High-bonding-strength finger joint process

Abstract

The invention relates to the technical field of finger joint board splicing methods, in particular to a finger joint process with high bonding strength, which comprises the following steps of: 1, applying 80-100 DEG C temperature to the tenon surface of a finger-shaped tenon, and keeping for 30-50 seconds; secondly, the temperature ranging from 260 DEG C to 280 DEG C is applied to the tenon face, and the temperature is kept for 10 s to 20 s; thirdly, the heat source is moved away, glue is applied to the tenon face, finger joint is conducted on the small materials, a spliced long batten is obtained, and at the moment, the temperature of the tenon face is not lower than 180 DEG C; and 4, external acting force of 1.2-1.5 MPa is applied to the two ends of the spliced long battens, the external acting force is kept for 45-55 s, and the long battens are obtained. Compared with the prior art, by means of the finger joint technology, the spliced plate with the relatively high bonding strength and finger joint strength can be obtained, meanwhile, no obvious needle holes exist in the plate face, and the spliced plate is attractive.

Description

Technical Field

[0001] The invention relates to the technical field of finger-jointed paneling methods, in particular to a finger-jointed process capable of forming a relatively high bonding strength. Background Art

[0002] Finger-jointed boarding is a processing technology that makes small-format wood boards widen and lengthen to make large-format wood boards. In the process of finger-jointed boarding, first, the two ends of the small-format wood boards in the length direction are processed into finger-shaped tenons, and the two sides in the width direction are sanded flat; then, the finger-shaped tenons of several adjacent small-format wood boards are connected and lengthened, and pressure is applied to both ends of the long board after lengthening and maintained for a period of time to allow the adhesive to solidify; finally, the sides of several long boards are spliced, and pressure is applied to both sides of the widened large-format board and maintained for a period of time to allow the adhesive to solidify.

[0003] For example, the technical solution recorded in the invention patent application with publication number CN105150302A and titled "Processing Technology of Finger-Jointed Wood Panels" is to comb the boards with sizes of 150~250mm to make finger-shaped tenons, apply glue at the finger-shaped tenons and extend them, and finally widen the extended strips horizontally to obtain finger-jointed panels. Summary of the invention

[0004] The tenon force formed by the finger-jointed panels is provided by two aspects. One is the bonding force provided by the adhesive on the joint surface of the tenon, and the other is the riveting force provided by the extrusion deformation of the wood. The wood has a certain deformation capacity. The pressure applied at both ends during finger jointing can cause extrusion deformation at the tooth top and tooth root. The bonding force between the tenons can be provided by relying on the extrusion deformation and the trend of deformation recovery.

[0005] However, the inventor of this case believes that due to the limitations of the processing technology of finger-jointed panels, it is inconvenient to provide temperature at the gluing position, so cold-curing adhesives are generally used in actual production, or although heat-curing adhesives are used, a long-term, cold-curing process is adopted, which means that there is still room for improvement in the bonding strength of the tenon joint surface.

[0006] At the same time, during the process of fixing the finger joints, the externally applied pressure acts on both ends of the long strips. The wood material strength of each finger tenon is different, so the top and root of each finger tenon form different degrees of extrusion deformation after extrusion, which leads to different bonding forces of the finger joints in the same finger jointed board. From the appearance point of view, the top of the finger tenon with smaller material strength can contact the root of the finger tenon with which it is mortised under the action of external force, but the top of the finger tenon with larger material strength cannot contact the root of the finger tenon with which it is mortised. When the finger tenon is an open tooth, a pinhole-shaped gap will be formed on the surface of the spliced ​​board, and when the finger tenon is a hidden tooth, a pinhole-shaped gap will be formed on the side of the spliced ​​board. The pinholes on the board surface will affect the appearance grade of the material, and the pinholes on the side will affect the waterproofness of the material.

