A "sea urchin" structure hyperbranched polyurethane acrylate prepolymer with EB curing activity and preparation method thereof

Abstract

The present invention belongs to the technical field of polymer materials, and specifically relates to a "sea urchin" structure hyperbranched polyurethane acrylate prepolymer with EB curing activity and a preparation method thereof. The prepolymer is composed of a "spherical body" and "thorns", the "spherical body" is formed by multiple esterification reactions of polyols and acid anhydrides, the "thorns" are formed by polyisocyanates capped with hydroxyalkyl acrylate, and the "spherical body" and "thorns" are connected by the reaction of hydroxyl groups and isocyanate groups; the preparation method comprises the following steps: under the action of a catalyst, polyols and acid anhydrides are subjected to multiple esterification reactions to obtain polyester polyols, and then polyisocyanates are added to react with amine alcohols, and finally hydroxyalkyl acrylates are added for end-capping to obtain a polyurethane acrylate prepolymer. The prepolymer of the present invention has many active sites and low viscosity, and only needs electron beam radiation to generate free radicals, thereby initiating a polymerization curing reaction by itself, and the curing is complete, and no initiator is required, which meets the requirements of EB curing.

Description

Technical Field

[0001] The invention belongs to the technical field of polymer materials, and in particular relates to a "sea urchin" structure hyperbranched polyurethane acrylate prepolymer with EB curing activity and a preparation method thereof. Background Art

[0002] Polyurethane acrylate (PUA resin) is a type of block copolymer with a microphase separation structure and tunable soft and hard segment structures. It exhibits excellent performance in the fields of coatings, adhesives, printing inks, etc. Most of the existing polyurethane acrylates are suitable for thermal curing or UV curing. Thermal curing technology is a common curing method. The thermal curing process mainly involves cross-linking reactions of polymer chains. These reactions are usually activated by heating. The dense cross-linked network formed by thermal curing can enhance the mechanical strength and thermal stability of the film, but the curing speed is slow, the energy consumption is high, the process is complex, and VOCs emissions affect the environment. Compared with thermal curing technology, UV curing has the advantages of fast curing speed, energy saving and high efficiency, and no VOCs emissions. However, UV curing requires photosensitizers (photoinitiators), which are generally toxic and harmful substances and are not suitable for food, medicine, daily chemical packaging, etc., and residual photosensitizers will further cause yellowing and deterioration. In addition, the viscosity of polyurethane acrylate prepolymers for UV curing is still relatively high, and there is a problem of poor penetration, especially for thicker or opaque coatings or slurries. UV light may not be able to fully penetrate and cure, resulting in a layer of low-viscosity residue on the surface, or incomplete internal curing.

[0003] To solve the above problems, more and more researchers have turned their attention to EB curing. Compared with UV curing, EB curing has obvious advantages: (1) Since the energy of electron beam is much higher than that of ultraviolet light, accelerated electrons can directly bombard active groups such as acrylic acid double bonds to initiate chain free radical polymerization reactions. Therefore, there is no need to add highly toxic photosensitizers to the EB curing formula, and there is no yellowing and deterioration caused by residual photosensitizers. It is especially suitable for surface printing of food and drug packaging materials; (2) EB curing has a higher dose rate, which can make the reaction system instantly generate a large number of free radicals, achieving millisecond-level room temperature rapid curing, and the electron beam can randomly generate active sites in the resin system to initiate polymerization and cross-linking reactions, so its curing degree is higher and the curing uniformity is better; (3) EB curing has strong penetration ability and is not affected by additives such as pigments or fillers in the coating. EB curing technology has many advantages, but its development is limited by prepolymers. Prepolymers are the core and indispensable components of EB curing materials. The performance of EB curing materials directly depends on the quality of prepolymers. As the basic component of EB curing materials, the chemical structure, functional group distribution and cross-linking reaction activity of prepolymers have profound effects on the physical and mechanical properties, weather resistance and chemical stability of the cured products. Therefore, the synthesis and modification technology of prepolymers has become a key link restricting the improvement of the performance of EB curing materials. However, there are relatively few studies on polyurethane acrylate prepolymers used for EB curing at home and abroad. For example, CN116042129A, CN110862511A and other documents are UV curing resins. The prepolymers used have irregular structures or are linear, easy to entangle, and have high viscosity. UV curing prepolymers are not suitable for EB curing. Polyurethane acrylate prepolymers with EB curing activity are urgently needed to be developed. Summary of the invention

[0004] In view of the shortcomings of the existing methods, the present invention provides a "sea urchin" structure hyperbranched polyurethane acrylate prepolymer with EB curing activity and a preparation method thereof, which solves the problems of high viscosity and incomplete curing of traditional prepolymers. After EB curing treatment, the molecular structure and cross-linking density network characteristics of the obtained prepolymer are transformed to form an interconnected network structure, and its mechanical properties are improved.

