A method for preparing cold-pressed formaldehyde-free plywood-based anti-deformation SPC cabinet door panels

Abstract

This invention belongs to the field of panel technology, specifically relating to a method for preparing a cold-pressed formaldehyde-free plywood-based anti-deformation SPC cabinet door panel. The invention uses a formaldehyde-free inorganic adhesive to coat wood veneers and assemble them into a plywood blank. The plywood blank is then placed in a cold-pressing mold for cold pressing and shaping, followed by demolding to obtain a shaped plywood blank. The shaped plywood blank is then allowed to cure statically before drying and shaping to obtain a dried and shaped plywood blank. The dried and shaped plywood blank undergoes surface treatment and is then laminated with SPC sheets to obtain an SPC substrate. Finally, a PET decorative film is laminated to both surfaces of the obtained SPC substrate to obtain the cold-pressed formaldehyde-free plywood-based anti-deformation SPC cabinet door panel. This invention effectively avoids the deformation of the panel caused by stress generated by rapid heating of wood, and features high strength, uniform moisture content, and significant anti-deformation properties, effectively solving the deformation problem of existing panel materials.

Description

Technical Field

[0001] This invention belongs to the field of board technology, specifically relating to a method for preparing a cold-pressed formaldehyde-free plywood-based anti-deformation SPC cabinet door panel. Background Technology

[0002] The problem of deformation in wood-based panels has always existed, especially in applications such as cabinet doors. On the one hand, wood, as a common door panel material, has natural anisotropy. When the ambient humidity changes, the wood absorbs or releases moisture, leading to dimensional instability and subsequent deformation. In traditional plywood manufacturing processes, the board blank is rapidly formed under high temperature and pressure during hot pressing. The moisture in the board evaporates quickly, causing plastic deformation of the wood. As the adhesive layer cures, localized stress concentrations occur. During use, the internal stress of the board is gradually released, causing door panel deformation, such as warping and twisting. This is especially noticeable when there are significant environmental changes, seriously affecting product quality and lifespan.

[0003] To address the issue of plywood deformation, current methods include using high-strength materials, grooving the back of the door panel, adding metal strips, adding a balancing layer, or using special adhesives. However, these methods only alleviate the problem. In contrast, cold pressing offers significant advantages in reducing door panel deformation. During cold pressing, the temperature is relatively low and the pressure is gentle and uniform. The wood does not undergo rapid heating and cooling, avoiding the plastic deformation and stress concentration problems caused by high temperature and high pressure. This allows the door panel to maintain better dimensional stability and shape integrity during use, effectively reducing the risk of deformation and improving the plywood's resistance to deformation.

[0004] However, current cold-pressing processes primarily involve applying adhesive to veneers, then cold-pressing them in a cold press for 1-3 days, followed by natural curing for 7-20 days. This process requires prolonged use of the cold press, and pressure fluctuations during this extended period can cause problems such as compression, deformation, and cracking of the cured adhesive, affecting its final curing. Furthermore, the prolonged natural curing process, limited by external environmental factors like weather, results in inconsistent adhesive curing levels and uneven moisture content distribution within the plywood, leading to inconsistent performance and dimensional stability across production batches. Therefore, existing cold-pressing technologies still suffer from the problem of plywood susceptibility to deformation. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing a cold-pressed formaldehyde-free plywood-based anti-deformation SPC cabinet door panel. The cold-pressed formaldehyde-free plywood-based anti-deformation SPC cabinet door panel prepared by this invention has the characteristics of high strength and uniform moisture content, and has a significant anti-deformation effect, thereby effectively solving the deformation problem of existing boards.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] This invention provides a method for preparing a cold-pressed formaldehyde-free plywood-based, deformation-resistant SPC cabinet door panel, comprising the following steps:

[0008] Formaldehyde-free inorganic adhesives are used to coat and assemble wood veneers to obtain plywood blanks.

[0009] The plywood blank is placed in a cold press mold for cold pressing and shaping, and after demolding, the shaped plywood blank is obtained.

[0010] The shaped plywood blank is subjected to static curing to obtain a statically cured plywood blank.

[0011] The plywood blanks after static curing are dried and shaped to obtain dried and shaped plywood blanks. The drying and shaping includes a first stage drying treatment, a second stage drying treatment, a third stage drying treatment, a fourth stage drying treatment, and a fifth stage drying treatment in sequence. The temperature of the first stage drying treatment is 60-75℃ and the relative humidity is 40-50%. The temperature of the second stage drying treatment is 70-80℃ and the relative humidity is 30-45%. The temperature of the third stage drying treatment is 70-80℃ and the relative humidity is 30-45%. The temperature of the fourth stage drying treatment is 40-50℃ and the relative humidity is 25-35%. The temperature of the fifth stage drying treatment is 30-45℃ and the relative humidity is 25-35%. The heat preservation time for drying and shaping is 42-62 hours.

[0012] The dried and shaped plywood blank is subjected to surface treatment to obtain plywood substrate;

[0013] An SPC substrate is obtained by flatly attaching SPC sheets to both surfaces of the plywood substrate.

[0014] A PET decorative film is flatly laminated onto both surfaces of the SPC substrate to obtain the cold-pressed formaldehyde-free plywood-based anti-deformation SPC cabinet door panel.

