A toughening aid with flame retardant effect, its preparation method and application

Abstract

The present invention provides a toughening aid with flame retardant effect, its preparation method and application, belonging to the field of plastic technology. The surface of nano-aluminum hydroxide particles doped with Ti element is modified by a silane coupling agent with amino groups, reacts with thiophene-2-carbaldehyde and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, and then is blended with calcium sulfate whiskers modified by surface polydopamine to obtain a toughening aid with flame retardant effect. The toughening aid with flame retardant effect prepared by the present invention can significantly improve the flame retardant effect of plastics, and can also play a connecting and buffering role between molecular chains, reduce cracks, has good toughening and impact resistance effects, can be widely applied to plastics, and plays a good role in flame retardancy and improving mechanical properties.

Description

Technical Field

[0001] The invention relates to the technical field of plastics, and in particular to a toughening auxiliary agent with flame retardant effect and a preparation method and application thereof. Background Art

[0002] Plastic is a high molecular compound made from monomers through addition polymerization or condensation polymerization. It has a medium deformation resistance, between fiber and rubber. It is composed of synthetic resin and additives such as fillers, toughening agents, stabilizers, lubricants, and colorants.

[0003] Toughening agents refer to substances that can increase the flexibility of the adhesive film layer. Some thermosetting resin adhesives, such as epoxy resins, phenolic resins and unsaturated polyester resins, have low elongation and high brittleness after curing. When the bonding part is subjected to external force, cracks are easily generated and rapidly expand, resulting in cracking of the adhesive layer. They are not fatigue-resistant and cannot be used for structural bonding. Therefore, it is necessary to find ways to reduce brittleness, increase toughness, and increase bearing strength. Any substance that can reduce brittleness, increase toughness, and does not affect other main properties of the adhesive is a toughening agent. It can be divided into rubber toughening agents and thermoplastic elastomer toughening agents. However, common toughening agents cannot meet the increasingly stringent toughness requirements. At the same time, the shortcomings of plastics such as high temperature resistance and non-flame retardancy have also seriously restricted the widespread application of plastics. Therefore, how to effectively improve the toughening and flame retardant properties of toughening agents has become an important issue that needs to be urgently solved in my country's plastic processing industry. Summary of the invention

[0004] The purpose of the present invention is to provide a toughening auxiliary agent with flame retardant effect and its preparation method and application, which can significantly improve the flame retardant effect of plastics, and can also play a connecting buffering role between molecular chains to reduce cracks, have good toughening and impact resistance effects, can be widely used in plastics, and play a good role in flame retardancy and improving mechanical properties.

[0005] The technical solution of the present invention is achieved in this way:

[0006] The invention provides a method for preparing a toughening aid with a flame retardant effect. The surface of nano aluminum hydroxide particles doped with Ti element is modified with a silane coupling agent with amino group, reacted with thiophene-2-carboxaldehyde and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, and then blended with calcium sulfate whiskers with surface modified with polydopamine to prepare the toughening aid with a flame retardant effect.

[0007] As a further improvement of the present invention, the following steps are included:

[0008] S1. Add an aqueous solution of aluminum chloride dropwise to the alkali solution, heat and stir for reaction. At this time, the pH value of the solution is 6.2 - 6.5. Then add an ethanol solution of tetrabutyl titanate, stir for reaction, centrifuge, wash, and dry to obtain nanoparticles.

[0009] S2. Add the nanoparticles and the silane coupling agent with an amino group to ethanol, heat and stir for reaction, centrifuge, wash, and dry to obtain amino-modified nanoparticles.

[0010] S3. Add the amino-modified nanoparticles to ethanol, add thiophene-2-carboxaldehyde, heat and stir for reaction, and then add 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, stir for reaction to obtain flame-retardant nanoparticles.

[0011] S4. Add calcium sulfate whiskers to water, add dopamine hydrochloride and a catalyst, heat and stir for reaction, filter, wash, and dry to obtain modified calcium sulfate whiskers.