[0007] The purpose of the present invention is to provide a finger-joining process with high bonding strength, which can overcome at least one of the above technical problems. The following technical solutions are specifically adopted: Finger-joining process with high gluing strength, take a small piece with a finger-shaped tenon at the end and carry out the following steps in sequence: Step 1, applying a temperature of 80-100° C. to the tenon surface of the finger tenon and maintaining it for 30-50 seconds; Step 2, applying a temperature of 260-280° C. to the tenon surface and maintaining it for 10-20 seconds; Step 3, removing the heat source, applying glue to the tenon surface, finger-joining the small materials, and obtaining a spliced ​​long strip, and at this time, the temperature of the tenon surface is not less than 180° C.; Step 4: Apply an external force of 1.2-1.5 MPa to both ends of the spliced ​​long strips and maintain it for 45-55 seconds to obtain the long strips.

[0008] By means of the above method, in step 1, the wood in the 3-5 mm thickness layer from the tenon surface to the inner side of the tenon surface can be dried by the contact between the heat source at a relatively low temperature and the tenon surface, and the moisture content of the wood in the thickness layer can be reduced to below 10% at a relatively fast speed. At the same time, the tenon surface can be made flat under the action of temperature, and the improvement of the flatness of the tenon surface is conducive to improving the gluing strength of the tenon surface.

[0009] In step 2, the contact between a heat source at a relatively high temperature (much higher than the softening point of wood) and the tenon surface can cause the wood in the 1 to 3 mm thick layer from the tenon surface to the inside to become softened and plastic.

[0010] In step three, gluing and finger jointing are completed in a short time so that the temperature of the tenon surface of the spliced ​​long strips after extension is lower than the softening temperature of the wood, but still has a relatively high temperature. At this time, the tenon surface temperature is higher than 160°C, which still meets the curing temperature condition of the thermosetting resin adhesive, so the thermosetting resin adhesive can be used to improve the bonding strength of the tenon surface. At the same time, the wood is in the process of recovering from plasticity to rigidity, and because the wood has a hysteresis in recovery, it still has a certain degree of plasticity.

[0011] Finally, in step 4, a specific pressure is applied to both ends of the spliced ​​long strips and maintained for a specific time to complete the curing of the adhesive and the interference fit of the finger tenons, thereby preparing the long strips. In this step, since the wood 1 to 3 mm inward from the tenon surface of the finger tenon is plastically softened, even if external force is still applied to both ends of the spliced ​​long strips, it can still be ensured that each joint finger tenon undergoes pressure deformation to form an interference fit relationship, thereby improving the mortise and tenon strength of the finger tenon. From the appearance point of view, the tooth top can contact the tooth root of the finger tenon to which it is mortised, so there are no obvious pinholes on the surface of the finger-jointed board, which is more beautiful.

[0012] Preferably, in step three, a phenolic resin adhesive, a polyurethane adhesive, a urea-formaldehyde resin adhesive, or a melamine-formaldehyde resin adhesive is used; or a modified adhesive of a phenolic resin adhesive, a polyurethane adhesive, a urea-formaldehyde resin adhesive, or a melamine-formaldehyde resin adhesive.

[0013] Preferably, the total time that the heat source contacts the tenon surface does not exceed 100 seconds, so as to avoid carbonization of the wood on the tenon surface and the thick layer close to the tenon surface.

[0014] As a further preference, the heat source includes a first heat source and a second heat source, the first heat source is suitable for providing a temperature of 80~100℃ to the tenon surface, and the second heat source is suitable for providing a temperature of 260~280℃ to the tenon surface.

[0015] Preferably, in step three, when the spliced ​​long strips are obtained, the temperature of the tenon surface is not lower than 180°C but not higher than 230°C.

[0016] By means of the above method, when the temperature of the tenon surface is reduced to the range of 180~230℃, the wood is in the process of recovering from plasticity to rigidity, and because the wood has a hysteresis in recovery, it still has a certain degree of plasticity. Specifically, factors such as the wood of the finger tenon being taken from different locations (differences between early and late wood, heartwood and sapwood), and different tree ages will affect the material of the wood, especially its strength. Even if the material temperature is higher than 230℃ and the wood is in a plastic state, its strength is also affected by this. However, the inventors have found that in the period of recovery from plasticity to rigidity, the material differences between different small materials have the least effect on the strength of the wood in this state. Therefore, applying an external force when the temperature of the tenon surface is reduced to the above-mentioned specific temperature range can make the tenon surfaces of each pair of mortises of the finger tenons be compressed to a similar degree as much as possible, so that the interference of each pair of finger tenons can be similar, avoiding the appearance of pinholes.

