CN104877166B - A kind of closing of suspension polymerisation original position prepares method of the low-density surface without osmotic polymer microballoon - Google Patents

Abstract

The invention relates to a method for preparing surface non-permeable low-density polymer microspheres by in-situ sealing by suspension polymerization, and belongs to the technical field of polymer functional materials. This method uses low-permeability porous or hollow microspheres with micropores on the surface as seeds, and utilizes the characteristics of good affinity between monomers and polymers to diffuse the monomers to the surface of the seed microspheres to form a monomer liquid layer, and then carry out The in-situ polymerization reaction forms a polymer coating to close the pores on the surface of the microspheres, and obtains the surface impermeable low-density polymer microspheres. The polymer microspheres sealed by the method of the present invention have properties such as good insulation, light dispersion, acoustic insulation, elasticity and compressive strength, so that they can be used in oil drilling additives, acid mist suppression, ultrasonic contrast reagents, photoelectric materials, coatings, etc. , Adhesives, papermaking, communications and other fields have broad application prospects.

Description

Preparation of Low Density Surface Impermeable Polymer Microspheres by Suspension Polymerization in Situ Sealing Methods

technical field

The invention relates to a method for preparing surface non-permeable low-density polymer microspheres by in-situ sealing by suspension polymerization, and belongs to the technical field of polymer functional materials.

Background technique

New polymer microspheres have been widely used in various fields. According to different needs, people have been able to prepare new polymer microspheres with various sizes, shapes and microstructures. Among them, hollow or porous polymer microspheres with low-density surface and impermeability have attracted extensive attention in order to meet the special needs in the fields of oil drilling additives and acid mist suppression.

At present, the research work on low-density hollow or porous polymer microspheres mainly focuses on the preparation of special structural characteristics (such as: shell-core , phase separation, etc.), and then assisted by extraction, dialysis, solvent evaporation, etching, spray drying, vacuum drying, etc., to remove the liquid phase from the microspheres to obtain hollow or porous microspheres. Among them, Chinese patent CN101250244B reported a method for preparing polymer hollow microspheres with a large amount of hollow microspheres and negative pressure inside the hollow microspheres by spray drying, and CN1303140C reported a method for preparing polymers by etching with strong acid. The method of hollow microspheres, CN100562358C reported a method for preparing polymer hollow microspheres with hydrogel templates, 201010543593.8, 201010624786.6, 201110040481.5, 201110052468.1, 201110150863.3, 201110150862.9, etc. reported the preparation of various polymer hollow microspheres or method. The polymer microspheres prepared by the above method need to remove the porogen (or solvent, template, etc.) or shell) and the internal holes (or cavities) are through-type and have strong permeability. When the microspheres are soaked in liquid for a long time, the liquid components will penetrate into the core through the micropores on the surface of the microspheres Holes (or cavities), resulting in a rapid increase in the density of microspheres, greatly reducing their buoyancy. Furthermore, due to the need for outward migration of the porogen, the shell thickness of these microspheres tends to be small, so the mechanical properties are generally poor. Therefore, it is necessary to improve and optimize the preparation method of hollow or porous polymer microspheres to prepare low-density surface-impermeable polymer microspheres with good mechanical properties and density retention.

