Single-component dealcoholized silicone sealant as well as preparation method and application thereof

Abstract

The invention relates to the technical field of silicone rubber, in particular to the field of IPC C08G77, and more particularly relates to a single-component dealcoholized silicone sealant as well as a preparation method and application thereof. The high-temperature-resistant silicone rubber is prepared from the following raw materials in parts by weight: 80 to 100 parts of alkoxy-terminated polydimethylsiloxane, 0 to 10 parts of dimethyl silicone oil, 2 to 12 parts of fumed silica, 0.8 to 1.6 parts of a cross-linking agent, 0.5 to 1.5 parts of an adhesion promoter and 0.04 to 0.15 part of a catalyst. The invention provides the dealcoholized silicone sealant capable of realizing effective adhesion of a PC base material in a high-temperature environment, and under the synergistic effect of the materials, better interaction is realized, and the dealcoholized silicone sealant has excellent adhesion to the PC base material in the high-temperature environment.

Description

Technical Field

[0001] The present invention relates to the technical field of silicone rubber, in particular to the field of IPC C08G77, and more specifically to a single-component dealcoholized silicone sealant and a preparation method and application thereof. Background Art

[0002] PC (polycarbonate) is a polymer material containing carbonate groups in the main chain of the molecule. It is widely used in the preparation of shell materials for electronic devices in the new energy vehicle industry. Although PC materials have the above-mentioned excellent properties, their low surface energy makes it difficult to achieve effective bonding with traditional silicone sealants. In particular, when electronic devices such as power batteries, motor controllers and lidars in new energy vehicles are in continuous operation, the internal temperature of the devices often rises to more than 100°C in a short time, which puts forward new requirements for the adhesion of electronic device sealing materials to PC materials in high temperature environments. Single-component dealcoholized room temperature vulcanized silicone rubber is a multifunctional silicone polymer adhesive with excellent weather resistance, insulation, high and low temperature resistance and hydrophobicity. It cures into an elastomer by contacting water molecules in the air and releases small molecules. It has the advantages of environmental protection, simple operation and construction, and high efficiency.

[0003] Chinese invention patent CN117050319A reports a modified MQ silicone resin obtained by the addition reaction of cyclohexyl acrylate. The polar group enhances the wettability of the alcohol-type adhesive to the substrate and improves the adhesion to the PC / PBT substrate. However, the preparation of the modified MQ resin is relatively complicated, which is not convenient for the large-scale preparation of downstream silicone adhesive products. Chinese invention patent CN108624274A reports a composite adhesion promoter obtained by the reaction of aminosilane, epoxysilane and isocyanatesilane, which is used to enhance the adhesion durability of the alcohol-type adhesive to plastics such as PC / PBT / PMMA. However, the composite adhesion promoter is not purified after synthesis, and the incompletely reacted isocyanate group remains in the adhesion promoter, which will react with other elements with active hydrogen in the alcohol-type adhesive and water vapor in the air to produce gas escape, resulting in the possibility of hidden bubbles in the cured colloid, which is not conducive to the sealing of the device. In addition, isocyanate has certain toxicity, which is not conducive to green environmental protection requirements. Summary of the invention

[0004] The first aspect of the present invention provides a one-component dealcoholized silicone sealant, which comprises, by weight, 80 to 100 parts of alkoxy-terminated polydimethylsiloxane, 0.1 to 10 parts of dimethyl silicone oil, 2 to 12 parts of fumed silica, 0.8 to 1.6 parts of a cross-linking agent, 0.5 to 1.5 parts of an adhesion promoter, and 0.04 to 0.15 parts of a catalyst.

[0005] Preferably, the raw materials include, by weight: 80-95 parts of alkoxy-terminated polydimethylsiloxane, 1-5 parts of dimethyl silicone oil, 5-12 parts of fumed silica, 0.8-1.6 parts of a crosslinking agent, 0.4-1.5 parts of an adhesion promoter, and 0.04-0.1 parts of a catalyst.

[0006] The adhesion promoter includes a silane compound and / or an oligomer containing an active group, and the active group includes at least one of an amino group, an epoxy group, and a urea group.

[0007] Preferably, the structure of the adhesion promoter includes at least one of Formulas 1-3;

[0008]

[0009] Wherein m is any integer from 1 to 8, and n is any integer from 1 to 8;

[0010] The content of the adhesion promoter in the sealant is 0.4-1.0wt%.

