Single-component dealcoholized organosilicon sealant composition with low compression set and preparation method thereof

Abstract

The invention provides a low-compression permanent deformation single-component dealcoholization type organic silicon sealant composition and a preparation method thereof, and the low-compression permanent deformation single-component dealcoholization type organic silicon sealant composition comprises the following components in parts by mass: alpha, alpha, beta, beta, beta, beta, beta, beta, beta- The silicone rubber is prepared from the following components in parts by weight: 95 to 105 parts of alpha, omega-dihydroxy polydimethylsiloxane, 20 to 30 parts of phenyl hydroxyl-containing terminated polysiloxane, 10 to 20 parts of hydrophobic fumed silica, 5 to 12 parts of hydrophobic nano-zinc oxide, 2 to 6 parts of cross-linking agent, 0.1 to 1 part of coupling agent and 1 to 3 parts of titanium complex. The phenyl-containing hydroxyl-terminated polysiloxane and the phenyl-containing cross-linking agent are introduced, so that a large-volume rigid phenyl structure can be contained in colloid, in a long molecular chain segment and in a cross-linking node, after curing, the phenyl structure can physically prop open a molecular chain, the friction resistance of chain segment movement can be reduced, the macroscopic resilience force can be improved, and the mechanical property of the adhesive is improved. Meanwhile, rigid phenyl is like a strut in a network, collapse under compression stress can be effectively resisted, and rebound force is provided for recovery after deformation.

Description

Technical Field

[0001] This invention belongs to the field of organosilicon sealant technology, and in particular relates to a low compression set, single-component, alcohol-free organosilicon sealant composition and its preparation method. Background Technology

[0002] One-component dealcohol-based silicone sealants are widely used due to their ease of use, non-toxicity, non-corrosiveness, and good deep curing properties. However, traditional dealcohol-based silicone sealants rely on the condensation reaction between hydroxyl-terminated polydimethylsiloxane and alkoxysilane crosslinking agents (such as methyltrimethoxysilane). The resulting crosslinked network structure has low regularity, and the molecular chains are prone to irreversible slippage and creep under long-term stress, leading to a generally high compression set (typically >20%). This severely limits their application in situations requiring long-term resistance to compressive stress (such as O-rings and gasket replacements).

[0003] For dealcohol-based products, existing technologies often improve compressive strength by adding large amounts of silica or inorganic fillers. However, this often comes at the cost of reduced processability (poor extrudability) and elasticity (decreased elongation at break), resulting in "rigid" reinforcement rather than "elastic" reinforcement. This often fails to fundamentally address the weaknesses and susceptibility to deformation inherent in the network structure. Addition-type products, while offering better compression set compared to dealcohol-based sealants, suffer from significantly lower adhesion to various substrates, leading to application limitations in bonding applications. Furthermore, they often require heat curing, posing inconvenience issues for handling large components. For example, Chinese patents CN111019595A and CN115386333A disclose low compression set addition-type thermosetting products. Summary of the Invention

[0004] The first objective of this invention is to provide a low-compression-permanent, one-component, de-alcoholized silicone sealant composition, in order to at least partially solve the aforementioned technical problems.

[0005] Therefore, the above-mentioned objective of the present invention is achieved through the following technical solution: A low-compression-permanent, one-component, alcohol-free silicone sealant composition, comprising the following components by weight: 95-105 parts of α,ω-dihydroxy polydimethylsiloxane, 20-30 parts of phenyl hydroxyl-terminated polysiloxane, 10-20 parts of hydrophobic fumed silica, 5-12 parts of hydrophobic nano zinc oxide, 2-6 parts of crosslinking agent, 0.1-1 parts of coupling agent, and 1-3 parts of titanium complex. The structure of the phenyl hydroxyl-terminated polysiloxane is as follows: Where a is an integer from 0 to 30, b is an integer from 0 to 20, and c is from 100 to 300; and a and b cannot both be 0; when a > 0, then b = 0; when b > 0, then a = 0. The crosslinking agent comprises methyltrimethoxysilane, phenyltrimethoxysilane and a multifunctional crosslinking agent, and the mass ratio of the three is (1-4):(0.5-3):1.

[0006] While adopting the above technical solutions, the present invention may also adopt or combine the following technical solutions: As a preferred embodiment of the present invention, the kinematic viscosity of the α,ω-dihydroxypolydimethylsiloxane at 25°C is 1000 mPas-80000 mPas.

