TWI557160B - Method of fabricating highly cross-linking polymer particles having uniform granular size - Google Patents

Description

Method for preparing high-crosslinking degree uniform particle size polymer microspheres

The invention relates to a method for preparing a high-crosslinking degree uniform particle size polymer microsphere, in particular to a method capable of accurately preparing a high-crosslinking polymer microsphere of a predetermined size by a dispersion polymerization method and a two-stage swelling polymerization method. Achieve heat and solvent resistance.

According to the conventional technique, a dispersion polymerization method and a seed polymerization method are used to prepare a large-sized and uniform polymer microsphere. The first stage uses a dispersion polymerization method to prepare particles having a particle diameter of 1-10 um as seeds. The second stage uses seed polymerization, including one-stage swelling and two-stage swelling, using the seeds prepared in the first stage, the main purpose is to increase the seed size and properties, including high cross-linking, preparation of the hole ball .

The above-mentioned dispersion polymerization method is used in the first stage to prepare PMMA seeds, similar to the recent literature, but in the second stage, the present invention uses a two-stage swelling method and changes the ratio of monomer to crosslinker to achieve large particle size. A goal with a high degree of cross-linking.

However, it has been found in the search for US 6228925 B1 and US 6949601 B1 that although it can achieve high crosslinkability and solvent resistance, its particle size is less than 5 μm (US 6228925 B1), and some literatures can be obtained. A uniform particle having a large particle diameter of more than 10 μm (US Pat. No. 5,216,096) can achieve a uniform particle of 15 μm using 0.26 g of a seed and 16.4 g of a monomer, but cannot have high crosslinkability.

In view of this, the inventors of this case have intensively discussed the above-mentioned problems of conventional inventions, and actively pursued solutions through years of experience in R&D and manufacturing of related industries. After long-term efforts in research and development, they finally succeeded in developing this book. The invention discloses a "method for preparing a high-crosslinking degree uniform particle size polymer microsphere", thereby improving various problems in the conventional use.

The main object of the present invention is to accurately prepare a polymer microsphere having a high degree of cross-linking of a predetermined size by a dispersion polymerization method and a two-stage swelling polymerization method, and to achieve heat resistance and solvent resistance.

In order to achieve the above object, the present invention is a method for preparing a high-crosslinking degree uniform particle size polymer microsphere, which comprises the following steps: Step 1: providing a seed obtained by a dispersion polymerization method; Step 2: different amounts The swelling agent is mixed with the surfactant, and then the seed is added to stir to form a seed mixture; Step 3: mixing different amounts of the monomer and the initiator, and then adding different amounts of the crosslinking agent and the surfactant, And homogenization to form a monomer emulsion; and step 4: mixing the seed mixture with the monomer emulsion, and then stirring the monomer after stirring, adding the stabilizer and the inhibitor after stirring, and stirring with nitrogen The mixture is uniformly mixed, and finally heated rapidly to carry out polymerization to form a uniform polymer microsphere having a high degree of crosslinking.

In the above embodiment of the present invention, in the first step, when the seed is prepared, the stabilizer is first added to the solvent, and after the magnet is stirred, nitrogen gas is introduced to form the first mixed liquid, and then added to the first mixed liquid. The monomer and the initiator are followed by nitrogen to form a second mixture, and the second mixture is placed in a water bath to carry out a reaction to obtain a sub-micron sphere emulsion of uniform particle size, and finally the sub-micron sphere emulsion is The water and methanol are subjected to repeated centrifugation to remove the remaining monomers and stabilizers to form seeds.

In the above embodiment of the present invention, the stabilizer in the first step may be polyvinylpyrrolidone (PVP), and is added to the solvent at a dose of 1 to 2 g.

In the above embodiment of the present invention, the solvent in the first step is methanol and deionized water in different proportions, and the ratio of the methanol to the deionized water is between 100:0 and 75:25, and 80: 20 is the best ratio.

In the above embodiment of the present invention, the time for introducing nitrogen into the step 1 is 20 to 30 minutes.

In the above embodiment of the present invention, the single system in the first step is Methyl methacrylate (MMA), and is added to the first mixed solution at a dose of 8-12 g.

In the above embodiment of the present invention, the initiator in the first step is 2,2'-azobisisobutyronitrile (AIBN), and is added to the first mixture at a dose of 0.1 g.

In the above embodiment of the present invention, the time for introducing nitrogen into the step 1 is 5 to 10 minutes.

