WO2018160112A1

WO2018160112A1 - Structural element and method for its manufacture

Info

Publication number: WO2018160112A1
Application number: PCT/SE2018/000004
Authority: WO
Inventors: Sören VIKLUND
Original assignee: Viklund Soeren
Priority date: 2017-03-01
Filing date: 2018-02-28
Publication date: 2018-09-07
Also published as: SE1730052A1; EP3612685A4; SE540654C2; EP3612685A1

Abstract

The present invention relates to a structural element (1) with reduced heat conductivity and with a reduced risk of rotting, mold growth and the like, as well as having improved fire protection, comprising at least one elongated object (2) of wood with one first side (3) having at least one first opposite side (4) and at least one second side (5) with at least one second opposite side (6) and a first end and a second end. The elongated object (2) comprises a plurality of holes essentially in the transverse direction of the wood fibers, and that the volume of the holes constitutes 20 to 80 percent of the elongated object's (2) volume. The holes form at least one transverse row (11) and at least one first adjacent transverse row of holes (12) that are mutually offset. The wood material in the structural element (1) is impregnated. The present invention also relates to a method of manufacturing the structural element.

Description

Structural Element and Method for its Manufacture

Field of the Invention

The present invention concerns a structural element as well as a method of manufacturing the structural element, in accordance with the claims. Background of the Invention and Prior Art

Several different types of structural elements for building construction have been developed over time. Traditionally, structural elements of wood have been used, such as logs, boards, beams, planks and the like, along with other materials for the outer (external) climate barrier of buildings. The use of structural elements of wood, however, presents a number of different problems. For example, wood has a relatively high thermal conductivity, and thus it can be difficult to achieve good thermal insulation in the climate barrier. Wood materials in building constructions have problems with moisture absorption. In the long run, all moist wood is degraded (damaged) by microorganisms, which can cause a variety of problems as described below. Furthermore, wood material is relatively sensitive to fire. Craftsmen learned early to use mature winter-felled wood for the climate barriers of wood buildings. Only mature well-dried wood was used for the exposed parts of houses' climate barrier. In modern industrialized construction it is difficult to select a similar sort of lumber because it requires a skilled craftsman or special equipment to see the difference between sapwood and heartwood in dry spruce timber. Mature timber, often called heartwood, consists of inactive cells where the openings between the cells are closed, which hinders water transport (diffusion). It is difficult for water to penetrate in the tangential but especially in the radial direction. Therefore, it is almost impossible to force in impregnation in the depths of mature wood. In end-cut wood, however, there is a certain absorption of liquid and therefore almost all wood can be impregnated a bit into the fiber direction via end-cut wood, although it is much slower in heartwood than sapwood. Moisture damage on wood usually starts from end-cut wood, especially when the end-cut wood from sapwood, without impregnation, is exposed to moisture.

Heartwood from pine contains more resins and it is possible to see, with the naked eye, a difference in sapwood and heartwood. The sapwood of conifers has a low resistance against rot and contain more water and hemicellulose. These sugars attract microorganisms and insects. In buildings, wood absorbs moisture and water if exposed to humid air or directly to water such as condensation or rain. Wood absorbs water at least 20 times faster in the fibers' radial direction compared to the tangential fiber direction and when moisture content rises above 20 percent, wood is attacked by fungi and other microorganisms. During parts of the year, moisture content is critically high for most wooden buildings, and especially where wood is combined with materials that do not absorb as much moisture such as mineral wool. The walls of well-insulated houses do not get as warm as the framework in older timber houses became. The coldest parts are also the moistest. The ability to absorb and emit moisture varies between different types of wood and must be considered when using different woods for different purposes.

Insects can also attack (infect) wood even though ants prefer moist organic insulation material such as EPS. Mice and rats prefer mineral wool where they can completely spoil the insulation properties of the climate barrier in a short period of time. The combination of moisture and droppings they leave behind is particularly beneficial for microbiological growth. When organic matter breaks down, a number of substances are emitted that can be toxic to human health and in some cases this has become known as the sick house syndrome. The only safe way to remedy affected structures is to replace all contaminated materials and try to build drier or more moisture-resistant structures which will always be expensive.

