Salt-fog corrosion resistant two-component silicone structural adhesive and preparation method thereof

Abstract

The application discloses a salt-mist corrosion resistant two-component silicone structural adhesive and a preparation method thereof. The salt-mist corrosion resistant two-component silicone structural adhesive comprises an A component and a B component. The A component comprises the following raw materials in mass fractions: 85-105 parts of 107 base glue, 90-120 parts of fillers and 10-30 parts of dimethyl silicone oil. The B component comprises the following raw materials in mass fractions: 4-10 parts of fumed silica, 15-20 parts of carbon black, 25-32 parts of dimethyl silicone oil, 12-40 parts of a crosslinking agent, 20-46 parts of a coupling agent, 0.01-0.1 part of a catalyst and 9-26 parts of an acrylic-modified epoxy silane oligomer. The epoxy groups and alkyl groups contained in the acrylic acid are hydrophobic groups. In a salt-mist environment, the possibility of water and chloride molecules contained in the water to pass through the silicone structural adhesive is greatly reduced, and the obtained structural adhesive has increased salt-mist corrosion resistance.

Description

Technical Field

[0001] This application relates to the field of silicone structural adhesives, and in particular to a salt spray corrosion resistant two-component silicone structural adhesive and its preparation method. Background Technology

[0002] Two-component silicone structural adhesives have excellent bonding performance, weather resistance, and UV aging resistance. They are mainly used for structural bonding and assembly of glass curtain walls, tightly bonding metal components to the glass in the building curtain wall.

[0003] However, as the performance requirements for structural adhesives in building curtain walls continue to increase, in addition to conventional mechanical and bonding properties, the impact of the environment on structural adhesives is receiving more and more attention. In particular, salt spray environments, especially in coastal cities, can damage structural adhesives and thus corrode metal components. Although structural adhesives that have undergone salt spray treatment have a certain degree of resistance to salt spray corrosion, their tensile retention rate has decreased significantly and fails to meet the standard requirements. Summary of the Invention

[0004] To obtain a two-component structural adhesive that combines salt spray corrosion resistance and high performance, this application provides a salt spray corrosion resistant two-component silicone structural adhesive and its preparation method.

[0005] In a first aspect, this application provides a salt spray resistant two-component silicone structural adhesive, comprising component A and component B, wherein component A and component B comprise the following raw materials in parts by weight:

[0006] Component A:

[0007] 85-105 parts of 107 base adhesive;

[0008] 90-120 parts of filler;

[0009] 10-30 parts of dimethyl silicone oil;

[0010] Component B:

[0011] 4-10 parts of fumed silica;

[0012] 15-20 parts carbon black;

[0013] 32-40 parts of dimethyl silicone oil;

[0014] Crosslinking agent 12-40 parts;

[0015] 20-46 parts of coupling agent;

[0016] Catalyst 0.01–0.1 parts;

[0017] The coupling agent comprises 9 to 26 parts by weight of acrylic acid-modified epoxy silane oligomers.

[0018] Preferably, during use, the volume ratio of component A to component B is (8-12):1.

[0019] Preferably, the average degree of polymerization of the acrylic acid-modified epoxy silane oligomer is 5 to 10.

[0020] Preferably, the viscosity of the 107-based adhesive is 20,000 to 50,000 cst.

[0021] Preferably, the filler comprises one or a combination of several of nano-calcium carbonate, diatomaceous earth, kaolin, and silica powder.

[0022] More preferably, the filler is nano-calcium carbonate with a particle size of 40–100 nm.

[0023] Preferably, the viscosity of the dimethyl silicone oil is 50–1000 mm. 2 / s.

[0024] By employing the above technical solution, in a salt spray environment, moisture and various chloride molecules dissolved in the moisture diffuse into the interior of the structural adhesive through the pores. Water molecules promote swelling of the silicone structural adhesive, while the entry of chloride solution creates a concentration difference between the interior and exterior of the structural adhesive. Under the action of osmotic pressure, water molecules in the air accelerate their penetration into the silicone structural adhesive. Phenolic ether bonds break between the molecules of the silicone structural adhesive, and water molecules disrupt the van der Waals forces and hydrogen bonds between the macromolecular chains in the silicone structural adhesive, leading to interfacial debonding. Adding epoxy-based silane oligomers allows for cross-linking reactions with the silicone bonds of the 107-based adhesive. On the one hand, this improves the density of the silicone structural adhesive, reducing the erosion by water and chloride molecules. On the other hand, the epoxy group, as a hydrophobic group, reduces the absorption of moisture by the silicone structural adhesive during use. Moisture is repelled to the outside of the silicone structural adhesive, making it less likely to cause swelling. Meanwhile, epoxy groups are highly reactive functional groups that can react with functional groups on the surface of the matrix material, increasing the adhesion between the structural adhesive and the matrix.

[0025] However, epoxy silane oligomers lack sufficient hydrophobicity to achieve good waterproofing and seepage prevention. Modifying epoxy silane oligomers with acrylic acid introduces hydrophobic alkyl groups, which further improves the hydrophobic properties of the structural adhesive. This significantly reduces the likelihood of water passing through the silicone structural adhesive, effectively preventing water molecules and various chloride molecules from penetrating the interface. Simultaneously, acrylic acid modification increases the branching degree of the epoxy silane oligomers, increasing the density of the silicone structural adhesive and enhancing its waterproofing and seepage prevention properties, thus helping to prevent salt spray corrosion.

[0026] Preferably, the acrylic acid-modified epoxy silane oligomer is prepared by reacting the oligomer of the epoxy silane coupling agent with an acrylic acid compound. The raw materials include an epoxy silane coupling agent, a modified crosslinking agent, a catalyst, and an acrylic acid compound in a mass ratio of 100:(45-50):(4-7):(10-13).

