JP4677196B2 - Silica particles, method for producing the same, and use thereof - Google Patents

Description

  The present invention relates to silica particles, a method for producing the same, and uses thereof. More specifically, the present invention relates to an adsorbent intended to adsorb various liquid substances such as fats and oils, petroleum, solvents, etc., and silica particles having a unique shape suitable for use in cosmetics that require a high sebum adsorbing action. , Its manufacturing method and its use.

  In the field of cosmetics and adsorbents, silica particles are used as components that adsorb various liquid articles such as fats and oils, petroleum, and solvents. As a method for producing silica particles, generally, a method for producing amorphous silica particles by a pulverization method, and a method for producing spherical silica particles by a seed polymerization method or a sol-gel method are known. However, all of these particles have a spherical shape or an irregular shape close to a spherical shape, so that the surface area is small and the adsorption ability is low. Therefore, in these silica particles, for example, makeup collapse due to sebum that could not be adsorbed when blended in cosmetics has been a problem.

  Accordingly, porous silica particles having a high oil absorption amount and a production method compared to spherical or amorphous silica particles and a production method have been proposed (Japanese Patent Application Laid-Open No. 2000-7320, Patent Document 1), and these particles are used as a paper ink permeation suppression material. ing. Moreover, JP, 10-182345, A (patent documents 2) is mentioned as an example of cosmetics using the same porous silica particles, and porous silica particles are used as a sebum control material.

JP 2000-7320 A Japanese Patent Laid-Open No. 10-182345

However, the amount of oil absorption of the porous silica particles is about 300 to 500 ml / 100 g, and the range of control is limited.
In order to improve the effect of suppressing ink penetration in paper and makeup collapse due to sebum in cosmetics, adsorbents that can adsorb a large amount of ink, oil, etc., and a large amount of sebum can be adsorbed, providing a wide range of sebum control. It has been desired to provide silica particles that can provide a cosmetic that can be applied.

  The inventor of the present invention has made extensive studies to solve the above problems, and as a result, the polymerizable monomer is suspended in an aqueous suspension in the presence of a polyalkoxysiloxane oligomer that is not copolymerizable with the polymerizable vinyl monomer. After the polymerization, the polyalkoxysiloxane oligomer is condensed to form composite particles coated with a silica coating derived from the polyalkoxysiloxane oligomer so that at least a part of the surface of the polymer particles is exposed, and the composite particles are fired. Thus, by removing the polymer particles, it was possible to obtain silica particles having a specific shape, and surprisingly found that the obtained silica particles had excellent adsorptivity, leading to the present invention.

Thus, according to the present invention, 100 parts by weight of a polymerizable vinyl monomer, 10 to 500 parts by weight of a polyalkoxysiloxane oligomer inert to the polymerizable vinyl monomer, and 0.01 to 10 parts by weight of a polymerization initiator are added. After uniformly mixing to obtain a monomer composition, the polymerizable vinyl monomer in the monomer composition is subjected to aqueous suspension polymerization in the presence of a suspension stabilizer to obtain polymer particles. A silica-coated polymer particle is obtained by condensing a polyalkoxysiloxane oligomer in the presence of an acid or base catalyst to form a silica film so that at least a part of the surface of the polymer particle is exposed, and the silica-coated polymer particle There is provided a method for producing silica particles, characterized in that the polymer particles are removed by baking to obtain silica particles .

Further, according to the present invention, the silica particles obtained by the above production method, wherein the opening ratio is 0.1 to 1, and the height h and the diameter D of the silica particles are 0.5 ≦ h / D. Spherical or substantially spherical silica particles having a hollow structure in which at least a portion having a relationship of <1 is opened are provided.

Furthermore, according to the present invention, the silica particles obtained by the above production method, the oil absorption measured by JIS K 5101 is more than 500 ml / 100 g and not more than 700 ml / 100 g, at least partly opened. Spherical or substantially spherical silica particles having a hollow structure are provided.

  As described above, the silica particles of the present invention have a very high oil absorption compared to the amorphous silica particles because the opening ratio is in the range of 0.1 to 1. . Therefore, for example, high liquid adsorption capability is obtained by mix | blending with an adsorbent. Moreover, the high sebum adsorption ability can be provided by mix | blending with cosmetics, and the effect which suppresses the makeup collapse by sebum can be anticipated. Furthermore, since the silica particles of the present invention have a larger oil absorption than the conventional porous silica particles, the sebum control property of the cosmetic can be widened.

  As shown in the cross-sectional view of FIG. 1, the silica particles of the present invention have a spherical or substantially spherical structure having a hollow structure that is at least partially opened with an aperture ratio of 0.1 to 1. By having such a structure, the adsorptivity is improved and more adsorbing components such as ink, oil agent, sebum and the like can be adsorbed.

