New use of wood specimen

The present invention relates to surface treatment of wood objects. In particular, the present invention relates to the use of surface-treated wood objects as casting beds for concrete and similar hardening masses

Wood panels and solid wood are commonly used as casting surfaces, for example when concrete casting is carried out An untreated wood surface adheres tightly to the material that is cast Because of th is adherence, it is very difficult to release the wood, which is used n the casting forms, from the concrete surface, without damaging the casting surface or the wood material that is used as the casting form The adherence significantly increases the work- required for detaching the casting surfaces, causing material loss and repair work on the casting surfaces The present invention relates to treatment of a wood surface with a highly water-repellent and moisture-insulating substance in a way that makes it easy to detach the wood from the casting surface The present invention relates to the substance in question (a "release agent ^" ), and to a wood product that is treated with the substance in question In previous solutions, the wood used as the casting surface is surface-treated with distillates of fossi l-derived crude oil, and mixtures thereof In known solutions, wood surfaces are treated, for example, with a mixture of two different commercial products: Nynas Nytex 81 0

(Distil lates petroleum, hydrotreated heavy naphthenic) and Neste engine fuel oil -5 - 1 5. Published Patent Application WO 20081 5442 1 describes a coating composition, which comprises a fluorine-containing compound and a polycarbodiimide The composition is applied onto the surface of a substrate such as wood

US Patent Specification No 3,497,375 describes a method of treating a wooden form which is used in concrete casting, by coating the surface of the wood. The coating is formed of two layers, in which case, first, a mixture is applied which is comprised of wax and ethylene- vinyl acetate copolymer, and this mixture forms a layer hav ing a thickness of 0 5 to 5 mm The wax and paraffin oil components of the compositions do not migrate into the wood.

US Published Patent Application No. 2009304939 and Published Patent Application WO 20090041 10 describe the application of an aqueous dispersion or aqueous solution of AKD onto a wood surface, thereby improving the hydrophobicity of the wood.

In previous solutions the detaching properties are either based on oiling the wood surface or based on a similar treatment, in order to improve the detaching properties. The treatment does not render the wood surface itself hydrophobic or otherwise highly water-repellent. It is possible that the detaching is based on the slippery surface of the wood fibre, or the fact that oils are usually not soluble in water.

Wood products which are used in casting for example on a construction site are exposed to rain and to the water that passes from the mass to the wood product. In these conditions, release agents, which are based on fossil-derived oil, migrate with the water to the

environment and are of concern regarding environmental damage.

When the release agent described above is applied onto wood in construction site conditions, it is not possible to completely prevent it from entering the environment, for example as splashes.

In addition, the treated wood products have an unpleasant smell and are unpleasant to handle. The smell clings to your skin, hair and clothing. People who use the substance and the wood products find this disagreeable.

The purpose of the present invention is to eliminate at least some of the problems associated with the known technology and to provide a new solution for treating wood surfaces which act as casting surfaces for concrete and other hardening masses (referred to below as "casting material").

The present invention is based on the idea that agents which render the wood surface hydrophobic are used as release agents, which effectively seal the surface of the wood. Reactive hydrophobing agents are such substances. They adhere to the surface of wood by reacting with functional groups in the wood. They thus form a slippery surface. Therefore, during casting, the casting material cannot penetrate into the wood fibre and thereby adhere to it.

More specifically, the use according to the present invention is mainly characterized by what is stated in the characterizing part of Claim 1.

Considerable advantages are achieved with the present invention. Thus, unlike previous solutions, raw materials that are based on fossil oils are not used in the invention. Solutions that are based on coating films, such as thermosetting resins which are impregnated into paper, or plastic films which can be laminated, are not used either.

The present invention relates to substances that act as release agents, at least as well as, and in most cases far better than, previously known solutions. In addition, the substances used in the present invention or at least part of them react with the wood, thereby adhering to the wood cells, and are not flushed out into the environment, for example when it rains. This is a significant advantage. The substances which the present invention relates to have no known environment-loading effects.

Another advantage is that the solutions are inexpensive. For example, the use of AKD in an optimal case results in a reduction of costs of at least 50 % compared to the known solutions.

