Preparation method of copolyester diol and waterborne polyurethane thereof

Abstract

The invention relates to the technical field of high polymer materials, in particular to a preparation method of copolyester diol and waterborne polyurethane thereof, which comprises the following steps: by taking aliphatic diol and aliphatic dicarboxylic acid as main bodies, adding one or more of aromatic dibasic acid and alicyclic diol to prepare a polyester diol compound; and the waterborne polyurethane is further prepared from the waterborne polyurethane. According to the waterborne polyurethane prepared by the method disclosed by the invention, after the soft segment is copolymerized and modified by the raw material with the cyclic structure, the glass-transition temperature is obviously increased, the thermal stability of a chain structure is improved, good heat resistance is shown, the tensile strength is obviously increased, and the mechanical property of the material is excellent.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, and in particular to a method for preparing a copolyester diol and its waterborne polyurethane. Background Technology

[0002] With increasing environmental regulations and public awareness, low-odor, environmentally friendly, and pollution-free waterborne polyurethanes are widely used as a replacement for solvent-based polyurethanes. However, waterborne polyurethanes typically require the introduction of sufficient hydrophilic groups into their molecular backbone to ensure good dispersibility in water. This can lead to a decrease in the mechanical properties, water resistance, corrosion resistance, and heat resistance of waterborne polyurethanes, limiting their applications. Adjusting the chemical structure and composition of waterborne polyurethanes can improve their heat resistance. Current research on the heat resistance of waterborne polyurethane materials is ongoing. Most studies on improving the heat resistance of waterborne polyurethanes focus on two modification methods: adjusting the hard segment structure of the polyurethane and copolymerizing with other monomers or polymers with good heat resistance.

[0003] The current improvement plan still has some problems: Decreased material flexibility, while increasing the hard segment content or introducing rigid groups can improve heat resistance, often reduces the material's flexibility; thus limiting its application in some scenarios that require both heat resistance and a certain degree of flexibility, such as in some sealing materials or flexible electronic devices that require dynamic stretching. Copolymerization is difficult to control, and achieving homogeneous copolymerization of two or more monomers or polymers is not easy. Different monomers or polymers may have different reactivity, which can easily lead to non-uniform composition and structure of the copolymer, affecting the stability and repeatability of heat resistance. For example, in free radical copolymerization, different reactivity ratios of monomers may lead to non-uniform distribution of monomer units in the polymer chain.

[0004] Compatibility is a crucial factor. Good compatibility between copolymerized monomers or polymers is essential; otherwise, phase separation can occur, reducing the overall performance of the material. Even if a homogeneous copolymer is formed during copolymerization, changes in environmental factors such as temperature and humidity can still trigger phase separation during material use. For example, when certain polyester-based polyurethanes are copolymerized with polyimide, the significant difference in polarity between the two can lead to phase separation at high temperatures, affecting the material's heat resistance and mechanical properties.

[0005] The challenge lies in balancing performance. Introducing other monomers or polymers, while improving heat resistance, may adversely affect other properties of waterborne polyurethanes, such as water resistance, air permeability, and adhesion. Significant time and effort are required for formulation optimization to find a balance between these various properties. For example, the introduction of certain heat-resistant monomers may reduce the hydrophilicity of waterborne polyurethanes, worsening their dispersibility in water and affecting the performance of products such as coatings or adhesives.

[0006] The market urgently needs a solution to improve the heat resistance of waterborne polyurethane by rationally designing and adjusting the structure of the soft segments. Summary of the Invention

[0007] The present invention aims to at least solve one of the technical problems existing in the related art. To this end, the present invention provides a method for preparing a copolyester diol and its aqueous polyurethane.

[0008] The first implementation plan is as follows: A method for preparing a copolyester diol, The copolyester diol is prepared from monomers containing the following components through esterification and polycondensation reactions. At least one aliphatic diol; At least one aliphatic dicarboxylic acid; At least one component selected from aromatic dicarboxylic acids and / or diols containing ester rings; The esterification reaction involves heating the monomer to a preset acid value under the action of a catalyst and under the protection of an inert gas to obtain the esterified product. The polycondensation reaction is carried out by polycondensing the esterified product under vacuum conditions until a predetermined molecular weight is reached, thereby obtaining a copolyester diol.

