Composite microcapsule, preparation method thereof and low-water-absorption water-based thermal insulation energy-saving coating

Abstract

The application provides a composite microcapsule, a preparation method thereof and a low-water-absorption water-based thermal insulation energy-saving coating. The composite microcapsule has a core-shell structure and comprises an inner core material and a shell layer wrapping the inner core material, wherein the inner core material is prepared from a temperature-resistant oily liquid material, and the shell layer is prepared from a starch material. The composite microcapsule of the application is added to the coating, so that the water storage space in the coating can be greatly reduced, and the water absorption of the coating is greatly reduced.

Description

Technical Field

[0001] This invention relates to the field of coating technology, and more specifically, to a composite microcapsule and its preparation method, and a water-based thermal insulation and energy-saving coating with low water absorption rate. Background Technology

[0002] Water-based thermal insulation coatings are environmentally friendly coatings that use water as a dispersion medium. They are widely used on the surfaces of petrochemical storage tanks, high-temperature pipelines, engines, and other equipment to provide thermal insulation, reduce heat transfer and energy consumption, and have advantages such as being green and environmentally friendly, easy to apply, and having a long service life.

[0003] After being applied to the bodies of petrochemical storage tanks, thermal insulation coatings are subjected to a variety of complex and variable conditions during actual use, including frequent exposure to sunlight, humidity, rain, and freezing. Especially in rainy weather, the coating easily absorbs water after prolonged immersion in rainwater; the water absorption rate typically exceeds 40% after 24 hours and 140% after 168 hours. Due to the high thermal conductivity of water, excessive water absorption leads to a decrease in the coating's insulation capacity and a significant reduction in its strength, resulting in problems such as blistering and peeling.

[0004] Chinese patent CN106433357 discloses an industrial thermal insulation coating, which includes a topcoat and a base coat. The base coat has thermal insulation function, and the topcoat has waterproof function. The composite coating formed by the two has the dual functions of thermal insulation and waterproof. Since the base thermal insulation coating does not have waterproof and low water absorption properties, it needs to be coated with a top waterproof coating before it can be used in humid and rainy environments. If the topcoat peels off or is damaged, the base coat will lose its waterproof protection.

[0005] Therefore, there is an urgent need to develop a water-based thermal insulation and energy-saving coating with low water absorption that can be used alone. Summary of the Invention

[0006] To address the aforementioned problems, this invention provides a composite microcapsule, its preparation method, and a low-water-absorption water-based thermal insulation and energy-saving coating. The composite microcapsules of this invention, when added to the coating, can significantly reduce the water storage space within the coating, thereby greatly reducing the coating's water absorption rate.

[0007] Firstly, one of the objectives of this invention is to provide a composite microcapsule.

[0008] Specifically, the composite microcapsule has a core-shell structure, comprising an inner core material and an outer shell layer enclosing the inner core material. The inner core material is made of a temperature-resistant oily liquid material, and the outer shell layer is made of a starch material.

[0009] Preferably, the particle size range of the composite microcapsules is 1 to 100 μm; more preferably, it is 1 to 90 μm. The composite microcapsules with the above particle size range can be uniformly dispersed in the coating system, which is beneficial to improving the waterproofness of the coating system.

[0010] Preferably, the heat-resistant oily liquid is one or a combination of liquid paraffin, mineral oil, and silicone oil.

[0011] Preferably, the starch material is one or a combination of corn starch, potato starch, tapioca starch, and sweet potato starch.

[0012] Secondly, another objective of this invention is to provide a method for preparing the composite microcapsules that is one of the objectives of this invention.

[0013] Specifically, the method includes the following steps:

[0014] Step 1: Add the heat-resistant oily liquid to the deionized water under stirring, add the emulsifier to emulsify the oil droplets, heat and stir, then cool to room temperature to obtain the inner core material;

[0015] Step 2: Dissolve the starch material in deionized water, heat and stir to obtain a starch paste-like outer shell solution;

[0016] Step 3: Under stirring conditions, add the inner core material dropwise to the outer shell solution. After the addition is complete, heat and stir, filter, rinse the filtrate, and dry the filter cake to obtain composite microcapsules.

