A hydrolysis-resistant photosensitive resin for a deep-sea pressure sensor and a method of preparing the same

Abstract

This invention belongs to the field of functional organic polymer materials, and the finished product is applied in the field of marine exploration. This invention provides a hydrolysis-resistant photosensitive resin for deep-sea pressure sensors and its preparation method. The raw materials for the hydrolysis-resistant photosensitive resin include: a photosensitive resin prepolymer, a chain extender, an anti-hydrolysis agent, an active diluent, an initiator, and other additives. It is prepared by mixing the raw materials to obtain a photosensitive resin slurry, followed by ultraviolet light curing and thermal curing. The photosensitive resin prepolymer is obtained by reacting isocyanate with oligomeric polyols to generate polyurethane, thereby introducing photosensitive groups. The chain extender is prepared from two ketone-containing protecting substances and a diamine. The hydrolysis-resistant photosensitive resin of this invention possesses excellent mechanical properties and hydrolysis resistance, maintaining the stability of its molecular structure and function in water, and has significant advantages in the field of marine exploration.

Description

Technical Field

[0001] This invention relates to the field of functional organic polymer materials, with the finished product applied in the field of marine exploration. In particular, it relates to a hydrolysis-resistant photosensitive resin for deep-sea pressure sensors and its preparation method, and more specifically, to a hydrolysis-resistant photosensitive resin for deep-sea 3D-printed flexible pressure sensors. Background Technology

[0002] In deep-sea exploration research, poor visibility and high water pressure are the main challenges faced by deep-sea exploration technology. Underwater robots and submersibles are currently the mainstream tools for deep-sea exploration. Underwater manipulators, capable of grasping minerals and capturing organisms, are core components of underwater robots and submersibles. These manipulators use internal pressure sensors to sense the various forces required for grasping, and these pressure sensors are themselves key components of the manipulator.

[0003] The high-pressure environment of the deep sea requires pressure sensors to withstand both high pressure (MPa level) and minute pressure (Pa to kPa level). Rigid pressure sensors, due to their rigid shells, can detect pressure across the entire ocean depth, but they struggle to detect pressure changes during grasping, as minute pressure is outside their detection range. Flexible pressure sensors, capable of sensing minute pressure, hold promise for conformal integration with rigid sensors, jointly contributing to deep-sea exploration. However, because flexible sensors cannot withstand the high pressure of the deep sea, research on flexible pressure sensors applicable to marine environments is currently limited.

[0004] Research has found that flexible pressure sensors with hollow microstructures, fabricated using digital light processing (DLP) 3D printing technology, can initially solve the problem of small sensing capabilities of flexible sensors under high pressure in the deep sea by introducing seawater to balance the pressure inside and outside the sensor. However, introducing seawater to balance the water pressure will inevitably lead to direct contact between the seawater and the hollow sensor itself.

[0005] Photosensitive resin is composed of prepolymer, initiator, reactive diluent, and various additives. Its most important component is the prepolymer. Polyurethane acrylate is widely used as a prepolymer for DLP printing resins due to its high elasticity, high tensile strength, and high resistance to ionic attack.

[0006] Currently, the main component of photosensitive resin raw materials for DLP printing is polyurethane elastomer with ester or urea groups. The inventors of this application recognize that polyurethane groups are highly susceptible to hydrolysis after contact with seawater for a period of time, altering the mechanical properties of the resin layer and consequently causing the sensor to malfunction. Therefore, for deep-sea pressure sensors, there is an urgent need to research a novel hydrolysis-resistant photosensitive resin. Summary of the Invention

[0007] According to one embodiment of the present invention, the objective is to provide a novel hydrolysis-resistant photosensitive resin with excellent mechanical properties, stable performance in water, and suitable for use in deep-sea flexible pressure sensors, as well as a method for preparing the same, to solve the problems of easy hydrolysis and decomposition and poor mechanical properties in existing deep-sea flexible pressure sensors. The above objective can be achieved through the following technical solutions:

[0008] According to one aspect of the present invention, a hydrolysis-resistant photosensitive resin for a deep-sea pressure sensor is provided. The hydrolysis-resistant photosensitive resin comprises, as follows: a photosensitive resin prepolymer, a chain extender, an anti-hydrolysis agent, an active diluent, an initiator, and other additives. It is prepared by mixing the raw materials to obtain a photosensitive resin slurry, followed by ultraviolet light curing and thermal curing. The photosensitive resin prepolymer is obtained by reacting isocyanate with oligomeric polyols to generate polyurethane, followed by introducing ultraviolet-curable groups. The chain extender is prepared by reacting the amino groups at both ends of the diamine with the ketone groups in the two ketone-containing protective substances.

[0009] Optionally, at least one of the two ketone-containing protecting substances contains a carbon-carbon double bond.

[0010] Optionally, the anti-hydrolysis agent is carbodiimide or N,N'-bis(2,6-diisopropylphenyl)carbodiimide.

[0011] Optionally, the molar ratio of the isocyanate to the oligomeric polyol is 1:2 to 2:1.

[0012] Optionally, the isocyanate is one or more of hexamethylene diisocyanate, isophorone diisocyanate, toluene diisocyanate, naphthalene diisocyanate, and trimethylhexamethylene diisocyanate, with a molecular weight of 100 to 300.

