CN112940160B - Method for synthesizing ultra-high molecular weight polymethyl methacrylate - Google Patents
Method for synthesizing ultra-high molecular weight polymethyl methacrylate Download PDFInfo
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- 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
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Abstract
The invention belongs to the field of synthesis of high polymer materials, and particularly relates to a synthesis method of ultra-high molecular weight polymethyl methacrylate. A method for synthesizing ultra-high molecular weight polymethyl methacrylate at least comprises the following steps: (1) introducing protective gas into a reaction container, adding deionized water, a first emulsifier, an auxiliary agent and methyl methacrylate, and heating to a first reaction temperature; (2) preparing a pre-emulsion of methyl methacrylate at room temperature; (3) and (2) after the temperature in the step (1) is raised to the specified temperature, sequentially adding a first initiator and/or a first auxiliary initiator, raising the temperature to a second reaction temperature, starting to dropwise add the pre-emulsion prepared in the step (2), after dropwise addition is finished, raising the temperature to a third reaction temperature, preserving heat, and obtaining solid polymethyl methacrylate after finishing dropwise addition. The synthesis method of the technical scheme is simple, environment-friendly, high in safety, low in requirement on refrigeration capacity in the synthesis process, and more suitable for industrial production.
Description
Technical Field
The invention belongs to the field of synthesis of high polymer materials, and particularly relates to a synthesis method of ultra-high molecular weight polymethyl methacrylate.
Background
Polymethyl methacrylate (PMMA), commonly known as plexiglass, is the best quality transparent polymeric material to date and is inexpensive. Compared with inorganic glass, the glass has high transparency and better impact resistance, the impact resistance is 200 times of that of inorganic glass products, and the risk of fracture is hardly caused. PMMA has stable chemical performance and balanced physical and mechanical properties, has weather resistance and excellent optical property, and the white light penetrability is up to 92 percent and is higher than that of common inorganic glass by more than 10 percent. Therefore, PMMA is widely applied to the fields of aviation, construction, agriculture, optical instruments and the like. The molecular weight of polymethyl methacrylate is found to be one of the most important indicators of product quality. The molecular weight of the modified polycarbonate not only affects the physical and mechanical properties of a finished product, but also affects the reprocessing and forming of the product, and is one of the main factors for restricting the application performance of the modified polycarbonate. Various properties of PMMA, such as heat resistance, abrasion resistance, organic solvent resistance, and room temperature creep resistance, are enhanced as the molecular weight of PMMA increases. The ordinary PMMA has poor wear resistance and impact resistance, the impact resistance of the PMMA can be greatly improved after the molecular weight of the PMMA is improved, the ultrahigh molecular weight PMMA can maintain the mechanical strength for a long time even at the high temperature of 213 ℃, has small deformation, strong toughness and scratch resistance hardness, high wear resistance and strong impact resistance, and can be used as a transparent cabin cover of a fighter.
The PMMA is synthesized mainly by bulk polymerization, the production process is simple, no solvent is recovered, no sewage is treated, the PMMA is pure and has no impurities, but the system is viscous, the mass transfer and the heat transfer are difficult, and the molecular weight of the PMMA is very low; solution polymerization, wherein the viscosity of a polymerization system is low, mass transfer, heat transfer and reaction temperature are easy to control, but the solvent amount in the system is large, the monomer concentration is low, the polymerization speed is low, the recovery energy consumption is large, the production efficiency is low, and the PMMA molecular weight is still low; suspension polymerization, high conversion rate, low system viscosity, easy control of reaction temperature and high PMMA molecular weight; emulsion polymerization, high polymerization speed, environmental protection, safety, easy removal of reaction heat, simple process, very high PMMA molecular weight and easy industrial production.
