Preparation method of tackified flame-retardant silicone pressure-sensitive adhesive

Abstract

The application discloses a preparation method of tackifying flame-retardant organic silicon pressure-sensitive adhesive, which comprises the following steps: synthesizing an organic silicon tackifier MQ-ETMS through a silicon-hydrogen addition reaction between a vinyl trimethoxysilane coupling agent and a methyl hydrogen-containing silicon resin; and preparing a flame retardant K-ADP by wet modification of an aluminum diethyl phosphinate containing an ethylenic bond, wherein the prepared organic silicon tackifier and the flame retardant are introduced into an organic silicon pressure-sensitive adhesive system, and then high-performance organic silicon pressure-sensitive adhesive tape is prepared through blending, coating, solvent evaporation and heating crosslinking. The tackifier synthesized by the application is rich in methoxy functional groups, which enhances the interaction between the organic silicon pressure-sensitive adhesive and the surface of the adherend. Meanwhile, the aluminum diethyl phosphinate containing an ethylenic bond is surface-modified by using the ethylenic bond-containing silane coupling agent, so that the dispersion problem of traditional flame retardants added in the organic silicon pressure-sensitive adhesive is solved, and the adhesion and flame retardation of the organic silicon pressure-sensitive adhesive are improved.

Description

Technical Field

[0001] This invention relates to the field of silicone pressure-sensitive adhesive technology, and in particular to a method for preparing a tackifying and flame-retardant silicone pressure-sensitive adhesive. Background Technology

[0002] Silicone pressure-sensitive adhesives (PSAs) exhibit irreplaceable value in high-end fields such as electronic packaging, new energy vehicle battery modules, and medical devices due to their unique high and low temperature resistance, chemical inertness, and dielectric properties. However, in the pursuit of higher safety and reliability, the insufficient adhesive performance (such as poor initial tack and short holding time) and flame retardancy defects of traditional PSAs severely restrict their application in safety-sensitive scenarios. For example, during thermal runaway of electric vehicle batteries, existing tapes pose a risk of fire spread due to their low flame retardancy efficiency and easy detachment; while in the packaging of high-frequency electronic devices, ordinary PSAs are prone to high-temperature aging, leading to a decrease in adhesive strength and detachment of packaging materials, which may cause equipment damage. In other words, in safety-sensitive scenarios, PSAs need to meet the dual requirements of improved adhesion and flame retardancy.

[0003] In existing technologies, flame retardants, such as aluminum diethylphosphinate, are typically added to improve the flame retardant properties of silicone pressure-sensitive adhesives. However, the addition of flame retardants often affects the physical properties of the adhesive and may alter its molecular structure and cohesive forces, thereby affecting the adhesive's bonding performance and leading to decreased peel performance. This invention investigates how to prepare a silicone pressure-sensitive adhesive that combines high bonding performance, excellent flame retardancy, and high-temperature stability to balance the dual requirements of improving both the adhesive and flame retardant properties of the pressure-sensitive adhesive. Summary of the Invention

[0004] To achieve the above objectives, the present invention adopts the following technical solution:

[0005] A method for preparing a tackifying and flame-retardant silicone pressure-sensitive adhesive includes the following steps:

[0006] S1 involves stirring and heating vinyltrimethoxysilane, solvent, and platinum catalyst under a nitrogen atmosphere to 70-95 °C, then adding a mixture of methyl hydrogen-containing silicone resin and solvent at constant pressure and maintaining the temperature for 3-6 h. Activated carbon is then added and mixed for 1-2 h before filtration. The filtrate is then distilled under reduced pressure to obtain the organosilicon thickener.

[0007] S2 disperses a certain amount of aluminum diethylphosphonate in anhydrous ethanol and sonicates it to obtain an aluminum diethylphosphonate solution. Separately, a silane coupling agent containing an olefin bond, anhydrous ethanol, and deionized water are mixed and an acid catalyst is added for hydrolysis. After hydrolysis, the mixture is allowed to stand at room temperature until it becomes transparent. The settled material is then poured into the aluminum diethylphosphonate solution and stirred and heated at 50-70 °C for 1-2 hours. After the reaction, the mixture is cooled to room temperature, centrifuged, and filtered to obtain a precipitate. The precipitate is washed with ethanol and dried at 60-80 °C to obtain a solid powder. The solid powder is then ground to obtain a modified aluminum diethylphosphonate flame retardant.

