JPH0786177B2 - Non-sedimentable silica composition for coating and method for producing the same - Google Patents

Description

TECHNICAL FIELD The present invention relates to a non-sedimentation silica composition for coating, which is transparent, has good adhesion, and is capable of forming a hard coating on a substrate, and a composition thereof. Regarding manufacturing method.

[Prior Art] It is possible to form a film by coating an inorganic oxide on a substrate such as plastic, glass, ceramic, or metal.
Various things are done. The film formed on the substrate in this manner has a function such as unique electrical characteristics, optical characteristics, chemical characteristics or mechanical characteristics due to the metal element derived from the inorganic oxide in the film, Depending on the function of this film, as a conductive film, an insulating film, an alignment film, a photomask, an alkali elution preventing film, a visible light antireflection film, an infrared reflecting film, an ultraviolet absorbing film, a mechanical protective film, etc. in the electronics field,
It is used in a wide range of fields including the optical equipment field.

In particular, thermal decomposition, alkoxide hydrolysis, sol-gel method, melting method and the like are known as methods for forming a transparent and hard coat film by a coating method.

Of these, the thermal decomposition method / melting method has a problem that the usable base material is limited by the heat resistance of the base material. In the alkoxide hydrolysis method, the alkoxide hydrolysis conditions (temperature, humidity, coating speed) are used. Therefore, the sol-gel method has a problem that the properties of the coating film are influenced by the balance between the sol and the gel. Further, the alkoxide hydrolysis method and the sol-gel method have a problem that the raw materials used in these methods are expensive.

In addition to these, as a method of forming a transparent coating having a hard coat property by a coating method, a method of using a coating liquid containing alkali silicate such as water glass as a main component is known. This method has a problem that a large amount of alkali (cation) remains in the formed coating film, which limits the use of the formed coating film.

Also known is a method of forming a transparent and hard-coating film using a silicic acid solution obtained by removing cations from alkali silicate. In this method, silicic acid is polymerized to produce colloidal particles when a silicic acid solution is produced, and
Since it is very unstable, it gels in a short time, which is not suitable as a coating solution.

Further, in the conventional coating method as described above, the properties of the coating film formed are generally affected by the coating method, and the coating solution used in the coating method is easily affected by the surrounding environment and has a long shelf life. However, most of them had a short pot life and a usable period of about 1 month).

[Problems to be Solved by the Invention] The present invention has been made in order to solve the problems associated with the conventional techniques such as miscellaneous wood, and is inexpensive and can be easily applied without being limited to the shape of the substrate. It is an object of the present invention to provide a non-sedimentation silica composition for coating, which can be stored for a long period of time and can form a transparent hard coat film having good adhesion, and a method for producing the same.

[Means for Solving Problems] The nonprecipitating silica composition for coating according to the present invention comprises:
An aqueous solution of non-precipitating silica defined as follows, which is obtained by removing an alkali (cation) from an aqueous solution of alkali silicate, contains glycols or their monoether / monoester derivatives, lactones or their derivatives, morpholines or At least one growth inhibitor selected from its derivative, 2-pyrrolidone or its derivative, dimethylsulfoxide or its derivative is added, and then a diluent is added. Non-precipitating silica: 2.0
When an aqueous solution containing silica by weight (converted to SiO ₂ ) is spun down at 250,000 G for 1 hour, the amount of precipitated silica is 30% by weight or less based on the total SiO ₂ contained in the aqueous solution. silica.

The method for producing a non-sedimentable silica composition for coating according to the present invention is a method in which an alkali silicate aqueous solution is contacted with a hydrogen type cation exchange resin to remove the alkali, and then a glycol or its monoether / monoester derivative, It is characterized in that at least one growth inhibitor selected from lactones or derivatives thereof, morpholines or derivatives thereof, 2-pyrrolidone or derivatives thereof, dimethylsulfoxide or derivatives thereof is added, and then a diluent is added.

The nonprecipitating silica composition for coating and the method for producing the same according to the present invention will be specifically described below.

The aqueous solution of alkali silicate used in the present invention is an aqueous solution of alkali silicate such as lithium silicate, sodium silicate, potassium silicate, and quaternary ammonium silicate. These can be used alone or in combination of two or more.
The SiO ₂ / M ₂ O molar ratio in the alkaline silicate aqueous solution is 0.5 to 4 when M is Na, 1 to 4 when M is K, and M is Li.
At this time, it is preferably 2 to 9.