Preparation of hollow or porous microspheres based on gas templates is a method to achieve impermeability on the surface of microspheres. So far, different research workers have used thermoplastic polymers to wrap inert gases and then solidify them when they are cooled (Sun Yanlin et al., A polymer hollow microsphere with no surface permeability and its preparation method, Chinese patent CN201310060560.1), and water Solidification of curing monomers on water vapor microbubbles (Toshinori Makuta, et al. Hollow microspheresfabricated from instant adhesive. Materials Letters, 2011, 65:3415- 3417), adsorption and precipitation of hydrophobic polymer nanospheres on the surface of microbubbles (Wolfgang Schmidt, et al. Novelmanufacturing process of hollow polymer microspheres. Chemical Engineering Science, 2006, 61:4973-4981.), spray drying method (Narayan PM; et al. Optimization of spray drying by factorial design for production of hollow microspheres for . Journal of Biomedical Materials Research, 2001, 56:333-341.), W/O/W (or O/W/O) double-layer emulsified solvent evaporation method (Kim JW, et al. Multi-hollow polymermicrocapsules by water- in-oil-in-water emulsion polymerization: morphological study and entrapment characteristics. Colloid and Polymer Science, 2003,281:157-163.) and freeze-drying (Sang Hyuk Im, et al. Polymer hollow particles with controllable holes in their surfaces. Nature Materials, 2005, 4:671-675) and other methods directly prepared polymer hollow microspheres. In the above methods, although the compactness of the shell is relatively good by controlling the reaction conditions, the formation of pores essentially still depends on processes such as gas transfer and polymer precipitation, so the compactness of the shell is still defective, so It is also permeable. In addition, the microspheres prepared by the above method either have limited shell thickness or limited size, thus further limiting the application of microspheres.

Another feasible way to achieve impermeability on the surface of porous or hollow polymer microspheres is to seal the porous or hollow polymer microspheres with pores on the surface. CN102585279A reports a method for preparing surface non-permeable low-density polymer microspheres by a gaseous suspension method. The method realizes sealing the pores on the surface of porous or hollow microspheres with water on the surface by using quick-drying monomers. , prepared a variety of density-tunable surface-impermeable polymer microspheres with good long-term floating properties. The key points of this inventive method are water-curable organic monomers, whose unique properties limit the wide application of this inventive method; in addition, the water-curable monomers exist in vapor form before contacting the hydration layer on the surface of microspheres, so in The monomer supply is limited during the water curing process, which is not conducive to the sealing of the large-diameter pores on the surface of the microspheres. Therefore, it is necessary to invent a more versatile coating method, so as to realize the closure of the pores on the surface of polymer porous or hollow microspheres.

The suspension polymerization in-situ sealing method adopted in the present invention has the advantages of simpler operation, no need for special equipment, lower production cost, and great significance for the popularization and application of polymer microspheres. In addition, by adopting the method of the present invention, by selecting monomers and crosslinking agents with different performance characteristics, it is also possible to adjust the coating thickness of the microspheres and functionalize the surface while sealing the microspheres. properties, so that the microspheres have more superior physical and chemical properties.

Contents of the invention

In order to overcome the deficiencies of the prior art in preparing surface-impermeable low-density polymer microspheres, the present invention provides a method for preparing surface-impermeable low-density polymer microspheres by suspension polymerization in-situ sealing. The method uses low-permeability porous or hollow microspheres with micropores on the surface as seeds, and utilizes the characteristics of good affinity between monomers and polymers to diffuse the monomers to the surface of the seed microspheres to form a monomer liquid layer, and then carry out The in-situ polymerization reaction forms a polymer coating to seal pores on the surface of the microspheres, and obtains surface-impermeable low-density polymer microspheres. The invention is realized through the following technical solutions.

A method for preparing low-density surface non-permeable polymer microspheres by in-situ sealing of suspension polymerization, using low-permeability microspheres with micropores on the surface as seeds, utilizing the characteristics of good affinity between monomers and polymers, The monomer is diffused to the surface of the seed microsphere to form a monomer liquid layer, and then in-situ polymerization is carried out to form a polymer coating to close the pores on the surface of the microsphere, and the surface impermeable low-density polymer microsphere is obtained.

