Highly phase-separated polyurethane as well as preparation method and application thereof

Abstract

The invention provides highly phase-separated polyurethane as well as a preparation method and application thereof, and belongs to the technical field of high polymer materials. The highly-phase-separated polyurethane is prepared from the following raw materials: hydrophilic modified polyether polyol, an isocyanate monomer, a catalyst and a chain extender, the hydrophilic modified polyether polyol is prepared from the following raw materials: a ring-opening initiator and an epoxy compound; the ring-opening initiator comprises dihydroxy carboxylic acid and / or dihydroxy sulfonate. The highly-phase-separated polyurethane is clear and stable in microphase structure and has excellent mechanical properties and water resistance.

Description

Technical Field

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

[0002] Polyurethane is a type of block polymer material composed of alternating soft segments and hard segments, and its properties largely depend on the microphase separation structure between the soft and hard segments. The soft segments usually originate from polyether or polyester polyols, endowing the material with good flexibility and ductility; the hard segments are formed by the reaction of diisocyanates with chain extenders, with a strong rigid structure, and can form aggregated phases through intermolecular hydrogen bond interactions, providing the mechanical strength, thermal stability, and chemical resistance of the material. An ideal microphase separation structure can simultaneously achieve the flexibility of the soft segments and the strengthening effect of the hard segments, which is the key to preparing high-performance polyurethane coatings.

[0003] To endow polyurethane with water dispersibility, hydrophilic chain extenders such as dimethylolpropionic acid (DMPA) are often used to introduce carboxylic acid or its salt groups. In traditional preparation methods of aqueous polyurethane, an isocyanate-terminated prepolymer is first synthesized, and then reacted with a hydrophilic chain extender to introduce hydrophilic groups. Since such chain extenders react with the -NCO-terminated groups, the reaction products are 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 the structure and properties. Hydrophilic groups such as -COOH or -COO - can undergo competitive hydrogen bond interactions with N-H in the hard segments, weakening the hydrogen bond network formed between the oxygen atom in the original carbonyl (-C=O) and the hydrogen atom in the imine group (-HN-), and reducing the aggregation ability of the hard segments. In addition, these strongly polar groups may also interact with the less polar soft segments, increasing the compatibility between the soft and hard segments and resulting in a blurred microphase interface. These factors jointly damage the aggregation ability of the hard segments, reduce the degree of phase separation, and ultimately affect the mechanical properties, water resistance, and environmental stability of the coating film.

[0005] Therefore, it is urgent to develop a new polyurethane structure design strategy to avoid the interference of hydrophilic groups on the hydrogen bond interaction between hard segments without sacrificing water dispersibility, so as to improve the microphase separation degree and comprehensive properties of the obtained polyurethane. Summary of the Invention

[0006] To solve the above technical problems, the present invention provides a highly phase-separated polyurethane and its preparation method and application. Through the optimized design of the molecular structure, the highly phase-separated polyurethane realizes effective phase separation between the soft and hard segments of the polyurethane at the nanoscale, thereby significantly improving the mechanical properties and water resistance of the obtained polyurethane, and is suitable for waterborne coating scenarios such as metals, plastics, and woodware with high requirements for coating performance.

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

[0008] In a first aspect, the present invention provides a highly phase-separated polyurethane. The raw materials for preparing the highly phase-separated polyurethane include a hydrophilic 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 epoxide compound;

[0010] The ring-opening initiator includes a dihydroxycarboxylic acid and / or a dihydroxy sulfonate.

[0011] The present invention optimizes the raw materials for preparing the highly phase-separated polyurethane. By preferentially using a ring-opening initiator and an epoxide compound as raw materials, a hydroxyl-terminated hydrophilic modified polyether polyol with hydrophilic side groups is prepared. Further, the hydrophilic modified polyether polyol is combined with an isocyanate monomer, a catalyst, and a chain extender to synthesize a polyurethane with an optimized structure. After film formation, it forms a highly microphase-separated structure, showing excellent mechanical properties and water resistance, and is suitable for waterborne coating scenarios such as metals, plastics, and woodware with high requirements for coating properties.

