KR0149694B1 - Emulsion polymer particle dispersion liquids having an inner air-hole - Google Patents

Abstract

The present invention relates to an emulsion polymer dispersion having internal pores and a method for preparing the same, and more particularly, to form a non-spherical form of micropores formed in the interior of particles during drying. The present invention relates to a multi-step emulsion polymerization method and a polymer particle dispersion according to the method for further maximizing its hiding efficiency by widening the light blocking area of the coating film surface using a particle agglomeration process.

Such polymer particle dispersions are used as opacifying agents in white or light aqueous coatings, paper coatings and molding compositions.

Description

Emulsified Polymer Particle Dispersion with Internal Pores and Manufacturing Method Thereof

The present invention relates to an emulsion polymer dispersion having internal pores and a method for preparing the same, and more particularly, to form a non-spherical form of micropores formed in the interior of particles during drying. The present invention relates to a multi-step emulsion polymerization method and an emulsion polymer particle dispersion according to the method for further maximizing its hiding efficiency by widening the light blocking area of the coating film surface using a particle aggregation process.

These emulsion particle dispersions are used as opacifying agents in white or light aqueous coatings, paper coatings and molding compositions.

BACKGROUND OF THE INVENTION The production of emulsion polymers having internal pores, which are used as partial substitutes for expensive titanium dioxide used as white pigments in aqueous paints, which contributes greatly to the cost savings of high quality aqueous paints, is already known. In general, there is a method of increasing hiding power by micropores in a method of using micropores in an open form and a method of using in a closed form.

A representative example of the open pores is a low-cost water-based paint, which uses an extender pigment to mix the pigment concentration of the paint to a critical pigment volume concentration or more, instead of the interface between the pigment and the resin binder. As a method of increasing the hiding power by forming a part of the interface between the air and the air, in this case, pores are large and continuously connected in the coating film, and thus the gloss, abrasion resistance, water resistance, and stain resistance of the coating film are deteriorated.

To solve this problem, polymer microparticles having a glass transition temperature of 40 ° C. or more and a particle diameter of 1.0 micron or less, for example, polystyrene emulsion polymers, are added to an aqueous paint to reduce the size of continuous pores and to add a coating agent (coalescent). The method of improving the water resistance and abrasion resistance by lowering the content of open pores in the coating film has been proposed.However, since the refractive index of the polymer fine particles is similar to the refractive index of the synthetic resin emulsion used as the binder of the aqueous paint, it has no self hiding power. There was a limit to maximizing concealment efficiency.

In order to improve the problems caused in the case of using the open pores in the coating as described above, a method for increasing the concealment efficiency by allowing the closed pores to exist inside the coating film. As a representative example, U.S. Patent No. 3,669,729 discloses a film-forming synthetic resin emulsion obtained by emulsifying an insoluble solvent in the manufacture of an aqueous coating, and when the coating is applied, the solvent evaporates to form closed pores inside the coating film. The method of increasing the hiding power has been published. According to this method, the increase of the hiding power can be expected to some extent, but the manufacturing process is complicated, the reproducibility and storage stability of the hiding power is poor, and the problem of air pollution due to the volatilization of the solvent during paint drying There was. Similarly, the method of emulsifying the insoluble solvent in the non-film-forming synthetic resin emulsion and incorporating it into the paint has been published in US Pat. No. 3,637,431, but it has not been very helpful in solving the above problems.

As a method for improving the drawbacks of the aforementioned methods, a method of increasing hiding power having reproducibility has been proposed by separately preparing polymer fine particles having micropores, that is, polymer beads, and adding them to a paint. That is, US Patent No. 3,891,577 discloses water / oil / water (w / o / w) by dispersing an emulsion of water / oil (w / o) form obtained by dispersing water in an unsaturated polyester solution dissolved in styrene monomer. After preparing a double emulsion emulsion in the form of), a method of increasing the hiding power by polymerizing the same to prepare a polymer beads having a size of 1 to 25 microns having closed pores and adding them to the paint is proposed. Since these porous beads have their own hiding power, they can play the role of pigments, but due to the fundamental disadvantage of the emulsification method by mechanical agitation used in manufacturing, the particle size cannot be lowered to less than 1 micron, which is why the titanium dioxide is used as a space agent. There is a problem of low contribution and settling during storage, and can not be used in glossy paints.

