JP2018095737A - Bowl-shaped hollow polymer particles and production method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide bowl-shaped hollow polymer particles having excellent homogeneous light diffusibility and adiabaticity, further, excellent concealment property to an undercoat.SOLUTION: When reflective light intensity is measured with a three-dimensional varied angle photometer by irradiating light on bowl-shaped hollow polymer particles at an incident angle of 60°, bowl-shaped hollow polymer particles have a difference (R2-R1) between reflective light intensity (R2)(%) at the measurement angle of 60°and the reflective light intensity (R1)(%) at 0°of 10% or larger.SELECTED DRAWING: None

Description

  The present invention relates to vertical hollow polymer particles, and in particular, relates to vertical hollow polymer particles that are excellent in uniform light diffusibility, heat insulation, etc., and also have excellent concealability with respect to the substrate, and a method for producing the same. is there.

Conventionally, polymer particles have been widely used as light diffusing agents for light reflecting materials such as paints and cosmetics, light diffusing plates for liquid crystal backlights, and projector screens. It is also known to use, as polymer particles, hollow polymer particles having a hollow portion inside and having improved light diffusibility due to a difference in refractive index from the polymer layer. Such hollow polymer particles are useful as microcapsules for imparting heat insulating properties, sound insulating properties, impact resistance, etc., and encapsulating various substances, and are used in various fields.
In recent years, polymer particles having uniform light diffusibility have been demanded for such polymer particles in the field of paints and cosmetics. By uniformly diffusing light, when a paint or cosmetic containing polymer particles is applied, there is no more unevenness and a good film appearance can be obtained.

  For example, Patent Document 1 discloses suspension polymerization of a mixture of a (meth) acrylic acid ester-styrene copolymer and a (meth) acrylic acid ester containing a crosslinkable vinyl monomer in the presence of an aqueous medium. A single hollow particle provided with an inner polymer layer and an outer polymer layer is disclosed, and a forming plate obtained using this is described as having high haze and good light diffusibility. Yes.

  Patent Document 2 discloses porous hollow polymer particles having a plurality of pores inside the particles, the outer surfaces of the particles and the inner surfaces of the particles being coated with polyvinyl alcohol, It is described that it is excellent in light diffusibility, liquid absorbability, body sensibility, solvent resistance and mechanical strength.

JP 2009-67946 A JP 2009-120806 A

  However, although the single hollow particle disclosed in Patent Document 1 has light diffusibility, the particle surface is a spherical particle with a smooth particle surface and does not have uniform light diffusibility.

  Further, it is described that the porous hollow polymer particles disclosed in Patent Document 2 can cope with any angle without variation in luminance distribution due to a difference in angle with respect to the light exit surface. However, the inside of the polymer particles is porous and does not have a single hollow portion, so that the light diffusibility may be insufficient. Moreover, it is inferior in heat-shielding property etc., and furthermore, it is difficult to use as a microcapsule for encapsulating various substances, particularly liquid substances, as compared with polymer particles having a single hollow portion.

  In recent years, vertical hollow polymer particles in which the hollow polymer particles are formed into a vertical shape have been studied from the request of light diffusibility and particle adhesion. In particular, in the cosmetics field, there is a high demand for concealment of the base.

  Accordingly, an object of the present invention is to provide vertical hollow polymer particles that are excellent in uniform light diffusibility, heat insulation, and the like, and also have excellent concealment properties with respect to the background.

  However, as a result of intensive studies in view of such circumstances, the present inventors have used a three-dimensional goniophotometer to measure the intensity of reflected light when light is irradiated on the vertical hollow polymer particles at an incident angle of 60 °. In addition, by making a vertical hollow polymer particle having a larger difference (R2−R1) between reflected light intensity (R2) (%) at a measurement angle of 60 ° and reflected light intensity (R1) (%) at 0 °, The inventors have found that the above object can be achieved and completed the present invention.

  That is, the gist of the present invention is that when using a three-dimensional goniophotometer to measure the intensity of reflected light when the vertical hollow polymer particles are irradiated with light at an incident angle of 60 °, the reflected light at a measurement angle of 60 ° is measured. The present invention relates to vertical hollow polymer particles characterized in that the difference (R2−R1) between intensity (R2) (%) and reflected light intensity (R1) (%) at 0 ° is 10% or more.

  Furthermore, in this invention, the manufacturing method of the said vertical hollow polymer particle is also provided.

  In the present invention, in suspension polymerization, by using a relatively large amount of a specific solvent having a relatively low specific gravity as a solvent for dissolving the monomer component, a polymer and a solvent obtained by polymerizing the monomer component at the initial stage of polymerization Phase-separated and deformed in a state where the solvent is stably present inside the particles through polymer polymerization, so that the hollow hollow particles with a polymer layer in the outer shell and voids inside are efficiently and stable. Can be manufactured automatically.

  The vertical hollow polymer particles of the present invention are excellent in uniform light diffusibility, heat insulation, and the like, and also have excellent concealability with respect to the base, and are suitably used in various fields such as cosmetics and paints.

It is a SEM photograph of typical vertical hollow polymer particles. It is a TEM photograph of a section of typical vertical hollow polymer particles. It is a TEM photograph of a section of typical vertical hollow polymer particles. It is a graph which shows the reflected light intensity in each measurement angle of the polymer particle of an Example and a comparative example.

Hereinafter, the present invention will be described in detail. In addition, description of the component requirements described below is an example of the embodiment of this invention, and is not limited to these content.
In the present invention, (meth) acryl means acryl or methacryl, (meth) acryloyl means acryloyl or methacryloyl, and (meth) acrylate means acrylate or methacrylate.