[0015] Preferably, the relative humidity of the first stage drying treatment, the second stage drying treatment, the third stage drying treatment, the fourth stage drying treatment, and the fifth stage drying treatment decreases sequentially; the heat preservation time of the first stage drying treatment is 10-14 hours, the heat preservation time of the second stage drying treatment is 10-12 hours, the heat preservation time of the third stage drying treatment is 8-10 hours, the heat preservation time of the fourth stage drying treatment is 8-12 hours, and the heat preservation time of the fifth stage drying treatment is 6-14 hours.

[0016] Preferably, the formaldehyde-free inorganic adhesive is a modified magnesium oxychloride adhesive, which comprises magnesium oxide, magnesium chloride, a modifier, and water. The molar ratio of magnesium oxide to magnesium chloride is 6-8:1. The modifier comprises nano-silica and phytic acid. The mass content of nano-silica in the formaldehyde-free inorganic adhesive is 3-7%, and the mass content of phytic acid in the modified magnesium oxychloride adhesive is 0.4-1%.

[0017] Preferably, the moisture content of the wood veneer is 8-10%, and the application amount of the formaldehyde-free inorganic adhesive is 300-400 g / m³. 2 ;

[0018] During the gluing and assembly process, the glued wood veneers are laid alternately in a longitudinal and transverse manner.

[0019] Preferably, the cold pressing mold is a separable steel plate frame mold, the cold pressing mold includes a first steel plate and a second steel plate, the first steel plate and the second steel plate are fixedly connected by bolts, and the space between the first steel plate and the second steel plate is used to place the plywood blank.

[0020] Preferably, the thickness tolerance of the plywood blank when placed in the cold pressing mold is ±1mm.

[0021] Preferably, the unit pressure for cold pressing is 2–2.2 MPa / m. 2 The setting time is 24 to 48 hours.

[0022] Preferably, the resting and conditioning time is 6 to 8 days.

[0023] Preferably, during the drying and shaping process, the plywood blanks after static curing are stacked; when stacking, a spacer is provided between adjacent layers of the statically cured plywood blanks.

[0024] Preferably, the moisture content of the dried and shaped plywood blank is 8±2%, and the standard deviation of the moisture content is ≤±1%.

[0025] This invention provides a method for preparing a cold-pressed formaldehyde-free plywood-based anti-deformation SPC cabinet door panel, comprising the following steps: applying a formaldehyde-free inorganic adhesive to a wood veneer to form a plywood blank; placing the plywood blank in a cold-pressing mold for cold pressing and shaping, and obtaining a shaped plywood blank after demolding; subjecting the shaped plywood blank to static curing to obtain a statically cured plywood blank; and subjecting the statically cured plywood blank to drying and shaping to obtain a dried and shaped plywood blank. The drying and shaping includes sequentially performing a first-stage drying treatment, a second-stage drying treatment, a third-stage drying treatment, a fourth-stage drying treatment, and a fifth-stage drying treatment. The temperature of the first-stage drying treatment is 60–75°C, and the relative humidity is 40%. The drying process is as follows: the first stage of drying is at a temperature of 70-80℃ and a relative humidity of 30-45%; the second stage of drying is at a temperature of 70-80℃ and a relative humidity of 30-45%; the third stage of drying is at a temperature of 70-80℃ and a relative humidity of 30-45%; the fourth stage of drying is at a temperature of 40-50℃ and a relative humidity of 25-35%; the fifth stage of drying is at a temperature of 30-45℃ and a relative humidity of 25-35%; and the heat preservation time for drying and shaping is 42-62 hours. The dried and shaped plywood blank is then surface-treated to obtain a plywood substrate. SPC sheets are then flatly laminated onto both surfaces of the plywood substrate to obtain an SPC substrate. Finally, PET decorative films are flatly laminated onto both surfaces of the SPC substrate to obtain the cold-pressed formaldehyde-free plywood-based anti-deformation SPC cabinet door panel. This invention uses a cold-pressing method to prepare cold-pressed formaldehyde-free plywood-based anti-deformation SPC cabinet door panels, fundamentally avoiding the stress concentration problem caused by thermoplastic deformation of wood in traditional hot-pressing processes. This invention uses a cold-pressing mold to replace the continuous pressure holding of a traditional cold press, shortening the single-cycle occupation time of the cold press. This not only reduces production machinery costs but also avoids pressure fluctuations caused by intermittent pressure replenishment during long-term pressure holding in a cold press, effectively preventing adhesive layer cracking. Simultaneously, this invention uses a drying and shaping process instead of traditional long-term natural curing. Furthermore, this invention employs a five-stage gradient drying method to achieve a final moisture content standard deviation of ≤1%, resulting in good moisture content uniformity. This solves the problems of low efficiency and unstable quality in existing cold-pressing processes during mass production. In summary, the preparation method provided by this invention, through improved cold-pressing and drying shaping operations, avoids wood stress caused by heat, leading to board deformation. It exhibits high strength, uniform moisture content, and significant anti-deformation effects, effectively solving the deformation problem of existing boards and significantly improving the bonding and mechanical properties of SPC boards, thus enhancing their resistance to deformation.As can be seen from the results of the embodiments, the present invention uses a cold pressing mold for cold pressing and shaping, which reduces the single occupation time of the cold press from 72 hours to 30 minutes, and increases the equipment utilization rate by 90%. The Class II bonding strength of the cold-pressed formaldehyde-free plywood-based anti-deformation SPC cabinet door panel prepared by the present invention is increased from 1.06MPa to 1.32MPa, and the final moisture content uniformity (standard deviation) is controlled at ≤1%.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] The cold-pressed formaldehyde-free plywood-based SPC cabinet door panels prepared by this invention exhibit significantly improved deformation resistance: Through the synergistic effect of cold pressing and gradient drying, after 130 days of vertical placement, the edge straightness change of the board prepared using the traditional hot pressing process in Comparative Example 6 was 0.91 mm / m, while the edge straightness change of the cold-pressed formaldehyde-free plywood-based SPC cabinet door panels prepared in Example 1 was 0.08 mm / m. The preparation method provided by this invention also improves production efficiency: the utilization rate of the cold press is increased. Furthermore, the preparation method provided by this invention offers high process stability: by controlling the drying and shaping process in five stages, and simultaneously controlling the temperature and relative humidity at each stage, the performance fluctuations between batches are small, meeting the requirements for large-scale production.