The method for preparing the surface-impermeable low-density polymer microspheres by in-situ sealing of the above-mentioned suspension polymerization, its specific steps are as follows:

Step 1. In the reactor equipped with a stirrer, reflux condensation and heating device, first add distilled water, start stirring and adjust the rotation speed to 100~500 rpm, and add porous or hollow For polymer seed microspheres, the mass ratio of distilled water to polymer seed microspheres is 3-1:1, and finally add the mixed solution of monomer, crosslinking agent and initiator, and then raise the temperature of the reaction system to 65-75°C for reaction 2 ~3 hours;

After step 2 and step 1 are completed, keep the temperature constant, increase the stirring speed to 400~1000 rpm, add the mixed solution of monomer, crosslinking agent and initiator dropwise to the reaction system in step 1, and control the drop The acceleration rate is such that the dropwise addition of the mixed solution is completed within 3 to 5 hours. After the dropwise addition, the system temperature is raised to 85°C to continue the reaction for 1 hour, the reaction is stopped and the temperature is naturally lowered. When the system temperature is lower than 50°C, it is filtered , washed with water and ethanol, soaked, dried and sieved to obtain surface-closed non-permeable low-density polymer microspheres.

The porous or hollow polymer seed microspheres in step 1 have a pore volume ratio of 1% to 70%, and a particle size of 1.0µm to 1000.0µm; the polymer seed microspheres can be obtained by emulsion polymerization (including seed polymerization, Porous or hollow polymer microspheres prepared by any of methods such as miniemulsion polymerization, microemulsion polymerization, soap-free emulsion polymerization, membrane emulsion polymerization, etc.), suspension polymerization, dispersion polymerization, precipitation polymerization, microfluidic polymerization, template synthesis, etc. .

The monomers in the steps 1 and 2 are one or more mixtures in arbitrary proportions of styrene, methyl methacrylate, acrylamide, NN dimethylacrylamide, butyl acrylate, and vinyl acetate. The addition amount of is calculated according to the thickness of the initial sealing layer and the thickness of the final sealing layer. The amount of monomer added in step 1 is calculated according to the thickness of the initial sealing layer, and the calculation formula is: , where: m is the amount of monomer, g; N is the number of polymer seed microspheres, piece; D ₁ is the diameter of polymer seed microspheres, cm; d ₁ is the thickness of the initial sealing layer, cm; r is the unit Bulk density, g/cm ³ . The amount of monomer added in step 2 is calculated according to the thickness of the final sealing layer, and the calculation formula is: , where: m is the amount of monomer, g; N is the number of polymer seed microspheres, number; D2 is the diameter of polymer seed microspheres after the initial sealing, cm ; d2 _is the thickness of the final sealing layer, cm _; r is the monomer density, g/cm ³ .

The crosslinking agent in described steps 1 and 2 is divinylbenzene, dicyclopentadiene, ethylene glycol dimethacrylate or methylcyclopentadiene, and the addition of crosslinking agent in step 1 is step 1 0% to 50% of the mass of the monomer, and the amount of the crosslinking agent added in step 2 is 0% to 50% of the mass of the monomer in step 2.

The initiator in the steps 1 and 2 is azobisisobutyronitrile, benzoyl peroxide or tert-butyl hydroperoxide, and the amount of the initiator in step 1 is 1% to 2.5% of the monomer mass in step 1. %, the amount of initiator added in step 2 is 1% to 2.5% of the monomer mass in step 2.

The beneficial effects of the present invention are: the present invention provides a method for preparing surface-impermeable low-density polymer microspheres which is very versatile, convenient, fast and economical, and the monomers are directly deposited on the microspheres through suspension polymerization. The surface is polymerized in situ to effectively fully seal the micropores on the surface of the microspheres. Since the method of the present invention utilizes the characteristics of good affinity between the monomer and the polymer, the monomer can be effectively diffused to the surface of the microsphere pore to form a liquid film layer of the monomer and polymerized in situ to form a polymer, so it can achieve a small size effective closure of the pores. The method of the present invention can treat hollow (or porous) polymers with a pore volume ratio between 1% and 70% (V/V), a micropore diameter ≤ 1.0µm, and a particle size range between 1.0µm and 1000.0µm The micropores on the surface of the microspheres are effectively sealed, which effectively avoids the disadvantage of density changes due to the penetration of liquid substances into the pores or cavities in the core through the micropores on the surface of the polymer microspheres during use. Under the premise of maintaining low density, it has excellent performance such as long-term floating. Simultaneously, because the method of the present invention carries out surface sealing under the condition of normal pressure, the air in the hole or the cavity of the sealed microsphere is equivalent to the external atmospheric pressure, so no internal stress will be produced, and the method of the present invention can pass the consumption of monomer The thickness of the microsphere sealing layer is adjusted, so that the prepared low-density surface-impermeable polymer microspheres have better mechanical properties and the density can be adjusted. The polymer microspheres sealed by the method of the present invention have properties such as good insulation, light dispersion, acoustic insulation, elasticity and compressive strength, so that they can be used in oil drilling additives, acid mist suppression, ultrasonic contrast reagents, photoelectric materials, coatings, etc. , Adhesives, papermaking, communications and other fields have broad application prospects.

