JP2007145896A - Coating liquid for wood surface and method for treating wood surface - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a coating liquid for the wood surface affording a coated film for the wood surface having excellent water repellency/water resistance, stable to ultraviolet light, etc., and having good durability. <P>SOLUTION: The coating liquid for the wood surface comprises a silane compound and a catalyst for curing and/or solidifying the silane compound as principal components. The silane compound is represented by formula (1) (wherein, R<SP>1</SP>, R<SP>2</SP>and R<SP>3</SP>are each a hydrogen atom or a 1-4C alkyl group which may each be same or different; R<SP>4</SP>is a 1-10C alkyl group, a 1-10C alkenyl group or a phenyl group which may contain a halogen atom or an epoxy group in the group; and n is 2-10). <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a wood surface coating solution capable of imparting good water repellency and durability to a wood surface, and a method for treating the wood surface using the same.

  Wood is a natural material and has been used for building materials and furniture. In particular, the significance of its existence has been increasing more and more now that the interest in the environment is increasing.

  When using wood for building materials, furniture, etc., surface treatment (surface coating) is required to enhance durability. Of course, the surface of the wood itself may be important without surface treatment. However, when water is applied to the surface of the wood, the water penetrates into the wood, resulting in the decay of the wood, which makes it unusable for long-term use. In addition, it is known that when water penetrates into the wood, mold or the like grows inside the wood, causing the durability of the wood to deteriorate. Therefore, surface treatment (surface coating) of wood is required (Non-Patent Document 1).

  Conventionally, urethane resins, acrylic resins, epoxy resins, and the like have been used as such surface treatment agents (paints). Since these resins are organic polymers, they exhibit sufficient water repellency. However, when organic polymers are applied to the surface of wood, the natural texture is lost from the surface.

  In addition, organic paints may burn when fire approaches and generate harmful gases. In addition, there is a problem of formaldehyde generation, and there are many safety problems.

  As a paint for solving such a problem, there is a paint derived from a natural product. Since this material uses natural oily physical properties as a raw material, it is possible to leave a natural texture, and it is an environmentally friendly paint that does not generate formaldehyde.

  However, it has been pointed out that the oily material of the raw material is not fixed on the surface of the wood, so that it leaches out when exposed to rain outdoors for a long time and cannot withstand long-term stable use. Moreover, when the surface is rubbed, it will detach | desorb, and it is pointed out also from this point that long-term stability is bad.

  As described above, the organic paint is excellent in water repellency and water resistance for a short period of time, but has a problem of poor weather resistance and poor long-term stability (durability).

  On the other hand, a siloxane bond (≡Si—O—Si≡) with high heat resistance and weather resistance is applied for the purpose of providing a coating film having high heat resistance and excellent long-term stability (durability). A polysiloxane-based resin coating material contained in a film has been developed.

  For example, a method of applying a clear paint containing a moisture curable polysiloxane resin is disclosed (Patent Document 1). Since this material contains a polysiloxane resin, it does not change from a resin coating that covers the entire surface so far, and there is a risk of impairing the porosity and moisture (humidity) adjustment function inherent to wood. .

Further, a solvent-free room temperature curable organosiloxane composition is disclosed (Patent Document 2). This is a ternary mixed solution composed of a liquid organopolysiloxane, a crosslinking agent and a curing catalyst. The purpose of this coating solution is to provide a coating film excellent in heat resistance such as non-flammability and flame retardancy, so that it contains 50% by weight or more of SiO ₂ component having high heat resistance. Mandatory. For this reason, the obtained coating film becomes hard, and when it exists on the wood surface for a long time, the coating film is cracked due to the expansion and contraction of the wood surface, and there is a possibility that the water resistance is lowered.

  In addition, it is characterized by impregnating a treating agent composed of a modified polysiloxane resin having a ladder structure and then performing a curing treatment to prevent the occurrence of mold, moss, etc. on the inorganic substrate or the wood surface. A pollution prevention method is disclosed (Patent Documents 3 and 4).

  The purpose of the coating solution made of a modified polysiloxane resin with a ladder structure is to prevent the occurrence of mold and moss on the wood surface, etc. It is a high condensate polymer compound having a molecular weight of 30 to 80 or an average molecular weight of 500 to 100,000. For this reason, this also does not change from the resin paint that covers the entire surface so far, and there is a possibility that the porosity and moisture (humidity) adjustment function inherent to the wood may be impaired.

  Recently, the so-called sol-gel method is applied to apply flame resistance and ant-repellency to wood by applying or impregnating siloxane bonds to the wood surface, which is thermally stable, that is, highly durable. Has been developed (Non-Patent Document 2).

In this technique, tetraalkoxysilane (Si (OR) ₄ ) which finally becomes an inorganic compound when completely reacted is infiltrated from the wood surface. The reason for impregnating the inorganic compound is to provide flame retardancy. Therefore, there remains a problem that the water repellency and water resistance of the surface are not sufficient.

  In addition, flame retardant properties are imparted in the same manner by applying colloidal silica (colloidal silica) to the wood surface (Non-patent Document 3). There remains a problem with poor performance.

  These inorganic coating materials are sufficient for the purpose of imparting flame retardancy, but the problem remains that water repellency, which is a characteristic of inorganic materials, is poor. In addition, since inorganic compounds are inflexible, it has been pointed out that when wood repeatedly expands and contracts for a long time, it peels off.

