High-strength waterborne polyurethane matt varnish and preparation method thereof

Abstract

The invention discloses high-strength waterborne polyurethane matt varnish and a preparation method thereof, and relates to the technical field of coatings. According to the method, firstly, graphene oxide is aminated through a silane coupling agent, then the aminated graphene oxide reacts with isocyanate, and an NCO-terminated functionalized graphene modified prepolymer is prepared. The preparation method comprises the following steps: firstly, synthesizing terminal amino hyperbranched polyamide, sequentially reacting the terminal amino hyperbranched polyamide with epoxy polysiloxane, isocyanate and amino-terminated polyether, and finally generating a hyperbranched polysiloxane hybrid modified nano silicon dioxide dispersion liquid in situ through a sol-gel method. And finally, synergistically introducing the two modified components into the polyurethane prepolymer, and carrying out neutralization, emulsification, chain extension and other steps to obtain the final product. According to the preparation method, a graphene high-strength framework and a hybrid silicon dioxide node with long flexible chain bridging are combined through chemical bonding, the problems of nanofiller interface bonding and steric hindrance shielding are cooperatively solved, and the obtained matte paint coating has excellent mechanical strength.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of coatings, belongs to the patent classification number C09D175 / 04, and specifically relates to a high-strength water-based polyurethane matt oil and a preparation method thereof. BACKGROUND

[0002] The matt oil belongs to an important subdivision category in the field of coatings, and more accurately, it is a kind of varnish coating with both decorative and functional properties, and its core feature lies in the absence of color fillers, and only the synergistic effect of film-forming substances and functional additives is relied on to realize the performance of the coating. The extinction principle of this kind of coating is very clear: by introducing silica, polyethylene wax, micronized wax and other extinction components into the polyurethane, acrylic and other base film-forming resins, the micro-rough structure formed by these components in the dry film of the coating is used to destroy the flatness of the paint film surface, so that the incident light is diffusely reflected in all directions instead of specular reflection, and finally the gloss of the coating is controlled in the low gloss range such as matte, semi-matte and the like, to meet the visual and functional requirements of specific scenes. With the improvement of global environmental awareness and the increasingly stringent ecological protection regulations, the coating industry is undergoing a revolutionary transformation from solvent-based to water-based. Under this background, the water-based polyurethane matt oil with water as the dispersion medium stands out with its outstanding advantages: on the one hand, its VOC emission can be as low as 50 g / L or less, fully meeting the requirements of environmental protection regulations, and the construction process is safe and pollution-free; on the other hand, thanks to the strong polarity and cross-linking characteristics of the polyurethane molecular chain, the paint film formed after curing of this kind of matt oil has high elasticity, excellent wear resistance and good adhesion to metal, plastic, composite and other substrates, so it has gradually replaced traditional solvent-based coatings and is widely used in high-end equipment manufacturing fields such as ships, aircraft, high-speed trains and marine engineering. However, the current commercialized water-based polyurethane matt oil still faces the key technical bottleneck of limited mechanical strength in actual engineering scenarios, which is difficult to fully match the severe service requirements of high-end equipment. SUMMARY

[0003] The present application aims to provide a high-strength water-based polyurethane matt oil and a preparation method thereof to solve the technical problems raised in the background.

[0004] To achieve the above-mentioned purpose, the present application provides the following technical solutions:

[0005] A preparation method of a high-strength water-based polyurethane matt oil, comprising the following steps:

[0006] S1, dispersing graphene oxide in anhydrous ethanol, adding silane coupling agent KH-550 and deionized water for reaction, and obtaining amino-functionalized graphene by centrifugation, washing and drying;

[0007] The obtained aminated graphene is mixed and dispersed with polycaprolactone polyol, isophorone diisocyanate and dibutyl tin dilaurate is added, and reaction is carried out under nitrogen protection to obtain an NCO-terminated GO modified prepolymer;

[0008] S2, under nitrogen protection, methyl acrylate is added dropwise into diethylenetriamine for reaction, then vacuum distillation amide polycondensation reaction is carried out to obtain an end-amino hyperbranched polyamide;

[0009] The end-amino hyperbranched polyamide is added into butanone, then epoxy-terminated polydimethylsiloxane is added for reaction, heating reaction is carried out, then butanone is added and hexamethylene diisocyanate is added for heating reaction, then an amino-terminated polyether is added for further reaction, finally tetraethyl orthosilicate and ammonia water are added for reaction to obtain a hyperbranched polysiloxane hybrid modified nanosilica dispersion liquid;

[0010] S3, the NCO-terminated GO modified prepolymer, polyester polyol, dimethylol propionic acid, isophorone diisocyanate and acetone are mixed, dibutyl tin dilaurate is added, and pre-polymerization is carried out under nitrogen protection, then triethylamine is added for neutralization and salt formation reaction to obtain an ionic prepolymer;

[0011] S4, under shearing condition, deionized water is added into the ionic prepolymer for phase inversion emulsification, and the hyperbranched polysiloxane hybrid modified nanosilica acetone dispersion liquid is added during the emulsification process to obtain a hybrid emulsion;

[0012] Ethylene diamine aqueous solution is added dropwise into the hybrid emulsion for post-chain extension reaction, then acetone is removed by vacuum distillation after the reaction is completed to obtain a water-based polyurethane slurry.

