JP2015134898A - Silica-coated organic particle, and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide silica-coated organic particles having excellent fluidity, and to provide a method for producing the same.SOLUTION: A method for producing silica-coated organic particles comprises: a cracking step of cracking raw material silica particles whose volume average particle diameter of the primary particles is 200 nm or less, in such a manner that a bulk density reaches 450 g/L or less by a jet mill; and a mixing step of mixing the silica particles obtained in the cracking step with organic particles having a volume average particle diameter larger than that of the silica particles to stick surfaces of the organic particles. By sticking the silica particles having the above characteristics to the surfaces of the organic particles, the stuck silica particles are interposed among the organic particles to improve the fluidity characteristics of the organic particles. The silica particles having the above characteristics constitute a powder in which the primary particles are separated from each other in spite of their particle diameters in the order of nanometer.

Description

  The present invention relates to silica-coated organic particles and a method for producing the same.

  The powder may not have sufficient handling properties such as fluidity. For example, when powder molding is performed, the flowability of powdered resin (fillability into a mold, etc.) becomes a problem. For example, if aggregation is likely to occur between resin powders, it will be difficult to supply into the mold, and even if it can be supplied into the mold, if the compressibility is not high, the physical properties of the final molded product will be sufficient. It becomes difficult to create.

JP 2011-213514 A

Surface and interface control technology of fluororesin and its application, Eiji Fujita, Daikin Industries, February 1, 2010, 3 pages, 3.1 PTFE, http://www.daikin.co.jp/chm/products/pdfDown .php? url = pdf / technology / technology01.pdf

  The present applicant has provided new knowledge about inorganic oxide particles (for example, Patent Document 1). It was found that the flow characteristics can be improved by attaching nanometer order silica particles to the surface of organic particles.

  This invention is completed in view of the said situation, and makes it the subject which should be solved to provide the silica coating organic substance particle | grains which made the silica particle of nanometer order adhere to the surface, and its manufacturing method.

(1) The method for producing silica-coated organic particles of the present invention that solves the above problems is pulverized so that the bulk density is 450 g / L or less with respect to raw material silica particles having a volume average particle size of primary particles of 200 nm or less. Crushing process to
A mixing step in which the silica particles obtained in the crushing step and organic particles having a volume average particle size larger than the primary particles of the silica particles are mixed to adhere the silica particles to the surface of the organic particles. And
The raw silica particles are
A surface treatment step of surface treatment with a silane coupling agent and an organosilazane in a liquid medium containing water;
Removing the liquid medium;
It is processed in the pretreatment process with
The silane coupling agent has three alkoxy groups, a phenyl group, a vinyl group, an epoxy group, a methacryl group, an amino group, a ureido group, a mercapto group, an isocyanate group, or an acrylic group,
The molar ratio of the silane coupling agent to the organosilazane is the silane coupling agent: the organosilazane = 1: 2 to 1:10.

  By attaching the silica particles having the above-mentioned characteristics to the surface of the organic particles, the adhered silica particles are interposed between the organic particles, and the flow characteristics of the organic particles are improved. Silica particles having the above-mentioned characteristics are powders that are almost separated into primary particles despite having a particle size on the order of nanometers.

Regarding (1) above, the following configuration (2) can be adopted.
(2) The surface treatment step includes
A first treatment step of treating with the silane coupling agent;
A second treatment step of treating with the organosilazane,
The second processing step is performed after the first processing step.

Separation of further agglomerated particles can be realized by surface-treating the raw material silica particles under the conditions disclosed in (2).
(3) The silica-coated organic particles of the present invention that solve the above-mentioned problem are silica particles whose primary particles have a volume average particle size of 200 nm or less and a bulk density of 450 g / L or less,
Organic particles having a volume average particle size larger than the primary particles of the silica particles and the silica particles attached to the surface,
The silica particles have a functional group represented by the formula (1): -OSiX ¹ X ² X ³ and a functional group represented by the formula (2): -OSiY ¹ Y ² Y ³ on the surface. (In the above formulas (1) and (2); X ¹ is a phenyl group, a vinyl group, an epoxy group, a methacryl group, an amino group, a ureido group, a mercapto group, an isocyanate group, or an acrylic group; X ² , X ³ Are independently selected from —OSiR ₃ and —OSiY ⁴ Y ⁵ Y ⁶ ; Y ¹ is R; Y ² and Y ³ are each independently selected from R and —OSiY ⁴ Y ⁵ Y ⁶ .Y ⁴ is an R; ^{Y 5} and ^{Y 6} is selected from R and -OSiR ₃ independently;. R is independently selected from alkyl groups of 1 to 3 carbon atoms Incidentally, ^{X 2} , X ³ , Y ² , Y ³ , Y ⁵ , and Y ⁶ are any of the adjacent functional groups X ² , X ³ , Y ² , Y ³ , Y ⁵ , and Y ⁶ , and —O—. May be combined with each other.)

  Since the silica-coated organic particles of the present invention are close to the state where the nanometer-order silica particles that tend to aggregate are separated into primary particles, they are present in a state close to the primary particles even when attached to the surface of the organic particles. It becomes possible. Therefore, an action like “roller” can be exerted on the surface of the organic particles.

