Reversible Diels-Alder reaction monomer modified nano magnesium hydroxide flame retardant as well as preparation method and application thereof

Abstract

The invention provides a reversible Diels-Alder reaction monomer modified nano magnesium hydroxide flame retardant as well as a preparation method and application thereof, and belongs to the technical field of inorganic flame retardants. According to the invention, maleic anhydride reacts with an amino-containing silane coupling agent to prepare a maleimide-silane coupling agent, and the coupling agent has both reversible DA double bonds and silane anchoring groups. And then carrying out modification reaction on the maleimide-silane coupling agent and nano magnesium hydroxide, and drying to obtain the reversible DA cross-linking monomer modified nano MDH flame retardant. When the flame retardant, TPU granules and a small amount of auxiliaries are blended and extruded, a maleic amide group and NCO in TPU are subjected to a DA cross-linking reaction, nano MDH is firmly anchored to a polyurethane main chain, the dispersity and interface bonding stability of nano MDH in a matrix are remarkably improved, and a halogen-free, efficient and reversible cross-linking flame-retardant TPU elastomer is achieved.

Description

Technical Field

[0001] This invention relates to the field of inorganic flame retardant technology, and in particular to a reversible Diels-Alder reaction monomer-modified nano-magnesium hydroxide flame retardant, its preparation method, and its application. Background Technology

[0002] Polymer materials have a wide range of applications, but they are flammable, and some release toxic and harmful gases during combustion, causing environmental pollution and secondary injuries to people. Therefore, it is usually necessary to modify polymer materials for flame retardancy, and a common method is to directly add flame retardants.

[0003] Magnesium hydroxide is a classic filler-type inorganic flame retardant, possessing excellent flame retardant, smoke suppressant, and filler functions. It is widely used in rubber, chemicals, building materials, plastics, electronics, unsaturated polyesters, paints, coatings, and other polymer materials. However, as an inorganic flame retardant, magnesium hydroxide requires a large amount to be added to the material to achieve a certain level of flame retardant performance, resulting in relatively low flame retardant efficiency. Adding large amounts of magnesium hydroxide can also reduce the mechanical properties of polymer materials, limiting its application range.

[0004] Nano-magnesium hydroxide flame retardants have relatively little damage to mechanical properties, but traditional nano-magnesium hydroxide has the following technical defects: (1) Low flame retardant efficiency: Traditional nano-magnesium hydroxide (nano-MH) usually requires a filling amount of ≥45 wt% to obtain the UL-94 V-0 rating, resulting in a significant decrease in the mechanical properties and processing fluidity of the material. (2) Difficult dispersion: nano-MH has serious secondary agglomeration, with an angle of repose >35°, and problems such as die accumulation and surface pitting often occur during melt extrusion. For example, patent CN109225085A discloses a single-layer microcapsule of phosphorus-nitrogen resin, but it only solves the problem of phase change material coating and lacks sufficient flame retardant synergy; patent CN105112020A uses reactive phosphonate-acrylic acid copolymer wall material without dynamic bond design; patent CN103740337A adopts a free radical polymerization multi-step solvent method, which is complex and produces a lot of wastewater. None of the above patents simultaneously solve the two major pain points of "flame retardant efficiency and processing fluidity".

[0005] To address the issues of low flame retardant efficiency, high addition amount, and poor compatibility with substrates of magnesium hydroxide, it is necessary to perform surface modification on magnesium hydroxide to form a uniform protective film on its surface. At the same time, by utilizing the reactivity of the coating layer, the dispersibility and compatibility of magnesium hydroxide can be improved, thereby enhancing the dispersibility and compatibility with substrates of nano-magnesium hydroxide.

[0006] Therefore, how to further improve the flame retardant efficiency of nano-magnesium hydroxide while maintaining its advantages, reduce the amount added, ensure uniform coating of magnesium hydroxide surface, and improve its compatibility with organic polymer materials are problems that urgently need to be solved by those skilled in the art. Summary of the Invention

[0007] The purpose of this invention is to provide a reversible Diels-Alder reaction monomer-modified nano-magnesium hydroxide flame retardant, its preparation method, and its application, in order to solve the above-mentioned technical problems.

