CN102423673A - Latent microcapsule curing agent initiating thermosetting epoxy resin curing at medium temperature and preparation method of adhesive thereof - Google Patents

Abstract

The invention relates to a preparation method of a latent microcapsule curing agent and an adhesive that initiates curing of a thermosetting epoxy resin at a medium temperature. As a wall material, a latent microcapsule curing agent with good curing performance and latent performance was prepared by using solvent volatilization technology, and it was applied to an epoxy resin system to prepare a one-component medium temperature curing epoxy resin adhesive. The microcapsules prepared by this method have high core content, smooth surface, narrow particle size distribution, good compatibility with matrix epoxy resin, and can be better dispersed in epoxy resin; the one-component adhesive prepared by it The agent can be cured at moderate temperature, has a long shelf life at room temperature, and has improved tensile shear strength properties.

Description

A kind of preparation method of latent microcapsule curing agent and its adhesive that initiates curing of thermosetting epoxy resin at medium temperature

technical field

The invention relates to a latent microcapsule curing agent for initiating curing of thermosetting epoxy resins, which can be used to prepare cured products with excellent physical properties, low viscosity and excellent processability. the

Background technique

Epoxy resins are excellent in adhesion, corrosion resistance, mechanical properties, thermal properties, and electrical properties, and are widely and widely used as adhesives, coatings, inks, laminates, castings, molds, etc. Plastic products and electronic insulation materials, etc. Epoxy adhesives used in these areas can be one-component or two-component systems. the

The most widely used epoxy adhesive is a two-component system, which consists of epoxy resin and curing agent, which are stored separately. Therefore, two-component adhesives not only need to be packaged, stored and transported separately, which brings many operational and environmental problems, but also measurement errors and uneven mixing during mixing and preparation can easily cause fluctuations in important properties such as the adhesive strength of the product. After the glue is prepared, the viscosity of the system increases continuously with the progress of the chemical reaction, and its pot life is limited. It is not suitable for the new automatic bonding process, and it is easy to cause scrap. Therefore, the research and development of single-component epoxy resin adhesives that simplify the operation process, are easy to implement, have little environmental pollution, and are beneficial to the improvement of the overall quality of the product and are suitable for new processes have always attracted people's attention. the

At present, the focus of research and development lies in the design and selection of curing agent molecules, the establishment of corresponding process conditions and the improvement of comprehensive performance, among which the research and development of latent curing agents is the most active and important. This type of curing agent is mainly implemented by temporarily blocking or passivating the active groups and structures of some curing agents with high reactivity and poor storage stability. However, since the curing agent is in direct contact with the matrix epoxy resin, the two-component epoxy adhesive prepared from this type of latent curing agent usually undergoes physical and chemical reactions during storage, resulting in the loss of the two-component epoxy adhesive. The storage period (pot life) of the adhesive is reduced, which in turn affects the effectiveness of the adhesive. At the same time, in the indicators of adhesives, the curing temperature and the storage period of the adhesive are usually a pair of contradictions: that is, the curing agent with a low curing temperature is selected, and the storage period of the adhesive prepared by it is relatively long; The curing agent with high curing temperature has a relatively short shelf life of the adhesive prepared from it. In order to solve the above problems, we prepared a new type of latent curing agent - microcapsule curing agent. the

Microcapsule curing agent means that the curing agent is encapsulated with microcapsule technology and can prevent it from reacting with the matrix resin (usually epoxy resin) at room temperature, so as to improve the room temperature storage period of the resin and its prepreg, and then in a certain Under certain conditions (temperature or pressure, etc.), the microcapsules are broken and the curing agent is released to complete the curing reaction. A new type of curing agent. Compared with general curing agents, microcapsule curing agents have a longer storage period, which can block the interaction between curing agent and matrix resin, so as to achieve the purpose of controlling curing. Moreover, due to the selection of a high-activity medium-temperature curing agent, the problem of curing temperature has also been solved. the

One-component adhesives can greatly improve production efficiency due to their long pot life, small measurement errors, stable glue quality, ready-to-use, fast and convenient. It has been used in many industrial sectors, such as the bonding of door folds on automobile production lines, the structural bonding of front and rear boxes of cars, the potting of electronic components in the electronics industry, and the production of mechanical and electrical products. In particular, the application of one-component epoxy adhesives on the assembly line of electrical components has great prospects for development. At present, the latent curing system obtained by microcapsule curing agent is an effective method to solve the contradiction between epoxy low-temperature curing and long room temperature storage period, and it is also the main development direction of latent curing agent for resin-based composite materials. the

