JP2897270B2 - High strength inorganic adhesive - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an improvement of an inorganic adhesive comprising silica sol and an inorganic refractory powder. When the adhesive of the present invention is cured, the cured product exhibits a remarkably high adhesive strength, and is made of the same or different materials such as ceramics, glass, slate, aluminum, stainless steel, iron, and other metal materials. Provides significant improvement in adhesion.

(Prior Art) JP-B-39-8547 discloses aqueous silica sol and 5-15
As an improvement of an adhesive for electric equipment composed of a refractory powder such as 0 micron silica, an adhesive obtained by further adding boron oxide, lead oxide, antimony trioxide or the like to these components is disclosed.

Japanese Patent Publication No. 51-34861 discloses a method in which an extremely low polymerization degree silica dispersion in the form of silicate ions is added to an acidic silica sol having a particle diameter of 7 to 150 mm, or a refractory powder is further added thereto. It is shown that an adhesive with improved adhesive strength can be obtained.

(Problem to be Solved by the Invention) The adhesive composed of silica sol and refractory powder or ceramic fiber is substantially composed of only an inorganic component and does not contain a vitrified component, so that it exhibits heat resistance to withstand high temperatures.
This adhesive does not show sufficient adhesive strength when cured by drying.

20 to 70 parts of an aqueous silica sol having a concentration of 2 to 40% described in JP-B-39-8547 and talc having a particle size of 5 to 15 microns;
Silica, marica, sillimanite, asbestos, clay, glass for electrical insulation, synthetic mica, magnesium silicate, aluminum silicate, magnesium oxide, aluminum oxide, etc.
30 to 95 parts and 10 such as boron oxide, lead oxide, antimony trioxide
An adhesive consisting of 100100 parts requires a stepwise heat treatment at around 100 ° C., 300 ° C., and 600 ° C. after standing at room temperature when bonding using the adhesive, and the bonding process is not simple. Further, this adhesive has insufficient heat resistance because the cured product is vitrified at a high temperature.

An adhesive comprising the silica sol described in JP-B-51-34861, a silica dispersion having a low degree of polymerization, and a refractory powder is difficult to obtain a material having sufficient long-term storage stability.

In order to apply an adhesive containing silica sol and refractory powder to adhesion between various adherends, it is still not enough to simply solve the problems of adhesive strength, long-term storage stability, heat resistance, etc., as described above. In addition, higher performance is desired. For example, in order to sufficiently fill an adhesive to a small gap using an automatic adhesive injection machine for bonding between members to be bonded, the adhesive is required to have good fluidity or workability, Dispersion stability is essential so that the components in the adhesive do not settle or cause caking.

Further, when the adhesive is cured by drying, it is desired to have good curability such that uneven shrinkage called sink mark does not occur, cracks occur, or foaming occurs. .

Furthermore, when a member bonded via an adhesive is subjected to temperature changes such as temperature rise and temperature decrease in practical use, it is possible to easily control the thermal expansion coefficient of the cured adhesive layer together with particularly high adhesive strength. An adhesive is desired. In particular, in a light bulb, an electric heater, or the like, the bonding portion between the bulb glass or the outer glass covering the heating element and the base is exposed to a so-called heat shock because the temperature change occurs in a short time. It is essential to have a heat shock resistance so that the bond is not broken even by the heat shock. And not only these light bulbs, electric heaters, etc., but also electric equipment, electric parts and the like, in general, a cured adhesive layer is also desired to have high electric insulation.

Further, when at least one of the members to be bonded is made of a metal material, it is desired to use an adhesive that does not cause corrosion of the cured adhesive layer in the metal material during practical use.

The present invention solves these problems,
An object of the present invention is to provide a substantially inorganic adhesive containing silica sol and an inorganic refractory powder for achieving improved adhesion between similar or different materials such as glass, slate, hardened cement, and metallic materials. .

(Means for Solving the Problems) The adhesive of the present invention comprises 100 parts by weight of an aqueous silica sol having an average particle diameter of 5 to ₂₀₀ millimicrons as SiO ₂ and two or three parts per molecule when hydrolyzed. A coupling agent having a structure in which a silanol group is generated or a hydrolyzate thereof as a coupling agent in an amount of 0.05 to 500 parts by weight, and a particle size of 0.1 to 500 parts by weight.
It is obtained by mixing 50 to 10,000 parts by weight of a 1000 micron inorganic refractory powder.

