Construction components for a building based on glued native green wood

Abstract

The present invention relates to a process for gluing native green wood with a high moisture content (above 20%) for use as building construction material, and to the use thereof on native species, such as roble beech, coigue, lenga beech and rauli beech.

Description

[0001] CONSTRUCTION COMPONENTS FOR BUILDINGS BASED ON NATIVE GLUED GREEN WOOD

[0002] DESCRIPTIVE MEMORANDUM

[0003] Technical field

[0004] The present invention, in general terms, relates to the technique of green gluing on native wood with a high moisture content (over 20%).

[0005] Green gluing does not require the wood layers to be initially dry, with a moisture content of less than 20%. The procedure used for gluing native wood involves the use of polyurethane-based adhesives.

[0006] Background

[0007] In Chilean native forests, resources shorter than those required by the construction sector are undervalued. A significant portion of this wood is used as fuel, since producing longer timber requires technology and techniques that are not readily available to producers.

[0008] One of the main costs associated with adding value to wood is artificial drying. This process reduces the moisture content of the pieces, allowing them to be processed for longitudinal and end-gluing, thus enabling the manufacture of structural and / or decorative products for the construction industry. The drying process typically involves long pieces (over 2.4 m) to eliminate defects or irregularities. This results in a loss or waste of sections of the piece that do not meet the requirements or standards of the final product, leaving "dried" pieces of varying lengths that are discarded from the gluing process and used for fuel or other low-value purposes.

[0009] Dry products, with a moisture content between 9% and 19%, meet the standards established for service classes 1 and 2, which are also within the national regulatory framework. However, it is possible to pre-select parts of the wood without artificial drying, using a natural drying technique that is entirely environmentally friendly. Once certain moisture levels are reached, the wood can be selected, its longitudinal or face profiled, and the gluing process carried out, with moisture levels between 21% and 35%, depending on the species used. The aim is to avoid conventional kiln drying, which would later result in waste, or, alternatively, to produce products intended for service class 3, which are typically used outdoors.

[0010] The traditional gluing process requires that the wood be in a dry state, with a moisture content of less than 15% (Doerner, 2009), in order to then remove any defects or attributes unsuitable for the final product or performance. For this purpose, the green wood sample is placed in a kiln for drying, after which it is necessary to remove the defects from the pieces, resulting in losses that typically range from 15% to 34% (Rozas et al., 2005). The resulting usable wood is then ready for final bonding and gluing, with the consequent loss of energy and competitiveness.

[0011] In contrast, gluing green wood allows for prior discarding before drying, joining sawn pieces before the drying process, achieving a reduction in the appearance of cracks and other defects associated with drying, resulting in energy gains and reduced associated costs.

[0012] The green gluing process differs from traditional gluing in that the adhesives used allow the wood to have a moisture content exceeding 20%, even permitting gluing at levels close to 30% (Clouet, 2015). This green gluing process can begin with removing defects from the pieces (knots, cracks), followed by gluing the resulting usable wood. Once glued, drying takes place, either in a kiln or using the racking technique, where the pieces are exposed to natural ventilation, achieving moisture levels close to equilibrium naturally. After drying and subsequent traditional manufacturing processes, the resulting product is glued timber for structural use in service class 1 and / or 2, or, if the laminated element has a moisture content between 20 and 25%, it can be used for service class 3.

[0013] This research is based on the adhesion response in glued laminates with wet wood, in 4 types of Nothofagus grown in Chile, the species Nothofagus pumilio (Lenga), Nothofagus dombeyi (Coigüe), Nothofagus alpina (Raulí), and Nothofagus obliqua (Roble), and with the use of a one-component polyurethane adhesive.

[0014] The adhesion quality indicators, measured through shear and delamination tests on the glue line, showed satisfactory results, but also raise questions about the standards used for this type of wood in the world.

[0015] Wood naturally contains a large amount of water. When it dries, it loses a significant amount of water, though not all of it, due to its hygroscopic nature. This means it has the property of gaining or losing moisture in exchange with the surrounding environment until it reaches equilibrium. This property ensures that wood, under normal use, always retains a certain amount of moisture in its cell walls.

