KR20010109013A - The synthesis method for capsulized emulsion having internal pore by multy-stage emulsion polymerization - Google Patents

Abstract

The present invention relates to a method for producing fine particles having internal pores used as a concealment material by emulsion polymerization, minimizing the reversal of the monomer through the multi-step emulsion polymerization, minimizing the generation of defective particles, due to swelling It is an object of the present invention to provide a method for producing fine particles having internal pores which prevents destruction of the shell coating and at the same time increases monodispersity efficiency. In the method for producing fine particles having internal pores composed of a swelling step and a shell forming step, an alkali metal phosphate is used as an abnormal particle formation inhibitor (dispersant) in the seed formation step of the initial stage and an alcohol as a radical fractionation rate enhancer. It is to provide a method for producing fine particles having internal pores, characterized in that the addition of.

Description

The synthesis method for capsulized emulsion having internal pore by multy-stage emulsion polymerization}

The present invention relates to a method for producing fine particles having internal pores used as a concealment material by emulsion polymerization, and more particularly, light scattering effect by pores formed in the core layer and the cell layer and formed therein using a seed It relates to a method for producing fine particles having an emulsion by polymerization.

Concealment agent is mainly used in the paint field, especially water-based white or light color paint, paper sizing agent or office concealment agent, and is used to prevent the pattern, etc. formed on the surface of the substrate from being exposed to the outside. Since titanium oxide, an inorganic pigment, has excellent hiding power, it is widely used as a pigment component of a concealment agent, but the price of titanium oxide is rising as the mineral containing titanium is gradually depleted. The use of is increasing the burden.

Due to this problem, much research is being conducted on the development of an alternative concealment agent that can be used in place of the concealing titanium oxide, and as a result of the study, particles of organic polymers having pores therein are formed. The light scattering effect is caused by the refractive index difference between the hollow layer and the shell layer in the inner layer, and the light hiding effect is enhanced by the light scattering effect, suggesting that it may be used as a pigment of the hiding agent.

Conceiving agents made of fine particles of organic polymer having pores therein are currently being actively studied for various factors affecting the structure and physical properties of the composite latex prepared through multistage emulsion polymerization.

For example, RYDickie, MFC Cheung, and S. Newman have been published in J. Appl. Polym Sci. 17, 65 1973. Composite latex particles of soft core / hard shell and hard core / soft shell structure by using polymethyl methacrylate and polybutyl acrylate as the seed particles form the core and the shell component is polymerized on the core surface. And M. Okubo, Y.Katsuta and T. T. Matsumoto et al., Through the Polymer Science Magazine (J. Polym Sci), used three methods of styrene as a batch method, a semi-batch method and an equilibrium swelling method using polystyrene and polybutyl acrylate as seed particles. To prepare a composite latex having an abnormal structure of raspberry or confetti shape, observe that the initiator affects the diffusion rate of the particles in the water phase, and to the surface of the particle by using a soap titration method. The surface properties of the particles were observed using the amount of the emulsifier adsorbed, and when the hydrophilic monomer was applied to the hydrophobic seed particles in the second step, a latex having a core / shell structure was formed regardless of the method of introducing the monomer. Method of adding monomer when styrene is added to the hydrophilic seed particles of methyl methacrylate and polymethacrylate Depending on the volume ratio of the monomer constituting the core / shell, various shapes such as the oil (Oil in Oil) structure and the raspberry structure of the polymer are observed, and thus the monomer input method, reaction temperature, compatibility between polymers, It was confirmed that flexibility and hydrophilicity were important factors influencing the structure of the particles.

In addition, Okubo et al. Observed that pores were formed when polymerizing styrene with polybutylacrylate as a seed particle, which was formed by the transmission beam when observed with a transmission electron microscope (TEM), thereby constituting the core. It is interpreted that phase separation occurs due to the low glass transition temperature of polybutyl acrylate.

A. Goodall, M. WilKinson, and J. Hearn observed the pore structure through styrene polymerization through the journal colloid interface science. It is reported that pores are generated due to the loss of monomers, oligomers, etc., which constitute the layer, and the pores decrease as the polymerization proceeds, and eventually spherical particles are produced.

