Preparation method of fluoride-free waterproof breathable film based on irradiation technology

Abstract

The invention discloses a preparation method of a fluoride-free waterproof breathable film based on an irradiation technology. Comprising the following steps: uniformly mixing chitosan, an organosilicon polymer, a cross-linking agent, a catalyst, a pore forming agent and a solvent according to a ratio, and stirring until complete dissolution to prepare a membrane casting solution; coating the surface of a membrane treated by an irradiation technology with the membrane casting solution by using a blade coating machine to form a coated membrane; and drying the coating film to obtain the waterproof breathable film. The structure of the base film and the coating is adopted, so that the overall structural strength is improved, and the membrane can be placed under certain water pressure. The pore diameter and the pore density of the base membrane can be regulated and controlled, a pore-foaming agent is added into the coating, and the overall air permeability of the waterproof and breathable membrane can be flexibly regulated and controlled according to requirements. The organosilicon polymer and the cross-linking agent in the coating enhance the hydrophobicity, the mechanical strength and the durability of the coating. The waterproof breathable film prepared by the invention adopts fluorine-free substances. The waterproof breathable film prepared by the invention has a good application prospect in the field of electronic products.

Description

Technical Field

[0001] The invention relates to the field of electronic products, and in particular to a method for preparing a fluorine-free waterproof and breathable membrane based on radiation technology. Background Art

[0002] At present, waterproof and breathable membranes used in the field of electronic products mostly rely on fluorine-containing materials, such as expanded polytetrafluoroethylene (made by unidirectional or biaxial mechanical stretching of polytetrafluoroethylene resin), or modified with fluorine-containing low surface energy substances.

[0003] In addition to using fluorine-containing substances to prepare waterproof and breathable membranes, it can also be prepared by stretching process, or by coating other low surface energy substances on the base membrane. However, there are no intuitive and reliable monitoring indicators and detection methods for the stretching process, which is prone to uncontrollable product quality and certain losses. Moreover, the use of stretching in the preparation process results in uneven pores on the surface of the film and poor air permeability. The use of fluorine-free and low surface energy coatings on the base membrane to prepare waterproof and breathable membranes requires consideration of many aspects, including the selection of base membrane materials, the environmental friendliness of the coating components, the compatibility of the coating components, the adhesion between the coating and the base membrane, and the coordination of the coating thickness and overall air permeability.

[0004] Patent CN116903907A discloses a method for coating a fluororesin waterproof coating on the surface of a irradiated base film. The method forms a microporous waterproof coating on the surface of the film through an extraction and curing process, and then the outer surface of the microporous waterproof coating is laminated with a release protective film and immersed in an etching solution to form a microporous base film. Finally, the release protective film is peeled off to obtain a waterproof and breathable film. In the preparation of the waterproof coating, fluororesin polyvinylidene fluoride (PVDF) is used as a waterproof material. Fluorine polymers are often used to modify the surface of the membrane due to their low surface energy characteristics to obtain excellent waterproof properties. However, fluorine substances have poor degradability in the environment and may have long-term negative effects on the ecosystem. In addition, the process flow of coating first and then etching in the preparation process may cause the waterproof coating to be impacted or dissolved during the etching process, thereby affecting the adhesion between the coating and the base film, and ultimately causing the coating to fall off or peel off. At the same time, the barrier formed by the waterproof coating during the etching process may hinder the uniform penetration of the etchant into the membrane surface, affecting the etching effect, and will have an adverse effect on subsequent applications.

