Flame-retardant and waterproof high-density fiberboard and its application

Abstract

The invention discloses a kind of flame retardant waterproof high density fiberboard and application thereof, belong to fiberboard technical field, the flame retardant waterproof high density fiberboard of the present invention, by weight, including the following components:100 200 parts of wood fiber, 15 30 parts of adhesive, 1 3 parts of waterproofing agent, the adhesive includes 10 20 parts of modified urea-formaldehyde resin, 5 10 parts of modified inorganic filler, 0.1 0.2 parts of ammonium chloride, the modified inorganic filler is polydopamine modified inorganic filler, the modified urea-formaldehyde resin is branched phenyl phosphorus polyol and 1,3 adamantane diamine modified urea-formaldehyde resin. The present invention, by adding the adhesive consisting of modified inorganic filler and modified urea-formaldehyde resin in wood fiber, obtains flame retardant waterproof high density fiberboard, significantly enhances the interfacial bonding strength between filler and wood fiber, improves the flame retardancy and waterproofness of fiberboard, reduces its formaldehyde emission, obtains the high density fiberboard with waterproof and flame retardant effect.

Description

Technical Field

[0001] The present invention relates to the technical field of fiberboards, in particular to a flame-retardant and waterproof high-density fiberboard and applications thereof. Background Art

[0002] Fiberboard is a man-made board made from wood or other plant fibers, treated with urea-formaldehyde resin or other adhesives. Fiberboard offers advantages such as uniform material quality, minimal longitudinal and transverse strength differences, and resistance to cracking. However, fiberboard is composed of organic combustibles, making it a flammable material and a significant safety risk in residential fire protection. It also has poor water resistance and readily swells upon absorbing moisture, making it susceptible to deformation in the humid southern climate, impacting its usability. Furthermore, urea-formaldehyde resin is often used as an adhesive in fiberboard production, posing a risk of formaldehyde release. In the prior art, a common method for improving the flame retardancy and waterproofness of fiberboard is to add separate flame retardants such as phosphorus-based flame retardants, nitrogen-based flame retardants and waterproofing agents such as paraffin and silicone. However, most flame retardants have problems such as high flame retardant costs, toxicity of the flame retardants themselves or the gas smoke generated by the decomposition of the flame retardants during the flame retardant process, and when the addition amount is too high, it is easy to have a significant negative impact on the performance and appearance of the board itself. When the addition amount is too low, the flame retardant performance is difficult to achieve. Therefore, research has been developed to add inorganic fillers such as calcium carbonate to fiberboard. The non-combustible nature of calcium carbonate itself is utilized to add it to the fiberboard to hinder the combustion of the fiberboard. Calcium carbonate will absorb heat and decompose at high temperatures to produce calcium oxide and carbon dioxide. The endothermic reaction process can lower the ambient temperature, and the released carbon dioxide can also dilute the combustible gas and oxygen, which can hinder the further spread of the fire. At the same time, the calcium carbonate inside the fiberboard will not cause pollution to the environment as the fiberboard degrades under natural conditions. However, in terms of production process, if the process of applying glue first and then adding powder is adopted, it is easy to cause uneven distribution of powder. However, if the powder is mixed with urea-formaldehyde resin first and then applied, it will affect the adhesive properties of urea-formaldehyde resin, thereby causing serious quality defects in the fiberboard. Currently, there are studies using silane coupling agents to regulate the surface of powder and wood fiber, but it still has a certain impact on the adhesive properties of urea-formaldehyde resin, and the performance of the fiberboard has not been significantly improved. Summary of the Invention

[0003] In order to overcome the shortcomings of the above-mentioned existing technologies, the present invention provides a flame-retardant and waterproof high-density fiberboard and its application. By adding an adhesive composed of modified inorganic fillers and modified urea-formaldehyde resin to wood fibers, the interfacial bonding strength between the filler and the wood fibers is significantly enhanced, the flame retardancy and water resistance of the fiberboard are improved, and its formaldehyde emission is reduced. At the same time, it has the advantages of flame retardancy, high waterproofness, and low formaldehyde emission.

