JPH1160231A - Amorphous silica particle having dual structure, its production and use - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce an amorphous silica particle having dual structure, having constant particle diameter without causing fine particles, and excellent in matting activities and anti-blocking activities by using a neutralizing reaction of an aqueous solution of an alkali silicate with an aqueous solution of a mineral acid, and precipitating amorphous silica particles by a sedimentation method on the surface of pulverized particles of an amorphous silica by a gel method. SOLUTION: An aqueous solution of an alkali silicate is neutralized with an aqueous solution of a mineral acid under a condition of pH 2-10 to provide an amorphous silica by a gel method, and the formed silica is subjected to a wet milling. The aqueous solution of the alkali silicate is neutralized with the aqueous solution of the mineral acid in the presence of the wet-milled amorphous silica particles by the gel method under a condition of pH 5-9 to precipitate the silica particles by the segmentation method on the amorphous silica particles by the gel method. The amorphous silica particle has a durable structure consisting of a dense amorphous silica core and a bulky amorphous silica shell, a median diameter within the range of 1-5 μm based on the volume, and <=10 vol.% content of fine particles having <=0.5 μm particle diameter.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an amorphous silica particle having a double structure, its production method and use,
More specifically, the present invention relates to amorphous silica particles having a dual structure of a dense amorphous silica core and a bulky amorphous silica shell, a method for producing the same, and applications such as a matting agent for paint.

[0002]

2. Description of the Related Art For the purpose of lowering the gloss of the surface of a coating film, silica fine powder or the like has been conventionally incorporated into a coating material as a matting agent. Is formed, thereby reducing the gloss value.

As such a matting agent silica, conventionally used is a wet-process silica, that is, a wet-process silica obtained by neutralizing sodium silicate with an acid. Contains finely divided silica having a refractive index of greater than about 1.448 and a loss on ignition value of not more than 2%, obtained by subjecting it to high-temperature heat treatment at a high temperature of about 800 ° C. or more after wet production by a conventional method. A matte composition that features is described.

Japanese Patent Application Laid-Open No. 1-298014 discloses that silica obtained by a wet method has an average particle diameter of 1-20.
It describes a method for producing a matting agent for paints, which comprises pulverizing to a size of μm and then heat-treating at a temperature of 400 to 1000 ° C. for 30 to 120 minutes.

Japanese Patent Application Laid-Open No. 2-289670 discloses an average particle size in the range of at least 1.0 ml / g pore volume of 1 to 10 microns and a specific particle size distribution when dispersed in a coating excipient. A matting agent comprising an inorganic hydrogel is described.

Further, Japanese Patent Application Laid-Open No. 5-117548 discloses a matte coating composition characterized by containing fine silica powder and resin particles having a positive zeta potential and an average particle diameter of 0.01 to 5 μm. Are listed.

Further, JP-A-7-166091 discloses that the BET specific surface area is 30 to 150 m ² / g, the oil absorption is 120 to 280 ml / 100 g, and the bulk specific gravity is 30 to 150 g / l. And a matting agent for paint obtained by subjecting wet-precipitated silica having an average particle diameter of 1.0 to 5.0 μm to a surface treatment with polyethylene wax, wherein the processing amount of the polyethylene wax is 100% or less. A matting agent for paint is described, which is 4 to 12 parts by weight based on parts by weight.

[0008]

The silica fine powder conventionally used as a matting agent has a fine primary particle size, but consists of irregular secondary particles in which these primary particles are aggregated. There is a problem that the particle shape is indefinite, the particle size distribution is wide and uneven, and it is difficult to control the dispersed particle size when dispersed in the paint.

That is, there is a certain limitation on the particle size of silica particles which effectively acts to reduce the gloss by forming irregularities on the surface of the coating film. Particles exceeding this effective particle size do not effectively contribute to the reduction and form particles on the surface of the coating film, which has the disadvantage of impairing the appearance and surface characteristics of the coating film. In addition, with a known silica-based matting agent, the content of particles larger than the effective particle size can be reduced by pulverization or classification, but the content of particles smaller than the effective particle size increases. This causes the following disadvantages.

First, since the content of particles having an effective particle size useful for reducing the surface gloss is small, the amount of the silica-based matting agent per coating material must be increased, which requires a cost. Is also troublesome. In addition, when particles having a particle size smaller than the effective particle size are contained in the paint,
As a result, there is a problem that the viscosity of the coating increases and the coating workability decreases, and further, due to the presence of small-sized particles present in the coating, the hue of the coating becomes dull or the toughness of the coating increases. There is also a drawback that mechanical properties such as properties are reduced. Further, a coating film containing agglomerated particles having a small particle diameter has a large tendency to scratch the surface due to friction or the like.

Further, even if the known amorphous silica-based matting agent has a somewhat satisfactory particle size composition before being compounded, it tends to disintegrate due to shearing force when it is dispersed in a coating material. Integration), which makes it impossible to avoid the disadvantages mentioned above.

Furthermore, one drawback in using amorphous silica is abrasion and scratching. When equipment handling paints is worn or when the coating is rubbed, the coating may be damaged. Scratching occurs. Of course, as seen in the above proposal, if the surface of the amorphous silica particles is surface-treated with polyethylene wax or the like, the slipperiness can be improved, but the above problem has not been completely solved.

