Characteristic crystal form cyanuric acid / melamine compound as well as preparation method and application thereof

Abstract

The invention discloses a cyanuric acid / melamine compound with a characteristic crystal form and a preparation method and application thereof, the cyanuric acid / melamine compound has characteristic XRD (X-Ray Diffraction) peaks, and the peak positions (2theta) of the XRD peaks are as follows: 2theta T1 = (10.93 + / -0.20) degrees, 2theta T2 = (11.89 + / -0.40) degrees, 2theta T3 = (21.96 + / -0.40) degrees, 2theta T4 = (28.01 + / -0.20) degrees and 2theta T5 = (33.20 + / -0.40) degrees. The preparation method has the beneficial effects that the template agent is used for inducing ordered arrangement of molecules, high temperature and high pressure are not needed, vacuum drying is not needed, the energy consumption is low, and the prepared cyanuric acid / melamine compound is consistent in crystal morphology, narrow in particle size distribution, wide in size regulation and control range and high in yield. The comprehensive performance is excellent.

Description

Technical Field

[0001] This invention relates to the field of flame retardant preparation technology, specifically to a cyanuric acid / melamine composite with a characteristic crystal form, its preparation method, and its application. Background Technology

[0002] Melamine / cyanuric acid composite is a white powder with a slippery texture and good flowability, formed by cyanuric acid molecules and melamine molecules linked by hydrogen bonds. It has excellent properties such as being non-toxic, odorless, highly efficient, and low-smoke, and is widely used in polymer materials such as nylon, polyolefins, rubber, phenolic resins, epoxy resins, and polyvinyl chloride.

[0003] Currently, melamine / cyanuric acid composites suffer from problems such as irregular crystal arrangement, low crystallinity, wide grain size distribution, and large secondary particle agglomeration size. During processing and application, these issues easily lead to uneven particle size, poor particle dispersion, and particle re-agglomeration, resulting in a decline in overall performance (such as mechanical properties, flame retardant properties, and electrical properties). Therefore, developing a melamine / cyanuric acid composite with a more ordered crystal arrangement, higher crystallinity, and more uniform grain size distribution is of great significance for improving its overall performance and processing adaptability in polymer materials. Summary of the Invention

[0004] The purpose of this invention is to solve the above-mentioned problems and to provide a cyanuric acid / melamine composite with a characteristic crystal form, its preparation method, and its application.

[0005] This invention relates to a cyanuric acid / melamine composite with a characteristic crystal form, wherein the cyanuric acid / melamine composite has characteristic XRD diffraction peaks, and the characteristic XRD diffraction peaks (2θ) are as follows: 2θ T1 =(10.93±0.20)°、2θ T2 =(11.89±0.40)°、2θ T3 =(21.96±0.40)°、2θ T4 =(28.01±0.20)°、2θ T5 = (33.20 ± 0.40)°.

[0006] Preferably, the cyanuric acid / melamine composite has characteristic XRD diffraction peaks, and its characteristic XRD diffraction peaks (2θ) are as follows: 2θ T1 =(10.93±0.10)°、2θ T2 =(11.89±0.20)°、2θ T3 =(21.96±0.20)°、2θ T4 =(28.01±0.10)°、2θ T5= (33.20 ± 0.20)°.

[0007] Preferably, the XRD characteristic diffraction peak intensity (PI) of the cyanuric acid / melamine composite satisfies: PI T4 >PI T1 >PI T2 >PI T3 >PI T5 .

[0008] Preferably, the relative peak intensities (PRI) of the XRD characteristic diffraction peaks of the cyanuric acid / melamine composite satisfy the following relationship: RPI T1 =PI T1 / PI T4 =0.65±0.20; RPI T2 =PI T2 / PI T4 =0.20±0.10; RPI T3 =PI T3 / PI T4 =0.15±0.10; RPI T5 =PI T5 / PI T4 =0.08±0.03.

