Flame-retardant coating based on PA-ARG flame-retardant curing agent as well as preparation method and application of flame-retardant coating

Abstract

The invention discloses a flame-retardant coating based on a PA-ARG flame-retardant curing agent, which takes urea and formaldehyde as main raw materials, takes melamine, KH550 and cellulose powder as auxiliaries, and takes phytic acid-glycine phytate PA-ARG as a full-bio-based flame-retardant curing agent. The temperature when the maximum decomposition rate is reached is 290.43 DEG C; and the mass retention amount at the temperature of 800 DEG C is 34.58 wt.%. The preparation method comprises the following steps: 1, preparing phytic acid-glycine phytate PA-ARG; 2, preparing urea resin emulsion MUF (urea formaldehyde resin); and 3, preparing the flame-retardant coating FRUF based on the PA-ARG flame-retardant curing agent. The flame-retardant coating is applied as a wood flame-retardant coating and has a flame-retardant property, and wood FRUFW coated with the flame-retardant coating passes a UL-94V-0 grade test in a UL-94 grade test; in a limit oxygen index test, the limit oxygen index is 30.2%; the maximum heat release rate is 16.97 kW / m < 2 >, the total heat release amount is 1.12 MJ / m < 2 >, the fire increase index is 0.07 kW / m < 2 > / s, and the mass retention amount of the sample is 72.20 wt.% after the test is finished.

Description

Technical Field

[0001] The present invention relates to the field of flame retardant materials, and in particular to a flame retardant coating based on a PA-ARG flame retardant curing agent, and a preparation method and application thereof. Background Art

[0002] To eliminate the potential fire safety hazards of wood, a material widely used in daily life, it is necessary to improve its flammability. Currently, the most common method for improving wood's flame retardancy is to apply flame-retardant coatings to the wood surface. When the wood burns, flame-retardant coatings form a thermally insulating, intumescent charcoal layer on the surface that acts as a spatial barrier, isolating the wood from the fire and thus achieving flame retardancy.

[0003] A common method for preparing flame-retardant coatings is to directly add flame retardants to wood coatings. While traditional halogen flame retardants offer advantages such as good flame retardancy and low cost, they can produce harmful substances such as dioxins during combustion. To reduce the use of halogen flame retardants, phosphorus-based flame retardants can be used as an alternative.

[0004] For example, in the existing document 1 (《A novel melamine formaldehyde resin coating with phosphoric acid, tannic acid and nano zinc oxide on wood with high flameretardancy and transparency》[J]. Progress in Organic Coatings 197(2024)108871), a new transparent flame retardant coating was prepared using water-based melamine formaldehyde resin as the gas source of wood coating and flame retardant system, phosphoric acid-tannic acid as acid and carbon source, and nano zinc oxide as flame retardant synergist. In the cone calorimetry test, the maximum heat release rate of the wood coated with the flame retardant coating increased from 324.47kW / m 2 Reduced to 164.54kW / m 2 The total heat release is 47.38MJ / m 2 Dropped to 34.96MJ / m 2 , showing good flame retardant properties.

[0005] While phosphorus-based flame retardants also offer good flame retardancy and low cost, they also contain phosphorus that can accumulate in the environment, leading to soil eutrophication. Therefore, to address the environmental accumulation of phosphorus-based flame retardants, current flame retardant research is primarily focused on biodegradable bio-based flame retardants.

[0006] Among bio-based flame retardants, phytic acid-based flame retardants are commonly used in flame-retardant coatings due to their green, renewable nature and high flame retardancy. For example, existing document 2 ("Novel design and synthesis of bio-based polyelectrolyte complexes for enhancing the flame retardancy of epoxy resin" [J]. Materials Chemistry and Physics 291 (2022) 126674) synthesizes a bio-based polyelectrolyte complex PA-Ni-PEI by reacting phytic acid, nickel ions, and polyethyleneimine. This is then added to epoxy resin (EP) as a flame retardant. Then, 4,4-diaminodiphenylmethane (DDM) is used as a curing agent to improve the flame retardancy of EP, achieving a UL-94 V-1 rating and a limiting oxygen index of 27%. However, a problem with this technical solution is that the modified epoxy resin has a low UL-94 rating and limiting oxygen index value, meaning that there is room for further improvement in the UL-94 rating and limiting oxygen index value. In addition, PA-Ni-PEI, as an additive flame retardant, only plays the role of improving the flame retardant performance, and the curing of thermosetting epoxy resin still requires the additional use of a curing agent.

[0007] Similarly, in existing document 3, the inventors of the present invention also found in their previous work ("A bio-based flame-retardant coating based on PGL, its preparation method and application" CN 118580739 A) that although the use of the phytic acid-based flame retardant PGL significantly improved the flame retardant properties of the coating, the wood coated with the flame retardant coating achieved a UL-94 V-0 rating and a limiting oxygen index of 36.5%. However, the prepared PGL was only used as an additive flame retardant and could not play a role in curing the coating. Therefore, the work required the addition of an additional curing agent to cure the thermosetting urea-formaldehyde resin coating.

[0008] Therefore, it can be seen from the existing documents 2 and 3 that such technical solutions require the addition of flame retardants and curing agents at the same time, that is, the curing agent needs to be added additionally, thereby increasing the cost of raw materials and increasing the complexity of the production process.

