Inorganic composite flame retardant, its preparation method and application

Abstract

The application relates to an inorganic composite flame retardant as well as a preparation method and application thereof, relates to the technical field of flame retardants, and comprises the following steps: stirring and mixing expanded graphite, magnesium hydroxide and aluminum hydroxide to obtain mixed dry materials; adding the mixed dry materials, a modifier and a diamino type silane coupling agent into an alcohol aqueous solution to perform heating and stirring, and then performing filtration and drying to obtain the inorganic composite flame retardant. Compared with the prior art, the application mainly uses expanded graphite, magnesium hydroxide and aluminum hydroxide which meet specific particle size relationships for compounding, and introduces a modifier and a diamino type silane coupling agent which have triazine ring structures and morpholine ring structures for chemical modification treatment, so that the obtained flame retardant has improved flame retardant performance, the interface interaction between the flame retardant and a high polymer matrix material is enhanced, the problems of poor compatibility between traditional inorganic flame retardants and high polymer matrix materials are solved, and the application prospect is wide.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of flame retardant technology, in particular to an inorganic composite flame retardant and a preparation method and application thereof. BACKGROUND

[0002] With the wide application of polymer materials in many fields such as building, electronics, transportation, aerospace, etc., the fire hazard problem caused by flammability of polymer materials is increasingly prominent, which poses a serious threat to people's life and property safety. Therefore, developing high-performance flame retardants to improve the flame retardant performance of polymer materials has become a key problem to be solved in the field of material science.

[0003] At present, the common flame retardants on the market are mainly divided into two categories: organic flame retardants and inorganic flame retardants. Among them, inorganic flame retardants are gradually favored by people due to their good thermal stability, low toxicity, strong smoke suppression and other obvious advantages. However, traditional inorganic flame retardants still have many shortcomings in practical application. Specifically, on the one hand, a single inorganic flame retardant often needs a large amount of addition to achieve an ideal flame retardant effect, but a large amount of addition will significantly change the physical and mechanical properties of the polymer material, such as reducing the strength, toughness and processing performance of the material, affecting the comprehensive performance and service life of the material. For example, a large amount of magnesium hydroxide or aluminum hydroxide is added in plastic products, which makes the plastic products brittle and hard, and it is difficult to meet the actual use requirements. In addition, the compatibility between traditional inorganic flame retardants and polymer matrix materials is poor, which reduces the dispersibility and stability of the flame retardant in the material, further affecting the durability and reliability of the flame retardant effect, thereby limiting the application of inorganic flame retardants in the preparation of polymer flame retardant materials. SUMMARY

[0004] To solve the above problems, the present application provides an inorganic composite flame retardant and a preparation method and application thereof.

[0005] In a first aspect, the present application provides a preparation method of an inorganic composite flame retardant, which comprises the following steps:

[0006] The expanded graphite, magnesium hydroxide and aluminum hydroxide are stirred and mixed to obtain a mixed dry material;

[0007] The mixed dry material, a modifier and a diamino type silane coupling agent are added to an alcohol aqueous solution for heating and stirring, and then filtered and dried to obtain an inorganic composite flame retardant;

[0008] The modifier has a triazine ring structure and a morpholine ring structure.

[0009] The D50 particle size A of the expanded graphite, the D50 particle size B of the magnesium hydroxide, and the D50 particle size C of the aluminum hydroxide satisfy the following relationship: 4.0≤(A / C)-(A / B)≤5.5.

[0010] Further, the D50 particle size A of the expanded graphite is 2-5 µm;

[0011] Further, the D50 particle size B of the magnesium hydroxide is 1.2-1.8 µm;

[0012] Further, the D50 particle size C of the aluminum hydroxide is 0.3-0.7 µm;

[0013] Further, the weight ratio of the expanded graphite, the magnesium hydroxide, and the aluminum hydroxide is 100:(5-10):(17-23).

[0014] Further, the added weight of the modifier accounts for 5-10% of the weight of the mixed dry materials.