Methods to improve wood's resistance to the mentioned problems with rot have been developed over time. Processes for charcoaling wood, as well as heat treating wood, have been around for a long time. When wood has been heat treated, it does not absorb as much moisture anymore, both across the fiber direction and along the fiber direction. For example, posts that have been sunk into the ground that have been heat treated (charcoaled) since ancient times. When wood is exposed to temperatures over one hundred degrees Celsius, changes in wood chemistry cause a lot of the hemicellulose to break down and make the wood less attractive to microorganisms, fungi and the like. The wood is not fully rot resistant, but it has an improved protection against degradation thanks to lower moisture content. The technical/physical properties of the wood are also affected to varying degrees. Wood gets a brownish color after a certain period of time at two hundred degrees Celsius, which becomes relatively grayish when exposed outdoors. It becomes more brittle than untreated wood, and its strength is significantly reduced. However, the compressive strength across the fibers is not significantly affected.

Another way to protect (preserve) wood is to impregnate (treat) it in various ways. A number of harmful for the environment impregnation methods have been developed with serious ecological impact as a consequence. A more environmentally friendly impregnation method consists of impregnation by so-called waterglass (liquid glass). Waterglass has long been used as fire protection and wood preservative. For example, treatment of wood with waterglass is previously known from US63618. The problem with waterglass is that it is water soluble when used on wood. It leaches out and rinses off with rainwater. Waterglass impregnation must therefore be rendered insoluble and cured when repeatedly exposed to water.

Waterglass can be prepared by combining quartz powder (silicic acid) and appropriate amounts of potash or soda. When the compound is heated, a smelt is formed which is water soluble. The smelt is diluted with water to the desired concentrations. Essentially, sodium and potassium are used for waterglass. Waterglass is a mineral, odorless, diffusion-free and no harmful substances are emitted from the liquid water glass or after it has cured. Waterglass has a high Ph value. Potassium waterglass is preferably used in paint manufacture and the cheaper sodium waterglass or a combination of these two will be used in the present waterglass impregnation. Preferably sodium silicate is used which is commonly referred to as sodium waterglass. Via SE535622, by Applicant Organowood, a variant of an environmentally friendly wood treatment method is described. In the process, preferably sodium silicate is used. The intention is to prevent rot, mold fungi or the like. The method describes how the waterglass can be made stable and insoluble in water and then used for impregnation. By polymerizing monomers of sodium silicate to long polymer chains, sodium silicate is rendered insoluble. When sodium silicate solution is acidified, this reaction takes place and Organowood has developed a method of low addition of an acid in the aqueous solution, thus facilitating the waterglass to become insoluble. The invention discloses that acid is added to the aqueous solution to be close to the gel point. The solution is then still stable during storage and when applied by dipping, steeping or spraying of the wood material. Agents are also added that affect viscosity. Then the solution is pressed into the fibers using a known vacuum/pressure impregnator method and then dried and cured. The technology described in SE535622 differs significantly from the technology in accordance with the present invention. The description discloses nothing about a structural element according to the present invention. Furthermore, nothing is said that wood is dipped or sprayed (showered, steeped) in a traditional waterglass solution without additives where only the concentration of sodium silicate in the solution varies but where the solution is acidified by carbon dioxide after the waterglass solution has penetrated into the wood without vacuum or pressure impregnation methods.

Other existing methods are to first impregnate with waterglass, dry and use an acidic solution in a second step. Additional two-step solutions are available. Despite the fact that vacuum and pressure chambers are used during impregnation, it is still difficult to penetrate through the growth rings, especially in mature heartwood. Drying by using a two-stage process makes the method time-consuming and expensive. The method according to the present invention with deep penetrating rapid permeation (saturation) without a vacuum/pressure chamber even for coarse (thick) dimensions, and that drying and insolubility occurs in one step via carbon dioxide means that the present technology differs significantly from these other methods.

