Filler, flame-retardant insulating material and preparation method and application thereof

Abstract

The invention belongs to the technical field of insulating materials, and particularly relates to a filler, a flame-retardant insulating material and a preparation method and application of the flame-retardant insulating material. The preparation method of the filler comprises the following steps: mixing calcium alginate with a dispersion liquid containing an Ag / oxide nano material, heating, and drying; the Ag / oxide nano material is a nano compound of oxide and Ag; the oxide comprises at least one of TiO2 and SiO2; the calcium ion mass concentration of the calcium alginate is 0.4-0.8%, and the average molecular weight of the calcium alginate is 25K-60K. The filler disclosed by the invention can improve the flame retardant property of polymers such as polyurea and the like, and meets the requirements on hydrophobicity, mechanical strength and insulating property at the same time.

Description

Technical Field

[0001] The present invention belongs to the technical field of insulating materials, and in particular relates to a filler, a flame-retardant insulating material, and a preparation method and application thereof. Background Art

[0002] With the development of ultra-high voltage (UHV) power grids, the insulation reliability of transmission towers in complex environments faces severe challenges. Traditional insulation materials such as ceramics and epoxy resins are brittle and have poor weather resistance, making them inadequate for the protection of irregular tower structures. Factors such as wind deflection, foreign objects, and bird damage can easily lead to frequent partial discharge and flashover incidents on transmission towers.

[0003] New polymer insulation materials have become a research hotspot due to their excellent comprehensive performance. Polyurea, in particular, offers unique advantages in localized protection applications such as tower crossarm cladding and bolt insulation, thanks to its high insulation, strong adhesion, rapid curing, and excellent weather resistance. However, with the rapid development of power systems, the insulation performance and fire safety requirements for transmission towers in operational environments are becoming increasingly stringent. In high-voltage transmission lines, the risk of fires caused by arcing, lightning strikes, or short circuits places even higher demands on the flame retardancy of the material. However, current polyurea materials do not offer good flame retardancy, and improvements are needed.

[0004] Flame retardant technologies such as nanofiller modification are expected to give polyurea materials flame retardant properties, but the improvement in flame retardant properties is limited, or it is difficult to meet the requirements of hydrophobicity, mechanical strength and insulation performance. Summary of the Invention

[0005] The object of the present invention is to provide a filler, a flame retardant insulating material and a preparation method and application thereof, which can improve the flame retardant properties of materials such as polyurea while meeting the requirements of hydrophobicity, mechanical strength and insulating properties.

[0006] To achieve the above objectives, the present invention adopts the following technical solutions.

[0007] In a first aspect, the present invention provides a method for preparing a filler, comprising:

[0008] Calcium alginate is mixed with a dispersion containing Ag / oxide nanomaterials, and then heated and dried;

[0009] Ag / oxide nanomaterial is a nanocomposite of oxide and Ag; the oxide includes at least one of TiO2 and SiO2;

[0010] The calcium ion mass concentration of calcium alginate is 0.4% to 0.8%, and the average molecular weight is 25K to 60K.

[0011] The filler of the present invention is obtained by heating and drying calcium alginate and Ag / oxide nanomaterials. Under the action of the Ag contained in the Ag / oxide nanomaterials, the Ag / oxide nanomaterials can be well loaded on the calcium alginate. Calcium alginate is a hydrogel material formed by cross-linking alginic acid and calcium ions. The present invention uses calcium alginate with a specific calcium ion mass concentration and molecular weight. Its molecular structure contains a large number of carboxyl groups and hydroxyl groups, which can form a three-dimensional network structure, thereby giving the material excellent gel strength and good compatibility with polymers such as polyurea. Oxides such as TiO2 and SiO2 have high mechanical strength and flame retardant effects. After being loaded on calcium alginate, they can play a synergistic role, so that the filler has good compatibility with polymers such as polyurea, and improve the flame retardant properties and mechanical properties of polymers such as polyurea.

[0012] At the same time, the Ag contained in Ag / oxide nanomaterials has certain antibacterial properties, which can effectively prevent the growth of fungi, thereby avoiding flashover accidents caused by the high conductivity of fungi, reducing the breakdown voltage, and improving the insulation properties of polymers such as polyurea.

[0013] In addition, experiments have shown that adding the filler of the present invention to polymers such as polyurea can also improve the hydrophobicity of the material.

[0014] Therefore, the filler of the present invention can improve the flame retardancy of polymers such as polyurea, while meeting the requirements of hydrophobicity, mechanical strength and insulation performance.