[0016] This variation in the amount of water has a direct impact on properties such as mechanical resistance, among others, and its ability to receive finishes and adhesives, the heat power it can generate, its resistance to fungal attack, etc., and on the changes that the wood undergoes due to these changes in humidity.

[0017] Excessive moisture in wood causes finishes such as lacquers, paints, varnishes, etc., to peel off, as they cannot adhere to the wood surface. This is due to the incompatibility between water and solvents, and also because water fills the wood's pores.

[0018] This research presents the implementation of the green gluing technique on native wood with high moisture content (over 20%).

[0019] The development of the green gluing technique involved the use of Nothofagus pumilio (Lenga), Nothofagus dombeyi (Coigüe), Nothofagus alpina (Raulí), and Nothofagus obliqua (Roble) species under varying moisture levels. Information regarding the green gluing technique in these species is scarce, which has posed a significant challenge in understanding the various factors involved in the successful development of the technique.

[0020] STATE OF THE ART

[0021] In terms of volume, glued laminated timber (GLT) is the most important product in the global engineered wood industry. A 2015 estimate indicates that global consumption of GLT reached 5.3 million m³. 3 This was more than double the consumption of laminated veneer lumber (LVL) (FEA, 2017). Other sources indicate that Europe and Japan dominate the glued laminated lumber market, together accounting for 84% of global consumption and 74% of production capacity (UNECE / FAO, 2020).

[0022] Squared boards undergo deformation during drying due to shrinkage caused by water loss. Traditional drying of a squared board before gluing results in deformation due to preferential shrinkage along the radial, tangential, and longitudinal axes of the wood. More specifically, these deformations occur at the cross-section of the wood, with tangential shrinkage twice as great as radial shrinkage, leading to warping of the squared board. Deformations along the longitudinal axis are generally related to the grain slope, that is, the angle formed by the wood grain direction and the sawing axis. The presence of knots can further disrupt the grain slope and accentuate longitudinal deformation.The squared board warps, and gives rise to a complex deformation that is also called warping, edge or front deflections, which is difficult to control.

[0023] The deformations induced by drying in two pieces to be glued result in an uneven joint thickness. Applying pressure to the gluing surface induces internal stresses within the wood, the greater the deformation. Consequently, during traditional gluing on a flat, dry piece of wood, it is necessary to plane or straighten the boards before gluing. Straightening ensures a flat reference surface along the length. Planing guarantees the parallelism of the boards' cross-section. Without planing or straightening, very strong gluing pressure must be applied to the boards' cross-section to correct these defects of warping and deformation and ensure continuous gluing across the entire surface.

[0024] The green gluing technique is a method where sawn wood is used with a moisture content not usual for the use of adhesives, meaning that, in the manufacture of glued laminated wood, pieces of wood with a high moisture content (or green wood) are used, and an adhesive capable of ensuring a performance of its glued joints adequate to the moisture levels present in the pieces, normally of the polyurethane type.

[0025] Lissouck et al (2022) used a one-component PU adhesive on 8 species of hardwood from the Congo Basin and evaluated its strength, finding that the wood failure trend was in accordance with several international requirements.

[0026] Gluing green wood allows you to work with a more flexible wood than the same wood in its dry state. Consequently, less pressure is needed to correct any geometric imperfections and ensure a tight bond between the squared boards that need to be glued.

[0027] Information on green gluing can be found in the state of the art.

[0028] Document ES2218423 (T3) presents a wood-polymer composite, characterized in that moist wood is used as the starting material for impregnation with polymerizable monomers. The object of the invention is to provide polymer-impregnated wood with high moisture content and improved hardness. This document does not describe the application of this technique to native woods, as presented in the application under consideration.