[0009] In order to solve the above-mentioned problem of needing to add additional curing agents, in another preliminary work of the inventors of the present invention, existing document 4 ("A flame-retardant coating based on PA-MEL flame-retardant curing agent, its preparation method and application" CN 117887324A) found that phytic acid and melamine can form ammonium phytate PM based on ion crosslinking. Ammonium phytate PM can be used as both an additive flame retardant and a curing agent for thermosetting urea-formaldehyde resin coatings, while giving urea-formaldehyde resin coatings flame retardant and curing effects. This not only avoids the additional addition of curing agents, but also enables wood coated with PM-cured coatings to exhibit high flame retardant properties, reaching UL-94V-0 grade and an LOI value of 32.1%. However, the problem with this technical solution is that melamine has poor water solubility (soluble in hot water at 80-90°C). During the preparation of the flame retardant curing agent, the temperature needs to be raised to achieve the purpose of dissolving melamine in water. In hot water greater than 80°C, melamine and other amino-containing substances may hydrolyze to produce ammonia, affecting the pH value of the system and thus affecting the reaction rate of the system. In addition, if the amount of ammonia released is large, an additional exhaust gas treatment system is required, increasing the equipment cost. Therefore, it is necessary to find an amino-containing substance that is better in water solubility than melamine and can undergo an ionic cross-linking reaction with phytic acid at room temperature to form ammonium phytate to replace it, so as to achieve the purpose of improving reaction efficiency and reducing production costs.

[0010] Therefore, through analysis of the existing technology, it can be seen that the practical problem that needs to be solved is: to prepare a degradable high-biobased flame retardant curing agent that can react at room temperature and has both flame retardant and curing functions, and while ensuring the flame retardant effect, it can effectively cure the coating and avoid the additional addition of curing agent, thereby reducing raw material costs. Summary of the Invention

[0011] The purpose of the present invention is to provide a flame retardant coating based on a PA-ARG flame retardant curing agent, a preparation method and an application thereof.

[0012] To address the problems of the existing technology, the ionic reaction between biomass phytic acid and biomass glycine is first used to prepare phytic acid-glycine phytic acid ammonium salt PA-ARG, which is then used as a fully bio-based flame retardant curing agent to cure the modified urea-formaldehyde resin to prepare a bio-based flame retardant coating. The flame retardant coating is then applied to wood to improve the flame retardant properties of the wood. Specifically,

[0013] The invention adopts melamine, KH550 and cellulose powder as additives for urea-formaldehyde resin coating and uses phytic acid-glycine phytic acid ammonium salt PA-ARG as a bio-based flame retardant curing agent to achieve the following technical effects:

[0014] 1. Adding melamine optimizes the molecular structure of urea-formaldehyde resin and improves the mechanical properties of flame-retardant coatings. In addition, melamine can block some hydrophilic groups of flame-retardant coatings and improve the water resistance of flame-retardant coatings;

[0015] 2. Adding KH550 can improve the dispersion of filler cellulose powder and flame retardant curing agent in flame retardant coatings, promote curing, and reduce the amount of curing agent. In addition, KH550 contains Si, which can improve the stability of the protective carbon layer formed by the combustion of urea-formaldehyde resin, which helps to improve the flame retardant performance;

[0016] 3. Adding cellulose powder as a filler to urea-formaldehyde resin can reduce the curing shrinkage of urea-formaldehyde resin and reduce cracking during curing. In addition, cellulose powder can provide a certain amount of carbon source for the protective expanded carbon layer formed in the flame retardant system, which helps to improve the flame retardant performance.

[0017] 4. PA-ARG, an environmentally friendly, all-biobased flame retardant curing agent, is synthesized by reacting phytic acid and glycine, renewable and widely available bio-based materials. This agent cures flame-retardant coatings while simultaneously improving flame retardancy, addressing the cost associated with the simultaneous addition of both a flame retardant and a curing agent in conventional flame-retardant modification. Furthermore, it can replace ammonium chloride, a commonly used full-halogen curing agent for urea-formaldehyde resins, avoiding the potential hazards of halogen combustion. Furthermore, the use of a fully bio-based flame retardant curing agent can increase the biobased content of the coating and improve its overall degradability.

[0018] In order to achieve the above-mentioned object of the invention, the technical solution adopted by the present invention is:

[0019] A flame-retardant coating based on PA-ARG flame retardant curing agent uses urea and formaldehyde as main raw materials, melamine, KH550 and cellulose powder as auxiliary agents, and phytic acid-glycine phytic acid ammonium salt PA-ARG as a bio-based flame retardant curing agent. The temperature at which the maximum decomposition rate is reached is 290.43°C; and the mass retention at 800°C is 34.58wt.%.

[0020] A method for preparing a flame retardant coating based on a PA-ARG flame retardant curing agent comprises the following steps:

[0021] Step 1, preparation of phytic acid-glycine ammonium phytate salt PA-ARG, first, under certain conditions, PA is dissolved in deionized water to obtain solution A, and stirred under certain conditions to obtain a clear solution B, then glycine is added to solution B to obtain solution C, under certain conditions, solution C is stirred to complete the reaction to obtain solution D, then, under certain conditions, solution D is rotary evaporated and purified to obtain a viscous liquid E, then the viscous liquid E is freeze-dried under certain conditions, and the solid F obtained after drying is crushed and ground into powder to obtain phytic acid-glycine ammonium phytate salt, i.e., PA-ARG.

