A delayed catalyst and its preparation method and application

Abstract

The present application provides a delayed catalyst, which comprises an imidazole ring carbene metal complex blocked by an organic acid and / or an organic base. The present application also provides a preparation method and application of the delayed catalyst. The delayed catalyst is prepared by an easy-to-operate method, can be used for delaying the polymerization of polyurethane, prolonging the pre-curing time, thereby providing a longer tack-free time and operation time, and can improve the heat conduction performance, elongation and bonding strength and other performances of the heat conduction structural adhesive when applied in a polyurethane heat conduction structural adhesive system.

Description

Technical Field

[0001] This invention relates to the field of catalytic synthesis of polyurethane, and more specifically to a delayed catalyst, its preparation method, and its application. This delayed catalyst is suitable for the catalytic synthesis of polyurethane. Background Technology

[0002] Current polyurethane thermally conductive structural adhesives for battery packaging have certain initial bonding and thermal conductivity properties. However, the surface of these adhesives is prone to skinning and curing, resulting in short surface drying and operating times. Consequently, the bonding performance of the polyurethane thermally conductive adhesives drops sharply during operation.

[0003] To slow down the reactivity of thermally conductive structural adhesive components and prolong curing time, delay catalysts are typically added. A typical catalyst is 2-hydroxy-N,N,N-trimethyl-1-propylaminocarbamate, and there are also some blocked amine catalysts. However, current delay catalysts for polyurethane thermally conductive structural adhesives cannot meet the requirements of actual production for long open-time bond strength.

[0004] Therefore, it is necessary to provide a novel delayed catalyst to solve the above problems. Summary of the Invention

[0005] In view of this, this application provides a delayed catalyst, its preparation method, and its application. This delayed catalyst is prepared by an easy-to-operate method and can be used to delay the polymerization of polyurethane, extending the curing time and thus providing a longer surface drying time and operating time. When applied to polyurethane thermally conductive structural adhesive systems, it can improve the adhesive strength and other properties of the thermally conductive structural adhesive over a long open time.

[0006] In a first aspect, this application provides a delayed catalyst, said delayed catalyst comprising an imidazole ring carbene metal complex blocked by an organic acid and / or an organic base.

[0007] The imidazole ring carbene metal complex is represented by the following formula (2):

[0008]

[0009] R 1 R 2 R 3 and R 4 Each is independently selected from H, substituted or unsubstituted C. 1-18 Alkyl, substituted or unsubstituted C 3-8 Cycloalkyl, substituted or unsubstituted C 6-10 Any of the aryl groups, where M is Fe, Sn, Cu, Zn or Pd, X is a halogen, and n is an integer from 1 to 3;

[0010] The organic acid includes one or more of carboxylic acids, sulfinic acids, and thiocarboxylic acids.

[0011] The organic base includes one or more of 1,8-diazabicyclo[5.4.0]undec-7-ene, cyclohexylamine, 1-methylcyclohexylamine, and N,N-dimethylamine.

[0012] The imidazole ring carbene carbon atom (NHC) coordinates with a metal to form a stable NHC-M bond, thus forming an imidazole ring carbene metal complex with certain catalytic activity. This imidazole ring carbene metal complex possesses a strong σ-electron-donating ability, which stabilizes its structure, prevents internal atomic inversions that could lead to configurational changes, and improves catalytic selectivity.

[0013] Alternatively, the structural formula of the imidazole ring carbene metal complex is shown by the following formula (2-1), formula (2-2), or formula (2-3):

[0014]

[0015] In the imidazole ring carbene metal complex of this invention, R 1 R 2 R 3 and R 4 Each is independently selected from H, substituted or unsubstituted C. 1-18 Alkyl, substituted or unsubstituted C 3-8 Cycloalkyl, substituted or unsubstituted C 6-10 Any one of the aryl groups. Preferably, R 1 R 2 R 3 and R 4 It can be selected from methyl, ethyl, propyl, cyclohexyl, and phenyl.