[0009] Preferably, the ratio of the relative peak intensity to the full width at half maximum (FWHM) of the XRD characteristic diffraction peaks of the cyanuric acid / melamine composite satisfies the following relationship: 0.5≤RPI / FWHM T1 ≤3.0; 0.4≤RPI / FWHM T2 ≤1.8; 0.2≤RPI / FWHM T3 ≤0.7; 0.1≤RPI / FWHM T5 ≤0.3.

[0010] Preferably, the pH value of the cyanuric acid / melamine complex is 4-7.

[0011] More preferably, the pH value of the cyanuric acid / melamine complex is 4.5-6.8.

[0012] Preferably, the equivalent particle size of the cyanuric acid / melamine composite is: Dv 50 The range is 0.30-1.50 μm, Dv 90 The range is 0.80-4.00 μm, Dv 99≤7.50μm.

[0013] More preferably, the equivalent particle size of the cyanuric acid / melamine composite is: Dv 90 The range is 0.90-3.50 μm, Dv 99 ≤6.50μm.

[0014] Preferably, the equivalent particle size of the cyanuric acid / melamine composite satisfies the following relationship: 1.50 ≤ Dv 90 / Dv 50 ≤2.50.

[0015] More preferably, the equivalent particle size of the cyanuric acid / melamine composite satisfies the following relationship: 1.70 ≤ Dv 90 / Dv 50 ≤2.30.

[0016] This invention also relates to a method for preparing a cyanuric acid / melamine composite with a characteristic crystal form, used to prepare the cyanuric acid / melamine composite as described in any one of the claims, comprising the following steps: S1. Disperse melamine in deionized water and keep it at 60-70℃ to prepare a melamine suspension for later use; S2. Add deionized water to the reaction vessel, and add template agent when the temperature is raised to 30-40℃ to obtain template agent dispersion; S3. Continue heating the template agent dispersion obtained in S2 to 45-50℃, add cyanuric acid, continue stirring and heat to 60-70℃.

[0017] S4. Slowly add the melamine suspension prepared in S1 to the solution in S3, and complete the addition within 40-50 minutes. Continue to heat to 85-95℃ and react at a constant temperature for 1-2 hours.

[0018] S5. After the reaction is completed, the mixture is cooled to room temperature at a cooling rate of (3-5)℃ / min, and then transferred, filtered, washed, dried and pulverized to obtain the cyanuric acid / melamine composite with the characteristic crystal form.

[0019] The preparation method of the cyanuric acid / melamine composite in this invention, wherein a melamine suspension is prepared in advance in step S1, aims to: ① improve reaction uniformity: melamine, in suspension, can be uniformly dispersed in the reaction system, thereby ensuring the uniformity and consistency of the reaction; ② improve assembly rate: the contact area between melamine and cyanuric acid is significantly increased when melamine is dispersed in suspension, which helps to accelerate the assembly efficiency of cyanuric acid molecules and melamine molecules; ③ improve assembly operability: by controlling the addition rate of the melamine suspension, the assembly rate and structural order can be adjusted, further strengthening the hydrogen bonding between cyanuric acid molecules and melamine molecules, and stabilizing the crystal structure; ④ avoid side reactions or agglomeration: adding melamine in suspension avoids side reactions or agglomeration caused by excessively high local concentrations, making the reaction more stable.

[0020] The preparation method of cyanuric acid / melamine composite in this invention involves cooling to room temperature at a cooling rate of (3-5) °C / min in step S5. The purpose of this method is to: ① reduce crystal breakage or impurity encapsulation caused by thermal stress, and improve structural integrity and crystal purity; ② avoid local overcooling and ensure a more uniform grain size distribution.

[0021] Preferably, the mass ratio of cyanuric acid to melamine is (1.015-1.030):1; the mass ratio of the sum of deionized water in S1 and deionized water in S2 to the cyanuric acid / melamine complex is (6-15):1; The mass ratio of the template agent to the cyanuric acid / melamine complex is (0.015-0.05):1; The template agent is one or more of the following: tetrabutylammonium chloride, polystyrene-b-polyacrylic acid, polyimide, polyvinylidene fluoride, polyacrylonitrile, polystyrene, graphene, montmorillonite, silica, zeolite, hydrotalcite, graphitic silicon nitride, porphyrins, phthalocyanines, phytic acid, and alumina.

