A weather-resistant waterborne polyurethane ink and a method for preparing the same

Abstract

The application relates to the technical field of inks, and specifically discloses a weather-resistant water-based polyurethane ink and a preparation method thereof. The preparation method of the weather-resistant water-based polyurethane ink comprises the following steps: I, preparing a water-based polyurethane emulsion; II, mixing high-dispersion nano SiO2, styrene, an acrylic compound and a chloroether resin, and reacting under the condition of adding an initiator, a surfactant and a silane coupling agent to obtain a modified acrylic ester emulsion; III, dispersing the water-based polyurethane emulsion, the modified acrylic ester emulsion, graphene oxide, hexagonal boron nitride, pigments and an additive in a solvent, and uniformly mixing to obtain the weather-resistant water-based polyurethane ink. The weather-resistant water-based polyurethane ink according to the application has the ink layer formed after film coating and curing, the gloss loss rate of the ink layer after aging is not higher than 30%, the color difference value is not larger than 1.2, the powdering is very slight or even no powdering, and the peeling area is not larger than 0.1%, so that the weather-resistant water-based polyurethane ink has good weather resistance.

Description

Technical Field

[0001] This application relates to the technical field of inks, and in particular to a weather-resistant waterborne polyurethane ink and its preparation method. Background Technology

[0002] Waterborne polyurethane ink is an environmentally friendly ink that uses water as a dispersion medium. The waterborne polyurethane binder is uniformly dispersed in the water in particle form. This ink does not contain volatile organic solvents, thus possessing characteristics such as non-flammability, non-toxicity, odorlessness, energy saving, and environmental friendliness. In recent years, it has received increasing attention and its applications in screen printing, composite film printing, and other fields have become increasingly widespread. It can also be used for 3D printing. By introducing nanofibers and solvent-induced rapid curing technology, room temperature 3D printing can be achieved, and the printed structures have excellent mechanical properties and resilience. At the same time, fluorescent inks can be prepared by introducing fluorescent monomers, which have good acid and alkali resistance, heat resistance, and adhesion strength to the substrate, making them suitable for fluorescent anti-counterfeiting applications on plastic packaging films.

[0003] However, the shortcomings of waterborne polyurethane inks cannot be ignored. Due to the presence of hydrophilic groups in their molecular structure, these groups are easily affected by ultraviolet radiation, moisture, and temperature changes in the natural environment, leading to aging phenomena such as fading, discoloration, cracking, chalking, and decreased strength. In other words, their weather resistance is poor, which greatly limits the diversified applications of waterborne polyurethane inks. To improve the weather resistance of waterborne polyurethane inks, researchers have adopted various modification methods, including introducing organosilicon or organofluorine groups to waterborne polyurethane to improve its water resistance, and adding crosslinking agents to enhance the intermolecular forces of waterborne polyurethane, enabling the formation of a more stable network structure. These measures can effectively improve the weather resistance of waterborne polyurethane inks. However, with practical use, it has been found that organosilicon-modified waterborne polyurethane has poor hardness and abrasion resistance, making it easily damaged during use; organofluorine-modified waterborne polyurethane has poor environmental friendliness; if the ink layer is damaged, fluorine components will enter the environment, especially water bodies, causing pollution; and the addition of crosslinking agents will affect the storage stability and viscosity of waterborne polyurethane inks. Therefore, improving the weather resistance of waterborne polyurethane inks remains a challenging problem for researchers. Summary of the Invention

[0004] To address the aforementioned technical problems, this application provides a weather-resistant waterborne polyurethane ink and its preparation method.

[0005] In a first aspect, this application provides a method for preparing a weather-resistant waterborne polyurethane ink, comprising the following steps:

[0006] I. Aqueous polyurethane emulsion was prepared using isophorone diisocyanate and PEG-2000 in a weight ratio of 1:(1.5-3).

[0007] II. Nano-SiO2 is ball-milled once at a temperature of 55-65℃ and a rotation speed of 700-750r / min for 0.5-1h. Then it is mixed with polyacrylate at a weight ratio of 1:(35-40). The temperature and rotation speed are kept constant, and the mixture is ball-milled a second time for 2.5-3.5h to obtain highly dispersed nano-SiO2. Then it is mixed with styrene, acrylic compounds and chlorinated ether resin at a weight ratio of (1-3):13:(13-15):3.2 and reacted under the condition of adding initiator, surfactant and silane coupling agent to obtain modified acrylate emulsion.

[0008] III. Mix waterborne polyurethane emulsion, modified acrylate emulsion, solvent, graphene oxide, hexagonal boron nitride, pigment and additives in a weight ratio of (35-40):18:20:(2.5-3):(1-1.5):5:0.4, stir, and obtain weather-resistant waterborne polyurethane ink.

