CN115215951B - Preparation method of polymethyl methacrylate - Google Patents
Preparation method of polymethyl methacrylate Download PDFInfo
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- CN115215951B CN115215951B CN202211032355.XA CN202211032355A CN115215951B CN 115215951 B CN115215951 B CN 115215951B CN 202211032355 A CN202211032355 A CN 202211032355A CN 115215951 B CN115215951 B CN 115215951B
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- 229920003229 poly(methyl methacrylate) Polymers 0.000 title claims abstract description 37
- 239000004926 polymethyl methacrylate Substances 0.000 title claims abstract description 37
- 238000002360 preparation method Methods 0.000 title claims abstract description 18
- 238000006116 polymerization reaction Methods 0.000 claims abstract description 59
- 238000006243 chemical reaction Methods 0.000 claims abstract description 46
- 239000002904 solvent Substances 0.000 claims abstract description 21
- 239000000178 monomer Substances 0.000 claims abstract description 20
- 238000007670 refining Methods 0.000 claims abstract description 12
- 238000005469 granulation Methods 0.000 claims abstract description 11
- 230000003179 granulation Effects 0.000 claims abstract description 11
- 238000001704 evaporation Methods 0.000 claims abstract description 7
- 230000008020 evaporation Effects 0.000 claims abstract description 6
- 238000001125 extrusion Methods 0.000 claims abstract description 6
- 239000007788 liquid Substances 0.000 claims abstract description 6
- VVQNEPGJFQJSBK-UHFFFAOYSA-N Methyl methacrylate Chemical group COC(=O)C(C)=C VVQNEPGJFQJSBK-UHFFFAOYSA-N 0.000 claims description 43
- 239000000243 solution Substances 0.000 claims description 39
- 239000003999 initiator Substances 0.000 claims description 33
- 238000003756 stirring Methods 0.000 claims description 20
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 20
- 238000000034 method Methods 0.000 claims description 19
- -1 ammonium salt compound Chemical group 0.000 claims description 14
- 239000000376 reactant Substances 0.000 claims description 11
- 238000002156 mixing Methods 0.000 claims description 10
- 239000002808 molecular sieve Substances 0.000 claims description 10
- LPNYRYFBWFDTMA-UHFFFAOYSA-N potassium tert-butoxide Chemical compound [K+].CC(C)(C)[O-] LPNYRYFBWFDTMA-UHFFFAOYSA-N 0.000 claims description 10
- URGAHOPLAPQHLN-UHFFFAOYSA-N sodium aluminosilicate Chemical compound [Na+].[Al+3].[O-][Si]([O-])=O.[O-][Si]([O-])=O URGAHOPLAPQHLN-UHFFFAOYSA-N 0.000 claims description 10
- NHGXDBSUJJNIRV-UHFFFAOYSA-M tetrabutylammonium chloride Chemical compound [Cl-].CCCC[N+](CCCC)(CCCC)CCCC NHGXDBSUJJNIRV-UHFFFAOYSA-M 0.000 claims description 10
- VDZOOKBUILJEDG-UHFFFAOYSA-M tetrabutylammonium hydroxide Chemical compound [OH-].CCCC[N+](CCCC)(CCCC)CCCC VDZOOKBUILJEDG-UHFFFAOYSA-M 0.000 claims description 10
- 239000006185 dispersion Substances 0.000 claims description 8
- 238000004519 manufacturing process Methods 0.000 claims description 8
- MFRIHAYPQRLWNB-UHFFFAOYSA-N sodium tert-butoxide Chemical compound [Na+].CC(C)(C)[O-] MFRIHAYPQRLWNB-UHFFFAOYSA-N 0.000 claims description 8
- BAPJBEWLBFYGME-UHFFFAOYSA-N Methyl acrylate Chemical compound COC(=O)C=C BAPJBEWLBFYGME-UHFFFAOYSA-N 0.000 claims description 6
- 239000012528 membrane Substances 0.000 claims description 6
- 239000000203 mixture Substances 0.000 claims description 6
- 238000007664 blowing Methods 0.000 claims description 5
- 238000004821 distillation Methods 0.000 claims description 5
- KWYHDKDOAIKMQN-UHFFFAOYSA-N N,N,N',N'-tetramethylethylenediamine Chemical compound CN(C)CCN(C)C KWYHDKDOAIKMQN-UHFFFAOYSA-N 0.000 claims description 4
- LZWQNOHZMQIFBX-UHFFFAOYSA-N lithium;2-methylpropan-2-olate Chemical compound [Li+].CC(C)(C)[O-] LZWQNOHZMQIFBX-UHFFFAOYSA-N 0.000 claims description 4
