The average composition formula of this oligomer was (CH ₃ SiO _1.5 ) _0.75 (PO _1.5 ) _0.25 , the average degree of polymerization was about 4, and the terminal group was a methoxy group.

Next, using this oligomer solution, modified wood was obtained in the same manner as in Example 1. Its weight increase rate was 11.1%. In the dissolution test, 9.2%
Of silicone resin was eluted. As a result of the thermogravimetric measurement test, the residual weight after flaming and burning after the dissolution test was 63%, and that without the dissolution test was 65%.

[Comparative Example 1] A soybean sapwood (50 m) extracted with Soxhlet for 24 hours using acetone and water, respectively.
(m × 100 mm × 1 mm), a reaction solution consisting of trimethyl phosphite, ethanol and acetic acid (molar ratio 1: 1: 0.01) was added to a 25% water content specimen obtained by controlling the humidity.
For 3 days at room temperature under reduced pressure. Thereafter, the specimen was heat-treated at 65 ° C. for 24 hours and at 105 ° C. for 24 hours to ripen the gel to obtain an inorganic composite wood. The weight increase rate of the composite wood due to the metal oxide was 9.4%. Next, 250 ml of distilled water was put into a 300 ml beaker, stirred at 160 ± 3 rpm, and the prepared specimen was put into the beaker and stirred for 4 hours. % Eluted. As a result of performing thermogravimetry using a thermogravimeter using this specimen, the residual weight after flaming combustion was 55%, but was 67% in another specimen not subjected to a dissolution test.

[0032]

According to the present invention, wood can be treated with a safe oligomer, it is stable without being eluted with water, and can be used for a long time even when exposed to rainwater or dew. Modified wood that maintains the flame retardant effect can be obtained, and the wood is provided with water repellency, and has excellent rot resistance and dimensional stability. Moreover, by implementing the method for producing modified wood according to the present invention, flame-retarded wood that can be used as a member of an opening conforming to the New Building Standard Law or as a building interior material or exterior material can be obtained. It has features such as mass production.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Akira Yamamoto 1-10 Hitomi, Matsuida-machi, Usui-gun, Gunma Prefecture Inside Silicone Electronics Materials Research Laboratory Shin-Etsu Chemical Co., Ltd. (72) Inventor Masayoshi Tanaka Major Chiyoda-ku, Tokyo 2-6-1 cho, Shin-Etsu Chemical Co., Ltd. (56) References JP-A-2-141202 (JP, A) JP-A-4-142901 (JP, A) JP-A-55-101402 (JP, A JP-A-7-150131 (JP, A) JP-A-4-12806 (JP, A) JP-A-5-57707 (JP, A) JP-A-56-4408 (JP, A) JP-A-2- 253902 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) B27K 3/00-3/52

Claims (2)

(57) [Claims] 1. The following average composition formula (1) (CH ₃ SiO _1.5 ) _m (MO _1.5 ) _n ... (1) (1) wherein M is one or more kinds selected from P, PO and B And m and n are positive numbers and m + n = 1, and the average ratio of m: n is in the range of 99: 1 to 50:50.), And the terminal is hydroxyl group and / or carbon number 1 A method for producing modified wood, comprising impregnating and curing a methylsiloxane oligomer containing phosphorus and / or boron, which are alkoxy groups of Nos. 1 to 4. 2. Impregnating the methylsiloxane oligomer, followed by hydrolysis or thermal decomposition, followed by polycondensation,
The method for producing modified wood according to claim 1, wherein the resin is cured to form a methylsilicone resin containing non-combustible phosphorus oxide and / or boron oxide in a cell wall.