A dual cure polyurethane acrylate resin and a method for its preparation

Abstract

The application relates to the technical field of polyurethane acrylate, and particularly discloses a double-curing polyurethane acrylate resin and a preparation method thereof. The raw materials for preparing the double-curing polyurethane acrylate resin include polyester polyol, polyether polyol, diisocyanate, hydroxy acrylate, chain extender, photoinitiator, cashew phenol glycidyl ether, polymerization inhibitor and modified nanoparticles. The nanoparticles are modified by citric acid and polyethylene imine in cooperation, the dispersion stability of the nanoparticles is improved, the mechanical properties of the resin are improved, the cashew phenol glycidyl ether and the photoinitiator produce a synergistic effect, the light curing promoted by the photoinitiator can make the resin quickly shape first, and the cashew phenol glycidyl ether participates in the subsequent heat curing reaction, the curing effect is improved, and the adhesion between the film layer and the base material is enhanced.

Description

Technical Field

[0001] This invention relates to the field of polyurethane acrylate technology, and in particular to a dual-curing polyurethane acrylate resin and its preparation method. Background Technology

[0002] Polyurethane acrylate resin is a functional material that combines the excellent mechanical properties of polyurethane with the high reactivity of acrylate. Its molecular structure consists of isocyanate segments as hard segments and polyol segments as soft segments. By adjusting the ratio of hard and soft segments, the mechanical properties, weather resistance, and processability of the resin can be regulated. Suitable formulations can be designed to meet different application requirements. Therefore, polyurethane acrylate resin has wide applications in coatings, adhesives, inks, and other fields. Especially in scenarios requiring rapid curing, ultraviolet (UV) curing or thermosetting technologies are often used.

[0003] Thermosetting technology primarily utilizes heat energy to induce the formation of chemical bonds between molecules, thereby hardening the material. Ultraviolet (UV) curing technology, on the other hand, uses the energy of ultraviolet light to excite photoinitiators in the resin, triggering a polymerization reaction and achieving rapid curing. Both technologies play important roles in their respective applicable scenarios.

[0004] However, using a single curing method has obvious limitations. Thermocuring requires a large amount of energy to maintain the high-temperature environment, and the curing process is relatively slow, resulting in low production efficiency. When dealing with problems such as oxygen inhibition, insufficient light irradiation depth of ultra-thick coatings, and difficulty in light penetration in shaded areas, UV curing often results in incomplete and uneven curing, leading to insufficient adhesion between the film layer and the substrate, which affects the quality and service life of the product. Summary of the Invention

[0005] In order to fully leverage the advantages of photocuring and thermal curing mechanisms and ensure that the material can achieve comprehensive and uniform curing in complex environments, thereby guaranteeing the stability and reliability of the resin material performance, this application provides a dual-curing polyurethane acrylate resin and its preparation method.

[0006] In a first aspect, this application provides a dual-curing polyurethane acrylate resin, which adopts the following technical solution: A dual-curing polyurethane acrylate resin, by weight, is prepared from raw materials comprising the following:

[0007] Polyester polyol 20-25 parts, polyether polyol 20-30 parts, diisocyanate 28-32 parts, hydroxyl acrylate 12-16 parts, chain extender 3-7 parts, photoinitiator 1-3 parts, cashew phenol glycidyl ether 2-4 parts, polymerization inhibitor 0.3-0.7 parts, modified nanoparticles 10-14 parts;

[0008] The raw materials for preparing the modified nanoparticles include nanoparticles, citric acid, and polyethyleneimine, wherein the weight ratio of the nanoparticles, citric acid, and polyethyleneimine is 1:(0.8-1.2):(0.5-0.7).