<Vertical hollow polymer particles>
The vertical hollow polymer particles of the present invention were measured using a three-dimensional goniophotometer when the reflected light intensity was measured when the vertical hollow polymer particles were irradiated with light at an incident angle of 60 °. The difference (R2−R1) between the reflected light intensity (R2) (%) and the reflected light intensity (R1) (%) at 0 ° is 10% or more, preferably 12% or more, Particularly preferably, it is 14% or more. The upper limit is usually 100%, preferably 99%.
If the difference (R2-R1) in the reflected light intensity is outside the above range, good optical characteristics are not exhibited, and the object of the present invention is not achieved.

The reflected light intensity in the present invention is a value obtained by measuring as follows.
First, a double-sided tape (3 cm x 5 cm) is affixed onto a commercially available black cardboard (5 cm x 5 cm), and polymethyl methacrylate particles (Soken Chemical Co., Ltd.) are placed on the adhesive surface opposite to the side coated with the cardboard. “SP-50” (shape: solid smooth particles) is applied and spread with a brush to obtain a sample for reference measurement of reflected light intensity.
Next, the vertical hollow polymer particles of the present invention to be measured are prepared, and a double-sided tape is applied on a commercially available black cardboard in the same manner as described above, and the vertical hollow polymer particles of the present invention are applied thereon. And a sample for measuring the reflected light intensity.
Using a three-dimensional variable angle photometer ("GP-200" manufactured by Murakami Color Research Laboratory Co., Ltd., using a halogen lamp), the incident angle is set to 60 °, and the reference measurement sample (smooth solid particles) is reflected. Adjust the HIGH VOLT so that the maximum SENSITIVITY when the light intensity is measured is 170, and the reflected light intensity of the target measurement sample is measured as the reflected light of the target measurement sample (saddle-shaped hollow polymer particle). Strength.

  In the present invention, from the viewpoint of optical characteristics, the reflected light intensity (R3) at a measurement angle of −55 ° is preferably 60% or less, particularly preferably 57% or less, more preferably 55% or less. It is. The lower limit is usually 0.1%, preferably 1%.

  The shape of the vertical hollow polymer particle of the present invention is, for example, as shown in FIG. 2, having an outer shell made of a polymer, having a single void inside the particle, and further deformed into a vertical shape. Is formed.

  As a monomer component constituting the polymer forming the outer shell, an ethylenically unsaturated compound having one ethylenically unsaturated group (hereinafter sometimes referred to as “monofunctional monomer”) or ethylenically unsaturated. And an ethylenically unsaturated compound having two or more groups (hereinafter sometimes referred to as “polyfunctional monomer”).

  Monofunctional monomers include, for example, styrenic monomers such as styrene and α-methylstyrene; vinyl formate, vinyl acetate, vinyl propionate, vinyl valerate, vinyl butyrate, vinyl isobutyrate, vinyl pivalate, vinyl caprate, laurin Vinyl ester monomers such as vinyl acidate, vinyl stearate, vinyl benzoate, vinyl versatate, vinyl 2-ethylhexanoate; methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, n-butyl ( (Meth) acrylate, i-butyl (meth) acrylate, t-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, cyclohexyl (meth) acrylate, lauryl (meth) acrylate, octyl (meth) acrylate, stearyl Aliphatic (meth) acrylate monomers such as (meth) acrylate; Alicyclic (meth) acrylate monomers such as isobornyl (meth) acrylate; Aromatic (meth) acrylate monomers such as phenoxy (meth) acrylate Halogen-based (meth) acrylate monomers such as (meth) acrylic acid trifluoroethyl; (meth) acrylonitrile, (meth) acrylamide, (meth) acrylic acid, glycidyl (meth) acrylate, 2-hydroxyethyl methacrylate, 2- Examples thereof include hydroxypropyl methacrylate, 2-acryloyloxyethyl phthalic acid, itaconic acid, fumaric acid, dimethylaminomethyl methacrylate and the like. These may be used alone or in combination of two or more.

Among these, it is preferable to contain a styrene monomer and / or a (meth) acrylate monomer from the viewpoint of the strength, flexibility, and handling of the vertical hollow polymer particles. It is 5 to 99.9% by weight, more preferably 20 to 99% by weight, and particularly preferably 40 to 99% by weight. When the content of the monofunctional monomer is too small, the shape of the polymer particles tends to be difficult to form a saddle shape, and when the content is too large, the hollow portion of the polymer particles tends to be difficult to maintain.
Among them, styrene monomers are styrene, and (meth) acrylate monomers are aliphatic (meth) acrylate monomers having 1 to 18, particularly 1 to 10, more preferably 1 to 6 carbon atoms of an alkyl group. Among them, methyl (meth) acrylate is particularly preferable.

Examples of the polyfunctional monomer include ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, 1,2-propylene glycol di (meth) acrylate, and 1,3-propylene. Such as glycol di (meth) acrylate, 1,4-butanediol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, trimethylolpropane di (meth) acrylate, etc. Di (meth) acrylate; tri (meth) acrylate such as trimethylolpropane tri (meth) acrylate, ethylene oxide modified trimethylolpropane tri (meth) acrylate, pentaerythritol tri (meth) acrylate Rate; monomer having two or more allyl groups such as divinylbenzene, diallyl phthalate, triallyl cyanurate, triallyl isocyanurate, triallyloxyethylene, diallyl maleate, tetraallyloxyethane; allyl (meth) acrylate, etc. It is done. These can be used alone or in combination of two or more.
Of these, divinylbenzene is preferably used from the viewpoint of polymerization stability.

  The content ratio of the polyfunctional monomer is preferably 0.1 to 50% by weight, more preferably 0.5 to 30% of the whole monomer component from the viewpoint of strength, flexibility, and handling of the vertical hollow polymer particles. % By weight, particularly preferably 1 to 15% by weight. If the content of the polyfunctional monomer is too small, the hollow part of the polymer particles tends to be difficult to maintain, and if it is too large, the shape of the polymer particles tends to be difficult to form a bowl shape.

