A rubber microcapsule, its preparation method and application

Abstract

The present invention provides a rubber microcapsule, its preparation method, and application, belonging to the field of polymer material technology. The rubber microcapsule of the present invention has a core-shell structure, wherein the shell is polystyrene and the core is liquid nitrile rubber dispersed with coated sulfur; the coated sulfur is sulfur coated with polystyrene on the surface; and the liquid nitrile rubber contains reactive end groups. By mixing the coated sulfur with the nitrile rubber containing reactive end groups and then coating the rubber particles with a polystyrene layer through suspension polymerization, rubber microcapsules with excellent toughening effects are produced. Epoxy resin compositions toughened with the rubber microcapsules exhibit excellent toughness, strength, and thermal properties.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer materials, in particular to a rubber microcapsule and a preparation method and application thereof. Background Art

[0002] Epoxy resin (EP) is a common thermosetting resin. With its excellent adhesion, chemical resistance, electrical insulation, good heat resistance, and mechanical properties, it is widely used in coatings, adhesives, electronics, composite materials, and other fields. It has become a current research hotspot for scholars.

[0003] However, epoxy resins generate high internal stress during the curing process and their molecular structure is too rigid, resulting in brittleness and poor toughness during use, which restricts their further use and development. Therefore, how to effectively improve the heat resistance and toughness of epoxy resins has become a research focus for scholars at home and abroad.

[0004] Rubber-toughened epoxy resins were one of the earliest methods studied and used as an effective method. Commonly used rubbers include nitrile rubber, polysulfide rubber, silicone rubber, and fluororubber. Liquid nitrile rubber has been the subject of extensive research. Liquid nitrile rubber can chemically crosslink with epoxy resin and has been a common toughening agent in recent years. Its toughening mechanism is that once dispersed within the resin matrix, the rubber acts as a mechanical rivet, bridging and terminating cracks, thereby achieving the toughening effect.

[0005] There are many reports on the use of liquid nitrile rubber to toughen epoxy resins, but most of them focus on the simple use of liquid rubber as a toughening agent. However, the use of a single liquid nitrile rubber to improve the toughness of epoxy resins still has the following drawbacks: (1) the introduced single liquid rubber toughening agent tends to aggregate in the epoxy resin system, resulting in the liquid rubber not being evenly dispersed in the epoxy resin matrix and prone to phase separation, which in turn affects the toughening effect of the epoxy resin; (2) while toughening the epoxy resin, the single liquid rubber will reduce its thermal performance, which is not conducive to the preparation of an epoxy resin composition with both high temperature resistance and good toughness.

[0006] Therefore, it is necessary to provide a toughening agent that has excellent toughening effect without affecting the heat resistance. Summary of the Invention

[0007] The present invention aims to overcome the drawback of poor toughening effect in the prior art and provide a rubber microcapsule. The coated microcapsule is prepared by coating a layer of coated sulfur on the surface of liquid rubber in which coated sulfur is dispersed. The coated microcapsule has good dispersibility in epoxy resin and has an excellent toughening effect, while also allowing the epoxy resin to maintain good heat resistance.

[0008] Another object of the present invention is to provide a method for preparing the rubber microcapsules.

[0009] Another object of the present invention is to provide applications of the rubber microcapsules.

[0010] To achieve the above object, the present invention adopts the following technical solutions:

[0011] A rubber microcapsule having a core-shell structure, wherein the shell is polystyrene and the core is liquid nitrile rubber dispersed with coated sulfur;

[0012] The coated sulfur is sulfur with polystyrene coated on the surface; the liquid nitrile rubber contains reactive end groups.

[0013] The present invention solves the problem of uneven distribution of vulcanizing agents in epoxy resin systems by introducing coated sulfur into the rubber. Furthermore, during the subsequent toughening of the epoxy resin, the addition of coated sulfur can effectively vulcanize the rubber and significantly improve the thermal properties of the epoxy resin.

[0014] Because the rubber surface is wrapped with a polystyrene coating, the aggregation of the rubber is effectively avoided, so that the nitrile rubber is well dispersed in the epoxy resin matrix, forming a relatively homogeneous system, which effectively improves the toughness of the epoxy resin.

