CN113292732B - Modified ethylene-methyl acrylate copolymer and preparation method and application thereof - Google Patents
Modified ethylene-methyl acrylate copolymer and preparation method and application thereof Download PDFInfo
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Abstract
The invention provides a modified ethylene-methyl acrylate copolymer and a preparation method and application thereof. The invention prepares the nickel complex catalyst, and utilizes the catalyst to carry out high-efficiency catalysis on the copolymerization process of ethylene and methyl acrylate, thereby obtaining the ethylene-methyl acrylate copolymer; and the modified ethylene-methyl acrylate copolymer is prepared by respectively reacting the ethylene-methyl acrylate copolymer and the silicon dioxide nanoparticles with vinyl trimethoxy silane and then blending and crosslinking. Through the mode, the structure and the performance of the ethylene-methyl acrylate copolymer can be regulated and controlled by using the catalyst so as to promote the efficient modification process, so that the prepared modified ethylene-methyl acrylate copolymer has higher melting point, excellent mechanical property and corrosion resistance, can be applied to a reverse osmosis membrane supporting material, and has higher practical application value.
Description
Technical Field
The invention relates to the technical field of synthesis and modification of copolymers, in particular to a modified ethylene-methyl acrylate copolymer and a preparation method and application thereof.
Background
The ethylene-methyl acrylate copolymer is a product prepared by copolymerizing ethylene serving as a main raw material with a polar monomer methyl acrylate, has excellent thermal stability, filling property, flexibility, cohesiveness and good compatibility, and is widely applied to the fields of films, extrusion coating, sheets, molding, blow molding, extrusion molding and the like. However, the performance requirements of the raw materials in different application fields are not consistent, and the ethylene-methyl acrylate copolymer prepared by the general method is difficult to be completely matched with the requirements of each field, so that the ethylene-methyl acrylate copolymer needs to be modified according to the required application field so that the performance of the ethylene-methyl acrylate copolymer meets the application requirements.
For example, patent publication No. CN103275383A provides a cable sheathing material containing modified ethylene-methyl acrylate, and a preparation method thereof, in which ethylene-methyl acrylate is modified to greatly improve properties such as tensile strength and elongation at break, so that it can be used as a cable sheathing material. However, the modification method provided by the patent is complex, the variety of raw materials required to be used is various, and the product modified according to the method is mainly applied to cable sheath materials, and if the product is applied to reverse osmosis membrane supporting materials, the corresponding modification method needs to be redesigned, so that the prepared modified ethylene-methyl acrylate meets the performance requirements of the reverse osmosis membrane supporting materials.
In addition, the modification of the ethylene-methyl acrylate copolymer is mainly based on grafting or compounding of the existing ethylene-methyl acrylate copolymer, and the preparation process of the ethylene-methyl acrylate copolymer is not adjusted. However, ethylene-methyl acrylate as a copolymer has a large difference in molecular weight and branching of products obtained by polymerization under different conditions, which affects the effective proceeding of grafting or compounding process, resulting in unsatisfactory actual modification effect.
In view of the above, there is a need to design a modified ethylene-methyl acrylate copolymer and a preparation method thereof according to the practical application field, and graft and compound modification are performed on the basis of improving the preparation process of the ethylene-methyl acrylate copolymer, so as to solve the above problems.
Disclosure of Invention
In view of the above-mentioned drawbacks of the prior art, the present invention aims to provide a modified ethylene-methyl acrylate copolymer, and a preparation method and applications thereof. The copolymerization process of ethylene and methyl acrylate is efficiently catalyzed by preparing a nickel complex catalyst to obtain an ethylene-methyl acrylate copolymer; the prepared ethylene-methyl acrylate copolymer is subjected to silane grafting and then is crosslinked with silane modified silicon dioxide nanoparticles, so that the modified ethylene-methyl acrylate copolymer with excellent mechanical property, corrosion resistance and high melting point is obtained, and the application requirement of the reverse osmosis membrane supporting material is met.
