Preparation method and application of magnesium hydroxide / phosphorus hybrid flame retardant

Abstract

The invention discloses a preparation method and application of a magnesium hydroxide / phosphorus hybrid flame retardant, and belongs to the technical field of environment-friendly flame retardant preparation and polymer composite materials. According to the technical scheme, the preparation method comprises the following steps: sequentially adding magnesium hydroxide, diphenyl phosphite, a hydrogen peroxide solution and an environment-friendly reaction medium into a hydrothermal reaction kettle, ultrasonically mixing uniformly, transferring into a drying oven for heating reaction, cooling, filtering and drying to obtain the magnesium hydroxide hybrid flame retardant. The preparation method of the magnesium hydroxide / phosphorus hybrid flame retardant provided by the invention is simple in process and low in cost, a target product can be prepared through one-pot heating, a reaction medium is green and environment-friendly, and the preparation method is suitable for mass production. Compared with a pure magnesium hydroxide flame retardant, the magnesium hydroxide / phosphorus hybrid flame retardant prepared by the preparation method disclosed by the invention shows an excellent flame retardant effect under a low filling amount, and meanwhile, the flame-retardant modified ethylene-butyl acrylate copolymer (EBA) cable material has good mechanical properties.

Description

Technical Field

[0001] The present invention belongs to the technical fields of environmental protection flame retardant preparation technology and polymer composite material technology, and specifically relates to a preparation method of magnesium hydroxide / phosphorus hybrid flame retardant and the application of the flame retardant in flame retardant cable materials. Background Art

[0002] Ethylene-butyl acrylate copolymer (abbreviated as EBA) is a thermoplastic elastomer material obtained by copolymerizing ethylene and butyl acrylate. As one of the copolymer modified products of polyethylene materials, EBA occupies an important position in the fields of cables, packaging, automobiles, electronics, medical treatment, etc. due to its excellent flexibility, thermal stability and compatibility. However, the limiting oxygen index (LOI) of EBA is only about 18.5%, belonging to flammable materials, and there is a significant fire risk under high-voltage electric field thermal effects, external heat sources or overload conditions, which greatly hinders its practical application.

[0003] Magnesium hydroxide (MH) is an important inorganic flame retardant, which has the advantages of non-toxicity, environmental protection, good long-term stability and strong weather resistance, and is widely used in the flame retardant modification of polymer materials. Due to the low flame retardant efficiency of magnesium hydroxide, a high addition amount (mass fraction ≥ 70%) is required in EBA to meet the flame retardant requirements. When an excessive amount of magnesium hydroxide is added, the flame retardant particles are prone to agglomeration, resulting in a significant reduction in the mechanical properties of the prepared flame retardant polymer composite material.

[0004] Currently, common magnesium hydroxide modification methods, such as surface treatment with stearic acid, titanate, silane coupling agent, etc., and coating inorganic particles such as polymethylsilsesquioxane on the surface of magnesium hydroxide, for example, CN103554364A, CN108285552A, CN113980351B, CN116948257. After modification, the dispersibility of the flame retardant particles in the polymer matrix is significantly improved, and to a certain extent, the mechanical properties of the flame retardant polymer are also improved, but there are still deficiencies such as low flame retardant efficiency, complicated modification steps, and non-environmental protection reaction media. Therefore, simplifying the preparation steps, using green and environmentally friendly reaction media, and at the same time improving the flame retardant efficiency of modified magnesium hydroxide are the key technical problems to be solved in the current modification and application of magnesium hydroxide. Summary of the Invention