[0007] As a preferred embodiment of the present invention: the hydrophobic fumed silica, after KH-570 surface treatment, has a specific surface area of ​​150-250 m² / g. 2 / g.

[0008] As a preferred embodiment of the present invention, the average particle size of the hydrophobic nano zinc oxide is 20-30 nm.

[0009] As a preferred embodiment of the present invention, the multifunctional crosslinking agent includes at least one of methyl orthosilicate, ethyl orthosilicate, 1,2-bis(triethoxysilyl)ethane, and 1,2-bis(trimethoxysilyl)ethane.

[0010] As a preferred embodiment of the present invention, the coupling agent is a mixture of epoxy silane and amino silane.

[0011] As a preferred embodiment of the present invention: the coupling agent is 3-(2,3-epoxypropoxy)propyltrimethoxysilane, 3-aminopropyltriethoxysilane, N A mixture of (2-aminoethyl)-3-aminopropyltrimethoxysilane in a molar ratio of 5:3:2.

[0012] As a preferred embodiment of the present invention, the titanium complex is Tyzor 726 from Doffcat Chemicals Ltd., India.

[0013] Another objective of this invention is to provide a method for preparing a low-compression-permanent single-component de-alcoholized silicone sealant.

[0014] Therefore, the above-mentioned objective of the present invention is achieved through the following technical solution: A method for preparing a low-compression-permanent, one-component, alcohol-free silicone sealant, the method being based on the composition described above and comprising the following steps: S1. Accurately metered α,ω-dihydroxy polydimethylsiloxane, phenyl hydroxyl-terminated polysiloxane, hydrophobic fumed silica, and hydrophobic nano zinc oxide are added to a planetary mixer. The mixture is stirred at atmospheric pressure for 5-15 min to basically mix the powder into the liquid. During the stirring process at a vacuum of 0.08-0.1 MPa, the system temperature is raised to 110-140℃. The vacuum and temperature are maintained for stirring for 2-4 h. After cooling, mixture A is obtained. S2. Add a precisely measured amount of phenyl-containing crosslinking agent to mixture A, and stir under a vacuum of 0.08–0.1 MPa for 0.3–1 h to obtain mixture B; S3. Add coupling agent and titanium complex to mixture B, and stir under vacuum of 0.08-0.1 MPa for 0.3-1 h to prepare a low compression set single-component de-alcoholized silicone sealant.

[0015] This invention provides a low-compression-permanent single-component dealcohol-type silicone sealant composition and its preparation method, which has the following beneficial effects: 1) By introducing phenyl hydroxyl-terminated polysiloxanes and phenyl crosslinking agents, large-volume rigid phenyl structures can be found in the colloid, in the long molecular chain segments and in the crosslinking nodes. After curing, the phenyl structures can physically "open up" the molecular chains, which can not only reduce the frictional resistance of chain segment movement and improve the macroscopic resilience, but also, the rigid phenyl acts as a "pillar" in the network, which can effectively resist the collapse under compressive stress and provide rebound force for recovery after deformation. 2) Introducing multifunctional crosslinking agents can form highly branched crosslinking nodes. These nodes are much more stable than traditional tri / bifunctional crosslinking links, which can greatly limit the relative slippage of molecular chains and suppress the generation of permanent deformation. 3) Phenyl linkages provide the "rebound force" and "elastic space" for recovery, while multifunctional crosslinking agents construct stable "anchor points." The two work together to provide a "dynamically enhanced crosslinking network" that is both strong and elastic, which can further achieve low compression set.

[0016] 4) The active groups on the surface of nano-ZnO promote a more complete and uniform cross-linking reaction, thereby optimizing the integrity of the entire network and reducing weak points. The nano-sized ZnO particles, uniformly dispersed and embedded in the cross-linked network of silicone rubber, possess a certain degree of rigidity and can act as numerous "micro-support points," effectively dispersing and transferring external compressive stress and preventing localized network damage caused by stress concentration. Simultaneously, nano-ZnO is an excellent heat stabilizer; its presence enhances the thermo-oxidative stability of the silicone matrix, indirectly ensuring the material's resistance to compressive deformation at higher temperatures. Detailed Implementation

[0017] The present invention will be described in further detail with reference to specific embodiments.

