Double-component silicone sealant resistant to damp-heat aging and preparation method of double-component silicone sealant

Abstract

The invention discloses a damp-heat aging resistant two-component silicone sealant and a preparation method thereof, and relates to the technical field of organosilicon materials, the sealant comprises a component A and a component B, the component A is prepared from 50 to 70 parts of filler nano calcium carbonate, 30 to 50 parts of 107 # silicone rubber, 0.003 to 0.3 part of polyphenol substances and 0.01 to 1 part of catalyst; the component B comprises 90-110 parts of a base material, 1-10 parts of a cross-linking agent, 0.4-3 parts of a coupling agent and 0.01-0.08 part of a catalyst, and the base material is prepared from 50-70 parts of filler nano calcium carbonate and 30-50 parts of 107 # silicone rubber. The method disclosed by the invention is mild in reaction condition, simple in process and low in equipment requirement, and the prepared two-component silicone sealant can meet deep and rapid curing, is excellent in adhesion to glass, metal and plastic, has excellent damp-heat aging resistance and has a wide application prospect in the field of sealants.

Description

Technical Field

[0001] The invention relates to the technical field of organic silicon materials, and in particular to a two-component silicone sealant resistant to moisture and heat aging and a preparation method thereof. Background Art

[0002] Condensation-type room temperature silicone rubber is an elastomeric material with a three-dimensional network structure formed by the reaction of linear polysiloxane (107# glue) and silane crosslinking agent. It is divided into deacetone type, deamidation type, deketoxime type and dealcoholization type according to the small molecular substances produced by the reaction. At present, the main practical applications in engineering are deketoxime type and dealcoholization type single-component room temperature vulcanized silicone sealants, especially the deketoxime type, which has the largest volume. Condensation-type room temperature silicone rubber has excellent electrical properties, chemical stability and bonding properties, and is also weather-resistant, water-resistant and ozone-resistant. Therefore, silicone sealants are widely used in construction, automobiles, electronic appliances, machinery, photovoltaics, chemicals and other fields.

[0003] In recent years, the photovoltaic field has developed rapidly, and the production and assembly technology of solar cell modules has become increasingly mature. The slow deep curing rate of single-component room temperature vulcanized silicone rubber has greatly limited the packaging efficiency of photovoltaic modules. The two-component room temperature vulcanized silicone rubber has the advantage of fast deep curing and is expected to be widely used in the bonding and sealing of photovoltaic modules. However, when silicone rubber is used for a long time in a hot and humid environment, its mechanical properties are significantly reduced. This may be due to the presence of water molecules that hydrolyze the siloxane in silicone rubber and crack the network structure of silicone rubber, which can seriously cause the silicone rubber to fall off from the substrate, greatly affecting the product quality and hindering the further development of silicone rubber in industries such as photovoltaic modules.

[0004] The Chinese patent document with publication number CN 115073750 A discloses a room temperature curing silicone rubber with humidity and heat resistance and a preparation method thereof. The method designs an organic polysilazane with a POSS structure and adds it to silicone rubber to effectively improve the humidity and heat aging resistance of silicone rubber. However, the synthesis method of polysilazane is relatively cumbersome and not suitable for industrial production and expansion. The Chinese patent document with publication number CN 108570304 A discloses a two-component silicone rubber adhesive with humidity and heat aging resistance and a preparation method thereof. The method is to modify the silane coupling agent, and the prepared two-component silicone rubber has improved double 85 (85°C, 85%RH, 1000h) resistance performance. However, the preparation process of this method requires modification of the silane coupling agent. In addition, component B uses polyether-modified silicone oil, which has a high application cost. Summary of the invention

[0005] A two-component silicone sealant resistant to moisture and heat aging, comprising component A and component B; The A component includes the following raw materials in parts by weight: 50 - 70 parts of filler nano calcium carbonate, 30 - 50 parts of 107# silicone rubber, 0.003 - 0.3 parts of polyphenols and 0.01 - 1 parts of catalyst; The B component includes the following raw materials in parts by weight: 90-110 parts of base material, 1-10 parts of cross-linking agent, 0.4-3 parts of coupling agent and 0.01-0.08 parts of catalyst, wherein the base material is composed of 50-70 parts of filler nano calcium carbonate and 30-50 parts of 107# silicone rubber.