[0004] The present invention aims to provide a flame-retardant and waterproof high-density fiberboard, which comprises the following components, in parts by weight: 100-200 parts of wood fiber, 15-30 parts of an adhesive, and 1-3 parts of a waterproofing agent. The adhesive comprises 10-20 parts of a modified urea-formaldehyde resin, 5-10 parts of a modified inorganic filler, and 0.1-0.2 parts of ammonium chloride. The modified inorganic filler is a polydopamine-modified inorganic filler. The preparation method of the modified urea-formaldehyde resin comprises the following steps:

[0005] S1. The formaldehyde solution is placed in a reactor, heated with stirring, the pH is adjusted to alkaline, the first batch of urea is slowly added, and a branched phenyl phosphorus polyol is added at the same time, wherein the amount of the branched phenyl phosphorus polyol added is 3-5 mol% of formaldehyde, and the reaction is stirred at 40-50 ° C for a period of time;

[0006] S2 continues to control the pH of the system to be alkaline, slowly add 1,3-adamantane diamine, the amount of 1,3-adamantane diamine added is 3-5 mol% of formaldehyde, the temperature is raised to 70-90 ℃, and the reaction is stirred for a period of time;

[0007] S3. Adjust the pH of the reaction system to acidic, slowly add the second batch of urea, control the temperature at 80-90 ° C, and stir the reaction for a while;

[0008] S4. After the reaction is completed, adjust the pH to alkaline, cool to 40-50°C and add the third batch of urea, continue stirring and reacting for a period of time before discharging.

[0009] Preferably, the branched phenylphosphine polyol is prepared by reacting phenylphosphine dichloride with a multifunctional polyol in the presence of a catalyst and an acid binding agent to obtain a branched phenylphosphine polyol having a hydroxyl group at the end.

[0010] Preferably, the multifunctional polyol is selected from at least one of glycerol, trimethylolpropane, and pentaerythritol, the catalyst is 4-dimethylaminopyridine, and the acid binding agent is triethylamine.

[0011] Specifically, the 1,3-adamantane diamine can be commercially available or homemade; preferably, the preparation method of the 1,3-adamantane diamine is as follows: at room temperature, adamantane and bromine water are mixed in a diphenyl ether solvent, iron powder is added as a catalyst, and dibromoadamantane is obtained after reaction; then urea and trifluoroacetic acid are added, and the reaction is carried out at 140-180°C to obtain 1,3-adamantane diamine.

[0012] Preferably, the preparation method of 1,3-adamantanediamine can also be: controlling the temperature at 0-10°C, mixing 1,3-adamantanedicarboxylic acid and dichloromethane, adding a catalyst, and dropwise adding a chlorination agent; stirring and heating to 37-38°C, reacting for 4 hours to obtain 1,3-adamantanedicarboxylic acid chloride; controlling the temperature at 10-0°C, dropwise adding 1,3-adamantanedicarboxylic acid chloride to 25% ammonia water, reacting for 1 hour, filtering, and drying to obtain adamantane 1,3-dicarboxamide; controlling the temperature at 0-10°C, adding adamantane 1,3-dicarboxamide to a sodium hydroxide aqueous solution, adding a halogenation agent, heating to 40°C, stirring and reacting for 6 hours, extracting with dichloromethane, separating the aqueous phase, and concentrating the dichloromethane phase to obtain a white solid, namely 1,3-adamantanediamine.

[0013] Preferably, the molar ratio of the first batch of urea, the second batch of urea and the third batch of urea is 1:(0.6-0.8):(0.1-0.2).

[0014] Preferably, the molar ratio of formaldehyde to urea in the modified urea-formaldehyde resin is (0.9-1.2):1.

[0015] Preferably, the modified inorganic filler is prepared by stirring an inorganic filler and ethanol to obtain an inorganic filler suspension, dissolving dopamine hydrochloride in deionized water, slowly adding the solution to the inorganic filler suspension, adding an ammonium hydroxide solution, and stirring the mixture at 30-40°C for a period of time to obtain a polydopamine-modified inorganic filler. Under alkaline conditions, dopamine can self-polymerize on the surface of the inorganic filler to obtain a polydopamine-modified inorganic filler.

[0016] Preferably, the inorganic filler in the modified inorganic filler is at least one of calcium carbonate, aluminum hydroxide, silicon dioxide, diatomaceous earth, bentonite, magnesium hydroxide or talc, and the mass ratio of polydopamine to the inorganic filler is (1-1.5):100.

