CN111349022B - Preparation method of AC foaming agent with uniform and controllable particle size - Google Patents
Preparation method of AC foaming agent with uniform and controllable particle size Download PDFInfo
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- CN111349022B CN111349022B CN201811574773.5A CN201811574773A CN111349022B CN 111349022 B CN111349022 B CN 111349022B CN 201811574773 A CN201811574773 A CN 201811574773A CN 111349022 B CN111349022 B CN 111349022B
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- C07C281/20—Derivatives of carbonic acid containing functional groups covered by groups C07C269/00 - C07C279/00 in which at least one nitrogen atom of these functional groups is further bound to another nitrogen atom not being part of a nitro or nitroso group the two nitrogen atoms of the functional groups being doubly-bound to each other, e.g. azoformamide
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Abstract
The invention provides a preparation method of an AC foaming agent with uniform and controllable particle size, which comprises the following steps: (1) preparing biurea; (2) preparing a fine-particle-size AC foaming agent; (3) adding AC foaming agent powder seed crystals; (4) The preparation method of the bimodal AC foaming agent with uniform and controllable particle size is simple in process, the prepared AC foaming agent with bimodal distribution has obvious bimodal characteristics, and the particle size distribution is more uniform near each peak.
Description
Technical Field
The invention relates to the field of AC foaming agents, in particular to a preparation method of an AC foaming agent with uniform and controllable particle size, and especially relates to a preparation method of an AC foaming agent with bimodal distribution and uniform and controllable particle size.
Background
The chemical name of the AC foaming agent azodicarbonamide is azodicarbonamide, which is a foaming agent with large gas evolution, excellent performance and no toxicity, and can be widely used in processing foaming products such as plastics, rubber and the like and additives of certain foods, but the AC foaming agents produced in the current market have the problem of too wide particle size distribution. The use of an AC blowing agent with an excessively broad particle size distribution poses a number of difficulties to the foaming process: when the particle size distribution of the foaming agent is too wide, on one hand, the foaming agent with small particle size has large specific surface area, strong activity and short decomposition process, and is easy to decompose and foam in advance, so that the defective products and the rejection rate of foaming products are high; on the other hand, the large-particle-size foaming agent has small specific surface area, low activity and long decomposition process, and tends to delay foaming or even not foam, so that the surface of a foamed product is yellowed, and the color and the quality of the foamed product are seriously influenced. Therefore, blowing agent manufacturers desire that the particle size distribution of the blowing agent be as narrow as possible, i.e., that the particle size of the blowing agent be as uniform as possible.
At present, the problem of over-wide distribution of foaming agent particles is generally solved by a physical method, a grader is mainly used for mechanical grading, a grading wheel of the grader rotates at a high speed, the foaming agent with over-large and over-small particle sizes is separated by utilizing the gravity principle, and the middle part is left, so that the particle size distribution range of the foaming agent is narrowed. The method not only has complicated steps, but also wastes foaming agents with excessively large and small particle sizes.
Furthermore, in foamed articles, there are generally divided into macroporous plastics (cell diameters of greater than 50 μm) and microporous plastics (cell diameters of between 0.1 and 10 μm). Macroporous plastics are low in density and poor in mechanical property and are commonly used as insulating and packaging materials; the microporous plastic has high density and good toughness, and is commonly used in the field with high requirements on mechanical properties. In recent years, foamed materials having a bimodal distribution have appeared on the market, which can combine the advantages of a lower foam density of macroporous plastics and a higher mechanical property of microporous plastics, and in particular, are very excellent in barrier properties, including sound insulation, heat insulation, and the like.
At present, the foaming material with bimodal distribution is mainly realized by regulating and controlling a foaming process, and generally comprises a two-step depressurization method, a cooling and depressurization cooperative method and a double-foaming agent method. The methods have the defects of complicated steps, high requirement on process control, difficulty in controlling the cell structure and low product percent of pass, and particularly the double-foaming agent method realizes the aim of preparing the foaming material with bimodal distribution by matching two foaming agents, and the foaming result is influenced by different foaming agent types, preparation processes, batches and the like. Therefore, the preparation of the foaming material with bimodal distribution is greatly limited, so that the price of the foaming material with bimodal distribution is far higher than that of common foaming plastics, and the application of the foaming material with bimodal distribution is severely limited.
The foaming agent with bimodal distribution can greatly simplify the preparation process of the foaming material with bimodal distribution, so that the aim of preparing the foaming material with bimodal distribution can be realized by simple temperature rise process control, but the existing foaming agent with bimodal distribution is realized by proportioning and mixing the foaming agent with fine particle size and the foaming agent with coarse particle size, and the foaming agent with bimodal distribution mainly has two defects: firstly, due to the superposition effect of large particles in the fine-particle-size foaming agent and small particles in the coarse-particle-size foaming agent, the double-peak effect is not obvious; secondly, due to the difference of the batches, preparation processes and manufacturers of the two foaming agents, the double-peak effect is unstable, so that the double-peak effect is extremely undesirable.
Therefore, it is one of the technical problems to be solved by the skilled person in the art to provide a method for preparing an AC foaming agent with uniformly controllable particle size, especially an AC foaming agent with uniformly controllable particle size having bimodal distribution, so as to prepare an AC foaming agent with uniformly controllable particle size having bimodal distribution, and to simplify the preparation process of a foaming material with bimodal distribution.
Disclosure of Invention
In view of the above, the present invention is directed to a method for preparing an AC foaming agent with uniformly controllable particle size, so as to prepare an AC foaming agent with uniformly controllable particle size having bimodal distribution.
In order to achieve the purpose, the technical scheme of the invention is realized as follows:
a preparation method of an AC foaming agent with uniform and controllable particle size comprises the following steps:
(1) Preparation of biurea:
adding a hydrazine hydrate solution with the mass concentration of 20-23% into a condensation kettle, adding a urea solution into the condensation kettle, so that the mass ratio of hydrazine hydrate to urea in the hydrazine hydrate solution is 1;
(2) Preparation of fine-particle-size AC foaming agent:
preparing a suspension containing 15-30 kg/L of biurea and water, adding an inorganic acid to adjust the acidity of the reaction system so that the acidity is 2.0-6.0 mol/L, adding a catalyst sodium bromide or potassium bromide in a concentration of 0.25-0.44 kg/L, opening the cover of a double-circulation reaction kettle, adding the prepared suspension of biurea into the double-circulation reaction kettle, introducing chlorine gas, stirring while heating to 25-35 ℃, and preparing a fine-grain-size AC foaming agent;
(3) Adding AC foaming agent powder seed crystal:
sampling, analyzing and monitoring the AC foaming agent in the double-circulation reaction kettle once every 2-5 min, and adding AC foaming agent powder crystal seeds with the average particle size of 20-30 mu m when the average particle size of the AC foaming agent reaches 6-10 mu m;
(4) Preparation of bimodal AC blowing agent:
and continuously stirring, carrying out heat preservation reaction for 6-7 h, and cooling to obtain the AC foaming agent with bimodal distribution.
