A urea-formaldehyde resin blended guanzo-phytic acid-copper flame-retardant resin coating material, a preparation method and application thereof

Abstract

The application discloses a urea-formaldehyde resin blended guanazole-phytic acid-copper flame-retardant resin coating, which is prepared from a GZ / PA / Cu flame retardant, urea and formaldehyde as main raw materials, DOP as a plasticizer and TA as a curing agent through three-stage reaction to obtain UF-GZ / PA / Cu; the raw materials of the GZ / PA / Cu flame retardant include GZ, PA and copper source as bio-based flame-retardant components; the UF-GZ / PA / Cu has a decomposition temperature of 195.5±2.1 DEG C, a temperature of maximum decomposition rate of 300.6±1.5 DEG C and a residual carbon content of 29.8±2.5 wt.%; and a dense residual carbon carbon layer can be formed. The preparation method comprises the following steps: 1, preparation of the GZ / PA / Cu flame retardant; 2, preparation of modified urea-formaldehyde resin emulsion UF; and when applied as a wood flame-retardant coating, UL-94 V-0 level test is passed; and the heat release rate HRR is 25.38±1.25 kW / m 2 .

Description

TECHNICAL FIELD

[0001] The present application relates to the field of flame-retardant materials, in particular to a urea-formaldehyde resin blended guanzole-phytic acid-copper flame-retardant resin coating and a preparation method and application thereof. BACKGROUND

[0002] Wood is widely used in our daily life, but wood has high flammability. In order to solve the problem of flammability of wood, a flame-retardant coating can be coated on the surface of wood to make the surface layer of wood produce a dense carbon layer when heated, thereby achieving the purpose of flame retardation. The common flame retardants are divided into two categories: additive flame retardants and reactive flame retardants. Among them, the additive flame retardant has the advantages of simple use and wide application range because of the method of directly adding flame retardant. Among the commonly used additive flame retardants, halogen-containing flame retardants have good flame-retardant effect, but such flame retardants have the problem of generating toxic substances when heated, thereby causing environmental pollution. The common solution is to replace halogen-containing flame retardants with phosphorus-containing flame retardants. The bio-based flame retardant in the phosphorus-containing flame retardant, for example, the bio-based flame retardant based on phytic acid, although the flame-retardant performance cannot reach the flame-retardant effect of halogen-containing flame retardants, but has the characteristics of low toxicity and green environmental protection.

[0003] In order to improve the flame-retardant performance of bio-based flame retardants, metal elements can be introduced into phytic acid to improve the flame-retardant performance. For example, existing document 1 (Experimental study on the synergistic flame retardanteffect of bio-based magnesium phytate and rice husk ash on epoxy resins[J].Journal of Thermal Analysis and Calorimetry,2021,146(1):153-164) synthesizes magnesium phytate flame retardant through a simple complexation reaction. The peak heat release rate of the epoxy resin added with 5% magnesium phytate flame retardant is only reduced by 28.6%, the LOI value is only 22.2%, and the residual carbon content at 800℃ is 19.69wt.%. The problem of this technical solution is that there are many pores on the surface of the carbon layer formed after combustion, that is, a dense residual carbon carbon layer cannot be formed. The reason is that the complex formed by magnesium and phytic acid has poor compatibility and dispersibility, thereby resulting in poor quality of the formed carbon layer.

[0004] Such Mg element-based flame retardants also have Prior Literature 2 (A novel bio-based charcoal-forming agent based on chitosan and phytate@mg to improve the flameretardancy of poly(lactic acid[J].Journal of Applied Polymer Science, 2024, 141(11): e55074) by synthesizing Mg@PA-CS flame retardant, the carbon residue rate is only 11.48wt.% at 800℃, and the LOI value is 34%. This technical solution also has the technical problem of being unable to form a dense carbon layer of residual carbon.

[0005] It can be confirmed from Prior Literature 1 and Prior Literature 2 that the introduction of metal elements in phytic acid can improve the flame retardant performance, but the type of metal elements will have the problem of poor compatibility and dispersibility due to the nature of the resulting phytic acid complex.

[0006] In order to solve the above-mentioned problems of Mg element-based flame retardants, other metal elements can be introduced to improve the flame retardant performance. For example, Prior Literature 3 (Rigid polyurethane foam composites based on bivalent metal phytate: thermal stability, flame retardancy, and fire toxicity[J]. Polymer-Plastics Technology and Materials, 2022, 61(11): 1204-1222) by synthesizing phytic acid copper and other phytic acid metal salt flame retardants, the carbon residue of phytic acid copper flame retardant at 700℃ is 26.2wt.%. The carbon layer formed after the combustion of the phytic acid copper flame retardant is dense and almost has no pores, so better flame retardant performance than Prior Literature 2 and Prior Literature 3 is obtained. The reason is that, compared with magnesium element, Cu element has stronger binding force with PA functional group, which is specifically reflected in Cu 2+ ions have stronger binding affinity, biocompatibility and ion dispersibility. However, this technical solution has the problem that the addition amount of phytic acid copper flame retardant needs to reach 30wt.% to obtain the flame retardant performance that meets the application requirements, that is, the problem of too large addition amount. SUMMARY

[0007] The purpose of the present application is to provide a urea-formaldehyde resin blended guanazole-phytic acid-copper flame retardant resin coating and its preparation method and application. According to the research of the inventors, the existing technology has the problem of excessive addition amount of phytic acid copper flame retardant, and the reason is that although the phytic acid copper flame retardant can promote the formation of a dense residual carbon layer during the combustion process, its own flame retardant performance is poor, so it cannot effectively improve the final flame retardant effect. Based on the above reasons, the inventors found that by introducing a nitrogen source and forming a synergistic effect with the phytic acid copper flame retardant, the flame retardant performance can be significantly improved, thereby greatly reducing the addition amount of the flame retardant while maintaining the flame retardant performance.

[0008] The specific invention idea is to introduce 3,5-diamino-1,2,4-triazole GZ containing amino groups as a nitrogen source, combine phytic acid PA and copper hydroxide Cu(OH)2, and prepare GZ / PA / Cu flame retardant through reaction; then, the GZ / PA / Cu flame retardant is added to the urea-formaldehyde resin, and tannic acid TA is used as a curing agent, and dioctyl phthalate is used as a plasticizer to prepare a bio-based flame retardant resin coating. The functions of each component in the technical solution are as follows:

[0009] 1. By introducing nitrogen-containing compounds, the flame retardant properties of phytic acid copper are significantly improved;

[0010] 2. By adjusting the preparation process, i.e. adding GZ / PA / Cu flame retardant in the acid stage of synthetic resin, the compatibility and dispersibility of the flame retardant are significantly improved;

[0011] 3. Using tannic acid TA as a curing agent not only has the effect of adjusting the curing speed of urea-formaldehyde resin, but also has the effect of improving the flame retardant properties of the matrix, and obtaining improved thermal insulation and heat preservation properties of the substrate;

[0012] 4. Using dioctyl phthalate as a plasticizer can effectively prevent cracking of urea-formaldehyde resin during the curing process, providing a uniform and dense matrix for subsequent formation of a dense residual carbon layer.

