CN100469703C - Preparation method of nano-scale ammonium octamolybdate - Google Patents

Abstract

The invention discloses a preparation method of nanoscale ammonium octamolybdate, which comprises the steps of adding high-purity molybdenum trioxide into an ammonium heptamolybdate solution for reaction, wherein the molar ratio of ammonium to molybdenum in the solution is 1: 2, adding a small amount of dodecyl trimethyl ammonium chloride as a surfactant into the solution for reaction, heating, preserving heat, stirring to generate a water-insoluble paste material in the solution, directly conveying the paste material into a GSX type rotary flash evaporation dryer, and synchronously realizing dynamic drying and crushing under the process conditions that the drying temperature is 100-106 ℃ and the vortex air flow speed is 320-380 m/s. The nanometer ammonium octamolybdate prepared by the invention has the advantages of fine particle size, good consistency, high yield, low moisture content and short working hours. The preparation method is suitable for mass production of the nano ammonium octamolybdate.

Description

Preparation method of nano-scale ammonium octamolybdate

technical field

The invention relates to a preparation method of a smoke-suppressing flame retardant, in particular, the invention relates to a preparation method of a smoke-suppressing flame retardant with an ultrafine particle size.

Background technique

Ammonium octamolybdate is a new type of smoke suppression flame retardant and a chemical additive. The prior art produces ammonium octamolybdate by utilizing the reaction of high-purity molybdenum trioxide in ammonium heptamolybdate solution to produce water-insoluble paste-like material. After the paste material is centrifuged and dehydrated, it is packed in a stainless steel container and sent to an oven for drying, and finally it is mechanically crushed into a powdered ammonium octamolybdate product; since the ammonium octamolybdate prepared by the prior art has a limit particle size of 0.9 ~6um, wide range of particle size distribution, small specific surface area per unit mass, which can no longer meet the actual needs of modern industry. In addition, in the prior art, the powder has the phenomenon of permeation during the preparation process, the yield of the finished product is low, the dehydration is not clean, the water evaporates slowly after standing dry, the particle agglomeration phenomenon is obvious, and the preparation process is long, which is easy to bring in mechanical impurities , Dust in the air falls into some obvious shortcomings such as excessive silicon content in the product.

Contents of the invention

The present invention mainly aims at the deficiencies of the prior art, and provides a preparation method of nanometer ammonium octamolybdate. The preparation method reduces the intermolecular attraction of ammonium molybdenum and the association force of ions in the solution by adding a small amount of surfactant, and adopts a synchronous process The method is dynamic drying plus vortex airflow crushing to produce nano-scale ammonium octamolybdate with a particle size of 250-500nm. The preparation method has short process flow, high yield, low water content and no pollution.

The present invention achieves the above-mentioned technical goals through the following technical solutions.

A preparation method of nano-scale ammonium octamolybdate, the method comprises adding high-purity molybdenum trioxide into ammonium heptamolybdate solution, the improvement is:

(1) The ammonium-molybdenum ratio in the solution is 1: 2 (molar ratio);

(2) add the cationic surfactant of 0.15% (weight percentage) in the solution;

(3) Heat the solution to 55-65°C, keep warm and stir for 0.5h;

(4) Then heat the solution to 95-105° C., keep warm and stir for 2 hours and keep the liquid level of the solution unchanged, and react in the solution to form a water-insoluble paste-like material, which is a collection of molecular-level products;

(5) The pasty material is continuously sent to the GSX type rotary flash dryer for drying, and at the same time, it is crushed by vortex air flow to make a finished product with a water content of ≤0.1% (weight percentage). The drying temperature is 100-106 °C, The swirling air velocity is 320-380m/s.

The cationic surfactant is an aqueous solution of dodecyltrimethylammonium chloride containing 30% by weight; the heating temperature of the solution is 100-102°C; the drying temperature is 102-105°C; Said vortex air velocity is 340～360m/s.

Compared with the prior art, the present invention has the following positive effects:

1. Adding a cationic surfactant to the solution system can effectively reduce the intermolecular attraction of ammonium molybdenum and the association force between ions. The paste-like material generated by the solution reaction is a collection of molecular-level products.

2. Under the same temperature environment, it is prepared by the synchronous process of hot air dynamic drying and vortex airflow pulverization. The process is short, the yield is high, the production efficiency is high, the operation is simple, easy to control and the product is not polluted by the environment.

3. There is a particle size classifier on the top of the GSX spin flash dryer, which automatically screens out nano-sized powder, and the powder with a slightly coarser particle size returns to continue to be crushed, and the finished product has a fine particle size and good consistency.

4. Although the process cost is slightly increased, the product performance index is increased by an order of magnitude, and the cost performance is high.

Detailed ways

A preparation method of nano-scale ammonium octamolybdate, the method comprises adding high-purity molybdenum trioxide into ammonium heptamolybdate solution, according to the ammonium-molybdenum ratio in the solution is 1:2 (molar ratio) to deploy, and to Add 0.15% (by weight) surfactant dodecyltrimethylammonium chloride to the solution, heat the solution to 55-65°C, keep warm and stir for 0.5h, then heat the solution to 95-105°C , keep warm and stir for 2 hours and keep the liquid level of the solution unchanged. The reaction in the solution generates a water-insoluble paste-like material, which is a collection of molecular-level products. The paste-like material is continuously sent to the GSX type spin flash dryer, and the hot air Enter the drying chamber of the dryer from the tangential direction, forming a drying temperature of 100-106°C, coupled with the agitation of the dryer to form a 340-360m/s vortex airflow to simultaneously dry and pulverize the paste material. The powder that is crushed into nanometer scale is discharged from the particle size classifier installed on the top of the dryer, and the powder with a slightly coarser particle size returns to continue to be crushed by the vortex airflow. The particle size of the nanometer ammonium octamolybdate prepared by the invention is 250-500nm, the water content is ≤0.1% (weight percentage), the finished product yield is 99.2%, and the processing time is 5h.

