JP2023181691A - Resin particle - Google Patents

Abstract

To provide a resin particle that has superior light diffusibility, a high specific gravity, and a reduced tendency to float even in low-viscosity liquid.SOLUTION: A resin particle comprises a resin polymerized from one or more polymerizable monomers comprising a polymerizable unsaturated bond, wherein the particle comprise one or more internal pores, and at least one of the one or more pores comprises a particle therein.SELECTED DRAWING: Figure 1

Description

The present invention relates to resin particles.

Spherical resin particles are used as a light reflecting material in paints, cosmetics, etc., and as a light diffusing material in light diffusing plates for liquid crystal backlights, etc. Among these, hollow resin particles having pores inside the particles have better light diffusing properties than solid resin particles having no pores, and are preferably used for the above-mentioned applications.

The following methods are known as methods for producing hollow resin particles.
- A method in which an oil-based surfactant and a water-soluble surfactant are used together in suspension polymerization, and the polymerization is completed while water is incorporated into the monomer droplets before polymerization (Patent Document 1).
- A method using a special polymeric surfactant (Patent Document 2).

Japanese Unexamined Patent Publication No. 59-193901 Japanese Patent Application Publication No. 2007-238792

However, because existing hollow resin particles are hollow, they have a low specific gravity, and when dispersed in a low-viscosity liquid, they tend to float due to the difference in specific gravity.
An object of the present invention is to provide resin particles that have excellent light diffusivity, have a high specific gravity, and are difficult to float even in a low-viscosity liquid.

The present invention has the following aspects.
[1] Consisting of a resin polymerized with one or more polymerizable monomers having a polymerizable unsaturated bond,
A resin particle having one or more pores therein, the particle being present in at least one of the one or more pores.
[2] The one or more polymerizable monomers include a (meth)acrylate monomer, and the ratio of the (meth)acrylate monomer to the total mass of the one or more polymerizable monomers is 50. The resin particles according to [1] above, which are at least % by mass.
[3] The resin particles according to [1] or [2] above, having a specific gravity of 0.8 g/cm ³ or more.
[4] The resin particles according to any one of [1] to [3] above, having an average particle diameter of 1.0 to 200 μm.
[5] The resin particles according to any one of [1] to [4] above, which have a haze of 50 to 90% as measured by the following measuring method.
Measurement method: 2.0 g of the resin particles and 45 g of a 40% by mass toluene solution of a resin having the same refractive index as the resin constituting the resin particles are placed in a glass bottle, mixed for 30 minutes with a shaker, and the obtained The resulting dispersion was applied to a 1 mm thick glass plate using an applicator with a gap of 150 μm, dried at 100° C. for 10 minutes, and the haze of the resulting test piece was measured.

According to the present invention, it is possible to provide resin particles that have excellent light diffusivity, have a high specific gravity, and are difficult to float even in a low-viscosity liquid.

FIG. 2 is a schematic cross-sectional view of resin particles according to one embodiment. 1 is an electron micrograph of the surface of resin particles obtained in Example 1. 1 is an electron micrograph of a cross section of resin particles obtained in Example 1.

The present invention will be described below based on preferred embodiments.
In the present invention, "(meth)acrylate" is a general term for methacrylate and acrylate. "(Meth)acryloyl" is a general term for methacryloyl and acryloyl. "(Meth)acrylic acid" is a general term for methacrylic acid and acrylic acid. "(Meth)acrylonitrile" is a general term for methacrylonitrile and acrylonitrile. "(Meth)acrylamide" is a general term for methacrylamide and acrylamide.

FIG. 1 is a schematic cross-sectional view of a resin particle 1 according to an embodiment of the present invention.
As shown in FIG. 1, one or more holes 3 are provided inside the resin particle 1. Particles 5 are also present in at least one of the one or more pores 3.
The resin particles 1, including the particles 5, are made of resin in which one or more types of polymerizable monomers are polymerized. The resin will be explained in detail later.