[0009] Furthermore, the molecular formula of the aliphatic diol is: HO-(CH 2 ) n -OH n = at least one of 2, 3, 4, 5, 6; The molecular formula of the aliphatic dicarboxylic acid is: HOOC-(CH 2 ) n -COOH at least one of n = 6 to 16; The aromatic dicarboxylic acid is one or more selected from phthalic acid, isophthalic acid, terephthalic acid, 1,4-cyclohexanedicarboxylic acid and 2,5-furandicarboxylic acid; The ester-containing diol is one or more of 1,4-cyclohexanediol, spirocyclodiol, isosorbide, and cyclohexanediol; The alcohol-acid ratio of the monomer is 1.2 to 1.4.

[0010] Furthermore, the esterification reaction is carried out at a temperature of 140–250 °C, and the preset acid value is 20–30 mg KOH / g. The reaction temperature of the polycondensation reaction is 240-250 °C, the vacuum degree is controlled at 700-1500 Pa, and the preset molecular weight is 800-2000.

[0011] Furthermore, the catalyst is selected from one or more of antimony trioxide, tetrabutyl titanate, and dibutyltin dilaurate, and the amount of catalyst used is 0.035% to 0.05% of the total mass of the monomers; The aliphatic diol used is 34% to 44% of the total mass of the monomers; The aliphatic dicarboxylic acid used is 26% to 49% of the total mass of the monomer; The amount of the aromatic dicarboxylic acid used is 7% to 37% of the total mass of the monomer; The amount of the ester-containing diol used is 1% to 14% of the total mass of the monomer.

[0012] A second implementation plan is also provided based on the first implementation plan: A method for preparing waterborne polyurethane, The copolyester diol and diisocyanate described in the aforementioned scheme are subjected to a prepolymerization reaction under the action of a catalyst until the content of isocyanate groups reaches the theoretical value, thereby obtaining a prepolymer. The prepolymer is chain extended using a hydrophilic chain extender. The chain-extended prepolymer was neutralized and emulsified to obtain an aqueous polyurethane emulsion. A diamine is added to the aqueous polyurethane emulsion. After the reaction consumes the residual isocyanate groups, the solvent is removed under reduced pressure to obtain the aqueous polyurethane.

[0013] Furthermore, the chain extension includes primary chain extension and secondary chain extension. The first chain extension involves adding a first chain extender to the prepolymer and reacting until the isocyanate group content reaches the theoretical value, thereby obtaining a prepolymer containing hydrophilic groups. The secondary chain extension involves adding a second chain extender to the prepolymer containing hydrophilic groups and reacting until the isocyanate group content reaches the theoretical value to obtain a chain-extended prepolymer. During the chain extension step, solvents are used to adjust the viscosity; The solvent is one or more of acetone, butanone, tetrahydrofuran, and N,N-dimethylformamide.

[0014] Furthermore, the neutralization involves adding a neutralizing agent to the secondary chain-extended prepolymer to react and obtain a neutralized prepolymer; The emulsification process involves adding the neutralized prepolymer to deionized water and shearing emulsifying it to obtain an aqueous polyurethane emulsion.

[0015] Further, the diisocyanate is one or more selected from isophorone diisocyanate, 1,6-hexane diisocyanate and diphenylmethane diisocyanate; The catalyst is one or more of antimony trioxide, tetrabutyl titanate, and dibutyltin dilaurate; The hydrophilic chain extender includes a first chain extender and a second chain extender. The first chain extender is one or more of 2,2-dimethylolpropionic acid and 2,2-dimethylolbutyric acid; The second chain extender is one or more of 1,4-butanediol, ethylene glycol, diethylene glycol, and hexanediol; The neutralizing agent is triethylamine; The diamine is ethylenediamine.

[0016] Furthermore, the amount of the polyester diol used is 43.2% to 58.3%; The amount of the diisocyanate used is 32.4% to 43.2%; The amount of catalyst used is 0.4%; The temperature of the prepolymerization reaction is 90–95 °C, the reaction time is 2–4 h, and the reaction is terminated when the isocyanate group content reaches the theoretical value. The dosage of the first chain extender is 4.3% to 6.8%; The amount of the second chain extender is 1.0% to 5.7%, and the temperature of the secondary chain extension reaction is 80 to 85 ℃; The amount of neutralizing agent used is 3.3% to 5.1%, and the neutralization reaction temperature is 45 to 55 °C. Post-treatment was carried out at room temperature, with the addition of deionized water, the solid content of the system controlled at 20%–50%, the shear rate at 400–2000 r / min, and the time at 0.5–1 h.

