Phosphate-based adhesive and method for preparing the same

Abstract

This invention provides a phosphate-based adhesive and its preparation method, belonging to the field of inorganic adhesives. The invention involves mixing a phosphoric acid solution with an aluminum source for an acid-base neutralization reaction to obtain a neutralized product; mixing the neutralized product with a trivalent metal halide for a metathesis reaction to obtain the phosphate-based adhesive; and providing a curing agent to obtain the phosphate-based adhesive. This invention incorporates heteroions into the aluminum phosphate adhesive system in the form of trivalent metal halides, eliminating the need for a reduction reaction and allowing direct use of the trivalent metal. The preparation method is simple, efficient, and easily scalable for industrial production. Furthermore, this invention limits the trivalent metal halide to one or more of chromium halides, iron halides, scandium halides, iridium halides, lanthanum halides, ruthenium halides, osmium halides, gallium halides, and molybdenum halides, expanding the range of heteroions and eliminating the need for highly toxic chromium trioxide, thus improving the safety of the preparation method.

Description

Technical Field

[0001] This invention relates to the field of inorganic adhesives, and more particularly to a phosphate-based adhesive and its preparation method. Background Technology

[0002] Aluminum phosphate adhesives are among the most commonly used phosphate-based inorganic adhesives. They are generally prepared from phosphoric acid and aluminum hydroxide or alumina. These adhesives possess excellent high and low temperature resistance, weather resistance, low curing shrinkage, good dielectric properties, non-destructive bonding, and low-temperature curing capabilities, making them widely used in high-temperature coatings, equipment bonding, refractory materials, composite materials, antenna windows, and aerospace applications. However, currently prepared liquid aluminum phosphate adhesives suffer from premature hardening, meaning they solidify during long-term storage, losing their fluidity and becoming unusable. Furthermore, during low-temperature curing, aluminum phosphate adhesives exhibit hygroscopicity, significantly affecting the curing speed due to environmental humidity. Existing technologies aim to increase the stability of aluminum phosphate adhesives by incorporating trivalent metal ions, such as chromium ions, to prepare aluminum-chromium phosphate adhesives. However, this requires heating to decompose or reduce chromium trioxide to obtain trivalent chromium ions, resulting in cumbersome and inefficient preparation methods. Summary of the Invention

[0003] In view of this, the purpose of this invention is to provide a phosphate-based adhesive and its preparation method. The preparation method provided by this invention incorporates hetero-ions into the aluminum phosphate adhesive system in the form of trivalent metal chlorides. The preparation method is simple, efficient, and easy to implement for industrial production.

[0004] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0005] This invention provides a method for preparing a phosphate-based adhesive, the phosphate-based adhesive comprising separate phosphate-based adhesive and curing agent, comprising the following steps:

[0006] A phosphoric acid solution was mixed with an aluminum source to carry out an acid-base neutralization reaction, yielding a neutralized product.

[0007] The neutralization product was mixed with a trivalent metal halide and subjected to a metathesis reaction to obtain the phosphate-based gum.

[0008] The curing agent is provided to obtain the phosphate-based adhesive.

[0009] Preferably, the trivalent metal halide includes one or more of chromium halide, iron halide, scandium halide, iridium halide, lanthanum halide, ruthenium halide, osmium halide, gallium halide, and molybdenum halide.

[0010] Preferably, the halogen in the trivalent metal halide is F, Cl, Br or I.

[0011] Preferably, the molar equivalent ratio of the trivalent metal halide to the aluminum source is 0 to 10:1, and is not 0.

[0012] Preferably, the temperature of the metathesis reaction is 80–270°C.

[0013] Preferably, the pH value of the gas produced during the metathesis reaction is also detected, and the endpoint of the metathesis reaction is when the pH value is greater than 6.5.

[0014] Preferably, during the metathesis reaction, a vacuum pump is used to depressurize and remove the gas generated in the reaction system.

[0015] Preferably, the mass ratio of the phosphoric acid solution to the aluminum source is 100:0 to 50, and the amount of aluminum source is not zero, and the mass fraction of phosphoric acid in the phosphoric acid solution is 10% to 100%.