[0028] Furthermore, in this invention, the relative humidity of the first, second, third, fourth, and fifth drying stages decreases sequentially; during the drying and shaping process, the plywood blanks after static curing are stacked; during the stacking, a spacer is provided between adjacent layers of statically cured plywood blanks; this invention, by controlling the relative humidity of the five stages in the drying and shaping process to decrease sequentially, and by setting spacers to separate the blanks during the drying and shaping process, is more conducive to the uniform heating and moisture content of the plywood blanks after static curing, thereby achieving full and efficient drying and shaping, and improving the quality stability of the deformation-resistant SPC board. Detailed Implementation

[0029] This invention provides a process for manufacturing cold-pressed formaldehyde-free plywood-based anti-deformation SPC cabinet door panels, comprising the following steps:

[0030] Formaldehyde-free inorganic adhesives are used to coat and assemble wood veneers to obtain plywood blanks.

[0031] The plywood blank is placed in a cold press mold for cold pressing and shaping, and after demolding, the shaped plywood blank is obtained.

[0032] The shaped plywood blank is subjected to static curing to obtain a statically cured plywood blank.

[0033] The plywood blanks after static curing are dried and shaped to obtain dried and shaped plywood blanks. The drying and shaping includes a first stage drying treatment, a second stage drying treatment, a third stage drying treatment, a fourth stage drying treatment, and a fifth stage drying treatment in sequence. The temperature of the first stage drying treatment is 60-75℃ and the relative humidity is 40-50%. The temperature of the second stage drying treatment is 70-80℃ and the relative humidity is 30-45%. The temperature of the third stage drying treatment is 70-80℃ and the relative humidity is 30-45%. The temperature of the fourth stage drying treatment is 40-50℃ and the relative humidity is 25-35%. The temperature of the fifth stage drying treatment is 30-45℃ and the relative humidity is 25-35%. The heat preservation time for drying and shaping is 42-62 hours.

[0034] The dried and shaped plywood blank is subjected to surface treatment to obtain plywood substrate;

[0035] An SPC substrate is obtained by flatly attaching SPC sheets to both surfaces of the plywood substrate.

[0036] A PET decorative film is flatly laminated onto both surfaces of the SPC substrate to obtain the cold-pressed formaldehyde-free plywood-based anti-deformation SPC cabinet door panel.

[0037] In this invention, unless otherwise specified, all raw materials / components used in the preparation are commercially available products well known to those skilled in the art.

[0038] This invention uses a formaldehyde-free inorganic adhesive to coat and assemble wood veneers to obtain plywood blanks. This invention does not have specific requirements regarding the type of wood veneer; in the embodiments, eucalyptus veneer or birch veneer can be used. In this invention, the moisture content of the wood veneer is preferably 8-10%.

[0039] In this invention, the formaldehyde-free inorganic adhesive is preferably a modified magnesium oxychloride adhesive. The modified magnesium oxychloride adhesive comprises magnesium oxide, magnesium chloride, a modifier, and water. The molar ratio of magnesium oxide to magnesium chloride is preferably 6-8:1, and in the examples, it can be 6.29:1. The molar ratio of water to magnesium chloride is preferably 16-18:1, and in the examples, it can be 16.44:1. The modifier preferably comprises nano-silica and phytic acid. The mass content of nano-silica in the modified magnesium oxychloride adhesive is preferably 3-7%, and in the examples, it can be 5%. The mass content of phytic acid in the modified magnesium oxychloride adhesive is preferably 0.4-1%, and in the examples, it can be 0.6%.

[0040] In this invention, the preferred method for preparing the modified magnesium oxychloride adhesive includes: ultrasonically mixing the water and nano-silica to obtain a nano-silica dispersion; mixing the nano-silica dispersion and magnesium chloride to obtain a first mixed solution; allowing the first mixed solution to stand, then mixing it with magnesium oxide and phytic acid to obtain the modified magnesium oxychloride adhesive. The preferred standing time is 20–25 minutes.