[0005] Patent CN117164995A discloses a composite material with a thermoplastic as the matrix and filled with a high content of inorganic particles, which is made into a film by calendering, casting, blow molding and other methods, and then a microporous film material with a small pore size and interconnected is obtained by uniaxial or biaxial stretching, thereby achieving a waterproof and breathable effect. However, during the stretching process, due to the influence of the anisotropy of the material, the mechanical properties of the film may be unevenly distributed, and it is difficult to accurately control the size, shape and distribution of the micropores. This uncertainty may lead to fluctuations in air permeability and waterproofness. Patent CN119076340A discloses a method for preparing a PDMS-based double-layer hydrophobic anti-reflective self-cleaning coating, wherein a PDMS sol is dip-coated on a hydroxylated substrate as a connecting layer; a PDMS-SiO2 sol is dip-coated on the PDMS connecting layer to obtain a PDMS-SiO2 hydrophobic layer, and the PDMS-SiO2 hydrophobic layer is subjected to an external flame carbonization treatment to introduce a carbonization template, and then annealed to obtain a PDMS-based double-layer hydrophobic anti-reflective self-cleaning coating containing a PDMS connecting layer and a PDMS-SiO2 carbonization annealing layer. The preparation of a double-layer PDMS-based hydrophobic coating involves multiple steps, including dip-coating, drying, and carbonization, which may increase errors in the preparation process and affect the uniformity and performance of the final product. In addition, there are problems with the adhesion between the double-layer hydrophobic coatings, which may cause interlayer peeling and reduce the overall performance of the coating during use. In order to solve the above problems, the present invention proposes a novel technical solution, that is, using a film etched by radiation technology as a base film, and using a fluorine-free silicon polymer to prepare a waterproof coating to obtain a waterproof and breathable membrane. Summary of the invention

[0006] The purpose of the present invention is to address the above-mentioned problems and shortcomings, and propose a method for preparing a fluorine-free waterproof and breathable membrane based on irradiation technology. The irradiated membrane is used as the base membrane with uniform pore size and adjustable pore density, which can achieve more accurate control of the permeability of water vapor and liquid water, and provide better durability and reliability. The use of fluorine-free coating to prepare a waterproof and breathable membrane is simple to operate, widely applicable, industrializable, and environmentally sustainable. The specific preparation method includes the following steps:

[0007] Step 1: Treating the base film using radiation technology;

[0008] Step 2, immersing the base film treated by irradiation in step 1 into an etching solution for etching to prepare a nuclear pore membrane;

[0009] Step 3: Dissolve an appropriate amount of chitosan in deionized water and stir until completely dissolved to prepare a chitosan solution with a concentration of 1-10%;

[0010] Step 4: Weigh the organosilicon polymer and the cross-linking agent according to the weight ratio, dissolve them in the solvent, and stir until they are completely dissolved to prepare a composite solution;

[0011] Step 5, weigh an appropriate amount of catalyst and add it to the complex solution, heat and stir until it is completely dissolved to prepare a mixed solution;

[0012] Step 6: Slowly pour the mixed solution into the chitosan solution and continue stirring until the solution is evenly mixed;

[0013] Step 7, weigh an appropriate amount of pore-forming agent and dissolve it in the solution in step 6, stir until completely dissolved, and prepare a casting solution;

[0014] Step 8: Apply the solution in step 7 to the surface of the film prepared in step 2 by using a doctor blade coating machine, wherein the coating thickness is 1-30 μm, to form a coating film;

[0015] Step nine: drying the coated film to obtain a waterproof and breathable film.

[0016] The irradiation technology in step 1 is high-energy electron beam, gamma ray, proton irradiation or heavy ion irradiation, the base film is polyimide film, polycarbonate film, polyethylene terephthalate film or polyurethane film, and the irradiation dose is: 1×10 6 -1×10 9 / cm 2 , base film thickness: 1-30µm.

[0017] Wherein, the etching solution in step 2 is a sodium hydroxide solution or a potassium hydroxide solution, the solution concentration is 10-60%, the temperature is: 30-80°C, and the etching time is: 1-50min.

[0018] Wherein, the concentration of the chitosan solution in step three is 1-10%.

[0019] Among them, the organic silicon polymer in the step 4 is one or a combination of methyltriethoxysilane, polydimethylsiloxane, and hexadecyltrimethoxysilane, with a weight ratio of 5-35%, the cross-linking agent is one or a combination of tetraethoxysilane, hexaethoxydisilane, and octaethoxytrisilane, with a weight ratio of 30-80%, and the solvent is ethanol, with a weight ratio of 10-50%.

[0020] Wherein, the catalyst in step five is acetic acid, the weight ratio is: 0.1-5%, and the heating temperature is: 20-50°C.

[0021] Wherein, the weight proportion of the chitosan solution in step six is ​​1-15%.

[0022] Wherein, the pore-forming agent in step seven is polyvinyl pyrrolidone or polyvinyl alcohol, and the weight ratio is 0.1-3%.