[0017] Furthermore, it also includes a preprocessing step. The hydrophilic chain extender was dried in an oven at 120–140 °C and then sealed for later use. Add an appropriate amount of activated molecular sieve to the solvent and seal for 48–72 h. The copolyester diol was dehydrated at 120–130 °C under reduced pressure of 700–1500 Pa.

[0018] The above-described one or more technical solutions in the embodiments of the present invention have at least one of the following technical effects: Waterborne polyurethane prepared by modification with copolyester diol exhibits good heat resistance and mechanical properties.

[0019] Modification treatment is performed on the soft segments of polyurethane to balance various mechanical properties, maintaining the elongation of the soft segments while providing high tensile strength.

[0020] While maintaining mechanical properties, a method for preparing waterborne polyurethane with higher heat resistance is provided by adjusting the soft and hard segments and the chain extension reaction.

[0021] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0023] Figure 1 This is the infrared spectrum of the polyester diol prepared in Example 1; Figure 2 The infrared spectrum of the polyester diol-modified waterborne polyurethane prepared in Example 7 is shown. Figure 3 The stress-strain diagram is shown for the aqueous polyurethane film prepared in Example 7. Figure 4 The stress-strain diagram is shown for the aqueous polyurethane film prepared in Example 8. Figure 5 The thermogravimetric analysis (TGA) results are shown for the aqueous polyurethane film prepared in Example 7. Figure 6 This is a thermogravimetric analysis (TGA) chart of the aqueous polyurethane film prepared in Example 8. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention. The following embodiments are used to illustrate this invention but should not be used to limit the scope of this invention.

[0025] The abbreviations used in this application are explained as follows: NCO: Isocyanate group.

[0026] A method for preparing copolyester diols involves preparing copolyester diol compounds by means of aliphatic diacids, aliphatic diols, aromatic diacids, and ester-containing cyclic diols under catalytic conditions.

[0027] The specific steps are as follows: (1) Esterification: One or more of aliphatic diols, aliphatic diacids, aromatic dicarboxylic acids or ester-containing diols and catalysts are added to a 250 mL four-necked flask. The reaction is carried out under argon protection and heated in an oil bath. When the acid value reaches the theoretical value, the polycondensation stage is entered. (2) Polycondensation: Control the temperature, connect the esterified product prepared in step (1) to the vacuum system, and stop the reaction after the acid value and hydroxyl value reach the theoretical value.

[0028] Polyester diol compounds are prepared by controlling the alcohol-acid ratio at 1.2–1.4 and using a catalyst with a mass fraction of 0.04%–0.05%, using one or more of aliphatic diols, aliphatic diacids, aromatic diacids, and / or ester-containing diols. The aliphatic diol has the molecular formula […]. HO-(CH 2 ) n -OH n = at least one of 2, 3, 4, 5, 6; The aliphatic dicarboxylic acid has the molecular formula... HOOC-(CH 2 ) n -COOH at least one of n = 6 to 16; The aromatic dicarboxylic acid is at least one selected from phthalic acid, isophthalic acid, terephthalic acid, 1,4-cyclohexanedicarboxylic acid, and 2,5-furandicarboxylic acid; The ester-containing cyclic diol is at least one of 1,4-cyclohexanediol, spirocyclodiol, isosorbide, and cyclohexanediol; The catalyst is at least one of antimony trioxide, tetrabutyl titanate, and dibutyltin dilaurate.

[0029] The preparation method of copolyester diol modified waterborne polyurethane involves first reacting diisocyanate with a self-made polyester diol under the action of a catalyst to obtain a prepolymer. If rod climbing occurs during the reaction, an appropriate amount of solvent is added to adjust the viscosity. Then, a hydrophilic chain extender is added to continue the reaction. Next, a small molecule chain extender is added to continue the reaction. Then, a neutralizing agent is added to neutralize the reaction. Finally, a diamine is used to consume the residual isocyanate ions to obtain copolyester diol waterborne polyurethane.