- CQEYYJKEWSMYFG-UHFFFAOYSA-N butyl acrylate Chemical compound CCCCOC(=O)C=C CQEYYJKEWSMYFG-UHFFFAOYSA-N 0.000 claims description 3
- 239000011261 inert gas Substances 0.000 claims description 3
- 239000011259 mixed solution Substances 0.000 claims description 3
- SZWHXXNVLACKBV-UHFFFAOYSA-N tetraethylphosphanium Chemical compound CC[P+](CC)(CC)CC SZWHXXNVLACKBV-UHFFFAOYSA-N 0.000 claims description 3
- 238000009826 distribution Methods 0.000 abstract description 8
- 238000010539 anionic addition polymerization reaction Methods 0.000 abstract description 7
- 229920000642 polymer Polymers 0.000 abstract description 4
- 239000004973 liquid crystal related substance Substances 0.000 abstract description 2
- 239000013307 optical fiber Substances 0.000 abstract description 2
- YXFVVABEGXRONW-UHFFFAOYSA-N Toluene Natural products CC1=CC=CC=C1 YXFVVABEGXRONW-UHFFFAOYSA-N 0.000 description 23
- 239000000047 product Substances 0.000 description 11
- JRMUNVKIHCOMHV-UHFFFAOYSA-M tetrabutylammonium bromide Chemical group [Br-].CCCC[N+](CCCC)(CCCC)CCCC JRMUNVKIHCOMHV-UHFFFAOYSA-M 0.000 description 8
- 208000005156 Dehydration Diseases 0.000 description 6
- 230000018044 dehydration Effects 0.000 description 6
- 238000006297 dehydration reaction Methods 0.000 description 6
- CERQOIWHTDAKMF-UHFFFAOYSA-N Methacrylic acid Chemical compound CC(=C)C(O)=O CERQOIWHTDAKMF-UHFFFAOYSA-N 0.000 description 5
- 238000010526 radical polymerization reaction Methods 0.000 description 5
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 4
- WYURNTSHIVDZCO-UHFFFAOYSA-N Tetrahydrofuran Chemical compound C1CCOC1 WYURNTSHIVDZCO-UHFFFAOYSA-N 0.000 description 4
- KWGKDLIKAYFUFQ-UHFFFAOYSA-M lithium chloride Chemical compound [Li+].[Cl-] KWGKDLIKAYFUFQ-UHFFFAOYSA-M 0.000 description 4
- 229910001507 metal halide Inorganic materials 0.000 description 4
- 150000005309 metal halides Chemical class 0.000 description 4
- 150000001339 alkali metal compounds Chemical class 0.000 description 3
- 125000000129 anionic group Chemical group 0.000 description 3
- 230000001276 controlling effect Effects 0.000 description 3
- 238000001816 cooling Methods 0.000 description 3
- 238000005516 engineering process Methods 0.000 description 3
- 238000010551 living anionic polymerization reaction Methods 0.000 description 3
- 230000001105 regulatory effect Effects 0.000 description 3
- 238000012360 testing method Methods 0.000 description 3
- KAKZBPTYRLMSJV-UHFFFAOYSA-N Butadiene Chemical compound C=CC=C KAKZBPTYRLMSJV-UHFFFAOYSA-N 0.000 description 2
- RRHGJUQNOFWUDK-UHFFFAOYSA-N Isoprene Chemical compound CC(=C)C=C RRHGJUQNOFWUDK-UHFFFAOYSA-N 0.000 description 2
- PPBRXRYQALVLMV-UHFFFAOYSA-N Styrene Chemical compound C=CC1=CC=CC=C1 PPBRXRYQALVLMV-UHFFFAOYSA-N 0.000 description 2
- 229910052782 aluminium Inorganic materials 0.000 description 2
- 229910052802 copper Inorganic materials 0.000 description 2
- 239000010949 copper Substances 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 238000005265 energy consumption Methods 0.000 description 2
- 239000012467 final product Substances 0.000 description 2
- 239000003112 inhibitor Substances 0.000 description 2
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 2
- 229910052742 iron Inorganic materials 0.000 description 2
- 229910052744 lithium Inorganic materials 0.000 description 2
- 238000010550 living polymerization reaction Methods 0.000 description 2
- 150000002736 metal compounds Chemical class 0.000 description 2
- 229910052759 nickel Inorganic materials 0.000 description 2
- PXHVJJICTQNCMI-UHFFFAOYSA-N nickel Substances [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 2
- 229910052757 nitrogen Inorganic materials 0.000 description 2
