A solid phase preparation method and application of nanoscale zinc molybdate

Abstract

The application discloses a kind of nanometer zinc molybdate solid-phase preparation method and application, with nanometer molybdenum trioxide and zinc acetate as reaction raw materials, under the condition of full solid phase, by subsection temperature control calcination complete solid-phase reaction, directly prepared nanometer zinc molybdate powder;The molar ratio of nanometer molybdenum trioxide and zinc acetate is Zn:Mo=1.00~1.05:1;The subsection temperature control calcination process is divided into two temperature rising procedures: the first section is low-temperature pre-decomposition section, and active zinc oxide is generated by in-situ thermal decomposition of zinc acetate;Second section is high-temperature crystallization section, realizes the solid-phase interface reaction of active zinc oxide and nanometer molybdenum trioxide and crystal phase formation;The method of the application is simple, environmental protection and pollution-free: using solid-phase dry method mixing, direct calcination process, without adding water or organic solvent, without wet ball milling and drying step, without industrial wastewater generation, simplify the technological process, reduce environmental protection treatment cost and energy consumption, comply with the development trend of green chemical industry.

Description

Technical Field

[0001] This invention belongs to the technical field of inorganic flame retardants and molybdate materials, specifically relating to a solid-phase preparation method and application of nano-sized zinc molybdate. Background Technology

[0002] Zinc molybdate (ZnMoO4) is a highly efficient, halogen-free, and low-toxicity flame retardant and smoke suppressant. It has multiple functions such as flame retardancy, smoke suppression, and smoke elimination. It is widely used in the fields of polyvinyl chloride (PVC), cables, epoxy resins, rubber and other polymer materials. It can effectively reduce the smoke density and toxic gas release during the combustion of materials, improve the flame retardant performance of materials, and conform to the current development trend of environmentally friendly flame retardancy.

[0003] Currently, the traditional method for preparing zinc molybdate mainly uses ordinary molybdenum trioxide (MoO3) as the molybdenum source, mixes it with zinc oxide (ZnO) in a certain proportion, and then performs wet ball milling, drying and dehydration, followed by long-term calcination at a high temperature of 550-650℃ to finally obtain the zinc molybdate product. However, this traditional method has many shortcomings: First, ordinary MoO3 has low reactivity, requiring high calcination temperature and long reaction time to ensure complete reaction, resulting in a significant increase in energy consumption, which does not meet the industrial demand for energy conservation and emission reduction; Second, the wet ball milling process requires the addition of a large amount of water or organic solvents, and the subsequent drying process not only consumes energy but also generates industrial wastewater, causing environmental pollution and increasing environmental treatment costs; Third, high-temperature and long-term calcination easily leads to sintering and agglomeration of product particles, resulting in poor dispersibility, which in turn affects its dispersion effect in polymer materials and reduces flame retardant and smoke suppression performance; Fourth, the zinc molybdate prepared by the traditional process has low purity and often retains unreacted MoO3, MoO2 and other impurity phases, further affecting product quality and application effect.

[0004] In existing technologies, some studies have attempted to use MoO3 hydrates to replace ordinary MoO3 as a molybdenum source. However, such hydrates are only simple hydrated forms of MoO3, without changing its core structure. The reactivity has not been significantly improved, and higher calcination temperatures and longer reaction times are still required, which cannot fundamentally solve the defects of traditional processes.

