JP6813227B1 - Method for manufacturing resin dispersion, resin particles, and resin dispersion - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a resin particle which can sufficiently contain a liquid inside the resin particle with respect to the volume of the resin particle, but easily removes the liquid contained therein or replaces the liquid with another liquid. A resin dispersion liquid containing the same is provided. A resin dispersion containing an aqueous medium and resin particles dispersed in the aqueous medium, wherein the resin dispersion further contains a nonionic emulsifier having an HLB value of 6 to 14. The resin particles are formed of a polymer containing a structural unit derived from a monofunctional monomer having one polymerizable unsaturated bond and a structural unit derived from a polyfunctional monomer having two or more polymerizable unsaturated bonds. The surface layer includes a surface layer and a liquid enclosed in the surface layer, and the surface layer provides a resin dispersion having an average of two or more through holes per resin particle. [Selection diagram] None

Description

The present invention relates to a resin dispersion liquid, resin particles, and a method for producing a resin dispersion liquid.

The resin particles having a hollow in the surface layer made of the polymer exhibit properties different from those of the resin particles having substantially no voids inside due to the presence of the hollow. The hollow resin particles are used in various applications such as heat-sensitive recording media, paints, adhesives, adhesives, fragrances, pesticides, pharmaceuticals, and liquid crystals, by utilizing the properties depending on the substances existing inside. Expected to be used.

For example, a resin particle whose inside is filled with air has a heat insulating property, is lightweight, and has a hiding property and glossiness due to diffused reflection of light in a hollow, as compared with a resin particle whose inside is solid. It has characteristics such as having. As an example of utilizing the heat insulating property, there is a use as a heat insulating material contained in an intermediate layer for increasing the recording sensitivity in a thermal recording medium such as a thermal recording paper or a heat transfer receiving paper. An example of utilizing the light weight is the use as a film forming material for the purpose of reducing the weight of the film. As an example of utilizing optical properties such as hiding property and glossiness, there is use as a pigment, a hiding agent, a light scattering agent and the like contained in paints, inks, various coating agents and the like. Further, for example, resin particles whose inside is filled with a substance such as a liquid have properties and functions derived from the substance, and can be used as microcapsules of the substance.

In order to fully exhibit the various characteristics described above in the hollow resin particles, it is desired to increase the hollow ratio of the resin particles. From that point of view, various techniques have been proposed so far.

For example, in Patent Document 1, a predetermined hollow resin particle having one hollow surrounded by a shell having a predetermined fine through hole is dispersed in an aqueous solution of a mixed solution containing a polyfunctional monomer and a non-reactive solvent. The method obtained by carrying out emulsion polymerization is described.

Further, in Patent Document 2, a mixture containing a polymerizable monomer for forming an outer shell of polymer fine particles and an organic solvent is emulsified and dispersed in an aqueous medium, the polymerizable monomer is suspended and polymerized, and the organic solvent is included. A method for producing hollow polymer fine particles by forming polymer fine particles, vaporizing an organic solvent contained in the polymer fine particles, and removing the organic solvent through the outer shell of the fine particles is described.

Japanese Unexamined Patent Publication No. 2016-190980 Japanese Unexamined Patent Publication No. 2013-22170

When resin particles having cavities are produced by emulsion polymerization as in the technique described in Patent Document 1, nano-sized resin particles having a particle diameter of 1 μm or less can be obtained by emulsion polymerization. Therefore, the hollowness ratio of the resin particles can be determined. It's hard to raise. Therefore, since the amount of substances (gas, liquid, etc.) that can be contained in the resin particles is reduced, it is difficult to sufficiently exhibit the various characteristics described above.

When the resin particles having a hollow are produced by suspension polymerization as in the technique described in Patent Document 2, since an organic solvent is used in the suspension polymerization, resin particles containing an organic solvent in the hollow portion can be obtained. Considering the above-mentioned applications and fields of use of the hollow resin particles, as well as the work environment and environmental load, it is usually the case that the resin particles containing the organic solvent used in the suspension polymerization are used. Few. Therefore, depending on the application or the like, the organic solvent contained inside the resin particles is removed or replaced with another liquid. However, in the process of removing the contained organic solvent, the hollow resin particles are easily crushed by negative pressure, making it difficult to retain the spherical shape, and it becomes difficult to sufficiently develop the various characteristics described above.

Therefore, according to the present invention, it is possible to sufficiently enclose a liquid inside the resin particles with respect to the volume of the resin particles, but it is easy to remove the liquid contained therein or replace it with another liquid. It is intended to provide a resin dispersion liquid containing particles.

That is, the present invention is a resin dispersion containing an aqueous medium and resin particles dispersed in the aqueous medium, and the resin dispersion further contains a nonionic emulsifier having an HLB value of 6 to 14. However, the resin particles are made from a polymer containing a structural unit derived from a monofunctional monomer having one polymerizable unsaturated bond and a structural unit derived from a polyfunctional monomer having two or more polymerizable unsaturated bonds. The surface layer includes a formed surface layer and a liquid enclosed in the surface layer, and the surface layer provides a resin dispersion having an average of two or more through holes per resin particle.

In addition, the present invention relates to at least an aqueous medium, a monofunctional monomer having one polymerizable unsaturated bond, a polyfunctional monomer having two or more polymerizable unsaturated bonds, and a nonionic emulsifier having an HLB value of 6 to 14. By mixing and dispersing a hydrophobic liquid and an oil-soluble polymerization initiator and performing suspension polymerization, the aqueous medium contains a structural unit derived from the monofunctional monomer and a structural unit derived from the polyfunctional monomer. Provided is a method for producing a resin dispersion liquid, which comprises obtaining resin particles containing a surface layer formed from a polymer and the hydrophobic liquid enclosed in the surface layer.

According to the present invention, it is possible to sufficiently enclose a liquid inside the resin particles with respect to the volume of the resin particles, but it is easy to remove the liquid contained therein or replace it with another liquid. A resin dispersion liquid containing resin particles can be provided.

It is an image when the surface of the sample which dried the resin dispersion liquid produced in Example 1 was observed with a scanning electron microscope (SEM). It is an image when the surface of the sample which dried the resin dispersion liquid produced in Example 4 was observed by SEM. It is an image when the surface of the sample which dried the resin dispersion liquid produced in Example 5 was observed by SEM. It is an image when the surface of the sample which dried the resin dispersion liquid produced in Example 6 was observed by SEM. It is an image when the surface of the sample which dried the resin dispersion liquid produced in the comparative example 3 was observed by SEM. It is an image when the cross section of the resin coating film produced using the resin dispersion liquid produced in Example 1 was observed by SEM. It is an image when the cross section after pressing of the resin coating film produced using the resin dispersion liquid produced in Example 1 was observed by SEM. It is an image when the cross section after pressing of the resin coating film produced by using the resin dispersion liquid produced in Comparative Example 5 was observed by SEM.

Hereinafter, embodiments of the present invention will be described, but the present invention is not limited to the following embodiments.

<Resin dispersion>
The resin dispersion liquid of one embodiment of the present invention contains an aqueous medium, resin particles dispersed in the aqueous medium, and a nonionic emulsifier having an HLB value of 6 to 14. The resin particles were formed from a polymer containing a structural unit derived from a monofunctional monomer having one polymerizable unsaturated bond and a structural unit derived from a polyfunctional monomer having two or more polymerizable unsaturated bonds. It contains a surface layer and a liquid enclosed in the surface layer. The surface layer has an average of two or more through holes per resin particle.

As will be described in detail later in the description of the method for producing the resin dispersion, the resin dispersion has a monofunctional monomer having one polymerizable unsaturated bond and two or more polymerizable unsaturated bonds in an aqueous medium. It can be produced by suspend-polymerizing a monomer component containing a polyfunctional monomer having. Further, the nonionic emulsifier having an HLB value of 6 to 14 contained in this resin dispersion liquid is contained in the resin dispersion liquid because it was used in the production of resin particles, and the surface layer at the time of the production. Can contribute to the formation of through holes in. The surface layer of the resin particles is formed of a polymer containing a structural unit derived from a monofunctional monomer and a structural unit derived from a polyfunctional monomer, and has an average of two or more through holes per resin particle. Have. Therefore, in the present technology, it is possible to sufficiently enclose the liquid inside the resin particles with respect to the volume of the resin particles, but it is easy to remove the liquid contained therein or replace it with another liquid. A resin dispersion liquid containing resin particles can be provided.

As used herein, the "inside" of the resin particles means a portion of the resin particles surrounded by a surface layer formed of a polymer. The fact that the resin particles have a surface layer and an inside (space) formed by the surface layer can be confirmed by, for example, a general observation method using a scanning electron microscope (SEM) or a transmission electron microscope (TEM). it can.

The inclusion of the resin particles as "a liquid surrounded by and contained in the surface layer" means that a liquid other than the polymer forming the surface layer of the resin particles is present inside the resin particles. As long as at least a liquid is present inside the resin particles, a gas and / or a solid may be mixed with the liquid inside the resin particles.

Hereinafter, preferable configurations and the like of the components such as resin particles in the resin dispersion liquid will be described from the viewpoint that the target resin dispersion liquid can be easily obtained.

(Resin particles)
The resin particles include a surface layer formed from the polymer and a liquid enclosed in the surface layer. That is, the surface layer of the resin particles is formed of a resin (polymer), but the resin is surrounded by the surface layer (polymer), including the liquid contained in the polymer (resin). Let's call it a particle. The liquid enclosed in the surface layer of the resin particles will be described in detail later, but hydrophobic liquids and other liquids (for example, water and other substances) that can be used in producing the resin dispersion liquid are described in detail later. Can be mentioned.