In order to achieve the above object, the present invention provides a method for preparing a modified ethylene-methyl acrylate copolymer, comprising the steps of:
s1, preparing a nickel complex catalyst;
s2, copolymerizing ethylene and methyl acrylate under the action of the nickel complex catalyst obtained in the step S1 to obtain an ethylene-methyl acrylate copolymer;
s3, melting and blending the ethylene-methyl acrylate copolymer obtained in the step S2, vinyl trimethoxy silane and di-tert-butyl peroxide according to a first preset mass ratio, and drying to obtain a mixture A; dispersing silicon dioxide nano particles in a first solvent, adding a predetermined amount of vinyl trimethoxy silane and ammonium persulfate, and fully reacting to obtain a mixture B; and then melting and blending the mixture A and the mixture B with sodium dodecyl benzene sulfonate according to a second preset mass ratio, placing the product in water for full reaction, taking out and drying to obtain the modified ethylene-methyl acrylate copolymer.
As a further improvement of the present invention, in step S2, the ethylene and methyl acrylate copolymer is carried out according to the following steps:
respectively dissolving methyl acrylate and the nickel complex catalyst obtained in the step S1 in a second solvent to obtain a methyl acrylate solution and a catalyst solution with preset concentrations; and then sequentially adding the catalyst solution and the methyl acrylate solution into a reaction kettle in an ethylene atmosphere, controlling the temperature in the reaction kettle to be 80-100 ℃, controlling the pressure of ethylene to be 0.8-1.2 MPa, and reacting for 4-6 hours to obtain the ethylene-methyl acrylate copolymer.
As a further improvement of the invention, in step S2, the concentration of the methyl acrylate solution is 0.04-0.06 mol/L, and the concentration of the catalyst solution is 0.03-0.07 mmol/L.
As a further improvement of the present invention, in step S1, the nickel complex catalyst is prepared according to the following steps:
mixing methallyl nickel chloride dimer, sodium tetrakis (3, 5-bis (trifluoromethyl) phenyl) borate and ligand according to a molar ratio of 1:2 (1-3), dissolving in a third solvent, fully stirring for reaction for 8-12 h, and filtering, evaporating and recrystallizing to obtain the nickel complex catalyst.
As a further improvement of the present invention, in step S1, the ligand is prepared according to the following steps:
dissolving aniline in dichloromethane, adding a predetermined amount of trimethyl phosphite and elementary iodine, fully stirring for 8-12 h, adding hydrochloric acid, and sequentially adding a sodium bicarbonate solution and a sodium chloride solution for extraction to obtain an extraction product; and (2) spin-drying the extraction product, dissolving the extraction product in tetrahydrofuran, dropwise adding n-butyllithium at 0 ℃, reacting for 2-3 h, then adding chlorobis (2-methoxyphenyl) phosphine, fully reacting for 8-12 h, and then extracting, concentrating and recrystallizing the obtained organic phase to obtain the ligand.
As a further improvement of the invention, in step S1, the molar ratio of aniline, trimethyl phosphite and iodine is 5:2:1, and the molar ratio of the extracted product, n-butyllithium and chlorobis (2-methoxyphenyl) phosphine is 1:1: 1.
As a further improvement of the invention, in step S3, the first preset mass ratio of the ethylene-methyl acrylate copolymer, the vinyltrimethoxysilane and the di-tert-butyl peroxide is 100 (1-3) to 0.1; the second preset mass ratio of the mixture A, the mixture B and the sodium dodecyl benzene sulfonate is 100 (1-5): 0.1.
As a further improvement of the present invention, the first solvent is ethanol, the second solvent is toluene, and the third solvent is dichloromethane.
In order to achieve the purpose, the invention also provides a modified ethylene-methyl acrylate copolymer, which is prepared according to any one of the technical schemes.
The invention also provides application of the modified ethylene-methyl acrylate copolymer in a reverse osmosis membrane supporting material.
The invention has the beneficial effects that:
(1) the invention efficiently catalyzes the copolymerization process of ethylene and methyl acrylate by preparing a nickel complex catalyst to obtain an ethylene-methyl acrylate copolymer; and the prepared ethylene-methyl acrylate copolymer is subjected to silane grafting and then is crosslinked with silane-modified silicon dioxide nanoparticles to obtain the modified ethylene-methyl acrylate copolymer. Based on the preparation method provided by the invention, the melting point of the modified ethylene-methyl acrylate copolymer obtained by the invention is 220-250 ℃, the tensile strength is 16.3-19.5 MPa, the elongation at break is 688-776%, the corrosion potential is-0.141-0.089V, the modified ethylene-methyl acrylate copolymer has a higher melting point and excellent mechanical properties and corrosion resistance, can be applied to a reverse osmosis membrane supporting material, and has a higher practical application value.