[0008] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a method for preparing a reversible Diels-Alder reaction monomer-modified nano-magnesium hydroxide flame retardant, comprising the following steps: Nano-sized magnesium hydroxide was mixed with a silane modifier containing a maleamide structure and coupled to obtain a nano-sized magnesium hydroxide flame retardant modified with a reversible Diels-Alder reaction monomer.

[0009] Furthermore, the silane modifier containing the maleamide structure is obtained by reacting maleic anhydride with a silane coupling agent.

[0010] Furthermore, the silane coupling agent comprises one or more of γ-aminopropyltriethoxysilane, γ-aminopropyltrimethoxysilane, γ-aminopropylmethyldiethoxysilane, γ-aminopropylmethyldimethoxysilane, γ-diethylenetriaminopropylmethyldimethoxysilane, and γ-diethylenetriaminopropyltrimethoxysilane.

[0011] Furthermore, the mass ratio of the nano-magnesium hydroxide to the maleamide-containing silane modifier is 20~200:1, and the particle size of the nano-magnesium hydroxide is 10~100nm.

[0012] Furthermore, the coupling reaction is carried out at a temperature of 100~150℃ and for a time of 3~15min; the coupling reaction is carried out in a mixed solvent, which is a mixture of organic solvent and water.

[0013] Furthermore, the organic solvent comprises one or more of diethylene glycol butyl ether, tripropylene glycol methyl ether, dipropylene glycol butyl ether, dipropylene glycol propyl ether, and diethylene glycol ethyl ether, and the mass ratio of the organic solvent to water is 1:0.2~5.

[0014] Furthermore, the ratio of the maleamide-containing silane modifier to the mixed solvent is 1~15g:100mL.

[0015] This invention also provides a nano-magnesium hydroxide flame retardant modified with a reversible Diels-Alder reactive monomer prepared by the above preparation method.

[0016] This invention also provides the application of a reversible Diels-Alder reaction monomer-modified nano-magnesium hydroxide flame retardant in the preparation of PU elastomers. The reversible Diels-Alder reaction monomer-modified nano-magnesium hydroxide flame retardant is added to TPU, and after adding the additives, melt extrusion is performed. During the extrusion process, a Diels-Alder reaction occurs to obtain a flame-retardant modified PU elastomer.

[0017] Furthermore, the mass ratio of the reversible Diels-Alder reactive monomer-modified nano-magnesium hydroxide flame retardant to TPU is 50~70:100.

[0018] The beneficial effects of this invention are: This invention has the advantages of scientific and reasonable design, simple operation, and easy large-scale production. Moreover, this invention utilizes the flame-retardant synergistic effect between magnesium and silicon, which helps to improve the strength of the char layer and increase the flame-retardant efficiency. It uses a modifier with silane structure at the end to modify the surface of magnesium hydroxide, improve its hydrophobicity and dispersion characteristics, and reduce particle agglomeration. It uses maleamide structure to carry out Diels-Alder reaction with NCO bonds in TPU material to anchor the modified nano-magnesium hydroxide on the TPU backbone, so as to improve the dispersibility of nano-magnesium hydroxide and the bonding stability with the substrate. This is of great significance for improving the comprehensive performance of composite materials and expanding the application fields of magnesium hydroxide. Attached Figure Description

[0019] Figure 1 SEM images of cross-sections of TPU / MH composites filled with unmodified (left) and modified magnesium hydroxide (right) from Example 1; Figure 2 SEM images of cross-sections of TPU / MH composites filled with unmodified (left) and modified magnesium hydroxide (right) as in Example 2; Figure 3 SEM images of cross-sections of TPU / MH composites filled with unmodified (left) and modified magnesium hydroxide (right) as described in Example 3. Detailed Implementation

[0020] This invention provides a method for preparing a reversible Diels-Alder reaction monomer-modified nano-magnesium hydroxide flame retardant, comprising the following steps: Nano-sized magnesium hydroxide was mixed with a silane modifier containing a maleamide structure and coupled to obtain a nano-sized magnesium hydroxide flame retardant modified with a reversible Diels-Alder reaction monomer.

[0021] In this invention, the silane modifier containing the maleamide structure is obtained by reacting maleic anhydride with a silane coupling agent.