[0012] The present invention adopts a specific hydrophilic modified polyether polyol, skillfully introducing hydrophilic groups into the flexible soft segment, avoiding interference with the hydrogen bond interaction between hard segments, and effectively improving the aggregation degree and phase region order of hard segments. After adopting the above molecular design, the obtained polyurethane material shows a more significant hard and soft segment phase separation structure: the hard segments are more closely aggregated, and the microphase interface is clearer; the soft segment has both flexibility and water dispersibility, which helps to improve the mechanical properties and water resistance of the obtained polyurethane.

[0013] The present invention adopts a structure reconstruction strategy, optimizes the combination of the raw material components of the polyurethane, and avoids the interference of hydrophilic groups with the hydrogen bond interaction between hard segments without sacrificing water dispersibility, thereby improving the microphase separation degree and comprehensive performance of the obtained polyurethane. It well solves the technical problems in the prior art that the microphase interface is blurred and the phase separation degree is reduced due to the introduction of a hydrophilic chain extender, ultimately affecting the mechanical properties, water resistance, and environmental stability of the obtained polyurethane.

[0014] The following are the preferred technical solutions of the present invention, but do not limit the technical solutions provided by the present invention. Through the following preferred technical solutions, the purpose 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 parts of the ring-opening initiator are 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 the specific point values between the above point values. Limited by space and for the sake of simplicity, the present invention does not exhaustively list the specific point values included in the range, and is further preferably 4-8 parts.

[0016] In the present invention, by optimizing the weight parts of the ring-opening initiator, while ensuring the water dispersibility of the polyurethane, a good microphase separation structure can be maintained, and the mechanical properties and water resistance of the coating film can be improved. When its content is too low, the hydrophilicity of the system is insufficient, the emulsion stability becomes poor, and problems such as difficult emulsification, incomplete dispersion or film-forming defects are likely to occur. When its content is too high, the molecular chain length of the polyether polyol decreases significantly, the flexible chain segment of the main chain shortens, the microphase structure becomes blurred, and it is difficult to form an effective hydrogen bond network, resulting in a decrease in the degree of microphase separation and mechanical properties of the polyurethane, and a significant increase in the water absorption rate of the coating film due to the too high density of polar groups.

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

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

[0019] Preferably, the weight parts of the epoxy compound are 60-130 parts, for example, it can be 60 parts, 70 parts, 80 parts, 90 parts, 100 parts, 110 parts, 120 parts or 130 parts, as well as the specific point values between the above point values. Limited by space and for the sake of simplicity, the present invention does not exhaustively list the specific point values included in the range.

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

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

[0022] Preferably, the weight parts of the basic catalyst are 1-3 parts, for example, it can be 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 the specific point values between the above point values. Limited by space and for the sake of simplicity, the present invention does not exhaustively list the specific point values included in the range.

[0023] Preferably, the basic catalyst comprises a basic alcohol solution with a mass percentage of 5-20%. Herein, 5-20% can be, for example, 5%, 8%, 10%, 12%, 14%, 16%, 18% or 20%, as well as specific point values between the above point values. Due to space limitations and for the sake of brevity, the specific point values included in this range are not exhaustively listed in the present invention.

[0024] Preferably, the basic alcohol solution comprises a NaOH alcohol solution and / or a KOH alcohol solution.

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

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

[0027] Preferably, the weight parts of the small molecule alcohol are 1-3.5 parts. Herein, 1-3.5 parts can be, for example, 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 brevity, the specific point values included in this range are not exhaustively listed in the present invention.

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

[0029] Preferably, the weight parts of the acidic catalyst are 0.1-0.5 parts. Herein, 0.1-0.5 parts can be, for example, 0.1 part, 0.15 part, 0.2 part, 0.25 part, 0.3 part, 0.35 part, 0.4 part, 0.45 part or 0.5 part, as well as specific point values between the above point values. Due to space limitations and for the sake of brevity, the specific point values included in this range are not exhaustively listed in the present invention.