Via WO20110904418 is known a variant of building construction technology in which structural elements are provided with longitudinal grooves. In an alternative embodiment, it is also disclosed that the elements are treated with impregnating agents. The technology described in the description differs to a significant extent from the technology in accordance with the present invention. For example, the structure has a lower shape stability. It has a plywood layer on either side of the wall and in thicker wall constructions also a sheet in the middle. It does not join together in a similar way and has longitudinal groves and no closed cells where end-cut wood is exposed. Should it be impregnated with waterglass, this impregnation would take considerably longer time because impregnation has to penetrate perpendicular to the direction of fiber. The penetration across the fibers goes so slowly that pressure impregnation is required to make this method work. There is no description of a drying method, temperatures or anything about making the impregnation solution insoluble.

In the present invention, the impregnation liquid is absorbed through end-cut wood exposed in the drilled (bored) holes, and neither a vacuum nor a pressure chamber is required to allow the liquid to penetrate even into the heartwood. The waterglass is dried and rendered insoluble in one step according to a new method. The purpose of the present invention is to create a structural element and a method of manufacturing the structural element, which solves or reduces at least one of the above mentioned problems. This purpose is achieved by a structural element and a method of manufacturing the structural element according to the claims. Brief Description of the Drawings

In the following detailed description of the present invention, reference and references to the following figures will occur. These figures are briefly described in the following figure list. The structures shown in the figures are exemplifying embodiments of the invention in accordance with the present patent application. Note that the figures are schematic and details may thus be omitted in these.

Fig. 1 shows a first embodiment of the present structural element in perspective askew from above.

Fig. 2A shows a cross-sectional view of the structural element in accordance with Fig. 1.

Figs. 2B to 2C shows cross-sectional views of alternate embodiments of the structural element.

Fig. 3 shows a part of the simplest type of body built-up of the structural element.

Fig. 4 shows a wider variant of body built-up of the structural element.

Fig. 5 shows a body with intermediate material layers with transverse fibers.

Fig. 6 shows a cross-sectional view of an element in accordance with Fig. 5. Figs. 7A and 7B show a structural element with at least one layer that has standing growth rings.

Detailed Description of the Invention

With reference to the figures, a structural element 1 and a method for making the structural element 1 will be described in more detail. The structural element 1 in the exemplifying embodiments are comprised of at least one elongated object 2 of wood. In alternative embodiments (not shown in figures) of the structural element 1, it is comprised of any other type of wood object having a shape other than an elongated shape. The elongated object 2 may, for example, consist of a stud, plank, beam or the like. The wood in the elongate objects 2 preferably has a fiber direction extending in the longitudinal direction of the elongate object 2.

The shape of the elongated objects 2 may vary within the scope of the present invention. In the exemplifying embodiments, the elongate objects 2 have a square cross-section, or essentially a square cross-section, which is preferably rectangular, square or is of another for the purpose suitable shape. In the exemplifying embodiment, the elongate objects are comprised of at least one first side 3 and at least one first opposite side 4 to the first side 3. The elongated objects are further comprised of a second side 5 and one to the second side 5 opposite side 6. The elongate objects 2 are further comprised of a first end (terminus) 7 and a second end (terminus) opposite to the first end 7.

In order to reduce the thermal conductivity of wood, a large number of holes are drilled in the elongate objects 2 (structural element 1) such as studs, planks or the like. Preferably the holes are 5 - 50 mm in diameter depending on the dimensions of the structural elements. In alternative embodiments, the holes may be of different dimensions which differ from the specified intervals.

With reference to Fig. 2 A, it is shown that the holes consist of bottom holes 8 which are not through holes but leave a remaining layer 9 that is saved on one side. In the embodiment of Fig. 2A, the remaining layer 9 consists of an unpierced (unbroken) layer. The holes are drilled so that the remaining layer consists of material closest to the core. This is done to achieve standing annular growth rings and maximal heartwood, which contributes to dimensional stability. The thickness of the remaining layer 9 and the depth of the holes can be varied respectively.

During the making of the holes 8 in the elongate objects 2, the longitudinal fibers are left along the sides and the underside untouched, that is, the outermost material layer is not pierced by the holes. In alternative embodiments, at least one of the holes may be a through hole 10, through holes are shown in Figs. 7 A and 7B.

With reference to Figs. 2B and 2C, embodiments are shown wherein the holes are drilled from two opposite sides. In the figure, these are drilled from sides 3 and 4. In Fig. 2B, the remaining layer 9 consists of a partially pierced layer. By this design, a part of the dimensional stability is maintained on both sides that are drilled (the surface of the holes is distributed on both sides).

