SE509980C2 - Procedure for bonding oil to wood - Google Patents

Abstract

The invention relates to a method for binding oil to wood and to a composition used in the method. According to the invention a wood product is contacted with a composition containing a solid anhydride, vegetable oil and alcohol. The treated wood product is dried and then subjected to a heat treatment at a temperature above 150 DEG C in order to bind the oil. The vegetable oil used preferably comprises at least one double bond, such as linseed oil, tall oil or rapeseed oil, and the anhydride used comprises maleic anhydride, succinic anhydride or phthalic anhydride. An auxiliary solvent, i.e. a lower aliphatic alcohol is used in order to help mixing the oil with the anhydride. By means of the invention the oil is so well bound to the wood that no oil seeps out of the wood even if it is heated above 70 DEG C. The oil-treated products can be used for outdoor furniture and boat boards.

Description

15 20 25 30 35 509 980 2 glycerol. As a result of the low pH value (1 - 2), the strength of the wood decreases. The acidity remaining in the wood can affect the long-term durability and cause e.g. corrosion of iron structures.

The object of the present invention is to remedy the disadvantages associated with the prior art and to provide a new technical solution for bonding oil to wood.

The invention is based on the formation of a treatment composition comprising at least one vegetable oil, at least one acid anhydride and at least one alcohol which is miscible with the oil and the acid anhydride. The acid anhydride is mixed with the oil under co-solvent. use of the alcohol as The wood product is impregnated with a desired amount of the composition and the oil is bound to the wood by heat.

More particularly, the method according to the invention is characterized mainly by what is stated in the characterizing part of claim 1.

The composition according to the invention is characterized by what is stated in the characterizing part of claim 11.

Essential features of the invention are polymerization of the oil absorbed in the inner parts of the wood to form a solid which does not penetrate to the surface of the wood even at a temperature of up to 100 ° C, as well as reduction of the swelling and maintaining the shape of compressed wood.

The vegetable oils used in the invention may be derived from annual or perennial plants. Typical oils pressed from plant seeds can be obtained, for example, from turnips, rapeseed, sunflower, flax, soybean, cotton, peanut, pumpkin, ricin, sesame, coconut, cocoa and almonds. You can also use oils derived from fruits that contain oil, e.g. oliver. In addition to the above-mentioned oils, crude tall oil, which is obtained as a by-product of cellulose cooking, and oils which can be separated from wood by, for example, steam distillation, such as tall oil, pre-distilled from tall oil and mixtures of turpentine oil, are also suitable.

A common feature of all the above oils is that they contain at least one double bond. However, many of the vegetable oils are polyunsaturated, ie. they contain a plurality of conjugated double bonds. usually Synthetic oils containing at least one double bond can of course also be used instead of the above-mentioned oils. These oils can be produced from short and long chain olefins by oligomerization.

According to the possible use of compositions containing mixtures of two or more oils, at least one of which belongs to the above-mentioned invention, it is the oils.

The vegetable oil is used together with an acid anhydride or a corresponding reactive substance, which is capable of producing esterification reactions in wood (esterifying component). According to one embodiment of the invention, acid anhydrides are used to bind oily substances to wood. The acid anhydrides can be aliphatic or aromatic. Preferably, acid anhydrides derived from dicarboxylic acids are used. Of the aromatic acid anhydrides, compositions containing a benzene ring are preferably used, and of the aliphatic, preferably saturated or unsaturated acid anhydrides containing 4 to 6 carbon atoms. These compounds are solids at room temperature 10 15 20 25 30 35 509 980 4 substances. Particularly maleic anhydride, preferred examples are succinic anhydride, glutaric anhydride and phthalic anhydride.

The alcohol used in the invention consists of an aliphatic or aromatic alcohol or phenol, preferably a lower aliphatic alcohol having 1 to 6 carbon atoms, such as netanol, ethanol, n-propanol, i-propanol, n-butanol, i-butanol, t-butanol or a pentanol or hexanol. The alcohol miscible with suitable alcohols is assumed to be the oil and most at least to some extent dissolve the acid anhydride used.

Without any intermediate or co-solvent, the esterified acid anhydride mixes. They do not mix the acid anhydride or the corresponding component and the oil with each other. Ethanol has proven to be a particularly advantageous co-solvent.

The alcohol used in the invention contains at most small amounts of water. Preferably, absolute alcohol with a water content is used in an azeotropic mixture of alcohol and water. Thus typically it amounts to over 90%, corresponding to the alcohol concentration preferably above 95%.

