One-component addition-curing silicone rubber with excellent adhesion to inert hard-to-bond substrates and its preparation method

Abstract

The present invention discloses a one-component addition-type silicone rubber having excellent adhesion to an inert and difficult-to-bond substrate and a preparation method thereof. The silicone rubber is composed of the following components by mass: 50-70 parts of base rubber, 10-20 parts of vinyl-terminated polydimethylsiloxane, 10-15 parts of polydimethylmethylvinylsiloxane, 7-15 parts of polydimethylmethylhydrogensiloxane, 0.5-2 parts of a first tackifier, 0.001-0.1 parts of a second tackifier, 0.1-0.5 parts of an inhibitor, and 0.1-0.5 parts of a catalyst. The above components are stirred and mixed in a planetary mixer at room temperature for 2 hours, and then subjected to vacuum degassing treatment at room temperature for 15 minutes to obtain a silicone rubber product; the viscosity of the silicone rubber is less than 40000mPa.s, and the bonding shear strength for nickel-nickel is greater than 4.0Mpa. It has excellent adhesion to inert and difficult-to-bond substrates (gold, silver, nickel, etc.) without using traditional primers. The operation is simple, convenient and efficient, which greatly expands the application scenarios of existing addition-type silicone rubber adhesives, especially in the field of electronic chip packaging.

Description

Technical Field

[0001] The present invention belongs to the technical field of polymer materials, and particularly relates to a one-component addition-curing silicone rubber having excellent adhesion to inert and difficult-to-bond substrates and a preparation method thereof. Background Art

[0002] Addition-curing liquid silicone rubber is a network structure polymer formed by the hydrosilylation cross-linking reaction of vinyl-containing organopolysiloxane and silicon-hydrogen bond-containing organopolysiloxane under the action of a platinum catalyst at room temperature or by heating. Since no by-products are generated during the cross-linking and curing process, and the obtained silicone rubber is non-toxic, environmentally friendly, and has a wide temperature resistance range, it is widely used in industries such as electronics and electric power. However, addition-curing liquid silicone rubber has a low molecular polarity, weak surface interaction with the adhered substrate after vulcanization, and poor adhesion performance.

[0003] Currently, a variety of methods have been developed to improve the adhesion performance of addition-curing liquid silicone rubber to substrates, such as using primer and tackifier. Using primer can increase the adhesion of silicone rubber to the substrate, but it will increase the production process and production time, reduce production efficiency, and a large amount of volatile and flammable solvents need to be used, which will cause transportation hazards, environmental pollution, human injury, etc. The method of adding tackifier to improve adhesion is simple and convenient to operate, and it is easy to control the product quality. Currently, many tackifiers have been applied to improve the adhesion performance of addition-curing liquid silicone rubber to metal substrates (such as aluminum, copper, and stainless steel) and non-metal substrates (such as PC, nylon, and PCB boards), but there is no obvious improvement in the adhesion to inert and difficult-to-bond substrates such as gold, silver, and nickel.

[0004] The existing patent document CN110387128A (a self-adhesive one-component addition-curing silicone rubber and its preparation method) discloses a one-component addition-curing silicone rubber having self-adhesion to nickel, silver, and gold substrates. It uses the polymerization product of borate and silane coupling agent as a tackifier. Borate is prone to hydrolysis and thus smokes in the air, so it is relatively dangerous and not easy to be produced on an industrial scale during the synthesis of the tackifier; in addition, this type of tackifier uses the electron-deficient structure of boron to form a coordination bond with the substrate to promote adhesion, and its coordination force is weak. Therefore, the shear strength of the self-adhesive silicone rubber for nickel-nickel adhesion is low (≤3.1 MPa) and the shear strength of adhesion fluctuates greatly and unstably (the fluctuation range is between 0.8 and 3.1 MPa). Therefore, there is an urgent need to develop an addition-curing silicone rubber with better adhesion to achieve excellent, stable, and reliable adhesion to difficult-to-bond substrates such as gold, silver, and nickel. Summary of the Invention

[0005] In order to solve the above technical problems, the present invention provides a one-component addition-type silicone rubber with excellent adhesion to inert and difficult-to-bond substrates (such as gold, silver, nickel, etc.). Two tackifiers of different compositions are used to cooperate with each other to make the silicone rubber and the substrate have a stronger bonding force. The silicone rubber has a nickel-nickel bonding shear strength of >4.0Mpa; and by adding white carbon black and selecting siloxanes of different composition structures that can form an optimized cross-linked network structure, the silicone rubber product can also have a lower viscosity (<40000mPa.s). The cured silicone rubber has very excellent physical and mechanical properties, with a tensile strength of more than 8MPa and an elongation at break of more than 400%, and is particularly suitable for use as a sealing adhesive and chip packaging adhesive in the electronics industry.

[0006] The purpose of the present invention is achieved through the following technical solutions:

[0007] A one-component addition silicone rubber having excellent adhesion to inert and difficult-to-bond substrates, comprising the following components in parts by mass:

[0008] 50-70 parts of base glue, 10-20 parts of vinyl-terminated polydimethylsiloxane, 10-15 parts of polydimethylmethylvinylsiloxane, 7-15 parts of polydimethylmethylhydrogensiloxane, 0.5-2 parts of first tackifier, 0.001-0.1 parts of second tackifier, 0.1-0.5 parts of inhibitor and 0.1-0.5 parts of catalyst.

[0009] In the present invention, the base rubber is obtained by kneading vinyl-terminated polydimethylsiloxane and surface-treated white carbon black: by weight, 40 to 70 parts of vinyl-terminated polydimethylsiloxane, 30 to 60 parts of white carbon black, 3 to 5 parts of hexamethyldisilazane, 0 to 1 part of tetramethyldivinyldisilazane and 1 to 2 parts of water are kneaded in a kneader for 3 to 6 hours, then the temperature is raised to 150°C, the vacuum degree is maintained at ≤-0.08MPa, and the kneading is continued for 2 to 4 hours to obtain the base rubber.

