Dual-reinforced silicone rubber composite breathable film cap and preparation method thereof

Abstract

The invention belongs to the technical field of biological process analysis and sensors, and discloses a double-reinforced silicone rubber composite breathable film cap and a preparation method thereof.The double-reinforced silicone rubber composite breathable film cap comprises a film cap shell and a composite breathable film, the composite breathable film is packaged on the film cap shell and is made of a double-reinforced silicone rubber composite material, and the composite breathable film is made of a silicone rubber composite material. The double-reinforced silicone rubber composite material comprises a silicone rubber base material, a chemical reinforcing agent, a physical conditioning agent, a cross-linking agent, an inhibitor and a catalyst, the silicone rubber base material is vinyl-terminated polydimethylsiloxane, the chemical reinforcing agent is vinyl MQ silicon resin, and the physical conditioning agent is a nanoscale lamellar material. Through the innovative chemical-physical double enhanced network design, the unification of quick response, high mechanical strength and low flow rate dependence of the gas-permeable membrane is successfully realized, and the material selection problem which puzzles the industry for a long time is solved.

Description

Technical Field

[0001] This invention relates to the field of bioprocess analysis and sensor technology, and more specifically, to a double-reinforced silicone rubber composite breathable membrane cap and its preparation method. Background Technology

[0002] Dissolved oxygen concentration is a critical physicochemical parameter in processes such as microbial fermentation, bioreactors, and cell culture. Accurate, real-time, and in-situ monitoring of this concentration is essential for process control and optimization. Polarographic dissolved oxygen sensors (also known as Clark type sensors) are widely used in these fields due to their stable performance and accurate measurement. The core component of this type of sensor is the top permeable membrane cap. This permeable membrane allows oxygen molecules to permeate into the sensor and participate in electrochemical reactions while blocking the electrolyte solution and the measured medium, thus achieving selective detection of dissolved oxygen.

[0003] Existing breathable membrane materials face fundamental material science challenges, making it difficult to simultaneously meet the multiple requirements of high-performance sensors:

[0004] On the one hand, traditional silicone rubber membranes (such as polydimethylsiloxane, PDMS) have extremely high oxygen permeability, giving the sensor a very fast response speed (t90 can be <10 seconds). However, their low mechanical strength and soft material (Shore A hardness is usually below 40) make them prone to deformation and damage during installation, autoclaving, or water pressure. More seriously, their excessively high oxygen flux causes the sensor output signal to be heavily dependent on the flow rate of the measured medium. The readings are low in static or low-stirring cultures, and strong stirring is required to obtain accurate values. This increases the risk of shear stress in cell culture and makes it unsuitable for shear-sensitive cell culture processes.

[0005] On the other hand, traditional fluoropolymer membranes (such as FEP and PTFE) have high mechanical strength and stable chemical properties, but their oxygen permeability is extremely low, resulting in slow sensor response speed (t90 is usually >60 seconds) and low sensitivity, making it difficult to meet the application requirements of cell culture and other processes that require rapid monitoring of dynamic oxygen changes.

[0006] Therefore, developing a novel breathable membrane material that combines rapid response, high mechanical strength, and low flow rate dependence has become a pressing technical challenge in this field. Summary of the Invention

[0007] The purpose of this invention is to overcome the shortcomings of the existing technology and proposes a double-reinforced silicone rubber composite breathable membrane cap and its preparation method.

[0008] To solve the above problems, the present invention adopts the following technical solution:

[0009] A dual-reinforced silicone rubber composite breathable membrane cap includes a membrane cap shell and a composite breathable membrane, wherein the composite breathable membrane is encapsulated on the membrane cap shell;

[0010] The composite breathable membrane is made of a dual-reinforced silicone rubber composite material, which includes: a silicone rubber substrate, a chemical reinforcing agent, a physical modifier, a crosslinking agent, an inhibitor, and a catalyst. The silicone rubber substrate is vinyl-terminated polydimethylsiloxane, the chemical reinforcing agent is vinyl MQ silicone resin, and the physical modifier is a nanoscale sheet material.

[0011] The vinyl MQ silicone resin and the silicone rubber substrate are cross-linked through a hydrosilylation reaction to form a chemically reinforced network, and the nanoscale sheet material is uniformly dispersed in the silicone rubber substrate to form a physically modulated network.

[0012] Preferably, the membrane cap shell is made of polysulfone material.

[0013] Preferably, the nanoscale sheet material is organo-modified montmorillonite, the crosslinking agent is hydrogen-containing silicone oil, the inhibitor is ethynylcyclohexanol, and the catalyst is a platinum catalyst.

[0014] Preferably, the thickness of the composite breathable membrane is 25–50 μm.