[0017] Preferably, the waterproofing agent is at least one of solid paraffin or emulsified paraffin.

[0018] Another object of the present invention is to provide a method for preparing the flame retardant and waterproof high-density fiberboard, comprising the following steps:

[0019] S1. The wood fiber is screened, impurities and metal hard objects are removed, and then placed in a cooking cylinder to soften it. It is then placed in a hot mill for hot grinding and then mixed with a waterproofing agent in a mixer;

[0020] S2. The modified urea-formaldehyde resin, modified inorganic filler and ammonium chloride are stirred to obtain an adhesive, the wood fiber is poured into a mixer, and the adhesive is evenly sprayed on the surface of the wood fiber with a spray gun during the stirring process. After the sizing is completed, the sizing fiber is dried to a moisture content of 5 to 8%;

[0021] S3. Weigh a certain mass of fibers, manually lay them out and pre-press them, and finally place them in a hot press for hot pressing to obtain a high-density fiberboard.

[0022] Another object of the present invention is to protect the application of the flame-retardant and waterproof high-density fiberboard in furniture manufacturing and interior decoration.

[0023] Beneficial effects

[0024] The present invention provides a flame-retardant and waterproof high-density fiberboard, which has the following beneficial effects by adding an adhesive composed of a modified inorganic filler and a modified urea-formaldehyde resin to wood fibers:

[0025] (1) Polydopamine has good adhesion properties and can form a uniform coating on the surface of inorganic fillers without causing a significant decrease in the adhesive properties of urea-formaldehyde resin. Branched phenylphosphine polyols are added to urea-formaldehyde resin for modification. Branched phenylphosphine polyols have multiple terminal active groups, which can increase the reaction sites of formaldehyde, increase the content of branched polymers in urea-formaldehyde resin, and increase the cross-linking density of urea-formaldehyde resin, thereby enhancing the bonding properties of urea-formaldehyde resin. The addition of 1,3-adamantane diamine introduces a heat-resistant adamantane structure into the cross-linking network of urea-formaldehyde resin, further improving the stability and heat resistance of urea-formaldehyde resin, and can also consume free formaldehyde, reducing the formaldehyde release of fiberboard.

[0026] (2) The method of mixing the polydopamine-modified inorganic filler with the modified urea-formaldehyde resin before applying the glue can improve the dispersion of the inorganic filler in the wood fiber, reduce the agglomeration phenomenon, significantly enhance the interfacial bonding strength between the inorganic filler and the wood fiber, and improve the flame retardant properties of the fiberboard. The modified urea-formaldehyde resin has better fluidity and permeability, which can better wrap and disperse the filler, further improving the dispersion effect of the filler. In addition, the introduction of branched phenyl phosphorus polyol and 1,3-adamantane diamine structure into the urea-formaldehyde resin improves the stability of the urea-formaldehyde resin, making the urea-formaldehyde resin flame retardant and heat-resistant, thereby further improving the flame retardant properties of the fiberboard.

[0027] (3) The inorganic filler modified with polydopamine can form a dense barrier layer, significantly improving the barrier properties of the material and reducing the permeation of water and gas. The modified urea-formaldehyde resin has better water resistance and can further improve the barrier properties of the composite material, thereby improving the waterproof performance of the fiberboard. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is the infrared spectrum of branched phenylphosphine polyol 1. DETAILED DESCRIPTION

[0029] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0030] In the examples, the experimental methods used are conventional methods unless otherwise specified, and the materials, reagents, etc. used are all commercially available unless otherwise specified.

[0031] The raw materials used in the embodiments and comparative examples are now described as follows:

[0032] Wood fiber: eucalyptus fiber; moisture content 10%, Guangxi Fenglin Wood Industry Group Co., Ltd.

[0033] Inorganic filler 1: aluminum hydroxide, 99%, 1 μm, Guangzhou Nalong Chemical Co., Ltd.

[0034] Inorganic filler 2: heavy calcium carbonate, 200 mesh, Hezhou Qifeng Powder Co., Ltd.