JP 9-94524 A JP-A-5-247347 JP-A-9-132733 JP-A-9-132756 15th Wood Painting Seminar, Proceedings P1, November 19, 2004, Wood Painting Study Group Wood industry, vol. 50 (No. 9), 400 (1995) Wood preservation, vol. 22, 254 (1996)

  The present invention has been made for the purpose of improving the problems of these conventional techniques, solves the problems of these organic paints and inorganic paints, has excellent water repellency and water resistance, and is resistant to ultraviolet rays and the like. An object of the present invention is to provide a wood surface coating film that is stable and has good durability.

  In order to achieve the above object, the present inventor conducted extensive research and applied a catalyst for polymerizing the silane compound represented by the following formula (1) to the surface of the wood. As a result of curing and solidification, water repellency and water resistance were imparted not only to the surface of the wood but also to the inside of the wood, and as a result, it was found that durability could be imparted, thereby completing the present invention.

（式（１）において、Ｒ^１、Ｒ^２及びＲ^３は、それぞれ同一又は異なってもよい、水素原子又は炭素数が１〜４のアルキル基であり、Ｒ^４はこれらの基内にハロゲン原子又はエポキシ基を含んでもよい、炭素数が１〜１０のアルキル基、アルケニル基又はフェニル基であり、ｎは２〜１０である） That is, the present invention provides the following wood surface coating liquid and wood surface coating method.
[1] A wood surface coating solution containing a silane compound represented by the following formula (1) and a catalyst for curing and / or solidifying the silane compound as main components.

(In the formula ^{(1), R 1, R} 2 and ^{R 3,} each of which may be the same or different, a hydrogen atom or a carbon number from 1 to 4 alkyl groups, ^{R 4} is a halogen atom in these groups Or an alkyl group having 1 to 10 carbon atoms, an alkenyl group or a phenyl group which may contain an epoxy group, and n is 2 to 10)

[2] The wood surface coating solution according to the above [1], wherein the content of the silane compound represented by the formula (1) is 20 to 75% by weight.

[3] The wood surface coating solution according to any one of the above [1] to [2], wherein the catalyst for curing and / or solidifying the silane-based coating solution is a hydrolyzable organometallic compound.

[4] The wood surface coating solution according to the above [3], wherein the hydrolyzable organometallic compound is an alkoxide of one or more metals selected from the group consisting of titanium, zirconium and aluminum.

（式（２）中、Ｒ^５及びＲ^７は、それぞれ同一又は異なっていてもよい、水素原子又は炭素数１〜１０のアルキル基又はアルケニル基であり、Ｒ^５Ｏ及びＲ^７ＯとＳｉとの結合はシロキサン結合であり、Ｒ^６及びＲ^８は、その基内にエポキシ基又はグリシジル基を含んでいてもよい、炭素数が１〜１０のアルキル基、アルケニル基又はフェニル基である。） [5] The wood surface coating solution according to any one of [1] to [4], further comprising a silane compound represented by the following formula (2).

(In the formula (2), R ⁵ and R ⁷ are each a hydrogen atom, an alkyl group having 1 to 10 carbon atoms or an alkenyl group, which may be the same or different, and R ⁵ O, R ⁷ O, and Si; Is a siloxane bond, and R ⁶ and R ⁸ are an alkyl group, an alkenyl group or a phenyl group having 1 to 10 carbon atoms, which may contain an epoxy group or a glycidyl group in the group.

[6] The wood surface coating solution according to any one of [1] to [5], further containing a silane compound represented by the following formula (3).
Si (OR ⁹ ) ₄ (3)
(In Formula (3), R ⁹ is a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, which may be the same or different.)

[7] A wood surface treatment method including a step of applying the wood surface coating liquid according to any one of [1] to [6] to a wood surface.

The present invention provides a wood surface coating solution capable of imparting good water repellency and water resistance to a wood surface.
The wood surface coating solution of the present invention is excellent in film-forming properties, that is, enables surface treatment that can maintain the water repellency and water resistance of wood for a long period of time.
According to the present invention, a highly durable protective coating can be formed without impairing the natural texture of the wood surface.

  Hereinafter, the present invention will be described in detail.

1. Wood surface coating liquid The wood surface coating liquid of the present invention (hereinafter sometimes referred to as the coating liquid of the present invention) is a silane (silicon) compound represented by the above formula (1) (hereinafter referred to as silane compound (1)). And a catalyst for curing and / or solidifying the silane compound as a main component.

Specifically, the silane compound (1) represented by the above formula (1) has three hydrolyzable substituents (R ¹ O, R ² O and R ³ O) and one non-hydrolyzable. It is characterized by having a substituent (R ⁴ ) in the molecule.

Here, the role of the ^three hydrolyzable substituents (R ¹ O, R ² O, and R ³ O) reacts with water, undergoes hydrolysis / condensation polymerization as shown in the following reaction formula 1, It is to form a strong three-dimensional siloxane bond (≡Si—O—Si≡) network.
Reaction formula 1;
(1) ≡Si—OR + H ₂ O → ≡Si—OH + ROH
(2) ≡Si—OH + HO—Si≡ → ≡Si—O—Si≡ + H ₂ O
(3) ≡Si—OH + RO—Si≡ → ≡Si—O—Si≡ + ROH
(In Reaction Scheme 1, OR corresponds to OR ¹ , OR ² or OR ³ )

  The bond energy of the siloxane bond obtained here is 106 kcal / mol. On the other hand, the binding energy of the C—C bond, which is a typical bond of an organic compound, is 82.6 kcal / mol. Therefore, the coating film having a siloxane bond, which is generated by hydrolysis / condensation polymerization of the silane compound (1), is much more thermally stable than a coating film derived from an organic compound. I understand that. The coating film formed by this thermally stable bond is excellent in heat resistance and wear resistance, and as a result, it is possible to produce a coating film excellent in heat resistance and wear resistance.

