Preparation method of low-precipitation mercaptan curing agent with micro-nano labyrinth structure

Abstract

The invention relates to the technical field of high polymer materials and adhesive curing agents, in particular to a preparation method of a low-precipitation mercaptan curing agent with a micro-nano labyrinth structure, which comprises the following steps: weighing raw materials in parts by weight; putting the epoxy prepolymer carrier containing the flexible chain segment and the excessive chain extension modified polyfunctional thiol compound into a reaction kettle, and heating, stirring and uniformly mixing the epoxy prepolymer carrier and the chain extension modified polyfunctional thiol compound; adding the surface oleophylic modified inorganic nano filler and a reaction accelerator into a reaction kettle to construct a micro-nano labyrinth structure prepolymer; cooling, adding an antioxidant stabilizer, continuously stirring, carrying out vacuum defoaming treatment on a reaction product, and filtering and discharging to obtain a modified thiol curing agent; according to the invention, thiol groups are grafted on the surfaces of the polymer skeleton and the modified nano filler through a chemical bonding technology to complete molecular structure design and multi-layer coating construction, so that the effect of inhibiting migration and precipitation of small molecules is achieved, and the low precipitation property of the epoxy adhesive in a high-temperature and high-humidity environment is improved while the rapid curing characteristic is maintained.

Description

Technical Field

[0001] This invention relates to the field of polymer materials and adhesive curing agents, specifically to a method for preparing a low-precipitation thiol curing agent with a micro-nano labyrinth structure. Background Technology

[0002] Thiol curing agents are widely used in the rapid bonding and encapsulation of electronic components due to their extremely fast curing speed at room temperature and even low temperatures. However, traditional small-molecule thiols or thioethers have fatal flaws such as high volatility, crystallization, and migration precipitation. This is especially problematic in the field of microelectronic packaging, where high temperature and humidity (e.g., 85°C) are critical. o In an environment of C / 85%RH, uncrosslinked free small molecule thiols will migrate and precipitate to the colloidal surface, not only contaminating the surface of electronic components, but also causing corrosion of metal pins, resulting in a sharp drop in surface insulation resistance (SIR) and seriously affecting electrical reliability.

[0003] In existing technologies, precipitation is typically suppressed by increasing the molecular weight of thiols or by adding inorganic fillers through physical blending. However, simple macromolecularization often leads to a sharp increase in viscosity and a significant decrease in curing activity; while simple physical blending cannot fundamentally lock in small molecules, the free volume at the filler interface may actually become a channel for small molecules to escape. Currently, the industry lacks a curing agent structure design that can achieve zero precipitation through the synergistic effect of chemical anchoring and physical barrier while maintaining rapid curing characteristics.

[0004] Based on this, the present invention provides a method for preparing a low-precipitation thiol curing agent with a micro-nano labyrinth structure. This curing agent, obtained through molecular structure design or molecular weight modification of traditional thiols, is a liquid at room temperature with excellent compatibility. Its core function is to solve the problems of volatility, crystallization, and migration of traditional small-molecule thiols. Organic modification achieves chemical bonding to eliminate small molecules, while inorganic modification constructs physical barriers to inhibit migration, achieving zero precipitation during storage and curing while retaining its rapid curing characteristics, thereby improving the storage stability and reliability of the adhesive.

[0005] In existing technologies, the easy migration and precipitation of small-molecule thiols or thioethers leads to surface contamination and decreased electrical reliability of electronic components under high temperature and humidity environments. Furthermore, traditional thiol curing agents lack effective chemical bonding and molecular weight control methods, making it difficult to suppress small molecule migration while maintaining rapid curing characteristics. They also exhibit poor compatibility with epoxy resin matrices, resulting in insufficient density and poor impermeability of the cured product, failing to meet the requirements for low precipitation and long-term stability in high-reliability fields such as microelectronic packaging. Therefore, this invention provides a method for preparing a low-precipitation thiol curing agent with a micro / nano labyrinth structure. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a method for preparing a low-precipitation thiol curing agent with a micro-nano labyrinth structure. This invention achieves partial end-capping prepolymerization of the epoxy resin with an excess of multifunctional thiols, while retaining a high amount of active thiol equivalent. This constructs a synergistic barrier system of chemical bonding and a multidimensional physical labyrinth, significantly improving the epoxy resin's anti-precipitation properties and electrical reliability under high temperature and high humidity environments.

[0007] To achieve the above objectives, the present invention provides the following technical solution: The objective is to provide a method for preparing a low-precipitation thiol curing agent with a micro-nano labyrinth structure. The curing agent prepared by the present invention has a low content of migratable thiols, a short gel time, and high shear strength.

[0008] To achieve the above objectives, the present invention provides the following technical solution:

[0009] A method for preparing a low-precipitation thiol curing agent with a micro / nano labyrinth structure includes the following steps:

[0010] S1. Preparation of epoxy prepolymer carriers containing flexible segments, chain-extended modified multifunctional thiols, and surface-lipophilic modified inorganic nanofillers.

[0011] S2. Under an inert atmosphere, the epoxy prepolymer carrier containing flexible segments and an excess of the chain-extended modified multifunctional thiol compound are added to a reaction vessel and heated and stirred until homogeneous.

[0012] S3. Add the surface-oil-modified inorganic nanofiller and reaction promoter to the reactor, raise the temperature and stir continuously to carry out a partial end-capping prepolymerization reaction, so that some thiol groups are chemically bonded to the surface of the epoxy prepolymerization carrier and nanofiller, and construct a micro-nano labyrinth structure prepolymer with the prepolymerization carrier and nanofiller as the core and the surface enriched with unreacted active thiol groups.

[0013] S4. After the reaction is complete, cool down and add antioxidant stabilizer. Continue stirring and then perform vacuum degassing on the reaction product. Filter the product to obtain the modified thiol curing agent.

