JP4976613B2 - Method for producing silica sol - Google Patents

Description

【００５８】
【表２】

【００５９】
（応用例）
実施例１で得たシリカゾルを入口温度３００℃、出口温度１２０℃のスプレードライヤーを用いて乾燥し、平均粒子径７．８μmの球状粒子を得た。この球状粒子を樹脂１００重量部当たり０．３重量部添加した厚さ１００μmのＬＬＤＰＥフィルムを作成し、フィルムのブロッキング性、スクラッチ性を測定した。
【００６０】
ブロッキング性は、２枚のフィルムを重ね、２００ｇ／ｃｍ^２の荷重をかけ４０℃で２４時間放置後、フィルムの剥がれ易さを調べたところ、フィルムが抵抗なく剥がれ、ブロッキング性が良好であることが確認された。
【００６１】
スクラッチ性については、製膜５時間後フィルム２枚を重ね指で擦ったときの傷付きの程度を調べたところ、フィルムにほとんど傷がついていなかった。
【００６２】
（参考例）
実施例２、比較例１で得られたシリカゾルを試験管に入れ静置して様子を観察した。実施例２の試料は３０日間静置しても沈降がほとんど起こっていなかったが、比較例１の試料は一週間で沈降が起こっていた。
【００６３】
【発明の効果】
本発明によれば、非晶質シリカ微粒子が細孔を有する状態で水中に安定にゾル化したシリカゾルの製造方法を提供することができる。
また、従来の解膠法と異なり簡単な操作で高濃度且つ安定性の高いシリカゾルを得ることができる。
更に本発明によるシリカゾルは適度な細孔を有しており、インクジェット用コート剤として用いた場合、従来のコート剤と比較して優れたインク吸着特性及び発色性能を示し有用である。
【図面の簡単な説明】
【図１】市販のシリカゾル（比較例２）を乾燥して、水銀圧入法により求めた細孔分布を示す図である。
【図２】市販のシリカゲル粒子について、水銀圧入法により求めた細孔分布を示す図である。
【図３】本発明のシリカゾル（実施例１）を乾燥し、水銀圧入法により求めた細孔分布を示す図である。
【図４】本発明の実施例１で得られたシリカゾルの粒子構造を示すＴＥＭ写真である。
【図５】本発明の実施例３で得られたシリカゾルの粒子構造を示すＴＥＭ写真である。[0001]
[Field of the Invention]
  The present invention relates to a stabilized silica solIs related to the manufacturing method ofMore specifically, a silica sol in which amorphous silica fine particles dispersed in an aqueous medium have pores.How to manufactureAbout.
[0002]
[Prior art]
In general, silica sol is a dispersion in which amorphous silica fine particles having a particle size of 1 nm to 1000 nm are stably dispersed in an aqueous medium without settling, and is also called colloidal silica.
[0003]
A typical method for producing an aqueous silica sol consists of dealkalising a dilute aqueous solution of alkali silicate by ion exchange, stabilizing, polymerizing, concentrating, modifying, and purifying as necessary. .
JP-A-61-158810 discloses a method in which an alkali metal silicate is diluted with pure water, contacted with a strong acid cation exchange resin, dealkalized, and further acidified to make it strongly acidic. Prepare a heel sol by adding ammonia to a part of the oligosilicic acid solution obtained by removing impurities using an outer filtration membrane and heating it, and gradually drop the remaining oligosilicic acid solution on this to produce a high-purity silica sol. How to do is described.
[0004]
It is already known to produce a stable silica sol by peptizing once gelled silica gel. Japanese Patent Publication No. 48-31839 discloses that once gelled silica gel is SiO 2.₂On the other hand, it is described that a stable silica sol is produced by peptization in the presence of 1 to 5 mol% ammonia or the like.
[0005]
Japanese Patent Publication No. 6-47450 discloses a method for producing silica sol by peptizing a silica hydrogel obtained by once gelling an aqueous solution of an alkali metal silicate.₂Ammonia gas is added to silica hydrogel with a concentration of 10 to 25% by weight.₂Against NH₃There is described a method for producing a silica sol, characterized in that it is pressure-absorbed to an amount of 10 mol% or more and peptized under heating at 100 to 200 ° C.
