Solvent-free latent-curing fireproof coating and preparation method thereof

Abstract

The invention discloses a solvent-free latent-curing fireproof coating and a preparation method thereof, and belongs to the technical field of fireproof flame-retardant materials. Polyphosphate, polyhydric alcohol and epoxy resin are used as raw materials to prepare the solvent-free latent curing fireproof coating, the polyphosphate is any one of ammonium salt and metal salt of polyphosphoric acid, the polyhydric alcohol is an alcohol compound containing two or more hydroxyl groups, and the epoxy resin is epoxy resin. The epoxy resin is an organic compound containing two or more epoxy groups. The solvent-free latent-curing fireproof coating disclosed by the invention can be stored for a long time at room temperature or low temperature, and epoxy resin is rapidly cured by a polyphosphate-polyol system at high temperature, so that the fireproof coating is obtained. The fireproof coating has the characteristics of high mechanical strength, flame retardance, low smoke, low toxicity and the like. The preparation process disclosed by the invention is simple, low in cost and high in operability.

Description

Technical Field

[0001] This invention relates to the field of fire-retardant materials technology, specifically to a solvent-free, latently curable fire-retardant coating and its preparation method. Background Technology

[0002] Epoxy resin, as an important thermosetting material, has wide applications in aerospace, electronic packaging, and protective coatings. However, epoxy resin materials are highly flammable and will burn rapidly upon contact with a flame, producing heat and smoke. This severely limits the application scenarios of epoxy resin materials and poses certain fire safety hazards. Therefore, enhancing the flame-retardant properties of epoxy resin is necessary.

[0003] Among common flame retardant systems, intumescent flame retardant systems have attracted much attention due to their green and environmentally friendly characteristics, high efficiency, and low cost. Ammonium polyphosphate has been found to be an excellent intumescent flame retardant, with advantages such as high flame retardant efficiency and low price.

[0004] For ease of on-site operation, epoxy resins, curing agents, and other functional additives are often pre-formulated into a "one-piece" material in practical applications such as electrical encapsulation and plastic processing. However, when traditional curing agents (amines, imidazoles) are mixed with epoxy resins, they can cause premature curing or increased viscosity, significantly shortening the epoxy resin's pot life and processing time.

[0005] Latent epoxy resin curing agents are a special type of curing agent that coexists stably with epoxy resin at room temperature and hardly reacts. They are only activated and rapidly initiate resin curing under specific external conditions (such as heating, ultraviolet light, or moisture). This "dormant" characteristic allows epoxy resin systems to be packaged as single components, greatly facilitating storage, transportation, and application. Common types include dicyandiamide, imidazole complexes, and microencapsulated curing agents. Summary of the Invention

[0006] The purpose of this invention is to provide a method for preparing a solvent-free, latently curable fire-retardant coating. The fire-retardant coating not only has latent curing characteristics, but also has high mechanical strength and excellent flame retardant, low smoke, and low toxicity properties.

[0007] To achieve the above-mentioned objectives, the present invention adopts the following technical solution:

[0008] A method for preparing a solvent-free, latently curable fire-retardant coating includes the following steps:

[0009] 1) Mix polyphosphate, polyol and epoxy resin at 160~200℃ for 10~50 min to obtain a mixture;

[0010] 2) Use a vacuum pump to remove air bubbles from the mixture, and then solidify it to obtain a fireproof coating.

[0011] Further, by weight, the polyphosphate, polyol, and epoxy resin are 5-40 parts, 2-15 parts, and 60-90 parts, respectively. Preferably, the polyphosphate, polyol, and epoxy resin are 20-30 parts, 3-7 parts, and 63-75 parts, respectively.

[0012] Furthermore, the reaction temperature in step 1) is 170~190℃ and the time is 20~40 min.

[0013] Further, in step 2), the curing process involves first curing at 160°C for 1-4 hours, and then curing at 180°C for 1-4 hours. Preferably, the curing process involves first curing at 160°C for 2-3 hours, and then curing at 180°C for 2-3 hours.

[0014] Furthermore, the polyphosphate is any one of the ammonium salt or metal salt of polyphosphate, preferably ammonium polyphosphate.

[0015] Furthermore, the polyol is an alcohol compound containing two or more hydroxyl groups, preferably 1,4-butanediol or 1,5-pentanediol.

[0016] Furthermore, the epoxy resin is an organic compound containing two or more epoxy groups, preferably a bisphenol A type epoxy resin.

