Preparation method of all-water-blown polyurethane thermal insulation material for environment-friendly ultrathin refrigerator

Abstract

The invention belongs to the field of thermal insulation materials, and particularly relates to a preparation method of an all-water-blown polyurethane thermal insulation material for an environment-friendly ultrathin freezer, which comprises the following steps: adding nickel nitrate hexahydrate, trimesic acid and polyvinylpyrrolidone into a mixed solvent of DMF (Dimethyl Formamide) and water, reacting under a vacuum condition, cleaning and drying to obtain the all-water-blown polyurethane thermal insulation material for the environment-friendly ultrathin freezer. The spherical nickel-based MOF material is obtained; calcining the obtained spherical nickel-based MOFs material in a nitrogen environment, and naturally cooling to obtain a spherical porous derived carbon material; mixing polyol, water, resin, triethanolamine and the obtained spherical porous derived carbon material, and performing ultrasonic dispersion to form a component A; stannous octoate and isocyanate are mixed to form a component B; and mixing the component A and the component B to obtain the target product. The environment is not polluted, the heat preservation performance is improved, meanwhile, the compression strength can be improved, and core burning and cracking are not likely to happen.

Description

Technical Field

[0001] The present invention belongs to the field of thermal insulation materials, and particularly relates to a preparation method of a water-blown polyurethane thermal insulation material for an environment-friendly ultra-thin refrigerator. Background Art

[0002] With the increasing awareness of food safety among consumers and the booming development of the refrigerator industry, the demand for refrigerator facilities with large capacity, small volume, and less odor is growing day by day, which places more stringent requirements on thermal insulation materials. In this context, it directly promotes the development of refrigerator thermal insulation materials towards the direction of environmental protection, high heat insulation performance, and high reliability. To meet the development needs, new materials and technologies are striving for leapfrog development, and high performance and compounding are the most important development directions for thermal insulation materials.

[0003] As a traditional thermal insulation material, polymer foam materials have excellent properties such as low density, high porosity, low thermal conductivity, and high impact resistance due to their porous structure. Among them, polyurethane foam (PUF) is an important thermal insulation material with characteristics such as easy preparation, low cost, high compressive strength, and good flame retardancy. The thermal insulation performance of polymer foam materials is mainly determined by the thermal conductivity of the cell walls, the thermal conductivity of the gas in the cells, refraction, radiative thermal conductivity, and convective thermal conductivity of the gas in the bubbles. For PUF, due to the very small pore diameter, the convective thermal conductivity and radiative thermal conductivity in the pores can be ignored. The thermal conductivity of the gas in the pores has the greatest impact on the thermal insulation performance of PUF. The main gas in the complete pores is carbon dioxide. Therefore, under the same conditions of using blowing agents, a complete pore structure is more conducive to improving the thermal insulation performance. Controlling the pore structure through traditional methods of optimizing the foaming process, reducing the thermal conductivity of the cell walls, and preparing small and complete pores are effective ways to improve the thermal insulation performance of PUF.

[0004] Under the high requirements of environmental protection and ultra-thinness in the refrigerator industry, based on the mature foaming process and output, using materials with excellent thermal insulation performance to compound with PUF to prepare foam materials with low density and strong thermal insulation performance has been recognized in the thermal insulation material industry. Common fillers for PUF composites include silica aerogel, hollow glass microspheres, graphene, etc. After these fillers are added to the polyurethane system, due to their good thermal insulation performance, they will reduce the thermal conductivity of the cell walls and improve the pore microstructure by increasing the number of nucleation sites of the pores. However, these common fillers have problems such as cumbersome preparation, difficult addition, and limited performance improvement. Summary of the Invention

[0005] The present invention aims to overcome the deficiencies of the prior art and provide a preparation method of a water-blown polyurethane thermal insulation material for an environment-friendly ultra-thin refrigerator, which has the advantages of simple method, green environmental protection, ideal thermal insulation performance, high compressive strength, and not easy to burn the core and crack.