[0005] Therefore, developing a simple, energy-efficient, pollution-free, high-quality, and innovative method for preparing zinc molybdate has become an urgent technical problem to be solved in this field. Summary of the Invention

[0006] This invention addresses the shortcomings of existing technologies by providing a solid-phase preparation method and application of nano-sized zinc molybdate. The method involves mixing nano-molybdenum trioxide with zinc acetate, and the calcination process is divided into two heating stages: the first stage is a low-temperature pre-decomposition stage, which completes the in-situ thermal decomposition of zinc acetate to generate active zinc oxide; the second stage is a high-temperature crystallization stage, which realizes the solid-phase interface reaction and crystal formation of active zinc oxide and nano-molybdenum trioxide.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] A solid-phase preparation method for nano-sized zinc molybdate is disclosed, which uses nano-molybdenum trioxide and zinc acetate as reactants, and completes the solid-phase reaction by segmented temperature-controlled calcination under all-solid-phase conditions to directly prepare nano-sized zinc molybdate powder. The molar ratio of the nano-molybdenum trioxide to zinc acetate is Zn:Mo = 1.00 to 1.05:1; The segmented temperature-controlled calcination process consists of two heating stages: the first stage is a low-temperature pre-decomposition stage, where the calcination temperature is controlled at 250–300℃ and the holding time is 1.5–2.5 h, to complete the in-situ thermal decomposition of zinc acetate to generate active zinc oxide; the second stage is a high-temperature crystallization stage, where the calcination temperature is controlled at 480–500℃ and the holding time is 2–4 h, to achieve the solid-phase interface reaction and crystal formation of active zinc oxide and nano molybdenum trioxide, with a heating rate of 3–5℃ / min.

[0009] Optionally, the molar ratio of the nano-molybdenum trioxide to zinc acetate is Zn:Mo = 1.02:1.

[0010] Optionally, the holding time for the first stage of low-temperature pre-decomposition is 2 hours, the holding time for the second stage of high-temperature crystallization is 3 hours, and the heating rate is 4℃ / min.

[0011] Optionally, the particle size range of the nano molybdenum trioxide and zinc acetate raw materials is 20-100 nm, the specific surface area is ≥25 m² / g, the purity of the raw materials is ≥99.9%, and there is no agglomeration or clumping.

[0012] Optionally, the prepared nanoscale zinc molybdate powder has a monoclinic crystal structure, a uniform particle size distribution of 20–100 nm, no obvious particle agglomeration, whiteness ≥85%, purity ≥99.5%, and no residual "small black spot" impurities.

[0013] Optionally, the solid-phase reaction is carried out entirely in an atmospheric pressure air atmosphere. After the reaction is completed, the mixture is naturally cooled to room temperature and then pulverized and sieved by airflow to obtain the finished nano zinc molybdate powder.

[0014] The nano-zinc molybdate powder prepared by any of the methods described in this invention can be used to prepare environmentally friendly flame retardant and smoke suppressant for ultra-high voltage cables.

[0015] Compared with the prior art, the present invention has the following advantages: 1. Creative selection of raw materials: This invention uses nano molybdenum oxide and zinc acetate, which can significantly reduce the calcination temperature and reaction time, solving the problem of high energy consumption in traditional processes; 2. Simple process, environmentally friendly and pollution-free: The solid-phase dry mixing and direct calcination process does not require the addition of water or organic solvents, wet ball milling and drying steps, and no industrial wastewater is generated. This simplifies the process flow, reduces environmental treatment costs and energy consumption, and is in line with the development trend of green chemical industry. 3. Excellent product quality: The prepared zinc molybdate is pure phase ZnMoO4, with no obvious MoO3 or MoO2 impurity peaks in the XRD pattern, and a purity of ≥99.5%; the product particles have good dispersibility, uniform particle size, and no obvious agglomeration, which facilitates subsequent dispersion in polymer materials and improves application effect; 4. High application value: The zinc molybdate prepared by this invention, as a halogen-free flame retardant and smoke suppressant, exhibits good dispersibility and high flame retardant and smoke suppressant efficiency when added to materials such as plastics, rubber, and coatings. Compared with traditional zinc molybdate, it can reduce the amount added and has broad industrial application prospects. Attached Figure Description