[0016] Preferably, the mass ratio of the phosphate-based adhesive to the curing agent is 100:1 to 1000.

[0017] The present invention also provides a phosphate-based adhesive prepared by the preparation method described above, comprising packaged phosphate-based adhesive and curing agent.

[0018] This invention provides a method for preparing a phosphate-based adhesive, the phosphate-based adhesive comprising separate phosphate-based adhesive and curing agent, comprising the following steps: mixing a phosphoric acid solution with an aluminum source to perform an acid-base neutralization reaction to obtain a neutralized product; mixing the neutralized product with a trivalent metal halide to perform a metathesis reaction to obtain the phosphate-based adhesive; and providing the curing agent to obtain the phosphate-based adhesive.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] This invention incorporates heteroions into the aluminum phosphate adhesive system in the form of trivalent metal halides, eliminating the need for a reduction reaction and allowing direct use of the trivalent metal. The preparation method is simple, efficient, and easy to implement for industrial production.

[0021] Furthermore, this invention further specifies that the trivalent metal halide includes one or more of chromium halide, iron halide, scandium halide, iridium halide, lanthanum halide, ruthenium halide, osmium halide, gallium halide, and molybdenum halide, thus expanding the range of heteroions. Simultaneously, it eliminates the need for highly toxic chromium trioxide, improving the safety of the preparation method. Moreover, the addition of trivalent metal cations increases the disorder of the adhesive system, lowers the system energy, and increases stability, thereby increasing the crystallization difficulty of the aluminum phosphate adhesive system. This results in a phosphate-based adhesive with a low freezing point, good fluidity at low temperatures, adjustable curing time when mixed with a curing agent, and cross-linking curing at room temperature.

[0022] This invention also provides a phosphate-based adhesive prepared by the preparation method described above. In the process of preparing phosphate-based adhesive, trivalent metal halides are introduced. The trivalent heteroatoms in the trivalent metal halides can promote the formation of an amorphous continuous structure during the gelation process of the phosphate-based adhesive. The final product has higher toughness and lower freezing point than traditional phosphate-based adhesives. Detailed Implementation

[0023] This invention provides a method for preparing a phosphate-based adhesive, the phosphate-based adhesive comprising separate phosphate-based adhesive and curing agent, comprising the following steps:

[0024] A phosphoric acid solution was mixed with an aluminum source to carry out an acid-base neutralization reaction, yielding a neutralized product.

[0025] The neutralization product was mixed with a trivalent metal halide and subjected to a metathesis reaction to obtain the phosphate-based gum.

[0026] The curing agent is provided to obtain the phosphate-based adhesive.

[0027] Unless otherwise specified, all raw materials used in this invention are commercially available products in the field.

[0028] This invention involves mixing a phosphoric acid solution with an aluminum source to perform an acid-base neutralization reaction, thereby obtaining a neutralized product.

[0029] In this invention, the mass ratio of the phosphoric acid solution to the aluminum source is preferably 100:0 to 50, and the amount of aluminum source is not 0. The mass fraction of phosphoric acid in the phosphoric acid solution is preferably 10% to 100%, more preferably 60% to 85%, because the main component in the aluminum phosphate-based adhesive that plays a good wetting and bonding role is aluminum dihydrogen phosphate, so the mass fraction of phosphoric acid in the phosphoric acid solution is preferably 60% to 85%.

[0030] In this invention, the aluminum source is preferably aluminum oxide or aluminum hydroxide.

[0031] In this invention, the temperature of the acid-base neutralization reaction is preferably 40-150°C, more preferably 50-100°C.

[0032] In this invention, the chemical reactions that occur during the acid-base neutralization reaction are as follows:

[0033]

[0034] Preferably, in this invention, at room temperature, the phosphoric acid solution is first added to the reaction vessel, the rotation speed is set to 200-400 r / min, and then the aluminum source is added to the reaction vessel, the temperature is set to 40-150℃ to carry out the acid-base neutralization reaction, until the aluminum source is fully dissolved, thus completing the acid-base neutralization reaction.

[0035] After obtaining the neutralization product, the present invention mixes the neutralization product with a trivalent metal halide to carry out a metathesis reaction to obtain the phosphate-based gum.