The term "co-solvents" includes all solvents which are miscible with the other components of the compositions, in particular with the oil (s) and the anhydride (s). The compositions according to the invention typically consist of emulsions containing an oil and an acid anhydride phase. However, at least some of the acid anhydride and also of the oil can be dissolved in the alcohol. For this reason, the compositions are hereinafter referred to as emulsions rather than simplicity rather than solutions.

Within the scope of the present invention, the term "the wood product intended for treatment" means a product made of wood (TI CD MD \ O CO CD 5), the shape or properties of which it is desired to change. For example, it is desired to bring the wood product a plastic mold to shape it, or the wood is treated to improve its dimensional stability, in particular its surface hardness.A product intended for the treatment according to the invention typically has an at least moderate thickness, which is usually greater than about 5 m (= solid piece of wood It may comprise a cohesive piece of solid wood, but it may also comprise a laminated product (eg a chipboard or a fibreboard) made of wood veneer or wood shavings, such as genonx compaction.

The wood product can also consist of a structure, whose continuous wooden layers are attached to each other to form a laminate. In the latter case, the term "wood product" refers to a layered or laminated product, which can be impregnated either before it is formed into a product or thereafter.

The method according to the invention comprises three steps, namely treatment of the wood pieces with a composition according to the invention, drying of the wood pieces and heat treatment thereof (to bind the oil components to the wood by means of heat).

In the first step, the pieces of wood are typically impregnated with an emulsion containing acid anhydride, oil and alcohol.

The emulsion may also contain additives known from the use of acid anhydrides, such as glycerol. Such a mixture is prepared by mixing together 1-1000 parts by weight of acid anhydride, 1-1000 parts by weight of vegetable oil and 1-1000 parts by weight of alcohol. Preferred mixing ratios (indicated in acid anhydride-oil-alcohol) are as follows: 1 - 20: 1 - 100: 1 - 100. The order 10 15 20 25 30 35 509 980 6 Preferably, the wood raw material is impregnated with an emulsion of said kind with a weight ratio of 1 : 10 - 10:10 the oil. Preferably between the maleic anhydride and used is a rather concentrated composition containing the above-mentioned components in a concentration of about 1 - 99% by weight, preferably about 20 - 85%, in particular about 40 - 70%.

The amount of emulsion with which the wood product is to be impregnated depends on the purpose of use of the wood product and on the wood raw material (type of wood, density and moisture). Usually the wood material is impregnated with so much substance that it penetrates significantly deeper into the wood than just below the surface.

Regarding the reduction of wood swelling and stabilization of compressed wood, it is important that the wood product contains a large amount of oil. Thus, the wood is impregnated with it, preferably at least about 20 kg, preferably about 25 - 300 kg and especially preferably about 30 - 140 kg per cubic meter of wood.

The moisture content of the wood impregnation preferably amounts to 5 - 30%, particularly preferably about 6 - 7%. The impregnation can be performed by removing air from the wood under reduced pressure in a pressure vessel. Thereafter, the liquid intended for impregnation is fed into the vessel and the said composition in an amount of intended to be impregnated under normal pressure or possibly under overpressure (a known as vacuum pressure process). Alternatively, the wood material is immersed in an impregnating liquid for so long that the composition has plenty of time to penetrate deep into the wood (immersion pre-vegetable method which it is desired to bring it only to the surface of the process). When the oil / acid anhydride is wood, the impregnation can also be performed by surface coating.

After treatment with the oil and the modifying chemical, the wood product is slowly dried at a low temperature to leave the active removal auxiliary solvent and the chemical left in the wood. The drying is allowed to proceed until the moisture content of the wood product is lower than at least 20%, preferably also lower than 15-17%. The drying can be carried out at room temperature, but is preferably carried out at an elevated temperature below 100 ° C. The temperature depends on the alcohol used. Particularly in the case of ethanol, the drying is preferably carried out at a temperature between 20 and 99 ° C, particularly preferably between 30 and 95 ° C, typically at about 70 ° C. In the heat treatment, any known device can be used, such as a drying oven, a heating chamber or the like, by means of which the piece of wood can be dried in the presence or absence of steam.