2 is a SEM photograph of silica-coated organic particles composed of silica particles of Test Example 1 and spherical polystyrene. It is a SEM photograph of spherical polystyrene. It is a graph which shows the result of the shear test of the silica covering organic substance particle | grains shown in FIG. 1, and the spherical polystyrene shown in FIG. It is a graph which shows the result of the flow rate test of the silica covering organic substance particle | grains shown in FIG. 1, and the spherical polystyrene shown in FIG. 2 is an SEM photograph of silica-coated organic particles composed of silica particles of Test Example 1 and polytetrafluoroethylene (PTFE) particles. It is a SEM photograph of PTFE particles. It is a graph which shows the result of the shear test of the silica covering organic substance particle | grains shown in FIG. 5, and the spherical polystyrene shown in FIG. It is a graph which shows the result of the flow rate test of the silica covering organic substance particle | grains shown in FIG. 5, and the spherical polystyrene shown in FIG. It is a SEM photograph in the test done in order to examine the density of adhesion of the test sample 1 to the particle | grain surface. It is a SEM photograph in the test done in order to examine the density of adhesion of the test sample 1 to the particle | grain surface. It is a SEM photograph which shows a mode when a shear force is applied with respect to PTFE (fine powder) used by evaluation 2B in an Example.

  The silica-coated organic particles of the present invention and the production method thereof will be described in detail below based on the embodiments.

  The silica-coated organic particles of the present invention may be used for any application. In particular, it is desirable that the final product is used in a particle state or a product that is handled in a particle state during production. Even when the particles are handled in a particle state, the silica-coated organic particles of the present invention are contained as they are in the final product, or the form of the silica-coated organic particles of the present invention cannot be found in the final product. In some cases, the silica-coated organic particles of the present invention may be employed as the main constituent or additive only in the process of producing the above.

  Specific applications that can be adopted include particles based on resins and organic substances, toners used in copiers and printing devices, inks, paints, substrates using fluororesins, flame retardants, and foaming agents. Applications can be exemplified.

  The use of the particles per se is not particularly limited. For example, in powder molding, the fluidity is high, so that the mold shape reproducibility and the filling speed into the mold can be expected.

  The toner may be used either in the case where it is mixed with the toner itself or in the case where it is used for the production of toner. Examples thereof include pigments, binders, external additives, and internal additives. The silica-coated organic particles of the present invention are excellent in fluidity and excellent in handleability regardless of whether they are used alone or mixed with other powders. Moreover, since it is excellent in fluidity | liquidity supposing the case where it adheres to the surface of another object, it is easy to make it adhere uniformly.

  For use in inks and paints, they can be used as pigments, dyes, and other additives (vehicles, dispersants, other additives). Furthermore, in the case of a powder coating material, it can also be employed as a powder fluidity modifier.

For substrates using fluororesin, adjust the amount of fluororesin mixed (for example, mixed with inorganic materials such as silica, alumina, etc., alone or even mixed with other organic materials) By doing so, properties such as dielectric constant can be adjusted (for example, low dielectric constant, suitable for applications using high frequency, etc., and can also be a multilayer substrate). Examples of the fluororesin include perfluoroalkyl polymers such as polytetrafluoroethylene, ethylene-tetrafluoroethylene copolymers, and polyvinylidene fluoride.
The surface of the object (textile products such as woven fabrics, knitted fabrics, non-woven fabrics, and fiber compressed products) that are desired to improve the flame retardancy in resin compositions obtained by mixing flame retardants with resin materials It is possible to improve the flame retardancy by adhering to. Since the fluidity can be improved by applying the present invention to a flame retardant, it can be more uniformly dispersed in the resin composition, and can be more uniformly adhered to the surface. As a result, the same flame retardancy can be imparted with a small amount.
The foaming agent is foamed by heating the resin composition obtained by mixing with a resin material or the like used as a raw material of a molded product under predetermined conditions. Since the fluidity can be improved by applying the present invention to a foaming agent, it is expected that the resin composition can be dispersed more uniformly in the resin composition, and as a result, the same foamability is imparted in a small amount. Can do.

(Silica-coated organic particles)
The silica-coated organic particles of the present embodiment include organic particles and silica particles attached to the surfaces of the organic particles. The method for attaching the silica particles to the surface of the organic particles is not particularly limited, and can be carried out by simply mixing or applying vibration after mixing. The silica particles can be attached to the surface of the organic particles in a dry state. The mixing ratio of organic particles and silica particles is not particularly limited. Even if the amount is small, if the silica particles are present on the surface of the organic particles, it is considered that the effect of improving the flow characteristics by the silica particles can be exhibited. For example, the content of silica particles can adopt the upper limit of about 10%, 5%, and 2% as a preferable range based on the mass of the organic particles, and the lower limit is about 0.001%, 0.005%, and 0.01%. Can be adopted as a preferred range.

  The organic particles are not particularly limited except that the organic material alone or the organic material is a main component (50% or more on a mass basis). The smaller the particle size, the higher the cohesiveness of the organic particles, and the higher the effect of making the silica-coated organic particles of the present invention. Accordingly, the volume average particle diameter of the organic particles is desirably 100 μm or less, more desirably 50 μm or less, and still more desirably 10 μm or less.

  Organic substances constituting the organic particles include resins (natural resins and synthetic resins) and polymers (some of which overlap with the above-mentioned resins, but natural and synthetic, synthetic polymers are polyolefins such as polyethylene polypropylene) , Polystyrene, polyamide, acrylic resin, fluororesin, and the like), or a compound that is not a polymer. Furthermore, if the additive (flame retardant, foaming agent, colorant, antioxidant, light stabilizer, nucleating agent, antistatic agent, plasticizer, etc.) to be added to the resin material is also in powder form, the resin Flowability can be improved by applying the present invention prior to mixing into the material.

  Fluororesin includes polytetrafluoroethylene (PTFE), tetrafluoroethylene / perfluoroalkoxyethylene copolymer (PFA), tetrafluoroethylene / hexafluoropropylene copolymer (FEP), ethylene / chlorotrifluoro Examples thereof include ethylene copolymer (PCTFE), ethylene / tetrafluoroethylene copolymer (ETFE), and polyvinylidene fluoride (PVDF).