In the above embodiment of the present invention, the second mixed liquid in the first step is placed in a water bath at 50 to 60 ° C for 24 hours.

In the above embodiment of the present invention, the second step to the fourth step are a two-stage swelling polymerization method.

In the above embodiment of the present invention, the swelling agent in the second step is cyclohexane.

In the above embodiment of the present invention, the surfactant in the second step is sodium dodecyl sulfate (SDS), and the concentration thereof is 0.25%, and the dose is 40-60 g.

In the above embodiment of the present invention, the dose of the seed in the second step is 0.1 to 0.2 g.

In the above embodiment of the present invention, the swelling agent, the surfactant and the seed in the second step are ultrasonically oscillated and magnetized for 30 to 40 minutes, and then stirred at a mechanical stirrer of 120 to 160 rpm at 25 to 35 ° C. 8~12 hours.

In the above embodiment of the present invention, the single system in the third step is Methyl methacrylate (MMA).

In the above embodiment of the present invention, the initiator in the third step is Benzoyl Peroxide (BPO).

In the above embodiment of the present invention, the crosslinking agent in the third step is Ethylene glycol dimethacrylate (EGDMA), and the content thereof is 15 to 25%.

In the above embodiment of the present invention, the surfactant in the third step is sodium dodecyl sulfate (SDS), and the concentration thereof is 0.25%, and the dose is 90-120 g.

In the above embodiment of the present invention, the monomer, the initiator, the crosslinking agent and the surfactant in the step 3 are homogenized by a homogenizer for 10-20 minutes at a high speed, and then uniformly dispersed by the ultrasonic oscillator 10-20. After a minute, a monomer emulsion was formed. In the above embodiment of the present invention, in the fourth step, the monomer is swelled at 25 to 40 ° C, and then stirred by a mechanical stirrer at 120 to 160 rpm for 9 to 12 hours to mix the seed mixture with the monomer emulsion. mixing.

In the above embodiment of the present invention, the stabilizer in the step 4 is polyvinyl alcohol (PVA), and the concentration thereof is 4 to 6%.

In the above embodiment of the present invention, the inhibitor in the fourth step is sodium nitrite (NaNO ₂ ).

In the above embodiment of the present invention, the fourth step is performed by stirring with a mechanical stirrer at a speed of 120 to 160 rpm for 25 to 40 minutes.

In the above embodiment of the present invention, in the fourth step, the temperature is raised to 65 to 80 ° C and then polymerized for 10 to 12 hours to form a highly crosslinked polymer microsphere. .

Please refer to FIG. 1 to FIG. 7 , which are schematic diagrams of the first step of the present invention, a schematic diagram of the second step of the present invention, a schematic diagram of the third step of the present invention, and a schematic diagram of the fourth step of the present invention. As shown in the figure: The present invention is a method for preparing a high-crosslinking degree uniform particle size polymer microsphere, which comprises at least the following steps:

Step 1: The stabilizer 11 is added to the solvent 12, and after the magnet is stirred, the nitrogen gas 13 is introduced to form the first mixed liquid 1 (as shown in FIG. 1), wherein the stabilizer 11 can be polyvinylpyrrolidone (as shown in FIG. 1). Polyvinylpyrrolidone, PVP), and added to the solvent 12 at a dose of 1 g, the solvent 12 is a different ratio of methanol and deionized water, and the ratio of the methanol to the deionized water is between 100:0 and 75:25. Between 80 and 20 is the optimum ratio, and the time for introducing nitrogen gas 13 is 25 minutes, and monomer 21 and initiator 22 are added to the first mixture 1, and then nitrogen gas 23 is introduced. Forming a second mixed liquid 2 (as shown in FIG. 2), wherein the monomer 21 is methyl methacrylate (MMA), and is added to the first mixed liquid 1 at a dose of 10 g. The initiator 22 is 2,2'-azobisisobutyronitrile (AIBN), and is added to the first mixture 1 at a dose of 0.1 g, and the time for introducing nitrogen 23 is 5 minutes. The second mixed liquid 2 is placed in the water bath pot 31 to obtain a sub-micron spherical emulsion 3 of uniform particle size (as shown in FIG. 3), wherein the second mixed liquid The liquid mixture is placed in a water bath at 55 ° C for 31 hours, and the secondary microsphere emulsion 3 is repeatedly centrifuged with water 41 and methanol 42 to remove the remaining monomer 21 and stabilizer 22 to form seed 4 ( As shown in Fig. 4, and the above step 1 is a dispersion polymerization method.

