A sealant and its preparation method and application

Abstract

The application provides a sealant and a preparation method and application thereof. The sealant comprises the following components in parts by weight: 100 parts of alpha, omega-dihydroxypolydimethylsiloxane, 2.5-6.5 parts of a plasticizer, 80-100 parts of a filler, 8-15 parts of a crosslinking agent, 1.5-2 parts of a coupling agent and 0.1-0.2 parts of a catalyst, wherein the coupling agent is a reactant of an amino silane coupling agent and a hydroxyl-terminated polybutadiene. The amino silane coupling agent is chemically modified by using the hydroxyl-terminated polybutadiene, so that the adhesion and the moisture and heat resistance of the sealant can be significantly improved.

Description

Technical Field

[0001] This invention relates to the field of rubber technology, and in particular to a sealant, its preparation method, and its application. Background Technology

[0002] In recent years, with the development of technology, electricity consumption has surged, driving the development of power generation systems. Photovoltaic power generation systems are an important way to generate electricity, and photovoltaic modules are an important component of photovoltaic power generation systems.

[0003] Photovoltaic modules are the downstream link in the photovoltaic industry chain, located between photovoltaic cells and photovoltaic systems. They are the smallest effective power generation unit and mainly consist of nine core components: solar cells, interconnecting strips, busbars, tempered glass, EVA, backsheet, aluminum alloy, silicone, and junction box. Because photovoltaic electronic modules need to be exposed to the outdoors for extended periods, they must withstand high and low temperatures, rain and snow erosion, and ultraviolet aging. Therefore, the performance requirements for the sealants used to connect the various components of the photovoltaic module are more stringent, especially in terms of resistance to damp heat.

[0004] Compared to other sealants, silicone sealants exhibit superior durability in harsh outdoor environments. They also possess excellent resistance to UV radiation and atmospheric aging, remaining crack-free, brittle, and undamaged for extended periods even under complex weather conditions (high and low temperatures, dryness, and humidity); furthermore, they demonstrate strong resistance to deformation and displacement. However, to further enhance the bond strength between silicone sealants and the substrate, coupling agents are typically added. Commonly used amino coupling agents, however, have strong hydrophilicity, which can lead to a decrease in the sealant's strength retention under high temperature and humidity conditions and even interfacial damage, ultimately failing to meet the performance requirements of photovoltaic modules under such conditions.

[0005] Therefore, there is a need for a sealant with high resistance to damp heat. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of existing sealants in terms of poor bonding strength under high humidity and heat conditions (e.g., water bath treatment at 55°C for 21 days, or treatment under high temperature and high humidity conditions for 1000 hours), and to provide a sealant with high resistance to humidity and heat. This invention utilizes hydroxyl-terminated polybutadiene to chemically modify an aminosilane coupling agent, which significantly improves the sealant's bonding performance and resistance to humidity and heat.

[0007] Another object of the present invention is to provide a method for preparing the sealant.

[0008] Another object of the present invention is to provide the application of the sealant in the photovoltaic field.

[0009] To achieve the above objectives, the present invention adopts the following technical solution:

[0010] A sealant comprising the following components in parts by weight:

[0011]

[0012] The coupling agent is a reaction product of an aminosilane coupling agent and hydroxyl-terminated polybutadiene.

[0013] Aminosilane coupling agents are highly polar, which is beneficial for improving the adhesion strength between the sealant and the substrate. However, their strong polarity also leads to good hydrophilicity, so excessive use of aminosilane coupling agents can affect the water resistance and adhesion of the substrate. The inventors of this invention have creatively discovered that by chemically modifying the aminosilane coupling agent with hydroxyl-terminated polybutadiene, the resulting modified coupling agent contains hydroxyl groups at one end. These hydroxyl groups can participate in the cross-linking and curing of the silicone sealant. By embedding the hydrophobic polybutadiene carbon chain into the sealant, the cured sealant, after being treated in a high-temperature and high-humidity environment, is less susceptible to moisture penetration into the sealant and the substrate interface, thus improving adhesion and strength retention after high-temperature and high-humidity treatment. Furthermore, the modified coupling agent contains amino groups at the other end. These amino groups form chemical bonds or hydrogen bonds with the hydroxyl groups at the substrate interface, further enhancing the adhesion strength between the sealant and the substrate.

