Microcapsule for rubber self-repairing, preparation method thereof, self-repairing fluorinated silicone rubber material and rubber product
By using urea, curing agent, emulsifier and core emulsifier in the preparation of microcapsules and polymerizing reaction at a specific temperature, the problem of poor coverage rate of traditional microcapsules is solved, and the strength and production efficiency of microcapsules are improved.
Patent Information
- Application Number
- CN202510324439.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-03-19
- Publication Date
- 2025-06-06
AI Technical Summary
During the preparation process, the wall material has poor coverage of the core material, which leads to prone to rupture during washing or drying, reducing production efficiency.
By mixing urea, curing agent, emulsifier, water and the core material to form an emulsifier, and adding formaldehyde under specific temperature conditions, microcapsules of urea-formaldehyde resin-coated core material are prepared by in-situ polymerization to ensure that the core material is completely coated.
The coating rate and strength of the microcapsules are improved, making it less likely to rupture during the subsequent treatment process, and the pass rate and production efficiency of the microcapsules are improved.
Smart Images
Figure CN120098442A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of self-repairing materials, and in particular to a self-repairing rubber microcapsule and a preparation method thereof, a self-repairing fluorosilicone rubber material and a rubber product. Background Art
[0002] As the capacity of the power system increases and the voltage level continues to rise, the power grid system has higher and higher requirements for power equipment such as transformers. As an important part of the transformer, rubber bushings are responsible for equipment connection, insulation protection, mechanical support, etc., and are prone to insulation failure. In particular, transformer bushings have been in service in a humid environment for a long time, which poses safety hazards such as structural moisture and bushing overheating, which has a great harm to the failure of bushing sealing performance.
[0003] Traditionally, the repair agent is encapsulated in the form of microcapsules and embedded in the rubber matrix. When the rubber matrix material is mechanically damaged due to aging or cracks appear under thermal stress, the microcapsules embedded in the rubber matrix rupture, and the repair agent in the microcapsules is released and cross-linked in the damaged area, thereby completing the repair of the damage and extending the service life of the rubber substrate.
[0004] In the traditional method for preparing microcapsules, there is a problem that the coverage rate of the wall material on the core material is poor, and the obtained microcapsules are easily broken during the washing or drying process, which reduces the production efficiency of the microcapsules. Summary of the invention
[0005] Based on this, it is necessary to provide a method for preparing rubber self-repairing microcapsules, which has a good coverage rate and is not easy to break; the method has high production efficiency. Furthermore, a self-repairing fluorosilicone rubber material and rubber products are provided.
[0006] The first aspect of the present application provides a method for preparing a rubber self-repairing microcapsule, comprising the following steps:
[0007] Mixing urea, a curing agent, an emulsifier, water and a core material to form an emulsion; wherein the core material is insoluble in water;
[0008] adding formaldehyde to the emulsion to obtain a polymerization reaction liquid, and subjecting the polymerization reaction liquid to a polymerization reaction to obtain the microcapsules;
[0009] The conditions of the polymerization reaction include: firstly heating from room temperature to 35°C~40°C at a rate of 0.5°C / min~1.5°C / min, and keeping warm for 15min~20min; then heating to 45°C~50°C at a rate of 0.5°C / min~1.5°C / min, and keeping warm for 15min~20min; then heating to 55°C~60°C at a rate of 0.5°C / min~1.5°C / min, and reacting at a constant temperature for 3.5h~5h.
[0010] In the above preparation method, urea, curing agent, emulsifier, water and core material are first mixed to form an emulsion, and then formaldehyde is added to prepare microcapsules with urea-formaldehyde resin coated core material by in-situ polymerization. Specifically, urea and curing agent are soluble in water, while core material is insoluble in water. Under the action of emulsifier, core material can form dispersed phase and emulsion; formaldehyde added subsequently can also be dissolved in water of continuous phase. Under specific temperature conditions, urea and formaldehyde, the raw materials of wall material in continuous phase, undergo cross-linking reaction; intermediate products in the process of wall material formation are insoluble in continuous phase, continuously precipitate from solution, and adsorb on the interface between dispersed phase and continuous phase (i.e., core material surface); intermediate products continue to react, thereby forming a continuous and dense film on the surface of dispersed phase, achieving complete coating of core material, and then obtaining microcapsules with urea-formaldehyde resin coated core material. Furthermore, the present application forms a uniform dense film on the entire outer surface of the core material by strictly controlling the temperature rising conditions during the polymerization process and controlling the cross-linking reaction rate; and the dense film has good strength and is not easily broken during the subsequent washing or drying process, thereby improving the qualified rate of microcapsules and improving the production efficiency of microcapsules.
[0011] In some embodiments, the preparation method satisfies at least one of the following conditions:
[0012] (1) The emulsion comprises, by weight: 1 part of urea, 0.1 to 0.5 parts of the curing agent, 0.05 to 0.2 parts of the emulsifier, 2 to 6 parts of the core material, and 40 to 60 parts of water;
[0013] (2) The mass ratio of the urea to the formaldehyde is 1:(0.5-1.5).