[0022] In step 1, the mass ratio of PA to deionized water is 22:200;

[0023] In step 1, the mass ratio of ARG and PA is 1:1;

[0024] In step 1, the reaction conditions for preparing PA-ARG are as follows: stirring temperature is room temperature (25° C.) and stirring speed is 300-400 rpm;

[0025] The stirring conditions of solution A are as follows: dissolution temperature is 25°C, dissolution stirring speed is 300-400 rpm, and dissolution stirring time is 5-10 min;

[0026] The stirring conditions of solution C are as follows: temperature of 25°C, stirring speed of 300-400 rpm, and stirring time of 30-40 min;

[0027] The rotary evaporation conditions of solution D were as follows: water bath temperature of 80°C, rotation speed of 30 rpm, and rotary evaporation time of 3 h;

[0028] The freeze-drying conditions of viscous liquid E were as follows: freeze-drying time was 24 h;

[0029] Step 2, preparing a modified urea-formaldehyde resin emulsion MUF, first, adding a sodium hydroxide solution with a mass fraction of 20 wt.% to a formaldehyde solution with a mass fraction of 37 wt.% to adjust the pH value of the solution to obtain a solution G, then, under certain conditions, heating the solution G, and finally, adding raw materials urea, melamine, silane coupling agent KH550, cellulose powder, acetic acid solution, and sodium hydroxide solution to the solution G for stirring and reacting to prepare a modified urea-formaldehyde resin emulsion MUF;

[0030] In step 2, the stirring reaction for preparing MUF is divided into three steps:

[0031] Step 2.1 is, under certain temperature conditions, first, adding the first-stage urea to solution G to obtain solution H, then adding melamine, silane coupling agent KH550 and cellulose powder to solution H, and continuing stirring under certain conditions to obtain solution I;

[0032] Step 2.2 comprises, under certain temperature conditions, first, adding a 20 wt.% acetic acid solution to solution I to adjust the pH of the solution to obtain solution J, then adding the second-stage urea to solution J to obtain solution K, and continuing stirring under certain conditions until the reaction endpoint is reached to obtain solution L;

[0033] Step 2.3 is, under certain temperature conditions, first, adding a 20 wt.% sodium hydroxide solution to solution L to adjust the pH value of the solution to obtain solution M, then adding the third-stage urea to solution M, adjusting the temperature, and stirring solution M under certain conditions to obtain MUF;

[0034] In step 2, the mass ratio of the total mass of formaldehyde solution, urea, melamine, KH550 and cellulose powder is 100:57:0.57:2.85:2.85;

[0035] In step 2, the amount of urea added in the three stages meets the mass ratio of 37:12.4:7.6;

[0036] In step 2, the pH value of the formaldehyde solution is adjusted to 8.0-8.5 by adding sodium hydroxide solution.

[0037] In step 2, the temperature of solution G is raised to 90° C. under a stirring speed of 400 rpm;

[0038] The conditions of step 2.1 are as follows: maintaining the temperature at 90°C and continuing stirring for 30 minutes after the addition is completed;

[0039] The conditions of step 2.2 are as follows: maintaining the temperature at 90°C, adding acetic acid solution to adjust the solution pH to 4.5-5.0, and stirring for 10-15 minutes after the addition of PGL to ensure that the reaction reaches the end point;

[0040] In step 2.2, the reaction endpoint is determined when, after solution L is dropped into water at a temperature of 30°C, solution L becomes a colloid that is insoluble in water.

[0041] The conditions of step 2.3 are as follows: maintaining the temperature at 90°C, adding sodium hydroxide solution to adjust the solution pH to 7.5-8.0, and after the addition of urea, stirring at 70°C for 30 minutes;

[0042] Step 3, preparation of a flame retardant coating FRUF based on a PA-ARG flame retardant curing agent, wherein MUF and the PA-ARG obtained in step 1 meet a certain mass ratio, PA-ARG is added to MUF to obtain a solution N. After the addition is completed, a 20 wt.% sodium hydroxide solution is added to the solution N to adjust the pH value of the solution to obtain a solution O. After the adjustment is completed, mechanical stirring is performed under certain conditions to uniformly mix the components to obtain a flame retardant coating based on a PA-ARG flame retardant curing agent, referred to as FRUF.

[0043] In step 3, the mass ratio of MUF to PA-ARG is 100:2;

[0044] In step 3, after the pH value is adjusted, the pH value of solution O is 4-4.5;

[0045] In step 3, the mechanical stirring conditions of solution O are as follows: a stirring speed of 400-500 rpm and a stirring time of 1-1.5 h.

[0046] A flame retardant coating based on a PA-ARG flame retardant curing agent is used as a flame retardant coating for wood. The flame retardant coating has flame retardant properties. The wood coated with the flame retardant coating passes the UL-94 V-0 rating test in the UL-94 rating test. The wood coated with the flame retardant coating has a limiting oxygen index of 30.2% in the limiting oxygen index test. The wood coated with the flame retardant coating has a maximum heat release rate of 16.97 kW / m in the cone calorimetry test. 2 The total heat release is 1.12MJ / m 2 , the fire growth index is 0.07kW / m 2 / s, and the mass retention of the sample after the test was 72.20wt.%.