[0023] Wherein, the coating thickness in step eight is: 1-30µm.

[0024] Wherein, the drying time in step nine is: 1-4h, and the drying temperature is: 30-100°C.

[0025] Beneficial effects of the present invention:

[0026] Excellent hydrophobicity. The organosilicon polymer in the present invention has good hydrophobicity and elasticity. The long chain structure of the organosilicon polymer provides excellent flexibility and water resistance, and can form a continuous hydrophobic phase in the coating. The addition of the porogen promotes the formation of a microporous structure inside the coating. This porous structure not only enhances the hydrophobicity of the coating, but also improves the lightweight characteristics and air permeability of the coating.

[0027] Good air permeability. The waterproof breathable membrane prepared by compounding the irradiated base membrane and the fluorine-free waterproof coating in the present invention has a uniform pore size and an adjustable pore density, which can achieve more accurate control of the permeability of water vapor and liquid water. The addition of a pore-forming agent in the waterproof coating forms a microporous structure in the coating, making the waterproof breathable membrane more breathable. The waterproof breathable membrane prepared by the present invention has a permeability flow rate of 2000 ml per minute under an air pressure of 7 KPa and an area of ​​1 square centimeter.

[0028] Good adhesion and mechanical properties. In the present invention, the organic silicon polymer and the cross-linking agent undergo hydrolysis and polycondensation to form a three-dimensional cross-linked network, thereby enhancing the mechanical strength and durability of the coating. The base film plus coating structure is adopted, and the base film provides support, improves the structural strength, and allows it to be placed under a certain water pressure.

[0029] Low cost and easy preparation: Compared with the fluoride coatings in other inventions, the raw materials used in the present invention are relatively economical, the preparation process is relatively simple, and it is suitable for large-scale production.

[0030] Environmentally friendly. Traditional hydrophobic coatings often rely on fluorine compounds, which have an impact on the environment during production and use. Fluorine-free coatings use safer and more environmentally friendly raw materials, such as silicone polymers and chitosan, which are all renewable or naturally derived, reducing the negative impact on the ecological environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is a scanning electron microscope image of the nuclear pore membrane in step 2 of the first embodiment of the present invention.

[0032] Figure 2 This is a scanning electron microscope image of the waterproof breathable membrane in step nine of the first embodiment of the present invention. DETAILED DESCRIPTION

[0033] The following is a further detailed description of a method for preparing a fluorine-free waterproof breathable membrane based on irradiation technology provided by the present invention in conjunction with specific embodiments. It should be understood that the specific examples are only used to explain and introduce the present invention and cannot limit the scope of application of the present invention. Any modifications and changes made to the present invention fall within the scope of protection of the present invention without departing from the purpose and scope of the present invention.

[0034] Embodiment 1:

[0035] Step 1: Treat the polycarbonate film with γ-rays. The base film thickness is 10 µm and the irradiation dose is 1×10 6 / cm 2 ;

[0036] Step 2: Immerse the irradiated basement membrane in step 1 in a sodium hydroxide solution with a concentration of 20% at a temperature of 30° C. for 40 minutes to prepare a nuclear pore membrane;

[0037] Step 3: Dissolve an appropriate amount of chitosan in deionized water and stir until completely dissolved to prepare a chitosan solution with a concentration of 2%;

[0038] Step 4: Weigh polydimethylsiloxane and tetraethoxysilane according to weight ratio and dissolve them in ethanol, stir until completely dissolved, and prepare a composite solution. Weight ratio of polydimethylsiloxane: 20%, weight ratio of tetraethoxysilane: 20%, weight ratio of ethanol: 50%;

[0039] Step 5, weigh 1.5% by weight of acetic acid and add it to the complex solution, stir at 40° C. until it is completely dissolved to prepare a mixed solution;

[0040] Step 6: Slowly pour the mixed solution into the 8% chitosan solution by weight, and continue stirring until the solution is evenly mixed;

[0041] Step 7, weigh 0.5% of the pore-forming agent by weight and dissolve it in the solution prepared in step 6, stir until completely dissolved, and prepare a casting solution;

[0042] Step 8: Apply the solution in step 7 to the surface of the film prepared in step 2 by using a doctor blade coater, wherein the coating thickness is 10 μm, to form a coating film;

[0043] Step nine: drying the coated film for 4 hours at a drying temperature of 60° C. to obtain a waterproof and breathable film.

