CN110465251B - Long-acting repairing type double-layer microcapsule - Google Patents

Long-acting repairing type double-layer microcapsule Download PDF

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CN110465251B
CN110465251B CN201910856494.6A CN201910856494A CN110465251B CN 110465251 B CN110465251 B CN 110465251B CN 201910856494 A CN201910856494 A CN 201910856494A CN 110465251 B CN110465251 B CN 110465251B
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pmma
styrene
divinylbenzene copolymer
zif
long
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CN110465251A (en
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廖益均
吴晓莉
曹剑飞
邱士安
梁昊天
唐海龙
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Chengdu Technological University CDTU
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J13/00—Colloid chemistry, e.g. the production of colloidal materials or their solutions, not otherwise provided for; Making microcapsules or microballoons
    • B01J13/02—Making microcapsules or microballoons
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J13/00—Colloid chemistry, e.g. the production of colloidal materials or their solutions, not otherwise provided for; Making microcapsules or microballoons
    • B01J13/02—Making microcapsules or microballoons
    • B01J13/06—Making microcapsules or microballoons by phase separation
    • B01J13/14—Polymerisation; cross-linking
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y40/00—Manufacture or treatment of nanostructures
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F2/00—Processes of polymerisation
    • C08F2/12—Polymerisation in non-solvents
    • C08F2/16—Aqueous medium
    • C08F2/22—Emulsion polymerisation
    • C08F2/24—Emulsion polymerisation with the aid of emulsifying agents
    • C08F2/26—Emulsion polymerisation with the aid of emulsifying agents anionic
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F212/00—Copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by an aromatic carbocyclic ring
    • C08F212/34—Monomers containing two or more unsaturated aliphatic radicals
    • C08F212/36—Divinylbenzene
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
    • C09D7/00—Features of coating compositions, not provided for in group C09D5/00; Processes for incorporating ingredients in coating compositions
    • C09D7/40—Additives
    • C09D7/70—Additives characterised by shape, e.g. fibres, flakes or microspheres

Abstract

The invention discloses a preparation method of a long-acting repairing type double-layer microcapsule, which comprises the following steps: (1) preparation of SDB nanospheres: adding azo initiator into the mixture of styrene, divinyl benzene and anionic surfactant to prepare oil-in-water Pickering emulsion; under the protection of nitrogen, heating the Pickering emulsion for reaction to obtain white solid SDB nanospheres; (2) preparing SDB/PMMA nano composite particles: adding PMMA into water, adding SDB nanospheres, and allowing PMMA to swell and enter SDB particles; adding an oxidant, and dropwise adding an inorganic acid to enable PMMA to be subjected to full polymerization reaction to obtain SDB/PMMA nano composite particles; (3) preparing ZIF-8/PMMA hollow microspheres: adding absolute methanol into SDB/PMMA nano composite particles and 2-methylimidazole, adding zinc nitrate, and reacting to obtain ZIF-8/SDB/PMMA composite particles; adding the mixture into an organic solvent, and removing the SDB template to obtain ZIF-8/PMMA hollow microspheres; (4) load repairing agent or corrosion inhibitor: and adding the ZIF-8/PMMA hollow microspheres into the repair liquid for soaking to obtain ZIF-8/PMMA/repair liquid microcapsules.

Description

Long-acting repairing type double-layer microcapsule
Technical Field
The invention relates to a microcapsule, in particular to a preparation method of a long-acting double-layer microcapsule, belonging to the technical field of coatings.
Background
The paint is a polymer-based composite material and has the characteristics of all polymer high-molecular long-chain sections. After the coating is constructed, the coating is gradually crosslinked, polymerized and cured, and the highest strength performance is achieved for a period of time after the coating is completely cured. Along with the increase of the time for finishing the coating construction, the internal crosslinking structure of the coating can be gradually damaged, so that the mechanical property of the coating is reduced, and if the environment fluctuates due to temperature difference, cracks are very easy to appear on the surface of the coating. Cracks are initially present only in the interior of the coating and are difficult to detect and repair, and macroscopic macro-cracks are formed as the cracks gradually crosslink and merge, which becomes very difficult if the coating is to be repaired.
The coating with the self-repairing function is the best scheme for solving the problem that the coating is effectively adaptive to various environmental damages after construction is finished. The key of the repair function is to provide substance supplement for the coating microcracks in time, fill the microcracks fully by the supplement substances and prevent the microcracks from growing and expanding to form macrocracks.
The embedded self-repairing coating is characterized in that microcapsules are added, so that when cracks are spread to the microcapsules, the microcapsules break to release a repairing agent, the repairing agent fills the cracks and is cured through a cross-linking reaction with coating matrixes on two sides of the cracks, and the cracks do not grow any more. The pre-embedded repairing agent has good universality, but the initiation of the cross-linking polymerization characteristic of the pre-embedded repairing agent is difficult to control, and if the cross-linking reaction quality of the pre-embedded repairing agent cannot be well controlled, the repairing effect is not good, and the surface appearance of the repaired coating is also deteriorated.
Most of capsule core materials wrapped by the existing microcapsule products are repairing core materials with strong activity, so that the microcapsule products cannot be stored for a long time in the application process, and the capsule cores of the microcapsules are gradually inactivated after being stored for a period of time. In addition, the weak wall structure of the microcapsule also causes a great amount of microcapsules to fail due to various internal and external causes before the microcapsules really exert the repairing effect, so that the final microcapsule product cannot exert the expected effect of design.
Disclosure of Invention
The invention aims to solve the problems that in the prior art, microcapsules are gradually inactivated in the storage process and the capsule wall structure of the microcapsules is weak, so that the microcapsules fail for various reasons and cannot exert the repairing effect, and provides a preparation method of long-acting repairing type double-layer microcapsules and a microcapsule product prepared by the preparation method.
In order to achieve the above purpose, the invention provides the following technical scheme:
a preparation method of a long-acting repairing type double-layer microcapsule comprises the following steps:
(1) preparation of styrene-divinylbenzene copolymer nanospheres
And (3) adding an azo initiator into a mixture of styrene, divinyl benzene and an anionic surfactant, and mixing to form an oil phase. Adding into deionized water, mixing, and homogenizing to obtain oil-in-water Pickering emulsion;
heating the Pickering emulsion to 70-80 ℃ under the protection of nitrogen, reacting for 10-20h, centrifugally washing for 2-5 times after the reaction is finished, and drying in vacuum to obtain white solid styrene-divinylbenzene copolymer nanospheres.
(2) Preparation of styrene-divinylbenzene copolymer/PMMA nanocomposite particles
Adding PMMA into water, and performing ultrasonic dispersion; then, adding the styrene-divinylbenzene copolymer nanospheres prepared in the step (1), performing ultrasonic treatment and stirring, and allowing PMMA to swell and enter styrene-divinylbenzene copolymer particles; adding an oxidant, uniformly stirring, dropwise adding an inorganic acid, stirring, reacting at 0-5 ℃ for 2-8h, then heating to room temperature of 15-35 ℃, and carrying out polymerization reaction for 14-28h to ensure that PMMA is fully polymerized; and after the reaction is finished, centrifuging, washing until the supernatant is colorless, and drying in vacuum to obtain the styrene-divinylbenzene copolymer/PMMA nano composite particles.