[0030] The steps are as follows: (1) Raw material processing: Dry the chain extender in an oven and seal it for later use. Put an appropriate amount of molecular sieve into the solvent used and seal it for later use. Remove the water from the polyester diol with ring structure under reduced pressure and start the reaction. (2) Preparation of prepolymer: The polyester diol containing the ring structure is added to a three-necked flask, and diisocyanate and catalyst are added dropwise. During the process, samples are taken and the isocyanate content is determined by the di-n-butylamine method. When the NCO content is lower than the theoretical value, the stage ends and the polyurethane prepolymer is obtained. (3) Chain extension 1: Add chain extender 1 to the prepolymer prepared in step (2) and react. When NCO reaches the theoretical value, control the temperature to carry out the next reaction. (4) Chain extension 2: Cool the prepolymer prepared in step (3), add chain extender 2 to react, and when NCO reaches the theoretical value, control the temperature and add neutralizer to continue the reaction; (5) Post-processing: After the reaction is completed, the reaction temperature is lowered to room temperature, deionized water is added, and shear emulsification is performed; (6) Post-chain extension: After shear emulsification, a diamine is added to consume the residual isocyanate and a modified waterborne polyurethane dispersion of a polyester diol with a cyclic structure is obtained. The diisocyanate is at least one of isophorone diisocyanate IPDI, 1,6-hexamethylene diisocyanate HDI and diphenylmethane diisocyanate MDI; The catalyst is at least one of antimony trioxide, tetrabutyl titanate, and dibutyltin dilaurate.

[0031] The chain extender 1 is at least one of 2,2-dimethylolpropionic acid and 2,2-dimethylolbutyric acid; The chain extender 2 is at least one of 1,4-butanediol, ethylene glycol, diethylene glycol monohydrate, and hexanediol. The solvent is at least one of acetone, butanone, tetrahydrofuran, and N,N-dimethylformamide; The neutralizing agent is triethylamine; The diamine is ethylenediamine; Example 1: Preparation of copolyester diol (1) Esterification: 107 g of propylene glycol, 50 g of terephthalic acid and 102 g of adipic acid were added to a 250 mL four-necked flask, and 0.1 g of catalyst was added dropwise. Under argon protection, the mixture was heated in an oil bath at 240 °C for about 8 h. During the reaction, the acid value was measured. When the acid value was 20-30 mg KOH / g, the esterification stage was completed. (2) Polycondensation: Control the temperature at 240-250 °C, connect the esterified compound prepared in step (1) to the oil pump, control the vacuum degree of the oil pump at 1500 Pa, after the reaction has been carried out for a certain time, take a sample to determine the acid value and hydroxyl value, use the terminal hydroxyl method to calculate the molecular weight, and stop the reaction when the molecular weight reaches 1000, thus obtaining the copolyester diol compound.

[0032] The obtained copolyester diol was subjected to infrared spectroscopy, and the results are as follows: Figure 1 As shown, by Figure 1 It is known that the stretching vibration of the OH group in carboxylic acids ranges from 3300 to 2500 cm. -1 The broad absorption band disappears, and the skeletal stretching vibrations of the benzene ring occur between 1600 and 1450 cm⁻¹. -1 Three spectral bands appeared, and another one appeared at 1720 cm. -1 There is a strong C=O stretching vibration of polyester at that location.

[0033] Example 2 Preparation of copolyester diol (1) Esterification: 87 g of ethylene glycol, 33 g of isophthalic acid and 117 g of octanoic acid were added to a 250 mL four-necked flask, and 0.1 g of catalyst was added dropwise. Under argon protection, the mixture was heated in an oil bath at 240 °C for about 7 h. During the reaction, the acid value was measured. When the acid value was 20-30 mg KOH / g, the esterification stage was completed. (2) Polycondensation: Control the temperature at 240-250 °C, connect the esterified compound prepared in step (1) to the oil pump, control the vacuum degree of the oil pump at 700 Pa, after the reaction has been carried out for a certain period of time, take a sample to determine the acid value and hydroxyl value, calculate the molecular weight using the terminal hydroxyl method, and stop the reaction when the molecular weight reaches 1800, thus obtaining the copolyester diol compound.

