Biomass-based composite heat-insulating coating as well as preparation method and application thereof

Abstract

The invention discloses a biomass-based thermal insulation coating as well as a preparation method and application thereof, and belongs to the technical field of thermal insulation materials. The heat-insulating coating is composed of a biomass-based supramolecular adhesive and a heat-insulating filler; the adhesive is formed by synergistic crosslinking of lipoic acid and tannic acid through dynamic covalent bonds and multiple hydrogen bonds, and the adhesive strength higher than 1.0 MPa can be provided; the heat insulation filler is a hollow glass bead system with optimized particle size and true density. The core of the invention lies in that a tough and dynamic supramolecular network formed by the biomass-based adhesive not only endows the coating with excellent interface bonding force and mechanical stability, but also can cooperatively construct a more efficient thermal barrier structure through tight compounding with a multi-scale thermal insulation filler, so that the heat conductivity coefficient of the coating can be as low as 0.03 W / (m.K). The coating has the comprehensive advantages of being environmentally friendly and efficient in heat insulation, and is suitable for the field with double strict requirements for reliability and heat insulation.

Description

Technical Field

[0001] This invention belongs to the field of functional composite materials and thermal insulation coating technology, specifically relating to a high-performance composite thermal insulation coating based on a biomass-based supramolecular adhesive, its preparation method, and its application. Background Technology

[0002] Traditional thermal insulation coating technology is widely used in building energy conservation, thermal management of electronic equipment, and industrial insulation. Its core performance lies in the synergistic effect between the adhesive matrix and the thermal insulation filler (such as hollow glass microspheres). Currently, mainstream high-performance coatings generally use petroleum-based synthetic polymers such as epoxy resin, polyurethane, or silicone as adhesives. While these materials provide a certain initial strength, their raw materials are non-renewable, lacking environmental friendliness. Furthermore, their inherent poor interfacial compatibility and mismatch in thermal expansion coefficients with inorganic fillers lead to interfacial debonding and microcrack formation under thermal cycling or mechanical stress, resulting in decreased thermal insulation performance and premature coating failure. This has been a long-standing technical bottleneck. To address this challenge, existing technologies have mainly attempted solutions from two directions, but neither has fundamentally solved the problem.

[0003] On the one hand, to improve environmental friendliness, the industry has attempted to introduce biomass components. For example, authorized patent CN109722134B discloses a biomass-reinforced coating using down powder, which improves the compatibility between down powder and resin through chemical grafting. However, in such solutions, biomass materials mainly serve as the functional units being carried, rather than the core matrix material responsible for structural bonding and stress transfer. The mechanical properties and durability of the coating still heavily rely on the coexisting traditional synthetic resin, failing to achieve a balance between the greening and toughening of the adhesive matrix. On the other hand, to improve thermal insulation efficiency and interfacial bonding, existing technologies focus on optimizing fillers and designing complex coating structures. For example, authorized patent CN119463608B provides a solution that improves the dispersion and interfacial bonding of graphene oxide and hollow glass microspheres through complex chemical modifications (such as using reagents like 1-amino-8-naphthol-3,6-disulfonic acid and trimethyltrivinylcyclotrisilane) in the resin matrix. While such methods may achieve some results, they are complex, costly, and may involve non-environmentally friendly modifying agents, and still rely on petroleum-based polymer adhesives.

[0004] In summary, existing technologies consistently face a core contradiction: achieving both environmental friendliness and superior mechanical properties (especially the high durability resulting from strong interfacial bonding) in a single material system is difficult. Simple physical blending of biomass fillers cannot replace the skeletal role of petroleum-based binders; while complex modifications to fillers or coating structures can locally improve performance, they come at the cost of sacrificing process simplicity, economy, and environmental friendliness, thus limiting their effectiveness. Therefore, there is an urgent need in this field for a new solution: developing a novel binder system that achieves a high degree of biomass-based and environmentally friendly properties at the molecular level, while also intrinsically forming a robust and stable interfacial chemical bond with inorganic fillers. This would provide a foundation for constructing next-generation coatings that combine excellent environmental friendliness, outstanding mechanical stability, and durable, efficient thermal insulation performance. This invention is proposed precisely based on this objective. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of existing thermal insulation coating materials in that it is difficult to coordinate environmental friendliness, high mechanical strength, and high thermal insulation performance, and to provide a composite thermal insulation coating based on a biomass-based supramolecular binder. The invention also aims to provide an energy-saving and simple preparation method for this coating and its application in the field of high-performance thermal insulation.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: In a first aspect, the present invention provides a biomass-based composite thermal insulation coating, which is composed of a biomass-based supramolecular binder and a thermal insulation filler; the biomass-based supramolecular binder is composed of a three-dimensional network formed by the synergistic cross-linking of lipoic acid and tannic acid through dynamic disulfide bonds and multiple hydrogen bonds. The thermal insulation filler is one or more hollow glass microspheres with varying true density and / or particle size, wherein the particle size in the present invention is measured in terms of D50.