The shape of the resin particles is spherical, and it is preferable that the resin particles are close to a true spherical shape. The number average particle size of the resin particles is preferably 0.5 to 30 μm, more preferably 0.8 to 20 μm, and even more preferably 1 to 10 μm. The number average particle size of the resin particles is a particle size that is 50% of the cumulative frequency based on the number of spheres in the number-based particle size distribution measured for the resin dispersion using a laser diffraction type particle size distribution measuring device. take.

The surface layer of the resin particles has a plurality of through holes on average per resin particle. That is, the surface layer has two or more through holes on average per resin particle. In the present specification, the average number of through-holes per resin particle in the surface layer may be simply referred to as "average number of through-holes". As will be described later, the through holes in the surface layer can be formed by using a nonionic emulsifier having an HLB value of 6 to 14 when producing the resin dispersion, so that the shape of the through holes is not particularly limited and is not limited. It may be a fixed form.

The size of the through hole in the surface layer can be expressed by the length of the longest portion in the hole of one through hole because the shape of the through hole can be irregular. The length of the longest portion in the through hole is preferably 0.1 μm or more, more preferably 0.15 μm or more, and further preferably 0.2 μm or more. Further, the length of the longest portion in the through hole is preferably 30 μm or less, more preferably 10 μm or less, and 1 μm or less so as to secure the strength of the surface layer of the resin particles and to easily retain the spherical shape. Is even more preferable.

Since the resin particles have an average number of through holes of 2 or more, it is easy to remove the liquid or replace it with another liquid while containing the liquid inside, and the inside of the resin particles becomes negative pressure. It is expected that it will not be crushed because it is difficult, and that the sustained release function of the contained liquid will be exhibited. From these viewpoints, the average number of through holes is preferably 3 or more, and more preferably 3.5 or more. On the other hand, the average number of through holes is preferably 20 or less, more preferably 15 or less, and 12 or less, from the viewpoint that the resin particles easily enclose the liquid inside and the strength of the surface layer can be easily secured. Is more preferable.

In the present specification, the length of the longest portion of the through hole provided on the surface layer and the average number of through holes are referred to as an image when observed with a scanning electron microscope (SEM) (hereinafter, referred to as “SEM image”). It may be required based on). Specifically, after removing the liquid existing inside the resin particles in the resin dispersion liquid, the resin dispersion liquid is dried to obtain an SEM image of the dried resin particle sample obtained. In the hole of the through hole on the surface of the particle in the SEM image, the length of the straight line portion that can be drawn the longest can be the length of the longest part of the through hole. In addition, 10 particles are randomly selected from the above SEM image, the number of through holes on the surface of the selected particles is counted, and the count is doubled to obtain the total number of through holes. The average number of through holes can be obtained by dividing the total number of particles by the number of particles (10 particles). It should be noted that the reason why the above count number is doubled is that since the SEM image is a flat image, it is considered that there is a similar through hole in the portion not observed. Further, if the through hole is too small, SEM observation may be difficult. Therefore, the through hole in the above SEM image is a through hole having a length of the longest portion in the through hole of 0.1 μm or more. Can be.

In the resin particles, the ratio of the internal volume in which the liquid is contained by the surface layer is preferably 60 to 95% with respect to the volume of the resin particles. The ratio of the internal volume to the volume of the resin particles is more preferably 65% or more, further preferably 70% or more, and further preferably 90% or less. The ratio of the internal volume to the volume of the resin particles can be obtained as follows.

Since the shape of the resin particles is spherical, the volume of the resin particles can be regarded as the volume of the sphere, 4/3 × π × r ³ (r is the radius of the resin particles). The internal volume of the resin particles can be regarded as 4/3 × π × (rt) ³ where t is the thickness of the surface layer. Therefore, in the present specification, the volume (average volume) of the resin particles contained in the resin dispersion is 4/3 × using the above-mentioned number average particle diameter (this is referred to as “D”). The value obtained by π × (D / 2) ³ can be taken. Further, the internal volume (average internal volume) of the resin particles contained in the resin dispersion can be a value obtained by 4/3 × π × (D / 2-t) ³ . Therefore, the ratio of the internal volume to the volume of the resin particles contained in the resin dispersion can be determined by [(D / 2-t) ³ / (D / 2) ³ ] × 100 (%).

The thickness of the surface layer is determined based on the SEM image in the same manner as in the case of determining the length of the longest portion of the through holes and the average number of through holes described above. Specifically, a coating liquid containing a resin dispersion liquid is applied and dried to obtain a resin coating film, and then an SEM image is acquired for a cross section of the resin coating film. After 10 particles are randomly selected from the above SEM image, the thickness of the surface layer for each selected particle is measured at a total of 4 points, one on each of the top, bottom, left and right, and the average is calculated to obtain the average of the surface layer of the 10 particles. The average value of the thickness can be taken.

The surface layer of the resin particles is a polymer (co-polymer) containing a structural unit derived from a monofunctional monomer having one polymerizable unsaturated bond and a structural unit derived from a polyfunctional monomer having two or more polymerizable unsaturated bonds. It is formed from a polymer). In the present specification, "a monofunctional monomer having one polymerizable unsaturated bond" may be simply referred to as "monofunctional monomer", and "a polyfunctional monomer having two or more polymerizable unsaturated bonds" is referred to as "polyfunctional monomer". It may be simply described as "polyfunctional monomer".

The polymer forming the surface layer preferably comprises a structural unit derived from a monofunctional monomer and a structural unit derived from a polyfunctional monomer as the structural unit derived from the polymerizable monomer constituting the polymer. .. Ratio of the content (mass%) of the structural unit derived from the polyfunctional monomer to the total content (mass%) of the structural unit derived from the monofunctional monomer and the structural unit derived from the polyfunctional monomer in the resin particles (surface layer) Is preferably 30 to 90%. As a result, it is possible to form a surface layer having good strength (pressure resistance) even if it has a plurality of through holes and the ratio of the internal volume to the volume of the resin particles is high, and it is difficult to be crushed. , It is possible to obtain resin particles that can easily maintain a spherical shape. As a result, it becomes possible to obtain resin particles that can fully utilize the characteristics due to the presence of the liquid inside. From these viewpoints, the above ratio of the content (mass%) of the structural unit derived from the polyfunctional monomer is more preferably 30 to 85%, further preferably 40 to 80%.

Ratio of the content (mass%) of the structural unit derived from the monofunctional monomer to the total content (mass%) of the structural unit derived from the monofunctional monomer and the structural unit derived from the polyfunctional monomer in the resin particles (surface layer) Is preferably 10 to 70%. The above ratio of the content (mass%) of the structural unit derived from the monofunctional monomer is more preferably 15 to 70%, further preferably 20 to 60%.

As the monofunctional monomer, at least one selected from the group consisting of monovinyl monomers and hydrophilic monomers can be preferably used. The monovinyl monomer means a monomer having one polymerizable vinyl functional group and a monomer other than the hydrophilic monomer. The hydrophilic monomer means one polymerizable vinyl functional group and a monomer having a hydrophilic group. The hydrophilic group refers to a group that exhibits an affinity with water, and includes a group that is ionized in water to become an ion and a group that is hydrated by a hydrogen bond. Examples of the hydrophilic group include an acid group, a hydroxy group, an amide group, a polyoxyethylene group and the like.

Examples of the monovinyl monomer include (meth) acrylic acid esters; styrene-based monomers; nitrile group-containing monomers such as acrylonitrile and methacrylonitrile; monoolefin monomers such as ethylene, propylene, and butylene; butadiene and Diene-based monomers such as isoprene; carboxylic acid vinyl ester monomers such as vinyl formate, vinyl acetate, and vinyl propionate; vinyl ether monomers such as methyl vinyl ether and ethyl vinyl ether; unsaturated such as vinyl alcohol and allyl alcohol Alcohol monomer; Vinyl halide monomer such as vinyl chloride and vinyl fluoride; Vinylidene halide monomer such as vinylidene chloride; N-vinylmorpholin, 4-acryloylmorpholin, 4-methacryloylmorpholin, 4-vinylpyridine , And a nitrogen atom-containing vinyl monomer such as 1-vinylimidazole; and the like. One or more of these monovinyl monomers can be used. Among these, (meth) acrylic acid ester and styrene-based monomer are preferable, and (meth) acrylic acid ester is more preferable.

As used herein, the term "(meth) acrylic" means that both the terms "acrylic" and "methacryl" are included. Similarly, the term "(meth) acrylate" means that the term "acrylate" and "methacrylate" are included.

Examples of the (meth) acrylic acid ester include (meth) acrylic acid alkyl ester, (meth) acrylic acid alkoxyalkyl ester, (meth) acrylic acid aralkyl ester, and (meth) acrylic acid aryl ester. .. One or more of these (meth) acrylic acid esters can be used. Of these, (meth) acrylic acid alkyl esters are preferred.

