A green gluing method for urea-formaldehyde resin glue

Abstract

The present invention discloses a green gluing method for urea-formaldehyde resin glue, which includes: preparing an upper wooden board and a lower wooden board, and making tenons and mortises on them through processing. The roughness of the tenons is gradually reduced from the head to the root through multi-stage sand filing. After the tenons are processed, the surface is gently wiped with a soft brush to remove residues. Then, the upper wooden board and the lower wooden board are placed in a heating water tank for hydrothermal treatment. Prepare a mixture of urea-formaldehyde resin glue powder and water to mix and reconcile the glue liquid until there are no particles. The glue liquid is evenly coated on the tenons and mortises. The tenons are inserted into the corresponding mortises to ensure correct alignment. A pressure device is used to fix the connection part and maintain pressure until the glue liquid cures. The glued wooden boards are inspected to ensure the quality of the glued wooden boards. By using the interference tenon method to splice the middle board, the wooden boards are glued with urea-formaldehyde resin glue liquid, thereby increasing the thickness of the middle board wooden strips, reducing the gluing area, reducing the usage amount of the adhesive, and reducing potential formaldehyde release.

Description

Technical Field

[0001] The present invention relates to the technical field of urea-formaldehyde resin gluing methods, and particularly to a green gluing method for urea-formaldehyde resin glue. Background Art

[0002] Urea-formaldehyde resin glue (UF) is a commonly used wood adhesive, which is favored for its good gluing performance, cost-effectiveness and wide application; the synthesis and modification of urea-formaldehyde resin glue to reduce formaldehyde release and improve environmental performance; the use of urea-formaldehyde resin glue with low formaldehyde release has become an important trend in the wood processing industry; and the tenon and mortise is a traditional connection method, which realizes the tight connection between woods through precisely processed tenons and mortises; the processing of tenon and mortise requires precise woodworking machinery to ensure the exact matching of the sizes and shapes of tenons and mortises; the tenon is usually designed to be slightly larger than the mortise so as to generate appropriate pressure during gluing and improve the tightness of the connection; applying urea-formaldehyde resin to tenon and mortise gluing can improve the stability and durability of the connection.

[0003] In the prior art, generally, the flat gluing method between wood boards is used to glue and fix them. The entire plane needs to be coated with the adhesive, involving a large contact area. On the one hand, this leads to a large amount of adhesive used, increasing the production cost. On the other hand, since it is difficult to fully ensure the uniformity of the adhesive when coating a large area, uneven coating will result in uneven strength of the glued parts, thus affecting the gluing quality; at the same time, during the process of coating the adhesive over a large area, the evaporation rate of the adhesive is relatively fast, which also pollutes the environment; in addition, the roughness of the head and root of the tenon is the same, and the adhesive may penetrate into the tenon too much, resulting in too much gluing amount, which not only increases the cost but also may cause the adhesive to overflow, and also affects the gluing quality to a certain extent. Summary of the Invention

[0004] The present invention overcomes the deficiencies of the prior art and provides a green gluing method for urea-formaldehyde resin glue.

[0005] To achieve the above object, the technical solution adopted by the present invention is: a green gluing method for urea-formaldehyde resin glue, comprising the following steps:

[0006] S1. Prepare wood: Prepare two wood boards, divided into an upper wood board and a lower wood board; several tenons and several mortises are made on the upper wood board and the lower wood board through processing.

[0007] S2. Change the roughness of the tenon: Determine the target roughness values of the head and root of the tenon according to requirements, and make the roughness of the tenon gradually decrease from the head to the root through multi-stage sand file processing.

[0008] S3. Hydrothermal treatment: After the tenons are processed, gently wipe the surface with a soft brush to remove residues. After cleaning, place the upper wooden board and the lower wooden board into the heating water tank to ensure that the wooden boards are completely immersed in water for a period of time. After soaking, turn off the heating function of the heating water tank and wait for the wood to cool naturally in the water, and then perform drying treatment;

[0009] S4. Adhesive preparation: Prepare a certain amount of urea-formaldehyde resin powder with low formaldehyde release. Mix the powder with an appropriate amount of water in proportion and stir evenly until there are no particles in the adjusted adhesive. Use an adhesive coating tool to evenly coat the adhesive on the head and root of the tenon, and at the same time evenly coat the adhesive on the inner surface of the mortise;

[0010] S5. Gluing and fixing: Insert the tenon coated with the adhesive into the corresponding mortise, ensure correct alignment, use a pressure device to fix the connection part to maintain pressure, and maintain a certain curing time until the adhesive cures;

[0011] S6. Quality inspection: Inspect the glued wooden board after curing. By observing the glued part, check for cracks, voids or looseness. Then use a tensiometer to conduct a tensile test on the glued part, and apply a certain load to the glued part of the glued wooden board to observe whether it can stably bear the load to ensure the quality of the glued wooden board.