The substances which the present invention relates to are not known to be used in casting. In fact, their suitability for said application is very surprising. When wood is used for casting beds or casting forms, for example in the casting of concrete, the wood object is exposed to a very intense and long-term contact with water and the hardening concrete. Wood treatment tests and the use of wood in concrete casting tests, according to the present invention, gave surprisingly good results, and the reference publications mentioned in the introduction, do not refer to the fact that wood which is treated as described above could be suitable as a casting bed. The accompanying drawings show photographs of samples described in the application examples.

Figure 1 is a photograph of untreated softwood plywood;

Figure 2 is a photograph of a plywood sample which is treated, according to known technology, with a fossil oil-based substance, Nytex 810 + engine fuel oil;

Figure 3 is a photograph of a sample which is treated with a 10 % aqueous dispersion of AKD (Ashland Aquapel 320);

Figure 4 is a photograph of a sample which is treated with a polymer adhesive (Basoplast 285 S); and

Figure 5 is a photograph of a sample which is treated with a tall pitch-based processed product (BT Water Repellent).

As will appear from the above, the present solution relates to casting bed use of a wood object which is obtained by treating a wood object with an agent that increases the hydrophobicity of wood, and which agent is capable of reacting with the wood.

In particular, the wood object is treated with an agent that increases the hydrophobicity of wood, and which agent is capable of reacting with the hydroxyl groups or similar functional groups in the wood.

In the present solution, the substance tightly adheres to the wood and possibly at least partially adheres to the wood cells. In one embodiment, the wood object is treated with a hydrophobic agent, by spreading, that is, by application of the agent onto the surface of the wood object at a temperature at which the agent that increases the hydrophobicity is in a fluid state, for example in a molten state.

In another embodiment, a wood object is treated with a liquid mixture which comprises an agent that increases the hydrophobicity, which agent, for example, has been added into the mixture in question, in the form of a liquid dispersion. It is possible to treat the whole surface with a hydrophobic agent, or the agent can be applied to the surface as discrete patterns, that is, patterns which are separate from each other, such as spots, streaks or stripes. In particular, however, at least 50 %, most suitably at least 75 %, especially 90-100 % of the casting surface is treated. The corresponding part of the surface will then be covered. If the hydrophobic agent is applied onto the surface as patterns, it is preferable to arrange the pattern in such a way that it covers the surface uniformly.

In general, approximately 10-200 g/m ² , particularly approximately 50-120 g/m ² , most suitably approximately 70-100 g/m ² of the hydrophobic treatment agent is applied onto the surface of a wood object.

The release agent to be used may be a synthetic or a natural substance, such as a monomeric molecule, a dimer, oligomer or polymer, or a mixture thereof

In one embodiment, the agent that increases the hydrophobicity is alkyl ketene dimer or alkenyl ketene dimer, i.e. AKD, or a mixture which comprises such a material.

In another embodiment, the agent that increases the hydrophobicity is resin adhesive, tall oil, especially crude tall oil (CTO) or a processed product of it, tall oil pitch or a processed product of it, other wax, paraffin or an oily material, or another agent that increases the

hydrophobicity. For example, tall oil and tall oil pitch and processed products of them, as well as paraffinic and oily substances and waxes, typically comprise acid compounds, for example fatty acids and/or resin acids that are capable of reacting with the functional groups, such as hydroxyl groups, in the wood.

If necessary, the reactivity of the treatment agent with the surface of the wood can be increased by including catalysts in the agent. Thus, for example the reactivity of crude tall oil can be increased by using iron catalysts, in particular iron(III) catalysts.

In addition to the preceding organic substances, the substance that is used in the present solution may be, for example, a non-organic hydrophobing agent, such as clay or silica or nanoclay or nanosilica. The agent may be in a solid state at room temperature during storage, and in a molten state, after having been heated, during application (such as AKD granulate). In addition, the agent may be a combination of the above substances, either with each other or together with another substance.

In one embodiment, a wood object is treated either with a molten form of alky I ketene dimer or alkenyl diketene dimer. or with a liquid mixture which mixture comprises alkyl ketene dimer or alkenyl diketene dimer 1-20 % by weight, particularly approximately 5-10 % by weight.

