A highly phase-separated polyurethane and its preparation method and application

Abstract

The present invention provides a highly phase-separated polyurethane, its preparation method, and application, belonging to the field of polymer materials technology. The highly phase-separated polyurethane is prepared from raw materials including a hydrophilically modified polyether polyol, an isocyanate monomer, a catalyst, and a chain extender. The raw materials for preparing the hydrophilically modified polyether polyol include a ring-opening initiator and an epoxy compound; the ring-opening initiator includes a dihydroxycarboxylic acid and / or a dihydroxysulfonate. The highly phase-separated polyurethane exhibits a clear and stable microphase structure and excellent mechanical properties and water resistance.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer materials, and in particular to a highly phase-separated polyurethane and a preparation method and application thereof. Background Art

[0002] Polyurethanes are a class of block polymers composed of alternating soft and hard segments. Their performance depends largely on the microphase separation between these segments. The soft segments, typically derived from polyether or polyester polyols, impart excellent flexibility and ductility to the material. The hard segments, formed by the reaction of diisocyanates and chain extenders, possess a strong structural rigidity and can form aggregates through intermolecular hydrogen bonding, contributing to the material's mechanical strength, thermal stability, and chemical resistance. An ideal microphase separation structure, which simultaneously achieves the flexibility of the soft segments and the reinforcing effects of the hard segments, is key to the preparation of high-performance polyurethane coatings.

[0003] To impart water-dispersibility to polyurethanes, hydrophilic chain extenders such as dimethylolpropionic acid (DMPA) are often used to introduce carboxylic acid groups or their salts. In traditional waterborne polyurethane preparation methods, an isocyanate-terminated prepolymer is first synthesized, which is then reacted with a hydrophilic chain extender to introduce hydrophilic groups. As these chain extenders react with the -NCO end-capping groups, the reaction product is incorporated into the hard segment structure of the polyurethane.

[0004] However, although this strategy can achieve stable dispersion of the emulsion, it also brings a series of adverse effects on structure and performance. - These highly polar groups can compete with the NH groups in the hard segments for hydrogen bonding, weakening the hydrogen bonding network originally formed between the oxygen atoms in the carbonyl groups (-C=O) and the hydrogen atoms in the imine groups (-HN-), thereby reducing the hard segment's ability to aggregate. Furthermore, these highly polar groups may interact with the less polar soft segments, increasing their compatibility and blurring the microphase interface. These factors collectively undermine the hard segment's ability to aggregate, reducing the degree of phase separation and ultimately impacting the coating's mechanical properties, water resistance, and environmental stability.

[0005] Therefore, it is urgent to develop a new polyurethane structure design strategy to avoid the interference of hydrophilic groups with the hydrogen bonding between hard segments without sacrificing water dispersibility, thereby improving the microphase separation degree and comprehensive performance of the obtained polyurethane. Summary of the Invention

[0006] To address the above technical issues, the present invention provides a highly phase-separated polyurethane, its preparation method, and its application. Through optimized molecular structure design, this highly phase-separated polyurethane achieves effective phase separation of the polyurethane's soft and hard segments at the nanoscale, significantly improving the mechanical properties and water resistance of the resulting polyurethane. This makes it suitable for water-based coating applications such as metal, plastic, and wood, where high coating performance is required.

[0007] To achieve this object, the present invention adopts the following technical solutions:

[0008] In a first aspect, the present invention provides a highly phase-separated polyurethane, wherein the raw materials for preparing the highly phase-separated polyurethane include a hydrophilically modified polyether polyol, an isocyanate monomer, a chain extender, and a catalyst;

[0009] The raw materials for preparing the hydrophilic modified polyether polyol include a ring-opening initiator and an epoxy compound;

[0010] The ring-opening initiator includes dihydroxycarboxylic acid and / or dihydroxysulfonate.

[0011] The present invention optimizes the raw materials for preparing highly phase-separated polyurethanes. By preferentially using a ring-opening initiator and an epoxy compound as the raw materials, a hydroxyl-terminated hydrophilic modified polyether polyol with a hydrophilic side group is prepared. The hydrophilic modified polyether polyol is further combined with an isocyanate monomer, a catalyst, and a chain extender to synthesize a structurally optimized polyurethane. After film formation, the polyurethane forms a highly microphase-separated structure, exhibiting excellent mechanical properties and water resistance, and is suitable for water-based coating scenarios such as metals, plastics, and wood that have high requirements for coating performance.

[0012] This invention utilizes a specific hydrophilically modified polyether polyol to cleverly introduce hydrophilic groups into the flexible soft segments, preventing them from interfering with hydrogen bonding between the hard segments. This effectively enhances the hard segment's aggregation and phase order. This molecular design results in a polyurethane material with a more pronounced soft- and hard-segment phase separation: the hard segments are more densely clustered and have a clearer microphase interface. The soft segments exhibit both flexibility and water dispersibility, further enhancing the mechanical properties and water resistance of the resulting polyurethane.

[0013] This invention employs a structural reconstruction strategy, optimizing the raw material composition of the polyurethane. This strategy avoids interference of hydrophilic groups with hydrogen bonding between hard segments without sacrificing water dispersibility, thereby enhancing the microphase separation and overall performance of the resulting polyurethane. This effectively addresses the prior art problem of the introduction of hydrophilic chain extenders, which can lead to blurred microphase interfaces and reduced phase separation, ultimately impacting the mechanical properties, water resistance, and environmental stability of the resulting polyurethane.

[0014] The following are preferred technical solutions of the present invention, but are not intended to limit the technical solutions provided by the present invention. Through the following preferred technical solutions, the objectives and beneficial effects of the present invention can be better achieved and realized.

[0015] As a preferred technical solution of the present invention, the weight ratio of the ring-opening initiator is 4-10 parts, for example, it can be 4 parts, 4.5 parts, 5 parts, 5.5 parts, 6 parts, 6.5 parts, 7 parts, 8 parts, 9 parts or 10 parts, as well as specific values ​​between the above points. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific values ​​included in the range, and is further preferably 4-8 parts.