[0012] In a preferred embodiment of the present invention, in the step S1, a number of tenons are arranged in an array on the upper wooden board, and each tenon is set as a conical structure and each mortise corresponds to the tenon.

[0013] In a preferred embodiment of the present invention, in the step S2, for the roughness of the head of the tenon, multi-stage sand files are used for processing. The sand files are coated with different particle sizes of sand powder in segments. The coarse sand powder part is filed starting from the root and gradually transitions to the fine sand powder part for processing the head. The particle sizes of the sand powder selected from the root to the head are controlled at 80 - 120 mesh, 120 - 180 mesh, and 180 - 240 mesh respectively.

[0014] In a preferred embodiment of the present invention, in the step S3, when using a soft brush to wipe the surface of the tenon, start from the head and wipe towards the root to avoid reducing the roughness.

[0015] In a preferred embodiment of the present invention, in the step S3, when putting the wood into the heating water tank, start the heating device and gradually increase the temperature. The heating rate is controlled at 8 - 10 °C / min, and the water temperature gradually rises to 150 - 220 °C. After rising to the set temperature, keep warm and soak for 18 - 24 h.

[0016] In a preferred embodiment of the present invention, when applying the adhesive liquid to the head of the tenon in step S4, due to the relatively large roughness, good wettability, and easier penetration and adsorption, the amount of the adhesive liquid can be appropriately increased; on the contrary, the roughness of the root of the tenon is relatively small, and the amount of the adhesive liquid can be appropriately reduced.

[0017] In a preferred embodiment of the present invention, the pressure applied by the pressure device in step S5 should be 0.5 - 1.5 MPa. Keep the applied pressure, wait for the adhesive liquid to cure, and the curing time is 8 - 22 h, and ensure that the connection part will not move or be adjusted during the curing process.

[0018] In a preferred embodiment of the present invention, the structure of the tenon can also be a needle shape, a cylindrical shape, or a square shape, and the corresponding mortise is processed according to the shape of the tenon.

[0019] In a preferred embodiment of the present invention, after the quality inspection of the glued wood board in step S6, the glued part is polished and trimmed to remove the excess adhesive liquid and uneven parts.

[0020] In a preferred embodiment of the present invention, good ventilation conditions are ensured during the processes of steps S1 to S6 to reduce the influence of the volatilization of the adhesive liquid on the environment and operators.

[0021] The present invention solves the defects in the background technology, and the present invention has the following beneficial effects:

[0022] (1) The present invention provides a green gluing method for urea-formaldehyde resin glue. By using the interference tenon method to splice the middle board and using the urea-formaldehyde resin glue to glue the wood board, the thickness of the middle board wood strips is increased, which not only reduces the gluing area, reduces the usage amount of the adhesive, reduces the potential formaldehyde release, but also helps to improve the gluing efficiency. The smaller gluing area can be cured faster, shortening the production cycle. At the same time, the interference tenon structure can provide good mechanical locking and increase the tensile and shear strength of the glued part.

[0023] (2) The present invention changes the roughness of the tenon, and the roughness gradually decreases from the head to the root of the tenon, thereby changing the wettability from the head to the root of the tenon and changing the penetration performance of the adhesive liquid, ensuring that the adhesive liquid decreases in turn from the head to the root of the tenon; the head of the tenon is the key area of the connection, and stronger gluing strength is required to bear the main stress. By increasing the roughness of the head, the contact area between the adhesive and the wood surface can be increased, thereby improving the gluing strength. The increase in roughness helps the adhesive to better penetrate into the micropores and fiber gaps of the wood to form a more firm bond; and the sand powder particle sizes selected from the root to the head are controlled at 100 mesh, 140 mesh, and 200 mesh respectively. The tenon and mortise glued with the tenon processed with this sand powder particle size have the best gluing strength for the spliced middle board.