[0027] Preferably, the epoxy silane coupling agent comprises one or a combination of several of γ-(2,3-epoxypropoxy)propyltrimethoxysilane, 3-(epoxypropoxypropyl)methyldiethoxysilane, and 3-(2,3-epoxypropoxy)propylmethyldimethoxysilane; the modified crosslinking agent comprises one or a combination of several of tetraethyl orthosilicate and methyl orthosilicate; and the catalyst is N,N-dimethylacetamide.

[0028] More preferably, the epoxy silane coupling agent is γ-(2,3-epoxypropoxy)propyltrimethoxysilane and 3-(2,3-epoxypropoxy)propylmethyldimethoxysilane in a mass ratio of (0.9 to 1.4):1.

[0029] Preferably, the acrylic compound comprises a mixture of methacrylic acid and propylacrylic acid in a mass ratio of (0.8 to 1.2):1.

[0030] Preferably, the preparation process of the acrylic acid-modified epoxy silane oligomer is as follows:

[0031] S1. After adding epoxy silane coupling agent, modified crosslinking agent and catalyst to solvent, adjust the pH of solution to 3-4, stir and mix at 45-60℃, add deionized water, heat to 100-120℃, stir and react for 2-4 hours to obtain pre-reactant.

[0032] S2. Adjust the temperature of the pre-reactant to 35-45℃, add the acrylic acid compound, stir and react for 3-6 hours, and obtain the acrylic acid modified epoxy silane oligomer by vacuum distillation.

[0033] Preferably, the pH of the solution is adjusted in step S1 using a saturated hydrochloric acid aqueous solution.

[0034] Preferably, the solvent includes one or more of methanol and ethanol.

[0035] Preferably, the solvent mass is 40-50% of the mass of the epoxy silane coupling agent; and the deionized water mass is 10-20% of the mass of the epoxy silane coupling agent.

[0036] By adopting the above technical solution, after the epoxy silane coupling agent is dissolved in the solvent, the solution undergoes alcoholysis under acidic conditions and with the help of a catalyst, hydrolyzing into organosilanes triols. In subsequent reactions, these triols gradually condense into silanol oligomers with higher polymerization degrees. Acrylic acid compounds are added to react with the silanol oligomers. The carboxyl groups in the acrylic acid compounds can undergo esterification with the silanol groups. Simultaneously, under the action of a type II crosslinking agent, it is beneficial to form acrylic acid-modified epoxy silane oligomers with a three-dimensional structure. The three-dimensional structure of acrylic acid-modified epoxy silane oligomers helps to increase the structural density of silicone structural adhesives and the crosslinking density of silicone structural adhesives, thereby increasing the waterproof and impermeable properties of silicone structural adhesives and improving their resistance to salt spray corrosion.

[0037] When selecting epoxy-based silane coupling agents and acrylic compounds, using a mixture of highly reactive γ-(2,3-epoxypropoxy)propyltrimethoxysilane and less reactive 3-(2,3-epoxypropoxy)propylmethyldimethoxysilane, or a mixture of highly reactive methacrylic acid and less reactive propylacrylic acid, can increase the stability of the reaction process and the products. This allows the reaction products to be controlled within a certain range, achieving the desired effect and effectively increasing the waterproof and impermeable properties of the silicone structural adhesive. Furthermore, the selected acrylic compounds are all short-chain acrylic acids, which are less prone to intermolecular entanglement during the reaction, thus improving the grafting rate between the acrylic compounds and the epoxy-based silane coupling agent.

[0038] Preferably, step S2 further includes the addition of a hydroxy acid compound at a mass of 3-5% of the epoxy silane coupling agent, wherein the hydroxy acid compound includes one or a combination of α-hydroxy acid, β-hydroxy acid, γ-hydroxy acid and δ-hydroxy acid.

[0039] By adopting the above technical solution, the acrylic-modified epoxy silane oligomer contains a large number of hydrophobic groups. Although this can improve the waterproof and impermeable properties of silicone structural adhesives, the large presence of hydrophobic groups will lead to significant steric hindrance, reduce the crosslinking degree of the silicone structural adhesive, and cause a decrease in the density of the silicone structural adhesive, resulting in reduced waterproof and impermeable properties and a significant decrease in salt spray corrosion resistance. Adding a small amount of hydroxyl groups to the acrylic-modified epoxy silane oligomer can act as active sites in the crosslinking process, compensating for the reduced crosslinking density caused by the increase of hydrophobic groups. The increased crosslinking density can increase the density of the silicone structural adhesive, effectively preventing water molecules from passing through as various chloride molecules. Simultaneously, the introduction of hydroxyl groups allows the silicone structural adhesive to form hydrogen bonds with the substrate, increasing the adhesion between the silicone structural adhesive and the substrate.

[0040] Preferably, the coupling agent further includes one or a combination of several of the following: γ-aminopropyltriethoxysilane, γ-aminopropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane, N-(2-aminoethyl)-3-aminopropylmethyldiethoxysilane, N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane, N-2-aminoethyl-3-aminopropyltriethoxysilane, triaminosilane, N-(piperazinylethyl)-3-aminopropylmethyldimethoxysilane, and triaminosilane 3-diethylenetriaminopropylmethyldimethoxysilane.

[0041] By adopting the above technical solution, the amino groups contained in the coupling agent can enhance the bonding strength between the silicone structural adhesive and the substrate, and effectively resist the penetration of moisture and various chloride molecules.

[0042] Preferably, the catalyst comprises one or a combination of several of dibutyltin dilaurate, dibutyltin diacetate, dioctyltin dilaurate, and stannous octoate.

[0043] Preferably, the crosslinking agent comprises one or a combination of several of the following: methyl orthosilicate, ethyl orthosilicate, methyltrimethoxysilane, dimethyldimethoxysilane, methyltriethoxysilane, dimethyldiethoxysilane, polyethyl orthosilicate, polymethyltriethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, and cyclopentyltriethoxysilane.