[0009] By adopting the above technical solution, this application first mixes PEG-2000 and isophorone diisocyanate, and then prepares an aqueous polyurethane emulsion under the condition of adding a chain extender and an initiator. This fully utilizes the low cohesive energy and easily rotating intermolecular ether bonds of PEG-2000, resulting in a stable structure that is not easily hydrolyzed. The resulting aqueous polyurethane emulsion exhibits strong water resistance, and the final weather-resistant aqueous polyurethane ink also possesses advantages of water resistance and flexibility. Simultaneously, this application strictly controls the weight ratio of isophorone diisocyanate to PEG-2000. The NCO / OH ratio within the system is controlled to ensure that the final ink has both good curability and flexibility. The resulting ink layer has a dense structure that is not prone to cracking and has better weather resistance. If the amount of isophorone diisocyanate is too large, it means that the NCO / OH ratio is too large, which will reduce the flexibility of the ink layer and make it prone to cracking and breakage during use. If the amount of PEG-2000 is too large, it means that the NCO / OH ratio is too small, which will reduce the curability of the ink, causing bubbles to appear in the ink layer during curing and reducing the surface smoothness.

[0010] Subsequently, this application subjected the nano-SiO2 to conventional ball milling, and then added a certain amount of polyacrylate for further ball milling. By controlling the ball milling temperature, time, and speed, the size of the nano-SiO2 particles was effectively reduced, and the specific surface area was increased. Furthermore, by controlling the ratio of nano-SiO2 to polyacrylate, the shearing effect during ball milling was optimized. Specifically, the polyacrylate can form a protective film to reduce the interaction forces between nano-SiO2 particles, promoting dispersion. At the same time, it chemically grafts onto the functional groups on the surface of the nano-SiO2 particles, improving the surface properties of the nano-SiO2 particles. The combined effect of ball milling physical dispersion and chemical modification can greatly enhance the dispersion ability of nano-SiO2 particles, resulting in highly dispersed nano-SiO2. Based on this, this application blended the highly dispersed nano-SiO2 with styrene, acrylic compounds, and chloroform resin. The highly dispersed nano-SiO2 can be fully dispersed in the system, while the styrene, acrylic compounds, and chloroform resin undergo polymerization reactions to obtain... The modified acrylic emulsion is then mixed with waterborne polyurethane emulsion, solvent, graphene oxide, hexagonal boron nitride, pigments, and additives in a specific weight ratio. During the mixing process, the modified acrylic emulsion and the waterborne polyurethane emulsion form hydrogen bonds through the polar hydrogen atoms on the urethane bonds and the oxygen atoms on the ester groups in the acrylic acid segments, thereby improving their compatibility within the system. The modified acrylic emulsion possesses excellent water resistance, heat resistance, and photoaging resistance, which can significantly improve the weather resistance of waterborne polyurethane inks. Furthermore, the highly dispersed nano-SiO2 can generate steric hindrance and reinforcing effects within the mixed system, thereby promoting the uniform dispersion of graphene oxide and hexagonal boron nitride. At the same time, the layered structure of graphene oxide and hexagonal boron nitride allows their good dispersion to, in turn, inhibit the aggregation of highly dispersed nano-SiO2. The three components work synergistically, not only promoting high dispersion and inhibiting aggregation but also enhancing the strength of the ink layer and reducing the possibility of cracking.

[0011] In general, this application utilizes modified acrylic emulsion and its internal highly dispersed nano-SiO2, graphene oxide, and hexagonal boron nitride to fully leverage the synergistic effect, thereby significantly improving the weather resistance of the ink. Testing shows that the weather-resistant waterborne polyurethane ink of this application, after coating and curing, exhibits a gloss loss rate of no more than 30%, a color difference value of no more than 1.2, very slight or even no chalking, and a peeling area of ​​no more than 0.1% after artificial aging treatment (under conditions of 480 hours of operation, black standard temperature of 65±2%, ambient temperature of 38±3℃, and continuous wetting and drying cycles). It possesses high practical value in natural environments.

[0012] Preferably, in step I, the weight ratio of isophorone diisocyanate to PEG-2000 is 1:2.

[0013] By adopting the above technical solution, this application strictly controls the weight ratio of isophorone diisocyanate to PEG-2000, thereby strictly controlling the NCO / OH ratio in the system, so that the curing degree and flexibility of the final ink are optimally balanced, the resulting ink layer is not easy to crack or break, has high surface smoothness, and its weather resistance is further improved.

[0014] Preferably, in step II, the temperature for ball milling nano-SiO2 is 60°C, the time for the first ball milling is 0.8 h, and the time for the second ball milling is 3 h.

[0015] By adopting the above technical solution, this application strictly controls the temperature and time of ball milling nano-SiO2, which greatly reduces the difference in particle size and improves dispersibility. At the same time, it ensures that there is almost no structural reorganization and wear on the particle surface, which improves the uniformity of particle size distribution. Thus, without affecting its mechanical properties, the dispersion effect of high-dispersion nano-SiO2 is improved as much as possible, which in turn improves the dispersion uniformity inside the ink layer and thus improves its weather resistance.

[0016] Preferably, in step II, the weight ratio of highly dispersed nano-SiO2, styrene, acrylic compounds and chlorinated ether resin is 2.4:13:14:3.2.

[0017] By adopting the above technical solution, this application strictly controls the weight ratio of highly dispersed nano-SiO2, styrene, acrylic compounds and chlorinated ether resin. At this time, highly dispersed nano-SiO2 can achieve better dispersion effect in the system, and the copolymer formed by the polymerization of styrene, acrylic compounds and chlorinated ether resin has higher stability. The modified acrylate emulsion obtained in the end has better polymerization effect.

