A flame-retardant PMMA resin, a fiber-reinforced flame-retardant PMMA resin composite material suitable for a molding process, and a preparation method thereof

Abstract

The application provides a flame-retardant PMMA resin suitable for a molding process, a fiber-reinforced flame-retardant PMMA resin composite and a preparation method thereof, and belongs to the technical field of high polymer flame-retardant materials.The flame-retardant PMMA resin is prepared from raw materials including the following components by weight: MMA slurry 30-85 parts, monomer copolymerizable with MMA 1-15 parts, surface-modified hydroxide 10-60 parts, organic phosphorus compound 5-15 parts, melamine and derivatives thereof 5-15 parts, surface-modified ammonium polyphosphate 5-20 parts, and initiator 0.1-4 parts.The flame-retardant PMMA resin and the composite prepared by the application have excellent flame-retardant function and good mechanical properties.

Description

Technical Field

[0001] This invention relates to the field of polymer flame retardant materials technology, and in particular to a flame retardant PMMA resin suitable for molding process, a fiber-reinforced flame retardant PMMA resin composite material and its preparation method. Background Technology

[0002] Polymethyl methacrylate (PMMA), commonly known as plexiglass, is a high-performance polymer material with excellent overall properties, including superior transparency, mechanical properties, and outstanding weather resistance. However, PMMA is inherently flammable, with a limiting oxygen index of only around 17. This limitation significantly restricts its application in certain fields where flame retardancy is critical.

[0003] Existing research on flame-retardant PMMA largely focuses on applications requiring high transparency. Improving flame retardancy must be balanced with maintaining optical transparency, significantly limiting the selection and dosage of flame retardants and hindering the full enhancement of flame retardant performance. In reality, PMMA, as a thermoplastic resin, shows broad application prospects in fiber-reinforced composite materials, particularly in recyclable green composite systems. In these engineering material applications, transparency requirements are lower, allowing for a degree of overcoming transparency limitations by introducing multiple flame-retardant components to significantly improve the material's flame retardancy rating. However, conventional methods often result in a significant decrease in mechanical properties alongside improved flame retardancy, a key contradiction that needs to be addressed.

[0004] On the other hand, most fiber-reinforced PMMA composites are currently prepared using melt molding, which requires heating the PMMA resin to a molten state before molding it with fibers. This process is energy-intensive and results in high costs.

[0005] Therefore, it is of great significance to provide a flame-retardant PMMA resin and its composite materials that can effectively improve the flame retardancy of materials, maintain good mechanical properties, and have energy-saving and environmental protection advantages. Summary of the Invention

[0006] In order to solve the above-mentioned technical problems, the purpose of this invention is to provide a flame-retardant PMMA resin suitable for molding process, a fiber-reinforced flame-retardant PMMA resin composite material and its preparation method.

[0007] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a flame-retardant PMMA resin suitable for molding processes, prepared from raw materials comprising the following parts by weight: 30-85 parts of MMA slurry 1-15 parts of monomers that can copolymerize with MMA 10-60 parts of surface-modified hydroxide, 5-15 parts of organophosphorus compounds, 5-15 parts of melamine and its derivatives 5-20 parts of surface-modified ammonium polyphosphate, Initiator 0.1 to 4 parts.

[0008] Furthermore, the MMA slurry is an MMA solution containing PMMA with a viscosity of 20~500 mPa·s.

[0009] Furthermore, the monomers that can copolymerize with MMA include one or more of isobornyl methacrylate, methacrylamide, hydroxyethyl methacrylate, butyl methacrylate, methacrylic acid, and tert-butyl acrylate. The melamine and its derivatives include one or more of melamine, melamine cyanurate and melamine polyphosphate; The initiator is an azo initiator, an organic peroxide initiator, or a redox initiator.

[0010] Furthermore, the surface-modified hydroxide is a hydroxide that has undergone surface modification, grafting modification, or microencapsulation modification with a modifier; The modifiers used in the surface modification of the modifier include coupling agent modifiers, surfactants, or organic polymer modifiers; The hydroxides include aluminum hydroxide and / or magnesium hydroxide.