[0009] By employing the above technical solutions, polyester polyols and polyether polyols, as soft segment components, help to regulate the flexibility and processing performance of the resin. Diisocyanate reacts with polyester polyols, polyether polyols, and chain extenders to form hard segments of the polyurethane structure, endowing the resin with good mechanical properties. Specifically, this application uses citric acid and polyethyleneimine to synergistically modify the nanoparticles. Citric acid contains carboxyl groups, which can undergo esterification with the hydroxyl groups on the nanoparticle surface, introducing carboxyl functional groups onto the nanoparticle surface. Polyethyleneimine is rich in amino groups, which can react with the carboxyl groups introduced by citric acid, thereby grafting them onto the nanoparticle surface and ensuring uniform dispersion in the resin matrix. This reduces the spontaneous spreading and collapse of nanoparticles, improves the dispersion stability of nanoparticles, and thus enhances the mechanical and processing properties of the resin.

[0010] Furthermore, photoinitiators possess higher reactivity, enabling them to more effectively promote resin polymerization and thus accelerate the curing process of the film. Cashew nut shell ether (DPGE) offers multiple advantages as a reactive diluent. On one hand, DPGE reduces resin viscosity, improves workability, and helps the film distribute more evenly on the substrate, reducing bubbles and defects. On the other hand, DPGE works synergistically with photoinitiators; the photoinitiator-promoted photocuring allows for rapid resin setting, while DPGE participates in the subsequent thermocuring reaction, improving the curing effect and enhancing the adhesion between the film and the substrate.

[0011] Preferably, the modified nanoparticles are prepared by:

[0012] (1) Disperse nanoparticles in a solvent and sonicate for 40-60 min. Adjust the pH of the solution to 3-5, add citric acid, and stir the reaction at 60-80℃ for 6-8 h. After the reaction is complete, filter, wash and dry to obtain citric acid modified nanoparticles; (2) Disperse polyethyleneimine in a solvent and sonicate for 40-60 min to obtain a polyethyleneimine solution. Disperse citric acid modified nanoparticles in a solvent and sonicate for 40-60 min to obtain a suspension. Slowly add the polyethyleneimine solution to the suspension and react at room temperature for 10-12 h. Filter, wash and dry to obtain modified nanoparticles.

[0013] By adopting the above technical solution, citric acid is used to modify nanoparticles. The carboxyl groups in the citric acid molecules can combine with the hydroxyl groups on the surface of the nanoparticles, so that the surface of the nanoparticles is coated with citric acid and carries carboxyl and hydroxyl groups, which increases the active groups on the surface of the nanoparticles and enhances the subsequent binding force with polyethyleneimine. By further modifying with polyethyleneimine, the carboxyl and hydroxyl groups in the citric acid molecules can combine with the amino groups in the polyethyleneimine molecules, so that polyethyleneimine is grafted onto the surface of the nanoparticles, improving the dispersibility of the nanoparticles in the resin system, thereby improving the mechanical properties of the resin.

[0014] Preferably, the nanoparticles are selected from one or more of the following: silicon dioxide, alumina, zirconium oxide, quartz powder, talc powder, mica powder, kaolin, and silica powder.

[0015] By adopting the above technical solution and adding the above nanoparticles, the mechanical properties, weather resistance, processability and other properties of the resin can be adjusted by utilizing the inherent properties of the nanoparticles.

[0016] Preferably, the hydroxy acrylate is selected from one or more of hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, trimethylolpropane diacrylate, and pentaerythritol triacrylate.

[0017] By employing the above technical solution, hydroxyl acrylate is used as a raw material to prepare dual-curing polyurethane acrylate resin. Utilizing the high reactivity of hydroxyl acrylate, combined with other components, it effectively compensates for problems such as low curing efficiency, incomplete and uneven curing, and weak adhesion between the film and the substrate. Specifically, the residual polymerization reaction of double bonds in the hydroxyl acrylate molecular structure facilitates cross-linking of the dual-curing polyurethane acrylate resin during UV curing, accelerating the curing speed and improving curing efficiency. Furthermore, the hydroxyl groups in the molecular structure can react with diisocyanates and other substances, helping to form urethane bonds, thereby constructing the molecular backbone of the resin and enhancing its mechanical properties and stability.

[0018] Preferably, the photoinitiator is one or more of α-hydroxy ketones, acetophenone and its derivatives, and acylphosphine oxides.

