Flame-retardant impact-resistant composite acrylic plate and preparation method thereof

Abstract

The invention discloses a flame-retardant impact-resistant composite acrylic plate and a preparation method thereof, belongs to the technical field of acrylic plate processing, and aims to solve the technical problem that the flame retardance and impact resistance of an acrylic plate in the prior art need to be further improved. The acrylic plate comprises the following raw materials in parts by weight: 80-100 parts of flame-retardant modified PMMA, 40-60 parts of polycarbonate, 25-35 parts of a modified toughening agent and 10-15 parts of an auxiliary additive, and is prepared by the following steps: putting the flame-retardant modified PMMA, the polycarbonate, the modified toughening agent and the auxiliary additive into a twin-screw extruder, carrying out melt extrusion, pouring into a mold, and carrying out post-treatment to obtain the acrylic plate. The flame retardant property and the impact resistance of the acrylic plate are improved, and the mechanical property of the acrylic plate is also improved.

Description

Technical Field

[0001] The present invention relates to the technical field of acrylic sheet processing, and particularly relates to a flame-retardant and impact-resistant composite acrylic sheet and a preparation method thereof. Background Art

[0002] In recent years, acrylic sheets have been widely used in fields such as building facades, automotive lamps, and electronic displays due to their high light transmittance, weather resistance, and easy processability. In the construction field, flame-retardant acrylic sheets are widely used in walls, roofs, partitions, etc. to improve building safety. In the transportation field, flame-retardant and impact-resistant acrylic sheets are not only used for the interiors and exteriors of vehicles such as cars and airplanes to improve the safety and reliability of transportation facilities, but also used in windows and windshields to reduce weight, lower fuel consumption, while maintaining clarity and transparency to ensure driving safety.

[0003] However, traditional acrylic sheets still have significant defects in terms of flame retardancy and impact resistance. In the existing technology, the main material for preparing acrylic sheets is polymethyl methacrylate. The main chain of polymethyl methacrylate is a saturated carbon-oxygen bond structure, which is prone to free radical chain degradation at high temperatures, generating combustible small molecules such as methyl methacrylate monomers and carbon dioxide.

[0004] At the same time, its molecular chain lacks flame-retardant groups and is difficult to form a carbon layer to block combustion. Moreover, the molecular chain of polymethyl methacrylate has high rigidity and large side groups, resulting in weak molecular chain slip ability. Under external force, stress concentration cannot be effectively dissipated through chain segment rearrangement, and cracks rapidly expand along the rigid interface. During conventional blending modification, polycarbonate and polymethyl methacrylate are prone to macroscopic phase separation due to polarity differences, and the interfacial bonding force is weak. And the toughening agent is prone to agglomeration to form stress defect points due to poor compatibility with the matrix, further exacerbating the attenuation of mechanical properties. Summary of the Invention

[0005] The purpose of the present invention is to provide a flame-retardant and impact-resistant composite acrylic sheet and a preparation method thereof, which are used to solve the technical problem that the flame retardancy and impact resistance of acrylic sheets in the existing technology need to be further improved.

[0006] The purpose of the present invention can be achieved by the following technical solutions: A flame-retardant and impact-resistant composite acrylic sheet, comprising the following raw materials in parts by weight: 80-100 parts of flame-retardant modified PMMA, 40-60 parts of polycarbonate, 25-35 parts of modified toughening agent, and 10-15 parts of auxiliary additive;

[0007] Among them, the preparation method of the flame-retardant modified PMMA is: putting methyl methacrylate, modified flame retardant, N,N-dimethylformamide, and initiator into a reaction kettle, mixing evenly, heating to 70-80 °C, holding for reaction for 1-2 h, and performing post-treatment to obtain flame-retardant modified PMMA.

[0008] The preparation reaction principle of flame-retardant modified PMMA is as follows:

[0009] During the reaction process, under the initiation of azobisisobutyronitrile, methyl methacrylate undergoes in-situ polymerization on the modified flame retardant to obtain flame-retardant modified PMMA.

[0010] Furthermore, the dosage ratio of methyl methacrylate, modified flame retardant, N,N-dimethylformamide and initiator is 10-20 g: 2-5 g: 150-200 mL: 0.1-0.2 g. The initiator is azobisisobutyronitrile. The post-treatment steps include: after the reaction is completed, the temperature is raised to 140-150 °C, and vacuum distillation is carried out until no liquid is drawn out to obtain flame-retardant modified PMMA. The auxiliary additives are composed of a light stabilizer, an antioxidant, a lubricant, a filler and a colorant according to a mass ratio of 3:2:5:15:10.

