Heat-resistant auxiliary agent for silicone rubber and preparation method of heat-resistant auxiliary agent
By synthesizing modified polyurethane containing polar groups and rigid chain segments and synergistically reinforcing it with nano-silica, the problem of free movement of molecular chains of silicone rubber at high temperatures is solved, better heat resistance and mechanical properties are achieved, a uniform physical cross-linking network is formed, and aging is delayed.
Patent Information
- Application Number
- CN202510911338.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-07-02
- Publication Date
- 2025-09-16
- Estimated Expiration
- Not applicable · inactive patent
AI Technical Summary
In the existing technology, silicone rubber is prone to segmental thermal oxidation degradation under high temperature environment, resulting in significant attenuation of tensile strength and elongation at break. In addition, traditional nanofillers are difficult to disperse evenly in the silicone rubber matrix, and the interfacial bonding force is weak, resulting in a decrease in the material's elastic modulus, complex processing and high cost.
By synthesizing modified polyurethane containing polar groups and rigid chain segments, and synergistically reinforcing it with nano-silica, a dynamic connection structure and a three-dimensional network with gradient transition are formed, which restricts the movement of molecular chains and improves the heat resistance and mechanical properties of the material.
It significantly improves the heat resistance and mechanical strength of silicone rubber, improves the dispersion state of inorganic fillers in silicone rubber, forms a uniform physical cross-linking network, delays high-temperature oxidation aging, and maintains structural stability.
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Abstract
Description
Technical Field
[0001] The present invention belongs to the technical field of silicone rubber, and in particular relates to a heat-resistant additive for silicone rubber and a preparation method thereof. Background Art
[0002] Silicone rubber has irreplaceable application value in high-temperature working conditions such as aerospace, new energy vehicles, and electronic packaging due to its excellent high and low temperature resistance, electrical insulation and chemical stability.
[0003] However, its flexible molecular structure, whose main chain is composed of -Si-O- bonds, is prone to segmental thermal oxidation degradation in high temperature environments (especially above 200°C), resulting in significant attenuation of mechanical properties such as tensile strength and elongation at break, limiting its application expansion in higher temperature scenarios. In the existing technology, the main means to improve the heat resistance of silicone rubber include adding inorganic fillers (such as nano-silica, mica powder) or introducing chemical modifiers. However, due to the high activity of surface hydroxyl groups, traditional nanofillers are very easy to form agglomerates in the silicone rubber matrix. Not only can they not be evenly dispersed, but they also cause stress concentration due to the weak bonding force between the filler and the matrix interface, resulting in a decrease in the elastic modulus of the material. Some methods of modification through small molecule coupling agents or ordinary polymers lack the coordinated design of polar groups and rigid structures, making it difficult to construct an effective physical cross-linking network in the silicone rubber matrix. The molecular chains are still relatively free to move at high temperatures, and the improvement in heat aging resistance is limited. In addition, the existing modification system also has problems such as the amount of filler is not proportional to the heat resistance effect, and the complex processing technology leads to increased production costs.
[0004] Therefore, in order to solve the above problems, the present invention provides a heat-resistant additive for silicone rubber and a preparation method thereof. Summary of the Invention
[0005] The purpose of the present invention is to overcome the defects of the prior art and provide a heat-resistant additive for silicone rubber and a preparation method thereof.
[0006] The purpose of the present invention can be achieved through the following technical solutions:
[0007] A method for preparing a heat-resistant additive for silicone rubber comprises the following steps:
[0008] Step 1: Add the modified monomer and toluene diisocyanate to N,N-dimethylformamide, stir evenly, then add dibutyltin dilaurate, stir and react at 90-100°C for 24 hours. After the reaction is completed, terminate the reaction with distilled water, filter, wash, and dry to obtain a modified polyurethane;
[0009] Step 2: Mix methyl vinyl silicone rubber, modified polyurethane and nano-silica, and stir at 100-120° C. for 1-2 hours to obtain a heat-resistant additive.