[0044] Secondly, this application also provides a method for preparing a salt spray resistant two-component silicone structural adhesive, comprising the following steps:

[0045] Preparation of component A: Add 107 base glue, filler and dimethyl silicone oil to the reaction vessel, and stir and mix for 1 to 2 hours under vacuum at 130 to 150°C to obtain component A;

[0046] Preparation of Component B: Carbon black and dimethyl silicone oil are premixed and then added to a reaction vessel. The mixture is stirred and mixed under vacuum at 140-160°C for 10-20 minutes. After mixing, crosslinking agent and fumed silica are added sequentially. The mixture is stirred and mixed under the same conditions for 20-40 minutes. After the mixture is homogeneous, coupling agent and catalyst are added, and stirring is continued for 50-70 minutes to obtain Component B.

[0047] Preferably, the vacuum conditions during the preparation of component A and component B are required to be within the range of -0.09 MPa to -0.1 MPa.

[0048] In summary, this application has the following beneficial effects:

[0049] 1. The raw materials used in the salt spray resistant two-component silicone structural adhesive provided in this application include acrylic acid modified epoxy silane oligomers. The epoxy groups and the alkyl groups contained in the acrylic acid are both hydrophobic groups, which can increase the hydrophobicity of the silicone structural adhesive. Under salt spray environment, moisture and chloride molecules contained in moisture are repelled, and the possibility of moisture passing through the silicone structural adhesive is greatly reduced, thereby increasing the waterproof and impermeable properties of the silicone structural adhesive, and thus increasing the salt spray corrosion resistance of the silicone structural adhesive.

[0050] 2. Hydroxy acids are added during the preparation of acrylic-modified epoxy silane oligomers. The increased hydrophobic groups lead to a significant steric hindrance effect, resulting in a decrease in the number of active groups per unit volume and a lower crosslinking density. The hydroxy acids and epoxy groups, as reactive groups, increase the crosslinking activity sites of the silicone structural adhesive, increasing the crosslinking density and improving structural compactness. Simultaneously, the hydroxyl groups can form hydrogen bonds with the substrate, increasing the adhesion between the silicone structural adhesive and the substrate. Detailed Implementation

[0051] Preparation example of acrylic acid modified epoxy silane oligomers

[0052] Preparation Example 1: An acrylic acid-modified epoxy silane oligomer was prepared according to the following method:

[0053] Take 1000g of epoxy silane coupling agent, including 550g of γ-(2,3-epoxypropoxy)propyltrimethoxysilane and 450g of 3-(2,3-epoxypropoxy)propylmethyldimethoxysilane, and add it to 450g of methanol. At the same time, add 480g of tetraethyl orthosilicate and 55g of N,N-dimethylacetamide to the methanol and mix well. Add saturated hydrochloric acid aqueous solution to adjust the pH of the mixed solution to 4. While stirring and mixing at 50℃, add 150g of deionized water. After mixing, adjust the solution temperature to 110℃ and stir for 3h to obtain the pre-reactant.

[0054] The temperature of the pre-reactant was adjusted to 40°C, and 120g of acrylic acid compound, including 60g of methacrylic acid and 60g of propylacrylic acid, was added. After stirring and reacting for 5 hours, the acrylic acid-modified epoxy silane oligomer was obtained by vacuum distillation.

[0055] Preparation Example 2: An acrylic acid-modified epoxy silane oligomer was prepared according to the following method:

[0056] Take 1000g of epoxy silane coupling agent, including 550g of γ-(2,3-epoxypropoxy)propyltrimethoxysilane and 450g of 3-(2,3-epoxypropoxy)propylmethyldimethoxysilane, and add it to 450g of methanol. At the same time, add 480g of tetraethyl orthosilicate and 55g of N,N-dimethylacetamide to the methanol and mix well. Add 38% hydrochloric acid solution to adjust the pH of the mixed solution to 4. While stirring and mixing at 50℃, add 150g of deionized water. After mixing, adjust the solution temperature to 110℃ and stir for 3h to obtain the pre-reactant.

[0057] The temperature of the pre-reactant was adjusted to 40°C, and 120g of acrylic acid compound, including 60g of methacrylic acid and 60g of propylacrylic acid, was added. After stirring for 30 minutes, 40g of β-hydroxy acid was added, and the stirring was continued for 5 hours. Then, the acrylic acid-modified epoxy silane oligomer was obtained by vacuum distillation.

[0058] Preparation Example 3 is an acrylic acid-modified epoxy silane oligomer, which differs from Preparation Example 2 only in that the amount of β-hydroxy acid added is 50g.

[0059] Preparation Example 4 is an acrylic acid-modified epoxy silane oligomer, which differs from Preparation Example 2 only in that the amount of β-hydroxy acid added is 30g.

[0060] Preparation Examples 5 to 8 describe an acrylic acid-modified epoxy silane oligomer, which differs from Preparation Example 1 only in the ratio of the raw materials used. The specific ratios are shown in Table 1.

[0061] Table 1 Formulation Tables for Preparation Examples 1, 5 to 8

[0062]

[0063] Preparation Example 9: An acrylic acid-modified epoxy silane oligomer, which differs from Preparation Example 1 only in that the amount of acrylic acid compound added remains the same, but the amount of methacrylic acid added is 53g and the amount of propylacrylic acid added is 67g.

[0064] Preparation Example 10: An acrylic acid-modified epoxy silane oligomer, which differs from Preparation Example 1 only in that the amount of acrylic acid compound added remains the same, but the amount of methacrylic acid added is 65g and the amount of propylacrylic acid added is 55g.

[0065] Preparation Example 11: An acrylic acid-modified epoxy silane oligomer, which differs from Preparation Example 1 only in that the amount of epoxy silane coupling agent added remains the same, but it includes only 1000g of γ-(2,3-epoxypropoxy)propyltrimethoxysilane.