  An aperture ratio of less than 0.1 is not preferable because sufficient adsorptivity is difficult to obtain. A more preferable aperture ratio is 0.1 to 0.8. The maximum value of the aperture ratio is 1. The method for measuring the aperture ratio is described in the examples.

  By having the above opening ratio, silica particles having an oil absorption amount (measurement method is described in the column of Examples) measured by JIS K 5101 exceeding 500 ml / 100 g and 700 ml / 100 g or less can be obtained. A more preferable oil absorption is 530 to 650 ml / 100 g. In the present specification, the adsorptivity is evaluated by measuring the oil absorption amount. However, the adsorbing component of the silica particles of the present invention is not limited to oil, and includes a component containing water.

  Further, the height h and the diameter D of the silica particles have a relationship of 0.5 ≦ h / D <1. When h / D is 1 or less than 0.5, the adsorptivity becomes poor, which is not preferable. In addition, the measuring method of h / D is described in an Example.

Hereinafter, the silica particles of the present invention will be described with reference to the production method.
First, the polymerizable vinyl monomer that can be used in the present invention is not particularly limited as long as it can be removed by baking after polymerization. For example, styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, p-ethylstyrene, 2,4-dimethylstyrene, pn-butylstyrene, p-tert-butylstyrene, pn-hexyl Styrene, pn-octyl styrene, pn-nonyl styrene, pn-decyl styrene, pn-dodecyl styrene, n-methoxy styrene, p-phenyl styrene, p-chloro styrene, 3,4-di Styrene and its derivatives such as chlorostyrene,

Ethylene unsaturated monoolefins such as ethylene, propylene, butylene and isobutylene, vinyl halides such as vinyl chloride, vinylidene chloride, vinyl bromide and vinyl fluoride, vinyl esters such as vinyl acetate, vinyl propionate and vinyl butyrate ,
Methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, propyl acrylate, n-octyl acrylate, dodecyl acrylate, 2-ethylhexyl acrylate, stearyl acrylate, lauryl acrylate, 2-acrylate Chlorethyl, phenyl acrylate, methyl α-chloroacrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, n-octyl methacrylate, dodecyl methacrylate, 2-ethylhexyl methacrylate , Stearyl methacrylate, lauryl methacrylate, phenyl methacrylate, dimethylaminoethyl acrylate, dimethylaminoethyl methacrylate, diethylaminoethyl acrylate, diethyl methacrylate α- methylene aliphatic monocarboxylic acid esters such as aminoethyl,

Acrylic acid or methacrylic acid derivatives such as acrylonitrile, methacrylonitrile, acrylamide, methacrylamide, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate,

In some cases, acrylic acid, methacrylic acid, maleic acid, fumaric acid and the like can also be used. Further, vinyl ethers such as vinyl methyl ether, vinyl ethyl ether, vinyl isobutyl ether, vinyl ketones such as vinyl methyl ketone, vinyl hexyl ketone, methyl isopropenyl ketone, N-vinyl pyrrole, N-vinyl carbazole, N-vinyl indole, N -N-vinyl compounds such as vinylpyrrolidone, vinyl naphthalene salts and the like can be used alone or in combination of two or more in a range that does not impair the effects of the present invention.

  Among these, inexpensive styrene, methyl methacrylate and the like are preferable in terms of cost. The polymer particles may be crosslinked with a monomer having two or more functional groups such as ethylene glycol dimethacrylate, polyethylene glycol dimethacrylate, divinylbenzene and the like.

  In the present invention, the polyalkoxysiloxane oligomer, which is a precursor of silica particles, is inert to the polymerizable vinyl monomer (meaning that it is not copolymerized), and those having the following structural formula can be used.

  Among the above structural formulas, for example, oligomers such as polymethoxysiloxane, polyethoxysiloxane, polypropoxysiloxane, polybutoxysiloxane, and the like can be given. Among these, polymethoxysiloxane oligomers and polybutoxysiloxane oligomers that are poorly water-soluble and have good phase separation from the resin are preferred, and particularly preferred are polymethoxysiloxane oligomers and polybutoxysiloxanes having a weight average molecular weight of 300 to 3000. It is an oligomer.

In addition, a weight average molecular weight is measured on condition of the following using GPC.
Column: “TSK GEL” (manufactured by Tosoh Corporation)
G-1000H,
G-2000H
G-4000H
Effluent: Tetrahydrofuran Outflow rate: 1 ml / min Outflow temperature: 40 ° C

  In low molecular weight alkoxysiloxanes such as tetramethoxysilane and tetraethoxysilane where n = 1-2 in the above molecular formula, water-solubility becomes stronger when the functional group is hydrolyzed. Is difficult and undesirable. In addition, a polyalkoxysiloxane oligomer in which n = 40 or more in the above molecular formula is not preferable because compatibility and condensability with a polymerizable vinyl monomer are lowered. The addition amount of the polyalkoxysiloxane oligomer is preferably 10 to 500 parts by weight, more preferably 20 to 300 parts by weight with respect to 100 parts by weight of the polymerizable vinyl monomer. When the amount is less than 10 parts by weight, it is difficult to cover the coated state of the present invention. When the amount is more than 500 parts by weight, it is difficult to partially expose the polymer particles.