detailed description

The present invention will be further described below in combination with specific embodiments.

Example 1

The basic parameters of the seed polymer microspheres to be sealed: polyphenylene with an average diameter of 10 µm, a pore volume ratio of 6.4% (V/V), an average surface micropore diameter of 0.5±0.08 µm, and a density of 0.94 g/cm ³ Ethylene porous microspheres, the amount of microspheres is 200.0g, the thickness of the initial sealing coating is about 0.05 μm, and the thickness of the final sealing coating is about 0.05 μm.

Then the total number of seed microspheres is: .

The addition of styrene monomer in step 1 is calculated according to the thickness of the initial sealing layer, and the calculation formula is , the amount added is .

The amount of styrene monomer added in step 2 is calculated according to the thickness of the final closed coating, and the calculation formula is , the amount added is .

The above-mentioned method for preparing surface-impermeable low-density polymer microspheres by in-situ sealing by suspension polymerization is characterized in that the specific steps are as follows:

Step 1. In a reactor equipped with a stirrer, reflux condensation and heating device, first add 300.0 g of distilled water, start stirring and adjust the speed to 400 rpm, then add 200.0 g of the above-mentioned polymer seed microspheres, distilled water and The mass ratio of polymer seed microspheres is 1.5:1, and finally 6.7g of styrene, 3.35g of divinylbenzene (50% of the mass of styrene) and 0.1g of azobisisobutyronitrile (1.5wt% of the mass of styrene) are added ), and then raise the temperature of the reaction system to 65°C for 3 hours.

After step 2 and step 1 are completed, keep the temperature constant, increase the stirring speed to 800 rpm, and add 6.8 g of styrene and 3.4 g of divinylbenzene (the mass of styrene) dropwise to the reaction system in step 1. 50%) and azobisisobutyronitrile 0.068g (1.0wt% of styrene mass) mixed solution, control the rate of addition so that the mixed solution is added dropwise within 5 hours, after the drop is completed, the temperature of the system is raised to Continue to react at 85°C for 1 hour, stop the reaction and cool down naturally. When the system temperature is lower than 50°C, filter, wash and soak with water and ethanol, dry and sieve to obtain non-permeable low-density polymer particles with closed surface. ball.

The surface-impermeable polymer microspheres prepared above have a density of 0.96 g/cm ³ . The polymer microspheres were pressed into a mixed solution of water and ethanol with a volume ratio of 1:3 and soaked for 30 days with a porous plate. After taking them out, they were naturally dried at room temperature. The density did not change, indicating that the surface of the polymer microspheres was non-permeable. .

Example 2

The basic parameters of the seed polymer microspheres to be sealed: polyphenylene with an average diameter of 50 µm, a pore volume ratio of 23.8% (V/V), an average surface micropore diameter of 0.2±0.05 µm, and a density of 0.68 g/cm ³ Ethylene hollow microspheres, the amount of microspheres is 100.0 g, the thickness of the initial sealing coating is about 3.0 μm, and the thickness of the final sealing coating is about 5.0 μm.

Then the total number of seed microspheres is: .

In step 1, the addition of styrene and methyl methacrylate monomer is calculated according to the thickness of the initial sealing layer, and the calculation formula is , the amount added is .

The amount of styrene and acrylamide monomer added in step 2 is calculated according to the thickness of the final closed coating, and the calculation formula is , the amount added is .