[0012] S5. Mix the flame-retardant nanoparticles and the modified calcium sulfate whiskers evenly to obtain a toughening aid with flame-retardant properties.

[0013] As a further improvement of the present invention, in step S1, the alkali solution is a 1 - 2 mol / L NaOH or KOH solution, and the mass ratio of the alkali solution, aluminum chloride, and tetrabutyl titanate is 100:4 - 7:1 - 2. The temperature of the heating and stirring reaction is 70 - 80 °C, the time is 0.5 - 1 h, and the time of the stirring reaction is 1 - 2 h.

[0014] As a further improvement of the present invention, in step S2, the silane coupling agent with an amino group is selected from at least one of KH550, KH602, and KH792. The mass ratio of the nanoparticles to the silane coupling agent with an amino group is 10 - 15:2 - 3. The temperature of the heating and stirring reaction is 40 - 50 °C, and the time is 2 - 3 h.

[0015] As a further improvement of the present invention, in step S3, the mass ratio of the amino-modified nanoparticles, thiophene-2-carboxaldehyde, and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide is 10:0.7 - 1.2:1.5 - 2.4. The temperature of the heating and stirring reaction is 75 - 85 °C, the time is 4 - 6 h, and the time of the stirring reaction is 10 - 12 h.

[0016] As a further improvement of the present invention, in step S4, the mass ratio of the calcium sulfate whiskers, dopamine hydrochloride, and the catalyst is 12 - 15:2 - 3:0.2 - 0.3. The catalyst is a Tris-HCl solution with pH = 7.5 - 8.5. The temperature of the heating and stirring reaction is 40 - 50 °C, and the time is 2 - 4 h.

[0017] As a further improvement of the present invention, the mass ratio of the flame retardant nanoparticles to the modified calcium sulfate whiskers in step S5 is 3-5:7.

[0018] As a further improvement of the present invention, it specifically includes the following steps:

[0019] S1. Drop 20 parts by weight of an aqueous solution containing 4-7 parts by weight of aluminum chloride into 100 parts by weight of a 1-2 mol / L NaOH or KOH solution, heat to 70-80 °C, stir and react for 0.5-1 h. At this time, the pH value of the solution is 6.2-6.5. Drop 20 parts by weight of an ethanol solution containing 1-2 parts by weight of tetrabutyl titanate, stir and react for 1-2 h, centrifuge, wash, and dry to obtain nanoparticles.

[0020] S2. Add 10-15 parts by weight of the nanoparticles and 2-3 parts by weight of an amino-functionalized silane coupling agent to ethanol, heat to 40-50 °C, stir and react for 2-3 h, centrifuge, wash, and dry to obtain amino-modified nanoparticles.

[0021] S3. Add 10 parts by weight of the amino-modified nanoparticles to ethanol, add 0.7-1.2 parts by weight of thiophene-2-carbaldehyde, heat to 75-85 °C, stir and react for 4-6 h, then add 1.5-2.4 parts by weight of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, stir and react for 10-12 h to obtain flame retardant nanoparticles.

[0022] S4. Add 12-15 parts by weight of calcium sulfate whiskers to water, add 2-3 parts by weight of dopamine hydrochloride and 0.2-0.3 parts by weight of a catalyst, heat to 40-50 °C, stir and react for 2-4 h, filter, wash, and dry to obtain modified calcium sulfate whiskers.

[0023] The catalyst is a Tris-HCl solution with a pH of 7.5-8.5;

[0024] S5. Mix 3-5 parts by weight of the flame retardant nanoparticles and 7 parts by weight of the modified calcium sulfate whiskers evenly to obtain a toughening aid with flame retardant properties.

[0025] The present invention further protects a toughening aid with flame retardant properties prepared by the above preparation method.

[0026] The present invention further protects the application of the above toughening aid with flame retardant properties in improving the flame retardancy and toughness of plastic products.