The aqueous silica sol used in the present invention is a liquid in which colloidal silica particles having an average particle diameter of 5 to 200, preferably 10 to 150 millimicrons are stably dispersed in water as a medium. The shape of the colloidal silica particles is spherical,
Any non-spherical shape may be used. The shape and size of the colloidal silica particles are determined by a method for producing an aqueous silica sol. This silica aqueous sol may be either alkaline or acidic, but has a SiO ₂ / M ₂ O (M represents an alkali metal atom or a molecule such as an amine or ammonium) molar ratio.
Alkaline ones having a pH of 30 or more are preferred.
About 12 are particularly preferred. Silica aqueous sols having a particle size of about 5 to 150 millimicrons are already commercially available as industrial products, so that it is convenient to use them. A mixture of silica aqueous sols having different particle sizes may be used,
For some applications, a more preferable adhesive can be obtained by using a mixed sol. The aqueous silica sol to be used preferably has an SiO ₂ concentration of about 1 to 50% by weight, and preferably contains as little impurity ions as possible.

The coupling agent used in the present invention is a compound having a structure in which two or three silanol groups are generated in the molecule when the coupling agent is hydrolyzed. A preferable example thereof is vinyltris (β-methoxyethoxy). Silane CH ₂
＝ CHSi (OC ₂ H ₄ OCH ₃ ) ₃ , vinyl triethoxysilane CH ₂ ＝ C
HSi (OC ₂ H ₅ ) ₃ , vinyltrimethoxysilane CH ₂ ＝ CHSi (OCH
₃ ) ₃ , vinyltriacetoxysilane γ-methacryloxypropyltrimethoxysilane β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane γ-glycidoxypropyltrimethoxysilane γ-glycidoxypropylmethyldiethoxysilane N-β (aminoethyl) γ-aminopropyl trimethoxysilane H ₂ NC ₂ H ₄ NHC ₃ H ₆ Si (OCH ₃ ) ₃ , N-β (aminoethyl) γ-aminopropylmethyldimethoxysilane γ-aminopropyltriethoxysilane H ₂ NC ₃ H ₆ Si (OC ₂ H
₅ ) ₃ , N-phenyl-γ-aminopropyltrimethoxysilane C ₆ H ₅ NHC ₃ H ₆ Si (OCH ₃ ) ₃ , γ-anilinopropyl trimethoxysilane C ₆ H ₅ NHC ₃ H ₆ Si (OCH _{3 3} ) and the like. An aqueous solution of the hydrolyzate of the coupling agent obtained by mixing these coupling agents with water can also be used.

As the inorganic refractory powder used in the present invention, quartz, silica stone, feldspar, aluminum silicate, zirconium silicate, mullite, zirconia, alumina, silicon nitride, silicon carbide, talc, mica and the like particle size 0.1 to 350 microns Powders such as glass fibers, alumina fibers, potassium titanate fibers, etc., with a long sleeve length of about 0.1 to 1000 microns and a short axis length of about 0.1 to 20 microns. These refractory powders may be used arbitrarily or may be mixed as required.

The adhesive of the present invention, the silica aqueous sol as SiO ₂
100 parts by weight, 0.05 to 500 parts by weight, preferably 0.5 to 100 parts by weight of the coupling agent or the hydrolyzate thereof as a coupling agent, and 50 to 10,000 parts by weight of the inorganic refractory powder are uniformly mixed. Can be easily obtained. As the adhesive of the present invention, as long as the object of the present invention is achieved,
Optional components may be further contained in addition to the above components. Examples of the added components include clay mineral powders such as bentonite as a thickener, cellulose derivatives such as hydroxyethylcellulose, and other synthetic organic polymer substances, and a coloring agent such as titanium oxide, red iron oxide, and chromium oxide.
And other inorganic pigments. Water can also be added to control the viscosity or solids concentration of the adhesive. Further, a small amount of methanol, ethanol, other hydrophilic organic solvents and the like may be contained.