When a quaternary ammonium silicate is used as the alkali silicate, in the present invention, the quaternary ammonium silicate is represented by the following formula: X (NR ₁ R ₂ R ₃ R ₄ ) ₂ O · YSiO ₂ · ZH ₂ O And X
= 1, Y = 0.5 to 20, Z = 0 to 99, and R _{1 to} R ₄ are preferably hydrogen or an alkyl group or an alkoxy group having 1 to 20 carbon atoms, respectively.

The non-sedimentable silica aqueous solution used in the present invention is obtained by exchanging the alkali and hydrogen in the above-mentioned alkaline silicate aqueous solution. As the method, a known method such as an ion exchange method or a dialysis method can be used.

The non-sedimentable silica aqueous solution used in the present invention is obtained by the above-mentioned method. At this time, the concentration of SiO ₂ in the aqueous alkali silicate solution is preferably 0.1 to 7% by weight and the temperature is preferably 0 to 35 ° C. More preferably, the concentration of SiO ₂ in the aqueous alkali silicate solution is adjusted to fall within the range shown by the shaded area in FIG. The concentration of SiO ₂ in the aqueous solution of alkali silicate is 8 wt%
Or more, or the temperature of the aqueous solution of alkali silicate is 35
When the temperature is higher than 0 ° C, the alkali silicate aqueous solution is gelated or a large amount of colloidal particles are generated in the alkali silicate aqueous solution while the alkali and hydrogen are exchanged by the above method. Further, if the temperature of the alkali silicate aqueous solution is less than 0 ° C., the ion exchange rate at the time of exchanging the alkali and hydrogen by the above method becomes slow, which is not industrial, and the alkali silicate aqueous solution is gelated at a temperature below the freezing point. .

The amount of alkali remaining in the non-precipitating silica aqueous solution is
O ₂ / M ₂ O (provided that MLi, Na, K or NR ₁ R ₂ R ₃ R ₄
R _{1 to} R ₄ represent the above meanings) and have a molar ratio of 200 or more, preferably 1000 or more, more preferably 10000 or more. When the SiO ₂ / M ₂ O molar ratio is less than 200, even if a growth inhibitor is added to a non-precipitating silica aqueous solution, the growth inhibitor has no effect, and the non-precipitating silica gels in a short time at room temperature. Will end up.

The silica in the non-sedimentable silica aqueous solution obtained as described above is unstable, so that colloidal particles are generated in the non-sedimentable silica aqueous solution, or the non-sedimentable silica is easily gelled.

Therefore, in the present invention, a growth inhibitor is added to the non-sedimentable silica aqueous solution to stabilize the non-sedimentable silica in the liquid. It is speculated that the nonprecipitating silica in the liquid is stabilized by the growth inhibitor because the hydroxyl groups of the silica form hydrogen bonds with the functional groups of the growth inhibitor, preventing the hydroxyl groups of the silica from contacting each other. To be done.

As the growth inhibitor according to the present invention, those having a functional group that causes a hydrogen bond with a hydroxyl group of silica in a hydrophilic organic solvent or a water-soluble crystal are used, and specifically, ethylene glycol, propylene glycol, ethylene glycol monomethyl are used. Glycols such as ethers and their monoether / monoester derivatives, butyrolactone, γ-valerolactone, γ-caprolactone and other lactones and their derivatives, morpholines and their derivatives, 2-
Pyrrolidone and its derivatives, dimethylsulfoxide and its derivatives. These are used alone or in combination of two or more.

The amount of the growth inhibitor may be at least 0.5 mol with respect to 1 mol of the non-precipitating silica (SiO ₂ ) in the non-precipitating silica aqueous solution. When the amount of this growth inhibitor is less than 0.5 mol, the stability of the non-precipitable silica in the non-precipitable silica aqueous solution becomes poor. Increasing the amount of growth inhibitor used does not cause any inconvenience to the present invention.

By mixing the solution containing the nonprecipitable silica stabilized by adding the growth inhibitor in this way with the diluent, the nonprecipitable silica composition for coating of the present invention can be obtained.

