Phosphorus-nitrogen flame retardant, magnesium hydroxide hybrid flame retardant material and preparation method and application thereof

Abstract

The application discloses a phosphorus-nitrogen flame retardant, a magnesium hydroxide hybrid flame retardant material and a preparation method and application thereof. The application firstly provides a novel structure phosphorus-nitrogen flame retardant, and then the phosphorus-nitrogen flame retardant is mixed with a magnesium hydroxide flame retardant to form a magnesium hydroxide hybrid flame retardant material. Based on a combination chemical synthesis method, the functional groups of the organic flame retardant containing phosphorus and nitrogen with high flame retardance are selectively synthesized with the environmentally-friendly magnesium hydroxide flame retardant with high thermal stability and low dielectric characteristics, so that the environmentally-friendly magnesium hydroxide hybrid functional material containing the halogen-free magnesium hydroxide containing phosphorus and nitrogen is obtained. The hybrid functional material is applied to an epoxy resin material, the flame retardant efficiency of the magnesium hydroxide is efficiently improved, the influence of the magnesium hydroxide on the mechanical performance of the epoxy resin is reduced, and the epoxy resin can simultaneously meet the high flame retardant performance and the high mechanical performance under the condition of low addition amount.

Description

Technical Field

[0001] This invention relates to the field of flame retardant materials technology, specifically to a phosphorus-nitrogen flame retardant, a magnesium hydroxide hybrid flame retardant material, its preparation method, and its application. Background Technology

[0002] Epoxy resin (EP) products are currently widely used in the manufacture of new energy vehicles to achieve the important goals of energy saving, consumption reduction, and increased driving range. They are used to manufacture components including engines, power battery systems, automotive exteriors, interiors, electronic appliances, and air conditioning systems, as well as charging pile components such as charging guns, connectors, and housings. Compared with metallic and inorganic materials, this material has superior performance characteristics such as energy saving, light weight, flexibility, and low cost. Meanwhile, the rapid development of 6G / 5G and other electronic communications, especially the large-scale construction of 5G base stations, will drive the demand for these polymer materials to a new peak.

[0003] Polyethylene (EP) is one of the most widely used polymer materials among thermosetting resins at present. It has excellent physical and chemical properties, electrical insulation properties, and adhesive properties. It is easy to process and mold, corrosion resistant, has low curing shrinkage, and low cost, and is widely used in electronic components, automobiles, aerospace and other fields. However, EP has high flammability, poor fire resistance, high smoke production during combustion, and is relatively brittle, which seriously restricts its further application. At present, flame retardants are mainly added to improve the flame retardancy, self-extinguishing or smoke suppression properties of materials. In the past decade, magnesium hydroxide (MDH) has become one of the most widely used flame retardants in the preparation of halogen-free or low-halogen flame retardant polymers. It has flame retardant and smoke-suppressing properties, high thermal stability, promotion of polymer matrix charring, and acid removal ability. It has been widely used in plastics, elastomers and rubber materials such as polyvinyl chloride (PVC), polypropylene (PP), polyethylene (PE), ethylene-vinyl acetate (EVA), and polyamide (PA).

[0004] Because MDH crystals exhibit strong polarity and hydrophilicity, and are prone to agglomeration due to intermolecular hydrogen bonding, they are difficult to disperse when melt-mixed and added to polymers. This results in poor compatibility with polymers, leading to internal defects in the material. Besides causing a rough appearance in flame-retardant products, this also severely deteriorates various material properties. Furthermore, due to the flame-retardant mechanism of MDH, a relatively large addition amount (usually greater than 30%) is typically required to achieve the desired flame retardancy, further impacting the processing and mechanical properties of the flame-retardant material. Summary of the Invention

[0005] In view of this, the present invention provides a phosphorus-nitrogen flame retardant, a magnesium hydroxide hybrid flame retardant material, a preparation method thereof, and an application thereof, in order to solve the problem of how to efficiently improve the flame retardant efficiency of magnesium hydroxide while reducing its impact on the mechanical properties of EP, so as to enable EP to simultaneously meet the requirements of high flame retardant performance and high mechanical properties at low addition amounts.