Examples of the (meth) acrylic acid alkyl ester include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, and isobutyl (meth). Acrylate, tert-butyl (meth) acrylate, sec-butyl (meth) acrylate, n-amyl (meth) acrylate, isoamyl (meth) acrylate, n-hexyl (meth) acrylate, n-octyl (meth) acrylate, isooctyl ( Meta) acrylate, 2-ethylhexyl (meth) acrylate, n-nonyl (meth) acrylate, isononyl (meth) acrylate, n-decyl (meth) acrylate, isodecyl (meth) acrylate, n-undecyl (meth) acrylate, n- Linear or branched chains such as dodecyl (meth) acrylate, n-tridecyl (meth) acrylate, n-tetradecyl (meth) acrylate, cetyl (meth) acrylate, stearyl (meth) acrylate, and behenyl (meth) acrylate. (Meta) acrylic acid alkyl ester having an alkyl group; as well as cyclohexyl (meth) acrylate, 4-tert-butylcyclohexyl (meth) acrylate, isobornyl (meth) acrylate, dicyclopentanyl (meth) acrylate, and dicyclopentenyl ( Examples thereof include an alicyclic (meth) acrylic acid alkyl ester such as a meta) acrylate. One or more of these (meth) acrylic acid alkyl esters can be used. Among these, a (meth) acrylic acid alkyl ester having a linear or branched alkyl group having 1 to 18 (more preferably 1 to 12) carbon atoms is preferable.

Examples of the (meth) acrylic acid alkoxyalkyl ester include 2-methoxyethyl (meth) acrylate, 2-ethoxyethyl (meth) acrylate, 2-butoxyethyl (meth) acrylate, ethoxyethoxyethyl (meth) acrylate, and 2. -Phenoxyethyl (meth) acrylate and the like can be mentioned. One or more of these can be used.

Examples of the (meth) acrylic acid aralkyl ester include benzyl (meth) acrylate, 2-phenylethyl (meth) acrylate, methylbenzyl (meth) acrylate, and naphthylmethyl (meth) acrylate. One or more of these can be used.

Examples of the (meth) acrylic acid aryl ester include phenyl (meth) acrylate, trill (meth) acrylate, and naphthyl (meth) acrylate. One or more of these can be used.

Examples of the styrene-based monomer include styrene, α-methylstyrene, o-, m-, p-methylstyrene, o-, m-, p-ethylstyrene, 4-tert-butylstyrene, o-, m. -, P-methoxystyrene, o-, m-, p-ethoxystyrene, o-, m-, p-chlorostyrene, o-, m-, p-bromostyrene, o-, m-, p-fluorostyrene , And o-, m-, p-chloromethylstyrene and the like. One or more of these can be used. Of these, styrene is preferable.

Examples of the hydrophilic monomer include an acid group-containing monomer, a hydroxy group-containing monomer, an amide group-containing monomer, and a polyoxyethylene group-containing monomer. One or more of these can be used.

Examples of the acid group-containing monomer include ethylenically unsaturated carboxylic acid monomers such as (meth) acrylic acid, crotonic acid, silicic acid, itaconic acid, maleic acid, fumaric acid, and citraconic acid; itaconic acid. Carboxy group-containing monomers such as monoalkyl esters of unsaturated dicarboxylic acids such as monoethyl, monobutyl fumarate, and monobutyl maleate; sulfonic acid group-containing monomers such as styrene sulfonic acid; and the like can be mentioned. One or more of these can be used. Among these, an ethylenically unsaturated carboxylic acid monomer is preferable.

Examples of the hydroxy group-containing monomer include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, and 3-hydroxy. (Meta) acrylic acid hydroxyalkyl esters such as butyl (meth) acrylates, 4-hydroxybutyl (meth) acrylates, and 6-hydroxyhexyl (meth) acrylates; having hydroxy groups such as 4-hydroxyphenyl (meth) acrylates ( Meta) acrylic acid aryl ester; (meth) acrylic acid alkoxyalkyl ester having a hydroxy group such as 2-hydroxy-3-phenoxypropyl (meth) acrylate; having a hydroxy group such as o-, m-, p-hydroxystyrene. Acrylate-based monomer; etc. can be mentioned. One or more of these can be used.

Examples of the amide group-containing monomer include (meth) acrylamide, N-methyl (meth) acrylamide, N-ethyl (meth) acrylamide, N, N-dimethyl (meth) acrylamide, and N, N-diethyl (meth). Acrylamide, N-isopropyl (meth) acrylamide, N-methylol (meth) acrylamide, N- (2-hydroxyethyl) acrylamide, N-butoxymethyl (meth) acrylamide, N-vinylacetamide, N-vinyl-N-methylacetamide , And N-vinyl-2-pyrrolidone and the like. One or more of these can be used.

Examples of the polyoxyethylene group-containing monomer include methoxydiethylene glycol (meth) acrylate, methoxytriethylene glycol (meth) acrylate, methoxypolyethylene glycol (meth) acrylate, ethoxydiethylene glycol (meth) acrylate, and ethoxypolyethylene glycol (meth). ) Acrylate and the like can be mentioned. One or more of these can be used.

Among the specific examples of the monofunctional monomers listed above, the monofunctional monomers preferably contain at least one selected from the group consisting of (meth) acrylic acid esters and ethylenically unsaturated carboxylic acid monomers. Furthermore, it is more preferable that the monofunctional monomer contains at least one selected from the group consisting of (meth) acrylic acid alkyl ester and (meth) acrylic acid.

The polyfunctional monomer may have two or more polymerizable unsaturated bonds in one molecule, and the upper limit of the number of polymerizable unsaturated bonds is not particularly limited, but from the viewpoint of availability and the like, 2 It is preferable to use a polyfunctional monomer having ~ 6 polymerizable unsaturated bonds.

Examples of the polyfunctional monomer include a polyfunctional monomer having two or more (meth) acryloyloxy groups (hereinafter, may be referred to as “(meth) acryloyloxy group-containing polyfunctional monomer”) and a vinyl group of 2. A polyfunctional monomer having one or more (hereinafter, may be referred to as "vinyl group-containing polyfunctional monomer") and a polyfunctional monomer having two or more allyl groups (hereinafter, referred to as "allyl group-containing polyfunctional monomer"). It may be done.) Etc. can be mentioned. Further, as the polyfunctional monomer, a polyfunctional monomer having two or more groups among groups having a polymerizable unsaturated bond such as a vinyl group, an allyl group, and a (meth) acryloyloxy group (hereinafter, "others"). It may be described as "polyfunctional monomer"). One or more of the above polyfunctional monomers can be used. Among them, a (meth) acryloyloxy group-containing polyfunctional monomer is preferable. In the present specification, the term "(meth) acryloyloxy group" means that the term "acryloyloxy group" and "methacryloyloxy group" are included.

Examples of the (meth) acryloyloxy group-containing polyfunctional monomer include ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, tetraethylene glycol di (meth) acrylate, and polyethylene glycol. Di (meth) acrylate, dipropylene glycol di (meth) acrylate, tripropylene glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate, 1,3-butylenediol di (meth) acrylate, 1,4-butanediol Examples thereof include (meth) acryloyloxy group-containing bifunctional monomers such as di (meth) acrylate and 1,6-hexanediol di (meth) acrylate.

Examples of the (meth) acryloyloxy group-containing polyfunctional monomer include a (meth) acryloyloxy group-containing trifunctional monomer such as trimethylolpropane tri (meth) acrylate and pentaerythritol tri (meth) acrylate; ditrimethylol propane. (Meta) acryloyloxy group-containing tetrafunctional monomer such as tetra (meth) acrylate and pentaerythritol tetra (meth) acrylate; (meth) acryloyloxy group-containing pentafunctional monomer such as dipentaerythritol penta (meth) acrylate; dipenta (Meta) acryloyloxy group-containing hexafunctional monomers such as erythritol hexa (meth) acrylate; and the like can be mentioned. One or more of (meth) acryloyloxy group-containing polyfunctional monomers can be used.

Examples of the vinyl group-containing polyfunctional monomer include divinylbenzene, divinylbiphenyl, and divinylnaphthalene. Examples of the allyl group-containing polyfunctional monomer include diallyl phthalate and triallyl isocyanurate. Examples of other polyfunctional monomers include allyl (meth) acrylate. As the vinyl group-containing polyfunctional monomer, the allyl group-containing polyfunctional monomer, and other polyfunctional monomers, one type or two or more types can be used, respectively.

Among the specific examples of the polyfunctional monomer described above, the polyfunctional monomer preferably contains at least one selected from the group consisting of ethylene glycol di (meth) acrylate and trimethylolpropane tri (meth) acrylate.

The content (mass%) of the resin particles in the resin dispersion is preferably 1 to 40% by mass, preferably 2 to 35% by mass, based on the total mass of the resin dispersion as the resin (surface layer) content. It is more preferable that the amount is 5 to 30% by mass.

Examples of the liquid surrounded by the surface layer of the resin particles and contained therein include hydrophobic liquids, water, and other liquids that can be used in producing the resin dispersion liquid, as described above. Among these, a hydrophobic liquid and water are preferable, and it is more preferable that the liquid contains water.

Examples of the hydrophobic liquid include the hydrophobic liquid described in the description of the method for producing the resin dispersion liquid described later. The other liquid may be the liquid itself, or may be a liquid such as water or a hydrophobic liquid containing a solid substance. Examples of other liquids include liquid compositions containing fragrances, antibacterial agents, disinfectants, deodorants, cleaning agents, pharmaceuticals, pesticides, heat storage materials, ultraviolet absorbers, dyes, pigments and the like. it can. Further, for example, substances such as fragrances, antibacterial agents, disinfectants, deodorants, cleaning agents, pharmaceuticals, pesticides and the like can be allowed to exist inside the resin particles as substances for sustained release. Since the resin particles have a plurality of through holes in the surface layer, it can be expected to exhibit the sustained release property of the above-mentioned substance for sustained release.

