Preparation process of environment-friendly foaming silicone rubber

Abstract

The invention discloses a preparation process of environment-friendly foamed silicone rubber, and relates to the technical field of silicone rubber. The environment-friendly foamed silicone rubber is prepared from the following raw materials in parts by mass: 90-100 parts of raw methyl vinyl silicone rubber, 20-30 parts of a reinforcing agent, 0.05-0.3 part of an inhibitor, 4-6 parts of hydroxyl silicone oil, 0.3-0.5 part of hydrogen-containing silicone oil, 2-4 parts of a foaming agent, 0.2-0.5 part of a catalyst and 0.2-1 part of an antibacterial agent. The antibacterial agent with a specific structure is adopted, the problems that a traditional silver or quaternary ammonium salt antibacterial agent is prone to migration and precipitation and poor in thermal stability are solved by means of the excellent compatibility and high temperature resistance of the antibacterial agent and a silicone rubber matrix, the material shows efficient antibacterial activity, the high-level antibacterial effect can still be kept after thermal aging, and the service life of the material is prolonged. The defects that a traditional antibacterial agent is prone to migration and precipitation and poor in thermal stability are overcome.

Description

Technical Field

[0001] This invention relates to the field of silicone rubber technology, specifically to the preparation process of environmentally friendly foamed silicone rubber. Background Technology

[0002] Foamed silicone rubber, as a lightweight, high-performance elastomer material, is widely used in aerospace, electronics, transportation, medical devices, and building decoration due to its excellent high-temperature resistance, weather resistance, electrical insulation, and good cushioning and shock absorption properties. With technological advancements and industrial upgrading, the market has placed higher demands on the comprehensive performance of foamed silicone rubber. These demands not only require a uniform cell structure, low density, and good mechanical properties, but also present new challenges to its functionality, such as antibacterial properties, mildew resistance, and processing stability.

[0003] Currently, the preparation of foamed silicone rubber mainly adopts the chemical foaming method, which involves adding azo or bicarbonate foaming agents during the silicone rubber compounding process. Heating decomposes these agents to generate gas, causing the rubber to crosslink and foam into shape. However, existing technologies have significant shortcomings in several aspects. First, traditional vulcanization processes often employ a single temperature range or a simple two-step vulcanization, making it difficult to simultaneously ensure sufficient crosslinking of the silicone rubber, complete decomposition of the foaming agent, and effective removal of low-molecular-weight volatiles. This affects the product's compression set, resilience, and mechanical strength, reducing its service life and reliability. Second, the expansion of functionalities such as antibacterial properties is insufficient, making it difficult to meet the needs of special application scenarios. In fields with strict antibacterial requirements, such as medical, food packaging, and public transportation, while existing technologies can impart antibacterial properties to silicone rubber by adding silver-based or quaternary ammonium salt antibacterial agents, these generally suffer from poor dispersibility, easy migration and precipitation, insufficient high-temperature resistance, and negative impacts on the vulcanization characteristics and mechanical properties of the silicone rubber itself. There is a lack of novel antibacterial systems that are highly compatible with the silicone rubber matrix, efficient, and durable.

[0004] Therefore, there is an urgent need to develop a new process for preparing foamed silicone rubber. By optimizing the formulation design, introducing highly efficient and compatible antibacterial components, and matching a multi-stage precise vulcanization foaming process, the precise control of the cell structure can be achieved, giving the material durable and stable antibacterial properties, while improving process stability and overall product performance, to meet the urgent needs of high-end application fields. Summary of the Invention

