Preparation method of anti-deformation moisture-proof shaving board and shaving board

Abstract

The invention relates to the technical field of shaving boards, and discloses a preparation method of an anti-deformation moisture-proof shaving board and the shaving board, the preparation method comprises the following steps: S1, sorting: sorting to obtain surface layer fine materials and core layer wood shavings; s2, glue applying, wherein urea-formaldehyde glue I is applied to the surface layer fine materials, and urea-formaldehyde glue II and MDI glue are applied to the core layer wood shavings; the urea-formaldehyde glue I and the urea-formaldehyde glue II are both melamine modified urea-formaldehyde glue; s3, moisture prevention is conducted, specifically, a waterproof agent and a mildew preventive are applied to the surface layer fine materials and the core layer wood shavings correspondingly, and then a curing agent is applied to the core layer wood shavings; s4, paving is conducted, specifically, laminated paving is conducted according to surface layer fine materials, core layer wood shavings and surface layer fine materials, and a plate blank is obtained; and S5, hot pressing, wherein the plate blank is subjected to hot pressing. Melamine modified urea-formaldehyde glue is adopted for sizing, different sizing processes are adopted for the surface layer and the core layer, the wood shaving units are tightly glued together, and the shaving board good in humidity resistance and size stability is prepared.

Description

Technical Field

[0001] The invention relates to the technical field of particle boards, in particular to a preparation method of a deformation-resistant and moisture-proof particle board and the particle board. Background Art

[0002] Wood is a naturally porous, hygroscopic material. When its moisture content falls below its fiber saturation point, it absorbs moisture from the surrounding air, which manifests itself as changes in size and shape. Particleboard, like other wood-based panels, shrinks and expands when wet. This shrinkage and expansion is caused by the increase or decrease in moisture in the cell walls of the wood fibers, resulting in dimensional changes.

[0003] Particleboard is a man-made board made from wood shavings, coated with synthetic resin, and then hot-pressed. During the hot-pressing process, varying internal stresses develop within the board, causing dimensional changes and thus affecting its stability. Furthermore, factors such as the uniformity of the board's surface density after installation and the wood's susceptibility to moisture also significantly impact the board's deformation during later use. For example, the patent with publication number CN119188925B discloses a low-density, high-strength, formaldehyde-free, moisture-proof and deformation-resistant particleboard process, which includes the following steps: particle production section: processing wood or non-wood plant fiber raw materials into particles; drying and sorting section: after the wet particles are dried, the dry particles are screened into surface dry particles and core dry particles; the surface particles are at least one of water bamboo, ma bamboo or Mengzong bamboo particles, and the core particles are fir particles; gluing section: injecting glue into the surface and core layer particle glue mixing machine to mix the surface and core layer dry particles; paving and hot pressing section: paving the surface and core layer glued particles into a continuous slab strip of composite structure; after the slab strip is pre-pressed and formed, it is hot-pressed and then cooled; sanding and cutting section: the sanded particleboard is sawn into finished boards of specification. Although this method can overcome the problem of poor moisture resistance, since the surface and core layers used are all large pieces of wood chips, different internal stresses will be generated inside the board during the hot pressing process, and the uniformity of the board surface density will also be affected. Therefore, the dimensional stability of the resulting particleboard is poor. Summary of the Invention

[0004] In order to overcome the shortcomings of traditional artificial board production technology in terms of dimensional deformation and poor moisture resistance, the present invention provides a method for preparing a deformation-resistant moisture-proof particleboard and a particleboard. The deformation-resistant moisture-proof and veneerable particleboard has excellent dimensional stability, good moisture resistance, good processability, is non-toxic and odorless, safe, healthy, and green and environmentally friendly; and the preparation process is simple and low-cost.

[0005] The purpose of the present invention is achieved through the following technical solutions: In a first aspect, the present invention provides a method for preparing a deformation-resistant moisture-proof particleboard, comprising the following steps: S1. Sorting: Sorting to obtain surface fines and core shavings; S2. Gluing: Apply urea-formaldehyde glue I to the surface fine material, and apply urea-formaldehyde glue II and MDI glue to the core wood chips; the raw materials of urea-formaldehyde glue I include 47-51 parts of urea, 47-49 parts of formaldehyde solution and 2.5-3.7 parts of melamine, and the raw materials of urea-formaldehyde glue II include 44-46 parts of urea, 49-51 parts of formaldehyde solution and 9-11 parts of melamine, calculated by weight; S3. Moisture-proof: Apply waterproofing agent and mildew-proofing agent to the surface fine material and core wood shavings respectively, and then apply curing agent to the core wood shavings; S4. Paving: Laying the surface fine material - core layer shavings - surface fine material in layers to obtain a slab; S5. Hot pressing: hot pressing the slab.