Recently, in order to compensate for the drawbacks in the above-described plastic pigment and manufacturing process, fine particles having a core-shell structure are dried and dried by a multi-stage continuous emulsion polymerization method in which an alkali swellable polymer is placed inside the particles (core). A method for producing hollow particles has been developed in which the water inside the particles is volatilized to form closed pores. In the continuous emulsion polymerization method having a core-shell structure, the composition of the monomers during the polymerization step and the glass transition temperature of the polymer formed, the type and concentration of the emulsifier, the type and concentration of the polymerization initiator, the reaction temperature, etc. affect the polymerization reaction. For example, if the core-forming polymer located inside the particle is more hydrophilic than the shell polymer forming the edge of the particle, an inverse core-shell polymer is easily formed or an abnormal structure of confetti is easily generated. In order to suppress the formation of abnormal particle structure, the reaction conditions should be appropriately adjusted to perform multistage polymerization.

According to U.S. Patent No. 4,427,836, to prepare such an emulsion polymer, a carboxylic acid group-containing hydrophilic polymer having a volume expanded twice or more upon neutralization by an aqueous solution of volatile base in the first stage of emulsion polymerization is synthesized, and then the second stage. In the present invention, a method of forming a polymer layer through which a base aqueous solution can permeate the surface of a hydrophilic core component by a thermal or redox initiated emulsion polymerization method has been proposed. This method used a mixture of at least 5% by weight or more of acid monomers and nonionic hydrophilic monomers for core formation, or a mixture of 15% or more by weight of acid monomers and common monomers. A mixture of monomers and up to 10% by weight of acid monomers was used, wherein the weight ratio of core-forming monomers to total monomers was about 1: 4 to 1: 100. The polymer forming the skin layer did not have permeability to inorganic bases at 20 ° C. and the glass transition temperature was 40 ° C. or higher so that a continuous film was not formed at room temperature regardless of the presence or absence of a coating film forming aid. In order to make the particle structure specific, multistage emulsion polymerization was carried out using a pre-emulsification monomer addition method in the presence of a minimum amount of emulsifier, in particular, a non-reactive emulsifier. It is difficult to achieve both synthetic stability and suppression of formation of new crops of secondary particles at the same time because it modulates the internal structure of the shell. In order to form concentric core-shell particle structures, shell-forming monomers are four times more than core-forming monomers. , Preferably it should be used more than 8 times, there is a problem that the wall thickness of the hollow particles becomes thicker than necessary.

In order to improve this problem, Korean Patent No. 25204 discloses a core portion formed of a monomer mixture including a monomer having a carboxylic acid group, and then effectively suppresses the formation of abnormal particles in the skin forming step and reproducibility and water resistance of the internal structure of the particles. A method of using a copolymerizable surfactant and selectively using a feed rate of a monomer, a kind of a polymerization initiator, and a reaction temperature has been proposed to obtain an emulsion polymer having excellent porosity and high closed stability. According to this method, it is possible to more easily control the formation of the abnormal particle structure to increase the encapsulation efficiency of the core portion of the outer layer, thereby obtaining a concentric core-shell particle dispersion having a relatively low proportion of shell-forming monomers. Could.

According to the conventional methods described above, although there is a difference in encapsulation efficiency, an emulsion polymer dispersion having an alkaline swelling polymer at the center of the particle and having a hydrophobic polymer surface layer could be prepared. However, these particles have only a single spherical pore in one particle, there is a limit in maximizing the area of the air layer that receives incident light and scatters to the surface when the coating film is formed by mixing a certain amount into the paint.