[0014] In some embodiments, the preparation method satisfies at least one of the following conditions:
[0015] (1) The core material is selected from at least one of polydimethylsiloxane, dicyclopentadiene and epoxy resin;
[0016] (2) The curing agent is selected from at least one of resorcinol and ammonium chloride;
[0017] (3) The emulsifier is at least one selected from polyvinyl alcohol, ethylene methyl acrylate copolymer, sodium dodecylbenzene sulfonate, dodecylphenol polyoxyethylene ether, sodium lignin sulfonate and nano titanium dioxide;
[0018] (4) The polymerization reaction is carried out under mechanical stirring conditions, and the stirring speed of the mechanical stirring is 400r / min~600r / min.
[0019] In some embodiments, the emulsifier is polyvinyl alcohol and ethylene methyl acrylate copolymer, and the mass ratio of polyvinyl alcohol to ethylene methyl acrylate copolymer is 1:(1.5-3).
[0020] In some embodiments, the emulsion further includes a surface tension regulator; the surface tension regulator satisfies at least one of the following conditions:
[0021] (1) The surface tension regulator is at least one selected from sodium chloride, potassium chloride and ammonium sulfate;
[0022] (2) In the emulsion, the mass fraction of the surface tension modifier is 0.8 parts to 1.2 parts.
[0023] In some embodiments, the preparation method further comprises adding a pH adjuster to the emulsion to adjust the pH value of the emulsion to 3.5-4.0.
[0024] In some embodiments, the following steps are also included:
[0025] A silane coupling agent is grafted onto the surface of the microcapsule.
[0026] The second aspect of the present application provides a rubber self-repairing microcapsule, which is prepared according to the preparation method described in the first aspect.
[0027] The third aspect of the present application provides a self-healing fluorosilicone rubber material, comprising a rubber substrate and the rubber self-healing microcapsules described in the first aspect.
[0028] A fourth aspect of the present application provides a rubber product, comprising the self-healing fluorosilicone rubber material described in the third aspect. BRIEF DESCRIPTION OF THE DRAWINGS
[0029] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the conventional technology, the drawings required for use in the embodiments or the conventional technology descriptions are briefly introduced below. Obviously, the drawings described below are merely embodiments of the present application, and ordinary technicians in this field can obtain other drawings based on the disclosed drawings without paying any creative work.
[0030] Figure 1This is a schematic diagram of the preparation principle of microcapsules in one embodiment of the present application;
[0031] Figure 2 This is a microscopic image of the polymerization reaction solution obtained in Example 1;
[0032] Figure 3 This is a microscopic image of the polymerization reaction solution when the temperature is raised to 55° C. in Example 1;
[0033] Figure 4 This is a microscopic image of the polymerization reaction solution after constant temperature reaction at 55° C. for 0.5 h in Example 1;
[0034] Figure 5 This is a microscopic image of the polymerization reaction liquid after constant temperature reaction at 55° C. for 1.5 hours in Example 1;
[0035] Figure 6 This is a microscopic image of the polymerization reaction solution after constant temperature reaction at 55° C. for 2.5 hours in Example 1;
[0036] Figure 7 This is a microscopic image of the polymerization reaction solution after constant temperature reaction at 55° C. for 3.5 hours in Example 1;
[0037] Figure 8 This is a microscopic morphology of the microcapsule product prepared in Example 1;
[0038] Fig. 9 This is a microscopic morphology of the microcapsule product prepared in Example 1. DETAILED DESCRIPTION
[0039] In order to facilitate the understanding of the present invention, the present invention is described more comprehensively below. And preferred embodiments of the present invention are given. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. It should be understood that the purpose of providing these embodiments is to make the understanding of the disclosure of the present invention more thorough and comprehensive.
[0040] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which the present invention belongs. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more of the related listed items.
[0041] In the description of the present invention, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.
[0042] The weight of the relevant components mentioned in the description of the embodiments of the present invention may not only refer to the specific content of each component, but also indicate the weight ratio between the components. Therefore, as long as the content of the relevant components is proportionally enlarged or reduced according to the description of the embodiments of the present invention, it is within the scope disclosed in the description of the embodiments of the present invention. Specifically, the weight described in the description of the embodiments of the present invention may be a mass unit known in the chemical industry such as μg, mg, g, kg, etc.
[0043] The room temperature in this application refers to 20°C to 30°C.
[0044] In one embodiment of the present application, a method for preparing a rubber self-repairing microcapsule is provided, comprising the following steps S10 to S20:
[0045] S10, mixing urea, a curing agent, an emulsifier, water and a core material to form an emulsion; wherein the core material is insoluble in water.
[0046] S20, adding formaldehyde to the emulsion to obtain a polymerization reaction liquid, and subjecting the polymerization reaction liquid to a polymerization reaction to obtain microcapsules.
[0047] The conditions for the polymerization reaction include: first, heating from room temperature to 35°C~40°C at a rate of 0.5°C / min~1.5°C / min, and keeping warm for 15min~20min; then, heating to 45°C~50°C at a rate of 0.5°C / min~1.5°C / min, and keeping warm for 15min~20min; then, heating to 55°C~60°C at a rate of 0.5°C / min~1.5°C / min, and reacting at a constant temperature for 3.5h~5h.