[0016] In the present invention, by optimizing the weight fraction of the ring-opening initiator, it is possible to maintain a good microphase separation structure while ensuring the water dispersibility of the polyurethane, thereby improving the mechanical properties and water resistance of the coating film. When its content is too low, the system's hydrophilicity is insufficient, the emulsion stability deteriorates, and problems such as difficulty in emulsification, incomplete dispersion, or film formation defects are prone to occur. When its content is too high, the molecular chain length of the polyether polyol is significantly reduced, the flexible segments of the main chain are shortened, the microphase structure becomes blurred, and it is difficult to form an effective hydrogen bond network, resulting in a decrease in the microphase separation degree and mechanical properties of the polyurethane. In addition, the water absorption rate of the coating film increases significantly due to the high density of polar groups.

[0017] Preferably, the dihydroxycarboxylic acid comprises 2,2-dimethylolpropionic acid (DMPA) and / or 2,2-dimethylolbutanoic acid (DMBA).

[0018] Preferably, the dihydroxysulfonate includes any one of sodium 2,5-dihydroxybenzenesulfonate, sodium 1,2-dihydroxy-3-propanesulfonate or sodium 1,4-dihydroxybutane-2-sulfonate, or a combination of at least two thereof.

[0019] Preferably, the weight proportion of the epoxy compound is 60-130 parts, for example, 60 parts, 70 parts, 80 parts, 90 parts, 100 parts, 110 parts, 120 parts or 130 parts, as well as specific values ​​between the above points. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific points included in the range.

[0020] Preferably, the epoxy compound includes any one of ethylene oxide, propylene oxide, butylene oxide or glycidol, or a combination of at least two thereof.

[0021] Preferably, the raw materials for preparing the hydrophilic modified polyether polyol further include an alkaline catalyst.

[0022] Preferably, the weight proportion of the alkaline catalyst is 1-3 parts, for example, 1 part, 1.2 parts, 1.4 parts, 1.6 parts, 1.8 parts, 2 parts, 2.2 parts, 2.4 parts, 2.6 parts, 2.8 parts or 3 parts, as well as specific values ​​between the above points. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific points included in the range.

[0023] Preferably, the alkaline catalyst comprises an alkaline alcohol solution with a mass percentage of 5-20%, wherein 5-20% can be, for example, 5%, 8%, 10%, 12%, 14%, 16%, 18% or 20%, as well as specific values ​​between the above points. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific points included in the range.

[0024] Preferably, the alkaline alcohol solution includes NaOH alcohol solution and / or KOH alcohol solution.

[0025] Preferably, the alcohol solution in the alkaline alcohol solution includes any one of methanol, ethanol, isopropanol or butanol, or a combination of at least two of them.

[0026] As a preferred technical solution of the present invention, the ring-opening initiator is dihydroxycarboxylic acid, and the raw materials for preparing the hydrophilic modified polyether polyol further include small molecule alcohol and an acidic catalyst.

[0027] Preferably, the weight proportion of the small molecule alcohol is 1-3.5 parts, for example, it can be 1 part, 1.2 parts, 1.5 parts, 1.8 parts, 2 parts, 2.3 parts, 2.5 parts, 2.8 parts, 3 parts, 3.2 parts or 3.5 parts, as well as specific point values ​​between the above point values. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the range.

[0028] Preferably, the small molecule alcohol includes any one of methanol, ethanol or butanol, or a combination of at least two of them.

[0029] Preferably, the weight portion of the acidic catalyst is 0.1-0.5 parts, for example, it can be 0.1 parts, 0.15 parts, 0.2 parts, 0.25 parts, 0.3 parts, 0.35 parts, 0.4 parts, 0.45 parts or 0.5 parts, as well as specific values ​​between the above points. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific points included in the range.

[0030] Preferably, the acidic catalyst is an organic acid.

[0031] Preferably, the organic acid includes any one of formic acid, benzenesulfonic acid or p-toluenesulfonic acid, or a combination of at least two thereof.

[0032] As a preferred technical solution of the present invention, when the ring-opening initiator is a dihydroxycarboxylic acid, the hydrophilic modified polyether polyol can be prepared illustratively by the following method, which comprises the following steps:

[0033] (a) A ring-opening initiator, a dihydroxycarboxylic acid, a small molecule alcohol, an acidic catalyst, and solvent A are mixed and added to a four-necked flask equipped with a reflux condenser and a water separator. The temperature is slowly raised to 100-120°C, and a dehydration esterification reaction is carried out under heating reflux conditions. The reaction is continued for 3-4 hours until the water content in the water separator stabilizes, thereby obtaining an esterification intermediate.

[0034] (b) The esterification intermediate system of step (a) is cooled to 40-50°C, a basic catalyst and an epoxy compound are added, and the temperature is then raised to 85-95°C. The pressure is then increased to 0.3-0.6 MPa to allow a ring-opening addition reaction to proceed for 2-3 hours. After the reaction, the solvent is removed by rotary evaporation to obtain a modified polyether polyol containing ester-protected hydrophilic groups in the main chain.

[0035] (c) adding water to the modified polyether polyol described in (b), adjusting the pH to 8-10 using an alkaline regulator, carrying out a hydrolysis reaction at 50-60° C. for 1-2 hours, then adding an acidic regulator to adjust the pH to 7, removing water and small molecule alcohols under vacuum, and filtering to remove inorganic matter to obtain the hydrophilic modified polyether polyol.

[0036] Preferably, the solvent A in step (a) comprises an ether solvent.

[0037] Preferably, the weight proportion of the solvent A in step (a) is 30-60 parts, for example, 30 parts, 35 parts, 40 parts, 45 parts, 50 parts, 55 parts or 60 parts, as well as specific values ​​between the above points. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific points included in the range.