[0013] In the technical scheme of the present application, the mechanical strength of the waterborne polyurethane flat oil is improved from two aspects. On the one hand, the functionalized graphene oxide is directly introduced into the polyurethane molecular chain segment through chemical bonding to build a high-strength intramolecular skeleton. The principle is to first modify the graphene oxide with amino groups by using silane coupling agent KH-550, and then react the surface amino groups with isophorone diisocyanate, so that the graphene becomes part of the polyurethane prepolymer with active NCO end-capping. This covalent bond anchoring method solves the problem of weak interfacial bonding of nanofillers in the polyurethane matrix. When the coating is subjected to high-speed impact load, the graphene two-dimensional sheet layer with ultra-high modulus can act as the core of stress transfer, and through its large specific surface area, the locally concentrated impact energy can be rapidly dispersed to the entire molecular skeleton. At the same time, the graphene sheet layer can forcibly change the propagation path of microcracks, producing crack deflection and bridging effects, thereby absorbing a large amount of impact work and significantly improving the impact toughness and ultimate bearing capacity of the flat oil coating. On the other hand, by constructing a hyperbranched polysiloxane hybrid silica structure, high-efficiency energy dissipation nodes are formed inside the coating. The principle is to use a hyperbranched polyamide with dense amino groups at the end as a template, on the one hand, introducing flexible silicone segments through epoxy-amino addition, and on the other hand, generating nano-silica in situ inside the cage-like space of the hyperbranched molecule through sol-gel method. This complex hybrid center undergoes multi-point chemical crosslinking with the polyurethane main chain during film formation, forming a three-dimensional interpenetrating network with high free volume. The unique morphology of the hyperbranched structure can provide a large amount of intramolecular space and branched segment rotation freedom, and when subjected to external force impact, these branched structures can generate internal friction through cooperative motion to convert kinetic energy into heat energy dissipation; at the same time, the introduced flexible silicone segments effectively relieve the stress concentration caused by the rigid core of silica. This rigid-flexible hybrid node cooperates with the graphene skeleton to make the flat oil coating maintain high hardness and deep flat light effect while having excellent anti-impact and anti-cracking performance.

[0014] In the experiment, the inventors found that when the functionalized graphene oxide is introduced into the polyurethane main chain, due to the huge steric hindrance and extremely high modulus of the graphene sheet layer, the segment movement ability (flexibility) of the polyurethane molecular chain is significantly reduced, and the molecular chain becomes "rigid". The hyperbranched polysiloxane hybrid modified nanometer silicon dioxide is a huge multi-limb hyperbranched sphere. During the film forming process, steric hindrance shielding occurs between the two: the rigid graphene-polyurethane chain segment is difficult to penetrate the dense functional group cloud on the outer layer of the hyperbranched sphere, resulting in that the chemical crosslinking between the two only stays on the surface and cannot form a deep network interpenetration, thereby affecting the synergistic improvement of the mechanical strength of the matte oil coating. To further solve this technical problem, in the process of preparing the hyperbranched polysiloxane hybrid modified nanometer silicon dioxide, after the introduction of the organic silicon modification, the remaining amino groups at the hyperbranched end are first reacted with hexamethylene diisocyanate, then the end amino polyether with high conformational freedom is grafted, and finally the sol-gel reaction of TEOS is carried out, generating a silicon dioxide rigid core in situ on the hyperbranched structure of the grafted polyether segment, forming a hybrid particle with a flexible polyether handle-rigid silicon dioxide core. The high conformational freedom of the polyether long chain enables it to cross the steric hindrance of the hyperbranched structure, actively penetrate and wrap around the rigid main chain reinforced by graphene, and build a bridging structure. This bridging effect breaks the rigid shielding, and the matte particle evolves from a simple physical filler to a globally networked core node. When the coating is impacted or stretched by external force, the flexible bridge acts as a nanoscale spring and deforms to absorb energy, and the stress is smoothly transmitted from the main chain to the reinforced node, effectively eliminating the interface stress concentration, thereby further improving the mechanical strength of the matte coating.

[0015] Preferably, in step S1, the mass ratio of graphene oxide to silane coupling agent KH-550 is 1:(1-2).

[0016] Preferably, in step S1, the mass ratio of polycaprolactone polyol to aminated graphene is 50:(0.2-1.5).

[0017] Preferably, in step S1, the mass ratio of polycaprolactone polyol to isophorone diisocyanate is 50:(10-20).

[0018] Preferably, in step S2, the mass ratio of methyl acrylate to diethylenetriamine is 25:(8-12).

[0019] Preferably, in step S2, the mass ratio of hyperbranched polyamide to epoxy-terminated polydimethylsiloxane is 20:(3-8).

[0020] Preferably, in step S3, the mass ratio of NCO-terminated GO modified prepolymer to polyester polyol is 40:(50-70).