[0029] ES2741206 (T3): This document discloses composite panels of at least three layers of wood, where the gluing is carried out in the green state. More specifically, the invention relates to a multi-layered wood panel made from squared wood boards cut and assembled in the green state. An adhesive composition is disclosed for gluing wood in the green state, directly after sawing. The application of the gluing to dense woods with a very stable medullary radius is mentioned. This document does not disclose the application of the technique to woods of the species Nothofagus pumilio (Lenga), Nothofagus dombeyi (Coigüe), Nothofagus alpina (Raulí), and Nothofagus obliqua (Roble), which are specific to cold climates.

[0030] ES2218423 (T3): This document describes a wood impregnation process where the starting material is green wood. The document specifies moisture content, among other things, of 25%. This document does not mention the type of wood used, nor does it mention the use of hardwoods such as raulí, lenga, coigüe, or oak.

[0031] Furthermore, we found non-patent documents in the art, such as “Experimental design for determining the manufacturing parameters of a green-glued plywood panel” by Ana Lavalette, Alain Cointe, Régis Pommier, and others, which investigated the technical feasibility of producing plywood using green-glued technology. Rotary-cut veneers 2.5 mm thick, obtained from steamed maritime pine (Pinus pinaster Ait.) logs were used. Five-layer plywood panels were produced using a one-component polyurethane adhesive to evaluate the effects of two parameters—the moisture content of the wood and the amount of adhesive—on the mechanical properties of the plywood. This document does not describe an application to native woods.

[0032] As can be seen, a green gluing material and an application technique are still necessary for native woods, such as Nothofagus pumilio (Lenga), Nothofagus dombeyi (Coigüe), Nothofagus alpina (Raulí), and Nothofagus obliqua (Roble), which are specific to cold climates.

[0033] Therefore, it is proposed to explore the use of the green gluing technique, to be used in native species grown in Chile, in order to enhance their value as a construction element and reverse their inappropriate use.

[0034] DESCRIPTION OF THE FIGURES

[0035] Figure 1: Woods used (a), coding and extraction of test specimens for anhydrous density determination (b).

[0036] Figure 2: Shear values ​​for different species glued in green, red line represents minimum standard required NCh2148.

[0037] Figure 3: Delamination. Values ​​for different species glued dry (12% CH) (a), Value obtained for green gluing (b).

[0038] DESCRIPTION OF THE INVENTION

[0039] The present invention aims at the use of native woods that are generally not found in large dimensions, to develop a gluing process and its application, in woods with a moisture content greater than 20%, which is known as green wood.

[0040] Gluing green wood allows you to work with a more flexible wood than the same wood in its dry state. Consequently, less pressure is needed to correct any geometric imperfections and ensure a tight bond between the squared boards that need to be glued.

[0041] To avoid deformations related to preferential shrinkage during wood drying, prior to gluing, an adhesive composition formulation has been developed with the aim of being able to glue wood in a green state.

[0042] Furthermore, the aim is to use smaller pieces of native wood. This requires research into the behavior of these woods, which has not been fully studied for the species Nothofagus pumilio (Lenga), Nothofagus dombeyi (Coigüe), Nothofagus alpina (Raulí), and Nothofagus obliqua (Roble), which are specific to cold climates.

[0043] This green gluing process was validated for the aforementioned species, through shear and delamination tests on samples of bilaminated pieces, green glued using a one-component PU adhesive, keeping the manufacturing and gluing parameters constant, to evaluate the feasibility of using this technique for Nothofagus species.

[0044] DETAILED DESCRIPTION OF THE INVENTION

[0045] For the Nothofagus family species grown in Chile, specifically Lenga, Raulí, Roble and Coigüe, the technique of gluing their faces with "green" wood (that which is within the moisture range of 21 to 35%) has not been developed, which has the advantage of lower energy consumption (by avoiding or reducing artificial drying times), and / or the allocation of glued wood for use in service class 3, which are products such as beams, pillars, handrails, elements of minor or decorative bridges, pergolas or garages or others that have requests of the protected exterior use type.