[0041] In this invention, the formaldehyde-free inorganic adhesive is preferably coated on both surfaces of the wood veneer. The preferred coating amount of the inorganic adhesive is 300–400 g / m². 2 More preferably, it is 320–360 g / m 2 .

[0042] In this invention, during the gluing and assembly process, the glued wood veneers are preferably laid alternately in a longitudinal and transverse pattern. This alternating longitudinal and transverse layering of wood veneers effectively improves the mechanical strength of the board. In this invention, the number of layers in the gluing and assembly process is preferably determined based on the thickness of the SPC board. In an embodiment of this invention, when the thickness of the cold-pressed formaldehyde-free plywood-based anti-deformation SPC cabinet door panel is 18mm and the thickness of the wood veneer is 1.7mm, the preferred number of layers is 9.

[0043] After obtaining the plywood blank, the present invention places the plywood blank in a cold pressing mold for cold pressing and shaping, and obtains the shaped plywood blank after demolding. In the present invention, the cold pressing mold is preferably a separable steel plate frame mold. The cold pressing mold preferably includes a first steel plate and a second steel plate, which are fixedly connected by bolts. The plywood blank is placed between the first steel plate and the second steel plate, and the bolts are used to press the plywood blank between the first steel plate and the second steel plate, thereby applying pressure to the plywood blank through the first steel plate and the second steel plate.

[0044] The thickness of the first steel plate is preferably 20 mm. The thickness of the second steel plate is preferably 20 mm. The first and second steel plates are preferably rectangular in shape, and bolt holes are provided around their perimeters. The first and second steel plates are preferably fixedly connected by bolts, which are used to fix the first and second steel plates together and to adjust the distance between them.

[0045] In this invention, the thickness tolerance of the plywood blank when placed in the cold pressing mold is preferably ±1mm.

[0046] Preferably, the cold pressing mold clamping of the plywood blank is completed in the cold press. Preferably, the plywood blank is placed in the cold pressing mold and then enters the cold press. The bolts between the first and second steel plates of the cold pressing mold are fixed and locked using the cold press. The fixing and locking pressure is preferably 2–2.2 MPa / m. 2 The locking mold blank is obtained. The locking mold blank is removed from the cold press and stored in the cold pressing area for cold pressing and shaping. In this invention, the locking process is preferably completed within 30 minutes. Then, the cold pressing mold after locking is removed from the cold press. This invention preferably uses a cold pressing mold for cold pressing and shaping, which can provide continuous pressure to the plywood blank. This reduces the cold press occupancy time from 72 hours to 30 minutes, improving equipment utilization.

[0047] In this invention, the pressure for cold pressing is preferably 2 to 2.2 MPa / m. 2 The preferred time is 24–48 hours. The cold pressing and shaping is preferably carried out indoors.

[0048] In this invention, after the cooling and shaping process is completed, a cold press is preferably used to disassemble the cold press mold and remove the shaped plywood blank. The disassembly pressure in the cold press is preferably 2.4 MPa / m. 2 .

[0049] After obtaining the shaped plywood blank, the present invention subjectes the shaped plywood blank to static curing to obtain a statically cured plywood blank. In the present invention, the static curing is preferably carried out in a curing area. The static curing time is preferably 6 to 8 days.

[0050] After obtaining the plywood blank after static curing, the present invention dries and shapes the plywood blank after static curing to obtain the dried and shaped plywood blank. In this invention, the drying and shaping process includes sequentially performing a first-stage drying process, a second-stage drying process, a third-stage drying process, a fourth-stage drying process, and a fifth-stage drying process. The temperature of the first-stage drying process is 60-75°C, preferably 75°C or 60°C in the embodiments, and the relative humidity is 40-50%, preferably 45%. The temperature of the second-stage drying process is 70-80°C, preferably 80°C, and the relative humidity is 30-45%, preferably 40%. The temperature of the third-stage drying process is 70-80°C, preferably 80°C, and the relative humidity is 30-45%, preferably 40% or 35% in the embodiments. The temperature of the fourth-stage drying process is 40-50°C, preferably 45°C or 40°C in the embodiments, and the relative humidity is 25-35%, preferably 30%. The temperature of the fifth-stage drying process is 30-45°C, preferably 45°C or 40°C in the embodiments, and the relative humidity is 25-35%, preferably 25%. The heat preservation time for drying and shaping is preferably 42-60 hours, preferably 48 hours or 50 hours in the embodiments. In this invention, the relative humidity of the first, second, third, fourth, and fifth drying stages preferably decreases sequentially. The holding time for the first drying stage is preferably 10–14 hours, more preferably 12 hours. The holding time for the second drying stage is preferably 10–12 hours, more preferably 12 hours. The holding time for the third drying stage is preferably 8–10 hours, more preferably 10 hours. The holding time for the fourth drying stage is preferably 8–12 hours, more preferably 8 hours. The holding time for the fifth drying stage is preferably 6–14 hours, more preferably 6 hours.

[0051] In embodiments of the present invention, the parameter settings for the first stage drying process, the second stage drying process, the third stage drying process, the fourth stage drying process, and the fifth stage drying process are shown in Table 1.