[0010] Further,

[0011] The viscosity of the vinyl-terminated polydimethylsiloxane used in the preparation of the base glue is 3000-50000 mPa.s;

[0012] The white carbon black is selected from 2 / g, 200m 2 / g, 250m 2 / g、300m 2 / g, 380m 2 / g of fumed silica or precipitated silica, or a mixture of one or more thereof.

[0013] In the present invention, vinyl-terminated polydimethylsiloxane is used as a chain extender; polydimethylmethylvinylsiloxane and polydimethylmethylhydrogensiloxane are used as crosslinking agents.

[0014] Furthermore,

[0015] The viscosity of the vinyl-terminated polydimethylsiloxane is 500 - 5000 mPa·s;

[0016] The viscosity of the polydimethylmethylvinylsiloxane is 200 - 2000 mPa·s, and the vinyl content (mass fraction) is 1 - 8%;

[0017] The viscosity of the polydimethylmethylhydrogensiloxane is 30 - 120 mPa·s, and the hydrogen content (mass fraction) is 0.2 - 1%.

[0018] In the present invention, the first tackifier is prepared by the following method: at room temperature, tetramethylcyclotetrasiloxane, an alkenyl-containing trialkoxysilane, and an alkenyl-containing succinic anhydride are mixed evenly; while stirring, a platinum catalyst is added, and after stirring evenly, the temperature is raised to 45 - 110 °C for reaction for 3 - 12 h; after the reaction is completed, it is cooled to room temperature, and low-boiling substances are removed by vacuum distillation to obtain a first tackifier containing alkoxy groups and succinic anhydride with a yield of more than 90%.

[0019] Furthermore,

[0020] The alkenyl-containing trialkoxysilane is selected from one or more of vinyltrimethoxysilane, vinyltriethoxysilane, allyltriethoxysilane, allyltrimethoxysilane, 5-hexenyltriethoxysilane, 5-hexenyltrimethoxysilane, 7-octenyltrimethoxysilane, 3-(acryloyloxy)propyltrimethoxysilane, and 3-(methacryloyloxy)propyltrimethoxysilane;

[0021] The alkenyl-containing succinic anhydride is selected from one or more of allyl succinic anhydride, 2-butenyl succinic anhydride, (2-methyl-2-propyl-1-)succinic anhydride, 2-hexen-1-yl succinic anhydride, 2-octenyl succinic anhydride, and 2-dodecenyl succinic anhydride;

[0022] The platinum catalyst is one of chloroplatinic acid, platinum-vinylsiloxane complex, or platinum-alcohol complex, and a platinum catalyst supported on a silica, carbon, or alumina carrier, and the mass content of platinum atoms in the reaction system for preparing the first tackifier is 0.5 - 15 ppm;

[0023] The molar ratio of the tetramethylcyclotetrasiloxane, the alkenyl-containing trialkoxysilane, and the alkenyl-containing succinic anhydride is 1: 0.1 - 5: 0.1 - 5.

[0024] In the present invention, the second tackifier is prepared by the following method: at room temperature, a mercapto-silane coupling agent is uniformly mixed with a compound containing an unsaturated double bond and an active hydroxyl group; while stirring, a titanate catalyst is added, and after stirring evenly, the temperature is raised to 50 - 120 °C and the reaction is carried out for 0.5 - 8 h to obtain a reaction mixture; then, under the conditions of 60 °C and a vacuum degree of -0.1 MPa, low-boiling substances are removed to obtain a second tackifier containing an unsaturated double bond and a mercapto group with a yield of more than 85%.

[0025] Furthermore,

[0026] The mercapto-silane coupling agent is selected from one or more of γ-mercaptopropyltrimethoxysilane, γ-mercaptopropyltriethoxysilane, γ-mercaptopropylmethyldimethoxysilane, γ-mercaptomethylmethyldiethoxysilane;

[0027] The compound containing an unsaturated double bond and an active hydroxyl group is selected from one or more of allyl alcohol, 3-buten-1-ol, 4-penten-1-ol, 5-hexen-1-ol, 9-decen-1-ol, ethylene glycol vinyl ether, cis-3-hexen-1-ol, vinyl hydroxy silicone oil;

[0028] The titanate catalyst is selected from one or more of tetrabutyl titanate, tetraisopropyl titanate, tetra-tert-butyl titanate, isooctyl titanate, diisopropoxytitanium bis(ethyl acetoacetate) complex, 1,3-propanedioxytitanium bis(ethyl acetoacetate) complex;

[0029] The molar ratio of the mercapto-silane coupling agent to the compound containing an unsaturated double bond and an active hydroxyl group is 1:0.2 - 1:2, and the mass fraction of the titanate catalyst in the reaction system for synthesizing the second tackifier is 0.05 - 3%.

[0030] In the present invention, the inhibitor is selected from one or more of 1-ethynyl-1-cyclohexanol, 2-methyl-3-butyn-2-ol, 3,5-dimethyl-1-hexyn-3-ol, diallyl maleate, polydivinyltetramethyldisiloxane.

[0031] In the present invention, the catalyst is selected from a platinum-alcohol complex or a platinum-vinylsiloxane complex, and the effective content of platinum atoms is 2000 - 7500 ppm.