[0008] S3 involves stirring methyl MQ silicone resin, 107 silicone rubber, and toluene under nitrogen protection until homogeneous, then adding a catalyst, stirring and heating to carry out a condensation reaction, and finally condensing and separating water and toluene to obtain the base liquid.

[0009] S4 mixes the base liquid prepared in S3, the flame retardant prepared in S2, and the silica filler evenly, then grinds and disperses them. Then, toluene solvent, initiator, and organosilicon tackifier prepared in S1 are added and thoroughly mixed to obtain a flame-retardant and tack-enhancing organosilicon pressure-sensitive adhesive solution. The organosilicon pressure-sensitive adhesive solution is coated on the substrate, and then the sample is subjected to solvent evaporation and crosslinking to obtain an organosilicon pressure-sensitive coating. A layer of polyester release film is then covered, and the other side of the substrate is coated in the same way to obtain an organosilicon pressure-sensitive tape.

[0010] The mass ratio of vinyltrimethoxysilane and methyl hydrogen-containing silicone resin in S1 is (1~1.2):1; the mass ratio of olefin-containing silane coupling agent, anhydrous ethanol and deionized water in S2 is 20:9:72; the mass ratio of 107 silicone rubber and methyl MQ silicone resin in S3 is 100:(30~100); and the mass ratio of tackifier, flame retardant, silica filler and base liquid in S4 is (0.5~3):(0.5~3):5:100.

[0011] Furthermore, in S1, the amount of platinum catalyst used is 0.5% to 2% of the total mass of vinyltrimethoxysilane and methyl hydrosilicone resin.

[0012] Furthermore, in S1, the solvent is toluene or xylene, and the amount of solvent used is 2 to 3 times the total mass of vinyltrimethoxysilane and methyl hydrosilicone resin.

[0013] Furthermore, in S2, the olefin-containing silane coupling agent is at least one of vinyltrimethoxysilane, vinyltriethoxysilane, and γ-methacryloyloxypropyltrimethoxysilane.

[0014] Furthermore, in S2, the acid catalyst is acetic acid or hydrochloric acid, and the hydrolysis pH is 4-5.

[0015] Furthermore, in S3, the catalyst is any one of acetic acid, triethylamine, or dibutyltin dibutylsilicate, and the amount of catalyst used is 0.5% to 2% of the total mass of 107 silicone rubber and methyl MQ silicone resin.

[0016] Furthermore, in S3, the condensation reaction temperature is 110~130 ℃, and the reaction time is 1~3 h.

[0017] Furthermore, in S4, after grinding and dispersion, the particle size of the dispersed particles, as determined by scraper particle size analysis, is less than 10 μm.

[0018] Furthermore, in S4, the initiator is 2,4-dichlorobenzoyl peroxide or benzoyl peroxide, the catalyst mass is 0.5-3% of the mass of the organosilicon pressure-sensitive adhesive base liquid, the solvent evaporation temperature is 60-100℃, the evaporation time is 60-150s, the crosslinking temperature is 150-180℃, the crosslinking time is 80-120s, and the organosilicon pressure-sensitive adhesive coating thickness is 15-30μm.

[0019] In the preparation method of the present invention, an organosilicon tackifier (MQ-ETMS) is synthesized by hydrosilylation reaction between a vinyltrimethoxysilane coupling agent and a methyl hydrogen-containing silicone resin. A modified diethylphosphinate flame retardant (K-ADP) is prepared by wet modification of aluminum diethylphosphinate with an olefin-containing silane coupling agent. The prepared organosilicon tackifier (MQ-ETMS) and flame retardant (K-ADP) are introduced into an organosilicon pressure-sensitive adhesive system, and then a high-performance organosilicon pressure-sensitive adhesive is prepared by blending, coating, solvent evaporation, and heating crosslinking.