- 230000035484 reaction time Effects 0.000 description 2
- 238000011160 research Methods 0.000 description 2
- 238000007086 side reaction Methods 0.000 description 2
- YLQBMQCUIZJEEH-UHFFFAOYSA-N tetrahydrofuran Natural products C=1C=COC=1 YLQBMQCUIZJEEH-UHFFFAOYSA-N 0.000 description 2
- 238000012546 transfer Methods 0.000 description 2
- 125000002915 carbonyl group Chemical group [*:2]C([*:1])=O 0.000 description 1
- 238000012670 controlled anionic polymerization Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 238000010292 electrical insulation Methods 0.000 description 1
- 230000005764 inhibitory process Effects 0.000 description 1
- 239000003446 ligand Substances 0.000 description 1
- 230000003287 optical effect Effects 0.000 description 1
- 150000004714 phosphonium salts Chemical group 0.000 description 1
- 230000008092 positive effect Effects 0.000 description 1
- 150000003242 quaternary ammonium salts Chemical class 0.000 description 1
- 229920006395 saturated elastomer Polymers 0.000 description 1
- 230000002194 synthesizing effect Effects 0.000 description 1
- ISXSCDLOGDJUNJ-UHFFFAOYSA-N tert-butyl prop-2-enoate Chemical compound CC(C)(C)OC(=O)C=C ISXSCDLOGDJUNJ-UHFFFAOYSA-N 0.000 description 1
- 125000003944 tolyl group Chemical group 0.000 description 1
- 238000002834 transmittance Methods 0.000 description 1
- 239000012780 transparent material Substances 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
- C08F120/00—Homopolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and only one being terminated by only one carboxyl radical or a salt, anhydride, ester, amide, imide or nitrile thereof
- C08F120/02—Monocarboxylic acids having less than ten carbon atoms; Derivatives thereof
- C08F120/10—Esters
- C08F120/12—Esters of monohydric alcohols or phenols
- C08F120/14—Methyl esters, e.g. methyl (meth)acrylate
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
- C08F2/00—Processes of polymerisation
- C08F2/01—Processes of polymerisation characterised by special features of the polymerisation apparatus used
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
- C08F220/00—Copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and only one being terminated by only one carboxyl radical or a salt, anhydride ester, amide, imide or nitrile thereof
- C08F220/02—Monocarboxylic acids having less than ten carbon atoms; Derivatives thereof
- C08F220/10—Esters
- C08F220/12—Esters of monohydric alcohols or phenols
- C08F220/14—Methyl esters, e.g. methyl (meth)acrylate
Landscapes
- Chemical & Material Sciences (AREA)
- Health & Medical Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Medicinal Chemistry (AREA)
- Polymers & Plastics (AREA)
- Organic Chemistry (AREA)
- Addition Polymer Or Copolymer, Post-Treatments, Or Chemical Modifications (AREA)
Abstract
The invention provides a preparation method of polymethyl methacrylate, belongs to the technical field of polymers, and can solve the problem that room-temperature controllable polymerization cannot be realized by active anion polymerization of polymethyl methacrylate. The preparation method comprises the steps of monomer and comonomer refining and rectifying, solvent refining and rectifying, preparing a polymerization preparation liquid, carrying out polymerization reaction, flash evaporation devolatilization and extrusion granulation. The polymethyl methacrylate product obtained by the technical scheme of the invention has adjustable molecular weight distribution, mild polymerization process and conversion rate of more than or equal to 97%, and can be applied to the fields of liquid crystal display, LED and optical fiber.
Description
Technical Field
The invention belongs to the technical field of polymers, and particularly relates to a preparation method of polymethyl methacrylate.