The role of one non-hydrolyzable substituent (R ⁴ ) is to impart water repellency to the obtained coating film. For this purpose, R ⁴ is preferably an alkyl group such as a methyl group, an ethyl group, a propyl group, or a butyl group, an alkenyl group, a phenyl group, or the like, and it contains a substituent such as a halogen atom or an epoxy group in the group. You may go out. By containing a halogen atom, the formed coating film has the advantage of exhibiting flame retardancy, but on the other hand, it may have an adverse effect on the environment and its use is limited.

  Thus, the role of one non-hydrolyzable substituent is to impart water repellency to the obtained coating film, but also has an effect of imparting flexibility to the coating film.

Since silicon is a tetravalent element, four siloxane bonds are formed when tetraalkoxysilane (Si (OR) ₄ ) having four hydrolyzable substituents is used. Since this bond is strong, there is no flexibility, it cannot withstand the shrinkage / expansion caused by the temperature difference of the wood, etc. that occurs after coating, and the coating film is often cracked, which causes a decrease in durability.

  In addition, since such tetraalkoxysilane is a completely inorganic substance, it has a poor compatibility with organic wood, and the adhesion strength between the wood / coating film is low and peeling is likely to occur. As described above, when a tetraalkoxysilane having four commonly hydrolyzable substituents is used, the coating film is easily cracked or peeled off, and a highly durable coating film cannot be obtained. .

The silane compound (1) used in the present invention has one non-hydrolyzable substituent (R ⁴ ) in its molecule. That is, when polymerized, a portion not associated with the bond remains in the network. As a result, the number of strong siloxane bonds between the adjacent silicon atoms is insufficient, but the unreacted bonds remain in the form of “dangling”. Thus, the obtained coating film exhibits flexibility. The flexibility of the coating film relieves stress caused by contraction and expansion of the wood, and plays a role in preventing cracks in the coating film.

  Therefore, the silane compound (1) used in the present invention needs to have three hydrolyzable substituents and one non-hydrolyzable substituent in the molecule. .

  Specific examples of such a silane compound (1) include methyltrimethoxysilane, ethyltrimethoxysilane, propyltrimethoxysilane, butyltrimethoxysilane, methyltriethoxysilane, ethyltriethoxysilane, propyltriethoxysilane, and butyl. Triethoxysilane, methyltripropoxysilane, ethyltripropoxysilane, vinyltrimethoxysilane, phenyltrimethoxysilane, γ- (methacryloxypropyl) trimethoxysilane, γ-glycidoxypropyltrimethoxysilane, aminopropyltrimethoxysilane , Β- (3,4 epoxycyclohexyl) ethyltrimethoxysilane, methyltriethoxysilane, ethyltriethoxysilane, propyltriethoxysilane, vinyltriethoxysilane, phenyl Reethoxysilane,-(methacryloxypropyl) triethoxysilane, γ-glycidoxypropyltriethoxysilane, aminopropyltriethoxysilane, vinyltris (βmethoxyethoxy) silane, etc., and condensates of about 2 to 10 molecules thereof Can be illustrated. In addition, the silane compound (1) may be a product obtained by condensing only one kind of such monomers, or may be a product obtained by condensing two or more kinds of the above exemplified monomers. Such a silane compound (1) may be used alone or as a mixture of two or more.

Here hydrolyzable substituent ^(R 1 O, ^{R 2} O and ^R 3 O), according to reaction with the water of the reaction formula 1 (1) to (3), eventually siloxane bond (≡Si -O-Si≡). Among these reactions, the reaction of the formula (1) is the slowest reaction (rate-limiting step), and it is important that the reaction of the formula (1) proceeds quickly. In order to make the reaction of formula (1) proceed rapidly, an acid catalyst and reaction water are usually added and the treatment is carried out at a high temperature.

  When an acid catalyst is used, the reaction starts when water and an acid are added to the reaction solution. When coating on the wood surface, fine colloidal silica is already generated in the coating solution. Since this material is colloidal, it does not penetrate into the wood surface, and is applied only to the wood surface or a portion close to the surface. Accordingly, even if such a colloidal silica solution is used, a sufficiently durable coating film having water resistance cannot be obtained.

  Moreover, since the acid catalyst contained in the reaction solution significantly accelerates the deterioration of wood, the use of an acid-containing coating solution is limited.

  In the present invention, the silane compound (1) that easily penetrates into the interior from the surface of the wood reacts with the water in the interior to cause a condensation / polymerization reaction on the spot, and a siloxane-bonded polymer grows from the interior of the wood. Assumes that As a result, the polymer is filled up to the details inside the wood, and the intrusion of water can be effectively suppressed. Therefore, the silane compound (1) used in the present invention needs to have a small molecular weight to some extent. Considering the penetrability into the wood, the monomer (monomer) is optimal. However, the monomer has a high vapor pressure, that is, it easily evaporates and scatters, and is difficult to handle. It is preferable to use an oligomer, that is, an oligomer having n = 2 to 10. Thereby, the objective of improving the permeability to the inside of wood can be achieved.

In addition, although such a silane compound (1) reacts with water to form a siloxane bond, in the present invention used as a wood treating agent, as a catalyst for accelerating the reaction, from the above problems, acid No catalyst was added. In the present invention, instead of the acid catalyst, a catalyst capable of proceeding with the hydrolysis and condensation / polymerization reaction of the silane compound (1) immediately upon encountering water is used. As such a catalyst, a hydrolyzable organometallic compound is used.
As the organometallic compound, for example, a metal alkoxide is used. Examples of the metal alkoxide used for such purpose include metal alkoxides such as aluminum, titanium, and zirconium.