[0020] The reaction formula for synthesizing organosilicon tackifier (MQ-ETMS) by hydrosilylation reaction between vinyltrimethoxysilane coupling agent and methyl hydrogen-containing silicone resin is as follows:

[0021] (Equation 1)

[0022] The silane coupling agent containing olefin bonds is at least one of vinyltrimethoxysilane, vinyltriethoxysilane, and γ-methacryloxypropyltrimethoxysilane. Its hydrolysis reaction under the action of an acid catalyst is a process in which its siloxane group is hydrolyzed into silanol group (Si-OH), which then wet-modifies aluminum diethylphosphinate. The introduction of silanol group can enable the modified aluminum diethylphosphinate flame retardant to be more uniformly distributed in the colloid, improving the problem of the influence of traditional flame retardants on the dispersibility in organosilicon pressure-sensitive adhesive system, thereby improving the flame retardant performance.

[0023] Introducing silicone tackifier (MQ-ETMS) and flame retardant (K-ADP) into a silicone pressure-sensitive adhesive (PSA) system, the silicone tackifier (MQ-ETMS), synthesized via hydrosilylation, enhances the wetting, penetration, and surface interaction of the PSA onto the substrate. Combined with a modified aluminum diethylphosphinate flame retardant (K-ADP) surface-modified with an olefin-containing silicone coupling agent, a silicone PSA system with both high adhesive strength and excellent flame retardancy is constructed. The silicone tackifier (MQ-ETMS) improves the mechanical properties and thermal stability of the PSA through a dynamic crosslinking network, while the modified aluminum diethylphosphinate flame retardant (K-ADP) improves dispersibility and enhances interfacial bonding through surface silanization modification. The synergistic effect of these two components simultaneously optimizes flame retardant efficiency and adhesive durability.

[0024] In the above preparation method, the substrate can be silicone rubber, PET film, PI film, etc.

[0025] The silicone pressure-sensitive adhesive prepared by the above method has both improved adhesive properties and flame retardant properties.

[0026] The beneficial effects of this invention are as follows:

[0027] In the preparation method of the tackifying and flame-retardant silicone pressure-sensitive adhesive of the present invention, the silicone tackifier (MQ-ETMS) is synthesized through a hydrosilylation reaction between a vinyltrimethoxysilane coupling agent and a methyl hydrogen-containing silicone resin. It is rich in active functional groups, which enhance the interaction between the silicone pressure-sensitive adhesive and the surface of the bonded material. Furthermore, its molecular structure forms a cross-linked network, which improves the mechanical properties and thermal stability of the pressure-sensitive adhesive. The flame retardant (K-ADP) is prepared by wet modification of aluminum diethylphosphinate using an alkene-containing silane coupling agent. This not only retains the flame-retardant properties, but the introduction of the silane coupling agent also improves the dispersibility of aluminum diethylphosphinate in the silicone pressure-sensitive adhesive system, effectively solving the dispersion problem of traditional flame retardants in silicone pressure-sensitive adhesives. This allows the flame retardant (K-ADP) to be more uniformly distributed in the colloid, improving the flame-retardant efficiency and adhesive performance of the prepared silicone pressure-sensitive adhesive.

[0028] This invention successfully developed an organosilicon pressure-sensitive adhesive system with both high adhesion and excellent flame retardancy through a synergistic modification strategy of the aforementioned organosilicon tackifier (MQ-ETMS) and flame retardant (K-ADP). In terms of flame retardancy, K-ADP, through a gas-phase-condensed phase synergistic mechanism, synergistically constructs an inorganic-organic hybrid carbon layer with silica filler, which can increase the limiting oxygen index (LOI) of the tape to 29.4% and achieve immediate self-extinguishing when burned vertically. In terms of adhesion, MQ-ETMS enhances interfacial bonding through a dynamic cross-linking network, improving the peel strength of the organosilicon pressure-sensitive adhesive to the silicone rubber substrate. Detailed Implementation

[0029] The present invention will be further illustrated below with reference to the embodiments, the purpose of which is to better understand the content of the present invention and to demonstrate the essential features of the present invention. Therefore, the examples given should not be regarded as a limitation on the scope of protection of the present invention.

