Urea-modified silicone sealant and preparation method thereof

Abstract

The invention discloses a urea-modified silicone sealant and a preparation method thereof. The urea-modified silicone sealant is prepared by the following components: 100 parts of amino-terminated α, ω-dihydroxy polydimethylsiloxane, 5-25 parts of fumed silica, 5-15 parts of isocyanate, and 800-900 parts of solvent; wherein the amino-terminated α, ω-dihydroxy polydimethylsiloxane is a primary amino group; the isocyanate includes isocyanate A and isocyanate B, the isocyanate A is one or a combination of isophorone diisocyanate and dicyclohexylmethane diisocyanate, and the isocyanate B is one or a combination of toluene diisocyanate, diphenylmethane diisocyanate, and hexamethylene diisocyanate. The urea-modified silicone sealant can self-heal at room temperature, and can be applied to the sealing of building joints to solve the problem that the sealing performance of silicone sealant products cannot be guaranteed after cracking.

Description

Technical Field

[0001] The invention belongs to the technical field of sealants, and in particular relates to a self-healing urea-based modified organic silicon sealant and a preparation method thereof. Background Art

[0002] Silicone sealants have good weather resistance and elasticity, and good adhesion to most building and industrial materials. They are widely used in joint waterproofing, door and window installation joint sealing, and weatherproof sealing of curtain walls and photovoltaic buildings. During the application of silicone sealants, if the design is wrong or the sealant is used improperly, such as the joint displacement exceeds the sealant displacement level, or it moves before curing, it will cause cracking or even large-scale debonding, and the fracture surface will lose its sealing performance.

[0003] Traditional silicone sealants are condensation-type silicone sealants with Si-O-Si bonds as the main chain. They are strong, weather-resistant and simple to construct. However, if cracks occur due to design or construction problems, condensation-type silicone sealants cannot repair themselves, which will cause the sealing function to fail and increase the probability of water and air leakage. In serious cases, this will affect the normal use of the building and even cause safety issues.

[0004] In recent years, domestic and foreign sealant manufacturers have also launched various types of silicone sealant products, but none of them can solve the problem of how to ensure sealing performance after cracking. There are currently no relevant literature reports or products launched on the market for silicone sealants that are synthesized, cured and self-healed at room temperature. Summary of the invention

[0005] The purpose of the present invention is to provide a self-healing urea-based modified silicone sealant, which can be cured at room temperature and can self-heal at room temperature. When applied to building joint sealing, it can effectively solve the problem that the sealing performance of silicone sealant products cannot be guaranteed after cracking.

[0006] The above-mentioned purpose is achieved by the following technical solutions.

[0007] A self-healing urea-modified silicone sealant is prepared from the following components in parts by weight:

[0008]

[0009]

[0010] Wherein, the terminal amino group of the terminal amino group-modified α,ω-dihydroxy polydimethylsiloxane is a primary amino group;

[0011] 5-15 parts of the isocyanate include 0-10 parts of isocyanate A and 0-10 parts of isocyanate B, wherein the isocyanate A is one or a combination of isophorone diisocyanate and dicyclohexylmethane diisocyanate, and the isocyanate B is one or a combination of toluene diisocyanate, diphenylmethane diisocyanate, and hexamethylene diisocyanate.

[0012] It can be understood that the urea-modified silicone sealant is generated by reacting isocyanate with terminal primary amino-modified α, ω-dihydroxy polydimethylsiloxane, wherein the terminal primary amino-modified α, ω-dihydroxy polydimethylsiloxane has the characteristics of high activity and can react with isocyanate to generate urea-modified silicone sealant without the need for other reaction reagents or catalysts. By introducing strong hydrogen bonds, the urea-modified silicone sealant is endowed with the ability to self-heal at room temperature. The chemical reaction formula is as follows:

[0013]

[0014] Among them, isocyanate A has a larger molecular group at the ortho position of isocyanate, which has a strong steric hindrance effect on the formation of strong hydrogen bonds. Isocyanate B does not have a larger molecular group at the ortho position of isocyanate, or although it has a steric hindrance effect, the conjugation effect also offsets part of the steric hindrance. The activity of isocyanate B is generally higher. The combination of isocyanate A and isocyanate B can effectively adjust the activity.