(Aqueous medium)
The resin dispersion liquid contains an aqueous medium in addition to the above-mentioned resin particles. The aqueous medium is a liquid containing at least water and is a dispersion medium in the resin dispersion. As the aqueous medium, only water may be used, or a mixed medium of water and a water-soluble organic solvent may be used. The content of water in the aqueous medium is preferably 50% by mass or more, more preferably 70% by mass or more, and further preferably 90% by mass or more, based on the total mass of the aqueous medium. .. As the water-soluble organic solvent, for example, a liquid exhibiting miscibility with water at 20 ° C. or a liquid having a solubility in water of 10 g / 100 g-H ₂ O or more can be preferably used. Examples of the water-soluble organic solvent include, but are not limited to, methanol, ethanol, propanol, isopropanol, ethyl carbitol, ethylene glycol, propylene glycol, glycerin, and N-methylpyrrolidone. One or more water-soluble organic solvents may be used.

The content (% by mass) of water in the resin dispersion is preferably 40 to 98% by mass, more preferably 50 to 95% by mass, and 60 to 60 to 95% by mass, based on the total mass of the resin dispersion. It is more preferably 92% by mass.

(Nonionic emulsifier with HLB value of 6 to 14)
The resin dispersion liquid contains the above-mentioned resin particles and an aqueous medium, as well as a nonionic emulsifier having an HLB value of 6 to 14. The HLB value is a value indicating the degree of affinity of the emulsifier for water and oil (organic compound insoluble in water), and is also called a hydrophilic lipophilic balance. In this specification, the HLB value by the Griffin method is taken. The HLB value by the Griffin method is determined by the sum of the formula amounts of the hydrophilic portions of the emulsifier / the molecular weight of the emulsifier.

Examples of the nonionic emulsifier include an ether type nonionic emulsifier, an ester type nonionic emulsifier, an ester ether type nonionic emulsifier, and an alkanolamide type nonionic emulsifier. Of these, one or more nonionic emulsifiers having an HLB value of 6 to 14 can be used, and the type of nonionic emulsifier is not particularly limited as long as the HLB value is 6 to 14.

As the ether type nonionic emulsifier, for example, a nonionic emulsifier obtained by adding ethylene oxide to a raw material having a hydroxyl group such as a higher alcohol or an alkylphenol can be used. Examples of ether-type nonionic emulsifiers include polyoxyethylene lauryl ether, polyoxyethylene cetyl ether, polyoxyethylene stearyl ether, polyoxyethylene oleyl ether, polyoxyethylene 2-ethylhexyl ether, polyoxyethylene isodecyl ether, and poly. Oxyethylene aryl ether, polyoxyethylene distyrene phenyl ether, polyoxyethylene tribenzylphenyl ether, polyoxyethylene p-cumylphenyl ether, polyoxyethylene polycyclic phenyl ether, polyoxyalkylene polycyclic phenyl ether, etc. Can be mentioned.

As the ester-type nonionic emulsifier, for example, a nonionic emulsifier having a structure in which a polyhydric alcohol such as glycerin or sorbitol and a fatty acid are ester-bonded can be used. Examples of the ester-type nonionic emulsifier include sorbitan monolaurate, sorbitan monopalmitate, sorbitan monocaprilate, polyoxyethylene monolaurate, polyoxyethylene monostearate, polyoxyethylene monooleate, and polyglycerin lauric acid. Examples thereof include esters, polyglycerin stearic acid esters, and polyglycerin oleic acid esters.

As the ester ether type nonionic emulsifier, for example, a nonionic emulsifier obtained by adding ethylene oxide to an ester composed of a polyhydric alcohol such as glycerin or sorbitol and a fatty acid can be used. Examples of the ester ether type nonionic emulsifier include polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitan monopalmitate, polyoxyethylene sorbitan monostearate, polyoxyethylene sorbitan tristearate, and polyoxyethylene sorbitan monoole. Examples thereof include ate and polyoxyethylene sorbitan trioleate.

As the alkanolamide type nonionic emulsifier, for example, a nonionic emulsifier obtained by reacting a fatty acid with diethanolamine or the like can be used. Examples of the alkanolamide type nonionic emulsifier include alkanol fatty acid amide, alkanol amide, alkanol alkane amide, and alkyrrole amide.

The content of the nonionic emulsifier having an HLB value of 6 to 14 is preferably 0.1 to 20 parts by mass with respect to 100 parts by mass in total of the monofunctional monomer and the polyfunctional monomer described above. The content of this nonionic emulsifier is more preferably 0.5 parts by mass or more, further preferably 1 part by mass or more, and particularly preferably 2 parts by mass or more. The content of the nonionic emulsifier is more preferably 15 parts by mass or less, further preferably 10 parts by mass or less, and particularly preferably 6 parts by mass or less.

The resin dispersion may contain the above-mentioned resin particles, an aqueous medium, a nonionic emulsifier having an HLB value of 6 to 14, and other components. Other components include, for example, emulsifiers other than nonionic emulsifiers having an HLB value of 6 to 14, dispersants, dyes, pigments, metal compounds, defoamers, foaming agents, lubricants, gelling agents, film-forming aids, etc. Antifreeze, pH adjuster, viscosity modifier, preservative, fungicide, bactericide, rust preventive, flame retardant, wetting agent, defoamer, antioxidant, antiaging agent, UV absorber, antistatic Agents, antiblocking agents and the like can be mentioned. One or more of these may be contained in the resin dispersion.

<Resin particles>
It is also possible to obtain the above-mentioned resin particles from the above-mentioned resin dispersion liquid. That is, in the present technology, it is also possible to provide liquid-encapsulating type resin particles obtained from the above-mentioned resin dispersion liquid. The liquid-encapsulating type resin particles can be obtained, for example, by solid-liquid separation of the above-mentioned resin dispersion liquid. Examples of the solid-liquid separation method include filtration and centrifugation. The liquid-encapsulated resin particles may be in the form of powder, in which the aqueous medium that was the dispersion medium in the above-mentioned resin dispersion is almost removed, or the dispersion medium is formed. It may be in a wet state or a slurry state in which a water-based medium remains.

The liquid-encapsulating type resin particles are a plurality (many) aggregates (resin particle group). As described above, the liquid-encapsulated resin particles are encapsulated in a surface layer formed of a polymer containing a structural unit derived from a monofunctional monomer and a structural unit derived from a polyfunctional monomer, and surrounded by the surface layer. Including liquids. Further, the surface layer of the liquid-encapsulating type resin particles has an average of two or more through holes per resin particle.

Since the liquid-encapsulating type resin particles contain a liquid inside, they have a higher specific gravity than the hollow resin particles having a hollow inside (filled with gas), so that they are less likely to float and are easily dispersed. There is also an advantage that it is easy to suppress the scattering of resin particles during handling. Therefore, for example, when these resin particles are mixed with a material containing a liquid medium such as that used for paints, inks, pressure-sensitive adhesives, adhesives, and various coating agents to prepare them, the liquid medium is used. The resin particles are easily dispersed in the ink, and the above preparation is facilitated. For example, if resin particles containing water inside are used, mixing and dispersion in water-based applications becomes easy, and they can be used in more applications.

It is also possible to obtain hollow resin particles in a dry powder state in which the inside is hollow (filled with gas) by drying the liquid-encapsulating type resin particles.

<Manufacturing method of resin dispersion>
The resin dispersion liquid described above can be obtained, for example, by using the method for producing a resin dispersion liquid according to the embodiment of the present invention described below. That is, the method for producing the resin dispersion according to the embodiment of the present invention is at least an aqueous medium, a monofunctional monomer having one polymerizable unsaturated bond, and a polyfunctional monomer having two or more polymerizable unsaturated bonds. It comprises mixing and dispersing a nonionic emulsifier having an HLB value of 6 to 14, a hydrophobic liquid, and an oil-soluble polymerization initiator to carry out suspension polymerization. In the method for producing this resin dispersion, the suspension polymerization is carried out to obtain a surface layer formed from a polymer containing a structural unit derived from a monofunctional monomer and a structural unit derived from a polyfunctional monomer in an aqueous medium. Including obtaining resin particles containing a hydrophobic liquid surrounded by and contained in the surface layer.

In this method for producing a resin dispersion, since an oil-soluble polymerization initiator is used as a polymerization initiator, suspension polymerization can be carried out by generating radicals in the oil phase. In this suspension polymerization, the oil-soluble polymerization initiator is dissolved in an oil phase containing a monofunctional monomer, a polyfunctional monomer, and a hydrophobic liquid, and the oil phase is suspended as droplets in an aqueous medium while being stirred and dispersed. Muddy polymerization can be performed. According to suspension polymerization, it is possible to obtain resin particles having a high ratio of internal volume to volume of resin particles as compared with the case where resin particles are obtained by emulsion polymerization.