[0011] Furthermore, the modified flame retardant is prepared by the following steps:

[0012] A1. Place 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide in a reaction kettle, raise the temperature to 115-125 °C, add 1-vinylimidazole, raise the temperature to 160-170 °C, keep the temperature for reaction for 10-12 h, and carry out post-treatment to obtain intermediate Ⅰ;

[0013] The preparation reaction formula of intermediate Ⅰ is:

[0014]

[0015] The preparation reaction principle of intermediate Ⅰ is:

[0016] During the reaction process, the P-H bond in the molecule of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide has high reactivity. When heated to 115-125 °C, the P-H bond is activated through thermal vibration to form an electron-rich phosphorus center. The C=C double bond in 1-vinylimidazole is polarized at high temperature to form a β-carbon atom with partial positive charge, enhancing its electrophilicity. The P-H bond directly undergoes a concerted nucleophilic addition with the C=C double bond to obtain intermediate Ⅰ. The mass spectrometry data of intermediate Ⅰ is m / z: 310.06 (100.0%), 311.06 (18.6%), 312.06 (2.2%).

[0017] A2. Place 2-methylimidazole, zinc nitrate hexahydrate and methanol in a reaction kettle, raise the temperature to 30-40 °C, keep the temperature for reaction for 1-2 h, and carry out post-treatment to obtain intermediate Ⅱ;

[0018] The preparation reaction principle of intermediate Ⅱ is:

[0019] During the reaction, zinc nitrate hexahydrate dissociates into zinc ions and nitrate ions in methanol. The pyridine-type nitrogen atom in the imidazole ring of 2-methylimidazole acts as an electron donor and forms a Zn-N coordination bond with the zinc ion to obtain intermediate II with an octahedral structure.

[0020] A3. Place intermediate I and methanol in a reaction kettle, add intermediate II, heat up to 30 - 40 °C, and perform post-treatment to obtain the modified flame retardant.

[0021] The preparation reaction principle of the modified flame retardant is as follows:

[0022] During the reaction, some coordination unsaturated sites of zinc ions in the framework of intermediate II are exposed in the methanol solvent to form active Lewis acid sites. The imidazole ring at the end of intermediate I forms an N→Zn coordination bond with the zinc ion to achieve chemical bonding. The oxygen atom of the P=O group in intermediate I undergoes weak coordination with the zinc ion through lone pair electrons to enhance the interfacial binding force. Intermediate I binds in the pores of intermediate II to form a modified flame retardant with intermediate II coating intermediate I.

[0023] Furthermore, in step A1, the dosage ratio of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide and 1-vinylimidazole is 4 - 6 g:1.5 - 2.5 g. The post-treatment steps include: after the reaction is completed, wait for the reaction to cool to room temperature, perform suction filtration, wash the filter cake with tetrahydrofuran 2 - 3 times, transfer it to an oven at 70 - 80 °C, and dry to constant weight to obtain intermediate I; in step A2, the dosage ratio of 2-methylimidazole, zinc nitrate hexahydrate and methanol is 1 - 2 g:0.5 - 1 g:30 - 40 mL. The post-treatment steps include: after the reaction is completed, wait for the reaction to cool to room temperature, perform suction filtration, wash the filter cake with methanol 2 - 3 times, transfer it to an oven at 60 - 70 °C, and dry to constant weight to obtain intermediate II; in step A3, the dosage ratio of intermediate I, intermediate II and methanol is 0.5 - 1 g:5 - 8 g:50 - 100 mL. The post-treatment steps include: after the reaction is completed, wait for the reaction to cool to room temperature, perform suction filtration, wash the filter cake with methanol 2 - 3 times, transfer it to an oven at 60 - 70 °C, and dry to constant weight to obtain the modified flame retardant.

[0024] Furthermore, the modified toughening agent is prepared by the following steps:

[0025] B1. Place hexamethylcyclotrisiloxane, 2,4,6-trivinyl-2,4,6-trimethylcyclotrisiloxane, sodium dodecylsulfonate, catalyst, deionized water and dodecylphenol polyoxyethylene ether in a reaction kettle, mix evenly to obtain an organosilicon monomer.

[0026] The preparation reaction principle of the organosilicon monomer is as follows:

[0027] During the reaction process, under the action of deionized water and a catalyst, the Si-O-Si bonds of hexamethylcyclotrisiloxane undergo hydrolysis in an environment formed by sodium dodecyl sulfonate, dodecylphenol polyoxyethylene ether, and deionized water to generate linear siloxane chains, which undergo a condensation reaction with the hydrolysis products of 2,4,6-trivinyl-2,4,6-trimethylcyclotrisiloxane to obtain organosilicon monomers.

[0028] B2. Place deionized water, sodium dodecyl sulfonate, and dodecylphenol polyoxyethylene ether in a reaction kettle, add the organosilicon monomer, stir for 3 - 5 min, add an aqueous sodium hydroxide solution to adjust the pH to 8 - 9, heat up to 75 - 85 °C, add the shell monomer, add an aqueous potassium persulfate solution, keep the temperature for reaction for 1 - 2 h, and perform post-treatment to obtain the modified toughening agent.

[0029] The preparation reaction formula of the modified toughening agent is:

[0030]

[0031] The preparation reaction principle of the modified toughening agent is:

[0032] During the reaction process, sodium dodecyl sulfonate and dodecylphenol polyoxyethylene ether act together to reduce the surface tension of the aqueous phase, enabling the organosilicon monomer to be uniformly dispersed in water in the form of tiny droplets. In an alkaline environment, potassium persulfate initiates a free radical polymerization reaction between the olefin groups of the organosilicon monomer and the olefin groups of the shell monomer to obtain a modified toughening agent with a soft core and a hard shell.

