阅读说明：本技术 纳米金属氢氧化物无卤阻燃剂及其复合材料的制备方法 (Nano metal hydroxide halogen-free flame retardant and preparation method of composite material thereof ) 是由 刘亭亭 王峰 阳明书 丁艳芬 张世民 高冲 刘鹏 陈娟 于 2020-05-09 设计创作，主要内容包括：本发明涉及一种纳米金属氢氧化物无卤阻燃剂及其复合材料的制备方法,属于高分子阻燃材料技术领域,解决了现有技术中金属氢氧化物类无卤阻燃剂阻燃效率低与力学性能差的问题。一种纳米金属氢氧化物无卤阻燃剂的制备方法,包括步骤1：以DOPO或其衍生物、硅烷偶联剂、催化剂为原料,制得含磷杂环化合物；步骤2：将纳米金属氢氧化物颗粒加入到有机溶剂中,制备纳米金属氢氧化物悬浮液；步骤3：将步骤1制得的含磷杂环化合物溶解在有机溶剂中形成溶液,再将形成的溶液加入到步骤2得到的纳米金属氢氧化物悬浮液中,进行纳米金属氢氧化物表面接枝,制得纳米金属氢氧化物无卤阻燃剂。本发明制得阻燃性能优异的纳米金属氢氧化物无卤阻燃剂复合材料。(The invention relates to a nano metal hydroxide halogen-free flame retardant and a preparation method of a composite material thereof, belongs to the technical field of high-molecular flame retardant materials, and solves the problems of low flame retardant efficiency and poor mechanical property of metal hydroxide halogen-free flame retardants in the prior art. A preparation method of a nano metal hydroxide halogen-free flame retardant comprises the following steps of 1: preparing a phosphorus-containing heterocyclic compound by using DOPO or derivatives thereof, a silane coupling agent and a catalyst as raw materials; step 2: adding the nano metal hydroxide particles into an organic solvent to prepare a nano metal hydroxide suspension; and step 3: and (2) dissolving the phosphorus-containing heterocyclic compound prepared in the step (1) in an organic solvent to form a solution, adding the formed solution into the nano metal hydroxide suspension obtained in the step (2), and carrying out nano metal hydroxide surface grafting to obtain the nano metal hydroxide halogen-free flame retardant. The invention prepares the halogen-free flame retardant composite material of nano metal hydroxide with excellent flame retardant property.)

1. A preparation method of a nano metal hydroxide halogen-free flame retardant is characterized by comprising the following steps:

step 1: preparing a phosphorus-containing heterocyclic compound by using DOPO or derivatives thereof, a silane coupling agent and a catalyst as raw materials;

step 2: adding the nano metal hydroxide particles into an organic solvent to prepare a nano metal hydroxide suspension;

and step 3: and (2) dissolving the phosphorus-containing heterocyclic compound prepared in the step (1) in an organic solvent to form a solution, adding the formed solution into the nano metal hydroxide suspension obtained in the step (2), and carrying out surface grafting on the nano metal hydroxide to prepare the nano metal hydroxide halogen-free flame retardant.

2. The preparation method of the halogen-free flame retardant of the nano metal hydroxide as claimed in claim 1, wherein in the step 1, 10-150 parts by weight of DOPO or the derivative thereof, 5-150 parts by weight of the silane coupling agent and 0.1-10 parts by weight of the catalyst are subjected to high-temperature reaction under the protection of nitrogen, and after the reaction is finished, the phosphorus-containing heterocyclic compound is prepared by rotary evaporation, washing and drying.

3. The method for preparing the nano metal hydroxide halogen-free flame retardant according to claim 2, wherein in the step 2, 100 parts by weight of nano metal hydroxide particles are added into an organic solvent and stirred to form a first solution, and the pH of the first solution is adjusted to 10-11 to prepare the nano metal hydroxide suspension.

4. The method for preparing the nano metal hydroxide halogen-free flame retardant according to claim 3, wherein in the step 3, 10 to 50 parts by weight of the phosphorus-containing heterocyclic compound obtained in the step 1 is dissolved in an organic solvent to form a second solution, the pH of the second solution is adjusted to 10 to 11, the second solution is added into the nano metal hydroxide suspension obtained in the step 2, the stirring reaction is carried out, and after the reaction is finished, the nano metal hydroxide halogen-free flame retardant is prepared by filtering, washing and drying.

5. The method for preparing nano metal hydroxide halogen-free flame retardant according to claim 2, wherein DOPO or the derivative thereof has a P-H bond in the step 1; DOPO or derivatives thereof have the structural formula I:

6. the method for preparing the nano metal hydroxide halogen-free flame retardant according to claim 5, wherein R in the formula I₁-R₈One selected from hydrogen atom, alkyl, nitro, alkoxy, aryl and aryloxy;

the alkyl is one of methyl, ethyl, propyl, butyl and pentyl;

the alkoxy is one of methoxy, ethoxy, propoxy and butoxy;

the aryl is one of phenyl, methylphenyl, dimethylphenyl, benzyl and benzyl ethyl;

the aryloxy group is phenoxy.

