Waterborne polyurethane prepolymer as well as preparation method and application thereof

Abstract

The invention relates to the technical field of high polymer materials, in particular to a waterborne polyurethane prepolymer as well as a preparation method and application thereof. The waterborne polyurethane prepolymer is prepared from the following raw materials in parts by weight; 5-15 parts of a hydrophilic monomer; 3 to 15 parts of small molecular dihydric alcohol; 0.2 to 2 parts of micromolecular trihydric alcohol; 20 to 120 parts of polyester glycol; 20 to 60 parts of aliphatic isocyanate; 0-3 parts of a salt-forming agent; and 20-50 parts of a solvent. According to the waterborne polyurethane prepolymer provided by the invention, all the components can be well matched under a specific ratio, and the obtained waterborne polyurethane prepolymer can be used for preparing a waterborne polyurethane emulsion with high strength, high hardness, good film-forming property and stability; the strict requirements of high-end application fields such as glass fibers on the material performance are met.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer materials, and particularly relates to an aqueous polyurethane prepolymer, a preparation method thereof, and an application thereof. Background Art

[0002] As an environment-friendly polymer material with water as the dispersion medium, aqueous polyurethane is composed of flexible soft segments and relatively rigid hard segments. Therefore, by adjusting the hard and soft segments of aqueous polyurethane, it can be designed into materials with high strength, high elasticity, high light transmittance, and high adhesiveness, and is widely used in fields such as coatings, adhesives, and leather finishing agents.

[0003] With the continuous development of technology, the advantages of high-hardness aqueous polyurethane, as a special type of aqueous polyurethane, have gradually emerged. Especially in the field of glass fibers, the application of high-strength and high-hardness aqueous polyurethane as a film-forming agent has opened up a new way for improving the performance of glass fibers. It can not only significantly enhance the stiffness and mechanical strength of glass fibers, making glass fibers show higher stability and durability when subjected to external forces, but also effectively solve the problems of fiber dispersion and fracture by improving the bundling property and structural stability of glass fibers. In addition, the application of high-strength and high-hardness aqueous polyurethane has also significantly improved the wear resistance and corrosion resistance of glass fibers, laying a solid foundation for the application of glass fibers in high-end fields such as aerospace and automotive manufacturing. At the same time, the introduction of high-strength and high-hardness aqueous polyurethane has also optimized the surface characteristics of glass fibers, such as improving the surface smoothness and uniformity, further enhancing the overall performance and market competitiveness of glass fibers.

[0004] Although the application potential of high-strength and high-hardness aqueous polyurethane in the field of glass fibers is huge, its formulation design and preparation process face many challenges.

[0005] In a waterborne wood lacquer with high hardness and wear resistance and its preparation method (CN102108247A), the hardness and wear resistance of the waterborne wood lacquer are improved by adding nano-aluminum oxide additives; in a high-hardness two-component waterborne polyurethane floor coating and its preparation method (CN105820738A), inorganic additives and high-strength ceramic microspheres are used; a high-hardness scratch-resistant two-component waterborne polyurethane wood varnish and its preparation method (CN102898937A) and a high-hardness and high-tolerance one-component waterborne clear coating material and its preparation method (CN111363429A) respectively use nano-scale silica glass powder and nano-ceramic powder to increase the hardness of waterborne polyurethane; there is also a high-hardness waterborne polyurethane coating and its preparation method (CN106280954A), which uses rutile titanium dioxide, nano-barium sulfate, a hardening ceramic additive, and a nano-silica dispersion to increase the hardness of waterborne polyurethane. This method of adding fillers to increase the film hardness of waterborne polyurethane may cause phenomena such as uneven dispersion of the reinforcing body or migration after film formation, thus affecting product quality.

[0006] Another method is to introduce hard and soft segments. For example, in a preparation method of an ultra-high-hardness polycarbonate-based waterborne polyurethane emulsion (CN106243312A), a new type of polycarbonate polyol is used; in a preparation method of a high-hardness water-soluble polyurethane resin (CN105175675A), terephthalic acid polyester diol is used. By solely introducing soft segments containing rigid structures to increase the hardness of waterborne polyurethane, the effect is often not obvious and it is difficult to meet the usage requirements; or by simultaneously introducing hard and soft segments and adding inorganic fillers. For example, in a high-hardness and ethanol-resistant waterborne polyurethane emulsion and its preparation method (CN109694456A), poly(propylene carbonate) polyol and nano-silica are used to achieve high hardness and solvent resistance of waterborne polyurethane. Similarly, the non-uniformity and metastability of the externally added inorganic fillers will cause demulsification when compounding glass fiber sizing agents, making it impossible to operate. Therefore, the method of externally adding fillers is not feasible; in a low-cost high-hardness waterborne polyurethane emulsion and its preparation method (CN105860005A), a higher-hardness film is obtained through the composite modification of polyacrylate emulsion. This method will reduce the bundling property of glass fibers and often results in more losses than gains.

[0007] Therefore, when preparing high-strength and high-hardness waterborne polyurethanes using existing technologies, it is often difficult to achieve good high strength, film-forming properties, and stability while maintaining the high hardness of the material. In addition to the above reasons, high strength and high hardness often imply stronger intermolecular interactions and higher crosslinking densities, which may cause problems such as cracks and embrittlement during the processing and use of the material, thereby affecting its comprehensive performance. Moreover, the selection of raw material types, the optimization of ratios, and the precise control of reaction conditions are all key factors affecting the performance of high-hardness waterborne polyurethanes, and the interactions between these factors are complex and difficult to precisely regulate, further increasing the difficulty of formulation design.

[0008] Therefore, there are obvious defects and deficiencies in the existing technologies for preparing high-strength and high-hardness waterborne polyurethanes. There is an urgent need for an innovative formulation design method and preparation process to ensure good film-forming properties, stability, and other key performance indicators while improving the high strength and high hardness of the material, so as to meet the actual requirements of high-end application fields such as glass fiber. Summary of the Invention

[0009] In view of this, the technical problem to be solved by the present invention is to provide a waterborne polyurethane prepolymer, its preparation method, and application. The waterborne polyurethane prepolymer can be used to prepare a waterborne polyurethane emulsion that has both high strength and high hardness, as well as good film-forming properties and stability, so as to meet the strict requirements for material performance in high-end application fields such as glass fiber.