[0015] In some embodiments, the terminal amino group of the amino-terminated α,ω-dihydroxy polydimethylsiloxane is -CH 2 NH 2 、-CH 2 CH 2 NH 2 、-CH 2 CH 2 CH 2 NH 2 、-CH 2 CH 2 CH 2 CH 2 NH 2 、-CH 2 CH=CHCH 2 NH 2 One of them.

[0016] In some embodiments, the composition is prepared from the following components, in parts by weight:

[0017]

[0018] In some embodiments, the viscosity of the amino-terminated α,ω-dihydroxy polydimethylsiloxane is in the range of 2000 cps to 20000 cps.

[0019] In some embodiments, the viscosity of the amino-terminated α,ω-dihydroxy polydimethylsiloxane is in the range of 5000 cps to 20000 cps.

[0020] In some embodiments, the amino-terminated α, ω-dihydroxy polydimethylsiloxane is prepared from octamethylcyclotetrasiloxane and a coupling agent in the presence of a catalyst; wherein the coupling agent is an amino-containing silane coupling agent, such as aminomethyldimethylmethoxysilane, 2-aminoethyldimethylmethoxysilane, 3-aminopropyldimethylmethoxysilane, 4-aminobutyldimethylmethoxysilane, and 4-aminobutenyldimethylmethoxysilane.

[0021] In some embodiments, the preparation method of the terminal amino-modified α, ω-dihydroxy polydimethylsiloxane is as follows: after stirring a mixture of octamethylcyclotetrasiloxane and potassium hydroxide and heating it to 45°C to 55°C, a coupling agent is added dropwise, and the temperature is continued to rise to 150°C to 170°C, and the reaction temperature is maintained for 8h to 10h. Low boiling substances are removed by vacuum to obtain the terminal amino-modified α, ω-dihydroxy polydimethylsiloxane.

[0022] In some embodiments, the mass ratio of the octamethylcyclotetrasiloxane to the coupling agent is 35-38:2-3, and the mass ratio of the catalyst to the coupling agent is 1:18-22.

[0023] In some embodiments, the fumed silica is hydrophobic fumed silica or hydrophilic fumed silica.

[0024] In some embodiments, the fumed silica is hydrophilic fumed silica.

[0025] In some embodiments, the solvent is an aprotic solvent.

[0026] In some embodiments, the solvent is one or more of acetone, tetrahydroxyfuran, dimethyl sulfoxide, and dimethylformamide.

[0027] A method for preparing the urea-modified silicone sealant as described above comprises the following steps:

[0028] The amino-terminated modified α,ω-dihydroxy polydimethylsiloxane and isocyanate are mixed with a solvent to obtain two groups of suspensions;

[0029] The two groups of suspensions were mixed evenly under nitrogen protection, and then washed with water, and then centrifuged to remove water;

[0030] Then, fumed silica is added, dispersed at high speed and vacuum degassed to obtain the urea-modified organic silicone sealant.

[0031] In some embodiments, the vacuum degree of vacuum degassing is -0.08 MPa to -0.1 MPa, and the vacuum degassing time is 20 min to 30 min.