Therefore, an object of the present invention is to prepare a form of fine pores in the form of two to three particles attached to the method for producing an alkali swellable core / hydrophobic shell emulsion polymer that can maximize the area of the air layer and a method for producing such It is to provide an emulsion particle dispersion according to.

Cores are formed from a mixture of a monomer having a carboxylic acid group and a general monomer as in the conventional hollow particle manufacturing method, and the envelope-forming monomer mixture is itself or in a pre-emulsified state in the presence of the core particles described above. In the two-step emulsion polymerization that is added to the reactor at a constant rate and polymerized, it is most important to optimize the type and concentration of the emulsifier in consideration of the generation, synthesis stability, and storage stability of the secondary particles.

However, in the present invention, in order to prepare a form in which two to three particles are attached, the stability of the core shell or the primary shell emulsion coated with the primary shell on the core particles intentionally prepared in the first step is appropriately lowered to prevent the core particles or After the primary shell particles are agglomerated with each other, as in the prior art, a process of neutralizing and forming a final outer skin layer and the like is performed, thereby producing an emulsion polymer having a shape of 2 to 3 particles attached thereto.

The present invention also relates to a coating or impregnating composition containing 30% by weight or less of the emulsion polymer particle dispersion according to the preparation method.

In the present invention, a small amount of electrolyte is used as a flocculant in order to reduce the stability of the emulsion to an appropriate level, the amount of the flocculant is controlled to below the critical coagulant concentration.

Hereinafter, the manufacturing process of the present invention will be described in detail for each step.

1) emulsion polymerizing core particles from an acid monomer having a carboxylic acid group and a general monomer mixture;

2) agglomerating the prepared core particles into a form in which two to three particles are attached using a flocculant;

3) encapsulating the core particles with a hard coat by continuously emulsifying the envelope forming monomer in the presence of the aggregated core particles; And

4) swelling the produced core-shell polymer particles with a base at an elevated temperature to have pores therein after drying.

The core particles may be prepared in a single step in the overall process, but the preparation of the core particles in a plurality of steps including the step of preparing the seed polymer facilitates the particle size and particle distribution of the final particle, the size of the pores and the distribution thereof. Do. Therefore, the seed step, which is the first step of the polymerization process, contains or does not contain a small amount of acid monomer because its purpose is to provide nuclear particles so that the monomer mixture can be polymerized and grown on the seed particles in the core forming step. It doesn't matter. The particle size is 20-500 nanometers, preferably 30-200 nanometers.

Acid monomers used here are commonly used in core and shell stages, and include acrylic acid, methacrylic acid, itaconic acid, crotonic acid, fumaric acid, aconitic acid, maleic acid or anhydrides thereof, monomethyl maleate, monomethyl fumarate, It is selected from acid compounds having an unsaturated double bond such as monomethyl itaconate, and the amount of use is preferably 0-10% by weight, preferably 0-5% by weight based on the monomer mixture.

In addition, the ethylenically unsaturated monomer is copolymerized with at least one selected from styrene, vinyltoluene, ethylene, butadiene, vinyl acetate, vinyl chloride, vinylidene chloride, acrylonitrile, alkyl (meth) acrylate.

As an emulsifier, 0.1-2.0 weight% of monomer weights are used individually or in combination with a nonionic and anionic emulsifier. Representative nonionic emulsifiers include octylphenoxyethylpolyethoxyethanol and nonylphenoxyethylpolyethoxyethanol. Representative anionic emulsifiers include sodium lauryl sulfate, sodium dodecylbenzenesulfonate, and sodium octylphenoxyethyl. Sodium salts of polyethylsulfate and sulfosuccinate derivatives.

The water-soluble radical initiator to be added to the reaction mixture is generally used alone or pyrolysis initiators such as alkali metal persulfate, ammonium persulfate, hydrogen peroxide, tertiary butyl hydroperoxide or the like and alkali metal sulfite, hyposulfite In the form of a mixture with a reducing agent such as sodium formaldehyde sulfoxylate, the redox initiator may be used, the amount of the redox initiator being in the range of 0.1-2.0% by weight based on the monomer, and the reaction temperature is 30- Set to 300 minutes. For example, when ammonium persulfate, potassium persulfate or sodium persulfate is used alone as a polymerization initiator, it is preferable to maintain the reaction temperature at 60 ° C to 90 ° C, and sodium sulfite or sodium formaldehyde sulfoxylate and When the same reducing agent is used in combination with the oxidizing agent, it is appropriate to adjust the reaction temperature to 30 ° C to 60 ° C.