[0015] Further, the modifier includes 4-(4,6-dimethoxytriazin-2-yl)-4-methylmorpholine hydrochloride.

[0016] Further, the added weight of the bis-amino type silane coupling agent accounts for 1-5% of the weight of the mixed dry materials.

[0017] Further, the bis-amino type silane coupling agent includes N-(2-aminoethyl)-3-aminopropyltrimethoxysilane.

[0018] Further, the added weight of the alcohol aqueous solution accounts for 5-8 times the weight of the mixed dry materials, and the alcohol aqueous solution is obtained by compounding ethanol and water in a volume ratio of (4-6):(1-2), and then adding glacial acetic acid to adjust the pH of the system to 4.2-5.0.

[0019] Further, the working condition parameters of the heating and stirring include a temperature of 40-50°C and a time of 1-2 hours.

[0020] In a second aspect, based on the same inventive concept, the present application provides an inorganic composite flame retardant prepared by the preparation method of the inorganic composite flame retardant of the first aspect.

[0021] In a third aspect, based on the same inventive concept, the present application provides the use of the inorganic composite flame retardant of the second aspect in the preparation of a flame-retardant material.

[0022] The above technical solutions provided by the embodiments of the present application have at least the following advantages compared with the prior art:

[0023] The embodiment of the present application provides an inorganic composite flame retardant and a preparation method and application thereof, compared with the prior art, the present application mainly uses expanded graphite, magnesium hydroxide and aluminum hydroxide which meet the specific particle size relationship for compounding, and introduces a modifier with triazine ring structure and morpholine ring structure and a diamino type silane coupling agent for chemical modification treatment, which not only improves the flame retardant performance of the obtained flame retardant, but also enhances the interface interaction between the flame retardant and the polymer matrix material, solves the problem of poor compatibility of traditional inorganic flame retardant and polymer matrix material, and has a wide application prospect. Specifically,

[0024] 1) On the one hand, the expanded graphite expands rapidly in volume at high temperature, forms a dense porous carbon layer, can effectively block heat transfer, oxygen diffusion and molten droplet spread, and forms a physical flame retardant barrier; at the same time, the magnesium hydroxide and aluminum hydroxide form a gradient heat absorption effect due to the difference in decomposition temperature when heated, which can effectively prolong the flame retardant duration. On this basis, the present application further controls the particle size relationship of expanded graphite, magnesium hydroxide and aluminum hydroxide, which can not only optimize the pore structure of the carbon layer, form a ceramic-carbon composite barrier layer, and improve the flame retardant effect; at the same time, the multi-stage filling effect is used to reduce the interface defects and avoid the phase separation of the polymer matrix material.

[0025] 2) On the other hand, the triazine ring structure (such as 4-(4, 6-dimethoxytriazin-2-yl)-4-methyl morpholine hydrochloride) in the modifier can catalyze the carbonization at high temperature, promote the formation of a dense carbon layer rich in aromatic rings, improve the thermal stability and oxidation resistance of the residual carbon, and further improve the flame retardant effect. At the same time, the polar groups on the morpholine ring structure and the chemical bridging effect of the diamino type silane coupling agent significantly enhance the interface bonding strength between the flame retardant and the polymer matrix, improve the compatibility of the inorganic flame retardant and the polymer matrix material, and thus improve the mechanical properties such as tensile strength and impact toughness of the material and ensure the durability and reliability of the flame retardant effect. DETAILED DESCRIPTION

[0026] In order to make the purpose, technical scheme and advantages of the embodiments of the present application more clear, the technical scheme in the embodiments of the present application will be clearly and completely described below. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor belong to the scope of protection of the present application.