[0034] Example 3 Preparation of copolyester diol (1) Esterification: 101 g of butanediol, 41 g of isosorbide, 83 g of terephthalic acid and 73 g of adipic acid were added to a 250 mL four-necked flask, and 0.1 g of catalyst was added dropwise. The mixture was heated in an oil bath at 240 °C under argon protection for about 8 h. During the reaction, the acid value was measured. When the acid value was 20-30 mg KOH / g, the esterification stage was completed. (2) Polycondensation: Control the temperature at 240-250 °C, connect the esterified compound prepared in step (1) to the oil pump, control the vacuum degree of the oil pump at 1400 Pa, after a certain reaction time, take a sample to determine the acid value and hydroxyl value, calculate the molecular weight using the terminal hydroxyl method, and stop the reaction when the molecular weight reaches 900, thus obtaining the copolyester diol compound.

[0035] Example 4 Preparation of copolyester diol (1) Esterification: 87 g of ethylene glycol, 69 g of 1,4-cyclohexanedicarboxylic acid and 88 g of adipic acid were added to a 250 mL four-necked flask, and 0.1 g of catalyst was added dropwise. Under argon protection, the mixture was heated in an oil bath at 250 °C for about 6 h. During the reaction, the acid value was measured. When the acid value was 20-30 mg KOH / g, the esterification stage was completed. (2) Polycondensation: Control the temperature at 240-250 °C, connect the esterified compound prepared in step (1) to the oil pump, control the vacuum degree of the oil pump at 1200 Pa, after a certain reaction time, take a sample to determine the acid value and hydroxyl value, calculate the molecular weight using the terminal hydroxyl method, and stop the reaction when the molecular weight reaches 1200, thus obtaining the copolyester diol compound.

[0036] Example 5 Preparation of copolyester diol (1) Esterification: 87 g of ethylene glycol, 94 g of 2,5-furandicarboxylic acid and 75 g of azelaic acid were added to a 250 mL four-necked flask, and 0.1 g of catalyst was added dropwise. Under argon protection, the mixture was heated in an oil bath at 200 °C for about 7 h. During the reaction, the acid value was measured. When the acid value was 20-30 mg KOH / g, the esterification stage was completed. (2) Polycondensation: Control the temperature at 240-250 °C, connect the esterified compound prepared in step (1) to the oil pump, control the vacuum degree of the oil pump at 1350 Pa, after the reaction has been carried out for a certain period of time, take a sample to determine the acid value and hydroxyl value, calculate the molecular weight using the terminal hydroxyl method, and stop the reaction when the molecular weight reaches 900, thus obtaining the copolyester diol compound.

[0037] Example 6 Preparation of copolyester diol (1) Esterification: 125 g of butanediol, 2 g of isosorbide, 83 g of terephthalic acid and 73 g of adipic acid were added to a 250 mL four-necked flask, and 0.1 g of catalyst was added dropwise. The mixture was heated in an oil bath at 240 °C under argon protection for about 8 h. During the reaction, the acid value was measured. When the acid value was 20-30 mg KOH / g, the esterification stage was completed. (2) Polycondensation: Control the temperature at 240-250 °C, connect the esterified compound prepared in step (1) to the oil pump, control the vacuum degree of the oil pump at 1400 Pa, after a certain reaction time, take a sample to determine the acid value and hydroxyl value, calculate the molecular weight using the terminal hydroxyl method, and stop the reaction when the molecular weight reaches 900, thus obtaining the copolyester diol compound.

