JP2006124667A - Aqueous silica-based resin composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain an aqueous nanosilica-based resin composition that has no adverse effect on the environment, has no problem of crack occurrence after curing without impairing merits of an inorganic curable composition containing a siloxane bond, is inexpensive, has normal-temperature curability and does not cause a remarkable change in physical properties by glass transition in a normal-temperature use range while retaining physical properties of a conventional organic coating film. <P>SOLUTION: The aqueous silica-based resin composition comprises a main agent composed of acidic water-dispersible colloidal silica and an organic acid, a curing agent composed of a silane coupling agent and an alkoxysilane oligomer and an alkoxysilane hydrolysis catalyst as essential components. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a resin composition for coating, and more particularly to an aqueous silica-based resin composition for forming an aqueous inorganic film using colloidal silica.

Conventionally, paints used around living environments such as buildings, building materials, metals, and woodwork are mainly organic resin compositions such as alkyd, acrylic, epoxy, and urethane. In addition, acrylic silicone resin-based and fluororesin-based compositions are used as high weather resistance grades, but most of them are solvent-soluble, which are undesirable for the environment, and have dirt and scratches at the initial stage of curing. There is a problem that it is easy.
Acrylic emulsion resins that have been used for interior and exterior of buildings are water-dispersed and environmentally friendly, but they are inferior in weather resistance and coating strength, easily soiled, easily damaged, and easily deteriorated by light. I have a problem.

  Examples of so-called hard coating agents applied for the purpose of protecting the surface of wood and plastics include UV curable resins and silicone coating agents, but the former requires a special device and is not convenient, and the latter is often In the case of the solvent type, it requires post-heating to the extent permitted by the substrate, and is not preferable for the environment.

In order to solve these problems, various hydrolyzable organosilane coating agents and colloidal silica coating agents have been proposed.
For example, Patent Document 1, Patent Document 2, Patent Document 3 and Patent Document 4 include an organoalkoxysilane, a hydrolysis and / or partial condensate of the organoalkoxysilane, and colloidal silica. A coating agent obtained by converting a group into silanol has been proposed. Films obtained with these coating agents have high hardness, good weather resistance, and are excellent for protecting the substrate.

  However, the coating agent proposed in the above publication requires baking at a high temperature of about 100 ° C. or higher for a long time in order to obtain the required film properties. Depending on the nature or in some places such as outdoors, it may not be applicable. Further, these coating compositions have the disadvantage that the activity of silanol obtained by hydrolysis of alkoxysilane is high, and their condensation reaction occurs gradually even at room temperature and gelation tends to occur, leading to poor stability.

  Patent Document 5 proposes a coating agent that converts an alkoxy group into silanol by adding water and a catalyst as a curing agent to a partially hydrolyzed or partially condensed product of alkoxysilane immediately before coating. The coating agent obtained in this way has good storage stability and is relatively stable even if it is made into a paint by adding a pigment. However, in order to obtain the required film properties, it is heated at a high temperature of about 100 ° C. or higher for a long time. Baking by treatment is necessary, and it may not be applied depending on the molding method, dimensions, heat resistance of the base material, or in places such as outdoors.

  For the purpose of eliminating such drawbacks, Patent Document 6 proposes a coating agent that is composed of a prepolymer mainly composed of silicon alkoxide, a curing catalyst, and water, and cures at room temperature. Unfortunately, there is a drawback that the curability is easily affected by humidity.

  On the other hand, a solvent-free, one-pack type room-temperature-curing organopolysiloxane composition having a liquid organopolysiloxane, a cross-linking agent composed of an organometallic compound, and a curing catalyst composed of a metal-containing compound as essential components has been proposed. (See Patent Document 7). However, in this solvent-free one-component room-temperature-curing organopolysiloxane composition, there is substantially no use such as using a volatile monomer as a cross-linking agent or using alcohol to delay the curing rate. It is difficult to say that it is a solvent. In addition, in the curable composition using this type of organopolysiloxane, it is considered difficult to solve the problem of cracking after curing during thick coating or contact with high concentration organic acid. Is still left. Moreover, it is also true that these organopolysiloxane resins are generally expensive and difficult to use for general purposes.