[0017] As a further preference, in step three, when obtaining the spliced ​​long strips, the temperature of the tenon surface is not lower than 215°C but not higher than 225°C.

[0018] Preferably, in step three, the time from removing the heat source to obtaining the spliced ​​long strips does not exceed 15 seconds.

[0019] Preferably, in step four, a flat pressing plate is used simultaneously to cover at least the surface of the finger-shaped tenons of the spliced ​​long planks.

[0020] As a further preference, the pressure applied by the planar pressure plate to at least the surface of the finger tenon is 0.3-0.5 MPa.

[0021] Preferably, the method further comprises step five of widening the long slats transversely.

[0022] Compared with the prior art, the finger-joining process of the present invention can obtain a spliced ​​board with relatively high gluing strength and finger-joining strength, and at the same time, the board surface has no obvious pinholes and is more beautiful.

[0023] Furthermore, when implementing step four, when the temperature of the tenon surface is 215-225°C, the tenon surfaces of each pair of mortises can be compressed to a similar degree as much as possible, so that the interference fit of each pair of finger tenons can be similar, avoiding the appearance of pinholes. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For those skilled in the art, other drawings can be obtained based on these drawings without paying any creative labor.

[0025] Figure 1 This is the mortise and tenon state of the vertical (V-shaped) finger tenon of the embodiment of the present application.

[0026] Figure 2 This is the mortise and tenon state of the horizontal (H-shaped) finger tenon of the embodiment of the present application.

[0027] In the figure: 100, small material, 210, male finger-shaped tenon, 220, female finger-shaped tenon, 201, tooth top, 202, tooth root. DETAILED DESCRIPTION

[0028] In order to enable those skilled in the art to better understand the technical solutions in the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of this application. Example

[0029] Reference Figure 1 As shown, a finger-joining process with high bonding strength is used, wherein a plurality of small materials 100 are taken, each of which has a vertical (V-shaped) finger tenon at both ends and two sides are sanded to meet the requirements of gluing flatness. The tooth shape of the finger tenon at one end and the finger tenon at the other end are in a structural relationship that can be mortised, so that a plurality of small materials can be mortised end to end. The finger tenon on the first end of the small material 100 is defined as a male finger tenon 210, and the finger tenon on the second end is defined as a female finger tenon 220. This embodiment takes 10 small materials with a length of 120 mm and a width of 45 mm as an example. The tree species of the small materials is poplar, and the length of the finger tenon is 10 mm. The adhesive used is a phenolic resin adhesive in the prior art.

[0030] The finger joint device used in this embodiment includes a workbench with a length of 2m, a long side backer located on one side of the workbench, a pneumatic push plate located on the opposite side of the long side backer, an end backer located at one end of the workbench, a pneumatic pressure plate located on the opposite side of the end backer, a glue brushing machine head, a driving travel track located above the workbench, and multiple heat sources installed through the driving travel track. The heat source has a contact heating surface that matches the shape of the male finger tenon 210 (i.e., a structural relationship that can be mortised), a flat bottom surface, and two heat transfer oil passages (which can be regarded as the first heat source and the second heat source, respectively).

[0031] In some other alternative embodiments, the shape of the contact heating surface may also match the shape of the thumb-shaped tenon 220 .

[0032] In some other alternative embodiments, when space permits, an independent first heat source and a second heat source may be provided and connected to the two heat transfer oil passages respectively.

[0033] Place 10 small pieces on the extension workbench at intervals along the length direction, and the spacing between adjacent small pieces should allow the heat source to fall into them. The male finger-shaped tenons 210 of the 10 small pieces are in the same direction, for example, all facing one end of the pneumatic pressing plate. Start the pneumatic push plate to make the 10 small pieces all lean against the long side. Then perform the following steps in sequence.

[0034] Step 1: Pass 80°C heat transfer oil into the heat source through the first heat transfer oil passage, and the contact heating surface has a temperature of 80°C. Lower the heat source so that the contact heating surface corresponds to the tenon surface of the corresponding male finger-shaped tenon 210, and manually push the small material so that the contact heating surface contacts the tenon surface of the male finger-shaped tenon 210. In some other alternative embodiments, a mechanical method can also be used to push the small material. After contact, the heat source heats the tenon surface of the male finger-shaped tenon 210 at the temperature of its contact heating surface, and keeps heating for 40 seconds.

