Preparation method of flame retardant coated with antimonate

Abstract

The invention relates to a preparation method of a coated antimonate flame retardant. The preparation method comprises the following steps: (1) reacting antimonate with saturated sodium metaaluminate to obtain aluminum hydroxide coated antimonate; and (2) coating antimonate with zinc oxide and aluminum hydroxide, and reacting to obtain the zinc oxide-aluminum hydroxide coated antimonate flame retardant. The aluminum hydroxide and the zinc oxide are used for carrying out double-layer coating on the prepared antimonate to obtain the coated antimonate flame retardant, and the coated antimonate can equivalently replace antimony trioxide to be applied to flame retardance.

Description

Technical Field

[0001] The present invention relates to the technical field of flame retardants, and particularly relates to a preparation method of a coated antimonate flame retardant. Background Art

[0002] A flame retardant is an auxiliary agent that can effectively prevent materials from burning. According to the existing classification of flame retardants, it can be divided into additive type and reactive type. The additive type flame retardant is the most important one because it can be directly mixed with materials and has simple processing. Among them, antimony trioxide is an important additive type flame retardant, which is widely used in polymer materials. However, when used alone, its flame retardant effect is not good, and its content and particle size will affect the flame retardant effect. Usually, it needs to be used in combination with halogen. With the decline of antimony reserves and the restrictions on antimony mining by the state, the price of antimony is getting higher and higher. There is an urgent need for a flame retardant that can replace antimony trioxide. As a derivative of antimony trioxide, antimonate has the same flame retardant effect, but the disadvantage of the decrease in oxygen index of antimonate in flame retardant applications has not been taken seriously. Summary of the Invention

[0003] To solve the above problems, the first object of the present invention is to provide a preparation method of a coated antimonate flame retardant to solve the problems raised in the above background art.

[0004] The second object of the present invention is to provide a coated antimonate flame retardant synthesized by the above method.

[0005] The third object of the present invention is to provide the application of the coated antimonate flame retardant synthesized by the above method in flame retardant PVC.

[0006] To achieve the first object of the present invention, the present invention provides the following technical solutions:

[0007] A preparation method of a coated antimonate flame retardant, comprising the following steps:

[0008] (1) Preparation of aluminum hydroxide-coated antimonate: Add antimonate to a saturated sodium metaaluminate solution, and react to obtain aluminum hydroxide-coated antimonate;

[0009] (2) Preparation of zinc oxide secondary-coated antimonate: Add zinc oxide to water, and then add the aluminum hydroxide-coated antimonate, and react to obtain a zinc oxide-aluminum hydroxide-coated antimonate flame retardant.

[0010] Preferably, in the step (1), add antimonate to a saturated sodium metaaluminate solution, ultrasonically disperse for 10 min - 60 min, adjust the reaction temperature to 50°C - 70°C, dropwise add an acidic solution to adjust the pH to 6 - 7, react for 1 - 2 hours, and after the reaction, filter, wash with water, and dry to obtain aluminum hydroxide-coated antimonate.

[0011] Preferably, in the step (1), the mass ratio of sodium aluminate to antimonate is 0.02 - 0.05:1.

[0013] Preferably, in the step (2), zinc oxide is added to water, and then the antimonate coated with aluminum hydroxide is added, and the reaction is carried out for 1 - 2 hours. After the reaction is completed, it is filtered, washed with water, and dried to obtain the zinc oxide - aluminum hydroxide coated antimonate flame retardant.

[0014] Preferably, in the step (2), the mass ratio of zinc oxide to the antimonate coated with aluminum hydroxide is 0.05 - 0.1:1.

[0015] Preferably, in the step (1), the preparation method of the antimonate includes the following steps:

[0016] 1) Add antimony trioxide, potassium hydroxide, and water into a reaction vessel and stir, then add 30% hydrogen peroxide to react to obtain potassium antimonate;

[0017] 2) Dissolve the metal salt in water, and drop it into the potassium antimonate solution. After the dropping is completed, react at a temperature of 20°C - 90°C for 2 - 3 hours. After the reaction is completed, filter and wash with water to obtain the antimonate.

[0018] Preferably, the molar ratio of antimony trioxide to potassium hydroxide is 1:2 - 2.6, the solid - liquid ratio is 1:1.7 - 2.7, the molar ratio of antimony trioxide to 30% hydrogen peroxide is 1:7.8, and the molar ratio of potassium antimonate to the metal salt is 2:1.