[0005] In view of the problem of low flame retardancy efficiency of magnesium hydroxide in cable materials, the present invention develops a simple and environmentally friendly preparation method of magnesium hydroxide / phosphorus hybrid flame retardant, and provides the application of magnesium hydroxide / phosphorus hybrid flame retardant in cable materials. To achieve this purpose, magnesium hydroxide, diphenyl phosphite, hydrogen peroxide solution and environmentally friendly reaction medium are successively added to a hydrothermal reaction kettle. After ultrasonic mixing evenly, one-pot heating reaction is carried out. After cooling, filtration and drying are carried out to obtain magnesium hydroxide / phosphorus hybrid flame retardant. During the reaction process, H2O2 in the hydrogen peroxide solution can not only activate magnesium hydroxide and increase the number of its surface hydroxyl groups (MH-OH), but also convert O=P-H in diphenyl phosphite into O=P-OH. Then, MH-OH and O=P-OH undergo an esterification reaction to form magnesium hydroxide / phosphorus hybrid flame retardant. Subsequently, the above-mentioned magnesium hydroxide / phosphorus hybrid flame retardant is added to ethylene-butyl acrylate copolymer (EBA) to prepare cable materials with good flame retardancy and excellent mechanical properties.

[0006] The technical solution of the present invention is as follows:

[0007] In the first aspect, the present invention provides a preparation method of magnesium hydroxide / phosphorus hybrid flame retardant. Magnesium hydroxide, diphenyl phosphite, hydrogen peroxide solution and environmentally friendly reaction medium are successively added to a hydrothermal reaction kettle, ultrasonically mixed evenly, and then transferred to an oven for heating reaction. After cooling, filtration and drying are carried out to obtain magnesium hydroxide / phosphorus hybrid flame retardant.

[0008] Preferably, magnesium hydroxide, diphenyl phosphite, hydrogen peroxide solution and environmentally friendly reaction medium are successively added to a hydrothermal reaction kettle, ultrasonically treated at 30-60 °C for 2-4 h, then transferred to an oven and heated to 110-150 °C for reaction for 3-5 h. After cooling and filtration, drying is carried out at 120-140 °C for 5-8 h to obtain magnesium hydroxide / phosphorus hybrid flame retardant.

[0009] Preferably, the mass fraction of magnesium hydroxide is 100 parts, the mass fraction of diphenyl phosphite is 40-60 parts, the mass fraction of hydrogen peroxide solution is 3-8 parts, and the mass fraction of environmentally friendly reaction medium is 320-480 parts.

[0010] Preferably, magnesium hydroxide is hexagonal flaky particles, diphenyl phosphite is a colorless transparent liquid, the mass concentration of hydrogen peroxide solution is 10-30%, and the environmentally friendly reaction medium is a mixture of ethanol and distilled water.

[0011] Preferably, the mass ratio of ethanol to distilled water in the environmentally friendly reaction medium is 5-15:1.

[0012] In the second aspect, the present invention also provides the application of the flame-retardant cable material of magnesium hydroxide / phosphorus hybrid flame retardant obtained by the above preparation method, specifically: melting and blending the magnesium hydroxide / phosphorus hybrid flame retardant and ethylene-butyl acrylate copolymer (EBA) and processing and molding to obtain a flame-retardant cable material.

[0013] Compared with the prior art, the present invention has the following beneficial effects:

[0014] 1. The preparation method of the magnesium hydroxide / phosphorus hybrid flame retardant provided by the present invention has a simple process and low cost. The target product can be prepared by heating in one pot, and the reaction medium is green and environmentally friendly, suitable for mass production.

[0015] 2. In the preparation method of the magnesium hydroxide / phosphorus hybrid flame retardant designed and developed by the present invention, the hydrogen peroxide solution plays a dual role of "killing two birds with one stone". It not only increases the number of surface hydroxyl groups (MH-OH) on magnesium hydroxide, but also converts the O=P-H in the phosphite into O=P-OH, and then promotes the grafting of diphenyl phosphite on the surface of magnesium hydroxide through an esterification reaction. The highest grafting rate of diphenyl phosphite reaches 38.7 wt%.

