Acid and alkali resistant silicone rubber and preparation method thereof

Abstract

The application provides an acid and alkali resistant silicone rubber which is prepared from the following raw materials in parts by weight: methyl vinyl silicone rubber, modified nano zirconium oxide, polytetrafluoroethylene dispersion liquid, polyvinylidene fluoride dispersion liquid, fumed silica, hydroxyl silicone oil, gamma-glycidyl ether oxypropyl trimethoxysilane and internal release agent; the methyl vinyl silicone rubber is used as a matrix; the modified nano zirconium oxide, the polytetrafluoroethylene dispersion liquid and the polyvinylidene fluoride dispersion liquid are compounded to construct a multi-component synergistic corrosion resistant system; the volume stability and the mechanical property retention rate of the silicone rubber in a long-term acid and alkali environment are significantly improved; and the corrosion problems such as swelling and degradation of the material are effectively avoided.

Description

Technical Field

[0001] This invention relates to the field of silicone rubber production, and more particularly to an acid and alkali resistant silicone rubber and its preparation method. Background Technology

[0002] Silicone rubber, as a high-performance elastomer material, has been widely used in aerospace, electronics, automobile manufacturing and other fields due to its outstanding high and low temperature resistance, good weather resistance and excellent electrical insulation properties.

[0003] In some applications, silicone rubber products need to be exposed to acidic or alkaline media for extended periods. The tolerance of existing silicone rubber materials to acidic and alkaline environments needs further improvement. This is mainly manifested in problems such as swelling, decreased mechanical properties, surface corrosion, and even molecular chain degradation under long-term exposure to acidic or alkaline media, thus affecting the product's service life and reliability.

[0004] To improve the acid and alkali resistance of silicone rubber, existing technologies have used fluorosilicone as an acid and alkali resistant material. However, how to effectively improve the long-term stability of silicone rubber in acid and alkali media while maintaining its good processing and mechanical properties remains a technical problem that needs to be solved in this field.

[0005] To address the aforementioned technical problems, this invention provides an acid and alkali resistant silicone rubber and its preparation method. Summary of the Invention

[0006] (a) Technical problems to be solved In view of the above-mentioned shortcomings and deficiencies of the prior art, the present invention provides an acid and alkali resistant silicone rubber and its preparation method, which solves the technical problem that the acid and alkali corrosion resistance of existing silicone rubber products is difficult to meet the increasingly complex and strict performance requirements, especially as a polymer material, its stability under long-term action in acid and alkali media is not ideal, and it is prone to swelling, degradation and other problems, resulting in a short service life.

[0007] (II) Technical Solution The purpose of this invention is to provide an acid and alkali resistant silicone rubber and its preparation method, which is prepared from the following raw materials in parts by weight: 100 parts of methyl vinyl silicone rubber; 5-10 parts of modified nano-zirconia; 15-20 parts of polytetrafluoroethylene dispersion; 5-8 parts of polyvinylidene fluoride dispersion; 30-35 parts of fumed silica; Hydroxysilicone oil 3.5-5 parts; 0.5-1.0 parts of γ-glycidyl oxypropyltrimethoxysilane; 0.1-0.15 parts of internal release agent.

[0008] Preferably, the modified nano-zirconia is nano-zirconia surface-treated with a silane coupling agent, and its average particle size is 20-80 nm.

[0009] Preferably, the fumed silica is hydrophilic fumed silica with a specific surface area of ​​150-380 m² / g.

[0010] Preferably, the internal release agent is at least one of zinc stearate, magnesium stearate, or calcium stearate.

[0011] On the other hand, a method for preparing an acid and alkali resistant silicone rubber includes the following steps: S1. Kneading: Methyl vinyl silicone rubber, modified nano zirconium oxide, fumed silica, hydroxyl silicone oil, γ-glycidyl etheroxypropyltrimethoxysilane and internal release agent are added to a kneader and kneaded for 1-3 hours at 100-150℃ and a vacuum of -0.08 to -0.095 MPa to obtain silicone rubber base material. S2. Feeding the open mill: Transfer the silicone rubber base material obtained in step S1 to the open mill, and add polytetrafluoroethylene dispersion and polyvinylidene fluoride dispersion in sequence at a temperature of 40-60℃. Mix evenly in a thin stream to obtain the compound. S3. Vulcanization molding: The compound obtained in step S2 is subjected to vulcanization treatment to obtain the acid and alkali resistant silicone rubber.