[0019] Preferably, the metal salt is one or more of soluble zinc salt, soluble magnesium salt, soluble calcium salt, and soluble tin salt.

[0020] To achieve the second object of the present invention, the technical solution provided by the present invention is: the coated antimonate flame retardant synthesized by the method described in any one of the above.

[0021] To achieve the third object of the present invention, the technical solution provided by the present invention is: the coated antimonate flame retardant synthesized by the method described in any one of the above is applied to flame - retardant PVC.

[0022] Compared with the prior art, the beneficial effects of the present invention are:

[0023] (1) The zinc oxide - aluminum hydroxide coated antimonate flame retardant prepared by the present invention can replace the use of antimony trioxide in flame retardancy, and the antimony content of the coated antimonate flame retardant is lower than that of antimony trioxide. Under the condition of adding the same number of parts, the same flame - retardant grade and oxygen index can be maintained, and actually less antimony content is consumed, reducing the cost.

[0024] (2) The zinc oxide-aluminum hydroxide coated antimonate flame retardant prepared by the present invention has a stable and dense coating layer, wherein the outermost coating is zinc oxide, which can play a role in blocking heat transfer, and the first coating is aluminum hydroxide. After absorbing heat and decomposing, aluminum hydroxide generates water and a dense aluminum oxide layer. The volatilization of water will continue to absorb heat and play a cooling role. The dense aluminum oxide layer can also play a role in blocking heat transfer. Zinc oxide and aluminum hydroxide jointly protect antimonate, delay the decomposition of antimonate, and improve the oxygen index of antimonate.

[0025] (3) The present invention uses antimony trioxide, potassium hydroxide, zinc salt, magnesium salt, calcium salt, tin salt and other metal salts as main raw materials, and prepares antimonate by combining a single salt or a plurality of salts in a ratio, and then double-coats the prepared antimonate with aluminum hydroxide and zinc oxide to obtain a coated antimonate flame retardant. When an equal amount of antimony trioxide is replaced in the flame retardant application, the same flame retardant grade and oxygen index can be maintained, thereby reducing the use of antimony in disguise and reducing costs.

[0026] (4) The coated antimonate prepared by the present invention has simple process, short reaction time, high yield and is environmentally friendly and pollution-free. DETAILED DESCRIPTION

[0027] The following describes the embodiments of the present invention through specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention.

[0028] Before further describing the specific embodiments of the present invention, it should be understood that the scope of protection of the present invention is not limited to the specific embodiments described below; it should also be understood that the terms used in the examples of the present invention are for describing specific embodiments rather than for limiting the scope of protection of the present invention.

[0029] When the embodiment gives a numerical range, it should be understood that, unless otherwise specified in the present invention, the two endpoints of each numerical range and any numerical value between the two endpoints can be selected. Unless otherwise defined, all technical and scientific terms used herein have the same meanings as those of ordinary skill in the art to which the present invention belongs.

[0030] The present invention does not limit the source of raw materials. Unless otherwise specified, the raw materials used are common commercial products.

[0031] Embodiment 1:

[0032] (1) Add 150 g of antimony trioxide, 75 g of potassium hydroxide and 600 g of water to a reaction flask. After stirring for 30 minutes, add 120 mL of 30% hydrogen peroxide dropwise, with the internal temperature controlled within 80 °C, and react to obtain a potassium antimonate solution.

[0033] (2) Weigh 147.9 g of zinc sulfate heptahydrate, dissolve it in 150 g of water, and slowly add it dropwise to the potassium antimonate solution at room temperature. It takes about 1 h to add it completely, then stir and react for 2 h, filter, wash with distilled water three times, and dry at 120 °C to obtain zinc antimonate.

[0034] (3) Add the obtained zinc antimonate to a saturated sodium metaaluminate solution, where the sodium metaaluminate is 5 g and the zinc antimonate is 250 g. Disperse it ultrasonically for 10 min, adjust the reaction temperature to 50 °C, add acetic acid solution to adjust the pH to 6, react for 1 h, filter, wash, and dry after the reaction to obtain zinc antimonate coated with aluminum hydroxide;

[0035] (4) Take zinc oxide and add it to water, then add zinc antimonate coated with aluminum hydroxide, where the zinc oxide is 12.5 g and the zinc antimonate coated with aluminum hydroxide is 255 g. The reaction temperature is 60 °C, react for 1 h, filter, wash, and dry after the reaction to obtain a zinc oxide - aluminum hydroxide coated zinc antimonate flame retardant.