Introducing a microcapsule curing agent into an epoxy resin system to prepare a one-component adhesive is one of the research hotspots in recent years. At present, in the preparation of one-component adhesives in China, the method of directly adding latent curing agent is mainly used to prolong its storage period, and there are few reports on the use of latent microcapsule curing agent. Xing Suli et al. used modified diaminodiphenylmethane as the core material and 2,2-toluene diisocyanate as the wall material monomer, and prepared a new type of polyurea microcapsule with narrow particle size distribution by interfacial polymerization technology. The prepared microcapsule curing agent has an average particle size of 2.54 μm and a wall thickness of about 100 nm. The microcapsule curing agent can not only successfully cure the E-51 epoxy resin, but also has excellent latent properties at room temperature with the E-51 epoxy resin system, and the storage period at room temperature can reach more than 6 months. Tong Suling and others dispersed the non-water-soluble 2-ethyl-4-methylimidazole (EMI) pre-reactant in water, and then made the melamine-formaldehyde prepolymer polymerize in situ on its surface to prepare an epoxy resin curing accelerator Microcapsules. The capsules are used in the preparation of epoxy tapes, and the obtained tapes have good storage performance and appearance, and the microcapsules have a good effect on promoting the curing of the tapes. Yuan Yanchao and others prepared polythiol microcapsules by in-situ polymerization in n-octanol. The core material is liquid polythiol, the wall material is melamine-formaldehyde resin, methanol etherified melamine-formaldehyde resin, urea-formaldehyde resin or their mixture, the weight ratio of core material/wall material is 1:5～1:6, and the diameter is 1 μm ~1mm, and the thickness of the cyst wall is 100nm~10μm. During the capsule preparation process, a small part of the core material and the wall material undergo cross-linking reactions and are consumed to form a part of the capsule wall, and most of the core material polythiol can maintain its activity before being coated. The polythiol microcapsule has sufficient mechanical strength and can withstand the external force during the production and processing of the composite material. Xu Hongxia and others prepared microcapsules with 2-phenylimidazole (2PZ) as the core material and polymethyl methacrylate (PMMA) as the wall material by S/O/W solvent evaporation method. The particle size of the microcapsule is about 10 μm, and the embedding rate of 2PZ is about 10wt%. And the EP/Micro20 (100 parts of epoxy/20 parts of microcapsules) system has a storage period of more than 6 months at room temperature, while the EP/2PZ system without curing agent has been cured after 7 days at room temperature. Xing Suli et al. used emulsion-solvent evaporation technology to successfully prepare spherical microcapsule curing agent with modified 2-ethyl-4-methylimidazole as the core material and polyetherimide as the wall material. The particle size distribution of the microcapsules is relatively narrow, and the average particle size is about 25 μm. The prepared curing agent microcapsules have excellent curing activity, release performance and latent performance, and can cure E-51 epoxy resin within 2 hours at 100°C, and the storage period at room temperature is more than 3 months. the

The reports on microcapsule curing agents in foreign countries are relatively active. There are a large number of patents on microcapsule curing agents in Japan and the United States every year. Shigeaki F and others used epoxy resin to modify 2-methylimidazole, and obtained micron-sized amine adducts after grinding, which were reacted with 4,4-diphenylmethane diisocyanate to obtain polyurea-coated 2-methylimidazole microcapsules. And the microcapsule resin system was prepared with 67 parts (mass fraction) of bisphenol A type epoxy resin and 33 parts of microcapsule curing agent. The solidification temperature is between 115 and 120°C as measured by DSC, and after being stored at 40°C for 30 days, the viscosity growth rate is less than 50% as measured by an E-type viscometer. Taketoshi U et al. used a similar method to synthesize polyurea-coated 2-methylimidazole microcapsules, and the curing temperature of the prepared microcapsules was between 100 and 130 °C. The difference is that it adopts a new method to determine the latent period of the microcapsule resin system: that is, after appropriate pretreatment (removal of volatile matter, etc.), it is stored at 50°C for 3 days, and the epoxy group (914cm ^-1 location) Survival rate before and after 3 days, and compare, can qualitatively analyze the incubation period of the microcapsule resin system with this. Masuko et al. prepared a low-temperature solvent-resistant microcapsule curing agent in Japanese standard No. 1 kerosene by in-situ polymerization. The core material is an adduct of epoxy resin and 2-ethyl-4-methylimidazole, and the wall material is multi- Adduct of functional isocyanate and ethyl cellulose. The particle size of the prepared microcapsule curing agent is about 5 μm. When the microcapsule curing agent is used to cure the epoxy resin, the corresponding temperature of the exothermic peak is measured to be about 120° C. In addition, due to the deep cross-linking between isocyanate and ethyl cellulose, the microcapsules have good solvent resistance.

At present, the preparation methods of microcapsules at home and abroad are mainly concentrated on in-situ polymerization method and interfacial polymerization method. There are problems such as long reaction time and slow polymerization reaction speed caused by chemical processes. At the same time, there are complex reaction equipment and required materials. Disadvantages such as high preparation costs. the

Contents of the invention

technical problem to be solved

In order to avoid the deficiencies of the prior art, the present invention proposes a method for preparing a latent microcapsule curing agent and an adhesive that initiates curing of a thermosetting epoxy resin at a medium temperature. the

Technical solutions

A preparation method of a latent microcapsule curing agent that initiates thermosetting epoxy resin curing at medium temperature, is characterized in that the steps are as follows:

Step 1: In a container equipped with an electric stirrer, add 50-100mL of 0.1-2wt% dispersant aqueous solution and 50-100mL of 0.1-2wt% emulsifier aqueous solution, and disperse under mechanical stirring at 500-1000r/min for 30-60min Obtain aqueous phase; Described emulsifying agent is one or more in sodium dodecylbenzene sulfonate, sodium lauryl sulfate and Tween and Span; Described dispersion agent is gelatin or polyvinyl alcohol one or more;

Step 2: Add 0.2-2g each of core material and wall material to 25-50mL of volatile solvent, and disperse evenly in an ultrasonic instrument until it dissolves to obtain an oil phase, and gradually add the oil phase to the In the water phase prepared in step 1; the above-mentioned water phase is 100 to 200 parts by mass, the oil phase is 50 to 100 parts by mass, and the water phase to oil ratio is 1:2 to 2:1; the core material is trifluoro One or more of boron and its amine complexes, aromatic polyamines, polyamine salts, alicyclic amines, organic acid hydrazides, etc.; the wall material is polyvinyl microspheres, polyphenylene One or more of vinyl microspheres and polyacrylate microspheres; the volatile solvent is one or more of dichloromethane, chloroform or acetone;

Step 3: Stir and emulsify for 30-60 minutes, raise the reaction temperature to 30-35°C and stir for 3-5 hours, then raise the temperature to 38-40°C and stir for 3-5 hours or more until the volatile solvent evaporates, centrifuge the suspension, wash with distilled water, and dry Promptly obtain the product microcapsule curing agent. the

The boron trifluoride and its amine complexes are boron trifluoride-monoethylamine, boron trifluoride-n-butylamine, boron trifluoride-bianamine, boron trifluoride-chloroaniline, trifluoride Boron trifluoride-dimethylaniline, boron trifluoride-diphenylamine, boron trifluoride-aniline, boron trifluoride-p-toluidine, boron trifluoride-o-toluidine, boron trifluoride-n-butylamine, One or more of boron trifluoride-ethylamine or boron trifluoride-piperidine. the