7. The method for preparing the nano metal hydroxide halogen-free flame retardant according to claim 2, wherein the silane coupling agent is one of vinyltriethoxysilane, vinyltrimethoxysilane, methylvinyldiethoxysilane, allyltrimethoxysilane, gamma-methacryloxypropyltrimethoxysilane, ethynyltrimethylsilane, 3-isocyanatopropyltrimethoxysilane, and 3-isocyanatopropyltriethoxysilane.

8. The method for preparing the nano metal hydroxide halogen-free flame retardant according to claim 2, wherein the nano metal hydroxide is one of aluminum hydroxide and magnesium hydroxide.

9. The method for preparing the nano metal hydroxide halogen-free flame retardant according to claims 1-8, wherein the chemical grafting amount of DOPO or the derivative thereof on the nano metal hydroxide in the nano metal hydroxide halogen-free flame retardant is 0.1-8 wt%.

10. A preparation method of a nano metal hydroxide halogen-free flame retardant composite material is characterized in that the nano metal hydroxide halogen-free flame retardant disclosed by claim 1-9 is blended with an ethylene-vinyl acetate copolymer to obtain the nano metal hydroxide halogen-free flame retardant composite material.

Technical Field

The invention relates to the technical field of high-molecular flame retardant materials, in particular to a nano metal hydroxide halogen-free flame retardant and a preparation method of a composite material thereof.

Background

To control the flammability of the polymer, the most common method is to add a flame retardant. Among the flame retardants, the halogen-based flame retardants are most widely used. However, the use of halogen-based flame retardants is accompanied by the generation of corrosive, toxic fumes and other negative effects. In addition, new regulations, such as european directives on Waste of Electrical and Electronic Equipment (WEEE) and hazardous substances restriction (RoHS), limit the use of some halogen based flame retardants. Therefore, the development of halogen-free, non-toxic and smoke-inhibiting flame retardant is widely regarded. Common halogen-free flame retardants include Magnesium Hydroxide (MH), aluminum hydroxide (ATH), organic phosphorus compounds, nitrogen-containing compounds, organosilicon compounds, and the like. Researches show that the nano metal hydroxide fillers such as magnesium hydroxide, aluminum hydroxide and the like are excellent halogen-free flame retardants and can play a flame retardant role in both a condensed phase and a gas phase. Inert gas (H) generated during combustion of metal hydroxide₂O) can be released into the gas phase, so that dilution is possibleThe concentration of the combustion gas and the suppression of combustion. In addition, the anhydrous magnesium oxide and aluminum oxide powder obtained by thermal decomposition has excellent fire resistance, and can play a role of a heat insulation layer when accumulated on the surface of the polymer to prevent heat from being transferred to the material from flame. However, when the amount of the nano metal hydroxide is more than 60 wt%, the ideal flame retardant effect can be achieved, and the flame retardant efficiency is relatively low. In addition, the nano metal hydroxide has poor compatibility with the polymer and is unevenly dispersed in the polymer matrix, thereby influencing the mechanical property of the composite material. Therefore, it remains a challenge to balance the flame retardancy and mechanical properties (especially toughness) of polymeric materials.

In order to improve the compatibility of the nano metal hydroxide and the polymer matrix, the surface modification of the metal magnesium hydroxide is carried out to improve the compatibility of the metal magnesium hydroxide and the ethylene-vinyl acetate copolymer, and the method is an important method at present. In the prior art, the modified magnesium hydroxide has better dispersibility in resin and improves the flame retardant property of the material. But the elongation at break of the material does not exceed 60%.

The ethylene-vinyl acetate copolymer (EVA) has good elasticity and physical properties, and is widely applied to the fields of household appliances, building industry, decorative materials, wires and cables and the like. In practical application, the EVA has the problems of easy flammability and easy dripping, large smoke generation amount in the combustion process and easy generation of toxic and harmful gases, which seriously limits the application of the EVA. Many attempts have been made to improve the flame retardant properties of EVA. In the prior art, a proper amount of multi-walled carbon nanotubes (MWNTs) and Magnesium Hydroxide (MH) are added into an EVA/MH/MWNT nano composite material for synergistic action. The LOI value of EVA was 34% at 50 wt% MH addition. In the EVA/MH/MWNT composite material, 2 wt% MWNTs replaces MH, and the LOI value can be improved to 39%. The LOI value decreased to 37% with increasing amounts of MWNTs up to 4 wt%.