Background
Polymethyl methacrylate (PMMA) has good electrical insulation, solvent resistance and weather resistance and certain heat and cold resistance, and is one of the most excellent high-molecular transparent materials at present. After being processed, the polymethyl methacrylate can be applied to the fields of advertising lamp boxes, labels, lamps, bathtubs, instruments, living goods, furniture and the like, and with the advent of the 5G age, the rapid development of the liquid crystal display, LED field and optical fiber field is driven, and the demand for high-end polymethyl methacrylate is also rapidly increased.
The traditional polymethyl methacrylate production mainly adopts free radical polymerization, polymerization is carried out by adopting a kettle type series connection or kettle pipe type series connection device, and the whole polymerization process adopts a sectional polymerization mode, but the limitation of the obtained product is determined due to uncontrollable free radical polymerization technology. The polymethyl methacrylate obtained by the free radical polymerization production method has wide molecular weight distribution, can only meet the common application, has long polymerization reaction time and relatively difficult mass and heat transfer control, and leads the conversion rate of the whole process device to only reach 60-70 percent at most, and the device utilization rate is low. If the high-end polymethyl methacrylate product with narrow molecular weight distribution is produced, the conversion rate needs to be controlled below 50%, then the polymerization solution is transferred to a devolatilization device, and finally the polymerization solution is granulated and molded by an extruder, so that the gel effect caused by overlarge viscosity is avoided. The method for producing the high-end polymethyl methacrylate has the defects of long overall reaction time, high energy consumption and high cost for recovering the monomer.
The role of living anionic polymerization in the fields of synthesizing polymers with narrow molecular weight distribution and polymers with controllable molecular weight and molecular structure is always important, and many research results have been industrialized. However, the advantages of living anionic polymerization are not fully utilized, and the anionic polymerization monomers which can be industrially produced are limited to only nonpolar monomers such as styrene, isoprene and butadiene. Anionic polymerization of polar monomers such as Methyl Methacrylate (MMA) has not been commercialized until now. In fact, as early as 1956, anionic living polymerization was found to synthesize polymethyl methacrylate, and although polymerization of polymethyl methacrylate was achieved, the entire polymerization process did not exhibit controllability. Subsequent studies have demonstrated that anionic polymerization of methyl methacrylate-based polar monomers is often accompanied by side reactions caused by reactive carbonyl groups. Thus, research into anionic polymerization of such monomers has been focused mainly on inhibition of side reactions, in which Teyssir uses LiCl as an inhibitor to achieve living anionic polymerization of t-butyl acrylate in tetrahydrofuran for the first time; kitayama uses tetramethyl ethylenediamine as an inhibitor, and achieves controlled polymerization of methyl methacrylate in tetrahydrofuran. Although these ligands can effectively realize the active controlled polymerization of methyl methacrylate, they have a serious disadvantage in the use process that they cannot complete the polymerization at room temperature or higher, for example LiCl loses effect at-40 ℃ or higher, the extremely low applicable temperature thereof greatly limits the controlled anionic polymerization of methyl methacrylate, and industrialization cannot be implemented.
Therefore, the industrial progress of living polymerization of polymethyl methacrylate has also a problem of how to allow the polymerization to be completed at room temperature or higher, and the molecular weight and distribution and molecular structure of polymethyl methacrylate to achieve controllability.
Disclosure of Invention
Aiming at the technical problem that the room temperature controllable polymerization cannot be realized by the active anion polymerization of polymethyl methacrylate, the invention provides a preparation method of polymethyl methacrylate, which has continuous and controllable polymerization process, high automation degree and adjustable molecular weight distribution.