[0014] The specific descriptions of S1, S2, S3, and S4 above are as follows:

[0015] Further, in step S1, the epoxy prepolymer carrier containing flexible segments is prepared by epoxy resin through ring-opening etherification with polyethylene glycol-400, followed by intercalation and composite with organically modified nano-montmorillonite.

[0016] The chain-extended modified multifunctional thiols were prepared by a stepwise reaction of pentaerythritol tetra-3-mercaptopropionate via Michael addition and transesterification with trimethylolpropane triacrylate.

[0017] The surface-adhesive modified inorganic nanofiller is prepared by a three-step step-by-step modification of zero-dimensional nano-silica through activation with aluminum sulfate octadecylhydrate, stearate esterification, and electrostatic adsorption with hexadecyltrimethylammonium bromide (CTAB).

[0018] Further, the weight ratio of each component in steps S1 to S4 is as follows: 30-50 parts of epoxy prepolymer carrier containing flexible segments, 20-40 parts of chain-extended modified multifunctional thiol compound, 10-25 parts of surface oleophilic modified inorganic nanofiller, 5-15 parts of reaction promoter, and 2-8 parts of antioxidant stabilizer.

[0019] Further, the preparation method of the epoxy prepolymer carrier containing flexible segments is as follows: epoxy resin dissolved in toluene is added to a reaction vessel, followed by polyethylene glycol-400 and triphenylphosphine. Nitrogen gas is introduced to replace the air in the vessel for ring-opening etherification reaction. Organically modified nano-montmorillonite is added to anhydrous ethanol and ultrasonically dispersed to obtain a montmorillonite suspension. The ring-opening etherification reaction product is added dropwise to the montmorillonite suspension for intercalation and composite reaction. After the reaction, vacuum distillation, drying, pulverization and sieving are performed sequentially to obtain the epoxy prepolymer carrier containing flexible segments. Flexible segments are introduced into the epoxy resin skeleton through ring-opening etherification with polyethylene glycol-400 to improve toughness. Then, organic montmorillonite intercalation and composite are performed to form a nano-barrier structure, which enhances the compatibility between the skeleton and thiol and inhibits the migration of small molecules, providing a polymer carrier with both high reactivity and low precipitation characteristics for the final curing agent.

[0020] Further, the epoxy resin comprises 100 parts by weight, toluene comprises 50-80 parts by weight, polyethylene glycol-400 comprises 20-40 parts by weight, and triphenylphosphine comprises 1-3 parts by weight; the organic modified nano-montmorillonite comprises 5-15 parts by weight, and anhydrous ethanol comprises 30-50 parts by weight.

[0021] Further, the preparation method of the chain-extended modified polyfunctional thiol compound is as follows: pentaerythritol tetra-3-mercaptopropionate dissolved in ethyl acetate is added to the reaction vessel, nitrogen gas is introduced to replace the air in the reaction vessel, and then trimethylolpropane triacrylate and dibutyltin dilaurate are mixed evenly and added dropwise to the reaction system to carry out Michael addition reaction; hydroquinone and dibutyltin dilaurate are added to the product, stirred and dissolved, and then trimethylolpropane triacrylate ethyl acetate solution is added to carry out transesterification reaction; after the reaction is completed, the product is washed, dried, distilled under reduced pressure and dried in sequence to obtain the chain-extended modified polyfunctional thiol compound.

[0022] Further, the pentaerythritol tetra-3-mercaptopropionate comprises 100 parts by weight, the ethyl acetate comprises 80-120 parts by weight, and in the Michael addition reaction, the trimethylolpropane triacrylate comprises 30-50 parts by weight and the dibutyltin dilaurate comprises 0.5-1.5 parts by weight; the hydroquinone comprises 0.3-0.8 parts by weight, and in the transesterification reaction, the dibutyltin dilaurate comprises 10-20 parts by weight and the ethyl acetate solution of trimethylolpropane triacrylate comprises 20-40 parts by weight.

[0023] Further, the preparation method of the surface-oil-modified inorganic nanofiller is as follows: zero-dimensional nano-silica is dispersed in anhydrous ethanol, aluminum sulfate octadecylhydrate aqueous solution is added, the pH is adjusted to 8.0-9.0 and then an activation reaction is carried out. After the reaction is completed, centrifugation and washing are performed to obtain activated nano-silica filter cake; the filter cake is redispersed in anhydrous ethanol, stearic acid ethanol solution is added to carry out an esterification reaction, centrifugation and washing are performed after the reaction is completed; the product is redispersed in deionized water, hexadecyltrimethylammonium bromide aqueous solution is added to carry out a modification reaction, centrifugation, washing, drying and sieving are performed after the reaction is completed to obtain surface-oil-modified inorganic nanofiller.

[0024] Furthermore, during the activation reaction, 100 parts of zero-dimensional nano-silica are dispersed in 300-500 parts of anhydrous ethanol; during the esterification reaction, the filter cake is dispersed in 200-400 parts of anhydrous ethanol; and during the modification reaction, the product is dispersed in 250-450 parts of deionized water.

[0025] Further, the aluminum sulfate octadechydrate aqueous solution consists of 5-15 parts aluminum sulfate octadechydrate dissolved in 50-100 parts deionized water; the stearic acid ethanol solution consists of 10-20 parts stearic acid dissolved in 50-100 parts anhydrous ethanol; and the hexadecyltrimethylammonium bromide aqueous solution consists of 3-8 parts hexadecyltrimethylammonium bromide dissolved in 30-60 parts deionized water.

[0026] Furthermore, the reaction promoter is DMP-30, and the antioxidant is a mixture of 2,6-di-tert-butyl-4-methylphenol and triphenyl phosphite in a mass ratio of 2-3:1.