[0022] In this invention, a template agent is used. The main function of the template agent is to regulate the nucleation and growth of crystals through steric hindrance, electrostatic or inductive effects, promote ordered crystallization, reduce defects, and thus play a role in regulating crystal structure, morphology and grain size.

[0023] The present invention also relates to the application of the cyanuric acid / melamine composite with the characteristic crystal form described above in polymer materials.

[0024] Preferably, the cyanuric acid / melamine composite is used in PA6, PBT, and PP materials.

[0025] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) This invention can prepare cyanuric acid / melamine composites with more ordered crystal arrangement, higher crystallinity, and more uniform grain size distribution. Sharp and narrow characteristic XRD diffraction peaks can be seen in the XRD pattern, with peak positions (2θ) as follows: 2θ T1 =(10.93±0.20)°、2θ T2 =(11.89±0.10)°、2θ T3 =(21.96±0.40)°、2θ T4 =(28.01±0.20)°、2θ T5 = (33.20±0.40)°, the relative peak intensity (RPI) satisfies the following relationship: RPI T1 =PI T1 / PI T4 =0.65±0.20, RPI T2 =PI T2 / PI T4 =0.20±0.10, RPI T3 =PI T3 / PI T4 =0.15±0.10, RPI T5 =PI T5 / PI T4 = The relative peak intensity to full width at half maximum (FWHM) ratio is 0.08 ± 0.03, satisfying the following relationship: 0.5 ≤ RPI / FWHM T1 ≤3.0, 0.4≤RPI / FWHM T2 ≤1.8, 0.2≤RPI / FWHM T3 ≤0.7, 0.1≤RPI / FWHM T5 ≤0.3; (2) The SEM images show uniformly dispersed nanosheets with a primary particle size in the nanometer range (nanofacial diameter < 300 nm, nanosheet thickness < 30 nm); the particle size distribution diagram shows that the secondary particle size range is: Dv 50 The range is 0.30-1.50 μm, Dv 90 The range is 0.80-4.00 μm, Dv 99 ≤7.50μm; (3) The preparation method of the cyanuric acid / melamine composite is simple, does not require high temperature and high pressure, does not require vacuum drying, has low energy consumption, and the prepared cyanuric acid / melamine composite has more ordered crystal arrangement, higher crystallinity and more uniform grain size distribution, so it can be uniformly dispersed in polymer materials, and has excellent mechanical, flame retardant and electrical properties. Attached Figure Description

[0026] Figure 1The X-ray diffraction (XRD) pattern of the cyanuric acid / melamine composite prepared in Example 1; Figure 2 The image shows a scanning electron microscope (SEM) image of the cyanuric acid / melamine composite prepared in Example 1. Figure 3 This is a secondary particle size distribution of the cyanuric acid / melamine composite prepared in Example 1. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0028] In this invention, T represents a diffraction peak, where T1 represents the first diffraction peak, T2 represents the second diffraction peak, and so on. The five diffraction peaks T1, T2, T3, T4, and T5 described in the product description of this invention correspond to diffraction peaks occurring at diffraction angles of (10.93±0.20)°, (11.89±0.40)°, (21.96±0.40)°, (28.01±0.20)°, and (33.20±0.40)°, respectively.

[0029] 2θ represents the diffraction angle, referring to the position where the diffraction peak appears. The five diffraction peaks described in this invention have 2θ values ​​of (10.93±0.20)°, (11.89±0.40)°, (21.96±0.40)°, (28.01±0.20)°, and (33.20±0.40)°, respectively. For example, 2θ... T1 This indicates the diffraction angle or peak position of T1.