[0038] It should be noted that there is no particular limitation on the type of the ether solvent, and all ether solvents in the art are used, including but not limited to diethylene glycol methyl ether, diethylene glycol ethyl ether, ethylene glycol monomethyl ether, and the like.

[0039] Preferably, the weight proportion of water in step (c) is 45-85 parts, for example, 45 parts, 50 parts, 55 parts, 60 parts, 65 parts, 70 parts, 75 parts, 80 parts or 85 parts, as well as specific values ​​between the above points. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific points included in the range.

[0040] Preferably, the alkaline regulator in step (c) comprises any one of NaOH, KOH or ammonia water, or a combination of at least two of them.

[0041] Preferably, the acidic regulator in step (c) comprises any one of hydrochloric acid, sulfuric acid, phosphoric acid or perchloric acid, or a combination of at least two thereof.

[0042] As a preferred technical solution of the present invention, when the ring-opening initiator is dihydroxy sulfonate, the hydrophilic modified polyether polyol is illustratively prepared by the following method, which comprises the following steps:

[0043] A ring-opening initiator, dihydroxysulfonate, is mixed with solvent B, and a basic catalyst and epoxy compound are added. The temperature is then raised to 85-95°C and the pressure is increased to 0.3-0.6 MPa to allow the ring-opening addition reaction to proceed for 2-3 hours. After the reaction is complete, the solvent is removed by rotary evaporation to obtain the hydrophilically modified polyether polyol.

[0044] Preferably, the solvent B comprises an ether solvent.

[0045] Preferably, the weight proportion of the solvent B is 30-60 parts, for example, 30 parts, 35 parts, 40 parts, 45 parts, 50 parts, 55 parts or 60 parts, as well as specific values ​​between the above points. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific points included in the range.

[0046] It should be noted that there is no particular limitation on the type of the ether solvent, and all ether solvents in the art are used, including but not limited to diethylene glycol methyl ether, diethylene glycol ethyl ether, ethylene glycol monomethyl ether, and the like.

[0047] It should be noted that in the present invention, the isocyanate monomer is a diisocyanate. There is no particular limitation on the type of diisocyanate. Isocyanate (IPDI), hexamethylene diisocyanate (HDI), diphenylmethane diisocyanate (MDI), toluene diisocyanate (TDI), tetramethylxylylene diisocyanate (TMXDI) and the like commonly used in the art are all applicable.

[0048] Preferably, the catalyst comprises an organometallic catalyst.

[0049] Preferably, the organometallic catalyst comprises organobismuth and / or organotin.

[0050] It should be noted that in the present invention, there are no specific restrictions on the types of organobismuth and organotin. Any organobismuth and / or organotin commonly used in the art is suitable. For example, organobismuths may include bismuth isooctanoate, bismuth laurate, bismuth neodecanoate, and bismuth cyclohexane. Organotin may include dibutyltin dilaurate (DBTDL), stannous octoate, dibutyltin diacetate, and di(dodecylsulfide)dibutyltin.

[0051] Preferably, the chain extender is a small molecule chain extender.

[0052] Preferably, the small molecule chain extender includes any one of ethylene glycol (EDO), 1,4-butanediol (BDO) or 1,6-hexanediol (HDO) or a combination of at least two thereof.

[0053] Preferably, the raw materials for preparing the highly phase-separated polyurethane further include water.

[0054] Preferably, the water comprises deionized water.

[0055] As a preferred technical solution of the present invention, the raw materials for preparing the highly phase-separated polyurethane include the following components in parts by weight:

[0056] 30-55 parts of hydrophilic modified polyether polyol;

[0057] 18-26 parts of isocyanate monomer;

[0058] 3-8 parts of chain extender;

[0059] 0.1-0.5 parts of catalyst;

[0060] 100-150 parts of water.

[0061] In the raw materials for preparing the highly phase-separated polyurethane of the present invention, the weight proportion of the hydrophilic modified polyether polyol can be 30 parts, 32 parts, 34 parts, 36 parts, 38 parts, 40 parts, 42 parts, 44 parts, 46 parts, 48 ​​parts, 50 parts, 52 parts or 55 parts; the weight proportion of the isocyanate monomer can be 18 parts, 19 parts, 20 parts, 21 parts, 22 parts, 23 parts, 24 parts, 25 parts or 26 parts; the weight proportion of the chain extender can be 3 parts, 3.5 parts, 4 parts, 4.5 parts, 5 parts, 5.5 parts, 6 parts, 6.5 parts, 7 parts, 8 parts, 9 parts, 10 parts, 11 parts, 12 parts, 13 parts, 14 parts, 15 parts, 16 parts, 17 parts, 18 parts, 19 parts, 20 parts, 21 parts, 22 parts, 23 parts, 24 parts, 25 parts or 26 parts; The weight parts of the catalyst can be 0.1 parts, 0.15 parts, 0.2 parts, 0.25 parts, 0.3 parts, 0.35 parts, 0.4 parts, 0.45 parts or 0.5 parts; the weight parts of water can be 100 parts, 105 parts, 110 parts, 115 parts, 120 parts, 125 parts, 130 parts, 135 parts, 140 parts, 145 parts or 150 parts, as well as specific point values ​​between the above point values. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the said range.

[0062] As a preferred technical solution of the present invention, the weight proportion of the hydrophilically modified polyether polyol is 35-45 parts, for example, it can be 35 parts, 36 parts, 37 parts, 38 parts, 39 parts, 40 parts, 41 parts, 42 parts, 43 parts, 44 parts or 45 parts, as well as specific values ​​between the above points. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific points included in the range.

