Optical copolymer flame retardant board and its preparation method and reactive extrusion device

Abstract

The present invention provides an optical copolymer flame-retardant board, a preparation method thereof, and a reactive extrusion device, relating to the technical field of acrylic material production. The preparation method comprises the following steps: placing a mixture comprising vinyl phosphate, methyl methacrylate, a comonomer, and a functional monomer into a prepolymerization reactor for polymerization to obtain a first prepolymer; mixing the mixture comprising methyl methacrylate, a comonomer, and a functional monomer with the first prepolymer, and placing the mixture into a tubular reactor for polymerization to obtain a second prepolymer; and mixing the mixture comprising methyl methacrylate, a comonomer, and a functional monomer with the second prepolymer, and placing the mixture into a devolatilization extruder. After discharge, the material is granulated and pressed to obtain an optical copolymer flame-retardant board. The preparation method of the optical copolymer flame-retardant board provided by the present invention incorporates phosphate into PMMA polymer chains, resulting in an optical copolymer flame-retardant board with high transparency and excellent flame retardancy.

Description

Technical Field

[0001] The invention relates to the technical field of acrylic material production, in particular to an optical copolymerization flame retardant board and a preparation method and a reaction extrusion device thereof. Background Art

[0002] Acrylic material (PMMA) has poor thermal stability and is extremely flammable, which limits its application in many fields. The limiting oxygen index of pure PMMA is only 17.0, and the peak heat release rate of PMMA in the cone calorimetry test is 1058kW / m 2 Furthermore, PMMA is a typical linear polymer material, and its combustion process is often accompanied by severe dripping, which can easily cause secondary disasters. Therefore, the research of flame-retardant acrylic materials is particularly important.

[0003] Conventional flame-retardant plastics achieve their flame-retardant properties by adding various additive flame retardants. For PMMA, commonly used flame retardants include halogen-containing phosphorus-based flame retardants such as chloroalkyl polyphosphates, TCPP, and TCEP. These flame retardants not only fail to meet environmental standards due to their halogen content, but also degrade the material's mechanical properties. Inorganic flame retardants such as aluminum hypophosphite are also available, but their addition can reduce the material's impact resistance and the sheet's transparency, making it difficult to meet optical performance requirements.

[0004] In view of this, providing a PMMA board that takes into account both flame retardancy and transparency is a technical problem that urgently needs to be solved. Summary of the Invention

[0005] The technical problem to be solved by the present invention is: in order to solve the problem that PMMA boards in the prior art are difficult to achieve both flame retardancy and transparency, the present invention provides an optical copolymer flame retardant board. The flame retardant board adopts a method of copolymerizing flame retardant monomers vinyl phosphate and methyl methacrylate and specific comonomers and functional monomers to introduce phosphate into the PMMA polymer chain, thereby obtaining an optical copolymer flame retardant board with high transparency, good flame retardancy and excellent mechanical properties, thereby solving the problem that PMMA boards in the prior art are difficult to achieve both flame retardancy and transparency.

[0006] The technical solution adopted by the present invention to solve its technical problem is:

[0007] A method for preparing an optical copolymer flame retardant board comprises the following steps:

[0008] S1: Mix 25-50 parts by weight of vinyl phosphate, 2 parts of methyl methacrylate, 1-3 parts of comonomer, and 1-3 parts of functional monomer, add the mixture into a prepolymerization reactor, and perform polymerization reaction at 130-140° C. to obtain a first prepolymer;

[0009] S2: Mixing 90 parts by weight of methyl methacrylate, 5-9 parts by weight of a comonomer, and 5-9 parts by weight of a functional monomer with the first prepolymer, placing the mixture into a tubular reactor, and performing a polymerization reaction at 170-190° C. to obtain a second prepolymer;

[0010] S3: 8 parts of methyl methacrylate, 1-3 parts of comonomer, 9-18 parts of functional monomer and the second prepolymer are mixed according to parts by weight, and the mixture is put into a devolatilizing extruder. After the material is discharged, it is granulated and pressed to obtain an optical copolymer flame retardant board.

