JPH0321402A - Manufacture of modified lumber - Google Patents

Abstract

PURPOSE:To improve fire retardant of inflammable lumber, by a method wherein the lumber is heat-treated, pressurization-treated and impregnated with aqueous solutions of aluminum sulfate and calcium halide. CONSTITUTION:A rubber tree is put into a pressure vessel, treated with pressurized saturated steam, equilibrium moisture content of former lumber is made low by 2-4% and hat-treated and pressurization-treated lumber whose rate of anti-expansion is 20-60% is obtained. Then after immersion into a treatment solution obtained by regulating an aqueous solution of aluminum sulfate to pH 12 with sodium hydroxide, the lumber is immersed into a treatment solution of calcium chloride as it is. Then reaction between the aluminum sulfate and calcium halide is advanced during hot curing and the lumber is modified by forming ettringite (sediment).

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a method for producing modified wood that imparts flame retardancy to wood.

Prior Art> There are various treatment methods for imparting flame retardancy to wood. Classified based on the mechanism of decombustion, the outline is as follows.

(a) Coating treatment with inorganic substances (C) Treatment to promote carbonization (C) Treatment to inhibit flaming combustion reactions (d) Treatment to generate nonflammable gas (e) Decomposition ● Treatment to absorb heat by releasing crystallized water (f) Among these treatments, Ettringai} (3)
CaO ●kllOB * 3CaSO4 * nH2
0. It was thought that modified wood with excellent flame retardancy could be obtained by incorporating ettringite (n = 28 to 32).
The above (
IL) The effects of the processing methods of Th and (e) can be expected together. Furthermore, since it is insoluble in water, there is no risk of it leaching out of the wood.

However, it has been found that even if ettringite is dispersed in 11 water and wood is soaked in this dispersed water, it is difficult to infiltrate ettringite into the wood. This is because the opening of the pit membrane in the cell wall pores, which are the narrowest passages for impregnation into wood, is very small.

OBJECT OF THE INVENTION The object of the present invention is to impregnate wood with ettringite by some method, which is to increase the voids of pit membranes in cell wall pores in wood.

DISCLOSURE OF THE INVENTION The present invention discloses that the equilibrium moisture content of original wood is reduced by heating and pressurizing.
A heat-pressure treated wood whose absolute value of <=b> is lowered by 2 to 4 times and whose anti-swelling coefficient is set to 20 to 601 is impregnated with an aluminum sulfate aqueous solution and a calcium halide aqueous solution, and the interior of the wood becomes alkaline. This is a method for producing modified wood, in which the wood is cured after being preserved.

Here, the anti-swelling coefficient is ASE (Anti-Sw
ellingEfficiency) using the following formula.

Do: Expansion coefficient of untreated material D: Expansion coefficient of treated material The heating and pressurizing operation in the present invention is usually carried out using water vapor under the conditions of 120 to 250°C and 2 to 40 hi/c-j. However, the processing time varies depending on the temperature and pressure.
．． 2 kg/d for 8 hours, 210℃, 20k
After 30 minutes of treatment at g/d, the absolute value of the equilibrium water content is about 21 lower, and the anti-swelling coefficient is about 20 centigrade.

Also, 150℃, 5kg/cj for 16 hours or 25
0℃. After treatment at 40 ki/d for 2 hours, the absolute value of the equilibrium water content was about 4 or less, and the anti-swelling coefficient was about 60 or more. If the temperature is below 120°C, the equilibrium moisture content cannot be lowered, and if the temperature is above 250°C, the cells of the wood will be destroyed, resulting in a decrease in strength.

Wood treated under heat and pressure in this way loses weight by approximately 1 (l) due to the elution of hemicellulose with a high equilibrium moisture content in the wood.The wood becomes bolus-like in structure, with more voids corresponding to the amount of hemicellulose eluted. Therefore, the amount of impregnated aluminum sulfate aqueous solution and calcium halide aqueous solution can be increased.

Next, the heat-pressure treated wood is made into approved shapes such as lumber products, sliced veneers, chips, etc., and aluminum sulfate (Al
z (804) 8) Impregnate the wood with an aqueous solution and an aqueous calcium halide solution, and react the aluminum sulfate and calcium halide in alkaline conditions to produce ettringite in the wood.