[0027] The present invention has the following beneficial effects:

[0028] The presence of nanoparticles causes microcracks to form in the matrix when it is subjected to impact. Yielding and plastic deformation occur between the particles, further absorbing the impact energy. As the particles are refined, more cracks are generated, thereby absorbing more energy and playing a toughening role. The smaller the particle size of the nanoparticles, the larger their specific surface area and the stronger the interfacial bonding force with the polymer matrix resin, thus being able to further toughen the plastic. The nano-aluminum hydroxide prepared in this invention is a good inorganic flame retardant. After reacting with tetrabutyl titanate, the resulting nanoparticles are doped with titanium elements. When added to ABS plastics, it can significantly improve the antibacterial, anti-aging, and anti-ultraviolet properties of the material, and at the same time improve the flame retardancy, showing a synergistic flame retardant effect.

[0029] The surface of the prepared nanoparticles is modified with a silane coupling agent with an amino group, and then thiophene-2-carboxaldehyde is added to form an N═C bond. The N═C bond can react with 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO), enabling 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide to be connected to the surface of the nanoparticles, thus obtaining nanoparticles containing organophosphorus. At the same time, the sulfur element contained plays an important role in improving the performance of the flame retardant. It can inhibit the pyrolysis reaction, preventing the material from decomposing violently prematurely. The sulfur element can combine with oxygen elements, thereby slowing down the propagation speed of the flame, thus achieving a synergistic flame retardant effect.

[0030] Calcium sulfate whiskers, as a material with needle-like single crystals, have a regular atomic arrangement and a complete crystal structure. After being added to plastics, they can be filled in polymer materials. When subjected to stress, the stress is transmitted to the calcium sulfate whiskers through molecular chains, reducing the impact of stress on subsequent molecular chains, and thus optimizing the impact strength and toughness of the composite material. After the surface of calcium sulfate whiskers is modified with polydopamine, the nitrogen element content in the flame retardant is greatly increased, improving the flame retardant effect, enhancing the compatibility of the prepared additive in plastics, having a free radical capture function, and enhancing the heat resistance, ultraviolet resistance, and aging resistance of the material. Due to its good adhesion, it can reduce the formation of cracks under stress and can also be well compounded with flame retardant nanoparticles to further improve mechanical properties such as toughness and impact resistance. At the same time, it has a good flame retardant effect.

[0031] The toughening additive with flame retardant properties prepared in this invention can significantly improve the flame retardant effect of plastics, and can also play a connection and buffering role between molecular chains, reducing cracks, having good toughening and anti-impact effects, and can be widely applied to plastics, playing a good role in flame retardancy and improving mechanical properties. Specific Embodiments

[0032] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Apparently, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0033] Example 1

[0034] This embodiment provides a preparation method of a toughening aid with flame retardant effect, which specifically includes the following steps:

[0035] S1. Add an aqueous solution containing 4 g of aluminum chloride to 100 g of 1 mol / L NaOH solution dropwise, heat to 70 °C, stir and react for 0.5 h. At this time, the pH value of the solution is 6.5. Add an ethanol solution containing 1 g of tetrabutyl titanate dropwise, stir and react for 1 h, centrifuge, wash, and dry to obtain nanoparticles.

[0036] S2. Add 10 g of nanoparticles and 2 g of silane coupling agent KH550 to 200 mL of ethanol, heat to 40 °C, stir and react for 2 h, centrifuge, wash, and dry to obtain amino-modified nanoparticles.

[0037] S3. Add 10 g of amino-modified nanoparticles to 200 mL of ethanol, add 0.7 g of thiophene-2-carboxaldehyde, heat to 75 °C, stir and react for 4 h, then add 1.5 g of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, stir and react for 10 h to obtain flame retardant nanoparticles.

[0038] S4. Add 12 g of calcium sulfate whiskers to 200 mL of water, add 2 g of dopamine hydrochloride and 0.2 g of catalyst, heat to 40 °C, stir and react for 2 h, filter, wash, and dry to obtain modified calcium sulfate whiskers.

