WO2022068065A1 - Preparation method for montmorillonite-magnesium hydroxide composite microencapsulated flame retardant - Google Patents

Abstract

A preparation method for a montmorillonite-magnesium hydroxide composite microencapsulated flame retardant, relating to the technical field of flame retardants. The method comprises the following steps: A. mixing sodium-based montmorillonite with nano-magnesium hydroxide, then adding long chain alkyl quaternary ammonium salt for reacting to prepare inorganic composite modified particles, and reserving same for later use; and B. adding the inorganic composite modified particles prepared in step A to an active monomer solution to prepare a montmorillonite-magnesium hydroxide composite microencapsulated flame retardant. A core material of the obtained composite microencapsulated flame retardant is at least composed of two different substances; magnesium hydroxide and montmorillonite are used as the flame retardant core material; since there is no chemical bond between molecules of magnesium hydroxide and montmorillonite, that is, there is no close interaction, the obtained composite microencapsulated flame retardant is composed of microencapsulated magnesium hydroxide and microencapsulated montmorillonite, and has good dispersibility; moreover, an addition amount of a magnesium hydroxide flame retardant is reduced, so that the inherent mechanical strength and toughness can still be maintained.

Description

[Name of invention formulated by ISA according to Rule 37.2] Preparation method of montmorillonite-magnesium hydroxide composite microencapsulated flame retardant technical field

The invention relates to the technical field of flame retardants, and more particularly, to a preparation method of a montmorillonite-magnesium hydroxide composite microencapsulated flame retardant.

Background technique

Magnesium hydroxide (MH), as a typical inorganic flame retardant, has received more and more attention in recent years due to its acid-free, low cost and good smoke suppression properties. However, magnesium hydroxide as a flame retardant also has the following disadvantages: on the one hand, the flame retardant efficiency is low, and a higher filling amount (>50%) is required to meet the flame retardant requirements, resulting in a decrease in the mechanical properties of the composite material. For this reason, the synergistic flame retardant effect produced by the introduction of synergists into the MH compounding can reduce the addition amount. Among many synergists, montmorillonite (MMT) has attracted much attention due to its good thermal stability, high efficiency, and little effect on the mechanical properties of polymers. On the other hand, the dispersion performance is poor, and the particle size of MH powder has a great influence on its dispersibility in the substrate. Large particle size will lead to poor dispersion performance, and small particle size will increase the purchase cost of the mixing machine. At the same time, MH is easy to agglomerate in the matrix; if a large amount of MH is incorporated into the polymer, the rheological properties and mechanical properties of the polymer will be destroyed.

The Chinese patent "Preparation of Organic Flame Retardant Transparent Composite Materials by One-Step In-situ Synthesis" (Application No.: 200910074574.2, Publication Date: 20091209) discloses the preparation of organic flame-retardant and transparent composite materials by one-step in-situ synthesis method, using methyl methacrylate as raw material , Using sodium-based montmorillonite and magnesium hydroxide as flame retardants, first purify the sodium-based montmorillonite, prefabricate a magnesium hydroxide microemulsion, add methyl methacrylate monomer in a four-necked flask, Under nitrogen protection, water circulation condensation, continuous constant temperature heating, uniform stirring, dropwise addition of initiator azobisisobutyronitrile absolute ethanol solution, one-step synthesis of polymethyl methacrylate + magnesium hydroxide + sodium montmorillonite three-phase The composite material is an organic flame retardant nanocomposite material. The material morphology is white loose composite particle powder. After film formation, the average particle size of magnesium hydroxide in the matrix is 60nm, and the sodium-based montmorillonite is peeled off. The light transmittance of the product is 85. %, the ultraviolet light absorption rate is 40%, the limiting oxygen index is increased from 19% to 26%, and the hardness can be increased by 10%. This method requires less equipment, short process flow, no environmental pollution and high yield.

The above-mentioned invention patent effectively solves the problem of the particle size of magnesium hydroxide, so that the dispersibility of the prepared organic flame-retardant transparent composite material is also improved, but the above-mentioned sodium-based montmorillonite and magnesium hydroxide need to be pretreated separately, Before adding it to the polymer matrix, it is necessary to use different processes and equipment to pre-treat the sodium-based montmorillonite and magnesium hydroxide, which is complicated in the process and high in cost.