[0014] In embodiments of the present invention, the coupling agent has the following structural formula:

[0015]

[0016] n is selected from natural numbers from 10 to 70. Within this range of degree of polymerization n, the coupling agent has a suitable viscosity (viscosity of 100-5000 mPa·s at 25°C), good compatibility with the sealant system, and a certain degree of fluidity. This is beneficial for the coupling agent to smoothly migrate its amino end to the interface between the sealant and the substrate during the sealant curing process, thereby enhancing the adhesive strength of the sealant.

[0017] In an embodiment of the present invention, the viscosity of the α,ω-dihydroxypolydimethylsiloxane at 25°C is 100–100,000 mPa·s. Within this viscosity range, the sealant exhibits good flowability and good wetting properties to the substrate, which is beneficial for improving the overall performance of the sealant.

[0018] In embodiments of the present invention, the plasticizer is dimethyl silicone oil containing terminal epoxy groups. During the process of bonding the sealant to the substrate, the sealant first wets the substrate, spreads on the substrate surface, and then forms hydrogen bonds or reacts to form chemical bonds. Therefore, the wettability of the sealant to the substrate also affects the adhesion between the sealant and the substrate. In this invention, a single-terminal epoxy group silicone oil is preferred. When the silicone oil has an epoxy group at one end, it can react with the hydroxyl groups at the substrate interface while wetting the substrate. Furthermore, the amount of plasticizer added is greater than that of the coupling agent. After the sealant cures, the remaining epoxy groups in the plasticizer can react with the active hydrogen on the unreacted amino groups, reducing the hydrophilicity of the amino groups, thereby reducing the degree of moisture penetration into the colloid and the substrate interface, and improving the adhesion and strength retention rate of the colloid after high temperature and high humidity treatment.

[0019] The plasticizer has the following structural formula:

[0020]

[0021] The plasticizer has a viscosity of 100–5000 mPa·s at 25°C. A suitable viscosity ensures good compatibility between the plasticizer and the sealant system, further improving the sealant's performance.

[0022] In embodiments of the present invention, the filler comprises at least one selected from fumed silica, calcium carbonate, alumina, silica fume, and kaolin. The particle size of the filler is 10–500 nm. In embodiments of the present invention, the crosslinking agent is a deoxime-type crosslinking agent, which comprises at least one selected from methyltributanone oxime silane, vinyltributanone oxime silane, phenyltributanone oxime silane, dimethyldibutylone oxime silane, and methylvinyl ketone oxime silane.

[0023] In embodiments of the present invention, the catalyst includes at least one of dibutyltin dilaurate, dibutyltin diacetate, and stannous octoate.

[0024] The preparation method of the above-mentioned sealant is also within the protection scope of this invention, and specifically includes the following steps:

[0025] According to the stated weight proportions, α,ω-dihydroxypolydimethylsiloxane, plasticizer, and filler are mixed, dehydrated, and then a crosslinking agent is added. After vacuum stirring and mixing at 50-60°C, a coupling agent and a catalyst are finally added and mixed to obtain the sealant.

[0026] In an embodiment of the present invention, the dehydration is performed by drying at 120–140°C for 2–3 hours.

[0027] In an embodiment of the present invention, the vacuum stirring time is 10 to 30 minutes; the vacuum degree is 0.08 to 0.095 Pa.

[0028] The application of the aforementioned sealant in the photovoltaic field is also within the scope of protection of this invention.

[0029] Compared with the prior art, the beneficial effects of the present invention are:

[0030] This invention utilizes hydroxyl-terminated polybutadiene to chemically modify an aminosilane coupling agent, significantly improving the adhesive properties and resistance to damp heat of the sealant. After chemical modification with hydroxyl-terminated polybutadiene, the resulting modified coupling agent contains a hydroxyl group at one end. This hydroxyl group can participate in the cross-linking and curing of the silicone sealant. By embedding the hydrophobic polybutadiene carbon chain into the sealant, the cured sealant is less susceptible to moisture penetration into the colloid and substrate interface after high-temperature and high-humidity treatment, thus improving adhesion and strength retention after such treatment. The other end of the modified coupling agent contains an amino group. The amino group forms chemical bonds or hydrogen bonds with the hydroxyl groups at the substrate interface, enhancing the adhesive strength between the sealant and the substrate.