[0006] To address the aforementioned problems, a first aspect of the present invention is to provide a phosphorus-nitrogen flame retardant, the molecular structural formula of which is as follows: .

[0007] Preferably, the molecular synthesis route of the phosphorus-nitrogen flame retardant is as follows: .

[0008] To address the aforementioned problems, a second aspect of the present invention is to provide a magnesium hydroxide hybrid flame retardant material comprising a co-crystallized magnesium hydroxide flame retardant and a phosphorus-nitrogen flame retardant as described above.

[0009] Preferably, in the magnesium hydroxide hybrid flame retardant material, the mass percentage content of the phosphorus-nitrogen flame retardant is 0.5% to 25%.

[0010] Preferably, the median particle size D50 of the magnesium hydroxide hybrid flame retardant material is 100nm≤D50≤5μm.

[0011] To address the aforementioned problems, a third aspect of the present invention provides a method for preparing the magnesium hydroxide hybrid flame retardant material as described above, comprising: The phosphorus-nitrogen flame retardant is mixed with a magnesium-containing compound solution to form a first mixed solution; The first mixed solution is heated to a first temperature, and an alkaline source solution is added to the first mixed solution and stirred to form a second mixed solution; The second mixed solution is heated to a second temperature to carry out a crystallization reaction. After the reaction is completed, it is cooled to room temperature, filtered, washed, and dried to obtain the magnesium hydroxide hybrid flame retardant material.

[0012] Preferably, the magnesium-containing compound is selected from one or more of magnesium chloride, magnesium sulfate, magnesium carbonate, magnesite, brucite, hydromagnesite, and magnesium oxide; the alkali source is selected from one or more of sodium hydroxide, ammonia, calcium hydroxide, potassium hydroxide, and lithium hydroxide.

[0013] Preferably, the mass concentration of the magnesium compound solution is 5% to 30%; the mass concentration of the alkali source solution is 5% to 30%.

[0014] Preferably, the second temperature is greater than the first temperature, wherein the first temperature is 40℃~250℃ and the second temperature is 50℃~260℃.

[0015] To address the aforementioned problems, a fourth aspect of the present invention is to provide an application of the magnesium hydroxide hybrid flame retardant material as described above, wherein the magnesium hydroxide hybrid flame retardant material is added to an epoxy resin to form a flame retardant epoxy resin.

[0016] This invention provides a phosphorus-nitrogen flame retardant, a magnesium hydroxide hybrid flame retardant material, its preparation method, and its application. First, a novel phosphorus-nitrogen flame retardant structure is provided. Then, this phosphorus-nitrogen flame retardant is co-crystallized and mixed with a magnesium hydroxide flame retardant. Based on a combinatorial chemical synthesis method, the functional groups of a phosphorus- and nitrogen-containing organic flame retardant with high flame retardancy are selectively hybridized with an environmentally friendly hydroxide flame retardant with high thermal stability and low dielectric properties to obtain a halogen-free environmentally friendly magnesium hydroxide hybrid functional material containing phosphorus and nitrogen. When applied to epoxy resin materials, this hybrid functional material can efficiently improve the flame retardant efficiency of magnesium hydroxide while reducing its impact on the mechanical properties of epoxy resin. It allows epoxy resin to simultaneously meet high flame retardant performance and high mechanical properties even with low addition amounts. Attached Figure Description

[0017] Figure 1 This is a SEM image of the magnesium hydroxide hybrid flame retardant material in Example 2 of this invention; Figure 2 This is a TEM image of the magnesium hydroxide hybrid flame retardant material in Example 2 of this invention; Figure 3 This is a SEM image of the magnesium hydroxide hybrid flame retardant material in Example 3 of this invention; Figure 4 This is a TEM image of the magnesium hydroxide hybrid flame retardant material in Example 3 of this invention; Figure 5 This is a SEM image of the magnesium hydroxide hybrid flame retardant material in Example 4 of this invention; Figure 6 This is a TEM image of the magnesium hydroxide hybrid flame retardant material in Example 4 of the present invention. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of the present invention clearer, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Examples of these preferred embodiments are illustrated in the drawings. The embodiments of the present invention shown in and described with reference to the drawings are merely exemplary, and the present invention is not limited to these embodiments.