[0016] The accompanying drawings are provided to further illustrate the present disclosure and form part of the specification. They are used together with the following detailed description to explain the present disclosure, but do not constitute a limitation thereof. In the drawings: Figure 1 The image shown is the XRD pattern of zinc molybdate obtained in Example 1 of this invention. Figure 2 This is a transmission electron microscope (TEM) image of zinc molybdate obtained in Example 1 of the present invention; Figure 3 This is an electron micrograph of zinc molybdate prepared in control group 1 in Example 2 of the present invention. The zinc molybdate particle size is 1.5-3 μm. Figure 4 This is an electron micrograph of zinc molybdate prepared in control group 2 in Example 2 of the present invention; Figure 5 In Example 2 of this invention, an electron micrograph of zinc molybdate prepared from control group 3. Detailed Implementation

[0017] The present invention will be further described in detail below with reference to specific embodiments and comparative examples. These embodiments are only used to explain the present invention and do not constitute a limitation on the scope of protection of the present invention.

[0018] This invention relates to a solid-phase preparation method and application of nano-sized zinc molybdate. The method involves mixing nano-molybdenum trioxide with zinc acetate at a precise molar ratio of Zn:Mo = 1.00–1.05:1, mixing thoroughly to obtain a mixed precursor powder, placing it in a ceramic boat, and then calcining it in a muffle furnace. The calcination process consists of two heating stages: the first stage is a low-temperature pre-decomposition stage, where the calcination temperature is controlled at 260–300℃ and the holding time is 1.5–2.5 h, completing the in-situ thermal decomposition of zinc acetate to generate active zinc oxide; the second stage is a high-temperature crystallization stage, where the calcination temperature is controlled at 480–500℃ and the holding time is 2–4 h, achieving the solid-phase interfacial reaction and crystal formation between active zinc oxide and nano-molybdenum trioxide, with a heating rate of 3–5℃ / min.

[0019] (1) Weigh out MoO3 and Zn(CH3COO)2·2H2O according to the following reaction formula; MoO3+Zn(CH3COO)2·2H2O=ZnMoO4+2CH3COOH↑+2H2O↑; (2) Mix MoO3 and Zn(CH3COO)2·2H2O evenly and put them into a porcelain boat; (4) The porcelain boat is placed in a muffle furnace for firing. The firing process is divided into two heating stages: the first stage is a low-temperature pre-decomposition stage, which completes the in-situ thermal decomposition of zinc acetate to generate active zinc oxide; the second stage is a high-temperature crystallization stage, which realizes the solid-phase interface reaction and crystal formation of active zinc oxide and nano molybdenum trioxide. (5) After naturally cooling to room temperature, the finished nano zinc molybdate powder can be obtained by air jet pulverization and sieving.

[0020] Specifically: Nanoscale zinc molybdate powder was directly prepared by using nano-molybdenum trioxide and zinc acetate as reaction raw materials under all-solid-phase conditions without solvents, liquid media, structure directing agents, or surfactants, through segmented temperature-controlled calcination.

[0021] In this invention, the particle size range of the nano molybdenum trioxide and zinc acetate Zn(CH3COO)2·2H2O (dihydrate) raw materials is 20-100nm, the specific surface area is ≥25m² / g, the purity of the raw materials is ≥99.9%, and there is no agglomeration or clumping.

[0022] In this invention, the molar ratio of nano-molybdenum trioxide to zinc acetate is accurately weighed according to Zn:Mo = 1.00 to 1.05:1, and mixed evenly to obtain a mixed precursor powder.

[0023] In this invention, the segmented temperature-controlled calcination process is divided into two heating stages: the first stage is a low-temperature pre-decomposition stage, where the calcination temperature is controlled at 260–300°C and the holding time is 1.5–2.5 h, to complete the in-situ thermal decomposition of zinc acetate to generate active zinc oxide; the second stage is a high-temperature crystallization stage, where the calcination temperature is controlled at 480–500°C and the holding time is 2–4 h, to realize the solid-phase interface reaction and crystal formation of active zinc oxide and nano molybdenum trioxide, with a heating rate of 3–5°C / min.