The aromatic polyamine is diaminodiphenylmethane, diaminodimethoxydiphenylmethane, diaminodicyclohexylmethane, diaminodichlorodiphenylmethane, m-phenylenediamine or diaminodiphenylsulfone one or more. the

The polyamine salt is the phenylphosphonate of o-phenylenediamine, m-phenylenediamine, aniline, diaminodiphenylmethane, p-phenylenediamine, m-xylenediamine, piperazine, benzylamine or ethylenediamine one or more of. the

The cycloaliphatic amine is N-aminoethylpiperazine, isophorone diamine, 1,3-bis(aminomethyl)cyclohexane, 4,4-diaminodicyclohexylmethane or bis(4- One or more of amino-3-methylcyclohexyl)methane. the

The organic acid hydrazide is propionic acid hydrazide, butyric acid hydrazide, hexanoic acid hydrazide, octanoic acid hydrazide, adipic acid dihydrazide, sebacic acid dihydrazide, isophthalic acid dihydrazide, salicyl One or more of acid hydrazide or phenylalanine hydrazide. the

The polyvinyls are one or more of polyvinyl acetate, polyvinyl alcohol or polyvinyl acetal. the

The polystyrenes are one or more of polystyrene, styrene-acrylonitrile copolymer, styrene-methyl methacrylate copolymer or styrene-divinylbenzene copolymer. the

The polyacrylic acid is one or more of polymethyl methacrylate, methyl methacrylate and styrene copolymer, poly α-methyl chloroacrylate or poly α-methyl cyanoacrylate. the

A method for preparing a medium-temperature curing one-component epoxy resin adhesive using the above-mentioned latent microcapsule curing agent that initiates thermosetting epoxy resin curing at medium temperature, characterized in that 100 parts by mass of thermosetting multifunctional Epoxy resin, 5-100 parts by mass of non-reactive diluent, 1-100 parts by mass of latent microcapsule curing agent that initiates curing of thermosetting epoxy resin at medium temperature, and 1-20 parts by mass of filler are mixed to obtain medium-temperature curing with long incubation period One-component epoxy resin adhesive; the thermosetting multifunctional epoxy resin is one or more of bisphenol A glycidyl ether or bisphenol F glycidyl ether; the non-reactive diluent is acetone, methyl ethyl ketone , one or more of cyclohexanone, ethanol or toluene; the filler is one or more of nano silicon dioxide, nano calcium carbonate, aluminum oxide or clay powder. the

Beneficial effect

The present invention proposes a method for preparing a latent microcapsule curing agent that initiates curing of a thermosetting epoxy resin at a medium temperature and an adhesive thereof. The microcapsules are prepared by a simple and easy-to-control solvent volatilization method. In addition, compared with similar methods, this method has more capsule core and wall materials to choose from; the prepared microcapsules have high content of capsule core, smooth surface, narrow particle size distribution, and good compatibility with matrix epoxy resin. , can be well dispersed in epoxy resin; the one-component adhesive prepared by it can be cured at medium temperature, has a long storage period at room temperature, and has improved tensile and shear strength properties. the

In summary, the present invention uses a high-activity medium-temperature curing agent as the core material, thermoplastic high polymer microspheres as the wall material, and adopts solvent volatilization technology to prepare a latent microcapsule curing agent with good curing performance and latent performance, and prepares it Apply it to the resin system to prepare a one-component medium temperature curing resin adhesive. The microcapsule curing agent prepared by the invention has a smooth surface, narrow particle size distribution, an average particle size of 10-20 μm, a wall material thickness of about 0.5-1.0 μm, and a core material content of 20-50 wt%. The one-component adhesive prepared by microcapsule curing agent and epoxy resin has excellent curing performance and latent performance. It can be cured within 30 minutes to 1 hour at 100-150 °C, and the storage period at room temperature is about 40-60 days. And the tensile shear strength is higher than that of the two-component adhesive directly adding curing agent. In addition, the present invention analyzes the chemical structure of the microcapsule curing agent, the core material content, The surface morphology and curing properties were characterized, which strongly proved the successful preparation of the microcapsule curing agent. the

The advantages of the present invention compared to traditional two-component adhesives are:

1. The preparation method (solvent volatilization method) is simple and easy, which is beneficial to mass production and adapts to modern assembly line production. the

2. The prepared microcapsule curing agent has narrow particle size distribution, excellent curing performance and latent performance, and can realize rapid curing at medium temperature. the

3. The one-component adhesive prepared by the microcapsule curing agent can block the interaction between the curing agent and the matrix epoxy resin, so as to achieve the purpose of controlling the curing. And one-time glue can be used for a long time, its measurement error is small, the quality of glue is stable, it can be taken at any time, fast and convenient, thus greatly improving production efficiency. the

Description of drawings

Figure 1 is an infrared spectrogram: (a) DDM (b) DDM-PMMA microcapsules (c) PMMA microspheres;

Fig. 2 is TGA and DTG curve: (a) DDM (b) PMMA microsphere (c) DDM-PMMA microcapsule;

Fig. 3 is scanning electron micrograph: (a) PMMA microsphere (b) DDM-PMMA microcapsule (c) DDM-PMMA microcapsule crushed sample;

Figure 4 is the DSC curve: (a) E-51/DDM-PMMA microcapsule system (c) E-51/DDM system. the

Detailed ways

Now in conjunction with embodiment, accompanying drawing, the present invention will be further described:

The microcapsule curing agent with diaminodiphenylmethane (DDM) as the core material and polymethyl methacrylate (PMMA) microspheres as the wall material is taken as an example to illustrate the characterization. the

1. Analysis method

(1) Composition of microcapsules

The sample was dissolved in dichloromethane to obtain a clear solution, dipped in a small amount of the above solution with a glass rod and evenly coated on the KBr pellet to form a liquid film, and baked under an infrared lamp until the solvent dichloromethane volatilized completely. Place the KBr pellet covered with liquid film in a Fourier transform infrared spectrometer, set the scanning parameters to scan, and obtain the infrared spectrogram. the

(2) Core material content

Weigh about 10mg of the prepared microcapsule curing agent or wall material microspheres and place them in the crucible, adjust the thermogravimetric analyzer to the ideal experimental state, the protective gas is N ₂ , the nitrogen flow rate is 100mL/min, starting from room temperature The temperature was raised to 800°C at 20°C/min, and the microcapsules were completely decomposed, and the experiment was stopped.