[0044] The waterproof breathable membrane produced by the process of Example 1 was tested by a flow monitor and found to be able to withstand a water pressure of 1 meter for 30 minutes without leaking. At the same time, it was measured that the air flow rate per minute was 2000 milliliters under an air pressure of 7 KPa and an area of ​​1 square centimeter. The strength bonding force between the multi-microporous waterproof coating and the microporous base membrane was tested by a tensile test machine, and the peeling force for peeling the waterproof coating from the base membrane was measured to be 90 g / cm.

[0045] Embodiment 2:

[0046] Step 1: Use heavy ion irradiation to treat polyethylene terephthalate film, the base film thickness is 20µm, and the irradiation dose is 1×10 7 / cm 2 ;

[0047] Step 2: Immerse the irradiated base film in step 1 in a potassium hydroxide solution with a concentration of 40% at a temperature of 50° C. for 30 minutes to prepare a nuclear pore membrane;

[0048] Step 3, dissolving an appropriate amount of chitosan in deionized water, stirring until completely dissolved, to prepare a chitosan solution with a concentration of 6%;

[0049] Step 4: Weigh polydimethylsiloxane and tetraethoxysilane according to weight ratio, dissolve them in ethanol, stir until completely dissolved, and prepare a composite solution. Weight ratio of polydimethylsiloxane: 10%, weight ratio of tetraethoxysilane: 45%, weight ratio of ethanol: 40%;

[0050] Step 5, weigh 2% acetic acid by weight and add it to the complex solution, heat and stir until it is completely dissolved to prepare a mixed solution;

[0051] Step 6: Slowly pour the mixed solution into a 1.5% by weight chitosan solution and continue stirring until the solution is evenly mixed;

[0052] Step 7, weigh 1.5% of the pore-forming agent by weight and dissolve it in the solution prepared in step 6, stir until completely dissolved, and prepare a casting solution;

[0053] Step 8: Apply the solution in step 7 to the surface of the film prepared in step 2 by using a doctor blade coating machine, wherein the coating thickness is 1-30 μm, to form a coating film;

[0054] Step nine: drying the coated film for 4 hours at a drying temperature of 60° C. to obtain a waterproof and breathable film.

[0055] The waterproof breathable membrane produced by the process of Example 1 was tested by a flow monitor and found to be able to withstand a water pressure of 3.5 meters for 30 minutes without leaking. At the same time, it was measured that the air flow rate per minute was 1500 milliliters under an air pressure of 7 KPa and an area of ​​1 square centimeter. The strength bonding force between the multi-microporous waterproof coating and the microporous base membrane was tested by a tensile test machine, and the peeling force for peeling the waterproof coating from the base membrane was 120 g / cm.

[0056] Embodiment 3:

[0057] Step 1: Use high-energy electron beam irradiation to treat the polyurethane film. The base film thickness is 30µm and the irradiation dose is 1×10 9 / cm 2 ;

[0058] Step 2: immerse the irradiated base film in step 1 in a sodium hydroxide solution with a concentration of 60% at a temperature of 80° C. for 10 minutes to prepare a nuclear pore membrane;

[0059] Step 3: Dissolve an appropriate amount of chitosan in deionized water and stir until completely dissolved to prepare a chitosan solution with a concentration of 8%;

[0060] Step 4: Weigh polydimethylsiloxane and tetraethoxysilane according to weight ratio, dissolve them in ethanol, stir until completely dissolved, and prepare a composite solution. Weight ratio of polydimethylsiloxane: 35%, weight ratio of tetraethoxysilane: 20%, weight ratio of ethanol: 30%;

[0061] Step 5, weigh 4% by weight of acetic acid and add it to the complex solution, heat and stir until it is completely dissolved to prepare a mixed solution;

[0062] Step 6: Slowly pour the mixed solution into a 10% chitosan solution by weight, and continue stirring until the solution is evenly mixed;

[0063] Step 7, weigh 1% of the pore-forming agent and dissolve it in the solution prepared in step 6, stir until completely dissolved, and prepare a casting solution;

[0064] Step 8: Apply the solution in step 7 to the surface of the film prepared in step 2 by using a doctor blade coater, wherein the coating thickness is 30 μm, to form a coating film;

[0065] Step nine: drying the coated film for 2 hours at a drying temperature of 80° C. to obtain a waterproof and breathable film.