[0011] Furthermore, the organophosphorus compound is a phosphate ester and / or a phosphonate ester; The phosphate ester includes one or more of triethyl phosphate, triphenyl phosphate, tricresyl phosphate, and tributyl phosphate; The phosphonates include dimethyl methylphosphonate and / or diethyl ethylphosphonate.

[0012] Furthermore, the surface-modified ammonium polyphosphate is ammonium polyphosphate that has been modified with a modifier or microencapsulated. The modifier used in the modification process is a coupling agent modifier, a surfactant, or an organic polymer modifier.

[0013] This invention provides a method for preparing the flame-retardant PMMA resin suitable for molding processes, comprising the following steps: After mixing MMA slurry, monomers that can copolymerize with MMA, organophosphorus compounds and initiators, melamine and its derivatives and surface-modified ammonium polyphosphate are added and mixed. Finally, surface-modified hydroxide is added and mixed to obtain a paste-like flame-retardant PMMA resin.

[0014] The present invention provides a fiber-reinforced flame-retardant PMMA resin composite material, comprising a fiber reinforcement and a flame-retardant PMMA resin coated or mixed on the fiber reinforcement; The fiber reinforcement is a fiber fabric or chopped fiber.

[0015] This invention also provides a method for preparing fiber-reinforced flame-retardant PMMA resin composite materials, comprising the following steps: S1. A paste-like flame-retardant PMMA resin is combined with fiber reinforcement to obtain a composite material preform; S2. Place the composite material preform in a mold for hot pressing and curing, then demold to obtain a flame-retardant fiber-reinforced PMMA composite material.

[0016] Furthermore, the mass ratio of the paste-like flame-retardant PMMA resin to the fiber reinforcement is 60~90:10~40; Alternatively, the coating amount of the paste-like flame-retardant PMMA resin accounts for 60-90% of the mass of the composite material; The temperature for hot pressing curing is 50~90℃, and the pressure for hot pressing curing is 2~30MPa.

[0017] The beneficial effects of this invention are: 1) This invention employs a hydroxide-nitrogen-phosphorus multi-component synergistic flame retardant system, which combines surface-modified aluminum hydroxide / magnesium hydroxide (inorganic flame retardant), organophosphorus compounds (phosphate esters / phosphonates), melamine and its derivatives with surface-modified ammonium polyphosphate to fully leverage the synergistic effect of different flame retardant mechanisms of each component: hydroxides achieve cooling and temperature reduction through endothermic dehydration, melamine compounds inhibit combustion through gas-phase heat insulation and dilution, and organophosphorus compounds and ammonium polyphosphate promote char formation to build a condensed phase barrier, ultimately achieving a highly efficient flame retardant effect.

[0018] 2) This invention employs surface treatment technologies such as coupling agent modification, grafting modification, and microencapsulation modification to modify inorganic flame retardants such as hydroxides and ammonium polyphosphate. By optimizing the flame retardant system and modification process, not only can the flame retardant performance of the material be significantly improved, but its interfacial compatibility with the PMMA matrix can also be effectively improved, and the aggregation of inorganic fillers in the matrix can be suppressed. Thus, while endowing the material with excellent flame retardant properties, the original mechanical properties of the matrix are preserved to the maximum extent.

[0019] 3) This invention successfully developed a paste-like flame-retardant PMMA resin by precisely controlling the viscosity of the MMA slurry and optimizing the feeding sequence. This paste-like resin can be molded at low temperatures without heating to a molten state (traditional PMMA melt molding typically requires temperatures above 180°C). The innovative introduction of a paste-like molding process enables in-situ polymerization of the resin within the fiber reinforcement at lower temperatures, thus avoiding the high energy consumption of traditional melt molding processes and achieving energy saving and consumption reduction. Compared to the traditional melt molding process used in Comparative Example 1, the process temperature of this invention is significantly lower, and energy consumption is also greatly reduced. Furthermore, this paste-like resin possesses excellent thixotropic properties and coating performance. It can not only be molded alone into flame-retardant PMMA sheets, but also easily combined with fiber fabrics or chopped fibers to prepare fiber-reinforced composite materials, demonstrating extremely wide process adaptability. Detailed Implementation

[0020] This invention provides a flame-retardant PMMA resin suitable for molding processes, prepared from raw materials comprising the following parts by weight: 30-85 parts of MMA slurry 1-15 parts of monomers that can copolymerize with MMA 10-60 parts of surface-modified hydroxide, 5-15 parts of organophosphorus compounds, 5-15 parts of melamine and its derivatives 5-20 parts of surface-modified ammonium polyphosphate, Initiator 0.1 to 4 parts.