According to a preferred embodiment, the oil-treated wood product is dried in such a way that the internal temperature and the temperature of the surface of the wood product are determined continuously and that the difference between them is kept rather small. Preferably, the said temperature difference amounts to a maximum of 30 ° C. The term "the internal temperature of the wood" refers to the temperature in the wood that can be measured at a distance from the outer surface of the wood. Depending on the shape of the pieces of wood, the "internal temperature" is typically measured at a depth of at least about 2 - 5 cm. The term "external temperature" refers to the temperature on the surface of the wood or something below it. In many cases, the "external temperature" corresponds essentially to the ambient temperature. The temperature is gradually raised in such a way that the temperature difference between the surface of the wood and its inner parts is kept constant with a deviation of at most about 5 ° C and does not become greater than 30 ° C.

Preferably the temperature difference is kept at 10 - 30 ° C.

This solution can be realized by arranging at least two sensors on a test piece, one of which measures the internal temperature of the wood and the other its external temperature. When drying large quantities of wood products, more than one test piece should be fitted with sensors. On an industrial scale, the invention can preferably be used in such a way that, based on the measurements, a suitable heating program is determined for each group of wood products, the heating program of the starting moisture taking into account the effect on the process.

After drying, the oil component of the wood product is bound, for example, in a heating chamber at a temperature of at least about 150 ° C, usually about 150 - 250 ° C. In the case of maleic anhydride, a preferred temperature range is 160 - 180 ° C. The time for the heat treatment typically amounts to about 10 minutes - 24 hours; however, the time of bonding or fixation depends on the size of the piece and the components of the treatment composition. You can use longer or even shorter time periods. In practice, it has been found that highly preferred results have been obtained if the temperature of the whole piece corresponds to the oven temperature for a period of at least 2 hours.

In connection with the heat treatment, the volatile constituents evaporate, which promotes the crosslinking reactions that take place in the wood.

By means of the invention considerable advantages are achieved. Thus, it is sufficient to bind the oil to wood so that the oil does not seep out even at high temperatures (not even at a temperature of over 100 ° C). Therefore, the surface of a wood product is according to sticky or sticky.

The treatment reduces swelling in wood up to 1/5 and stabilizes compressed wood so that it becomes moisture-proof. The pH of the solution used remains neutral. the invention neither The invention provides a modified wood product which (in addition to possible solvent residues) contains acid anhydride and vegetable oil and possibly reaction products thereof. 10 15 20 25 30 35 mc: \ o »o oo c: 9 Treated wood products according to the invention, sun-free from seeping oil, can preferably be used for the following purposes: furniture, boat boards, wooden bridge beams, wet constructions, outdoor furniture, needle-shaped constructions (noise barriers ) etc. In the following, the invention is described in more detail by means of an exemplary embodiment.

Examples Samples were treated as follows: Solutions consisting of a vegetable oil, maleic anhydride and an auxiliary solvent were formed.

Their compositions are given in Tables 1 and 2.

Wood pieces in the dimension 20x40x400 mm were impregnated with the solutions. After impregnation, the treated specimens were subjected to an intermediate drying at 70 ° C. Then the specimens were cured at a temperature of 160 ° C.

The curing time depended on the size of the specimen (approx. 2 - 6 hours). however, the sample was the same as the above-mentioned oven temperature for at least 2 hours.

The temperature of the entire swelling (thickness swelling and width swelling) of the specimens was determined by measuring the dimensions of the specimens at absolute dryness and after immersion in water.

Wood pieces that have been subjected to a conventional oil treatment and dried at an elevated temperature were used as control pieces. No acid anhydride was used to bind the oils and the temperature was not raised above 150 ° C either. The linseed oil treated pieces were first kept at 50 ° C for 3 days. Then they were exposed to a temperature of 70 509 980 10 ° C for one day. This resulted in about 1.5% oil (calculated based on the weight of the pieces) leaking out of the pieces. When the pieces were subjected to further treatment for 24 hours at 70 ° C, their weight decreased by a further 0.4%. The control pieces also included linseed oil impregnated test pieces, which were not kept in a heating chamber. Their weight changed by about 3% at 70 ° C (one day). The surface of the specimens was oily.

Each series of samples according to the invention contained at least one sample which was treated at a temperature of more than 150 ° C, but which did not contain any acid anhydride.

Table 1 below shows the swelling of birch pieces impregnated according to the invention with different soluents (maleic anhydride, oil, ethanol) and immersed for 1 day resp. 21 days in water.

