A silicone adhesive and a method for preparing the same

Abstract

The application discloses a kind of organic silicon glue and its preparation method.The present application belongs to the field of organic silicon, the technical problem to be solved is that the leakage phenomenon or self-flowing phenomenon of existing organic silicon glue appears on the surface of substrate in the case of low viscosity, or the difficulty and inconvenience brought by construction in the case of high viscosity, or the problem of poor elasticity and reliable bonding in the sealing bonding use scene caused by high permanent compression deformation and low glue strength of existing organic silicon glue.The organic silicon glue disclosed by the present application comprises the following components by weight: 60-80 parts of vinyl silicone oil, 4-6 parts of high thixotropy index fumed white carbon black, 5-8 parts of reinforcing fumed white carbon black, 10-15 parts of silicon powder, 5-10 parts of base glue, 1.5-3 parts of crosslinking agent, 0.1-1 part of catalyst and 0.1-1.5 parts of coupling agent.The organic silicon glue of the present application has high thixotropy index and low permanent compression deformation.

Description

Technical Field

[0001] This invention belongs to the field of organosilicon and relates to an organosilicon adhesive and its preparation method, particularly an organosilicon adhesive with high thixotropic index and low permanent compression set and its preparation method. Background Technology

[0002] Currently, commonly used adhesives for sealing and bonding in the automotive, home appliance, photovoltaic, and industrial fields include polyurethane adhesives, epoxy resin adhesives, and silicone adhesives. Polyurethane adhesives are resistant to acids, alkalis, temperatures, and ozone, but have poor aging resistance and are prone to failure over time during bonding. Epoxy resin adhesives have high hardness and brittleness, which can lead to insufficient toughness and affect bonding performance. Silicone adhesives are environmentally friendly, non-toxic, and low-odor, and possess high aging resistance, overcoming the shortcomings of polyurethane and epoxy resin adhesives, and are gradually gaining widespread application.

[0003] When using silicone adhesives, certain application scenarios may encounter loose or uneven substrates, leading to adhesive flow or leakage, resulting in insufficient adhesive on the surface and inadequate bonding strength. If encountering vertical substrates, the weight of the adhesive can also cause flow, resulting in insufficient bonding strength and increased costs. Furthermore, the reduced elasticity of the adhesive after compression can also cause insufficient bonding strength between seals. All of these situations can lead to adhesive layer detachment, failure, and other bonding quality issues, resulting in the scrapping of bonded components and significant economic losses. Silicone adhesives can be improved by adding appropriate inorganic powders to increase viscosity and address adhesive flow issues. However, excessively high viscosity can cause difficulties in application due to nozzle blockage. Summary of the Invention

[0004] The technical problems to be solved by the present invention are: leakage or self-flowing phenomena on the substrate surface of existing silicone adhesives under low viscosity conditions, or construction difficulties and inconveniences caused by high viscosity conditions, or poor elasticity and bonding reliability in sealing and bonding applications due to the high permanent compression deformation and low colloid strength of existing silicone adhesives.

[0005] Therefore, this invention provides an organosilicon adhesive with a high thixotropic index and low permanent compression set. By adding highly thixotropic and highly reinforcing inorganic powders, this invention maintains high thixotropic properties while keeping the viscosity of the organosilicon adhesive within a low range. This avoids the difficulties and inconveniences of application caused by high viscosity and minimizes the risk of leakage on porous substrates or flow loss on vertical substrates. Furthermore, by adding highly thixotropic and highly reinforcing inorganic powders, the adhesive maintains low permanent compression set and high strength, ensuring good elasticity, bonding reliability, and adhesion performance in sealing and bonding applications.

[0006] The silicone adhesive provided by this invention comprises the following components in parts by weight:

[0007]

[0008]

[0009] The high thixotropic index fumed silica refers to fumed silica with a particle size of 6-15 nm and a pH value of 5-8 that has been surface-treated with chlorosilane.

[0010] The reinforcing fumed silica refers to fumed silica with a particle size of 8-15 nm and a pH value of 5-8 that has been surface-treated with silazane.