Patent No. CN109280114A discloses a method for preparing PMMA with high molecular weight and narrow molecular weight distribution, which comprises the steps of synthesizing a target product through the combined action of an iodo compound generated in situ and an additive, wherein the prepared PMMA has a molecular weight of 3.7-17 ten thousand, too small, poor heat resistance, wear resistance and impact resistance, and complicated operation process, which is not suitable for industrial production. Patent No. CN108948243A discloses a method for preparing polymethyl methacrylate with narrow distribution of high molecular weight, which comprises preparing PMMA with narrow distribution of high molecular weight by living radical polymerization under visible light irradiation, wherein the molecular weight of the PMMA is 3.5-13 ten thousand, the molecular weight is too small, the heat resistance, wear resistance and impact resistance are poor, and a light source with specific power needs to be controlled, the controllability of the reaction process is low, and the method is not suitable for industrial production. There is a need for a method for synthesizing ultra-high molecular weight polymethylmethacrylate.
Disclosure of Invention
In order to solve the above technical problems, a first aspect of the present invention provides a method for synthesizing ultra-high molecular weight polymethyl methacrylate, comprising at least the following steps:
(1) introducing protective gas into a reaction container, adding deionized water, a first emulsifier, an auxiliary agent and methyl methacrylate, and heating to a first reaction temperature;
(2) preparing a pre-emulsion of methyl methacrylate at room temperature;
(3) and (2) after the temperature in the step (1) is raised to a specified temperature, sequentially adding a first initiator and/or a first auxiliary initiator, raising the temperature to a second reaction temperature, starting to dropwise add the pre-emulsion prepared in the step (2), after dropwise addition is finished, raising the temperature to a third reaction temperature, preserving heat, and obtaining the solid polymethyl methacrylate with the molecular weight of more than 3000 ten thousand.
Preferably, the first emulsifier is an anionic emulsifier and/or a nonionic emulsifier.
Preferably, the auxiliary agent is at least one selected from sodium pyrophosphate, disodium ethylene diamine tetraacetate, sodium hydroxide, potassium chloride, sodium bicarbonate, acetic acid, ferrous sulfate and copper sulfate.
Preferably, the proportion of the deionized water, the emulsifier, the auxiliary agent and the methyl methacrylate in the step (1) is 100 (0.1-5) to (13-100).
Preferably, when the first initiator and the first co-initiator are added in the step (3), the mass ratio of the first initiator to the first co-initiator is 1: (0.5-5).
Preferably, the main raw materials for preparing the pre-emulsion of methyl methacrylate in the step (2) comprise deionized water, a second emulsifier, a second initiator and/or a second co-initiator, and methyl methacrylate, and the mass ratio of the deionized water, the second emulsifier, the second initiator and/or the second co-initiator, and the methyl methacrylate is 100 (0.5-5): (0.01-0.5): 10-300).
Preferably, the first initiator and the second initiator are selected from at least one of persulfates, hydroperoxides, peroxydicarbonates, benzoyl peroxide, azobisisobutyronitrile, and azodiisopropylamidine oxazoline hydrochloride.
Preferably, the first co-initiator and the second co-initiator are selected from at least one of sulfite, ferrous sulfate, sodium formaldehyde sulfoxylate, thiosulfate, polyamine, tertiary amine, and alcohol.
Preferably, the mass ratio of the methyl methacrylate in the step (1) to the methyl methacrylate in the step (2) is 1: (0.1-4).
Preferably, when the temperature is increased to the second reaction temperature in the step (3), the temperature increase speed is 0.01-1 ℃/min.
Has the advantages that: in the technical scheme, the inventor synthesizes the polymethyl methacrylate with the ultrahigh molecular weight by a simple method, improves the heat resistance, the wear resistance and the impact resistance of the polymethyl methacrylate, and leads the applicability of the polymethyl methacrylate to be wider. The synthesis method of the technical scheme is simple, low in energy consumption, environment-friendly, high in safety, low in requirement on refrigeration capacity in the synthesis process, and more suitable for industrial production. The inventor adds the first initiator, the first auxiliary initiator and the related auxiliary agents, so that the reaction temperature is reduced, the reaction speed and the reaction degree are improved, and the molecular weight of the polymethyl methacrylate is improved; when the pre-emulsion is added, a dropwise adding process is adopted, reaction heat can be removed more quickly, the reduction of the molecular weight of the polymethyl methacrylate caused by severe temperature rise is prevented, meanwhile, a proper second initiator and/or a second auxiliary initiator are/is added into the pre-emulsion, the continuous and stable reaction is ensured, meanwhile, residual monomers in the emulsion are continuously reacted through the temperature rise and heat preservation operation completed by dropwise adding, the molecular weight of the polymethyl methacrylate is improved, the heat preservation time is shortened, the reduction of the molecular weight caused by adding the initiator is avoided, the reaction process is easier to control, and the method is suitable for industrial production. The molecular weight of the polymethyl methacrylate prepared by the technical scheme reaches more than 3000 ten thousand.