[0036] Example 2:

[0037] (1) Add 150 g of antimony trioxide, 70 g of potassium hydroxide and 500 g of water to a reaction flask. After stirring for 30 minutes, add 120 mL of 30% hydrogen peroxide dropwise, with the internal temperature controlled within 80 °C, to obtain a potassium antimonate solution.

[0038] (2) Weigh 121.5 g of calcium nitrate tetrahydrate, dissolve it in 150 g of water, and slowly add it dropwise to the potassium antimonate solution at 40 °C. It takes about 1 h to add it completely, then stir and react for 2 h, filter, wash with distilled water three times, and dry at 120 °C to obtain calcium antimonate.

[0039] (3) Add the obtained calcium antimonate to a saturated sodium metaaluminate solution, where the sodium metaaluminate is 7.5 g and the calcium antimonate is 248 g. Disperse it ultrasonically for 20 min, adjust the reaction temperature to 55 °C, add sulfuric acid solution to adjust the pH to 7, react for 1 h, filter, wash, and dry after the reaction to obtain calcium antimonate coated with aluminum hydroxide.

[0040] (4) Take zinc oxide and add it to water, then add calcium antimonate coated with aluminum hydroxide, where the zinc oxide is 15 g and the calcium antimonate coated with aluminum hydroxide is 255 g. The reaction temperature is 65 °C, react for 2 h, filter, wash, and dry after the reaction to obtain a zinc oxide - aluminum hydroxide coated calcium antimonate flame retardant.

[0041] Example 3:

[0042] (1) Add 150 g of antimony trioxide, 75 g of potassium hydroxide, and 400 g of water to a reaction flask. After stirring for 30 minutes, add 120 mL of 30% hydrogen peroxide dropwise, and control the internal temperature within 80 °C to obtain a potassium antimonate solution.

[0043] (2) Weigh 104.6 g of magnesium chloride hexahydrate, dissolve it in 150 g of water, and slowly add it dropwise to the potassium antimonate solution at 60 °C. The addition is completed in about 1 h. After stirring and reacting for 2 h, filter, wash three times with distilled water, and dry at 120 °C to obtain magnesium antimonate.

[0044] (3) Add the obtained magnesium antimonate to a saturated sodium metaaluminate solution, where the sodium metaaluminate is 10 g and the magnesium antimonate is 245 g. Disperse ultrasonically for 40 min, adjust the reaction temperature to 60 °C, add acetic acid solution to adjust the pH to 7, react for 2 h, and after the reaction, filter, wash, and dry to obtain magnesium antimonate coated with aluminum hydroxide.

[0045] (4) Take zinc oxide and add it to water, and then add magnesium antimonate coated with aluminum hydroxide, where the zinc oxide is 18 g and the magnesium antimonate coated with aluminum hydroxide is 255 g. The reaction temperature is 70 °C, and the reaction is carried out for 1 h. After the reaction, filter, wash, and dry to obtain a zinc oxide - magnesium antimonate coated with aluminum hydroxide flame retardant.

[0046] Example 4:

[0047] (1) Add 150 g of antimony trioxide, 72 g of potassium hydroxide, and 500 g of water to a reaction flask. After stirring for 30 minutes, add 120 mL of 30% hydrogen peroxide dropwise, and control the internal temperature within 80 °C to obtain a potassium antimonate solution.

[0048] (2) Weigh 118.35 g of zinc sulfate heptahydrate and 21 g of magnesium chloride hexahydrate, dissolve them in 150 g of water, and slowly add them dropwise to the potassium antimonate solution at 80 °C. The addition is completed in about 1 h. After stirring and reacting for 2 h, filter, wash three times with distilled water, and dry at 120 °C to obtain zinc - magnesium antimonate.

[0049] (3) Add the obtained zinc - magnesium antimonate to a saturated sodium metaaluminate solution, where the sodium metaaluminate is 13 g and the zinc - magnesium antimonate is 252 g. Disperse ultrasonically for 50 min, adjust the reaction temperature to 65 °C, add acetic acid solution to adjust the pH to 6, react for 2 h, and after the reaction, filter, wash, and dry to obtain zinc - magnesium antimonate coated with aluminum hydroxide.

