Microcapsules and compositions comprising the same

Abstract

This invention provides a microcapsule and a composition comprising the same. The microcapsule comprises an organometallic promoter and a polyurea, wherein the polyurea encapsulates the organometallic promoter. The content of the organometallic promoter can be from 5 wt% to 50 wt%, based on the total weight of the microcapsule.

Description

Technical Field

[0001] This invention relates to a microcapsule and a composition comprising the same. Background Technology

[0002] Epoxy resins are widely used in insulating materials, sealing materials, adhesives, and conductive materials for electronic and electrical components. In particular, with the increasing functionality, shrinking size and thickness of electronic devices, as well as the miniaturization of semiconductor chips and the increase in circuit density, higher demands are being placed on the production efficiency, portability, and reliability of electronic devices in mobile applications.

[0003] Traditional epoxy resin compositions used in semiconductor packaging require high-temperature, long-duration curing (curing temperature approximately 150℃~180℃, curing time approximately 2~4 hours), leading to increased carbon emissions. Under the trend towards net-zero carbon emissions, the semiconductor industry will inevitably face the need for carbon reduction.

[0004] Due to the low reactivity between epoxy resins and aromatic amine curing agents, high curing temperatures and long curing times are generally required to manufacture high-performance crosslinked polymer materials. Increasing curing temperature and time leads to higher processing costs and reduced productivity, thus limiting the application of aromatic amine curing agents. Accelerators used in epoxy resin compositions can speed up the reaction and allow it to proceed at lower temperatures. However, epoxy resin compositions with conventional accelerators often exhibit poor storage stability, affecting the room temperature stability and pot life of the resin composition.

[0005] Therefore, the industry is actively developing novel epoxy resin compositions. Summary of the Invention

[0006] According to embodiments of the present invention, a microcapsule is provided. The microcapsule comprises an organometallic promoter and a polyurea, wherein the polyurea encapsulates the organometallic promoter. The content of the organometallic promoter can be from 5 wt% to 50 wt%, based on the total weight of the microcapsule. The organometallic promoter is an organotin compound, an organochromium compound, or a combination thereof.

[0007] According to embodiments of the present invention, the present invention also provides a composition (e.g., a thermosetting composition) comprising a liquid aromatic epoxy resin; an aromatic polyamine compound; and the microcapsules described in the present invention. Attached Figure Description

[0008] Figure 1This is a focused ion beam scanning electron microscope (FIB-SEM) image of the microcapsule (1) described in this invention. Detailed Implementation

[0009] The microcapsules and compositions described below provide a detailed description of the present invention. It should be understood that the following description provides many different embodiments for implementing different variations of the invention. The specific components and arrangements described below are merely illustrative of the invention. Of course, these are only examples and not limitations of the invention. In this invention, the term "about" means that the specified amount can be increased or decreased by an amount that is generally and reasonably understood by those skilled in the art.

[0010] The use of ordinal numbers such as "first," "second," "third," etc., in the specification and claims to modify the components of the claims does not imply or represent any prior ordinal number of the claimed component, nor does it represent the order of one claimed component with another, or the order of manufacturing methods. The use of these ordinal numbers is only to enable a claimed component with a certain name to be clearly distinguished from another claimed component with the same name.

[0011] In the accompanying drawings, the shape or thickness of the embodiments may be enlarged and indicated in a simplified or convenient manner. Furthermore, portions of the components in the drawings will be described separately. It is worth noting that components not shown or described in the drawings are those known to those skilled in the art. Moreover, specific embodiments are merely to illustrate particular ways of using the invention and are not intended to limit the invention. Unless otherwise defined, all terms used in this invention (including technical and scientific terms) have the same meaning as commonly understood by those skilled in the art to which this invention pertains. It will be further understood that terms defined in common dictionaries should be interpreted as having the same meaning as in the relevant art and the content of this invention, and unless explicitly defined herein, will not be interpreted in an idealized or overly formal sense.