[0038] Example 7 Preparation of copolyester diol waterborne polyurethane (1) Raw material processing: The chain extender was dried in an oven at 120-140 °C and sealed for later use. An appropriate amount of activated molecular sieve was added to the solvent and sealed for 48 h for later use. The cyclic polyester diol prepared in Example 1 was reacted after removing water at 120-130 °C under reduced pressure of 1500 Pa. (2) Preparation of prepolymer: 60.0 g of copolyester diol was added to a 500 mL three-necked flask, and 33.3 g of isophorone diisocyanate and 0.4 g of dibutyltin dilaurate were added dropwise to raise the temperature to 90-95 °C. The reaction was carried out for 2 h, and the reaction was stopped when NCO reached the theoretical value to obtain the prepolymer. (3) Chain extension 1: Add 4.7 g of 2,2-dihydroxymethylpropionic acid to the prepolymer prepared in step (2) and react for 2 h. When NCO reaches the theoretical value, control the temperature to carry out the next step of reaction. (4) Chain extension 2: Cool the prepolymer prepared in step (3) to 80-85 °C, add 1.0 g of 1,4-butanediol, react for 2 h, and when NCO reaches the theoretical value, control the temperature to 45-55 °C and add 3.4 g of triethylamine to continue the reaction for 0.5 h; (5) Post-treatment: After the reaction is completed, the reaction temperature is lowered to room temperature, 396 g of deionized water is added, and shear emulsification is performed at 400 r / min for 0.5 h; (6) Post-chain extension: After shear emulsification, add ethylenediamine in an amount equal to the residual isocyanate and react for 30 min to consume the residual isocyanate; remove the solvent by rotary evaporation under reduced pressure at 0.09 MPa and 50-55 ℃ to obtain the modified waterborne polyurethane dispersion of copolyester diol. Infrared spectroscopy was performed on the obtained copolyester diol-modified waterborne polyurethane dispersion, and the results are as follows: Figure 2 As shown, by Figure 2 It can be known that 3353 cm -1 A -NH stretching vibration peak appeared at 1531 cm⁻¹. -1 A bending vibration peak of -NH appeared at 2270 cm⁻¹, corresponding to the absorption peak of CN stretching vibration, and at 2270 cm⁻¹. -1 No absorption was observed, indicating that the isocyanate ions of -NCO had reacted completely. At 1655 cm⁻¹ -1 The characteristic peaks on the left and right indicate the formation of urea groups.

[0039] The tensile properties of the obtained copolyester diol-modified waterborne polyurethane dispersion were tested, and the results are as follows: Figure 3 As shown, by Figure 3It can be seen that its tensile strength is 48.5 MPa and its elongation at break is 468.6%. In applications where high strength is required, the tensile strength requirement is 30-50 MPa and the tensile strength requirement is 300%-600%. The waterborne polyurethane prepared in this embodiment can meet the requirements and is at a high performance level.

[0040] Thermogravimetric analysis was performed on the obtained copolyester diol-modified waterborne polyurethane dispersion, and the results are as follows: Figure 5 As shown, the temperature corresponding to a 50% mass loss is 376.4 ℃. High-end waterborne polyurethanes are generally at the 350 ℃ level, and the one prepared in this embodiment has exceeded the level of high-end waterborne polyurethanes.

[0041] Example 8 Preparation of copolyester diol waterborne polyurethane (1) Raw material processing: The chain extender was dried in an oven at 120-140 °C and sealed for later use. An appropriate amount of activated molecular sieve was added to the solvent and sealed for 72 h for later use. The cyclic polyester diol prepared in Example 1 was reacted after removing water at 120-130 °C under reduced pressure of 1200 Pa. (2) Preparation of prepolymer: 20.0 g of copolyester diol was added to a 500 mL three-necked flask, and 20.0 g of isophorone diisocyanate and 0.2 g of dibutyltin dilaurate were added dropwise to raise the temperature to 90-95 °C. The reaction was carried out for 2-4 h, and the reaction was stopped when NCO reached the theoretical value to obtain the prepolymer. (3) Chain extension 1: Add 2.0 g of 2,2-dimethylolpropionic acid to the prepolymer prepared in step (2) and react for 3 h. When NCO reaches the theoretical value, control the temperature to carry out the next step of reaction. (4) Chain extension 2: Cool the prepolymer prepared in step (3) to 80-85 °C, add 2.6 g of 1,4-butanediol, react for 3 h, and when NCO reaches the theoretical value, control the temperature to 45-55 °C and add 1.5 g of triethylamine to continue the reaction for 0.8 h; (5) Post-treatment: After the reaction is completed, the reaction temperature is lowered to room temperature, 43.0 g of deionized water is added, and shear emulsification is performed at 500 r / min for 0.7 h; (6) Post-chain extension: After shear emulsification, add ethylenediamine in an amount equal to the residual isocyanate in the system, and react for 10-30 min to consume the residual isocyanate; remove the solvent by rotary evaporation under reduced pressure at 0.08 MPa and 50-55 ℃ to obtain the modified waterborne polyurethane dispersion of copolyester diol. The tensile properties of the obtained copolyester diol-modified waterborne polyurethane dispersion were tested, and the results are as follows: Figure 4 As shown, by Figure 4It can be seen that its tensile strength is 63.7 MPa and its elongation at break is 10.9%.