[0052] Table 1 Parameter settings for each stage of drying and setting

[0053]

[0054] In this invention, during the drying and shaping process, the plywood blanks after static curing are preferably stacked. When stacked, spacers are preferably provided between adjacent layers of statically cured plywood blanks. In this invention, the spacers are preferably wooden strips, which can separate adjacent layers of statically cured plywood blanks by a certain distance, forming an air gap between them. The spacers ensure uniform heating and moisture content of the plywood blanks during the drying and shaping process. In this invention, the spacers are preferably birch wood spacers, and the dimensions of the birch wood spacers are preferably 10mm × 10mm × 2440mm. Preferably, five spacers are provided between adjacent layers of statically cured plywood blanks. The stacking arrangement is preferably on a pallet, and the number of stacked layers is preferably 70. The spacers form uniform ventilation channels, resulting in more uniform heating and heat dissipation of the boards, leading to a uniform final moisture content.

[0055] In this invention, the moisture content of the dried and shaped plywood blank is preferably 8±2%, and the moisture content uniformity (standard deviation) is preferably ≤1%.

[0056] In this invention, after the drying and shaping process is completed, an initially dried and shaped plywood blank is obtained. Preferably, the initially dried and shaped plywood blank is horizontally placed, then the spacers between the boards are removed, and finally, the boards are re-stacked (without spacers). The horizontal placement time is preferably ≥48 hours, more preferably 48–72 hours. The horizontal placement temperature is preferably 20–35°C. The removal of the spacers between the boards is preferably performed in the spacer area. Before removing the spacers, the moisture content of the initially dried and shaped plywood blank after horizontal placement is preferably measured. If the moisture content is ≤10%, the spacers between the boards are removed; if the moisture content is >10%, the entire drying and shaping process is repeated.

[0057] After obtaining the dried and shaped plywood blank, the present invention performs surface treatment on the dried and shaped plywood blank to obtain a plywood substrate. In the present invention, the surface treatment preferably includes sequentially performing edge trimming, sanding, and puttying.

[0058] After obtaining the plywood substrate, the present invention applies SPC thin sheets to both surfaces of the plywood substrate to obtain an SPC substrate, and applies PET decorative films to both surfaces of the SPC substrate to obtain a deformation-resistant SPC sheet.

[0059] In this invention, the thickness of the SPC sheet is preferably 1.5 mm, and the thickness of the PET decorative film is preferably 0.15 to 0.40 mm.

[0060] In this invention, the preferred method for flat-laying the SPC sheet is to use PUR hot melt adhesive. Similarly, the preferred method for flat-laying the PET decorative film is to use PUR hot melt adhesive.

[0061] In this invention, the preferred method for flat-laying the SPC sheet includes: cleaning the surface of the plywood substrate, melting PUR hot melt adhesive using a melting mechanism (preferably at 125°C), and then applying the molten PUR hot melt adhesive to the surface of the plywood substrate using a roller coating device (preferably at a coating amount of 40-50 g / m²). 2 The coating roller is preferably 110°C, and then the surface is smoothed by a mirror-smoothing roller at a temperature preferably 130°C. After smoothing, the SPC sheet is flatly adhered to the PUR hot melt adhesive on the surface of the plywood substrate. After curing, it undergoes a curing process. The curing time is preferably 48–60 hours, after which the SPC substrate is obtained.

[0062] In this invention, the preferred method for applying the PET decorative film includes: cleaning the surface of the SPC substrate, melting PUR hot melt adhesive using a melting mechanism (preferably at 125°C), and then applying the molten PUR hot melt adhesive to the surface of the SPC substrate using a roller coating device (preferably at a coating amount of 40-50 g / m²). 2 The coating roller is preferably 110℃, and then the surface is smoothed by a mirror-smoothing roller at a temperature preferably 130℃. After smoothing, the PET decorative film is flatly applied to the PUR hot melt adhesive on the SPC substrate surface; after curing, it is cured. The curing time is preferably 48-60 hours, and after curing, a cold-pressed formaldehyde-free plywood-based anti-deformation SPC cabinet door panel is obtained.

[0063] The cold-pressed formaldehyde-free plywood-based SPC cabinet door panel prepared by this invention has excellent anti-deformation ability and good mechanical properties.

[0064] The cold-pressed formaldehyde-free plywood-based anti-deformation SPC cabinet door panel prepared by this invention can be used as a cabinet door or wardrobe door.

[0065] To further illustrate the present invention, the technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0066] Example 1:

[0067] This invention provides the preparation of eucalyptus SPC cabinet door panels with a thickness of 18mm and a size of 2750×1220mm, as detailed below:

[0068] Step 1, Preparation of Modified Magnesium Oxide Chloride Adhesive: 14 parts by weight of water and nano-silica were mixed and homogenized using an ultrasonic mixer. Then, 4.5 parts by weight of magnesium chloride were slowly added, stirred until homogenized, and allowed to stand for 20 minutes. Subsequently, 12 parts by weight of magnesium oxide and phytic acid were added. After stirring until homogenized, the modified magnesium oxychloride adhesive was obtained. The modified magnesium oxychloride adhesive contained 0.6% phytic acid and 5% nano-silica by weight.

