CN1279068C - Crosslinked core-shell structure nano-polymer microsphere and its preparation method - Google Patents

Abstract

The invention relates to a cross-linked core-shell structure nano polymer microsphere and a preparation method thereof, belonging to the technical field of polymer materials. The present invention uses a variety of organic olefin monomers as raw materials, and is prepared by emulsion or suspension polymerization with water as the medium under the condition of the presence of emulsifiers and initiators; the product has a core-shell structure, and both the inside of the core and the inside of the shell present Linked, the core and the shell are connected by chemical bonds, and the particle size is less than 100nm. In the present invention, by changing the composition and structure of the core and the shell, a variety of soft-core hard-shell or hard-core soft-shell nano-polymer microspheres with different physical and chemical properties are obtained, which has a high degree of freedom in the choice of structure design. The invention not only solves the problem that the core-shell polymer microspheres do not have a nanometer scale, but also solves the problem that the core and the shell are mostly linear polymers in the past, so that it has wider application prospects in the field of nanotechnology.

Description

Cross-linked core-shell nano-polymer microspheres and preparation method thereof

technical field

The invention relates to a nano-polymer microsphere with a cross-linked core-shell structure and a preparation method thereof, belonging to the technical field of polymer materials.

Background technique

The preparation of polymer microspheres with core-shell structure has attracted more and more researchers' attention in recent years. Polymers polymerized from polymerizable monomers of different components can act as core or shell components in core-shell microspheres. Using the different properties of these polymers, soft-core hard shells or hard cores with different physical and chemical properties can be synthesized. Soft-shell nano-polymer microspheres. At the same time, this synthesis embodies the concept of molecular design. Not only the components of the core and shell can be changed according to the needs, but also the scale can be controlled by corresponding methods to achieve the purpose of application. It is the diversity of components and structures of this kind of nano-microspheres and the very high degree of design freedom that make them have extremely broad prospects in the research and application of new materials.

However, the previous preparation technologies in this field mainly have the following deficiencies: first, the preparation of core-shell polymer microspheres is generally limited to the micron scale, and the particle size is mostly hundreds of nanometers to tens of microns. The special properties of nanoparticles have been lost; secondly, the core-shell polymer microspheres synthesized by predecessors generally have a linear polymer core or shell, and the swelling ratio of the microspheres in the solvent is very low, and the solvent resistance and oil absorption properties are also relatively low. Difference. In addition, the complex process and low yield are also important shortcomings of previous research in this field. Therefore, the present invention is based on solving the above defects in terms of scale, structural composition and synthesis process.

Contents of the invention

The purpose of the present invention is to provide a cross-linked core-shell nano-polymer microsphere and its preparation method. On the one hand, the method reduces the size of the previous polymer core-shell particles to the nanoscale range, and at the same time makes the core and shell of the product A cross-linked structure is formed inside, which not only solves the problem of preparing nanoscale core-shell latex particles, but also solves the problems of poor solvent resistance and oil absorption of core-shell latex particles in the past, and can finally be shown in practical applications. All kinds of good properties. The present invention can design the composition, structure and scale of the core and shell according to the needs, so as to obtain various soft-core hard-shell or hard-core soft-shell nanoparticles with different physical and chemical properties and application significance. The high degree of freedom greatly broadens its application fields and application prospects.

The purpose of the present invention is achieved through the following technical solutions:

A cross-linked core-shell structure nano-polymer microsphere, characterized in that: the nano-polymer microsphere has a typical core-shell structure, and both the inside of the core and the inside of the shell are cross-linked, and the core and the shell are connected by chemical bonds , whose particle size is less than 100nm; it is prepared from the following substances as raw materials by emulsion polymerization or suspension polymerization using water as the medium:

1) Monoolefin monomer: the total mass of core layer monoolefin monomer and shell layer monoolefin monomer is 100 parts; wherein the mass of core layer monoolefin monomer is between 30-70 parts, and the shell layer monoolefin monomer is corresponding Between 70-30 copies;

2) polyene monomer: the total mass of the core layer polyene monomer and the shell layer polyene monomer is between 2-50 parts, and both of the core layer polyene monomer and the shell layer polyene monomer are greater than or equal to 1 copy;

3) Emulsifier: 2 to 7 parts;

4) Initiator: 0.5-2 parts.

