A heat-insulating coating, a paper container and a preparation method thereof

Abstract

The present invention relates to the technical field of thermal insulation coatings, and specifically discloses a thermal insulation coating, a paper container and a preparation method thereof. A thermal insulation coating comprises water-based polyurethane, ceramic hollow microspheres, aerogel particles, water, sodium starch phosphate, propylene glycol alginate, ethylene carbonate and triethanolamine. A paper container comprises a three-layer structure, which comprises a thermal insulation layer, a paper substrate layer and a PE coating layer from top to bottom. A preparation method for a paper container comprises coating PE on the surface of a paper substrate layer through a coating process, and then preparing the obtained material into a paper container embryo, and finally covering the outer surface of the paper container embryo with a thermal insulation coating through an impregnation process to obtain a paper container. The thermal insulation coating of the present application has excellent thermal insulation properties and, by coating the thermal insulation coating of the present application on the outside of a paper container as a thermal insulation coating, the paper container can be endowed with good thermal insulation properties.

Description

Technical Field

[0001] The present invention relates to the technical field of thermal insulation coatings, and in particular to a thermal insulation coating, a paper container and a preparation method thereof. Background Art

[0002] To reduce environmental pollution, replacing traditional paper lunch boxes with paper lunch boxes has become a trend in the catering industry. Traditional paper lunch boxes have poor insulation, making it difficult to maintain the temperature of food for extended periods. To overcome this issue, paper lunch boxes are often covered with insulation bags, allowing the food inside to maintain a constant temperature for extended periods. However, this wastes resources and contradicts the original goal of reducing environmental pollution. Therefore, there is an urgent need to enhance the insulation properties of paper lunch boxes.

[0003] Existing technology generally enhances the thermal insulation performance of paper lunch boxes by coating the outer layer with a coating containing thermal insulating fillers. Thermal insulating fillers are often particulates such as ceramic particles and aerogels. These particles have poor dispersibility in the coating and tend to aggregate, affecting the uniformity and stability of the coating. This ultimately results in an uneven distribution of the thermal insulating filler in the applied coating, with some areas of the coating containing no or minimal thermal insulating filler, resulting in a reduction in the overall thermal insulation performance of the coating. Therefore, further improvements are needed to ensure that the thermal insulating filler is evenly dispersed in the coating. Summary of the Invention

[0004] To ensure that the insulating filler is evenly dispersed in the coating, the present application provides a thermal insulation coating, a paper container, and a method for preparing the same. The thermal insulation coating of the present application has excellent thermal insulation properties and a simple preparation process. When applied to the outside of a paper container as an insulating coating, the thermal insulation coating can impart excellent thermal insulation properties to the paper container.

[0005] In the first aspect, the present application provides a thermal insulation coating that adopts the following technical solution:

[0006] A thermal insulation coating comprises the following components by weight: 90 to 100 parts of waterborne polyurethane, 25 to 35 parts of ceramic hollow microspheres, 8 to 12 parts of aerogel particles, 45 to 55 parts of water, 1 to 1.5 parts of

[0007] Sodium starch phosphate, 0.5-1 part of propylene glycol alginate, 0.5-1 part of ethylene carbonate, 0.3-0.7 part of triethanolamine.

[0008] In the above technical solution, the present application adds ceramic hollow microspheres and aerogel particles as thermal insulation fillers into the coating, thereby giving the coating a certain thermal insulation performance; the present application then adds ethylene carbonate and triethanolamine, and the two act synergistically to promote better dispersion of the thermal insulation filler in the coating, and the coating can be evenly coated on the paper substrate, thereby improving the stability of the thermal insulation performance of the coating; further, the present application improves the coating's coating of the thermal insulation filler by adding sodium starch phosphate and propylene glycol alginate, and after the coating dries to form a thermal insulation layer , which can ensure the smoothness of the coating surface and further improve the usage experience of the coating; furthermore, the present application simultaneously adds sodium starch phosphate, propylene glycol alginate, ethylene carbonate and triethanolamine to the thermal insulation coating to achieve synergistic effects, which can well adjust the polymerization degree and cross-linking degree of the coating, change the molecular structure and arrangement order of the coating, change the extension degree of the polymer chain, increase the micropore structure in the coating, further improve the dispersion of the thermal insulation filler and reduce the thermal conductivity of the coating, and obtain a thermal insulation coating with good thermal insulation properties.