  Furthermore, Patent Document 8 proposes an inorganic paint having hydrophilicity and crack resistance by adding a specified amount of mica, talc, glass flake or sepiolite to water-dispersed colloidal silica, but colloidal silica has a film-forming property. Since it is low and contains a pigment substantially, it is inferior in transparency and smoothness of the coating film, hardly glossy, and it is difficult to say that it has improved the problem of microcracks caused by various external stimuli.

  In other words, the curable resin composition having an inorganic siloxane skeleton proposed so far has no problems of film formation, impact resistance, and crack generation due to various external stimuli, and is inexpensive and cure at room temperature. A substantially water-based curable resin composition for forming a hard film has not yet been put into practical use.

JP-A 51-2736 Japanese Patent Laid-Open No. 51-2737 JP-A-53-130732 JP 63-168470 A Japanese Unexamined Patent Publication No. 64-168 Japanese Unexamined Patent Publication No. 63-268772 Japanese Patent Laid-Open No. 5-247347 JP 2003-55581 A

  The present invention does not adversely affect the environment, and does not impair the characteristics of the inorganic curable composition having a siloxane bond, and has been considered to be a difficult problem to be solved in this type of inorganic curable composition. A curable resin composition for forming an aqueous inorganic hard film that does not cause problems, is inexpensive, has room temperature curability, and does not cause significant physical property changes due to glass transition in the room temperature use range (aqueous silica system) It is an object to provide a resin composition.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors have found that an aqueous silica-based resin composition in which a silane coupling agent, an alkoxysilane oligomer, and a catalyst are added to an acidic water-dispersed colloidal silica to which an organic acid is added. However, the present inventors have found that the above problems can be solved at a high level and completed the present invention. Specifically, the present invention is the following <1> to <7>.

  <1> An aqueous composition comprising, as essential components, a main agent composed of acidic water-dispersed colloidal silica and an organic acid, a curing agent composed of a silane coupling agent and an alkoxysilane oligomer, and an alkoxysilane hydrolysis catalyst. Silica-based resin composition.

  <2> As the silane coupling agent, methyltrimethoxysilane, an epoxy group-containing silane coupling agent, a silane coupling agent having a functional group capable of reacting with an epoxy group, and an alkyltrimethoxy whose alkyl group has 3 or more carbon atoms Silane and the compound shown by following Structural formula 1 are contained, The aqueous silica-type resin composition as described in <1> characterized by the above-mentioned.

<3> The blending ratio of the curing agent is
50-90% by mass of methyltrimethoxysilane,
0.5 to 20% by mass of an epoxy group-containing silane coupling agent,
0.5 to 20% by mass of a silane coupling agent having a functional group capable of reacting with an epoxy group,
0.5 to 20% by mass of alkyltrimethoxysilane having 3 or more carbon atoms in the alkyl group,
0.5 to 20% by mass of a compound represented by the following structural formula 1,
0.5-20% by mass of the alkoxysilane oligomer,
<3> The aqueous silica-based resin composition according to <2>.

<4> The water content of 80 to 200 mol% with respect to the total number of moles of hydrolyzable alkoxysilyl groups in the curing agent is blended so as to be supplied by the water contained in the acidic water-dispersed colloidal silica. The aqueous silica-based resin composition according to any one of <1> to <3>, wherein
<5> The aqueous silica-based resin composition according to <4>, further including an organic polymer having a functional group that causes a hydrogen bond with the —SiOH group.

<6> The aqueous silica-based resin composition according to <4>, which does not exhibit a remarkable glass transition temperature in the range of 0 ° C to 50 ° C.
<7> The aqueous silica-based resin composition according to any one of <1> to <6> used for forming a cured film, wherein the cured film formed thereby is substantially colorless and transparent. An aqueous silica-based resin composition.

  According to the aqueous silica-based resin composition of the present invention or the coating comprising the aqueous silica-based resin composition, the colloidal silica base material and the silane coupling agent have a hybrid structure in which they are integrated by a siloxane bond and an organic bond. Is hardened, has high transparency, has high transparency, does not have a remarkable glass transition temperature in the operating temperature range (preferably in the range of 0 to 50 ° C.), has no deterioration in physical properties in the operating temperature range, and is sensitive to temperature. It is possible to form a cured film (coating film) having low properties, high water resistance and water repellency, and excellent solvent resistance. Therefore, it is a coating solution that is suitably used as a surface protection film for buildings, civil engineering, various inorganic or organic materials, room temperature dry ceramic coatings, and heat-resistant coatings. Inexpensive.