[0005] The purpose of this invention is to address the problems in existing technologies for the vulcanization process of foamed silicone rubber, such as difficulty in achieving sufficient cross-linking leading to reduced mechanical strength, insufficient antibacterial functionality, poor dispersibility of antibacterial agents, easy migration and precipitation, and impact on bulk properties. This invention provides an environmentally friendly preparation process for foamed silicone rubber. This process optimizes the formulation design, introduces highly efficient and compatible antibacterial components, and matches a multi-stage, precise vulcanization and foaming process to achieve precise control of the cell structure, imparting long-lasting and stable antibacterial properties to the material while improving the overall performance of the product.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: Environmentally friendly foamed silicone rubber is prepared from the following raw materials in parts by weight: 90-100 parts of methyl vinyl silicone rubber raw rubber, 20-30 parts of reinforcing agent, 0.05-0.3 parts of inhibitor, 4-6 parts of hydroxyl silicone oil, 0.3-0.5 parts of hydrogen-containing silicone oil, 2-4 parts of foaming agent, 0.2-0.5 parts of catalyst, and 0.2-1 parts of antibacterial agent; The antibacterial agent is a compound represented by Formula 1 below: Formula 1: ; In Formula 1, R1 is a substituent, specifically R1 being any one of alkyl, amino, or methoxy groups having 1-5 carbon atoms. The alkyl groups having 1-5 carbon atoms are: methyl, ethyl, and isopropyl.

[0007] Furthermore, the methyl vinyl silicone rubber has a vinyl molar content of 0.04-0.2% and a number-average molecular weight of 450,000-550,000.

[0008] Furthermore, the reinforcing agent is at least one of fumed silica, precipitated silica, and calcium carbonate.

[0009] Furthermore, the inhibitor is at least one of ethynylcyclohexanol, diallyl maleate, and methylbutynol.

[0010] Furthermore, the hydroxyl content of the hydroxyl silicone oil is 5-12%.

[0011] Furthermore, the hydrogen content of the hydrogen-containing silicone oil is 0.08-0.4%.

[0012] Furthermore, the foaming agent is at least one of azodicarbonamide, sodium bicarbonate, and N,N-dinitrospentamethylenetetramine.

[0013] Furthermore, the catalyst is at least one of a platinum-vinylsiloxane complex or a platinum-alkynyl complex.

[0014] Furthermore, the antibacterial agent is any one of the compounds shown in the following structures: ; .

[0015] Furthermore, fluorosilicone rubber may also be added to the environmentally friendly foamed silicone rubber.

[0016] The preparation process of environmentally friendly foamed silicone rubber includes the following steps: S1. Add the raw methyl vinyl silicone rubber to a mixer and plasticize it for 5-10 minutes at a temperature of 50-60℃ and a speed of 50-100 r / min. Then add the reinforcing agent and hydroxyl silicone oil, raise the temperature to 80-100℃, and continue mixing for 20-30 minutes to obtain a premixed rubber. S2. Add the premixed rubber to the open mill, adjust the roller gap to 1-3mm, and pass through the mill 3-5 times; then add the hydrogen-containing silicone oil, inhibitor, foaming agent, and antibacterial agent in sequence, and mix for 10-20 minutes until the material is evenly dispersed; finally add the catalyst, and mix at 80-100r / min for 3-5 minutes to obtain the compounded rubber. S3. Place the compound into a mold preheated to 100-120℃, apply a pressure of 5-10MPa, hold the pressure for 5-10min for preliminary molding, and then send the pre-molded material together with the mold into a vulcanizing box. Maintain the vulcanizing box pressure at 0.3-0.6MPa, first vulcanize and foam at 140-150℃ for 10-15min, then raise the temperature to 160-170℃ and continue vulcanizing for 10-20min. S4. After vulcanization, remove the product from the mold and place it in an oven at 60-80℃ for constant temperature drying for 2-4 hours to remove residual low-molecular-weight volatiles inside the product. Allow it to cool naturally to room temperature to obtain environmentally friendly foamed silicone rubber.

[0017] Furthermore, the roll temperature of the open mill in S2 is controlled at 40-60℃.

[0018] Furthermore, the ventilation rate of the oven in S4 is 0.5-1 m / s, and the product is turned over once every 1 hour during the drying process to ensure uniform drying.