[0033] Furthermore, in step B1, the dosage ratio of hexamethylcyclotrisiloxane, 2,4,6-trivinyl-2,4,6-trimethylcyclotrisiloxane, sodium dodecyl sulfonate, catalyst, deionized water, and dodecylphenol polyoxyethylene ether is 4 - 8 g: 0.5 - 1 g: 0.1 - 0.2 g: 2 - 5 mL: 50 - 70 mL: 0.05 - 0.1 g, and the catalyst is a 20 wt% aqueous formic acid solution; in step B2, the shell monomer is composed of methyl methacrylate, acrylic acid, and butyl acrylate in a mass ratio of 2.5: 0.1: 1, the concentration of the aqueous potassium persulfate solution is 8 - 10 wt%, the concentration of the aqueous sodium hydroxide solution is 3 - 5 wt%, and the dosage ratio of deionized water, sodium dodecyl sulfonate, dodecylphenol polyoxyethylene ether, organosilicon monomer, shell monomer, and aqueous potassium persulfate solution is 150 - 200 mL: 1 - 2 g: 0.5 - 1 g: 15 - 20 g: 12 - 16 g: 1 - 2 mL. The post-treatment steps include: after the reaction is completed, wait for the reaction to cool to room temperature, add a 10 wt% calcium chloride aqueous solution for demulsification, perform suction filtration, wash the filter cake with deionized water 1 - 2 times, transfer it to an oven at a temperature of 60 - 70 °C, and dry it to a constant weight to obtain the modified toughening agent.

[0034] The present invention also provides a method for preparing a flame-retardant and impact-resistant composite acrylic sheet, which includes the following steps: placing flame-retardant modified PMMA, polycarbonate, modified toughening agent and auxiliary additives into a twin-screw extruder, melt-extruding, pouring into a mold, and performing post-treatment to obtain the acrylic sheet.

[0035] Further, the auxiliary additives are composed of a light stabilizer, an antioxidant, a lubricant, a filler and a colorant in a mass ratio of 3:2:5:15:10. The light stabilizer is one or more of 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-n-octoxybenzophenone or 2-(2-hydroxy-5-methylphenyl)benzotriazole. The antioxidant is one or more of 2,6-di-tert-butyl-4-methylphenol, pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] or 4,4'-thiobis(6-tert-butyl-3-methylphenol). The lubricant is one or both of stearic acid and oleic acid. The filler is magnesium oxide. The colorant is one or more of chrome yellow, ultramarine or phthalocyanine blue. The thickness of the acrylic sheet is 1-5 mm. The post-treatment steps include: pressing the plate, cooling at room temperature, and demolding to obtain the acrylic sheet.

[0036] The present invention has the following beneficial effects:

[0037] 1. In the present invention, intermediate I is prepared through the nucleophilic reaction of phosphaphenanthrene and vinylimidazole, and then organic framework intermediate II is further prepared. Intermediate I and octahedral intermediate II are combined through a coordination bond to prepare a modified flame retardant coated with an organic framework. Poly(methyl methacrylate) is synthesized on the modified flame retardant by in-situ polymerization to obtain flame-retardant modified PMMA. A modified toughening agent with a soft core and a hard shell is prepared using an olefin-containing polysiloxane as the soft core and an acrylate as the hard core. The flame-retardant modified PMMA, auxiliary additives, polycarbonate and modified toughening agent are melt-extruded, injection-molded, pressed and demolded to obtain the composite acrylic sheet. By preparing intermediate I containing a phosphaphenanthrene ring of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide and combining intermediate I with organic framework intermediate II containing a zinc-based imidazole complex, the modified flame retardant can release phosphorus-containing free radicals at high temperatures, efficiently capture free radicals in the flame, interrupt the combustion chain reaction, catalyze the crosslinking of the decomposition products of the composite acrylic matrix into carbon, form a dense carbon layer, and inhibit the diffusion of heat and oxygen. The dual effects of the gas-phase quenching of phosphorus in intermediate I and the catalytic carbonization of zinc in intermediate II significantly reduce the amount of flame retardant and improve the flame retardancy of the composite acrylic sheet.

[0038] 2. The present invention also uses a polysiloxane containing olefins as the soft core and an acrylate substance as the hard core to prepare a modified toughening agent with a soft core and a hard shell. The polysiloxane soft core containing olefins has highly flexible Si-O-Si segments, enabling the modified toughening agent to absorb external impact energy, disperse stress, inhibit crack propagation, and improve the impact resistance of the composite acrylic sheet. At the same time, the hard shell prepared from acrylate has a high modulus, providing rigid support to prevent excessive deformation of the soft core. Moreover, the shell layer of the modified toughening agent contains polymethyl methacrylate, which has a polar match with the flame-retardant modified PMMA, promoting molecular chain entanglement during the melting process, enhancing the interfacial bonding force between materials, and improving the mechanical properties of the composite acrylic sheet. When preparing the composite acrylic sheet, polycarbonate is added. Polycarbonate is an engineering plastic with a relatively high chain entanglement density. Through the transesterification reaction catalyzed by magnesium oxide, a copolyester structure can be formed between the polycarbonate and polymethyl methacrylate chain segments, forming a chemical bond connection, reducing the interfacial tension, enhancing the compatibility of the two-phase interface, and further improving the impact resistance of the composite acrylic sheet. Detailed Embodiments

[0039] The technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of them. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative work shall fall within the scope of protection of the present invention.