[0019] It should also be noted that, in order to avoid obscuring the present invention with unnecessary details, only the structures and / or processing steps closely related to the present invention are shown in the accompanying drawings, while other details that are not closely related to the present invention are omitted.

[0020] This invention first provides a phosphorus-nitrogen flame retardant, the molecular structural formula of which is as follows: .

[0021] Specifically, the molecular synthesis route of the phosphorus-nitrogen flame retardant is as follows: .

[0022] Based on the phosphorus-nitrogen flame retardant as described above, embodiments of the present invention also provide a magnesium hydroxide hybrid flame retardant material, which includes a co-crystallized magnesium hydroxide flame retardant and the phosphorus-nitrogen flame retardant as described above.

[0023] Preferably, in the magnesium hydroxide hybrid flame retardant material, the mass percentage content of the phosphorus-nitrogen flame retardant is 0.5% to 25%.

[0024] In some specific embodiments, the median particle size D50 of the magnesium hydroxide hybrid flame retardant material is controlled to be 100nm≤D50≤5μm. In a preferred embodiment, the median particle size D50 is controlled to be 300nm≤D50≤3μm, and more preferably, the median particle size D50 is controlled to be 500nm≤D50≤2μm.

[0025] This invention also provides a method for preparing the magnesium hydroxide hybrid flame retardant material as described above, the method comprising the following steps: Step S1: Mix the phosphorus-nitrogen flame retardant with a magnesium-containing compound solution to form a first mixed solution.

[0026] Specifically, a phosphorus-nitrogen flame retardant and a magnesium-containing compound solution of a certain concentration are added to a reactor at a certain mass fraction ratio and stirred to form a first mixed solution. The magnesium-containing compound can be selected from one or more of magnesium chloride, magnesium sulfate, magnesium carbonate, magnesite, brucite, hydromagnesite, and magnesium oxide. The mass concentration of the magnesium-containing compound solution is preferably 5% to 30%.

[0027] Step S2: Heat the first mixed solution to a first temperature, add an alkaline source solution to the first mixed solution and stir to form a second mixed solution.

[0028] Specifically, the first temperature can be 40℃~250℃.

[0029] Specifically, the alkali source can be selected from one or more of sodium hydroxide, ammonia, calcium hydroxide, potassium hydroxide, and lithium hydroxide. The mass concentration of the alkali source solution is preferably 5% to 30%.

[0030] In a preferred embodiment, an alkaline source solution is added to the first mixed solution while continuously stirring. The stirring speed can be 500 rpm to 10000 rpm, and the rate at which the alkaline source solution is added can be 5 mL / min to 150 mL / min.

[0031] Step S3: Heat the second mixed solution to a second temperature to carry out a crystallization reaction. After the reaction is completed, cool it to room temperature, filter, wash and dry to obtain the magnesium hydroxide hybrid flame retardant material.

[0032] Specifically, the second temperature is greater than the first temperature, and the second temperature can be 50℃~260℃.

[0033] It should be noted that steps S2 and S3 above are a continuous process. The crystal structure and particle size of the magnesium hydroxide hybrid flame retardant material can be controlled by adjusting the temperature, stirring method and feeding speed. Once the particle size and morphology of the magnesium hydroxide hybrid flame retardant material crystals meet the preset target, after cooling to room temperature, it can be filtered, washed and dried to obtain the magnesium hydroxide hybrid flame retardant material.

[0034] This invention also provides an application of the magnesium hydroxide hybrid flame retardant material described above, wherein the magnesium hydroxide hybrid flame retardant material is added to an epoxy resin to form a flame-retardant epoxy resin. Specifically, the amount of the magnesium hydroxide hybrid flame retardant material added can be 1% to 10%, preferably 3% to 5%.