[0063] By optimizing the weight fraction of the hydrophilically modified polyether polyol, the present invention achieves highly phase-separated polyurethanes with enhanced overall properties, including mechanical properties and water resistance. When the hydrophilically modified polyether polyol dosage is high, the proportion of flexible soft segments in the system increases, helping to enhance the compliance of the polyurethane segments and, in turn, improve the material's elongation at break. However, this increased soft segment proportion also dilutes the hard segment content, weakening hydrogen bonding between polyurethane chains and leading to a decrease in microphase separation, manifested as a decrease in the hydrogen bonding index (HBI) and tensile strength. Furthermore, an increase in the total hydrophilic polyether dosage also leads to an increase in the total amount of hydrophilic groups, resulting in a slight increase in water absorption. Conversely, when the hydrophilically modified polyether polyol dosage is low, the proportion of hard segments in the system increases, favoring the formation of denser hydrogen-bonded aggregates, thereby strengthening the microphase separation structure and improving tensile strength, resulting in an increase in the HBI. However, due to the insufficient soft segments, the overall segment compliance decreases, resulting in a decrease in elongation at break. In addition, the reduction in the absolute amount of hydrophilic groups can reduce the water absorption rate of the material and improve the density and environmental stability of the coating to a certain extent.

[0064] In a second aspect, the present invention provides a method for preparing the highly phase-separated polyurethane as described in the first aspect, the preparation method comprising the following steps:

[0065] The hydrophilic modified polyether polyol, isocyanate monomer and catalyst are mixed and reacted to obtain a prepolymer; a chain extender is added to the prepolymer to carry out a chain extension reaction, and then optional water is added to obtain the highly phase-separated polyurethane.

[0066] Preferably, the reaction temperature is 75-85°C, for example, it can be 75°C, 76°C, 77°C, 78°C, 79°C, 80°C, 81°C, 82°C, 83°C, 84°C or 85°C, as well as specific point values ​​between the above point values. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the range.

[0067] Preferably, the reaction time is 2-3 h, for example, 2 h, 2.2 h, 2.4 h, 2.6 h, 2.8 h or 3 h, as well as specific point values ​​between the above point values. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the range.

[0068] Preferably, the reaction is carried out under a protective gas atmosphere.

[0069] Preferably, the protective gas includes any one of nitrogen, argon or helium, or a combination of at least two of them.

[0070] Preferably, the prepolymer system needs to be cooled before the chain extender is added.

[0071] Preferably, the cooling treatment is to cool to 60-65°C, for example, it can be 60°C, 60.5°C, 61°C, 61.5°C, 62°C, 62.5°C, 63°C, 63.5°C, 64°C, 64.5°C or 65°C, as well as specific point values ​​between the above point values. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the range.

[0072] Preferably, the chain extension reaction time is 1-2 h, for example, 1 h, 1.2 h, 1.4 h, 1.6 h, 1.8 h or 2 h, as well as specific point values ​​between the above point values. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the range.

[0073] Specifically, the preparation method of the highly phase-separated polyurethane of the present invention comprises the following steps:

[0074] (1) The hydrophilic modified polyether polyol, isocyanate monomer and solvent were mixed and placed in a four-necked flask. The flask was protected by nitrogen and heated to 75-85 °C. An organic metal catalyst was added and the reaction was carried out for 2-3 h to obtain a prepolymer.

[0075] (2) Cooling the prepolymer system of step (1) to 60-65°C, adding a chain extender for chain extension, and the reaction time is 1-2 hours.

[0076] (3) Slowly adding deionized water under high-speed stirring to emulsify and obtain the highly phase-separated polyurethane.

[0077] The present invention uses the preparation method to anchor the ring-opening initiator to the flexible polyether side chain, thereby making the polarity distribution more uniform and the microphase structure more stable, thereby making the obtained polyurethane have better mechanical properties and water resistance.

[0078] It should be noted that, in the present invention, the addition of deionized water makes the obtained highly phase-separated polyurethane in an emulsion state. In production applications, highly phase-separated polyurethanes in different states can be prepared according to the needs of actual application scenarios.

[0079] Preferably, the rotation speed of the high-speed stirring is 800-1200 rpm, for example, it can be 800 rpm, 850 rpm, 900 rpm, 950 rpm, 1000 rpm, 1050 rpm, 1100 rpm, 1150 rpm or 1200 rpm, as well as specific point values ​​between the above point values. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the range.

[0080] In a third aspect, the present invention provides a use of the highly phase-separated polyurethane as described in the first aspect in a water-based coating system.

[0081] Compared with the prior art, the present invention has at least the following beneficial effects:

[0082] (1) The present invention optimizes the raw materials for the preparation of highly phase-separated polyurethanes. By preferentially using a ring-opening initiator and an epoxy compound as the raw materials, a hydrophilic modified polyether polyol with a hydrophilic side group and a hydroxyl end-capping is prepared. The hydrophilic modified polyether polyol is further combined with an isocyanate monomer, a catalyst, and a chain extender to synthesize a structurally optimized polyurethane. After film formation, the polyurethane forms a highly microphase-separated structure and exhibits excellent mechanical properties and water resistance. It is suitable for water-based coating scenarios such as metals, plastics, and wood products that have high requirements for coating performance.

[0083] (2) The highly phase-separated polyurethane provided by the present invention has an HBI of 0.85-0.98, a tensile strength of 41-53 MPa, an elongation at break of 460-573%, and a water absorption rate of 2.1-4.2%. DETAILED DESCRIPTION

[0084] For the convenience of understanding the present invention, the present invention is given below with examples. It should be understood by those skilled in the art that the examples are only for the purpose of helping to understand the present invention and should not be regarded as specific limitations of the present invention.

[0085] Unless otherwise specified, the raw materials and reagents used in the following preparations, examples, and comparative examples are all commercially available products. Some raw material information is as follows:

[0086] Polyether polyol: PPG 1000, purchased from Nantong Yixun Chemical Co., Ltd.

[0087] Preparation Example 1

[0088] This preparation example provides a hydrophilic modified polyether polyol 1. The raw materials for preparing the hydrophilic modified polyether polyol include the components in parts by weight as shown in Table 1.