(3) Preparation of ZIF-8/PMMA hollow microspheres
Taking the styrene-divinylbenzene copolymer/PMMA nano composite particles obtained in the step (2) and 2-methylimidazole, adding anhydrous methanol, and uniformly dispersing; adding zinc nitrate, stirring for reacting for 2-8h, and centrifuging and washing to obtain ZIF-8/styrene-divinylbenzene copolymer/PMMA composite particles;
and adding the ZIF-8/styrene-divinylbenzene copolymer/PMMA composite particles into an organic solvent, removing a styrene-divinylbenzene copolymer template, filtering, and drying to obtain the ZIF-8/PMMA hollow microspheres.
(4) Load repairing agent or corrosion inhibitor
Adding the ZIF-8/PMMA hollow microspheres into the repair liquid for soaking, and stirring for reaction to enable the repair liquid to enter the ZIF-8/PMMA hollow microspheres; and filtering, washing, centrifuging and drying in vacuum to obtain the ZIF-8/PMMA/repair liquid microcapsule.
The microcapsule designed by the preparation method is a long-acting repairing MOF/PMMA/double-layer microcapsule and has a metal-organic framework (MOF) structure. The microcapsule core forms Pickering emulsion (Pickering emulsion), which is stable emulsion formed by solid particles adsorbed to two-phase interface. The solid particles are combined on the surface of the interface to prevent liquid drops from coalescing, so that the emulsion is stable, the dosage of the emulsifier is low, the environment is friendly, the stability is strong, the emulsion is not easily influenced by factors such as the pH value of a system, the salt concentration, the temperature and the oil phase composition, and the long-acting advantage is achieved. Then, the microcapsule adopts a core-shell wrapping structure, has the structural characteristics of a double-layer core @ shell, and can play an excellent composite enhancement promoting role by fully combining the property characteristics of different core-shell structures. The load repairing liquid of the multilayer core-shell structure has higher content, more various release diffusion characteristics and excellent repairing effect. The shell layer of the microcapsule has a ZIF-8 structure (Zeolite Imidazolate Frameworks, a zeolite imidazole ester framework structure material), is a porous crystal material, can well help the microcapsule to slowly release to play an effect, and has an excellent lasting repair effect.
In the preparation method, firstly, the styrene-divinylbenzene copolymer/PMMA nano composite particles are permeated into the styrene-divinylbenzene copolymer nano microspheres by utilizing PMMA to prepare the styrene-divinylbenzene copolymer shell and PMMA core nano particles. The expression of styrene-divinylbenzene copolymer/PMMA, ZIF-8/PMMA/repair fluid microcapsule and the like is used for indicating that the component A wraps the component B or forms a shell-core microsphere structure, for example, "styrene-divinylbenzene copolymer/PMMA" indicates a styrene-divinylbenzene copolymer wrapped PMMA nanometer microsphere structure, and "ZIF-8/PMMA/repair fluid microcapsule" indicates that ZIF-8 is positioned at the outermost layer and PMMA is wrapped inside, and the repair fluid component is loaded in the nanometer microsphere structure.
Further, in the step (1), the azo initiator is one or more of Azobisisobutyronitrile (AIBN), Azobisisoheptonitrile (ABVN), azobisisobutyramidine hydrochloride (AIBA), azobisisobutyrimidazoline hydrochloride (AIBI), and the like.
Preferably, the azo-type initiator is AIBN. The azodiisobutyronitrile has stable decomposition reaction, only generates 1 kind of free radicals, and does not generate induced decomposition side reaction.
Preferably, the azo-type initiator is used in an amount of 0.1 to 6% by mass based on the first polymerization raw material including styrene and divinylbenzene.
Further, in the step (1), the anionic surfactant is at least one of sodium alkyl sulfate C12-C16 and sodium alkyl sulfonate C12-C16. Preferably, the anionic surfactant is sodium lauryl sulfate. Where the sodium C12-C16 alkyl sulfate is an alkyl-linked sodium sulfate having 12-16 carbon atoms, such as sodium dodecyl sulfate, sodium tetradecyl sulfate.
Preferably, the anionic surfactant is used in an amount of 0.5 to 2 times by mass of the first polymerization raw material including styrene and divinylbenzene. E.g., 0.7, 0.9, 1, 1.1, 1.3, 1.5 times, etc.
Further, the divinylbenzene in step (1) is divinylbenzene, DVB, having a purity of 80%, isomer mixture comprising 4 ⁃ t-butylcatechol inhibitor at a concentration of less than 0.1%.
Preferably, the weight ratio of divinylbenzene to styrene is styrene: divinylbenzene =1: 0.5-2.
Further, after the water phase and the oil phase in the step (1) are mixed, a high-speed homogenizer is adopted for homogenization treatment. Preferably, the rotating speed of the homogenizer is more than or equal to 12000 r/min. Preferably, homogenization treatment is carried out for 2-5 min. Wherein deionized water is used as the water phase.
Further, heating the pickering emulsion to 72-88 ℃ for reaction in the step (1). Preferably, a water bath is used for heating. The heating temperature of the water bath is accurately controlled, and the fluctuation is less.
Further, the centrifugal washing process in the step (1) has a centrifugal rotation speed of 2000-.
Further, the step (1) is to carry out centrifugal washing process and wash by using C1-C6 low molecular alcohol. The C1-C6 low molecular weight alcohol is at least one of methanol, ethanol, n-propanol, isopropanol, n-butanol and isobutanol. Preferably anhydrous ethanol.
Further, the vacuum drying temperature in the step (1) is less than or equal to 50 ℃. Preferably, the vacuum drying temperature is ≦ 45 deg.C, e.g., 40 deg.C. The vacuum drying temperature is controlled to be not more than 50 ℃, the integral core-shell structure of the microcapsule is not deformed, and the structure is more compact.
Further, the PMMA in the step (2) is polymethyl methacrylate, and the molecular weight of the PMMA is in the range of 6 to 30 ten thousand.
Further, in the step (2), the styrene-divinylbenzene copolymer nanospheres and the PMMA raw material are added in a weight ratio of styrene-divinylbenzene copolymer nanospheres: PMMA =1:40-1: 2. E.g., 1:20, 1:15, 1:10, 1:8, 1:5, etc.
Further, in the step (2), after the styrene-divinylbenzene copolymer nanospheres are added, the mass concentration of the styrene-divinylbenzene copolymer nanospheres in the mixed solution is 2-10%.
Further, in the step (2), the oxidizing agent is one or two of potassium persulfate, ammonium persulfate and peroxy oxidizing agent. The peroxy-based oxidizing agent includes benzoyl peroxide and the like. Preferably, the oxidizing agent is potassium persulfate.
Preferably, the molar ratio of oxidizing agent to PMMA is between 1:0.8 and 1.2, preferably 1: 1. The molar ratio of the oxidant to the PMMA is close to 1:1, and the good ratio of the oxidant to the PMMA is controlled, so that the subsequent swelling polymerization reaction of the PMMA is facilitated.
Further, in the step (2), the inorganic acid is one or more of hydrochloric acid, sulfuric acid, perchloric acid, nitric acid and the like. Hydrochloric acid is preferred.