In addition, DI Lee, Preprints, etc., polymerized styrene / butadiene with polystyrene as a seed through coatings plastic chem, polymerizing the ratio of monomer and polymer, compatibility of core / shell polymer and reaction condition. Investigating the effect of these on the structure of the particles, and the phase separation phenomenon in the shell formation step, it was found that when the ratio of monomer and polymer is increased and the compatibility between polymers is increased, By forming particles, but lowering the ratio, hemispheric or asymmetrical particles were observed to confirm that the surface of the side latex particles was an important polymerization point for the shell-forming monomers, and Diiri and Ishikawa reported the journal Polymer Science. Using a copolymer of polyethylene acrylate and polymethacrylic acid as a seed through N- or styrene-butadiene was polymerized to produce particles of reverse core / shell structure.The hydrophilicity and polarity of the surface were increased by the acid component in the seed, resulting in phase separation due to the movement of the polymer chain constituting the particles. It has been confirmed that a favorable reverse phase core / shell structure is achieved, and the hydrophilicity, surface tension, molecular weight, etc. of the polymer are confirmed by reducing the molecular weight of the sheath latex and the surface tension at the interface between the core and the shell layer. It has been reported to contribute to this phase separation phenomenon.

I. CHO and KW Lee, through Polymer Science, prepared composite latex consisting of polymethylmethacrylate and polystyrene using various initiators, and added potassium persulfate, a water-soluble initiator. It was confirmed that the core / shell structure was formed in spite of the core component and the hydrophobic shell component when the polymerization was carried out. The hydrophobic group was introduced into the polystyrene by the anchoring effect of the sulfate group, thereby preventing the reverse phase phenomenon. It is reported that the movement of the polymer chain due to the viscosity of the shell-forming polymer on the surface of the latex particles affected by the ratio also affects the core / shell structure.

T. I. Min, A. Klein, M. MS El-Aasser, J. Vanderhoff and V. Dimon have many effects on the shape of particles by grafting core and shell polymer chains. The degree of grafting is confirmed and the degree of grafting depends on the surface area of the seed latex particles and is reported to be advantageously formed in the case of relatively small particles, and Segall uses polybutyl acrylate as the seed and polybenzyl methacrylate. The composite latex of the core / shell structure was prepared by using polystyrene as a shell, and when the monomer was added semi-continuously in the shell step and the amount of the shell monomer was increased, more uniformly encapsulated particles were prepared when no chain transfer agent was added. It was. On the basis of these experimental results, they report that the thermodynamic surface tension, the viscosity at the kinematic polymerization point, and the flexibility of the chain have a great influence on the morphology of the particles.

D. R. Stutteam, A. Kelin, M. MS El-Aasser and J. V. Vanderhoff, et al. Prepared latex core / shell structures using polybutylacrylate and polystyrene, including pH, initiator concentration, stirring speed, and solid content. In the shell stage, it was confirmed that the input speed of monomer and emulsifier, the size of the seed, the ionic force, etc. have a great influence on the formation of particles. Using the mechanism of adsorption and growth on the surface of polybutyl acrylate, the compound is confirmed to be a latex composite latex particles observed after polymerization, Y. CHung-Li, J. Goodwin And RH Ottewill et al. Produced polystyrene from the monomer particles swollen with monomers. The complex latex of the abnormal structure was prepared by the growth of the surrounding particles through the heterogeneous aggregation adsorbed on the surface of the particles, and EBradford, J.W. Vanderhoff, etc. The morphological study of synthetic latex explained that the particles of abnormal structure were greatly affected by the splitting of the shell-forming monomer into the seed particles because the polymers were locally polymerized on the surface of the seed particles.

yen. N. Sutterlin reported that particles of the core shell structure can be more easily produced when the ratio between components of the core / shell structure, compatibility, water-soluble initiator and polymerization temperature are low.

As explained above, many studies on porous particles with a core / shell structure demonstrate that they are solidifying their position as an important pigment component that has significant utility as a shielding agent by dispersing light in pores. would.

However, according to Kubelka Munch's theory, the light scattering coefficient which represents the measure of light scattering is known to be represented by Equation 1 below, and according to Ross, the rutile titanium oxide having the largest light scattering coefficient as a white pigment is 0.56. The light scattering coefficient shows the maximum value of 3.3 when the particle size is 0.2㎛ at the single wavelength of μm, but the maximum light scattering coefficient of about 0.4 when the pore size is 0.23㎛ for the light having the same wavelength in the case of spherical pores It is said to have an efficiency of about 12% of rutile titanium.

SX = 1-T / T

In the formula S is a light scattering coefficient, T is the light transmittance, X means the thickness of the coating film.