In view of this, it is necessary to research and develop a flame retardant with good dispersibility and easy preparation.

SUMMARY OF THE INVENTION

The present invention aims to overcome at least one defect (deficiency) of the above-mentioned prior art, and provides a preparation method of a montmorillonite-magnesium hydroxide composite microencapsulated flame retardant, which is used to solve the problems of poor dispersion and filling amount of the flame retardant. high cost and high production cost.

The present invention also aims to provide a montmorillonite-magnesium hydroxide composite microencapsulated flame retardant.

The technical scheme adopted in the present invention is that a preparation method of a montmorillonite-magnesium hydroxide composite microencapsulated flame retardant comprises the following steps:

A. After mixing sodium-based montmorillonite and nano-magnesium hydroxide, add long-chain alkyl quaternary ammonium salt to react to prepare inorganic composite modified particles, and reserve for use;

B. Adding the inorganic composite modified particles obtained in step A to the active monomer solution to prepare a montmorillonite-magnesium hydroxide composite microencapsulated flame retardant.

Further, include the following steps:

A. Disperse sodium-based montmorillonite and nano-magnesium hydroxide in deionized water, keep stirring under constant temperature water bath, and let stand to obtain montmorillonite-magnesium hydroxide mixed solution; take long-chain alkyl quaternary ammonium salt and add deionized Water, heated and stirred to dissolve and slowly added dropwise to the montmorillonite-magnesium hydroxide mixed solution, heated in a constant temperature water bath, passed in an inert gas, and reacted under stirring. Dry in vacuum, grind and sieve to obtain inorganic composite modified particles, which are reserved for future use;

B. After the active monomer, surfactant and distilled water are stirred in the reactor to make it completely emulsified, the inorganic composite modified particles obtained in step A are slowly added to the reactor, and then polyvinylpyrrolidone and titanate are added. The joint agent is heated up after stirring evenly. Under the protection of inert gas, the initiator solution is slowly added dropwise, and the temperature of the mixture is continued. After the reaction is completed, precipitation, filtration and drying are performed to obtain montmorillonite-magnesium hydroxide composite microencapsulated flame retardant. agent.

Further, include the following steps:

A. Weigh 5-10 parts of sodium-based montmorillonite and 15-20 parts of nano-magnesium hydroxide and disperse them in deionized water. ~2 parts of long-chain alkyl quaternary ammonium salt, add 20-30 parts of deionized water, heat and stir to dissolve it, slowly add its solution dropwise to the mixed solution of montmorillonite and magnesium hydroxide, at 60-75 ℃ Heating in a constant temperature water bath, introducing nitrogen, and reacting under stirring for 2 to 4 hours at a stirring speed of 250 to 350/min. After the reaction is completed, the reaction solution is suction filtered and cleaned until no _Cl can be detected with 0.1 mol/L AgNO . In the presence of ^- , the samples were vacuum-dried at 80-100 °C to constant weight, ground in a mortar and sieved to obtain inorganic composite modified particles, which were reserved for future use;

B. After weighing 10-20 parts of active monomer, 1-2 parts of surfactant and 150-200 parts of distilled water and stirring in the reactor to make it completely emulsified, the inorganic composite modified particles obtained in step A are slowly added to the reaction Add 0.1-1 part of polyvinyl pyrrolidone and 0.1-1 part of titanate coupling agent to the container, stir evenly and then heat up to 60-75 ℃, under nitrogen protection, slowly add 0.3-0.5 part of initiator solution dropwise, continue The mixture was heated to 80-85° C. and reacted for 4-6 hours; then, the mixture was precipitated with methanol, filtered, and dried to constant weight to obtain a montmorillonite-magnesium hydroxide composite microencapsulated fuel.

Further, in the described step A, sodium-based montmorillonite comprises the following components:

The cation exchange capacity was 100 mmol/100 g.