[0027] Compared with the prior art, the beneficial effects of the present invention are:

[0028] 1. Resolving the contradiction between curing activity and low precipitation: This invention abandons the traditional full grafting approach and creatively employs a partially end-capped prepolymerization reaction. By controlling the thiol compound to be in an excess state, a small number of epoxy groups on the support backbone consume a very small portion of the thiol groups for chemical anchoring, resulting in a core-shell / star structure in the final product. This structure achieves a significant increase in molecular weight (effectively suppressing volatilization and migration) while retaining a large number of highly active free thiol groups (-SH) on the molecular periphery, perfectly balancing low precipitation and rapid curing characteristics.

[0029] 2. A multidimensional micro-nano maze synergistic barrier effect was constructed: This invention introduces a two-dimensional (2D) layered organic montmorillonite structure into an epoxy prepolymer carrier containing flexible segments, and simultaneously introduces zero-dimensional (0D) nano-silica modified with a three-step oleophilic method. During the partial end-capping prepolymerization process, the zero-dimensional silica and two-dimensional montmorillonite sheets intertwine in the system, constructing a multidimensional micro-nano maze structure. This physical maze greatly reduces the free volume within the system, significantly extending the escape path of unreacted small molecule thiols; combined with the anchoring effect of chemical bonding, an unexpected synergistic anti-precipitation effect is produced, completely solving the industry problem of thiols migration causing short circuits or corrosion of electronic components under high temperature and high humidity. Detailed Implementation

[0030] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0031] It should be noted that the raw materials used in the following embodiments are all commercially available.

[0032] Example 1: A method for preparing a low-precipitation thiol curing agent with a micro / nano labyrinth structure, comprising the following steps:

[0033] S1. Preparation of epoxy prepolymer carriers containing flexible segments, chain-extended modified multifunctional thiols, and surface-lipophilic modified inorganic nanofillers.

[0034] S2. Under an inert atmosphere, the epoxy prepolymer carrier containing flexible segments and an excess of chain-extended modified multifunctional thiols are added to the reactor and heated and stirred until homogeneous.

[0035] S3. Add surface-lipophilic modified inorganic nanofillers and reaction promoters to the reactor, raise the temperature and stir continuously to carry out partial end-capping prepolymerization reaction, so that some thiol groups are chemically bonded to the surface of epoxy prepolymer carrier and nanofiller, and construct a micro-nano labyrinth structure prepolymer with the prepolymer carrier and nanofiller as the core and the surface enriched with unreacted active thiol groups.

[0036] S4. After the reaction is complete, cool down and add antioxidant stabilizer. Continue stirring and then perform vacuum degassing on the reaction product. Filter the product to obtain the modified thiol curing agent.

[0037] In step S1, the epoxy prepolymer carrier containing flexible segments is prepared by epoxy resin through ring-opening etherification with polyethylene glycol-400, followed by intercalation and composite with organically modified nano-montmorillonite.

[0038] The chain-extended modified multifunctional thiols were prepared by a stepwise reaction of pentaerythritol tetra-3-mercaptopropionate via Michael addition and transesterification with trimethylolpropane triacrylate.

[0039] The surface-modified oleophilic inorganic nanofiller was prepared by a three-step process of zero-dimensional nano-silica activation with aluminum sulfate octadecylhydrate, stearate esterification, and electrostatic adsorption with hexadecyltrimethylammonium bromide (CTAB).

[0040] The weight ratio of each component in steps S1 to S4 is as follows: 30 parts of epoxy prepolymer carrier containing flexible segments, 20 parts of chain-extended modified multifunctional thiol compound, 10 parts of surface oleophilic modified inorganic nanofiller, 5 parts of reaction promoter, and 2 parts of antioxidant stabilizer.

[0041] The preparation method of epoxy prepolymer carrier containing flexible segments is as follows: epoxy resin dissolved in toluene is added to a reaction vessel, followed by polyethylene glycol-400 and triphenylphosphine. Nitrogen gas is introduced to replace the air in the vessel, stirring is started, and the mixture is heated to 80°C for 3 hours to carry out a ring-opening etherification reaction to generate an epoxy prepolymer containing flexible segments. Organically modified nano-montmorillonite is added to anhydrous ethanol and ultrasonically dispersed to obtain a montmorillonite suspension. The ring-opening etherification reaction product is cooled to 60°C and added dropwise to the montmorillonite suspension under stirring. After the addition is complete, the temperature is raised to 70°C, and stirring is continued for 2 hours to carry out an intercalation composite reaction. After the reaction is completed, the solvent and unreacted small molecules are removed by vacuum distillation to obtain a viscous product. The product is placed in a vacuum drying oven and vacuum dried at 60°C for 6 hours to remove residual solvent. The product is then pulverized and sieved to obtain an epoxy prepolymer carrier containing flexible segments.

[0042] The epoxy resin comprises 100 parts by weight, toluene comprises 50 parts by weight, polyethylene glycol-400 comprises 20 parts by weight, triphenylphosphine comprises 1 part by weight, organic modified nano-montmorillonite comprises 5 parts by weight, and anhydrous ethanol comprises 30 parts by weight.

