TW202039416A - The crosslinking agents of silica sol - Google Patents

Abstract

Silica sol is applied as paint and adhesive for many decades. Compare with sodium silicate and potasium silicate, it get dried much quicker and the dry film is water insolubale. However, the film formed there after is weaker and easy to get powdering and fall off from the painted surface.

Ethylenediamine and hexamethylenediamine can be the crosslinkng agents of silica sol, and meke the film much stronger. These diamine can also react between silica sol and polyacrylic resin, polyurethae, epoxy and cellulose, and hence increase the adhesion.

Description

Crosslinking agent for silica gel

The present invention is an adhesive and coating material using silica gel as the substrate.

Silicate (commonly known as water glass) has been used as an inorganic adhesive and paint for decades. However, after it is painted and dried, it must take about 2 weeks to absorb carbon dioxide before it becomes an insoluble substance. During these two weeks, if it rains, the coating film will be destroyed.

The chemical industry has developed sodium hexafluorosilicate Na ₂ SiF ₆ and sodium hexametaphosphate (NaPO ₃ ) ₆ as the hardener of silicate to solve the above problems. However, sodium fluoride or sodium phosphate will be produced after hardening. Salts give rise to other problems.

Silica gel does not require a hardener. After drying, it forms a water-insoluble transparent coating, and it has no salts, but it is relatively fragile and easy to powder and fall off.

If a cross-linking reaction occurs between linear molecules, the structure will be better and stronger. The most typical example is the rubber vulcanization reaction.

Diamine substances, such as hexamethylenddiamine or ethylenediamine, can undergo dehydration and condensation reactions with the hydroxyl groups of silica gel. The reaction formula for each molecule of ethylenediamine is as follows:

HO-Si(SiO ₂ ) _n Si-OH+NH ₂ C ₂ H ₄ NH ₂ →HO-Si(SiO ₂ ) _n Si-NHC ₂ H ₄ NH ₂ +H ₂ O

The reaction formula of multiple ethylenediamine and multiple silica gel molecules is as follows:

mHO-Si(SiO ₂ ) _n Si-OH+mNH ₂ C ₂ H ₄ NH ₂ →HO-[Si(SiO ₂ ) _n Si-NHC ₂ H ₄ ] _m NH ₂ +m H ₂ O

The reaction of hexamethylene diamine and silica gel is similar, so I will not repeat it.

There are many Si-OH functional machines around each silica gel, and each diamine has an amine group at the head and tail (as shown in Figure 1), so multiple silica gels can interact with multiple diamines. Linking reaction, the cross-linking reaction combines the two into a strong network structure (as shown in Figure 2).

Diamine can also react with polyacrylic resin to form a bridge between silica gel and resin, making the coating film stronger and more durable.

Diamines can also react between silica gel and cellulose to create molecular bonds and improve the binding force between the two.

Diamine and silica gel will solidify into a "gel" in about 2 days, so the two are manufactured with a "two-part coating" (commonly known as AB glue), packaged, and sold in combination. The user combines the two before use Use after mixing and use up before curing.

Applying the above two-component paints to rusty ironware will form a glass-like film that blocks the air, thereby stopping oxidation, that is, preventing rust. Then you can apply commercially available paints or water-based paints with good adhesion. .

Applying the above-mentioned two-component paint on combustible wood will form a glass-like film that blocks air and delays burning.

Mix the above-mentioned two-component paint with the sand for the mold and dry it to form a strong mold with good dimensional stability and can be used as a "precision mold."

1: Silica gel linear molecule

2: Crosslinker molecule

3: Cross-linked structure

Figure 1: Schematic diagram of the cross-linking reaction between diamine and silica gel.

Figure 2: Schematic diagram of cross-linking reaction between diamine and silica gel.

In 100 grams of commercially available silica gel, the weight containing silica SiO ₂ is about 30 grams, and 0.3 to 3 grams of ethylene diamine is added. , Can increase the strength and toughness of the coating film, but the mixed liquid will solidify into a gel after 2 days.

In 100 grams of commercially available silica gel, add 0.6 to 6 grams of hexamethylene diamine (the weight of hexamethylene diamine is 2% to 20% of silica), which can increase the strength and toughness of the coating film, but the mixed liquid It solidified into a gel after 2 days.

The silica gel and the ethylenediamine aqueous solution are separately bottled, manufactured in a "two-part coating" method, packaged, combined, mixed in proportion before use, and used before curing the gel.

The silica gel and the hexamethylene diamine aqueous solution are bottled separately, manufactured by the "two-part coating" method, packaged, combined, mixed in proportion before use, and used before curing the gel. Because the molecular weight of hexamethylene diamine is ethylene diamine Twice the amount of amine, so the addition amount also needs to be twice to have the same effect.

Apply the above two-component paint on the rusty iron sheet to prevent rust.

Coating the above two-component paint on the wood can delay the burning.

Mix the above two-component paint with sand to make a mold, which dries quickly, has a strong structure, and has good dimensional stability. Pour into molten metal liquid. After cooling, take out the metal casting, and the mold becomes gray-black because of ethylenediamine or hexamethylenediamine Carbonized at high temperatures, these carbon powders reduce the adhesion between the metal and the mold, and facilitate the removal of metal castings.

Apply the above two-component paint to the leaking cement wall to prevent leakage.

1: Silica gel linear molecule

2: Crosslinker molecule

Claims (5)

A cross-linking agent for silica gel, including: Diamine compounds can be used as crosslinking agents for silica gel; Silica gel and cross-linking agent are bottled separately and used in combination of two-part coating and adhesive. Mix the two before use, and then apply to the solid surface. After drying, it becomes a water-insoluble glassy transparent film. According to the first item of the scope of patent application, the crosslinking agent of silica gel is a "diamine" type substance, and its general formula is NH ₂ (CH ₂ ) _n NH ₂ where n is 2 to 10 Between the numbers. According to the first item of the scope of patent application, the cross-linking agent of silica gel, wherein the molecular formula of silica gel is H ₂ O. nSiO ₂ where n is a number between 1 and 10. According to the first item of the scope of patent application, the cross-linking agent of silica gel, in which the two-part coating and adhesive composed of silica gel and its cross-linking agent are used as transparent, flame-resistant, rust-proof and leak-proof coatings. According to the first item of the scope of patent application, the cross-linking agent of silica gel, in which the two-part coating and adhesive composed of silica gel and its cross-linking agent are used as the adhesive for making molds.

Images