E NF Preparation process of flame-retardant fiberboard

Abstract

This invention belongs to the field of engineered wood products technology, and relates to an E NF The preparation process of flame-retardant fiberboard includes: pre-dispersing a specific compounded powdered flame retardant in a modified urea-formaldehyde resin solution with a high melamine ratio during adhesive application, and then applying it to the fiber surface to achieve uniform coating of the flame retardant by the adhesive solution; and applying two UV-cured coatings to the surface of the hot-pressed board to form a sealed layer. The resulting fiberboard exhibits a stable formaldehyde emission level reaching E... NF The product achieves a flame retardant rating of B1 as specified in GB 8624-2012, while also possessing excellent internal bond strength, static bending strength, and low water absorption thickness swelling rate, resulting in consistent and stable product quality. This invention solves the challenge of simultaneously achieving environmental friendliness, flame retardancy, and mechanical properties in fiberboard through the synergistic application of three technologies. The use of UV-cured coating as a formaldehyde-sealing method is efficient and environmentally friendly, and the coating itself also enhances the surface wear resistance and scratch resistance of the board, increasing the product's added value.

Description

Technical Field

[0001] This invention belongs to the field of engineered wood products technology, and relates to the preparation of fiberboard, particularly to an E... NF Preparation process of flame-retardant fiberboard. Background Technology

[0002] Fiberboard is one of the three major types of boards in my country. Due to its uniform material, dense structure, ease of processing, and high cost-effectiveness, it is widely used in various fields such as building decoration, furniture manufacturing, interior decoration, vehicle and ship interiors, and packaging containers, becoming an important basic material in the national economy. With the upgrading of downstream consumption and the popularization of green building concepts, the market has placed more stringent dual requirements on the quality of fiberboard: environmental protection standards and safety performance. Currently, most mainstream products use conventional urea-formaldehyde resin as an adhesive. This type of adhesive is inexpensive and has mature technology, but it has inherent defects: firstly, the free formaldehyde content is high, making it difficult to consistently meet E6 formaldehyde emission standards. NF Grade (≤0.025mg / m³) 3 Secondly, long-term use poses a risk of continuous formaldehyde release, failing to meet indoor environmental health requirements. Although some companies attempt to control formaldehyde by reducing the amount of adhesive used, this directly leads to a significant decrease in the mechanical properties of the board, such as internal bond strength and static bending strength, and even quality problems such as delamination and deformation, seriously affecting product reliability and service life.

[0003] Currently, many engineered wood products manufacturers use isocyanate adhesives to produce E... NF While fiberboard is classified as high-grade, isocyanate adhesives contain trace amounts of isocyanate monomers and diluents. Inhalation of these substances can cause significant damage to the respiratory system, skin, mucous membranes, and immune system, posing a clear occupational health and safety risk. Furthermore, the use of isocyanate adhesives in fiberboard production presents a series of problems, including pipe blockage, board bursting, steel strip adhesion, low yield of high-quality boards, poor dimensional stability, and poor secondary processing performance. With increasing emphasis on fire safety, traditional fiberboard is a flammable material, easily ignited, spreading rapidly, and producing large amounts of smoke, making it difficult to meet the B1-level flame retardant and higher safety standards required for interior decoration and high-end furniture. To address this issue, the industry commonly uses powdered flame retardants. However, adding powdered flame retardants presents compatibility problems. Insufficient addition results in weak flame retardant effects, while excessively increasing the amount to achieve high standards can damage the internal structure of the board, leading to decreased mechanical properties, a surge in water absorption and thickness expansion rates, poor water resistance, and even board bursting during hot pressing, severely reducing the yield of high-quality products. At the same time, when the amount of powdered flame retardant is large, more flame retardant will fall to the lower surface due to gravity, resulting in significant differences in appearance, flame retardant performance, and mechanical properties between the upper and lower surfaces of the fiberboard, which can lead to deformation of the board during later use.

[0004] Therefore, how to achieve E-grade fiberboard without sacrificing physical and mechanical properties through synergistic innovation in adhesives, flame retardants, and processes is a key challenge. NF The dual unification of ultra-high environmental protection and high-performance flame retardancy (B1 grade) is a technical challenge that urgently needs to be solved. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides an E NF The manufacturing process of flame-retardant fiberboard can resolve the conflict between the physical and mechanical properties, environmental performance, and flame-retardant properties of fiberboard.

[0006] Technical solution

[0007] A type of E NF The preparation process of grade flame-retardant fiberboard includes the following steps: wood peeling → chipping → screening → washing → pre-cooking → cooking → hot grinding → gluing → drying → laying → pre-pressing → hot pressing → cooling → sanding → curing → surface treatment → curing → inspection and grading → packaging and warehousing; among which,

[0008] In the adhesive application process, the adhesive and flame retardant are first mixed evenly in proportion to form a suspension mixture, and then applied to the fiber surface through the adhesive spray tube.

