An ultra-thin shaving board and a continuous flat-press manufacturing method thereof

Abstract

The present application provides a kind of ultra-thin shaving board and its continuous flat pressing manufacturing method, the ultra-thin shaving board is three layers, the mass ratio of upper surface layer, core layer, lower surface layer is 3:4:3, by adding 0.6% to 1.2% of the core layer shaving quality of calcium oxide microspheres in the core layer, promote the rapid curing of adhesive and effectively reduce the water vapor remaining in the board to cause the generation of defects such as blistering / delamination; At the same time, the shaving board continuous flat pressing manufacturing process is optimized, the humidification preheating parameters are adjusted (high temperature hot saturated steam is used for about 2-4 seconds of steam treatment, the surface temperature is raised to 180-200℃), and a shaving board with a thickness of 1.8-3.3mm, a density of 800-900kg / m 3 The performance of the ultra-thin shaving board is excellent.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of shaving board manufacturing, in particular to a super-thin shaving board and a continuous flat pressing manufacturing method thereof. BACKGROUND

[0002] Thin artificial boards with a thickness of less than 5 mm are widely used in the production of plywood facings and high-grade boards instead of veneers and technical veneers, in the fields of electronic circuit boards, high-grade gift box packaging liners, furniture non-load-bearing partitions, and curved modeling in indoor decoration, and have good market potential. However, most thin artificial boards are made of fiber boards, and most thin shaving boards made of shaving boards have a thickness of more than 5 mm.

[0003] Shaving boards are divided into low-density (0.25-0.45 g / cm3), medium-density (0.45-0.60 g / cm3), and high-density (0.60-1.3 g / cm3) according to the product, but most shaving boards produced are of a density of 0.60-0.70 g / cm3. According to the structure of the board blank, there are single-layer, three-layer (including multi-layer), and gradient structures. For multi-layer shaving boards, the production process is "laying, pre-pressing, and hot pressing". During the hot pressing process of thin shaving boards with a conventional thickness of less than 5 mm, the following problems exist: when a three-layer structure is used, the core layer shaving is large in size, and the surface layer shaving is thin, which causes the core layer shaving to appear on the board surface through the surface layer, resulting in poor board surface quality and poor flatness; due to the thinness of the board, there is not enough wood to balance the density, resulting in excessive local density deviation and warping deformation during use; when a single-layer structure is used, the shaving is mostly micro-shaving with a small size and shape, which is compressed greatly, resulting in poor exhaust during hot pressing, the need to greatly extend the hot pressing time, and the influence on production efficiency. There are also super-thin bamboo shaving boards prepared from bamboo shaving, but there are great technical difficulties in raw material processing and shaving preparation, special equipment is required, and the above-mentioned problems still exist in bamboo shaving boards.

[0004] Patent 202111119282.3 relates to a production method of a thin shaving board, which includes wood material, chip, shaving, shaving drying, screening, glue application, laying, pre-pressing, hot pressing, edge cutting, cooling, conditioning, sanding, inspection and grading, and packaging and storage, to produce a 5-6 mm shaving board. By optimizing the shaving process, applying vinyl acetate modified resin, and adjusting the proportion of surface and core layer shaving board, the problems in the production process of thin fiber boards are solved, and the percentage of high-quality products is greatly improved. However, it mainly solves the problem of surface quality of thin shaving boards, and does not improve the strength of thin shaving boards and reduce the problem of board explosion during production, nor can it improve the production speed.

[0005] Patent 202311386923.0 A kind of ultra-thin fireproof bamboo plywood manufacturing process, first, thin bamboo slice is planed and soaked, then high temperature and high pressure treatment is carried out, then low temperature drying treatment is carried out under vacuum condition, after drying, cold plasma treatment (high-energy electron, ion bombardment wood surface produces etching effect;Active particles and surface molecules grafting, form crosslinking structure, the appearance of concave-convex structure is favorable to surface activity and specific surface area, further lay a good foundation for subsequent gluing, and then improve the fire resistance and mechanical properties of finished product bamboo plywood).The patent has good improvement effect on bamboo plywood, but bamboo is stronger than wood shaving and fiber, and the same method cannot be applied to shaving board or fiber board, the defects and strength problems of ultra-thin shaving board / fiber board still exist.