The monoolefin in the present invention refers to an α-olefin containing a carbon-carbon double bond (C=C) in the molecule, which can be selected from one of styrene, vinyl chloride, acrylonitrile, acrylate, and methacrylate or several; the polyene substances refer to substances containing two or more carbon-carbon double bonds in the molecule, selected from butadiene, isobutadiene, isoprene, divinylbenzene , one or more of trimethylolpropane trimethacrylate. And it should be ensured that the monoolefin monomer of the core layer is not exactly the same as the monoolefin monomer of the shell layer.

The emulsifying agent described in the present invention can adopt one or more in the following materials:

a. Cationic type: including tri-C _1-18 alkyl methyl ammonium chloride, tri-C _1-18 alkyl methyl ammonium bromide, tri-C _1-18 alkyl benzyl ammonium chloride, tri-C _1-18 Alkyl benzyl ammonium bromide, or tri-C _1-18 alkyl methyl benzyl ammonium chloride, tri-C _1-18 alkyl ethyl benzyl ammonium chloride, tri-C _1-18 alkyl methyl benzyl ammonium Ammonium bromide, three C _1~18 alkyl ethyl benzyl ammonium bromide;

b. Anionic type: including C _12~18 alkyl sodium sulfate, C _12~18 alkyl potassium sulfate, C _12~18 alkyl sulfonate sodium, C _12~18 alkyl sulfonate potassium, C _12~18 alkyl Sodium benzenesulfonate, potassium C _12-18 alkylbenzenesulfonate.

c. Non-ionic type: including C _3-10 alkylphenol polyoxyethylene ether, C _2-18 fatty alcohol polyoxyethylene ether, polyoxyethylene sorbitol mono-C _11-18 fatty acid ester or polyoxyethylene sorbitol tri-C _11-18 fatty acid esters, the number of repeating units of polyoxyethylene is 4-50.

The initiator refers to a water-soluble persulfate, hydrogen peroxide or a substance that has a dissociation energy of 30 to 35 kcal/mol and can generate free radicals at a temperature of 40 to 95°C, which can lead to the polymerization of olefin monomers. Oil-soluble azo and peroxide substances. Can be selected from potassium persulfate, ammonium persulfate, azobisisobutyronitrile or azobisisoheptanonitrile, or hydrogen peroxide, dibenzoyl peroxide and ferrous salt, sulfite, thiosulfuric acid respectively Salt redox system.

A method for preparing cross-linked core-shell structure nano-polymer microspheres provided by the present invention is characterized in that an emulsion polymerization method is adopted, and the method uses the following materials as raw materials:

Monoolefin monomer: the total mass of the core layer monoolefin monomer and the shell layer monoolefin monomer is 100 parts; the mass of the core layer monoolefin monomer is between 30-70 parts, and the shell layer monoolefin monomer is correspondingly 70 parts Between -30 copies;

Multiolefin monomer: the total mass of the core layer polyene monomer and the shell layer polyene monomer is between 2-50 parts, and both the core layer polyene monomer and the shell layer polyene monomer are greater than or equal to 1 share;

Emulsifier: 2 to 7 parts;

Water-soluble initiator: 0.5-2 parts;

The concrete processing step of this method is as follows:

(1) Preparation of the nuclear layer:

(a) Mix 30-70% of the core layer monoolefin monomer and 30-70% of the core layer polyolefin monomer according to the above-mentioned raw material ratio and put them into the mixture containing deionized water and emulsifier and raise the temperature to 40°C~ A uniform emulsion is formed in a reactor at 50°C, and a water-soluble initiator accounting for 20% to 80% of the total amount is added to the reactor, and the temperature is raised to a temperature range of 70°C to 95°C for 0.5 to 2 hours;

(b) Mixing the remaining monoolefin monomer of the core layer with the remaining polyolefin monomer of the core layer and uniformly adding it to the above system, and reacting at a temperature range of 70°C to 95°C for 1 to 3 hours;

(2) Preparation of the shell:

(c) According to the ratio of the raw materials, a monoolefin monomer different from the core layer monoolefin monomer is selected as the shell monoolefin monomer and the shell polyolefin monomer is mixed evenly and added to the system after step (b) reaction , then add the remaining water-soluble initiator, and react at a temperature range of 70°C to 95°C for 1 to 3 hours;

(d) After cooling and discharging, and after demulsification, washing, drying and other steps, the cross-linked core-shell nano-polymer microspheres proposed by the present invention can be obtained.