[0032] In the present invention, urea-modified organic silicone sealant is generated by reacting isocyanate with terminal primary amino-modified α, ω-dihydroxy polydimethylsiloxane, wherein the terminal primary amino-modified α, ω-dihydroxy polydimethylsiloxane has the characteristic of high activity and can react with isocyanate to generate urea-modified organic silicone sealant without the action of other reaction reagents or catalysts. By introducing strong hydrogen bonds, the urea-modified organic silicone sealant is endowed with the ability to self-heal at room temperature, and after adding fumed silica, good construction performance can be obtained, so that the urea-modified organic silicone sealant can be applied to the sealing of building joints, which well solves the problem that the sealing performance of organic silicone sealant products cannot be guaranteed after cracking. DETAILED DESCRIPTION

[0033] In order to facilitate the understanding of the present invention, the present invention will be described more fully below. The present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the understanding of the disclosure of the present invention more thorough and comprehensive.

[0034] The experimental methods in the following examples without specifying specific conditions are usually carried out under conventional conditions or conditions recommended by the manufacturers. The various commonly used chemical reagents used in the examples are all commercially available products.

[0035] Unless otherwise defined, all technical and scientific terms used in the present invention have the same meaning as those commonly understood by those skilled in the art to which the present invention belongs. The terms used in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used in the present invention includes any and all combinations of one or more of the related listed items.

[0036] The following are specific embodiments.

[0037] Example 1

[0038] The preparation method of the self-healing urea-modified silicone sealant provided in this embodiment comprises the following steps:

[0039] A mixture of 350 parts of octamethylcyclotetrasiloxane and 1 part of potassium hydroxide was stirred and heated to 50°C, and then 20 parts of 3-aminopropyldimethylmethoxysilane were added dropwise, and the temperature was continued to rise to 160°C. The reaction temperature was maintained for 9 hours, and low-boiling substances were removed by vacuum to obtain α, ω-diaminopropyl polydimethylsiloxane;

[0040] 100 parts of 20,000 cps α, ω-diaminopropyl polydimethylsiloxane and 800 parts of acetone were mixed evenly, and 10 parts of diphenylmethane diisocyanate and 30 parts of acetone were premixed to obtain two groups of suspensions;

[0041] N 2 The two groups of suspensions were uniformly dispersed for 3 h under protection, and then washed three times with 2000 parts of deionized water, and then centrifuged to remove water after washing;

[0042] Then, 10 parts of hydrophobic fumed silica were added, dispersed at high speed, and vacuum degassing was started for 20 minutes with a vacuum degree of -0.09 MPa to obtain a urea-modified silicone sealant.

[0043] Example 2

[0044] The preparation method of the self-healing urea-modified silicone sealant provided in this embodiment comprises the following steps:

[0045] A mixture of 385 parts of octamethylcyclotetrasiloxane and 1 part of potassium hydroxide was stirred and heated to 50°C, and then 22 parts of 2-aminoethyldimethylmethoxysilane were added dropwise, and the temperature was continued to rise to 160°C. The reaction temperature was maintained for 8 hours, and low-boiling substances were removed by vacuum to obtain α,ω-diaminoethyl polydimethylsiloxane;

[0046] 100 parts of 5000 cps α, ω-diaminoethyl polydimethylsiloxane and 800 parts of tetrahydrofuran were mixed evenly, and 10 parts of isophorone diisocyanate and 30 parts of tetrahydrofuran were premixed to obtain two groups of suspensions;

[0047] N 2 The two groups of suspensions were uniformly dispersed for 3 h under protection, and then washed three times with 2000 parts of deionized water, and then centrifuged to remove water after washing;

[0048] Then, 10 parts of hydrophilic fumed silica were added, dispersed at high speed, and vacuum degassing was started for 30 minutes with a vacuum degree of -0.09 MPa to obtain a urea-modified silicone sealant.