[0016] MX n Representing metal halides, in some embodiments of this application, MX n It can be FeCl2, FeCl, SnCl, CuCl, ZnCl, or PdCl.

[0017] Blocking imidazole ring carbene metal complexes with organic acids and / or organic bases as blocking agents can resist the influence of external strong acids and / or strong bases on the catalytic system. This delays the initial curing reaction after the binder components are mixed, providing a longer pot life and effectively increasing the working time. After the pot life, the binder cures rapidly at a faster rate, shortening the time required for post-curing. Blocking of imidazole ring carbene metal complexes with organic acids and / or organic bases means that the imidazole ring carbene metal complex can coordinate with the organic acid and / or organic base to form a stable state. Preferably, the mass ratio of the imidazole ring carbene metal complex to the organic acid and / or organic base is 0.1-2:30-90.

[0018] In some embodiments of this application, the delayed catalyst comprises an imidazole ring carbene metal complex blocked by an organic acid. This organic acid-blocked catalyst is based on an SN2 reaction mechanism, where the imidazole ring carbene metal complex can coordinate with the organic acid. Simultaneously, O- ions from the organic acid attack XMn, causing partial charge migration within the imidazole ring carbene ring, breaking old C-C bonds, and forming new CO bonds. At the same time, electrons migrate within the carbene ring, forming a cyclic structure.

[0019] In some embodiments of this application, the delayed catalyst comprises an imidazole ring carbene metal complex blocked by an organic base. The imidazole ring carbene metal complex can coordinate with an organic base, which provides an amine cation R3HN. + The nitrogen atom forms a stable chemical bond with the carbene carbon atom, and the reaction is roughly predicted as follows.

[0020]

[0021] In a further embodiment, the delayed catalyst comprises an imidazole ring carbene metal complex co-blocked by an organic acid and an organic base. The imidazole ring carbene metal complex can coordinate with both the organic base and the organic acid, and the catalyst blocked by the organic base and organic acid has a synergistic effect during the post-curing process, thereby achieving rapid curing of the system.

[0022] The organic acid is selected from one or more of carboxylic acids, sulfinic acids, and thiocarboxylic acids. The carboxylic acid contains a carboxyl group (-COOH). In some embodiments of this application, the carboxylic acid is a monocarboxylic acid, which can be a saturated or unsaturated carboxylic acid, or an aryl carboxylic acid. Preferred carboxylic acids include one or more of formic acid, acetic acid, propionic acid, benzoic acid, and 3-pyrrolic carboxylic acid, but are not limited thereto. The sulfinic acid contains a sulfinic acid group (-SOOH). In some embodiments of this application, the sulfinic acid includes one or more of formamidinic acid, 4-acetamidobenzenesulfinic acid, benzenesulfinic acid, and p-toluenesulfinic acid, but is not limited thereto. The thiocarboxylic acid contains a thiocarboxylic acid group (-COSH). In some embodiments of this application, the thiocarboxylic acid includes one or more of thioformic acid, thioacetic acid, thiopropionic acid, thiobenzoic acid, and 3-pyrrolic thiocarboxylic acid, but is not limited thereto.

[0023] The organic base is an amine-containing compound, and the amine group includes primary, secondary, and tertiary amines. In some embodiments of this application, the organic base includes one or more of 1,8-diazabicyclo[5.4.0]undec-7-ene, cyclohexylamine, 1-methylcyclohexylamine, and N,N-dimethylamine. In further embodiments, the organic base may also include one or more of pyridine, imidazole, and pyrrole.

[0024] In some embodiments of this application, the delayed catalyst may be dispersed in a diluent. Preferably, the diluent may be a liquid flame retardant, and examples of diluents include dimethyl methylphosphonate, triethyl phosphate, diphenyl toluene phosphate, and isopropylated triphenyl phosphate. Preferably, the mass ratio of the delayed catalyst to the diluent is 5-20:80-95, more preferably 15:85.