[0030] PI represents the diffraction peak intensity, or simply peak intensity. It refers to the height or area of ​​the diffraction peak and reflects the relative scattering ability of that crystal plane. For example, the peak intensity of T1 can be expressed as PI. T1 .

[0031] RPI stands for Relative Diffraction Peak Intensity, or simply Relative Peak Strength. It refers to the ratio of the peak intensity of other diffraction peaks to the T4 peak intensity (PI). T4 The ratio. For example, the RPI of T3 can be expressed as: RPI T3 =PI T3 / PI T4 .

[0032] FWHM represents the half-width at half maximum (FWHM) of a diffraction peak, also known as the half-maximum width. For example, the FWHM of T3 can be represented as FWHM0.T3 .

[0033] RPI / FWHM represents the ratio of relative peak intensity to full width at half maximum (FWHM), reflecting the orderliness of the crystal arrangement, crystallinity, and grain size distribution of that crystal plane. For example, the RPI / FWHM of T3 can be expressed as RPI / FWHM. T3 .

[0034] Primary particle size refers to the size of a single nanosheet, that is, the size of the nanosheet in its independent state, including the nanosheet diameter and nanosheet thickness, which can be seen by SEM.

[0035] Secondary particle size refers to the particle size distribution (Dv) measured using a laser particle size analyzer. 50 Dv 90 and Dv 99 Median particle size (Dv) 50 Also known as median particle size, it is the particle size value that is in the middle position after arranging the particle sizes of a group in ascending order.

[0036] Example A cyanuric acid / melamine composite with a characteristic crystal form, the preparation method of which includes the following steps: S1. Disperse melamine in deionized water and keep it at 60-70℃ to prepare a melamine suspension for later use; S2. Add deionized water to the reaction vessel, and add template agent when the temperature is raised to 30-40℃ to obtain template agent dispersion; S3. Continue to heat the template agent dispersion prepared in S2 to 45-50℃, add cyanuric acid, continue stirring and heat to 60-70℃; S4. Slowly add the melamine suspension prepared in S1 to the solution in S3, and complete the addition within 40-50 minutes. Continue to heat to 85-95℃ and react at a constant temperature for 1-2 hours. S5. After the reaction is completed, the mixture is cooled to room temperature at a cooling rate of (3-5)℃ / min, and then transferred, filtered, washed, dried and pulverized to obtain the cyanuric acid / melamine composite with the characteristic crystal form.

[0037] Specifically, the preparation methods of the cyanuric acid / melamine composites in Examples 1-8 and Comparative Examples 1-4 are shown in Table 1.

[0038] Table 1 Specifically, the peak position (2θ), peak intensity (PI) relationship, relative peak intensity (PRI), and ratio of relative peak intensity to full width at half maximum (RPI / FWHM) of the cyanuric acid / melamine composites prepared in Examples 1-8 and Comparative Examples 1-4 are shown in Tables 2 and 3, and their secondary particle size is shown in Table 4.

[0039] Table 2 As shown in Table 2, the peak positions (2θ) of Examples 1-8 are all at (10.93±0.20)°, (11.89±0.40)°, (21.96±0.40)°, (28.01±0.20)°, and (33.20±0.40)°. Meanwhile, the RPI of Examples 1-8 are all at: RPI T1 =0.65±0.20, RPI T2 =0.20±0.10, RPI T3 =0.15±0.10, RPI T5 =0.08±0.03. If a non-uniform cooling method is used (Comparative Example 1), the dropping speed of the melamine suspension is too fast (Comparative Example 2), or no template agent is added (Comparative Example 3), the RPI will change. In comparison, the T1, T2, T3, and T5 peaks of the RPI in Comparative Example 4 are stronger, which indirectly indicates that its crystal form is impure, the crystal arrangement is disordered, and the crystallinity is low.