[0021] Preferably, in step S3, the mass ratio of the NCO-terminated GO modified prepolymer to dimethylol propionic acid is 40:(4-6).

[0022] Preferably, in step S3, the mass ratio of the NCO-terminated GO modified prepolymer to isophorone diisocyanate is 40:(25-30).

[0023] A high-strength waterborne polyurethane matte oil is prepared by the method described above.

[0024] Compared with the prior art, the present application has the following advantages:

[0025] 1. By covalently connecting the functionalized graphene oxide into the polyurethane molecular chain, a high-strength skeleton is constructed, and the graphene sheet layer can effectively disperse the impact stress and hinder crack propagation, greatly enhancing the impact toughness and load-bearing capacity of the coating.

[0026] 2. The hyperbranched polysiloxane hybrid silica, as an energy dissipation node, combines its three-dimensional interpenetrating network with flexible silicone segments, and when stressed, it consumes energy through intramolecular friction, relieving stress concentration, so that the coating has excellent anti-cracking property while maintaining high hardness and matte effect.

[0027] 3. By introducing an amino-terminated polyether long chain into the hyperbranched structure, a flexible bridging structure is formed, effectively overcoming the steric hindrance between the graphene rigid chain segment and the hyperbranched particle, promoting deep interpenetration and stress transfer between the two, and further improving the overall mechanical strength and interface bonding effect. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 SEM image of the surface of the coating formed after the matte oil prepared in Example 4 is coated.

[0029] Figure 2 XPS spectrum of the coating formed after the matte oil prepared in Example 4 is coated. DETAILED DESCRIPTION

[0030] The technical solutions in the embodiments of the present application will be described below in a clear and complete manner. Obviously, the described embodiments are only a part of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0031] Example 1

[0032] A preparation method of a high-strength waterborne polyurethane matte oil, comprising the following steps:

[0033] Step 1: 1.0 g of graphene oxide was weighed and dispersed in 200 mL of anhydrous ethanol, and ultrasonic stripping was performed at a power of 400 W for 2 h until a uniform dark suspension was formed. Then 1.8 g of silane coupling agent KH-550 and 0.1 mL of deionized water were added, and the reaction was refluxed at 75°C for 8 h. After the reaction was completed, the mixture was centrifuged at 8000 r / min and washed with anhydrous ethanol for 3 times, and the obtained solid was dried at 60°C under vacuum to obtain amino-functionalized graphene (NH2-GO).

[0034] 1.2 g of the above NH2-GO powder was added to 50 g of polycaprolactone polyol (PCL2000), and a high-shear dispersing machine was used for pre-dispersion at 2000 rpm for 30 min. Then 18 g of isophorone diisocyanate (IPDI) and 0.02 g of dibutyltin dilaurate were added, and the reaction was carried out at 60°C under nitrogen protection for 4 h to obtain a GO-modified prepolymer capped with NCO.

[0035] Step 2: In a three-necked flask, 11 g of diethylenetriamine was added, and 25 g of methyl acrylate was slowly added under nitrogen protection and ice water bath conditions. After the addition was completed, the ice bath was removed, and the temperature was increased to 50°C for stirring reaction for 12 h. Then a vacuum distillation device was switched on, and the temperature was slowly increased to 130°C for amide condensation and continuous vacuum removal of generated methanol. When the viscosity of the system increased significantly and no liquid flowed out, the reaction was stopped, and an amino-terminated hyperbranched polyamide was obtained. 20 g of the amino-terminated hyperbranched polyamide was taken, and the system was cooled to 60°C. 40 g of butanone was added for dilution, then 7 g of epoxy polydimethylsiloxane (E-PDMS, Mn≈1000) was added, and the temperature was increased to 80°C for reaction for 5 h. The system was cooled to 40°C, and 10 g of butanone was added. 2 g of hexamethylene diisocyanate was slowly added dropwise, and the reaction was carried out for 2 h. Then 10 g of amino-terminated polyether (D-2000) was added, and the temperature was increased to 55°C for reaction for 3 h. Finally, 5 g of tetraethyl orthosilicate (TEOS) and 2 g of 10% ammonia water were added, and the high-speed shearing reaction was carried out at room temperature for 12 h to obtain a hyperbranched polysiloxane hybrid modified nanosilica dispersion;

[0036] Step 3: In a reaction kettle, 40 g of NCO-terminated GO modified prepolymer, 65 g of polyester polyol (PEA2000), 5.5 g of hydrophilic chain extender dimethylol propionic acid (DMPA), and 29 g of isophorone diisocyanate were sequentially added, 30 g of acetone was added to adjust the viscosity, and 0.015 g of dibutyltin dilaurate was added; the stirring was started and the temperature was raised to 85°C under nitrogen protection for about 3.5 h, after the DMPA was completely dissolved and involved in the reaction, the NCO content was detected by di-n-butylamine titration every 1 h, when the NCO mass fraction was reduced to 2.5%-3.0%, the heating was stopped, and after the system was cooled to below 40°C, 3.6 g of triethylamine (TEA) was slowly added for neutralization and salt formation reaction, and the stirring was maintained for 30 min to obtain an ionic prepolymer.