[0089] Table 1

[0090]

[0091] The hydrophilic modified polyether polyol is prepared by the following method, which comprises the following steps:

[0092] (a) 2,2-Dihydroxymethylpropionic acid (DMPA), methanol, p-toluenesulfonic acid, and 45 parts of diethylene glycol methyl ether were mixed and added to a four-necked flask equipped with a reflux condenser and a water separator. The temperature was slowly raised to 110°C, and a dehydration esterification reaction was carried out under heating and reflux conditions. The reaction was continued for 3.5 hours until the water content in the water separator stabilized, thereby obtaining an esterification intermediate.

[0093] (b) The esterification intermediate system of step (a) was cooled to 45°C, a basic catalyst and propylene oxide were added, and the temperature was then raised to 90°C and pressurized to 0.5 MPa for a ring-opening addition reaction for 2.5 hours. After the reaction, the solvent was removed by rotary evaporation to obtain a modified polyether polyol containing ester-protected hydrophilic groups in the main chain.

[0094] (c) Add 60 parts of deionized water to the modified polyether polyol described in (b), add 0.1 M NaOH solution to adjust the pH to 9, react at 55° C. for 1.5 h, then add 0.1 M HCl solution to adjust the pH to 7, remove water and small molecular alcohol in vacuo, and filter to remove inorganic matter to obtain the hydrophilic modified polyether polyol 1.

[0095] Preparation Example 2

[0096] This preparation example provides a hydrophilic modified polyether polyol 2. The raw materials for preparing the hydrophilic modified polyether polyol include the components in parts by weight as shown in Table 2.

[0097] Table 2

[0098]

[0099] The hydrophilic modified polyether polyol is prepared by the following method, which comprises the following steps:

[0100] (a) 2,2-Dihydroxymethylbutyric acid (DMBA), butanol, formic acid, and 32 parts of diethylene glycol methyl ether were mixed and added to a four-necked flask equipped with a reflux condenser and a water separator. The temperature was slowly raised to 100°C, and a dehydration esterification reaction was carried out under heating and reflux conditions. The reaction was continued for 3 hours until the water content in the water separator stabilized, thereby obtaining an esterification intermediate.

[0101] (b) The esterification intermediate system of step (a) was cooled to 40°C, and a basic catalyst and glycidol were added. The temperature was then raised to 85°C and pressurized to 0.5 MPa for a ring-opening addition reaction for 2 hours. After the reaction, the solvent was removed by rotary evaporation to obtain a modified polyether polyol 2 containing ester-protected hydrophilic groups in the main chain.

[0102] (c) Add 45 parts of deionized water to the modified polyether polyol described in (b), add 0.1 M NaOH solution to adjust the pH to 8, react at 50° C. for 1 hour, add 0.1 M HCl solution to adjust the pH to 7, remove water and small molecular alcohol in vacuo, and filter to remove inorganic matter to obtain the hydrophilic modified polyether polyol.

[0103] Preparation Example 3

[0104] This preparation example provides a hydrophilic modified polyether polyol 3. The raw materials for preparing the hydrophilic modified polyether polyol include the components in parts by weight as shown in Table 3.

[0105] Table 3

[0106]

[0107] The hydrophilic modified polyether polyol is prepared by the following method, which comprises the following steps:

[0108] (a) 2,2-Dihydroxymethylpropionic acid (DMPA), ethanol, benzenesulfonic acid, and 60 parts of diethylene glycol methyl ether were mixed and added to a four-necked flask equipped with a reflux condenser and a water separator. The temperature was slowly raised to 120°C, and a dehydration esterification reaction was carried out under heating and reflux conditions. The reaction was continued for 4 hours until the water content in the water separator stabilized, thereby obtaining an esterification intermediate.

[0109] (b) The esterification intermediate system of step (a) was cooled to 50°C, a basic catalyst and butylene oxide were added, and the temperature was then raised to 95°C and pressurized to 0.5 MPa for a ring-opening addition reaction for 3 hours. After the reaction, the solvent was removed by rotary evaporation to obtain a modified polyether polyol containing ester-protected hydrophilic groups in the main chain.

[0110] (c) 82 parts of deionized water were added to the modified polyether polyol described in (b), and a 0.1 M NaOH solution was added to adjust the pH to 10. After reacting at 60° C. for 2 h, a 0.1 M HCl solution was added to adjust the pH to 7. Water and small molecular alcohol were removed under vacuum, and inorganic matter was removed by filtration to obtain the hydrophilic modified polyether polyol 3.

[0111] Preparation Example 4

[0112] This preparation example provides a hydrophilically modified polyether polyol 4, which includes the following raw materials in parts by weight: 6.5 parts of dihydroxysulfonate (sodium 2,5-dihydroxybenzenesulfonate), 90 parts of propylene oxide, and 2 parts of an alkaline catalyst (10% NaOH-ethanol solution).

[0113] The hydrophilic modified polyether polyol is prepared by the following method, which comprises the following steps:

[0114] The dihydroxysulfonate was mixed with 45 parts of diethylene glycol methyl ether, and a basic catalyst and propylene oxide were added. The temperature was then raised to 90°C and the pressure was increased to 0.5 MPa for a ring-opening addition reaction for 2.5 hours. After the reaction, the solvent was removed by rotary evaporation to obtain the hydrophilically modified polyether polyol 4.

[0115] Preparation Example 5

[0116] This preparation example provides a hydrophilically modified polyether polyol 5, which differs from Preparation Example 1 only in that the weight fraction of 2,2-dihydroxymethylpropionic acid (DMPA) is adjusted from 5.5 parts to 4 parts, and the other raw materials, addition amounts and preparation methods are the same as those in Preparation Example 1.

[0117] Preparation Example 6

[0118] This preparation example provides a hydrophilically modified polyether polyol 6, which differs from Preparation Example 1 only in that the weight fraction of 2,2-dihydroxymethylpropionic acid (DMPA) is adjusted from 5.5 parts to 8 parts, and the other raw materials, addition amounts and preparation methods are the same as those in Preparation Example 1.

