JPH0647712A - Composition for modifying wood - Google Patents

Abstract

PURPOSE:To improve dimensional stability, resistance to rotting, mechanical characteristics and the like without losing the wood texture feeling of material wood by a method wherein composition consisting of low molar ratio Novolak- type phenolic resin, the specified amount of hixamethyleneteramine and methanol-containing aqueous solution is infiltrated in wood and hardened. CONSTITUTION:Low molar ratio Novolak-type phenolic resin is obtained by condensing 0.1-0.4mol of formalin to 1mol of phenol by employing oxalic acid as catalyst until the amount of residual formalin becomes too small to be detected so as to employ 2.5-4.5 pts.wt. of hexamethylenetetramine to 10 pts.wt. of the above-mentioned resin. As solvent, 75-95wt.% of 10-50% methanol- containing water is employed. Further, in order to shorten the hardening time, 1-10wt.% of acid compound to Novolak, preferably weak acid substance and more preferably acid, which can be decomposed by heat, such as oxalic acid may well be employed.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION This invention relates to wood modifying compositions. More specifically, the present invention relates to a modified composition for modified wood that imparts dimensional stability, decay resistance, mechanical properties, and the like to wood used for civil engineering, building materials, railways, and the like.

[0002]

2. Description of the Related Art Conventionally, wood has been used in various fields depending on its characteristics, but due to the original characteristics of wood,
Its use was limited to fields requiring water resistance, decay resistance, mechanical properties, etc.

As a method of improving the drawbacks, a low molecular weight resol type phenol resin (hereinafter referred to as resole) is impregnated into a single plate, dried, laminated, and hot pressed at high temperature and high pressure.
A general method is a method of obtaining a cured laminated material, a method of injecting the resin into a raw material and heat-treating at a high temperature to obtain a resin injection treated material. Further, a method has also been proposed in which a two-liquid type of formalin source and phenols is mixed, and either one or both of them is mixed with an alkaline catalyst, which is sequentially impregnated and reacted in wood. Furthermore, the present inventor previously proposed a two-liquid type of hexamethylenetetramine and phenols, which was sequentially impregnated to form a complex in the wood and then immobilized,
There are methods such as heating reaction.

When resole is used as a resin for injection, a method of decreasing the viscosity of the resole in order to increase the impregnation rate is to add an alkaline substance such as caustic soda to the resole to increase the water dilution rate. In this case, the alkaline substance used not only deteriorates the mechanical strength of wood, but also has a problem of coloring due to residual alkali, so that the field of use has been limited. Further, since the alkaline resole is rich in self-condensation property, it is difficult to reuse the solution once used because of its remarkable change with time, and there is a problem from the economical aspect. In addition, since formalin remains during the production of the resole, a formalin odor is generated during drying or curing, which causes a problem that environmental measures must be taken.

The other two-liquid type method has a problem that the impregnation step becomes complicated.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to improve the dimensional stability, decay resistance, mechanical properties, etc. of wood without changing the texture of wood raw materials. To provide a quality composition.

[0007]

Means for Solving the Problems As a result of intensive studies to solve the above-mentioned problems, the present inventor did not use an alkaline resol, but instead used a novolak-type phenol resin condensed at a low molar ratio with hexahexanone. It has been found that the above problems can be solved all at once by using a composition that cures in wood using methylenetetramine as a curing agent, and completed the present invention.

That is, according to the present invention,
Formalin 0.1 to 0.4 mol, a low molar ratio novolac type phenolic resin 5 to 25% by weight, and 2.5 to 4.5 parts by weight of hexamethylenetetramine with respect to 10 parts by weight of the novolac type fail resin. A wood-modifying composition comprising 10 to 50 parts by weight of a methanol-containing water solvent of 75 to 95% by weight. Moreover, it is the said wood improvement composition which mix | blended an acidic compound as a hardening catalyst.

The present invention will be described in detail below. First, the low molar ratio novolac type phenol resin used in the present invention (hereinafter simply referred to as novolac) is 0.1 mol of formalin to 0.1 mol of phenol, and oxalic acid is used as a catalyst to remove residual formalin. It is obtained by conducting a condensation reaction until it becomes undetectable. After completion of the condensation reaction, dehydration treatment may be performed under reduced pressure, or the water may be left as it is. The obtained novolak has an average molecular weight of 100 to 3
It is a liquid novolac of about 00. If the amount of formalin is less than 0.1 mol with respect to 1 mol of phenol, unreacted phenol monomer forms a complex with hexamethylenetetramine (hereinafter referred to as hexamine) to cause white precipitation and cannot be liquefied. On the other hand, if the content of formalin exceeds 0.4 mol, the water solubility of novolak is almost lost, and the required amount of methanol as a solvent increases, which is not preferable from the economical and harmful viewpoint.