[0006]
[Problems to be solved by the invention]
The known silica sol has a large specific surface area because the particle size of the amorphous silica particles is fine, but has almost no adsorptivity as seen in silica gel because there are no pores inside. Not.
[0007]
For this reason, silica sol has little effect as an ink receiving layer for ink jet recording, and in order to solve this problem, in Japanese Patent Application Laid-Open No. 60-219083, cationic colloidal silica and anionic colloidal are included in the ink receiving layer. By containing silica, adsorptivity to the dye is imparted.
[0008]
  The present inventors have shown that amorphous silica fine particles can be stably solated in water with pores, and that this silica sol exhibits excellent adsorption performance when applied to a substrate such as paper.Found.
  That is, an object of the present invention is to provide a silica sol that is stably solated in water with amorphous silica fine particles having pores.A method for manufacturingprovideIt is in.
[0009]
[Means for Solving the Problems]
  According to the present invention, an alkali silicate solution and a mineral acid solution, Mix at a temperature of 50 ° C. or lower so that the pH during neutralization is 7 to 11,The granular hydrogel is gelled into a granular alkaline hydrogel and the substantially granular form is maintained.Pre-wash, then acid treatment to pH below 4;A method for producing a silica sol is provided by subjecting the silica hydrogel after the main washing to peptization under hydrothermal conditions while being immersed in water.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
[Action]
  Of the present inventionManufactured by the methodSilica sol(Hereinafter, it may be called the silica sol of the present invention)Is composed of amorphous silica fine particles dispersed in an aqueous medium, and the amorphous silica fine particles have a pore radius of 30 to 300 angstroms, preferably 30 to 200 angstroms, measured in a dry state. It has a distribution peak and has a pore volume in the range of the pore radius of 0.30 to 1.00 mL / g, preferably 0.35 to 0.90 mL / g.
[0011]
As already pointed out, the known silica sol (colloidal silica) has lost pores at the stage of stabilization and polymerization, and has a pore distribution peak at a pore radius of 30 to 300 angstroms, preferably 30 to 200 angstroms. Does not have. FIG. 1 of the accompanying drawings shows the pore distribution obtained by drying a commercially available silica sol and obtained by mercury porosimetry. According to this pore distribution curve, pores due to inter-particle gaps are observed at pore radii of 100,000 angstroms or more, but there are only a few pores of 0.1 mL / g or less at pore radii of 300 angstroms or less. .
[0012]
On the other hand, ordinary silica gel used as a desiccant has a pore distribution peak in a region having a smaller pore radius, that is, a pore radius of 40 angstroms or less. It is understood that the hole is an adsorption site for moisture in the air.
FIG. 2 shows the pore distribution obtained by the mercury intrusion method for commercially available silica gel particles. According to this pore distribution curve, there are almost no pores with a pore radius of 1000 to 100 mm, and It is suggested that a distribution peak exists in pores having a pore radius of 40 angstroms or less, which is close to the measurement lower limit.
[0013]
On the other hand, FIG. 3 shows the pore distribution obtained by drying the silica sol of the present invention and determining by mercury porosimetry. According to this pore distribution curve, the amorphous silica fine particles have a pore distribution peak at a pore radius of 30 to 300 angstroms, preferably 30 to 200 angstroms, and have unique pores (mesopores). It is clear to have.
[0014]
In addition to this feature, the amorphous silica sol particles according to the present invention are also obtained by mercury porosimetry in a dry state, and 0.30 to 1.00 mL / g, preferably within a pore radius range of 30 to 300 angstroms, It has a pore volume of 0.35 to 0.90 mL / g.
For this reason, mesopores exhibit excellent adsorptivity to various effective substances and also have a large adsorption capacity.
[0015]
In fact, when the silica sol according to the present invention is used for coating of an ink jet recording element, the print density is remarkably superior to that of conventional silica.
See the examples below.
For example, for black ink, a recording paper coated with commercially available silica sol (colloidal silica) exhibits an image density of 1.85, and a recording paper coated with commercially available inkjet silica exhibits an image density of 1.96. In contrast, the recording paper coated with the silica sol of the present invention shows an image density of 2.45, and the unexpected effect of the present invention is clear.