[0018] Preferably, in step II, the acrylic compounds include butyl acrylate, hydroxyethyl acrylate, methacrylic acid, isooctyl acrylate and methyl methacrylate in a weight ratio of 25:(8-13):3:(20-25):8.

[0019] By adopting the above technical solution, the various acrylic compounds of this application are blended with styrene and participate together in the polymerization reaction of chloroether resin, which can balance the ratio of soft and hard segments in the system, so that the modified acrylic emulsion has suitable toughness and rigidity, and each acrylic compound can give full play to its own advantages, and optimize its weather resistance without affecting the mechanical properties of waterborne polyurethane emulsion.

[0020] Preferably, the weight ratio of butyl acrylate, hydroxyethyl acrylate, methacrylic acid, isooctyl acrylate and methyl methacrylate is 25:11:3:22:8.

[0021] By adopting the above technical solution, this application strictly controls the weight ratio of butyl acrylate, hydroxyethyl acrylate, methacrylic acid, isooctyl acrylate and methyl methacrylate. At this time, the synergistic effect between various acrylic compounds can be maximized, the number of soft and hard segments in the system is further balanced, and the synergistic effect with styrene is optimized, thereby greatly improving the weather resistance of waterborne polyurethane ink.

[0022] Preferably, in step III, the weight ratio of the aqueous polyurethane emulsion to the modified acrylate emulsion is 38:18.

[0023] By adopting the above technical solution, this application strictly controls the weight ratio of waterborne polyurethane emulsion and modified acrylic emulsion. At this time, the two emulsions have good compatibility, good overall water resistance, heat resistance and light aging resistance, and the toughness and rigidity are in a better balance. The resulting waterborne polyurethane ink has better weather resistance.

[0024] Preferably, in step III, the weight ratio of the modified acrylate emulsion, graphene oxide, and hexagonal boron nitride is 18:2.7:1.2.

[0025] By adopting the above technical solution, this application strictly controls the proportion between various substances, thereby further improving the weather resistance of the final waterborne polyurethane ink.

[0026] Secondly, this application provides a weather-resistant waterborne polyurethane ink prepared by the above-mentioned method for preparing weather-resistant waterborne polyurethane ink.

[0027] In summary, this application has the following beneficial technical effects:

[0028] 1. This application utilizes modified acrylic emulsion to significantly improve the weather resistance of waterborne polyurethane emulsion. According to the test, the ink layer formed by the weather-resistant waterborne polyurethane ink of this application after coating and curing, after artificial aging treatment (under the conditions of 480h running time, black standard temperature 65±2%, ambient temperature 38±3℃ and continuous operation of wetting and drying cycle), has a gloss loss rate of no more than 30%, a color difference value of no more than 1.2, very slight or even no chalking, and a peeling area of ​​no more than 0.1%, which has high use value in the natural environment.

[0029] 2. By controlling key process parameters and feeding ratios, and by utilizing the synergistic effect of highly dispersed nano-SiO2, graphene oxide, and hexagonal boron nitride, this application can significantly optimize the weather resistance of waterborne polyurethane emulsions without negatively impacting their mechanical properties. Detailed Implementation

[0030] Material source

[0031] Unless otherwise specified, all raw materials used in this application are commercially available products, specifically:

[0032] PEG-2000 was purchased from Haian Petrochemical Plant in Jiangsu Province;

[0033] Isophorone diisocyanate was purchased from Anhui Jinyueguan New Material Technology Co., Ltd.

[0034] Dibutyltin dilaurate was purchased from Jinan Hongboli Chemical Co., Ltd.

[0035] Butyl acrylate, hydroxyethyl acrylate, isooctyl acrylate, methyl methacrylate, and methacrylic acid were all purchased from Sinopharm Chemical Reagents.

[0036] Polyacrylate was purchased from Shanghai Kaiyin Chemical Co., Ltd., with a total exchange capacity ≥10.8 mmol / g (dry).

[0037] The chloroether resin was purchased from BASF, model MP-45, CAS number;

[0038] Sodium olefin sulfonate was purchased from Jining Fangyu Chemical Co., Ltd., CAS No. 68439-57-6;

[0039] Ammonium persulfate was purchased from Maclean's.

[0040] Graphene oxide was purchased from Jiangxi Shuobang New Material Technology Co., Ltd., with a particle size of 0.335-4 μm for the undersize.

[0041] Hexagonal boron nitride was purchased from Aladdin, with an average particle size of 1-2 μm;

[0042] The wetting agent was purchased from Hangzhou Lin'an Digo Organic Chemical Co., Ltd., and its model was TEGO-245.

[0043] The leveling agent was purchased from BYK Chemicals, model BYK-306;

[0044] The drying agent was purchased from Shanghai Tianyu Chemical Technology Co., Ltd., model A-16;

[0045] The defoamer was purchased from Xipusen New Materials (Ningbo) Co., Ltd., model DF800;

[0046] The hydrophilic titanium dioxide was purchased from Jiangsu Hehai Nanotechnology Co., Ltd., model number NY-010A.

[0047] The present application will be further described in detail below with reference to embodiments and comparative examples.