[0005] To achieve the above object, the present invention adopts the following technical solution: A "sea urchin" structure hyperbranched polyurethane acrylate prepolymer with EB curing activity, the prepolymer consists of a "spherical body" and "thorns", the "spherical body" is formed by multiple esterification reactions of polyol and acid anhydride, the "thorns" are formed by polyisocyanate capped with hydroxyalkyl acrylate, and the "spherical body" and the "thorns" are connected by the reaction of hydroxyl and isocyanate.

[0006] A method for preparing a "sea urchin" structure hyperbranched polyurethane acrylate prepolymer with EB curing activity comprises the following steps: Under the action of a catalyst, the polyol and the acid anhydride undergo multiple esterification reactions to obtain a polyester polyol, and then polyisocyanate is added to carry out an amine alcohol reaction, and finally hydroxyalkyl acrylate is added for end-capping to obtain a polyurethane acrylate prepolymer.

[0007] Preferably, in the presence of a catalyst, the polyol and the acid anhydride undergo multiple esterification reactions to obtain a polyester polyol, including: Under the action of a catalyst, the polyol and the acid anhydride are subjected to an esterification reaction, and then the polyol, the acid anhydride, and the polyol are added alternately for multiple times to carry out multiple esterification reactions until a polyester polyol with a target molecular weight is obtained.

[0008] Preferably, the polyol is pentaerythritol or propylene glycol, the acid anhydride is pyromellitic anhydride or maleic anhydride, and the molar ratio of the polyol to the acid anhydride is 1-4:4-1.

[0009] Preferably, the solvent for the esterification reaction of the polyol and the acid anhydride is one or more of N,N-dimethylformamide DMF, triethylamine, ethanol and toluene.

[0010] Preferably, the catalyst is concentrated sulfuric acid, p-toluenesulfonamide or 4-dimethylaminopyridine, and the catalyst is added in multiple times, and the catalyst added in each esterification reaction accounts for 0.1% to 5% of the molar amount of the corresponding polyol / anhydride added.

[0011] Preferably, the esterification reaction temperature of the polyol and the acid anhydride is 150-220°C.

[0012] Preferably, the polyisocyanate is one or more of toluene diisocyanate TDI, isophorone diisocyanate IPDI, hexamethylene diisocyanate HDI and diphenylmethane diisocyanate MDI; the hydroxyalkyl acrylate is one or more of hydroxyethyl acrylate HEA, hydroxypropyl acrylate HPA and hydroxybutyl acrylate HBA.

[0013] Preferably, the molar ratio of the polyisocyanate to hydroxyalkyl acrylate is 0.5-2:1; the molar ratio of the polyisocyanate to the outermost polyol of the polyester polyol is 1-1.5:1, and the molar amount of the outermost polyol of the polyester polyol is the molar amount of the polyol added in the last esterification reaction.

[0014] Preferably, the amine alcohol reaction and the capping reaction temperature are both 40-100°C.

[0015] The positive beneficial effects of the present invention are: 1. The prepolymer of the present invention is composed of a "spherical body" and "thorns". The "spherical body" is formed by multiple esterification reactions of polyols and acid anhydrides to synthesize a large-mass, high-density, low-viscosity "spherical body". As the main structure of the prepolymer, the "thorns" are formed by polyisocyanate capped with hydroxyalkyl acrylate. The "spherical body" and the "thorns" are connected by the reaction of hydroxyl groups and isocyanate groups. The "thorn" structure can provide a large number of active groups, greatly improving the curing effect of the prepolymer and meeting the requirements of EB curing.

[0016] 2. The molar ratio of the polyol to the acid anhydride of the present invention is determined according to the structures of the selected polyol and the acid anhydride. The molar amount of the acid anhydride in each esterification reaction is related to the molar amount of the exposed hydroxyl groups of the polyester intermediate in the previous step, and the molar amount of the polyol is related to the molar amount of the exposed carboxyl groups of the polyester intermediate in the previous step. The amount of each raw material is appropriate, and the obtained prepolymer has many active sites and low viscosity. It only needs electron beam radiation to generate free radicals, thereby initiating a polymerization curing reaction by itself. The curing is complete, no initiator is required, and the requirements of EB curing are met. The reaction speed is fast, and the obtained EB cured film has excellent mechanical properties, which expands the scope of application.

[0017] 3. The polyol and the acid anhydride of the present invention are both highly symmetrical in structure. A series of esterification reactions are performed alternately to obtain a polyester polyol with a structure closer to a sphere. The reaction is controllable, and the viscosity of the polyester polyol is effectively reduced. In addition, the spherical structure has more vinyl active sites, the prepolymer structure is regular, and the active sites are highly divergent, which effectively enhances the reaction activity of EB curing from a spatial perspective. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is one of the reaction equations for the preparation method of the "sea urchin" structure hyperbranched polyurethane acrylate prepolymer with EB curing activity of the present invention.

[0019] Figure 2 This is the second reaction equation of the preparation method of the "sea urchin" structure hyperbranched polyurethane acrylate prepolymer with EB curing activity of the present invention.