[0012] This invention provides a microcapsule applicable to epoxy resin curing processes (e.g., one-liquid encapsulation resin systems). The microcapsule comprises an organometallic accelerator and polyurea, wherein the organometallic accelerator can be encapsulated by the polyurea to form the microcapsule. Furthermore, this invention provides a composition (e.g., an epoxy resin composition) comprising the microcapsule described herein. Because the organometallic accelerator contained in the microcapsule is protected by the polyurea at room temperature, it will not react with other components of the composition. When the composition is heated, the microcapsule softens, releasing the accelerator and accelerating the curing of the composition, thereby reducing the reaction temperature and saving power consumption. Based on the above, by introducing the microcapsule described herein and combining it with liquid aromatic epoxy resin and aromatic polyamine compounds, the composition of this invention can be rapidly cured (e.g., 2 to 4 hours) at relatively low temperatures (e.g., 130°C to 150°C), while exhibiting good reactivity and storage stability.

[0013] According to embodiments of the present invention, the microcapsule comprises an organometallic accelerator and a polyurea. The polyurea encapsulates the organometallic accelerator and the polyurea, thus forming the microcapsule. According to embodiments of the present invention, the microcapsule may have an inner layer of the organometallic accelerator and an outer layer of polyurea encapsulation, or an inner layer of a mixture of the polyurea and the organometallic accelerator and an outer layer of polyurea encapsulation.

[0014] According to embodiments of the present invention, the organometallic accelerator content of the microcapsule can be from 5 wt% to 50 wt% (e.g., 10 wt%, 15 wt%, 20 wt%, 25 wt%, 30 wt%, 35 wt%, 40 wt%, or 45 wt%), based on the weight of the microcapsule. When the organometallic accelerator content is too low, the amount of accelerator released by the microcapsule after heating is too low, which cannot effectively increase the reactivity of the composition. When the organometallic accelerator content of the microcapsule is too high, its encapsulation effect may be poor.

[0015] According to embodiments of the present invention, the organometallic accelerator may be an organotin accelerator, an organochromium accelerator, or a combination thereof. According to embodiments of the present invention, the organotin(II) compound may be a divalent tin metal complex, such as a divalent tin metal complex having a carboxylate ligand.

[0016] According to embodiments of the present invention, the organometallic accelerator is stannous octoate, tin(II)acetylacetonate, tin(II)acetate, tin(II)oxalate, chromium(III)octoate, chromium(III)acetylacetonate, chromium(III)acetate, chromium(III)oxalate, or a combination thereof.

[0017] According to an embodiment of the present invention, the polyurea may be a polymer of an isocyanate prepolymer. According to an embodiment of the present invention, the isocyanate prepolymer may have the structure shown in formula (I).

[0018] ,

[0019] Where n can be 1, 2, 3, 4, 5, or 6; and R 1 Can be used independently

[0020] According to embodiments of the present invention, the particle size distribution D50 of the microcapsules can be from 0.5 μm to 600 μm (e.g., 1 μm, 5 μm, 10 μm, 20 μm, 50 μm, 80 μm, 100 μm, 200 μm, 300 μm, 400 μm, 450 μm, 500 μm, or 550 μm). This allows the resulting composition containing the microcapsules to have room temperature storage safety, and the microcapsules can release a promoter upon heating, increasing the reactivity of the composition. The particle size distribution D50 of the microcapsules is measured using dynamic light scattering (DLS).

[0021] According to embodiments of the present invention, a thermosetting composition, such as a thermosetting epoxy resin composition, is also provided. According to embodiments of the present invention, the composition comprises a liquid aromatic epoxy resin, an aromatic polyamine compound, and the microcapsules described herein.

[0022] According to embodiments of the present invention, the liquid aromatic epoxy resin of the present invention may be a liquid aromatic epoxy resin having at least two terminal epoxy groups. According to embodiments of the present invention, the liquid aromatic epoxy resin of the present invention refers to an aromatic epoxy resin that is liquid at room temperature (e.g., about 18°C ​​to 35°C). According to embodiments of the present invention, the liquid aromatic epoxy resin may have at least two epoxy functional groups. For example, the liquid aromatic epoxy resin grease of the present invention includes bisphenol A type epoxy resin, bisphenol F type epoxy resin, naphthalene type epoxy resin, aminophenol type epoxy resin, or a combination thereof. For example, the structure of the bisphenol A type epoxy resin may be...

[0023]

[0024] (n≥1); and the structure of bisphenol F epoxy resin can be:

[0025]

[0026] (n≥1).