[0048] In the above preparation method, urea, curing agent, emulsifier, water and core material are first mixed to form an emulsion, and then formaldehyde is added to prepare microcapsules of urea-formaldehyde resin coated core material by in-situ polymerization. Figure 1As shown, urea and curing agent are dissolved in water to form a water phase; the core material is insoluble in water to form an oil phase; the emulsifier has a hydrophilic group and a hydrophobic group, wherein the hydrophobic group is close to the core material and covers the core material, so that the core material forms a stable dispersed phase, and then forms an emulsion. The formaldehyde added later dissolves in water and reacts with urea and curing agent to complete the microcapsule coating process. Under specific temperature conditions, the wall material monomer raw materials urea and formaldehyde in the continuous phase undergo a cross-linking reaction; the intermediate product in the wall material formation process is insoluble in the continuous phase, continuously precipitates from the solution, and is adsorbed at the interface between the dispersed phase and the continuous phase (i.e., the core material surface); the intermediate product continues to react, thereby forming a continuous and dense film on the surface of the dispersed phase, achieving complete coating of the core material, and then obtaining a microcapsule with a urea-formaldehyde resin coated core material. Furthermore, the present application forms a uniform dense film on the entire outer surface of the core material by strictly controlling the temperature rising conditions during the polymerization process and controlling the cross-linking reaction rate; and the dense film has good strength and is not easily broken during the subsequent washing or drying process, thereby improving the qualified rate of microcapsules and improving the production efficiency of microcapsules.
[0049] As an example, in the polymerization reaction conditions, the temperature can be first raised from room temperature to 35°C~40°C at a rate of 0.5°C / min, 0.6°C / min, 0.7°C / min, 0.8°C / min, 0.9°C / min, 1°C / min, 1.1°C / min, 1.2°C / min, 1.3°C / min, 1.4°C / min or 1.5°C / min; further, the above-mentioned heating rate can be any value within the range formed by any two of the above-mentioned point values as end values. Then, the temperature can be raised from 35°C~40°C to 45°C~50°C at a rate of 0.5°C / min, 0.6°C / min, 0.7°C / min, 0.8°C / min, 0.9°C / min, 1°C / min, 1.1°C / min, 1.2°C / min, 1.3°C / min, 1.4°C / min or 1.5°C / min. Then increase the temperature from 45℃~50℃ to 55℃~60℃ at a speed of 0.5℃ / min, 0.6℃ / min, 0.7℃ / min, 0.8℃ / min, 0.9℃ / min, 1℃ / min, 1.1℃ / min, 1.2℃ / min, 1.3℃ / min, 1.4℃ / min or 1.5℃ / min.
[0050] In some embodiments, the emulsion includes, by weight: 1 part of urea, 0.1 to 0.5 parts of curing agent, 0.05 to 0.2 parts of emulsifier, 2 to 6 parts of core material, and 40 to 60 parts of water.
[0051] As an example, the mass fraction of curing agent in the emulsion can be 0.1 part, 0.12 part, 0.14 part, 0.15 part, 0.16 part, 0.18 part, 0.2 part, 0.22 part, 0.24 part, 0.25 part, 0.26 part, 0.28 part, 0.3 part, 0.35 part, 0.38 part, 0.4 part, 0.42 part, 0.45 part, 0.48 part or 0.5 part. Further, the mass fraction of curing agent in the emulsion can be the range value consisting of the above-mentioned arbitrary two point values as the end value. Preferably, the mass fraction of curing agent in the emulsion can be 0.15 part ~ 0.3 part. Curing agent can improve the polymerization reaction speed of urea and formaldehyde, and controlling the addition amount of curing agent can control the reaction rate of the controller, and then control the speed and coverage of the dense film on the surface of the core material.
[0052] As an example, the mass fraction of the emulsifier in the emulsion can be 0.05 parts, 0.06 parts, 0.08 parts, 0.1 parts, 0.12 parts, 0.14 parts, 0.15 parts, 0.16 parts, 0.17 parts, 0.18 parts, 0.19 parts or 0.2 parts. Further, the mass fraction of the emulsifier can be a range value consisting of any two of the above point values as end values. Preferably, the mass fraction of the emulsifier can be 0.08 parts to 0.11 parts. When preparing microcapsules by in-situ polymerization, the type and concentration of the emulsifier have an important influence on the preparation effect of the microcapsules. In the preparation process, the emulsifier generally plays two roles: during emulsification, the emulsifier allows the dispersed phase to form a stable, uniform particle size emulsion in the continuous phase; when the microcapsules are formed, the emulsifier allows the core material surface to have a lower surface energy, which is conducive to the deposition of the wall material monomer on the core material surface.