[0035] Step 2: After the heat source contacts the tenon surface at a temperature of 80°C for 40 seconds, the heat-conducting oil in the first heat-conducting oil passage and the heat source is withdrawn, and the heat-conducting oil at 260°C is introduced into the heat source through the second heat-conducting oil passage. At this time, the contact heating surface has a temperature of 260°C, and the tenon surface of the male finger-shaped tenon 210 is heated, and the heating is maintained for 10 seconds. In order to ensure that the total time that the heat source contacts the tenon surface does not exceed 100 seconds, the switching process of the heat-conducting oil in the first heat-conducting oil passage and the second heat-conducting oil passage shall not exceed 50 seconds. Generally speaking, this process only takes about 30 seconds to complete.

[0036] Step 3: After the heat source contacts the tenon surface at a temperature of 260°C for 10 seconds, the heat source is withdrawn, and the tenon surface of the heated male finger tenon 210 is quickly glued by the glue brushing machine head, and the pneumatic pressing plate is pushed out to make the adjacent small materials finger-joined to obtain a spliced ​​long strip. The process of gluing and finger-joining, that is, the process from removing the heat source to obtaining the spliced ​​long strip, takes no more than 15 seconds. The purpose is to ensure that the tenon surface still has a temperature of not less than 180°C after completing the above actions. According to the method of this embodiment, the tenon surface has a temperature of about 193°C at this time.

[0037] Step 4: withdraw all the heat transfer oil from the heat source, adjust the lateral position of the heat source so that it is above the tenon joint, lower the heat source so that its bottom surface covers the surface of the tenon, and apply a pressure of 0.3MPa. The bottom surface covering the surface of the tenon can prevent the finger joint from arching when the pneumatic pressure plate squeezes the end, and avoid the rapid cooling of the tenon surface. Then, start the pneumatic pressure plate to squeeze the end of the spliced ​​long strip, and cooperate with the end backing to apply pressure from both ends of the spliced ​​long strip along the length direction. The pressure value is 1.3MPa, and it is maintained for 45s to obtain the long strip.

[0038] In some other alternative embodiments, the heat transfer oil from the second heat transfer oil passage may be replaced by the heat transfer oil from the first heat transfer oil passage, so that the heat source has a temperature of 80°C.

[0039] Step five, apply latex glue on both sides of the long strips, and widen the long strips horizontally by cold pressing to prepare finger-jointed panels.

[0040] In other alternative embodiments, multiple small materials can also be stacked to complete the processing and manufacturing of multiple long strips at one time. In this scheme, the shape of the contact heating surface of the heat source matches the continuous tenon surface formed by multiple stacked finger tenons. Example

[0041] The difference between this embodiment and embodiment 1 is that: In step 1, the heat source applies a temperature of 100°C to the tenon surface of the finger tenon for 50 seconds; In step 2, the heat source applies a temperature of 280°C to the tenon surface of the finger tenon for 20 seconds; In step 3, when the long strips are spliced, the temperature of the tenon surface is about 218°C; In step 4, the pressure of the pneumatic pressure plate is maintained for 55 seconds. Example

[0042] The difference between this embodiment and embodiment 2 is that, referring to Figure 2 As shown, both ends of the small material 100 have horizontal (H-shaped) finger-shaped tenons 210 , 220 .

[0043] Comparative Example 1 The finger-jointed panels are made of small pieces of poplar wood with a length of 120 mm and a width of 45 mm. Both ends of the small pieces have vertical (V-shaped) finger tenons and are prepared using white glue, four-way cold pressing for 45 minutes, and a cold pressing pressure of 1.5 MPa.

[0044] Comparative Example 2 The finger-jointed panels are made of small pieces of poplar wood with a length of 120 mm and a width of 45 mm. Both ends of the small pieces have horizontal (H-shaped) finger tenons and are prepared by using white glue, four-way cold pressing for 45 minutes, and a cold pressing pressure of 1.5 MPa.