[0025] Secondly, this application provides a method for preparing a delayed catalyst, the method comprising:

[0026] An organic acid and / or organic base are added to an imidazole ring carbene metal complex to obtain an imidazole ring carbene metal complex blocked by an organic acid and / or organic base, wherein the mass ratio of the imidazole ring carbene metal complex to the organic acid and / or organic base is 0.1-2:30-90.

[0027] The imidazole ring carbene metal complex is represented by the following formula (2):

[0028]

[0029] R 1 R 2 R 3 and R 4 Each is independently selected from H, substituted or unsubstituted C. 1-18 Alkyl, substituted or unsubstituted C 3-8 cycloalkyl, substituted or unsubstituted C 6-10 Any of the aryl groups, where M is Fe, Sn, Cu, Zn or Pd, X is a halogen, and n is an integer from 1 to 3;

[0030] The organic acid includes one or more of carboxylic acids, sulfinic acids, and thiocarboxylic acids;

[0031] The organic base includes one or more of 1,8-diazabicyclo[5.4.0]undec-7-ene, cyclohexylamine, 1-methylcyclohexylamine, and N,N-dimethylamine.

[0032] In some embodiments, imidazole ring carbene metal complexes are prepared by the following steps:

[0033] Step (1) involves reacting an imidazole ionic liquid with a metal-organic base to obtain an imidazole cyclic carbene intermediate represented by the following formula (1):

[0034]

[0035] R 1 R 2 R 3 and R 4 Each is independently selected from H, substituted or unsubstituted C. 1-18Alkyl, substituted or unsubstituted C 3-8 cycloalkyl, C 6-10 Any one of aryl group substitution or non-substitution;

[0036] Step (2) involves reacting the imidazole ring carbene intermediate with a metal halide to obtain an imidazole ring carbene metal complex represented by the following formula (2):

[0037]

[0038] M is Fe, Sn, Cu, Zn or Pd, X is a halogen, and n is an integer from 1 to 3.

[0039] In the imidazole ring carbene metal complex of this invention, R 1 R 2 R 3 and R 4 Each is independently selected from H, substituted or unsubstituted C. 1-18 Alkyl, substituted or unsubstituted C 3-8 Cycloalkyl, substituted or unsubstituted C 6-10 Any one of the aryl groups. Preferably, R 1 R 2 R 3 and R 4 It can be selected from methyl, ethyl, propyl, cyclohexyl, and phenyl.

[0040] In some embodiments of this application, the imidazole ionic liquid includes imidazole tetrafluoroborate, such as one or more of 1,3-dimethylimidazole tetrafluoroborate, 1-methyl-3-ethylimidazole tetrafluoroborate, and 1,3-dicyclohexylimidazole tetrafluoroborate.

[0041] In some embodiments of this application, the organometallic base includes one or more of lithium methoxide, lithium ethoxide, lithium isopropoxide, lithium n-butoxide, lithium tert-butoxide, sodium methoxide, sodium ethoxide, sodium isopropoxide, sodium n-butoxide, sodium tert-butoxide, potassium methoxide, potassium ethoxide, potassium isopropoxide, potassium n-butoxide, and potassium tert-butoxide.

[0042] In some embodiments of this application, in step (1), the imidazole ionic liquid and the organometallic base react in an organic solvent at 15-25°C in a molar ratio of 1:4 to 4:1. Preferably, the molar ratio of the imidazole ionic liquid to the organometallic base is 1:1 to 2:1, more preferably 1.5:1.

[0043] In some embodiments of this application, the metal halide includes one or more of FeCl3, FeCl2, SnCl2, CuCl2, ZnCl2, and PdCl2.

[0044] In some embodiments of this application, in step (2), the imidazole cyclic carbene intermediate reacts with the metal halide in an organic solvent at 25-85°C, wherein the molar ratio of the imidazole ionic liquid to the metal halide is 2:1 to 4:1. Preferably, the molar ratio of the imidazole ionic liquid to the organometallic base is 2.5:1 to 4:1, more preferably 3:1.