[0013] Optionally, the oligomeric polyol is one or more of anhydrous polybutanediol, polycaprolactone polyol, polypropylene glycol, and polyether, with a molecular weight of 500 to 2000.

[0014] Optionally, the UV-curable group is introduced by adding acrylate hydroxy esters.

[0015] Further optionally, the acrylate hydroxy ester is 2-methyl-2-acrylate-2-[(1,1-dimethylethyl)amino]ethyl ester.

[0016] Optionally, the hydrolysis-resistant photosensitive resin is a polyurethane resin copolymer having a three-dimensional network structure of linear thermoplastic polyurethane and cross-linked thermosetting polyurethane.

[0017] Optionally, the reactive diluent is one or more of lauryl methacrylate, glyceryl carbonate methacrylate, and polyethylene glycol diacrylate.

[0018] Optionally, the initiator is one or more of TPO, 819, 1173, 1490, and BP.

[0019] Optionally, the other additives include one or more of antioxidants, light stabilizers, and trace additives.

[0020] Optionally, the trace additives include one or more of the following: defoamers, antisettling agents, thickeners, light absorbers, and light inhibitors.

[0021] According to another aspect of the present invention, a method for preparing the above-mentioned hydrolysis-resistant photosensitive resin for deep-sea pressure sensors includes the following steps:

[0022] Step S1: Polyurethane is generated by reacting isocyanate and oligomeric polyol as raw materials, and UV-curable groups are introduced into the polyurethane to generate photosensitive resin prepolymer.

[0023] Step S2: Using diamine and two ketone-containing protective substances as raw materials, the chain extender is prepared by reacting the amino groups at both ends of the diamine with the ketone groups in the two ketone-containing protective substances.

[0024] Step S3: Mix the anti-hydrolysis agent, reactive diluent, initiator and other additives, stir to dissolve, add the photosensitive resin prepolymer and stir to react, add the chain extender and continue stirring to react, to obtain photosensitive resin slurry;

[0025] Step S4: The photosensitive resin slurry is cured and molded under ultraviolet light;

[0026] Step S5: Perform thermosetting treatment on the photocured resin to obtain a hydrolysis-resistant photosensitive resin.

[0027] Optionally, step S2 includes: dissolving the diamine and two ketone-containing protecting substances in a solvent, heating to a first temperature, and stirring the reaction; then heating to a second temperature and continuing to stir the reaction; after the reaction is complete, removing the solvent by vacuum distillation to obtain the chain extender. Further optionally, the first temperature is 120–140°C, and the reaction time is 1–3 h; the second temperature is 150°C–170°C, and the reaction time is 7–9 h; the vacuum distillation temperature is 120–140°C, and the vacuum distillation time is 2–3 h.

[0028] Optionally, in step S5, the photocured resin is placed in an oven for heat curing. Further optionally, the humidity of the oven is 60-90%, the heat curing temperature is 80-150°C, and the heat curing time is 6-10 hours.

[0029] Optionally, in step S1, the reaction temperature is 30℃~80℃.

[0030] Optionally, in step S3, the stirring speed is 1000-2500 r / min and the stirring reaction time is 4-8 min; and the stirring speed after adding the chain extender is higher than the stirring speed after adding the photosensitive resin prepolymer.

[0031] Optionally, in step S4, the ultraviolet light wavelength is 200–410 nm; the ultraviolet light intensity is 5–100 mW / cm². 2 Exposure time is 0.1 to 30 seconds.

[0032] Optionally, step S1 further includes: a step of storing the photosensitive resin prepolymer; wherein the storage conditions are: storing in a constant temperature oven at 40°C in the dark.

[0033] Optionally, step S2 further includes a step of preserving the chain extender; wherein the preservation conditions are: frozen preservation at -5°C.

[0034] Optionally, before step S4, the method further includes: mixing polyether acrylate resin into the photosensitive resin slurry in any proportion.

[0035] Beneficial Effects: According to one embodiment of the present invention, isocyanate reacts with polyol to generate polyurethane, and then photosensitive groups capable of UV curing are introduced to obtain a photosensitive resin prepolymer. This prepolymer remains in a liquid state and has good stability. Simultaneously, to enhance the molecular weight and mechanical properties of the resin, a chain extender mainly composed of a diamine mixture is prepared. Furthermore, to enhance the resin's resistance to hydrolysis, an anti-hydrolysis group is introduced, whose curing reaction rate is not affected under UV light conditions. By mixing the aforementioned specific photosensitive resin prepolymer, chain extender, and anti-hydrolysis agent with an active diluent, initiator, and other additives to obtain a photosensitive resin slurry, a hydrolysis-resistant photosensitive resin is prepared using UV curing and thermal curing treatments. After the resin completes the UV curing reaction, under thermosetting conditions, the blocked isocyanate groups in the resin undergo cleavage to expose them for further curing. Simultaneously, the protecting groups in the chain extender that protect the amino groups also cleave, exposing the amino groups and causing them to crosslink with the isocyanate groups, forming a polyurethane resin copolymer with a three-dimensional network structure of linear thermoplastic polyurethane and crosslinked thermosetting polyurethane. This copolymer retains the advantages of traditional photosensitive resins while also exhibiting excellent mechanical stability and good mechanical properties, and can resist seawater erosion to a certain extent, demonstrating good hydrolytic stability. Attached Figure Description

[0036] Figure 1 The infrared spectrum of prepolymer A, the product of Example 1 of this invention;

[0037] Figure 2 The infrared spectrum of chain extender B, the product of Example 2 of this invention;

[0038] Figure 3 The infrared spectra of liquids ABCDEFG in Examples 1-5 of this invention are shown in comparison.

