Polyurethane / epoxy resin thermosetting insulating adhesive and preparation method thereof

Abstract

The invention relates to the technical field of thermosetting insulating adhesives, and discloses a polyurethane / epoxy resin thermosetting insulating adhesive and a preparation method thereof. The invention comprises the following steps: adding 2,3,5,6-tetrafluorobenzyl alcohol and potassium carbonate into N,N-dimethylformamide, stirring evenly under ice bath conditions, adding allyl chloride, reacting at room temperature for 24 hours, extracting with ethyl acetate, washing, and drying to obtain a fluorine-containing suspension monomer; stirring evenly polyurethane-modified epoxy resin and a fluorine-containing suspension monomer, adding tetrakis(3-mercaptopropionic acid) pentaerythritol ester, 2-hydroxy-2-methylpropiophenone, 2,4,6-tris(dimethylaminoethyl)phenol, and a composite curing agent, stirring evenly to obtain a polyurethane / epoxy resin thermosetting insulating adhesive.

Description

Technical Field

[0001] The invention relates to the technical field of thermosetting insulating adhesives, in particular to a polyurethane / epoxy resin thermosetting insulating adhesive and a preparation method thereof. Background Art

[0002] As one of the thermosetting resins, epoxy resin is widely used in industrial fields such as electronics, automobile transportation, and aerospace. It is favored for its excellent mechanical properties, electrical insulation properties, and bonding properties. However, its long molding cycle and high-temperature curing limit its cutting-edge applications. In order to solve this problem, photo-thermal dual curing technology has been introduced into epoxy resin to achieve the goal of rapid curing and shaping and maintaining good mechanical properties and bonding properties. Traditional epoxy resins are difficult to effectively photo-thermal dual cross-link due to the lack of groups dedicated to photo-cross-linking. Although the thiol-ene click chemistry reaction has the advantages of fast speed, low by-products, and a uniform three-dimensional cross-linked network, it has attracted much attention in thermosetting materials. However, the cross-linked network formed solely by the thiol-ene click reaction has weak mechanical and thermomechanical properties.

[0003] Therefore, it is of great significance to invent a polyurethane / epoxy resin thermosetting insulating adhesive to improve the mechanical and thermomechanical properties of light-heat dual-curing epoxy resin. Summary of the invention

[0004] The object of the present invention is to provide a polyurethane / epoxy resin thermosetting insulating adhesive and a preparation method thereof to solve the problems raised in the above background technology.

[0005] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0006] A method for preparing a polyurethane / epoxy resin thermosetting insulating adhesive comprises the following steps:

[0007] S1: Stir anhydrous ethanol and anhydrous methanol evenly, preheat to 35-40°C, add deionized water, adjust the pH to 3-4, add β-(3,4-epoxycyclohexyl)-ethyltrimethoxysilane and fluorinated triethoxysilane, keep warm for 48 hours, adjust the pH to neutral, distill under reduced pressure, wash, filter, and dry to obtain epoxy POSS;

[0008] S2: Evenly stir resorcinol diglycidyl ether and epoxy POSS, add tetrabutylammonium bromide, heat to 130-135°C in a carbon dioxide atmosphere, react for 5.5-6 hours, add the product to dichloromethane, extract with deionized water, remove the catalyst, and vacuum dry to obtain a composite intermediate; evenly stir the composite intermediate and polyetheramine, heat to 100-105°C in a nitrogen atmosphere, react for 3-4 hours, and obtain a composite curing agent;

[0009] S3: Add toluene diisocyanate to N,N-dimethylformamide, stir evenly, preheat to 50-55°C, add polytetrahydrofuran diol and dibutyltin dilaurate under nitrogen atmosphere, keep warm and react until the isocyanate reaches the theoretical value to obtain a prepolymer; add 1,2,4-benzenetricarboxylic anhydride to the prepolymer, heat to 80-85°C, stir until 1,2,4-benzenetricarboxylic anhydride is completely dissolved, heat to 100-105°C and react for 3-4h, and distill under reduced pressure to obtain a carboxyl-terminated polyurethane;

[0010] S4: Epichlorohydrin, 2,2'-diallylbisphenol A and tetramethylammonium bromide are stirred evenly, heated to 100-105°C for reaction for 2-2.5h, sodium hydroxide solution is added, azeotropic dehydration is performed at normal pressure, rotary evaporation is performed, toluene is added to dissolve the crude product, deionized water is washed, the water layer is removed, 5% v / v sodium hydroxide solution is added, the reaction is performed at 85°C for 2h, the water layer is removed, the pH of the organic phase is adjusted to neutral, deionized water is washed, the water layer is removed, and distillation is performed to obtain diallyl diglycidyl ether; carboxyl-terminated polyurethane and diallyl diglycidyl ether are added to N,N-dimethylformamide, stirred evenly, heated to 100-105°C for reaction until the characteristic absorption peak of the epoxy group disappears, and polyurethane-modified epoxy resin is obtained;

[0011] S5: Add 2,3,5,6-tetrafluorobenzyl alcohol and potassium carbonate to N,N-dimethylformamide, stir evenly in an ice bath, add allyl chloride, react at room temperature for 24 hours, extract with ethyl acetate, wash, and dry to obtain a fluorine-containing pendant monomer;

[0012] S6: The polyurethane modified epoxy resin and the fluorine-containing suspension monomer are stirred evenly, and pentaerythritol tetrakis(3-mercaptopropionate), 2-hydroxy-2-methylpropiophenone, 2,4,6-tris(dimethylaminoethyl)phenol, a composite curing agent, and polyetheramine are added and stirred evenly to obtain a polyurethane / epoxy resin thermosetting insulating adhesive.