However, when viewed from the actual state of use, since the titanium oxide is present in the aggregated state in the coating film, the light scattering coefficient of titanium oxide is reduced to 2 to 3, so that the relative concealment rate of the spherical pores is more than 12%. Will be.

Since the pores in the particles have the same effect as above, researches having a core / shell structure having better pores are being actively conducted. As a result, US Patent No. 3,669,729 discloses emulsions obtained by emulsifying with a non-soluble solvent. Provided is a method for forming closed pores by incorporation during manufacture and volatilization of the solvent in the drying step, US Patent No. 3,637,431 proposes a method for forming fine pores using a non-insoluble solvent and a non-filmable latex have.

The above method is based on the premise of volatilization of the solvent, which implies pollution problems such as air pollution due to volatilization of the solvent during drying, and in order to solve such a problem, plastic beads having fine pores are added to the paint. For example, U.S. Patent No. 3,891,577 describes a two-phase emulsion emulsion having a water / oil / water structure by mechanically stirring a polyester solution dissolved in styrene and then closing the closed pores by polymerization. It proposes a method of preparing a polyester beads having a particle diameter of 1 to 25㎛ having and mixing with the paint, US Patent No. 3,615972 to polymerize a polymer material containing a blowing agent to form a plastic bead and then heated It discloses a technique for forming micropores by foaming.

However, in the above method, since the beads have a hiding power, they are difficult to act as pigments, but the particle size is uneven and the porosity contribution is low at the critical surface, the problem of sedimentation during storage, pore size and cell wall thickness There was a problem that was difficult to control.

In US Patent No. 3,914,338, a core / shell structured emulsion polymer having a polymethyl methacrylate having a refractive index of about 1.49 as a skin layer using a crosslinked polystyrene having a refractive index of about 1.59 as a seed was prepared. Proposed a method for producing particles having a hiding power by using as a surface processing agent of paper, but there is a limit to increase the hiding power only by the difference in refractive index.

In order to solve the above problems, Kim Dong-jin, Eun Jung-sik, Han Sang-no, etc. are using a hydrophilic monomer having a carboxyl group, a single double-bonding monomer and a cross-linking monomer. Korean Patent Publication No. 93-891 discloses a technique for containing a metal or an amphoteric compound having a high refractive index in the core pores of a pigment beads having a closed pore made of a polymeric material. Patent Publication No. 93-890 discloses a method for preparing an emulsion polymer having internal pores by adding a group transition polymerization initiator or an oil-soluble initiator to the core and the shell forming reaction solution.

From the above invention, it is possible to produce bead particles having internal pores excellent in hiding power and wash resistance, but in the inversion of particles by hydrophilicity, destruction of particles due to overswelling, and generation of initial defective particles There were still many problems.

In order to solve the above problems, the present invention minimizes the inversion of monomers through multi-step emulsion polymerization, minimizes generation of defective particles, and prevents destruction of the shell coating due to swelling, and at the same time, increases internal porosity. It is an object of the present invention to provide a method for producing microparticles having a diameter.

The present invention for solving the above problems is a seed of the initial stage in the method for producing fine particles having internal pores by the emulsion polymerization method consisting of a seed forming step, core forming step, swelling step and shell forming step It can be achieved by providing a method for producing fine particles having internal pores, characterized in that the formation of the seed by adding an alkali metal phosphate as an abnormal particle formation inhibitor to the formation process, and alcohol as a radical fractionation rate enhancer.

As the alkali metal phosphate added for the purpose of preventing abnormal particle formation by improving the dispersibility, lithium phosphate, potassium phosphate, sodium phosphate may be used, and any one of the first phosphate, the second phosphate, and the regular salt may be used, but in terms of cost In consideration of the above, it is preferable to use sodium-based phosphate, and when the addition amount is less than 10 parts by weight based on 100 parts by weight of the total solid content of the monomer component, a problem occurs in that a large amount of abnormal particles, that is, defective particles are generated. In the case of using 20 parts by weight or more, it is preferable to use within the range of 10 parts by weight to 20 parts by weight since water resistance may be reduced, resulting in a problem of poor coating film formation, which causes the coating film to float after coating.