[0032] The present invention also provides a preparation method of a one-component addition-curing silicone rubber having excellent adhesiveness to inert hard-to-stick substrates: 50 to 70 parts of base rubber, 10 to 20 parts of vinyl-terminated polydimethylsiloxane, 10 to 15 parts of polydimethylmethylvinylsiloxane, 7 to 15 parts of polydimethylmethylhydrogensiloxane, 0.5 to 2 parts of a first tackifier, 0.001 to 0.1 part of a second tackifier, 0.1 to 0.5 part of an inhibitor, and 0.1 to 0.5 part of a catalyst are stirred and mixed at room temperature in a planetary mixer for 2 h, and then vacuum degassed at room temperature for 15 min to obtain a silicone rubber product; the viscosity of the silicone rubber product < 40000 mPa·s, and the adhesive shear strength for nickel-nickel > 4.0 Mpa; after curing at 150 °C for 30 min, the tensile strength of the silicone rubber > 8 MPa, and the elongation at break > 400%.

[0033] The beneficial effects of the present invention are as follows:

[0034] 1. In the formulation of the present invention, vinyl-terminated polydimethylsiloxane in an appropriate proportion is used as a chain extender, surface-treated fumed silica is used as a reinforcing filler, polydimethylmethylvinylsiloxane and polydimethylmethylhydrogensiloxane are used as crosslinking agents, and a one-component addition-curing silicone rubber prepared with a tackifier, an inhibitor, and a catalyst can be rapidly cured under heating conditions, and no small molecule by-products are released during the crosslinking and curing process. It is packaged in a single component, and the use operation is simple, convenient, and efficient. Moreover, using fumed silica with a high specific surface area as a reinforcing filler can adjust the ratio of the chain extender to the crosslinking agent to optimize the crosslinking network structure. The prepared silicone rubber product has a low viscosity (< 40000 mPa·s), and the cured silicone rubber has very excellent physical and mechanical properties, with a tensile strength greater than 8 MPa and an elongation at break greater than 400%.

[0035] 2. In the formulation of the present invention, two tackifiers are used in synergy to promote adhesion to the substrate. The alkoxy groups and anhydride groups contained in the first tackifier can react with the surface groups of the substrate efficiently and rapidly to form covalent bonds. The sulfur atoms contained in the second tackifier can form coordination with gold, silver, and nickel substrates to form hydrogen bonds and van der Waals forces. Moreover, the Si-H contained in the first tackifier and the unsaturated double bonds contained in the second tackifier can participate in the crosslinking network of the silicone rubber. Therefore, compared with the coordination bond formed by boron atoms and the substrate in the existing patent CN110387128A, the combination of the two tackifiers in the present invention makes the binding force between the silicone rubber and the substrate stronger, resulting in a higher adhesive shear strength (the adhesive shear strength for nickel-nickel > 4.0 MPa).

[0036] 3. The preparation and synthesis method of the tackifier adopted by the present invention is novel, simple and efficient. The yield of the first tackifier product can reach over 90%, and the yield of the second tackifier product can reach over 85%. Moreover, industrial low-cost raw materials are used, and there are no potential major risks during the preparation and synthesis process, which is suitable for industrial synthesis production.

[0037] 4. In the preparation process of the present invention, first, polydimethylsiloxane, fumed silica, and silazane surface treatment agent are simply kneaded and mixed to form a base rubber, and then a crosslinking agent, a tackifier, an inhibitor, and a catalyst are added and simply stirred and mixed to obtain a silicone rubber product. The whole process is simple and controllable, which is suitable for large-scale batch production.

[0038] 5. The one-component addition-curing silicone rubber containing a specific tackifier prepared by the present invention has excellent adhesion to inert and difficult-to-bond substrates such as gold, silver, and nickel, with high adhesive shear strength, further expanding the application scenarios of addition-curing silicone rubber adhesives, especially meeting the requirements in fields such as sealing adhesives and chip encapsulation adhesives in the electronics industry. Specific Embodiments

[0039] The technical solutions of the present invention will be further described in detail below with reference to specific embodiments, but the embodiments of the present invention are not limited thereto.

[0040] Example 1

[0041] A one-component addition-curing silicone rubber with excellent adhesion to inert and difficult-to-bond substrates is composed of the following components in parts by mass:

[0042] 70 parts of base rubber, 12 parts of vinyl-terminated polydimethylsiloxane (viscosity of 1200 mPa·s), 10 parts of polydimethylmethylvinylsiloxane [viscosity of 1000 mPa·s, vinyl content (mass fraction) of 6%], 8 parts of polydimethylmethylhydrogensiloxane [viscosity of 100 mPa·s, hydrogen content (mass fraction) of 0.8%], 1 part of the first tackifier, 0.05 part of the second tackifier, 0.3 part of inhibitor (1-ethynyl-1-cyclohexanol), 0.4 part of catalyst (platinum-vinylsiloxane complex with an effective platinum atom content of 5000 ppm).

[0043] Among the above components,

[0044] The base rubber is obtained by kneading vinyl-terminated polydimethylsiloxane and surface-treated fumed silica: In parts by mass, 60 parts of vinyl-terminated polydimethylsiloxane with a viscosity of 8000 mPa·s and 40 parts of fumed silica with a specific surface area of 200 m 23.5 parts of fumed silica per gram, 3.5 parts of hexamethyldisilazane, 0.5 part of tetramethyldivinyldisilazane and 1.4 parts of water were kneaded in a kneader for 5 h, then the temperature was raised to 150 °C, and the vacuum was maintained at ≤ -0.08 MPa, and kneading was continued for 3 h to obtain the base rubber.