  Among these, PTFE is known as a fine powder obtained by emulsion polymerization and as a molding powder obtained by suspension polymerization (Non-patent Document 1). Fine powder is easily deformed and fiberized by shearing force. When it is used as organic particles constituting the silica-coated organic particles of this embodiment when fiberization is not desired, fiber formation becomes difficult even when an external force such as a shearing force is applied, and the characteristics as a powder for a long time even during handling. Can keep. As an aspect of using the fine powder as a powder, there is use as an anti-drip agent. The anti-drip agent is used to prevent the dropping of dripping when the resin burns, and is added for the purpose of preventing the spread of fire. Molding powder is not easily deformed by external force and is easy to adopt for compression molding.

  Resins and polymers have excellent flow characteristics when the resin or polymer compound is shaped (powder molding, injection molding, etc.). When pharmaceuticals are formulated in a powder state, the formulation (tabletting etc.) is appropriately performed by adopting the powder of drugs, excipients, additives, etc. contained in the formulation as organic particles. It becomes possible.

  The silica particles have a primary particle volume average particle size of 200 nm or less and a bulk density of 450 g / L or less. As a preferable upper limit of the volume average particle diameter of the primary particles, 100 nm, 70 nm, and 50 nm may be mentioned. Moreover, 1 nm is mentioned as a preferable minimum. The silica particles preferably have a particle size of 300 nm or less.

  The measurement of the bulk density in this specification is performed using the Tsutsui-Rikagakuki Co., Ltd. product: electromagnetic vibration type | mold beak density measuring device (MVD-86 type | mold). Specifically, after the sample to be measured is put into the upper 500 μm sieve as the sample tank, the sample is dispersed through the two upper and lower 500 μm sieves under electromagnetic acceleration conditions, and dropped into a 100 mL sample container. The mass was measured, and the bulk density was calculated from the mass and volume. In order to prevent a decrease in bulk density due to its own weight, measurement should be performed within 1 hour after dropping.

  Preferred upper limits for the bulk density include 400 g / L, 370 g / L, 350 g / L, 300 g / L, 280 g / L, and 250 g / L. A preferred lower limit is 100 g / L. By setting the bulk density to a value below these upper limits, primary particles can be separated more reliably. Moreover, when the bulk density is set to a value higher than these lower limits, the bulk is small and the handling becomes easy.

  In the silica particles of this embodiment, functional groups containing carbon are introduced on the surface. The specific structure of the functional group containing carbon and the method of introducing it onto the surface of the silica particles will be described in detail in the method for producing silica particles, which will be described later.

(Method for producing silica-coated organic particles)
The method for producing silica-coated organic particles of the present embodiment is a method in which silica particles produced by performing a crushing step on raw silica particles are adhered to the surface of the organic particles. This is a method that can be suitably used for the production of the silica-coated organic particles of the present embodiment described above. The raw material silica particles have a large proportion of primary particles bonded together, but the bonds can be separated in the crushing step.

  The method for the crushing step is not particularly limited. Preferably, a method of adding an effect of separating the aggregates of the aggregates is preferable, and a method that does not destroy the primary particles constituting the aggregates is preferable. For example, it can be performed by a method similar to pulverization performed in a dry state, and examples thereof include a jet mill, a pin mill, and a hammer mill. It is particularly desirable to use a jet mill. The final stage of the process is judged from the value of the bulk density of the raw silica particles. After the proper bulk density, it can be selected from the range described above. The jet mill is a device that performs pulverization by placing raw material silica particles in an air stream. Any type of jet mill is acceptable. Crushing by a jet mill is desirably performed by a dry method.

  The raw material silica particles have a primary particle size volume average particle size of 200 nm or less. In addition, examples of the upper limit include 100 nm, 70 nm, and 50 nm. The method for producing the raw material silica particles is not particularly limited. For example, a water glass method, an alkoxide method, and a VMC method can be exemplified, and it is desirable to employ the water glass method. The water glass method is a method of precipitating raw material silica particles by performing ion exchange, introduction / desorption of substituents by chemical reaction, control of pH, temperature, and the like on water glass. For example, an aqueous slurry in which nanometer order silica particles are dispersed can be prepared by ion exchange of water glass with an ion exchange resin. The particle diameter of the secondary particles constituting the raw silica particles is not particularly limited, but the volume average particle diameter may be 10 μm or more, 100 μm or more. Furthermore, the raw material silica particles can be produced by dissolving metal silicon in an alkali solution or the like and then depositing it (a method similar to the water glass method).

  A pretreatment process is applied to the preparation of the raw silica particles. The pretreatment process includes a surface treatment process and a process for removing the liquid medium (solidification process). The surface treatment step is a step of performing a surface treatment with a silane coupling agent and an organosilazane in a liquid medium containing water (water, one containing alcohol in addition to water). The silane coupling agent has three alkoxy groups and a phenyl group, vinyl group, epoxy group, methacryl group, amino group, ureido group, mercapto group, isocyanate group, or acrylic group. The molar ratio of the silane coupling agent to the organosilazane is (silane coupling agent) :( organosilazane) = 1: 2 to 1:10.

  The surface treatment step includes a first treatment step for treating with the above-described silane coupling agent and a second treatment step for treating with organosilazane thereafter.

In the surface treatment step, the functional group represented by the formula (1): -OSiX ¹ X ² X ³ and the formula (2): -OSiY ¹ Y ² Y are applied to the silica particles obtained by the above-described method. ³ is a step of obtaining raw material silica particles in which the functional group represented by ³ is bonded to the surface. Hereinafter, the functional group represented by the formula (1) is referred to as a first functional group, and the functional group represented by the formula (2) is referred to as a second functional group.

X ¹ in the first functional group is a phenyl group, vinyl group, epoxy group, methacryl group, amino group, ureido group, mercapto group, isocyanate group, or acrylic group. X ² and X ³ are —OSiR ₃ or —OSiY ⁴ Y ⁵ Y ⁶ , respectively. Y ⁴ is R. Y ⁵ and Y ⁶ are each R or —OSiR ₃ .