In the above suspension polymerization, since the oil-soluble polymerization initiator is dissolved in the oil phase to generate radicals, the above-mentioned mixed dispersion does not need to be performed separately for the oil phase and the aqueous phase, and is performed collectively. It is also possible to mix and disperse with. From the viewpoint of easy operation of suspension polymerization, the above-mentioned mixed dispersion is to obtain an oil phase mixed solution; to obtain an aqueous phase mixed solution; and to mix and disperse the oil phase mixed solution and the aqueous phase mixed solution. It is preferable to include it. As the oil phase mixture, a mixture obtained by mixing a monofunctional monomer, a polyfunctional monomer, a hydrophobic liquid, and an oil-soluble polymerization initiator can be used. Further, as the aqueous phase mixed solution, one obtained by mixing an aqueous medium and a nonionic emulsifier having an HLB value of 6 to 14 can be used.

As described above, the hydrophobic liquid is a hydrophobic liquid because it is used for suspend polymerization of monofunctional and polyfunctional monomers in the oil phase in the presence of an oil-soluble polymerization initiator. Good. As the hydrophobic liquid, a non-reactive hydrophobic liquid can be preferably used, and it is preferable to use a liquid that is immiscible with water or a liquid having low solubility in water at 20 ° C. The solubility of the hydrophobic liquid in water at 20 ° C. is preferably less than 1 g / 100 g-H ₂ O, more preferably 0.5 g / 100 g-H ₂ O or less.

Suitable hydrophobic liquids include aromatic hydrocarbons such as benzene, toluene, and xylene; aliphatic hydrocarbons such as hexane, cyclohexane, heptane, octane, various paraffins, and various olefins; capryl alcohols, lauryl alcohols, etc. Higher alcohols having 8 or more carbon atoms (more preferably 8 to 22) such as myristyl alcohol, cetyl alcohol, stearyl alcohol, isostearyl alcohol, oleyl alcohol, and behenyl alcohol; carboxylic acid esters obtained by dehydration condensation of carboxylic acids and alcohols. , And an ester obtained by dehydration condensation of an oxo acid other than carboxylic acid (for example, carbonic acid, phosphoric acid, nitric acid, sulfuric acid, boric acid, sulfonic acid, etc.) and an alcohol, and (poly) ester such as a polymer of these esters. Kind; mineral oils; vegetable oils such as soybean oil, olive oil, flaxseed oil, cottonseed oil, rapeseed oil, and castor oil; and the like. One or more hydrophobic liquids can be used. Among the above hydrophobic liquids, aromatic hydrocarbons, aliphatic hydrocarbons, and higher alcohols are preferable, and aromatic hydrocarbons and aliphatic hydrocarbons are more preferable.

The amount of the hydrophobic liquid used is preferably 150 to 2000 parts by mass with respect to 100 parts by mass in total of the monofunctional monomer and the polyfunctional monomer described above. From the viewpoint of securing the internal volume of the resin particles, the amount of the hydrophobic liquid used is preferably 150 parts by mass or more, more preferably 200 parts by mass or more, and further preferably 300 parts by mass or more. preferable. On the other hand, from the viewpoint of ensuring the strength of the surface layer of the resin particles, the amount of the hydrophobic liquid used is preferably 2000 parts by mass or less, more preferably 1500 parts by mass or less, and 1000 parts by mass or less. Is even more preferable.

As the oil-soluble polymerization initiator, a polymerization initiator that is oil-soluble and generates radicals in the oil phase can be used. Examples of the oil-soluble polymerization initiator include organic peroxides and azo compounds. Examples of the organic peroxide include benzoyl peroxide, lauroyl peroxide, benzoyl orthochloro peroxide, benzoyl orthomethoxy benzoyl peroxide, 3,5,5-trimethylhexanoyl peroxide, and t-butylperoxy-2-ethylhexa. Noate, di-t-butyl peroxide and the like can be mentioned. Examples of the azo compound include 2,2'-azobisisobutyronitrile, 2,2'-azobis (2,4-dimethylvaleronitrile), and 2,2'-azobis (4-methoxy-2,4-). Dimethylvaleronitrile), 1,1'-azobiscyclohexanecarbonitrile, 2,2'-azobis (2-methylbutyronitrile), 2,2'-azobis (2,4,4-trimethylpentane), etc. Can be mentioned. One or more oil-soluble polymerization initiators can be used.

The amount of the oil-soluble polymerization initiator used is preferably 0.1 to 10 parts by mass, preferably 0.2 to 8 parts by mass, based on 100 parts by mass of the total of the monofunctional monomer and the polyfunctional monomer described above. More preferably, it is more preferably 0.5 to 5 parts by mass.

In the method for producing the resin dispersion, the above-mentioned aqueous medium can be used. As the aqueous medium, at least water can be used, and ion-exchanged water is preferably used. The amount of water used during mixing and dispersion is preferably 400 to 2000 parts by mass, more preferably 500 to 1500 parts by mass, based on 100 parts by mass of the total of the monofunctional monomer and the polyfunctional monomer described above. , 600 to 1200 parts by mass is more preferable.

In the method for producing a resin dispersion, at least the above-mentioned nonionic emulsifier having an HLB value of 6 to 14 is used as the emulsifier used for the mixed dispersion. This makes it possible to obtain resin particles containing a surface layer having an average number of through holes of 2 or more after the suspension polymerization step. It is considered that this is because the use of a nonionic emulsifier having an HLB value of 6 to 14 causes a kind of film formation inhibition on the surface layer of the resin particles.

The amount of the nonionic emulsifier having an HLB value of 6 to 14 is preferably 0.1 to 20 parts by mass with respect to 100 parts by mass in total of the monofunctional monomer and the polyfunctional monomer described above. By adjusting the amount of the nonionic emulsifier having an HLB value of 6 to 14 within the above range, it is possible to adjust the average number of through-holes and the size of the through-holes, and thereby, of the resin particles. It is also possible to adjust the time required to remove the hydrophobic liquid contained therein. The amount of the nonionic emulsifier having an HLB value of 6 to 14 is more preferably 0.5 parts by mass or more, further preferably 1 part by mass or more, and particularly preferably 2 parts by mass or more. The amount of the nonionic emulsifier used is more preferably 15 parts by mass or less, further preferably 10 parts by mass or less, and particularly preferably 6 parts by mass or less.

In the method for producing a resin dispersion, it is preferable to use a dispersant in addition to a nonionic emulsifier having an HLB value of 6 to 14 when performing mixing and dispersion. Examples of the dispersant include polymer dispersants and emulsifiers other than nonionic emulsifiers having an HLB value of 6 to 14 (hereinafter, may be referred to as "other emulsifiers"). One or more of these dispersants can be used. The amount of the dispersant used is preferably 0.1 to 20 parts by mass, more preferably 0.5 to 10 parts by mass, based on 100 parts by mass of the total of the monofunctional monomer and the polyfunctional monomer described above. It is preferably 1 to 8 parts by mass, and more preferably 1 to 8 parts by mass.

Examples of the polymer dispersant include polyvinyl alcohol; polyvinylpyrrolidone; polycarboxylic acids such as polyacrylic acid; celluloses such as hydroxyethyl cellulose and carboxymethyl cellulose; and the like.

Examples of other emulsifiers include those having an HLB value outside the range of 6 to 14, anionic emulsifiers, cationic emulsifiers, and zwitterionic emulsifiers among the above-mentioned specific examples of nonionic emulsifiers. Of these, anionic emulsifiers are preferred.

Examples of the anionic emulsifier include fatty acid salts such as sodium stearate; alkyl sulfates such as sodium lauryl sulfate; polyoxyalkylene alkyl ether sulfates such as polyoxyethylene alkyl ether sulfate; sodium dodecylbenzene sulfonate and the like. Alkylbenzene sulfonate; sodium dialkylsulfosuccinate; sodium alkyldiphenyl ether disulfonate; and reactive anionic emulsifiers such as polyoxyalkylene alkenyl ether ammonium sulfate and polyoxyethylene styrenated propenylphenyl ether ammonium sulfate.

Examples of the cationic emulsifier include alkyltrimethylammonium salt, alkyltriethylammonium salt, dialkyldimethylammonium salt, dialkyldiethylammonium salt, N-polyoxyalkylene-N, N, N-trialkylammonium salt and the like. it can. Examples of the zwitterionic emulsifier include alkyldimethylamine oxide and alkylcarboxybetaine.

By performing mixed dispersion, monomer droplets (oil phase droplets) containing a monofunctional monomer and a polyfunctional monomer can be formed in an aqueous medium (aqueous phase) to obtain a preemulsion. Various emulsification dispersers can be used for mixing and dispersing. Examples of the emulsification / dispersion machine include a propeller mixer, a homomixer, a rotary stirring type emulsifier such as a homodisper, an ultrasonic homogenizer, and a pressurized homogenizer.

By performing suspension polymerization using the above preemulsion, resin particles containing a surface layer containing structural units derived from monofunctional monomers and polyfunctional monomers, and a hydrophobic liquid surrounded by the surface layer and contained therein. Can be obtained in an aqueous medium. The polymerization temperature at the time of carrying out suspension polymerization is preferably 20 to 100 ° C, more preferably 40 to 90 ° C. The polymerization time is preferably 1 to 15 hours.

In producing the resin particles as described above, the mixed liquid for mixing and dispersing includes the hydrophobic liquid and other substances such as the above-mentioned substances for sustained release (for example, fragrance, antibacterial agent, and removal). Bacterial agents, deodorants, cleaning agents, pharmaceuticals, pesticides, heat storage materials, ultraviolet absorbers, dyes, pigments, etc.) may be mixed. Thereby, it is also possible to obtain microcapsule type resin particles in which a liquid composition containing a hydrophobic liquid and other substances is encapsulated inside the resin particles.

