A silicone pressure-sensitive adhesive for autoclave molding and a method for preparing the same

Abstract

The present application provides a kind of hot press tank forming organic silicon pressure sensitive adhesive and its preparation method, the pressure sensitive adhesive includes the following weight parts of each component: modified silicone resin 40-50 parts, fiber prepreg 10-30 parts, methyl vinyl silicone rubber 30-50 parts, reinforcing filler 10-30 parts, catalyst 0.1-1.0 parts, half reinforcing filler 20-50 parts, heat-resistant agent 0.1-5 parts, peroxide 1-3 parts.The present application solves the brittleness problem of material after high temperature curing by grafting modification of straight chain and stereoscopic structure siloxane, while adding binary acid anhydride and binary amine modification, reduces the vulcanization temperature, improves the bonding strength with PI film, substrate peeling without residue after high temperature and excellent air tightness.

Description

Technical Field

[0001] This invention relates to the field of organosilicon technology, specifically to an organosilicon pressure-sensitive adhesive and its preparation method. Background Technology

[0002] Currently, there are no such products in China, creating a gap in the market. Foreign products are expensive, have long lead times, and are subject to uncertainty, severely hindering the development of new materials in my country. Compared to ordinary silicone pressure-sensitive adhesives, this product has the following advantages:

[0003] (1) Solvent-free, high solids content, relatively safe production, and extrusion molding process, no baking required, reducing energy consumption;

[0004] (2) Generally, high-temperature resistant silicone resins become brittle after high-temperature curing, which increases the risk of pressure leakage and makes the cleaning of the substrate after film removal more difficult. The main reason is that the skeleton material is not resistant to temperature and not flexible enough, and the silicone resin used has a low crosslinking density and no flexible segments.

[0005] (3) The surface of polyimide film is smooth and has poor adhesion. It is difficult to bond effectively with general adhesives, which leads to slippage or detachment during vacuuming, resulting in failure of sealing and pressure holding. Conventional treatment methods include alkali treatment, plasma treatment or acetone wiping of the polyimide film surface, which increases the process flow and reduces production efficiency.

[0006] Currently, the methods for preparing organosilicon pressure-sensitive adhesives involve polycondensation of fluorinated benzene silicone resin and silicone rubber, followed by peroxide vulcanization and coating. Solvents are also used, resulting in high material costs and complex molding processes (see Chinese Patent Application No. CN110144192A, which discloses a method for preparing organosilicon pressure-sensitive adhesives). (Other patents include EP,0328021; EP,0295561; US,6,291,341; EP,1161455; Japanese Patent Publication, JP2003-321691, JP2004-346118, JP2006-111110.) Summary of the Invention

[0007] This invention provides an organosilicon pressure-sensitive adhesive and its preparation method. This invention addresses the brittleness problem of materials after high-temperature curing through graft modification with linear and stereochemical siloxanes. Simultaneously, the addition of diacid anhydrides and diamines lowers the vulcanization temperature, improves adhesion strength to PI films, ensures no residue after high-temperature substrate peeling, and enhances airtightness.

[0008] The objective of this invention is achieved through the following technical solution:

[0009] This invention provides a pressure-sensitive adhesive, comprising the following components in parts by weight:

[0010]

[0011]

[0012] The modified silicone resin is prepared from the following components in parts by weight:

[0013]

[0014] The dimethylsiloxane is selected from aminopropyl-terminated polydimethylsiloxane and aminopropyl-terminated polymethylphenylsiloxane.

[0015] The dicarboxylic anhydride includes at least one of 3,3',4,4'-benzophenone tetracarboxylic anhydride, 3,3',4,4'-biphenyltetracarboxylic anhydride, bisphenol A type diether dianhydride, and 4,4'-(hexafluoroisopropene) phthalic anhydride.

[0016] The diamine includes at least one of 4,4'-diaminodiphenyl ether, 2,2-bis[4-(4-aminophenoxy)phenyl]propane, 2,2'-bis(trifluoromethyl)-4,4-diaminobiphenyl, and 2-(4-aminophenyl)-5-aminobenzimidazole.

[0017] Solvent 1 is selected from cyclohexanone or N-methylpyrrolidone; solvent 2 is selected from at least one of toluene, xylene, and chloroform.

[0018] The preparation method of the modified silicone resin includes the following steps:

[0019] Step 1: Mix dimethylsiloxane and diamine in solvent 1 (50-60% by mass) to prepare mixture 1 for later use;

[0020] Step 2: In the reaction vessel, add diacid anhydride and the remaining solvent 1, stir evenly at 23℃-32℃ and add mixture 1 dropwise, raise the temperature to 80-90℃ and react for 1.5-2h; add solvent 2 again, raise the temperature to 140-110℃ and maintain for 2-3h to carry out imidization reaction, the product is a yellowish-brown liquid.