[0048] Example 1.1

[0049] A method for preparing a weather-resistant waterborne polyurethane ink includes the following steps:

[0050] 1. 4.8 kg of PEG-2000 was heated and melted at 60°C. After more than 60% of the PEG-2000 melted, stirring was started, the temperature was raised to 110°C, and the system was evacuated to a vacuum degree of 0.08 MPa. The system was dehydrated for 2 hours under this environment. Then, 1.6 kg of isophorone diisocyanate and 48 g of dibutyltin dilaurate were added, mixed and dispersed in acetone, the system temperature was adjusted to 70°C, and the reaction was carried out for 1.5 hours to obtain polyurethane ionomer. Water was added and stirred to carry out phase transfer. Acetone was recovered by distillation to obtain an aqueous polyurethane emulsion.

[0051] II. 4 kg of nano-SiO2 was ball-milled for 0.5 h at 65 °C and 700 r / min. Then, it was mixed with 160 kg of polyacrylate, and ball-milled a second time for 3.5 h while maintaining the temperature and speed, to obtain highly dispersed nano-SiO2. Subsequently, 1 kg of highly dispersed nano-SiO2, 13 kg of styrene, 15 kg of acrylic compounds (10 kg of butyl acrylate, 1.25 kg of methacrylic acid, and 3.75 kg of methyl methacrylate), and 3.2 kg of chloroether resin were mixed. The resulting mixture was divided into two equal parts by weight. One part by weight was mixed with 17.6 kg of deionized water, 240 g of sodium bicarbonate, and 640 g of sodium olefin sulfonate, and stirred at 650 rpm for 30 min. Add 600g of 5wt% ammonium persulfate solution, and while stirring at 250rpm, raise the system temperature to 70℃ at a biological rate of 5℃ / min. Then add another 600g of 5wt% ammonium persulfate solution and raise the system temperature to 80℃. Maintain the temperature for 15min. At this time, add another part by weight of the mixture and 4.2kg of 5wt% ammonium persulfate solution to the system. Keep the temperature for 3h. Then add another 600g of 5wt% ammonium persulfate solution and keep the temperature for 1.5h. After the reaction is completed, turn off the heating but do not stop stirring until the system temperature drops to about 40℃. Add ammonia water to adjust the pH of the system to >7, and continue stirring for 20min. Filter through a 200-mesh screen to obtain the modified acrylate emulsion.

[0052] III. Add 3.5 kg of the waterborne polyurethane emulsion obtained in step I, 1.8 kg of the modified acrylic emulsion obtained in step II, 250 g of graphene oxide, 150 g of hexagonal boron nitride, 500 g of pigment (hydrophilic titanium dioxide), and 40 g of additives (10 g of wetting agent, 5 g of leveling agent, 10 g of defoamer, and 20 g of drying agent) to deionized water, control the solid content of the system to be 30 ± 0.5%, and stir at a speed of 600 r / min to obtain weather-resistant waterborne polyurethane ink.

[0053] Example 1.2

[0054] A method for preparing a weather-resistant waterborne polyurethane ink includes the following steps:

[0055] 1. 3.84 kg of PEG-2000 was heated and melted at 60°C. After more than 60% of the PEG-2000 melted, stirring was started, the temperature was raised to 110°C, and the system was evacuated to a vacuum degree of 0.08 MPa. The system was dehydrated for 2 hours under this environment. Then, 2.56 kg of isophorone diisocyanate and 48 g of dibutyltin dilaurate were added, mixed and dispersed in acetone, and the system temperature was adjusted to 70°C. After reacting for 1.5 hours, a polyurethane ionomer was obtained. Water was added and stirred to carry out phase transfer. The acetone was recovered by distillation to obtain an aqueous polyurethane emulsion.

[0056] II. 4 kg of nano-SiO2 was ball-milled once at 55℃ and 750 r / min for 1 h. Then, it was mixed with 140 kg of polyacrylate, and ball-milled a second time for 2.5 h while maintaining the temperature and speed, to obtain highly dispersed nano-SiO2. Subsequently, 3 kg of highly dispersed nano-SiO2, 13 kg of styrene, 13 kg of acrylic compounds (8.7 kg butyl acrylate, 1.08 kg methacrylic acid, and 3.22 kg methyl methacrylate), and 3.2 kg of chloroprene resin were mixed. The resulting mixture was divided into two equal parts by weight. One part by weight was mixed with 16.5 kg of deionized water, 225 g of sodium bicarbonate, and 600 g of sodium olefin sulfonate, and stirred at 650 rpm for 30 min. Add 560g of 5wt% ammonium persulfate solution, and while stirring at 250rpm, raise the system temperature to 70℃ at a biological rate of 5℃ / min. Then add another 560g of 5wt% ammonium persulfate solution and raise the system temperature to 80℃. React at this temperature for 15min. At this time, add another part by weight of the mixture and 4.4kg of 5wt% ammonium persulfate solution to the system. Keep the temperature for 3h. Then add another 560g of 5wt% ammonium persulfate solution and keep the temperature for 1.5h. After the reaction is completed, turn off the heating but do not stop stirring until the system temperature drops to about 40℃. Add ammonia water to adjust the pH of the system to >7, and continue stirring for 20min. Filter through a 200-mesh screen to obtain the modified acrylate emulsion.