Alcohols added as radical fractionation rate promoters are used to assist the radical formation of water-soluble initiators and to enhance the stability of the initial micelles to improve the fractionation rate of radicals. Ethylene glycol, propylene glycol, methyl alcohol, ethyl alcohol, etc. The primary or secondary alcohols of may be used, and when the addition amount is less than 10 parts by weight based on 100 parts by weight of the total solids of the monomer, the fractionation rate is lowered, so that the hollow formation rate, If the proportion is lowered, and if more than 20 parts by weight is added, the problem of the presence of a large amount of unreacted monomer in the final product due to the increase in the fractionation rate of the initiator occurs within the range of 10 parts by weight to 20 parts by weight Preference is given to using at.

In the present invention, in which the abnormal particle formation inhibitor and the radical fractionation rate enhancer are added in the formation of the seed, a swelling step is set between the core forming step and the shell forming step to form a shell layer on the swollen core surface. It is characterized by.

In the case of swelling after forming the shell layer as in the general method, there is a problem in that the shell layer, which is a surface layer, is destroyed and the hiding power of particles generated by the generation of defective particles is lowered. However, in the present invention, the swelling process is introduced after the core forming process. The shell layer is formed by using the surface of the swollen core particles as a polymerization point, thereby bringing the effect of healing the fractures generated on the surface of the core during the swelling process in the shell layer formation process, thereby minimizing the generation of defective particles, thereby hiding the manufactured fine particles. Will be able to improve.

In addition, the present invention for solving the above problems has at least one hydrophobic monomer and carboxyl group having a double bond as the forming material of the seed in the seed forming process, it may contain more than 20 times the water molecules when swelling. The present invention provides a method for preparing fine particles having internal pores having better hiding power by using mixed hydrophilic monomers.

In addition, the present invention for solving the above problems has a hydrophobic monomer having a double bond with a hydrophilic monomer having a double bond and a hydrophobic monomer having a double bond and two or more double bonds by using the surface of the seed as a polymerization point in the core forming process Provided is a method for producing fine particles having internal pores mixed with monomers.

In addition, the present invention for solving the above problems is formed by forming a shell layer of the internal pores having a better hiding power by using a mixture of a hydrophobic monomer having one double bond and a hydrophobic monomer having two or more double bonds are formed. It provides a method for producing microparticles.

The method for producing the fine particles having the internal pores of the present invention having the configuration as described above is made of a step-by-step process as follows.

(1) 20 to 60 parts by weight of a copolymerizable emulsifier containing 40 to 80 parts by weight of a hydrophobic monomer having a double bond and at least one carboxyl group and containing 20 times or more water molecules when swelled 10 parts by weight to 20 parts by weight of sodium phosphate is added as a water-soluble initiator of less than 20 parts by weight, an inhibitor of the generation of abnormal particles, and 60 parts by weight to 20 parts by weight of alcohol based on the total monomer as the radical fractionation rate enhancer. Seed forming process for forming the seed at a temperature of ℃ to 90 ℃,

(2) 60 parts by weight to 70 parts by weight of a hydrophilic monomer having a double bond and 15 parts by weight to 27 parts by weight of a hydrophobic monomer having a double bond, and a double bond of the seed formed from the seed forming step PRE-EM consisting of 3 parts by weight to 10 parts by weight of monomer having two or more and 0.05 parts by weight to 0.1 parts by weight of a copolymerizable emulsifier is added at a ratio of 3: 7 based on the solid content of the seed and the core. Core forming step of polymerization by the semi-batch method at a temperature of 60 ℃ to 90 ℃,

(3) neutralizing the reaction product passed through the core forming step to pH 8 to 10 with ammonia water at a temperature of 60 ℃ to 90 ℃ and stirred for 20 minutes to 30 minutes at a speed of 250RPM to 300RPM Swelling process to increase the volume of the seed part

(4) Free of 90 to 99 parts by weight of a hydrophobic monomer having one double bond, 1 to 10 parts by weight of a hydrophobic monomer having two or more double bonds and 0.2 to 0.5 parts by weight of a copolymerizable emulsifier Shell forming step of adding and polymerizing EM (PRE-EM).

As the hydrophobic monomer having a double bond used in the seed forming step, alkyl acrylates such as styrene, vinyltoluene, α-methylstyrene, butyl acrylate, isobutyl acrylate, 2-ethylhexyl acrylate, and isobutyl Methacrylates such as methacrylate, lauryl methacrylate and ethyl methacrylate may be used, and monomers having at least one carboxyl group having a double bond used for hollow formation in particles include acrylic acid, methacrylic acid, Itaconic acid or the like can be used, and polyoxyethylene phosphate ester, sodium dodecyl benzene sulfonate, sodium lauryl sulfonate and the like are used as an emulsifier, and ammonium persulfate, potassium persulfate, sodium persulfate, etc. are used as the water-soluble initiator. Persulfate compounds may be used.