[0027] According to embodiments of the present invention, the aromatic polyamine compound of the present invention may be a liquid aromatic polyamine compound having at least two terminal amine groups. For example, the aromatic polyamine compound of the present invention may be diethyltoluenediamine, dimethylthiotoluenediamine, 4,4'-methylenebis(2-ethyl)aniline, poly-1,4-butanediol bis(4-aminobenzoate), or a combination thereof.

[0028] According to embodiments of the present invention, the polymer obtained after curing the composition of the present invention comprises bonds formed by the uniform interleaving of epoxy resin and aromatic polyamine compound. Therefore, the composition of the present invention comprises a liquid aromatic epoxy resin having at least two terminal epoxy groups and an aromatic compound having at least two terminal amine groups.

[0029] According to an embodiment of the present invention, the equivalent ratio of the liquid aromatic epoxy resin to the aromatic polyamine compound can be from 100:80 to 100:100.

[0030] According to embodiments of the present invention, the content of the microcapsules in the composition of the present invention can be from 0.5 wt% to 8 wt% (e.g., 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%, 6 wt%, or 7 wt%), based on the total weight of the liquid aromatic epoxy resin. When the microcapsule content is too low, the degree of crosslinking of the cured product obtained under lower temperature curing conditions (e.g., reaction at 130°C for 4 hours) is poor. When the microcapsule content is too high, the composition is less suitable for storage at room temperature.

[0031] According to embodiments of the present invention, the composition may further include 0.1 to 10 wt% (e.g., 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%, 6 wt%, or 7 wt%) of a coupling agent, based on the weight of the liquid aromatic epoxy resin. For example, the coupling agent may include glycidyl etheroxypropyltrimethoxysilane, trimethoxy[2-(7-oxabicyclo[4.1.0]hept-3-yl)ethyl]silane, 3-glycidyl oxypropylmethyldiethoxysilane, n-hexyltrimethoxysilane, 3-thiopropyltrimethoxysilane, aminoethylaminopropyltrimethoxysilane, or combinations thereof.

[0032] To make the above-mentioned and other objects, features and advantages of the present invention more apparent and understandable, preferred embodiments are described below in detail with reference to the accompanying drawings.

[0033] Preparation of isocyanate prepolymers

[0034] Preparation Example 1: Isocyanate Prepolymer (1)

[0035] Isophorone diisocyanate (IPDI) (0.21 mole), 2-ethyl-2-hydroxymethyl-1,3-propanediol (TMP) (0.07 mole), and anhydrous ethyl acetate (50 ml) were added to a reaction flask. The reaction flask was heated to 60°C under nitrogen atmosphere. After the isophorone diisocyanate and 2-ethyl-2-hydroxymethyl-1,3-propanediol were completely dissolved in ethyl acetate by continuous stirring, one drop of dibutyltin dilaurate (DBTDL) was added to the reaction flask. The reaction flask was heated to 75°C and reacted for 8 hours. The ethyl acetate solvent was then removed by vacuum system to obtain isocyanate prepolymer (1) (white solid).

[0036] The reaction equations for the above reactions are shown below:

[0037]

[0038] The isocyanate prepolymer (1) was titrated according to the method specified in ASTM D2572 (using 0.1N hydrochloric acid), and the isocyanate group content of the isocyanate prepolymer (1) was found to be approximately 15 wt%.

[0039] Preparation Example 2: Isocyanate Prepolymer (2)

[0040] 0.03 mol of 4,4'-Methylene diphenyl diisocyanate (MDI) and 0.07 mol of 2-ethyl-2-hydroxymethyl-1,3-propanediol (TMP) were added to 20 ml of anhydrous ethyl acetate. The mixture was stirred thoroughly at 50 °C to obtain a diphenylmethane diisocyanate solution. 0.01 mol of 2-ethyl-2-hydroxymethyl-1,3-propanediol (TMP) was added to 50 ml of anhydrous ethyl acetate. The mixture was stirred thoroughly to obtain a 2-ethyl-2-hydroxymethyl-1,3-propanediol solution. The 2-ethyl-2-hydroxymethyl-1,3-propanediol solution was added dropwise to the diphenylmethane diisocyanate solution under nitrogen atmosphere. Next, the obtained product was heated to 50°C and reacted for 5 hours. Then, the ethyl acetate solvent was dried using a vacuum system to obtain isocyanate prepolymer (2) (white solid).