[0015] Preferably, the composite breathable membrane has a Shore A hardness greater than 60 and an oxygen permeability coefficient of 3 × 10⁻⁶. -9 cm² / (s·cmHg) up to 8×10 -9 Tensile strength ≥ 8.0 MPa, with a value between cm² / (s·cmHg).

[0016] A method for preparing a dual-reinforced silicone rubber composite breathable membrane, comprising the following steps:

[0017] Step S1: Premixing and devolatilization: The vinyl-terminated polydimethylsiloxane silicone rubber substrate is mixed with vinyl MQ silicone resin and heated and stirred under vacuum to remove moisture and gas;

[0018] Step S2: Nanoscale dispersion: Add nanoscale sheet material to the mixture obtained in step S1, and mechanically grind it to fully peel off and uniformly disperse it to form a homogeneous paste;

[0019] Step S3: Adhesive preparation: Cool the paste obtained in step S2, add the crosslinking agent and inhibitor in sequence, mix evenly, add the platinum catalyst under air-isolated conditions, mix evenly to obtain the adhesive solution.

[0020] Step S4: Coating and curing: The adhesive obtained in step S3 is coated onto the substrate and cured by heating to form a film;

[0021] Step S5: Post-processing: After cooling, the film is peeled off from the substrate to obtain the double-reinforced silicone rubber composite breathable membrane.

[0022] Preferably, the curing process in step S4 is a stepped curing process, in which the first stage is preliminary gelation at 70-90°C and the second stage is complete cross-linking and curing at 140-160°C.

[0023] Preferably, the mechanical grinding in step S2 is a three-roll mill for circulating grinding.

[0024] A method for preparing a double-reinforced silicone rubber composite breathable membrane cap includes:

[0025] The composite breathable membrane was prepared using the above method;

[0026] The composite breathable membrane is cut and placed in a membrane cap shell mold, and then integrally encapsulated with polysulfone material through injection molding to obtain the composite breathable membrane cap.

[0027] Preferably, the injection molding process is a two-stage injection overmolding process.

[0028] Compared with the prior art, the advantages of this invention are:

[0029] I. Breakthrough in performance bottlenecks: This invention, through its innovative "chemical-physical dual-reinforcement network" design, successfully achieves a balance between rapid response (T90 approximately 20-30 seconds), high mechanical strength (withstanding autoclave sterilization and hydrostatic pressure), and low flow rate dependence of the breathable membrane, solving the material selection problem that has long plagued the industry.

[0030] Second, it improves measurement reliability: The membrane material has high strength, low installation damage rate, and small deformation, which ensures the long-term stability and consistency of sensor readings under different pressure and sterilization conditions.

[0031] Third, the user experience has been optimized: the sensor is less dependent on the flow rate of the medium, and users do not need to deliberately increase the stirring speed in order to obtain accurate readings, thereby reducing the risk of shear force on cell culture and making it more suitable for gentle biological culture processes.

[0032] IV. Simple industrialization: All raw materials used are industrially available, the preparation process is compatible with existing coating equipment, the formula has a wide range of adjustable options, and it is easy to achieve large-scale production. Attached Figure Description

[0033] Figure 1 This is a flowchart illustrating the preparation process of the composite breathable membrane of the present invention.

[0034] Figure 2 This is an assembly diagram of the membrane cap of the present invention. Detailed Implementation

[0035] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0036] Example 1: Preparation of a dual-reinforced silicone rubber composite breathable membrane

[0037] This embodiment provides a preparation process for a composite breathable membrane that conforms to the technical solution of the present invention.

[0038] I. Raw material formula (by weight):

[0039] Silicone rubber substrate: Vinyl-terminated polydimethylsiloxane (viscosity 30,000 cps): 100 parts;

[0040] Chemical reinforcing agent: Vinyl MQ silicone resin (vinyl content 2.0%): 30 parts;

[0041] Physical conditioner: Organo-modified montmorillonite (OMMT): 8 parts;

[0042] Crosslinking agent: Hydrogen-containing silicone oil (active hydrogen content 0.8%): appropriate amount, so that the molar ratio of Si-H to total vinyl groups is 1.8:1;

[0043] Inhibitor: Ethynylcyclohexanol: 0.05 parts;

[0044] Catalyst: Platinum catalyst (Pt content 3000ppm): 15ppm (based on platinum metal)

[0045] II. Preparation process (e.g.) Figure 1 (as shown)

[0046] 1. Premixing and devolatilization: The silicone rubber substrate and vinyl MQ resin in the above proportions are put into a planetary mixer and stirred, dehydrated and degassed for 1 hour at 100°C and -0.095MPa vacuum to obtain a premix.

