The present invention relates to a method of protecting wood objects against external threats, such as the unwanted effects of fire and micro-organisms or insects.

The present invention relates especially to a method according to the preamble of Claim 1.

The present invention also relates to a wood object which is treated with the present method, and a liquid mixture which is usable in the present method.

The present invention also relates to the use of an agent which increases the

hydrophobicity of wood, in order to prevent washing out of wood preservatives and, correspondingly, fire retardants, from the wood.

It is already known how to protect wood against mould, blue staining and insects by means of different commercial wood preservatives which comprise biocides, such as IPBC (3- iodo-2-propynyl butyl carbamate), propiconazole, tebuconazole or cypermethrin. In addition, there are known non-biocidal protective substances, such as tall oil and its derivatives, and tall oil pitch and derivatives and processed products of it, which prevent detrimental biological effects.

It is also known how to improve the fire resistance of wood by way of various fire retardants, such as salts of formic acid, citric acid, phosphoric acid, phosphonic acid or boric acid.

There are problems associated with the known technology. Thus, the known wood preservatives do not prevent or significantly delay the absorption of rainwater into the wood. Rainwater is known to flush mould retardants and other wood preservatives off the wood. For example, splash/rainwater have been found to significantly reduce the efficiency of commercial protective materials based on IPBC and propiconazole.

Fire retardants are generally soluble in water and a widely known problem is that they are washed out during building work, particularly when it is raining.

It is also known how to use substances which make the wood surface hydrophobic (for example AKD, wood oils, waxes). Known hydrophobing agents make the surface of the wood hydrophobic, but do not significantly protect the wood from mould.

US Patent Specification No. 4,404,239 describes a wood treatment using a water-repellent mixture which comprises alpha-olefin or paraffin or a mixture thereof; a wood

preservative, and an organic solvent. The mixture is applied onto the wood surface by brushing. After treatment, drying is carried out.

US Patent Specification No. 4,913,972 relates to a method for improving the weather resistance of wood, which method is comprised of at least two stages of operation. First, a transparent mixture which comprises an organic compound containing silicon is applied. This mixture may also comprise hydrophobing agents and wood preservatives. After that, a composition which generates a transparent film is applied. Conventional methods are used in the application.

US Published Patent Application No. 2008/0193785 describes a wood surface treatment in which the wood is first impregnated with a curable water-based mixture, which is allowed to cure at an elevated temperature. Finally, a surface layer is applied. The curable water- based mixture comprises a cross-linkable compound, and includes a catalyst, which may be formic acid. The coating film or the coating substance is applied as a separate stage of operation under reduced pressure.

FI Patent Application No. 20085652 describes a method in which a composition which comprises a hydrophobing agent and a coating substance is applied onto the surface of a wood board. This composition and coating material can be applied using heat and pressure. However, the above-mentioned composition does not contain any substance that acts to protect against the unwanted effects of fire and/or micro-organisms or insects.

WO Published Patent Application No. 2009/004110 relates to an aqueous solution of formate and alkyl ketene dimer (AKD), which is intended for the treatment of wood. FI Patent Application No. 122723 describes a composition suitable for wood treatment in which composition a monocarboxylic acid and a chelating substance are dissolved in a water-based carrier. Furthermore, it is possible to add hydrophobing agents, such as AKD and organic biocides, into the composition. The application is carried out in a pressure impregnation process which consists of two phases, i.e. vacuum treatment and

overpressure treatment.

US Patent Publication No. 4,009,307 describes attachment of a surface film onto a wood product. According to the publication, the coating can be cured by means of heat setting. The solution described in the publication is only related to the attachment of the coating film, and there is no reference to application of a repellent mixture.

The known solutions are multi-staged, and yet they fail to effectively migrate the active substance deep into the wood and remain there, in which case it would be possible to prevent or significantly delay rainwater washing it out.

Furthermore, in the previously known solutions, the wood is separately protected against detrimental biological effects, such as mould, blue staining and insects.