Depending on the type of base material to which the non-sedimentable silica composition for coating is applied, the water content of this composition adversely affects the coating film / molded product obtained by applying this composition onto the base material (homogeneity / adhesion). Therefore, dehydration may be performed before adding the diluent to the solution containing the nonprecipitating silica stabilized by adding the growth inhibitor. A known method such as a distillation method or an ultramembrane method can be used for dehydrating the solution containing the nonprecipitating silica stabilized by adding the growth inhibitor. At this time, unless dehydration is carried out at a temperature of 90 ° C. or lower, the stability of the non-sedimentable silica in the liquid deteriorates, colloidal particles are generated in the liquid, or the non-sedimentable silica gels.

The composition ratio of the non-sedimentable silica, the growth inhibitor and the water content before adding the diluent satisfies the condition that the growth inhibitor is 0.5 mol or more to 1 mol of the non-sedimentable silica, and then the non-sedimentable silica. The nonprecipitating silica is 0.5 to 25% by weight, preferably 0.5 to
It is desirable that the content is 15% by weight, the water content is 0.1 to 99.3% by weight, and the growth inhibitor is 0.2 to 99.4% by weight. When the content of non-sedimentable silica is 15% by weight or more, the stability of the liquid containing the non-sedimentable silica is shortened, and when the content of non-sedimentable silica is 25% by weight or more, the stability of the liquid containing the non-sedimentable silica is further increased. It becomes short and the non-sedimentable silica easily gels. If the amount of the growth inhibitor is 0.2% by weight or less, the effect of the growth inhibitor is lost and the non-precipitating silica is apt to gel.

The diluent for diluting the three components of the non-sedimentable silica, the growth inhibitor and the water may be any one that does not affect the stability of the non-sedimentable silica. The mixing amount of the diluent can be arbitrarily selected so that the viscosity and the film thickness can be adjusted according to the coating method. As the diluent used in the present invention,
For example, methanol, ethanol, n-propanol,
i-propanol, n-butanol, i-butanol,
alcohol such as t-butanol, acetic acid methyl ester,
Examples thereof include acidic esters such as ethyl acetate, ethers such as diethyl ether, and acetone. These are used alone or in combination of two or more.

When the nonprecipitating silica composition for coating of the present invention is used as a coating solution as it is, the composition is prepared by a known method such as a spinner method, a spray method, a dip method, a bar coating method, a roll coating method, or a printing method. It can be applied to the material surface. After coating, baking may be performed at a temperature at which the diluent, water, and growth inhibitor in the composition evaporate or decompose.

The present invention will be described below with reference to examples, but the present invention is not limited to these examples.

[Example] 5 wt% of sodium silicate aqueous solution as in Example _{1 SiO 2 (SiO 2 / Na} 2 O =
3mol / mol) 4800 g was passed through a cation exchange resin column at a space velocity SV of 5 while keeping it at 15 ° C to obtain a non-sedimentable silica aqueous solution (I). 100 g of the non-sedimentable silica aqueous solution (I) thus obtained was added with ethylene glycol.
After 44 g was added and sufficiently dispersed, 94 ° g of water was distilled off by heating to 70 ° C under reduced pressure with a rotary evaporator.
Dispersion I was obtained. The dispersion I was cooled and 200 g of ethanol was added to obtain a non-sedimentable silica composition for coating.

Example 2 Of the non-sedimentable silica aqueous solution (I) obtained in Example 1,
27 g of N-methyl-2-pyrrolidone was added to 100 g and sufficiently dispersed to obtain a dispersion liquid II. Methanol was added to this dispersion II.
123 g of / n-butanol (weight ratio 1/1) was added to obtain a non-sedimentable silica composition for coating.

0.5 wt% of sodium silicate aqueous solution as in Example _{3 SiO 2 (SiO 2 / Na} 2 O
= 3 mol / mol) 240 g was passed through a cation exchange resin column at a space velocity SV of 2 while keeping it at 25 ° C to obtain a non-sedimentable silica aqueous solution. 9 g of N-methyl-2-pyrrolidone was added to 100 g of the nonprecipitating silica aqueous solution thus obtained and sufficiently dispersed, and then heated to 70 ° C. under reduced pressure with a rotary evaporator to distill 99 g of water. Remove, Dispersion I
I got II. Cool Dispersion III and add 1 more ethanol.
A non-sedimentable silica composition for coating was obtained by adding 0 g.