Calcium chloride (CICA'l) is usually used as the calcium halide, but calcium bromide, calcium iodide, etc. may also be used.Aluminum sulfate aqueous solution and calcium halide aqueous solution are directly mixed. When producing ettringite, it is usually preferable to use aluminum sulfate and calcium halide in a molar ratio of 1:60, so even in the case of a two-stage treatment as in the present invention, the molar concentration ratio is 1:1. It is preferable to set it to 6.

Since ettringite formation or reaction proceeds in alkaline conditions,
It is necessary to keep the reaction system alkaline.

Therefore, the aluminum sulfate aqueous solution is usually made alkaline with sodium hydroxide or the like. and,
Dissolve aluminum in the aluminum sulfate aqueous solution in the form of aluminate ions, and cause a reaction to occur on the alkaline side with the calcium halide aqueous solution r=
It is best to set the pH to 10 or higher, and it is even better to set it to around 11! Impregnation of wood with an aqueous solution as a treatment liquid is carried out by dipping or the like. For air-dried or bone-dry wood, saturation 1
It takes a considerable amount of time to impregnate with an aqueous solution. Therefore, if the wood is saturated with water in advance, such as by steeching, impregnating under reduced pressure, impregnating under pressure, etc., and then the wood is brought into contact with an aqueous solution, such as by soaking, it is possible to combine aluminum sulfate and halogen as a treatment agent. Calcium chloride diffuses quickly through the water in the wood, requiring less soaking time.

During heat curing after impregnation, it is preferable to carry out heat curing at a temperature Jf of 40°C or more for 3 hours or more (for example, curing at 70°C for about 5 hours). During the curing, the reaction between aluminum sulfate and calcium halide progresses to form ettringite (precipitate).

In ettringite, in the treatment method (e) above, decomposition refers to, for example, the release of water by hydroxide etc. according to the following formula.

Ca (OH)2 − CaO + H202Al(O
H) 8 -4kl20s + H20 This reaction is an endothermic reaction. The reaction of releasing water of crystallization is also an endothermic reaction,
Combining a combustible material with a nonflammable inorganic substance capable of undergoing a flame reaction can improve the flame retardancy of the combustible material.

Next, examples will be described.

Example 1, 30°C. Equilibrium moisture content 1 0 1iD5 with all704
When a 0-thick rubber tree was placed in a pressure vessel and treated with saturated steam of 10 #/d at 175°C for 2 hours, the equilibrium moisture content was 6 D and the anti-swelling coefficient was 40 D. Treated wood was obtained.

Next, the wood was made into a 21-thick veneer, the moisture content was adjusted to over 200, and the next treatment solution A. Immersed in B.

Treatment solution A: 1 mol aqueous aluminum sulfate solution adjusted to pH 1-2 with sodium hydroxide. Treatment solution B: 6 mol calcium chloride aqueous solution. After immersing in treatment solution A at 70°C for 6 hours, the wood was left to dry. The case was immersed in treatment solution B and left at 70°C for 12 hours.Comparative Example 1, Example 1 was treated in the same manner as in Example 1, except that a 2fl thick veneer of rubber tree to be heat-pressure treated was used. .

Next, the impregnation rate (the following formula) and the anti-swelling coefficient (ASE, the above formula) of the treated wood according to Example 1 and Comparative Example 1 were measured, and the results were as shown in Table 1.

Impregnation rate = (A-B)/B A: Absolute dry weight after treatment B: Absolute dry weight before treatment 1st Effect of the invention> Table 1 b1 The heat and pressure treated wood of the present invention was treated with an aluminum sulfate aqueous solution and When impregnated with a calcium halogonide aqueous solution, both the impregnation rate and the anti-swelling coefficient are higher than when untreated wood is impregnated, and modified wood with excellent flame retardancy and dimensional stability can be obtained.

Therefore, the modified wood obtained according to the present invention is useful as a wood material for building construction materials, furniture, fittings, etc., which require flame retardancy and dimensional stability.

Claims (1)

[Claims] (1) The equilibrium moisture content (%) of the original wood is
) by 2 to 4% and the anti-swelling rate to 20 to 4%.
The method is characterized by impregnating heat-pressure-treated wood with an aluminum sulfate aqueous solution and a calcium halide aqueous solution to maintain an alkaline inside of the wood, and then curing the wood. A method for producing modified wood.