[0013] In order to achieve the above invention purposes, the technical solution adopted by the present application is as follows:

[0014] A urea-formaldehyde resin blended guanazole-phytic acid-copper flame retardant resin coating is prepared by using guanazole-phytic acid-copper flame retardant GZ / PA / Cu, combining urea and formaldehyde as main raw materials, using dioctyl phthalate DOP as a plasticizer, and using tannic acid TA as a curing agent, and through three-stage reaction, the urea-formaldehyde resin blended guanazole-phytic acid-copper flame retardant resin coating UF-GZ / PA / Cu is prepared;

[0015] The GZ / PA / Cu is prepared by using 3,5-diamino-1,2,4-triazole GZ, phytic acid PA and copper source as bio-based flame retardant components as raw materials through complexation reaction;

[0016] The obtained GZ / PA / Cu comprises Cu4O(PO4)2, CuO, -NH2, P=O and O-P-C;

[0017] The UF-GZ / PA / Cu has a temperature of 195.5±2.1℃ at a mass loss of 5%, a temperature of 300.6±1.5℃ at a maximum decomposition rate, and a carbon residue of 29.8±2.5wt.% at 800℃;

[0018] A dense carbon residue carbon layer is formed when the addition amount of GZ / PA / Cu is 1wt.%.

[0019] A preparation method of a urea-formaldehyde resin blended guanazole-phytic acid-copper flame-retardant resin coating, comprising the following steps:

[0020] Step 1, preparation of GZ / PA / Cu flame retardant, first, 3,5-diamino-1,2,4-triazole GZ is dissolved in water to obtain a GZ solution, then under certain conditions, the phytic acid PA solution is added dropwise into the GZ solution to obtain a GZ / PA solution, finally, under certain conditions, copper hydroxide is added to the GZ / PA solution for reaction, after the reaction is completed, the obtained product is filtered, washed, dried, and ground into powder to obtain a guanazole-phytic acid-copper flame retardant, abbreviated as GZ / PA / Cu;

[0021] The washing condition is that the pH of the washing liquid is 5.0-6.0;

[0022] The drying condition is that the drying temperature is 80℃ and the drying time is 24h;

[0023] In step 1, the mass ratio of GZ, PA and Cu(OH)2 is 1:6:1;

[0024] In step 1, the preparation condition of GZ / PA solution is that the stirring temperature is 70℃, the stirring speed is 500-600rpm, the stirring time is 30min, and the dropwise adding rate is 0.5 drop / s;

[0025] In step 1, the reaction condition is that the reaction temperature is 90℃ and the reaction time is 3h;

[0026] Step 2, preparation of modified urea-formaldehyde resin emulsion UF, first, a certain amount of sodium hydroxide solution is added to the formaldehyde solution to adjust the pH value of the solution to obtain solution A, then under certain conditions, urea, GZ / PA / Cu and other raw materials are added in three stages to prepare a urea-formaldehyde resin blended guanazole-phytic acid-copper flame-retardant resin coating, abbreviated as UF-GZ / PA / Cu,

[0027] In step 2, the mass ratio of the total amount of GZ / PA / Cu, formaldehyde and urea added in step 1 is 1:100:57.

[0028] In step 2, the conditions for preparing solution A are as follows: the pH value of the solution is adjusted to 8.0-8.5;

[0029] In step 2, the conditions for adding urea are: stirring speed of 400-500 rpm and reaction temperature of 90℃.

[0030] In step 2, the three stages of adding urea are as follows:

[0031] Step 2.1 involves adding the first stage of urea while maintaining a certain temperature. After the addition is complete, stirring is continued for a certain period of time.

[0032] In step 2.1, the amount of urea added is 64.9% of the total urea, the temperature in step 2.1 is 90℃, and the stirring time is 30 minutes.

[0033] Step 2.2 involves first adding acetic acid solution to adjust the pH value of the solution while maintaining a certain temperature, then adding the second-stage urea, and finally adding GZ / PA / Cu. After the addition is complete, continue stirring for a certain period of time until the reaction endpoint is reached.

[0034] The endpoint of the second stage reaction is determined by dropping a drop of the solution into water at 30°C; the solution will solidify and not disperse in the water.

[0035] In step 2.2, the amount of urea added is 21.6% of the total amount of urea, the pH of the solution is adjusted to 4.5-5.0, the temperature in step 2.2 is 90℃, and the stirring time is 15min.

[0036] Step 2.3 involves first adjusting the pH value by adding sodium hydroxide solution while maintaining a certain temperature, then adding urea in the third stage. After the addition is complete, the mixture is stirred under the specified conditions to obtain UF-GZ / PA / Cu.

[0037] In step 2.3, the amount of urea added is 13.3% of the total amount of urea, the pH of the solution is adjusted to 7.5-8.0, the temperature in step 2.2 is 90℃ when adjusting the pH, and after the pH is adjusted, the temperature is adjusted to 70℃, and the stirring time is 30-40 minutes.

[0038] The application of a urea-formaldehyde resin blended guanazole-phytic acid-copper flame-retardant resin coating as a wood flame-retardant coating has flame-retardant properties and can form a continuous and dense residual carbon layer after burning; in UL-94 level testing, it passes the UL-94 V-0 level testing; in the cone calorimeter test, the heat release rate HRR is 25.38±1.25kW / m 2 .

[0039] The technical effects of the urea-formaldehyde resin blended guanazole-phytic acid-copper flame-retardant resin coating obtained by the application are as follows:

[0040] The TG test results show that when the UF-GZ / PA / Cu decomposition mass is 5%, the temperature is 195.5±2.1℃, the temperature at the maximum decomposition rate is 300.6±1.5℃, and the residual carbon content at 800℃ is 29.8±2.5wt.%. The addition of GZ / PA / Cu can improve the residual carbon rate of the material, and a more stable residual carbon layer is generated in the high temperature region.

[0041] Further SEM testing of the expanded carbon layer formed on the surface of the NW after burning after coating the UF-GZ / PA / Cu flame-retardant coating. UF-GZ / PA / Cu can form a dense carbon layer, and there are almost no holes. The test results show that UF-GZ / PA / Cu can form a high-quality residual carbon layer after burning, which can achieve the effect of isolating oxygen and heat, thereby improving the flame-retardant performance of NW.