[0047] The technical effects of the bio-based wood flame retardant coating obtained by the present invention have been tested as follows:

[0048] The TG test results show that using PA-ARG as a curing agent can increase the temperature at which the material reaches the maximum decomposition rate, that is, improve thermal stability, and at the same time significantly improve the quality retention at high temperatures.

[0049] The results of the vertical burning test show that applying flame retardant coating can improve the UL-94 rating of wood. Using PA-ARG as a curing agent can also improve the UL-94 rating of wood after applying flame retardant coating.

[0050] The results of the limiting oxygen index test show that applying flame retardant coating can significantly improve the limiting oxygen index of wood. Using PA-ARG as a curing agent can also improve the limiting oxygen index of wood after applying flame retardant coating.

[0051] The cone calorimetry test results show that the maximum heat release rate of the wood coated with the bio-based flame retardant coating obtained by the present invention is 16.97kW / m 2 The total heat release is 1.12MJ / m 2 , the fire growth index is 0.07kW / m 2 / s, and the sample's mass retention after the test was 72.20 wt.%. Applying a flame-retardant coating can reduce the wood's maximum heat release rate, total heat release, and fire growth index, increasing the wood's mass retention after the combustion test. Using the bio-based flame retardant curing agent PA-ARG significantly reduces the maximum heat release rate, total heat release, and fire growth index of wood after the flame-retardant coating, increasing the sample's mass retention after the combustion test and reducing the fire hazard.

[0052] Therefore, the green bio-based wood flame retardant coating of the present invention has the following advantages over the prior art:

[0053] 1. The bio-based flame retardant coating prepared by the present invention significantly improves the flame retardant effect on wood, and the wood coated with the flame retardant coating has excellent flame retardant properties;

[0054] 2. The bio-based flame retardant curing agent PA-ARG used in the present invention not only significantly improves the flame retardant properties of flame retardant coatings, but also can replace the use of ammonium chloride, a full-halogen curing agent for urea-formaldehyde resin, eliminating the safety hazards caused by halogen combustion. At the same time, as a fully bio-based additive, it is easily degraded in the environment, does not cause much impact on the environment, and is more environmentally friendly;

[0055] 3. The additives melamine, KH550 and cellulose powder used in the present invention are low-cost and environmentally friendly. The modified urea-formaldehyde resin obtained by optimizing the molecular structure of the urea-formaldehyde resin also has environmentally friendly properties. At the same time, the amount of curing agent used is relatively low. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] Figure 1 This is the FT-IR spectrum of the phytic acid-glycine phytate ammonium salt PA-ARG prepared in Example 1;

[0057] Figure 2 FT-IR images of Example 1, Comparative Example 2, and Example 2;

[0058] Figure 3 TG diagrams of Example 1, Comparative Example 2, and Example 2;

[0059] Figure 4 The figures are comparisons before and after the vertical combustion test of Example 1, Comparative Example 1, Comparative Example 2, and Example 2;

[0060] Figure 5 The cone calorimetry test diagrams of Example 1, Comparative Example 1, Comparative Example 2, and Example 2 are shown in FIG. Figure 5 a is the heat map released during the test, Figure 5 b is the mass change diagram of the sample during the test;

[0061] Figure 6It is a comparison chart before and after cone calorimetry test of Example 1, Comparative Example 1, Comparative Example 2, and Example 2. DETAILED DESCRIPTION

[0062] The present invention is further described in detail through embodiments and in conjunction with the accompanying drawings, but the present invention is not limited thereto.

[0063] Example 1

[0064] A method for preparing a flame retardant coating based on a PA-ARG flame retardant curing agent comprises the following steps:

[0065] Step 1, preparation of phytic acid-glycine phytate ammonium salt PA-ARG, first, at room temperature (25 ° C), 22 g of PA was dissolved in 200 g of deionized water to obtain solution A, then the solution was clarified under mechanical stirring conditions of 400 rpm for 5 minutes to obtain solution B, then 22 g of glycine was added to solution B to obtain solution C, the stirring rate was kept constant, and stirring was continued for 30 minutes to complete the reaction to obtain solution D, and then the obtained solution D was rotary evaporated and purified at a water temperature of 80 ° C for 3 hours to obtain a viscous liquid E. After the rotary evaporation is completed, the obtained viscous liquid E was taken out and freeze-dried for 24 hours by a freeze-drying method. After drying, the obtained solid F was crushed and ground into powder to obtain phytic acid-glycine phytate ammonium salt, namely PA-ARG;

[0066] In order to prove the composition of PA-ARG, i.e., successful synthesis, FT-IR test was performed, and the test results are shown in Figure 4. Figure 1 As shown, PA-ARG contains both characteristic peaks belonging to ARG and characteristic peaks belonging to PA. The test results show that PA-ARG was successfully synthesized;