[0009] Preferably, the mass ratio of the sodium starch phosphate, propylene glycol alginate, ethylene carbonate and triethanolamine is 1.2:1:0.8:0.5.

[0010] In the above technical solution, this application limits the mass ratio of sodium starch phosphate, propylene glycol alginate, ethylene carbonate and triethanolamine to 1.2:1:0.8:0.5, so that the four achieve a better coordination effect, further increase the micropore structure in the coating, further reduce the thermal conductivity of the coating, and further improve the thermal insulation performance of the thermal insulation coating.

[0011] Preferably, the preparation method of the waterborne polyurethane comprises the following steps:

[0012] Step 1, preparation of prepolymer:

[0013] Step 1-1, modification of isocyanate: based on the mass fraction of the modified isocyanate, take 100 parts of isocyanate, heat it to 70-80°C, slowly add 30-35 parts of trimethylolpropane while stirring, and then add 1-2 parts of catalyst. After continuous stirring for 2-3 hours, filter to obtain the modified isocyanate;

[0014] Step 1-2, modification of polyol: based on the mass fraction of the modified polyol, mix 100 parts of polyol and 100 parts of adipic acid and stir evenly, heat to 100-120° C., add 1-2 parts of catalyst, and continue stirring for 5-6 hours to obtain the modified polyol;

[0015] Step 1-3: Based on the mass of the prepolymer, 50 parts of modified isocyanate and 100-140 parts of modified polyol are mixed, heated to 90-110° C. at 120-150 r / min, and reacted for 2-3 hours to obtain a prepolymer;

[0016] Step 2: Based on the mass fraction of the waterborne polyurethane, 130 to 150 parts of water, 150 to 190 parts of prepolymer, 2.5 to 5 parts of chain extender, and 0.5 to 1 part of catalyst are mixed and stirred to obtain a waterborne polyurethane.

[0017] In the above technical solution, the present application prepares waterborne polyurethane by using modified isocyanate and modified polyol, so that the prepared waterborne polyurethane has better flexibility and wear resistance, thereby improving the mechanical properties of the thermal insulation coating.

[0018] Preferably, the polyol is composed of a polyether polyol with a molecular weight of 4000 g / mol to 5000 g / mol and a polyester polyol with a molecular weight of 3000 g / mol to 6000 g / mol, and the mass ratio of the polyether polyol to the polyester polyol is (50-70):(50-70).

[0019] In the above technical solution, by selecting and using polyester polyol and polyether polyol, the advantages of the two complement each other, and water-based polyurethane with better flexibility and wear resistance can be obtained.

[0020] Preferably, the isocyanate is one or a combination of two of toluene diisocyanate, diphenylmethane diisocyanate, hexamethylene-1,6-diisocyanate, and isophorone diisocyanate.

[0021] Preferably, the isocyanate is prepared by compounding toluene diisocyanate and hexamethylene-1,6-diisocyanate in a mass ratio of (30-40): (10-20).

[0022] In the above technical solution, by selecting toluene diisocyanate and hexamethylene-1,6-diisocyanate as cross-linking agents, a water-based polyurethane with better flexibility and wear resistance can be obtained.

[0023] Preferably, the raw materials for preparing the waterborne polyurethane further include trimethylolpropane tripropylene glycol ether (amino terminated) and octadecylamine polyoxyethylene ether, and step 2 in the preparation method of the waterborne polyurethane is as follows:

[0024] Calculated by weight of water-based polyurethane, 130-150 parts of water, 150-190 parts of prepolymer, 2.5-5 parts of chain extender, 0.5-1 part of catalyst, 0.5-1 part of trimethylolpropane tripropylene glycol ether (amino terminated) and 0.2-0.5 part of octadecylamine polyoxyethylene ether are mixed and stirred to obtain water-based polyurethane.