[0010] The present invention provides a waterborne polyurethane prepolymer, which is prepared from raw materials including the following components in parts by weight;

[0011]

[0012] Preferably, the hydrophilic monomer includes one or more of polyethylene glycol, methoxypolyethylene glycol, 2,2-dimethylolpropionic acid, and 2,2-dimethylolbutyric acid.

[0013] Preferably, the small molecule diol includes one or more of butanediol, hexanediol, hydroquinone bis(2-hydroxyethyl) ether, and hydroquinone;

[0014] The small molecule triol includes one or more of trimethylolpropane, glycerol, triethanolamine, and 1,1,1-(trimethylol)ethane.

[0015] Preferably, the polyester diol includes one or more of poly(butylene adipate) glycol, poly(hexylene adipate) glycol, poly(hexylene phthalate) glycol, poly(ethylene terephthalate / adipate) glycol, poly(butylene terephthalate / neopentyl glycol) glycol, and polycarbonate diol;

[0016] The aliphatic isocyanate includes one or more of hexamethylene diisocyanate, isophorone diisocyanate, dicyclohexylmethane diisocyanate, 1,4-cyclohexane diisocyanate, trimethylhexamethylene diisocyanate, and dicyclohexylmethane diisocyanate.

[0017] Preferably, the salt-forming agent includes one or more of triethylamine, ammonia water, sodium hydroxide, and potassium hydroxide;

[0018] The solvent includes one or more of acetone, methyl ethyl ketone, toluene, xylene, and N-methylpyrrolidone.

[0019] The present invention also provides a method for preparing an aqueous polyurethane prepolymer, comprising the following steps:

[0020] a) Mix a hydrophilic monomer, a small molecule diol, a small molecule triol, and a polyester diol, stir and heat up to 100-120 °C, and then remove water under vacuum;

[0021] b) Under an inert gas atmosphere, at 70-80 °C, dropwise add the aliphatic isocyanate into the solution obtained in step a);

[0022] c) Maintain the temperature at 70-80 °C and continuously stir. When the isocyanate group content in the solution obtained in step b) is equal to the theoretical reaction end point value, cool down to 40-45 °C, mix with the solvent and the salt-forming agent, and after reaction, obtain an aqueous polyurethane prepolymer.

[0023] The present invention also provides an aqueous polyurethane emulsion, which is prepared from raw materials including an aqueous polyurethane prepolymer, an aqueous solution of a diamine, polycarbodiimide, and water;

[0024] The mass ratio of the aqueous polyurethane prepolymer, the diamine, and the polycarbodiimide is 100:1.5-10:0-0.5;

[0025] The aqueous polyurethane prepolymer is the aqueous polyurethane prepolymer described above, or the aqueous polyurethane prepolymer prepared by the preparation method described above.

[0026] Preferably, the diamine includes one or more of ethylenediamine, hexamethylenediamine, neopentanediamine, 2-methylpentanediamine, and hydrazine hydrate;

[0027] The mass concentration of the aqueous solution of the diamine is 10%-40%;

[0028] The polycarbodiimide includes one or more of XL-701, XL-725, XL-732, LA-50M, and OS8000.

[0029] The present invention also provides a method for preparing an aqueous polyurethane emulsion, comprising the following steps:

[0030] A) Under stirring conditions, deionized water is added to the aqueous polyurethane prepolymer until a phase transition state appears. After continuing to stir and mix evenly, the remaining deionized water is added;

[0031] The aqueous polyurethane prepolymer is the aqueous polyurethane prepolymer described above, or the aqueous polyurethane prepolymer prepared by the preparation method described above;

[0032] B) It is mixed with an aqueous solution of diamine, and a chain extension reaction is carried out under stirring conditions. Then, acetone is removed by vacuum at 50 - 60 °C to obtain an aqueous polyurethane emulsion;

[0033] Or it is mixed with an aqueous solution of diamine, and a chain extension reaction is carried out under stirring conditions. Then, acetone is removed by vacuum at 50 - 60 °C, and then it is mixed evenly with polycarbodiimide at room temperature to obtain an aqueous polyurethane emulsion.

[0034] Preferably, in step A), the shear rate of the stirring is 1500 - 2500 rpm;

[0035] In step B), the shear rate of the stirring is 300 - 700 rpm; the temperature of the chain extension reaction is 10 - 35 °C, and the time is 60 - 120 min.

[0036] The present invention provides an aqueous polyurethane prepolymer, which is prepared from raw materials including the following components in parts by weight; 5 - 15 parts of hydrophilic monomer; 3 - 15 parts of small molecule diol; 0.2 - 2 parts of small molecule triol; 20 - 120 parts of polyester diol; 20 - 60 parts of aliphatic isocyanate; 0 - 3 parts of salt-forming agent; 20 - 50 parts of solvent. In the aqueous polyurethane prepolymer provided by the present invention, each component can cooperate well under specific ratios. When the obtained aqueous polyurethane prepolymer is used to prepare an aqueous polyurethane emulsion, the cross-linking between polyurethane chains formed by aliphatic isocyanate and polyol, the cross-linking between polycarbodiimide and carboxyl group, and weak interactions such as possible hydrogen bonds cooperate with each other to construct a multi-component synergistic cross-linking network. After the polyester is hydrolyzed, polycarbodiimide can combine with carboxyl group and also play a role in preventing hydrolysis and inhibiting hydrolysis. This multi-component cross-linking network improves the mechanical properties of the material while enhancing the tolerance of the material to environmental factors (such as temperature, humidity, chemical medium), endowing the material with unique stability and durability. It can meet the strict requirements for material properties in high-end application fields such as glass fiber. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 It is a schematic structural diagram of the aqueous polyurethane with a multi-component synergistic cross-linking network provided by the present invention;

[0038] Figure 2 It is an infrared spectrogram of the aqueous polyurethane emulsion of Example 1 of the present invention;

[0039] Figure 3 Film hardness diagrams of the aqueous polyurethane emulsions of Examples 1 to 5;

[0040] Figure 4 Film hardness diagrams of the aqueous polyurethane emulsions of Example 3 and Comparative Examples 1 to 5;

[0041] Figure 5 Film tensile strength and elongation at break diagrams of the aqueous polyurethane emulsions of Examples 1 to 5;

[0042] Figure 6 Film tensile strength and elongation at break diagrams of the aqueous polyurethane emulsions of Example 3 and Comparative Examples 1 to 5. Detailed implementation manners

[0043] Next, in combination with the embodiments of the present invention, the technical solutions of the present invention will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present invention.