[0036] In this invention, the trivalent metal halide preferably includes one or more of chromium halide, iron halide, scandium halide, iridium halide, lanthanum halide, ruthenium halide, osmium halide, gallium halide, and molybdenum halide.

[0037] In this invention, the halogen in the trivalent metal halide is preferably F, Cl, Br or I, and more preferably Cl.

[0038] In a specific embodiment of the present invention, the trivalent metal halide is preferably gallium chloride, chromium chloride, or scandium chloride.

[0039] In this invention, the molar equivalent ratio of the trivalent metal halide to the aluminum source is preferably 0 to 10:1, and not 0.

[0040] In this invention, the temperature of the metathesis reaction is preferably 80–270°C, more preferably 175–200°C.

[0041] In this invention, it is preferable to also detect the pH value of the gas produced during the metathesis reaction, and the endpoint of the metathesis reaction is preferably when the pH value is greater than 6.5.

[0042] In this invention, it is preferable to use a vacuum pump to depressurize and remove the gas generated in the reaction system during the metathesis reaction process.

[0043] During the decompression and evacuation process, the present invention preferably introduces a cold trap between the vacuum pump and the reaction system to prevent HX gas from corroding the vacuum pump.

[0044] In this invention, the chemical reactions that occur during the metathesis reaction are as follows:

[0045]

[0046] MX3 is a trivalent metal halide, and X is F, Cl, Br or I.

[0047] After the metathesis reaction is completed, the present invention preferably keeps the obtained metathesis product at a temperature of 80-270°C, more preferably 175-200°C, and for a time of 0.5-10 hours. The purpose of keeping the product at a temperature of 80-270°C, more preferably 175-200°C, is to remove moisture.

[0048] After the heat preservation is completed, the present invention preferably allows the material to cool naturally to room temperature to obtain the phosphate-based adhesive.

[0049] After obtaining the phosphate-based gum, the present invention preferably measures the ion concentration of the phosphate-based gum by ICP. If X - If the concentration is below 0.1 wt%, the product is qualified because X - The residue of X can affect subsequent gelation, therefore X must be treated. - The content of [the substance] is strictly controlled. This invention does not impose any specific limitations on the method of ICP determination; any method well-known to those skilled in the art can be used.

[0050] In this invention, the mass ratio of the phosphate-based adhesive to the curing agent is preferably 100:1 to 1000, more preferably 1:1.5 to 3, and most preferably 1:2 to 2.5. The curing agent not only functions as a curing agent but also partially acts as a filler to reinforce the adhesive.

[0051] In this invention, the curing agent preferably comprises a metal oxide, which preferably comprises one or more of copper oxide, aluminum oxide, calcium oxide, magnesium oxide, zinc oxide, zirconium oxide, ferric oxide, chromium oxide, scandium oxide, and gallium oxide, more preferably a mixture of copper oxide, magnesium oxide, and chromium oxide, wherein the mass ratio of copper oxide, magnesium oxide, and chromium oxide in the mixture is 100:5:0.5.

[0052] In this invention, the particle size of the curing agent is preferably no greater than 0.075 mm, which is sufficient to pass through a 200-mesh standard sieve, and more preferably through a 300-mesh standard sieve.

[0053] In this invention, the curing agent is preferably dried, and the drying temperature is preferably 80-100°C, and the drying time is preferably 10-12 hours.

[0054] The present invention also provides a phosphate-based adhesive prepared by the preparation method described above, comprising packaged phosphate-based adhesive and curing agent.

[0055] This invention also provides applications of the above-mentioned phosphate-based adhesives. This invention does not specifically limit the specific methods of application, and any method known to those skilled in the art can be used. Specifically, it can be used in the fields of high-temperature coatings, equipment bonding, refractory materials, composite materials, antenna windows, and spacecraft.