Detailed Description
For purposes of the following detailed description, it is to be understood that the invention may assume various alternative variations and step sequences, except where expressly specified to the contrary. Moreover, other than in any operating examples, or where otherwise indicated, all numbers expressing, for example, quantities of ingredients used in the specification and claims are to be understood as being modified in all instances by the term "about". Accordingly, unless indicated to the contrary, the numerical parameters set forth in the following specification and attached claims are approximations that may vary depending upon the desired properties to be obtained by the present invention. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques.
Notwithstanding that the numerical ranges and parameters setting forth the broad scope of the invention are approximations, the numerical values set forth in the specific examples are reported as precisely as possible. Any numerical value, however, inherently contains certain errors necessarily resulting from the standard deviation found in their respective testing measurements.
When a range of values is disclosed herein, the range is considered to be continuous and includes both the minimum and maximum values of the range, as well as each value between such minimum and maximum values. Further, when a range refers to an integer, each integer between the minimum and maximum values of the range is included. Further, when multiple range-describing features or characteristics are provided, the ranges may be combined. In other words, unless otherwise indicated, all ranges disclosed herein are to be understood to encompass any and all subranges subsumed therein. For example, a stated range from "1 to 10" should be considered to include any and all subranges between the minimum value of 1 and the maximum value of 10. Exemplary subranges of the range 1 to 10 include, but are not limited to, 1 to 6.1, 3.5 to 7.8, 5.5 to 10, and the like.
In order to solve the above technical problems, a first aspect of the present invention provides a method for synthesizing ultra-high molecular weight polymethyl methacrylate, comprising at least the following steps:
(1) introducing protective gas into a reaction container, adding deionized water, a first emulsifier, an auxiliary agent and methyl methacrylate, and heating to a first reaction temperature;
(2) preparing a pre-emulsion of methyl methacrylate at room temperature;
(3) and (2) after the temperature in the step (1) is raised to the specified temperature, sequentially adding a first initiator and/or a first auxiliary initiator, starting to dropwise add the pre-emulsion prepared in the step (2), after dropwise addition is finished, raising the temperature to a second reaction temperature, preserving heat, and obtaining the solid polymethyl methacrylate with the molecular weight of more than 3000 ten thousand.
As a preferable technical scheme, the method for synthesizing the ultra-high molecular weight polymethyl methacrylate at least comprises the following steps:
(1) introducing nitrogen into a reaction container, adding deionized water, a first emulsifier, an auxiliary agent and methyl methacrylate, stirring and heating to 30-70 ℃;
(2) preparing a pre-emulsion of methyl methacrylate at room temperature;
(3) and (2) after the temperature in the step (1) is raised to 30-50 ℃, sequentially adding a first initiator and/or a first auxiliary initiator, raising the temperature to 33-53 ℃, starting to dropwise add the pre-emulsion prepared in the step (2), after dropwise addition is finished, raising the temperature to 75-90 ℃, preserving heat, and obtaining the solid polymethyl methacrylate with the molecular weight of more than 3000 ten thousand after finishing.
As a preferred technical solution, the first emulsifier is an anionic emulsifier and/or a nonionic emulsifier.
As a preferred technical scheme, the first emulsifier is an anionic emulsifier and a nonionic emulsifier.
When the anionic emulsifier and the nonionic emulsifier are compounded for use, the anionic emulsifier and the nonionic emulsifier have complementary performances, have a synergistic effect and improve the stability of the reaction.
In a preferred embodiment, the anionic emulsifier is at least one selected from alkyl sulfates, alkyl sulfonates, fatty acid salts, and naphthenates.
In a preferred embodiment, the nonionic emulsifier is at least one selected from the group consisting of alkylphenol ethoxylates, benzyl phenol ethoxylates, phenethylphenol ethoxylates, fatty alcohol ethoxylates, and polyoxyethylene sorbitan monostearate.