[0016]
In the silica sol of the present invention, it is preferable that the amorphous silica fine particles have a primary particle diameter of less than 100 nm, preferably 50 nm or less, as determined by an electron micrograph. Within the above range of the primary particle diameter, the amorphous silica fine particles are stabilized against gravity sedimentation by Brownian motion, and the sedimentation can be suppressed to substantially zero even when actually left for 30 days.
FIG. 4 is an electron micrograph of amorphous silica in the silica sol of the present invention, showing that the primary particle diameter is 30 nm or less.
[0017]
The silica sol of the present invention preferably has a silica concentration in the range of 5 to 30% by weight, particularly 10 to 20% by weight. When the concentration is within the above range, this silica sol can be advantageously used as it is for coating on various substrates. If the concentration is below the above range, the cost for transporting the sol is high, and the energy cost for evaporating the moisture during coating is not preferable, and if the concentration is above the above range, the viscosity is low. This is not preferable because it tends to be too high and difficult to handle.
The silica sol of the present invention has a relatively low viscosity despite the concentration being in the above range, for example, the viscosity at a temperature of 20 ° C. is 50 centipoise or less.
[0018]
The amorphous silica fine particles in the silica sol of the present invention are generally 100 to 200 m as measured in a dry state.²/ G, especially 100-160m²It preferably has a BET specific surface area of / g. In general, the specific surface area is closely related to the particle diameter and the micropores. That is, the specific surface area increases as the particle size decreases, and the specific surface area decreases as the micropores disappear and migrate to mesopores.
[0019]
The silica sol of the present invention preferably has a sodium content of 1000 ppm or less, preferably 600 ppm or less.
[0020]
(Preparation of silica sol)
According to the present invention, the raw material alkali silicate is an easily reactive silica recovered from clay-based raw materials such as water glass sodium silicate and potassium silicate, which are standardized as industrial products, and acid clay. It is possible to use an alkali silicate obtained by reacting an alkali metal hydroxide solution.
SiO in alkali silicate aqueous solution₂The concentration should be in the range of 6 to 28% by weight, SiO 2₂: R₂The molar ratio of O (R is an alkali metal) should generally be in the range of 2: 1 to 4: 1, especially 2.5: 1 to 3.5: 1.
[0021]
As the mineral acid used for the neutralization reaction, hydrochloric acid, sulfuric acid, etc. are generally used, but these mixed acids can also be used. The concentration of the aqueous mineral acid solution should generally be in the range of 5 to 75% by weight, in particular 10 to 60% by weight.
[0022]
Moreover, the component of aluminum and an alkaline-earth metal component can also be contained in a silica gel particle.
Aluminum component is SiO₂  Based on 1 mole, Al₂O₃Is preferably used in an amount of 1 mol or less, while the alkaline earth metal component is SiO 2₂  It is preferable to use 1 mol or less as an oxide standard (MO) based on 1 mol.
[0023]
  Neutralization reaction by contact of both raw materials is a method of adding one raw material of both raw materials to the other solution with stirring, a method of simultaneously contacting both raw material solutions under a certain condition, such as a two-fluid nozzle There is a way to mix instantly.The neutralization temperature is 50 ° C. or lower, and an alkali sol is generated by setting the pH at the end of neutralization to 7 to 11.
[0024]
(Preliminary cleaning)
In order to obtain high-purity and high-concentration silica sol in the present invention, it is necessary to remove by-product salts such as sodium at this stage. A fixed-type cleaning device is recommended for the preliminary cleaning, but a continuous cleaning device may be used as long as it can remove by-product salts as long as the spherical gel is not destroyed.
[0025]
(Acid treatment / water washing process)
When the silica hydrogel is an alkali gel, acid treatment is performed with an acid such as sulfuric acid or hydrochloric acid in order to remove the alkali content in the gel. The degree of acid treatment is not particularly limited as long as the pH of the hydrogel is 4 or less.
Further, in order to remove impurities (by-product salts, etc.) contained in the hydrosol, further washing with water is performed. The degree of washing with water is that the content of impurities in the hydrosol is SiO 2₂As long as it is 0.5% by weight or less based on the above.
