Epoxy-based liquid silicone rubber with high adhesive strength and use thereof

Abstract

The application discloses a high-bonding-strength epoxy liquid silicone rubber prepared by high-efficiency catalysis of ring-opening polymerization of cyclosiloxane monomers by using an organic phosphorus azide catalyst and application of the high-bonding-strength epoxy liquid silicone rubber as an adhesive. The high-bonding-strength epoxy liquid silicone rubber has the advantages of simple preparation process, high polymerization efficiency, short reaction time and mild reaction temperature, can be applied to the bonding of various polar and non-polar substrates, and has high practical application value.

Description

Technical Field

[0001] This invention provides an application of a high-adhesion-strength epoxy-based liquid silicone rubber, specifically relating to the application of an epoxy-based liquid silicone rubber with improved strength and heterogeneous interfacial adhesion properties in adhesives. Background Technology

[0002] Chemically, silicone rubber's main chain consists of alternating silicon and oxygen atoms, with substituent groups on the silicon atoms, giving it a wide range of functionalities. Structurally, silicone rubber is an organic-inorganic hybrid polymer, possessing characteristics of both inorganic and organic materials. It exhibits excellent heat resistance, cold resistance, radiation resistance, oxidation resistance, weather resistance, and physiological inertness, making it widely used in defense, aerospace, electrical, electronic, instrumentation, automotive, and construction industries.

[0003] Although silicone rubber has a wide range of applications, the molecular chain segments of vulcanized silicone rubber are helical, and the helical shielding effect makes it non-polar. Therefore, silicone rubber exhibits excellent hydrophobicity and poor adhesion, making it difficult to achieve effective adhesion to polar substrates.

[0004] To improve adhesion, a primer is usually pre-coated on the bottom of the silicone rubber. The primer has good compatibility with both silicone rubber and substrate, and usually contains polar groups that interact with the polar substrate to improve interfacial adhesion. However, the volatilization process of the diluent contained in the primer not only pollutes the environment, but also easily affects its adhesion performance when exposed to air for a long time.

[0005] Addition-type liquid silicone rubber is an elastomer with a network structure formed by the hydrosilylation of a vinyl-containing linear polysiloxane as a base polymer and a hydrogen-containing polymer. It has advantages such as being less prone to deformation, having low shrinkage, and not producing by-products, and has extremely high application value.

[0006] Therefore, introducing epoxy groups into liquid silicone rubber enhances its polarity, making it a bridge between polar and non-polar materials. The epoxy groups can react with the polar substrate to form bonds, and the vinyl groups undergo hydrosilylation with hydrogen-containing silicone oil to form silicone rubber. Epoxy-based liquid silicone rubber not only improves the environmental pollution problem of primers but also enhances the adhesion strength between the polar and non-polar heterogeneous phase interfaces. Simultaneously, epoxy-based liquid silicone rubber also demonstrates excellent performance in the field of polar substrate bonding. Summary of the Invention

[0007] The present invention aims to provide a use of a high-adhesion-strength epoxy-based liquid silicone rubber, specifically relating to the application of an epoxy-based liquid silicone rubber with improved strength and heterogeneous interfacial adhesion properties in adhesives.

[0008] In a first aspect, the present invention provides a high-adhesion-strength epoxy-based liquid silicone rubber. According to an embodiment of the present invention, the high-adhesion-strength liquid silicone rubber is a compound of formula (I).

[0009]

[0010] (I)

[0011] in,

[0012] R is an optionally substituted alkyl, optionally substituted aryl, or optionally substituted benzyl group.

[0013] R 3 It is at least one of SiMe3 and SiMe2Vi.

[0014] m is an integer, and 1 < m < 10.

[0015] x is an integer from 1 to 10000.

[0016] y is an integer from 0 to 10000.

[0017] z is an integer from 1 to 10000.

[0018] In some embodiments of the present invention, the average molecular weight of the epoxy-based liquid silicone rubber is 4000~90000 g / mol.