In the method for producing the resin dispersion liquid, after obtaining the resin particles as described above, the hydrophobic liquid surrounded by the surface layer and contained therein may be replaced with another liquid. As a result, resin particles containing the surface layer and other liquids enclosed and contained in the surface layer can be obtained. In this case, it is preferable that almost all of the hydrophobic liquid contained inside the resin particles is replaced with another liquid, but a part of the hydrophobic liquid may be replaced with another liquid. After the replacement, a part of the hydrophobic liquid may remain inside the resin particles together with other liquids.

As a method of replacing the hydrophobic liquid contained inside the resin particles with an aqueous medium, for example, a method of depressurizing the obtained resin dispersion and vaporizing the hydrophobic liquid contained inside the resin particles. It is preferable to adopt (a reduced pressure treatment method), a method of vaporizing the contained hydrophobic liquid by heating (distillation treatment method), or the like. By removing the hydrophobic liquid contained inside the resin particles in the resin dispersion as in these methods, the hydrophobic liquid contained inside the resin particles can be replaced with an aqueous medium. It is possible to obtain resin particles in which an aqueous medium is contained therein. From the viewpoint that this method can be adopted, the other liquid to be replaced from the hydrophobic liquid preferably contains an aqueous medium, and more preferably water.

When replacing the hydrophobic liquid contained inside the resin particles with a liquid other than the aqueous medium, for example, the following method can be adopted. First, as will be described later, the resin dispersion is solid-liquid separated to obtain resin particles separated from an aqueous medium, and then the hydrophobic liquid contained inside the resin particles is subjected to the above-mentioned decompression treatment method or distillation. It can be removed by a treatment method. As a result, resin particles (hollow resin particles) containing gas (air) can be obtained. Then, by adding the resin particles to the other liquid, it is possible to enclose the other liquid inside the resin particles. As the other liquid, a liquid composition containing water or another substance such as the above-mentioned substance for sustained release can be used. When a liquid composition containing another substance is used as the other liquid, the substance and the resin particles are subjected to conditions of stirring, ultrasonic waves, or vibration so that the substance can easily enter the inside of the resin particles. It is preferable to bring them into contact with each other. A resin dispersion can be obtained by encapsulating another liquid inside the resin particles and then returning the resin particles to the aqueous medium again.

After obtaining the resin dispersion, it is preferable to add a neutralizing agent to the resin dispersion to neutralize the resin dispersion. Examples of the neutralizing agent include alkali metal compounds such as sodium hydroxide and potassium hydroxide; alkaline earth metal compounds such as calcium hydroxide and calcium carbonate; ammonia; monomethylamine, dimethylamine, trimethylamine, monoethylamine, diethylamine, and the like. Examples thereof include organic amines such as triethylamine, monoethanolamine, diethanolamine, triethanolamine, ethylenediamine, and diethylenetriamine. One or more of these neutralizers may be used. The neutralizer is preferably used in the form of an aqueous solution.

The pH of the resin dispersion is preferably 6.0 to 10.0, more preferably 6.5 to 9.5, and even more preferably 7.0 to 9.0. In the present specification, the pH of the resin dispersion liquid can take a value measured according to the provisions of JIS K6833-1: 2008, and is a value at 25 ° C.

As described above, a resin dispersion liquid containing resin particles containing a hydrophobic liquid; or resin particles containing another liquid; can be obtained. Further, by solid-liquid separation of these resin dispersions by a method such as filtration or centrifugation, liquid-encapsulated resin particles in a powdery, wet, or slurry state can be obtained. Further, by drying the liquid-encapsulated resin particles, it is also possible to obtain gas (air) -encapsulated resin particles in a dry powder state from which the liquid inside has been removed.

As described in detail above, the resin dispersion of one embodiment of the present invention suspend-polymerizes a monofunctional monomer and a polyfunctional monomer in an aqueous medium in the presence of a nonionic emulsifier having an HLB value of 6 to 14. Can be obtained by The resin particles contained in the resin dispersion liquid include a surface layer and a liquid enclosed in the surface layer, and the surface layer contains a weight containing structural units derived from each of the monofunctional monomer and the polyfunctional monomer. It is formed from coalescence and has an average number of through holes of 2 or more. Therefore, according to this resin dispersion, the ratio of the internal volume to the volume of the resin particles is high, and it is possible to sufficiently enclose the liquid inside the resin particles, but it is possible to remove the liquid contained therein. Easy to replace with other liquids. Therefore, this resin dispersion can be expected to be used in various applications such as heat-sensitive recording media, paints, inks, coating agents, adhesives, and adhesives.

Further, since the resin particles contained in the above-mentioned resin dispersion have an average number of through holes of 2 or more in the surface layer, the inside of the resin particles is unlikely to become a negative pressure and is not easily crushed, or is contained therein. The expression of the sustained release function of the liquid can also be expected. For example, by encapsulating a substance for sustained release such as a fragrance, an antibacterial agent, a disinfectant, a deodorant, a cleaning agent, a medicine, or a pesticide inside the resin particles, the sustained release property of the substance can be improved. Can be expected to show. Therefore, the resin particles can be expected to be used as, for example, sustained-release microcapsules containing various substances for sustained-release as described above.

As described above, the present technology can have the following configurations, for example.
[1] A resin dispersion containing an aqueous medium and resin particles dispersed in the aqueous medium, wherein the resin dispersion further contains a nonionic emulsifier having an HLB value of 6 to 14. The resin particles were formed from a polymer containing a structural unit derived from a monofunctional monomer having one polymerizable unsaturated bond and a structural unit derived from a polyfunctional monomer having two or more polymerizable unsaturated bonds. A resin dispersion liquid containing a surface layer and a liquid enclosed in the surface layer, and the surface layer has an average of two or more through holes per resin particle.
[2] The resin dispersion liquid according to the above [1], wherein the surface layer has an average of 3 or more through holes per resin particle.
[3] The resin dispersion liquid according to the above [1] or [2], wherein the through hole is a through hole having a length of the longest portion in the through hole of 0.1 μm or more.
[4] The resin dispersion liquid according to any one of the above [1] to [3], wherein the number average particle diameter of the resin particles is 0.5 to 30 μm.
[5] The resin dispersion liquid according to any one of the above [1] to [4], wherein the ratio of the internal volume in which the liquid is contained by the surface layer to the volume of the resin particles is 60 to 95%.
[6] The content of the nonionic emulsifier is any one of the above [1] to [5], which is 0.1 to 20 parts by mass with respect to 100 parts by mass in total of the monofunctional monomer and the polyfunctional monomer. The resin dispersion liquid according to.
[7] The content (mass) of the structural unit derived from the polyfunctional monomer with respect to the total content (mass%) of the structural unit derived from the monofunctional monomer and the structural unit derived from the polyfunctional monomer in the resin particles. The resin dispersion liquid according to any one of the above [1] to [6], wherein the ratio of%) is 30 to 90%.
[8] The above-mentioned [1] to [7], wherein the monofunctional monomer contains at least one selected from the group consisting of a (meth) acrylic acid ester and an ethylenically unsaturated carboxylic acid monomer. Resin dispersion.
[9] The above-mentioned [1] to [8], wherein the polyfunctional monomer contains at least one selected from the group consisting of ethylene glycol di (meth) acrylate and trimethylolpropane tri (meth) acrylate. Resin dispersion.
[10] The resin dispersion liquid according to any one of the above [1] to [9], wherein the liquid contains water.
[11] Liquid-encapsulated resin particles obtained from the resin dispersion liquid according to any one of the above [1] to [10].
[12] At least an aqueous medium, a monofunctional monomer having one polymerizable unsaturated bond, a polyfunctional monomer having two or more polymerizable unsaturated bonds, a nonionic emulsifier having an HLB value of 6 to 14, and a hydrophobic liquid. , And an oil-soluble polymerization initiator are mixed and dispersed, and suspension polymerization is carried out to obtain a polymer containing a structural unit derived from the monofunctional monomer and a structural unit derived from the polyfunctional monomer in the aqueous medium. A method for producing a resin dispersion liquid, which comprises obtaining resin particles containing the formed surface layer and the hydrophobic liquid enclosed in the surface layer.
[13] After obtaining the resin particles, the hydrophobic liquid is replaced with another liquid to obtain resin particles containing the surface layer and the other liquid surrounded by and contained in the surface layer. The method for producing a resin dispersion liquid according to the above [12].
[14] The method for producing a resin dispersion liquid according to the above [13], wherein the other liquid contains water.
[15] In the mixed dispersion, the monofunctional monomer, the polyfunctional monomer, the hydrophobic liquid, and the oil-soluble polymerization initiator are mixed to obtain an oil phase mixed solution; the aqueous medium and the nonionic emulsifier. The resin according to any one of [12] to [14] above, which comprises mixing to obtain an aqueous phase mixed solution; and mixing and dispersing the oil phase mixed solution and the aqueous phase mixed solution; Method for producing dispersion.
[16] The resin according to any one of [12] to [15] above, wherein 0.1 to 20 parts by mass of the nonionic emulsifier is used with respect to a total of 100 parts by mass of the monofunctional monomer and the polyfunctional monomer. Method for producing dispersion.

Hereinafter, further specific examples of the above-described embodiment will be described with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples.