[0019] By adopting the above technical solution, the photoinitiator generates free radicals under ultraviolet light irradiation, which initiates double bond polymerization to form a cross-linked network, enabling the film layer to dry and set quickly, reducing deformation caused by fluidity in the subsequent curing stage. At the same time, it forms a synergistic effect with the subsequent thermal curing, enabling it to be deeply cured, thereby achieving optimal performance of the material through complete curing.

[0020] Preferably, the polymerization inhibitor is one or more of p-hydroxyanisole, hydroquinone, and p-benzoquinone.

[0021] By adopting the above technical solution, the addition of polymerization inhibitors helps to suppress free radical polymerization reactions, prevent the resin from undergoing premature polymerization during the preparation process, and ensure the stability and controllability of the resin preparation process.

[0022] Preferably, the polyester polyol is selected from one or more of polyethylene adipate diol, polypentyl adipate diol, polycaprolactone, and polycarbonate diol; the polyether polyol is selected from one or two of polypropylene glycol and polytetrahydrofuran ether diol.

[0023] By adopting the above technical solution, the ratio of soft and hard segments of the resin is adjusted by using polyester polyol and polyether polyol, thereby achieving the adjustment of the resin's mechanical properties, weather resistance, processability, and other properties.

[0024] Preferably, the diisocyanate is selected from one or more of dicyclohexylmethane diisocyanate, isophorone diisocyanate, and hexamethylene diisocyanate.

[0025] By adopting the above technical solution, the aliphatic isocyanate used in this application has better weather resistance and anti-yellowing properties, which makes the resin less prone to discoloration and aging during long-term use.

[0026] Preferably, the chain extender is selected from one or more of ethylenediamine, neopentyl glycol, sorbitol, and diethanolamine.

[0027] By adopting the above technical solution, adding chain extenders helps to adjust the length and structure of resin molecular chains, thereby achieving the adjustment of resin mechanical properties, weather resistance, processability and other properties.

[0028] Secondly, this application provides a method for preparing a dual-curing polyurethane acrylate resin, which adopts the following technical solution:

[0029] A method for preparing a dual-curing polyurethane acrylate resin includes the following steps:

[0030] S1: Weigh the raw materials according to the composition ratio, mix the polyester polyol and polyether polyol, introduce nitrogen gas, stir and react at 120-130℃ for 1-2 hours, cool down to 60-70℃, add diisocyanate, chain extender and acetone, react for 1-2 hours to obtain polyurethane prepolymer.

[0031] S2: Mix the polyurethane prepolymer, polymerization inhibitor, and catalyst evenly. Under stirring conditions at 60-65℃, add hydroxyl acrylate dropwise over 1.5-2 hours. After the addition is complete, maintain the reaction temperature and continue the reaction for 0.5-1 hours. Raise the temperature to 70-75℃ and stir the reaction for 0.5-1 hours to remove acetone and obtain the polyurethane acrylate prepolymer.

[0032] S3: Mix polyurethane acrylate prepolymer, photoinitiator, cashew phenol glycidyl ether, and modified nanoparticles evenly, and ultrasonically disperse for 30-40 minutes to obtain double-cured polyurethane acrylate resin, which should be stored in the dark at low temperature.

[0033] Preferably, the catalyst is an organotin catalyst.

[0034] By adopting the above technical solution, the preparation method enables polyurethane acrylate resin to possess dual curing characteristics, overcoming the problems of high energy consumption and low efficiency of single thermal curing, and the incomplete and uneven curing that easily occurs with single UV curing, resulting in weak adhesion between the film layer and the substrate. Specifically, the addition of modified nanoparticles to the resin system enhances the overall performance of the resin. Due to the large specific surface area and unique surface effects of nanoparticles, after modification, they can better integrate with the resin matrix, effectively improving the mechanical properties of the resin, increasing its strength and toughness, and maintaining stable performance under different environmental conditions. Simultaneously, it contributes to improving the resin's processing performance.

