JPH04337303A - Production of monodisperse particle - Google Patents

Abstract

PURPOSE:To efficiently produce monodisperse polymer particles arbitrarily controlled in softening temperature and particle diameter. CONSTITUTION:Polymer particles dispersed in an aqueous dispersion medium are formed as seed particles and subjected to seed polymerization. In this time, seed particles having 1-10mum average particle diameter are used as these seed particles and absorption and polymerization of monomer is continuously carried out.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for efficiently producing monodisperse particles having excellent sphericity by polymerizing unsaturated monomers in an aqueous dispersion medium.

0002

BACKGROUND OF THE INVENTION Hitherto, dispersion polymerization and seed polymerization have been used to produce monodisperse particles obtained by polymerizing unsaturated monomers. In the dispersion polymerization method, when a crosslinkable unsaturated monomer is used as the unsaturated monomer, the content of the crosslinkable unsaturated monomer in the unsaturated monomer is 0.05 mol% or more. It has been reported that deformation occurs in the particles, making it impossible to obtain monodisperse particles (G.M. Tseng, Y.
Y. Lu, M. S. El-Aasser and
J. W. Vanderhoff, J. Poly
mer, Sci. A Polym. Ch
em. Ed. 24, 2995 (1986)). Therefore, it has been impossible to obtain monodisperse particles with a high degree of crosslinking. The seed polymerization method is a two-step method in which seed polymer particles are synthesized by emulsion polymerization, the unsaturated monomer is absorbed into the seed polymer particles, the seed polymer particles are swollen, and then polymerization is carried out, or the above steps are performed. A method is used in which the particle size is repeatedly increased several times. In this method, the particle size of the monodisperse particles obtained is determined by the ability of the seed polymer particles to absorb unsaturated monomers, and the production of monodisperse particles of about 20 μm requires multiple absorption, swelling, and polymerization steps. The problem is that it has to go through the process.

Furthermore, as described in Japanese Patent Publication No. 57-24369, there is a method in which seed polymer particles are made to absorb a hydrophobic organic compound to increase their swelling ability, and then an unsaturated monomer is absorbed to carry out polymerization. be. However, this method has problems such as a complicated manufacturing process and generally a long swelling time. Furthermore, since the absorption and swelling of the unsaturated monomer into the seed particles and the polymerization of the unsaturated monomer are separate processes, the crosslinking density of the particles after polymerization is almost uniform within the particles, and the density of crosslinking between the inside and outside of the particles is almost uniform. It is not possible to produce particles with different shell crosslink densities.

0004

[Problems to be Solved by the Invention] The present invention solves the above-mentioned problems, and is produced by simultaneously performing two steps: absorption of an unsaturated monomer into seed polymer particles, swelling, and polymerization of the unsaturated monomer. The present invention aims to provide a method for producing monodisperse particles that can shorten the steps. Furthermore, the present invention aims to provide a method for producing monodisperse particles that can produce monodisperse particles in which the crosslink density of the inside of the particle and the outer shell are different, which has been impossible with the prior art. Furthermore, the present invention aims to provide a method for producing monodisperse particles in which the particle size and softening temperature of the monodisperse particles during polymerization can be easily controlled, and the yield can be increased without causing agglomeration.

[0005]

[Means for Solving the Problems] The present invention involves absorbing an oil-soluble unsaturated monomer into seed polymer particles dispersed in an aqueous dispersion medium, and then absorbing the oil-soluble unsaturated monomer in the presence of an oil-soluble polymerization initiator. In the method for producing monodisperse particles by polymerizing an unsaturated monomer, the seed polymer particles are crosslinked monodisperse particles or uncrosslinked monodisperse particles with an average particle size of 1 to 10 μm produced by dispersion polymerization of an unsaturated monomer, Absorption of an oil-soluble unsaturated monomer in which a non-crosslinkable unsaturated monomer and a crosslinkable unsaturated monomer are mixed so that the molar ratio of the crosslinkable unsaturated monomer is 0 to 35 mol%. The present invention provides a method for producing monodisperse particles, characterized in that an oil-soluble unsaturated monomer is continuously added to a reaction solution during polymerization so that polymerization is carried out continuously.

[0006] As the seed polymer particles used in the present invention, styrene-based, acrylic-based polymers, and the like are preferably used. Specifically, for example, crosslinked monodisperse particles or uncrosslinked monodisperse particles having an average particle diameter of 1 to 10 μm manufactured by dispersion polymerization are preferable. If the average particle size is less than 1 μm, the initial monomer absorption capacity is small and aggregation tends to occur during seed polymerization, and if it exceeds 10 μm, deformation tends to occur during seed polymerization. Here, the average particle diameter is determined by scanning electron micrographs.

