High air permeability fluororubber, and preparation method and use thereof

Abstract

The application provides a high-air-permeability fluororubber and a preparation method and application thereof, and belongs to the field of chemical materials. The fluororubber is prepared from the following raw materials in parts by weight: 100 parts of fluororubber raw rubber, 10-25 parts of inorganic salt, 5-15 parts of surface fluorination modified mesoporous silica, 1-5 parts of vulcanizing agent and 1-5 parts of accelerator; the inorganic salt is composed of inorganic salt with a particle size of 30-60 mu m and inorganic salt with a particle size of 2-10 mu m, and the mass ratio is 5:2-8:2. The application constructs micron-level main air passage through gradient bimodal particle size inorganic salt, provides nanometer-level secondary diffusion network by using surface fluorination modified mesoporous silica and forms rigid skeleton support, so that the fluororubber has high porosity while still maintaining high tensile strength and tear strength, the fluororubber has high air permeability and mechanical properties, and the defect of low strength of traditional porous rubber is overcome.

Description

Technical Field

[0001] This invention belongs to the field of chemical materials, specifically relating to a highly permeable fluororubber, its preparation method, and its uses. Background Technology

[0002] Fluororubber (FKM) possesses excellent high-temperature resistance, oil resistance, chemical corrosion resistance, and aging resistance due to the high bond energy of the CF bonds in its molecular chain and the strong shielding effect of fluorine atoms, making it widely used in aerospace, automotive, and chemical industries. However, the dense molecular structure and strong polarity of fluororubber result in extremely low gas permeability (oxygen permeability is typically only 40-60 cm⁻¹). 3 •mm / (m 2 •d•atm)), which limits its application in scenarios requiring "breathing" functionality, such as smartwatch straps worn for extended periods (which can easily cause skin allergies), medical bandage bases (which are not conducive to wound healing), and precision seals that need to expel internal moisture in high-humidity and hot environments.

[0003] Existing methods for improving the air permeability of rubber mainly include physical foaming and filler filling. Physical foaming generates bubbles by adding chemical foaming agents, but it is often difficult to control the uniformity and connectivity of the bubbles, and closed cells are easily formed, resulting in poor air permeability. Simultaneously, the presence of a large number of bubbles significantly reduces the tensile strength and tear strength of the rubber, making the material unable to meet the requirements of structural components. Filler filling typically involves adding porous fillers, but ordinary porous fillers (such as ordinary calcium carbonate and unmodified diatomaceous earth) have poor dispersibility in fluororubber matrices, easily agglomerate and block pores, and due to interfacial compatibility issues, often lead to a significant decrease in mechanical properties. Furthermore, traditional single-peak particle size pore-forming agents create a simple pore structure, making it difficult to simultaneously achieve high air permeability and high skeletal strength.

[0004] Therefore, how to construct a porous network structure to improve the air permeability of fluororubber while ensuring its mechanical properties is a technical problem that urgently needs to be solved. Summary of the Invention

[0005] The purpose of this invention is to provide a highly permeable fluororubber, its preparation method, and its uses.

[0006] This invention provides a fluororubber, which is made from raw materials comprising the following parts by weight: 100 parts of fluororubber raw rubber, 10-25 parts of inorganic salt, 5-15 parts of surface fluorinated modified mesoporous silica, 1-5 parts of vulcanizing agent, and 1-5 parts of accelerator; wherein the inorganic salt is composed of inorganic salt with a particle size of 30-60 μm and inorganic salt with a particle size of 2-10 μm.

[0007] Furthermore, fluororubber is made from raw materials comprising the following parts by weight: 100 parts of fluororubber raw rubber, 20-25 parts of inorganic salt, 5-15 parts of surface-fluorinated modified mesoporous silica, 2-4 parts of vulcanizing agent, and 1-2.5 parts of accelerator.

[0008] Furthermore, the mass ratio of the inorganic salt with a particle size of 30~60μm to the inorganic salt with a particle size of 2~10μm is 5:2~8:2.

