CN1258544C - Nano macromolecule microball of carboxy function type cross-linked nucleocapsid structure and preparation process thereof - Google Patents

Abstract

The invention discloses a method for preparing carboxyl functional cross-linked core-shell structure nano polymer microspheres, which belongs to the technical field of polymer materials. The invention uses a variety of organic olefin monomers and olefin monomers with carboxyl functional groups as raw materials, and prepares them through soap-free emulsion or soap-free suspension polymerization with water as the medium; the product has a core-shell structure, and the inside of the core and the inside of the shell are both It is cross-linked, the core and the shell are connected by chemical bonds, and the carboxyl functional group is grafted on the surface of the microsphere, and its particle size is less than 100nm. The invention obtains various nano-polymer microspheres with different physical and chemical properties by changing the composition and structure of the core and the shell, and has a high degree of freedom in the choice of structure design. The soap-free polymerization method adopted in the invention makes the product easy to purify, is applicable to various fields requiring high purity, and greatly reduces the production cost. At the same time, the introduction of carboxyl functional groups with high reactivity and ionization makes it have a very broad application prospect in the field of nanotechnology.

Description

Preparation method of carboxyl functional cross-linked core-shell nano-polymer microspheres

technical field

The invention relates to a method for preparing carboxyl-functional cross-linked core-shell nano-polymer microspheres, belonging to polymer materials

technology field.

Background technique

In recent years, the preparation of nano-polymer microspheres with core-shell structure has attracted more and more attention of researchers. This core-shell polymer microsphere not only has a nanoscale, but also can change the composition of the core and shell according to the needs, and obtain products with different physical and chemical properties, which has a high degree of freedom in design. Conventional emulsion polymerization or suspension polymerization is an important means to synthesize such nanospheres.

The present inventors have successfully prepared cross-linked core-shell nano-polymer microspheres, and functionalized them with carboxyl groups on the surface, which solved the previous problem that the core-shell polymer microspheres do not have a nanometer scale, and solved the previous problems. The core-shell polymer microspheres synthesized by humans are generally linear polymers in the core or shell, the swelling ratio of the microspheres in the solvent is very low, the solvent resistance and oil absorption performance are also poor, and they will have high reactivity And ionizable carboxyl functional groups are grafted on the surface of cross-linked core-shell nano-polymer microspheres, so that its application value in reactive blending and many related fields has been qualitatively improved. However, the synthesis of this carboxyl-functional nano-polymer microspheres adopts conventional emulsion polymerization or suspension polymerization, and the use of emulsifiers or dispersants brings great difficulties to the separation, purification and purification of the product, making it difficult for Applications in fields with high product purity requirements are greatly restricted. At the same time, increasing the difficulty of purification means increasing the production cost, and the use of emulsifier or dispersant itself will greatly increase the production cost.

Contents of the invention

The purpose of the present invention is to adopt the method of soap-free polymerization to synthesize a kind of carboxyl functional cross-linked core-shell nano-polymer microspheres. The method intends to select a variety of olefin monomers through soap-free polymerization reaction means, so that it first forms a core-shell Structured nano-polymer microspheres, and then introduce carboxyl functional groups that can react with various polymer substrates and have ionization properties on the shell surface of the microspheres. The soap-free polymerization method described in the present invention does not use an additional emulsifier, but selects a monomer with a carboxyl functional group that can participate in the polymerization reaction as an emulsifier, and finally the monomer becomes a part of the composite particle through the reaction, eliminating the need for an emulsifier. Steps for washing emulsifiers. This can not only solve the cost increase caused by the use of emulsifiers in the previous production process, but also the difficulty of product separation and purification, so that the product can be used in applications that require high purity; The highly reactive and ionizable carboxyl functional groups make it widely used in polymer material modifiers, water treatment agents, catalysts, sensing agents, protein carriers, microcapsule embedding and other fields, greatly improving its application. value. The soap-free polymerization method used in the present invention prepares carboxyl functional nano-polymer microspheres, which not only can maintain the size of the nano-sized particles, but also has very high design freedom in terms of particle structure, particle size, particle surface physical and chemical properties, etc. Therefore, it is a very valuable method for the preparation of composite nanoparticles.