[0020] Figure 3 It is the chemical structural formula of the "sea urchin" structure hyperbranched polyurethane acrylate prepolymer with EB curing activity of the present invention. DETAILED DESCRIPTION

[0021] The present invention is further described below in conjunction with some specific embodiments.

[0022] Example 1 A method for preparing a "sea urchin" structure hyperbranched polyurethane acrylate prepolymer with EB curing activity, see Figure 1-2 , including the following steps: 1) First, mix pentaerythritol (0.001 mol) and pyromellitic anhydride (0.004 mol) evenly and place them in a four-necked flask, add 100 ml of DMF and 0.000015 mol of p-toluenesulfonamide, and slowly heat to 200 ° C under N2 protection and react for 4 hours; 2) After the reaction is completed, add 3 times (0.000045 mol) of p-toluenesulfonamide in the step, add pentaerythritol (0.012 mol) and continue to react for 4 hours; add 3 times (0.000135 mol) of p-toluenesulfonamide in the step, add pyromellitic anhydride (0.036 mol) and continue to react for 4 hours; add 3 times (0.000405 mol) of p-toluenesulfonamide in the step, add pentaerythritol (0.108 mol) and continue to react for 4 hours; add 3 times (0.001215 mol) of p-toluenesulfonamide in the step, add pyromellitic anhydride (0.324 mol) and continue to react for 4 hours; add 3 times (0.003645 mol) of p-toluenesulfonamide in the step, add pentaerythritol (0.972 mol) and continue to react for 4 hours, reduce the reaction temperature to 80°C, add 0.972 mol of TDI and react for 2 hours, then add 0.972 mol HEA continued to react for 2h; wherein "the previous step" refers to "the step before the current step", and the meanings expressed in the following embodiments are the same; 3) After the reaction is completed, cool to room temperature, dissolve in a mixed solution of acetone and methanol (volume ratio 1:1), and precipitate in anhydrous petroleum ether to obtain a polyurethane acrylate prepolymer with a molecular weight of about 500,000.

[0023] The chemical structure of the "sea urchin" structure hyperbranched polyurethane acrylate prepolymer with EB curing activity obtained in Example 1 of the present invention is as follows: Figure 3 In the formula, purple represents the structure formed by the reaction of anhydride and polyol, blue represents anhydride, and green represents polyol. The prepolymer is composed of a "spherical body" and "thorns". The "spherical body" is formed by multiple esterification reactions of polyol and anhydride to synthesize a large-mass, high-density, and low-viscosity "spherical body". As the main structure of the prepolymer, the "thorns" are formed by polyisocyanate capped with hydroxyalkyl acrylate. The "thorn" structure can provide a large number of active groups, which greatly improves the curing effect of the prepolymer and meets the needs of EB curing. The "spherical body" and the "thorns" are connected by the reaction of hydroxyl and isocyanate.

[0024] Example 2 A method for preparing a "sea urchin" structure hyperbranched polyurethane acrylate prepolymer with EB curing activity comprises the following steps: 1) First, mix pentaerythritol (0.001 mol) and pyromellitic anhydride (0.004 mol) evenly and place them in a four-necked flask, add 500 ml DMF and 0.000015 mol p-toluenesulfonamide, and slowly heat to 200 ° C under N2 protection and react for 4 hours; 2) After the reaction is completed, add 3 times of p-toluenesulfonamide in the step, add pentaerythritol (0.012 mol) and continue to react for 4 hours; add 3 times of p-toluenesulfonamide in the step, add pyromellitic anhydride (0.036 mol) and react for 4 hours; add 3 times of p-toluenesulfonamide in the step, add pentaerythritol (0.108 mol) and continue to react for 4 hours; add 3 times of p-toluenesulfonamide in the step, add pyromellitic anhydride (0.324 mol) and react for 4 hours; add 3 times of p-toluenesulfonamide in the step, add pentaerythritol (0.972 mol) and continue to react for 4 hours; add 3 times of p-toluenesulfonamide in the step, add pyromellitic anhydride (2.916 mol) and react for 4 hours; add 3 times of p-toluenesulfonamide in the step, add pentaerythritol (8.748 mol) and continue to react for 4 hours, reduce the reaction temperature to 80°C, add 8.748 mol of TDI and react for 2 hours, then add 8.748 mol HEA continued to react for 2 h; 3) After the reaction is completed, cool to room temperature, dissolve in a mixed solution of acetone and methanol (volume ratio 1:1), and precipitate in anhydrous petroleum ether to obtain a polyurethane acrylate prepolymer with a molecular weight of about 2.3 million.