[0037] Step 4: The speed was increased to 3000 rpm, and 255 mL of deionized water was slowly added to the above ionic prepolymer under severe shearing conditions for phase transfer emulsification, after about half of the water was added, 10 g of hyperbranched polysiloxane hybrid modified nano-silica dispersion was added to the kettle for shearing emulsification for 5 min to form a uniform hybrid emulsion; then the speed was reduced to 500 rpm, and a post-chain extender solution composed of 1.8 g of ethylenediamine and 10 mL of water was slowly added, and the stirring was continued at room temperature for 2 h to complete the molecular chain growth; after the reaction was completed, the vacuum device was started to remove the acetone solvent in the system by distillation under reduced pressure at 45°C, and finally filtered through a 200 mesh filter screen to obtain a high-strength waterborne polyurethane paste.

[0038] Example 2

[0039] A method for preparing a high-strength waterborne polyurethane paste, comprising the following steps:

[0040] Step 1: 1.0 g of graphene oxide was dispersed in 200 mL of anhydrous ethanol, and ultrasonic stripping was performed at 400 W power for 2 h until a uniform dark suspension was formed, then 1.2 g of silane coupling agent KH-550 and 0.1 mL of deionized water were added, and the temperature was raised to 75°C for reflux reaction for 8 h; after the reaction was completed, the mixture was centrifuged at 8000 r / min and washed with anhydrous ethanol for 3 times, and the obtained solid was dried at 60°C under vacuum to obtain amino-functionalized graphene (NH2-GO).

[0041] 0.5 g of the above NH2-GO powder was added to 50 g of polycaprolactone polyol (PCL2000), and pre-dispersed at 2000 rpm for 30 min using a high-shear disperser, then 13 g of isophorone diisocyanate (IPDI) and 0.02 g of dibutyltin dilaurate were added, and the reaction was carried out at 60°C under nitrogen protection for 4 h to obtain an NCO-terminated GO modified prepolymer.

[0042] Step 2: In a three-necked flask, 9 g of diethylenetriamine was added, and 25 g of methyl acrylate was slowly added dropwise under nitrogen protection and ice water bath conditions. After the dropwise addition was completed, the ice bath was removed, and the temperature was increased to 50°C for stirring reaction for 12 h. Then, the reaction was switched to a reduced pressure distillation device, and the temperature was slowly increased to 130°C for amide condensation polymerization. The generated methanol was continuously removed by vacuum. When the viscosity of the system increased significantly and no liquid flowed out, the reaction was stopped. Thus, an end-amino hyperbranched polyamide was obtained. 20 g of the end-amino hyperbranched polyamide was taken, and the system was cooled to 60°C. 40 g of butanone was added for dilution. Then, 5 g of epoxy polydimethylsiloxane (E-PDMS, Mn≈1000) was added. The temperature was increased to 80°C for reaction for 5 h. The system was cooled to 40°C, and 10 g of butanone was added. 2 g of hexamethylene diisocyanate was slowly added dropwise. The reaction was performed for 2 h. Then, 10 g of an amino-terminated polyether (D-2000) was added dropwise. The temperature was increased to 55°C for reaction for 3 h. Finally, 5 g of tetraethyl orthosilicate (TEOS) and 2 g of ammonia water with a concentration of 10% were added. The system was subjected to high-speed shearing reaction at room temperature for 12 h. Thus, a hyperbranched polysiloxane hybrid modified nano-silica dispersion was obtained.

[0043] Step 3: In a reaction kettle, 40 g of GO modified prepolymer capped with NCO, 55 g of polyester polyol (PEA2000), 4.5 g of hydrophilic chain extender dimethylol propionic acid (DMPA), and 26 g of isophorone diisocyanate were sequentially added. 30 g of acetone was added to adjust the viscosity, and 0.015 g of dibutyltin dilaurate was additionally added. The stirring was started, and the temperature was increased to 85°C under nitrogen protection for reaction for about 3.5 h. After the DMPA was completely dissolved and involved in the reaction, the NCO content was detected by di-n-butylamine titration every 1 h. When the NCO mass fraction was reduced to 2.5% to 3.0%, the heating was stopped. When the system was cooled to below 40°C, 3.6 g of triethylamine (TEA) was slowly added for neutralization and salt formation reaction. The stirring was maintained for 30 min. Thus, an ionic prepolymer was obtained.

[0044] Step 4: The rotation speed was increased to 3000 rpm. The ionic prepolymer was slowly added with 255 mL of deionized water for phase inversion emulsification under severe shearing conditions. After about half of the water was added, 10 g of the hyperbranched polysiloxane hybrid modified nano-silica dispersion was added into the kettle for shearing emulsification for 5 min. Thus, a uniform hybrid emulsion was formed. Then, the rotation speed was reduced to 500 rpm. A post chain extender solution composed of 1.8 g of ethylenediamine and 10 mL of water was slowly added dropwise. The stirring was continuously performed at room temperature for 2 h to complete the molecular chain growth. After the reaction was completed, the acetone solvent in the system was removed by reduced pressure distillation at 45°C. Finally, the high-strength waterborne polyurethane paste was obtained by filtration through a 200-mesh filter screen.