Y ¹ in the second functional group is R. Y ² and Y ³ are each —OSiR ₃ or —OSiY ⁴ Y ⁵ Y ⁶ .

The more —OSiR ₃ contained in the first functional group and the second functional group, the more R on the surface of the raw silica particles. As the R (the alkyl group having 1 to 3 carbon atoms) contained in the first functional group and the second functional group increases, the raw silica particles are less likely to aggregate.

Regarding the first functional group, when X ² and X ³ are each —OSiR ₃ , the number of R is minimized. Further, ^{X 2} and ^{X 3} is -OSiY ⁴ Y ⁵ Y ^6, respectively, ^and, if Y 5, ^{Y 6} is -OSiR ₃ respectively, the number of R is maximized.

Regarding the second functional group, when Y ² and Y ³ are each —OSiR ₃ , the number of R is minimized. Further, ^{Y 2} and ^{Y 3} are -OSiY ⁴ Y ⁵ Y ^6, respectively, ^and, if Y 5, ^{Y 6} is -OSiR ₃ respectively, the number of R is maximized.

The number of X ¹ contained in the first functional group, the number of R contained in the first functional group, and the number of R contained in the second functional group are the abundance ratio of R and X ¹ What is necessary is just to set suitably according to the particle size and use of a silica particle.

^{Incidentally, X 2, X 3, Y} 2, Y 3, Y 5, and any of ^{Y 6, X} 2 of the adjacent ^{functionality, X 3, Y 2, Y} 3, Y 5, and any ^{Y 6} You may combine with heel -O-. For example, any one of the first functional group X ² , X ³ , Y ⁵ , and Y ⁶ is the first functional group adjacent to the first functional group X ² , X ³ , Y ⁵ , and It may be bonded to any of Y ⁶ by —O—. Similarly, any of Y ² , Y ³ , Y ⁵ , and Y ⁶ of the second functional group is replaced with Y ² , Y ³ , Y ⁵ , Y ² of the second functional group adjacent to the second functional group. And Y ⁶ may be bonded to each other by —O—. Furthermore, any one of the first functional groups X ² , X ³ , Y ⁵ , and Y ⁶ is the second functional group adjacent to the first functional group, Y ² , Y ³ , Y ⁵ , And Y ⁶ may be bonded to each other by —O—.

In the raw material silica particles, the presence ratio of the first functional groups and second functional groups is 1: 12-1: if 60, the surface of the raw material silica particles and X ¹ and R are present good balance. For this reason, the raw material silica particle whose abundance ratio of the first functional group and the second functional group is 1:12 to 1:60 is particularly excellent in the affinity for the resin and the aggregation suppressing effect. Further, if X ¹ is 0.5 to 2.5 per unit surface area (nm ² ) of the raw silica particles, a sufficient number of first functional groups are bonded to the surface of the raw silica particles, and the first There are also a sufficient number of Rs derived from the functional group and the second functional group. Therefore, also in this case, the affinity for the resin and the aggregation suppressing effect of the raw silica particles are sufficiently exhibited.

In any case, R per unit surface area (nm ² ) of the raw silica particles is preferably 1 to 10. In this case, the balance between the number of X ¹ present on the surface of the raw silica particles and the number of R is improved, and both the affinity for the resin and the aggregation suppressing effect of the raw silica particles are exhibited in a well-balanced manner.

In the raw material silica particles, it is preferable that all of the hydroxyl groups present on the surface of the silica particles are substituted with the first functional group or the second functional group. If the sum of the first functional group and the second functional group is 2.0 or more per unit surface area (nm ² ) of the raw silica particles, the raw silica particles were present on the surface of the silica particles. It can be said that almost all of the hydroxyl groups are substituted with the first functional group or the second functional group.

The raw silica particles have R on the surface. This can be confirmed by an infrared absorption spectrum. Specifically, when the infrared absorption spectrum of the raw silica particles is measured by the solid diffuse reflection method, there is a maximum absorption of C—H stretching vibration at 2962 ± 2 cm ⁻¹ .

  Further, as described above, the raw material silica particles hardly aggregate.

  Note that the raw silica particles can be dispersed again by ultrasonic treatment even if they are slightly agglomerated. Specifically, the raw silica particles can be substantially dispersed to primary particles by irradiating the raw silica particles dispersed in methyl ethyl ketone with ultrasonic waves having an oscillation frequency of 39 kHz and an output of 500 W. The ultrasonic irradiation time at this time may be 10 minutes or less. Whether or not the raw material silica particles are dispersed to the primary particles can be confirmed by measuring the particle size distribution. Specifically, when the methyl ethyl ketone dispersion material of the raw material silica particles is measured with a particle size distribution measuring device such as a microtrack device, and there is a particle size distribution of the raw material silica particles, it can be said that the raw material silica particles are dispersed to primary particles.

  Since the raw silica particles hardly aggregate, they can be provided as raw silica particles that are not dispersed in a liquid medium such as water or alcohol. In this case, since no liquid medium is brought in, it is preferably used as a filler for a resin material.

  Further, since the raw silica particles are difficult to aggregate, they can be easily washed with water.

The raw material silica particles are treated in a step of treating the silica particles with a silane coupling agent and an organosilazane (surface treatment step) in a liquid medium containing water. The silane coupling agent has three alkoxy groups and a phenyl group, a vinyl group, an epoxy group, a methacryl group, an amino group, a ureido group, a mercapto group, an isocyanate group, or an acrylic group (that is, X ¹ described above).