In order to achieve the above purpose, the invention adopts the following technical scheme: a method for preparing polymethyl methacrylate, comprising the following steps:
refining and rectifying the monomer and comonomer: after the methyl methacrylate monomer and the comonomer are subjected to water removal treatment by a molecular sieve tower, respectively carrying out reduced pressure distillation to obtain a refined methyl methacrylate monomer and a refined comonomer;
refining and rectifying the solvent: after the solvent is dehydrated by a molecular sieve tower, blowing inert gas to obtain an anhydrous and anaerobic solvent;
preparing a polymerization preparation liquid: adding an initiator A into a stirring kettle containing a refined methyl methacrylate monomer or a mixture of the refined methyl methacrylate monomer and a refined comonomer, and stirring to obtain a reaction solution A; adding an initiator B into a stirring kettle containing an anhydrous and anaerobic solvent, and stirring to obtain a reaction solution B;
polymerization reaction: dispersing the reaction solution A into the reaction solution B through a micro mixer with a film dispersion for mixing reaction, and after the reaction solution A and the reaction solution B are fully and uniformly mixed, entering a micro reactor for carrying out an enhanced heat exchange process and a polymerization reaction to obtain a polymerization reactant, wherein the polymerization conversion rate is more than or equal to 97%;
flash devolatilization and extrusion granulation: and (3) adding the polymerization reactant into a flash tank for flash evaporation, and then, putting the polymerization reactant into a devolatilizing double-screw extruder for devolatilizing granulation to obtain polymethyl methacrylate.
Preferably, the comonomer is at least one of methyl acrylate or butyl acrylate.
Preferably, the mass ratio of the methyl methacrylate monomer to the comonomer is (19-2): 1.
Preferably, the mass ratio of the refined methyl methacrylate monomer or the mixture of the refined methyl methacrylate monomer and the refined comonomer to the solvent is 1: (0.2-10). Preferably, the initiator A is a metal compound, and at least one of a metal halide, an organic alkali metal compound or an organic aluminum compound is adopted, wherein the metal halide comprises at least one of copper halide, lithium halide, iron halide or nickel halide.
Preferably, the initiator B is an ammonium salt compound, and at least one of N, N, N, N-tetramethyl ethylenediamine, tetraethyl phosphine bromide, tetrabutylammonium chloride and tetrabutylammonium hydroxide is adopted.
Preferably, the molar ratio of initiator a to initiator B is 1: (0.5-2), the mole ratio of the initiator A to the methyl methacrylate monomer is 1: (100-1000).
Preferably, the structure of the membrane dispersion micromixer is a transverse T-shaped mixing structure.
Preferably, the residence time of the mixed solution of the reaction solution A and the reaction solution B in the micro-channel of the micro-reactor is 4s to 120s.
Preferably, the microreactor adopts a tubular reactor or a plate-type micro-mixing structure; the micro mixer and the micro reactor are externally connected with circulating water, and the temperature of the circulating water is set to be-10 ℃ to 40 ℃.
Compared with the prior art, the invention has the advantages and positive effects that: the invention uses the technological scheme that the anionic active polymerization technology is combined with the micromixer device, and utilizes the advantages of efficient heat transfer and mixing of the micromixer to realize the room temperature controllable polymerization of PMMA active anionic polymerization; the device used in the technical scheme is smaller than the container space of the traditional free radical polymerization device, the molecular weight distribution of PMMA products is adjustable, the polymerization conversion rate is more than or equal to 97%, the differentiated production of different types of products can be realized, the utilization rate of the device is greatly improved, the potential safety hazard caused by the traditional strong heat release of polymerization is eliminated, the safety risk is reduced, the space, the labor and the cost are saved, the continuous and controllable polymerization process is realized, and the degree of automation is high.