[0039] Figure 4 This is a columnar comparison of the tensile properties of the spline abcdefg in Examples 1-5 of the present invention;

[0040] Figure 5 This is a schematic diagram of the fabrication process of the hydrolysis-resistant deep-sea pressure sensor in this embodiment of the invention. Detailed Implementation

[0041] The technical solution of the present invention will be clearly and completely described below with reference to embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use. 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.

[0042] This invention proposes a novel hydrolysis-resistant photosensitive resin with excellent mechanical properties, stable performance in water, and suitable for use in deep-sea (flexible) pressure sensors, along with its preparation method. The raw materials for the hydrolysis-resistant photosensitive resin include a photosensitive resin prepolymer, a chain extender, an anti-hydrolysis agent, an active diluent, an initiator, and other additives. First, isocyanate is reacted with a polyol to generate polyurethane, and UV-curable groups are introduced to generate the photosensitive resin prepolymer. Using diamine and two ketone-containing protecting substances as raw materials, a chain extender is prepared by reacting the amino groups at both ends of the diamine with the ketone groups in the two ketone-containing protecting substances. Then, the raw materials are uniformly mixed into a slurry and cured under UV light of a specific wavelength. After photocuring, this photosensitive resin undergoes a subsequent heat treatment process to further increase the crosslinking density between resin components, thereby enhancing the mechanical properties of the cured resin. Because this novel photosensitive resin significantly enhances the chemical bond forces between groups through heat curing crosslinking and chain extension, it exhibits excellent tensile strength and low hysteresis. Furthermore, this invention introduces a hydrolysis-resistant agent into the resin, which can neutralize the carboxylic acid groups generated during resin hydrolysis, preventing autocatalytic hydrolysis of the resin, thus improving the hydrolytic decomposition resistance of the photosensitive resin without affecting its mechanical properties. In addition, the hydrolysis-resistant photosensitive resin described in this invention can be miscibly blended with other resins of the same type.

[0043] A method for preparing a hydrolysis-resistant photosensitive resin for a flexible deep-sea pressure sensor, provided in one embodiment of the present invention, may include the following steps:

[0044] The first step is the synthesis of the prepolymer.

[0045] Soft-segment monomers (isocyanates) and hard-segment monomers (oligomeric polyols) are added to a light-proof, sealed three-necked flask. Air is removed from the sealed container, and appropriate amounts of solvent and reaction aids are added and stirred. The mixture is stirred and reacted at a certain temperature. The isocyanate group (-NCO) in the isocyanate combines with the hydroxyl group (-OH) in the long-chain diol. After a period of reaction, polyurethane is generated. Then, a substance that can introduce UV-curable groups is added and the reaction is continued with stirring to obtain a UV-curable polyurethane acrylate.

[0046] The reaction temperature for synthesizing the prepolymer is controlled between 30℃ and 80℃; the heating and stirring reaction time after adding isocyanate and oligomeric polyol is 2 to 4 hours; and the deheating and stirring reaction time after adding acrylate hydroxy ester is 4 to 48 hours. Furthermore, the prepolymer is synthesized under light-shielding and sealed vacuum conditions and needs to be stored in a constant temperature oven at 40℃ in the dark.

[0047] The molar ratio of the isocyanate to the polyol is 1:2 to 2:1. The oligomeric polyol can be one or more of anhydrous polybutanediol (PTMG), polycaprolactone diol (PCL), polypropylene glycol (PPG), and polyether (PO), with a molecular weight range of 500 to 2000. The isocyanate can be one or more of hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), toluene diisocyanate (TDI), and 1,5-naphthalene diisocyanate (NDI), with a molecular weight range of 100 to 300.

[0048] The substance capable of introducing UV-curable groups (photosensitive groups) is an acrylate, which contains photocurable carbon-carbon double bonds. Photocuring is achieved by adding acrylate. Furthermore, the reactive end groups contained in the acrylate include, but are not limited to, epoxy, olefin, alkynyl, thio, vinyl, and amino groups. For example, the acrylate can be 2-methyl-2-acrylate-2-[(1,1-dimethylethyl)amino]ethyl ester (tBAEMA). TBAEMA has an amino end capped to protect the NCO group, while the other end contains a photocurable carbon-carbon double bond. Introducing carbon-carbon double bonds through tBAEMA yields a UV-curable polyurethane resin prepolymer.

[0049] Furthermore, the solvent can be one of tetrahydrofuran, ethyl acetate, benzene, toluene, xylene, or an alkane solvent. Further, the amount of solvent used can be 1 to 6 times the volume of prepolymer A. The reaction aids can include a polymerization inhibitor and a polyurethane catalyst. Further, the polymerization inhibitor can be MEHQ; the polyurethane catalyst can be dibutyltin dilaurate (DBTDL).

[0050] The second step is the synthesis of chain extenders.