The amount of the monomer having a double bond and having at least one carboxyl group is a factor for determining the size of the hollow, and when used at less than 20 parts by weight, the size of the hollow becomes small and the expected concealing effect cannot be obtained. If more than 40 parts by weight is added, the particle structure is destroyed during swelling, which causes the generation of defective particles.

The polymerization conditions were polymerized by semi-batch method and injected for 10 to 20 minutes and then aged for 10 to 20 minutes to prepare a seed. The monomers generated during the initial seed formation were transferred to the polymerization place even during the core formation process. In order to be able to be used, the sum of the infusion rate and the aging time should be less than 40 minutes.

The monomer having high polarity used in the formation of the core may be prepared by using a monomer having a molecular structure similar to that used in the seed forming process to prevent inversion with the seed upon polymerization on the surface of the hydrophilic seed. It is preferable to use methyl acrylate or methyl methacrylate as added in order to facilitate polymerization to the monomer radical generated in the seed process.

The hydrophobic monomer in the core forming step is added to facilitate polymerization with the hydrophobic shell layer and polymerization with the monomer used in the seed forming process. Styrene, vinyltoluene, α-methylstyrene, and butyl acrylate Alkyl acrylates such as isobutyl acrylate, 2-ethylhexyl acrylate, isobutyl methacrylate, lauryl methacrylate, 2-ethylhexyl methacrylate, etc. Butyl acrylate, 2-ethylhexyl acrylate and styrene are particularly preferred.

In addition, the monomer having two or more double bonds in the core forming step is added to prevent the destruction of the particle structure during expansion due to swelling of the seed portion, ethylene glycol dimethacrylate, trimetholpropane triacrylate, 1,6-hexanediol diacrylate and tripropylene glycol diacrylate may be used, and emulsifiers include phosphate compounds, sodium dodecylbenzenesulfonate, sodium laurylsulfonate, etc. If less than 3 parts by weight based on the total amount of the monomer used, the phenomenon of hollow breakage occurs when swelling, and when using more than 10 parts by weight of the emulsion caused by the generation of superpolymers Since it is made, it is preferable to add it within the said range.

The reaction process in the core forming step is easier to control the concentration of the emulsifier than the monomer dropping method, and forms a pre-em, which is a mixed solution of the monomer, the emulsifier and the water, in order to maintain the particle size from 60 minutes to 80 minutes. Inject for minutes, then aged at 60-90 ° C. for 30-50 minutes.

Hydrophobic monomers having a double bond used for shell formation include alkyl acrylates such as styrene, vinyltoluene, α-methylstyrene, butyl acrylate, isobutyl acrylate, 2-ethylhexyl acrylate, and isobutyl methacrylate. Alkyl methacrylates, such as lauryl methacrylate and ethyl methacrylate, are used, and monomers having two or more double bonds are used to minimize the destruction of the shape of particles even when the water contained in the carboxyl group is released during swelling. Ethylene glycol dimethacrylate, trimetholpropane triacrylate, 1,6-hexanediol diacrylate, tripropylene glycol diacrylate may be used, and when used in an amount of 10 parts by weight or more, no hollow formation is achieved. There is a problem that a large amount of defective particles occur.

The emulsifier is a phosphate compound, sodium dodecylbenzenesulfonate, sodium laurylsulfonate, etc., which are the same emulsifiers as used in the former, and the reaction step in the shell forming step is a mixed solution of monomers, emulsifiers and water in the same manner as the core forming step The pre-form is formed and injected over 50 to 80 minutes, and aged at 60 to 90 ° C. for 60 to 100 minutes to complete the reaction.

The particles having the micropores prepared by the method of the present invention as described above are spherical particles having a particle diameter of 450 nm to 550 nm to form hollows of 250 nm to 350 nm, and exhibit high encapsulation efficiency of 95% or more.

Hereinafter, the present invention will be described in more detail with reference to the following examples, but the present invention is not limited to the following examples.