[0069] Step 2, Veneer gluing and assembly: Select 1.7mm thick eucalyptus veneer with a moisture content controlled at 8-10%. Use a three-roller coating machine to apply the glue. The amount of modified magnesium oxychloride adhesive applied is 350g / m2. Lay the layers alternately in the longitudinal and transverse directions, for a total of 9 layers to assemble the veneer.

[0070] Step 3, Pre-pressing and Mold Locking: The plywood blank is placed in the cold press mold and enters the cold press, at 2MPa / m 2 Under pressure, the mold is locked, and the single-plate assembly and mold fixing are completed within 30 minutes, controlling the plate thickness tolerance to ±1mm.

[0071] Step 4, cold pressing and shaping: After the pre-pressed mold blank is taken out of the cold press, it is stored indoors for 24 hours to allow the modified magnesium oxychloride adhesive to initially cure.

[0072] Step 5, Mold Disassembly and Curing: After the mold blank has been shaped, it is reused in a cold press at 2.4 MPa / m 2 The molds were removed and separated under pressure. The slabs, after mold removal, were cured indoors at 25±2℃ and 40±5% humidity for 6 days. After curing, the slabs were split, spacers were placed between them, and they were re-stacked. The cured slabs were then transported to the spacer separation area for separation, with 5 spacers placed between every two slabs, and 70 slabs per pallet.

[0073] Step Six, Drying and Shaping: The boards with spacers placed are transported to a greenhouse for gradient drying treatment, which takes 50 hours. The gradient temperature and humidity in the greenhouse are as follows:

[0074] Gradient drying is specifically divided into five stages:

[0075] The first stage involves drying at 75℃ and 45% humidity for 12 hours with heating and heat preservation.

[0076] The second stage involves drying at 80℃ and 40% humidity for 12 hours with heating and heat preservation.

[0077] The third stage involves drying at 80℃ and 35% humidity for 10 hours with heating and heat preservation.

[0078] The fourth stage involves drying at 45℃ and 30% humidity for 8 hours with heating and heat preservation.

[0079] The fifth stage involves drying at 45℃ and 25% humidity for 8 hours with heating and heat preservation.

[0080] The final moisture content of the board is controlled at 8±2%. After the board has been dried and shaped, it is transported to the spacer strip dismantling area and left to cool horizontally for 48 hours before the spacers are dismantled.

[0081] Step 7, Sanding and smoothing: The anti-deformation plywood blank obtained in Step 6 is processed through conventional processes such as sawing, sanding, and scraping to obtain the plywood substrate.

[0082] Step 8, SPC finish treatment:

[0083] SPC sheet lamination: A flat-lay process is used. The surface of the plywood substrate is cleaned, and PUR hot melt adhesive is melted using a melting mechanism at a melting temperature of 125℃. The molten PUR hot melt adhesive is then roller-coated onto the surface of the plywood substrate using a roller coating device, with a coating amount of 50g / m². 2 The preferred temperature of the coating roller is 110℃. Then, it is smoothed by a mirror-smoothing roller with a temperature of 130℃. After smoothing, the SPC sheet is flatly attached to the PUR hot melt adhesive on the surface of the plywood substrate. After curing, it is cured for 60 hours to obtain the SPC substrate.

[0084] The SPC substrate surface is cleaned, and PUR hot melt adhesive is melted using a melting mechanism at a temperature of 125℃. The molten PUR hot melt adhesive is then applied to the SPC substrate surface using a roller coating device, with a coating amount of 50g / m². 2 The coating roller is heated to 110℃, and then the surface is smoothed by a mirror-smoothing roller at 130℃. After smoothing, the PET decorative film is flatly applied to the PUR hot melt adhesive on the SPC substrate surface. Curing is then performed. The curing time is 60 hours, resulting in a cold-pressed, formaldehyde-free plywood-based, deformation-resistant SPC cabinet door panel.

[0085] Example 2

[0086] The difference between this embodiment and Embodiment 1 is that the drying and shaping process in step six is ​​changed, as shown in Table 2:

[0087] Table 2. Drying and setting conditions in Example 2

[0088] one 60 45 10 two 80 40 10 three 80 35 10 Four 40 30 10 five 40 25 10

[0089] Comparative Example 1:

[0090] The difference between this comparative example and Example 2 is the drying and shaping process in step six, as shown in Table 3:

[0091] Table 3 shows the drying and setting conditions in Comparative Example 1.

[0092] one 80 45 10 two 60 40 10 three 60 35 10 Four 40 30 10 five 40 25 10

[0093] Comparative Example 2:

[0094] The difference between this comparative example and Example 2 is the drying and shaping process in step six, as shown in Table 4:

[0095] Table 4. Drying and setting conditions in Comparative Example 2

[0096]

[0097]

[0098] Comparative Example 3:

[0099] The difference between this comparative example and Example 2 is in the drying and shaping process in step six, as shown in Table 5:

[0100] Table 5. Drying and setting conditions in Comparative Example 1

[0101] one 60 45 10 two 40 40 10 three 40 35 10 Four 80 30 10 five 80 25 10

[0102] Comparative Example 4: Gradient-free drying process

[0103] Step 1, Preparation of Modified Magnesium Oxide Chloride Adhesive: 14 parts by weight of water and nano-silica were mixed and homogenized using an ultrasonic mixer. Then, 4.5 parts by weight of magnesium chloride were slowly added, stirred until homogenized, and allowed to stand for 20 minutes. Subsequently, 12 parts by weight of magnesium oxide and phytic acid were added. After stirring until homogenized, the modified magnesium oxychloride adhesive was obtained. The modified magnesium oxychloride adhesive contained 0.4% phytic acid and 1% nano-silica by weight.