  The monomer component can be suspension polymerized to produce the polymer particle suspension of the present invention. Further, the vertical hollow polymer particles of the present invention can be produced using the polymer particle suspension.

<Method for producing polymer particle suspension>
In the present invention, when manufacturing vertical hollow polymer particles, a polymer particle suspension obtained by suspension polymerization of a monomer solution containing a monomer component and a non-reactive solvent in an aqueous medium is used. It is preferable to carry out a step of removing the non-reactive solvent encapsulated in the polymer particles dispersed in the particle suspension.
The above-mentioned method for producing a polymer particle suspension is a suspension polymerization of a monomer solution containing a monomer component and a non-reactive solvent in an aqueous medium.

The non-reactive solvent is a solvent that does not polymerize with the monomer component, and in the method for producing a polymer particle suspension of the present invention, the non-reactive solvent has a volume density at 15 ° C. of 1.2 g / cm ³ or less. Is important, preferably 0.5 to 1.0 g / cm ³ , particularly preferably 0.6 to 0.9 g / cm ³ .
By using such a solvent, the polymer obtained by polymerizing the monomer component at the initial stage of polymerization and the solvent are phase-separated, and the solvent is stably present inside the particles throughout the polymer polymerization. It is possible to efficiently and stably produce vertical hollow polymer particles having void portions.

Examples of the solvent having a volume density at 15 ° C. of 1.2 g / cm ³ or less include polybutene, ethylene-α-olefin oligomer, α-olefin oil, liquid paraffin (0.9 g / cm ³ ) and liquid isoparaffin ( Liquid paraffins such as 0.8 g / cm ³ ), squalane (0.8 g / cm ³ ), glyceryl trimyristate, cetyl octanoate, tri (capryl, capric acid) glycerin, methylpolysiloxane (1.0 g / cm ³ ), cyclomethicone (1.0 g / cm ³ ), liquid lanolin (1.0 g / cm ³ ), lanolin fatty acid isopropyl, isopropyl myristate (0.9 g / cm ³ ), isopropyl palmitate (0.9 g / cm ^3), butyl stearate (0.9g / cm ^3), app thing Cannell oil (0.9g / m ^3), wheat germ oil, evening primrose oil (0.9g / cm ^3), squalene (0.9g / cm ^3), tocopherol acetate (1.0g / cm ^3), retinol palmitate (0.9 g / cm ³ ), avocado oil (0.9 g / cm ³ ), cottonseed oil, mink oil, castor oil, olive oil, jojoba oil (0.9 g / cm ³ ), various oils such as silicone oil, glycerides, triglycerides and naphthalene Examples thereof include oils, hydrocarbon-containing solvents, and mixtures thereof. The parenthesis is the volume density at 15 ° C.
Among them, it is preferable to use liquid paraffins from the viewpoint of low compatibility with an aqueous medium, excellent compatibility with the monomer component and the balance of specific gravity, and excellent polymerization stability of vertical hollow polymer particles, In particular, liquid isoparaffin is preferable.

  About the usage-amount of this non-reactive solvent, it is preferable that it is 85-200 weight part with respect to 100 weight part of monomer components, More preferably, it is 85-175 weight part, Most preferably, it is 85-150 weight part. If the amount of the solvent is too large, the strength of the polymer particles decreases, and it becomes difficult to maintain the hollow portions of the particles, and the uniform light diffusibility tends to decrease. If the amount is too small, the internal porosity decreases and the reflected light intensity decreases. Tend to increase, and the soft focus effect tends to decrease.

  Examples of the aqueous medium include water and alcoholic solvents mainly composed of water, preferably water.

  In the present invention, it is preferable to contain a dispersion stabilizer in the aqueous medium from the viewpoint of improving the suspension stability and improving the polymerization stability.

  Specific examples of the dispersion stabilizer include inorganic compounds; surfactants such as anionic surfactants, cationic surfactants, nonionic surfactants and zwitterionic surfactants; Functional polymers; and water-soluble oligomers.

  Examples of the inorganic compound include phosphates such as calcium phosphate, magnesium phosphate, aluminum phosphate, and zinc phosphate, pyrophosphates such as calcium pyrophosphate, magnesium pyrophosphate, aluminum pyrophosphate, and zinc pyrophosphate, calcium carbonate, Examples thereof include magnesium carbonate, calcium hydroxide, magnesium hydroxide, aluminum hydroxide, calcium metasilicate, calcium sulfate, barium sulfate, colloidal silica, talc, and tricalcium phosphate. These may be used alone or in combination of two or more.

Examples of the anionic surfactant include fatty acid oils such as sodium oleate and castor oil potassium soap, alkyl sulfate salts such as sodium lauryl sulfate and ammonium lauryl sulfate, alkylbenzene sulfonates such as sodium dodecylbenzenesulfonate, alkyl Naphthalene sulfonate, alkane sulfonate, dialkyl sulfosuccinate, alkyl phosphate ester salt, naphthalene sulfonate formalin condensate, polyoxyethylene alkylphenyl ether sulfate, polyoxyethylene alkyl sulfate, surfactin sodium ( C _55-n H _95.5-2n N ₇ O ₁₃ Na _1.5 ) manufactured by Kaneka Corporation. These may be used alone or in combination of two or more.

  Examples of the cationic surfactant include alkylamine salts such as laurylamine acetate and stearylamine acetate, and quaternary ammonium salts such as lauryltrimethylammonium chloride. These may be used alone or in combination of two or more.

  Examples of the nonionic surfactant include polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether, polyoxyethylene fatty acid ester, sorbitan fatty acid ester, polyoxysorbitan fatty acid ester, polyoxyethylene alkylamine, glycerin fatty acid ester, Examples thereof include oxyethylene-oxypropylene block polymers. These may be used alone or in combination of two or more.