[0006] The melamine modification ratios used in urea-formaldehyde glue I and urea-formaldehyde glue II are different. Urea-formaldehyde glue I uses less melamine addition, and the reaction of urea, melamine and formaldehyde is more complete, with less free formaldehyde, which can significantly reduce the formaldehyde release from the surface of the board; urea-formaldehyde glue II uses more melamine addition. The rigid triazine ring and multi-functional characteristics of the melamine molecule are conducive to increasing the branching degree of urea-formaldehyde resin through co-condensation reaction, and also block a large number of water-absorbing groups such as -CH2OH and -CONH-, which can significantly improve the bonding strength and water resistance of urea-formaldehyde resin.

[0007] In addition, the core wood particles are sized with both melamine-modified urea-formaldehyde glue and MDI glue. Melamine-modified urea-formaldehyde glue improves the water resistance of the urea-formaldehyde resin by reducing hydrophilic groups such as -OH and -CO-NH- in the adhesive resin. The hydrophobic groups in MDI glue significantly enhance the moisture resistance of the board, thereby improving the moisture resistance of the core layer. The addition of MDI glue to the mix also improves water resistance and strength while reducing formaldehyde emissions.

[0008] Therefore, by applying urea-formaldehyde glue I to the surface fine material and urea-formaldehyde glue II and MDI glue to the core wood particles, the formaldehyde emission can be reduced while ensuring the bonding strength and waterproofness of the particleboard.

[0009] Preferably, in S1, the particle size of the surface layer fines is 0.5-1.5 mm; the core layer wood chips are 25-35 mm long, 5-6 mm wide, and ≤0.7 mm thick. The use of fines in the surface layer fills the gaps between the wood chips, resulting in a denser structure and less surface density variation. The core layer utilizes slender, thin wood chips with a uniform particle shape, resulting in a more uniform density within the finished hot-pressed board.

[0010] Preferably, in S2, the amount of urea-formaldehyde glue I applied is 12-14% of the absolute dry weight of the surface fine material; the amount of urea-formaldehyde glue II applied is 10-12% of the absolute dry weight of the core wood chips; and the amount of MDI glue applied is 0.5-2% of the absolute dry weight of the core wood chips.

[0011] Preferably, in S2, the raw materials of urea-formaldehyde glue I include 47-51 parts of urea, 47-49 parts of formaldehyde solution, 0.3-0.6 parts of pH regulator and 2.5-3.7 parts of melamine, and the raw materials of urea-formaldehyde glue II include 44-46 parts of urea, 49-51 parts of formaldehyde solution, 1-3 parts of pH regulator and 9-11 parts of melamine.

[0012] Preferably, in S2, the urea-formaldehyde glue I and urea-formaldehyde glue II are both melamine-modified urea-formaldehyde glues, and their preparation method comprises the following steps: mixing and heating urea and formaldehyde solution, adding a pH regulator and stirring, and then adding melamine and continuing to stir to obtain melamine-modified urea-formaldehyde glue.

[0013] Preferably, the mass concentration of the formaldehyde solution is 35-40%; the heating is to raise the temperature to 60-80° C.; the pH regulator is triacetamide; the stirring time is 30-50 minutes; and the continued stirring time is 1-2 hours.

[0014] Preferably, in S3, the amount of the waterproofing agent added to the surface fine material is 2-4% of the absolute dry weight of the surface fine material; the amount of the waterproofing agent added to the core wood shavings is 1-3% of the absolute dry weight of the core wood shavings.

[0015] The present invention adopts melamine-modified urea-formaldehyde resin to improve the waterproof performance of urea-formaldehyde glue, but the improvement of its waterproof performance has certain limitations, and it is still necessary to apply a waterproofing agent and melamine-modified urea-formaldehyde glue to synergistically improve the waterproof performance.

[0016] Preferably, in S3, the waterproofing agent is emulsified paraffin or liquid paraffin. Adding the waterproofing agent further enhances the waterproof performance of the particleboard and reduces deformation of the board due to moisture during subsequent use.

[0017] Preferably, in S3, the amount of the mildew preventer added to the surface fine material is 4-6‰ of the absolute dry weight of the surface fine material; the amount of the mildew preventer added to the core layer shavings is 1-3‰ of the absolute dry weight of the core layer shavings.

[0018] Preferably, in S3, the antifungal agent is 2-butyl-1,2-benzisothiazol-3-one (BBIT).

[0019] Preferably, in S3, the amount of the curing agent added to the core layer wood chips is 1 to 3% of the absolute dry weight of the core layer wood chips.

[0020] Preferably, in S3, the curing agent is ammonium chloride or ammonium sulfate.

[0021] Preferably, in S4, the surface layer fine material is directly paved, and the core layer wood chips are dried to a moisture content of 7-9% before being paved.

[0022] Preferably, in S5, the hot pressing temperature is 220-240° C., and the time is 2-5 minutes.

