A dirt-resistant and chemical detergent-resistant microstructure functional film and a method for preparing the same

Abstract

This invention discloses a microstructured functional membrane resistant to dirt and chemical detergents, and its preparation method, specifically relating to the field of thermoplastic polyurethane membrane materials. The raw materials, by weight, include: 12-25 parts of amino-functionalized silicon-based block prepolymer, 40-60 parts of oligomeric diol, 22-38 parts of aliphatic diisocyanate, 4-12 parts of heterocyclic modified chain extender, 2.5-7 parts of composite functional additives, and 0.01-0.06 parts of composite catalyst; wherein the composite functional additives include 1-3 parts of anti-aging agent and 0.2-0.8 parts of anti-hydrolysis stabilizer. The above functional membrane possesses resistance to dirt and acid / alkali detergent erosion.

Description

Technical Field

[0001] This invention relates to the field of thermoplastic polyurethane (TPU) membrane materials, and more particularly to a microstructured functional membrane that is resistant to dirt and chemical detergents and its preparation method. This functional membrane is suitable for drag reduction and anti-icing scenarios that require frequent cleaning and long-term exposure to outdoor environments. Background Technology

[0002] TPU membranes are widely used in outdoor applications due to their excellent elasticity, abrasion resistance, and weather resistance. However, in outdoor use, the membrane material is easily contaminated with dust and oil, requiring frequent cleaning with acidic or alkaline detergents. The ester and urethane bonds in the conventional TPU molecular structure are easily hydrolyzed in acidic or alkaline media, leading to a decrease in mechanical properties; at the same time, its strong polarity also makes it easy for stains to be absorbed and penetrate, resulting in poor stain resistance. Existing technologies mostly use siloxane block copolymerization modification to improve stain resistance by utilizing its low polarity, but single-silicone modification has limited improvement on the performance of acid and alkali detergent resistance, making it difficult to meet the needs of complex outdoor environments. Summary of the Invention

[0003] The main objective of this application is to provide a microstructured functional membrane that is resistant to dirt and chemical detergents and its preparation method, aiming to solve the problem that existing TPU membranes are difficult to have both dirt resistance and acid and alkali detergent resistance.

[0004] To achieve the above objectives, this application provides a microstructured functional membrane resistant to dirt and chemical detergents. The raw materials, by weight, include: 12-25 parts of amino-functionalized silicon-based block prepolymer, 40-60 parts of oligomeric diol, 22-38 parts of aliphatic diisocyanate, 4-12 parts of heterocyclic modified chain extender, 2.5-7 parts of composite functional additives, and 0.01-0.06 parts of composite catalyst; wherein the composite functional additives include 1-3 parts of anti-aging agent and 0.2-0.8 parts of anti-hydrolysis stabilizer; the functional membrane has a micron-scale uneven composite structure; the amino-functionalized silicon-based block prepolymer has a molecular weight of 1200-2800, and its general formula is: OCN-R1-NH-CO-NH-(X)-Si(R2)2-O-[Si(R3)(R4)-O] n -O-CO-NH-R1-NCO, where R1 is an aliphatic diisocyanate residue, R2 is -OH, -OCH3, -OC2H5 or -CH3, R3 and R4 are both methyl or phenyl, n is 5~200, and X is the linking group of the aminosilane coupling agent.

[0005] Optionally, the raw materials include, by weight, 18-22 parts of amino-functionalized silicon-based block prepolymer, 48-55 parts of oligomeric diol, 28-32 parts of aliphatic diisocyanate, 6-9 parts of heterocyclic modified chain extender, 4-6 parts of composite functional additive, and 0.02-0.04 parts of composite catalyst.

[0006] Optionally, the amino-functionalized silicon-based block prepolymer is obtained by condensation reaction of a hydroxyl-terminated silicon-based polymer with an aminosilane coupling agent to obtain an amino-functionalized silicon-based polymer, and by nucleophilic addition reaction of the amino-functionalized silicon-based polymer with an aliphatic diisocyanate; the molar ratio of the hydroxyl-terminated silicon-based polymer to the aminosilane coupling agent is 1:1.05~1.15, and the molar ratio of the amino-functionalized silicon-based polymer to the aliphatic diisocyanate is 1:2.2~2.5.

[0007] Optionally, the hydroxyl-terminated silane polymer is at least one of polydimethylsiloxane diol and polymethylphenylsiloxane diol; the aminosilane coupling agent is at least one of 3-aminopropyltriethoxysilane and N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane.

[0008] Optionally, the oligomeric diol has a molecular weight of 1800-3500, and is a compound of polytetrahydrofuran ether diol and polycarbonate diol in a weight ratio of 1.3-3:1; the aliphatic diisocyanate is hexamethylene diisocyanate and / or isophorone diisocyanate; the heterocyclic modified chain extender is a compound of nitrogen-containing heterocyclic diol and aliphatic diol in a weight ratio of 1.5-5:1.