[0010] More optimally, the modified polyurethane raw material includes the following substances: by weight, 10-15 parts of modified monomer, 10-20 parts of toluene diisocyanate, 80-100 parts of N,N-dimethylformamide, and 0.1-0.5 parts of dibutyltin dilaurate.
[0011] More optimally, the heat-resistant auxiliary agent raw materials include the following substances: 10-12 parts by weight of methyl vinyl silicone rubber, 1-2 parts of modified polyurethane, and 3-5 parts of nano-silicon dioxide.
[0012] More optimally, the preparation process of the modified monomer is:
[0013] S1: Diethanolamine and paraformaldehyde were mixed, heated to 60-70°C under a protective atmosphere, and stirred continuously for 1-2 hours. The mixture was then cooled to room temperature, and eugenol was added. The mixture was heated to 90-100°C and the reaction was continued for 6-7 hours. After the reaction was completed, the mixture was post-processed to obtain intermediate A.
[0014] S2: Mix the intermediate A, 6-chloro-1-hexanol, and ethanol, stir evenly, add sodium hydroxide solution, continue stirring to fully mix the reaction system, then increase the temperature to 90-100°C, reflux reaction for 10-12 hours, and after the reaction is completed, cool the reaction solution to room temperature, filter, wash, and dry to obtain a modified monomer.
[0015] In the scheme, paraformaldehyde decomposes under heating conditions to generate formaldehyde molecules. Formaldehyde undergoes a nucleophilic addition reaction with the amino group in diethanolamine to generate an intermediate with a nitrogen heterocyclic structure. This intermediate then undergoes a condensation reaction with eugenol to obtain intermediate A. The specific synthesis process is shown below:
[0016]
[0017] More optimally, the intermediate A raw material includes the following components: 3-4 parts of diethanolamine, 1-2 parts of paraformaldehyde, and 5-6 parts of eugenol, by weight.
[0018] In the scheme, under alkaline conditions (sodium hydroxide solution), the phenolic hydroxyl group in intermediate A is deprotonated, and then undergoes a nucleophilic substitution reaction with the chlorinated carbon atom in 6-chloro-1-hexanol to obtain a modified monomer. The specific synthesis process is as follows:
[0019]
[0020] More optimally, the modified monomer raw material includes the following components: 10-12 parts of intermediate A, 8-10 parts of 6-chloro-1-hexanol, and 60-80 parts of ethanol, by weight.
[0021] More optimally, the concentration of the sodium hydroxide solution is 2.5-3 mol / L.
[0022] Beneficial effects of the present invention:
[0023] The present invention synthesizes modified polyurethane containing polar groups and rigid segments, and synergistically enhances it with nano-silicon dioxide, significantly improving the heat resistance stability and mechanical strength of silicone rubber. The details are as follows:
[0024] First, the polar functional groups (such as hydroxyl and carbamate groups) introduced into the modified polyurethane form a dynamic connection structure with the surface of the nanosilica, reducing the surface activity of the filler and preventing nanoparticle aggregation. This effect allows the inorganic filler to form a more uniform dispersion in the silicone rubber, improving the interfacial bonding between the two phases and thus enhancing the overall mechanical properties of the material.
[0025] Second, through molecular structural design, a rigid molecular chain with a specific structure containing aromatic rings and long side chains is constructed in the modified polyurethane. These rigid units form physical crosslinks within the silicone rubber matrix. Through intermolecular forces, they create a multi-layered network that restricts the high-temperature motion of the matrix molecular chains, significantly improving the material's heat resistance and maintaining structural stability even in high-temperature environments.
[0026] Third, the carbon-carbon double bonds retained by the modified monomers can undergo a cross-linking reaction with the vinyl groups in the silicone rubber molecular chains, forming a gradient, three-dimensional network structure at the interface. This in-situ covalent bonding not only improves the uniformity of the cross-link density but also dissipates energy through dynamic reactions when heated, delaying the material's aging due to high-temperature oxidation. DETAILED DESCRIPTION
[0027] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.