[0007] Furthermore, it is desirable that particles have an area average particle diameter/number average particle diameter (ds/dn), which is an index of monodispersity, of 1.01 or less. If it exceeds this, the particle size distribution of the particles after seed polymerization will become wider. Further, the degree of crosslinking of the seed polymer particles is preferably 0 to 0.04%. If the degree of crosslinking of the seed polymer particles is high, the polymerization initiator will be difficult to absorb into the seed polymer particles, and when polymerization starts, polymerization will occur outside the seed polymer particles, causing particles with non-uniform particle sizes. Note that the degree of crosslinking was calculated based on the ratio of crosslinkable unsaturated monomers in the added unsaturated monomers.

In the present invention, a seed polymer particle dispersion liquid in which seed polymer particles are dispersed in water together with a surfactant is prepared. Further, an oil-soluble unsaturated monomer having an oil-soluble polymerization initiator dissolved therein is added in an amount of 1 to 5% by volume of the seed polymer particles and absorbed into the seed polymer particles. The oil-soluble polymerization initiator is preferably an oil-soluble peroxide initiator such as benzoyl peroxide or an oil-soluble azo initiator. Use of a water-soluble initiator is undesirable because it causes generation of particles other than seed polymer particles. Furthermore, if the amount of the oil-soluble unsaturated monomer dissolved in the oil-soluble polymerization initiator added is too large, it will not be absorbed into the seed polymer particles and will cause generation of particles other than the seed polymer particles.

[0009] The above reaction solution was heated to the polymerization initiation temperature,
One or more oil-soluble unsaturated monomers are continuously added to the reaction solution as soon as the reaction solution reaches the polymerization initiation temperature. The oil-soluble unsaturated monomer added to the reaction solution is absorbed into the seed polymer particles and polymerized. Since the polymerization reaction mainly takes place on the surface of the seed polymer particles, the particle size of the seed polymer particles gradually increases. When the desired particle size is reached, the continuous addition of the unsaturated monomer is stopped, the reaction solution is cooled, and the polymerization reaction is stopped.

[0010] Here, in order to continuously add the oil-soluble unsaturated monomer to the reaction solution, it is necessary to add 1 to 10
The addition timing is at least 2 times with an addition rate of ml/hr.
Must be within 0 intervals. In addition, as a method of adding the oil-soluble unsaturated monomer, the oil-soluble unsaturated monomer is a mixture of two or more types of uncrosslinked and crosslinked monomers, and the crosslinkable unsaturated monomer is added in the first half of the polymerization reaction. A monomer mixed solution with a reduced proportion of monomers is continuously added and polymerized on the surface of the seed polymer particles to form a surface layer with a low crosslink density, and then added in the latter half of the polymerization reaction. Non-crosslinkable unsaturated monomers and crosslinkable unsaturated monomers, such as a method in which a monomer mixed solution with a high proportion of crosslinkable unsaturated monomers is continuously added and further polymerized on the surface of the seed polymer particles. A preferred method is to add the polymer by changing the ratio of the polymer over time. This makes it possible to produce monodisperse particles having two layers: a layer with a low crosslink density and a layer with a high crosslink density above that layer.

Furthermore, by controlling the seed polymer particle size and the ratio of non-crosslinkable unsaturated monomers and crosslinkable unsaturated monomers of the oil-soluble monomers added, the softening temperature can be adjusted to 100%.
℃ ~ 155 ℃ range, and average particle size 1.5 ~ 25 μm
It is possible to produce monodisperse crosslinked particles arbitrarily controlled within this range. The non-crosslinkable monomers used in the present invention include styrene, ethyl acrylate, methyl acrylate, ethyl methacrylate, methyl vinyl ether, vinyl acetate, N
- Methylacrylamide, acrylonitrile, etc. can be mentioned. Furthermore, examples of crosslinkable monomers include divinylbenzene and ethylene glycol monoacrylate. The mole fraction of the crosslinkable monomer in the monomer is 0 to 35 mol%. If it exceeds 35 mol%, the particles will be deformed and crushed after polymerization, making it impossible to obtain sphericity. Also,
As seed polymer particles, the average particle size is 1 due to dispersion polymerization.
When monodispersed particles of ~10 μm are used, the addition rate of the unsaturated monomer becomes faster, probably because the seed polymer particles easily absorb the added oil-soluble unsaturated monomer, and the average particle size of 1.0 μm is increased in a short time. Monodisperse particles can be produced arbitrarily within the range of 5 to 25 μm.