[0043] The preparation method of chain-extended modified multifunctional thiols is as follows: Pentaerythritol tetra-3-mercaptopropionate dissolved in ethyl acetate is added to a reaction vessel. Nitrogen gas is introduced to replace the air in the reaction vessel. Stirring is started, and the mixture is heated to 40°C. Then, trimethylolpropane triacrylate and dibutyltin dilaurate are mixed evenly and added dropwise to the reaction system. After the addition is complete, the temperature is raised to 55°C, and the reaction is maintained for 2 hours to allow the mercapto group and the acrylate double bond to undergo a Michael addition reaction, generating a thiols prepolymer containing multiple reactive sites. The product is cooled to 40°C, and hydroquinone is added as a polymerization inhibitor to prevent free radical side reactions in subsequent reactions. Then, dibutyltin dilaurate is added as a transesterification catalyst. After stirring and dissolving, trimethylolpropionate is added... An ethyl acetate solution of trimethylolpropane triacrylate was heated to 70°C and reacted for 3 hours to allow the residual mercapto groups in the prepolymer to further react with trimethylolpropane triacrylate, while a partial transesterification reaction occurred, forming a modified polyfunctional thiol compound with a moderately branched structure. After the reaction was completed, the reaction solution was cooled to below 30°C, and 50 parts of deionized water were added to wash twice to remove the catalyst and unreacted small molecules. The organic phase was collected, dried overnight with anhydrous sodium sulfate, filtered to remove the desiccant, and the filtrate was placed in a rotary evaporator and distilled under reduced pressure at 40°C to remove the solvent, yielding a pale yellow viscous product. The product was placed in a vacuum drying oven and dried under vacuum at 40°C for 4 hours to obtain the chain-extended modified polyfunctional thiol compound.

[0044] The pentaerythritol tetra-3-mercaptopropionate comprises 100 parts by weight, ethyl acetate comprises 80 parts by weight, trimethylolpropane triacrylate comprises 30 parts by weight and dibutyltin dilaurate comprises 0.5 parts by weight in the Michael addition reaction, hydroquinone comprises 0.3 parts by weight, and dibutyltin dilaurate comprises 10 parts by weight and ethyl acetate solution of trimethylolpropane triacrylate comprises 20 parts by weight in the transesterification reaction.

[0045] The preparation method of surface-lipophilic modified inorganic nanofiller is as follows: Zero-dimensional nano-silica is dispersed in anhydrous ethanol and ultrasonically treated for 30 min. Aqueous solution of aluminum sulfate octadecylhydrate is added, and the pH is adjusted to 8.0 with sodium hydroxide solution. The temperature is raised to 70℃ and stirred for 2 h for activation reaction. After the reaction is completed, centrifugation and washing are performed to obtain activated nano-silica filter cake. The filter cake is redispersed in anhydrous ethanol, and stearic acid ethanol solution is added. The temperature is raised to 75℃ for esterification reaction for 3 h. After the reaction is completed, centrifugation and washing with ethanol are performed to remove unreacted stearic acid. The product is redispersed in deionized water, and hexadecyltrimethylammonium bromide aqueous solution is added. The modification reaction is performed at 40℃ for 1.5 h. After the reaction is completed, centrifugation, washing, drying and sieving are performed to obtain surface-lipophilic modified inorganic nanofiller.

[0046] During the activation reaction, 100 parts of zero-dimensional nano-silica were dispersed in 300 parts of anhydrous ethanol; during the esterification reaction, the filter cake was dispersed in 200 parts of anhydrous ethanol; and during the modification reaction, the product was dispersed in 250 parts of deionized water.

[0047] The aqueous solution of aluminum sulfate octadechydrate consists of 5 parts aluminum sulfate octadechydrate dissolved in 50 parts deionized water; the ethanol solution of stearic acid consists of 10 parts stearic acid dissolved in 50 parts anhydrous ethanol; and the aqueous solution of hexadecyltrimethylammonium bromide consists of 3 parts hexadecyltrimethylammonium bromide dissolved in 30 parts deionized water.

[0048] The reaction promoter is DMP-30, and the antioxidant is a mixture of 2,6-di-tert-butyl-4-methylphenol and triphenyl phosphite in a mass ratio of 2:1.

[0049] Example 2: Based on Example 1, a method for preparing a low-precipitation thiol curing agent with a micro / nano labyrinth structure, comprising the following steps:

[0050] S1. Preparation of epoxy prepolymer carriers containing flexible segments, chain-extended modified multifunctional thiols, and surface-lipophilic modified inorganic nanofillers.

[0051] S2. Under an inert atmosphere, the epoxy prepolymer carrier containing flexible segments and an excess of chain-extended modified multifunctional thiols are added to the reactor and heated and stirred until homogeneous.

[0052] S3. Add surface-lipophilic modified inorganic nanofillers and reaction promoters to the reactor, raise the temperature and stir continuously to carry out partial end-capping prepolymerization reaction, so that some thiol groups are chemically bonded to the surface of epoxy prepolymer carrier and nanofiller, and construct a micro-nano labyrinth structure prepolymer with the prepolymer carrier and nanofiller as the core and the surface enriched with unreacted active thiol groups.

[0053] S4. After the reaction is complete, cool down and add antioxidant stabilizer. Continue stirring and then perform vacuum degassing on the reaction product. Filter the product to obtain the modified thiol curing agent.

[0054] In step S1, the epoxy prepolymer carrier containing flexible segments is prepared by epoxy resin through ring-opening etherification with polyethylene glycol-400, followed by intercalation and composite with organically modified nano-montmorillonite.

[0055] The chain-extended modified multifunctional thiols were prepared by a stepwise reaction of pentaerythritol tetra-3-mercaptopropionate via Michael addition and transesterification with trimethylolpropane triacrylate.

[0056] The surface-modified oleophilic inorganic nanofiller was prepared by a three-step process of zero-dimensional nano-silica activation with aluminum sulfate octadecylhydrate, stearate esterification, and electrostatic adsorption with hexadecyltrimethylammonium bromide (CTAB).

[0057] The weight ratio of each component in steps S1 to S4 is as follows: 40 parts of epoxy prepolymer carrier containing flexible segments, 30 parts of chain-extended modified multifunctional thiol compound, 17.5 parts of surface oleophilic modified inorganic nanofiller, 10 parts of reaction promoter, and 5 parts of antioxidant stabilizer.