[0025] Example 3 A method for preparing a "sea urchin" structure hyperbranched polyurethane acrylate prepolymer with EB curing activity comprises the following steps: 1) First, mix pentaerythritol (0.001 mol) and pyromellitic anhydride (0.004 mol) evenly and place them in a four-necked flask, add 200 ml DMF and 0.000015 mol p-toluenesulfonamide, and slowly heat to 200 ° C under N2 protection and react for 4 hours; 2) After the reaction is completed, add 3 times the amount of p-toluenesulfonamide in the step, add pentaerythritol (0.012 mol) and continue to react for 4 hours; add 3 times the amount of p-toluenesulfonamide in the step, add maleic anhydride (0.036 mol) and continue to react for 4 hours; add an equal amount of p-toluenesulfonamide in the step, add pentaerythritol (0.036 mol) and continue to react for 4 hours; add 3 times the amount of p-toluenesulfonamide in the step, add maleic anhydride (0.108 mol) and continue to react for 4 hours; add an equal amount of p-toluenesulfonamide in the step, add pentaerythritol (0.10 8mol) and continue to react for 4h; add 3 times the amount of p-toluenesulfonamide in the step, and then add maleic anhydride (0.324mol) and react for 4h; add the same amount of p-toluenesulfonamide in the step, and then add pentaerythritol (0.324mol) and continue to react for 4h; add 3 times the amount of p-toluenesulfonamide in the step, and then add maleic anhydride (0.972mol) and react for 4h; add the same amount of p-toluenesulfonamide in the step, and then add pentaerythritol (0.972mol) and continue to react for 4h, reduce the reaction temperature to 80℃, add 0.972mol TDI and react for 2h, and then add 0.972mol HEA and continue to react for 2h; 3) After the reaction is completed, cool to room temperature, dissolve in a mixed solution of acetone and methanol (volume ratio 1:1), and precipitate in anhydrous petroleum ether to obtain a polyurethane acrylate prepolymer with a molecular weight of about 600,000.

[0026] Example 4 A method for preparing a "sea urchin" structure hyperbranched polyurethane acrylate prepolymer with EB curing activity comprises the following steps: 1) First, mix pentaerythritol (0.001 mol) and pyromellitic anhydride (0.004 mol) evenly and place them in a four-necked flask, add 500 ml DMF and 0.000015 mol p-toluenesulfonamide, and slowly heat to 200 ° C under N2 protection and react for 4 hours; 2) After the reaction is completed, add 3 times of p-toluenesulfonamide in the step, add glycerol (0.012 mol) and continue to react for 4 hours; add 2 times of p-toluenesulfonamide in the step, add maleic anhydride (0.024 mol) and react for 4 hours; add an equal amount of p-toluenesulfonamide in the step, add glycerol (0.024 mol) and continue to react for 4 hours; add 2 times of p-toluenesulfonamide in the step, add maleic anhydride (0.048 mol) and react for 4 hours; add an equal amount of p-toluenesulfonamide in the step, add glycerol (0.048 mol) and continue to react for 4 hours; add 2 times of p-toluenesulfonamide in the step, add maleic anhydride (0.096 mol) and react for 4 hours; add an equal amount of p-toluenesulfonamide in the step, add glycerol (0.096 mol) and continue to react for 4 hours; add 2 times of p-toluenesulfonamide in the step, add maleic anhydride (0. 192mol) for 4h; add an equal amount of p-toluenesulfonamide in the step, add glycerol (0.192mol) and continue to react for 4h; add 2 times of p-toluenesulfonamide in the step, add maleic anhydride (0.384mol) and continue to react for 4h; add an equal amount of p-toluenesulfonamide in the step, add glycerol (0.384mol) and continue to react for 4h; add 2 times of p-toluenesulfonamide in the step, add maleic anhydride (0.768mol) and continue to react for 4h; add 2 times of p-toluenesulfonamide in the step, add maleic anhydride (0.768mol) and continue to react for 4h; add 2 times of p-toluenesulfonamide in the step, add maleic anhydride (1.536mol) and continue to react for 4h; add an equal amount of p-toluenesulfonamide in the step, add glycerol (1.536mol) and continue to react for 4h, reduce the reaction temperature to 80°C, and add 1.536mol TDI was reacted for 2 h, and then 1.536 mol HEA was added and the reaction continued for 2 h; 3) After the reaction is completed, cool to room temperature, dissolve in a mixed solution of acetone and methanol (volume ratio 1:1), and precipitate in anhydrous petroleum ether to obtain a polyurethane acrylate prepolymer with a molecular weight of about 1 million.

[0027] Example 5 A method for preparing a "sea urchin" structure hyperbranched polyurethane acrylate prepolymer with EB curing activity comprises the following steps: 1) First, mix pentaerythritol (0.001 mol) and pyromellitic anhydride (0.004 mol) evenly and place them in a four-necked flask, add 100 ml of DMF and 0.000015 mol of p-toluenesulfonamide, and slowly heat to 200 ° C under N2 protection and react for 4 hours; 2) After the reaction is completed, add 3 times of p-toluenesulfonamide in the step, add pentaerythritol (0.012 mol) and continue to react for 4 hours; add 3 times of p-toluenesulfonamide in the step, add pyromellitic anhydride (0.036 mol) and continue to react for 4 hours; add 3 times of p-toluenesulfonamide in the step, add pentaerythritol (0.108 mol) and continue to react for 4 hours; add 3 times of p-toluenesulfonamide in the step, add pyromellitic anhydride (0.324 mol) and react for 4 hours; add 3 times of p-toluenesulfonamide in the step, add pentaerythritol (0.972 mol) and continue to react for 4 hours, reduce the reaction temperature to 80°C, add 0.972 mol TDI and react for 2 hours, and then add 0.972 mol HPA and continue to react for 2 hours; 3) After the reaction is completed, cool to room temperature, dissolve in a mixed solution of acetone and methanol (1:1), and precipitate in anhydrous petroleum ether to obtain a polyurethane acrylate prepolymer with a molecular weight of about 500,000.

