MXPA00003664A - Novel material and process for its production - Google Patents

Abstract

The invention relates to a process for greatly increasing the elasticity and bendability of diffuse-porous wood and comprises the following steps:a) supplying a specimen of diffuse-porous wood;and b) isostatically pressing the specimen in a) with a pressure of at least 500 bar. The rigidity is increased once again by immersing the wood specimen in a liquid for up to 2 hours, after which the specimen is dried. This can be utilized when producing shaped products made of diffuse-porous wood.

Description

NOVELTY MATERIAL AND PROCESS FOR ITS PRODUCTION FIELD JE 1A NVEITION The invention relates to a process for producing a wood material having controllable bending properties. The process can be used to produce a wood material that has a high degree of elasticity and a high degree of bending capacity. The resulting wood material can be immediately deformed to a desired shape after which it is possible to block this shape in a simple manner, so that the wood material retains normal bending properties while the shape has been permanently altered, the invention it also refers to a wood material that has been produced using the above mentioned process. BACKGROUND OF THE INVENTION Constructions and objects of bent wood have been used by man since time immemorial. Since wood is a rigid material it has to be softened before it conforms and flexes so that it does not separate. Traditionally this softening has been achieved using heat, or alternatively using a combination of heat and moisture (for example using steam). The wood has also been softened by impregnating it with chemical agents such as ammonia, polyethylene glycol and pyridine.

In modern times, alternative wood materials have been developed that possess a high degree of bending and conformational flexibility, a type of the process based on thin wooden discs that stick together to form a laminated structure whose plasticity is greater than that of the raw wood material. Examples of this are described in JP-A, 9/70804 and JP-A, 7/246605. However, the flexibility described in these documents is not entirely satisfactory. Heat is required in connection with the bending stage. In addition, the wood material is unable to recover its normal stiffness after the desired deformation has taken place. There is therefore a need for an improved process to temporarily increase the elasticity of the materials and to decrease this elasticity to the normal level once the desired bending has taken place. SUMMARY OF THE INVENTION It has now been found that it is possible to greatly increase the elasticity and flexibility of diffuse pore wood, by means of a process comprising the following steps: a) supplying a specimen of the diffuse pore wood; and b) isostatically pressing the specimen of a) as a pressure of at least 500 bar.