[0067] Step 2, preparation of modified urea-formaldehyde resin emulsion MUF, first, adding a 20 wt.% sodium hydroxide solution to 100 g of a 37 wt.% formaldehyde solution to adjust the pH of the solution to 8.0-8.5 to obtain solution G, then heating solution G to 90° C. at a stirring speed of 400 rpm, and finally adding raw materials urea, melamine, silane coupling agent KH550, cellulose powder, acetic acid solution, and sodium hydroxide solution to solution G for stirring and reaction to prepare modified urea-formaldehyde resin emulsion MUF;

[0068] In step 2, the stirring reaction for preparing MUF is divided into three steps:

[0069] Step 2.1 is to first add 37 g of urea to solution F while maintaining the temperature at 90° C. to obtain solution H. Then, 0.57 g of melamine, 2.85 g of silane coupling agent KH550, and 2.85 g of cellulose powder are added to solution H, and stirring is continued for 30 minutes to obtain solution I.

[0070] Step 2.2 is, while maintaining the temperature at 90°C, first, adding 20 wt.% acetic acid solution to solution I to adjust the pH of the solution to 4.5-5.0 to obtain solution J, then adding 12.4 g of urea to solution J to obtain solution K, and continuing stirring for 10 minutes until the reaction reaches the endpoint to obtain solution L;

[0071] In step 2.2, the reaction endpoint is determined when, after solution L is dropped into water at a temperature of 30°C, solution L becomes a colloid that is insoluble in water.

[0072] Step 2.3 is to first add a 20 wt.% sodium hydroxide solution to solution L while maintaining the temperature at 90°C to adjust the pH of the solution to 7.5-8.0 to obtain solution M. Then, 7.6 g of urea is added to solution M, and the temperature is adjusted. Solution M is stirred at a stirring temperature of 70°C and a stirring time of 30 minutes to obtain MUF.

[0073] Step 3, preparation of a flame retardant coating FRUF based on a PA-ARG flame retardant curing agent, with a mass ratio of MUF to PA-ARG obtained in step 1 of 100:2, adding 2 g of PA-ARG to 100 g of MUF obtained in step 2 to obtain a solution N. After the addition is completed, a 20 wt.% sodium hydroxide solution is added to the solution N to adjust the pH value of the solution to 4.0-4.5 to obtain a solution O. Subsequently, mechanical stirring is performed at a stirring speed of 400 rpm and a stirring time of 1 h to uniformly mix the components to obtain a flame retardant coating based on a PA-ARG flame retardant curing agent, referred to as FRUF. The FRUF prepared in specific Example 1 is referred to as FRUF-2.

[0074] In order to prove the composition of FRUF-2, FT-IR test was carried out, and the test results are as follows Figure 2 As shown in the figure, FRUF-2 contains characteristic peaks of pure urea-formaldehyde resin UF and PA-ARG. The test results show that PA-ARG has successfully infiltrated FRUF-2.

[0075] In order to prove the thermal stability of FRUF-2 and the high quality retention at high temperature, TG test was carried out. The test results are as follows: Figure 3As shown in Table 1, the temperature at which FRUF-2 reaches the maximum decomposition rate is 290.43°C, and the mass retention at 800°C is 34.58 wt.%. The test results show that the high peak decomposition temperature indicates that FRUF-2 has high thermal stability and also has high mass retention at high temperatures.

[0076] Table 1 Thermogravimetric test results

[0077]

[0078]

[0079] In order to demonstrate the technical effect of FRUF as a wood flame retardant coating, FRUF was coated on the wood surface to prepare the flame retardant wood FRUFW for flame retardant testing.

[0080] The specific preparation method of FRUFW is to coat FRUF on the wood surface with a coating thickness of 0.3 mm. After coating, the coating is dried under the condition of a drying time of 24 hours to obtain FRUFW. The FRUFW prepared based on FRUF-2 in Example 1 is named FRUFW-2.

[0081] In order to further prove the flame retardant performance of FRUFW-2, vertical burning test and limiting oxygen index test were carried out. Figure 4 As shown in Table 2, FRUFW-2 passed the UL-94 V-0 rating test after a vertical combustion test, with only slight burns at the bottom. Furthermore, the limiting oxygen index of FRUFW-2 was as high as 30.2%. These test results demonstrate FRUFW-2's excellent flame retardancy.

[0082] Table 2 Vertical combustion test and oxygen index test results

[0083]

[0084] In order to further prove the flame retardant performance of FRUFW-2 under real combustion conditions, cone calorimetry test was carried out. Figure 5 、 Figure 6 As shown in Table 3, the maximum heat release rate of FRUFW-2 is 16.97kW / m 2 The total heat release is 1.12MJ / m 2 , the fire growth index is 0.07kW / m 2 / s, and the sample's mass retention after the test was 72.20 wt.%. An expanded char layer appeared on the surface of the FRUFW-2 after the test. The test results indicate that the low fire growth index indicates that FRUFW-2 has a low fire hazard, indicating that FRUFW-2 has excellent flame retardant properties. The formation of the expanded char layer demonstrates that FRUFW-2's excellent flame retardancy is due to the flame-retardant coating on the surface forming a spatial barrier effect during combustion, isolating the heat and oxygen generated during combustion, thereby protecting the wood substrate and improving flame retardancy.