[0015] In some embodiments, the calcium alginate has a calcium ion mass concentration of 0.6% and an average molecular weight of 30K.

[0016] In some embodiments, the average particle size of calcium alginate is 100-140 mesh, for example 120 mesh.

[0017] In some embodiments, the mass ratio of Ag / oxide nanomaterial to calcium alginate is (0.3-1.5):1.

[0018] In some embodiments, in the Ag / oxide nanomaterial, the mass ratio of oxide to Ag is (19-49):1.

[0019] In some embodiments, both the oxide and Ag in the Ag / oxide nanomaterial may exist in the form of nanoparticles, and Ag may be deposited on the surface of the oxide or composited with the oxide in other forms.

[0020] In some embodiments, the average particle size of the Ag / oxide nanomaterial is 20 nm to 75 nm. For example, the average particle size of the Ag / TiO2 nanomaterial can be 20 nm to 50 nm; and the average particle size of the Ag / SiO2 nanomaterial can be 55 nm to 75 nm.

[0021] In some embodiments, the concentration of the dispersion containing the Ag / oxide nanomaterial is 0.05 g / mL to 0.1 g / mL, for example 0.075 g / mL. The dispersion can use water as a solvent.

[0022] In some embodiments, the heating temperature is 40° C. to 80° C., for example, 60° C. The heating time is 1 h to 5 h, for example, 3 h.

[0023] In some embodiments, the drying temperature is 70° C. to 100° C., for example, 80° C. The drying time is 1 h to 5 h, for example, 3 h.

[0024] In some embodiments, Ag / oxide nanomaterials can be prepared by the following method 1) or 2):

[0025] 1) providing a mixed solution comprising oxide nanoparticles and AgNO3, and reducing the mixed solution;

[0026] 2) providing a mixture comprising oxide nanoparticles and AgNO 3 , or providing a mixture comprising a precursor of oxide nanoparticles and AgNO 3 , and calcining the mixture.

[0027] In some embodiments, in method 1), the mixed solution containing oxide nanoparticles and AgNO 3 can be obtained by mixing the oxide nanoparticles with an AgNO 3 solution. The concentration of the AgNO 3 solution can be 0.05 mol / L to 0.2 mol / L, for example, 0.1 mol / L.

[0028] In some embodiments, in method 1), the reduction method includes: irradiating the mixed solution with ultraviolet light. The ultraviolet light parameters include: wavelength λ = 250nm ~ 370nm, for example, λ = 365nm; power 80W ~ 120W, for example, 100W. Under ultraviolet light irradiation, Ag in AgNO3 + It is reduced to Ag element, thereby forming a nanocomposite of oxide and Ag.

[0029] In some embodiments, in method 2), the precursor of the oxide nanoparticles refers to a material that can form oxide nanoparticles. For example, for TiO2, its precursor can be tetrabutyl titanate; for SiO2, its precursor can be ethyl silicate.

[0030] In some embodiments, in method 2), the mixture comprising oxide nanoparticles and AgNO3, and the mixture comprising a precursor of oxide nanoparticles and AgNO3, can be independently a solid mixture or a gel. The mixture can be obtained by mixing the oxide nanoparticles (or the precursor of the oxide nanoparticles) with an AgNO3 solution, or by drying the mixture. The concentration of the AgNO3 solution can be 0.05 mol / L to 0.2 mol / L, for example 0.1 mol / L.

[0031] In some embodiments, in method 2), the calcination temperature is 400° C. to 600° C., for example, 450° C. The calcination is performed in a protective atmosphere (e.g., a nitrogen atmosphere). Under high-temperature calcination, AgNO3 thermally decomposes to form elemental Ag, while the precursor of the oxide nanoparticles decomposes to form oxide nanoparticles, thereby forming a nanocomposite of oxide and Ag.

[0032] In a second aspect, the present invention provides a filler obtained by the above preparation method.

[0033] In a third aspect, the present invention provides a flame-retardant insulating material comprising a polymer and the above-mentioned filler, wherein the polymer comprises at least one of polyurea and epoxy resin.

[0034] The filler of the present invention is used to modify polymers such as polyurea and epoxy resin, thereby improving the flame retardancy of the material while meeting the requirements of hydrophobicity, mechanical strength and insulation performance.

[0035] In some embodiments, the mass ratio of polymer to filler is (13-38):1. For example, for polyurea, the mass ratio of polyurea to filler can be set to (17-38):1; for epoxy resin, the mass ratio of epoxy resin to filler can be set to (13-37.5):1.