[0035] Waterproofing agent: solid paraffin, commercially available;

[0036] 1,3-adamantanediamine: Homemade, the preparation method is as follows: at room temperature, adamantane and bromine water are mixed in diphenyl ether solvent, iron powder is added as a catalyst to obtain dibromoadamantane, urea and trifluoroacetic acid are added, and the reaction is carried out at 140-180°C for 1.5 hours. After cooling, hydrochloric acid is added and stirred to dissolve the product, and insoluble impurities are removed by filtration. The filtrate is neutralized by sodium hydroxide solution, and then an excess of organic solvent is added for extraction. The obtained extract is distilled under reduced pressure to remove the solvent, and vacuum dried to obtain 1,3-adamantanediamine.

[0037] Branched phenylphosphine polyol 1: homemade, prepared as follows: 0.1 mol of 4-dimethylaminopyridine, 2 mol of triethylamine, and 1.5 mol of pentaerythritol were dissolved in 80 g of dichloromethane. The reaction temperature was set at 45°C. Under nitrogen purge and stirring at reflux, 1 mol of a dichloromethane solution of phenylphosphonic acid dichloride was slowly added dropwise. The reaction was allowed to proceed for 24 hours, filtered, and the filtrate was washed three times with distilled water, dehydrated with sodium sulfate, and dried in vacuo to obtain the final product.

[0038] Branched phenyl phosphorus polyol 2: homemade. The preparation method is similar to that of branched phenyl phosphorus polyol 1, except that pentaerythritol is replaced by glycerol.

[0039] Linear phenyl phosphine polyol: homemade. The preparation method is similar to branched phenyl phosphine polyol 1, except that pentaerythritol is replaced by ethylene glycol.

[0040] The chemical structure of branched phenylphosphine polyol 1 was characterized by Fourier transform infrared spectroscopy (FT-IR, Nicolet 6700, Thermo Fisher Scientific, USA). Figure 1 As shown, the peaks of hydroxyl group -OH, C=C bond on the benzene ring and P=O were detected simultaneously in the infrared spectrum of the product, proving the successful synthesis of the target product.

[0041] Modified inorganic filler 1: Homemade, the preparation method is as follows: 100g of inorganic filler 1 and 1000ml of ethanol are stirred and mixed at 30°C for 30min, 1.5g of dopamine hydrochloride is weighed and dissolved in 30mL of deionized water, the dopamine hydrochloride solution is slowly added to the suspension of inorganic filler 1, stirred for 30min, and then 9ml of 30% ammonium hydroxide solution is added, and the reaction is continuously stirred for 24h, filtered, washed three times with deionized water, and vacuum dried in an 80°C oven to obtain a polydopamine modified inorganic filler.

[0042] Modified inorganic filler 2: homemade. The preparation method is similar to that of modified inorganic filler 1, except that inorganic filler 1 is replaced by inorganic filler 2.

[0043] Modified inorganic filler 3: Homemade, the preparation method is as follows: 100g of inorganic filler 1 and 1000ml of deionized water are stirred and mixed at 30°C for 30min, 1.5g of KH550 silane coupling agent is weighed and dissolved in 10v / v% ethanol aqueous solution, stirred for 30min, the inorganic filler 1 suspension is added to 80°C, KH550 solution is added, the reaction is kept warm for 2 hours, filtered and vacuum dried in an oven at 80°C to obtain KH550 modified inorganic filler.

[0044] Modified urea-formaldehyde resin 1: Homemade, preparation method is as follows:

[0045] S1. A 37% formaldehyde aqueous solution was placed in a reactor, stirred and heated to 40°C, sodium hydroxide solution was added to adjust the pH to 8.0-8.5, and the first batch of urea was slowly added. The total molar ratio of urea to formaldehyde was 1:1, and the amount of the first batch of urea added was 50% of the total amount of urea added. The branched phenyl phosphorus polyol 1 was dissolved in deionized water under slightly heated conditions and then added to the reactor system. The amount of branched phenyl phosphorus polyol 1 was 3 mol% of the total mass of formaldehyde. The temperature was raised to 40°C and the reaction was stirred for 30 minutes.

[0046] S2. Control the pH of the system to 8.0-8.5, dissolve 1,3-adamantanediamine in deionized water and slowly add it to the reaction system. The amount of 1,3-adamantanediamine added is 3 mol% of the total mass of formaldehyde, and the temperature is raised to 70 ° C and the reaction is stirred for 2 hours.