[0040] Example 1

[0041] This example provides a preparation method of a modified flame retardant for preparing flame-retardant modified PMMA used in a flame-retardant and impact-resistant composite acrylic sheet, including the following steps:

[0042] Step (1), preparing Intermediate I

[0043] Weigh 40 g of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide and place it in a reaction kettle. Heat it to 115°C, add 15 g of 1-vinylimidazole, then heat it to 160°C and keep the temperature for 10 h. After the reaction is completed, wait for the reaction to cool to room temperature, filter by suction. Wash the filter cake twice with tetrahydrofuran, transfer it to an oven at 70°C, and dry it to a constant weight to obtain Intermediate I.

[0044] Step (2), preparing Intermediate II

[0045] Weigh 10 g of 2-methylimidazole, 5 g of zinc nitrate hexahydrate and 300 mL of methanol and place them in a reaction kettle. Heat it to 30°C and keep the temperature for 1 h. After the reaction is completed, wait for the reaction to cool to room temperature, filter by suction. Wash the filter cake twice with methanol, transfer it to an oven at 60°C, and dry it to a constant weight to obtain Intermediate II.

[0046] Step ⑶. Prepare the modified flame retardant

[0047] Weigh: 5 g of Intermediate Ⅰ and 500 mL of methanol and place them in a reaction kettle. Add 50 g of Intermediate Ⅱ, heat up to 30 °C. After the reaction is completed, wait for the reaction to cool down to room temperature, carry out suction filtration, wash the filter cake twice with methanol, transfer it to an oven at 60 °C, and dry it to constant weight to obtain the modified flame retardant.

[0048] Example 2

[0049] This example provides a preparation method of a modified flame retardant for preparing flame-retardant modified PMMA for a flame-retardant and impact-resistant composite acrylic sheet, including the following steps:

[0050] Step ⑴. Prepare Intermediate Ⅰ

[0051] Weigh: 50 g of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide and place it in a reaction kettle. Heat up to 120 °C, add 20 g of 1-vinylimidazole, heat up to 165 °C, keep the temperature for reaction for 11 h. After the reaction is completed, wait for the reaction to cool down to room temperature, carry out suction filtration, wash the filter cake twice with tetrahydrofuran, transfer it to an oven at 75 °C, and dry it to constant weight to obtain Intermediate Ⅰ.

[0052] Step ⑵. Prepare Intermediate Ⅱ

[0053] Weigh: 15 g of 2-methylimidazole, 7 g of zinc nitrate hexahydrate and 350 mL of methanol and place them in a reaction kettle. Heat up to 35 °C, keep the temperature for reaction for 1.5 h. After the reaction is completed, wait for the reaction to cool down to room temperature, carry out suction filtration, wash the filter cake twice with methanol, transfer it to an oven at 65 °C, and dry it to constant weight to obtain Intermediate Ⅱ.

[0054] Step ⑶. Prepare the modified flame retardant

[0055] Weigh: 7 g of Intermediate Ⅰ and 700 mL of methanol and place them in a reaction kettle. Add 70 g of Intermediate Ⅱ, heat up to 35 °C. After the reaction is completed, wait for the reaction to cool down to room temperature, carry out suction filtration, wash the filter cake twice with methanol, transfer it to an oven at 65 °C, and dry it to constant weight to obtain the modified flame retardant.

[0056] Example 3

[0057] This example provides a preparation method of a modified flame retardant for preparing flame-retardant modified PMMA for a flame-retardant and impact-resistant composite acrylic sheet, including the following steps:

[0058] Step ⑴. Prepare Intermediate Ⅰ

[0059] Weigh: 60 g of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide and place it in a reaction kettle. Heat up to 125 °C, add 25 g of 1-vinylimidazole, heat up to 170 °C, and keep the temperature for reaction for 12 h. After the reaction is completed, wait for the reaction to cool down to room temperature, perform suction filtration, wash the filter cake with tetrahydrofuran three times, transfer it to an oven at 80 °C, and dry it to constant weight to obtain Intermediate I.

[0060] Step (2), prepare Intermediate II

[0061] Weigh: 20 g of 2-methylimidazole, 10 g of zinc nitrate hexahydrate, and 400 mL of methanol and place them in a reaction kettle. Heat up to 40 °C, keep the temperature for reaction for 2 h. After the reaction is completed, wait for the reaction to cool down to room temperature, perform suction filtration, wash the filter cake with methanol three times, transfer it to an oven at 70 °C, and dry it to constant weight to obtain Intermediate II.