These initiators and the criteria for setting the reaction temperature are common to the general emulsion polymerization, and are also applied to subsequent core and shell manufacturing steps.

When the seed is formed through the seed forming step, a secondary synthesis step using a hydrophilic monomer, that is, a core synthesis step is performed. In the core synthesis step, 15-60% by weight of acid monomer, 39-85% by weight of common ethylenically unsaturated monomer, and 0-2% by weight of crosslinkable monomer are contained. Representative types of acid monomers and general ethylene unsaturated monomers are as described above. Examples of the crosslinkable monomer include ethylene glycol di (meth) acrylate, 1,3-butanediol di (meth) acrylate, diethylene glycol di (meth) acrylate, trimethylpropane trimethacrylate, divinylbenzene, Allyl (meth) acrylate, tripropylene glycol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, and the like can be used. The amount of this monomer mixture should be in the range of 2-40% by weight, based on the monomer mixture used in the whole process, with or without the presence of a side step, and in the seed step, about 4-20 times that of the seed forming monomer. It is good to be. When the monomer mixture is added to the reaction system, it should be maintained within the selected speed range in consideration of the stability of the synthesis, the control of exotherm and the particle growth behavior, but usually in the range of 30 minutes to 3 hours.

The selection of emulsifier, initiator and reaction temperature in the core formation step is the same as in the seed formation step and is designed such that the particle size of the synthetic polymer is 0.1-0.5 micron in the non-swelled state below pH 5, regardless of the presence of the seed step. Should be.

The core polymer aqueous solution is stored in a semi-finished state as it is, and is introduced in a shell forming step, and prepared in the form of a plurality of core particles attached through a flocculation process, which is a feature of the present invention, immediately before the shell forming reaction. In particular, since the flocculation effect continues over time, it cannot be used while storing the polymer aqueous dispersion which has undergone the flocculation process for a long time. Therefore, as in the present invention, in a process in which the shell forming process with the core-first shell-secondary shell consists of a plurality of stages, the coagulation process after the first shell formation is performed in terms of continuity of the process or in a specific form intended by the present invention. It is more advantageous in terms of pore formation. In other words, when the coagulation process is followed by the coagulation process, an elliptical single pore having a larger diameter adhered to one particle is formed, and when the coagulation process is manufactured after the coagulation process after the primary shell formation, Like a peanut, two separate pores are formed in one adherent particle, or pores with a close surface are formed while preserving a spherical shape.

Although the temperature in the flocculation process is wide, it is preferable to add the flocculant solution at room temperature and to raise the reaction temperature of the shell forming step with stirring. The electrolyte flocculant used herein is one or more selected from sodium chloride, potassium chloride, calcium chloride, sodium sulfate, magnesium sulfate, barium perchlorate, and is introduced into the reactor as a 10% solution. The amount used at this time should be used in the range below the critical aggregation concentration which does not cause excessive coagulation effect.

The monomer mixture used in the shell forming step contains at least one of the general ethylenically unsaturated monomers mentioned in the core forming step, and it is preferable to use an acid monomer of 0-5% by weight. Selection criteria for general ethylenically unsaturated monomers should take into account glass transition temperature and toughness index.

The emulsifier and polymerization initiator used in the shell forming step are selected from those generally used in the emulsion polymerization. Those illustrated in the core forming step are used, and the amount of the emulsifier used must be maintained to satisfy the synthetic stability and the grain growth behavior at the same time. Usually 0.01 to 2.0% by weight of the monomer is suitable.