[0042] Thermogravimetric analysis was performed on the obtained copolyester diol-modified waterborne polyurethane dispersion, and the results are as follows: Figure 6 As shown, the temperature corresponding to a 50% mass loss is 383.1 ℃, demonstrating outstanding temperature resistance.

[0043] Example 9 Preparation of copolyester diol waterborne polyurethane (1) Raw material processing: The chain extender was dried in an oven at 120-140 °C and sealed for later use. An appropriate amount of activated molecular sieve was added to the solvent and sealed for 66 h for later use. The cyclic polyester diol prepared in Example 6 was reacted after removing water at 120-130 °C under reduced pressure of 700 Pa. (2) Preparation of prepolymer: 31.0 g of copolyester diol was added to a 500 mL three-necked flask, and 26.7 g of isophorone diisocyanate and 0.3 g of dibutyltin dilaurate were added dropwise to raise the temperature to 90-95 °C. The reaction was carried out for 2-4 h, and the reaction was stopped when NCO reached the theoretical value to obtain the prepolymer. (3) Chain extension 1: Add 4.6 g of 2,2-dimethylolpropionic acid to the prepolymer prepared in step (2) and react for 3 h. When NCO reaches the theoretical value, control the temperature to carry out the next step of reaction. (4) Chain extension 2: Cool the prepolymer prepared in step (3) to 80-85 °C, add 1.8 g of 1,4-butanediol, react for 3 h, and when NCO reaches the theoretical value, control the temperature to 45-55 °C and add 7.5 g of triethylamine to continue the reaction for 0.8 h; (5) Post-treatment: After the reaction is completed, the reaction temperature is lowered to room temperature, 96.0 g of deionized water is added, and shear emulsification is performed at 500 r / min for 0.7 h; (6) Post-chain extension: After shear emulsification, add ethylenediamine in an amount equal to the residual isocyanate in the system and react for 10-30 min to consume the residual isocyanate; remove the solvent by rotary evaporation at 0.08 MPa and 50-55 ℃ to obtain the modified waterborne polyurethane dispersion of copolyester diol.

[0044] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a copolyester diol, characterized in that, The copolyester diol is prepared from monomers containing the following components through esterification and polycondensation reactions. At least one aliphatic diol; At least one aliphatic dicarboxylic acid; At least one component selected from aromatic dicarboxylic acids and / or diols containing ester rings; The esterification reaction involves heating the monomer to a preset acid value under the action of a catalyst and under the protection of an inert gas to obtain the esterified product. The polycondensation reaction is carried out by polycondensing the esterified product under vacuum conditions until a predetermined molecular weight is reached, thereby obtaining a copolyester diol.

2. The method for preparing copolyester diol according to claim 1, characterized in that, The molecular formula of the aliphatic diol is: HO-(CH 2 ) n -OH n = at least one of 2, 3, 4, 5, 6; The molecular formula of the aliphatic dicarboxylic acid is: HOOC-(CH 2 ) n -COOH at least one of n = 6 to 16; The aromatic dicarboxylic acid is one or more selected from phthalic acid, isophthalic acid, terephthalic acid, 1,4-cyclohexanedicarboxylic acid and 2,5-furandicarboxylic acid; The ester-containing diol is one or more of 1,4-cyclohexanediol, spirocyclodiol, isosorbide, and cyclohexanediol; The alcohol-acid ratio of the monomer is 1.2 to 1.

4.

3. The method for preparing copolyester diol according to claim 1, characterized in that, The esterification reaction is carried out at a temperature of 140–250 °C, with a preset acid value of 20–30 mg KOH / g. The reaction temperature of the polycondensation reaction is 240-250 °C, the vacuum degree is controlled at 700-1500 Pa, and the preset molecular weight is 800-2000.