[0006] At present, the production of domestic thin shaving board requires high equipment, and there are corresponding technical difficulties in the production process, and there are certain defects in physical properties and appearance quality.Therefore, the production technology of thin shaving board needs to be optimized. SUMMARY

[0007] In view of the problems of poor board surface quality, poor flatness and easy warping deformation in the prior art, the present application provides an ultra-thin shaving board and a continuous flat pressing manufacturing method, which adopts a three-layer structure to avoid the problem of poor exhaust caused by single-layer structure.The problem of three-layer structure is improved by adjusting the quality ratio of the surface core layer shaving.The increase of the quality ratio of the surface layer will also cause the extension of the hot pressing time, so calcium oxide microspheres are added to release heat and promote the curing of the adhesive during hot pressing, while absorbing water vapor to reduce the accumulation of water vapor in the board blank, thereby improving the production speed of the board and avoiding the generation of defects such as bubbling and delamination.The density of the board in the present application is about 900 kg / m 3 , the density of the board blank is more easily balanced after the addition of raw materials, and the warping deformation of the finished board caused by insufficient wood density deviation is avoided;At the same time, the continuous flat pressing manufacturing process of shaving board is optimized, the humidification and preheating parameters are adjusted, and an ultra-thin shaving board with excellent performance of 1.8-3.3 mm is prepared.

[0008] A continuous flat pressing manufacturing method of ultra-thin shaving board, comprising the following steps: board blank preparation, humidification and preheating, rapid compression, high temperature thickness setting, surface heat transfer, pressure relief and aging;

[0009] The above board blank includes upper surface layer, core layer and lower surface layer;The core layer of the above board blank is added with 0.6%-1.2% calcium oxide microspheres of core layer shaving quality;The humidification and preheating temperature is 180-200 DEG C.

[0010] A continuous flat pressing manufacturing method of ultra-thin shaving board, comprising the following steps:

[0011] (1) Slab preparation: according to the mass ratio of upper layer, core layer, lower layer (3-4):(2-4):(3-4) group slab, the thickness of the slab before hot pressing is 6-11 mm, and the thickness of the finished plate after hot pressing is 3.6-6.6 mm;

[0012] (2) Humidification and preheating: use high-temperature hot saturated steam to spray the slab for about 2-4 seconds, according to the thickness of the finished plate, the surface temperature is raised to 180-200℃, and the temperature is increased with the increase of the thickness of the finished plate;

[0013] (3) Fast compression: fast compression is carried out in the first 10% frame of the continuous flat pressing machine, the temperature is 150-180℃, the hot pressing machine speed is 580-600 mm / s, and the compression amount is 50%-70% of the thickness of the slab;

[0014] (4) High temperature thickness setting: high temperature thickness setting is carried out in the first 10%-60% frame of the continuous flat pressing machine, linear compression to finished thickness, temperature is 190-220℃;

[0015] (5) Interfacial heat transfer: interfacial heat transfer is carried out in the first 60%-80% frame of the continuous flat pressing machine, in two stages, 60%-75% for lower heating, 75%-80% for upper heating, the temperature of the corresponding surface steel plate is controlled to be 40℃ lower than that of the heating surface, and the heating surface temperature is 190-220℃;

[0016] (6) Pressure relief: the last 5% of the frame slowly releases the pressure of the plate, and the pressure relief speed is linear;

[0017] (7) Aging: the finished plate is stacked and placed in a well-ventilated environment for 7 days, and then it can be produced.

[0018] During the hot pressing process of the particle board, the water in the shavings escapes in the form of water vapor, enhancing the heat conduction function, and the calcium oxide microspheres replace part of the steam heat conduction function, release sufficient heat energy to promote the rapid curing of the adhesive, at the same time absorb the excess water, effectively reduce the water vapor remaining in the plate to cause the generation of defects such as blistering and delamination, and the rapid curing of the adhesive can effectively shorten the hot pressing time.

[0019] Preferably, 1% of the core layer shavings mass of calcium oxide microspheres is added to the core layer of the slab, and the temperature during humidification and preheating is 200℃.