[0019] This invention utilizes a multi-stage process with its various components to specifically address core issues in traditional foamed silicone rubber, such as insufficient crosslinking, poor mechanical properties, poor dispersion of antibacterial agents, and insufficient antibacterial durability. Methyl vinyl silicone rubber raw material serves as the matrix, providing a stable framework for the crosslinking reaction. It is precisely matched with hydrogen-containing silicone oil and platinum-based catalysts, gradually completing crosslinking in a multi-stage vulcanization process: the low-temperature stage ensures the foaming agent fully decomposes to form uniform cells, while the high-temperature stage achieves complete crosslinking of the matrix, avoiding conflicts between crosslinking and foaming at a single temperature. The reinforcing agent works synergistically with hydroxyl silicone oil; the hydroxyl silicone oil improves the dispersibility of the reinforcing agent in the raw rubber, reduces agglomeration, and significantly enhances the material's mechanical strength, overcoming the defects of large compression set and poor resilience caused by uneven reinforcement in traditional processes. The antibacterial agent of this invention, with its specific structure and hydrophilic-hydrophobic balance of carbon alkyl and amino groups, exhibits excellent compatibility with the silicone rubber matrix, overcoming the problems of poor dispersion and easy migration of traditional silver-based and quaternary ammonium salt antibacterial agents. It is stably dispersed in the compound, and its high-temperature resistance is adapted to the vulcanization temperature, without interfering with the crosslinking reaction, thus endowing the material with durable antibacterial properties. Inhibitors regulate the vulcanization rate, preventing premature crosslinking during mixing or initial molding stages and ensuring simultaneous decomposition of the foaming agent and cell formation. Subsequent oven drying processes work in synergy with the components to remove low-molecular-weight volatiles, further optimizing product stability. Through multi-dimensional synergy in matrix crosslinking, reinforcement dispersion, antibacterial stabilization, and reaction regulation, combined with precise multi-stage processes, foamed silicone rubber with uniform cell structure, excellent mechanical properties, and long-lasting antibacterial stability is ultimately achieved, meeting the demands of high-end applications.

[0020] Compared with the prior art, the beneficial effects of the present invention are: (1) Mechanical properties are fully optimized: Through multi-stage precise vulcanization process and component synergistic design, the crosslinking reaction of silicone rubber matrix and the decomposition process of foaming agent are better coordinated, solving the problem of insufficient crosslinking caused by traditional single temperature vulcanization, and effectively improving the comprehensive mechanical properties of the material such as compression set, resilience and tensile strength.

[0021] (2) Significantly enhanced antibacterial durability: The antibacterial agent with a specific structure overcomes the problems of easy migration and precipitation and poor thermal stability of traditional silver-based or quaternary ammonium salt antibacterial agents by virtue of its excellent compatibility with silicone rubber matrix and high temperature resistance. This makes the material exhibit highly efficient antibacterial activity and can still maintain a high level of antibacterial effect after thermal aging, thus overcoming the defects of easy migration and precipitation and poor thermal stability of traditional antibacterial agents. Attached Figure Description

[0022] Figure 1 This is the NMR spectrum of intermediate 1 described in this invention.

[0023] Figure 2 This is the NMR spectrum of the antibacterial agent 1 described in this invention. Detailed Implementation

[0024] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are merely some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] Preparation Example 1: Preparation of antibacterial agent 1: ; Step 1: Under a nitrogen atmosphere, 5.00 g of compound 1 (CAS: 29218-27-7), 3.78 g of compound 2 (CAS: 88-04-0), 12.85 g of potassium phosphate trihydrate, 0.23 g of CuI, 0.03 g of pyridine-2-carboxylic acid, and 100 ml of DMSO were added to the reaction system. The reaction mixture was heated at 85 °C for 16 h. After the reaction was completed, the mixture was filtered through silica gel while hot. The organic phase was washed five times with water and then twice with saturated sodium chloride aqueous solution. Finally, the combined organic phase was dried over anhydrous magnesium sulfate, concentrated, and purified by silica gel column chromatography using a mixed solvent of n-heptane and ethyl acetate as the eluent. The mixture was then evaporated to dryness to obtain 5.73 g of intermediate 1.