Drawings
FIG. 1 is a process flow diagram of a first embodiment of a method for preparing polymethyl methacrylate according to the present invention;
FIG. 2 is a process flow diagram of a second embodiment of a method for preparing polymethyl methacrylate according to the present invention;
Detailed Description
The following description of the technical solutions in the embodiments of the present invention will be clear and complete, and it is obvious that the described embodiments are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
The embodiment of the invention provides a preparation method of polymethyl methacrylate, which adopts a process scheme of combining an anionic active polymerization technology with a micromixer device, wherein the used device has smaller container space than a traditional free radical polymerization device, can realize the differentiated production of different types of products, greatly improves the utilization rate of the device, eliminates the potential safety hazard caused by the traditional strong heat release of polymerization, saves space, manpower and cost, realizes the continuous and controllable polymerization process, has high degree of automation, has adjustable molecular weight distribution of polymethyl methacrylate, and has the polymerization conversion rate of more than or equal to 97 percent. As shown in fig. 1, in a first embodiment of the present invention, the method specifically includes the following steps:
refining and rectifying the monomer and comonomer: after methyl methacrylate monomer and comonomer are subjected to fixed bed dehydration treatment of a molecular sieve tower, detecting the water content to be less than or equal to 90ppm, and respectively carrying out reduced pressure distillation to obtain anhydrous, anaerobic and polymerization inhibitor-free refined methyl methacrylate monomer and refined comonomer, wherein the comonomer is at least one of methyl acrylate or butyl acrylate, and the mass ratio of the methyl methacrylate monomer to the comonomer is (19-2) 1;
refining and rectifying the solvent: after the solvent is subjected to fixed bed dehydration treatment of a molecular sieve tower, detecting that the water content is less than or equal to 120ppm, preferably the water content is less than or equal to 90ppm, and blowing by using inert gas to obtain an anhydrous and anaerobic solvent;
preparing a polymerization preparation liquid: adding an initiator A into a stirring kettle containing a mixture of a refined methyl methacrylate monomer and a refined comonomer, and stirring at 40-80 ℃ for 30-60 min to fully dissolve the initiator A to obtain a reaction solution A; adding an initiator B into a stirring kettle containing a solvent, and stirring at 40-80 ℃ for 30-60 min to obtain a reaction solution B;
polymerization reaction: dispersing the prepared reaction solution A into a solution B through a micro-mixer with a membrane dispersion for mixed reaction, fully and uniformly mixing the solution A and the solution B, and then entering a tubular reactor or a plate-type micro-mixing structure and other micro-reactors for enhanced heat exchange process and polymerization reaction to obtain a polymerization reactant, wherein the structure of the micro-mixer with the membrane dispersion is a transverse T-shaped mixed structure, the residence time of the mixed solution of the reaction solution A and the reaction solution B in a micro-reactor micro-channel is 4-120 s, the micro-mixer and the micro-reactor are externally connected with circulating water, and the temperature of the circulating water is set to be-10-40 ℃;
flash devolatilization and extrusion granulation: preheating the polymerization reactant to 150-240 ℃, controlling the pressure to be 1.5 MPaG-2 MPaG, ensuring the pressure in the preheating process to be larger than the saturated vapor pressure of volatile matters at the temperature, preventing the volatile matters in the preheating process from evaporating in advance, cooling and reducing the pressure through a pressure regulating valve, then introducing the preheated volatile matters into a flash tank for flash evaporation for 5-10 min, removing the solvent added in the polymerization reaction and unreacted monomers, and then introducing the obtained product into a devolatilizing twin-screw extruder for devolatilization granulation to obtain polymethyl methacrylate.
In an alternative embodiment, the solvent is preferably toluene, and the mass ratio of the mixture of refined methyl methacrylate monomer and refined comonomer to the solvent is 1: (0.2-10).
In an alternative embodiment, the initiator a is a metal compound, and at least one of a metal halide, an organic alkali metal compound or an organic aluminum compound is used, wherein the metal halide comprises at least one of a copper halide, a lithium halide, an iron halide or a nickel halide, and the organic alkali metal compound comprises at least one of potassium tert-butoxide, sodium tert-butoxide or lithium tert-butoxide; the initiator B is an ammonium salt compound, specifically an organic ammonium salt compound, comprising quaternary ammonium salt and quaternary phosphonium salt, and adopts at least one of N, N, N, N-tetramethyl ethylenediamine, tetraethyl phosphine bromide, tetrabutylammonium chloride and tetrabutylammonium hydroxide. Wherein, the mol ratio of the initiator A to the initiator B is 1: (0.5-2), the mole ratio of the initiator A to the methyl methacrylate monomer is 1: (100-1000).
As shown in FIG. 2, another embodiment of the present invention differs from the specific embodiment in that no comonomer is used in the process flow and no comonomer finishing rectification is required.
In order to more clearly and in detail describe the preparation method of polymethyl methacrylate provided by the embodiment of the present invention, the following description will be made with reference to specific examples.
