Nanoparticulate alkali-resistant hydrophobic modifier

Abstract

The present application relates to the technical field of high polymer material, and particularly relates to a kind of nanoparticle alkali-resistant hydrophobic modifier.The nanoparticle alkali-resistant hydrophobic modifier is composed of 25-55 parts of skeleton resin, 15-45 parts of anchoring agent, 1-10 parts of reinforcing agent and 100-300 parts of solvent.The present application uses perfluoropolymer system, so that the modifier is resistant to temperature of 400 DEG C or above and strong alkali corrosion;After sintering, it forms homogeneous and firm combination with PTFE matrix, solving the problem of interface peeling.The modifier is particularly suitable for preparing sealing gasket for alkaline electrolytic cell in high-salt and high-humidity environment at sea, significantly improving the dimensional stability and service life of the gasket.

Description

Technical Field

[0001] This invention belongs to the field of polymer materials technology, specifically relating to a nanoparticle alkali-resistant hydrophobic modifier. Background Technology

[0002] Alkaline water electrolysis for hydrogen production has become one of the mainstream routes for large-scale green hydrogen production due to its advantages such as low cost and long lifespan. In alkaline electrolyzers, sealing gaskets are key components, typically prepared by modifying polytetrafluoroethylene (PTFE) with inorganic nanoparticles to improve their mechanical properties and sealing reliability. However, as applications expand to offshore hydrogen production platforms, electrolyzers face the harsh challenges of high-salt and high-humidity marine environments.

[0003] In this environment, existing nanoparticle modification technologies have significant drawbacks:

[0004] Insufficient alkali resistance leads to failure: Traditional hydrophobic modification of nanoparticles often uses fluorinated silane coupling agents (such as perfluorooctyltriethoxysilane). These modifiers rely on siloxane bonds (Si-O-Si) as the backbone. However, in alkaline electrolytic cells, the siloxane bonds are easily hydrolyzed and broken at the 30% KOH solution and the operating temperature of 80-90℃, causing the hydrophobic layer to detach. The nanoparticles are then re-exposed and absorb water, swelling, ultimately leading to a decrease in the mechanical properties of the gasket and sealing failure.

[0005] The heat resistance is insufficient for processing: PTFE materials typically require high-temperature sintering (360-400℃) to melt and bond PTFE particles into a dense whole. However, the thermal decomposition temperature of existing organosilane modifiers is usually below 300℃. During PTFE sintering, these modifiers will decompose, carbonize, or volatilize prematurely, losing their hydrophobic properties and potentially generating gas that can lead to bubbles or defects inside the gasket.

[0006] Weak interfacial bonding: Existing modifiers and PTFE matrix are heterogeneous materials, mainly relying on physical adsorption or weak chemical bonds for bonding. Under long-term thermal cycling and chemical corrosion stress, the modified layer is prone to peeling off from the PTFE matrix, leading to the aggregation of nanofillers and failing to exert a reinforcing effect.

[0007] Therefore, there is an urgent need to develop a nanoparticle hydrophobic modifier that can withstand strong alkali corrosion, endure high-temperature sintering at 400℃, and form a strong bond with the PTFE matrix, in order to solve the long-term reliability problem of electrolyzer sealing gaskets in marine hydrogen production environments. Summary of the Invention

[0008] To address the problems of existing nanoparticle modifiers being prone to hydrolysis in strong alkaline environments, decomposition during the high-temperature sintering process of PTFE, and poor interfacial bonding with the PTFE matrix leading to sealing failure, this invention provides a nanoparticle alkali-resistant and hydrophobic modifier based on a perfluoropolymer system. This modifier exhibits excellent resistance to strong alkali corrosion, high-temperature resistance (≥400℃), and homogeneity with the PTFE matrix, significantly improving the long-term stability of nanofillers in harsh marine environments.

[0009] To achieve the above objectives, the present invention adopts the following technical solution:

[0010] The technical solution provided by this invention is as follows:

[0011] In a first aspect, the present invention provides a nanoparticle alkali-resistant hydrophobic modifier, wherein the nanoparticle alkali-resistant hydrophobic modifier comprises the following components by weight: 25-55 parts of skeleton resin, 15-45 parts of anchoring agent, 1-10 parts of reinforcing agent, and 100-300 parts of solvent.

[0012] Preferably, the skeleton resin is selected from at least one of polytetrafluoroethylene (PTFE) micro powder, fusible polytetrafluoroethylene (PFA) powder, and fluorinated ethylene propylene copolymer (FEP) micro powder, with an average particle size D50 of 0.1-5 μm.