[0016] 3. The magnesium hydroxide / phosphorus hybrid flame retardant prepared by the present invention exhibits excellent flame retardant effects at low filling amounts compared with pure magnesium hydroxide, and at the same time has better mechanical properties in the prepared cable compound. In an ethylene-butyl acrylate copolymer (EBA) matrix, to achieve the UL-94 vertical burning test V-0 level, the mass fraction of pure magnesium hydroxide to be added is 70%, while the mass fraction of the magnesium hydroxide / phosphorus hybrid flame retardant of the present invention to be added is only 45%. And, on the premise of adding the same mass of flame retardant in EBA, the tensile strength and notched impact strength of the EBA cable compound prepared by adding the magnesium hydroxide / phosphorus hybrid flame retardant of the present invention are higher than those of the EBA cable compound prepared by adding pure magnesium hydroxide, which indicates that the magnesium hydroxide / phosphorus hybrid flame retardant not only improves the flame retardant performance of the EBA cable compound, but also synchronously enhances its mechanical properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is the reaction route diagram for preparing the magnesium hydroxide / phosphorus hybrid flame retardant (MH-g-DPP) of the present invention

[0018] Figure 2 It is the scanning electron microscope images of (a) the magnesium hydroxide / phosphorus hybrid flame retardant (MH-g-DPP) and (b) pure magnesium hydroxide (MH) prepared in Example 1 of the present invention

[0019] Figure 3 It is the infrared spectra of the magnesium hydroxide / phosphorus hybrid flame retardant (MH-g-DPP) and pure magnesium hydroxide (MH) prepared in Example 1 of the present invention

[0020] Figure 4 It is the X-ray photoelectron spectroscopy diagrams of the magnesium hydroxide / phosphorus hybrid flame retardant (MH-g-DPP) and pure magnesium hydroxide (MH) prepared in Example 1 of the present invention DETAILED DESCRIPTION OF THE INVENTION

[0021] To enable those skilled in the art to better understand the technical solutions in the present invention, the technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments.

[0022] Performance test description:

[0023] Limiting oxygen index test (LOI) test: Tested according to the method described in GB / T 2046-2009, and the test sample size is 100mm×6.5mm×3.2mm.

[0024] Vertical burning test: Tested according to the method described in GB / T2408-2008, and the test sample size is 100mm×13mm×3.2mm.

[0025] Mechanical property test (including tensile test and notched impact test): The tensile test is carried out according to the method described in GB / T1040.1-2018, and the effective part size of the test sample is 20mm×4mm×1mm. The notched impact test is carried out according to the method described in GB / T1843-2008, and the test sample size is 80mm×10mm×4.0mm.

[0026] Reaction mechanism description:

[0027] As Figure 1 shown, the reaction route for preparing magnesium hydroxide / phosphorus hybrid flame retardant (MH-g-DPP) by one-pot method: In a hydrothermal reaction kettle, magnesium hydroxide (MH) reacts with hydrogen peroxide (H2O2) in the hydrogen peroxide solution to generate hydroxyl groups (MH-OH) on its surface; at the same time, O=P-H in diphenyl phosphite (DPP) also reacts with H2O2 to be converted into O=P-OH; subsequently, MH-OH and O=P-OH undergo an esterification reaction (O=P-OH is acidic, self-catalytic esterification reaction) to generate magnesium hydroxide / phosphorus hybrid flame retardant (MH-g-DPP).

[0028] Example 1

[0029] The synthesis method of the magnesium hydroxide / phosphorus hybrid flame retardant in this example includes the following steps:

[0030] 100 parts of magnesium hydroxide, 50 parts of diphenyl phosphite, 3 parts of 20% hydrogen peroxide solution and 440 parts of environmentally friendly reaction medium (400 parts of ethanol and 40 parts of distilled water) are successively added into a hydrothermal reaction kettle, ultrasonically treated at 40°C for 2 h, then transferred to an oven and heated to 110°C for reaction for 3 h, filtered after cooling, and dried at 130°C for 5 h to obtain the magnesium hydroxide / phosphorus hybrid flame retardant, named MH-g-DPP1.

[0031] By weighing before and after the reaction and calculating, the grafting rate of diphenyl phosphite in the prepared MH-g-DPP1 in this example is 34.6 wt%.