The bottom holes 8, and possibly any through holes 10, can be drilled (milled) in different designs, such as for example in honeycomb patterns (but with round holes instead of hexagonal) where adjacent rows of holes are offset (displaced) in relation to each other as shown in Figs. 1, 3 and 4 . These figures show that row 11 and adjacent rows 12 are offset (displaced) relative to row 11. The holes 10 may be of the same size or alternatively the size of the holes may vary.

Referring to Fig. 2C, alternative embodiments are shown in which the unpierced remaining layer 9 is located at a distance from either of the sides 3 and 4. Thus, the structural elements 1 (elongate objects 2) are drilled from both sides with an unpierced layer 9 in the center. In the left part of the figure there is shown an embodiment in which the remaining layer is located in the middle of the structural element or essentially in the middle. In the alternative

embodiment shown in the center portion of Fig. 2C, the remaining material layer is positioned adjacent to one of the sides 3 or 4.

In further alternative embodiments, shown in the right-hand portion of Fig. 2C, at least one sub-area (part, section) 13 of the structural elements 1 (the elongate objects 2) is not drilled (not bored) or only partially milled (drilled, bored). The area (part) 13 size relative to the structural element 1, as well as the location of the area 13, may vary. For example, the area (part) 13 may be used for attachment or assembly.

The area 13 may also include fewer holes per surface unit and/or have holes substantially less deep than holes in other sub-areas of the structural elements 1.

The end-cut wood of the structural element 1 (the elongated object 2) is left untouched, that is, no holes are drilled that extend out to the end. In the preferred embodiment of Fig. 1, after two rows of holes 11 and 12 have been drilled (milled), all longitudinal fibers apart from a thin layer on three of the sides have been cut. Between 20 and 80 percent of the wood is removed in this way. Hole volume constitutes 20 to 80 percent of the structural element's volume.

In preferred embodiments, about 45 to 55 percent of the wood is removed by drilling. The volume of the holes is 45 to 55 percent of the structural element's volume. In a particularly preferred embodiment, 50 percent of the wood is drilled (milled) away which causes the structural elements 1 (wood) to thereby decrease to half their weight after drilling. The volume of the holes amounts to 50 percent of the structural element's volume. By way of the surface enlargement of the structural element 1 (via the surfaces of the holes 8) and the reduced volume of wood, the time required for heating and drying of the structural element decreases.

When the holes 8 of the structural elements 1 are drilled, to the suitable (intended) extent as previously mentioned, the elements are dipped or sprayed (doused, showered, steeped) in a silicate solution and then dried and sometimes cured. The drilled and impregnated structural elements 1 are then laid on each other and glued together. The structural elements 1 thus recover their structural stability when the drilled side is glued to the next structural element's 1 cohesive layer. The reduced surface remaining on the structural elements 1 after the holes are drilled increases at the same time the element's compliance with the substrate. It becomes easier to bend and twist the structural element until gluing occurs. This means that when the structural elements 1 are glued, the compression pressure can be reduced to one third or lower.

Referring to Fig. 3, a part of a body consisting of the structural elements 1, which are joined together by gluing, is shown. The figure shows three horizontally oriented structural elements joined together with a width of a structural element. The body is built-up of an arbitrary number of structural elements at an arbitrary number of vertical levels (strata, layers). Joints between structural elements at two adjacent vertical levels are offset (shifted) relative to each other. In alternative embodiments, the body may be built-up of structural elements in a direction other than horizontally oriented, such as vertically oriented or other for the purpose suitable direction.

Referring to Fig. 4, a section of the body is shown that is comprised of multiple layers (strata) of horizontally oriented structural elements. The thickness of the body can be varied depending on the number of structural elements 1 (the elongated objects 2) placed side-by- side with each other in each respective layer (vertical level). The longitudinal joints 14 are covered by an overlapping structural element. Preferably, the structural elements 1 are placed so that a longitudinal gap 15 to the next structural element is obtained. The gap 15 breaks down thermal bridges which in turn results in improved insulation ability. The body is built- up of an arbitrary number of structural elements with an arbitrary number of vertical levels (strata, layers). The joints between the structural elements at two adjacent vertical levels are offset (shifted) in relation to each other. The design provides a finished body of wood that contains closed cells and where all wood can be completely impregnated with insoluble waterglass.