[0025] In the above technical scheme, the present application can further improve the stability of water-based polyurethane by further adding trimethylolpropane tripropylene glycol ether (amino terminated) and octadecylamine polyoxyethylene ether to the water-based polyurethane. At the same time, it can be combined with sodium starch phosphate, propylene glycol alginate, ethylene carbonate and triethanolamine to increase the micropore structure in the coating while promoting the formation of more cross-linking points in the coating, thereby increasing the cross-linking density in the coating to further improve the coating bonding strength. This ensures that the coating has good bonding strength, avoids slagging, large-scale falling off, etc. when using the coating, and further improves the user experience of the thermal insulation coating.

[0026] Preferably, the particle size of the ceramic hollow microspheres is between 80 and 120 μm, and the particle size of the aerogel particles is between 80 and 90 μm.

[0027] In the above technical solution, by selecting the ceramic hollow microspheres and aerogel particles of the above particle size, the dispersibility of the thermal insulation filler in the coating is further improved, and the thermal insulation performance of the coating is further improved.

[0028] In a second aspect, the present application provides a paper container using the following technical solution:

[0029] A paper container comprises a three-layer structure, comprising, from top to bottom, a thermal insulation layer, a paper base material layer, and a PE coating layer; the thermal insulation layer is prepared from the thermal insulation coating described in the first aspect.

[0030] In the above technical solution, this application can effectively reduce the impact of external temperature on the items in the paper container and reduce the temperature change of the items in the paper container by attaching a thermal insulation layer on the paper base material layer, thereby providing a more stable storage environment for the items in the paper container. It can be applied to the production of thermal insulation paper lunch boxes and has broad application prospects.

[0031] In a third aspect, the present application provides a method for preparing a paper container using the following technical solution:

[0032] A method for preparing a paper container comprises the following steps:

[0033] Step a: preparing a paper substrate layer;

[0034] Step b: PE is coated on the surface of the paper substrate layer by a laminating process to obtain a PE laminating layer; wherein the amount of PE is 2g / m 2 ;

[0035] Step c: preparing a paper container body from the material obtained in step b, wherein the PE coating layer is located on the inner surface of the paper container body;

[0036] Step d: Covering the outer surface of the paper container embryo with a thermal insulation coating through an impregnation process, and then drying and curing the coating to obtain a thermal insulation layer, thereby obtaining a paper container;

[0037] In the step d, the dipping and drying steps can be repeated multiple times before aging to make the thickness of the thermal insulation layer reach 1 to 10 mm.

[0038] In the above technical solution, this application evenly applies the thermal insulation coating on the paper substrate, dries it, and then performs a maturation treatment to promote better bonding between the coating and the paper substrate, thereby giving the paper container good thermal insulation properties. In the actual production process, the paper substrate is generally paper cup paper, paper cup lid paper, paper bowl paper or paper bowl lid paper, etc. According to different insulation requirements, the thickness of the thermal insulation coating is generally between 1 and 10 mm.

[0039] In summary, this application includes at least one of the following beneficial technical effects:

[0040] 1. The present application improves the dispersibility of thermal insulation fillers in the coating by adding ethylene carbonate and triethanolamine, and improves the surface smoothness of the coating formed by the coating by adding sodium starch phosphate and propylene glycol alginate. Through the synergistic effect of sodium starch phosphate, propylene glycol alginate, ethylene carbonate and triethanolamine, the polymerization degree and cross-linking degree of the coating are well regulated, thereby achieving the effect of increasing the micropore structure in the coating, further reducing the thermal conductivity of the coating, and obtaining a thermal insulation coating with good thermal insulation properties.

[0041] 2. This application adds trimethylolpropane tripropylene glycol ether (amino terminated) and octadecylamine polyoxyethylene ether during the preparation process of water-based polyurethane. The synergistic effect of the two can increase the cross-linking density in the coating, thereby further improving the bonding strength of the coating and ensuring that the thermal insulation coating has good bonding strength. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 This is a detailed schematic diagram of the three-layer structure of the paper container. DETAILED DESCRIPTION

[0043] In order to better illustrate the purpose, technical solutions and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments.