[0009] Further, the inorganic salt is selected from at least one of sodium chloride, sodium sulfate, or sodium bicarbonate; the vulcanizing agent is selected from at least one of 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane, 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexyn-3, or dicumyl peroxide; and the accelerator is selected from at least one of triallyl isocyanurate, trimethylolpropane trimethacrylate, or divinylbenzene.

[0010] Further, the surface-fluorinated modified mesoporous silica is prepared by the following method: dispersing mesoporous silica in an anhydrous organic solvent, adding a fluorinated silane coupling agent, reacting under inert gas protection, and washing and drying after the reaction to obtain surface-fluorinated modified mesoporous silica.

[0011] Further, the mass ratio of the mesoporous silica to the fluorinated silane coupling agent is 8~12:2~3; the organic solvent is selected from at least one of toluene, xylene, and chloroform; the reaction temperature is 100~120℃ and the time is 12~24h; the fluorinated silane coupling agent is selected from at least one of tridecafluorooctyltrimethoxysilane and tridecafluorooctyltriethoxysilane.

[0012] Furthermore, fluororubber also includes raw materials: 1 to 5 parts of processing aids.

[0013] Furthermore, fluororubber also includes raw materials: 1-2 parts of processing aids.

[0014] Furthermore, the processing aid is selected from at least one of fluorosilicone oil, fluorowax, polyethylene wax, stearic acid, stearate, fatty acid ester, and organosilicon additives.

[0015] This invention also provides a method for preparing fluororubber, comprising the following steps: (1) Masterbatch mixing: Plasticize the raw fluororubber, add surface fluorinated modified mesoporous silica, mix evenly, and cool to room temperature to obtain masterbatch; or plasticize the raw fluororubber, add surface fluorinated modified mesoporous silica and processing aids, mix evenly, and cool to room temperature to obtain masterbatch. (2) Low temperature salt addition: Add inorganic salt, vulcanizing agent and accelerator to the masterbatch, mix and extrude to obtain rubber sheet; (3) Vulcanization molding: Place the rubber sheet in a mold and mold it to vulcanize it to obtain vulcanized rubber; (4) Water washing to create holes: Place the vulcanized rubber in water to wash until the conductivity of the washing solution is constant, and then dry it to obtain the product.

[0016] The present invention also provides the use of fluororubber in the preparation of breathable products for skin contact and precision seals for high humidity and heat environments.

[0017] Furthermore, the skin-contact breathable products include smartwatch straps, wristband linings, skin-adhesive cushioning layers, or medical bandage bases.

[0018] This invention constructs a micron-scale main air passage using gradient bimodal particle size inorganic salts, and utilizes surface-fluorinated mesoporous silica to provide a nanoscale secondary diffusion network and form a rigid skeleton support, thereby achieving a synergistic improvement in the air permeability and mechanical properties of fluororubber.

[0019] Experiments have shown that the mass ratio of large-diameter inorganic salt particles to small-diameter inorganic salt particles has a significant impact on the air permeability and mechanical properties of fluororubber: when the ratio is too small (<5:2), with too many small-diameter inorganic salt particles, the porosity is too high, and the rubber skeleton is excessively cut, which is not only detrimental to the tensile strength and tear strength of the rubber, but also causes local structural collapse. It also hinders the air permeability channels of the fluororubber, thus reducing both its air permeability and mechanical properties. When the ratio is too large (>8:2), with too many large-diameter inorganic salt particles, the lack of small particles connecting to large particles leads to… The large pores reduce the pore connectivity and thus the permeability of fluororubber. Only when the mass ratio of large-diameter inorganic salt particles to small-diameter inorganic salt particles is controlled within a suitable range can they form a three-dimensional interconnected network with surface-fluorinated mesoporous silica, characterized by "macropore dominance and micropore connectivity." This network provides both efficient gas transport channels and a sufficiently thick rubber skeleton to effectively support the porous structure. Furthermore, the key to effectively supporting the porous structure lies in the uniform nano-reinforcement network formed by the surface-fluorinated mesoporous silica within the matrix.

