CN107366021B

CN107366021B - Induced nucleation crystallization process for preventing dimethyl azodiisobutyrate storage hardening

Info

Publication number: CN107366021B
Application number: CN201710526186.8A
Authority: CN
Inventors: 王学重; 李敏章; 张扬; 姚金宇
Original assignee: South China University of Technology SCUT
Current assignee: South China University of Technology SCUT
Priority date: 2017-06-30
Filing date: 2017-06-30
Publication date: 2020-09-22
Anticipated expiration: 2037-06-30
Also published as: CN107366021A

Abstract

The invention discloses an induced nucleation crystallization process for preventing dimethyl azodiisobutyrate storage plate from hardening. The process adopts an induced crystallization method, under the stirring, seed crystals are added into the solution of the dimethyl azodiisobutyrate to perform induced crystallization to prepare crystal nuclei, and then the crystal nuclei are cooled to perform secondary crystallization to obtain the dimethyl azodiisobutyrate crystal. The dimethyl azodiisobutyrate crystal obtained by the process has regular shape, large granularity, uniform distribution and good particle fluidity, can reduce the contact area among crystal particles, improve the filtration efficiency, has no hardening phenomenon after being refrigerated and stored for three months, keeps good particle fluidity, solves the problem of easy hardening in the existing dimethyl azodiisobutyrate crystal storage process, and is convenient for the storage, transportation and subsequent use of the dimethyl azodiisobutyrate crystal; meanwhile, the method has the advantages of simple and easy operation of the process, good reproducibility and easy realization of industrial production.

Description

Induced nucleation crystallization process for preventing dimethyl azodiisobutyrate storage hardening

Technical Field

The invention relates to the technical field of dimethyl azodiisobutyrate crystallization processes, in particular to an induced nucleation crystallization process for preventing dimethyl azodiisobutyrate storage hardening.

Background

Dimethyl azodiisobutyrate (2, 2' -azobis (2-methylpropionate), AIBME) is also named as V-601, and the molecular formula is C₁₀H₁₈N₂O₄The chemical structural formula is shown as formula I, the molecular weight is 230.3, and the melting point is 22-28 ℃.

Dimethyl azodiisobutyrate is insoluble in water, soluble in organic solvents such as methanol, toluene and the like, is an oil-soluble azo free radical reaction initiator, has the characteristics of moderate initiation activity, easy control of polymerization reaction and the like, and is widely used as an initiator in the production of polymer polyol (POP). However, most of the commercially available compound products have short storage period, hardening phenomenon of the products occurs in about three months, the free flowing state of the products is damaged, manual or mechanical damage treatment is needed before use, danger such as explosion easily occurs, production is inconvenient, and safe use needs to be solved urgently. Crystallization is a key production step to obtain its solid form from its synthesis mother liquor. At present, few documents are available on the crystallization of dimethyl azobisisobutyrate, and Chinese patents CN 101481326A and CN 104945275A mention reports on the preparation method of dimethyl azobisisobutyrate, but there is no introduction on the crystal shape and the method for preventing hardening.

The hardening is caused by caking, which is a common phenomenon in solid storage, and is more obvious in humid and hot seasons, long-term storage and package and extrusion. The currently widely accepted crystal agglomeration mechanism is the crystal bridge theory: due to the influence of the factors of the crystal (the property, chemical composition, granularity distribution and the geometric shape of the crystal) and the external factors (humidity, temperature, pressure, impurities and the like), the surface of the crystal is dissolved and recrystallized, so that crystal bridges are formed on mutual contact points among crystal grains, and the crystal grains are bonded together to gradually form huge lumps. The main measures for preventing the crystal from caking are: controlling the product particle size distribution, improving the drying operation to reduce the moisture content, granulating to reduce the contact among particles, reducing the packaging environment humidity, adding a small amount of anti-caking additive and the like. Dimethyl azodiisobutyrate melts at room temperature, so that it is difficult to prevent crystal agglomeration in drying, granulating and other operations, and the product is a polymerization initiator and has high purity requirement, so that addition of an anti-agglomeration additive is not allowed. Therefore, the selection of the process for controlling the product particle size distribution by optimizing the crystallization process becomes an important measure for reducing or preventing the agglomeration of the crystals of dimethyl azodiisobutyrate.