(3) Microcapsule morphology

Disperse the sample powder in absolute ethanol, drop the suspension on the silicon wafer, spray it with gold after it is evenly distributed and dry, and observe it under a scanning electron microscope. the

(4) Curing performance

The TAInstrument-2910 DSC instrument of Waters-TA Company in the United States was used in the _N2 atmosphere, the sample weight was about 5 mg, the heating rate was 10 °C/min, and the temperature range was 25-300 °C. The curve was processed by TA Universal Analysis software.

(5) Latent performance

The microcapsule curing agent, the mixture of the curing agent and the wall material, and the curing agent were made into a resin system, and placed on the test bench. The time for the system to agglomerate at room temperature was used as the room temperature storage period of the system to characterize its latent performance. the

2. Source of raw materials

Core material: diaminodiphenylmethane, chemically pure, Sinopharm Chemical Reagent Co., Ltd.; wall material: polymethyl methacrylate, self-made; emulsifier: sodium dodecylbenzenesulfonate (SDBS), chemically pure, Sinopharm Chemical Reagent Co., Ltd.; dispersant: gelatin, chemically pure, Tianda Chemical Reagent Factory, Dongli District, Tianjin; solvent: dichloromethane, analytically pure, Tianjin Fuyu Fine Chemical Co., Ltd.; dispersion medium: distilled water, self-made ; E-51 (WSR618): industrial grade, Wuxi Resin Factory of Bluestar Chemical New Materials Co., Ltd.; absolute ethanol, analytically pure, Tianjin Fuyu Fine Chemical Co., Ltd. the

Embodiment 1: Take gelatin as dispersant, sodium dodecylbenzenesulfonate as emulsifier, and dichloromethane as solvent

In a fume hood, directly add 50mL of 0.5wt% gelatin aqueous solution and 100mL of 0.2wt% sodium dodecylbenzenesulfonate aqueous solution into a 500ml three-necked flask equipped with an electric stirrer, a condenser tube and a thermometer. Stir and disperse for 30 minutes to obtain a stable and uniform water phase; respectively add 1 g of diaminodiphenylmethane and 1 g of polymethyl methacrylate to two beakers filled with 20 mL of dichloromethane, and disperse evenly in an ultrasonic instrument until they dissolve The oily phase was obtained, and the oily phase was gradually added dropwise to the three-necked flask within 5 minutes. Stir for about 30 minutes to make the oil phase and water phase form a uniform and stable emulsion. Slowly raise the reaction temperature to 30°C and stir for 3 hours, then raise the temperature to 38°C and stir for more than 3 hours until the dichloromethane volatilizes completely. The suspension is centrifuged, washed with distilled water and dried to obtain a microcapsule solidifying agent with a product particle diameter of 2-10 μm. the

Uniformly mix 20 parts of the obtained microcapsule curing agent, 50 parts of acetone, 100 parts of E-54 epoxy resin, and 1 part of nano silicon dioxide to obtain a one-component epoxy resin adhesive. It can be cured within 1 hour at 120°C, and the storage period at room temperature can reach more than 46 days. the

Embodiment 2: Take polyvinyl alcohol as a dispersant, sodium dodecylbenzenesulfonate as an emulsifier, and dichloromethane as a solvent

In a fume hood, directly add 40mL of 0.2wt% polyvinyl alcohol aqueous solution and 80mL of 0.2wt% sodium dodecylbenzenesulfonate aqueous solution into a 500ml three-necked flask equipped with an electric stirrer, a condenser tube and a thermometer, and heat at 1000r/min disperse under mechanical stirring for 30min to obtain a stable and uniform water phase; add 1g N-aminoethylpiperazine and 2g polystyrene to two beakers containing 20mL of dichloromethane respectively, and disperse evenly in an ultrasonic instrument until The oil phase was obtained by dissolving, and the oil phase was gradually added dropwise into the three-necked flask within 5 minutes. Stir for about 30 minutes to make the oil phase and water phase form a uniform and stable emulsion. Slowly raise the reaction temperature to 30°C and stir for 3 hours, then raise the temperature to 35°C and stir for more than 3 hours until the dichloromethane volatilizes completely. Centrifuge the suspension, wash with distilled water, and dry to obtain a microcapsule curing agent with a product particle size of 2-11 μm. the

15 parts of the obtained microcapsule curing agent, 40 parts of methyl ethyl ketone, 100 parts of CYDF-170 epoxy resin, and 2 parts of nano-calcium carbonate were uniformly mixed to obtain a one-component epoxy resin adhesive. It can be cured within 30 minutes at 120°C, and the storage period at room temperature can reach more than 42 days. the

Embodiment 3: take gelatin as dispersant, Tween and Span as emulsifier, methylene chloride as solvent

In a fume hood, directly add 50mL of 0.3wt% gelatin aqueous solution, 90mL of 0.1wt% Tween and Sipan (1:1) aqueous solution into a 500ml three-necked flask equipped with an electric stirrer, a condenser tube and a thermometer, and heat the mixture at 700r/min. disperse under mechanical stirring for 30min to obtain a stable and uniform aqueous phase; add 2g m-phenylenediamine and 1g styrene-methyl methacrylate copolymer to two beakers containing 20mL dichloromethane respectively, and Disperse until it dissolves to obtain an oil phase, and gradually add the oil phase to the three-necked flask within 5 minutes. Stir for about 30 minutes to make the oil phase and water phase form a uniform and stable emulsion. Slowly raise the reaction temperature to 30°C and stir for 3 hours, then raise the temperature to 40°C and stir for more than 3 hours until the dichloromethane volatilizes completely. The suspension is centrifuged, washed with distilled water and dried to obtain a microcapsule curing agent with a product particle size of 0.5-12 μm. the