[0011] The base adhesive is a linear polysiloxane containing fumed silica;

[0012] The crosslinking agent refers to a reagent that can crosslink a polymer to form a three-dimensional structure; in some embodiments, the crosslinking agent is a hydrogen-containing silicone oil, whose -H group can undergo an addition reaction with the -CH=CH2 of vinyl silicone oil to crosslink the polymer to form a three-dimensional structure;

[0013] The catalyst is a reagent that increases the crosslinking reaction rate during the organosilicon curing process; in some embodiments, the catalyst is a platinum catalyst, which is a complex catalyst made of platinum metal as the main active component, and can effectively increase the crosslinking reaction rate during the organosilicon curing process.

[0014] The coupling agent refers to an organosilicon monomer with two or more different reactive groups, which can bond with organic and inorganic materials. The reactive groups are mainly divided into hydrolyzable groups and organic groups, which can improve the adhesion effect of organosilicon adhesives to substrates.

[0015] In some embodiments, the vinyl silicone oil in the above-mentioned silicone adhesive is 60, 70, or 80 parts by weight, or any value or range between these values; and / or

[0016] The high thixotropic index fumed silica is present in parts by weight of 4, 5, or 6, or any value or range between these values; and / or

[0017] The reinforcing fumed silica is present in parts by weight of 5, 6, 7, or 8, or any combination thereof or a range thereof; and / or

[0018] The silicon micropowder is present in parts by weight of 10, 11, 12, 13, 14, or 15, or any value or range between these values; and / or

[0019] The base adhesive is present in parts by weight of 5, 6, 7, 8, 9, or 10, or any value or range between these values; and / or

[0020] The crosslinking agent is present in parts by weight of 1.5, 2, 2.5, or 3 parts, or any value or range between these values; and / or

[0021] The catalyst is present in parts by weight of 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, or 1.0 parts, or any value or range between these values; and / or

[0022] The coupling agent is present in parts by weight of 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, or 1.5 parts, or any value or range between any two of these values.

[0023] In some embodiments, in any of the above-described silicone adhesives, the vinyl silicone oil has a viscosity of 500-10000 cp at 25°C and a vinyl content of 0.10-0.45 wt%, and can be an end-vinyl silicone oil, such as one or more of Vi1311 and Vi303 from Ningbo Runhe High-Tech Materials Technology Co., Ltd.; in some embodiments, the vinyl silicone oil is Vi303 and Vi1311 in a mass ratio of 3:4.

[0024] In some embodiments, in any of the above-described silicone adhesives, the high thixotropic index fumed silica has a particle size of 8-14 nm and a pH of 6-7, for example, one or more of SD3006CA and SD3001PH from Hubei Yingxing Adhesives Co., Ltd.

[0025] In some embodiments, in any of the above-described silicone adhesives, the reinforcing fumed silica has a particle size of 12-14 nm and a pH of 6-7, for example, one or more of Qingdao Evonik Chemical Co., Ltd.'s R8200 and Hubei Yingxing Adhesives Co., Ltd.'s 2002P.

[0026] In some embodiments, in any of the above-described silicone adhesives, the particle size of the silica powder is 1-3 μm, for example, one or more of CS1002 and NQS002 from Jiangsu Lianrui New Material Co., Ltd.

[0027] In some embodiments, the fumed silica content of the base adhesive in any of the above-described silicone adhesives is 23-32 wt%, for example, one or more of LSR3950-50JT and LSR1550-50JT from Ningbo Runhe Advanced Materials Technology Co., Ltd.

[0028] In some embodiments, in any of the above-described silicone adhesives, the crosslinking agent has a hydrogen content of 0.5-1.0 wt%, for example 0.7-0.8%, such as H502 from Ningbo Runhe High-Tech Materials Technology Co., Ltd.

[0029] In some embodiments, in any of the above-described silicone adhesives, the coupling agent comprises a hydrolyzable group and an organic group, wherein the hydrolyzable group is a methoxy group, and the organic group is one or more of an epoxy group and a methacryloyloxy group, such as one or more of KH560 and KH570 from Hubei Xinlantian New Material Co., Ltd.; in some embodiments, the coupling agent is KH570 and KH560 in a mass ratio of 2:3.

[0030] In some embodiments, the catalyst in any of the above-described silicone adhesives is MP2000 from Wanhua Chemical Group Co., Ltd.

[0031] In some embodiments, the thixotropic index of any of the above-described silicone adhesives is 6.7 to 7.5, and the permanent compression set is 6.5 to 8.0.