[0041] The reaction equations for the above reactions are shown below:

[0042]

[0043] The isocyanate prepolymer (2) was titrated according to the method specified in ASTM D2572 (using 0.1N hydrochloric acid), and the isocyanate group content of the isocyanate prepolymer (2) was found to be approximately 14 wt%.

[0044] Preparation of microcapsules

[0045] Preparation Example 3: Microcapsules (1)

[0046] A first solution was obtained by mixing deionized water (330 g), sodium dodecyl sulfate (SDS) (1.23 g), and polyvinyl alcohol (with a molecular weight distribution ranging from approximately 13,000 to 23,000 kg / mol) (3.96 g). A second solution was obtained by mixing isocyanate prepolymer (1) (13.2 g), stannous octoate (Sn(Oct)2) (13.2 g) (as an accelerator), and anhydrous ethyl acetate (45 g).

[0047] Next, using an emulsifier, the first solution (aqueous phase) and the second solution (organic phase) were emulsified at a speed of 10,000 rpm. After 5 minutes, the resulting emulsified solution was introduced into a reaction vessel and heated to 70°C under nitrogen atmosphere. The isocyanate prepolymer (1) was polymerized (forming polyurea) and coated with stannous octoate for 15 hours under mechanical stirring (speed of 500 rpm). The product was then separated by centrifugation, and the precipitate was washed three times with deionized water to completely remove the additives (sodium dodecyl sulfate and polyvinyl alcohol). After drying the product under vacuum at 35°C, microcapsules (1) were obtained.

[0048] The microcapsules (1) obtained were observed using focused ion beam scanning electron microscopy (FIB-SEM). A platinum electroplating layer (approximately 300-400 nm thick) was pre-formed to facilitate nanoscale cutting and observation of the sample by the FIB ion beam at specific locations. The results are as follows: Figure 1 As shown. Next, the cross-section of the obtained microcapsule (1) was analyzed by energy dispersive X-ray spectroscopy (EDS), which revealed that the microcapsule (1) contained tin.

[0049] Preparation Example 4: Microcapsules (2)

[0050] Preparation Example 4 was carried out according to the preparation method of microcapsules (1) described in Preparation Example 3, except that the amount of isocyanate prepolymer (1) was reduced from 13.2 g to 11.5 g and the amount of stannous octoate was increased from 13.2 g to 14.9 g, resulting in microcapsules (2).

[0051] Preparation Example 5: Microcapsules (3)

[0052] Preparation Example 5 was carried out according to the preparation method of microcapsules (1) described in Preparation Example 3, except that the amount of isocyanate prepolymer (1) was reduced from 13.2 g to 10.1 g and the amount of stannous octoate was increased from 13.2 g to 16.3 g, resulting in microcapsules (3).

[0053] Preparation Example 6: Microcapsules (4)

[0054] Preparation Example 5 was carried out according to the preparation method of microcapsule (1) described in Preparation Example 3, except that 13.2 g of isocyanate prepolymer (1) was replaced with 15.8 g of isocyanate prepolymer (2), and the amount of stannous octoate was reduced from 13.2 g to 10.5 g, to obtain microcapsule (4).

[0055] Preparation Example 7: Microcapsules (5)

[0056] Preparation Example 7 was carried out according to the preparation method of microcapsules (1) described in Preparation Example 3, except that 13.2 g of isocyanate prepolymer (1) was replaced with 23.4 g of isocyanate prepolymer (2), and the amount of stannous octoate was reduced from 13.2 g to 2.6 g, to obtain microcapsules (5).

[0057] Preparation Example 8: Microcapsules (6)

[0058] Preparation Example 8 was carried out according to the preparation method of microcapsules (1) described in Preparation Example 3, except that the amount of isocyanate prepolymer (1) was reduced from 13.2 g to 5.0 g and the amount of stannous octoate was reduced from 13.2 g to 11.6 g, and microcapsules (6) were obtained.

[0059] Preparation Example 9: Microcapsules (7)

[0060] Preparation Example 9 was carried out according to the preparation method of microcapsules (1) described in Preparation Example 3, and the reaction was carried out by mechanical stirring (500 rpm) only (without using an emulsifying homogenizer) to obtain microcapsules (7).

[0061] Preparation Example 10: Microcapsules (8)

[0062] Preparation Example 10 was carried out according to the preparation method of microcapsules (1) described in Preparation Example 3, except that stannous octoate was replaced with chromium(III) octoate (Cr(Oct)3) (as a promoter) to obtain microcapsules (8).