[0022] In this invention, a silane modifier containing a maleamide structure is prepared into a solution of a certain concentration and added to nano-magnesium hydroxide. The magnesium hydroxide is modified using a silane coupling agent and dried to obtain a nano-magnesium hydroxide flame retardant modified with a reversible Diels-Alder reaction monomer.

[0023] In this invention, the silane coupling agent comprises one or more of γ-aminopropyltriethoxysilane, γ-aminopropyltrimethoxysilane, γ-aminopropylmethyldiethoxysilane, γ-aminopropylmethyldimethoxysilane, γ-diethylenetriaminopropylmethyldimethoxysilane, and γ-diethylenetriaminopropyltrimethoxysilane, preferably one or more of γ-aminopropyltriethoxysilane, γ-aminopropyltrimethoxysilane, γ-aminopropylmethyldiethoxysilane, and γ-aminopropylmethyldimethoxysilane.

[0024] In this invention, the mass ratio of the nano-magnesium hydroxide to the maleamide-containing silane modifier is 20-200:1, preferably 40-150:1, and more preferably 50-120:1; the particle size of the nano-magnesium hydroxide is 10-100 nm, preferably 20-80 nm, and more preferably 40-60 nm.

[0025] In this invention, the temperature of the coupling reaction is 100~150℃, preferably 110~140℃, and more preferably 120~130℃; the time of the coupling reaction is 3~15min, preferably 5~12min, and more preferably 8~10min; the coupling reaction is carried out in a mixed solvent, which is a mixture of organic solvent and water.

[0026] In this invention, the organic solvent comprises one or more of diethylene glycol butyl ether, tripropylene glycol methyl ether, dipropylene glycol butyl ether, dipropylene glycol propyl ether, and diethylene glycol ethyl ether, and the mass ratio of the organic solvent to water is 1:0.2~5, preferably 1:1~4, and more preferably 1:2~3.

[0027] In this invention, the ratio of the maleamide-containing silane modifier to the mixed solvent is 1~15g:100mL, preferably 2~10g:100mL, and more preferably 4~8:100mL.

[0028] This invention also provides a nano-magnesium hydroxide flame retardant modified with a reversible Diels-Alder reactive monomer prepared by the above preparation method.

[0029] This invention also provides the application of a reversible Diels-Alder reaction monomer-modified nano-magnesium hydroxide flame retardant in the preparation of PU elastomers. The reversible Diels-Alder reaction monomer-modified nano-magnesium hydroxide flame retardant is added to TPU, and after adding the additives, melt extrusion is performed. During the extrusion process, a Diels-Alder reaction occurs to obtain a flame-retardant modified PU elastomer.

[0030] In this invention, the mass ratio of the reversible Diels-Alder reactive monomer-modified nano-magnesium hydroxide flame retardant to TPU is 50~70:100, preferably 60:100.

[0031] In this invention, the formulation of the PU elastomer, based on 100 parts by weight of TPU, is shown in Table 1 below: Table 1 Proportions

[0032] In this invention, a nano-magnesium hydroxide flame retardant modified with a reversible Diels-Alder reaction monomer is used to modify TPU materials. The maleamide structure is used to carry out a Diels-Alder reaction with the NCO bonds in the TPU material, anchoring the modified nano-magnesium hydroxide onto the TPU main chain, thereby improving the dispersibility and bonding stability of the nano-magnesium hydroxide with the substrate.

[0033] In this invention, the preparation process of the PU elastomer includes the following steps: Drying: TPU granules 80 ℃ × 4 h; MDH 110 ℃ × 2 h; Blending: Twin-screw extruder L / D ≥36, temperature 170-190-185 ℃, main extruder 200-300 rpm, side feed with MDH; Pelletizing: After water ring heat cutting, dry at 80 ℃ for 2 h to obtain flame-retardant TPU pellets; Product processing: Injection / extrusion temperature 180-200 ℃, mold temperature 30-50 ℃.

[0034] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0035] Example 1

[0036] 20g The modifier was added to a 500 mL mixture of diethylene glycol butyl ether and water (mass ratio 1:1) and stirred until the solute was evenly dispersed to obtain the modifier solution.