Example 4 7 wt% aqueous solution of sodium silicate as SiO ₂ (SiO ₂ / Na ₂ O =
200 g of 3 mol / mol) was passed through a cation exchange resin column at a space velocity SV of 6 while keeping it at 15 ° C. to obtain a non-precipitating silica aqueous solution. To 100 g of the non-sedimentable silica aqueous solution thus obtained, 600 g of N-methyl-2-pyrrolidone was added and sufficiently dispersed to obtain a dispersion IV. To this dispersion IV, 700 g of methanol / n-butanol (weight ratio 1/1) was added to obtain a non-sedimentable silica composition for coating.

Example 5 As SiO ₂ , 5 wt% sodium silicate aqueous solution (SiO ₂ / Na ₂ O =
While maintaining 200 g of 3 mol / mol) at 2 ° C., it was passed through a cation exchange resin column at a space velocity SV = 4 to obtain a non-precipitating silica aqueous solution. Of the nonprecipitating silica aqueous solution thus obtained, 14.9 g of N-methyl-2-pyrrolidone was added to 100 g.
Was added to sufficiently disperse the mixture, and the mixture was heated to 70 ° C. under reduced pressure with a rotary evaporator to distill off 94.9 g of water to obtain a dispersion liquid V. The dispersion V was cooled and 80 g of ethanol was added to obtain a non-sedimentation silica composition for coating.

Example 6 6 wt% aqueous solution of sodium silicate as SiO ₂ (SiO ₂ / Na ₂ O =
While maintaining 200 g of 3 mol / mol) at 25 ° C., it was passed through a cation exchange resin column at a space velocity SV = 8 to obtain a non-precipitating silica aqueous solution. 900 g of N-methyl-2-pyrrolidone was added to 100 g of the nonprecipitating silica aqueous solution thus obtained, and the mixture was sufficiently dispersed to obtain a dispersion liquid VI. 1000 g of methanol / n-butanol (weight ratio 1/1) was added to this dispersion liquid VI to obtain a non-sedimentation silica composition for coating.

Example 7 5 wt% aqueous solution of sodium silicate as SiO ₂ (SiO ₂ / K ₂ O = 4
200 g of mol / mol) was passed through a cation exchange resin column at a space velocity SV of 3 while keeping it at 15 ° C. to obtain a non-precipitating silica aqueous solution. After adding 600 g of ethylene glycol monoethyl ether to 100 g of the nonprecipitating silica aqueous solution thus obtained and sufficiently dispersing, an ultrafiltration membrane (Asahi Kasei, SIP-3013, 15 ° C, ΔP = 1 kg / cm ² ) with water 9
3.3 g was removed to obtain Dispersion VII. The dispersion VII was cooled, and 300 g of ethanol was added to obtain a non-sedimentation silica composition for coating.

Tetraethylammonium silicate aqueous 5 wt% as in Example _{8 SiO 2 {(N (C} 2 H 5) 4) 2 O · 13.5SiO 2} 200g of 15 ℃
Space velocity SV in the cation exchange resin column
= 5 to give a non-sedimentable silica aqueous solution. Non-precipitating silica composition for coating was prepared using Dispersion VIII and this Dispersion VIII in the same manner as in Example 1 except that 44 g of morpholine was added to 100 g of the non-sedimentable silica aqueous solution thus obtained and sufficiently dispersed. I got a thing.

Example 9 Of the non-sedimentable silica aqueous solution (I) obtained in Example 1,
After adding 5 g of N-methyl-2-pyrrolidone to 100 g and thoroughly dispersing the mixture, the pressure was reduced to 70 on a rotary evaporator.
The mixture was heated to ℃ and 55 g of water was distilled off to obtain a dispersion IX. The dispersion IX was cooled and 200 g of methanol / n-butanol (weight ratio 1/1) was added to obtain a non-sedimentable silica composition for coating.

Example 10 Of the non-sedimentable silica aqueous solution (I) obtained in Example 1,
After 20 g of N-methyl-2-pyrrolidone was added to 100 g and sufficiently dispersed, 70 g of water was distilled off by heating to 70 ° C. under reduced pressure with a rotary evaporator to obtain a dispersion liquid X. This dispersion X was cooled, and 200 g of ethanol / n-butanol (weight ratio 1/1) was added to obtain a non-sedimentable silica composition for coating.