[0009] Optionally, the nitrogen-containing heterocyclic diol is at least one of 2-methylpiperazine-1,4-diethanol and piperidine-3,5-diethanol; the aliphatic diol is at least one of 1,4-butanediol (BDO) and 1,6-hexanediol (HDO).

[0010] Optionally, the composite catalyst is a mixture of organotin catalyst, tertiary amine catalyst and organobismuth catalyst; the anti-aging agent is at least one of hindered phenolic anti-aging agent and phosphite anti-aging agent; the anti-hydrolysis stabilizer is a mixture of organic amine salt anti-hydrolysis agent and metal ion chelating agent in a weight ratio of 2 to 3:1.

[0011] Optionally, the organic amine salt anti-hydrolysis agent is a condensation product of caprolactam and diethylenetriamine; The metal ion chelating agent is at least one of disodium ethylenediaminetetraacetate and trisodium citrate.

[0012] To achieve the above objectives, this application also provides a method for preparing a microstructured functional membrane resistant to dirt and chemical detergents, comprising: adding an amino-functionalized silicon-based block prepolymer and a portion of a composite catalyst to an oligomeric diol, reacting at 75-85°C for 1.5-2 hours to obtain a silicon-based block polyol intermediate with urethane bonds; adding an aliphatic diisocyanate to the silicon-based block polyol intermediate with urethane bonds, reacting at 90-100°C until the urethane bond content in the reaction system is 8%-12%, and adding a heterocyclic chain extender, a composite functional agent, and the remaining composite catalyst, heating to 105-115°C to obtain a functionalized silicon-based modified TPU melt; calendering and microstructure imprinting of the TPU melt in an integrated molding process, followed by annealing to obtain a functional membrane with a micron-scale concave-convex composite structure.

[0013] Optionally, the TPU melt is integrally formed by calendering and microstructure imprinting, including: extruding the TPU melt into a casting and imprinting machine at 170~190℃ for calendering and microstructure imprinting to obtain a functional film with a micron-level concave-convex composite structure; wherein the calendering roller temperature is 90~110℃, and the pressure is held at 3~8MPa for 10~30s; the annealing temperature is 60~70℃, and the time is 30~50min.

[0014] Compared with the prior art, the beneficial effects of this application are as follows: The present invention relates to a microstructured functional membrane resistant to dirt and chemical detergents. It utilizes amino-functionalized silicon-based block copolymers, aliphatic diisocyanates, and oligomeric diols as raw materials for block copolymerization. The amino-functionalized silicon-based block copolymers introduce silicon segments and reactive amino sites into the TPU backbone. These silicon segments accumulate on the TPU backbone surface, forming a low surface energy anti-fouling layer that reduces dirt adhesion at its source, maintaining the cleanliness of the micron-level uneven structure and significantly improving dirt resistance. Simultaneously, the reactive amino sites retained on the molecular chain preferentially neutralize penetrating acidic media on the material surface, forming the first acidic protective barrier. The introduction of an anti-hydrolysis stabilizer into the copolymer system ensures uniform dispersion within the matrix, achieving comprehensive hydrolysis protection from the surface to the interior, significantly extending the membrane's lifespan under frequent cleaning and humid / heated environments. The intrinsic alkali-resistant structure of the oligomeric diol soft segments and heterocyclic chain extenders enhances the intrinsic stability of the polymer matrix in alkaline environments, endowing the material with excellent resistance to alkaline detergent erosion. Detailed Implementation

[0015] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions in this application are described clearly and completely below. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0016] The first embodiment of the present invention provides a microstructured functional membrane resistant to dirt and chemical detergents, characterized in that its raw materials, by weight, comprise: 12-25 parts of amino-functionalized silicon-based block prepolymer, 40-60 parts of oligomeric diol, 22-38 parts of aliphatic diisocyanate, 4-12 parts of heterocyclic modified chain extender, 2.5-7 parts of composite functional additives, and 0.01-0.06 parts of composite catalyst; wherein the amino-functionalized silicon-based block prepolymer has a molecular weight of 1200-2800 and its general formula is: OCN-R1-NH-CO-NH-(X)-Si(R2)2-O-[Si(R3)(R4)-O] n -O-CO-NH-R1-NCO, where R1 is an aliphatic diisocyanate residue, R2 is -OH, -OCH3, -OC2H5 or -CH3, R3 and R4 are both methyl or phenyl, n is 5~200, and X is the linking group of the aminosilane coupling agent.