[0015] The rubber microcapsules of the present invention can be well dispersed within the epoxy resin. When the material is subjected to external forces, they act as stress concentration points, causing the resin matrix around the rubber microcapsules to undergo plastic deformation, thereby achieving a toughening effect. Furthermore, the rubber microcapsules, as particulate morphology, easily form cavities when distributed within the epoxy resin. These cavities absorb energy during impact, thereby increasing fracture toughness by reducing local yield stress and inducing large-scale shear yield, thereby achieving a toughening effect. Therefore, by modifying epoxy resin with the rubber microcapsules of the present invention, epoxy resin materials with both excellent thermal properties and toughness can be produced.

[0016] The coated sulfur involved in this application can be purchased from the market, or can be prepared by oneself or by referring to the existing technology.

[0017] Optionally, the coated sulfur can be prepared by the following method:

[0018] The sulfur powder is uniformly dispersed in an organic solvent, and a suspending agent, a stabilizer, styrene and hydroxyethyl methyl methacrylate are added. After uniform stirring, an initiator and an organic solution containing cage-type polysilsesquioxane are added. The reaction is carried out under nitrogen conditions, and the solid is cooled to room temperature and then filtered. The sulfur powder on the surface of the filtered solid is removed, and the solid is vacuum dried to obtain sulfur coated with polystyrene.

[0019] Preferably, the average particle size of the rubber microcapsules is 1 to 1.5 μm.

[0020] Preferably, the weight of the shell accounts for 8 to 12 wt.% of the rubber microcapsule.

[0021] Preferably, the weight of the coated sulfur in the core accounts for 2 to 3.5 wt.% of the liquid nitrile rubber.

[0022] Preferably, the proportion of sulfur in the coated sulfur is 50 to 95 wt.%.

[0023] More preferably, the proportion of sulfur in the coated sulfur is 70-85 wt.%.

[0024] The weight percentage of sulfur in coated sulfur should be within an appropriate range. Sulfuric acid is the primary substance that promotes rubber vulcanization, thereby improving the thermal properties of epoxy resins. Therefore, the weight percentage of sulfur in coated sulfur should not be too low, as this will hinder effective vulcanization. However, as the sulfur content increases, the weight percentage of polystyrene coated on the surface decreases. This decrease in the coating ratio impairs the dispersibility of the sulfur and negatively impacts its vulcanization performance.

[0025] Preferably, the liquid nitrile rubber is at least one of epoxy-terminated nitrile rubber (ETBN), carboxyl-terminated liquid nitrile rubber (CTBN), and amino-terminated liquid nitrile rubber (ATBN).

[0026] The chemical structure of ETBN is The chemical structure of CTBN is The chemical structure of ATBN is

[0027] Preferably, the liquid nitrile rubber is ETBN.

[0028] The inventors have found that when ETBN is used, the rubber microcapsules prepared have a better toughening effect on epoxy resin.

[0029] The present invention also protects a method for preparing the above-mentioned rubber microcapsules, comprising the following steps:

[0030] Under the protection of inert gas, liquid nitrile rubber containing reactive end groups is mixed with water, a suspending agent and an initiator, and coated sulfur and styrene monomer are added in sequence under stirring to react, and the rubber microcapsules are obtained through post-treatment.

[0031] Preferably, the stirring speed is 200 to 400 rpm.

[0032] At a higher stirring speed, the coated sulfur can be well dispersed in the liquid nitrile rubber, and the styrene monomer can be polymerized into a shell with a more uniform coating effect.

[0033] Preferably, the volume ratio of the nitrile rubber containing reactive end groups to deionized water is 1:(3-6).

[0034] Preferably, the weight of the suspending agent is 1 to 3 wt.% of the nitrile rubber containing reactive end groups.

[0035] Preferably, the weight of the initiator is 0.1 to 0.3 wt.% of the nitrile rubber containing reactive end groups.

[0036] Preferably, the suspending agent is at least one of SiO2, acrylic acid, polyvinyl alcohol, sodium polyacrylate, methyl cellulose, gelatin, and sodium alginate.

[0037] Preferably, the initiator is at least one of an azo initiator and a peroxide initiator.