Example 11 5 wt% aqueous solution of sodium silicate as SiO ₂ (SiO ₂ / Na ₂ O =
480 g (3 mol / mol) was passed through a cation exchange resin column at a space velocity SV of 15 while keeping it at 5 ° C. to obtain a non-sedimentable silica aqueous solution. To 100 g of the non-precipitating silica aqueous solution thus obtained, 150 g of N-methyl-2-pyrrolidone / ethylene glycol (weight ratio 1/1) was added and sufficiently dispersed to obtain a dispersion liquid XI. Add 250 g of ethanol to this dispersion XI.
A non-sedimentable silica composition for coating was obtained by addition.

Example 12 5 wt% aqueous solution of sodium silicate as SiO ₂ (SiO ₂ / Na ₂ O =
3 mol / mol) (480 g) was passed through a cation exchange resin column at a space velocity SV of 10 while maintaining it at 10 ° C to obtain a non-sedimentable silica aqueous solution. In the same manner as in Example 11 except that the dispersion XII obtained by adding 150 g of N-methyl-2-pyrrolidone to 100 g of the thus obtained non-precipitating silica aqueous solution and thoroughly dispersing it was used. A non-sedimentable silica composition for coating was obtained.

Comparative Example 1 5 wt% aqueous solution of sodium silicate as SiO ₂ (SiO ₂ / Na ₂ O =
480 g of 3 mol / mol) was passed through a cation exchange resin column at a space velocity SV of 10 while maintaining it at 5 ° C. to obtain a non-precipitating silica aqueous solution. 400 g of N-methyl-2-pyrrolidone was added to 100 g of the non-sedimentable silica aqueous solution thus obtained and sufficiently dispersed, but the dispersion liquid gelled in a few minutes.

Comparative Example 2 Of the non-sedimentable silica aqueous solution (I) obtained in Example 1,
150 g of ethanol was added to 100 g and sufficiently dispersed to obtain a non-sedimentable silica composition for coating.

Comparative Example 3 Of the non-sedimentable silica aqueous solution (I) obtained in Example 1,
After 72.5 g of N-methyl-2-pyrrolidone was added to 100 g to sufficiently disperse it, the mixture was heated to 70 ° C. under reduced pressure with a rotary evaporator to remove 947.5 g of water to obtain a dispersion liquid.
The thus obtained dispersion liquid gelled in a few minutes.

The results are shown in Table 1.

Coating film test Using the non-precipitating silica composition for coating obtained in the above Examples and Comparative Examples, the following substrate, coating method, drying and
A coating film was obtained under firing conditions. The obtained coating film was evaluated for appearance, adhesion and film hardness.

Substrate: PETT film, acrylic plate, glass plate, aluminum plate, (shape, 10cm x 10cm) Coating method: Spinner method (2000r.pm), Bar coating method (# 0 is used for the bar) Drying and baking conditions: PET film・ Acrylic board is 110 ℃ ・ 2
0 minutes. After drying glass plate and aluminum plate at 110 ℃ for 1 hour
Baked at 200 ° C for 1 hour.

<Evaluation method> Appearance: Visually observe the presence or absence of mottle or cracks in the film,
Those that occurred even in one place were marked with x, and those that did not occur were marked with o.

Transparency: Total light transmittance (Tt) and haze (H) were measured with a haze computer (manufactured by Suga Test Instruments).

Adhesion: Measured by the cross-cut test of JIS D0202-71.

In this test, the coating film was cut with a cutter knife into 100 pieces at 1 mm intervals with a cutter knife, a part of commercially available 12 mm wide cellophane tape was attached, the rest of the cellophane tape was kept at a right angle to the film, and it was peeled off momentarily. The number of slices left on the substrate was counted.

Hardness: Measured by the pencil hardness test of JIS D0202-71.

In this test, a commercially available pencil was placed at an angle of 45 ° to the coating film, and the pencil was pressed to visually inspect the coating film for scratches.

The results are shown in Table 2.