  Examples of the zwitterionic surfactant include lauryl dimethylamine oxide.

  Examples of the water-soluble polymer having protective colloid ability include cellulose resins such as hydroxyethyl cellulose, methyl cellulose, and carboxyalkyl cellulose, polyvinyl alcohol resins, and polyvinyl pyrrolidone.

  As the water-soluble oligomer, for example, a polymer having a hydrophilic group such as a sulfonic acid group, a carboxyl group, a hydroxyl group, and an alkylene glycol group is preferable, and among them, a polymer or copolymer having a degree of polymerization of about 10 to 500 is preferable. Preferably mentioned. Specific examples of the water-soluble oligomer include, for example, amide copolymers such as 2-methacrylamide-2-methylpropanesulfonic acid copolymer, sodium methacrylate-4-styrenesulfonate copolymer, styrene / maleic acid copolymer. Examples include polymers, melamine sulfonic acid formaldehyde condensates, poly (meth) acrylates, and the like. Furthermore, specific examples include a monomer having a sulfonic acid group, a carboxyl group, a hydroxyl group, an alkylene glycol group or the like, a water-soluble oligomer obtained by copolymerizing a radical polymerizable reactive emulsifier in advance alone or with another monomer, and the like. It is done. These may be used alone or in combination of two or more.

  In the present invention, polyvinyl alcohol is used as a dispersion stabilizer from the viewpoint of stably dispersing oil droplets containing a monomer component and imparting polymerization stability, and imparting stability of the resulting polymer particle suspension. It is preferable to use a resin based on resin (hereinafter sometimes referred to as PVA resin).

The average saponification degree of the PVA resin is preferably 70 to 99.9 mol%, particularly preferably 80 to 99.5 mol%, and further preferably 85 to 99.0 mol%.
If the average degree of saponification is too low, it is difficult for the polymerization to proceed stably, and even when the polymerization is completed, the storage stability of the polymer particle suspension tends to decrease. There is a tendency for the stability of the to decrease.
The average saponification degree can be determined according to the saponification degree calculation method described in JIS K 6726.

The average degree of polymerization of the PVA resin is preferably 50 to 5,000, particularly preferably 150 to 4,000, and further preferably 300 to 3,000. If the average degree of polymerization is too low, the protective colloid ability is insufficient and the polymerization tends to be difficult to proceed stably. If it is too high, the reaction system becomes unstable due to thickening during polymerization and the dispersion stability decreases. Tend to.
The average degree of polymerization can be determined according to the method for calculating the average degree of polymerization described in JIS K 6726.

  In the present invention, unmodified PVA or a modified PVA resin modified with various modified species can be used as the PVA resin, and the amount of modification is usually 20 mol% or less, preferably 15 mol% or less, More preferably, it is 10 mol% or less.

  Examples of the modified PVA resin include an anion modified PVA resin modified with an anionic group such as a carboxylic acid group, a sulfonic acid group, and a phosphoric acid group, and a cationic group such as a quaternary ammonium group. Cationic modified PVA resin, modified PVA resin modified with various functional groups such as acetoacetyl group, diacetone acrylamide group, mercapto group, silanol group, etc., modified with 1,2-diol bond in the side chain Examples thereof include PVA-based resins.

In the present invention, the amount of the dispersion stabilizer used is preferably 0.1 to 60 parts by weight, particularly preferably 0.3 to 45 parts by weight, more preferably 100 parts by weight of the monomer component. Is 0.5 to 30 parts by weight.
If the amount of the dispersion stabilizer used is too small, the dispersion stability of the monomer solution tends to be lowered, and the polymerization stability tends to be lowered. If the amount used is too large, polymerized polymer particles are aggregated to cause polymerization stability. Tend to decrease.

As a method for adding the dispersion stabilizer to the aqueous medium, it can be added in advance in the aqueous medium or the monomer solution to which the dispersion stabilizer is added can be dispersed in the aqueous medium. It is preferable to add to the aqueous medium in advance.
In addition, the dispersion stabilizer may be added by (1) a method in which the dispersion stabilizer is added to the monomer solution in a batch and (2) in the course of the polymerization as necessary with the progress of the polymerization. A method in which a dispersion stabilizer is further added once or more can be used.

  Furthermore, it is usually preferable to use a polymerization initiator in the polymerization, and a polymerization adjusting agent, a pH adjusting agent and the like can be blended as necessary.

  Examples of the polymerization initiator include 2,2′-azobisisobutyronitrile, dimethyl-2,2′-azobisisobutyrate, 2,2′-azobis (2,4-dimethylvaleronitrile), 2,2'-azobis (2-methylbutyronitrile), 4,4'-azobis-4-cyanovaleric acid ammonium (amine) salt, 2,2'-azobis (2-methylamidooxime) dihydrochloride 2,2'-azobis (2-methylbutanamidooxime) dihydrochloride tetrahydrate, 2,2'-azobis {2-methyl-N- [1,1-bis (hydroxymethyl) -2-hydroxyethyl] -Propionamide}, azo compounds such as 2,2′-azobis [2-methyl-N- (2-hydroxyethyl) -propionamide]; persulfuric acid Inorganic peroxides such as lithium, sodium persulfate, ammonium persulfate; alkyl peroxides, t-butyl hydroperoxide, cumene hydroperoxide, p-methane hydroperoxide, lauroyl peroxide, 3,5,5-trimethylhexa Noyl peroxide, octanoyl peroxide, t-butylcumyl peroxide, benzoyl peroxide, dichlorobenzoyl peroxide, dicumyl peroxide, di-t-butyl peroxide, 1,1-bis (t-butylperoxy ) -3,3,5-trimethylcyclohexane, 3,3,5-trimethylcyclohexanone peroxide, methylcyclohexanone peroxide, di-isobutyl peroxydicarbonate, di-2-ethylhexyl pero Organic peroxides such as sidicarbonate, t-butylperoxyisobutyrate, hydrogen peroxide, etc .; various redox catalysts (in this case, as the oxidizing agent, ammonium persulfate, potassium persulfate, sodium persulfate, hydrogen peroxide, t -Butyl hydroperoxide, benzoyl peroxide, cumene hydroperoxide, p-methane hydroperoxide, etc., and sodium sulfite, acidic sodium sulfite, Rongalite, ascorbic acid, etc. are used as the reducing agent.