[0032] The present invention also provides a method for preparing any of the above-described silicone adhesives, comprising the following steps:

[0033] Step 1: First, add the high thixotropic index fumed silica to the vinyl silicone oil at a uniform rate (e.g., at a rate of 1 part / min) and mix well (e.g., mix at a speed of 20-40 rpm for 10-20 min) to obtain the first intermediate.

[0034] Step 2: Add the reinforcing fumed silica to the first intermediate at a uniform rate (e.g., at a rate of 1 part / min) and mix well (e.g., stir at a speed of 20-40 rpm for 10-20 min) to obtain the second intermediate;

[0035] Step 3: Add the base adhesive and the silicon micro powder to the second intermediate, mix well (e.g., stir at 50-70 rpm for 20-40 min), then heat to 100-120°C, keep warm and continue mixing (e.g., by stirring), while continuously vacuuming (e.g., for 0.5-1.5 h) to extract small molecules from the system. After completion, cool to room temperature to obtain the third intermediate;

[0036] Step 4: Add the catalyst and the coupling agent to the third intermediate and mix well (e.g., stir at 40-60 rpm for 10-30 min) to obtain the fourth intermediate;

[0037] Step 5: Add the crosslinking agent to the fourth intermediate, mix well (e.g., stir at 40-60 rpm) and remove air bubbles by vacuuming (e.g., for 10-30 min) to obtain the product, which is an organosilicon adhesive with high thixotropic index and low permanent compression set.

[0038] The silicone adhesive provided by this invention has a viscosity of approximately 28,500–34,000 mPa·s at 25°C and a thixotropic index of 6.7–7.5. This meets the requirements of no leakage of the adhesive on porous substrates and no flow loss on vertical substrates, while ensuring normal extrusion. After curing, the permanent compression set can be as low as 6.5%, and the tensile strength and shear strength can reach over 2.5 MPa, maintaining high elasticity and high strength.

[0039] Compared with the prior art, the present invention uses a compound of fumed silica with high thixotropic properties and reinforcing fumed silica, which ensures that the silicone adhesive has high thixotropic properties while ensuring that the silicone adhesive has low permanent compression set and high strength. Detailed Implementation

[0040] The technical solutions in the embodiments of the present invention will be clearly and completely described below; obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments, and do not constitute a limitation on the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of the present invention.

[0041] First, the following explanations are provided for the terms that may be used in this article:

[0042] The terms “including,” “comprising,” “containing,” “having,” or other similar semantic descriptions should be interpreted as non-exclusive inclusion. For example, “including a technical feature element (such as raw material, component, ingredient, carrier, dosage form, material, size, part, component, mechanism, device, step, process, method, reaction conditions, processing conditions, parameter, algorithm, signal, data, product or article of manufacture, etc.)” should be interpreted as including not only the expressly listed technical feature element, but also other technical feature elements that are not expressly listed and are well-known in the art.

[0043] The term "parts by weight" indicates the mass ratio between multiple components. For example, if component X is described as x parts by weight and component Y as y parts by weight, then the mass ratio of component X to component Y is x:y. One part by weight can represent any mass; for example, one part by weight can represent 1 kg or 3.1415926 kg, etc. The sum of the parts by weight of all components is not necessarily 100 parts; it can be greater than 100 parts, less than 100 parts, or equal to 100 parts. Unless otherwise stated, parts, proportions, and percentages mentioned herein are all by mass.

[0044] When concentration, temperature, pressure, size, or other parameters are expressed as numerical ranges, such ranges should be understood to specifically disclose all ranges formed by any pairing of upper limits, lower limits, and preferred values ​​within that range, regardless of whether the range is explicitly stated; for example, if the numerical range "2 to 8" is stated, then that range should be interpreted to include ranges such as "2 to 7", "2 to 6", "5 to 7", "3 to 4", "6 to 7", "3 to 5", etc. Unless otherwise stated, the numerical ranges described herein include both their endpoints and all integers and fractions within that range.

[0045] The following provides a detailed description of the silicone adhesive with high thixotropic index and low permanent compression set, and its preparation method. Contents not described in detail in the embodiments of this invention are prior art known to those skilled in the art. Where specific conditions are not specified in the embodiments of this invention, they are performed according to conventional conditions in the art or conditions recommended by the manufacturer. Reagents or instruments used in the embodiments of this invention, unless otherwise specified, are all commercially available products.