Referring to Figs. 5 and 6, a body (a composite structural element) is shown which comprises two or more structural elements 1 side-by-side. Further, the body comprises at least one material layer 16, with a transverse fiber direction relative to the longitudinal direction of the structural element 1, between at least two layers of structural element. The intermediate material layer 16 may be located between each vertical layer of structural element 1. In alternative embodiments, two or more layers of structural element are placed between at least one first material layer 16 and at least one second material layer 16. Fig. 6 shows a cross- section of the design according to Fig. 5.

With reference to Figs. 7A and 7B, structural elements 1 are shown which are comprised of at least one covering material layer 17. The covering material layer 17 preferably consists of a layer of material with standing annular growth rings (in the vertical direction). The structural element and the layer of material, alternatively the layers, form a beam. The material layer with standing annular growth rings causes impregnation to penetrate more easily while also improving the dimensional stability. The thin material with standing annular growth rings is impregnated in the same way as the structural element. Wood shrinks and swells considerably less in the radial direction than in the tangential direction. In Fig. 7A, an embodiment is shown with bottom holes as well as with a covering material layer 17. In Fig. 7B, one embodiment is shown with through holes with two covering layers 17.

It has previously been known to use waterglass to provide wood with protection from microbiological growth and protection against harmful insects. This impregnation also provides boards (structural elements) with better fire protection. The present invention describes a new method for reducing thermal conductivity of wood in structural elements. The present method achieves this by closed cells in the structural elements, and the wood must therefore be protected against the increased risk of insect infestation.

Waterglass is previously known to provide microbiological protection as well as protection against harmful insects. Moreover, by impregnating the structural elements 1 with waterglass, they also have better fire protection, which is also well known. The structural elements 1 are impregnated by rapidly absorbing a silicate solution into the fiber direction, then dried and rendered insoluble in a new way.

If wood is used as an outside climate barrier, above all end-cut wood exposed to water must be sealed as water is absorbed far into the wood along the fiber direction. This feature is utilized via a new impregnation technique where the structural elements are impregnated in an environmentally friendly way with waterglass.

Bottom holes are drilled in different patterns, for example in honeycomb patterns. The holes are made with drills, mills, hole saws or similar tools. By way of the bottom holes drilled in the structural elements, end-cut wood is thereby exposed inside the boreholes. When the drilled structural elements are dipped or sprayed (showered, doused, steeped) in an aqueous solution, the solution is almost immediately absorbed into the wood along the fiber's direction, which occurs at least 20 times faster than penetration in the fiber's perpendicular direction. Since the penetration (absorption) in the fiber direction occurs from two directions, the impregnation time is further halved. No additives are needed that change the viscosity of the aqueous solution and it is possible to impregnate coarse (thick) structural elements without a pressure and vacuum chamber.

By known methods, it is generally not suitable for spruce wood, heartwood and wood rich in resins to be completely penetrated by pressure impregnation. This is because it is difficult to push impregnation across the fiber direction. The said problem is eliminated, or substantially reduced, by the design of the present structural element due to the holes in the structural element exposing end-cut wood, whereby the impregnation rapidly penetrates into such wood even in coarse (thick) dimensions.

When drying wood, moisture content decreases quite rapidly down to about 30 percent. There the equilibrium moisture ratio is reached with air that has 100 percent relative humidity. Then the free water between the cells is gone while the cells are still largely unaffected and a large part of the water in the cell is chemically bound. When drying continues, some of the chemically bound water also dries. This shrinks the wood and changes its shape, which means that the finished wood should have a moisture content that fits well with the moisture content of the finished building structure. Impregnated wood should be as dry as practically and economically possible as impregnation can not penetrate where the wood is already saturated with water. With the present method and structural elements, the drying of the structural element 1 is facilitated by the boreholes providing shorter paths for moisture transport and almost all moisture transport (evaporation) takes place in the direction of the fibers. In addition, the boreholes may have removed more than half the volume of wood and increased the surface areas of the structural element.