[0045] In some embodiments of this application, the organic solvents used in steps (1) and (2) may be those commonly used in the art to enable the reaction to proceed in a solvent, and examples of such organic solvents include, but are not limited to, tetrahydrofuran and methanol.

[0046] In some embodiments of this application, an organic acid can be slowly added dropwise to the imidazole ring carbene metal complex under a nitrogen atmosphere at room temperature. In other embodiments of this application, an organic base can be slowly added dropwise under a nitrogen atmosphere at room temperature.

[0047] In some embodiments of obtaining imidazole ring carbene metal complexes blocked by organic acids and organic bases, the order in which the organic acid and organic base are added is not limited; for example, the organic acid may be added before the organic base, or the organic base may be added before the organic acid.

[0048] Thirdly, this application provides a composition for forming a polyurethane thermally conductive structural adhesive, the composition comprising the following components: a delayed catalyst, a diluent, an isocyanate, a polyol, and a filler, wherein the delayed catalyst is the delayed catalyst provided in the first aspect of this application.

[0049] In some embodiments of this application, isocyanate and filler can be used as component A, and delayed catalyst, diluent, and polyol as component B. Preferably, the mass ratio of delayed catalyst to diluent is 5-20:80-95. In use, component A (containing isocyanate component) and component B (containing polyol component) are thoroughly mixed, and the mixture is applied to the substrate to be bonded. Components A and B are stored separately and mixed before use to prevent premature curing.

[0050] In some embodiments of this application, isocyanates include, but are not limited to, hexamethylene diisocyanate, cyclohexane diisocyanate, isophorone diisocyanate, dicyclohexylmethane diisocyanate, and tetramethylphenyldimethyl diisocyanate.

[0051] In some embodiments of this application, polyols include, but are not limited to, polyether polyols and polyester polyols.

[0052] The delayed catalyst of this application comprises an imidazole ring carbene metal complex blocked by an organic acid and / or an organic base. The isocyanate reacts with the organic acid and / or organic base as a blocking agent to undergo a sustained reaction, generating a catalytically active imidazole ring carbene metal complex, which further reacts with the isocyanate to obtain R”[O-CONH]nR.

[0053] In some embodiments of this application, the diluent may be a liquid flame retardant, and examples of diluents include dimethyl methylphosphonate, triethyl phosphate, diphenyl toluene phosphate, and isopropylated triphenyl phosphate.

[0054] In some embodiments of this application, the filler includes one or more of alumina, boron nitride, graphene, talc, calcium carbonate, silicon dioxide, and calcium sulfate. Preferred fillers include one or more of alumina, boron nitride, and graphene.

[0055] In some embodiments of this application, the composition further includes one or more additives, such as antioxidants, accelerators, plasticizers, pigments, colorants, and lubricants.

[0056] Fourthly, this application provides a battery encapsulated by a polyurethane thermally conductive structural adhesive formed from the composition described in the third aspect of this application.

[0057] The delayed catalyst provided in this application is prepared by an easy-to-operate method and can be used to delay the polymerization of polyurethane, extend the curing time, and thus provide a longer surface drying time and operating time. When applied to polyurethane thermally conductive structural adhesive systems, it can improve the thermal conductivity, elongation and bond strength of the thermally conductive structural adhesive. Detailed Implementation

[0058] The technical solutions of the embodiments of this application will be described in detail below through multiple examples and comparative examples.