[0031] After being treated in a water bath at 55°C for 21 days, the sealant of this invention maintains a bond strength retention rate of over 75% with the substrate, reaching as high as 98%, while the degree of interface damage remains below 20%, even as low as 0%. After undergoing a double 85% treatment for 1000 hours, the sealant maintains a bond strength retention rate of over 75% with the substrate, reaching as high as 93%, while the degree of interface damage remains below 25%, even as low as 0%. Detailed Implementation

[0032] To better illustrate the purpose, technical solution, and advantages of this invention, specific embodiments will be used to further describe the invention below. However, these embodiments do not limit the invention in any way. Unless otherwise specified, the reagents, methods, and equipment used in this invention are conventional reagents, methods, and equipment in this technical field. Unless otherwise specified, all reagents and materials used in this invention are commercially available.

[0033] The following raw materials are selected in the embodiments of the present invention:

[0034] Matrix resin (α,ω-dihydroxypolydimethylsiloxane) :

[0035] 1#: RTV-107-2, with a viscosity of 20000 mPa·s at 25℃, purchased from Zhejiang Xin'an Chemical Group Co., Ltd.;

[0036] 2#: RTV-107-5, with a viscosity of 50,000 mPa·s at 25℃, purchased from Zhejiang Xin'an Chemical Group Co., Ltd.;

[0037] plasticizer The structural formula is as follows:

[0038]

[0039] 1#: In the above molecular structural formula, n = 400, and the viscosity at 25℃ is 1100 mPa·s;

[0040] 2#: In the above molecular structural formula, n = 666, and the viscosity at 25℃ is 5120 mPa·s;

[0041] 3#: In the above molecular structural formula, n = 500, and the viscosity at 25℃ is 1800 mPa·s;

[0042] 4#: Dimethyl silicone oil, with a viscosity of 1000 mPa·s at 25°C;

[0043] filler :

[0044] Calcium carbonate: CCS-25i, average particle size 70nm, purchased from Guangxi Huana New Materials Co., Ltd.

[0045] Fumed silica: LM150, particle size 200-300nm, purchased from Foshan Yasino Chemical Technology Co., Ltd.;

[0046] Alumina: BAK-10, particle size D 50 The nanometer diameter is 10.03nm, and it was purchased from Ya'an Baitu High-Tech Materials Co., Ltd.

[0047] Crosslinking agent:

[0048] Methyltributanone oxime silane: Commercially available;

[0049] Phenylacetone oxime silane: Commercially available;

[0050] Vinyltributylone oxime silane: commercially available;

[0051] Coupling agents have the following structural formula:

[0052]

[0053] 1#: In the above molecular structural formula (n=50), the viscosity at 25℃ is 2300 mPa·s;

[0054] 2#: In the above molecular structural formula (n=55), the viscosity at 25℃ is 2900 mPa·s;

[0055] 3#: In the above molecular structural formula (n=60), the viscosity at 25℃ is 3600 mPa·s;

[0056] 4#: Hydroxyl-terminated polybutadiene, with the molecular formula HO-[CH2CH=CHCH2] 50 -OH;

[0057] 5#: Aminosilane coupling agent, commercially available;

[0058] catalyst:

[0059] Dibutyltin dilaurate: Commercially available;

[0060] Stannous octoate: Commercially available.

[0061] Examples 1-16, Comparative Examples 1-4

[0062] A series of sealants are provided, prepared by a method including the following steps:

[0063] According to the formulations described in Tables 1 and 2, α,ω-dihydroxypolydimethylsiloxane, plasticizer, and filler are stirred and mixed evenly, then dehydrated at 130°C for 3 hours. A crosslinking agent is added, and the mixture is stirred and mixed evenly under vacuum (0.09 Pa) at 60°C for about 10 to 30 minutes. Finally, a coupling agent and catalyst are added and mixed evenly for about 15 minutes to obtain the sealant.

[0064] Table 1. Formulations (parts by weight) of the sealants in Examples 1-5

[0065]

[0066]

[0067] Table 2. Formulations (parts by weight) of the sealants in Examples 6-16 and Comparative Examples 1-4.

[0068]

[0069] Performance testing

[0070] The performance of the sealants obtained in the above embodiments and comparative examples was tested as follows: The sealants prepared in the above embodiments and comparative examples were used to prepare H-type specimens according to 6.8 of GB 16776-2005. The substrates were galvanized aluminum sheet and glass, and the specimens were cured for 21 days under standard conditions (23℃, 50%RH).