[0045] The finger-jointed panels prepared in Examples 1 to 3 are marked as 1, 2, and 3, respectively, and the finger-jointed panels of Control Examples 1 and 2 are marked as C1 and C2. The surface quality of each finger-jointed panel is observed in the same way as the "wormholes" in the appearance quality (6.4) of "Non-structural Finger-joined Timbers" (GB / T 21140-2017), and the number of "pinholes" is obtained; the immersion peeling and finger-surface bending strength of test specimens 1 to 3 and control specimens 1 and 2 are tested in accordance with the provisions of 7.3 Physical and Chemical Properties in "Non-structural Finger-joined Timbers" (GB / T 21140-2017). The above test results are shown in Table 1.

[0046] Table 1 * Indicates that in one of the six specimens 1, the adhesive layer peeling length exceeds 1 / 3 of the total length of the adhesive layer.

[0047] The above description is intended to be illustrative and not limiting. Upon reading the above description, many embodiments and many applications beyond the examples provided will be apparent to those skilled in the art. Therefore, the scope of the present teachings should not be determined with reference to the above description, but should be determined with reference to the appended claims and the full scope of equivalents to which such claims are entitled. For the purpose of comprehensiveness, all articles and references, including disclosures of patent applications and publications, are incorporated herein by reference. The omission of any aspect of the subject matter disclosed herein in the preceding claims is not intended to be a waiver of the subject matter, nor should it be considered that the applicant has not considered the subject matter to be part of the disclosed application subject matter.

Claims

1. A finger-joining process with high bonding strength, characterized in that: Take a small piece of material with a finger-shaped tenon at the end and follow the steps below in order: Step 1, applying a temperature of 80-100° C. to the tenon surface of the finger tenon and maintaining it for 30-50 seconds; Step 2, applying a temperature of 260-280° C. to the tenon surface and maintaining it for 10-20 seconds; Step 3, removing the heat source, applying glue to the tenon surface, finger-joining the small materials, and obtaining a spliced ​​long strip, and at this time, the temperature of the tenon surface is not less than 180° C.; Step 4: Apply an external force of 1.2-1.5 MPa to both ends of the spliced ​​long strips and maintain it for 45-55 seconds to obtain the long strips.

2. The finger-joining process with high bonding strength according to claim 1, characterized in that: In step three, a phenolic resin adhesive, a polyurethane adhesive, a urea-formaldehyde resin adhesive, a melamine-formaldehyde resin adhesive, or a modified adhesive of the phenolic resin adhesive, the polyurethane adhesive, the urea-formaldehyde resin adhesive, or the melamine-formaldehyde resin adhesive is used.

3. The finger-joining process with high bonding strength according to claim 1, characterized in that: The total time that the heat source contacts the tenon surface does not exceed 100 seconds.

4. The finger-joining process with high bonding strength according to claim 3, characterized in that: The heat source includes a first heat source and a second heat source, wherein the first heat source is suitable for providing a temperature of 80-100° C. to the tenon surface, and the second heat source is suitable for providing a temperature of 260-280° C. to the tenon surface.

5. The finger-joining process with high bonding strength according to claim 1, characterized in that: In step three, when the spliced ​​long strips are obtained, the temperature of the tenon surface is not lower than 180°C but not higher than 230°C.

6. The finger-joining process with high bonding strength according to claim 5, characterized in that: In step three, when the spliced ​​long strips are obtained, the temperature of the tenon surface is not lower than 215°C but not higher than 225°C.

7. The finger-joining process with high bonding strength according to claim 1, characterized in that: In step three, it takes no more than 15 seconds from removing the heat source to obtaining the spliced ​​long strips.

8. The finger-joining process with high bonding strength according to claim 1, characterized in that: In step four, a flat pressing plate is used at the same time to at least cover the surface of the finger-shaped tenons of the spliced ​​long planks.

9. The finger-joining process with high bonding strength according to claim 8, characterized in that: The flat pressure plate applies a pressure of at least 0.3-0.5 MPa to the surface of the finger tenon.

10. The finger-joining process with high bonding strength according to claim 1, characterized in that: The method further comprises step five of widening the long planks transversely.

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