[0013] Through the above technical solutions, the skeleton resin serves as the alkali-resistant and heat-resistant main skeleton of the coating, providing homogeneity and compatibility with the PTFE matrix, and melts to form a dense and continuous protective layer under high-temperature sintering.

[0014] Preferably, the anchoring agent is selected from at least one of hydroxyl-terminated perfluoropolyether, amino-terminated perfluoropolyether, and perfluoro compounds containing phosphate ester groups.

[0015] Through the above technical solutions, the strong polar functional groups of the anchoring agent end group form chemical bonds or strong coordination bonds with the surface of nanoparticles. At the same time, its perfluorinated backbone is compatible with the skeleton resin, playing a coupling role of molecular bridge.

[0016] Preferably, the reinforcing agent is selected from at least one of hexamethylene diisocyanate, isophorone diisocyanate, and phenolic resin.

[0017] Through the above technical solutions, the active functional groups of the reinforcing agent and the anchoring agent undergo a cross-linking reaction to construct a three-dimensional network structure, thereby improving the mechanical strength and chemical penetration resistance of the coating.

[0018] Preferably, the solvent is selected from at least one of N-methylpyrrolidone (NMP), xylene, and perfluorinated mixed solvents.

[0019] Preferably, the perfluorinated mixed solvent is selected from at least one of perfluorobutyltetrahydrofuran and perfluoronaphthalene.

[0020] Through the above technical solution, the solvent is a non-aqueous solvent, which ensures that the components are uniformly dispersed and avoids the nanoparticles absorbing water prematurely during the modification process.

[0021] Secondly, the present invention also provides a method for preparing alkali-resistant hydrophobic modified nanoparticles, comprising the following steps:

[0022] Step (1) Dry the nanoparticles at 100-150℃ for 2-6 hours to obtain dried nanoparticles;

[0023] Step (2) In a nitrogen atmosphere, dissolve 15-45 parts of anchoring agent and 1-10 parts of reinforcing agent in 30-50 parts of solvent, stir at 300-500 rpm at 40-60℃ for 20-60 min for pre-reaction, then add 25-55 parts of skeleton resin and the remaining solvent, and disperse at 3000-5000 rpm for 30-60 min by high-speed shearing, and then disperse by ultrasonication at 300-500W for 20-40 min to obtain the modifier dispersion;

[0024] Through the above technical solutions, the pre-reaction partially activates the grafting of reinforcing agents and anchoring agents; high-speed shearing and ultrasound ensure that the skeleton resin is fully deagglomerated in the solvent.

[0025] Step (3) Mix the dried nanoparticles and the modifier dispersion at a mass ratio of 1:(3-8), stir at 500-800 rpm for 30-60 min, and then heat and stir at 80-120℃ for 1-3 h to obtain the pre-cured modified nanoparticle precursor.

[0026] Step (4) The pre-cured modified nanoparticle precursor is heated to 360-380℃ at a heating rate of 5-10℃ / min and heat-treated for 1-2 hours to obtain alkali-resistant hydrophobic modified nanoparticles.

[0027] Through the above technical solutions, the skeleton resin is melted and sintered to form a continuous and dense perfluorinated coating, while the anchoring agent and reinforcing agent complete a deep cross-linking reaction to form a stable chemical bonding network.

[0028] Preferably, the nanoparticles are selected from at least one of silicon dioxide, titanium dioxide, and aluminum oxide.

[0029] Preferably, the present invention also provides the use of the aforementioned nanoparticle alkali-resistant hydrophobic modifier in the preparation of sealing gaskets for alkaline electrolytic cells used in seawater environments.

[0030] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0031] 1. This invention abandons the traditional siloxane (Si-O-Si) framework and adopts a perfluoropolymer system composed of carbon-fluorine (CF) and carbon-oxygen-fluorine (COCF) bonds. The backbone resin is selected from PTFE, PFA, or FEP, all with melting points above 300℃ and thermal decomposition temperatures exceeding 400℃. This allows the modifier to be compatible with the high-temperature sintering process of PTFE gaskets. During sintering, the modifier not only does not decompose and volatilize to generate bubbles, but also fills the gaps between nanoparticles through melt flow, forming a denser protective layer, ensuring the yield rate of gasket processing and the integrity of the final product.

[0032] 2. The outer layer of the modifier in this invention is primarily composed of perfluororesin, which is homogeneous or nearly homogeneous with the PTFE gasket matrix. During sintering, the molecular chains of both materials diffuse and entangle with each other, forming a metallurgical bond and eliminating the risk of interfacial delamination between dissimilar materials.