<Example 1>

A 2-liter four-necked flask equipped with a condenser, a thermometer, a monomer dropping funnel, a nitrogen injection tube, and a stirrer is 804 g of ion-exchanged water, 0.5 g of polyoxyethylene phosphate ester as an emulsifier, and helps to radically form the water-soluble initiator. 2.0 g of ethylene glycol is used as a radical fractionation speed increasing agent, 2.0 g of sodium phosphate (Na ₃ PO ₄ ) is used as an inhibitor of abnormal particle generation to minimize the generation of abnormal particles during the reaction, and 3.5 g of potassium persulfate is added as a water-soluble initiator. While injecting at a rate of ㏄ / min, the stirring speed was 250 RPM and the temperature was raised to 80 ° C., and then 5.0 g of styrene and 8.0 g of acrylic acid were uniformly mixed and placed in a dropping funnel into the reactor flask for about 20 minutes. After dropping, the mixture was aged for about 10 minutes to form a seed, and then 0.5 g of polyoxyethylene phosphate ester was added to 50 g of ionized water. After dissolving, the core-forming solution, which was uniformly mixed with 70 g of methyl methacrylate, 20 g of butyl acrylate, and 1.0 g of trimetholpropane triacrylate, was injected into a uniformly formed container over about 45 minutes and aged for 60 minutes. After forming a core layer, 7.5 g of 25% ammonia water was injected at a time and left for about 30 minutes to swell the core layer, and 1.0 g of polyoxyethylene phosphate ester was dissolved in 142.5 g of ion-exchanged water. After injecting a shell forming solution prepared by uniformly mixing 500 g and 5.0 g of trimethylolpropane triacrylate over 90 minutes, the mixture was left to stand for 90 minutes to mature, and the temperature inside the reaction vessel was cooled to 40 ° C. or lower. After filtration.

The product at this time was obtained in the form of a white turbidity having a pH of 9.5, a solid content of 37.5%, a viscosity of 50 CPS, an average particle diameter of 500 nm and a hollow particle diameter of 350 nm.

<Example 2>

2 L four-necked flask equipped with condenser, thermometer, monomer dropping funnel, nitrogen injection tube and stirrer, 811 g of ion-exchanged water, 0.5 g of sodium dodecylbenzenesulfonate as emulsifier, 2.0 g of ethyl alcohol as radical fractionation rate enhancer, 2.0 g of sodium phosphate dibasic (Na ₂ HPO ₄ ) as an abnormal particle generation inhibitor and 2.0 g of ammonium persulfate as a water-soluble initiator were added and nitrogen gas was injected at a rate of 60 kW / min while the stirring rate was 250 RPM, and the temperature was raised to 80 ° C. Then, 5.0 g of butyl acrylate and 8.0 g of acrylic acid are uniformly mixed, placed in a dropping funnel, and dropwise into the reactor flask for about 30 minutes, and aged for about 10 minutes to form a seed. 0.5 g of sodium dodecylbenzenesulfonate was dissolved in 50 g of ionized water, followed by 70 g of methyl methacrylate, 20 g of butyl acrylate, and 2.0 g of ethylene glycol dimethacrylate. The uniformly mixed solution for forming a core is injected into a container with a uniformly shaped seed for about 45 minutes, and aged for 60 minutes to form a core layer. Then, 7.5g of 25% aqueous ammonia is temporarily injected and left for about 30 minutes. Swelling the core layer, and a solution for shell formation prepared by uniformly mixing 500 g of styrene monomer and 5.0 g of ethylene glycol dimethacrylate in a solution of 3.0 g of sodium dodecylbenzenesulfonate dissolved in 142.5 g of ion-exchanged water. Injected over a minute and left to mature again for 80 minutes, then cooled the temperature inside the reaction vessel below 40 ℃ and filtered.

In this case, the product was obtained in a pale white phase having a pH of 9.8, a solid content of 37.4%, a viscosity of 55 CPS, an average particle diameter of 490 nm, and a hollow particle diameter of 350 nm.