Mix 30 parts of microcapsule curing agent, 60 parts of cyclohexanone, 100 parts of E-51 epoxy resin, and 1 part of alumina to obtain a one-component epoxy resin adhesive. It can be cured within 30 minutes at 100°C, and the storage period at room temperature can reach more than 45 days. the

Embodiment 4: Take polyvinyl alcohol as a dispersant, Tween and Span as an emulsifier, and dichloromethane as a solvent

In a fume hood, directly add 40mL of 0.3wt% polyvinyl alcohol aqueous solution, 100mL of 0.2wt% Tween and Span (1:1) aqueous solution to a 500ml three-necked flask equipped with an electric stirrer, a condenser tube and a thermometer. Disperse for 30min under mechanical stirring at /min to obtain a stable and uniform aqueous phase; add 0.5g p-phenylenediamine and 1g styrene-divinylbenzene copolymer to two beakers containing 20mL dichloromethane respectively, and Disperse evenly in the instrument until it dissolves to obtain an oil phase, and gradually add the oil phase to the three-necked flask within 5 minutes. Stir for about 30 minutes to make the oil phase and water phase form a uniform and stable emulsion. Slowly raise the reaction temperature to 32°C and stir for 3 hours, then raise the temperature to 37°C and stir for more than 3 hours until the dichloromethane volatilizes completely. The suspension is centrifuged, washed with distilled water and dried to obtain a microcapsule solidifying agent with a product particle diameter of 1-12 μm. the

Uniformly mix 40 parts of the obtained microcapsule curing agent, 40 parts of acetone, 100 parts of CYDF-180 epoxy resin, and 1 part of clay powder to obtain a one-component epoxy resin adhesive. It can be cured within 30 minutes at 100°C, and the storage period at room temperature can reach more than 45 days. the

Embodiment 5: Taking gelatin as a dispersant, sodium dodecylbenzenesulfonate as an emulsifier, and chloroform as a solvent

In the fume hood, 50mL of 0.2wt% gelatin aqueous solution and 80mL of 0.2wt% sodium dodecylbenzenesulfonate aqueous solution were directly added to a 500ml three-necked flask equipped with an electric stirrer, a condenser tube and a thermometer. Stir and disperse for 30 minutes to obtain a stable and uniform aqueous phase; respectively add 1 g of propionic acid hydrazide and 1 g of polymethyl methacrylate to two beakers filled with 20 mL of chloroform, and disperse evenly in an ultrasonic instrument until they dissolve to obtain For the oil phase, the oil phase was gradually added dropwise to the three-necked flask within 5 minutes. Stir for about 30 minutes to make the oil phase and water phase form a uniform and stable emulsion. Slowly raise the reaction temperature to 30°C and stir for 3 hours, then raise the temperature to 38°C and stir for more than 3 hours until the chloroform is completely volatilized. The suspension is centrifuged, washed with distilled water and dried to obtain a microcapsule solidifying agent with a product particle diameter of 2-10 μm. the

Uniformly mix 30 parts of the obtained microcapsule curing agent, 60 parts of methyl ethyl ketone, E-44 epoxy resin, and 1 part of nano silicon dioxide to obtain a one-component epoxy resin adhesive. It can be cured within 1 hour at 150°C, and the storage period at room temperature can reach more than 52 days. the

Embodiment 6: Take polyvinyl alcohol as a dispersant, sodium dodecylbenzenesulfonate as an emulsifier, and chloroform as a solvent

In a fume hood, directly add 30mL of 0.1wt% polyvinyl alcohol aqueous solution and 60mL of 0.2wt% sodium dodecylbenzenesulfonate aqueous solution into a 500ml three-neck flask equipped with an electric stirrer, a condenser tube and a thermometer, at 900r/min Disperse under mechanical stirring for 30min to obtain a stable and uniform water phase; respectively add 2g of boron trifluoride-monoethylamine and 1g of polystyrene to two beakers containing 20mL of chloroform, and disperse evenly in an ultrasonic instrument until It was dissolved to obtain an oil phase, which was gradually added dropwise into the three-necked flask within 5 minutes. Stir for about 30 minutes to make the oil phase and water phase form a uniform and stable emulsion. Slowly raise the reaction temperature to 30°C and stir for 3 hours, then raise the temperature to 40°C and stir for more than 3 hours until the chloroform is completely volatilized. The suspension is centrifuged, washed with distilled water and dried to obtain a microcapsule curing agent with a product particle size of 2.5-10 μm. 20 parts of the obtained microcapsule curing agent, 50 parts of acetone, and 100 parts of bisphenol A glycidyl ether were uniformly mixed to obtain a one-component epoxy resin adhesive. the

Uniformly mix 40 parts of the obtained microcapsule curing agent, 50 parts of cyclohexanone, 100 parts of NPEF-170 epoxy resin, and 1 part of nano-calcium carbonate to obtain a one-component epoxy resin adhesive. It can be cured within 1 hour at 120°C, and the storage period at room temperature can reach more than 45 days. the

Embodiment 7: Take gelatin as dispersant, Tween and Span as emulsifier, and chloroform as solvent

In a fume hood, directly add 40mL of 0.2wt% gelatin aqueous solution, 100mL of 0.2wt% Tween and Siban (1:1) aqueous solution into a 500ml three-necked flask equipped with an electric stirrer, a condenser tube and a thermometer, at 700r/min disperse under mechanical stirring for 30min to obtain a stable and uniform aqueous phase; add 1g of butyric acid hydrazide and 1g of styrene-methyl methacrylate copolymer to two beakers containing 20mL of chloroform respectively, and Disperse evenly until it dissolves to obtain an oil phase, and gradually drop the oil phase into a three-necked flask within 5 minutes. Stir for about 30 minutes to make the oil phase and water phase form a uniform and stable emulsion. Slowly raise the reaction temperature to 32°C and stir for 3 hours, then raise the temperature to 39°C and stir for more than 3 hours until the chloroform is completely volatilized. The suspension is centrifuged, washed with distilled water and dried to obtain a microcapsule curing agent with a product particle size of 0.5-12 μm. the