[0013] Furthermore, in the polyurethane / epoxy resin thermosetting insulating adhesive, the proportions of each component are calculated by weight: 100-120 parts of polyurethane modified epoxy resin, 5-15 parts of fluorine-containing suspension monomer, 120-140 parts of pentaerythritol tetrakis(3-mercaptopropionate), 0.1-0.2 parts of 2-hydroxy-2-methylpropiophenone, 0.05-0.06 parts of 2,4,6-tris(dimethylaminoethyl)phenol, 5-10 parts of composite curing agent, and 40-50 parts of polyetheramine.

[0014] Furthermore, in the carboxyl-terminated polyurethane, the molar ratio of toluene diisocyanate: polytetrahydrofuran diol: 1,2,4-benzenetricarboxylic anhydride is 2:1:2.

[0015] Furthermore, in the diallyl diglycidyl ether, the molar ratio of epichlorohydrin:2,2'-diallyl bisphenol A is 10:1; in the polyurethane-modified epoxy resin, the mass ratio of diallyl diglycidyl ether:carboxyl-terminated polyurethane is 1:(0.1-0.4).

[0016] Furthermore, in the epoxy POSS, the molar ratio of deionized water:silane is 2:1; the molar ratio of β-(3,4-epoxycyclohexyl)-ethyltrimethoxysilane:fluorinated triethoxysilane is (2-3):(5-6).

[0017] Furthermore, the fluorine-containing triethoxysilane is any one of perfluorobutylethyltriethoxysilane and monofluorotriethoxysilane.

[0018] Furthermore, in the composite intermediate, the mass ratio of resorcinol diglycidyl ether:epoxy POSS is (6-8):(2-4); in the composite curing agent, the molar ratio of composite intermediate:polyetheramine is 1:(4-5).

[0019] Furthermore, in the fluorine-containing pendant monomer, the molar ratio of 2,3,5,6-tetrafluorobenzyl alcohol to allyl chloride is 1:(1.2-2).

[0020] Compared with the prior art, the beneficial effects achieved by the present invention are:

[0021] The present invention uses epichlorohydrin and 2,2'-diallyl bisphenol A as raw materials to prepare an epoxy resin-diallyl diglycidyl ether containing a double bond structure through a one-pot method, and uses it as the epoxy resin insulation adhesive matrix, and then modifies it through the carboxyl-terminated polyurethane prepared by toluene diisocyanate, polytetrahydrofuran diol, and 1,2,4-benzenetricarboxylic anhydride. Since there is no hydroxyl group in the structure of the homemade diallyl diglycidyl ether, it is not easy to be modified by grafting polyurethane in a traditional way. The present invention achieves the purpose of toughening the modified epoxy resin by reacting the carboxyl group of the carboxyl-terminated polyurethane with the epoxy group in the diallyl diglycidyl ether. The carboxyl-terminated polyurethane introduces a large number of soft / hard block structures into the epoxy resin matrix, and the urethane group in the structure can give the epoxy resin excellent interfacial bonding properties, thereby achieving the effect of toughening the epoxy resin, and greatly enhancing the mechanical properties and bonding properties of the epoxy resin insulation adhesive.

[0022] The present invention uses β-(3,4-epoxycyclohexyl)-ethyltrimethoxysilane and fluorine-containing triethoxysilane as raw materials to prepare epoxy POSS, and prepares a composite intermediate containing a cyclocarbonate group by a carbon dioxide insertion method with epoxy POSS and resorcinol diglycidyl ether, and finally reacts with polyetheramine to prepare a composite curing agent. In order to further improve the mechanical properties and bonding properties of the polyurethane / epoxy resin insulating adhesive, the present invention utilizes the characteristics of the epoxy resin itself containing both C=C double bonds and epoxy groups in its molecular structure, and simultaneously introduces tetrakis(3-mercaptopropionic acid) pentaerythritol ester and a composite curing agent into the epoxy resin matrix to prepare a polyurethane / epoxy resin insulating adhesive with light-heat dual crosslinking curing properties. The reinforcing filler POSS is introduced into the epoxy resin matrix in the form of a curing agent. The rigid cage structure provided by the POSS structure connects the curing groups, which forms a dense cross-linking system in the internal structure of the insulating glue during the curing process of the epoxy resin, further enhancing the mechanical properties and thermal stability of the insulating glue. At the same time, the cross-linking network formed by the thiol-olefin click chemistry reaction has a large number of flexible thioether bonds, which together with the rigid network form a three-dimensional network structure inside the insulating glue, further enhancing the mechanical properties, bonding properties and thermal stability of the insulating glue.