[0042] The vertical burning test shows that the NW coated with the UF-GZ / PA / Cu flame-retardant coating passes the UL-94 V-0 level.

[0043] The limiting oxygen index test shows that the UF-GZ / PA / Cu flame-retardant coating can improve its limiting oxygen index, and the LOI reaches 32.0%.

[0044] The cone calorimeter test results show that the wood coated with the UF-GZ / PA / Cu flame-retardant coating has a heat release rate of 25.38±1.25%, which can significantly reduce the heat release rate of NW.

[0045] Therefore, the bio-based flame-retardant urea-formaldehyde resin of the application has the following advantages over the prior art:

[0046] 1. The bio-based flame-retardant resin coating of the application significantly improves the flame-retardant performance while greatly reducing the addition amount, specifically, the addition amount of the GZ / PA / Cu flame retardant of the application is only 1wt.%, while the addition amount of the prior art (existing document 3) is 30wt.%.

[0047] 2. All raw materials involved in this invention are commercially available and are low-cost, thus meeting the application requirements for large-scale production. Attached Figure Description

[0048] Figure 1 The XRD patterns are of Example 1, Comparative Example 4, Comparative Example 5 and Comparative Example 6;

[0049] Figure 2 FT-IR plots of Example 1, Comparative Example 4, Comparative Example 5, and Comparative Example 6;

[0050] Figure 3 FT-IR plots of Example 1, Comparative Example 4, Comparative Example 5, and Comparative Example 6;

[0051] Figure 4 EDS diagram of Example 1;

[0052] Figure 5 The TG plots are for Example 1, Comparative Example 4, Comparative Example 5, and Comparative Example 6.

[0053] Figure 6 This is a SEM image of Example 1;

[0054] Figure 7 The figures show vertical combustion test results for Example 1, Comparative Example 2, and Example 2.

[0055] Figure 8 HRR plots for Example 1, Comparative Example 4, Comparative Example 5, and Comparative Example 6;

[0056] Figure 9 This is the SEM image of Comparative Example 1;

[0057] Figure 10 This is the SEM image of Comparative Example 2;

[0058] Figure 11 The TG plot is for Comparative Example 3;

[0059] Figure 12 The EDS plot is shown in Comparative Example 4;

[0060] Figure 13 The SEN plot is shown in Comparative Example 4;

[0061] Figure 14 This is the EDS plot for Comparative Example 5;

[0062] Figure 15 This is the SEM image of Comparative Example 5;

[0063] Figure 16 The EDS plot is shown in Comparative Example 6;

[0064] Figure 17 This is the SEM image of Comparative Example 6. DETAILED DESCRIPTION

[0065] The present application is further described in detail by the embodiments, combined with the drawings of the specification, but is not limited to the present application.

[0066] Example 1

[0067] A preparation method of a urea-formaldehyde resin blended guanazole-phytic acid-copper flame retardant resin coating, comprising the following steps:

[0068] Step 1, preparation of GZ / PA / Cu flame retardant, first, 4.459g of 3,5-diamino-1,2,4-triazole GZ is dissolved in 150mL of water to obtain a GZ solution, then, under the conditions of stirring temperature of 70℃, stirring speed of 600rpm, stirring time of 30min, and dropwise adding rate of 0.5 drops / s, 14.25mL of 37wt.% phytic acid PA solution is added dropwise into the GZ solution to obtain a GZ / PA solution, finally, under the conditions of reaction temperature of 90℃ and reaction time of 3h, 8.664g of copper hydroxide is added into the GZ / PA solution for reaction, after the reaction is completed, the obtained product is filtered, washed, dried, and ground into powder to obtain a guanazole-phytic acid-copper flame retardant, abbreviated as GZ / PA / Cu;

[0069] The washing conditions are that the pH of the washing liquid is 5-6;

[0070] The drying conditions are that the drying temperature is 80℃ and the drying time is 24h;

[0071] In order to prove the composition of GZ / PA / Cu, i.e. successful synthesis, XRD test is carried out. The test results are shown in Figure 1 It is shown that GZ / PA / Cu contains characteristic peaks of Cu4O(PO4)2 and CuO at the same time. The test results show that the Cu element is successfully complexed with PA.

[0072] In order to prove the composition of GZ / PA / Cu, i.e. successful synthesis, FT-IR test is carried out. The test results are shown in Figure 2 It is shown that GZ / PA / Cu contains characteristic peaks of -NH2, P=O and O-P-C at the same time, wherein the characteristic peak of -NH2 belongs to GZ, and the characteristic peaks of P=O and O-P-C belong to PA.

[0073] The XRD and FT-IR test results prove that the GZ / PA / Mg flame retardant is successfully synthesized.

[0074] Step 2, Preparation of UF-GZ / PA / Cu, first, 20wt.% sodium hydroxide solution is added to 100g 37wt.% formaldehyde solution, adjust the pH value of the solution to 8.0-8.5, to obtain solution A, then, under the conditions of stirring speed of 400rpm and reaction temperature of 90℃, add urea, GZ / PA / Cu and other raw materials in three stages, namely, to prepare urea-formaldehyde resin blend guanazole-phytic acid-copper flame retardant resin coating, referred to as UF-GZ / PA / Cu,

[0075] The three stages are,

[0076] Step 2.1 is to add 37g of the first stage urea first under the condition of maintaining the temperature at 90℃, and continue to stir for 30min after the addition is completed;

[0077] Step 2.2 is to add 20wt.% acetic acid solution first under the condition of maintaining the temperature at 90℃, adjust the pH value of the solution to 4.5-5.0, then add 12.4g of the second stage urea, and finally add 1g of GZ / PA / Cu, continue to stir for 15min after the addition is completed until the reaction endpoint is reached;

[0078] The judgment mark of the second stage reaction endpoint is that a drop of the solution is dropped into 30℃ water, and the dropped solution coagulates without dispersing in the water;

[0079] Step 2.3 is to add 20wt.% sodium hydroxide solution first under the condition of maintaining the temperature at 90℃, adjust the pH value to 7.5-8.0, then add 7.6g of the third stage urea, and adjust the temperature after the addition is completed, stir under the condition of stirring temperature of 70℃ and stirring time of 30min, to obtain UF-GZ / PA / Cu;

[0080] Since subsequent tests need to be carried out after the curing of UF-GZ / PA / Cu, a specific curing method is provided. The curing method is that first, dioctyl phthalate, tannic acid and UF-GZ / PA / Cu meet the mass ratio of 0.1:0.1:10, namely, 0.3g of dioctyl phthalate and 0.3g of tannic acid are added to 30g of UF-GZ / PA / Cu, to obtain GZ / PA / Cu flame retardant resin coating under the conditions of stirring speed of 400rpm and stirring time of 30min, then, according to the experimental needs, the GZ / PA / Cu flame retardant resin coating is placed in a mold for direct curing or coated on the surface of wood, and the curing time is 72h, to obtain GZ / PA / Cu-based flame retardant resin coating, since there is no need to distinguish, the material obtained by curing is still referred to as UF-GZ / PA / Cu;

[0081] The specific method for coating the wood surface is that the UF-GZ / PA / Cu is uniformly coated on the wood surface with a coating thickness of 0.3 mm, and then drying is performed under the condition of a drying time of 24 h.