[0009] The adhesive is melamine-modified urea-formaldehyde resin, wherein the melamine used to synthesize the resin accounts for 30-35% of the total resin content by mass; the amount of adhesive applied, in liquid form, is 180-250 kg / m³ of board. 3 ;

[0010] The flame retardant is a mixed flame retardant, composed of the following components by mass percentage: ammonium polyphosphate 40-60%, zinc borate 10-20%, magnesium hydroxide 10-20%, and aluminum hydroxide 10-20%; the application rate of the flame retardant is 20-60 kg / m³. 3 The flame retardant has an average particle size of 400-800 mesh.

[0011] The surface treatment process involves first removing dust from the upper and lower surfaces of the fiberboard, then applying a UV-curable coating, followed by UV curing. After UV curing, a second UV-curable coating is applied and cured. The first UV-curable coating application rate is 20-40 g / m². 2 The second UV-cured coating application rate is 15-25 g / m². 2 .

[0012] In a preferred embodiment of the present invention, the wood species used in the wood peeling process is poplar.

[0013] In a preferred embodiment of the present invention, in the adhesive application process, the melamine content accounts for 30% of the total resin content by mass, and the liquid adhesive application rate is 220 kg / m³. 3 .

[0014] In a preferred embodiment of the present invention, the mixed flame retardant, in the sizing step, comprises the following components by mass percentage: 60% ammonium polyphosphate, 10% zinc borate, 15% magnesium hydroxide, and 15% aluminum hydroxide; its average particle size is 500 mesh, and the application rate is 25 kg / m³. 3 .

[0015] In a preferred embodiment of the present invention, the ammonium polyphosphate is a high-polymer type with a degree of polymerization greater than 1000.

[0016] In a preferred embodiment of the present invention, in the surface treatment process, the first UV-cured coating has a single-sided coating amount of 30 g / m². 2 The second UV-cured coating has a single-sided coating coverage of 20 g / m². 2 .

[0017] The E disclosed in this invention NF The manufacturing process of this advanced flame-retardant fiberboard uses poplar wood as the raw material. The fibers, after hot grinding, are longer and have higher porosity, resulting in stronger adsorption capacity for adhesives and flame retardants. This allows the flame retardant to be evenly dispersed on the fiber surface, improving the flame-retardant uniformity of the fiberboard. Using an adhesive with a high melamine content, the flame-retardant melamine is incorporated into the adhesive. This reduces the proportion of powdered flame retardant, mitigating the uneven distribution and unstable physical and mechanical properties of the fiberboard caused by excessive addition. Furthermore, using flame-retardant melamine as an adhesive raw material reduces raw material costs, resulting in higher cost-effectiveness. This technology also improves the waterproofing of the fiberboard. The powdered flame retardant is evenly added to melamine-urea-formaldehyde resin and mixed thoroughly before being applied to the fiberboard surface. The flame retardant is encapsulated by the adhesive, resulting in more even application and solving the problem of uneven flame retardant distribution in conventional fiberboard, as well as the resulting instability in the physical and mechanical properties of the fiberboard. The use of a composite flame retardant technology results in a more significant synergistic flame retardant effect. Applying a UV-cured coating to the fiberboard surface fixes formaldehyde molecules within the board, drastically reducing formaldehyde emissions. This allows the formaldehyde emission level of the fiberboard, even when using melamine-urea-formaldehyde resin, to reach E... NF class.

[0018] This invention premixes and disperses powdered flame retardant in a liquid adhesive before applying it together. This ensures that the flame retardant particles are encapsulated by the adhesive, achieving a uniform distribution on the fiber surface and completely solving the problem of uneven flame retardant distribution in traditional processes. Simultaneously, it uses high-content melamine-modified urea-formaldehyde resin, leveraging its inherent flame retardancy and excellent water resistance to reduce reliance on large amounts of powdered flame retardant. This ensures the board's internal bond strength, static bending strength, and other key mechanical properties, as well as its water resistance, from the source. Finally, two UV-cured coating treatments form a dense sealing layer on the board surface, physically preventing the release of trace amounts of residual formaldehyde from the board, cleverly reducing the formaldehyde release of the melamine-urea-formaldehyde resin-based board to E0.05. NF Level 1.