[0044] Preparation Example 1

[0045] A method for preparing waterborne polyurethane comprises the following steps:

[0046] Step 1, preparation of prepolymer:

[0047] Step 1-1, modification of isocyanate: 100 kg of isocyanate was heated to 80° C., 30 kg of trimethylolpropane was slowly added at a stirring rate of 40 r / min, and the addition time was controlled within 40 min. Then, 1 kg of organic bismuth catalyst DY-20 was added. After continuous stirring at 100 r / min for 3 h, the mixture was filtered to obtain modified isocyanate.

[0048] Step 1-2, modification of polyol: 100 kg of polyol and 100 kg of adipic acid were mixed and stirred evenly, heated to 100° C., 2 kg of 83% sulfuric acid was added, and the mixture was stirred at 100 rpm for 6 h to obtain modified polyol.

[0049] Step 1-3: Mix 50 kg of modified isocyanate and 140 kg of modified polyol, heat to 90° C. at 120 r / min, and react for 3 h to obtain a prepolymer.

[0050] Step 2: 130 kg of water, 150 kg of prepolymer, 2.5 kg of chain extender, and 0.5 kg of catalyst were mixed and stirred evenly to obtain waterborne polyurethane.

[0051] The polyol is a mixture of polyether polyol with a molecular weight of 4000 g / mol to 5000 g / mol and polyester polyol with a molecular weight of 3000 g / mol to 6000 g / mol in a mass ratio of 50:70. The polyol was purchased from Huafeng Group Co., Ltd.

[0052] Among them, isocyanate is a mixture of toluene diisocyanate and diphenylmethane diisocyanate in a mass ratio of 30:20, and the isocyanates are all purchased from Wanhua Chemical Group Co., Ltd.

[0053] Wherein, the chain extender is butanediol.

[0054] Among them, the organic bismuth catalyst DY-20 was purchased from Shanghai Deyin Chemical Co., Ltd.

[0055] Among them, the catalyst is the highly active bismuth catalyst NIAX MC-710, which was purchased from Shandong Jiaying Chemical Technology Co., Ltd.

[0056] Preparation Example 2

[0057] A method for preparing waterborne polyurethane, which differs from Preparation Example 1 in that it comprises the following steps:

[0058] Step 1, preparation of prepolymer:

[0059] Step 1-1, modification of isocyanate: 100 kg of isocyanate was heated to 70°C, and 35 kg of trimethylolpropane was slowly added at a stirring rate of 30 r / min. The addition time was controlled within 30 min. Then, 2 kg of organic bismuth catalyst DY-20 was added. After continuous stirring at 120 r / min for 2 h, the mixture was filtered to obtain modified isocyanate.

[0060] Step 1-2, modification of polyol: 100 kg of polyol and 100 kg of adipic acid were mixed and stirred evenly, heated to 120° C., 1 kg of 83% sulfuric acid was added, and the mixture was stirred at 120 rpm for 5 h to obtain modified polyol.

[0061] Step 1-3: Mix 50 kg of modified isocyanate and 100 kg of modified polyol, heat to 110° C. at 150 r / min, and react for 2 h to obtain a prepolymer.

[0062] Step 2: 150 kg of water, 190 kg of prepolymer, 5 kg of chain extender, and 1 kg of catalyst were mixed and stirred evenly to obtain waterborne polyurethane.

[0063] The polyol is prepared by mixing a polyether polyol with a molecular weight of 4000 g / mol to 5000 g / mol and a polyester polyol with a molecular weight of 3000 g / mol to 6000 g / mol in a mass ratio of 70:50.

[0064] The isocyanate is a mixture of toluene diisocyanate and isophorone diisocyanate in a mass ratio of 40:10.

[0065] Wherein, the chain extender is propylene glycol.

[0066] Preparation Example 3

[0067] A method for preparing waterborne polyurethane, which differs from Preparation Example 1 in that it comprises the following steps:

[0068] Step 1, preparation of prepolymer:

[0069] Step 1-1, modification of isocyanate: 100 kg of isocyanate was heated to 75° C., 32 kg of trimethylolpropane was slowly added at a stirring rate of 35 r / min, and the addition time was controlled within 35 min. Then, 1.5 kg of organic bismuth catalyst DY-20 was added. After continuous stirring at 110 r / min for 2.5 h, the mixture was filtered to obtain modified isocyanate.