Preferably, the molar ratio of the inorganic acid to the PMMA is 1: 0.7-1.2. The molar weight of the inorganic acid is close to 1:1 with that of PMMA, and the inorganic acid is matched with the oxidant to realize the polymerization reaction of the composite particles. The molar amount of the inorganic acid added is calculated as the reaction equivalent, so as to ensure that the polymerization reaction is fully carried out.
Further, PMMA is taken in the step (2) and added into water, and ultrasonic dispersion is carried out at the temperature of 0-5 ℃. Firstly, PMMA is subjected to ultrasonic dispersion under a low-temperature condition, so that the uniformity is improved, ultrasonic heating is inhibited, and unexpected polymerization reaction is avoided.
Further, the styrene-divinylbenzene copolymer nanospheres are added in the step (2), and the temperature of the mixed feed liquid is kept at 0-5 ℃.
Further, the step (2) makes the PMMA fully swelled into the styrene-divinylbenzene copolymer nanospheres. Under observation of an optical microscope, the PMMA drops gradually disappear, which shows that PMMA is fully swelled into the styrene-divinylbenzene copolymer nanospheres.
Further, the step (2) of adding the oxidizing agent is adding an aqueous solution of the oxidizing agent. Such as aqueous potassium persulfate. An oxidant (such as potassium persulfate) is dissolved in water to be prepared into the oxidant for use, so that the materials are mixed more uniformly.
Further, in the step (2), the solid content of the styrene-divinylbenzene copolymer emulsion is kept unchanged at 4 wt%, and the weight ratio of the PMMA raw material to the seed emulsion is 1:40-1: 2.
Further, in the step (3), the styrene-divinylbenzene copolymer/PMMA nano composite particles and 2-methylimidazole are taken, anhydrous methanol is added, and the ultrasonic dispersion is uniform. The anhydrous methanol is used as a solvent, and the nano composite particles and the 2-methylimidazole are dissolved and matched to be mutually dispersed and mixed, so that the reaction uniformity of a shell layer is improved.
Further, in the step (3), the mass ratio of the styrene-divinylbenzene copolymer/PMMA nanocomposite particles and 2-methylimidazole is styrene-divinylbenzene copolymer/PMMA nanocomposite particles: 2-methylimidazole mass ratio =1: 0.5-5.
Further, the zinc nitrate is zinc nitrate hexahydrate.
Further, the weight ratio of the 2-methylimidazole added in the step (3) to the zinc nitrate hexahydrate is 25: 1-2.
Further, in the step (3), ZIF-8/styrene-divinylbenzene copolymer/PMMA composite particles are added into an organic solvent, and a styrene-divinylbenzene copolymer template is removed. Preferably, the organic solvent is a polar inert solvent. Preferably, the organic solvent is any one of DMF and DMAC. The DMF refers to N, N-dimethylformamide, the DMAC refers to N, N-dimethylacetamide, both are polar inert solvents, the solubility is good, the reaction is avoided, and the effect of dissolving and removing the styrene-divinylbenzene copolymer template is good.
Further, in the step (4), the repairing liquid is one or more of unsaturated fatty oils such as tung oil, linseed oil and sodium alginate. For example, the repairing liquid can be single tung oil, or a mixed repairing liquid of tung oil and linseed oil, or a composite repairing liquid of tung oil, linseed oil, sodium alginate and the like. Preferably one or a mixture of two of tung oil and linseed oil.
Further, adding the ZIF-8/PMMA hollow microspheres in the step (4) into the repair liquid to be soaked for 4-20 h; then heating to 30-40 ℃, and continuing stirring for 4-12h to enable the repair liquid to enter the ZIF-8/PMMA hollow microspheres. The hollow microspheres are added into the repairing solution to be soaked for a period of time, then the hollow microspheres are heated slightly and soaked continuously, the speed and the quality of the repairing solution penetrating into the hollow microspheres are improved, and the high-quality microcapsules are obtained.
Further, after the filtration of the step (4), washing with ultrapure water and/or C1-C6 low molecular alcohol is carried out 2 to 5 times, preferably 3 times. Preferably, the washing is performed alternately by water and ethanol, and the washing is performed 3 times by water and ethanol respectively.
Further, after the washing in the step (4) is finished, separating by a centrifugal machine, and drying for 5-10h, preferably 6-8h in vacuum. Preferably, the vacuum drying temperature is less than or equal to 45 ℃. Preferably, the centrifugal rotation speed is 2000-18000r/min, preferably 6000-8000 r/min.
Compared with the prior art, the invention has the beneficial effects that:
1. the long-acting type double-layer microcapsule comprises a capsule core formed by matching repair liquid (corrosion inhibitor or linseed oil) through an MOF/PMMA double-layer microcapsule structure. The outer shell of the MOF is hollow microspheres and coats the capsule core, the PMMA is the inner capsule wall, and the hollow layer between the two capsule walls is filled with the capsule core. The microcapsule has the advantages of high total amount of the whole load capsule core emulsion, good activity performance, multiple repair effects, high content of the microcapsule load repair tung oil component and good and durable repair effect.
2. According to the long-acting type double-layer microcapsule, the double-layer microcapsule coats repair liquid (repair liquid) or a corrosion inhibitor, so that the long-acting repair effect is achieved, the repair liquid between capsule walls seeps out to repair after the MOf porous layer is punctured by cracks, when the cracks with poor first repair effect expand, the second PMMA layer is punctured, and the capsule core in the inner layer overflows to repair for the second time; if the first-time effect is ideal, the remaining inner-layer microcapsules can generate the self-repairing effect after cracks are generated by the second-time corrosion, and meanwhile, the service life of the self-repairing can be prolonged.
3. The long-acting repairing MOF/PMMA/double-layer microcapsule takes MOf as a porous structure, can repair through two modes of pore exudation and crack rupture, and has various repairing modes. The repairing liquid tung oil in the microcapsules has better lasting stability, can keep good activity in the long-term storage process, and avoids the problem of microcapsule failure.
Description of the drawings:
FIG. 1 is ZIF-8/PMMA/linseed oil microcapsules.
Fig. 2 shows the resistance change of the coating layer after the microcapsule is soaked for different time.
Detailed Description
The present invention will be described in further detail with reference to test examples and specific embodiments. It should be understood that the scope of the above-described subject matter is not limited to the following examples, and any techniques implemented based on the disclosure of the present invention are within the scope of the present invention.
<Example 1>
Preparing long-acting double-layer microcapsule
(1) Preparation of styrene-divinylbenzene copolymer nanospheres
0.0078g of azobisisobutyronitrile was taken and added to a mixture of 1.4g of styrene, 2.1g of DVB (divinylbenzene (DVB, 80%, isomer mixture, containing 4-tert-butylcatechol inhibitor in a concentration of less than 0.1%) and 4g of sodium lauryl sulfate, stirring and mixing uniformly to form an oil phase, adding 50mL of deionized water, mixing uniformly, homogenizing for 2min at the rotating speed of 15000r/min by using a high-speed homogenizer to obtain a stable oil-in-water Pickering emulsion, adding the obtained emulsion into a 100mL double-neck round-bottom flask, and after cooling, introducing nitrogen for 20min to replace air, then heating the emulsion in a water bath at 75 ℃ for 16h, centrifuging at 6000r/min for 2min after reaction, collecting a product, washing with 10mL of absolute ethyl alcohol, repeatedly centrifuging and washing for 3 times, and performing vacuum drying at 40 ℃ for 2h to obtain the white solid styrene-divinylbenzene copolymer nanospheres.