[0006] The amount of cross-linking agent is related to the curing speed and storage period. Too little cross-linking agent will lead to poor storage time, and too much cross-linking agent will lead to a decrease in the internal deep curing rate. The coupling agent is an important component for providing adhesion. Too little will lead to a decrease in adhesion performance, and too much will easily cause problems such as yellowing and short storage period. The catalyst can accelerate the cross-linking reaction and achieve faster curing. Too little catalyst will slow down the deep curing, and excessive catalyst will easily cause problems such as short storage period and poor aging effect, and may even cause potential environmental problems. Therefore, preferably, the amount of the catalyst in component A is 0.02-0.05 parts, and the amount of the polyphenols is 0.005-0.04 parts; the amount of the cross-linking agent in component B is 2-8 parts, the amount of the coupling agent is 0.8-2.4 parts, and the amount of the catalyst is 0.025-0.06 parts.

[0007] The polyphenolic substance contains a catechol structure and is at least one of dopa, dopamine, tannic acid, catechol or catechin compounds. The catechin compounds include at least one of epicatechin, epigallocatechin, epicatechin gallate or epigallocatechin gallate.

[0008] The auxiliary agent used in the existing room temperature vulcanized silicone rubber preparation process is organic siloxane. After the organic siloxane is hydrolyzed, it reacts with the 107# silanol group to gradually form a three-dimensional network structure. However, because water molecules can cause the siloxane bonds to break in a hot and humid environment, the performance is reduced; polyphenols have the adhesion characteristics of self-polymerization, and can achieve adhesion to almost all substances. The present invention adds polyphenols to component A, and the polyphenols form a three-dimensional network structure after self-polymerization, so that a large number of polar groups such as hydroxyl groups and amino groups appear in the silicone rubber system, which can not only improve the adhesion performance of silicone sealant to the substrate, but also these polar groups can interact with the residual hydroxyl groups after the silicone rubber is cracked to produce hydrogen bonds, thereby improving the resistance to wet and hot aging.

[0009] The viscosity of the 107# silicone rubber is 5 - 1000 Pa·s, preferably 10 - 80 Pa·s.

[0010] The viscosity of 107# glue directly affects the extrusion and mechanical properties of silicone sealant. If the viscosity is too low, the system may be extruded too quickly and the prepared silicone rubber will have poor elasticity. If the viscosity is too high, the system will be thicker, making it difficult to apply in practice, and there may be problems such as poor deep curing.

[0011] The crosslinking agent is at least one of vinyltributylacetoximosilane, methyltributylacetoximosilane or phenyltributylacetoximosilane.

[0012] The activity of the crosslinking agent is directly related to the speed of curing. Since methyl tributylacetonate oxime silane has low crosslinking activity, too much methyl tributylacetonate oxime silane will slow down the deep curing. Therefore, when methyl tributylacetonate oxime silane is used as the crosslinking agent, it needs to be used in combination with other crosslinking agents, wherein the amount of methyl tributylacetonate oxime silane is 0.1 - 1 part.

[0013] The catalyst is a tin catalyst, which is at least one of dibutyltin dilaurate, chelated tin, dibutyltin or dibutyltin diacetate, preferably one or two of chelated tin or dibutyltin dilaurate are used in combination; the coupling agent is at least one of γ-aminopropyltriethoxysilane, γ-aminoethylaminopropyltrimethoxysilane or γ-glycidyloxypropyltrimethoxysilane.