[0006] To solve the above technical problems, the present invention is implemented as follows: A preparation method of a fully water - foamed polyurethane thermal insulation material for an environment - friendly ultra - thin refrigerator is implemented according to the following steps: (1) Preparation of spherical nickel - based MOFs Nickel nitrate hexahydrate, trimesic acid and polyvinylpyrrolidone are added to a mixed solvent of DMF and water. After reaction under vacuum conditions, it is then washed and dried to obtain spherical nickel - based MOF materials; (2) Preparation of spherical porous derived carbon materials The spherical nickel - based MOF materials obtained in step (1) are calcined in a nitrogen environment and then naturally cooled to obtain spherical porous derived carbon materials; (3) Preparation of the target product Polyol, water, resin, triethanolamine and the spherical porous derived carbon materials obtained in step (2) are mixed and ultrasonically dispersed to form component A; stannous octoate and isocyanate are mixed to form component B; the component A and component B are mixed to obtain the target product.

[0007] Furthermore, in step (1), the mass ratio of nickel nitrate hexahydrate, trimesic acid and polyvinylpyrrolidone is successively 2.5 - 2.6:0.9 - 1:3 - 15.

[0008] Furthermore, in step (1), nickel nitrate hexahydrate, trimesic acid and polyvinylpyrrolidone are added to a mixed solvent of DMF and water, and ultrasonically dispersed for 1 - 1.5 h to make them uniformly dispersed.

[0009] Furthermore, in step (1), the reaction is carried out for 8 - 12 h under vacuum conditions at 120 - 180 °C.

[0010] Furthermore, in step (1), after the reaction is completed, the powder sample is washed 4 - 8 times with DMF and absolute ethanol and then dried to obtain spherical nickel - based MOF materials.

[0011] Furthermore, in step (2), the spherical nickel - based MOF materials obtained in step (1) are calcined at 200 - 400 °C for 3 h in a nitrogen environment, and then continue to be naturally cooled in a nitrogen environment to obtain spherical porous derived carbon materials.

[0012] Furthermore, in step (3), polyol, water, resin, triethanolamine and the spherical porous derived carbon materials obtained in step (2) are mixed and ultrasonically dispersed for 30 - 40 min to form component A.

[0013] Furthermore, in step (3), the mass ratio of polyol, water, resin, triethanolamine and spherical porous derived carbon materials is successively 59 - 63:1.5 - 2:0.6 - 1:0.2 - 0.4:0.3 - 1.2.

[0014] As a typical three-dimensional porous material, metal-organic framework (MOF) materials are formed by the self-assembly connection of inorganic metal centers and bridging organic ligands. They have high designability and structural diversity, and their structures can be designed and regulated at the molecular scale. The derived carbon materials obtained after calcining MOFs have a richer hierarchical structure, uniformly distributed pores, and good stability. Modifying PUF with them can greatly improve the thermal insulation and mechanical properties, and have many potential application values. Considering the environmental protection and high-performance requirements of the refrigerator industry, in the present invention, a one-step method is used to add it to the polyurethane system for all-water foaming, and at the same time, a solvothermal method is used to synthesize spherical nickel-based metal framework materials. After high-temperature calcination under nitrogen conditions, spherical porous derived carbon materials with nickel-based metal framework materials as precursors are obtained. The derived carbon microspheres are used as fillers to prepare PUF composites. Due to its special pore structure, the thermal conductivity of the cell wall of the composite material is reduced. At the same time, the microspheres act as nucleation sites in the system to effectively regulate the cell structure, which can reduce the thermal conductivity of the gas in the cells and the radiative thermal conductivity, so as to achieve the purpose of improving the thermal insulation performance of the foam material. While improving the performance of the foam material, the preparation process of this invention is simple and environmentally friendly, and can realize industrial production. Compared with the prior art, the method of this invention is simple, and a polyurethane thermal insulation material for ultra-thin refrigerators with good thermal insulation performance can be obtained; while improving the thermal insulation performance, the compressive strength can also be improved and it is not easy to burn the core and crack; using water as a blowing agent does not pollute the environment, is green and environmentally friendly, and can ensure that there is no peculiar smell during the foaming and the use of the refrigerator. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The present invention will be described in detail below through specific embodiments. These embodiments are provided to more thoroughly understand the present invention and to completely convey the scope of the present invention to those skilled in the art. As mentioned throughout the specification and claims, "comprising" or "including" is an open-ended term, interpreted as "including but not limited to". The subsequent description of the specification is a preferred embodiment for implementing the present invention, but the description is for the purpose of the general principles of the specification and is not used to limit the scope of the present invention. The protection scope of the present invention shall be subject to what is defined by the appended claims. Unless otherwise specified, various reagents and materials used in the present invention can be purchased from the market.