(2) Preparation of styrene-divinylbenzene copolymer/PMMA nanocomposite particles
0.5g of PMMA was added to 50mL of water and sonicated at 0 ℃ for 15 minutes. Then, 4g of styrene-divinylbenzene copolymer nanospheres were added, the mixture was continuously ultrasonically stirred at 0 ℃ for 30 minutes to fully swell PMMA into the styrene-divinylbenzene copolymer particles, and after the PMMA droplets disappeared gradually under observation by an optical microscope. The PMMA swollen styrene-divinylbenzene copolymer particles were then transferred to a three-necked round-bottomed flask in an ice bath. 0.05g of potassium persulfate solution was dissolved in 1L of deionized water to obtain an oxidizing agent solution, and 10mL of the oxidizing agent solution was taken and then added to the dispersion in one portion. Then, 0.5mL of hydrochloric acid (0.5mol/L) was added thereto, and dropped by a syringe. The temperature is kept at 0 ℃ for 5h, and the polymerization is carried out at room temperature of 26 ℃ for 18 h to fully polymerize the PMMA. The obtained green styrene-divinylbenzene copolymer/PMMA composite particles are centrifuged at 6000r/min for 2min, washed with 10mL of ethanol, and the centrifugation and washing are repeated for 3 times until the supernatant is colorless. Finally, the product was dried in a vacuum oven at 40 ℃ for 48 h.
(3) Preparation of ZIF-8/PMMA hollow microspheres
1g of styrene-divinylbenzene copolymer/PMMA solid powder and 11.3 g of 2-methylimidazole were weighed into a single-neck flask, 50mL of anhydrous methanol was added, and magnetic stirring was carried out for 30min after 3min of ultrasonic dispersion. And then adding a methanol solution containing 0.59g of zinc nitrate hexahydrate, continuously stirring for 3 hours, centrifuging at 6000r/min for 3 minutes, carrying out 10mL of absolute ethanol, and repeatedly centrifuging and washing for 3 times to obtain the ZIF-8/styrene-divinylbenzene copolymer/PMMA composite particles. Adding the mixture into 50mL of DMF, soaking for 3h, removing a styrene-divinylbenzene copolymer template, filtering, washing for 3 times by 10mL of absolute ethyl alcohol, and drying for 2h in vacuum at 45 ℃ to obtain the ZIF-8/PMMA hollow microspheres.
(4) Load repairing agent or corrosion inhibitor
Adding the dried ZIF-8/PMMA hollow microspheres into 20mL of linseed oil, soaking at the room temperature of 25 ℃ and stirring for 12 hours, and then heating in a 35 ℃ water bath kettle and reacting for 12 hours by magnetic stirring. Filtering, alternately washing with 10mL of ultrapure water and 10mL of absolute ethyl alcohol, repeating the washing treatment for three times, centrifuging for 3min by using a centrifuge 6000r/min, and finally putting the washed linseed oil-loaded microcapsule into a vacuum drying oven for vacuum drying for 8h at 60 ℃ to obtain the ZIF-8/PMMA/linseed oil microcapsule.
<Testing>
The microcapsules prepared in example 1 were subjected to scratch resistance testing as follows:
control group: 50g of bisphenol A epoxy resin E-44 is taken, 9.2g of diethylenetriamine is added, two drops of dispersing agent and two drops of leveling agent are added dropwise, and the mixture is stirred and mixed uniformly. Then the paint is coated on a clean iron sheet which is derusted and washed by absolute ethyl alcohol. The iron sheet was placed horizontally until the coating was naturally dried overnight. After the coating was completely dried, the film was scratched with a blade. The patch electrodes are adhered to the surface of the coating film, the distance between the patch electrodes is controlled to be 10cm, the distance between the two patch electrodes and the scratch is equal, and the resistance change condition of the patch electrodes is tested
Test groups: 50g of bisphenol A epoxy resin E-44 is taken, 9.2g of diethylenetriamine is added, two drops of dispersing agent and two drops of leveling agent are added dropwise, and the mixture is stirred and mixed uniformly. Then 4g of microcapsules are added, stirred evenly and then coated on the iron sheet which is derusted and washed clean by absolute ethyl alcohol. The iron sheet was placed horizontally until the coating was naturally dried overnight. After the coating was completely dried, the film was scratched with a blade. And (3) adopting the patch electrodes to be adhered on the surface of the coating film, controlling the distance between the patch electrodes to be 10cm, and testing the resistance change condition of the patch electrodes, wherein the distance between the two patch electrodes and the scratch is equal.
The results are shown in FIG. 2. Wherein, curve 2a is the variation of the resistance of the common microcapsule coating with the scratch damage time; curve 2b is the variation with scratch failure time with the addition of ZIF-8/PMMA/linseed oil microcapsule coating. The impedance is lower during the coating time of 0-1 hour, and the impedance increases after 1 hour because the coating self-heals; after 10 hours, the impedance of the common coating is always reduced, the impedance of the double-layer microcapsule is recovered within 10-20 hours, the process is the second microcapsule repairing process, the microcapsules only puncture the first layer when the coating is scratched for the first time, and the subsequent microcapsules continuously release the repairing liquid to realize the repairing effect on the coating, so the resistance is continuously changed.
<Example 2>
Preparing long-acting double-layer microcapsule
(1) Preparation of styrene-divinylbenzene copolymer nanospheres
0.0078g of azobisisobutyronitrile was taken and added to a mixture of 1.5g of styrene, 2.2g of DVB (divinylbenzene (DVB, 80%, isomer mixture, containing 4-tert-butylcatechol inhibitor in a concentration of less than 0.1%) and 4.3g of sodium lauryl sulfate, stirring and mixing uniformly to form an oil phase, adding 50mL of deionized water, mixing uniformly, homogenizing for 3min at a rotation speed of 12000r/min by using a high-speed homogenizer to obtain a stable oil-in-water Pickering emulsion, transferring the obtained emulsion into a 100mL double-neck round-bottom flask, after cooling, nitrogen was introduced for 25min, the emulsion was then heated in a water bath at 73 ℃ for 24h, centrifuged at 6000r/min for 2min after reaction, and the product was collected and purified by mixing with 10mL of mixed alcohol (absolute ethanol: mixed alcohol of methanol =1: 1), and centrifugal washing was repeated 3 times, and vacuum drying was performed at 45 ℃ for 2 hours to obtain white solid styrene-divinylbenzene copolymer nanospheres.