[0020] The above method for manufacturing calcium oxide microspheres is: mixing calcium hydroxide and excess 20% concentration glucose solution, and reacting under subcritical hydrothermal conditions for a period of time, then cooling, centrifuging, washing and drying the product to obtain calcium oxide microspheres with a particle size of 3.5 μm.

[0021] The above-mentioned super-thin shaving board is a three-layer structure shaving board, and the wood used for preparing the board blank is one or several of pine wood, eucalyptus wood, poplar wood and other commonly used wood for shaving board.

[0022] The mass ratio of the upper layer, the core layer and the lower layer in step (1) is 3:4:3.

[0023] The shaving size of the upper and lower layers is 8-12 mm in length, 1-3 mm in width and 0.1-0.4 mm in thickness; and the shaving size of the core layer is 12-20 mm in length, 3-6 mm in width and 0.1-0.4 mm in thickness.

[0024] Preferably, the shaving size of the upper and lower layers is 12 mm in length, 2 mm in width and 0.2 mm in thickness; and the core layer is 16 mm in length, 4 mm in width and 0.3 mm in thickness.

[0025] The shavings of the upper and lower layers and the core layer are all sprayed with glue (commercially available exogenous urea-formaldehyde resin adhesive), and the moisture content of the upper layer after gluing is controlled at 12%-15%, and the moisture content of the core layer after gluing is controlled at 8%-11%. Under this moisture content, the water can provide good initial adhesion for the board blank, so that the board blank can be kept as a whole during transportation and will not be scattered to cause the board to crack or collapse before hot pressing. In addition, the super-thin board is too thin, and too low moisture content will cause the board to dry quickly after entering the press, resulting in insufficient heat transfer time.

[0026] The average moisture content of the board blank surface layer after the treatment in step (2) is 18-22% of the thickness.

[0027] The density of the above-mentioned super-thin shaving board is 800-900 kg / m 3 , and the thickness is 1.8-3.3 mm.

[0028] Compared with the prior art, the present application has the following advantages:

[0029] (1) In the hot pressing process of the shaving board of the present application, the water in the shaving escapes in the form of water vapor, enhancing the heat conduction function, and the calcium oxide microspheres added in the core layer replace part of the heat conduction function of the steam, release sufficient heat energy to promote the rapid curing of the adhesive, at the same time, absorb the excess water, effectively reduce the water vapor remaining in the board to cause the generation of defects such as blistering and delamination, and the rapid curing of the adhesive can effectively shorten the hot pressing time.

[0030] (2) The shaving board continuous flat pressing manufacturing process is optimized, the humidification and preheating parameters are adjusted, high-temperature hot saturated steam is used for steam treatment, the surface temperature is raised to 180-200℃, and a 1.8-3.3 mm super-thin shaving board with excellent performance is prepared, which has good market potential. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 Example 1 super thin shaving board;

[0032] Figure 2 Example 1 super thin shaving board;

[0033] Figure 3 Example 1 super thin shaving board; DETAILED DESCRIPTION

[0034] The technical solutions of the present application will be described clearly and completely below in combination with the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0035] Example 1

[0036] The mass ratio of the upper surface layer, the core layer and the lower surface layer is 3:4:3. The thickness of the board blank before hot pressing is 8 mm, and the thickness of the finished board after hot pressing is 4 mm.

[0037] The wood used is pine wood, and the upper and lower surface layers are processed from peeled wood, and the core layer can mix up to 30% of bark.

[0038] The upper and lower surface layers are 12 mm long, 2 mm wide and 0.2 mm thick; the core layer is 16 mm long, 4 mm wide and 0.3 mm thick.

[0039] The shaving of the upper and lower surface layers is applied by atomization, and the moisture content of the surface layer after sizing is controlled at 12%, and the moisture content of the core layer after sizing is controlled at 8%, and 1% of calcium oxide microspheres with a particle size of 3.5 μm is added to the core layer.

[0040] The continuous flat pressing method of the super thin shaving board includes the following steps:

[0041] (1) humidification and preheating, humidifying and preheating the board blank, using high-temperature hot saturated steam for spraying treatment for about 4 seconds, so that the surface temperature rises to 200℃, and the average moisture content of the surface layer of the board blank is 22% of the thickness.