[0040] Table 3 As can be seen from Table 3, PI in Examples 1-8 all satisfy PI. T4 >PI T1 >PI T2 >PI T3 >PI T5 Compared to the examples, the PI of Comparative Example 4... T1 >PI T4 This indicates that its T1 peak is stronger than T4. Furthermore, the RPI / FWHM values ​​for Examples 1-8 all satisfy the condition: 0.5 ≤ RPI / FWHM. T1 ≤3.0, 0.4≤RPI / FWHM T2 ≤1.8, 0.2≤RPI / FWHM T3 ≤0.7, 0.1≤RPI / FWHM T5 ≤0.3. If a non-uniform cooling method is used (Comparative Example 1), the dropping speed of the melamine suspension is too fast (Comparative Example 2), or no template agent is added (Comparative Example 3), the RPI / FWHM will increase and the peak shape will become broader. In contrast, the RPI / FWHM of Comparative Example 4 is larger and the peak shape is broader. This also indirectly indicates that its crystal form is impure, the crystal arrangement is disordered, and the crystallinity is low.

[0041] Table 4 As can be seen from Table 4, the particle size range of Examples 1-8 is: Dv 50 The range is 0.30-1.50 μm, Dv 90 The range is 0.80-4.00 μm, Dv 99 ≤7.50μm, 1.50≤Dv 90 / Dv 50 ≤2.50. If a non-uniform cooling method is used (Comparative Example 1), the dropping speed of the melamine suspension is too fast (Comparative Example 2), or no template agent is added (Comparative Example 3), the particle size distribution will become wider, and there may even be a trend of increasing particle size. In contrast, the particle size of Comparative Example 4 is larger and the particle size distribution is wider.

[0042] Experimental Example 1 The cyanuric acid / melamine composites provided in Examples 1-4 and Comparative Examples 1-4 of the present invention were respectively added to PA6, and the formulations and extrusion processes are as follows: The formula includes the following components: PA6 material: 89%; cyanuric acid / melamine compound: 10%; processing aids such as antioxidants and lubricants: 1%.

[0043] Extrusion process: The components were mixed evenly and granulated using a twin-screw extruder (50 mill). The extrusion temperature was 210-240℃, and the feeding speed was 300-320 rpm. After drying the granules (120℃ / 2h), relevant test strips were prepared by injection molding at a temperature of 220-235℃. After constant temperature (23℃±2℃) and constant humidity (50%±10%) treatment, the test strips underwent relevant performance tests, and the data are shown in Table 5.

[0044] Tensile strength and elongation at break shall be tested in accordance with GB / T 1040.1-2006; vertical burning performance shall be tested in accordance with GB / T 2408-2021; LOI shall be tested in accordance with GB / T 2406-93; GWIT shall be tested in accordance with GB / T 5169.11-2006; and CTI shall be tested in accordance with GB / T 4207-2003.

[0045] The dispersion grade test is as follows: the extruded granules are pressed into tablets of 0.1-0.2mm in a tablet press, and then observed under light to see if there are any dispersed powder packets. The grade is judged from 0 to 10: 0 no powder packets, 1-2 slightly, 3-4 obvious, 5 and above more, and 10 the most.

[0046] Table 5 Table 5 shows the advantages of Examples 1-4: significantly better tensile properties compared to the comparative example, significantly better GWIT performance compared to the comparative example, and better dispersion. In other words, the products of this invention, due to their more ordered crystal arrangement, higher crystallinity, and more uniform grain size distribution, fully demonstrate their mechanical, flame-retardant, and electrical properties.

[0047] Experimental Example 2 The cyanuric acid / melamine composites provided in Examples 1-4 and Comparative Examples 1-4 of this invention were added to PBT (30%GF) in equal proportions with aluminum diethylphosphite. The formulations and extrusion processes are as follows: The formula includes the following components: PBT material: 51%; GF: 30%; cyanuric acid / melamine composite and aluminum diethylphosphite: 18%; processing aids such as antioxidants and lubricants: 1%.