[0014] A method for preparing a two-component silicone sealant resistant to moisture and heat aging comprises the following steps: Preparation of component A: A1: Stir 107# glue, nano calcium carbonate and polyphenols; A2: After being evenly dispersed, add the catalyst and stir to obtain component A; Preparation of component B: B1: Mix nano calcium carbonate and 107# silicone rubber under high temperature vacuum and disperse them evenly to obtain the base material; B2: The base material, crosslinking agent, coupling agent and catalyst are stirred under vacuum to obtain component B; The stirring time of A1 is 30 - 80 min; the stirring time of A2 is 5 - 30 min, the stirring time of B1 is 60 - 240 min, the temperature is 120 - 160°C, and the vacuum degree is not less than -20 KPa, preferably the stirring temperature is 140 - 170°C and the stirring time is 120 - 240 min; the vacuum degree of B2 is not less than -20 KPa; the stirring speeds of A1, A2, B1 and B2 are 50 - 150 rpm / min.

[0015] The crosslinking agent, coupling agent and catalyst described in B2 are added in batches, with only 2-6 parts of the crosslinking agent added in the first batch and stirred for 10-30 minutes; then the second batch is added, the second batch contains 0-2 parts of the crosslinking agent, 0.6-2 parts of the coupling agent and 0.01-0.08 parts of the catalyst, and stirring is continued for 10-30 minutes.

[0016] The application of two-component silicone sealant resistant to moisture and heat aging in the bonding field, especially for the bonding of aluminum sheets.

[0017] Compared with the prior art, the present invention has the following beneficial effects: (1) The preparation method of the present invention is simple, the reaction conditions are mild, the raw material cost is low, there is no complicated reaction process, and it is convenient for large-scale industrial production.

[0018] (2) The two-component silicone sealant resistant to moisture and heat aging prepared by the present invention has a network structure formed by polyphenols containing a large number of polar groups such as amino groups and hydroxyl groups and non-polar groups such as benzene rings, which can provide additional interactions (intermolecular forces, hydrogen bonds and hydrophobic interactions, etc.). After the system has been subjected to moisture and heat aging, the polar groups can produce hydrogen bonds and other interactions with the residual hydroxyl groups after the cracking of the silicone rubber, thereby producing a reinforcement effect, thereby greatly improving the moisture and heat resistance. In addition, the presence of a large number of polar groups further enhances the bonding performance.

[0019] (3) Compared with the formulation without adding polyphenols, the heat-resistant two-component silicone sealant PCT (121°C, gauge pressure 0.11 MPa, 16 h) prepared by the present invention by adding specific polyphenols has a strength increase of about 100% after aging, and a strength increase of about 100% for double 85 (85°C, 85% RH, 1000 h), and the bonding performance of the two forms can still be maintained after aging. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 The states of the two-component silicone sealant film prepared in Example 2 at different times: (a) before aging; (b) PCT aging for 16 h; (c) double 85 aging for 1000 h.

[0021] Figure 2 The states of the aluminum sheet shear samples bonded with the sealant prepared in Example 2 after the shear test: (1) shear before aging; (2) shear after PCT aging for 16 h; (3) shear after double 85 aging for 1000 h. DETAILED DESCRIPTION

[0022] The embodiments of the present invention will be described in detail below with reference to examples. The following examples are only used to illustrate the present invention and should not be construed as limiting the scope of the present invention.

[0023] Example 1 40 parts of 5 Pa·s 107# silicone rubber, 55 parts of filler nano calcium carbonate and 0.3 parts of dopamine were placed in a planetary stirring pot, stirred at 120 rpm / min for 40 min, then 0.05 parts of chelated tin were added and the stirring was continued for 30 min to obtain component A; 40 parts of 20Pa·s 107# silicone rubber and 55 parts of filler nano calcium carbonate were placed in a planetary stirring pot, stirred at 170°C and 120 rpm / min for 120 min to obtain component B base material; 95 parts of B base material were placed in a planetary stirring pot, 5 parts of crosslinking agent vinyl trisbutyl ketoxime silane were added and stirred at 120 rpm / min for 15 min, then 0.6 parts of γ-aminopropyl triethoxysilane, 0.2 parts of γ-aminoethylaminopropyl trimethoxysilane and 0.025 parts of dibutyltin dilaurate were added and the stirring was continued for 15 min to obtain component B.

[0024] Example 2 The difference from Example 1 is that dopamine is replaced by gallic acid.

[0025] Example 3 The difference from Example 1 is that dopamine is replaced by tannic acid.