Step 2: mixing different amounts of the swelling agent 51 and the surfactant 52, and then adding the seed 4 to stir to form a seed mixture 5 (as shown in FIG. 5), wherein the swelling agent 51 is a ring. Cyclohexane, the surfactant 52 is sodium dodecyl sulfate (SDS), and its concentration is 0.25%, the dosage is 40 g, and the dose of the seed 4 is 0.1 g. The swelling agent 51, the surfactant 52 and the seed 4 were ultrasonically shaken and magnetized for 30 minutes, and then stirred at 30 ° C for 10 hours with a mechanical stirrer at 140 rpm.

Step 3: mixing different amounts of the monomer 61 and the initiator 62 uniformly, adding different amounts of the crosslinking agent 63 and the surfactant 64, and homogenizing to form a monomer emulsion 6 (as shown in FIG. 6). Wherein the monomer 61 is methyl methacrylate (MMA), the initiator 62 is Benzoyl Peroxide (BPO), and the crosslinking agent 63 is dimethyl Ethylene glycol dimethacrylate (EGDMA), and its content is 20%, the surfactant 64 is sodium dodecyl sulfate (SDS), and its concentration is 0.25%, the dose 100 g, and the monomer 61, the initiator 62, the crosslinking agent 63 and the surfactant 64 are homogenized at a high speed for 10 minutes, and then uniformly dispersed in an ultrasonic oscillator for 10 minutes to form a monomer emulsion. 6.

Step 4: Mix the seed mixture 5 with the monomer emulsion 6, and then stir the monomer and then stir. After stirring, the stabilizer 71 and the inhibitor 72 are added, and the nitrogen gas 73 is stirred and mixed uniformly. The temperature is rapidly increased to 70 ° C and then polymerized for 10 hours to form a high cross-linking polymer microsphere 7 (as shown in Fig. 7), and the second step to the fourth step is a two-stage swelling method. The monomer was swollen at 30 ° C, and then stirred with a mechanical stirrer at 140 rpm for 6 hours to mix the seed mixture 5 with the monomer emulsion 6, wherein the stabilizer 71 was polyvinyl alcohol (PVA). And the concentration of the inhibitor 72 is sodium nitrite (NaNO2), and after mixing with nitrogen gas 73, the mixture is stirred by a mechanical stirrer at 140 rpm for 30 minutes and uniformly mixed.

Thus, in the first step, the submicron spheres having a particle diameter of 3.5 μm to 10.2 μm can be prepared by changing the ratio of the solvent 12 and the content of the monomer 21, and the methanol to water ratio is selected according to the particle size and the Cv flow rate of 80:20. The subsequent second stage of synthesis was carried out with a particle size of about 5.2 μm and a Cv % of 5.9%.

And in step 2 to step 4, it is found that when the content of the swelling agent 51 is too small or too much, small particles are easily caused, and when the amount is 0.1 g-0.2 g, particles having a uniform particle diameter can be obtained; the monomer 61 is swollen. When the ratio is 10 times and 20 times, the particle size does not increase significantly, but when the swelling ratio of the monomer 61 reaches 100 times, the (MMA) microspheres with a particle size larger than 10 μm can be successfully obtained due to the water phase. There are some monomers 61 that are not swelled into the seed 4, so the present invention needs to inhibit the reaction by adding an aqueous phase inhibitor 72 to prevent the remaining monomer 61 from forming a new core, and the content of the enhancer inhibitor 72 is 0.1. Above g, it is possible to effectively avoid the generation of new nuclei, thereby obtaining microspheres of uniform particle size. When the cross-linking agent 63 is added, it is found that although the particle size can be greatly increased, the Cv value is also increased, so the present invention will use When the amount of monomer 61 is reduced to 5-6 g, the polymer microspheres (MMA/EGDMA) with a crosslinking degree of 20% and uniformity can be successfully obtained. After the solvent resistance test and the heat resistance test, the degree of crosslinking can be found to be 20%. The polymer microspheres are indeed effective against solvents. And heat-resistant properties than 4 seed or not to add a crosslinking agent microspheres have significantly improved.