[0048] Extrusion process: The components were mixed evenly and granulated using a twin-screw extruder (50 mill). The extrusion temperature was 210-240℃, and the feeding speed was 320-350 rpm. After drying the granules (120℃ / 2h), relevant test strips were prepared by injection molding at a temperature of 230-240℃. After constant temperature (23℃±2℃) and constant humidity (50%±10%) treatment, the test strips underwent relevant performance tests, and the data are shown in Table 6.

[0049] Tensile strength and elongation at break were tested according to GB / T 1040.1-2006, vertical burning performance was tested according to GB / T 2408-2021, GWIT was tested according to GB / T 5169.11-2006, and CTI was tested according to GB / T 4207-2003.

[0050] The dispersion grade test is as follows: the extruded granules are pressed into tablets of 0.1-0.2mm in a tablet press, and then observed under light to see if there are any dispersed powder packets. The grade is judged from 0 to 10: 0 no powder packets, 1-2 slightly, 3-4 obvious, 5 and above more, and 10 the most.

[0051] Table 6 Table 6 shows the advantages of Examples 1-4: significantly better tensile properties compared to the comparative example, significantly better GWIT performance compared to the comparative example, and better dispersion. In other words, the products of this invention, due to their more ordered crystal arrangement, higher crystallinity, and more uniform grain size distribution, fully demonstrate their mechanical, flame-retardant, and electrical properties.

[0052] Experimental Example 3 The cyanuric acid / melamine composites provided in Examples 1-4 and Comparative Examples 1-4 of the present invention, along with coated ammonium polyphosphate and a charring agent, were added to PP in equal proportions. The formulations and extrusion processes are as follows: The formula includes the following components: PP material: 71%; cyanuric acid / melamine composite with coated ammonium polyphosphate and charring agent: 28%; antioxidants, lubricants and other processing aids: 1%.

[0053] Extrusion process: The components were mixed evenly and granulated using a twin-screw extruder (50 mill). The extrusion temperature was 170-200℃, and the feeding speed was 280-300 rpm. After drying the granules (105℃ / 2h), relevant test strips were prepared by injection molding at a temperature of 200-210℃. After constant temperature (23℃±2℃) and constant humidity (50%±10%) treatment, the test strips underwent relevant performance tests, and the data are shown in Table 7.

[0054] Tensile strength and elongation at break shall be tested according to GB / T 1040.1-2006, flexural strength shall be tested according to GB / T 9341-2008, vertical burning performance shall be tested according to GB / T 2408-2021, LOI shall be tested according to GB / T 2406-93, and MI shall be tested according to GB / T 3682-00.

[0055] The dispersion grade test is as follows: the extruded granules are pressed into tablets of 0.1-0.2mm in a tablet press, and then observed under light to see if there are any dispersed powder packets. The grade is judged from 0 to 10: 0 no powder packets, 1-2 slightly, 3-4 obvious, 5 and above more, and 10 the most.

[0056] Table 7 Table 7 shows the advantages of Examples 1-4: they exhibit significant advantages in mechanical properties, LOI, and flowability compared to the comparative examples, and demonstrate better dispersion. In other words, the products of this invention, due to their more ordered crystal arrangement, higher crystallinity, and more uniform grain size distribution, fully demonstrate superior mechanical properties, flame retardant properties, and processing flowability.

[0057] While embodiments of the present invention have been described in detail above, it will be apparent to those skilled in the art that various modifications and variations can be made to these embodiments. However, it should be understood that such modifications and variations fall within the scope and spirit of the invention as set forth in the claims. Furthermore, the invention described herein may have other embodiments and can be implemented or carried out in various ways.

Claims

1. A cyanuric acid / melamine composite with a characteristic crystal form, characterized in that, The cyanuric acid / melamine composite exhibits characteristic XRD diffraction peaks, with the following characteristic XRD diffraction peaks (2θ): 2θ T1 =(10.93±0.20)°、2θ T2 =(11.89±0.40)°、2θ T3 =(21.96±0.40)°、2θ T4 =(28.01±0.20)°、2θ T5 = (33.20 ± 0.40)°.