[0026]
(Peptization process)
The hydrosol after washing with water is peptized under hydrothermal conditions in a water immersion state. This treatment is performed using an autoclave. The temperature is suitably 120 to 180 ° C., particularly 150 to 170 ° C., and the treatment time is generally about 0.5 to 10 hours, although it varies depending on the concentration and temperature of the hydrosol. At this time, a peptizer may be added as necessary. Peptization aids (ammonia water, amine compounds, alkali metal hydroxides, etc.) are intended to promote peptization by bringing the atmosphere to the alkali side and are effective in peptization. Any one is acceptable, but ammonia water is particularly recommended.
It is effective to add the peptization aid at 0 to 20% by weight based on the hydrogel weight.
[0027]
(Use)
The silica sol of the present invention includes, for example, abrasives, phosphor adhesive binders in the manufacture of cathode ray tubes, pigments and ceramic glazes, pigments, ink matting agents, media for improving the defoaming effect, catalysts, as well as inkjet recording element coatings Carrier, sand-type filler in casting, anti-slip when forming film and paper, anti-slip and anti-contamination medium for floor wax, binder when forming phosphor, anti-static film forming medium, resin filler, It is also useful as a gelling agent for electrolyte in a battery, a medium (battery separator) for preventing fluctuation and scattering, and a fiber treatment agent.
[0028]
The silica sols of the present invention are particularly useful for coating inkjet recording elements. Inkjet recording has advantages such as low noise, high-speed recording, and easy multi-coloring, and is applied to various printers, facsimiles, and the like. With coated paper used for this purpose, ink droplets adhering to the paper surface are quickly absorbed into the paper, spreading and bleeding of the ink droplets on the paper surface are suppressed, and a clear image with high density is formed. And characteristics such as excellent fastness of the image.
[0029]
The recording paper coated with the silica sol of the present invention can satisfy both the requirements for preventing the spread and bleeding of ink droplets and the requirement for improving the density and sharpness of the image in ink jet recording. Dye dots formed by inkjet on recording paper using silica sol are excellent not only in color sharpness and density in the initial state, but also in that there is no photobleaching or discoloration over time.
[0030]
According to the present invention, in order to provide the above-described silica sol on the surface of a substrate such as paper, the silica sol is 5 to 30% by weight, particularly 15 to 30% by weight, and if necessary, the binder is 0 to 15% by weight. In particular, it contains 0 to 10% by weight, and silica sol is 3 to 20 g / m.², Especially 5 to 15 g / m²Apply at a coating amount such that
[0031]
As the binder, an aqueous binder is advantageous, for example, carboxymethyl cellulose, ethyl cellulose, hydroxyethyl cellulose, starch, carboxymethyl starch, cyanoethylated starch, casein, gum arabic, tragacanth gum, dextrin, polyvinyl alcohol, Water-soluble binders such as vinyl ether / maleic acid copolymer, polyvinyl pyrrolidone, and water-soluble acrylic resin; Self-emulsifying binders such as self-emulsifying acrylic resin; Aqueous latex type binders such as styrene-butadiene copolymer latex A dressing or the like is used.
[0032]
The silica sol of the present invention can be used alone as a filler for ink jet recording, and can be used in combination with other fillers known per se, such as alumina sol, titania sol, kaolin, ordinary silica, calcium carbonate and the like. You can also.
[0033]
Furthermore, the silica sol of the present invention (including the silica sol to which aluminum and alkaline earth metal are added) has a volume median diameter of 3 to 20 μm by spray drying granulation of the sol as well as the above-mentioned uses. It can be used as spherical silica gel particles.
In this case, the spherical silica gel particles can be obtained by using a two-fluid nozzle (gas-liquid mixing), atomizing silica sol droplets, and spraying them in a drying atmosphere temperature (exit temperature) of 90 to 150 ° C. .
[0034]
The spherical silica gel particles thus obtained are useful as a thermoplastic resin, a thermosetting resin or a filler for blending various rubbers, particularly as an antiblocking agent.