[0045] Example 3

[0046] A method for preparing a high-strength waterborne polyurethane paste, comprising the following steps:

[0047] Step 1: 1.0 g of graphene oxide was weighed and dispersed in 200 mL of anhydrous ethanol, and ultrasonic stripping was performed at a power of 400 W for 2 h until a uniform dark suspension was formed. Then 1.5 g of silane coupling agent KH-550 and 0.1 mL of deionized water were added, and the reaction was refluxed at 75°C for 8 h. After the reaction was completed, the mixture was centrifuged at 8000 r / min and washed with anhydrous ethanol for 3 times, and the obtained solid was dried at 60°C under vacuum to obtain amino-functionalized graphene (NH2-GO).

[0048] 0.8 g of the above NH2-GO powder was added to 50 g of polycaprolactone polyol (PCL2000), and a high-shear dispersing machine was used for pre-dispersion at 2000 rpm for 30 min. Then 15 g of isophorone diisocyanate (IPDI) and 0.02 g of dibutyltin dilaurate were added, and the reaction was carried out at 60°C under nitrogen protection for 4 h to obtain a GO-modified prepolymer capped with NCO.

[0049] Step 2: In a three-necked flask, 10 g of diethylenetriamine was added, and 25 g of methyl acrylate was slowly added under nitrogen protection and ice water bath conditions. After the addition was completed, the ice bath was removed, and the temperature was increased to 50°C for stirring reaction for 12 h. Then a vacuum distillation device was switched on, and the temperature was slowly increased to 130°C for amide condensation and continuous vacuum removal of generated methanol. When the viscosity of the system increased significantly and no liquid flowed out, the reaction was stopped, and an amino-terminated hyperbranched polyamide was obtained. 20 g of the amino-terminated hyperbranched polyamide was taken, and the system was cooled to 60°C. 40 g of butanone was added for dilution, then 6 g of epoxy polydimethylsiloxane (E-PDMS, Mn≈1000) was added, and the temperature was increased to 80°C for reaction for 5 h. The system was cooled to 40°C, and 10 g of butanone was added. 2 g of hexamethylene diisocyanate was slowly added dropwise, and the reaction was carried out for 2 h. Then 10 g of amino-terminated polyether (D-2000) was added, and the temperature was increased to 55°C for reaction for 3 h. Finally, 5 g of tetraethyl orthosilicate (TEOS) and 2 g of 10% ammonia water were added, and the high-speed shearing reaction was carried out at room temperature for 12 h to obtain a hyperbranched polysiloxane hybrid modified nanosilica dispersion;

[0050] Step 3: In a reaction kettle, 40 g of NCO-terminated GO modified prepolymer, 60 g of polyester polyol (PEA2000), 5 g of hydrophilic chain extender dimethylol propionic acid (DMPA), and 27 g of isophorone diisocyanate were sequentially added, 30 g of acetone was added to adjust the viscosity, and 0.015 g of dibutyltin dilaurate was added; the stirring was started and the temperature was raised to 85°C under nitrogen protection for about 3.5 h, after the DMPA was completely dissolved and involved in the reaction, the NCO content was detected by di-n-butylamine titration every 1 h, when the NCO mass fraction was reduced to 2.5%-3.0%, the heating was stopped, and after the system was cooled to below 40°C, 3.6 g of triethylamine (TEA) was slowly added for neutralization and salt formation reaction, and the stirring was maintained for 30 min to obtain an ionic prepolymer.

[0051] Step 4: The speed was increased to 3000 rpm, and 255 mL of deionized water was slowly added to the above ionic prepolymer under severe shearing conditions for phase transfer emulsification, after about half of the water was added, 10 g of hyperbranched polysiloxane hybrid modified nano-silica dispersion was added to the kettle for shearing emulsification for 5 min to form a uniform hybrid emulsion; then the speed was reduced to 500 rpm, and a post-chain extender solution composed of 1.8 g of ethylenediamine and 10 mL of water was slowly added, and the stirring was continued at room temperature for 2 h to complete the molecular chain growth; after the reaction was completed, the vacuum device was started to remove the acetone solvent in the system by distillation under reduced pressure at 45°C, and finally filtered through a 200 mesh filter screen to obtain a high-strength waterborne polyurethane paste.

[0052] Example 4

[0053] A method for preparing a high-strength waterborne polyurethane paste, comprising the following steps:

[0054] Step 1: 1.0 g of graphene oxide was dispersed in 200 mL of anhydrous ethanol, and ultrasonic peeling was performed at a power of 400 W for 2 h until a uniform dark suspension was formed, then 2.0 g of silane coupling agent KH-550 and 0.1 mL of deionized water were added, and the temperature was raised to 75°C for reflux reaction for 8 h; after the reaction was completed, the mixture was centrifuged at 8000 r / min and washed with anhydrous ethanol for 3 times, and the obtained solid was dried at 60°C under vacuum to obtain amino-functionalized graphene (NH2-GO).