The rigidity is increased again by immersing the wood specimen in a liquid for a period long enough for the liquid to be able to penetrate the entire specimen of the wood and then dry the specimen. Definitions: The finished "isostatic pressure" that is used here refers to a pressing with a pressure that is equally great in all directions in a space. The pressing of wood with a pressure of this nature is described in W095 / 13908, diffuse porous wood, is wood where the vessels are uniformly distributed and are approximately uniform in size throughout an annual ring. Examples of trees with diffuse pore wood are: alder, poplar, birch, beech, maple, eucalyptus, Canadian maple, Betula pendula, Acer seudopantanus, Acer rubrum, Nyssa sylvativa, Liquidambar styraciflua, Popolus balsa ifera, Fagus sylvativa, Banksia prionotes and Banksia ilicifolia. The finished "wood specimen" is used to indicate a diffuse porous wood specimen. A "composite wood specimen" refers to one that consists of several smaller specimens of diffuse pore wood that have been glued together in parallel to the direction of the fibers in the constituent specimens. In principle, most types of glue that are suitable for wood can be used to produce composite wood specimens. Examples that may be mentioned are cold water glues, hot melt glue, solvent-based glue, emulsion-based glue and polymerization-based glue having one or two components, use can be made in particular of glue having emulsions of polyvinyl acetate, PVC, polystyrene, urea, melamine, melamine formaldehyde, Phenol and polyurethane, it is simple for a technician to select a suitable type of glue based on the given conditions. The finished "liquid" is used here to indicate a liquid that is capable of penetrating the diffuse pore wood, examples of such liquids are water and flax oil / turpentine in a weight ratio of 1 / 100-100 / 1. The liquid may also contain other substances such as dyes and substances that increase the resistance to rot and fire. BRIEF DESCRIPTION OF THE DRAWINGS The invention will now be described in greater detail with reference to the appended figures in which: FIGURE 1 shows how the elasticity is altered by the process according to claim 1; FIGURE 2A shows a disc that has been cut directly from a tree trunk; FIGURE 2B shows a horizontal cross section of the disc, the annual rings are indicated; FIGURE 2C shows the formation of the disc (in a horizontal cross section) in connection with immersion in water; FIGURE 2D shows a horizontal cross section of the bowl that was obtained after drying; FIGURE 3, shows co-specimens of wood that have a high degree of elasticity can be produced by isostatically pressing diffuse porous wood that has been sawn and stuck in a specific template. The annual rings are fully indicated in this figure; and FIGURE 4 shows the result of a bending experiment using a composite wood specimen that was produced from specimens of diffuse pore wood whose elasticity had been increased by the process according to the invention. DETAILED DESCRIPTION OF THE INVENTION As already mentioned, the invention is based on the unexpected discovery that the elasticity of a specimen of diffuse pore wood is greatly increased after the wood has been pressed isostatically with a pressure of at least 500 bar, without trying to link the invention to any particular theory, it is assumed that the increase in elasticity after isostatic pressing is due to the vessels or pores remaining quite large and uniformly distributed in the diffuse pore wood collapsing in a structure ordered. It seems that the strength of the fibers does not change, since the force required to break them is the same as for ordinary wood material. The increased elasticity does not therefore occur in all directions. Fig. 1 shows how the elasticity is altered in the diffuse pore wood after isostatic pressing according to the invention. Fig. 1, shows a specimen of diffuse pore wood in which the woods are oriented from the surface A, B, C, D to the surface E, F, G, H, the annual rings are indicated on the surface, A, B, C, D. Fig. Ib shows the D, C, G, H side of the wood specimen. Here the fibers are therefore oriented from the side D, C, to the side G, H. If a pressure is applied in the center of the section D, H, no increase in elasticity can be observed. Fig. 1 shows the side C, B, C, D, of the aforementioned specimen. Pro contrast if a pressure is applied in the center of section A, D, it is possible to observe a clear increase in elasticity. The result of this is shown in Fig. Id, when sticking specimens of diffuse pore wood together in parallel in the wood shown in Fig. Id, a wood material having a very high degree of flexibility is obtained. As already mentioned above, it has been found that it is possible to decrease the elasticity of wood material that has been isostatically pressed according to the invention. The wood material recovers its rigidity after it has been immersed in a liquid for a long enough time so that the liquid is able to penetrate the entire wood specimen. The time by which the wood material has been submerged, to recover its rigidity again depends on the size of specimen that must be conformed. For relatively small specimens that have a cross-sectional area of 20 x 40mm, an immersion time of 5-15min. it is entirely adequate, while immersion times of up to 2 hours may be required for larger specimens. In principle, the immersion can take place at any temperature, as long as the wood material is not damaged and the liquid is still fluid. It is convenient that the immersion step be carried out at room temperature. By means of simple tests the technician is able to determine suitable immersion times and immersion temperatures in each individual case. Without linking the invention to a particular theory it is assumed that during immersion the liquid penetrates the previously collapsed pores with the help of osmotic forces and / or a hydrophobic interaction., resulting in the pores being restored to their original volume. As already mentioned, this invention is very useful in connection to forming wood material, for example in association with manufacturing furniture, even quite complicated shapes can be obtained. A wood material having an increased degree of elasticity occurs first, if a suitable work piece is required, it is sawn from the said material. The workpiece is then shaped to the desired shape for example using molds and / or jaws. The desired shape can then be fixed by immersing in a suitable liquid under suitable conditions, (such as those mentioned) followed by drying. There are no restrictions with respect to the size of the wood specimen different from those that refer to the size of the pressing device that is used. However, it is particularly advantageous to press specimens of wood in the form of discs and wood specimens having surface areas of more than 2m2, they can be pressed without difficulty as long as the size of the press allows. Presses of the pressure cell type described in SE-C-452436, represent an example of a suitable press device and the reader refers to the aforementioned WO95 / 13908 with respect to wood isostatic pressing. The wood specimen must have dried before the isostatic pressing takes place. It is advantageous if the humidity has decreased to a maximum of 50% of the content in the living matter. However, it is also possible to press isostatically wet wood if it can be ensured that the liquid that is squeezed is removed by means of absorption or away from the pressing device. The wet wood isostatic press technique is described in WO97 / 02936. The invention will now be described in greater detail with reference to the following examples given for purposes of illustration and not limiting the present invention. Example 1 A wooden specimen in the form of a disk having a diameter of 19.3cm, and a thickness of 1cm was cut from an aspen trunk. The disc was debarked and dried to a moisture content that was 48% of the original (see Fig. La and Ib) then pressed isostatically in a pressure cell type press (ABB Pressure Systems, Vásteras, Suecia) in the manner described in Example 1 in WO95 / 13908. The maximum pressure was 850 bar and the temperature 33 ° C. The total pressing time was 2 minutes. The following steps are performed at room temperature. The resulting elastic disk was placed in a bowl mold with a maximum depth of 4 cm, and clamped so as to take the form of a mold (Fig. 2c). The mold and wooden disc were immersed in water for 2 minutes, and then the elasticity of the disc was allowed to dry and retained its bowl shape even when it had been released from the mold (Fig. 2d). Example 2 A poplar specimen with dimensions 550 x 170 x 35mm. { Fig. 3a) indicating the annual rings and a moisture content remains 48% of the living tree, was used as a starting material. The specimen was pressed isostatically in the same manner as in Example 1. The maximum pressure was 1000 bar the temperature 34 C and the pressure time 2 minutes. After pressing the specimen dimensions were 438 xl36 x 22mm. It was flattened by hand to make the specimen completely smooth, then sawed through its length to give three specimens with the dimensions 146xl36x22mm. These specimens were in turn sawed into lamellae approximately 20mm wide and the surfaces were leveled by hand flattening, the lamellae were placed against each other, so that they would be in the same way as before sawing (Fig. 3B). And also in such a way that the three original specimens lean against each other. Therefore 21 lamellae were left against each other in the manner shown in Fig. 3C. A glue or cold water binder (Casco 3305, Casco, Suecia) was applied on the upper surface of all the lamellae, except the most to the right (Fig. 3D). All the lamellae were then turned a quarter of a revolution in clockwise direction (Fig. 3E) and subsequently pressed against each other (Fig. 3F) using jaws, then the glue was allowed to dry. The result was a specimen composed of wood (Fig. 3G) that had the dimensions 146x410x22mm. The specimen was transected 15tnm along its length resulting in a specimen having the dimensions 15x410x22mm, the specimen was then bent by hand until it had the shape of a horseshoe with an internal diameter of 125mm (Fig. 4). They observed cracks. Example 3 This example relates to determining the modulus of elasticity of the wood material of the present invention. Poplar wood that has a diffuse pore was compressed isostatically with a pressure of lOOObar, subsequently the wood was sawn into pieces of 20mmx20mmx200mm. The direction of the fibers of the pieces was perpendicular to the longitudinal direction of the piece. A first group (A) of pieces of 20mmx20m? R * x20trmrx200mm has been provided. The pieces of this group were sawn and glued in the same way as the pieces of group B, but the wood had not been compressed asystically. The pieces of the second group (B) were neither sawed nor glued together again. The pieces of the third group (C) were sawn in three pieces of 20mmx20mmxß0mm, 20mmx2OmmxdOmm and 20m? R? X20mmx60mm respectively. These pieces were glued together again using the same glue as in Example 2, in such a way that a new combined piece of 20mmx20mmx20Omm was obtained and the direction of the fibers of the piece was perpendicular to the longitudinal direction of the piece, the pieces of the fourth group (D) were sawed into five pieces of 20mmx20mmx40mm, then these pieces were glued together again using the new glue that in example 2, in such a way that a new combined piece of 20mmx20mmx20Omm was obtained and the direction of the fibers of the piece was perpendicular to the longitudinal direction of the piece. The modulus of elasticity was determined for all groups, the determination was carried out in accordance with European standard EN 310,1993 (European Committee for Standardization, Brussels BEL.), The equipment used in the experiments is shown in Fig. 5. The distance lx between the two supports 2 and 3 was 150mm. A deflecting member F deflects the piece to be tested 1, at a point located precisely in the center between the support members 2 and 3, the results obtained are summarized in table 1. TABLE 1 Test group Modulus of elasticity At 615 MPa 699 MPa B 348 MPa 319 MPa C 172 MPa 201 MPa D 25.0 MPa 64.2 MPa It should be noted that the wood material according to the invention (group C and D) have a much lower modulus of elasticity compared to the material of the control groups, groups A and B. It should also be noted, by the Fig. 8 that the group E test piece was so flexible that it did not crash during the deflection tests. All the pieces of groups A-C, broke.