[0030] Example 1

[0031] The preparation of the tackifying and flame-retardant silicone pressure-sensitive adhesive includes the following steps:

[0032] S1. 15 g of vinyltrimethoxysilane, 30 g of toluene, and 0.15 g of Karstedt platinum catalyst (CAS No.: 81032-58-8) were added to a three-necked flask equipped with a condenser and a magnetic stirrer. After heating to 70 °C under a nitrogen atmosphere, 15 g of methyl hydrogen-containing silicone resin (0.7 mol / 100 g hydrogen content) and 30 g of toluene were mixed evenly and added dropwise to the three-necked flask through a constant pressure dropping funnel. The mixture was kept at this temperature for 3 h, and activated carbon was added and mixed for 1 h. The mixture was then filtered through a 0.22 µm filter to remove residual platinum catalyst. The filtrate was then distilled under reduced pressure to remove unreacted monomers and toluene, yielding a colorless and transparent organosilicon thickener (MQ-ETMS).

[0033] S2 uses γ-methacryloxypropyltrimethoxysilane (silane coupling agent KH-570, CAS No. 2530-85-0) to perform wet modification on aluminum diethylphosphonate (ADP-02, CAS No. 225789-38-8). First, a certain amount of aluminum diethylphosphonate is dispersed in anhydrous ethanol and ultrasonically treated for 30 min to obtain an aluminum diethylphosphonate solution. Then, silane coupling agent KH-570, anhydrous ethanol and deionized water are mixed at a mass ratio of 20:9:72. The pH value is adjusted to 4 by adding acetic acid to hydrolyze the mixture to obtain a mixture. The mixture is allowed to stand at room temperature for about 0.5 h until it becomes transparent. Then, the hydrolyzed and stood material is poured into the pre-dispersed aluminum diethylphosphonate solution and magnetically stirred at 50 °C for 2 h. After the reaction was completed, the mixture was cooled to room temperature. The resulting white suspension was centrifuged and filtered to obtain a white precipitate. The precipitate was washed with ethanol 2-3 times to obtain a white solid. The washed white solid was placed in a forced-air drying oven and dried at 60 °C for 12 h. The solid powder was then ground to obtain the modified aluminum diethylphosphinate flame retardant (K-ADP).

[0034] In a three-necked flask equipped with a water separator and a mechanical stirrer, S3 was added to 30 parts of methyl MQ silicone resin (M / Q = 0.65–0.75), 100 parts of 107 silicone rubber (molecular weight approximately 500,000), and 156 parts of toluene. The mixture was stirred under nitrogen protection, and 0.5% dibutyltin dilaurate was added while stirring. The stirring rate was controlled at 300 r / min. The temperature was raised to 110 °C, and the condensation reaction was carried out for 3 h. The mixture was then refluxed to separate water and toluene, yielding a colorless, transparent, viscous organosilicon pressure-sensitive adhesive liquid.

[0035] S4 was added to a high-speed mixer at 1500 r / min, along with 100 parts of silicone pressure-sensitive adhesive base solution, 0.5 parts of K-ADP, and 5 parts of silica filler. The mixture was then further dispersed using a three-roll mill until the particle size was less than 10 μm according to a scraper particle size test. Next, 80 parts of toluene solvent, 0.5 parts of 2,4-dichlorobenzoyl peroxide (DCBP), and 0.5 parts of MQ-ETMS were added and thoroughly mixed using a high-speed mixer to prepare a flame-retardant and tackifying silicone pressure-sensitive adhesive solution. The mixture was then coated onto the front side of a PET film, and the sample was baked in a 60 °C oven for 150 s to remove the solvent. Thermal crosslinking was then performed at 150 °C for 120 s to form a coating approximately 15 μm thick. After crosslinking, a polyester release film was applied to protect the adhesive layer. The same coating, baking, and thermal crosslinking process was then repeated on the back side of the PET film.