[0011] Optionally, the vinyl phosphate is dialkyl vinyl phosphate.

[0012] Optionally, the vinyl dialkyl phosphate is selected from at least one of dimethyl vinyl phosphonate, diethyl vinyl phosphonate, and diisopropyl vinyl phosphonate.

[0013] Optionally, the comonomer is selected from at least one of acrylonitrile, α-methylstyrene, and methyl vinyl ether.

[0014] Optionally, the functional monomer is selected from at least one of vinyl acetate and ethyl vinyl ether.

[0015] Another object of the present invention is to provide an optical copolymer flame retardant board, which is prepared by the above-mentioned method for preparing the optical copolymer flame retardant board.

[0016] Another object of the present invention is to provide a reaction extrusion device for an optical copolymer flame retardant plate, which is used to prepare an optical copolymer flame retardant plate according to the preparation method of the optical copolymer flame retardant plate as described above;

[0017] The reactive extrusion device comprises a prepolymerization reactor, a tubular reactor, and a devolatilization extruder which are arranged in sequence and connected through a pipeline;

[0018] A first material delivery pump is provided on the pipeline between the prepolymerization reactor and the tubular reactor;

[0019] A plurality of first feed ports are provided on the pipeline between the prepolymerization reactor and the tubular reactor, and on the tubular reactor;

[0020] A plurality of second feed ports are provided on the pipeline between the tubular reactor and the devolatilizing extruder, and on the devolatilizing extruder.

[0021] Optionally, a mixer is provided on the pipeline between the prepolymerization reactor and the tubular reactor, and on the pipeline between the tubular reactor and the devolatilization extruder.

[0022] Optionally, the mixer is a static mixer.

[0023] Optionally, the first feed port is connected to a second material delivery pump; the second feed port is connected to a third material delivery pump.

[0024] The beneficial effects of the present invention are:

[0025] The preparation method of the optical copolymer flame retardant board provided by the present invention adopts the method of copolymerizing the flame retardant monomers vinyl phosphate and methyl methacrylate to connect the phosphate into the PMMA polymer chain, thereby obtaining the optical copolymer flame retardant board with high transparency, good flame retardancy and excellent mechanical properties, which helps to expand the application range of the optical copolymer flame retardant board. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The present invention will be further described below with reference to the accompanying drawings and examples.

[0027] Figure 1 It is a schematic structural diagram of the reactive extrusion device in the present invention.

[0028] In the figure: 1-prepolymerization reactor; 2-tubular reactor; 3-devolatilization extruder; 4-first material delivery pump; 5-first feed inlet; 6-second feed inlet; 7-second material delivery pump; 8-third material delivery pump; 9-mixer. DETAILED DESCRIPTION

[0029] The present invention will now be described in further detail. The embodiments described below are exemplary and intended to explain the present invention, but should not be construed as limiting the present invention. All other embodiments obtained by persons of ordinary skill in the art based on the embodiments of the present invention without creative effort are intended to fall within the scope of protection of the present invention.

[0030] In the description of the present invention, it should be understood that the terms "first" and "second" are used only to simplify the description and should not be understood to indicate or imply relative importance, or implicitly specify the number of the technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "plurality" is two or more, unless otherwise specifically defined.

[0031] In order to solve the problem in the prior art that PMMA boards are difficult to achieve both flame retardancy and transparency, the present invention provides a method for preparing an optical copolymer flame retardant board, comprising the following steps:

[0032] S1: Mix 25-50 parts by weight of vinyl phosphate, 2 parts of methyl methacrylate (MMA), 1-3 parts of comonomer, and 1-3 parts of functional monomer, put the mixture into a prepolymerization reactor, and carry out polymerization reaction at 130-140° C. to obtain a first prepolymer;

[0033] S2: Mixing 90 parts by weight of methyl methacrylate, 5-9 parts by weight of a comonomer, and 5-9 parts by weight of a functional monomer with the first prepolymer, placing the mixture into a tubular reactor, and polymerizing the mixture at 170-190° C. to obtain a second prepolymer;

[0034] S3: According to parts by weight, 8 parts of methyl methacrylate, 1-3 parts of comonomer, 9-18 parts of functional monomer and the second prepolymer are mixed, and the mixture is put into a devolatilizing extruder. After discharge, the mixture is granulated and pressed to obtain an optical copolymer flame retardant board.