[0023] In order to improve the dispersibility of the composite curing agent in the matrix and further improve the mechanical properties of the mercapto-ene flexible network, the present invention reacts 2,3,5,6-tetrafluorobenzyl alcohol with allyl chloride, and the prepared fluorine-containing suspension monomer is cross-linked with tetrakis (3-mercaptopropionic acid) pentaerythritol ester by a click reaction, and exists in the curing network of the insulating glue as a suspension chain. On the one hand, the introduction of the fluorine-containing suspension monomer can enhance the compatibility of the composite curing agent with the matrix and enhance its dispersibility in the matrix; on the other hand, as a suspension chain, it can produce an internal anti-plasticization effect in the mercapto-ene flexible network, thereby limiting the movement of the molecular chain, reducing the volume of free radicals, and improving the cohesive energy of the matrix. Since the bond length of the CF bond is larger than that of the CH bond, the distance between the molecular chains increases, and the stacking structure is looser. At the same time, the fluorine-containing suspension monomer containing benzyl carbon and allyl structure exhibits flexible molecular rotational motion. Such structural features enable the molecule to have a higher chain mobility, which helps to improve the toughness of the material when subjected to a large strain, and further improves the mechanical properties and bonding properties of the insulating glue. DETAILED DESCRIPTION

[0024] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0025] In the following examples, the polyetheramine model is D230, CAS9046-10-0; polytetrahydrofuran diol Mn=1000, purchased from Sigma-Aldrich; the specification of 2,2'-diallyl bisphenol A is diallyl ether containing 15% bisphenol A, CAS1745-89-7; and the other raw materials are commercially available.

[0026] Example 1: A method for preparing a polyurethane / epoxy resin thermosetting insulating adhesive: S1: Stir anhydrous ethanol and anhydrous methanol evenly, preheat to 35°C, add 2 mol of deionized water, adjust the pH to 3-4, add 0.375 mol of β-(3,4-epoxycyclohexyl)-ethyltrimethoxysilane and 0.625 mol of monofluorotriethoxysilane, keep warm for 48 hours, adjust the pH to neutral, distill under reduced pressure, wash, filter, and dry to obtain epoxy POSS;

[0027] S2: 8g of resorcinol diglycidyl ether and 2g of epoxy POSS were stirred evenly, 0.1g of tetrabutylammonium bromide was added, and the mixture was heated to 130°C for reaction for 5.5h under a carbon dioxide atmosphere. The product was added to dichloromethane, extracted with deionized water, the catalyst was removed, and vacuum dried to obtain a composite intermediate; 1mol of the composite intermediate and 5mol of polyetheramine were stirred evenly, and the mixture was heated to 100°C for reaction for 3h under a nitrogen atmosphere to obtain a composite curing agent;

[0028] S3: Add 2 mol of toluene diisocyanate to N,N-dimethylformamide, stir evenly, preheat to 50°C, add 1 mol of polytetrahydrofuran diol and 0.02 mol of dibutyltin dilaurate under nitrogen atmosphere, and keep warm to react until the isocyanate reaches the theoretical value to obtain a prepolymer; add 2 mol of 1,2,4-benzenetricarboxylic anhydride to the prepolymer, heat to 80°C, stir until the 1,2,4-benzenetricarboxylic anhydride is completely dissolved, heat to 100°C for reaction for 3 hours, and distill under reduced pressure to obtain a carboxyl-terminated polyurethane;

[0029] S4: 10 mol of epichlorohydrin, 1 mol of 2,2'-diallyl bisphenol A and tetramethylammonium bromide were stirred evenly, heated to 100°C for reaction for 2 hours, 48% v / v sodium hydroxide solution was added, azeotropic dehydration was performed at normal pressure, rotary evaporation was performed, toluene was added to dissolve the crude product, deionized water was washed, the water layer was removed, 5% v / v sodium hydroxide solution was added, the reaction was carried out at 85°C for 2 hours, the water layer was removed, the pH of the organic phase was adjusted to neutral, deionized water was washed, the water layer was removed, and distillation was performed to obtain diallyl diglycidyl ether; 10 g of carboxyl-terminated polyurethane and 100 g of diallyl diglycidyl ether were added to N,N-dimethylformamide, stirred evenly, heated to 100°C for reaction until the characteristic absorption peak of the epoxy group disappeared, and polyurethane-modified epoxy resin was obtained;

[0030] S5: Add 1 mol of 2,3,5,6-tetrafluorobenzyl alcohol and 0.1 mol of potassium carbonate to N,N-dimethylformamide, stir evenly in an ice bath, add 1.2 mol of allyl chloride, react at room temperature for 24 hours, extract with ethyl acetate, wash, and dry to obtain a fluorinated pendant monomer;

[0031] S6: 100g of polyurethane modified epoxy resin and 5g of fluorine-containing suspension monomer are stirred evenly, and 120g of pentaerythritol tetrakis(3-mercaptopropionate), 0.1g of 2-hydroxy-2-methylpropiophenone, 0.05g of 2,4,6-tris(dimethylaminoethyl)phenol, 5g of composite curing agent and 40 parts of polyetheramine are added, and stirred evenly to obtain polyurethane / epoxy resin thermosetting insulating adhesive.