Further, the method comprises the following steps:
(1) Preparation of biurea:
adding a hydrazine hydrate solution with the mass concentration of 22% into a condensation kettle, adding a urea solution into the condensation kettle, leading the mass ratio of hydrazine hydrate to urea in the hydrazine hydrate solution to be 1;
(2) Preparation of fine-particle-size AC foaming agent:
preparing biurea and water into suspension with the content of biurea of 20 percent kg/L, adding inorganic acid to adjust the acidity of a reaction system to ensure that the acidity is between 4.0mol/L, adding sodium bromide or potassium bromide serving as a catalyst with the concentration of 0.3 percent, opening a cover body of a double-circulation reaction kettle, adding the prepared biurea suspension into the double-circulation reaction kettle, introducing chlorine gas, stirring and simultaneously heating to 30 ℃ to prepare a fine-grain-size AC foaming agent;
(3) Adding AC foaming agent powder seed crystal:
sampling, analyzing and monitoring the AC foaming agent in the double-circulation reaction kettle once every 3min, and adding AC foaming agent powder crystal seeds with the average particle size of 25 micrometers when the average particle size of the AC foaming agent reaches 8 micrometers;
(4) Preparation of bimodal AC blowing agent:
and continuously stirring, keeping the temperature and reacting for 6.5 hours, and cooling to obtain the AC foaming agent with bimodal distribution.
Further, the inorganic acid is hydrochloric acid, and the concentration of the hydrochloric acid is 20-30%.
Further, the step (4) comprises the steps of continuously stirring, carrying out heat preservation reaction for 6.5 hours, cooling to obtain oxidation mother liquor, and carrying out centrifugal washing on the oxidation mother liquor through a high-efficiency centrifugal machine to obtain inorganic acid and an AC foaming agent with bimodal distribution.
Further, the inorganic acid is hydrochloric acid.
Further, the step (4) comprises the steps of:
(41) Continuously stirring, reacting for 6.5h under heat preservation, cooling to obtain an oxidation mother liquor, and performing centrifugal separation on the oxidation mother liquor through the high-efficiency centrifugal machine to obtain an AC foaming agent precipitate and a centrifugal mother liquor;
(42) Performing five times of centrifugal washing on the AC foaming agent precipitate, respectively recovering removal liquid obtained by different times of centrifugal washing into different containers, mechanically applying the removal liquid obtained by different batches of centrifugal washing of the AC foaming agent, and taking the removal liquid obtained by the first centrifugal washing as a primary acid and taking the removal liquid obtained by the second centrifugal washing as a secondary acid;
(43) Directly recycling the centrifugal mother liquor with the hydrochloric acid mass concentration of 20% or more for condensation reaction, or mixing the centrifugal mother liquor with the hydrochloric acid mass concentration of less than 20% with the hydrochloric acid with high mass concentration to prepare the condensation reaction for preparing the biurea with the hydrochloric acid mass concentration of 20% or more;
(44) Mixing the primary acid with high-quality-concentration hydrochloric acid to prepare a condensation reaction for preparing biurea, wherein the mass concentration of the hydrochloric acid is 20% or more;
(45) And recovering the secondary acid for preparing the biurea into the oxidation reaction kettle.
Further, the step (42) includes five centrifugal washes of the AC foaming agent precipitate, wherein the removal liquid from different centrifugal washes is recovered into different containers, and the removal liquid is reused for different batches of centrifugal washes of the AC foaming agent: and taking the removal liquid of the third centrifugal washing as the washing water of the next round of first centrifugal washing, taking the removal liquid of the fourth centrifugal washing as the washing water of the next round of second centrifugal washing, taking the removal liquid of the fifth centrifugal washing as the washing water of the next round of third centrifugal washing, introducing clean water as the washing water of the fourth centrifugal washing and the fifth centrifugal washing, sequentially carrying out five centrifugal washing on the AC foaming agent, taking the removal liquid of the first centrifugal washing as a primary acid, taking the removal liquid of the second centrifugal washing as a secondary acid, and regulating the amount of the clean water introduced in the fourth centrifugal washing and the fifth centrifugal washing so as to enable the mass concentration of hydrochloric acid in the primary acid and the secondary acid to be not higher than 30%.
Furthermore, the double-circulation reaction kettle comprises an inner barrel and a cover body covering the inner barrel, the center of the inner barrel is connected with a second driving motor through a second driving shaft, the center of the cover body is connected with a first driving motor through a first driving shaft, the end part, located on the inner side of the bottom of the inner barrel, of the second driving shaft is provided with a stirring blade, the second driving motor can drive the stirring blade to rotate, a water pressing disc is arranged at one end, close to the inner barrel, of the first driving shaft, the water pressing disc is located at one side, close to the inner barrel, of the cover body, the water pressing disc is contained in a hollow cylindrical water distribution cover, a water passing hole is formed in the water distribution cover, and the first driving motor can drive the water pressing disc to do circulating reciprocating motion in the water distribution cover along the central axis of the water pressing disc.
Furthermore, the projection area of the stirring blade at the bottom of the inner cylinder is gradually increased from one end close to the second driving shaft to one end far away from the second driving shaft.
Compared with the prior art, the preparation method of the AC foaming agent with uniform and controllable particle size has the following advantages:
(1) According to the preparation method of the AC foaming agent, the AC foaming agent powder seed crystal is added in the middle stage of the reaction, so that the aim of preparing the AC foaming agent with bimodal distribution is fulfilled.
(2) According to the preparation method of the AC foaming agent, provided by the invention, the repeated utilization rate of the raw materials is improved through the cyclic utilization of the hydrochloric acid, the controllability of the preparation process of the biurea is improved, the uniformity of the particle size of the biurea is improved, and the realization of the AC foaming agent with bimodal distribution in the later period is facilitated.
(3) According to the preparation method of the AC foaming agent, the double-circulation reaction kettle is adopted, so that the uniformity of the reaction liquid is improved, and the preparation of the AC foaming agent with bimodal distribution and uniform and controllable particle size is facilitated.
In conclusion, the preparation method of the AC foaming agent has simple process, the prepared AC foaming agent with bimodal distribution has obvious bimodal characteristics, and the particle size distribution is more uniform near each peak value
Drawings
The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate an embodiment of the invention and, together with the description, serve to explain the invention and not to limit the invention. In the drawings:
FIG. 1 is a flow chart of a process for preparing a blowing agent according to an embodiment of the present invention;
FIG. 2 is a schematic structural view of a double loop reactor according to an embodiment of the present invention;
FIG. 3 is a schematic cross-sectional view of a double loop reactor according to an embodiment of the present invention;
FIG. 4 is another schematic cross-sectional view of a double loop reactor according to an embodiment of the present invention;
FIG. 5 is a schematic structural diagram of a stirring blade of a double loop reactor according to an embodiment of the present invention;
FIG. 6 is a flow diagram of a hydrochloric acid recycling process according to an embodiment of the present invention;
FIG. 7 is a schematic structural diagram of a high efficiency centrifuge according to an embodiment of the present invention;
FIG. 8 is a schematic structural diagram of a first inner chamber of a high efficiency centrifuge according to an embodiment of the present invention;
FIG. 9 is a schematic structural diagram of a high efficiency centrifuge according to an embodiment of the present invention during low speed rotation;
FIG. 10 is a schematic structural diagram of a high-efficiency centrifuge according to an embodiment of the present invention during high-speed rotation;
FIG. 11 is a particle size distribution diagram for a fine particle size AC blowing agent according to an embodiment of the present invention;
FIG. 12 is a particle size distribution diagram of an AC blowing agent having a bimodal distribution according to an embodiment of the present invention.