[0035] This application has the following beneficial effects:

[0036] This application uses polyester polyols and polyether polyols as soft segment components, which helps to regulate the flexibility and processing properties of the resin. Diisocyanate reacts with polyester polyols, polyether polyols, and chain extenders to form hard segments of the polyurethane structure, giving the resin good mechanical properties. Specifically, this application uses citric acid and polyethyleneimine to synergistically modify the nanoparticles. Citric acid contains carboxyl groups, which can undergo esterification with the hydroxyl groups on the nanoparticle surface, introducing carboxyl functional groups onto the nanoparticle surface. Polyethyleneimine is rich in amino groups, which can react with the carboxyl groups introduced by citric acid, thereby grafting them onto the nanoparticle surface and ensuring uniform dispersion in the resin matrix. This reduces the spontaneous spreading and collapse of nanoparticles, improves the dispersion stability of nanoparticles, and thus enhances the mechanical and processing properties of the resin.

[0037] Furthermore, photoinitiators possess higher reactivity, enabling them to more effectively promote resin polymerization and thus accelerate the curing process of the film. Cashew nut shell ether (DPGE) offers multiple advantages as a reactive diluent. On one hand, DPGE reduces resin viscosity, improves workability, and helps the film distribute more evenly on the substrate, reducing bubbles and defects. On the other hand, DPGE works synergistically with photoinitiators; the photoinitiator-promoted photocuring allows for rapid resin setting, while DPGE participates in the subsequent thermocuring reaction, improving the curing effect and enhancing the adhesion between the film and the substrate. Detailed Implementation

[0038] Preparation Example

[0039] Preparation Example 1

[0040] Preparation of modified nanoparticles:

[0041] (1) Disperse 100g of mica powder in 250mL of deionized water, ultrasonically disperse for 40min, adjust the pH of the solution to 3, add 80g of citric acid, stir and react at 60℃ for 6h, after the reaction is completed, filter, wash and dry to obtain citric acid modified nanoparticles.

[0042] (2) Disperse 50g of polyethyleneimine (Shuer 9002-98-6) in 100mL of deionized water and sonicate for 40min to obtain a polyethyleneimine solution. Disperse citric acid modified nanoparticles in 250mL of deionized water and sonicate for 40min to obtain a suspension. Slowly add the polyethyleneimine solution to the suspension and react at room temperature for 10h. Filter, wash and dry to obtain modified nanoparticles.

[0043] Preparation Example 2

[0044] Preparation of modified nanoparticles:

[0045] (1) 120g of silica was dispersed in 250mL of deionized water and ultrasonically dispersed for 50min. The pH of the solution was adjusted to 4. 120g of citric acid was added and stirred at 70℃ for 7h. After the reaction was completed, the solution was filtered, washed and dried to obtain citric acid modified nanoparticles.

[0046] (2) Disperse 72g of polyethyleneimine (Shuer 9002-98-6) in 120mL of deionized water and sonicate for 50min to obtain a polyethyleneimine solution. Disperse citric acid modified nanoparticles in 250mL of deionized water and sonicate for 50min to obtain a suspension. Slowly add the polyethyleneimine solution to the suspension and react at room temperature for 11h. Filter, wash and dry to obtain modified nanoparticles.

[0047] Preparation Example 3

[0048] Preparation of modified nanoparticles:

[0049] (1) Disperse 70g alumina and 70g zirconium oxide in 250mL of deionized water, sonicate for 60min, adjust the pH of the solution to 5, add 168g citric acid, stir and react at 80℃ for 8h, filter, wash and dry to obtain citric acid modified nanoparticles.

[0050] (2) 98g of polyethyleneimine (Shuer 9002-98-6) was dispersed in 150mL of deionized water and ultrasonically dispersed for 60min to obtain a polyethyleneimine solution. Citric acid modified nanoparticles were dispersed in 250mL of deionized water and ultrasonically dispersed for 60min to obtain a suspension. The polyethyleneimine solution was slowly added dropwise to the suspension and reacted at room temperature for 12h. After filtration, washing and drying, modified nanoparticles were obtained.