  In addition, hydrolysable alkoxy metal compounds other than silicon-based compounds can be added to these polyalkoxysiloxane oligomers for the purpose of adding functions such as ultraviolet absorption.

  A polymerization initiator is used for the polymerization of the polymerizable vinyl monomer. Examples of the polymerization initiator include oil-soluble peroxide polymerization initiators and azo polymerization initiators that are usually used in aqueous suspension polymerization. Specific examples include benzoyl peroxide, lauroyl peroxide, octanoyl peroxide, orthochlorobenzoyl peroxide, orthomethoxybenzoyl peroxide, methyl ethyl ketone peroxide, diisopropyl peroxydicarbonate, cumene hydroperoxide, cyclohexanone peroxide, t-butyl. Peroxide polymerization initiators such as hydroperoxide and diisopropylbenzene hydroperoxide, 2,2′-azobisisobutyronitrile, 2,2′-azobis (2,4-dimethylvaleronitrile), 2,2 '-Azobis (2,3-dimethylbutyronitrile), 2,2'-azobis (2-methylbutyronitrile), 2,2'-azobis (2,3,3-trimethylbutyronitrile), 2, 2'-azobis (2-isopropylbutyronitrile ), 1,1′-azobis (cyclohexane-1-carbonitrile), 2,2′-azobis (4-methoxy-2,4-dimethylvaleronitrile, (2-carbamoylazo) isobutyronitrile, 4,4 Examples thereof include azo initiators such as' -azobis (4-cyanovaleric acid) and dimethyl-2,2'-azobisisobutyrate.

  Among these, 2,2′-azobisisobutyronitrile, 2,2′-azobis (2,4-dimethylvaleronitrile), benzoyl peroxide, lauroyl peroxide, and the like are in terms of the decomposition rate of the polymerization initiator. Is preferable. The polymerization initiator is preferably used in an amount of 0.01 to 10 parts by weight, more preferably 0.1 to 5.0 parts by weight, based on 100 parts by weight of the polymerizable vinyl monomer.

  In order to color the silica particles, metal oxide pigments such as titanium oxide, zinc oxide, magnesium oxide, chromium oxide, and zirconium oxide may be used. However, organic pigments, metal hydroxide pigments, dyes and the like are not preferable because they cause combustion or structural changes during sintering.

  The polymerizable vinyl monomer, the polyalkoxysiloxane oligomer, the polymerization initiator, and other components are uniformly mixed by a known method to form a monomer composition.

  Next, examples of the aqueous medium for aqueous suspension polymerization of the monomer composition include water or a mixed medium of water and a water-soluble solvent such as alcohol. The amount of the aqueous medium used is usually 100 to 1000 parts by weight with respect to a total of 100 parts by weight of the polymerizable vinyl monomer and polyalkoxysiloxane oligomer in order to stabilize the suspension polymerized particles.

  In order to suppress the generation of emulsified particles in an aqueous system, water-soluble polymerization inhibitors such as nitrites, sulfites, hydroquinones, ascorbic acids, water-soluble vitamin Bs, citric acid, and polyphenols may be used. Good.

  Furthermore, you may add a suspension stabilizer to an aqueous medium as needed. For example, phosphates such as calcium phosphate, magnesium phosphate, aluminum phosphate, zinc phosphate, pyrophosphates such as calcium pyrophosphate, magnesium pyrophosphate, aluminum pyrophosphate, zinc pyrophosphate, calcium carbonate, magnesium carbonate, calcium hydroxide And dispersion stabilizers of poorly water-soluble inorganic compounds such as magnesium hydroxide, aluminum hydroxide, calcium metasilicate, calcium sulfate, barium sulfate, and colloidal silica. Among these, tricalcium phosphate, magnesium pyrophosphate, calcium pyrophosphate, and colloidal silica produced by the metathesis method are preferable because polymer particles can be stably obtained.

  The suspension stabilizer can be used in combination with a surfactant such as an anionic surfactant, a cationic surfactant, an amphoteric surfactant, and a nonionic surfactant.

  Examples of the anionic surfactant include fatty acid oils such as sodium oleate and castor oil potassium, alkyl sulfate salts such as sodium lauryl sulfate and ammonium lauryl sulfate, alkylbenzene sulfonates such as sodium dodecylbenzenesulfonate, and alkylnaphthalene sulfone. Acid salts, alkane sulfonates, dialkyl sulfosuccinates, alkyl phosphate esters, naphthalene sulfonate formalin condensates, polyoxyethylene alkyl phenyl ether sulfates, polyoxyethylene alkyl sulfates and the like.