[0057] III. Add 4 kg of the waterborne polyurethane emulsion obtained in step I, 1.8 kg of the modified acrylic emulsion obtained in step II, 300 g of graphene oxide, 100 g of hexagonal boron nitride, 500 g of pigment (hydrophilic titanium dioxide), and 40 g of additives (10 g of wetting agent, 5 g of leveling agent, 10 g of defoamer, and 20 g of drying agent) to deionized water, control the solid content of the system to be 30 ± 0.5%, and stir at a speed of 600 r / min to obtain weather-resistant waterborne polyurethane ink.

[0058] Example 1.3

[0059] A method for preparing a weather-resistant waterborne polyurethane ink differs from Example 1.1 in that: in step III, the amount of waterborne polyurethane emulsion obtained in step I is 3.8 kg, while the rest is the same as in Example 1.1.

[0060] Example 1.4

[0061] A method for preparing a weather-resistant waterborne polyurethane ink differs from Example 1.1 in that: in step III, the amount of graphene oxide is 270g and the amount of hexagonal boron nitride is 120g, while the rest are the same as in Example 1.1.

[0062] Example 1.5

[0063] A method for preparing a weather-resistant waterborne polyurethane ink differs from Example 1.1 in that: in step III, the amount of waterborne polyurethane emulsion obtained in step I is 3.8 kg, the amount of graphene oxide is 270 g, and the amount of hexagonal boron nitride is 120 g, while the rest are the same as in Example 1.1.

[0064] Example 2.1

[0065] A method for preparing a weather-resistant waterborne polyurethane ink differs from Example 1.1 in that: in step I, the amount of isophorone diisocyanate is 2.35 kg, the amount of PEG-2000 is 4.05 kg, and the rest is the same as in Example 1.1.

[0066] Example 2.2

[0067] A method for preparing a weather-resistant waterborne polyurethane ink differs from Example 1.1 in that: in step I, the amount of isophorone diisocyanate is 2.13 kg, the amount of PEG-2000 is 4.27 kg, and the rest is the same as in Example 1.1.

[0068] Example 2.3

[0069] A method for preparing a weather-resistant waterborne polyurethane ink differs from Example 1.1 in that: in step I, the amount of isophorone diisocyanate is 1.98 kg, the amount of PEG-2000 is 4.42 kg, and the rest is the same as in Example 1.1.

[0070] Example 2.4

[0071] A method for preparing a weather-resistant waterborne polyurethane ink differs from Example 1.1 in that: in step I, the amount of isophorone diisocyanate is 1.83 kg, the amount of PEG-2000 is 4.57 kg, and the rest is the same as in Example 1.1.

[0072] Example 2.5

[0073] A method for preparing a weather-resistant waterborne polyurethane ink differs from Example 1.1 in that: in step I, the amount of isophorone diisocyanate is 1.72 kg, the amount of PEG-2000 is 4.68 kg, and the rest is the same as in Example 1.1.

[0074] Example 3.1

[0075] A method for preparing a weather-resistant waterborne polyurethane ink differs from Example 1.1 in that: in step II, the temperature for ball milling nano-SiO2 is 60°C, the time for the first ball milling is 0.8 h, and the time for the second ball milling is 3 h, while the rest are the same as in Example 1.1.

[0076] Example 3.2

[0077] A method for preparing a weather-resistant waterborne polyurethane ink differs from Example 1.1 in that: in step II, the temperature for ball milling nano-SiO2 is 65°C, the time for the first ball milling is 0.8 h, and the time for the second ball milling is 3 h, while the rest are the same as in Example 1.1.

[0078] Example 3.3

[0079] A method for preparing a weather-resistant waterborne polyurethane ink differs from Example 1.1 in that: in step II, the temperature for ball milling nano-SiO2 is 60°C, the time for the first ball milling is 0.6 h, and the time for the second ball milling is 3.4 h, while the rest are the same as in Example 1.1.

[0080] Example 4.1

[0081] A method for preparing a weather-resistant waterborne polyurethane ink differs from Example 1.1 in that: in step II, the amount of highly dispersed nano-SiO2 is 2.4 kg, and the amount of acrylic compounds is 14 kg (9.35 kg butyl acrylate, 1.15 kg methacrylic acid and 3.49 kg methyl methacrylate), while the rest are the same as in Example 1.1.

[0082] Example 4.2

[0083] A method for preparing a weather-resistant waterborne polyurethane ink differs from Example 1.1 in that: in step II, the amount of highly dispersed nano-SiO2 is 2 kg, and the amount of acrylic compounds is 14 kg (9.35 kg butyl acrylate, 1.15 kg methacrylic acid and 3.49 kg methyl methacrylate), while the rest are the same as in Example 1.1.

[0084] Example 4.3

[0085] A method for preparing a weather-resistant waterborne polyurethane ink differs from Example 1.1 in that: in step II, the amount of highly dispersed nano-SiO2 is 2.4 kg, and the amount of acrylic compounds is 14.5 kg (9.68 kg butyl acrylate, 1.19 kg methacrylic acid and 3.63 kg methyl methacrylate), while the rest is the same as in Example 1.1.