[0023] Preferably, in S5, the hot pressing is a three-stage hot pressing, specifically: the first stage is a high-pressure stage, the pressure is 13-16 MPa, and the time is 10-60 s; the second stage is a low-pressure stage, the pressure is 7-9 MPa, and the time is 30-90 s; the third stage is a medium-pressure stage, the pressure is 10-13 MPa, and the time is 80-150 s.

[0024] This invention utilizes a three-stage hot-pressing process: the first, a high-pressure stage, rapidly compresses the slab to the specified thickness, significantly reducing the pre-cured layer on the surface; the second, a low-pressure stage, facilitates the removal of moisture from the slab, preventing excessive internal pressure that can reduce bonding strength or cause the board to burst; and the third, a medium-pressure stage, further solidifies the glue within the slab, promoting the bonding of the wood particles and increasing bonding strength, while controlling moisture content variations within the board and reducing internal stress. This three-stage hot-pressing process prevents warping and deformation caused by uneven moisture content and density during subsequent use.

[0025] In a second aspect, the present invention further provides a deformation-resistant and moisture-proof particleboard produced by the above-mentioned preparation method, wherein the particleboard comprises a core layer and surface layers arranged on the upper and lower surfaces of the core layer, and is a three-layer symmetrical structure.

[0026] Compared with the prior art, the present invention has the following beneficial effects: (1) The core layer of wood chips is made of narrow and long pieces, and the surface layer uses loose and fine materials to fill the gaps between the wood chips. The structure is denser, the board surface density deviation is small, the size is stable, and the thickness direction is a uniform three-layer symmetrical structure; (2) By using melamine-modified urea-formaldehyde glue for gluing, and using different gluing processes for the surface layer and the core layer, each particle unit is tightly glued together to prepare a high-strength particleboard with excellent mechanical properties and not easy to bend and deform; (3) Meet the P6 grade moisture-proof performance test requirements of particleboard, the 24-hour water absorption thickness expansion rate is ≤8%, and the performance remains stable in a humid environment, the expansion deformation is very small, and the size is stable. DETAILED DESCRIPTION

[0027] The technical solutions of the present invention are described below with specific embodiments, but the protection scope of the present invention is not limited thereto.

[0028] Example 1 S1. Sorting: The logs are first debarked in a debarking machine and then cleaned in a clean water tank to remove surface impurities and veneer debris. The treated logs are then steamed and softened, then shaved into 3-4 cm long chips. These chips are then processed through an Italian Grubas ring flaker to produce wood shavings ≤35 mm in length and ≤7 mm in width for later use. The shavings are then dried in a drum dryer and then, via an air supply system, sent to an airflow separator for further sorting to remove veneer debris and other impurities. The sorted shavings are then screened on a rectangular oscillating screen to select fine powder with a particle size of 0.5-1.5 mm, resulting in the surface layer fine material. Coarse shavings with a length of 25-35 mm, a width of 5-6 mm, and a thickness of ≤0.7 mm are then selected to form the core layer shavings. These shavings are then conveyed via belt conveyors for the surface and core layers to their respective silos for later use.

[0029] S2. Gluing: Apply urea-formaldehyde glue I to the surface fine material, the addition amount is 13% of the absolute dry weight of the surface fine material, and stir evenly; apply urea-formaldehyde glue II and MDI glue to the core layer wood chips, the addition amount of urea-formaldehyde glue II is 12% of the absolute dry weight of the core layer wood chips, and the addition amount of MDI glue is 1% of the absolute dry weight of the core layer wood chips, and stir evenly.

[0030] Preparation of urea-formaldehyde glue I by mass: add 49 parts of urea and 48 parts of formaldehyde solution with a mass concentration of 37% into a reactor, heat to 70°C, add 0.5 parts of pH regulator (triacetamide), stir at a speed of 700 r / min for 0.5 h, then add 2.7 parts of melamine, and stir for another 1 h to prepare melamine-modified urea-formaldehyde glue I.

[0031] Preparation of urea-formaldehyde glue II by mass: add 44 parts of urea and 50 parts of formaldehyde solution with a mass concentration of 37% into a reactor, heat to 70°C, add 2 parts of pH regulator (triacetamide), stir at a speed of 700 r / min for 0.5 h, then add 10.2 parts of melamine, and stir for another 1.5 h to prepare melamine-modified urea-formaldehyde glue II.

[0032] S3, moisture-proof: add waterproofing agent (50% solid content of emulsified paraffin) to the surface fine material and the core shavings respectively: the amount of waterproofing agent added to the surface fine material is 3% of the absolute dry weight of the surface fine material, and stir evenly; the amount of waterproofing agent added to the core shavings is 2% of the absolute dry weight of the core shavings, and stir evenly; Add mildew preventer (BBIT) to the surface fine material and core wood shavings respectively: the amount of mildew preventer added to the surface fine material is 5‰ of the absolute dry weight of the surface fine material, and stir evenly; the amount of mildew preventer added to the core wood shavings is 3‰ of the absolute dry weight of the core wood shavings, and stir evenly; add curing agent (ammonium chloride) to the core wood shavings: the amount of curing agent added is 2% of the absolute dry weight of the core wood shavings, and stir evenly.