[0066] The waterproof breathable membrane produced by the process of Example 1 was tested by a flow monitor and found to be able to withstand a water pressure of 2 meters for 30 minutes without leaking. At the same time, it was measured that the air flow rate per minute was 900 milliliters under an air pressure of 7 KPa and an area of ​​1 square centimeter. The strength bonding force between the multi-microporous waterproof coating and the microporous base membrane was tested by a tensile test machine, and the peeling force for peeling the waterproof coating from the base membrane was 100 g / cm.

[0067] The above is only a preferred embodiment of the present invention, and does not limit the present invention in other forms. Any technician familiar with the profession may use the above disclosed technical content to change or modify it into an equivalent embodiment with equivalent changes. However, any simple modification, equivalent change and improvement made to the above embodiment according to the technical essence of the present invention without departing from the technical solution of the present invention still belongs to the protection scope of the technical solution of the present invention.

Claims

1. A method for preparing a fluorine-free waterproof and breathable membrane based on irradiation technology, characterized by the following steps: Step 1: Treating the base film using radiation technology; Step 2, immersing the base film treated by irradiation in step 1 into an etching solution for etching to prepare a nuclear pore membrane; Step 3: Dissolve an appropriate amount of chitosan in deionized water and stir until completely dissolved to prepare a chitosan solution with a concentration of 1-10%; Step 4: Weigh the organosilicon polymer and the cross-linking agent according to the weight ratio, dissolve them in the solvent, and stir until they are completely dissolved to prepare a composite solution; Step 5, weigh an appropriate amount of catalyst and add it to the complex solution, heat and stir until it is completely dissolved to prepare a mixed solution; Step 6: Slowly pour the mixed solution into the chitosan solution and continue stirring until the solution is evenly mixed; Step 7, weigh an appropriate amount of pore-forming agent and dissolve it in the solution in step 6, stir until completely dissolved, and prepare a casting solution; Step 8: Apply the solution in step 7 to the surface of the film prepared in step 2 by using a doctor blade coating machine, wherein the doctor blade coating thickness is 1-30 μm, to form a coating film; Step nine: drying the coated film to obtain a waterproof and breathable film.

2. The preparation method according to claim 1, characterized in that: The irradiation technology in step 1 is high-energy electron beam, gamma ray, proton irradiation or heavy ion irradiation, the base film is polyimide film, polycarbonate film, polyethylene terephthalate film or polyurethane film, and the irradiation dose is: 1×10 6 -1×10 9 / cm 2 , base film thickness: 1-30µm.

3. The preparation method according to claim 1, characterized in that: The etching solution in step 2 is a sodium hydroxide solution or a potassium hydroxide solution, the solution concentration is 10-60%, the temperature is 30-80° C., and the etching time is 1-50 min.

4. The preparation method according to claim 1, characterized in that: The concentration of the chitosan solution in step 3 is 1-10%.

5. The preparation method according to claim 1, characterized in that: The organosilicon polymer in step 4 is one or a combination of methyltriethoxysilane, polydimethylsiloxane, and hexadecyltrimethoxysilane, with a weight ratio of 5-35%. The crosslinking agent is one or a combination of tetraethoxysilane, hexaethoxydisilane, and octaethoxytrisilane, with a weight ratio of 30-80%. The solvent is ethanol, with a weight ratio of 10-50%.

6. The preparation method according to claim 1, characterized in that: The catalyst in step 5 is acetic acid, the weight ratio is 0.1-5%, and the heating temperature is 20-50°C.

7. The preparation method according to claim 1, characterized in that: The weight proportion of the chitosan solution in step six is ​​1-15%.

8. The preparation method according to claim 1, characterized in that: The pore-forming agent in step seven is polyvinyl pyrrolidone or polyvinyl alcohol, and the weight ratio is 0.1-3%.

9. The preparation method according to claim 1, characterized in that: The coating thickness in step eight is 1-30 μm.

10. The preparation method according to claim 1, characterized in that: The drying time in step nine is 1-4 hours, and the drying temperature is 30-100°C.

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