[0007] Preferably, the mass ratio of lipoic acid to tannic acid is 1:1 to 3:1.

[0008] Preferably, the true density of the hollow glass microspheres in the insulating filler is selected from 0.18-0.42 g / cm³. 3 The particle size D50 is selected from 30-80 μm.

[0009] More preferably, the heat-insulating filler is selected from at least one of HL32 type hollow glass microspheres and HL38 type hollow glass microspheres, wherein the true density of the HL32 type hollow glass microspheres is 0.30-0.34 g / cm³. 3 The particle size D50 is 40-50 μm; the true density of the HL38 hollow glass microspheres is 0.36-0.40 g / cm³. 3The particle size D50 is 35-45 μm; more preferably, the heat insulation filler includes HL32 type hollow glass microspheres and HL38 type hollow glass microspheres, and the mass ratio of the two types of microspheres is 1:3 to 3:1.

[0010] More preferably, the mass ratio of lipoic acid to tannic acid is 2:1.

[0011] More preferably, the filler has a true density of 0.31-0.33 g / cm³. 3 HL32 type microspheres with a true density of 0.37-0.39 g / cm³ 3 The HL38 microspheres are composed of microspheres in a 1:1 mass ratio.

[0012] Preferably, the total mass ratio of the biomass-based supramolecular adhesive to the total mass ratio of the graded thermal insulation filler is 1:1 to 1:4. More preferably, it is 1:3.

[0013] Secondly, the present invention provides a method for preparing the above-mentioned biomass-based composite heat-insulating coating, comprising the following steps: (1) Prepolymer preparation: Dissolve lipoic acid and tannic acid in a solvent and stir until completely dissolved to allow them to undergo a pre-crosslinking reaction and form a homogeneous and viscous adhesive prepolymer solution; (2) Slurry compounding: The heat insulation filler is added to the prepolymer solution and dispersed by mechanical stirring and ultrasonic treatment to form a uniform and stable coating slurry; (3) Curing and molding: The slurry is applied to the substrate and / or injected into the mold and cured at 15-40°C to obtain the heat insulation coating.

[0014] Preferably, in step (2), the ultrasonic processing power is 300-500 W and the processing time is 10-30 min.

[0015] Preferably, the coating after curing in step (3) can also be subjected to vapor phase silanization treatment to obtain a hydrophobic surface.

[0016] Thirdly, the present invention provides the application of the above-mentioned biomaterial-based composite thermal insulation coating in the fields of building energy conservation, thermal management of electronic equipment, or thermal protection of power battery packs.

[0017] Compared with the prior art, the beneficial effects of the present invention are mainly reflected in the following three aspects: Simultaneous achievement of green source and enhanced performance: A fully biomass-based supramolecular adhesive constructed from lipoic acid and tannic acid replaces petroleum-based resins, improving environmental friendliness from the source. This adhesive network, through the synergy of dynamic covalent and non-covalent bonds, intrinsically forms a strong and tough interface with inorganic fillers, simultaneously solving the core problems of insufficient mechanical strength and weak interfacial bonding in traditional biomass materials.

[0018] Enhanced thermal insulation performance and durability: Based on strong interfacial bonding, the graded hollow glass microsphere filler is uniformly and stably dispersed, constructing a highly efficient thermal barrier structure. This structure not only endows the coating with excellent thermal insulation performance (thermal conductivity as low as 0.03 W / (m·K)), but also possesses outstanding crack resistance and long-term thermal cycling stability due to its strong interfacial bonding.