[0011] The present application has found that the adhesion promoter includes silane compounds and / or oligomers containing active groups, and the content of the adhesion promoter in the sealant is 0.4-1.0wt%, the bonding strength at 25°C is greater than 1.2MPa, and the surface drying time is controlled within 30min. Further research has found that selecting at least one adhesion promoter in formula 1-3 can make the sealant have a bonding strength greater than 1.4MPa at 25°C, and the surface drying time is controlled within 15min. The content of the adhesion promoter in the sealant is further limited to 0.5-0.9wt%, which can further improve the high-temperature bonding performance of the sealant, the bonding strength at 110°C is greater than 0.8MPa, and the failure form is cohesive failure (CF). It may be that the adhesion promoter of a specific weight and content improves the surface polarity of the colloid, so that the shear strength at room temperature is significantly enhanced. At the same time, it avoids excessive oligomer molecules migrating to the surface between the colloid and the substrate to form a thicker low-molecular film, which in turn causes the thermal movement of excessive free oligomer molecules at high temperatures to destroy the interface between the molecular film and the substrate, thereby causing the bonding to fail.

[0012] Further research found that by selecting an adhesion promoter with the structure of Formula 1 and using it in an amount of 0.7wt%, the adhesion failure form of the sealant at 110°C can be 100% CF. This may be because the active hydrogen of the secondary amine group contained in the urea group further promotes the synergistic catalytic effect with organic tin, while when the adhesion promoter content is too low, it is not enough to form a close interface interaction between the colloid and the substrate.

[0013] Preferably, the content of the adhesion promoter in the sealant is 0.5-0.9wt%.

[0014] Further preferably, the content of the adhesion promoter in the sealant can be listed as follows: 0.55wt%, 0.6wt%, 0.65wt%, 0.7wt%, 0.75wt%, 0.8wt%.

[0015] The end-capping structure of the alkoxy-terminated polydimethylsiloxane includes methyldimethoxy end-capping or trimethoxy end-capping. The viscosity of the alkoxy-terminated polydimethylsiloxane at a temperature of 25° C. is 1000 to 80000 mPa·s.

[0016] Preferably, the end-capping structure of the alkoxy-terminated polydimethylsiloxane includes a trimethoxy end-capping structure, and the viscosity of the alkoxy-terminated polydimethylsiloxane at a temperature of 25° C. is 1500 to 20000 mPa·s.

[0017] The specific surface area of ​​the fumed silica is 80 to 220 m 2 / g; the fumed silica is treated with a modifier for hydrophobicity, and the modifier includes at least one of polydimethylsiloxane, hexamethyldisilazane, and dimethyldichlorosilane.

[0018] Preferably, the specific surface area of ​​the fumed silica is 150 to 200 m 2 / g; the fumed silica is treated with a modifier for hydrophobicity, and the modifier includes hexamethyldisilazane or dimethyldichlorosilane.

[0019] Further preferably, the modifier includes hexamethyldisilazane.

[0020] The viscosity of the dimethyl silicone oil at a temperature of 25° C. is 100 to 500 mPa·s.

[0021] Preferably, the viscosity of the dimethyl silicone oil at a temperature of 25° C. is 200 to 350 mPa·s.

[0022] The catalyst includes at least one of an organic tin catalyst, an organic tin chelate catalyst, a titanate catalyst, and a titanate chelate catalyst.

[0023] Preferably, the catalyst comprises an organotin catalyst, including at least one of dibutyltin dilaurate, dibutyltin diacetate or dioctyltin dilaurate;

[0024] Further preferably, the organotin catalyst includes dibutyltin dilaurate.

[0025] The crosslinking agent includes alkoxysilane, the number of alkoxy groups of the alkoxysilane is ≥3, and the alkoxysilane includes at least one of methyltrimethoxysilane, methyltriethoxysilane, ethyltrimethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, phenyltrimethoxysilane and phenyltriethoxysilane.

[0026] Preferably, the alkoxysilane includes at least one of methyltrimethoxysilane and methyltriethoxysilane.

[0027] More preferably, the alkoxysilane includes methyltrimethoxysilane.

[0028] The second aspect of the present invention provides a method for preparing a one-component dealcoholized silicone sealant, comprising the following steps:

[0029] Stirring and evenly dispersing the alkoxy-terminated polydimethylsiloxane and dimethyl silicone oil to obtain a first mixture;

[0030] Adding fumed silica to the first mixture, stirring and dispersing the mixture evenly, and performing vacuum dehydration to obtain a second mixture;

[0031] Add the crosslinking agent, adhesion promoter and catalyst into the second mixture, stir and disperse them evenly to obtain the product.

[0032] The vacuum degree of the vacuum dehydration is -0.09 to 0.095 MPa, and the dehydration time is 10 to 20 minutes.

[0033] Preferably, the vacuum degree of the vacuum dehydration is -0.09 MPa, and the dehydration time is 15 min.