  These polymerization initiators may be used alone or in combination of two or more. Among these, an oil-soluble initiator such as an azo compound or an organic peroxide is preferable from the viewpoint of excellent polymerization stability.

  The amount of the polymerization initiator used varies depending on the type of monomer component used and the polymerization conditions, but is usually preferably 0.01 to 10 parts by weight, more preferably 0, per 100 parts by weight of the monomer component. 0.5-7 parts by weight, particularly preferably 1-5 parts by weight. When the amount of the polymerization initiator used is too small, the polymerization rate tends to be slow, and when it is too large, the molecular weight of the resulting copolymer tends to decrease and the strength of the polymer particles tends to decrease.

  The polymerization initiator may be added as a whole by adding it to the monomer solution and adding it all at once, or dividing the reactor into multiple portions during the polymerization as needed as the polymerization progresses. The method of adding to can be used.

Examples of the polymerization regulator include chain transfer agents and pH buffering agents.
Examples of the chain transfer agent include alcohols such as methanol, ethanol, propanol and butanol; aldehydes such as acetaldehyde, propionaldehyde, n-butyraldehyde, furfural and benzaldehyde; n-dodecyl mercaptan, thioglycolic acid and thioglycolic acid And mercaptans such as octyl and thioglycerol. These may be used alone or in combination of two or more.

  Examples of the pH buffering agent include soda ash (sodium carbonate), sodium bicarbonate, potassium bicarbonate, monosodium phosphate, monopotassium phosphate, disodium phosphate, trisodium phosphate, sodium acetate, acetic acid. Examples include ammonium, sodium formate, and ammonium formate. These may be used alone or in combination of two or more.

Further, in the polymerization, an inorganic salt or a water-soluble polymerization inhibitor may be added to the aqueous medium in order to suppress the generation of polymer particles due to the polymerization occurring in a place other than the oil droplets of the monomer solution for polymerization. . By adding an inorganic salt, the solubility of the monomer component in the aqueous medium can be reduced, and polymerization in the aqueous medium phase can be suppressed. Further, by adding the water-soluble polymerization inhibitor, polymerization in the aqueous medium phase can be suppressed.
Examples of the inorganic salt include sodium chloride, calcium chloride, sodium carbonate and the like. Examples of the water-soluble polymerization inhibitor include sodium sulfite, sodium nitrite, copper chloride, iron chloride, titanium chloride, hydroquinone and the like.

More specifically, the polymer particle suspension used in the present invention can be produced through the following steps [I] to [III].
[I] A step of preparing a monomer solution by mixing a monomer component, a non-reactive solvent, and a polymerization initiator.
[II] A step of preparing a suspension in which the monomer solution is dispersed as oil droplets in an aqueous medium.
[III] A step of producing a polymer particle suspension in which polymer particles are dispersed in an aqueous medium by polymerizing the monomer components in the monomer solution dispersed in the suspension.

  In the adjustment of the suspension in the step [II], first, water, a dispersion stabilizer, and a polymerization adjusting agent, a pH adjusting agent and the like were charged in a reaction can, and then separately adjusted in the step [I]. By adding the monomer solution, stirring and dispersing, a suspension in which the monomer solution is dispersed in water as oil droplets can be prepared.

  As the dispersion method by stirring, there are a method of dispersing into monomer droplets by a stirring force such as a propeller blade, a method using a high shearing force using a device composed of a rotor and a stator, a static mixer, a bipro mixer, and a homogenizer. And a method using a known disperser such as a homomixer, an ultrasonic disperser, and a high-pressure homogenizer.

  The temperature condition at the time of stirring may be a temperature at which the polymerization reaction does not start, usually at ordinary temperature, and preferably about 25 ± 15 ° C.

  The average particle size of the oil droplets of the monomer solution prepared by stirring and dispersed in water can be appropriately adjusted according to the amount of the dispersion stabilizer used and the stirring and dispersion conditions in the above step [II]. However, it is usually from 0.01 to 100 μm, preferably from 0.1 to 50 μm, particularly preferably from 0.5 to 30 μm. If the average particle size of the oil droplets in the monomer solution is too large, the stability of the monomer suspension tends to be reduced, and if it is too small, the polymerization stability tends to be reduced, and stable polymer particles tend not to be obtained.

In the present invention, the average particle size of the oil droplets is a value measured by using a laser diffraction / scattering particle size distribution measuring device (manufactured by HORIBA, etc.).
Examples of the method of making the average particle diameter of the oil droplets include a method of using a high-pressure disperser that utilizes a collision between droplets such as a microfluidizer or a nanomizer or a collision force against a machine wall.

  The polymerization conditions in the step [III] can be appropriately selected according to the type of monomer component, the polymerization scale, etc., but the temperature conditions during the reaction are usually 40 to 100 ° C. under normal pressure, particularly preferably. Is 60-90 ° C.

  The time required for the polymerization reaction is preferably, for example, 1 to 48 hours, and more preferably 3 to 24 hours.

  Further, it is preferable to stir at the time of polymerization, and the stirrer at that time may be any device used for suspension polymerization. For example, a paddle type, turbine type, impeller type rod / plate / propeller type Stirring by a stirring blade such as a device in which the stirring bar rotates in the tank can be used, and stirring mixing by a stirring blade is particularly preferable. Moreover, you may use the superposition | polymerization can with a baffle plate.