[0051] Preparation Example 4

[0052] The difference between this preparation example and preparation example 2 is that an equal amount of silicon micropowder is used instead of silicon dioxide.

[0053] Preparation Example 5

[0054] The difference between this preparation example and Preparation Example 2 is that citric acid was not added; that is, the preparation method of the modified nanoparticles is as follows:

[0055] 120g of silica was dispersed in 250mL of deionized water and ultrasonically dispersed for 50min to obtain a suspension. 72g of polyethyleneimine (Shuer 9002-98-6) was dispersed in 120mL of deionized water and ultrasonically dispersed for 50min to obtain a polyethyleneimine solution. The polyethyleneimine solution was slowly added dropwise to the suspension and reacted at room temperature for 11h. After filtration, washing, and drying, modified nanoparticles were obtained.

[0056] Preparation Example 6

[0057] The difference between this preparation example and Preparation Example 2 is that polyethyleneimine was not added; that is, the preparation method of the modified nanoparticles is as follows:

[0058] 120g of silica was dispersed in 250mL of deionized water and ultrasonically dispersed for 50min. The pH of the solution was adjusted to 4, and 120g of citric acid was added. The mixture was stirred at 70℃ for 7h. After the reaction was completed, the mixture was filtered, washed, and dried to obtain modified nanoparticles.

[0059] Example

[0060] Example 1

[0061] A dual-curing polyurethane acrylate resin, the raw materials for which are prepared include:

[0062] 200g polyethylene adipate diol (Plulux 25212-06-0), 200g polypropylene oxide diol (Mikerui 25322-69-4), 280g dicyclohexylmethane diisocyanate, 120g hydroxyethyl acrylate, 30g ethylenediamine, 10g 3-hydroxy-3-methyl-2-butanone, 20g cashew phenol glycidyl ether (Hongrun 171263-25-5), 3g hydroquinone, and 100g modified nanoparticles (prepared in Preparation Example 1).

[0063] The preparation method of the dual-curing polyurethane acrylate resin in this embodiment includes the following steps:

[0064] S1: Weigh the raw materials according to the components, mix the polyethylene adipate diol and polypropylene oxide diol, introduce nitrogen gas, stir and react at 120°C for 1 hour, cool down to 60°C, add dicyclohexylmethane diisocyanate, ethylenediamine and acetone, react for 1 hour to obtain polyurethane prepolymer.

[0065] S2: Mix polyurethane prepolymer, hydroquinone, and 1.5g dibutyltin dilaurate evenly. Under stirring conditions at 60℃, add hydroxyethyl acrylate dropwise over 1.5h. After the addition is complete, maintain the reaction temperature and continue the reaction for 0.5h. Then, raise the temperature to 70℃ and stir the reaction for 1h to remove acetone and obtain polyurethane acrylate prepolymer.

[0066] S3: Mix polyurethane acrylate prepolymer, 3-hydroxy-3-methyl-2-butanone, cashew phenol glycidyl ether, and modified nanoparticles evenly, and ultrasonically disperse for 30 min to obtain double-cured polyurethane acrylate resin, which should be stored in the dark at low temperature.

[0067] Example 2

[0068] A dual-curing polyurethane acrylate resin, the raw materials for which are prepared include:

[0069] 230g of polypentyl adipate (Xinyuhong 27925-07-1), 250g of polytetrahydrofuran ether diol (Deyitai 25190-06-1), 300g of isophorone diisocyanate, 140g of hydroxypropyl acrylate, 50g of sorbitol, 20g of dimethoxyphenyl acetophenone, 30g of cashew phenol glycidyl ether (Hongrun 171263-25-5), 5g of p-hydroxyanisole, and 120g of modified nanoparticles (prepared in Preparation Example 2).