[0013] Such disadvantages of the amorphous silica are not limited to the matting agent for paints, but also occur when the amorphous silica is applied to use as an anti-blocking agent for resin films.

Accordingly, an object of the present invention is to solve the above-mentioned problems, and the particle diameter is constant not only in the state of powder but also in the state of being blended in paint or resin, so that no fine particles are generated. Another object of the present invention is to provide amorphous silica particles having a novel structure, which is excellent in matting and anti-blocking effects, has a low tendency to abrasion, and is excellent in scratch resistance or scratch resistance. Another object of the present invention is to provide a method for easily producing the above-mentioned amorphous silica particles having a novel structure with excellent productivity and economic efficiency. Still another object of the present invention is to provide uses of the above-mentioned amorphous silica particles having a novel structure, particularly, a matting agent for paints and an antiblocking agent for films.

[0015]

According to the present invention, the present invention has a double structure of a dense amorphous silica core and a bulky amorphous silica shell, and has a volume-based median diameter of 1 to 5 μm.
And the content of fine particles having a particle size of 0.5 μm or less is 10% by volume or less. In the amorphous silica particles of the present invention, 1. The BET specific surface area is in the range of 150 to 400 m ² / g, and the pore volume in the BET method is in the range of 0.2 to 2 ml / g. 2. the dense amorphous silica core and the bulky amorphous silica shell are present in a weight ratio of 2: 8 to 7: 3, especially in a weight ratio of 3: 7 to 5: 5; 3. The dense amorphous silica core is a gel-formed amorphous silica particle, and the bulky amorphous silica shell is composed of precipitated amorphous silica particles deposited on the surface of the core particle. 200-800 m dense amorphous silica core
² / g BET specific surface area, 0.2 to 2 ml / g
It is preferable that the BET method has a pore volume distribution such that the pore volume of the BET method and the pore volume with a pore radius of 10 to 150 angstroms are 40 to 80% of the total pore volume.

According to the present invention, there is further provided a step of neutralizing an aqueous solution of an alkali silicate and an aqueous solution of a mineral acid under conditions of pH 2 to 10 to produce a gel amorphous silica; A step of wet-milling silica, and a step of neutralizing an aqueous solution of alkali silicate and an aqueous solution of mineral acid under conditions of pH 5 to 9 in the presence of wet-milled gel-processed amorphous silica particles. The present invention provides a method for producing amorphous silica particles having a double structure, wherein silica particles are precipitated on the surface of the gel method amorphous silica particles. In the production method of the present invention, 1. Production of the gel method amorphous silica particles at a temperature of 50 ° C. or less; 2. wet-milling the gel-process amorphous silica so that the volume-based median diameter is 0.5 to 3 μm; 60 to 100 ° C by precipitation of amorphous silica particles
It is preferred to carry out at a temperature of

According to the present invention, there are further provided a matting agent for paints and an antiblocking agent for films comprising the above-mentioned amorphous silica particles.

[0018]

DETAILED DESCRIPTION OF THE INVENTION

[Double Structure Amorphous Silica Particles] (1) The amorphous silica particles of the present invention have a double structure of a dense amorphous silica core and a bulky amorphous silica shell. It is characteristic. This double structure is obtained by observing amorphous silica particles with a transmission electron microscope.
You can check.

(2) FIG. 1 of the accompanying drawings is a transmission electron micrograph of amorphous silica particles having a double structure according to the present invention, while FIG. 2 is a gel amorphous silica particle for comparison. And FIG. 3 is a transmission electron micrograph of the precipitated amorphous silica particles for comparison. From these comparative observations, in the amorphous silica particles having a double structure of the present invention, dense amorphous silica nuclei (cores) are present in the center and bulky amorphous silica which appears to be cotton-like around the core. It can be seen that the coating (shell) exists.

(3) In the present invention, the dense amorphous silica is a component that increases the strength of the particles to prevent the collapsing and powdering of the particles, and also enhances the transparency by improving the refractive index of the particles. It is a component that improves. On the other hand, bulky amorphous silica is a component that contributes to the matting action and the antiblocking action, and also improves the wear resistance and the scratch resistance.

(4) However, when dense amorphous silica particles are incorporated into a paint or a resin, satisfactory matting and anti-blocking effects are not exhibited, and there is a remarkable tendency to abrasion. The coating film has a remarkable tendency to be scratched (see Comparative Example 2 described later). On the other hand, when a bulky amorphous silica is incorporated into a paint or resin, although a certain degree of matting action and antiblocking action can be obtained, the viscosity of the paint and resin tends to increase, and the transparency tends to be poorer. (See Comparative Example 3 described later). This is because bulky amorphous silica particles cause disintegration (disintegration) of the particles, and the proportion of particles having a particle size that effectively acts on matting and anti-blocking is reduced.
It is considered that this is because the fine particles generated by the collapse increase the viscosity. The same tendency as described above is also observed when dense amorphous silica and bulky amorphous silica are simply mixed and used (see Comparative Example 4).

(5) On the other hand, according to the present invention, when a double-particle structure in which dense amorphous silica is used as a core and bulky amorphous silica is used as a shell is used, the powdery state Needless to say, the particle size is constant even when incorporated in a paint or resin, and there is no generation of fine particles: excellent matting action and anti-blocking action, little abrasion tendency, scratch resistance or resistance Excellent abrasion: The coating or resin composition containing the amorphous silica particles is excellent in transparency and gives a deep appearance: the following effects can be obtained (Example 1). reference).