[0024] (3) The present invention improves the stability of wood through hydrothermal treatment. Hydrothermal treatment can change the internal structure of wood, reduce the hygroscopicity and swelling rate of wood, thereby improving the dimensional stability of wood under different environmental conditions, and also helping to prevent the problems of deformation and cracking of wood caused by humidity changes.

[0025] (4) By changing the tenon structure of the present invention and combining it with the roughness size, it is obtained that the tenon of the rhombus structure has the best gluing strength for the assembled middle board. Moreover, the tenon of the rhombus structure has a larger length and width on the surface combined with the upper wood board, increasing the contact area between the tenon and the mortise, which is beneficial to the stability and strength of gluing. At the same time, the tenon of the rhombus structure adopts a rhomboid shape design, enabling it to provide more supporting area during connection, reducing the shaking and deformation of the tenon during the connection process, and being beneficial to the firmness of gluing. Description of the Drawings

[0026] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments recorded in the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings;

[0027] Figure 1 It is a flow chart of the green gluing method of urea-formaldehyde resin glue for the preferred embodiment of the present invention; Detailed Embodiments

[0028] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0029] Many specific details are set forth in the following description in order to fully understand the present invention. However, the present invention can also be implemented in other ways different from those described herein. Therefore, the scope of protection of the present invention is not limited by the specific embodiments disclosed below; in the description of the present invention, unless otherwise specified, the meaning of "a plurality" is two or more; for those of ordinary skill in the art, the specific meanings of the above terms in this application can be understood through specific circumstances.

[0030] As Figure 1 shown, a green gluing method of urea-formaldehyde resin glue includes the following steps:

[0031] S1. Prepare the wood: Prepare two wooden boards, namely the upper wooden board and the lower wooden board. A number of tenons and mortises are made on the upper wooden board and the lower wooden board through processing.

[0032] Among them, a number of tenons are arranged in an array on the upper wooden board. Each tenon is set as a conical structure and each mortise corresponds to the tenon. The structure of the tenon can also be needle-shaped, cylindrical or square-shaped, and the corresponding mortise is processed according to the shape of the tenon.

[0033] S2. Change the roughness of the tenon: Determine the roughness target values of the head and root of the tenon according to requirements. Make the roughness of the tenon gradually decrease from the head to the root through multi-stage sand file processing. For the roughness of the tenon head, multi-stage sand file processing is selected. The sand file is segmented and coated with different particle sizes of sand powder. The coarse sand powder part starts filing from the root and gradually transitions to the fine sand powder part to process the head. The particle sizes of the sand powder selected from the root to the head are controlled at 80-120 mesh, 120-180 mesh, and 180-240 mesh respectively.

[0034] S3. Hydrothermal treatment: After the tenon is processed, gently wipe the surface with a soft brush to remove the residue. After cleaning, put the upper wooden board and the lower wooden board into a heating water tank to ensure that the wooden boards are completely immersed in water for a period of time. After soaking, turn off the heating function of the heating water tank and wait for the wood to cool naturally in the water, and then carry out drying treatment. It should be noted that when wiping the surface of the tenon with a soft brush, start from the head and wipe towards the root to avoid reducing the roughness.

[0035] S4. Prepare the glue: Prepare a certain amount of urea-formaldehyde resin glue powder with low formaldehyde release. Mix the glue powder with an appropriate amount of water in proportion and stir evenly until there are no particles. Use a glue coating tool to evenly coat the glue on the head and root of the tenon, and at the same time evenly coat the glue on the inner surface of the mortise. When coating the glue on the head of the tenon, due to the larger roughness, good wettability and easier penetration and adsorption, the amount of glue can be appropriately increased. On the contrary, the roughness of the root of the tenon is smaller, and the amount of glue can be appropriately reduced.

[0036] S5. Glue and fix: Insert the tenon coated with glue into the corresponding mortise, ensure correct alignment, use a pressure device to fix the connection part to maintain pressure, and maintain a certain curing time until the glue cures.

[0037] S6. Quality inspection: Inspect the glued wooden board after curing. By observing the glued part, check whether there are cracks, voids or looseness. Then use a tensiometer to conduct a tensile test on the glued part, and apply a certain load to the glued part of the glued wooden board to observe whether it can stably bear the load to ensure the quality of the glued wooden board.