[0035] In some preferred embodiments, the amount of magnesium hydroxide hybrid flame retardant material added is 3%, that is, 3% by mass of magnesium hydroxide hybrid flame retardant material and 97% by mass of epoxy resin are blended to form a flame retardant epoxy resin composite material. Its flame retardant properties, mechanical properties, thermal stability, and processing properties were characterized. The results showed that the flame retardant rating was UL-94 V0, the limiting oxygen index (LOI) was ≥32%, and the peak heat release rate (pHRR) was ≥32% (kW / m³). 2 Compared to pure EP, it has reduced heat release by more than 50%, total heat release (THR) by more than 55%, smoke emission rate (SPR) by more than 70%, tensile strength ≥ 55.0 MPa, elongation at break ≥ 360%, and initial thermal decomposition temperature T. 5% ≥350℃, glass transition temperature T g ≥180℃, coefficient of thermal expansion ≤60ppm / ℃ <T g ) and ≤180ppm / ℃ (>T g ), dielectric constant D k ≤3.0, dielectric loss D f≤0.003. With the addition of 3% (wt%) of hybrid materials, the mechanical properties of EP composite flame retardant materials were enhanced, achieving high flame retardancy, low dielectric and high thermal stability.

[0036] Example 1 This embodiment first provides a phosphorus-nitrogen flame retardant, the molecular structural formula of which is as follows: .

[0037] DOPO is primarily composed of phenyl groups, making it non-flammable, and it forms a char layer during combustion, providing flame retardancy. The presence of phosphorus contributes to the formation of phosphoric acid and phosphate free radicals. Nitrogen-based flame retardants are widely used in various polymers due to their low toxicity, low corrosiveness, and high thermal decomposition temperature. In this embodiment, the functional groups of a highly flame-retardant phosphorus-containing (DOPO) and a nitrogen-containing (3,5-diamino-1,2,4-triazole, C2H5N5) organic flame retardant are integrated through organic synthesis to create a new molecular structure with dual functions, thus forming a novel phosphorus-nitrogen flame retardant, denoted as NSC-Di-DOPO. The synthetic route is as follows: .

[0038] Example 2 5.3g of NSC-Di-DOPO synthesized in Example 1 was added to a reactor and mixed with 4.2L of a 30% MgCl2 solution. The solution temperature was raised to 40°C, and then 3.85L of a 30% sodium hydroxide solution was added to the reactor at a rate of 50mL / min while stirring at 5000rpm. After the sodium hydroxide solution was added, the temperature was raised to 60°C to initiate a crystallization reaction. The crystal structure and particle size were controlled by adjusting the temperature and stirring speed. Once the particle size and morphology met the preset targets, the mixture was cooled to room temperature, filtered, washed, and dried to obtain a magnesium hydroxide hybrid flame retardant material, designated as 0.5% NSC-Di-DOPO / MDH hybrid material. This means that the phosphorus-nitrogen flame retardant content in the magnesium hydroxide hybrid flame retardant material is 0.5% by mass.

[0039] Figure 1 This is a SEM image of the magnesium hydroxide hybrid flame retardant material obtained in this embodiment. Figure 2 This is a TEM image of the magnesium hydroxide hybrid flame retardant material obtained in this embodiment. Referring to the accompanying drawings, the NSC-Di-DOPO / MDH hybrid material in this embodiment exhibits hydrophobicity, with an activation index of 100%. Compared to pure MDH, the contact angle is increased by 416%, significantly improving filtration performance, with a median particle size D50 ≤ 750 nm.

[0040] 30g of the 0.5% NSC-Di-DOPO / MDH hybrid material from this embodiment was weighed and added to 970g of EP. A composite flame-retardant material with a composition of 3% (NSC-Di-DOPO / MDH) / 97% EP was prepared by blending. The flame-retardant properties, mechanical properties, and thermal stability of the obtained composite flame-retardant material were characterized. The results showed that the flame-retardant rating was UL-94 V0, the limiting oxygen index (LOI) was ≥32.5%, and the peak heat release rate (pHRR) was (kW / m²). 2 Compared with pure EP, the total heat release (THR) was reduced by 65.7%, the smoke release rate (SPR) was reduced by 57.5%, the tensile strength was 55.9 MPa, and the elongation at break was 362%.