The shape of each of the resin particles 1 and particles 5 is not particularly limited, and may be, for example, a perfect sphere, an ellipsoid, an irregular shape, or the like.
The particles 5 may or may not be fixed to the walls of the holes 3. The number of particles 5 existing in one hole 3 may be one or two or more.
The pores 3 may or may not communicate with the outside of the resin particle 1.

Although FIG. 1 shows an example in which a plurality of holes 3 are provided inside the resin particle 1, the number of holes 3 may be one.
From the viewpoint of light diffusivity, the number of holes 3 is preferably two or more, more preferably five or more, and even more preferably ten or more.
The number of pores 3 is measured by observing the cross section of the resin particle with an electron microscope. Note that holes 3 that exist separately in the cross section even if they communicate with each other in a portion other than the cross section observed with an electron microscope are counted as different holes 3.

When preparing a test piece for cross-sectional observation of the resin particles 1, some particles 5 fall out from the holes 3, so it is difficult to calculate an accurate value of the proportion of particles 5 contained inside the resin particles 1. Have difficulty. On the other hand, the specific gravity of the resin particles 1 is considered to be sufficient to infer the presence of the particles 5 in the pores 3. The closer the value obtained by dividing the specific gravity of resin particle 1 by the specific gravity of the resin constituting resin particle 1 (specific gravity of resin particle 1/specific gravity of resin constituting resin particle 1) to 1, the more it is contained inside resin particle 1. It is considered that the existence ratio of particles 5 is high.
The value of specific gravity of resin particles 1/specific gravity of the resin constituting resin particles 1 is preferably 0.5 or more, more preferably 0.7 or more, from the viewpoint of specific gravity and strength. The value of specific gravity of resin particles 1/specific gravity of resin constituting resin particles 1 is typically less than 1, and preferably 0.95 or less from the viewpoint of light diffusivity.

The diameter of the pores 3 in the resin particles 1 is not particularly limited, but from the viewpoint of light diffusion, it is preferably 5 to 40% of the particle diameter of the resin particles 1.
The diameter of the pores 3 and the particle size of the resin particles 1 are measured by observing a cross section of the resin particles with an electron microscope.
When a plurality of holes 3 are provided inside the resin particle 1, the diameter of the hole 3 is the diameter of each of the plurality of holes 3. Pores whose diameter is less than 5% or more than 40% of the particle diameter of the resin particles 1 may coexist.

Since one or more holes 3 are provided inside the resin particles 1, the specific gravity of the resin particles 1 is lower than the specific gravity of the resin constituting the resin particles 1. The specific gravity of the resin is generally within the range of 0.9 to 1.2 g/cm ³ .
On the other hand, particles having holes inside the particles, generally called hollow particles, have voids inside, and therefore have an extremely lower specific gravity than normal resins.
In the resin particles 1, since the particles 5 are present in at least one pore 3, the specific gravity of the resin particles 1 is higher than when the particles 5 are not present. The specific gravity of the resin particles 1 is preferably 0.8 g/cm ³ or more, more preferably 0.9 g/cm ³ or more, from the viewpoint of dispersion stability of the resin particles 1 in a low-viscosity liquid.

The average particle diameter of the resin particles 1 is preferably 1.0 to 200 μm from the viewpoint of light diffusivity.
The average particle diameter of the resin particles 1 is a volume-based value measured by a laser diffraction particle size distribution analyzer.

The haze of the resin particles 1 measured by the following measuring method is preferably 50 to 90%, more preferably 70 to 90%. If the haze is 50% or more, the light diffusivity is better, and if the haze is 90% or less, the light transmittance is better.
Measurement method: 2.0 g of resin particles and 45 g of a 40% by mass toluene solution of a resin having the same refractive index as the resin constituting the resin particles were placed in a glass bottle and mixed for 30 minutes with a shaker. The dispersion is applied to a 1 mm thick glass plate using an applicator with a gap of 150 μm, dried at 100° C. for 10 minutes, and the haze of the resulting test piece is measured.
Haze is measured using a haze meter.