[0017] In step one, the mass ratio of the added heat-resistant oily liquid to deionized water is 1:4 to 10; the emulsifier is one or a combination of Tween 80 and Span 80; the mass ratio of the added heat-resistant oily liquid to the emulsifier is 1:0.4 to 1; in step two, the mass ratio of the added starch material to deionized water is 1:8 to 20.

[0018] More specifically, the preparation method of the composite microcapsules includes the following steps:

[0019] Step 1: Add one or more of the following liquid paraffin, mineral oil, and silicone oil to deionized water under stirring. Add a mixed solution of emulsifiers Tween 80 and Span 80 to emulsify the oil droplets. After heating to 60°C and stabilizing, continue stirring for 1 hour. Cool to room temperature to obtain the core material of the composite microcapsules.

[0020] Step 1: Dissolve one or more of corn starch, potato starch, tapioca starch, and sweet potato starch in excess deionized water, stir at 85°C for 0.5 hours, and cool to 60°C to obtain the outer shell solution of the starch paste solution.

[0021] Step 3: Under stirring conditions, the inner core material, which is the oil phase droplet, is slowly added dropwise to the outer shell solution (i.e., the starch paste solution), forming an O / W type emulsion. After the oil phase droplets are completely added, the mixture is stirred at 60°C for 1 hour. The suspension is then filtered, and the filter is washed with warm ethanol and warm deionized water alternately. After washing and filtration are completed, the filter cake is placed in a vacuum drying oven at 40°C for 24 hours to obtain composite microcapsules, which are then dried and stored.

[0022] It is worth mentioning that, under the combined action of emulsifiers Tween 80 and Span 80, the oil phases of the liquid paraffin, mineral oil, and silicone oil of the present invention form small droplets with hydrophilic groups on their surfaces, which are dispersed in the mixed solution. Starch molecules form a helical structure by means of intermolecular and intramolecular hydrogen bonds. The outer part of the helical structure is hydrophilic and the inner part is hydrophobic. When the oil phase droplets are dropped into the starch solution, the hydrophilic groups in the starch structure interact with the hydrophilic groups on the surface of the oil phase droplets and gradually deposit on the surface of the oil phase droplets, forming a stable composite microcapsule with starch as the outer shell and oil phase droplets as the inner core material.

[0023] Thirdly, the purpose of this invention is to provide a water-based thermal insulation and energy-saving coating with low water absorption rate.

[0024] Specifically, the coating components of the present invention include composite microcapsules of one objective of the present invention and / or composite microcapsules obtained by the preparation method of another objective of the present invention.

[0025] More specifically, the above-mentioned coating is made from raw materials comprising the following components, each component being in parts by weight:

[0026]

[0027] Preferably, the components are expressed in parts by weight as follows:

[0028]

[0029] The present invention adds composite microcapsules to the coating components, which can be evenly distributed in the gaps of the heat-insulating filler. After the coating film is formed, due to the starch gelatinization of the starch shell during the drying and heating process, the heat-resistant oily liquid encapsulated inside flows into the air gaps in the coating as the shell breaks, filling the air gaps. This greatly reduces the water storage gaps in the coating and significantly reduces the water absorption rate of the coating.

[0030] Preferably, the film-forming emulsion is selected from one or a combination of pure acrylic emulsion, styrene-acrylic emulsion, acrylic emulsion, and phenolic emulsion.

[0031] Preferably, the heat-insulating filler is hollow glass microspheres modified with a coupling agent; wherein the coupling agent is selected from one of γ-aminopropyltriethoxysilane (KH550), γ-glycidoxypropyltrimethoxysilane (KH560), γ-methacryloyloxypropyltrimethoxysilane (KH570), and aluminate coupling agents. Since the heat-insulating filler itself has a high water absorption rate, this invention uses hollow glass microspheres surface-treated with a coupling agent as a low-density filler. The inorganic end of the coupling agent reacts with the hydroxyl groups on the surface of the hollow glass microspheres, effectively improving the interfacial compatibility between the hollow glass microspheres and the film-forming emulsion, reducing the water absorption rate of the heat-insulating filler, and thus reducing the water absorption rate of the coating.