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

A soap-free emulsion polymerization method of carboxyl functional crosslinked core-shell nano-polymer microspheres, characterized in that the method uses the following materials as raw materials:

Monoolefin monomer: 100 parts based on the total mass of core layer monoolefin monomer and shell layer monoolefin monomer (other components are quantified based on this); wherein the core layer monoolefin monomer quality is between 30- Between 70 parts, the shell monoolefin monomer is between 70-30 parts;

Multi-olefin 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 copy;

Olefin monomers with carboxyl or carboxylate functional groups: 2 to 40 parts;

Water-soluble initiator: 0.2 to 3 parts;

Its specific process steps are as follows:

(a) Add the water-soluble alkali whose mass is 50-150% of the olefin monomer containing carboxyl functional group to the olefin monomer containing carboxyl functional group; if the olefin monomer containing carboxylate group is used, no alkali is needed ;

(b) Mix 30-70% of the core layer monoolefin monomer with 30-70% of the core layer polyolefin monomer according to the above raw material ratio, and set aside;

(c) Add 20 to 80% of the total material obtained in step (a) to a reactor containing deionized water and heated to 40°C to 50°C, and then add the mixture obtained in step (b) to form a uniform emulsion ;

(d) 20-50% of all water-soluble initiators are added in the same reactor, and the temperature is raised to 60°C-95°C for 0.5-6 hours;

(e) Add 20% to 30% of all water-soluble initiators, then mix the remaining monoolefin monomers of the core layer with the remaining polyolefin monomers of the core layer and add them into the above system evenly, and react within the above temperature range for 0.5 ~ 6 Hour;

(f) Add the remaining water-soluble initiator, and then select a monoolefin monomer different from the core layer monoolefin monomer according to the proportion of the raw materials as the shell monoolefin monomer and the shell polyolefin monomer to mix and evenly add the step (e) in the system after the reaction, then react at a temperature range of 60°C to 95°C for 0.5 to 4 hours;

(g) adding remaining material obtained by step (a), and reacting within the above-mentioned temperature range for 0.5 to 4 hours;

(h) After cooling and discharging, add a water-soluble acid with a mass of 50% to 150% of the mass of olefin monomers containing carboxyl functional groups, and after demulsification, washing and drying steps, the carboxyl functional type proposed by the present invention can be obtained. Cross-linked core-shell structure nano-polymer microspheres.

The monoolefin monomer described in the present invention refers to one or more of α-olefins, styrene, vinyl chloride, acrylonitrile, acrylate, and methacrylate containing only one carbon-carbon double bond in the molecule; The polyene monomer mentioned above refers to a substance containing two or more carbon-carbon double bonds in the molecule, selected from butadiene, isobutadiene, isoprene, divinylbenzene, trimethacrylic acid One or more of trimethylolpropane esters.

The carboxyl group or carboxylate group functional group olefin monomer in the present invention refers to the carbon-carbon unsaturated double bond represented by the chemical structure simplified formula (a) and the carbon-carbon unsaturated double bond represented by the formula (b) in the molecular structure. An olefinic substance with a carboxyl functional group; or an olefinic substance with a carbon-carbon unsaturated double bond represented by the simplified chemical structure formula (a) and a carboxylate functional group represented by the formula (c) in the molecular structure.

-COOH - (b)

-COO ^ M ^ ——(c) M ^ = Li ^ or Na ^ or K ^ or NH ₄ ^

The water-soluble initiator described in the present invention refers to persulfate and hydrogen peroxide water-soluble substances that have a dissociation energy of 30-35 kcal/mol and can generate free radicals to cause the polymerization of olefin monomers under the condition of 40-95°C . For example, potassium persulfate, ammonium persulfate, azobisisobutyronitrile or azobisisoheptanonitrile, or hydrogen peroxide, dibenzoyl peroxide and ferrous salt, sulfite, thiosulfate respectively Composed redox system.