[0085] Table 3 Cone calorimetry test results

[0086]

[0087]

[0088] In order to demonstrate the effect of the flame retardant coating FRUF-2 on the flame retardant properties of wood, a comparative example 1 is provided, which is pure wood not coated with FRUF.

[0089] Comparative Example 1

[0090] A pure wood that is not coated with FRUF, referred to as pure wood.

[0091] The results of vertical burning test and limiting oxygen index test of pure wood are as follows Figure 4 As shown in Table 2, in the vertical burning test, the pure wood burned completely and failed the UL-94 rating test, and its limiting oxygen index was 18.7%.

[0092] Compared with Example 1, it can be seen that coating with FRUF-2 improves the UL-94 grade of wood from failing the test to V-0 grade, and significantly increases the limiting oxygen index from 18.7% to 30.2%, an increase of 161.49%. That is, the test results show that FRUF-2 significantly improves the flame retardant properties of FRUFW.

[0093] The cone calorimetry test results of pure wood are as follows Figure 5 、 Figure 6 As shown in Table 3, in the cone calorimetry test, the maximum heat release rate of pure wood is 195.35kW / m 2 The total heat release is 11.31MJ / m 2 The fire growth index is 1.67kW / m 2 / s, and the mass retention of the sample after the test was 24.10wt.%, and it was almost completely burned after the test.

[0094] Compared to Example 1, coating with FRUF-2 reduced the maximum heat release rate of the flame-retardant wood by 91.31%, the total heat release by 90.10%, the fire growth index by 95.81%, and the mass retention by 48.10 wt.%. A dense, expanded char layer formed on the surface after combustion. These test results demonstrate that coating with FRUF-2 creates a spatial barrier effect on the surface of the flame-retardant wood during real-world combustion, isolating the heat and oxygen generated by combustion from the wood matrix. This significantly improves flame retardancy, reduces fire hazard, and increases wood mass retention.

[0095] In order to demonstrate the effect of flame retardant curing agent PA-ARG on the performance of flame retardant coating FRUF and flame retardant wood FRUFW, comparative example 2 is provided, in which PA-ARG is not used as curing agent, but conventional coating is prepared using commercial curing agent ammonium chloride as curing agent.

[0096] Comparative Example 2

[0097] A method for preparing a flame-retardant coating based on ammonium chloride curing agent, wherein the steps not otherwise specified are the same as those in Example 1, except that step 1 is not required, and in step 3, ammonium chloride is used instead of PA-ARG. The obtained flame-retardant coating is named FRUF-0, and the obtained flame-retardant wood is named FRUFW-0.

[0098] The TG test results of FRUF-0 are as follows Figure 3 As shown in Table 1, the temperature at which FRUF-0 reaches the maximum decomposition rate is 247.16°C, and the mass retention at 800°C is 19.93 wt.%.

[0099] Compared with Example 1, the use of PA-ARG as a curing agent can increase the temperature at which the maximum decomposition rate is reached by 43.27°C and the mass retention at 800°C by 14.65 wt.%. This proves that the use of PA-ARG as a curing agent can improve the thermal stability of FRUF and significantly improve the mass retention of FRUF at high temperatures.

[0100] The vertical combustion test and limiting oxygen index test results of FRUFW-0 are as follows Figure 4 As shown in Table 2, in the vertical burning test, FRUFW-0 passed the UL-94V-1 rating test with a limiting oxygen index of 27.7%.

[0101] Compared with Comparative Example 1, it can be seen that applying conventional flame retardant coating can only improve the UL-94 grade of wood from failing the test to V-1 grade, but cannot reach V-0 grade, and increase the limiting oxygen index by 9%.

[0102] Compared with Example 1, it can be seen that the use of PA-ARG as a curing agent can improve the UL-94 grade from V-1 to V-0, and can increase the limiting oxygen index of FRUFW-2 by 2.5%. This proves that the use of PA-ARG as a curing agent can improve the UL-94 grade and limiting oxygen index, thereby improving the flame retardant properties.

[0103] The cone calorimetry test results of FRUFW-0 are as follows: Figure 5 、 Figure 6 As shown in Table 3, in the cone calorimetry test, the maximum heat release rate of FRUFW-0 is 70.2kW / m 2 The total heat release is 1.67MJ / m 2 , the fire growth index is 1.01kW / m 2 / s, and the mass retention of the sample after the test was 63.54wt.%. The cracks in the expanded carbon layer on the surface of FRUFW-0 were large and numerous, and the quality of the expanded carbon layer was poor.

[0104] Compared with Comparative Example 1, applying a conventional flame-retardant coating with a V-1 rating reduced the maximum heat release rate of wood by 63.85%, the total heat release by 85.23%, the fire growth index by 39.52%, and the mass retention by 39.44 wt.%. However, the maximum heat release rate, total heat release, and fire growth index still did not meet the application requirements.

[0105] Compared with Example 1, the use of PA-ARG as a curing agent can reduce the maximum heat release rate of flame-retardant wood by 75.96%, the total heat release by 32.93%, the fire growth index by 93.07%, and the mass retention by 8.66 wt.%. The resulting expanded char layer is taller and more dense. Test results show that the use of PA-ARG as a curing agent can result in a taller, higher-quality, and more robust spatial barrier effect of the expanded char layer formed by flame-retardant wood in real combustion conditions, significantly improving flame retardancy, significantly reducing fire hazard, and increasing wood mass retention.