[0066] Preparation Example 12 is an acrylic acid-modified epoxy silane oligomer, which differs from Preparation Example 1 only in that the amount of epoxy silane coupling agent added remains the same, but it includes only 1000g of 3-(2,3-epoxypropoxy)propylmethyldimethoxysilane.

[0067] Preparation Example 13 is an acrylic acid-modified epoxy silane oligomer, which differs from Preparation Example 1 only in that the amount of acrylic acid compound added remains the same, but the amount of methacrylic acid added is 80g and the amount of propylacrylic acid added is 40g.

[0068] Preparation Example 14: An acrylic acid-modified epoxy silane oligomer, which differs from Preparation Example 1 only in that the amount of acrylic acid compound added remains the same, but the amount of methacrylic acid added is 40g and the amount of propylacrylic acid added is 80g.

[0069] Preparation Example 15 is an acrylic acid-modified epoxy silane oligomer, which differs from Preparation Example 1 only in that the amount of acrylic acid compound added remains the same, but it includes only 120g of methacrylic acid.

[0070] Preparation Example 16 is an acrylic acid-modified epoxy silane oligomer, which differs from Preparation Example 1 only in that the amount of acrylic acid compound added remains the same, but it includes only 120g of propyl acrylic acid.

[0071] Preparation Example 17: An epoxy silane oligomer was prepared according to the following method:

[0072] Take 1000g of epoxy silane coupling agent, including 55g of γ-(2,3-epoxypropoxy)propyltrimethoxysilane and 45g of 3-(2,3-epoxypropoxy)propylmethyldimethoxysilane, and add it to 450g of methanol. At the same time, add 480g of tetraethyl orthosilicate and 55g of N,N-dimethylacetamide to the methanol and mix well. Add saturated hydrochloric acid aqueous solution to adjust the pH of the mixed solution to 4. While stirring and mixing at 50℃, add 150g of deionized water. After mixing, adjust the solution temperature to 110℃ and stir for 5h. After stirring, distill under reduced pressure to obtain epoxy silane oligomers.

[0073] Preparation Example 18: An acrylic acid-modified aminosilane oligomer was prepared according to the following method:

[0074] Take 960g of aminosilane coupling agent, which contains 450g of N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, 270g of N-(piperazinylethyl)-3-aminopropylmethyldimethoxysilane and 240g of 3-diethylenetriaminopropylmethyldimethoxysilane. Mix them evenly and add 150g of methanol. Continue stirring and mixing. Add 45g of dimethyl sulfoxide. Raise the temperature to 50℃ and add 82g of deionized water. Raise the temperature to 100℃ and stir the reaction for 4h at a constant temperature to obtain a pre-reaction solution.

[0075] The temperature of the pre-reaction solution was adjusted to 40℃. 60g of acrylic acid compound, which contains 40g of methacrylic acid and 20g of propylacrylic acid, was mixed evenly and added to the pre-reaction solution. After stirring and reacting for 5 hours, the acrylic acid-modified aminosilane oligomer was obtained by vacuum distillation. Example

[0076] Example 1: A salt spray resistant two-component silicone structural adhesive was prepared according to the following method:

[0077] Preparation of Component A: Take 1 kg of 107 base rubber (average viscosity 25000 cst), 1.1 kg of nano-calcium carbonate (particle size 50-80 nm), and 0.2 kg of dimethyl silicone oil (average viscosity 350 mm). 2 Add ( / s) to the reactor, adjust the reactor temperature to 140℃ and the vacuum degree to -0.1MPa, and stir for 1.5h to obtain component A.

[0078] Preparation of Component B: Take 0.18 kg of carbon black (type N220) and 0.36 kg of dimethyl silicone oil (average viscosity 350 mm). 2 After mixing evenly, add the mixture to the reactor. Adjust the reactor temperature to 150℃ and the vacuum degree to -0.1 MPa. After stirring and mixing for 20 min, add 0.26 kg of methyl orthosilicate. Stir and mix for 30 min under the same conditions. After stirring, add 0.07 kg of fumed silica (model LM-150). Continue stirring and mixing for 30 min under the same conditions. Finally, add 0.18 kg of acrylic acid modified epoxy silane oligomer obtained in Preparation Example 1, 0.15 kg of γ-aminopropyltrimethoxysilane, and 0.0005 kg of dibutyltin dilaurate. Stir and mix for 60 min under the same conditions to obtain component B.

[0079] When using, mix component A and component B at a mass ratio of 10:1.

[0080] Examples 2 to 9 describe a salt spray resistant two-component silicone structural adhesive, differing from Example 1 only in the proportions of the raw materials used, as shown in Table 2.

[0081] Table 2: Formulas for Examples 1 to 9

[0082] Example Amount / kg Raw Material Name Example 1 Example 2 Example 3 Example 4 Example 5 107 base adhesive 1 1 1 1 1 Nano calcium carbonate 1.1 0.9 1.2 1.1 1.1 Dimethyl silicone oil 0.2 0.2 0.2 0.1 0.3 Carbon black 0.18 0.15 0.2 0.18 0.18 Dimethyl silicone oil 0.36 0.36 0.36 0.32 0.4 Methyl orthosilicate 0.26 0.12 0.4 0.26 0.26 Fumed silica 0.07 0.04 0.1 0.07 0.07 Acryl-modified epoxy silane oligomer 0.18 0.18 0.18 0.18 0.18 Gamma-aminopropyl trimethoxysilane 0.15 0.15 0.15 0.15 0.15 Dibutyl tin dilaurate 0.0005 0.0002 0.001 0.0005 0.0005 Example Amount / kg Raw Material Name Example 6 Example 7 Example 8 Example 9 / 107 base adhesive 0.85 1.05 1 1 / Nano calcium carbonate 1.1 1.1 1.1 1.1 / Dimethyl silicone oil 0.2 0.2 0.2 0.2 / Carbon black 0.18 0.18 0.18 0.18 / Dimethyl silicone oil 0.36 0.36 0.36 0.36 / Methyl orthosilicate 0.26 0.26 0.26 0.26 / Fumed silica 0.07 0.07 0.07 0.07 / Acryl-modified epoxy silane oligomer 0.18 0.18 0.1 0.1 / Gamma-aminopropyl trimethoxysilane 0.15 0.15 0.25 0.2 / Dibutyl tin dilaurate 0.0005 0.0005 0.0005 0.0005 /