[0046] The use of these native species does not require preservation treatment because they possess medium to high natural durability, which undoubtedly contributes to the effectiveness of this technology. There are different types of Nothofagus, depending on where they grow, humidity levels, temperature, and other factors. The size of their pores causes their properties to vary from one species to another. For example, American oak, French oak, and Chilean oak are not identical in their characteristics; therefore, their treatment cannot be the same.

[0047] The present invention is unique in that it works with native species that have not been previously green glued, such as Nothofagus pumilio (Lenga), Nothofagus dombeyi (Coigüe), Nothofagus alpina (Raulí), and Nothofagus obliqua (Roble), which are specific to cold climates. Specifically, this process details how to proceed with green gluing these native species.

[0048] It is also possible to find many studies that have focused more on gluing softwoods or pine species. The techniques or operating parameters used for gluing dry softwoods are not replicable in the proposed technique for various reasons, including the required moisture range, surface treatment, waiting times before pressing, the type and quantity of adhesive used, among others.

[0049] The protocols used for working with wood are based on pine wood. Therefore, if the defined protocols are followed for any other species, the results will not be as described by the inventors. Only average results will be obtained.

[0050] This makes it clear that the same procedure does not work for all species, nor will the protocols used for dry wood work for green wood.

[0051] This gluing process is for exterior use, for light loads. This includes the construction of garages, pergolas, etc.

[0052] The adhesive used in this native wood gluing process employs precise operating parameters to obtain glued green wood. Specifically, the green gluing process for native woods for exterior use, which allows for greater dimensional stability and mechanical strength, comprises at least the following stages: a) dimensioning sawn pieces with a low moisture content, between 21 and 35%; b) planing the sawn pieces, ensuring the surface is clean of dust and sawdust; c) stabilizing the low-moisture wood pieces by slatting them with spacers to ensure ventilation, allowing a drying time of 8 hours or more in a well-ventilated area; d) sanding the faces of the pieces to be glued to an average roughness of 3.2 micrometers; e) gluing the pieces, for which 150 to 200 g / m² should be applied. 2of a PU prepolymer-based adhesive with homogeneous application and with a notched trowel to ensure uniformity on each piece to be joined, in a place that allows maintaining ambient temperature conditions between 15 and 21 °C, with relative humidity between 50 and 65%. f) join two pieces of wood to generate the bi-laminate in a period of less than 20 minutes, preferably less than 7 minutes; g) press the bi-laminate to 0.6 MPa in a hydraulic, pneumatic, vacuum or manual press for at least 3h; and h) allow adhesive curing for at least 48 h.

[0053] Advantageously, in some indicators, such as shear stress, the product obtained with the application of this process in these species presents improved results compared to the same, without considering process parameters, such as surface treatment, waiting time before gluing, open / closed time, temperature and humidity of the place, among others.

[0054] This process was validated through shear and delamination tests on samples of the aforementioned species. These tests refer to the effort required to separate one layer of wood from another (shear) and the accelerated aging of the wood (delamination).

[0055] It should be noted that the standards used for gluing radiata pine, which is commonly used as dry wood, were taken as a reference. There are no standards for green wood that can be applied to the treated wood used in this project.

[0056] In one particular modality, a green gluing procedure for native woods for exterior use is described, which allows for greater dimensional stability and mechanical resistance, comprising: a) dimensioning sawn pieces with a low moisture range, between 21-35%; b) planing the sawn pieces, taking care to clean the surface of dust and sawdust; c) stabilizing the wood pieces from the low moisture range, by means of a palletizing process, using spacers to ensure ventilation of the sawn pieces, with a drying time of 8 hours or more, in a place with adequate ventilation conditions; d) sanding the faces of the pieces to be glued, to an average roughness of 3.2 micrometers; e) gluing the pieces, applying PU prepolymer-based adhesive with a notched trowel to uniformly cover each piece to be joined, in a place that allows maintaining ambient temperature conditions between 15 and 21 °C, with relative humidity between 50 and 65%.f) joining two pieces of wood to generate the laminate in a period of less than 20 minutes, preferably less than 7 minutes; g) pressing the laminate; and h) allowing adhesive to cure for at least 48 h. In another preferred embodiment, the above procedure is described, where in step f) between 150 and 200 g / m are applied. 2 PU prepolymer-based adhesive, with homogeneous application.