Claims (8)

1. NOVELTY OF THE INVENTION Having described the invention as above, the content of the following is claimed as property: CLAIMS 1.- Process for producing a composite specimen of wood having a highly increased elasticity, a process comprising the steps of: a) supplying when minus two specimens of diffuse pore wood that have been made elastic by an isostatic pressing of specimen, with a pressure of at least 500 bar; and b) gluing the specimens in a) together in such a way that the fibers are oriented in parallel in the resulting composite wood specimen.
2. 2. Method according to claim 1, characterized in that the isostatic pressure is at least 850 bar and preferably greater than 1000 bar and the pressing temperature is at plus 40 ° C and preferably at more than 35 ° C and the time Pressing is when more than 5 minutes.
3. 3. - Process for producing molded products of diffuse pore wood comprising the steps of: a) supplying a specimen of diffuse pore wood or a specimen composed of diffuse pore wood whose elasticity has been increased by means of a process in accordance with any of claims 1, 2; b) forming the elastic wood specimen obtained in a) to the desired shape to which it follows to fix the specimen in the desired shape using fasteners which are normal within the technical field; c) immerse the fixed elastic wood specimen that has been obtained in b) in a liquid for a period of time that is sufficiently long for the liquid to penetrate the entire specimen of the wood, -d) dry the wood specimen resulting; and e) releasing the specimen from the fixing elements.
4. 4. - Procedure according to the claim 3, characterized in that the elastic wood specimen is immersed in water at room temperature.
5. 5. - Procedure according to the claim 4, characterized in that the elastic wood specimen is immersed in flax oil / turpentine in a weight ratio of 1 / 100-100 / 1.
6. 6. Procedure according to claim 4, 5, characterized in that the immersion time is between 5 minutes and 2 hours.
7. 7. Diffused wood powder material having an increased elasticity, which is produced using a process according to claims 1-2.
8. 8. - Diffused shaped or molded wood powder material that is produced using a process according to any of claims 3-5.