[0070] The preparation method of the dual-curing polyurethane acrylate resin in this embodiment includes the following steps:

[0071] S1: Weigh the raw materials according to the components, mix polypentyl adipate and polytetrahydrofuran ether diol, introduce nitrogen gas, stir and react at 125°C for 1.5 h, cool to 65°C, add isophorone diisocyanate, sorbitol and acetone, react for 1.5 h to obtain polyurethane prepolymer.

[0072] S2: Mix polyurethane prepolymer, p-hydroxyanisole, and 2g dibutyltin dilaurate evenly. Add hydroxypropyl acrylate dropwise over 2 hours at 65°C with stirring. After the addition is complete, maintain the reaction temperature and continue the reaction for 1 hour. Raise the temperature to 75°C and stir for 1 hour to remove acetone and obtain polyurethane acrylate prepolymer.

[0073] S3: Mix polyurethane acrylate prepolymer, dimethoxyphenyl acetophenone, cashew phenol glycidyl ether, and modified nanoparticles evenly, and ultrasonically disperse for 35 min to obtain double-cured polyurethane acrylate resin, which should be stored in the dark at low temperature.

[0074] Example 3

[0075] A dual-curing polyurethane acrylate resin is prepared from the following raw materials: 250g polycarbonate diol (Lanabai 29862-10-0), 300g polytetrahydrofuran ether diol (Deyitai 25190-06-1), 320g hexamethylene diisocyanate, 160g pentaerythritol triacrylate, 70g diethanolamine, 30g BAPO, 40g cashew phenol glycidyl ether (Hongrun 171263-25-5), 7g p-benzoquinone, and 140g modified nanoparticles (prepared in Preparation Example 3).

[0076] The preparation method of the dual-curing polyurethane acrylate resin in this embodiment includes the following steps:

[0077] S1: Weigh the raw materials according to the components, mix polycarbonate diol and polytetrahydrofuran ether diol, introduce nitrogen gas, stir and react at 130°C for 2 hours, cool down to 70°C, add hexamethylene diisocyanate, diethanolamine and acetone, react for 2 hours to obtain polyurethane prepolymer;

[0078] S2: Mix polyurethane prepolymer, p-benzoquinone, and 2.5g dibutyltin dilaurate evenly. Under stirring conditions at 65℃, add pentaerythritol triacrylate dropwise over 2 hours. After the addition is complete, maintain the reaction temperature and continue the reaction for 1 hour. Raise the temperature to 75℃ and stir for 1 hour to remove acetone and obtain polyurethane acrylate prepolymer.

[0079] S3: Mix polyurethane acrylate prepolymer, BAPO, cashew phenol glycidyl ether, and modified nanoparticles evenly, and ultrasonically disperse for 40 min to obtain double-cured polyurethane acrylate resin, which should be stored in the dark at low temperature.

[0080] Example 4

[0081] The difference between this embodiment and Example 2 is that the modified nanoparticles prepared in Example 4 are used.

[0082] Example 5

[0083] The difference between this embodiment and Embodiment 2 is that an equal amount of hydroxypropyl methacrylate is used instead of hydroxypropyl acrylate.

[0084] Example 6

[0085] The difference between this embodiment and Embodiment 2 is that an equal amount of trimethylolpropane diacrylate is used instead of hydroxypropyl acrylate.

[0086] Comparative Example

[0087] Comparative Example 1

[0088] A dual-curing polyurethane acrylate resin differs from Example 2 in that it uses the modified nanoparticles obtained in Preparation Example 5.

[0089] Comparative Example 2

[0090] A dual-curing polyurethane acrylate resin differs from Example 2 in that it uses the modified nanoparticles obtained in Preparation Example 6.

[0091] Comparative Example 3

[0092] A dual-curing polyurethane acrylate resin differs from Example 2 in that an equal amount of silica is used instead of modified nanoparticles.

[0093] Comparative Example 4

[0094] A dual-curing polyurethane acrylate resin, which differs from Example 2 in that no modified nanoparticles are added.

[0095] Comparative Example 5

[0096] A dual-curing polyurethane acrylate resin differs from Example 2 in that an equal amount of ethyl acrylate is used instead of hydroxypropyl acrylate.