[0119] Preparation Example 7

[0120] This preparation example provides a hydrophilically modified polyether polyol 7, which differs from Preparation Example 1 only in that the weight fraction of 2,2-dihydroxymethylpropionic acid (DMPA) is adjusted from 5.5 parts to 10 parts, and the other raw materials, addition amounts and preparation methods are the same as those in Preparation Example 1.

[0121] Example 1

[0122] This embodiment provides a highly phase-separated polyurethane, which includes the following components in parts by weight:

[0123] 40 parts of hydrophilic modified polyether polyol 1 (Preparation Example 1);

[0124] 20 parts of isophorone diisocyanate (IPDI);

[0125] 3 parts of chain extender 1,4-butanediol (BDO);

[0126] 0.2 parts of dibutyltin dilaurate (DBTDL);

[0127] 130 parts of deionized water.

[0128] The preparation method of the highly phase-separated polyurethane specifically comprises the following steps:

[0129] (1) Hydrophilic modified polyether polyol 1 (Preparation Example 1), IPDI and diethylene glycol methyl ether were mixed and placed in a four-necked flask. The mixture was protected by nitrogen and heated to 80°C. Catalyst DBTDL was added and the reaction was continued for 2.5 h to obtain a prepolymer.

[0130] (2) The prepolymer system of step (1) was cooled to 63°C, and a chain extender BDO was added for chain extension. The reaction time was 1.5 h.

[0131] (3) Deionized water was slowly added to emulsify the mixture while stirring at 1000 rpm to obtain the highly phase-separated polyurethane.

[0132] Example 2

[0133] This embodiment provides a highly phase-separated polyurethane, which includes the following components in parts by weight:

[0134] 30 parts of hydrophilic modified polyether polyol 2 (Preparation Example 2);

[0135] Hexamethylene diisocyanate (HDI) 18 parts;

[0136] 3 parts of chain extender ethylene glycol (EDO);

[0137] 0.1 part of bismuth neodecanoate;

[0138] 100 parts of deionized water.

[0139] The preparation method of the highly phase-separated polyurethane specifically comprises the following steps:

[0140] (1) Hydrophilic modified polyether polyol 2 (Preparation Example 2), HDI and diethylene glycol methyl ether were mixed and placed in a four-necked flask. The mixture was protected by nitrogen and heated to 75°C. Bismuth neodecanoate as a catalyst was added and reacted for 2 h to obtain a prepolymer.

[0141] (2) The prepolymer system of step (1) was cooled to 60°C, and chain extender EDO was added for chain extension, with a reaction time of 1 h.

[0142] (3) Deionized water was slowly added to emulsify the mixture while stirring at 1000 rpm to obtain the highly phase-separated polyurethane.

[0143] Example 3

[0144] This embodiment provides a highly phase-separated polyurethane, which includes the following components in parts by weight:

[0145] 50 parts of hydrophilic modified polyether polyol 3 (Preparation Example 3);

[0146] 26 parts of diphenylmethane diisocyanate (MDI);

[0147] 6 parts of chain extender 1,6-hexanediol (HDO);

[0148] 0.5 parts of stannous octoate;

[0149] 150 parts of deionized water.

[0150] The preparation method of the highly phase-separated polyurethane specifically comprises the following steps:

[0151] (1) The hydrophilic modified polyether polyol (Preparation Example 3), MDI and diethylene glycol methyl ether were mixed and placed in a four-necked flask. The mixture was protected by nitrogen and heated to 85°C. The catalyst stannous octoate was added and the mixture was reacted for 3 h to obtain a prepolymer.

[0152] (2) The prepolymer system of step (1) was cooled to 65°C, and chain extender HDO was added for chain extension, with a reaction time of 2 h.

[0153] (3) Deionized water was slowly added to emulsify the mixture while stirring at 1000 rpm to obtain the highly phase-separated polyurethane.

[0154] Example 4

[0155] This embodiment provides a highly phase-separated polyurethane, which includes the following components in parts by weight:

[0156] 43 parts of hydrophilic modified polyether polyol 4 (Preparation Example 4);

[0157] Toluene diisocyanate (TDI) 22 parts;

[0158] 6 parts of chain extender 1,4-butanediol (BDO);

[0159] 0.2 parts of dibutyltin dilaurate (DBTDL);

[0160] 130 parts of deionized water.

[0161] The preparation method of the highly phase-separated polyurethane is the same as that in Example 1.

[0162] Example 5

[0163] This embodiment provides a highly phase-separated polyurethane, which differs from Example 1 only in that hydrophilic-modified polyether polyol 1 (Preparation Example 1) is replaced by hydrophilic-modified polyether polyol 5 (Preparation Example 5) of equal mass, and other raw materials, addition amounts and preparation methods are the same as those in Example 1.

[0164] Example 6

[0165] This example provides a highly phase-separated polyurethane, which differs from Example 1 only in that hydrophilic-modified polyether polyol 1 (Preparation Example 1) is replaced with hydrophilic-modified polyether polyol 6 (Preparation Example 6) of equal mass, and other raw materials, addition amounts, and preparation methods are the same as those in Example 1.

[0166] Example 7

[0167] This embodiment provides a highly phase-separated polyurethane, which differs from Example 1 only in that hydrophilic-modified polyether polyol 1 (Preparation Example 1) is replaced with hydrophilic-modified polyether polyol 7 (Preparation Example 7) of equal mass, and other raw materials, addition amounts and preparation methods are the same as those in Example 1.

[0168] Example 8

[0169] This embodiment provides a highly phase-separated polyurethane, which differs from Example 1 only in that the weight of hydrophilically modified polyether polyol 1 (Preparation Example 1) is adjusted from 40 parts to 30 parts, and the other raw materials, addition amounts and preparation methods are the same as those in Example 1.