By performing the surface treatment with the silane coupling agent, the hydroxyl group present on the surface of the silica particles is substituted with a functional group derived from the silane coupling agent. The functional group derived from the silane coupling agent is represented by the formula (3); —OSiX ¹ X ⁴ X ⁵ . The functional group represented by the formula (3) is referred to as a third functional group. X ¹ in the third functional group is the same as X ¹ in the functional group represented by the formula (1). X ⁴ and X ⁵ are each an alkoxy group. By surface-treating with organosilazane, the third functional group X ⁴ and X ⁵ are derived from organosilazane —OSiY ¹ Y ² Y ³ (the functional group represented by the formula (2), the second functional group ). When all of the hydroxyl groups present on the surface of the silica particles are not substituted with the third functional group, the hydroxyl groups remaining on the surface of the silica particles are substituted with the second functional group. For this reason, on the surface of the surface-treated raw material silica particles, a functional group represented by the formula (1): -OSiX ¹ X ² X ³ (that is, the first functional group) and a formula (2): -OSiY ^The functional group represented by ¹ Y ² Y ³ is bonded to the functional group (that is, the second functional group). In addition, since the molar ratio of the silane coupling agent and the organosilazane is silane coupling agent: organosilazane = 1: 2 to 1:10, the first functional group and the second functional group in the obtained raw material silica particles are used. The abundance ratio with the functional group is theoretically from 1:12 to 1:60.

In the surface treatment step, the silica particles may be simultaneously surface treated with a silane coupling agent and an organosilazane. Alternatively, the silica particles may first be surface treated with a silane coupling agent and then surface treated with organosilazane. Alternatively, the silica particles may be first surface treated with organosilazane, then surface treated with a silane coupling agent, and then surface treated with organosilazane. In any case, the amount of organosilazane may be adjusted so that all the hydroxyl groups present on the surface of the silica particles are not substituted with the second functional group. The hydroxyl groups present on the surface of the silica particles may all be substituted with the third functional group, or only a part may be substituted with the third functional group, and the other part may be substituted with the second functional group. It may be replaced. All of X ⁴ and X ⁵ contained in the third functional group may be substituted with the second functional group.

A part of organosilazane may be replaced with the second silane coupling agent. As the second silane coupling agent, one having three alkoxy groups and one alkyl group can be used. In this case, X ⁴ and X ⁵ contained in the third functional group are substituted with the fourth functional group derived from the second silane coupling agent. The fourth functional group has the formula (4); - represented by OSiY ¹ X ⁶ X ^7. Y ¹ is the same R as ^{Y 1} in the second functional ^{group, X 6,} X ⁷ is an alkoxy group or a hydroxyl group, respectively. X ⁶ and X ⁷ contained in the fourth functional group are substituted with the second functional group derived from organosilazane, or are substituted with another fourth functional group. In this case, the amount of R present on the surface of the raw silica particles can be further increased. When a part of the organosilazane is replaced with the second silane coupling agent, it is necessary to surface-treat with the organosilazane again after the surface treatment with the second silane coupling agent. This is because X ⁶ and X ⁷ contained in the fourth functional group are finally substituted with the second functional group derived from organosilazane.

When a part of the organosilazane is replaced with the second silane coupling agent, X ⁴ and X ⁵ contained in the first functional group described above are substituted with the second functional group derived from the organosilazane, Substitution with a fourth functional group derived from the second silane coupling agent. When X ⁴ and X ⁵ are substituted with the fourth functional group, X ⁶ and X ⁷ contained in the fourth functional group are substituted with the second functional group or another fourth functional group. Is replaced by If X ^6, X ⁷ contained in the fourth functional group has been replaced by another fourth functional group, X ^6, X ⁷ contained in the fourth functional groups is substituted with the second functional group The For this reason, the second silane coupling agent is an organosilazane set when the surface treatment is performed only with the first coupling agent and the organosilazane (when the organosilazane is not replaced with the second silane coupling agent). A maximum of 5a / 3 mol can be substituted for the amount (a) mol. The amount of organosilazane required in this case is 8a / 3 mol.

  The alkoxy groups of the silane coupling agent and the second silane coupling agent are not particularly limited, but those having a relatively small carbon number are preferred, and those having 1 to 12 carbon atoms are preferred. Considering the hydrolyzability of the alkoxy group, the alkoxy group is more preferably any one of a methoxy group, an ethoxy group, a propoxy group, and a butoxy group.

  Specific examples of silane coupling agents include phenyltrimethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, and 3-glycidoxypropyltrimethoxysilane. 3-glycidoxypropyltriethoxysilane, p-styryltrimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-acryloxypropyltrimethoxysilane, N-phenyl-3 -Aminopropyltrimethoxysilane.

  Any organosilazane may be used as long as it can replace the hydroxyl group present on the surface of the silica particles and the alkoxy group derived from the silane coupling agent with the second functional group described above. preferable. Specific examples include tetramethyldisilazane, hexamethyldisilazane, pentamethyldisilazane, and the like.

  Examples of the second silane coupling agent include methyltrimethoxysilane, methyltriethoxysilane, n-propyltrimethoxysilane, n-propyltriethoxysilane, hexyltrimethoxysilane, and hexyltriethoxysilane.

  In the surface treatment step, a polymerization inhibitor may be added in order to suppress polymerization of the silane coupling agent or polymerization of the second silane coupling agent. As the polymerization inhibitor, common ones such as 3,5-dibutyl-4-hydroxytoluene (BHT) and p-methoxyphenol (methoquinone) can be used.

  The raw silica particles may be provided with a solidification step after the surface treatment step. The solidification step is a step in which the raw material silica particles after the surface treatment are precipitated with a mineral acid, and the precipitate is washed with water and dried to obtain a solid material of the raw material silica particles. As described above, since general silica particles are very likely to aggregate, it is very difficult to disperse once solidified silica particles. However, since the raw silica particles are difficult to agglomerate, they are difficult to agglomerate even if solidified, and are easily redispersed even if agglomerated. In the washing step, washing is preferably repeated until the electrical conductivity of the extraction water of the raw silica particles (specifically, the water in which the silica particles are immersed at 121 ° C. for 24 hours) is 50 μS / cm or less.