(6) The reason is that the bulky amorphous silica shell contributes to the improvement of the matting action and the antiblocking action, the reduction of the abrasion tendency and the improvement of the scratch resistance, and the dense non-silica shell. Amorphous silica core prevents particle disintegration and powdering, keeps amorphous silica particle size in the most convenient range for matting and anti-blocking effects, and suppresses viscosity increase due to powdering It is considered that this contributes to the improvement of transparency.

(7) In the amorphous silica particles of the present invention, the content of fine particles having a volume-based median diameter in the range of 1 to 5 μm and a particle diameter of 0.5 μm or less is 10% by volume.
It is also important that: That is, since the median diameter is within the above range, the matting action and the anti-blocking action can be maximized even with a small amount of compounding, and the compounding is performed by suppressing the content of fine particles below the above range. An increase in the viscosity of the paint or resin can be suppressed.

(8) The amorphous silica particles of the present invention have the following powder characteristics in connection with having the above-mentioned double structure.
The BET specific surface area is in the range of 150 to 400 m ² / g, and the pore volume in the BET method is in the range of 0.2 to 2 ml / g. If the specific surface area is smaller than the above range, the transparency tends to decrease, while if it is larger than the above range, the particle strength tends to decrease. Further, when the pore volume is larger than the above range, the particle strength also tends to decrease, while when the pore volume is smaller than the above range, the abrasion tends to increase.

(9) In the amorphous silica particles of the present invention, the dense amorphous silica core and the bulky amorphous silica shell have a weight ratio of 2: 8 to 7: 3, particularly 3: 3. : 7 to 5: 5 by weight ratio is good on the above-mentioned balance of performance. When the amount of the dense amorphous silica core is less than the above range, the tendency to powder increases, When the amount of the bulky amorphous silica shell is less than the above range, the matting effect and the anti-blocking effect tend to decrease, and the abrasion and the like tend to increase.

(10) In the amorphous silica particles of the present invention, the core of dense amorphous silica is a gel-processed amorphous silica particle, and the bulky amorphous silica shell is formed on the surface of the core particle. It is preferable in terms of production that the particles are composed of precipitated amorphous silica particles precipitated, but of course, the amorphous silica particles of the present invention are not limited to those produced by this method.

(11) The dense amorphous silica core has a BET specific surface area of 200 to 800 m ² / g and a pore volume of 0.2 to 2 ml / g at a pore radius of 10 to 150 Å. In this range, a bulky amorphous silica shell is formed most smoothly and reliably, and the combination of various actions is excellent.

[Production of Double-Structured Amorphous Silica Particles] (1) In the production method of the double-structured amorphous silica particles of the present invention, an alkali silicate aqueous solution and a mineral acid aqueous solution are prepared under conditions of pH 2 to 10. A step (A) of producing a gel amorphous silica by neutralization, a step (B) of wet-grinding the resulting gel amorphous silica, and the presence of the wet-milled gel amorphous silica particles Below, the aqueous solution of alkali silicate and the aqueous solution of mineral acid are p
(C) neutralizing under conditions of H5 to 9 to precipitate the precipitated amorphous silica particles on the surface of the gel amorphous silica particles.

(2) In the step (A), a silica gel having a uniform composition can be produced by the neutralization reaction at the above-mentioned pH, and this is subjected to the wet pulverization treatment in the step (B) to obtain a homogeneous silica gel. It is possible to produce seed (core) particles in a wide range of particle sizes. In the step (C), by performing a neutralization reaction in the above pH range in the presence of the seed particles, a bulky amorphous silica shell can be reliably formed on the surface of the seed particles, This has the advantage that by-products of bulky amorphous silica particles are extremely small.

(3) In the production method of the present invention, the production of gel method amorphous silica particles is carried out at a temperature of 50 ° C. or less.
Preferred in that it forms gel silica with a uniform structure,
Amorphous silica particles using seeds produced under these conditions,
Excellent in various physical properties.

(4) It is preferable that the wet grinding of the gel-process amorphous silica is performed so that the median diameter on a volume basis is 0.5 to 5 μm. The double-structured amorphous silica particles used for the seeds are:
Inferior in matting and anti-blocking effects, with remarkable abrasion tendency.

(5) Further, the precipitation of the precipitated amorphous silica particles is preferably carried out at a temperature of 60 to 100 ° C., thereby preventing the deposition of free and bulky amorphous silica while providing a matting effect. And a double-structured amorphous silica particle having excellent antiblocking action and abrasion resistance can be produced with good yield and reproducibility.

(Production of Gel Method Amorphous Silica) In the production of a silica hydrogel slurry, an alkali silicate aqueous solution is reacted with an acid aqueous solution to first produce a silica hydrogel.

Alkali silicate as a raw material is converted into an alkali product such as sodium silicate or potassium silicate, such as water glass, which is JIS standardized as an industrial product, and easily reactive silica recovered from a clay raw material, such as acid clay. An alkali silicate or the like obtained by reacting a metal hydroxide solution can be used. The SiO ₂ concentration in the aqueous alkali silicate solution is 6
To 28% by weight, SiO ₂ : M
The molar ratio of ₂ O (M is an alkali metal) should generally be in the range from 2: 1 to 4: 1, especially from 2.5: 1 to 3: 1.