More specifically, tetrapropoxy titanate, tetrabutoxy titanate, tetrapropoxy zirconate, tetrabutoxy zirconate, tripropoxy aluminate, aluminum acetylacetonate and the like can be exemplified.
Taking a titanium alkoxide as an example, the reaction of the silane compound (1) proceeds as follows.

Reaction formula 2;
(4) ≡Ti—OR + H ₂ O → ≡Ti—OH + ROH
(5) ≡Ti—OH + RO—Si≡ → ≡Ti—O—Si≡ + ROH
(In Reaction Formula 2, OR represents OR ¹ , OR ² or OR ³ )

As described above, when the coating liquid of the present invention containing the metal alkoxide and the silane compound (1), which easily reacts with water, is applied to the wood surface, both liquids penetrate into the wood, and the water and the metal present inside the wood. The alkoxide first reacts ((4) in the reaction formula 2), and the decomposed metal alkoxide reacts with the silane compound (1) ((5) in the reaction formula 2) to form a polymer from the inside of the wood. As a result, a film having a strong adhesive force with the wood structure is obtained on the wood surface. Thereby, a coating film with high water resistance can be formed. On the other hand, the durability of the coating film can be further improved by the water repellency and flexibility derived from the substituent (R ⁴ ) that is not involved in the reaction.

  The catalyst content in the coating liquid of the present invention is the molar ratio (M / Si) of the silicon atom in the silane compound and the metal atom (M) in the metal alkoxide, usually M / Si = 0.001 to 0. .1, preferably 0.005 to 0.05. When the catalyst content (M / Si) is less than 0.001, the reaction does not proceed in a short time, so that the reaction is not performed for a long time, that is, a wet state, not only the workability is poor, but also the strength of the film. May cause a drop. On the other hand, if it exceeds 0.1, the reaction between the silane compound and the metal alkoxide becomes non-uniform (the metal alkoxides react first), and the balance of the silicon atoms and metal atoms in the coating film becomes poor, and the film strength It may cause a decrease in

  The coating film formed on the surface of the wood in this way is not a polymer coating layer that exists only on the surface of the wood, but actually enters from the surface to the inside of the wood, where the fine coating of the wood is present. Plays the role of filling holes. Therefore, unlike a conventional coating solution, only a thin coating film (coat layer) exists on the surface of the wood, and as a result, the natural texture of the wood can be left without being impaired. That is, surface treatment that imparts water repellency and durability can be performed without impairing the humidity adjustment function and texture inherent to wood.

The content of the silane compound (1) used in the coating solution of the present invention in the coating solution should be appropriately selected depending on the purpose of coating and the surface state of the wood, but it penetrates into the interior of the wood. In consideration of easiness, it is usually 20 to 75% by weight, preferably 25 to 60% by weight with respect to 100% by weight of the total weight of the coating liquid. If the content of the silane compound (1) is less than 20% by weight, the obtained coating film may be too thin, and performance such as water repellency and durability may not be sufficiently exhibited. On the other hand, when it is more than 75% by weight, the obtained coating film is too thick and the performance such as water repellency is improved, but there is a possibility that cracking may occur.
In addition, when a coating liquid contains the organic solvent mentioned later, content of the silane compound (1) in 100 weight% of solid content whole quantity of a coating liquid is 10-99 weight% normally, Preferably it is 30-98 weight%. It is.

  As described above, the silane compound (1) may be used alone or in combination of two or more. In the present invention, a coating solution containing only the silane compound (1) as a silane compound is further added with a silane compound represented by the following formula (2) (hereinafter sometimes referred to as silane compound (2)). It is also preferable to use a working solution. By adding the silane compound (2), organic properties such as imparting properties such as flexibility of the silane compound (2) to the coating film or improving water repellency and adhesion to wood. Can be increased.

In the silane compound (2), of the four substituents of silicon, two are hydrolyzable substituents (R ⁵ O and R ⁷ O), and the other two are non-hydrolyzable substituents. (R ⁶ and R ⁸ ). In Formula (2), R ⁵ and R ⁷ may be the same or different and each represents hydrogen, an alkyl group having 1 to 10 carbon atoms, or an alkenyl group, and a bond between R ⁵ O and R ⁷ O and Si. Is a siloxane bond, and R ⁶ and R ⁸ are an alkyl group, an alkenyl group or a phenyl group having 1 to 10 carbon atoms which may contain an epoxy group or a glycidyl group in the molecule.

  Specific examples of the silane compound (2) include, for example, dimethyldimethoxysilane, dimethyldiethoxysilane, diethyldimethoxysilane, diethyldiethoxysilane, diphenyldimethoxysilane, diphenyldiethoxysilane, methylvinyldimethoxysilane, and methylvinyldiethoxysilane. And a condensate of about 2 to 10 molecules thereof. The silane compound (2) may be two or more kinds of condensates of such monomers, and also when two or more molecules of condensates are used, two or more kinds of such monomers are used. The condensate may be used.

  By adding the silane compound (2) as described above to the coating solution, the water repellency and flexibility of the coating film or the adhesion to the organic components of the wood can be further improved, and as a result, the wood The durability can be further improved.