[0038] Among them, in step S3, the wood is placed in the heating water tank, the heating device is started, and the temperature is gradually increased at a heating rate controlled at 8 - 10 °C / min until the water temperature gradually rises to 150 - 220 °C. After the temperature rises to the set temperature, heat preservation and soaking are carried out for 18 - 24 h;

[0039] It should be noted that the pressure applied by the pressure device in step S5 should be 0.5 - 1.5 MPa. The applied pressure is maintained, and the adhesive is waited to cure for 8 - 22 h, and it is ensured that the connection part will not move or be adjusted during the curing process.

[0040] In step S6, after the quality inspection of the glued wooden board is completed, the glued part is polished and trimmed to remove the excess adhesive and uneven parts; during the process from step S1 to S6, good ventilation conditions are ensured to reduce the impact of adhesive volatilization on the environment and operators.

[0041] Example:

[0042] I. Test method

[0043] The glued part is subjected to a tensile test with a tensiometer to obtain the tensile value when the glued part breaks, and then the size of the gluing strength is calculated according to the gluing area;

[0044] Among them, the calculation of the conical gluing area: π×r 2 ;

[0045] The calculation of the needle-shaped gluing area: 2π×r×h + π×r 2 ;

[0046] For the square structure, a rhomboid structure is selected, and its gluing area is calculated according to the length, width and height of five faces;

[0047] II. Experimental part

[0048] Example 1:

[0049] Prepare the upper wooden board and the lower wooden board. A number of tenons and a number of mortises are processed and made on the upper wooden board and the lower wooden board. The tenons are arranged in an array on the upper wooden board, and each tenon is set as a conical structure. Among them, the upper wooden board and the lower wooden board are made of medium plates, the medium plate material is red maple, the size is 900 mm×460 mm, the thickness is 22 mm, and the length of the processed conical tenon is set to 15 mm, the bottom circular diameter is 30 mm, and the distance between every two tenons is 102 mm;

[0050] Through multi-stage sand filing processing, the roughness of the tenon gradually decreases from the head to the root of the tenon. Multi-stage sand filing processing is selected, and different particle sizes of sand powder are coated on different segments of the sand file. The coarse sand powder part starts filing from the root and gradually transitions to the fine sand powder part for processing the head. The particle sizes of the sand powder selected from the root to the head are controlled at 80 mesh, 120 mesh, and 180 mesh respectively. Then, according to the size of the tenon, the corresponding mortise is processed on the lower wooden board.

[0051] After the tenon is processed, use a soft brush to gently wipe from the surface of the tenon starting from the head towards the root to remove the residues to prevent the roughness from decreasing. Then use a soft brush to wipe and clean the lower wooden board. After all the cleaning is completed, put the upper wooden board and the lower wooden board into a heating water tank, start the heating device to gradually increase the temperature, and control the heating rate at 8 °C / min. The water temperature gradually rises to 190 °C, then keep it warm and soak for 20 h. After the soaking is completed, turn off the heating function of the heating water tank and wait for the wood to cool naturally in the water. Then take out the wooden boards for drying treatment.

[0052] The weight of the two wooden boards is about 15 kg. Correspondingly, prepare 2 kg of urea-formaldehyde resin powder with low formaldehyde release. Mix the powder with 4 kg of water in a ratio of 1:2 and stir evenly until there are no particles to prepare the adhesive liquid. Use an adhesive liquid coating tool to evenly coat the adhesive liquid on the head and the root of the tenon, and at the same time evenly coat the adhesive liquid on the inner surface of the mortise.

[0053] It should be noted that when coating the adhesive liquid on the head of the tenon, due to the relatively large roughness, good wettability, and easier penetration and adsorption, the amount of the adhesive liquid can be appropriately increased. On the contrary, when coating the adhesive liquid on the root of the tenon, the roughness is relatively small, and the amount of the adhesive liquid can be appropriately reduced.

[0054] Then insert the tenon coated with the adhesive liquid into the corresponding mortise, ensure correct alignment, use a pressure device to fix the connection part to maintain pressure, and keep a certain curing time until the adhesive liquid cures. Among them, the pressure applied by the pressure device should be 1.1 MPa. Keep the applied pressure and wait for the adhesive liquid to cure. The curing time is 12 h, and ensure that the connection part will not move or be adjusted during the curing process.

[0055] For the glued wooden board after curing, conduct inspections. By observing the glued part, check whether there are cracks, voids, or looseness. Then use a tensiometer to conduct a tensile test on the glued part, and apply a certain load to the glued part of the glued wooden board to observe whether it can stably bear the load to ensure the quality of the glued wooden board.