[0070] Step 1-2, modification of polyol: 100 kg of polyol and 100 kg of adipic acid were mixed and stirred evenly, heated to 110° C., 1.5 kg of 83% sulfuric acid was added, and the mixture was stirred at 110 r / min for 5.5 h to obtain modified polyol.

[0071] Step 1-3: Mix 50 kg of modified isocyanate and 120 kg of modified polyol, heat to 100° C. at 130 r / min, and react for 2.5 h to obtain a prepolymer.

[0072] Step 2: 140 kg of water, 180 kg of prepolymer, 3 kg of chain extender, and 0.7 kg of catalyst were mixed and stirred uniformly to obtain waterborne polyurethane.

[0073] The polyol is prepared by mixing a polyether polyol with a molecular weight of 4000 g / mol to 5000 g / mol and a polyester polyol with a molecular weight of 3000 g / mol to 6000 g / mol in a mass ratio of 60:65.

[0074] The isocyanate is a mixture of toluene diisocyanate and hexamethylene-1,6-diisocyanate in a mass ratio of 35:15.

[0075] Preparation Example 4

[0076] A method for preparing waterborne polyurethane is different from Preparation Example 1 in that the isocyanate is prepared by mixing toluene diisocyanate and hexamethylene-1,6-diisocyanate in a mass ratio of 30:20.

[0077] Preparation Example 5

[0078] A method for preparing waterborne polyurethane, which differs from Preparation Example 1 in that step 2 is as follows:

[0079] 130 kg of water, 150 kg of prepolymer, 2.5 kg of chain extender, 0.5 kg of catalyst, 0.5 kg of trimethylolpropane tripropylene glycol ether (amino terminated) and 0.5 kg of octadecylamine polyoxyethylene ether were mixed and stirred uniformly to obtain waterborne polyurethane.

[0080] Among them, trimethylolpropane tripropylene glycol ether (amino terminated) was purchased from Hubei Qifei Pharmaceutical Chemical Co., Ltd., CAS number: 39423-51-3.

[0081] Among them, octadecylamine polyoxyethylene ether was purchased from Shandong Xingguang Chemical Co., Ltd., CAS number: 26635-92-7.

[0082] Preparation Example 6

[0083] A method for preparing waterborne polyurethane, which differs from Preparation Example 1 in that step 2 is as follows:

[0084] 130 kg of water, 150 kg of prepolymer, 2.5 kg of chain extender, 0.5 kg of catalyst, 1 kg of trimethylolpropane tripropylene glycol ether (amino terminated) and 0.2 kg of octadecylamine polyoxyethylene ether were mixed and stirred uniformly to obtain waterborne polyurethane.

[0085] Preparation Example 7

[0086] A method for preparing waterborne polyurethane, which differs from Preparation Example 5 in that step 2 does not contain trimethylolpropane tripropylene glycol ether (amino terminated).

[0087] Preparation Example 8

[0088] A method for preparing waterborne polyurethane, which differs from Preparation Example 5 in that step 2 does not contain octadecylamine polyoxyethylene ether.

[0089] Example 1

[0090] A thermal insulation coating comprises the following components: 90 kg of waterborne polyurethane, 35 kg of ceramic hollow microspheres, 8 kg of aerogel particles, 55 kg of water, 1.5 kg of sodium starch phosphate, 0.5 kg of propylene glycol alginate, 1 kg of ethylene carbonate, and 0.7 kg of triethanolamine.

[0091] Wherein, the waterborne polyurethane is prepared by Preparation Example 1.

[0092] Among them, sodium starch phosphate was purchased from Nantong Runfeng Petrochemical Co., Ltd., CAS number: 53241-15-9.

[0093] Among them, propylene glycol alginate was purchased from Shanghai Yuanye Biotechnology Co., Ltd., product number: S68741.

[0094] Among them, triethanolamine was purchased from Sigma-Aldrich (Shanghai) Trading Co., Ltd., item number: V900257. Among them, the particle size of ceramic hollow microspheres was between 80 and 120 μm, and was purchased from Shanghai Huijing Sub-Nano New Materials Co., Ltd.