[0047] S3. Hydrochloric acid solution was added to adjust the pH of the reaction system to 4.5-5.5, and a second batch of urea was slowly added. The second batch of urea was added in an amount of 40% of the total amount of urea added. The temperature was raised to 85 ° C and the reaction was stirred for 1 to 2 hours; the reaction endpoint was determined by regularly measuring the viscosity of the solution;

[0048] S4. After the reaction is completed, the pH is adjusted to 8-8.5, the temperature is continued to be lowered and a third batch of urea is added. The amount of the third batch of urea added is 10 mol% of the total amount of urea added. After cooling to 40 ° C, the reaction is continued with stirring for 30 minutes, the pH is adjusted to 9, and the material is discharged.

[0049] Modified urea-formaldehyde resin 2: homemade. The preparation method is the same as that of Example 1, except that branched phenyl phosphorus polyol 1 is replaced by branched phenyl phosphorus polyol 2.

[0050] Modified urea-formaldehyde resin 3: homemade, the preparation method is the same as that of Example 1, except that the amount of branched phenyl phosphorus polyol 1 added is 5 mol% of the total mass of formaldehyde;

[0051] Modified urea-formaldehyde resin 4: homemade. The preparation method is the same as that of Example 1, except that the amount of 1,3-adamantanediamine added is 5 mol% of the total mass of formaldehyde.

[0052] Modified urea-formaldehyde resin 5: homemade, the preparation method is the same as that of Example 1, except that the amount of branched phenyl phosphorus polyol 1 added is 1 mol% of the total mass of formaldehyde;

[0053] Modified urea-formaldehyde resin 6: homemade. The preparation method is the same as that in Example 1, except that the amount of 1,3-adamantane diamine added is 1 mol% of the total mass of formaldehyde.

[0054] Modified urea-formaldehyde resin 7: homemade. The preparation method is the same as that of Example 1, except that branched phenyl phosphorus polyol 1 is replaced by linear phenyl phosphorus polyol.

[0055] Urea-formaldehyde resin: homemade. The preparation method is the same as that in Example 1, except that branched phenyl phosphorus polyol and 1,3-adamantane diamine are not added.

[0056] Unless otherwise specified, the components and raw materials used in the examples and comparative examples of the present invention are all commercially available raw materials, and the components and raw materials used in each parallel experiment are all of the same kind.

[0057] Example 1 A flame retardant and waterproof high-density fiberboard, parts by weight and preparation method are as follows:

[0058] 150 parts of wood fiber, 20.15 parts of adhesive, 2 parts of waterproofing agent, the adhesive includes 15 parts of modified urea-formaldehyde resin, 5 parts of modified inorganic filler, and 0.15 parts of ammonium chloride, the modified urea-formaldehyde resin is modified urea-formaldehyde resin 1, and the modified inorganic filler is modified inorganic filler 1. The preparation method is as follows:

[0059] S1. The wood fiber was screened, impurities and metal hard objects were removed, and the mixture was placed in a cooking cylinder for softening. The cooking time was 8min, the steam pressure was 0.8MPa, and then placed in a hot mill for hot grinding, and then mixed with a waterproofing agent in a mixer;

[0060] S2. The modified urea-formaldehyde resin, curing agent and modified inorganic filler are mixed and stirred to obtain an adhesive, the wood fiber is poured into a blender, and the adhesive is evenly sprayed on the surface of the wood fiber with a spray gun during the stirring process. After the sizing is completed, the sizing fiber is dried to a moisture content of 5%;

[0061] S3. A certain mass of fibers was weighed, manually laid, and pre-pressed. Finally, fibers were placed in a hot press and hot-pressed to obtain a high-density fiberboard. The pre-pressing pressure was controlled at 4 MPa, the hot-pressing pressure was 18 MPa, the hot-pressing temperature was 200°C, and the hot-pressing time was 6 minutes. The resulting high-density fiberboard had a thickness of 12 mm.