[0032] Example 2: A method for preparing a polyurethane / epoxy resin thermosetting insulating adhesive: S1: Stir anhydrous ethanol and anhydrous methanol evenly, preheat to 35°C, add 2 mol of deionized water, adjust the pH to 3-4, add 0.375 mol of β-(3,4-epoxycyclohexyl)-ethyltrimethoxysilane and 0.625 mol of monofluorotriethoxysilane, keep warm for 48 hours, adjust the pH to neutral, distill under reduced pressure, wash, filter, and dry to obtain epoxy POSS;

[0033] S2: 6 g of resorcinol diglycidyl ether and 4 g of epoxy POSS were stirred evenly, 0.1 g of tetrabutylammonium bromide was added, and the mixture was heated to 130° C. under a carbon dioxide atmosphere for reaction for 5.5 h. The product was added to dichloromethane, extracted with deionized water, the catalyst was removed, and vacuum dried to obtain a composite intermediate; 1 mol of the composite intermediate and 5 mol of polyetheramine were stirred evenly, and the mixture was heated to 100° C. under a nitrogen atmosphere for reaction for 3 h to obtain a composite curing agent;

[0034] S3: Add 2 mol of toluene diisocyanate to N,N-dimethylformamide, stir evenly, preheat to 50°C, add 1 mol of polytetrahydrofuran diol and 0.02 mol of dibutyltin dilaurate under nitrogen atmosphere, and keep warm to react until the isocyanate reaches the theoretical value to obtain a prepolymer; add 2 mol of 1,2,4-benzenetricarboxylic anhydride to the prepolymer, heat to 80°C, stir until the 1,2,4-benzenetricarboxylic anhydride is completely dissolved, heat to 100°C for reaction for 3 hours, and distill under reduced pressure to obtain a carboxyl-terminated polyurethane;

[0035] S4: 10 mol of epichlorohydrin, 1 mol of 2,2'-diallyl bisphenol A and tetramethylammonium bromide were stirred evenly, heated to 100°C for reaction for 2 hours, 48% v / v sodium hydroxide solution was added, azeotropic dehydration was performed at normal pressure, rotary evaporation was performed, toluene was added to dissolve the crude product, deionized water was washed, the water layer was removed, 5% v / v sodium hydroxide solution was added, the reaction was carried out at 85°C for 2 hours, the water layer was removed, the pH of the organic phase was adjusted to neutral, deionized water was washed, the water layer was removed, and distillation was performed to obtain diallyl diglycidyl ether; 10 g of carboxyl-terminated polyurethane and 100 g of diallyl diglycidyl ether were added to N,N-dimethylformamide, stirred evenly, heated to 100°C for reaction until the characteristic absorption peak of the epoxy group disappeared, and polyurethane-modified epoxy resin was obtained;

[0036] S5: Add 1 mol of 2,3,5,6-tetrafluorobenzyl alcohol and 0.1 mol of potassium carbonate to N,N-dimethylformamide, stir evenly in an ice bath, add 1.2 mol of allyl chloride, react at room temperature for 24 hours, extract with ethyl acetate, wash, and dry to obtain a fluorinated pendant monomer;

[0037] S6: 100g of polyurethane modified epoxy resin and 5g of fluorine-containing suspension monomer are stirred evenly, and 120g of pentaerythritol tetrakis(3-mercaptopropionate), 0.1g of 2-hydroxy-2-methylpropiophenone, 0.05g of 2,4,6-tris(dimethylaminoethyl)phenol, 5g of composite curing agent and 40 parts of polyetheramine are added, and stirred evenly to obtain polyurethane / epoxy resin thermosetting insulating adhesive.

[0038] Example 3: A method for preparing a polyurethane / epoxy resin thermosetting insulating adhesive: S1: Stir anhydrous ethanol and anhydrous methanol evenly, preheat to 35°C, add 2 mol of deionized water, adjust the pH to 3-4, add 0.375 mol of β-(3,4-epoxycyclohexyl)-ethyltrimethoxysilane and 0.625 mol of monofluorotriethoxysilane, keep warm for 48 hours, adjust the pH to neutral, distill under reduced pressure, wash, filter, and dry to obtain epoxy POSS;