[0036] In some embodiments, when the polymer is epoxy resin, the flame-retardant insulating material may further include additives such as a curing agent and an accelerator. The mass ratio of the curing agent to the epoxy resin may be (2-3):1, and the mass ratio of the accelerator to the epoxy resin may be (0.01-0.05):1. Exemplary curing agents include methyltetrahydrophthalic anhydride, and exemplary accelerators include 2,4,6-tris(dimethylaminomethyl)phenol.

[0037] In a fourth aspect, the present invention provides a method for preparing a flame retardant insulating material, comprising: mixing a filler with a polymer.

[0038] In some embodiments, when the polymer is polyurea, the method for preparing the flame retardant insulation material may include:

[0039] S1. dispersing the filler in an organic solvent (such as dimethylacetamide) to obtain a filler dispersion;

[0040] S2. Add the filler dispersion into the polyurea solution and stir.

[0041] In step S1, the concentration of the filler dispersion may be 0.08 g / mL to 0.18 g / mL, such as 0.13 g / mL.

[0042] In step S2, the concentration of the polyurea solution can be 0.5 g / mL to 1 g / mL, such as 0.67 g / mL. The polyurea solution can be obtained by reacting an isocyanate with an amino compound in an organic solvent (such as dimethylacetamide). Exemplary isocyanates include isophorone diisocyanate, and exemplary amino compounds include polyetheramine modified with diethyl maleate. The reaction is carried out in a protective atmosphere (such as a nitrogen atmosphere). The reaction can be carried out at ambient temperature for a reaction time of 20 min to 40 min.

[0043] In step S2, the stirring time is more than 3 hours, and the stirring process can be performed at ambient temperature.

[0044] In some embodiments, when the polymer is epoxy resin, the method for preparing the flame retardant insulating material may include:

[0045] Add filler, curing agent and accelerator to epoxy resin at 40°C to 60°C (such as 50°C), stir and degas.

[0046] The stirring temperature is 40° C. to 60° C. (eg, 50° C.), the stirring is performed under vacuum conditions (eg, vacuum degree>0.08 MPa), and the stirring time is 20 min to 40 min.

[0047] In a fifth aspect, the present invention provides the use of the flame-retardant insulating material in transmission towers, chemical plant storage tanks, chemical plant pipelines, truck cargo boxes or ship decks.

[0048] The flame retardant insulating material of the present invention has good flame retardancy, hydrophobicity, mechanical strength and insulating properties, and can be widely used in various fields.

[0049] For example, when the polymer in a flame-retardant insulation material is polyurea, it has excellent mechanical properties and environmental adaptability. It cures extremely quickly, gelling within seconds after spraying and reaching surface dryness in 10 to 30 minutes, making it suitable for efficient construction. Polyurea also typically has a tensile strength between 15 MPa and 30 MPa, and an elongation at break of 300% to 1000%. It also offers excellent wear resistance, impact resistance, and fatigue resistance. Furthermore, polyurea is highly weather-resistant, resistant to UV rays, extreme temperatures, acid and alkali corrosion, and salt spray erosion. It can form a seamless coating with excellent waterproof properties and extremely low water vapor permeability, making it suitable for use in a variety of applications.

[0050] In some embodiments, the flame-retardant insulating material can be applied to the surface of the device by spraying, brushing, pouring, or other methods, and then dried or heat-cured to form a coating. If the polymer is polyurea, a drying method is used, with a drying temperature of 100°C to 120°C, such as 110°C, and a drying time of 20 to 30 hours, such as 24 hours. If the polymer is epoxy resin, a heat-curing method is used, with a heat-curing temperature of 95°C to 110°C, such as 100°C, and a heat-curing time of 2 to 3 hours, such as 2.5 hours.

[0051] Flame-retardant insulating materials can form a coating on the surface of equipment, thereby exerting their flame retardant, insulating, hydrophobic and mechanical strength enhancing effects. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] Figure 1 The SEM images of pure polyurea and different modified polyureas;

[0053] Figure 2 Static contact angle images of pure polyurea and different modified polyureas. DETAILED DESCRIPTION

[0054] 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.

[0055] Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in the art and can be purchased or prepared according to common methods in the art.

[0056] The preparation method of calcium alginate used in the following examples and comparative examples is as follows:

[0057] Add 10g of sodium alginate to 1L of deionized water and stir to form a gel. Continue to add CaCl2 solution (concentration of 45mg / L) until the calcium ion mass concentration reaches 0.6%, 1.0%, and 1.4%.