As a preferable technical scheme, the auxiliary agent is at least one selected from sodium pyrophosphate, disodium ethylene diamine tetraacetate, sodium hydroxide, potassium chloride, sodium bicarbonate, acetic acid, ferrous sulfate and copper sulfate.
As a preferable technical scheme, the proportion of the deionized water, the emulsifier, the auxiliary agent and the methyl methacrylate in the step (1) is 100 (0.1-5) to (13-100).
As a preferable technical solution, when the first initiator and the first co-initiator are added in the step (3), the mass ratio between the first initiator and the first co-initiator is 1: (0.5-5).
When the initiator and the co-initiator are used together, the activation energy of the initiator can be effectively reduced, namely, the initiation temperature of the reaction is reduced, and the using amount of the initiator is reduced, wherein the lower the reaction temperature, the smaller the using amount of the initiator is, the higher the molecular weight of the polymethyl methacrylate is.
As a preferable technical scheme, the main preparation raw materials of the methyl methacrylate pre-emulsion in the step (2) comprise deionized water, a second emulsifier, a second initiator and/or a second co-initiator and methyl methacrylate, and the mass ratio of the deionized water, the second emulsifier, the second initiator and/or the second co-initiator and the methyl methacrylate is 100 (0.5-5): (0.01-0.5): (10-300).
In a preferred embodiment, the first initiator and the second initiator are selected from at least one of persulfates, hydroperoxides, peroxydicarbonates, benzoyl peroxide, azobisisobutyronitrile, and azodiisopropylamidine oxazoline hydrochloride.
In a preferred embodiment, the first co-initiator and the second co-initiator are at least one selected from sulfite, ferrous sulfate, sodium formaldehyde sulfoxylate, thiosulfate, polyamine, tertiary amine, and alcohol.
As a preferable technical solution, the mass ratio of the methyl methacrylate in the step (1) to the methyl methacrylate in the step (2) is 1: (0.1-4).
As a preferable technical scheme, the time for dripping the pre-emulsion is controlled to be 30-600 min.
As a preferable technical scheme, when the temperature is increased to the second reaction temperature in the step (3), the temperature increasing speed is 0.01-1 ℃/min.
Controlling the temperature rise speed to enable the reaction to be carried out more stably and rapidly, so that the molecular weight of the polymethyl methacrylate reaches the requirement, and if the temperature rise speed is too high, the molecular chain growth is stopped, so that the molecular weight is reduced; if the temperature rise rate is too slow, the reaction time will be too long, which is not favorable for production.
In addition, the starting materials used are all commercially available, unless otherwise specified.
Example 1
In order to solve the above technical problems, a first aspect of this embodiment provides a method for synthesizing ultra-high molecular weight polymethyl methacrylate, specifically including the steps of:
(1) introducing nitrogen into a 1000ml four-neck flask, sequentially adding 400g of deionized water, 1.6g of sodium dodecyl sulfate, 1g of sodium pyrophosphate and 160g of methyl methacrylate, stirring and heating to 50 ℃;
(2) at room temperature, adding 80g of deionized water, 1.6g of sodium dodecyl sulfate and 0.08g of sodium bisulfite into a beaker in sequence, stirring until the deionized water, the sodium dodecyl sulfate and the sodium bisulfite are completely dissolved, and then slowly adding 160g of methyl methacrylate to obtain milky pre-emulsion;
(3) and (2) sequentially adding 0.16g of potassium persulfate and 0.16g of sodium bisulfite into the four-neck flask with the temperature of 50 ℃ in the step (1), controlling the temperature rise speed to be 0.3 ℃/min, slowly raising the temperature to 53 ℃, starting to dropwise add the pre-emulsion prepared in the step (2), controlling the dropwise adding time to be 60min, raising the internal temperature of the four-neck flask to 90 ℃ after the dropwise adding is finished, preserving the temperature for 1 hour to eliminate unreacted methyl methacrylate, drying after the reaction is finished to obtain solid polymethyl methacrylate, and testing that the molecular weight of PMMA reaches 3172 ten thousands.