[0039] The catalyst is a Tris-HCl solution with pH = 7.5.

[0040] S5. Stir and mix 3 g of flame retardant nanoparticles and 7 g of modified calcium sulfate whiskers for 20 min to obtain a toughening aid with flame retardant effect.

[0041] Example 2

[0042] This embodiment provides a preparation method of a toughening aid with flame retardant effect, which specifically includes the following steps:

[0043] S1. Add an aqueous solution containing 7 g of aluminum chloride dropwise to 100 g of 2 mol / L NaOH solution, heat to 80 °C, stir and react for 1 h. At this time, the pH value of the solution is 6.2. Then add an ethanol solution containing 2 g of tetrabutyl titanate dropwise, stir and react for 2 h, centrifuge, wash, and dry to obtain nanoparticles.

[0044] S2. Add 15 g of nanoparticles and 3 g of silane coupling agent KH602 to 200 mL of ethanol, heat to 50 °C, stir and react for 3 h, centrifuge, wash, and dry to obtain amino-modified nanoparticles.

[0045] S3. Add 10 g of amino-modified nanoparticles to 200 mL of ethanol, add 1.2 g of thiophene-2-carboxaldehyde, heat to 85 °C, stir and react for 6 h. Then add 2.4 g of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, stir and react for 12 h to obtain flame-retardant nanoparticles.

[0046] S4. Add 15 g of calcium sulfate whiskers to 200 mL of water, add 3 g of dopamine hydrochloride and 0.3 g of catalyst, heat to 50 °C, stir and react for 4 h, filter, wash, and dry to obtain modified calcium sulfate whiskers.

[0047] The catalyst is a Tris-HCl solution with a pH of 8.5.

[0048] S5. Stir and mix 5 g of flame-retardant nanoparticles and 7 g of modified calcium sulfate whiskers for 20 min to obtain a toughening aid with flame-retardant properties.

[0049] Example 3

[0050] This example provides a preparation method of a toughening aid with flame-retardant properties, which specifically includes the following steps:

[0051] S1. Add an aqueous solution containing 5.5 g of aluminum chloride dropwise to 100 g of 1.5 mol / L NaOH solution, heat to 75 °C, stir and react for 1 h. At this time, the pH value of the solution is 6.3. Then add an ethanol solution containing 1.5 g of tetrabutyl titanate dropwise, stir and react for 1.5 h, centrifuge, wash, and dry to obtain nanoparticles.

[0052] S2. Add 12 g of nanoparticles and 2.5 g of silane coupling agent KH792 to 200 mL of ethanol, heat to 45 °C, stir and react for 2.5 h, centrifuge, wash, and dry to obtain amino-modified nanoparticles.

[0053] S3. Add 10 g of amino-modified nanoparticles into 200 mL of ethanol, add 1 g of thiophene-2-carboxaldehyde, heat to 80 °C, stir and react for 5 h, then add 2.1 g of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, stir and react for 11 h to obtain flame-retardant nanoparticles;

[0054] S4. Add 13.5 g of calcium sulfate whiskers into 200 mL of water, add 2.5 g of dopamine hydrochloride and 0.25 g of catalyst, heat to 45 °C, stir and react for 3 h, filter, wash, and dry to obtain modified calcium sulfate whiskers;

[0055] The catalyst is a Tris-HCl solution with pH = 8;

[0056] S5. Stir and mix 4 g of flame-retardant nanoparticles and 7 g of modified calcium sulfate whiskers for 20 min to obtain a toughening aid with flame-retardant effect.

[0057] Comparative Example 1

[0058] Compared with Example 3, the difference is that tetrabutyl titanate was not added in step S1.