[0035] The preparation method of the optical copolymer flame retardant board provided by the present invention adopts the method of copolymerizing the flame retardant monomers vinyl phosphate and methyl methacrylate to connect the phosphate into the PMMA polymer chain, thereby obtaining the optical copolymer flame retardant board with high transparency, good flame retardancy and excellent mechanical properties, which helps to expand the application range of the optical copolymer flame retardant board.

[0036] Specifically, in the present invention, the vinyl phosphate is preferably vinyl dialkyl phosphate, and further preferably the vinyl dialkyl phosphate is at least one selected from dimethyl vinyl phosphonate, diethyl vinyl phosphonate, and diisopropyl vinyl phosphonate.

[0037] Due to the molecular structure of vinyl phosphate, after the C=C double bond is initiated to form a free radical, this radical is unstable and will transfer to the α-CH, resulting in low polymerization activity of vinyl phosphate. The reactivity ratios of MMA and vinyl phosphate copolymerization are r1 = 3.98 and r2 = 0.07. If MMA and vinyl phosphate are mixed in a proportion, such as a molar ratio of 7:3, for bulk polymerization, MMA will preferentially polymerize itself, with only a small amount of vinyl phosphate participating in the copolymerization. Only after a large amount of MMA is consumed does the vinyl phosphate gradually and slowly participate in the polymerization, making it difficult to introduce phosphate into the PMMA molecular chain through copolymerization.

[0038] In order to increase the proportion of vinyl phosphate participating in copolymerization, thereby making the prepared optical copolymer flame-retardant board have both transparency and flame retardancy, the present invention provides a segmented feeding process during the preparation process, and introduces comonomers and functional monomers. The segmented feeding process of the present invention controls the concentration ratio of several monomers at each stage of the reaction, thereby affecting the copolymerization ratio. The comonomer is a monomer that can simultaneously copolymerize with vinyl phosphate and MMA, so that the comonomer makes it easier for vinyl phosphate and MMA to undergo polymerization reaction, thereby increasing the proportion of vinyl phosphate participating in the copolymerization.

[0039] Specifically, in the present invention, the comonomer is preferably selected from at least one of acrylonitrile (AN), α-methylstyrene (α-MS), and methyl vinyl ether (MVE).

[0040] The functional monomer in the present invention is more reactive than vinyl phosphate, thereby increasing the conversion rate of vinyl phosphate during the copolymerization reaction and, in turn, the proportion of vinyl phosphate participating in the copolymerization. Furthermore, the functional monomer can be devolatilized and removed in a devolatilizing extruder during the preparation process, so its addition does not affect the performance of the optical copolymer flame-retardant board.

[0041] Specifically, the preferred functional monomer of the present invention is at least one selected from vinyl acetate (VAC) and ethyl vinyl ether (EVE).

[0042] In addition, in order to further increase the proportion of vinyl phosphate participating in the copolymerization, the present invention preferably adopts a step-by-step addition of reactants during the preparation process, and then combines the comonomers and functional monomers in the system to inhibit the polymerization reaction of MMA itself, promote the copolymerization of MMA and vinyl phosphate, thereby increasing the proportion of vinyl phosphate participating in the copolymerization and increasing the content of phosphate in the optical copolymer flame retardant board, so that the prepared optical copolymer flame retardant board can have both transparency and flame retardancy while also having excellent mechanical properties.

[0043] To ensure the smooth progress of the reaction, the present invention preferably adds a first auxiliary agent in step S1, a second auxiliary agent in step S2, and a third auxiliary agent in step S3; and further preferably, the first auxiliary agent, the second auxiliary agent, and the third auxiliary agent are all selected from at least one of an antioxidant, an initiator, and a chain transfer agent. The specific selection can be made according to actual needs.