[0053] As an example, the mass fraction of the core material in the emulsion can be 2 parts, 2.2 parts, 2.4 parts, 2.5 parts, 2.6 parts, 2.7 parts, 2.8 parts, 3 parts, 3.2 parts, 3.4 parts, 3.5 parts, 3.8 parts, 4 parts, 4.2 parts, 4.5 parts, 4.6 parts, 5 parts, 5.2 parts, 5.5 parts, 5.8 parts or 6 parts. Further, the mass fraction of the core material can be a range value consisting of any two of the above-mentioned point values as end values. Preferably, the mass fraction of the core material can be 3.5 parts to 4.5 parts. Controlling the mass fraction of the core material within the above range is conducive to forming microcapsules with suitable particle size, smoother surface, higher coverage and better stability. Too high a mass fraction of the core material in the emulsifier may result in poor emulsification, larger microcapsule size, reduced coating efficiency, and increased risk of system stratification. Controlling the mass fraction of the core material below the above range may cause excessive dispersion of the droplets, resulting in too small a particle size of the microcapsules. Too small droplets may make the subsequent polymer film thin or difficult to form stably, the surface of the microcapsules may be rough, and they may stick and agglomerate with each other, thereby reducing the coating efficiency.
[0054] As an example, the mass fraction of water in the emulsion can be 40 parts, 42 parts, 45 parts, 46 parts, 48 parts, 50 parts, 52 parts, 55 parts, 56 parts, 58 parts, 59 parts or 60 parts.
[0055] In some embodiments, the mass ratio of urea to formaldehyde is 1:(0.5-1.5). As an example, the mass ratio of urea to formaldehyde is 1:0.5, 1:0.7, 1:08, 1:0.9, 1:1, 1:1.2, 1:1.2, 1:1.3, 1:1.4 or 1:1.5. Further, the mass ratio of urea to formaldehyde can also be any other ratio within the above range. Preferably, the mass ratio of urea to formaldehyde is 1:(0.8-1.2).
[0056] In some embodiments, the core material is selected from at least one of polydimethylsiloxane, dicyclopentadiene and epoxy resin. Preferably, the core material is selected from polydimethylsiloxane. Polydimethylsiloxane has excellent chemical stability, flexibility and thermal stability. As a core material, it can enhance self-repairing ability, improve material weather resistance, enhance fatigue resistance, maintain mechanical properties, and adapt to extreme environments.
[0057] In some embodiments, the curing agent is selected from at least one of resorcinol and ammonium chloride.
[0058] In some embodiments, the mass ratio of resorcinol to ammonium chloride is 1:1.
[0059] In some embodiments, the emulsifier is selected from at least one of polyvinyl alcohol, ethylene methyl acrylate copolymer, sodium dodecylbenzene sulfonate, polyoxyethylene dodecylphenol ether, sodium lignin sulfonate and nano titanium dioxide. Preferably, the emulsifier is selected from polyvinyl alcohol and ethylene methyl acrylate copolymer. Further, the mass ratio of polyvinyl alcohol and ethylene methyl acrylate copolymer is 1: (1.5-3), preferably, the mass ratio of polyvinyl alcohol and ethylene methyl acrylate copolymer is 1: (2-2.2). Polyvinyl alcohol and ethylene methyl acrylate copolymer have a high molecular weight and strong interfacial adsorption capacity, and can form a dense and stable adsorption layer at the oil-water interface, thereby significantly improving the stability of the emulsion and reducing the coalescence and splitting of droplets.
[0060] In some embodiments, when the emulsifier is mixed with the urea, curing agent, water and core material, it is added in the form of an emulsifier aqueous solution. The concentration of the emulsifier in the emulsifier aqueous solution is 2wt% to 5wt%.
[0061] In some embodiments, the emulsion further includes a surface tension adjuster.
[0062] In some embodiments, the surface tension modifier is selected from at least one of sodium chloride, potassium chloride and ammonium sulfate. Preferably, the surface tension modifier is sodium chloride.
[0063] In some embodiments, the emulsion includes: 1 part urea, 0.1 to 0.5 parts of curing agent, 0.05 to 0.2 parts of emulsifier, 2 to 6 parts of core material and 0.8 to 1.2 parts of surface tension regulator. Adding an appropriate amount of surface tension regulator to the emulsion can improve the double electric layer structure of the emulsion droplets, significantly enhance the enrichment of the emulsifier at the interface, and thus reduce the surface tension. Adding an appropriate amount of surface tension regulator when preparing microcapsules can significantly improve the morphology of the microcapsules and the core material coating effect.
[0064] In some embodiments, the above preparation method further comprises the following step S11:
[0065] S11. Add a pH adjuster to the emulsion to adjust the pH value of the emulsion to 3.5-4.0.
[0066] The emulsion under this pH condition is conducive to the coating of the core material by the wall material, and can also reduce the surface roughness of the microcapsule and improve the uniformity of the wall material thickness.
[0067] In some embodiments, the above preparation method further comprises step S12:
[0068] S12, after mixing urea, curing agent, emulsifier, water and core material, the mixed liquid is homogenized to form a stable emulsion.
[0069] In some embodiments, formaldehyde is added to the emulsion under mechanical stirring.
[0070] In some embodiments, the speed of mechanical stirring is 400 r / min~600 r / min.
[0071] In some embodiments, formaldehyde is added to the emulsion in the form of an aqueous formaldehyde solution.
[0072] In some embodiments, the concentration of formaldehyde in the aqueous formaldehyde solution is 30 wt % to 40 wt %.