Mix 20 parts of microcapsule curing agent, 40 parts of acetone, 100 parts of E-42 epoxy resin, and 2 parts of aluminum oxide evenly to obtain a one-component epoxy resin adhesive. It can be cured within 1 hour at 150°C, and the storage period at room temperature can reach more than 50 days. the

Embodiment 8: Take polyvinyl alcohol as a dispersant, Tween and Span as an emulsifier, and chloroform as a solvent

In a fume hood, directly add 50mL of 0.2wt% polyvinyl alcohol aqueous solution, 100mL of 0.1wt% Tween and Span (1:1) aqueous solution into a 500ml three-necked flask equipped with an electric stirrer, a condenser tube and a thermometer, Disperse for 30min under mechanical stirring at /min to obtain a stable and uniform aqueous phase; add 1g of aniline and 0.5g of styrene-divinylbenzene copolymer to two beakers containing 20mL of chloroform respectively, and disperse in an ultrasonic instrument Homogenize until it dissolves to obtain an oil phase, and gradually drop the oil phase into a three-necked flask within 5 minutes. Stir for about 30 minutes to make the oil phase and water phase form a uniform and stable emulsion. Slowly raise the reaction temperature to 30°C and stir for 3 hours, then raise the temperature to 38°C and stir for more than 3 hours until the chloroform is completely volatilized. The suspension is centrifuged, washed with distilled water and dried to obtain a microcapsule curing agent with a product particle size of 3-13 μm. the

Mix 25 parts of the obtained microcapsule curing agent, 40 parts of methyl ethyl ketone, 100 parts of EP-4901 epoxy resin, and 1 part of clay powder to obtain a one-component epoxy resin adhesive. It can be cured within 30 minutes at 100°C, and the storage period at room temperature can reach more than 45 days. the

Comparative example 1: gelatin without dispersant

In a fume hood, directly add 100mL of 0.2wt% sodium dodecylbenzenesulfonate aqueous solution into a 500ml three-necked flask equipped with an electric stirrer, a condenser tube and a thermometer, and disperse for 30min under mechanical stirring at 500r/min to obtain a stable Uniform water phase; add 1g of diaminodiphenylmethane and 1g of polymethyl methacrylate to two beakers containing 20mL of dichloromethane respectively, and disperse evenly in an ultrasonic instrument until it dissolves to obtain an oil phase. After 5min The oil phase was gradually added dropwise into the three-necked flask. Stir for about 30 minutes to make the oil phase and water phase form a uniform and stable emulsion. Slowly raise the reaction temperature to 30°C and stir for 3 hours, then raise the temperature to 38°C and stir for more than 3 hours until the dichloromethane volatilizes completely. The suspension is centrifuged, washed with distilled water and dried to obtain a microcapsule curing agent with a product particle size of 0.5-25 μm. the

Mix 50 parts of the obtained microcapsule curing agent, 50 parts of acetone, 100 parts of E-51 epoxy resin, and 1 part of nano-silica to obtain a one-component epoxy resin adhesive. It can be cured within 1 hour at 120°C, and the storage period at room temperature can reach more than 42 days. the

Comparative example 2: direct heating

In a fume hood, directly add 40mL of 0.2wt% polyvinyl alcohol aqueous solution and 80mL of 0.2wt% sodium dodecylbenzenesulfonate aqueous solution into a 500ml three-necked flask equipped with an electric stirrer, a condenser tube and a thermometer, and heat at 1000r/min Disperse for 30 minutes under mechanical stirring to obtain a stable and uniform water phase; respectively add 1 g of N-aminoethylpiperazine and 2 g of polystyrene to two beakers filled with 20 mL of dichloromethane, and disperse evenly in an ultrasonic instrument until they dissolve The oily phase was obtained, and the oily phase was gradually added dropwise to the three-necked flask within 5 minutes. Stir for about 30 minutes to make the oil phase and water phase form a uniform and stable emulsion. Slowly raise the reaction temperature to 38°C and stir for 6h until the chloroform is completely volatilized. The suspension is centrifuged, washed with distilled water and dried to obtain a microcapsule curing agent with a product particle size of 0.5-18 μm. the

Uniformly mix 15 parts of the obtained microcapsule curing agent, 40 parts of methyl ethyl ketone, 100 parts of EP-4930 epoxy resin, and 2 parts of nano-calcium carbonate to obtain a one-component epoxy resin adhesive. It can be cured within 30 minutes at 120°C, and the storage period at room temperature can reach more than 40 days. the

It can be seen from the comparative examples that without adding a dispersant or directly raising the temperature will lead to a broadening of the microcapsule distribution, which is not conducive to the dispersion of the microcapsules in the one-component adhesive, and also affects the room temperature storage of the one-component adhesive to a certain extent. Expect. the

Now analyze in conjunction with accompanying drawing, embodiment and table 1 and table 2:

Fig. 1 is the infrared spectrogram of DDM, DDM-PMMA microcapsule and PMMA microsphere. Spectral line (b) is the infrared spectral line of DDM-PMMA microcapsules, and spectral line (c) is the infrared spectral line of PMMA. It can be seen from spectral lines (b) and (c): at 2997cm ^-1 , 2953cm Near ^-1 is the vibration absorption peak of CH, 1730cm ^-1 is -C=O stretching vibration absorption peak, 1241cm ^-1 and 1150cm ^-1 are CO stretching vibration absorption peaks, that is, there is wall material PMMA in the microcapsules. The spectral line (a) is the infrared spectral line of the epoxy resin curing agent DDM, the stretching vibration peak of NH near 3443cm ^-1 , and the C=C on the skeleton of the benzene ring near 1628cm ^-1 , 1514cm ^-1 and 1431cm ^-1 In the stretching vibration band, the stretching vibration peak of CN is around 1280 cm ^-1 , and the out-of-plane bending vibration peak of NH is around 900 cm ^-1 ~ 766 cm ^-1 . Spectrum line (b) In DDM-PMMA microcapsules, characteristic peaks that do not exist in spectral line (c) PMMA appear at 3443cm ^-1 , 1628cm ^-1 , 1514cm ^-1 , 1431cm ^{-1 ,} etc., and these characteristic peaks are It is the characteristic peak of spectral line (a) core material curing agent DDM. To sum up, DDM-PMMA does contain curing agent DDM.