[0062] Step (3), prepare the modified flame retardant

[0063] Weigh: 10 g of Intermediate I and 1000 mL of methanol and place them in a reaction kettle. Add 80 g of Intermediate II, heat up to 40 °C. After the reaction is completed, wait for the reaction to cool down to room temperature, perform suction filtration, wash the filter cake with methanol three times, transfer it to an oven at 70 °C, and dry it to constant weight to obtain the modified flame retardant.

[0064] Example 4

[0065] This example provides a preparation method of flame retardant modified PMMA for flame retardant and impact resistant composite acrylic plates, including the following steps:

[0066] Weigh: 100 g of methyl methacrylate, 20 g of the modified flame retardant prepared in Example 1, 1500 mL of N,N-dimethylformamide, and 1 g of azobisisobutyronitrile and place them in a reaction kettle. Mix them evenly, heat up to 70 °C, keep the temperature for reaction for 1 h. After the reaction is completed, heat up to 140 °C, and perform vacuum distillation until no liquid is collected to obtain flame retardant modified PMMA.

[0067] Example 5

[0068] This example provides a preparation method of flame retardant modified PMMA for flame retardant and impact resistant composite acrylic plates, including the following steps:

[0069] Weigh: 150 g of methyl methacrylate, 30 g of the modified flame retardant prepared in Example 2, 1700 mL of N,N-dimethylformamide, and 1.5 g of azobisisobutyronitrile and place them in a reaction kettle. Mix them evenly, heat up to 75 °C, keep the temperature for reaction for 1.5 h. After the reaction is completed, heat up to 145 °C, and perform vacuum distillation until no liquid is collected to obtain flame retardant modified PMMA.

[0070] Example 6

[0071] This embodiment provides a preparation method of flame-retardant modified PMMA for a flame-retardant and impact-resistant composite acrylic sheet, comprising the following steps:

[0072] Weigh: 200 g of methyl methacrylate, 50 g of the modified flame retardant prepared in Example 3, 2000 mL of N,N-dimethylformamide, and 2 g of azobisisobutyronitrile, place them in a reaction kettle, mix evenly, heat up to 80 °C, keep the temperature for reaction for 2 h, after the reaction is completed, heat up to 150 °C, and perform vacuum distillation until no liquid is collected, to obtain flame-retardant modified PMMA.

[0073] Example 7

[0074] This embodiment provides a preparation method of a modified toughening agent for a flame-retardant and impact-resistant composite acrylic sheet, comprising the following steps:

[0075] Step ①, prepare organosilicon monomers

[0076] Weigh: 40 g of hexamethylcyclotrisiloxane, 5 g of 2,4,6-trivinyl-2,4,6-trimethylcyclotrisiloxane, 1 g of sodium dodecylsulfonate, 20 mL of 20 wt% formic acid aqueous solution, 500 mL of deionized water, and 0.5 g of dodecylphenol polyoxyethylene ether, place them in a reaction kettle, mix evenly, to obtain organosilicon monomers.

[0077] Step ②, prepare the modified toughening agent

[0078] Mix methyl methacrylate, acrylic acid, and butyl acrylate evenly according to a mass ratio of 2.5:0.1:1 to obtain the shell monomer, and set it aside;

[0079] Weigh: 1500 mL of deionized water, 10 g of sodium dodecylsulfonate, and 5 g of dodecylphenol polyoxyethylene ether, place them in a reaction kettle, add 150 g of organosilicon monomers, stir for 3 min, add 3 wt% sodium hydroxide aqueous solution to adjust the pH = 8, heat up to 75 °C, add 120 g of the shell monomer, add 10 mL of 8 wt% potassium persulfate aqueous solution, keep the temperature for reaction for 1 h, after the reaction is completed, wait for the reaction to cool to room temperature, add 10 wt% calcium chloride aqueous solution for demulsification, perform suction filtration, wash the filter cake with deionized water once, transfer it to an oven at 60 °C, and dry to constant weight to obtain the modified toughening agent.

[0080] Example 8

[0081] This embodiment provides a preparation method of a modified toughening agent for a flame-retardant and impact-resistant composite acrylic sheet, comprising the following steps:

[0082] Step ①, prepare organosilicon monomers

[0083] Weigh: 60 g of hexamethylcyclotrisiloxane, 7 g of 2,4,6-trivinyl-2,4,6-trimethylcyclotrisiloxane, 1.5 g of sodium dodecylsulfonate, 35 mL of 20 wt% formic acid aqueous solution, 600 mL of deionized water and 0.7 g of dodecylphenol polyoxyethylene ether into a reaction kettle, mix evenly to obtain an organosilicon monomer.

[0084] Step ②, prepare a modified toughening agent

[0085] Mix methyl methacrylate, acrylic acid and butyl acrylate evenly according to the mass ratio of 2.5:0.1:1 to obtain a shell monomer for standby.