[0058] The calcium ion mass concentration is determined by ethylenediaminetetraacetic acid (EDTA) titration. Specifically, after calcium alginate is incinerated, it reacts with acid to form a soluble calcium salt solution (digestive fluid sample). Take 10mL of digestive fluid sample in a test tube and add 3 to 5 drops of EBT indicator (the solution is wine red). Titrate with EDTA standard solution until the color changes to pure blue (end point), and record the titration volume V of EDTA standard solution. EDTA Calculate the calcium ion concentration in the digestive fluid sample according to the following formula: C Ca =(V EDTA ×C EDTA ×M Ca ×1000) / V 样品 .

[0059] Among them, C Ca : calcium ion concentration in digestive fluid sample (mg / mL); V EDTA : titration volume of EDTA standard solution (mL); C EDTA : concentration of EDTA standard solution (mol / mL); V 样品 : Volume of digestive fluid sample (mL). Combined with the mass of calcium alginate, the calcium ion concentration in calcium alginate is obtained.

[0060] Calcium alginate of the desired molecular weight can be obtained by using sodium alginate of varying molecular weights as raw material. The average molecular weight of calcium alginate is determined by gel permeation chromatography. The corresponding molecular weights of sodium alginate and calcium alginate are shown in the table below.

[0061] [Table 1]

[0062]

[0063] It is understandable that the calcium alginate of the present invention can also be prepared using other methods well known in the art, or can be directly purchased.

[0064] Example 1

[0065] This embodiment provides a filler, and uses the filler in preparing a flame-retardant insulating material.

[0066] 1. Filler and its preparation

[0067] The filler in this embodiment is Ag / TiO2 / calcium alginate, and its preparation method includes:

[0068] ①Preparation of Ag / TiO2 nanomaterial dispersion

[0069] Tetrabutyl titanate was dissolved in anhydrous ethanol (15 mL:60 mL by volume), nitric acid was added dropwise to adjust the pH to 3, and the mixture was stirred for 2 hours to form a transparent sol. After standing for 24 hours, the mixture was dried at 80°C for 24 hours to obtain a nano-TiO2 gel. Anatase TiO2 nanoparticles were then calcined at 400°C for 5 hours. 10 g of anatase TiO2 nanoparticles were dispersed in 50 mL of deionized water, 50 mL of AgNO3 solution (0.1 mol / L) was added, and magnetic stirring was performed for 3 hours. The mixture was then irradiated with ultraviolet light (λ = 365 nm, 100 W) for 2 hours to obtain a Ag / TiO2 nanomaterial dispersion. The Ag / TiO2 nanomaterial dispersion was then dried at 70°C to obtain the Ag / TiO2 nanomaterial. After testing, the mass ratio of TiO2 nanoparticles and Ag nanoparticles in the Ag / TiO2 nanomaterial is 97:3 (since the Ag in the AgNO3 solution cannot actually be completely compounded with the TiO2 nanoparticles, the mass ratio of TiO2 nanoparticles and Ag nanoparticles in the final Ag / TiO2 nanomaterial is different from the feed ratio in the preparation process).

[0070] ② Loading Ag / TiO2 nanomaterials onto calcium alginate

[0071] Take 3g of calcium alginate (120 mesh, calcium ion mass concentration of 0.6%, average molecular weight of 30K) and put it into a 50mL beaker. Pour the above-mentioned Ag / TiO2 nanomaterial dispersion containing 1.5g of Ag / TiO2 nanomaterial into the beaker, add 20mL of deionized water, heat in a 60℃ oil bath and stir continuously for 3h, pour the liquid in the beaker into a clean stainless steel tray, and dry it in an 80℃ forced air drying oven for 3h.

[0072] The filler Ag / TiO2 / calcium alginate prepared in this embodiment includes calcium alginate and Ag / TiO2 nanomaterials, and the Ag / TiO2 nanomaterials are loaded on the calcium alginate; the Ag / TiO2 nanomaterials are nanocomposites of TiO2 nanoparticles and Ag nanoparticles, and the Ag nanoparticles are distributed on the surface of the TiO2 nanoparticles.

[0073] The mass ratio of Ag / TiO2 nanomaterial to calcium alginate is 0.5:1; the mass ratio of TiO2 nanoparticles to Ag nanoparticles is 97:3. The average particle size of the Ag / TiO2 nanomaterial is 36nm. The calcium ion concentration of the calcium alginate is 0.6% and the average molecular weight is 30K.

[0074] 2. Flame retardant insulation materials and their preparation

[0075] The flame-retardant insulating material of this embodiment is modified polyurea, including polyurea and the above-mentioned filler (Ag / TiO2 / calcium alginate).