[0086] Example 5.1

[0087] A method for preparing a weather-resistant waterborne polyurethane ink differs from Example 4.1 in that: in step II, the acrylic compounds are 5.07 kg butyl acrylate, 1.62 kg hydroxyethyl acrylate, 0.62 kg methacrylic acid, 5.07 kg isooctyl acrylate and 1.62 kg methyl methacrylate, while the rest are the same as in Example 4.1.

[0088] Example 5.2

[0089] A method for preparing a weather-resistant waterborne polyurethane ink differs from Example 4.1 in that: in step II, the acrylic compounds are 5.07 kg butyl acrylate, 2.63 kg hydroxyethyl acrylate, 0.62 kg methacrylic acid, 4.06 kg isooctyl acrylate and 1.62 kg methyl methacrylate, while the rest are the same as in Example 4.1.

[0090] Example 5.3

[0091] A method for preparing a weather-resistant waterborne polyurethane ink differs from Example 5.1 in that: in step II, the amount of hydroxyethyl acrylate is 1.9 kg and the amount of isooctyl acrylate is 4.79 kg, while the rest are the same as in Example 5.1.

[0092] Example 5.4

[0093] A method for preparing a weather-resistant waterborne polyurethane ink differs from Example 5.1 in that: in step II, the amount of hydroxyethyl acrylate is 2.23 kg and the amount of isooctyl acrylate is 4.46 kg, while the rest are the same as in Example 5.1.

[0094] Example 5.5

[0095] A method for preparing a weather-resistant waterborne polyurethane ink differs from Example 5.1 in that: in step II, the amount of hydroxyethyl acrylate is 2.45 kg and the amount of isooctyl acrylate is 4.24 kg, while the rest are the same as in Example 5.1.

[0096] Comparative Example 1.1

[0097] The difference from Example 1.1 is that in step I, the amount of isophorone diisocyanate used is 3.2 kg, the amount of PEG-2000 used is 3.2 kg, and the rest is the same as in Example 1.1.

[0098] Comparative Example 1.2

[0099] The difference from Example 1.1 is that in step I, the amount of isophorone diisocyanate used is 1 kg, the amount of PEG-2000 used is 5.4 kg, and the rest is the same as in Example 1.1.

[0100] Comparative Example 2.1

[0101] The difference from Example 1.1 is that the highly dispersed nano-SiO2 in step II is removed, while the rest is the same as in Example 1.1.

[0102] Comparative Example 2.2

[0103] The difference from Example 1.1 is that in step II, the amount of highly dispersed nano-SiO2 used is 0.8 kg, while the rest is the same as in Example 1.1.

[0104] Comparative Example 2.3

[0105] The difference from Example 1.1 is that in step II, the amount of highly dispersed nano-SiO2 used is 3.5 kg, while the rest is the same as in Example 1.1.

[0106] Comparative Example 3.1

[0107] The difference from Example 1.1 is that in step II, the amount of acrylic compound used is 10 kg (6.7 kg butyl acrylate, 0.83 kg methacrylic acid and 2.47 kg methyl methacrylate), and the rest is the same as in Example 1.1.

[0108] Comparative Example 3.2

[0109] The difference from Example 1.1 is that in step II, the amount of acrylic compounds used is 18 kg (12 kg butyl acrylate, 1.5 kg methacrylic acid and 4.5 kg methyl methacrylate), and the rest is the same as in Example 1.1.

[0110] Comparative Example 4.1

[0111] The difference from Example 1.1 is that in step III, the amount of waterborne polyurethane emulsion obtained in step I is 3 kg, and the amount of modified acrylate emulsion obtained in step II is 2.3 kg. All other aspects are the same as in Example 1.1.

[0112] Comparative Example 4.2

[0113] The difference from Example 1.1 is that in step III, the amount of waterborne polyurethane emulsion obtained in step I is 4 kg, and the amount of modified acrylate emulsion obtained in step II is 1.3 kg. All other aspects are the same as in Example 1.1.

[0114] Comparative Example 5.1

[0115] The difference from Example 1.1 is that in step III, the amount of graphene oxide used is 200g and the amount of hexagonal boron nitride used is 200g, while the rest are the same as in Example 1.1.

[0116] Comparative Example 5.2

[0117] The difference from Example 1.1 is that in step III, the amount of graphene oxide used is 350g and the amount of hexagonal boron nitride used is 50g, while the rest are the same as in Example 1.1.

[0118] Performance testing

[0119] The water-based polyurethane inks obtained in the examples and comparative examples were coated onto tinplate, with a wet film thickness controlled at 8-10 μm. The ink layers were then cured for 10-15 hours at 23±℃ and 50±5% relative humidity to obtain ink layer samples. Four identical samples were prepared for each example or comparative example group. One sample was placed in darkness as a control, while the other three samples underwent artificial aging treatment according to the method in GB / T 1865-2009. The ink layer samples were placed on a sample holder made of inert material, ensuring air circulation. Xenon lamps were used to irradiate the samples, controlling the average irradiance on the ink layer sample surface between 300-400 nm to 60 W / m². 2 The standard temperature for black is 65±2%, the ambient temperature is 38±3℃, and a continuous wetting and drying cycle of 18 min wetting and 102 min drying is performed. The relative humidity during drying should be between 40-60%, and the radiation exposure should not be interrupted during the wetting process. The running time is controlled to be 480h. After the end, the average values ​​of four data points, namely gloss loss rate, color difference value, chalking condition and peeling area, are measured for three identical samples in each group. The results are recorded in Table 1.