[0044] The present invention provides an aqueous polyurethane prepolymer, which is prepared from raw materials including the following components in parts by weight;

[0045]

[0046]

[0047] In some embodiments of the present invention, the hydrophilic monomer is selected from one or more of polyethylene glycol (PEG), methoxypolyethylene glycol (N120), 2,2-dimethylolpropionic acid (DMPA), and 2,2-dimethylolbutyric acid (DMBA). The number average molecular weight of the polyethylene glycol is 1000 to 10000 g / mol. Specifically, the polyethylene glycol (PEG) can be PEG10000 or PEG8000.

[0048] In some embodiments of the present invention, the small molecule diol is selected from one or more of butanediol (BDO), hexanediol (HDO), hydroquinone dihydroxyethyl ether (HQEE), and hydroquinone (HQ).

[0049] In some embodiments of the present invention, the small molecule triol is selected from one or more of trimethylolpropane (TMP), glycerol, triethanolamine, and 1,1,1-(trimethylol)ethane.

[0050] In some embodiments of the present invention, the polyester diol is selected from one or more of butanediol adipate, hexanediol adipate, hexanediol phthalate, ethylene glycol terephthalate / adipate, butanediol / neopentyl glycol terephthalate, and polycarbonate diol.

[0051] In some embodiments of the present invention, the aliphatic isocyanate is selected from one or more of hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), dicyclohexylmethane diisocyanate (HMDI), 1,4-cyclohexane diisocyanate (CHDI), trimethylhexamethylene diisocyanate, and dicyclohexylmethane diisocyanate.

[0052] In some embodiments of the present invention, the salt-forming agent is selected from one or more of triethylamine (TEA), ammonia water, sodium hydroxide, and potassium hydroxide.

[0053] In some embodiments of the present invention, the solvent is selected from one or more of acetone, butanone, toluene, xylene, and N-methylpyrrolidone.

[0054] The present invention also provides a method for preparing the aqueous polyurethane prepolymer described above, comprising the following steps:

[0055] a) Mix the hydrophilic monomer, small molecule diol, small molecule triol, and polyester diol, stir and heat up to 100 - 120 °C, and then remove water under vacuum;

[0056] b) Under an inert gas atmosphere, at 70 - 80 °C, drop the aliphatic isocyanate into the solution obtained in step a);

[0057] c) Maintain the temperature at 70 - 80 °C, and continuously stir. When the isocyanate group content in the solution obtained in step b) is equal to the theoretical reaction end point value, cool down to 40 - 45 °C, mix with the solvent and the salt-forming agent, and after reaction, obtain the aqueous polyurethane prepolymer.

[0058] In some embodiments of the present invention, the preparation of the aqueous polyurethane prepolymer is carried out in a reaction kettle.

[0059] Regarding step a):

[0060] Mix the hydrophilic monomer, small molecule diol, small molecule triol, and polyester diol, stir and heat up to 100 - 120 °C, and then remove water under vacuum.

[0061] In some embodiments of the present invention, the stirring is uniform stirring. The heating rate is 2 - 5 °C / min, such as 3 °C / min, 2 °C / min. Specifically, stir and heat up to 110 °C. The time for removing water under vacuum is 1 - 3 h, such as 2 h.

[0062] Regarding step b):

[0063] Under an inert gas atmosphere, at 70 - 80 °C, the aliphatic isocyanate is dropped into the solution obtained in step a).

[0064] In some embodiments of the present invention, the inert gas is nitrogen. The inert gas is a dry inert gas.

[0065] In some embodiments of the present invention, the aliphatic isocyanate is uniformly dropped into the stirred solution obtained in step a). Specifically, the dropping temperature is 75 °C. The time required for all dropping is 30 - 60 min, such as 30 min.

[0066] Regarding step c):

[0067] Maintain the temperature at 70 - 80 °C and continue stirring. When the isocyanate group content in the solution obtained in step b) is equal to the theoretical reaction end point value, cool down to 40 - 45 °C, mix with a solvent and a salt-forming agent, and after reaction, an aqueous polyurethane prepolymer is obtained.

[0068] Specifically, maintain the temperature at 75 °C. Cool down to 42 °C.

[0069] In some embodiments of the present invention, the temperature of the reaction is 40 - 45 °C, such as 42 °C; the time is 15 - 25 min, such as 20 min.

[0070] In some embodiments of the present invention, the isocyanate group index R value in the aqueous polyurethane prepolymer is 1.0 - 2.5.

[0071] The present invention also provides an aqueous polyurethane emulsion, which is prepared from raw materials including an aqueous polyurethane prepolymer, an aqueous solution of a diamine, polycarbodiimide, and water;

[0072] The mass ratio of the aqueous polyurethane prepolymer, the diamine, and the polycarbodiimide is 100:1.5 - 10:0 - 0.5;

[0073] The aqueous polyurethane prepolymer is the aqueous polyurethane prepolymer described above, or the aqueous polyurethane prepolymer prepared by the preparation method described above.

[0074] In some embodiments of the present invention, the diamine is selected from one or more of ethylenediamine, hexamethylenediamine, neopentyl diamine, 2-methylpentamethylenediamine, and hydrazine hydrate. The mass concentration of the aqueous solution of the diamine is 10% - 40%, such as 22.60%, 15.05%, 17.83%, 12.66%, 16.48%. The aqueous solution of the diamine is obtained by diluting the diamine with water. The water is deionized water.

[0075] In some embodiments of the present invention, the polycarbodiimide is selected from one or more of XL-701, XL-725, XL-732, LA-50M, and OS8000.

[0076] In some embodiments of the present invention, the water is deionized water.

[0077] The present invention also provides a method for preparing the aqueous polyurethane emulsion described above, comprising the following steps:

[0078] A) Under stirring conditions, add deionized water to the aqueous polyurethane prepolymer until a phase transition state appears. After continuing to stir and mix evenly, add the remaining deionized water.