<Resin>
The resin constituting the resin particles 1 is one in which one or more types of polymerizable monomers are polymerized.
The polymerizable monomer has a polymerizable unsaturated bond. Examples of the polymerizable unsaturated bond include a polymerizable carbon-carbon double bond and a polymerizable carbon-carbon triple bond.
Examples of the polymerizable monomer include (meth)acrylate monomers, aromatic vinyl monomers, and other polymerizable monomers.

Examples of the (meth)acrylate monomer include monofunctional (meth)acrylates having one (meth)acryloyl group and polyfunctional (meth)acrylates having two or more (meth)acryloyl groups.

Examples of monofunctional (meth)acrylates include alkyl (meth)acrylates, alkoxyalkyl (meth)acrylates, (meth)acrylates having an alicyclic structure, and (meth)acrylates having a functional group.

Alkyl (meth)acrylates include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate, and heptyl (meth)acrylate. , octyl (meth)acrylate, and the like.
Examples of alkoxyalkyl (meth)acrylates include 2-methoxyethyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, 2-(n-propoxy)ethyl (meth)acrylate, and 2-(n-butoxy)ethyl (meth)acrylate. ) acrylate, 3-methoxypropyl (meth)acrylate, 3-ethoxypropyl (meth)acrylate, 2-(n-propoxy)propyl (meth)acrylate, 2-(n-butoxy)propyl (meth)acrylate, etc. .
Examples of the (meth)acrylate having an alicyclic structure include cyclohexyl (meth)acrylate, dicyclopentanyl (meth)acrylate, and isobornyl (meth)acrylate.

In the (meth)acrylate having a functional group, examples of the functional group include an amino group, a hydroxy group, a carboxy group, a polyoxyalkylene group, and an epoxy group.
Examples of the (meth)acrylate having an amino group include dimethylaminoethyl (meth)acrylate, diethylaminoethyl (meth)acrylate, and the like.
Examples of the (meth)acrylate having a hydroxy group include hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, hydroxybutyl (meth)acrylate, and glycerin mono(meth)acrylate.
Examples of the (meth)acrylate having a polyoxyalkylene group include polyethylene glycol mono(meth)acrylate, polypropylene glycol mono(meth)acrylate, polyethylene glycol-polypropylene glycol mono(meth)acrylate, and the like.
Examples of the (meth)acrylate having an epoxy group include glycidyl (meth)acrylate.

Examples of polyfunctional (meth)acrylates include (poly)ethylene glycol di(meth)acrylates having 1 to 9 moles of ethylene oxide (EO) added, and alkylene glycol di(meth)acrylates having alkylene groups having 4 to 9 carbon atoms. , trimethylolpropane tri(meth)acrylate, and the like.

Examples of the aromatic vinyl monomer include styrene monomers and divinylbenzene, with styrene monomers being preferred.
Examples of the styrenic monomer include styrene, α-methylstyrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, o-chlorostyrene, m-chlorostyrene, p-chlorostyrene, and the like.

Examples of other polymerizable monomers include (meth)acrylic acid, polymerizable monomers having an amide group, vinyl acetate, vinyl propionate, vinyl chloride, and (meth)acrylonitrile.
Examples of the polymerizable monomer having an amide group include (meth)acrylamide, hydroxyethylacrylamide, dimethylacrylamide, diethylacrylamide, isopropylacrylamide, dimethylaminopropylacrylamide, and the like.
These polymerizable monomers may be used alone or in combination of two or more.

The polymerizable monomer preferably contains a (meth)acrylate monomer because it is easy to stably obtain the desired structure.
The ratio of the (meth)acrylate monomer to the total mass of polymerizable monomers is preferably 50% by mass or more, more preferably 70% by mass or more, and may be 100% by mass.