[0034] Preferably, the steps include:

[0035] Stirring and dispersing the alkoxy-terminated polydimethylsiloxane and dimethyl silicone oil for 10 to 20 minutes to obtain a first mixture;

[0036] Adding fumed silica to the first mixture, stirring and dispersing for 10 to 20 minutes, and performing vacuum dehydration to obtain a second mixture;

[0037] Add the crosslinking agent, adhesion promoter and catalyst into the second mixture, and stir and disperse for 10 to 20 minutes to obtain the product.

[0038] The third aspect of the present invention provides an application of a one-component dealcoholized silicone sealant for bonding PC substrates.

[0039] Preferably, it is used for bonding PC substrates in high temperature environments (greater than 80°C).

[0040] Beneficial Effects

[0041] 1. The specific raw material composition: 80-100 parts of alkoxy-terminated polydimethylsiloxane, 0.1-10 parts of dimethyl silicone oil, 2-12 parts of fumed silica, 0.8-1.6 parts of cross-linking agent, 0.5-1.5 parts of adhesion promoter, 0.04-0.15 parts of catalyst can improve the adhesion to PC substrate in high temperature environment.

[0042] 2. By selecting a silane compound and / or an oligomer adhesion promoter containing an active group, the prepared sealant has a shear strength greater than 1 MPa.

[0043] 3. The content of the adhesion promoter in the sealant is 0.4-1.0wt%, which can make the adhesive strength of the sealant greater than 1.2MPa at 25°C, and the surface drying time is controlled within 30min.

[0044] 4. At least one adhesion promoter selected from formulas 1 to 3 can make the adhesive strength of the sealant greater than 1.4 MPa at 25° C., and the surface drying time can be controlled within 15 minutes.

[0045] 5. The content of the adhesion promoter in the sealant is limited to 0.5-0.9wt%, which can further improve the high-temperature bonding performance of the sealant. The bonding strength at 110°C is greater than 0.8MPa, and the failure form is cohesive failure (CF).

[0046] 6. Selecting an adhesion promoter of formula 1 and using it in an amount of 0.7 wt % can make the adhesion failure form of the sealant at 110° C. 100% CF. DETAILED DESCRIPTION

[0047] Examples 1-3, Comparative Examples 1-4

[0048] A one-component dealcoholized silicone sealant, the raw materials of which are shown in Table 1 in parts by weight.

[0049] Table 1

[0050]

[0051]

[0052] The adhesion promoter (I), adhesion promoter (II), adhesion promoter (III), adhesion promoter (IV) and adhesion promoter (V) are shown in the following formula:

[0053]

[0054] Wherein m is any integer from 1 to 8, and n is any integer from 1 to 8;

[0055]

[0056] A method for preparing a one-component dealcoholized silicone sealant comprises the following steps:

[0057] 1. Add the alkoxy-terminated polydimethylsiloxane and dimethyl silicone oil into a planetary stirring kettle, and stir and disperse at room temperature for 15 minutes;

[0058] 2. Add the fumed silica into a planetary stirred tank and stir and disperse at room temperature for 15 minutes;

[0059] 3. After scraping the wall, the vacuum degree was maintained at -0.09MPa, and dehydration, stirring and dispersion were performed at room temperature for 90 minutes;

[0060] 4. After dehydration, add the crosslinking agent, adhesion promoter and catalyst into the planetary stirring kettle in sequence, stirring and dispersing each one at room temperature for 15 minutes;

[0061] 5. Maintain the vacuum degree at -0.09MPa, dehydrate, stir and disperse at room temperature for 15 minutes.

[0062] The room temperature is 25°C.

[0063] Performance testing methods and data

[0064] The above performance tests were performed on the dealcoholized silicone sealants provided in Examples 1 to 3 and Comparative Examples 1 to 2 after curing at 25°C and 55% RH (after curing for 7 days at 25°C and 55% RH): the dry time was tested according to the test method described in GB / T13477.5-2002 Test Methods for Building Sealing Materials; the PC-PC shear strength of the silicone sealant was tested according to the test method described in GB / T 7124-2008 Determination of Tensile Shear Strength of Adhesives, wherein the high temperature test was performed using an electronic universal tensile machine equipped with a high and low temperature test chamber, and the shear piece was heated to 110°C in the high and low temperature test chamber and kept warm for 10 minutes before the test began. The test results are shown in Table 2.