[0056] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0057] Example 1

[0058] A phosphate-based adhesive is prepared using a phosphoric acid solution (85% by mass), analytical grade aluminum hydroxide, and scandium chloride as raw materials. An analytical grade copper oxide, magnesium oxide, and chromium trioxide are used to prepare a curing agent. The preparation method of the phosphate-based adhesive includes the following steps:

[0059] a) At room temperature, add 1000 mL of phosphoric acid solution to a 2 L three-necked flask. Set the stirring speed to 250 rpm. Add 50 g of analytical grade aluminum hydroxide to the system. Set the heating temperature to 100 °C. After stirring for 0.5 h, the reaction system becomes basically clear. Add scandium chloride of different masses to the reaction system and stir until dissolved. Heat the reaction system to 200 °C and maintain this temperature for 2 h. Connect a vacuum pump to the flask and a cold trap between them. Continue to maintain the reaction system at 200 °C for 0.5 h. When the pH value of the gas evaporating from the flask is greater than 6.5, stop heating. Seal the flask tightly with a rubber stopper and allow it to cool naturally to room temperature. Detect X using ICP. - When the ion concentration is less than 0.1 wt%, the final product is obtained. Then, the freezing temperature range of the product is tested using an ice point apparatus. The results are shown in Table 1. As can be seen from Table 1, the phosphate-based adhesive prepared in this example has a low freezing point.

[0060] b) Mix copper oxide, magnesium oxide, and chromium trioxide in a mass ratio of 100:5:0.5, then grind thoroughly and dry in an oven at 80°C for 10 hours. After drying, pass the mixture through a 300-mesh sieve to obtain the curing agent, and then seal and store the sample.

[0061] c) Tensile strength tests were conducted using 25mm × 12.5mm tensile sheets. 60g of phosphate-based adhesive was mixed with different amounts of curing agent (Table 2) at room temperature. The adhesive was then coated onto the tensile sheets to prepare tensile sheet samples. Tensile strength was tested after curing at room temperature for 6h, 12h, and 18h. Samples with dimensions of 2mm × 4mm × 20mm were prepared using a mold at room temperature. The fracture toughness of the adhesive after curing for 24h was determined by a three-point bending test on a single-sided notched beam. The results are shown in Table 3. Table 3 shows that the phosphate-based adhesive prepared in this embodiment exhibits good fracture toughness and high tensile strength.

[0062] Table 1 Freezing point of phosphate-based gel in Example 1

[0063] Serial Number Scandium chloride dosage Solidification temperature range 1 0g 1～2℃ 2 0.25g -5～-4℃ 3 0.5g -11～-10℃ 4 2.5g <-15℃

[0064] Note: In Table 1, item 4, due to the increased amount of scandium chloride, the aluminum phosphate adhesive system is difficult to crystallize or crystallizes in an amorphous manner, and therefore has no fixed solidification point.

[0065] Table 2. Dosage of each component in the phosphate-based adhesive of Example 1 (scandium chloride dosage 2.5g)

[0066] Serial Number Phosphate-based adhesive dosage Curing agent dosage 1 60g 600g 2 60g 180g 3 60g 150g 4 60g 120g 5 60g 90g

[0067] Table 3 Mechanical property test of phosphate-based adhesive during curing process in Example 1 (scandium chloride dosage 2.5g)

[0068]

[0069] Example 2

[0070] A phosphate-based adhesive is prepared using a phosphoric acid solution (85% by mass), analytically pure aluminum hydroxide, and gallium chloride as raw materials. An analytically pure copper oxide, magnesium oxide, and chromium trioxide are used to prepare a curing agent. The preparation method of the phosphate-based adhesive includes the following steps:

[0071] a) At room temperature, add 1000 mL of phosphoric acid solution to a 2 L three-necked flask. Set the stirring speed to 250 rpm. Add 50 g of analytical grade aluminum hydroxide to the system. Set the heating temperature to 100 °C. After stirring for 0.5 h, the reaction system becomes basically clear. Add scandium chloride of different masses to the reaction system and stir until dissolved. Heat the reaction system to 175 °C and maintain this temperature for 2 h. Connect a vacuum pump to the flask and a cold trap between them. Continue to maintain the reaction system at 175 °C for 0.5 h. When the pH value of the gas evaporating from the flask is greater than 6.5, stop heating. Seal the flask tightly with a rubber stopper and allow it to cool naturally to room temperature. Detect X using ICP. -When the ion concentration is less than 0.1 wt%, the final product is obtained. Then, the freezing temperature range of the product is tested using an ice point apparatus. The results are shown in Table 4. As can be seen from Table 4, the phosphate-based adhesive prepared in this example has a low freezing point.