Disclosure of Invention

Aiming at the defects of the prior art, the invention provides an induced nucleation crystallization process for preventing the hardening of the dimethyl azobisisobutyrate storage plate, the granularity of the dimethyl azobisisobutyrate crystal prepared by the process is large, the fluidity is good, and the problem of hardening easiness of the dimethyl azobisisobutyrate crystal in the storage process is solved.

The purpose of the invention is realized by the following technical scheme.

The method adopts an induced crystallization method, under the stirring, seed crystals are added into dimethyl azodiisobutyrate solution to perform induced crystallization to prepare crystal nuclei, and then the crystal nuclei are cooled and crystallized for the second time to obtain dimethyl azodiisobutyrate crystals.

The specific technical scheme of the invention is as follows.

An induced nucleation crystallization process for preventing the hardening of dimethyl azodiisobutyrate storage plates comprises the following steps:

(1) under the condition of stirring, adding seed crystals into the dimethyl azodiisobutyrate solution, uniformly mixing, using an online turbidity meter to assist in monitoring the process of induced nucleation, and carrying out primary crystallization under the condition of stirring;

(2) and after the first crystallization is finished, cooling, keeping stirring in the cooling process for second crystallization, performing suction filtration, washing and drying to obtain dimethyl azodiisobutyrate crystals, and refrigerating and storing.

Further, in the step (1), the solvent of the dimethyl azodiisobutyrate solution is an organic solvent or a mixed solvent of an organic solvent and water.

Further, in the step (1), the organic solvent includes one of methanol, ethanol and acetone.

Further, in the step (1), the seed crystal is azodiisobutyrate dimethyl ester crystal with the particle size of 300-800 μm.

Further, in the step (1), the temperature at the time of adding the seed crystal is in the temperature range of the metastable zone of crystallization of dimethyl azodiisobutyrate, preferably 0 to 20 ℃, and more preferably 0 to 10 ℃.

In step (1), the concentration of the dimethyl azodiisobutyrate solution is 0.3-1.0 g/g, preferably 0.7-1.0 g/g.

Further, in the step (1), the addition amount of the seed crystal is 1-5 wt%, preferably 1-3 wt% of the mass of the dimethyl azodiisobutyrate in the dimethyl azodiisobutyrate solution.

Further, in the step (1), the time of the first crystallization is 0.5 to 2 hours, preferably 0.5 to 1 hour, the crystallization temperature is kept at the temperature when the seed crystal is added, and the crystallization is carried out under stirring.

Further, in the step (2), the cooling rate is 3-15 ℃/h, preferably 6-12 ℃/h.

Further, in the step (2), the temperature for finishing the second crystallization is-5 to-10 ℃, preferably-5 to-6 ℃, the whole second crystallization process is carried out in the cooling process, the second crystallization is carried out while the temperature is reduced, and the temperature reached by the cooling process is the temperature for finishing the second crystallization.

Further, in the step (2), the washing is performed by using more than one of water, methanol, ethanol and acetone.

Further, in the step (2), the drying is carried out for 6-12 hours in a cold air drying environment lower than room temperature.

Further, in the step (2), the refrigerated storage is performed in a refrigerator at 5-10 ℃.

Further, in the steps (1) and (2), the rotation speed of stirring is 150-400 rpm, preferably 300-400 rpm, and the crystallization is carried out in a state of stirring in the whole process.

Compared with the prior art, the invention has the following advantages and beneficial effects:

(1) the dimethyl azodiisobutyrate crystal obtained by the process has the advantages of regular shape, large granularity, uniform distribution and good particle fluidity, and can reduce the contact area among crystal particles and improve the filtration efficiency;

(2) the dimethyl azodiisobutyrate crystal obtained by the process has no hardening phenomenon after being refrigerated and stored for three months, the particle fluidity is kept good, the problem that the existing dimethyl azodiisobutyrate crystal is easy to harden in the storage process is solved, and the dimethyl azodiisobutyrate crystal is convenient to store, transport and use subsequently;

(3) the method has the advantages of simple and easily-operated process, good reproducibility and easy realization of industrial production.