[0083] In Example 2, the acrylic acid-modified epoxy silane oligomer obtained in Preparation Example 5 was used; in Example 3, the acrylic acid-modified epoxy silane oligomer obtained in Preparation Example 6 was used; in Example 4, the acrylic acid-modified epoxy silane oligomer obtained in Preparation Example 7 was used; in Example 5, the acrylic acid-modified epoxy silane oligomer obtained in Preparation Example 8 was used; in Example 6, the acrylic acid-modified epoxy silane oligomer obtained in Preparation Example 9 was used; and in Example 7, the acrylic acid-modified epoxy silane oligomer obtained in Preparation Example 10 was used.

[0084] Example 10, a salt spray resistant two-component silicone structural adhesive, differs from Example 1 only in that an equal amount of acrylic acid modified epoxy silane oligomer prepared in Preparation Example 2 is used to replace the acrylic acid modified epoxy silane oligomer prepared in Preparation Example 1.

[0085] Example 11, a salt spray resistant two-component silicone structural adhesive, differs from Example 1 only in that an equal amount of acrylic acid modified epoxy silane oligomer prepared in Preparation Example 3 is used to replace the acrylic acid modified epoxy silane oligomer prepared in Preparation Example 1.

[0086] Example 12, a salt spray resistant two-component silicone structural adhesive, differs from Example 1 only in that an equal amount of acrylic acid modified epoxy silane oligomer prepared in Preparation Example 4 is used to replace the acrylic acid modified epoxy silane oligomer prepared in Preparation Example 1.

[0087] Example 13, a salt spray resistant two-component silicone structural adhesive, differs from Example 1 only in that an equal amount of acrylic acid modified epoxy silane oligomer prepared in Preparation Example 11 is used to replace the acrylic acid modified epoxy silane oligomer prepared in Preparation Example 1.

[0088] Example 14, a salt spray resistant two-component silicone structural adhesive, differs from Example 1 only in that an equal amount of acrylic-modified epoxysilane oligomer prepared in Preparation Example 12 is used to replace the acrylic-modified epoxysilane oligomer prepared in Preparation Example 1.

[0089] Example 15, a salt spray resistant two-component silicone structural adhesive, differs from Example 1 only in that an equal amount of acrylic acid modified epoxy silane oligomer prepared in Preparation Example 13 is used to replace the acrylic acid modified epoxy silane oligomer prepared in Preparation Example 1.

[0090] Example 16, a salt spray resistant two-component silicone structural adhesive, differs from Example 1 only in that an equal amount of acrylic-modified epoxysilane oligomer prepared in Preparation Example 14 is used to replace the acrylic-modified epoxysilane oligomer prepared in Preparation Example 1.

[0091] Example 17, a salt spray resistant two-component silicone structural adhesive, differs from Example 1 only in that an equal amount of acrylic-modified epoxysilane oligomer prepared in Preparation Example 15 is used to replace the acrylic-modified epoxysilane oligomer prepared in Preparation Example 1.

[0092] Example 18, a salt spray resistant two-component silicone structural adhesive, differs from Example 1 only in that an equal amount of acrylic-modified epoxysilane oligomer prepared in Preparation Example 16 is used to replace the acrylic-modified epoxysilane oligomer prepared in Preparation Example 1.

[0093] Example 19, a salt spray resistant two-component silicone structural adhesive, differs from Example 1 only in that, in the preparation of component A, the amount of dimethyl silicone oil added is 0.08 kg; and in the preparation of component B, the amount of dimethyl silicone oil added is 0.3 kg.

[0094] Example 20: A salt spray resistant two-component silicone structural adhesive, differing from Example 1 only in that, in the preparation of component A, the amount of dimethyl silicone oil added is 0.32 kg; and in the preparation of component B, the amount of dimethyl silicone oil added is 0.42 kg. Comparative Example

[0095] Comparative Example 1, a salt spray resistant two-component silicone structural adhesive, differs from Example 1 only in that the amount of acrylic acid modified epoxy silane oligomer added in Preparation Example 1 is 0.08 kg.

[0096] Comparative Example 2, a salt spray resistant two-component silicone structural adhesive, differs from Example 1 only in that the amount of acrylic acid modified epoxy silane oligomer added in Preparation Example 1 is 0.27 kg.

[0097] Comparative Example 3 is a salt spray resistant two-component silicone structural adhesive, which differs from Example 1 only in that an equal amount of the epoxy silane oligomer prepared in Preparation Example 17 is used to replace the acrylic acid modified epoxy silane oligomer prepared in Preparation Example 1.

[0098] Comparative Example 4 is a salt spray resistant two-component silicone structural adhesive, which differs from Example 1 only in that an equal amount of γ-aminopropyltrimethoxysilane is used to replace the acrylic-modified epoxysilane oligomer prepared in Example 1.

[0099] Comparative Example 5 is a salt spray resistant two-component silicone structural adhesive, which differs from Example 1 only in that an equal amount of acrylic acid modified aminosilane oligomer prepared in Preparation Example 18 is used to replace the acrylic acid modified epoxy silane oligomer prepared in Preparation Example 1.

[0100] Performance testing

[0101] 1. Basic Performance Tests of Salt Spray Corrosion Resistant Two-Component Silicone Structural Adhesive: According to JG / T 475-2015 "Silicone Structural Sealants for Building Curtain Walls," the tensile bond strength at 23°C, tensile bond strength retention rate at 80°C, shear strength at 23°C, and tear resistance of the salt spray corrosion resistant two-component silicone structural adhesives prepared in Examples 1-20 and Comparative Examples 1-5 were tested respectively. Tear resistance was characterized by the tensile bond strength retention rate. The test results are shown in Table 3.