[0051] Diamine and two ketone-containing protective substances are added to a light-proof, sealed reactor and dissolved in a solvent. An appropriate amount of auxiliary agent is added, and the temperature is raised to a first temperature of 120–140°C, for example, 130°C, for 1–3 hours. The mixture is stirred and azeotropically removed to remove the generated water, thus protecting the amino groups at both ends of the diamine with ketone groups. The temperature is then raised to a second temperature of 150–170°C, for example, 160°C, and azeotropically continued for 7–9 hours. The solvent is removed by vacuum distillation at 120–140°C for 2–3 hours to obtain the chain extender. The chain extender is a slightly yellow, transparent liquid with a pungent odor at room temperature and needs to be stored frozen at -5°C, such as in a -5°C refrigerator.

[0052] The solvent can be one of tetrahydrofuran, benzene, toluene, xylene, or alkane solvents, and the amount of solvent used is 1 to 3 times the volume of the chain extender raw material; the auxiliary agent can be a catalyst, such as dibutyltin dilaurate or hydroquinone.

[0053] In this invention, the chain extender is a diamine chain extender in which both amino groups at both ends of the diamine are protected by ketone groups. The chain extender is obtained by reacting the amino groups at both ends of the diamine with the ketone groups in the two ketone-protected substances, using the diamine as the main raw material. This chain extender enhances the molecular weight and mechanical properties of the resin.

[0054] Furthermore, the diamine has the molecular formula NH2(R)NH2, where R is selected from C5-C6. 36 The straight chain of alkyl, alkylene, alkenyl, or alkenyl groups or the branched chain selected from cycloalkyl or cycloalkenyl groups.

[0055] The ketone-containing protective substance refers to a substance whose structural formula contains a ketone group (-CO-), which can protect the amino group in the diamine. For example, the ketone-containing protective substance can be a ketone compound, but is not limited to this, as long as it contains a ketone group that can react with the amino group in the diamine. Specifically, for example, it can be a ketone-containing substance such as methyl isobutyl ketone (MIBK). Due to the high reactivity of amino groups, they readily react with isocyanates or aldehyde groups in water molecules. In this invention, two of the above-mentioned ketone-containing protective substances are used to protect the amino groups at both ends of the diamine through their ketone groups, thereby improving the stability of the chain extender. When different components are stored together, the isocyanate group of the polyurethane prepolymer and the amino group of the chain extender will not undergo a cross-linking reaction prematurely; the curing and chain extension reaction between the amino group and the isocyanate group can be controlled so that it only occurs when the protecting group is removed. When a printing paste containing this chain extender is exposed to ultraviolet light to cure and form a printing intermediate, the intermediate contains the chain extender in cured form. Therefore, the cured intermediate exhibits better mechanical properties and a more easily handled thermosetting process. During thermosetting, the protecting groups of the amino groups in the cured chain extender cleave, exposing the amino groups. The amino groups then react with the isocyanate groups in the similarly exposed prepolymer to form a polyurethane resin copolymer with a three-dimensional network structure of linear thermoplastic polyurethane and crosslinked thermosetting polyurethane.

[0056] The two "protective substances with ketone groups" can be the same or different.

[0057] In a preferred embodiment, at least one "ketone-protected substance" contains a carbon-carbon double bond, meaning the protective substance contains both a ketone group and a carbon-carbon double bond. For example, it can be acetylacetone, 2-methyl-1-buten-3-one, 3-methyl-3-buten-2-one, 2-cyclohexenone, 2-(1-cyclohexenyl)cyclohexanone, etc. In this preferred embodiment, when the amino groups at both ends of the diamine are protected by ketone groups, the chain extender also contains a carbon-carbon double bond, allowing it to participate in the photocuring reaction. The inventors of this application have discovered that if the protective substance does not contain a carbon-carbon double bond, during the photocuring process, the prepolymer in the printing paste will have solidified, while the chain extender will still be in a liquid state (i.e., the printing intermediate contains a curing agent in an uncured form), which will greatly reduce the effectiveness of the chain extender. The presence of carbon-carbon double bonds allows the chain extender, prepolymer, and diluent to remain uniformly mixed during the photocuring process. Because the curing intermediate contains the chain extender in cured form, it facilitates the subsequent thermosetting and chain extension of the intermediate to form a cross-linked network structure. This network structure comprises the following components: (a) linear thermoplastic polyurethane, polyurea, and copolymers thereof; (b) cross-linked thermosetting polyurethane, polyurea, and copolymers thereof; and (c) UV-curable polyacrylate (linear or cross-linked). The network can be one or more of interpenetrating polymer networks (IPNs), semi-interpenetrating or pseudo-IPNs, and sequential IPNs.

[0058] For example, of the two "ketone-containing protecting substances", one ketone-containing protecting substance without carbon-carbon double bonds is methyl isobutyl ketone (MIBK), and the other ketone-containing protecting substance with carbon-carbon double bonds is acetylacetonate (APMA), and the diamine is decanediamine (molecular formula is C10). 10 H 24 Chain extender B was prepared by reacting N2 with the ketone groups of MIBK and APMA, respectively, to protect the amino groups. Simultaneously, the chain extender retains the carbon-carbon double bonds of APMA at its ends after the reaction, allowing it to participate in the photocuring reaction. This ensures that the chain extender is also cured during the curing of the prepolymer, improving its effectiveness. Furthermore, the molar ratio of MIBK, decanediamine, and APMA in the chain extender B raw material can be controlled as 1:(0.7~0.95):1.