The (meth)acrylate monomer preferably contains a monofunctional (meth)acrylate from the viewpoint of polymerization stability.
As the (meth)acrylate monomer, a monofunctional (meth)acrylate and a polyfunctional (meth)acrylate may be used in combination. By using polyfunctional (meth)acrylate, a crosslinked structure is introduced into the resin, improving solvent resistance, heat resistance, etc.
A (meth)acrylate monomer and an aromatic vinyl monomer may be used in combination. By using an aromatic vinyl monomer, the compatibility with the resin or solvent serving as the dispersion medium can be adjusted, and for example, the dispersibility in the medium can be improved.

Although the ratio of monofunctional (meth)acrylate, polyfunctional (meth)acrylate, and aromatic vinyl monomer in the polymerizable monomer is not particularly limited, for example, the ratio of monofunctional (meth)acrylate to the total mass of the polymerizable monomer is The content may be 20 to 100% by weight of (meth)acrylate, 0 to 30% by weight of polyfunctional (meth)acrylate, and 0 to 50% by weight of aromatic vinyl monomer.

<Method for manufacturing resin particles>
The resin particles 1 can be obtained, for example, by adjusting the suspension conditions in a method in which one or more polymerizable monomers are dispersed in an aqueous medium, suspended, and polymerized.
For example, resin particles 1 can be manufactured by a manufacturing method including steps 1 to 3 below.

(Step 1)
a polymerization initiator, one or more polymerizable monomers, an aqueous medium (a first aqueous medium), and a first surfactant; A W/O type (water in oil) dispersion liquid (first mixed liquid) in which the medium is the dispersed phase is prepared.
Specifically, a mixed solution of a polymerization initiator, one or more polymerizable monomers, and a first surfactant is prepared, and this mixed solution is stirred using a stirrer such as a homomixer. The first mixed liquid is prepared by dispersing the first aqueous medium in the stirred mixed liquid.
The aqueous medium, polymerization initiator, and first surfactant will be explained in detail later.
If necessary, additives such as a chain transfer agent may be included in the first mixed liquid.

(Step 2)
After step 1, adding a mixture (second mixture) of a second surfactant or dispersant and an aqueous medium (second aqueous medium) to the first mixture being stirred with a stirrer. In this way, the continuous phase becomes an aqueous medium and the dispersed phase becomes one or more polymerizable monomers (dispersed phase inversion), resulting in a W/O/W (water in oil in water) suspension. Prepare a suspension.
The aqueous medium, second surfactant, and dispersant will be explained in detail later.
In step 2, when adding the second mixed liquid to the first mixed liquid, the first mixed liquid is stirred using a stirrer equipped with rotary blades, and the circumferential speed at the tip of the rotary blade (stirring circumferential speed) is 4. This is done so that the speed is 3 to 17.6 m/s. By setting the stirring circumferential speed within the above range, it is easy to obtain the desired structure. The peripheral stirring speed is preferably 5.1 to 16.9 m/s, more preferably 5.9 to 16.1 m/s.
Examples of the stirrer equipped with rotary blades include a high-speed shear type disperser.

(Step 3)
After step 2, the suspension is polymerized. As a result, resin particles 1 are generated, and a dispersion in which the resin particles 1 are dispersed in an aqueous medium is obtained.
After Step 3, the resin particles 1 may be collected from the dispersion, if necessary. The recovery method is not particularly limited, and any known method can be used.

In addition, in this manufacturing method, when adding the aqueous medium in two steps, in order to easily understand which step the aqueous medium is added, "first aqueous medium", It is called the "second aqueous medium." The first aqueous medium and the second aqueous medium may be the same or different. The same applies to surfactants.

(aqueous medium)
The "aqueous medium" is a medium containing water, and may be composed only of water, or may further contain an organic solvent within a range that does not impair the purpose and effects of the present invention.
As the water, known water such as ion exchange water can be used.
The organic solvent may be one that is miscible with water, and examples thereof include alcohols such as methanol, ethanol, and isopropyl alcohol.
The proportion of water to the total mass of the aqueous medium is not particularly limited, but may be 50% by mass or more, 70% by mass or more, 90% by mass or more, and 100% by mass. Good too.