[0033] S4. Paving: The surface layer is paved directly and the core layer is paved after drying: the surface layer fine material is divided into two equal parts by weight, one of which is paved on the bottom layer and the other on the top layer; the core layer shavings are dried to a moisture content of 8%, and then evenly paved on the core layer to obtain a three-layer slab with a dense and symmetrical structure, the upper and lower surface layers are both surface fine materials, and the core layer is coarse shavings.

[0034] S5. Hot pressing: The slab is fed into a continuous flat-plate hot press. The hot pressing temperature is 210°C. The first section is a high-pressure section with a pressure of 15 MPa and a time of 30 seconds. The second section is a low-pressure section with a pressure of 9 MPa and a time of 50 seconds. The third section is a medium-pressure section with a pressure of 12 MPa and a time of 100 seconds. The total hot pressing time is 3 minutes.

[0035] S6. Post-processing: The rough-edged boards produced by hot pressing are subjected to post-processing such as cutting, trimming, turning over for cooling, aging, and surface sanding to obtain deformation-resistant and moisture-proof particleboard.

[0036] Example 2 S1. Sorting: The same surface fines and core shavings as in Example 1 are used.

[0037] S2. Gluing: Apply urea-formaldehyde glue I (the same as in Example 1) to the surface fine material, and add 14% of the absolute dry weight of the surface fine material, and stir evenly; apply urea-formaldehyde glue II (the same as in Example 1) and MDI glue to the core layer wood chips, and add urea-formaldehyde glue II in an amount of 11% of the absolute dry weight of the core layer wood chips, and add MDI glue in an amount of 1.5% of the absolute dry weight of the core layer wood chips, and stir evenly.

[0038] S3, moisture-proof: add waterproofing agent (emulsified paraffin with a solid content of 50%) to the surface fine material and the core shavings respectively, the amount of waterproofing agent added to the surface fine material is 3.5% of the absolute dry weight of the surface fine material, and stir evenly; the amount of waterproofing agent added to the core shavings is 1.5% of the absolute dry weight of the core shavings, and stir evenly; Add mildew preventer (BBIT) to the surface fine material and core wood shavings respectively: the amount of mildew preventer added to the surface fine material is 5‰ of the absolute dry weight of the surface fine material, and stir evenly; the amount of mildew preventer added to the core wood shavings is 3‰ of the absolute dry weight of the core wood shavings, and stir evenly; add curing agent (ammonium chloride) to the core wood shavings: the amount of curing agent added is 2% of the absolute dry weight of the core wood shavings, and stir evenly.

[0039] S4. Paving: The surface layer is paved directly and the core layer is paved after drying: the surface layer fine material is divided into two equal parts by weight, one of which is paved on the bottom layer and the other on the top layer; the core layer shavings are dried to a moisture content of 8%, and then evenly paved on the core layer to obtain a three-layer slab with a dense and symmetrical structure, the upper and lower surface layers are both surface fine materials, and the core layer is coarse shavings.

[0040] S5. Hot pressing: The slab is fed into a continuous flat-plate hot press. The hot pressing temperature is 220°C. The first section is a high-pressure section with a pressure of 15 MPa and a time of 25 seconds. The second section is a low-pressure section with a pressure of 8 MPa and a time of 58 seconds. The third section is a medium-pressure section with a pressure of 13 MPa and a time of 85 seconds. The total hot pressing time is 2.8 minutes.

[0041] S6. Post-processing: The rough-edged boards produced by hot pressing are subjected to post-processing such as cutting, trimming, turning over for cooling, aging, and surface sanding to obtain deformation-resistant and moisture-proof particleboard.

[0042] Example 3 S1. Sorting: The same surface fines and core shavings as in Example 1 are used.

[0043] S2. Gluing: Apply urea-formaldehyde glue I (the same as in Example 1) to the surface fine material, and add 15% of the absolute dry weight of the surface fine material, and stir evenly; apply urea-formaldehyde glue II (the same as in Example 1) and MDI glue to the core layer wood chips, and add urea-formaldehyde glue II in an amount of 10% of the absolute dry weight of the core layer wood chips, and add MDI glue in an amount of 2% of the absolute dry weight of the core layer wood chips, and stir evenly.