[0104] Step 2: Applying adhesive to the veneer and assembling the blank: This is the same as Step 2 in Example 1;

[0105] Step 3: Pre-compression and mold clamping: Same as step 3 in Example 1;

[0106] Step 4: Cold pressing and shaping, consistent with Step 4 of Example 1;

[0107] Step 5, Mold Disassembly and Curing: After the mold blank has been shaped, it is reused in a cold press at 2.4 MPa / m 2 The mold was removed and separated under pressure. The slab after mold removal was then cured indoors at 25±2℃ and 40±5% humidity for 6 days.

[0108] Step 6, Drying and Shaping: The boards with spacers placed are transported to a greenhouse for gradient drying treatment at a temperature of 45℃ and a humidity of 30% for 50 hours.

[0109] Step 7, Sanding and leveling: Same as step 7 in Example 1.

[0110] Step 8: SPC finish treatment: Same as step 8 in Example 1.

[0111] Comparative Example 5: Conventional Cold Pressing Process

[0112] Step 1, Preparation of Modified Magnesium Oxide Chloride Adhesive: 14 parts by weight of water and nano-silica were mixed and homogenized using an ultrasonic mixer. Then, 4.5 parts by weight of magnesium chloride were slowly added, stirred until homogenized, and allowed to stand for 20 minutes. Subsequently, 12 parts by weight of magnesium oxide and phytic acid were added. After stirring until homogenized, the modified magnesium oxychloride adhesive was obtained. The modified magnesium oxychloride adhesive contained 0.6% phytic acid and 5% nano-silica by weight.

[0113] Step 2, veneer gluing and assembly: consistent with Step 2 of Example 1.

[0114] Step 3: Cold pressing process: After assembly, press the blanks in a cold press at 2MPa / m 2 Cold press for 72 hours, then naturally cure for 20 days;

[0115] Step 4: Sanding and leveling: Same as step 7 in Example 1;

[0116] Step 5: SPC finish treatment: Same as step 8 in Example 1.

[0117] Comparative Example 6: Traditional Hot Pressing Process

[0118] Step 1: Glue Application and Assembly: Urea-formaldehyde resin is used, and a three-roller coater is employed for glue application. The glue application rate is 180g / m2. The veneers are assembled in a vertically and horizontally staggered manner, with a total of 9 layers laid out, and 70 veneers are considered as one unit.

[0119] Step 2, Cold Pressing: After the assembled plates have been laid out for 1 hour, they are sent to a cold press at 0.7 MPa / m. 2 After cold pressing for 1.5 hours, it is cold-pressed into shape.

[0120] Step 3: Repair: Repair surface defects on the cold-pressed board to ensure a smooth surface without delamination, holes, or other defects.

[0121] Step 4: Hot and cold pressing: Hot press the repaired board at a temperature of 125℃ for 50 minutes. After hot pressing, let it stand until it cools down.

[0122] Step 5, sanding and leveling: consistent with step 7 of Example 1.

[0123] Step Six: SPC Finishing: Same as Step Eight in Example One.

[0124] Test example:

[0125] The following testing experiments were conducted on the SPC cabinet door panels obtained in the above embodiments and comparative examples:

[0126] (1) Moisture content uniformity refers to GB / T 1931-2009. A total of 9 sampling points (including the edge, diagonal and central areas) are taken in the transverse and longitudinal directions of the board, and 3 parallel samples are taken at each point. Using a CNC milling machine, samples of the upper and lower surface layers and the core layer are taken in the thickness direction. The standard deviation of moisture content is calculated to characterize the moisture content uniformity between sampling points.

[0127] (2) The bonding strength, static bending strength and elastic modulus, 72h water absorption swelling rate and formaldehyde release were tested in accordance with GB / T17657-2022.

[0128] (3) For edge straightness, refer to GB / T 19367-2022. Prepare a cabinet door with dimensions of 2700mm × 800mm × plate thickness and install it vertically on the test rack. Place it indoors at 20℃ and 50% humidity for 130 days to test the edge straightness along the length. Calculate the difference between the initial edge straightness and the edge straightness after 130 days.

[0129] The performance test results are shown in Table 6.

[0130] Table 6. Performance test results of cabinet door panels prepared in the examples and comparative examples.

[0131]

[0132] As shown in the table above, Examples 1-2 and Comparative Examples 2-5 exhibit a higher modulus of elasticity parallel to the grain and a smaller change in edge straightness compared to Comparative Example 6, indicating that the cold pressing process can effectively reduce plywood deformation. Compared to Comparative Example 4, Examples 1-2 demonstrate that the gradient drying process exhibits lower moisture content uniformity and higher bonding strength, static bending strength, and modulus of elasticity compared to the traditional cold pressing process. This demonstrates the significant advantages of gradient drying under cold pressing. Examples 1-2 show significantly lower 72-hour absorption thickness expansion rate and moisture content standard deviation compared to Comparative Examples 1-3, indicating that adjusting the gradient drying temperature can improve the curing degree of the adhesive layer and make the moisture content of the board more uniform, ultimately achieving a significant anti-deformation effect. Therefore, the SPC anti-deformation board prepared by this invention has high strength, uniform moisture content, and significant anti-deformation properties, effectively solving the deformation problem of existing boards.