[0027] Unless otherwise specifically indicated, all raw materials, reagents, instruments and equipment used in the present application can be purchased on the market or prepared by existing methods; for example, 4-(4,6-dimethoxytriazin-2-yl)-4-methylmorpholine hydrochloride (CAS No. 3945-69-5), expanded graphite, magnesium hydroxide, aluminum hydroxide, etc. can be directly used as commercially available products. At the same time, the steps and condition parameters involved in the present application, if there is no special limitation or specific description, can be carried out according to the existing technology disclosed in the preparation process of inorganic composite flame retardant or directly using existing equipment, for example, the expanded graphite, magnesium hydroxide and aluminum hydroxide with specific particle size in the present application can be directly used as commercially available products to prepare by grinding and screening process. In addition, D50 in the present application refers to the particle size value corresponding to the cumulative volume percentage of 50% in the cumulative particle size distribution curve of the substance, which can be determined by existing detection methods such as sieving method (grading particles by sieves with different pore sizes, weighing the mass of particles remaining on each sieve, and calculating the cumulative distribution curve to determine D50), laser diffraction / scattering method (laser beam passing through the sample, particles scattering light, detecting the intensity and angle of scattered light, and using Mie scattering theory to inverse the particle size distribution). At the same time, "A / C" in "(A / C)-(A / B)" represents the ratio of A to C and "A / B" represents the ratio of A to B.

[0028] The present application will be further described in conjunction with specific examples. It should be understood that these examples are only used to illustrate the present application and not to limit the scope of the present application. The experimental methods in the following examples without specific conditions are generally determined according to national standards. If there is no corresponding national standard, it is carried out according to the general international standard, conventional conditions, or according to the conditions suggested by the manufacturer.

[0029] Example 1

[0030] This example provides an inorganic composite flame retardant, and the preparation method of the inorganic composite flame retardant comprises the following steps:

[0031] The expanded graphite, magnesium hydroxide and aluminum hydroxide with a weight ratio of 100:7:20 are stirred and mixed to obtain a mixed dry material;

[0032] The obtained mixed dry material, modifier and diamino type silane coupling agent are added into an alcohol aqueous solution for heating and stirring, the temperature is 45°C, and the time is 1.5 hours. After heating and stirring, filtration and drying are carried out to obtain an inorganic composite flame retardant;

[0033] The modifier is specifically 4-(4,6-dimethoxytriazin-2-yl)-4-methylmorpholinium hydrochloride, and the addition weight accounts for 8% of the weight of the mixed dry material; the amino silane coupling agent is specifically N-(2-aminoethyl)-3-aminopropyl trimethoxysilane, and the addition weight accounts for 2.5% of the weight of the mixed dry material; the alcohol aqueous solution is specifically obtained by compounding ethanol and water in a volume ratio of 5:1.5, adding appropriate glacial acetic acid to adjust the pH of the system to 4.6, and then adding an appropriate amount, and the addition weight accounts for 7 times the weight of the mixed dry material.

[0034] The D50 particle size A of the expanded graphite is 2.4 µm, the D50 particle size B of the magnesium hydroxide is 1.5 µm, and the D50 particle size C of the aluminum hydroxide is 0.4 µm, and the three satisfy the following relationship: (A / C)-(A / B)=4.4.

[0035] Example 2

[0036] The preparation method of the inorganic composite flame retardant provided in this example comprises the following steps:

[0037] The expanded graphite, the magnesium hydroxide, and the aluminum hydroxide in a weight ratio of 100:5:23 are stirred and mixed to obtain a mixed dry material.

[0038] The obtained mixed dry material, the modifier, and the amino silane coupling agent are added into an alcohol aqueous solution for heating and stirring, the temperature is 40°C, and the time is 2 hours. After heating and stirring, filtration and drying are performed to obtain the inorganic composite flame retardant.

[0039] The modifier is specifically 4-(4,6-dimethoxytriazin-2-yl)-4-methylmorpholinium hydrochloride, and the addition weight accounts for 5% of the weight of the mixed dry material; the amino silane coupling agent is specifically N-(2-aminoethyl)-3-aminopropyl trimethoxysilane, and the addition weight accounts for 1% of the weight of the mixed dry material; the alcohol aqueous solution is specifically obtained by compounding ethanol and water in a volume ratio of 4:1, adding appropriate glacial acetic acid to adjust the pH of the system to 4.2, and then adding an appropriate amount, and the addition weight accounts for 7 times the weight of the mixed dry material.