  The silane compound (2) is generally applied in a range where the total amount does not exceed 50 parts by weight with respect to 100 parts by weight of the silane compound (1), which is the main silane compound component of the coating liquid. It is preferable to add to the liquid. When the added amount exceeds this range, in the process of applying the coating liquid to wood and performing hydrolysis / condensation polymerization, a bond is not formed well with the silane compound (1) which is the main silane compound component, This is because the strength of the coating film may be insufficient. Therefore, when the silane compound (2) is actually added, it is assumed that the strength of the coating film is lowered depending on the addition amount, and the addition is suppressed to the minimum necessary depending on the purpose. It is preferable.

The primary role of the non-hydrolyzable substituents (R ⁶ , R ⁸ ) in the silane compound (2) is to give flexibility to the coating film. Since it is an organic substituent, it also serves to impart water repellency to the coating film. In general, the organic substituent increases as the number of carbon atoms increases, that is, the water repellency increases.However, if the carbon number is too large, distortion occurs in the coating film due to steric hindrance, which causes a decrease in film strength. Become.

  By the way, a siloxane bond having high heat resistance and wear resistance is also a so-called “hard” bond. Because of this “hardness”, wear resistance can be imparted to the material by applying it to wood, which is the material to which the coating liquid is applied. However, the coating film on the surface of the wood needs to have flexibility, and sometimes the same flexibility as that of the wood as the material is required.

Tetraalkoxysilane (Si (OR) ₄ ) and oligomers thereof are used as starting materials in sol-gel coating solutions that have been generally used. When this is completely hydrolyzed and polycondensed ((1) to (3) in the above reaction formula 1) to form a coating film, a network of hard siloxane bonds in which all four bonds of silicon atoms are hard. As a result, a hard coating film is formed as in the case of ceramic. However, since it becomes a brittle film lacking in flexibility, it is practically impossible to produce a wood surface coating solution that takes advantage of the flexibility of wood.

  In contrast, in the present invention, the silane compound (1) in which one of the four substituents of the silicon atom is not hydrolyzed is used as the main silane compound component of the wood surface coating solution, thereby solving this problem. Is. Moreover, in this invention, it becomes possible to increase the softness | flexibility etc. of a coating film further by adding the silane compound (2) which each has two substituents which are not hydrolyzed to a wood surface coating liquid.

  The content of the silane compound (2) should be appropriately determined according to the required properties, but is generally 0 to 50% by weight, preferably 0 to 50% by weight, preferably based on the total solid content excluding the organic solvent in the coating liquid. 5 to 20% by weight. When the content of the silane compound (2) exceeds 50% by weight, the silane compound (1), which is the main silane compound component, is applied in the process of applying the coating liquid to wood as described above and performing hydrolysis and condensation polymerization. This is because there is a possibility that the bond is not formed well with the coating film and the strength of the coating film is insufficient.

Of course, if the resulting coating film requires wear resistance, the silane compound (1) alone may not be sufficient. In this case, a silane compound represented by the following formula (3) (tetraalkoxysilane; hereinafter referred to as a silane compound (3) may be obtained. ) And oligomers thereof are added to the coating solution containing the silane compound (1) or the silane compound (1) and the silane compound (2) to give a coating film with improved wear resistance. Can be obtained.
Si (OR ⁹ ) ₄ (3)
(In Formula (3), R ⁹ is a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, which may be the same or different.)

  The content of the silane compound (3) should be appropriately determined according to the required properties, but is generally 0 to 50% by weight, preferably 0 to 50% by weight, preferably based on the total solid content excluding the organic solvent in the coating liquid. 5 to 20% by weight. When content of a silane compound (3) exceeds 50 weight%, the obtained coating film will become hard too much, ie, a softness | flexibility will be lost and there exists a possibility of a crack.

  That is, the characteristics of the three types of silane compounds used in the present invention are as shown in Table 1 below.

  Thus, the coating liquid of the present invention contains the silane compound (1) as an essential component, and the silane compound (2) according to the degree of water repellency, flexibility, or wear resistance required for the wood surface coating liquid. And / or adding the silane compound (3) as necessary adds or improves the practical performance required of a wood surface coating film, such as wear resistance and flexibility, as well as water repellency. Can be made.

  In addition, an organic solvent may be added to the coating liquid of the present invention in order to uniformly mix the silane compound (1) and, if necessary, the silane compound (2) and / or the silane compound (3), and the catalyst. it can. Alcohols are preferred as the organic solvent used for this purpose. More specifically, methanol, ethanol, propanol, isopropanol, butanol, pentanol, hexanol and the like can be exemplified. In addition, the viscosity and drying speed of the coating liquid can be adjusted by controlling the amount of addition. The content of the organic solvent in the coating liquid of the present invention is the total solid content in the coating liquid (that is, the silane compound (1) + the silane compound (2) and / or (3) + the catalyst as required). The total amount) is usually 10 to 400 parts by weight, preferably 30 to 200 parts by weight per 100 parts by weight. When the content of the organic solvent is less than 10 parts by weight, the viscosity of the coating liquid becomes too high, and there is a possibility that the liquid agent does not reach the inside and details of the wood sufficiently, and a uniform coating film cannot be obtained. There is a fear. On the other hand, when the amount is more than 400 parts by weight, the solid content of the coating liquid becomes low (thinner), and there is a possibility that sufficient performance cannot be exhibited.

  In addition, components, such as various additives, can be added to the coating liquid of the present invention in accordance with required characteristics within a range that does not impair the object of the present invention. Examples of components that can be optionally added include colorants, ultraviolet light inhibitors, antifungal agents, antibacterial agents, and anti-anticides.