Example 2
In order to solve the above technical problems, a first aspect of this embodiment provides a method for synthesizing ultra-high molecular weight polymethyl methacrylate, specifically including the steps of:
(1) introducing nitrogen into a 1000ml four-neck flask, sequentially adding 400g of deionized water, 1.2g of sodium dodecyl benzene sulfonate, 0.4g of tween-60, 1g of sodium pyrophosphate and 160g of methyl methacrylate, and stirring and heating to 30 ℃;
(2) at room temperature, adding 80g of deionized water, 1.2g of sodium dodecyl benzene sulfonate, 0.4g of tween-60 and 0.08g of sodium bisulfite into a beaker in sequence, stirring until the deionized water is completely dissolved, and slowly adding 160g of methyl methacrylate to obtain milky pre-emulsion;
(3) and (2) after 0.16g of potassium persulfate and 0.16g of sodium formaldehyde sulfoxylate are sequentially added into the four-neck flask with the temperature of 30 ℃ in the step (1), the temperature rising speed is controlled to be 0.2 ℃/min, when the temperature is slowly raised to 33 ℃, the pre-emulsion prepared in the step (2) is started to be dripped, the dripping time is controlled to be 60min, after the dripping is finished, the internal temperature of the four-neck flask is raised to 75 ℃, the temperature is kept for 1 hour, unreacted methyl methacrylate is eliminated, after the reaction is finished, the solid methyl methacrylate is obtained by drying, and the molecular weight of PMMA is tested to be 3500 ten thousand.
Example 3
In order to solve the above technical problems, a first aspect of this embodiment provides a method for synthesizing ultra-high molecular weight polymethyl methacrylate, specifically including the steps of:
(1) introducing nitrogen into a 1000ml four-neck flask, sequentially adding 400g of deionized water, 1.6g of sodium dodecyl sulfate, 0.5g of sodium bicarbonate, 0.5g of sodium hydroxide and 200g of methyl methacrylate, and stirring and heating to 50 ℃;
(2) at room temperature, sequentially adding 80g of deionized water, 1.6g of sodium dodecyl sulfate and 0.08g of sodium bisulfite into a beaker, stirring until the deionized water, the sodium dodecyl sulfate and the sodium bisulfite are completely dissolved, and slowly adding 120g of methyl methacrylate to obtain milky pre-emulsion;
(3) and (2) sequentially adding 0.16g of potassium persulfate and 0.16g of sodium bisulfite into the four-neck flask with the temperature of 50 ℃ in the step (1), controlling the heating rate to be 0.3 ℃/min, slowly heating to 53 ℃, starting to dropwise add the pre-emulsion prepared in the step (2), controlling the dropwise adding time to be 60min, raising the internal temperature of the four-neck flask to 90 ℃ after the dropwise adding is finished, keeping the temperature for 1 hour to eliminate unreacted methyl methacrylate, drying after the reaction is finished to obtain solid polymethyl methacrylate, and testing that the molecular weight of PMMA reaches 3253 ten thousand.
Example 4
In order to solve the above technical problems, a first aspect of this embodiment provides a method for synthesizing ultra-high molecular weight polymethyl methacrylate, specifically including the steps of:
(1) introducing nitrogen into a 1000ml four-neck flask, sequentially adding 400g of deionized water, 1.6g of sodium dodecyl sulfate, 1g of sodium pyrophosphate and 160g of methyl methacrylate, and stirring and heating to 50 ℃;
(2) at room temperature, sequentially adding 80g of deionized water, 1.6g of sodium dodecyl sulfate and 0.1g of tert-butyl hydroperoxide into a beaker, stirring until the deionized water, the sodium dodecyl sulfate and the tert-butyl hydroperoxide are completely dissolved, and slowly adding 160g of methyl methacrylate to obtain a milky pre-emulsion;
(3) and (2) after 0.3g of tert-butyl hydroperoxide and 0.5g of rongalite are sequentially added into the four-neck flask with the temperature of 50 ℃ in the step (1), the heating speed is controlled to be 0.3 ℃/min, when the temperature is slowly increased to 53 ℃, the pre-emulsion prepared in the step (2) is started to be dripped, the dripping time is controlled to be 60min, after the dripping is finished, the internal temperature of the four-neck flask is increased to 90 ℃, the temperature is kept for 1 hour, unreacted methyl methacrylate is eliminated, after the reaction is finished, the solid polymethyl methacrylate is obtained by drying, and the molecular weight of PMMA reaches 3137 ten thousand through testing.