0012

EXAMPLES The present invention will be explained in detail below based on Examples, but the present invention is not limited thereto. (1) Example 1 of manufacturing seed polymer particles by dispersion polymerization (
No. 1 to 7) Ethanol (EtOH) in the proportions shown in Table 1
), polyacrylic acid (PAA) was dissolved in 2-methoxyalcohol (MeCell) solution at a concentration of 1.7% by weight. There, benzoyl peroxide (B) is added as a polymerization initiator.
Styrene monomer (St) containing 1.0% by weight of PO) dissolved therein was added in the proportion shown in Table 1. Thereafter, the temperature was raised to 70° C. in a N2 gas atmosphere to initiate polymerization, and the polymerization reaction was carried out for 24 hours to obtain monodispersed uncrosslinked polystyrene particles. At this time, by changing the ratio of ethanol, 2-methoxyalcohol, and styrene, the average particle diameter of the monodispersed uncrosslinked polystyrene particles obtained could be arbitrarily controlled within the range of 1 to 10 μm. However, as shown in Table 1, when trying to produce particles of 10 μm or more, No. 7 like ds/
When the dn was 1.1 or more, the particles became polydisperse and were not suitable as seed polymer particles.

[0013]

[Table 1]

(2) Production example 2 of seed polymer particles by dispersion polymerization (No. 8 to 13) EtOH 20% by volume, M
It was produced under the same conditions as Production Example 2, using eCell at 65% by volume and St and divinylbenzene (DVB) shown in Table 2 at 15% by volume. Divinylbenzene (DVB) was added to produce crosslinkable particles. However, D
When the content of VB is increased, No. As shown in Figure 13, the particle size distribution is wide, and particle deformation occurs.
It was not suitable as a seed polymer particle.

[0015]

[Table 2]

Example 1 No. 1 in Table 1. Monodispersed uncrosslinked polystyrene particles of dn=5.53 μm of No. 4 were used as seed polymer particles. 20 parts by weight of seed polymer particles, 2000 parts by weight of H2O, and 0.5 parts by weight of sodium lauryl sulfate as a surfactant were mixed, and ultrasonic vibration was applied to disperse the seed polymer particles. Further, 500 parts by weight of a 3% by weight aqueous polyvinyl alcohol solution was added thereto as a particle aggregation inhibitor. Into this solution, a mixture of 30 parts by weight of styrene monomer and 3 parts by weight of benzoyl peroxide as an initiator was added with N2
The mixture was added in an atmosphere and stirred at 30° C. for 1 hour. Thereafter, the temperature was raised to 70°C to start polymerization. Also, the solution temperature is 70
As soon as the temperature reached .degree. C., a mixed monomer of DVB and St having a DVB content of 4.5 mol% was continuously added to the seed polymer particle solution at a rate of 40 ml/hour. After 7 hours, continuous dropping of the mixed monomer was stopped, and the mixture was left at 70° C. for 2 hours. After cooling to room temperature, 23° C., the polymerized particles were taken out and the particle size was measured. As a result, dn=13.28
Monodisperse crosslinked polystyrene particles with excellent sphericity and ds/dn=1.0072 were obtained.

Example 2, Example 3 and Comparative Example 1 No. 1 in Table 1 was used as the seed polymer particles. dn of 6=10.2μm
, ds/dn=1.0091 using monodispersed uncrosslinked polystyrene particles, and other manufacturing conditions were the same as in Example 1. However, the continuous dropping time of the monomer was changed to 4 hours (Example 2), 6 hours (Example 3), and 8 hours (Comparative Example 1).
) was carried out under the following three conditions. By changing the continuous addition time of monomer, the total amount of monomer added to the seed polymer particles will vary. Table 3 shows the results. Table 3
In Comparative Example 1, dn=27 μm, which is large, but ds/dn, which is an index of monodispersity, is 1.031, and the range of particle size distribution is wide. In the current polymerization method, the maximum value of dn of monodisperse particles is considered to be about 25 μm. Furthermore, it can be seen that the particle size after seed polymerization can be controlled by adjusting the amount of monomer added.