The 9, 10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) has the characteristics of high flame retardant efficiency and low smoke toxicity, and is widely concerned in the field of flame retardance. In the thermosetting polymer materials such as epoxy resin and the like, because DOPO can react with an epoxy group, good carbon forming and flame retardant effects can be achieved. However, because of the relatively low decomposition temperature, DOPO is difficult to be directly applied to many thermoplastic polymer materials with high processing temperature. The DOPO is chemically grafted to the surface of the inorganic nano metal hydroxide halogen-free flame retardant, so that the halogen-free flame retardant is prepared, on one hand, the good synergistic flame retardant effect can be exerted, on the other hand, the interfacial interaction between the inorganic flame retardant and a high polymer material can be effectively improved, and the method is a method for effectively improving the flame retardant efficiency and the dispersibility of the halogen-free flame retardant.

Disclosure of Invention

In view of the above analysis, the embodiments of the present invention are directed to providing a method for preparing a high-efficiency halogen-free nano metal hydroxide flame retardant and a composite material thereof, so as to solve the problems of low flame retardant efficiency and poor mechanical properties of the existing halogen-free flame retardant.

The invention is realized by the following technical scheme:

a preparation method of a nano metal hydroxide halogen-free flame retardant comprises the following steps:

step 1: preparing a phosphorus-containing heterocyclic compound by using DOPO or derivatives thereof, a silane coupling agent and a catalyst as raw materials;

step 2: adding the nano metal hydroxide particles into an organic solvent to prepare a nano metal hydroxide suspension;

and step 3: and (2) dissolving the phosphorus-containing heterocyclic compound prepared in the step (1) in an organic solvent to form a solution, adding the formed solution into the nano metal hydroxide suspension obtained in the step (2), and carrying out surface grafting on the nano metal hydroxide to prepare the nano metal hydroxide halogen-free flame retardant.

Further, in the step 1, 10-150 parts by weight of DOPO or a derivative thereof, 5-150 parts by weight of a silane coupling agent and 0.1-10 parts by weight of a catalyst are subjected to high-temperature reaction under the protection of nitrogen, and after the reaction is finished, the phosphorus-containing heterocyclic compound is obtained by rotary evaporation, washing and drying.

Further, in the step 2, 100 parts by weight of nano metal hydroxide particles are added into an organic solvent and stirred to form a first solution, and the pH of the first solution is adjusted to 10-11 to prepare the nano metal hydroxide suspension.

Further, in the step 3, 10-50 parts by weight of the phosphorus-containing heterocyclic compound obtained in the step 1 is dissolved in an organic solvent to form a second solution, the pH value of the second solution is adjusted to 10-11, the second solution is added into the nano metal hydroxide suspension obtained in the step 2, stirring and reacting are carried out, and after the reaction is finished, filtering, washing and drying are carried out to prepare the nano metal hydroxide halogen-free flame retardant.

Further, DOPO or a derivative thereof in step 1 has a P — H bond; DOPO or derivatives thereof have the structural formula I:

further, in the formula I, R₁-R₈One selected from hydrogen atom, alkyl, nitro, alkoxy, aryl and aryloxy; the alkyl is one of methyl, ethyl, propyl, butyl and pentyl; the alkoxy is one of methoxy, ethoxy, propoxy and butoxy; the aryl is one of phenyl, methylphenyl, dimethylphenyl, benzyl and benzyl ethyl; aryloxy is phenoxy.

Further, the silane coupling agent is one of vinyltriethoxysilane, vinyltrimethoxysilane, methylvinyldiethoxysilane, allyltrimethoxysilane, gamma-methacryloxypropyltrimethoxysilane, ethynyltrimethylsilane, 3-isocyanatopropyltrimethoxysilane and 3-isocyanatopropyltriethoxysilane.

Further, the nano metal hydroxide is one of aluminum hydroxide and magnesium hydroxide.

Furthermore, in the halogen-free flame retardant of the nano metal hydroxide, the chemical grafting amount of DOPO or the derivative thereof on the nano metal hydroxide is 0.1 to 8 weight percent.

The invention also provides a preparation method of the nano metal hydroxide halogen-free flame retardant composite material, and the nano metal hydroxide halogen-free flame retardant composite material is obtained by blending the nano metal hydroxide halogen-free flame retardant and the ethylene-vinyl acetate copolymer.

Compared with the prior art, the invention can realize at least one of the following beneficial effects:

1. the invention takes silane coupling agent as bridging, chemically grafts the phosphorus-containing flame retardant DOPO or the derivative thereof to the surface of magnesium hydroxide or aluminum hydroxide, and the introduction of organic groups changes the surface property of the nano hydroxide, so that the surface of the nano hydroxide becomes oleophilic and hydrophobic, the compatibility of the hydroxide nano particles and the EVA matrix is improved, and the mechanical property of the composite material is improved.

2. The invention relates to a preparation method of a nano metal hydroxide halogen-free flame retardant and a composite material thereof, which utilizes the synergistic effect of a phosphorus-containing flame retardant DOPO and derivatives thereof and a gas phase and a solid phase of a nano metal hydroxide: the nanometer hydroxide is heated and decomposed to generate solid oxide and water vapor, the solid oxide can form a protective layer on the surface of a combustion material to prevent the further combustion of the material, and the solid flame retardant effect is achieved; the water vapor can dilute the oxygen of the combustible gas and play a role in gas phase flame retardance, so that the flame retardance of the EVA is improved from the gas phase and the solid phase simultaneously, and the flame retardance efficiency of the metal hydroxide is effectively improved.