[0021] In this invention, the mass of the MMA slurry is preferably 35 to 80 parts by weight, and more preferably 40 to 75 parts by weight.

[0022] In this invention, the MMA slurry is an MMA solution containing PMMA with a viscosity of 20 to 500 mPa·s, preferably 50 to 450 mPa·s, and more preferably 100 to 400 mPa·s.

[0023] In this invention, the MMA slurry is a solution formed by dissolving polymethyl methacrylate (PMMA) in methyl methacrylate (MMA) monomer, wherein the PMMA content results in a viscosity of 20~500 mPa·s for the MMA slurry at 25°C.

[0024] In this invention, the monomer that can copolymerize with MMA is preferably 3 to 12 parts by weight, and more preferably 5 to 10 parts by weight.

[0025] In this invention, the monomers that can copolymerize with MMA include one or more of isobornyl methacrylate, methacrylamide, hydroxyethyl methacrylate, butyl methacrylate, methacrylic acid, and tert-butyl acrylate, preferably one or more of isobornyl methacrylate, methacrylamide, hydroxyethyl methacrylate, butyl methacrylate, and tert-butyl acrylate, and more preferably one or more of isobornyl methacrylate, methacrylamide, hydroxyethyl methacrylate, and tert-butyl acrylate.

[0026] In this invention, the surface-modified hydroxide is preferably 15 to 55 parts by weight, and more preferably 20 to 50 parts by weight.

[0027] In this invention, the surface-modified hydroxide is a hydroxide that has been treated with a modifier for surface modification, graft modification, or microencapsulation modification; The modifiers used in the surface modification of the modifier include coupling agent modifiers, surfactants or organic polymer modifiers, preferably coupling agent modifiers and / or surfactants, and more preferably coupling agent modifiers; The hydroxide includes aluminum hydroxide and / or magnesium hydroxide, preferably aluminum hydroxide.

[0028] In this invention, the coupling modifier includes KH550 and / or titanate JN-201; The surfactant includes one or more of saturated fatty acid salts, unsaturated fatty acids and sodium oleate, preferably saturated fatty acid salts and / or sodium oleate, and more preferably sodium oleate. The organic polymer modifier includes silicone oil and / or polyacrylic acid, preferably silicone oil.

[0029] In this invention, graft modification is performed by grafting with methyl methacrylate (MMA).

[0030] In this invention, the microencapsulation modification treatment is performed by microencapsulation modification with polyurethane.

[0031] In this invention, the organophosphorus compound is preferably 6 to 13 parts by weight, and more preferably 8 to 11 parts by weight.

[0032] In this invention, the organophosphorus compound is a phosphate ester and / or a phosphonate ester, preferably a phosphate ester; The phosphate ester includes one or more of triethyl phosphate, triphenyl phosphate, tricresyl phosphate and tributyl phosphate, preferably one or more of triethyl phosphate, triphenyl phosphate and tributyl phosphate, and more preferably triethyl phosphate and / or triphenyl phosphate. The phosphonate includes dimethyl methylphosphonate and / or diethyl ethylphosphonate, preferably dimethyl methylphosphonate.

[0033] In this invention, the melamine and its derivatives are preferably 6 to 14 parts by weight, and more preferably 7 to 13 parts by weight.

[0034] In this invention, the surface-modified ammonium polyphosphate is ammonium polyphosphate that has been modified by a modifier or microencapsulated. The modifier used in the modification is a coupling modifier, a surfactant, or an organic polymer modifier, preferably a coupling modifier and / or a surfactant, and more preferably a coupling modifier.