[0059] The third step is the preparation of hydrolysis-resistant photosensitive resin slurry.

[0060] First, the initiator, anti-hydrolysis agent, and other additives are dissolved in the reactive diluent monomer and stirred in a planetary mixer at a first stirring speed for a certain period of time. Then, prepolymer A is added to the stirred mixture, and it is stirred again at the first stirring speed for the same time. Next, chain extender B is added to the mixture, and it is stirred at a higher second speed for the same time. By stirring and removing air bubbles, a uniformly mixed hydrolysis-resistant photosensitive resin slurry is obtained. The first and second stirring speeds can both be 1000-2500 r / min, with the second stirring speed being higher than the first, and the stirring time is 4-8 min. The hydrolysis-resistant photosensitive resin slurry prepared by this invention is a colorless or slightly yellow transparent liquid and has good fluidity at 50℃.

[0061] Furthermore, the anti-hydrolysis agent is carbodiimide or N,N'-bis(2,6-diisopropylphenyl)carbodiimide. By using this anti-hydrolysis agent, an anti-hydrolysis group is introduced, enhancing the resin's resistance to hydrolysis. Moreover, the curing reaction rate of this anti-hydrolysis group is not affected under ultraviolet light conditions, and it does not affect the mechanical properties of the resin.

[0062] The initiator can be a photoinitiator, specifically one or more of photoinitiator 819, photoinitiator TPO, photoinitiator 1173, photoinitiator 1490, and photoinitiator BP. The reactive diluent is a mono / bifunctional diluent monomer that forms a cross-linked oligomer, and can be one or more of lauryl methacrylate (LMA), glyceryl carbonate methacrylate (GCMA), polyethylene glycol (400) acrylate (PEG400DMA), and polyethylene glycol (600) acrylate (PEG600DMA). Other additives may include one or more of antioxidants, light stabilizers, and other trace additives. These other trace additives can be one or more of defoamers, anti-settling agents, thickeners, light absorbers, and light inhibitors commonly used in polyurethane resin synthesis.

[0063] In an optional embodiment, the hydrolysis-resistant photosensitive resin slurry can also be blended with other acrylic resins, such as polyether acrylate resin, in any proportion, and then subjected to UV curing and thermosetting molding.

[0064] The fourth step is to cure the mold with ultraviolet light.

[0065] The resin slurry is UV-cured using either casting or photopolymer 3D printing. The cured resin is a colorless or slightly yellow solid. Specifically, it is cured under UV light at a fixed wavelength (UV wavelength 200–410 nm) and intensity (UV light intensity 5–100 mW / cm²). 2 The polymer is obtained by UV curing through exposure time (0.1–30 s). Furthermore, the printer can print layers with a thickness of 10–30 μm, and the molding layer thickness can be 2 mm.

[0066] Step 5: Post-treatment with heat curing.

[0067] The resin, which is cured by ultraviolet light, is heated in an oven for a certain period of time while the humidity of the oven is maintained at a high level. This allows it to complete thermal curing under the conditions of heating, microwave radiation, and humidity, thereby obtaining a stable hydrolysis-resistant polymer, namely a hydrolysis-resistant photosensitive resin product. This resin has good mechanical properties, excellent toughness and hydrolysis resistance, and can maintain the stability of its molecular structure and function in water.

[0068] The oven humidity is 60-90%; the thermosetting temperature is 80-150℃; and the thermosetting time is 6-10 hours. After the hydrolysis-resistant photosensitive resin slurry completes the ultraviolet curing reaction, under the above-mentioned thermosetting reaction conditions, the blocked isocyanate groups in the resin undergo cleavage to expose them for further curing; simultaneously, the protecting groups protecting the amino groups also undergo cleavage, exposing the amino groups and reacting with the isocyanate groups to form a polyurethane resin copolymer with a three-dimensional network structure of linear thermoplastic polyurethane and cross-linked thermosetting polyurethane.

[0069] Furthermore, in some preferred embodiments of the present invention, the component dosages are further optimized based on the aforementioned component types. Specifically, the hydrolysis-resistant photosensitive resin, by weight, comprises: 40-80 parts of photosensitive resin prepolymer; 7.0-11 parts of chain extender; 0.5-1.5 parts of anti-hydrolysis agent; 18-29 parts of reactive diluent; 0.5-0.8 parts of initiator; and 1.0-1.5 parts of other additives. Based on the above formulation, the cured resin can maintain a 93% strain retention rate and a 90% stress retention rate after being immersed in deionized water at 60°C for 15 days.

[0070] Figure 5 The fabrication process of a hydrolysis-resistant deep-sea pressure sensor in one embodiment is illustrated schematically. (Reference) Figure 5 As shown, the process may include: using the resin prepolymer and resin chain extender of the present invention, adding active additives to prepare a photocurable molding resin slurry with high curing rate and high mechanical properties; adding an anti-hydrolysis agent to the photocurable molding resin slurry to improve hydrolysis resistance, thereby obtaining a hydrolysis-resistant photosensitive resin slurry; subjecting the hydrolysis-resistant photosensitive resin slurry to photocuring and thermal curing to obtain a hydrolysis-resistant photosensitive resin; and preparing a hydrolysis-resistant deep-sea pressure sensor by sculpting the shape of the hydrolysis-resistant photosensitive resin and applying surface adsorption conductivity.