[0019] Beneficial effects

[0020] This invention develops E through the synergistic combination of three technologies: "high melamine ratio adhesive", "adhesive-flame retardant premix application", and "UV coating sealing". NF Grade 1 flame-retardant fiberboard, with formaldehyde emission reaching the highest environmental protection level E. NF Grade (≤0.025mg / m³) 3 The flame retardant rating reaches Class B1 of GB 8624-2012 "Classification of Burning Performance of Building Materials and Products", resolving the contradiction between environmental protection, flame retardancy, and mechanical properties. Melamine's flame-retardant elements are incorporated into the adhesive structure, partially replacing the amount of externally added solid flame retardants. This reduces the damage to the physical and mechanical properties and water resistance of fiberboard caused by large amounts of added inorganic powder. The product has high internal bond strength, low water absorption thickness expansion rate, and good dimensional stability. The flame retardant is dispersed in powder form and encapsulated in the adhesive solution. Compared to traditional separate application or direct powder application processes, the flame retardant is distributed extremely uniformly along the thickness direction of the fiberboard, effectively preventing warping and deformation of the finished board and ensuring the uniformity and reliability of flame retardant performance. Ultraviolet curing coating is used as a formaldehyde sealing method, a highly efficient and environmentally friendly process. The coating itself also improves the surface wear resistance and scratch resistance of the board, increasing the product's added value. Detailed Implementation

[0021] The present invention will be described in detail below with reference to embodiments, so that those skilled in the art can better understand the present invention, but the present invention is not limited to the following embodiments.

[0022] Unless otherwise specified, the following uniform process conditions were used in the following embodiments and comparative examples:

[0023] Mixing the sizing agent and flame retardant: Slowly add the powdered flame retardant to the melamine-modified urea-formaldehyde resin liquid adhesive under continuous stirring at a stirring speed of 1000 rpm for 18 minutes until a uniform suspension is formed.

[0024] Drying process: After sizing, the fibers are dried by airflow through pipes, and the moisture content of the fibers is controlled at 9-11% after drying.

[0025] Hot pressing process: Five temperature and pressure zones are used. Zone 1 hot pressing temperature is 220-225℃, with a maximum hot pressing pressure of 350 N / m²; Zone 2 hot pressing temperature is 225-230℃, with a maximum hot pressing pressure of 290 N / m²; Zone 3 hot pressing temperature is 200-205℃, with a maximum hot pressing pressure of 160 N / m²; Zone 4 hot pressing temperature is 185-190℃, with a maximum hot pressing pressure of 100 N / m²; Zone 5 is the thickness-fixing zone, with a hot pressing temperature of 170-180℃. After hot pressing, the surface is cooled and sanded.

[0026] Although the following examples use poplar as the raw material, the concept of this invention can also be applied to other long-fiber broad-leaved woods or coniferous woods with modified processes.

[0027] The UV-curable coatings mentioned are not specifically limited, such as commercially available polyurethane acrylate UV furniture primers.

[0028] Example 1

[0029] A type of E NF The preparation process of grade flame-retardant fiberboard includes the following steps: wood peeling → chipping → screening → washing → pre-cooking → cooking → hot grinding → gluing → drying → laying → pre-pressing → hot pressing → cooling → sanding → curing → surface treatment → curing → inspection and grading → packaging and warehousing; among which,

[0030] In the wood peeling process, the wood species is poplar.

[0031] In the sizing process, the adhesive and flame retardant are mixed evenly in a certain proportion and then applied to the fiber surface; the adhesive is melamine-modified urea-formaldehyde resin, and the amount of melamine added during its synthesis accounts for 30% of the total amount of material, with an application rate of 220 kg / m³. 3 (Based on liquid adhesive); the mixed flame retardant consists of 60% ammonium polyphosphate (degree of polymerization > 1000), 10% zinc borate, 15% magnesium hydroxide, and 15% aluminum hydroxide, with an average particle size of 500 mesh and an application rate of 25 kg / m³. 3 .

[0032] In the surface treatment process, the upper and lower surfaces of the fiberboard are first dusted, then a UV-curable coating is applied to both surfaces. After UV curing, a second UV-curable coating is applied, followed by another UV curing. The first UV-curable coating has a single-sided coating weight of 30 g / m². 2 The second UV-cured coating has a single-sided coating coverage of 20 g / m². 2 One finished board was obtained.

[0033] The test data of the finished board are shown in Table 1.

[0034] Table 1. Inspection Data of Finished Board

[0035]

[0036] Comparative Example 1

[0037] The only difference between this comparative example and Example 1 is that the UV curing coating step in the surface treatment process is omitted, resulting in the second finished board.

[0038] The test data of the finished board are shown in Table 2.