Table 1. Wood swelling Thickness width Width swelling M: 0: E * ällning,% ing,% 1 day 21 days 1 day 21 days Linseed oil (1: 1: 1) 0.80 1.82 1.42 3.07 (0: 1 : l) 2.35 7.44 2.52 7.54 Rapeseed oil (1: 1: 1) 0.35 0.41 0.59 1.23 (0: 1: 1) 1.78 5.11 3, 50 10.58 Tall oil (1: 1: 1) 0.49 0.90 1.17 3.35 (1: 2, 5: 2, 0.66 2.34 1.15 4.52 5) 1.02 3.08 1.26 3.74 (l: 5: 6) 1.14 V 3.12 1.68 4.73 (0: 1: l) 509 980 ll Control 8.52 8.89 11.53 12 , 51 maleic anhydride vegetable oil ethanol 1) MOE The samples according to the invention showed a dry surface and no seepage. oil out of them, not even at a temperature of 70 ° C. The swelling of the sample is also very small. The table clearly shows that the addition of acid anhydride in the treatment composition reduces the swelling by more than 50%. The more acid anhydride was included in the composition, the less swelling was observed in the wood.

Table 2 below shows the thickness swelling of birch pieces impregnated with different mixtures (maleic anhydride, oil, ethanol) and then compressed by 30% after immersion for 1 day resp. 21 days in an aqueous solution.

Table 2. Stabilization of compressed wood Thickness swelling, M: 0: E *% 1 day 21 days Linseed oil (l: l: l) 3.42 5.79 (O: l: l) 31.11 33.71 Rape oil (l : 1: 1) 1.41 6.83 (O: 1: 1) 28.51 35.97 Tall oil (1: 1: 1) 1.82 9.50 (1: 2, 5: 2, 1.43 12.14 5) 3.54 17.59 10 (1: 5: 6) 26.44 (0: 1: 1) *> The favorable wood stabilization table 1. 12 37.07 M = maleic anhydride 0 = vegetable oil E = ethanol's effect of acid anhydride on is even clearer from Table 2 than from

Claims (15)

5 10 15 20 25 30 35 40 m c: »o no oo <:> 13 PATENT REQUIREMENTS: Process for binding oil to wood, characterized in that: - the wood product is brought into contact with a composition containing a solid acid anhydride, a vegetable oil and an alcohol, and - the wood product treated with said composition is subjected to a heat treatment at elevated temperature. Process according to Claim 1, characterized in that an oil containing at least one double bond is used. Process according to Claim 1 or 2, characterized in that rapeseed, rapeseed, sunflower, flax, soybean, cotton, peanut, pumpkin, ricin, sesame, coconut are used as vegetable oil. -, cocoa, almond or olive oil, or crude pine oil, distilled pine oil, a pre-distilled pine oil or turpentine oil or a mixture thereof. 4. A process according to claim 1, 2 or 3, characterized in that a lower aliphatic alcohol such as ethanol is used as the aliphatic alcohol. Process according to one of Claims 1 to 4, characterized in that maleic anhydride, succinic anhydride or phthalic anhydride is used as the acid anhydride. Process according to one of Claims 1 to 5, in that the wood product is dried at a temperature of at least 15 hours after treatment with a composition of acid anhydride, vegetable oil and alcohol at a temperature of about 50 - 100 ° C and then subjected to a heat treatment at a temperature of over 150 ° C to bind the oil to the wood. Process according to any one of the preceding claims, characterized in that the composition contains at least a small amount of glycerol. Method according to one of the preceding claims, characterized in that the wood product is treated with the composition by impregnating, pressure-impregnating or vacuum-impregnating the wood with the composition. Use of an acid anhydride to bind vegetable oil to wood. Use according to claim 9, characterized in that the acid anhydride and the vegetable oil are mixed with an auxiliary solvent such as ethanol before the mixture of vegetable oil and acid anhydride is brought into contact with the wood. 11. Composition for oil treatment of wood, containing - 1 - 1000 parts by weight of vegetable oil and - 1 - 1000 parts by weight of alcohol miscible therewith, characterized in that the composition further comprises - 1 - 1000 parts by weight of acid anhydride. Composition according to Claim 11, characterized in that it contains 1 to 20 parts by weight of acid anhydride, 1 to 100 parts by weight of vegetable oil and 1 to 100 parts by weight of alcohol. Composition according to Claim 11 or 12, characterized in that it contains linseed oil, tall oil, crude tall oil or rapeseed oil or a mixture thereof, maleic anhydride, succinic anhydride or phthalic anhydride and a lower aliphatic alcohol. 14. Modified wood product, characterized in that - it contains acid anhydride, vegetable oil and possibly reaction products thereof, and - no vegetable oil substantially leaks out of it. Wood product according to claim 14, characterized in that it is used for indoor and outdoor furniture, boat boards, wooden bridge beams, wet room constructions and environmental constructions.