[0044] Specifically, the present invention preferably selects the above-mentioned antioxidant from one of aromatic amine antioxidants, hindered phenol antioxidants, and phosphite antioxidants; and further preferably selects the antioxidant from at least one of antioxidant 2246 and antioxidant Irgafos168.

[0045] The preferred initiators of the present invention are tert-butyl peroxy-3,5,5-trimethylhexanoate (TBPIN), tert-butyl peroxylaurate, tert-butyl peroxyisopropyl monocarbonate, tert-hexyl peroxyisopropyl monocarbonate (Nouruon 117), tert-butyl peroxyacetate, 1,1-bis(tert-butylperoxy)3,3,5-trimethylcyclohexane (Nouruon 117), 42S), 1,1-bis(tert-butylperoxy)cyclohexane, tert-butylperoxy 2-ethylhexanoate, tert-butylperoxyisobutyrate, tert-hexyl-hexylperoxy 2-ethylhexanoate, di-tert-butyl peroxide, 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane and other organic peroxides; one of the azo compounds such as 2-(carbamoyl azo)-isobutyronitrile, 1,1'-azobis(1-cyclohexanecarbonitrile), 2,2'-azobisisobutyronitrile, 2,2'-azobis(2-methylbutyronitrile), dimethyl 2,2'-azobisisobutyrate, 2,2'-azobis(2,4,4-trimethylpentane) and 2,2'-azobis(2-methylpropane).

[0046] In the present invention, the chain transfer agent is preferably a thiol compound, and more preferably the thiol compound is a primary, secondary or tertiary thiol having an alkyl group or a substituted alkyl group such as n-butyl, isobutyl, n-octyl, n-dodecyl, sec-butyl, sec-dodecyl, tert-butyl mercaptan; an aromatic thiol such as phenyl mercaptan, thiocresol, 4-tert-butyl-o-thiocresol; thioglycolic acid and its esters; a thiol having 3 to 18 carbon atoms such as ethanedithiol.

[0047] Another object of the present invention is to provide an optical copolymer flame retardant board, which is prepared by the preparation method described above.

[0048] The optical copolymer flame retardant board provided by the present invention adopts the method of copolymerizing the flame retardant monomer vinyl phosphate and methyl methacrylate to connect the phosphate into the PMMA polymer chain, thereby obtaining an optical copolymer flame retardant board with high transparency, good flame retardancy and excellent mechanical properties, which helps to expand the scope of application of the optical copolymer flame retardant board.

[0049] The method for preparing the optical copolymer flame retardant board provided by the present invention can be prepared by batch operation or continuous operation. In order to ensure the smooth progress of the reaction and improve the reaction efficiency, another object of the present invention is to provide a reaction extrusion device for the optical copolymer flame retardant board, which is used to prepare the optical copolymer flame retardant board according to the method for preparing the optical copolymer flame retardant board as described above. For details, see Figure 1As shown, the reaction extrusion device includes a prepolymerization reactor 1, a tubular reactor 2, and a devolatilization extruder 3, which are arranged in sequence and connected by pipelines; a first material delivery pump 4 is provided on the pipeline between the prepolymerization reactor 1 and the tubular reactor 2; a plurality of first feed ports 5 are provided on the pipeline between the prepolymerization reactor 1 and the tubular reactor 2, and on the tubular reactor 2; a plurality of second feed ports 6 are provided on the pipeline between the tubular reactor 2 and the devolatilization extruder 3, and on the devolatilization extruder 3.