[0045] The first tackifier was prepared by the following method: At room temperature, 240.51 g (1 mol) of tetramethylcyclotetrasiloxane, 148.23 g (1 mol) of vinyltrimethoxysilane and 140.14 g (1 mol) of allyl succinic anhydride were mixed evenly in a three-necked flask; while stirring, 80 mg of a platinum catalyst supported on a silica carrier (the amount of platinum atoms was 4 ppm) was added, and after stirring evenly, the temperature was raised to 80 °C and reacted for 5 h; after the reaction was completed, it was cooled to room temperature, and the supported platinum catalyst was removed by suction filtration, and then the low-boiling substances were removed by vacuum distillation to obtain 501.50 g (the yield was 94.82%) of the first tackifier containing alkoxy groups and succinic anhydride.

[0046] The second tackifier was prepared by the following method: At room temperature, 392.68 g (2 mol) of γ-mercaptopropyltrimethoxysilane and 174.24 g (3 mol) of allyl alcohol were mixed evenly in a three-necked flask; while stirring, 0.57 g of tetrabutyl titanate was added, and after stirring evenly, the temperature was raised to 70 °C and reacted for 2 h to obtain a reaction mixture; then, the low-boiling substances were removed under the conditions of 60 °C and a vacuum of -0.1 MPa to obtain 483.67 g (the yield was 85.32%) of the second tackifier containing unsaturated double bonds and mercapto groups.

[0047] 70 parts of the base rubber, 12 parts of vinyl-terminated polydimethylsiloxane, 10 parts of polydimethylmethylvinylsiloxane, 8 parts of polydimethylmethylhydrogensiloxane, 1 part of the first tackifier, 0.05 part of the second tackifier, 0.3 part of inhibitor, and 0.4 part of catalyst were stirred and mixed in a planetary mixer for 2 h, and then vacuum degassed at room temperature for 15 min to obtain the silicone rubber product.

[0048] The silicone rubber product and the cured silicone rubber elastomer were subjected to relevant performance tests (including the viscosity of the silicone rubber, the adhesive shear strength for aluminum-aluminum and nickel-nickel, mechanical properties, hardness, etc.), and the results are shown in Table 1.

[0049] Example 2

[0050] A one-component addition-curing silicone rubber having excellent adhesion to inert and difficult-to-bond substrates, which is composed of the following components by mass parts:

[0051] 60 parts of base rubber, 18 parts of vinyl-terminated polydimethylsiloxane (viscosity: 3000 mPa·s), 12 parts of polydimethylmethylvinylsiloxane [viscosity: 700 mPa·s, vinyl content (mass fraction): 4%], 10 parts of polydimethylmethylhydrosiloxane [80 mPa·s, hydrogen content (mass fraction): 0.5%], 1.5 parts of the first tackifier, 0.07 parts of the second tackifier, 0.4 parts of inhibitor (diallyl maleate), 0.5 parts of catalyst (platinum-alcohol complex with an effective platinum atom content of 5000 ppm);

[0052] Among the above components,

[0053] The base rubber is obtained by kneading vinyl-terminated polydimethylsiloxane and surface-treated fumed silica: By mass parts, 50 parts of vinyl-terminated polydimethylsiloxane with a viscosity of 5000 mPa·s, 50 parts of fumed silica with a specific surface area of 300 m 2 / g, 5 parts of hexamethyldisilazane, 0.7 parts of tetramethyldivinyldisilazane and 2 parts of water are kneaded in a kneader for 6 h, then heated to 150 °C, and kept under a vacuum of ≤ -0.08 MPa, and continuously kneaded for 4 h to obtain the base rubber;

[0054] The first tackifier is prepared by the following method: At room temperature, 240.51 g (1 mol) of tetramethylcyclotetrasiloxane, 324.52 g (2 mol) of allyltrimethoxysilane and 210.21 g (1.5 mol) of allylsuccinic anhydride are mixed evenly in a three-necked flask; While stirring, 140 mg of a platinum catalyst supported on an alumina carrier (where the amount of platinum atoms is 10 ppm) is added, and after stirring evenly, the temperature is raised to 85 °C and reacted for 6 h. After the reaction is completed, it is cooled to room temperature, the supported platinum catalyst is removed by filtration, and then the low-boiling substances are removed by vacuum distillation to obtain 721.98 g (yield: 93.13%) of the first tackifier containing alkoxy groups and succinic anhydride.

[0055] The second tackifier is prepared by the following method: At room temperature, 392.68 g (2 mol) of γ-mercaptopropyltrimethoxysilane and 176.22 g (2 mol) of ethylene glycol vinyl ether are mixed evenly in a three-necked flask; While stirring, 6.53 g of 1,3-propanedioxytitanium bis(ethyl acetoacetate) complex is added, and after stirring evenly, the temperature is raised to 100 °C and reacted for 1 h to obtain a reaction mixture; Then, the low-boiling substances are removed under the conditions of 60 °C and a vacuum of -0.1 MPa to obtain 502.64 g (yield: 88.35%) of the second tackifier containing unsaturated double bonds and mercapto groups;

[0056] Mix 60 parts of base rubber, 18 parts of vinyl-terminated polydimethylsiloxane, 12 parts of polydimethylmethylvinylsiloxane, 10 parts of polydimethylmethylhydrogensiloxane, 1.5 parts of the first tackifier, 0.07 parts of the second tackifier, 0.4 parts of inhibitor, and 0.5 parts of catalyst in a planetary mixer for 2 h, and then carry out vacuum degassing treatment at room temperature for 15 min to obtain the silicone rubber product.

[0057] Carry out relevant performance tests on the silicone rubber product and the cured silicone rubber elastomer (including the viscosity of the silicone rubber, the adhesive shear strength for aluminum-aluminum and nickel-nickel, the cohesive failure rate, mechanical properties, and hardness, etc.), and the results are shown in Table 1.