[0037] 1 kg of magnesium hydroxide with an average particle size of 50 nm was added to a high-speed disperser. After heating to 120 °C, a modifier solution was added and the mixture was stirred at 500 r / min for 15 min to obtain modified magnesium hydroxide (product 1). During the high-speed stirring process, the moisture could be naturally dried.

[0038] Repeat the above steps to obtain Product 2 and Product 3.

[0039] Products 1 to 3 were added to TPU at a dosage of 50 parts each to obtain three different TPU materials. Performance tests were then conducted on the modified magnesium hydroxide and the three different TPU materials.

[0040] The specific test methods are as follows: (1) Whiteness: tested according to GB / T5950-2008 standard; (2) Oil absorption: tested according to DB / T5211.15-2014 standard; (3) Limiting oxygen index: tested according to GB / T2406.2-2009 standard; (4) Particle size distribution: particle distribution was measured using SEM; (5) Moisture content: tested according to GB / T 6284; (6) Agglomeration index: tested using a Zeta potentiometer. The specific test results are shown in Table 2.

[0041] Table 2 Performance test results of unmodified magnesium hydroxide and modified magnesium hydroxide products 1-3

[0042] Table 2 shows that the cyanide content of magnesium hydroxide decreased slightly after modification, but not significantly, and the particle size did not change much; neither index affected its use. The oil absorption and moisture absorption decreased significantly, indicating that the modified magnesium hydroxide had enhanced hydrophobicity. The flame retardant properties of TPU / MH were further improved after using modified nano-magnesium hydroxide.

[0043] Figure 1 SEM images of cross-sections of TPU / MH composites filled with unmodified (left) and modified magnesium hydroxide (right) from Example 1.

[0044] Example 2

[0045] 25g The modifier was added to a 1000 mL mixture of tripropylene glycol methyl ether and water (mass ratio 2:1) and stirred until the solute was evenly dispersed to obtain the modifier solution.

[0046] 1 kg of 70 nm nano-magnesium hydroxide was added to a high-speed disperser, heated to 80 °C, and then a modifier solution was added. The mixture was stirred at 600 r / min for 20 min to obtain modified magnesium hydroxide containing a triazine structure (product 4).

[0047] Repeat the above steps to obtain product 5 and product 6.

[0048] Products 4 to 6 were added to TPU at a dosage of 60 parts each to obtain three different TPU materials. Performance tests were conducted on the modified magnesium hydroxide and the three different TPU materials. The test results are shown in Table 3.

[0049] Table 3. Performance test results of unmodified magnesium hydroxide and modified magnesium hydroxide products 4-6

[0050] Table 3 shows that after modification, the cyanide content of magnesium hydroxide decreased slightly, but not significantly, and the particle size increased slightly. Neither of these indicators affected its use. The oil absorption and moisture absorption decreased significantly, indicating that the modified magnesium hydroxide exhibited enhanced hydrophobicity. The flame retardant properties of TPU / MH were further improved after using modified nano-magnesium hydroxide.

[0051] Figure 2 SEM images of cross sections of TPU / MH composites filled with unmodified (left) and modified magnesium hydroxide (right) as described in Example 2.

[0052] Example 3

[0053] 10g The modifier was added to a 1000 mL mixture of diethylene glycol ethyl ether and water (mass ratio 1:5) and stirred until the solute was evenly dispersed to obtain the modifier solution.

[0054] 1 kg of magnesium hydroxide with a particle size of 80 nm was added to a high-speed disperser, heated to 140 °C, and then a modifier solution was added. The mixture was stirred at 450 r / min for 10 min to obtain modified magnesium hydroxide containing a triazine structure (product 7).

[0055] Repeat the above steps to obtain product 8 and product 9.

[0056] Products 7-9 were added to TPU at a dosage of 60 parts each to obtain three different TPU materials. Performance tests were conducted on the modified magnesium hydroxide and the three different TPU materials. The test results are shown in Table 4.

[0057] Table 4. Performance test results of unmodified magnesium hydroxide and modified magnesium hydroxide products (7-9).

[0058] As shown in Table 4, after modification, the cyanide content of magnesium hydroxide decreased slightly, but not significantly, and the particle size did not change much; neither index affected its use. Oil absorption and moisture absorption decreased significantly, while the contact angle increased significantly to 113.2°. o This indicates that the modified magnesium hydroxide exhibits enhanced hydrophobicity.