[0076] The preparation method of modified polyurea comprises:

[0077] (1) Preparation of polyurea solution

[0078] Dissolve 10.2 g of isophorone diisocyanate in 15 mL of dimethylacetamide to obtain an isocyanate solution. Dissolve 20.3 g of diethyl maleate-modified polyetheramine in 30 mL of dimethylacetamide to obtain a polyetheramine solution. Add the isocyanate solution dropwise to the polyetheramine solution. The reaction is carried out under a nitrogen atmosphere with continuous stirring for 30 minutes to ensure sufficient reaction of all components, obtaining a pure polyurea solution (containing 30.5 g of pure polyurea).

[0079] (2) Preparation of modified polyurea

[0080] Take 1.3g of filler and add it to 10mL of dimethylacetamide. Ultrasonic dispersion is performed for 30 minutes to obtain a filler dispersion. Pour the filler dispersion into the pure polyurea solution and stir continuously for more than 3 hours to obtain a modified polyurea solution.

[0081] (3) Pour the modified polyurea solution into a polytetrafluoroethylene mold that has been molded, dry it in a vacuum drying oven at 110°C for 24 hours, and cool it to room temperature to form a coating.

[0082] The modified polyurea comprises polyurea and filler (Ag / TiO2 / calcium alginate), and the mass ratio of polyurea to filler is 30.5g:1.3g, that is, 23.5:1.

[0083] Example 2

[0084] The difference between this embodiment and embodiment 1 is that in the preparation process of the filler, calcium alginate with a calcium ion concentration of 0.4% and an average molecular weight of 60K is used as the raw material.

[0085] Example 3

[0086] The difference between this embodiment and embodiment 1 is that in the preparation process of the filler, calcium alginate with a calcium ion mass concentration of 0.8% and an average molecular weight of 25K is used as the raw material.

[0087] Example 4

[0088] This example differs from Example 1 in that, during the filler preparation process, the mass of the anatase-phase TiO2 nanoparticles in step ① was adjusted to 7.5 g. Thus, the mass ratio of the TiO2 nanoparticles to the Ag nanoparticles in the filler was 95:5, and the average particle size of the Ag / TiO2 nanomaterial was 23 nm.

[0089] Example 5

[0090] This embodiment differs from Example 1 in that, during the filler preparation process, the mass of the anatase-phase TiO2 nanoparticles in step ① was adjusted to 12.5 g. Thus, the mass ratio of the TiO2 nanoparticles to the Ag nanoparticles in the filler was 98:2, and the average particle size of the Ag / TiO2 nanomaterial was 49 nm.

[0091] Example 6

[0092] The difference between this embodiment and embodiment 1 is that in the preparation process of the filler, the amount of calcium alginate in step ② is adjusted to 2g. Thus, the mass ratio of Ag / TiO2 nanomaterial to calcium alginate in the filler is 1.5g:2g, or 0.75:1.

[0093] Example 7

[0094] The difference between this embodiment and embodiment 1 is that in the preparation process of the filler, the amount of calcium alginate in step ② is adjusted to 4g. Thus, the mass ratio of Ag / TiO2 nanomaterial to calcium alginate in the filler is 1.5g:4g, or 0.375:1.

[0095] Example 8

[0096] This embodiment differs from Example 1 in that, during the filler preparation process, the amount of calcium alginate used in step ② was adjusted to 2 g, and the Ag / TiO2 nanomaterial dispersion in step ② was adjusted to contain 3 g of Ag / TiO2 nanomaterial. Thus, the mass ratio of Ag / TiO2 nanomaterial to calcium alginate in the filler was 3 g:2 g, or 1.5:1.

[0097] Example 9

[0098] The difference between this embodiment and embodiment 1 is that during the filler preparation process, the Ag / TiO2 nanomaterial dispersion in step ② was adjusted to contain 3g of Ag / TiO2 nanomaterial. Thus, the mass ratio of Ag / TiO2 nanomaterial to calcium alginate in the filler was 3g:3g, or 1:1.

[0099] Example 10

[0100] The difference between this embodiment and embodiment 1 is that in the preparation process of the modified polyurea, the amount of filler in step (2) is adjusted to 0.8 g. Thus, the mass ratio of polyurea to filler in the modified polyurea is 30.5 g:0.8 g, i.e., 38:1.

[0101] Example 11

[0102] The difference between this embodiment and embodiment 1 is that in the preparation process of the modified polyurea, the amount of filler in step (2) is adjusted to 1.8 g. Thus, the mass ratio of polyurea to filler in the modified polyurea is 30.5 g:1.8 g, i.e., 17:1.