[0059] Specifically as follows:

[0060] S1. Drop an aqueous solution containing 5.5 g of aluminum chloride into 100 g of 1.5 mol / L NaOH solution, heat to 75 °C, stir and react for 1 h. At this time, the pH value of the solution is 6.3. Centrifuge, wash, and dry to obtain nanoparticles;

[0061] S2. Add 12 g of nanoparticles and 2.5 g of silane coupling agent KH792 into 200 mL of ethanol, heat to 45 °C, stir and react for 2.5 h, centrifuge, wash, and dry to obtain amino-modified nanoparticles;

[0062] S3. Add 10 g of amino-modified nanoparticles into 200 mL of ethanol, add 1 g of thiophene-2-carboxaldehyde, heat to 80 °C, stir and react for 5 h, then add 2.1 g of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, stir and react for 11 h to obtain flame-retardant nanoparticles;

[0063] S4. Add 13.5 g of calcium sulfate whiskers into 200 mL of water, add 2.5 g of dopamine hydrochloride and 0.25 g of catalyst, heat to 45 °C, stir and react for 3 h, filter, wash, and dry to obtain modified calcium sulfate whiskers;

[0064] The catalyst is a Tris-HCl solution with pH = 8;

[0065] S5. Stir and mix 4 g of flame retardant nanoparticles and 7 g of modified calcium sulfate whiskers for 20 min to obtain a toughening aid with flame retardant effect.

[0066] Comparative Example 2

[0067] Compared with Example 3, the difference lies in that steps S2 and S3 are not carried out.

[0068] Specifically as follows:

[0069] S1. Drop 20 g of an aqueous solution containing 5.5 g of aluminum chloride into 100 g of a 1.5 mol / L NaOH solution, heat to 75 °C, stir and react for 1 h. At this time, the pH value of the solution is 6.3. Drop 20 g of an ethanol solution containing 1.5 g of tetrabutyl titanate, stir and react for 1.5 h, centrifuge, wash, and dry to obtain nanoparticles.

[0070] S2. Add 13.5 g of calcium sulfate whiskers to 200 mL of water, add 2.5 g of dopamine hydrochloride and 0.25 g of catalyst, heat to 45 °C, stir and react for 3 h, filter, wash, and dry to obtain modified calcium sulfate whiskers.

[0071] The catalyst is a Tris-HCl solution with pH = 8.

[0072] S3. Stir and mix 4 g of nanoparticles and 7 g of modified calcium sulfate whiskers for 20 min to obtain a toughening aid with flame retardant effect.

[0073] Comparative Example 3

[0074] Compared with Example 3, the difference lies in that step S3 is not carried out.

[0075] Specifically as follows:

[0076] S1. Drop 20 g of an aqueous solution containing 5.5 g of aluminum chloride into 100 g of a 1.5 mol / L NaOH solution, heat to 75 °C, stir and react for 1 h. At this time, the pH value of the solution is 6.3. Drop 20 g of an ethanol solution containing 1.5 g of tetrabutyl titanate, stir and react for 1.5 h, centrifuge, wash, and dry to obtain nanoparticles.

[0077] S2. Add 12 g of nanoparticles and 2.5 g of silane coupling agent KH792 to 200 mL of ethanol, heat to 45 °C, stir and react for 2.5 h, centrifuge, wash, and dry to obtain amino-modified nanoparticles.

[0078] S3. Add 13.5 g of calcium sulfate whiskers to 200 mL of water, add 2.5 g of dopamine hydrochloride and 0.25 g of catalyst, heat to 45 °C, stir and react for 3 h, filter, wash, and dry to obtain modified calcium sulfate whiskers.

[0079] The catalyst is a Tris-HCl solution with a pH of 8;

[0080] S4. Stir and mix 4 g of amino-modified nanoparticles and 7 g of modified calcium sulfate whiskers for 20 min to obtain a toughening agent with flame retardancy.

[0081] Comparative Example 4

[0082] Compared with Example 3, the difference lies in that step S4 is not carried out.