[0106] In order to demonstrate the effect of the addition amount of PA-ARG on the performance of the flame retardant coating FRUF and the flame retardant wood FRUFW, Example 2 is provided, in which the flame retardant coating has a PA-ARG addition amount of 1 wt.%.

[0107] Example 2

[0108] A method for preparing FRUF with a PA-ARG addition amount of 1 wt.%, wherein the steps are the same as those in Example 1 unless otherwise specified, except that in step 3, the mass of PA-ARG is 1 wt.% of MUF, i.e., 1 g of PA-ARG. The obtained bio-based flame retardant coating is named FRUF-1, and the obtained flame retardant wood is named FRUFW-1.

[0109] The TG test results of FRUF-1 are as follows Figure 3 As shown in Table 1, the temperature at which FRUF-1 reaches the maximum decomposition rate is 275.44°C, and the mass retention at 800°C is 26.75 wt.%.

[0110] Compared with Example 1, increasing the amount of PA-ARG by 1 wt.% increases the temperature at which the maximum decomposition rate is reached by 14.99°C and improves the mass retention at 800°C by 7.83 wt.%. These test results demonstrate that increasing the amount of PA-ARG increases the temperature at which the FRUF reaches its maximum decomposition rate, thereby improving its thermal stability, while also increasing the FRUF's mass retention at high temperatures.

[0111] The vertical combustion test and limiting oxygen index test results of FRUFW-1 are as follows Figure 4 As shown in Table 2, in the vertical burning test, FRUFW-1 passed the UL-94 V-0 rating test with a limiting oxygen index of 28.6%.

[0112] Compared with Example 1, increasing the amount of PA-ARG by 1 wt.% does not affect the UL-94 rating, but does increase the limiting oxygen index by 1.6%. The test results show that increasing the amount of PA-ARG does not affect the UL-94 rating of FRUFW, but does improve its limiting oxygen index, thereby enhancing its flame retardancy.

[0113] The cone calorimetry test results of FRUFW-1 are as follows Figure 5 、 Figure 6 As shown in Table 3, in the cone calorimetry test, the maximum heat release rate of FRUFW-1 is 62.30kW / m 2 The total heat release is 1.41MJ / m 2 The fire growth index is 0.98kW / m 2 / s, and the mass retention of the sample after the test was 64.44wt.%. The expanded carbon layer on the surface of FRUFW-1 contained some cracks, and the expansion height was low, and the quality of the expanded carbon layer was average.

[0114] Compared with Example 1, adding 1 wt.% PA-ARG reduced the maximum heat release rate of the flame-retardant wood by 72.76%, the total heat release by 20.57%, the fire growth index by 92.85%, and the mass retention by 7.76 wt.%. The resulting expanded char layer was taller and of better quality. Test results show that adding 1 wt.% PA-ARG can result in a taller, higher-quality expanded char layer formed in flame-retardant wood under real combustion conditions, with a stronger spatial barrier effect, significantly improving flame retardancy and reducing fire hazard.

[0115] Through Comparative Example 1, Comparative Example 2, Example 1, and Example 2, the following conclusions can be obtained:

[0116] 1. The flame retardant properties of FRUFW coated with FRUF are greatly improved compared to uncoated pure wood. The flame retardant coating can form a dense expanded carbon layer on the wood surface during combustion, forming a spatial barrier effect, isolating the contact between heat, oxygen and the wood matrix during combustion, thereby effectively improving the flammability of wood and making the wood have high flame retardant properties;

[0117] 2. Using PA-ARG as a fully bio-based flame retardant curing agent can effectively improve the flame retardant properties of FRUFW. As its content increases, the flame retardant properties of FRUFW will also improve. In addition, the increase in its content will improve the thermal stability of FRUF.

Claims

1. A flame retardant coating based on PA-ARG flame retardant curing agent, characterized by: The main raw materials are urea and formaldehyde, melamine, KH550 and cellulose powder are auxiliary agents, and phytic acid-glycine salt PA-ARG is a bio-based flame retardant curing agent.

2. The flame retardant coating based on PA-ARG flame retardant curing agent according to claim 1, characterized in that: The temperature at which the decomposition rate reaches the maximum is 290.43°C; and the mass retention at 800°C is 34.58 wt.%.