[0039] S2: 6 g of resorcinol diglycidyl ether and 4 g of epoxy POSS were stirred evenly, 0.1 g of tetrabutylammonium bromide was added, and the mixture was heated to 130° C. under a carbon dioxide atmosphere for reaction for 5.5 h. The product was added to dichloromethane, extracted with deionized water, the catalyst was removed, and vacuum dried to obtain a composite intermediate; 1 mol of the composite intermediate and 5 mol of polyetheramine were stirred evenly, and the mixture was heated to 100° C. under a nitrogen atmosphere for reaction for 3 h to obtain a composite curing agent;

[0040] S3: Add 2 mol of toluene diisocyanate to N,N-dimethylformamide, stir evenly, preheat to 50°C, add 1 mol of polytetrahydrofuran diol and 0.02 mol of dibutyltin dilaurate under nitrogen atmosphere, and keep warm to react until the isocyanate reaches the theoretical value to obtain a prepolymer; add 2 mol of 1,2,4-benzenetricarboxylic anhydride to the prepolymer, heat to 80°C, stir until the 1,2,4-benzenetricarboxylic anhydride is completely dissolved, heat to 100°C for reaction for 3 hours, and distill under reduced pressure to obtain a carboxyl-terminated polyurethane;

[0041] S4: 10 mol of epichlorohydrin, 1 mol of 2,2'-diallyl bisphenol A and tetramethylammonium bromide were stirred evenly, heated to 100°C for reaction for 2 hours, 48% v / v sodium hydroxide solution was added, azeotropic dehydration was performed at normal pressure, rotary evaporation was performed, toluene was added to dissolve the crude product, deionized water was washed, the water layer was removed, 5% v / v sodium hydroxide solution was added, the reaction was carried out at 85°C for 2 hours, the water layer was removed, the pH of the organic phase was adjusted to neutral, deionized water was washed, the water layer was removed, and distillation was performed to obtain diallyl diglycidyl ether; 40 g of carboxyl-terminated polyurethane and 100 g of diallyl diglycidyl ether were added to N,N-dimethylformamide, stirred evenly, heated to 100°C for reaction until the characteristic absorption peak of the epoxy group disappeared, and polyurethane-modified epoxy resin was obtained;

[0042] S5: Add 1 mol of 2,3,5,6-tetrafluorobenzyl alcohol and 0.1 mol of potassium carbonate to N,N-dimethylformamide, stir evenly in an ice bath, add 1.2 mol of allyl chloride, react at room temperature for 24 hours, extract with ethyl acetate, wash, and dry to obtain a fluorinated pendant monomer;

[0043] S6: 100g of polyurethane modified epoxy resin and 5g of fluorine-containing suspension monomer are stirred evenly, and 120g of pentaerythritol tetrakis(3-mercaptopropionate), 0.1g of 2-hydroxy-2-methylpropiophenone, 0.05g of 2,4,6-tris(dimethylaminoethyl)phenol, 5g of composite curing agent and 40 parts of polyetheramine are added, and stirred evenly to obtain polyurethane / epoxy resin thermosetting insulating adhesive.

[0044] Example 4: A method for preparing a polyurethane / epoxy resin thermosetting insulating adhesive: S1: Stir anhydrous ethanol and anhydrous methanol evenly, preheat to 35°C, add 2 mol of deionized water, adjust the pH to 3-4, add 0.375 mol of β-(3,4-epoxycyclohexyl)-ethyltrimethoxysilane and 0.625 mol of monofluorotriethoxysilane, keep warm for 48 hours, adjust the pH to neutral, distill under reduced pressure, wash, filter, and dry to obtain epoxy POSS;

[0045] S2: 6 g of resorcinol diglycidyl ether and 4 g of epoxy POSS were stirred evenly, 0.1 g of tetrabutylammonium bromide was added, and the mixture was heated to 130° C. under a carbon dioxide atmosphere for reaction for 5.5 h. The product was added to dichloromethane, extracted with deionized water, the catalyst was removed, and vacuum dried to obtain a composite intermediate; 1 mol of the composite intermediate and 5 mol of polyetheramine were stirred evenly, and the mixture was heated to 100° C. under a nitrogen atmosphere for reaction for 3 h to obtain a composite curing agent;

[0046] S3: Add 2 mol of toluene diisocyanate to N,N-dimethylformamide, stir evenly, preheat to 50°C, add 1 mol of polytetrahydrofuran diol and 0.02 mol of dibutyltin dilaurate under nitrogen atmosphere, and keep warm to react until the isocyanate reaches the theoretical value to obtain a prepolymer; add 2 mol of 1,2,4-benzenetricarboxylic anhydride to the prepolymer, heat to 80°C, stir until the 1,2,4-benzenetricarboxylic anhydride is completely dissolved, heat to 100°C for reaction for 3 hours, and distill under reduced pressure to obtain a carboxyl-terminated polyurethane;