Drawings

FIG. 1 is a 5-fold microscopic image of the AIBME crystal in example 1;

FIG. 2 is a 5-fold microscope image of the AIBME crystal in example 2;

FIG. 3 is a 5-fold microscope image of the AIBME crystal in example 3;

FIG. 4 is a 5-fold microscopic image of the AIBME crystal in example 4;

FIG. 5 is a 5-fold microscopic image of the AIBME crystal in example 5;

FIG. 6 is a 5-fold microscope image of the AIBME crystal in example 6;

figure 7 is a graph comparing the malvern granulometer measurements of AIBME crystals of example 1 with AIBME crystals of example 2 after three months of storage.

Detailed Description

For better clarity of description of the objects, technical solutions and advantages of the present invention, the present invention will be further described in detail with reference to the accompanying drawings and specific embodiments. The specific embodiments described herein are merely illustrative of the invention and are not intended to be limiting.

The invention provides an induced nucleation crystallization process for preventing solidification of dimethyl azodiisobutyrate storage plates, which specifically comprises the following steps:

(1) under the stirring condition of 150-400 rpm, adding seed crystals with the mass of 1-5 wt% of dimethyl azodiisobutyrate in a solution at the temperature of 0-20 ℃ into the dimethyl azodiisobutyrate solution with the concentration of 0.3-1.0 g/g, monitoring the induced nucleation process by using an online turbidity meter in an auxiliary way, keeping the temperature of 0-20 ℃ when the seed crystals are added unchanged, and continuously stirring for 0.5-2 h to carry out primary crystallization;

(2) and after the first crystallization is finished, cooling at the speed of 3-15 ℃/h, keeping stirring and cooling to-5 to-10 ℃ in the cooling process, finishing the second crystallization, performing reduced pressure suction filtration and washing, drying for 6-12 h by cold air in an environment lower than room temperature to obtain dimethyl azodiisobutyrate crystals, and refrigerating and storing at the temperature of 5-10 ℃.

The seed crystal adopted in the specific embodiment of the invention is azodiisobutyrate dimethyl ester crystal with the particle size of 300-800 mu m.

In a specific embodiment of the invention, characterization of the prepared AIBME crystals includes:

and (4) microscopic observation: the microscopic image was taken by a BX-53 microscope from Olympus under a temperature condition of-5 ℃.

And (3) testing the granularity: the malvern particle sizer model Mastersizer 3000 was used, the measurement was dry, and the test was performed at below 20 ℃.

Example 1

The spontaneous nucleation crystallization process (namely the original process) for easy hardening of dimethyl azodiisobutyrate after storage specifically comprises the following steps:

adding 500g of AIBME and 500g of anhydrous methanol into a 2L jacket crystallization kettle, setting the water bath temperature to be 20 ℃, stirring at 150rpm to clarify the solution, continuously stirring, cooling to-5 ℃ at the cooling rate of 30 ℃/h, finishing crystallization, quickly performing suction filtration by using a precooled Buchner funnel, washing by using methanol refrigerated at 0 ℃, drying for 6h by using cold air under reduced pressure at 10 ℃, and storing the product in a refrigerator at 5 ℃.

The 5-fold microscopic image of the AIBME crystal is shown in figure 1, the AIBME crystal is a irregularly-shaped crystal, the crystal size is small, the crystal grains are easy to adhere, the flowability is poor, and the hardening is serious after the AIBME crystal is stored for three months.

Example 2

The induced nucleation crystallization process for preventing the solidification of the azodiisobutyrate dimethyl ester storage plate specifically comprises the following steps:

(1) adding 500g of AIBME and 500g of anhydrous methanol into a 2L jacket crystallization kettle, setting the water bath temperature to be 20 ℃, stirring at 250rpm to clarify the solution, cooling to 5 ℃ at the cooling rate of 6 ℃/h, adding 5g of seed crystal, and stirring at the constant temperature of 5 ℃ for 0.5h to perform primary crystallization;

(2) and after the first crystallization is finished, continuously stirring and cooling to-5 ℃ at a cooling rate of 6 ℃/h to finish the second crystallization, after the crystallization is finished, quickly performing suction filtration by using a precooled Buchner funnel, washing by using methanol refrigerated at the temperature of 0 ℃, drying for 12h by using reduced pressure cold air at the temperature of 10 ℃, and then storing the product in a refrigerator at the temperature of 5 ℃.

The yield is 76%, and the filtrate obtained by suction filtration can be repeatedly reused in the preparation process.