[Effect of the invention] The non-sedimentable silica composition for coating according to the present invention comprises:
A non-precipitating silica aqueous solution obtained by removing alkali (cations) from an alkali silicate aqueous solution is added with a growth inhibitor to stabilize the non-precipitating silica in the solution, so it is inexpensive and has a long pot life (room temperature). (3 months or more) It can be easily coated on the base material without being restricted by the shape of the base material.

Further, by applying the non-sedimentable silica composition for coating according to the present invention to plastics, glass, ceramics, metals, etc., it is possible to easily obtain a coating film having a transparent and good adhesion hard coat at low temperature. You can Further, the non-sedimentable silica composition for coating according to the present invention can be used as a component of an inorganic binder composition of a coating material by mixing with a conventional coating material. Further, by mixing an inorganic or organic metal salt, colloidal particles, inorganic fibers, tabular particles, etc. in the non-sedimentable silica composition for coating according to the present invention, the non-sedimentable silica composition for coating can be obtained. It is also possible to impart a new function to the coating film. For example, when SnCl ₄ , SbCl ₃ , or InCl ₃ is mixed, a coating film having conductivity is obtained, and when colloidal particles of titanium oxide are mixed, a coating film having an ultraviolet absorbing function is obtained.

[Brief description of drawings]

FIG. 1 is a graph showing preferable conditions for producing non-sedimentable silica.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Kenji Mizoguchi 2-21-20 Higashi-nijima, Wakamatsu-ku, Kitakyushu City, Fukuoka Prefecture 2-72-20 Inventor Keiichi Mihara 4-92 Rokukodai, Matsudo-shi, Chiba Kintetsu Heights Rokumitsu No. 503 (56) References JP-A-51-108696 (JP, A) JP-A-49-63696 (JP, A) JP-A-54-5835 (JP, A)

Claims (7)

[Claims] 1. An aqueous solution of non-precipitating silica defined as follows, which is obtained by removing alkali from an aqueous solution of alkali silicate, and glycols or monoether / monoester derivatives thereof, lactones or derivatives thereof, and morpholines. Or a derivative thereof, 2-pyrrolidone or a derivative thereof, at least one growth inhibitor selected from dimethyl sulfoxide or a derivative thereof, and then a diluent, which is a nonprecipitating silica composition for coating. Non-precipitating silica: When an aqueous solution containing 2.0% by weight (converted to SiO ₂ ) of silica is centrifugally sedimented at 250,000 G for 1 hour, the amount of silica that precipitates is relative to the total SiO ₂ contained in the aqueous solution.
Silica less than 30% by weight. 2. The coating according to claim 1, wherein the growth inhibitor is one kind or two or more kinds selected from ethylene glycol, N-methyl-2-pyrrolidone, morpholine and ethylene glycol monoethyl ether. Non-precipitating silica composition. 3. The nonprecipitating silica composition for coating according to claim 1, wherein the growth inhibitor is at least 0.5 mol per mol of nonprecipitating silica. 4. The method according to claim 1, wherein the residual alkali has a SiO ₂ / M ₂ O molar ratio (where M is an alkali metal or a quaternary ammonium group) of 200 or more.
A non-sedimentable silica composition for coating according to any one of items. 5. An alkali silicate aqueous solution is brought into contact with a hydrogen type cation exchange resin to remove alkali, and then glycols or monoether / monoester derivatives thereof, lactones or derivatives thereof, morpholines or derivatives thereof, 2- At least one growth inhibitor selected from pyrrolidone or its derivative, dimethylsulfoxide or its derivative, and then a diluent, characterized by the following: Method for producing a precipitating silica composition: Non-precipitating silica: when an aqueous solution containing 2.0% by weight (converted to SiO ₂ ) of silica is subjected to centrifugal sedimentation at 250,000 G for 1 hour, the amount of silica that precipitates is included in the aqueous solution. For all SiO ₂
Silica less than 30% by weight. 6. The method according to claim 5, wherein the growth inhibitor is one or more selected from ethylene glycol, N-methyl-2-pyrrolidone, morpholine and ethylene glycol monoethyl ether. . 7. The SiO ₂ conversion concentration in the alkali silicate aqueous solution is 0.
The production according to claim 5 or 6, wherein the temperature is 1 to 7% by weight, and the temperature when the alkali silicate aqueous solution is brought into contact with the hydrogen type cation exchange resin to remove the alkali is 0 to 35 ° C. Law.