[0062] Example 2

[0063] Compared with Example 1, the difference is that the modified urea-formaldehyde resin 1 is replaced by the modified urea-formaldehyde resin 2;

[0064] Example 3

[0065] Compared with Example 1, the difference is that the modified urea-formaldehyde resin 1 is replaced by the modified urea-formaldehyde resin 3;

[0066] Example 4

[0067] Compared with Example 1, the difference is that the modified urea-formaldehyde resin 1 is replaced by the modified urea-formaldehyde resin 4;

[0068] Example 5

[0069] Compared with Example 1, the difference is that the modified inorganic filler 1 is replaced by the modified inorganic filler 2;

[0070] Compared with Example 1, the difference is that the modified urea-formaldehyde resin 1 is replaced by the modified urea-formaldehyde resin 5; Comparative Example 2

[0071] Compared with Example 1, the difference is that the modified urea-formaldehyde resin 1 is replaced by the modified urea-formaldehyde resin 6; Comparative Example 3

[0072] Compared with Example 1, the difference is that the modified inorganic filler 1 is replaced by the modified inorganic filler 3; Comparative Example 4

[0073] Compared with Example 1, the difference is that the modified urea-formaldehyde resin 1 is replaced by the modified urea-formaldehyde resin 7; Comparative Example 5

[0074] Compared with Example 1, the difference is that the modified urea-formaldehyde resin 1 is replaced by urea-formaldehyde resin;

[0075] Comparative Example 6

[0076] Compared with Example 1, the difference is that no modified inorganic filler is added to the adhesive.

[0077] The adhesives and high-density fiberboards prepared in the examples and comparative examples were subjected to the following performance tests, and the results are shown in Table 1.

[0078] 1. Viscosity: The viscosity of the adhesive was measured using an NDJ-5S rotational viscometer in accordance with GB / T 14074-2017, Test Methods for Adhesives and Resins for Wood Industry. The temperature of the adhesive was maintained at 25°C. Each adhesive was measured three times, and the arithmetic mean of the three viscosity measurements was taken as the test result.

[0079] 2. Free formaldehyde content: The free formaldehyde content of the adhesive is determined by hydrochloric acid titration. The specific process is as follows: Add 5g of adhesive, 35mL of distilled water and 15mL of anhydrous ethanol to a 250mL conical flask and mix well. After adding 8 drops of methyl red-methylene blue mixed indicator, neutralize with hydrochloric acid, and then quickly add 10mL of NH4C1 solution (mass fraction of 10%) and 10mL of sodium hydroxide solution (1mol / L), mix well, and let stand at room temperature for 30min. Neutralize with hydrochloric acid and record the volume of hydrochloric acid standard solution consumed. Set up a blank test, do not add adhesive, do not neutralize after adding the indicator, and the rest of the steps are the same. Each adhesive is measured twice in parallel, and the arithmetic mean of the two measurement results is taken as the test result. The free formaldehyde content is calculated as follows:

[0080]

[0081] Where: F is the free formaldehyde content, expressed as a percentage (%); V1 is the volume of the hydrochloric acid standard solution consumed in the blank test, in milliliters (mL); V2 is the volume of the hydrochloric acid standard solution consumed in the titration sample, in milliliters (mL); c is the molar concentration of the hydrochloric acid standard solution, in moles per liter (mol / L); G is the mass of the adhesive, in grams (g).

[0082] 3. Static flexural strength and elastic modulus: Tested using the three-point bending method in accordance with GB / T 17657-2013, Test Methods for Physical and Chemical Properties of Wood-Based Panels and Faced Wood-Based Panels. Uniform loading was applied at a speed of 20 mm / min on an MWW-10 universal mechanical testing machine. The specimens measured 300 mm × 50 mm × 12 mm. Two specimens were measured for each fiberboard.

[0083] 4. Internal bond strength: With reference to GB / T 17657-2013, Test methods for physical and chemical properties of wood-based panels and veneered wood-based panels, uniform loading was applied at a speed of 2 mm / min on an MWW-10 universal mechanical testing machine. The specimens were sized at 50 mm × 50 mm × 12 mm. Five specimens were taken from each fiberboard for testing.