(Polymerization initiator)
As the polymerization initiator, known polymerization initiators can be used, such as peroxide-based initiators such as benzoyl peroxide and lauroyl peroxide, and 2,2'-azobis(2-methylbutyroyl). Examples include oil-soluble azo polymerization initiators such as nitrile) and 2,2'-azobis(isobutyronitrile).

The amount of the polymerization initiator used may be, for example, 0.05 to 3.0 parts by mass, and 0.1 to 2.0 parts by mass, based on a total of 100 parts by mass of one or more polymerizable monomers. It is preferably 0.2 to 1.5 parts by weight, more preferably 0.2 to 1.5 parts by weight. When the amount of the polymerization initiator used is 0.05 parts by mass or more, the proportion of unreacted polymerizable monomers during polymerization can be reduced. On the other hand, if the amount of the polymerization initiator used is 3.0 parts by mass or less, it is possible to suppress the decomposition products of the polymerization initiator from remaining as impurities.

(First surfactant)
The first surfactant includes surfactant A represented by the following formula (1). When the first surfactant contains surfactant A, the desired structure can be easily obtained. The reason for this is that when the polymerizable monomer is suspended at the above-mentioned predetermined peripheral stirring speed in the presence of surfactant A, fine particles of the polymerizable monomer are formed in the droplets of the polymerizable monomer. It is conceivable that water droplets containing liquid droplets may be taken in.
T ¹ O-(RO) _n (EO) _m -T ² ... (1)

In formula (1), T ¹ is a hydrogen atom, an alkyl group having 1 to 18 carbon atoms, or an alkenyl group having 2 to 18 carbon atoms, and T ² is a hydrogen atom, a sulfonic acid group, a sulfonic acid group, or a carboxylic acid group. , a carboxylic acid group, a phosphoric acid group, a phosphate group, an amino group, or an ammonium group, RO is an oxyalkylene group having 3 to 18 carbon atoms, n is an integer of 1 to 50, and EO is oxyethylene group, and m is an integer from 0 to 200.
T ¹ is preferably an alkenyl group in that bleeding can be suppressed when the surfactant remains in the resin particles.

As the surfactant A, a commercially available product can be used. For example, commercially available anionic surfactants A include Daiichi Kogyo Seiyaku's Aquaron KH series, Hytenor XJ-630S, and Kao's Latemul PD-104. Commercially available nonionic surfactants A include Daiichi Kogyo Seiyaku Co., Ltd.'s Neugen XL series, Kao Corporation's Latemul-420, 430, and 450, Emulgen LS series, Emulgen MS series, Emulgen PP series, and Aoki Yushi Kogyo Co., Ltd. Examples include the Fine Surf NDB series, IDEP series, Wonder Surf NDR series, ID series, and S series.
Surfactant A may be used alone or in combination of two or more.

The amount of surfactant A used in Step 1 is preferably 0.05 to 5.0 parts by mass, for example, based on 100 parts by mass of the one or more polymerizable monomers. When the amount of surfactant A used is within the above range, resin particles 1 are likely to be stably formed. If the amount of surfactant A used is less than 0.05 parts by mass, the structure will be incomplete, and if it exceeds 5.0 parts by mass, there is a risk that the properties of the resin constituting the resin particles may be impaired.

The first surfactant may further contain a surfactant different from surfactant A (another surfactant) to the extent that the effects of the present invention are not impaired.
As other surfactants, known surfactants can be used, such as the anionic surfactants and cationic surfactants shown below.