[0019] The preparation process is energy-efficient, simplified, and functionally expandable: the entire coating preparation and curing process is completed at room temperature through molecular self-assembly, requiring no external heating, making the process energy-efficient, simple, and environmentally friendly. Furthermore, this coating system is easily functionalized; for example, a superhydrophobic surface can be imparted through vapor-phase silanization post-treatment, further enhancing its environmental adaptability and application potential.

[0020] In summary, this invention, through the unique design of a biomass-based supramolecular adhesive, has made systematic innovations at three levels: material source, composite structure, and preparation process. It has successfully prepared a composite coating that combines excellent environmental friendliness, high-efficiency thermal insulation, and good functional scalability, providing an effective solution for the development of a new generation of high-performance green thermal insulation materials and has broad prospects for market application. Attached Figure Description

[0021] Figure 1 The adhesive strength of the adhesive under different ratios of tannic acid: lipoic acid (TA:LA = 1:1, 1:2, 1:3) in Examples 2-4; Figure 2 The temperature control curves of the 2mm samples in Examples 1, 5, and 6 at 250°C; Figure 3 The temperature control curves of the 2mm samples in Examples 1, 7, and 8 at 250°C; Figure 4 Temperature control curves of the 2mm heat insulation coating of Optimal Ratio Example 1 at 150℃, 250℃, and 350℃; Figure 5 The contact angle of the sample in Optimal Proportion Example 1; Figure 6 The contact angles of the samples in Examples 1, 7, and 8 with different ratios of adhesive to thermal insulation filler (1:1, 1:2, and 1:3); Figure 7 The long-term effect (change over time) of the 2mm sample chamber in the optimal ratio Example 1 is shown by the temperature control curve at 250°C (room placement for 1 day, 5 days, 15 days, and 30 days). Figure 8 The temperature control curve of the 2mm sample of the optimal ratio Example 1 at 90% humidity and 250°C (1h, 6h, 12, 24, 48h). Figure 9 Temperature control curves of a 2mm sample from Optimal Ratio Example 1 placed outdoors for different durations; Figure 10 Temperature control curve (6h) of the 2mm sample of the optimal ratio Example 1 with long-term stable heat insulation at 250°C. Figure 11 The image shows a physical example of the heat-insulating coating prepared in Example 1, which is applied to a glass fiber mat and cured to form a heat-insulating coating. Detailed Implementation

[0022] To better clarify and understand the objectives, process solutions, and advantages of this invention, the technical solutions and implementation methods of this invention will be further described clearly, completely, and in detail below through specific embodiments and in conjunction with the accompanying drawings. It should be understood that the embodiments described in this invention are implemented under the premise of the technical solutions of this invention, providing detailed implementation methods and specific operating procedures, but are only some embodiments of this invention, not all embodiments. The specific implementation methods described are limited to illustrating and explaining this invention and do not limit this invention. Based on the embodiments of this invention, all other implementation methods obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0023] Unless otherwise specified, the experimental methods and conditions used in the embodiments of this invention are conventional methods and conditions. The materials, reagents, instruments, and equipment used in the embodiments, unless otherwise specified, are all conventional substances or equipment known to those skilled in the art and can be obtained commercially or prepared by conventional methods. The reaction conditions described in the invention's content can all achieve the stated reactions and obtain the desired products. Due to space limitations, some embodiments are listed below to further illustrate the advantages of the technical solution of this invention.

[0024] In this invention, some raw material information is as follows, but it is only for example and does not constitute a limitation on this invention: thioctic acid was purchased from Shanghai Titan Technology Co., Ltd., tannic acid was purchased from Ron Reagent, HL38 hollow glass microspheres were purchased from Henan Jieyang New Material Co., Ltd., and HL32 hollow glass microspheres were purchased from Henan Jieyang New Material Co., Ltd. Among them, HL38 hollow glass microspheres have a true density of 0.37-0.39 g / cm³. 3 The bulk density is 0.19-0.22 g / cm³. 3 D50 is 40μm, and D90 is 65μm; HL32 hollow glass microspheres: true density 0.31-0.33 g / cm³ 3 The bulk density is 0.17-0.19 g / cm³. 3D50 is 45μm, and D90 is 80μm.