[0073] In some embodiments, after adding formaldehyde to the emulsion, a step of adding a defoaming agent is also included. By adding the defoaming agent, bubbles generated during the stirring of the polymerization reaction liquid can be removed.
[0074] In some embodiments, the defoaming agent is selected from n-octanol.
[0075] In some embodiments, the polymerization reaction is carried out under mechanical stirring conditions, and the stirring speed of the mechanical stirring is 400 r / min~600 r / min.
[0076] In some embodiments, after the polymerization reaction is completed, the following preparation steps S30 to S40 are also included.
[0077] S30. Under stirring conditions of 400 r / min to 600 r / min, air-cool the remaining liquid after the polymerization reaction to room temperature, and filter to obtain filter material.
[0078] S40. Wash the filter material with n-hexane and anhydrous ethanol alternately for 3 to 5 times, then rinse with deionized water; and dry.
[0079] In some embodiments, the drying conditions in step S40 include drying at 50° C. to 65° C. for 1 h to 3 h, and then air-drying at room temperature to obtain microcapsules.
[0080] In some embodiments, the above preparation method further includes step S50:
[0081] S50, grafting silane coupling agent on the surface of microcapsules.
[0082] In some embodiments, the silane coupling agent is selected from at least one of KH570, KH550, and KH560.
[0083] In some embodiments, the step of grafting a silane coupling agent on the surface of the microcapsule includes the following steps S51-S53:
[0084] S51, adding a pH adjuster to the aqueous solution of ethanol to adjust the pH value of the solution to 4.0-4.5, and then adding microcapsules to obtain a first dispersion. Ethanol can dissolve the silane coupling agent (the hydrophobic part is difficult to dissolve in water) and promote uniform dispersion and sufficient hydrolysis of the silane coupling agent by reducing the surface tension of the solution.
[0085] In some embodiments, the pH adjuster is dilute hydrochloric acid.
[0086] S52, hydrolyzing the silane coupling agent in an aqueous solution of ethanol to obtain a hydrolyzate of the silane coupling agent.
[0087] In some embodiments, the hydrolysis step comprises ultrasonicating the mixture formed by the aqueous solution of the silane coupling agent and ethanol for 20 min to 30 min.
[0088] S53, mixing the first dispersion and the hydrolyzate of the silane coupling agent, reacting at 60°C to 80°C for 2h to 4h; then cooling, filtering, washing and drying.
[0089] There is no order requirement for step S51 and step S52, and step S51 can be performed first, or step S52 can be performed first.
[0090] In some embodiments, the mass of the silane coupling agent is 2 wt% to 5 wt% of the mass of the microcapsules.
[0091] In one embodiment of the present application, a rubber self-repairing microcapsule obtained according to the above preparation method is provided.
[0092] In some embodiments, the rubber self-repairing microcapsule comprises a core material and a wall material, wherein the wall material covers the entire outer surface of the core material.
[0093] In some embodiments, the thickness of the wall material is 1 μm to 2 μm.
[0094] In some embodiments, the mass of the core material accounts for 80% to 90% of the mass of the rubber self-repairing microcapsules.
[0095] In some embodiments, the rubber self-repairing microcapsules are spherical or quasi-spherical.
[0096] In some embodiments, the particle size of the rubber self-repairing microcapsules is 80 μm to 230 μm.
[0097] In some embodiments, a silane coupling agent is grafted onto the surface of the wall material of the rubber self-repairing microcapsule.
[0098] In some embodiments, the mass of the silane coupling agent is 2 wt % to 5 wt % of the mass of the rubber self-repairing microcapsules.
[0099] In one embodiment of the present application, a self-repairing fluorosilicone rubber material is provided. The self-repairing fluorosilicone rubber material includes a rubber substrate and the above-mentioned rubber self-repairing microcapsules.
[0100] In some embodiments, the mass ratio of the rubber substrate to the rubber self-repairing microcapsules in the self-repairing fluorosilicone rubber material is 100:(5-15).
[0101] In some embodiments, the rubber substrate is a conventional rubber, including but not limited to one or more of fluorosilicone rubber and silicone rubber.
[0102] In one embodiment of the present application, a method for preparing a self-repairing fluorosilicone rubber material is provided, comprising the following steps:
[0103] Mix room temperature vulcanized liquid fluorosilicone rubber with rubber self-repairing microcapsules and then cure for 48h~50h.
[0104] In some embodiments, after mixing the room temperature vulcanized liquid fluorosilicone rubber with the rubber self-repairing microcapsules, the step of degassing the mixture under vacuum conditions is also included.
[0105] In some embodiments, the curing is performed at room temperature. In one embodiment of the present application, a rubber product is provided, the rubber product comprising the self-repairing fluorosilicone rubber material.
[0106] In some embodiments, the rubber products include but are not limited to rubber bushings for transformers.
[0107] In order to make the purpose, technical solutions and advantages of the present invention more concise and clear, the present invention is described with the following specific embodiments, but the present invention is by no means limited to these embodiments. The embodiments described below are only preferred embodiments of the present invention, which can be used to describe the present invention and cannot be understood as limiting the scope of the present invention. It should be pointed out that any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.