[0033] 3. The polar end groups of the anchoring agent in this invention form strong chemical bonds with the surface of the nanoparticles, and the three-dimensional cross-linked network constructed by the reinforcing agent firmly locks the particles in the perfluorinated matrix. This dual anchoring mechanism significantly improves the tensile strength and creep resistance of the composite material.

[0034] 4. The extremely low surface energy and dense cross-linked structure of the perfluoropolymer of this invention create a highly efficient hydrophobic barrier. This effectively prevents water molecule penetration even in high-salt and high-humidity marine environments, preventing gasket size changes and sealing failures caused by water absorption and swelling of nanoparticles, and significantly extending the service life of the electrolyzer. Attached Figure Description

[0035] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0036] Figure 1 This is a SEM image of the uncoated nanoparticles of the present invention;

[0037] Figure 2 This is a SEM image of the alkali-resistant hydrophobic modified nanoparticles of the present invention. Detailed Implementation

[0038] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only 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.

[0039] Example 1

[0040] This embodiment discloses a nanoparticle alkali-resistant hydrophobic modifier, which specifically includes the following components by weight: 30 parts PTFE, 10 parts hydroxyl-terminated perfluoropolyether (PFPE-Diol), 3 parts hexamethylene diisocyanate, and 150 parts NMP and xylene mixed solvent in a volume ratio of 1:1.

[0041] This embodiment also discloses a method for preparing alkali-resistant hydrophobic modified nanoparticles, including the following steps:

[0042] Step (1) Dry 10 parts of fumed silica nanoparticles with a particle size of 20 nm at 120 °C for 4 h to remove surface moisture and obtain dried silica nanoparticles.

[0043] Step (2) In a dry reaction vessel under nitrogen protection, add 10 parts of terminal hydroxyl perfluoropolyether and 3 parts of hexamethylene diisocyanate, then add 50 parts of mixed solvent, heat to 50°C and stir at 400 rpm for 40 min, then add 30 parts of PTFE micro powder and the remaining 100 parts of mixed solvent to the reaction vessel, and disperse at 4000 rpm for 45 min by high-speed shearing, then disperse by ultrasonication at 400W for 30 min to obtain the modifier dispersion;

[0044] Step (3) The dried silica nanoparticles are slowly added to the modifier dispersion in step (2), and stirred at 600 rpm for 45 min. Then the temperature is raised to 100℃ and stirred for 2 h to evaporate and remove the solvent, thus obtaining the pre-cured modified nanoparticle precursor.

[0045] Step (4) The pre-cured modified nanoparticle precursor is placed in a muffle furnace and heated to 370°C at a heating rate of 7°C / min. The mixture is then heat-treated for 1.5 h to obtain alkali-resistant hydrophobic modified silica powder.

[0046] like Figure 2 As shown, the silica particles treated with the modifier of the present invention are covered with a dense organic-inorganic hybrid coating with rounded edges and no exposed inorganic cores, indicating complete coating.

[0047] Example 2

[0048] This embodiment discloses a nanoparticle alkali-resistant hydrophobic modifier, which specifically includes the following components by weight: 40 parts PFA, 8 parts perfluorinated compound containing phosphate ester groups, 5 parts phenolic resin, and 120 parts of a mixed solvent of NMP and xylene in a volume ratio of 1:1.

[0049] Perfluorinated compounds containing phosphate groups are bis(perfluorohexyl)phosphonic acids.

[0050] This embodiment also discloses a method for preparing alkali-resistant hydrophobic modified nanoparticles, including the following steps:

[0051] Step (1) Dry 10 parts of nano-titanium dioxide particles with a particle size of 30nm at 130℃ for 3h to remove surface moisture and obtain dried nano-titanium dioxide particles.

[0052] Step (2) In a dry reaction vessel under nitrogen protection, add 8 parts of perfluorinated compound containing phosphate ester group and 5 parts of phenolic resin, then add 40 parts of mixed solvent, heat to 55℃ and stir at 300 rpm for 50 min, then add 40 parts of PFA powder and the remaining 80 parts of mixed solvent to the reaction vessel, and shear disperse at 3000 rpm for 60 min, then ultrasonically disperse at 500W for 20 min to obtain the modifier dispersion;

[0053] Step (3) The dried nano-titanium dioxide particles are slowly added to the modifier dispersion in step (2), stirred at 600 rpm for 45 min, and then heated to 80℃ and stirred for 3 h to evaporate and remove the solvent, thus obtaining the pre-cured modified nanoparticle precursor.