Example 1
In this embodiment, the initiator a is potassium tert-butoxide, the initiator B is tetrabutylammonium bromide, the molar ratio of the potassium tert-butoxide, the tetrabutylammonium bromide and the methyl methacrylate monomer is 1:1:800, the mass ratio of the methyl methacrylate monomer to toluene is 1:2, the temperature of the circulating water is set to 5 ℃, and the method specifically comprises the following operation steps:
refining and rectifying monomers: after the methyl methacrylate monomer is subjected to fixed bed dehydration treatment of a molecular sieve tower, detecting the water content to be less than or equal to 90ppm, and then carrying out reduced pressure distillation to obtain the anhydrous, anaerobic and polymerization inhibitor-free refined methyl methacrylate monomer;
refining and rectifying the solvent: after the toluene solvent is subjected to dehydration treatment by a molecular sieve tower fixed bed, detecting that the water content is less than or equal to 120ppm, and blowing nitrogen to obtain an anhydrous and anaerobic toluene solvent;
preparing a polymerization preparation liquid: adding potassium tert-butoxide into a stirring kettle containing refined methyl methacrylate monomer, and stirring at 40 ℃ for 30min to obtain a reaction solution A; adding tetrabutylammonium bromide into a stirring kettle containing anhydrous and anaerobic toluene solvent, and stirring at 80 ℃ for 60min to obtain a reaction solution B;
polymerization reaction: dispersing the prepared reaction solution A into the reaction solution B through a micro-mixer with a membrane dispersion for mixed reaction, fully and uniformly mixing the reaction solution A and the reaction solution B, and then entering a tubular reactor for a reinforced heat exchange process and polymerization reaction for 100s to obtain a polymerization reactant;
flash devolatilization and extrusion granulation: preheating the polymerization reactant to 150-240 ℃, controlling the pressure to be 1.5 MPaG-2 MPaG, cooling and depressurizing through a pressure regulating valve, then entering a flash tank for flash evaporation, and then entering a devolatilizing double-screw extruder for devolatilizing granulation to obtain a final product.
Example 2
Unlike example 1, in this example, initiator A was sodium t-butoxide, initiator B was tetrabutylammonium chloride, the molar ratio of sodium t-butoxide, tetrabutylammonium chloride and methyl methacrylate monomer was 1:1:800, the mass ratio of methyl methacrylate monomer to toluene was 1:3, and the circulating water temperature was set to 10 ℃.
The preparation method is the same as in example 1.
Example 3
Unlike example 1, in this example, initiator A was lithium t-butoxide, initiator B was tetrabutylammonium bromide, the molar ratio of lithium t-butoxide, tetrabutylammonium bromide to methyl methacrylate monomer was 1:1:800, the mass ratio of methyl methacrylate monomer to toluene was 1:3, and the circulating water temperature was set to 10 ℃.
The preparation method is the same as in example 1.
Example 4
In this embodiment, the initiator a is potassium tert-butoxide, the initiator B is tetrabutylammonium hydroxide, the molar ratio of potassium tert-butoxide, tetrabutylammonium hydroxide and methyl methacrylate monomer is 1:1:800, the mass ratio of methyl methacrylate monomer, methacrylic acid monomer and toluene is 2:1:5, and the temperature of circulating water is set to 3 ℃, and the method specifically comprises the following steps:
refining and rectifying the monomer and comonomer: after the methyl methacrylate monomer and the methacrylic acid monomer are subjected to fixed bed dehydration treatment of a molecular sieve tower, detecting the water content to be less than or equal to 90ppm, and respectively carrying out reduced pressure distillation to obtain an anhydrous, anaerobic and polymerization inhibitor-free refined methyl methacrylate monomer and a refined methacrylic acid monomer;
refining and rectifying the solvent: after the toluene solvent is subjected to dehydration treatment by a molecular sieve tower fixed bed, detecting that the water content is less than or equal to 120ppm, and blowing nitrogen to obtain an anhydrous and anaerobic toluene solvent;
preparing a polymerization preparation liquid: adding potassium tert-butoxide into a stirring kettle containing a refined methyl methacrylate monomer and a refined methacrylic acid monomer, and stirring for 30min at 40 ℃ to obtain a reaction solution A; adding tetrabutylammonium bromide into a stirring kettle containing anhydrous and anaerobic toluene solvent, and stirring at 80 ℃ for 60min to obtain a reaction solution B;
polymerization reaction: dispersing the prepared reaction solution A into the reaction solution B through a micro-mixer with a membrane dispersion for mixed reaction, fully and uniformly mixing the reaction solution A and the reaction solution B, and then entering a tubular reactor for a reinforced heat exchange process and polymerization reaction for 100s to obtain a polymerization reactant;
flash devolatilization and extrusion granulation: preheating the polymerization reactant to 150-240 ℃, controlling the pressure to be 1.5 MPaG-2 MPaG, cooling and depressurizing through a pressure regulating valve, then entering a flash tank for flash evaporation, and then entering a devolatilizing double-screw extruder for devolatilizing granulation to obtain a final product.