[0044] S3, moisture-proof: add waterproofing agent (emulsified paraffin with a solid content of 50%) to the surface fine material and the core shavings respectively, the amount of waterproofing agent added to the surface fine material is 4% of the absolute dry weight of the surface fine material, and stir evenly; the amount of waterproofing agent added to the core shavings is 1% of the absolute dry weight of the core shavings, and stir evenly; Add mildew preventer (BBIT) to the surface fine material and core wood shavings respectively: the amount of mildew preventer added to the surface fine material is 5‰ of the absolute dry weight of the surface fine material, and stir evenly; the amount of mildew preventer added to the core wood shavings is 3‰ of the absolute dry weight of the core wood shavings, and stir evenly; add curing agent (ammonium chloride) to the core wood shavings: the amount of curing agent added is 2% of the absolute dry weight of the core wood shavings, and stir evenly.

[0045] S4. Paving: The surface layer is paved directly and the core layer is paved after drying: the surface layer fine material is divided into two equal parts by weight, one of which is paved on the bottom layer and the other on the top layer; the core layer shavings are dried to a moisture content of 8%, and then evenly paved on the core layer to obtain a three-layer slab with a dense and symmetrical structure, the upper and lower surface layers are both surface fine materials, and the core layer is coarse shavings.

[0046] S5. Hot pressing: The slab is fed into a continuous flat-plate hot press. The hot pressing temperature is 230°C. The first section is a high-pressure section with a pressure of 14 MPa and a time of 30 seconds. The second section is a low-pressure section with a pressure of 9 MPa and a time of 30 seconds. The third section is a medium-pressure section with a pressure of 11 MPa and a time of 90 seconds. The total hot pressing time is 2.5 minutes.

[0047] S6. Post-processing: The rough-edged boards produced by hot pressing are subjected to post-processing such as cutting, trimming, turning over for cooling, aging, and surface sanding to obtain deformation-resistant and moisture-proof particleboard.

[0048] Example 4 S1. Sorting: The same surface fines and core shavings as in Example 1 are used.

[0049] S2. Gluing: Apply urea-formaldehyde glue I (the same as in Example 1) to the surface fine material, and add 16% of the absolute dry weight of the surface fine material, and stir evenly; apply urea-formaldehyde glue II (the same as in Example 1) and MDI glue to the core layer wood chips, and add urea-formaldehyde glue II in an amount of 9% of the absolute dry weight of the core layer wood chips, and add MDI glue in an amount of 2.5% of the absolute dry weight of the core layer wood chips, and stir evenly.

[0050] S3, moisture-proof: add waterproofing agent (emulsified paraffin with a solid content of 50%) to the surface fine material and the core shavings respectively, the amount of waterproofing agent added to the surface fine material is 4.5% of the absolute dry weight of the surface fine material, and stir evenly; the amount of waterproofing agent added to the core shavings is 0.5% of the absolute dry weight of the core shavings, and stir evenly; Add mildew preventer (BBIT) to the surface fine material and core wood shavings respectively: the amount of mildew preventer added to the surface fine material is 5‰ of the absolute dry weight of the surface fine material, and stir evenly; the amount of mildew preventer added to the core wood shavings is 3‰ of the absolute dry weight of the core wood shavings, and stir evenly; add curing agent (ammonium chloride) to the core wood shavings: the amount of curing agent added is 2% of the absolute dry weight of the core wood shavings, and stir evenly.

[0051] S4. Paving: The surface layer is paved directly and the core layer is paved after drying: the surface layer fine material is divided into two equal parts by weight, one of which is paved on the bottom layer and the other on the top layer; the core layer shavings are dried to a moisture content of 8%, and then evenly paved on the core layer to obtain a three-layer slab with a dense and symmetrical structure, the upper and lower surface layers are both surface fine materials, and the core layer is coarse shavings.

[0052] S5. Hot pressing: The slab is fed into a continuous flat-plate hot press. The hot pressing temperature is 240°C. The first section is a high-pressure section with a pressure of 14 MPa and a time of 18 seconds. The second section is a low-pressure section with a pressure of 8 MPa and a time of 40 seconds. The third section is a medium-pressure section with a pressure of 11 MPa and a time of 80 seconds. The total hot pressing time is 2.3 minutes.

[0053] S6. Post-processing: The rough-edged boards produced by hot pressing are subjected to post-processing such as cutting, trimming, turning over for cooling, aging, and surface sanding to obtain deformation-resistant and moisture-proof particleboard.

[0054] Comparative Example 1 The difference from Example 1 is that urea-formaldehyde glue I is applied to both the surface fine material and the core wood chips.

[0055] S1. Sorting: The same surface fines and core shavings as in Example 1 are used.

[0056] S2. Gluing: Apply urea-formaldehyde glue I (the same as in Example 1) to the surface fine material, and add 13% of the absolute dry weight of the surface fine material, and stir evenly; apply urea-formaldehyde glue I (the same as in Example 1) to the core layer of wood chips, and add 12% of the absolute dry weight of the core layer of wood chips, and apply MDI glue, and add 1% of the absolute dry weight of the core layer of wood chips, and stir evenly.