(2) In the process of preparing the nickel complex catalyst, the ligand with asymmetric electrons and large volume substituent is prepared by regulating and controlling the reaction between aniline, trimethyl phosphite and chlorodi (2-methoxyphenyl) phosphine, so that the nickel complex catalyst with high reaction activity is formed by utilizing the coordination of the ligand and methallyl nickel chloride dimer. On the basis, the prepared nickel complex catalyst is used in the copolymerization process of ethylene and methyl acrylate, so that the reaction rate can be improved, the number of active sites on ethylene can be effectively increased, the insertion rate of methyl acrylate is improved, and the prepared ethylene-methyl acrylate has higher molecular weight and melting point, so as to meet the application requirement in a reverse osmosis membrane support material. Meanwhile, the invention also regulates and controls the concentration of the methyl acrylate solution, and reserves partial active sites for ethylene while introducing a large amount of methyl acrylate, so as to promote the grafting reaction in the subsequent modification process and further improve the performance of the ethylene-methyl acrylate copolymer.
(3) According to the invention, the prepared ethylene-methyl acrylate reacts with the vinyltrimethoxysilane, and the silane can be grafted on the main chain of the ethylene-methyl acrylate copolymer by utilizing rich active sites in the ethylene-methyl acrylate copolymer, so that the compatibility, the mechanical property, the heat resistance and the corrosion resistance of the ethylene-methyl acrylate copolymer are improved. Meanwhile, the invention also utilizes vinyl trimethoxy silane to carry out silanization modification on silicon dioxide, and the silicon dioxide reacts with the ethylene-methyl acrylate copolymer grafted with silane, so that the silicon dioxide nano particles can be fully dispersed and tightly combined in the ethylene-methyl acrylate copolymer by utilizing the excellent compatibility between the silicon dioxide nano particles and the ethylene-methyl acrylate copolymer, and the strength, the thermal stability and the corrosion resistance of the ethylene-methyl acrylate copolymer are improved; the copolymer can be crosslinked to form a network structure by utilizing hydrolytic condensation among silanes, and the strength and toughness of the ethylene-methyl acrylate copolymer are further improved, so that the prepared modified ethylene-methyl acrylate copolymer has excellent mechanical property, thermal stability and corrosion resistance, and the application requirements are met.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in detail below with reference to specific embodiments.
In addition, it is also to be noted that the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus.
The invention provides a preparation method of a modified ethylene-methyl acrylate copolymer, which comprises the following steps:
s1, preparing a nickel complex catalyst;
s2, copolymerizing ethylene and methyl acrylate under the action of the nickel complex catalyst obtained in the step S1 to obtain an ethylene-methyl acrylate copolymer;
s3, melting and blending the ethylene-methyl acrylate copolymer obtained in the step S2, vinyl trimethoxy silane and di-tert-butyl peroxide according to a first preset mass ratio, and drying to obtain a mixture A; dispersing the silicon dioxide nano particles in a first solvent, adding a predetermined amount of vinyl trimethoxy silane and ammonium persulfate, and fully reacting to obtain a mixture B; and then melting and blending the mixture A and the mixture B with sodium dodecyl benzene sulfonate according to a second preset mass ratio, placing the product in water for full reaction, taking out and drying to obtain the modified ethylene-methyl acrylate copolymer.
In step S1, the nickel complex catalyst is prepared as follows:
mixing methallyl nickel chloride dimer, sodium tetrakis (3, 5-bis (trifluoromethyl) phenyl) borate and ligand according to a molar ratio of 1:2 (1-3), dissolving in a third solvent, fully stirring for reaction for 8-12 h, and filtering, evaporating and recrystallizing to obtain the nickel complex catalyst.