[0041] Example 3 5.3 g of NSC-Di-DOPO synthesized in Example 1 was added to a reactor and mixed with 8.4 L of a 15% MgCl2 solution. The solution temperature was raised to 60°C, and then 7.705 L of a 15% sodium hydroxide solution was added to the reactor at a rate of 100 mL / min while stirring at 10000 rpm. After the sodium hydroxide solution was added, the temperature was raised to 100°C to initiate a crystallization reaction. The crystal structure and particle size were controlled by adjusting the temperature and stirring speed. Once the particle size and morphology met the preset targets, the mixture was cooled to room temperature, filtered, washed, and dried to obtain a magnesium hydroxide hybrid flame retardant material, denoted as 5% NSC-Di-DOPO / MDH hybrid material, meaning that the mass percentage content of the phosphorus-nitrogen flame retardant in the magnesium hydroxide hybrid flame retardant material is 5%.

[0042] Figure 3 This is a SEM image of the magnesium hydroxide hybrid flame retardant material obtained in this embodiment. Figure 4 This is a TEM image of the magnesium hydroxide hybrid flame retardant material obtained in this embodiment. Referring to the accompanying drawings, the NSC-Di-DOPO / MDH hybrid material in this embodiment exhibits hydrophobicity, with an activation index of 100%. Compared to pure MDH, the contact angle is increased by 450%, significantly improving filtration performance, with a median particle size D50 ≤ 1.2 μm.

[0043] 30g of the 5% NSC-Di-DOPO / MDH hybrid material of this embodiment was weighed and added to 970g of EP to prepare a 3% (NSC-Di-DOPO / MDH) / 97% EP composite flame retardant material by blending. The flame retardant properties, mechanical properties, and thermal stability of the obtained composite flame retardant material were characterized. The results showed that the flame retardant rating was UL-94 V0, the limiting oxygen index (LOI) was ≥45.7%, and the peak heat release rate (pHRR) was (kW / m²). 2Compared with pure EP, the total heat release (THR) is reduced by 58.5%, the smoke release rate (SPR) is reduced by 66.5%, the tensile strength is 60.8 MPa, and the elongation at break is 454%.

[0044] Example 4 250g of NSC-Di-DOPO synthesized in Example 1 was added to a reactor and mixed with 16.8L of a 7.5% MgCl2 solution. The solution temperature was raised to 120°C, and then 15.4L of a 7.5% sodium hydroxide solution was added to the reactor at a rate of 150mL / min while stirring at 15000rpm. After the sodium hydroxide solution was added, the temperature was raised to 250°C for crystallization. The crystal structure and particle size were controlled by adjusting the temperature and stirring speed. Once the particle size and morphology met the preset targets, the mixture was cooled to room temperature, filtered, washed, and dried to obtain a magnesium hydroxide hybrid flame retardant material, designated as 20% NSC-Di-DOPO / MDH hybrid material, meaning that the mass percentage content of the phosphorus-nitrogen flame retardant in the magnesium hydroxide hybrid flame retardant material is 20%.

[0045] Figure 5 This is a SEM image of the magnesium hydroxide hybrid flame retardant material obtained in this embodiment. Figure 6 This is a TEM image of the magnesium hydroxide hybrid flame retardant material obtained in this embodiment. Referring to the accompanying drawings, the NSC-Di-DOPO / MDH hybrid material in this embodiment exhibits hydrophobicity, with an activation index of 100%. Compared to pure MDH, the contact angle is increased by 650%, significantly improving filtration performance, with a median particle size D50 ≤ 2.4 μm.

[0046] 30g of the 20% NSC-Di-DOPO / MDH hybrid material from this embodiment was weighed and added to 970g of EP. A composite flame-retardant material with a composition of 3% (NSC-Di-DOPO / MDH) / 97% EP was prepared by blending. The flame-retardant properties, mechanical properties, and thermal stability of the obtained composite flame-retardant material were characterized. The results showed that the flame-retardant rating was UL-94 V0, the limiting oxygen index (LOI) was ≥55.1%, and the peak heat release rate (pHRR) was (kW / m²). 2 Compared with pure EP, the total heat release (THR) was reduced by 55.7%, the smoke release rate (SPR) was reduced by 59.3%, the tensile strength was 65.5 MPa, and the elongation at break was 555%.