[0020] This invention enables fluororubber to maintain high tensile strength and tear strength while having high porosity, thus achieving a combination of high air permeability and mechanical properties, overcoming the shortcomings of low strength in traditional porous rubbers.

[0021] Obviously, based on the above description of the present invention, and according to common technical knowledge and conventional methods in the field, various other modifications, substitutions, or alterations can be made without departing from the basic technical concept of the present invention.

[0022] The following detailed embodiments further illustrate the above-described content of the present invention. However, this should not be construed as limiting the scope of the present invention to the following embodiments. All technologies implemented based on the above-described content of the present invention fall within the scope of the present invention. Detailed Implementation

[0023] The raw materials and equipment used in this invention are all known products, obtained by purchasing commercially available products.

[0024] In a specific embodiment of the present invention, the fluororubber raw material was purchased from Shandong Dongyue Shenzhou New Material Co., Ltd., and is type 246 peroxyfluororubber; the fluorosilicone oil was purchased from Shandong Dongyue Shenzhou New Material Co., Ltd., and is methyl fluorosilicone oil DS401.

[0025] Example 1: Preparation of highly permeable fluororubber (1) Preparation of surface-fluorinated modified mesoporous silica 10.0 g of mesoporous silica (SBA-15) was weighed and dried under vacuum at 120 °C for 4 hours; then dispersed in 200 mL of anhydrous toluene and sonicated for 30 minutes; subsequently, 2.5 g of tridecafluorooctyltrimethoxysilane was added, and the mixture was heated to 110 °C and refluxed for 24 hours under nitrogen protection; after the reaction was completed, the mixture was centrifuged, washed three times with anhydrous ethanol, and dried under vacuum at 80 °C for 12 hours to obtain surface-fluorinated modified mesoporous silica (F-Meso-SiO2); the water contact angle of F-Meso-SiO2 was >110° and the surface pH was neutral. (2) Preparation of fluororubber Formula (parts by weight): 100 parts of fluororubber raw rubber, 20 parts of NaCl (the ratio of NaCl with different particle sizes is: 40~50μm: 5~8μm=7:2), 10 parts of F-Meso-SiO2, 3.0 parts of 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, 1.5 parts of triallyl isocyanurate, and 1.0 part of fluorosilicone oil; Prepare according to the formula as follows: S1. Masterbatch mixing: After the fluororubber raw rubber is passed through a two-roll mill, F-Meso-SiO2 and fluorosilicone oil are added, mixed and dispersed evenly, and then removed and cooled. S2. Low-temperature salt addition: Control the roller temperature <35℃, add NaCl, 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane and triallyl isocyanurate, mix for 5 minutes, and immediately unload the film to obtain the film. S3. Vulcanization molding: After the prepared film has been left to stand for 24 hours, it is vulcanized at 180°C for 5 minutes in a flat vulcanizing machine to obtain vulcanized rubber. S4. Water washing and pore making: The vulcanized rubber is ultrasonically cleaned with deionized water at 70°C for 36 hours and vacuum dried at 80°C for 12 hours to obtain highly permeable fluororubber.

[0026] Example 2: Preparation of highly permeable fluororubber Referring to Example 1, the only difference is that the amount of NaCl in the formula is 25 parts.

[0027] Example 3: Preparation of highly permeable fluororubber Referring to Example 1, the only difference is that the ratio of NaCl particles of different sizes in the formulation is: 40~50μm : 5~8μm = 8 : 2.

[0028] Example 4: Preparation of highly permeable fluororubber Referring to Example 1, the only difference is that the ratio of NaCl particles of different sizes in the formulation is: 40~50μm : 5~8μm = 5 : 2.

[0029] Example 5: Preparation of highly permeable fluororubber Referring to Example 1, the only difference is that 20 parts of NaCl in the formula (the ratio of NaCl with different particle sizes is 40~50μm: 5~8μm=7:2) are replaced with 20 parts of sodium sulfate (the ratio of sodium sulfate with different particle sizes is 40~50μm: 5~8μm=8:2).