[0056] At the same time, after the quality inspection of the glued wooden board is completed, polish and trim the glued part to remove the excess adhesive liquid and uneven parts. It should be noted that good ventilation conditions should be ensured during the overall processing to reduce the impact of the volatilization of the adhesive liquid on the environment and operators.

[0057] Example 2:

[0058] The operation steps are generally the same as those in Example 1. The difference is that, based on Example 1, the particle sizes of the abrasive powder selected from the root to the head are changed and controlled at 90 mesh, 130 mesh, and 190 mesh respectively.

[0059] Example 3:

[0060] The operation steps are generally the same as those in Example 1. The difference is that, based on Example 1, the particle sizes of the abrasive powder selected from the root to the head are changed and controlled at 100 mesh, 140 mesh, and 200 mesh respectively.

[0061] Example 4:

[0062] The operation steps are generally the same as those in Example 1. The difference is that, based on Example 1, the particle sizes of the abrasive powder selected from the root to the head are changed and controlled at 110 mesh, 150 mesh, and 210 mesh respectively.

[0063] The interference-fit tenon-connected spliced middle plates obtained according to the above method are detected, and the following results are obtained:

[0064] Table 1 Gluing strength detection results of the spliced middle plates

[0065] Gluing part Tensile strength Load-bearing capacity Gluing strength Example 1 No looseness 43.27MPa 6.13kN 16.65MPa Example 2 No looseness 44.62MPa 6.27kN 16.12MPa Example 3 No looseness 48.75MPa 6.93kN 17.05MPa Example 4 No looseness 47.58MPa 6.07kN 16.23MPa

[0066] According to the above table, the particle sizes of the abrasive powder selected from the root to the head are controlled at 100 mesh, 140 mesh, and 200 mesh respectively. The tenon and mortise glued with this abrasive powder particle size have the best gluing strength for the obtained spliced middle plate. It can also be known that from the head to the root of the tenon, the roughness gradually decreases, thereby changing the wettability from the head to the root of the tenon, changing the penetration performance of the glue, and ensuring that the glue decreases in turn from the head to the root of the tenon; the head of the tenon is the key connection area and requires stronger gluing strength to bear the main stress; by increasing the roughness of the head, the contact area between the adhesive and the wood surface can be increased, thereby improving the gluing strength; the increase in roughness helps the adhesive to better penetrate into the micropores and fiber gaps of the wood, forming a more firm bond.

[0067] Due to the relatively rough head of the tenon, the glue is more likely to penetrate and adsorb. Appropriately increasing the amount of glue can better fill the gaps on the surface of the tenon, improving the firmness and quality of gluing; at the root of the tenon, since the stress borne is smaller, the amount of glue used can be appropriately reduced. By reducing the roughness at the root, the penetration of the adhesive can be reduced, thereby reducing the use of glue, lowering costs, and at the same time reducing possible environmental pollution; then gradually reducing the gluing amount from the head to the root can avoid the formation of too thick a glue layer between the tenons, which may increase the vulnerability of the glued part, thus improving the strength and stability of gluing; and by precisely controlling the amount of glue used in different parts, the overflow and waste of glue can be reduced, ensuring that the glue is only used in the required parts and improving production efficiency.

[0068] Example Five:

[0069] The operation steps are generally the same as those in Example One. The difference is that, based on Example Three, the structure of the tenon is changed, and a tenon with a needle-like structure is selected. The length of the needle-like structure is 15 mm, and the bottom circumferential diameter is 6 mm.

[0070] Example Six:

[0071] The operation steps are generally the same as those in Example One. The difference is that, based on Example Three, the structure of the tenon is changed, and a tenon with a cylindrical structure is selected. The length is 15 mm, and the bottom circumferential diameter is 30 mm.

[0072] Example Seven:

[0073] The operation steps are generally the same as those in Example One. The difference is that, based on Example Three, the structure of the tenon is changed, and a tenon with a rhomboid structure is selected. It adopts a diamond structure, with a length of 15 mm, and the length of the surface combined with the upper wooden board is 30 mm and the width is 20 mm.