Thanks to the design of the structural elements 1, the moisture transport does not need to occur transversely to the fiber direction of the structural element 1, which means that the amount of time needed for drying is reduced.

The risk of microbiological growth in untreated wood starts at about a 20 percent moisture ratio and upward. Timber temporarily exposed to water should have a hydrophobic surface or otherwise be protected. Impregnation (treatment) should also be water insoluble so that it is not rinsed off by water. Waterglass in wood that has not been rendered insoluble is such an impregnation and therefore the impregnation must be rendered insoluble when the wood is to be used in outdoor environments.

The structural elements 1 are dipped (steeped) in a silicate solution. The elements remain in the solution the required time period needed for the solution to be absorbed into the element's heartwood (heartwood needs twice as much time to absorb the silicate solution compared to sapwood). After this the surplus solution can drain (drip, run) off. The solution remains in the wood as long as the relative humidity of the surrounding air (gas mixture) is 100 percent. Preferably, the surrounding air (gas mixture) has an increased content of carbon dioxide. Alternatively, the carbon dioxide content corresponds to the air's natural proportion of carbon dioxide. In this state, the structural elements 1 are held for a period of time in a space with 100 percent relative humidity. The silicate solution is acidified via the carbonic acid formed in the aqueous solution when it comes into contact with the carbon dioxide of the air (gas mixture). The required time is adjusted to the temperature the solution gets when mixed with cold water, but room temperature or a slightly elevated room temperature is preferable.

Impregnation of the structural elements 1 is rendered insoluble by means of carbon dioxide. When flue gases are added to the wood dryer, the carbon dioxide content increases in the moisture-saturated air. The increased surface areas of the structural elements 1 created by the boreholes speeds up the process. When the structural elements 1 are dried, the temperature is increased at a slow pace using hot moisture-saturated flue gases. The acidic substances that are naturally formed when wood is heated together with the carbonic acid formed in the aqueous solution keeps the silicate solution suitably acidic throughout the drying process. Long polymer chains can then be formed on a continuous basis. When the relative moisture ratio is decreased, the release of moisture increases as the temperature slowly increases.

The temperature increase continues so slowly that a polymerization can take place at 100-120 degrees C. The temperature, time and flue gases' relative humidity ratio determines the amount of bound water remaining in the cells. When the structural elements 1 have dried sufficiently, the temperature is rapidly raised to 150 degrees C for less than 10 minutes for the waterglass to cure. In alternative procedures, the curing time may be 10 minutes or longer and the temperature may exceed 150 degrees C. The process proceeds rapidly because the structural elements 1 surface has increased by the drilled holes and the volume of wood may have been reduced to more than half relative to the original volume. To avoid self-combustion during drying and curing with flue gases, a lambda (oxygen) sensor is used to check that the oxygen level is kept at a level where wood does not ignite. When the structural elements 1 are then aired for remoisturization, it will take a long time before the moisture content of the wood increases, which is an advantage in transport, assembly and storage.

In case of alternative drying other than with flue gases, the closed drying room is filled with the desired concentration of carbon dioxide. When the temperature is increased, carbon dioxide is continuously fed from below. Being a heavy gas carbon dioxide then expels the oxygen in the drying room. Thus, the structural elements 1 can not self-combust, or not easily self-combust. When the temperature rises further by way of an external heat source, the relative humidity of the air can be controlled via a cold surface where the steam can condense. The structural elements 1 can also be dried in a traditional wood dryer.

The absorption of moisture from the surrounding air progresses slower and the impregnated wood in the structural elements 1 also absorbs less water during a temporary water exposure compared to untreated wood, which improves and makes the building construction process safer. By absorbing moisture at a slower pace, dimensional stability is increased, which is also good when some thin wood layers are glued to the fiber direction at 90 degrees to the underlying fiber direction. The advantages achieved are that the finished wall has less moisture diffusion, thermal conductivity decreases and the risk of damage by microorganisms is further reduced. Moreover, the finished structural elements 1 are not as sensitive to temporary exposure to moisture as untreated wood and become more fire-resistant. With the present method, sapwood from conifers and especially young wood form pinewood can be used because it is less resistant than heartwood and more easily absorbs liquid. It is therefore inappropriate to use such wood in exposed areas of the climate barrier if it is not impregnated. Defective wood such as stress (bent) wood, wood with resin globs and large knots is equally unsuitable to use. This lumber (wood) is suitable to drill and make beams of when they are impregnated and glued together. Thereafter, it is possible to use these structural elements 1 in different construction designs and exposed positions where no flexural strength requirements are present. Said wood is also the cheapest lumber.