Since the homogeneity of the high cross-linking polymer microspheres 7 is determined by the coefficient of particle size distribution (Cv value), generally, when the Cv value is less than 8%, it can be regarded as a uniform particle diameter. In addition, the difference between the number-average diameter (Dn) and the volume-average diameter (Dv) can be used to determine whether the uniformity is uniform. When the polymer microspheres are more uniform, the difference is smaller. . At the same time, the distribution range of particle size can be estimated by σ standard deviation (General Deviation). Generally, about 68% of the sample number in the normal distribution is distributed within a standard deviation from the average value. The distance is 95% within two standard deviations and 99% within three standard deviations. The formula and definition are as follows:

Dn=(ΣD _i /n)

Dv=(ΣD _i ³ /n) ^1/3

σ=(Σ(D _i -D _n ) ² /n) ^1/2

Cv=(σ/D _n )×100

Where D _i is a single particle size and n is the number of particles.

The D _n , D _v , σ standard deviation and Cv value can be obtained by taking the SEM image and taking 100 microspheres by the above formula.

Preparation of uniform particle size submicron ball seed: The present invention firstly prepares a uniform particle size submicron ball seed by a dispersion polymerization method, MMA is a monomer for selecting a submicron sphere, and a fixed ratio of initiator (AIBN) is added and stabilized. Agent (PVP), select different ratios of solution (methanol: water), and different content of monomer (MMA) content to prepare uniform size submicron spheres. Submicron spheres prepared at different solvent ratios (methanol: water), the higher the proportion of water, the smaller the particle size of the sphere and the more uniform the particle size, because MMA is a hydrophobic monomer, when water When the content rises, the time for precipitation nucleation becomes shorter, and because the nucleation time is short, the critical chain length of the molecule is also shortened, and the number of nuclei is also increased, so the particle size becomes smaller under the average dispersion of the monomer, and A short nuclear time results in a more uniform particle size.

As seen from the table below, Table 1 shows the average particle size, Cv % and standard deviation of different solvent ratios. It can be seen that the particle size changes with the water content, so the solvent ratio can be changed by the dispersion polymerization method to prepare the granules. Microspheres with a diameter ranging from 3.5 to 10.2 μm. The invention can use the coefficient of particle size distribution (Cv value) to judge the degree of uniformity. Generally, when the Cv value is less than 8%, it can be regarded as a uniform particle size. It can be seen from Table 1 that when the water content is low At 10%, the Cv value is more than 8%, so when the water content is more than 10%, the microspheres can be regarded as a uniform particle size. Considering the two factors of particle size and Cv value, the present invention selects the second stage of synthesis with a methanol to water ratio of 80:20, and has a particle size of about 5.2 μm and a Cv value of 5.4%.

As shown in the following table, Table 2 shows the average particle size, Cv % and standard deviation of different monomer contents. When the monomer content increases from 10% to 15%, the particle size of the ball does not change significantly, but it can be found. Some small pellets were produced. From the particle size, Cv% to monomer content distribution table 2, the monomer content was also increased to 15%, and the Cv value also increased from 5.4% to 15.7%, and if the monomer content rose to 20%, The particle size obviously increased from 5.2 μm to 7.47 μm, and the number of small balls was also significantly increased. It can be judged from the increase in the number of small balls that the second nucleation period is likely to occur when the monomer content is increased. Because when the monomer content is increased, the solubility of the monomer in the solution phase is increased, the time for the nucleation phase is increased, and the critical chain length of the molecule is lengthened, thereby causing the particle size of the microsphere to rise. At the same time, the nucleation period increases, and the second nucleation period is prone to occur. Because when the nucleus grows to a certain size, the stabilizer is also physically or chemically adsorbed on the surface of the sphere, so the newly precipitated core and monomer are not easy. Diffusion into the stable core leads to the additional growth of the newly precipitated core, which is the second nucleation period, which is also the main cause of the uneven particle size. Since increasing the amount of monomer added contributes to the growth of the particle size, it seriously affects the uniformity of the particle size, so the present invention also chooses to maintain the monomer content of 10% in this variation.