Example 5
In order to solve the above technical problems, a first aspect of this embodiment provides a method for synthesizing ultra-high molecular weight polymethyl methacrylate, specifically including the steps of:
(1) introducing nitrogen into a 1000ml four-neck flask, sequentially adding 400g of deionized water, 1.6g of sodium dodecyl sulfate, 0.13g of disodium ethylene diamine tetraacetate, 1g of sodium pyrophosphate and 160g of methyl methacrylate, stirring and heating to 50 ℃;
(2) at room temperature, sequentially adding 80g of deionized water and 1.6g of sodium dodecyl sulfate into a beaker, stirring until the deionized water and the sodium dodecyl sulfate are completely dissolved, and slowly adding 160g of methyl methacrylate to obtain milky pre-emulsion;
(3) and (2) sequentially adding 0.16g of potassium persulfate, 0.16g of sodium bisulfite and 0.1g of ferrous sulfate into the four-neck flask with the temperature of 50 ℃ in the step (1), controlling the heating rate to be 0.3 ℃/min, slowly heating to 53 ℃, starting to dropwise add the pre-emulsion prepared in the step (2), controlling the dropwise adding time to be 60min, raising the internal temperature of the four-neck flask to 90 ℃ after the dropwise adding is finished, preserving the heat for 1 hour, eliminating unreacted methyl methacrylate, drying after the reaction is finished to obtain solid polymethyl methacrylate, and testing that the molecular weight of PMMA reaches 3116 ten thousand.
Comparative example 1
The difference between this embodiment and embodiment 2 is that a method for synthesizing ultra-high molecular weight polymethyl methacrylate specifically includes the steps of:
(1) introducing nitrogen into a 1000ml four-neck flask, sequentially adding 400g of deionized water, 1.6g of Tween-60, 1g of sodium pyrophosphate and 160g of methyl methacrylate, stirring and heating to 30 ℃;
(2) at room temperature, sequentially adding 80g of deionized water, 1.6g of Tween-60 and 0.08g of sodium bisulfite into a beaker, stirring until the deionized water, the Tween-60 and the sodium bisulfite are completely dissolved, and slowly adding 160g of methyl methacrylate to obtain milky pre-emulsion;
(3) and (2) after 0.16g of potassium persulfate and 0.16g of sodium formaldehyde sulfoxylate are sequentially added into the four-neck flask with the temperature of 30 ℃ in the step (1), the temperature rising speed is controlled to be 0.2 ℃/min, when the temperature is slowly raised to 33 ℃, the pre-emulsion prepared in the step (2) is started to be dripped, the dripping time is controlled to be 60min, after the dripping is finished, the internal temperature of the four-neck flask is raised to 75 ℃, the temperature is kept for 1 hour, unreacted methyl methacrylate is eliminated, after the reaction is finished, the solid polymethyl methacrylate is obtained by drying, and the molecular weight of PMMA reaches 3112 ten thousand by testing.
Comparative example 2
The comparative example is different from example 2 in that a method for synthesizing ultra-high molecular weight polymethyl methacrylate specifically comprises the steps of:
(1) introducing nitrogen into a 1000ml four-neck flask, sequentially adding 400g of deionized water, 1.6g of sodium dodecyl benzene sulfonate, 1g of sodium pyrophosphate and 160g of methyl methacrylate, and stirring and heating to 30 ℃;
(2) at room temperature, adding 80g of deionized water, 1.6g of sodium dodecyl benzene sulfonate and 0.08g of sodium bisulfite into a beaker in sequence, stirring until the deionized water, the sodium dodecyl benzene sulfonate and the sodium bisulfite are completely dissolved, and slowly adding 160g of methyl methacrylate to obtain milky pre-emulsion;
(3) and (2) after 0.16g of potassium persulfate and 0.16g of sodium formaldehyde sulfoxylate are sequentially added into the four-neck flask with the temperature of 30 ℃ in the step (1), the temperature rising speed is controlled to be 0.2 ℃/min, when the temperature is slowly raised to 33 ℃, the pre-emulsion prepared in the step (2) is started to be dripped, the dripping time is controlled to be 60min, after the dripping is finished, the internal temperature of the four-neck flask is raised to 75 ℃, the temperature is kept for 1 hour, unreacted methyl methacrylate is eliminated, after the reaction is finished, the solid polymethyl methacrylate is obtained by drying, and the molecular weight of PMMA reaches 3337 ten thousand by testing.