From the component analysis of the DDM-PMMA microcapsules in Figure 2, it can be seen that the prepared microcapsules do contain the capsule core material DDM. In order to further obtain the exact content of DDM, we used thermogravimetric analysis to quantify this content, and the results are shown in Figure 2. Comprehensive analysis shows that: curve (a) is the thermal weight loss curve of the core material curing agent DDM, which decomposes from about 180 °C to about 300 °C; curve (b) is the thermal weight loss curve of the shell material PMMA, and its decomposition range It is roughly 180～420 ℃; Curve (c) is the thermal weight loss and differential curve of DDM-PMMA microcapsules, which is different from simple core material and wall material, and its decomposition curve shows two obvious decomposition steps, which is also It can be confirmed from its DTG curve that the first DTG peak appears at about 283 °C, which is attributed to the decomposition of DDM, while the other DTG peak appears at a temperature of about 431 °C, which is the decomposition area of PMMA capsule shell material. This study considered that when the PMMA in the DDM-PMMA microcapsules began to decompose, the DDM decomposition ended. From this, it can be calculated that the core material DDM content in the DDM-PMMA microcapsules is about 49.82wt%. the

The morphology of PMMA microspheres and DDM-PMMA microcapsules in Figure 3 was characterized by scanning electron microscopy (Figure 4). It can be seen from Figure 3(a) and 3(b) that PMMA microspheres and DDM-PMMA microcapsules are regular spherical, the particle size of PMMA microspheres is about 2.65 μm, and that of DDM-PMMA microcapsules is about 6.57 μm. All are very smooth, and the particle size of DDM-PMMA microcapsules is significantly larger than that of PMMA microspheres. At the same time, it can be seen from Figure 3(b) that the particle size distribution of DDM-PMMA microcapsules is relatively narrow, which ensures that the microcapsule curing agent can be uniformly dispersed in the epoxy resin to a certain extent, so as to play a better role. the

In addition, Figure 3(c) is a sample obtained after grinding the DDM-PMMA microcapsules, washing them thoroughly with DDM good solvent ethanol, and drying them. It can be seen from Figure 4(c) that the DDM-PMMA microcapsules have a capsule-core capsule-wall structure. In summary, DDM-PMMA microcapsules are core-shell microcapsules with DDM as the core and PMMA as the shell. the

In Figure 4, the DDM curing agent and DDM-PMMA microcapsules were prepared into a one-component adhesive system as shown in Table 1, and the DSC was measured respectively to study the curing reaction characteristics. The results are shown in Figure 4. It can be seen from the figure that the peak temperature (T _p ) of the E-51/DDM-PMMA microcapsule system is about 180°C, which is about 10°C behind that of the E-51/DDM system, which shows that the E-51/DDM-PMMA microcapsule system The curing agent coated with microcapsules can delay the curing reaction of epoxy resin. This is because: in the E-51/DDM system, DDM and epoxy resin are in direct contact, and there is no physical obstacle when the curing reaction occurs; while in the E-51/DDM-PMMA microcapsule system, the curing agent DDM It is wrapped in a PMMA container and cannot contact with epoxy resin. Only when PMMA softens and DDM penetrates through the pores on the membrane can it contact with it, so that a curing reaction occurs.

Storage stability at a certain temperature is a major advantage of microcapsule curing agents, therefore, latent performance is also an important performance index that must be investigated. At room temperature, according to the proportioning (mass parts) shown in Table 1, DDM-PMMA microcapsules and DDM were made into E-51/DDM-PMMA and E-51/DDM single sheets with epoxy resin E-51 respectively. After the component adhesive is fully stirred evenly, it is placed on the test bench, and when it is cured, its storage period at room temperature is measured. Due to the existence of the wall material, the amount of effective curing component is about 49.82wt% (by 50%) in the DDM-PMMA microcapsule, so the consumption (56phr) of the microcapsule curing agent in the E-51/DDM-PMMA microcapsule system ) is twice the amount of curing agent (28phr) in the E-51/DDM system. the

It can be seen from Table 1 that the E-51/DDM-PMMA one-component adhesive system has the longest storage period at room temperature, about 50 days; while the common E-51/DDM/PMMA and E-51/DDM resin systems Mostly cured after only 5 days. That is, the prepared DDM-PMMA microcapsule curing agent can greatly prolong the room temperature storage period of DDM curing agent, indicating that microencapsulation coating can effectively realize the isolation of active components (curing agent). After careful analysis and comparison of E-51/DDM/PMMA and E-51/DDM resin systems, it can also be found that the storage period of E-51/DDM/PMMA resin systems is slightly longer, which may be because the added PMMA can be used to a certain extent. It hinders the crosslinking reaction of DDM at room temperature and then cures. the

According to the ratio shown in Table 1, two kinds of one-component adhesives were prepared for bonding test, and solidified at 100°C/30min while cooling in the furnace. The obtained tensile shear strength values are listed in Table 2. the

As shown in Table 2, the average tensile shear strength of the E-51/DDM-PMMA one-component adhesive is 15.56MPa, which is higher than that of the E-51/2PZ two-component adhesive directly adding curing agent. The average tensile shear strength is 0.93MPa higher. This is because the PMMA in the E-51/DDM-PMMA one-component adhesive has a toughening effect, that is, the prepared E-51/DDM-PMMA one-component adhesive has good bonding performance . the