3. A method for preparing a flame retardant coating based on PA-ARG flame retardant curing agent, characterized in that The following steps are involved: Step 1, preparation of phytic acid-glycine ammonium phytate salt PA-ARG, first, under certain conditions, PA is dissolved in deionized water to obtain solution A, and stirred under certain conditions to obtain a clear solution B, then glycine is added to solution B to obtain solution C, under certain conditions, solution C is stirred to complete the reaction to obtain solution D, then, under certain conditions, solution D is rotary evaporated and purified to obtain a viscous liquid E, then the viscous liquid E is freeze-dried under certain conditions, and the solid F obtained after drying is crushed and ground into powder to obtain phytic acid-glycine ammonium phytate salt, i.e., PA-ARG; Step 2, preparing a modified urea-formaldehyde resin emulsion MUF, first, adding a sodium hydroxide solution with a mass fraction of 20 wt.% to a formaldehyde solution with a mass fraction of 37 wt.% to adjust the pH value of the solution to obtain a solution G, then, under certain conditions, heating the solution G, and finally, adding raw materials urea, melamine, silane coupling agent KH550, cellulose powder, acetic acid solution, and sodium hydroxide solution to the solution G for stirring and reacting to prepare a modified urea-formaldehyde resin emulsion MUF; In step 2, the stirring reaction for preparing MUF is divided into three steps: Step 2.1 is, under certain temperature conditions, first, adding the first-stage urea to solution G to obtain solution H, then adding melamine, silane coupling agent KH550 and cellulose powder to solution H, and continuing stirring under certain conditions to obtain solution I; Step 2.2 comprises, under certain temperature conditions, first, adding a 20 wt.% acetic acid solution to solution I to adjust the pH of the solution to obtain solution J, then adding the second-stage urea to solution J to obtain solution K, and continuing stirring under certain conditions until the reaction endpoint is reached to obtain solution L; Step 2.3 is, under certain temperature conditions, first, adding a 20 wt.% sodium hydroxide solution to solution L to adjust the pH value of the solution to obtain solution M, then adding the third-stage urea to solution M, adjusting the temperature, and stirring solution M under certain conditions to obtain MUF; Step 3, preparation of a flame retardant coating FRUF based on a PA-ARG flame retardant curing agent, wherein MUF and the PA-ARG obtained in step 1 satisfy a certain mass ratio, PA-ARG is added to MUF to obtain a solution N. After the addition is completed, a 20 wt.% sodium hydroxide solution is added to the solution N to adjust the pH value of the solution to obtain a solution O. After the adjustment is completed, mechanical stirring is performed under certain conditions to uniformly mix the components to obtain a flame retardant coating based on a PA-ARG flame retardant curing agent, referred to as FRUF.

4. The preparation method according to claim 3, wherein: In step 1, the mass ratio of PA to deionized water is 1:

1. In step 1, the mass ratio of ARG and PA is 1:1; In step 2, the mass ratio of the total mass of formaldehyde solution, urea, melamine, KH550 and cellulose powder is 100:57:0.57:2.85:2.85; In step 2, the amount of urea added in the three stages meets the mass ratio of 37:12.4:7.6; In step 3, the mass ratio of MUF to PA-ARG is 100:

2.

5. The preparation method according to claim 3, wherein: In step 1, the reaction conditions for preparing PA-ARG are as follows: stirring temperature is room temperature (25° C.) and stirring speed is 400 rpm; The stirring conditions of solution A are as follows: dissolution temperature is 25°C, dissolution stirring speed is 300-400 rpm, and dissolution stirring time is 5-10 min; The stirring conditions of solution C are as follows: temperature of 25°C, stirring speed of 300-400 rpm, and stirring time of 30-40 min; The rotary evaporation conditions of solution D were as follows: water bath temperature of 80°C, rotation speed of 30 rpm, and rotary evaporation time of 3 h; The freeze-drying conditions of the viscous liquid E are as follows: the freeze-drying time is 24 h.

6. The preparation method according to claim 3, wherein: In step 2, the pH value of the formaldehyde solution is adjusted to 8.0-8.5 by adding sodium hydroxide solution. In step 2, the temperature of solution G is raised to 90° C. under a stirring speed of 400 rpm; The conditions of step 2.1 are as follows: maintaining the temperature at 90°C and continuing stirring for 30 minutes after the addition is completed; The conditions of step 2.2 are as follows: maintaining the temperature at 90°C, adding acetic acid solution to adjust the solution pH to 4.5-5.0, and stirring for 10-15 minutes after the addition of PGL to ensure that the reaction reaches the end point; In step 2.2, the reaction endpoint is determined when, after solution L is dropped into water at a temperature of 30°C, solution L becomes a colloid that is insoluble in water. The conditions of step 2.3 are as follows: maintaining the temperature at 90° C., adding sodium hydroxide solution to adjust the solution pH to 7.5-8.0, and after the addition of urea, stirring at 70° C. for 30 minutes.

7. The preparation method according to claim 3, wherein: In step 3, after the pH value is adjusted, the pH value of solution O is 4-4.5; In step 3, the mechanical stirring conditions of solution O are as follows: a stirring speed of 400-500 rpm and a stirring time of 1-1.5 h.

8. Application of a flame retardant coating based on PA-ARG flame retardant curing agent as a wood flame retardant coating, characterized in that: The wood coated with the flame retardant coating has flame retardant properties and passes the UL-94V-0 test in the UL-94 rating test.

9. Application of a flame retardant coating based on PA-ARG flame retardant curing agent as a wood flame retardant coating, characterized in that: The wood coated with flame retardant coating has a limiting oxygen index of 30.2% in the limiting oxygen index test.

10. A bio-based flame retardant coating based on PA-ARG, characterized by: When used as a wood flame retardant coating, the wood coated with the flame retardant coating has a maximum heat release rate of 16.97kW / m in the cone calorimetry test. 2 The total heat release is 1.12MJ / m 2 , the fire growth index is 0.07kW / m 2 / s, and the mass retention of the sample after the test was 72.20wt.%.

Images