Examples of anionic surfactants include higher fatty acid salts such as sodium oleate and sodium stearate; alkyl (or aryl) sulfonates such as sodium dodecylbenzenesulfonate and disodium dodecyl diphenyl ether sulfonate; lauryl Alkyl (or alkenyl) sulfate esters such as sodium sulfate and sodium oleyl sulfate; polyoxyethylene alkyl (or alkenyl) esters such as sodium polyoxyethylene lauryl ether sulfate, ammonium polyoxyethylene oleyl ether sulfate, ammonium polyoxyethylene styrenated phenyl ether sulfate, etc. Ether sulfates; polyoxyethylene alkylaryl ether sulfate ester salts such as polyoxyethylene nonylphenyl ether sodium sulfate; sodium monooctyl sulfosuccinate, sodium di-2-ethylhexyl sulfosuccinate, sodium dioctyl sulfosuccinate, polyoxyethylene lauryl Examples include alkyl sulfosuccinate salts such as sodium sulfosuccinate, derivatives thereof, and the like. These anionic surfactants may be used alone or in combination of two or more.

Specifically, the cationic surfactants include alkylbenzylmethylammonium salts such as dodecylbenzylmethylammonium chloride; alkyltrimethylammonium salts such as dodecyltrimethylammonium chloride, stearyltrimethylammonium chloride, and cetyltrimethylammonium chloride; didecyldimethyl Quaternary ammonium salts include dialkyldimethylammonium salts such as ammonium chloride and distearyldimethylammonium chloride; alkylbenzyldimethylammonium salts such as dodecylbenzyldimethylammonium chlorite; and the like. These cationic surfactants may be used alone or in combination of two or more.

(Second surfactant)
The second surfactant is used for the purpose of improving polymerization stability.
The second surfactant is not particularly limited, and for example, surfactant A, other surfactants, or a combination of these may be used.
The second surfactant may be used alone or in combination of two or more.

(dispersant)
The dispersant, like the second surfactant, is used for the purpose of improving polymerization stability.
Examples of the dispersant include organic dispersants and inorganic dispersants.
Examples of organic dispersants include polyvinyl alcohol, cellulose, polyvinylpyrrolidone, and the like.
Examples of inorganic dispersants include tricalcium phosphate and calcium carbonate.
These dispersants may be used alone or in combination of two or more.

(Other additives)
In the present invention, other additives may be used as long as they do not impair the properties of the resin particles. Examples of other additives include chain transfer agents such as organic sulfur compounds, preservatives, and antioxidants. Further, pigments and dyes for coloring the particles, and metal particles, inorganic fine particles, and organic fine particles for the purpose of modifying the particles can also be added.

<Effect>
Since the resin particle 1 described above has one or more holes 3 provided inside, light is scattered at the interface between them due to the difference in refractive index between the hole 3 portion (air) and the resin portion. Excellent diffusivity.
In addition, since the resin particles 1 have particles 5 in at least one pore 3, the specific gravity is close to that of solid resin particles without pores 3, and the resin particles 1 have a low viscosity liquid (aqueous medium, low viscosity organic It does not easily float even in solvents, low viscosity resin solutions, etc.).

Although the embodiments of the resin particles of the present invention have been described above, the present invention is not limited to the above embodiments. The configurations and combinations thereof in the above embodiments are merely examples, and additions, omissions, substitutions, and other changes to the configurations are possible without departing from the spirit of the present invention.

The use of the resin particles of the present invention is not particularly limited, but can be used, for example, as a light reflecting material or matte material in paints, cosmetics, etc., and a light diffusing material in light diffusing plates for liquid crystal backlights.
For example, when the resin particles of the present invention are incorporated into a paint or the like as a light-reflecting material or a matting material, an excellent light-reflecting effect or matting effect is exhibited. When the resin particles of the present invention are included as a light diffusing material in a light diffusing plate for a liquid crystal backlight, etc., an excellent light diffusing effect is exhibited.

EXAMPLES Hereinafter, the present invention will be specifically explained with reference to Examples, but the present invention is not limited thereto.
"Part" means "part by mass."