[0133] As can be seen from the above embodiments, the present invention uses a cold-pressing process to prepare plywood, fundamentally avoiding the stress concentration problem caused by thermoplastic deformation of wood in the traditional hot-pressing process. By replacing the traditional cold press with a separable cold-pressing mold for continuous pressure holding, the single-cycle occupation time of the cold press is shortened from 72 hours to 30 minutes, increasing equipment utilization by 90%. This not only reduces production machinery costs but also avoids pressure fluctuations caused by intermittent pressure replenishment during long-term pressure holding in the cold press, effectively preventing glue layer cracking and increasing the Class II bond strength from 1.06 MPa to 1.32 MPa. In addition, through the board splitting process and the five-stage gradient temperature control technology in the drying oven, the final moisture content uniformity (standard deviation) of the board is controlled at ≤1%, solving the problems of low efficiency and unstable quality of existing cold-pressing processes in mass production. The cold-pressed formaldehyde-free plywood-based SPC cabinet door panel prepared by the present invention has excellent deformation resistance and good mechanical properties.

[0134] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention, and not all embodiments. Other embodiments can be obtained based on these embodiments without creative effort, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A method for preparing a cold-pressed formaldehyde-free plywood-based anti-deformation SPC cabinet door panel, characterized in that, Includes the following steps: A formaldehyde-free inorganic adhesive is used to coat and assemble wood veneers to obtain plywood blanks. The formaldehyde-free inorganic adhesive is a modified magnesium oxychloride adhesive, which comprises magnesium oxide, magnesium chloride, a modifier, and water. The molar ratio of magnesium oxide to magnesium chloride is 6-8:

1. The modifier comprises nano-silica and phytic acid. The mass content of nano-silica in the formaldehyde-free inorganic adhesive is 3-7%, and the mass content of phytic acid in the modified magnesium oxychloride adhesive is 0.4-1%. The plywood blank is placed in a cold press mold for cold pressing and shaping, and after demolding, the shaped plywood blank is obtained. The shaped plywood blank is subjected to static curing to obtain a statically cured plywood blank. The plywood blanks after static curing are dried and shaped to obtain dried and shaped plywood blanks. The drying and shaping includes a first stage drying treatment, a second stage drying treatment, a third stage drying treatment, a fourth stage drying treatment, and a fifth stage drying treatment in sequence. The temperature of the first stage drying treatment is 60~75℃, the relative humidity is 40~50%, and the holding time is 10~14h. The temperature of the second stage drying treatment is 70~80℃, the relative humidity is 30~45%, and the holding time is 10~12h. The third stage of drying is performed at a temperature of 70-80℃ and a relative humidity of 30-45%, with a holding time of 8-10 hours. The fourth stage of drying is performed at a temperature of 40-50℃ and a relative humidity of 25-35%, with a holding time of 8-12 hours. The fifth stage of drying is performed at a temperature of 30-45℃ and a relative humidity of 25-35%, with a holding time of 6-14 hours. The holding time for drying and shaping is 42-62 hours. The dried and shaped plywood blank is then subjected to surface treatment to obtain plywood substrate. An SPC substrate is obtained by flatly attaching SPC sheets to both surfaces of the plywood substrate. A PET decorative film is flatly laminated onto both surfaces of the SPC substrate to obtain the cold-pressed formaldehyde-free plywood-based anti-deformation SPC cabinet door panel.

2. The preparation method according to claim 1, characterized in that, The relative humidity decreases sequentially in the first, second, third, fourth, and fifth stages of drying treatment.

3. The preparation method according to claim 1, characterized in that, The moisture content of the wood veneer is 8-10%, and the application amount of the formaldehyde-free inorganic adhesive is 300-400 g / m³. 2 ; During the gluing and assembly process, the glued wood veneers are laid alternately in a longitudinal and transverse manner.

4. The preparation method according to claim 1, characterized in that, The cold pressing mold is a separable steel plate frame mold. The cold pressing mold includes a first steel plate and a second steel plate, which are fixedly connected by bolts. The space between the first steel plate and the second steel plate is used to place the plywood blank.

5. The preparation method according to claim 1 or 4, characterized in that, The thickness tolerance of the plywood blank when placed in the cold pressing mold is ±1mm.

6. The preparation method according to claim 1, characterized in that, The unit pressure for cold pressing is 2~2.2 MPa / m. 2 The setting time is 24~48 hours.

7. The preparation method according to claim 1, characterized in that, The resting and conditioning period is 6 to 8 days.

8. The preparation method according to claim 1, characterized in that, During the drying and shaping process, the plywood blanks after static curing are stacked together; during the stacking process, a spacer is provided between two adjacent layers of the statically cured plywood blanks.

9. The preparation method according to claim 1, characterized in that, The moisture content of the dried and shaped plywood blank is 8±2%, and the standard deviation of the moisture content is ≤±1%.

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