The present invention also provides another method for preparing cross-linked core-shell nano-polymer microspheres, which is characterized in that it is prepared by a suspension polymerization method, and the method uses the following materials as raw materials:

Monoolefin monomer: the total mass of the core layer monoolefin monomer and the shell layer monoolefin monomer is 100 parts; the mass of the core layer monoolefin monomer is between 30-70 parts, and the shell layer monoolefin monomer is correspondingly 70 parts Between -30 copies;

Multiolefin monomer: the total mass of the core layer polyene monomer and the shell layer polyene monomer is between 2-50 parts, and both the core layer polyene monomer and the shell layer polyene monomer are greater than or equal to 1 share;

Emulsifier: 2 to 7 parts;

Oil-soluble initiator: 0.5 to 2 parts;

The concrete processing step of this method is as follows:

(1) Preparation of the nuclear layer:

(a) mix 30-70% core layer monoolefin monomer, 30-70% core layer polyolefin monomer and 20-80% oil-soluble initiator according to the proportioning ratio in the raw material Deionized water and emulsifier are pre-heated to 40°C to 50°C in a reactor to form a uniform emulsion, and the temperature is raised to 70°C to 95°C to react for 0.5 to 2 hours;

(b) Mix the remaining monoolefin monomers of the core layer and the polyolefin monomers of the core layer and uniformly add them to the above system, and react at a temperature range of 70° C. to 95° C. for 1 to 3 hours;

(2) Preparation of the shell:

(c) select the monoolefin monomer different from the core layer monoolefin monomer according to the proportioning in the raw material as the shell monoolefin monomer and the shell polyolefin monomer and the remaining oil-soluble initiator to mix uniformly Adding to the system after the reaction of step (b), reacting at a temperature range of 70°C to 95°C for 1 to 3 hours;

(d) After cooling and discharging, and after demulsification, washing, drying and other steps, the cross-linked core-shell nano-polymer microspheres proposed by the present invention can be obtained.

The cross-linked core-shell structure nano-polymer microspheres and the preparation method thereof proposed by the present invention, under the condition of the presence of emulsifiers and initiators, obtain high-density nanospheres with core-shell structure and nanoscale through emulsion or suspension polymerization with water as the medium. molecular microspheres. In the cross-linked core-shell structure nano-polymer microspheres of the present invention, the core layer and the shell layer are connected by chemical bonds, and have a strong interfacial effect; both the core and the shell are in a cross-linked state, which not only solves the problem of preparing nano The problem of scale core-shell latex particles, and also solve the problem that the core and shell of core-shell latex particles are mostly linear polymers, so the solvent resistance and oil absorption performance are low, and finally show various good properties in practical applications. nature. At the same time, the composition, structure and scale of the core and shell can be designed according to the needs, so as to obtain various soft-core hard-shell or hard-core soft-shell nano-polymer microspheres with different physical and chemical properties and application significance, and the core-shell can be placed for a long time The structure will not be reversed, and there is a high degree of freedom in the design of form and structure. The total reaction yield and gel rate are generally above 90%. In addition, the preparation process is simple and easy to realize industrial production, and the prepared nano-polymer microspheres can be stored for a long time, and can also be dried into a powder state, which is easy to store and use. The particle size of the cross-linked core-shell nano-polymer microspheres is less than 100nm, and has the special properties of nanoscale and nano-particles. These characteristics will make the cross-linked core-shell nano-polymer microspheres of the present invention have a wide range of applications in the future development of nano-material science and technology.

Description of drawings

Figure 1(a): Electron micrograph of cross-linked soft-core hard-shell nano-polymer PBA/PMMA microspheres;

Figure 1(b): Electron micrograph of crosslinked hard-core soft-shell nanopolymer PS/PBA microspheres;

Figure 2(a): The particle size distribution curve of crosslinked soft-core hard-shell nano-polymer PBA/PMMA microspheres;

Figure 2(b): The particle size distribution curve of crosslinked hard-core soft-shell nanopolymer PS/PBA microspheres.

Detailed ways

The present invention will be further described below by embodiment, to further understand the present invention.