[0047] 2. Nanodispersion: Add OMMT to the premix and circulate it 5 times using a three-roll mill. The strong shearing force of the three-roll mill ensures that the nanosheets of OMMT are fully exfoliated and evenly dispersed in the matrix, forming a uniform paste without any grainy texture.

[0048] 3. Adhesive preparation: Cool the dispersed paste to room temperature, then add the hydrogen-containing silicone oil and ethynylcyclohexanol sequentially while stirring at low speed until homogeneous. Finally, add the platinum catalyst under low temperature and air-free conditions (such as nitrogen protection), mix thoroughly to obtain the adhesive solution to be coated, and use immediately or store at low temperature for later use.

[0049] 4. Coating and Curing: Using a precision slot coater, the above adhesive solution is evenly coated onto the PET release film, controlling the wet film thickness to 80μm. The coated film is then placed in an oven for stepped curing: the first stage is maintained at 80℃ for 5 minutes to allow the adhesive layer to initially gel and evaporate any remaining trace moisture; the second stage is maintained at 150℃ for 10 minutes to allow the adhesive layer to undergo a complete hydrosilylation reaction, completing the crosslinking and curing.

[0050] 5. Post-treatment: After curing, cool to room temperature and carefully peel off from the PET release film to obtain a uniform, transparent reinforced silicone rubber film with a thickness of about 40±3μm, which is the composite breathable film of the present invention.

[0051] Working principle:

[0052] This invention achieves a breakthrough in breathable membrane performance through an innovative "chemical-physical dual-reinforcement network" design:

[0053] Chemically reinforced network (main network): Vinyl-terminated polydimethylsiloxane is used as the continuous phase, and vinyl MQ silicone resin is introduced as a multifunctional reinforcing agent. Under the action of a platinum catalyst, the vinyl groups in the MQ resin molecules undergo a hydrosilylation reaction with a hydrogen-containing silicone oil crosslinking agent, forming a dense three-dimensional network of interpenetrating "rigid spherical nodes" and "flexible linear segments." This is equivalent to embedding countless nanoscale rigid crosslinking points into a soft rubber matrix, significantly improving the tensile modulus, hardness, and tear resistance of the cured material, enabling it to withstand installation stress, sterilization cycles, and hydrostatic pressure without deformation.

[0054] Physical regulation network (auxiliary network): Nanoscale sheet materials (such as organo-modified montmorillonite OMMT) are uniformly dispersed within the aforementioned chemical network. These sheets create a "maze effect" in the matrix, making the diffusion path of oxygen molecules within the membrane more tortuous. Their key role is to "fine-tune" the excessively high oxygen permeability coefficient without significantly sacrificing the high permeability of silicone rubber. By controlling the amount added, the oxygen permeability coefficient of the material can be adjusted to 3 × 10⁻⁶. -9 Up to 8×10 -9 The ideal range of cm² / (s·cmHg) maintains far superior air permeability compared to fluoropolymer membranes (achieving a rapid response of approximately 20-30 seconds at t90), while effectively reducing the sensitivity of sensor signals to medium flow rate, thus solving the problem of traditional silicone membranes requiring strong stirring.

[0055] Example 2: Membrane Cap Assembly and Performance Testing

[0056] 1. Membrane cap assembly:

[0057] The reinforced silicone rubber film obtained in Example 1 was cut into circular pieces. A two-stage injection molding process was used, placing the cut film pieces into a precision mold, and then injecting molten polysulfone (PSU) resin for integral injection molding. After the PSU resin cooled and solidified, it formed a cap shell, firmly and airtightly sealing the edges of the reinforced silicone rubber film onto the shell, resulting in the final double-reinforced silicone rubber composite breathable cap (e.g., ...). Figure 2 As shown in the figure, this process ensures the long-term reliability of diaphragm pre-tensioning and sealing.

[0058] 2. Performance Testing:

[0059] The assembled membrane caps were mounted on a standard polarographic dissolved oxygen sensor for key performance tests, with traditional pure silicone membrane caps and traditional FEP membrane caps used as comparative examples. The test results are summarized in the table below.

[0060] Performance indicators Traditional pure silicone membrane Traditional FEP membrane Membrane of the present invention Shore A hardness ～30 >95 62-65 Tensile strength (MPa) ～2.5 ～20 >8.0 Oxygen permeability coefficient [cm² / (s·cmHg)] <![CDATA[~12 ×10 -9 ]]> <![CDATA[~0.5 ×10 -9 ]]> <![CDATA[5.2 ×10 -9 ]]> Sensor response time t90 (seconds) <10 >60 22-25 0.1 MPa hydrostatic pressure deformation rate >15% <1% <3% Flow rate dependence (static / turbulent signal ratio) <0.3 ～0.95 >0.85

[0061] Note: Flow rate dependence is obtained by measuring the ratio of signals with the same oxygen concentration in a static medium and a well-stirred turbulent medium. The closer the ratio is to 1, the less sensitive it is to flow rate.