[0032] Preferably, the film-forming aid is one or a combination of Texanol (the main component of which is 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate), DBE-IB (diisobutyl nylonate), Nexcoat 795 (2,2,4-trimethyl-1,3-pentanediol), OE400 (triethylene glycol diisooctanoate), and 2,2,4-trimethyl-1,3-pentanediol).

[0033] Preferably, the reinforcing filler is one or a combination of calcium carbonate, talc, mica powder, kaolin, barium sulfate, and silicon dioxide.

[0034] Preferably, the raw material components of the coating of the present invention further include pigments, and the amount of added pigments is 1 to 20 parts by weight; more preferably, it is 3 to 12 parts by weight; more preferably, the pigments are one or a combination of titanium dioxide, phthalocyanine green, phthalocyanine blue, carbon black, and iron oxide yellow.

[0035] Preferably, the raw material components of the coating further include a defoamer, and the added defoamer is 0.2 to 2 parts by weight; more preferably, it is 0.3 to 1.5 parts by weight; more preferably, the defoamer is one or a combination of BYK-028, BYK-071, BYK-141, AFCONA-2020, AFCONA-2040, and DELTA-1040.

[0036] Finally, a fourth objective of the present invention is to provide a method for preparing a low-water-absorption water-based thermal insulation and energy-saving coating, which is also an objective of the present invention.

[0037] Specifically, the preparation method of the coating is as follows:

[0038] After mixing the film-forming emulsion with the film-forming aid, stir in a high-speed mixer at a speed of 500-1000 r / min for 15-30 min. Then add the defoamer and stir for 10-15 min. Adjust the speed of the high-speed mixer to 200-500 r / min, and slowly add the heat-insulating filler, reinforcing filler, pigment, and composite microcapsules. After all the fillers are added, stir for 30-60 min. Finally, filter the mixture through a 120-mesh copper screen to obtain the coating.

[0039] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0040] 1. This invention effectively solves the problem of high water absorption rate of thermal insulation fillers. This invention utilizes the inorganic end of the coupling agent to react with the hydroxyl groups on the surface of hollow glass microspheres, effectively improving the interfacial compatibility between the hollow glass microspheres and the film-forming emulsion. Furthermore, the hollow glass microspheres, after surface treatment with the coupling agent, serve as a low-density thermal insulation filler with a low water absorption rate, thereby reducing the water absorption rate of the coating.

[0041] 2. This invention effectively solves the problem of excessive water absorption caused by the accumulation of large air gaps in coatings due to the large particle size and dosage of heat-insulating fillers. This invention adds self-made composite microcapsules to the coating. These microcapsules have a core-shell structure with starch as the shell and a heat-resistant oily liquid encapsulated inside. The diameter of the microcapsules is between 1 and 100 μm. After being added to the coating, the composite microcapsules are evenly distributed in the aforementioned gaps. After the coating film is formed, during the drying and heating process, the starch shell continuously absorbs water and swells under high temperature and moisture conditions, eventually rupturing and gelatinizing the starch. The encapsulated oily liquid flows into the air gaps in the coating as the shell ruptures. The flowing liquid fills these air gaps, significantly reducing the water-retaining gaps in the coating and thus greatly reducing the water absorption rate of the coating.

[0042] 3. The coating provided by this invention has the advantages of low water absorption, low thermal conductivity, good heat insulation performance, high mechanical strength and high adhesion. It can be applied to various substrates and parts and scenarios with diverse structures, such as building exterior walls, petrochemical storage tank bodies, high-temperature pipelines, and engines, and has great application value.

[0043] 4. The coating provided by the present invention has a dry film water absorption rate of less than 2% in 24 hours and less than 6% in 168 hours, which has a low water absorption rate.

[0044] 5. The coating of the present invention can be used alone in humid, rainy environments without the need for an additional waterproof coating. It is a single-component water-based system and is easy to apply. Detailed Implementation

[0045] The present invention will now be described in detail with reference to specific embodiments. It should be noted that the following embodiments are only used to further illustrate the present invention and should not be construed as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the content of the present invention are still within the scope of protection of the present invention.