  Examples of the mineral acid used in the solidification step include hydrochloric acid, nitric acid, sulfuric acid, and phosphoric acid, and hydrochloric acid is particularly desirable. The mineral acid may be used as it is, but is preferably used as a mineral acid aqueous solution. The concentration of the mineral acid in the aqueous mineral acid solution is preferably 0.1% by mass or more, and more preferably 0.5% by mass or more. The amount of the mineral acid aqueous solution can be about 6 to 12 times based on the mass of the raw silica particles to be cleaned.

  The cleaning with the mineral acid aqueous solution can be performed a plurality of times. The washing with the mineral acid aqueous solution is preferably performed after the raw silica particles are immersed in the mineral acid aqueous solution and then stirred. Further, it can be left in the immersed state for 1 to 24 hours, and further for about 72 hours. When it is allowed to stand, stirring can be continued or not stirred. When washing in the mineral acid-containing liquid, it can be heated to room temperature or higher.

  Thereafter, the raw silica particles washed and suspended are collected by filtration and then washed with water. It is desirable that the water used does not contain ions such as alkali metals (for example, 1 ppm or less on a mass basis). For example, ion exchange water, distilled water, pure water and the like. Washing with water is the same as washing with an aqueous mineral acid solution, after the raw silica particles are dispersed and suspended, they can be filtered, or by continuously passing water through the filtered raw silica particles. Is possible. The end of washing with water may be determined by the electrical conductivity of the extracted water described above, or may be the time when the alkali metal concentration in the waste water after washing the raw silica particles becomes 1 ppm or less, It is good also as the time of the alkali metal concentration of extraction water becoming 5 ppm or less. When washing with water, it can be heated to a room temperature or higher.

  Drying of the raw silica particles can be performed by a conventional method. For example, heating or leaving under reduced pressure (vacuum).

  The silica-coated organic particles and the production method thereof of the present invention will be described based on examples. In this example, when mentioning the particle size, the particle size of the secondary particles is described unless there is a description that the particle size of the primary particles.

[Test Example 1]
(Manufacture of silica particles)
・ Production of raw silica particles Colloidal silica snowtex OS (silica content 20%: manufactured by Nissan Chemical Industries, Ltd .: primary particle size is 10 nm) as 100 parts by weight as an aqueous slurry in which silica particles are dispersed in water as an aqueous medium The pretreatment process (surface treatment process and drying process) was performed.

(Surface treatment process)
(1) Preparatory process 40 mass parts of isopropanol was added to 100 mass parts of aqueous slurry, and the dispersion liquid by which a silica particle was disperse | distributed to the liquid medium was obtained by mixing at room temperature (about 25 degreeC).
(2) First Step 1.82 parts by mass of phenyltrimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd., KBM103) was added to this dispersion and mixed at 40 ° C. for 72 hours. By this step, the hydroxyl group present on the surface of the silica particles was surface treated with a silane coupling agent. At this time, phenyltrimethoxysilane was calculated and added so that a necessary amount of hydroxyl groups (partially) remained without being surface-treated.
(3) Second Step Next, 3.71 parts by mass of hexamethyldisilazane was added to this mixture and left at 40 ° C. for 72 hours. Through this step, the silica particles were surface-treated to obtain a silica particle material. As the surface treatment progressed, the silica particles that became hydrophobic could no longer exist stably in water and isopropanol, and agglomerated and precipitated. The molar ratio of phenyltrimethoxysilane to mexamethyldisilazane was 2: 5.

(Solidification process)
4.8 parts by mass of 35% aqueous hydrochloric acid solution was added to the mixture obtained in the surface treatment step to precipitate the silica particle material. The precipitate was filtered with a filter paper (5A manufactured by Advantech). The filtration residue (solid content) was washed with pure water and then vacuum-dried at 100 ° C. to obtain a silica particle material solid material (raw material silica particles).

  The obtained silica particles had D10 of 8.8 μm, D50 of 124.5 μm, and D90 of 451.9 μm.

(Crushing process)
A crushing step was performed on the obtained raw material silica particles to obtain silica particles of this test example. The crushing step was carried out under the conditions of a crushing pressure of 0.3 MPa and a supply rate of 10 kg / h using a jet mill (manufactured by Seishin Enterprises, model number STJ-200). The obtained silica particles had a bulk density of 251.7 g / L, D10 of 0.8 μm, D50 of 1.8 μm, D90 of 4.0 μm, and primary particles having a volume average particle size of 10 nm.

[Test Example 2]
Instead of the crushing step in Test Example 1, what was spray dried by the spray drying method was used as a test sample of this Test Example. Specifically, 100 parts by mass of the raw material silica particles obtained in the solidification step were dispersed in 200 parts by mass of IPA, which was sprayed at a flow rate of 180 ° C. and 5 L / h and dried. The obtained silica particles had a bulk density of 341.3 g / L.

[Test Example 3]
What was obtained in the solidification step without carrying out the crushing step in Test Example 1 was used as the test sample of this Test Example. The obtained silica particles had a bulk density of 0.769 kg / L, D10 of 8.8 μm, D50 of 124.5 μm, and D90 of 451.9 μm, and the volume average particle size of the primary particles was 10 nm.

[Test Example 4]
Commercially available silica particles (AEROSIL R972, manufactured by Nippon Aerosil Co., Ltd.) were used as test samples in this test example. The silica particles of this test example had a bulk density of 41.0 g / L.

[Test Examples 5 to 7]
In the crushing step in Test Example 1, the bulk density was adjusted by adjusting the crushing pressure and the supply amount. The bulk density of the test sample of Test Example 5 was 271.3 g / L, the test sample of Test Example 6 was 364.6 g / L, and the test sample of Test Example 7 was 249.8 g / L. There was a tendency for the bulk density to increase by increasing the crushing pressure. Although the detailed results are not shown in the following table, it has been clarified that the same effect as the test sample of Test Example 1 is exhibited by performing the same test as the following evaluation test.