Comparative example 3
The comparative example is different from example 2 in that a method for synthesizing ultra-high molecular weight polymethyl methacrylate specifically comprises the following steps:
(1) introducing nitrogen into a 1000ml four-neck flask, sequentially adding 400g of deionized water, 1.2g of sodium dodecyl benzene sulfonate, 0.4g of tween-60, 1g of sodium pyrophosphate and 160g of methyl methacrylate, stirring and heating to 30 ℃;
(2) at room temperature, adding 80g of deionized water, 1.2g of sodium dodecyl benzene sulfonate, 0.4g of tween-60 and 0.08g of sodium bisulfite into a beaker in sequence, stirring until the deionized water is completely dissolved, and slowly adding 160g of methyl methacrylate to obtain milky pre-emulsion;
(3) and (2) after 0.16g of potassium persulfate and 0.16g of sodium formaldehyde sulfoxylate are sequentially added into the four-neck flask with the temperature of 30 ℃ in the step (1), the temperature rising speed is controlled to be 3 ℃/min, when the temperature is slowly raised to 33 ℃, the pre-emulsion prepared in the step (2) is started to be dripped, the dripping time is controlled to be 60min, after the dripping is finished, the internal temperature of the four-neck flask is raised to 75 ℃, the temperature is kept for 1 hour, unreacted methyl methacrylate is eliminated, after the reaction is finished, the solid polymethyl methacrylate is obtained by drying, and the molecular weight of PMMA reaches 2257 ten thousand.
Comparative example 4
In order to solve the above technical problems, a first aspect of this embodiment provides a method for synthesizing ultra-high molecular weight polymethyl methacrylate, specifically including the steps of:
(1) introducing nitrogen into a 1000ml four-neck flask, sequentially adding 400g of deionized water, 1.2g of sodium dodecyl benzene sulfonate, 0.4g of tween-60, 1g of sodium pyrophosphate and 160g of methyl methacrylate, and stirring and heating to 30 ℃;
(2) at room temperature, adding 80g of deionized water, 1.2g of sodium dodecyl benzene sulfonate, 0.4g of tween-60 and 0.08g of sodium bisulfite into a beaker in sequence, stirring until the deionized water is completely dissolved, and slowly adding 160g of methyl methacrylate to obtain milky pre-emulsion;
(3) sequentially adding 0.16g of potassium persulfate into the four-neck flask with the temperature of 30 ℃ in the step (1), controlling the temperature rise speed to be 0.2 ℃/min, starting to dropwise add the pre-emulsion prepared in the step (2) when the temperature is slowly raised to 33 ℃, controlling the dropwise adding time to be 60min, raising the internal temperature of the four-neck flask to 75 ℃ after the dropwise adding is finished, preserving the temperature for 1 hour to eliminate unreacted methyl methacrylate, drying after the reaction is finished to obtain solid polymethyl methacrylate, and testing that the molecular weight of PMMA reaches 3015 ten thousands.