[0055] 1.5 g of the above NH2-GO powder was added to 50 g of polycaprolactone polyol (PCL2000), and pre-dispersed at 2000 rpm for 30 min using a high-shear dispersing machine, then 20 g of isophorone diisocyanate (IPDI) and 0.02 g of dibutyltin dilaurate were added, and the reaction was carried out at 60°C under nitrogen protection for 4 h to obtain an NCO-terminated GO modified prepolymer.

[0056] Step 2: In a three-necked flask, 12 g of diethylenetriamine was added, and 25 g of methyl acrylate was slowly added dropwise under nitrogen protection and ice water bath conditions. After the dropwise addition was completed, the ice bath was removed, and the temperature was increased to 50°C for stirring reaction for 12 h. Then, the reaction was switched to a reduced pressure distillation device, and the temperature was slowly increased to 130°C for amide condensation polymerization. The generated methanol was continuously removed by vacuum. When the viscosity of the system was significantly increased and no liquid was discharged, the reaction was stopped. Thus, an end-amino hyperbranched polyamide was obtained. 20 g of the end-amino hyperbranched polyamide was taken, and the system was cooled to 60°C. 40 g of butanone was added for dilution. Then, 8 g of epoxy polydimethylsiloxane (E-PDMS, Mn≈1000) was added. The temperature was increased to 80°C for reaction for 5 h. The system was cooled to 40°C, and 10 g of butanone was added. 2 g of hexamethylene diisocyanate was slowly added dropwise. The reaction was performed for 2 h. Then, 10 g of an amino-terminated polyether (D-2000) was added dropwise. The temperature was increased to 55°C for reaction for 3 h. Finally, 5 g of tetraethyl orthosilicate (TEOS) and 2 g of ammonia water with a concentration of 10% were added. The high-speed shearing reaction was performed at room temperature for 12 h. Thus, a hyperbranched polysiloxane hybrid modified nano-silica dispersion was obtained.

[0057] Step 3: In a reaction kettle, 40 g of GO modified prepolymer capped with NCO, 70 g of polyester polyol (PEA2000), 6 g of hydrophilic chain extender dimethylol propionic acid (DMPA), and 30 g of isophorone diisocyanate were sequentially added. 30 g of acetone was added to adjust the viscosity, and 0.015 g of dibutyltin dilaurate was additionally added. The stirring was started, and the temperature was increased to 85°C under nitrogen protection for reaction for about 3.5 h. After the DMPA was completely dissolved and involved in the reaction, the NCO content was detected by the di-n-butylamine titration method every 1 h. When the NCO mass fraction was reduced to 2.5% to 3.0%, the heating was stopped. When the system was cooled to below 40°C, 3.6 g of triethylamine (TEA) was slowly added for neutralization and salt formation reaction. The stirring was maintained for 30 min. Thus, an ionic prepolymer was obtained.

[0058] Step 4: The rotation speed was increased to 3000 rpm. The ionic prepolymer was slowly added with 255 mL of deionized water for phase inversion emulsification under the condition of severe shearing. After about half of the water was added, 10 g of the hyperbranched polysiloxane hybrid modified nano-silica dispersion was added into the kettle for shearing emulsification for 5 min. Thus, a uniform hybrid emulsion was formed. Then, the rotation speed was reduced to 500 rpm. A post chain extender solution composed of 1.8 g of ethylenediamine and 10 mL of water was slowly added dropwise. The stirring was continuously performed at room temperature for 2 h to complete the molecular chain growth. After the reaction was completed, the acetone solvent in the system was removed by reduced pressure distillation at 45°C. Finally, the high-strength waterborne polyurethane paste was obtained by filtration through a 200-mesh filter screen.

[0059] Example 5

[0060] A method for preparing a high-strength waterborne polyurethane paste, comprising the following steps:

[0061] Step 1: 1.0 g of graphene oxide was weighed and dispersed in 200 mL of anhydrous ethanol, and ultrasonic stripping was performed at a power of 400 W for 2 h until a uniform dark suspension was formed. Then 1.0 g of silane coupling agent KH-550 and 0.1 mL of deionized water were added, and the reaction was refluxed at 75°C for 8 h. After the reaction was completed, the mixture was centrifuged at 8000 r / min and washed with anhydrous ethanol for 3 times, and the obtained solid was dried at 60°C under vacuum to obtain amino-functionalized graphene (NH2-GO).

[0062] 0.2 g of the above NH2-GO powder was added to 50 g of polycaprolactone polyol (PCL2000), and a high-shear dispersing machine was used for pre-dispersion at 2000 rpm for 30 min. Then 10 g of isophorone diisocyanate (IPDI) and 0.02 g of dibutyltin dilaurate were added, and the reaction was carried out at 60°C under nitrogen protection for 4 h to obtain a GO-modified prepolymer capped with NCO.