[0016] Figure 1 Schematic diagram of the preparation process of the low thermal conductivity PUF composite material of the present invention; Figure 2 Finished product diagram of the low thermal conductivity PUF composite material of the present invention; Figure 3Electron micrograph of the present invention; among them, (a) Scanning electron micrograph of nickel-based MOF microspheres; (b) Scanning electron micrograph of nickel-based MOF microsphere-derived carbon material; (c) Transmission electron micrograph of nickel-based MOF microspheres; (d) Transmission electron micrograph of nickel-based MOF microsphere-derived carbon material; (e) Unmodified PUF composite; (f) Nickel-based MOF microsphere-derived carbon material-modified PUF composite; Figure 4 Thermal conductivity, specific heat capacity and compressive strength diagrams of PUF composites with different components of the present invention; among them, a, Thermal conductivity of PUF composites with different components; b, Specific heat capacity of PUF composites with different components; c, Compressive strength of PUF composites with different components. Specific implementation manners

[0017] Example 1 The preparation method of the all-water foamed polyurethane thermal insulation material for an environment-friendly ultra-thin cold cabinet is implemented according to the following steps: (1) Preparation of spherical nickel-based MOFs: Disperse 2.5 g of nickel nitrate hexahydrate, 0.95 g of trimesic acid, and 10 g of polyvinylpyrrolidone in a mixed solvent of DMF and water, and ultrasonically disperse for 1.2 h to make it uniformly dispersed. After putting it into a polytetrafluoroethylene liner, it is loaded into a reaction kettle and reacted under vacuum at 160 °C for 11 h. After the reaction is completed, the powder sample is washed 6 times with DMF and absolute ethanol, and then dried to obtain spherical nickel-based MOF material.

[0018] (2) Preparation of spherical porous derived carbon material: The obtained nickel-based MOF material is calcined at 350 °C for three hours in a nitrogen environment and then naturally cooled in a nitrogen environment to obtain spherical porous derived carbon material.

[0019] (3) Preparation of low thermal conductivity PUF composite: Ultrasonically disperse 61 parts of polyol, 0.9 part of spherical porous derived carbon material, 1.8 parts of water, 0.9 part of resin, and 0.35 part of triethanolamine for 35 min as component A material, and 0.14 part of stannous octoate and 91.8 parts of isocyanate as B; (4) Use a high-speed mixer to stir component A and component B for 10 s and then pour them into a free foaming mold, and cure for three days to obtain a PUF composite with good heat insulation performance, that is, the all-water foamed polyurethane thermal insulation material for an environment-friendly ultra-thin cold cabinet.

[0020] Example 2 The preparation method of the all-water foamed polyurethane thermal insulation material for an environment-friendly ultra-thin cold cabinet is implemented according to the following steps: (1) Preparation of spherical nickel-based MOFs: 2.6 g of nickel nitrate hexahydrate, 0.98 g of trimesic acid, and 12 g of polyvinylpyrrolidone were dispersed in a mixed solvent of DMF and water, and ultrasonicated for 1.3 h to make them evenly dispersed. After placing it in a Teflon liner, it was loaded into a reaction kettle and reacted under vacuum at 145 °C for 12 h. After the reaction was completed, the powder sample was washed 7 times with DMF and absolute ethanol, and then dried to obtain the spherical nickel-based MOF material.

[0021] (2) Preparation of spherical porous derived carbon material: The obtained nickel-based MOF material was calcined at 280 °C for three hours in a nitrogen atmosphere and then naturally cooled in a nitrogen atmosphere to obtain the spherical porous derived carbon material.