[0102] 2. Salt spray corrosion resistant two-component silicone structural adhesive acid spray corrosion resistance test: According to GB / T 37126-2018 "Test Methods for Building Sealants for Structural Assembly", the salt spray corrosion resistant two-component silicone structural adhesives prepared in Examples 1-20 and Comparative Examples 1-5 were tested according to GB / T 10125-2021 "Artificial Atmosphere Corrosion Test Salt Spray Test".

[0103] The samples prepared according to the standard were treated in a neutral salt spray (NSS) environment specified in the standard for 480 h, and then placed under standard experimental conditions for (24±4) h for tensile adhesion testing. The retention rate was calculated. The test results are shown in Table 3.

[0104] Table 3. Test Results of Basic Performance and Salt Spray Corrosion Resistance

[0105] Item Sample Tensile bond strength at 23°C / MPa Tensile bond strength retention rate at 80°C / % Shear strength at 23°C / MPa Tear resistance at 23°C / % Tensile bond strength retention rate after salt spray treatment / % Example 1 1.16 88 0.68 91 99 Example 2 1.15 87 0.65 89 97 Example 3 1.15 87 0.66 89 98 Example 4 1.13 86 0.66 88 98 Example 5 1.14 87 0.67 90 98 Example 6 1.16 86 0.65 90 99 Example 7 1.15 86 0.68 89 97 Example 8 1.13 85 0.65 88 98 Example 9 1.14 86 0.66 89 97 Example 10 1.23 91 0.72 93 99 Example 11 1.22 90 0.71 92 99 Example 12 1.23 90 0.72 92 98 Example 13 1.05 81 0.61 83 95 Example 14 1.06 78 0.58 81 91 Example 15 1.08 82 0.6 84 94 Example 16 1.04 79 0.59 82 90 Example 17 1.03 78 0.57 80 86 Example 18 1.01 76 0.55 78 82 Example 19 0.92 81 0.6 82 86 Example 20 0.98 80 0.59 77 80 Comparative Example 1 0.84 72 0.51 82 76 Comparative Example 2 0.93 74 0.53 79 81 Comparative Example 3 0.73 71 0.48 75 74 Comparative Example 4 0.65 68 0.42 69 68 Comparative Example 5 1.13 82 0.65 87 78

[0106] According to Table 3, and in conjunction with Example 1, Comparative Example 1 and Comparative Example 2, it can be seen that the tensile bond strength, shear strength and tear resistance of Comparative Example 1 and Comparative Example 2 at 23°C are lower than those of Example 1. The tensile bond strength retention rate at 80°C is lower than that of Example 1. The tensile bond strength retention rate after salt spray treatment is also lower. This indicates that the basic performance of Comparative Example 1 and Comparative Example 2 is lower than that of Example 1, the stability is lower, and the salt spray corrosion resistance is lower. The reason may be that in Comparative Example 1, the amount of acrylic acid-modified epoxy silane oligomer added was lower than the required range, resulting in a decrease in the number of hydrophobic groups in the prepared silicone structural adhesive, thus reducing its waterproof and impermeable properties. At the same time, the decrease in oligomer content led to a decrease in the structural density of the structural adhesive, resulting in a decrease in the performance of the silicone structural adhesive and a decrease in its salt spray corrosion resistance. In Comparative Example 2, the amount of acrylic acid-modified epoxy silane oligomer added was higher than the required range. During the preparation of the silicone structural adhesive, the oligomers were prone to self-entanglement and cross-linking. After the components A and B were mixed, the cross-linking density of the structural adhesive decreased, leading to a decrease in overall performance and salt spray corrosion resistance.

[0107] Combining Example 1 and Comparative Example 3, it can be seen that the tensile bond strength, shear strength, and tear resistance of Comparative Example 3 at 23°C are significantly lower than those of Example 1, and the tensile bond strength retention rate at 80°C is significantly lower than that of Example 1. The tensile bond strength retention rate after salt spray treatment is also significantly lower, indicating that the basic properties of Comparative Example 3 are significantly lower than those of Example 1, with a significant decrease in stability and salt spray corrosion resistance. This may be because the epoxy silane oligomer in Comparative Example 3 was not modified with acrylic acid, resulting in a decrease in the content of hydrophobic groups, which significantly reduces the waterproof and impermeable properties of the resulting structural adhesive, and consequently, its salt spray corrosion resistance.

[0108] Combining Example 1 and Comparative Example 4, it can be seen that the tensile bond strength, shear strength, and tear resistance of Comparative Example 4 at 23°C are significantly lower than those of Example 1. The tensile bond strength retention rate at 80°C is also significantly lower than that of Example 1. The tensile bond strength retention rate after salt spray treatment is also significantly lower, indicating that the basic properties of Comparative Example 4 are significantly lower than those of Example 1, with a significant decrease in stability and salt spray corrosion resistance. This may be because Comparative Example 4 did not contain acrylic acid-modified epoxy silane oligomers. On the one hand, the content of hydrophobic groups is significantly reduced, resulting in a significant decrease in the waterproof and impermeable properties of the structural adhesive, and consequently, a significant decrease in salt spray corrosion resistance. On the other hand, the lack of crosslinking action of oligomers leads to a decrease in the crosslinking density and structural density of the structural adhesive, resulting in a significant reduction in the various properties of the obtained structural adhesive.