[0017] Because the microstructure is a biomimetic structure, such as a micron-level concave-convex composite structure, it is used to achieve drag reduction and anti-icing. Compared to TPU films without microstructures, these films are more prone to becoming breeding grounds for dirt and grime, thus requiring frequent cleaning. The microstructured functional film in this embodiment has antifouling and cleaning agent resistance, reducing damage to the film from dirt and cleaning agents. Specifically, block copolymerization is carried out using amino-functionalized silicon-based block prepolymers, aliphatic diisocyanates, and oligomeric diols as raw materials. The amino-functionalized silicon-based block prepolymers introduce silicon segments and reactive amino sites into the TPU backbone. The silicon segments accumulate on the TPU backbone surface, forming a low surface energy antifouling layer, reducing stain adhesion at the source and keeping the micron-level uneven structure clean, significantly improving its dirt resistance. Simultaneously, the reactive amino sites retained on the molecular chain preferentially neutralize penetrating acidic media on the material surface, forming the first acidic protective barrier. An anti-hydrolysis stabilizer is introduced into the copolymer system, ensuring uniform dispersion in the matrix, achieving comprehensive hydrolysis protection from the surface to the interior, significantly extending the service life of the membrane material under frequent cleaning and humid / hot environments. The intrinsic alkali-resistant structure of the oligomeric diol soft segments and heterocyclic chain extenders enhances the intrinsic stability of the polymer matrix in alkaline environments, giving the material excellent resistance to alkaline detergent erosion. The modified TPU was then processed using a casting and imprinting process to produce a functional film with a microstructured surface. This film exhibits excellent resistance to dirt and chemical detergents, making it suitable for a wide range of applications in outdoor scenarios such as drag reduction and anti-icing.

[0018] Furthermore, the raw materials, by weight, include: 18-22 parts of amino-functionalized silicon-based block prepolymer, 48-55 parts of oligomeric diol, 28-32 parts of aliphatic diisocyanate, 6-9 parts of heterocyclic modified chain extender, 4-6 parts of composite functional additives, and 0.02-0.04 parts of composite catalyst. The amino-functionalized silicon-based block prepolymer is obtained by a condensation reaction between a hydroxyl-terminated silicon-based polymer and an aminosilane coupling agent, followed by a nucleophilic addition reaction between the amino-functionalized silicon-based polymer and the aliphatic diisocyanate. The molar ratio of the hydroxyl-terminated silicon-based polymer to the aminosilane coupling agent is 1:1.05-1.15, and the molar ratio of the amino-functionalized silicon-based polymer to the aliphatic diisocyanate is 1:2.2-2.5.

[0019] Specifically, the preparation method of amino-functionalized silicon-based block prepolymer is as follows: The hydroxyl-terminated silane polymer was dehydrated at 85-95℃ and vacuum degree ≤-0.09MPa for 1-1.5 h. After cooling to 55-65℃, an aminosilane coupling agent was added, and the mixture was kept at this temperature for 1.5-2.5 h to carry out a condensation reaction. The silanol and alkoxy groups formed a siloxane bond and the small molecule alcohol was removed, thereby introducing an amino group to obtain an amino-functionalized silane polymer. The polymer was then cooled to 45-55℃, and an aliphatic diisocyanate was added. After keeping the mixture at this temperature for 2-3 h, a nucleophilic addition reaction was carried out. The amino group and the residual hydroxyl group formed a urea bond and a urethane bond with the isocyanate group to obtain an amino-functionalized silane block prepolymer with isocyanate-terminated groups.

[0020] For example, the hydroxyl-terminated silicone polymer is at least one of polydimethylsiloxane diol and polymethylphenylsiloxane diol; the aminosilane coupling agent is at least one of 3-aminopropyltriethoxysilane and N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane. The oligomeric diol has a molecular weight of 1800-3500 and is a compound of polytetrahydrofuran ether diol (PTMG) and polycarbonate diol (PCDL) in a weight ratio of 1.3-3:1; wherein, PTMG imparts excellent hydrolysis resistance to the material, while PCDL, due to its carbonate bond structure, possesses good alkali resistance, and the compound of the two can balance the chemical resistance of the material. The aliphatic diisocyanate is hexamethylene diisocyanate (HDI) and / or isophorone diisocyanate (IPDI); the heterocyclic modified chain extender is a compound of nitrogen-containing heterocyclic diol and aliphatic diol in a weight ratio of 1.5-5:1.

[0021] Furthermore, the nitrogen-containing heterocyclic diol is at least one of 2-methylpiperazine-1,4-diethanol and piperidine-3,5-diethanol; the aliphatic diol is at least one of 1,4-butanediol (BDO) and 1,6-hexanediol (HDO). The nitrogen atom in the nitrogen-containing heterocyclic structure has a lone pair of electrons, which can form intermolecular hydrogen bonds with the hydrogen atom at the amino site (-NH2). This hydrogen bond network reduces the electron cloud density of the nitrogen atom in the heterocyclic structure, weakening the resistance to alkaline media (such as OH-). - On the one hand, the amino group exhibits a nucleophilic tendency to attack heterocycles; on the other hand, the amino group is "anchored" to the vicinity of the heterocycle through hydrogen bonds, making it less prone to deprotonation and deactivation in alkaline environments. Together, these two factors enhance the structural stability of the polymer chain under acidic and alkaline conditions.