Another soap-free suspension polymerization method of carboxyl-functional cross-linked core-shell nano-polymer microspheres provided by the present invention is characterized in that the method uses the following substances as raw materials:

Monoolefin monomer: 100 parts based on the total mass of core layer monoolefin monomer and shell layer monoolefin monomer (other components are quantified based on this); wherein the core layer monoolefin monomer quality is between 30- Between 70 parts, the shell monoolefin monomer is between 70-30 parts;

Multi-olefin 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 copy;

Olefin monomers with carboxyl or carboxylate functional groups: 2 to 40 parts;

Oil-soluble initiator: 0.2 to 3 parts;

Its process steps are as follows:

(a) Add the water-soluble alkali whose mass is 50-150% of the olefin monomer containing carboxyl functional group to the olefin monomer containing carboxyl functional group; if the olefin monomer containing carboxylate group is used, no alkali is needed ;

(b) mix uniformly 30-70% of the core layer monoolefin monomer, 30-70% of the core layer polyolefin monomer and 20% to 50% of all oil-soluble initiators according to the above raw material ratio, and set aside;

(c) Add 20 to 80% of the total material obtained in step (a) to a reactor containing deionized water and heated to 40°C to 50°C, and then add the mixture obtained in step (b) to form a uniform emulsion ;

(d) heating the system obtained in step (c) to a temperature range of 60° C. to 95° C. and reacting for 0.5 to 6 hours;

(e) Mixing the remaining monoolefin monomer of the nuclear layer, the remaining multiolefin monomer of the nuclear layer and all oil-soluble initiators into the above-mentioned system, and reacting within the above-mentioned temperature range for 0.5 to 6 hours;

(f) select the monoolefin monomer different from the core layer monoolefin monomer as the shell monoolefin monomer and the shell polyolefin monomer and the remaining oil-soluble initiator according to the proportioning ratio of the raw materials to mix and evenly add the step (e) in the system after the reaction, then react at a temperature range of 60°C to 95°C for 0.5 to 4 hours;

(g) adding remaining material obtained by step (a), and reacting within the above-mentioned temperature range for 0.5 to 4 hours;

(h) After cooling and discharging, add a water-soluble acid with a mass of 50% to 150% of the mass of olefin monomers containing carboxyl functional groups, and after demulsification, washing and drying steps, the carboxyl functional type proposed by the present invention can be obtained. Cross-linked core-shell structure nano-polymer microspheres.

The oil-soluble initiator in the present invention refers to azo and peroxide oil-soluble substances that have a dissociation energy of 30-35 kcal/mol and can generate free radicals to lead to the polymerization of olefin monomers under the condition of 40-95°C. A redox system composed of azobisisobutyronitrile, dibenzoyl peroxide or dibenzoyl peroxide and ferrous salt, sulfite and thiosulfate respectively can be used.

The preparation method of the carboxyl functional cross-linked core-shell nano-polymer microspheres proposed by the present invention does not use an additional emulsifier, which significantly reduces the production cost, and at the same time, the olefin monomer with a carboxyl functional group that acts as an emulsifier reacts to become A part of the particle saves the step of washing the emulsifier, facilitates the separation and purification of the product, improves the production efficiency, and makes the product widely used in fields that require high purity. The carboxyl functional cross-linked core-shell nano-polymer microspheres of the present invention are connected by chemical bonds between the core layer and the shell layer, and have a strong interfacial effect. The total reaction yield and gel rate are generally 90 %above. Both the core and the shell are in a cross-linked state, which not only solves the problem of preparing nanoscale core-shell latex particles, but also solves 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 poor. Lower problems eventually exhibit various favorable properties in practical applications. At the same time, the present invention introduces highly reactive and ionizable carboxyl functional groups on the surface of cross-linked core-shell nano-polymer microspheres, so that it has broad application prospects in the fields of reaction blending, water purifiers, catalysts, protein carriers, etc. . In addition, 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 nano-polymer microspheres with different physical and chemical properties and application significance, and can be used for a long time Placing the core-shell structure will not reverse, and there is a high degree of freedom in the design of the shape and structure. The preparation and operation of the carboxyl functional joint core-shell nano-polymer microsphere is simple, and industrial production is easy to realize. The manufactured product can be stored stably for a long time, and can also be dried into a powder state, which is easy to store and use. These characteristics will make the carboxyl functional crosslinked core-shell nano-polymer microspheres of the present invention have a wide range of applications in the future development of nanomaterial science and technology.