In the process consisting of core-primary shell-secondary shell as in the present invention, it is preferable to proceed the neutralization process, which is an essential process of pore formation, after the final skin formation step or in the middle of the plurality of avoidance formation steps, that is, after primary shell formation. The neutralization temperature should be selected in consideration of the glass transition temperature of the primary shell to maximize the swelling of the core-shell polymer accompanying neutralization. In general, the range of 50-100 ° C. is suitable, and it is preferable to proceed continuously without changing the polymerization temperature in the whole process, so the correlation with the neutralization temperature should be considered. In this continuous multistage emulsion polymerization, the main role of the primary shell is to control the sharp center of gravity due to the neutralization of the core particles and to suppress the degradation of the encapsulation efficiency of the secondary shell by hydrophilicity due to ionization of the core particle surface layer. The weight ratio is suitably in the range of 1: 1 to 1:50, more preferably in the range of 1: 4 to 1:10 for core particles. On the other hand, since the primary role of the secondary shell is to prevent particle dent in the drying process, it is necessary to use a monomer mixture having appropriate toughness and maintain an appropriate shell thickness. Therefore, the weight ratio is suitably in the range of 1: 1 to 1: 100, preferably 1: 1 to 1:10, for the particles up to the primary shell. Moreover, it is good to use 0.01 (confirmation required)-5 weight%, More preferably, 0.05-2.0 weight% of a crosslinkable monomer.

The base used in the neutralization process is selected from volatile bases of ammonia and tertiary amines or from fixed bases of alkali metal hydroxides such as sodium hydroxide and potassium hydroxide, and the amount of the base used is 7- pH of the emulsion dispersion after neutralization. It is good to be 12. In addition, a small amount of organic solvent may be used during or before neutralization in order to facilitate the penetration of the base into the particles, which has a higher affinity to core particles than shell polymers, and has a limited solubility in water. Specific examples thereof include alcohols such as ethanol, propanol, pentanol, hexanol, texanol, or the like alone or in mixture, and the amount thereof is preferably 2 to 30% by weight based on the primary shell.

The particle size of the final emulsion polymer prepared by the present invention is suitable for 0.2 to 10 microns, preferably 0.2 to 5.0 microns and the diameter of the internal pores after drying is preferably 0.1 to 5.0 microns is preferably 0.15 to 2.0 microns. This is a case of measuring particles separated from peanuts or triangles, and the specific shape of particle distribution of the present invention is that the number average number of single particles constituting aggregated particles ranges from 1.2 to 10, more preferably. Preferably in the range of 1.5 to 5.

Emulsifying polymers having a specific form of pores prepared by the present invention and conventional spherical single pore emulsions are blended in an acrylic latex forming a continuous coating film at room temperature so as to have a weight fraction of 30% by weight or less for each hiding power. As a result of comparison, the emulsion polymer according to the present invention was superior to the conventional products. This is because the emulsion polymer according to the present invention is arranged in the form of pores lying sideways on the surface of the coating film, so that the scattering air layer for incident light is formed more broadly, and when the same amount is added, the concealment effect is further enhanced.

The following examples are intended to embody the invention, which does not limit the scope of the invention and unless otherwise indicated, percentages and parts refer to weight values.

Example 1

Into a 1 liter four-necked flask equipped with a thermometer, a nitrogen inlet tube, a dropping channel, a stirrer and a reflux condenser, 400 g of ion-exchanged water, 0.5 g of sodium bicarbonate, and 1.5 g of sodium dodecylbenzene sulfonate were added, followed by blowing nitrogen. Heat to 80 ° C while adding. When the temperature reaches 80 ° C, an aqueous solution of 0.60 g of sodium persulfate dissolved in 30 g of ion-exchanged water is added to the flask. While maintaining the reaction temperature at 80 ° C., an emulsified mixture consisting of 40 g of ion-exchanged water, 0.05 g of sodium dodecylbenzenesulfonate, 68 g of butyl acrylate, 50 g of methyl methacrylate, and 1.4 g of methacrylic acid was heated for about 60 minutes. The mixture was dropped into the flask uniformly, aged at the same temperature for 60 minutes, and then cooled to prepare a seed polymer.