From Table 3, Table 3 shows the average particle size, Cv % and standard deviation of different swelling agents, and the two-stage seed swelling method prepares highly cross-linking uniform particle size microspheres: due to the uniform particle size submicron sphere The seed preparation is selected by a dispersion polymerization method to prepare a submicron sphere of uniform particle size. Although the dispersion polymerization method can simply prepare a microsphere of uniform particle size, the ultimate goal of the present invention is to prepare a highly crosslinkable one. Solvent-resistant microspheres, and the presence of cross-linking agents is not easy in the system of dispersion polymerization, because the presence of cross-linking agents often destroys the mechanism of nucleation and growth of the dispersion polymerization method, resulting in condensation of the emulsion. A phenomenon occurs. Furthermore, since the selected monomer is MMA, the solution system must be mainly methanol, and the reaction temperature can only be set at 55 ° C. If the reaction temperature is not high enough, the crosslinked ball will have insufficient bridging density and solvent resistance. Sex will not be good enough, so in order to overcome the above two shortcomings, a two-stage swelling method was selected in the second step of the experiment. According to the result of seed preparation of the uniform particle size submicron sphere, the present invention selects the pellet prepared by the dispersion polymerization method with the solvent MeOH:H ₂ O=8:2 and the monomer content of 10% as the seed emulsion of the second step. .

In the two-stage swelling method, it is mainly divided into two stages of assisted swelling and main swelling. The first stage of assisted swelling is to introduce a low molecular weight compound which is more hydrophobic than the monomer to activate the seed. By assisting in this stage of swelling, it is possible to increase the rate and extent of absorption of monomer by the seed microspheres, that is, the stage of main swelling. In the present invention, the swelling aid selected in the present invention is cyclohexane, the molecular weight is 84.16 g/mol, the solubility parameter is 8.2 (cal/cm ³ ) ^1/2 , and the solubility parameter of the seed PMMA of the present invention is about 9.24. (cal/cm ³ ) ^1/2 , the difference between the two is about 1. Generally, the closer the solubility parameter is, the better the compatibility is, and the solubility parameter is within 1 range of the swelling system. The invention changes the content of cyclohexane, from 0.05g, 0.1g, 0.2g and 0.3g, and finds that the content of cyclohexane is 0.05g, the particle size is the largest, but some small particles can be found, and the particle size is found. It is not very uniform, and its particle size distribution range is quite large, which may be caused by the insufficient content of the swelling agent to cause the seed microspheres to absorb cyclohexane. When the cyclohexane content was added to 0.1 g and 0.2 g, it can be seen from Table 3 that the data size and Cv value of the two groups are quite close. It can be inferred that the saturation concentration of PMMA seed microspheres absorbs cyclohexane is about 0.1 g. Between 0.2 g, but 0.2 g of cyclohexane has a narrow particle size distribution range, so 0.2 g of cyclohexane is the best condition. When the cyclohexane content was 0.3 g, a large amount of small particles were observed, and the particle size distribution was broader than the cyclohexane content of 0.05 g. Because when the cyclohexane content rises above the saturation value that the seed can absorb, excess cyclohexane is present in the system, which hinders the main swelling and competes with the seed microspheres to absorb the monomer, resulting in the appearance of a new core. Affect the monodispersity of the particles.

From Table 4, Table 4 shows the average particle size, Cv % and standard deviation of different monomer contents. When changing the amount of monomer MMA, from 1 g, 2 g, 5 g to 10 g, observe high. The particle size and shape change of the molecular microspheres. From Table 4, it can be found that when the monomer content is 1 g and 2 g, the particle diameters are 5.58 and 5.69 μm, respectively, and the particle size increase is small compared to the seed particle size of 5.2 μm. The reason may be that when the polymerization polymerization of the present invention is 70 ° C, the water solubility of MMA is 1.6 g / 100 g of water at 70 ° C, and the aqueous solution used in the experiment is about 220 g, that is, at 70 ° C. MMA, which is more than 3.5 g, can be dissolved in the aqueous phase without spreading to the seeds, so when the monomer is added at 1 g and 2 g, most of the monomers are stably dissolved in the aqueous phase. In this case, the particle size of the particles obtained by the present invention will only grow slightly. The amount of monomer added was increased to 10 g, and a microsphere having a particle size of 11.7 μm and uniformity was obtained. It can be seen from Table 4 that when the amount of monomer added increases, Cv% also increases, but both are below 8%, so they are all uniform particles, so the present invention selects 10 g of added monomer and has a particle size of 11.7 μm. And Cv% was 5.8% as the best condition for subsequent experiments.