[0049] Example 3

[0050] The preparation method of the self-healing urea-modified silicone sealant provided in this embodiment comprises the following steps:

[0051] A mixture of 210 parts of octamethylcyclotetrasiloxane and 1 part of potassium hydroxide was stirred and heated to 50°C, and then 18 parts of 4-aminobutyldimethylmethoxysilane were added dropwise, and the temperature was continued to rise to 170°C. The reaction temperature was maintained for 10 hours, and low-boiling substances were removed by vacuum to obtain α,ω-diaminobutyl polydimethylsiloxane;

[0052] 100 parts of 10000 cps α, ω-diaminobutyl polydimethylsiloxane and 800 parts of tetrahydrofuran were uniformly mixed, and then 5 parts of dicyclohexylmethane diisocyanate (HMDI), 5 parts of hexamethylene diisocyanate (HDI) and 30 parts of tetrahydrofuran were premixed to obtain two groups of suspensions;

[0053] N 2 The two groups of suspensions were uniformly dispersed for 3 h under protection, and then washed three times with 2000 parts of deionized water, and then centrifuged to remove water after washing;

[0054] Then, 20 parts of hydrophilic fumed silica were added, dispersed at high speed, and vacuum degassing was started for 30 minutes with a vacuum degree of -0.09 MPa to obtain a urea-modified silicone sealant.

[0055] Comparative Example 1

[0056] The difference between this comparative example and Example 2 is that this comparative example provides a method for preparing a traditional condensation-type organic silicone sealant, comprising the following steps:

[0057] 100 parts of 20000cps α, ω-dihydroxypolydimethylsiloxane, 5 parts of aminopropyltriethoxysilane, 25 parts of methyltributylidene oxime silane, 10 parts of hydrophobic fumed silica, and 0.2 parts of dibutyltin dilaurate were mixed evenly, dispersed evenly at high speed, and vacuum degassing was started for 20 minutes with a vacuum degree of -0.09MPa to obtain a traditional condensation type silicone sealant.

[0058] Comparative Example 2

[0059] The difference between this comparative example and Example 2 is that the α,ω-diaminoethyl polydimethylsiloxane is increased from 100 parts to 200 parts.

[0060] The preparation method of the self-healing urea-modified silicone sealant provided in this comparative example comprises the following steps:

[0061] A mixture of 385 parts of octamethylcyclotetrasiloxane and 1 part of potassium hydroxide was stirred and heated to 50°C, and then 22 parts of 2-aminoethyldimethylmethoxysilane were added dropwise, and the temperature was continued to rise to 160°C. The reaction temperature was maintained for 8 hours, and low-boiling substances were removed by vacuum to obtain α,ω-diaminoethyl polydimethylsiloxane;

[0062] 200 parts of 5000 cps α, ω-diaminoethyl polydimethylsiloxane and 800 parts of tetrahydrofuran were mixed evenly, and 10 parts of isophorone diisocyanate and 30 parts of tetrahydrofuran were premixed to obtain two groups of suspensions;

[0063] N 2 The two groups of suspensions were evenly dispersed for 3 hours under protection. Then 2000 parts of deionized water were added for washing 3 times, and after washing, the water was removed by centrifugation;

[0064] Then, 10 parts of hydrophilic fumed silica were added, dispersed at high speed, and vacuum degassing was started for 30 minutes with a vacuum degree of -0.09 MPa to obtain a urea-modified silicone sealant.

[0065] The urea-modified silicone sealants prepared in the examples and comparative examples were subjected to the following performance tests and mechanical performance tests according to the standard: GB / T 13477.8-2002. Under standard conditions, the tensile bonding strength and the maximum tensile strength elongation were both required to be cured for 28 days at (23±2)°C and relative humidity (50±5)%.

[0066] Self-healing test: Cut the H-type test piece cured under standard conditions for 28 days into two sections with a blade, gently splice the broken ends at (23±2)℃ and relative humidity (50±5)%, let it stand for 72 hours, and then conduct a tensile adhesion test. Healing efficiency = bonding strength after self-healing / bonding strength under standard conditions × 100%.

[0067] The test results are shown in Table 1.