[0046] Unless otherwise specified, all raw materials used in the following examples and comparative examples are commercially available products.

[0047] Example 1

[0048] This embodiment illustrates the preparation of composite microcapsules, and the steps are as follows:

[0049] Step 1: In a four-necked flask equipped with a temperature control device, a condenser, a stirring device, and a liquid uniform dripping device, 50 parts by weight of liquid paraffin are dropped into 250 parts by weight of deionized water. Then, 10 parts by weight of Tween 80 and 15 parts by weight of Span 80 are dropped into the mixed solution of liquid paraffin and deionized water. The temperature is raised to 60°C and stabilized, and then stirred continuously for 1 hour. After cooling to room temperature, the inner core material of oily droplets is obtained.

[0050] Step 2: Dissolve 100 parts by weight of corn starch in 1000 parts by weight of deionized water, heat to 85°C and stir for 0.5 hours, then maintain the temperature at 60°C and continue stirring for 1 hour. Stop heating and cool to room temperature while stirring to obtain the outer shell solution of the starch paste solution.

[0051] Step 3: Under stirring conditions, the oily liquid obtained in Step 1 is added dropwise to the starch paste solution obtained in Step 2. After stirring at 60°C for 1 hour, the suspension is filtered. The filter is washed with warm ethanol and warm deionized water alternately. After washing and filtration are completed, the filter cake is placed in a vacuum drying oven at 40°C for 24 hours to obtain composite microcapsules MC1. The microcapsules are dried and stored with a particle size range of 1–100 μm.

[0052] Example 2

[0053] This embodiment illustrates the preparation of composite microcapsules, and the steps are as follows:

[0054] Step 1: In a four-necked flask equipped with a temperature control device, a condenser, a stirring device, and a liquid uniform dripping device, 30 parts by weight of silicone oil are dropped into 150 parts by weight of deionized water. Then, 10 parts by weight of Tween 80 and 5 parts by weight of Span 80 are dropped into the mixed solution of silicone oil and deionized water. The temperature is raised to 60°C and stabilized. The mixture is stirred continuously for 1 hour and then cooled to room temperature to obtain the inner core material of the oil droplet.

[0055] Step 2: Dissolve 80 parts by weight of sweet potato starch in 800 parts by weight of deionized water, heat to 85°C and stir for 0.5 hours, then maintain the temperature at 60°C and continue stirring for 1 hour. Stop heating and cool to room temperature while stirring to obtain the outer shell solution of the starch paste solution.

[0056] Step 3: Under stirring conditions, the oily liquid obtained in Step 1 is added dropwise to the starch paste solution obtained in Step 2. After stirring at 60°C for 1 hour, the suspension is filtered. The filter is washed with warm ethanol and warm deionized water alternately. After washing and filtration are completed, the filter cake is placed in a vacuum drying oven at 40°C for 24 hours to obtain composite microcapsules MC2. The microcapsules are dried and stored with a particle size range of 1-80 μm.

[0057] Example 3

[0058] This embodiment illustrates the preparation of composite microcapsules, and the steps are as follows:

[0059] Step 1: In a four-necked flask equipped with a temperature control device, a condenser, a stirring device, and a liquid uniform dripping device, 60 parts by weight of mineral oil are dropped into 300 parts by weight of deionized water. Then, 15 parts by weight of Tween 80 and 15 parts by weight of Span 80 are dropped into the mixed solution of mineral oil and deionized water. The temperature is raised to 60°C and stirred continuously for 1 hour. The heating is stopped, and the solution is cooled to room temperature while stirring to obtain the inner core material of the oil droplet.

[0060] Step 2: Dissolve 90 parts by weight of tapioca starch in 900 parts by weight of deionized water, heat to 85°C and stir for 0.5 hours, then maintain the temperature at 60°C and continue stirring for 1 hour to obtain the outer shell solution of the starch paste solution.