[0046] In the following embodiments and comparative examples, the viscosity, thixotropic index, permanent compression set, shear strength, and tensile strength tests were performed according to the following methods:

[0047] Viscosity: The viscosity of the adhesive at 25°C was measured using the cone-plate viscometer method of ASTM D4287 with a 52# rotor and a rotation speed of 10 rpm.

[0048] Thixotropic index: The viscosity was measured using a cone-plate viscometer at 25°C with a 52# rotor at two speeds: 1 rpm and 10 rpm. The thixotropic index of the adhesive is calculated as: viscosity at 1 rpm / viscosity at 10 rpm.

[0049] Permanent compression deformation: The standard GB / T 7759-1996 was adopted, and the compression amount was selected as 30%. According to the test standard, the sample height was compressed by 30%, and after being placed in an environment of 177℃ for 22 hours, it was taken out and the permanent compression deformation was measured.

[0050] Shear strength: Using ASTM D412 standard, an aluminum sheet with dimensions of 101mm*25.4mm*1.6mm was selected. Adhesive was applied to the designated locations as required, with an adhesive layer size of 25.4mm*12.5mm*0.1~0.2mm. After curing, the shear strength of the sample was measured using a universal tensile testing machine at a tensile rate of 5mm / min. The result was the average of three tests.

[0051] Tensile strength: Using ASTM D412 standard, a 2mm thick dumbbell-shaped standard sample was prepared and a universal tensile testing machine was used to measure the tensile strength of the sample at a tensile rate of 500mm / min. The result was the average of three tests.

[0052] Fumed silica SD3006CA and SD3001PH are products of Hubei Yingxing Adhesives Co., Ltd. Among them, SD3006CA is surface treated with chlorosilane, with a particle size of 12-14nm and a pH of 7; SD3001PH is surface treated with chlorosilane, with a particle size of 8-11nm and a pH of 7.

[0053] Fumed silica RY50 is a product of Qingdao Evonik Chemical Co., Ltd., which is surface treated with silazane and has a particle size of 10-40nm.

[0054] Fumed silica LM150 is a product of Shanghai Cabot Chemical Co., Ltd., with a particle size of 0.2-0.35μm.

[0055] Vinyl silicone oils Vi1311 and Vi303 are products of Ningbo Runhe High-Tech Materials Technology Co., Ltd., both of which are vinyl-terminated silicone oils. Vi1311 has a vinyl content of 0.43±0.02% (mass percentage) and a viscosity of 500cp at room temperature (25℃); Vi303 has a vinyl content of 0.12±0.02% (mass percentage) and a viscosity of 10000cp at room temperature (25℃).

[0056] Fumed silica R8200 is a product of Qingdao Evonik Chemical Co., Ltd. It is surface-treated with silazane, has a particle size of 12-14nm, and a pH of 7.

[0057] Fumed silica 2002P is a product of Hubei Yingxing Adhesives Co., Ltd. It is surface-treated with silazane, has a particle size of 12-14nm, and a pH of 7.

[0058] The base adhesives LSR3950-50JT and LSR1550-50JT are products of Ningbo Runhe High-Tech Materials Technology Co., Ltd., and are both polymer materials made of linear polysiloxane. Among them, the fumed silica content of LSR3950-50JT is 25±2% (mass percentage); the fumed silica content of LSR1550-50JT is 30±2% (mass percentage).

[0059] The silicon micropowders CS1002 and NQS002 are products of Jiangsu Lianrui New Materials Co., Ltd., with CS1002 having a particle size of 3μm and NQS002 having a particle size of 1μm.

[0060] The catalyst MP2000 is a product of Wanhua Chemical Group Co., Ltd., and the active content of MP2000 is 2000ppm.

[0061] Coupling agents KH560 and KH570 are products of Hubei Xinlantian New Materials Co., Ltd. Both of them have methoxy groups as their hydrolyzable groups. In addition, the organic group of KH560 is an epoxy group, and the organic group of KH570 is a methacryloyloxy group.

[0062] Crosslinking agent H502 is a product of Ningbo Runhe High-Tech Materials Technology Co., Ltd., with a hydrogen content of 0.75-0.77% (by mass).