[0019] In some embodiments of the present invention, the epoxy group content of the epoxy liquid silicone rubber is 0.5 to 25 mol%, and the vinyl content is 0 to 10 mol%.

[0020] In a second aspect, the present invention provides a method for preparing and applying the high-adhesion-strength epoxy-based liquid silicone rubber according to the above embodiments of the present invention. According to an embodiment of the present invention, the method includes:

[0021] (1) Mix tetracyclooxysiloxane, octamethylcyclotetrasiloxane and tetramethyltetravinylcyclotetrasiloxane in a certain proportion until homogeneous;

[0022] (2) Mix the initiator and phosphazene catalyst evenly and add them to the (1) system. Perform ring-opening copolymerization at 50°C. After a certain reaction time, add a terminator to terminate the reaction. Epoxy liquid silicone rubber can be obtained without post-treatment.

[0023] (3) Epoxy liquid silicone rubber and any diamine curing agent are mixed evenly according to a specific ratio, applied between the polar substrates to be bonded, and cured at a certain temperature to achieve bonding of polar substrates;

[0024] (4) Epoxy liquid silicone rubber and any diamine curing agent are mixed evenly according to a specific ratio and applied to the surface of a polar substrate. A layer of silicone rubber or hydrogen-containing silicone oil is laid on top of the coating and cured at a certain temperature to achieve bonding between the polar substrate and the non-polar material.

[0025] In some embodiments of the present invention, in step (1), the tetraepoxycyclosiloxane, octamethylcyclotetrasiloxane and tetramethyltetravinylcyclotetrasiloxane are all commercially available products and do not require any purification treatment.

[0026] In some embodiments of the present invention, in step (1), the certain proportion is 0.5-25 mol of tetracyclooxysiloxane, 73-89.5 mol of octamethylcyclotetrasiloxane, and 2-10 mol of tetramethyltetravinylcyclotetrasiloxane.

[0027] In some embodiments of the present invention, in step (2), the catalyst is a phosphazene compound of formula (II).

[0028]

[0029] (ІI)

[0030] In some embodiments of the present invention, in step (2), the initiator is at least one of water, benzyl alcohol, ethylene glycol, 1,2-propanediol, 2,3-butanediol, terephthalic acid glycol, cyclohexanediol, glycerol, trimethylolpropane, pentaerythritol, xylitol, inositol, glucose, lithium hydroxide, sodium hydroxide, potassium hydroxide, lithium methoxide, sodium methoxide, potassium methoxide, lithium tert-butoxide, sodium tert-butoxide, potassium tert-butoxide, lithium methylsilanolate, sodium methylsilanolate, and potassium methylsilanolate.

[0031] In some embodiments of the present invention, in step (2), the anhydrous reagent is at least one of tetrahydrofuran and toluene.

[0032] In some embodiments of the present invention, in steps (3) and (4), the diamine curing agent is at least one of any commercially available diamine compound such as ethylenediamine, propylenediamine, p-phenylenediamine, o-phenylenediamine, m-phenylenediamine, polyetheramine, 4,4'-diaminodiphenyl disulfide, etc., preferably 4,4'-diaminodiphenyl disulfide.

[0033] In some embodiments of the present invention, in steps (3) and (4), the diamine curing agent and the epoxy liquid rubber are fed in a ratio of [NH]:[Epoxy] = 1:1.

[0034] In some embodiments of the present invention, in steps (3) and (4), the substrate is at least one of aluminum plate, stainless steel, wood board, PC board, and glass.

[0035] In some embodiments of the present invention, in steps (3) and (4), the curing temperature is 60 ~ 120°C and the curing time is 4 ~ 36 hours.

[0036] In some embodiments of the present invention, in step (4), the hydrogen-containing silicone oils are all commercially available products with hydrogen content of 0.07%, 0.1%, 0.18%, 0.5%, 0.75% and 1.58%, and are mixed with platinum catalyst to perform hydrosilylation with vinyl groups in epoxy liquid silicone rubber to achieve adhesion of non-polar materials to the surface of polar substrates.