[0057] S3, moisture-proof: add waterproofing agent (emulsified paraffin with a solid content of 50%) to the surface fine material and the core shavings respectively, the amount of waterproofing agent added to the surface fine material is 3% of the absolute dry weight of the surface fine material, and stir evenly; the amount of waterproofing agent added to the core shavings is 2% of the absolute dry weight of the core shavings, and stir evenly; Add mildew preventer (BBIT) to the surface fine material and core wood shavings respectively: the amount of mildew preventer added to the surface fine material is 5‰ of the absolute dry weight of the surface fine material, and stir evenly; the amount of mildew preventer added to the core wood shavings is 3‰ of the absolute dry weight of the core wood shavings, and stir evenly; add curing agent (ammonium chloride) to the core wood shavings: the amount of curing agent added is 2% of the absolute dry weight of the core wood shavings, and stir evenly.

[0058] S4. Paving: The surface layer is paved directly and the core layer is paved after drying: the surface layer fine material is divided into two equal parts by weight, one of which is paved on the bottom layer and the other on the top layer; the core layer shavings are dried to a moisture content of 8%, and then evenly paved on the core layer to obtain a three-layer slab with a dense and symmetrical structure, the upper and lower surface layers are both surface fine materials, and the core layer is coarse shavings.

[0059] S5. Hot pressing: The slab is fed into a continuous flat-plate hot press. The hot pressing temperature is 210°C. The first section is a high-pressure section with a pressure of 15 MPa and a time of 30 seconds. The second section is a low-pressure section with a pressure of 9 MPa and a time of 50 seconds. The third section is a medium-pressure section with a pressure of 12 MPa and a time of 100 seconds. The total hot pressing time is 3 minutes.

[0060] S6. Post-processing: The rough-edged boards produced by hot pressing are subjected to post-processing such as cutting, trimming, turning over for cooling, aging, and surface sanding to obtain deformation-resistant and moisture-proof particleboard.

[0061] Comparative Example 2 The difference from Example 1 is that urea-formaldehyde glue II is applied to both the surface layer fines and the core layer wood chips, and MDI glue is not applied to the core layer wood chips.

[0062] S1. Sorting: The same surface fines and core shavings as in Example 1 are used.

[0063] S2. Gluing: Apply urea-formaldehyde glue II (the same as in Example 1) to the surface fine material, and add 13% of the absolute dry weight of the surface fine material, and stir evenly; apply urea-formaldehyde glue II (the same as in Example 1) to the core layer wood chips, and add 12% of the absolute dry weight of the core layer wood chips, and stir evenly.

[0064] S3, moisture-proof: add waterproofing agent (emulsified paraffin with a solid content of 50%) to the surface fine material and the core shavings respectively, the amount of waterproofing agent added to the surface fine material is 3% of the absolute dry weight of the surface fine material, and stir evenly; the amount of waterproofing agent added to the core shavings is 2% of the absolute dry weight of the core shavings, and stir evenly; Add mildew preventer (BBIT) to the surface fine material and core wood shavings respectively: the amount of mildew preventer added to the surface fine material is 5‰ of the absolute dry weight of the surface fine material, and stir evenly; the amount of mildew preventer added to the core wood shavings is 3‰ of the absolute dry weight of the core wood shavings, and stir evenly; add curing agent (ammonium chloride) to the core wood shavings: the amount of curing agent added is 2% of the absolute dry weight of the core wood shavings, and stir evenly.

[0065] S4. Paving: The surface layer is paved directly and the core layer is paved after drying: the surface layer fine material is divided into two equal parts by weight, one of which is paved on the bottom layer and the other on the top layer; the core layer shavings are dried to a moisture content of 8%, and then evenly paved on the core layer to obtain a three-layer slab with a dense and symmetrical structure, the upper and lower surface layers are both surface fine materials, and the core layer is coarse shavings.

[0066] S5. Hot pressing: The slab is fed into a continuous flat-plate hot press. The hot pressing temperature is 210°C. The first section is a high-pressure section with a pressure of 15 MPa and a time of 30 seconds. The second section is a low-pressure section with a pressure of 9 MPa and a time of 50 seconds. The third section is a medium-pressure section with a pressure of 12 MPa and a time of 100 seconds. The total hot pressing time is 3 minutes.

[0067] S6. Post-processing: The rough-edged boards produced by hot pressing are subjected to post-processing such as cutting, trimming, turning over for cooling, aging, and surface sanding to obtain deformation-resistant and moisture-proof particleboard.

[0068] Comparative Example 3 The difference from Example 1 is that urea-formaldehyde glue II is applied to the surface fine material, and urea-formaldehyde glue I is applied to the core wood chips.

[0069] S1. Sorting: The same surface fines and core shavings as in Example 1 are used.