[0079] B) Mix with an aqueous solution of diamine and carry out a chain extension reaction under stirring conditions. Then, evacuate acetone at 50-60 °C to obtain an aqueous polyurethane emulsion.

[0080] Or mix with an aqueous solution of diamine and carry out a chain extension reaction under stirring conditions. Then, evacuate acetone at 50-60 °C, and then mix evenly with polycarbodiimide at room temperature to obtain an aqueous polyurethane emulsion.

[0081] In some embodiments of the present invention, the preparation of the aqueous polyurethane emulsion is carried out in an emulsifying kettle.

[0082] Regarding step A):

[0083] Under stirring conditions, add deionized water to the aqueous polyurethane prepolymer until a phase transition state appears. After continuing to stir and mix evenly, add the remaining deionized water.

[0084] In some embodiments of the present invention, before adding deionized water to the aqueous polyurethane prepolymer, it further includes:

[0085] Adjust the temperature of the aqueous polyurethane prepolymer to 20-30 °C.

[0086] Specifically, adjust the temperature of the aqueous polyurethane prepolymer to 25 °C.

[0087] In some embodiments of the present invention, the shear rate of the stirring is 1500-2500 rpm, such as 2000 rpm.

[0088] When continuing to stir and mix evenly, stop adding deionized water.

[0089] In some embodiments of the present invention, it takes 50-60 min, such as 60 min, to add the remaining deionized water.

[0090] Regarding step B):

[0091] Mix with an aqueous solution of a diamine and carry out a chain extension reaction under stirring, and then remove acetone by vacuum at 50-60 °C to obtain an aqueous polyurethane emulsion;

[0092] Or mix with an aqueous solution of a diamine, carry out a chain extension reaction under stirring, then remove acetone by vacuum at 50-60 °C, and then mix with polycarbodiimide at room temperature to obtain an aqueous polyurethane emulsion.

[0093] In some embodiments of the present invention, the shear rate of the stirring is 300-700 rpm, such as 500 rpm.

[0094] In some embodiments of the present invention, the temperature of the chain extension reaction is 10-35 °C, such as 25 °C; the time is 60-120 min, such as 60 min.

[0095] In some embodiments of the present invention, the temperature for removing acetone by vacuum is 50-60 °C, such as 55 °C.

[0096] In some embodiments of the present invention, the solid content of the aqueous polyurethane emulsion is 43%-47%, such as 45%.

[0097] Figure 1 It is a schematic structural diagram of the aqueous polyurethane with a multi-component synergistic crosslinking network provided by the present invention. From Figure 1 It can be seen that the aqueous polyurethane structure provided by the present invention contains crosslinking points, crystallization of hard and soft segments, hydrogen bonds and polycarbodiimide crosslinking. Experimental results show that the aqueous polyurethane with this structure has better hardness, mechanical properties and good film-forming properties.

[0098] The present invention has no special restrictions on the sources of the raw materials used above, and they can be generally commercially available.

[0099] Beneficial effects:

[0100] 1. Construction and strengthening of the multi-component synergistic crosslinking network; in the present invention, by calculating the crosslinking density, the crosslinking between polyurethane chains formed by aliphatic isocyanate and polyol, the crosslinking between polycarbodiimide and carboxyl group, and weak interactions such as possible hydrogen bonds cooperate with each other to construct a multi-component synergistic crosslinking network. After the polyester is hydrolyzed, polycarbodiimide can combine with the carboxyl group and also play a role in preventing and inhibiting hydrolysis. This multi-component crosslinking network not only improves the mechanical properties of the material, but also enhances the tolerance of the material to environmental factors (such as temperature, humidity, chemical media), endowing the material with unique stability and durability, far exceeding the effect of a single crosslinking method.

[0101] 2. Multi-scale structure regulation to enhance comprehensive performance; in the molecular structure design of the present invention, through the fine screening and combination of raw materials such as hydrophilic monomers, small molecule polyols, and polyester diols, multi-scale precise regulation from microscopic molecular chain segments to macroscopic aggregated structures is achieved. The sequence structures and distributions of hard segments and soft segments formed by different raw materials during the polymerization process determine the crystallization behavior, phase separation degree, and intermolecular interactions of the material. For example, the selection of a specific polyester diol affects the formation and growth of crystal regions, interweaves with hard segments to construct a unique microscopic structure, and then macroscopically exhibits the synergistic optimization of high strength, high hardness, good flexibility, and film-forming properties, breaking through the limitation that it is difficult to balance multiple properties by traditional single-scale regulation.

[0102] 3. Synergistic effect of salt-forming agent and solvent; in the preparation process of the present invention, salt-forming agents such as triethylamine and ammonia water, and solvents such as acetone and butanone are particularly selected. By precisely controlling the amounts of the salt-forming agent and the solvent, the salt-forming agent and the solvent play a synergistic role, which helps to regulate the dispersibility and stability of the waterborne polyurethane.

[0103] To further illustrate the present invention, the following provides a detailed description of a waterborne polyurethane prepolymer, its preparation method, and applications provided by the present invention in conjunction with examples, but it should not be construed as a limitation to the protection scope of the present invention.

[0104] Example 1

[0105] The preparation raw materials of the waterborne polyurethane prepolymer are shown in Table 1;

[0106] Table 1 Preparation raw materials of the waterborne polyurethane prepolymer

[0107]

[0108] The preparation method of the waterborne polyurethane prepolymer includes the following steps:

[0109] (1) Add PEG10000, DMBA, HDO, TMP, and polyhexylene adipate diol into the reaction kettle, stir evenly and heat up (the heating rate is 3 °C / min) to 110 °C, and then carry out vacuum dehydration for 2 h;

[0110] (2) After the vacuum dehydration is completed, introduce dry N2, continuously stir and maintain the temperature at 75 °C, and evenly drop HDI; the total dropping time required is 30 min;

[0111] (3) Maintain the temperature at 75 °C and keep stirring. When the isocyanate group content in the solution obtained in step (2) equals the theoretical reaction end point value, cool down to 42 °C, add acetone, mix well, then add TEA, and maintain the reaction at 42 °C for 20 min to obtain a waterborne polyurethane prepolymer 1 with a multi-component synergistic crosslinking network. The isocyanate index R value of the waterborne polyurethane prepolymer 1 is 1.73.