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

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

[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 exemplarily prepared by the following method, and the method comprises the following steps:

[0033] (a)Mix the ring-opening initiator dihydroxycarboxylic acid, small molecule alcohol, acidic catalyst and solvent A, add them into a four-necked flask equipped with a reflux condenser and a water separator, slowly heat up to 100 - 120 °C, and carry out dehydration esterification reaction under heating reflux conditions for 3 - 4 h until the water in the water separator tends to be stable to obtain an esterification intermediate.

[0034] (b)Cool the system of the esterification intermediate obtained in step (a) to 40 - 50 °C, add a basic catalyst and an epoxide, then heat up to 85 - 95 °C, pressurize to 0.3 - 0.6 Mpa and carry out ring-opening addition reaction for 2 - 3 h. After the reaction is completed, remove the solvent by rotary evaporation to obtain a modified polyether polyol with an ester group-protected hydrophilic group in the main chain.

[0035] (c)Add water to the modified polyether polyol obtained in (b), adjust the pH to 8 - 10 with a basic regulator, carry out hydrolysis reaction at 50 - 60 °C for 1 - 2 h, then add an acidic regulator to adjust the pH to 7, remove water and small molecule alcohol under vacuum, and filter to remove inorganic substances to obtain the hydrophilic modified polyether polyol.

[0036] Preferably, the solvent A in step (a) includes ether solvents.

[0037] Preferably, the weight parts of the solvent A in step (a) are 30 - 60 parts, for example, it can be 30 parts, 35 parts, 40 parts, 45 parts, 50 parts, 55 parts or 60 parts, and the specific point values between the above point values. Due to space limitations and for the sake of simplicity, the present invention does not exhaustively list the specific point values included in the range.

[0038] It should be noted that the types of the ether solvents are not particularly limited, and ether solvents in the art are all used, including but not limited to diglycol methyl ether, diglycol ethyl ether, ethylene glycol monomethyl ether, etc.

[0039] Preferably, the weight parts of the water in step (c) are 45 - 85 parts, for example, it can be 45 parts, 50 parts, 55 parts, 60 parts, 65 parts, 70 parts, 75 parts, 80 parts or 85 parts, and the specific point values between the above point values. Due to space limitations and for the sake of simplicity, the present invention does not exhaustively list the specific point values included in the range.

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

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

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

[0043] Mix the ring-opening initiator dihydroxy sulfonate with solvent B, add a basic catalyst and an epoxide, and then raise the temperature to 85-95 °C and pressurize to 0.3-0.6 Mpa for a ring-opening addition reaction for 2-3 h. After the reaction is completed, the solvent is removed by rotary evaporation to obtain the hydrophilic modified polyether polyol.

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

[0045] Preferably, the weight parts of the solvent B are 30-60 parts, for example, it can be 30 parts, 35 parts, 40 parts, 45 parts, 50 parts, 55 parts or 60 parts, as well as the specific point values between the above point values. Due to space limitations and for the sake of brevity, the present invention does not exhaustively list the specific point values included in the range.

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

[0047] It should be noted that in the present invention, the isocyanate monomer is a diisocyanate, and there is no special limitation on the selection of the type of diisocyanate. Commonly used isophorone diisocyanate (IPDI), hexamethylene diisocyanate (HDI), diphenylmethane diisocyanate (MDI), toluene diisocyanate (TDI), tetramethylxylylene diisocyanate (TMXDI), etc. in the art are all applicable.

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

[0049] Preferably, the organometallic catalyst comprises organic bismuth and / or organic tin.

[0050] It should be noted that in the present invention, there is no special limitation on the selection of the type of organic bismuth and organic tin, and commonly used organic bismuth and / or organic tin in the art are all applicable. For example, organic bismuth can be selected from bismuth isooctanoate, bismuth laurate, bismuth neodecanoate, bismuth naphthenate, etc.; organic tin can be selected from dibutyltin dilaurate (DBTDL), stannous octoate, dibutyltin diacetate, bis(dodecylthio)dibutyltin, etc.

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

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

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

[0054] Preferably, the water includes 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] Hydrophilic modified polyether polyol: 30 - 55 parts;

[0057] Isocyanate monomer: 18 - 26 parts;

[0058] Chain extender: 3 - 8 parts;

[0059] Catalyst: 0.1 - 0.5 parts;

[0060] Water: 100 - 150 parts.