[0063] Example 1:

[0064] Step 1: First, add 5 kg of high thixotropic index fumed silica SD3006CA to 30 kg of vinyl silicone oil Vi303 and 40 kg of vinyl silicone oil Vi1311 at a rate of 1 kg / min. After the addition is complete, premix at 30 rpm for 15 min to obtain the first intermediate.

[0065] Step 2: Add 5 kg of reinforcing fumed silica R8200 to the first intermediate at a rate of 1 kg / min, and stir at 30 rpm for 15 min to obtain the second intermediate;

[0066] Step 3: Add 8 kg of base adhesive LSR1550-50JT and 11 kg of silicon micro powder CS1002 to the second intermediate, stir at 60 rpm for 30 min, then heat to 110±2℃, keep warm and continue stirring, while continuously vacuuming for 1 h, and then cool to room temperature to obtain the third intermediate.

[0067] Step 4: Add 0.5 kg of catalyst MP2000, 0.4 kg of coupling agent KH570 and 0.6 kg of coupling agent KH560 to the third intermediate, and stir at 50 rpm for 20 min to obtain the fourth intermediate;

[0068] Step 5: Add 2.5 kg of crosslinking agent H502 to the fourth intermediate, stir at 50 rpm and vacuum for 20 min to obtain the product, which is an organosilicon adhesive with high thixotropic index and low permanent compression set.

[0069] The viscosity, thixotropic index, permanent compression set, tensile strength, and shear strength test results of the silicone adhesive in this embodiment are shown in Table 1.

[0070] Example 2:

[0071] Repeat the steps of Example 1, except that the base adhesive LSR1550-50JT in step 3 of Example 1 is replaced with LSR3950-50JT. This yields an organosilicon adhesive with a high thixotropic index and low permanent compression set.

[0072] The viscosity, thixotropic index, permanent compression set, tensile strength, and shear strength test results of the silicone adhesive in this embodiment are shown in Table 1.

[0073] Example 3:

[0074] Repeat the steps of Example 1, except that: 1. Replace the reinforcing fumed silica R8200 in step 2 of Example 1 with reinforcing fumed silica 2002P; 2. Replace the silica powder CS1002 in step 3 of Example 1 with silica powder NQS002. An organosilicon adhesive with a high thixotropic index and low permanent compression set is obtained.

[0075] The viscosity, thixotropic index, permanent compression set, tensile strength, and shear strength test results of the silicone adhesive in this embodiment are shown in Table 1.

[0076] Example 4:

[0077] The steps of Example 1 are repeated, except that: 1. the reinforcing fumed silica R8200 in step 2 of Example 1 is replaced with reinforcing fumed silica 2002P; 2. the 11 kg of silica powder CS1002 in step 3 of Example 1 is replaced with 10 kg of silica powder NQS002. An organosilicon adhesive with a high thixotropic index and low permanent compression set is obtained.

[0078] The viscosity, thixotropic index, permanent compression set, tensile strength, and shear strength test results of the silicone adhesive in this embodiment are shown in Table 1.

[0079] Example 5:

[0080] The steps of Example 1 are repeated, except that: 1. the reinforcing fumed silica R8200 in step 2 of Example 1 is replaced with reinforcing fumed silica 2002P; 2. the 11 kg of silica powder CS1002 in step 3 of Example 1 is replaced with 15 kg of silica powder NQS002. An organosilicon adhesive with a high thixotropic index and low permanent compression set is obtained.

[0081] The viscosity, thixotropic index, permanent compression set, tensile strength, and shear strength test results of the silicone adhesive in this embodiment are shown in Table 1.

[0082] Example 6:

[0083] Repeat the steps of Example 1, except that the amount of reinforcing fumed silica R8200 added in step 2 of Example 1 is replaced with 8 kg. This yields an organosilicon adhesive with a high thixotropic index and low permanent compression set.

[0084] The viscosity, thixotropic index, permanent compression set, tensile strength, and shear strength test results of the silicone adhesive in this embodiment are shown in Table 1.

[0085] Example 7:

[0086] Repeat the steps of Example 1, except that the 5 kg of high thixotropic index fumed silica SD3006CA in step 1 of Example 1 is replaced with 5 kg of high thixotropic index fumed silica SD3001PH. This yields an organosilicon adhesive with a high thixotropic index and low permanent compression set.