From Table 5, Table 5 shows the average particle size, Cv value and standard deviation of different inhibitor contents. Since the monomer MMA is partially dissolved in the aqueous phase, the present invention requires the addition of the aqueous phase inhibitor NaNO ₂ to suppress The reaction of the monomers in the aqueous phase to avoid self-polymerization of the monomers into new particles. Therefore, the addition amount of the inhibitor of the present invention is 0.01 g, 0.05 g, 0.1 g and 0.2 g, respectively. Experimental results: when the inhibitor When the addition amount is 0.01 g and 0.05 g, a large number of small particles are found, and the Cv value is also quite large from Table 5. It can be understood that when the inhibitor addition amount is small, it inhibits the polymerization of the aqueous monomer. The ability is still not enough. Therefore, when the addition amount of the inhibitor is 0.1 g and 0.2 g, it is found that almost no small particles are present, and the Cv values of both are reduced to below 8%, which is a uniform particle diameter, thereby demonstrating that the content of the inhibitor is increased. Helps reduce the phenomenon of self-polymerization of monomers in the aqueous phase. According to the experimental results, the present invention chose to add 0.2 g of inhibitor, a particle size of 11.7 μm, and a Cv value of 5.8% as the optimum conditions for the subsequent reaction.

From Table 6 and Table 7, the table 6 is the average particle size, Cv % and standard deviation of different crosslinker contents. Table 7 is the fixed crosslinker 20%, changing the average particle size of the total monomer content, Cv% and standard deviation, the present invention will add a crosslinking agent to observe the particle size and shape change, respectively, adding 0%, 20%, 30% and 40% of the cross-linking agent EGDMA, found that when the content of the cross-linking agent from When 0% rises to 20%, the particle size increases from 11.7 μm to 15.5 μm, and the Cv value also increases from 5.8 to 19.4. This is because the mechanism relied on the difference in the hydrophilic and hydrophobic properties during the swelling step. While the cross-linking agent EGDMA is a more hydrophobic monomer than the monomeric MMA, when a cross-linking agent is added to the system, the cross-linking agent tends to diffuse more into the seed, so the seed is equal to the non-added cross-linking agent. It absorbs more monomers and causes a significant increase in particle size. After the addition of the crosslinking agent, the Cv value also increases with the particle size for two reasons. First, under the same conditions, a more hydrophobic cross-linking agent was added, which destroyed the swelling system of the monomer MMA in the original system, resulting in uneven distribution coefficient of swelling and resulting in different particle sizes. Another reason is that the cross-linking agent is more reactive than the monomer, so when the polymerization reaction is heated, once the cross-linking agent is completely reacted to form a structure with a high bridge density, the remaining monomers are difficult to diffuse into the particles. Inside, while the excess monomer is present in the aqueous phase, it is easy to form a new core and cause a phenomenon of non-uniformity. When the amount of cross-linking agent is 20%, 30% and 40%, the average particle size is slightly decremented from Table 6. The reason is as mentioned in the above paragraph. When the cross-linking agent content rises, the particle size is not easily caused. The appearance of uniform and small particles, so when calculating the average particle size, the presence of more small particles will lower the average value. When the amount of cross-linking agent is 20%, 30% and 40%, the Cv values are very close, and the particle diameters are very uneven. However, the higher the cross-linking agent content, the more difficult to prepare the micro-spheres with uniform particle size. However, the particles having a crosslinking degree of 20% are sufficient to have solvent resistance. Therefore, the present invention selects 20% of the fixed crosslinking agent to obtain particles having a uniform particle diameter. When the particle size and the Cv value of the particles prepared by using the monomer 10 g and the crosslinking degree of 20% in the invention are 15.5 μm and 19.4%, respectively, the particles are uniformly poor, so the present invention attempts to reduce the monomer addition. The amount of the monomer is reduced to cause the particle size to be different, and the reduction of the monomer is also expected to decrease the particle size of the monomer. However, the particle size prepared by the monomer 10 g and the crosslinking degree is 20% than that of the present invention. The target 10 μm is much larger, so the present invention is intended to improve the non-uniformity by reducing the amount of monomer added, and to maintain the particle size above 10 μm. The experimental results are shown in Table 7. In the present invention, the amount of monomer added is reduced from 10 g to 8 g, 7 g, 6 g, and 5 g, and it can be found that the particle size of the particles decreases when the amount of monomer added decreases downward. And the Cv value also decreases as expected, because the amount of monomer added is reduced, the present invention can control and then find the saturation value of its swelling system, when the monomer addition amount is 8 g and 7 g, there are still some small particles. Existence, from Table 7 found that its Cv value decreased, but still higher than 8%. When the monomer addition amount decreased from 7g to 6g, the Cv value also decreased from 13.4% to 4.7%, the particle size was also maintained at 10.8 μm, which was twice the seed particle size, and 5 g was added compared to the monomer. The Cv values of the two were almost the same, and the particle size of the monomer added 6 g was slightly larger. Therefore, the present invention decided to select a particle obtained by adding 6 g of a monomer and a crosslinking degree of 20% to perform a solvent resistance test.