[0061] In the raw materials for preparing the highly phase-separated polyurethane of the present invention, the weight parts 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 parts 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 parts 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, 7.5 parts or 8 parts; the weight parts of the catalyst can be 0.1 part, 0.15 part, 0.2 part, 0.25 part, 0.3 part, 0.35 part, 0.4 part, 0.45 part or 0.5 part; 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 the specific point values between the above point values. Due to space limitations and for the sake of simplicity, the present invention does not exhaustively list the specific point values included in the above range.

[0062] As a preferred technical solution of the present invention, the weight parts of the hydrophilic modified polyether polyol are 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 the specific point values between the above point values. Due to space limitations and for the sake of simplicity, the present invention does not exhaustively list the specific point values included in the above range.

[0063] By optimizing the weight fraction of the hydrophilic modified polyether polyol, the present invention can obtain a highly phase-separated polyurethane with better comprehensive properties such as mechanical properties and water resistance. When the dosage of the hydrophilic modified polyether polyol is relatively high, the proportion of flexible soft segments in the system increases, which helps to enhance the flexibility of the polyurethane segments, thereby improving the elongation at break of the material. However, the increase in the proportion of soft segments also dilutes the hard segment content, weakens the hydrogen bond interaction between polyurethane chains, and leads to a decrease in the degree of microphase separation, manifested as a decrease in the hydrogen bond index (HBI) and tensile strength. At the same time, the increase in the total amount of hydrophilic polyether also brings an increase in the total amount of hydrophilic groups, resulting in an increase in the water absorption rate. On the contrary, when the dosage of the hydrophilic modified polyether polyol is relatively low, the proportion of hard segments in the system increases, which is beneficial to the formation of denser hydrogen bond aggregates, thereby enhancing the microphase separation structure and increasing the tensile strength, and the HBI increases. However, due to the insufficient flexible segments, the overall flexibility of the segments decreases, resulting in a decrease in the elongation at break. In addition, the absolute amount of hydrophilic groups decreases, which can reduce the water absorption rate of the material and improve the denseness and environmental stability of the coating film 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, and the preparation method includes the following steps:

[0065] Mix the hydrophilic modified polyether polyol, isocyanate monomer and catalyst and react to obtain a prepolymer; after adding a chain extender to the prepolymer for chain extension reaction, add optional water to obtain the highly phase-separated polyurethane.

[0066] Preferably, the temperature of the reaction 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 the specific point values between the above point values. Due to space limitations and for the sake of brevity, the present invention does not exhaustively list the specific point values included in the above range.

[0067] Preferably, the reaction time is 2-3 h, for example, it can be 2 h, 2.2 h, 2.4 h, 2.6 h, 2.8 h or 3 h, as well as the specific point values between the above point values. Due to space limitations and for the sake of brevity, the present invention does not exhaustively list the specific point values included in the above range.

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

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

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

[0071] Preferably, the cooling treatment is to cool down 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 the specific point values between the above point values. Due to space limitations and for the sake of simplicity, the present invention does not exhaustively list the specific point values included in the said range.

[0072] Preferably, the time of the chain extension reaction is 1 - 2 h, for example, it can be 1 h, 1.2 h, 1.4 h, 1.6 h, 1.8 h or 2 h, as well as the specific point values between the above point values. Due to space limitations and for the sake of simplicity, the present invention does not exhaustively list the specific point values included in the said range.

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

[0074] (1) Mix the hydrophilic modified polyether polyol, isocyanate monomer and solvent, put them into a four - necked flask, protect with nitrogen and heat up to 75 - 85 °C, add an organometallic catalyst, and react for 2 - 3 h to obtain a prepolymer.

[0075] (2) Cool the system of the prepolymer obtained in step (1) to 60 - 65 °C, add a chain extender for chain extension, and the reaction time is 1 - 2 h.

[0076] (3) Slowly add deionized water for emulsification under high - speed stirring to obtain the highly phase - separated polyurethane.