(Evaluation 1: Adopting spherical polystyrene as organic particles)
The obtained silica particles of each test example were 0.5 parts by mass, and spherical polystyrene having a volume average particle size of 5 μm (hereinafter referred to as “spherical polystyrene”, manufactured by Soken Chemical Co., Ltd., Chemisnow SX-500H) was 100 parts by mass. The mixture was shaken at 250 rpm for 1 minute using a shaker (Yamato Scientific Co., Ltd .: SA300). An FE-SEM photograph of the obtained mixture is shown in FIG. An FE-SEM photograph of spherical polystyrene alone is shown in FIG.

  As is clear from the figure, it was found that the test sample of Test Example 1 (FIG. 1) had silica particles attached to the surface of spherical polystyrene in the form of primary particles. The primary particles constituting the attached test sample are not aggregated and are attached to the surface of the spherical polystyrene.

  About the obtained mixture and spherical polystyrene alone, adhesion (Cohesion) and basic fluidity energy (Basic Flowability Energy) were measured with a powder layer shear force measuring apparatus (Spectres Co., Ltd., powder rheometer FT4). Adhesiveness was calculated from the results of a shear test (FIG. 3: obtained by extrapolating the value of the shearing force of 0 kPa), and the basic fluidity energy was calculated from the results of the flow rate test (FIG. 4: results at a flow rate of 100 mm / s). Calculated. As a result, spherical polyethylene alone had an adhesion of 0.59 kPa and a basic fluidity energy of 257 mJ, whereas the mixture of Example 1 (silica-coated organic particles) had an adhesion of -0.16 kPa and a basic fluidity. The energy was 50 mJ. That is, it was found that the fluidity is improved by attaching silica particles to the surface of the spherical polystyrene.

(Evaluation 2A: Polytetrafluoroethylene particles (PTFE particles) are adopted as organic particles)
A shaker (Yamato Scientific Co., Ltd.) of the mixture of 0.5 mass parts of the obtained silica particles and 100 mass parts of PTFE particles having a volume average particle diameter of 3 μm (manufactured by Seishin Enterprise Co., Ltd., TFW-3000FK). Using a company manufactured by SA300), shaking was performed at 250 rpm for 5 minutes. An FE-SEM photograph of the obtained mixture is shown in FIG. FIG. 6 shows an FE-SEM photograph of PTFE particles alone.

  As is apparent from the figure, it was found that the silica particles adhered to the surface of the PTFE particles in the state of primary particles in the test sample of Test Example 1 (FIG. 5). The primary particles constituting the adhered test sample are not aggregated and are adhered to the surface of the PTFE particles.

  For the obtained mixture and PTFE particles alone, adhesion and basic fluidity energy were measured in the same manner as in Evaluation 1. Adhesion was calculated from the result of the shear test (FIG. 7), and the basic fluidity energy was calculated from the result of the flow rate test (FIG. 8). As a result, PTFE particles alone had an adhesion of 2.62 kPa and a basic fluidity energy of 1198 mJ, whereas the mixture of Test Example 1 (silica-coated organic particles) had an adhesion of 0.57 kPa and a basic fluidity energy. Was 830 mJ. That is, it was found that fluidity is improved by attaching silica particles to the surface of PTFE particles.

(Evaluation 2B: Adopting polytetrafluoroethylene particles (PTFE particles) as organic particles)
0.5 parts by mass of the silica particles obtained in each test example and 100 masses of PTFE particles having a volume average particle diameter of 3 μm (manufactured by Daikin Industries, Ltd., FA-500H (average particle diameter of 400-500 μm, produced by emulsion polymerization)) The mixture was shaken for 5 minutes at 250 rpm using a shaker (manufactured by Yamato Kagaku Co., Ltd .: SA300) The PTFE particles used (Daikin Industries) can also be used as a drip inhibitor. The agent is related to a plastic flame retardant, and is an additive for imparting anti-drip properties to the resin when it is burned. (Refer to FIG. 11: FIG. 11 (a) to FIG. 11 (c) show the state of fiberization by applying a shearing force. Left as (a), (b), (c) progresses) It can be seen that the particles present in the vicinity of the center of the direction is elongated).

  The tactile sensation of the obtained mixture and PTFE particles alone was compared. As a result, in the mixture (silica-coated organic particles) in which the sample of Test Example 1 was mixed, the feeling of touch was increased.

  Further, adhesion and basic fluidity energy were measured in the same manner as in Evaluation 1. Adhesion was calculated from the results of the shear test, and basic fluidity energy was calculated from the results of the flow velocity test. As a result, PTFE particles alone had an adhesion of 6.7 kPa, and the basic fluidity energy was not measurable because it was fiberized by the weak force applied during measurement, whereas the mixture of the sample of Test Example 1 (silica coating) Organic particles) had an adhesion of 5.1 kPa and a basic fluidity energy of 3200 mJ. That is, it was found that fluidity is improved by attaching silica particles to the surface of PTFE particles.

  As described above, the fluidity can be improved by attaching silica particles in the state of primary particles (silica particles of Test Example 1) to the surface of the organic particles.

  Although detailed numerical data is not shown, the silica particles of Test Examples 2 to 4 were prepared in the same manner as the silica particles of Test Example 1 and the tactile sensations were compared. As a result, the silica particles of Test Example 1 were used. Compared with the silica-coated organic particles, the feeling of smoothness was low.