The 5-fold microscopic image of the AIBME crystal is shown in figure 2, the AIBME crystal is a quadrilateral or hexagonal massive crystal, the crystal has large granularity, uniform distribution and good fluidity, and the AIBME crystal does not cause hardening after being stored for three months.

Example 3

(1) adding 150g of AIBME and 500g of anhydrous methanol into a 2L jacket crystallization kettle, setting the water bath temperature to be 20 ℃, stirring at 400rpm to clarify the solution, cooling to 5 ℃ at a cooling rate of 15 ℃/h, adding 7.5g of seed crystal at the time of clarifying the solution, and stirring at the constant temperature of 5 ℃ for 2h to perform primary crystallization;

(2) and after the first crystallization is finished, continuously stirring and cooling to-10 ℃ at a cooling rate of 15 ℃/h to finish the second crystallization, after the crystallization is finished, quickly performing suction filtration by using a precooled Buchner funnel, washing by using methanol refrigerated at the temperature of 0 ℃, drying for 6h by using reduced pressure cold air at the temperature of 10 ℃, and then storing the product in a refrigerator at the temperature of 10 ℃.

The yield is 85%, and the filtrate obtained by suction filtration can be repeatedly reused in the preparation process.

The 5-fold microscopic image of the AIBME crystal is shown in figure 3, the AIBME crystal is a quadrilateral or hexagonal massive crystal, the crystal has large particle size, uniform distribution and good fluidity, a small amount of agglomeration phenomenon occurs after the AIBME crystal is stored for three months, and the AIBME crystal is dispersed after slight shaking.

Example 4

(1) adding 350g of AIBME and 500g of anhydrous methanol into a 2L jacket crystallization kettle, setting the water bath temperature to be 20 ℃, stirring at 400rpm to clarify the solution, cooling to 5 ℃ at a cooling rate of 3 ℃/h, adding 10.5g of seed crystal at the time of clarifying the solution, and stirring at the constant temperature of 5 ℃ for 1h to perform primary crystallization;

(2) and after the first crystallization is finished, continuously stirring and cooling to-5 ℃ at a cooling rate of 3 ℃/h to finish the second crystallization, after the crystallization is finished, quickly performing suction filtration by using a precooled Buchner funnel, washing by using methanol refrigerated at the temperature of 0 ℃, drying for 12h by using reduced pressure cold air at the temperature of 10 ℃, and then storing the product in a refrigerator at the temperature of 5 ℃.

The yield is 75%, and the filtrate obtained by suction filtration can be repeatedly reused in the preparation process.

The 5-fold microscopic image of the AIBME crystal is shown in FIG. 4, and the AIBME crystal is a quadrilateral or hexagonal massive crystal, has large crystal grain size, uniform distribution and good fluidity, and does not cause hardening after being stored for three months.

Example 5

(1) adding 500g of AIBME and 500g of anhydrous methanol into a 2L jacket crystallization kettle, setting the water bath temperature to be 20 ℃, stirring at 250rpm to clarify the solution, cooling to 5 ℃ at the cooling rate of 6 ℃/h, adding 15g of seed crystal, and stirring at the constant temperature of 5 ℃ for 0.5h to perform primary crystallization;

The yield is 80%, and the filtrate obtained by suction filtration can be repeatedly reused in the preparation process.

The 5-fold microscopic image of the AIBME crystal is shown in FIG. 5, and the AIBME crystal is a quadrilateral or hexagonal massive crystal, has large crystal grain size, uniform distribution and good fluidity, and does not cause hardening after being stored for three months.

Example 6

(1) adding about 400g of AIBME, 400g of anhydrous methanol and 171.4g of deionized water into a 2L jacket crystallization kettle, setting the water bath temperature to be 20 ℃, stirring at 400rpm to clarify the solution, cooling to 10 ℃ at a cooling rate of 15 ℃/h, still clarifying the solution, adding 20.0g of seed crystal, and stirring at the constant temperature of 8 ℃ for 1h to perform primary crystallization;

(2) and after the first crystallization is finished, continuously stirring and cooling to-5 ℃ at a cooling rate of 15 ℃/h, finishing the second crystallization, after the crystallization is finished, quickly performing suction filtration by using a precooled Buchner funnel, washing by using a water-methanol mixed solution (the mass ratio is 3:7) refrigerated at the temperature of 5 ℃, drying for 6h under reduced pressure and cold air at the temperature of 10 ℃, and then storing the product in a refrigerator at the temperature of 10 ℃.