[0077] Through the above - mentioned preparation method, the present invention anchors the ring - opening initiator to the flexible polyether side chain, so that the polar distribution is more uniform and the microphase structure is more stable, and further makes 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 requirements of the 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 the specific point values between the above point values. Due to space limitations and for the sake of simplicity, the present invention does not exhaustively list the specific point values included in the said range.

[0080] In the third aspect, the present invention provides an application of the highly phase - separated polyurethane as described in the first aspect in an aqueous 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 preparing highly phase-separated polyurethane. By preferentially using ring-opening initiators and epoxides as raw materials, a hydrophilic modified polyether polyol with hydrophilic side groups and hydroxyl-terminated is prepared. Further, the hydrophilic modified polyether polyol is combined with isocyanate monomers, catalysts, and chain extenders to synthesize a polyurethane with an optimized structure, which forms a highly microphase-separated structure after film formation, exhibits excellent mechanical properties and water resistance, and is suitable for water-based coating scenarios such as metals, plastics, and woodware with high requirements for coating performance.

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

[0084] To facilitate the understanding of the present invention, the following examples are listed. Those skilled in the art should understand that the examples are only for helping to understand the present invention and should not be regarded as specific limitations on the present invention.

[0085] Unless otherwise specified, the raw materials and reagents used in the following preparation examples, 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, and the raw materials for preparing the hydrophilic modified polyether polyol include the components in the weight parts shown in Table 1.

[0089] Table 1

[0090]

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

[0092] (a) Mix 2,2-dimethylolpropionic acid (DMPA), methanol, p-toluenesulfonic acid with 45 parts of diethylene glycol methyl ether, add them into a four-necked flask equipped with a reflux condenser and a water separator, slowly heat up to 110 °C, and carry out dehydration esterification reaction under heating and reflux conditions for 3.5 h until the water in the water separator tends to be stable to obtain an esterification intermediate.

[0093] (b) Cool the system of the esterification intermediate described in step (a) to 45 °C, add a basic catalyst and propylene oxide, then heat up to 90 °C and pressurize to 0.5 Mpa for ring-opening addition reaction for 2.5 h. After the reaction is completed, remove the solvent by rotary evaporation to obtain a modified polyether polyol with an ester group-protected hydrophilic group in the main chain.

[0094] (c) Add 60 parts of deionized water to the modified polyether polyol described in (b), adjust the pH to 9 with 0.1 M NaOH solution, 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 molecule alcohols under vacuum, and filter to remove inorganic substances to obtain the hydrophilic modified polyether polyol 1.

[0095] Preparation Example 2

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

[0097] Table 2

[0098]

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

[0100] (a) Mix 2,2-dimethylolbutyric acid (DMBA), butanol, formic acid with 32 parts of diethylene glycol methyl ether, add them to a four-necked flask equipped with a reflux condenser and a water separator, slowly heat up to 100 °C, and carry out dehydration esterification reaction under heating reflux for 3 h until the water in the water separator tends to be stable to obtain an esterification intermediate.

[0101] (b) Cool the system of the esterification intermediate described in step (a) to 40 °C, add a basic catalyst and glycidol, then heat up to 85 °C and pressurize to 0.5 Mpa for ring-opening addition reaction for 2 h. After the reaction is completed, remove the solvent by rotary evaporation to obtain a modified polyether polyol 2 with an ester group-protected hydrophilic group in the main chain.

[0102] (c) Add 45 parts of deionized water to the modified polyether polyol described in (b), adjust the pH to 8 with 0.1 M NaOH solution, react at 50 °C for 1 h, add 0.1 M HCl solution to adjust the pH to 7, remove water and small molecule alcohols under vacuum, and filter to remove inorganic substances to obtain the hydrophilic modified polyether polyol.

[0103] Preparation Example 3

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

[0105] Table 3

[0106]

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

[0108] (a) Mix 2,2-dimethylolpropionic acid (DMPA), ethanol, benzenesulfonic acid with 60 parts of diethylene glycol methyl ether, add them into a four-necked flask equipped with a reflux condenser and a water separator, slowly heat up to 120 °C, and carry out dehydration esterification reaction under heating reflux conditions for 4 h until the water in the water separator tends to be stable to obtain an esterification intermediate.