[0063] Step 2: In a three-necked flask, 8 g of diethylenetriamine was added, and 25 g of methyl acrylate was slowly added under nitrogen protection and ice water bath conditions. After the addition was completed, the ice bath was removed, and the temperature was increased to 50°C for stirring reaction for 12 h. Then a vacuum distillation device was switched on, and the temperature was slowly increased to 130°C for amide condensation and continuous vacuum removal of generated methanol. When the viscosity of the system increased significantly and no liquid flowed out, the reaction was stopped, and an amino-terminated hyperbranched polyamide was obtained. 20 g of the amino-terminated hyperbranched polyamide was taken, and the system was cooled to 60°C. 40 g of butanone was added for dilution, then 3 g of epoxy polydimethylsiloxane (E-PDMS, Mn≈1000) was added, and the temperature was increased to 80°C for reaction for 5 h. The system was cooled to 40°C, and 10 g of butanone was added. 2 g of hexamethylene diisocyanate was slowly added dropwise, and the reaction was carried out for 2 h. Then 10 g of amino-terminated polyether (D-2000) was added, and the temperature was increased to 55°C for reaction for 3 h. Finally, 5 g of tetraethyl orthosilicate (TEOS) and 2 g of 10% ammonia water were added, and the high-speed shearing reaction was carried out at room temperature for 12 h to obtain a hyperbranched polysiloxane hybrid modified nanosilica dispersion;

[0064] Step 3: In a reaction kettle, NCO-terminated GO modified prepolymer 40 g, polyester polyol (PEA2000) 50 g, hydrophilic chain extender dimethylol propionic acid (DMPA) 4 g and isophorone diisocyanate 25 g were sequentially added, 30 g of acetone was added to adjust the viscosity, and 0.015 g of dibutyltin dilaurate was added; the stirring was started and the temperature was raised to 85°C under nitrogen protection for about 3.5 h, after DMPA was completely dissolved and involved in the reaction, the NCO content was detected by di-n-butylamine titration every 1 h, when the NCO mass fraction was reduced to 2.5% to 3.0%, the heating was stopped, after the system was cooled to below 40°C, 3.6 g of triethylamine (TEA) was slowly added for neutralization and salt formation reaction, and the stirring was maintained for 30 min to obtain an ionic prepolymer.

[0065] Step 4: The speed was increased to 3000 rpm, and 255 mL of deionized water was slowly added to the above ionic prepolymer under severe shearing conditions for phase inversion emulsification, after about half of the water was added, 10 g of hyperbranched polysiloxane hybrid modified nano-silica dispersion was added to the kettle for shearing emulsification for 5 min to form a uniform hybrid emulsion; then the speed was reduced to 500 rpm, and a post-chain extender solution composed of 1.8 g of ethylenediamine and 10 mL of water was slowly added, and the stirring was continued at room temperature for 2 h to complete the molecular chain growth; after the reaction was completed, the vacuum device was started to remove the acetone solvent in the system by distillation under reduced pressure at 45°C, and finally filtered through a 200 mesh filter screen to obtain a high-strength waterborne polyurethane paste.

[0066] Comparative Example 1: The difference between Comparative Example 1 and Example 1 is that Step 1 is omitted in the preparation process of the waterborne polyurethane paste, and the NCO-terminated GO modified prepolymer in Step 3 is replaced by an equal amount of graphene oxide.

[0067] Comparative Example 2: The difference between Comparative Example 2 and Example 1 is that Step 2 is omitted in the preparation process of the waterborne polyurethane paste, and the hyperbranched polysiloxane hybrid modified nano-silica dispersion in Step 4 is replaced by an equal amount of nano-silica.

[0068] Comparative Example 3: The difference between Comparative Example 3 and Example 1 is that in Step 2 of the preparation of the waterborne polyurethane paste, no hexamethylene diisocyanate and amino-terminated polyether D-2000 are added.

[0069] Performance test:

[0070] 1. Impact resistance test: The sample paint to be tested was uniformly coated on the surface of a standard tin plate (120 mm x 25 mm x 0.3 mm), and after curing and maintenance, the film thickness was about 25 μm. Using a paint film impact tester, a 1 kg weight was lifted to a certain height and then dropped freely to impact the sample plate. The maximum height (cm) at which the weight did not cause the paint film to crack, wrinkle or peel was recorded, which represented the impact resistance of the paint film. The test results are shown in Table 1.

[0071] 2. Tensile strength test: The waterborne polyurethane oil of each example and the comparative example was uniformly coated in a polytetrafluoroethylene mold, and after curing at 25°C and a relative humidity of 50% for 72 h, a film sample with a thickness of 0.2 mm was prepared; a universal material testing machine was used for testing, the tensile rate was set to 50 mm / min, 5 parallel samples were prepared for each group, and the average value after testing was taken as the final result. The test results are shown in Table 1.

[0072] 3. 60° gloss test: Referring to GB / T 9754-2007 "Determination of 20°, 60° and 85° specular gloss of paint films - non metallic paint", a gloss meter was used to test the cured coating sample, a 60° test angle (core evaluation angle of the matt oil) was selected, 5 test points were selected in different areas of each sample, the influence of surface flatness difference was eliminated, and the average value after testing was taken as the final gloss value. The test results are shown in Table 1.