[0082] In order to prove the composition of the UF-GZ / PA / Cu, i.e. successful synthesis, FT-IR test is performed, and at the same time, since the FT-IR test cannot prove the existence of metal elements, EDS test is performed on the UF-GZ / PA / Cu after combustion.

[0083] The FT-IR test result is shown in Figure 3 There is no substantial difference between the UF-GZ / PA / Cu and the GZ / PA / Cu, i.e. characteristic peaks of -NH2, P=O and O-P-C are contained at the same time, wherein the characteristic peak of -NH2 is attributed to the GZ, and the characteristic peaks of P=O and O-P-C are attributed to the PA;

[0084] The EDS test result is shown in Figure 4 The carbon layer surface of the UF-GZ / PA / Cu after combustion contains not only N elements and P elements, but also Cu elements, wherein the N elements are derived from the GZ, the P elements are derived from the PA, and the Cu elements are derived from the Cu(OH)2;

[0085] The FT-IR test and the EDS test results show that the UF-GZ / PA / Cu flame-retardant coating is composed of GZ, PA and Cu elements, i.e. the UF-GZ / PA / Cu is successfully synthesized.

[0086] In order to prove the technical effect of the UF-GZ / PA / Cu as the wood flame-retardant coating, TG test is performed. The test result is shown in Figure 5 and Table 1. When the decomposition mass of the UF-GZ / PA / Cu is 5%, the temperature is 195.5°C, the temperature when the maximum decomposition rate is reached is 300.6°C, and the carbon residue amount at 800°C is 29.8 wt.%.

[0087] Table 1 is a summary table of the TG test results

[0088]

[0089] In order to further prove the micro-morphology of the carbon residue carbon layer, the surface of the UF-GZ / PA / Cu after the TG test is performed is subjected to SEM test. The test result is shown in Figure 6 The UF-GZ / PA / Cu can form a dense carbon residue carbon layer, and there is almost no hole, which is referred to as a dense structure. The test result shows that the UF-GZ / PA / Cu can form a high-quality carbon residue carbon layer after combustion, so as to achieve the effect of isolating oxygen and heat, thereby improving the flame-retardant performance of the wood.

[0090] To further prove the flame retardancy of UF-GZ / PA / Cu, vertical burning test and limiting oxygen index test were carried out.

[0091] The vertical burning test results are shown in Table 2 and Figure 1. Figure 7 As shown in Table 2 and Figure 1, the flaming time of UF-GZ / PA / Cu after the first ignition was 0.9 s, and the flaming and non-flaming combustion time after the second ignition was 1.4 s, and there was no dripping, which indicated that UF-GZ / PA / Cu passed the UL-94 V-0 level.

[0092] The limiting oxygen index test results are shown in Table 2 and Figure 2.

[0093] Table 2 Vertical burning test and oxygen index test results

[0094]

[0095]

[0096] To further quantify the flame retardancy of UF-GZ / PA / Cu, a cone calorimeter test was carried out. The test results are shown in Table 3 and Figure 3. Figure 8 As shown in Table 3 and Figure 3, the heat release rate HHR of UF-GZ / PA / Cu was 25.38 kW / m 2 .

[0097] To prove the effect of UF-GZ / PA / Cu on the flame retardancy of wood, Comparative Example 1, wood without coating flame retardant, was provided as a basic reference sample, and Comparative Example 2, pure urea-formaldehyde resin UF without adding GZ / PA / Cu flame retardant, was provided.

[0098] Comparative Example 1

[0099] A kind of wood without coating flame retardant, referred to as NW.

[0100] To prove the micro-morphology of the carbon layer of residual carbon, SEM test was carried out after complete combustion of NW. The test results are shown in Table 4 and Figure 4. Figure 9 As shown in Table 4 and Figure 4, the carbon layer after combustion of NW was almost completely broken, referred to as broken structure. Compared with Example 1, it can be seen that coating UF-GZ / PA / Cu can form a dense residual carbon carbon layer, i.e. improve the flame retardancy.

[0101] To further prove the flame retardancy of NW, vertical burning test and limiting oxygen index test were carried out.

[0102] The vertical burning test results are shown in Table 5 and Figure 5. Figure 7As shown in Table 2, the flaming time of NW after the first ignition is greater than 60 s, and there is dripping, which indicates that the NW does not pass the UL-94 V-0 level. In comparison with Example 1, it can be seen that coating UF-GZ / PA / Cu can make the NW pass the UL-94 level test.

[0103] The limiting oxygen index test results are shown in Table 2. The limiting oxygen index of NW is 20.3%, and in comparison with Example 1, it can be seen that coating UF-GZ / PA / Cu can increase the limiting oxygen index from 20.0% to 32.0%.

[0104] In order to further quantify the flame retardancy of NW, a cone calorimeter test is performed. The test results are shown in Table 2. Figure 8 As shown in Table 2, the HRR of NW is 206.73 kW / m 2 . In comparison with Example 1, it can be seen that coating UF-GZ / PA / Cu can reduce the HRR by 87.70%, i.e. significantly reduce the heat release rate, thereby significantly improving the flame retardancy.

[0105] Comparative Example 2

[0106] A preparation method of a pure urea-formaldehyde resin UF without adding a GZ / PA / Cu flame retardant. The steps are not particularly specified and are the same as in Example 1, except that: there is no need to perform the step 1, and in the step 2, the step 2.2 does not add GZ / PA / Cu, i.e. a pure urea-formaldehyde resin UF without adding a GZ / PA / Cu flame retardant, referred to as UF for short, is obtained.

[0107] In order to prove the technical effect of UF as a wood flame retardant coating, a TG test is performed. The test results are shown in Table 1. Figure 5 As shown in Table 1, the temperature at which the UF decomposes 5% of the mass is 204.2°C, the temperature at which the maximum decomposition rate is reached is 304.2°C, and the amount of residual carbon at 800°C is 10.0 wt.%. In comparison with Example 1, it can be seen that adding UF-GZ / PA / Cu can increase the amount of residual carbon from 10.0 wt.% to 29.8 wt.%, with an increase of 198.0%, i.e. adding UF-GZ / PA / Cu can significantly increase the amount of residual carbon.