The ligand is prepared according to the following steps:
dissolving aniline in dichloromethane, adding a predetermined amount of trimethyl phosphite and elementary iodine, fully stirring for 8-12 h, adding hydrochloric acid, and sequentially adding a sodium bicarbonate solution and a sodium chloride solution for extraction to obtain an extraction product; the extraction product is dried in a spinning mode and then dissolved in tetrahydrofuran, n-butyl lithium is added dropwise at the temperature of 0 ℃, after reaction for 2-3 hours, chlorobis (2-methoxyphenyl) phosphine is added, after full reaction for 8-12 hours, the obtained organic phase is extracted, concentrated and recrystallized in sequence to obtain a ligand; the molar ratio of the aniline to the trimethyl phosphite to the iodine is 5:2:1, and the molar ratio of the extraction product to the n-butyllithium to the chlorobis (2-methoxyphenyl) phosphine is 1:1: 1.
In step S2, the ethylene and methyl acrylate copolymer is carried out according to the following steps:
respectively dissolving methyl acrylate and the nickel complex catalyst obtained in the step S1 in a second solvent to obtain a methyl acrylate solution and a catalyst solution with preset concentrations; then sequentially adding the catalyst solution and the methyl acrylate solution into a reaction kettle in an ethylene atmosphere, controlling the temperature in the reaction kettle to be 80-100 ℃, controlling the pressure of ethylene to be 0.8-1.2 MPa, and reacting for 4-6 hours to obtain an ethylene-methyl acrylate copolymer; the concentration of the methyl acrylate solution is 0.04-0.06 mol/L, and the concentration of the catalyst solution is 0.03-0.07 mmol/L.
In step S3, the first preset mass ratio of the ethylene-methyl acrylate copolymer, the vinyltrimethoxysilane and the di-tert-butyl peroxide is 100 (1-3) to 0.1; the second preset mass ratio of the mixture A, the mixture B and the sodium dodecyl benzene sulfonate is 100 (1-5): 0.1.
The first solvent is ethanol, the second solvent is toluene, and the third solvent is dichloromethane.
The invention also provides a modified ethylene-methyl acrylate copolymer prepared according to the technical scheme.
The invention also provides application of the modified ethylene-methyl acrylate copolymer in a reverse osmosis membrane supporting material.
The following describes a modified ethylene-methyl acrylate copolymer, a preparation method and applications thereof, with reference to specific examples.
Example 1
This example provides a method for preparing a modified ethylene-methyl acrylate copolymer, comprising the following steps:
s1 preparation of nickel complex catalyst
Dissolving aniline in dichloromethane, adding trimethyl phosphite and iodine in a molar ratio of 5:2:1, fully stirring for reaction for 10 hours, adding hydrochloric acid (12mol/L), and sequentially adding sodium bicarbonate solution and sodium chloride solution for extraction to obtain an extraction product; and (2) spin-drying the extraction product, dissolving the extraction product in tetrahydrofuran, dropwise adding n-butyllithium at 0 ℃, fully reacting for 2 hours, then adding chlorobis (2-methoxyphenyl) phosphine, controlling the molar ratio of the extraction product to the n-butyllithium to the chlorobis (2-methoxyphenyl) phosphine to be 1:1:1, fully reacting for 10 hours, and then extracting, concentrating and recrystallizing the obtained organic phase to obtain the ligand.
Mixing methallyl nickel chloride dimer, sodium tetrakis (3, 5-bis (trifluoromethyl) phenyl) borate and the ligand according to a molar ratio of 1:2:2, dissolving in dichloromethane, fully stirring for reaction for 10 hours, and filtering, evaporating and recrystallizing to obtain the nickel complex catalyst.
S2 preparation of ethylene-methyl acrylate copolymer
And respectively dissolving methyl acrylate and the nickel complex catalyst in toluene to obtain a methyl acrylate solution with the concentration of 0.05mol/L and a catalyst solution with the concentration of 0.05 mmol/L. And then vacuumizing the reaction kettle, sequentially adding the catalyst solution and the methyl acrylate solution into the reaction kettle in an ethylene atmosphere, controlling the temperature in the reaction kettle to be 90 ℃, continuously introducing ethylene gas to ensure that the pressure in the reaction kettle is 1MPa, fully reacting for 5 hours, adding ethanol to terminate the reaction, and filtering, washing and drying to obtain the ethylene-methyl acrylate copolymer.
By testing, the nickel complex prepared in this exampleThe activity of the catalyst was 3.6X 104g/(mol. h), the molecular weight of the ethylene-methyl acrylate copolymer obtained was 4.3X 104Wherein the mass fraction of methyl acrylate is 20.63%.