Hereinafter, the aqueous silica-based resin composition of the present invention will be described in detail.
The aqueous silica-based resin composition of the present invention is mainly composed of acidic water-dispersed colloidal silica whose electrophilicity is improved with an organic acid without using only expensive alkoxysilane as a main raw material, and further includes a silane coupling agent and an alkoxy A curing agent comprising a silane oligomer and an alkoxysilane hydrolysis catalyst are essential components.
Hereinafter, each component will be described.

[Main agent]
(Acid water dispersion type colloidal silica)
The acidic water-dispersed colloidal silica used in the present invention (hereinafter sometimes simply referred to as “colloidal silica”) is an aqueous silica sol in which fine particles of high molecular weight anhydrous silicic acid are dispersed in water. The thing of the range of hydrogen ion concentration (pH) 4-5 is preferable. By adding an organic acid to be described later, the hydrogen ion concentration (pH) of the main agent as a whole becomes about 2 to 4.

It is also possible to use modified colloidal silica in which a general colloidal silica having a hydrogen ion concentration (pH) of 8 to 11 is used and the hydrogen ion concentration (pH) is changed to 2 to 4 by an inorganic acid. In this case, since the obtained SiOH type colloidal silica is active and unstable, it is necessary to be careful to use it immediately after preparation.
Further, colloidal silica having a large particle diameter of 50 nm or more is disadvantageous for the transparency of the coating film, and may be used depending on the purpose, but is not preferable.

(Organic acid)
The organic acid used in the present invention is added to increase the reactivity with the curing agent described later, and is a component that performs a catalytic function. Incidentally, even if the same acid is used, an inorganic acid makes it easy to agglomerate the colloidal silica. Therefore, in order to function as a catalyst, an organic acid is an essential condition.

The organic acid used in the present invention is a so-called proton acid that is soluble in water, has a role of generating H ⁺ in water and acidifying the pH of the system. Specifically, fatty acids such as formic acid, acetic acid, propionic acid, butyric acid, caproic acid and caprylic acid; dibasic acids such as oxalic acid, malonic acid, succinic acid, glutaric acid and adipic acid; benzenesulfonic acid and p-toluene Aromatic fatty acids such as sulfonic acid; and the like.

  As a compounding quantity of the organic acid used by this invention, the inside of the range of 0.01-10 mass% is preferable with respect to the said colloidal silica, The inside of the range of 0.1-5 mass% is more preferable, 0.5- More preferably within the range of 0.8% by weight. When the amount of the organic acid is too large, the stability of the colloidal silica is impaired. On the other hand, when the amount is too small, the effect of addition becomes insufficient, which is not preferable.

[Curing agent]
(Silane coupling agent)
The silane coupling agent used in the present invention is a substance added to act on colloidal silica, and various conventionally known silane coupling agents can be used. However, in view of the object of the present invention, as the silane coupling agent, methyltrimethoxysilane, epoxy group-containing silane coupling agent, silane coupling agent having a functional group capable of reacting with an epoxy group, carbon number of alkyl group Is preferably an alkyltrimethoxysilane having 3 or more and a compound represented by the following structural formula 1, more preferably all of them.

Examples of the epoxy group-containing silane coupling agent (epoxy-type silane coupling agent) include γ-glycidoxypropyltrimethoxysilane, β- (3,4-epoxycyclohexyl) ethyltriethoxysilane, and the like.
In the silane coupling agent having a functional group that can react with an epoxy group, examples of the functional group that can react with an epoxy group include an OH group, an amino group, a thiol group, a carboxyl group, and a ureido group. Examples of the coupling agent include γ-aminopropyltriethoxysilane, γ-mercaptopropyltrimethoxysilane, and γ-ureidopropyltriethoxysilane, but of course, the present invention is not limited thereto. .

  Alkyltrimethoxysilane having 3 or more carbon atoms in the alkyl group is compared with the above-mentioned methyltrimethoxysilane, epoxy group-containing silane coupling agent, and silane coupling agent having a functional group capable of reacting with an epoxy group. It is a silane coupling agent with poor hydrolyzability. Examples of the alkyltrimethoxysilane having 3 or more carbon atoms in the alkyl group include n-propyltrimethoxysilane and n-hexyltrimethoxysilane.