As the mineral acid used in the neutralization reaction, hydrochloric acid, sulfuric acid and the like are generally used, but a mixed acid thereof can also be used. The concentration of the aqueous mineral acid is generally 10 to 75% by weight,
In particular, it is preferably in the range of 20 to 60% by weight.

The neutralization reaction by contacting both raw materials includes a method in which either raw material of both raw materials is added to the other solution with stirring, and a method in which both raw materials solutions are simultaneously contacted under certain conditions. . The neutralization temperature is not particularly limited, but is generally 50 ° C. or less, and the pH at the end of neutralization is suitably in the range of 4 to 7.

The neutralization produces a silica hydrosol, which is converted into a silica hydrogel by leaving the hydrosol generally for 30 minutes or more.

The concentration of SiO ₂ in the hydrogel to be formed is generally as low as 5 to 30% by weight, but in the present invention, in addition to controlling the pores of the hydrogel, controlling the water content (SiO ₂₎
Heat treatment of the silica hydrogel,
A silica hydrogel having a SiO ₂ concentration of 5% or more is used.
The temperature of this heat treatment is suitably 100 to 170 ° C.,
For example, it can be performed in an autoclave.

[0040] After washing the silica hydrogel after the heat treatment, generally diameter coarsely pulverized so that 20 to 100 [mu] m, which SiO ₂ concentration of 15 to 25 wt% and above
And then wet-milled under high-speed shearing. For wet pulverization, a friction inner plate mill known per se, for example, (Dyno mill manufactured by Willy A. Bakkofen) is preferably used, but if high-speed shearing is possible, other wet pulverizers are used. You can also.
In this case, it is important that the temperature of the slurry does not exceed 50 ° C. in order to reduce aggregation between particles.

(Production of Double-Structure Amorphous Silica Particles) According to the present invention, an alkali silicate aqueous solution and a mineral acid aqueous solution are prepared in the presence of the gel-processed amorphous silica particles wet-milled as described above. Is neutralized under the condition of pH 2 to 7 to precipitate the precipitated amorphous silica particles on the surface of the gel amorphous silica particles.

The precipitated amorphous silica is produced by reacting sodium silicate with a mineral acid such as hydrochloric acid, nitric acid and sulfuric acid in a concentrated alkali metal salt solution, as shown in the examples described later.

In this case, as the alkali metal salt solution, an alkali metal salt of an inorganic acid or an organic acid can be used alone or in combination of two or more. The alkali metal salt is suitable in terms of the sedimentation action of amorphous silica and the cost, and if a combination that produces salt as the silicic acid raw material and the acid component is selected, it can be easily recycled as a metal salt solution.

Simultaneous injection of sodium silicate and hydrochloric acid into a concentrated saline solution produces silica by a metathesis reaction, but it is necessary to control the pH at this reaction stage, and during the simultaneous injection, The ripening is carried out while maintaining the pH in the range of 2 to 7, particularly preferably in the range of 3.5 to 6, and after completion of the simultaneous pouring, in the range of 2 to 5. The concentration at the start of simultaneous injection of the saline solution is generally 5 to 30% by weight,
Particularly preferably, the content is in the range of 13 to 18% by weight, while the silica concentration at the end of simultaneous pouring is 1 to 20%.
It should be in the range of weight percent. The temperature during the co-pouring reaction is preferably in the range of 50 to 100 ° C., and the co-pouring reaction is preferably completed in 3 to 20 hours.
After completion of simultaneous pouring, aging is performed at a temperature of
It is preferable to carry out for about a minute to 25 hours. The silica formed is separated from the mother liquor, then washed with water, dried and, if necessary, classified to give the product.

[Use] The amorphous silica particles of the present invention are particularly useful as a matting agent for paints due to having the above-mentioned properties.

The double-structured amorphous silica particles of the present invention have the following formula (1) GPV = P / 100 Pa (1) wherein P is a coating necessary for satisfying a reflectance of 50% at 60 ° gloss. Pa is the number of grams of matting pigment added per 100 g of resin, and Pa is the loose apparent density of matting pigment (g / m
l) The matte pigment volume concentration (ml /
g resin) is in the range of 0.10 to 0.20.

The matting pigment volume concentration (GP) of the above formula (1)
V) represents the volume of the matting agent effectively acting on matting per g of resin in the coating film to be formed. In the eraser, this is 0.21 to 0.50 ml / g resin, whereas in the present invention, it is 0.10 to 0.20 ml / g.
It is evident that the volume of matting agent in the resin range and required to achieve the same matte level has been reduced to a significantly smaller volume than conventional silica-based matting agents.

The surface of the amorphous silica particles used in the present invention is made of an inorganic oxide such as titanium oxide, silicon oxide, zirconium oxide, zinc oxide, barium oxide, magnesium oxide, calcium oxide; It can be coated or surface-treated with a zirconium-based coupling agent.