[0038] Optionally, the azo initiator is at least one of azobisisobutyronitrile (AIBN) and azobisisoheptanenitrile.

[0039] Optionally, the peroxide initiator is at least one of cumene hydroperoxide, dicumyl peroxide, di-tert-butyl peroxide, benzoyl peroxide, tert-butyl benzoyl peroxide, and diisopropyl peroxydicarbonate.

[0040] Preferably, the inert gas is nitrogen.

[0041] Preferably, the reaction temperature is 80-100° C., and the reaction time is 12-16 hours.

[0042] Carrying out the reaction at a relatively high temperature not only improves the reaction efficiency, but also allows the coated sulfur to be more tightly bonded to the nitrile rubber, resulting in a better toughening effect of the rubber microcapsules.

[0043] Preferably, the post-processing includes filtration, separation and drying.

[0044] The present invention also protects an epoxy resin composition comprising the following components in parts by weight:

[0045] 100 parts of epoxy resin, 5-20 parts of curing agent, and 5-20 parts of the rubber microcapsules.

[0046] Preferably, the epoxy resin is bisphenol A epoxy resin and / or polyethylene glycol diglycidyl ether (PEGDGE).

[0047] Preferably, the curing agent is 4,4-diaminodiphenyl sulfone (DDS) and / or diaminodiphenylmethane (DDM).

[0048] The present invention also provides a method for preparing the epoxy resin composition, comprising the following steps:

[0049] The epoxy resin, the curing agent and the rubber microcapsules are uniformly mixed, bubbles are removed, and the epoxy resin composition is obtained by curing.

[0050] Preferably, the method of removing bubbles is by vacuuming.

[0051] Preferably, the curing is carried out in the following manner: curing at 100-130° C. for 1-2 hours, curing at 150-170° C. for 1-3 hours, and post-curing at 180-200° C. for 1-2 hours, until the curing is complete.

[0052] Preferably, the mixing is as follows: heating the epoxy resin to 130° C., adding a curing agent, cooling to 80° C. after the curing agent is completely dissolved, adding the rubber microcapsules, and stirring until the mixture is uniformly mixed.

[0053] Compared with the prior art, the present invention has the following beneficial effects:

[0054] The invention prepares rubber microcapsules with excellent toughening effect by mixing coated sulfur with nitrile rubber containing reactive end groups and then coating the surface of rubber particles with a polystyrene layer through suspension polymerization.

[0055] The rubber microcapsules of the present invention are used as toughening agents in epoxy resin systems, overcoming the problems of traditional liquid rubber toughening agents in epoxy resin systems that easily aggregate, resulting in increased viscosity of the entire system and inability to be evenly dispersed in the epoxy resin matrix. They also have a better toughening effect, while also allowing the epoxy resin to maintain a relatively high glass transition temperature and good thermal properties. DETAILED DESCRIPTION

[0056] In order to better illustrate the purpose, technical solutions and advantages of the present invention, the present invention will be further described below with reference to specific embodiments, but the embodiments do not limit the present invention in any form.

[0057] The sources of raw materials used in the examples and comparative examples of the present invention are as follows:

[0058] ETBN, purchased from Shandong Weishang Chemical Co., Ltd., TL910;

[0059] CTBN was purchased from Jingjiang Tonggao Chemical Co., Ltd.

[0060] ATBN, purchased from Shandong Weishang Chemical Co., Ltd., TL55;

[0061] Styrene monomer, Jinan Mingxin Chemical Co., Ltd., 100-42-5;

[0062] Suspension agent, SiO2, Shanghai Shuangjin Electronics Co., Ltd., specification 0.05 μm;

[0063] Initiator, AIBN, was purchased from Shanghai Chemical Reagent Company, brand 78-67-1;

[0064] Epoxy resin, E51 bisphenol A epoxy resin, purchased from Shenzhen Jitian Chemical Co., Ltd. E51;

[0065] Curing agent, DDS, was purchased from Shandong Chuangying Chemical Co., Ltd.;

[0066] Coated sulfur, homemade, the preparation method is:

[0067] 100phr industrial sulfur powder is added to a mixed solution of 200phr toluene and 2phr DMF, uniformly dispersed under stirring, then 10phr concentration of 5% SiO2 suspension and 2phr concentration of 1% PVA solution are added, 15phr styrene and hydroxyethyl methyl methacrylate (mol ratio 4:6) are added after uniform stirring, stirring is continued for 20min, then an acetone solution containing 0.05phr AIBN and 0.1phr of MMA-POSS is added, the reaction is carried out at 80°C for 12h under nitrogen, filtered after cooling to room temperature, and the filtrate is recycled, the filtered solid is cleaned and surface sulfur powder is removed through CS2, and then vacuum-dried at 50°C for 4h to obtain sulfur coated with polystyrene on the surface;

[0068] By adjusting the addition amount of industrial sulfur powder, styrene and hydroxyethyl methyl methacrylate, coated sulfur with different sulfur contents can be obtained.

[0069] The prepared coated sulfur-1 contains 84 wt.% sulfur; the prepared coated sulfur-2 contains 72 wt.% sulfur; the prepared coated sulfur-3 contains 51 wt.% sulfur; and the prepared coated sulfur-4 contains 95 wt.% sulfur.

[0070] Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in the art. Unless otherwise specified, the reagents and materials used in the present invention are commercially available.

[0071] Example 1

[0072] This embodiment provides a rubber microcapsule, and the preparation method is as follows:

[0073] 50g of ETBN was added to a nitrogen-filled reactor, followed by 6 volumes of deionized water, 1.5g of SiO2 suspension agent, and 0.05g of AIBN initiator. Under nitrogen atmosphere and stirring at 300 rpm, 1g of coated sulfur (coated sulfur-1) was first added, followed by 5g of styrene monomer. The mixture was reacted at 60°C for 24h, cooled, filtered, and dried to obtain rubber microcapsules.

[0074] Example 2

[0075] This embodiment provides a rubber microcapsule, and the preparation method is the same as that of Example 1 except that:

[0076] The added amount of coated sulfur was 1.25 g.

[0077] Example 3

[0078] This embodiment provides a rubber microcapsule, and the preparation method is the same as that of Example 1 except that:

[0079] The added amount of coated sulfur is 1.5 g.

[0080] Example 4

[0081] This embodiment provides a rubber microcapsule, and the preparation method is the same as that of Example 1 except that:

[0082] The added amount of coated sulfur was 1.75 g.

[0083] Example 5

[0084] This embodiment provides a rubber microcapsule, and the preparation method is the same as that of Example 1 except that:

[0085] The reaction temperature was 70°C and the reaction time was 20 h.

[0086] Example 6

[0087] This embodiment provides a rubber microcapsule, and the preparation method is the same as that of Example 1 except that:

[0088] The reaction temperature was 85°C and the reaction time was 16 h.

[0089] Example 7

[0090] This embodiment provides a rubber microcapsule, and the preparation method is the same as that of Example 1 except that:

[0091] The reaction temperature was 100°C and the reaction time was 12 h.

[0092] Example 8

[0093] 50g of ETBN was added to a nitrogen-filled reactor, followed by 3 times the volume of deionized water, 0.5g of SiO2 suspension agent, and 0.15g of AIBN initiator. Under nitrogen atmosphere and stirring at 400 rpm, 1g of coated sulfur (coated sulfur-1) was first added, followed by 6g of styrene monomer. The mixture was reacted at 100°C for 12h, cooled, filtered, and dried to obtain rubber microcapsules.

[0094] Example 9

[0095] Example 9 provides a rubber microcapsule, and the preparation method is the same as that of Example 1 except that:

[0096] ETBN was replaced with CTBN in equal amounts.

[0097] Example 10

[0098] Example 10 provides a rubber microcapsule, and the preparation method is the same as that of Example 1 except that:

[0099] ETBN was replaced with ATBN in equal amounts.

[0100] Examples 11 to 13

[0101] Examples 11 to 13 provide a rubber microcapsule, respectively. The preparation method is the same as that of Example 1 except that:

[0102] In Example 11, the mass of coated sulfur-1 was replaced with coated sulfur-2;

[0103] In Example 12, the mass of coated sulfur-1 was replaced with coated sulfur-3;

[0104] In Example 13, the mass of coated sulfur-1 was replaced by coated sulfur-4.