(2) Preparation of styrene-divinylbenzene copolymer/PMMA nanocomposite particles
Styrene-divinylbenzene copolymer/PMMA nanocomposite particles were prepared by a swelling-diffusion-interface-polymerization method. First, 0.5g of PMMA was added to 50mL of water and ultrasonically dispersed at 0 ℃ for 20 minutes. Then, adding 4g of styrene-divinylbenzene copolymer nanospheres, keeping the mixture at 0 ℃, continuing to stir ultrasonically for 35 minutes to ensure that PMMA is fully swelled into styrene-divinylbenzene copolymer particles, and observing by an optical microscope until PMMA drops gradually disappear; the PMMA swollen styrene-divinylbenzene copolymer particles were transferred to a three-necked round-bottomed flask in an ice bath. 10mL of the oxidizing agent solution prepared in step 2 of example 1 was added to the dispersion in one portion, and then 0.5mL of sulfuric acid (0.3mol/L) was added thereto and dropped by a syringe. The temperature was maintained at 0 ℃ for 6 hours, and polymerization was further carried out at room temperature (28 ℃) for 16 hours, to thereby sufficiently polymerize PMMA. The obtained green styrene-divinylbenzene copolymer/PMMA composite particles are centrifuged at 6000r/min for 2min, then washed with 10mL of ethanol, and the centrifugation and washing are repeated for 3 times until the supernatant is colorless. Finally, drying in a vacuum oven at 45 ℃ for 24 h.
(3) Preparation of ZIF-8/PMMA hollow microspheres
1g of styrene-divinylbenzene copolymer/PMMA solid powder and 11.5 g of 2-methylimidazole were weighed into a single-neck flask, 50mL of anhydrous methanol was added, and magnetic stirring was carried out for 45min after 3min of ultrasonic dispersion. And then adding a methanol solution containing 0.62g of zinc nitrate hexahydrate, continuously stirring for 5h, centrifuging at 6000r/min for 3min, 10mL of absolute ethanol, and repeatedly centrifuging and washing for 3 times to obtain the ZIF-8/styrene-divinylbenzene copolymer/PMMA composite particles. Adding the mixture into 50mL of DMF, soaking for 3h, removing a styrene-divinylbenzene copolymer template, filtering, washing for 3 times by 10mL of absolute ethyl alcohol, and drying for 2h in vacuum at 45 ℃ to obtain the ZIF-8/PMMA hollow microspheres.
(4) Load repairing agent or corrosion inhibitor
The dried ZIF-8/PMMA microcapsules were put into 20mL of tung oil and stirred for 10 hours. And then heating the mixture in a water bath kettle at 36 ℃, magnetically stirring the mixture for 14 hours, alternately washing the mixture for three times by using 10mL of ultrapure water and 10mL of absolute ethyl alcohol, centrifugally separating the mixture for 3 minutes by using a centrifuge 6000r/min, and finally putting the washed negative microcapsules into a vacuum drying oven for vacuum drying at 58 ℃ for 8 hours to obtain the ZIF-8/PMMA/repair liquid microcapsules.
<Comparative example 1>
A microcapsule product was prepared in the same manner as in example 2 except that the sulfuric acid solution required for the reaction was added in one portion without dropping it by a syringe in the addition of the sulfuric acid in step (2), and stirred and mixed uniformly. The remaining preparation steps were as in example 2.
<Example 3>
Preparing long-acting double-layer microcapsule
(1) Preparation of styrene-divinylbenzene copolymer nanospheres
Taking 0.008g of azobisisobutyronitrile, adding 1.5g of styrene, 2.1g of DVB (divinylbenzene (DVB, 80%, isomer mixture, containing 4-tert-butylcatechol inhibitor with the concentration of less than 0.1%) and 4.1g of tetradecyl sodium sulfate, mixing uniformly to form an oil phase, adding 50mL of deionized water, mixing uniformly, homogenizing for 4min at the rotating speed of 15000r/min by using a high-speed homogenizer to obtain stable oil-in-water Pickering emulsion, adding the obtained emulsion into a 100mL double-neck round-bottom flask, and after cooling, introducing nitrogen for 15min to replace air, then heating the emulsion in a water bath at 79 ℃ for 12h, centrifuging at 6000r/min for 2min after reaction, collecting a product, washing with 10mL of absolute ethyl alcohol, repeatedly centrifuging and washing for 3 times, and performing vacuum drying at 40 ℃ for 2h to obtain the white solid styrene-divinylbenzene copolymer nanospheres.
(2) Preparation of styrene-divinylbenzene copolymer/PMMA nanocomposite particles
0.5g of PMMA was added to 50mL of water and ultrasonically dispersed at 0 ℃ for 20 minutes. Then, 4g of styrene-divinylbenzene copolymer nanospheres were added, the mixture was continuously ultrasonically stirred at 0 ℃ for 35 minutes to fully swell PMMA into the styrene-divinylbenzene copolymer particles, and after the PMMA droplets disappeared gradually under observation by an optical microscope. The PMMA swollen styrene-divinylbenzene copolymer particles were then transferred to a three-necked round-bottomed flask in an ice bath. 10mL of the oxidizer solution prepared in step 2 of example 1 was added to the dispersion in one portion. Then, 0.5mL of hydrochloric acid (1mol/L) was added thereto, and dropped by a syringe. The mixture was kept at 0 ℃ for 5 hours and polymerized at room temperature for a further 18 hours to fully polymerize PMMA. The obtained green styrene-divinylbenzene copolymer/PMMA composite particles are centrifuged at 6000r/min for 2min, then washed with 10mL of ethanol, and the centrifugation and washing are repeated for 3 times until the supernatant is colorless. Finally, the product obtained is dried in a vacuum oven at 50 ℃ for 24 h.
(3) Preparation of ZIF-8/PMMA hollow microspheres
1g of styrene-divinylbenzene copolymer/PMMA solid powder and 11.5 g of 2-methylimidazole were weighed into a single-neck flask, 50mL of anhydrous methanol was added, and magnetic stirring was carried out for 50min after 3min of ultrasonic dispersion. And then adding a methanol solution containing 0.59g of zinc nitrate hexahydrate, continuously stirring for 3 hours, centrifuging at 6000r/min for 3 minutes, carrying out 10mL of absolute ethanol, and repeatedly centrifuging and washing for 3 times to obtain the ZIF-8/styrene-divinylbenzene copolymer/PMMA composite particles. Adding the mixture into 50mL of DMF, soaking for 3h, removing a styrene-divinylbenzene copolymer template, filtering, washing for 3 times by 10mL of absolute ethyl alcohol, and drying for 2h in vacuum at 45 ℃ to obtain the ZIF-8/PMMA hollow microspheres.
(4) Load repairing agent or corrosion inhibitor
Putting the dried ZIF-8/PMMA hollow microspheres into 20mL of tung oil, soaking and stirring for 6 hours. Then, the mixture is transferred to a 35 ℃ water bath to be heated, and the reaction is carried out for 12 hours by magnetic stirring. Filtering, alternately washing with 10mL of ultrapure water and 10mL of absolute ethyl alcohol for three times, centrifuging for 3min by using a centrifuge 6000r/min, and finally putting the washed tung oil-loaded microcapsule into a vacuum drying oven for vacuum drying for 12h at 55 ℃ to obtain the ZIF-8/PMMA/tung oil microcapsule.
<Comparative example 2>
A microcapsule product was prepared in the same manner as in example 3, omitting step 2, applying the styrene-divinylbenzene copolymer nanospheres prepared in step 1 directly to step 3, and preparing ZIF-8/styrene-divinylbenzene copolymer composite particles without removing the styrene-divinylbenzene copolymer template by DMF immersion. And finally, adding the composite particles into tung oil according to the process in the step 4, and soaking to obtain the tung oil-loaded ZIF-8/styrene-divinylbenzene copolymer composite particles.