[0025] Example 1 First, add 0.2g of lipoic acid (LA) to a beaker, then add 0.1g of tannic acid (TA) to the beaker. Add 1mL of anhydrous ethanol and stir thoroughly until the solution becomes a pale yellow, transparent liquid with a stringy consistency. This part is the adhesive component of the heat insulation coating. The stirring speed is 300rpm, and the stirring time is 15min.

[0026] Then, hollow glass microspheres of different sizes were added: 0.45g of HL38 hollow glass microspheres and 0.45g of HL32 hollow glass microspheres. Following this, 1ml of anhydrous ethanol was added; this portion serves as the heat-insulating filler for the heat-insulating coating. The added sample was ultrasonically stirred for 20 minutes to fully mix, resulting in a fluid sample. The ultrasonic power was 400W, and the stirring speed was 300rpm.

[0027] The slurry is then placed in a mold and cured at room temperature for 12 hours to complete the process.

[0028] Alternatively, the cured sample can be placed in a 3L sealed container with nitrogen and 45% humidity for 1 hour to adapt, and then 800μL of trichloroethylsilane can be injected into the sealed container to cover the sample surface. After reacting for another 12 hours, a sample with hydrophobic treatment of long silicon filaments can be obtained.

[0029] The average thermal conductivity of the sample prepared in this example is 0.03 W / (m*K).

[0030] Figure 4 The following are the temperature control curves for Example 1, set at 150°C, 250°C, and 350°C on the heating stage. It can be seen that after heating at 150°C for five minutes, the sample surface temperature was 65°C; after heating at 250°C for five minutes, the sample surface temperature was 86°C; and after heating at 350°C for five minutes, the sample surface temperature was 98°C.

[0031] The method for testing the temperature control curve is as follows: place the sample on a heating stage with controlled temperature, place a thermocouple on the sample surface, and record the sample surface temperature displayed by the thermocouple in real time.

[0032] Examples 2-4: Changing the proportion of adhesive components to explore the effect of different proportions on bonding performance.

[0033] Example 2

[0034] Based on Example 1, only the adhesive was prepared without adding heat-insulating filler. Specifically, 0.2g of lipoic acid (LA) was first placed in a beaker, followed by 0.1g of tannic acid (TA). Anhydrous ethanol was added at a ratio of 0.3g (TA+LA) / mL and stirred thoroughly to dissolve, thus obtaining the adhesive portion of the heat-insulating coating. The stirring speed was 300 rpm, and the stirring time was 15 min, resulting in a biomass adhesive with a lipoic acid:tannic acid ratio of 2:1.

[0035] Example 3 Based on Example 2, the ratio of lipoic acid to tannic acid was changed. Specifically, 0.1g of lipoic acid (LA) was first placed in a beaker, followed by 0.1g of tannic acid (TA). Anhydrous ethanol was added at a ratio of 0.3g (TA+LA) / mL and stirred thoroughly to dissolve the lipoic acid, thus obtaining the adhesive portion of the heat-insulating coating. The stirring speed was 300 rpm, and the stirring time was 15 min, resulting in a biomass binder with a lipoic acid:tannic acid ratio of 1:1.

[0036] Example 4 Based on Example 2, the ratio of lipoic acid to tannic acid was changed. Specifically, 0.3g of lipoic acid (LA) was first placed in a beaker, followed by 0.1g of tannic acid (TA). Anhydrous ethanol was added at a ratio of 0.3g (TA+LA) / mL and stirred thoroughly to dissolve the lipoic acid, thus obtaining the adhesive portion of the heat-insulating coating. The stirring speed was 300 rpm, and the stirring time was 15 min, resulting in a biomass binder with a lipoic acid:tannic acid ratio of 3:1.