[0059] Example 1

[0060] 1,3-Dimethylimidazolium tetrafluoroborate and potassium tert-butoxide were weighed into a round-bottom flask, and tetrahydrofuran was added and stirred continuously at room temperature for 8 h. After the reaction was complete, the unreacted reagent was removed by filtration under reduced pressure. SnCl2 was added to the solution, and the reaction was continued at 25 °C for 6 h. After removing the solvent, an imidazole ring carbene metal complex was obtained. Then, 1,8-diazabicyclo[5.4.0]undec-7-ene and formic acid were added, wherein the mass ratio of the imidazole ring carbene metal complex, 1,8-diazabicyclo[5.4.0]undec-7-ene, and formic acid was 1:54:55, to obtain an imidazole ring carbene metal complex blocked by 1,8-diazabicyclo[5.4.0]undec-7-ene and formic acid as a catalyst.

[0061] The obtained catalyst was thoroughly mixed with isopropyltriphenyl phosphate at a mass ratio of 15:85, and then mixed with polyol to obtain component B. Component B was added to component A, which includes isocyanate and filler, and cured at room temperature to form a polyurethane thermally conductive structural adhesive.

[0062] Example 2

[0063] 1,3-Dicyclohexylimidazolium tetrafluoroborate and potassium tert-butoxide were weighed into a round-bottom flask, and tetrahydrofuran was added. The mixture was stirred continuously at room temperature for 8 hours. After the reaction was complete, the unreacted reagents were removed by filtration under reduced pressure. FeCl3 was added to the solution, and the reaction was continued at 25°C for 6 hours. After removing the solvent, an imidazole ring carbene metal complex was obtained. Cyclohexylamine and acetic acid were then added, with the mass ratio of imidazole ring carbene metal complex, cyclohexylamine, and acetic acid being 1:54:55. This yielded an imidazole ring carbene metal complex blocked by cyclohexylamine and acetic acid, which served as a catalyst.

[0064] The obtained catalyst was thoroughly mixed with isopropyltriphenyl phosphate at a mass ratio of 15:85, and then mixed with polyol to obtain component B. Component B was added to component A, which includes isocyanate and filler, and cured at room temperature to form a polyurethane thermally conductive structural adhesive.

[0065] Example 3

[0066] 1,3-Dimethylimidazolium tetrafluoroborate and potassium tert-butoxide were weighed into a round-bottom flask, and tetrahydrofuran was added and stirred continuously at room temperature for 8 h. After the reaction was complete, the unreacted reagent was removed by filtration under reduced pressure. PbCl2 was added to the solution, and the reaction was continued at 25 °C for 6 h. After removing the solvent, an imidazole ring carbene metal complex was obtained. Then, 1,8-diazabicyclo[5.4.0]undec-7-ene and formic acid were added, wherein the mass ratio of the imidazole ring carbene metal complex, 1,8-diazabicyclo[5.4.0]undec-7-ene, and formic acid was 1:54:55, to obtain an imidazole ring carbene metal complex blocked by 1,8-diazabicyclo[5.4.0]undec-7-ene and formic acid as a catalyst.

[0067] The obtained catalyst was thoroughly mixed with isopropyltriphenyl phosphate at a mass ratio of 15:85, and then mixed with polyol to obtain component B. Component B was added to component A, which includes isocyanate and filler, and cured at room temperature to form a polyurethane thermally conductive structural adhesive.

[0068] Example 4

[0069] 1-Methyl-3-ethylimidazolium tetrafluoroborate and sodium methoxide were weighed into a round-bottom flask, and methanol was added. The mixture was stirred continuously at room temperature for 8 hours. After the reaction was complete, the unreacted reagent was removed by filtration under reduced pressure. ZnCl2 was added to the solution, and the reaction was continued at 25°C for 6 hours. After removing the solvent, an imidazole ring carbene metal complex was obtained. Then, N,N-dimethylamine and benzoic acid were added, with the mass ratio of imidazole ring carbene metal complex, N,N-dimethylamine, and benzoic acid being 1:54:55, to obtain an imidazole ring carbene metal complex blocked by N,N-dimethylamine and benzoic acid, which served as a catalyst.

[0070] The obtained catalyst was thoroughly mixed with isopropyltriphenyl phosphate at a mass ratio of 15:85, and then mixed with polyol to obtain component B. Component B was added to component A, which includes isocyanate and filler, and cured at room temperature to form a polyurethane thermally conductive structural adhesive.