[0024] In this invention, the prepared nanoscale zinc molybdate powder has a monoclinic crystal structure, a uniform particle size distribution of 20-100 nm, no obvious particle agglomeration, whiteness ≥85%, purity ≥99.5%, and no residual "small black spot" impurities.

[0025] In this invention, the solid-phase reaction is carried out in an atmospheric pressure air atmosphere without the need for inert gas protection and without the discharge of waste gas or waste liquid. After the reaction is completed, the product nano zinc molybdate powder is obtained by natural cooling to room temperature and then pulverizing and sieving by airflow.

[0026] The application of the nano-sized zinc molybdate powder prepared by this invention is to use the prepared nano-zinc molybdate powder as an environmentally friendly flame retardant and smoke suppressant for ultra-high voltage cables. It is added to polyolefin and epoxy resin cable substrates to synergistically improve the flame retardant rating and smoke suppression performance of the cable, while ensuring that the cable's elasticity, elongation and other mechanical properties meet the standards.

[0027] Example 1: Solid-phase preparation of nano-sized zinc molybdate 1. Raw material preparation: Select nano molybdenum trioxide (MoO3) with a particle size of 20-100nm, a specific surface area of ​​28m² / g, and a purity of 99.92%, and zinc acetate (Zn(CH3COO)2·2H2O) to ensure that the two raw materials are free of impurities and agglomeration.

[0028] 2. Raw material mixing and grinding: According to the molar ratio of Zn:Mo=1.02:1, accurately weigh 14.4g of nano molybdenum trioxide and 22-22.4g of zinc acetate, mix them evenly, and obtain a white precursor powder without obvious particle agglomeration.

[0029] 3. Segmented temperature-controlled calcination: The above-mentioned precursor powder is placed in a muffle furnace and calcined in a segmented temperature-controlled manner under normal pressure air atmosphere, with the heating rate controlled at 4℃ / min; the first stage is low-temperature pre-decomposition, where the temperature is raised to 250-300℃ and held for 2 hours to complete the in-situ thermal decomposition of zinc acetate to generate active zinc oxide; the second stage is high-temperature crystallization, where the temperature is raised to 480-500℃ and held for 3 hours to allow the active zinc oxide and nano molybdenum trioxide to fully undergo solid-phase interface reaction to form zinc molybdate crystalline phase.

[0030] 4. Preparation of finished product: After calcination, the product is naturally cooled to room temperature and then pulverized in an air jet mill to obtain white nano-sized zinc molybdate powder.

[0031] Performance testing: Combination Figure 1 and 2 The prepared nano-zinc molybdate powder was subjected to performance tests, and the results are as follows: XRD detection confirmed that the crystal phase is monoclinic (Jade PDF No. 35-0765), the particle size distribution is 20-100 nm (TEM detection), the whiteness is 86%, the purity is 99.7%, there is no "small black spot" impurity residue, the specific surface area is 32 m² / g, and there is no obvious particle agglomeration. All indicators meet the requirements of the claims.

[0032] Example 2: Comparison of preparation under different process parameters To verify the superiority of the technical solution of this invention, a control experiment was set up, as follows: Combination Figure 3 Control group 1: Zinc molybdate was prepared using micron-sized MoO3 (particle size 1-5 μm) and zinc acetate according to the process parameters of Example 1. The product had a particle size of 1.5-3 μm, obvious "small black spots" phenomenon, whiteness of 78%, and purity of 98.2%, which did not meet the requirements of high-end applications.

[0033] Combination Figure 4 Control group 2: Nano MoO3 and zinc acetate were used, and the product was directly calcined at 480℃ for 5 hours without segmented calcination. The product contained undecomposed zinc acetate impurities, obvious agglomeration, purity of 97.5%, and uneven crystal phase.