[0112] The raw materials for preparing the aqueous emulsion are shown in Table 2;

[0113] Table 2 Raw materials for preparing the aqueous emulsion

[0114] Raw material type Parts by weight Waterborne polyurethane prepolymer 1 152.15 Hexamethylenediamine 7.30 Deionized water 1 25.00 Deionized water 2 121.00

[0115] The preparation method of the waterborne polyurethane emulsion includes the following steps:

[0116] 1) Pour the waterborne polyurethane prepolymer 1 into the emulsification kettle, and adjust the temperature to 25 °C; then set the stirring and shearing rate of the emulsification kettle to 2000 rpm. When adding part of deionized water 2 until the phase transition state appears, stop adding deionized water 2, continue to stir and mix well, and then add the remaining deionized water 2; it takes 60 min to add the remaining deionized water 2;

[0117] Mix hexamethylenediamine with deionized water 1 to obtain a hexamethylenediamine solution with a mass concentration of 22.60%;

[0118] 2) Mix the obtained phase transition product and the aqueous solution of hexamethylenediamine, and carry out a chain extension reaction at 25 °C for 60 min under stirring (the stirring and shearing rate is 500 rpm), and then remove acetone under vacuum at 55 °C to obtain the waterborne polyurethane emulsion, that is, the waterborne polyurethane emulsion 1 with a multi-component synergistic crosslinking network.

[0119] Figure 2 This is the infrared spectrum of the waterborne polyurethane emulsion in Example 1 of the present invention. From Figure 2 it can be seen that there is no peak at 2260 cm -1 ~2280 cm -1 indicating that the isocyanate reaction is complete, while 3319 cm -1 is the N-H stretching vibration of the urethane bond, 1536 cm -1 is the N-H bending vibration, combined with the carbonyl C=O stretching vibration at 1728 cm -1 indicating that the polyester-based waterborne polyurethane in Example 1 has been successfully synthesized.

[0120] Example 2

[0121] The raw materials for preparing the waterborne polyurethane prepolymer are shown in Table 3;

[0122] Table 3 Raw materials for preparing the waterborne polyurethane prepolymer

[0123]

[0124] The preparation method of the aqueous polyurethane prepolymer comprises the following steps:

[0125] (1) Add PEG8000, DMBA, BDO, TMP and polyethylene glycol terephthalate / adipate glycol into a reaction kettle, stir evenly and heat up (the heating rate is 2 °C / min) to 110 °C, and then carry out vacuum dehydration for 2 h;

[0126] (2) After the vacuum dehydration is completed, introduce dry N2, continuously stir and maintain the temperature at 75 °C, and uniformly dropwise add IPDI; the total dropping time required is 30 min;

[0127] (3) Maintain the temperature at 75 °C and continuously stir. When the isocyanate group content in the solution obtained in step (2) is equal to the theoretical reaction end point value, cool down to 42 °C, add acetone, mix evenly and then add TEA, and maintain the reaction at 42 °C for 20 min to obtain an aqueous polyurethane prepolymer 2 with a multi-component synergistic cross-linked network. The isocyanate group index R value in the aqueous polyurethane prepolymer 2 is 1.71.

[0128] The raw materials for preparing the aqueous emulsion are shown in Table 4;

[0129] Table 4 Raw materials for preparing the aqueous emulsion

[0130] Raw material type Parts by weight Waterborne polyurethane prepolymer 2 157.65 Ethylenediamine 1.27 Hydrazine hydrate 3.16 Deionized water 1 25.00 Deionized water 2 148.65 XL-701 0.20

[0131] The preparation method of the aqueous polyurethane emulsion comprises the following steps:

[0132] 1) Pour the aqueous polyurethane prepolymer 2 into an emulsifying kettle, and adjust the temperature to 25 °C; then set the stirring and shearing rate of the emulsifying kettle to 2000 rpm. When adding part of deionized water 2 until the phase transition state appears, stop adding deionized water 2, continue to stir and mix evenly, and then add the remaining deionized water 2; the time taken to add the remaining deionized water 2 is 60 min;

[0133] Mix ethylenediamine, hydrazine hydrate and deionized water 1 to obtain an aqueous solution of diamine with a mass concentration of 15.05%;

[0134] 2) Mix the obtained phase transition product, the aqueous solution of diamine and XL-701, and carry out a chain extension reaction at 25 °C for 60 min under stirring (the stirring and shearing rate is 500 rpm), and then evacuate acetone at 55 °C to obtain an aqueous polyurethane emulsion, namely the aqueous polyurethane emulsion 2 with a multi-component synergistic cross-linked network.

[0135] Example 3

[0136] The raw materials for preparing the aqueous polyurethane prepolymer are shown in Table 5;

[0137] Table 5 Raw materials for preparing the aqueous polyurethane prepolymer

[0138]

[0139]

[0140] The preparation method of the aqueous polyurethane prepolymer includes the following steps:

[0141] (1) Add PEG1000, DMPA, HDO, glycerol and poly(butylene adipate) diol into the reaction kettle, stir evenly and heat up (the heating rate is 2 °C / min) to 110 °C, and then carry out vacuum dehydration for 2 h;

[0142] (2) After the vacuum dehydration is completed, introduce dry N2, continue stirring and maintain the temperature at 75 °C, and evenly drop CHDI; the total dropping time required is 30 min;

[0143] (3) Maintain the temperature at 75 °C and continue stirring. When the isocyanate group content in the solution obtained in step (2) is equal to the theoretical reaction end point value, cool down to 42 °C, add acetone, mix evenly and then add TEA, and maintain the reaction at 42 °C for 20 min to obtain an aqueous polyurethane prepolymer 3 with a multi-component synergistic cross-linked network. The isocyanate group index R value in the aqueous polyurethane prepolymer 3 is 1.67.