The granular amorphous silica can be coated with a metal soap, a resin acid soap, a coating of various resins or waxes, etc., if desired. In particular, treatment with an olefin resin wax such as a polyethylene wax, an oxidized polyethylene wax, and an acid-modified polyethylene wax, or a wax such as an animal and plant wax or a mineral wax is effective in increasing the matting effect and improving the scratch resistance. This coating treatment can be easily carried out by adding an aqueous emulsion of wax to the washed amorphous silica cake and mixing. Amorphous silica particles 10
It is preferable that the surface is treated with 1 to 20 parts by weight of wax per 0 part by weight.

In the present invention, the above-mentioned porous silica may be used alone as a matting agent, or may be used in combination with other fillers or pigments in the formulation of paint. Inorganic components used in combination include alumina, Attapull Guide, kaolin, carbon black, graphite, finely divided silica,
Calcium silicate, diatomaceous earth, magnesium oxide, magnesium hydroxide, aluminum hydroxide, slate powder,
Sericite, flint, calcium carbonate, talc, feldspar powder, molybdenum disulfide, barite, vermiculite, whiting, mica, pyroxene clay, gypsum, silicon carbide, zircon, glass beads, shirasu balloon, asbestos,
Glass fiber, carbon fiber, rock wool, slag wool, boron watermelon, stainless steel fiber, titanium white, zinc white, red iron oxide, yellow iron oxide, zeolite, hydrotalcite, lithium, aluminum, carbonate, titanium yellow, chrome oxide green , Ultramarine, navy blue and the like.

The amorphous silica particles of the present invention can be blended into a coating material known per se to form a matte coating composition.

As the paint, oily paint, nitrocellulose paint, alkyd resin paint,
In addition to commonly known coatings such as aminoalkyd coatings, vinyl resin coatings, acrylic resin coatings, epoxy resin coatings, polyester resin coatings, chlorinated rubber coatings, rosin, ester gum, pentaresin, cumarone indene resin, phenol Resin, modified phenol resin, malein resin, alkyd resin, amino resin, vinyl resin, petroleum resin, epoxy resin, polyester resin, styrene resin, acrylic resin, silicone resin, rubber base Paints containing one or more resins, such as resins, chlorinated resins, urethane resins, polyamide resins, polyimide resins, fluorine resins, natural or synthetic lacquers, and the like.

The paint used may be any of solvent-based paints, water-based paints, UV-curable paints, powder paints, etc., depending on how it is used, but the present invention relates to solvent-based paints and water-based paints. Particularly suitable.

The organic solvent for the solution type paint includes: aromatic hydrocarbon solvents such as toluene and xylene; aliphatic hydrocarbon solvents such as n-heptane, n-hexane and isoper; alicyclic solvents such as cyclohexane and the like. Hydrocarbon solvents; acetone, methyl ethyl ketone, methyl isobutyl ketone,
Ketone solvents such as cyclohexanone; alcohol solvents such as ethanol, propanol, butanol, diacetone alcohol; ether solvents such as tetrahydrofuran and dioxane; cellosolve solvents such as ethyl cellosolve and butyl cellosolve; ester solvents such as ethyl acetate and butyl acetate Solvent: One or more kinds of aprotic polar solvents such as dimethylformamide, dimethylacetamide, dimethylsulfoxide and the like can be used. It is appropriate that the resin concentration in the raw material solution is generally in the range of 5 to 70% by weight, particularly 10 to 60% by weight.

As the water-based coating material, a self-emulsifying type or a surfactant emulsifying type coating material is used in addition to an aqueous solution type coating material. Examples of the resin of the water-based paint include an alkyd resin, a polyester resin, an acrylic resin, an epoxy resin, or a combination of two or more of these, which are water-soluble or self-emulsified in an aqueous medium. In a self-emulsifying resin, self-emulsifiability is imparted by neutralizing a carboxyl group with ammonia or amines, or by quaternizing the contained amine. Also, various latex resins are used. Generally, the resin concentration is 1
Suitably, it is in the range of 0 to 70% by weight, especially 20 to 60% by weight.

As the ultraviolet (UV) curable paint, a high solid resin, for example, a UV curable acrylic resin, epoxy resin, vinyl urethane resin, acrylic urethane resin, polyester resin, or the like is used alone or in combination of two or more. You.

Powder coatings include thermoplastic resins such as polyamide, polyester, acrylic resin, olefin resin, cellulose derivative, polyether and vinyl chloride resin, as well as epoxy resin, epoxy / novolak resin, isocyanate or epoxy-curable polyester resin. And the like.

According to the present invention, the above-mentioned paint is prepared by adding the above-mentioned matting agent to a matting pigment having a matting pigment volume concentration (ml / 100 g resin) defined by the formula (1) of 0.10 to 0.20. It is blended to be within the range. As a result, a high matting effect can be imparted to the coating film surface with a small amount of compounding.

The amorphous silica particles of the present invention are also useful as fillers for blending thermoplastic resins, thermosetting resins or various rubbers, especially as antiblocking agents. That is, the amorphous silica particles of the present invention, by suppressing the equilibrium moisture content at a relatively high humidity to a relatively low range, there is no inconvenience such as foaming with low water absorption, and with other additives. There is no inconvenience such as color development due to adsorption or performance deterioration of the additive, and the compound can be an excellent compounding agent for a resin film, particularly an antiblocking agent. In addition, although the adsorption rate of water vapor is not so high, it exhibits sustained adsorbability to water vapor, and exhibits stable and sustained hygroscopicity as a moisture absorbing agent for resin blending.
In other words, it has the property that it does not absorb moisture quickly, but does not want to release moisture once absorbed, so it is used for resin that absorbs moisture in the package or captures moisture that tries to pass through the container. Particularly useful as a hygroscopic agent.