[0012] Preferably, the vulcanization process is divided into two stages: the first stage vulcanization temperature is 160-180℃, the pressure is 10-15 MPa, and the time is 10-20 minutes; the second stage vulcanization temperature is 200-220℃, and the time is 2-4 hours.

[0013] Preferably, the number of times the thin-walled mixing is uniform in step S2 is 6-10 times, and the roller gap is 0.5-1.5 mm.

[0014] (III) Beneficial Effects Using methyl vinyl silicone rubber as the matrix, a multi-component synergistic corrosion-resistant system was constructed by compounding modified nano-zirconia, polytetrafluoroethylene dispersion, and polyvinylidene fluoride dispersion. Both polytetrafluoroethylene and polyvinylidene fluoride are fluoropolymers with extremely low surface energy and excellent chemical inertness, forming stable hydrophobic and oleophobic barriers on and within the silicone rubber surface, effectively hindering the penetration and diffusion of acidic and alkaline media. The modified nano-zirconia, surface-treated with a silane coupling agent, forms a good interfacial bond with the silicone rubber matrix. Its nanoscale effect further fills microscopic defects in the matrix, inhibiting the intrusion path of corrosive media, significantly improving the volume stability and mechanical property retention of silicone rubber under long-term acidic and alkaline environments, and effectively avoiding corrosion problems such as swelling and degradation. Detailed Implementation

[0015] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0016] First, all raw materials used in the following examples are commercially available products. Methyl vinyl silicone rubber is a commercially available conventional product with a vinyl molar fraction of 0.1%-2%. Modified nano-zirconia is nano-zirconia surface-treated with a silane coupling agent (such as KH-570) with an average particle size of 20-80 nm. Polytetrafluoroethylene dispersion and polyvinylidene fluoride dispersion are both aqueous dispersions, with a solid content of 60% for polytetrafluoroethylene dispersion and 30% for polyvinylidene fluoride dispersion. Fumed silica is hydrophilic fumed silica with a specific surface area of ​​150-380 m² / g. Hydroxysilicone oil (α,ω-dihydroxypolydimethylsiloxane) has a hydroxyl mass fraction of 8%-10%. γ-glycidyl etheroxypropyltrimethoxysilane (KH-560) is analytical grade. The internal release agent is one or more of zinc stearate, magnesium stearate, or calcium stearate.

[0017] This application provides the following four embodiments and one comparative example, as detailed below: Example 1

[0018] An acid and alkali resistant silicone rubber is prepared from the following raw materials in parts by weight: 100 parts of methyl vinyl silicone rubber; 5 parts of modified nano-zirconia; 15 parts of polytetrafluoroethylene dispersion; 5 parts of polyvinylidene fluoride dispersion; Fumed silica (specific surface area 200 m² / g) 30 parts; 3.5 parts of hydroxyl silicone oil; 0.5 parts of γ-glycidyl oxypropyltrimethoxysilane; Internal release agent (zinc stearate) 0.1 parts.

[0019] The preparation method in this embodiment is as follows: S1. Kneading: Methyl vinyl silicone rubber, modified nano zirconium oxide, fumed silica, hydroxyl silicone oil, γ-glycidyl etheroxypropyltrimethoxysilane and internal release agent are added to a kneader and kneaded for 2 hours at 120°C and a vacuum of -0.09 MPa to obtain silicone rubber base material.

[0020] S2. Feeding the open mill: Transfer the silicone rubber base material obtained in step S1 to the open mill. At a temperature of 50°C, add polytetrafluoroethylene dispersion and polyvinylidene fluoride dispersion in sequence. Mix evenly by passing through a thin stream 8 times with a roller gap of 1.0 mm to obtain the compound.