[0058] Example 3

[0059] A one-component addition-curing silicone rubber with excellent adhesion to inert and difficult-to-bond substrates, which is composed of the following components by mass parts:

[0060] 55 parts of base rubber, 20 parts of vinyl-terminated polydimethylsiloxane (viscosity of 1000 mPa·s), 15 parts of polydimethylmethylvinylsiloxane [viscosity of 500 mPa·s, vinyl content (mass fraction) of 3%], 10 parts of polydimethylmethylhydrogensiloxane [viscosity of 50 mPa·s, hydrogen content (mass fraction) of 0.6%], 2 parts of the first tackifier, 0.1 parts of the second tackifier, 0.2 parts of inhibitor (polydivinyltetramethyldisiloxane), 0.5 parts of catalyst (platinum-vinylsiloxane complex with an effective platinum atom content of 5000 ppm);

[0061] Among the above components,

[0062] The base rubber is obtained by kneading vinyl-terminated polydimethylsiloxane with surface-treated white carbon black: By mass parts, 55 parts of vinyl-terminated polydimethylsiloxane with a viscosity of 10000 mPa·s, 45 parts of an equimolar mixture of fumed white carbon black with a specific surface area of 200 m 2 / g and 380 m 2 / g, 4 parts of hexamethyldisilazane, 0.5 parts of tetramethyldivinyldisilazane, and 1.5 parts of water are kneaded in a kneader for 5 h, then the temperature is raised to 150 °C, and the vacuum degree is maintained at ≤ -0.08 MPa, and kneading is continued for 3 h to obtain the base rubber;

[0063] The first tackifier is prepared by the following method: At room temperature, 240.51 g (1 mol) of tetramethylcyclotetrasiloxane, 613.02 g (3 mol) of 5-hexenyltrimethoxysilane, and 105.14 g (0.5 mol) of 2-octenylsuccinic anhydride are mixed evenly in a three-necked flask. While stirring, 180 mg of a platinum catalyst supported on a carbon carrier (with a platinum atom dosage of 15 ppm) is added. After stirring evenly, the temperature is raised to 90 °C and the reaction is carried out for 7 h. After the reaction is completed, it is cooled to room temperature, and the supported platinum catalyst is removed by suction filtration, and then the low-boiling substances are removed by vacuum distillation to obtain 877.37 g (yield: 91.52%) of the first tackifier containing alkoxy groups and succinic anhydride.

[0064] The second tackifier is prepared by the following method: At room temperature, 476.84 g (2 mol) of γ-mercaptopropyltriethoxysilane and 500 g (0.5 mol) of vinyl hydroxy silicone oil are mixed evenly in a three-necked flask; while stirring, 3.51 g of diisopropoxytitanium bis(ethyl acetoacetate) complex is added. After stirring evenly, the temperature is raised to 110 °C and the reaction is carried out for 3 h to obtain a reaction mixture. Then, under the conditions of 60 °C and a vacuum degree of -0.1 MPa, the low-boiling substances are removed to obtain 844.67 g (yield: 86.47%) of the second tackifier containing unsaturated double bonds and mercapto groups.

[0065] 55 parts of base rubber, 20 parts of vinyl-terminated polydimethylsiloxane, 15 parts of polydimethylmethylvinylsiloxane, 10 parts of polydimethylmethylhydrogensiloxane, 2 parts of the first tackifier, 0.1 part of the second tackifier, 0.2 part of inhibitor, and 0.5 part of catalyst are stirred and mixed in a planetary mixer for 2 h, and then vacuum degassed at room temperature for 15 min to obtain a silicone rubber product.

[0066] The silicone rubber product and the cured silicone rubber elastomer are subjected to relevant performance tests (including the viscosity of the silicone rubber, the adhesive shear strength for aluminum-aluminum and nickel-nickel, the cohesive failure rate, mechanical properties, and hardness, etc.), and the results are shown in Table 1.

[0067] Example 4

[0068] A one-component addition-curing silicone rubber having excellent adhesiveness to inert and difficult-to-bond substrates, which is composed of the following components by mass parts:

[0069] 50 parts of base gum, 20 parts of vinyl-terminated polydimethylsiloxane (composed of 10 parts of vinyl-terminated polydimethylsiloxane with a viscosity of 5000 mPa·s and 10 parts of vinyl-terminated polydimethylsiloxane with a viscosity of 500 mPa·s), 15 parts of polydimethylmethylvinylsiloxane [viscosity of 2000 mPa·s, vinyl content (mass fraction) of 8%], 15 parts of polydimethylmethylhydrosiloxane [viscosity of 120 mPa·s, hydrogen content (mass fraction) of 1%], 1.3 parts of the first tackifier, 0.05 parts of the second tackifier, 0.3 parts of inhibitor (diallyl maleate), 0.3 parts of catalyst (platinum-vinylsiloxane complex with an effective platinum atom content of 7500 ppm).

[0070] Among the above components,

[0071] The base gum is obtained by kneading vinyl-terminated polydimethylsiloxane with surface-treated fumed silica: By mass parts, 50 parts of vinyl-terminated polydimethylsiloxane (wherein, 20 parts with a viscosity of 50000 mPa·s and 30 parts with a viscosity of 3000 mPa·s), 50 parts of fumed silica with a specific surface area of 380 m 2 / g, 4.5 parts of hexamethyldisilazane, 0.1 part of tetramethyldivinyldisilazane and 2 parts of water are kneaded in a kneader for 4 h, then heated to 150 °C, maintaining a vacuum degree ≤ -0.08 MPa, and continuously kneaded for 4 h to obtain the base gum.