[0071] The technical solution and its effects of the present invention will be further explained below with reference to specific embodiments:

[0072] Example 1

[0073] Synthesis of polyurethane prepolymer A.

[0074] 200 g of anhydrous polybutylene glycol (PTMG2000) and 47.8 g of isophorone diisocyanate (IPDI) were mixed and stirred under vacuum at 2000 rpm for 600 s using a planetary stirrer. The mixture was then added to a 500 mL three-necked flask equipped with a stirrer, nitrogen protection, and a thermometer. 0.021 g of dibutyltin dilaurate (DBTL) was added as a catalyst, and the reaction was carried out at 70 °C with stirring for 2.5 h.

[0075] After stirring for 2.5 h, 0.03 g of p-hydroxyanisole was added as a catalyst. Then, stirring continued for 10 h, and 43.0 g of 2-methyl-2-acrylate-2-[(1,1-dimethylethyl)amino]ethyl ester (TBAEMA) was added dropwise. The reaction yielded a transparent liquid product, prepolymer A. The infrared spectrum of prepolymer A is as follows: Figure 1 As shown.

[0076] The reaction formula for synthesizing prepolymer A is as follows:

[0077]

[0078] Where m is 100 to 300 and n is 5 to 30.

[0079] Example 2

[0080] Synthesis of chain extender B.

[0081] Raw materials: The two ketone-containing protecting substances are acetyl propylmethacrylate (APMA, structural formula shown in the reaction formula) and methyl isobutyl ketone (MIBK), and the diamine is a long-chain diamine, specifically decanediamine. APMA is obtained by esterification of 5-hydroxy-2-pentanone and 2-methacrylic acid under a phase transfer catalyst containing an amine salt at 120–180 °C under reflux for 6–12 hours.

[0082] The raw materials, acetylacetyl methacrylate, methyl isobutyl ketone, and decanediamine, were placed in a three-necked flask at a molar ratio of 1:1:0.8. The flask was protected from light and heated in an oil bath with stirring. First, the temperature was raised to 130°C to initiate a reflux reaction. After reacting for 2 hours, the temperature was raised to 160°C to continue the reflux reaction for 8 hours. After the reaction was complete, the mixture was purified by vacuum distillation at 130°C for 2-3 hours to remove water, excess methyl isobutyl ketone, and decanediamine, yielding a light yellow transparent liquid. The infrared spectrum of chain extender B is as follows: Figure 2 As shown.

[0083] The reaction formula for synthesizing chain extender B is as follows:

[0084]

[0085] Example 3

[0086] Resin slurries were prepared using the products of Examples 1 and 2, and curing tests were performed.

[0087] The weight fraction of each component is shown in Table 1.

[0088] Table 1: Weight fraction ratio of each component in Example 3

[0089]

[0090] Photoinitiator 819, antioxidant 1135, and light stabilizer 292 were dissolved in lauryl methacrylate (LMA) and polyethylene glycol (600) dimethacrylate (PEG(400)DMA), and stirred in a planetary mixer at 2000 r / min for 360 s.

[0091] Then, the prepolymer A from Example 1 was added to the solution, and the mixture was stirred again in a planetary mixer at 2000 r / min for 360 s to further mix and prepare a liquid, which was labeled as Liquid A.

[0092] Take half of liquid A and add chain extender B (the product of Example 2) to the solution. Then, stir again in a planetary mixer at 2000 rpm for 360 seconds, followed by stirring at 2200 rpm for 240 seconds. The resulting homogeneous mixture is labeled as liquid B.

[0093] Dumbbell-shaped test specimens were prepared according to the Type 2 specimen parameters specified in GB / T 528-2009, using either molding or DLP 3D printing. The photocuring time was set to 10 seconds, the UV wavelength to 405 nm, and the UV intensity to 10 mW / cm². 2 After curing, the specimens were cleaned with isopropanol and then heat-cured at 75% humidity and 120°C for 10 hours. The tensile properties of the cured specimens were tested using a universal testing machine (Instron-5943, Instron, USA) according to ASTM standard D412.

[0094] Example 4

[0095] The resin with added anti-hydrolysis agent was subjected to a curing test.

[0096] The weight fraction of each component is shown in Table 2.

[0097] Table 2: Weight fraction ratio of each component in Example 4

[0098]

[0099] Photoinitiator 819, antioxidant 1135, and light stabilizer 292 were dissolved in lauryl methacrylate (LMA) and polyethylene glycol (600) dimethacrylate (PEG(400)DMA), and stirred in a planetary mixer at 2000 r / min for 360 s.

[0100] Then, the prepolymer A from Example 1 was added to the solution, and the mixture was stirred again in a planetary mixer at 2000 r / min for 360 s to further mix and prepare a liquid, which was labeled as Liquid A.

[0101] Liquid A was divided into two portions, and the anti-hydrolysis agent carbodiimide and N,N'-bis(2,6-diisopropylphenyl)carbodiimide were added to each portion. The chain extender B, the product of Example 2, was added to each of the two solutions. The mixtures were then stirred again in a planetary mixer at 2000 rpm for 360 s, followed by stirring at 2200 rpm for 240 s. The resulting homogeneous mixtures were labeled Liquid C and Liquid D, respectively.