[0036] Example 2

[0037] The preparation of the tackifying and flame-retardant silicone pressure-sensitive adhesive includes the following steps:

[0038] S1. 15 g of vinyltrimethoxysilane, 41 g of toluene, and 0.55 g of Karstedt platinum catalyst were added to a three-necked flask equipped with a condenser and a magnetic stirrer. After heating to 95°C under a nitrogen atmosphere, 12.5 g of methyl hydrogen-containing silicone resin (0.7 mol / 100 g hydrogen content) and 41 g of toluene were mixed evenly and then added dropwise to the three-necked flask through a constant pressure dropping funnel. The mixture was kept at this temperature for 6 h, and activated carbon was added and mixed for 2 h. The mixture was then filtered through a 0.22 µm filter to remove residual platinum catalyst. The filtrate was then distilled under reduced pressure to remove unreacted monomers and toluene, yielding a colorless and transparent organosilicon thickener (MQ-ETMS).

[0039] S2 uses γ-methacryloxypropyltrimethoxysilane (silane coupling agent KH-570) to wet modify aluminum diethylphosphonate (ADP-02). First, a certain amount of aluminum diethylphosphonate is dispersed in anhydrous ethanol and ultrasonically treated for 30 min to obtain an aluminum diethylphosphonate solution. Then, silane coupling agent KH-570, anhydrous ethanol and deionized water are mixed at a mass ratio of 20:9:72. The pH value is adjusted to about 5 by adding acetic acid to hydrolyze the mixture. The mixture is allowed to stand at room temperature for about 2 h until it becomes transparent. Then, the hydrolyzed and stood material is poured into the pre-dispersed aluminum diethylphosphonate solution and magnetically stirred at 70°C for 1 h. After the reaction was completed, the mixture was cooled to room temperature. The resulting white suspension was centrifuged and filtered to obtain a white precipitate. The precipitate was washed with ethanol 2-3 times to obtain a white solid. The washed white solid was placed in a forced-air drying oven and dried at 80 °C for 12 h. The solid powder was then ground to obtain the modified aluminum diethylphosphinate flame retardant (K-ADP).

[0040] In a three-necked flask equipped with a water separator and a mechanical stirrer, S3 was added to 100 parts of methyl MQ silicone resin (M / Q = 0.65–0.75), 100 parts of 107 silicone rubber (molecular weight approximately 500,000), and 160 parts of toluene. The mixture was stirred under nitrogen protection, and 2% dibutyltin dilaurate was added during stirring. The stirring rate was controlled at 300 r / min, and the temperature was raised to 130 °C. The condensation reaction was carried out for 1 h, and the mixture was refluxed to separate water and toluene, yielding a colorless, transparent, viscous organosilicon pressure-sensitive adhesive liquid.

[0041] S4 was added to a high-speed mixer with 100 parts of silicone pressure-sensitive adhesive base liquid, 3 parts of K-ADP and 5 parts of silica filler. The mixture was stirred at 1500 r / min for 30 min and then further ground and dispersed using a three-roll mill until the particle size of the dispersed particles was less than 10 μm according to the scraper particle size test. Then, 80 parts of toluene solvent, 3 parts of 2,4-dichlorobenzoyl peroxide (DCBP) and 3 parts of MQ-ETMS were added and mixed thoroughly with a high-speed mixer to prepare a flame-retardant and tackifying silicone pressure-sensitive adhesive solution. The mixture was then coated on the front side of a PET film and baked in an oven at 100 ℃ for 60 s to remove the solvent. Then, it was thermally crosslinked at 180 ℃ for 80 s to form a coating with a thickness of about 30 μm. After crosslinking, a polyester release film was applied to protect the adhesive layer. The same coating, baking and thermal crosslinking were then performed on the back side of the PET film.