[0097] Comparative Example 6

[0098] A dual-curing polyurethane acrylate resin differs from Example 2 in that an equal amount of cashew phenol is used instead of cashew phenol glycidyl ether.

[0099] Comparative Example 7

[0100] A dual-curing polyurethane acrylate resin, which differs from Example 2 in that it does not contain cashew phenol glycidyl ether.

[0101] Performance testing

[0102] The dual-curing polyurethane acrylate resins prepared in Examples 1-6 and Comparative Examples 1-7 were uniformly coated onto the substrate and, after defoaming, placed under light with an intensity of 600 mW / cm². 2Cured in a UV curing machine, and then heat-cured at 80-120℃ after removal.

[0103] 1. Drying time: According to the national standard GB / T 1728-2020, the surface drying time of the film is determined by method B - finger touch method, and the actual drying time of the film is determined by method C - blade method.

[0104] 2. Adhesion test: The adhesion of the coating is determined by cross-cut test according to the national standard GB / T 9286-2021.

[0105] 3. Mechanical property testing: The tensile strength and elongation at break of the cured strips were tested using a universal electronic tensile testing machine (Shenzhen Sansi Zongheng, UTM4103X). Each formulation sample was tested 5 times, and the average value was taken. The test results are recorded in Table 1.

[0106] Table 1

[0107]

[0108] Based on the comparison between Example 2 and Comparative Examples 1-2, and the data in Table 1, it can be seen that: Comparative Example 1 only used polyethyleneimine to modify the nanoparticles, and Comparative Example 2 only used citric acid to modify the nanoparticles. Neither of these modification methods can achieve a good dispersion effect for the nanoparticles, and the resin drying time is long, causing the nanoparticles to settle and agglomerate, affecting the resin performance. In contrast, this application uses citric acid and polyethyleneimine to synergistically modify the nanoparticles, enabling the nanoparticles to be uniformly dispersed in the resin matrix, reducing spontaneous spreading and collapse of the nanoparticles, improving the dispersion stability of the nanoparticles, shortening the drying time, and improving the mechanical properties of the resin.

[0109] Based on the comparison of Examples 2 and Comparative Examples 3-4, and the data in Table 1, it can be seen that: in Comparative Example 3, the silica was not modified. Due to the high surface energy of silica, it is prone to agglomeration, which affects the performance of the resin; in Comparative Example 4, no modified nanoparticles were added, resulting in a significant reduction in the mechanical properties of the resin film. This application uses citric acid and polyethyleneimine to synergistically modify the nanoparticles, enabling them to be uniformly dispersed in the resin matrix, reducing spontaneous spreading and collapse of the nanoparticles, improving the dispersion stability of the nanoparticles, shortening the drying time, and improving the mechanical properties of the resin.

[0110] Based on the comparison between Example 2 and Comparative Example 5, and the data in Table 1, it can be seen that ethyl acrylate does not contain hydroxyl groups in its molecular structure, resulting in relatively weak reactivity and a weaker bonding force with polyurethane prepolymer compared to hydroxyl acrylate. This application uses hydroxyl acrylate to react with polyurethane prepolymer, and the resulting polyurethane acrylate exhibits good tensile properties and adhesion.

[0111] Based on the comparison between Example 2 and Comparative Examples 6-7 and the data in Table 1, it can be seen that: the cashew phenol glycidyl ether molecule contains epoxy groups, which eliminates free radical interference, while retaining the flexibility and hydrophobicity of long-chain alkyl groups. Furthermore, cashew phenol glycidyl ether does not interfere with free radical polymerization during the photocuring stage, while the epoxy ring-opening reaction deeply crosslinks during the thermocuring stage, solving the problem of inner layer curing in thick coatings or complex structures and improving the adhesion of resin film layers.