[0037] In some embodiments of the present invention, in step (4), the silicone rubber is a commercially available addition-cured room temperature vulcanizing silicone rubber, which can undergo hydrosilylation with epoxy-based liquid silicone rubber to achieve bonding of non-polar silicone rubber materials to the surface of a polar substrate. Attached Figure Description

[0038] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which:

[0039] Appendix Figure 1 This is the GPC curve of the epoxy-based liquid silicone rubber in Example 1 of the present invention.

[0040] Appendix Figure 2 This is the GPC curve of the epoxy-based liquid silicone rubber in Example 2 of the present invention.

[0041] Appendix Figure 3 This is the GPC curve of the epoxy-based liquid silicone rubber in Example 3 of the present invention.

[0042] Appendix Figure 4 The data are the adhesive strength, tensile strength and elongation at break of the epoxy-based liquid silicone rubber in Examples 1 to 4 of this invention. Detailed Implementation

[0043] The embodiments of the present invention are described in detail below. These embodiments are exemplary and are only used to explain the present invention, and should not be construed as limiting the invention. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in the art or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all commercially available conventional products.

[0044] Example 1

[0045] Under nitrogen protection, 0.0125 mmol of phosphazene catalyst and 0.0125 mmol of benzyl alcohol were uniformly mixed in 400 μL of toluene and added to a mixed solution of 11.875 mmol of octamethylcyclotetrasiloxane and 0.625 mmol of tetraepoxycyclosiloxane. The mixture was stirred at 50 °C to initiate the polymerization reaction. After 4 h of reaction, acetic acid was added to terminate the reaction, yielding epoxy liquid silicone rubber with an epoxy content of 5.1 mol% and Mn = 38.2 kg / mol.

[0046] The above liquid silicone rubber was mixed with 4,4'-diaminodiphenyl disulfide at a ratio of [NH]:[Epoxy] = 1:1, and then applied to the surface of an aluminum plate. After curing at 80 °C for 4 h, the mixture was cured at 120 °C for 18 h. The lap shear strength of the aluminum plate was 2.24 MPa.

[0047] Example 2

[0048] Under nitrogen protection, 0.0125 mmol of phosphazene catalyst and 0.0125 mmol of benzyl alcohol were uniformly mixed in 400 μL of toluene and added to a mixed solution of 11.25 mmol of octamethylcyclotetrasiloxane and 1.25 mmol of tetracyclooxysiloxane. The mixture was stirred at 50 °C to initiate the polymerization reaction. After 16 h of reaction, acetic acid was added to terminate the reaction, yielding epoxy liquid silicone rubber with an epoxy content of 9.2 mol% and Mn = 30.4 kg / mol.

[0049] The above liquid silicone rubber was mixed with 4,4'-diaminodiphenyl disulfide at a ratio of [NH]:[Epoxy] = 1:1, and then applied to the surface of an aluminum plate. After curing at 80 °C for 4 h, the mixture was cured at 120 °C for 18 h. The lap shear strength of the aluminum plate was 2.41 MPa.

[0050] Example 3

[0051] Under nitrogen protection, 0.0125 mmol of phosphazene catalyst and 0.0125 mmol of benzyl alcohol were uniformly mixed in 400 μL of toluene and added to a mixed solution of 10.625 mmol of octamethylcyclotetrasiloxane and 1.875 mmol of tetracyclic cyclosiloxane. The mixture was stirred at 50 °C to initiate the polymerization reaction. After 36 h of reaction, acetic acid was added to terminate the reaction, yielding epoxy liquid silicone rubber with an epoxy content of 14.4 mol% and Mn = 23.4 kg / mol.

[0052] The above liquid silicone rubber was mixed with 4,4'-diaminodiphenyl disulfide at a ratio of [NH]:[Epoxy] = 1:1, and then applied to the surface of an aluminum plate. After curing at 80 °C for 4 h, the mixture was cured at 120 °C for 12 h. The lap shear strength of the aluminum plate was 2.75 MPa.