  Nonionic surfactants include, for example, 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, oxy Examples include ethylene-oxypropylene block polymers.

  Examples of the cationic surfactant include alkylamine salts such as laurylamine acetate and stearylamine acetate, and quaternary ammonium salts such as lauryltrimethylammonium chloride.

  Examples of the zwitterionic surfactant include lauryl dimethylamine oxide and phosphate ester or phosphite ester surfactants.

  These suspension stabilizers and surfactants may be used alone or in combination of two or more. However, in consideration of the particle diameter of the obtained polymer particles and the dispersion stability during polymerization, the suspension stabilizer It is used by appropriately adjusting the selection and use amount of the agent. Usually, the addition amount of the suspension stabilizer is 0.5 to 15 parts by weight with respect to 100 parts by weight of the polymerizable vinyl monomer, and the addition amount of the surfactant is 0.00 with respect to 100 parts by weight of the aqueous medium. 001 to 0.1 parts by weight.

The monomer composition is added to the aqueous medium thus prepared, and aqueous suspension polymerization is performed.
As a method for dispersing the monomer composition, for example, a method in which the monomer composition is directly added to an aqueous medium and dispersed in the aqueous medium as monomer droplets by a stirring force of a propeller blade or the like, a high shear force composed of a rotor and a stator Examples thereof include a method of dispersing using a homomixer that is a dispersing machine to be used, an ultrasonic dispersing machine, or the like. Among these, the monomer composition is pressed into an aqueous medium through a high-pressure type disperser or MPG (microporous glass) porous film using collision of monomer droplets such as microfluidizer and nanomizer and collision force to the machine wall. It is preferable to disperse by a method such as that because the particle diameters can be made more uniform.

  Next, suspension polymerization is initiated by heating the aqueous medium in which the monomer composition is dispersed as spherical monomer droplets. During the polymerization reaction, it is preferable to stir the aqueous medium. For example, the stirring may be performed so gently that the droplets of the monomer and the particles after polymerization are prevented from being settled. In the suspension polymerization, the polymerization temperature is preferably about 30 to 100 ° C, more preferably about 40 to 80 ° C. The time for maintaining this polymerization temperature is preferably about 0.1 to 20 hours.

  In addition, when the boiling point of the polymerizable vinyl monomer and the polyalkoxysiloxane oligomer is near the polymerization temperature or higher than the polymerization temperature, the pressure resistant polymerization equipment such as an autoclave is prevented so that the polymerizable vinyl monomer and the polyalkoxysiloxane oligomer do not volatilize. It is preferable to polymerize under sealing or under pressure.

  Next, a silica-coated polymer particle having a silica coating formed so that at least a part of the surface of the polymer particle is exposed can be obtained by condensing the polyalkoxysiloxane oligomer. Examples of the condensation method of the polyalkoxysiloxane oligomer include dehydration condensation using an acid catalyst or a base catalyst. As the acid catalyst and the base catalyst, hydrochloric acid, sulfuric acid, nitric acid, ammonia, sodium hydroxide, potassium hydroxide, ammonium nitrate and the like can be used. When the production container is made of steel or stainless steel, basic sodium hydroxide, ammonia, or the like is preferable from the viewpoint of corrosion or the like. The addition amount of the catalyst is preferably 0.01 to 30 parts by weight with respect to 100 parts by weight of the polyalkoxysiloxane oligomer. More preferably, it is 1 to 15 parts by weight.

  After the condensation, if necessary, the suspension stabilizer is decomposed with hydrochloric acid, etc., and the silica-coated polymer particles are separated as a hydrous cake by a method such as suction filtration, centrifugal dehydration, centrifugal separation, and pressure dehydration. The resulting water-containing cake can be washed with water and dried to separate the particles.

  The silica-coated polymer particles thus obtained are fired to obtain the silica particles of the present invention. Although it does not specifically limit as a baking method, There exist the method of baking in inert gas atmosphere, such as argon, xenon, nitrogen, or the method of baking in air, for example in air. In view of economics, firing in air is preferable. Moreover, it is preferable that a calcination temperature is 500 degreeC or more. If the firing temperature is less than 500 ° C., the silica particles are colored by the residue of the carbon residue of the fired resin, which is not preferable. A more preferable firing temperature is 500-1500 ° C.

  The size and shape of the silica particles of the present invention are not particularly limited. According to the method for producing silica particles, particles having an average particle diameter of 1 to 500 μm can be obtained. Here, the average particle diameter of the particles can be adjusted by adjusting the mixing conditions of the monomer composition and water, the addition amount of the suspension stabilizer, the surfactant, and the like, the stirring conditions of the agitator, and the dispersion conditions. is there.