[0032] The scanning electron microscope image of the MH-g-DPP1 prepared in this example is as Figure 2 shown in a. The surface of the lamella becomes rough, and protruding particles can be observed, while the Figure 2 surface of pure magnesium hydroxide (MH) in b for comparison is smooth. At the same time, Figure 3 the infrared spectra of MH-g-DPP1 and MH are shown. By comparison, it is found that MH-g-DPP1 shows a C-H absorption peak of the benzene ring structure at 3055 cm -1 ; a benzene ring (Ph) skeletal absorption peak appears at 1595 cm -1 ; a strong O=P-O absorption peak appears at 1235 cm -1 ; O-P-Ph absorption peaks appear at 1080 cm -1 and 956 cm -1 . This indicates that MH-g-DPP1 contains the typical groups in the diphenyl phosphite molecule. Subsequently, Figure 3 the X-ray photoelectron spectra of MH and MH-g-DPP1 are shown. By comparison, new peaks of C 1s , P 2s and P 2P appear in MH-g-DPP1, which also correspond to the elemental composition in diphenyl phosphite. Thus, it is determined that diphenyl phosphite has been successfully grafted onto the surface of MH.

[0033] In this example, MH-g-DPP1 is used to prepare ethylene-butyl acrylate copolymer (EBA) composites. The specific method is as follows: 55 parts of EBA and 45 parts of MH-g-DPP1 are stirred and mixed, then polyethylene composites are prepared by melt blending, and finally test specimens are prepared by hot pressing.

[0034] Example 2

[0035] The preparation method of the magnesium hydroxide / phosphorus hybrid flame retardant in this example includes the following steps:

[0036] 100 parts of magnesium hydroxide, 40 parts of diphenyl phosphite, 5 parts of 10% hydrogen peroxide solution, and 330 parts of environmentally friendly reaction medium (300 parts of ethanol and 30 parts of distilled water) are successively added to a hydrothermal reaction kettle, ultrasonicated at 30 °C for 3 h, then transferred to an oven and heated to 130 °C for reaction for 4 h, cooled and filtered, and dried at 120 °C for 8 h to obtain the magnesium hydroxide / phosphorus hybrid flame retardant, named MH-g-DPP2.

[0037] By weighing before and after the reaction and calculating, the grafting rate of diphenyl phosphite in MH-g-DPP2 prepared in this example is 31.2 wt%.

[0038] In this example, MH-g-DPP2 was used in the EBA composite material, and the specific method was the same as that in Example 1.

[0039] Example 3

[0040] The preparation method of the magnesium hydroxide / phosphorus hybrid flame retardant in this example includes the following steps:

[0041] 100 parts of magnesium hydroxide, 40 parts of diphenyl phosphite, 8 parts of 30% hydrogen peroxide solution, and 330 parts of environmentally friendly reaction medium (275 parts of ethanol and 55 parts of distilled water) were successively added to a hydrothermal reaction kettle, ultrasonicated at 30 °C for 2 h, then transferred to an oven and heated to 150 °C for reaction for 4 h. After cooling, it was filtered and dried at 130 °C for 6 h to obtain the magnesium hydroxide / phosphorus hybrid flame retardant, named MH-g-DPP3.

[0042] By weighing before and after the reaction and calculating, the grafting rate of diphenyl phosphite in MH-g-DPP3 prepared in this example is 32.5 wt%.

[0043] In this example, MH-g-DPP3 was used in the EBA composite material, and the specific method was the same as that in Example 1.

[0044] Example 4

[0045] The preparation method of the magnesium hydroxide / phosphorus hybrid flame retardant in this example includes the following steps:

[0046] 100 parts of magnesium hydroxide, 60 parts of diphenyl phosphite, 6 parts of 20% hydrogen peroxide solution, and 480 parts of environmentally friendly reaction medium (450 parts of ethanol and 30 parts of distilled water) were successively added to a hydrothermal reaction kettle, ultrasonicated at 60 °C for 4 h, then transferred to an oven and heated to 140 °C for reaction for 5 h. After cooling, it was filtered and dried at 120 °C for 6 h to obtain the magnesium hydroxide / phosphorus hybrid flame retardant, named MH-g-DPP4.