[0058] The preparation method of epoxy prepolymer carrier containing flexible segments is as follows: epoxy resin dissolved in toluene is added to a reaction vessel, followed by polyethylene glycol-400 and triphenylphosphine. Nitrogen gas is introduced to replace the air in the vessel, stirring is started, and the mixture is heated to 90°C for 4 hours to carry out a ring-opening etherification reaction to generate an epoxy prepolymer containing flexible segments. Organically modified nano-montmorillonite is added to anhydrous ethanol and ultrasonically dispersed to obtain a montmorillonite suspension. The ring-opening etherification reaction product is cooled to 65°C and added dropwise to the montmorillonite suspension under stirring. After the addition is complete, the temperature is raised to 75°C, and stirring is continued for 2.5 hours for intercalation and composite reaction. After the reaction is completed, the solvent and unreacted small molecules are removed by vacuum distillation to obtain a viscous product. The product is placed in a vacuum drying oven and vacuum dried at 70°C for 9 hours to remove residual solvent. The product is then pulverized and sieved to obtain an epoxy prepolymer carrier containing flexible segments.

[0059] The epoxy resin comprises 100 parts by weight, toluene comprises 65 parts by weight, polyethylene glycol-400 comprises 30 parts by weight, triphenylphosphine comprises 2 parts by weight, organic modified nano-montmorillonite comprises 10 parts by weight, and anhydrous ethanol comprises 40 parts by weight.

[0060] The preparation method of chain-extended modified multifunctional thiols is as follows: Pentaerythritol tetra-3-mercaptopropionate dissolved in ethyl acetate is added to a reaction vessel. Nitrogen gas is introduced to replace the air in the reaction vessel. Stirring is started, and the mixture is heated to 45°C. Then, trimethylolpropane triacrylate and dibutyltin dilaurate are mixed evenly and added dropwise to the reaction system. After the addition is complete, the temperature is raised to 60°C, and the reaction is maintained for 3 hours to allow the mercapto groups to undergo a Michael addition reaction with the acrylate double bonds, generating a thiols prepolymer containing multiple reactive sites. The product is cooled to 45°C, and hydroquinone is added as a polymerization inhibitor to prevent free radical side reactions in subsequent reactions. Then, dibutyltin dilaurate is added as a transesterification catalyst. After stirring and dissolving, trimethylolpropionate is added... An ethyl acetate solution of trimethylolpropane triacrylate was heated to 75°C and reacted for 4 hours to allow the residual mercapto groups in the prepolymer to further react with trimethylolpropane triacrylate, while a partial transesterification reaction occurred, forming a modified polyfunctional thiol compound with a moderately branched structure. After the reaction was completed, the reaction solution was cooled to below 30°C, and 65 parts of deionized water were added to wash three times to remove the catalyst and unreacted small molecules. The organic phase was collected, dried overnight with anhydrous sodium sulfate, filtered to remove the desiccant, and the filtrate was placed in a rotary evaporator and the solvent was removed by vacuum distillation at 45°C to obtain a pale yellow viscous product. The product was placed in a vacuum drying oven and dried under vacuum at 45°C for 5 hours to obtain the chain-extended modified polyfunctional thiol compound.

[0061] The components are: pentaerythritol tetra-3-mercaptopropionate (100 parts by weight), ethyl acetate (100 parts by weight), trimethylolpropane triacrylate (40 parts by weight), dibutyltin dilaurate (1 part by weight), hydroquinone (0.5 parts by weight), dibutyltin dilaurate (15 parts by weight), and an ethyl acetate solution of trimethylolpropane triacrylate (30 parts by weight).

[0062] The preparation method of surface-lipophilic modified inorganic nanofiller is as follows: Zero-dimensional nano-silica is dispersed in anhydrous ethanol and ultrasonically treated for 30 min. Aqueous solution of aluminum sulfate octadechydrate is added, and the pH is adjusted to 8.5 with sodium hydroxide solution. The temperature is raised to 80℃ and stirred for 3 h for activation reaction. After the reaction is completed, centrifugation and washing are performed to obtain activated nano-silica filter cake. The filter cake is redispersed in anhydrous ethanol, and stearic acid ethanol solution is added. The temperature is raised to 80℃ for 4 h for esterification reaction. After the reaction is completed, centrifugation and washing with ethanol are performed to remove unreacted stearic acid. The product is redispersed in deionized water, and hexadecyltrimethylammonium bromide aqueous solution is added. The modification reaction is performed at 45℃ for 2 h by stirring. After the reaction is completed, centrifugation, washing, drying and sieving are performed to obtain surface-lipophilic modified inorganic nanofiller.

[0063] During the activation reaction, 100 parts of zero-dimensional nano-silica were dispersed in 400 parts of anhydrous ethanol; during the esterification reaction, the filter cake was dispersed in 300 parts of anhydrous ethanol; and during the modification reaction, the product was dispersed in 350 parts of deionized water.

[0064] The aqueous solution of aluminum sulfate octadechydrate consists of 10 parts aluminum sulfate octadechydrate dissolved in 75 parts deionized water; the ethanol solution of stearic acid consists of 15 parts stearic acid dissolved in 75 parts anhydrous ethanol; and the aqueous solution of hexadecyltrimethylammonium bromide consists of 5.5 parts hexadecyltrimethylammonium bromide dissolved in 45 parts deionized water.

[0065] The reaction promoter is DMP-30, and the antioxidant is a mixture of 2,6-di-tert-butyl-4-methylphenol and triphenyl phosphite in a mass ratio of 2.5:1.