[0095] The aerogel particles are silica aerogels with a particle size of 80 to 90 μm, purchased from Shanghai Koraman Reagent Co., Ltd., with the product number 091458.

[0096] The preparation method of the thermal insulation coating is as follows:

[0097] A thermal insulation coating is obtained by mixing waterborne polyurethane, ceramic hollow microspheres, aerogel particles, water, sodium starch phosphate, propylene glycol alginate, ethylene carbonate and triethanolamine and stirring at 100 r / min for 10 minutes.

[0098] Example 2

[0099] A thermal insulation coating, which differs from Example 1 in that it includes the following components: 100 kg of water-based polyurethane, 25 kg of ceramic hollow microspheres, 12 kg of aerogel particles, 45 kg of water, 1 kg of sodium starch phosphate, 1 kg of propylene glycol alginate, 0.5 kg of ethylene carbonate, and 0.3 kg of triethanolamine.

[0100] Wherein, the waterborne polyurethane is prepared by Preparation Example 2.

[0101] The preparation method of the thermal insulation coating is as follows:

[0102] A thermal insulation coating is obtained by mixing waterborne polyurethane, ceramic hollow microspheres, aerogel particles, water, sodium starch phosphate, propylene glycol alginate, ethylene carbonate and triethanolamine and stirring at 120 r / min for 8 minutes.

[0103] Example 3

[0104] A thermal insulation coating, which differs from Example 1 in that it includes the following components: 5 kg of water-based polyurethane, 30 kg of ceramic hollow microspheres, 12 kg of aerogel particles, 50 kg of water, 1.2 kg of sodium starch phosphate, 1 kg of propylene glycol alginate, 0.8 kg of ethylene carbonate, and 0.5 kg of triethanolamine.

[0105] Among them, the water-based polyurethane was prepared by Preparation Example 3.

[0106] Example 4

[0107] A thermal insulation coating, which is different from Example 3 in that the water-based polyurethane is prepared by Preparation Example 4.

[0108] Example 5

[0109] A thermal insulation coating, which is different from Example 1 in that the water-based polyurethane is prepared by Preparation Example 5.

[0110] Example 6

[0111] A thermal insulation coating, which is different from Example 1 in that the water-based polyurethane is prepared by Preparation Example 6.

[0112] Example 7

[0113] A thermal insulation coating, which is different from Example 1 in that the water-based polyurethane is prepared by Preparation Example 7.

[0114] Example 8

[0115] A thermal insulation coating, which is different from Example 1 in that the water-based polyurethane is prepared by Preparation Example 8.

[0116] Comparative Example 1

[0117] A thermal insulation coating, which differs from Example 1 in that it does not contain sodium starch phosphate.

[0118] Comparative Example 2

[0119] A thermal insulation coating, which differs from Example 1 in that it does not contain propylene glycol alginate.

[0120] Comparative Example 3

[0121] A thermal insulation coating, which differs from Example 1 in that it does not contain ethylene carbonate.

[0122] Comparative Example 4

[0123] A thermal insulation coating, which is different from Example 1 in that it does not contain triethanolamine.

[0124] Application Example 1

[0125] A paper container, such as Figure 1 As shown, it includes a three-layer structure, which includes a thermal insulation layer, a paper base material layer and a PE coating layer from top to bottom.

[0126] The method for preparing the paper container comprises the following steps:

[0127] Step a: preparing a paper substrate layer, which can be paper cup paper, paper cup cover paper, paper bowl paper, or paper bowl cover paper.

[0128] Step b: PE is coated on the surface of the paper substrate layer through a laminating process to obtain a PE laminating layer; wherein the amount of PE is 2g / m 2 .

[0129] Step c: preparing the material obtained in step b into a paper container embryo, wherein the PE coating layer is located on the inner surface of the paper container embryo. The paper container embryo can be a paper cup, a paper cup lid, a paper bowl or a paper bowl lid, etc.

[0130] Step d: Covering the outer surface of the paper container embryo with a thermal insulation coating through an impregnation process, drying the moisture at 50° C. and aging at 70° C. for 8 minutes to obtain a thermal insulation layer, thereby obtaining a paper container.