[0030] Comparative Example 1: Preparation of Fluororubber Referring to Example 1, the only difference is that the ratio of NaCl particles of different sizes in the formulation is: 40~50μm : 5~8μm = 5 : 4.

[0031] Comparative Example 2: Preparation of Fluororubber Referring to Example 1, the only difference is that the ratio of NaCl particles of different sizes in the formulation is: 40~50μm : 5~8μm = 10 : 2.

[0032] Comparative Example 3: Preparation of Fluororubber Referring to Example 1, the only difference is that the NaCl in the formula only contains NaCl with a particle size of 40~50μm, and does not contain NaCl with a particle size of 5~8μm.

[0033] Comparative Example 4: Preparation of Fluororubber Referring to Example 1, the only difference is that F-Meso-SiO2 in the formula is replaced with ordinary silicon dioxide.

[0034] Experimental Example 1: Performance Testing of Fluororubber 1. Experimental Methods (1) Oxygen permeability test: Refer to GB / T 7755.1-2018, test conditions 23℃; (2) Tensile strength test: The test standard is GB / T 528-2009 for testing the tensile strength of dumbbell type 1 specimens; (3) Tear strength test: The test standard is GB / T 529-2008, and the tear strength of the right-angled specimen is tested.

[0035] 2. Experimental Results As shown in Table 1, the fluororubbers prepared in Examples 1-5 have high oxygen permeability, ranging from 148 to 182 cm⁻¹. 3 •mm / (m 2 It has high tensile strength (7.8~10.8MPa) and tear strength (21~31.5kN / m), and significantly improved air permeability compared with comparative examples 1~4, proving that the present invention has produced fluororubber with both high air permeability and excellent mechanical properties.

[0036] Compared with Example 1, the total amount of NaCl added in Example 2 was increased, and the oxygen permeability of the resulting fluororubber was increased. However, the NaCl in Comparative Example 3 was of a single particle size, and the oxygen permeability of the resulting fluororubber was significantly reduced, decreasing by 40.6% compared with Example 1. This indicates that when the same amount of NaCl is added, NaCl of a single particle size is not conducive to the air permeability of fluororubber.

[0037] Comparative Example 1 shows a fluororubber prepared with a large-particle size NaCl to small-particle size NaCl ratio of 5:4. Compared with Examples 1-5, the proportion of small-particle size NaCl is higher, resulting in a significantly lower oxygen permeability, tensile strength, and tear strength of the final fluororubber. This indicates that too many small-particle size particles not only negatively impact the air permeability of the fluororubber but also significantly reduce its mechanical properties. Comparative Example 2 shows a fluororubber prepared with a large-particle size NaCl to small-particle size NaCl ratio of 10:2. Compared with Examples 1-5, the proportion of large-particle size NaCl is higher, resulting in a significantly lower oxygen permeability of the fluororubber. This indicates that too many large-particle size particles reduce the air permeability of the fluororubber. The above experimental results show that a suitable ratio of large-particle size NaCl to small-particle size NaCl (5:2~8:2) is necessary to ensure both high air permeability and good mechanical properties in fluororubber.

[0038] Comparative Example 4: When the surface-fluorinated mesoporous silica was replaced with ordinary silica, the oxygen permeability of the resulting fluororubber was only 95 cm⁻¹. 3 •mm / (m 2 The d atm value was reduced by 42.4% compared to Example 1, indicating that surface fluorination-modified mesoporous silica plays a key role in improving the permeability of fluororubber.