[0042] (2) rapid compression, rapid compression is carried out at the front 10% frame of the continuous flat pressing machine, the temperature is 190℃, and the compression amount is 70% of the required compression thickness.

[0043] (3) high-temperature thickness setting, high-temperature thickness setting is carried out at the front 10%-60% frame of the continuous flat pressing machine, linear compression to the finished thickness of 3.3 mm, and the temperature is 220℃.

[0044] (4) Face heat transfer, heat transfer in the first 60%-80% of the frame of the continuous flat press, in two stages, 60%-75% for the bottom heating, 75%-80% for the top heating, the temperature of the corresponding face steel plate is controlled to be 40°C lower than the heating face, and the temperature of the heating face is 220°C.

[0045] (5) Pressure relief, the last 5% of the frame slowly relieves the pressure on the plate, and the pressure relief speed is linear.

[0046] (6) Curing, the cost plate is stacked and placed in a well-ventilated environment for one week, at this time, the moisture content is stable, about 5%, the internal stress of the finished plate is completely released and is not easy to deform, that is, the ultra-thin chipboard can be obtained.

[0047] The ultra-thin chipboard is a three-layer structure chipboard, the thickness is 3.3mm, and the density is 900kg / m 3 .

[0048] Example 2

[0049] The difference from Example 1 is that the density of the prepared ultra-thin chipboard is 900kg / m 3 , the thickness is 2.5mm, and the surface temperature rises to 190°C during humidification and preheating.

[0050] Example 3

[0051] The difference from Example 1 is that the density of the prepared ultra-thin chipboard is 900kg / m 3 , the thickness is 1.8mm, and the surface temperature rises to 180°C during humidification and preheating.

[0052] Example 4

[0053] The difference from Example 1 is that the core layer adds calcium oxide microspheres, which are 0.6% of the mass of the core layer chip.

[0054] Example 5

[0055] The difference from Example 1 is that the core layer adds calcium oxide microspheres, which are 1.2% of the mass of the core layer chip.

[0056] Example 6

[0057] The difference from Example 1 is that the density of the prepared ultra-thin chipboard is 900kg / m 3 , the thickness is 2.5mm, and the surface temperature rises to 200°C during humidification and preheating.

[0058] Example 7

[0059] The difference from Example 1 is that the density of the prepared ultra-thin chipboard is 900kg / m 3 , the thickness is 1.8mm, and the surface temperature rises to 200°C during humidification and preheating.

[0060] Comparative Example 1

[0061] The difference from Example 1 is that no calcium oxide microspheres are added to the core layer.

[0062] Comparative Example 2

[0063] The difference from Example 1 is that 0.5% of calcium oxide microspheres by mass of the core layer shavings are added to the core layer.

[0064] Comparative Example 3

[0065] The difference from Example 1 is that 1.5% of calcium oxide microspheres by mass of the core layer shavings are added to the core layer.

[0066] Comparative Example 4

[0067] The difference from Example 1 is that 2% of calcium oxide microspheres by mass of the core layer shavings are added to the core layer.

[0068] Comparative Example 5

[0069] The difference from Example 1 is that the surface temperature is raised to 210°C during the humidification preheating.

[0070] Comparative Example 6

[0071] The difference from Example 1 is that the surface temperature is raised to 190°C during the humidification preheating.

[0072] Comparative Example 7

[0073] The difference from Example 1 is that a curing agent is added to the core layer instead of calcium oxide microspheres; the curing agent is ammonium sulfate, and the amount is 2% by mass of the core layer shavings.

[0074] Test Example 1: Mechanical Property Test

[0075] The test methods for internal bond strength, static bending strength, elastic modulus, 2h water absorption thickness expansion rate, and other properties refer to GBT 17657-2013 “Test Methods for Physical and Chemical Properties of Wood-based Panels and Veneered Wood-based Panels”; the standard values refer to the requirements (P2) for furniture-type particle boards (18mm) used in a dry state specified in GB / T 4897-2015 “Particle Board”.