[0021] Step 3: After cooling the yellowish-brown liquid to ambient temperature, add methanol solution to precipitate it. Filter the precipitate and dry it to obtain the modified silicone resin.

[0022] The fiber prepreg is prepared from the following components in parts by weight:

[0023] 50-60 parts of dimethyl silicone oil

[0024] 30-40 parts fiber

[0025] 10-20 parts of coupling agent.

[0026] The method for preparing the fiber prepreg includes the following steps:

[0027] Add a coupling agent to dimethyl silicone oil, then add the fiber in batches, and mix at 80-100℃ for 2-3 hours.

[0028] The dimethyl silicone oil is methyl-terminated polydimethyl silicone oil;

[0029] The fiber is selected from at least one of aramid fiber, carbon fiber, alkali-free glass fiber, regenerated fiber, nitrate optical fiber, polytetrafluoroethylene fiber, polyimide fiber, and ceramic fiber; the fiber is used to improve dimensional stability at high temperatures and its structure is not easily degraded.

[0030] The coupling agent includes at least one of aminopropyltriethoxysilane and glycidyl etheroxypropyltrimethoxysilane.

[0031] The preparation method includes the following steps:

[0032] Modified silicone resin, fiber prepreg, reinforcing filler, heat resistant agent, methyl vinyl silicone rubber and catalyst are added sequentially to a mixer or kneader. The temperature is controlled at 90-110℃, and the reaction is carried out for 2-3 hours until the mixture is uniform. Then, semi-reinforcing filler is added, the temperature is lowered to 50-60℃, peroxide is added and stirred evenly. The mixture is then discharged and allowed to stand before being extruded and molded.

[0033] The reinforcing filler is at least one of precipitated silica, hydrophilic fumed silica, and hydrophobic fumed silica with a surface treated with hexamethyldisilazane; it increases tensile strength and thixotropy at high temperatures.

[0034] The semi-reinforcing filler is selected from one or two of zinc oxide, aluminum hydroxide, titanium dioxide, mica powder, calcium carbonate, and talc powder, which reduces costs while increasing dimensional stability.

[0035] The peroxide is one of 2,4-dichlorobenzoyl peroxide, 2,5-dimethyl-2,5-bis(tert-butylperoxide)hexane, and dicumyl peroxide; through vulcanization, film formation is achieved at low temperature and quickly, reducing the resin crosslinking temperature and improving the initial strength.

[0036] The catalyst is one or two of the following: dibutyltin dilaurate, nitrate, etc., which polymerize hydroxyl functional groups and co-sulfurize different types of resins.

[0037] The modified silicone resin of this invention uses an organopolysiloxane with at least two amino groups at the end groups and a diacid anhydride for polycondensation, while simultaneously using a diamine for chain extension.

[0038] Dicarboxylic acid anhydrides can be:

[0039]

[0040]

[0041] Diamines can be:

[0042]

[0043]

[0044] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0045] (1) By using silicone resin material with a three-dimensional network structure as the main body, the temperature resistance of the skeleton material is improved to above 300℃, and the crosslinking density of the resin is increased by modifying different functional groups, thereby improving the heat resistance to 421℃.

[0046] (2) By selecting intermediates and designing curing agents, the material can undergo a certain cross-linking reaction with the polyimide film after heating, which improves its adhesion.

[0047] (3) By adding some functional fillers and fibers, not only is the high temperature stability increased, but the product cost is also reduced, making it more cost-effective than competing products.

[0048] (4) By adopting the method of the present invention, a putty pressure-sensitive adhesive that is resistant to high temperature of 421℃, does not become brittle, has high air tightness, low peeling residue, and good PI film adhesion was prepared. It can be used for polyimide materials or other special materials that require high temperature and high temperature vacuum assisted molding. Moreover, all the materials used are domestic raw materials, which are independently controllable, solve the gap in domestic products, and provide a guarantee for the research and development of aerospace materials.

[0049] (5) The product prepared by this method is a putty-like pressure-sensitive adhesive. The manufacturing process is relatively safe, easy to form, and convenient to construct. At the same time, it increases the utilization rate of the mold, reduces the risk of pressure leakage, and improves the product qualification rate. Detailed Implementation

[0050] The present invention will be described in detail below with reference to embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make several adjustments and improvements without departing from the concept of the present invention. These all fall within the protection scope of the present invention.