[0170] Example 9

[0171] This embodiment provides a highly phase-separated polyurethane, which differs from Example 1 only in that the weight of hydrophilically modified polyether polyol 1 (Preparation Example 1) is adjusted from 40 parts to 35 parts, and the other raw materials, addition amounts and preparation methods are the same as those in Example 1.

[0172] Example 10

[0173] This embodiment provides a highly phase-separated polyurethane, which differs from Example 1 only in that the weight fraction of hydrophilically modified polyether polyol 1 (Preparation Example 1) is adjusted from 40 parts to 45 parts, and the other raw materials, addition amounts and preparation methods are the same as those in Example 1.

[0174] Example 11

[0175] This embodiment provides a highly phase-separated polyurethane, which differs from Example 1 only in that the weight of hydrophilically modified polyether polyol 1 (Preparation Example 1) is adjusted from 40 parts to 50 parts, and the other raw materials, addition amounts and preparation methods are the same as those in Example 1.

[0176] Comparative Example 1

[0177] This comparative example provides a polyurethane, the raw materials for preparing the polyurethane include the following components in parts by weight:

[0178] Polyether polyol PPG 100040 parts;

[0179] Isocyanate monomer IPDI 20 parts;

[0180] 2.4 parts of hydrophilic chain extender DMPA;

[0181] Chain extender BDO 0.6 parts;

[0182] Catalyst DBTDL 0.2 parts;

[0183] 130 parts of deionized water.

[0184] The preparation method of the polyurethane specifically comprises the following steps:

[0185] (1) Polyether polyol PPG 1000, isocyanate monomer IPDI and diethylene glycol methyl ether were mixed and placed in a four-necked flask. The flask was protected by nitrogen and heated to 80 °C. Catalyst DBTDL was added and the reaction was continued for 2.5 h to obtain a prepolymer.

[0186] (2) Add the hydrophilic chain extender DMPA to the prepolymer obtained in step (1) for chain extension and react at 80°C for 0.5 h.

[0187] (3) The system described in step (2) was cooled to 63°C and chain extender BDO was added for chain extension. The reaction time was 1.5 h.

[0188] (4) Deionized water was slowly added under stirring at 1000 rpm to emulsify the mixture to obtain the polyurethane.

[0189] The polyurethane emulsions obtained in Examples 1-11 and Comparative Example 1 were added dropwise to a clean glass container to a thickness of about 1 mm. After a uniform film was formed at 25° C., performance tests were performed. The test methods / standards are as follows:

[0190] (1) Degree of phase separation

[0191] FT-IR has been used as a sensitive tool to compare the degree of phase separation in different materials. The characteristic peaks of waterborne polyurethane films in the ester carbonyl absorption region were separated and fitted using the Gaussian method. The hydrogen bonding index (HBI) was calculated based on the absorption peak areas of free carbonyl groups, disordered hydrogen-bonded carbonyl groups, and ordered hydrogen-bonded carbonyl groups. A larger HBI value indicates a higher degree of hydrogen bonding, indicating a higher degree of microphase separation.

[0192]

[0193] in, is the peak area of ​​hydrogen-bonded C=O; is the peak area of ​​free C=O.

[0194] (2) Tensile strength and elongation at break: Cut the film into a dumbbell shape and set the tensile rate to 100 mm / min according to GB / T 528-2009.

[0195] (3) Water absorption rate: Cut the film into 3 cm × 3 cm samples, refer to T / CWA 206-2021, weigh the sample mass and record it as m0, soak it in deionized water for 24 h, take it out and use filter paper to absorb the surface moisture, weigh the mass and record it as m1, and calculate the water absorption rate. Perform calculations.

[0196] The test results are shown in Table 4.

[0197] Table 4

[0198]

[0199] The test results show that:

[0200] (1) As can be seen from Examples 1 to 11, the present invention can obtain highly phase-separated polyurethanes with excellent mechanical properties and water resistance by combining a hydrophilic modified polyether polyol with hydrophilic side groups prepared from a ring-opening initiator and an epoxy compound with a polyurethane, a catalyst, and a chain extender. The polyurethanes have an HBI of 0.85-0.98, a tensile strength of 41-53 MPa, an elongation at break of 460-573%, and a water absorption of 2.1-4.2%.

[0201] (2) By comparing Example 1 with Examples 5-7, it can be seen that the content of the ring-opening initiator used in the raw materials for preparing the hydrophilic modified polyether polyol used in Example 7 is too high, which significantly reduces the number average molecular weight of the polyether polyol, shortens the flexible segments of the main chain, and makes it difficult to form a continuous phase region in the polyurethane. At the same time, the hydrophilic groups are excessively accumulated, which interferes with the formation of hydrogen bonds between the hard segments, thereby reducing the degree of microphase separation of the obtained polyurethane, weakening the tensile strength, and significantly increasing the water absorption rate. This shows that the present invention can further improve the microphase structure orderliness and comprehensive application performance of the obtained polyurethane on the basis of ensuring the water dispersibility of the polyurethane by designing and optimizing the raw materials for preparing the hydrophilic modified polyether polyol.

[0202] (3) It can be seen from Examples 8-11 that, compared with Examples 9 and 10, the weight fraction of the hydrophilic modified polyether polyol in Example 8 is lower, the proportion of hard segments in the system is increased, the hydrogen bonding effect is enhanced, the HBI is improved, and the tensile strength is increased, but the flexible segments are reduced, the elongation at break is significantly reduced, and at the same time, the water absorption rate is slightly reduced due to the reduction in the total amount of hydrophilic groups. The weight fraction of the hydrophilic modified polyether polyol in Example 11 is higher, resulting in an increase in the proportion of flexible segments, which helps to enhance the flexibility of the segments and further improve the elongation at break, but at the same time dilutes the proportion of hard segments, weakens hydrogen bonding aggregation, and causes a decrease in hydrogen bonding index (HBI) and tensile strength. In addition, due to the increase in the total amount of hydrophilic groups, its water absorption rate increases. This shows that by optimizing the weight fraction of the hydrophilic modified polyether polyol, the present invention can obtain polyurethane with better comprehensive properties such as phase separation effect, mechanical properties and water resistance.