<Example 4>
Preparing long-acting double-layer microcapsule
(1) Preparation of styrene-divinylbenzene copolymer nanospheres
Taking 0.0078g of azobisisoheptonitrile, adding a mixture of 1.5g of styrene, 2.1g of DVB (divinylbenzene (DVB, 80%, isomer mixture containing 4-tert-butylcatechol inhibitor with concentration less than 0.1%) and 4.1g of sodium dodecyl sulfate, stirring and mixing uniformly to form an oil phase, adding 50mL of deionized water, mixing uniformly, homogenizing with a high-speed homogenizer at a rotating speed of 12000r/min for 4min to obtain a stable oil-in-water Pickering emulsion, adding the obtained emulsion into a 100mL double-neck round-bottom flask, and after cooling, introducing nitrogen for 23min to replace air, then heating the emulsion in a water bath at 75 ℃ for 17h, centrifuging at 6000r/min for 2min after reaction, collecting a product, washing with 10mL of absolute ethyl alcohol, repeatedly centrifuging and washing for 3 times, and performing vacuum drying at 42 ℃ for 2h to obtain the white solid styrene-divinylbenzene copolymer nanospheres.
(2) Preparation of styrene-divinylbenzene copolymer/PMMA nanocomposite particles
0.5g of PMMA was added to 50mL of water, and the solution was ultrasonically dispersed for 25 minutes while maintaining the temperature of 2 to 3 ℃. Then, 4g of styrene-divinylbenzene copolymer nanospheres are added, the mixture is continuously stirred for 30 minutes under the condition that the temperature of the material liquid is kept at 1-3 ℃, so that PMMA is fully swelled into styrene-divinylbenzene copolymer particles, and after PMMA drops gradually disappear under the observation of an optical microscope. The PMMA swollen styrene-divinylbenzene copolymer particles were then transferred to a three-necked round-bottomed flask in an ice bath. 10mL of the oxidizing agent solution prepared in step 2 of example 1 was added to the dispersion in one portion, and then 0.5mL of hydrochloric acid (0.5mol/L), which was also an equimolar amount with respect to PMMA, was added dropwise via a syringe. The mixture was kept at 0 ℃ for 6 hours and polymerized at room temperature for a further 20 hours to fully polymerize PMMA. The obtained green styrene-divinylbenzene copolymer/PMMA composite particles are centrifuged at 6000r/min for 2min, then washed with 10mL of ethanol, and the centrifugation and washing are repeated for 3 times until the supernatant is colorless. Finally, the product was dried in a vacuum oven at 40 ℃ for 48 h.
(3) Preparation of ZIF-8/PMMA hollow microspheres
1g of styrene-divinylbenzene copolymer/PMMA solid powder and 11.5 g of 2-methylimidazole were weighed into a single-neck flask, 50mL of anhydrous methanol was added, and magnetic stirring was carried out for 30min after 3min of ultrasonic dispersion. And then adding a methanol solution containing 0.59g of zinc nitrate hexahydrate, continuously stirring for 3 hours, centrifuging at 6000r/min for 3 minutes, carrying out 10mL of absolute ethanol, and repeatedly centrifuging and washing for 3 times to obtain the ZIF-8/styrene-divinylbenzene copolymer/PMMA composite particles. Adding the mixture into 50mL of DMF, soaking for 3h, removing a styrene-divinylbenzene copolymer template, filtering, washing for 2 times by 10mL of absolute ethyl alcohol, and drying for 2h in vacuum at 45 ℃ to obtain the ZIF-8/PMMA hollow microspheres.
(4) Load repairing agent or corrosion inhibitor
And adding the dried ZIF-8/PMMA hollow microspheres into a solvent of tung oil, soaking and stirring for 7 hours. Then, the mixture was transferred to a 35 ℃ water bath and reacted for 11 hours with magnetic stirring. Filtering, washing with ultrapure water and ethanol for three times, separating with a centrifuge, and finally putting the washed tung oil-loaded microcapsule into a vacuum drying oven for vacuum drying for 8 hours at 60 ℃ to obtain the ZIF-8/PMMA/tung oil microcapsule.
<Comparative example 3>
A microcapsule product was prepared in the same manner as in example 4, except that after the styrene-divinylbenzene copolymer/PMMA composite particles were prepared in step 2, they were dried in a hot air oven at 65 ℃ and the remaining preparation process steps were kept unchanged. The microcapsules are partially bonded together and lose the original dispersed particle state, so that the original dispersed state of the microcapsules is difficult to maintain.
<Comparative example 4>
A microcapsule product is prepared in the same manner as in example 4, except that the microcapsule loaded with tung oil is prepared in step 4, a hot air oven is adopted for drying treatment at 70 ℃, and the other preparation process steps are kept unchanged. The microcapsules are partially bonded together, and part of the microcapsules are broken, the tung oil in the microcapsules flows out, and the microcapsules are integrally bonded together.
<Comparative example 5>
A microcapsule product is prepared in the same manner as in example 4, except that the microcapsule loaded with tung oil is prepared in step 4, and vacuum drying is adopted, the drying temperature is 80 ℃, and the other preparation process steps are kept unchanged. The microcapsules are broken, the tung oil in the microcapsules flows out, and the microcapsules are integrally bonded together.
<Example 5>
Preparing long-acting double-layer microcapsule
(1) Preparation of styrene-divinylbenzene copolymer nanospheres
0.008g of azobisisoheptonitrile was taken and added to a mixture of 2g of styrene, 2.5g of DVB (divinylbenzene (DVB, 80%, isomer mixture containing 4-tert-butylcatechol inhibitor at a concentration of less than 0.1%) and 4.5g of sodium lauryl sulfate, stirring and mixing uniformly to form an oil phase, adding 50mL of deionized water, mixing uniformly, homogenizing for 2min at the rotating speed of 15000r/min by using a high-speed homogenizer to obtain a stable oil-in-water Pickering emulsion, adding the obtained emulsion into a 100mL double-neck round-bottom flask, and after cooling, introducing nitrogen for 20min to replace air, then heating the emulsion in water bath at 78 ℃ for 16h, centrifuging at 6000r/min for 2min after reaction, collecting a product, washing with 10mL of absolute ethyl alcohol, repeatedly centrifuging and washing for 3 times, and performing vacuum drying at 40 ℃ for 2h to obtain the white solid styrene-divinylbenzene copolymer nanospheres.
(2) Preparation of styrene-divinylbenzene copolymer/PMMA nanocomposite particles
0.6 g of PMMA was added to 50mL of water and sonicated at 0 ℃ for 22 minutes. Then, 5g of styrene-divinylbenzene copolymer nanospheres were added, the mixture was continuously ultrasonically stirred at 0 ℃ for 30 minutes to fully swell PMMA into the styrene-divinylbenzene copolymer particles, and after the PMMA droplets disappeared gradually under observation by an optical microscope. The PMMA swollen styrene-divinylbenzene copolymer particles were then transferred to a three-necked round-bottomed flask in an ice bath. 10mL of the oxidizing agent solution prepared in step 2 of example 1 was added to the dispersion in one portion, and then 0.5mL of hydrochloric acid (0.5mol/L), which was also an equimolar amount with respect to PMMA, was added dropwise via a syringe. The temperature was maintained at 0 ℃ for 6.5 hours, and polymerization was continued at room temperature for 16.5 hours to sufficiently polymerize PMMA. The obtained green styrene-divinylbenzene copolymer/PMMA composite particles are centrifuged at 6000r/min for 2min, then washed with 10mL of ethanol, and the centrifugation and washing are repeated for 3 times until the supernatant is colorless. Finally, the product is dried in a vacuum oven for 36 hours at 40 ℃.