[0062] As can be seen from the data in the table above, the composite breathable membrane cap of this invention achieves an excellent balance in several key performance aspects. Its response time (24 seconds) is much faster than that of the FEP membrane, while its mechanical strength (hardness 64, tensile strength 8.5 MPa) and pressure resistance (deformation rate <2.5%) are far superior to those of the pure silicone membrane. Furthermore, its dependence on flow rate (0.88) is significantly lower than that of the pure silicone membrane (<0.3). The signal consistency of the membrane cap of this invention under both static and turbulent conditions is far superior to that of the traditional silicone membrane. This fully demonstrates that this invention has successfully broken through the performance bottleneck of the prior art through the "chemical-physical dual reinforcement network".

[0063] The above description is merely a preferred embodiment of the present invention; however, the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and its improved concept, should be covered within the scope of protection of the present invention.

Claims

1. A double-reinforced silicone rubber composite breathable membrane cap, characterized in that: It includes a membrane cap shell and a composite breathable membrane, wherein the composite breathable membrane is encapsulated on the membrane cap shell; The composite breathable membrane is made of a dual-reinforced silicone rubber composite material, which comprises: The invention comprises a silicone rubber substrate, a chemical reinforcing agent, a physical modifier, a crosslinking agent, an inhibitor, and a catalyst, wherein the silicone rubber substrate is vinyl-terminated polydimethylsiloxane, the chemical reinforcing agent is vinyl MQ silicone resin, and the physical modifier is a nanoscale sheet material.

2. The double-reinforced silicone rubber composite breathable membrane cap according to claim 1, characterized in that: The membrane cap shell is made of polysulfone material.

3. The double-reinforced silicone rubber composite breathable membrane cap according to claim 1, characterized in that: The nanoscale sheet material is organo-modified montmorillonite, the crosslinking agent is hydrogen-containing silicone oil, the inhibitor is ethynylcyclohexanol, and the catalyst is a platinum catalyst.

4. The double-reinforced silicone rubber composite breathable membrane cap according to claim 1, characterized in that: The thickness of the composite breathable membrane is 25–50 μm.

5. The double-reinforced silicone rubber composite breathable membrane cap according to claim 1, characterized in that: The composite breathable membrane has a Shore A hardness greater than 60 and an oxygen permeability coefficient of 3×10⁻⁶. -9 cm² / (s·cmHg) up to 8×10 -9 Tensile strength ≥ 8.0 MPa, with a value between cm² / (s·cmHg).

6. A method for preparing a dual-reinforced silicone rubber composite breathable membrane, used to prepare the composite breathable membrane as described in any one of claims 1 to 5, characterized in that, Includes the following steps: Step S1: Premixing and devolatilization: The vinyl-terminated polydimethylsiloxane silicone rubber substrate is mixed with vinyl MQ silicone resin and heated and stirred under vacuum to remove moisture and gas; Step S2: Nanoscale dispersion: Add nanoscale sheet material to the mixture obtained in step S1, and mechanically grind it to fully peel off and uniformly disperse it to form a homogeneous paste; Step S3: Adhesive preparation: Cool the paste obtained in step S2, add the crosslinking agent and inhibitor in sequence, mix evenly, add the platinum catalyst under air-isolated conditions, mix evenly to obtain the adhesive solution. Step S4: Coating and curing: The adhesive obtained in step S3 is coated onto the substrate and cured by heating to form a film; Step S5: Post-processing: After cooling, the film is peeled off from the substrate to obtain the double-reinforced silicone rubber composite breathable membrane.

7. The method for preparing the double-reinforced silicone rubber composite breathable membrane according to claim 6, characterized in that: The curing process described in step S4 adopts a stepped curing process. The first stage involves preliminary gelation at 70-90℃, and the second stage involves complete cross-linking and curing at 140-160℃.

8. The method for preparing the double-reinforced silicone rubber composite breathable membrane according to claim 6, characterized in that: The mechanical grinding described in step S2 is a three-roll mill for circulating grinding.

9. A method for preparing a double-reinforced silicone rubber composite breathable membrane cap, characterized in that, include: The composite breathable membrane is prepared by the method described in any one of claims 6 to 8; The composite breathable membrane is cut and placed in a membrane cap shell mold, and then integrally encapsulated with polysulfone material through injection molding to obtain the composite breathable membrane cap.

10. The method for preparing the double-reinforced silicone rubber composite breathable membrane cap according to claim 9, characterized in that: The injection molding process is a two-stage injection overmolding process.

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