When the impregnated structural element 1 is dried and the temperature is increased to cure the waterglass solution, the hemicellulose is partially degraded but the high temperatures and long processing times required for heat treating wood are avoided. A reduced amount of hemicellulose in wood does not protect it from fungi and microflora but the wood is not as easily affected as many attractive ingredients for these organisms are already dehydrated at the low temperatures that cure waterglass. In the detailed description of the present invention, design details and methods (processes) may have been omitted which are apparent to persons skilled in the art in the field of the method and device. Such obvious design details and methods are included to the extent necessary so that the proper and full performance of the present invention is achieved.

Even if certain preferred embodiments have been described in detail, variations and modifications of the method and device may become apparent for specialists in the field of the invention. All such are variations and modifications are regarded as falling within the scope of the following claims.

In alternative embodiments, other for the purpose suitable, or other suitable impregnating agents other than those mentioned in the patent application, can be used for impregnation (treatment). For example, impregnating agents containing metals. In alternative embodiments of the method (process), the penetration of the impregnating agents can be accelerated by vacuum or pressure.

Advantages of the Invention

The present invention achieves several advantages. The most obvious is that an improved structural element and method of manufacturing it is achieved.

Claims

1. A structural element (1) comprising at least one elongated object (2) of wood having a first side (3) with at least one first opposite side (4) and at least one second side (5) with at least one second opposite side (6) and a first end and a second end wherein the elongate object (2) comprises a plurality of holes essentially in the transverse direction of the wood fibers, and that the volume of the holes constitutes 20 to 80 percent of the elongated object's (2) volume and that the holes form at least one transverse row (11) in in relation to the longitudinal direction of the elongated object (2), and at least one first adjacent transverse row of holes (12) relative to the longitudinal direction of the elongate object (2) that are mutually offset and that the wood material is impregnated.

2. A structural element (1) in accordance with claim 1 wherein the volume of the holes consist of 20 to 80 percent of the structural element's (1) volume.

3. A structural element (1) in accordance with one of the previous claims wherein the holes are comprised of bottom holes (8) with a remaining layer 9 that consists of material close to the heartwood.

4. A structural element (1) in accordance with one of the previous claims 1 or 2 wherein the holes consist of through holes (10).

5. A structural element (1) in accordance with at least one of the previous claims

wherein the structural element (1) on at least one of its sides is covered by a material layer (17) chosen from wood near the timber core, so called heartwood.

6. A structural element (1) in accordance with at least one of the previous claims

wherein the structural element (1) includes at least two elongated objects (2) which are glued together directly ontop each other with offset joints.

7. A structural element (1) in accordance with claim 6 wherein the structural element (1) comprises at least one material layer (16) with its fiber direction in the transverse direction in relation to the elongated object's (2) fiber direction.

8. A method for manufacturing structural elements (1) in accordance with at least one of claims 1 to 7 wherein wood material is provided, after which a plurality of holes are bored in the wood material, essentially in the transverse direction of the wood fibers, then the wood material is impregnated with impregnating agents introduced by dipping, steeping or spraying, after which the wood material remains in the impregnation agent a period of time which depends on the extent of penetration of the sapwood or heartwood of the impregnating agent that is desired, then the excess impregnating agent is allowed to drain off after which the structural elements are placed to dry in air initially moisture saturated and where carbon dioxide is supplied in concentrated form or via flue gases while the temperature is slowly raised to 100-120 degrees C, after which the temperature is raised to about 150 degrees after which the material is allowed to air and cool.

9. A method in accordance with claim 8 wherein the impregnating agents consist of silica sol that include salts, whose level of salts may vary.

10. A method in accordance with claims 8 and 9 wherein the impregnating agents consist of waterglass.

11. A method in accordance with claims 8 to 10 wherein the level of carbon dioxide exceeds the normal carbon dioxide levels of the atmosphere.