It is an aim of the present invention to eliminate at least some of the problems of the prior art, and to provide a method to protect a wood object against external threats, such as the unwanted effects of fire and micro-organisms or insects. In particular, it is an aim to provide a method according to which the active substances, that is, wood preservatives, such as biocides, as well as fire retardants, remain well in the wood after the treatment and are not flushed out of the wood for example by the impact of rainwater during building work. The method according to the present invention is based on the surprising finding that by adding wood preservative or fire retardant into the agent which increases the

hydrophobicity of wood, particularly into AKD, i.e. alkyl ketene dimer or a corresponding unsaturated diketene dimer derivative (alkenyl diketene dimer, also abbreviated as AKD), and by applying this mixture onto the surface of the wood object at a temperature at which the agent that increases the hydrophobicity is in a molten state, and finally, by hot- pressing, it is possible to make the AKD penetrate very deep into the wood. By means of the new mixture, which is applied as described above, it is possible to migrate the active substance deep into the wood and to remain there, in which case it is possible to prevent or significantly delay rainwater from flushing it away. A completely new type of wood object is generated. Furthermore, the present invention relates to the usage of an agent that increases the hydrophobicity of wood in order to prevent the washing out of active substances from the wood. The active substance generates an action that protects against the unwanted effects of fire and/or micro-organisms or insects, and the active substance or substances have been mixed with the agent that increases the hydrophobicity of wood, in order to form a protective product.

More specifically, the method according to the present invention is mainly characterized by what is stated in the characterizing part of Claim 1. The wood object according to the present invention is, in turn, characterized by what is stated in the characterization part of Claim 13, and the mixture according to the present invention is characterized by what is stated in the characterizing part of Claim 21. The use according to the present invention is defined in Claim 24. Good treatment outcome is achieved with the present invention. As a result of the treatment, the applied mixture can penetrate significantly deep into the wood. It is possible that the AKD or a similar substance identifies the hydroxyl groups in the wood and binds to the wood by way of them. It is therefore probable that the AKD or a similar substance is also capable of binding other active substances, including water-soluble substances, to the wood to prevent them from being easily washed out.

However, this is only one theoretical possibility, and the present invention is not limited in any way to this explanation. However, it has been possible to establish that due to the present solution, the impact of rainwater during building work, transportation and storage does not significantly decrease the functionality of the active substances, such as the functionality of wood preservatives and fire retardants, because the hydrophobing agent prevents the protective substance from being washed out. The ability to protect against biological threats (such as mould, blue stain, rotting, termites) can be maintained despite rain during the building work stage. In this way, the wooden parts of the building can be protected long-term against biological and other threats. Because also the coating film, or the substance which generates the coating film, is applied to the wood object during the same hot-pressing step as happens with the other

components of the board, it is possible to avoid separate steps of operation, intermediate storage of semi-finished products, etc.

In the following, the present invention will be examined in more detail with the aid of a detailed description.

In the present invention, the term "active substance" means a substance that acts to protect against the unwanted effects of fire (fire retardant) and/or micro-organisms or insects (wood preservative).

Based on the above, the present invention relates to a method of protecting a wood object against external threats, which threats are unwanted effects of fire and, correspondingly, micro-organisms or insects. According to the method, a wood object is treated with a mixture comprising at least one active substance, which active substance acts to protect against the unwanted effects of fire and/or micro-organisms or insects.

Typically, the protective product is applied onto the surface of the wood object, at a temperature at which the agent, which increases the hydrophobicity, is in fluid form, for example in a molten state, and a coating film is formed on the wood object which is treated in this way, for example by fitting onto it a coating film or by applying onto the treated wood object a coating product which generates a coating film, after which hot-pressing is carried out. In a more preferable embodiment, the active substance or active substances are mixed with the agent which increases the hydrophobicity of the wood, in order to form a mixture, and

- the mixture thus obtained is applied onto the surface of the wood object at a

temperature at which the agent that increases the hydrophobicity is in fluid form, particularly in a molten state, after which

- a coating film for the wood object is applied onto the wood object, or a coating substance which generates a coating film is applied onto the treated wood object, and finally

- the object which is generated as described above is hot-pressed.

The wood preservative can be a biocide, such as IPBC (3-iodo-2-propynylbutyl- carbamate), propiconazole, tebuconazole, or cypermethrin. Alternatively, the wood preservative can be a non-biocide, such as tall oil and its derivatives, and tall-oil pitch and its derivatives and processed products.

The fire retardant is typically a salt of an acid. Examples are salts of formic acid, citric acid, phosphoric acid, phosphonic acid or boric acid.

The product which comprises an active substance or active substances includes one or more wood preservatives (wood protection product), or one or more fire retardants (fire protection product). The product may also comprise both wood preservatives and fire retardants.

The active substance or active substances in the product have first been mixed with an agent which increases the hydrophobicity of wood. Typically, the agent which increases the hydrophobicity is a wax, oil, fat, saturated hydrocarbon, such as an alkane, or a mixture thereof. Particularly suitable are AKD (alkyl or alkenyl ketene dimers), wood oil and paraffin wax. It is also possible to apply onto the surface to be treated one of the above-mentioned agents that increases hydrophobicity, in a fluid form other than the molten state. Thus, the agent which increases hydrophobicity can be applied as a solution, dispersion, suspension and emulsion. Of particular interest are oil solutions and oil dispersions, in which the solvent or, correspondingly, the dispersion medium is an oil.