  Thus, according to the method for producing a polymer particle suspension used in the present invention, a polymer particle suspension in which polymer particles are dispersed in an aqueous medium is obtained. Such polymer particles are those in which a non-reactive solvent is encapsulated inside the polymer.

  The solid concentration of the suspension obtained by the production method of the present invention is preferably 10 to 60% by weight, particularly preferably 20 to 55% by weight, and further preferably 30 to 50% by weight. When the solid content concentration is too low, the productivity tends to decrease, and when it is too high, the polymerization stability tends to decrease.

<Method for producing vertical hollow polymer particles>
After producing the polymer particle suspension obtained by the above production method, the aqueous medium and the non-reactive solvent encapsulated in the polymer particles are removed from the polymer particle suspension to have a single void inside. The vertical hollow polymer particles of the present invention are obtained.

  As a method for removing the aqueous medium and the non-reactive solvent encapsulated in the polymer particles from the polymer particle suspension, for example, the polymer particle suspension is filtered to obtain a solid content (polymer particles) and the aqueous medium. After the separated polymer particles are stirred in an organic solvent at room temperature (about 25 ° C.) for about 1 to 24 hours, the polymer particles are collected by filtration again, and then the collected polymer particles are heated and / or There is a method of vacuum drying.

  Examples of the organic solvent include lower alcohols such as methanol, ethanol, n-propanol, isopropanol and isobutanol, ketones such as acetone, lower hydrocarbons such as pentane, hexane, heptane, octane and cyclohexane, diethyl ether, and the like. Further, ethers such as dibutyl ether can be used. Among these, it is preferable to use lower alcohols, particularly isopropanol, from the viewpoints of excellent detergency and ease of handling.

As said heat drying, it can heat-dry using, for example, a circulating air dryer, a spray dryer, a fluidized bed type dryer, etc. As heating conditions, for example, when using a circulating air dryer, it is 30-90. It is preferable to heat-dry at 3 degreeC temperature conditions for 3 to 24 hours.
As said vacuum drying, it is preferable to heat-dry, for example for 3 to 20 hours on 10-90 degreeC temperature conditions on the reduced pressure conditions of 0-90 kPa using a vacuum dryer etc., for example.

  The average particle size of the cage hollow polymer particles thus obtained is preferably 0.05 to 50 μm, more preferably 0.1 to 20 μm, and particularly preferably 0.1 to 15 μm. If the average particle size of the saddle-shaped hollow polymer particles is too large, light diffusion becomes insufficient and the feeling of use (roughness) in cosmetic applications tends to be reduced. Moreover, when an average particle diameter is too small, there exists a tendency for the handling at the time of use to become difficult.

  The average particle diameter of the vertical hollow polymer particles is 50 by taking a vertical hollow polymer particle using a desktop SEM (scanning electron microscope: Phenom proX manufactured by Jusco International Co., Ltd.) and using a major function based on the result of shooting. The particle diameter of the hollow polymer particles is measured, and the average value is defined as the average particle diameter of the vertical hollow polymer particles. As a measurement condition, a non-deposition observation is performed at an acceleration voltage of 5 kV using a charge reduction holder.

  The vertical hollow polymer particles of the present invention thus obtained are excellent in uniform light diffusibility, heat insulation, etc., and also have excellent concealment properties with respect to the base, and are suitably used in various fields such as cosmetics and paints. .

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples unless it exceeds the gist. In the examples, “parts” and “%” mean weight standards.

[Example 1]
<Production of polymer particle suspension (A-1)>
95 parts of styrene as a monomer component, 5 parts of divinylbenzene (manufactured by Nippon Steel & Sumikin Chemical Co., Ltd .: “DVB-570”), 2,2′-azobis (2,4-dimethylvaleronitrile) as a polymerization initiator (Wako Pure Chemical Industries, Ltd.) Company: “V-65”) 2 parts, oil-soluble solvent isoparaffin (Idemitsu Kosan Co., Ltd .: “IP Solvent 1620MU” (volume density 0.762 g / cm ^{3 at} 15 ° C.)) 89 parts, These were mixed and stirred to prepare a monomer solution.

Next, PVA (manufactured by Nippon Gosei Kagaku Kogyo Co., Ltd .: “GOHSENOL EG-40”) was added to ion-exchanged water as a dispersion stabilizer to a concentration of 1.03% to prepare an aqueous PVA solution. Subsequently, 401 parts of the PVA aqueous solution was added to the monomer solution, and the mixture was stirred with a homomixer (900 rpm × 5 minutes), and the resulting suspension was subjected to a high-pressure emulsification dispersion device (manufactured by APV GAULIN: “15MR-8TA”, Conditions: 60 kg / cm ² × 2 times, 100 kg / cm ² × 3 times, 200 kg / cm ² × 3 times), and the monomer solution is dispersed as oil droplets in the PVA aqueous solution (aqueous medium). A suspension was obtained.
The average particle size of the oil droplets in the suspension was measured using a laser diffraction / scattering particle size distribution measuring device manufactured by HORIBA. As a result, the average particle size of the oil droplets was about 4 μm.

  Subsequently, a 2000 ml polymerization vessel equipped with a stirrer, a jacket, a reflux condenser and a thermometer was prepared, and after the above suspension was charged all at once into this polymerization vessel, the polymerization vessel was stirred at 110 rpm. The temperature was raised to 75 ° C. to initiate the polymerization reaction of the monomer component of the oil droplets. After the polymerization reaction is carried out at 75 ° C. for 5 hours, the polymer vessel is cooled to room temperature (25 ° C.), whereby polymer particles in which a non-reactive solvent is encapsulated are dispersed in an aqueous medium. A particle suspension (A-1) was obtained.