[0042] Example 3

[0043] The preparation of the tackifying and flame-retardant silicone pressure-sensitive adhesive includes the following steps:

[0044] S1. 15 g of vinyltrimethoxysilane, 40 g of toluene, and 0.5 g of Karstedt platinum catalyst were added to a three-necked flask equipped with a condenser and a magnetic stirrer. After heating to 85°C under a nitrogen atmosphere, 14 g of methyl hydrogen-containing silicone resin (0.7 mol / 100 g hydrogen content) and 40 g of toluene were mixed evenly and added dropwise to the three-necked flask through a constant pressure dropping funnel. The mixture was kept at this temperature for 5 h, and activated carbon was added and mixed for 2 h. The mixture was then filtered through a 0.22 µm filter to remove residual platinum catalyst. The filtrate was then distilled under reduced pressure to remove unreacted monomers and toluene, yielding a colorless and transparent organosilicon thickener (MQ-ETMS).

[0045] S2 employs a wet modification process for aluminum diethylphosphonate (ADP-02) using γ-methacryloxypropyltrimethoxysilane (silane coupling agent KH-570). First, a certain amount of aluminum diethylphosphonate is dispersed in anhydrous ethanol and ultrasonically treated for 30 min to obtain an aluminum diethylphosphonate solution. Then, silane coupling agent KH-570, anhydrous ethanol, and deionized water are mixed at a mass ratio of 20:9:72. The pH is adjusted to approximately 4 by adding acetic acid, and hydrolysis is performed to obtain a mixture. This mixture is allowed to stand at room temperature for about 1 hour until it becomes transparent. Next, the hydrolyzed and stood material is poured into the pre-dispersed aluminum diethylphosphonate solution and magnetically stirred at 70°C for 2 hours. After the reaction is complete, the mixture is cooled to room temperature, and the resulting white suspension is centrifuged and filtered to obtain a white precipitate. The precipitate is washed 2-3 times with ethanol to obtain a white solid. The washed white solid is then placed in a forced-air drying oven and dried at 60°C for 12 minutes. h, then the solid powder is ground to finally obtain the modified aluminum diethylphosphonate flame retardant (K-ADP).

[0046] In a three-necked flask equipped with a water separator and a mechanical stirrer, S3 was added 40 parts of methyl MQ silicone resin (M / Q = 0.65-0.75), 100 parts of 107 silicone rubber (molecular weight approximately 500,000), and 140 parts of toluene. The mixture was stirred under nitrogen protection, and 1% dibutyltin dilaurate was added during stirring. The stirring rate was controlled at 300 r / min, and the temperature was raised to 125 °C. The condensation reaction was carried out for 2 hours, followed by reflux to separate water and toluene, yielding a colorless, transparent, viscous organosilicon pressure-sensitive adhesive liquid.

[0047] S4 was added to a high-speed mixer with 100 parts of silicone pressure-sensitive adhesive base liquid, 1.5 parts of K-ADP and 5 parts of silica filler. The mixture was stirred at 1500 r / min for 20 min and then further ground and dispersed using a three-roll mill until the particle size of the dispersed particles was less than 10 μm according to the scraper particle size test. Then, 80 parts of toluene solvent, 1.5 parts of 2,4-dichlorobenzoyl peroxide (DCBP) and 1.5 parts of MQ-ETMS were added and mixed thoroughly with a high-speed mixer to prepare a flame-retardant and tackifying silicone pressure-sensitive adhesive solution. The mixture was then coated on the front side of a PET film and baked in an oven at 80 ℃ for 90 s to remove the solvent. Then, it was thermally crosslinked at 150 ℃ for 90 s to form a coating with a thickness of about 25 μm. After crosslinking, a polyester release film was applied to protect the adhesive layer. The same coating, baking and thermal crosslinking were then performed on the back side of the PET film.

[0048] Comparative Example 1

[0049] Compared to Example 3, the silicone tackifier MQ-ETMS and flame retardant K-ADP were not added.

[0050] Comparative Example 2

[0051] Compared to Example 3, no silicone tackifier MQ-ETMS was added.

[0052] Comparative Example 3

[0053] Compared to Example 3, no flame retardant K-ADP was added.

[0054] Comparative Example 4

[0055] Compared to Example 3, the flame retardant used is aluminum diethylphosphonate (ADP-02, CAS No. 225789-38-8).