[0105] Application Examples 1 to 13

[0106] Application Examples 1 to 13 respectively provide an epoxy resin composition comprising the following components in parts by weight:

[0107] 100 parts of epoxy resin, 20 parts of DDS, 20 parts of rubber microcapsules;

[0108] The rubber microcapsules of the epoxy resin compositions of Application Examples 1 to 13 are the rubber microcapsules of Examples 1 to 13, respectively.

[0109] The preparation methods of the epoxy resin compositions of Application Examples 1 to 13 are as follows:

[0110] The epoxy resin was added to a three-necked flask and heated to 130° C. DDS was added and stirred for half an hour until the DDS was completely dissolved. The mixture was cooled to 80° C. and the rubber microcapsules prepared in Examples 1 to 13 were added. After stirring evenly, the mixture was poured into a polytetrafluoroethylene mold and placed in an oven for heating and curing. The curing procedure was as follows: curing at 100 to 130° C. for 1 to 2 hours, curing at 150 to 170° C. for 1 to 3 hours, and post-curing at 180 to 200° C. for 1 to 2 hours to obtain an epoxy resin composition.

[0111] Comparative Example 1

[0112] Comparative Example 1 provides an epoxy resin composition, and the preparation method is as follows:

[0113] Epoxy resin (100 parts by weight) was added to a three-necked flask and heated to 130° C. DDS (20 parts by weight) was added and stirred for half an hour until DDS was completely dissolved. The mixture was cooled to 80° C. and ETBN (20 parts by weight) was added. After stirring evenly, the mixture was poured into a polytetrafluoroethylene mold and placed in an oven for heating and curing. The curing procedure was as follows: curing at 100-130° C. for 1-2 hours, curing at 150-170° C. for 1-3 hours, and post-curing at 180-200° C. for 1-2 hours to obtain an epoxy resin composition.

[0114] Comparative Example 2

[0115] Comparative Example 2 provides an epoxy resin composition, and the preparation method is as follows:

[0116] Epoxy resin (100 parts by weight) is added to a three-necked flask and heated to 130° C. DDS (20 parts by weight) is added and stirred for half an hour until DDS is completely dissolved. The mixture is cooled to 80° C. and coated sulfur (20 parts by weight) is added. After stirring evenly, the mixture is poured into a polytetrafluoroethylene mold and placed in an oven for heating and curing. The curing procedure is as follows: curing at 100-130° C. for 1-2 hours, curing at 150-170° C. for 1-3 hours, and post-curing at 180-200° C. for 1-2 hours to obtain an epoxy resin composition.

[0117] Comparative Example 3

[0118] Comparative Example 3 provides an epoxy resin composition, and the preparation method is as follows:

[0119] Epoxy resin (100 parts by weight) was added to a three-necked flask and heated to 130° C. DDS (20 parts by weight) was added and stirred for half an hour until DDS was completely dissolved. The mixture was cooled to 80° C. and S@ETBN@PS (20 parts by weight) was added. After stirring evenly, the mixture was poured into a polytetrafluoroethylene mold and placed in an oven for heating and curing. The curing procedure was as follows: curing at 100-130° C. for 1-2 hours, curing at 150-170° C. for 1-3 hours, and post-curing at 180-200° C. for 1-2 hours to obtain an epoxy resin composition.

[0120] S@ETBN@PS was prepared by the following method:

[0121] 50g of ETBN was added to a nitrogen-filled reactor, followed by 6 volumes of deionized water, 1.5g of SiO2 suspension agent, 0.05g of AIBN initiator, 1g of uncoated sulfur (S), and then 5g of styrene monomer. The mixture was reacted at 60°C for 24h under nitrogen atmosphere and vigorous stirring. After cooling, the mixture was filtered and dried to obtain S@ETBN@PS.

[0122] Comparative Example 4

[0123] Comparative Example 4 provides an epoxy resin composition, and the preparation method is as follows:

[0124] Epoxy resin (100 parts by weight) is added to a three-necked flask and heated to 130° C. DDS (20 parts by weight) is added and stirred for half an hour until DDS is completely dissolved. The mixture is cooled to 80° C. and rubber microcapsules (20 parts by weight) are added. After stirring evenly, the mixture is poured into a polytetrafluoroethylene mold and placed in an oven for heating and curing. The curing procedure is as follows: curing at 100-130° C. for 1-2 hours, curing at 150-170° C. for 1-3 hours, and post-curing at 180-200° C. for 1-2 hours to obtain an epoxy resin composition.