[0047] S4: 10 mol of epichlorohydrin, 1 mol of 2,2'-diallyl bisphenol A and tetramethylammonium bromide were stirred evenly, heated to 100°C for reaction for 2 hours, 48% v / v sodium hydroxide solution was added, azeotropic dehydration was performed at normal pressure, rotary evaporation was performed, toluene was added to dissolve the crude product, deionized water was washed, the water layer was removed, 5% v / v sodium hydroxide solution was added, the reaction was carried out at 85°C for 2 hours, the water layer was removed, the pH of the organic phase was adjusted to neutral, deionized water was washed, the water layer was removed, and distillation was performed to obtain diallyl diglycidyl ether; 40 g of carboxyl-terminated polyurethane and 100 g of diallyl diglycidyl ether were added to N,N-dimethylformamide, stirred evenly, heated to 100°C for reaction until the characteristic absorption peak of the epoxy group disappeared, and polyurethane-modified epoxy resin was obtained;

[0048] S5: Add 1 mol of 2,3,5,6-tetrafluorobenzyl alcohol and 0.1 mol of potassium carbonate to N,N-dimethylformamide, stir evenly in an ice bath, add 1.2 mol of allyl chloride, react at room temperature for 24 hours, extract with ethyl acetate, wash, and dry to obtain a fluorinated pendant monomer;

[0049] S6: 100g of polyurethane modified epoxy resin and 10g of fluorine-containing suspension monomer are stirred evenly, and 120g of pentaerythritol tetrakis(3-mercaptopropionate), 0.1g of 2-hydroxy-2-methylpropiophenone, 0.05g of 2,4,6-tris(dimethylaminoethyl)phenol, 8g of composite curing agent and 40 parts of polyetheramine are added, and stirred evenly to obtain polyurethane / epoxy resin thermosetting insulating adhesive.

[0050] Example 5: A method for preparing a polyurethane / epoxy resin thermosetting insulating adhesive: S1: Stir anhydrous ethanol and anhydrous methanol evenly, preheat to 35°C, add 2 mol of deionized water, adjust the pH to 3-4, add 0.375 mol of β-(3,4-epoxycyclohexyl)-ethyltrimethoxysilane and 0.625 mol of monofluorotriethoxysilane, keep warm for 48 hours, adjust the pH to neutral, distill under reduced pressure, wash, filter, and dry to obtain epoxy POSS;

[0051] S2: 6 g of resorcinol diglycidyl ether and 4 g of epoxy POSS were stirred evenly, 0.1 g of tetrabutylammonium bromide was added, and the mixture was heated to 130° C. under a carbon dioxide atmosphere for reaction for 5.5 h. The product was added to dichloromethane, extracted with deionized water, the catalyst was removed, and vacuum dried to obtain a composite intermediate; 1 mol of the composite intermediate and 5 mol of polyetheramine were stirred evenly, and the mixture was heated to 100° C. under a nitrogen atmosphere for reaction for 3 h to obtain a composite curing agent;

[0052] S3: Add 2 mol of toluene diisocyanate to N,N-dimethylformamide, stir evenly, preheat to 50°C, add 1 mol of polytetrahydrofuran diol and 0.02 mol of dibutyltin dilaurate under nitrogen atmosphere, and keep warm to react until the isocyanate reaches the theoretical value to obtain a prepolymer; add 2 mol of 1,2,4-benzenetricarboxylic anhydride to the prepolymer, heat to 80°C, stir until the 1,2,4-benzenetricarboxylic anhydride is completely dissolved, heat to 100°C for reaction for 3 hours, and distill under reduced pressure to obtain a carboxyl-terminated polyurethane;

[0053] S4: 10 mol of epichlorohydrin, 1 mol of 2,2'-diallyl bisphenol A and tetramethylammonium bromide were stirred evenly, heated to 100°C for reaction for 2 hours, 48% v / v sodium hydroxide solution was added, azeotropic dehydration was performed at normal pressure, rotary evaporation was performed, toluene was added to dissolve the crude product, deionized water was washed, the water layer was removed, 5% v / v sodium hydroxide solution was added, the reaction was carried out at 85°C for 2 hours, the water layer was removed, the pH of the organic phase was adjusted to neutral, deionized water was washed, the water layer was removed, and distillation was performed to obtain diallyl diglycidyl ether; 40 g of carboxyl-terminated polyurethane and 100 g of diallyl diglycidyl ether were added to N,N-dimethylformamide, stirred evenly, heated to 100°C for reaction until the characteristic absorption peak of the epoxy group disappeared, and polyurethane-modified epoxy resin was obtained;

[0054] S5: Add 1 mol of 2,3,5,6-tetrafluorobenzyl alcohol and 0.1 mol of potassium carbonate to N,N-dimethylformamide, stir evenly in an ice bath, add 1.2 mol of allyl chloride, react at room temperature for 24 hours, extract with ethyl acetate, wash, and dry to obtain a fluorinated pendant monomer;

[0055] S6: 100g of polyurethane modified epoxy resin and 15g of fluorine-containing suspension monomer are stirred evenly, and 120g of pentaerythritol tetrakis(3-mercaptopropionate), 0.1g of 2-hydroxy-2-methylpropiophenone, 0.05g of 2,4,6-tris(dimethylaminoethyl)phenol, 10g of composite curing agent and 40 parts of polyetheramine are added, and stirred evenly to obtain polyurethane / epoxy resin thermosetting insulating adhesive.