[0035] In this invention, the coupling modifier includes KH570; The surfactant includes sodium oleate; The organic polymer modifier includes polyacrylic acid.

[0036] In this invention, the microencapsulation modification treatment is performed by microencapsulation modification with melamine-formaldehyde resin.

[0037] In this invention, the surface-modified ammonium polyphosphate is preferably 7 to 17 parts by weight, and more preferably 10 to 15 parts by weight.

[0038] In this invention, the melamine and its derivatives include one or more of melamine, melamine cyanurate and melamine polyphosphate, preferably melamine and / or melamine cyanurate, and more preferably melamine.

[0039] In this invention, the initiator is preferably 0.3 to 3.7 parts by weight, and more preferably 0.5 to 3.5 parts by weight.

[0040] In this invention, the initiator is an azo initiator, an organic peroxide initiator, or a redox initiator, preferably an azo initiator or an organic peroxide initiator, and more preferably an azo initiator.

[0041] In this invention, the azo initiator includes azobisisobutyronitrile; The organic peroxide initiator includes one or more of benzoyl peroxide, dodecyl peroxide, tert-butyl hydroperoxide, cumene hydroperoxide, and tert-butyl peroxide, preferably one or more of benzoyl peroxide, tert-butyl hydroperoxide, cumene hydroperoxide, and tert-butyl peroxide, and more preferably one or more of benzoyl peroxide, cumene hydroperoxide, and tert-butyl peroxide; The redox initiator includes the oxidant benzoyl peroxide (BPO) and the reducing agent N,N-dimethylaniline (DMA).

[0042] In this invention, the MMA slurry has a certain viscosity, which enables the flame retardant to be effectively dispersed; the monomers that can copolymerize with MMA free radicals can provide toughness or strength to the PMMA flame retardant resin.

[0043] In this invention, the hydroxides include aluminum hydroxide and magnesium hydroxide, both of which possess excellent flame-retardant properties and are smokeless and non-toxic. However, hydroxides are inorganic flame retardants and are not well compatible with polymers, easily agglomerating and clumping within the polymer, leading to a decrease in the polymer's mechanical properties. Therefore, surface modification of the hydroxides is necessary. Currently, the mainstream modification methods include: modifier modification, grafting modification, and microencapsulation modification.

[0044] The melamine and its derivatives used in this invention are nitrogen-based flame retardants. Due to their high efficiency and environmental protection characteristics, they are widely used in the field of fire protection for polymer materials. They generate inert gas through endothermic decomposition and promote the formation of a dense carbon layer, thereby achieving a dual flame retardant effect.

[0045] The ammonium polyphosphate (APP) selected in this invention is a highly efficient and environmentally friendly inorganic phosphorus-based flame retardant. Its flame-retardant effect is achieved through the synergistic effect of condensed-phase flame retardancy and gas-phase flame retardancy. However, despite being a highly efficient flame retardant, it has poor compatibility with polymer materials, resulting in uneven material properties and poor mechanical properties. To overcome this defect, surface modification treatment is required.

[0046] This invention provides a method for preparing the flame-retardant PMMA resin suitable for molding processes, comprising the following steps: After mixing MMA slurry, monomers that can copolymerize with MMA, organophosphorus compounds and initiators, melamine and its derivatives and surface-modified ammonium polyphosphate are added and mixed. Finally, surface-modified hydroxide is added and mixed to obtain a paste-like flame-retardant PMMA resin.

[0047] The present invention provides a fiber-reinforced flame-retardant PMMA resin composite material, comprising a fiber reinforcement and a flame-retardant PMMA resin coated or mixed on the fiber reinforcement; The fiber reinforcement is a fiber fabric or chopped fiber, preferably chopped fiber.

[0048] This invention also provides a method for preparing fiber-reinforced flame-retardant PMMA resin composite materials, comprising the following steps: S1. A paste-like flame-retardant PMMA resin is combined with fiber reinforcement to obtain a composite material preform; S2. Place the composite material preform in a mold for hot pressing and curing, then demold to obtain a flame-retardant fiber-reinforced PMMA composite material.