[0125] The difference between the preparation method of the rubber microcapsules used in this comparative example and that in Example 1 is that:

[0126] The reaction temperature was 50°C and the reaction time was 24 h.

[0127] Comparative Example 5

[0128] Comparative Example 5 provides an epoxy resin composition, and the preparation method is as follows:

[0129] Epoxy resin (100 parts by weight) is added to a three-necked flask and heated to 130° C. DDS (20 parts by weight) is added and stirred for half an hour until DDS is completely dissolved. The mixture is cooled to 80° C. and rubber microcapsules (20 parts by weight) are added. After stirring evenly, the mixture is poured into a polytetrafluoroethylene mold and placed in an oven for heating and curing. The curing procedure is as follows: curing at 100-130° C. for 1-2 hours, curing at 150-170° C. for 1-3 hours, and post-curing at 180-200° C. for 1-2 hours to obtain an epoxy resin composition.

[0130] The rubber microcapsules used in this comparative example are prepared in the following manner:

[0131] The reaction temperature is 120°C and the reaction time is 24 hours.

[0132] Performance Testing

[0133] The morphology test of the rubber microcapsules prepared in the above embodiment was performed as follows:

[0134] Average particle size: The embedding-SEM cross-sectional analysis method was used, and the cross-sectional test of the cast body was observed using a JSM-IT300 lanthanum hexaboride scanning electron microscope. The statistical average of the diameter of the rubber microcapsules was calculated using statistical analysis software.

[0135] Shell weight ratio: The core-shell content ratio was calculated using the FTIR model standard curve method;

[0136] The properties of the epoxy resin compositions obtained in the above application examples and comparative examples were characterized. The specific test items and test methods are as follows:

[0137] Tensile strength: GB / T 2567-2008, select defect-free specimens for testing, and average the values of 5 specimens in each group;

[0138] Bending strength: GB / T 2567-2008, select defect-free specimens for testing, and average the values of 5 specimens in each group;

[0139] Izod notched impact strength: GB / T 1843-2008, select defect-free specimens for testing, and average the values of 5 specimens per group;

[0140] Glass transition temperature: GB / T 19466.2-2004, using a TA differential scanning calorimeter with a heating rate of 10°C / min.

[0141] The morphology test results of the rubber microcapsules prepared in Examples 1 to 13 are shown in Table 1.

[0142] Table 1

[0143]

[0144] According to the test results in Table 1, the average particle size of the rubber microcapsules prepared in the examples of the present application is between 1 and 1.5 μm, and the shell accounts for about 10 wt.%.

[0145] The test results of the epoxy resin compositions of the application examples and comparative examples are shown in Table 2.

[0146] Table 2 Epoxy resin composition test results

[0147]

[0148]

[0149] According to the test results in Table 2, the notched Izod impact strength of the epoxy resin composition containing the rubber toughening agent of the present invention is ≥17.1 KJ / m 2 , tensile strength ≥55MPa, flexural strength ≥93MPa, glass transition temperature ≥163℃.

[0150] According to the test results in Table 2, by comparing Application Examples 9 to 10 with Application Examples 1 to 4, it can be seen that for different nitrile rubbers containing reactive end groups, the epoxy-terminated nitrile rubber has a relatively better toughening effect on epoxy resin.

[0151] From Application Examples 5 to 8, different reaction times and temperatures will affect the degree of bonding between the coated sulfur and the nitrile rubber in the rubber microcapsules. Reaction at a relatively high temperature can make the coated sulfur and the nitrile rubber bond more tightly, resulting in a better toughening effect of the rubber microcapsules.

[0152] According to Application Examples 1 and 17 to 19, when the sulfur content in the coated sulfur is 70 to 85 wt.%, both good sulfur dispersion and effective vulcanization of the epoxy resin can be achieved, thereby improving the toughness of the epoxy resin after curing.