Example 1: 70 parts of butyl acrylate (BA) as the core layer monoolefin monomer and 7 parts of trimethylolpropane trimethacrylate (TM) as the core layer polyolefin monomer were mixed uniformly and set aside. Add 360 parts of deionized water, 4 parts of sodium dodecylsulfonate (SDS) and 0.5 part of nonylphenol polyoxyethylene ether into a four-necked bottle equipped with mechanical stirring, reflux condenser and thermometer, and raise the temperature to 50°C , add 30% of the previously prepared mixture to form a uniform emulsion. Then add 80% of the initiator aqueous solution made up of 0.5 parts of water-soluble initiator ammonium persulfate and 72 parts of deionized water, and raise the temperature to 82° C. for 1.5 hours. Then, dropwise add the remaining previously prepared mixture to the system, and react for 1.5 hours after the dropwise addition is completed. Then add the remaining initiator solution, and dropwise add 30 parts of methyl methacrylate (MMA) (as shell monoolefin monomer) and 3 parts of trimethylolpropane trimethacrylate (TM) to the system ( As a mixture of shell polyene monomers), react for 1.5 hours after the dropwise addition. The temperature was raised to 90° C., and the reaction was continued for 0.5 hours, and then the material was cooled and discharged. Part of the emulsion after discharge was demulsified, washed, and dried to obtain a white powder product. The other part of the emulsion was placed in a test tube. It was found that no precipitation occurred after storage for 6 months, and the core-shell of microsphere particles was found under electron microscope observation. The structure is still well maintained, and no inversion phenomenon occurs. The total reaction yield was calculated to be 91.2%. After extracting the dried cross-linked core-shell nano-polymer microspheres with chloroform for 12 hours, the gel rate was measured to be 93.7%, indicating that the core-shell structure exists in a cross-linked form. From Figure 1a (electron microscope photo of PBA/PMMA), the expected core-shell structure can be clearly seen, while Figure 2a (particle size distribution test of PBA/PMMA) can be seen, its average particle size is in the range of 40 ~ 50nm, The particle size distribution is very narrow.

Example 2: 30 parts of styrene (St) as the core layer monoolefin monomer and 3 parts of divinylbenzene (DVB) as the core layer polyolefin monomer were mixed uniformly and set aside. Add 360 parts of deionized water, 6.5 parts of sodium dodecylsulfonate (SDS) and 0.5 part of nonylphenol polyoxyethylene ether into a four-necked bottle equipped with mechanical stirring, reflux condenser and thermometer, and raise the temperature to 50°C , add 70% of the previously prepared mixture to form a uniform emulsion. Then add 20% of the initiator aqueous solution made up of 0.5 parts of water-soluble initiator ammonium persulfate and 72 parts of deionized water, and raise the temperature to 82° C. for 40 minutes. Then the rest of the previously prepared mixture was added to the system, and the reaction was continued for 1 hour. Then add all the remaining initiator solution, and add 70 parts of butyl acrylate (BA) (as the shell monoolefin monomer) and 7 parts of divinylbenzene (DVB) (as the shell polyene monomer) to the system The mixture was then reacted for 2 hours. The temperature was raised to 90° C., and the reaction was continued for 0.5 hours, and then the material was cooled and discharged. Part of the emulsion after discharge was demulsified, washed, and dried to obtain a white powder product. The other part of the emulsion was placed in a test tube. It was also found that no precipitation occurred after storage for 6 months, and the nucleus of the microsphere particles was found under electron microscope observation. The shell structure is still well maintained, and no inversion phenomenon occurs. The total reaction yield was calculated to be 94.1%. After extracting the dried cross-linked core-shell nano-polymer microspheres with chloroform for 12 hours, the gel rate was measured to be 90.8%, which also indicated that both the core-shell existed in a cross-linked form. From Figure 1b (electron microscope photo of PS/PBA), the expected core-shell structure can be clearly seen, while Figure 2b (particle size distribution test of PS/PBA) can be seen, its average particle size is 40 ~ 50nm, particle size The distribution is very narrow.

Embodiment 3: the core layer monoolefin monomer in embodiment 1 is changed into the mixture of butyl acrylate and methyl acrylate of equal mass, and the shell layer monoolefin monomer is changed into the mixture of St and MMA, wherein MMA and St Mass ratio is 2: 1, all the other formulations are identical with example 1. The performance index of the obtained product is shown in Table 1.