[0056] The silicone pressure-sensitive adhesive samples prepared in the above embodiments and comparative examples were tested for peel strength, limiting oxygen index, and vertical burning performance. The test standards are as follows:

[0057] Peel strength test: The standard ASTM-D3330 is followed. The pressure-sensitive tape is fully bonded to a 15mm×30mm silicone plate, and after being rolled by a 2kg pressure roller, a 180° peel test is performed on a universal testing machine at a speed of 50mm / min.

[0058] Limiting oxygen index test: The limiting oxygen index of 150 mm × 58 mm flame-retardant silicone double-sided tape was determined using an HC-2 oxygen index tester (Nanjing, China) in accordance with GB / T 5454-1997.

[0059] Vertical burning performance test: According to standard AATCC 6941, a vertical burning test was conducted on a 150×60mm double-sided tape using a Jiangning CZF-3 device at an ignition time of 12 s and a flame height of 40 mm.

[0060] Table 1. Performance test results of silicone pressure-sensitive adhesives in Examples 1-3 and Comparative Examples 1-4

[0061] Preparation Example Peel strength N / 25mm Limiting oxygen index % Flame retardancy Example 1 >16.0 28.5 UL94-V0 Example 2 >16.0 29.0 UL94-V0 Example 3 >16.0 29.4 UL94-V0 Comparative Example 1 11.3 24.0 UL94-V1 Comparative Example 2 10.6 29.2 UL94-V0 Comparative Example 3 >16.0 24.5 UL94-V1 Comparative Example 4 10.2 28.3 UL94-V0

[0062] As can be seen from the table, in Examples 1-3, both peel strength and flame retardancy are significantly improved. That is, the present invention prepares an organosilicon pressure-sensitive adhesive system with both high adhesion and excellent flame retardancy through the synergistic modification strategy of tackifier (MQ-ETMS) and flame retardant (K-ADP).

[0063] In terms of adhesion performance, the peel strength of the samples prepared in Example 3 and Comparative Example 3 both exceeded the peak value >16.0 N / 25 mm. That is, the tackifier (MQ-ETMS) in the preparation method of the present invention has a good tackifying effect as an additive. The tackifier (MQ-ETMS) can enhance the interfacial bonding through a dynamic cross-linking network, which greatly improves the 180° peel strength of the silicone pressure-sensitive adhesive to the silicone rubber substrate.

[0064] Regarding flame retardant performance, the samples prepared in Example 3 and Comparative Example 2 showed a significant improvement in limiting oxygen index. Compared to Comparative Example 1 and Comparative Example 3, where no flame retardant (K-ADP) was added during preparation, the limiting oxygen index could be increased from approximately 24% to 29.4%. That is, the flame retardant (K-ADP) in the preparation method of this invention has a good flame retardant effect as an additive on its own. Its mechanism lies in the fact that it works in conjunction with silica filler to construct an inorganic-organic hybrid carbon layer through a gas-phase-condensed phase synergistic mechanism, thereby improving the limiting oxygen index (LOI) of the tape. During the test, it can burn vertically and achieve immediate self-extinguishing.

[0065] As can be seen from the comparison between Example 3 and Comparative Example 4, the preparation process of the silicone pressure-sensitive adhesive of the present invention is the same. Under the same conditions of adding the same amount (1.5 parts) of tackifier (MQ-ETMS), the flame retardant K-ADP is replaced with aluminum diethylphosphinate ADP-02, which improves the flame retardant performance, but affects the adhesive performance and significantly reduces the peel strength. That is, compared with the unmodified aluminum diethylphosphinate ADP-02, the flame retardant K-ADP improves the compatibility of a silicone material, which is beneficial to the dispersion of the flame retardant in the silicone material and can improve the peel strength of the flame-retardant silicone pressure-sensitive adhesive.