[0054] Step (4) The pre-cured modified nanoparticle precursor is placed in a muffle furnace and heated to 380°C at a heating rate of 5°C / min. The mixture is then heat-treated for 2 hours to obtain alkali-resistant hydrophobic modified titanium dioxide powder.

[0055] Example 3

[0056] This embodiment discloses a nanoparticle alkali-resistant hydrophobic modifier, which specifically includes the following components by weight: 25 parts FEP, 15 parts amino-terminated perfluoropolyether (PFPE Diamine), 4 parts isophorone diisocyanate, and 200 parts NMP solvent.

[0057] This embodiment also discloses a method for preparing alkali-resistant hydrophobic modified nanoparticles, including the following steps:

[0058] Step (1) Dry 10 parts of nano-alumina particles with a particle size of 20nm at 120℃ for 4h to remove surface moisture and obtain dried nano-alumina particles.

[0059] Step (2) In a dry reaction vessel under nitrogen protection, add 15 parts of terminal amino perfluoropolyether and 4 parts of isophorone diisocyanate, then add 60 parts of NMP solvent, heat to 45°C and stir at 400 rpm for 40 min, then add 25 parts of FEP micro powder and the remaining 140 parts of NMP solvent to the reaction vessel, and disperse at 5000 rpm for 30 min, then disperse ultrasonically at 300W for 40 min to obtain the modifier dispersion;

[0060] Step (3) Slowly add 10 parts of dry nano alumina particles to the modifier dispersion in step (2), stir at 600 rpm for 45 min, then heat and stir at 100℃ for 2 h to evaporate and remove the solvent, and obtain the pre-cured modified nanoparticle precursor.

[0061] Step (4) The pre-cured modified nanoparticle precursor is placed in a muffle furnace and heated to 360°C at a heating rate of 10°C / min. The mixture is then heat-treated for 1 hour to obtain alkali-resistant hydrophobic modified alumina powder.

[0062] Comparative Example 1

[0063] This comparative example uses a traditional perfluorosilane coupling agent for modification, and the specific scheme is as follows:

[0064] Ten parts of fumed silica with a particle size of 20 nm were dispersed in 100 parts of a 95:5 volume ratio of ethanol to water mixed solvent. 0.2 parts of perfluorooctyltriethoxysilane were added, and the pH value was adjusted to 4.5. The mixture was subjected to hydrolysis and condensation reaction at 50 °C for 2 h. The solvent was then removed by drying, and the mixture was cured at 200 °C for 1 h.

[0065] Comparative Example 2

[0066] Comparative Example 2 was formulated and prepared in the same manner as Example 1, but without the addition of a reinforcing agent. The formulation consisted of 30 parts PTFE, 10 parts hydroxyl-terminated perfluoropolyether, and 150 parts mixed solvent. The preparation steps were the same as in Example 1, except that the step of adding the reinforcing agent and pre-reaction in step (2) was omitted, and the anchoring agent was directly mixed and dispersed with the skeleton resin.

[0067] Comparative Example 3

[0068] Comparative Example 3 was formulated and prepared in the same manner as Example 1, but without the addition of an anchoring agent. The formulation consisted of 30 parts PTFE, 3 parts hexamethylene diisocyanate, and 150 parts mixed solvent. The preparation steps were the same as in Example 1, except that the step of adding the anchoring agent in step (2) was omitted, and the reinforcing agent was directly mixed and dispersed with the skeleton resin.

[0069] Performance testing:

[0070] Hydrophobicity test: The water contact angle is measured using a contact angle meter.

[0071] Salt and alkali resistance test: The sample was immersed in a solution containing 30% KOH and 3.5 wt% NaCl, heated at 90℃ for 72 hours, removed, cleaned and dried, and the contact angle was measured.

[0072] Heat resistance test: The sample was placed in a muffle furnace and heated at 400°C for 2 hours. The contact angle and weight loss rate were then measured.

[0073] Mechanical properties: Modified nanoparticles were filled into a PTFE matrix at 10 wt%, pressed and sintered to form specimens, and tensile strength, weight loss and resilience were tested.

[0074] The test results are shown in Table 1:

[0075] Table 1

[0076]

[0077] Table 2

[0078]

[0079] Based on the performance data comparison of Examples 1-3 and Comparative Examples 1-3 in Tables 1 and 2, the alkali-resistant hydrophobic modified nanoparticles prepared by the present invention have excellent comprehensive performance, specifically manifested as high hydrophobicity, excellent resistance to strong alkalis and heat, and outstanding interfacial bonding and mechanical reinforcement effects.