[0084] 5. 24-hour water absorption thickness expansion rate: Referring to GB / T 17657-2013, "Test methods for physical and chemical properties of wood-based panels and veneered wood-based panels," immerse the specimen in a constant-temperature water bath at a pH of 7 and a temperature of 20°C. The specimen surface is perpendicular to the water surface, and the upper portion of the specimen is 25 mm below the water surface. Immerse in water for 24 hours and measure the thickness change before and after water absorption. The specimen dimensions are 50 mm × 50 mm × 12 mm. Three specimens are taken from each fiberboard. The formula for calculating the water absorption thickness expansion rate is as follows:

[0085]

[0086] Where: T is the water absorption thickness expansion rate, expressed as a percentage (%); t1 is the thickness of the specimen before immersion in water, in millimeters (mm); t2 is the thickness of the specimen after immersion in water, in millimeters (mm).

[0087] 6. Formaldehyde emission: Refer to GB / T17657-2013 "Test methods for physical and chemical properties of artificial boards and veneer artificial boards", and use the perforation extraction method for determination. The specimen size is 25mm×25mm×12mm. Take two 50g specimens to determine the moisture content, and take 110g of the specimen for extraction with toluene to obtain a formaldehyde aqueous solution. Then add the formaldehyde aqueous solution to a mixed solution of acetylacetone and ammonium acetate, heat it in a water tank at 60°C for 10 minutes, take it out and let it stand in a dark place for 60 minutes. Set up a blank test group. In the blank test group, deionized water is added to the mixed solution of acetylacetone and ammonium acetate, and the rest of the steps are the same. Use distilled water as the reference solution at 412nm on the ultraviolet spectrophotometer and adjust to zero. Use a cuvette to measure the absorbance of the extraction solution and the absorbance of the blank solution. The calculation formula for formaldehyde emission is as follows:

[0088]

[0089] Where: E is the formaldehyde release, in milligrams per 100 g (mg / 100 g); A2 is the absorbance of the extract; A1 is the absorbance of the blank solution; f is the slope of the standard curve, in milligrams per milliliter (mg / mL); H is the moisture content of the specimen, expressed as a percentage (%); V is the volume of the volumetric flask, V = 2000 mL; m is the mass of the specimen for the extraction test, in grams (g).

[0090] 7. Cone calorimetry test: The measurement was carried out according to the procedure described in the Chinese national standard GB / T34749-2017. The sample size was 100 mm × 100 mm × 12 mm. The irradiance during the test was 50 kW m -2 , the exhaust system flow rate is 0.024m 3 ·s -1 Before the test, place the sample in the middle of the aluminum foil and wrap its bottom and sides. When the temperature of the back-fire surface of the sample reaches 140°C, the test is terminated. Record the ignition time and continuous burning time. Take 3 specimens from each fiberboard for measurement.

[0091] Table 1 Performance test results of modified urea-formaldehyde resin

[0092]

[0093] It can be seen that adding branched phenyl phosphorus polyol and 1,3-adamantane diamine to urea-formaldehyde resin for modification can increase the cross-linking network density of urea-formaldehyde resin, consume formaldehyde, and effectively reduce the free amount of formaldehyde. When the modified urea-formaldehyde resin is modified by adding linear phenyl phosphorus polyol, the cross-linking density is insufficient, and the viscosity and solid content of the resin are poor.

[0094] Table 2 Performance test results of fiberboard

[0095]

[0096]

[0097] Test results for fiberboard demonstrate that high-density fiberboard prepared with an adhesive made from a mixture of modified urea-formaldehyde resin and modified inorganic fillers exhibits high strength, high modulus, flame retardancy, water resistance, and low formaldehyde emission, overcoming the low adhesive properties and agglomeration associated with the addition of inorganic fillers in existing technologies. Modification of urea-formaldehyde resin by adding branched phenylphosphine polyol and 1,3-adamantanediamine not only increases the branched polymer content and reduces its crystallinity, but also introduces flame retardant groups while maintaining adhesive properties and thermal stability, demonstrating broad application prospects.