[0021] S3. Vulcanization molding: The compound obtained in step S2 is subjected to a two-stage vulcanization process. The first stage vulcanization temperature is 170℃, the pressure is 12 MPa, and the time is 15 minutes; the second stage vulcanization temperature is 210℃, and the time is 3 hours, thus obtaining the acid and alkali resistant silicone rubber. Example 2

[0022] An acid and alkali resistant silicone rubber is prepared from the following raw materials in parts by weight: 100 parts of methyl vinyl silicone rubber; 8 parts of modified nano-zirconia; 18 parts of polytetrafluoroethylene dispersion; 6.5 parts of polyvinylidene fluoride dispersion; Fumed silica (specific surface area 300 m² / g) 33 parts; 4.2 parts of hydroxyl silicone oil; 0.8 parts of γ-glycidyl oxypropyltrimethoxysilane; Internal release agent (magnesium stearate) 0.12 parts.

[0023] The preparation method of this embodiment is basically the same as that of Example 1, except that: in step S1, the kneading temperature of the kneader is 130°C and the kneading time is 1.5 hours; in step S2, the number of thin passes of the open mill is 7; in step S3, the first vulcanization temperature is 165°C, the pressure is 13 MPa and the time is 12 minutes, and the second vulcanization temperature is 200°C and the time is 4 hours. Example 3

[0024] An acid and alkali resistant silicone rubber is prepared from the following raw materials in parts by weight: 100 parts of methyl vinyl silicone rubber; 10 parts of modified nano-zirconia; 20 parts of polytetrafluoroethylene dispersion; 8 parts of polyvinylidene fluoride dispersion; Fumed silica (specific surface area 250 m² / g) 35 parts; 5 parts hydroxyl silicone oil; 1.0 part of γ-glycidyl oxypropyltrimethoxysilane; 0.15 parts of internal release agent (calcium stearate).

[0025] The preparation method of this embodiment is basically the same as that of Example 1, except that: in step S1, the kneading temperature of the kneader is 140°C and the kneading time is 2.5 hours; in step S2, the number of passes of the open mill is 10; in step S3, the first vulcanization temperature is 175°C, the pressure is 14 MPa and the time is 18 minutes, and the second vulcanization temperature is 220°C and the time is 2 hours. Example 4

[0026] An acid and alkali resistant silicone rubber is prepared from the following raw materials in parts by weight: 100 parts of methyl vinyl silicone rubber; Modified nano-zirconia, 6 parts; 16 parts of polytetrafluoroethylene dispersion; 7 parts of polyvinylidene fluoride dispersion; Fumed silica (specific surface area 150 m² / g) 32 parts; 4 parts hydroxyl silicone oil; 0.6 parts of γ-glycidyl oxypropyltrimethoxysilane; 0.12 parts of internal release agent (a mixture of zinc stearate and calcium stearate in a 1:1 mass ratio).

[0027] The preparation method of this embodiment is basically the same as that of Example 1, except that: in step S1, the kneading temperature of the kneader is 100°C and the kneading time is 3 hours; in step S2, the number of thin passes of the open mill is 6; in step S3, the first vulcanization temperature is 160°C, the pressure is 10 MPa and the time is 20 minutes, and the second vulcanization temperature is 200°C and the time is 4 hours.

[0028] Comparative Example 1 Compared with Example 1, Comparative Example 1 differs in that: no polyvinylidene fluoride dispersion was added, and the amount of polytetrafluoroethylene dispersion was adjusted to 20 parts to maintain a similar total amount of fluoropolymer added. The remaining raw materials and preparation methods are the same as in Example 1.

[0029] The silicone rubber materials prepared in Examples 1-4 and Comparative Example 1 were subjected to the following performance tests, and the results are shown in Table 1:

[0030] Test method: 1. Mechanical property testing: The tensile strength and elongation at break of the material are tested using a universal testing machine in accordance with GB / T 528-2009 standard.

[0031] 2. Acid and alkali resistance test: The standard test pieces were immersed in 10% sulfuric acid solution (H2SO4) and 10% sodium hydroxide solution (NaOH) respectively for 7 days at 80℃. After removal, they were cleaned with distilled water and dried at 70℃ to constant weight. Then, the tensile strength retention rate (the percentage of tensile strength after immersion to the tensile strength before immersion), elongation at break retention rate, and volume change rate (the percentage change of volume after immersion to the volume before immersion) were tested.

[0032] Results analysis: The test results in Table 1 show that: The silicone rubber materials prepared in Examples 1-4 exhibited excellent acid and alkali resistance while maintaining good initial mechanical properties (tensile strength 8.5-9.8 MPa, elongation at break 420%-480%). After immersion in 10% sulfuric acid and 10% sodium hydroxide solutions at 80℃ for 7 days, their tensile strength and elongation at break were retained at over 86%, and the volume change was small (less than 5%), indicating that the material structure was stable and no significant swelling or degradation occurred.