[0018]

[Table 3]

Examples 4 to 9 and Comparative Example 2 No. 1 in Table 1 was used as the seed polymer particles. dn of 6 = 10.2 μm, ds
Using monodispersed uncrosslinked polystyrene particles with /dn=1.0091, using 30 parts by weight of monomers with the ratio of DVB and St added as shown in Table 4, and setting the monomer addition time to 4 hours, Example 1 Seed polymerization was carried out in the same manner. The softening temperature of the obtained monodisperse polystyrene particles was measured using a flow tester. As a result, the softening temperature varies depending on the ratio of DVB and St in the monomers added, and ranges from 100°C to
It was found that the temperature can be controlled arbitrarily between 150°C. This is considered to be because the crosslinking density of the monodisperse particles after polymerization is determined by the ratio of DVB and St added. Furthermore, when the content of DVB was set to 40 mol% (Comparative Example 2), the particles were deformed and crushed after polymerization, and sphericity could not be obtained.

[0020]

[Table 4]

Examples 10 to 15 No. 1 in Table 1 was used as seed polymer particles. 1~No. Seed polymerization was performed using six types of No. 6. The added monomer is S
30 parts by weight of a mixed monomer of T and DVB with a DVB content of 10 mol% was used. Seed polymerization was carried out in the same manner as in Example 1, changing the monomer addition rate to 40 ml/hour and the monomer addition time. As a result, monodisperse particles having the particle sizes shown in Table 5 were obtained. In addition, as a result of measuring the softening temperature of the particles, it was found that the softening temperature was approximately 1
The temperature was constant at 15°C.

[0022]

[Table 5]

From Examples 2 to 3, 4 to 9, and 10 to 15, the particle size of the seed polymer, the total amount of monomer added, and the DV
By adjusting the content of B, the particle size can be adjusted from 1.5 to 25μ.
It can be seen that monodisperse particles whose particle diameter and softening temperature are independently controlled within a softening temperature range of 100°C to 150°C can be obtained.

Example 16, Example 17 No. 1 in Table 1 was used as the seed polymer particles. dn of 6=10
．． Seed polymerization was carried out using monodisperse uncrosslinked polystyrene particles of 2 μm, at a monomer addition rate of 40 ml/hour, for a monomer addition time of 4 hours, and with the concentration of DVB as the added monomer varied as shown in Table 6. After measuring the softening temperature of the particles after polymerization, the surface condition of the particles was observed.
Comparing Example 7 with Example 16, a lot of fusion between particles was observed in Example 16. However, in Example 17, almost no fusion occurred. Furthermore, the softening temperature of Example 17 is higher than that of Example 16. This is presumed to be because, even though the overall concentration of DVB added was the same, the addition timing was changed, resulting in a higher crosslinking density inside the particles in Example 16.

[0025]

[Table 6]

[0026]

Effects of the Invention According to the method for producing monodisperse particles using the seed polymerization method of the present invention, by continuously adding an oil-soluble unsaturated monomer during polymerization, unsaturated particles can be produced on the surface or inside of the seed polymer particles. The absorption of the saturated monomer and the polymerization reaction are carried out continuously, and the two steps of absorption of the oil-soluble unsaturated monomer into the seed polymer particles, swelling, and polymerization of the oil-soluble unsaturated monomer are carried out simultaneously. The process can be shortened. Further, the particle size of the seed polymer particles gradually increases due to a polymerization reaction on the surface or inside the particles. By changing the composition of the unsaturated monomer added for this purpose, particles having different compositions or crosslinking densities from the center to the outside of the particle can be produced.

Claims (2)

[Claims] Claim 1: Monodispersed particles of monodisperse particles, which absorb an oil-soluble unsaturated monomer into seed polymer particles dispersed in an aqueous dispersion medium and polymerize the oil-soluble unsaturated monomer in the presence of an oil-soluble polymerization initiator. In the production method, the seed polymer particles are produced by dispersion polymerizing unsaturated monomers and have an average particle size of 1 to 1.
10 μm crosslinked monodisperse particles or uncrosslinked monodisperse particles, and the uncrosslinkable unsaturated monomer and crosslinkable unsaturated monomer are mixed so that the molar ratio of the crosslinkable unsaturated monomer is 0 to 35 mol%. Monodispersion characterized by continuously adding the oil-soluble unsaturated monomer to the reaction solution during polymerization so that the absorption and polymerization of the oil-soluble unsaturated monomer mixed with the monomer are continuously carried out. Method of manufacturing particles. 2. The oil-soluble unsaturated monomer that is continuously added is a mixture of an uncrosslinkable unsaturated monomer and a crosslinkable unsaturated monomer, and the inner and outer shells of the resulting monodisperse particles are 2. The method for producing monodisperse particles according to claim 1, wherein the ratio of the uncrosslinkable unsaturated monomer and the crosslinkable unsaturated monomer is changed over time so that the crosslinking density is different.