The method for preparing the surface-impermeable low-density polymer microspheres by in-situ sealing of the above-mentioned suspension polymerization, its specific steps are as follows:

Step 1. In a reactor equipped with a stirrer, reflux condensation and heating device, first add 300.0 g of distilled water, start stirring and adjust the speed to 500 rpm, then add 100.0 g of the above-mentioned polymer seed microspheres, distilled water and The mass ratio of polymer seed microspheres is 3:1, and finally add 26.3g of styrene, 26.3g of methyl methacrylate, 15.78g of dicyclopentadiene (30wt% of the mass of styrene and methyl methacrylate) and peroxide A mixed solution of 1.315g of benzoyl (2.5wt% of the mass of styrene and methyl methacrylate), and then raise the temperature of the reaction system to 75°C for 2 hours.

After step 2 and step 1 are completed, keep the temperature constant, increase the stirring speed to 1000 rpm, and add 65.45 g of styrene, 65.45 g of acrylamide, and 26.18 g of dicyclopentadiene dropwise to the reaction system in step 1 (20% of the mass of styrene and acrylamide) and benzoyl peroxide 3.27g (2.5wt% of the mass of styrene and acrylamide), the rate of addition is controlled so that the mixed solution is added dropwise within 3 hours After the dropwise addition, raise the system temperature to 85°C to continue the reaction for 1 hour, stop the reaction and lower the temperature naturally. When the system temperature is lower than 50°C, filter, wash and soak with water and ethanol, dry and sieve to obtain the surface Closed non-permeable low density polymer microspheres.

The surface-impermeable polymer microspheres prepared above have a density of 0.82 g/cm ³ . The polymer microspheres were pressed into a mixed solution of water and ethanol with a volume ratio of 1:3 and soaked for 30 days with a porous plate. After taking them out, they were naturally dried at room temperature. The density did not change, indicating that the surface of the polymer microspheres was non-permeable. .

Example 3

The basic parameters of the seed polymer microspheres to be sealed: polyphenylene with an average diameter of 100 µm, a pore volume ratio of 45.6% (V/V), an average surface micropore diameter of 0.3±0.05 µm, and a density of 0.51 g/cm ³ Ethylene hollow microspheres, the amount of microspheres is 100.0 g, the thickness of the initial sealing coating is about 1.0 μm, and the thickness of the final sealing coating is about 3.0 μm.

Then the total number of seed microspheres is: .

In step 1, the addition amount of NN dimethylacrylamide and butyl acrylate monomer is calculated according to the thickness of the initial sealing layer, and the calculation formula is , the amount added is .

The amount of styrene and acrylamide monomer added in step 2 is calculated according to the thickness of the final closed coating, and the calculation formula is , the amount added is .

The method for preparing the surface-impermeable low-density polymer microspheres by in-situ sealing of the above-mentioned suspension polymerization, its specific steps are as follows:

Step 1. In a reactor equipped with a stirrer, reflux condensation and heating device, first add 100.0 g of distilled water, start stirring and adjust the speed to 100 rpm, then add 100.0 g of the above-mentioned polymer seed microspheres, distilled water and The mass ratio of polymer seed microspheres is 1:1, and finally add 5.5g of N-N dimethylacrylamide, 5.5g of butyl acrylate, and 4.4g of ethylene glycol dimethacrylate (the addition amount is N-N dimethylacrylamide and 40% of the mass of butyl acrylate) and tert-butyl hydroperoxide 0.11g (addition amount is 1.0wt% of the mass of N-N dimethylacrylamide and butyl acrylate), and then raise the temperature of the reaction system to 70°C React for 2.5 hours.