Embodiment 4: Change the monoolefin monomer of the core layer in embodiment 1 into the same amount of methyl acrylate, the amount of initiator is increased to 2 parts, the system temperature is 70 ° C, and the reaction time under each step is 2 hours, 3 hours, 3 hours, and finally omit the step of raising the temperature to 90° C. and reacting for 0.5 hours, and the rest of the formula is the same as in Example 1. The performance index of the obtained product is shown in Table 1.

Embodiment 5: Change the core layer polyene monomer and the shell layer polyene monomer in embodiment 2 into 1 part of N, N-methylenebisacrylamide, and the emulsifier adopts 2 parts of sodium lauryl sulfate , the system temperature is 95° C., and the reaction time in each step is 0.5 hour, 1 hour, and 1 hour, respectively. All the other prescriptions are identical with embodiment 2. The performance index of the obtained product is shown in Table 1.

Example 6: 30 parts of styrene as the core layer monoolefin monomer and 20 parts of isoprene as the core layer polyene monomer were mixed uniformly and set aside. Add 360 parts of deionized water and 2 parts of tripropylmethylammonium chloride into a four-necked bottle equipped with mechanical stirring, reflux condenser and thermometer, raise the temperature to 50°C, add 70% of the previously prepared mixture and 0.1 part of oil-soluble initiator azobisisobutyronitrile forms a uniform emulsion. The temperature was raised to 70° C. for 2 hours. Then add the remaining mixture of St and DVB to the system, and continue to react for 3 hours. Then add the mixture of all remaining initiators, 70 parts of butyl acrylate (BA) (as the shell monoolefin monomer) and 30 parts of oligobutadiene (as the shell polyene monomer) in the system, and then React for 3 hours. The temperature was raised to 90° C., and the reaction was continued for 0.5 hours, and then the material was cooled and discharged. The performance index of the obtained product is shown in Table 1.

Embodiment 7: the emulsifier in embodiment 6 adopts the mixture of 6 parts of tripropylbenzyl ammonium chloride and 1 part of lauryl alcohol polyoxyethylene ether, and azobisisobutyronitrile is changed into the same amount of oil For the soluble initiator dibenzoyl peroxide, the temperature of the system is 95° C., and the time of each step is 0.5 hour, 1 hour, and 1 hour respectively, and the rest of the formula is the same as in Example 1. The performance index of the obtained product is shown in Table 1.

Embodiment 8: Change the sodium dodecylsulfonate in embodiment 6 into sodium dodecylbenzenesulfonate, change the monoolefin monomer of the core layer into 70 parts of BA, and change the monoolefin monomer of the shell layer into 30 parts MMA, initiator is the oil-soluble initiator azobisisobutyronitrile of the same amount, and all the other formulas are identical with embodiment 1. The performance index of the obtained product is shown in Table 1.

Embodiment 9: Change the emulsifier among the embodiment 6 into the same amount of tripropylmethylammonium bromide, and the initiator is 2 parts of oil-soluble initiator BPO, and all the other formulas are the same as in embodiment 1. The performance index of the obtained product is shown in Table 1.

Comparative Example 1: The preparation method is the same as in Example 1, but no polyene monomer is added to BA and MMA, and the performance indicators of the obtained product are shown in Table 1.

Comparative Example 2: The preparation method is the same as that of Example 2, but no emulsifier is added, the water and oil in the system are separated, and massive precipitates appear after the polymerization starts.

The results of the above examples are shown in Table 1.

Among the above examples, examples 1, 2, 3, 4, and 5 belong to the method of emulsion polymerization, and examples 6, 7, 8, and 9 belong to the method of suspension polymerization.

The present invention may be embodied in other specific forms without departing from the spirit or main characteristics of the invention. Therefore, no matter from which point of view, the above-mentioned embodiments of the present invention can only be regarded as descriptions of the present invention and cannot limit the present invention. The claims have pointed out the scope of the present invention. Any changes within the equivalent inclusion and range should be considered to be included in the scope of the claims.