[0120] in:

[0121] The loss rate (%) was determined according to GB / T 9754-2007;

[0122] Color difference values ​​were determined according to GB / T 11186.2 and GB / T 11186.3;

[0123] The degree of chalking was determined according to ISO 4628-7, and the grade evaluation was recorded. Grade 0 was no chalking, Grade 1 was very slight chalking (pigment particles could just be observed on the test cloth), Grade 2 was slight chalking (a small amount of pigment particles were on the test cloth), Grade 3 was obvious chalking (a lot of pigment particles were on the test cloth), Grade 4 was heavy chalking (a lot of pigment particles were on the test cloth), and Grade 5 was severe chalking (the test cloth was covered with pigment particles or the sample showed the substrate).

[0124] The peeling area (%) was determined in accordance with GB / T 1766-2008.

[0125] Table 1 Performance Test Table

[0126]

[0127] Data Analysis:

[0128] As can be seen from Table 1, the gloss loss rate of Examples 1.1-1.2 is 29.8-30.0%, the color difference value is 1.2, the chalking grade is 1, and the peeling area is 0.098-0.099%. This proves that the present application utilizes modified acrylic emulsion and its internal highly dispersed nano-SiO2, graphene oxide and hexagonal boron nitride to fully exert the synergistic effect, thereby greatly improving the weather resistance of the ink.

[0129] The difference between Examples 1.1 and 1.5 lies in the different weight ratios of the waterborne polyurethane emulsion, modified acrylate emulsion, graphene oxide, and hexagonal boron nitride in step III. Data shows that the gloss loss rate, color difference value, and peeling area of ​​Example 1.5 are all lower than those of Example 1.1, and the chalking grade is also downgraded. This proves that by strictly controlling the proportions between the various substances, the weather resistance of the final waterborne polyurethane ink is further improved. Furthermore, the data of Examples 1.3-1.4 are all inferior to those of Example 1.5, proving that the waterborne polyurethane emulsion, modified acrylate emulsion, graphene oxide, and hexagonal boron nitride have a better synergistic effect under optimized weight ratios.

[0130] The difference between Examples 2.1-2.5 and Example 1.1 is that the weight ratio of isophorone diisocyanate and PEG-2000 is different in step I. The data of Example 2.2 is significantly better than the other groups, which proves that this application strictly controls the NCO / OH ratio in the system by strictly controlling the weight ratio of isophorone diisocyanate and PEG-2000. This results in the final ink having the best balance between curing degree and flexibility, and the resulting ink layer is not easy to crack or break, has high surface smoothness, and further improves weather resistance.

[0131] The difference between Examples 3.1-3.3 and Example 1.1 lies in the different temperatures and times used for ball milling nano-SiO2 in step II. The data from Example 3.1 are significantly better than those from other groups, demonstrating that this application, by strictly controlling the temperature and time of ball milling nano-SiO2, greatly reduces the size difference between particles, improves dispersibility, and ensures that almost no structural reorganization or wear occurs on the particle surface, thereby improving the uniformity of particle size distribution. Thus, without affecting its mechanical properties, the dispersion effect of highly dispersed nano-SiO2 is improved as much as possible, which in turn improves the dispersion uniformity within the ink layer, thereby improving its weather resistance.

[0132] The difference between Examples 4.1-4.3 and Example 1.1 is that the weight ratio of highly dispersed nano-SiO2 and acrylic compounds is different in step II. The data of Example 4.1 is significantly better than those of other groups, proving that this application achieves better dispersion of highly dispersed nano-SiO2 in the system by strictly controlling the weight ratio of the two, and the copolymer formed when styrene, acrylic compounds and chloroether resin are polymerized has higher stability. The modified acrylate emulsion obtained in the end has better polymerization effect.

[0133] The difference between Examples 5.1-5.2 and Example 4.1 is that the composition of the acrylic compounds in step II is different, and the data of Examples 5.1-5.2 are significantly better than those of Example 4.1. This demonstrates that by using multiple compounds such as butyl acrylate, hydroxyethyl acrylate, methacrylic acid, isooctyl acrylate, and methyl methacrylate to blend with styrene and participate in the polymerization reaction of chloroether resin, this application can balance the ratio of soft and hard segments in the system, so that the modified acrylic emulsion has suitable toughness and rigidity, and each acrylic compound can give full play to its own advantages, optimizing the weather resistance of the waterborne polyurethane emulsion with almost no impact on its mechanical properties.

[0134] The difference between Examples 5.3-5.5 and Example 5.1 is that the weight ratios of butyl acrylate, hydroxyethyl acrylate, methacrylic acid, isooctyl acrylate, and methyl methacrylate are different in step II. The data of Example 5.4 are significantly better than those of the other groups, proving that by strictly controlling the weight ratios of butyl acrylate, hydroxyethyl acrylate, methacrylic acid, isooctyl acrylate, and methyl methacrylate, this application can maximize the synergistic effect among various acrylic compounds, further balance the number of soft and hard segments in the system, and optimize the synergistic effect with styrene, thereby greatly improving the weather resistance of waterborne polyurethane inks.