The number of carbon atoms of the alkyl group is essential to be 3 or more, more preferably 6 or more. By using an alkyl group having a reasonably large carbon number, the function of reducing the curing shrinkage of the coating film and preventing cracks is fully exhibited. However, if the alkyl group has too many carbon atoms, the hydrolyzability of the alkoxysilyl group portion decreases, so the upper limit is preferably 10 or less, and more preferably 8 or less.
The compound represented by the structural formula 1 is a polyfunctional silane coupling agent and has a function of improving the crosslinking density.

(Alkoxysilane oligomer)
The alkoxysilane oligomer used in the present invention plays a role of a compatibilizer between the silane coupling agent and colloidal silica, and R _4-n Si (OR) _n (R is an alkyl such as a methyl group or an ethyl group). Is an oligomer polymerized to some extent. In the present invention, a tetrafunctional compound (n = 4) or a trifunctional compound (n = 3) may be used. Is preferably used.

As the alkoxysilane oligomer used in the present invention, it is preferable to use a dimer to 10 mer, and it is more preferable to use a 3 to 6 mer. Those exceeding the 10-mer are not preferable because the hydrolyzability of the alkoxysilyl group portion is lowered.
Examples of the alkoxysilane oligomer are commercially available under the product names such as ES-40 (manufactured by Tama Chemical Industries) and MS-51 (manufactured by Tama Chemical Industries).

(Mixing ratio)
As a compounding ratio of the silane coupling agent and the alkoxysilane oligomer in the curing agent, the compounding ratio of the alkoxysilane oligomer is preferably in the range of 0.1 to 20% by mass, and 0.8 to 1.2% by mass. It is more preferable to set the range. If the blending proportion of the alkoxysilane oligomer is too small, the effect of blending it becomes difficult to be exhibited, which is not preferable, and on the contrary, if it is too large, it remains as an unreacted product, resulting in poor curing and reduced hardness, This is not preferable because it leads to a decrease in water resistance and chemical resistance.

  In addition, as the silane coupling agent, methyltrimethoxysilane, an epoxy group-containing silane coupling agent, a silane coupling agent having a functional group capable of reacting with an epoxy group, an alkyltrimethoxysilane having an alkyl group with 3 or more carbon atoms In the case where all of the compounds represented by the structural formula 1 are included, the mixing ratio thereof is as shown below as the ratio in the precuring agent.

・ Methyltrimethoxysilane: 50 to 90% by mass
Epoxy group-containing silane coupling agent: 0.5 to 20% by mass
Silane coupling agent having a functional group capable of reacting with an epoxy group: 0.5 to 20% by mass
-Alkyltrimethoxysilane having 3 or more carbon atoms in the alkyl group: 0.5 to 20% by mass
Compound represented by the above structural formula 1: 0.5 to 20% by mass

The remaining proportion in the pre-curing agent is, of course, the alkoxysilane oligomer and is in the range of 0.1 to 20% by mass.
Since methyltrimethoxysilane is easily hydrolyzed, has excellent reactivity, and plays a role as a base material, it is preferable to add a relatively large amount as described above. More preferably, it exists in the range of 70-85 mass%.

  On the other hand, the other silane coupling agent is suitably about 0.5 to 20% by mass, more preferably about 2 to 6% by mass, as described above, due to its reactivity. If the blending ratio of the silane coupling agent other than methyltrimethoxysilane is too small, the effect of blending them becomes difficult to be exhibited. This is not preferable because it leads to a failure and a decrease in hardness, and leads to a decrease in water resistance and chemical resistance.

  As a blending ratio of the curing agent and the main agent, a water amount of 80 to 200 mol% (more preferably 90 to 150 mol%) with respect to the total number of moles of hydrolyzable alkoxysilyl groups in the curing agent is the acidic water dispersion. It is preferable to be blended so as to be supplied by moisture contained in the type colloidal silica.

If too much water is supplied, the amount of water in the system increases, which may cause problems such as delaying curing and clouding of the coating film. This is not preferable because the hydrolysis of the group becomes insufficient, poor curing and curing inhibition are likely to occur, and the cost becomes high and deviates from the original purpose.
Here, the “hydrolyzable alkoxysilyl group” refers to a so-called —SiOR (R is an alkyl group component of an alcohol) that generates a silanol group and an alcohol upon hydrolysis.