Description of reference numerals:
1-inner cylinder, 2-cover body, 3-first driving shaft, 4-first driving motor, 5-second driving shaft, 6-second driving motor, 7-stirring blade, 8-water distribution cover, 9-water passing hole, 10-water pressing disc, 11-bracket, 12-outer chamber, 13-first inner chamber, 131-side wall, 132-first through hole, 14-second inner chamber and 15-particle.
Detailed Description
It should be noted that the embodiments and features of the embodiments may be combined with each other without conflict.
The present invention will be described in detail below with reference to the embodiments with reference to the attached drawings.
Example 1
A preparation method of an AC foaming agent with uniform and controllable particle size is shown in figure 1 and comprises the following steps:
(1) Preparing biurea;
(2) Preparing a fine-particle-size AC foaming agent;
(3) Adding AC foaming agent powder seed crystal;
(4) Preparation of bimodal AC blowing agent.
Specifically, the step (1) comprises the following steps: adding a hydrazine hydrate solution with the mass concentration of 20% into a condensation kettle, adding a urea solution into the condensation kettle, so that the mass ratio of hydrazine hydrate to urea in the hydrazine hydrate solution is 1, dropwise adding hydrochloric acid with the concentration of 20% at the temperature of 130 ℃ and the pressure of 0.23MPa for condensation reaction, cooling to 80 ℃ when the reaction is carried out until the concentration of residual hydrazine hydrate in a reaction liquid in the condensation kettle is less than 1g/L, discharging, carrying out solid-liquid separation, washing and drying a solid phase, and obtaining a biurea finished product;
specifically, the step (2) includes: preparing a suspension of biurea and water with a biurea content of 15% kg/L, adjusting the acidity of the reaction system to 2.0mol/L by adding an inorganic acid, adding sodium bromide or potassium bromide as a catalyst in a concentration of 0.25% kg/L, opening the lid of the double loop reactor, adding the prepared suspension of biurea to the double loop reactor, introducing chlorine gas, and heating to 25 ℃ while stirring to prepare a fine-particle-size AC foaming agent.
Further, the step (3) comprises: sampling, analyzing and monitoring the AC foaming agent in the double-circulation reaction kettle once every 5min, and adding AC foaming agent powder seed crystals with the average particle size of 20 micrometers when the particle size of the AC foaming agent reaches 6 micrometers.
Further, the step (4) comprises: and continuously carrying out heat preservation reaction for 7 hours, cooling and separating to obtain the AC foaming agent with bimodal distribution.
Example 2
A preparation method of an AC foaming agent with uniform and controllable particle size comprises the following steps:
(1) Preparing biurea;
adding a hydrazine hydrate solution with the mass concentration of 23% into a condensation kettle, adding a urea solution into the condensation kettle, so that the mass ratio of hydrazine hydrate to urea in the hydrazine hydrate solution is 1.2.5, dropwise adding hydrochloric acid with the concentration of 30% at the temperature of 140 ℃ and the pressure of 0.20MPa for condensation reaction, cooling to 90 ℃ when the concentration of residual hydrazine hydrate in a reaction liquid in the condensation kettle is less than 1g/L, discharging, performing solid-liquid separation, washing and drying a solid phase, and obtaining a biurea finished product;
(2) Preparation of fine-particle-size AC foaming agent:
preparing biurea and water into a suspension with the content of biurea of 30 percent kg/L, adding inorganic acid to adjust the acidity of a reaction system to ensure that the acidity is between 6.0mol/L, adding sodium bromide or potassium bromide serving as a catalyst with the concentration of 0.4 percent kg/L, opening a cover body of a double-circulation reaction kettle, adding the prepared biurea suspension into the double-circulation reaction kettle, introducing chlorine gas, stirring and simultaneously heating to 35 ℃ to prepare the fine-grain-size AC foaming agent.
(3) Adding AC foaming agent powder seed crystal:
sampling, analyzing and monitoring the AC foaming agent in the double-circulation reaction kettle once every 2min, and adding AC foaming agent powder crystal seeds with the average particle size of 30 mu m when the average particle size of the AC foaming agent reaches 10 mu m.
(4) Preparation of bimodal AC blowing agent:
and continuously stirring, carrying out heat preservation reaction for 6 hours, cooling and separating to obtain the AC foaming agent with bimodal distribution.
Example 3
A preparation method of an AC foaming agent with uniform and controllable particle size comprises the following steps:
(1) Preparing biurea;
adding a hydrazine hydrate solution with the mass concentration of 22% into a condensation kettle, adding a urea solution into the condensation kettle, leading the mass ratio of hydrazine hydrate to urea in the hydrazine hydrate solution to be 1;
(2) Preparation of fine-particle-size AC foaming agent:
preparing a suspension of biurea and water with a biurea content of 20% kg/L, adjusting the acidity of the reaction system to 4.0mol/L by adding an inorganic acid, adding sodium bromide or potassium bromide as a catalyst in a concentration of 0.3% kg/L, opening the lid of the double loop reactor, adding the prepared suspension of biurea to the double loop reactor, introducing chlorine gas, and heating to 30 ℃ while stirring to prepare a fine-particle-size AC foaming agent.
(3) Adding AC foaming agent powder seed crystal:
sampling, analyzing and monitoring the AC foaming agent in the double-circulation reaction kettle once every 3min, and adding AC foaming agent powder seed crystals with the average particle size of 25 micrometers when the average particle size of the AC foaming agent reaches 8 micrometers.
(4) Preparation of bimodal AC blowing agent:
and continuously stirring, keeping the temperature and reacting for 6.5 hours, cooling and separating to obtain the AC foaming agent with bimodal distribution.
Example 4
A preparation method of an AC foaming agent with uniform and controllable particle size comprises the following steps:
(1) Preparing biurea;
adding a hydrazine hydrate solution with the mass concentration of 22% into a condensation kettle, adding a urea solution into the condensation kettle, leading the mass ratio of hydrazine hydrate to urea in the hydrazine hydrate solution to be 1;
(2) Preparation of fine-particle-size AC foaming agent:
preparing biurea and water into suspension with the content of biurea of 20 percent kg/L, adding hydrochloric acid with the concentration of 20-30 percent to adjust the acidity of a reaction system to ensure that the acidity is between 4.0mol/L, adding sodium bromide or potassium bromide serving as a catalyst with the concentration of 0.3 percent kg/L, opening a cover body of a double-circulation reaction kettle, adding the prepared biurea suspension into the double-circulation reaction kettle, introducing chlorine gas, stirring and simultaneously heating to 30 ℃ for oxidation reaction, and preparing the fine-grain-size AC foaming agent.
(3) Adding AC foaming agent powder seed crystal:
sampling, analyzing and monitoring the AC foaming agent in the double-circulation reaction kettle once every 3min, and adding AC foaming agent powder seed crystals with the average particle size of 25 micrometers when the average particle size of the AC foaming agent reaches 8 micrometers.
(4) Preparation of bimodal AC blowing agent:
continuously stirring, reacting for 6.5h under heat preservation, cooling to obtain an oxidation mother liquor, and centrifugally washing the oxidation mother liquor by a high-efficiency centrifuge to obtain hydrochloric acid with the concentration of 20-30% and an AC foaming agent with bimodal distribution.