[0049] Furthermore, the mass ratio of the paste-like flame-retardant PMMA resin to the fiber reinforcement is 60~90:10~40, preferably 65~85:15~35, and more preferably 70~80:20~30; Alternatively, the coating amount of the paste-like flame-retardant PMMA resin accounts for 60-90% of the mass of the composite material; The temperature for hot pressing curing is 50~90℃, preferably 55~85℃, and more preferably 60~80℃; the pressure for hot pressing curing is 2~30MPa, preferably 5~27MPa, and more preferably 10~25MPa.

[0050] In this invention, a post-curing step is also included after demolding.

[0051] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0052] Example 1

[0053] At room temperature, 45 parts with a viscosity of 80 mPa After mixing 5 parts of MMA slurry, 5 parts of methacrylic acid, 5 parts of triethyl phosphate (TEP) and 0.1 parts of benzoyl peroxide (BPO), 5 parts of melamine and 20 parts of ammonium polyphosphate modified with silane coupling agent KH550 are added and stirred until uniform. Finally, 20 parts of aluminum hydroxide (ATH) modified with silane coupling agent KH570 are added and mixed until uniform, to obtain a paste-like flame-retardant PMMA resin.

[0054] The paste-like flame-retardant PMMA resin is placed into the flat mold of the molding machine and molded at 50°C and 10MPa for 2 hours to obtain the molded plate.

[0055] Tensile, bending, and vertical burning specimens were fabricated using a laser engraving machine according to national standards GB / T2567 and GBT 2408-2021 and then tested. The test results show that the tensile strength is 60 MPa, the bending strength is 80 MPa, and the UL94 rating is V0.

[0056] Example 2

[0057] At room temperature, 45 parts with a viscosity of 120 mPa were... After mixing 5 parts of MMA slurry, 5 parts of isobornyl methacrylate, 5 parts of dimethyl methylphosphonate (DMMP), and 0.2 parts of azobisisobutyronitrile (AIBN), 5 parts of melamine polyphosphate and 15 parts of ammonium polyphosphate modified with surfactant sodium oleate were added and stirred until uniform. Finally, 10 parts of magnesium hydroxide (MH) grafted with methyl methacrylate MMA and 15 parts of aluminum hydroxide (ATH) modified with coupling agent titanate JN-201 were added and mixed until uniform to obtain a paste-like flame-retardant PMMA resin.

[0058] The paste-like flame-retardant PMMA resin is placed into the flat mold of the molding machine and molded at 60°C and 12MPa for 0.5 hours to obtain the molded plate.

[0059] Tensile, bending, and vertical burning specimens were fabricated using a laser engraving machine according to national standards GB / T2567 and GBT 2408-2021 and then tested. The test results show that the tensile strength is 53 MPa, the bending strength is 75 MPa, and the UL94 rating is V0.

[0060] Example 3

[0061] At room temperature, 50 parts with a viscosity of 150 mPa The following mixtures were prepared: 5 parts MMA slurry, 5 parts hydroxyethyl methacrylate, 5 parts trimethyl phosphate (TPP), 0.4 parts benzoyl peroxide (BPO), and 0.2 parts N,N-dimethylaniline (DMA). Then, 10 parts melamine urate and 20 parts ammonium polyphosphate modified by melamine-formaldehyde resin microencapsulation were added and stirred until homogeneous. Finally, 5 parts magnesium hydroxide (MH) grafted with methyl methacrylate MMA and 5 parts aluminum hydroxide (ATH) modified by polyurethane microencapsulation were added and stirred until homogeneous to obtain a paste-like flame-retardant PMMA resin.

[0062] 90 parts of paste-like flame-retardant PMMA resin and 10 parts of chopped glass fiber were mixed evenly in a planetary mixer and then placed into a flat mold of a molding machine. The mixture was then hot-pressed and cured at 50°C and 14 MPa. After hot-pressing and curing, the mixture was demolded and then post-cured to obtain a fiber-reinforced flame-retardant PMMA resin composite material.

[0063] Tensile, bending, and vertical burning specimens were fabricated using a laser engraving machine according to national standards GBT 1447, GB1449, and GBT 2408, and then tested. The test results show that the tensile strength is 81 MPa, the bending strength is 92 MPa, and the UL94 rating is V0.