<Example 3>

In a 2-liter four-necked flask equipped with a condenser, a thermometer, a monomer dropping funnel, a nitrogen injection tube and a stirrer, 828.5 g of ion-exchanged water, 0.5 g of sodium lauryl sulfate as an emulsifier, and 2.0 g of propylene glycol as a radical fractionation rate enhancer. 2.0 g of sodium phosphate monohydrate (NaH ₂ PO ₄ ) as a particle-generating agent and 1.8 g of sodium persulfate as a water-soluble initiator were added and nitrogen gas was injected at a rate of 60 kW / min while the stirring rate was 300 RPM, and the temperature was raised to 80 ° C. Next, 7.0 g of methyl acrylate and 7.0 g of methacrylic acid are uniformly mixed, placed in a dropping funnel, and dropwise into the reactor flask for about 15 minutes, and aged for about 20 minutes to form a seed. 0.8 g of sodium lauryl sulfate was dissolved in 70 g of ionized water, followed by 60 g of methyl methacrylate, 30 g of 2-ethylhexyl acrylate, and 2.0 g of 1,6-hexanediol diacrylate. The work-mixing solution for core formation is injected into a container with a uniform seed over about 45 minutes, and aged for 60 minutes to form a core layer. Then, 8.0 g of 25% ammonia water is injected at a time and left for approximately 30 minutes. Swelling the core layer, and a solution for shell formation prepared by uniformly mixing 500 g of styrene monomer and 4.0 g of 1,6 hexanediol diacrylate in a solution of 3.0 g of sodium lauryl sulfonate dissolved in 142.5 g of ion-exchanged water. The mixture was uniformly mixed over 90 minutes, left to mature for 80 minutes, and then cooled. The temperature inside the reaction vessel was cooled to 40 ° C. or lower and filtered.

The product at this time was pH 10.8, solid content was 37.0%, the viscosity was 52 CPS, the average particle diameter was 500 nm, and the hollow particle diameter was obtained as the white turbid phase which is 350 nm.

Comparative Example 1

In the same manner as in Example 1, the compound and the addition ratio thereof were emulsified in the same manner, but in the order of the seed forming step, core forming step, shell forming step, and swelling step without using a radical fractionation rate increasing agent and an abnormal particle generation preventing agent. As a result of the preparation of the emulsion particles having a hollow, the product was obtained with a pH of 9.3, a solid content of 37.5%, a viscosity of 55 CPS, an average particle diameter of 550 nm, and a cloudy state.

Experimental Example 1

After mixing the pigments of the emulsion polymer prepared in Examples 1 to 3 and Comparative Examples above to the volume concentration of the styrene acrylic emulsion (SR0714 paint) pigment to 50%, and then concealed paper (KS M 5435 2A) was coated with a wet coating thickness of 130 μm, and the hiding rate was measured by the method specified in KS M 5435. The results are shown in Table 1.

Example 1 Example 2 Example 3 Comparative Example 1 Concealment 84 86 84 80

As can be seen from the results of Table 1, it can be seen that the particles obtained from Examples 1 to 3 exhibited a high concealment rate as compared to the particles prepared by Comparative Example 1.

Experimental Example 2

The emulsion polymer pigments prepared from Examples 1 to 3 and Comparative Example 1 were mixed with a paint prepared by the method and composition as shown in Table 2 to have a pigment concentration of 75% by volume, and a coating film After drying for 6 days at room temperature and dried in a constant temperature bath maintained at 60 ℃ for 24 hours, the concealment rate, wash resistance, 45 degrees / 0 degree diffusion reflectance, shelf life, wet coating hiding rate and the like are shown in Table 3.

Way compound Addition amount (part by weight) High speed stirring Ion exchange water 16.25 Thickener: Natrosol MC 0.3 Dispersant: Nofdidission 0,3 Wetting Agent: Coremol NP-1018 0.3 Preservative: Proxel XL-2 0.2 Defoamer: Nofco 313K 0.2 pH regulator: AMP-95 0.15 Freeze Stabilizer: Ethylene Glycol 1.0 Pigment Talc # 325 6.5 Calcium Carbonate # 325 5 Titanium dioxide 25 Let down Melting Agent: Texanol 1.8 Binder: Styrene Acrylic Latex 38 Emulsion Polymer Pigments 5 Amount 100

Example 1 Example 2 Example 3 Comparative Example 1 Viscosity (KU) 87 87 88 86 Heat storage viscosity (60 ℃ 5 days) 89 88 90 91 Concealment Dry film 0.985 0.985 0.983 0.963 Wet coating 0.960 0.961 0.960 0.949 car 0.025 0.024 0.023 0.014 Diffuse reflectance 90.87 90.88 90.88 90.85 Detergency 2000 2000 2000 1800 Low temperature coating film formation Good Good Good Good Nangas Good Good Good Good Dichroic clear clear clear clear