[0109] Combining Example 1 and Comparative Example 5, it can be seen that the tensile bond strength, shear strength, and tear resistance of Comparative Example 5 at 23°C are not significantly different from those of Example 1. The tensile bond strength retention rate at 80°C is slightly lower than that of Example 1, and the tensile bond strength retention rate after salt spray treatment is significantly lower. This indicates that the basic properties and stability of Comparative Example 5 are not significantly different from those of Example 1, but its salt spray corrosion resistance is significantly reduced. The reason for this may be that Comparative Example 5 uses an acrylic acid-modified aminosilane oligomer, which lacks the hydrophobic effect of the epoxy group compared to the acrylic acid-modified epoxy silane oligomer used in Example 1. Although the amino group can increase the crosslinking density to some extent, it does not provide good resistance to salt spray corrosion. The epoxy group, as a hydrophobic functional group, can synergize with the hydrophobic alkyl groups in acrylic acid, resulting in good resistance to salt spray corrosion.

[0110] Combining Examples 1 and 2 through 9, it can be seen that the tensile bond strength, shear strength, and tear resistance of Examples 2 through 9 at 23°C showed no significant change compared to Example 1. The retention rate of tensile bond strength at 80°C also showed no significant change compared to Example 1, and the retention rate of tensile bond strength after salt spray treatment showed no significant change. This indicates that the basic properties, stability, and salt spray corrosion resistance of Examples 2 through 9 did not change significantly compared to Example 1. This may be because Examples 2 through 9 only adjusted the proportions of the raw materials, demonstrating that changing the proportions of the raw materials within the required range has no significant impact on the performance of the resulting silicone structural adhesive.

[0111] Combining Examples 1 and 10, it can be seen that the tensile bond strength, shear strength, and tear resistance of Example 10 at 23°C are improved compared to Example 1, and the tensile bond strength retention rate at 80°C is also increased compared to Example 1. The tensile bond strength retention rate after salt spray treatment shows no significant change, indicating that the basic performance and stability of Example 10 are improved compared to Example 1, while the salt spray corrosion resistance remains largely unchanged. This may be because hydroxy acid compounds were added during the preparation of the acrylic acid-modified epoxy silane oligomer used in Example 10. Although Example 1 already met the requirements for salt spray corrosion resistance, the rigidity of the silicone structural adhesive increased with the increase of hydrophobic groups, but the tensile bond strength decreased. Although this was compensated for by adding dimethyl silicone oil plasticizer, the crosslinking density of the silicone structural adhesive decreased. Adding hydroxy acid compounds increases the crosslinking active sites in the system, improving the performance and salt spray corrosion resistance of the resulting structural adhesive, while also generating hydrogen bonds with the substrate to improve tensile bond strength.

[0112] As can be seen from Examples 10, 11, and 12, the tensile bond strength, shear strength, and tear resistance of Examples 11 and 12 at 23°C showed no significant change compared to Example 10. The tensile bond strength retention rate at 80°C also showed no significant change compared to Example 10, and the tensile bond strength retention rate after salt spray treatment showed no significant change. This indicates that the basic properties, stability, and salt spray corrosion resistance of Examples 11 and 12 were not significantly different from those of Example 10. This may be because Examples 11 and 12 only adjusted the amount of hydroxy acid compound added, indicating that varying the amount of hydroxy acid compound added within the required range has no significant impact on the performance of the resulting silicone structural adhesive.

[0113] Based on Examples 1, 13, and 14, it can be seen that the tensile bond strength, shear strength, and tear resistance of Examples 13 and 14 at 23°C are slightly lower than those of Example 1. The tensile bond strength retention rate at 80°C is also lower than that of Example 1. The tensile bond strength retention rate after salt spray treatment is also lower. This indicates that the basic performance of Examples 13 and 14 is slightly lower than that of Example 1. The stability is slightly lower, and the salt spray corrosion resistance is also slightly lower. The reason may be that, in the preparation process of the acrylic-modified epoxy silane oligomer added in Example 13, only γ-(2,3-epoxypropoxy)propyltrimethoxysilane was selected as the epoxy silane coupling agent. Trimethoxysilane has high activity and is prone to condensation during the modification process, resulting in an unstable reaction process. The resulting acrylic-modified epoxy silane oligomer has a low grafting rate, a decreased crosslinking density, and reduced waterproof and impermeable properties, thus reducing the salt spray corrosion resistance of the resulting structural adhesive. In the preparation process of the acrylic-modified epoxy silane oligomer added in Example 14, only 3-(2,3-epoxypropoxy)propylmethyldimethoxysilane was selected as the epoxy silane coupling agent. Dimethoxysilane has low reactivity, and during the preparation process, the probability of the acrylic compound reacting with it decreases, resulting in a decrease in the hydrophobic group content of the resulting oligomer and a decrease in the salt spray corrosion resistance of the silicone structural adhesive.

[0114] Based on Examples 1 and 15-18, it can be seen that the tensile bond strength, shear strength, and tear resistance of Examples 15-18 at 23°C are slightly lower than those of Example 1. The tensile bond strength retention rate at 80°C is also lower than that of Example 1. The tensile bond strength retention rate after salt spray treatment is also lower. This indicates that the basic performance of Examples 15-18 is slightly lower than that of Example 1, and the stability and salt spray corrosion resistance are also slightly lower. The reason may be that, in the preparation process of the acrylic acid-modified epoxy silane oligomers added in Examples 15 and 17, the amount of methacrylic acid in the selected acrylic acid compound was increased. Methacrylic acid has strong reactivity and the reaction process is unstable. As a result, the grafting rate of the obtained acrylic acid-modified epoxy silane oligomers is low, the crosslinking density is reduced, the waterproof and impermeable properties are reduced, and the salt spray corrosion resistance of the obtained structural adhesive is reduced. In the preparation process of the acrylic acid-modified epoxy silane oligomers added in Examples 16 and 18, the amount of propylacrylic acid in the selected acrylic acid compound was increased. Propylacrylic acid has weak reactivity. During the esterification reaction, the grafting rate is reduced, the content of hydrophobic groups in the obtained oligomers is reduced, and the salt spray corrosion resistance of the silicone structural adhesive is reduced.