[0026] Example 4 Different from Example 2, the viscosity of 107# used to prepare components A and B is 10 Pa·s.

[0027] Example 5 Different from Example 1, dopamine is replaced by a mixture of gallic acid and tannic acid, and the mass ratio of the two in the mixture is 1:3.

[0028] Example 6 The difference from Example 1 is that the amount of catalyst added in component A is 0.025 parts, and the crosslinking agent added in component B is: 4.5 parts of vinyl tributylacetoximate silane, 2 parts of phenyl tributylacetoximate silane and 1 part of methyl tributylacetoximate silane.

[0029] Example 7 The difference from Example 1 is that dopamine is replaced by epigallocatechin gallate.

[0030] Comparative Example 1 The difference from Example 1 is that no dopamine is added.

[0031] Sample Analysis: The two-component silicone sealant components A and B prepared in the above examples and comparative examples were mixed in a volume ratio of 1:1 to prepare a silicone sealant film.

[0032] The two-component silicone sealant components A and B prepared in the above examples and comparative examples were mixed in a volume ratio of 1:1 to prepare aluminum sheet-aluminum sheet shear samples with a sample area of ​​12.5*25 mm and a sealant thickness of 1±0.1 mm.

[0033] The films and shear samples were vulcanized in an environment of 23±2℃ and 50±5% relative humidity for 7 days. For the vulcanized films and shear samples, two aging methods were adopted, namely double 85 aging (85℃, 85% humidity, 1000 h) and PCT aging (121℃, gauge pressure 0.11 MPa, 16 h). The aged samples were placed at 23±2℃ and 50±5% relative humidity for 1 day for testing.

[0034] Mechanical tests were performed on the samples before and after aging. Strength and elongation at break were tested according to the standard for determination of tensile stress-strain properties of vulcanized rubber or thermoplastic rubber (GB / T 528 2009), and shear strength was tested according to GB / T 7124-2008. When the shear surface breaks from the inside of the glue for more than 80%, it is considered as cohesive failure, which indicates that the adhesive has excellent bonding performance to the substrate; otherwise, the failure form is cohesive failure. The test environment conditions are 23±2 ℃ and 50±5% relative humidity. Table 1 shows the strength and elongation at break test results of the film before and after aging, Table 2 shows the shear strength of the film before and after aging, and Table 3 shows the bonding failure form of the shear sample.

[0035] Table 1 Test results of strength and elongation at break of films prepared in Examples and Comparative Examples before and after aging

[0036] Table 2 Shear strength of films prepared in Examples and Comparative Examples before and after aging

[0037] Table 3 Adhesion failure forms of aluminum sheet-aluminum sheet shear samples obtained in the examples and comparative examples

[0038] Compared with Comparative Example 1, the shear strength of the embodiments is improved, which is due to the fact that the polyphenol monomers provide a large number of polar groups after self-polymerization, which increases the interaction between the adhesive and the aluminum sheet substrate, thereby obtaining a higher shear force. In addition, after the film is aged, the shear strength retention rate exceeds 70%, and compared with the comparative example, the bonding performance after aging is significantly improved.

[0039] Polyphenols have a great influence on the bonding performance after aging. Compared with dopamine, when tannic acid and catechin polyphenols are used, the strength and shear strength after aging are higher, and the resistance to moisture and heat aging is relatively better. This is due to the fact that tannic acid and catechins have more polar groups than dopamine.

[0040] Depend on Figure 1 It can be seen that the film prepared in Example 2 has no obvious change in appearance after PCT aging and / or double 85 aging.

[0041] The samples bonded to the aluminum sheet in the embodiment and the comparative example all had cohesive failure in the initial shear failure mode. However, after aging, the comparative example could not maintain the bonding performance to the aluminum sheet substrate and showed cohesive failure.