[0018] Example 1 30 parts of α,ω-dihydroxypolydimethylsiloxane with a kinematic viscosity of 1000 mPas, 40 parts of α,ω-dihydroxypolydimethylsiloxane with a kinematic viscosity of 10000 mPas, 30 parts of α,ω-dihydroxypolydimethylsiloxane with a kinematic viscosity of 80000 mPas, 25 parts of phenyl hydroxyl-terminated polysiloxane, and 18 parts of KH-570 surface-treated polysiloxane with a specific surface area of ​​200 m² were combined. 2 / g of hydrophobic fumed silica and 8 parts of hydrophobic zinc oxide with an average particle size of 20 nm were added to a planetary mixer. The mixture was first stirred at atmospheric pressure for 10 min, and then the temperature of the system was raised to 120℃ during stirring under a vacuum of 0.08-0.1 MPa. The mixture was stirred under vacuum and temperature for 3 h, and then cooled to obtain mixture A.

[0019] Add 2 parts of methyltrimethoxysilane, 2 parts of phenyltrimethoxysilane and 0.8 parts of methyl orthosilicate to mixture A, and stir under a vacuum of 0.08-0.1 MPa for 0.5 h to obtain mixture B.

[0020] Add 0.31 parts of 3-(2,3-epoxypropoxy)propyltrimethoxysilane, 0.17 parts of 3-aminopropyltriethoxysilane, and 0.12 parts of... to mixture B. N A mixture of (2-aminoethyl)-3-aminopropyltrimethoxysilane and 2.4 parts Tyzor726 is stirred at a vacuum of 0.08–0.1 MPa for 0.5 h to obtain a low compression set, one-component dealcoholized silicone sealant.

[0021] The structural formula of the phenyl hydroxyl-terminated polysiloxane is as follows: Examples 2-5 In Examples 2 to 5, the phenyl hydroxyl-terminated polysiloxane was the same as in Example 1, and the amounts of other components are shown in Table 1 below.

[0022] Example 6 The difference from Example 5 is that the phenyl hydroxyl-terminated polysiloxane has the following structural formula: Example 7 The difference from Example 5 is that the phenyl hydroxyl-terminated polysiloxane has the following structural formula: Example 8 The difference from Example 5 is that the phenyl hydroxyl-terminated polysiloxane has the following structural formula: Comparative Examples 1-3 The component dosages for Comparative Examples 1 to 3 are shown in Table 2 below.

[0023] Table 1 Table 2 Performance testing standards and methods: 1. Hardness: Tested according to GB / T 531.1-2008. The sample was cured for 7 days in an environment of 25℃±2℃ / 50%±5%RH before testing.

[0024] 2. Tensile strength and elongation at break: Tested according to GB / T 528-2009. The specimens were cured for 7 days at 25℃±2℃ / 50%±5%RH before testing.

[0025] 3. Shear strength: Tested according to GB / T 7124-2008. The sample was cured for 7 days at 25℃±2℃ / 50%±5%RH before testing.

[0026] 4. Compression set: Tested according to GB / T775.1-2015, type B specimen, compression rate 25%, high temperature use method A, the specimen is tested after curing in an environment of 25℃±2℃ / 50%±5%RH for 14 days.

[0027] The test results are shown in Tables 3 and 4 below: Table 3 Table 4 Comparative Example 3 (without phenyl groups, multifunctional crosslinking agents, and hydrophobic nano-zinc oxide): This example showed the highest compression set. Simply adding filler (fumed silica) could not fundamentally solve the problem of a weak network structure. However, Comparative Example 1, which added nano-zinc oxide, and Comparative Example 2, which added phenyl structures and multifunctional crosslinking agents, both showed a decrease in compression set. Specifically, under the test conditions of 23℃*168 hours, the compression set decreased from 25.20% in Comparative Example 3 to 22.30% in Comparative Example 1 and 15.40% in Comparative Example 2; under the test conditions of 100℃*24 hours, the compression set decreased from 34.30% in Comparative Example 3 to 31.60% in Comparative Example 1 and 20.30% in Comparative Example 2. In Comparative Example 2, no nano zinc oxide was added. Compared with Example 5, under the test conditions of 23℃*168 hours, the content increased from 8.2% in Example 5 to 15.40%; under the test conditions of 100℃*24 hours, the content increased from 9.7% in Example 5 to 20.30%. This shows that adding nano zinc oxide to the system can have a synergistic promoting effect and improve the compression set performance.