[0066] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0067] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A method for preparing a tackifying and flame-retardant organosilicon pressure-sensitive adhesive, characterized in that, Includes the following steps: S1 involves stirring and heating vinyltrimethoxysilane, solvent, and platinum catalyst under a nitrogen atmosphere to 70-95 °C, then adding a mixture of methyl hydrogen-containing silicone resin and solvent at constant pressure and maintaining the temperature for 3-6 h. Activated carbon is then added and mixed for 1-2 h before filtration. The filtrate is then distilled under reduced pressure to obtain the organosilicon thickener. S2 disperses a certain amount of aluminum diethylphosphonate in anhydrous ethanol and sonicates it to obtain an aluminum diethylphosphonate solution. Separately, a silane coupling agent containing an olefin bond, anhydrous ethanol, and deionized water are mixed and an acid catalyst is added for hydrolysis. After hydrolysis, the mixture is allowed to stand at room temperature until it becomes transparent. The material after standing is then poured into the aluminum diethylphosphonate solution and stirred and heated at 50-70 °C for 1-2 hours. After the reaction, the mixture is cooled to room temperature, centrifuged, and filtered to obtain a precipitate. The precipitate is washed with ethanol and dried at 60-80 °C to obtain a solid powder. The solid powder is then ground to obtain a modified aluminum diethylphosphonate flame retardant. S3 involves stirring methyl MQ silicone resin, 107 silicone rubber, and toluene under nitrogen protection until homogeneous, then adding a catalyst, stirring and heating to carry out a condensation reaction, and finally condensing and separating water and toluene to obtain the base liquid. S4 mixes the base liquid prepared in S3, the flame retardant prepared in S2, and the silica filler evenly, then grinds and disperses them. Then, toluene solvent, initiator, and organosilicon tackifier prepared in S1 are added and thoroughly mixed to obtain a flame-retardant and tack-enhancing organosilicon pressure-sensitive adhesive solution. The organosilicon pressure-sensitive adhesive solution is coated on the substrate, and then the sample is subjected to solvent evaporation and crosslinking to obtain an organosilicon pressure-sensitive coating. A layer of polyester release film is then covered, and the other side of the substrate is coated in the same way to obtain an organosilicon pressure-sensitive tape. The mass ratio of vinyltrimethoxysilane and methyl hydrogen-containing silicone resin in S1 is (1~1.2):1; the mass ratio of olefin-containing silane coupling agent, anhydrous ethanol and deionized water in S2 is 20:9:72; the mass ratio of 107 silicone rubber and methyl MQ silicone resin in S3 is 100:(30~100); and the mass ratio of tackifier, flame retardant, silica filler and base liquid in S4 is (0.5~3):(0.5~3):5:

100.

2. The preparation method according to claim 1, characterized in that, In S1, the amount of platinum catalyst used is 0.5% to 2% of the total mass of vinyltrimethoxysilane and methyl hydrogen silicone resin.

3. The preparation method according to claim 1, characterized in that, In S1, the solvent is toluene or xylene, and the amount of solvent used is 2 to 3 times the total mass of vinyltrimethoxysilane and methyl hydrogen-containing silicone resin.

4. The preparation method according to claim 1, characterized in that, In S2, the olefin-containing silane coupling agent is at least one of vinyltrimethoxysilane, vinyltriethoxysilane, and γ-methacryloyloxypropyltrimethoxysilane.

5. The preparation method according to claim 1, characterized in that, In S2, the acid catalyst is acetic acid or hydrochloric acid, and the hydrolysis pH is 4-5.

6. The preparation method according to claim 1, characterized in that, In S3, the catalyst is any one of acetic acid, triethylamine or dibutyltin dilaurate, and the amount of catalyst used is 0.5% to 2% of the total mass of 107 silicone rubber and methyl MQ silicone resin.

7. The preparation method according to claim 1, characterized in that, In S3, the condensation reaction temperature is 110~130 ℃ and the reaction time is 1~3 h.

8. The preparation method according to claim 1, characterized in that, In S4, after grinding and dispersion, the particle size of the dispersed particles, as determined by scraper particle size testing, is less than 10 μm.

9. The preparation method according to claim 1, characterized in that, In S4, the initiator is 2,4-dichlorobenzoyl peroxide or benzoyl peroxide, the solvent evaporation temperature is 60~100℃, the evaporation time is 60~150s, the crosslinking temperature is 150~180℃, the crosslinking time is 80~120s, and the thickness of the silicone pressure-sensitive adhesive coating is 15~30μm.