[0056] Comparative Example 1: A method for preparing a polyurethane / epoxy resin thermosetting insulating adhesive: S2: 6 g of resorcinol diglycidyl ether and 6 g of epoxy POSS were stirred evenly, 0.1 g of tetrabutylammonium bromide was added, and the mixture was heated to 130° C. under a carbon dioxide atmosphere for reaction for 5.5 h. The product was added to dichloromethane, extracted with deionized water, the catalyst was removed, and vacuum dried to obtain a composite intermediate; 1 mol of the composite intermediate and 5 mol of polyetheramine were stirred evenly, and the mixture was heated to 100° C. under a nitrogen atmosphere for reaction for 3 h to obtain a composite curing agent;

[0057] The remaining steps are the same as those in Example 1.

[0058] Comparative Example 2: A method for preparing a polyurethane / epoxy resin thermosetting insulating adhesive: S6: 100 g of polyurethane-modified epoxy resin and 20 g of fluorine-containing suspension monomer are stirred evenly, and 120 g of pentaerythritol tetrakis(3-mercaptopropionic acid), 0.1 g of 2-hydroxy-2-methylpropiophenone, 0.05 g of 2,4,6-tris(dimethylaminoethyl)phenol, 5 g of composite curing agent, and 40 parts of polyetheramine are added, and stirred evenly to obtain a polyurethane / epoxy resin thermosetting insulating adhesive;

[0059] The remaining steps are the same as those in Example 1.

[0060] Comparative Example 3: A method for preparing a polyurethane / epoxy resin thermosetting insulating adhesive: S6: 100 g of polyurethane-modified epoxy resin and 5 g of fluorine-containing suspension monomer are stirred evenly, and 120 g of pentaerythritol tetrakis(3-mercaptopropionic acid), 0.1 g of 2-hydroxy-2-methylpropiophenone, 0.05 g of 2,4,6-tris(dimethylaminoethyl)phenol, 15 g of composite curing agent, and 40 parts of polyetheramine are added, and stirred evenly to obtain a polyurethane / epoxy resin thermosetting insulating adhesive;

[0061] The remaining steps are the same as those in Example 1.

[0062] Experiment: Adhesion performance test:

[0063] Shear strength test: According to GB / T 7124-2008 standard, the tensile shear strength of the insulating adhesive was tested; a 1060 aluminum plate with a specification of 3mm×20mm×60mm was selected as the substrate, and the surface oxide was removed by grinding with 80-grit sandpaper. It was placed in a mixed oxidation solution at 60°C and a mass ratio of K2Cr2O7: concentrated H2SO4: H2O of 1:10:30 for 10 minutes, washed with deionized water, and used as a test substrate after drying.

[0064] Peel strength test: According to GB / T 7122-1996 standard, the peel strength of the insulating adhesive was tested; a 1060 aluminum plate with a specification of 2mm×75mm×200mm was selected as the substrate, the surface grease was removed, and it was placed in a 30℃ 5wt% sodium hydroxide solution. After it turned black, it was taken out and washed with deionized water, and then placed in a 25℃ 10wt% nitric acid solution for 3 minutes. After the black color faded, it was taken out and washed with deionized water. After drying, it was placed in a 25℃ 10wt% phosphoric acid solution as an anodizing electrolyte for 30 minutes, washed with deionized water, and dried as a test substrate.

[0065] 90° peel strength calculation formula: 90° peel strength = F / b; where F: average peel force applied to the sample (N); b: width of the sample during testing (mm).

[0066] Mechanical properties test:

[0067] Tensile properties: According to GB / T 2567-2008 standard, the tensile properties of the resin casting body are tested. The test sample size is a square test specimen of 80mm×10mm×4mm.

[0068] The samples used in the above bonding performance test and mechanical property test were all cured by UV light with an energy of 1000 mj, and then thermally cured at 60° C. for 30 min.

[0069] Table 1 Performance test data of polyurethane / epoxy resin thermosetting insulation adhesive

[0070]

[0071] Conclusion: The polyurethane / epoxy resin thermosetting insulating adhesive prepared by the present invention has excellent bonding properties and mechanical properties.

[0072] In comparative example 1, too much epoxy POSS was added during the preparation of the composite curing agent, resulting in an increase in the rigid structure and reduced mechanical properties and bonding properties; in comparative example 2, excessive fluorine-containing suspension monomers were added during the preparation of the polyurethane / epoxy resin thermosetting insulating adhesive, resulting in a decrease in the cross-linking density of the system and a decrease in various performances; in comparative example 3, excessive composite curing agent was added, resulting in an excessively large cross-linking density of the system and reduced mechanical properties and bonding properties.