[0135] The data of Comparative Examples 1.1-1.2 are all inferior to those of Example 1.1, proving that this application strictly controls the NCO / OH ratio in the system by strictly controlling the weight ratio of isophorone diisocyanate to PEG-2000, so that the curing degree and flexibility of the final ink are optimally balanced, the resulting ink layer is not easy to crack and break, has high surface smoothness, and further improves weather resistance.

[0136] The data of Comparative Example 2.1 are all inferior to those of Example 1.1, proving that this application effectively reduces the size of nano-SiO2 particles and increases the specific surface area by performing ordinary ball milling on nano-SiO2 and then adding a certain amount of polyacrylate for further ball milling. By controlling the ball milling temperature, time, and speed, the application optimizes the shearing effect during ball milling. Specifically, polyacrylate can form a protective film to reduce the interaction force between nano-SiO2 particles and promote dispersion. At the same time, it chemically grafts onto the functional groups on the surface of nano-SiO2 particles, improving the surface properties of nano-SiO2 particles. The ball milling physical dispersion combined with chemical modification can greatly enhance the dispersion ability of nano-SiO2 particles.

[0137] The data of Comparative Examples 2.2-2.3 are all inferior to those of Example 1.1, proving that this application achieves better dispersion of highly dispersed nano-SiO2 in the system by strictly controlling the amount of highly dispersed nano-SiO2.

[0138] The data of Comparative Examples 3.1-3.2 are all inferior to those of Example 1.1, proving that by strictly controlling the amount of acrylic compounds, this application makes the copolymer formed by the polymerization of styrene, acrylic compounds and chloro ether resin more stable, and the modified acrylic emulsion obtained has a better polymerization effect.

[0139] The data in Examples 4.1-4.2 are all inferior to those in Example 1.1, proving that by strictly controlling the weight ratio of waterborne polyurethane emulsion and modified acrylate emulsion, the weather resistance of the final waterborne polyurethane ink is further improved.

[0140] The data in Examples 5.1-5.2 are all inferior to those in Example 1.1, proving that this application, by strictly controlling the weight ratio of graphene oxide and hexagonal boron nitride, further improves the weather resistance of the final waterborne polyurethane ink.

[0141] The embodiments described in this specific implementation are preferred embodiments of this application and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. A method for preparing a weather-resistant waterborne polyurethane ink, characterized in that, Includes the following steps: I. Aqueous polyurethane emulsion was prepared using isophorone diisocyanate and PEG-2000 in a weight ratio of 1:(1.5-3). II. Nano-SiO2 is ball-milled once at a temperature of 55-65℃ and a rotation speed of 700-750r / min for 0.5-1h. Then it is mixed with polyacrylate at a weight ratio of 1:(35-40). The temperature and rotation speed are kept constant, and the mixture is ball-milled a second time for 2.5-3.5h to obtain highly dispersed nano-SiO2. Then it is mixed with styrene, acrylic compounds and chlorinated ether resin at a weight ratio of (1-3):13:(13-15):3.2 and reacted under the condition of adding initiator, surfactant and silane coupling agent to obtain modified acrylate emulsion. III. A waterborne polyurethane emulsion, modified acrylate emulsion, graphene oxide, hexagonal boron nitride, pigments and additives in a weight ratio of (35-40):18:(2.5-3):(1-1.5):5:0.4 are dispersed in a solvent and mixed evenly to obtain a weather-resistant waterborne polyurethane ink.

2. The method for preparing a weather-resistant waterborne polyurethane ink according to claim 1, characterized in that, In step I, the weight ratio of isophorone diisocyanate to PEG-2000 is 1:

2.

3. The method for preparing a weather-resistant waterborne polyurethane ink according to claim 1, characterized in that, In step II, the temperature for ball milling nano-SiO2 is 60℃, the time for the first ball milling is 0.8h, and the time for the second ball milling is 3h.

4. The method for preparing a weather-resistant waterborne polyurethane ink according to claim 1, characterized in that, In step II, the weight ratio of highly dispersed nano-SiO2, styrene, acrylic compounds and chlorinated ether resin is 2.4:13:14:3.

2.

5. The method for preparing a weather-resistant waterborne polyurethane ink according to claim 1, characterized in that, In step II, the acrylic compounds include butyl acrylate, hydroxyethyl acrylate, methacrylic acid, isooctyl acrylate and methyl methacrylate in a weight ratio of 25:(8-13):3:(20-25):

8.

6. The method for preparing a weather-resistant waterborne polyurethane ink according to claim 5, characterized in that, The weight ratio of butyl acrylate, hydroxyethyl acrylate, methacrylic acid, isooctyl acrylate and methyl methacrylate is 25:11:3:22:

8.

7. The method for preparing a weather-resistant waterborne polyurethane ink according to claim 1, characterized in that, In step III, the weight ratio of the waterborne polyurethane emulsion to the modified acrylate emulsion is 38:

18.

8. The method for preparing a weather-resistant waterborne polyurethane ink according to claim 1, characterized in that, In step III, the weight ratio of modified acrylate emulsion, graphene oxide, and hexagonal boron nitride is 18:2.7:1.

2.

9. A weather-resistant waterborne polyurethane ink prepared by the method of any one of claims 1-8.

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