[0076] The test results of each example and comparative example are shown in Table 1:

[0077] Table 1

[0078] Internal bond strength / MPa Static bending strength / MPa Elastic modulus / MPa 2h TS / % Standard value ≥0.47 ≥12.5 ≥2000 ≤4 Example 1 0.50 13.8 2106 2.5 Example 2 0.53 14 2257 2.7 Example 3 0.57 16 2300 2.2 Example 4 0.49 13.1 2067 2.9 Example 5 0.48 12.7 2013 3.4 Example 6 0.46 12.7 1870 4.2 Example 7 0.43 13.7 2085 3.9 Comparative Example 1 0.33 9 1428 5.8 Comparative Example 2 0.44 10.8 1710 5.2 Comparative Example 3 0.40 10 1510 6.2 Comparative Example 4 0.31 8 1420 5.4 Comparative Example 5 0.46 11.7 1833 3.3 Comparative Example 6 0.44 11.5 1775 3.6 Comparative Example 7 0.44 12.6 1999 3.7

[0079] From the test results in Table 1, it can be seen that the physical properties of each of Examples 1-3 meet the standard value requirements of P2 shaving board. Due to the thinner thickness, the properties of Example 3 are slightly higher than those of the other examples, which is a normal phenomenon:

[0080] The difference between Comparative Example 1 and Example 1 is that no calcium oxide microspheres are added, and the physical properties of the board, especially the internal bonding strength, are all less than those of the examples. This is because during hot pressing, the water in the shavings escapes in the form of water vapor, enhancing the heat conduction function. In Example 1, the calcium oxide microspheres replace part of the steam heat conduction function, release sufficient heat energy to promote rapid curing of the adhesive, and at the same time absorb excess water, effectively reducing the water vapor remaining in the board to cause defects such as blistering and delamination. At the same time, the rapid curing of the adhesive can effectively shorten the hot pressing time, so under the same hot pressing time, the mechanical strength of Comparative Example 1, in which the adhesive has not fully cured, is less than that of each example.

[0081] The difference between Comparative Example 2 and Example 1 is that the mass of the added calcium oxide microspheres accounts for 0.5% of the mass of the core layer shavings, and the physical properties of the board are all less than those of the examples. This is because the amount of calcium oxide microspheres is not enough to release sufficient heat energy to promote the curing of the core layer adhesive, and the adhesive curing degree is insufficient and the water vapor is not completely discharged, which will affect the performance of the board.

[0082] The difference between Comparative Example 3 and Example 1 is that the amount of calcium oxide microspheres added is 1.5% of the mass of the core layer shavings, and the physical properties of the board are all less than those of the examples. This is because the amount of calcium oxide microspheres is too high, releasing excess heat energy, and the board continues to be heated in the hot press after the adhesive is cured, making the board brittle and reducing the performance of the board.

[0083] The difference between Comparative Example 4 and Example 1 is that the amount of calcium oxide microspheres added is 2% of the mass of the core layer shavings, and the physical properties of the board are all significantly less than those of the examples. The reason for the decrease in performance of the board is the same as that of Comparative Example 3, but the performance of Comparative Example 4 is lower, further supporting the reason for the decrease in performance of the board in Comparative Example 3.

[0084] The difference between Comparative Example 5 and Example 1 is that the surface temperature of the board blank is increased to 210°C during humidification and preheating, and the physical properties of the board are all less than those of the examples. This is because the temperature is too high during humidification and preheating of the board, causing the core layer adhesive to pre-cure, then become brittle in the press, reducing the performance of the board.

[0085] The difference between Comparative Example 6 and Example 1 is that the surface temperature of the board blank is increased to 180°C during the humidification preheating, and the physical properties of the board are all less than those of the example. This is because the temperature of the board during the humidification preheating is insufficient, and the board blank needs more time to complete the curing of the core adhesive after entering the press. Therefore, under the same hot-pressing time, the curing degree of the adhesive is lower than that of the example, and the performance of the board is reduced.

[0086] The difference between Comparative Example 7 and Example 1 is that the curing agent ammonium sulfate is used instead of calcium oxide microspheres, which leads to insufficient water vapor removal in the board of Comparative Example 7 under the same conditions, and the risk of bubbling is generated. The bubbling delamination will significantly reduce the inner glue strength.

[0087] Although the embodiments of the present application have been shown and described, it will be understood by those of ordinary skill in the art that various changes, modifications, substitutions and alterations can be made thereto without departing from the principles and spirit of the present application, and the scope of the present application is defined by the appended claims and their equivalents.