[0022] (3) Preparation of low thermal conductivity PUF composite: 62 parts of polyol, 1.1 parts of spherical porous derived carbon material, 2 parts of water, 0.7 parts of resin, and 0.28 parts of triethanolamine were ultrasonicated for 38 min as component A, and 0.15 parts of stannous octoate and 92 parts of isocyanate as B; (4) Using a high-speed mixer, stir component A and component B for 10 s and then pour them into a free-foaming mold, and cure for three days to obtain a PUF composite with good heat insulation performance, that is, a full-water foaming polyurethane thermal insulation material for an environment-friendly ultra-thin refrigerator.

[0023] Example 3 A preparation method of a full-water foaming polyurethane thermal insulation material for an environment-friendly ultra-thin refrigerator is implemented according to the following steps: (1) Preparation of spherical nickel-based MOFs: 2.59 g of nickel nitrate hexahydrate, 0.90 g of trimesic acid, and 9 g of polyvinylpyrrolidone were dispersed in a mixed solvent of DMF and water, and ultrasonicated for 1 h to make them evenly dispersed. After placing it in a Teflon liner, it was loaded into a reaction kettle and reacted under vacuum at 150 °C for 10 h. After the reaction was completed, the powder sample was washed 8 times with DMF and absolute ethanol, and then dried to obtain the spherical nickel-based MOF material.

[0024] (2) Preparation of spherical porous derived carbon material: The obtained nickel-based MOF material was calcined at 300 °C for three hours in a nitrogen atmosphere and then naturally cooled in a nitrogen atmosphere to obtain the spherical porous derived carbon material.

[0025] (3) Preparation of low thermal conductivity PUF composite: 60 parts of polyol, 0.9 part of spherical porous derived carbon material, 1.6 parts of water, 0.8 part of resin, and 0.3 part of triethanolamine were ultrasonicated for 30 min as component A, and 0.13 part of stannous octoate and 91.7 parts of isocyanate as B; (4) Using a high-speed mixer, stir component A and component B for 10 s and then pour them into a free-foaming mold, and cure for three days to obtain a PUF composite with good heat insulation performance, that is, a full-water foaming polyurethane thermal insulation material for an environment-friendly ultra-thin refrigerator.

[0026] Schematic diagram of the preparation process of low thermal conductivity PUF composites, as shown in Figure 1 the figure. Schematic diagram of the preparation process of low thermal conductivity PUF composites, as shown in Figure 1 the figure. Photograph of the finished product of low thermal conductivity PUF composites, as shown in Figure 2 the figure. Figure 3 (a) and 3(b) are the scanning electron microscope images of nickel-based MOF microspheres and nickel-based MOF-derived carbon materials respectively. It can be seen from the figure that the particles are spherical both before and after high-temperature calcination. Such regular and smooth spheres can serve as excellent nucleation sites in the polyurethane system to regulate the cell structure of PUF. Figure 3 (c) and 3(d) are the transmission electron microscope images of nickel-based MOF microspheres and nickel-based MOF-derived carbon materials. It can be seen that the porous derived carbon material formed by high-temperature calcination has a core-shell structure, which can effectively block the heat conduction and is beneficial to the heat insulation performance of the PUF composite. The structure of the nickel-based MOF-derived carbon material modified PUF composite is as shown in Figure 3 (f). By comparing with the scanning electron microscope of the unmodified PUF composite in Figure 3 (e), it can be clearly observed that the cell size of the PUF with spherical porous derived carbon material added is more uniform and the cell structure is more complete.

[0027] It can be seen that compared with the unblended and unmodified PU, adding nickel-based MOF-derived carbon material to the polyurethane system reduces the thermal conductivity of the PUF composite by 23.13%, which is lower than that of the nickel-based MOF modified PUF. This is because the derived carbon material and the microspherical morphology of nickel-based MOF play advantages in the polyurethane system. The uniformly sized and flat-surfaced microspheres are evenly dispersed in the polyurethane system as nucleation sites during the foaming process, making the cells evenly distributed and the foam structure more regular. The nickel-based MOF-derived carbon material has a more abundant pore structure than nickel-based MOF, which also makes it have better dispersibility in the system. In addition, the special core-shell structure generated after calcination can effectively hinder the heat transfer and reduce the thermal conductivity of the cell wall. Figure 4 (b) Specific heat capacity of PUF composites with different components. It can be seen that the specific heat capacity of the PUF modified by nickel-based MOF-derived carbon material increases by 30.24% compared with that of the unmodified one. Figure 4 (c) Compressive strength of PUF composites with different components. Compared with the unmodified PUF, the compressive strength of the PUF modified by nickel-based MOF-derived carbon material increases by 55.18%. In addition to the good cell structure brought by the abundant pore structure, the stable structure of the nickel-based MOF-derived carbon material itself plays an important supporting role in the cell wall, which is also a key factor for the increase in compressive strength. The significant increase in compressive strength makes the PUF composite not easily burn out and crack during use.