Description of drawings

Figure 1 is an electron microscope photo of carboxyl-functional cross-linked core-shell nano-PBA/PMMA/POA polymer microspheres.

Fig. 2 is a particle size distribution curve of carboxyl-functional cross-linked core-shell nano-PBA/PMMA/POA polymer microspheres.

Detailed ways

The following examples further illustrate the invention.

Example 1: Add 20 parts of a mixed solution made of 40 parts of oleic acid (OA), 20 parts of sodium hydroxide and 100 parts of deionized water into a reactor containing 370 parts of deionized water and heated up to 40-50 ° C. %, and then add 30% of a homogeneous mixture of 70 parts of butyl acrylate (BA) as the core layer monoolefin monomer and 7 parts of trimethylolpropane trimethacrylate (TM) as the core layer multiolefin monomer. Heat up to 60°C, add 50% of the solution made of 0.2 parts of ammonium persulfate and 50ml of deionized water, and then react at 80°C for 1.5 hours. Add 30% of the total initiator solution, add the remaining mixture of BA and TM to the above system, and continue the reaction for 1.5 hours. Add the remaining initiator solution, and add 30 parts of methyl methacrylate (MMA) (as shell monoolefin monomer) and 3 parts of trimethylolpropane trimethacrylate (TM) to the system (as shell Layer multi-olefin monomer) mixture, reacted for 1 hour after the dropwise addition. Slowly drop the remaining mixed solution of oleic acid and sodium hydroxide into the above system, and react within the above temperature range for 1 hour. After a part of the emulsion was cooled and discharged, 20 parts of 1mol/l hydrochloric acid were added, and after demulsification and drying treatment, a white powder product was obtained. The other part of the emulsion was placed in a test tube, and it was found that no precipitation occurred after storage for 6 months. Figure 1 is an electron micrograph of the synthesized PBA/PMMA/POA carboxyl functional cross-linked core-shell polymer microspheres, from which the expected clear core-shell structure can be seen, the total reaction yield is 97.1%, and the gel rate 93.6%; Figure 2 is the particle size distribution curve of the microspheres, it can be seen that the particle size distribution is within the range of 40-50nm.

Embodiment 2: Add 80% of 10 parts of sodium acrylate to the reactor containing 370 parts of deionized water and be warmed up to 40～50 ℃, then add 30 parts of styrene (St) as the core layer monoolefin monomer and 3 Parts of divinylbenzene (DVB) as 70% of the homogeneous mixture of core layer polyene monomers. Heat up to 60°C, add 20% of the solution made of 3 parts of ammonium persulfate and 50ml of deionized water, and then react at 60°C for 6 hours. Add 20% of the total initiator solution, add the remaining mixture of St and DVB to the above system, and continue to react for 6 hours. Add the remaining initiator solution and add a mixture of 7 parts of methyl acrylate (BMA) (as the shell monoolefin monomer) and 3 parts of divinylbenzene (DVB) (as the shell polyene monomer) to the system , and then reacted for 4 hours. Add the remaining sodium acrylate to the above system, and react within the above temperature range for 4 hours. After cooling and discharging, add 15 parts of 1mol/l sulfuric acid, break the emulsion and dry. The total reaction yield is 97.1%, the gel rate is 93.6%, and the particle size distribution is in the range of 40-50nm.