[0115] Based on Examples 1, 19, and 20, it can be seen that the tensile bond strength, shear strength, and tear resistance of Examples 19 and 20 at 23°C are slightly lower than those of Example 1. The tensile bond strength retention rate at 80°C is significantly lower than that of Example 1. The tensile bond strength retention rate after salt spray treatment is also lower. This indicates that the basic performance of Examples 19 and 20 is slightly lower than that of Example 1, the stability is significantly lower, and the salt spray corrosion resistance is slightly lower. The reason may be that the amount of dimethyl silicone oil added was reduced in the preparation process of Example 19, while the amount of dimethyl silicone oil added was increased in the preparation process of Example 20. When the amount of dimethyl silicone oil added to the structural adhesive is reduced, the rigidity of the structural adhesive increases due to the increase of hydrophobic groups in the acrylic-modified epoxy silane oligomer. Without the plasticizer effect, the tensile adhesion of the structural adhesive decreases and the stability decreases. On the other hand, when the amount of dimethyl silicone oil added to the structural adhesive is increased, since dimethyl silicone oil is a non-reactive plasticizer, it will dilute the active molecules in the structural adhesive, reduce the number of active groups per unit volume, decrease the crosslinking density of the structural adhesive, and reduce the various properties of the structural adhesive.

[0116] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A salt spray resistant two-component silicone structural adhesive, characterized in that, It includes component A and component B, wherein component A and component B comprise the following raw materials in parts by mass: Component A: 85-105 parts of 107 base adhesive; 90-120 parts of filler; 10-30 parts of dimethyl silicone oil; Component B: 4-10 parts of fumed silica; 15-20 parts carbon black; 32-40 parts of dimethyl silicone oil; Crosslinking agent 12-40 parts; 20-46 parts of coupling agent; Catalyst 0.01–0.1 parts; The coupling agent comprises an acrylic acid-modified epoxy silane oligomer in parts by weight of 9 to 26. The acrylic acid-modified epoxy silane oligomer is prepared by reacting the oligomer of epoxy silane coupling agent with an acrylic acid compound. The raw materials include an epoxy silane coupling agent, a modified crosslinking agent, a catalyst, and an acrylic acid compound in a mass ratio of 100:(45-50):(4-7):(10-13).

2. The salt spray resistant two-component silicone structural adhesive according to claim 1, characterized in that, The epoxy silane coupling agent includes one or a combination of several of γ-(2,3-epoxypropoxy)propyltrimethoxysilane, 3-(epoxypropoxypropyl)methyldiethoxysilane, and 3-(2,3-epoxypropoxy)propylmethyldimethoxysilane; the modified crosslinking agent includes one or a combination of several of tetraethyl orthosilicate and methyl orthosilicate; and the catalyst is N,N-dimethylacetamide.

3. The salt spray resistant two-component silicone structural adhesive according to claim 1, characterized in that, The acrylic compound comprises a mixture of methacrylic acid and propylacrylic acid in a mass ratio of (0.8 to 1.2):

1.

4. The salt spray resistant two-component silicone structural adhesive according to claim 1, characterized in that, The preparation process of the acrylic acid-modified epoxy silane oligomer is as follows: S1. After adding epoxy silane coupling agent, modified crosslinking agent and catalyst to solvent, adjust the pH of solution to 3-4, stir and mix at 45-60℃, add deionized water, heat to 100-120℃, stir and react for 2-4 hours to obtain pre-reactant. S2. Adjust the temperature of the pre-reactant to 35-45℃, add the acrylic acid compound, stir and react for 3-6 hours, and obtain the acrylic acid modified epoxy silane oligomer by vacuum distillation.

5. The salt spray resistant two-component silicone structural adhesive according to claim 4, characterized in that, In step S2, a hydroxy acid compound is added at a mass of 3-5% of the epoxy silane coupling agent. The hydroxy acid compound includes one or a combination of several of α-hydroxy acids, β-hydroxy acids, γ-hydroxy acids, and δ-hydroxy acids.

6. The salt spray resistant two-component silicone structural adhesive according to claim 1, characterized in that, The coupling agent further includes one or a combination of several of the following: γ-aminopropyltriethoxysilane, γ-aminopropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane, N-(2-aminoethyl)-3-aminopropylmethyldiethoxysilane, N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane, N-2-aminoethyl-3-aminopropyltriethoxysilane, triaminosilane, N-(piperazinylethyl)-3-aminopropylmethyldimethoxysilane, and triaminosilane 3-diethylenetriaminopropylmethyldimethoxysilane.

7. The salt spray resistant two-component silicone structural adhesive according to claim 1, characterized in that, The catalyst comprises one or a combination of several of the following: dibutyltin dilaurate, dibutyltin diacetate, dioctyltin dilaurate, and stannous octoate.

8. The salt spray resistant two-component silicone structural adhesive according to claim 1, characterized in that, The crosslinking agent includes one or a combination of several of the following: methyl orthosilicate, ethyl orthosilicate, methyltrimethoxysilane, dimethyldimethoxysilane, methyltriethoxysilane, dimethyldiethoxysilane, polyethyl orthosilicate, polymethyltriethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, and cyclopentyltriethoxysilane.

9. A method for preparing a salt-resistant two-component silicone structural adhesive according to any one of claims 1 to 8, characterized in that, It is prepared by the following steps: Preparation of component A: Add 107 base glue, filler and dimethyl silicone oil to the reaction vessel, and stir and mix for 1 to 2 hours under vacuum at 130 to 150°C to obtain component A; Preparation of Component B: Carbon black and dimethyl silicone oil are premixed and then added to a reaction vessel. The mixture is stirred and mixed under vacuum at 140-160°C for 10-20 minutes. After mixing, crosslinking agent and fumed silica are added sequentially. The mixture is stirred and mixed under the same conditions for 20-40 minutes. After the mixture is homogeneous, coupling agent and catalyst are added, and stirring is continued for 50-70 minutes to obtain Component B.

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