[0050] (4) Take zinc oxide and add it to water, and then add zinc - magnesium antimonate coated with aluminum hydroxide, where the zinc oxide is 21 g and the zinc - magnesium antimonate coated with aluminum hydroxide is 265 g. The reaction temperature is 80 °C, and the reaction is carried out for 2 h. After the reaction, filter, wash, and dry to obtain a zinc oxide - zinc - magnesium antimonate coated with aluminum hydroxide flame retardant.

[0051] Example 5:

[0052] (1) Add 150 g of antimony trioxide, 75 g of potassium hydroxide, and 550 g of water to a reaction flask. After stirring for 30 minutes, add 120 mL of 30% hydrogen peroxide dropwise while controlling the internal temperature within 80 °C to obtain a potassium antimonate solution.

[0053] (2) Weigh 111 g of zinc sulfate heptahydrate, 21 g of magnesium chloride hexahydrate, and 6 g of stannous chloride dihydrate. After dissolving in 150 g of water, slowly add the solution dropwise to the potassium antimonate solution at 90 °C. It takes about 1 h to add it completely. After stirring and reacting for 2 h, filter, wash three times with distilled water, and dry at 120 °C to obtain a zinc magnesium tin antimonate product.

[0054] (3) Add the obtained zinc magnesium tin antimonate to a saturated sodium metaaluminate solution, where the amount of sodium metaaluminate is 12.75 g and the amount of zinc magnesium tin antimonate is 255 g. Disperse ultrasonically for 60 min, adjust the reaction temperature to 70 °C, add a sulfuric acid solution dropwise to adjust the pH to 7, react for 1 h, filter, wash, and dry after the reaction to obtain aluminum hydroxide-coated zinc magnesium tin antimonate.

[0055] (4) Add zinc oxide to water, and then add aluminum hydroxide-coated zinc magnesium tin antimonate, where the amount of zinc oxide is 26.7 g and the amount of aluminum hydroxide-coated zinc magnesium tin antimonate is 267 g. The reaction temperature is 90 °C, and the reaction time is 1 h. After the reaction, filter, wash, and dry to obtain a zinc oxide-aluminum hydroxide-coated zinc magnesium tin antimonate flame retardant.

[0056] Comparative Example 1:

[0057] (1) Add 150 g of antimony trioxide, 75 g of potassium hydroxide, and 600 g of water to a reaction flask. After stirring for 30 minutes, add 120 mL of 30% hydrogen peroxide dropwise while controlling the internal temperature within 80 °C to obtain a potassium antimonate solution by reaction.

[0058] (2) Weigh 147.9 g of zinc sulfate heptahydrate. After dissolving in 150 g of water, slowly add the solution dropwise to the potassium antimonate solution at room temperature. It takes about 1 h to add it completely. After stirring and reacting for 2 h, filter, wash three times with distilled water, and dry at 120 °C to obtain a zinc antimonate product.

[0059] Comparative Example 2:

[0060] (1) Add 150 g of antimony trioxide, 70 g of potassium hydroxide, and 500 g of water to a reaction flask. After stirring for 30 minutes, add 120 mL of 30% hydrogen peroxide dropwise while controlling the internal temperature within 80 °C to obtain a potassium antimonate solution by reaction.

[0061] (2) Take 121.5 g of calcium nitrate tetrahydrate, dissolve it in 150 g of water, and slowly add it dropwise to the potassium antimonate solution at 40 °C. The addition is completed in about 1 h. Then stir and react for 2 h, filter, wash three times with distilled water, and dry at 120 °C to obtain the calcium antimonate product.

[0062] Comparative Example 3:

[0063] (1) Add 150 g of antimony trioxide, 75 g of potassium hydroxide, and 400 g of water to the reaction flask. After stirring for 30 minutes, add 120 mL of 30% hydrogen peroxide dropwise, and control the internal temperature within 80 °C to obtain the potassium antimonate solution;

[0064] (2) Weigh 104.6 g of magnesium chloride hexahydrate, dissolve it in 150 g of water, and slowly add it dropwise to the potassium antimonate solution at 60 °C. The addition is completed in about 1 h. Stir and react for 2 h, filter, wash three times with distilled water, and dry at 120 °C to obtain the magnesium antimonate product.