The silica particles of the present invention are preferably used as a raw material for adsorbents, cosmetics and paints.
When used as an adsorbent, it is preferable to use silica particles having an average particle diameter of 3 to 500 μm. In the present specification, the adsorbent is an ink permeation suppression material used for paper surface treatment, an adsorbent powder or adsorbent mat for adsorbing oil or oil, a cleaning article for adsorbing and cleaning oil and fat components, etc. It is used for adsorbing all liquid articles such as fats and oils, petroleum, solvent, ink, water, etc., and may be used alone or absorbed or dispersed in a base material.

  Here, in order to use silica particles alone as an adsorbent, an average particle diameter of about 100 to 500 μm, which is difficult to cause scattering and easy to handle, is preferable. Especially preferably, it is about 200-500 micrometers. When the average particle diameter exceeds 500 μm, the retention of the oil agent once absorbed in the particles is weak and easy to be detached, which is not preferable.

  Moreover, when making a silica particle support on a base material, the average particle diameter of 3-100 micrometers is preferable, and 3-50 micrometers is more preferable in order to prevent the drop-off from a base material. In particular, when the base material is paper, an average particle diameter of about 3 to 20 μm is preferable because unevenness due to particles does not appear on the surface of the paper.

  The base material is not particularly limited, but paper made from known papermaking pulp such as sulfite pulp, kraft pulp, soda pulp, semi-chemical pulp, mechanical pulp, or rayon, acetate, acrylic, polyester, polypropylene Polyurethane, polyamide, cotton, and woven or non-woven fabrics of these may be used.

  Examples of the method for supporting the silica particles on the base material include a method in which when the base material is paper, the silica particles are mixed in a slurry state with the raw material of the paper and supported by making paper using a known wet paper machine. . In addition, the silica particles can be directly mixed with the raw material of the paper without making it into a slurry state and re-dispersed in water to make paper.

  In the case where the substrate is a fiber, for example, silica particles made into a slurry with water or a solvent can be permeated into the fiber, and can be supported as it is or dried and attached to the fiber surface or inside. .

  As the wet paper machine, for example, a commercial paper machine such as a round net paper machine, a short net paper machine, a long net paper machine, or a twin wire paper machine can be used according to the purpose.

  In addition, sizing agents, slime control agents, dyes, coloring pigments, fluorescent dyes, dry paper strength enhancers, wet paper strength enhancers, drainage improvers, starch, polyvinyl alcohol, polyacrylamide, and yield improvers are required. Can be added to raw materials.

  When used in cosmetics, the average particle diameter is preferably about 3 to 50 μm from the viewpoint of feeling of use and preventing falling off from the base material when formed into a sheet. When it exceeds 50 μm, the usability may be deteriorated. Particularly preferably, it is about 3 to 20 μm which makes the feel smoother.

  Specific cosmetics include solid cosmetics such as funny and foundation, powder cosmetics such as baby powder and body powder, liquid cosmetics such as lotion, milky lotion, cream and body lotion, and body wiping Examples thereof include sheet-like cosmetics such as sheets and oil removing paper.

  The blending ratio in these cosmetics varies depending on the type of cosmetic, but it is preferably 1 to 20% by weight and particularly preferably 3 to 15% by weight in the case of solid cosmetics such as funny and foundation. Moreover, in the case of powdery cosmetics such as baby powder and body powder, the content is preferably 1 to 20% by weight, particularly preferably 3 to 15% by weight. Furthermore, in the case of liquid cosmetics such as lotion, milky lotion, cream, liquid foundation, body lotion, pre-shave lotion, the content is preferably 1 to 15% by weight, more preferably 3 to 10% by weight. Furthermore, in the case of a sheet-like cosmetic, 1 to 20% by weight is preferable, and more preferably 1 to 15% by weight.

  In the cosmetic of the present invention, other necessary components can be used in addition to the silica particles. For example, in order to improve the slipperiness with the skin, it can be used by mixing with organic fine particles or spherical silica. In addition, in order to improve optical functions and touch, inorganic compounds such as mica and talc, coloring pigments such as iron oxide, titanium oxide, ultramarine blue, bitumen, and carbon black, or synthetic dyes such as azo-based compounds, etc. Can be added.

  In the case of liquid cosmetics, the liquid medium is not particularly limited, but water, alcohol, hydrocarbons, silicone oil, vegetable or animal oils and the like can also be used.

  In the case of sheet-like cosmetics, any of woven or non-woven fabrics of natural fibers or synthetic fibers can be used as the base material. Specifically, rayon, acetate, acrylic, polyester, polypropylene, polyurethane, polyamide, cotton, and woven or non-woven fabrics of these, as well as dry and wet pulp sheets, thermoplastic resins (polyethylene, polypropylene, polyethylene terephthalate, etc.) And pulp sheet reinforced with The pulp sheet reinforced with the thermoplastic resin can be embossed or the like, and a sheet with a wiping finish can be obtained by using several sheets stacked.