<Example 1>
(Preparation of resin particles)
Resin particles according to Example 1 were prepared according to the formulation shown in Table 1.
In preparing resin particles, a suspension is prepared in which the continuous phase is a polymerization initiator, polymerizable monomer, and surfactant, and the dispersed layer is water. By adding a mixture of the agent and water, a suspension in which the continuous phase was water and the dispersed layer was a polymerizable monomer was obtained, and then polymerization was performed to obtain resin particles. The details are as follows.
For a total of 100 parts of 60 parts of methyl methacrylate (MMA), 30 parts of styrene (St), and 10 parts of ethylene glycol dimethacrylate (EGDMA) as polymerizable monomers, 2.0 parts of Emulgen PP-290 was used as a surfactant. The mixed liquid was put into a container equipped with a homomixer, and mixed with the homomixer to obtain a first mixed liquid.
Separately, 1.0 part of polyvinyl alcohol as a dispersant and 270 parts of water were mixed to obtain a second liquid mixture.
A W/O/W type (water in oil in water) suspension was obtained by adding the second mixed liquid to the first mixed liquid being stirred at a peripheral stirring speed of 14.7 m/s. Ta.
The resulting suspension was placed in a 4-necked flask equipped with a stirrer, a condenser, a thermometer, and a nitrogen inlet tube, and the temperature was raised to 75° C. under nitrogen gas, followed by reaction at 75° C. for 4 hours. Thereafter, the obtained resin particle dispersion was filtered, and the filtered resin particles were washed with 500 parts of water and dried at 60° C. for 12 hours to recover the resin particles.
The following evaluations were performed on the collected resin particles.

(shape)
The surface of the resin particles and the cross section of the resin particles were observed using a scanning electron microscope (SEM, manufactured by JEOL Ltd.). To observe the cross section of the resin particles, the resin particles were dispersed in an ultraviolet curable resin, the resin was irradiated with ultraviolet rays to cure it, and the cured product was cut using a microtome to create a section. As a result, a porous structure was confirmed inside the resin particles, and the presence of pores in which the particles were encapsulated was observed within the porous structure.
FIG. 2 shows a scanning electron micrograph of the surface of the resin particle. FIG. 3 shows a scanning electron micrograph of a cross section of a resin particle.

(Average particle size)
0.1 g of the recovered resin particles were mixed with 100 g of a dilute aqueous solution of a surfactant, and the resin particles were dispersed in a medium using an ultrasonic irradiator. The volume-based particle size distribution of the obtained resin particle dispersion was measured using a laser diffraction particle size distribution analyzer (manufactured by Shimadzu Corporation), and the average particle size was determined. As a result, the average particle diameter of the resin particles was 3.1 μm.

(specific gravity)
The specific gravity of the resin particles was determined by immersion in methanol. The results are shown in Table 1.
The methanol immersion was performed according to the following procedure.
5 g of resin particles were accurately weighed and put into a 50 mL volumetric flask. Next, methanol was introduced into the volumetric flask, and the volume filled in the volumetric flask was adjusted to 50 mL while the resin particles were being absorbed into the methanol. Accurately weigh the combined mass of the volumetric flask and its contents (A), subtract the previously measured tare of the volumetric flask (B) and the mass of the resin particles (C) from that mass, and calculate the mass of the methanol added ( D) was calculated. The volume (E) of methanol in the volumetric flask was calculated by dividing the calculated mass (D) of methanol by the specific gravity of methanol at 20°C, 0.792 g/cm ³ . The volume (F) of the resin particles was calculated by subtracting the volume (E) of methanol from the volume (50 mL) of the contents of the volumetric flask. The specific gravity of the resin particles was calculated by dividing the mass (C) of the resin particles by the volume (F) of the obtained resin particles.