[0037] In Examples 2-4, the mass ratio of lipoic acid and tannic acid in the adhesive was varied to demonstrate the effect of different lipoic acid-tannic acid ratios on the adhesive strength. Specifically, lipoic acid and tannic acid were mixed in different mass ratios, and the adhesive strength of the mixed adhesives was tested and compared with that of the adhesive in Example 2. The test method involved preparing the adhesive on a substrate and measuring it using a computerized tensile and compressive strength testing machine. The result was the average of three tests. Specific results are shown in Table 1 below. Figure 1 As shown, Figure 1 The adhesive strength of the adhesives under different ratios of lipoic acid and tannic acid in Examples 2-4 is as follows:

[0038] Examples 5-6: Exploring the impact of different thermal insulation filler systems on thermal insulation performance.

[0039] Example 5 Based on Example 1, the condition that HL32 hollow glass microspheres and HL38 hollow glass microspheres each account for 50% of the thermal insulation filler was changed to HL38 hollow glass microspheres accounting for 100% of the thermal insulation filler, while other conditions remained the same as in Example 1.

[0040] Example 6 Based on Example 1, the condition that HL32 hollow glass microspheres and HL38 hollow glass microspheres each account for 50% of the thermal insulation filler was changed to HL32 hollow glass microspheres accounting for 100% of the thermal insulation filler, while other conditions remained the same as in Example 1.

[0041] In Examples 1, 5, and 6, the mass ratio of HL38 and HL32 in the insulating filler was varied to demonstrate the effect of different hollow glass microsphere ratios on the packing density, and thus on the thermal insulation performance. Specifically, hollow glass microspheres of HL38 and HL32 were mixed at different mass ratios, and the thermal insulation performance of the mixed insulating samples was tested and compared with that of Example 1. Details are shown in Table 2 below. Figure 2 As shown, Figure 2 The temperature control curves for Examples 1, 5, and 6 at a controlled temperature of 250°C on the heating platform are as follows:

[0042] Examples 7-8 and Comparative Examples 1-2: Exploring the effects of different binder-to-insulating filler ratios on coatings and their properties.

[0043] Example 7 Based on Example 1, the ratio of biomass binder to heat insulation filler was changed from 1:3 to 1:1, while other conditions remained the same as in Example 1.

[0044] Example 8 Based on Example 1, the ratio of biomass binder to heat insulation filler was changed from 1:3 to 1:2, while other conditions remained the same as in Example 1.

[0045] In Examples 1, 7, and 8, the mass ratio of adhesive to insulating filler in the insulation samples was varied to demonstrate the effect of different insulating filler ratios on the insulation performance of the insulation samples. Specifically, adhesive and insulating filler were mixed in different mass ratios and compared with Example 1. Details are shown in Table 3 below. Figure 3 As shown, Figure 3 The temperature control curves for Examples 1, 6, and 7 at a controlled temperature of 250°C on the heating platform are as follows:

[0046] Comparative Example 1 Based on Example 1, the ratio of biomass binder to heat-insulating filler was changed from 1:3 to 1:4. Specifically, 0.2g of thioctic acid and 0.1g of tannic acid were dissolved in 1mL of anhydrous ethanol by stirring. 0.6g each of HL32 and HL38 type hollow glass microspheres were added, with other conditions remaining the same as in Example 1. This resulted in poor curing, with only partial curing and the remainder dispersed.

[0047] Comparative Example 2 Based on Example 1, the ratio of biomass adhesive to heat-insulating filler was changed from 1:3 to 1:5. Specifically, 0.2g of thioctic acid and 0.1g of tannic acid were dissolved in 1mL of anhydrous ethanol. 0.75g each of HL32 and HL38 type hollow glass microspheres were used, with other conditions remaining the same as in Example 1. This resulted in very poor curing, to the point of non-curing. After the anhydrous ethanol evaporated, the entire product remained in powder form and could not be used as a coating.

[0048] Figure 5 The image shows the contact angle of a water droplet on the sample surface in Example 1. Figure 6 The contact angles of samples from Examples 1, 7, and 8 with different binder-to-insulating filler ratios (1:1, 1:2, and 1:3) were measured using an optical contact angle meter. The results demonstrate good hydrophobic properties, indicating that the insulating coating of this invention is also suitable for other functionalized applications.