The above-mentioned mixing for preparing the adhesive of the present invention can be easily performed by using a conventionally known ordinary mixer. This mixing can be carried out by adding the above components at once or in any order, but preferably at a temperature and pressure at which drying does not occur. By mixing for about 0.5 to 4 hours, a preferable adhesive can be obtained.

The preferred adhesive of the present invention contains about 60 to 90% by weight as a solid content, exhibits a viscosity of about 10 to 1000 poise at 20 ° C., and has storage stability that does not cause deterioration for several months or more when stored at room temperature and in a closed state. Having.

The adhesive of the present invention is cured by drying. When the adhesive is cured with the adhesive at 80 to 300 ° C., particularly high adhesive strength can be exhibited.

(Action) Although it is difficult to completely elucidate the action of the coupling agent used to prepare the adhesive of the present invention, it is considered as follows.

In an alkylalkoxysilane in which two or three alkoxy groups are bonded to a silicon atom in one molecule, the alkoxy group is converted to a silanol group upon contact with water contained in the aqueous silica sol. The silanol group chemically or physically binds to the surface of the colloidal silica particles and the surface of the inorganic refractory powder during mixing with the aqueous silica sol and the inorganic refractory powder. Further, when an aqueous solution of a hydrolyzate of a coupling agent is used, the same bond as described above occurs. as a result,
In the mixed system, the dispersibility of the inorganic refractory powder is remarkably improved, and when the adhesive is cured by drying, the bonding amount between the colloidal silica particles and the surface of the inorganic refractory powder particles increases dramatically, and After curing, a cured product having significantly improved strength is formed. Such an effect due to the interposition of silanol groups generated as a result of hydrolysis of the coupling agent also appears in the bond between the surface of the material to be bonded and the colloidal silica particles, and as a result, after curing of the adhesive,
It is considered that the bonding force between the surface of the material to be bonded and the cured adhesive layer is dramatically improved. That is, the adhesive of the present invention has a function of forming a cured adhesive layer which is dense and has remarkably improved strength, and remarkably increases the bonding strength between the cured adhesive layer and the surface of the material to be bonded.

Further, the improvement of the dispersibility of the inorganic refractory powder by the action of silanol groups generated based on the hydrolysis of the coupling agent improves the fluidity and workability of the adhesive. Further, by improving the dispersibility of the inorganic refractory powder, it is possible to increase the amount of the inorganic refractory powder with respect to the amount of colloidal silica in the adhesive, and thereby, sink marks when the adhesive is cured,
The generation of cracks, foaming, and the like can be significantly suppressed, and the coefficient of thermal expansion of the cured adhesive layer can be easily controlled.

Further, the organic group bonded to the silicon atom in the coupling agent molecule via a carbon atom significantly reduces the hygroscopicity of the cured adhesive layer and enhances the electrical insulation.

It has been found that such an improved adhesive is obtained by a preferred preparation method therefor.

If the colloidal silica particle size of the aqueous silica sol used is less than 5 millimicrons, the aqueous silica sol composed of such particles has poor stability, and when preparing an adhesive, it is difficult to obtain an adhesive of constant quality. On the other hand, if the colloidal silica particle diameter is larger than 200 millimicrons, the particles of the aqueous sol composed of such particles are liable to settle, the specific surface area of silica is reduced, and the bonding strength is not sufficient.
In particular, a commercially available silica aqueous sol having a particle size of about 5 to 150 millimicrons has a constant quality and is easily available, and is preferable for preparing the adhesive of the present invention. In this aqueous silica sol, an alkaline one gives higher adhesive strength to the adhesive than an acidic one. When a mixture of silica aqueous sols having different particle diameters is used, the packing density is increased when the particles are aggregated, which is advantageous for obtaining an adhesive having high adhesive strength. If the SiO ₂ concentration of the aqueous silica sol used is too high, such sols have poor stability and tend to thicken or gel. As such a sol free from such a concern, a sol having a SiO ₂ concentration of 50% by weight or less is preferable.
Although a sol having a SiO ₂ concentration of 1% by weight or less can be used, the bonding strength of the adhesive tends to be poor, and it is not efficient to concentrate the adhesive.