3. Compared with the prior art, the nano metal hydroxide halogen-free flame retardant prepared by the invention is an organic-inorganic hybrid nano metal hydroxide halogen-free flame retardant, the nano hydroxide is subjected to surface modification, the phosphorus-containing heterocyclic compound is grafted to the surface of the hydroxide, the active sites on the surface of the nano hydroxide are increased, the specific surface area of the nano hydroxide is increased, and after the nano hydroxide halogen-free flame retardant is formed and prepared into a composite material with EVA, the nano hydroxide halogen-free flame retardant has good flame retardant property and mechanical property and good fluidity, and can meet the industrial requirements of EVA products.

In the invention, the technical schemes can be combined with each other to realize more preferable combination schemes. Additional features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and drawings.

Drawings

The drawings are only for purposes of illustrating particular embodiments and are not to be construed as limiting the invention, wherein like reference numerals are used to designate like parts throughout.

FIG. 1 is an infrared spectrum of magnesium hydroxide particles surface-grafted with DOPO of example 1;

FIG. 2 is a transmission electron micrograph of a magnesium hydroxide starting material;

FIG. 3 is a transmission electron micrograph of magnesium hydroxide particles with DOPO grafted on the surface;

FIG. 4 is an X-ray photoelectron spectrum of the magnesium hydroxide particles of example 1 and magnesium hydroxide particles having DOPO grafted on the surface thereof;

FIG. 5 is a scanning electron microscope photograph of a liquid nitrogen quenched section of the ethylene-vinyl acetate copolymer/magnesium hydroxide composite of comparative example 2;

FIG. 6 is a scanning electron microscope photograph of a liquid nitrogen quenched section of the ethylene-vinyl acetate copolymer/magnesium hydroxide composite with surface grafted DOPO of example 1;

FIG. 7 is a scanning electron microscope photograph of a liquid nitrogen quenched section of an ethylene-vinyl acetate copolymer/magnesium hydroxide/silicon-containing organic group DOPO derivative composite material of comparative example 1;

FIG. 8 is a graph of the thermal weight loss for four different samples under an air atmosphere;

wherein: a: ethylene-vinyl acetate copolymer raw material;

b: comparative example 2 the mass ratio of ethylene-vinyl acetate copolymer to magnesium hydroxide was 50 wt%: 50 wt% of ethylene-vinyl acetate copolymer/magnesium hydroxide composite material;

c: example 1 mass ratio of ethylene-vinyl acetate copolymer to magnesium hydroxide surface-grafted with DOPO 48.6 wt%: 51.4 wt% of ethylene-vinyl acetate copolymer/magnesium hydroxide composite material with DOPO grafted on the surface;

d: comparative example 1 the mass ratio of the ethylene-vinyl acetate copolymer to the magnesium hydroxide and the silicon-containing organic group-containing DOPO derivative was 48.6 wt%: 50 wt%: 1.4 wt% of ethylene-vinyl acetate copolymer/magnesium hydroxide/DOPO derivative composite material containing silicon organic group;

FIG. 9 shows the limiting oxygen index test results for four different samples;

e0: ethylene-vinyl acetate copolymer raw material;

E/M: comparative example 2 the mass ratio of ethylene-vinyl acetate copolymer to magnesium hydroxide was 50 wt% to 50 wt% of the ethylene-vinyl acetate copolymer/magnesium hydroxide composite;

E/MDW: example 1 mass ratio of ethylene-vinyl acetate copolymer to magnesium hydroxide with DOPO grafted on surface 48.6 wt% 51.4 wt% ethylene-vinyl acetate copolymer/magnesium hydroxide with DOPO grafted on surface composite;

E/M/DW: comparative example 1 the mass ratio of ethylene-vinyl acetate copolymer to magnesium hydroxide and silicon-containing organic group DOPO derivative was 48.6 wt% to 50 wt% to 1.4 wt% of ethylene-vinyl acetate copolymer/magnesium hydroxide/silicon-containing organic group DOPO derivative composite material.

FIG. 10 is a graph of tensile strength test results for four different samples;

e0: ethylene-vinyl acetate copolymer raw material;

E/M: comparative example 2 the mass ratio of ethylene-vinyl acetate copolymer to magnesium hydroxide was 50 wt% to 50 wt% of the ethylene-vinyl acetate copolymer/magnesium hydroxide composite;

E/MDW: example 1 mass ratio of ethylene-vinyl acetate copolymer to magnesium hydroxide with DOPO grafted on surface 48.6 wt% 51.4 wt% ethylene-vinyl acetate copolymer/magnesium hydroxide with DOPO grafted on surface composite;

E/M/DW: comparative example 1 the mass ratio of ethylene-vinyl acetate copolymer to magnesium hydroxide and silicon-containing organic group DOPO derivative was 48.6 wt% to 50 wt% to 1.4 wt% of ethylene-vinyl acetate copolymer/magnesium hydroxide/silicon-containing organic group DOPO derivative composite material.