2. Wood surface treatment method In the wood surface treatment method including the step of applying the coating liquid of the present invention to the wood surface, first, any wood is cut and processed into any size and shape, and the above-described method of the present invention is applied thereto. Apply coating solution. Although the specific application method is not particularly limited, for example, it can be performed by immersing wood in a coating liquid, applying the coating liquid to wood, or spraying the coating liquid onto wood.

  When immersing wood in the coating solution, the immersion conditions may be performed at normal pressure, or may be performed under reduced pressure or under pressure. In order to allow the liquid agent to penetrate more into the wood, it is generally performed under reduced pressure or under pressure. However, considering workability, it is preferably performed under normal pressure.

  The time for dipping in the coating liquid varies depending on the composition, concentration, and type of wood of the coating liquid and cannot be uniquely determined, but is generally sufficient in the range of 10 seconds to 1 hour.

  In the case of brush coating, two coatings are sufficient. Even if it is applied more than this, not only is the coating amount too much, the liquid agent is wasted, but also the refractive index of the surface changes and the natural texture of the wood is impaired. Further, the thicker the coating film, the higher the possibility that the coating film will crack.

  In order to leave a natural texture on the wood surface even if it is applied using any of the impregnation method, brush coating method, or spray method, wipe off the excess coating solution on the wood surface with a cloth or paper. It is preferable.

  There is no particular limitation on the wood to which the coating liquid of the present invention is applied. In addition, after application | coating of the coating liquid of this invention, a post-process can also be given with respect to wood. Thereby, the durability of the wood surface can be further increased. As chemicals used for this post-treatment, commonly used natural oils and resins can be used without any particular limitation. Of course, these chemicals can be used in the same way not as a post-treatment but as a pre-treatment.

  As described above, the present invention requires the silane compound (1) as an essential silane compound component, and further, the silane compound (1) penetrates into the wood, reacts with moisture inside the wood, and is fixed inside the wood. As a catalyst, a metal alkoxide coexists and, if necessary, the silane compound (2) and / or the silane compound (3) depending on the degree of water repellency, flexibility, or abrasion resistance required for the wood coating film. By adding, it is possible to add and improve practical performances required for surface-treated wood, such as water repellency, flexibility, and wear resistance of the resulting coating film.

  EXAMPLES Hereinafter, although this invention is demonstrated further more concretely based on an Example, an Example is an example to the last, Comprising: This invention is not limited at all.

[Manufacture of coating liquid]
Example 1
Methyl trimethoxysilane condensate (corresponding to MTM, silane compound (1). For the synthesis method, see Japanese Patent No. 3456956) (average polymerization degree 7-8, trifunctional silane) 57.7 g (0.6 mol as Si) Dissolved in 40.6 g of isopropyl alcohol, 1.7 g of titanium tetrapropoxide (Ti / Si = 0.01) was added thereto as a catalyst, and the mixture was sufficiently stirred to prepare a coating solution A.

Example 2
Methyltrimethoxysilane condensate (corresponding to MTM, silane compound (1)) (average polymerization degree 7-8, trifunctional silane) 48.1 g (0.5 mol as Si) and polymethylphenylsiloxane (MPS, GE Toshiba) Made of silicone, equivalent to silane compound (2), 8.0 g of bifunctional silane) is dissolved in 42.2 g of isopropyl alcohol, and 1.7 g of titanium tetrapropoxide is added thereto as a catalyst, followed by thorough stirring and coating. Liquid C was produced.

Example 3
Methyltrimethoxysilane condensate (MTM, corresponding to silane compound (1)) (average polymerization degree 7-8, trifunctional silane) 28.9 g (0.3 mol as Si) and tetramethoxysilane condensate (MS-51 , Equivalent to silane compound (3) manufactured by Colcoat Co., Ltd.) 35.3 g (average mol 3-4, tetrafunctional silane) 30.3 g (0.3 mol as Si) was dissolved in 34.1 g isopropyl alcohol, and titanium was used as a catalyst there. Tetrapropoxide 1.7g (Ti / Si = 0.01) was added and stirred sufficiently to produce a coating solution.

Example 4
Methyltrimethoxysilane condensate (MTM, equivalent to silane compound (1)) (average polymerization degree 7-8, trifunctional silane) 48.1 g (0.5 mol as Si) and bifunctional silane (manufactured by GE Toshiba Silicone, 8.0 g of dimethyl silicone) is dissolved in 42.2 g of isopropyl alcohol, 1.7 g of titanium tetrapropoxide (Ti / Si = 0.01) is added thereto as a catalyst, and the mixture is sufficiently stirred. Manufactured.

Comparative Example 1
Tetramethoxysilane condensate (corresponding to MS-51, silane compound (3)) (average polymerization degree 3-4, tetrafunctional silane) 70.7 g (0.6 mol as Si) was dissolved in 27.6 g of isopropyl alcohol, Thereto was added 1.7 g of titanium tetrapropoxide (Ti / Si = 0.01) as a catalyst, and the mixture was sufficiently stirred to produce a coating solution.

Comparative Example 2
Methyltrimethoxysilane condensate (corresponding to MTM, silane compound (1)) (average polymerization degree 7-8, trifunctional silane) 57.7 g (0.6 mol as Si) was dissolved in 42.3 g of isopropyl alcohol, To prepare a coating solution.

Comparative Example 3
As a wood surface coating material, a typical commercial product, Osmo Color (Clear Type) (manufactured by Nippon Osmo Co., Ltd.) was used as it was.

Test Example 1: 60 ° C. Hot Water Treatment Water Resistance Test Wood Sample A commercially available cedar material was cut into a length of 4 cm, a width of 4 cm, and a thickness of 1 cm to obtain a test specimen for coating. The cedar material was used as it was without any special treatment such as degreasing. In addition, each test piece was processed 3 each and the average was taken.