[0022] The anti-aging agent is a hindered phenolic anti-aging agent and / or a phosphite anti-aging agent; further, the anti-aging agent is at least one of anti-aging agent 1010, anti-aging agent 1076, and anti-aging agent 168. The composite catalyst is a mixture of organotin catalysts, tertiary amine catalysts, and organobismuth catalysts, which optimizes the reaction activity and selectivity through the mixture; specifically, it is a mixture of dibutyltin dilaurate (DBTDL), triethylamine (TEA), and bismuth isooctanoate in a weight ratio of 2:3:5. The anti-hydrolysis stabilizer is a mixture of an organic amine salt anti-hydrolysis agent and a metal ion chelating agent in a weight ratio of 2~3:1; wherein, the organic amine salt anti-hydrolysis agent can capture and neutralize the acidic end groups (carboxyl groups) generated during the hydrolysis of the material, blocking the autocatalytic hydrolysis cycle; the metal ion chelating agent passivates the catalytic activity of residual metal ions in the system through chelation (such as catalyst residue, environmental introduction, etc.), eliminating their catalytic effect on the hydrolysis reaction. The two work together to achieve comprehensive hydrolytic protection from the surface to the interior, significantly improving the service life of the membrane material in frequent cleaning and humid and hot environments.

[0023] For example, the organic amine salt anti-hydrolysis agent is a condensation product of caprolactam and diethylenetriamine (specifically, anti-hydrolysis agent HY-109); the metal ion chelating agent is at least one of disodium ethylenediaminetetraacetate and trisodium citrate.

[0024] The second embodiment of the present invention provides a method for preparing a microstructured functional membrane that is resistant to dirt and chemical detergents, specifically including the following steps: Step S1: Add amino-functionalized silicon-based block prepolymer and composite catalyst to oligomeric diol, and react at 75~85℃ for 1.5~2h to obtain silicon-based block polyol intermediate with urethane bonds; Before the reaction, the oligomeric diol is dehydrated at 90-100°C and under a vacuum of ≤-0.09 MPa for 1.5-2.5 hours and then cooled for later use. The heterocyclic chain extender and composite functional additives are mixed and dried until the moisture content is ≤0.05%. Before adding the amino-functionalized silicon-based block prepolymer and the composite catalyst, the oligomeric diol is first heated to 75-85°C. In this embodiment, the composite catalyst is divided into two parts. The first part is added in step S1, and its content is 65%-75% of its total weight.

[0025] Step S2: Add aliphatic diisocyanate to a silicon-based block polyol intermediate with urethane bonds, and react at 90~100℃ until the urethane bond content is 8%~12%. Then add heterocyclic chain extender, composite functional additive and second part composite catalyst, and heat to 105~115℃ to obtain functionalized silicon-based modified TPU melt. In this embodiment, the composite catalyst is added in two stages. The first stage, in step S1, involves adding the catalyst to synthesize the silicon-based block polyol intermediate at low temperature. The second stage, in step S2, involves adding the catalyst after heating to efficiently complete chain extension and molecular weight increase, while controlling side reactions and viscosity increases. Adding the catalyst all at once in the first stage would easily lead to uncontrolled reaction in the first stage, while the reaction in the second stage would be incomplete.

[0026] Step S3: The TPU melt is calendered and microstructure imprinted in an integrated molding process, and then annealed to obtain a functional film with a micron-level concave-convex composite structure. Specifically, TPU melt is extruded into a casting and imprinting machine at 170~190℃ for calendering and microstructure imprinting to obtain a functional film with a micron-level concave-convex composite structure; wherein, the calendering roller temperature is 90~110℃, and the pressure is held at 3~8MPa for 10~30s; the annealing process temperature is 60~70℃, and the time is 30~50min.

[0027] In this embodiment, firstly, the isocyanate group (-NCO) at the end of the amino-functionalized silicon-based block prepolymer molecule reacts with the hydroxyl group (-OH) at the end of the oligomeric diol molecule to generate a urethane bond, thereby chemically inserting the siloxane segment into the oligomeric diol backbone to obtain a silicon-based grafted polyol intermediate. Next, the aliphatic diisocyanate undergoes a nucleophilic addition reaction with the previously generated silicon-based block polyol intermediate and the residual hydroxyl group in the system, further forming urethane bonds and causing initial chain growth. Subsequently, the heterocyclic chain extender and the aliphatic diisocyanate continue to react until the system viscosity reaches 15000~25000 mPa·s (25°C). At this viscosity, the TPU melt exhibits moderate fluidity and melt strength; too viscous, and the microstructure is insufficiently filled; too viscous, and the microstructure is prone to collapse.