(3) Preparation of ZIF-8/PMMA hollow microspheres
1g of styrene-divinylbenzene copolymer/PMMA solid powder and 12.1 g of 2-methylimidazole are weighed into a single-neck flask, 50mL of anhydrous methanol is added, ultrasonic dispersion is carried out for 2min, and magnetic stirring is carried out for 25 min. And then adding a methanol solution containing 0.63g of zinc nitrate hexahydrate, continuously stirring for 4h, centrifuging at 6000r/min for 3min, 10mL of absolute ethanol, and repeatedly centrifuging and washing for 3 times to obtain the ZIF-8/styrene-divinylbenzene copolymer/PMMA composite particles. Adding the mixture into 50mL of DMF, soaking for 3h, removing a styrene-divinylbenzene copolymer template, filtering, washing for 3 times by 10mL of absolute ethyl alcohol, and drying for 2h in vacuum at 45 ℃ to obtain the ZIF-8/PMMA hollow microspheres.
(4) Load repairing agent or corrosion inhibitor
Putting the dried ZIF-8/PMMA hollow microspheres into 20mL of tung oil solvent, soaking and stirring for 10 hours, and then carrying out magnetic stirring reaction for 14 hours in a 35 ℃ water bath kettle. Filtering, washing with 10mL of ultrapure water and 10mL of mixed alcohol (methanol: ethanol =2:8, volume ratio) for three times, centrifuging for 3min by using a centrifuge 6000r/min, and finally putting the washed tung oil-loaded microcapsule into a vacuum drying oven for vacuum drying for 8h at 60 ℃ to obtain the ZIF-8/PMMA/tung oil microcapsule.
<Comparative example 6>
A microcapsule product was prepared in the same manner as in example 5 except that, in step 2, PMMA and styrene-divinylbenzene copolymer nanospheres were dispersed in the solution with magnetic stirring without the aid of ultrasound. The effect of sonication on the binding of styrene-divinylbenzene copolymer nanospheres and PMMA was compared. In the experimental process, the swelling speed of PMMA (polymethyl methacrylate) into the styrene-divinylbenzene copolymer nanospheres is very slow, so that the structural appearance of the microcapsules is influenced.
<Comparison ofExample 7>
A microcapsule product is prepared in the same manner as in example 5, except that in the loading process in the step 4, tung oil is heated to 35 ℃ in advance, and then ZIF-8/PMMA hollow microspheres are put into the microcapsule product to react for 14 hours under magnetic stirring, and the influence of different soaking loading processes on the loading efficiency is compared. The tung oil has higher temperature, the speed of penetrating into the microcapsule is not accelerated, the mutual polymerization reaction of the ZIF-8 on the surface of the microcapsule and the tung oil is mainly caused by the temperature rise, the pore channel of the microcapsule is sealed, the weight of the microcapsule is weighed and compared after the microcapsule before and after soaking is dried in vacuum, the weight increase of the microcapsule is reduced from 46.7 percent to 6.8 percent, the weight increase is obviously reduced, and the total amount of the tung oil entering the microcapsule is reduced.
<Testing>
The microcapsules prepared in example 5 and comparative examples 6 to 7 were subjected to scratch test as follows:
firstly, varnish is prepared: 50g of bisphenol A epoxy resin E-44 is taken, 9.2g of diethylenetriamine is added, two drops of dispersing agent and two drops of leveling agent are added dropwise, and the mixture is stirred and mixed uniformly. Then 4g of microcapsules are added, stirred evenly and then coated on the iron sheet which is derusted and washed clean by absolute ethyl alcohol. The iron sheet was placed horizontally until the coating was naturally dried overnight. And (3) scratching the film by using a blade after the film is completely dried, wherein the width of the scratch is from thin to thick, the coarsest scratch is about 1mm, transferring the iron sheet after scratching into an oven with the humidity of 100% and the temperature of 35 ℃, baking for 4h, taking out and observing the change condition of each scratch.
The varnish of the microcapsules prepared in application example 5 was added, and the coating layer was free from rust at the scratch after the scratch test was completed. And the position with the largest scratch is fully soaked and repaired, and the scratch damage is lowest.
The varnish using the microcapsule prepared in comparative example 6 was added, and after the iron sheet was coated, the varnish had a certain repairing effect on fine scratches with less rust, but for scratches larger than 0.5mm, the effect of flowing and filling with tung oil was not good, and slight rust was observed. The analysis reason is mainly that the PMMA microcapsule wall is thin in structure and poor in structural strength due to the fact that necessary assistance is lacked in the process that PMMA is dispersed into the styrene-divinylbenzene copolymer nano microspheres, the structural shape strength of the subsequent wrapping ZIF-8 is low, the quality of the loaded tung oil is poor, and the repairing effect is weak.
The microcapsule prepared in the comparative example 7 is added into the varnish, the scratch experimental result of the coating is obviously differentiated, the repairing effect is better for the condition of smaller scratch, and the repairing capability is obviously insufficient for the condition of more serious scratch, and the analysis reason is mainly that the temperature in the tung oil loading process reduces the efficiency of the tung oil entering the microcapsule and influences the actual maximum repairing capability of the microcapsule.
<Example 6>
Preparing long-acting double-layer microcapsule
(1) Preparation of styrene-divinylbenzene copolymer nanospheres
0.008g of azobisisoheptonitrile was taken and added to a mixture of 1.5g of styrene, 2.0g of DVB (divinylbenzene (DVB, 80%, isomer mixture containing 4-tert-butylcatechol inhibitor at a concentration of less than 0.1%) and 0.5g of sodium lauryl sulfate, stirring and mixing uniformly to form an oil phase, adding 50mL of deionized water, mixing uniformly, homogenizing for 2min at the rotating speed of 15000r/min by using a high-speed homogenizer to obtain a stable oil-in-water Pickering emulsion, adding the obtained emulsion into a 100mL double-neck round-bottom flask, and after cooling, introducing nitrogen for 18min to replace air, then heating the emulsion in water bath at 78 ℃ for 16h, centrifuging at 6000r/min for 2min after reaction, collecting a product, washing with 10mL of absolute ethyl alcohol, repeatedly centrifuging and washing for 2 times, and performing vacuum drying at 40 ℃ for 2h to obtain the white solid styrene-divinylbenzene copolymer nanospheres.