[0071] 1. The cured H-type specimens were subjected to tensile adhesion tests at 25℃ and a tensile rate of 5-6 mm / min. The tensile adhesion strength was recorded (denoted as σ0, in MPa).

[0072] 2. Two other sets of H-type specimens were subjected to water bath and high temperature and humidity treatments, respectively, and then placed under standard conditions (23℃, 50% RH) for 24 hours. The bond strength (σ) of the treated specimens was then tested. t ) and degree of adhesive failure (A tThe bonding strength retention rate (%) before and after treatment was calculated. The water bath treatment conditions were 55℃ water bath for 21 days; the high temperature and high humidity treatment conditions were 85℃ temperature and 85%RH humidity for 1000 hours. After treatment, tensile adhesion tests were performed.

[0073] Bond strength retention rate (%) = σ t / σ0*100%.

[0074] For detailed test results, please refer to Table 3.

[0075] Table 3. Performance test results of the sealants in the examples and comparative examples.

[0076]

[0077] The results above show that:

[0078] The sealant prepared according to the above embodiments of the present invention exhibits excellent resistance to damp heat. After being treated in a water bath at 55°C for 21 days, the retention rate of the bond strength between the sealant and the substrate is above 75%, reaching as high as 98%, and the degree of interface damage remains below 20%, even as low as 0%. After being treated with a double 85% method for 1000 hours, the retention rate of the bond strength between the sealant and the substrate is above 75%, reaching as high as 93%, and the degree of interface damage remains below 25%, even as low as 0%.

[0079] The results of Examples 1 and 7-9 show that selecting a dimethyl silicone oil plasticizer with terminal epoxy groups within a suitable viscosity range can significantly improve the moisture and heat resistance of the sealant.

[0080] The results of Examples 1 and 10-14 show that conventional fillers, crosslinking agents, and catalysts in the art can all be used in this invention.

[0081] The results of Examples 1, 15-16, and Comparative Examples 1-4 show that selecting coupling agents within the scope of protection of this invention can significantly improve the moisture and heat resistance of photovoltaic sealants. In Comparative Example 1, only hydroxyl-terminated polybutadiene was added, but the resulting sealant had poor adhesion to the substrate. In Comparative Example 2, only an aminosilane coupling agent was added, and the moisture and heat resistance of the resulting sealant significantly deteriorated. In Comparative Example 3, hydroxyl-terminated polybutadiene and an aminosilane coupling agent were physically mixed, and the resulting sealant also had poor moisture and heat resistance. In Comparative Example 4, neither a coupling agent nor hydroxyl-terminated polybutadiene was added, and the resulting sealant had significantly worse adhesion strength and moisture and heat resistance than those in the examples.

[0082] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A sealant, characterized in that, The components include the following parts by weight: The coupling agent is a reaction product of an aminosilane coupling agent and hydroxyl-terminated polybutadiene, and the structural formula of the coupling agent is as follows: n is a natural number selected from 10 to 70; The plasticizer is dimethyl silicone oil containing terminal epoxy groups.

2. The sealant according to claim 1, characterized in that, The viscosity of the α,ω-dihydroxypolydimethylsiloxane at 25°C is 100–100,000 mPa·s.

3. The sealant according to claim 1, characterized in that, The plasticizer has the following structural formula: The plasticizer has a viscosity of 100–5000 mPa·s at 25°C.

4. The sealant according to claim 1, characterized in that, The filler includes at least one of fumed silica, calcium carbonate, alumina, silica powder, and kaolin.

5. The sealant according to claim 1, characterized in that, The crosslinking agent is a deoxime-type crosslinking agent, which includes at least one of methyltributanone oxime silane, vinyltributanone oxime silane, phenyltributanone oxime silane, dimethyldibutylone oxime silane, and methylvinylone oxime silane.

6. The sealant according to claim 1, characterized in that, The catalyst includes at least one of dibutyltin dilaurate, dibutyltin diacetate, and stannous octoate.

7. The method for preparing the sealant according to any one of claims 1 to 6, characterized in that, Includes the following steps: According to the stated weight proportions, α,ω-dihydroxypolydimethylsiloxane, plasticizer, and filler are mixed, dehydrated, and then a crosslinking agent is added. After vacuum stirring and mixing at 50-60°C, a coupling agent and a catalyst are finally added and mixed to obtain the sealant.

8. The application of the sealant according to any one of claims 1 to 6 in the photovoltaic field.

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