[0108] In order to further prove the micro-morphology of the residual carbon layer, the surface of UF after the TG test is performed is subjected to SEM test. The test results are shown in Table 1. Figure 9 As shown in Table 1, the residual carbon layer formed after the combustion of UF has a serious fragmentation phenomenon, i.e. a fragmented structure,

[0109] In comparison with Comparative Example 1, it can be seen that coating UF can slightly reduce the fragmentation degree of the residual carbon layer and slightly improve the flame retardancy, but the residual carbon layer formed has no substantial change compared with NW, and is also a fragmented structure;

[0110] Compared with Example 1, it can be seen that the addition of the GZ / PA / Cu flame retardant can convert the broken structure of the carbon residue carbon layer into a dense structure.

[0111] In order to further prove the flame retardancy of the UF, vertical combustion tests and limiting oxygen index tests were carried out.

[0112] The vertical combustion test results are shown in Table 1 and Table 2. Figure 7 As shown in Table 1 and Table 2, the open flame time of the UF after the first ignition is 10.2s, and the open flame and flameless combustion time after the second ignition is 12.6s, and there is no dripping, which indicates that the UF passes the UL-94 V-1 level.

[0113] Compared with Comparative Example 1, it can be seen that coating the UF can improve the NW from no level to UL-94 V-1 level, that is, coating the UF can improve the flame retardancy;

[0114] Compared with Example 1, it can be seen that the addition of the GZ / PA / Cu flame retardant can improve the UL-94 level from V-1 to V-0.

[0115] The limiting oxygen index test results are shown in Table 2, and the limiting oxygen index of the UF is 27.8%.

[0116] Compared with Comparative Example 1, it can be seen that coating the UF can improve the limiting oxygen index from 20.0% to 27.8%, that is, coating the UF can improve the flame retardancy;

[0117] Compared with Example 1, it can be seen that the addition of the GZ / PA / Cu flame retardant can further improve the limiting oxygen index from 27.8% to 32.0%.

[0118] In order to further quantify the flame retardancy of the NW, a cone calorimeter test was carried out. The test results are shown in Table 3 and Table 4. Figure 8 As shown in Table 3 and Table 4, the HRR of the UF reaches 70.90kW / m 2 ,

[0119] Compared with Comparative Example 1, it can be seen that the HRR reduction rate achieved by coating the UF is 65.70%, that is, reducing the heat release rate and improving the flame retardancy;

[0120] Compared with Example 1, it can be seen that the addition of the GZ / PA / Cu flame retardant can further reduce the HRR amplitude by 61.65%.

[0121] From Example 1, Comparative Example 1 and Comparative Example 2, it can be seen that the improvement of the flame retardancy by coating the UF is essentially derived from the flame retardancy of the UF itself, which is embodied in that the addition of the UF can not only obtain a very low carbon residue amount, but also obtain a broken carbon residue carbon layer, that is, poor quality, thereby failing to effectively improve the flame retardancy;

[0122] And adding GZ / PA / Cu flame retardant can significantly improve the amount of residual carbon and form a dense carbon layer, ultimately achieving the effect of significantly improving the flame retardancy.

[0123] To prove the influence of GZ / PA / Cu adding condition, i.e. the preparation process on the flame retardant performance, comparative example 3 is provided, which uses the conventional method to add GZ / PA / Cu to prepare urea-formaldehyde resin blended guanazole-phytic acid-copper flame retardant resin coating.

[0124] It is explained that the urea added in step 2 is divided into three stages, wherein the adding method of example 1 is to add GZ / PA / Cu flame retardant in step 2.2,

[0125] And the conventional method is to add the flame retardant after the urea is added, i.e. at step 2.3.

[0126] Comparative example 3

[0127] A method for preparing a urea-formaldehyde resin blended guanazole-phytic acid-copper flame retardant resin coating by adding GZ / PA / Cu in step 2.3, which is not particularly explained as the same as example 1, except that in step 2, GZ / PA / Cu is not added in step 2.2, but in step 2.3, the obtained urea-formaldehyde resin blended guanazole-phytic acid-copper flame retardant resin coating is referred to as UF-GZ / PA / Cu-2.3.

[0128] In order to prove the technical effect of UF-GZ / PA / Cu-2.3 as a wood flame retardant coating, TG test is carried out. The test results are shown in Figure 11 As shown in the table, the amount of residual carbon of UF-GZ / PA / Cu-2.3 at 800.0℃ is 13.2wt.%.

[0129] As compared with comparative example 1, it can be seen that when adding UF-GZ / PA / Cu flame retardant in step 2.3, only the amount of residual carbon can be slightly improved, and the improvement range is only 32.0%;

[0130] As compared with example 1, it can be seen that when adding in step 2.2, the amount of residual carbon can be significantly improved.

[0131] The reason is that in the preparation of GZ / PA / Cu, the pH value of GZ / PA / Cu is weakly acidic, and the acid-base environment of the solution in the three stages in step 2 is alkaline, acidic and alkaline respectively, therefore, the technical solution of example 1 adds GZ / PA / Cu in step 2.2 which is acidic, which can improve the compatibility of the reactants, i.e. improve the dispersibility of GZ / PA / Cu in the emulsion; on the contrary, the technical solution of comparative example 3 will reduce the dispersibility of GZ / PA / Cu in the emulsion, thereby directly affecting the final flame retardant performance.

[0132] To prove the effect of metal elements on the flame retardant performance, i.e. the role of Cu element, Comparative Example 4, Comparative Example 5 and Comparative Example 6 are provided, in which Mg element, Ca element and Mn element are introduced into GZ / PA respectively to prepare guanazole-phytic acid metal salt flame retardant resin coating.

[0133] Comparative Example 4

[0134] A guanazole-phytic acid metal salt flame retardant resin coating based on Mg element, the steps are the same as those in Example 1 unless otherwise specified, except that in Step 1, Mg element is introduced instead of Cu element, specifically, 3.954 g of magnesium hydroxide is added instead of 8.664 g of copper hydroxide, and the material obtained in Step 1 is referred to as GZ / PA / Mg. In subsequent Step 2, GZ / PA / Mg is added instead of GZ / PA / Cu, and the material obtained in Step 2 is referred to as UF-GZ / PA / Mg.

[0135] To prove the composition of GZ / PA / Mg, i.e. successful synthesis, XRD test is performed. The test results are shown in Figure 1 As shown in the figure, GZ / PA / Mg contains characteristic peaks of Mg3P2 and Mg2P2O7. The test results show that Mg element is successfully complexed with PA.