[0071] Example 5

[0072] 1,3-Dimethylimidazolium tetrafluoroborate and potassium tert-butoxide were weighed into a round-bottom flask, and tetrahydrofuran was added and stirred continuously at room temperature for 8 h. After the reaction was complete, the unreacted reagent was removed by filtration under reduced pressure. SnCl2 was added to the solution, and the reaction was continued at 25 °C for 6 h. After removing the solvent, an imidazole ring carbene metal complex was obtained. Then, 1,8-diazabicyclo[5.4.0]undec-7-ene was added, wherein the mass ratio of the imidazole ring carbene metal complex to 1,8-diazabicyclo[5.4.0]undec-7-ene was 1:54, to obtain an imidazole ring carbene metal complex blocked by 1,8-diazabicyclo[5.4.0]undec-7-ene as a catalyst.

[0073] The obtained catalyst was thoroughly mixed with isopropyltriphenyl phosphate at a mass ratio of 15:85, and then mixed with polyol to obtain component B. Component B was added to component A, which includes isocyanate and filler, and cured at room temperature to form a polyurethane thermally conductive structural adhesive.

[0074] Example 6

[0075] 1,3-Dimethylimidazolium tetrafluoroborate and potassium tert-butoxide were weighed into a round-bottom flask, and tetrahydrofuran was added. The mixture was stirred continuously at room temperature for 8 hours. After the reaction was complete, the unreacted reagent was removed by filtration under reduced pressure. SnCl2 was added to the solution, and the reaction was continued at 25°C for 6 hours. After removing the solvent, an imidazole ring carbene metal complex was obtained. Formic acid was then added, with the mass ratio of the imidazole ring carbene metal complex to formic acid being 1:55, to obtain an imidazole ring carbene metal complex blocked by formic acid, which served as a catalyst.

[0076] The obtained catalyst was thoroughly mixed with isopropyltriphenyl phosphate at a mass ratio of 15:85, and then mixed with polyol to obtain component B. Component B was added to component A, which includes isocyanate and filler, and cured at room temperature to form a polyurethane thermally conductive structural adhesive.

[0077] Comparative Example 1

[0078] Using dibutyltin dilaurate as a catalyst, it is thoroughly mixed with isopropyltriphenyl phosphate at a mass ratio of 15:85, and then mixed with polyol to obtain component B. Component B is added to component A, which includes isocyanate and filler, and cured at room temperature to form a polyurethane thermally conductive structural adhesive.

[0079] Comparative Example 2

[0080] The delayed catalyst was prepared according to the steps described in Example 1 and used to form a polyurethane thermally conductive structural adhesive, except that the imidazole ring carbene metal complex was not blocked by organic acids and organic bases, but the obtained imidazole ring carbene metal complex was directly used as the catalyst.

[0081] Test case

[0082] The technical solution provided in this application is evaluated based on the surface drying time of the thermally conductive structural adhesive and the shear strength, tensile strength, and elongation at break under operating times of 0 min and 50 min.

[0083] The dryness of the structural adhesive sample surface was measured by touch; the time required until no sample adhered to the finger was defined as the surface drying time. The shear strength, tensile strength, and elongation at break of the structural adhesive sample were tested using a universal tensile testing machine at room temperature. The specific test procedures are as follows:

[0084] 0min-24h shear strength: The thermally conductive structural adhesive is applied to the surface of the aluminum sheet, and another aluminum sheet is immediately overlapped to form a sandwich shear strip of aluminum material-thermally conductive structural adhesive-aluminum material. After being placed at room temperature for 24 hours, the shear strength of the thermally conductive structural adhesive is measured using a universal tensile testing machine at a rate of 500mm / min.