[0068] Table 1. Mechanical properties and self-healing performance tests of silicone sealants

[0069]

[0070] As shown in Table 1, the urea-modified silicone sealant prepared in Examples 1 to 3 has good strength, good elasticity, and also has good self-healing ability. It can self-heal at room temperature, and the fracture surface is cured at room temperature for 72 hours, and the healing efficiency can reach more than 90%, which is significantly better than Comparative Examples 1 to 2. Comparative Example 1 is a traditional condensed silicone sealant prepared using terminal hydroxyl polydimethylsiloxane, which has no self-healing ability and cannot be self-repaired after cracking, which will cause the sealing effect to fail; Compared with Example 2, Comparative Example 2 adds too much α, ω-diaminoethyl polydimethylsiloxane, and part of the isocyanate cannot participate in the reaction to generate urea groups, and cannot participate in the formation of strong hydrogen bonds, so curing and self-healing are affected. At this time, the strength, elasticity and healing efficiency of the prepared urea-modified silicone sealant are all deteriorated, indicating that the ratio of isocyanate to terminal primary amino-modified α, ω-dihydroxy polydimethylsiloxane is also crucial to the mechanical properties and self-healing properties of the prepared urea-modified silicone sealant.

[0071] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described 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.

[0072] The above-mentioned embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A urea-modified silicone sealant, characterized in that: The invention is prepared by the following components in parts by weight: Wherein, the amino-terminated α,ω-dihydroxy polydimethylsiloxane is α,ω-diaminoethyl polydimethylsiloxane; The isocyanate is isophorone diisocyanate.

2. The urea-modified silicone sealant according to claim 1, characterized in that: The viscosity of the amino-terminated α,ω-dihydroxy polydimethylsiloxane is in the range of 2000cps to 20000cps.

3. The urea-modified silicone sealant according to claim 1, characterized in that: The viscosity of the amino-terminated α,ω-dihydroxy polydimethylsiloxane is in the range of 5000cps to 20000cps.

4. The urea-modified silicone sealant according to claim 1, characterized in that: The amino-terminated modified α,ω-dihydroxy polydimethylsiloxane is prepared from octamethylcyclotetrasiloxane and a coupling agent under the action of a catalyst; wherein the coupling agent is an amino-containing silane coupling agent.

5. The urea-modified silicone sealant according to claim 4, characterized in that: The preparation method of the amino-terminated modified α, ω-dihydroxy polydimethylsiloxane is as follows: after stirring a mixture of octamethylcyclotetrasiloxane and potassium hydroxide and heating it to 45° C. to 55° C., a coupling agent is added dropwise, the temperature is continued to be raised to 150° C. to 170° C., the reaction temperature is maintained for 8 h to 10 h, and low-boiling substances are removed by vacuuming to obtain the amino-terminated modified α, ω-dihydroxy polydimethylsiloxane.

6. The urea-modified silicone sealant according to claim 5, characterized in that: The mass ratio of the octamethylcyclotetrasiloxane to the coupling agent is 35-38:2-3, and the mass ratio of the catalyst to the coupling agent is 1:18-22.

7. The urea-modified silicone sealant according to claim 1, characterized in that: The fumed silica is hydrophobic fumed silica or hydrophilic fumed silica.

8. The urea-modified silicone sealant according to claim 7, characterized in that: The fumed silica is hydrophilic fumed silica.

9. The urea-modified silicone sealant according to claim 1, characterized in that: The solvent is an aprotic solvent.

10. The urea-modified silicone sealant according to claim 9, characterized in that: The solvent is one or more of acetone, tetrahydroxyfuran, dimethyl sulfoxide and dimethylformamide.

11. A method for preparing the urea-modified silicone sealant according to any one of claims 1 to 10, characterized in that: The following steps are involved: The amino-terminated modified α,ω-dihydroxy polydimethylsiloxane and isocyanate are mixed with a solvent to obtain two groups of suspensions; The two groups of suspensions were mixed evenly under nitrogen protection, and then washed with water, and then centrifuged to remove water; Then, fumed silica is added, dispersed at high speed and vacuum degassed to obtain the urea-modified organic silicone sealant.

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