Coating processing method Containers in which each coating liquid is put at a depth of 4 cm or more with the cut surface of the coating test piece facing up, using the coating liquid manufactured in Examples 1 to 3 and Comparative Examples 1 to 3 It was immersed in and impregnated for 1 minute. After impregnation, it was taken out from the container, and the excess liquid on the surface of the wood sample was lightly wiped off with paper and left at room temperature for 4 days. The coating amount (%) was calculated from the following calculation formula (1).
Formula (1)
Coating amount (%) = (weight after coating (g) −weight before coating (g)) / weight before coating (g) × 100

Test Method Each coating test piece treated with the coating solution produced in Examples 1 to 3 and Comparative Examples 1 to 3 and untreated wood test piece as Comparative Example 4 were placed in a 100 ml polyethylene cup (capacity). : About 120 ml, height: about 7.5 cm), the cut surface was put up, filled with hot water at 60 ° C., the upper part was covered with a polyethylene sheet (saran wrap), and sealed with a rubber band.

This container was immersed in a 60 ° C. hot water bath for 7 hours. After the hot water treatment, the wood sample was taken out from the container, the moisture on the sample surface was lightly wiped with paper, and the weight of the sample was immediately measured. The weight increase rate (%) was calculated from the following calculation formula (2). Here, the pre-treatment weight (g) is the same as the post-coating weight (g) in the above formula (1).
Formula (2)
Weight increase rate (%) = (weight after treatment (g) −weight before treatment (g)) / weight before treatment (g) × 100

  The obtained results are shown in Table 2.

Test Example 2: Accelerated weather resistance characteristics-1
The purpose of the test The coating liquid of the present invention forms a transparent coating film mainly composed of an inorganic compound, and thus it seems difficult to protect the underlying wood from ultraviolet rays. However, the inorganic coating film itself mainly composed of siloxane bonds can be expected to be stable against ultraviolet rays. Therefore, in order to confirm the stability against ultraviolet rays, a 1500 hour accelerated weathering test was conducted.

Coating liquid Three types of coating liquids A, C, and B manufactured in Examples 1, 2, and 4 were used as the coating liquid.

Wood Sample and Coating Treatment Method The coating specimen was subjected to coating treatment in the same manner as in Evaluation Example 1 using the same cedar material as in Evaluation Example 1 above. Each test piece was processed two by two.

Accelerated weathering test The accelerated weathering test was carried out at 250, 500, 1000 and 1500 hours in accordance with the exposure test method specified in JIS K 7350-2-1995. The measuring instrument used was a weatherometer Ci4000 manufactured by Astra. A xenon lamp was used as the light source.
Color difference test method After the accelerated weather resistance test, the color difference (ΔE *) was examined using a colorimeter. For the color measurement, a simple spectral color difference meter NF-333 manufactured by Nippon Denshoku Industries Co., Ltd. was used.

Water Repellency Test Method The water repellency (%) was calculated from the following calculation formula (3) by dropping 1 g of water onto a test piece, wiping off after 1 minute, measuring the weight at that time. Here, the weight (g) before dropping is the weight of wood immediately after the accelerated weather resistance test.
Formula (3)
Water repellency (%) = (weight after wiping (g) −weight before dropping (g)) / weight before dropping (g) × 100

  The results are shown in FIGS. FIG. 1 shows a change in color difference (ΔE *) on the wood surface, and FIG. 2 shows a change in water repellency. From FIG. 1, since the coating film of this invention was transparent, it was not able to pass the ultraviolet-ray as expected and to prevent the photolysis of the lignin on the wood surface. On the other hand, from FIG. 2, in particular, in the coating film generated from the coating liquid C (silane compound (1); trifunctional silane + silane compound (2); bifunctional silane), even after 1500 hours of ultraviolet irradiation, It was recognized that there was almost no change in the water repellency. That is, it was confirmed that the coating film of the present invention was held on the wood surface without any change even after the ultraviolet irradiation.

  This is because the coating film obtained by applying the coating liquid of the present invention is transparent, so that the decomposition of lignin on the wood surface by ultraviolet rays cannot be prevented, but the siloxane bond covering the wood surface is not resistant to ultraviolet rays. And stable, it is possible to prevent desorption (separation) from the surface of the decomposition product or the like. That is, it was recognized that the surface state after coating could be stably maintained for a long time, and as a result, there was no change in the water repellency.

  From the above results, if the coating liquid of the present invention is used in combination with another coating liquid that has an effect of preventing ultraviolet rays, it is possible to protect the wood surface from decomposition by ultraviolet rays and ideally not to detach (separate). This means that a simple coating film can be obtained.

Test Example 3: Weather resistance characteristics-2
The wood surface deterioration with respect to ultraviolet rays was shown by the amount of water absorbed by using an undercoat of an ultraviolet absorber and a coating piece A or a piece of wood coated with the same ultraviolet absorber as the undercoat.

Wood The same specimen for coating cedar as in Test Example 1 was used.

Coating liquid As a coating liquid A and UV absorption, “Ribos Color Oil” (importer, Ikeda Corporation) and “Koshibijin” (Miyaki Co., Ltd.) are used. An accelerated weather resistance test was performed on wood specimens surface treated with a combination of topcoats.

Test Method Accelerated Weather Resistance Test An exposure test method defined in JIS K 7350-2-1995 was followed. A xenon lamp was used as the light source.