FIG. 11 is a graph of elongation at break test results for four different samples;

e0: ethylene-vinyl acetate copolymer raw material;

E/M: comparative example 2 the mass ratio of ethylene-vinyl acetate copolymer to magnesium hydroxide was 50 wt% to 50 wt% of the ethylene-vinyl acetate copolymer/magnesium hydroxide composite;

E/MDW: example 1 mass ratio of ethylene-vinyl acetate copolymer to magnesium hydroxide with DOPO grafted on surface 48.6 wt% 51.4 wt% ethylene-vinyl acetate copolymer/magnesium hydroxide with DOPO grafted on surface composite;

E/M/DW: comparative example 1 the mass ratio of ethylene-vinyl acetate copolymer to magnesium hydroxide and silicon-containing organic group DOPO derivative was 48.6 wt% to 50 wt% to 1.4 wt% of ethylene-vinyl acetate copolymer/magnesium hydroxide/silicon-containing organic group DOPO derivative composite;

FIG. 12 is a schematic diagram of a process for producing three phosphorus-containing heterocyclic compounds;

FIG. 13 is a schematic view of a process for preparing a nano metal hydroxide halogen-free flame retardant by a nano hydroxide surface grafting reaction.

Detailed Description

The accompanying drawings, which are incorporated in and constitute a part of this application, illustrate preferred embodiments of the invention and together with the description, serve to explain the principles of the invention and not to limit the scope of the invention.

The invention provides a preparation method of a nano metal hydroxide halogen-free flame retardant, which comprises the following steps as shown in figures 1-8:

step 1: reacting DOPO or a derivative thereof with a silane coupling agent to prepare a phosphorus-containing heterocyclic compound;

under the protection of nitrogen, 10-150 parts by weight of DOPO or derivatives thereof, 5-150 parts by weight of silane coupling agent and 0.1-10 parts by weight of catalyst react for more than 24 hours at 130-140 ℃ under an anaerobic condition, and after the reaction is finished, the mixture is subjected to rotary evaporation, washed by detergent and dried to obtain the phosphorus-containing heterocyclic compound.

The catalyst is selected from one of triethylamine and azodiisobutyronitrile.

The purpose of washing is to wash away unreacted DOPO or a derivative thereof; the detergent is selected from one or more of cyclohexane, n-hexane and ethanol.

Specifically, DOPO or its derivatives need to have a P-H bond structure, i.e., a structure represented by structural formula I:

in the structural formula I, R₁-R₈Can be independently selected from one of hydrogen atom, alkyl, nitro, alkoxy, aryl and aryloxy. R₁-R₈The alkyl in (A) can be independently selected from one of methyl, ethyl, propyl, butyl and pentyl; the alkoxy can be independently selected from one of methoxy, ethoxy, propoxy and butoxy; the aryl group can be independently selected from one of phenyl, methylphenyl, dimethylphenyl, benzyl and benzyl ethyl; the aryloxy group may be selected from phenoxy.

In particular, when R in formula I₁-R₈When all the groups are hydrogen atoms, the DOPO is obtained: 9, 10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, the structure of which is shown in formula II:

the silane coupling agent can be one selected from the group consisting of vinyltriethoxysilane, vinyltrimethoxysilane, methylvinyldiethoxysilane, allyltrimethoxysilane, gamma-methacryloxypropyltrimethoxysilane, ethynyltrimethylsilane, 3-isocyanatopropyltrimethoxysilane, and 3-isocyanatopropyltriethoxysilane.

Illustratively, in the presence of Azobisisobutyronitrile (AIBN) as a catalyst, DOPO and Vinyltriethoxysilane (VTES) react to form three phosphorus-containing heterocyclic compounds, as shown in fig. 12.

Step 2: preparing a nano metal hydroxide suspension;

adding 100 parts by weight of nano metal hydroxide particles of raw materials into an organic solvent, stirring to form a first solution, and adjusting the pH of the first solution to 10-11 to form a nano metal hydroxide suspension.

The hydrolysis speed of the silane can be accelerated by adjusting the pH value of the first solution to be acidic or alkaline, and the product in the step (1) is adjusted to be alkaline by ammonia water before the reaction because the experimental raw material hydroxide suspension is alkaline. By optimizing experimental parameters, the grafting ratio of the phosphorus-containing heterocyclic compound on the surface of the magnesium hydroxide is preferably 2.4% when the pH of the first solution is adjusted to 10.5.

The nano metal hydroxide is one or a mixture of magnesium hydroxide and aluminum hydroxide.