[0028] The compression set rates of all examples (Examples 1-8) at both room temperature (23℃ × 168 h) and high temperature (100℃ × 24 h) were significantly lower than those of the comparative examples (Comparative Examples 1-3), and were all below 15%. The best example 7 showed rates as low as 7.4% (23℃ × 168 h) and 8.6% (100℃ × 24 h), respectively. The diphenyl structure was more favorable for compression set than the monophenyl structure. Comparing the data of the examples and the comparative examples, the simultaneous introduction of phenyl groups, multifunctional crosslinking agents, and nano-zinc oxide resulted in a synergistic effect that improved the compression set performance.

[0029] While achieving low compressive strength, the examples all maintained an elongation at break of over 375%, with some even exceeding 420% (e.g., Examples 1 and 5), demonstrating excellent high elasticity. Their hardness (Shore A) also primarily falls within the practical range of 38A-49A, making them promising candidates for applications in the sealing of batteries, electronic controls, and motors in new energy vehicles, where long-term reliability is required to withstand vehicle vibration, impact, and temperature changes.

[0030] The above specific embodiments are used to explain and illustrate the present invention, and are only preferred embodiments of the present invention, not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made to the present invention within the spirit and scope of the claims shall fall within the protection scope of the present invention.

Claims

1. A low-compression-permanent, one-component, alcohol-free silicone sealant composition, characterized in that: Based on parts by weight, it includes the following components: 95-105 parts of α,ω-dihydroxy polydimethylsiloxane, 20-30 parts of phenyl hydroxyl-terminated polysiloxane, 10-20 parts of hydrophobic fumed silica, 5-12 parts of hydrophobic nano zinc oxide, 2-6 parts of crosslinking agent, 0.1-1 parts of coupling agent, and 1-3 parts of titanium complex. in, The structure of phenyl hydroxyl-terminated polysiloxanes is as follows: Where a is an integer from 0 to 30, b is an integer from 0 to 20, and c is from 100 to 300; and a and b cannot both be 0; when a > 0, then b = 0; when b > 0, then a = 0. The crosslinking agent comprises methyltrimethoxysilane, phenyltrimethoxysilane and a multifunctional crosslinking agent, and the mass ratio of the three is (1-4):(0.5-3):

1.

2. The composition according to claim 1, characterized in that: The kinematic viscosity of the α,ω-dihydroxypolydimethylsiloxane at 25°C is 1000 mPas-80000 mPas.

3. The composition according to claim 1, characterized in that: The hydrophobic fumed silica, after KH-570 surface treatment, has a specific surface area of ​​150-250 m². 2 / g.

4. The composition according to claim 1, characterized in that: The average particle size of the hydrophobic nano zinc oxide is 20-30 nm.

5. The composition according to claim 1, characterized in that: The multifunctional crosslinking agent includes at least one of methyl orthosilicate, ethyl orthosilicate, 1,2-bis(triethoxysilyl)ethane, and 1,2-bis(trimethoxysilyl)ethane.

6. The composition according to claim 1, characterized in that: The coupling agent is a mixture of epoxy silane and amino silane.

7. The composition according to claim 1, characterized in that: The coupling agent is 3-(2,3-epoxypropoxy)propyltrimethoxysilane, 3-aminopropyltriethoxysilane, N A mixture of (2-aminoethyl)-3-aminopropyltrimethoxysilane in a molar ratio of 5:3:

2.

8. The composition according to claim 1, characterized in that: The titanium complex is Tyzor 726 from Dolph Cement Chemicals Ltd., India.

9. A method for preparing a low-compression-permanent, one-component, alcohol-free silicone sealant, characterized in that: The preparation method is based on the composition according to any one of claims 1-8 and includes the following steps: S1. Accurately metered α,ω-dihydroxy polydimethylsiloxane, phenyl hydroxyl-terminated polysiloxane, hydrophobic fumed silica, and hydrophobic nano zinc oxide are added to a planetary mixer. The mixture is stirred under normal pressure for 5-15 min, and the powder is then mixed into the liquid. During the stirring process under a vacuum of 0.08-0.1 MPa, the system temperature is raised to 110-140℃. The vacuum and temperature are maintained for stirring for 2-4 h. After cooling, mixture A is obtained. S2. Add a precisely measured amount of phenyl-containing crosslinking agent to mixture A, and stir under a vacuum of 0.08–0.1 MPa for 0.3–1 h to obtain mixture B; S3. Add coupling agent and titanium complex to mixture B, and stir under vacuum of 0.08-0.1 MPa for 0.3-1 h to prepare a low compression set single-component de-alcoholized silicone sealant.

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