[0028] Example 1 The functional membrane is prepared from the following raw materials in parts by weight: 20 parts of amino-functionalized silicon-based block prepolymer, 50 parts of oligomeric diol (PTMG and PCDL in a weight ratio of 5:2, number average molecular weight 2500), 30 parts of HDI, 8 parts of heterocyclic modified chain extender (2-methylpiperazine-1,4-diethanol and 1,4-butanediol in a weight ratio of 4:1), 4 parts of composite functional additives (including 3 parts of anti-aging agent and 1.0 part of anti-hydrolysis stabilizer (anti-hydrolysis agent HY-109 and trisodium citrate in a weight ratio of 2.5:1), and 0.03 parts of composite catalyst (dibutyltin dilaurate, triethylamine, and bismuth isooctanoate in a weight ratio of 2:3:5). In step S10, polydimethylsiloxane diol is dehydrated at 90°C and vacuum degree -0.095MPa for 1.2h. After cooling to 60°C, 3-aminopropyltriethoxysilane is added to it according to the mass molar ratio of hydroxyl-terminated silicone polymer to aminosilane coupling agent of 1:1.1. The reaction is kept at this temperature for 2h to obtain amino-functionalized silicone polymer. Then, it is cooled to 50°C, and HDI (molar ratio of DI to amino-functionalized silicone polymer of 1:2.3) is added. The reaction is kept at this temperature for 2.5h to obtain amino-functionalized silicone block prepolymer with isocyanate-terminated end-capping and a number average molecular weight of 2000.

[0029] Step S20: Place the oligomeric diol in a vacuum drying oven and dehydrate it for 2 hours at 95°C and a vacuum of -0.095 MPa. After dehydration, allow it to cool naturally to room temperature for later use. Place the heterocyclic chain extender and composite functional additives in a mixing dryer, mix them evenly, and then dry them until the moisture content is ≤0.05%. Step S30: Add the oligomeric diol to the reactor, turn on the stirring device, raise the reactor temperature to 80°C, add the amino-functionalized silicon-based block prepolymer, and then add 70% (i.e., 0.021 parts) of the total amount of composite catalyst. Keep the temperature constant at 80°C, stir and keep the reaction for 1.8 hours to obtain the silicon-based grafted polyol intermediate. Step S40: Add HDI to the reactor, raise the reactor temperature to 95°C, maintain constant temperature and stir, periodically sample and test the -NCO content of the system until the -NCO content of the system reaches 10%; then add the mixed and dried heterocyclic chain extender, composite functional additives, and the remaining 30% of composite catalyst (i.e., 0.009 parts), raise the reactor temperature to 110°C, and continue stirring the reaction, continuously testing the system viscosity until the system viscosity reaches 20000 mPa·s (25°C), then stop the reaction to obtain functionalized silicon-based modified TPU melt; Step S50: TPU melt is extruded through a screw extruder, with the temperature of each section of the screw controlled at 180℃. The extruded melt is then fed into a casting and imprinting machine for integrated calendering and microstructure imprinting. The temperature of the calendering roller is controlled at 100℃, and the imprinting mold adopts a micron-level concave-convex composite structure template (convex part height 5μm, spacing 10μm, concave part depth 3μm, spacing 10μm). The mold is held under 5MPa pressure for 20s to form a film material with a micron-level concave-convex composite structure on the surface. Step S60: The membrane material is sent into an annealing furnace and annealed at 65°C for 40 minutes. After annealing, it is taken out and allowed to cool naturally to room temperature. Then it is wound up by a winding machine to obtain a microstructured functional membrane that is resistant to dirt and chemical detergents.

[0030] Example 2 The difference from Example 1 is that the amino-functionalized silicon-based block prepolymer is 10 parts. The specific raw material composition is as follows: 10 parts amino-functionalized silicon-based block prepolymer, 50 parts oligomeric diol (PTMG and PCDL weight ratio 5:2, number average molecular weight 2500), 30 parts HDI, 8 parts heterocyclic modified chain extender (2-methylpiperazine-1,4-diethanol and 1,4-butanediol weight ratio 4:1), 4 parts composite functional additives (including 3 parts anti-aging agent, 1.0 part anti-hydrolysis stabilizer (anti-hydrolysis agent HY-109 and trisodium citrate compounded in a weight ratio of 2.5:1), and 0.03 parts composite catalyst (dibutyltin dilaurate, triethylamine, and bismuth isooctanoate compounded in a weight ratio of 2:3:5).

[0031] Example 3 The difference from Example 1 is that the hydrolysis stabilizer is 0.7 parts, and an organic amine salt hydrolysis stabilizer is used. The specific raw material composition is as follows: 20 parts of amino-functionalized silicon-based block prepolymer, 50 parts of oligomeric diol (PTMG and PCDL weight ratio 5:2, number average molecular weight 2500), 30 parts of HDI, 8 parts of heterocyclic modified chain extender (2-methylpiperazine-1,4-diethanol and 1,4-butanediol weight ratio 4:1), and 4 parts of composite functional additives (including 3 parts of anti-aging agent, 0.7 parts of organic amine salt hydrolysis stabilizer, and 0.03 parts of composite catalyst (dibutyltin dilaurate, triethylamine, and bismuth isooctanoate compounded in a weight ratio of 2:3:5).