[0017] This invention provides a solvent-free, latently curable fire-retardant coating that can be stored for extended periods at room temperature or low temperatures. At high temperatures, the polyphosphate undergoes alcoholysis to produce acidic phosphates, which are then cross-linked and cured by the polyol under acid catalysis. Due to the presence of polyphosphates (such as ammonium polyphosphate), the fire-retardant coating provided by this invention exhibits excellent flame-retardant, low-smoke, and low-toxicity properties. More notably, despite the high polyphosphate content, the coating's mechanical properties are not severely degraded; on the contrary, it possesses high mechanical strength.

[0018] The present invention provides a simple preparation process for a solvent-free, latently curable fire-retardant coating, which is safe and stable in reaction process, does not require the use of solvents, conforms to the sustainable development strategy, and is convenient for industrial production. Attached Figure Description

[0019] Figure 1 Non-isothermal DSC curves of ammonium polyphosphate-polyol-epoxy resin

[0020] Figure 2The results of cone calorimeter tests on the fire-retardant coatings prepared in Examples 3, 4, and 5 are shown; where (c1) is the instantaneous heat release rate, (c2) is the total heat release, (c3) is the instantaneous smoke release rate, and (c4) is the total smoke release. Detailed Implementation

[0021] Unless otherwise specified, all raw materials or reagents used in this invention are commercially available products well known in the art.

[0022] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments. However, it should be noted that these embodiments should not be construed as limiting the scope of protection of the present invention.

[0023] Example 1

[0024] 20 parts of ammonium polyphosphate (APP), 5 parts of 1,4-butanediol (BDO), and 75 parts of bisphenol A epoxy resin (DGEBA) were mixed at 170°C for 40 min. Then, air bubbles in the mixture were removed using a vacuum pump, and the mixture was cured at 160°C for 3 h and then at 180°C for 3 h. After that, it was cooled to room temperature within 1 h to obtain fire-retardant coating 1, denoted as APP2 / BDO5 / EP.

[0025] Example 2

[0026] Mix 25 parts APP, 5 parts BDO, and 70 parts DGEBA at 180°C for 30 min; then use a vacuum pump to remove air bubbles from the mixture, and then cure the mixture at 160°C for 2 h and 180°C for 3 h. Finally, cool it to room temperature within 1 h to obtain fire-retardant coating 2, denoted as APP2.5 / BDO5 / EP.

[0027] Example 3

[0028] Mix 30 parts APP, 5 parts BDO, and 65 parts DGEBA at 190℃ for 25 min; then use a vacuum pump to remove air bubbles from the mixture, and then cure the mixture at 160℃ for 3 h and 180℃ for 2 h. Finally, cool it to room temperature within 1 h to obtain fire-retardant coating 3, denoted as APP3 / BDO5 / EP.

[0029] Example 4

[0030] 30 parts of APP, 3 parts of BDO, and 67 parts of DGEBA were mixed at 180°C for 40 min. Then, air bubbles were removed from the mixture using a vacuum pump. The mixture was then cured at 160°C for 2 h and at 180°C for 2 h. Finally, it was cooled to room temperature within 1 h to obtain fire-retardant coating 4, denoted as APP3 / BDO3 / EP.

[0031] Example 5

[0032] Mix 30 parts APP, 7 parts BDO, and 63 parts DGEBA at 180°C for 20 min; then use a vacuum pump to remove air bubbles from the mixture, and then cure the mixture at 160°C for 3 h and 180°C for 3 h. Finally, cool it to room temperature within 1 h to obtain fire-retardant coating 5, denoted as APP3 / BDO7 / EP.

[0033] Example 6

[0034] 30 parts of APP, 3 parts of 1,5-pentanediol (PDO), and 67 parts of DGEBA were mixed at 180°C for 50 min. Then, air bubbles were removed from the mixture using a vacuum pump. The mixture was then cured at 160°C for 3 h and at 180°C for 3 h. Finally, it was cooled to room temperature within 1 h to obtain fire-retardant coating 6, denoted as APP3 / PDO3 / EP.

[0035] Example 7

[0036] Mix 30 parts APP, 5 parts PDO, and 65 parts DGEBA at 180°C for 40 min; then use a vacuum pump to remove air bubbles from the mixture, and then cure the mixture at 160°C for 3 h and 180°C for 3 h. Finally, cool it to room temperature within 1 h to obtain fire-retardant coating 7, denoted as APP3 / PDO5 / EP.