[0136] To prove the composition of GZ / PA / Mg, i.e. successful synthesis, FT-IR test is performed. The test results are shown in Figure 2 As shown in the figure, GZ / PA / Mg and GZ / PA / Cu have no substantial difference, i.e. both contain characteristic peaks of -NH2, P=O and O-P-C, wherein the characteristic peak of -NH2 belongs to GZ, and the characteristic peaks of P=O and O-P-C belong to PA.

[0137] The XRD and FT-IR test results prove that the GZ / PA / Mg flame retardant is successfully synthesized.

[0138] To prove the composition of UF-GZ / PA / Mg, i.e. successful synthesis, FT-IR test is performed, and since FT-IR test cannot prove the existence of metal elements, EDS test is performed on the UF-GZ / PA / Mg after combustion.

[0139] The FT-IR test results are shown in Figure 3 As shown in the figure, UF-GZ / PA / Mg and GZ / PA / Cu have no substantial difference, i.e. both contain characteristic peaks of -NH2, P=O and O-P-C, wherein the characteristic peak of -NH2 belongs to GZ, and the characteristic peaks of P=O and O-P-C belong to PA.

[0140] The EDS test results are shown in Figure 12As shown, the carbon layer surface of the UF-GZ / PA / Mg after combustion contains not only N and P elements, but also Mg element, wherein the N element is derived from GZ, the P element is derived from PA, and the Mg element is derived from Mg(OH)2.

[0141] The FT-IR test and EDS test results show that the UF-GZ / PA / Mg flame retardant coating is composed of GZ, PA and Mg elements, i.e. the UF-GZ / PA / Mg is successfully synthesized.

[0142] In order to prove the technical effect of UF-GZ / PA / Mg as wood flame retardant coating application, TG test is carried out. The test results are as follows Figure 5 As shown in Table 1 and Table 2, the decomposition temperature of UF-GZ / PA / Mg when 5% is decomposed is 205.2°C. The temperature when reaching the maximum decomposition rate is 302.8°C, and the carbon residue at 800.0°C is 27.3wt.%. Compared with Example 1, it can be seen that replacing Mg with Cu has negligible effect on the improvement of carbon residue, i.e. the type of metal element has no substantial effect on the carbon residue.

[0143] In order to further prove the micro-morphology of the residual carbon carbon layer, the surface of the UF-GZ / PA / Mg after TG test is subjected to SEM test. The test results are as follows Figure 13 As shown in Table 3, the residual carbon carbon layer formed by UF-GZ / PA / Mg has many pores, i.e. cannot form a dense residual carbon carbon layer.

[0144] Compared with Comparative Example 2, it can be seen that adding GZ / PA / Mg can convert the residual carbon carbon layer from a broken structure to a pore structure;

[0145] Compared with Example 1, it can be seen that replacing Mg with Cu can convert the residual carbon carbon layer from a pore structure to a dense structure, i.e. improve the quality of the residual carbon carbon layer.

[0146] In order to further prove the flame retardancy of UF-GZ / PA / Mg, vertical combustion test and limiting oxygen index test are carried out.

[0147] The vertical combustion test results are as follows Figure 7 As shown in Table 2, the UF-GZ / PA / Mg has a flaming time of 1.1s after the first ignition, a flaming and non-flaming combustion time of 3.9s after the second ignition, and no dripping, i.e. the UF-GZ / PA / Mg passes the UL-94 V-0 level. Compared with Example 1, it can be seen that coating UF-GZ / PA / Cu and UF-GZ / PA / Mg can both pass the UL-94 level test, i.e. the type of metal element has no substantial effect on the UL-94 level.

[0148] The limiting oxygen index test results are shown in Table 2, and the limiting oxygen index of UF-GZ / PA / Mg is 31.5%. Compared with Example 1, it can be seen that the increase of limiting oxygen index is negligible when Mg is replaced by Cu, i.e. it indicates that the type of metal element has no substantial effect on the limiting oxygen index.

[0149] In order to further quantify the flame retardancy of UF-GZ / PA / Mg, a cone calorimeter test is performed. The test results are shown in Table 3, and the HRR of UF-GZ / PA / Mg reaches 39.20 kW / m Figure 8 2 Compared with Example 1, it can be seen that replacing Mg with Cu can significantly reduce HRR.

[0150] Through the analysis test, it can be seen that the type of metal element has no substantial effect on the amount of residual carbon, UL-94 grade and limiting oxygen index; the role of metal element Cu in the technical scheme is to promote the formation of a dense structure of the residual carbon layer, thereby reducing HRR, and ultimately achieving improved flame retardant performance.

[0151] Comparative Example 5

[0152] A guanazole-phytic acid metal salt flame-retardant resin coating based on Mg element, without specifically described steps being the same as Example 1, the difference is that in step 1, Ca element is introduced instead of Cu element, specifically, 5.042 g of calcium hydroxide is added instead of 8.664 g of copper hydroxide, and the material obtained in step 1 is referred to as GZ / PA / Ca, and in subsequent step 2, GZ / PA / Ca is added instead of GZ / PA / Cu, and the material obtained in step 2 is referred to as UF-GZ / PA / Ca.

[0153] In order to prove that the composition of GZ / PA / Ca, i.e. successful synthesis, an XRD test is performed. The test results are shown in Table 4, and GZ / PA / Ca contains the characteristic peaks of Ca(PO3)2. Figure 1

[0154] In order to prove that the composition of GZ / PA / Ca, i.e. successful synthesis, an FT-IR test is performed. The test results are shown in Table 5, and GZ / PA / Ca has no substantial difference from GZ / PA / Cu, i.e. it contains the characteristic peaks of -NH2, P=O and O-P-C, wherein the characteristic peak of -NH2 belongs to GZ, and the characteristic peaks of P=O and O-P-C belong to PA. Figure 2

[0155] The XRD and FT-IR test results prove that the flame retardant GZ / PA / Ca is successfully synthesized.

[0156] ​​​In order to prove the composition of UF-GZ / PA / Ca, i.e. successful synthesis, FT-IR test was carried out, and since FT-IR test cannot prove the existence of metal elements, EDS test was carried out on UF-GZ / PA / Ca after combustion.

[0157] The FT-IR test results are shown in Figure 3 As shown in the table, UF-GZ / PA / Ca has no substantial difference with GZ / PA / Cu, i.e. containing characteristic peaks of -NH2, P=O and O-P-C at the same time, wherein the characteristic peak of -NH2 is attributed to GZ, and the characteristic peaks of P=O and O-P-C are attributed to PA.