[0103] Example 12

[0104] The difference between this embodiment and embodiment 1 is that the filler is Ag / SiO2 / calcium alginate, and the difference between this embodiment and the filler Ag / TiO2 / calcium alginate of embodiment 1 is that TiO2 is replaced by SiO2.

[0105] Specifically, the filler of this embodiment is prepared by the following method:

[0106] ①Preparation of Ag / SiO2 nanomaterial dispersion

[0107] 1.2 g of ethyl silicate was added to 25 mL of 0.1 mol / L AgNO3 solution to form a composite sol. The composite gel was calcined (450°C, 3.5 h) to obtain Ag / SiO2 nanomaterials.

[0108] The Ag / SiO2 nanomaterial is dispersed in deionized water to obtain an Ag / SiO2 nanomaterial dispersion.

[0109] ② Loading Ag / SiO2 nanomaterials onto calcium alginate

[0110] Take 3g of calcium alginate and put it into a 50mL beaker. Pour the above-mentioned Ag / SiO2 nanomaterial dispersion containing 1.5g of Ag / SiO2 nanomaterial into the beaker. Add 20mL of deionized water, heat in a 60℃ oil bath and stir continuously for 3h. Pour the liquid in the beaker into a clean stainless steel tray and dry it in an 80℃ forced air drying oven for 3h.

[0111] The filler Ag / SiO2 / calcium alginate prepared in this embodiment includes calcium alginate and Ag / SiO2 nanomaterials, and the Ag / SiO2 nanomaterials are loaded on the calcium alginate; the Ag / SiO2 nanomaterials are nanocomposites of SiO2 nanoparticles and Ag nanoparticles, and the Ag nanoparticles are distributed on the surface of the SiO2 nanoparticles.

[0112] The mass ratio of Ag / SiO2 nanomaterial to calcium alginate is 0.5:1; the mass ratio of SiO2 nanoparticles to Ag nanoparticles is 95:5, and the average particle size of the Ag / SiO2 nanomaterial is 75 nm.

[0113] Comparative Example 1

[0114] The difference between this comparative example and Example 1 is that the filler is calcium alginate, and the calcium ion mass concentration and molecular weight of the calcium alginate are the same as those in Example 1.

[0115] Comparative Example 2

[0116] The difference between this comparative example and Example 1 is that the filler is Ag / TiO2 nanomaterial.

[0117] Ag / TiO2 nanomaterials were prepared by the following method:

[0118] According to step ① of Example 1, a Ag / TiO2 nanomaterial dispersion was prepared, and the Ag / TiO2 nanomaterial dispersion was dried at 70°C to obtain an Ag / TiO2 nanomaterial.

[0119] Comparative Example 3

[0120] The difference between this comparative example and Example 1 is that the filler is a physical mixture of calcium alginate and Ag / TiO2 nanomaterials, and the calcium ion mass concentration and molecular weight of the calcium alginate are the same as those in Example 1.

[0121] The preparation method of the filler is:

[0122] Calcium alginate was mixed with Ag / TiO2 nanomaterials. The mass ratio of Ag / TiO2 nanomaterials to calcium alginate was the same as that in Example 1, and the preparation method of the Ag / TiO2 nanomaterials was the same as that in Comparative Example 2.

[0123] Comparative Example 4

[0124] The difference between this comparative example and Example 1 is that the filler is TiO2 / calcium alginate.

[0125] Specifically, the filler includes calcium alginate and TiO2 nanoparticles, wherein the TiO2 nanoparticles are loaded on the calcium alginate, wherein the mass ratio of the TiO2 nanoparticles to the calcium alginate is 98:2, and the average particle size of the TiO2 nanoparticles is 30 nm.

[0126] TiO2 / calcium alginate was prepared by the following method:

[0127] ①Preparation of nano-TiO2 dispersion

[0128] Tetrabutyl titanate was dissolved in anhydrous ethanol (volume ratio of 15 mL:60 mL), nitric acid was added dropwise to adjust to pH = 3, and stirred for 2 h to form a transparent sol. After standing for 24 h, nano-TiO2 gel was obtained after drying at 80 ° C for 24 h. Anatase phase TiO2 nanoparticles were obtained by calcining at 400 ° C for 5 h.

[0129] Anatase phase TiO2 nanoparticles are dispersed in deionized water to obtain a nano-TiO2 dispersion.

[0130] ② Loading TiO2 nanoparticles onto calcium alginate

[0131] Take 3g of calcium alginate and put it into a 50mL beaker. Pour the above-mentioned nano-TiO2 dispersion containing 1.5g of nano-TiO2 into the beaker. Add 20mL of deionized water. Heat in a 60℃ oil bath and stir continuously for 3h. Pour the liquid in the beaker into a clean stainless steel tray and dry it in an 80℃ forced air drying oven for 3h.