[0061] Step 3: Under stirring conditions, the oily liquid obtained in Step 1 is added dropwise to the starch paste solution obtained in Step 2. After stirring at 60°C for 1 hour, the suspension is filtered. The filter is washed with warm ethanol and warm deionized water alternately. After washing and filtration are completed, the filter cake is placed in a vacuum drying oven at 40°C for 24 hours to obtain composite microcapsules MC3. The microcapsules are dried and stored with a particle size range of 1-90 μm.

[0062] Example 4

[0063] This embodiment illustrates the preparation of a low-water-absorption water-based thermal insulation and energy-saving coating, wherein the weight parts of each raw material component are as follows:

[0064]

[0065] The preparation process is as follows:

[0066] S1: Add styrene-acrylic emulsion, defoamer BYK-028, and film-forming aid alcohol ester twelve into a high-speed mixer and mix;

[0067] S2: Add aluminate-modified hollow glass microspheres, fumed silica, carbon black, etc. to the above emulsion and mix and stir evenly;

[0068] S3: Pour the evenly mixed coating into a basket mill and grind it to a fineness of 100µm;

[0069] S4: Add the composite microcapsules and stir until well mixed;

[0070] S5: Apply by brushing, air spraying or high-pressure airless spraying. After application, cure at 80℃ for 2 hours to obtain a water-based thermal insulation coating with low water absorption.

[0071] Example 5

[0072] This embodiment illustrates the preparation of a low-water-absorption water-based thermal insulation and energy-saving coating, wherein the weight parts of each raw material component are as follows:

[0073]

[0074] The preparation process of the coating in this embodiment is the same as that in Example 4.

[0075] Example 6

[0076] This embodiment illustrates the preparation of a low-water-absorption water-based thermal insulation and energy-saving coating, wherein the weight parts of each raw material component are as follows:

[0077]

[0078] The preparation process of the coating in this embodiment is the same as that in Example 4.

[0079] Example 7

[0080] This embodiment illustrates the preparation of a low-water-absorption water-based thermal insulation and energy-saving coating, wherein the weight parts of each raw material component are as follows:

[0081]

[0082] The preparation process of the coating in this embodiment is the same as that in Example 4.

[0083] Comparative Example 1

[0084] This comparative example illustrates the preparation of the coating, wherein the weight parts of each raw material component are as follows:

[0085]

[0086] The preparation process of the coating in this comparative example is the same as that in Example 4.

[0087] Comparative Example 2

[0088] This comparative example illustrates the preparation of the coating, wherein the weight parts of each raw material component are as follows:

[0089]

[0090]

[0091] The preparation process of the coating in this comparative example is the same as that in Example 4.

[0092] Comparative Example 3

[0093] This comparative example illustrates the preparation of the coating, wherein the weight parts of each raw material component are as follows:

[0094]

[0095] The preparation process of the coating in this comparative example is the same as that in Example 4.

[0096] Table 1 shows the dosage data of each raw material component added in Examples 4-7 and Comparative Examples 1-3.

[0097] Table 1:

[0098]

[0099]

[0100] Table 2 shows the performance data of the coatings prepared in Examples 4-7 and Comparative Examples 1-3.

[0101] Table 2:

[0102]

[0103] As shown in Table 2, the coatings obtained in Examples 4 to 7 have good waterproof performance, tensile strength and high thermal insulation. However, the coatings in Comparative Examples 1 to 3, when unmodified hollow glass beads are added or composite microcapsules are not added, have high water absorption and poor waterproof performance. Furthermore, due to water absorption, the thermal insulation performance and tensile strength of the coating are reduced.

[0104] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A composite microcapsule, characterized by, The composite microcapsule is a core-shell structure, comprising an inner core material and a shell layer wrapping the inner core material; the inner core material is made of a temperature-resistant oily liquid material, and the shell layer is made of a starch material; The temperature-resistant oily liquid is one or a combination of liquid paraffin, mineral oil, and silicone oil; and / or, The starch material is one or a combination of corn starch, potato starch, cassava starch, and sweet potato starch; The preparation method of the composite microcapsule comprises the following steps: Step one, add the temperature-resistant oily liquid into the deionized water in a stirring state, add an emulsifier to emulsify the oil droplets, heat and stir, and then cool to room temperature to obtain the inner core material; Step two, dissolve the starch material in the deionized water, heat and stir to obtain a starch paste-shaped shell layer solution; Step three, under stirring conditions, add the inner core material dropwise into the shell layer solution, heat and stir after the dropwise addition is completed, perform suction filtration treatment, rinse the filtrate, dry the filter cake, and obtain the composite microcapsule.