[Alkoxysilane hydrolysis catalyst]
The alkoxysilane hydrolysis catalyst used in the present invention acts on the alkoxysilyl group to promote hydrolysis reaction of -SiOH (silanol group) and alcohol, and promotes condensation of the generated active silanol group, A catalyst that promotes the polymerization of a resin. Specific examples of the alkoxysilane hydrolysis catalyst include organic tin compounds such as dibutyltin dilaurate, dioctyltin dilaurate, dibutyltin diacetate, dioctyltin diacetate, dibutyltin diacetylacetonate, and dibutyltin bistriethoxysilicate; bismuth compounds Organic titanates such as tetrabutoxy titanium; organic zirconium compounds such as tetrabutoxy zirconium; and the like.

  In the present invention, the compounding amount of the alkoxysilane hydrolysis catalyst is preferably in the range of 0.01 to 3% by mass, more preferably in the range of 0.1 to 1% by mass, with respect to the curing agent, and 0.4 to The range of 0.6% by mass is more preferable. If the amount of the alkoxysilane hydrolysis catalyst is too large, gelation may be fast and the pot life may not be obtained. On the other hand, if the amount is too small, it is difficult to obtain the effect of the addition, which is not preferable.

[Operations and effects of the aqueous silica-based resin composition of the present invention]
An acidic colloidal silica whose electrophilicity has been improved by the addition of an organic acid is added to a silane coupling agent (preferably a methyltrimethoxysilane as a main component, an epoxy group-containing silane coupling agent, and a functional group capable of reacting with an epoxy group. A silane coupling agent having, an alkyltrimethoxysilane having an alkyl group with 3 or more carbon atoms, and a compound represented by the structural formula 1 above), an alkoxysilane oligomer, and an alkoxysilane hydrolysis catalyst, Hydrolysis starts quickly and the temperature of the system rises (usually 50 ° C. or higher). At this time, it is considered that the condensation of the alkoxysilyl group further proceeds due to an epoxy addition reaction or a compatibilization phenomenon caused by various organic groups, and the film is cured at room temperature without being heated.

  More specifically, first, the skeleton has a colloidal silica siloxane bond, and the alkoxysilane oligomer is compatible with the siloxane bond and serves as a compatibilizer with various silane coupling agents. In the case of a silane coupling agent having a preferred formulation, the epoxy group in the epoxy group-containing silane coupling agent reacts or interacts with the functional group in the silane coupling agent having a functional group capable of reacting with the epoxy group. The compound represented by the structural formula 1 promotes the improvement of the crosslinking density, and realizes an increase in hardness together with the alkoxysilane oligomer. In addition, alkyltrimethoxysilane having an alkyl group with 3 or more carbon atoms serves to reduce the crosslink density by creating spatial defects, reduce cure shrinkage, and prevent cracks.

[—Organic polymer having a functional group causing hydrogen bonding with SiOH group]
In the aqueous silica-based resin composition of the present invention, an optional component “an organic polymer having a functional group that causes hydrogen bonding with a —SiOH group” (hereinafter sometimes simply referred to as “organic polymer”). explain.

  An organic polymer derived from acidic colloidal silica and / or having a functional group that causes hydrogen bonding with a —SiOH group produced by hydrolysis of a silane coupling agent is stabilized in the aqueous silica-based resin composition. And when a coating film is formed, a transparent film is formed. By using such an organic polymer, it plays the role of reducing the crosslinking density, reducing curing shrinkage, and preventing cracks.

  Examples of the organic polymer include a polymer that generates -SiOH group by hydrolysis; a polymer having urethane condensation, amide condensation, OH group, or butyral group in the molecule or in a side chain (for example, polyurethane, polyamide, polyvinyl alcohol, Polyvinyl butyral, polyvinyl acetate partial hydrolyzate, etc.); or polyoxazoline which forms an amide ester by a ring-opening reaction.

  The addition amount of the organic polymer is preferably in the range of 0.1% by mass to 80% by mass with respect to the converted mass of the hydrolyzed solid of the acidic colloidal silica and the silane coupling agent, and 0.5% by mass to 50%. The range of mass% is more preferable, and the range of 1 mass% to 25 mass% is more preferable. If the added amount of the organic polymer is too small, the effect due to the addition of the organic polymer, that is, the effect of reducing curing shrinkage and the effect of improving crack resistance cannot be achieved. If the added amount is too large, the hardness may not be sufficient. In some cases, the scratch resistance may be inferior.