[0102] Dumbbell-shaped test specimens were prepared according to the Type 2 specimen parameters specified in GB / T 528-2009, using either molding or DLP 3D printing. The photocuring time was set to 10 seconds, the UV wavelength to 405 nm, and the UV intensity to 10 mW / cm². 2 After curing, the specimens were cleaned with isopropanol and then heat-cured at 75% humidity and 120°C for 10 hours. The tensile properties of the cured specimens were tested using a universal testing machine (Instron-5943, Instron, USA) according to ASTM standard D412.

[0103] Example 5

[0104] Hydrolysis-resistant resins blended with polyether acrylates were tested for curing.

[0105] The weight fraction of each component is shown in Table 3 below.

[0106] Table 3: Weight fraction ratio of each component in Example 5

[0107]

[0108] Take liquid B from Example 3.

[0109] Add the anti-hydrolysis agent according to the mass fractions in Table 3, then add the polyether acrylate, and stir in a planetary mixer at 2000 rpm for 360 s. Label them as liquid E, liquid F, and liquid G.

[0110] Dumbbell-shaped test specimens were prepared according to the Type 2 specimen parameters specified in GB / T 528-2009, using either molding or DLP 3D printing. The photocuring time was set to 10 seconds, the UV wavelength to 405 nm, and the UV intensity to 10 mW / cm². 2After curing, the specimens were cleaned with isopropanol and then heat-cured at 75% humidity and 120°C for 10 hours. The tensile properties of the cured specimens were tested using a universal testing machine (Instron-5943, Instron, USA) according to ASTM standard D412.

[0111] Figure 3 The infrared spectra of liquids ABCDEFG prepared in Examples 3-5 are compared. The vertical axis shows a decreasing trend in the absorption rate of infrared light by the AG sample from top to bottom.

[0112] from Figure 3 It can be seen that: 1175cm -1 and 1222cm -1 The characteristic absorption peak of C—O—C in polyether acrylate is 2868 cm⁻¹. -1 -2960cm -1 The broad absorption band of —CH2— in liquids, 1175 cm⁻¹ after introducing new ether groups into the blended polyether acrylate YC2509, is observed. -1 The intensity of the C—O—C absorption peak at 3330 cm⁻¹ increases slightly. -1 The area at 1732 cm⁻¹ shows a strong amino absorption peak, indicating the formation of associated hydrogen bonds between amino groups. With increasing YC₂₅O₉ content, the absorption peak at 1732 cm⁻¹... -1 The position represents an increase in peak intensity for the free carbonyl group –C=O, while 1700 cm⁻¹ represents an increase in peak intensity. -1 The carbonyl peak at the junction weakens. This indicates that with the incorporation of YC2509, the number of hydrogen bonds formed between the hard and soft segments increases. These hydrogen bonds cause the hard segments to become mixed with the soft segments, affecting the microphase separation of PUA. Consequently, the ordered nature of the hard segments in the prepared PUA resin is weakened, the crystallization of the soft segments is hindered, and the tensile strength decreases. The mechanical property test results also confirm this.

[0113] Figure 4 The tensile properties of specimens (labeled as specimens abcdefg, respectively) cured from liquid ABCDEFG are shown. Figure 4 It can be seen that the fracture stress and strain of the resin sample after curing with the addition of chain extender B are significantly improved. There are certain differences in the mechanical properties of the resin under different formulations. The tensile strength of the iForm86202 blend sample efg decreases due to the weakening of resin order.

[0114] By comparing liquid samples b and a, it can be seen that chain extender B has a significant impact on the tensile properties of the cured resin, greatly increasing the molecular weight and crosslinking degree of the cured resin. Therefore, the use of the chain extender of this invention improves the mechanical properties of the resin.

[0115] This application enhances the resin's resistance to hydrolysis by adding an anti-hydrolysis agent. Comparing samples c / d with b shows that the introduction of the anti-hydrolysis agent has little effect on the resin's mechanical properties. The anti-hydrolysis agent has high dispersibility in liquid resin, making it difficult to observe the characteristic peaks of carbodiimide in infrared spectroscopy. The mechanical properties of samples b, c, and d demonstrate that trace amounts of carbodiimide-based anti-hydrolysis agents have little impact on the mechanical properties of the resin samples.

[0116] The description of this invention is given for illustrative and descriptive purposes only and is not intended to be exhaustive or to limit the invention to the forms disclosed. Many modifications and variations will be apparent to those skilled in the art. The embodiments were chosen and described in order to better illustrate the principles and practical application of the invention and to enable those skilled in the art to understand the invention and to design various embodiments with various modifications suitable for a particular purpose.