After step 2 and step 1 are completed, keep the temperature constant, increase the stirring speed to 400 rpm, and add 21.8 g of styrene, 21.8 g of acrylamide, and ethylene dimethacrylate dropwise to the reaction system in step 1. A mixed solution of 8.72g of alcohol ester (the amount added is 20wt% of the mass of styrene and acrylamide) and 1.09g of tert-butyl hydroperoxide (the amount added is 2.5wt% of the mass of styrene and acrylamide), and the dropping rate is controlled Make the dropwise addition of the mixed solution within 5 hours. After the dropwise addition, raise the system temperature to 85°C to continue the reaction for 1 hour, stop the reaction and lower the temperature naturally. When the system temperature is lower than 50°C, filter, water and ethanol After washing, soaking, drying and sieving, the surface-closed non-permeable low-density polymer microspheres are obtained.

The surface-impermeable polymer microspheres prepared above had a density of 0.68 g/cm ³ . The polymer microspheres were pressed into a mixed solution of water and ethanol with a volume ratio of 1:3 and soaked for 30 days with a porous plate. After taking them out, they were naturally dried at room temperature. The density did not change, indicating that the surface of the polymer microspheres was non-permeable. .

Example 4

The basic parameters of the seed polymer microspheres to be sealed: the average diameter is 500µm, the pore volume ratio is 70.0% (V/V), the average surface micropore diameter is 0.5±0.05µm, and the density is 0.31g/cm ³ Methyl acrylate hollow microspheres, the amount of microspheres is 100.0g, the thickness of the initial sealing coating is about 0.5 μm, and the thickness of the final sealing coating is about 1.5 μm.

Then the total number of seed microspheres is:

The addition of methyl methacrylate monomer in step 1 is calculated according to the thickness of the initial sealing layer, and the calculation formula is , the amount added is .

The amount of methyl methacrylate monomer added in step 2 is calculated according to the thickness of the final sealing coating, and the calculation formula is , the amount added is .

The method for preparing the surface-impermeable low-density polymer microspheres by in-situ sealing of the above-mentioned suspension polymerization, its specific steps are as follows:

Step 1. In the reactor equipped with a stirrer, reflux condensation and heating device, first add 200.0 g of distilled water, start stirring and adjust the speed to 350 rpm, then add 100.0 g of the above-mentioned polymer seed microspheres, distilled water and The mass ratio of polymer seed microspheres is 2:1, and finally add 1.8 g of methyl methacrylate, 0.9 g of methylcyclopentadiene (the amount added is 50% of the mass of methyl methacrylate) and tert-butyl peroxide A mixed solution of 0.018 g of hydrogen (the amount added is 1.0 wt % of the mass of methyl methacrylate), and then the temperature of the reaction system was raised to 70° C. for 2.5 hours.

After step 2 and step 1 are completed, keep the temperature constant, increase the stirring speed to 700 rpm, and add 5.5 g of methyl methacrylate and 2.75 g of methylcyclopentadiene dropwise to the reaction system in step 1 (the amount added is 50wt% of the mass of methyl methacrylate) and 0.11g of tert-butyl hydroperoxide (the amount added is 2.0wt% of the mass of methyl methacrylate), and the rate of addition is controlled so that the mixed solution The dropwise addition is completed within 5 hours. After the dropwise addition, raise the system temperature to 85°C to continue the reaction for 1 hour, stop the reaction and lower the temperature naturally. When the system temperature is lower than 50°C, filter, wash with water and ethanol, and dry And after sieving, the surface-closed non-permeable low-density polymer microspheres are obtained.

The surface-impermeable polymer microspheres prepared above had a density of 0.38 g/cm ³ . The polymer microspheres were pressed into a mixed solution of water and ethanol with a volume ratio of 1:3 and soaked for 30 days with a porous plate. After taking them out, they were naturally dried at room temperature. The density did not change, indicating that the surface of the polymer microspheres was non-permeable. .

Example 5

The basic parameters of the seed polymer microspheres to be sealed: polymelamine with an average diameter of 1 µm, a pore volume ratio of 1.0% (V/V), an average surface micropore diameter of 0.02±0.005 µm, and a density of 0.91 g/cm ³ For formaldehyde porous microspheres, the dosage of the microspheres is 100.0 g, the thickness of the initial sealing coating is about 0.01 μm, and the thickness of the final sealing coating is about 0.02 μm.