[0063] Preparation Example 11:

[0064] Preparation Example 11 was carried out according to the preparation method of microcapsules (1) described in Preparation Example 3, except that stannous octoate was replaced with zirconium tetrakis (acetylacetonate), Zr(acac)4 (as an accelerator), and isocyanate prepolymer (1) was replaced with isocyanate prepolymer (2). After drying and centrifugation, it was observed that the product aggregated and could not yield particulate microcapsules.

[0065] Preparation Example 12:

[0066] Preparation Example 11 was carried out according to the preparation method of microcapsules (1) described in Preparation Example 3. Except that stannous octoate was replaced with zinc acetylacetonate (Zn(acac)2) (as a promoter) after drying and centrifugation, it was observed that the product aggregated and granular microcapsules could not be obtained.

[0067] Preparation Example 13:

[0068] Preparation Example 11 was carried out according to the preparation method of microcapsules (1) described in Preparation Example 3, except that stannous octoate was replaced with dibutyltin dilaurate (DBTDL) (as an accelerator). After drying and centrifugation, it was observed that the product aggregated and could not yield granular microcapsules.

[0069] Next, the particle size distribution D50 of microcapsules (1) to (8) was measured, and the weight percentage of the promoter in microcapsules (1) to (8) was evaluated. The results are shown in Table 1. Here, the particle size distribution D50 of the microcapsules was measured by dynamic light scattering (DLS). The weight percentage of the promoter in the microcapsules was evaluated by solvent extraction, which included the following steps. The purified and dried microcapsules (weight W0) were mixed with anhydrous ethyl acetate. The resulting mixture was heated under reflux at 75°C and stirred for 8 hours. After cooling to room temperature, the solid and liquid were separated by centrifugation, and the solid was collected. The solid was then washed with ethyl acetate and centrifuged again. After repeating the above steps twice, the resulting solid (polyurea) was dried under vacuum at 35°C, and the resulting product was weighed after drying (weight W1). Finally, the promoter content of the microcapsules was calculated using formula (1).

[0070]

[0071] Table 1

[0072]

[0073]

[0074] Table 1 shows that the higher the weight ratio of the accelerator to the isocyanate prepolymer used to prepare the microcapsules, the higher the accelerator content of the resulting microcapsules. Furthermore, as shown in Preparation Examples 3 and 9, the particle size of the obtained microcapsules can be controlled by adjusting the experimental parameters of mixing the first solution (aqueous phase) and the second solution (organic phase).

[0075] thermosetting compositions

[0076] Example 1: Thermosetting Composition (1)

[0077] Bisphenol F type epoxy compound (trade name EXA-830LVP, manufactured by DIC) (average epoxy equivalent weight (EEW) of 162) and aminophenol type epoxy resin (trade name JER) were used. TM 630 (manufactured by Mitsubishi Chemical) (average epoxy equivalent weight (EEW) of 96 g / equivalent), 4,4'-methylenebis(2-ethylaniline) (trade name KHAA, manufactured by Nippon Kayaku), diethyltoluene diamine (manufactured by Aldrich), glycidoxypropyltrimethoxysilane (as a coupling agent) The agent () and microcapsules (1) were mixed in a stirrer at room temperature to obtain a thermosetting composition (1). Here, the equivalent ratio of bisphenol F type epoxy compound, aminophenol type epoxy resin, 4,4'-methylenebis(2-ethyl)aniline, and diethyltoluenediamine is 9:1:8:2; and the amount of coupling agent added is 1 wt%, and the amount of microcapsules (1) added is 1 wt%, based on the total weight of the bisphenol F type epoxy compound and the aminophenol type epoxy resin.

[0078] Example 2: Thermosetting Composition (2)

[0079] Example 2 was prepared according to the method of preparing the thermosetting composition (1) described in Example 1, except that the amount of microcapsules (1) was increased from 1 wt% to 3 wt% to obtain the thermosetting composition (2).

[0080] Example 3: Thermosetting Composition (3)

[0081] Example 3 was prepared according to the method of preparing the thermosetting composition (1) described in Example 1, except that the amount of microcapsules (1) was increased from 1 wt% to 5 wt% to obtain the thermosetting composition (3).