[0080] The comparison between Comparative Example 1 and Examples 1-3 shows that: the nanoparticles modified with traditional perfluorosilane coupling agents have acceptable initial hydrophobicity, but under the harsh environment of "high temperature, high alkali, and high salt" (30% KOH, 90℃), their contact angle drops sharply to below 90°, and they undergo severe carbonization failure at 400℃. The composite material exhibits severe agglomeration and interfacial delamination.

[0081] The comparison between Comparative Example 2 and Example 1 shows that: the system lacking hexamethylene diisocyanate, relying only on the physically mixed PTFE skeleton and anchoring agent, although the initial contact angle is slightly higher, the alkali resistance and heat resistance completely collapse (contact angle < 90°, weight loss rate 20%), and the composite material has an extremely low resilience (15%), and microcracks appear at the interface.

[0082] The comparison between Comparative Example 3 and Example 1 shows that the system lacking terminal hydroxyl perfluoropolyethers, directly mixing the PTFE skeleton with the crosslinking agent, results in a lack of chemical bonding "bridges" between the modified particles and the inorganic core. The consequence is that the alkali and heat resistance also fails, and the composite material exhibits the worst mechanical properties.

[0083] The above description is only a preferred embodiment of the present invention, but 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 inventive concept of the present invention, should be covered within the scope of protection of the present invention.

[0084] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to specific implementations. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A nanoparticle alkali-resistant hydrophobic modifier, characterized in that, The nanoparticle alkali-resistant hydrophobic modifier specifically comprises the following components by weight: 25-55 parts of skeleton resin, 15-45 parts of anchoring agent, 1-10 parts of reinforcing agent, and 100-300 parts of solvent.

2. The nanoparticle alkali-resistant hydrophobic modifier according to claim 1, characterized in that, The skeleton resin is selected from at least one of polytetrafluoroethylene (PTFE) micro powder, fusible polytetrafluoroethylene (PFA) powder, and fluorinated ethylene propylene copolymer (FEP) micro powder.

3. The nanoparticle alkali-resistant hydrophobic modifier according to claim 1, characterized in that, The anchoring agent is selected from at least one of hydroxyl-terminated perfluoropolyether, amino-terminated perfluoropolyether, and perfluoro compounds containing phosphate ester groups; the reinforcing agent is selected from at least one of hexamethylene diisocyanate, isophorone diisocyanate, and phenolic resin; and the solvent is a non-aqueous organic solvent.

4. The nanoparticle alkali-resistant hydrophobic modifier according to claim 3, characterized in that, The solvent is selected from at least one of N-methylpyrrolidone (NMP), xylene, and perfluorinated mixed solvents.

5. The nanoparticle alkali-resistant hydrophobic modifier according to claim 2, characterized in that, The average particle size D50 of the skeleton resin is 0.1-5 μm.

6. A method for preparing alkali-resistant hydrophobic modified nanoparticles, characterized in that, Includes the following steps: Step (1) Dry the nanoparticles at 100-150℃ for 2-6 hours to obtain dried nanoparticles; Step (2) In a nitrogen atmosphere, dissolve 15-45 parts of anchoring agent and 1-10 parts of reinforcing agent in 30-50 parts of solvent, and stir at 40-60℃ for 20-60 min for pre-reaction; then add 25-55 parts of skeleton resin and the remaining solvent, and perform high-speed shear dispersion and ultrasonic dispersion to obtain the modifier dispersion. Step (3) Mix the dried nanoparticles with the modifier dispersion at a mass ratio of 1:(3-8), stir and heat to 80-120℃ for 1-3 hours to obtain the pre-cured modified nanoparticle precursor. Step (4) Heat the pre-cured modified nanoparticle precursor to 360-380℃ and heat-treat for 1-2 hours to obtain alkali-resistant hydrophobic modified nanoparticles.

7. The method for preparing alkali-resistant hydrophobic modified nanoparticles according to claim 6, characterized in that, In step (2), the high-speed shear dispersion speed is 3000-5000 rpm and the time is 30-60 min; the ultrasonic dispersion power is 300-500 W and the time is 20-40 min.

8. The method for preparing alkali-resistant hydrophobic modified nanoparticles according to claim 6, characterized in that, In step (4), the heating rate is 5-10℃ / min.

9. The method for preparing alkali-resistant hydrophobic modified nanoparticles according to claim 6, characterized in that, The nanoparticles are selected from at least one of silicon dioxide, titanium dioxide, and aluminum oxide.

10. The use of the nanoparticle alkali-resistant hydrophobic modifier as described in claim 1 in the preparation of sealing gaskets for alkaline electrolytic cells in seawater environments.

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