<Manufacturing of resin dispersion>
(Example 1)
10 parts by mass of methyl methacrylate and 20 parts by mass of methacrylate as a monofunctional monomer; 70 parts by mass of ethylene glycol dimethacrylate as a polyfunctional monomer; 2,2'-azobis (2,4-dimethylvaleronitrile) 1 as an oil-soluble polymerization initiator .5 parts by mass; 400 parts by mass of cyclohexane was mixed as a hydrophobic liquid to prepare an oil phase mixture.

In 900 parts by mass of ion-exchanged water, 5 parts by mass of polyoxyethylene polycyclic phenyl ether as a nonionic emulsifier having an HLB value of 9.2 (trade name "Newcol 704", 5 parts by mass, manufactured by Nippon Emulsifier Co., Ltd .; active ingredient 100% by mass), and 2 parts by mass of polyoxyethylene alkyl ether sodium sulfate which is an anionic emulsifier as a dispersant (trade name "Latemuru WX" 7.7 parts by mass, manufactured by Kao Co., Ltd .; active ingredient 26.0% by mass) Was mixed to prepare an aqueous phase mixture.

The prepared oil phase mixture and aqueous phase mixture were mixed and mixed and dispersed using a homodisper to prepare an emulsified pre-emulsion. A four-necked separable flask equipped with a stirrer, a thermometer, a cooler, and a dropping funnel is charged with the entire amount of the above preemulsion, and the internal temperature is raised to 65 ° C. while stirring, and suspension polymerization is carried out for 3 hours. Was done. By this polymerization reaction, a resin dispersion containing cyclohexane-encapsulating hydrophobic liquid-encapsulating resin particles was obtained.

After that, while maintaining the internal temperature at 65 ° C., the pressure inside the flask was reduced to -0.05 MPa, and by maintaining that state, the cyclohexane inside the particles was vaporized and distilled off, and at the same time, water was added to the inside of the resin particles. It was replaced. This operation was continued until the distillation of cyclohexane stopped.

After cooling the obtained resin dispersion, 6 parts by mass of aqueous ammonia having a concentration of 25% by mass was added to neutralize the resin dispersion. After adjusting the pH of the resin dispersion, the mixture was filtered using a 120-mesh filter cloth to obtain a resin dispersion containing water-encapsulated resin particles.

(Characteristics of Resin Dispersion Solution Obtained in Example 1)
The resin dispersion obtained in Example 1 above was measured at 25 ° C. according to the provisions of JIS K6833-1: 2008, and found that the pH was 8.5 and the non-volatile content (solid content) was 10. It was 0% by mass and had a viscosity of 300 mPa · s.

(Examples 2 to 7)
The types and amounts of the monofunctional monomer, polyfunctional monomer, oil-soluble polymerization initiator, hydrophobic liquid, nonionic emulsifier, and dispersant used in Example 1 were changed as shown in Table 1-1. In the example in which toluene was used as the hydrophobic liquid, the resin containing water-encapsulated resin particles was obtained in the same manner as in Example 1 except that the temperature at the time of suspension polymerization and the temperature at the time of reduced pressure were changed. A dispersion was obtained. For Examples 2, 5 and 6 in which toluene was used instead of cyclohexane used in Example 1 as the hydrophobic liquid, the temperature during suspension polymerization was set to 80 ° C., and after the polymerization, the pressure was reduced to reduce the toluene inside the particles. The temperature at which the above was removed was set to 85 ° C. Although the boiling point of toluene is about 110 ° C., it can be distilled off because it azeotropes with water even under the above temperature conditions.

(Comparative Examples 1 and 2)
The types and / or amounts of the monofunctional monomer, polyfunctional monomer, and oil-soluble polymerization initiator used in Example 1 were changed as shown in Table 1-2, and the oil phase mixture was further added as an oil or fat. Himashi oil (trade name "Himashi oil", manufactured by Hayashi Junyaku Kogyo Co., Ltd.) was used, the amount of ion-exchanged water used was 1100 parts by mass, and no monomeric emulsifier was used in the aqueous phase mixture. A resin dispersion containing water-encapsulated resin particles was obtained in the same manner as in Example 1 except for the above.

(Comparative Examples 3 to 5)
The types and / or amounts of the monofunctional monomer, polyfunctional monomer, oil-soluble polymerization initiator, hydrophobic liquid, and dispersant used in Example 1 were changed as shown in Table 1-2, HLB. Other emulsifiers were used instead of the nonionic emulsifiers having a value of 6 to 14, and in Comparative Example 3, the temperature at the time of suspension polymerization and the temperature at the time of reduced pressure were the same as those of Examples 2, 5 and 6 described above. A resin dispersion liquid containing water-encapsulated resin particles was obtained in the same manner as in Example 1 except for the above.

Among the materials used in the above Examples and Comparative Examples, those shown in Tables 1-1 and 1-2 (hereinafter, these are collectively referred to as "Table 1") are as follows.
(Nonionic emulsifier)
-Nonionic emulsifier with an HLB value of 3.4: sorbitan trioleate (trade name "Newcol 3-80", manufactured by Nippon Emulsifier Co., Ltd .; 100% by mass of active ingredient)
-Nonionic emulsifier with HLB value of 6.4: Sorbitan monooleate (trade name "Newcol 80", manufactured by Nippon Emulsifier Co., Ltd .; 100% by mass of active ingredient)
-Nonionic emulsifier with an HLB value of 9.2: polyoxyethylene polycyclic phenyl ether (trade name "Newcol 704", manufactured by Nippon Emulsifier Co., Ltd .; 100% by mass of active ingredient)
Nonionic emulsifier with HLB value of 12.3: Polyoxyethylene polycyclic phenyl ether (trade name "Newcol 707", manufactured by Nippon Emulsifier Co., Ltd .; 100% by mass of active ingredient)
Nonionic emulsifier with HLB value of 16.6: Polyoxyethylene polycyclic phenyl ether (trade name "Newcol 723", manufactured by Nippon Emulsifier Co., Ltd .; 100% by mass of active ingredient)
(Dispersant)
-Anionic emulsifier: Polyoxyethylene alkyl ether sodium sulfate (trade name "Latemuru WX", manufactured by Kao Corporation; active ingredient 26.0% by mass)
-Polyvinyl alcohol (brand name "PVA-22-88", manufactured by Kuraray Co., Ltd.)

<Evaluation>
With respect to the resin dispersions obtained in each of the above Examples and Comparative Examples, the distillation time of the hydrophobic liquid, the specific gravity of the liquid after the distillation of the hydrophobic liquid, the number average particle diameter, and the resin particles were determined by the methods described below. The shape, the average number of through holes, the ratio of the internal volume to the volume of the resin particles, and the strength of the resin particles (surface layer) were evaluated.

(Distillation time of hydrophobic liquid)
In the resin dispersion liquid containing water-encapsulated resin particles prepared in each Example and Comparative Example, the resin dispersion liquid containing the hydrophobic liquid-encapsulated resin particles in the previous step of replacing the inside of the resin particles with water was performed. The time (minutes) required for distillation of the hydrophobic liquid (cyclohexane or toluene) by vaporization was recorded. The vaporized hydrophobic liquid is cooled by the cooler provided in the four-necked separable flask used for producing the resin dispersion, and is stored in the lower part of the cooler. Distillation (progress and stop) of the hydrophobic liquid was confirmed by observing. Further, the method for confirming whether or not the hydrophobic liquid contained in the resin particles was completely distilled off was performed by measuring the liquid specific gravity described below.

(Specific gravity of the liquid after distilling off the hydrophobic liquid)
The liquid specific gravity of the resin dispersion liquid after distilling off the hydrophobic liquid contained in the resin particles was measured. A resin dispersion having a solid content of 10% by mass, which is composed of water and resin particles, has a specific gravity of about 1.02. On the other hand, since the hydrophobic liquid remains inside the resin particles, when the hydrophobic liquid remains in the resin dispersion liquid, the specific gravity of the liquid is less than 1.01. Therefore, when the measured value of the liquid specific gravity is 1.01 or more, it can be evaluated that the hydrophobic liquid is completely distilled off.

(Number average particle size)
The number of resin dispersions containing water-encapsulated resin particles produced in each Example and Comparative Example was measured using a laser diffraction type particle size distribution measuring device (trade name "SALD-7100", manufactured by Shimadzu Corporation). In the standard particle size distribution, the particle size at which the cumulative frequency of the number standard of the equivalent sphere diameter was 50% was measured as the number average particle size.

(Shape of resin particles and average number of through holes)
The shape of the resin particles and the average number of through holes were confirmed in the resin dispersion liquid containing the water-encapsulated resin particles prepared in each Example and Comparative Example. Specifically, a resin dispersion containing water-encapsulated resin particles is dried to prepare a dried resin particle sample, and then the surface of the dried resin particle sample is surfaced with a scanning electron microscope (SEM; trade name "JSM-". The shape of the resin particles was confirmed by observing with "IT500HR", manufactured by Nippon Denshi Co., Ltd.). In addition, 10 particles are randomly selected from the obtained SEM image, the number of through holes on the surface of the selected particles is counted, and the same number of through holes are present in the portion not appearing in the SEM image. The value obtained by doubling the count number was taken as the total number of through holes, and the value obtained by dividing the total number of through holes by the number of particles (10 particles) was taken as the average number of through holes. The count of the through holes was made for the through holes having the length of the longest portion in the through holes of 0.1 μm or more. Of the SEM images obtained above, the SEM images obtained in Examples 1 and 4 to 6 are shown in FIGS. 1A to 1D, and the SEM images obtained in Comparative Example 3 are shown in FIG. 1E.