And step 3: carrying out grafting reaction on the surface of the nano metal hydroxide to prepare the nano metal hydroxide halogen-free flame retardant;

dissolving 10-50 parts by weight of the phosphorus-containing heterocyclic compound in the step (1) in an organic solvent to form a second solution, adjusting the pH of the second solution to 10-11, adding the second solution into the suspension obtained in the step (2), and reacting for 6 hours at the temperature of 60-70 ℃ and the rotating speed of 200-300 rpm, and stirring for reaction. And after the reaction is finished, filtering, washing with a washing solvent, and drying to prepare the nano metal hydroxide halogen-free flame retardant.

The organic solvent in the steps 2 and 3 is one selected from benzene, toluene, xylene, N-dimethylformamide, N-dimethylacetamide, dichloromethane, chloroform, ethanol and acetone.

Illustratively, 9, 10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) and gamma-methacryloxypropyltrimethoxysilane (WD70) are used as raw materials to perform grafting reaction on the surface of the nano hydroxide to prepare the nano metal hydroxide halogen-free flame retardant, and the process is shown in FIG. 13.

The chemical grafting amount of DOPO or the derivative thereof on the nano metal hydroxide in the nano metal hydroxide compound is 0.1 to 8 weight percent.

In the prior art, the dispersibility of a metal hydroxide flame retardant in a matrix is improved through surface modification, or the flame retardant efficiency of the metal hydroxide is improved through simple synergistic compounding.

In the heating process of the DOPO-containing halogen-free flame retardant, more non-volatile molecular fragments can be generated by material degradation, including the sub-fragments of the phosphaphenanthrene group, aryl phosphoric acid, phosphorous acid compounds and the like, and the compounds are beneficial to carbon formation and can play a condensed phase flame retardant role on polymers; from the gas phase perspective, the phosphaphenanthrene group can generate P-C fracture at high temperature to form benzofuran, phosphorus oxygen free radical and the like, and the phosphorus oxygen free radical can quench alkane free radical, hydroxyl free radical and the like generated in the combustion process to stop chain reaction and play a role in gas phase flame retardance.

The invention provides a preparation method of a nano metal hydroxide halogen-free flame retardant composite material.

Specifically, according to the following ethylene-vinyl acetate copolymer (EVA): adding the halogen-free flame retardant of the nano metal hydroxide into blending equipment according to the proportion of 1: 1-1: 1.5. Uniformly mixing EVA and the organic-inorganic hybrid nano metal hydroxide halogen-free flame retardant, adding the mixture into blending equipment, and banburying for 1.5-2 min. Banburying conditions are as follows: the temperature is 140-150 ℃, the feeding speed is 10-15 r/min, the rotating speed is 50-70 r/min, and the time is 5.5-7 min.

In addition, EVA can also be added in batches, firstly a part of ethylene-vinyl acetate copolymer is added, then the organic-inorganic hybrid nano metal hydroxide high-efficiency halogen-free flame retardant is added for continuously mixing uniformly, and then the rest ethylene-vinyl acetate copolymer is added for blending. And obtaining the composite material obtained by blending the organic-inorganic hybrid nano metal hydroxide high-efficiency halogen-free flame retardant and the ethylene-vinyl acetate after blending. When the EVA is added for multiple times, the nano particles and the EVA are mixed more uniformly, and the nano particles can be completely wrapped in the EVA.

Example 1

Preparation of phosphorus-containing hybridsA cyclic compound: 2.6mol of DOPO was added to a 250mL four-necked flask and N was allowed to flow through for 5min₂And heated to 140 ℃. When DOPO was completely melted, 1mol of gamma-methacryloxypropyltrimethoxysilane (WD70) and 1mL of triethylamine were added to the four-necked flask, and N was continuously introduced₂And reacting for 24 hours under the anaerobic condition to obtain the phosphorus-containing heterocyclic compound (DOPO-WD70) containing silicon organic groups.

78.0g of Magnesium Hydroxide (MH) powder was prepared into a slurry having a concentration of 0.1g/mL and placed in a 1L three-necked flask, the pH of the slurry was adjusted to 10.5, and the slurry was heated to 80 ℃. 20g of DOPO-WD70 was weighed out and dissolved in an appropriate amount of ethanol solvent (pH of the ethanol solvent was adjusted to 10.5), and added to the slurry. The reaction was carried out at 80 ℃ and 200rpm for 6 h. The reaction solution was filtered under positive pressure to obtain a product nano metal hydroxide complex (MH-WD70-DOPO), which MH-WD70-DOPO was washed 3 times with ethanol. MH-WD70-DOPO was dried overnight in a vacuum oven at 80 ℃ for use. FIG. 1 and FIGS. 3 to 4 show the IR spectrum, TEM image and photoelectron spectrum of MH-WD70-DOPO prepared in this example. In comparison with the transmission electron microscope image of magnesium hydroxide of FIG. 2, it can be seen from FIG. 1 that example 1 successfully produces surface-grafted magnesium hydroxide particles.