[0028] It is understandable that the above specific description of the present invention is only for explaining the present invention and is not limited to the technical solutions described in the embodiments of the present invention. Those of ordinary skill in the art should understand that the present invention can still be modified or equivalently replaced to achieve the same technical effects; as long as the usage requirements are met, they are all within the protection scope of the present invention.

Claims

1. A preparation method of a fully water-blown polyurethane thermal insulation material for an environment-friendly ultra-thin freezer, characterized in that, It is implemented according to the following steps: (1)Preparation of spherical nickel-based MOFs Nickel nitrate hexahydrate, trimesic acid and polyvinylpyrrolidone are added to a mixed solvent of DMF and water. After reaction under vacuum conditions, it is washed and dried to obtain a spherical nickel-based MOF material; (2)Preparation of spherical porous derived carbon material The spherical nickel-based MOFs material obtained in step (1) is calcined in a nitrogen environment and naturally cooled to obtain a spherical porous derived carbon material; (3)Preparation of the target product Polyol, water, resin, triethanolamine and the spherical porous derived carbon material obtained in step (2) are mixed and ultrasonically dispersed to form component A; stannous octoate and isocyanate are mixed to form component B; the component A and component B are mixed to obtain the target product.

2. The preparation method of the all-water foamed polyurethane thermal insulation material for the environment-friendly ultra-thin refrigerator according to claim 1, characterized in that: In step (1), the mass ratio of nickel nitrate hexahydrate, trimesic acid and polyvinylpyrrolidone is 2.5-2.6:0.9-1:3-15 in sequence.

3. The preparation method of the all-water foamed polyurethane thermal insulation material for the environment-friendly ultra-thin refrigerator according to claim 2, wherein: In step (1), nickel nitrate hexahydrate, trimesic acid and polyvinylpyrrolidone are added to a mixed solvent of DMF and water, and ultrasonicated for 1-1.5 h to make them uniformly dispersed.

4. The preparation method of the all-water foamed polyurethane thermal insulation material for the environment-friendly ultra-thin refrigerator according to claim 3, wherein: In step (1), the reaction is carried out under vacuum conditions at 120-180 °C for 8-12 h.

5. The preparation method of the all-water foamed polyurethane thermal insulation material for the environment-friendly ultra-thin refrigerator according to claim 4, characterized in that: In step (1), after the reaction is completed, the powder sample is washed 4-8 times with DMF and absolute ethanol, and then dried to obtain a spherical nickel-based MOF material.

6. The preparation method of the all-water foamed polyurethane thermal insulation material for the environment-friendly ultra-thin cold cabinet according to claim 5, wherein: In step (2), the spherical nickel-based MOFs material obtained in step (1) is calcined at 200-400 °C in a nitrogen environment for 3 hours, and then continuously naturally cooled in a nitrogen environment to obtain a spherical porous derived carbon material.

7. The preparation method of the all-water foamed polyurethane thermal insulation material for the environment-friendly ultra-thin refrigerator according to claim 6, characterized in that: In step (3), polyol, water, resin, triethanolamine and the spherical porous derived carbon material obtained in step (2) are mixed and ultrasonically dispersed for 30-40 min to form component A.

8. The preparation method of the all-water foamed polyurethane thermal insulation material for the environment-friendly ultra-thin refrigerator according to claim 7, characterized in that: In step (3), the mass ratio of the polyol, water, resin, triethanolamine and the spherical porous derived carbon material is 59-63:1.5-2:0.6-1:0.2-0.4:0.3-1.2 in sequence.

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