[0050] The prepolymerization reactor 1 is used to carry out a prepolymerization reaction on the mixed material. The present invention preferably provides the prepolymerization reactor 1 with a stirring device, a torque sensor, a pressure sensor, a temperature sensor, a mixed material feeding heat exchanger, a heating and cooling jacket, etc., wherein the stirring device is used to stir and mix the mixed material continuously entering the prepolymerization reactor 1 with the original internal material; the torque sensor is used to detect the viscosity of the material in the prepolymerization reactor 1 (by converting the viscosity data into a polymerization rate), and the feed temperature is controlled by the mixed material feeding heat exchanger to adjust the viscosity of the material; the mixed material feeding heat exchanger is connected to chilled water and heat transfer oil, and the feed temperature of the mixed material is controlled by switching between hot and cold; the temperature sensor is used to feedback the material temperature; the pressure sensor is used to control the pressure in the prepolymerization reactor 1 to prevent the material from gasifying.

[0051] The first material delivery pump 4 is used to continuously deliver the material in the prepolymerization reactor 1 to the subsequent pipeline. The first material delivery pump 4 is preferably a gear pump.

[0052] Furthermore, in the present invention, a mixer 9 is preferably provided on the pipeline between the prepolymerization reactor 1 and the tubular reactor 2, and on the pipeline between the tubular reactor 2 and the devolatilization extruder 3. The mixer 9 is preferably a static mixer, which is mainly used to mix the materials added from each feed port with the materials in the main line. The mixer 9 is provided with a heating jacket, which can also play the role of heat preservation and heating of the materials.

[0053] The present invention preferably has a tubular reactor 2 with a built-in static mixing device, which is mainly used to promote the mixing and stirring of materials, the reaction of materials and uniform heating; and is provided with a heating jacket, which can play the role of heat preservation and heating materials. The design of the tubular reactor 2 can be flexibly designed and used according to the residence time of the materials.

[0054] The present invention further preferably connects the first feed port 5 to the second material delivery pump 7; the second feed port 6 to the third material delivery pump 8, so that the corresponding materials can be continuously delivered to the tubular reactor 2 and the devolatilization extruder 3 through the second material delivery pump 7 and the third material delivery pump 8 respectively; and, further preferably, each feed port is installed with an electric flow control valve, and the second material delivery pump 7 and the third material delivery pump 8 are both precise feed pumps, so that the required materials can be accurately added to the main line according to the replenishment flow requirements of different pipeline positions; the electric flow control valves and the material delivery pumps are arranged along the main line, and the number and flow requirements are calculated according to information such as the material flow at each position of the main line and the pipeline length.

[0055] The devolatilizing extruder 3 in the present invention is mainly used to devolatilize the unreacted monomers entering therein, and at the same time has a partial reaction extrusion function. It transports the PMMA solution with a polymerization rate of 100% to the pelletizing device or the plate-making device through the end. The devolatilizing extruder 3 is also provided with a functional additive addition port to which various functional additives can be added.

[0056] The reactive extrusion device provided by the present invention can add corresponding reaction materials to the reaction system in batches at different reaction stages, thereby enabling smooth copolymerization of vinyl phosphate and methyl methacrylate, ensuring the proportion of vinyl phosphate participating in the copolymerization, and further enabling the phosphate to be incorporated into the PMMA polymer chain through the copolymerization method, thereby obtaining an optical copolymerization-type flame-retardant board with high transparency, good flame retardancy, and excellent mechanical properties, which helps to expand the scope of application of the optical copolymerization-type flame-retardant board.

[0057] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, specific embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0058] Example 1

[0059] This embodiment provides a method for preparing an optical copolymer flame-retardant board, comprising the following steps:

[0060] S1: According to the formula, dimethyl vinylphosphonate (VPDM), methyl methacrylate (MMA), a comonomer, and a functional monomer are mixed, and a first auxiliary agent is added. After mixing evenly, the mixture is uniformly injected into a prepolymerization reactor 1 at a flow rate of 6500 L / h. The volume of the prepolymerization reactor 1 is 30T. The temperature of the mixture entering the prepolymerization reactor 1 is controlled at 0-10°C. After the mixture enters the prepolymerization reactor 1, a polymerization reaction is carried out at a temperature of 130-140°C. The mixture is polymerized to a polymerization rate of 40-45% and a viscosity of 4000 cp to obtain a first prepolymer. The amount of each material added in this step is shown in Table 1.