The preparation method of the nano metal hydroxide halogen-free flame retardant composite material comprises the following steps:

ethylene-vinyl acetate copolymer: 48.6 wt.%

Nano metal hydroxide halogen-free flame retardant (MH-WD 70-DOPO): 51.4 wt.%

Specifically, 31.8g of ethylene-vinyl acetate copolymer and 33.6g of MH-WD70-DOPO are weighed and added into an internal mixer in batches for melting and blending, wherein the internal mixing temperature is 135 ℃, the rotating speed is 50r/min, and the time is 7 min. After the blending is finished, the equilibrium torque of the obtained nano metal hydroxide halogen-free flame retardant composite material is 20.1 N.m, the melt index is 6.01%, the limiting oxygen index is 32.8%, the tensile strength is 11.48MPa, and the elongation at break is 209.13%.

Example 2

Preparing a phosphorus-containing heterocyclic compound: 2.6mol of DOPO was added to a 250mL four-necked flask and N was allowed to flow through for 5min₂And heat upTo 140 ℃. When DOPO was completely melted, 1mol VTES and 1mL triethylamine were added to the four-necked flask, and N was continuously introduced₂And reacting for 24 hours under the anaerobic condition to obtain the phosphorus-containing heterocyclic compound (DOPO-VTES).

78.0g of aluminum hydroxide (ATH) powder is prepared into slurry with the concentration of 0.1g/mL and placed in a 1L three-neck flask, the pH of the slurry is adjusted to 10.5, and the slurry is heated to 80 ℃. 20g of DOPO-WD70 was weighed out and dissolved in an appropriate amount of ethanol solvent (pH of the ethanol solvent was adjusted to 10.5), and added to the slurry. The reaction was carried out at 80 ℃ and 200rpm for 6 h. And (3) filtering the reaction liquid at positive pressure to obtain a product of the nano metal hydroxide halogen-free flame retardant (ATH-WD70-DOPO), and washing the ATH-WD70-DOPO with ethanol for 3 times. The ATH-WD70-DOPO was dried overnight in a vacuum oven at 80 ℃ for further use.

The preparation method of the nano metal hydroxide halogen-free flame retardant composite material comprises the following steps:

ethylene-vinyl acetate copolymer: 48.6 wt.%

Nanometer metal hydroxide halogen-free flame retardant (ATH-WD 70-DOPO): 51.4 wt.%

32.0g of ethylene-vinyl acetate copolymer and 33.8g of ATH-WD70-DOPO are weighed and added into an internal mixer in batches for melting and blending, the internal mixing temperature is 135 ℃, the rotating speed is 50r/min, and the time is 7 min. After the blending is finished, the equilibrium torque of the obtained nano metal hydroxide halogen-free flame retardant composite material is 10.2 N.m, the limiting oxygen index is 31.6%, the tensile strength is 12.13MPa, and the elongation at break is 170.57%.

Example 3

Preparing a phosphorus-containing heterocyclic compound: 2.6mol of DOPO was added to a 250mL four-necked flask and N was allowed to flow through for 5min₂And heated to 140 ℃. When DOPO was completely melted, 1mol Vinyltriethoxysilane (VTES) and 1mL triethylamine were added to the four-necked flask, and N was continuously introduced₂And reacting for 24h under the anaerobic condition to obtain the DOPO derivative (DOPO-VTES).

78.0g of Magnesium Hydroxide (MH) powder was prepared into a slurry having a concentration of 0.1g/mL and placed in a 1L three-necked flask, the pH of the slurry was adjusted to 10.5, and the slurry was heated to 80 ℃. 20g of DOPO-VTES was weighed out and dissolved in an appropriate amount of ethanol solvent (pH of the ethanol solvent was adjusted to 10.5), and added to the slurry. The reaction was carried out at 80 ℃ and 200rpm for 6 h. And filtering the reaction liquid under positive pressure to obtain a nano metal hydroxide halogen-free flame retardant (MH-VTES-DOPO), and washing the MH-VTES-DOPO with ethanol for 3 times. MH-WD70-DOPO was dried overnight in a vacuum oven at 80 ℃ for use.

The preparation method of the nano metal hydroxide halogen-free flame retardant composite material comprises the following steps:

ethylene-vinyl acetate copolymer: 48.6 wt.%

Nano metal hydroxide halogen-free flame retardant (MH-VTES-DOPO): 51.4 wt.%

31.8g of ethylene-vinyl acetate copolymer and 33.6g of MH-VTES-DOPO particles are weighed and added into an internal mixer in batches for melt blending, the internal mixing temperature is 135 ℃, the rotating speed is 50r/min, and the time is 7 min. After the blending is finished, the equilibrium torque of the obtained nano metal hydroxide halogen-free flame retardant composite material is 20.1 N.m, the limiting oxygen index is 32.5%, the tensile strength is 11.48MPa, and the elongation at break is 209.13%.

Comparative example 1

Preparing a phosphorus-containing heterocyclic compound: 2.6mol of DOPO was added to a 250mL four-necked flask and N was allowed to flow through for 5min₂And heated to 140 ℃. When DOPO was completely melted, 1mol VTES and 1mL triethylamine were added to the four-necked flask, and N was continuously introduced₂And reacting for 24 hours under the anaerobic condition to obtain the phosphorus-containing heterocyclic compound (DOPO-VTES).