[0053] Example 4

[0054] Under nitrogen protection, 0.0125 mmol of phosphazene catalyst and 0.0125 mmol of benzyl alcohol were uniformly mixed in 400 μL of toluene and added to a mixed solution of 10 mmol of octamethylcyclotetrasiloxane and 2.5 mmol of tetracyclooxy cyclosiloxane. The mixture was stirred at 50 °C to initiate the polymerization reaction. After 48 h of reaction, acetic acid was added to terminate the reaction, yielding epoxy liquid silicone rubber with an epoxy content of 21.2 mol% and Mn = 17.3 kg / mol.

[0055] The above liquid silicone rubber was mixed with 4,4'-diaminodiphenyl disulfide at a ratio of [NH]:[Epoxy] = 1:1, and then applied to the surface of an aluminum plate. After curing at 80 °C for 4 h, the mixture was cured at 120 °C for 12 h. The lap shear strength of the aluminum plate was 2.96 MPa.

[0056] Example 5

[0057] Under nitrogen protection, 0.0125 mmol of phosphazene catalyst and 0.0125 mmol of benzyl alcohol were uniformly mixed in 400 μL of toluene and added to a mixed solution of 10 mmol of octamethylcyclotetrasiloxane, 1.25 mmol of tetracyclooxycyclosiloxane, and 1.25 mmol of tetramethyltetravinylcyclotetrasiloxane. The mixture was stirred at 50 °C to initiate the polymerization reaction. After 16 h of reaction, acetic acid was added to terminate the reaction, yielding epoxy-based liquid silicone rubber with an epoxy content of 9.3 mol%, a vinyl content of 9.8 mol%, and Mn = 32.4 kg / mol.

[0058] The above liquid silicone rubber was mixed with 4,4'-diaminodiphenyl disulfide at a ratio of [NH]:[Epoxy] = 1:1 and applied evenly to the surface of an aluminum plate. A layer of hydrogen-containing silicone oil with a hydrogen content of 0.5% was then laid on the surface of the epoxy liquid silicone rubber at a ratio of [H]:[Vinyl] = 1.2. The mixture was cured at 80 ℃ for 4 h and then at 120 ℃ for 18 h. A pull-out test was performed, and the bonding strength was 1.45 MPa.

[0059] Example 6

[0060] Under nitrogen protection, 0.0125 mmol of phosphazene catalyst and 0.0125 mmol of benzyl alcohol were uniformly mixed in 400 μL of toluene and added to a mixed solution of 10 mmol of octamethylcyclotetrasiloxane, 1.25 mmol of tetracyclooxycyclosiloxane, and 1.25 mmol of tetramethyltetravinylcyclotetrasiloxane. The mixture was stirred at 50 °C to initiate the polymerization reaction. After 16 h of reaction, acetic acid was added to terminate the reaction, yielding epoxy-based liquid silicone rubber with an epoxy content of 9.3 mol%, a vinyl content of 9.8 mol%, and Mn = 32.4 kg / mol.

[0061] The above liquid silicone rubber was mixed with 4,4'-diaminodiphenyl disulfide at a ratio of [NH]:[Epoxy] = 1:1 and applied evenly to a glass surface. A layer of hydrogen-containing silicone oil with a hydrogen content of 0.5% was then laid on the surface of the epoxy liquid silicone rubber at a ratio of [H]:[Vinyl] = 1.2. The mixture was cured at 80 ℃ for 4 h and then at 120 ℃ for 6 h. A pull-out test was performed, and the adhesive strength was 1.89 MPa.

Claims

1. A high-adhesion-strength epoxy-based liquid silicone rubber, having the structure shown in formula (I), ； in, R is an optionally substituted alkyl, optionally substituted aryl, or optionally substituted benzyl group. R 3 It is at least one of SiMe3 and SiMe2Vi. m is an integer, and 1 < m < 10. x is an integer from 1 to 10000. y is an integer from 0 to 10000. z is an integer from 1 to 10000. The epoxy-based liquid silicone rubber has a number-average molecular weight of 4000-90000 g / mol, and the epoxy group content in the epoxy-based liquid silicone rubber is 0.5-25 mol%, and the vinyl content is 0-10 mol%.