[0047] In summary, the technical solution of this invention involves organically synthesizing the functional groups of a phosphorus- and nitrogen-containing organic flame retardant with high flame retardancy to form a new organic molecular structure phosphorus-nitrogen flame retardant, NSC-Di-DOPO. Besides the characteristics of DOPO phosphorus flame retardants, the addition of dual DOPO flame retardant molecules, and the formation of carbon in the presence of oxides formed by the thermal decomposition of hydroxide layers during thermal decomposition due to the benzene ring, makes EP more prone to carbonization during thermal decomposition or combustion, significantly improving the carbonization rate of EP resin. The addition of nitrogen-containing bimolecular DOPO improves the quality of residual char, forming a denser barrier layer that effectively provides heat and oxygen insulation, achieving excellent condensed phase flame retardancy. Both P and N significantly enhance the flame retardant index. Simultaneously, the phosphorus-containing triazole contains hydrogen bonds and π-π bonds, which enhance the mechanical properties of EP. Furthermore, based on combinatorial chemical synthesis methods, the functional groups of phosphorus and nitrogen-containing organic flame retardants with high flame retardancy are selectively hybridized with environmentally friendly hydroxide flame retardants with high thermal stability and low dielectric properties to obtain halogen-free environmentally friendly magnesium hydroxide hybrid functional materials containing phosphorus and nitrogen. When applied to epoxy resin materials, this hybrid functional material can effectively improve the flame retardancy efficiency of magnesium hydroxide while reducing its impact on the mechanical properties of epoxy resin. It can enable epoxy resin to simultaneously meet the requirements of high flame retardancy and high mechanical properties with low addition amounts.

[0048] The above description is only a specific embodiment of this application. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of this application, and these improvements and modifications should also be considered within the scope of protection of this application.

Claims

1. A magnesium hydroxide hybrid flame retardant material, characterized in that, The mixture includes a co-crystallized magnesium hydroxide flame retardant and a phosphorus-nitrogen flame retardant, wherein the phosphorus-nitrogen flame retardant has a mass percentage content of 0.5% to 25%, and the molecular structural formula of the phosphorus-nitrogen flame retardant is as follows: , The median particle size D50 of the magnesium hydroxide hybrid flame retardant material is 300 nm to 3 μm, and the magnesium hydroxide hybrid flame retardant material is hydrophobic with an activation index of 100%.

2. A method for preparing the magnesium hydroxide hybrid flame retardant material as described in claim 1, characterized in that, include: The phosphorus-nitrogen flame retardant is mixed with a magnesium-containing compound solution to form a first mixed solution; The first mixed solution is heated to a first temperature, and an alkaline source solution is added to the first mixed solution and stirred to form a second mixed solution; The second mixed solution is heated to a second temperature to carry out a crystallization reaction. After the reaction is completed, it is cooled to room temperature, filtered, washed, and dried to obtain the magnesium hydroxide hybrid flame retardant material.

3. The method for preparing the magnesium hydroxide hybrid flame retardant material according to claim 2, characterized in that, The magnesium-containing compound is selected from one or more of magnesium chloride, magnesium sulfate, magnesium carbonate, magnesite, brucite, hydromagnesite, and magnesium oxide; the alkali source is selected from one or more of sodium hydroxide, ammonia, calcium hydroxide, potassium hydroxide, and lithium hydroxide.

4. The method for preparing the magnesium hydroxide hybrid flame retardant material according to claim 3, characterized in that, The magnesium compound solution has a mass concentration of 5% to 30%; the alkali source solution has a mass concentration of 5% to 30%.

5. The method for preparing the magnesium hydroxide hybrid flame retardant material according to claim 2, characterized in that, The second temperature is greater than the first temperature, where the first temperature is 40℃~250℃ and the second temperature is 50℃~260℃.

6. An application of the magnesium hydroxide hybrid flame retardant material as described in claim 1, wherein the magnesium hydroxide hybrid flame retardant material is added to an epoxy resin to form a flame retardant epoxy resin.

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