S3 preparation of modified ethylene-methyl acrylate copolymer
And (3) mixing the ethylene-methyl acrylate copolymer obtained in the step (S2), vinyl trimethoxy silane and di-tert-butyl peroxide according to a first preset mass ratio of 100:2:0.1, and then carrying out melt blending, granulation and drying to obtain a mixture A.
Dispersing the silicon dioxide nano particles in ethanol, adding vinyl trimethoxy silane and ammonium persulfate (the mass ratio of the silicon dioxide nano particles to the vinyl trimethoxy silane to the ammonium persulfate is controlled to be 100:50:0.1), fully reacting for 5 hours at 80 ℃, and performing suction filtration, washing and drying to obtain a mixture B.
And mixing the mixture A, the mixture B and sodium dodecyl benzene sulfonate according to a second preset mass ratio of 100:3:0.1, performing melt blending, performing extrusion molding, placing in water at 80 ℃ for fully reacting for 2 hours, and drying to obtain the modified ethylene-methyl acrylate copolymer.
In order to examine the mechanical properties and corrosion resistance of the modified ethylene-methyl acrylate copolymer prepared in this example, the tensile strength, elongation at break and corrosion potential were measured. Wherein the tensile strength and elongation at break are tested according to GB/T1040.3-2006; in the corrosion potential test, a stainless steel electrode coated with the modified ethylene-methyl acrylate copolymer is used as a working electrode, a saturated calomel electrode is used as a reference electrode, a platinum electrode is used as an auxiliary electrode, a NaCl solution with the mass fraction of 3% is used as an electrolyte, and scanning is carried out at the scanning speed of 10mV/s within the scanning voltage range of-1.0-0.5V.
Tests prove that the modified ethylene-methyl acrylate copolymer prepared by the embodiment has the melting point of 240 ℃, the tensile strength of 19.2MPa, the elongation at break of 758% and the corrosion potential of-0.093V, and has higher melting point, excellent mechanical property and corrosion resistance.
The embodiment also provides an application of the prepared modified ethylene-methyl acrylate copolymer in a reverse osmosis membrane supporting material, and the preparation of the reverse osmosis membrane supporting material specifically comprises the following steps:
(1) preparation of polyester non-woven fabric by papermaking method
Mixing polyester fibers and bonding fibers according to a mass ratio of 65:35, placing the mixture into a pulping machine, and adding water for pulping to obtain fiber pulp; and adding water into the fiber slurry, uniformly stirring, fully diluting the fiber slurry into fiber suspension, making the fiber suspension into a net by a paper making machine, and drying at 80 ℃ to obtain the polyester non-woven fabric. Wherein the process bonding temperature of the bonding fiber is 180-200 ℃.
(2) Preparation of melt-blown nonwoven fabrics
Adding the modified ethylene-methyl acrylate copolymer prepared in the embodiment into a screw extruder, heating and melting at 270 ℃, then spraying out from a spinneret orifice on a melt-blowing die head, and drawing by hot air flow at 280 ℃ at the speed of 150m/s to form superfine fibers; and depositing the superfine fibers on the surface of a receiving device which is 10cm away from the spinneret orifice, and cooling to obtain the melt-blown non-woven fabric. Wherein the average diameter of the ultrafine fibers is 0.8 μm.
(3) Preparation of composite support material for reverse osmosis membrane
And (4) superposing the melt-blown non-woven fabric obtained in the step (S2) on the upper surface of the polyester non-woven fabric obtained in the step (S1), and performing hot pressing treatment at 190 ℃ to obtain the composite supporting material for the reverse osmosis membrane.
In the preparation process, the modified ethylene-methyl acrylate copolymer prepared in the embodiment is used as a raw material to carry out melt-blown spinning, so that superfine fibers with the average diameter of 0.5-1 mu m can be formed, and further the melt-blown non-woven fabric with excellent filtering performance is obtained. On this basis, because the modified ethylene-methyl acrylate copolymer prepared by the embodiment has a higher melting point, the integrity of the pore structure of the melt-blown non-woven fabric can be ensured in the hot pressing process, and the bonding fibers in the polyester non-woven fabric are melted and then permeate into the melt-blown non-woven fabric, so that the bonding strength between the polyester non-woven fabric and the melt-blown non-woven fabric layer can be effectively improved, the mechanical strength of the prepared support material is improved, the problem that the melt-blown non-woven fabric is not suitable for a hot pressing process in the prior art can be solved, the melt-blown non-woven fabric and the polyester non-woven fabric have a synergistic effect after hot pressing integration, the average pore size of the support material is further reduced, and the filtering performance of the support material is improved.