[0108] In order to better illustrate the present invention, the present invention is further described below in conjunction with the embodiments. The following are specific embodiments.
[0109] Example 1
[0110] 1. Preparation of microcapsules:
[0111] (1) Preparation of emulsifier aqueous solution:
[0112] An EMA aqueous solution with a concentration of 2.5 wt% and a PVA aqueous solution with a concentration of 2.5 wt% were prepared for use.
[0113] (2) Emulsion configuration:
[0114] According to the mass proportion of the emulsion: 1 part urea, 0.1 part resorcinol, 0.1 part ammonium chloride, 1 part sodium chloride, 0.03 part PVA, 0.065 part EMA and 53.705 parts deionized water, weigh appropriate amounts of urea, resorcinol, ammonium chloride, sodium chloride, EMA aqueous solution, PVA aqueous solution and deionized water, and then mix them; mechanically stir and use ultrasonic dispersion to fully dissolve all substances. Then use dilute hydrochloric acid and dilute sodium hydroxide solution to adjust the solution pH to 3.5~4.0.
[0115] (3) Homogeneous dispersion
[0116] Polydimethylsiloxane was dropped into the emulsion prepared in step (2) at a mass ratio of urea to polydimethylsiloxane of 1:4, and the solution was fully homogenized for 60 minutes using a homogenizer to form a stable emulsion.
[0117] (4) Mixing preparation
[0118] The emulsion was transferred to a three-necked flask, and under the condition of mechanical stirring speed of 500 r / min, a formaldehyde solution with a concentration of 37wt% was dripped in a ratio of 1:2.56 of urea to formaldehyde solution, and stirring was continued for emulsification, and a few drops of n-octanol were dripped to eliminate the bubbles generated during the emulsification process to obtain a polymerization reaction solution. Then the solution was heated uniformly in a water bath, heated to 35℃ at a heating rate of 1℃ / min and kept warm for 15 min, then heated to 45℃ at a heating rate of 1℃ / min and kept warm for 15 min, and finally heated to 55℃ at a heating rate of 1℃ / min and kept warm for 3.5 h.
[0119] (5) Washing and drying
[0120] After the reaction, the solution was cooled to room temperature under magnetic stirring at a speed of 500 r / min. The cooled microcapsule solution was vacuum filtered to obtain the microcapsule product. The obtained product was washed alternately with n-hexane and anhydrous ethanol for 3 times, and then thoroughly washed with deionized water. Finally, it was dried at 60°C for 1 h and then thoroughly air-dried at room temperature to obtain a white powder microcapsule product.
[0121] 2. Microcapsule surface modification
[0122] (1) Prepare a mixture of 75 mL of anhydrous ethanol and 25 mL of deionized water, and adjust the pH value to 4.0-4.5 with dilute hydrochloric acid. Add 5 g of the microcapsules prepared in the above steps, stir mechanically to disperse the microcapsules evenly, and transfer the solution to a flask equipped with a condensation reflux device.
[0123] (2) Dissolve 0.15 g of silane coupling agent KH570 in 20 mL of 50 wt% ethanol solution and hydrolyze it by ultrasonication for 20 min. Add the hydrolyzed silane coupling agent dropwise to the solution prepared in step (1), stir magnetically and heat to 70°C at a rate of 1°C / min, and react for 2.5 h.
[0124] (3) After the reaction is completed, the modified microcapsules are obtained by cooling, filtering, washing and drying.
[0125] 3. Preparation of self-repairing fluorosilicone rubber composite materials
[0126] (1) Blend the fluorosilicone rubber substrate and the microcapsules in a mass ratio of 100:5, perform ultrasonic dispersion and mechanical stirring, and stir thoroughly to make the raw materials evenly mixed.
[0127] (2) Use a vacuum oven to remove the bubbles that are mixed in during the stirring process. Pour the degassed mixture into a polytetrafluoroethylene mold and vacuum degas again.
[0128] (3) The mixture was cured at room temperature for 48 h and then demolded to obtain a self-healing fluorosilicone rubber sample.
[0129] Example 2
[0130] The preparation method of this embodiment is basically the same as that of embodiment 1, except that no sodium chloride component is added during the emulsion preparation process of this embodiment. Other preparation steps and process conditions are the same as those of embodiment 1.
[0131] Example 3
[0132] The preparation method of this embodiment is basically the same as that of embodiment 1, except that the components of the emulsifier are different. The emulsifier used in this embodiment is sodium dodecylbenzene sulfonate of the same mass. The other preparation steps and process conditions are the same as those of embodiment 1.
[0133] Example 4
[0134] The preparation method of this embodiment is basically the same as that of embodiment 1, except that, during the emulsion preparation process, the mass ratio of each component in the emulsion is different. The emulsion ratio of this embodiment is: 1 part of urea, 0.1 part of resorcinol, 0.1 part of ammonium chloride, 1 part of sodium chloride, 0.075 part of PVA, 0.1125 part of EMA and 57.3125 parts of deionized water, which are weighed and mixed. Other process conditions are basically the same as those in embodiment 1.