[0026] Step 2: Under a nitrogen atmosphere, 5.73 g of intermediate 1, 4.54 g of compound 3 (CAS: 1141-38-4), and 100 ml of DMF were added sequentially to a dry reactor. After stirring until uniformly dispersed, 0.05 g of concentrated sulfuric acid was slowly added dropwise. The temperature was raised to 110 °C, and the reaction was stirred for 3 h. After the reaction was completed, the pH of the system was adjusted to neutral with a 0.1 mol / L sodium carbonate aqueous solution. After shaking and standing, the liquid was separated, and the organic phase was retained. The organic phase was dried with anhydrous magnesium sulfate, filtered, and evaporated to dryness. Silica gel column chromatography was performed, using a mixed solution of petroleum ether and ethyl acetate as the eluent. After evaporation, 6.04 g of antibacterial agent 1 was obtained.

[0027] Structural assessment: Mass spectrometry (MS) of intermediate 1 [M+H] + =328, NMR of intermediate 1 as Figure 1 As shown.

[0028] Mass spectrometry (MS) of antibacterial agent 1 [M+H] + =526, NMR of antibacterial agent 1 as follows Figure 2 As shown.

[0029] NMR of antibacterial agent 1: Preparation Examples 2-5: In Preparation Examples 2-5, antibacterial agents 2-5 were prepared sequentially, following the same preparation method as in Preparation Example 1, except that compound 2 was replaced, while the rest remained the same. Specific structures of compound 2, antibacterial agents 2-5, and mass spectrometry (MS [M+H]) are detailed below. + See Table 1.

[0030] Table 1 Example 1: Preparation of environmentally friendly foamed silicone rubber: 1. Raw material ratio: Methyl vinyl silicone rubber raw material: 95 parts, vinyl molar content of 0.07-0.1%, number average molecular weight of 450,000-500,000, purchased from: Zhejiang Hengyecheng Organosilicon Co., Ltd. Reinforcing agent: 25 parts, SDR-200 hydrophobic fumed silica, specific surface area 150±10m² 2 / g, purchased from: Anhui Sailike Silicon Materials Co., Ltd.; Inhibitor: 0.15 parts, which is ethynylcyclohexanol; Hydroxy silicone oil: 5 parts, hydroxyl content 6-9%, purchased from: Shandong Longhui Chemical Co., Ltd.; Hydrogen-containing silicone oil: 0.4 parts, hydrogen content 0.1-0.2%, purchased from: Shanghai Silicon Friend New Materials Technology Co., Ltd.; Foaming agent: 2.5 parts, azodicarbonamide; Catalyst: 0.3 parts, which is a platinum(0)-1,3-divinyl-1,1,3,3-tetramethyldisiloxane complex, purchased from Beijing Bailingwei Technology Co., Ltd.; Antibacterial agent: 0.7 parts, which is the antibacterial agent 1 prepared in Preparation Example 1.

[0031] 2. Preparation process: S1. Add 95 parts of methyl vinyl silicone rubber raw rubber to a mixer and plasticize for 8 minutes at a temperature of 55℃ and a speed of 80 r / min to fully soften the raw rubber; then add 25 parts of reinforcing agent and 5 parts of hydroxyl silicone oil, heat to 90℃, and continue mixing for 25 minutes to obtain a premixed rubber. S2. Transfer the premixed rubber to a two-roll mill, adjust the roll gap to 2 mm, and pass through the mill 4 times. Then, add 0.4 parts of hydrogen-containing silicone oil, 0.15 parts of inhibitor, 2.5 parts of foaming agent, and 0.7 parts of antibacterial agent in sequence, control the two-roll mill temperature to 45℃, and mix for 15 min until all materials are evenly dispersed. Finally, add 0.3 parts of catalyst and mix at 90 r / min for 3 min to obtain the compounded rubber. S3. Place the compound into a mold preheated to 110°C, apply a pressure of 7 MPa, and hold the pressure for 8 minutes for preliminary molding; then send the pre-molded material along with the mold into a vulcanizing chamber, maintain the vulcanizing chamber pressure at 0.4 MPa, first vulcanize and foam at 145°C for 12 minutes to decompose the foaming agent and form a uniform cell structure, then raise the temperature to 165°C and continue vulcanizing for 15 minutes to ensure that the silicone rubber is fully crosslinked; S4. After vulcanization, remove the product from the mold and place it in a 70℃ oven for constant temperature drying for 3 hours with a ventilation rate of 0.7 m / s. Turn the product over every 1 hour during the drying process to remove residual low-molecular-weight volatiles. Finally, let it cool naturally to room temperature to obtain environmentally friendly foamed silicone rubber.