Further, in the step A, the nano-magnesium hydroxide is lamellar rhombus, and the particle size is 380-430 nm.

Further, in the step A, the nano-magnesium hydroxide is lamellar rhombus, and the particle size is 400 nm.

Further, in the step A, the long-chain alkyl quaternary ammonium salt is prepared from dodecyl ammonium bromide, cetyl ammonium bromide, and octadecyl ammonium bromide at a ratio of 0 to 1:1:0 to 1 made.

Further, in the step B, the active monomer is one or both of styrene monomer, methyl methacrylate, butyl methacrylate, ethyl acrylate, and butyl acrylate compound; styrene monomer The mass ratio to methyl methacrylate is 1:0～2, the mass ratio of styrene monomer to butyl methacrylate is 1:0～2, and the mass ratio of styrene monomer to ethyl acrylate is 1:0～2 , the mass ratio of styrene monomer and butyl acrylate is 1:0～2.

Further, in the described step B, the surfactant is sodium dodecyl sulfate, sodium dodecyl benzene sulfonate, sodium ethoxylated fatty acid methyl ester sulfonate, sodium secondary alkyl sulfonate, alcohol ether hydroxy acid A kind of salt, alcohol ether phosphate.

Further, in the step B, the titanate coupling agent is isopropyl tris (dioctyl pyrophosphate acyloxy) titanate, isopropyl tris (dioctyl phosphoric acid acyloxy) titanate, Isopropyl dioleic acid acyloxy (dioctyl phosphoric acid acyloxy) titanate, monoalkoxy unsaturated fatty acid titanate, bis (dioctyl pyrophosphate acyloxy) ethylene titanate, One of tetraisopropyl bis (dioctyl phosphite) titanate.

Further, in the step B, the initiator is a kind of potassium persulfate and ammonium persulfate.

A flame retardant prepared by the above-mentioned preparation method of a montmorillonite-magnesium hydroxide composite microencapsulated flame retardant is composed of montmorillonite-magnesium hydroxide as a core material and a polymer material as a shell.

Compared with the prior art, the beneficial effects of the present invention are as follows: the core material of the composite microencapsulated flame retardant prepared by the present invention is composed of at least two different substances, and magnesium hydroxide and montmorillonite are used as the flame retardant core material. , because there is no chemical bond between their molecules, that is, there is no close interaction, the obtained composite microencapsulated flame retardant is composed of microencapsulated magnesium hydroxide and microencapsulated montmorillonite, which has good dispersibility, At the same time, the addition of magnesium hydroxide flame retardant is reduced, and the inherent mechanical strength and toughness can still be maintained.

Detailed ways

The present invention is only used for exemplary illustration, and should not be construed as a limitation of the present invention.

Example 1

(1) Weigh 5 parts of nano-montmorillonite (Na-MMT) and 15 parts of nano-magnesium hydroxide (MH) and disperse them in an appropriate amount of deionized water, place them in a constant temperature water bath, and stir continuously at a certain speed. For a period of time, stand still for 3 hours, weigh 1 part of cetyl trimethyl ammonium bromide and add it to a 100 mL reactor, add 20 parts of deionized water, heat and stir to dissolve it, and slowly add its solution dropwise to Mongolia In the mixed solution of de-soil and magnesium hydroxide, heat in a constant temperature water bath at 60°C, pass _N2 , and react under stirring for 4 hours at a stirring speed of 300 r/min. Then, the reaction solution was suction filtered and washed until the presence of Cl ^- could not be detected with 0.1 mol/L AgNO ₃ . The samples were vacuum-dried at 80°C for 24 hours, ground in a mortar and sieved to prepare the desired inorganic composite modified particles, which were reserved for future use.

(2) After weighing 6 parts of styrene, 4 parts of methyl methacrylate, 1.5 parts of sodium lauryl sulfate and 200 parts of distilled water and stirring in the reactor to make it completely emulsified, the inorganic composite modified particles obtained above were slowly Add to the reactor, then add 0.5 part of polyvinylpyrrolidone and 0.4 part of tetraisopropyl bis (dioctyl phosphite) titanate, stir evenly and then heat up to 70 ° C, under the protection of N ₂ , slowly dropwise add 0.5 part of Potassium sulfate solution, continue to heat the mixture to 80°C, and react for 4 hours; then, precipitate with methanol, filter, and dry to constant weight to obtain montmorillonite-magnesium hydroxide composite microencapsulated fuel.