[0047] By weighing before and after the reaction and calculating, the grafting rate of diphenyl phosphite in MH-g-DPP4 prepared in this example is 38.7 wt%.

[0048] In this example, MH-g-DPP4 was used in the EBA composite material, and the specific method was the same as that in Example 1.

[0049] Example 5

[0050] The preparation method of the magnesium hydroxide / phosphorus hybrid flame retardant in this example includes the following steps:

[0051] 100 parts of magnesium hydroxide, 40 parts of diphenyl phosphite, 3 parts of 30% hydrogen peroxide solution, and 320 parts of environmentally friendly reaction medium (300 parts of ethanol and 20 parts of distilled water) were successively added to a hydrothermal reaction kettle, ultrasonically treated at 40 °C for 4 h, then transferred to an oven, heated to 130 °C and reacted for 4 h, filtered after cooling, and dried at 140 °C for 8 h to obtain a magnesium hydroxide / phosphorus hybrid flame retardant, named MH-g-DPP5.

[0052] By weighing before and after the reaction and calculating, the grafting rate of diphenyl phosphite in MH-g-DPP5 prepared in this example was 31.8 wt%.

[0053] In this example, MH-g-DPP5 was used to prepare an EBA composite material, and the specific method was the same as that in Example 1.

[0054] Example 6

[0055] The preparation method of the magnesium hydroxide / phosphorus hybrid flame retardant in this example includes the following steps:

[0056] 100 parts of magnesium hydroxide, 50 parts of diphenyl phosphite, 6 parts of 30% hydrogen peroxide solution, and 330 parts of environmentally friendly reaction medium (300 parts of ethanol and 30 parts of distilled water) were successively added to a hydrothermal reaction kettle, ultrasonically treated at 50 °C for 3 h, then transferred to an oven, heated to 140 °C and reacted for 5 h, filtered after cooling, and dried at 130 °C for 6 h to obtain a magnesium hydroxide / phosphorus hybrid flame retardant, named MH-g-DPP6.

[0057] By weighing before and after the reaction and calculating, the grafting rate of diphenyl phosphite in MH-g-DPP6 prepared in this example was 33.2 wt%.

[0058] In this example, MH-g-DPP6 was used to prepare an EBA composite material, and the specific method was the same as that in Example 1.

[0059] Comparative Example 1

[0060] 45 parts of pure magnesium hydroxide flame retardant was used to prepare an EBA composite material, and the specific method was the same as that in Example 1.

[0061] Comparative Example 2

[0062] The difference from Comparative Example 1 was that the addition amount of the pure magnesium hydroxide flame retardant was 70 parts.

[0063] Comparative Example 3

[0064] Without adding a flame retardant, 100 parts of EBA was directly melt-extruded, and the specific method was the same as that in Example 1.

[0065] The flame retardancy and mechanical properties of the polymer composites of Examples 1-6 and Comparative Examples 1-3 were tested, and the test results are shown in Table 1.

[0066] Table 1 Flame retardancy and mechanical properties of the polymer composites in Examples 1-6 and Comparative Examples 1-3

[0067]

[0068] As can be seen from Examples 1-6 in Table 1, when 45 parts of the magnesium hydroxide / phosphorus hybrid flame retardant prepared by the present invention was added to the EBA matrix, the limiting oxygen index of the obtained EBA composite materials all exceeded 31%, and the vertical burning grade all reached V-0. In Comparative Example 1, when the same amount of pure magnesium hydroxide flame retardant was added, the limiting oxygen index of the prepared EBA composite material was only 25.8%, and the vertical burning grade only reached V-2. This shows that the magnesium hydroxide / phosphorus hybrid flame retardant is more remarkable in improving the limiting oxygen index value of the EBA composite material and enhancing the vertical burning grade. Therefore, the magnesium hydroxide / phosphorus hybrid flame retardant of the present invention is a highly efficient flame retardant.