[0086] Weigh: 1700 mL of deionized water, 15 g of sodium dodecylsulfonate and 7 g of dodecylphenol polyoxyethylene ether into a reaction kettle, add 170 g of the organosilicon monomer, stir for 4 min, add 4 wt% sodium hydroxide aqueous solution to adjust the pH = 8.5, heat up to 80 °C, add 140 g of the shell monomer, add 15 mL of 9 wt% potassium persulfate aqueous solution, keep the temperature for reaction for 1.5 h. After the reaction is completed, wait for the reaction to cool to room temperature, add 10 wt% calcium chloride aqueous solution for demulsification, filter by suction, wash the filter cake with deionized water twice, transfer it to an oven at 65 °C and dry to constant weight to obtain a modified toughening agent.

[0087] Example 9

[0088] This example provides a preparation method of a modified toughening agent for a flame-retardant and impact-resistant composite acrylic board, including the following steps:

[0089] Step ①, prepare an organosilicon monomer

[0090] Weigh: 80 g of hexamethylcyclotrisiloxane, 10 g of 2,4,6-trivinyl-2,4,6-trimethylcyclotrisiloxane, 2 g of sodium dodecylsulfonate, 50 mL of 20 wt% formic acid aqueous solution, 700 mL of deionized water and 1 g of dodecylphenol polyoxyethylene ether into a reaction kettle, mix evenly to obtain an organosilicon monomer.

[0091] Step ②, prepare a modified toughening agent

[0092] Mix methyl methacrylate, acrylic acid and butyl acrylate evenly according to the mass ratio of 2.5:0.1:1 to obtain a shell monomer for standby.

[0093] Weigh: 2000 mL of deionized water, 20 g of sodium dodecyl sulfonate and 10 g of polyoxyethylene dodecyl phenyl ether and place them in a reaction kettle. Add 200 g of organosilicon monomer, stir for 5 min, add 5 wt% sodium hydroxide aqueous solution to adjust the pH to 9, heat up to 85 °C, add 160 g of shell monomer, add 20 mL of 10 wt% potassium persulfate aqueous solution, keep the temperature for reaction for 2 h. After the reaction is completed, wait for the reaction to cool to room temperature, add 10 wt% calcium chloride aqueous solution for demulsification, filter by suction, wash the filter cake with deionized water twice, transfer it to an oven at 70 °C, and dry to constant weight to obtain the modified toughening agent.

[0094] Example 10

[0095] This example provides a preparation method of a flame-retardant and impact-resistant composite acrylic board, which includes the following steps:

[0096] Mix 2-hydroxy-4-methoxybenzophenone, pentaerythritol tetra[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], stearic acid, magnesium oxide and phthalocyanine blue evenly according to the mass ratio of 3:2:5:15:10 to obtain the auxiliary additive for standby;

[0097] Weigh by mass parts: 80 parts of the flame-retardant modified PMMA prepared in Example 4, 40 parts of polycarbonate, 25 parts of the modified toughening agent in Example 7 and 10 parts of the auxiliary additive, place them in a twin-screw extruder, melt and extrude, pour into a mold, press the plate, cool at room temperature, and demold to obtain the acrylic board;

[0098] The temperatures of the eight temperature sections of the twin-screw extruder from the feed port to the discharge port direction are 170 °C, 170 °C, 185 °C, 185 °C, 200 °C, 200 °C, 210 °C, 210 °C in sequence. The main machine speed of the twin-screw extruder is 120 rpm, the pressure is 80 bar, and the thickness of the acrylic board is 1 mm.

[0099] Example 11

[0100] This example provides a preparation method of a flame-retardant and impact-resistant composite acrylic board, which includes the following steps:

[0101] Mix 2-hydroxy-4-methoxybenzophenone, pentaerythritol tetra[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], stearic acid, magnesium oxide and phthalocyanine blue evenly according to the mass ratio of 3:2:5:15:10 to obtain the auxiliary additive for standby;

[0102] Weigh by mass parts: 900 parts of the flame-retardant modified PMMA prepared in Example 5, 50 parts of polycarbonate, 30 parts of the modified toughening agent in Example 8 and 13 parts of the auxiliary additive, place them in a twin-screw extruder, melt and extrude, pour into a mold, press the plate, cool at room temperature, and demold to obtain the acrylic board;

[0103] The temperatures of the eight temperature zones of the twin-screw extruder from the feed inlet towards the discharge outlet are 170 °C, 170 °C, 185 °C, 185 °C, 200 °C, 200 °C, 210 °C, and 210 °C in sequence. The main machine speed of the twin-screw extruder is 140 rpm, the pressure is 100 bar, and the thickness of the acrylic sheet is 3 mm.

[0104] Example 12

[0105] This example provides a preparation method for a flame-retardant and impact-resistant composite acrylic sheet, which includes the following steps:

[0106] Mix 2-hydroxy-4-methoxybenzophenone, pentaerythritol tetrakis [β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate], stearic acid, magnesium oxide, and phthalocyanine blue evenly according to the mass ratio of 3:2:5:15:10 to obtain the auxiliary additive for standby;

[0107] Weigh by mass parts: 100 parts of the flame-retardant modified PMMA prepared in Example 6, 60 parts of polycarbonate, 35 parts of the modified toughening agent in Example 9, and 15 parts of the auxiliary additive, place them in a twin-screw extruder, melt and extrude, pour into a mold, press the plate, cool at room temperature, and demold to obtain the acrylic sheet;

[0108] The temperatures of the eight temperature zones of the twin-screw extruder from the feed inlet towards the discharge outlet are 170 °C, 170 °C, 185 °C, 185 °C, 200 °C, 200 °C, 210 °C, and 210 °C in sequence. The main machine speed of the twin-screw extruder is 160 rpm, the pressure is 120 bar, and the thickness of the acrylic sheet is 5 mm.