The average particle diameter at this time was 57 nm as a result of a light scattering measuring device, and the solid content was 19.7%.

Into a 1 liter four-necked flask equipped with the same apparatus as the one prepared for the seed, 505 g of ion-exchanged water and 75 g of the seed polymer were heated and heated to 80 ° C. Then, an aqueous solution of 1.0 g of sodium persulfate dissolved in 25 g of ion-exchanged water was added. . While maintaining the reaction temperature at 80 ° C, 57.5 g of ion-exchanged water, 0.25 g of sodium dodecylbenzenesulfonate, 22.5 g of butyl acrylate, 100 g of methyl methacrylate, 52.5 g of methacrylic acid, and 0.75 g of ethylene glycol dimethacrylate The composed emulsion mixture is slowly added dropwise over about 120 minutes, then aged at the same temperature for 60 minutes and then cooled to prepare a core polymer. The average particle diameter of the core polymer measured by the light scattering measuring instrument was 152 nm, and solid content was 22.9%.

632 g of ion-exchanged water and 160 g of core polymer were added to a 2-liter four-necked flask, and 88 g of a 0.5% aqueous calcium chloride solution was slowly added dropwise over 20 minutes while stirring at about 120 rpm, followed by heating to 77 ° C. Then, an aqueous solution of 0.87 g of sodium persulfate dissolved in 25 g of ion-exchanged water was added thereto, 220 g of ion-exchanged water, 3.5 g of sodium dodecylbenzenesulfonate, 2.2 g of Triton X-100 (from Rohm and Haas), 20 g of styrene, and methyl methacrylate. A mixture of 83 g and 42 g of butyl acrylate was slowly added dropwise over 90 minutes, and then aged at the same temperature for 60 minutes. Then, the pH was adjusted to 10-11 by adding ammonia water and maintained at the same temperature for 60 minutes. do. Subsequently, while maintaining the same temperature, an aqueous solution of 1.74 g of sodium persulfate dissolved in 20 g of ion-exchanged water was added thereto, and a monomer mixture consisting of 67 g of butyl acrylate, 42 g of methyl methacrylate, and 181 g of styrene was slowly added dropwise over about 180 minutes. Proceed. When the dropping of the monomer mixture is completed, it is aged for 60 minutes at the same temperature and then cooled. At 55 ° C., 0.4 g of sodium formaldehyde sulfoxide sulfate and 0.3 cc of tertiary butyl hydroperoxide in a 70% aqueous solution are added, followed by slow cooling to complete the polymerization.

The final emulsion polymer was observed under a transmission electron microscope. The size of the single particles was about 450 nm in diameter, and the distribution of the attached particles was as follows. About 10% of single particles, about 60% of two particles, about 25% of three particles, and about 5% of four or more particles. Moreover, the average shell thickness was about 75 nm and solid content was 29.9%.

Example 2

A core polymer was prepared in the same manufacturing process as in Example 1, and then 632 g of ion-exchanged water and 160 g of core polymer were placed in a 2-liter four-necked flask, heated to 77 ° C., and heated. Then, an aqueous solution of 0.87 g of sodium persulfate dissolved in 25 g of ion-exchanged water was added thereto, 189 g of ion-exchanged water, 3.5 g of sodium dodecylbenzenesulfonate, 2.2 g of Triton X-100 (Rom and Haas), 20 g of styrene, and methyl methacrylate. 83 g of butyl acrylate 42 g of an emulsified mixture was slowly added dropwise over 90 minutes, and then aged at the same temperature for 60 minutes, 119 g of calcium chloride 0.5% aqueous solution was slowly added dropwise over 30 minutes and maintained for 10 minutes. The pH is adjusted to near 10-11 by the addition of ammonia water and again maintained at the same temperature for 60 minutes. Subsequently, while maintaining the same temperature, an aqueous solution in which 1.74 g of sodium persulfate was dissolved in 20 g of ion-exchanged water was added thereto, and a monomer mixture consisting of 67 g of butyl acrylate, 42 g of methyl methacrylate, and 181 g of styrene was slowly added dropwise over about 180 minutes. Proceed.