[0132] Comparative Example 5

[0133] The difference between this comparative example and Example 1 is that the filler is Ag / TiO2 / chitosan, and the difference between this comparative example and the Ag / TiO2 / calcium alginate of Example 1 is only that the calcium alginate is replaced by chitosan of equal mass.

[0134] Comparative Example 6

[0135] The difference between this comparative example and Example 1 is that the filler is Ag / TiO2 / potassium alginate, and the difference between this comparative example and the Ag / TiO2 / calcium alginate of Example 1 is only that the calcium alginate is replaced by potassium alginate of equal mass.

[0136] Comparative Example 7

[0137] This comparative example differs from Example 1 in that the calcium ion concentration and molecular weight of the calcium alginate were varied during filler preparation. The calcium ion mass concentration of the calcium alginate ranged from 0.6% to 1.4%, and the average molecular weight ranged from 30K to 150K. Details are shown in the table below. For ease of comparison, the table also lists the relevant technical parameters of the calcium alginate from Examples 1 to 3.

[0138] [Table 2]

[0139]

[0140] Blank control group

[0141] Pure polyurea without any filler was used as the blank control group.

[0142] Specifically, a pure polyurea solution was obtained according to step (1) of Example 1; the pure polyurea solution was poured into a pre-molded polytetrafluoroethylene mold, dried at 110° C. in a vacuum drying oven for 24 h, and cooled to room temperature to form a pure polyurea coating.

[0143] The structural characterization and performance testing of pure polyurea and different modified polyureas were carried out, and the results are as follows:

[0144] (1) Surface roughness

[0145] The SEM images of pure polyurea and different modified polyureas are shown in Figure 2. Figure 1As shown in the figure, the surface of the pure polyurea without any filler in the blank control group is relatively rough, while the addition of calcium alginate alone in Comparative Example 1, the addition of Ag / TiO2 nanomaterials alone in Comparative Example 2, and the addition of a physical mixture of calcium alginate and Ag / TiO2 nanomaterials in Comparative Example 3 all show poor compatibility, resulting in an abnormally rough surface of the material, which is not conducive to improving the overall performance. However, after the addition of Ag / TiO2 / calcium alginate in Example 1, the compatibility between Ag / TiO2 / calcium alginate and polyurea is greatly improved, making the coating surface smoother, which is conducive to improving its overall performance.

[0146] (2) Hydrophobicity

[0147] The static contact angle test results of pure polyurea and different modified polyurea (the droplet in the test is water) are as follows: Figure 2 As shown. The surface contact angles of the polyurea materials in the blank control group, comparative example 1, and comparative example 2 were 35°, 57°, and 72°, respectively, while that of Example 1 was 93°. The results show that the pure polyurea in the blank control group without any filler added had poor hydrophobicity, while the addition of calcium alginate alone in comparative example 1 or the addition of Ag / TiO2 nanomaterials alone in comparative example 2 showed poor compatibility, had little effect on improving the static contact angle, and still had the problem of poor hydrophobicity. However, after adding Ag / TiO2 / calcium alginate to Example 1, the static contact angle of the material surface was greatly improved, and the hydrophobicity was greatly improved.

[0148] (3) Insulation properties, mechanical properties, and flame retardant properties

[0149] The insulation performance of pure polyurea and different modified polyureas was tested with reference to GB1408.1-2016, and the tensile strength of pure polyurea and different modified polyureas was tested with reference to GB / T1040.1-2018.

[0150] Pure polyurea and various modified polyureas were also tested for flame retardancy. Burning duration, defined as the time from ignition to self-extinguishing, was measured using the Limiting Oxygen Index (LOI) standard of ISO 4589-2:2006, while flame retardancy ratings were measured using the ANSI / UL94-2013 standard. Shorter burning durations and higher LIO values ​​indicate better flame retardancy, while lower flame retardancy ratings indicate better performance. The results are shown in the table below.

[0151] [Table 3]

[0152]

[0153]

[0154]

[0155] The results show that the fillers formed by adding Ag / TiO2 nanomaterials or Ag / SiO2 nanomaterials loaded on calcium alginate with a suitable molecular weight and calcium ion mass concentration in Examples 1 to 12 make the modified polyurea have high breakdown strength and high tensile strength, short burning duration, high limiting oxygen index, and high flame retardant grade.

[0156] In contrast, the pure polyurea in the blank control group without any filler had lower breakdown strength and tensile strength and was flammable.