[0032] Examples 2-5: The preparation of environmentally friendly foamed silicone rubber is carried out in accordance with the preparation process of Example 1, except that antibacterial agent 1 is replaced with antibacterial agent 2-antibacterial agent 5 prepared in Preparation Examples 2 to 5, and the rest of the preparation process is the same as that of Example 1.

[0033] Comparative Example 1: The preparation of environmentally friendly foamed silicone rubber follows the same process as in Example 1, except that antibacterial agent 1 is replaced with nano-silver particles, and the rest of the preparation process remains the same as in Example 1.

[0034] Comparative Example 2: The preparation of environmentally friendly foamed silicone rubber follows the same process as in Example 1, except that antibacterial agent 1 is replaced with triclosan (a commonly used organic antibacterial agent), and the rest of the preparation process remains the same as in Example 1.

[0035] Comparative Example 3: The preparation of environmentally friendly foamed silicone rubber follows the same process as in Example 1, except that no antibacterial agent is added. The rest of the preparation process is the same as in Example 1.

[0036] Comparative Example 4: The preparation of environmentally friendly foamed silicone rubber follows the same process as in Example 1, except that no reinforcing agent is added and the rest of the preparation process remains the same as in Example 1.

[0037] Comparative Example 5: The preparation of environmentally friendly foamed silicone rubber follows the same process as in Example 1, except that no hydrogen-containing silicone oil is added, and the rest of the preparation process remains the same as in Example 1.

[0038] Performance testing: 1. Compression set test: Referring to GB / T 7759.1-2015 standard, the environmentally friendly foamed silicone rubber prepared in the examples and comparative examples was used as samples to test its compression set rate. The results are shown in Table 2.

[0039] 2. Tensile strength and elongation at break test: Referring to GB / T 528-2009 standard, the environmentally friendly foamed silicone rubber prepared in the examples and comparative examples was used as a sample to test its tensile strength and elongation at break. The results are shown in Table 2.

[0040] 3. Antibacterial performance test: Referring to GB / T 31402-2023 standard, the environmentally friendly foamed silicone rubber prepared in the examples and comparative examples was used as a sample to test its antibacterial rate (Escherichia coli ATCC 25922); then the sample was subjected to hot air aging according to GB / T 3512-2014, and after aging, it was taken out and cooled to room temperature, and its antibacterial rate after aging was tested. The results are shown in Table 2.

[0041] Table 2 Table 2 shows that the sample examples using the antibacterial agent of this invention exhibit balanced and excellent comprehensive performance in terms of compression set, tensile strength, elongation at break, and antibacterial properties, and their antibacterial effect remains at a high level even after thermal aging. In contrast, the comparative samples using traditional nano-silver or triclosan antibacterial agents have significantly lower antibacterial rates and insufficient thermal stability, with a significant decrease in antibacterial performance after aging. The comparative samples lacking reinforcing agents or hydrogen-containing silicone oil show significant deterioration in compression set, tensile strength, and elongation at break, indicating that these components are crucial to the material properties. Overall, the formulation system of this invention achieves a balance between mechanical properties and durable antibacterial properties through the synergistic effect of its components.