The polymer microspheres prepared by preparing 0.1 g of seed, 0.2 g of swelling agent cyclohexane, 6 g of monomer (MMA + EGDMA 20%), 0.6 g of initiator BPO and 0.2 g of inhibitor NaNO ₂ were washed by water and dried by centrifugation. Thereafter, the mixture was immersed in THF at a solid content of 10% for 24 hours at room temperature, and the particle size pattern was observed by SEM. The morphology of 0% cross-linking degree and 20% cross-linking degree microspheres before and after immersion in THF is shown in Table 8. The 0% cross-linking microspheres are completely dissolved after immersion in THF, 20% cross-linking. After soaking in THF, the microspheres can still maintain their spherical shape, and the volume swelling rate before and after soaking is 102%, and the particle size is only slightly increased, which proves that it has good solvent resistance.

Using a Thermo Gravimetric Analyzer (TGA), it is possible to analyze the weight loss caused by the organic matter as the temperature rises, and the heat resistance and thermal cracking of the substance can be observed by the weight loss condition. It can be clearly seen from Table 9 that the maximum thermal weight loss rate of seed (a) occurs at 308 ° C, while 0% cross-linking microspheres (b) occur at 311 ° C, so without adding cross-linking agent, The maximum thermal weight loss temperature of the particles, that is, their heat resistance properties, is not improved. The 20% cross-linking microsphere (C) has a maximum thermal weight loss temperature of 340 ° C, which is a significant improvement compared to (a) and (b), so it can be proved that the microspheres with bridging structure have heat-resisting properties. It has indeed improved.

In summary, the preparation method of the high-crosslinking degree uniform particle size polymer microsphere of the invention can effectively improve various disadvantages of the conventional use, and can uniformly prepare a high degree of cross-linking degree of a predetermined size by a dispersion polymerization method and a two-stage swelling polymerization method. The polymer microspheres have a particle size of twice the particle size of the seed, and achieve the properties of heat resistance and solvent resistance; thereby making the production of the present invention more progressive, more practical, and more suitable for consumer use, indeed The requirements for the invention patent application, and the patent application is filed according to law.

However, the above is only the preferred embodiment of the present invention, and the scope of the present invention is not limited thereto; therefore, the simple equivalent changes and modifications made in accordance with the scope of the present invention and the contents of the invention are modified. All should remain within the scope of the invention patent.

1. . . First mixture

11. . . stabilizer

12 in. . . Solvent

13. . . Nitrogen

2. . . Second mixture

twenty one. . . monomer

twenty two. . . Starter

twenty three. . . Nitrogen

3. . . Submicron ball emulsion

31. . . Water bath

4. . . seed

41. . . water

42. . . Methanol

5. . . Seed mixture

51. . . Swelling agent

52. . . Interface active agent

6. . . Monomer emulsion

61. . . monomer

62. . . Starter

63. . . Crosslinker

64. . . Interface active agent

7. . . High cross-linking polymer microspheres

71. . . stabilizer

72. . . Inhibitor

73. . . Nitrogen

1 to 4 are schematic views showing the first step of the present invention.

Figure 5 is a schematic view of the second step of the present invention.

Figure 6 is a schematic diagram of the third step of the present invention.

Figure 7 is a schematic view of the fourth step of the present invention.

5. . . Seed mixture

6. . . Monomer emulsion

7. . . High cross-linking polymer microspheres

71. . . stabilizer

72. . . Inhibitor

73. . . Nitrogen

Claims (15)