[0135] Example 5
[0136] The preparation method of this embodiment is basically the same as that of embodiment 1, and the only difference is that in the step of preparing the self-healing material, the mass ratio of the fluorosilicone rubber substrate to the microcapsules is different. In this embodiment, the mass ratio of the fluorosilicone rubber substrate to the microcapsules is 100:10.
[0137] Example 6
[0138] The preparation method of this embodiment is basically the same as that of embodiment 1, and the only difference is that in the self-healing material preparation step, the mass ratio of the fluorosilicone rubber substrate to the microcapsule is different. In this embodiment, the mass ratio of the fluorosilicone rubber substrate to the microcapsule is 100:15.
[0139] Comparative Example 1
[0140] The preparation method of this comparative example is basically the same as that of Example 1, except that the polymerization reaction conditions are different. In the microcapsule preparation process of this comparative example, the specific steps of stirring preparation in step (4) are as follows:
[0141] The emulsion was transferred to a three-necked flask and mechanically stirred at a speed of 500 r / min. A 37wt% formaldehyde solution was added according to a mass ratio of urea to formaldehyde solution of 1:2.56, and then a few drops of n-octanol were added to eliminate the bubbles generated during the emulsification process. The solution was heated evenly in a water bath, and the temperature was directly increased from room temperature to 60℃ at a rate of 1℃ / min for 4 h.
[0142] The component ratios in the emulsion when preparing the microcapsules in each embodiment and comparative example, and the mass ratios of the fluorosilicone rubber substrate and the microcapsules in the self-healing fluorosilicone rubber composite material are shown in Table 1.
[0143]
[0144] Performance Testing
[0145] The products at different polymerization stages in Example 1 were observed using a scanning electron microscope.
[0146] Tensile strength: The tensile strength of the self-healing fluorosilicone rubber composite materials prepared in each embodiment and comparative example was tested according to the method specified in GB / T 528-2009 "Determination of tensile stress-strain properties of vulcanized rubber or thermoplastic rubber". Specifically, a universal tensile testing machine was used to test the tensile strength and elongation at break of the silicone rubber material. 3 to 5 specimens were measured for each formula, and the average value was taken as the test result. When the material is pulled apart, the repair agent is released and cross-linked in the broken area, thereby completing the repair of the damage. The broken silicone rubber specimens were spliced and aligned, and clamped with two glass slides to ensure good contact between the broken samples. The specimens were then repaired at room temperature for 24 hours and at 60°C for 24 hours for a total of 48 hours, and the tensile strength of the specimens was measured again.
[0147] The performance test data of the microcapsules and self-healing fluorosilicone rubber composite materials prepared in each embodiment and comparative example are shown in Table 2 below.
[0148] Table 2
[0149]
[0150] Note: In Table 1, the core material content is the mass fraction of the core material in the microcapsule to the total weight of the microcapsule. If the core material content of the microcapsule is too low, it means that the content of the active ingredient in the microcapsule is low, which will inevitably increase the amount of microcapsules used, and may cause a significant decrease in the mechanical and electrical properties of the composite material; if the core material content of the microcapsule is too high, it means that the wall thickness of the microcapsule is too low, which may lead to high permeability and insufficient mechanical strength of the wall material. In the preparation of the composite material, the microcapsule is easy to break and fail.
[0151] The core material utilization rate refers to the ratio of the core material mass in the microcapsule to the core material mass added during preparation. The low core material utilization rate of the microcapsule is usually caused by the inability of the wall material to effectively coat the core material: either a complete capsule wall cannot be formed, resulting in the loss of the core material and the formation of a hollow spherical shell; or although a complete capsule wall is formed, the wall thickness is extremely thin and the mechanical strength of the wall material is insufficient, resulting in the rupture of the microcapsule and the loss of the core material during the filtration and washing process of the microcapsule. In addition, considering the economic efficiency of the preparation method, the core material used should be coated as a microcapsule as much as possible when preparing the microcapsule. In summary, the core material utilization rate of the microcapsule should be increased as much as possible.