2. The composite microcapsule according to claim 1, wherein the particle size of the composite microcapsule ranges from 1 to 100 um.

3. The composite microcapsule according to claim 2, wherein the particle size of the composite microcapsule ranges from 1 to 90 um. The method comprises the following steps: Step one, add the temperature-resistant oily liquid into the deionized water in a stirring state, add an emulsifier to emulsify the oil droplets, heat and stir, and then cool to room temperature to obtain the inner core material; 4. The method for producing composite microcapsules according to any one of claims 1 to 3, characterized by, Step two, dissolve the starch material in the deionized water, heat and stir to obtain a starch paste-shaped shell layer solution; Step three, under stirring conditions, add the inner core material dropwise into the shell layer solution, heat and stir after the dropwise addition is completed, perform suction filtration treatment, rinse the filtrate, dry the filter cake, and obtain the composite microcapsule.

5. The preparation method of the composite microcapsule according to claim 4, wherein in step one, the mass ratio of the temperature-resistant oily liquid to the deionized water is 1:4-10; the emulsifier is one or a combination of Tween 80 and Span 80; and the mass ratio of the temperature-resistant oily liquid to the emulsifier is 1:0.4-1; In step two, the mass ratio of the starch material to the deionized water is 1:8-20. The coating components include the composite microcapsule of any one of claims 1-3 and / or the composite microcapsule obtained by the preparation method of any one of claims 4-5, and the components are as follows in parts by weight: Film-forming material emulsion 100 parts by weight; Thermal insulation filler 20-55 parts by weight; 6. A low water absorption water-based thermal insulation energy-saving paint, characterized in that, Film-forming aid 3-6 parts by weight; Reinforcing filler 15-30 parts by weight; Composite microcapsule 45-75 parts by weight; The thermal insulation filler is hollow glass microbeads modified by a coupling agent. The components are as follows in parts by weight: Film-forming material emulsion 100 parts by weight; Thermal insulation filler 25-50 parts by weight; 7. The low water absorption water-based thermal insulation energy-saving coating according to claim 6, characterized in that, Film-forming aid 4-5 parts by weight; Reinforcing filler 16-28 parts by weight; Composite microcapsule 48-72 parts by weight.

8. The low-water-absorption water-based thermal insulation and heat preservation energy-saving coating according to claim 6, wherein the film-forming material emulsion is selected from one or a combination of pure acrylic emulsion, styrene-acrylic emulsion, acrylic emulsion, and phenolic emulsion. ​ ​ ​ ​ 9.The low water absorption water-based thermal insulation energy-saving coating of claim 6, wherein the coupling agent is selected from one of γ-aminopropyl triethoxysilane, γ-glycidoxypropyl trimethoxysilane, γ-methacryloxypropyl trimethoxysilane, and aluminate coupling agent. 10.The low water absorption water-based thermal insulation energy-saving coating of claim 6, wherein the film-forming aid is one or a combination of 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate, nylon acid diisobutyl ester, 2,2,4-trimethyl-1,3-pentanediol, triethylene glycol diisooctanoate, and alcohol ester twelve; and / or, the reinforcing filler is one or a combination of calcium carbonate, talc powder, mica powder, kaolin, precipitated barium sulfate, and silicon dioxide. The raw material components of the coating further include pigments and / or defoaming agents, with 100 parts by weight of the film-forming material emulsion, 1 to 20 parts by weight of pigments; 11. The low water absorption water-based thermal insulation energy-saving coating according to claim 6, characterized in that, 0.2 to 2 parts by weight of defoaming agents. 12.The low water absorption water-based thermal insulation energy-saving coating of claim 11, wherein with 100 parts by weight of the film-forming material emulsion, 3 to 12 parts by weight of pigments; 0.3 to 1.5 parts by weight of defoaming agents. ​ ​ ​ ​

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