[0028] Example 6 A method for preparing a "sea urchin" structure hyperbranched polyurethane acrylate prepolymer with EB curing activity comprises the following steps: 1) First, mix pentaerythritol (0.001 mol) and pyromellitic anhydride (0.004 mol) evenly and place them in a four-necked flask, add 100 ml of DMF and 0.000015 mol of p-toluenesulfonamide, and slowly heat to 200 ° C under N2 protection and react for 4 hours; 2) After the reaction is completed, add 3 times of p-toluenesulfonamide in the step, add pentaerythritol (0.012 mol) and continue to react for 4 hours; add 3 times of p-toluenesulfonamide in the step, add pyromellitic anhydride (0.036 mol) and continue to react for 4 hours; add 3 times of p-toluenesulfonamide in the step, add pentaerythritol (0.108 mol) and continue to react for 4 hours; add 3 times of p-toluenesulfonamide in the step, add pyromellitic anhydride (0.324 mol) and continue to react for 4 hours; add 3 times of p-toluenesulfonamide in the step, add pentaerythritol (0.972 mol) and continue to react for 4 hours, reduce the reaction temperature to 80°C, add 0.972 mol TDI and react for 2 hours, and then add 0.972 mol HBA and continue to react for 2 hours; 3) After the reaction is completed, cool to room temperature, dissolve in a mixed solution of acetone and methanol (volume ratio 1:1), and precipitate in anhydrous petroleum ether to obtain a polyurethane acrylate prepolymer with a molecular weight of about 500,000.

[0029] Example 7 A method for preparing a "sea urchin" structure hyperbranched polyurethane acrylate prepolymer with EB curing activity comprises the following steps: 1) First, mix pentaerythritol (0.001 mol) and pyromellitic anhydride (0.004 mol) evenly and place them in a four-necked flask, add 500 ml DMF and 0.000015 mol p-toluenesulfonamide, and slowly heat to 200 ° C under N2 protection and react for 4 hours; 2) After the reaction is completed, add 3 times of p-toluenesulfonamide in the step, add glycerol (0.012 mol) and continue to react for 4 hours; add 2 times of p-toluenesulfonamide in the step, add maleic anhydride (0.024 mol) and react for 4 hours; add an equal amount of p-toluenesulfonamide in the step, add glycerol (0.024 mol) and continue to react for 4 hours; add 2 times of p-toluenesulfonamide in the step, add maleic anhydride (0.048 mol) and react for 4 hours; add an equal amount of p-toluenesulfonamide in the step, add glycerol (0.048 mol) and continue to react for 4 hours; add 2 times of p-toluenesulfonamide in the step, add maleic anhydride (0.096 mol) and react for 4 hours; add an equal amount of p-toluenesulfonamide in the step, add glycerol (0.096 mol) and continue to react for 4 hours; add 2 times of p-toluenesulfonamide in the step, add maleic anhydride (0. 192mol) for 4h; add an equal amount of p-toluenesulfonamide in the step, add glycerol (0.192mol) and continue to react for 4h; add 2 times of p-toluenesulfonamide in the step, add maleic anhydride (0.384mol) and continue to react for 4h; add an equal amount of p-toluenesulfonamide in the step, add glycerol (0.384mol) and continue to react for 4h; add 2 times of p-toluenesulfonamide in the step, add maleic anhydride (0.768mol) and continue to react for 4h; add 2 times of p-toluenesulfonamide in the step, add maleic anhydride (0.768mol) and continue to react for 4h; add 2 times of p-toluenesulfonamide in the step, add maleic anhydride (1.536mol) and continue to react for 4h; add an equal amount of p-toluenesulfonamide in the step, add glycerol (1.536mol) and continue to react for 4h, reduce the reaction temperature to 80°C, and add 1.536mol IPDI was reacted for 2 h, and then 1.536 mol HEA was added and the reaction continued for 2 h; 3) After the reaction is completed, cool to room temperature, dissolve in a mixed solution of acetone and methanol (volume ratio 1:1), and precipitate in anhydrous petroleum ether to obtain a polyurethane acrylate prepolymer with a molecular weight of about 1 million.