Meanwhile, the modified ethylene-methyl acrylate copolymer prepared based on the embodiment has excellent mechanical property and corrosion resistance, and can further improve the mechanical property of the prepared support material, so that the support material has better corrosion resistance, is not easy to damage in a long-term use process, and effectively prolongs the service life of the support material so as to meet the requirements of practical application.
The performance of the composite support material for reverse osmosis membrane prepared in this example was tested and found to be 96.2 μm thick and 80.1g/m gram weight2The average pore diameter was 13.8 μm, the porosity was 30.8%, the tensile strength was 8.8KN/m, and the elongation at break was 17%. Therefore, the support material has smaller average pore diameter, higher porosity and higher mechanical strength, and the modified ethylene-methyl acrylate copolymer prepared by the method provided by the embodiment can be used for preparing the reverse osmosis membrane support material, and the polymer has higher melting point, excellent mechanical property and corrosion resistance, is favorable for improving the filtering property and the mechanical property of the reverse osmosis membrane support material, and has higher application value.
Examples 2 to 11 and comparative examples 1 to 3
Examples 2 to 11 and comparative examples 1 to 3 each provide a method for preparing a modified ethylene-methyl acrylate copolymer, which is different from example 1 in that corresponding process parameters in each step are changed, corresponding parameter values of each example and comparative example are shown in table 1, and the remaining steps and parameters are the same as those of example 1, and are not repeated herein.
TABLE 1 Process parameters for examples 2-11 and comparative examples 1-3
The results of the tests on the properties of the modified ethylene-methyl acrylate copolymers prepared in examples 2 to 11 and comparative examples 1 to 3 are shown in Table 2.
TABLE 2 Properties of modified ethylene-methyl acrylate copolymers prepared in examples 2 to 11 and comparative examples 1 to 3
As can be seen from Table 2, the adjustment of the process parameters in each step has a great influence on the properties of the finally obtained modified ethylene-methyl acrylate copolymer.
It can be seen from comparison of examples 1-3 and comparative example 1 that, as the content of the ligand increases, the melting point, tensile strength, elongation at break and corrosion potential of the prepared modified ethylene-methyl acrylate copolymer tend to increase first and then decrease second. Mainly because when the content of the ligand is too low, the ligand is difficult to provide a bulky substituent for the catalyst, so that the steric hindrance of the catalyst is increased, and the increase of active sites in an ethylene main chain is not facilitated, so that the insertion rate of methyl acrylate is reduced, and the silane grafting rate in the subsequent modification process is reduced, so that the melting point, the mechanical property and the corrosion resistance of the prepared modified ethylene-methyl acrylate copolymer are reduced. Therefore, the catalyst prepared in comparative example 1 without adding a ligand is difficult to effectively catalyze the copolymerization of ethylene and methyl acrylate, resulting in significantly lower product properties than the examples of the present application. Meanwhile, when the content of the ligand is too high, the substituent group is difficult to be further introduced into the nickel complex catalyst, the improvement effect on the activity of the catalyst is not obvious, and the performance of the catalyst is influenced by redundant ligand. Therefore, the present invention preferably has a molar ratio of methallyl nickel chloride dimer, sodium tetrakis (3, 5-bis (trifluoromethyl) phenyl) borate, and ligand of 1:2 (1-3).