As the thermoplastic resin to be blended as the anti-blocking agent, olefin resins are suitable, especially low-, medium- or high-density polyethylene, isotactic polypropylene, syndiotactic polypropylene, or these. Ethylene to α-
Polypropylene-based copolymer which is a copolymer with olefin, linear low-density polyethylene, ethylene-propylene copolymer, polybutene-1, ethylene-butene-1 copolymer, propylene-butene-1 copolymer, ethylene- Propylene-butene-1 copolymer, ethylene-vinyl acetate copolymer, ion-crosslinked olefin copolymer (ionomer), ethylene-acrylate copolymer, and the like. These may be used alone or as a blend of two or more. It can also be used in the form of objects. The amorphous silica particles of the present invention are useful as an anti-blocking agent for an olefin-based resin film produced using a metallocene catalyst, and can eliminate the coloring tendency observed in conventional anti-blocking agents.

Of course, the antiblocking agent of the present invention
It can be blended with other resin films known per se, for example, nylon 6, nylon 6-6, nylon 6
10, polyamides such as nylon 11, nylon 12, thermoplastic polyesters such as polyethylene terephthalate, polybutylene terephthalate, polycarbonate, polysulfone, vinyl chloride resin, vinylidene chloride resin,
It can also be blended with a vinyl fluoride resin or the like.

When used as an anti-blocking agent, the amorphous silica particles are used in an amount of 0.005 to 10 parts by weight, preferably 0.05 to 3.0 parts by weight, more preferably 100 to 100 parts by weight of the thermoplastic resin. 0.005 to 1.
It is preferably used in an amount of 0 parts by weight.

Of course, the amorphous silica particles of the present invention can be blended with the above-mentioned thermoplastic resins, various rubbers, or thermosetting resins as a filler.

As the elastomer polymer for rubber, for example, nitrile-butadiene rubber (NBR), styrene-
Butadiene rubber (SBR), chloroprene rubber (C
R), polybutadiene (BR), polyisoprene (II
B), butyl rubber, natural rubber, ethylene-propylene rubber (EPR), ethylene-propylene-diene rubber (E
PDM), polyurethane, silicone rubber, acrylic rubber, etc .; thermoplastic elastomers such as styrene-butadiene-styrene block copolymer, styrene-isoprene-styrene block copolymer, hydrogenated styrene-butadiene-styrene block copolymer, hydrogen Styrene-
And isoprene-styrene block copolymer.

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 Resin, bismaleimide resin, triallyl cyanurate resin, thermosetting acrylic resin, silicone resin, or a combination of two or more of these.

In the case of use as a filler, it can be added in an amount of 0.5 to 20 parts by weight, particularly 2 to 10 parts by weight, per 100 parts by weight of the above-mentioned thermoplastic resin, thermosetting resin or elastomer.

For use as a hygroscopic filler,
Depending on the purpose, it can be blended in an amount of 0.5 to 20 parts by weight, especially 2 to 10 parts by weight, per 100 parts by weight of the thermoplastic resin, thermosetting resin or elastomer.

Further, the amorphous silica of the present invention can be used for a coating agent for paper, a chromatographic carrier, a cosmetic base, a paint for electronic parts, a moisture absorbent for electronic parts, and other uses of amorphous silica. Can be.

[0069]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail with reference to the following examples. The physical properties and evaluation methods of the matting agent and the like used in the present invention are as follows.

(1) Particle size An aperture tube of 50 μm was obtained by a Coulter counter (TA-II type manufactured by Coulter Electronics Co., Ltd.).
m.

(2) Specific surface area and pore volume: Sorptomatic Seri manufactured by Carlo Elba
es 1800 was used and measured by the BET method.

(3) Matting effect test method A baking melamine paint (Amilac # 1400 manufactured by Kansai Paint Co., Ltd.) was used as a coating film forming agent.
After adding 5 parts of the matting agent sample to 00 parts by weight and dispersing it at 2500 rpm for 5 minutes using a disper disperser, it was applied to mirror-coated paper using a bar coater # 14, and allowed to stand at room temperature for 20 minutes. Next, baking was performed at 140 ° C. for 20 minutes to prepare a coated plate. Then, 60 ° gloss (gloss (%)) was measured using a digital gloss meter GM-3D manufactured by Murakami Color Research Laboratory.

(4) Test Method for Sedimentation in Resin Two-component polyurethane resin (Normal dry type Retan Clear No. 2)
026 Kansai Paint) diluted with a special thinner
o.4 Adjust viscosity with Ford Cup. Weigh 100 g of this diluted resin into a 200 ml beaker,
3.0 g (2.91 wt%) of the matting agent sample is added, and the mixture is dispersed with a disper at 2500 rpm for 10 minutes. After the completion of the dispersion, the mixed slurry is placed in a 100 ml colorimetric tube with a scale and allowed to stand. A photograph was taken of the settling state 30 days after the start of standing. Further, the slurry was redispersed by shaking the colorimetric tube, and the sedimentation property was evaluated as follows. Sedimentation: Redispersibility ○: The generated precipitate is lightly shaken and redispersed. Δ: The generated precipitate is shaken strongly and redispersed. ×: The resulting precipitate does not redisperse even if shaken vigorously.