[0069] Comparing Examples 1-6 with Comparative Example 1, it can be seen that on the premise of the same amount of flame retardant, the tensile strength and notched impact strength of the EBA composite material prepared by adding the magnesium hydroxide / phosphorus hybrid flame retardant are higher than those of the EBA composite material prepared by adding pure magnesium hydroxide. This shows that the magnesium hydroxide / phosphorus hybrid flame retardant improves the flame retardancy while simultaneously enhancing the mechanical properties of the EBA composite material.

[0070] As can be seen from Examples 1-6 in Table 1 and Comparative Example 2, to reach the vertical burning V-0 grade in the EBA system, only 45 parts of the magnesium hydroxide / phosphorus hybrid flame retardant need to be added, while 70 parts of the pure magnesium hydroxide flame retardant need to be added. This fully shows that after the magnesium hydroxide of the present invention is modified by phosphorus hybridization, its flame retardancy efficiency is greatly improved. At the same time, the tensile strength and notched impact strength in Examples 1-6 are higher than those in Comparative Example 2, which shows that the magnesium hydroxide / phosphorus hybrid flame retardant helps to enhance the mechanical properties of the EBA composite material.

[0071] Finally, Comparative Example 3 gives the flame retardancy of pure EBA without using any flame retardant, which is used to compare with Examples 1-6 to further illustrate that the magnesium hydroxide / phosphorus hybrid flame retardant prepared by the present invention can be applied to the preparation of flame retardant cable materials.

[0072] Although the present invention has been described in detail by reference to the accompanying drawings and in conjunction with the preferred embodiments, the present invention is not limited thereto. Without departing from the spirit and essence of the present invention, those of ordinary skill in the art can make various equivalent modifications or substitutions to the embodiments of the present invention, and these modifications or substitutions should all fall within the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.

Claims

1. A preparation method of a magnesium hydroxide / phosphorus hybrid flame retardant, characterized in that, Magnesium hydroxide, diphenyl phosphite, hydrogen peroxide solution and an environmentally friendly reaction medium were successively added into a hydrothermal reaction kettle, ultrasonically mixed evenly, then transferred to an oven for heating reaction, and after cooling, filtered and dried to obtain a magnesium hydroxide / phosphorus hybrid flame retardant.

2. The preparation method of a magnesium hydroxide / phosphorus hybrid flame retardant according to claim 1, characterized in that, The mass fraction of magnesium hydroxide was 100 parts, the mass fraction of diphenyl phosphite was 40 - 60 parts, the mass fraction of hydrogen peroxide solution was 3 - 8 parts, and the mass fraction of the environmentally friendly reaction medium was 320 - 480 parts.

3. The preparation method of a magnesium hydroxide / phosphorus hybrid flame retardant according to claim 1, characterized in that, The magnesium hydroxide was hexagonal flaky particles, the diphenyl phosphite was a colorless transparent liquid, the mass concentration of the hydrogen peroxide solution was 10 - 30%, the environmentally friendly reaction medium was a mixture of ethanol and distilled water, and the mass ratio of ethanol to distilled water was 5 - 15:

1.

4. The preparation method of a magnesium hydroxide / phosphorus hybrid flame retardant according to claim 1, characterized in that, Ultrasonic treatment was carried out at 30 - 60 °C for 2 - 4 h, then transferred to an oven and heated to 110 - 150 °C for reaction for 3 - 5 h. After cooling and filtering, drying was carried out at 120 - 140 °C for 5 - 8 h to obtain the magnesium hydroxide / phosphorus hybrid flame retardant.

5. Use of the magnesium hydroxide / phosphorus hybrid flame retardant obtained by the preparation method according to any one of claims 1-4, characterized in that The magnesium hydroxide / phosphorus hybrid flame retardant and ethylene-butyl acrylate copolymer (EBA) were melt-blended and processed into shape to obtain a flame-retardant cable material.

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