The value of "specific gravity of resin particles/specific gravity of resin constituting resin particles" was calculated from the determined specific gravity of the resin particles and the specific gravity of a resin having the same refractive index as the resin component constituting the resin particles. The results are shown in Table 1 as "particle specific gravity/resin specific gravity".
In this example, the refractive index of the acrylic component constituting the resin particles is 1.49 of PMMA, and the refractive index of the styrene component is 1.59 of polystyrene. The copolymerization ratio of methyl methacrylate and styrene was calculated so that the copolymerization ratio was calculated, and a copolymer having this copolymerization ratio was produced and used as a resin having a refractive index equivalent to that of the resin component constituting the resin particles.

(Haze)
As an index of light diffusivity of resin particles, haze was measured according to the following procedure. The results are shown in Table 1.
2.0 g of the recovered resin particles and 45 g of a 40% by mass toluene solution of a resin having the same refractive index as the resin component constituting the resin particles are placed in a glass bottle and mixed for 30 minutes using a shaker to create a resin. A particle dispersion was obtained. The obtained resin particle dispersion was applied to a glass plate with a thickness of 1 mm using an applicator with a gap of 150 μm, and a test piece was obtained by drying at 100° C. for 10 minutes. The haze of the obtained test piece was measured using a haze meter (manufactured by Murakami Color Research Institute).

<Examples 2 to 7, Comparative Examples 2 and 4>
The same operation as in Example 1 (preparation of resin particles) was performed except that the peripheral stirring speed or monomer composition when obtaining a W/O/W type suspension was changed as shown in Table 1. The obtained resin particles were evaluated in the same manner as in Example 1. The results are shown in Table 1.
In addition, in Comparative Example 2, the polymer became lumpy and did not form particles, so no evaluation was performed.

The abbreviations in Table 1 indicate the following.
MMA: Methyl methacrylate.
nBA: n-butyl acrylate.
EMA: ethyl methacrylate.
EGDMA: ethylene glycol dimethacrylate.
St: Styrene.
nBMA: n-butyl methacrylate.
AMBN: 2,2'-azobis(2-methylbutyronitrile).
PP-290: "Emulgen PP-290" manufactured by Kao Corporation, polyoxyethylene (160) polyoxypropylene (30) glycol, solid content 100%.
D-3-D: "EMAL D-3-D" manufactured by Kao Corporation, aqueous solution of sodium polyoxyethylene alkyl ether sulfate, solid content 26%.
PVA: polyvinyl alcohol, average degree of polymerization 3500.

In Table 1, "porous with particles" in "shape" indicates that a porous structure was confirmed inside the resin particles, and the existence of pores in which particles were encapsulated was observed within the porous structure. show. "True spherical" indicates that the particle has a spherical appearance and no pores exist in the cross section of the particle.

The resin particles of Examples 1 to 7 had a high haze of 50% or more in the test piece and had excellent light diffusivity. In addition, the specific gravity was as high as 0.8 g/cm ³ or more, and it was difficult to float even in a low-viscosity liquid.

1 resin particles, 3 holes, 5 particles

Claims (5)

Consisting of a resin polymerized with one or more polymerizable monomers having a polymerizable unsaturated bond,
A resin particle having one or more pores therein, the particle being present in at least one of the one or more pores. The one or more polymerizable monomers include a (meth)acrylate monomer, and the ratio of the (meth)acrylate monomer to the total mass of the one or more polymerizable monomers is 50% by mass or more. The resin particles according to claim 1. The resin particles according to claim 1 or 2, having a specific gravity of 0.8 g/cm ³ or more. The resin particles according to claim 1 or 2, having an average particle diameter of 1.0 to 200 μm. The resin particles according to claim 1 or 2, having a haze of 50 to 90% as measured by the following measuring method.
Measurement method: 2.0 g of the resin particles and 45 g of a 40% by mass toluene solution of a resin having the same refractive index as the resin constituting the resin particles are placed in a glass bottle, mixed for 30 minutes with a shaker, and the obtained The resulting dispersion was applied to a 1 mm thick glass plate using an applicator with a gap of 150 μm, dried at 100° C. for 10 minutes, and the haze of the resulting test piece was measured.

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