Further, hydrochloric acid having the concentration of 20 to 30% is used in the step (1) and the step (2).
Specifically, as shown in fig. 6, the step (4) includes: (41) Continuously stirring, reacting for 6.5h under heat preservation, cooling to obtain an oxidation mother liquor, and performing centrifugal separation on the oxidation mother liquor through the high-efficiency centrifugal machine to obtain an AC foaming agent precipitate and a centrifugal mother liquor; (42) Carrying out five times of centrifugal washing on the AC foaming agent precipitate, respectively recovering removal liquid obtained by different times of centrifugal washing into different containers, wherein the removal liquid is reused when different batches of AC foaming agents are subjected to centrifugal washing, and the removal liquid obtained by the first time of centrifugal washing is used as a primary acid and the removal liquid obtained by the second time of centrifugal washing is used as a secondary acid; (43) Directly recycling the centrifugal mother liquor with the hydrochloric acid mass concentration of 20% or more for condensation reaction, or mixing the centrifugal mother liquor with the hydrochloric acid mass concentration of less than 20% with the hydrochloric acid with high mass concentration to prepare the condensation reaction for preparing the biurea with the hydrochloric acid mass concentration of 20%; (44) Mixing the primary acid with high-quality-concentration hydrochloric acid to prepare a condensation reaction for preparing biurea, wherein the mass concentration of the hydrochloric acid is 20%; (45) And recovering the secondary acid for preparing biurea into an oxidation reaction kettle.
Furthermore, the AC foaming agent is centrifugally washed for five times, the removal liquid of different centrifugal washing times is respectively recycled into different containers, and the removal liquid is reused when different batches of AC foaming agent are centrifugally washed: returning the removal liquid of the third centrifugal washing to the high-efficiency centrifuge as the washing water of the next round of first centrifugal washing, returning the removal liquid of the fourth centrifugal washing to the high-efficiency centrifuge as the washing water of the next round of second centrifugal washing, returning the removal liquid of the fifth centrifugal washing to the high-efficiency centrifuge as the washing water of the next round of third centrifugal washing, introducing clear water as the washing water of the fourth and fifth centrifugal washing, sequentially carrying out five centrifugal washing on the AC foaming agent, taking the removal liquid of the first centrifugal washing as primary acid, and taking the removal liquid of the second centrifugal washing as secondary acid.
In the production process of the AC foaming agent, hydrochloric acid is recycled, and hydrochloric acid with the mass concentration of 20-30% is used for replacing the traditional 98% concentrated sulfuric acid to carry out condensation reaction, so that the reaction process is easier to control, the yield of the biurea is stable, the reaction time and the reaction end point are controllable, the reaction intensity is reduced, the particle size distribution of the prepared biurea is more uniform, and a good basis is provided for the subsequent preparation of AC foaming agent particles with uniform particle sizes. In addition, the complexity of the work of operators is reduced after 98% concentrated sulfuric acid is replaced, and the production safety is higher. Also realizes the cyclic utilization of the hydrochloric acid, reduces the production cost and improves the utilization rate of the raw materials.
Example 5
A preparation method of an AC foaming agent with uniform and controllable particle size comprises the following steps:
(1) Preparing biurea;
adding a hydrazine hydrate solution with the mass concentration of 22% into a condensation kettle, adding a urea solution into the condensation kettle, leading the mass ratio of hydrazine hydrate to urea in the hydrazine hydrate solution to be 1;
(2) Preparation of fine-particle-size AC foaming agent:
preparing biurea and water into suspension with the content of biurea of 20 percent kg/L, adding hydrochloric acid with the concentration of 20-30 percent to adjust the acidity of a reaction system to ensure that the acidity is between 4.0mol/L, adding sodium bromide or potassium bromide serving as a catalyst with the concentration of 0.3 percent kg/L, opening a cover body of a double-circulation reaction kettle, adding the prepared biurea suspension into the double-circulation reaction kettle, introducing chlorine gas, stirring and simultaneously heating to 30 ℃ for oxidation reaction, and preparing the fine-grain-size AC foaming agent.
(3) Adding AC foaming agent powder seed crystal:
sampling, analyzing and monitoring the AC foaming agent in the double-circulation reaction kettle once every 3min, and adding AC foaming agent powder crystal seeds with the average particle size of 25 mu m when the average particle size of the AC foaming agent reaches 8 mu m.
(4) Preparation of bimodal AC blowing agent:
continuously stirring, reacting for 6.5h under heat preservation, cooling to obtain an oxidation mother liquor, and centrifugally washing the oxidation mother liquor by a high-efficiency centrifuge to obtain hydrochloric acid with the concentration of 20-30% and an AC foaming agent with bimodal distribution.
Further, hydrochloric acid having the concentration of 20 to 30% is used in the step (1) and the step (2).
Specifically, as shown in fig. 6, the step (4) includes: (41) Continuously stirring, reacting for 6.5h under heat preservation, cooling to obtain an oxidation mother liquor, and performing centrifugal separation on the oxidation mother liquor through the high-efficiency centrifugal machine to obtain an AC foaming agent precipitate and a centrifugal mother liquor; (42) Carrying out five times of centrifugal washing on the AC foaming agent precipitate, respectively recovering removal liquid obtained by different times of centrifugal washing into different containers, wherein the removal liquid is reused when different batches of AC foaming agents are subjected to centrifugal washing, and the removal liquid obtained by the first time of centrifugal washing is used as a primary acid and the removal liquid obtained by the second time of centrifugal washing is used as a secondary acid; (43) Directly recycling the centrifugal mother liquor with the hydrochloric acid mass concentration of 20% or more for condensation reaction, or mixing the centrifugal mother liquor with the hydrochloric acid mass concentration of less than 20% with the hydrochloric acid with high mass concentration to prepare the condensation reaction for preparing the biurea with the hydrochloric acid mass concentration of 25%; (44) Mixing the primary acid with high-quality-concentration hydrochloric acid to prepare a condensation reaction for preparing biurea, wherein the mass concentration of the hydrochloric acid is 30%; (45) And recovering the secondary acid for preparing biurea into an oxidation reaction kettle.
Furthermore, the AC foaming agent is centrifugally washed for five times, the removal liquid of different times of centrifugal washing is respectively recovered into different containers, and the removal liquid is reused when different batches of AC foaming agents are centrifugally washed: specifically, in the present round of five centrifugal washes, the removal liquid of the previous round of the third centrifugal wash is used as the wash water of the present round of the first centrifugal wash, the removal liquid of the previous round of the fourth centrifugal wash is used as the wash water of the present round of the second centrifugal wash, the removal liquid of the previous round of the fifth centrifugal wash is used as the wash water of the present round of the third centrifugal wash, and the clear water is used as the wash water of the present round of the fourth and fifth centrifugal washes, and the AC foaming agent is sequentially subjected to five centrifugal washes. Returning the removal liquid of the third centrifugal washing to the high-efficiency centrifuge as the washing water of the next round of first centrifugal washing, returning the removal liquid of the fourth centrifugal washing to the high-efficiency centrifuge as the washing water of the next round of second centrifugal washing, returning the removal liquid of the fifth centrifugal washing to the high-efficiency centrifuge as the washing water of the next round of third centrifugal washing, taking the removal liquid of the first centrifugal washing of the round as primary acid, and taking the removal liquid of the second centrifugal washing as secondary acid. And simultaneously, regulating and controlling the amount of the clear water introduced in the fourth centrifugal washing and the fifth centrifugal washing so that the mass concentration of hydrochloric acid in the primary acid and the secondary acid is not higher than 30%.