[0028] Example 1: A method for preparing a heat-resistant additive for silicone rubber, comprising the following steps:
[0029] Step 1: Add 10 parts of modified monomer and 10 parts of toluene diisocyanate to 80 parts of N,N-dimethylformamide, stir evenly, add 0.1 parts of dibutyltin dilaurate, stir and react at 90°C for 24 hours. After the reaction is completed, terminate the reaction with distilled water, filter, wash, and dry to obtain a modified polyurethane;
[0030] Step 2: Mix 10 parts of methyl vinyl silicone rubber, 1 part of modified polyurethane, and 3 parts of nano-silica, and stir at 100°C for 1 hour to obtain a heat-resistant additive;
[0031] Wherein, the preparation process of the modified monomer is:
[0032] S1: Mix 3 parts of diethanolamine and 1 part of paraformaldehyde, heat to 60°C under protective atmosphere, and continue stirring for 1 hour. Then cool to room temperature, add 5 parts of eugenol, raise the temperature to 90°C, and continue the reaction for 6 hours. After the reaction is completed, post-process and obtain intermediate A;
[0033] S2: 10 parts of intermediate A, 8 parts of 6-chloro-1-hexanol, and 60 parts of ethanol were mixed and stirred evenly. Sodium hydroxide solution (concentration of 2.5 mol / L) was added and stirred continuously to fully mix the reaction system. The temperature was then raised to 90°C and refluxed for 10 hours. After the reaction was completed, the reaction solution was cooled to room temperature, filtered, washed, and dried to obtain a modified monomer.
[0034] Example 2: A method for preparing a heat-resistant additive for silicone rubber, comprising the following steps:
[0035] Step 1: Add 15 parts of the modified monomer and 20 parts of toluene diisocyanate to 100 parts of N,N-dimethylformamide, stir evenly, add 0.5 parts of dibutyltin dilaurate, stir and react at 100°C for 24 hours. After the reaction is completed, terminate the reaction with distilled water, filter, wash, and dry to obtain a modified polyurethane;
[0036] Step 2: Mix 12 parts of methyl vinyl silicone rubber, 2 parts of modified polyurethane, and 5 parts of nano-silica, and stir at 120°C for 2 hours to obtain a heat-resistant additive;
[0037] Wherein, the preparation process of the modified monomer is:
[0038] S1: Mix 4 parts of diethanolamine and 2 parts of paraformaldehyde, heat to 70°C under protective atmosphere, and continue stirring for 2 hours. Then cool to room temperature, add 6 parts of eugenol, raise the temperature to 100°C, and continue the reaction for 7 hours. After the reaction is completed, post-process and obtain intermediate A;
[0039] S2: 12 parts of intermediate A, 10 parts of 6-chloro-1-hexanol, and 80 parts of ethanol were mixed and stirred evenly. Sodium hydroxide solution (concentration of 3 mol / L) was added and stirred continuously to fully mix the reaction system. The temperature was then raised to 100°C and refluxed for 12 hours. After the reaction was completed, the reaction solution was cooled to room temperature, filtered, washed, and dried to obtain a modified monomer.
[0040] Example 3: A method for preparing a heat-resistant additive for silicone rubber, comprising the following steps:
[0041] Step 1: Add 12.5 parts of the modified monomer and 15 parts of toluene diisocyanate to 90 parts of N,N-dimethylformamide, stir evenly, add 0.3 parts of dibutyltin dilaurate, stir and react at 95°C for 24 hours. After the reaction is completed, terminate the reaction with distilled water, filter, wash, and dry to obtain a modified polyurethane;
[0042] Step 2: 11 parts of methyl vinyl silicone rubber, 1.5 parts of modified polyurethane, and 4 parts of nano-silica were mixed and stirred at 110° C. for 1.5 hours to obtain a heat-resistant additive;
[0043] Wherein, the preparation process of the modified monomer is:
[0044] S1: 3.5 parts of diethanolamine and 1.5 parts of paraformaldehyde were mixed, heated to 65°C under a protective atmosphere, and stirred for 1.5 hours. The mixture was then cooled to room temperature, and 5.5 parts of eugenol were added. The mixture was heated to 95°C and the reaction was continued for 6.5 hours. After the reaction was completed, the mixture was post-treated to obtain intermediate A.