[0085] 50min-24h shear strength: The thermally conductive structural adhesive is applied to the surface of the aluminum sheet. After 50 minutes, another aluminum sheet is overlapped to form a sandwich shear strip of aluminum material-thermally conductive structural adhesive-aluminum material. After being placed at room temperature for 24 hours, the shear strength of the thermally conductive structural adhesive is measured using a universal tensile testing machine at a rate of 500mm / min.

[0086] 0min-Completely cured shear strength: The thermally conductive structural adhesive is applied to the surface of the aluminum sheet, and another aluminum sheet is immediately overlapped to form a sandwich shear strip of aluminum material-thermally conductive structural adhesive-aluminum material. After being placed at room temperature for 24 hours, it is baked in an oven at 80℃ for 6 hours to ensure complete reaction. Then, the shear strength of the thermally conductive structural adhesive is measured using a universal tensile testing machine at a rate of 500mm / min.

[0087] 50min-Completely cured shear strength: The thermally conductive structural adhesive is applied to the surface of the aluminum sheet. After 50min, another aluminum sheet is overlapped to form a sandwich shear strip of aluminum material-thermally conductive structural adhesive-aluminum material. After being placed at room temperature for 24h, it is baked in an 80℃ oven for 6h to ensure complete reaction. Then, the shear strength of the thermally conductive structural adhesive is measured using a universal tensile testing machine at a rate of 500mm / min.

[0088] 24h tensile strength and elongation at break: The thermally conductive structural adhesive was pressed into a sheet of uniform thickness and left to stand at room temperature for 24 hours. Then, it was cut into dumbbell-shaped pieces for testing using a dumbbell-shaped cutter. The tensile strength and elongation at break of the thermally conductive structural adhesive were measured using a universal tensile testing machine at a speed of 100 mm / min.

[0089] The test results for each embodiment are recorded in Table 1.

[0090] Table 1 Test results of the examples and comparative examples

[0091]

[0092] Comparing the above test results, it can be seen that for the 0-min-24h and 50-min-24h shear strength of the thermally conductive structural adhesive, compared with Comparative Examples 1 and 2, Examples 1-6 enhanced the post-curing rate, with the 24h shear strength increasing by approximately 4 times. For the 50-min fully cured shear strength of the thermally conductive structural adhesive, compared with Comparative Examples 1 and 2, Examples 1-6 effectively increased the operating time under the action of the delayed catalyst, and the 50-min fully cured shear strength was quite close to the 0-min fully cured shear strength.

[0093] Furthermore, the longer the elongation at break in the thermally conductive structural adhesive system, the less complete the curing. The changes in tensile strength and elongation at break of the thermally conductive structural adhesive of the present invention over 24 hours further demonstrate that the delayed catalyst enhances the post-curing rate.

[0094] The above description is an exemplary embodiment of this application. It should be noted that, for those skilled in the art, several improvements and modifications can be made without departing from the principle of this invention, and these improvements and modifications are also considered to be within the scope of protection of this application.

Claims

1. A delayed catalyst, characterized in that, The delayed catalyst comprises an imidazole ring carbene metal complex blocked by an organic acid and / or an organic base. The imidazole ring carbene metal complex is represented by the following formula (2): R 1 R 2 R 3 and R 4 Each is independently selected from H, substituted or unsubstituted C. 1-18 Alkyl, substituted or unsubstituted C 3-8 cycloalkyl, substituted or unsubstituted C 6-10 Any of the aryl groups, where M is Fe, Sn, Cu, Zn or Pd, X is a halogen, and n is an integer from 1 to 3; The organic acid includes one or more of carboxylic acids, sulfinic acids, and thiocarboxylic acids; The organic base includes one or more of 1,8-diazabicyclo[5.4.0]undec-7-ene, cyclohexylamine, 1-methylcyclohexylamine, and N,N-dimethylamine.