In the production process of the AC foaming agent, hydrochloric acid is recycled, and the hydrochloric acid with the mass concentration of 20-30% is used for replacing the traditional 98% concentrated sulfuric acid to carry out condensation reaction, so that the reaction process is easier to control, the yield of the biurea is stable, the reaction time and the reaction end point are controllable, the reaction intensity is reduced, the particle size distribution of the prepared biurea is more uniform, and a good basis is provided for the subsequent preparation of AC foaming agent particles with uniform particle sizes. In addition, the complexity of the work of operators is reduced after 98% concentrated sulfuric acid is replaced, and the production safety is higher. Also realizes the cyclic utilization of the hydrochloric acid, reduces the production cost and improves the utilization rate of the raw materials.
Example 6
In the process of recycling the hydrochloric acid, the sufficient washing of the AC foaming agent precipitate particles is a key factor for realizing the recycling of the hydrochloric acid, if the washing is not sufficient, the quality of the AC foaming agent is affected, and if the washing frequency is too large, on one hand, a large amount of washing wastewater is generated, and on the other hand, the AC foaming agent is dissolved and abraded to affect the product particle size of the AC foaming agent.
7-10, centrifuge is horizontal centrifuge, including the cylindrical cavity who holds the mixture, the setting of edge horizontal direction of cavity, the cavity includes inner chamber, outer chamber 12 and support 11, inner chamber sets up outer chamber 12 is inboard, inner chamber includes first inner chamber 13 and second inner chamber 14, first inner chamber 13 sets up the inboard of second inner chamber 14, first inner chamber 13, second inner chamber 14 and the coaxial setting of outer chamber 12, first inner chamber 13, second inner chamber 14 and outer chamber 12 are connected with driving motor through the drive shaft, first inner chamber 13, second inner chamber 14 and outer chamber 12 can be in synchronous rotation under driving motor's the drive, have the space that holds the AC foamer between second inner chamber 14 and the outer chamber 12, be equipped with particulate matter 15 in the first inner chamber 13, be equipped with between first inner chamber 13 and the second inner chamber 14 and hold the space of particulate matter 15, be equipped with on the lateral wall 131 of first inner chamber 13, be equipped with the outer diameter of second through-hole 132 and be greater than the diameter of second through-hole 132 the diameter of first particulate matter is less than the diameter of second through-hole 132.
Furthermore, the inner chamber is detachably connected with the outer chamber 12, and when the sediment is discharged, the inner chamber can be taken out from the outer chamber 12, so that the sediment can be discharged conveniently.
Furthermore, the high-efficiency centrifugal machine is provided with a liquid outlet, the liquid outlet is located on the side wall of one end of the first inner chamber 13, and the clear liquid in the high-efficiency centrifugal machine can be discharged through the liquid outlet.
Furthermore, the inner chamber and the outer chamber 12 are rotatably connected with the bracket 11, and during centrifugation, the inner chamber and the outer chamber 12 can be horizontally and rotatably fixed above the bracket 11.
Furthermore, the frame 11 has a hydraulic lifting device (not shown) which can incline the inner and outer chambers 12 in the horizontal direction when discharging liquid, so as to facilitate the liquid discharge. Likewise, removal of the precipitate may also be facilitated.
When in use, the oxidation mother liquor is firstly put into the first inner chamber 13 of the centrifuge; then the centrifuge is driven by the driving motor to rotate at a high speed (> 1000 r/min), at this time, because the centrifuge has a high rotation speed and generates a large centrifugal force, the particles 15 enter between the first inner chamber 13 and the second inner chamber 14 through the first through holes 132 and then rotate along the side wall of the second inner chamber 14, the AC foaming agent in the oxidation mother liquor passes through the through holes on the first inner chamber 13 and the second inner chamber 14 due to the action of the centrifugal force and is deposited on the side wall of the outer chamber 12, and no sediment is formed on the side wall of the inner chamber due to the action of the particles 15, and then the liquid discharge port of the centrifuge is opened to discharge the clarified liquor to obtain the centrifuge mother liquor.
Further, the AC foamer precipitate particles were subjected to five centrifugal washes with the high efficiency centrifuge. First centrifugation washing process:
step one, stirring at low speed: and (2) putting the AC foaming agent precipitate into the first inner chamber 13, adding a removing liquid of the previous third centrifugal washing as first centrifugal washing water according to the requirements, and then driving the high-efficiency centrifuge to perform low-speed (less than or equal to 700 r/min) forward rotation by the driving motor, wherein at the moment, as the rotating speed of the high-efficiency centrifuge is lower and the generated centrifugal force is smaller, the particulate matters 15 are continuously taken up and thrown down in the second inner chamber 14 along with the rotation of the inner chamber, and simultaneously continuously pass through the first through holes 132 on the first inner chamber 13 and continuously penetrate into and penetrate out of the first inner chamber 13. In the process, the mixture in the inner cavity can be stirred by the particles 4, and large particles of the AC foaming agent are sufficiently scattered, so that the AC foaming agent can be sufficiently contacted with the primary centrifugal washing water, and hydrochloric acid can be sufficiently dissolved. Preferably, the driving motor drives the high-efficiency centrifugal machine to rotate positively for 1-3 min at the rotating speed of 400-550 r/min.
Step two, high-speed centrifugal separation: the high-efficiency centrifuge is driven by the driving motor to rotate at a high speed (> 1000 r/min), at the moment, due to the fact that the rotating speed of the centrifuge is high and the generated centrifugal force is large, the particulate matters 15 gradually and completely enter between the first inner chamber 13 and the second inner chamber 14 in the inner chamber along with the rotation of the inner chamber and rotate along the side wall of the second inner chamber 14, the AC foaming agent passes through holes in the inner chamber under the action of the centrifugal force and is deposited on the side wall of the outer chamber 12, then a liquid discharge port of the centrifuge is opened, and clarified liquid is discharged, and primary acid is obtained. Preferably, the driving motor drives the centrifuge to rotate for 3-7 min at the rotating speed of 1000-1700 r/min.
Further, the AC foaming agent is subjected to second to fifth centrifugal washing by sequentially using the second centrifugal washing water, the third centrifugal washing water and the clear water according to the operation sequence and requirements of the first centrifugal washing process.
The arrangement of the first inner chamber 13 and the second inner chamber 14, on the one hand, enables the AC foaming agent precipitate to be separated from the particulate matter 15, facilitating the discharge of the AC foaming agent precipitate; on the other hand, the particles 15 can disperse the AC foaming agent precipitate during the low-speed centrifugation process, so as to facilitate the sufficient washing of the particles, and during the high-speed centrifugation process, the particles 15 can be located in a relatively independent space, so as to reduce the impact and abrasion of the particles 15 on the AC foaming agent precipitate, which is beneficial to maintaining the original particle size distribution of the AC foaming agent precipitate.