[0066] Example 3: Based on Example 1, a method for preparing a low-precipitation thiol curing agent with a micro / nano labyrinth structure, comprising the following steps:

[0067] S1. Preparation of epoxy prepolymer carriers containing flexible segments, chain-extended modified multifunctional thiols, and surface-lipophilic modified inorganic nanofillers.

[0068] S2. Under an inert atmosphere, the epoxy prepolymer carrier containing flexible segments and an excess of chain-extended modified multifunctional thiols are added to the reactor and heated and stirred until homogeneous.

[0069] S3. Add surface-lipophilic modified inorganic nanofillers and reaction promoters to the reactor, raise the temperature and stir continuously to carry out partial end-capping prepolymerization reaction, so that some thiol groups are chemically bonded to the surface of epoxy prepolymer carrier and nanofiller, and construct a micro-nano labyrinth structure prepolymer with the prepolymer carrier and nanofiller as the core and the surface enriched with unreacted active thiol groups.

[0070] S4. After the reaction is complete, cool down and add antioxidant stabilizer. Continue stirring and then perform vacuum degassing on the reaction product. Filter the product to obtain the modified thiol curing agent.

[0071] In step S1, the epoxy prepolymer carrier containing flexible segments is prepared by epoxy resin through ring-opening etherification with polyethylene glycol-400, followed by intercalation and composite with organically modified nano-montmorillonite.

[0072] The chain-extended modified multifunctional thiols were prepared by a stepwise reaction of pentaerythritol tetra-3-mercaptopropionate via Michael addition and transesterification with trimethylolpropane triacrylate.

[0073] The surface-modified oleophilic inorganic nanofiller was prepared by a three-step process of zero-dimensional nano-silica activation with aluminum sulfate octadecylhydrate, stearate esterification, and electrostatic adsorption with hexadecyltrimethylammonium bromide (CTAB).

[0074] The weight ratio of each component in steps S1 to S4 is as follows: 50 parts of epoxy prepolymer carrier containing flexible segments, 40 parts of chain-extended modified multifunctional thiol compound, 25 parts of surface oleophilic modified inorganic nanofiller, 15 parts of reaction promoter, and 8 parts of antioxidant stabilizer.

[0075] The preparation method of epoxy prepolymer carrier containing flexible segments is as follows: epoxy resin dissolved in toluene is added to a reaction vessel, followed by polyethylene glycol-400 and triphenylphosphine. Nitrogen gas is introduced to replace the air in the vessel, stirring is started, and the mixture is heated to 100°C for 5 hours to carry out a ring-opening etherification reaction to generate an epoxy prepolymer containing flexible segments. Organically modified nano-montmorillonite is added to anhydrous ethanol and ultrasonically dispersed to obtain a montmorillonite suspension. The ring-opening etherification reaction product is cooled to 70°C and added dropwise to the montmorillonite suspension under stirring. After the addition is complete, the temperature is raised to 80°C, and stirring is continued for 3 hours to carry out an intercalation composite reaction. After the reaction is completed, the solvent and unreacted small molecules are removed by vacuum distillation to obtain a viscous product. The product is placed in a vacuum drying oven and vacuum dried at 80°C for 12 hours to remove residual solvent. The product is then pulverized and sieved to obtain an epoxy prepolymer carrier containing flexible segments.

[0076] The epoxy resin comprises 100 parts by weight, toluene comprises 80 parts by weight, polyethylene glycol-400 comprises 40 parts by weight, triphenylphosphine comprises 3 parts by weight, organic modified nano-montmorillonite comprises 15 parts by weight, and anhydrous ethanol comprises 50 parts by weight.

[0077] The preparation method of chain-extended modified multifunctional thiols is as follows: Pentaerythritol tetra-3-mercaptopropionate dissolved in ethyl acetate is added to a reaction vessel. Nitrogen gas is introduced to replace the air in the reaction vessel. Stirring is started, and the mixture is heated to 50°C. Then, trimethylolpropane triacrylate and dibutyltin dilaurate are mixed evenly and added dropwise to the reaction system. After the addition is complete, the temperature is raised to 65°C, and the reaction is maintained for 4 hours to allow the mercapto group and the acrylate double bond to undergo a Michael addition reaction, generating a thiols prepolymer containing multiple reactive sites. The product is cooled to 50°C, and hydroquinone is added as a polymerization inhibitor to prevent free radical side reactions in subsequent reactions. Then, dibutyltin dilaurate is added as a transesterification catalyst. After stirring and dissolving, trimethylolpropionate is added... An ethyl acetate solution of trimethylolpropane triacrylate was heated to 80°C and reacted for 5 hours to allow the residual mercapto groups in the prepolymer to further react with trimethylolpropane triacrylate, while a partial transesterification reaction occurred, forming a modified polyfunctional thiol compound with a moderately branched structure. After the reaction was completed, the reaction solution was cooled to below 30°C, and 80 parts of deionized water were added to wash four times to remove the catalyst and unreacted small molecules. The organic phase was collected, dried overnight with anhydrous sodium sulfate, filtered to remove the desiccant, and the filtrate was placed in a rotary evaporator and distilled under reduced pressure at 50°C to remove the solvent, yielding a pale yellow viscous product. The product was placed in a vacuum drying oven and dried under vacuum at 50°C for 6 hours to obtain the chain-extended modified polyfunctional thiol compound.

[0078] The pentaerythritol tetra-3-mercaptopropionate comprises 100 parts by weight, ethyl acetate comprises 120 parts by weight, trimethylolpropane triacrylate comprises 50 parts by weight and dibutyltin dilaurate comprises 1.5 parts by weight in the Michael addition reaction, hydroquinone comprises 0.8 parts by weight, and dibutyltin dilaurate comprises 20 parts by weight and ethyl acetate solution of trimethylolpropane triacrylate comprises 40 parts by weight in the transesterification reaction.