Comparative example 5
The comparative example is different from example 2 in that a method for synthesizing ultra-high molecular weight polymethyl methacrylate specifically comprises the steps of:
(1) introducing nitrogen into a 1000ml four-neck flask, sequentially adding 400g of deionized water, 1.2g of sodium dodecyl benzene sulfonate, 0.4g of tween-60, 1g of sodium pyrophosphate and 60g of methyl methacrylate, and stirring and heating to 30 ℃;
(2) at room temperature, adding 80g of deionized water, 1.2g of sodium dodecyl benzene sulfonate, 0.4g of tween-60 and 0.08g of sodium bisulfite into a beaker in sequence, stirring until the deionized water is completely dissolved, and slowly adding 180g of methyl methacrylate to obtain milky pre-emulsion;
(3) and (2) after 0.16g of potassium persulfate and 0.16g of sodium formaldehyde sulfoxylate are sequentially added into the four-neck flask with the temperature of 30 ℃ in the step (1), the temperature rising speed is controlled to be 0.2 ℃/min, when the temperature is slowly raised to 33 ℃, the pre-emulsion prepared in the step (2) is started to be dripped, the dripping time is controlled to be 60min, after the dripping is finished, the internal temperature of the four-neck flask is raised to 75 ℃, the temperature is kept for 1 hour, unreacted methyl methacrylate is eliminated, after the reaction is finished, the solid polymethyl methacrylate is obtained by drying, and the molecular weight of PMMA reaches 3252 ten thousand by testing.
Performance testing
The PMMA obtained in examples 1 to 5 and comparative examples 1 to 5 were subjected to molecular weight measurement by gel permeation chromatography.
| Weight average molecular weight | |
| Example 1 | 3172 ten thousand |
| Example 2 | 3500 ten thousand |
| Example 3 | 3253 Chinese medicinal composition |
| Example 4 | 3137 Ten thousand |
| Example 5 | 3116 ten thousand |
| Comparative example 1 | 3112 ten thousand |
| Comparative example 2 | 3337 ten thousand |
| Comparative example 3 | 2257 Chinese medicine composition |
| Comparative example 4 | 3015 million |
| Comparative example 5 | 3252 Wan |
While the invention has been described with reference to the preferred embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention.
Claims (6)
1. A method for synthesizing ultra-high molecular weight polymethyl methacrylate is characterized by at least comprising the following steps:
(1) introducing protective gas into a reaction container, adding deionized water, a first emulsifier, an auxiliary agent and methyl methacrylate, and heating to a first reaction temperature;
(2) preparing a pre-emulsion of methyl methacrylate at room temperature;
(3) after the temperature in the step (1) is raised to a specified temperature, sequentially adding a first initiator and/or a first auxiliary initiator, raising the temperature to a second reaction temperature, starting to dropwise add the pre-emulsion prepared in the step (2), after dropwise addition is completed, raising the temperature to a third reaction temperature, preserving heat, and obtaining solid polymethyl methacrylate with the weight average molecular weight of more than 3000 ten thousand after finishing dropwise addition;
the first emulsifier is an anionic emulsifier and a nonionic emulsifier;
the main preparation raw materials of the methyl methacrylate pre-emulsion in the step (2) comprise deionized water, a second emulsifier, a second initiator and/or a second auxiliary initiator and methyl methacrylate, and the mass ratio of the deionized water, the second emulsifier, the second initiator and/or the second auxiliary initiator to the methyl methacrylate is 100 (0.5-5): 0.01-0.5): 10-300;
when the temperature is increased to the second reaction temperature in the step (3), the temperature increasing speed is 0.01-1 ℃/min;
the mass ratio of the methyl methacrylate in the step (1) to the methyl methacrylate in the step (2) is 1: (0.1-4).
2. The method as claimed in claim 1, wherein the auxiliary agent is at least one selected from sodium pyrophosphate, disodium edta, sodium hydroxide, potassium chloride, sodium bicarbonate, acetic acid, ferrous sulfate and copper sulfate.
3. The method as claimed in claim 1, wherein the ratio of deionized water, emulsifier, auxiliary agent and methyl methacrylate in step (1) is 100 (0.1-5) to (13-100).
4. The method for synthesizing ultra-high molecular weight polymethyl methacrylate according to claim 1, wherein when the first initiator and the first co-initiator are added in the step (3), the mass ratio of the first initiator to the first co-initiator is 1: (0.5-5).
5. The method as claimed in claim 1, wherein the first and second initiators are selected from at least one of persulfates, hydroperoxides, peroxydicarbonates, benzoyl peroxide, azobisisobutyronitrile and azobisdiisopropylamidine oxazoline hydrochloride.
6. The method as claimed in claim 1, wherein the first co-initiator and the second co-initiator are selected from at least one of sulfite, ferrous sulfate, sodium formaldehyde sulfoxylate, and thiosulfate.
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