[0051] Preparation Example 1: Preparation of Modified Silicone Resin

[0052] The preparation method of the modified silicone resin includes the following steps:

[0053] 1. Preparation of Mixture 1: Mixture 1 is prepared by mixing 60.0g of aminopropyl-terminated polydimethylsiloxane (average degree of polymerization 40) and 20.0g of diamine with 80.0g of cyclohexanone solvent and letting it stand for later use.

[0054] 2. Prepare a 1000mL glass reactor, purge with nitrogen, add 20.0g of diacid anhydride and 10.0g of cyclohexanone solvent, stir at low temperature (23℃-32℃) until homogeneous, and slowly add the prepared mixture 1 dropwise. After the addition is complete, slowly raise the temperature to 80℃ and react for 1.5h. Add 50.0g of toluene solution again, raise the temperature to 160℃, and maintain for 3h to carry out the imidization reaction. The product is a yellowish-brown liquid.

[0055] Post-processing: After cooling the yellowish-brown liquid obtained from the reaction to room temperature, pour it into a methanol solution to precipitate the modified silicone resin. Filter the precipitate and dry it for later use.

[0056] The raw material components and contents are shown in Table 1.

[0057] Table 1 Units (mass, g)

[0058]

[0059]

[0060] Preparation Example 2: Preparation of Fiber Prepreg

[0061] Dimethyl silicone oil is added in an internal mixer (or kneader) according to the dosage in Table 2, then a coupling agent is added, and aramid fiber or carbon fiber is added in batches. The temperature is controlled at 80-100℃, and the mixture is stirred for 3 hours until it is uniform to obtain fiber prepreg.

[0062] The raw material composition and content of the fiber prepreg are shown in Table 2.

[0063] Table 2 (Unit: mass g)

[0064]

[0065] Examples 1-4

[0066] Examples 1-4 provide a pressure-sensitive adhesive and its preparation method.

[0067] The preparation method of pressure-sensitive adhesive is as follows:

[0068] The modified resin of Preparation Example 1 was added to a mixer (or a kneader), and then the fiber prepreg of Preparation Example 2, reinforcing filler, heat resistant agent, methyl vinyl silicone rubber and catalyst were added in sequence. The temperature was controlled at 90-110℃, and the reaction was carried out for 2-3 hours until the mixture was uniform. Then, semi-reinforcing filler was added, the temperature was lowered to 50-60℃, peroxide was added and stirred evenly. The mixture was then discharged and allowed to stand, and then extruded into strips.

[0069] The components and contents of the pressure-sensitive adhesive are shown in the table below:

[0070] Table 3 Units (weight)

[0071]

[0072] Comparative Example 1

[0073] The difference between this comparative example and Example 1 is that the modified silicone resin is replaced with pure polymethyl silicone resin. It hardens significantly at 400°C and undergoes slight deformation due to vacuum conditions. Cracking occurs during the deformation process, leading to vacuum failure (vacuum degree drops from -0.068MPa to 0MPa), and the product is scrapped.

[0074] Comparative Example 2

[0075] The difference between this comparative example and Example 1 is that the modified silicone resin was replaced with acrylic modified silicone resin (Shenzhen Jipeng Silicon Fluorine Materials). At 350°C, aging and degradation occurred, the adhesive softened and began to deform, leading to sealing failure, vacuum depressurization (vacuum degree dropped from -0.068MPa to 0MPa), and the product was scrapped.

[0076] Comparative Example 3

[0077] The difference between this comparative example and Example 1 is that the fiber prepreg was replaced with direct aramid fiber (1.5D / 3mm, Taihe New Material). After the product was heated to high temperature, abnormalities such as collapse, unevenness, and pinholes appeared, and the deformation was severe. In 10 tests, there were 9 instances of pressure loss (vacuum degree reduction value exceeded 0.03MPa).

[0078] Comparative Example 4

[0079] The difference between this comparative example and Example 1 is that cerium oxide is replaced with iron oxide heat resistant agent. After the product is kept at 421°C for 2 hours, it will show severe discoloration, thinning, softening and deformation.

[0080] Comparative Example 5

[0081] The difference between this comparative example and Example 1 is that the ratio of modified silicone resin to 110-2 methyl vinyl silicone rubber is 90:10. The rubber compound has higher hardness and lower elasticity. When bonding complex tooling, it may cause lifting after vulcanization and failure to bond tightly, resulting in vacuum leakage (vacuum degree drops from -0.068MPa to 0MPa).

[0082] Comparative Example 6

[0083] The difference between this comparative example and Example 1 is that the ratio of modified silicone resin to 110-2 methyl vinyl silicone rubber is 20:80. The strength of the rubber compound after vulcanization is lower, and the adhesion to the substrate is reduced.