The invention relates to a method for preparing a high-crosslinking degree uniform particle size polymer microsphere, comprising the following steps: Step 1: providing a seed obtained by a dispersion polymerization method, the seed is polymethylmethacrylate (PMMA); 2: mixing the amount of the swelling agent between 0.05 and 0.3 g and the surfactant of 40 to 60 g, and then adding the seed to stir to form a seed mixture, wherein the swelling agent is cyclohexane (cyclohexane) Step 3: Mix the monomer with the addition amount of 1~10g and the initiator with the dosage of 0.6g, and then add the crosslinking agent with the content of 15~25% and the surfactant with the dosage of 90~120g. And homogenizing to form a monomer emulsion, wherein the single system is methyl methacrylate (MMA); and step 4: mixing the seed mixture with the monomer emulsion, and performing at 25-40 ° C After the monomer is swollen, it is stirred again. After stirring, the stabilizer and the inhibitor are added, and the mixture is uniformly stirred by nitrogen gas, and finally heated to 65-80 ° C for polymerization to form a high cross-linking polymer. Ball, its grain The diameter system is between 10 and 11.75 μm, which is twice the seed particle size. The method for preparing a high-crosslinking degree uniform particle size polymer microsphere according to the first aspect of the patent application, wherein in the first step, when the seed is prepared, the stabilizer is first added to the solvent, and after the magnet is stirred, The first mixed liquid is formed by introducing nitrogen gas, and then the monomer and the starter are added to the first mixed liquid, then nitrogen gas is introduced to form a second mixed liquid, and the second mixed liquid is placed in a water bath to carry out the reaction. A sub-micron sphere emulsion of uniform particle size can be obtained, and finally the sub-micron sphere emulsion is repeatedly centrifuged with water and methanol to remove the remaining monomers and stabilizers. seed. The method for preparing a high-crosslinking degree uniform particle size polymer microsphere according to the first aspect of the patent application scope, wherein the second step to the fourth step is a two-stage swelling polymerization method. The method for preparing a high-crosslinking degree uniform particle size polymer microsphere according to the first aspect of the patent application, wherein the surfactant in the second step is sodium dodecyl sulfate (SDS). And its concentration is 0.25%. The method for preparing a high-crosslinking degree uniform particle size polymer microsphere according to the first aspect of the patent application, wherein the dose of the seed in the second step is 0.1 to 0.2 g. The method for preparing a high-crosslinking degree uniform particle size polymer microsphere according to the first aspect of the patent application scope, wherein the swelling agent, the surfactant agent and the seed system in the second step are ultrasonically oscillated and the magnet is stirred 30~ After 40 minutes, stir at a temperature of 25 to 35 ° C for 8 to 12 hours with a mechanical stirrer at 120 to 160 rpm. The method for preparing a high-crosslinking degree uniform particle size polymer microsphere according to the first aspect of the patent application, wherein the initiator in the third step is Benzoyl Peroxide (BPO). The method for preparing a high-crosslinking degree uniform particle size polymer microsphere according to the first aspect of the patent application, wherein the crosslinking agent in the third step is Ethylene glycol dimethacrylate (EGDMA). ). The method for preparing a high-crosslinking degree uniform particle size polymer microsphere according to the first aspect of the patent application, wherein the surfactant in the step (3) is sodium dodecyl sulfate (SDS). And its concentration is 0.25%. The method for preparing a high-crosslinking degree uniform particle size polymer microsphere according to the first aspect of the patent application, wherein the monomer, the initiator, the crosslinking agent and the surfactant in the step 3 are homogenized at a high speed. The mixture is homogenized for 10 to 20 minutes, and then uniformly dispersed by an ultrasonic oscillator for 10 to 20 minutes to form a monomer emulsion. The method for preparing a high-crosslinking degree uniform particle size polymer microsphere according to the first aspect of the patent application, wherein in the fourth step, the monomer is swollen at 25-40 ° C, and then the mechanical stirrer is used at 120. The seed mixture was mixed with the monomer emulsion by stirring at ~160 rpm for 5-8 hours. The method for preparing a high-crosslinking degree uniform particle size polymer microsphere according to the first aspect of the patent application, wherein the stabilizer in the step 4 is polyvinyl alcohol (PVA), and the concentration thereof is 4. ~6%. The method for preparing a high-crosslinking degree uniform particle size polymer microsphere according to the first aspect of the patent application, wherein the inhibitor in the step 4 is sodium nitrite (NaNO ₂ ), and the dosage is 0.1~ 0.2g. The method for preparing a high-crosslinking degree uniform particle size polymer microsphere according to the first aspect of the patent application scope, wherein the step four is carried out by stirring with a mechanical stirrer at a speed of 120 to 160 rpm for 25 to 40 minutes after passing through a nitrogen gas. Evenly. The method for preparing a high-crosslinking degree uniform particle size polymer microsphere according to the first aspect of the patent application scope, wherein in the fourth step, the temperature is raised to 65-80 ° C, and the polymerization is carried out for 9 to 12 hours to form a high degree of crosslinking. Uniform polymeric microspheres having a particle size twice the seed size.