Example 7
In the preparation process of the AC foaming agent, in order to prepare the foaming agent with uniform particle size, the reactants need to be uniformly stirred in the reaction process, so that the reactants are uniformly heated and uniformly distributed.
Specifically, as shown in fig. 2 to 5, the double-circulation reaction kettle includes an inner cylinder 1 and a cover body 2 covering the inner cylinder 1, the center of the inner cylinder 1 is connected to a second driving motor 6 through a second driving shaft 5, the center of the cover body 2 is connected to a first driving motor 4 through a first driving shaft 3, the end of the second driving shaft 5 located at the inner side of the bottom of the inner cylinder 1 is provided with a stirring blade 7, the second driving motor 6 can drive the stirring blade 7 to rotate through the second driving shaft 5, one end of the first driving shaft 3 close to the inner cylinder 1 is provided with a water pressing disc 10, the water pressing disc 10 is located at one side of the cover body 2 close to the inner cylinder 1, the water pressing disc 10 is accommodated in a hollow cylindrical water distribution cover 8, the water distribution cover 8 is provided with water through holes 9, and the first driving motor 4 can drive the water pressing disc 10 through the first driving shaft 3 to make a circulating reciprocating motion in the water distribution cover 8 along its central axis.
Further, an outer cylinder is arranged on the outer side of the inner cylinder 1, and a heating structure is arranged between the outer cylinder and the inner cylinder 1.
Preferably, the projection area of the stirring blade 7 on the bottom of the inner cylinder 1 gradually increases from the end close to the second driving shaft 5 to the end far from the second driving shaft 5.
More preferably, as shown in fig. 5, the stirring vanes 7 extend spirally from the center to the edge of the inner cylinder 1, and the stirring vanes 7 extend spirally from a side close to the bottom of the inner cylinder 1 to a side away from the bottom of the inner cylinder 1. The cross-sectional area of the stirring blade 7 is gradually reduced from the side close to the bottom of the inner cylinder 1 to the side far away from the bottom of the inner cylinder 1. The spiral structure of the stirring blade 7 is beneficial to the formation of circulation on one hand, and is beneficial to the consistency of the angular velocities of circulation in the horizontal direction on different radiuses on the other hand, so that the angular velocity of the fluid at the center is not easy to be large, and the angular velocity of the fluid at the edge is not easy to be small.
Preferably, the number of the stirring vanes 7 is 2 to 8.
The existing oxidation kettle is generally provided with a stirring structure in the center, for example, a stirring paddle is arranged at the central axis, when the stirring structure in the center is used, a circulation flow distributed along the horizontal direction should be formed in the reaction kettle through the rotation of the stirring structure, so that the reactant and the temperature are uniformly distributed. However, due to the differences in density and morphology of the reaction materials, the centrifugal force applied is not uniform, so that the distribution of the reaction materials is often uneven, and particularly, the reaction liquid at the center and at the edge is often stirred unevenly, so that the temperature and the density of the reaction materials are greatly different, and the preparation of the precipitate particles with uniform particle size is greatly limited.
During the oxidation reaction, on one hand, the double-circulation reaction kettle of the embodiment can generate a circulation in a horizontal direction in the double-circulation reaction kettle through the rotation of the stirring blade 7; on the other hand, a circulation flow in a vertical direction can be generated by the up-and-down reciprocating motion of the water pressing disk 10. Through the circulation in the horizontal direction and the vertical direction, the temperature, the density and the like of the reaction liquid in the double circulation reaction kettle can reach a highly consistent state, and further the particle size uniformity of the generated precipitate is improved.
Specifically, when the water pressing disc 10 moves downwards, the reaction liquid below the water pressing disc 10 is subjected to the pressure of the water pressing disc 10, and flows outwards from the inside of the water diversion cover 8, while negative pressure is generated above the water pressing disc 10, and under the action of the negative pressure, the upper liquid outside the water diversion cover 8 flows towards the inside of the water diversion cover 8; when the water pressing disc 10 moves upwards, reaction liquid above the water pressing disc 10 is pushed by the water pressing disc 10 to flow outwards from the water distribution cover 8, negative pressure is generated below the water pressing disc 10, liquid below the water distribution cover 8 flows towards the water distribution cover 8 under the action of the negative pressure, and then a vertical circulation is formed in the double-circulation reaction kettle, particularly in the center.
Comparative example 1
(1) Preparing biurea;
adding a hydrazine hydrate solution with the mass concentration of 22% into a condensation kettle, adding a urea solution into the condensation kettle, so that the mass ratio of hydrazine hydrate to urea in the hydrazine hydrate solution is 1.2, dropwise adding concentrated sulfuric acid with the concentration of 98% at the temperature of 135 ℃ and the pressure of 0.22MPa for condensation reaction, cooling to 85 ℃ when the concentration of residual hydrazine hydrate in a reaction liquid in the condensation kettle is less than 1g/L, discharging, performing solid-liquid separation, washing and drying a solid phase, and obtaining a biurea finished product;
(2) Preparation of fine-particle-size AC foaming agent:
preparing biurea and water into suspension with the content of biurea of 20 percent kg/L, adding inorganic acid to adjust the acidity of a reaction system to ensure that the acidity is between 4.0mol/L, adding sodium bromide or potassium bromide serving as a catalyst with the concentration of 0.3 percent, opening a cover body of a double-circulation reaction kettle, adding the prepared biurea suspension into the double-circulation reaction kettle, introducing chlorine gas, stirring and simultaneously heating to 30 ℃ to prepare the fine-grain-size AC foaming agent.
(3) Adding AC foaming agent powder seed crystal:
sampling, analyzing and monitoring the AC foaming agent in the double-circulation reaction kettle once every 3min, and adding AC foaming agent powder seed crystals with the average particle size of 25 micrometers when the average particle size of the AC foaming agent reaches 8 micrometers.
(4) Preparation of bimodal AC blowing agent:
and continuously stirring, carrying out heat preservation reaction for 6.5 hours, cooling, and carrying out suction filtration to obtain the AC foaming agent with bimodal distribution.
Comparative example 2
(1) Preparing biurea;
adding a hydrazine hydrate solution with the mass concentration of 22% into a condensation kettle, adding a urea solution into the condensation kettle, so that the mass ratio of hydrazine hydrate to urea in the hydrazine hydrate solution is 1.2, dropwise adding hydrochloric acid with the concentration of 25% at the temperature of 135 ℃ and the pressure of 0.22MPa for condensation reaction, cooling to 85 ℃ when the concentration of residual hydrazine hydrate in a reaction liquid in the condensation kettle is less than 1g/L, discharging, performing solid-liquid separation, washing and drying a solid phase, and obtaining a biurea finished product;
(2) Preparation of fine-particle-size AC foaming agent:
preparing biurea and water into a suspension with the content of biurea of 20 percent kg/L, adding inorganic acid to adjust the acidity of a reaction system to ensure that the acidity is between 4.0mol/L, adding sodium bromide or potassium bromide serving as a catalyst with the concentration of 0.3 percent, opening a cover body of a reaction kettle, adding the prepared biurea suspension into the reaction kettle, introducing chlorine gas, heating to 30 ℃ while stirring, and preparing the fine-particle-size AC foaming agent. The reaction kettle is an electric heating type reaction kettle produced by the Weihai chemical machinery Co.