[Other ingredients]
Other components that can be added to the aqueous silica-based resin composition of the present invention include resin emulsions, curing agents that react with compounded organic groups, organic binders such as wax emulsions, inorganic binders such as metal alkoxides and alkali silicates, and curing acceleration. An agent, a thickener, an antifoaming agent, a surface conditioner, a color pigment, an extender pigment, fibers and the like can be mentioned, and they can be blended unless they deviate from the object of the present invention.

[Production and Use of Aqueous Silica Resin Composition of the Present Invention]
For the production of the aqueous silica-based resin composition (or paint) of the present invention, a usual method for producing a water-based paint can be employed.
In the aqueous silica-based resin composition (or paint) of the present invention, all the constituents may be mixed at the time of use. For example, in the distribution stage of a product as a paint, The components may be divided into two or more liquids and mixed at the stage of use.

  In this case, what kind of combination is used as another liquid may be appropriately selected in light of the purpose, for example, a main agent composed of acidic water-dispersed colloidal silica and an organic acid, a silane coupling agent, and an alkoxysilane. It is exemplified as a preferable embodiment that the curing agent made of an oligomer is separated.

  When the aqueous silica-based resin composition of the present invention is applied as a paint, the application method is as a stock solution or, if necessary, a dispersion medium such as water or alcohol is added, and an aqueous brush, roller, air spray, air It is preferable to apply the coating film with a thickness of 5 to 50 μm by a less spray or the like. The aqueous silica-based resin composition (or paint) of the present invention is cured at room temperature, but can be baked and cured at an appropriate temperature.

  The aqueous silica-based resin composition or paint of the present invention preferably does not have a remarkable glass transition temperature in the normal temperature range of 0 ° C. to 50 ° C. In this case, there is little deterioration in physical properties in the use temperature range, and cracks Resistant to cracking and peeling, and has low temperature sensitivity, it is possible to form an excellent coating surface against contamination.

Next, although an Example and a comparative example are given and this invention is demonstrated concretely, it cannot be overemphasized that this invention is not limited by this.
Table 1 below summarizes the compositions and evaluations of the paints (aqueous silica resin compositions) of Examples and Comparative Examples.

  According to the composition shown in Table 1, nine types of coating materials of Examples 1 to 6 and Comparative Examples 1 to 3 were prepared, and an evaluation test described below was performed on the coating film obtained by applying the coating material to the test piece.

Each component used in this test will be described in detail.
As colloidal silica, silica doll # 33A (manufactured by Nippon Chemical Industry Co., Ltd.) was used. This colloidal silica has an average particle size of 10 to 20 nm, a hydrogen ion concentration (pH) of 2 to 4, and a non-volatile content (NV) of 33%.

As the epoxy group-containing silane coupling agent, γ-glycidoxypropyl trimethoxysilane (trade name: Silaace S-510, manufactured by Chisso) was used.
As a silane coupling agent having a functional group capable of reacting with an epoxy group, γ-ureidopropyltriethoxysilane (trade name NUC Silicone A-1160, manufactured by Nihon Unicar Co., Ltd.) was used. "Silane coupling agent".)

  As the alkyltrimethoxysilane having 3 or more carbon atoms in the alkyl group, n-hexyltrimethoxysilane (trade name KBM3063, manufactured by Shin-Etsu Chemical Co., Ltd., having 6 carbon atoms in the alkyl group) was used (in FIG. 1, "n = 6 alkyltrimethoxysilane ").

As the alkoxysilane oligomer (tetrafunctional), orthomethyl silicate partial hydrolysis condensate (trade name: M silicate 51, manufactured by Tama Chemical Co., Ltd.) was used.
Moreover, the brand name "NUC silicone Y-11597" (made by Nihon Unicar) was used for the compound shown by the following structural formula 1 (it describes with "structural formula 1 silane coupling agent" in FIG. 1). .

  -As an organic polymer having a functional group that causes a hydrogen bond with SiOH group, the acrylic silicone resin is a trade name "COMPOBRID AB3073I" (methanol / IPA solution, nonvolatile content (NV) 50%, manufactured by Atomix), polyurethane resin is a product. Name “MT Olester NL2532” (solvent type: toluene / IPA, nonvolatile content (NV) 30%, manufactured by Mitsui Takeda Chemical), nylon resin is “Toresin F30K” (produced by Nagase ChemteX), nonvolatile content (NV) 20 % Isopropanol (IPA) solution was used.