[0109] Comparative Example 1

[0110] The difference between this comparative example and Example 12 is that during the preparation of the flame-retardant modified PMMA, the use of the modified flame retardant was cancelled.

[0111] Comparative Example 2

[0112] The difference between this comparative example and Example 12 is that during the preparation of the composite acrylic sheet, the use of the modified toughening agent was cancelled.

[0113] Comparative Example 3

[0114] The difference between this comparative example and Example 12 is that during the preparation of the composite acrylic sheet, the use of magnesium oxide in the auxiliary additive was cancelled.

[0115] Performance test:

[0116] The limiting oxygen index of the composite acrylic sheets prepared in Examples 10-12 and Comparative Examples 1-3 was tested with reference to the standard GB / T 2406.2-2009 "Determination of Combustion Behavior of Plastics by Oxygen Index Method Part 2: Room Temperature Test";

[0117] The vertical burning rating of the composite acrylic sheets prepared in Examples 10-12 and Comparative Examples 1-3 was tested with reference to the standard GB / T 26526-2011 "Specification for Thermoplastic Elastomer Low Smoke Halogen-Free Flame Retardant Materials";

[0118] With reference to the standard GB / T 15597.2-2024 "Plastic polymethyl methacrylate (PMMA) molding and extrusion materials Part 2: Sample preparation and performance determination", the tensile fracture stress, elongation at break and cantilever beam notched impact strength of the composite acrylic plates prepared in Examples 10-12 and Comparative Examples 1-3 were tested, and the specific data are shown in Table 1.

[0119] Table 1-Performance test data of each sample

[0120]

[0121]

[0122] Data Analysis:

[0123] Comparative analysis of the data in Table 1 above shows that the composite acrylic sheet prepared by the present invention has a limiting oxygen index of 39.6%, a vertical combustion grade of V-0, a tensile stress of 46.9 MPa, an elongation at break of 12.1%, and an Izod notched impact strength of 21.0 kJ·m -2 ;

[0124] By comparing the data of Example 12 and Comparative Example 1, it can be found that the limiting oxygen index and vertical combustion grade of Comparative Example 1 are significantly reduced, indicating that the present invention prepares an intermediate I containing 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide containing a phosphaphenanthrene ring, and combines the intermediate I with an organic skeleton intermediate II containing a zinc-based imidazole complex, so that the modified flame retardant can release phosphorus-containing free radicals at high temperatures, efficiently capture free radicals in the flame, interrupt the combustion chain reaction, catalyze the cross-linking of the decomposition products of the composite acrylic matrix into carbon, form a dense carbon layer, and inhibit the diffusion of heat and oxygen, wherein the gas phase quenching of phosphorus in the intermediate I and the catalytic carbonization of zinc in the intermediate II have dual effects, which significantly reduce the amount of flame retardant and improve the flame retardant properties of the composite acrylic board;

[0125] By comparing the data of Example 12 and Comparative Example 2, it can be found that the tensile fracture stress, elongation at break and notched Izod impact strength of Comparative Example 2 decreased significantly. This shows that the modified toughening agent with a soft core and a hard shell is prepared by using a polysiloxane containing olefins as the soft core and an acrylate as the hard core. The polysiloxane soft core containing olefins has highly flexible Si-O-Si segments, enabling the modified toughening agent to absorb external impact energy, disperse stress, inhibit crack propagation, and improve the impact resistance of the composite acrylic sheet. At the same time, the hard shell prepared from acrylate has a high modulus, providing rigid support to prevent excessive deformation of the soft core. Moreover, the shell layer of the modified toughening agent contains polymethyl methacrylate, which has a polar match with the flame-retardant modified PMMA, promotes molecular chain entanglement during the melting process, enhances the interfacial bonding force between materials, and improves the mechanical properties of the composite acrylic sheet;

[0126] By comparing the data of Example 12 and Comparative Example 3, it can be found that the tensile fracture stress, elongation at break and notched Izod impact strength of Comparative Example 3 decreased significantly. This shows that when preparing the composite acrylic sheet, adding polycarbonate, which is an engineering plastic with a relatively high chain entanglement density. Through the transesterification reaction catalyzed by magnesium oxide, a copolyester structure can be formed between the polycarbonate and polymethyl methacrylate chain segments, forming a chemical bond connection, reducing the interfacial tension, enhancing the compatibility of the two-phase interface, and further improving the impact resistance of the composite acrylic sheet.