[0109] (b) Cool the system of the esterification intermediate obtained in step (a) to 50 °C, add a basic catalyst and epoxy butane, then heat up to 95 °C and pressurize to 0.5 Mpa for ring-opening addition reaction for 3 h. After the reaction is completed, remove the solvent by rotary evaporation to obtain a modified polyether polyol with an ester group-protected hydrophilic group in the main chain.

[0110] (c) Add 82 parts of deionized water to the modified polyether polyol obtained in (b), add 0.1 M NaOH solution to adjust the pH to 10, react at 60 °C for 2 h, then add 0.1 M HCl solution to adjust the pH to 7, remove water and small molecular alcohols under vacuum, and filter to remove inorganic substances to obtain the hydrophilic modified polyether polyol 3.

[0111] Preparation Example 4

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

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

[0114] Mix the dihydroxy sulfonate with 45 parts of diethylene glycol methyl ether, add a basic catalyst and propylene oxide, then heat up to 90 °C and pressurize to 0.5 Mpa for ring-opening addition reaction for 2.5 h. After the reaction is completed, remove the solvent by rotary evaporation to obtain the hydrophilic modified polyether polyol 4.

[0115] Preparation Example 5

[0116] This preparation example provides a hydrophilic modified polyether polyol 5, the difference from Preparation Example 1 being only that the weight fraction of 2,2-dimethylolpropionic 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 of Preparation Example 1.

[0117] Preparation Example 6

[0118] This preparation example provides a hydrophilic modified polyether polyol 6, the difference from Preparation Example 1 being only that the weight fraction of 2,2-dimethylolpropionic 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 of Preparation Example 1.

[0119] Preparation Example 7

[0120] This preparation example provides a hydrophilic modified polyether polyol 7, the difference from Preparation Example 1 being only that the weight fraction of 2,2-dimethylolpropionic 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 of Preparation Example 1.

[0121] Example 1

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

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

[0124] Isophorone diisocyanate (IPDI) 20 parts;

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

[0126] Dibutyltin dilaurate (DBTDL) 0.2 part;

[0127] Deionized water 130 parts.

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

[0129] (1) Mix hydrophilic modified polyether polyol 1 (Preparation Example 1), IPDI and diethylene glycol methyl ether, put them into a four-necked flask, protect with nitrogen and heat up to 80 °C, add the catalyst DBTDL, and react for 2.5 h to obtain a prepolymer.

[0130] (2) Cool the system of the prepolymer obtained in step (1) to 63 °C, add the chain extender BDO for chain extension, and the reaction time is 1.5 h.

[0131] (3) Slowly add deionized water for emulsification under stirring at 1000 rpm to obtain the highly phase-separated polyurethane.

[0132] Example 2

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

[0134] Hydrophilic modified polyether polyol 2 (Preparation Example 2): 30 parts;

[0135] Hexamethylene diisocyanate (HDI): 18 parts;

[0136] Chain extender ethylene glycol (EDO): 3 parts;

[0137] Bismuth neodecanoate: 0.1 part;

[0138] Deionized water: 100 parts.

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

[0140] (1) Mix hydrophilic modified polyether polyol 2 (Preparation Example 2), HDI and diethylene glycol methyl ether, put them into a four-necked flask, protect with nitrogen and heat to 75 °C, add the catalyst bismuth neodecanoate, and react for 2 h to obtain a prepolymer.

[0141] (2) Cool the prepolymer system obtained in step (1) to 60 °C, add the chain extender EDO for chain extension, and the reaction time is 1 h.

[0142] (3) Slowly add deionized water for emulsification under stirring at 1000 rpm to obtain the highly phase-separated polyurethane.

[0143] Example 3

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

[0145] Hydrophilic modified polyether polyol 3 (Preparation Example 3): 50 parts;

[0146] Diphenylmethane diisocyanate (MDI): 26 parts;

[0147] Chain extender 1,6-hexanediol (HDO): 6 parts;

[0148] Stannous octoate: 0.5 part;

[0149] Deionized water: 150 parts.