[0098] The preferred embodiments of the present invention disclosed above are intended only to help illustrate the present invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the present invention to the specific embodiments described. Obviously, many modifications and variations are possible based on the content of this specification. These embodiments are selected and described in detail in this specification to better explain the principles and practical applications of the present invention, thereby enabling those skilled in the art to better understand and utilize the present invention. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. A flame retardant and waterproof high-density fiberboard, characterized in that: The invention comprises the following components in parts by weight: 100-200 parts of wood fiber, 15-30 parts of adhesive, and 1-3 parts of waterproofing agent. The adhesive comprises 10-20 parts of modified urea-formaldehyde resin, 5-10 parts of modified inorganic filler, and 0.1-0.2 parts of ammonium chloride. The modified inorganic filler is a polydopamine-modified inorganic filler. The preparation method of the modified urea-formaldehyde resin comprises the following steps: S1. The formaldehyde solution is placed in a reactor, stirred and heated, the pH of the reaction system is adjusted to alkaline, the first batch of urea is slowly added, and a branched phenyl phosphorus polyol is added at the same time, the amount of the branched phenyl phosphorus polyol added is 3-5mol% of formaldehyde, and the temperature is raised to 40-50 ° C and the reaction is stirred for a period of time; S2. Continue to control the pH of the reaction system to be alkaline, slowly add 1,3-adamantane diamine, the amount of 1,3-adamantane diamine added is 3-5 mol% of formaldehyde, heat to 70-90 ° C, stir the reaction for a while; S3. Adjust the pH of the reaction system to acidic, slowly add the second batch of urea, control the temperature at 80-90 ° C, and stir the reaction for a while; S4. After the reaction, the pH of the reaction system was adjusted to alkaline, the temperature was lowered to 40-50 ° C, and a third batch of urea was added, and the reaction was continued with stirring for a period of time and then discharged; The branched phenylphosphine polyol is prepared by reacting phenylphosphine dichloride with a multifunctional polyol in the presence of a catalyst and an acid-binding agent to obtain a branched phenylphosphine polyol with a hydroxyl terminal. The multifunctional polyol is selected from at least one of glycerol, trimethylolpropane, and pentaerythritol. The inorganic filler in the modified inorganic filler is at least one of calcium carbonate, aluminum hydroxide, silicon dioxide, diatomaceous earth, bentonite, magnesium hydroxide, or talc.

2. The flame retardant and waterproof high-density fiberboard according to claim 1, characterized in that: The catalyst is 4-dimethylaminopyridine, and the acid binding agent is triethylamine.

3. The flame retardant and waterproof high-density fiberboard according to claim 1, characterized in that: The preparation method of 1,3-adamantane diamine comprises: mixing adamantane and bromine water in a diphenyl ether solvent at room temperature, adding iron powder as a catalyst, reacting to obtain dibromoadamantane, then adding urea and trifluoroacetic acid, and reacting at 140-180° C. to obtain 1,3-adamantane diamine.

4. The flame retardant and waterproof high-density fiberboard according to claim 1, characterized in that: The molar ratio of the first batch of urea, the second batch of urea and the third batch of urea is 1: (0.6-0.8): (0.1-0.2).

5. The flame retardant and waterproof high-density fiberboard according to claim 1, characterized in that: The molar ratio of formaldehyde to urea in the modified urea-formaldehyde resin is (0.9-1.2):

1.

6. The flame retardant and waterproof high-density fiberboard according to claim 1, characterized in that: The preparation method of the modified inorganic filler comprises: stirring and mixing an inorganic filler and ethanol to obtain an inorganic filler suspension, dissolving dopamine hydrochloride in deionized water, slowly adding the solution to the inorganic filler suspension, adding ammonium hydroxide solution, and stirring and reacting at 30-40° C. for a period of time to obtain a polydopamine-modified inorganic filler.

7. The method for preparing the flame retardant and waterproof high-density fiberboard according to any one of claims 1 to 6, characterized in that: The following steps are involved: S1. The wood fiber is screened, impurities and metal hard objects are removed, and then placed in a cooking cylinder to soften it. It is then placed in a hot mill for hot grinding and then mixed with a waterproofing agent in a mixer; S2. The modified urea-formaldehyde resin, modified inorganic filler, and ammonium chloride are mixed to obtain an adhesive. The wood fibers are then placed in a mixer and the adhesive is evenly sprayed onto the surface of the wood fibers using a spray gun during mixing. After the adhesive is applied, the fibers are dried to a moisture content of 5-8%. S3. Weigh a certain mass of fibers, manually lay them out and pre-press them, and finally place them in a hot press for hot pressing to obtain a high-density fiberboard.

8. Use of the flame-retardant and waterproof high-density fiberboard according to any one of claims 1 to 7 in furniture manufacturing and interior decoration.

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