  In addition to these other ingredients, these cosmetics have various functions by adding moisturizers, anti-inflammatory agents, whitening agents, UV care agents, bactericides, antiperspirants, refreshing agents, fragrances, and the like. It can also be added.

  The cosmetic material of the present invention can absorb and remove excess sebum and suppress makeup collapse by using silica particles having a high oil absorption. In particular, by having an oil absorption amount exceeding 500 ml / 100 g, a high sebum adsorbing ability can be exhibited, and a range of sebum control properties can be given when blending cosmetics.

  The average particle diameter of the silica-coated polymer particles and silica particles of the present invention, and the oil absorption, opening ratio, and h / D of the silica particles were measured by the following methods.

(Measurement method of average particle diameter)
The average particle diameter was measured using a multi-image analyzer (Beckman Coulter, Inc.). The multi-image analyzer irradiates a light beam with a strobe behind the aperture tube when particles pass through the aperture, and takes a projected image of each particle passing through the aperture with a CCD camera. It is a device that calculates as a value. The value of the average particle diameter is a number average value of measured values of 1000 to 1500 particles.
The measuring method is shown below.

Device preparation A 100 μm aperture was set in the device, and the position was adjusted so that the whole image of the aperture pore was reflected on the CCD camera. To adjust the focus, the focus was first adjusted to the aperture pore and the focus adjustment knob was moved back by 4 scales.
Sample preparation 0.01 g of a sample was dispersed in 10 ml of a nonionic surfactant 0.1% aqueous solution.

Measurement The beaker equipped with the apparatus was filled with ISOTON II (manufactured by Beckman Coulter, Inc.), and the prepared sample dispersion was dropped with a 1 to 3 drop pipette. In the beaker, gently agitate the sample so that it does not settle, and according to the multi-image analyzer instruction manual (Beckman Coulter, Inc.), measure 1000 to 1500 particles passing through the aperture with a CCD camera with a lens magnification of 40 times. For each photographed particle image, the average particle diameter was measured with a pixel calibration value of 0.219 μm.

(Measurement of oil absorption)
The oil absorption was measured by the method of JIS K 5101. Details are as follows.
-Apparatus and instrument measuring plate A smooth glass plate larger than 300 x 400 x 5 mm.
Spatula with a blade made of steel or stainless steel.
Weighing instrument: Can measure up to 10mg order.
Buret JIS R 3505, up to 10ml.

-Material linseed oil (as defined in JIS K 5421; this time, special grade linseed oil (Wako Pure Chemical Industries) was used.)
·Measuring method
(1) Before performing the following operations, check the approximate value of oil absorption in advance by preliminary tests. (2) Take 1 g of the sample in the center of the measuring plate, and drop 4 or 5 drops of linseed oil from the burette at a time into the center of the sample, and knead the whole thoroughly with a spatula each time. (3) Repeat dripping and kneading, and when the whole becomes a hard putty lump, knead each drop, and when the last one drop is ready to be spirally wound with a spatula, end point And However, if it cannot be spirally wound, the end point is the point immediately before it softens suddenly with one drop of linseed oil. (4) Adjust the operations in (1) and (2) so that the operation time to the end point is 7 to 15 minutes. (5) Read the amount of linseed oil dropped on the burette when the end point is reached.

・ Calculation method Oil absorption is calculated by the following formula.
O = (V / m) × 100
O: Oil absorption (ml / 100g)
m: Mass of the sample (g)
V: Volume of linseed oil dripped (ml)

(Measurement method of aperture ratio)
The silica particles were photographed with a scanning electron microscope (manufactured by JEOL Ltd .: GMS-820-A). From the photographed images, 50 arbitrary silica particles having openings on the top are selected, and each silica particle is manually selected by using a trace measurement of an image analyzer (Omron: Image-Ana LITE). The contour of the opening and the contour of the opening were specified, and the projected area (S2) and the area of the opening (S1) of the silica particles were measured as illustrated in FIG.

From the measured areas, the aperture ratios of the individual silica particles were determined by the following formula, and the average value was shown in the examples.
Opening ratio = area of the opening of silica particles (S1) ÷ projected area of silica particles (S2)

(Measurement of h / D)
In addition, as shown in FIG. 1, when the diameter of the silica particle is D and the height of the silica particle is h, the value of h / D is measured by the following method, and the value is taken as an example. Indicated.

  In the same manner as the aperture ratio measurement method, a scanning electron micrograph of silica particles is taken, and 50 particles whose silica particle opening surface is perpendicular to the imaging surface are selected from the photographed images. did. The value of D and h of each particle was measured with the image analysis apparatus, and h / D was calculated. In this specification, h / D means an average value of 50 h / Ds.