[0057] In yet another preferred modality, the above procedure is described, where the environmental conditions for gluing are a temperature between 15 and 21 °C, with relative humidity between 50 and 65%.

[0058] In another preferred modality, the above is described, where the gluing step is performed in a hydraulic, pneumatic, vacuum or manual press.

[0059] In another preferred embodiment, the procedure is described where in step g) the bilaminate is pressed with 0.6 MPa, where the press time is a minimum of 3 hours.

[0060] In another preferred embodiment, the above procedure is described, where in step f) the moisture difference between the pieces must be less than 3%.

[0061] In yet another preferred modality, the above procedure is described, where after surface treatment, brushing and sanding, there is moisture stabilization, and a depth of cut in sanding of less than 0.2 mm.

[0062] In addition, another preferred method is described, which is the use of the green gluing procedure described above, because it is suitable for gluing native woods.

[0063] In another preferred method, the aforementioned use is described, where native woods are selected from Nothofagus pumilio (Lenga), Nothofagus dombeyi (Coigüe), Nothofagus alpina (Raulí), and Nothofagus obliqua (Roble). This use is further described because it provides building materials for construction.

[0064] APPLICATION EXAMPLE

[0065] Tests are presented to establish the process conditions for using the green gluing technique, to achieve improvements in dimensional stability and mechanical resistance for different species.

[0066] The bilaminated pieces used in the study were constructed using the species Nothofagus pumilio (Lenga), Nothofagus dombeyi (Coigüe), Nothofagus alpina (Raulí), and Nothofagus obliqua (Roble).

[0067] The work with wood from these species was carried out in three different moisture ranges: Low Range (21-28.9%), Medium Range (29-35.9%), and High Range (36-43.9%). Sawn timber was used for all the species studied to manufacture the laminated pieces, producing the laminates using the different processes.

[0068] The main focus was developing strategies to improve adhesion. To this end, various wood pretreatments were evaluated, and several parameters were adjusted during the green gluing technique. These strategies included trials with different surface treatments, pressing times, pressure applied during the gluing process, and different polyurethane-based adhesives; in particular, the commercial adhesives Meister pur 5082 and Jowapur 685.12 were tested.

[0069] Previous tests studied the behavior of Meister PUR 5082 adhesive, a one-component liquid polyurethane adhesive. Initial trials were conducted using Nothofagus alpina (Raulí) with a moisture content of approximately 11%, testing three specimens. Subsequently, six specimens of the same species were tested in the medium moisture range (29-35.9%) and six in the high moisture range (36-43.9%).

[0070] For the species Nothofagus obliqua (Oak), 15 specimens were tested in the Low Moisture Range (21-28.9%), 15 specimens in the Medium Moisture Range (29-35.9%), and 3 specimens in the High Moisture Range (36-43.9%). For Coigüe, results were obtained from 9 specimens in the Low Moisture Range (21-28.9%) and 6 in the Medium Moisture Range (29-35.9%).

[0071] Regarding Lenga, there are no previous results. Because the shear tests were unsatisfactory, due to high variability in the results, it was decided to use another adhesive.

[0072] Preliminary tests with Jowapur brand PU prepolymer-based adhesive on Nothofagus obliqua (oak) specimens, consisting of six samples with a low moisture range (21-28.9%), showed a satisfactory response compared to other adhesives tested. The results presented here correspond to those obtained with this adhesive and with controlled applied pressure. This allowed for greater reliability in the results and improved data reproducibility.

[0073] The results indicate that Nothofagus alpina (Raulí) is the best candidate to proceed to the next stage. This conclusion can be drawn after analyzing the shear test values ​​for a total of 318 manufactured and tested samples, including different gluing pressures tested during the experimental period.