That is, the spherical silica gel particles have a low water absorption and no inconvenience such as foaming because the equilibrium moisture content at a relatively high humidity is suppressed to a relatively low range, and also between other additives. There are no inconveniences such as coloring due to adsorption and performance deterioration of additives, and it can be an excellent compounding agent for resin films, particularly an antiblocking agent.
[0035]
As the thermoplastic resin to be blended as the antiblocking agent, an olefin resin is suitable, and particularly, low-, medium- or high-density polyethylene, isotactic polypropylene, syndiotactic polypropylene, or ethylene or these a polypropylene polymer which is a copolymer with α-olefin, linear low density polyethylene, ethylene-propylene copolymer, polybutene-1, ethylene-butene-1 copolymer, propylene-butene-1 copolymer, An ethylene-propylene-butene-1 copolymer, an ethylene-vinyl acetate copolymer, an ion-crosslinked olefin copolymer (ionomer), an ethylene-acrylic acid ester copolymer, etc. may be mentioned. These may be used alone or in combination of two or more. Can also be used in the form of blends. The spherical silica gel-based particles of the present invention are useful as an anti-blocking agent for olefin resin films produced using a metallocene catalyst, and can eliminate the coloring tendency seen in conventional anti-blocking agents.
[0036]
Of course, the antiblocking agent of the present invention can be blended with other resin films known per se, such as polyamides such as nylon 6, nylon 6-6, nylon 6-10, nylon 11 and nylon 12, and polyethylene. It can also be blended in thermoplastic polyesters such as terephthalate and polybutylene terephthalate, polycarbonate, polysulfone, vinyl chloride resin, vinylidene chloride resin, and vinyl fluoride resin.
[0037]
In the case of use as an antiblocking agent, the spherical silica gel particles are used in an amount of 0.1 to 1.0 parts by weight, particularly 0.3 to 0.5 parts by weight, per 100 parts by weight of the thermoplastic resin. Good.
[0038]
Of course, the spherical silica gel particles of the present invention can be blended with the thermoplastic resin, various rubbers, or thermosetting resins as a filler.
[0039]
Examples of elastomer polymers for rubber include nitrile-butadiene rubber (NBR), styrene-butadiene rubber (SBR), chloroprene rubber (CR), polybutadiene (BR), polyisoprene (IIB), butyl rubber, natural rubber, ethylene- Propylene rubber (EPR), ethylene-propylene-diene rubber (EPDM), polyurethane, silicone rubber, acrylic rubber, etc .; thermoplastic elastomers such as styrene-butadiene-styrene block copolymer, styrene-isoprene-styrene block copolymer, hydrogen Styrene-butadiene-styrene block copolymer, hydrogenated styrene-isoprene-styrene block copolymer, and the like.
[0040]
Examples of the thermosetting resin include phenol-formaldehyde resin, furan-formaldehyde resin, xylene-formaldehyde resin, ketone-formaldehyde resin, urea formaldehyde resin, melamine-formaldehyde resin, alkyd resin, unsaturated polyester resin, epoxy resin, bis A maleimide resin, a triallyl cyanurate resin, a thermosetting acrylic resin, a silicone resin, or a combination of two or more of these may be used.
[0041]
In the case of use as a filler, it can be blended in an amount of 10 to 100 parts by weight, particularly 30 to 60 parts by weight per 100 parts by weight of the thermoplastic resin, thermosetting resin or elastomer.
[0042]
In the case of a resin compounding agent, when used as a composition of the spherical silica gel particles of the present invention and a solid organic binding medium that melts at a temperature lower than the molding temperature of the resin to be blended, dispersion into the resin This is advantageous because it can be performed uniformly and uniformly and the wear tendency due to silica can be further reduced.
The solid organic binding medium used in this composition includes (a) hydrocarbons such as natural or synthetic paraffin, microwax, polyethylene wax, chlorinated polyethylene wax, and (b) fatty acids such as stearic acid and lauric acid. (C) fatty acid monoamide type or bisamide type such as stearic acid amide, valmitic acid amide, oleic acid amide, esylic acid amide, methylene bisstearamide, ethylene bisstearamide, (d) butyl stearate , Ester casts such as hydrogenated castor oil, ethylene glycol monostearate, (e) alcohols such as cetyl alcohol, stearyl alcohol, (f) metal soaps such as lead stearate, calcium stearate, and (g) Initial condensate of thermosetting resin or a combination of two or more thereof Combined, and the like.