[0157] Comparative Example 1, however, uses calcium alginate alone as a filler, which has limited effect on improving the flame retardancy, insulation, and mechanical properties of the modified polyurea. Comparative Example 2 uses Ag / TiO2 nanomaterials alone as a filler, Comparative Example 3 uses a physical mixture of calcium alginate and Ag / TiO2 nanomaterials as a filler, Comparative Example 4 uses Ag-free TiO2 / calcium alginate as a filler, Comparative Examples 5 and 6 use chitosan or potassium alginate as a support material for the Ag / TiO2 nanomaterial, and Comparative Examples 7-1 and 7-8 use calcium alginate with inappropriate calcium ion mass concentration and molecular weight as a support material for the Ag / TiO2 nanomaterial, resulting in material incompatibility issues, all of which lead to reduced insulation, mechanical, and flame retardancy of the modified polyurea.

[0158] Example 13

[0159] This embodiment provides a flame-retardant insulating material, which is a modified epoxy resin, including epoxy resin and the filler, curing agent and accelerator of Example 1.

[0160] The preparation method of modified epoxy resin is:

[0161] Apply the release agent evenly to the surface of the steel mold, then preheat the mold in a 130°C oven for 2 hours. Weigh E51 epoxy resin into a three-necked flask and heat to 50°C. Add the filler from Example 1 to 30g of E51 epoxy resin. Then, weigh 80g of the curing agent, methyltetrahydrophthalic anhydride, and 1g of the accelerator, 2,4,6-tris(dimethylaminomethyl)phenol, and add them to the flask. Stir and degas at 50°C and a vacuum of >0.08MPa for 30 minutes. Pour the mixture in the flask into the preheated mold and heat-cure (100°C, 2.5 hours). Remove after molding.

[0162] The quality of the filler is as follows:

[0163] Example 13-1: 0.8g; Example 13-2: 1.3g; Example 13-3: 1.8g; Example 13-4: 2.3g.

[0164] Comparative Example 8

[0165] This comparative example provides a pure epoxy resin, which differs from Example 13 in that no filler is added.

[0166] Comparative Example 9

[0167] The difference between this comparative example and Example 13 is that the filler is replaced by the Ag / TiO2 nanomaterial of comparative example 2, and the amount of filler used is 1.3 g.

[0168] Referring to the aforementioned test method for modified polyurea, the insulation properties, mechanical properties, and flame retardancy tests were performed on the modified epoxy resins of Example 13 and Comparative Example 8. The results are shown in the following table.

[0169] [Table 4]

[0170]

[0171] The results show that the epoxy resin modified by the Ag / TiO2 / calcium alginate of the present invention has better insulation properties, mechanical properties and flame retardant properties than the unmodified pure epoxy resin and the epoxy resin modified by Ag / TiO2 nanomaterials.

[0172] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A method for preparing a filler, characterized in that: include: Calcium alginate is mixed with a dispersion containing Ag / oxide nanomaterials, and then heated and dried; The Ag / oxide nanomaterial is a nanocomposite of oxide and Ag; the oxide includes at least one of TiO2 and SiO2; The calcium ion mass concentration of the calcium alginate is 0.4% to 0.8%, and the average molecular weight is 25K to 60K.

2. The method for preparing the filler according to claim 1, wherein: The mass ratio of the Ag / oxide nanomaterial to the calcium alginate is (0.3-1.5):

1.

3. The method for preparing the filler according to claim 1, wherein: In the Ag / oxide nanomaterial, the mass ratio of the oxide to the Ag is (19-49):

1.

4. The method for preparing the filler according to any one of claims 1 to 3, characterized in that: The average particle size of the Ag / oxide nanomaterial is 20nm to 75nm.

5. The method for preparing the filler according to claim 1, characterized in that: The heating temperature is 40 to 80° C. And / or, the heating time is 1 hour to 5 hours.

6. A filler, characterized in that The method is obtained by any one of claims 1 to 5.

7. A flame retardant insulating material, characterized in that: The invention comprises a polymer and the filler according to claim 6, wherein the polymer comprises at least one of polyurea and epoxy resin.

8. The flame-retardant insulating material according to claim 7, characterized in that: The mass ratio of the polymer to the filler is (13-38):

1.

9. A method for preparing the flame-retardant insulating material according to claim 7 or 8, characterized in that: include: The filler is mixed with the polymer.

10. Use of the flame-retardant insulating material according to claim 7 or 8 in transmission towers, chemical plant storage tanks, chemical plant pipelines, truck cargo boxes or ship decks.

Images