[0032] Comparative Example 1 The difference from Example 1 is that no amino-functionalized silicon-based block prepolymer is added, and the oligomeric diol is 70 parts. The specific raw material composition is as follows: 70 parts oligomeric diol (PTMG and PCDL weight ratio 5:2, number average molecular weight 2500), 30 parts HDI, 8 parts heterocyclic modified chain extender (2-methylpiperazine-1,4-diethanol and 1,4-butanediol weight ratio 4:1), 4 parts composite functional additives (including 3 parts anti-aging agent, 1.0 part anti-hydrolysis stabilizer (anti-hydrolysis agent HY-109 and trisodium citrate compounded in a weight ratio of 2.5:1), and 0.03 parts composite catalyst (dibutyltin dilaurate, triethylamine, and bismuth isooctanoate compounded in a weight ratio of 2:3:5).

[0033] Comparative Example 2 The difference from Example 1 is that 3 parts of the composite functional additive are used, and an anti-aging agent is employed. The specific raw material composition is as follows: 20 parts of amino-functionalized silicon-based block prepolymer, 50 parts of oligomeric diol (PTMG and PCDL weight ratio 5:2, number average molecular weight 2500), 30 parts of HDI, 8 parts of heterocyclic modified chain extender (2-methylpiperazine-1,4-diethanol and 1,4-butanediol weight ratio 4:1), 3 parts of anti-aging agent, and 0.03 parts of composite catalyst (dibutyltin dilaurate, triethylamine, and bismuth isooctanoate compounded in a weight ratio of 2:3:5).

[0034] Comparative Example 3 The difference from Example 1 is that the oligomeric diol used is PTMG, and the heterocyclic chain extender used is BDO. The specific raw material composition is as follows: 20 parts of amino-functionalized silicon-based block prepolymer, 50 parts of PTMG (number average molecular weight 2500), 30 parts of HDI, 8 parts of BDO, 4 parts of composite functional additives (including 3 parts of anti-aging agent, 1.0 part of anti-hydrolysis stabilizer (anti-hydrolysis agent HY-109 and trisodium citrate are compounded in a weight ratio of 2.5:1), and 0.03 parts of composite catalyst (dibutyltin dilaurate, triethylamine, and bismuth isooctanoate are compounded in a weight ratio of 2:3:5).

[0035] The present invention tested the functional membranes obtained in Examples 1-3 and Comparative Examples 1-3. The test items and methods are as follows: 1. Surface contact angle: The contact angle between the membrane surface and deionized water is measured using a contact angle meter. The larger the contact angle, the better the surface hydrophobicity and the better the dirt resistance (contact angle ≥100° indicates good hydrophobicity).

[0036] 2. Stain Resistance: In accordance with GB / T 30693-2014 "Determination of Stain Resistance of Plastic Films and Sheets", ink was used as the stain. The stain was evenly applied to the surface of the film material and left to stand for 24 hours. Then, it was rinsed with water (no detergent needed). The amount of stain residue on the surface of the film material was observed and divided into 5 levels (Level 1: Stain completely remains and cannot be rinsed; Level 2: Most stain remains and there are obvious traces after rinsing; Level 3: Some stain remains and there are slight traces after rinsing; Level 4: A small amount of stain remains and there are basically no traces after rinsing; Level 5: No stain remains and the surface is smooth).

[0037] 3. Chemical detergent resistance: Use industrial laundry detergent (adjust pH=12) and acidic detergent such as toilet cleaner (adjust pH=4). Soak the membrane material in the above two detergents at room temperature (25℃) for 72 hours. After soaking, rinse with clean water and dry. Test the tensile strength change rate of the membrane material. The tensile strength change rate ≤±5% is qualified. The smaller the change rate, the better the chemical detergent resistance.

[0038] 4. Hydrolytic stability: Place the membrane material in a constant temperature and humidity chamber, control the temperature at 85℃ and the relative humidity at 85%, and leave it for 500 hours. After that, take it out and cool it to room temperature. Test the tensile strength retention rate of the membrane material (the tensile strength test method is the same as the above chemical detergent resistance test). A retention rate of ≥85% is considered qualified. The higher the retention rate, the better the hydrolytic stability.