(3) Adding AC foaming agent powder seed crystal:
sampling, analyzing and monitoring the AC foaming agent in the double-circulation reaction kettle once every 3min, and adding AC foaming agent powder crystal seeds with the average particle size of 25 mu m when the average particle size of the AC foaming agent reaches 8 mu m.
(4) Preparation of bimodal AC blowing agent:
and continuously stirring, carrying out heat preservation reaction for 6.5 hours, cooling, and carrying out suction filtration to obtain the AC foaming agent with bimodal distribution.
Experimental example 1
The influence of the concentration of the inorganic acid during the preparation of biurea was investigated.
The reaction conditions of example 3 and comparative example 1 are shown in the following table:
it can be seen from table 1 that a higher yield of biurea can be obtained with 25% hydrochloric acid than with 98% concentrated sulfuric acid. Furthermore, during the experiment it was found that: by adopting the AC foaming agent centrifugal mother liquor with the hydrochloric acid mass concentration of 25% to replace the traditional 98% concentrated sulfuric acid for condensation reaction, the reaction process is easier to control, the yield of the biurea is stable, the reaction time and the reaction end point are controllable, the particle size distribution of the biurea is more uniform, the complex degree of the work of operators is reduced after the 98% concentrated sulfuric acid is replaced, and the production safety is higher.
Experimental example 2
The influence of an oxidation reaction container in the preparation process of the AC foaming agent is researched:
example 3 and comparative example 2 except that the reaction vessel was different, the reaction conditions and operation were the same, and when the average particle size of the AC foaming agent reached 8 μm and the reaction end point was reached, the samples of example 3 and comparative example 2 were sampled, and the particle size distribution of the samples was measured and analyzed by using a BECKMAN coddle LS200 laser particle sizer, us, and the results are shown in fig. 10 and fig. 11.
As can be seen from FIG. 10, when the average particle size of the AC blowing agent reached 8 μm, a more uniform particle size distribution was obtained with the double circulation oxidation reactor of the present invention, and the particle size ratio around 8 μm was higher. As can be seen from FIG. 11, the double-circular-flow oxidation reaction kettle of the present invention can obtain the AC foaming agent with more obvious bimodal characteristics and more uniform particle size distribution near each peak.
In addition, the ratio of the large-particle-size AC foaming agent to the small-particle-size AC foaming agent in the AC foaming agent can be adjusted by adjusting the amount of the added AC foaming agent powder seed crystal.
Experimental example 3
The impact of the bimodal AC blowing agent described herein on the barrier properties of the foamed material was investigated:
preparation of foam material 1: the preparation method comprises the following raw materials in parts by weight: 80 parts of polyvinyl chloride, 40 parts of dioctyl phthalate, 1 part of dispersant, 2 parts of stabilizer and 5 parts of AC foaming agent are poured into a mixer and stirred and mixed uniformly at the temperature of 60 ℃; plasticizing the uniformly mixed materials in an internal mixer at 140 ℃ for 5min, transferring the obtained materials to a double-roller open plasticator for further melting and plasticizing at 145 ℃ for 8min, introducing the plasticized materials into a foaming furnace at 180-220 ℃ for 2min, and cooling after foaming to obtain a foam material finished product. The AC foaming agent is the AC foaming agent with bimodal distribution prepared in the example 3 of the application.
(II) preparation of foam material 2: the preparation method comprises the following raw materials in parts by weight: 80 parts of polyvinyl chloride, 40 parts of dioctyl phthalate, 1 part of dispersant, 2 parts of stabilizer and 5 parts of AC foaming agent are poured into a mixer and stirred and mixed uniformly at the temperature of 60 ℃; plasticizing the uniformly mixed materials in an internal mixer at the plasticizing temperature of 140 ℃ for 5min, transferring the obtained materials to a double-roller open plasticator for further melting and plasticizing at the plasticizing temperature of 145 ℃ for 8min, introducing the plasticized materials into a foaming furnace at the foaming furnace temperature of 180-220 ℃ for foaming for 2min, and cooling after foaming to obtain a foam material finished product. The AC foaming agent was the AC foaming agent prepared in comparative example 2.
(III) preparation of foam 3: the preparation method comprises the following raw materials in parts by weight: 80 parts of polyvinyl chloride, 40 parts of dioctyl phthalate, 1 part of dispersant, 2 parts of stabilizer and 5 parts of AC foaming agent are poured into a mixer and stirred and mixed uniformly at the temperature of 60 ℃; plasticizing the uniformly mixed materials in an internal mixer at the plasticizing temperature of 140 ℃ for 5min, transferring the obtained materials to a double-roller open plasticator for further melting and plasticizing at the plasticizing temperature of 145 ℃ for 8min, introducing the plasticized materials into a foaming furnace at the foaming furnace temperature of 180-220 ℃ for foaming for 2min, and cooling after foaming to obtain a foam material finished product. The AC foaming agent is a commercially available AC foaming agent with the average particle size of 20 mu m.
(IV) preparation of foam 4: the preparation method comprises the following raw materials in parts by weight: 80 parts of polyvinyl chloride, 40 parts of dioctyl phthalate, 1 part of dispersant, 2 parts of stabilizer and 5 parts of AC foaming agent are poured into a mixer and stirred and mixed uniformly at the temperature of 60 ℃; plasticizing the uniformly mixed materials in an internal mixer at 140 ℃ for 5min, transferring the obtained materials to a double-roller open plasticator for further melting and plasticizing at 145 ℃ for 8min, introducing the plasticized materials into a foaming furnace at 180-220 ℃ for 2min, and cooling after foaming to obtain a foam material finished product. The AC foaming agent is a commercial AC foaming agent with the average particle size of 50 mu m.
And (V) testing the foam material 1, the foam material 2, the foam material 3 and the foam material 4, wherein the sound insulation coefficient is detected according to GBT23451-2009, the tensile strength is tested according to GB/T2568 by adopting a CTM2500 microcomputer control electronic universal material testing machine, and the heat conductivity is tested according to GB/T10294, and the test results are shown in the following table:
as can be seen from the above table, foams having higher sound damping and tensile strength and lower thermal conductivity can be made using the bimodal AC blowing agents described herein.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.