[0083] Specifically as follows:

[0084] S1. Drop 20 g of an aqueous solution containing 5.5 g of aluminum chloride into 100 g of a 1.5 mol / L NaOH solution, heat to 75 °C, stir and react for 1 h. At this time, the pH value of the solution is 6.3. Drop 20 g of an ethanol solution containing 1.5 g of tetrabutyl titanate, stir and react for 1.5 h, centrifuge, wash, and dry to obtain nanoparticles;

[0085] S2. Add 12 g of nanoparticles and 2.5 g of silane coupling agent KH792 to 200 mL of ethanol, heat to 45 °C, stir and react for 2.5 h, centrifuge, wash, and dry to obtain amino-modified nanoparticles;

[0086] S3. Add 10 g of amino-modified nanoparticles to 200 mL of ethanol, add 1 g of thiophene-2-carbaldehyde, heat to 80 °C, stir and react for 5 h, then add 2.1 g of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, stir and react for 11 h to obtain flame-retardant nanoparticles;

[0087] S4. Stir and mix 4 g of flame-retardant nanoparticles and 7 g of calcium sulfate whiskers for 20 min to obtain a toughening agent with flame retardancy.

[0088] Test Example 1

[0089] Add the toughening agents with flame retardancy prepared in Examples 1-3 and Comparative Examples 1-4 to polypropylene resin (PP resin, T30S, Yuyao Jinlang Trading Co., Ltd.) at a content of 2 wt%, mix for 10 min at 85 °C by a high-speed mixer, place in a HAKKE torque rheometer for kneading for 10 min, and set the processing temperature to 180 °C. After the kneading is completed, wait for the sample to cool to room temperature, then use a pulverizer to crush it, and then use a flat vulcanizing machine (the press is set at a temperature of 180 °C) to press the crushed sample into various thickness sheets and cut them into various test-specification strips.

[0090] Limiting oxygen index (LOI) test: Conduct the test according to GB / T2406-2009, and the size of the test strip is 80 mm × 10 mm × 4 mm;

[0091] Vertical burning (UL94) test: The test was conducted in accordance with GB / T2408-2021, and the dimensions of the specimen were 125 mm × 13 mm × 3.2 mm;

[0092] The impact performance was tested according to GB / T1043-2008. The dimensions of the specimen were 80 mm × 10 mm × 3.2 mm. Three specimens were tested in each group, and the average value of each group of results was taken;

[0093] The tensile performance was tested according to GB / T1040-2006. The tensile speed was 50 mm / min. The thickness of the specimen was 2 mm, and the width of the narrow part was 4 mm. Each group was tested 3 times, and the average value of the results was taken;

[0094] The flexural performance was tested according to GB / T9341-2008. The test speed was set at 2 mm / min. The dimensions of the specimen were 80 mm × 10 mm × 4 mm, the span was 64 mm, and the radius of the indenter was 5 mm. Each group was tested 3 times, and the average value of the results was taken.

[0095] The results are shown in Table 1 and Table 2.

[0096] Table 1

[0097] Group LOI(%) UL-94 (4mm) Rating Example 1 32.2 V-0 Example 2 32.7 V-0 Example 3 33.1 V-0 Comparative Example 1 29.4 V-1 Comparative Example 2 25.7 V-1 Comparative Example 3 21.8 V-2 Comparative Example 4 30.4 V-0

[0098] As can be seen from the above table, the toughening and flame-retardant additives prepared in Examples 1-3 of the present invention can significantly improve the flame-retardant performance of PP resin.

[0099] Table 2

[0100]

[0101] As can be seen from the above table, the toughening and flame-retardant additives prepared in Examples 1-3 of the present invention can significantly improve the mechanical properties of PP resin.