[0082] Comparative Example 1: Thermosetting Composition (4)

[0083] Comparative Example 1 was prepared according to the method of preparing the thermosetting composition (1) described in Example 1, except that microcapsules (1) were not added, and a thermosetting composition (4) was obtained.

[0084] Comparative Example 2: Thermosetting Composition (5)

[0085] Comparative Example 2 was prepared according to the method of preparing the thermosetting composition (1) described in Example 1, except that the microcapsules (1) were replaced with stannous octoate (Sn(Oct)2) to obtain the thermosetting composition (5).

[0086] Viscosity stability test

[0087] The viscosity stability of thermosetting compositions (1) to (5) was evaluated, and the results are shown in Table 2. The viscosity stability was evaluated as follows: First, immediately after the thermosetting composition was prepared, its viscosity (V1) at 25°C was measured. Then, after the thermosetting composition was placed at 25°C for 7 hours, its viscosity (V2) was measured again, and the viscosity increase of thermosetting composition (1) was calculated ([(V2-V1) / V1] x 100%). The viscosity was measured using a viscometer (Brookfield DV-III ultra).

[0088] Reactivity analysis

[0089] The gel time of thermosetting compositions (1) to (5) was evaluated, and the results are shown in Table 2. The gel time was evaluated as follows: the viscosity of the thermosetting composition was analyzed over time using a gel testing machine (temperature set at 130°C), and the gel time was defined as the point at which the viscosity of the thermosetting composition rapidly increased.

[0090] Table 2

[0091]

[0092]

[0093] As shown in Table 2, compared with Comparative Example 1, since the thermosetting compositions (1) to (3) of Examples 1 to 3 contain the microcapsules described in this invention, the resulting thermosetting compositions can be rapidly gelled at relatively low temperatures (gelling time of less than 21 minutes at 130°C) while maintaining storage stability at room temperature (viscosity increase of less than 25% after 7 hours at room temperature). Thus, the thermosetting compositions of Examples 1 to 3 are not rendered unusable in product processes due to viscosity increase, and the microcapsules they contain can increase the reaction rate between the epoxy resin and the aromatic amine curing agent, allowing the thermosetting compositions of this invention to cure at lower temperatures and shorten curing time (increasing yield and reducing energy consumption). Furthermore, compared with Examples 1 to 3, since the thermosetting composition (5) of Comparative Example 2 uses an uncoated accelerator (i.e., stannous octoate (Sn(Oct)2) instead of microcapsules and directly mixed with the epoxy resin and aromatic amine curing agent), the viscosity increase of the resulting thermosetting composition (5) is as high as 153%. However, such poor viscosity stability will increase the difficulty of the process and reduce the product yield when the thermosetting composition (5) is applied to subsequent processes.

[0094] Evaluation of curing conditions and post-curing properties of thermosetting compositions

[0095] Example 4

[0096] Two stainless steel molds (0.5mm x 1cm x 10cm in size) were taken, and the thermosetting composition (1) was placed into each mold. Next, one mold was placed in an oven and the thermosetting composition (1) was baked at 130°C for 4 hours to obtain a hardened layer (1). Then, the other mold was placed in an oven and the thermosetting composition (1) was baked at 150°C for 2 hours to obtain a hardened layer (2).

[0097] Example 5

[0098] Example 5 was prepared according to the method of preparing the hardened layers (1) and (2) described in Example 4, except that the thermosetting composition (1) was replaced by the thermosetting composition (2) to obtain the hardened layers (3) and (4).

[0099] Example 6

[0100] Example 6 was prepared according to the method of preparing the hardened layers (1) and (2) described in Example 4, except that the thermosetting composition (1) was replaced by the thermosetting composition (3) to obtain the hardened layers (5) and (6).

[0101] Comparative Example 3

[0102] Take three stainless steel molds (0.5mm x 1cm x 10cm in size) and place the thermosetting composition (4) into each mold. Then, place one stainless steel mold in an oven and bake the thermosetting composition (4) at 130°C for 4 hours to obtain a hardened layer (7). In addition, place the second stainless steel mold in an oven and bake the thermosetting composition (4) at 150°C for 2 hours to obtain a hardened layer (8). In addition, place the third stainless steel mold in an oven and bake the thermosetting composition (4) at 150°C for 4 hours to obtain a hardened layer (9).