(5) Friction test (scratch resistance) Test piece 1 (3 × 3 cm cut paper) and test piece 2 (20 × 4 cm cut paper) were prepared from the coated paper obtained in (3).
The test piece 2 was fixed on a glass plate with the coating of test piece 2 facing up.
Is placed on the test piece 2 so that it fits. In this case, per 1cm ² carrying a weight of 900g on the test piece 1 100
g of load was applied. Next, the test piece 1 was moved from one end of the test piece 2 to the other end, and the surface condition of the rubbed coated plate was observed. The number of times of friction (reciprocation / times) of 5, 15, and 25 was evaluated by visual observation below for the scratch resistance of the coating film. Evaluation by visual observation Evaluation rank Streak Mottled pattern 1 Slightly visible None 2 Clearly visible None 3 Clearly visible 30-70% of the whole 4 Clearly visible 70% or more of the whole

Example 1 (First Step) 86 kg of No. 3 sodium silicate (SiO ₂ concentration: 22%) and 253 water were placed in a 500 L stainless steel container.
After adding Kg, the temperature was raised to 35 ° C. while stirring. After the temperature was raised, sulfuric acid was added thereto until the pH reached 2.5, to obtain a gel method amorphous silica sol. After completion of the pouring, aging was performed for 5 hours. After the completion of ripening, wet pulverization was performed with a mycolloider. (Second step) 60 kg (3 kg of SiO ₂ ) of the gel method amorphous silica sol obtained in the first step is weighed in a 150 L stainless steel container and heated to 85 ° C. with stirring. After heating, 1% sodium silicate diluted to 13% silica concentration was added to 1
3.6 kg was added at a rate of 0.35 L / min, and 30% sulfuric acid was added simultaneously while adjusting the reaction pH to 7.5.
Minutes of simultaneous dosing. After completion of the simultaneous pouring, aging was performed for 30 minutes. After the ripening, sulfuric acid was added to adjust the pH to 3.5. After the pH was adjusted, filtration and washing were performed to obtain a cake. Thereafter, the filter cake was dried, pulverized and classified to obtain amorphous silica particles having a double structure. Table 1 shows the physical property values and evaluation results of the obtained powder.

(Example 2) In the second step of Example 1, the amount of the amorphous silica sol of the gel method was 90 kg (SiO 2).
_The procedure was performed in the same manner as in Example 1 except that the amount was 4.5 kg for ₂ minutes. Table 1 shows the physical property values and evaluation results of the obtained powder.

Example 3 In the second step of Example 1, the amount of the amorphous silica sol of the gel method was changed to 40 kg (SiO 2).
_The procedure was carried out in the same manner as in Example 1 except that ₂ minutes was 2 kg). Table 1 shows the physical property values and evaluation results of the obtained powder.

Example 4 The same procedure as in Example 1 was carried out except that the reaction pH was changed to 6 in the precipitation of amorphous silica particles by the precipitation method in the second step of Example 1. Table 1 shows the physical property values and evaluation results of the obtained powder.

Example 5 In the second step of Example 1, the reaction temperature was set to 70 in the precipitation of the precipitated silica particles by the precipitation method.
The procedure was performed in the same manner as in Example 1 except that the temperature was changed to ° C. Table 1 shows the physical property values and evaluation results of the obtained powder.

(Example 6) A low molecular weight polypropylene wax emulsion (UMEX EM-100, manufactured by Sanyo Chemical Co., Ltd.) was added to the cake after the filtration and washing in the second step of Example 1, and polypropylene was mixed with 100 parts by weight of silica. Amorphous silica surface-treated was added by adding 10 parts by weight of pure wax. Table 1 shows the physical property values and evaluation results of the obtained powder.

(Example 7) The same procedure as in Example 1 was carried out except that the temperature in the first step of Example 1 was 45 ° C. Table 1 shows the physical property values and evaluation results of the obtained powder.

(Example 8) A polyethylene wax emulsion (Hi-Wax 110P: manufactured by Mitsui Chemicals, Inc.) was added to the cake after the filtration and washing in the second step of Example 7, and pure polypropylene wax was added to 100 parts by weight of silica. In minutes,
It was added so as to be 15 parts by weight to obtain surface-treated amorphous silica. Table 1 shows the physical property values and evaluation results of the obtained powder.

Example 9 Example 9 was carried out in the same manner as in Example 1 except that the temperature in the first step was 25 ° C. Table 1 shows the physical property values and evaluation results of the obtained powder.

(Example 10) A polyethylene wax emulsion (Permarin: manufactured by Sanyo Chemical Co., Ltd.) was added to the cake after the filtration and washing in the second step of Example 9 by using pure polypropylene wax with respect to 100 parts by weight of silica. Addition was made to 5 parts by weight to obtain surface-treated amorphous silica. Table 1 shows the physical property values and evaluation results of the obtained powder.

Comparative Example 1 The same procedure as in Example 1 was carried out except that the reaction pH was changed to 4 in the precipitation of amorphous silica particles by the precipitation method in the second step of Example 1. Table 2 shows the physical property values and evaluation results of the obtained powder.