[0131] In step d, the steps of dipping and drying are repeated multiple times before aging, so that the thickness of the thermal insulation layer reaches between 1 and 10 mm.

[0132] Among them, the thermal insulation coating is from Examples 1-8.

[0133] Experimental Example 1

[0134] Surface morphology sensory evaluation:

[0135] The thermal insulation coatings of the above-mentioned embodiments and comparative examples were prepared into paper containers using the preparation method of Application Example 1, wherein the thickness of the thermal insulation layer was about 0.4 mm. A jury composed of 10 volunteers then conducted a sensory evaluation of the surface morphology of the thermal insulation layer. The evaluation results were averaged, as shown in Table 1.

[0136] Evaluation criteria:

[0137] 0-2 points: visually inspected, with a sense of concavity and convexity, and resistance when touched, and uneven;

[0138] 3-4 points: Slightly concave and convex feeling when visually inspected, and uneven when touched;

[0139] 5-6 points: The surface is smooth when visually inspected, without any bumps or depressions, and smooth and without resistance when touched.

[0140] Experimental Example 2

[0141] Thermal conductivity: The test was conducted according to the method specified in GB / T 10294-2008 “Determination of steady-state thermal resistance and related properties of insulating materials – Heat flow meter method”. The test results are shown in Table 1.

[0142] Experimental Example 3

[0143] Adhesion: With reference to the standard GB / T 5210-2006 "Paints and varnishes adhesion test by pull-off method", a test rod with a diameter of 20 mm was used, with the upper and lower test rods coaxially connected to the sample for testing. The test results are shown in Table 1.

[0144] Table 1:

[0145]

[0146]

[0147] Combining the analysis of Examples 1-8 and Comparative Examples 1-4, it is not difficult to see that Examples 1-8 have good appearance, good thermal insulation performance and bonding strength.

[0148] Specifically analyzing in combination with Example 1 and Comparative Examples 1-4, the difference between Comparative Examples 1-4 and Example 1 is that no sodium starch phosphate is added in Comparative Example 1, no propylene glycol alginate is added in Comparative Example 2, no ethylene carbonate is added in Comparative Example 3, and no triethanolamine is added in Comparative Example 4. The appearance of Example 1 is better than that of Comparative Examples 1-2 to a certain extent, and the thermal insulation performance and bonding strength of Example 1 are better than those of Comparative Examples 1-4 to a certain extent. In this regard, the applicant believes that the synergistic effect of sodium starch phosphate and propylene glycol alginate can enable the coating to completely bury the thermal insulation filler, thereby showing to the outside that the coating has good flatness, ethylene carbonate and triethanolamine can improve the dispersibility of the thermal insulation filler in the coating, thereby showing to the outside that the coating has better flatness and thermal insulation performance, and the synergistic effect of sodium starch phosphate, propylene glycol alginate, ethylene carbonate and triethanolamine can further increase the micropore structure in the coating from a microscopic level, thereby obtaining a thermal insulation coating with better thermal insulation performance.

[0149] Specifically analyzing in combination with Example 1 and Examples 5-8, the difference between Example 5-8 and Example 1 is that, in Example 5-6, trimethylolpropane tripropylene glycol ether (amino terminated) and octadecylamine polyoxyethylene ether were added when preparing the waterborne polyurethane, Example 7 added trimethylolpropane tripropylene glycol ether (amino terminated), and Example 8 added octadecylamine polyoxyethylene ether. The bonding strength of Example 5-6 is better than that of Examples 7-8 and Example 1 to a certain extent. Therefore, the applicant believes that trimethylolpropane tripropylene glycol ether (amino terminated) and octadecylamine polyoxyethylene ether have a synergistic effect, and the two can cooperate with each other to achieve the effect of increasing the crosslinking density in the coating, thereby further improving the bonding strength of the coating.

[0150] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make non-creative modifications to the present embodiment as needed, but as long as they are within the scope of the claims of the present application, they are protected by the patent law.