2. A method for preparing a delayed catalyst, characterized in that, The method includes: An organic acid and / or organic base are added to an imidazole ring carbene metal complex to obtain an imidazole ring carbene metal complex blocked by an organic acid and / or organic base, wherein the mass ratio of the imidazole ring carbene metal complex to the organic acid and / or organic base is 0.1-2:30-90. The imidazole ring carbene metal complex is represented by the following formula (2): R 1 R 2 R 3 and R 4 Each is independently selected from H, substituted or unsubstituted C. 1-18 Alkyl, substituted or unsubstituted C 3-8 cycloalkyl, substituted or unsubstituted C 6-10 Any of the aryl groups, where M is Fe, Sn, Cu, Zn or Pd, X is a halogen, and n is an integer from 1 to 3; The organic acid includes one or more of carboxylic acids, sulfinic acids, and thiocarboxylic acids; The organic base includes one or more of 1,8-diazabicyclo[5.4.0]undec-7-ene, cyclohexylamine, 1-methylcyclohexylamine, and N,N-dimethylamine.

3. The preparation method according to claim 2, characterized in that, MXn can be FeCl2, FeCl, SnCl, CuCl, ZnCl, or PdCl.

4. The preparation method according to claim 2, characterized in that, The imidazole ring carbene metal complex was prepared by the following steps: Step (1): The imidazole ionic liquid is reacted with a metal-organic base to obtain an imidazole ring carbene intermediate represented by the following formula (1): R 1 R 2 R 3 and R 4 Each is independently selected from H, substituted or unsubstituted C. 1-18 Alkyl, substituted or unsubstituted C 3-8 cycloalkyl, C 6-10 Any one of aryl group substitution or non-substitution; Step (2): The imidazole ring carbene intermediate is reacted with a metal halide to obtain an imidazole ring carbene metal complex represented by the following formula (2): M is Fe, Sn, Cu, Zn or Pd, X is a halogen, and n is an integer from 1 to 3.

5. The preparation method according to claim 4, characterized in that, The imidazole ionic liquid includes one or more of 1,3-dimethylimidazolium tetrafluoroborate, 1-methyl-3-ethylimidazolium tetrafluoroborate, and 1,3-dicyclohexylimidazolium tetrafluoroborate.

6. The preparation method according to claim 4, characterized in that, The organometallic base includes one or more of lithium methoxide, lithium ethanol, lithium isopropoxide, lithium n-butoxide, lithium tert-butoxide, sodium methoxide, sodium ethanol, sodium isopropoxide, sodium n-butoxide, sodium tert-butoxide, potassium methoxide, potassium ethanol, potassium isopropoxide, potassium n-butoxide, and potassium tert-butoxide.

7. The preparation method according to claim 4, characterized in that, In step (1), the imidazole ionic liquid and the organometallic base react in an organic solvent at 15-25°C with a molar ratio of 1:4 to 4:

1.

8. The preparation method according to claim 4, characterized in that, The metal halide includes one or more of FeCl3, FeCl2, SnCl2, CuCl2, ZnCl2, and PdCl2.

9. The preparation method according to claim 4, characterized in that, In step (2), the imidazole cyclic carbene intermediate and the metal halide are reacted in an organic solvent at 25-85°C, wherein the molar ratio of the imidazole cyclic carbene intermediate to the metal halide is 2:1 to 4:

1.

10. The preparation method according to claim 7 or 9, characterized in that, The organic solvents include tetrahydrofuran and methanol.

11. A composition for forming a polyurethane thermally conductive structural adhesive, characterized in that, The composition comprises the following components: the delayed catalyst as described in claim 1, a diluent, an isocyanate, a polyol, and a filler.

12. The composition according to claim 11, characterized in that, The diluent includes one or more of dimethyl methylphosphonate, triethyl phosphate, toluene diphenyl phosphate, and isopropylated triphenyl phosphate.

13. The composition of claim 11, characterized in that, The filler includes one or more of alumina, boron nitride, graphene, talc, calcium carbonate, silicon dioxide, and calcium sulfate.

14. A battery, said battery being encapsulated by a polyurethane thermally conductive structural adhesive formed from the composition of claim 11.

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