Example 1
A dispersion medium in which 5 g of magnesium pyrophosphate by metathesis method is mixed as a suspension stabilizer with 200 g of water is placed in a 500 ml separable flask, 0.04 g of sodium lauryl sulfate as a surfactant, and sodium nitrite as a polymerization inhibitor. 0.02 g was dissolved in the dispersion medium.

  Separately, 70 g of methyl methacrylate as a monofunctional polymerizable vinyl monomer, MKC silicate MS57 (Mitsubishi Chemical Corporation: average molecular weight 1300 to 1500 as polyalkoxysiloxane oligomer), R in the above structural formula is methyl, and the average of n is 15 -18) 30 g and a monomer composition prepared by uniformly dissolving 0.25 g of 2,2′-azobis (2,4-dimethylvaleronitrile) as a polymerization initiator was prepared.

  This monomer composition was added to the above dispersion medium, and stirred at 8000 rpm for about 10 seconds with a homomixer (trade name: ULTRA TURRAX T-25, manufactured by IKA) to finely disperse the monomer composition. A separable flask, a thermometer and a reflux condenser were attached to the separable flask, and after replacing with nitrogen, it was placed in a constant temperature water bath (water bath) at 60 ° C. Stirring is continued in the separable flask at a stirring speed of 200 rpm, and the polymerizable vinyl monomer is subjected to suspension polymerization for 10 hours after the temperature of the dispersion medium added with the monomer composition in the separable flask reaches 60 ° C. And 2 g of sodium hydroxide was added to condense the polyalkoxysiloxane oligomer.

  Next, the separable flask is taken out from the constant temperature water bath, the reaction liquid in the separable flask is cooled to room temperature while stirring the separable flask, and hydrochloric acid is added until the pH of the slurry becomes about 2 to obtain a suspension stabilizer. Was decomposed to obtain silica-coated polymer particles in which a part of the surface of the polymer particles was exposed. The obtained particles were subjected to suction filtration with a Buchner funnel using filter paper, washed with 1.2 L of ion exchange water to remove the suspension stabilizer, and dried to take out the target particles. The silica-coated polymer particles obtained have an average particle diameter of 5.8 μm.

  Next, the silica-coated polymer particles were fired in an electric furnace at 500 ° C. to obtain silica particles (average particle diameter 5.6 μm). The shape of the obtained silica particles was observed with an electron micrograph. An electron micrograph is shown in FIG. Table 1 shows the oil absorption, opening ratio, and h / D.

Example 2
The polymer particles were prepared in the same manner as in Example 1 except that 30 g of methyl methacrylate, 70 g of MKC silicate MS57, and 2,2′-azobis (2,4-dimethylvaleronitrile) were changed to 0.15 g. Silica-coated polymer particles with part of the surface exposed were obtained. The average particle diameter of the obtained silica-coated polymer particles is 116.3 μm.

  Next, the silica-coated polymer particles were fired in the same manner as in Example 1 to obtain silica particles (average particle diameter 112.7 μm). The shape of the obtained silica particles was observed with an electron micrograph. An electron micrograph is shown in FIG. Table 1 shows the oil absorption, opening ratio, and h / D.

Example 3
The same method as in Example 1 except that MKC silicate MS51 (Mitsubishi Chemical Co., Ltd .: average molecular weight of 500 to 700, R in the above structural formula is methyl, and n is an average of 5 to 10) was used as the polyalkoxysiloxane oligomer. Thus, silica-coated polymer particles in which a part of the surface of the polymer particles was exposed were obtained. The obtained silica-coated polymer particles have an average particle diameter of 6.4 μm, and the polymer portion derived from the polymerizable vinyl monomer has a Tg of 105 ° C.

  Next, the silica-coated polymer particles were fired in the same manner as in Example 1 to obtain silica particles (average particle diameter 6.1 μm). The shape of the obtained silica particles was observed with an electron micrograph. An electron micrograph is shown in FIG. Table 1 shows the oil absorption, opening ratio, and h / D.

Example 4
The same method as in Example 1 except that MKC silicate MS58B15 (manufactured by Mitsubishi Chemical Corporation: average molecular weight of 1600 to 1800, R in the above structural formula is butyl, and n is an average of 11 to 13) was used as the polyalkoxysiloxane oligomer. Thus, silica-coated polymer particles in which a part of the surface of the polymer particles was exposed were obtained. The average particle diameter of the obtained silica-coated polymer particles is 17.1 μm.

  Next, the silica-coated polymer particles were fired in the same manner as in Example 1 to obtain silica particles (average particle diameter 16.5 μm). The shape of the obtained silica particles was observed with an electron micrograph. An electron micrograph is shown in FIG. Table 1 shows the oil absorption, opening ratio, and h / D.

Example 5
Except that styrene was used as the polymerizable vinyl monomer, silica-coated polymer particles in which a part of the surface of the polymer particles was exposed were obtained in the same manner as in Example 1. The average particle diameter of the obtained silica-coated polymer particles is 12.5 μm.