[0127] The preferred embodiments of the present invention disclosed above are only used to help illustrate the present invention. The preferred embodiments do not describe all the details in detail, nor do they limit the invention to only the specific implementation manners. Obviously, many modifications and changes can be made according to the content of this specification. These embodiments are selected and specifically described in this specification to better explain the principle and practical application of the present invention, so that those skilled in the art can well understand and utilize the present invention. The present invention is only limited by the claims and their full scope and equivalents.

Claims

1. A flame-retardant and impact-resistant composite acrylic sheet, characterized in that, Comprising the following raw materials by weight: 80 - 100 parts of flame-retardant modified PMMA, 40 - 60 parts of polycarbonate, 25 - 35 parts of modified toughening agent, and 10 - 15 parts of auxiliary additive; Among them, the preparation method of the flame-retardant modified PMMA is: putting methyl methacrylate, modified flame retardant, N,N-dimethylformamide, and initiator into a reaction kettle, mixing evenly, heating to 70 - 80 °C, holding for reaction for 1 - 2 h, and performing post-treatment to obtain flame-retardant modified PMMA.

2. A flame-retardant and impact-resistant composite acrylic board according to claim 1, characterized in that, The auxiliary additive is composed of a light stabilizer, antioxidant, lubricant, filler, and colorant in a mass ratio of 3:2:5:15:10; the dosage ratio of methyl methacrylate, modified flame retardant, N,N-dimethylformamide, and initiator is 10 - 20 g:2 - 5 g:150 - 200 mL:0.1 - 0.2 g, and the initiator is azobisisobutyronitrile.

3. A flame-retardant and impact-resistant composite acrylic sheet according to claim 1, characterized in that, The modified flame retardant is prepared by the following steps: A1. Putting 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide into a reaction kettle, heating to 115 - 125 °C, adding 1-vinylimidazole, heating to 160 - 170 °C, holding for reaction for 10 - 12 h, and performing post-treatment to obtain intermediate I; A2. Putting 2-methylimidazole, zinc nitrate hexahydrate, and methanol into a reaction kettle, heating to 30 - 40 °C, holding for reaction for 1 - 2 h, and performing post-treatment to obtain intermediate II; A3. Putting intermediate I and methanol into a reaction kettle, adding intermediate II, heating to 30 - 40 °C, and performing post-treatment to obtain the modified flame retardant.

4. A flame-retardant and impact-resistant composite acrylic sheet according to claim 3, wherein, In step A1, the dosage ratio of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide and 1-vinylimidazole is 4 - 6 g:1.5 - 2.5 g; in step A2, the dosage ratio of 2-methylimidazole, zinc nitrate hexahydrate, and methanol is 1 - 2 g:0.5 - 1 g:30 - 40 mL; in step A3, the dosage ratio of intermediate I, intermediate II, and methanol is 0.5 - 1 g:5 - 8 g:50 - 100 mL.

5. A flame-retardant and impact-resistant composite acrylic board according to claim 1, wherein, The modified toughening agent is prepared by the following steps: B1. Putting hexamethylcyclotrisiloxane, 2,4,6-trivinyl-2,4,6-trimethylcyclotrisiloxane, sodium dodecyl sulfate, catalyst, deionized water, and dodecylphenol polyoxyethylene ether into a reaction kettle, mixing evenly to obtain an organosilicon monomer; B2. Putting deionized water, sodium dodecyl sulfate, and dodecylphenol polyoxyethylene ether into a reaction kettle, adding the organosilicon monomer, stirring for 3 - 5 min, adding sodium hydroxide aqueous solution to adjust the pH = 8 - 9, heating to 75 - 85 °C, adding a shell monomer, adding potassium persulfate aqueous solution, holding for reaction for 1 - 2 h, and performing post-treatment to obtain the modified toughening agent.

6. A flame-retardant and impact-resistant composite acrylic sheet according to claim 5, characterized in that, In step B1, the dosage ratio of hexamethylcyclotrisiloxane, 2,4,6-trivinyl-2,4,6-trimethylcyclotrisiloxane, sodium dodecylsulfonate, catalyst, deionized water and dodecylphenol polyoxyethylene ether is 4-8 g: 0.5-1 g: 0.1-0.2 g: 2-5 mL: 50-70 mL: 0.05-0.1 g, and the catalyst is 20 wt% formic acid aqueous solution; in step B2, the shell monomer is composed of methyl methacrylate, acrylic acid and butyl acrylate in a mass ratio of 2.5: 0.1: 1, the concentration of the potassium persulfate aqueous solution is 8-10 wt%, the concentration of the sodium hydroxide aqueous solution is 3-5 wt%, and the dosage ratio of deionized water, sodium dodecylsulfonate, dodecylphenol polyoxyethylene ether, organosilicon monomer, shell monomer and potassium persulfate aqueous solution is 150-200 mL: 1-2 g: 0.5-1 g: 15-20 g: 12-16 g: 1-2 mL.

7. A method for preparing a flame-retardant and impact-resistant composite acrylic sheet according to any one of claims 1-6, characterized in that, It includes the following steps: placing flame-retardant modified PMMA, polycarbonate, modified toughening agent and auxiliary additive in a twin-screw extruder, melt-extruding, pouring into a mold, and post-treating to obtain an acrylic sheet.

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