[0037] Example 8

[0038] Mix 30 parts APP, 7 parts PDO, and 63 parts DGEBA at 180°C for 30 min; then use a vacuum pump to remove air bubbles from the mixture, and then cure the mixture at 160°C for 3 h and 180°C for 3 h. After that, cool to room temperature within 1 h. After the process is completed, fire-retardant coating 8 is obtained, which is denoted as APP3 / PDO7 / EP.

[0039] Characterization and performance testing

[0040] Figure 1 The figures show the non-isothermal DSC test curves of the APP3-BDO7-DGEBA mixture in Example 5 at different heating rates. It can be observed that in all heating rate curves, no exothermic peak appears below 120°C, but an exothermic curing peak of the epoxy resin appears once the temperature exceeds 150°C, demonstrating the high-temperature latent curing characteristics of APP3 / BDO7 / EP.

[0041] Figure 2 The results of cone calorimeter tests on the fire-retardant coatings prepared in Examples 3, 4, and 5 are shown. Where (c1) is the instantaneous heat release rate, (c2) is the total heat release, (c3) is the instantaneous smoke release rate, and (c4) is the total smoke release. Figure 2As can be seen from (c1) and (c2), due to the intumescent flame-retardant effect of ammonium polyphosphate, the fire-retardant coatings all exhibit excellent flame-retardant properties, with a peak heat release rate of only 160 kW·m. 2 The total smoke production is only 4-6m³ 2 Furthermore, it was observed that slight changes in polyol content at low addition levels did not significantly affect the flame retardant properties of the material. Ammonium polyphosphate releases ammonia (NH3) through thermal decomposition during combustion, diluting the oxygen and combustible gas concentrations in the flame zone. Therefore, the peak smoke release and total smoke release of the material are both at low levels. In summary, the fire-retardant coating exhibits good flame retardant and smoke-suppressing effects.

[0042] The flame retardant performance of the fireproof coating was tested using a vertical burning tester and a limiting oxygen index tester. The results are shown in Table 1.

[0043] Table 1 shows the vertical burning and limiting oxygen index test results of the example samples. It can be seen that all flame-retardant materials (fire-retardant coatings) passed the V-0 level test, demonstrating good flame-retardant effects and meeting national fire safety standards. While the limiting oxygen index decreased with decreasing ammonium polyphosphate content, the lowest value sample (APP3 / PDO7 / EP) still reached 37.6.

[0044] Table 1 Combustion performance test results

[0045]

[0046] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a solvent-free, latently curable fire-retardant coating, characterized in that, Includes the following steps: 1) Mix polyphosphate, polyol and epoxy resin at 160~200℃ for 10~50 min to obtain a mixture; 2) Use a vacuum pump to remove air bubbles from the mixture, and then solidify it to obtain a fireproof coating.

2. The method for preparing a solvent-free, latently curable fire-retardant coating according to claim 1, characterized in that, By weight, the polyphosphate, polyol, and epoxy resin are 5-40 parts, 2-15 parts, and 60-90 parts, respectively.

3. The method for preparing a solvent-free, latently curable fire-retardant coating according to claim 2, characterized in that, The polyphosphate, polyol, and epoxy resin are present in parts of 20-30, 3-7, and 63-75, respectively.

4. The method for preparing a solvent-free, latently curable fire-retardant coating according to claim 1, characterized in that, The reaction temperature in step 1) is 170~190℃, and the time is 20~40 min.

5. The method for preparing a solvent-free, latently curable fire-retardant coating according to claim 1, characterized in that, Step 2) involves curing at 160°C for 1-4 hours, followed by curing at 180°C for 1-4 hours.

6. The method for preparing a solvent-free, latently curable fire-retardant coating according to claim 5, characterized in that, The curing process involves first curing at 160℃ for 2-3 hours, and then curing at 180℃ for 2-3 hours.

7. The method for preparing a solvent-free, latently curable fire-retardant coating according to claim 1, characterized in that, The polyphosphate is any one of the ammonium salt or metal salt of polyphosphate.

8. The method for preparing a solvent-free, latently curable fire-retardant coating according to claim 1, characterized in that, The polyols mentioned are alcohol compounds containing two or more hydroxyl groups.

9. The method for preparing a solvent-free, latently curable fire-retardant coating according to claim 1, characterized in that, The epoxy resin is an organic compound containing two or more epoxy groups, preferably a bisphenol A type epoxy resin.

10. The fire-retardant coating obtained by the preparation method according to any one of claims 1 to 9.

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