2. The cyanuric acid / melamine composite with the characteristic crystal form according to claim 1, characterized in that, The XRD characteristic diffraction peak intensity (PI) of the cyanuric acid / melamine composite satisfies: PI T4 >PI T1 >PI T2 >PI T3 >PI T5 .

3. The cyanuric acid / melamine composite with the characteristic crystal form according to claim 1, characterized in that, The relative peak intensities (PRI) of the XRD characteristic diffraction peaks of the cyanuric acid / melamine composite satisfy the following relationship: RPI T1 =PI T1 / PI T4 =0.65±0.20; RPI T2 =PI T2 / PI T4 =0.20±0.10; RPI T3 =PI T3 / PI T4 =0.15±0.10; RPI T5 =PI T5 / PI T4 =0.08±0.03 4. The cyanuric acid / melamine composite with the characteristic crystal form according to claim 1, characterized in that, The ratio of the relative peak intensity to the full width at half maximum (FWHM) of the XRD characteristic diffraction peaks of the cyanuric acid / melamine composite satisfies the following relationship: 0.5≤RPI / FWHM T1 ≤3.0; 0.4≤RPI / FWHM T2 ≤1.8; 0.2≤RPI / FWHM T3 ≤0.7; 0.1≤RPI / FWHM T5 ≤0.3。 5. The cyanuric acid / melamine composite with the characteristic crystal form according to claim 1, characterized in that, The pH value of the cyanuric acid / melamine complex is 4-7.

6. The cyanuric acid / melamine composite with the characteristic crystal form according to claim 1, characterized in that, The equivalent particle size of the cyanuric acid / melamine composite is: Dv 50 The range is 0.30-1.50 μm, Dv 90 The range is 0.80-4.00 μm, Dv 99 ≤7.50μm.

7. The cyanuric acid / melamine composite with the characteristic crystal form according to claim 1, characterized in that, The equivalent particle size of the cyanuric acid / melamine composite satisfies the following relationship: 1.50 ≤ Dv 90 / Dv 50 ≤2.

50.

8. A method for preparing a cyanuric acid / melamine composite with the characteristic crystal form according to any one of claims 1-7, characterized in that, Includes the following steps: S1. Disperse melamine in deionized water and keep it at 60-70℃ to prepare a melamine suspension for later use; S2. Add deionized water to the reaction vessel, and add template agent when the temperature is raised to 30-40℃ to obtain template agent dispersion; S3. Continue to heat the template agent dispersion prepared in S2 to 45-50℃, add cyanuric acid, continue stirring and heat to 60-70℃; S4. Slowly add the melamine suspension prepared in S1 to the solution in S3, and complete the addition within 40-50 minutes. Continue to heat to 85-95℃ and react at a constant temperature for 1-2 hours. S5. After the reaction is completed, the mixture is cooled to room temperature at a cooling rate of (3-5)℃ / min, and then transferred, filtered, washed, dried and pulverized to obtain the cyanuric acid / melamine composite with the characteristic crystal form.

9. The method for preparing the characteristic crystalline form of the cyanuric acid / melamine composite according to claim 8, characterized in that, The mass ratio of cyanuric acid to melamine is (1.015-1.030):1; the mass ratio of the sum of deionized water in S1 and deionized water in S2 to the cyanuric acid / melamine complex is (6-15):1; The mass ratio of the template agent to the cyanuric acid / melamine complex is (0.015-0.05):1; The template agent is one or more of the following: tetrabutylammonium chloride, polystyrene-b-polyacrylic acid, polyimide, polyvinylidene fluoride, polyacrylonitrile, polystyrene, graphene, montmorillonite, silica, zeolite, hydrotalcite, graphitic silicon nitride, porphyrins, phthalocyanines, phytic acid, and alumina.

10. The application of a cyanuric acid / melamine composite with the characteristic crystal form as described in any one of claims 1-7 in polymer materials.

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