[0073] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein by equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing a polyurethane / epoxy resin thermosetting insulating adhesive, characterized in that: The following steps are involved: S1: Add 2,3,5,6-tetrafluorobenzyl alcohol and potassium carbonate to N,N-dimethylformamide, stir evenly in an ice bath, add allyl chloride, react at room temperature, extract with ethyl acetate, wash, and dry to obtain a fluorine-containing pendant monomer; In the fluorinated pendant monomer, the molar ratio of 2,3,5,6-tetrafluorobenzyl alcohol to allyl chloride is 1:(1.2-2); S2: The polyurethane modified epoxy resin and the fluorine-containing suspension monomer are stirred evenly, and pentaerythritol tetrakis(3-mercaptopropionate), 2-hydroxy-2-methylpropiophenone, 2,4,6-tris(dimethylaminoethyl)phenol, a composite curing agent, and polyetheramine are added and stirred evenly to obtain a polyurethane / epoxy resin thermosetting insulating adhesive; In the polyurethane / epoxy resin thermosetting insulating adhesive, the proportions of each component are calculated by weight: 100-120 parts of polyurethane modified epoxy resin, 5-15 parts of fluorine-containing suspension monomer, 120-140 parts of pentaerythritol tetrakis(3-mercaptopropionate), 0.1-0.2 parts of 2-hydroxy-2-methylpropiophenone, 0.05-0.06 parts of 2,4,6-tris(dimethylaminoethyl)phenol, 5-10 parts of composite curing agent, and 40-50 parts of polyetheramine; The preparation method of the polyurethane modified epoxy resin comprises the following steps: Add toluene diisocyanate to N,N-dimethylformamide, stir evenly, preheat to 50-55°C, add polytetrahydrofuran diol and dibutyltin dilaurate under nitrogen atmosphere, keep warm and react until the isocyanate reaches the theoretical value to obtain a prepolymer; add 1,2,4-benzenetricarboxylic anhydride to the prepolymer, heat to 80-85°C, stir until 1,2,4-benzenetricarboxylic anhydride is completely dissolved, heat to 100-105°C and react for 3-4h, and distill under reduced pressure to obtain a carboxyl-terminated polyurethane; Epichlorohydrin, 2,2'-diallyl bisphenol A and tetramethylammonium bromide are stirred evenly, heated to 100-105°C for reaction for 2-2.5h, 48-50% v / v sodium hydroxide solution is added, azeotropic dehydration is performed at normal pressure, rotary evaporation is performed, and purification is performed to obtain diallyl diglycidyl ether; carboxyl-terminated polyurethane and diallyl diglycidyl ether are added to N,N-dimethylformamide, stirred evenly, heated to 100-105°C for reaction until the characteristic absorption peak of the epoxy group disappears, and polyurethane-modified epoxy resin is obtained; The preparation method of the composite curing agent comprises the following steps: Stir anhydrous ethanol and anhydrous methanol evenly, preheat to 35-40°C, add deionized water, adjust the pH to 3-4, add β-(3,4-epoxycyclohexyl)-ethyltrimethoxysilane and fluorine-containing triethoxysilane, keep warm for reaction, adjust the pH to neutral, distill under reduced pressure, wash, filter, and dry to obtain epoxy POSS; In the epoxy POSS, the molar ratio of deionized water: silane is 2:1; the molar ratio of β-(3,4-epoxycyclohexyl)-ethyltrimethoxysilane: fluorine-containing triethoxysilane is (2-3):(5-6); The resorcinol diglycidyl ether and epoxy POSS are stirred evenly, tetrabutylammonium bromide is added, and the mixture is heated to 130-135°C under a carbon dioxide atmosphere for reaction for 5.5-6 hours. The product is added to dichloromethane, extracted with deionized water, the catalyst is removed, and vacuum dried to obtain a composite intermediate. The composite intermediate and polyetheramine are stirred evenly, and the mixture is heated to 100-105°C under a nitrogen atmosphere for reaction for 3-4 hours to obtain a composite curing agent. In the composite intermediate, the mass ratio of resorcinol diglycidyl ether:epoxy POSS is (6-8):(2-4); in the composite curing agent, the molar ratio of composite intermediate:polyetheramine is 1:(4-5).

2. The method for preparing a polyurethane / epoxy resin thermosetting insulating adhesive according to claim 1, characterized in that: In the carboxyl-terminated polyurethane, the molar ratio of toluene diisocyanate: polytetrahydrofuran diol: 1,2,4-tricarboxylic anhydride is 2:1:

2.

3. The method for preparing a polyurethane / epoxy resin thermosetting insulating adhesive according to claim 1, characterized in that: In the diallyl diglycidyl ether, the molar ratio of epichlorohydrin:2,2'-diallyl bisphenol A is 10:1; in the polyurethane-modified epoxy resin, the mass ratio of diallyl diglycidyl ether:carboxyl-terminated polyurethane is 1:(0.1-0.4).

4. The polyurethane / epoxy resin thermosetting insulating adhesive prepared according to the method for preparing the polyurethane / epoxy resin thermosetting insulating adhesive according to any one of claims 1 to 3.

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