[0040] The D50 particle size A of the expanded graphite is 2.1 µm, the D50 particle size B of the magnesium hydroxide is 1.2 µm, and the D50 particle size C of the aluminum hydroxide is 0.3 µm, and the three satisfy the following relationship: (A / C)-(A / B)=5.3.

[0041] Example 3

[0042] The preparation method of the inorganic composite flame retardant provided in this example comprises the following steps:

[0043] The expanded graphite, the magnesium hydroxide, and the aluminum hydroxide in a weight ratio of 100:10:17 are stirred and mixed to obtain a mixed dry material.

[0044] The obtained mixed dry material, modifier and bis-amino silane coupling agent are added into an alcohol aqueous solution for heating and stirring, the temperature is 50°C, the time is 1 hour, after heating and stirring, filtration and drying are performed to obtain the inorganic composite flame retardant;

[0045] The modifier is specifically 4-(4, 6-dimethoxytriazin-2-yl)-4-methyl morpholine hydrochloride, and the addition weight accounts for 10% of the weight of the mixed dry material; the bis-amino silane coupling agent is specifically N-(2-aminoethyl)-3-aminopropyl trimethoxysilane, and the addition weight accounts for 4.6% of the weight of the mixed dry material; the alcohol aqueous solution is specifically obtained by compounding ethanol and water in a volume ratio of 6:1, adding appropriate glacial acetic acid to adjust the pH of the system to 4.8, and the addition weight accounts for 5 times of the weight of the mixed dry material;

[0046] The D50 particle size A of the expanded graphite is 4.8 µm, the D50 particle size B of the magnesium hydroxide is 1.8 µm, and the D50 particle size C of the aluminum hydroxide is 0.7 µm, and the three satisfy the following relationship: (A / C)-(A / B)=4.2.

[0047] Comparative Example 1

[0048] This example provides an inorganic composite flame retardant and a preparation method thereof, which is only different from Example 1 in that:

[0049] (1) the D50 particle size A of the expanded graphite is 8.4 µm, the D50 particle size B of the magnesium hydroxide is 2.5 µm, and the D50 particle size C of the aluminum hydroxide is 0.5 µm, and the three satisfy the following relationship: (A / C)-(A / B)=13.4.

[0050] Comparative Example 2

[0051] This example provides an inorganic composite flame retardant and a preparation method thereof, which is only different from Example 1 in that:

[0052] (1) no modifier is added.

[0053] Comparative Example 3

[0054] This example provides a traditional flame retardant, which is specifically magnesium hydroxide (D50 particle size is 1.5 µm).

[0055] Test Example

[0056] The inorganic composite flame retardant obtained in the above examples and comparative examples is applied to preparation of a flame-retardant polymer material to investigate its flame-retardant effect. Specifically, the following process is included: 74 parts of polyethylene, 25 parts of the inorganic composite flame retardant, 0.5 parts of tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid]pentaerythritol ester and 0.5 parts of polyethylene wax are weighed according to the weight fraction, and are blended at a temperature of 148℃ for 20 minutes, and then granulated to obtain a flame-retardant polymer material; then the obtained flame-retardant polymer material is subjected to oxygen index (OI, %) testing according to the GB / T 2406.2-2009 testing standard and tensile strength (Mpa) testing according to the ISO 527-1:2012 testing standard, and the testing results are shown in Table 1.

[0057] Table 1

[0058]

[0059] From Table 1, it can be seen that:

[0060] 1) Compared with the traditional inorganic flame retardant provided in Comparative Example 1, the flame-retardant performance and mechanical properties of the flame-retardant polymer material obtained by using the inorganic composite flame retardant provided in the examples of the present application are both significantly improved, indicating that the inorganic composite flame retardant provided in the examples of the present application can significantly improve the compatibility between the polymer matrix material while imparting excellent flame-retardant effect to the polymer flame-retardant material.