AKD is applied onto the surface of the wood object approximately 1 -30 g/nr, particularly approximately 5-12 g/m ² , which corresponds, as an aqueous dispersion, to approximately 50- 120 g/m ² (of the dry matter). It is also possible to treat the wood object with at least one such active substance, which acts to protect against the unwanted effects of fire and/or micro-organisms or insects.

Such an active substance or active substances can be applied onto the wood simultaneously with the agent that increases the hydrophobicity. For example, the procedure is that, before the application, the active substance or the active substances are mixed into a liquid intermediate substance, which comprises an agent that increases the hydrophobicity.

Examples of suitable substances are the following. 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 derivatives and processed products of it. The fire retardant can be, for example, a salt of an acid, such as formic acid, citric acid, phosphoric acid, phosphonic acid or boric acid The product which comprises the active substance or active substances, includes one or more wood preservatives (wood protection products), or one or more fire retardants (fire protection products). The product may also comprise both wood preservatives and fire retardants. In one embodiment, the hydrophobic agent is applied by paint-brushing, rolling, other brushing or by spraying or immersion treatment.

In the present solution, the shape of the wood object is, for example, a board or a beam, and it can be a single piece, or the wood object can be a combination of several layers (laminate or composite).

Examples of wood objects are the following: single-piece wood boards and wood beams, wood veneer, fibre board, chipboard, lumber, glue-laminated wood, plywood, LVL (laminated veneer lumber) board or beam, or OSB (oriented strand board). Of particular interest are planar pieces, such as boards.

The treated wood surfaces can be directly used two-dimensionally, that is, for example directly as (base)plates for cast-in-situ concrete or as a surface of a casting form. However, it is possible to use them to produce desired three-dimensional structures for casting of concrete elements of various types and shapes.

Typically, the material to be cast comprises a mixture of a hydraulically hardening binder and a filler (aggregate). The binder may be, for example, clinker-based or pozzolan-based. It is known that typical binders of concrete masses are for example. Portland cement, Portland blended cement, blast furnace slag cement, pozzolan cement and blended cement, particular examples of which cements are also sulphate resistant Portland cement, Portland limestone cement and Portland blast furnace slag cement.

Due to their good detaching properties, the wood surfaces can also be used as casting surfaces for other masses that are mineral-bearing and which harden, as well as for polymer masses and composite masses. The following non-limiting examples clarify the present invention.

Example: Treatment of wood with a hydrophobing agent that reacts with the hydroxy! groups in the wood

An aqueous dispersion of AKD is mixed into water at a ratio of 1 : 1 , in which case the resulting release agent solution comprises AKD approximately 10 % by weight. This solution is applied onto the surface of spruce plywood on an industrial surface treatment line.

When the AKD dries, it reacts with the hydroxyl groups in the wood and makes the wood surface highly water-repellent and, at the same time, generates a waxy layer on the surface of the wood.

Concrete casting forms are prepared using the wood board which is treated in this way. The wet concrete is poured into the forms and allowed to dry. When the concrete has dried, the form structures are dismantled, that is, the plywood parts are detached from the concrete. The plywood parts, which are treated according to the present invention, can be easily detached from the surface of the concrete, without damaging the boards or the concrete, thus the need for any repair of the concrete surface is reduced and the recycling of the boards is improved. In addition, the working safety and comfort are improved.

Casting experiments have been carried out with the spruce plywood that is treated with the AKD dispersion described above. The tests also involved other solutions which the present invention relates to, and which solutions are suitable for this example. The procedure and the results of the test are described in the following casting test.

Casting test

This test examines the adhesion of the wood surface to the concrete. The test demonstrates well the detaching properties of the release agents. In this test, "concrete cakes" are cast onto a treated softwood-plywood surface, which cakes are detached from the surface, after drying. The detachability, the quality of the casting surface, and the amount of concrete remaining on the wood board are compared in the analysis of the results.

The most significant property with regard to the application is the detachability, that is, how easily the wood surface is detached from the casting surface.

The table below describes the results. The figures show the board surface and the concrete surface after the drying of the casting.

Table

List of References

Patent Publications

WO 2008154421

US 3,497,375

US 2009304939

WO 2009004110