[0042] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. An environmentally friendly foamed silicone rubber, characterized in that, It is prepared from the following raw materials in parts by weight: 90-100 parts of methyl vinyl silicone rubber raw rubber, 20-30 parts of reinforcing agent, 0.05-0.3 parts of inhibitor, 4-6 parts of hydroxyl silicone oil, 0.3-0.5 parts of hydrogen-containing silicone oil, 2-4 parts of foaming agent, 0.2-0.5 parts of catalyst, and 0.2-1 parts of antibacterial agent; The antibacterial agent is a compound represented by Formula 1 below: Formula 1: ; In Formula 1, R1 is a substituent, specifically R1 being any one of alkyl, amino, or methoxy groups having 1-5 carbon atoms. The alkyl groups having 1-5 carbon atoms are: methyl, ethyl, and isopropyl.

2. The environmentally friendly foamed silicone rubber according to claim 1, characterized in that, The methyl vinyl silicone rubber has a vinyl molar content of 0.04-0.2% and a number average molecular weight of 450,000-550,000.

3. The environmentally friendly foamed silicone rubber according to claim 1, characterized in that, The reinforcing agent is at least one of fumed silica, precipitated silica, and calcium carbonate.

4. The environmentally friendly foamed silicone rubber according to claim 1, characterized in that, The inhibitor is at least one of ethynylcyclohexanol, diallyl maleate, and methylbutynol.

5. The environmentally friendly foamed silicone rubber according to claim 1, characterized in that, The hydroxyl content of the hydroxyl silicone oil is 5-12%; the hydrogen content of the hydrogen-containing silicone oil is 0.08-0.4%.

6. The environmentally friendly foamed silicone rubber according to claim 1, characterized in that, The foaming agent is at least one of azodicarbonamide, sodium bicarbonate, and N,N-dinitrospentamethylenetetramine.

7. The environmentally friendly foamed silicone rubber according to claim 1, characterized in that, The catalyst is at least one of a platinum-vinylsiloxane complex or a platinum-alkynyl group complex.

8. The environmentally friendly foamed silicone rubber according to claim 1, characterized in that, The antibacterial agent is any one of the compounds shown in the following structures: ； 。 9. A preparation process for the environmentally friendly foamed silicone rubber according to any one of claims 1-8, characterized in that, Includes the following steps: S1. Add the raw methyl vinyl silicone rubber to a mixer and plasticize it for 5-10 minutes at a temperature of 50-60℃ and a speed of 50-100 r / min. Then add the reinforcing agent and hydroxyl silicone oil, raise the temperature to 80-100℃, and continue mixing for 20-30 minutes to obtain a premixed rubber. S2. Add the premixed rubber to the open mill, adjust the roller gap to 1-3mm, and pass through the mill 3-5 times; then add the hydrogen-containing silicone oil, inhibitor, foaming agent, and antibacterial agent in sequence, and mix for 10-20 minutes until the material is evenly dispersed; finally add the catalyst, and mix at 80-100r / min for 3-5 minutes to obtain the compounded rubber. S3. Place the compound into a mold preheated to 100-120℃, apply a pressure of 5-10MPa, hold the pressure for 5-10min for preliminary molding, and then send the pre-molded material together with the mold into a vulcanizing box. Maintain the vulcanizing box pressure at 0.3-0.6MPa, first vulcanize and foam at 140-150℃ for 10-15min, then raise the temperature to 160-170℃ and continue vulcanizing for 10-20min. S4. After vulcanization, remove the product from the mold and place it in an oven at 60-80℃ for constant temperature drying for 2-4 hours to remove residual low-molecular-weight volatiles inside the product. Allow it to cool naturally to room temperature to obtain environmentally friendly foamed silicone rubber.

10. The preparation process of the environmentally friendly foamed silicone rubber according to claim 9, characterized in that, In S2, the roller temperature of the open mill is controlled at 40-60℃; in S4, the ventilation rate of the drying oven is 0.5-1m / s, and the product is turned over once every 1 hour during the drying process to ensure uniform drying.

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