(2) Preparation of styrene-divinylbenzene copolymer/PMMA nanocomposite particles
0.5g of PMMA was added to 50mL of water and sonicated at 0 ℃ for 22 minutes. Then, 4g of styrene-divinylbenzene copolymer nanospheres were added, the mixture was continuously ultrasonically stirred at 0 ℃ for 30 minutes to fully swell PMMA into the styrene-divinylbenzene copolymer particles, and after the PMMA droplets disappeared gradually under observation by an optical microscope. The PMMA swollen styrene-divinylbenzene copolymer particles were then transferred to a three-necked round-bottomed flask in an ice bath. 10mL of the oxidizing agent solution prepared in step 2 of example 1 was added to the dispersion in one portion, and then 0.5mL of hydrochloric acid (0.8mol/L) was added thereto, followed by dropwise addition via a syringe. The temperature was maintained at 0 ℃ for 6.5 hours, and polymerization was continued at room temperature for 16.5 hours to sufficiently polymerize PMMA. The obtained green styrene-divinylbenzene copolymer/PMMA composite particles are centrifuged at 6000r/min for 2min, then washed with 10mL of ethanol, and the centrifugation and washing are repeated for 3 times until the supernatant is colorless. Finally, the product is dried in a vacuum oven for 36 hours at 40 ℃.
(3) Preparation of ZIF-8/PMMA hollow microspheres
1g of styrene-divinylbenzene copolymer/PMMA solid powder and 13.2 g of 2-methylimidazole were weighed into a single-neck flask, 50mL of anhydrous methanol was added, ultrasonic dispersion was carried out for 2.5min, and magnetic stirring was carried out for 25 min. And then adding a methanol solution containing 0.63g of zinc nitrate hexahydrate, continuously stirring for 4h, centrifuging at 6000r/min for 3min, 10mL of absolute ethanol, and repeatedly centrifuging and washing for 3 times to obtain the ZIF-8/styrene-divinylbenzene copolymer/PMMA composite particles. Adding the mixture into 50mL of DMF, soaking for 3h, removing a styrene-divinylbenzene copolymer template, filtering, washing for 3 times by 10mL of absolute ethyl alcohol, and drying for 2h in vacuum at 45 ℃ to obtain the ZIF-8/PMMA hollow microspheres.
(4) Load repairing agent or corrosion inhibitor
Adding the dried ZIF-8/PMMA hollow microspheres into a solution of 20mL of sodium alginate, soaking and stirring for 14 hours, and then carrying out magnetic stirring reaction for 14 hours in a 35 ℃ water bath kettle. Filtering, washing with 10mL of ultrapure water and 10mL of mixed alcohol (n-butyl alcohol: ethanol =1:9, volume ratio) for three times, centrifuging for 3min by using a centrifuge 6000r/min, and finally putting the washed sodium alginate-loaded microcapsule into a vacuum drying oven for vacuum drying for 8h at 60 ℃ to obtain the ZIF-8/PMMA/sodium alginate microcapsule.

Claims (10)

1. A preparation method of a long-acting repairing type double-layer microcapsule is characterized by comprising the following steps:
(1) preparation of styrene-divinylbenzene copolymer nanospheres
Adding azo initiator into the mixture of styrene, divinyl benzene and anionic surfactant, and mixing to form oil phase; adding into deionized water, mixing, and homogenizing to obtain oil-in-water Pickering emulsion;
under the protection of nitrogen, heating the Pickering emulsion to 70-80 ℃ for reaction for 10-20h, after the reaction is finished, centrifugally washing for 2-5 times, and drying in vacuum to obtain white solid styrene-divinylbenzene copolymer nanospheres;
(2) preparation of styrene-divinylbenzene copolymer/PMMA nanocomposite particles
Adding PMMA into water, and performing ultrasonic dispersion; then, adding the styrene-divinylbenzene copolymer nanospheres prepared in the step (1), performing ultrasonic treatment and stirring, and allowing PMMA to swell and enter the styrene-divinylbenzene copolymer nanospheres;
adding an oxidant, uniformly stirring, dropwise adding an inorganic acid, stirring, reacting at 0-5 ℃ for 2-8h, then heating to room temperature of 15-35 ℃, and carrying out polymerization reaction for 14-28h to ensure that PMMA is fully polymerized; after the reaction is finished, centrifuging and washing until the supernatant is colorless, and drying in vacuum to obtain styrene-divinylbenzene copolymer/PMMA nano composite particles;
(3) preparation of ZIF-8/PMMA hollow microspheres
Taking the styrene-divinylbenzene copolymer/PMMA nano composite particles obtained in the step (2) and 2-methylimidazole, adding anhydrous methanol, and uniformly dispersing; adding zinc nitrate, stirring for reacting for 2-8h, and centrifuging and washing to obtain ZIF-8/styrene-divinylbenzene copolymer/PMMA composite particles;
adding the ZIF-8/styrene-divinylbenzene copolymer/PMMA composite particles into an organic solvent, removing a styrene-divinylbenzene copolymer template, filtering, and drying to obtain ZIF-8/PMMA hollow microspheres;
(4) load repairing agent or corrosion inhibitor
Adding the ZIF-8/PMMA hollow microspheres into the repair liquid for soaking, and stirring for reaction to enable the repair liquid to enter the ZIF-8/PMMA hollow microspheres; and filtering, washing, centrifuging and drying in vacuum to obtain the ZIF-8/PMMA/repair liquid microcapsule.
2. The method for preparing long-acting repairing type double-layer microcapsule according to claim 1, wherein the azo initiator in the step (1) is one or more of azobisisobutyronitrile, azobisisoheptonitrile, azobisisobutyramidine hydrochloride and azobisisobutyrimidazoline hydrochloride.
3. The method for preparing long-acting repairing double-layer microcapsule according to claim 1, wherein in the step (1), the anionic surfactant is at least one of sodium alkyl sulfate C12-C16 and sodium alkyl sulfonate C12-C16.
4. The method for preparing a long-acting repairing double-layer microcapsule according to claim 1, wherein the PMMA obtained in the step (2) is polymethyl methacrylate, and the molecular weight of the PMMA is 6-30 ten thousand.
5. The method for preparing a long-term repair type double-layer microcapsule according to claim 1, wherein in the step (2), the oxidizing agent is one or two of potassium persulfate, ammonium persulfate and peroxy oxidizing agent.
6. The method for preparing long-acting repairing type double-layer microcapsule according to claim 1, wherein the step (2) makes PMMA fully swell into the styrene-divinylbenzene copolymer nanosphere; under observation of an optical microscope, the PMMA drops gradually disappear, which shows that PMMA is fully swelled into the styrene-divinylbenzene copolymer nanospheres.
7. The method for preparing a long-term repair type double-layer microcapsule according to claim 1, wherein in the step (3), the mass ratio of the styrene-divinylbenzene copolymer/PMMA nanocomposite particles to the 2-methylimidazole is as follows: 2-methylimidazole mass ratio =1: 0.5-5.
8. The preparation method of the long-acting repairing double-layer microcapsule according to claim 1, wherein in the step (3), zinc nitrate is added in the form of zinc nitrate hexahydrate, and the weight ratio of 2-methylimidazole to zinc nitrate hexahydrate is 25: 1-2.
9. The method for preparing a long-term repair-type double-layered microcapsule according to claim 1, wherein the ZIF-8/styrene-divinylbenzene copolymer/PMMA composite particles of step (3) are added to an organic solvent, and the styrene-divinylbenzene copolymer template is removed, the organic solvent being a polar inert solvent.
10. The preparation method of the long-acting repairing double-layer microcapsule according to claim 1, wherein in the step (4), the repairing liquid is one or more of tung oil, linseed oil and sodium alginate.
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