[0074] According to the above method, the interference tenon-connected spliced middle board obtained is detected, and the following results are obtained:

[0075] Table 2 Gluing Strength Detection Results of Spliced Middle Boards with Different Tenon Structures

[0076] Gluing part Tensile strength Load-bearing capacity Gluing strength Example 3 No looseness 48.75MPa 6.93kN 17.05MPa Example 5 No looseness 42.37MPa 6.03kN 16.45MPa Example 6 No looseness 51.86MPa 6.87kN 16.82MPa Example 7 No looseness 55.41MPa 7.15kN 17.75MPa

[0077] As can be seen from the above table, tenons with different structures also have an impact on the gluing strength. The magnitude of the gluing strength is: rhombic > cylindrical > conical > needle-shaped. Among them, the tenon with a rhombic structure generates the greatest gluing strength. Since the tenon with a rhombic structure has a larger length and width on the surface combined with the upper wooden board, this increases the contact area between the tenon and the mortise, which is beneficial to the stability and strength of gluing. At the same time, the tenon with a rhombic structure is designed in a rhomboid shape, enabling it to provide more supporting area during connection, reducing the swaying and deformation of the tenon during the connection process, and being beneficial to the firmness of gluing.

[0078] Example Eight:

[0079] The operation steps are generally the same as those in Example One. The difference is that, on the basis of Example Seven, the spacing when arranging several tenon arrays is changed. In Example One above, the size of the wooden board is 900mm×460mm, the spacing in the length direction when arranging the tenon array is 102mm, and the spacing in the width direction is 68mm; in this example, the spacing in the length direction is selected to be 86mm, and the spacing in the width direction remains unchanged.

[0080] Example Nine:

[0081] The operation steps are generally the same as those in Example One. The difference is that, on the basis of Example Seven, the spacing when arranging several tenon arrays is changed. The spacing in the length direction is selected to be 76mm, and the spacing in the width direction remains unchanged.

[0082] Example Ten:

[0083] The operation steps are generally the same as those in Example One. The difference is that, on the basis of Example Seven, the spacing when arranging several tenon arrays is changed. The spacing in the length direction is selected to be 63mm, and the spacing in the width direction remains unchanged.

[0084] According to the above method, the assembled middle board with interference fit tenons obtained is detected, and the following results are obtained:

[0085] Table 3 Detection Results of Gluing Strength of Assembled Middle Boards with Different Tenon Structures

[0086] Gluing part Tensile strength Load-bearing capacity Gluing strength Example 7 No looseness 55.41MPa 7.15kN 17.75MPa Example 8 No looseness 56.49MPa 7.69kN 17.93MPa Example 9 No looseness 49.32MPa 6.51kN 16.57MPa Example 10 No looseness 46.24MPa 6.05kN 15.73MPa

[0087] As can be seen from the above table, when the number of coated tenons is too large, it will affect the volatilization of the urea-formaldehyde resin adhesive solution, which may lead to a decrease in the viscosity of the adhesive solution. Specifically, an increase in the number of coated tenons will increase the surface area of the adhesive solution, resulting in a slower evaporation rate of the volatile components. The adhesive solution may not have enough time to dry and cure during the coating process, causing the adhesive solution to still maintain a high fluidity and viscosity after coating. In this case, the decrease in the viscosity of the adhesive solution may affect the curing speed and gluing effect of the adhesive solution, and may even lead to quality problems such as insecure gluing.

[0088] It can be seen from the above three tables that the roughness of the tenon, the shape and structure of the tenon, and the spacing between the tenons will all affect the bonding strength of the assembled wooden boards. A control experiment was conducted, and it was found that the wooden boards assembled with a sand powder particle size of 100 mesh, 140 mesh, 100 mesh, a diamond-shaped tenon structure, and a tenon spacing of 86 mm had the best bonding strength. Moreover, the tenon-mortise joint usually provides a relatively high bonding strength, especially at the head of the tenon. Due to the increased roughness, the contact area between the adhesive and the wood is larger, which helps to form a stronger bond. In addition, the tenon-mortise joint also utilizes the mechanical interlocking effect of the wood, further improving the structural stability. At the same time, the tenon-mortise joint usually involves a relatively small contact area, and only the part where the tenon is inserted into the mortise participates in gluing, which can also reduce the amount of glue used because the glue is mainly distributed in the contact area between the tenon and the mortise. Compared with the flat gluing method, this method provides better structural stability and load-bearing capacity.

[0089] Based on the ideal embodiments of the present invention as an inspiration, through the above description, relevant personnel can completely make various changes and modifications without departing from the technical idea of this invention. The technical scope of this invention is not limited to the content in the specification, and the technical scope must be determined according to the scope of the claims.