[0033] Compared to Example 1, Comparative Example 1 (without added polyvinylidene fluoride dispersion) showed a significant decrease in mechanical property retention and an increase in volume change rate after acid and alkali immersion. This indicates that the synergistic use of polyvinylidene fluoride and polytetrafluoroethylene (PTFE) is crucial for constructing a denser and more stable corrosion-resistant barrier, and that using PTFE alone is insufficient to achieve the desired effect.

[0034] In summary, this application uses methyl vinyl silicone rubber as the matrix and constructs a multi-component synergistic corrosion-resistant system by compounding modified nano-zirconia, polytetrafluoroethylene dispersion, and polyvinylidene fluoride dispersion. Polytetrafluoroethylene and polyvinylidene fluoride are both fluoropolymers with extremely low surface energy and excellent chemical inertness, forming stable hydrophobic and oleophobic barriers on and inside the silicone rubber surface, effectively hindering the penetration and diffusion of acidic and alkaline media. The modified nano-zirconia, after surface treatment with a silane coupling agent, forms a good interfacial bond with the silicone rubber matrix. Its nanoscale effect can further fill microscopic defects in the matrix, inhibiting the intrusion path of corrosive media, significantly improving the volume stability and mechanical property retention of silicone rubber under long-term acidic and alkaline environments, and effectively avoiding corrosion problems such as swelling and degradation.

[0035] Although embodiments of the present invention have been shown above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make modifications and variations to the above embodiments, but all such modifications are included within the broad scope of the foregoing disclosure and claims.

Claims

1. An acid and alkali resistant silicone rubber and its preparation method, characterized in that, It is prepared from the following raw materials in parts by weight: 100 parts of methyl vinyl silicone rubber; 5-10 parts of modified nano-zirconia; 15-20 parts of polytetrafluoroethylene dispersion; 5-8 parts of polyvinylidene fluoride dispersion; 30-35 parts of fumed silica; Hydroxysilicone oil 3.5-5 parts; 0.5-1.0 parts of γ-glycidyl oxypropyltrimethoxysilane; 0.1-0.15 parts of internal release agent.

2. The acid and alkali resistant silicone rubber according to claim 1, characterized in that: The modified nano-zirconia is nano-zirconia surface-treated with a silane coupling agent, with an average particle size of 20-80 nm.

3. The acid and alkali resistant silicone rubber according to claim 1, characterized in that: The fumed silica is hydrophilic fumed silica with a specific surface area of ​​150-380 m² / g.

4. The acid and alkali resistant silicone rubber according to claim 1, characterized in that: The internal release agent is at least one of zinc stearate, magnesium stearate, or calcium stearate.

5. A method for preparing acid and alkali resistant silicone rubber as described in any one of claims 1-4, characterized in that, Includes the following steps: S1. Kneading: Methyl vinyl silicone rubber, modified nano zirconium oxide, fumed silica, hydroxyl silicone oil, γ-glycidyl etheroxypropyltrimethoxysilane and internal release agent are added to a kneader and kneaded for 1-3 hours at 100-150℃ and a vacuum of -0.08 to -0.095 MPa to obtain silicone rubber base material. S2. Feeding the open mill: Transfer the silicone rubber base material obtained in step S1 to the open mill, and add polytetrafluoroethylene dispersion and polyvinylidene fluoride dispersion in sequence at a temperature of 40-60℃. Mix evenly in a thin stream to obtain the compound. S3. Vulcanization molding: The compound obtained in step S2 is subjected to vulcanization treatment to obtain the acid and alkali resistant silicone rubber.

6. The acid and alkali resistant silicone rubber according to claim 5, characterized in that: The vulcanization process is divided into two stages: the first stage vulcanization temperature is 160-180℃, the pressure is 10-15 MPa, and the time is 10-20 minutes; the second stage vulcanization temperature is 200-220℃, and the time is 2-4 hours.

7. The acid and alkali resistant silicone rubber according to claim 5, characterized in that: In step S2, the thin-pass mixing is performed 6-10 times, and the roller gap is 0.5-1.5 mm.

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