78.0g of magnesium hydroxide powder is taken to prepare slurry with the concentration of 0.1g/mL and placed in a 1L three-neck flask, the pH of the slurry is adjusted to 10.5, and the slurry is heated to 80 ℃. 20g of DOPO-VTES was weighed out, dissolved in an appropriate amount of ethanol solvent (pH of the ethanol solvent was adjusted to 10.5), and added to the slurry. The reaction was carried out at 80 ℃ and 200rpm for 6 h. The reaction liquid is filtered under positive pressure to obtain a product of the nano metal hydroxide halogen-free flame retardant (MH-VTES-DOPO), and the product is washed for 3 times by ethanol. The product was dried overnight in a vacuum oven at 80 ℃ until use.

The preparation method of the nano metal hydroxide halogen-free flame retardant composite material comprises the following steps:

ethylene-vinyl acetate copolymer: 48.6 wt.%

Aluminum hydroxide: 50 wt.%

Nano metal hydroxide halogen-free flame retardant (MH-VTES-DOPO): 1.4 wt.%

32.0g of ethylene-vinyl acetate copolymer, 32.9g of MH-VTES-DOPO and 1.0g of DOPO derivative are weighed and added into an internal mixer in batches for melting and blending, the internal mixing temperature is 135 ℃, the rotating speed is 50r/min, and the time is 7 min. After the blending is finished, the equilibrium torque of the obtained nano metal hydroxide halogen-free flame retardant composite material is 19.2 N.m, the limiting oxygen index is 30.5%, the tensile strength is 7.78MPa, and the elongation at break is 138.70%.

Comparative example 2

The flame retardant composite material comprises the following components in percentage by weight:

ethylene-vinyl acetate copolymer: 50 wt.%

Magnesium hydroxide: 50 wt.%

32.7g of ethylene-vinyl acetate copolymer and 32.7g of magnesium hydroxide particles are weighed and added into an internal mixer in batches for melt blending, the internal mixing temperature is 135 ℃, the rotating speed is 50r/min, and the time is 7 min. After blending, a composite material was prepared as shown in fig. 5. The composite material obtained had an equilibrium torque of 31.09 N.m, a melt index of 1.57g/min, a limiting oxygen index of 28.2%, a tensile strength of 8.18MPa and an elongation at break of 127.58%.

Comparative example 3

The flame retardant composite material comprises the following components in percentage by weight:

ethylene-vinyl acetate copolymer: 50 wt.%

Aluminum hydroxide: 50 wt.%

32.9g of ethylene-vinyl acetate copolymer and 32.9g of aluminum hydroxide particles are weighed and added into an internal mixer in batches for melt blending, the internal mixing temperature is 135 ℃, the rotating speed is 50r/min, and the time is 7 min. After the blending, the balance torque of the obtained composite material is 32.1 N.m, the limiting oxygen index is 28.8%, the tensile strength is 11.59MPa, and the elongation at break is 148.75%.

Comparing with fig. 5-7, it can be seen that in the prior art, the nano metal hydroxide halogen-free flame retardant composite material prepared by directly mixing the ethylene-vinyl acetate copolymer and the hydroxide has large granularity and rough particles, and the composite material prepared by mixing the nano hydroxide with the ethylene-vinyl acetate copolymer after surface modification has small granularity and smooth surface.

The smaller the equilibrium torque of the flame retardant, the better the flowability of the flame retardant material, the better its processability and the better its mechanical properties. Examples 1 to 3 and comparative examples 1 to 3, the equilibrium torque of the nano metal hydroxide halogen-free flame retardant composite material prepared in examples 1 to 3 is lower than that of the flame retardant in comparative examples 1 to 3, and the tensile strength and the elongation at break of the flame retardant in examples 1 to 3 are higher than those of comparative examples 1 to 3. As shown in FIGS. 10 to 11, the tensile strength and elongation at break of example 1 are superior to those of comparative examples 1 and 2. The mechanical property of the nano metal hydroxide halogen-free flame retardant composite material prepared by the invention is superior to that of the flame retardant composite material prepared by the prior art.

The higher the melt index and the limited oxygen index are, the better the flame retardant performance of the flame retardant is, as shown in fig. 9, the limited oxygen index of example 1 is higher than that of comparative examples 1-2. Therefore, the flame retardant prepared by the preparation method of the halogen-free flame retardant of nano metal hydroxide provided by the invention has better mechanical property and flame retardant property than the flame retardant in the prior art. As shown in fig. 8, the decomposition temperature of the flame retardant composite prepared by grafting the surface of the metal hydroxide in example 1 and comparative example 1 was higher than that of the flame retardant composite prepared by directly mixing the ethylene-vinyl acetate copolymer with magnesium hydroxide in comparative example 2.

The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are included in the scope of the present invention.