[0153] Comparative Examples 1 and 2, respectively, used liquid nitrile rubber and coated sulfur to modify epoxy resin. It can be seen that using either nitrile rubber or coated sulfur alone did not provide satisfactory toughening effects on epoxy resin and also reduced the thermal performance of the epoxy resin. Comparative Example 3 used a rubber microcapsule toughening agent made with uncoated sulfur to modify epoxy resin. Compared with Example 1, the sulfur was not surface-coated, resulting in uneven distribution in the epoxy resin system and poor toughening effects.

[0154] In Comparative Example 4, the reaction temperature during the preparation of the rubber microcapsules was too low, the polystyrene coating effect was poor, and the toughening effect of the obtained rubber microcapsules on the epoxy resin was limited; in Comparative Example 5, the reaction temperature during the preparation of the rubber microcapsules was too high, the sulfur aged prematurely, and the overall performance of the epoxy resin composition was poor.

[0155] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A rubber microcapsule, characterized in that: It has a core-shell structure, wherein the shell is polystyrene and the core is liquid nitrile rubber dispersed with coated sulfur, the weight of the coated sulfur in the core accounts for 2-3.5 wt.% of the liquid nitrile rubber, and the proportion of sulfur in the coated sulfur is 50-95 wt.%; The coated sulfur is sulfur coated with polystyrene on the surface; the liquid nitrile rubber contains reactive end groups; The preparation method of the coated sulfur is as follows: sulfur powder is uniformly dispersed in an organic solvent, a suspending agent, a stabilizer, styrene and hydroxyethyl methyl methacrylate are added, an initiator and an organic solution containing MMA-POSS are added after uniform stirring, a reaction is carried out under nitrogen, the reaction is carried out, the solid is cooled to room temperature and then filtered, sulfur powder on the surface of the filtered solid is removed, and the solid is vacuum dried to obtain sulfur coated with polystyrene; The preparation method of the rubber microcapsules comprises the following steps: under the protection of an inert gas, mixing liquid nitrile rubber containing reactive end groups with water, a suspending agent, and an initiator; sequentially adding coated sulfur and styrene monomer under stirring conditions, reacting the mixture, and obtaining the rubber microcapsules through post-treatment, wherein the reaction temperature is 60-100° C. and the reaction time is 12-24 hours.

2. The rubber microcapsule according to claim 1, characterized in that: The average particle size of the rubber microcapsules is 1-1.5 μm.

3. The rubber microcapsule according to claim 1, characterized in that: The weight of the shell accounts for 8-12 wt.% of the rubber microcapsule.

4. The rubber microcapsule according to claim 1, characterized in that: The liquid nitrile rubber is at least one of epoxy-terminated nitrile rubber, carboxyl-terminated liquid nitrile rubber, and amino-terminated liquid nitrile rubber.

5. The method for preparing the rubber microcapsules according to any one of claims 1 to 4, characterized in that: The steps include: Under the protection of inert gas, liquid nitrile rubber is mixed with water, a suspending agent, and an initiator. Under stirring conditions, coated sulfur and styrene monomer are added in sequence to react at a temperature of 60 to 100° C. for 12 to 24 hours. The rubber microcapsules are obtained through post-treatment, wherein the liquid nitrile rubber contains reactive end groups.

6. The preparation method according to claim 5, characterized in that: The stirring speed is 200-400 rpm.

7. The preparation method according to claim 5, characterized in that: Includes at least one of the following features (a) to (c): (a) the volume ratio of the liquid nitrile rubber to water is 1:(3-6); (b) The weight of the suspending agent is 1-3 wt.% of the liquid nitrile rubber; (c) The weight of the initiator is 0.1-0.3 wt.% of the liquid nitrile rubber.

8. An epoxy resin composition, characterized in that The invention comprises the following components in parts by weight: 100 parts of epoxy resin, 5 to 20 parts of curing agent, and 5 to 20 parts of the rubber microcapsules according to any one of claims 1 to 4.

9. The method for preparing the epoxy resin composition according to claim 8, comprising the steps of: The epoxy resin, the curing agent and the rubber microcapsules are uniformly mixed, bubbles are removed, and the epoxy resin composition is obtained by curing.

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