[0087] The viscosity, thixotropic index, permanent compression set, tensile strength, and shear strength test results of the silicone adhesive in this embodiment are shown in Table 1.

[0088] Comparative Example 1:

[0089] Repeat the steps of Example 1, except that the high thixotropic index fumed silica SD3006CA of Example 1 is replaced with ordinary thixotropic index fumed silica RY50.

[0090] The viscosity, thixotropic index, permanent compression set, tensile strength, and shear strength test results of the silicone adhesive in this comparative example are shown in Table 1.

[0091] Comparative Example 2:

[0092] Step 1: Add 10 kg of reinforcing fumed silica R8200 to 30 kg of vinyl silicone oil Vi303 and 40 kg of vinyl silicone oil Vi1311 at a rate of 1 kg / min. After the addition is complete, premix at 30 rpm for 15 min to obtain the first intermediate.

[0093] Step 2: Add 8 kg of base adhesive LSR1550-50JT and 11 kg of silica powder CS1002 to the first intermediate. Stir at 60 rpm for 30 min, then heat to 110±2℃. After reaching the temperature, keep warm and continue stirring while continuously vacuuming for 1 h. After the process is completed, cool to room temperature to obtain the second intermediate.

[0094] Step 3: Add 0.5 kg of catalyst MP2000, 0.4 kg of coupling agent KH570 and 0.6 kg of coupling agent KH560 to the second intermediate, and stir at 50 rpm for 20 min to obtain the third intermediate;

[0095] Step 4: Add 2.5 kg of crosslinking agent H502 to the third intermediate, stir at 50 rpm and vacuum for 20 min to obtain the product, namely the organosilicon adhesive.

[0096] The viscosity, thixotropic index, permanent compression set, tensile strength, and shear strength test results of the silicone adhesive in this comparative example are shown in Table 1.

[0097] Comparative Example 3:

[0098] Repeat the steps of Example 1, except that the high thixotropic index fumed silica SD3006CA of Example 1 is replaced with fumed silica LM150.

[0099] The viscosity, thixotropic index, permanent compression set, tensile strength, and shear strength test results of the silicone adhesive in this comparative example are shown in Table 1.

[0100] Comparative Example 4:

[0101] Repeat the steps of Example 1, except that the amount of high thixotropic index fumed silica SD3006CA added in step 1 of Example 1 is replaced with 3 kg.

[0102] The viscosity, thixotropic index, permanent compression set, tensile strength, and shear strength test results of the silicone adhesive in this comparative example are shown in Table 1.

[0103] Comparative Example 5:

[0104] Repeat the steps of Example 1, except that the amount of high thixotropic index fumed silica SD3006CA added in step 1 of Example 1 is replaced with 7 kg.

[0105] The viscosity, thixotropic index, permanent compression set, tensile strength, and shear strength test results of the silicone adhesive in this comparative example are shown in Table 1.

[0106] Table 1

[0107]

[0108] As can be seen from Table 1:

[0109] The silicone adhesives prepared in Examples 1 to 7 of the present invention have a viscosity of approximately 28,500 to 34,000 mPa·s at room temperature (25°C) and a thixotropic index of 6.7 to 7.5, which meet the requirements that the adhesive does not leak on porous substrates and does not flow or lose on vertical substrates.

[0110] Comparing Example 1 with Comparative Examples 4 and 5, it can be seen that as the amount of high thixotropic index fumed silica SD3006CA added increases, the thixotropic index of the silicone adhesive continuously increases. It should be noted that excessive addition of SD3006CA can easily cause poor extrusion of the adhesive; at the same time, appropriate addition of SD3006CA can keep the permanent compression set of the adhesive at a low level.

[0111] A comparison of Example 1 and Example 2 shows that the change in the type of base adhesive has no significant effect on the thixotropy, strength, and permanent compression set of the adhesive.

[0112] Comparing Example 1 with Example 3, it can be seen that the change in the type of reinforcing fumed silica and silica powder has no significant effect on the thixotropy and strength of the adhesive, but has a certain effect on the permanent compression set. Meanwhile, comparing Example 1 with Example 6, it can be seen that the permanent compression set increases with the increase of the amount of reinforcing fumed silica R8200 added.