[0039] Table 2. Inspection data for finished board 2

[0040]

[0041] A comparison of Table 2 and Table 1 shows that the formaldehyde emission of the boards without UV coating increases sharply (0.062–0.065 mg / m³). 3 (far exceeding E) NF The limit value strongly demonstrates the effectiveness of UV-cured coatings in sealing formaldehyde and achieving E2O2 emission standards. NF The decisive role of environmental protection standards.

[0042] Comparative Example 2

[0043] The only difference between this comparative example and Example 1 is that the adhesive is replaced with melamine-modified urea-formaldehyde resin with a melamine content of only 5% by mass, and the finished board 3 is obtained.

[0044] The three test data of the finished board are shown in Table 3.

[0045] Table 3. Three-inspection data of finished boards

[0046]

[0047] Comparative testing results showed that adhesives with a low melamine content severely degraded the water resistance of the boards (24-hour water absorption thickness expansion rate of 13.6%–15.1%), and also failed to meet the flame retardant standard (B2 level). This confirms that a melamine content of at least 30% is indispensable for ensuring the overall performance of the boards.

[0048] Comparative Example 3

[0049] The only difference between this comparative example and Example 1 is that, in the adhesive application process, the adhesive and flame retardant are not pre-mixed, but applied separately by applying the adhesive first and then the powdered flame retardant separately. Finished board four was obtained.

[0050] The test data of the finished board are shown in Table 4.

[0051] Table 4. Inspection Data of Finished Boards

[0052]

[0053] Test data shows that applying the different methods leads to a greater difference in the density of the boards, a significantly wider range of fluctuations in internal bond strength and static bending strength, and a differentiation in flame retardant performance from B1 to B2 within a single board. This clearly highlights the core value of the "adhesive-resistance premix" process used in this invention in ensuring product quality uniformity.

[0054] The embodiments described above are merely specific implementations of the present invention and do not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made using the present invention specification, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. An E NF The preparation process of grade flame-retardant fiberboard includes the following steps: wood peeling → chipping → screening → washing → pre-cooking → cooking → hot grinding → gluing → drying → laying → pre-pressing → hot pressing → cooling → sanding → curing → surface treatment → curing → inspection and grading → packaging and warehousing; characterized in that, In the adhesive application process, the adhesive and flame retardant are first mixed evenly in proportion to form a suspension mixture, and then applied to the fiber surface through the adhesive spray tube. The adhesive is melamine-modified urea-formaldehyde resin, wherein the melamine used to synthesize the resin accounts for 30-35% of the total mass of the raw materials; the application rate of the adhesive, in liquid form, is 180-250 kg / m³ of board. 3 ; The flame retardant is a mixed flame retardant, composed of the following components by mass percentage: ammonium polyphosphate 40-60%, zinc borate 10-20%, magnesium hydroxide 10-20%, and aluminum hydroxide 10-20%; the application rate of the flame retardant is 20-60 kg / m³. 3 The flame retardant has an average particle size of 400-800 mesh. The surface treatment process involves first removing dust from the upper and lower surfaces of the fiberboard, then applying a UV-curable coating, followed by UV curing. After UV curing, a second UV-curable coating is applied and cured. The first UV-curable coating application rate is 20-40 g / m². 2 The second UV-cured coating has a single-sided coating weight of 15-25 g / m². 2 .

2. The E according to claim 1 NF The manufacturing process of flame-retardant fiberboard is characterized by: In the wood peeling process, the wood species is poplar.

3. The E according to claim 1 NF The manufacturing process of flame-retardant fiberboard is characterized by: In the adhesive application process, the melamine content accounts for 30% of the total content by mass, and the amount of liquid adhesive applied is 220 kgm³. 3 .

4. The E according to claim 1 NF The manufacturing process of flame-retardant fiberboard is characterized by: In the sizing step, the mixed flame retardant is composed of the following components by mass percentage: 60% ammonium polyphosphate, 10% zinc borate, 15% magnesium hydroxide, and 15% aluminum hydroxide.

5. The E according to claim 1 NF The manufacturing process of flame-retardant fiberboard is characterized by: The mixed flame retardant has an average particle size of 500 mesh and is applied at a rate of 25 kg / m³. 3 .

6. The E according to claim 1 NF The manufacturing process of flame-retardant fiberboard is characterized by: The ammonium polyphosphate is a high-polymer type with a degree of polymerization greater than 1000.

7. The E according to claim 1 NF The manufacturing process of flame-retardant fiberboard is characterized by: In the surface treatment process, the first UV-cured coating application rate is 30 g / m². 2 The second UV-cured coating has a single-sided coating coverage of 20 g / m². 2 .

8. An E NF Grade 1 flame-retardant fiberboard, characterized in that: It is prepared by the process described in any one of claims 1-7.

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