[0152] Combination Figure 2~Figure 9 ,in, Figure 2 This is a microscopic image of the polymerization reaction solution obtained in Example 1; Figure 3 This is a microscopic image of the polymerization reaction solution when the temperature is raised to 55° C. in Example 1; Figure 4 This is a microscopic image of the polymerization reaction solution after constant temperature reaction at 55° C. for 0.5 h in Example 1; Figure 5 This is a microscopic image of the polymerization reaction solution after constant temperature reaction at 55° C. for 1.5 h in Example 1; Figure 6 This is a microscopic image of the polymerization reaction solution after constant temperature reaction at 55° C. for 2.5 h in Example 1; Figure 7 This is a microscopic image of the polymerization reaction solution after constant temperature reaction at 55° C. for 3.5 h in Example 1; Figure 8 and Fig. 9 They are microscopic morphology pictures of the microcapsule products prepared in Example 1. Figure 1 to Figure 7 It can be seen that after the emulsification is completed, the droplets in the polymerization reaction liquid are stably dispersed in the solution, and the solution is translucent. During the heating process, the droplets exist stably, the wall material has not yet precipitated from the solution, and the solution gradually turns into a milky white opaque liquid. After 0.5 min of constant temperature reaction, the wall material begins to precipitate from the solution, and the surface of the droplet is covered by a layer of opaque material (unformed wall material). At this time, some droplets are no longer regular spheres. After 1.5 hours of constant temperature reaction, the core material droplets have been basically covered by the wall material, the thickness of the wall material has increased, and basically all microcapsules are suspended in the solution. After 2.5 hours of constant temperature reaction, the morphology of the microcapsules has not changed significantly, but stratification occurs in the solution. The precipitated substances are a few small molecular PUF particles and microcapsules with thicker walls. At this time, the wall material of the microcapsule is still not completely cross-linked. If the reaction is stopped and filtered and washed at this time, it is easy to cause the microcapsules to break during the washing process, and filtration is difficult, and the resulting product is oily. After 3.5 hours of constant temperature reaction, the sample morphology did not change significantly, and the wall material had basically completed cross-linking. After filtration, washing and drying, microcapsules with good morphology were obtained. Figure 8 and Fig. 9 It can be seen that the microcapsules are spherical substances with full shapes and tiny protrusions on the surface. Their particle sizes are generally between 80μm and 230μm, with an average particle size of 198μm.
[0153] In comparative example 1, when preparing microcapsules, the temperature was directly raised to 60° C. for preheating treatment. Many microcapsules prepared therefrom were broken during the washing and drying processes.
[0154] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.
[0155] The above-mentioned embodiments only express several implementation methods of the present invention, and the description is relatively specific and detailed, but it cannot be understood as limiting the scope of the invention patent. It should be pointed out that for ordinary technicians in this field, several modifications and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be based on the attached claims, and the description can be used to interpret the content of the claims.
Claims
1. A method for preparing microcapsules for rubber self-repairing, characterized in that: The steps include: Mixing urea, a curing agent, an emulsifier, water and a core material to form an emulsion; wherein the core material is insoluble in water; adding formaldehyde to the emulsion to obtain a polymerization reaction liquid, and subjecting the polymerization reaction liquid to a polymerization reaction to obtain the microcapsules; The conditions of the polymerization reaction include: firstly heating from room temperature to 35°C~40°C at a heating rate of 0.5°C / min~1.5°C / min, and keeping warm for 15min~20min; then heating to 45°C~50°C at a heating rate of 0.5°C / min~1.5°C / min, and keeping warm for 15min~20min; then heating to 55°C~60°C at a heating rate of 0.5°C / min~1.5°C / min, and reacting at a constant temperature for 3.5h~5h.
2. The preparation method according to claim 1, characterized in that The preparation method satisfies at least one of the following conditions: (1) The emulsion comprises, by weight: 1 part of urea, 0.1 to 0.5 parts of the curing agent, 0.05 to 0.2 parts of the emulsifier, 2 to 6 parts of the core material, and 40 to 60 parts of water; (2) The mass ratio of the urea to the formaldehyde is 1:(0.5-1.5).
3. The preparation method according to any one of claims 1 to 2, characterized in that The preparation method satisfies at least one of the following conditions: (1) The core material is selected from at least one of polydimethylsiloxane, dicyclopentadiene and epoxy resin; (2) The curing agent is selected from at least one of resorcinol and ammonium chloride; (3) The emulsifier is at least one selected from polyvinyl alcohol, ethylene methyl acrylate copolymer, sodium dodecylbenzene sulfonate, dodecylphenol polyoxyethylene ether, sodium lignin sulfonate and nano titanium dioxide; (4) The polymerization reaction is carried out under mechanical stirring conditions, and the stirring speed of the mechanical stirring is 400r / min~600r / min.
4. The preparation method according to claim 3, characterized in that: The emulsifier is polyvinyl alcohol and ethylene methyl acrylate copolymer, and the mass ratio of polyvinyl alcohol to ethylene methyl acrylate copolymer is 1: (1.5-3).
5. The preparation method according to claim 2, characterized in that: The emulsion further includes a surface tension regulator; the surface tension regulator satisfies at least one of the following conditions: (1) The surface tension regulator is at least one selected from sodium chloride, potassium chloride and ammonium sulfate; (2) In the emulsion, the mass fraction of the surface tension modifier is 0.8 parts to 1.2 parts.
6. The preparation method according to any one of claims 1 to 2, 4 to 5, characterized in that: The preparation method further comprises adding a pH adjuster to the emulsion to adjust the pH value of the emulsion to 3.5-4.
0.
7. The preparation method according to any one of claims 1 to 2, 4 to 5, characterized in that: The following steps are also included: A silane coupling agent is grafted onto the surface of the microcapsule.
8. A microcapsule for rubber self-repairing, characterized in that: Prepared according to the preparation method according to any one of claims 1 to 7.
9. A self-repairing fluorosilicone rubber material, characterized in that: It comprises a rubber substrate and the rubber self-repairing microcapsule as claimed in claim 8.
10. A rubber product, characterized in that: Comprising the self-repairing fluorosilicone rubber material as described in claim 9.