The spherical silica-based particles and the solid organic binding medium are desirably used in combination at a weight ratio of 1: 1 to 1: 2.
[0043]
Further, the spherical silica gel particles are useful as a carrier for chromatography. Chromatography is a method of separating substances by passing a sample of gas, liquid, solution, etc. through a stationary phase filled with solid adsorbent particles in a cylindrical or strip-like layer and using the difference in the distribution coefficient of each component. Known as.
[0044]
Spherical silica gel-based particles have moderate adsorption activity dropped on a chromatography carrier, have a uniform particle size distribution, and have a shape close to a true sphere, so that operations such as stationary phase formation, adsorption, and desorption can be performed. It is easy and is particularly suitable for this application.
[0045]
Moreover, this spherical silica gel type particle | grain can be used as a hygroscopic filler for semiconductor sealing. The particles are not only excellent in the compounding property and moldability of the resin composition, but also excellent in the fluidity of the compounded resin, and also in the moisture adsorption property, moisture retention property and sustainability in the resin. Are better.
In preparing the resin composition for encapsulating a semiconductor containing this hygroscopic filler, an epoxy resin, a curing agent, a hygroscopic filler or further an inorganic filler is blended and kneaded with a mixer or a roller, and then molded. This composition is used for molding a semiconductor element such as a transistor, IC, LSI, etc., molding, molding mold, storage container (package) and the like. Of course, the resin composition for encapsulating a semiconductor can also be used for bonding a package container and a lid in a liquid or semi-solid form.
[0046]
【Example】
The present invention is specifically described in the following examples. In addition, the measuring method about various physical properties is as follows.
[0047]
[Measuring method]
(1) Pore distribution (mercury intrusion method)
A pore size of 18 to 43500 angstroms was measured for 0.5 g of a sample dried at 150 ° C. for 3 hours using a mercury intrusion porosimeter (Autopore 9220 manufactured by Micromeritics) to determine the pore volume.
[0048]
(2) Particle size
The primary particle size of the particles was determined from TEM (transmission electron micrograph).
[0049]
(3) BET specific surface area
ASAP2010 manufactured by Micromeritics was used, and measurement was performed by the BET method.
[0050]
(4) Na content
It was determined by atomic absorption analysis. The silica sol was dried and measured.
[0051]
(5) Evaluation of inkjet paper
Disperse 6.5 g of filler in 30 g of water at 900 RPM for 10 minutes with a homodesper. Thereafter, 20 g of a 13% PVA117 solution was added (however, it was not added in the case of the present product, SNOWTEX C), and after 900 RPM dispersion for 10 minutes, it was applied to plain paper (8 g / m 2).
After air drying overnight, printing was performed with EPSON PM-750C, and the printing density was measured with Fuji densitometer FSD-103.
[0052]
Example 1
SiO₂Using a two-fluid nozzle having a mixing part at the tip of a 22 wt% sodium silicate solution (A liquid) and 13 wt% sulfuric acid (B liquid) so that the pH is 9 Were mixed and then discharged to obtain a spherical hydrogel. The collected spherical gel was immediately pre-washed. The spherical hydrogel that had been sufficiently pre-washed was placed in a tank filled with a sulfuric acid solution and stirred, and then acid-treated until the pH became 1.0 or less. The hydrogel after acid treatment was washed thoroughly with water to obtain a spherical water-washed gel. Next, the spherical water-washed gel was transferred to an autoclave and immersed in water for peptization. At this time, 1% ammonia water with respect to the hydrogel weight was added as a peptizer. After treatment at 170 ° C. for 4 hours, when the autoclave was opened, there was no substantial residue, and a milky white silica sol having a low viscosity and a transparent feeling was obtained.
The physical properties of silica sol were measured and the results are shown in Table 1. A TEM photograph is shown in FIG.
[0053]
(Example 2)
The spherical water-washed gel prepared in the same manner as in Example 1 was subjected to peptization at 170 ° C. for 4 hours using an autoclave without adding a peptizer. The product obtained by this treatment was a sol-like substance that was not inferior to Example 1. Physical properties of the obtained silica sol were measured, and the results are shown in Table 1.