Example 2

(1) Weigh 15 parts of nano-montmorillonite (Na-MMT) and 17 parts of nano-magnesium hydroxide (MH) and disperse them in an appropriate amount of deionized water, place them in a constant temperature water bath, and stir continuously at a constant stirring speed For a period of time, stand still for 2.1 hours, weigh 1 part of hexadecyl ammonium bromide and 0.6 part of octadecyl ammonium bromide into a 100 mL reactor, add 30 parts of deionized water, heat and stir to dissolve, and then add The solution was slowly added dropwise to the mixed solution of montmorillonite and magnesium hydroxide, heated in a constant temperature water bath at 75°C, and reacted under argon for 2 hours under stirring at a stirring speed of 250 rpm. Then, the reaction solution was suction filtered and washed until the presence of Cl ^- could not be detected with 0.1 mol/L AgNO ₃ . The samples were vacuum-dried at 100°C for 30 hours, ground in a mortar and sieved to prepare the desired inorganic composite modified particles, which were reserved for future use.

(2) After weighing 5 parts of styrene, 4 parts of butyl methacrylate, 2 parts of sodium dodecyl benzene sulfonate and 150 parts of distilled water and stirring in the reactor to make it completely emulsified, the above obtained inorganic composite modified The particles were slowly added to the reactor, and then 0.1 part of polyvinylpyrrolidone and ₁ part of isopropyl tris (dioctyl pyrophosphate acyloxy) titanate were added, and the temperature was raised to 70 ° C after stirring evenly. Add 0.3 part of ammonium persulfate solution, continue to heat the mixture to 81°C, and react for 6 hours; then, precipitate with methanol, filter, and dry to constant weight to obtain montmorillonite-magnesium hydroxide composite microencapsulated fuel.

Example 3

(1) Weigh 12 parts of nano-montmorillonite (Na-MMT) and 19 parts of nano-magnesium hydroxide (MH) and disperse them in an appropriate amount of deionized water, place them in a constant temperature water bath, and stir continuously at a certain stirring speed. For a period of time, stand still for 2 hours, weigh 1 part of cetyl ammonium bromide and 1 part of dodecyl ammonium bromide into a 100 mL reactor, add 28 parts of deionized water, heat and stir to dissolve, The solution was slowly added dropwise to the mixed solution of montmorillonite and magnesium hydroxide, heated in a constant temperature water bath at 64° C., passed into nitrogen, and reacted under stirring for 2.5 hours at a stirring speed of 350 rpm. Then, the reaction solution was suction filtered and washed until the presence of Cl ^- could not be detected with 0.1 mol/L AgNO ₃ . The samples were vacuum-dried at 100°C for 24 hours, ground in a mortar, and sieved to prepare the desired inorganic composite modified particles, which were reserved for future use.

(2) After weighing 6 parts of styrene, 6 parts of ethyl acrylate, 1 part of sodium ethoxylated fatty acid methyl ester sulfonate and 200 parts of distilled water and stirring in the reactor to make it completely emulsified, the inorganic composite modification obtained above was The particles were slowly added to the reactor, and then 0.5 part of polyvinylpyrrolidone and 0.1 part of isopropyl dioleic acid acyloxy (dioctyl phosphoric acid acyloxy) titanate _were added, and the temperature was raised to 75 °C after stirring, and N Then, 0.5 part of potassium persulfate solution was slowly added dropwise, and the mixture was heated to 85° C. and reacted for 4.6 hours; then, it was precipitated with methanol, filtered, and dried to constant weight to obtain montmorillonite-magnesium hydroxide composite microencapsulation. fuel.