[0072] b) Mix copper oxide, magnesium oxide, and chromium trioxide in a mass ratio of 100:5:0.5, then grind thoroughly and dry in an oven at 80°C for 10 hours. After drying, pass the mixture through a 300-mesh sieve to obtain the curing agent, and then seal and store the sample.

[0073] c) Tensile strength tests were conducted using 25mm × 12.5mm tensile sheets. 60g of phosphate-based adhesive was mixed with different amounts of curing agent (Table 5) at room temperature. The adhesive was then coated onto the tensile sheets to prepare tensile sheet samples. Tensile strength was tested after curing at room temperature for 6h, 12h, and 18h. Samples with dimensions of 2mm × 4mm × 20mm were prepared using a mold at room temperature. The fracture toughness of the adhesive after curing for 24h was determined by a three-point bending test on a single-sided notched beam. The results are shown in Table 6. Table 6 shows that the phosphate-based adhesive prepared in this embodiment exhibits good fracture toughness and high tensile strength.

[0074] Table 4 Freezing point of phosphate-based gel in Example 2

[0075] Serial Number Gallium chloride dosage Solidification temperature range 1 0g 1～2℃ 2 0.25g -8～-6℃ 3 0.5g -12～-11℃ 4 2.5g <-15℃

[0076] Note: In Table 4, item 4, due to the increased amount of gallium chloride, makes it difficult for the aluminum phosphate adhesive system to crystallize or to crystallize in an amorphous manner, and therefore has no fixed solidification point.

[0077] Table 5. Dosage of each component in the phosphate-based adhesive of Example 2 (Gallium chloride dosage: 2.5g)

[0078] Serial Number Phosphate-based adhesive dosage Curing agent dosage 1 60g 600g 2 60g 180g 3 60g 150g 4 60g 120g 5 60g 90g

[0079] Table 6 Mechanical property test of phosphate-based adhesive during curing process in Example 2 (Gallium chloride dosage 2.5g)

[0080]

[0081] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a phosphate-based adhesive, wherein the phosphate-based adhesive comprises separate phosphate-based adhesive and curing agent, characterized in that, Includes the following steps: A phosphoric acid solution was mixed with an aluminum source to carry out an acid-base neutralization reaction, yielding a neutralized product. The neutralization product was mixed with a trivalent metal halide and subjected to a metathesis reaction to obtain the phosphate-based gum. The curing agent is provided to obtain the phosphate-based adhesive; The trivalent metal halide is one or more of the following: chromium halide, iron halide, scandium halide, iridium halide, lanthanum halide, ruthenium halide, osmium halide, gallium halide, and molybdenum halide.

2. The preparation method according to claim 1, characterized in that, The halogen in the trivalent metal halide is F, Cl, Br or I.

3. The preparation method according to claim 1, characterized in that, The molar equivalent ratio of the trivalent metal halide to the aluminum source is 0 to 10:1, and is not 0.

4. The preparation method according to claim 1, characterized in that, The temperature for the metathesis reaction is 80~270℃.

5. The preparation method according to claim 1 or 4, characterized in that, The pH value of the gas produced during the metathesis reaction is also detected, and the endpoint of the metathesis reaction is when the pH value is greater than 6.

5.

6. The preparation method according to claim 1, characterized in that, During the metathesis reaction, a vacuum pump is also used to depressurize and remove the gas generated in the reaction system.

7. The preparation method according to claim 1, characterized in that, The mass ratio of the phosphoric acid solution to the aluminum source is 100:0~50, and the amount of aluminum source used is not 0. The mass fraction of phosphoric acid in the phosphoric acid solution is 10%~100%.

8. The preparation method according to claim 1, characterized in that, The mass ratio of the phosphate-based adhesive to the curing agent is 100:1 to 1000.

9. The phosphate-based adhesive prepared by the method according to any one of claims 1 to 8, characterized in that, This includes repackaged phosphate-based adhesives and curing agents.

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