[0034] Combination Figure 5 Control group 3: Zinc molybdate was prepared by hydrothermal method (160℃, 4h) using zinc acetate and ammonium molybdate as raw materials. The product had a particle size of 60-120nm, exhibited agglomeration and poor dispersibility, and the process involved liquid phase, which is fundamentally different from the all-solid phase process of this invention.

[0035] Experimental results show that the nano zinc molybdate prepared by the preparation method of the present invention (Example 1) is superior to the control group in terms of particle size, purity, whiteness and dispersibility, and the process is all solid phase and without additives.

[0036] Example 3: Application of nano-zinc molybdate in ultra-high voltage cables Table 1 Smoke Density Test Grades

[0037] Based on the data in Table 1, the nano-zinc molybdate powder prepared in Example 1 was added to the polyolefin cable substrate as a flame retardant and smoke suppressant at a dosage of 9–11 wt%. After thorough mixing, cable samples were prepared and their performance was tested. Except for the test duration, all other test conditions were consistent. The SDR (smoke density rating) < 50 and MSD (maximum instantaneous smoke density) both met the GB / T8627-2007 smoke density standard. The elongation remained above 280% (280%–298%), and the elasticity met the requirements, satisfying the usage requirements for flame retardants and smoke suppressants for ultra-high voltage cables. It has successfully passed the US UL system certification.

[0038] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A solid-phase preparation method for nano-sized zinc molybdate, characterized in that, Nanoscale zinc molybdate powder was directly prepared by using nano-molybdenum trioxide and zinc acetate as reactants and completing the solid-phase reaction through segmented temperature-controlled calcination under all-solid-phase conditions. The molar ratio of the nano-molybdenum trioxide to zinc acetate is Zn:Mo = 1.00 to 1.05:1; The segmented temperature-controlled calcination process consists of two heating stages: the first stage is a low-temperature pre-decomposition stage, where the calcination temperature is controlled at 250–300℃ and the holding time is 1.5–2.5 h, to complete the in-situ thermal decomposition of zinc acetate to generate active zinc oxide; the second stage is a high-temperature crystallization stage, where the calcination temperature is controlled at 480–500℃ and the holding time is 2–4 h, to achieve the solid-phase interface reaction and crystal formation of active zinc oxide and nano molybdenum trioxide, with a heating rate of 3–5℃ / min.

2. The solid-phase preparation method of nano-sized zinc molybdate according to claim 1, characterized in that, The molar ratio of the nano-molybdenum trioxide to zinc acetate is Zn:Mo = 1.02:

1.

3. The solid-phase preparation method of nano-sized zinc molybdate according to claim 1, characterized in that, The first stage of low-temperature pre-decomposition has a holding time of 2 hours, the second stage of high-temperature crystallization has a holding time of 3 hours, and the heating rate is 4℃ / min.

4. The solid-phase preparation method of nano-sized zinc molybdate according to any one of claims 1-3, characterized in that, The nano-molybdenum trioxide and zinc acetate raw materials have a particle size range of 20-100 nm, a specific surface area ≥25 m² / g, a raw material purity ≥99.9%, and are free from agglomeration and clumping.

5. The solid-phase preparation method of nano-sized zinc molybdate according to any one of claims 1-3, characterized in that, The prepared nanoscale zinc molybdate powder has a monoclinic crystal structure, with a uniform particle size distribution of 20-100 nm, no obvious particle agglomeration, whiteness ≥85%, purity ≥99.5%, and no residual "small black spot" impurities.

6. The solid-phase preparation method of nano-sized zinc molybdate according to any one of claims 1-3, characterized in that, The solid-phase reaction is carried out entirely under normal pressure air atmosphere. After the reaction is completed, it is naturally cooled to room temperature, and the finished nano zinc molybdate powder can be obtained by air jet pulverization and sieving.

7. The application of the nano zinc molybdate powder prepared by any one of claims 1-6 in the preparation of an environmentally friendly flame retardant and smoke suppressant for ultra-high voltage cables.

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