[0144] The raw materials for preparing the aqueous emulsion are shown in Table 6;

[0145] Table 6 Raw materials for preparing the aqueous emulsion

[0146] Raw material type Parts by weight Waterborne polyurethane prepolymer 3 157.80 Ethylenediamine 1.86 Hydrazine hydrate 4.65 Deionized water 1 30.00 Deionized water 2 146.38 XL-701 0.20

[0147] The preparation method of the aqueous polyurethane emulsion includes the following steps:

[0148] 1) Pour the aqueous polyurethane prepolymer 3 into the emulsifying kettle and adjust the temperature to 25 °C; then set the stirring and shearing rate of the emulsifying kettle to 2000 rpm. When phase inversion occurs after adding part of deionized water 2, stop adding deionized water 2, continue stirring and mixing evenly, and then add the remaining deionized water 2; it takes 60 min to add the remaining deionized water 2;

[0149] Mix ethylenediamine, hydrazine hydrate and deionized water 1 to obtain an aqueous solution of diamine with a mass concentration of 17.83%;

[0150] (2) Mix the obtained phase change product, the aqueous solution of diamine, and XL-701, and carry out a chain extension reaction at 25 °C for 60 min under stirring (the stirring shear rate is 500 rpm), and then remove acetone by vacuum at 55 °C to obtain an aqueous polyurethane emulsion, that is, the aqueous polyurethane emulsion 3 of the multi-component synergistic cross-linked network.

[0151] Example 4

[0152] The raw materials for preparing the aqueous polyurethane prepolymer are shown in Table 7;

[0153] Table 7 Raw Materials for Preparing Aqueous Polyurethane Prepolymer

[0154]

[0155] The preparation method of the aqueous polyurethane prepolymer includes the following steps:

[0156] (1) Add N120, DMPA, HQEE, glycerol, and polycarbonate diol into the reaction kettle, stir evenly and heat up (the heating rate is 2 °C / min) to 110 °C, and then carry out vacuum dehydration for 2 h;

[0157] (2) After the vacuum dehydration is completed, introduce dry N2, continuously stir and maintain the temperature at 75 °C, and uniformly drop HMDI and IPDI; the total dropping time required is 30 min;

[0158] (3) Maintain the temperature at 75 °C and continuously stir. When the isocyanate group content in the solution obtained in step (2) is equal to the theoretical reaction end point value, cool down to 42 °C, add acetone, mix evenly and then add TEA, and maintain the reaction at 42 °C for 20 min to obtain an aqueous polyurethane prepolymer 4 of a multi-component synergistic cross-linked network. The isocyanate group index R value in the aqueous polyurethane prepolymer 4 is 1.34.

[0159] The raw materials for preparing the aqueous emulsion are shown in Table 8;

[0160] Table 8 Raw Materials for Preparing Aqueous Emulsion

[0161] Raw material type Parts by weight Waterborne polyurethane prepolymer 4 166.80 Hexamethylenediamine 4.78 Ethylenediamine 2.47 Pure water 1 50.00 Pure water 2 126.07

[0162] The preparation method of the aqueous polyurethane emulsion includes the following steps:

[0163] 1) Pour the aqueous polyurethane prepolymer 4 into the emulsifying kettle, and adjust the temperature to 25 °C; then set the stirring shear rate of the emulsifying kettle to 2000 rpm, add part of deionized water 2 until the phase transition state appears, stop adding deionized water 2, continue to stir and mix evenly, and then add the remaining deionized water 2; it takes 60 min to add the remaining deionized water 2;

[0164] Mix hexamethylenediamine, ethylenediamine with deionized water 1 to obtain an aqueous solution of diamine with a mass concentration of 12.66%.

[0165] 2) Mix the obtained phase change product and the aqueous solution of diamine, and carry out a chain extension reaction at 25 °C for 60 min under stirring (the stirring shear rate is 500 rpm), and then remove acetone by vacuum at 55 °C to obtain an aqueous polyurethane emulsion, namely the aqueous polyurethane emulsion 4 with a multi-component synergistic cross-linked network.

[0166] Example 5

[0167] The raw materials for preparing the aqueous polyurethane prepolymer are shown in Table 9;

[0168] Table 9 Raw materials for preparing the aqueous polyurethane prepolymer

[0169]

[0170] The preparation method of the aqueous polyurethane prepolymer includes the following steps:

[0171] (1) Add N120, DMPA, HDO, HQEE, TMP and poly(hexylene adipate) diol into the reaction kettle, stir evenly and heat up (the heating rate is 2 °C / min) to 110 °C, and then carry out vacuum dehydration for 2 h;

[0172] (2) After the vacuum dehydration is completed, introduce dry N2, continuously stir and maintain the temperature at 75 °C, and uniformly drop HMDI; the total dropping time required is 30 min;

[0173] (3) Maintain the temperature at 75 °C and continuously stir. When the isocyanate group content in the solution obtained in step (2) is equal to the theoretical reaction end point value, cool down to 42 °C, add acetone, mix evenly and then add TEA, and maintain the reaction at 42 °C for 20 min to obtain an aqueous polyurethane prepolymer 5 with a multi-component synergistic cross-linked network. The isocyanate group index R value in the aqueous polyurethane prepolymer 5 is 1.62.

[0174] The raw materials for preparing the aqueous emulsion are shown in Table 10;

[0175] Table 10 Raw materials for preparing the aqueous emulsion

[0176]

[0177]

[0178] The preparation method of the aqueous polyurethane emulsion includes the following steps:

[0179] 1) Pour the aqueous polyurethane prepolymer 5 into the emulsification kettle and adjust the temperature to 25°C; then set the stirring and shearing rate of the emulsification kettle to 2000 rpm. Add part of deionized water 2 until the phase transition state appears, then stop adding deionized water 2, continue to stir and mix evenly, and then add the remaining deionized water 2; it takes 60 minutes to add the remaining deionized water 2.

[0180] Mix hexamethylenediamine with deionized water 1 to obtain an aqueous solution of diamine with a mass concentration of 16.48%.

[0181] 2) Mix the obtained phase change product, the aqueous solution of diamine and XL-732, and carry out a chain extension reaction at 25°C for 60 minutes under stirring (the stirring and shearing rate is 500 rpm), and then remove acetone by vacuum at 55°C to obtain an aqueous polyurethane emulsion, that is, the aqueous polyurethane emulsion 5 of the multi-component synergistic cross-linked network.

[0182] Comparative Example 1

[0183] The difference from Example 3 is that:

[0184] The preparation raw materials of the aqueous polyurethane prepolymer do not contain small molecule diol, that is, the weight fraction of small molecule diol is 0;

[0185] The remaining steps and parameters are the same as those in Example 3.