[0059] Figure 3 SEM images of cross-sections of TPU / MH composites filled with unmodified (left) and modified magnesium hydroxide (right) as described in Example 3.

[0060] As can be seen from the above embodiments, the present invention provides a reversible Diels-Alder reaction monomer-modified nano-magnesium hydroxide flame retardant, its preparation method, and its application. The present invention utilizes a modifier with silane-containing end-capacitor structures to surface-modify magnesium hydroxide, improving its hydrophobicity and dispersion characteristics, and reducing particle agglomeration. By utilizing the maleamide structure to conduct a Diels-Alder reaction with the NCO bonds in TPU materials, the modified nano-magnesium hydroxide is anchored onto the TPU backbone, thereby improving the dispersibility and bonding stability of the nano-magnesium hydroxide with the substrate. This is of great significance for improving the overall performance of composite materials and expanding the application fields of magnesium hydroxide.

[0061] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a reversible Diels-Alder reaction monomer-modified nano-magnesium hydroxide flame retardant, characterized in that, Includes the following steps: Nano-sized magnesium hydroxide was mixed with a silane modifier containing a maleamide structure and coupled to obtain a nano-sized magnesium hydroxide flame retardant modified with a reversible Diels-Alder reaction monomer.

2. The method for preparing the reversible Diels-Alder reaction monomer-modified nano-magnesium hydroxide flame retardant according to claim 1, characterized in that, The silane modifier containing the maleamide structure is obtained by reacting maleic anhydride with a silane coupling agent.

3. The method for preparing the reversible Diels-Alder reaction monomer-modified nano-magnesium hydroxide flame retardant according to claim 2, characterized in that, The silane coupling agent comprises one or more of γ-aminopropyltriethoxysilane, γ-aminopropyltrimethoxysilane, γ-aminopropylmethyldiethoxysilane, γ-aminopropylmethyldimethoxysilane, γ-diethylenetriaminopropylmethyldimethoxysilane, and γ-diethylenetriaminopropyltrimethoxysilane.

4. The method for preparing the reversible Diels-Alder reaction monomer-modified nano-magnesium hydroxide flame retardant according to any one of claims 1 to 3, characterized in that, The mass ratio of the nano-magnesium hydroxide to the maleamide-containing silane modifier is 20~200:1, and the particle size of the nano-magnesium hydroxide is 10~100nm.

5. The method for preparing the reversible Diels-Alder reaction monomer-modified nano-magnesium hydroxide flame retardant according to claim 4, characterized in that, The coupling reaction is carried out at a temperature of 100~150℃ and for a time of 3~15min. The coupling reaction is carried out in a mixed solvent, which is a mixture of organic solvent and water.

6. The method for preparing the reversible Diels-Alder reaction monomer-modified nano-magnesium hydroxide flame retardant according to claim 5, characterized in that, The organic solvent comprises one or more of diethylene glycol butyl ether, tripropylene glycol methyl ether, dipropylene glycol butyl ether, dipropylene glycol propyl ether, and diethylene glycol ethyl ether, and the mass ratio of the organic solvent to water is 1:0.2~5.

7. The method for preparing the reversible Diels-Alder reaction monomer-modified nano-magnesium hydroxide flame retardant according to claim 5 or 6, characterized in that, The ratio of the maleamide-containing silane modifier to the mixed solvent is 1~15g:100mL.

8. The nano-magnesium hydroxide flame retardant modified with reversible Diels-Alder reactive monomers prepared by the preparation method according to any one of claims 1 to 7.

9. The application of the reversible Diels-Alder reaction monomer-modified nano-magnesium hydroxide flame retardant according to claim 8 in the preparation of PU elastomers, characterized in that, A nano-sized magnesium hydroxide flame retardant modified with a reversible Diels-Alder reaction monomer was added to TPU. After adding the additives, the mixture was melt-extruded. During the extrusion process, a Diels-Alder reaction occurred, resulting in a flame-retardant modified PU elastomer.

10. The application according to claim 9, characterized in that, The mass ratio of the reversible Diels-Alder reactive monomer-modified nano-magnesium hydroxide flame retardant to TPU is 50~70:100.

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