[0030] Example 8 A method for preparing a "sea urchin" structure hyperbranched polyurethane acrylate prepolymer with EB curing activity comprises the following steps: 1) First, mix pentaerythritol (0.001 mol) and pyromellitic anhydride (0.004 mol) evenly and place them in a four-necked flask, add 500 ml DMF and 0.000015 mol p-toluenesulfonamide, and slowly heat to 200 ° C under N2 protection and react for 4 hours; 2) After the reaction is completed, add 3 times of p-toluenesulfonamide in the step, add glycerol (0.012 mol) and continue to react for 4 hours; add 2 times of p-toluenesulfonamide in the step, add maleic anhydride (0.024 mol) and react for 4 hours; add an equal amount of p-toluenesulfonamide in the step, add glycerol (0.024 mol) and continue to react for 4 hours; add 2 times of p-toluenesulfonamide in the step, add maleic anhydride (0.048 mol) and react for 4 hours; add an equal amount of p-toluenesulfonamide in the step, add glycerol (0.048 mol) and continue to react for 4 hours; add 2 times of p-toluenesulfonamide in the step, add maleic anhydride (0.096 mol) and react for 4 hours; add an equal amount of p-toluenesulfonamide in the step, add glycerol (0.096 mol) and continue to react for 4 hours; add 2 times of p-toluenesulfonamide in the step, add maleic anhydride (0. 192mol) for 4h; add an equal amount of p-toluenesulfonamide in the step, add glycerol (0.192mol) and continue to react for 4h; add 2 times of p-toluenesulfonamide in the step, add maleic anhydride (0.384mol) and continue to react for 4h; add an equal amount of p-toluenesulfonamide in the step, add glycerol (0.384mol) and continue to react for 4h; add 2 times of p-toluenesulfonamide in the step, add maleic anhydride (0.768mol) and continue to react for 4h; add 2 times of p-toluenesulfonamide in the step, add maleic anhydride (0.768mol) and continue to react for 4h; add 2 times of p-toluenesulfonamide in the step, add maleic anhydride (1.536mol) and continue to react for 4h; add an equal amount of p-toluenesulfonamide in the step, add glycerol (1.536mol) and continue to react for 4h, reduce the reaction temperature to 80°C, and add 1.536mol MDI was reacted for 2 h, and then 1.536 mol HEA was added and the reaction continued for 2 h; 3) After the reaction is completed, cool to room temperature, dissolve in a mixed solution of acetone and methanol (volume ratio 1:1), and precipitate in anhydrous petroleum ether to obtain a polyurethane acrylate prepolymer with a molecular weight of about 1 million.

[0031] The "sea urchin" structure hyperbranched polyurethane acrylate prepolymer with EB curing activity prepared in the above Examples 1 to 8 is composed of a "spherical body" and "thorns", the "spherical body" is formed by multiple esterification reactions of polyols and acid anhydrides, the "thorns" are formed by polyisocyanate capped with hydroxyalkyl acrylate, and the "spherical body" and the "thorns" are connected by the reaction of hydroxyl groups and isocyanate groups.

[0032] Comparative Example 1 A method for preparing a polyurethane acrylate prepolymer, except that TDI and HEA are not added in the last step of the reaction, the remaining steps are the same as those in Example 1, and the method comprises the following steps: 1) First, mix pentaerythritol (0.001 mol) and pyromellitic anhydride (0.004 mol) evenly and place them in a four-necked flask, add 100 ml of DMF and 0.000015 mol of p-toluenesulfonamide, and slowly heat to 200 ° C under N2 protection and react for 4 hours; 2) After the reaction is completed, add 3 times of p-toluenesulfonamide in the step, add pentaerythritol (0.012 mol) and continue to react for 4 hours; add 3 times of p-toluenesulfonamide in the step, then add pyromellitic anhydride (0.036 mol) and continue to react for 4 hours; add 3 times of p-toluenesulfonamide in the step, then add pentaerythritol (0.108 mol) and continue to react for 4 hours; add 3 times of p-toluenesulfonamide in the step, then add pyromellitic anhydride (0.324 mol) and continue to react for 4 hours; add 3 times of p-toluenesulfonamide in the step, then add pentaerythritol (0.972 mol) and continue to react for 4 hours; 3) After the reaction is completed, cool to room temperature, dissolve in a mixed solution of acetone and methanol (volume ratio 1:1), and precipitate in anhydrous petroleum ether to obtain a polyurethane acrylate prepolymer with a molecular weight of about 250,000.

[0033] Comparative Example 2 A method for preparing a polyurethane acrylate prepolymer, except that HEA is not added in the last step of the reaction, the remaining steps are the same as those in Example 1, and the method comprises the following steps: 1) First, mix pentaerythritol (0.001 mol) and pyromellitic anhydride (0.004 mol) evenly and place them in a four-necked flask, add 100 ml of DMF and 0.000015 mol of p-toluenesulfonamide, and slowly heat to 200 ° C under N2 protection and react for 4 hours; 2) After the reaction is completed, add 3 times of p-toluenesulfonamide in the step, add pentaerythritol (0.012 mol) and continue to react for 4 hours; add 3 times of p-toluenesulfonamide in the step, then add pyromellitic anhydride (0.036 mol) and continue to react for 4 hours; add 3 times of p-toluenesulfonamide in the step, then add pentaerythritol (0.108 mol) and continue to react for 4 hours; add 3 times of p-toluenesulfonamide in the step, then add pyromellitic anhydride (0.324 mol) and react for 4 hours; add 3 times of p-toluenesulfonamide in the step; then add pentaerythritol (0.972 mol) and continue to react for 4 hours, reduce the reaction temperature to 80°C, and then add 0.972 mol TDI and react for 2 hours; 3) After the reaction is completed, cool to room temperature, dissolve in a mixed solution of acetone and methanol (volume ratio 1:1), and precipitate in anhydrous petroleum ether to obtain a polyurethane acrylate prepolymer with a molecular weight of about 500,000.