Claims (6)
1. The preparation method of the AC foaming agent with the uniform and controllable particle size is characterized by comprising the following steps:
(1) Preparation of biurea:
adding a hydrazine hydrate solution with the mass concentration of 20-23% into a condensation kettle, adding a urea solution into the condensation kettle, so that the mass ratio of hydrazine hydrate to urea in the hydrazine hydrate solution is 1;
(2) Preparation of fine-particle-size AC foaming agent:
preparing biurea and water into suspension with biurea content of 15-30 kg/L, adding inorganic acid to adjust the acidity of a reaction system to ensure that the acidity is 2.0-6.0 mol/L, adding sodium bromide or potassium bromide serving as a catalyst with the concentration of 0.25-0.4 kg/L, opening a cover body of a double-circulation reaction kettle, adding the prepared biurea suspension into the double-circulation reaction kettle, introducing chlorine gas, stirring and simultaneously heating to 25-35 ℃ to prepare a fine-particle-diameter AC foaming agent;
(3) Adding AC foaming agent powder seed crystal:
sampling, analyzing and monitoring the AC foaming agent in the double-circulation reaction kettle once every 2-5 min, and adding AC foaming agent powder seed crystals with the average particle size of 20-30 mu m when the average particle size of the AC foaming agent reaches 6-10 mu m;
(4) Preparation of bimodal AC blowing agent:
continuously stirring, reacting for 6-7 h under heat preservation, and cooling to obtain the AC foaming agent with bimodal distribution;
the inorganic acid is hydrochloric acid, and the mass concentration of the hydrochloric acid is 20-30%; the double-circulation reaction kettle comprises an inner cylinder (1) and a cover body (2) covering the inner cylinder (1), wherein the center of the inner cylinder (1) is connected with a second driving motor (6) through a second driving shaft (5), the center of the cover body (2) is connected with a first driving motor (4) through a first driving shaft (3), the end part, located on the inner side of the bottom of the inner cylinder (1), of the second driving shaft (5) is provided with a stirring blade (7), the second driving motor (6) can drive the stirring blade (7) to rotate, one end, close to the inner cylinder (1), of the first driving shaft (3) is provided with a water pressing disc (10), the water pressing disc (10) is located on one side, close to the inner cylinder (1), of the cover body (2), the water pressing disc (10) is accommodated in a hollow cylindrical water distribution cover (8), the water distribution cover (8) is provided with water through holes (9), and the first driving motor (4) can drive the water pressing disc (10) to make reciprocating motion in the water distribution cover (8) along the central axis thereof;
the projection area of the stirring blade (7) at the bottom of the inner cylinder (1) is gradually increased from one end close to the second driving shaft (5) to one end far away from the second driving shaft (5); the stirring blade (7) extends spirally from the center to the edge of the inner cylinder (1), the stirring blade (7) extends spirally from the side close to the bottom of the inner cylinder (1) to the side far away from the bottom of the inner cylinder (1), and the cross sectional area of the stirring blade (7) is gradually reduced from the side close to the bottom of the inner cylinder (1) to the side far away from the bottom of the inner cylinder (1); the number of the stirring blades (7) is 2-8.
2. The method for preparing an AC foaming agent with uniformly controllable particle size according to claim 1, which comprises the following steps:
(1) Preparation of biurea:
adding a hydrazine hydrate solution with the mass concentration of 22% into a condensation kettle, adding a urea solution into the condensation kettle, leading the mass ratio of hydrazine hydrate to urea in the hydrazine hydrate solution to be 1;
(2) Preparation of fine-particle-size AC foaming agent:
preparing a suspension of biurea and water with a biurea content of 20 kg/L, adjusting the acidity of the reaction system to 4.0mol/L by adding an inorganic acid, adding sodium bromide or potassium bromide as a catalyst in a concentration of 0.3 kg/L, opening the lid of a double-loop reactor, adding the prepared suspension of biurea to the double-loop reactor, introducing chlorine gas, and heating to 30 ℃ while stirring to prepare a fine-particle-size AC foaming agent;
(3) Adding AC foaming agent powder seed crystal:
sampling, analyzing and monitoring the AC foaming agent in the double-circulation reaction kettle once every 3min, and adding AC foaming agent powder crystal seeds with the average particle size of 25 micrometers when the average particle size of the AC foaming agent reaches 8 micrometers;
(4) Preparation of bimodal AC blowing agent:
and continuously stirring, keeping the temperature and reacting for 6.5 hours, and cooling to obtain the AC foaming agent with bimodal distribution.
3. The method for preparing the AC foaming agent with the uniformly-controlled particle size according to claim 1, wherein the step (4) comprises the steps of continuously stirring, carrying out heat preservation reaction for 6.5 hours, cooling to obtain oxidation mother liquor, and carrying out centrifugal washing on the oxidation mother liquor through a high-efficiency centrifugal machine to obtain the inorganic acid and the AC foaming agent with the bimodal distribution.
4. The method for preparing an AC foaming agent with uniformly controllable particle size according to claim 3, wherein the inorganic acid is hydrochloric acid.
5. The method for preparing an AC foaming agent with uniformly controllable particle size according to claim 4, wherein the step (4) comprises the steps of:
(41) Continuously stirring, carrying out heat preservation reaction for 6.5 hours, cooling to obtain oxidation mother liquor, and carrying out centrifugal separation on the oxidation mother liquor through the high-efficiency centrifugal machine to obtain AC foaming agent precipitate and centrifugal mother liquor;
(42) Performing five times of centrifugal washing on the AC foaming agent precipitate, respectively recovering removal liquid obtained by different times of centrifugal washing into different containers, mechanically applying the removal liquid obtained by different batches of centrifugal washing of the AC foaming agent, and taking the removal liquid obtained by the first centrifugal washing as a primary acid and taking the removal liquid obtained by the second centrifugal washing as a secondary acid;
(43) Directly recycling the centrifugal mother liquor with the hydrochloric acid mass concentration of 20% or more for condensation reaction, or mixing the centrifugal mother liquor with the hydrochloric acid mass concentration of less than 20% with the hydrochloric acid with high mass concentration to prepare the condensation reaction for preparing the biurea with the hydrochloric acid mass concentration of 20% or more;
(44) Mixing the primary acid with high-quality-concentration hydrochloric acid to prepare a condensation reaction for preparing biurea, wherein the mass concentration of the hydrochloric acid is 20% or more;
(45) And recovering the secondary acid for preparing biurea into an oxidation reaction kettle.
6. The method for preparing the AC foaming agent with the uniformly controllable particle size according to claim 5, wherein the step (42) comprises five centrifugal washes of the AC foaming agent precipitate, the removal liquid of each centrifugal wash is recycled to a different container, and the removal liquid is reused for different batches of centrifugal washes of the AC foaming agent: and taking the removal liquid of the third centrifugal washing as the washing water of the next round of first centrifugal washing, taking the removal liquid of the fourth centrifugal washing as the washing water of the next round of second centrifugal washing, taking the removal liquid of the fifth centrifugal washing as the washing water of the next round of third centrifugal washing, introducing clean water as the washing water of the fourth centrifugal washing and the fifth centrifugal washing, sequentially carrying out five centrifugal washing on the AC foaming agent, taking the removal liquid of the first centrifugal washing as a primary acid, taking the removal liquid of the second centrifugal washing as a secondary acid, and regulating the amount of the clean water introduced in the fourth centrifugal washing and the fifth centrifugal washing so as to enable the mass concentration of hydrochloric acid in the primary acid and the secondary acid to be not higher than 30%.
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| CN101838224B (en) * | 2009-03-19 | 2013-01-09 | 华东理工大学 | Method for reducing grain size of AC foaming agent |
| CN102850243B (en) * | 2012-09-24 | 2013-12-11 | 杭州海虹精细化工有限公司 | Preparation method of ADC (azodicarbonamide) foaming agent with uniform grain diameter |
| CN102964275A (en) * | 2012-12-06 | 2013-03-13 | 杭州海虹精细化工有限公司 | Preparation method of azodicarbonamide (ADC) foaming agent having ultrafine particle size |
| CN104478764A (en) * | 2014-11-19 | 2015-04-01 | 杭州海虹精细化工有限公司 | Method for reducing particle size of foaming agent |
| CN104892464A (en) * | 2015-05-21 | 2015-09-09 | 杭州海虹精细化工有限公司 | Novel method of simply controlling particle sizes of ADC (azodicarbonamide) product |
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