[0186] Obtain an aqueous polyurethane prepolymer d1. The isocyanate index R value in the aqueous polyurethane prepolymer d1 is 5.45.

[0187] The obtained aqueous polyurethane emulsion is the aqueous polyurethane emulsion D1.

[0188] Comparative Example 2

[0189] The difference from Example 3 is that:

[0190] The preparation raw materials of the aqueous polyurethane prepolymer do not contain small molecule triol, that is, the weight fraction of small molecule triol is 0;

[0191] The remaining steps and parameters are the same as those in Example 3.

[0192] Obtain an aqueous polyurethane prepolymer d2. The isocyanate index R value in the aqueous polyurethane prepolymer d2 is 1.72.

[0193] The obtained aqueous polyurethane emulsion is the aqueous polyurethane emulsion D2.

[0194] Comparative Example 3

[0195] The difference from Example 3 is that:

[0196] The raw materials for preparing the aqueous polyurethane prepolymer do not contain a salifying agent, that is, the weight fraction of the salifying agent is 0;

[0197] The remaining steps and parameters are the same as those in Example 3.

[0198] The aqueous polyurethane prepolymer d3 is obtained. The isocyanate group index R value in the aqueous polyurethane prepolymer d3 is 1.67.

[0199] The obtained aqueous polyurethane emulsion is the aqueous polyurethane emulsion D3.

[0200] Comparative Example 4

[0201] The difference from Example 3 is as follows:

[0202] The small molecule diol HDO is replaced with neopentyl glycol.

[0203] The remaining steps and parameters are the same as those in Example 3.

[0204] The aqueous polyurethane prepolymer d4 is obtained. The isocyanate group index R value in the aqueous polyurethane prepolymer d4 is 1.55.

[0205] The obtained aqueous polyurethane emulsion is the aqueous polyurethane emulsion D4.

[0206] Comparative Example 5

[0207] The difference from Example 3 is as follows:

[0208] The small molecule diol HDO is replaced with diethylene glycol.

[0209] The remaining steps and parameters are the same as those in Example 3.

[0210] The aqueous polyurethane prepolymer d5 is obtained. The isocyanate group index R value in the aqueous polyurethane prepolymer d5 is 1.53.

[0211] The obtained aqueous polyurethane emulsion is the aqueous polyurethane emulsion D5.

[0212] The solid content of the aqueous polyurethane emulsion was measured using a CS101-1FB type forced air oven (Chongqing Hengda Instrument Co., Ltd.) in accordance with GB / T 1725-2007.

[0213] The pH value of the aqueous polyurethane emulsion was tested using a PHS-3C type pH meter (Shanghai Jingke Instrument Co., Ltd.) in accordance with GB / T 9724-2007.

[0214] The particle size of the aqueous polyurethane emulsion was tested using a 90Plus type laser particle size analyzer (Brookhaven Corporation, USA) in accordance with GB / T 19077-2016.

[0215] The viscosity of the aqueous polyurethane emulsion was measured using an LVDV-3ultra viscometer (Brookfield, USA) in accordance with GB / T 9751.1-2008.

[0216] The test results are shown in Table 11.

[0217] Table 11 Performance test results of aqueous polyurethane emulsion

[0218] Name Solid content / % pH value Particle size / nm Viscosity / mPa·s Example 1 45.1 7.3 642 115 Example 2 45.0 7.3 618 104 Example 3 45.1 7.2 577 152 Example 4 45.2 7.5 780 79 Example 5 45.1 7.3 842 50 Comparative example 1 45.0 7.4 248 507 Comparative example 2 45.0 7.5 371 241 Comparative example 3 45.0 5.4 2684 23 Comparative example 4 45.0 7.4 627 134 Comparative example 5 45.0 7.3 522 98

[0219] As can be seen from Table 11, since there is no small molecule diol in Comparative Example 1 and no small molecule triol in Comparative Example 2, the resin prepolymer has a large NCO content and a small viscosity. Therefore, the emulsion particle size is small and the viscosity is large. It should be noted that since there is no salifying agent in Comparative Example 3, the emulsion is a pure non-ionic aqueous polyurethane and contains a large amount of carboxyl groups. The emulsion particle size is extremely large, the emulsion is very unstable and prone to stratification. Therefore, the absence of a salifying agent will cause the emulsion to be unstable. Since the hard segment in Comparative Example 4 contains a side methyl group, the aggregation of the hard segment is relatively loose, resulting in a slightly increased particle size and a slight decrease in viscosity. Since the diethylene glycol in the hard segment of Comparative Example 5 contains an ether bond, the flexibility increases, the resin prepolymer is smaller, and the particle size and viscosity are further reduced.

[0220] The film hardness of the aqueous polyurethane emulsion was measured using an LX-D-2 Shore hardness tester (Wenzhou Haibao Instrument Co., Ltd.) in accordance with GB / T 2411-2008. The results are as Figure 3 、 Figure 4 shown. Figure 3 is the film hardness diagram of the aqueous polyurethane emulsions of Examples 1 to 5, Figure 4 is the film hardness diagram of the aqueous polyurethane emulsions of Example 3 and Comparative Examples 1 to 5. As can be seen from Figures 3 - 4 it, the large absence of the hard segment represented by the small molecule diol will cause a sharp decrease in hardness. Since the amount of the small molecule triol is small, the hardness of Comparative Example 2 decreases less, but the decrease rate also exceeds 13.95%. Since what is lacking in Comparative Example 3 is the salifying agent, the influence on the hardness of the polyurethane film formation is small. Since the neopentyl glycol in Comparative Example 4 has a side methyl group structure, which hinders the crystallization of the hard segment, the hardness decreases. The diethylene glycol ether bond in Comparative Example 5 has good flexibility, resulting in a significant decrease in the Shore hardness.