[0070] S2. Gluing: Apply urea-formaldehyde glue II (the same as in Example 1) to the surface fine material, and add 13% of the absolute dry weight of the surface fine material, and stir evenly; apply urea-formaldehyde glue I (the same as in Example 1) and MDI glue to the core layer wood chips, and add urea-formaldehyde glue I in an amount of 12% of the absolute dry weight of the core layer wood chips, and add MDI glue in an amount of 1% of the absolute dry weight of the core layer wood chips, and stir evenly.

[0071] S3, moisture-proof: add waterproofing agent (emulsified paraffin with a solid content of 50%) to the surface fine material and the core shavings respectively, the amount of waterproofing agent added is 3% of the absolute dry weight of the surface fine material, and stir evenly; the amount of waterproofing agent added is 2% of the absolute dry weight of the core shavings, and stir evenly; Add mildew inhibitor (BBIT) to the surface fine material and core wood shavings respectively: the amount of mildew inhibitor added is 5‰ of the absolute dry weight of the surface fine material, and stir evenly; the amount of mildew inhibitor added is 3‰ of the absolute dry weight of the core wood shavings, and stir evenly; Add curing agent (ammonium chloride) to the core layer wood chips: the amount of curing agent added is 2% of the absolute dry weight of the core layer wood chips, and stir evenly.

[0072] S4. Paving: The surface layer is paved directly and the core layer is paved after drying: the surface layer fine material is divided into two equal parts by weight, one of which is paved on the bottom layer and the other on the top layer; the core layer shavings are dried to a moisture content of 8%, and then evenly paved on the core layer to obtain a three-layer slab with a dense and symmetrical structure, the upper and lower surface layers are both surface fine materials, and the core layer is coarse shavings.

[0073] S5. Hot pressing: The slab is fed into a continuous flat-plate hot press. The hot pressing temperature is 210°C. The first section is a high-pressure section with a pressure of 15 MPa and a time of 30 seconds. The second section is a low-pressure section with a pressure of 9 MPa and a time of 50 seconds. The third section is a medium-pressure section with a pressure of 12 MPa and a time of 100 seconds. The total hot pressing time is 3 minutes.

[0074] S6. Post-processing: The rough-edged boards produced by hot pressing are subjected to post-processing such as cutting, trimming, turning over for cooling, aging, and surface sanding to obtain deformation-resistant and moisture-proof particleboard.

[0075] Comparative Example 4 The difference from Example 4 is that the three-stage hot pressing process is different. Specifically, the three-stage hot pressing process is as follows: the hot pressing temperature is 210°C, the first stage is a low-pressure stage, the pressure is 9 MPa, and the time is 50 seconds; the second stage is a medium-pressure stage, the pressure is 12 MPa, and the time is 100 seconds; the third stage is a high-pressure stage, the pressure is 15 MPa, and the time is 30 seconds; the total hot pressing time is 3 minutes.

[0076] Comparative Example 5 The difference from Example 1 is that urea-formaldehyde glue I and urea-formaldehyde glue II are not modified with melamine.

[0077] Preparation of urea-formaldehyde glue I: 49 parts of urea and 48 parts of formaldehyde solution with a mass concentration of 37% are added to a reactor, heated to 70°C, 0.5 parts of pH regulator (triacetamide) are added, and stirred at a speed of 700 r / min for 0.5 h to prepare urea-formaldehyde glue I.

[0078] Preparation of urea-formaldehyde glue II by mass: add 44 parts of urea and 50 parts of formaldehyde solution with a mass concentration of 37% into a reactor, heat to 70°C, add 2 parts of pH regulator (triacetamide), stir at a speed of 700 r / min for 0.5 h, and prepare urea-formaldehyde glue II.

[0079] Table 1 As shown in Table 1, Comparative Example 5 utilizes urea-formaldehyde adhesive that has not been modified with melamine to produce particleboard. Compared to the particleboards produced in Examples 1-4 using urea-formaldehyde adhesive that has been modified with melamine, the particleboard produced in Comparative Example 5 exhibits inferior moisture resistance and dimensional stability, demonstrating that conventional urea-formaldehyde adhesive cannot produce particleboards meeting the performance requirements even when prepared according to the present invention. Comparing Comparative Examples 1-3 with Example 1 reveals that, despite the application of melamine-modified urea-formaldehyde adhesive to the surface and core layers, the particleboards produced in Comparative Examples 1-3 still exhibit significantly higher 24-hour water absorption thickness expansion and dimensional deformation. This demonstrates that the melamine-modified urea-formaldehyde adhesive used in the surface and core layers of the present invention is specifically selected based on the different properties of the surface and core layers. Specifically, in Comparative Example 2, the absence of MDI adhesive in the core layer results in reduced moisture resistance and dimensional stability, and the application of urea-formaldehyde adhesive II to the surface fines increases formaldehyde emissions. In comparative example 1, urea-formaldehyde glue I was applied to the surface fine material, and urea-formaldehyde glue I and MDI glue were applied to the core wood particles. In comparative example 3, urea-formaldehyde glue II was applied to the surface fine material, and urea-formaldehyde glue I and MDI glue were applied to the core wood particles. Since urea-formaldehyde glue I uses a relatively small amount of melamine added, it is more suitable for the surface fine material. Applying it to the core wood particles cannot obtain the required high bonding strength and water resistance. Even if urea-formaldehyde glue II is applied to the surface fine material at the same time, the moisture resistance and dimensional stability of the resulting particleboard are poorer than those of the particleboard obtained in Example 1.