Then the total number of seed microspheres is: .

The addition of vinyl acetate monomer in step 1 is calculated according to the thickness of the initial sealing layer, and the calculation formula is , the amount added is .

The amount of styrene monomer added in step 2 is calculated according to the thickness of the final closed coating, and the calculation formula is , the amount added is .

The method for preparing the surface-impermeable low-density polymer microspheres by in-situ sealing of the above-mentioned suspension polymerization, its specific steps are as follows:

Step 1. In a reactor equipped with a stirrer, reflux condensation and heating device, first add 300.0 g of distilled water, start stirring and adjust the speed to 400 rpm, then add 100.0 g of the above-mentioned polymer seed microspheres, distilled water and The mass ratio of the polymer seed microspheres is 3:1, and finally a mixed solution of 6.1 g of vinyl acetate and 0.153 g of benzoyl peroxide (the amount added is 2.5 wt % of the mass of vinyl acetate) is added, and then the temperature of the reaction system is raised to React at 70°C for 3 hours without cross-linking agent;

After step 2 and step 1 are completed, keep the temperature constant, increase the stirring speed to 900 rpm, and add 14.4 g of styrene and 0.36 g of benzoyl peroxide dropwise to the reaction system in step 1 (the addition amount is 2.5wt% of the mass of styrene), control the rate of addition to complete the dropwise addition of the mixed solution within 3 hours, after the addition, raise the temperature of the system to 85°C and continue the reaction for 1 hour, stop the reaction and cool down naturally , when the temperature of the system is lower than 50 DEG C, after filtering, washing with water and ethanol, soaking, drying and sieving, the surface-closed non-permeable low-density polymer microspheres are obtained. Does not contain crosslinkers.

The surface-impermeable polymer microspheres prepared above have a density of 0.96 g/cm ³ . The polymer microspheres were pressed into a mixed solution of water and ethanol with a volume ratio of 1:3 and soaked for 30 days with a porous plate. After taking them out, they were naturally dried at room temperature. The density did not change, indicating that the surface of the polymer microspheres was non-permeable. .

Example 6

The basic parameters of the seed polymer microspheres to be sealed: the average diameter is 1000µm, the pore volume ratio is 21.5% (V/V), the average surface micropore diameter is 0.9±0.1µm, and the density is 0.83g/cm ³ Methyl acrylate porous microspheres, the amount of microspheres is 100.0 g, the thickness of the initial sealing coating is about 10.0 μm, and the thickness of the final sealing coating is about 30.0 μm.

Then the total number of seed microspheres is: .

The addition amount of styrene ester monomer in step 1 is calculated according to the thickness of the initial sealing layer, and the calculation formula is , adding an amount of .

The amount of styrene monomer added in step 2 is calculated according to the thickness of the final closed coating, and the calculation formula is , the amount added is .

The method for preparing the surface-impermeable low-density polymer microspheres by in-situ sealing of the above-mentioned suspension polymerization, its specific steps are as follows:

Step 1. In a reactor equipped with a stirrer, reflux condensation and heating device, first add 3200.0 g of distilled water, start stirring and adjust the speed to 400 rpm, then add 100.0 g of the above-mentioned polymer seed microspheres, distilled water and The mass ratio of polymer seed microspheres is 3:1, and finally 7.6g of styrene, 3.8g of divinylbenzene (the addition amount is 50% of the mass of styrene) and 0.076g of azobisisobutyronitrile (the addition amount is benzene 1.0wt% of the mass of ethylene), and then raise the temperature of the reaction system to 75°C for 3 hours.

After step 2 and step 1 are completed, keep the temperature constant, increase the stirring speed to 900 rpm, and add 23.7 g of styrene and 2.37 g of divinylbenzene dropwise to the reaction system in step 1 (the addition amount is benzene 10% of the mass of ethylene) and azobisisobutyronitrile 0.474g (the addition amount is 2.0wt% of the mass of styrene), and the rate of addition is controlled so that the mixed solution is added dropwise within 4 hours. Finally, raise the system temperature to 85°C to continue the reaction for 1 hour, stop the reaction and lower the temperature naturally. When the system temperature is lower than 50°C, filter, wash and soak with water and ethanol, dry and sieve to obtain a surface-closed non-permeable low-density polymer microspheres.