As can be seen from comparative examples 4 to 7, with the increase of the methyl acrylate content, the reaction temperature and the pressure, the melting point, the tensile strength, the elongation at break and the corrosion potential of the prepared modified ethylene-methyl acrylate copolymer tend to increase first and then decrease. When the content of methyl acrylate is too low, although ethylene has abundant active sites under the action of a catalyst, the reduction of the insertion rate of methyl acrylate still affects the product performance; when the content of methyl acrylate is too high, the too high insertion rate of methyl acrylate causes a large consumption of ethylene active sites, so that the content of active sites available for silane grafting subsequently is reduced, and the performance of the prepared modified ethylene-methyl acrylate copolymer is also reduced. Meanwhile, when the reaction temperature and pressure in the polymerization reaction process are too low, the reaction is insufficient, and the performance of the product is reduced; too high a reaction temperature or pressure does not significantly improve the performance of the product, but rather leads to increased energy consumption. Therefore, the concentration of the methyl acrylate solution is preferably 0.04-0.06 mol/L, the concentration of the catalyst solution is preferably 0.03-0.07 mmol/L, the temperature in the reaction kettle is 80-100 ℃, and the pressure of ethylene is preferably 0.8-1.2 MPa.
It can be seen from comparison of examples 8 to 9 and comparative example 2 that, as the content of vinyltrimethoxysilane reacted with the ethylene-methyl acrylate copolymer increases, the melting point, tensile strength, elongation at break and corrosion potential of the modified ethylene-methyl acrylate copolymer as a whole tend to increase and then decrease. Mainly because when the content of the vinyltrimethoxysilane is too low, the grafting ratio of silane in the ethylene-methyl acrylate copolymer is low, the modification effect on the ethylene-methyl acrylate is weak, the compatibility of the ethylene-methyl acrylate copolymer and silicon dioxide nano particles is influenced, and the mechanical property and the corrosion resistance of the prepared modified ethylene-methyl acrylate copolymer are further influenced. Thus, the modified ethylene methyl acrylate copolymer obtained in comparative example 2 without the addition of vinyltrimethoxysilane exhibited significantly lower properties than the examples of the present invention. In addition, when the vinyltrimethoxysilane content is too high, the improvement of the properties of the ethylene-methyl acrylate is not significant enough since the number of active sites available for grafting is effective. Therefore, the first preset mass ratio of the ethylene-methyl acrylate copolymer, the vinyltrimethoxysilane and the di-tert-butyl peroxide is preferably 100 (1-3) to 0.1.
It can be seen from comparison of examples 10 to 11 and comparative example 3 that, as the content of the modified silica nanoparticles increases, the melting point, tensile strength and corrosion potential of the prepared modified ethylene-methyl acrylate copolymer tend to increase first and then decrease, and the change in elongation at break is opposite. Therefore, the mechanical properties and corrosion resistance of the product obtained in comparative example 3 without the addition of the modified silica nanoparticles were inferior to those of the examples of the present invention. In addition, too many silica nanoparticles, while effective in improving the strength and corrosion resistance of ethylene-methyl acrylate, can reduce its toughness. Therefore, in order to ensure that the prepared modified ethylene-methyl acrylate copolymer has higher tensile strength, elongation at break and corrosion resistance, the second preset mass ratio of the mixture A, the mixture B and the sodium dodecyl benzene sulfonate is preferably 100 (1-5): 0.1.
Therefore, the catalyst prepared in comparative example 1 without adding a ligand is difficult to effectively catalyze the copolymerization of ethylene and methyl acrylate, resulting in significantly lower product properties than the examples of the present application. Meanwhile, when the content of the ligand is too high, the substituent group is difficult to be further introduced into the nickel complex catalyst, the improvement effect on the activity of the catalyst is not obvious, and the performance of the catalyst is influenced by redundant ligand. Therefore, the present invention preferably has a molar ratio of methallyl nickel chloride dimer, sodium tetrakis (3, 5-bis (trifluoromethyl) phenyl) borate, and ligand of 1:2 (1-3).
Therefore, the preparation method provided by the invention can effectively improve the performance of the ethylene-methyl acrylate copolymer, and the modified ethylene-methyl acrylate copolymer with higher melting point, excellent mechanical property and corrosion resistance is obtained, so that the modified ethylene-methyl acrylate copolymer can meet the application of a reverse osmosis membrane support material.
In conclusion, the invention provides a modified ethylene-methyl acrylate copolymer, and a preparation method and application thereof. The invention prepares the nickel complex catalyst, and utilizes the catalyst to carry out high-efficiency catalysis on the copolymerization process of ethylene and methyl acrylate, thereby obtaining the ethylene-methyl acrylate copolymer; and the modified ethylene-methyl acrylate copolymer is prepared by respectively reacting the ethylene-methyl acrylate copolymer and the silicon dioxide nanoparticles with vinyl trimethoxy silane and then blending and crosslinking. Through the mode, the structure and the performance of the ethylene-methyl acrylate copolymer can be regulated and controlled by using the catalyst so as to promote the efficient modification process, so that the prepared modified ethylene-methyl acrylate copolymer has higher melting point, excellent mechanical property and corrosion resistance, can be applied to a reverse osmosis membrane supporting material, and has higher practical application value.