  As a comparison, the repose angle when the silica particles of Test Example 4 (fumed silica (Aerosil Co., Ltd. Aerosil R972)) were added in the same manner was 60 ° for polystyrene powder alone, and 0 for the silica particles of Test Example 1 for polystyrene powder. .5 mass parts added was 23 °, polystyrene powder added 0.5 mass parts of the silica particles of Test Example 4 was 30 °, and compared with the case where Test Example 4 (fumed silica) was added. The silica particles of Test Example 1 were effective in fluidization.

(Evaluation of silica particle adhesion)
Using a shaker (Yamato Scientific Co., Ltd .: SA300), a mixture obtained by mixing 0.33 parts by mass of test sample 1 with 100 parts by mass of particles (silica) having a volume average particle size of 0.5 μm, at 250 rpm for 1 minute. Shake (mixture A).

  Using a shaker (Yamato Scientific Co., Ltd .: SA300), which is a mixture of 0.25 parts by mass of test sample 1 with 100 parts by mass of particles (silica) having a volume average particle size of 1.5 μm, at 250 rpm for 1 minute. Shake (mixture B).

The FE-SEM photograph of each obtained mixture is shown in FIGS. From the figure, the average value of the amount of silica particles (test sample 1) adhering per unit area (300 nm square) was calculated. Result, mixture A (FIG. 9) in 5 / (300 ^{nm) 2,} was a mixture B (FIG. 10) 6 / (300 ^{nm) 2.}

It is clear that the fluidity is improved in both the mixture A and B before the test sample 1 is added, and the effect is ensured by attaching silica particles to the surface at a density of 5 particles / (300 nm) ² or more. It was found that can be expressed.

  The number of silica particles is measured using a photograph taken with an FE-SEM, 10 regions of 300 nm × 300 nm are randomly selected from the surface of the particle material, and the average value is obtained by counting the number of silica particles present there. Do it by asking. Whether or not it is a silica particle of the present embodiment is determined by whether or not the particle exists as a primary particle on the surface of the particle material. Here, the presence of primary particles means particles in a state where the particles are in contact with each other in a SEM photograph. In addition, although this test is testing with silica (inorganic oxide), the results can be applied to the organic particles of the present invention.

(Evaluation 3: Adopting flame retardant as organic particles)
The fluidity of the obtained silica particles of Test Example 1 mixed with various flame retardants and foaming agents in the proportions shown in Table 1 was evaluated. The numerical value described in the type of flame retardant / foaming agent shown in Table 1 means the average particle diameter. The fluidity was evaluated based on basic fluidity data (BFE: measured with a powder rheometer) or compression rate, which is appropriately selected from properties such as powder bulk density and powder morphology. The BFE and the compression rate were measured using a powder rheometer (Spectres Corporation, powder rheometer FT4). The results are shown in Table 1. Table 1 shows only one of the BFE and the compression ratio, and each shows a relative value when the value when the silica particles of Test Example 1 are not added is 100. The smaller the values of both BFE and compression ratio, the higher the fluidity.

  As apparent from the table, it was found that the fluidity was improved by adding silica particles. From these results, it is presumed that the effect of improving the fluidity can be exhibited no matter what organic particles are employed.

Claims (5)

A crushing step of crushing so that the bulk density is 450 g / L or less with respect to the raw material silica particles having a volume average particle size of the primary particles of 200 nm or less,
A mixing step in which the silica particles obtained in the crushing step and organic particles having a volume average particle size larger than the primary particles of the silica particles are mixed to adhere the silica particles to the surface of the organic particles. And
The raw silica particles are
A surface treatment step of surface treatment with a silane coupling agent and an organosilazane in a liquid medium containing water;
Removing the liquid medium;
It is processed in the pretreatment process with
The silane coupling agent has three alkoxy groups, a phenyl group, a vinyl group, an epoxy group, a methacryl group, an amino group, a ureido group, a mercapto group, an isocyanate group, or an acrylic group,
The molar ratio of the silane coupling agent to the organosilazane is the silane coupling agent: the organosilazane = 1: 2 to 1:10.
A method for producing silica-coated organic particles characterized by the above. The surface treatment step includes
A first treatment step of treating with the silane coupling agent;
A second treatment step of treating with the organosilazane,
The method for producing silica-coated organic particles according to claim 1, wherein the second treatment step is performed after the first treatment step. 3. The method for producing silica-coated organic particles according to claim 1, wherein 5 or more of the silica particles are present per ² (300 nm) ^{2 on} the surface of the organic particles. Silica particles having a primary particle volume average particle size of 200 nm or less and a bulk density of 450 g / L or less;
Organic particles having a volume average particle size larger than the primary particles of the silica particles and the silica particles attached to the surface,
The silica particles are coated with silica having a functional group represented by the formula (1): -OSiX ¹ X ² X ³ and a functional group represented by the formula (2): -OSiY ¹ Y ² Y ³ on the surface. Organic particles. (In the above formulas (1) and (2); X ¹ is a phenyl group, a vinyl group, an epoxy group, a methacryl group, an amino group, a ureido group, a mercapto group, an isocyanate group, or an acrylic group; X ² , X ³ Are independently selected from —OSiR ₃ and —OSiY ⁴ Y ⁵ Y ⁶ ; Y ¹ is R; Y ² and Y ³ are each independently selected from R and —OSiY ⁴ Y ⁵ Y ⁶ .Y ⁴ is an R; ^{Y 5} and ^{Y 6} is selected from R and -OSiR ₃ independently;. R is independently selected from alkyl groups of 1 to 3 carbon atoms Incidentally, ^{X 2} , X ³ , Y ² , Y ³ , Y ⁵ , and Y ⁶ are any of the adjacent functional groups X ² , X ³ , Y ² , Y ³ , Y ⁵ , and Y ⁶ , and —O—. May be combined with each other.) 5. The silica-coated organic particles according to claim 4, wherein 5 or more of the silica particles are present per ² (300 nm) ^{2 on} the surface of the organic particles.