[0061] S2: After mixing methyl methacrylate, comonomer, and functional monomer with the first prepolymer according to the formula, a second auxiliary agent is added, and after mixing evenly, the mixture is uniformly injected into the tubular reactor 2 through each first feed port 5 of the tubular reactor 2, and a polymerization reaction is carried out at 170-190° C. The temperature of the material transported to the devolatilization extruder 3 is controlled at 170-190° C. The material is polymerized to a polymerization rate of 70-75% and a viscosity of 20,000 cp to obtain a second prepolymer. The amount of each material added in this step is shown in Table 2;

[0062] S3: According to the formula, methyl methacrylate, comonomer, functional monomer and second prepolymer are mixed, and the third auxiliary agent is added. After mixing evenly, the mixture is uniformly injected into the devolatilizing extruder 3 through each second feed port 6. The materials are reacted and polymerized by the devolatilizing extruder 3 to a polymerization rate of 80-85% and a viscosity of 25000cp. The extruder adopts a twin-screw co-rotating extruder with a screw diameter of 248mm and a power of 1050kW. The remaining 15-20% of unreacted residual monomers are discharged through the devolatilization port of the devolatilizing extruder 3 and collected in a mixed monomer tank after condensation. The automatic sampling equipment automatically samples from the tank every 5 minutes, automatically tests the gas chromatography, and calculates the ratio of MMA, comonomer and functional monomer by program. At the same time, the mass ratio of each material in step S2 is automatically supplemented with monomers to the same mass ratio as that in step S2, and the materials are continuously fed into the tubular reactor 2. After discharge, the materials are granulated and pressed to obtain an optical copolymer flame retardant board. The addition amount of each material in this step is shown in Table 3.

[0063] The preparation process of Example 2 to Example 4 is the same as that of Example 1. The amount of materials added in each step is shown in Table 1 to Table 3, respectively.

[0064] Table 1-Amount of each material added in prepolymerization reactor 1 (the volume of prepolymerization reactor 1 is 30 tons)

[0065]

[0066]

[0067] Table 2 - Addition amount of each material in tubular reactor 2

[0068] Material Name Example 1 Example 2 Example 3 Example 4 MMA(ton) 90 90 90 90 AN (tons) 5 2 α-MS (tons) 2 6 MVE (tons) 9 2 VAC (tons) 5 6 EVE (tons) 9 8 Irgafos 168 (tons) 1 1 1 1 Nouruon 117 (tons) 0.0050 0.0050 Nouruon 42S (tons) 0.0050 0.0050 n-Dodecyl mercaptan 0.0050 0.0050 0.0050 0.0050 Single feed inlet flow 2188L / hour 2362L / hour 2232L / hour 2275L / hour

[0069] Table 3 - Addition amount of each material in devolatilization extruder 3

[0070]

[0071]

[0072] The properties of the optical copolymer flame retardant panels prepared in the above embodiments were tested, and the test results are shown in Table 4:

[0073] Table 4

[0074] Test items Example 1 Example 2 Example 3 Example 4 Appearance Colorless and transparent Colorless and transparent Colorless and transparent Colorless and transparent Transmittance 91.6％ 92.5％ 91.9％ 92.2％ Haze 0.3％ 0.1％ 0.1％ 0.2％ Rockwell hardness 99 93 96 95 Heat deformation temperature 98℃ 91℃ 96℃ 93℃ Notched impact strength <![CDATA[19KJ / m 2 ]]> <![CDATA[25KJ / m 2 ]]> <![CDATA[22KJ / m 2 ]]> <![CDATA[23KJ / m 2 ]]> tensile strength 66MPa 60MPa 65MPa 63MPa Elongation 3.2％ 4.8％ 3.9％ 4.5％ Water absorption 0.1％ 0.4％ 0.3％ 0.3％ UL9 flame retardant rating V0 level V0 level V0 level V0 level

[0075] The preparation process of Comparative Examples 1 to 4 is the same as that of Example 1. The addition amount of each material in step S1 is shown in Table 5, the addition amount of each material in step S2 is shown in Table 6, and the addition amount of each material in step S3 is shown in Table 7.