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

[0151] (1) Mix hydrophilic modified polyether polyol (Preparation Example 3), MDI and diethylene glycol methyl ether, put them into a four-necked flask, protect with nitrogen and heat to 85 °C, add the catalyst stannous octoate, and react for 3 h to obtain a prepolymer.

[0152] (2) Cool down the system of the prepolymer described in step (1) to 65 °C, add chain extender HDO for chain extension, and the reaction time is 2 h.

[0153] (3) Slowly add deionized water for emulsification under stirring at 1000 rpm to obtain the highly phase-separated polyurethane.

[0154] Example 4

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

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

[0157] Toluene diisocyanate (TDI) 22 parts;

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

[0159] Dibutyltin dilaurate (DBTDL) 0.2 part;

[0160] Deionized water 130 parts.

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

[0162] Example 5

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

[0164] Example 6

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

[0166] Example 7

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

[0168] Example 8

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

[0170] Example 9

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

[0172] Example 10

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

[0174] Example 11

[0175] This example provides a highly phase-separated polyurethane, which is only different from Example 1 in that the weight fraction of the hydrophilic modified polyether polyol 1 (Preparation Example 1) is adjusted from 40 parts to 50 parts, and 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, and the preparation raw materials of the polyurethane include the following components in parts by weight:

[0178] Polyether polyol PPG 1000 40 parts;

[0179] Isocyanate monomer IPDI 20 parts;

[0180] Hydrophilic chain extender DMPA 2.4 parts;

[0181] Chain extender BDO 0.6 parts;

[0182] Catalyst DBTDL 0.2 parts;

[0183] Deionized water 130 parts.

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

[0185] (1) Mix polyether polyol PPG 1000, isocyanate monomer IPDI and diethylene glycol methyl ether, put them into a four-necked flask, protect with nitrogen and heat up to 80 °C, add catalyst DBTDL, and react 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) Cool the system described in step (2) to 63 °C, add the chain extender BDO for chain extension, and the reaction time is 1.5 h.

[0188] (4) Slowly add deionized water for emulsification under stirring at 1000 rpm to obtain the polyurethane.

[0189] Drop the polyurethane emulsions obtained in Examples 1-11 and Comparative Example 1 into the cleaned glassware, control the thickness to be about 1 mm, and form a uniform film at 25 °C, then conduct performance tests. 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 in the ester carbonyl absorption region of the aqueous polyurethane film are deconvoluted by the Gaussian method, and the hydrogen bond index (HBI) is calculated according to the absorption peak areas of free carbonyl, disordered hydrogen-bonded carbonyl, and ordered hydrogen-bonded carbonyl. The larger the HBI value, the higher the degree of hydrogen bonding and the higher the microphase separation degree.

[0192]

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

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

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

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

[0197] Table 4

[0198]

[0199] It can be seen from the test results that:

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

[0201] (2)It can be seen from the comparison between Example 1 and Examples 5 - 7 that the content of the ring-opening initiator used in the preparation raw materials of 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 chain segments of the main chain, making it difficult to form a continuous phase region in the polyurethane. At the same time, the hydrophilic groups are excessively accumulated, interfering with the formation of hydrogen bonds between the hard segments, resulting in a decrease in the microphase separation degree of the obtained polyurethane, a weakening of the tensile strength, and a significant increase in the water absorption rate. This shows that by designing and optimizing the preparation raw materials of the hydrophilic modified polyether polyol, the present invention can further improve the microphase structure orderliness and comprehensive application performance of the obtained polyurethane while ensuring the water dispersibility of the polyurethane.

[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 increases, the hydrogen bond interaction is enhanced, the HBI increases, the tensile strength rises, but the flexible chain segments decrease, and the elongation at break decreases significantly. At the same time, due to the decrease in the total amount of hydrophilic groups, the water absorption rate decreases slightly. In Example 11, the weight fraction of the hydrophilic modified polyether polyol is higher, resulting in an increase in the proportion of flexible chain segments, which helps to enhance the chain segment flexibility and further improve the elongation at break. However, at the same time, it dilutes the proportion of hard segments, weakens the hydrogen bond aggregation, resulting in a decrease in the hydrogen bond index (HBI) and tensile strength, and 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 a polyurethane with better comprehensive properties such as phase separation effect, mechanical properties, and water resistance.