[0072] The first tackifier is prepared by the following method: At room temperature, 240.51 g (1 mol) of tetramethylcyclotetrasiloxane, 117.16 g (0.5 mol) of 3-(acryloyloxy)propyltrimethoxysilane and 350.35 g (2.5 mol) of allylsuccinic anhydride are mixed evenly in a three-necked flask; while stirring, 6 mg of platinum-alcohol complex catalyst (where the platinum atom dosage is 1 ppm) is added, and after stirring evenly, it is heated to 110 °C and reacted for 8 h; after the reaction is completed, it is cooled to room temperature, and low-boiling substances are removed by vacuum distillation to obtain 667.52 g (yield of 94.28%) of the first tackifier containing alkoxy and succinic anhydride.

[0073] The second tackifier is prepared by the following method: At room temperature, 392.68 g (2 mol) of γ-mercaptopropyltrimethoxysilane and 200.32 g (2 mol) of 5-hexen-1-ol are mixed evenly in a three-necked flask; while stirring, 1.78 g of 1,3-propanedioxytitanium bis(ethyl acetoacetate) complex is added, and after stirring evenly, it is heated to 90 °C and reacted for 5 h to obtain a reaction mixture; then, under the conditions of 60 °C and a vacuum degree of -0.1 MPa, low-boiling substances are removed to obtain 516.98 g (yield of 87.18%) of the second tackifier containing unsaturated double bonds and mercapto groups;

[0074] Mix 50 parts of base rubber, 20 parts of vinyl-terminated polydimethylsiloxane, 15 parts of polydimethylmethylvinylsiloxane, 15 parts of polydimethylmethylhydrogensiloxane, 1.3 parts of the first tackifier, 0.05 part of the second tackifier, 0.3 part of inhibitor, and 0.3 part of catalyst in a planetary mixer for 2 h, and then conduct vacuum degassing treatment at room temperature for 15 min to obtain the silicone rubber product.

[0075] Conduct relevant performance tests on the silicone rubber product and the cured silicone rubber elastomer (including the viscosity of the silicone rubber, the adhesive shear strength for aluminum-aluminum and nickel-nickel, the adhesive shear strength for aluminum-aluminum, mechanical properties, hardness, etc.), and the results are shown in Table 1.

[0076] Example 5

[0077] A one-component addition-curing silicone rubber with excellent adhesiveness to inert and difficult-to-bond substrates, which is composed of the following components by mass parts:

[0078] 66 parts of base rubber, 14 parts of vinyl-terminated polydimethylsiloxane (viscosity of 1500 mPa·s), 11 parts of polydimethylmethylvinylsiloxane [viscosity of 850 mPa·s, vinyl content (mass fraction) of 5%], 9 parts of polydimethylmethylhydrogensiloxane [viscosity of 90 mPa·s, hydrogen content (mass fraction) of 0.7%], 1.5 parts of the first tackifier, 0.07 part of the second tackifier, 0.4 part of inhibitor (diallyl maleate), 0.4 part of catalyst (platinum-vinylsiloxane complex with an effective platinum atom content of 7500 ppm).

[0079] Among the above components,

[0080] The base rubber is obtained by kneading vinyl-terminated polydimethylsiloxane with surface-treated fumed silica: By mass parts, mix 55 parts of vinyl-terminated polydimethylsiloxane with a viscosity of 8000 mPa·s, 45 parts of fumed silica with a specific surface area of 250 m 2 / g, 4.5 parts of hexamethyldisilazane, 0.3 part of tetramethyldivinyldisilazane, and 1.8 parts of water in a kneader for 5 h, then raise the temperature to 150 °C, keep the vacuum degree ≤ -0.08 MPa, and continue kneading for 3 h to obtain the base rubber;

[0081] The first tackifier is prepared by the following method: At room temperature, 240.51 g (1 mol) of tetramethylcyclotetrasiloxane, 496.70 g (2 mol) of 3-(methacryloyloxy)propyltrimethoxysilane and 140.14 g (1 mol) of allyl succinic anhydride are mixed evenly in a three-necked flask. While stirring, 20 mg of a platinum-vinylsiloxane complex catalyst (with a platinum atom dosage of 2 ppm) is added. After stirring evenly, the temperature is raised to 100 °C and the reaction is carried out for 7 h. After the reaction is completed, it is cooled to room temperature, and the low-boiling substances are removed by vacuum distillation to obtain 828.83 g (yield 94.47%) of the first tackifier containing alkoxy groups and succinic anhydride.

[0082] The second tackifier is prepared by the following method: At room temperature, 392.68 g (2 mol) of γ-mercaptopropyltrimethoxysilane and 223.94 g (2.6 mol) of 4-penten-1-ol are mixed evenly in a three-necked flask. While stirring, 0.34 g of tetra-isopropyl titanate is added. After stirring evenly, the temperature is raised to 120 °C and the reaction is carried out for 4 h to obtain a reaction mixture. Then, the low-boiling substances are removed under the conditions of 60 °C and a vacuum degree of -0.1 MPa to obtain 529.54 g (yield 85.88%) of the second tackifier containing unsaturated double bonds and mercapto groups.

[0083] 66 parts of base rubber, 14 parts of vinyl-terminated polydimethylsiloxane, 11 parts of polydimethylmethylvinylsiloxane, 9 parts of polydimethylmethylhydrogensiloxane, 1.5 parts of the first tackifier, 0.07 part of the second tackifier, 0.4 part of inhibitor, and 0.4 part of catalyst are stirred and mixed in a planetary mixer for 2 h, and then vacuum degassed at room temperature for 15 min to obtain a silicone rubber product.

[0084] The silicone rubber product and the cured silicone rubber elastomer are subjected to relevant performance tests (including the viscosity of the silicone rubber, the adhesive shear strength for aluminum-aluminum and nickel-nickel, the adhesive shear strength for aluminum-aluminum, mechanical properties, hardness, etc.), and the results are shown in Table 1.