  In addition, 30% by mass aqueous solution of p-toluenesulfonic acid (reagent special grade, manufactured by Wako Pure Chemical Industries) is used as the organic acid, and Sn-type catalyst (Neostan U303, manufactured by Nitto Kasei) is diluted with methyltrimethoxysilane (MTMS) as the curing catalyst. The product (30% by mass) was used.

The outline of the evaluation test for each coating film of the comparative example is described below from the example tail.
(Appearance of coating film)
The appearance of the coating film was visually evaluated according to the following evaluation criteria with respect to each coating film formed by applying to a glass test piece using a 5 mil applicator (corresponding to 125 μm in terms of wet film thickness). At that time, the transparency of the coating film and the presence or absence of cracks were also evaluated.
-Evaluation criteria-
A: Very good.
○: Good.
X: Cracks, cracks, peeling, or opaque white.

(Curable)
Curing is carried out according to JIS K5600-3 “curing drying” for each coating film formed by applying to a glass test piece using a 5 mil applicator (corresponding to a wet film thickness of 125 μm). Evaluation was made according to the following evaluation criteria.
A: Within 30 minutes.
○: Within 1 hour.
X: Over 1 hour.

(Heat shock)
The heat shock property was applied to a 150 ° C oven together with each test piece for each coating film formed by applying to a test piece made of bonderite steel sheet using a 5 mil applicator (corresponding to a wet film thickness of 125 µm). Immediately after that, the product was taken out of the oven, rapidly cooled to room temperature, allowed to stand for 1 hour, the surface state was visually observed, and evaluated according to the following evaluation criteria.
A: No abnormalities such as cracks are observed.
○: Some cracks are observed, but almost satisfactory.
X: Cracks occurred on the entire surface.

(Water immersion resistance)
The water immersion resistance was determined by immersing each test piece in water for 5 days using a 5 mil applicator (corresponding to 125 μm in wet film thickness) and leaving it at room temperature for 3 days. The subsequent coating film appearance was evaluated according to the following evaluation criteria.
A: No abnormality.
○: Some abnormalities are observed, but almost satisfactory.
X: Abnormalities such as cracks, blisters, and whitening occurred.

  In FIG. 1, the image figure of the cured film by a water-based silica-type resin composition (Example 1) is mounted. As can be seen from the image diagram shown in FIG. 1, the cured film formed by the paint composed of the aqueous silica-based resin composition of this example has a colloidal silica base material and a silane coupling agent formed by a siloxane bond and an organic bond. It has an integrated hybrid structure.

In FIG. 2, the microscope picture after the test of the water immersion resistance in the coating film of Example 1 is mounted.
In FIG. 3, the microscope picture after the test of the water immersion resistance in the coating film of the comparative example 1 is mounted.
FIG. 4 shows dynamic viscoelastic profiles E ′, E ″ and tan δ in the respective coating materials of Example 1 and Comparative Example 1.
In FIG. 5, the graph which shows the pencil hardness time-dependent change in the coating film of Example 1 is put.

In addition, about the coating material of Example 1, several tests shown below were also performed.
・ Heat resistance test (cigarette resistance)
Even if a cigarette fire was pressed against the painted surface, no traces remained. By the way, although the heat resistance (tobacco resistance) test was similarly performed on the coatings obtained with acrylic urethane paints and thermoplastic acrylic paints, both remained traces, and acrylic urethane paints partially dissolved the coating surface. However, the thermoplastic acrylic paint was partially carbonized.

・ Heat resistance field test (ashtray application test)
The paint of Example 1 was applied to an ashtray, and it was actually used as an ashtray in a smoking room within the company. During use, the ashtray was kept in use by simply discarding the collected butts and ash without washing. After the lapse of 3 months, the surface stained with ash and candy was simply wiped with Kimwipe (trade name, manufactured by Kimberley Clark), and a clean surface state almost identical to the initial one was obtained.

-Water repellent treatment test A solution obtained by diluting the paint of Example 1 with ethanol 10 times was prepared, and a business card was dip-coated on the solution. The obtained business card was confirmed to be water repellent and show sufficient water repellent even when it is dipped in water, even though its appearance and feel do not change at all compared to a normal business card that has not been applied. It was.