The yield is 90%, and the filtrate obtained by suction filtration can be repeatedly reused in the preparation process.

The 5-fold microscopic image of the AIBME crystal is shown in FIG. 6, and the AIBME crystal is a quadrilateral or hexagonal massive crystal, has large crystal particle size, uniform distribution and good fluidity, has a small amount of agglomeration after being stored for three months, and can disperse after being slightly shaken.

From the observation of 5-fold microscope of the AIBME crystals prepared in examples 1 to 6, it can be seen that:

crystal particles of the AIBME crystal prepared in example 1 (original process) are easily adhered, and dispersion fluidity is poor; the AIBME crystals prepared in the embodiments 2-6 (the process of the invention) are all quadrilateral or hexagonal blocky crystals, and have large granularity, uniform distribution and good dispersibility.

The AIBME crystals prepared in example 1 (original process) have serious hardening phenomenon after being stored for three months at 5 ℃, while the AIBME crystals prepared in examples 2-6 (the process of the invention) have intact grains; the products of examples 2, 4 and 5 did not cake after three months of storage and were excellent in fluidity, and the products of examples 3 and 6 did not cake after three months of storage, but they were dispersed by slight shaking without affecting the subsequent use of the product.

And (3) comparing the measurement results of the Malvern particle analyzer:

the malvern granulometer measurements of AIBME crystals prepared in example 2 after three months of storage (curve a) and before hardening (curve B) are shown in fig. 7, as compared to AIBME crystals prepared in example 1 (original process), and it can be seen from fig. 7 that the crystal size of AIBME crystals prepared in example 2 is greatly improved compared to the original process.

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 and improvements made within the spirit and principle of the present invention are intended to be included within the scope of the present invention.

Claims

1. An induced nucleation crystallization process for preventing hardening of dimethyl azodiisobutyrate storage plates is characterized by comprising the following steps:

(1) under the condition of stirring, adding seed crystals into the dimethyl azodiisobutyrate solution, uniformly mixing, using an online turbidity meter to assist in monitoring the process of induced nucleation, and carrying out primary crystallization under the condition of stirring; the seed crystal is azodiisobutyrate dimethyl ester crystal with the particle size of 300-800 mu m; the temperature of the seed crystal during the addition is in the temperature range of the metastable zone of the crystallization of the dimethyl azodiisobutyrate; the rotating speed of the stirring is 150-400 rpm; the concentration of the dimethyl azodiisobutyrate solution is 0.3-1.0 g/g; the adding amount of the seed crystal is 1-5 wt% of the mass of the dimethyl azodiisobutyrate in the dimethyl azodiisobutyrate solution; the time of the first crystallization is 0.5-2 h, and the crystallization temperature is kept to be the temperature when the seed crystal is added;

(2) after the first crystallization is finished, cooling, and carrying out second crystallization while keeping stirring in the cooling process, wherein the cooling rate is 3-15 ℃/h; the temperature of the second crystallization is-5 to-10 ℃; filtering, washing and drying to obtain dimethyl azodiisobutyrate crystal, and refrigerating for storage.

2. The process of claim 1, wherein in the step (1), the solvent of the solution of dimethyl azobisisobutyrate is an organic solvent or a mixed solvent of an organic solvent and water; the organic solvent includes one of methanol, ethanol and acetone.

3. The process of claim 1, wherein in the step (1), the addition amount of the seed crystal is 1-3 wt% of the mass of the dimethyl azodiisobutyrate in the dimethyl azodiisobutyrate solution; the time of the first crystallization is 0.5-1 h, and the crystallization temperature is kept at the temperature when the seed crystal is added.

4. The process of claim 1, wherein in the step (2), the temperature reduction rate is 6-12 ℃/h; the temperature of the second crystallization is-5 to-6 ℃.

5. The process of claim 1, wherein in step (2), the washing is performed by rinsing with one or more of water, methanol, ethanol and acetone; the drying is carried out for 6-12 h in a cold air drying environment below room temperature; the refrigeration storage is performed in a refrigerator at 5-10 ℃.