[0079] The preparation method of surface-lipophilic modified inorganic nanofiller is as follows: zero-dimensional nano-silica is dispersed in anhydrous ethanol and ultrasonically treated for 30 min. Aqueous solution of aluminum sulfate octadecylhydrate is added, and the pH is adjusted to 9.0 with sodium hydroxide solution. The temperature is raised to 90℃ and stirred for 4 h for activation reaction. After the reaction is completed, centrifugation and washing are performed to obtain activated nano-silica filter cake. The filter cake is redispersed in anhydrous ethanol, and stearic acid ethanol solution is added. The temperature is raised to 85℃ for esterification reaction for 5 h. After the reaction is completed, centrifugation and washing with ethanol are performed to remove unreacted stearic acid. The product is redispersed in deionized water, and hexadecyltrimethylammonium bromide aqueous solution is added. The modification reaction is performed by stirring at 50℃ for 2.5 h. After the reaction is completed, centrifugation, washing, drying and sieving are performed to obtain surface-lipophilic modified inorganic nanofiller.

[0080] During the activation reaction, 100 parts of zero-dimensional nano-silica were dispersed in 500 parts of anhydrous ethanol; during the esterification reaction, the filter cake was dispersed in 400 parts of anhydrous ethanol; and during the modification reaction, the product was dispersed in 450 parts of deionized water.

[0081] The aqueous solution of aluminum sulfate octadechydrate consists of 15 parts aluminum sulfate octadechydrate dissolved in 100 parts deionized water; the ethanol solution of stearic acid consists of 20 parts stearic acid dissolved in 100 parts anhydrous ethanol; and the aqueous solution of hexadecyltrimethylammonium bromide consists of 8 parts hexadecyltrimethylammonium bromide dissolved in 60 parts deionized water.

[0082] The reaction promoter is DMP-30, and the antioxidant is a mixture of 2,6-di-tert-butyl-4-methylphenol and triphenyl phosphite in a mass ratio of 3:1.

[0083] Comparative Example 1: The difference between this comparative example and Example 1 is that the modified epoxy resin skeleton in this comparative example is replaced with untreated epoxy resin.

[0084] Comparative Example 2 differs from Example 1 in that the modified polyfunctional thiol compound is replaced with untreated pentaerythritol tetra-3-mercaptopropionate.

[0085] Comparative Example 3 differs from Example 1 in that the modified inorganic nanofiller is replaced with untreated zero-dimensional nano silica.

[0086] Performance testing: The curing agents obtained in Examples 1 to 3 and Comparative Examples 1 to 4 were mixed with standard bisphenol A type epoxy resin (jER 828US) ​​at a ratio of thiol equivalent / epoxy equivalent = 1:1 to prepare epoxy adhesive test strips.

[0087] In addition to routine testing, a double 85 aging test (85) was added. o The test results for surface insulation resistance (SIR) at 85%RH (1000 hours of aging) and surface insulation resistance (SIR) (using IPC-TM-650 2.6.3.7 standard, comb electrode test) are recorded in Table 1 below:

[0088] Table 1 - Performance Test Table of Modified Thiol Curing Agent

[0089]

[0090] Among them, the test method in GB / T31877-2015 was used to test the migratable thiol content of the modified thiol curing agent of the low-precipitation epoxy resin prepared in Examples 1, 2, 3, Comparative Examples 1, 2, and 3.

[0091] The gel time of the modified thiol curing agent for the low-precipitation epoxy resins prepared in Examples 1, 2, 3, Comparative Examples 1, 2, and 3 was tested using the test methods in GB / T12007.7-2010.

[0092] The shear strength of the low-precipitation epoxy resins prepared by the modified thiol curing agent was tested according to the test methods in GB / T7124-2008 in Examples 1, 2, 3, Comparative Examples 1, 2, and 3.

[0093] In addition to the above routine tests, the double 85 aging test (85) is also included. o C / 85%RH, aging for 1000 hours) and surface insulation resistance (SIR) tests (using IPC-TM-650 2.6.3.7 standard, comb electrode test).

[0094] Comparative examples and comparative examples show that the curing agent prepared by the present invention not only has excellent initial mechanical properties, but more importantly, it exhibits excellent performance at 85°C. o Under harsh aging conditions of C / 85%, the shear strength retention rate is above 80%, and the surface insulation resistance after aging is above 10. 12 Ω level (far exceeding the 10 required for electronic packaging) 10 Ω safety line). In contrast, in Comparative Example 2 (unextended chain) and Comparative Example 4 (commercially available macromolecular thiols), due to the lack of chemical anchoring and the synergistic barrier of the multidimensional micro-nano maze, a large number of small thiols migrated and precipitated under high temperature and high humidity, resulting in an exponential decrease in SIR values ​​(10). 8 (At the Ω level), and even triggered electrode corrosion. This fully demonstrates that the present invention has outstanding substantial features and significant progress in solving the pain point of precipitation in high-reliability microelectronic packaging.

[0095] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0096] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A method for preparing a low-precipitation thiol curing agent with a micro / nano labyrinth structure, characterized in that, Includes the following steps: S1. Preparation of epoxy prepolymer carriers containing flexible segments, chain-extended modified multifunctional thiols, and surface-lipophilic modified inorganic nanofillers. S2. Under an inert atmosphere, the epoxy prepolymer carrier containing flexible segments and an excess of the chain-extended modified multifunctional thiol compound are added to a reaction vessel and heated and stirred until homogeneous. S3. Add the surface-oil-modified inorganic nanofiller and reaction promoter to the reactor, raise the temperature and stir continuously to carry out a partial end-capping prepolymerization reaction, so that some thiol groups are chemically bonded to the surface of the epoxy prepolymerization carrier and nanofiller, and construct a micro-nano labyrinth structure prepolymer with the prepolymerization carrier and nanofiller as the core and the surface enriched with unreacted active thiol groups. S4. After the reaction is complete, cool down and add antioxidant stabilizer. Continue stirring and then perform vacuum degassing on the reaction product. Filter the product to obtain the modified thiol curing agent.