[0039] Table 1. Performance test results of the fluororubber obtained in Examples 1-5 and Comparative Examples 1-4 In summary, this invention improves the air permeability of fluororubber by combining gradient bimodal particle size inorganic salts and surface-fluorinated mesoporous silica, while ensuring high tensile and tear strength. Experiments have shown that single-size inorganic salts and ordinary silica cannot produce fluororubber with high air permeability. Furthermore, the mass ratio of large-size to small-size inorganic salt particles significantly affects the air permeability and mechanical properties of fluororubber: when the proportion of large-size inorganic salt particles is too low (<5:2), the air permeability, tensile strength, and tear strength of fluororubber are significantly reduced; when the proportion of large-size inorganic salt particles is too high (>8:2), the air permeability of fluororubber is significantly reduced. Only by controlling the mass ratio within a suitable range can fluororubber achieve a balance of high air permeability, tensile strength, and tear strength.

Claims

1. A fluororubber, characterized in that, It is made from raw materials comprising the following parts by weight: 100 parts of fluororubber raw rubber, 10-25 parts of inorganic salt, 5-15 parts of surface fluorinated modified mesoporous silica, 1-5 parts of vulcanizing agent, and 1-5 parts of accelerator; wherein the inorganic salt is composed of inorganic salt with a particle size of 30-60 μm and inorganic salt with a particle size of 2-10 μm.

2. The fluororubber according to claim 1, characterized in that, It is made from the following raw materials in parts by weight: 100 parts of fluororubber raw rubber, 20-25 parts of inorganic salt, 5-15 parts of surface fluorinated modified mesoporous silica, 2-4 parts of vulcanizing agent, and 1-2.5 parts of accelerator.

3. The fluororubber according to any one of claims 1 to 2, characterized in that, The mass ratio of the inorganic salt with a particle size of 30~60μm to the inorganic salt with a particle size of 2~10μm is 5:2~8:

2.

4. The fluororubber according to any one of claims 1 to 2, characterized in that, The inorganic salt is selected from at least one of sodium chloride, sodium sulfate, or sodium bicarbonate; the vulcanizing agent is selected from at least one of 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane, 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexyn-3, or dicumyl peroxide; the accelerator is selected from at least one of triallyl isocyanurate, trimethylolpropane trimethacrylate, or divinylbenzene.

5. The fluororubber according to any one of claims 1 to 2, characterized in that, The surface-fluorinated modified mesoporous silica is prepared by the following method: mesoporous silica is dispersed in an anhydrous organic solvent, a fluorinated silane coupling agent is added, and the reaction is carried out under inert gas protection. After the reaction is completed, the silica is washed and dried to obtain surface-fluorinated modified mesoporous silica.

6. The fluororubber according to claim 5, characterized in that, The mass ratio of the mesoporous silica to the fluorinated silane coupling agent is 8-12:2-3; the organic solvent is selected from at least one of toluene, xylene, and chloroform; the reaction temperature is 100-120℃ and the time is 12-24h; the fluorinated silane coupling agent is selected from at least one of tridecafluorooctyltrimethoxysilane and tridecafluorooctyltriethoxysilane.

7. The fluororubber according to any one of claims 1 to 2, characterized in that, The raw materials also include 1 to 5 parts of processing aids.

8. The method for preparing fluororubber according to any one of claims 1 to 7, characterized in that, Includes the following steps: (1) Masterbatch mixing: Plasticize the raw fluororubber, add surface fluorinated modified mesoporous silica, mix evenly, and cool to room temperature to obtain masterbatch; or plasticize the raw fluororubber, add surface fluorinated modified mesoporous silica and processing aids, mix evenly, and cool to room temperature to obtain masterbatch. (2) Low temperature salt addition: Add inorganic salt, vulcanizing agent and accelerator to the masterbatch, mix and extrude to obtain rubber sheet; (3) Vulcanization molding: Place the rubber sheet in a mold and mold it to vulcanize it to obtain vulcanized rubber; (4) Water washing to create holes: Place the vulcanized rubber in water to wash until the conductivity of the washing solution is constant, and then dry it to obtain the product.

9. Use of the fluororubber according to any one of claims 1 to 7 in the preparation of breathable products for skin contact and precision seals for high humidity and heat environments.

10. The use according to claim 9, characterized in that, The skin-contact breathable products include smartwatch straps, wristband linings, skin-friendly cushioning layers, or medical bandage bases.

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