When the dropping of the monomer mixture is completed, it is aged for 60 minutes at the same temperature and then cooled. At 55 ° C., 0.4 g of sodium formaldehyde sulfoxylate and 0.3 cc of tertiary butylhydroperoxide in a 70% aqueous solution were added, followed by slow cooling to complete the polymerization.

The final emulsion polymer was observed under a transmission electron microscope, and the size and distribution of particles of a single particle were almost the same as in Example 1. In addition, the average shell thickness was about 75 nm and the solid content was 29.9%.

Example 3

It was prepared in the same manufacturing process as in Example 2, but was prepared using the flocculant in the flocculation process at the same concentration using a barium perchlorate as a 0.5% aqueous solution. In this case, the particle size distribution of the final emulsion polymer was 10% for single particles, 45% for two particles, 35% for three particles, and 10% for four or more particles.

Example 4

Prepared in the same manufacturing process as in Example 2, but the retention time after administration of the coagulant in the coagulation process is extended three times to about 30 minutes and then proceeded to a final emulsion polymer. The particle distribution of the final emulsion was 5% single particles, 35% two particles, 45% three particles, 15% four or more particles.

Example 5

It was prepared by the same production process as in Example 2, but prepared by doubling the amount of flocculant used in the flocculation process. The particle distribution of the final emulsion was 5% single particles, 25% two particles, 45% three particles, and 25% four or more particles.

[Comparative Example]

In order to compare with Example 1 was prepared in the same manufacturing process as in Example 1, except that the final emulsion polymer was prepared without proceeding the aggregation process. At this time, the final emulsion polymer was observed by transmission electron microscopy, and no particles were attached. The average particle diameter was about 450 nm and the shell thickness was about 75 nm.

[Application Example]

In order to compare the hiding efficiency of the emulsion polymers prepared in Examples 1-5 and Comparative Examples, each of the compositions prepared by mixing each of the compositions prepared with a film-forming latex (H5250, Koryo Chemicals) by 30% by weight of solids Covering force test paper was applied using a bird applicator with a wet film thickness of 3mil, then dried at 25 ℃, 55% relative humidity for more than 24 hours to prepare a test piece for hiding power.

The spectrophotometer was used to measure the hiding power of the Kubelkamunk scattering coefficient (S) by the method described in Australian OCCA Proceedings and News, Nov., 1982, p.4-13 by K.Nyi. The test results are posted in Table 1 below.

Claims (7)

A method for producing an emulsion polymer particle dispersion, which is prepared by the following multistage continuous emulsion polymerization method. 1) emulsion polymerizing core particles from an acid monomer having a carboxylic acid group and a general monomer mixture; 2) Aggregate the prepared core particles by treating at least one coagulant selected from sodium chloride, potassium chloride, calcium chloride, sodium sulfate, magnesium sulfate and barium perchlorate to below the critical coagulant concentration to aggregate them in the form of 2 to 3 particles. step; 3) encapsulating the core particles with a hard coat by continuously emulsifying the envelope forming monomer in the presence of the aggregated core particles; And 4) swelling the produced core-shell polymer particles with a base at an elevated temperature to have pores therein after drying. The method of claim 1, wherein the core forming step consists of a single step or a method for producing an emulsion polymer particle dispersion, characterized in that it consists of a plurality of steps, including a seed production step. The method of claim 1, wherein the shell forming step comprises a single or a plurality of steps. The method of claim 1, wherein the flocculation process is carried out after the primary skin forming step when the skin forming process is made of a plurality of steps. The method of claim 1, wherein the neutralizing swelling process is performed after the final skin forming step or in the middle of the plurality of skin forming steps. The method according to claim 1, wherein the weight ratio of the shell component to the core component is 1: 1 to 1:50. The method of claim 1, wherein the size of the final emulsion particles are 0.2 to 10.0 microns.