[0034] Comparative Example 3 A method for preparing a polyurethane acrylate prepolymer comprises the following steps: 1) First, mix pentaerythritol (0.001 mol) and pyromellitic anhydride (0.004 mol) evenly and place them in a four-necked flask, add 100 ml of DMF and 0.000015 mol of p-toluenesulfonamide, and slowly heat to 200 ° C under N2 protection and react for 4 hours; 2) After the reaction is completed, add 3 times the amount of p-toluenesulfonamide in the step, add pentaerythritol (0.012 mol) and continue the reaction for 4 hours; lower the reaction temperature to 80°C, add 0.012 mol TDI and react for 2 hours, then add 0.012 mol HEA and continue the reaction for 2 hours; 3) After the reaction is completed, cool to room temperature, dissolve in a mixed solution of acetone and methanol (volume ratio 1:1), and precipitate in anhydrous petroleum ether to obtain a polyurethane acrylate prepolymer with a molecular weight of about 6000.

[0035] Comparative Example 4 A method for preparing a polyurethane acrylate prepolymer comprises the following steps: 1) First, mix pentaerythritol (0.001 mol) and pyromellitic anhydride (0.004 mol) evenly and place them in a four-necked flask, add 100 ml of DMF and 0.000015 mol of p-toluenesulfonamide, and slowly heat to 200 ° C under N2 protection and react for 4 hours; 2) After the reaction is completed, add 3 times of p-toluenesulfonamide in the step, add glycerol (0.012 mol) and continue to react for 4 hours; add 2 times of p-toluenesulfonamide in the step, add maleic anhydride (0.024 mol) and continue to react for 4 hours; add an equal amount of p-toluenesulfonamide in the step, add glycerol (0.024 mol) and continue to react for 4 hours; add 2 times of p-toluenesulfonamide in the step, add maleic anhydride (0.048 mol) and react for 4 hours; add an equal amount of p-toluenesulfonamide in the step, add glycerol (0.048 mol) and continue to react for 4 hours; add 2 times of p-toluenesulfonamide in the step, add maleic anhydride (0.096 mol) and react for 4 hours; add an equal amount of p-toluenesulfonamide in the step, add glycerol (0.096 mol) and continue to react for 4 hours, reduce the reaction temperature to 80°C, add 0.096 mol TDI and react for 2 hours, and then add 0.096 mol HEA and continue to react for 2 hours; 3) After the reaction is completed, cool to room temperature, dissolve in a mixed solution of acetone and methanol (volume ratio 1:1), and precipitate in anhydrous petroleum ether to obtain a polyurethane acrylate prepolymer with a molecular weight of about 60,000.

[0036] The polyurethane acrylate prepolymers prepared in the above Examples 1 to 8 and Comparative Examples 1 to 4 were coated and EB cured. Finally, the cured coatings were tested for maximum tensile force, ultimate tensile strength, and breaking deformation rate. The test results are shown in Table 1 below.

[0037] Table 1 Prepolymer film performance test results project Maximum tensile force / N Ultimate tensile strength / MPa Fracture deformation rate / % Example 1 23.964 106.517 23.35 Example 2 22.636 100.605 23.77 Example 3 22.428 99.681 22.67 Example 4 21.160 94.045 19.03 Example 5 20.912 92.934 17.96 Example 6 20.627 91.689 26.52 Example 7 23.059 102.483 22.05 Example 8 22.258 102.376 23.48 Comparative Example 1 5.266 25.592 18.38 Comparative Example 2 6.129 30.746 19.66 Comparative Example 3 8.777 48.241 20.34 Comparative Example 4 6.041 30.614 17.63 As shown in Table 1, the EB cured films prepared from the prepolymers obtained in Examples 1-8 have excellent tensile strength and can be used in a variety of occasions. The maximum tensile force and ultimate tensile strength of the prepolymer films obtained in Comparative Examples 1-4 are relatively poor, which is because: in Comparative Example 1, no polyisocyanate and hydroxyalkyl acrylate were added, and the prepolymer lacked crosslinking substances and reactive substances; in Comparative Example 2, no hydroxyalkyl acrylate was added, the polyisocyanate was not capped, and the prepolymer lacked active sites; the spherical structures synthesized in Comparative Examples 3 and 4 were not large enough, and the spherical structures were not round enough, resulting in still high viscosity, incomplete curing during EB curing, and fracture caused by low-intensity stretching.