[0085] Example 6

[0086] On the basis of Example 1, only the dosages of the following components are adjusted in this example, and the other schemes are the same as those in Example 1, aiming to consider whether there are significant differences in the performance of the silicone rubber prepared in this example and the silicone rubber in Example 1 when changing the component dosages within the use range.

[0087] 10 parts of vinyl-terminated polydimethylsiloxane, 7 parts of polydimethylmethylhydrogensiloxane, 0.5 part of the first tackifier, 0.001 part of the second tackifier, 0.5 part of inhibitor, 0.1 part of catalyst; the viscosity of the polydimethylmethylhydrogensiloxane is 30 mPa·s, and the hydrogen content (mass fraction) is 1%.

[0088] The relevant performance parameters of the silicone rubber products and the cured silicone rubber elastomers in this embodiment (including the viscosity of the silicone rubber, the adhesive shear strength for aluminum-aluminum and nickel-nickel, mechanical properties, hardness, etc.) are shown in Table 1 below.

[0089] Comparative Example 1

[0090] This comparative example is a comparative example of Example 1. In Example 1, the second tackifier is not added, and other conditions are the same as those in Example 1.

[0091] Comparative Example 2

[0092] This comparative example is a comparative example of Example 3. In Example 3, the first tackifier is not added, and other conditions are the same as those in Example 3.

[0093] Comparative Example 3

[0094] This comparative example is a comparative example of Example 5. The first tackifier and the second tackifier in Example 5 are simultaneously replaced with a conventional commercial tackifier system: an equal weight ratio mixture of γ-glycidoxypropyltrimethoxysilane (KH-560) and 3-(methacryloyloxy)propyltrimethoxysilane (KH-570), and other conditions are the same as those in Example 5.

[0095] The viscosities of the 9 silicone rubber products prepared in the above Examples 1 to 6 and Comparative Examples 1, 2, and 3 were measured using a rheometer respectively; the silicone rubber elastomers cured at 150 °C for 30 min were made into mechanical property sheets, and the shear property sheets of aluminum-aluminum (Al-Al) and nickel-nickel (Ni-Ni) were made by heating at 150 °C for 30 min; and the silicone rubber elastomer was coated on the interface of a gold or silver substrate, and after heating at 150 °C for 30 min, a shear force was applied to the interface of the gold and silver substrates to cause failure, and the interface failure situation was observed. The results are shown in Table 1 below:

[0096]

[0097] As can be seen from the data in Table 1, the one-component addition-curing silicone rubber prepared by the present invention not only has a low viscosity (<40,000 mPa·s), but also the silicone rubber elastomer cured at 150 °C for 30 min also exhibits excellent mechanical properties, with a tensile strength greater than 8 MPa and an elongation at break greater than 400%.

[0098] The one-component addition-curing silicone rubber containing two specific tackifiers (Examples 1-6) has very excellent adhesiveness to Al, Ni, Au, and Ag substrates when the two tackifiers are used in combination compared with the silicone rubber using only one tackifier (Comparative Examples 1-2); compared with the conventional commercial tackifier system (Comparative Example 3), the conventional commercial tackifier system has certain adhesiveness only to the Al substrate and basically has no adhesiveness to the inert and difficult-to-bond substrates (gold, silver, nickel). This shows that the excellent, stable and reliable adhesion to the difficult-to-bond substrates such as gold, silver, and nickel can be achieved by using the two compounded tackifiers of the present invention. Therefore, the one-component addition-curing silicone rubber prepared by the present invention can be used as a sealing adhesive and a chip encapsulation adhesive in the electronic industry.

[0099] The above-described embodiments are only the preferred embodiments of the present invention. The embodiments of the present invention are not limited by any of the above embodiments. Therefore, any other modifications, decorations, substitutions, combinations, and simplifications made without departing from the spirit and principle of the present invention shall be regarded as equivalent replacement methods and are all included in the protection scope of the technical solution of the present invention.

Claims

1. A one-component addition-curing silicone rubber with excellent adhesiveness to inert and difficult-to-bond substrates, characterized in that: The following components are calculated by weight: composition: 50-70 parts of base glue, 10-20 parts of vinyl-terminated polydimethylsiloxane, 10-15 parts of polydimethylmethylvinylsiloxane, 7-15 parts of polydimethylmethylhydrogensiloxane, 0.5-2 parts of first tackifier, 0.001-0.1 parts of second tackifier, 0.1-0.5 parts of inhibitor, and 0.1-0.5 parts of catalyst; The base rubber is obtained by kneading vinyl-terminated polydimethylsiloxane and surface-treated white carbon black: by weight, 40 to 70 parts of vinyl-terminated polydimethylsiloxane, 30 to 60 parts of white carbon black, 3 to 5 parts of hexamethyldisilazane, 0 to 1 part of tetramethyldivinyldisilazane and 1 to 2 parts of water are kneaded in a kneader for 3 to 6 hours, then the temperature is raised to 150° C., the vacuum degree is maintained at ≤-0.08 MPa, and the kneading is continued for 2 to 4 hours to obtain the base rubber; The first tackifier is prepared by the following method: at room temperature, tetramethylcyclotetrasiloxane, alkenyl-containing trialkoxysilane and alkenyl-containing succinic anhydride are uniformly mixed; while stirring, a platinum catalyst is added, stirred uniformly, and then heated to 45-110° C. for reaction for 3-12 hours; after the reaction is completed, the mixture is cooled to room temperature, and low-boiling substances are removed by reduced pressure distillation to obtain a first tackifier containing alkoxy groups and succinic anhydride; The second thickener is prepared by the following method: at room temperature, a mercaptosilane coupling agent and a compound containing an unsaturated double bond and an active hydroxyl group are mixed uniformly; while stirring, a titanate catalyst is added, and after stirring uniformly, the mixture is heated to 50 to 120° C. and reacted for 0.5 to 8 hours to obtain a reaction mixture; then, low boiling substances are removed at 60° C. and a vacuum degree of -0.1 MPa to obtain a second thickener containing unsaturated double bonds and mercapto groups.