The following is an example of the preparation method of nanometer ammonium octamolybdate, through which the impact on particle size, yield and processing time under different process conditions is illustrated.

Example 1

Add high-purity molybdenum trioxide into the ammonium heptamolybdate solution, prepare according to the ammonium-molybdenum ratio in the solution as 1:2 (molar ratio), and add 0.15% (weight percent) surfactant decachloride to the solution. Dialkyl trimethyl ammonium, heat the solution to 58°C, keep warm and stir for 0.5h, then heat the solution to 98°C, keep warm and stir for 2h and keep the liquid level of the solution unchanged, the solution gradually reacts to form a white paste For pasty materials, the pasty materials are continuously fed into the GSX rotary flash dryer, and are simultaneously dried and pulverized under the conditions of a drying temperature of 100°C and a vortex air flow of 380m/s. The nano-scale ammonium octamolybdate particle size, yield, water content and processing time prepared under this working condition are shown in the table below.

Example 2

Add high-purity molybdenum trioxide into the ammonium heptamolybdate solution, prepare according to the ammonium-molybdenum ratio in the solution as 1:2 (molar ratio), and add 0.15% (weight percent) surfactant decachloride to the solution. Dialkyl trimethyl ammonium, heat the solution to 60°C, keep warm and stir for 0.5h, then heat the solution to 100°C, keep warm and stir for 2h and keep the liquid level of the solution unchanged, the solution gradually reacts to form a white paste For pasty materials, the pasty materials are continuously fed into the GSX rotary flash dryer, and are simultaneously dried and pulverized under the conditions of a drying temperature of 105°C and a vortex airflow of 340m/s. The nano-scale ammonium octamolybdate particle size, yield, water content and processing time prepared under this working condition are shown in the table below.

Example 3

Add high-purity molybdenum trioxide into the ammonium heptamolybdate solution, prepare according to the ammonium-molybdenum ratio in the solution as 1:2 (molar ratio), and add 0.15% (weight percent) surfactant decachloride to the solution. Dialkyl trimethyl ammonium, heat the solution to 60°C, keep warm and stir for 0.5h, then heat the solution to 102°C, keep warm and stir for 2h and keep the liquid level of the solution unchanged, the solution gradually reacts to form a white paste For pasty materials, the pasty materials are continuously fed into the GSX rotary flash dryer, and are simultaneously dried and pulverized under the conditions of a drying temperature of 105°C and a vortex airflow of 340m/s. The nano-scale ammonium octamolybdate particle size, yield, water content and processing time prepared under this working condition are shown in the table below.

(The rest of the content is the same as in Example 1, only the heating temperature is changed from 58°C to 60°C, from 98°C to 102°C, and from 100°C to 105°C)

Example 4

(The rest of the content is the same as in Example 1, only the heating temperature is changed from 58°C to 65°C, from 98°C to 105°C, and from 100°C to 105°C)

Preparation results test table under different process conditions

name Particle size (nm) Yield (%) Preparation time (h) Moisture content (%) Overview Example 1 1000 85 5.5 0.8 Difference Example 2 500 94 6.0 0.08 generally Example 3 300 99.2 5.0 0.07 excellent Example 4 240-1200 90.2 4.5 0.6 The product is impure

It can be seen from the above table that the process parameters in Example 3 are preferred parameters, and the prepared nano-scale ammonium octamolybdate has the smallest particle size, the highest yield of finished product, and the least water content.

Claims (6)

1, a kind of preparation method of nm-class ammonium octamolybdate, this method comprise high-purity molybdic oxide are joined in the Ammoniun Heptamolybdate Solution, it is characterized in that:

(1) mol ratio of ammonium and molybdenum is 1: 2 in the solution;

(2) adding weight percent in solution is 0.15% cats product;

(3) solution is heated to 55～65 ℃, insulation is also stirred 0.5h;

(4) then heat to 95～105 ℃ to solution, insulated and stirred 2h also keeps liquid level of solution constant, and the water-fast plaster pasty materials of reaction generation is the set of molecular level product in the solution;

(5) plaster pasty materials is sent continuously to drying in the GSX type Rotatingandflashstreamingdrier, pulverized the finished product of making moisture content≤0.1% through eddy airstream simultaneously, drying temperature is 100～106 ℃, and eddy airstream speed is 320～380m/s.

2, according to the preparation method of the described nm-class ammonium octamolybdate of claim 1, it is characterized in that: described cats product is that a kind of weight percent that contains is 30% the chlorination dodecyl trimethyl ammonium aqueous solution.

3, according to the preparation method of the described nm-class ammonium octamolybdate of claim 1, it is characterized in that: described solution divides two sections heating, and final Heating temperature is 100～102 ℃.

4, according to the preparation method of the described nm-class ammonium octamolybdate of claim 1, it is characterized in that: described drying temperature is 102～105 ℃.

5, according to the preparation method of the described nm-class ammonium octamolybdate of claim 1, it is characterized in that: described eddy airstream speed is 340～360m/s.

6, according to the preparation method of the described nm-class ammonium octamolybdate of claim 1, it is characterized in that: described GSX type Rotatingandflashstreamingdrier top is provided with particle sizer.