[0045] S2: 11 parts of intermediate A, 9 parts of 6-chloro-1-hexanol, and 70 parts of ethanol were mixed and stirred evenly. Sodium hydroxide solution (concentration of 2.75 mol / L) was added and stirred continuously to fully mix the reaction system. The temperature was then raised to 95°C and refluxed for 11 hours. After the reaction was completed, the reaction solution was cooled to room temperature, filtered, washed, and dried to obtain a modified monomer.
[0046] Comparative Example 1: The modified polyurethane is replaced with a borate coupling agent, as follows:
[0047] 11 parts of methyl vinyl silicone rubber, 1.5 parts of borate coupling agent, and 4 parts of nano-silica were mixed, and stirred at 110° C. for 1.5 hours to obtain a heat-resistant additive.
[0048] Comparative Example 2: polyether polyol was used instead of the modified monomer, and the rest was the same as in Example 3.
[0049] Detection test:
[0050] 1. Test object: The heat-resistant additive obtained in the embodiment and the comparative example is added to the raw material of the silicone rubber. The specific preparation method is as follows: 10 kg of methyl vinyl silicone rubber and 2 kg of heat-resistant additive are put into an internal mixer (volume 500 L, speed 30±5 rpm), mixed at 25 ° C for 30 min until the filler is completely dispersed, then transferred to an open mill, tert-butyl hydroperoxide is slowly added, and thinly passed 5 times (roller spacing 1.0 mm) to ensure uniform dispersion; the mixed rubber is placed in a flat vulcanizer and molded and vulcanized at 180 ° C and a pressure of 10 MPa for 3 h. After vulcanization is completed, it is cooled to below 50 ° C at room temperature and demolded to obtain a silicone rubber product.
[0051] 2. Detection method:
[0052] (1) The tensile strength of the silicone rubber products obtained in the examples and comparative examples was tested according to GB / T528-2009 Determination of tensile stress-strain properties of vulcanized rubber or thermoplastic rubber;
[0053] (2) According to GB / T3512-2001 Vulcanized rubber or thermoplastic rubber hot air accelerated aging and heat resistance test, the silicone rubber products obtained in the examples and comparative examples were subjected to heat aging treatment at 300°C for 48 hours, and then the tensile strength was tested;
[0054] The obtained data is shown in the following table:
[0055]
[0056] Conclusion: This invention significantly improves the heat stability and mechanical strength of silicone rubber by synthesizing a modified polyurethane containing polar groups and rigid segments and synergistically reinforcing it with nano-silica. The examples show that after the heat-resistant additives prepared in Examples 1, 2, and 3 were added to silicone rubber, their tensile strengths reached 11.9 MPa, 12.3 MPa, and 12.8 MPa, respectively. After heat aging at 300°C for 48 hours, the tensile strengths remained at 10.8 MPa, 11.2 MPa, and 11.5 MPa, respectively. This demonstrates that the heat-resistant additive can effectively improve the mechanical properties of silicone rubber and has good structural stability in high-temperature environments.
[0057] In contrast, in comparative example 1, the modified polyurethane is replaced with a borate coupling agent, and the tensile strength and tensile strength after heat aging of its silicone rubber product are 9.8MPa and 8.6MPa respectively, both lower than those in the embodiment; in comparative example 2, the modified monomer is replaced with a polyether polyol, and the performance is even worse, with a tensile strength of only 8.8MPa, which is reduced to 4.7MPa after heat aging. This shows that the polar functional groups introduced into the modified polyurethane can form a dynamic connection structure with the surface of nano-silica, prevent nanoparticle aggregation, and improve the two-phase interface bonding; the rigid molecular chains of aromatic rings and long side chains contained therein can form physical crosslinking points in the silicone rubber matrix, limiting the high-temperature movement of the matrix molecular chains; the carbon-carbon double bonds retained by the modified monomer undergo a co-crosslinking reaction with the vinyl groups in the silicone rubber molecular chains, and the three-dimensional network structure formed can dissipate energy and delay material aging. These factors work together to make the heat-resistant additive of the present invention significantly better than other alternatives.