[0065] Comparative Example 4:

[0066] (1) Add 150 g of antimony trioxide, 72 g of potassium hydroxide, and 500 g of water to the reaction flask. After stirring for 30 minutes, add 120 mL of 30% hydrogen peroxide dropwise, and control the internal temperature within 80 °C to obtain the potassium antimonate solution;

[0067] (2) Take 118.35 g of zinc sulfate heptahydrate and 21 g of magnesium chloride hexahydrate, dissolve them in 150 g of water, and slowly add them dropwise to the potassium antimonate solution at 80 °C. The addition is completed in about 1 h. Stir and react for 2 h, filter, wash three times with distilled water, and dry at 120 °C to obtain the zinc magnesium antimonate product.

[0068] Comparative Example 5:

[0069] (1) Add 150 g of antimony trioxide, 75 g of potassium hydroxide, and 550 g of water to the reaction flask. After stirring for 30 minutes, add 120 mL of 30% hydrogen peroxide dropwise, and control the internal temperature within 80 °C to obtain the potassium antimonate solution.

[0070] (2) Weigh 111 g of zinc sulfate heptahydrate, 21 g of magnesium chloride hexahydrate, and 6 g of stannous chloride dihydrate, dissolve them in 150 g of water, and slowly add them dropwise to the potassium antimonate solution at 90 °C. The addition is completed in about 1 h. Stir and react for 2 h, filter, wash three times with distilled water, and dry at 120 °C to obtain the zinc magnesium tin antimonate product.

[0071] Take the coated antimonate flame retardants prepared in Examples 1 - 5 and Comparative Examples 1 - 5, as well as antimony trioxide, and apply them to the flame retardancy of PVC. Table 1 shows the flame retardant PVC formulation.

[0072] Table 1: Flame Retardant PVC Formulation

[0073] Raw materials 1 2 3 4 5 6 7 8 9 10 11 PVC (g) 100 100 100 100 100 100 100 100 100 100 100 Plasticizer (g) 60 60 60 60 60 60 60 60 60 60 60 Stabilizer (g) 4 4 4 4 4 4 4 4 4 4 4 Antimony trioxide (g) 3 / / / / / / / / / / Example 1 (g) / 3 / / / / / / / / / Example 2 (g) / / 3 / / / / / / / / Example 3 (g) / / / 3 / / / / / / / Example 4 (g) / / / / 3 / / / / / / Example 5 (g) / / / / / 3 / / / / / Comparative Example 1 (g) / / / / / / 3 / / / / Comparative Example 2 (g) / / / / / / / 3 / / / Comparative Example 3 (g) / / / / / / / / 3 / / Comparative Example 4 (g) / / / / / / / / / 3 / Comparative Example 5 (g) / / / / / / / / / / 3

[0074] The flame retardant properties and limiting oxygen index of the finished products obtained from antimony trioxide, Examples 1-5 and Comparative Examples 1-5 were tested. The specific test methods are as follows:

[0075] Flame retardant rating UL94: The vertical method in GB / T 2048-2008 "Determination of flammability of plastics - Horizontal and vertical methods" was used;

[0076] Oxygen index: The top surface ignition method in GB / T 2046-2008 "Determination of combustion behavior of plastics by the oxygen index method" was used.

[0077] The test results are shown in Table 2.

[0078] Table 2 Performance test data of antimony trioxide, Examples 1-5 and Comparative Examples 1-5 applied to PVC flame retardancy

[0079]

[0080] As can be seen from Table 1 and Table 2, compared with the performance of Formulation 1 with antimony trioxide added, the performance of Formulations 2-6 with the zinc oxide-aluminum hydroxide coated antimonate flame retardant of Examples 1-5 added is such that the flame retardant performance of Formulations 2-6 is comparable to that of Formulation 1 with antimony trioxide added. However, this comparable performance is presented under the condition that the addition amount of antimony trioxide is the same as that of the coated antimonate flame retardant prepared in Examples 1-5. This means that compared with Formulation 1, the antimony content in Formulations 2-6 is reduced by at least 23%. This further shows that the coated antimonate flame retardant prepared in the present invention can replace the use of antimony trioxide in flame retardant materials, and can maintain a comparable flame retardant rating and oxygen index with antimony trioxide under the condition of adding the same number of parts, and unexpectedly reduces the cost of using antimony in flame retardant materials.