[0103] Comparative Example 4

[0104] The thermosetting composition (5) was placed into a stainless steel mold. The stainless steel mold was then placed in an oven and baked at 130°C for 4 hours to obtain a hardened layer (10). The hardened layers (1) to (10) were then cut into specimens with dimensions of 0.5 mm x 1 cm x 7 cm, and their elastic modulus and glass transition temperature (Tg) were measured. The results are shown in Table 3. The elastic modulus and glass transition temperature were measured using a dynamic mechanical analyzer (DMA).

[0105] Table 3

[0106]

[0107]

[0108] The curing conditions for the hardened layers (1), (3), (5), and (7) are also 130°C for 4 hours. Compared to the hardened layer (7), the hardened layers (1), (3), and (5) prepared using the thermosetting composition of the present invention have significantly higher glass transition temperatures (i.e., these hardened layers have a higher degree of crosslinking), indicating that the thermosetting composition of the present invention has relatively high reactivity at 130°C. Furthermore, if the hardened layer formed by the thermosetting composition (4) (i.e., without the addition of an accelerator) is to achieve the same degree of crosslinking as the hardened layer of the present invention, the curing temperature of the thermosetting composition (4) needs to be increased to 150°C and the curing time needs to be extended to 4 hours. On the other hand, compared to the hardened layer (10), although the thermosetting composition of the present invention uses microcapsules instead of accelerators, the microcapsules can release the accelerators located therein upon heating, and the thermosetting composition of the present invention can also be cured at 130°C while maintaining the high elastic modulus and glass transition temperature of the hardened layer.

[0109] In summary, because the organometallic accelerator contained in the microcapsules is protected by polyurea at room temperature, it will not react with other components of the composition. When the composition is heated, the microcapsules soften, releasing the accelerator and accelerating the curing of the composition, thereby reducing the reaction temperature and saving power consumption. Based on the above, by introducing the microcapsules described in this invention and combining them with liquid aromatic epoxy resin and aromatic polyamine compounds, the composition of this invention can be rapidly cured (e.g., 2 to 4 hours) at relatively low temperatures (e.g., 130°C to 150°C), while exhibiting good reactivity and storage stability.

[0110] Although the present invention has been disclosed above with reference to several embodiments, it is not intended to limit the present invention. Anyone with common knowledge in the art can make any modifications and refinements without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention shall be determined by the scope defined in the appended claims.

Claims

1. A microcapsule comprising: An organometallic accelerator, which is an organotin compound, an organochromium compound, or a combination thereof; and A polyurea, wherein the polyurea encapsulates the organometallic accelerator, wherein the content of the organometallic accelerator is 5 wt% to 50 wt%, based on the total weight of the microcapsule.

2. The microcapsule according to claim 1, wherein the organometallic promoter is stannous octoate, stannous acetylacetonate, stannous acetate, stannous oxalate, chromium octoate, chromium acetylacetonate, chromium acetate, chromium oxalate, or a combination thereof.

3. The microcapsule according to claim 1, wherein the polyurea is a polymer of an isocyanate prepolymer.

4. The microcapsule according to claim 3, wherein the isocyanate prepolymer has the structure shown in formula (I). ， wherein n is 1, 2, 3, 4, 5, or 6; and, R 1 independently 5. The microcapsule according to claim 1, wherein the particle size distribution D50 of the microcapsule is from 0.5 μm to 600 μm.

6. A composition comprising: A liquid aromatic epoxy resin; Aromatic polyamine compounds; and The microcapsules as described in any one of claims 1 to 5.

7. The composition according to claim 6, wherein the equivalent ratio of the liquid aromatic epoxy resin to the aromatic polyamine compound is 100:80 to 100:

100.

8. The composition according to claim 6, wherein the content of the microcapsules is from 0.5 wt% to 8 wt%, based on the total weight of the liquid aromatic epoxy resin.

9. The composition according to claim 6, wherein the liquid aromatic epoxy resin is a bisphenol A type epoxy resin, a bisphenol F type epoxy resin, a naphthalene type epoxy resin, an aminophenol type epoxy resin, or a combination thereof.

10. The composition according to claim 6, wherein the aromatic polyamine compound is diethyltoluenediamine, dimethylthiotoluenediamine, 4,4'-methylenebis(2-ethyl)aniline, poly-1,4-butanediol bis(4-aminobenzoate), or a combination thereof.

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