<Manufacture of vertical hollow polymer particles (P-1)>
The polymer particle suspension (A-1) obtained above was filtered to separate the solid content (polymer particles) and the aqueous solution. The collected solid content was stirred in isopropanol at 25 ° C. for 1 hour and then filtered to collect the solid content in the same manner, and the collected solid content was dried at 50 ° C. for about 24 hours to obtain a vertical hollow polymer. Particles (P-1) were obtained.
The average particle size of the obtained hollow hollow polymer particles (P-1) was measured using a laser diffraction / scattering particle size distribution measuring device manufactured by HORIBA, and as a result, the average particle size was about 4 μm.

  The shape of the vertical hollow polymer particles (P-1) obtained in Example 1 was observed using a desktop scanning electron microscope (SEM) (Phenom proX, manufactured by Jusco International). As a result, the particle surface had irregularities (wrinkled depressions).

For the vertical hollow polymer particles (P-1) obtained in Example 1 above, the vertical hollow polymer particles are encapsulated with an epoxy resin and sliced with a microtome (Leica Microsystems: ULTRACUT UCT). An epoxy resin section in which hollow mold polymer particles were included was prepared, this section was stained with ruthenium tetroxide (RuO ₄ ), and observed with a transmission electron microscope (TEM) (JEOL JEM-1400). As a result, it was found that the particles had a single void portion inside the particles and had a bowl shape.

[Example 2]
<Production of polymer particle suspension (A-2)>
When the polymerization reaction was carried out at 75 ° C. for 3 hours, an aqueous solution in which PVA (manufactured by Nippon Synthetic Chemical Industry Co., Ltd .: Gohsenol EG-40) as a dispersion stabilizer was dissolved in ion-exchanged water at a concentration of 5.00% 13 A polymer particle suspension obtained by dispersing polymer particles containing a non-reactive solvent in an aqueous medium in the same manner as in Example 1 except that the polymerization reaction was continued for 2 hours at 75 ° C. (A-2) was obtained.

<Manufacture of vertical hollow polymer particles (P-2)>
Using the polymer particle suspension (A-2) obtained above, vertical hollow polymer particles (P-2) were obtained in the same manner as in Example 1.
The average particle diameter of the obtained vertical hollow polymer particles (P-2) was about 5 μm.

[Comparative Example 1]
As Comparative Example 1, polymethyl methacrylate particles (P′-1) (manufactured by Soken Chemical Co., Ltd., “SP-50”, average particle diameter of 5 μm) were prepared. As a result of SEM observation of the shape of the particles, it was confirmed that the particles were solid particles having a smooth surface.

[Comparative Example 2]
63 parts of ethylene glycol dimethacrylate as a monomer component, 1 part of 2,2′-azobis (2,4-dimethylvaleronitrile) (manufactured by Wako Pure Chemical Industries, Ltd .: V-65) as a polymerization initiator, oil-soluble surfactant 0.2 parts of hexaglyceryl polyricinoleate (manufactured by Nikko Chemicals Co., Ltd .: hexagrin PR-15 (HLB3.2)) as an agent (0.38% with respect to the acrylic monomer) were mixed, stirred. As a result, a monomer solution was prepared.

  On the other hand, sodium chloride was added to ion exchange water to a concentration of 1% to prepare an aqueous solution (inner aqueous phase). Next, 64 parts of the monomer solution and 28 parts of the sodium chloride aqueous solution are mixed and emulsified using an ultrasonic treatment apparatus (350 μA × 4.5 minutes), whereby the aqueous solution (inside A water-in-oil (Wi / O) type suspension in which the (aqueous phase) was dispersed was formed.

  Next, PVA (manufactured by Nippon Synthetic Chemical Industry Co., Ltd .: Gohsenol EG-05) as a dispersion stabilizer was added to ion-exchanged water so as to have a concentration of 1.6% to prepare an aqueous solution. Next, 222 parts of the aqueous solution is added to the water-in-oil (Wi / O) type suspension, and the mixture is stirred with a homomixer (5,000 rpm × 1 minute). An oil-in-water (Wi / O / Wo) type suspension in which oil droplets (including many fine water droplets) composed of a middle water (Wi / O) type suspension (I) were dispersed was obtained.

  A 300 ml polymerization vessel equipped with a stirrer, a jacket, a reflux condenser and a thermometer was prepared, and the oil-in-water (Wi / O / Wo) type suspension was put into the polymerization vessel at a time, and then the rotation speed was 150 rpm. With stirring, the inside of the polymerization vessel was set to a nitrogen atmosphere over 30 minutes.

  Thereafter, the temperature of the polymerization vessel was raised to 70 ° C. under normal pressure to initiate the polymerization reaction of the monomer component of the oil droplets. After the polymerization reaction is carried out at 70 ° C. for 6 hours, the polymerization vessel is cooled to room temperature (25 ° C.), whereby the polymer particles containing water (aqueous solution) are dispersed in the aqueous medium. A turbid liquid (A′-1) was obtained.

<Manufacture of hollow polymer particles>
The polymer particle suspension (A′-1) obtained above was filtered to separate a solid (polymer particles) and an aqueous solution. The collected solid content was heated and dried in an oven at 70 ° C. to obtain hollow polymer particles (P′-2).
The average particle diameter of the obtained hollow polymer particles (P′-2) was about 14 μm.
As a result of SEM observation of the shape of the obtained hollow polymer particles (P′-2), it was confirmed that the hollow polymer particles were smooth hollow particles.

  Each polymer particle obtained in the above Examples and Comparative Examples was evaluated for the following reflected light characteristics and hiding properties.

<Reflected light characteristics>
Using each polymer particle obtained in the above Examples and Comparative Examples, the light reflectance was measured by the following method to evaluate the reflected light characteristics. The results are shown in Table 1.