Claims

1. A green gluing method using urea-formaldehyde resin glue, characterized in that: The following steps are involved: S1. Prepare wood: prepare two wooden boards, divided into an upper wooden board and a lower wooden board; process the upper wooden board and the lower wooden board to make a plurality of tenons and a plurality of mortises; S2. Changing the roughness of the tenon: determining the roughness target values ​​of the tenon head and root according to the requirements, and gradually reducing the roughness of the tenon from the head to the root through multi-stage sand filing processing; S3. Hydrothermal treatment: After the tenon processing is completed, use a soft brush to gently wipe the surface to remove the residue. After cleaning, put the upper and lower wooden boards into the heating water tank to ensure that the wooden boards are completely immersed in water for a period of time. After the immersion is completed, turn off the heating function of the heating water tank, wait for the wood to cool naturally in the water, and then dry it; S4. Preparation of glue: prepare a certain amount of urea-formaldehyde resin glue powder with low formaldehyde release, mix the glue powder with an appropriate amount of water according to the proportion, and stir evenly, and adjust the glue until there are no particles. Use a glue coating tool to evenly coat the glue on the head and root of the tenon, and evenly coat the glue on the inner surface of the mortise; S5. Gluing and fixing: insert the tenon coated with glue into the corresponding mortise, ensure correct alignment, use pressure equipment to fix the connection part to maintain pressure, and maintain a certain curing time until the glue is cured; S6. Quality inspection: After curing, inspect the plywood. Observe the glued parts to check for cracks, gaps or looseness. Use a tensile gauge to perform a tensile test on the glued parts. Apply a certain load to the glued parts to observe whether the plywood can stably withstand the load to ensure the quality of the plywood.

2. A green gluing method using urea-formaldehyde resin glue according to claim 1, characterized in that: In step S1, a plurality of tenons are arranged in array on the upper wooden board, each tenon is configured as a conical structure and each mortise corresponds to the tenon.

3. A green gluing method using urea-formaldehyde resin glue according to claim 1, characterized in that: In step S2, a multi-stage sand file is used to process the roughness of the tenon head, and sand powder of different particle sizes is applied to the sand file in sections. The coarse sand powder part is filed from the root and gradually transitions to the fine sand powder part to process the head. The particle sizes of the sand powder selected from the root to the head are controlled at 80-120 mesh, 120-180 mesh, and 180-240 mesh, respectively.

4. A green gluing method using urea-formaldehyde resin glue according to claim 1, characterized in that: In step S3, a soft brush is used to wipe the surface of the tenon starting from the head and wiping toward the root to avoid reducing the roughness.

5. The green gluing method of urea-formaldehyde resin glue according to claim 1, characterized in that: In step S3, the wood is placed in a heating water tank, the heating equipment is started, the temperature is gradually increased, the heating rate is controlled at 8-10°C / min, the water temperature is gradually increased to 150-220°C, and after the temperature reaches the set temperature, it is kept warm and soaked for 18-24 hours.

6. The green gluing method of urea-formaldehyde resin glue according to claim 1, characterized in that: When applying glue to the head of the tenon in step S4, the amount of glue can be appropriately increased due to its greater roughness, good wettability and easier penetration and adsorption; on the contrary, the root of the tenon has a smaller roughness and the amount of glue can be appropriately reduced.

7. The green gluing method of urea-formaldehyde resin glue according to claim 1, characterized in that: The pressure applied by the pressure equipment in step S5 should be 0.5-1.5 MPa. The applied pressure is maintained and the glue is allowed to solidify for 8-22 hours. It is ensured that the connection part will not be moved or adjusted during the solidification process.

8. The green gluing method of urea-formaldehyde resin glue according to claim 2, characterized in that: The structure of the tenon can also be a needle-shaped, cylindrical, or square structure, and the corresponding mortise is processed and manufactured according to the shape of the tenon.

9. The green gluing method of urea-formaldehyde resin glue according to claim 1, characterized in that: In step S6, after the quality inspection of the plywood is completed, the glued parts are polished and trimmed to remove excess glue and uneven parts.

10. The green gluing method of urea-formaldehyde resin glue according to claim 1, characterized in that: During the steps S1 to S6, good ventilation conditions are ensured to reduce the impact of the volatilization of the glue on the environment and operators.

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