[0221] The film mechanical properties of the aqueous polyurethane emulsion were measured using an Instron 5982 universal material testing machine (Instron, USA) in accordance with GB / T 1040-2018. The results are as Figure 5 、 Figure 6 shown. Figure 5 is the film tensile strength and elongation at break diagram of the aqueous polyurethane emulsions of Examples 1 to 5. Figure 6The figure shows the tensile strength and elongation at break of the coatings of the aqueous polyurethane emulsions of Comparative Examples 1 to 5. From Figure 3 It can be seen that, similar to the case of hardness, when the dosage of the small molecule diol is large, the tensile strength will be greatly reduced after the absence of Comparative Example 1. The absence of hard segment crystallization makes the resin softer, so the elongation at break is larger. The small molecule triol provides crosslinking points. After the absence of Comparative Example 2, the elongation at break will increase and the tensile strength will decrease. In Comparative Example 3, due to the absence of the salt-forming agent, the mechanical properties of the aqueous polyurethane film formation are less affected, mainly affecting the emulsification effect and the stability of the aqueous polyurethane. In Comparative Example 4, neopentyl glycol is used to replace hexanediol. The side methyl group of neopentyl glycol destroys the molecular chain symmetry, hinders the ordered arrangement of the hard segments, and reduces the crystallinity. Moreover, the side group increases the distance between the hard segments, decreases the hydrogen bond density, and reduces the physical crosslinking points, resulting in a decrease in tensile strength. The hard segments are loosely aggregated, the degree of microphase separation between the hard and soft segments is reduced, and the glass transition temperature of the soft segment rises limitedly, and the elongation at break increases slightly. In Comparative Example 5, diethylene glycol is used to replace hexanediol. Diethylene glycol contains ether bonds and has extremely high molecular chain flexibility. It is difficult for the hard segments to form an ordered structure, and the microphase separation is significantly weakened. The flexibility of the ether bond disperses the hard segments in the soft segments, and the hydrogen bond interaction is further weakened, resulting in a significant decrease in tensile strength. Also, due to the large dosage of diethylene glycol and the relatively large content of hard segments, the hard segments still dominate the material properties, and the elongation at break increases relatively large, but the absolute value is not large.

[0222] The descriptions of the above embodiments are only used to help understand the method and its core idea of the present invention. Various modifications to these embodiments will be obvious to those skilled in the art. The general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to these embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A waterborne polyurethane prepolymer prepared from raw materials comprising the following components in parts by weight; 2. The waterborne polyurethane prepolymer according to claim 1, characterized in that The hydrophilic monomer includes one or more of polyethylene glycol, polyethylene glycol monomethyl ether, 2,2-dimethylol propionic acid and 2,2-dimethylol butyric acid.

3. The waterborne polyurethane prepolymer according to claim 1, characterized in that The small molecule diol includes one or more of butanediol, hexanediol, hydroquinone dihydroxyethyl ether and hydroquinone; The small molecule triol includes one or more of trimethylolpropane, glycerol, triethanolamine and 1,1,1-(trimethylol)-ethane.

4. The waterborne polyurethane prepolymer according to claim 1, characterized in that The polyester diol includes one or more of polybutylene adipate diol, polyhexylene adipate diol, polyhexylene phthalate diol, polyethylene terephthalate / adipate diol, polybutylene terephthalate / neopentyl glycol ester diol, and polycarbonate diol; The aliphatic isocyanate includes one or more of hexamethylene diisocyanate, isophorone diisocyanate, dicyclohexylmethane diisocyanate, 1,4-cyclohexane diisocyanate, trimethylhexamethylene diisocyanate and dicyclohexylmethane diisocyanate.

5. The waterborne polyurethane prepolymer according to claim 1, characterized in that The salt-forming agent includes one or more of triethylamine, ammonia water, sodium hydroxide and potassium hydroxide; The solvent includes one or more of acetone, butanone, toluene, xylene and N-methylpyrrolidone.

6. A method for preparing an aqueous polyurethane prepolymer, comprising the following steps: a) mixing a hydrophilic monomer, a small molecule diol, a small molecule triol and a polyester diol, stirring and heating to 100-120° C., and removing water in vacuo; b) under an inert gas atmosphere at 70-80° C., dripping an aliphatic isocyanate into the solution obtained in step a); c) maintaining the temperature at 70-80° C. and stirring continuously, and when the isocyanate content in the solution obtained in step b) is equal to the theoretical reaction endpoint value, cooling to 40-45° C., mixing with the solvent and the salt-forming agent, and reacting to obtain a waterborne polyurethane prepolymer.

7. An aqueous polyurethane emulsion prepared from raw materials including an aqueous polyurethane prepolymer, an aqueous solution of a diamine, polycarbodiimide and water; The mass ratio of the waterborne polyurethane prepolymer, diamine and polycarbodiimide is 100:1.5-10:0-0.5; The waterborne polyurethane prepolymer is the waterborne polyurethane prepolymer according to any one of claims 1 to 5, or is the waterborne polyurethane prepolymer prepared by the preparation method according to claim 6.

8. The aqueous polyurethane emulsion according to claim 7, characterized in that The diamine includes one or more of ethylenediamine, hexamethylenediamine, neopentyldiamine, 2-methylpentanediamine and hydrazine hydrate; The mass concentration of the aqueous solution of the diamine is 10% to 40%; The polycarbodiimide includes one or more of XL-701, XL-725, XL-732, LA-50M and OS8000.

9. A method for preparing an aqueous polyurethane emulsion, comprising the following steps: A) adding deionized water to the waterborne polyurethane prepolymer under stirring until a phase transition state occurs, continuing to stir and mix, and then adding the remaining deionized water; The waterborne polyurethane prepolymer is the waterborne polyurethane prepolymer according to any one of claims 1 to 5, or is the waterborne polyurethane prepolymer prepared by the preparation method according to claim 6; B) mixing with an aqueous solution of a diamine, carrying out a chain extension reaction under stirring, and then removing acetone under vacuum at 50-60° C. to obtain an aqueous polyurethane emulsion; Or it is mixed with an aqueous solution of a diamine, and a chain extension reaction is carried out under stirring, and then the acetone is removed by vacuum at 50-60°C, and then mixed with polycarbodiimide at room temperature to obtain an aqueous polyurethane emulsion.

10. The preparation method according to claim 9, characterized in that: In step A), the shear rate of the stirring is 1500-2500 rpm; In step B), the shear rate of the stirring is 300-700 rpm; the temperature of the chain extension reaction is 10-35° C., and the time is 60-120 min.

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