[0084] Performance testing

[0085] 1. Test conditions

[0086] Referring to HB5481-1991 regarding room temperature and high temperature sealing performance and cleanability after high temperature, the test temperature was changed from 180℃ to 421℃.

[0087] 2. Test Results

[0088]

[0089]

[0090] The specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various modifications or variations within the scope of the claims, which do not affect the essence of the present invention.

Claims

1. A pressure-sensitive adhesive, characterized in that, The components include the following parts by weight: 40-50 parts of modified silicone resin 10-30 parts of fiber prepreg 30-50 parts of methyl vinyl silicone rubber 10-30 parts of reinforcing filler Catalyst 0.1-1.0 parts 20-50 parts of semi-reinforcing filler Heat resistant agent 0.1-5 parts Peroxide 1-3 parts; The modified silicone resin is prepared from the following components in parts by weight: 60-80 parts of dimethylsiloxane 20-30 parts of dicarboxylic anhydride 20-30 parts of diamine Solvent 1100-150 parts Solvent 250-100 parts; The dimethylsiloxane is selected from aminopropyl-terminated polydimethylsiloxane and aminopropyl-terminated polymethylphenylsiloxane. The dicarboxylic anhydride includes at least one of 3,3',4,4'-benzophenone tetracarboxylic anhydride, 3,3',4,4'-biphenyl tetracarboxylic anhydride, bisphenol A type diether dianhydride, and 4,4'-(hexafluoroisopropene) phthalic anhydride; Solvent 1 is selected from cyclohexanone or N-methylpyrrolidone; solvent 2 is selected from at least one of toluene, xylene, and chloroform. The diamine includes at least one of 4,4'-diaminodiphenyl ether, 2,2-bis[4-(4-aminophenoxy)phenyl]propane, 2,2'-bis(trifluoromethyl)-4,4-diaminobiphenyl, and 2-(4-aminophenyl)-5-aminobenzimidazole; The reinforcing filler is at least one of precipitated silica, hydrophilic fumed silica, and hydrophobic fumed silica with a surface treated with hexamethyldisilazane. The semi-reinforcing filler is selected from one or two of zinc oxide, aluminum hydroxide, titanium dioxide, mica powder, calcium carbonate, and talc.

2. The pressure-sensitive adhesive according to claim 1, characterized in that, The preparation method of the modified silicone resin includes the following steps: Step 1: Mix dimethylsiloxane and diamine in solvent 1 (50-60% by mass) to prepare mixture 1 for later use; Step 2: In the reaction vessel, add diacid anhydride and the remaining solvent 1, stir evenly at 23℃-32℃ and add mixture 1 dropwise, raise the temperature to 80-90℃ and react for 1.5-2h; add solvent 2 again, raise the temperature to 140-170℃ and maintain for 2-3h to carry out the imidization reaction, the product is a yellowish-brown liquid. Step 3: After cooling the yellowish-brown liquid to ambient temperature, add methanol solution to precipitate it. Filter the precipitate and dry it to obtain the modified silicone resin.

3. The pressure-sensitive adhesive according to claim 1, characterized in that, The fiber prepreg is prepared from the following components in parts by weight: 50-60 parts of dimethyl silicone oil 30-40 parts fiber 10-20 parts of coupling agent.

4. The pressure-sensitive adhesive according to claim 3, characterized in that, The method for preparing the fiber prepreg includes the following steps: Add a coupling agent to dimethyl silicone oil, then add the fiber in batches, and mix at 80-100℃ for 2-3 hours.

5. The pressure-sensitive adhesive according to claim 3, characterized in that, The dimethyl silicone oil is methyl-terminated polydimethyl silicone oil; The fiber is selected from at least one of aramid fiber, carbon fiber, alkali-free glass fiber, regenerated fiber, nitrate optical fiber, polytetrafluoroethylene fiber, polyimide fiber, and ceramic fiber; The coupling agent includes at least one of aminopropyltriethoxysilane and glycidyl etheroxypropyltrimethoxysilane.

6. A method for preparing a pressure-sensitive adhesive as described in any one of claims 1-5, characterized in that, The preparation method includes the following steps: Modified silicone resin, fiber prepreg, reinforcing filler, heat resistant agent, methyl vinyl silicone rubber and catalyst are added sequentially to a mixer or kneader. The temperature is controlled at 90-110℃. After reacting for 2-3 hours until the mixture is uniform, semi-reinforcing filler is added, the temperature is lowered to 50-60℃, peroxide is added and stirred evenly. The mixture is then discharged and allowed to stand before being extruded into shape.

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