2. The one-component addition-curing silicone rubber with excellent adhesiveness to inert and difficult-to-bond substrates according to claim 1, wherein: The viscosity of the vinyl-terminated polydimethylsiloxane used in the preparation of the base glue is 3000 to 50000 mPa·s; the silica is selected from fumed silica or precipitated silica with a specific surface area of 100 m 2 / g, 200 m 2 / g, 250 m 2 / g, 300 m 2 / g, 380 m 2 / g, which is one or a mixture of more than one of them.

3. A one-component addition-curing silicone rubber having excellent adhesiveness to inert and difficult-to-bond substrates according to claim 1, characterized in that: The viscosity of the vinyl-terminated polydimethylsiloxane is 500-5000 mPa.s; the viscosity of the polydimethylmethylvinylsiloxane is 200-2000 mPa.s, and the vinyl content is 1-8%; the viscosity of the polydimethylmethylhydrogensiloxane is 30-120 mPa.s, and the hydrogen content is 0.2-1%.

4. The one-component addition-curing silicone rubber with excellent adhesion to inert and difficult-to-bond substrates according to claim 1, wherein: In the first tackifier, the molar ratio of tetramethylcyclotetrasiloxane, alkenyl-containing trialkoxysilane and alkenyl-containing succinic anhydride is 1: 0.1-5: 0.1-5.

5. The one-component addition-curing silicone rubber with excellent adhesiveness to inert and difficult-to-bond substrates according to claim 1, wherein: In the first tackifier, the alkenyl group-containing trialkoxysilane is selected from one or more of vinyltrimethoxysilane, vinyltriethoxysilane, allyltriethoxysilane, allyltrimethoxysilane, 5-hexenyltriethoxysilane, 5-hexenyltrimethoxysilane, 7-octenyltrimethoxysilane, 3-(acryloyloxy)propyltrimethoxysilane, and 3-(methacryloyloxy)propyltrimethoxysilane; the alkenyl group-containing succinic anhydride is selected from one or more of allylsuccinic anhydride, 2-butenylsuccinic anhydride, 2-hexen-1-ylsuccinic anhydride, 2-octenylsuccinic anhydride, and 2-dodecenylsuccinic anhydride; the platinum catalyst is one of chloroplatinic acid, platinum-vinylsiloxane complex, or platinum-alcohol complex, and a platinum catalyst supported on a silica, carbon, or alumina support, and the mass content of platinum atoms in the reaction system for preparing the first tackifier is 0.5 to 15 ppm.

6. The one-component addition-curing silicone rubber with excellent adhesiveness to inert and difficult-to-bond substrates according to claim 1, characterized in that: In the second tackifier, the molar ratio of the mercapto-silane coupling agent to the compound containing an unsaturated double bond and an active hydroxyl group is 1:0.2 to 1:2; the mass fraction of the titanate catalyst in the reaction system for synthesizing the second tackifier is 0.05 to 3%.

7. A one-component addition-curing silicone rubber having excellent adhesiveness to an inert and difficult-to-bond substrate according to claim 1 or 6, characterized in that: In the second tackifier, the mercapto-silane coupling agent is selected from one or more of γ-mercaptopropyltrimethoxysilane, γ-mercaptopropyltriethoxysilane, γ-mercaptopropylmethyldimethoxysilane, and γ-mercaptomethylmethyldiethoxysilane; the compound containing an unsaturated double bond and an active hydroxyl group is selected from one or more of allyl alcohol, 3-buten-1-ol, 4-penten-1-ol, 5-hexen-1-ol, 9-decen-1-ol, ethylene glycol vinyl ether, cis-3-hexen-1-ol, and vinyl hydroxy silicone oil; the titanate catalyst is selected from one or more of tetrabutyl titanate, tetraisopropyl titanate, tetra-tert-butyl titanate, isooctyl titanate, diisopropoxytitanium bis(ethyl acetoacetate) complex, and 1,3-propanedioxytitanium bis(ethyl acetoacetate) complex.

8. The one-component addition-curing silicone rubber having excellent adhesiveness to inert hard-to-bond substrates according to claim 1, characterized in that: The inhibitor is selected from one or more of 1-ethynyl-1-cyclohexanol, 2-methyl-3-butyn-2-ol, 3,5-dimethyl-1-hexyn-3-ol, diallyl maleate, and polydivinyltetramethyldisiloxane; the catalyst is selected from a platinum-alcohol complex or a platinum-vinylsiloxane complex, and the effective content of platinum atoms is 2000 to 7500 ppm.

9. The preparation method of a one-component addition-curing silicone rubber having excellent adhesion to an inert and difficult-to-bond substrate according to claim 1, characterized in that: Mix 50 - 70 parts of base rubber, 10 - 20 parts of vinyl-terminated polydimethylsiloxane, 10 - 15 parts of polydimethylmethylvinylsiloxane, 7 - 15 parts of polydimethylmethylhydrogensiloxane, 0.5 - 2 parts of the first tackifier, 0.001 - 0.1 part of the second tackifier, 0.1 - 0.5 part of inhibitor, and 0.1 - 0.5 part of catalyst in a planetary mixer at room temperature for 2 h, and then conduct vacuum degassing treatment at room temperature for 15 min to obtain a silicone rubber product; the viscosity of the silicone rubber product < 40000 mPa·s, and the adhesive shear strength for nickel-nickel > 4.0 Mpa; after curing at 150 °C for 30 min, the tensile strength of the silicone rubber > 8 MPa, and the elongation at break > 400%.

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