[0049] Figure 7 The temperature control curve at 250°C shows the change in the long-term effect (change over time) of the 2mm sample chamber in Example 1 (after 1 day, 5 days, 15 days, and 30 days of indoor placement). Figure 8 The temperature control curve of the 2mm sample in Example 1 at 250°C under 90% humidity (1h, 6h, 12, 24, 48h). Figure 9 Temperature control curves of a 2mm sample from Example 1 placed outdoors for different durations; Figure 10 The temperature control curve (6h) for the long-term stable thermal insulation of the 2mm sample in Example 1 at 250℃ is shown. The detection methods involved are as follows: The prepared coating sample (2 mm thick) is placed on a heating stage set to a specific temperature (e.g., 150°C, 250°C, 350°C). A thermocouple is used to measure the temperature change at the center point of the sample's surface over time (e.g., 0-5 minutes), with the ambient temperature at 25 ± 2°C. Durability testing involves placing the sample in a specific environment for a specified time, followed by the aforementioned temperature control test (e.g., ...). Figure 7 For different numbers of days indoors, the relative humidity was 50±10%. Figure 8 For 90% humidity chamber, Figure 9 For different numbers of days outdoors, Figure 10 (For indoor direct measurement, continuous heating on a heating table for 6 hours).

[0050] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the present invention in any way. Other variations and modifications may be made without departing from the technical solutions described in the claims.

Claims

1. A biomass-based composite thermal barrier coating, characterized in that, The biomass-based supermolecular adhesive is formed by cross-linking of lipoic acid and tannic acid through dynamic disulfide bond exchange reaction and hydrogen bond interaction at room temperature; and the thermal insulation filler comprises one or more hollow glass microspheres.

2. The biomass-based composite thermal barrier coating of claim 1, wherein, The mass ratio of the lipoic acid to the tannic acid is 1:1 to 3:

1.

3. The biomass-based composite thermal barrier coating of claim 1, wherein, The mass ratio of the lipoic acid to the tannic acid is 2:

1.

4. The biomass-based composite thermal barrier coating of claim 2, wherein, The biomass-based supermolecular adhesive has a biomass carbon content of not less than 90%.

5. The biomass-based composite thermal barrier coating of claim 1, wherein, The hollow glass microspheres have a true density selected from the range of 0.18 to 0.42 g / cm 3 and a particle size selected from the range of 30 to 80 μm.

6. The biomass-based composite thermal barrier coating of claim 5, wherein, said heat insulating filler is selected from at least one of the hollow glass microbeads of type HL32 and the hollow glass microbeads of type HL38, said HL32 type having a true density of 0.30-0.34 g / cm 3 , a particle size of 40-50 μm; said HL38 type having a true density of 0.36-0.40 g / cm 3 , a particle size of 35-45 μm; The thermal insulation filler comprises hollow glass microspheres of type HL32 and hollow glass microspheres of type HL38, and the mass ratio of the two types of microspheres is 1:3 to 3:

1.

7. The biomass-based composite thermal barrier coating of claim 1, wherein, The total mass ratio of the biomass-based supermolecular adhesive to the thermal insulation filler is 1:1 to 1:

4.

8. The biomass-based composite thermal barrier coating of claim 1, wherein, the mass ratio of lipoic acid to tannic acid is 2:1; the thermal insulation filler has a true density of 0.31-0.33 g / cm 3 HL32 type microbeads with a particle size of 45±5 μm and a true density of 0.37-0.39 g / cm 3 a mixture of HL38 type microbeads with a particle size of 40±5 μm at a mass ratio of 1:1; and the total mass of the biomass-based supermolecular adhesive to the total mass of the thermal insulation filler is 1:

3.

9. A method of producing a biomass-based composite thermal barrier coating according to any one of claims 1 to 8, characterized in that, The method comprises the following steps: (1) dissolving lipoic acid and tannic acid in a solvent, stirring and mixing to form an adhesive prepolymer solution; (2) adding thermal insulation filler to the solution obtained in step (1) and uniformly dispersing to obtain a coating slurry; (3) applying the slurry to a substrate and / or a mold and allowing it to stand and solidify at 15-40°C.

10. Use of the biomass-based composite thermal insulation coating according to any one of claims 1-8 in the field of electronic equipment heat dissipation management, power battery thermal protection or building envelope.

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