Hexamine is used in an amount of 2.5 to 4.5 parts by weight, preferably 3 to 4 parts by weight, based on 10 parts by weight of the novolak.

If the amount of hexamine is less than 2.5 parts by weight with respect to 10 parts by weight of novolac, the resin curing reaction is insufficient, and if it exceeds 4.5 parts by weight, the amount of formalin source is more than sufficient for the crosslinking reaction of novolac. , Economically meaningless. The solvent used in the present invention is a water solvent containing 10 to 50% methanol, and the amount used is 75 to 95% by weight. When the methanol-containing water solvent is less than 75% by weight, the resin concentration becomes high and the resin impregnation is not uniformly impregnated in the whole wood,
On the other hand, if it exceeds 95% by weight, the resin concentration becomes too low and the impregnation rate of the resin decreases. The resin concentration of the solution used in this way is related to the resin impregnation rate in wood and is appropriately determined according to a predetermined impregnation rate. The content of methanol in the solution is used to uniformly dissolve the low molecular weight phenolic resin in water. If the content of methanol is less than 10%, it is difficult to uniformly dissolve the resin in the solvent, which is not preferable. If it exceeds, it is not preferable in terms of economy. Also, as an advantage of using methanol as a solvent, after impregnating wood,
The volatilization of methanol first makes the resin insoluble in water, so that the resin is fixed in the wood when the water is dried, and a uniform impregnation state can be maintained.

Next, since the curing reaction of the present invention uses hexamine as the curing agent, ammonia generated during the decomposition reaction of hexamine acts as a catalyst for the curing reaction and can be performed without a catalyst, but further curing time is required. For the purpose of shortening, acid compounds such as hydrochloric acid, oxalic acid, and phosphoric acid are added to the novolak in an amount of 1 to 1
Although 0% by weight may be used, a weakly acidic substance is preferable, and an acid such as oxalic acid which can be decomposed by heat is preferable. In the case of a strong acid catalyst, the curing speed can be increased, but there are problems such as deterioration and discoloration of wood due to the residual catalyst,
Not preferable.

In order to modify wood using the wood modifying composition of the present invention, various impregnation methods such as reduced pressure impregnation, normal pressure impregnation, and heating and pressure impregnation are possible. Is used to impregnate the wood with the wood-modifying composition, and then air-dry or pre-dry at a low temperature of 60 ° C. or lower. At this time, first, the methanol in the composition evaporates, the novolac becomes insoluble and fixed in the wood, and the resin is uniformly contained in the wood.

The impregnation time is several tens of minutes to several tens of hours, the processing pressure is 30 mmHg to 10 kg / cm ² , and the processing temperature is room temperature to 70 ° C. Since the impregnation conditions differ depending on the type of wood, it is preferable to select appropriate conditions depending on the type of wood.

Then, the pre-dried resin-impregnated wood is mixed with 10
The mixture is placed in a hot-air dryer at 0 to 150 ° C. and cured by reaction. The reaction time is several hours to several tens hours, and can be appropriately changed depending on the presence or absence of the reaction catalyst and the size and thickness of the wood. When the reaction temperature is low, the reaction time becomes long and it is not practical. On the other hand, if the reaction temperature is too high, the composition of wood may be adversely affected, which is not preferable.

The resin impregnation rate for wood varies depending on the intended use, but in order to modify physical properties such as dimensional stability and decay resistance, it is 5 to 40% by weight (impregnated resin amount / untreated wood weight × 100). Is preferably adjusted so that

[0017]

The conventional method of impregnating a resole type phenolic resin with a wood is not only long injecting time and curing time but also high in cost, but also has problems in physical properties such as deterioration and discoloration of wood due to residual catalyst. was there. Also, 2
In the case of the liquid type, there is also a problem that the impregnation step becomes complicated. With the composition according to the invention, the injection time is reduced to a fraction of that of the prior art due to the extremely low viscosity of the injected solution. Also, the curing time is reduced to a fraction of that of the resole reaction due to the hexamine-novolak reaction, and the manufacturing cost can be reduced. Further, since there is no catalyst used or its degradability, the deterioration of the properties of the wood can be minimized without causing a chemical change to the structure of the wood, and the discoloration of the phenol resin can also be prevented. In addition, since the nitrogen compound is contained in the skeleton of the cured product of the novolac produced in the present invention, not only is it more effective in preventing discoloration of the resin, but also the resin itself has high water repellency and moisture absorption. Modified wood with excellent characteristics can be obtained.

[0018]

EXAMPLES Examples of the present invention will be described below, but the present invention is not limited to these examples. (Production Example 1) Phenol 1 was added to a 20-liter phenol reaction kettle.
0 kg, 2.5 kg of 37% formalin (molar ratio of about 0.3) and 100 g of oxalic acid were added, and the mixture was reacted under reflux for 5 hours. After the reaction was completed, it was confirmed that formalin was not detected.
This resin was used as an impregnating resin. (Production Example 2) The amount of 37% formalin in Production Example 1 was 0.9 kg.
An impregnating resin was obtained in the same manner except that the molar ratio was changed to about 0.1.