Claims

1. A hydrolysis-resistant photosensitive resin for use in deep-sea pressure sensors, characterized in that, The hydrolysis-resistant photosensitive resin is shaped with a hollow microstructure to balance the internal and external pressure of the sensor by introducing seawater; the deep-sea pressure sensor is formed by adsorbing conductive material on the surface of the hydrolysis-resistant photosensitive resin with the hollow microstructure. The hydrolysis-resistant photosensitive resin, by weight, comprises the following raw materials: 40-80 parts of photosensitive resin prepolymer, 7.0-11 parts of chain extender, 0.5-1.5 parts of anti-hydrolysis agent, 18-29 parts of reactive diluent, 0.5-0.8 parts of initiator, and 1.0-1.5 parts of other additives. It is a polyurethane resin copolymer with a three-dimensional network structure of linear thermoplastic polyurethane and cross-linked thermosetting polyurethane, prepared by mixing the raw materials to obtain a photosensitive resin slurry and then curing it with ultraviolet light and humid heat. The photosensitive resin prepolymer is obtained by reacting isocyanate with oligomeric polyol to generate polyurethane, followed by introducing groups capable of UV curing; the isocyanate is one or more selected from hexamethylene diisocyanate, isophorone diisocyanate, toluene diisocyanate, naphthalene diisocyanate, and trimethylhexamethylene diisocyanate; the oligomeric polyol is one or more selected from anhydrous polybutanediol, polycaprolactone polyol, and polypropylene glycol. The chain extender is prepared by reacting the amino groups at both ends of the diamine with the ketone groups in the two protecting substances, using diamine and two ketone-containing protecting substances as raw materials. At least one of the two ketone-containing protecting substances contains a carbon-carbon double bond, and the ketone-containing substance containing the carbon-carbon double bond is one of acetylacetone, 2-methyl-1-buten-3-one, 3-methyl-3-buten-2-one, 2-cyclohexenone, and 2-(1-cyclohexenyl)cyclohexanone. The anti-hydrolysis agent is carbodiimide or N,N'-bis(2,6-diisopropylphenyl)carbodiimide; The reactive diluent is one or more of lauryl methacrylate, glyceryl carbonate methacrylate, and polyethylene glycol diacrylate.

2. The hydrolysis-resistant photosensitive resin for deep-sea pressure sensors according to claim 1, characterized in that, The molar ratio of the isocyanate to the oligomeric polyol is 1:2 to 2:1; The isocyanate has a molecular weight of 100 to 300. The oligomeric polyol has a molecular weight of 500 to 2000; The UV-curable groups are introduced by adding acrylate.

3. The hydrolysis-resistant photosensitive resin for deep-sea pressure sensors according to claim 1, characterized in that, The initiator is one or more of TPO, 819, 1173, 1490, and BP; The other additives include one or more of antioxidants, light stabilizers, and trace additives; wherein the trace additives include one or more of defoamers, anti-settling agents, thickeners, light absorbers, and light inhibitors.

4. A process for the preparation of a hydrolysis resistant photosensitive resin for deep-sea pressure sensors according to any one of claims 1 to 3, characterized in that, Includes the following steps: Step S1: Polyurethane is generated by reacting isocyanate and oligomeric polyol as raw materials, and UV-curable groups are introduced into the polyurethane to generate photosensitive resin prepolymer. Step S2: Using diamine and two ketone-containing protective substances as raw materials, the chain extender is prepared by reacting the amino groups at both ends of the diamine with the ketone groups in the two ketone-containing protective substances. Step S3: Mix the anti-hydrolysis agent, reactive diluent, initiator and other additives, stir to dissolve, add the photosensitive resin prepolymer and stir to react, add the chain extender and continue stirring to react, to obtain photosensitive resin slurry; Step S4: The photosensitive resin slurry is cured and molded under ultraviolet light; Step S5: Perform thermosetting treatment on the photocured resin to obtain a hydrolysis-resistant photosensitive resin.

5. The method for preparing the hydrolysis-resistant photosensitive resin for deep-sea pressure sensors according to claim 4, characterized in that, Step S2 includes: dissolving the diamine and two ketone-containing protecting substances in a solvent, heating to a first temperature, and stirring the reaction; then heating to a second temperature and continuing to stir the reaction; after the reaction is completed, removing the solvent by vacuum distillation to obtain the chain extender; The first temperature is 120–140℃, and the reaction time is 1–3 h; the second temperature is 150℃–170℃, and the reaction time is 7–9 h; the vacuum distillation temperature is 120–140℃, and the vacuum distillation time is 2–3 h.

6. The method for preparing the hydrolysis-resistant photosensitive resin for deep-sea pressure sensors according to claim 4, characterized in that, In step S5, the light-cured resin is placed in an oven for heat curing post-treatment. The oven has a humidity of 60-90%, a heat curing temperature of 80-150℃, and a heat curing time of 6-10 hours.

7. The method for preparing the hydrolysis-resistant photosensitive resin for deep-sea pressure sensors according to claim 4, characterized in that, In step S1, the reaction temperature is 30℃~80℃; In step S3, the stirring speed is 1000-2500 r / min and the stirring reaction time is 4-8 min; and the stirring speed after adding the chain extender is higher than the stirring speed after adding the photosensitive resin prepolymer. In step S4, the ultraviolet light wavelength is 200–410 nm; the ultraviolet light intensity is 5–100 mW / cm². 2 Exposure time is 0.1 to 30 seconds.

8. The method for preparing the hydrolysis-resistant photosensitive resin for deep-sea pressure sensors according to claim 4, characterized in that, Step S1 also includes: a step of preserving the photosensitive resin prepolymer; wherein the preservation conditions are: preservation in a constant temperature oven at 40°C in the dark. Step S2 also includes the step of preserving the chain extender; wherein the preservation conditions are: frozen preservation at -5°C.

9. The method for preparing the hydrolysis-resistant photosensitive resin for deep-sea pressure sensors according to claim 4, characterized in that, Before step S4, the method further includes: mixing polyether acrylate resin into the photosensitive resin slurry in any proportion.

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