[0039] The test standards and results are shown in Table 1: Table 1 Test Standards and Results

[0040] Based on the test results of Examples 1-3 and Comparative Examples 1-3 in Table 1, the following core conclusions can be drawn: 1. Stain Resistance: This invention introduces amino-functionalized silicon-based block prepolymers into the TPU backbone, which accumulate on the film surface to form a low surface energy anti-fouling layer, effectively reducing stain adhesion and keeping the micron-level uneven structure clean, thus significantly improving stain resistance. Example 1 (containing 20 parts of amino-functionalized silicon-based block prepolymer) achieved a surface contact angle of 118°, demonstrating a high stain resistance level; Comparative Example 1 (without amino-functionalized silicon-based block prepolymer) showed a contact angle reduced to 105°, with a significantly deteriorated stain resistance level (4 / 3 / 3 / 2), fully verifying the core anti-fouling effect of the amino-functionalized silicon-based block prepolymer; Example 2 (10 parts of amino-functionalized silicon-based block prepolymer) showed a slight decrease in stain resistance due to the reduced dosage, further proving that the dosage is positively correlated with the anti-fouling effect.

[0041] 2. Chemical Detergent Resistance: In terms of acid resistance, Comparative Example 1 (which could not neutralize the penetrating acidic medium through the reactive amino sites on the molecular chain, with a tensile strength change rate of +3.5% after immersion in acidic detergent, significantly higher than Example 1 (+1.7%), verified the effectiveness of the acidic protective barrier formed by the amino-functionalized silicon-based block prepolymer); In terms of alkali resistance, Comparative Example 3 (single PTMG + single BDO, without PCDL compound and nitrogen-containing heterocyclic chain extender) lacked the intrinsic stability of the polymer matrix in alkaline environment, with a tensile strength change rate of +3.8% after immersion in alkaline detergent, showing significant deterioration, proving that the synergistic effect of PTMG compound with PCDL and nitrogen-containing heterocyclic chain extender can effectively improve the membrane material's resistance to alkaline detergent erosion.

[0042] 3. Hydrolysis Stability: This invention introduces an anti-hydrolysis stabilizer, a compound of organic amine salt anti-hydrolysis agent and metal ion chelating agent, to form an internal hydrolysis inhibition system, achieving comprehensive hydrolysis protection from the surface to the interior. Example 1 (compound anti-hydrolysis stabilizer) exhibits the best hydrolysis stability, with a tensile strength retention rate of 93.5% after 1000 hours; Example 3 (single anti-hydrolysis agent, without metal ion chelating agent) shows a retention rate reduced to 87.6%, demonstrating that the synergistic effect of the two components can significantly improve the hydrolysis protection effect; Comparative Example 2 (without anti-hydrolysis stabilizer) shows a retention rate of only 75.2%, with significant material degradation, further verifying the core role of the anti-hydrolysis stabilizer in improving the service life of the membrane material under frequent cleaning and humid and hot environments.

[0043] 4. Overall Performance: Example 1, as the optimal formulation, exhibits superior performance across all core components. It demonstrates balanced resistance to dirt, chemical detergents, and hydrolytic stability. The amino-functionalized silicon-based blocks accumulate on the surface, forming an antifouling layer and preferentially neutralizing acidic media, thus constructing surface protection. The hydrolytic stabilizer (organic amine salt and metal ion chelator) internally captures carboxyl groups, passivates metal catalysis, and blocks the autocatalytic hydrolysis cycle. The PCDL / PTMG complex and nitrogen-containing heterocyclic chain extender endow the matrix with intrinsic alkali resistance and, through intermolecular hydrogen bonds, couples with amino sites, preventing amino groups from deactivating in alkaline environments. The heterocyclic structure reduces carboxyl groups generated by alkaline hydrolysis, lowering the neutralization pressure on the hydrolytic stabilizer. The hydrogen bond network between amino and heterocyclic groups ensures structural stability over a wide pH range. Therefore, Example 1 achieves optimal balanced performance due to the completeness of its three components; the absence of any one component would break the synergistic chain, leading to degradation, fully demonstrating the synergistic effect of 1+1+1>3. Examples 2 and 3 showed a slight decrease in performance due to the adjustment of a single component, but were still superior to all comparative examples. Comparative examples 1-3, lacking the core component of the present invention, showed varying degrees of deterioration in all aspects of their performance, fully demonstrating the synergistic effect of the components of the present invention, which can significantly improve the overall performance of the microstructured functional membrane and meet the requirements for resistance to dirt and chemical detergents.

[0044] The above are merely preferred embodiments of this application and do not limit the patent scope of this application. Any equivalent structural or procedural transformations made using the content of this application's specification, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of this application.

Claims

1. A microstructured functional membrane resistant to dirt and chemical detergents, characterized in that, Its raw materials, by weight, include: 12-25 parts of amino-functionalized silicon-based block prepolymer, 40-60 parts of oligomeric diol, 22-38 parts of aliphatic diisocyanate, 4-12 parts of heterocyclic modified chain extender, 2.5-7 parts of composite functional additives, and 0.01-0.06 parts of composite catalyst. The composite functional additive includes 1-3 parts of an anti-aging agent and 0.2-0.8 parts of an anti-hydrolysis stabilizer; The amino-functionalized silicon-based block prepolymer has a molecular weight of 1200-2800 and its general formula is: OCN-R1-NH-CO-NH-(X)-Si(R2)2-O-[Si(R3)(R4)-O] n -O-CO-NH-R1-NCO, where R1 is an aliphatic diisocyanate residue, R2 is -OH, -OCH3, -OC2H5 or -CH3, R3 and R4 are both methyl or phenyl, n is 5~200, and X is the linking group of the aminosilane coupling agent.