Example 1 Novolak for impregnation 2.8 kg,
Hexamine 1 kg, water 11 kg, methanol 8 kg, oxalic acid 0.
An impregnation solution was prepared by mixing and dissolving 1 kg. Viscosity is 5 cp /
It was 20 ° C. 100 mm for impregnating machine that can heat under reduced pressure
A cedar material having a diameter and a length of 500 mm was put in, depressurized to 650 mmHg and deaerated for 2 hours, then the prepared impregnating solution was put in, and then pressurized to 10 kg / cm ² to impregnate for 5 hours. The weight after impregnation was about 3 times the weight of the cedar wood before treatment. Remove the above impregnated cedar wood from the impregnation machine and set the temperature to 30
℃ humidity 40% in the atmosphere of cedar wood before treatment,
It was left until it became about 1.5 times. Then, it was placed in a hot air dryer at 130 ° C. and reaction-cured for 8 hours to obtain a phenol resin-treated modified cedar material.

(Example 2) 4.2 kg of novolak for impregnation,
Hexamine (1.2 kg), water (13 kg), methanol (6 kg) and oxalic acid (0.1 kg) were mixed and dissolved to prepare an impregnation solution. Viscosity 7
It was cp / 20 ° C. 10 for impregnating machines that can heat under reduced pressure
Put cedar wood with 0 mm diameter and 500 mm length, depressurize to 650 mmHg and degas for 2 hours, then add the prepared impregnation solution,
Then, the pressure was increased to 10 kg / cm ² and impregnation was performed for 5 hours. The weight after impregnation was about 3 times the weight of the cedar wood before treatment. (Example 3) Novolak for impregnation 2.8 kg, hexamine 1
An impregnation solution was prepared by mixing and dissolving Kg, 14 kg of water, and 5 kg of methanol, and a phenol resin-treated modified cedar material was obtained in the same manner as in Example 1. The cedar material subjected to the impregnation treatment was taken out from the impregnation machine and left in an atmosphere of a temperature of 30 ° C. and a humidity of 40% until the weight became about 1.5 times the weight of the cedar material before the treatment.
Then, it was placed in a hot air dryer at 130 ° C. and reaction-cured for 8 hours to obtain a phenol resin-treated modified cedar material.

COMPARATIVE EXAMPLE 1 Resol was condensed with a catalyst having a molar ratio of phenol to formalin of 1: 1.2 and caustic soda of 2%. The molecular weight was 185, and a product having a concentration of 60% containing 10% of unreacted phenol was obtained. To this product, 10% caustic soda and 100% water were added to obtain a resol for injection prepared to have a concentration of 30% and a viscosity of 40 cps / 20 ° C. The surface of the impregnated cedar material treated with the cedar material under the same impregnation conditions as in Example 1 was washed with methanol in an impregnating machine capable of heating under reduced pressure and pressure, and water was adjusted to 130 ° C.
By carrying out reaction curing for 8 hours, a modified resin-impregnated wood was obtained. The molecular weight of the resole after the impregnation is 310,
The viscosity changed with time to 250 cps / 20 ° C. and it was difficult to reuse. (Comparative Example 2) Phenol monomer and hexamine were mixed with 3
It was mixed with a 0% aqueous solution of methanol, but white precipitation occurred and it did not become a solution. (Comparative Example 3) A novolak resin having a molar ratio of 0.6 mol was produced and mixed with a 50% aqueous methanol solution, but it could not be completely dissolved. (Comparative Example 4) A phenol resin-treated modified cedar material was obtained in the same manner as in Example 1 except that the amount of hexamine was changed to 0.4 kg. Table 1 shows the impregnation effect conditions and physical properties of Examples 1 to 3 and Comparative Examples 1 to 4.

[0022]

[Table 1]

[0023]

EFFECTS OF THE INVENTION When the composition of the present invention is used, it is a low-viscosity solution that can be easily injected into wood, and the curing reaction is completed in a short time due to the hexane-novolak reaction, which is dried and reaction-cured. As a result, modified wood with improved dimensional stability, decay resistance and mechanical properties of wood can be obtained at low cost, and there is little discoloration. The economic effect is extremely remarkable.

Claims (2)

[Claims] 1. Formalin 0.
1 to 0.4 mol of a low molar ratio novolac type phenolic resin 5 to 25% by weight, and the novolac type phenolic resin 10
A wood-modifying composition comprising 2.5 to 4.5 parts by weight of hexamethylenetetramine and 10 to 50% by weight of a methanol-containing water solvent of 75 to 95% by weight. 2. The wood-modifying composition according to claim 1, which comprises an acidic compound as a curing catalyst.