[0080] In addition, the pressure of the three-stage hot pressing was changed in Comparative Example 4, and the results showed that the strength of the obtained particleboard was relatively low. However, since the core layer particles of the particleboard in the present invention are made of narrow and long pieces and the surface layer uses loose and fine materials, the limited high pressure-low pressure-medium pressure three-stage hot pressing method is more conducive to obtaining a particleboard with high strength and high dimensional stability.

[0081] The above are only preferred embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the description of the present invention, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A method for preparing a deformation-resistant moisture-proof particleboard, characterized in that: The steps include: S1. Sorting: Sorting to obtain surface fines and core shavings; S2. Gluing: Apply urea-formaldehyde glue I to the surface fine material, and apply urea-formaldehyde glue II and MDI glue to the core wood chips; by weight, the raw materials of urea-formaldehyde glue I include 47-51 parts of urea, 47-49 parts of formaldehyde solution and 2.5-3.7 parts of melamine, and the raw materials of urea-formaldehyde glue II include 44-46 parts of urea, 49-51 parts of formaldehyde solution and 9-11 parts of melamine; S3. Moisture-proof: Apply waterproofing agent and mildew-proofing agent to the surface fine material and core wood shavings respectively, and then apply curing agent to the core wood shavings; S4. Paving: Laying the surface fine material - core wood shavings - surface fine material in layers to obtain a slab; S5. Hot pressing: hot pressing the slab.

2. The method for preparing the deformation-resistant moisture-proof particleboard according to claim 1, characterized in that: In S1, the particle size of the surface layer fine material is 0.5-1.5 mm; the length of the core layer wood chips is 25-35 mm, the width is 5-6 mm, and the thickness is ≤0.7 mm.

3. The method for preparing the deformation-resistant moisture-proof particleboard according to claim 1, characterized in that: In S2, the amount of urea-formaldehyde glue I applied is 12-14% of the absolute dry weight of the surface fine material; the amount of urea-formaldehyde glue II applied is 10-12% of the absolute dry weight of the core wood chips; and the amount of MDI glue applied is 0.5-2% of the absolute dry weight of the core wood chips.

4. The method for preparing the deformation-resistant moisture-proof particleboard according to any one of claims 1 to 3, characterized in that: In S2, the urea-formaldehyde glue I and urea-formaldehyde glue II are both melamine-modified urea-formaldehyde glues, and their preparation method includes the following steps: mixing urea and formaldehyde solution and heating them, adding a pH regulator and stirring, and then adding melamine and continuing to stir to obtain melamine-modified urea-formaldehyde glue.

5. The method for preparing the deformation-resistant moisture-proof particleboard according to claim 4, characterized in that: The mass concentration of the formaldehyde solution is 35-40%; the heating is to raise the temperature to 60-80° C.; the pH adjuster is triacetamide; the stirring time is 30-50 minutes; and the stirring time is continued for 1-2 hours.

6. The method for preparing the deformation-resistant moisture-proof particleboard according to claim 1, characterized in that: In S3, the amount of the waterproofing agent added to the surface fine material is 2-4% of the absolute dry weight of the surface fine material; the amount of the waterproofing agent added to the core wood shavings is 1-3% of the absolute dry weight of the core wood shavings.

7. The method for preparing the deformation-resistant moisture-proof particleboard according to claim 1, characterized in that: In S3, the amount of the anti-mildew agent added to the surface fine material is 4-6‰ of the absolute dry weight of the surface fine material; the amount of the anti-mildew agent added to the core layer shavings is 1-3‰ of the absolute dry weight of the core layer shavings.

8. The method for preparing the deformation-resistant moisture-proof particleboard according to claim 1 or 7, characterized in that: In S3, the amount of the curing agent added to the core layer wood chips is 1-3% of the absolute dry weight of the core layer wood chips.

9. The method for preparing the deformation-resistant moisture-proof particleboard according to claim 1, characterized in that: In S5, the hot pressing is a three-stage hot pressing, specifically: the first stage is a high-pressure stage with a pressure of 13-16 MPa; the second stage is a low-pressure stage with a pressure of 7-9 MPa; and the third stage is a medium-pressure stage with a pressure of 10-13 MPa.

10. A deformation-resistant and moisture-proof particleboard prepared by the preparation method according to any one of claims 1 to 9, characterized in that: It includes a core layer and surface layers arranged on the upper and lower surfaces of the core layer.

Images