[0081] Compared with the performance of Formulations 7-11 with the antimonate prepared in Comparative Examples 1-5 added, the antimony content in Formulations 2-6 with the zinc oxide-aluminum hydroxide coated antimonate flame retardant of Examples 1-5 added is reduced by about 6%. At the same time, the oxygen index is increased by about 2%. Thus, it can be seen that under the condition of comparable flame retardant performance, the double-layer coating technology not only further reduces the cost of using antimony in flame retardant materials, but also reversely increases the oxygen index, enhancing the application status and scope of antimonate in the field of flame retardancy.

[0082] In summary, under the combined action of aluminum hydroxide and zinc oxide in the coated antimonate flame retardant prepared in the present invention to reduce temperature and block heat transfer, the decomposition of antimonate is delayed, and then the oxygen index is increased. Moreover, the antimony content in the coated antimonate is lower than that in the antimonate.

[0083] The above are only the preferred embodiments of the present invention and do not impose any formal restrictions on the present invention. Although the present invention has been disclosed above with the preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some changes or modifications to equivalent embodiments of equivalent changes within the scope of the technical solution of the present invention by using the technical content disclosed above. However, as long as it does not depart from the content of the technical solution of the present invention, any brief modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A preparation method of an antimony salt flame retardant coating, characterized in that: It includes the following steps: (1) Preparation of aluminum hydroxide-coated antimonate: Add antimonate to a saturated sodium metaaluminate solution, and react to obtain aluminum hydroxide-coated antimonate; (2) Preparation of zinc oxide secondary-coated antimonate: Add zinc oxide to water, and then add the aluminum hydroxide-coated antimonate, and react to obtain a zinc oxide-aluminum hydroxide-coated antimonate flame retardant.

2. The preparation method of the coated antimonate flame retardant according to claim 1, wherein: In the step (1), add antimonate to a saturated sodium metaaluminate solution, ultrasonically disperse for 10 min - 60 min, adjust the reaction temperature to 50 °C - 70 °C, add an acidic solution to adjust the pH to 6 - 7, react for 1 - 2 hours, and after the reaction, filter, wash with water, and dry to obtain aluminum hydroxide-coated antimonate.

3. The preparation method of the coated antimonate flame retardant according to claim 1 or 2, characterized in that: In the step (1), the mass ratio of sodium metaaluminate to antimonate is 0.02 - 0.05:

1.

4. The preparation method of the coated antimonate flame retardant according to claim 1, characterized in that: In the step (2), add zinc oxide to water, and then add the aluminum hydroxide-coated antimonate, react for 1 - 2 hours, and after the reaction, filter, wash with water, and dry to obtain a zinc oxide-aluminum hydroxide-coated antimonate flame retardant.

5. The preparation method of the coated antimonate flame retardant according to claim 1 or 4, characterized in that: In the step (2), the mass ratio of zinc oxide to aluminum hydroxide-coated antimonate is 0.05 - 0.1:

1.

6. The preparation method of the coated antimonate flame retardant according to claim 1, characterized in that: In the step (1), the preparation method of the antimonate includes the following steps: 1) Add antimony trioxide, potassium hydroxide, and water to a reaction vessel and stir, and then add 30% hydrogen peroxide to react to obtain potassium antimonate; 2) Dissolve the metal salt in water, and drop it into the potassium antimonate solution. After the dropping is completed, react at a temperature of 20 °C - 90 °C for 2 - 3 hours. After the reaction is completed, filter and wash with water to obtain antimonate.

7. The preparation method of the coated antimonate flame retardant according to claim 6, wherein: The molar ratio of antimony trioxide to potassium hydroxide is 1:2 - 2.6, the solid-liquid ratio is 1:1.7 - 2.7, the molar ratio of antimony trioxide to 30% hydrogen peroxide is 1:7.8, and the molar ratio of potassium antimonate to the metal salt is 2:

1.

8. The preparation method of the coated antimonate flame retardant according to claim 6, characterized in that: The metal salt is one or more of soluble zinc salt, soluble magnesium salt, soluble calcium salt, and soluble tin salt.

9. A coated antimonate flame retardant, characterized in that: The coated antimonate flame retardant is prepared as described in any one of claims 1 - 8.

10. A flame-retardant PVC, characterized in that: It includes a coated antimonate flame retardant, and the coated antimonate flame retardant is prepared as described in any one of claims 1 - 8.

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