The mixture which is intended for use, in the method according to the present invention, for treatment of a wood object, in one embodiment comprises wood preservative 0.1-5 % by weight and/or fire retardant 5-60 % by weight, and substance that increases the hydrophobicity 50-95 % by weight.

Preferably, the mixture comprises IPBC approximately 0.6-0.8 % by weight,

propiconazole approximately 0.2-0.3 % by weight and AKD 95-99 % by weight.

The mixture may also comprise fire retardants.

The mixture is applied onto the surface of a wood object by roller, spray, brush or by casting or another similar surface application method, optionally by utilizing compression. Naturally, it is also possible to immerse the piece to be treated into the mixture. The surface may be completely covered, which is advantageous. Alternatively, it is possible to form patterns on it or streaks can be applied. If the agent which increases the

hydrophobicity is solid at room temperature, such as waxes, and (undissolved/undispersed) AKD, the mixture must first be heated until the agent which increases hydrophobicity melts. Typically, waxes melt at a temperature of above 45 °C; the melting temperature of AKD is typically approximately 50-60 °C, for example 53 °C, depending on the type of AKD. Thus, it is easy to bring the AKD to a molten state by heating it, and to apply it onto the surface of the object to be treated. The AKD compound may also be unsaturated, in which case it is typically liquid at room temperature (approximately at 20-30 °C). An unsaturated AKD compound (for example alkenyl diketene dimer) provides a surface the properties of hydrophobicity of which are good. After a molten or liquid mixture has been applied onto the surface of wood object, a coating film is placed on the treated surface. Alternatively, it is possible to apply onto the surface a coating substance which generates a coating film. Typically, such a coating substance is a resin, lacquer or paint.

Finally, hot-pressing is carried out. Hot-pressing of plywood is typically carried out in the temperature range of 100-190 °C, for example approximately 100-170 °C. When choosing the hot-pressing temperature, the heat resistance of the active substances must naturally be taken into account. At least IPBC and propiconazole are able to withstand temperatures of up to 160 °C.

The wood surface to be treated can be suitably preheated before the mixture of the active substance and the agent that increases the hydrophobicity is applied. Preheating facilitates the absorption of the mixture into the wood. By treating the wood with this mixture, it is possible to bring a sufficient amount of active substance into the wood. Above all, the active substance will remain in the wood and it will not be washed out by rainwater.

The present invention also relates to a wood object which is treated with the method according to the present invention.

The shape of the wood object to be treated may be, for example, a board or a beam. The wood object may be a single piece (homogeneous throughout) or the wood object may be a combination of several different kinds of layers.

The wood object may be, for example, a wood board or wood beam, wood veneer, fibre board, chipboard, lumber, glue- laminated wood, plywood, LVL (laminated veneer lumber) board or beam, or OSB (oriented strand board). The present invention is described in more detail in the following non-limiting example.

Example: Protection of plywood with biocide-containing AKD

Granulates of AKD are melted and 0.5-1 % IPBC and 0.5-1 % propiconazole or an adequate amount of other biocides are blended into the molten mass. The molten mixture of AKD and biocide is applied onto the surface of a wood board with a roller. After the rolling, a paper film which is impregnated with phenolic resin is spread onto the surface of the wood board. This paper film is attached to the surface of the board by using hot- pressing, between hot-press plates at a high surface pressure, usually a pressure of -1.7 MPa, and usually at a temperature of -135 °C.

The high temperature renders the above mixture very free-running and allows it to migrate into the wood cells. The high surface pressure pushes this mixture deep into the wood board, in the example, plywood. The mixture penetrates as deep as the third layer of the veneer (3-4.5 mm deep). This good penetration results in a significantly improved protective effect, compared to mere surface treatment. In commonly known surface treatments, the protective substances are only on the surface of the product, thus the protecting effect is only local, protecting only the wood surface. In the present method, the wood matrix is treated with the protective substance to a greater depth, in which case the protective effect is significantly better.

An experiment found that AKD occurred at depths of as great as three layers of veneer.

The present invention is not intended to be limited only to the above examples of embodiments. The present invention is intended to be widely applied within the scope of protection of the claims below. References

Patent Literature

US Patent Specification No. 4,404,239

US Patent Specification No. 4,913,972

US Published Patent Application No. 2008/0193785

FI Patent Application No. 20085652

WO Published Patent Application No. 2009/004 110

FI Patent Application No. 122723

US Patent Specification No. 4,009,307