[0112] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this specific embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A dual-curing polyurethane acrylate resin, characterized in that, It is prepared from the following raw materials in parts by weight: Polyester polyol 20-25 parts, polyether polyol 20-30 parts, diisocyanate 28-32 parts, hydroxyl acrylate 12-16 parts, chain extender 3-7 parts, photoinitiator 1-3 parts, cashew phenol glycidyl ether 2-4 parts, polymerization inhibitor 0.3-0.7 parts, modified nanoparticles 10-14 parts; The raw materials for preparing the modified nanoparticles include nanoparticles, citric acid, and polyethyleneimine, wherein the weight ratio of the nanoparticles, citric acid, and polyethyleneimine is 1:(0.8-1.2):(0.5-0.7). The method for preparing the modified nanoparticles is as follows: (1) Disperse nanoparticles in a solvent, ultrasonically disperse for 40-60 min, adjust the pH of the solution to 3-5, add citric acid, stir and react at 60-80℃ for 6-8 h, after the reaction is completed, filter, wash and dry to obtain citric acid modified nanoparticles; (2) Disperse polyethyleneimine in a solvent and ultrasonically disperse for 40-60 min to obtain a polyethyleneimine solution. Disperse citric acid modified nanoparticles in a solvent and ultrasonically disperse for 40-60 min to obtain a suspension. Slowly add the polyethyleneimine solution dropwise to the suspension and react at room temperature for 10-12 h. Filter, wash and dry to obtain modified nanoparticles. The preparation method of the dual-curing polyurethane acrylate resin includes the following steps: S1: Weigh the raw materials according to the composition ratio, mix the polyester polyol and polyether polyol, introduce nitrogen gas, stir and react at 120-130℃ for 1-2 hours, cool down to 60-70℃, add diisocyanate, chain extender and acetone, react for 1-2 hours to obtain polyurethane prepolymer. S2: Mix the polyurethane prepolymer, polymerization inhibitor, and catalyst evenly. Under stirring conditions at 60-65℃, add hydroxyl acrylate dropwise over 1.5-2 hours. After the addition is complete, maintain the reaction temperature and continue the reaction for 0.5-1 hours. Raise the temperature to 70-75℃ and stir the reaction for 0.5-1 hours to remove acetone and obtain the polyurethane acrylate prepolymer. S3: Mix polyurethane acrylate prepolymer, photoinitiator, cashew phenol glycidyl ether, and modified nanoparticles evenly, and ultrasonically disperse for 30-40 minutes to obtain double-cured polyurethane acrylate resin, which should be stored in the dark at low temperature.

2. The dual-curing polyurethane acrylate resin according to claim 1, characterized in that, The nanoparticles are selected from one or more of the following: silicon dioxide, alumina, zirconium oxide, quartz powder, talc powder, mica powder, kaolin, and silica powder.

3. The dual-curing polyurethane acrylate resin according to claim 1, characterized in that, The hydroxy acrylate is selected from one or more of hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, trimethylolpropane diacrylate, and pentaerythritol triacrylate.

4. The dual-curing polyurethane acrylate resin according to claim 1, characterized in that, The photoinitiator is one or more of α-hydroxy ketones, acetophenone and its derivatives, and acylphosphine oxides.

5. The dual-curing polyurethane acrylate resin according to claim 1, characterized in that, The polymerization inhibitor is one or more of p-hydroxyanisole, hydroquinone, and p-benzoquinone.

6. The dual-curing polyurethane acrylate resin according to claim 1, characterized in that, The polyester polyol is selected from one or more of polyethylene adipate diol, polypentyl adipate diol, and polycarbonate diol; the polyether polyol is selected from one or two of polypropylene glycol and polytetrahydrofuran ether diol.

7. The dual-curing polyurethane acrylate resin according to claim 1, characterized in that, The diisocyanate is selected from one or more of dicyclohexylmethane diisocyanate, isophorone diisocyanate, and hexamethylene diisocyanate.

8. The dual-curing polyurethane acrylate resin according to claim 1, characterized in that, The chain extender is selected from one or more of ethylenediamine, neopentyl glycol, sorbitol, and diethanolamine.

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