Table 1 The product performance index of each embodiment Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Example 8 Example 9 Comparative example 1 Comparative example 2 basic phenomenon good good good good good good good good good A precipitation Yield(%) 91.2 94.1 89.6 95.2 93.5 87.4 92.6 95.5 90.0 88.4 - Gel rate (%) 93.7 90.8 94.3 98.7 86.2 91.7 96.1 92.8 94.6 0 - Particle size (nm) 40～50 40～50 40～50 40～50 40～50 40～50 40～50 40～50 40～50 30～60 -

Note: A. The phenomenon is that the gel rate is 0, and the shape of the product microspheres is irregular spherical, and the particle size distribution is wide.

Claims (7)

1. A cross-linked core-shell nano-polymer microsphere, characterized in that: the microsphere has a core-shell structure, and the inside of the core and the inside of the shell are all cross-linked structures, and the core and the shell are connected by chemical bonds. The diameter is less than 100nm; it is prepared from the following substances by emulsion polymerization or suspension polymerization with water as the medium: 1) Monoolefin monomer: the total mass of core layer monoolefin monomer and shell layer monoolefin monomer is 100 parts; wherein the mass of core layer monoolefin monomer is between 30-70 parts, and the shell layer monoolefin monomer is corresponding Between 70-30 copies; 2) polyene monomer: the total mass of the core layer polyene monomer and the shell layer polyene monomer is between 2-50 parts, and both of the core layer polyene monomer and the shell layer polyene monomer are greater than or equal to 1 copy; 3) Emulsifier: 2 to 7 parts; 4) Initiator: 0.5-2 parts. The monoolefin monomer refers to a monomer containing only one carbon-carbon double bond in the molecule, and one or more of vinyl chloride, acrylonitrile, acrylate or methacrylate is used. The multiolefin mono Monomer refers to a monomer containing two or more carbon-carbon double bonds in its molecule. 2. according to the described cross-linked core-shell structure nano polymer microsphere of claim 1, it is characterized in that: described polyene monomer adopts butadiene, isobutadiene, isoprene, divinyl One or more of benzene and trimethylolpropane trimethacrylate. 3. according to the described cross-linked core-shell structure nano polymer microsphere of claim 1, it is characterized in that: described emulsifying agent adopts one or more in the following substances: a. Cationic type: including tri-C _1-18 alkyl methyl ammonium chloride, tri-C _1-18 alkyl methyl ammonium bromide, tri-C _1-18 alkyl benzyl ammonium chloride, tri-C _1-18 Alkyl benzyl ammonium bromide, or tri-C _1-18 alkyl methyl benzyl ammonium chloride, tri-C _1-18 alkyl ethyl benzyl ammonium chloride, tri-C _1-18 alkyl methyl benzyl ammonium Ammonium bromide, three C _1~18 alkyl ethyl benzyl ammonium bromide; b. Anionic type: including C _12~18 alkyl sodium sulfate, C _12~18 alkyl potassium sulfate, C _12~18 alkyl sulfonate sodium, C _12~18 alkyl sulfonate potassium, C _12~18 alkyl Sodium benzenesulfonate, potassium C _12-18 alkylbenzenesulfonate; c. Non-ionic type: including C3~10 alkylphenol polyoxyethylene (4~50) ether, C2~18 fatty alcohol polyoxyethylene (4~50) ether, polyoxyethylene (4~50) sorbitol single C11 ～18 fatty acid ester or polyoxyethylene (4～50) sorbitol three C11～18 fatty acid ester. 4. The cross-linked core-shell structure nano-polymer microsphere according to claim 1, characterized in that: the initiator is capable of dissociation energy of 30-35 kcal/mol and capable of Water-soluble persulfate substances or oil-soluble azo and peroxide substances that produce free radicals that lead to the polymerization of olefin monomers. 5. according to the described cross-linked core-shell structure nano polymer microsphere of claim 4, it is characterized in that: described initiator is potassium persulfate, ammonium persulfate, azobisisobutyronitrile or azobisisoheptyl One of nitriles; or a redox system composed of hydrogen peroxide, dibenzoyl peroxide, ferrous salt, sulfite, and thiosulfate respectively. 