[0073] 4. Adhesion test: Referring to GB / T 1720-1979 "Paint film adhesion test method", a circle method was used to test the coating sample coated on the tin plate, a circle adhesion tester was used, after drawing a circle on the coating surface, the paint debris drawn by the soft brush was removed, the peeling of the coating on the inside of the circle was observed, and the adhesion was classified into 1-7 grades according to the standard, grade 1 was the best (no peeling), and grade 7 was the worst (large area peeling). The test results are shown in Table 1.

[0074] Table 1:

[0075] Impact resistance (cm) Tensile strength (MPa) 60° gloss (°) Adhesion (scale) Example 1 50 22.8 3.7 1 Example 2 45 21.3 4.1 1 Example 3 50 22.1 4.8 1 Example 4 50 23.6 3.2 1 Example 5 45 20.5 5.0 1 Comparative Example 1 20 9.2 6.5 3 Comparative Example 2 25 11.5 15.8 2 Comparative Example 3 35 14.3 4.5 1

[0076] Although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art can modify the technical solutions described in the foregoing embodiments, or make equivalent substitutions for part of the technical features, and any modification, equivalent substitution, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A method for preparing a high-strength waterborne polyurethane matte oil, characterized in that, Includes the following steps: S1. Graphene oxide is dispersed in anhydrous ethanol, and silane coupling agent KH-550 and deionized water are added to react. After centrifugation, washing and drying, amino-based graphene is obtained. The obtained amino-enhanced graphene was mixed and dispersed with polycaprolactone polyol, and isophorone diisocyanate and dibutyltin dilaurate were added. The mixture was reacted under nitrogen protection to obtain NCO-terminated GO modified prepolymer. S2. Under nitrogen protection, methyl acrylate is added dropwise to diethylenetriamine to react, and then vacuum distillation amidation polycondensation reaction is carried out to obtain terminal amino hyperbranched polyamide. The terminal amino hyperbranched polyamide was added to methyl ethyl ketone (MEK), followed by the addition of epoxy-terminated polydimethylsiloxane (PDMS) and the reaction was carried out under heat. MEK and hexamethylene diisocyanate were then added to the system and the reaction was carried out under heat. The terminal amino polyether was then added and the reaction was continued. Finally, tetraethyl orthosilicate and ammonia were added and the reaction was carried out to obtain a hyperbranched polysiloxane hybrid modified nano silica dispersion. S3. Mix the NCO-terminated GO modified prepolymer, polyester polyol, dimethylolpropionic acid, isophorone diisocyanate and acetone, add dibutyltin dilaurate, carry out the prepolymerization reaction under nitrogen protection, and then add triethylamine to carry out the neutralization and salt formation reaction to obtain the ionic prepolymer. S4. Under shear conditions, deionized water is added to the ionic prepolymer to perform phase inversion emulsification, and the hyperbranched polysiloxane hybrid modified nano-silica acetone dispersion is added during the emulsification process to obtain a hybrid emulsion. An aqueous solution of ethylenediamine was added dropwise to the hybrid emulsion to carry out a post-chain extension reaction. After the reaction was completed, acetone was removed by vacuum distillation to obtain an aqueous polyurethane matte oil.

2. The method for preparing a high-strength waterborne polyurethane matte oil according to claim 1, characterized in that, In step S1, the mass ratio of graphene oxide to silane coupling agent KH-550 is 1:(1-2).

3. The method for preparing a high-strength waterborne polyurethane matte oil according to claim 1, characterized in that, In step S1, the mass ratio of polycaprolactone polyol to amino graphene is 50:(0.2-1.5).

4. The method for preparing a high-strength waterborne polyurethane matte oil according to claim 1, characterized in that, In step S1, the mass ratio of polycaprolactone polyol to isophorone diisocyanate is 50:(10-20).

5. The method for preparing a high-strength waterborne polyurethane matte oil according to claim 1, characterized in that, In step S2, the mass ratio of methyl acrylate to diethylenetriamine is 25:(8-12).

6. The method for preparing a high-strength waterborne polyurethane matte oil according to claim 1, characterized in that, In step S2, the mass ratio of hyperbranched polyamide to epoxy-terminated polydimethylsiloxane is 20:(3-8).

7. The method for preparing a high-strength waterborne polyurethane matte oil according to claim 1, characterized in that, In step S3, the mass ratio of NCO-terminated GO-modified prepolymer to polyester polyol is 40:(50-70).

8. The method for preparing a high-strength waterborne polyurethane matte oil according to claim 1, characterized in that, In step S3, the mass ratio of the NCO-terminated GO-modified prepolymer to dimethylolpropionic acid is 40:(4-6).

9. The method for preparing a high-strength waterborne polyurethane matte oil according to claim 1, characterized in that, In step S3, the mass ratio of the NCO-terminated GO-modified prepolymer to isophorone diisocyanate is 40:(25-30).

10. A high-strength waterborne polyurethane matte oil, characterized in that, It is prepared by the method described in any one of claims 1 to 9 above.

Images