The amount of the coupling agent used is
If the amount is less than 0.05 part by weight with respect to 100 parts by weight of SiO _2, an adhesive having the improved performance cannot be obtained. Conversely, if the amount is more than 500 parts by weight with respect to 100 parts by weight of SiO _{2 in the} aqueous silica sol, the prepared adhesive will have significantly reduced stability. Particularly, a preferable adhesive can be obtained by using 0.5 to 100 parts by weight of the coupling agent with respect to 100 parts by weight of SiO _{2 of the} aqueous silica sol.

The particle size of the refractory powder used does not significantly affect the performance of the adhesive, but non-fibrous powder of about 0.1 to 350 microns, short axis of about 0.1 to 20 microns and long axis of 1000 microns or less. Certain fibrous forms are convenient for use.
In particular, it is preferable to use a combination of powders having different particle sizes so as to increase the packing density when the adhesive is cured. However, the amount of this refractory powder
When the content of SiO ₂ is less than 50 parts by weight, the prepared adhesive hardens, and when it is cured, the shrinkage ratio becomes large, or uneven shrinkage easily occurs, and sink marks, cracks, and the like are liable to occur. Conversely, if the amount is more than 10,000 parts by weight with respect to 100 parts by weight of SiO _{2 of the} aqueous silica sol, the fluidity of the adhesive, the workability and the like are likely to be reduced, and the amount of colloidal silica is relatively short, so that An adhesive having high adhesive strength cannot be obtained.

When mixing the above amount of the aqueous silica sol, the coupling agent and the inorganic refractory powder, if the mixture is performed at an excessively high temperature, the mixture is liable to gel, so it is preferably performed at a temperature of about 40 ° C. or lower, preferably at room temperature. Good. When the solid content concentration or viscosity in the adhesive obtained by mixing is too high, a preferable adhesive can be obtained by diluting with water.

(Examples) The following commercially available aqueous silica sols A ₁ , A ₂ , A ₃ and A ₄ obtained by diluting A ₁ with water, commercially available coupling agents B ₁ , B ₂ , B ₃ , B ₄ and B ₅ , and commercially available inorganic refractory powder C ₁
And we were prepared C _2.

A ₁ ... An alkaline aqueous sol having an average particle size of colloidal silica of 10 to 20 mm and an SiO ₂ concentration of 40% by weight.

A ₂ ... An alkaline aqueous sol having an average particle size of colloidal silica of 70 to 100 mm and an SiO ₂ concentration of 40% by weight.

A ₃ ... An acidic aqueous sol having an average particle size of colloidal silica of 10 to 20 mm and an SiO ₂ concentration of 20% by weight.

A ₄ ... An alkaline aqueous sol having a SiO ₂ concentration of 5% by weight obtained by diluting the sol of A ₁ with water.

B ₁ γ-glycidoxypropyltrimethoxysilane.

B ₂ N-β (aminoethyl) γ-aminopropyltrimethoxysilane.

B ₃ ... vinyl troacetoxysilane.

B ₄ γ-methacryloxypropyltrimethoxysilane.

B ₅ γ-glycidoxypropylmethyldiethoxysilane.

C ₁ … Quartz powder with a particle size of 5 to 150 microns.

C ₂ … Alumina powder with a particle size of 5 to 60 microns.

And Example 1 The silica aqueous sol A ₁ 250 parts by weight, and the coupling agent B ₁ 10 parts by weight, and the refractory powder C ₁ 370 parts by weight,
To obtain an adhesive to Q ₁ the invention by mixing 1 hour and the refractory powder C ₂ 370 parts by weight at room temperature in a mixer.

Then according to the following test method, were tested the performance of the adhesive Q _1, the results in Table 2 described were obtained.

Stability test After the adhesive is allowed to stand in a glass container at 20 ° C. for 24 hours in a sealed state, the presence or absence of fluidity of the adhesive is visually determined.

Workability test After putting the amount of adhesive that will be 15 cm deep in a glass container,
After standing at 20 ° C. for 24 hours, a stainless steel rod having a diameter of 5 mm is inserted vertically into the adhesive, and the presence or absence of sedimentation and solidification is determined based on whether or not the tip of the rod has hit the bottom of the container.

Curing test After applying an adhesive to a thickness of 2 mm on the entire surface of a 20 mm square glass plate, leaving it in a dryer at 110 to 150 ° C for 30 minutes, drying it, taking it out, and taking out the obtained cured product At the same time, the presence or absence of cracks is visually determined, and the pencil hardness of the surface of the cured product is measured.