[0074] The bilaminated Raulí samples, classified in the Low Moisture Range (21-28.9%) and using the PU prepolymer-based adhesive (Jowapur 685.12), showed the best results. The average shear test yielded a value of 6.82 N / mm 2 with a standard deviation of 1.6, with a 58.33% success rate for the Low Humidity Range (21-28.9%). However, this value increases to 7.42 N / mm 2 ± 0.55 with a 77.8% success rate, for samples with a moisture content of less than 24%.

[0075] The simplified green gluing process for this species consisted of:

[0076] 1. dimension sawn pieces with a Low Moisture Range (21 - 28.9%);

[0077] 2. Brush the sawn pieces, making sure to clean the surface of dust and sawdust; 3. Apply 150 g / m 2 of Jowapur 685.12 one-component PU adhesive, with a notched trowel for smoothing;

[0078] 4. Join both pieces of wood to create the laminate in less than 7 minutes;

[0079] 5. Press the bilaminate with 0.6 MPa for 2 hours; and

[0080] 6. Allow adhesive to cure for at least 48 hours.

[0081] Procedure for the tests.

[0082] Obtaining physical properties:

[0083] The wood used came from two local producers, Maderas Nalcahue and Maderas Martini, located in the Araucanía region of Chile. The moisture content studied ranged between 21.0 and 28.9%.

[0084] Samples were taken from the wooden pieces to determine the moisture content, reference density and anhydrous density (see Figure 1), according to the procedures stipulated by the Chilean standard NCh176 / 1 : Of2003 (Wood - Part 1 : Determination of moisture content) and the standard NCh176 / 2. Of86 Modified 1988 (Wood - Part 2 : Determination of density).

[0085] The samples were obtained by cutting with a panel saw. Measurements were taken with a digital caliper with a precision of 0.01 mm, and the mass was determined with a balance with a precision of 0.01 g. The samples were then anhydrous and dried in an oven at 103 °C ± 2 °C for 24 hours, and subsequently measured and weighed again.

[0086] Manufacturing of bilaminates:

[0087] The sawn timber pieces were surface-worked and shaped using traditional woodworking machinery. Pieces measuring 20 mm x 120 mm x 300 mm were obtained and glued on one side with JOWAT brand one-component polyurethane adhesive. The adhesive weight used was 150 g / m². 2and then pressed in a press for 3 hours. This allowed the production of 40 x 120 x 300 mm bilaminates, which were left to rest outside the press for 48 h. The environmental conditions of the gluing, pressing and resting processes were 16 ± 3 °C and 55 ± 5% relative humidity, which were monitored with a thermometer and a hygrometer.

[0088] Test specimens were extracted from each laminate for subsequent evaluation of delamination and shear in the tail line according to the recommendations of the NCh 2148:2013 standard extracted from ISO 12580 / 2007 which indicates that the delamination test specimens must be the width and thickness of the bilaminate and 75 mm long, at a minimum distance of 50 mm from the end.

[0089] For the shear tests, all samples were measured with calipers (0.01 mm accuracy) at the shear point. They were then tested in a universal testing machine equipped with a 50 kN load cell and the corresponding shear device. A compressive load was applied at a constant rate of 0.6 mm / min until each sample sheared, corresponding to the maximum load expressed in kN.

[0090] Shear values:

[0091] The values ​​obtained in the mechanical shear tests, on pieces glued in green and then conditioned to 12% moisture content for the test, showed that the best results are obtained in the Nothofagus alpina species, as shown in Figure 2, with an average value of 6.82 N / mm 2Using a moisture content range for gluing of 21 to 28.9%, a success rate of 58% was achieved against the standard value. If the gluing moisture content was less than 24%, the success rate against the standard value increased to 77.8% of the samples, with an average value of 7.42 N / mm 2 The other species did not reach the minimum value required by the standard. Figure 2 shows shear strength values ​​for different species glued while green. The dashed line represents a value of 6 N / mm. 2 , represents the minimum required standard NCh2148.

[0092] Delamination values:

[0093] The results indicate that all Nothofagus species presented problems with delamination, for the same moisture content range used in green gluing (21.0 to 28.9%).