Example 4

(1) Weigh 8 parts of nano-montmorillonite (Na-MMT) and 20 parts of nano-magnesium hydroxide (MH) and disperse them in an appropriate amount of deionized water, place them in a constant temperature water bath, and stir continuously at a certain stirring speed. For a period of time, stand still for 2 hours, weigh 0.4 part of octadecyl ammonium bromide, 0.8 part of hexadecyl trimethyl ammonium bromide, 0.4 part of dodecyl ammonium bromide into a 100mL reactor, add 20 deionized water, heated and stirred to dissolve it, slowly added its solution dropwise to the mixed solution of montmorillonite and magnesium hydroxide, heated in a constant temperature water bath at 60 °C, passed _N2 , and reacted for 4 hours under stirring, stirring Speed 300 rpm. Then, the reaction solution was suction filtered and washed until the presence of Cl ^- could not be detected with 0.1 mol/L AgNO ₃ . The samples were placed under vacuum at 80°C for 24 hours, then ground in a mortar and sieved to prepare the desired inorganic composite modified particles, which were reserved for future use.

(2) After weighing 6 parts of styrene, 4 parts of butyl acrylate, 1.2 parts of alcohol ether hydroxy acid salt and 200 parts of distilled water and stirring in the reactor to make it completely emulsified, the inorganic composite modified particles obtained above were slowly added to the reactor , add 1 part of polyvinylpyrrolidone and 0.5 part of monoalkoxy unsaturated fatty acid titanate, stir evenly and heat up to 70 °C, under the protection of N, slowly add _0.5 part of potassium persulfate solution dropwise, continue to heat the mixture to 80° C., react for 4 hours; then, precipitate with methanol, filter, and dry to constant weight to obtain montmorillonite-magnesium hydroxide composite microencapsulated fuel.

Comparative Example 1

Czochralski purchased a commercially available magnesium hydroxide flame retardant material to replace the nano-magnesium hydroxide described in this application, and other implementation steps were consistent with implementation 1.

Comparative Example 2

50 parts of polyvinyl chloride resin, 1.4 parts of barium zinc stabilizer, 0.6 parts of calcium stearate, 4.5 parts of PE wax, 10.5 parts of diisononyl phthalate, and 8 parts of nano-montmorillonite (Na-MMT) and 20 parts of nano-magnesium hydroxide (MH), mixed with high-speed stirring, and fed into a twin-screw extruder to obtain a flame-retardant melt with a polymer melting point of 8 to 16 ° C, and then extruded, cooled and cut to obtain non-microcapsules. Chemical flame retardant masterbatch.

The flame retardants prepared in Examples 1 to 4 and Comparative Examples 1 to 2 were respectively added to TK-1000 produced by ShinEtsu (Shin-Etsu, Japan), P70 produced by Germany Vinnolit (Vinnolit, Germany), and Taiwan Taiwan at a proportion of 15wt%. In the PR-415 polyvinyl chloride (PVC) produced by plastic, and prepared into several test strips, the corresponding indicators were determined according to the following measurement methods:

(1) Burning performance test Limiting Oxygen Index (LOI) test, measured according to ASTM D2863, the sample bar is taken from the sample bar pressed by the pressure molding machine, the size is 100×6.5×3mm ³ , and the data is shown in Table 1:

Table 1 Polyvinyl Chloride (PVC) Test Limiting Oxygen Index

Oxygen Index/%	Example 1	Example 2	Example 3	Example 4	Comparative Example 1	Comparative Example 2	PVC
TK-1000	24.8	25.7	25.8	28.1	21.5	23.4	21.2
P70	23.9	26.1	26.4	26.7	20.9	22.7	21.8
PR-415	24.6	25.9	27.4	27.1	21.1	22.1	21.4

It can be found from Table 1 that the flame retardants of Examples 1 to 4 are used in three types of polyvinyl chloride (PVC) raw materials of TK-1000, P70 and PR-415, and the flame retardants of Comparative Examples 1 to 2 are used for TK-1000, P70, PR-415 three types of polyvinyl chloride (PVC) raw materials have higher oxygen index, which means they have better flame retardant effect. The flame retardants of Examples 1 to 4 can all achieve flame retardancy for TK-1000, P70, PR-415 three types of polyvinyl chloride (PVC), and the inorganic magnesium hydroxide is uniformly dispersed in the polyvinyl chloride (PVC) substrate. It has good compatibility; especially the flame retardant of Example 4 has excellent flame retardant effect on HTK-1000 and the flame retardant of Example 3 on PR-415.