[0058] Throughout the specification, references to terms such as "one embodiment," "example," or "specific example" indicate that the specific features, structures, materials, or characteristics described in conjunction with that embodiment or example are included in at least one embodiment or example of the present invention. In this specification, schematic representations of these terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.
[0059] The above contents are merely examples and explanations of the present invention. Those skilled in the art may make various modifications or additions to the described specific embodiments or replace them in similar ways. As long as they do not deviate from the invention or exceed the scope defined by the claims, they should all fall within the scope of protection of the present invention.
Claims
1. A method for preparing a heat-resistant additive for silicone rubber, characterized in that: The following steps are involved: Step 1: Add the modified monomer and toluene diisocyanate to N,N-dimethylformamide, stir evenly, then add dibutyltin dilaurate, stir and react at 90-100°C for 24 hours. After the reaction is completed, terminate the reaction with distilled water, filter, wash, and dry to obtain a modified polyurethane; Step 2: Mix methyl vinyl silicone rubber, modified polyurethane and nano-silica, and stir at 100-120° C. for 1-2 hours to obtain a heat-resistant additive.
2. The method for preparing a heat-resistant additive for silicone rubber according to claim 1, characterized in that: The modified polyurethane raw material comprises the following substances: by weight, 10-15 parts of a modified monomer, 10-20 parts of toluene diisocyanate, 80-100 parts of N,N-dimethylformamide, and 0.1-0.5 parts of dibutyltin dilaurate.
3. The method for preparing a heat-resistant additive for silicone rubber according to claim 1, characterized in that: The heat-resistant auxiliary agent raw materials include the following substances: 10-12 parts by weight of methyl vinyl silicone rubber, 1-2 parts of modified polyurethane, and 3-5 parts of nano silicon dioxide.
4. The method for preparing a heat-resistant additive for silicone rubber according to claim 1, characterized in that: The preparation process of the modified monomer is: S1: Diethanolamine and paraformaldehyde were mixed, heated to 60-70°C under a protective atmosphere, and stirred continuously for 1-2 hours. The mixture was then cooled to room temperature, and eugenol was added. The mixture was heated to 90-100°C and the reaction was continued for 6-7 hours. After the reaction was completed, the mixture was post-processed to obtain intermediate A. S2: Mix the intermediate A, 6-chloro-1-hexanol, and ethanol, stir evenly, add sodium hydroxide solution, continue stirring to fully mix the reaction system, then increase the temperature to 90-100°C, reflux reaction for 10-12 hours, and after the reaction is completed, cool the reaction solution to room temperature, filter, wash, and dry to obtain a modified monomer.
5. The method for preparing a heat-resistant additive for silicone rubber according to claim 4, characterized in that: The intermediate A raw material includes the following components: 3-4 parts of diethanolamine, 1-2 parts of paraformaldehyde, and 5-6 parts of eugenol in parts by weight.
6. The method for preparing a heat-resistant additive for silicone rubber according to claim 4, characterized in that: The modified monomer raw material comprises the following components: by weight, 10-12 parts of intermediate A, 8-10 parts of 6-chloro-1-hexanol, and 60-80 parts of ethanol.
7. The method for preparing a heat-resistant additive for silicone rubber according to claim 4, characterized in that: The concentration of the sodium hydroxide solution is 2.5-3 mol / L.
8. A heat-resistant additive obtained by the method for preparing a heat-resistant additive for silicone rubber according to any one of claims 1 to 7.