[0158] The EDS test results are shown in Figure 14 As shown in the table, the carbon layer surface of UF-GZ / PA / Ca after combustion contains not only N element and P element, but also Ca element, wherein the N element is derived from GZ, the P element is derived from PA, and the Ca element is derived from Ca(OH)2.

[0159] The FT-IR test and EDS test results show that UF-GZ / PA / Ca flame retardant coating is composed of GZ, PA and Ca elements, i.e. UF-GZ / PA / Ca is successfully synthesized.

[0160] In order to prove the technical effect of UF-GZ / PA / Ca as wood flame retardant coating, TG test was carried out. The test results are shown in Figure 5 and Table 1. When 5% is decomposed, the decomposition temperature of UF-GZ / PA / Ca is 191.4°C. The temperature at which the maximum decomposition rate is reached is 301.5°C, and the carbon residue at 800.0°C is 29.4wt.%. Compared with Example 1, it can be seen that replacing Ca with Cu has negligible effect on the improvement of carbon residue, i.e. indicating that the type of metal element has no substantial effect on the carbon residue.

[0161] In order to further prove the micro-morphology of the carbon residue carbon layer, SEM test was carried out on the surface of UF-GZ / PA / Ca after TG test. The test results are shown in Figure 15 The carbon residue carbon layer formed by UF-GZ / PA / Ca has many pores, i.e. cannot form a dense carbon residue carbon layer.

[0162] Compared with Comparative Example 2, it can be seen that adding GZ / PA / Ca can convert the carbon residue carbon layer from a broken structure to a porous structure;

[0163] Compared with Example 1, it can be seen that replacing Ca with Cu can convert the carbon residue carbon layer from a porous structure to a dense structure, i.e. improve the quality of the carbon residue carbon layer.

[0164] In order to further prove the flame retardancy of UF-GZ / PA / Ca, vertical combustion test and limiting oxygen index test were carried out.

[0165] Vertical burning test results are as follows Figure 7 As shown in Table 2, the open flame time after the first ignition of UF-GZ / PA / Ca is 1.2s, and the open flame and flameless combustion time after the second ignition is 2.0s, with no dripping, indicating that UF-GZ / PA / Ca passes the UL-94 V-0 rating. Comparison with Example 1 shows that both UF-GZ / PA / Cu and UF-GZ / PA / Ca coatings pass the UL-94 rating test, indicating that the type of metal element has no substantial impact on the UL-94 rating.

[0166] The limiting oxygen index test results are shown in Table 2. The limiting oxygen index of UF-GZ / PA / Ca is 30.0%. Compared with Example 1, it can be seen that replacing Ca with Cu has a negligible effect on the limiting oxygen index, indicating that the type of metal element has no substantial impact on the limiting oxygen index.

[0167] To further quantify the flame retardancy of UF-GZ / PA / Ca, a cone calorimeter test was conducted. The test results are as follows: Figure 8 As shown, the HRR of UF-GZ / PA / Ca reaches 43.30 kW / m. 2 As can be seen from the comparison with Example 1, replacing Ca with Cu can significantly reduce HRR.

[0168] Comparative Example 6

[0169] A guanidine azole-phytate metal salt flame retardant resin coating based on Mg element, unless otherwise specified, is the same as in Example 1, except that in step 1, Mn element is introduced to replace Cu element, specifically 5.224g of manganese dioxide is added to replace 8.664g of copper hydroxide. The material obtained in step 1 is referred to as GZ / PA / Mn. In subsequent step 2, GZ / PA / Mn is added to replace GZ / PA / Cu. The material obtained in step 2 is referred to as UF-GZ / PA / Mn.

[0170] To confirm the successful synthesis of the GZ / PA / Mn composition, XRD analysis was performed. The test results are as follows: Figure 1 As shown, GZ / PA / Mn simultaneously contains the characteristic peaks of Mn(PO3)3. Test results indicate that the Mn element successfully complexes with PA.

[0171] To confirm the composition of GZ / PA / Mn, i.e., successful synthesis, FT-IR testing was performed. The test results are as follows: Figure 2 As shown, GZ / PA / Mn and GZ / PA / Cu are not substantially different, that is, they both contain characteristic peaks of -NH2, P=O and OPC. Among them, the characteristic peak of -NH2 belongs to GZ, and the characteristic peaks of P=O and OPC belong to PA.

[0172] The XRD and FT-IR test results prove that the GZ / PA / Mn flame retardant is successfully synthesized.

[0173] In order to prove the composition of the UF-GZ / PA / Mn, i.e. successful synthesis, the FT-IR test is performed, and at the same time, since the FT-IR test cannot prove the existence of metal elements, the EDS test is performed on the UF-GZ / PA / Mn after combustion.

[0174] The FT-IR test results are shown in Figure 3 There is no substantial difference between the UF-GZ / PA / Mn and the GZ / PA / Cu, i.e. they both contain the characteristic peaks of -NH2, P=O and O-P-C, wherein the characteristic peak of -NH2 belongs to GZ, and the characteristic peaks of P=O and O-P-C belong to PA.

[0175] The EDS test results are shown in Figure 16 The carbon layer surface of the UF-GZ / PA / Mn after combustion contains not only N elements and P elements, but also Mn elements, wherein the N elements come from GZ, the P elements come from PA, and the Mn elements come from MnO2.

[0176] The FT-IR test and EDS test results show that the UF-GZ / PA / Mn flame retardant coating is composed of GZ, PA and Mn elements, i.e. the UF-GZ / PA / Mn is successfully synthesized.

[0177] In order to prove the technical effect of the UF-GZ / PA / Mn as a wood flame retardant coating, the TG test is performed. The test results are shown in Figure 5 and Table 1. When 5% is decomposed, the UF-GZ / PA / Mn decomposition temperature is 184.0℃. The temperature at which the maximum decomposition rate is reached is 304.1℃, and the carbon residue at 800.0℃ is 26.0wt.%. Compared with Example 1, it can be seen that replacing Mn with Cu has negligible effect on the improvement of the carbon residue, i.e. it indicates that the type of metal elements has no substantial effect on the carbon residue.

[0178] In order to further prove the micro-morphology of the carbon residue carbon layer, the surface of the UF-GZ / PA / Mn after the TG test is performed is subjected to the SEM test. The test results are shown in Figure 17 The carbon residue carbon layer formed by the UF-GZ / PA / Mn has many pores, i.e. it cannot form a dense carbon residue carbon layer.

[0179] Compared with Comparative Example 2, it can be seen that adding GZ / PA / Mn can convert the carbon residue carbon layer from a broken structure to a porous structure;

[0180] Compared with Example 1, it can be seen that replacing Ca with Cu can convert the carbon residue carbon layer from a porous structure to a dense structure, i.e. improve the quality of the carbon residue carbon layer.