[0054]
(Example 3)
The silica sol obtained in Example 1 is subjected to a concentration treatment by an evaporation method to obtain SiO.₂A concentrated silica sol having a concentration of 20% was obtained. A TEM photograph of the obtained sol is shown in FIG.
The physical properties of the concentrated sol were measured, and the results are shown in Table 1. In addition, Table 2 shows the results of measuring the color development performance when the concentrated sol was actually applied to plain paper and printed by the inkjet method.
[0055]
(Comparative Example 1)
After preparing spherical silica gel in the same manner as in Example 1, acid treatment and washing in the same manner as in Example 1 were performed without preliminary washing to obtain a spherical water washing gel. In the same manner as in Example 2, the peptization treatment was performed in an autoclave without adding the peptization aid. After the treatment at 170 ° C. for 4 hours, when the autoclave was opened, a silica slurry which was cloudy and relatively viscous was obtained although no spherical hydrogel residue was observed. The physical properties of the obtained silica slurry were measured and the results are shown in Table 1.
[0056]
(Comparative Example 2)
Commercially available colloidal silica (Snowtex C) was prepared. The results of physical property measurement are shown in Table 1. In addition, Table 2 shows the results of coating on plain paper according to the prescription, actually printing by the ink jet method, and measuring the color development performance.
[0057]
[Table 1]

[0058]
[Table 2]

[0059]
(Application examples)
The silica sol obtained in Example 1 was dried using a spray dryer having an inlet temperature of 300 ° C. and an outlet temperature of 120 ° C. to obtain spherical particles having an average particle size of 7.8 μm. An LLDPE film having a thickness of 100 μm was prepared by adding 0.3 part by weight of the spherical particles per 100 parts by weight of the resin, and the blocking property and scratch property of the film were measured.
[0060]
The blocking property is 200g / cm by stacking two films.²When the film was allowed to stand at 40 ° C. for 24 hours and the ease of peeling of the film was examined, it was confirmed that the film peeled without resistance and the blocking property was good.
[0061]
As for the scratch property, when the degree of scratching when two films were rubbed with a finger after 5 hours of film formation was examined, the film was hardly scratched.
[0062]
(Reference example)
The silica sol obtained in Example 2 and Comparative Example 1 was placed in a test tube and allowed to stand to observe the state. The sample of Example 2 had hardly settled even after standing for 30 days, but the sample of Comparative Example 1 had settled in one week.
[0063]
【The invention's effect】
  According to the present invention, a silica sol in which amorphous silica fine particles are stably solated in water with pores.Manufacturing methodCan be provided.
  Also, unlike conventional peptization methods, high concentration and stability can be achieved with simple operations.highA silica sol can be obtained.
  Furthermore, the silica sol according to the present invention has moderate pores, and when used as an inkjet coating agent, it is useful because it exhibits excellent ink adsorption characteristics and color development performance as compared with conventional coating agents.
[Brief description of the drawings]
BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a graph showing pore distributions obtained by drying a commercially available silica sol (Comparative Example 2) and obtaining by mercury porosimetry.
FIG. 2 is a diagram showing the pore distribution obtained by a mercury intrusion method for commercially available silica gel particles.
FIG. 3 is a diagram showing the pore distribution obtained by drying the silica sol of the present invention (Example 1) and determining by mercury porosimetry.
FIG. 4 is a TEM photograph showing the particle structure of the silica sol obtained in Example 1 of the present invention.
FIG. 5 is a TEM photograph showing the particle structure of the silica sol obtained in Example 3 of the present invention.

Claims (2)

An alkali silicate solution and a mineral acid solution are mixed at a temperature of 50 ° C. or lower so that the pH during neutralization is 7 to 11, and gelled into a granular alkaline hydrogel. , Pre-washing while maintaining a substantially granular form , then acid-treating so that the pH is 4 or less, and then subjecting to main washing, and hydrothermally hydrolyzing the silica hydrogel after water washing A process for producing a silica sol by peptizing under conditions. The method according to claim 1, wherein the silica sol is used as an inkjet coating agent.

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