The surface-impermeable polymer microspheres prepared above have a density of 0.92 g/cm ³ . The polymer microspheres were pressed into a mixed solution of water and ethanol with a volume ratio of 1:3 and soaked for 30 days with a porous plate. After taking them out, they were naturally dried at room temperature. The density did not change, indicating that the surface of the polymer microspheres was non-permeable. .

The specific embodiments of the present invention have been described in detail above, but the present invention is not limited to the above embodiments, and various changes can be made without departing from the gist of the present invention within the scope of knowledge possessed by those of ordinary skill in the art .

Claims (5)

1. a kind of suspension polymerization in-situ sealing prepares the method for surface non-permeability low-density polymer microsphere, it is characterized in that: with the low-permeability microsphere that surface has micropore channel as seed, utilize monomer and polymer to have good The characteristics of affinity make the monomer diffuse to the surface of the seed microsphere to form a monomer liquid layer, and then perform in-situ polymerization to form a polymer coating to seal the pores on the surface of the microsphere, and obtain a non-permeable low-density polymer microsphere on the surface; The low-permeability microspheres are porous or hollow polymer seed microspheres with a surface micropore diameter ≤ 1.0 µm; the porous or hollow polymer seed microspheres have a pore volume ratio of 1% to 70% and a particle size of 1.0 µm ~1000.0 µm. 2. the method for preparing surface impermeable low-density polymer microspheres by suspension polymerization in situ sealing according to claim 1, is characterized in that concrete steps are as follows: Step 1. In the reactor equipped with a stirrer, reflux condensation and heating device, first add distilled water, start stirring and adjust the rotation speed to 100~500 rpm, and add porous or hollow For polymer seed microspheres, the mass ratio of distilled water to polymer seed microspheres is 3-1:1, and finally add the mixed solution of monomer, crosslinking agent and initiator, and then raise the temperature of the reaction system to 65-75°C for reaction 2 ~3 hours; After step 2 and step 1 are completed, keep the temperature constant, increase the stirring speed to 400~1000 rpm, add the mixed solution of monomer, crosslinking agent and initiator dropwise to the reaction system in step 1, and control the drop The acceleration rate is such that the dropwise addition of the mixed solution is completed within 3 to 5 hours. After the dropwise addition, the system temperature is raised to 85°C to continue the reaction for 1 hour, the reaction is stopped and the temperature is naturally lowered. When the system temperature is lower than 50°C, it is filtered , washed with water and ethanol, dried and sieved, the surface impermeable low-density polymer microspheres were obtained. 3. the method for preparing surface impermeable low-density polymer microspheres by suspension polymerization in-situ sealing according to claim 2, characterized in that: the monomers in the steps 1 and 2 are styrene, methyl methacrylate One or several mixtures in arbitrary proportions of ester, acrylamide, N-N dimethylacrylamide, butyl acrylate, and vinyl acetate. The amount of monomer added is calculated according to the thickness of the initial sealing layer and the thickness of the final sealing layer. 4. The method for preparing surface-impermeable low-density polymer microspheres by suspension polymerization in-situ sealing according to claim 2, characterized in that: the crosslinking agent in the steps 1 and 2 is divinylbenzene, bicyclic Pentadiene, ethylene glycol dimethacrylate or methylcyclopentadiene, the amount of crosslinking agent added in each step is 0% to 50% of the monomer mass in this step. 5. the method for preparing surface-impermeable low-density polymer microspheres by suspension polymerization in situ sealing according to claim 2, is characterized in that: the initiator in described steps 1 and 2 is azobisisobutyronitrile, For benzoyl peroxide or tert-butyl hydroperoxide, the amount of initiator added in each step is 1% to 2.5% of the monomer mass in this step.