Method of measuring water absorption 1 g of water was dropped on the test piece, and after 1 minute, the surface water was wiped off, the weight of the test piece at that time was measured, and the water absorption was calculated by the following formula (4). Here, the weight before dropping (mg) is the weight of wood immediately after the accelerated weathering test.
Formula (4)
Water absorption (mg) = weight after wiping (mg) −weight before dropping (mg)

  Table 3 shows the results of water absorption up to 500 hours after the accelerated weather resistance test.

  From the results shown in Table 3, the amount of water absorbed was the least when the coating liquid A was used for undercoating and overcoating. Also from this, it was confirmed that the wood surface coating film coated with the coating liquid of the present invention has high stability to ultraviolet rays. However, the decoloration of wood was not suppressed only by the coating liquid A.

  The amount of water absorption when using the anti-UV agents “Ribos” and “Beautiful skin” as the undercoat and using the coating liquid A as the overcoat is less than when using only the anti-UV agent, It was a good result.

  In addition, when comparing the decolorization properties of the wood surface, the degree of decolorization was less in the test piece primed with the UV absorber than when only the coating liquid A of the present invention, which is clearly clear coating, was applied. .

  From this, the effectiveness of the UV resistance was found in the combination of the UV absorber and the coating liquid of the present invention.

  When the silane compound (1) is applied to the surface of the wood, it penetrates into the wood due to capillary action. Thereafter, the siloxane polymer grown by the hydrolysis of the three alkoxy groups of the compound of the formula (1) by the moisture (humidity) in the wood, on the surface or in the air, through the polycondensation reaction, Bond strongly. The coating film thus obtained suppresses the capillary phenomenon inside the wood, and as a result, prevents water from penetrating from the wood surface, thereby improving the water resistance and durability of the wood.

  In addition, these alkoxy groups themselves are slowly hydrolyzed and polycondensed in the presence of water, but the rate is said to be very slow. The catalyst for promoting the hydrolysis / polycondensation reaction is a metal alkoxide, and the coating liquids of the present invention in which the catalyst coexists (Examples 1 to 4) are coating liquids that do not allow the catalyst to coexist (Comparative Example 2). ) Was found to be much more water resistant.

On the other hand, since one non-hydrolyzable substituent (R ⁴ ) is an organic substituent, it exhibits strong water repellency. In addition, the organic nature of this substituent imparts organicity to the coating film, improves the affinity with organic components such as lignin and cellulose inside the wood, and adheres the coating film inside the wood. Has the effect of improving the performance.

In addition, the presence of one non-hydrolyzable substituent (R ⁴ ) in the compound of formula (1) requires only one strong siloxane bond with the adjacent silicon atom. However, the unreacted bond remains in the form of “hanging” so that the flexibility of the coating film can be maintained, and as a result, the structure can absorb the stress during expansion and contraction of the wood. Contributes to improved adhesion between the coating film and the wood interior.

  Moreover, since the siloxane bond itself is a completely inorganic bond, it is known that the siloxane bond is resistant to photodecomposition reaction by ultraviolet rays and does not undergo photodegradation. For this reason, even if it uses outdoors, the coating film stable for a long period of time can be obtained.

The wood surface coating solution of the present invention can form a coating film having excellent water resistance and water repellency on the wood surface and good durability against ultraviolet rays, etc., and can improve the durability of wood. Therefore, it is useful in that the long-term storage stability of wood used for various applications can be greatly improved.
According to the present invention, a protective coating can be formed without impairing the natural texture of the wood surface, and thus is very useful in situations where it is desired to make use of the texture of the wood surface.

It is a graph which shows the change of the color difference ((DELTA) E *) of the wood surface by the accelerated weathering test of the wood test piece which coated the coating film of this invention. It is a graph which shows the change of the water repellency by the accelerated weathering test of the wood test piece which coated the coating film of this invention.

Claims (7)

A wood surface coating solution containing a silane compound represented by the following formula (1) and a catalyst for curing and / or solidifying the silane compound as main components.

(In the formula ^{(1), R 1, R} 2 and ^{R 3,} each of which may be the same or different, a hydrogen atom or a carbon number from 1 to 4 alkyl groups, ^{R 4} is a halogen atom in these groups Or an alkyl group having 1 to 10 carbon atoms, an alkenyl group or a phenyl group which may contain an epoxy group, and n is 2 to 10)   The wood surface coating solution according to claim 1, wherein the content of the silane compound represented by the formula (1) is 20 to 75% by weight.   The wood surface coating solution according to any one of claims 1 to 3, wherein the catalyst for curing and / or solidifying the silane coating solution is a hydrolyzable organometallic compound.   The wood surface coating solution according to claim 3, wherein the hydrolyzable organometallic compound is an alkoxide of one or more metals selected from the group consisting of titanium, zirconium and aluminum. Furthermore, the wood surface coating liquid of any one of Claims 1-4 containing the silane compound shown by following formula (2).

(In the formula (2), R ⁵ and R ⁷ are each a hydrogen atom, an alkyl group having 1 to 10 carbon atoms or an alkenyl group, which may be the same or different, and R ⁵ O, R ⁷ O, and Si; Is a siloxane bond, and R ⁶ and R ⁸ are an alkyl group, an alkenyl group or a phenyl group having 1 to 10 carbon atoms, which may contain an epoxy group or a glycidyl group in the group. Furthermore, the wood surface coating liquid of any one of Claims 1-5 containing the silane compound shown by following formula (3).
Si (OR ⁹ ) ₄ (3)
(In Formula (3), R ⁹ is a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, which may be the same or different.)   The wood surface treatment method which has the process of apply | coating the wood surface coating liquid of any one of Claims 1-6 on a wood surface.

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