[0203] (4)It can be seen from Example 1 and Comparative Example 1 that in Comparative Example 1, while keeping the content of the hydrophilic chain extender DMPA and the ratio of the hard segment to the soft segment unchanged, DMPA was directly introduced into the main chain of the hard segment by the traditional preparation method, resulting in a competitive hydrogen bond interaction between the hydrophilic group and the N-H in the urethane, which destroyed the aggregation of the hard segment and significantly decreased the degree of microphase separation (HBI decreased to 0.65). The hard segment could not effectively aggregate and was dispersed in the soft segment, causing physical interference to the flexible chain segment and reducing the elongation at break to 440%; at the same time, the polar structure of the hard segment was locally enriched, which was prone to form water adsorption points and increased the water absorption rate to 7.8%. In contrast, in Example 1, DMPA was anchored on the flexible polyether side chain, with a more uniform polar distribution and a more stable microphase structure, thus having better mechanical properties and water resistance.

[0204] In summary, the present invention first prepared a hydroxyl-terminated hydrophilic modified polyether polyol with hydrophilic side groups by using a ring-opening initiator and an epoxide compound. Further, the hydrophilic modified polyether polyol was combined with a polyurethane, a catalyst, and a chain extender to form a highly phase-separated polyurethane with a highly microphase-separated structure, which has excellent mechanical properties and water resistance and is suitable for waterborne coating scenarios such as metals, plastics, and woodware with high requirements for coating performance.

[0205] The above are only specific embodiments 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 the 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 a hydrophilic modified polyether polyol, an isocyanate monomer, a catalyst, and a chain extender; The raw materials for preparing the hydrophilic modified polyether polyol include a ring-opening initiator and an epoxide compound; The ring-opening initiator includes a dihydroxy carboxylic acid and / or a dihydroxy sulfonate.

2. The height-separated polyurethane according to claim 1, wherein The weight parts of the ring-opening initiator are 4-10 parts; The weight parts of the epoxide compound are 60-130 parts; The epoxide compound includes any one or a combination of at least two of ethylene oxide, propylene oxide, butylene oxide, or glycidol.

3. The height-separated polyurethane according to claim 2, characterized in that, When the ring-opening initiator is a dihydroxy carboxylic acid, the raw materials for preparing the hydrophilic modified polyether polyol further include a small molecule alcohol, an acidic catalyst, and a basic catalyst; The weight parts of the small molecule alcohol are 1-3.5 parts; The weight parts of the acidic catalyst are 0.1-0.5 parts; The weight parts of the basic catalyst are 1-3 parts.

4. The height-separated polyurethane according to claim 1, wherein The catalyst includes an organometallic catalyst.

5. The height-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 or a combination of at least two of ethylene glycol, 1,4-butanediol, or 1,6-hexanediol.

6. The height-separated polyurethane according to claim 1, wherein The raw materials for preparing the highly phase-separated polyurethane include the following components in weight parts: Hydrophilic modified polyether polyol 30-55 parts; Isocyanate monomer 18-26 parts; Chain extender 3-8 parts; Catalyst 0.1-0.5 parts; Water 100-150 parts.

7. The height-separated polyurethane according to claim 6, wherein The weight parts of the hydrophilic modified polyether polyol are 35-45 parts.

8. A method for preparing a polyurethane with highly separated heights according to any one of claims 1-7, characterized in that, The preparation method includes the following steps: Mix the hydrophilic modified polyether polyol, the isocyanate monomer, and the catalyst and react to obtain a prepolymer; after adding the chain extender to the prepolymer for chain extension reaction, add optional water to obtain the highly phase-separated polyurethane.

9. The preparation method of the height-separated polyurethane according to claim 8, characterized in that, The temperature of the reaction is 75-85 °C; The time of the reaction is 2-3 h; The system of the prepolymer needs to be cooled before adding the chain extender; The cooling treatment is to cool down to 60-65 °C; The time of the chain extension reaction is 1-2 h.

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

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