4. The method for preparing copolyester diol according to claim 1, characterized in that, The catalyst is selected from one or more of antimony trioxide, tetrabutyl titanate, and dibutyltin dilaurate, and the amount of catalyst used is 0.035% to 0.05% of the total mass of the monomers. The aliphatic diol used is 34% to 44% of the total mass of the monomers; The aliphatic dicarboxylic acid used is 26% to 49% of the total mass of the monomer; The amount of the aromatic dicarboxylic acid used is 7% to 37% of the total mass of the monomer; The amount of the ester-containing diol used is 1% to 14% of the total mass of the monomer.

5. A method for preparing waterborne polyurethane, characterized in that, The copolyester diol described in any one of claims 1 to 4 is subjected to a prepolymerization reaction with diisocyanate under the action of a catalyst until the content of isocyanate groups reaches the theoretical value, thereby obtaining a prepolymer. The prepolymer is chain extended using a hydrophilic chain extender. The chain-extended prepolymer was neutralized and emulsified to obtain an aqueous polyurethane emulsion. A diamine is added to the aqueous polyurethane emulsion. After the reaction consumes the residual isocyanate groups, the solvent is removed under reduced pressure to obtain the aqueous polyurethane.

6. The method for preparing waterborne polyurethane according to claim 5, characterized in that, The chain extension includes primary chain extension and secondary chain extension. The first chain extension involves adding a first chain extender to the prepolymer and reacting until the isocyanate group content reaches the theoretical value, thereby obtaining a prepolymer containing hydrophilic groups. The secondary chain extension involves adding a second chain extender to the prepolymer containing hydrophilic groups and reacting until the isocyanate group content reaches the theoretical value to obtain a chain-extended prepolymer. During the chain extension step, solvents are used to adjust the viscosity; The solvent is one or more of acetone, butanone, tetrahydrofuran, and N,N-dimethylformamide.

7. The method for preparing waterborne polyurethane according to claim 6, characterized in that, The neutralization process involves adding a neutralizing agent to the secondary chain-extended prepolymer to react and obtain a neutralized prepolymer. The emulsification process involves adding the neutralized prepolymer to deionized water and shearing emulsifying it to obtain an aqueous polyurethane emulsion.

8. The method for preparing waterborne polyurethane according to claim 7, characterized in that, The diisocyanate is one or more of isophorone diisocyanate, 1,6-hexanediisocyanate and diphenylmethane diisocyanate; The catalyst is one or more of antimony trioxide, tetrabutyl titanate, and dibutyltin dilaurate; The hydrophilic chain extender includes a first chain extender and a second chain extender. The first chain extender is one or more of 2,2-dimethylolpropionic acid and 2,2-dimethylolbutyric acid; The second chain extender is one or more of 1,4-butanediol, ethylene glycol, diethylene glycol, and hexanediol; The neutralizing agent is triethylamine; The diamine is ethylenediamine.

9. The method for preparing waterborne polyurethane according to claim 8, characterized in that, The amount of the polyester diol used is 43.2% to 58.3%; The amount of the diisocyanate used is 32.4% to 43.2%; The amount of catalyst used is 0.4%; The temperature of the prepolymerization reaction is 90–95 °C, the reaction time is 2–4 h, and the reaction is terminated when the isocyanate group content reaches the theoretical value. The dosage of the first chain extender is 4.3% to 6.8%; The amount of the second chain extender is 1.0% to 5.7%, and the temperature of the secondary chain extension reaction is 80 to 85 ℃; The amount of neutralizing agent used is 3.3% to 5.1%, and the neutralization reaction temperature is 45 to 55 °C. Post-treatment was carried out at room temperature, with the addition of deionized water, the solid content of the system controlled at 20%–50%, the shear rate at 400–2000 r / min, and the time at 0.5–1 h.

10. The method for preparing waterborne polyurethane according to claim 9, characterized in that, It also includes a preprocessing step, The hydrophilic chain extender was dried in an oven at 120–140 °C and then sealed for later use. Add an appropriate amount of activated molecular sieve to the solvent and seal for 48–72 h. The copolyester diol was dehydrated at 120–130 °C under reduced pressure of 700–1500 Pa.

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