Claims

1. A method for continuous flat pressing manufacturing of ultra-thin particleboard, characterized in that, Includes the following steps: Slab preparation, humidification and preheating, rapid compression, high temperature thickness determination, surface heat transfer, pressure relief, and curing; The slab includes an upper surface layer, a core layer, and a lower surface layer; The core layer of the slab contains 0.6%-1.2% calcium oxide microspheres by weight of the core layer wood shavings; The humidification and preheating temperature is 180-200℃; Specifically, the following steps are included: (1) The blanks are assembled according to the mass ratio of the upper surface layer, core layer and lower surface layer as (3-4):(2-4):(3-4). The thickness of the blanks before hot pressing is 6-11mm, and the thickness of the finished plate after hot pressing is 3.6-6.6mm. (2) Humidification and preheating: Use high-temperature hot saturated steam to spray the slab for 2-4 seconds to raise the surface temperature to 180-200℃; (3) Rapid compression: Rapid compression is carried out on the first 10% frame of the continuous flat press at a temperature of 150-180℃, a hot press speed of 580-600mm / s, and a compression amount of 50%-70% of the slab thickness. (4) High temperature thickness determination: The frame is subjected to high temperature thickness determination in the first 10%-60% of the continuous flat press, and linearly compressed to the finished thickness at a temperature of 190-220℃. (5) Surface heat transfer: Surface heat transfer is carried out in the first 60%-80% of the frame of the continuous flat press, in two stages: heating from the bottom at 60%-75% and heating from the top at 75%-80%. The temperature of the corresponding steel plate is controlled to be at least 40°C lower than that of the heated surface. The heating surface temperature is 190-220℃; (6) Depressurization: The last 5% of the frame is slowly depressurized on the plate, and the depressurization rate is linear. (7) Preservation: Stack the cost boards in a well-ventilated environment for 7 days before production.

2. The method for continuous flat pressing of ultra-thin particleboard according to claim 1, characterized in that: In step (1), calcium oxide microspheres of 1% of the core layer shavings mass are added to the core layer, and in step (2), the temperature is 200℃ during humidification and preheating.

3. The method for continuous flat pressing of ultra-thin particleboard according to claim 1, characterized in that: The calcium oxide microspheres are obtained by mixing calcium hydroxide and an excess of 20% glucose solution, reacting them under subcritical hydrothermal conditions for a period of time, and then cooling, centrifuging, washing and drying the product; the particle size of the calcium oxide microspheres is 3.5 μm.

4. The continuous flat-press manufacturing method for ultra-thin particleboard according to claim 1, characterized in that: In step (1), the mass ratio of the upper surface layer, core layer, and lower surface layer is 3:4:

3.

5. The continuous flat-press manufacturing method for ultra-thin particleboard according to claim 1, characterized in that: The dimensions of the upper and lower surface layer wood shavings are 8-12mm in length, 1-3mm in width, and 0.1-0.4mm in thickness; the dimensions of the core layer wood shavings are 12-20mm in length, 3-6mm in width, and 0.1-0.4mm in thickness.

6. The continuous flat-press manufacturing method for ultra-thin particleboard according to claim 5, characterized in that: The dimensions of the upper and lower surface shavings are 12mm in length, 2mm in width, and 0.2mm in thickness; the core layer is 16mm in length, 4mm in width, and 0.3mm in thickness.

7. The method for continuous flat pressing of ultra-thin particleboard according to claim 6, characterized in that: The shavings in the upper and lower surface layers and the core layer are all applied by atomization. After the surface layer is applied, the moisture content is controlled at 12-15%, and the moisture content of the core layer is controlled at 8-11%.

8. The continuous flat-press manufacturing method for ultra-thin particleboard according to claim 1, characterized in that: The average moisture content of the 10% thickness of the slab surface after step (2) is 18-22%.

9. The ultra-thin particleboard obtained by the continuous flat pressing manufacturing method for ultra-thin particleboard according to any one of claims 1-8, characterized in that: The ultra-thin particleboard has a density of 800-900 kg / m³ and a thickness of 1.8-3.3 mm.

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