6. an emulsion polymerization method preparing crosslinked core-shell structure nano-polymer microspheres as claimed in claim 1, is characterized in that: the method uses monoolefin monomer, multiolefin monomer, emulsifier and initiator as Raw materials, wherein the content of each component is: Monoolefin monomer: the total mass of the core layer monoolefin monomer and the shell layer monoolefin monomer is 100 parts; the mass of the core layer monoolefin monomer is between 30-70 parts, and the shell layer monoolefin monomer is correspondingly 70 parts Between -30 copies; Multiolefin monomer: the total mass of the core layer polyene monomer and the shell layer polyene monomer is between 2-50 parts, and both the core layer polyene monomer and the shell layer polyene monomer are greater than or equal to 1 share; Emulsifier: 2 to 7 parts; Water-soluble initiator: 0.5-2 parts; The monoolefin monomer refers to a monomer containing only one carbon-carbon double bond in the molecule, and one or more of vinyl chloride, acrylonitrile, acrylate or methacrylate is used. The multiolefin mono Monomer refers to a monomer containing two or more carbon-carbon double bonds in its molecule. The processing steps of the method are as follows: (1) Preparation of the nuclear layer: (a) Mix 30-70% of the core layer monoolefin monomer and 30-70% of the core layer polyolefin monomer according to the above-mentioned raw material ratio and put them into the mixture containing deionized water and emulsifier and raise the temperature to 40°C~ A uniform emulsion is formed in a reactor at 50°C, and a water-soluble initiator accounting for 20% to 80% of the total amount is added to the reactor, and the temperature is raised to a temperature range of 70°C to 95°C for 0.5 to 2 hours; (b) Mixing the remaining monoolefin monomer of the core layer with the remaining polyolefin monomer of the core layer and uniformly adding it to the above system, and reacting at a temperature range of 70°C to 95°C for 1 to 3 hours; (2) Preparation of the shell: (c) According to the ratio of the raw materials, a monoolefin monomer different from the core layer monoolefin monomer is selected as the shell monoolefin monomer and the shell polyolefin monomer is mixed evenly and added to the system after step (b) reaction , then add the remaining water-soluble initiator, and react at a temperature range of 70°C to 95°C for 1 to 3 hours; (d) After cooling and discharging, and after the steps of demulsification, washing and drying, the nano-polymer microspheres with cross-linked core-shell structure proposed by the present invention can be obtained. 7. A suspension polymerization method for preparing crosslinked core-shell structure nano-polymer microspheres as claimed in claim 1, characterized in that: the method takes monoolefin monomers, polyolefin monomers, emulsifiers and initiators as raw materials , wherein the content of each component is: Monoolefin monomer: the total mass of the core layer monoolefin monomer and the shell layer monoolefin monomer is 100 parts; the mass of the core layer monoolefin monomer is between 30-70 parts, and the shell layer monoolefin monomer is correspondingly 70 parts Between -30 copies; Multiolefin monomer: the total mass of the core layer polyene monomer and the shell layer polyene monomer is between 2-50 parts, and both the core layer polyene monomer and the shell layer polyene monomer are greater than or equal to 1 share; Emulsifier: 2 to 7 parts; Oil-soluble initiator: 0.5 to 2 parts; The monoolefin monomer refers to a monomer containing only one carbon-carbon double bond in the molecule, and one or more of vinyl chloride, acrylonitrile, acrylate or methacrylate is used. The multiolefin mono Monomer refers to a monomer containing two or more carbon-carbon double bonds in its molecule. The processing steps of the method are as follows: (1) Preparation of the nuclear layer: (a) mix 30-70% core layer monoolefin monomer, 30-70% core layer polyolefin monomer and 20-80% oil-soluble initiator according to the proportioning ratio in the raw material Deionized water and emulsifier are pre-heated to 40°C to 50°C in a reactor to form a uniform emulsion, and the temperature is raised to 70°C to 95°C to react for 0.5 to 2 hours; (b) Mixing the remaining monoolefin monomers of the core layer and the polyolefin monomers of the core layer and uniformly adding them to the reaction system of the above step (a), and reacting at a temperature range of 70°C to 95°C for 1 to 3 hours; (2) Preparation of the shell: (c) Select the monoolefin monomer different from the core layer monoolefin monomer according to the proportioning ratio in the raw material as the shell monoolefin monomer and the shell polyolefin monomer and the remaining oil-soluble initiator to mix evenly into the In the system after the reaction of step (b), react within the temperature range of 70°C to 95°C for 1 to 3 hours; (d) After cooling and discharging, and after the steps of demulsification, washing and drying, the nano-polymer microspheres with cross-linked core-shell structure proposed by the present invention can be obtained.

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