[0094] For its part, the Nothofagus alpina (raulí) species achieved the best performance in this test, with 11.22% delamination, when the gluing process is contrasted by doing it dry (12% moisture content), as shown in Figure 3.

[0095] Gluing process

[0096] 1. Inspection of incoming material

[0097] The classification method, described in standard NCh3226:2010, consisted of a visual inspection of the defects or attributes present in each piece of wood to be used, considering the face, edges, and end. However, for the green gluing process, the wood could not contain enclosed or exposed pith, bark or missing edges, holes, and / or cracks or splits.

[0098] 2. Processes for each operation

[0099] Once the species was selected and inspected as indicated in the previous stage, the following processes and their controls were carried out, as detailed below: i. Longitudinal Cutting: If necessary, the pieces were cut lengthwise using any of the following equipment: scribing saw, panel saw, radial arm saw, or any other machine that allows the operation. If the cut is for a final laminated element, an additional amount of material, at least 10 mm in length, will be provided.

[0100] i. Longitudinal splicing: For short pieces of wood that must be used to form a longer element, various longitudinal splicing techniques may be used, including finger jointing, complying with the requirements established in the structural standards, and with adhesives that can achieve the desired structural performance. Depending on the adhesive used, the curing process may require at least 8 hours before the next step. iii. Planing: The pieces to be glued must be planed either on both faces (S2S) or on both faces and edges (S4S), achieving a surface quality sufficient for the subsequent process. A minimum planing quality of 10 marks per inch is established. The result of this process will be a uniform thickness “e”, with a tolerance of + / - 0.3 mm. iv.Moisture stabilization: After the planing process or during execution, the wood pieces must be stored in the processing area (covered-protected space), with a spacing or separation process between the faces of the wood pieces. This is done with 20 x 20 mm dry wooden spacers (moisture content less than 20%), placed every 200 to 400 mm, allowing air to circulate. The time before the next process, which can be 8 hours or more, must be considered. v. Sanding of face(s): The next stage consists of sanding with a calibrating sander, performing the roughing with sandpaper with a grit size between No. 40 and 100 (GRIT 40 to 100), in a single pass, achieving a thickness “e” - 0.2 mm per face, and an average roughness of 3.2 micrometers.After sanding the faces, the pieces must be palletized according to the instructions in the previous "moisture stabilization" process. A waiting period of less than 2 hours should be considered for the next step. vi. Gluing: The moisture difference between the two pieces of wood to be glued must be + / - 3%. The gluing process is carried out with a one-component polyurethane adhesive from the Jowat brand (Jowapur 685.12). The adhesive was applied to the surface at a spread of 150 to 200 g / m². 2with a medium that ensures homogeneous application. A gluing environment with a temperature between 15 and 21 °C and a relative humidity between 50 and 65% should be considered. The open time of the application should not exceed 10 minutes, and the closed time should not exceed 20 minutes; these should be minimized as much as possible. vii. Laminate pressing: This process may be carried out in a hydraulic, pneumatic, vacuum, or manual press, provided that the pressing time is a minimum of 3 hours. The pressure must be homogeneous throughout the element, ensuring specific pressures greater than 0.3 N / mm². 2and, if necessary, adjust pressure every 15 minutes. The pressing time must not be less than 3 hours, considering a pressing and resting environment with a temperature between 15 and 21 °C, and a relative humidity between 50 and 65%. The laminated element, once removed from the press and during the resting period, must not be subjected to mechanical stress, such as by loading and moving with a forklift, pallet jack, or overhead crane, without taking the necessary precautions. The resting period must be at least 48 hours. viii. Forming: the process of achieving the required dimensions for the laminated element. Common operations include S2S or S4S planing, final length cutting, and / or sanding. ix. Milling / cutting: the process of creating shapes, recesses, and / or impressions on the glued laminated element. x. Packaging: the process of providing protection, according to the transport and / or consumer specifications. 3.Quality control, inspection and testing procedure.