(2) Vertical burning test (UL-94) level determination, following the American national standard UL-94, the sample size is 130×13×3mm ³ , placed vertically, with absorbent cotton placed directly below, and applied twice for 10 seconds to record the combustion phenomenon, the material is subjected to combustion assessment. Each group of samples was measured five times in parallel to ensure the reliability and reproducibility of the data. The data is shown in Table 2-5:

Table 2 Polyvinyl chloride (PVC) test horizontal burning rate

Horizontal burn rate	Example 1	Example 2	Example 3	Example 4	Comparative Example 1	Comparative Example 2	PVC
TK-1000	HB	HB	HB	HB	HB75	HB	HB75
P70	HB	HB	HB	HB	HB75	HB75	HB75
PR-415	HB	HB	HB	HB	HB75	HB75	HB75

Table 3 Polyvinyl chloride (PVC) test vertical burning rate

vertical burn rate	Example 1	Example 2	Example 3	Example 4	Comparative Example 1	Comparative Example 2	PVC
TK-1000	V-0	V-0	V-0	V-0	V-2	V-0	V-2
P70	V-0	V-0	V-0	V-0	V-2	V-2	V-2
PR-415	V-0	V-0	V-0	V-0	V-2	V-2	V-2

Table 4 Ethylene-Vinyl Acetate Copolymer (EVA) Test Droplet

droplet	Example 1	Example 2	Example 3	Example 4	Comparative Example 1	Comparative Example 2	PVC
TK-1000	no dripping	no dripping	no dripping	no dripping	very intense	fierce	very intense
P70	no dripping	no dripping	no dripping	no dripping	very intense	very intense	very intense
PR-415	no dripping	no dripping	no dripping	no dripping	very intense	very intense	very intense

Table 5 Polyvinyl chloride (PVC) test automatic fire extinguishing time/second

It can be found from Table 2-5 that the flame retardants of Examples 1 to 4 and the flame retardants of Comparative Examples 1 to 2 are used in three types of polyvinyl chloride (PVC) raw materials of TK-1000, P70 and PR-415, The flame retardants of Examples 1 to 4 are significantly better than the flame retardants of Comparative Examples 1 to 2 in terms of horizontal burning rate, vertical burning rate, molten drop, and automatic extinguishing time. The flame retardants of Examples 1 to 4 can well achieve flame retardancy for TK-1000, P70, PR-415 three types of polyvinyl chloride (PVC), and inorganic magnesium hydroxide is resistant to polyvinyl chloride (PVC) substrates. The combustion efficiency is good; the flame retardant of Example 3 has excellent flame retardant effect on TK-1000 and the flame retardant of Example 2 on PR-415.

Obviously, the above-mentioned embodiments of the present invention are only examples for clearly illustrating the technical solutions of the present invention, and are not intended to limit the specific embodiments of the present invention. Any modifications, equivalent replacements and improvements made within the spirit and principle of the claims of the present invention shall be included within the protection scope of the claims of the present invention.

Claims (10)

1. A preparation method of a montmorillonite-magnesium hydroxide composite microencapsulated flame retardant, characterized in that it comprises the following steps:

   A. After mixing sodium-based montmorillonite and nano-magnesium hydroxide, add long-chain alkyl quaternary ammonium salt to react to prepare inorganic composite modified particles, and reserve for use;

   B. Adding the inorganic composite modified particles obtained in step A to the active monomer solution to prepare a montmorillonite-magnesium hydroxide composite microencapsulated flame retardant.
2. The preparation method of a kind of montmorillonite-magnesium hydroxide composite microencapsulated flame retardant according to claim 1, is characterized in that, comprises the steps:

   A. Disperse sodium-based montmorillonite and nano-magnesium hydroxide in deionized water, keep stirring under constant temperature water bath, and let stand to obtain montmorillonite-magnesium hydroxide mixed solution; take long-chain alkyl quaternary ammonium salt and add deionized Water, heated and stirred to dissolve it, and then slowly added dropwise to the montmorillonite-magnesium hydroxide mixed solution, heated in a constant temperature water bath, passed in an inert gas, and reacted under stirring. Dry in vacuum, grind and sieve to obtain inorganic composite modified particles, which are reserved for future use;

   B. After the active monomer, surfactant and distilled water are stirred in the reactor to make it completely emulsified, the inorganic composite modified particles obtained in step A are slowly added to the reactor, and then polyvinylpyrrolidone and titanate are added. The joint agent is heated up after stirring evenly. Under the protection of inert gas, the initiator solution is slowly added dropwise, and the temperature of the mixture is continued. After the reaction is completed, precipitation, filtration and drying are performed to obtain montmorillonite-magnesium hydroxide composite microencapsulated flame retardant. agent.
3. The preparation method of a kind of montmorillonite-magnesium hydroxide composite microencapsulated flame retardant according to claim 1 or 2, characterized in that, in the step A, the sodium-based montmorillonite comprises the following components:

   Moisture<10wt%

   Silica 48～51wt%

   Alumina 13～16wt%

   Magnesium oxide 3.721wt%

   Calcium oxide 3.712wt%

   Ferric oxide 1.858wt%

   Potassium oxide 0.748wt%

   The cation exchange capacity was 100 mmol/100 g.
4. The preparation method of a kind of montmorillonite-magnesium hydroxide composite microencapsulated flame retardant according to claim 1 or 2, characterized in that, in the step A, the nano-magnesium hydroxide is a lamellar rhombus, and the particle size is 380～430nm.
5. The preparation method of a kind of montmorillonite-magnesium hydroxide composite microencapsulated flame retardant according to claim 1 or 2, characterized in that, in the step A, the long-chain alkyl quaternary ammonium salt is dodecyl Ammonium bromide, hexadecyl ammonium bromide and octadecyl ammonium bromide are prepared according to 0～1:1:0～1.
6. The preparation method of a montmorillonite-magnesium hydroxide composite microencapsulated flame retardant according to claim 2, wherein the active monomer in the step B is styrene monomer, methyl methacrylate , one or two of butyl methacrylate, ethyl acrylate and butyl acrylate.
7. The preparation method of a montmorillonite-magnesium hydroxide composite microencapsulated flame retardant according to claim 6, wherein the mass ratio of styrene monomer to methyl methacrylate in the active monomer is 1:0～2, the mass ratio of styrene monomer to butyl methacrylate is 1:0～2, the mass ratio of styrene monomer to ethyl acrylate is 1:0～2, the mass ratio of styrene monomer to butyl acrylate is 1:0～2 The mass ratio is 1:0～2.
8. The preparation method of a montmorillonite-magnesium hydroxide composite microencapsulated flame retardant according to claim 2, wherein the surfactant in the step B is sodium dodecyl sulfate, dodecane One of sodium benzene sulfonate, sodium ethoxylated fatty acid methyl ester sulfonate, sodium secondary alkyl sulfonate, alcohol ether hydroxy acid salt, alcohol ether phosphate; or the titanate coupling agent is isopropyl Tris (dioctyl pyrophosphate acyloxy) titanate, isopropyl tris (dioctyl phosphoric acid acyloxy) titanate, isopropyl dioleic acid acyloxy (dioctyl phosphoric acid acyloxy) One of titanate, monoalkoxy unsaturated fatty acid titanate, bis(dioctyl pyrophosphate acyloxy) ethylene titanate, tetraisopropyl bis(dioctyl phosphite) titanate kind.
9. The preparation method of a montmorillonite-magnesium hydroxide composite microencapsulated flame retardant according to claim 2, wherein the initiator in the step B is a kind of potassium persulfate and ammonium persulfate .
10. A flame retardant prepared by the preparation method of the montmorillonite-magnesium hydroxide composite microencapsulated flame retardant described in any one of claims 1-9, characterized in that the montmorillonite-magnesium hydroxide is The core material and the polymer material are composed of the shell.