(Ratio of internal volume to volume of resin particles)
After preparing a resin coating film using the resin dispersion liquid containing the water-encapsulated resin particles prepared in each Example and Comparative Example, the cross section of the resin coating film is observed by SEM to obtain the resin particles. The presence of the inside and the surface layer was confirmed, and the ratio of the internal volume to the volume of the resin particles was determined. Specifically, it is as follows. The resin dispersion and styrene-butadiene rubber (SBR) latex (trade name "SB latex L-7063", manufactured by Asahi Kasei Co., Ltd .; solid content 48% by mass) have a solid content mass ratio of 2 (resin dispersion): A coating liquid was prepared by mixing with a composition of 1 (SBR latex). This coating liquid was applied to a polyethylene terephthalate (PET) film so that the dry film thickness was 50 μm, and dried to prepare a resin coating film in which resin particles were dispersed. This coating film was cut with a razor, and the cross section thereof was observed with the above SEM. After randomly selecting 10 particles from the obtained SEM image, the thickness of the surface layer for each selected particle was measured at a total of 4 points, one on each of the top, bottom, left and right, and the average was calculated. The average value in was taken as the thickness of the surface layer. From the thickness t of the surface layer and the measured value D of the number average particle diameter described above, [(D / 2-t) ³ / (D / 2) ³ ] × 100 (%) is used with respect to the volume of the resin particles. (Ratio of internal volume) was calculated. Of the SEM images obtained above, the SEM image obtained in Example 1 is shown in FIG.

(Surface strength)
A resin coating film was produced on the PET film in the same manner as the resin coating film described in the above evaluation of "ratio of internal volume to volume of resin particles". A pressure of 100 MPa was applied from above the surface of the resin coating film using a press machine (equipment name "MP-WNL", manufactured by Toyo Seiki Seisakusho Co., Ltd.). The resin coating film after pressing was cut with a razor, and the cross section thereof was observed by SEM. By confirming the state of the resin particles in the obtained SEM image, the strength of the resin particles (surface layer) was evaluated according to the following evaluation criteria. Of the SEM images obtained above, the SEM image obtained in Example 1 is shown in FIG. 3A, and the SEM image obtained in Comparative Example 5 is shown in FIG. 3B.
A: Almost all of the observed resin particles maintain a spherical shape.
B: Some of the observed resin particles have a crushed spherical shape, and more than half maintain the spherical shape.
C: The spherical shape of more than half of the observed resin particles is crushed.
D: The spherical shape is crushed in almost all of the observed resin particles.

Table 1 shows the materials used for producing the resin dispersions of the above Examples and Comparative Examples, their amounts used, and the evaluation results of each resin dispersion.

From the above results, the resin dispersion liquid containing the water-encapsulated resin particles obtained in each example includes a surface layer on which a monofunctional monomer and a polyfunctional monomer are polymerized, and water enclosed in the surface layer. It was confirmed that the resin dispersion liquid contained resin particles containing. Further, it was confirmed that the resin particles in the resin dispersion liquid obtained in each example had an average of 3 or more through holes per resin particle in the surface layer thereof. Further, the resin particles in the resin dispersion obtained in each example have a spherical shape close to a true sphere, the ratio of the internal volume to the volume of the resin particles is high, and the resin particles are contained inside before being replaced with water. It was confirmed that it was easy to remove the hydrophobic liquid.

On the other hand, the resin dispersions obtained in Comparative Examples 1 to 5 did not use a nonionic emulsifier having an HLB value of 6 to 14 for producing the resin particles, so that the average number of through holes of the resin particles was less than 2. there were. Therefore, it is considered that when the hydrophobic liquid contained inside the resin particles was removed by the reduced pressure treatment and replaced with water, the resin particles were crushed by negative pressure. Since the resin particles in these comparative examples could not maintain the spherical shape, the result was that the ratio of the internal volume to the volume of the resin particles, which was calculated on the premise of the volume of the sphere, could not be obtained. Further, in the resin dispersions obtained in Comparative Examples 1 to 5, the specific gravity of the liquid after distilling off the hydrophobic liquid was less than 1.01, so that the hydrophobic liquid remained inside the resin particles. Is recognized. Since the average number of through-holes of the resin particles in the resin dispersions of these comparative examples was less than 2, it was confirmed that it was difficult to remove the hydrophobic liquid contained inside the resin particles.

Claims (17)

A resin dispersion liquid containing an aqueous medium and resin particles dispersed in the aqueous medium.
The resin dispersion further contains a nonionic emulsifier having an HLB value of 6 to 14.
The resin particles are formed from a polymer containing a structural unit derived from a monofunctional monomer having one polymerizable unsaturated bond and a structural unit derived from a polyfunctional monomer having two or more polymerizable unsaturated bonds. Containing the surface layer and the liquid contained in the surface layer.
The surface layer may have a average 2 or more through-holes per one said resin particles,
A resin dispersion liquid in which the ratio of the internal volume in which the liquid is contained by the surface layer to the volume of the resin particles is 60 to 95% . The resin dispersion liquid according to claim 1, wherein the number average particle diameter of the resin particles is 0.5 to 30 μm. A resin dispersion liquid containing an aqueous medium and resin particles dispersed in the aqueous medium.
The resin dispersion further contains a nonionic emulsifier having an HLB value of 6 to 14.
The resin particles are formed from a polymer containing a structural unit derived from a monofunctional monomer having one polymerizable unsaturated bond and a structural unit derived from a polyfunctional monomer having two or more polymerizable unsaturated bonds. Containing the surface layer and the liquid contained in the surface layer.
The surface layer may have a average 2 or more through-holes per one said resin particles,
A resin dispersion having an average particle size of 0.5 to 30 μm . The content (% by mass) of the structural unit derived from the polyfunctional monomer with respect to the total content (mass%) of the structural unit derived from the monofunctional monomer and the structural unit derived from the polyfunctional monomer in the resin particles. The resin dispersion according to any one of claims 1 to 3, wherein the ratio is 30 to 90%. A resin dispersion liquid containing an aqueous medium and resin particles dispersed in the aqueous medium.
The resin dispersion further contains a nonionic emulsifier having an HLB value of 6 to 14.
The resin particles are formed from a polymer containing a structural unit derived from a monofunctional monomer having one polymerizable unsaturated bond and a structural unit derived from a polyfunctional monomer having two or more polymerizable unsaturated bonds. Containing the surface layer and the liquid contained in the surface layer.
The surface layer may have a average 2 or more through-holes per one said resin particles,
The content (% by mass) of the structural unit derived from the polyfunctional monomer with respect to the total content (mass%) of the structural unit derived from the monofunctional monomer and the structural unit derived from the polyfunctional monomer in the resin particles. A resin dispersion having a ratio of 30 to 90% . The resin dispersion liquid according to any one of claims 1 to 5, wherein the surface layer has an average of 3 or more through holes per resin particle. The resin dispersion liquid according to any one of claims 1 to 6, wherein the through hole is a through hole having a length of the longest portion in the through hole of 0.1 μm or more. The resin according to any one of claims 1 to 7 , wherein the content of the nonionic emulsifier is 0.1 to 20 parts by mass with respect to 100 parts by mass in total of the monofunctional monomer and the polyfunctional monomer. Dispersion solution. The resin dispersion according to any one of claims 1 to 8 , wherein the monofunctional monomer contains at least one selected from the group consisting of a (meth) acrylic acid ester and an ethylenically unsaturated carboxylic acid monomer. The resin dispersion according to any one of claims 1 to 9 , wherein the polyfunctional monomer contains at least one selected from the group consisting of ethylene glycol di (meth) acrylate and trimethylolpropane tri (meth) acrylate. The resin dispersion liquid according to any one of claims 1 to 10 , wherein the liquid contains water. A liquid-encapsulating type resin particle obtained from the resin dispersion liquid according to any one of claims 1 to 11 . At least an aqueous medium, a monofunctional monomer with one polymerizable unsaturated bond, a polyfunctional monomer with two or more polymerizable unsaturated bonds, a nonionic emulsifier with an HLB value of 6-14, a hydrophobic liquid, and an oil. By mixing and dispersing a soluble polymerization initiator and performing suspension polymerization, it was formed from a polymer containing a structural unit derived from the monofunctional monomer and a structural unit derived from the polyfunctional monomer in the aqueous medium. A method for producing a resin dispersion liquid, which comprises obtaining resin particles containing a surface layer and the hydrophobic liquid enclosed in the surface layer. A claim comprising obtaining the resin particles and then substituting the hydrophobic liquid with another liquid to obtain the resin particles containing the surface layer and the other liquid enclosed in the surface layer. Item 3. The method for producing a resin dispersion liquid according to Item 13 . The method for producing a resin dispersion according to claim 14 , wherein the other liquid contains water. In the mixed dispersion, the monofunctional monomer, the polyfunctional monomer, the hydrophobic liquid, and the oil-soluble polymerization initiator are mixed to obtain an oil phase mixed solution;
Mixing the aqueous medium and the nonionic emulsifier to obtain an aqueous phase mixture; and mixing and dispersing the oil phase mixture and the aqueous phase mixture;
The method for producing a resin dispersion according to any one of claims 13 to 15 . The production of the resin dispersion according to any one of claims 13 to 16 , wherein 0.1 to 20 parts by mass of the nonionic emulsifier is used with respect to 100 parts by mass of the monofunctional monomer and the polyfunctional monomer in total. Method.