[0101] Green-glued laminated elements may be tested following the recommendations of the following standards and conformity tests:

[0102] NCh2148:2014 Structural glued laminated timber - Requirements, sampling methods and inspection:

[0103] In the shear test, the average shear strength value of all glue lines on a specimen obtained from the cross-section of a glued timber structural element must be at least 6 MPa. This value requires a minimum average wood failure rate of 90%.

[0104] ISO 12580, delamination tests according to methods A, B or D and E defined in this standard.

[0105] This standard establishes the humidity and aging cycles for a laminated element. It has been mentioned as a method for testing green bonded elements.

[0106] In view of the foregoing, those skilled in the art will understand that changes can be made to the specific aspects described and still achieve the same or a similar result without departing from the spirit and scope of the invention. Therefore, the specific functional and structural details described herein should not be interpreted as exhaustive. It should be understood that the full description of each reference cited herein is incorporated within the description of this application.

[0107] While this invention has been described in the embodiments indicated above, it might seem obvious that other alternatives, modifications, or variations would yield the same results. However, we have established that the subject matter described in this application is fundamental to the success of the invention described herein. Consequently, the embodiments of the invention are intended to be illustrative, not limiting. Various changes may be made without departing from the spirit and scope of the invention as defined in the following claims.

[0108] All patents, patent applications, scientific articles and other public documents that, to the applicant's knowledge, constitute the state of the art, have been duly cited in this application.

Claims

CLAIMS 1. A green gluing procedure for native woods for exterior use, which allows for greater dimensional stability and mechanical resistance, CHARACTERIZED in that it comprises: a) dimensioning sawn pieces with a low moisture content, between 21-35%; b) planing the sawn pieces, ensuring the surface is clean of dust and sawdust; c) stabilizing the wood pieces from the low moisture content, by means of a palletizing process, using spacers to ensure ventilation of the sawn pieces, with a drying time of 8 hours or more, in a place with adequate ventilation conditions; d) sanding the faces of the pieces to be glued, to an average roughness of 3.2 micrometers; e) gluing the pieces, applying PU prepolymer-based adhesive with a notched trowel to ensure uniformity on each piece to be joined, under ambient temperature conditions between 15 and 21 °C, with relative humidity between 50 and 65%.f) join two pieces of wood to create the laminate in less than 20 minutes; g) press the laminate; and h) allow adhesive to cure for at least 48 hours.

2. The process according to claim 1, CHARACTERIZED in that in step e) between 150 and 200 g / m are applied 2 PU prepolymer-based adhesive, with homogeneous application.

3. The procedure according to claim 2, CHARACTERIZED in that the environmental conditions for gluing are a temperature between 15 and 21 °C and relative humidity between 50 and 65%.

4. The procedure according to claim 1, CHARACTERIZED in that step f) is performed in a hydraulic, pneumatic, vacuum or manual press.

5. The process according to claim 1, CHARACTERIZED in that in step g) the bilaminate is pressed with 0.6 MPa, where the pressing time is a minimum of 3 hours, in a pressing and resting environment with a temperature between 15 and 21 °C, and relative humidity between 50 and 65%.

6. The procedure according to claim 1, CHARACTERIZED in that in the gluing step the difference in humidity between the pieces must be + / - 3%.

7. The method according to claim 1, CHARACTERIZED in that after surface treatment, brushing and sanding, there is moisture stabilization, and a depth of cut in sanding of less than 0.2 mm.

8. The procedure according to claim 1, CHARACTERIZED in that in step f) the two pieces of wood are joined to generate the bilaminate in a period of less than 7 minutes.

9. Use of the green gluing procedure described in claim 1, CHARACTERIZED in that it serves to glue native woods.

10. The use according to claim 9, CHARACTERIZED in that the native woods are chosen from among Nothofagus pumilio (Lenga), Nothofagus dombeyi (Coigüe), Nothofagus alpina (Raulí), and Nothofagus obliqua (Roble).

11. Use of the green gluing procedure described in claim 1, CHARACTERIZED in that it serves to provide construction materials for building.

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