[Preparation of measurement sample]
First, a double-sided tape (3 cm × 5 cm) was affixed onto a commercially available black cardboard (5 cm × 5 cm), and the polymethyl methacrylate of Comparative Example 1 was placed on the adhesive surface opposite to the side attached to the cardboard. Particles (“SP-50” manufactured by Soken Chemical Co., Ltd., shape: solid smooth particles) were applied and spread uniformly with a brush to obtain a sample for reference measurement of reflected light intensity.

  Next, a double-sided tape was applied to a commercially available black cardboard in the same manner as described above, and the vertical hollow polymer particles and hollow polymer particles produced in Examples 1 and 2 and Comparative Example 2 were applied thereon, and then reflected. A sample for measuring the light intensity was used.

Using a three-dimensional variable angle photometer ("GP-200" manufactured by Murakami Color Research Laboratory Co., Ltd., using a halogen lamp), the incident angle was set to 60 °, and a sample for reference measurement (polymer particles of Comparative Example 1) The HIGH VOLT was adjusted so that the maximum SENSITIVITY when the reflected light intensity of the sample was measured was 170, and the reflected light intensity (% of the target measurement samples (hollow polymer particles produced in Examples 1 and 2 and Comparative Example 2)) ) Was measured from −90 ° to 90 °, and values of 0 ° and 60 ° were read.
The measurement results are shown in FIG.

The reflected light intensity at a measurement angle of −55 ° was evaluated.
(Evaluation criteria)
○: Reflected light intensity at a measurement angle of −55 ° is 60% or less ×: Reflected light intensity at a measurement angle of −55 ° is greater than 60%

From the above results, the difference between the reflected light intensity at the measurement angle of 60 ° and the reflected light intensity at the measurement angle of 0 ° with respect to the incident angle of 60 ° is 10% or more in all the measured samples and expresses good optical characteristics. I understand.
Among them, the vertical hollow polymer particles of Examples 1 and 2 have a reflected light intensity at a measurement angle of −55 ° with respect to an incident angle of 60 ° (can be regarded as corresponding to the maximum reflected light intensity). It can be seen that it is low compared to the polymer particles, and is excellent in light diffusibility. Comparative Example 2 relates to hollow polymer particles, and the reflected light intensity at each measurement angle is higher than that of the Example, and this does not provide a sufficient soft focus effect.
The characteristics of the saddle-shaped hollow polymer particles of these examples are superior in, for example, cosmetic applications.

<Evaluation of concealment>
[Preparation of measurement sample]
A test piece of 4 cm × 4 cm was prepared as a reference measurement sample.

  Next, the particles of Examples 1 and 2 and Comparative Examples 1 and 2 were applied on the same test piece as described above, and spread with a brush to obtain a sample for measurement. At this time, the weight of the particles applied on the test piece was also measured.

  Using a color difference meter (“SE-6000” manufactured by Nippon Denshoku Industries Co., Ltd.), the light receiving condition was set to reflection, and L * (lightness) of the reference measurement sample (artificial leather sample) was measured. Thereafter, L * (lightness) of the target measurement samples (particles of Examples 1 and 2 and Comparative Examples 1 and 2) was measured, and ΔL * was calculated. The results are shown in Table 2.

From the above results, the vertical hollow polymer particles of Examples 1 and 2 have a small coating amount compared to solid particles having a smooth particle surface (Comparative Example 1) and hollow particles having a smooth surface (Comparative Example 2). Since ΔL * is large, it can be seen that it has a high hiding power.
The characteristics of the vertical hollow polymer particles of this example are superior in, for example, cosmetic use.

The vertical hollow polymer particles of the present invention are excellent in hiding properties and are suitably used in various fields such as cosmetics and paints. For example, since the background is well concealed, a skin color correction effect for cosmetics can be obtained.
Further, since a high effect can be obtained with a small amount of use, it is advantageous in terms of economy.

  The vertical hollow polymer particles of the present invention are excellent in uniform light diffusibility, heat insulation, and the like, and also have excellent concealability with respect to the base, and are suitably used in various fields such as cosmetics and paints.

Claims (6)

  Using a three-dimensional goniophotometer, when the reflected light intensity was measured when the hollow hollow polymer particles were irradiated with light at an incident angle of 60 °, the reflected light intensity (R2) (%) at a measurement angle of 60 ° A vertical hollow polymer particle having a difference (R2−R1) in reflected light intensity (R1) (%) at 0 ° of 10% or more.   Using a three-dimensional goniophotometer, when the reflected light intensity was measured when the hollow hollow polymer particles were irradiated with light at an incident angle of 60 °, the reflected light intensity at a measurement angle of −55 ° (R3) (%) The vertical hollow polymer particles according to claim 1, wherein the content is 60% or less.   A method for producing vertical hollow polymer particles according to claim 1 or 2, wherein a suspension of polymer particles obtained by suspension polymerization of a monomer solution containing a monomer component and a non-reactive solvent in an aqueous medium is used. A method for producing vertical hollow polymer particles, comprising a step of removing a non-reactive solvent encapsulated in polymer particles dispersed in the polymer particle suspension. The method for producing vertical hollow polymer particles according to claim 3, wherein a solvent having a volume density at 15 ° C of 1.2 g / cm ³ or less is used as the non-reactive solvent.   The method for producing vertical hollow polymer particles according to claim 3 or 4, wherein the amount of the non-reactive solvent used is 85 to 200 parts by weight with respect to 100 parts by weight of the monomer component.   The soot according to any one of claims 3 to 5, wherein the monomer component contains an ethylenically unsaturated compound having two or more ethylenically unsaturated groups in an amount of 0.1 to 50% by weight based on the whole monomer component. Type hollow polymer particle manufacturing method.

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