[0064] Example 4

[0065] At room temperature, 55 parts with a viscosity of 200 mPa were... After mixing 5 parts of butyl methacrylate, 5 parts of triethyl phosphate (TEP) and 1 part of benzoyl peroxide (BPO), 5 parts of melamine and 20 parts of ammonium polyphosphate modified by melamine-formaldehyde resin microencapsulation were added and stirred until uniform. Finally, 10 parts of ammonium polyphosphate modified by organic polymer silicone oil and 19 parts of aluminum hydroxide (ATH) modified by urea-formaldehyde resin microencapsulation were added and mixed until uniform, resulting in a paste-like flame-retardant PMMA resin.

[0066] Cut 6 layers (300mm x 300mm) with a density of 400g / m². 2 At room temperature, a layer of flame-retardant PMMA resin paste is applied to the warp and weft fabric. The amount of the flame-retardant PMMA resin paste accounts for 75% of the mass of the composite material. The coated warp and weft fabric is then placed into a flat mold of a molding machine and hot-pressed and cured at 60°C and 12MPa. After hot-pressing and curing, the fabric is demolded and finally post-cured for 0.5 hours to obtain a fiber-reinforced flame-retardant PMMA resin composite material.

[0067] Tensile, bending, and vertical burning specimens were fabricated using a laser engraving machine according to national standards GBT 1447, GB1449, and GBT 2408, and then tested. The test results show that the tensile strength is 210 MPa, the bending strength is 302 MPa, and the UL94 rating is V0.

[0068] Comparative Example 1

[0069] PMMA granules of grade COM205 produced by Zhenjiang Qimei Chemical Co., Ltd. were placed into a flat mold in a molding machine and molded at a heating temperature of 180℃ and a molding pressure of 10MPa. After 1 hour, PMMA resin boards were obtained.

[0070] Tensile, bending, and vertical burning specimens were fabricated using a laser engraving machine according to national standards GB / T2567 and GBT 2408-2021 and then tested. The test results show that the tensile strength is 68 MPa, the bending strength is 98 MPa, and the UL94 rating is non-NR.

[0071] Comparative Example 2

[0072] The difference between Comparative Example 2 and Example 1 is that the ammonium polyphosphate and aluminum hydroxide were not modified.

[0073] Tensile, bending, and vertical burning specimens were fabricated using a laser engraving machine according to national standards GB / T2567 and GBT 2408-2021 and then tested. The test results show that the tensile strength is 18 MPa, the bending strength is 51 MPa, and the UL94 rating is V0.

[0074] The test results of Examples 1-4 show that the PMMA resin boards and fiber-reinforced composite materials prepared by this invention both meet the UL94 V-0 flame retardant standard, with a significantly improved limiting oxygen index, exhibiting excellent flame retardant performance. Comparative Example 1, using commercially available PMMA particles directly molded without any added flame retardant, achieved a flame retardant rating of No rating (NR), which fully confirms the effectiveness of the flame retardant system of this invention. Under similar total flame retardant addition conditions, Comparative Example 2, using unmodified inorganic flame retardant, had a tensile strength of only 18 MPa and a flexural strength of 51 MPa; while Example 1, using surface-modified inorganic flame retardant, achieved a tensile strength as high as 60 MPa and a flexural strength of 80 MPa, demonstrating a significant improvement in mechanical properties. The results of Examples 3-4 further show that the fiber-reinforced composite materials prepared using the resin of this invention possess excellent mechanical properties and can meet the application requirements of structural materials.

[0075] As can be seen from the above embodiments, the present invention provides a flame-retardant PMMA resin suitable for molding processes, a fiber-reinforced flame-retardant PMMA resin composite material, and a method for preparing the same. The flame-retardant PMMA resin of the present invention is prepared from raw materials comprising the following parts by weight: 30-85 parts MMA slurry, 1-15 parts monomers copolymerizable with MMA, 10-60 parts surface-modified hydroxide, 5-15 parts organophosphorus compound, 5-15 parts melamine and its derivatives, 5-20 parts surface-modified ammonium polyphosphate, and 0.1-4 parts initiator. The flame-retardant PMMA resin and composite material prepared by the present invention exhibit excellent flame-retardant properties and good mechanical properties.