Example 5
Unlike example 4, in this example, initiator A was potassium t-butoxide, initiator B was tetrabutylammonium bromide, the molar ratio of potassium t-butoxide, tetrabutylammonium bromide to methyl methacrylate monomer was 1:1:800, the mass ratio of methyl methacrylate monomer, methacrylic acid monomer to toluene was 3:1:8, and the circulating water temperature was set to 4 ℃.
The preparation method is the same as in example 4.
Performance testing
The products prepared in examples 1-5 above were tested for the following criteria, and the specific data are shown in Table 1.
TABLE 1 product Performance index test data
As can be seen from the test data of the product performance indexes in Table 1, the transmittance of the polymethyl methacrylate prepared by the technical scheme of the invention is more than 92%, the product reaches the use standard of the optical PMMA product, the monomer conversion rate is more than or equal to 97%, and the energy consumption for recovering the monomer is reduced.
Claims (4)
1. The preparation method of polymethyl methacrylate is characterized by comprising the following steps of:
refining and rectifying the monomer and comonomer: after the methyl methacrylate monomer and the comonomer are subjected to water removal treatment by a molecular sieve tower, respectively carrying out reduced pressure distillation to obtain a refined methyl methacrylate monomer and a refined comonomer;
refining and rectifying the solvent: after the solvent is dehydrated by a molecular sieve tower, blowing inert gas to obtain an anhydrous and anaerobic solvent;
preparing a polymerization preparation liquid: adding an initiator A into a stirring kettle containing a refined methyl methacrylate monomer or a mixture of the refined methyl methacrylate monomer and a refined comonomer, and stirring at 40-80 ℃ for 30-60 min to fully dissolve the initiator A to obtain a reaction solution A; adding an initiator B into a stirring kettle containing an anhydrous anaerobic solvent, and stirring at 40-80 ℃ for 30-60 min to obtain a reaction solution B;
polymerization reaction: dispersing the reaction solution A into the reaction solution B through a micro mixer with a film dispersion for mixing reaction, and after the reaction solution A and the reaction solution B are fully and uniformly mixed, entering a micro reactor for carrying out an enhanced heat exchange process and a polymerization reaction to obtain a polymerization reactant, wherein the polymerization conversion rate is more than or equal to 97%; the molar ratio of initiator A to initiator B is 1: (0.5-2), wherein the molar ratio of the initiator A to the methyl methacrylate monomer is 1: (100-1000); the residence time of the mixed solution of the reaction solution A and the reaction solution B in the micro-channel of the micro-reactor is 4-120 s;
flash devolatilization and extrusion granulation: the polymerization reactant is added into a flash tank for flash evaporation, and then enters a devolatilizing double-screw extruder for devolatilization and granulation to obtain polymethyl methacrylate;
the initiator A is at least one of potassium tert-butoxide, sodium tert-butoxide or lithium tert-butoxide;
the initiator B is an ammonium salt compound and adopts at least one of N, N, N, N-tetramethyl ethylenediamine, tetraethyl phosphine bromide, tetrabutylammonium chloride and tetrabutylammonium hydroxide;
the structure of the membrane dispersion micromixer is a transverse T-shaped mixed structure;
the micro-reactor adopts a tubular reactor or a plate type micro-mixing structure; the micro mixer and the micro reactor are externally connected with circulating water, and the temperature of the circulating water is set to be-10 ℃ to 40 ℃.
2. The method for producing polymethyl methacrylate according to claim 1, wherein the comonomer is at least one of methyl acrylate or butyl acrylate.
3. The method for producing polymethyl methacrylate according to claim 1, wherein the mass ratio of the methyl methacrylate monomer to the comonomer is (19-2): 1.
4. The method for producing polymethyl methacrylate according to claim 1, wherein the mass ratio of the purified methyl methacrylate monomer or the mixture of the purified methyl methacrylate monomer and the purified comonomer to the solvent is 1: (0.2-10).
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