[0113] A comparison of Examples 3, 4, and 5 shows that the change in silica powder content has a certain impact on the viscosity and mechanical properties of the adhesive. The greater the amount added, the higher the viscosity and the better the mechanical properties; however, it has no significant effect on thixotropy and permanent compression set.

[0114] Comparing Example 1 with Comparative Examples 1, 2, and 3, it can be seen that: without adding thixotropic silica, or by replacing it with ordinary thixotropic silica RY50, the adhesive has a low thixotropic index and a high permanent compression set, which does not meet the product design requirements; with the addition of another high thixotropic silica LM150, the thixotropic value of the adhesive can reach 7.3, but the permanent compression set increases significantly, and the adhesive strength decreases significantly.

[0115] In summary, the silicone adhesive of this invention maintains high thixotropic properties while maintaining a low viscosity, avoiding the difficulties and inconveniences of application such as nozzle clogging caused by high viscosity. It also solves the problem of leakage or flow loss that occurs with existing silicone adhesives at low viscosity on substrates under special conditions. Simultaneously, this silicone adhesive maintains low permanent compression set and high strength, ensuring good elasticity, bonding reliability, and adhesion performance in sealing and bonding applications. The silicone adhesive of this invention can be widely used for sealing and bonding in the automotive, home appliance, photovoltaic, and industrial fields.

[0116] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. An organosilicon adhesive, comprising the following components in parts by weight: 60-80 parts of vinyl silicone oil 4-6 parts of high thixotropic index fumed silica 5-8 parts of reinforcing fumed silica 10-15 parts of silica powder 5-10 parts base adhesive, Crosslinking agent 1.5~3 parts, Catalyst 0.1~1 part, 0.1 to 1.5 parts of coupling agent; The high thixotropic index fumed silica refers to fumed silica with a particle size of 6-15 nm and a pH value of 5-8 that has been surface-treated with chlorosilane. The reinforcing fumed silica refers to fumed silica with a particle size of 8-15 nm and a pH value of 5-8 that has been surface-treated with silazane. The base adhesive is a linear polysiloxane containing fumed silica; The silicone adhesive has a viscosity of 28,500~34,000 mPa·s at 25°C, a thixotropic index of 6.7~7.5, and a permanent compression set of 6.5~8.

0.

2. The silicone adhesive according to claim 1, characterized in that: The vinyl silicone oil has a viscosity of 500-10000 cp at 25°C and a vinyl content of 0.10-0.45 wt%.

3. The silicone adhesive according to claim 1, characterized in that: The high thixotropic index fumed silica has a particle size of 8-14 nm and a pH of 6-7.

4. The silicone adhesive according to any one of claims 1-3, characterized in that: The reinforcing fumed silica has a particle size of 12-14 nm and a pH of 6-7.

5. The silicone adhesive according to any one of claims 1-3, characterized in that: The particle size of the silicon micropowder is 1-3 μm.

6. The silicone adhesive according to any one of claims 1-3, characterized in that: The fumed silica content of the base adhesive is 23-32 wt%.

7. The silicone adhesive according to any one of claims 1-3, characterized in that: The hydrogen content of the crosslinking agent is 0.5-1.0 wt%.

8. The silicone adhesive according to any one of claims 1-3, characterized in that: The coupling agent comprises a hydrolyzable group and an organic group, wherein the hydrolyzable group is a methoxy group and the organic group is one or more of an epoxy group and a methacryloyloxy group.

9. A method for preparing the silicone adhesive according to any one of claims 1-8, comprising the following steps: Step 1: First, add the high thixotropic index fumed silica to the vinyl silicone oil at a uniform rate and mix well to obtain the first intermediate. Step 2: Add the reinforcing fumed silica to the first intermediate at a uniform rate and mix well to obtain the second intermediate; Step 3: Add the base adhesive and the silicon micro powder to the second intermediate, mix well, heat to 100~120℃, keep warm and continue mixing, while vacuuming, and then cool to room temperature to obtain the third intermediate; Step 4: Add the catalyst and the coupling agent to the third intermediate, mix well, and obtain the fourth intermediate; Step 5: Add the crosslinking agent to the fourth intermediate, mix well and vacuum to obtain the product.

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