Embodiment 3: change the methyl methacrylate in embodiment 1 into equivalent ethyl acrylate, and change the initiator into the redox initiation system of 2 parts of hydrogen peroxide and 1 part of sodium sulfite, and add the initiator for the second time The amount of agent is 30% of whole initiator solution, and all the other formulas and steps are identical with embodiment 1. The yield and gel rate of the obtained product are 89.2%, 3478% and 88.1% respectively, and the particle size distribution is 40-50nm.

Embodiment 4: change 30 parts of styrene in embodiment 2 into methyl methacrylate of the same weight, and change all divinylbenzene into isoprene of the same weight, and the initiator is an equivalent amount of over Potassium sulfate, all the other formulas and steps are identical with embodiment 1. The yield, grafting rate and grafting efficiency of the obtained product are 86.4%, 3639% and 92.2% respectively, and the particle size distribution is 50-60nm.

Example 5: The sodium acrylate in Example 2 was changed to 2 parts of sodium 1-dodecenate, the reaction was carried out at 95° C., and the reaction time of each step was 0.5 hour. The rest of the formula and steps were the same as in Example 2. The yield and gel rate of the obtained product are 91.3% and 89.5% respectively, and the particle size distribution is 40-50nm.

Example 6: Add 20% of the mixed solution made of 40 parts of acrylic acid (MAA), 20 parts of potassium hydroxide and 100 parts of deionized water into a reactor containing 370 parts of deionized water and warming up to 40-50 °C , and then add 70 parts of oligobutadiene (LPB) as the core layer monoolefin monomer and 7 parts of trimethylolpropane trimethacrylate (TM) as the core layer polyene monomer and 0.1 part of azobis 30% of a homogeneous mixture of isobutyronitrile. Then, it was reacted at 80°C for 1.5 hours. A mixture of 0.06 parts of azobisisobutyronitrile and the remaining LPB and TM was added, and the reaction was continued for 1.5 hours. A mixture of 0.04 parts of azidoisobutyronitrile and 30 parts of methyl methacrylate (MMA) (as the shell monoolefin monomer) and 3 parts of trimethylolpropane trimethacrylate (TM) (as the shell poly olefin monomer) and then reacted for 1 hour. The remaining mixed solution of oleic acid and potassium hydroxide was slowly added dropwise to the above system, and reacted within the above temperature range for 1 hour after the dropwise addition. After cooling and discharging, add 60 parts of 1mol/l hydrochloric acid, and after demulsification and drying treatment, a white powdery product is obtained. The total reaction yield is 97.1%, the gel rate is 93.6%, and the particle size distribution is within the range of 40-50nm.

Example 7: Add 1.6 parts of sodium dodecenoate to a reactor containing 370 parts of deionized water and heat up to 40-50°C, and then add 70 parts of styrene (St) as the core monoolefin monomer 30% of a homogeneous mixture formulated with 7 parts of trimethylolpropane trimethacrylate (TM) as the core layer polyene monomer and 0.04 parts of dibenzoyl peroxide. Then, it was reacted at 60°C for 6 hours. Add 0.06 parts of dibenzoyl peroxide and the remaining mixture of St and TM, and continue the reaction for 6 hours. A mixture of 0.1 parts of dibenzoyl peroxide and 30 parts of ethyl acrylate (MBA) (as the shell monoolefin monomer) and 3 parts of divinylbenzene (DVB) (as the shell polyolefin monomer) was added, Then react for 4 hours. 0.4 part of sodium 1-dodecenate was added to the above system, and then reacted within the above temperature range for 4 hours. After cooling and discharging, add 1 part of 1mol/l sulfuric acid, and after demulsification and drying treatment, a white powdery product is obtained. The total reaction yield is 97.1%, the gel rate is 93.6%, and the particle size distribution is within the range of 60-70nm.