Although the present invention has been described in detail 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 spirit and scope of the present invention.
Claims (6)
1. A preparation method of a modified ethylene-methyl acrylate copolymer is characterized by comprising the following steps:
s1, mixing methallyl nickel chloride dimer, sodium tetrakis (3, 5-bis (trifluoromethyl) phenyl) borate and ligand according to the molar ratio of 1:2 (1-3), dissolving in a third solvent, fully stirring for reacting for 8-12 h, and filtering, evaporating and recrystallizing to obtain a nickel complex catalyst;
s2, respectively dissolving methyl acrylate and the nickel complex catalyst obtained in the step S1 in a second solvent to obtain a methyl acrylate solution and a catalyst solution with preset concentrations; then sequentially adding the catalyst solution and the methyl acrylate solution into a reaction kettle in an ethylene atmosphere, controlling the temperature in the reaction kettle to be 80-100 ℃, controlling the pressure of ethylene to be 0.8-1.2 MPa, and reacting for 4-6 hours to obtain an ethylene-methyl acrylate copolymer; the concentration of the methyl acrylate solution is 0.04-0.06 mol/L, and the concentration of the catalyst solution is 0.03-0.07 mmol/L;
s3, melting and blending the ethylene-methyl acrylate copolymer obtained in the step S2, vinyl trimethoxy silane and di-tert-butyl peroxide according to a first preset mass ratio, and drying to obtain a mixture A; dispersing the silicon dioxide nano particles in a first solvent, adding a predetermined amount of vinyl trimethoxy silane and ammonium persulfate, and fully reacting to obtain a mixture B; then melting and blending the mixture A, the mixture B and sodium dodecyl benzene sulfonate according to a second preset mass ratio, placing the product in water for full reaction, taking out and drying to obtain a modified ethylene-methyl acrylate copolymer; the first preset mass ratio of the ethylene-methyl acrylate copolymer to the vinyl trimethoxy silane to the di-tert-butyl peroxide is 100 (1-3) to 0.1; the second preset mass ratio of the mixture A, the mixture B and the sodium dodecyl benzene sulfonate is 100 (1-5): 0.1.
2. The process for producing a modified ethylene-methyl acrylate copolymer according to claim 1, wherein: in step S1, the ligand is prepared as follows:
dissolving aniline in dichloromethane, adding a predetermined amount of trimethyl phosphite and elementary iodine, fully stirring for 8-12 h, adding hydrochloric acid, and sequentially adding a sodium bicarbonate solution and a sodium chloride solution for extraction to obtain an extraction product; and (2) spin-drying the extraction product, dissolving the extraction product in tetrahydrofuran, dropwise adding n-butyl lithium at 0 ℃, reacting for 2-3 h, then adding chlorobis (2-methoxyphenyl) phosphine, fully reacting for 8-12 h, and then extracting, concentrating and recrystallizing the obtained organic phase to obtain the ligand.
3. The process for producing a modified ethylene-methyl acrylate copolymer according to claim 2, wherein: in step S1, the molar ratio of aniline, trimethyl phosphite and iodine was 5:2:1, and the molar ratio of the extracted product, n-butyllithium and chlorobis (2-methoxyphenyl) phosphine was 1:1: 1.
4. The process for producing a modified ethylene-methyl acrylate copolymer according to claim 1, wherein: the first solvent is ethanol, the second solvent is toluene, and the third solvent is dichloromethane.
5. A modified ethylene methyl acrylate copolymer characterized by: the modified ethylene-methyl acrylate copolymer is prepared by the preparation method of any one of claims 1 to 4.
6. Use of the modified ethylene-methyl acrylate copolymer prepared by the preparation method according to any one of claims 1 to 4 or the modified ethylene-methyl acrylate copolymer according to claim 5, wherein: the modified ethylene-methyl acrylate copolymer is used in the technical field of reverse osmosis membrane supporting materials.
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