[0181] To further prove the flame retardance of UF-GZ / PA / Mn, vertical burning test and limiting oxygen index test were carried out.

[0182] The vertical burning test results are shown in Table 2 and Figure 1. Figure 7 As shown in Table 2 and Figure 1, the flaming time of UF-GZ / PA / Mn after the first ignition is 1.7s, and the flaming and non-flaming combustion time after the second ignition is 1.8s, and there is no dripping, which indicates that UF-GZ / PA / Mn passes the UL-94 V-0 level. Compared with Example 1, it can be seen that both UF-GZ / PA / Cu and UF-GZ / PA / Mn can pass the UL-94 level test, which indicates that the type of metal element has no substantial effect on the UL-94 level.

[0183] The limiting oxygen index test results are shown in Table 2. The limiting oxygen index of UF-GZ / PA / Mn is 29.0%. Compared with Example 1, it can be seen that replacing Mn with Cu has negligible effect on the improvement of limiting oxygen index, which indicates that the type of metal element has no substantial effect on the limiting oxygen index.

[0184] To further quantify the flame retardance of UF-GZ / PA / Mn, a cone calorimeter test was carried out. The test results are shown in Table 2 and Figure 2. Figure 8 As shown in Table 2 and Figure 2, the HRR of UF-GZ / PA / Mn reaches 47.00 kW / m 2 Compared with Example 1, it can be seen that replacing Mn with Cu can significantly reduce the HRR.

[0185] From Example 1, Comparative Example 4, Comparative Example 5 and Comparative Example 6, the following conclusions can be drawn:

[0186] 1. The type of metal element has no substantial effect on the residual carbon content, UL-94 level and limiting oxygen index;

[0187] 2. The metal element has a significant effect on the carbon layer quality and HRR value formed after combustion. The reason is that the metal element Cu plays a role in the technical solution, which promotes the residual carbon layer to form a dense structure, thereby reducing the HRR and improving the flame retardance, while other metal elements Mg, Ca and Mn can only form a residual carbon layer with a porous structure, which cannot effectively improve the flame retardance.

Claims

1. A method for preparing a urea-formaldehyde resin blended with guanidine-phytic acid-copper flame-retardant resin coating, characterized in that, Includes the following steps: Step 1, Preparation of GZ / PA / Cu flame retardant: First, 3,5-diamino-1,2,4-triazole GZ is dissolved in water to obtain a GZ solution. Then, phytic acid PA solution is added dropwise to the GZ solution to obtain a GZ / PA solution. Finally, copper hydroxide is added to the GZ / PA solution to react. After the reaction is complete, the resulting product is filtered, washed, dried, and ground into powder to obtain the guanidineazole-phytic acid-copper flame retardant, abbreviated as GZ / PA / Cu. The washing conditions are as follows: the pH of the washing solution is 5.0-6.0; The drying conditions are as follows: drying temperature is 80℃, and drying time is 24 h. Step 2, preparation of UF-GZ / PA / Cu: First, sodium hydroxide solution is added to formaldehyde solution to adjust the pH value of the solution to obtain solution A. Then, urea, GZ / PA / Cu and other raw materials are added according to steps 2.1, 2.2 and 2.3 to obtain UF-GZ / PA / Cu. Step 2.1 involves first adding the first stage of urea, and then continuing to stir after the addition is complete. Step 2.2 involves first adding acetic acid solution to adjust the pH of the solution, then adding the second-stage urea, and finally adding GZ / PA / Cu. After all additions are complete, continue stirring until the reaction endpoint is reached. The endpoint of the reaction is determined by the following criterion: when a drop of the solution is added to water at 30°C, the solution solidifies in the water without dispersing. Step 2.3 involves first adding sodium hydroxide solution to adjust the pH value, then adding urea from the third stage, and stirring after the addition is complete to obtain UF-GZ / PA / Cu. Step 3: Under the conditions of stirring speed of 400 rpm and stirring time of 30 min, dioctyl phthalate, tannic acid and UF-GZ / PA / Cu are added to UF-GZ / PA / Cu in a mass ratio of 0.1:0.1:10 to obtain the coating.

2. The preparation method according to claim 1, characterized in that: In step 1, the mass ratio of GZ, PA and copper hydroxide is 1:6:1; In step 1, the conditions for preparing the GZ / PA solution are: stirring temperature of 70℃, stirring speed of 500-600 rpm, stirring time of 30 min, and dropping rate of 0.5 drops / s. In step 1, the reaction conditions are: a reaction temperature of 90°C and a reaction time of 3 hours.

3. The preparation method according to claim 1, characterized in that: In step 2, the mass ratio of the total amount of GZ / PA / Cu, formaldehyde solution and urea added in step 1 is 1:100:

57. In step 2, the conditions for preparing solution A are as follows: the pH value of the solution is adjusted to 8.0-8.5; In step 2, the conditions for adding urea are: stirring speed of 400-500 rpm and reaction temperature of 90 ℃.

4. The preparation method according to claim 1, characterized in that: In step 2.1, the amount of urea added is 64.9% of the total amount of urea, the temperature in step 2.1 is 90℃, and the stirring time is 30 min. In step 2.2, the amount of urea added is 21.8% of the total amount of urea, the pH of the solution is adjusted to 4.5-5.0, the temperature in step 2.2 is 90 ℃, and the stirring time is 15 min. In step 2.3, the amount of urea added is 13.3% of the total amount of urea, the pH of the solution is adjusted to 7.5-8.0, the temperature in step 2.3 is 90 ℃ when adjusting the pH, and after the pH is adjusted, the temperature is adjusted to 70 ℃, and the stirring time is 30-40 min.

5. The preparation method according to claim 1, characterized in that: The decomposition temperature of the obtained urea-formaldehyde resin blend guanidazole-phytic acid-copper flame retardant resin coating at 5% mass was 195.5±2.1℃, the temperature at which the maximum decomposition rate was reached was 300.6±1.5℃, and the residual carbon content at 800℃ was 29.8±2.5wt.%.

6. The preparation method according to claim 1, characterized in that: When the obtained urea-formaldehyde resin blended with guanidine-phytic acid-copper flame-retardant resin is used as a flame-retardant coating for wood, it exhibits flame-retardant properties and forms a continuous and dense char layer after combustion; in the UL-94 rating test, it passed the UL-94 V-0 rating test.

7. The preparation method according to claim 1, characterized in that: When the obtained urea-formaldehyde resin blended with guanidine-phytic acid-copper flame-retardant resin is used as a flame-retardant coating for wood, the heat release rate (HRR) in the cone calorimetry test is 25.38 ± 1.25 kW / m². 2 .

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