Embodiment 8: Change the amount of initiator added in each step in Example 6 to 1.5 parts, 0.9 parts, and 0.6 parts respectively, and the reaction is carried out at 95° C., and the reaction time of each step is 0.5 hours. Example 6 is the same. The reaction yield is 88.7%, the gel rate is 93.5%, and the particle size distribution is 60-70nm.

Embodiment 9: Change the initiator of each step among the embodiment 7 into the redox initiation system that the dibenzoyl peroxide of equal consumption and sodium sulfite (the two mass ratios are 2: 1) form, and adopt oligomeric butanedi Alkene is used as the core layer polyene monomer, and the reaction time of each step is 1 hour. All the other formulas and steps are identical with embodiment 7. The reaction yield is 95.2%, the gel rate is 92.8%, and the particle size distribution is 50-60nm.

Comparative Example 1: The preparation method is the same as in Example 1, but the mixed solution of oleic acid and sodium hydroxide is added to the system all at once, and the system is slightly demulsified with precipitation. The yield and gel rate of the obtained product were 72.3% and 46.8% respectively, and the particle size distribution was 30-110 nm (very wide distribution).

Comparative Example 2: The preparation method is the same as in Example 6, but no potassium hydroxide is added to the acrylic acid, and the system is separated during the reaction process, and severe demulsification and precipitation occur.

In above each embodiment, embodiment 1,2,3,4,5 belongs to the method for soap-free emulsion polymerization, and embodiment 6,7,8,9 belongs to the method for soap-free 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, and the claims have pointed out the scope of the present invention, therefore, within the scope of the claims of the present invention Any changes within should be considered to be included in the scope of the claims.

Claims (8)

1. a kind of soap-free emulsion polymerization method of carboxyl functional type cross-linked core-shell structure nano polymer microsphere, it is characterized in that, this method is raw material with following material: 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 parts; the monoolefin monomer refers to one of α-olefins, styrene, vinyl chloride, acrylonitrile, acrylate, and methacrylate containing only one carbon-carbon double bond in the molecule species or several; 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 part; the polyene monomer refers to a substance containing two or more carbon-carbon double bonds in the molecule; 3) Olefin monomers with carboxyl or carboxylate functional groups: 2 to 40 parts; 4) Water-soluble initiator: 0.2 to 3 parts; Its specific process steps are as follows: (a) Add the water-soluble alkali whose mass is 50-150% of the olefin monomer containing carboxyl functional group to the olefin monomer containing carboxyl functional group; if the olefin monomer containing carboxylate group is used, no alkali is needed ; (b) Mix 30-70% of the core layer monoolefin monomer with 30-70% of the core layer polyolefin monomer according to the above raw material ratio, and set aside; (c) Add 20 to 80% of the total material obtained in step (a) to a reactor containing deionized water and heated to 40°C to 50°C, and then add the mixture obtained in step (b) to form a uniform emulsion ; (d) 20-50% of all water-soluble initiators are added in the same reactor, and the temperature is raised to 60°C-95°C for 0.5-6 hours; (e) Add 20% to 30% of all water-soluble initiators, then mix the remaining monoolefin monomers of the core layer with the remaining polyolefin monomers of the core layer and add them into the above system evenly, and react within the above temperature range for 0.5 ~ 6 Hour; (f) Add the remaining water-soluble initiator, and then select a monoolefin monomer different from the core layer monoolefin monomer according to the proportion of the raw materials as the shell monoolefin monomer and the shell polyolefin monomer to mix and evenly add the step (e) in the system after the reaction, then react at a temperature range of 60°C to 95°C for 0.5 to 4 hours; (g) adding remaining material obtained by step (a), and reacting within the above-mentioned temperature range for 0.5 to 4 hours; (h) After cooling and discharging, add a water-soluble acid with a mass of 50% to 150% of the mass of olefin monomers containing carboxyl functional groups, and after demulsification, washing and drying steps, the carboxyl functional type proposed by the present invention can be obtained. Cross-linked core-shell structure nano-polymer microspheres. 2. according to the described preparation method of claim 1, it is characterized in that: the material containing two or more carbon-carbon double bonds is selected from butadiene, isobutadiene, isoprene, diethylene One or more of phenylbenzene and trimethylolpropane trimethacrylate. 3. according to the described preparation method of claim 1, it is characterized in that: described carboxyl-containing or carboxylate functional group olefin monomer, refers to containing simultaneously in molecular structure represented by chemical structure simplified formula (a) Carbon-carbon unsaturated double bonds and olefinic substances represented by carboxyl functional groups represented by formula (b), or containing carbon-carbon unsaturated double bonds represented by chemical structure (a) and represented by formula (c) in the molecular structure ) represents the olefinic substance of the carboxylate functional group.