[0065] Table 2

[0066]

[0067] From the data in the above table, it can be seen that Examples 1 to 3 have significantly better adhesion than Comparative Examples 1 to 2 under high temperature conditions, and the damage forms of the dealcoholized silicone sealants prepared by Examples 1 and 2 to the PC substrate under high temperature are all cohesive failure (CF accounts for 90% to 100%). From the comparison of the adhesion promoter structures used in Examples 1 to 3 and Comparative Examples 1 to 2, it can be seen that although the aminosilane in Comparative Example 2 has excellent PC adhesion performance under normal temperature conditions, it fails to adhere under high temperature conditions; while the adhesion promoter of Example 1 is a macromolecular silane trimer with a multi-alkoxy and urea structure, and the adhesion promoter of Example 2 is a hydrolyzed oligomer with amino and urea groups. The above two silane compounds have strong weathering stability and are suitable for effective adhesion to PC substrates under high temperature conditions.

[0068] By comparing Example 1 with Comparative Examples 3 to 4, it can be seen that the amount of the same structural adhesion promoter has a great influence on the dry time of the sealant, the shear strength under different temperature conditions, and the form of adhesion failure. Comparative Example 4 adds a higher content of type (I) adhesion promoter, which improves the surface polarity of the colloid, so that the shear strength at room temperature is significantly enhanced. However, excessive oligomer molecules migrate to the surface between the colloid and the substrate to form a thicker low-molecular film. Although the adhesion is significantly improved at high temperatures, the thermal motion of too many free oligomer molecules at high temperatures will destroy the interface between the molecular film and the substrate, thereby causing the adhesion to fail. In addition, with the increase in the amount of type (I) adhesion promoter, the active hydrogen of the secondary amine group contained in the urea group further promotes the synergistic catalytic effect with organic tin, accelerating the dry time of Comparative Example 4. The content of type (I) adhesion promoter in Comparative Example 3 is less, which is not enough to form a close interface interaction between the colloid and the substrate. Comprehensively comparing Example 1 with Comparative Examples 3-4, it is found that the (I) type adhesion promoter needs to be added in a more appropriate amount to achieve better adhesion durability.

Claims

1. A one-component dealcoholized silicone sealant, characterized in that: The raw materials include, by weight: 80-100 parts of alkoxy-terminated polydimethylsiloxane, 0.1-10 parts of dimethyl silicone oil, 2-12 parts of fumed silica, 0.8-1.6 parts of a crosslinking agent, 0.4-1.5 parts of an adhesion promoter, and 0.04-0.15 parts of a catalyst.

2. The one-component dealcoholized silicone sealant according to claim 1, characterized in that: The adhesion promoter includes a silane compound and / or an oligomer containing an active group, and the active group includes at least one of an amino group, an epoxy group, and a urea group.

3. The one-component dealcoholized silicone sealant according to claim 2, characterized in that: The structure of the adhesion promoter includes at least one of Formulas 1-3; Wherein, m is any integer from 1 to 8, and n is any integer from 1 to 8.

4. The one-component dealcoholized silicone sealant according to claim 2 or 3, characterized in that: The content of the adhesion promoter in the sealant is 0.4-1.0wt%.

5. The one-component dealcoholized silicone sealant according to claim 4, characterized in that: The end-capping structure of the alkoxy-terminated polydimethylsiloxane includes methyldimethoxy or trimethoxy. The viscosity of the alkoxy-terminated polydimethylsiloxane at 25° C. is 1000-80000 mPa·s.

6. The one-component dealcoholized silicone sealant according to claim 5, characterized in that: The specific surface area of ​​the fumed silica is 80 to 220 m 2 / g; the fumed silica is treated with a modifier for hydrophobicity, and the modifier includes at least one of polydimethylsiloxane, hexamethyldisilazane, and dimethyldichlorosilane.

7. The one-component dealcoholized silicone sealant according to claim 6, characterized in that: The viscosity of the dimethyl silicone oil at 25° C. is 100 to 500 mPa·s.

8. A method for preparing the one-component dealcoholized silicone sealant according to any one of claims 1 to 7, characterized in that: The following steps are involved: Stirring and evenly dispersing the alkoxy-terminated polydimethylsiloxane and dimethyl silicone oil to obtain a first mixture; Adding fumed silica to the first mixture, stirring and dispersing the mixture evenly, and performing vacuum dehydration to obtain a second mixture; Add the crosslinking agent, adhesion promoter and catalyst into the second mixture, stir and disperse them evenly to obtain the product.

9. The preparation method according to claim 8, characterized in that: The vacuum degree of the vacuum dehydration is -0.09 to 0.095 MPa, and the dehydration time is 10 to 20 minutes.

10. An application of the one-component dealcoholized silicone sealant according to any one of claims 1 to 7, characterized in that: Applied for bonding PC substrates.

Images