[0061] 2) From the testing results of Example 1 and Comparative Example 1, it can be seen that by selecting the expandable graphite, magnesium hydroxide and aluminum hydroxide with suitable particle size relationship for compounding use, the flame-retardant performance and mechanical properties of the flame-retardant polymer material can be significantly improved, especially the improvement in mechanical properties is more significant.

[0062] 3) From the testing results of Example 1 and Comparative Example 2, it can be seen that by introducing the specific modifier with triazine ring structure and morpholine ring structure, the flame-retardant performance and mechanical properties of the flame-retardant polymer material can be improved to a certain extent, especially the improvement in flame-retardant performance is more significant.

[0063] Various embodiments of the present application can exist in the form of a range; it should be understood that the description in the form of a range is merely for the sake of convenience and brevity, and should not be understood as a rigid limitation on the scope of the present application; therefore, it should be considered that the described range has specifically disclosed all possible sub-ranges and single values within the range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., as well as single numbers within the described range, such as 1, 2, 3, 4, 5 and 6, regardless of the range. In addition, whenever a numerical range is indicated in this document, it refers to any cited number (fraction or integer) within the indicated range.

[0064] The foregoing is considered as illustrative only of the principles of the application. Numerous modifications and changes will readily occur to those skilled in the art, and the generic principles defined herein can be applied to other embodiments without departing from the spirit or scope of the application. Therefore, the scope of the application is indicated by the claims rather than by the foregoing description, and all changes that come within the meaning and range of equivalents are intended to be embraced therein.

Claims

1. A method for preparing an inorganic composite flame retardant, characterized in that, The preparation method of the inorganic composite flame retardant includes the following steps: Expanded graphite, magnesium hydroxide, and aluminum hydroxide are stirred and mixed to obtain a dry mixture; The mixed dry materials, modifier and diamino silane coupling agent were added to an alcohol-water solution and heated and stirred, then filtered and dried to obtain an inorganic composite flame retardant. The modifier has a triazine ring structure and a morpholine ring structure; The D50 particle size A of the expanded graphite, the D50 particle size B of the magnesium hydroxide, and the D50 particle size C of the aluminum hydroxide satisfy the following relationship: 4.0 ≤ (A / C) - (A / B) ≤ 5.5; The D50 particle size A of the expanded graphite is 2~5µm; The D50 particle size B of the magnesium hydroxide is 1.2~1.8µm; The D50 particle size C of the aluminum hydroxide is 0.3~0.7µm; The weight ratio of the expanded graphite, the magnesium hydroxide, and the aluminum hydroxide is 100:(5~10):(17~23).

2. The method for preparing the inorganic composite flame retardant according to claim 1, characterized in that, The modifier is added at a weight percentage of 5-10% of the weight of the mixed dry material.

3. The method for preparing the inorganic composite flame retardant according to claim 2, characterized in that, The modifier includes 4-(4,6-dimethoxytriazine-2-yl)-4-methylmorpholine hydrochloride.

4. The method for preparing the inorganic composite flame retardant according to claim 1, characterized in that, The weight percentage of the added diamino silane coupling agent is 1-5% of the weight of the mixed dry material.

5. The method for preparing the inorganic composite flame retardant according to claim 4, characterized in that, The diamino silane coupling agent includes N-(2-aminoethyl)-3-aminopropyltrimethoxysilane.

6. The method for preparing the inorganic composite flame retardant according to claim 1, characterized in that, The added alcohol-water solution accounts for 5 to 8 times the weight of the mixed dry material. The alcohol-water solution is obtained by mixing ethanol and water in a volume ratio of (4 to 6): (1 to 2) and then adding glacial acetic acid to adjust the pH of the system to 4.2 to 5.

0.

7. The method for preparing the inorganic composite flame retardant according to claim 1, characterized in that, The working conditions for heating and stirring include: temperature of 40~50℃ and time of 1~2 hours.

8. An inorganic composite flame retardant, characterized in that, The inorganic composite flame retardant is prepared by the method described in any one of claims 1 to 7.

9. The application of the inorganic composite flame retardant according to claim 8 in the preparation of flame retardant materials.

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