M ^ = Li ^ or Na ^ or K ^ or NH ₄ ^ 4. according to the preparation method described in claim 1, it is characterized in that: described water-soluble initiator refers to under the condition of 40～95 ℃, has 30～35kcal/mol dissociation energy and can produce free radical to lead to olefin monomer Polymeric persulfate and hydrogen peroxide water soluble substances. 5. according to the described preparation method of claim 4, it is characterized in that: described water-soluble initiator is potassium persulfate, ammonium persulfate or hydrogen peroxide and ferrous salt, sulfite, thiosulfate respectively composition of the redox system. 6. A soap-free suspension polymerization method of carboxyl functional crosslinked core-shell nano-polymer microspheres, characterized in that: the method uses the following substances as raw materials, 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) Olefin monomers with carboxyl or carboxylate functional groups: 2 to 40 parts; 4) Oil-soluble initiator: 0.2 to 3 parts; Its process steps are as follows: (a) Add the water-soluble alkali whose mass is 50-150% of the olefin monomer containing carboxyl functional group to the olefin monomer containing carboxyl functional group; if the olefin monomer containing carboxylate group is used, no alkali is needed ; (b) Mix 30-70% of the core layer monoolefin monomer, 30-70% of the core layer polyolefin monomer and 20% to 50% of all oil-soluble initiators uniformly according to the above raw material ratio, and set aside; (c) Add 20 to 80% of the total material obtained in step (a) to a reactor containing deionized water and heated to 40°C to 50°C, and then add the mixture obtained in step (b) to form a uniform emulsion ; (d) heating the system obtained in step (c) to a temperature range of 60° C. to 95° C. and reacting for 0.5 to 6 hours; (e) Mixing the remaining monoolefin monomer of the core layer, the polyolefin monomer of the remaining core layer, and 20% to 30% of all oil-soluble initiators into the above system, and reacting in the above temperature range for 0.5 to 6 hours; (f) select the monoolefin monomer different from the core layer monoolefin monomer as the shell monoolefin monomer and the shell polyolefin monomer and the remaining oil-soluble initiator according to the proportioning ratio of the raw materials to mix and evenly add the step (e) in the system after the reaction, then react in the temperature range of 60°C to 95°C for 0.5 to 4 hours; (g) adding remaining material obtained by step (a), and reacting within the above-mentioned temperature range for 0.5 to 4 hours; (h) After cooling and discharging, add a water-soluble acid with a mass of 50% to 150% of the mass of olefin monomers containing carboxyl functional groups, and after demulsification, washing and drying steps, the carboxyl functional type proposed by the present invention can be obtained. Cross-linked core-shell structure nano-polymer microspheres. 7. according to the preparation method described in claim 6, it is characterized in that: described oil-soluble initiator refers to under the condition of 40～95 ℃, has 30～35kcal/mol dissociation energy and can produce free radical to lead to olefin monomer Polymeric azo and peroxide oil soluble substances. 8. according to the described preparation method of claim 7, it is characterized in that: described oil-soluble initiator is azobisisobutyronitrile, dibenzoyl peroxide or dibenzoyl peroxide respectively with ferrous salt, A redox system composed of sulfite and thiosulfate.