[0076] Table 5

[0077]

[0078]

[0079] Table 6

[0080] Material Name Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 VPDM 10 0 0 0 MMA 90 90 90 90 AN 2 2 2 α-MS 2 2 2 MVE 2 2 2 VAC 6 6 6 6 Irgafos 168 1 1 1 1 Nouruon 117 0.0050 0.0050 0.0050 0.0050 n-Dodecyl mercaptan 0.0050 0.0050 0.0050 0.0050

[0081] Table 7

[0082] Material Name Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 VPDM 10 0 0 0 MMA 8 8 8 8 AN 1 1 1 α-MS 1 1 1 MVE 1 1 1 VAC 15 15 15 15 Irgafos 168 1 1 1 1 Nouruon 117 0.0010 0.0010 0.0010 0.0010 n-Dodecyl mercaptan 0.0010 0.0010 0.0010 0.0010

[0083] Comparative Example 5

[0084] This comparative example provides a method for preparing a flame retardant board, comprising the following steps:

[0085] S1: After mixing 35 parts of dimethyl vinylphosphonate (VPDM), 100 parts of methyl methacrylate (MMA), 4 parts of AN, 4 parts of α-MS, 4 parts of MVE, and 23 parts of VAC in parts by weight, 3 parts of Irgafos 168 and 0.009 parts of Nouruon 117 were added, and after mixing evenly, the mixture was uniformly injected into the prepolymerization reactor 1. The temperature of the mixture entering the prepolymerization reactor 1 was controlled at 0-10° C. After entering the prepolymerization reactor 1, the mixture was polymerized at a temperature of 130-140° C. to obtain a first prepolymer;

[0086] S2: injecting the first prepolymer into the tubular reactor 2 at a uniform speed, carrying out polymerization reaction at 170-190°C, controlling the temperature of the material transported to the devolatilization extruder 3 at 170-190°C, and reacting to obtain a second prepolymer;

[0087] S3: The second prepolymer is uniformly injected into the devolatilizing extruder 3. After the reaction is carried out in the devolatilizing extruder 3, the extruder adopts a twin-screw co-rotating extruder with a screw diameter of 248 mm and a power of 1050 kW. The remaining unreacted residual monomer is discharged through the devolatilization port of the devolatilizing extruder 3 and collected into a mixed monomer tank after condensation. The automatic sampling equipment automatically samples from the tank every 5 minutes, and automatically tests the gas chromatography, and the program calculates the ratio of MMA, comonomer, and functional monomer. According to the mass ratio of each material in step S1, the monomer is supplemented until the mass ratio of MMA, comonomer, and functional monomer is the same as that in S1, and then continues to be fed into the prepolymerization reactor 1; after discharging, it is granulated and pressed to obtain a flame retardant board;

[0088] In the preparation process provided in this comparative example, all reactants were added into the system from the prepolymerization reactor 1, and the flow rate was controlled at 6500 L / h, so that the materials passed through the prepolymerization reactor 1, the tubular reactor 2, and the devolatilization extruder 3 in sequence for reaction.

[0089] The properties of the optical copolymer flame retardant panels prepared in the above comparative examples were tested, and the test results are shown in Table 8:

[0090] Table 8

[0091]

[0092]

[0093] Each test item in the present invention is tested according to the following methods or standards:

[0094] Appearance: Standard light box D65 light source, visual inspection;

[0095] Transmittance: Tested using a spectrophotometer in accordance with GB / T 2410.

[0096] Haze: Tested using a spectrophotometer in accordance with GB / T 2410.

[0097] Rockwell hardness: tested according to standard GB / T 3398

[0098] Heat deformation temperature: tested in accordance with standard GB / T 1633;

[0099] Notched impact strength: tested in accordance with standard GB / T 1043.1;

[0100] Tensile strength: tested in accordance with standard GB / T 1040;

[0101] Elongation: Tested in accordance with standard GB / T 1040;

[0102] Water absorption: tested in accordance with standard GB / T 1034;

[0103] UL9 flame retardant rating: tested according to the standard UL 94 combustion test method.