  Next, the silica-coated polymer particles were fired in the same manner as in Example 1 to obtain silica particles (average particle diameter 12.3 μm). The shape of the obtained silica particles was observed with an electron micrograph. An electron micrograph is shown in FIG. Table 1 shows the oil absorption, opening ratio, and h / D.

Example 6
Except that n-butyl acrylate was used as the polymerizable vinyl monomer, silica-coated polymer particles in which a part of the surface of the polymer particles was exposed were obtained in the same manner as in Example 1. The obtained silica-coated polymer particles have an average particle diameter of 19.5 μm.

  Next, the silica-coated polymer particles were fired in the same manner as in Example 1 to obtain silica particles (average particle diameter 18.8 μm). The shape of the obtained silica particles was observed with an electron micrograph. Table 1 shows the oil absorption, opening ratio, and h / D.

Comparative Example 1
Silica-coated polymer particles were obtained in the same manner as in Example 1 except that tetramethoxysilane (KBM04 manufactured by Shin-Etsu Chemical Co., Ltd.) was used in place of the polyalkoxysiloxane oligomer. The agglomerated irregular shape was a lump larger than 500 μm. When this lump was pulverized, it became amorphous silica particles of 1 μm or less, and the oil absorption was not measured because it was difficult to handle.

Comparative Example 2
The same as in Example 1 except that γ-methacryloxypropyltrimethoxysilane (SZ-6030 manufactured by Toray Dow Corning Silicone Co., Ltd.) having polymerizability with a polymerizable vinyl monomer was used instead of the polyalkoxysiloxane oligomer. Particles were obtained by this method, but in the obtained particles, the resin part derived from the polymer vinyl monomer was dispersed in the particles.

  Next, the particles were fired in the same manner as in Example 1 to obtain porous silica particles (average particle diameter: 6.7 μm). The shape of the obtained silica particles was observed with an electron micrograph. An electron micrograph is shown in FIG. Table 1 shows the amount of oil absorption. The aperture ratio and h / D were not measurable because the silica particles were porous.

The following can be seen from the examples and comparative examples.
From Examples 1 to 6 and Comparative Example 1, it can be seen that when silane which is a monomer is used instead of the polyalkoxysiloxane oligomer, the particles are aggregated and silica particles having a specific shape cannot be obtained.

  From Examples 1 to 6 and Comparative Example 2, when a polymerizable monomer and a polymerizable silane are used in place of the polyalkoxysiloxane oligomer, the polymerizable monomer and the silane are mixed by polymerization to form a unique shape silica. It can be seen that particles cannot be obtained. Moreover, it turns out that oil absorption amount can also be increased because an aperture ratio exists in the range of 0.1-1.

It is a schematic sectional drawing of the silica particle of this invention. 2 is an electron micrograph of silica particles of Example 1. FIG. 2 is an electron micrograph of silica particles of Example 2. 4 is an electron micrograph of silica particles of Example 3. 4 is an electron micrograph of silica particles of Example 4. 6 is an electron micrograph of silica particles of Example 5. 4 is an electron micrograph of silica particles of Comparative Example 2. It is a conceptual diagram for demonstrating the measuring method of the aperture ratio in this invention.

Explanation of symbols

D Diameter of silica particle h Height of silica particle S1 Open area of silica particle S2 Projected area of silica particle

Claims (4)

  Monomer composition by uniformly mixing 100 parts by weight of a polymerizable vinyl monomer, 10 to 500 parts by weight of a polyalkoxysiloxane oligomer inert to the polymerizable vinyl monomer, and 0.01 to 10 parts by weight of a polymerization initiator. After obtaining the polymer particles by subjecting the polymerizable vinyl monomer in the monomer composition to aqueous suspension polymerization in the presence of a suspension stabilizer, the polyalkoxysiloxane oligomer is acid or By condensing in the presence of a base catalyst, silica-coated polymer particles having a silica coating formed so that at least a part of the surface of the polymer particles are exposed are obtained, and the silica-coated polymer particles are baked to obtain a polymer. A method for producing silica particles, wherein the particles are removed to obtain silica particles. The method for producing silica particles according to claim 1 , wherein the polyalkoxysiloxane oligomer has a weight average molecular weight of 300 to 3,000. It is the silica particle obtained by the manufacturing method of Claim 1 or 2, Comprising: The opening ratio of 0.1-1 and the height h and the diameter D of a silica particle are 0.5 <= h / D <. 1. Spherical or substantially spherical silica particles having a hollow structure having at least a part having the relationship of 1. A silica particle obtained by the production method according to claim 1, wherein the oil absorption measured by JIS K 5101 is more than 500 ml / 100 g and not more than 700 ml / 100 g. Spherical or substantially spherical silica particles having a structure.

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