[0203] (4) As can be seen from Example 1 and Comparative Example 1, Comparative Example 1 maintains the hydrophilic chain extender DMPA content and the ratio of soft and hard segments unchanged, and uses a traditional preparation method to directly introduce DMPA into the hard segment main chain, resulting in competitive hydrogen bonding between the hydrophilic group and the NH in the carbamate, destroying the hard segment aggregation and significantly reducing the degree of microphase separation (HBI dropped to 0.65). The hard segment cannot effectively aggregate and is dispersed in the soft segment, forming a physical interference with the flexible segment, reducing the elongation at break to 440%; at the same time, the polar structure of the hard segment is locally enriched, easily forming water adsorption points, and the water absorption rate increases to 7.8%. In contrast, in Example 1, DMPA is anchored to the flexible polyether side chain, resulting in a more uniform polarity distribution and a more stable microphase structure, thus having better mechanical properties and water resistance.

[0204] In summary, the present invention preferentially prepares a hydroxyl-terminated hydrophilic modified polyether polyol with a hydrophilic side group by using a ring-opening initiator and an epoxy compound, and further combines the hydrophilic modified polyether polyol with a polyurethane, a catalyst, and a chain extender to form a highly phase-separated polyurethane with a highly microphase-separated structure. The polyurethane has excellent mechanical properties and water resistance, and is suitable for water-based coating scenarios such as metals, plastics, and wood that have high requirements for coating performance.

[0205] The above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention fall within the protection scope and disclosure scope of the present invention.

Claims

1. A highly phase-separated polyurethane, characterized in that: The raw materials for preparing the highly phase-separated polyurethane include hydrophilic modified polyether polyol, isocyanate monomer, catalyst and chain extender; The raw materials for preparing the hydrophilic modified polyether polyol include a ring-opening initiator and an epoxy compound; The ring-opening initiator includes dihydroxycarboxylic acid and / or dihydroxysulfonate; When the ring-opening initiator is a dihydroxycarboxylic acid, the preparation method of the hydrophilically modified polyether polyol comprises the following steps: (a) A ring-opening initiator, a dihydroxycarboxylic acid, a small molecule alcohol, an acidic catalyst, and solvent A are mixed and added to a four-necked flask equipped with a reflux condenser and a water separator. The temperature is slowly raised to 100-120°C, and a dehydration esterification reaction is carried out under heating reflux conditions. The reaction is continued for 3-4 hours until the water content in the water separator tends to be stable, thereby obtaining an esterification intermediate. (b) cooling the system of the esterification intermediate described in step (a) to 40-50° C., adding a basic catalyst and an epoxy compound, then heating to 85-95° C. and pressurizing to 0.3-0.6 MPa to carry out a ring-opening addition reaction for 2-3 hours; after the reaction, removing the solvent by rotary evaporation to obtain a modified polyether polyol containing an ester group protecting a hydrophilic group in the main chain; (c) adding water to the modified polyether polyol described in (b), adjusting the pH to 8-10 with an alkaline regulator, carrying out a hydrolysis reaction at 50-60° C. for 1-2 hours, then adding an acidic regulator to adjust the pH to 7, removing water and small molecule alcohols under vacuum, and filtering to remove inorganic matter to obtain the hydrophilic modified polyether polyol; The small molecule alcohol includes any one of methanol, ethanol or butanol, or a combination of at least two of them.

2. The highly phase-separated polyurethane according to claim 1, characterized in that The weight portion of the ring-opening initiator is 4-10 parts; The weight proportion of the epoxy compound is 60-130 parts; The epoxy compound includes any one of ethylene oxide, propylene oxide, butylene oxide or glycidol, or a combination of at least two of them.

3. The highly phase-separated polyurethane according to claim 1, characterized in that The weight portion of the small molecule alcohol is 1-3.5 parts; The weight portion of the acidic catalyst is 0.1-0.5 parts; The weight proportion of the alkaline catalyst is 1-3 parts.

4. The highly phase-separated polyurethane according to claim 1, characterized in that The catalyst includes an organometallic catalyst.

5. The highly phase-separated polyurethane according to claim 1, characterized in that The chain extender is a small molecule chain extender; The small molecule chain extender includes any one of ethylene glycol, 1,4-butanediol or 1,6-hexanediol, or a combination of at least two thereof.

6. The highly phase-separated polyurethane according to claim 1, characterized in that The raw materials for preparing the highly phase-separated polyurethane include the following components in parts by weight: 30-55 parts of hydrophilic modified polyether polyol; 18-26 parts of isocyanate monomer; 3-8 parts of chain extender; 0.1-0.5 parts of catalyst; 100-150 parts of water.

7. The highly phase-separated polyurethane according to claim 6, characterized in that The weight proportion of the hydrophilic modified polyether polyol is 35-45 parts.

8. A method for preparing a highly phase-separated polyurethane according to any one of claims 1 to 7, characterized in that: The preparation method comprises the following steps: The hydrophilic modified polyether polyol, isocyanate monomer and catalyst are mixed and reacted to obtain a prepolymer; a chain extender is added to the prepolymer to carry out a chain extension reaction, and then optional water is added to obtain the highly phase-separated polyurethane.

9. The method for preparing a highly phase-separated polyurethane according to claim 8, wherein: The reaction temperature is 75-85°C; The reaction time is 2-3 h; The system of the prepolymer needs to be cooled before the chain extender is added; The cooling treatment is to cool the temperature to 60-65°C; The chain extension reaction time is 1-2 h.

10. Use of the highly phase-separated polyurethane according to any one of claims 1 to 7 in a water-based coating system.

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