[0076] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A flame-retardant PMMA resin suitable for molding processes, characterized in that, It is prepared from raw materials comprising the following parts by weight: 30-85 parts of MMA slurry 1-15 parts of monomers that can copolymerize with MMA 10-60 parts of surface-modified hydroxide, 5-15 parts of organophosphorus compounds, 5-15 parts of melamine and its derivatives 5-20 parts of surface-modified ammonium polyphosphate, Initiator 0.1 to 4 parts.

2. The flame-retardant PMMA resin suitable for molding process according to claim 1, characterized in that, The MMA slurry is an MMA solution containing PMMA with a viscosity of 20~500 mPa·s.

3. The flame-retardant PMMA resin suitable for molding process according to claim 1 or 2, characterized in that, The monomers that can copolymerize with MMA include one or more of isobornyl methacrylate, methacrylamide, hydroxyethyl methacrylate, butyl methacrylate, methacrylic acid, and tert-butyl acrylate. The melamine and its derivatives include one or more of melamine, melamine cyanurate and melamine polyphosphate; The initiator is an azo initiator, an organic peroxide initiator, or a redox initiator.

4. The flame-retardant PMMA resin suitable for molding process according to claim 3, characterized in that, The surface-modified hydroxide is a hydroxide that has been treated with a modifier for surface modification, graft modification, or microencapsulation modification; The modifiers used in the surface modification of the modifier include coupling agent modifiers, surfactants, or organic polymer modifiers; The hydroxides include aluminum hydroxide and / or magnesium hydroxide.

5. The flame-retardant PMMA resin suitable for molding process according to claim 4, characterized in that, The organophosphorus compound is a phosphate ester and / or a phosphonate; The phosphate ester includes one or more of triethyl phosphate, triphenyl phosphate, tricresyl phosphate, and tributyl phosphate; The phosphonates include dimethyl methylphosphonate and / or diethyl ethylphosphonate.

6. The flame-retardant PMMA resin suitable for molding process according to claim 5, characterized in that, The surface-modified ammonium polyphosphate is ammonium polyphosphate that has been modified with a modifier or microencapsulated. The modifier used in the modification process is a coupling agent modifier, a surfactant, or an organic polymer modifier.

7. A method for preparing a flame-retardant PMMA resin suitable for molding process according to any one of claims 1 to 6, characterized in that, Includes the following steps: After mixing MMA slurry, monomers that can copolymerize with MMA, organophosphorus compounds and initiators, melamine and its derivatives and surface-modified ammonium polyphosphate are added and mixed. Finally, surface-modified hydroxide is added and mixed to obtain a paste-like flame-retardant PMMA resin.

8. A fiber-reinforced flame-retardant PMMA resin composite material, characterized in that, Includes fiber reinforcement, and flame-retardant PMMA resin as described in any one of claims 1 to 6 coated or mixed on the fiber reinforcement; The fiber reinforcement is a fiber fabric or chopped fiber.

9. A method for preparing a fiber-reinforced flame-retardant PMMA resin composite material, characterized in that, Includes the following steps: S1. The paste-like flame-retardant PMMA resin and fiber reinforcement described in any one of claims 1 to 6 are combined to obtain a composite material preform; Alternatively, the paste-like flame-retardant PMMA resin described in any one of claims 1 to 6 is coated onto the surface of the fiber reinforcement to obtain a composite material preform; S2. Place the composite material preform in a mold for hot pressing and curing, then demold to obtain a flame-retardant fiber-reinforced PMMA composite material.

10. The preparation method according to claim 9, characterized in that, The mass ratio of the paste-like flame-retardant PMMA resin to the fiber reinforcement is 60~90:10~40; Alternatively, the coating amount of the paste-like flame-retardant PMMA resin accounts for 60-90% of the mass of the composite material; The temperature for hot pressing curing is 50~90℃, and the pressure for hot pressing curing is 2~30MPa.