2. The dirt-resistant and chemical-detergent-resistant microstructured functional membrane according to claim 1, characterized in that, The raw materials, by weight, include: 18-22 parts of amino-functionalized silicon-based block prepolymer, 48-55 parts of oligomeric diol, 28-32 parts of aliphatic diisocyanate, 6-9 parts of heterocyclic modified chain extender, 4-6 parts of composite functional additives, and 0.02-0.04 parts of composite catalyst.

3. The microstructured functional membrane resistant to dirt and chemical detergents according to claim 1, characterized in that, The amino-functionalized silicon-based block prepolymer is obtained by condensation reaction of terminal hydroxyl silicon-based polymer and aminosilane coupling agent to obtain amino-functionalized silicon-based polymer, and then by nucleophilic addition reaction of amino-functionalized silicon-based polymer with aliphatic diisocyanate. The molar ratio of the hydroxyl-terminated silicone polymer to the aminosilane coupling agent is 1:1.05~1.15, and the molar ratio of the amino-functionalized silicone polymer to the aliphatic diisocyanate is 1:2.2~2.

5.

4. The dirt-resistant and chemical-detergent-resistant microstructured functional membrane according to claim 1, characterized in that, The hydroxyl-terminated silicone polymer is at least one of polydimethylsiloxane diol and polymethylphenylsiloxane diol; The aminosilane coupling agent is at least one of 3-aminopropyltriethoxysilane and N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane.

5. The dirt-resistant and chemical-detergent-resistant microstructured functional membrane according to claim 1, characterized in that, The oligomeric diol has a molecular weight of 1800-3500 and is a compound of polytetrahydrofuran ether diol and polycarbonate diol in a weight ratio of 1.3-3:

1. The aliphatic diisocyanate is hexamethylene diisocyanate and / or isophorone diisocyanate; The heterocyclic modified chain extender is a compound of nitrogen-containing heterocyclic diols and aliphatic diols in a weight ratio of 1.5 to 5:

1.

6. The dirt-resistant and chemical-detergent-resistant microstructured functional membrane according to claim 5, characterized in that, The nitrogen-containing heterocyclic diol is at least one of 2-methylpiperazine-1,4-diethanol and piperidine-3,5-diethanol; The aliphatic diol is at least one of 1,4-butanediol (BDO) and 1,6-hexanediol (HDO).

7. The dirt-resistant and chemical-detergent-resistant microstructured functional membrane according to claim 1, characterized in that, The composite catalyst is a mixture of organotin catalysts, tertiary amine catalysts and organobismuth catalysts; The anti-aging agent is at least one of hindered phenolic anti-aging agents and phosphite anti-aging agents; The anti-hydrolysis stabilizer is a compound of organic amine salt anti-hydrolysis agent and metal ion chelating agent in a weight ratio of 2 to 3:

1.

8. The dirt-resistant and chemical-detergent-resistant microstructured functional membrane according to claim 7, characterized in that, The organic amine salt anti-hydrolysis agent is a condensation product of caprolactam and diethylenetriamine; The metal ion chelating agent is at least one of disodium ethylenediaminetetraacetate and trisodium citrate.

9. A method for preparing a microstructured functional membrane resistant to dirt and chemical detergents as described in any one of claims 1-8, characterized in that, include: Amino-functionalized silicon-based block prepolymer and part of a composite catalyst were added to an oligomeric diol and reacted at 75-85°C for 1.5-2 hours to obtain a silicon-based block polyol intermediate with urethane bonds. Aliphatic diisocyanate is added to the silicon-based block polyol intermediate containing urethane bonds, and the reaction is carried out at 90~100℃ until the urethane bond content in the reaction system is 8%~12%. Heterocyclic chain extender, composite functional additive and remaining composite catalyst are added to it, and the temperature is raised to 105~115℃ to obtain functionalized silicon-based modified TPU melt. The TPU melt is calendered and microstructure imprinted in an integrated molding process, and then annealed to obtain a functional film with a micron-level concave-convex composite structure.

10. The method for preparing the dirt-resistant and chemical detergent-resistant microstructured functional membrane according to claim 9, characterized in that, The integrated molding of the TPU melt by calendering and microstructure imprinting includes: The TPU melt is extruded into a casting and imprinting machine at 170~190℃ for calendering and microstructure imprinting to obtain a functional film with a micron-level concave-convex composite structure; wherein the temperature of the calendering roller is 90~110℃, and the pressure is held at 3~8MPa for 10~30s. The annealing process is carried out at a temperature of 60-70°C for 30-50 minutes.

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