Claims

1. A two-component silicone sealant resistant to moisture and heat aging, characterized in that: It includes component A and component B; The A component includes the following raw materials in parts by weight: 50-70 parts of filler nano calcium carbonate, 30-50 parts of 107# silicone rubber, 0.003-0.3 parts of polyphenols and 0.01-1 parts of catalyst; The B component includes the following raw materials in parts by weight: 90-110 parts of base material, 1-10 parts of cross-linking agent, 0.4-3 parts of coupling agent and 0.01-0.08 parts of catalyst, wherein the base material is composed of 50-70 parts of filler nano calcium carbonate and 30-50 parts of 107# silicone rubber.

2. The two-component silicone sealant resistant to moisture and heat aging according to claim 1, characterized in that: The amount of the catalyst in the component A is 0.02-0.05 parts, and the amount of the polyphenols is 0.005-0.04 parts; the amount of the crosslinking agent in the component B is 2-8 parts, the amount of the coupling agent is 0.8-2.4 parts, and the amount of the catalyst is 0.025-0.06 parts.

3. A two-component silicone sealant resistant to moisture and heat aging according to claim 1, characterized in that: The polyphenolic substance contains a catechol structure and is at least one of dopa, dopamine, tannic acid, catechol or catechin compounds. The catechin compounds include at least one of epicatechin, gallic acid, epigallocatechin, epicatechin gallate or epigallocatechin gallate.

4. The two-component silicone sealant resistant to moisture and heat aging according to claim 1, characterized in that: The viscosity of the 107# silicone rubber is 5 - 1000 Pa·s, preferably 10 - 80 Pa·s.

5. The two-component silicone sealant resistant to moisture and heat aging according to claim 1, characterized in that: The crosslinking agent is at least one of vinyl tributylacetoximate silane, methyl tributylacetoximate silane or phenyl tributylacetoximate silane; when methyl tributylacetoximate silane is selected as the crosslinking agent, it needs to be compounded with other crosslinking agents, wherein the amount of methyl tributylacetoximate silane is 0.1-1 part.

6. The two-component silicone sealant resistant to moisture and heat aging according to claim 1, characterized in that: The catalyst is a tin catalyst, which is at least one of dibutyltin dilaurate, chelated tin, dibutyltin or dibutyltin diacetate, preferably one or two of chelated tin or dibutyltin dilaurate are used in combination; the coupling agent is at least one of γ-aminopropyltriethoxysilane, γ-aminoethylaminopropyltrimethoxysilane or γ-glycidyloxypropyltrimethoxysilane.

7. The method for preparing the two-component silicone sealant resistant to moisture and heat aging according to any one of claims 1 to 6, characterized in that: The following steps are involved: Preparation of component A: A1: Stir 107# glue, nano calcium carbonate and polyphenols; A2: After being evenly dispersed, add the catalyst and stir to obtain component A; Preparation of component B: B1: Mix nano calcium carbonate and 107# silicone rubber under high temperature vacuum and disperse them evenly to obtain the base material; B2: The base material, crosslinking agent, coupling agent and catalyst are stirred under vacuum to obtain component B.

8. The method for preparing the two-component silicone sealant resistant to moisture and heat aging according to claim 7, characterized in that: The stirring time of A1 is 30 - 80 min; the stirring time of A2 is 5 - 30 min, the stirring time of B1 is 60 - 240 min, the temperature is 120 - 160 ° C, and the vacuum degree is not less than -20 KPa, preferably the stirring temperature is 140 - 170 ° C, and the stirring time is 120 - 240 min; the vacuum degree of B2 is not less than -20KPa; the stirring speed of A1, A2, B1 and B2 is 50 - 150rpm / min.

9. The method for preparing the two-component silicone sealant resistant to moisture and heat aging according to claim 7, characterized in that: The crosslinking agent, coupling agent and catalyst described in B2 are added in batches, with only 2-6 parts of the crosslinking agent added in the first batch and stirred for 10-30 min; then the second batch is added, the second batch contains 0-2 parts of the crosslinking agent, 0.6-2 parts of the coupling agent and 0.01-0.08 parts of the catalyst, and stirring is continued for 10-30 min.

10. Application of a two-component silicone sealant resistant to moisture and heat aging in the field of sealants, characterized in that: Used in the bonding field, including bonding of aluminum sheets.

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