2. The preparation method according to claim 1, characterized in that: In step S1, the epoxy prepolymer carrier containing flexible segments is prepared by epoxy resin through ring-opening etherification with polyethylene glycol-400, followed by intercalation and composite with organically modified nano-montmorillonite. The chain-extended modified multifunctional thiols were prepared by a stepwise reaction of pentaerythritol tetra-3-mercaptopropionate via Michael addition and transesterification with trimethylolpropane triacrylate. The surface-adhesive modified inorganic nanofiller is prepared by a three-step step-by-step modification of zero-dimensional nano-silica through activation with aluminum sulfate octadecylhydrate, stearate esterification, and electrostatic adsorption with hexadecyltrimethylammonium bromide (CTAB).

3. The preparation method according to claim 1, characterized in that: The weight ratio of each component in steps S1 to S4 is as follows: 30-50 parts of epoxy prepolymer carrier containing flexible segments, 20-40 parts of chain-extended modified multifunctional thiol compound, 10-25 parts of surface oleophilic modified inorganic nanofiller, 5-15 parts of reaction promoter, and 2-8 parts of antioxidant stabilizer.

4. The preparation method according to claim 1, characterized in that, The preparation method of the epoxy prepolymer carrier containing flexible segments is as follows: epoxy resin dissolved in toluene is added to a reaction vessel, followed by polyethylene glycol-400 and triphenylphosphine. Nitrogen gas is introduced to replace the air in the vessel to carry out a ring-opening etherification reaction. Organically modified nano-montmorillonite is added to anhydrous ethanol and ultrasonically dispersed to obtain a montmorillonite suspension. The ring-opening etherification reaction product is added dropwise to the montmorillonite suspension to carry out an intercalation composite reaction. After the reaction is completed, the epoxy prepolymer carrier containing flexible segments is obtained by vacuum distillation, drying, pulverizing and sieving.

5. The preparation method according to claim 4, characterized in that: The epoxy resin comprises 100 parts by weight, toluene comprises 50-80 parts by weight, polyethylene glycol-400 comprises 20-40 parts by weight, and triphenylphosphine comprises 1-3 parts by weight; the organic modified nano-montmorillonite comprises 5-15 parts by weight, and anhydrous ethanol comprises 30-50 parts by weight.

6. The preparation method according to claim 1, characterized in that, The method for preparing the chain-extended modified multifunctional thiol compound is as follows: pentaerythritol tetra-3-mercaptopropionate dissolved in ethyl acetate is added to a reaction vessel, nitrogen gas is introduced to replace the air in the reaction vessel, and then trimethylolpropane triacrylate and dibutyltin dilaurate are mixed evenly and added dropwise to the reaction system to carry out a Michael addition reaction; hydroquinone and dibutyltin dilaurate are added to the product, stirred and dissolved, and then an ethyl acetate solution of trimethylolpropane triacrylate is added to carry out a transesterification reaction; after the reaction is completed, the product is washed, dried, distilled under reduced pressure, and dried in sequence to obtain the chain-extended modified multifunctional thiol compound.

7. The preparation method according to claim 6, characterized in that: The pentaerythritol tetra-3-mercaptopropionate comprises 100 parts by weight, ethyl acetate comprises 80-120 parts by weight, and in the Michael addition reaction, trimethylolpropane triacrylate comprises 30-50 parts by weight, and dibutyltin dilaurate comprises 0.5-1.5 parts by weight; the hydroquinone comprises 0.3-0.8 parts by weight, and in the transesterification reaction, dibutyltin dilaurate comprises 10-20 parts by weight, and the ethyl acetate solution of trimethylolpropane triacrylate comprises 20-40 parts by weight.

8. The preparation method according to claim 1, characterized in that, The preparation method of the surface-oil-modified inorganic nanofiller is as follows: zero-dimensional nano-silica is dispersed in anhydrous ethanol, aluminum sulfate octadecylhydrate aqueous solution is added, the pH is adjusted to 8.0-9.0 and then an activation reaction is carried out. After the reaction is completed, centrifugation and washing are performed to obtain activated nano-silica filter cake; the filter cake is redispersed in anhydrous ethanol, stearic acid ethanol solution is added to carry out an esterification reaction, and centrifugation and washing are performed after the reaction is completed. The product was redispersed in deionized water, and a hexadecyltrimethylammonium bromide aqueous solution was added for modification. After the reaction was completed, the product was centrifuged, washed, dried, and sieved to obtain an inorganic nanofiller with a lipophilic surface.

9. The preparation method according to claim 8, characterized in that: The activation reaction involves dispersing 100 parts of zero-dimensional nano-silica in 300-500 parts of anhydrous ethanol; the esterification reaction involves dispersing the filter cake in 200-400 parts of anhydrous ethanol; the modification reaction involves dispersing the product in 250-450 parts of deionized water; the aluminum sulfate octadechydrate aqueous solution involves dissolving 5-15 parts of aluminum sulfate octadechydrate in 50-100 parts of deionized water; the stearic acid ethanol solution involves dissolving 10-20 parts of stearic acid in 50-100 parts of anhydrous ethanol; and the hexadecyltrimethylammonium bromide aqueous solution involves dissolving 3-8 parts of hexadecyltrimethylammonium bromide in 30-60 parts of deionized water.

10. The preparation method according to claim 1, characterized in that: The reaction promoter is DMP-30, and the antioxidant is a mixture of 2,6-di-tert-butyl-4-methylphenol and triphenyl phosphite in a mass ratio of 2-3:1.

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