[0104] It can be seen from the data in Table 4 that the flame retardant boards prepared in various embodiments of the present invention have the advantages of high transparency and good flame retardant performance, and also have excellent mechanical properties.

[0105] Compared with Example 3, the total amount of VPDM added in Comparative Example 1 remains unchanged. The difference is that the amount of VPDM added in the prepolymerization reactor 1 is reduced, and the amount of VPDM added in the tubular reactor 2 and the devolatilization extruder 3 is increased, resulting in an increased difficulty in copolymerizing VPDM and MMA, a reduced VPDM reaction rate, and a reduced flame retardant performance, which does not reach the V0 level.

[0106] Compared with Example 3, in Comparative Example 2, the amount of VPDM added was reduced, and the flame retardant performance of the flame retardant board was reduced, failing to reach the V0 level.

[0107] Compared with Example 3, in Comparative Example 3, no comonomer was added, the copolymerization effect became worse, and the flame retardant board became yellow and foggy; due to the lack of comonomer, the self-inhibition of VPDM was significant, resulting in low molecular weight, performance deviation, and decreased flame retardancy.

[0108] Compared with Example 3, in Comparative Example 4, no functional monomer was added, and the conversion rate of VPDM decreased. The functional monomer is a monomer that is easy to copolymerize but difficult to self-polymerize, which can promote the improvement of the conversion rate of VPDM. After removal, the content of VPDM in the flame retardant board is greatly reduced, and the flame retardancy is reduced.

[0109] Compared with Example 3, the addition amount of each material in Comparative Example 5 remains unchanged. The difference is that all materials are added in the prepolymerization kettle, and the real-time concentration of each monomer in the reaction system is not controlled, resulting in abnormal copolymerization reaction and VPDM not participating in the copolymerization normally.

[0110] With the above-described preferred embodiments of the present invention as a guide, and with reference to the above description, relevant personnel are fully capable of making various changes and modifications without departing from the technical scope of this invention. The technical scope of this invention is not limited to the contents of the specification and must be determined according to the scope of the claims.

Claims

1. A method for preparing an optical copolymer flame retardant board, characterized in that: The steps include: S1: Mix 25-50 parts by weight of vinyl phosphate, 2 parts of methyl methacrylate, 1-3 parts of comonomer, and 1-3 parts of functional monomer, add the mixture into a prepolymerization reactor, and perform polymerization reaction at 130-140° C. to obtain a first prepolymer; S2: Mixing 90 parts by weight of methyl methacrylate, 5-9 parts by weight of a comonomer, and 5-9 parts by weight of a functional monomer with the first prepolymer, placing the mixture into a tubular reactor, and performing a polymerization reaction at 170-190° C. to obtain a second prepolymer; S3: Mixing 8 parts of methyl methacrylate, 1-3 parts of comonomer, and 9-18 parts of functional monomer with the second prepolymer in parts by weight, feeding the mixture into a devolatilizing extruder, and granulating and pressing the mixture after discharge to obtain an optical copolymer flame retardant board; The comonomer is selected from at least one of acrylonitrile, α-methylstyrene, and methyl vinyl ether; The functional monomer is selected from at least one of vinyl acetate and ethyl vinyl ether.

2. The method for preparing the optical copolymer flame retardant board according to claim 1, wherein: The vinyl phosphate is vinyl dialkyl phosphate.

3. The method for preparing the optical copolymer flame retardant board according to claim 2, wherein: The vinyl dialkyl phosphate is selected from at least one of dimethyl vinyl phosphonate, diethyl vinyl phosphonate, and diisopropyl vinyl phosphonate.

4. An optical copolymer flame retardant board, characterized in that: The optical copolymer flame retardant board is prepared by the preparation method of any one of claims 1 to 3.

Images