2. A method for preparing and applying the high adhesive strength epoxy-based liquid silicone rubber of claim 1, characterized in that, include: (1) Under a nitrogen atmosphere, tetracyclooxysiloxane, octamethylcyclotetrasiloxane and tetramethyltetravinylcyclotetrasiloxane are mixed evenly in a certain proportion; (2) Under a nitrogen atmosphere, the initiator and phosphazene catalyst are uniformly mixed under anhydrous reagent conditions and injected into the (1) system. Ring-opening copolymerization is carried out at 50°C. After a certain reaction time, a terminator is added to terminate the reaction. The epoxy liquid silicone rubber can be obtained without post-treatment. (3) The epoxy-based liquid silicone rubber and any diamine curing agent are mixed evenly according to a specific ratio, applied between the polar substrates to be bonded, and cured at a certain temperature to achieve bonding of polar substrates; (4) The epoxy liquid silicone rubber and any diamine curing agent are mixed evenly according to a specific ratio, applied to the surface of the polar substrate, and a layer of silicone rubber or hydrogen-containing silicone oil is laid on top of the coating. The mixture is then cured at a certain temperature to achieve bonding between the polar substrate and the non-polar material.

3. The method according to claim 2, characterized in that, In step (1), the certain proportion is 0.5 ~ 25 mol of tetracyclooxysiloxane, 73 ~ 89.5 mol of octamethylcyclotetrasiloxane, and 2 ~ 10 mol of tetramethyltetravinylcyclotetrasiloxane.

4. The method according to claim 2, characterized in that, In step (2), the catalyst is a phosphazene compound of formula (II).

5. The method according to claim 2, characterized in that, In step (2), the initiator is at least one of water, benzyl alcohol, ethylene glycol, 1,2-propanediol, 2,3-butanediol, terephthalic acid glycol, cyclohexanediol, glycerol, trimethylolpropane, pentaerythritol, xylitol, inositol, glucose, lithium hydroxide, sodium hydroxide, potassium hydroxide, lithium methoxide, sodium methoxide, potassium methoxide, lithium tert-butoxide, sodium tert-butoxide, potassium tert-butoxide, lithium methylsilanolate, sodium methylsilanolate, and potassium methylsilanolate; and the anhydrous reagent is at least one of tetrahydrofuran and toluene.

6. The method according to claim 2, characterized in that, In steps (3) and (4), the diamine curing agent is at least one of any commercially available diamine compounds such as ethylenediamine, propylenediamine, p-phenylenediamine, o-phenylenediamine, m-phenylenediamine, polyetheramine, and 4,4'-diaminodiphenyl disulfide, preferably 4,4'-diaminodiphenyl disulfide; the ratio of the diamine curing agent to the epoxy-based liquid rubber is [NH]:[Epoxy] = 1:

1.

7. The method according to claim 2, characterized in that, In steps (3) and (4), the substrate is at least one of aluminum plate, stainless steel, wood board, PC board, and glass; the curing temperature is 60 ~ 120 ℃, and the curing time is 4 ~ 36 hours.

8. The method according to claim 2, characterized in that, In step (4), the hydrogen-containing silicone oils are all commercially available products with hydrogen content of 0.07%, 0.1%, 0.18%, 0.5%, 0.75% and 1.58%, and are mixed with platinum catalyst to perform hydrosilylation with vinyl groups in epoxy liquid silicone rubber to achieve adhesion of non-polar materials to the surface of polar substrates.

9. The method according to claim 2, characterized in that, In step (4), the silicone rubber is a commercially available addition-cured room temperature vulcanizing silicone rubber, which can undergo hydrosilylation with epoxy-based liquid silicone rubber to achieve bonding of non-polar silicone rubber materials to the surface of a polar substrate.

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