-Styrofoam whiteboard formation test The coating material of Example 1 was apply | coated to one surface of the flat plate made from a polystyrene foam. An operation of writing letters, figures, etc. on the surface with a whiteboard pen and wiping it with a whiteboard eraser was repeated several times. On the surface, characters and figures can be written without any trouble, and by wiping with an eraser, it can be erased clean each time. By the paint of Example 1, a styrene foam flat plate is used as a white board. It was confirmed that it was ready for use.

<Consideration of results>
From the above results, the aqueous silica-based resin composition according to the present invention and the coating material based thereon have a hybrid structure in which a colloidal silica base material and a silane coupling agent are integrated by siloxane bonds and organic bonds, cured at room temperature, and hardness (See FIG. 5. In Example 1, the pencil hardness reached 7H.), High transparency, no glass transition temperature in the operating temperature range of 0 to 50 ° C., and physical properties in the operating temperature range No decrease in temperature, low temperature sensitivity, high water and water repellency, and excellent solvent resistance.

  Further, all of the coating films of Examples 4 to 6 which also have an organic-inorganic hybrid structure as well as a hybrid structure between the colloidal silica substrate and the silane coupling agent by adding an organic polymer. High performance was confirmed in the evaluation items.

  On the other hand, for each of the coating films of Comparative Examples 1 to 3, some of the evaluation test items have good or comparatively good results, but the composite with the aqueous resin composition of the present invention. There is no one that can satisfy all items like a coating film.

  Therefore, the aqueous silica-based resin composition of the present invention and the coating material obtained therefrom are suitable as a coating liquid for forming various inorganic or organic material surface protective films, room temperature dry ceramic coating films, and heat resistant coatings for construction and civil engineering. Can be used. Moreover, it is much cheaper than the coating liquid which used the conventional alkoxysilane single-piece | unit as a raw material.

It is an image figure of a water-based silica-type resin composition (Example 1). It is the microscope picture (150-times multiplication factor) after the test of the water-immersion resistance in the coating film of Example 1. It is a microscope picture (magnification 150 times) after the test of water immersion resistance in the coating film of Comparative Example 1. It is the profile of dynamic viscoelastic profile E ', E ", and tan-delta in each coating material of Example 1 and Comparative Example 1. FIG. 3 is a graph showing changes in pencil hardness with time in the coating film of Example 1.

Claims (7)

An aqueous silica-based resin comprising, as essential components, a main agent composed of acidic water-dispersed colloidal silica and an organic acid, a curing agent composed of a silane coupling agent and an alkoxysilane oligomer, and an alkoxysilane hydrolysis catalyst Composition. Examples of the silane coupling agent include methyltrimethoxysilane, an epoxy group-containing silane coupling agent, a silane coupling agent having a functional group capable of reacting with an epoxy group, an alkyltrimethoxysilane having an alkyl group having 3 or more carbon atoms, and The aqueous silica-based resin composition according to claim 1, comprising a compound represented by the following structural formula 1.

The blending ratio of the curing agent is
50-90% by mass of methyltrimethoxysilane,
0.5 to 20% by mass of an epoxy group-containing silane coupling agent,
0.5 to 20% by mass of a silane coupling agent having a functional group capable of reacting with an epoxy group,
0.5 to 20% by mass of alkyltrimethoxysilane having 3 or more carbon atoms in the alkyl group,
0.5 to 20% by mass of a compound represented by the following structural formula 1,
0.5-20% by mass of the alkoxysilane oligomer,
The aqueous silica-based resin composition according to claim 2, wherein The water content of 80 to 200 mol% with respect to the total number of moles of hydrolyzable alkoxysilyl groups in the curing agent is blended so as to be supplied by the water contained in the acidic water-dispersed colloidal silica. The aqueous silica-based resin composition according to any one of claims 1 to 3. The aqueous silica-based resin composition according to claim 4, further comprising an organic polymer having a functional group that causes hydrogen bonding with the —SiOH group. 5. The aqueous silica-based resin composition according to claim 4, which does not exhibit a remarkable glass transition temperature in the range of 0 ° C. to 50 ° C. 5. The aqueous silica-based resin composition according to any one of claims 1 to 6, which is used for forming a cured film, wherein the cured film formed thereby is substantially colorless and transparent. Resin composition.

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