Table 1 Room temperature storage period of each one-component adhesive

Tensile shear strength of each adhesive in table 2

Claims (10)

1. preparation method who under middle temperature, causes the latency microcapsules curing agent that thermosetting epoxy resin solidifies is characterized in that step is following:

Step 1: in the container of electric mixer is housed, add 0.1～2wt% aqueous dispersant, 50～100mL, 0.1～2wt% emulsifier aqueous solution, 50～100mL disperses 30～60min to obtain water under the mechanical agitation of 500～1000r/min; Said emulsifying agent is one or more among neopelex, lauryl sodium sulfate and tween and the Si Ban; Said dispersant is one or more in gelatin or the polyvinyl alcohol;

Step 2: in 25～50mL volatile solvent is housed, add respectively 0.2～2g of core and wall material, and in Ultrasound Instrument, be uniformly dispersed to its dissolving and obtain oil phase, in 5～10min, oil phase is added drop-wise to the prepared aqueous phase of step 1 gradually; Above-mentioned water be 100～200 mass parts, oil phase be 50～100 mass parts, water oil be in a ratio of 1: 2～2: 1; Said core is one or more in boron trifluoride and amine complex compound thereof, aromatic polyamine, polyamines salt, aliphatic cyclic amine, organic acid hydrazides etc.; Said wall material is one or more in polyethylene base class microballoon, polystyrene type microballoon, the polyacrylate microballoon; Said volatile solvent is one or more in carrene, chloroform or the acetone;

Step 3: stirring and emulsifying 30～60min, 3～5h is stirred in rising reaction temperature to 30～35 ℃, is warming up to 38～40 ℃ again and stirs above suspension is centrifugal to the volatile solvent volatilization, the distilled water washing of 3～5h, is drying to obtain product microcapsules curing agent.

2. according to the said preparation method who under middle temperature, causes the latency microcapsules curing agent of thermosetting epoxy resin curing of claim 1, it is characterized in that: said boron trifluoride and amine complex compound thereof are one or more in boron triflouride-mono aminoethane, boron trifluoride-n-butylamine, boron trifluoride-Bian amine, boron trifluoride-chloroaniline, boron trifluoride-dimethylaniline, boron trifluoride-diphenylamines, boron trifluoride-aniline, boron trifluoride-para-totuidine, boron trifluoride-ortho-aminotoluene, boron trifluoride-n-butylamine, boron trifluoride-ethamine or the boron trifluoride-piperidines.

3. according to the said preparation method who under middle temperature, causes the latency microcapsules curing agent of thermosetting epoxy resin curing of claim 1, it is characterized in that: said aromatic polyamine is one or more in MDA, diaminourea dimethoxy diphenyl-methane, diamino-dicyclohexyl methane, diaminourea dichloro diphenyl methane, m-phenylene diamine (MPD) or the DADPS.

4. according to the said preparation method who under middle temperature, causes the latency microcapsules curing agent of thermosetting epoxy resin curing of claim 1, it is characterized in that: one or more in the Phenylphosphine hydrochlorate that said polyamines salt is o-phenylenediamine, m-phenylene diamine (MPD), aniline, MDA, p-phenylenediamine (PPD), m-xylene diamine, piperazine, benzylamine or ethylenediamine.

5. according to the said preparation method who under middle temperature, causes the latency microcapsules curing agent of thermosetting epoxy resin curing of claim 1; It is characterized in that: said aliphatic cyclic amine is N-amine ethyl piperazidine, different fluorine that ketone diamines, 1; Two (aminomethyl) cyclohexanes, 4 of 3-, one or more in 4-diamino-dicyclohexyl methane or two (4-amino-3-methylcyclohexyl) methane.

6. according to the said preparation method who under middle temperature, causes the latency microcapsules curing agent of thermosetting epoxy resin curing of claim 1, it is characterized in that: said organic acid hydrazides is one or more in propionic acid hydrazides, butyric acid hydrazides, caproic acid hydrazides, sad hydrazides, adipic dihydrazide, sebacic dihydrazide, isophthalic dihydrazide, salicylic acid hydrazides or the phenyl amino propionic acid hydrazides.

7. according to the said preparation method who under middle temperature, causes the latency microcapsules curing agent of thermosetting epoxy resin curing of claim 1, it is characterized in that: said polyethylene base class is one or more in polyvinyl acetate, polyvinyl alcohol or the Pioloform, polyvinyl acetal.

8. according to the said preparation method who under middle temperature, causes the latency microcapsules curing agent of thermosetting epoxy resin curing of claim 1, it is characterized in that: said polystyrene type is one or more in polystyrene, SAN, styrene-methylmethacrylate copolymer or the styrene diethylene benzene copoly mer.

9. according to the said preparation method who under middle temperature, causes the latency microcapsules curing agent that thermosetting epoxy resin solidifies of claim 1, it is characterized in that: said polyacrylic is polymethyl methacrylate, methyl methacrylate and styrol copolymer, gather methyl or gather in the Mecrilate one or more.

10. one kind is utilized said any of claim 1～9 under middle temperature, to cause the method that latency microcapsules curing agent that thermosetting epoxy resin solidifies prepares intermediate temperature setting single-component epoxy resin adhesive; It is characterized in that the latency microcapsules curing agent and 1～20 mass parts filler that the thermosetting polyfunctional epoxy resin, 5～100 mass parts non-activated thinners, 1～100 mass parts that under the 100 mass parts room temperatures are liquid state are caused thermosetting epoxy resin curing under middle temperature mix, and obtain long latency intermediate temperature setting single-component epoxy resin adhesive; Said thermosetting polyfunctional epoxy resin is one or more in bisphenol-A glycidol ether or the Bisphenol F glycidol ether; Said non-activated thinner is one or more in acetone, MEK, cyclohexanone, ethanol or the toluene; Said filler is one or more in nano silicon, nano-calcium carbonate, aluminium oxide or the potter's clay powder.

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