Claims

1. A thermal insulation coating, characterized in that: The composition includes the following parts by weight: 90-100 parts of waterborne polyurethane, 25-35 parts of ceramic hollow microspheres, 8-12 parts of aerogel particles, 45-55 parts of water, 1-1.5 parts of sodium starch phosphate, 0.5-1 part of propylene glycol alginate, 0.5-1 part of ethylene carbonate, and 0.3-0.7 part of triethanolamine; The preparation method of the waterborne polyurethane comprises the following steps: Step 1, preparation of prepolymer: Step 1-1, modification of isocyanate: based on the mass fraction of the modified isocyanate, take 100 parts of isocyanate, heat it to 70-80°C, slowly add 30-35 parts of trimethylolpropane while stirring, and then add 1-2 parts of catalyst. After continuous stirring for 2-3 hours, filter to obtain the modified isocyanate; Step 1-2, modification of polyol: based on the mass fraction of the modified polyol, mix 100 parts of polyol and 100 parts of adipic acid and stir evenly, heat to 100-120°C, add 1-2 parts of catalyst, and continue stirring for 5-6 hours to obtain the modified polyol; Step 1-3: Based on the mass of the prepolymer, 50 parts of modified isocyanate and 100-140 parts of modified polyol are mixed, heated to 90-110°C at 120-150 rpm, and reacted for 2-3 hours to obtain a prepolymer; Step 2: Based on the mass fraction of the waterborne polyurethane, 130-150 parts of water, 150-190 parts of a prepolymer, 2.5-5 parts of a chain extender, and 0.5-1 part of a catalyst are mixed and stirred to obtain a waterborne polyurethane; The polyol is composed of a polyether polyol with a molecular weight of 4000 g / mol to 5000 g / mol and a polyester polyol with a molecular weight of 3000 g / mol to 6000 g / mol, and the mass ratio of the polyether polyol to the polyester polyol is (50-70): (50-70).

2. A thermal insulation coating according to claim 1, characterized in that: The mass ratio of the sodium starch phosphate, propylene glycol alginate, ethylene carbonate and triethanolamine is 1.2:1:0.8:0.

5.

3. The thermal insulation coating according to claim 1, characterized in that: The isocyanate is a compound of one or two of toluene diisocyanate, diphenylmethane diisocyanate, hexamethylene-1,6-diisocyanate and isophorone diisocyanate.

4. A thermal insulation coating according to claim 3, characterized in that: The isocyanate is prepared by compounding toluene diisocyanate and hexamethylene-1,6-diisocyanate in a mass ratio of (30-40): (10-20).

5. The thermal insulation coating according to claim 1, characterized in that: The raw materials for preparing the waterborne polyurethane further include trimethylolpropane tripropylene glycol ether (amino terminated) and octadecylamine polyoxyethylene ether. Step 2 in the preparation method of the waterborne polyurethane is as follows: Calculated by weight of the waterborne polyurethane, 130-150 parts of water, 150-190 parts of prepolymer, 2.5-5 parts of chain extender, 0.5-1 part of catalyst, 0.5-1 part of trimethylolpropane tripropylene glycol ether (amino terminated) and 0.2-0.5 part of octadecylamine polyoxyethylene ether are mixed and stirred to obtain a waterborne polyurethane.

6. The thermal insulation coating according to claim 1, characterized in that: The particle size of the ceramic hollow microspheres is between 80 and 120 μm, and the particle size of the aerogel particles is between 80 and 90 μm.

7. A paper container, characterized in that: The paper container comprises a three-layer structure, which comprises, from top to bottom, a thermal insulation layer, a paper base material layer and a PE coating layer; the thermal insulation layer is prepared from the thermal insulation coating according to any one of claims 1 to 6.

8. A method for preparing a paper container according to claim 7, characterized in that: The following steps are involved: Step a: preparing a paper substrate layer; Step b: PE is coated on the surface of the paper substrate layer by a laminating process to obtain a PE laminating layer; wherein the amount of PE is 2g / m 2 ; Step c: preparing a paper container body from the material obtained in step b, wherein the PE coating layer is located on the inner surface of the paper container body; Step d: Covering the outer surface of the paper container embryo with a thermal insulation coating through an impregnation process, and then drying and curing the coating to obtain a thermal insulation layer, thereby obtaining a paper container; In the step d, the dipping and drying steps can be repeated multiple times before aging to make the thickness of the thermal insulation layer reach 1-10 mm.

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