Electrical insulation test After filling the glass tube with an outer diameter of 8 mm, inner diameter of 6 mm and length of 20 mm with adhesive, insert a lead wire of diameter 0.7 mm from the center of both ends into each 5 mm depth, and then at 110 to 150 ° C. After drying for 30 minutes and then standing in a room at 20 ° C. and a relative temperature of 90% for 24 hours, a power supply voltage of 500 V DC by a battery is applied to measure the electric resistance.

Adhesive strength test Two glass plates of 20 mm square and 20 mm square were bonded to each other with the adhesive thickness shown in Table 1 using an adhesive, and then 110 to 150 ° C.
And then dried by heating at 200 ° C. for 30 minutes, and the two glass plates are bonded. Next, the fixtures were attached to both sides of this glass plate with a commercially available cooperating adhesive, and then, using a tensile tester, in the direction perpendicular to the glass plate.
A tension is applied at a rate of 1 mm / min to measure the tension when the bond is broken, and the broken surface is observed with a small eye. The time due to peeling from the surface is represented by S.

To test the performance of the adhesive by the above test method to prepare the adhesive Q ₂ to Q ₁₃ of Table 1 described in the same manner to obtain the results of Table 2 wherein.

Comparative Example 1 except that the mixed composition of Table 1, wherein employed is prepared adhesive R ₁ to R ₅ of the comparative example in the same manner as in Example 1, was tested by the test method, the results in Table 2, wherein was gotten. Adhesive R ₂ of the comparative example, gelation was not tested occurred while allowed to stand overnight after preparation. R ₃ were measured for insulation testing is difficult. R ₄ is prepared has been difficult for the ratio of the inorganic refractory powder was too high.

While the test results of the above embodiments are all good,
In Comparative Examples adhesive R ₅ was not mixed coupling agent,
Workability, curability, electric resistance, adhesive strength are all extremely low, even in the case of R _{1 with} a small amount of coupling agent,
It shows that workability, curability, electric resistance and adhesive strength are not improved. Adhesive R ₃ and R ₄ is a mixing amount is insufficient and excessive refractory powder shows that the workability is insufficient improvement of such curable.

After the end of the stainless steel wire of Example 2 thickness 1mm inserted into the connecting portion of the connecting ceramic insulators, filled with an adhesive Q ₁₃ obtained in Example 1 in the connecting portion, in a dryer 110 to 150 ° C
For 30 minutes and then at 200 ° C. for 30 minutes to connect the wire and the insulator. Next, a tension of 50 kg was applied to the insulator and the stainless steel wire, but no breakage of the bond occurred.

(Effect of the Invention) The adhesive of the present invention can be easily produced, and when it is cured, it is changed into a preferred cured product only by heating at room temperature to 300 ° C., and is made of ceramics, glass, metal materials, and other cements. It provides a significant improvement in the adhesion between these same or different materials over a wide range, such as quality materials.

The adhesive of the present invention has good stability and workability, and automatic adhesive injection using a machine is also possible. Since no sink marks, cracks, etc. occur during curing, even if the cured adhesive is exposed, the appearance is not impaired. This adhesive has a remarkably high adhesive strength, and has high heat shock resistance and electrical insulation, so it is suitable for bonding electrical parts, electronic parts or members in these devices, as well as bonding metal plates and ceramic fiber mats. Also used for bonding mortar boards.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-60-219275 (JP, A) JP-A-52-6340 (JP, A) JP-A-64-43570 (JP, A) JP-A 64-64 69673 (JP, A) (58) Field surveyed (Int. Cl. ⁶ , DB name) C09J 1/00 C09J 11/06

Claims (1)

(57) [Claims] 1. A coupling agent having a structure in which 100 parts by weight of a silica aqueous sol having an average particle diameter of 5 to ₂₀₀ millimicrons as SiO ₂ and two or three silanol groups are generated in a molecule when hydrolyzed. Alternatively, a high-strength inorganic adhesive obtained by mixing a hydrolyzate thereof in an amount of 0.05 to 500 parts by weight as a coupling agent and 50 to 10,000 parts by weight of an inorganic refractory powder having a particle size of 0.1 to 1000 microns.