[0038] Preparation and testing of PP / Al composite film: The aluminum foil (30-50µm) and PP film (20-40µm) were cleaned and dried with ethanol, and the aluminum foil was laid flat on a silica gel plate and coated with prepolymer. The amount of glue applied was controlled at 2±0.5g / m 2 , the PP film was covered on the aluminum foil, and the air between the aluminum foil and the PP film was driven out, and it was EB cured to obtain a PP / Al composite film, and a mechanical tensile test was performed. The test results are shown in Table 2 below.

[0039] Table 2 Performance test results of PP / Al composite film project Maximum peeling force / N Average peeling force / N Example 1 15.762 15.539 Example 2 15.083 14.853 Example 3 14.572 14.234 Example 4 14.537 14.082 Example 5 14.528 14.361 Example 6 14.384 14.116 Example 7 15.913 15.444 Example 8 14.837 14.267 Comparative Example 1 2.733 2.362 Comparative Example 2 3.398 3.037 Comparative Example 3 4.659 4.079 Comparative Example 4 3.785 3.447 It can be seen from Table 2 that, compared with Comparative Examples 1-4, the polyurethane acrylate prepolymer of the present invention has good mechanical properties and high EB curing activity, is suitable for use in PP / Al composite films, and the obtained PP / Al composite films have good anti-peeling effect.

[0040] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Other modifications or equivalent substitutions made to the technical solution of the present invention by ordinary technicians in the field should be included in the scope of the claims of the present invention as long as they do not depart from the spirit and scope of the technical solution of the present invention.

Claims

1. A "sea urchin" structure hyperbranched polyurethane acrylate prepolymer with EB curing activity, characterized in that: The prepolymer is composed of a "spherical body" and "thorns", wherein the "spherical body" is formed by multiple esterification reactions of polyol and acid anhydride, and the "thorns" are formed by polyisocyanate capped with hydroxyalkyl acrylate, and the "spherical body" and the "thorns" are connected by the reaction of hydroxyl and isocyanate.

2. A method for preparing the "sea urchin" structure hyperbranched polyurethane acrylate prepolymer with EB curing activity according to claim 1, characterized in that: The steps include: Under the action of a catalyst, the polyol and the acid anhydride undergo multiple esterification reactions to obtain a polyester polyol, and then polyisocyanate is added to carry out an amine alcohol reaction, and finally hydroxyalkyl acrylate is added for end-capping to obtain a polyurethane acrylate prepolymer.

3. The method for preparing the "sea urchin" structure hyperbranched polyurethane acrylate prepolymer with EB curing activity according to claim 2, characterized in that: The polyol and the acid anhydride undergo multiple esterification reactions under the action of a catalyst to obtain a polyester polyol, including: Under the action of a catalyst, the polyol and the acid anhydride are subjected to an esterification reaction, and then the polyol, the acid anhydride, and the polyol are added alternately for multiple times to carry out multiple esterification reactions until a polyester polyol with a target molecular weight is obtained.

4. The method for preparing the "sea urchin" structure hyperbranched polyurethane acrylate prepolymer with EB curing activity according to claim 3, characterized in that: The polyol is pentaerythritol or propylene glycol, the acid anhydride is pyromellitic anhydride or maleic anhydride, and the molar ratio of the polyol to the acid anhydride is 1-4:4-1.

5. The method for preparing the "sea urchin" structure hyperbranched polyurethane acrylate prepolymer with EB curing activity according to claim 3, characterized in that: The solvent for the esterification reaction of the polyol and the acid anhydride is one or more of DMF, triethylamine, ethanol and toluene.

6. The method for preparing the "sea urchin" structure hyperbranched polyurethane acrylate prepolymer with EB curing activity according to claim 3, characterized in that: The catalyst is concentrated sulfuric acid, p-toluenesulfonamide or 4-dimethylaminopyridine, and the catalyst is added in multiple times, and the catalyst added in each esterification reaction accounts for 0.1% to 5% of the molar amount of the corresponding polyol / anhydride added.

7. The method for preparing the "sea urchin" structure hyperbranched polyurethane acrylate prepolymer with EB curing activity according to claim 3, characterized in that: The esterification reaction temperature of the polyol and the acid anhydride is 150-220°C.

8. The method for preparing the "sea urchin" structure hyperbranched polyurethane acrylate prepolymer with EB curing activity according to claim 3, characterized in that: The polyisocyanate is one or more of TDI, IPDI, HDI and MDI; the hydroxyalkyl acrylate is one or more of HEA, HPA and HBA.

9. The method for preparing the "sea urchin" structure hyperbranched polyurethane acrylate prepolymer with EB curing activity according to claim 3, characterized in that: The molar ratio of the polyisocyanate to the hydroxyalkyl acrylate is 0.5-2:1; the molar ratio of the polyisocyanate to the outermost polyol of the polyester polyol is 1-1.5:

1.

10. The method for preparing the "sea urchin" structure hyperbranched polyurethane acrylate prepolymer with EB curing activity according to claim 3, characterized in that: The temperatures of the amine alcohol reaction and the end-capping reaction are both 40-100°C.

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