As confirmed from Table 3 above, the case where the emulsion polymer microparticles prepared according to Examples 1 to 3 were added was higher than that of the emulsion polymer microparticles prepared from Comparative Example 1. In the examples of the present invention, the difference is represented by 1 or 2 KU, but in the comparative example, the difference is represented by 5 KU, and in the concealment ratio of the dry coating, the examples of the present invention are 0.983 to 0.985. In the case of the present invention, the wet coating film hiding rate is 0.963, which is about 0.020, which is about 0.020. The wet coating film hiding rate is 0.960 to 0.961 in the case of the present invention, which is similar to the dry coating hiding rate of the comparative example. It can be seen that there is a difference in the high concealment rate, especially the washability In comparison example case, or about 1800 times, the embodiment of the present invention, it reaches to 2000 times was found indicating the difference to 200 also in washability.

As can be seen from the results obtained from the above examples and comparative examples, the emulsion polymer having the internal pores prepared by the present invention not only has excellent hiding power and wash resistance, but also a multistage emulsification method according to the present invention. It is a useful invention to minimize the inversion of monomers and the generation of defective particles through the polymerization, to prevent the destruction of the shell coating due to swelling and to produce fine particles having internal pores to increase the monodispersity efficiency.

Claims (6)

In the method for producing fine particles having internal pores consisting of a seed forming step, a core forming step, a swelling step and a shell forming step, an alkali metal phosphate is added to the seed forming step of the initial stage as an abnormal particle formation inhibitor. A method for producing fine particles having internal pores, characterized in that alcohol is added as a radical fractionation rate enhancer. The method for producing microparticles having internal pores according to claim 1, wherein the method for producing microparticles having internal pores performs a swelling step between the core forming step and the shell forming step. The method of claim 1 or 2, wherein the alcohol added as a radical fractionation rate enhancer of the fine particles having internal pores, characterized in that selected from primary or secondary alcohols such as ethylene glycol, propylene glycol, methyl alcohol, ethyl alcohol Manufacturing method. The preparation of the fine particles having internal pores according to claim 3, wherein the alcohol added as the radical fractionation rate increasing agent is added in a proportion of 10 parts by weight to 20 parts by weight with respect to 100 parts by weight of solids for seed formation. Way. The internal pore of claim 4, wherein the phosphate selected from alkali metal phosphates added as an abnormal particle formation inhibitor is added at a ratio of 10 parts by weight to 20 parts by weight based on 100 parts by weight of the total solid content of the seed forming monomer. Method for producing a fine particle having. The method of claim 5, wherein the manufacturing process of the fine particles having internal pores (1) 20 to 60 parts by weight and 0.01 parts by weight of a copolymerizable emulsifier containing 40 to 80 parts by weight of a hydrophobic monomer having a double bond and at least one carboxyl group and containing at least 20 times water molecules when swelled; 10 parts by weight to 20 parts by weight of sodium phosphate is added as a water-soluble initiator of less than 20 parts by weight, an abnormal particle formation inhibitor, and 10 to 20 parts by weight of alcohol based on the total monomer as the radical fractionation rate enhancer. Seed forming process of forming a seed at a temperature of 90 ℃, (2) 60 parts by weight to 70 parts by weight of a hydrophilic monomer having a double bond and 15 parts by weight to 27 parts by weight of a hydrophobic monomer having a double bond, and a double bond of the seed formed from the seed forming step PRE-EM consisting of 3 parts by weight to 10 parts by weight of monomer having two or more and 0.05 parts by weight to 0.1 parts by weight of a copolymerizable emulsifier is added at a ratio of 3: 7 based on the solid content of the seed and the core. Core forming step of polymerization by the semi-batch method at a temperature of 60 ℃ to 90 ℃, (3) neutralize the carboxyl portion of the seed to pH 8 to 10 with ammonia water at a temperature of 60 ℃ to 90 ℃ and then stirred for 20 to 30 minutes at a rate of 250 RPM at a temperature of 60 ℃ to 90 ℃ Swelling process to increase the volume of the part (4) Free of 90 to 99 parts by weight of a hydrophobic monomer having one double bond, 1 to 10 parts by weight of a hydrophobic monomer having two or more double bonds and 0.2 to 0.5 parts by weight of a copolymerizable emulsifier Shell forming step of adding and polymerizing EM (PRE-EM). Method for producing fine particles having internal pores, characterized in that consisting of.