[0102] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for preparing a flame retardant toughening agent, characterized in that: The following steps are involved: S1. Add an aqueous solution of aluminum chloride to the alkali solution, heat and stir to react, at which time the solution has a pH value of 6.2-6.5, add an ethanol solution of tetrabutyl titanate, stir to react, centrifuge, wash, and dry to obtain nanoparticles; the mass ratio of the alkali solution, aluminum chloride, and tetrabutyl titanate is 100:4-7:1-2; S2. The nanoparticles and the silane coupling agent with an amino group are added to ethanol, heated and stirred for reaction, centrifuged, washed, and dried to obtain amino-modified nanoparticles; the mass ratio of the nanoparticles to the silane coupling agent with an amino group is 10-15:2-3; S3. Adding the amino-modified nanoparticles to ethanol, adding thiophene-2-carboxaldehyde, heating and stirring to react, and then adding 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, stirring to react, to obtain flame-retardant nanoparticles; the mass ratio of the amino-modified nanoparticles, thiophene-2-carboxaldehyde, and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide is 10:0.7-1.2:1.5-2.4; S4. The calcium sulfate whiskers were added to water, dopamine hydrochloride and a catalyst were added, the reaction was heated and stirred, filtered, washed, and dried to obtain modified calcium sulfate whiskers; the mass ratio of the calcium sulfate whiskers, dopamine hydrochloride and the catalyst was 12-15:2-3:0.2-0.3; S5. The flame retardant nanoparticles and the modified calcium sulfate whiskers are mixed evenly to obtain a toughening agent with flame retardant effect; the mass ratio of the flame retardant nanoparticles and the modified calcium sulfate whiskers is 3-5:

7.

2. The preparation method according to claim 1, characterized in that: In step S1, the alkali solution is 1-2 mol / L NaOH or KOH solution, the temperature of the heating and stirring reaction is 70-80°C, the time is 0.5-1h, and the stirring reaction time is 1-2h.

3. The preparation method according to claim 1, characterized in that: In step S2, the silane coupling agent with amino group is selected from at least one of KH550, KH602 and KH792, and the temperature of the heating and stirring reaction is 40-50° C. and the time is 2-3 hours.

4. The preparation method according to claim 1, characterized in that: The temperature of the heating and stirring reaction in step S3 is 75-85°C, the time is 4-6h, and the time of the stirring reaction is 10-12h.

5. The preparation method according to claim 1, characterized in that: In step S4, the catalyst is a Tris-HCl solution with a pH of 7.5-8.5, and the temperature of the heating and stirring reaction is 40-50° C. for 2-4 hours.

6. The preparation method according to claim 1, characterized in that: The specific steps include: S1. Add 20 parts by weight of an aqueous solution containing 4-7 parts by weight of aluminum chloride to 100 parts by weight of a 1-2 mol / L NaOH or KOH solution, heat to 70-80°C, stir and react for 0.5-1h, at which time the pH value of the solution is 6.2-6.5, add 20 parts by weight of an ethanol solution containing 1-2 parts by weight of tetrabutyl titanate, stir and react for 1-2h, centrifuge, wash, and dry to obtain nanoparticles; S2. 10-15 parts by weight of the nanoparticles and 2-3 parts by weight of a silane coupling agent with an amino group are added to ethanol, heated to 40-50 ° C, stirred for 2-3h, centrifuged, washed, and dried to obtain amino-modified nanoparticles; S3. Add 10 parts by weight of amino-modified nanoparticles to ethanol, add 0.7-1.2 parts by weight of thiophene-2-carboxaldehyde, heat to 75-85 ° C, stir and react for 4-6 hours, then add 1.5-2.4 parts by weight of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, stir and react for 10-12 hours to obtain flame retardant nanoparticles; S4. 12-15 parts by weight of calcium sulfate whiskers are added to water, 2-3 parts by weight of dopamine hydrochloride and 0.2-0.3 parts by weight of a catalyst are added, heated to 40-50 ° C, stirred for 2-4h, filtered, washed, and dried to obtain modified calcium sulfate whiskers; The catalyst is a Tris-HCl solution with a pH of 7.5-8.5; S5. Mix 3-5 parts by weight of flame-retardant nanoparticles and 7 parts by weight of modified calcium sulfate whiskers to obtain a toughening agent with flame retardant effect.

7. A toughening agent with flame retardant effect obtained by the preparation method according to any one of claims 1 to 6.

8. Use of the flame retardant toughening agent as claimed in claim 7 for improving the flame retardancy and toughness of plastic products.

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