(Comparative Example 2) A physical property value was measured and evaluated using a commercially available gel type silica, Sylysia # 350 (manufactured by Fuji Silysia Ltd.). Table 2 shows the results.

(Comparative Example 3) The physical property values were measured and evaluated using a commercial product Mizukasil P-526 (manufactured by Mizusawa Chemical Industry Co., Ltd.), which is a precipitated silica. Table 2 shows the results.

Comparative Example 4 The silica powders of Comparative Example 2 and Comparative Example 3 were mixed at a weight ratio of 1: 1 and measured and evaluated for physical properties. Table 2 shows the results.

[0089]

[Table 1] Example 1 2 3 4 5 6 7 8 9 10 Average particle size (μm) 2.5 2.5 2.5 2.5 2.5 2.5 2.0 2.0 3.0 3.0 3.0 Specific surface area (m ² / g) 180 200 175 210 198 170 210 195 170 160 Pore volume (ml / g) 0.6 0.7 0.6 0.8 0.7 0.6 0.7 0.7 0.6 0.6 Matting (%) 15 15 16 16 15 15 16 15 15 15 Sedimentation △ △ △ △ △ ○ ○ ○ △ △ Scratch resistance 5 times 1 1 1 1 1 1 1 1 1 1 15 times 1 1 1 1 1 1 1 1 1 1 25 times 2 2 2 2 2 2 2 2 2 2

[0090]

[Table 2]

[0091]

According to the present invention, an aqueous solution of an alkali silicate and an aqueous solution of a mineral acid are neutralized under conditions of pH 2 to 10 to produce a gel-process amorphous silica, which is wet-pulverized. By neutralizing the aqueous alkali silicate solution and the aqueous mineral acid solution under conditions of pH 5 to 9 in the presence of the wet-milled silica particles, a dense amorphous silica core and a bulky amorphous silica shell are formed. Having a volume-based median diameter in the range of 1 to 10 μm and a particle size of 0.5
The production of amorphous silica having a double-walled structure in which the content of fine particles having a particle size of μm or less is 10% by volume or less becomes possible.

The amorphous silica particles having a double-walled structure have a uniform particle size in a state of being mixed with a coating material or a resin as well as in a powder state, and do not generate fine particles. It has excellent action and anti-blocking action, has a low tendency to wear, and has excellent scratch resistance and abrasion resistance.

[Brief description of the drawings]

FIG. 1 is a transmission electron micrograph (magnification: 30,000 times) of a double-structured amorphous silica particle according to Example 1 of the present invention.
It is.

FIG. 2 is a transmission electron micrograph (magnification: 30,000 times) of gel method amorphous silica particles.

FIG. 3 is a transmission electron micrograph (magnification: 30,000 times) of a precipitated amorphous silica particle.

──────────────────────────────────────────────────続 き Continued on front page (51) Int.Cl. ⁶ Identification code FI C09D 7/12 C09D 7/12 Z

Claims (12)

[Claims] 1. It has a dual structure of a dense amorphous silica core and a bulky amorphous silica shell, a volume-based median diameter in the range of 1 to 5 μm, and a particle size of 0.5 μm.
Amorphous silica particles, wherein the content of the following fine particles is 10% by volume or less. 2. A BET specific surface area of 150 to 400 m
² / g and a pore volume of 0.2 to 2 by the BET method.
2. The amorphous silica particles according to claim 1, which is in the range of ml / g. 3. The amorphous silica particles according to claim 1, wherein the dense amorphous silica core and the bulky amorphous silica shell are present in a weight ratio of 2: 8 to 7: 3. 4. The dense amorphous silica core is a gel amorphous silica particle, and the bulky amorphous silica shell is a sedimentation amorphous silica particle deposited on the surface of the core particle. The amorphous silica particles according to claim 1. 5. A dense amorphous silica core having a BET specific surface area of 200 to 800 m ² / g and a pore volume of 0.2 to 0.2 at a pore radius of 10 to 150 Å.
The amorphous silica particles according to any one of claims 1 to 4, having a pore volume of from 2.0 to 2.0 ml / g. 6. A process for producing a gel-process amorphous silica by neutralizing an aqueous solution of an alkali silicate and an aqueous solution of a mineral acid under conditions of pH 2 to 10, and wet-grinding the resulting gel-process amorphous silica. And an aqueous solution of alkali silicate and an aqueous solution of mineral acid are neutralized under conditions of pH 5 to 9 in the presence of wet-milled gel-processed amorphous silica particles, and the precipitated amorphous silica particles are subjected to gel-process. A method for producing amorphous silica particles having a double structure, wherein the amorphous silica particles are precipitated on the surface of the amorphous silica particles. 7. The production of gel-process amorphous silica particles at 50 ° C.
The method according to claim 6, which is performed at the following temperature. 8. The method according to claim 6, wherein the wet pulverization of the gel-process amorphous silica is performed so that the volume-based median diameter is 0.5 to 3 μm. 9. The method according to claim 6, wherein precipitation of the amorphous silica particles is carried out at a temperature of 60 to 100 ° C. 10. A matting agent for paints comprising the amorphous silica particles according to claim 1. Description: 11. A matting agent for paints, which is surface-treated with 1 to 20 parts by weight of a wax per 100 parts by weight of the amorphous silica particles according to claim 1. 12. An anti-blocking agent for a film comprising the amorphous silica particles according to claim 1. Description: