CN111087325B - Polymerization inhibitor, preparation method thereof and application thereof in polyacrylonitrile production - Google Patents
Polymerization inhibitor, preparation method thereof and application thereof in polyacrylonitrile production Download PDFInfo
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- CN111087325B CN111087325B CN201811242768.4A CN201811242768A CN111087325B CN 111087325 B CN111087325 B CN 111087325B CN 201811242768 A CN201811242768 A CN 201811242768A CN 111087325 B CN111087325 B CN 111087325B
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- C08F20/00—Homopolymers and copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and only one being terminated by only one carboxyl radical or a salt, anhydride, ester, amide, imide or nitrile thereof
- C08F20/02—Monocarboxylic acids having less than ten carbon atoms, Derivatives thereof
- C08F20/42—Nitriles
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Abstract
The invention belongs to the technical field of polyacrylonitrile production, and particularly relates to a polymerization inhibitor, and further discloses a preparation method and application of the polymerization inhibitor in polyacrylonitrile production. The polymerization inhibitor is prepared from 2, 6-tetramethyl-4-piperidinol and amine oxide free radical compounds serving as compound raw materials, is in a liquid form, can be dissolved in water and acrylonitrile monomers, can be prepared into aqueous solution with any proportion for use, can also be directly added into recovered monomers, can be prepared into a solution with a certain concentration and then is adjusted to be alkaline by adjusting the pH value of the solution system, so that the polymerization inhibition effect of the polymerization inhibitor is optimal, the problems of poor compatibility with water, poor polymerization inhibition effect and low efficiency of the existing polymerization inhibitor are solved, and remarkable economic benefit and social benefit can be brought to a polyacrylonitrile production device.
Description
Technical Field
The invention belongs to the technical field of polyacrylonitrile production, and particularly relates to a polymerization inhibitor, and further discloses a preparation method and application of the polymerization inhibitor in polyacrylonitrile production.
Background
Polyacrylonitrile is a polymer obtained by radical polymerization of acrylonitrile, which is a monomer, and acrylonitrile units in the macromolecular chain are connected in a joint-tail manner. The polyacrylonitrile is mainly used for preparing polyacrylonitrile fiber, namely acrylic fiber. The polyacrylonitrile fiber has the advantages of good weather resistance, chemical reagent resistance and sun resistance, can keep 77 percent of the original strength after being placed outdoors for 18 months, and has the defects of low strength and poor wear resistance and fatigue resistance.
The existing polymerization process of acrylonitrile polymers is mainly ternary polymerization, usually adopted polymerization monomers comprise Acrylonitrile (AN), methyl Acrylate (MA) and Sodium Styrene Sulfonate (SSS), the adopted polymerization method is mainly aqueous suspension polymerization, a catalyst and AN activating agent are added to initiate polymerization after the pH value of a polymerization system is adjusted by sulfur dioxide, and Ethylene Diamine Tetraacetic Acid (EDTA) is adopted to terminate the reaction. However, in actual production, it is found that about 20% of the unreacted monomers still remain in the reaction system after the polymerization reaction is terminated in the prior art, and therefore, it is necessary to send the residual monomers to a recovery system for recovery in order to improve the efficiency of the polymerization reaction.
The recovery process of the unreacted monomer in the prior art mainly comprises the following steps: firstly, polymer slurry overflowing from a polymerization kettle is washed, filtered and the like to separate unreacted monomers in the slurry, and then the unreacted monomers are sent to a recovery system in the form of aqueous solution, wherein the concentration of the monomers (mainly AN, MA and SSS are low in content) is about 2%, and the filtrate is rectified, condensed, cooled, decanted and the like in the recovery system to obtain recovered monomers with the concentration of 99%; then the recovered monomer and fresh acrylonitrile monomer are mixed according to a certain proportion and then are used as main raw materials for polymer production and sent to a polymerization kettle for polymerization. In the monomer recovery process, in order to prevent the acrylonitrile monomer from self-polymerizing, a polymerization inhibitor such as Hydroquinone (HQ) or p-hydroxyanisole (MEHQ) is generally added to improve the monomer recovery efficiency.
However, in practical application, the problem that polymerization inhibition effect of hydroquinone or p-hydroxyanisole used in the prior art is poor, and polymer scaling and blocking are still frequently generated on a tower tray at the top of a monomer recovery tower and a condenser at the top in a recovery system is also caused, so that material loss or device shutdown is caused due to blockage of the units and equipment, and long-period safe and stable operation of a polyacrylonitrile device is seriously influenced and restricted. On the other hand, in order to prolong the production cycle, the amount of the polymerization inhibitor needs to be increased, but the increase of the amount of the polymerization inhibitor causes the increase of the amount of the polymerization inhibitor entering a polymerization system, thereby affecting the polymerization reaction, causing the increase of the polymerization time and the deterioration of the product performance. Meanwhile, hydroquinone or p-hydroxyanisole is a solid, and needs to be prepared into an aqueous solution to be added when in use, but due to the fact that the water solubility is low, the preparation concentration is low, the preparation time is long, and flying dust is easily caused in the preparation process to influence the body health of workers.
In order to solve the above problems, for example, chinese patent CN106905188A discloses a ternary composite polymerization inhibitor to reduce the tendency of acrylonitrile self-polymerization, but the polymerization inhibitor mainly aims at the problem of acrylonitrile self-polymerization, and does not consider the residual initiator in the subsequently recovered monomer and the influence of the residual polymerization inhibitor on the polymerization of acrylonitrile. Therefore, it is necessary to find a suitable polymerization inhibitor which not only increases the polymerization inhibiting effect on the recovered monomer, but also helps to alleviate the fouling problem of the monomer recovery column, does not affect the polymerization reaction, and has positive significance for the polymerization process of polyacrylonitrile.
Disclosure of Invention
Therefore, the technical problem to be solved by the invention is to provide a polymerization inhibitor, which can greatly prolong the polymerization time of the recovered monomer, thereby effectively inhibiting polymerization caused by the initiator remaining in the recovered monomer, greatly prolonging the production operation cycle of the device, and simultaneously, the residual initiator does not influence the subsequent acrylonitrile polymerization.
In order to solve the technical problem, the polymerization inhibitor comprises the following components in a mass ratio of 5-10:1-4 of 2, 6-tetramethyl-4-piperidinol and amine oxide radical compounds.
Preferably, the mass ratio of the 2, 6-tetramethyl-4-piperidinol to the amine oxide radical compound is 6-8:2-3.
In particular, the amine oxidizes a radical compound, the radical of which has a structure such as RNH or R 2 NH, wherein R is a hydrocarbyl group.
Preferably, the amine oxide radical compound is 1, 1-diphenyl-2-picrylhydrazine.
Preferably, the polymerization inhibitor of the present invention further comprises an auxiliary polymerization inhibitor.
Specifically, the polymerization-assistant inhibitor comprises beta-phenyl naphthylamine.
The invention also discloses a method for preparing the polymerization inhibitor, which comprises the step of mixing a selected amount of the 2, 6-tetramethyl-4-piperidinol and amine oxide free radical compounds.
Preferably, the method for preparing the polymerization inhibitor further comprises the step of adding NaOH or KOH to adjust the pH value of the polymerization inhibitor to 9-10.
The invention also discloses application of the polymerization inhibitor in polyacrylonitrile production.
Specifically, the polymerization inhibitor is added into the liquid phase of the polyacrylonitrile production device, and the adding concentration of the polymerization inhibitor is controlled to be 2.5-25ppm, preferably 5-15ppm.
The invention also discloses a polyacrylonitrile polymerization process, which comprises the step of mixing the polymerization inhibitor and the material to be recovered and injecting the mixture into a recovery tower, and preferably, the polymerization inhibitor is injected continuously on line.
The polymerization inhibitor is prepared by taking 2, 6-tetramethyl-4-piperidinol and amine oxide free radical compounds as compound raw materials, is in a liquid form, can be dissolved in water and acrylonitrile monomers, can be prepared into aqueous solution in any proportion for use, can also be directly added into recycled monomers, can be prepared into a certain concentration, and then is adjusted to be alkaline by adjusting the pH value of a solution system, so that the polymerization inhibition effect of the polymerization inhibitor is optimal. Meanwhile, the toxicity of the product is far lower than that of the currently adopted MEHQ and other products, and the product belongs to a low-toxicity and high-efficiency polymerization inhibitor. The polymerization inhibitor is added into a polyacrylonitrile recovery system, and under the condition of the same dosage as the existing polymerization inhibitor, the operation cycle of the recovery system can be effectively prolonged, so that the polymerization caused by the residual initiator in the recovered monomer can be effectively inhibited, the production operation cycle of the device is greatly prolonged, meanwhile, the residual polymerization inhibitor can not generate any influence on subsequent acrylonitrile ternary polymerization reaction products and downstream devices, the use is safe and environment-friendly, the problems of poor compatibility with water, poor polymerization inhibition effect and low efficiency of the existing polymerization inhibitor are solved, and the obvious economic benefit and social benefit can be brought to a polyacrylonitrile production device.
When the polymerization inhibitor is used, a high-concentration aqueous solution can be prepared and added into a recovery system, and compared with the existing polymerization inhibitors such as hydroquinone and the like which have poor solubility with water and cause the low concentration of the aqueous solution and need a large amount of water, the polymerization inhibitor greatly reduces the addition of water and effectively reduces the energy consumption and material consumption required by water recovery of a device. After the polymerization inhibitor is used, the cleaning period of the polyacrylonitrile recovery system is changed from 2-year cleaning to 4-year cleaning, so that the energy and the cost are effectively saved.
Detailed Description
Example 1
The polymerization inhibitor described in this example contained 5kg of 2, 6-tetramethyl-4-piperidinol and 1kg of 1, 1-diphenyl-2-picrylhydrazine.
The preparation method of the polymerization inhibitor comprises the following steps: mixing a selected amount of 2, 6-tetramethyl-4-piperidinol and 1, 1-diphenyl-2-picrylhydrazine, and adding NaOH or KOH to adjust the pH value of the polymerization inhibitor to 9-10.
Example 2
The polymerization inhibitor described in this example contained 5kg of 2, 6-tetramethyl-4-piperidinol and 2kg of 1, 1-diphenyl-2-picrylhydrazine.
The preparation method of the polymerization inhibitor comprises the following steps: mixing a selected amount of 2, 6-tetramethyl-4-piperidinol and 1, 1-diphenyl-2-picrylhydrazine, and adding NaOH or KOH to adjust the pH value of the polymerization inhibitor to 9.
Example 3
The polymerization inhibitor described in this example contained 6kg of 2,2,6,6-tetramethyl-4-piperidinol and 2kg of 1, 1-diphenyl-2-picrylhydrazine.
The preparation method of the polymerization inhibitor comprises the following steps: mixing a selected amount of 2, 6-tetramethyl-4-piperidinol and 1, 1-diphenyl-2-picrylhydrazine, and adding NaOH or KOH to adjust the pH value of the polymerization inhibitor to 9-10 to obtain the product.
Example 4
The polymerization inhibitor described in this example contained 8kg of 2,2,6,6-tetramethyl-4-piperidinol and 3kg of 1, 1-diphenyl-2-hydrazineol.
The preparation method of the polymerization inhibitor comprises the following steps: mixing a selected amount of 2, 6-tetramethyl-4-piperidinol and 1, 1-diphenyl-2-picrylhydrazine, and adding NaOH or KOH to adjust the pH value of the polymerization inhibitor to 9-10 to obtain the product.
Example 5
The polymerization inhibitor described in this example contained 10kg of 2, 6-tetramethyl-4-piperidinol and 3kg of 1, 1-diphenyl-2-picrylhydrazine.
The preparation method of the polymerization inhibitor in this embodiment includes: mixing a selected amount of 2, 6-tetramethyl-4-piperidinol and 1, 1-diphenyl-2-picrylhydrazine, and adding NaOH or KOH to adjust the pH value of the polymerization inhibitor to 9-10.
Example 6
The polymerization inhibitor described in this example contained 10kg of 2,2,6,6-tetramethyl-4-piperidinol and 4kg of 1, 1-diphenyl-2-hydrazineol.
The preparation method of the polymerization inhibitor comprises the following steps: mixing a selected amount of 2, 6-tetramethyl-4-piperidinol and 1, 1-diphenyl-2-picrylhydrazine, and adding NaOH or KOH to adjust the pH value of the polymerization inhibitor to 10.
Example 7
The polymerization inhibitor described in this example contained 6kg of 2,2,6,6-tetramethyl-4-piperidinol, 4kg of 1, 1-diphenyl-2-picrylhydrazine, and 2kg of β -phenylnaphthylamine.
The preparation method of the polymerization inhibitor in this embodiment includes: mixing selected amounts of the 2, 6-tetramethyl-4-piperidinol, the 1, 1-diphenyl-2-picrylhydrazine and the beta-phenyl naphthylamine, and adding NaOH or KOH to adjust the pH value of the polymerization inhibitor to 9-10 to obtain the product.
Comparative example 1
The polymerization inhibitor adopts the conventional product in the prior art, namely 10kg of hydroquinone is taken.
Comparative example 2
The polymerization inhibitor adopts the conventional product in the prior art, namely 6kg of p-hydroxyanisole.
Comparative example 3
The polymerization inhibitor of the comparative example adopts a conventional product in the prior art, namely 15kg of butyl hydroxy anisol and 3kg of tert-butyl catechol.
Examples of the experiments
1. Solubility test
The solubility of the polymerization inhibitors obtained in examples 1 to 7 and comparative examples 1 to 3 was measured by mutual solubility in water.
Because hydroquinone and other substances have poor solubility with water, the comparative examples 1-3 can only be prepared into aqueous solution with the concentration of 1%, and after the concentration is increased, the polymerization inhibitor can be layered with water, so that the dispersion effect is poor; the polymerization inhibitors prepared in examples 1 to 7 of the present invention can be prepared in solutions with a concentration of 15%. Therefore, the polymerization inhibitor has good intersolubility with water, and can be prepared into aqueous solution for use in practical application.
2. Test of polymerization inhibition effect at different pH values
The polymerization inhibitors prepared in the above examples 1-2 were added to the recovered monomers in appropriate amounts, and the total reflux operation was carried out under the following pH conditions (operation temperature 85 ℃ C.), and then the polymerization times of bletilla striata after addition of different polymerization inhibitor products were measured, and the results are shown in Table 1 below.
TABLE 1 polymerization inhibiting effect of polymerization inhibitor at different pH values
As can be seen from Table 1 above, the polymerization inhibitor has a lower polymerization inhibiting effect at weakly acidic and neutral pH values than at weakly alkaline pH values.
3. Test of polymerization inhibition effect in practical application
The polymerization inhibitors prepared in the above examples 1 to 7 and comparative examples 1 to 3 were added to the recovered monomers, and the total reflux operation was performed under alkaline pH conditions (operation temperature 85 ℃ C.), and then the polymerization time and the amount of the polymerization inhibitor were measured after the addition of air and various polymerization inhibitor products, and the results are shown in Table 2 below.
TABLE 2 results of using polymerization inhibitors of comparative examples and examples
| Amount of polymerization inhibitor used, ppm | Polymerization time/min | |
| Blank sample | - | 6min30s |
| Comparative example 1 | 50 | 7min30s |
| Comparative example 2 | 50 | 7min35s |
| Comparative example 3 | 50 | 9min30s |
| Example 1 | 50 | 45min |
| Example 2 | 50 | 47min |
| Example 3 | 50 | 45min30s |
| Example 4 | 50 | 48min |
| Example 5 | 50 | 44min |
| Example 6 | 50 | 46min45s |
| Example 7 | 50 | 65min |
As can be seen from the above table 2, the polymerization inhibition effect of the polymerization inhibitor product of the invention on the recovered monomers is far greater than that of the conventional polymerization inhibitors such as MEHQ, HQ and the like under the same concentration, and after the polymerization inhibitor is added, the polymerization inhibition effect of the polymerization inhibitor is greatly improved compared with that of two polymerization inhibitors.
4. Test of polymerization inhibition effect of different amounts of polymerization inhibitor
The polymerization inhibitors prepared in the above examples 1 to 7 and comparative examples 1 to 3 were added to the recovered monomers in the amounts selected in the following table, and the total reflux operation was performed under alkaline conditions of pH (operation temperature 85 ℃), and then the polymerization time and the amount of the polymerization inhibitor were measured after the addition of different amounts of the polymerization inhibitor, and the results are shown in the following table 3.
TABLE 3 results of using polymerization inhibitors for comparative examples and examples
| Amount of polymerization inhibitor used, ppm | Polymerization time/min | |
| Blank sample | - | 6min30s |
| Comparative example 1 | 50 | 7min30s |
| Comparative example 2 | 50 | 7min35s |
| Comparative example 3 | 50 | 9min30s |
| Example 1 | 5 | 45min |
| Example 2 | 7 | 47min |
| Example 3 | 6 | 45min30s |
| Example 4 | 7 | 48min |
| Example 5 | 8 | 44min |
| Example 6 | 7 | 46min45s |
| Example 7 | 3 | 45min |
As can be seen from Table 3, the amount of the polymerization inhibitor prepared in the examples of the present invention is much smaller than that of the conventional polymerization inhibitor under the same polymerization time of acrylonitrile.
5. Influence of polymerization inhibitor on product performance of acrylonitrile ternary polymerization system
The polymerization inhibitors prepared in the above examples 1 to 7 were added to the recovered monomer of the acrylonitrile terpolymer system, and the total reflux operation was performed under the alkaline condition of pH (operation temperature 85 ℃), and then the performance of the product prepared from air and different products at different polymerization times was tested, and the results are shown in table 4 below.
TABLE 4 influence of polymerization inhibitors on the acrylonitrile terpolymerization system and product Properties
| Polymerization time/min | Product performance | |
| Blank sample | 3min30s | Superior food |
| Practice ofExample 1 | 3min45s | Youyou (an instant noodle) |
| Example 2 | 3min50s | Youyou (an instant noodle) |
| Example 3 | 3min45s | Youyou (an instant noodle) |
| Example 4 | 3min25s | Youyou (an instant noodle) |
| Example 5 | 4min05s | Superior food |
| Example 6 | 4min10s | Superior food |
| Example 7 | 4min50s | Youyou (an instant noodle) |
As can be seen from Table 4, the polymerization inhibitor prepared by the present invention has no adverse effect on the polymerization time and product performance of subsequent polyacrylonitrile after being added, and can be used for the polymerization of polyacrylonitrile.
It should be understood that the above examples are only for clarity of illustration and are not intended to limit the embodiments. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. And obvious variations or modifications therefrom are within the scope of the invention.
Claims (6)
1. The polymerization inhibitor for producing polyacrylonitrile is characterized by being prepared by the following method, wherein the method comprises the following steps of: 1-4 of 2, 6-tetramethyl-4-piperidinol and 1, 1-diphenyl-2-picrylhydrazine, and further comprises a step of adding NaOH or KOH to adjust the pH value of the polymerization inhibitor to 9-10.
2. The polymerization inhibitor according to claim 1, wherein the mass ratio of the 2, 6-tetramethyl-4-piperidinol to the 1, 1-diphenyl-2-picrylhydrazine is 6-8:2-3.
3. Use of the polymerization inhibitor according to claim 1 or 2 in the production of polyacrylonitrile.
4. The use according to claim 3, wherein the polymerization inhibitor is added to the liquid phase of the polyacrylonitrile production apparatus at a concentration controlled within a range of 2.5 to 25ppm.
5. A process for polymerizing polyacrylonitrile, characterized by comprising a step of mixing the polymerization inhibitor described in claim 1 with a material to be recovered and injecting the mixture into a recovery column.
6. The polymerization process according to claim 5, wherein the polymerization inhibitor is injected continuously in-line.
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Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1443748A (en) * | 2002-03-12 | 2003-09-24 | 株式会社日本触媒 | Polymerization inhibition of (methyl) acrylic ester |
| JP2007161624A (en) * | 2005-12-12 | 2007-06-28 | Tosoh Corp | Method for producing high purity fluorine-containing (meth)acrylate ester |
| CN102126910A (en) * | 2010-12-15 | 2011-07-20 | 兰州大洋化学有限责任公司 | Butadiene polymerization inhibitor used in separation system of ethylene unit |
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Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1443748A (en) * | 2002-03-12 | 2003-09-24 | 株式会社日本触媒 | Polymerization inhibition of (methyl) acrylic ester |
| JP2007161624A (en) * | 2005-12-12 | 2007-06-28 | Tosoh Corp | Method for producing high purity fluorine-containing (meth)acrylate ester |
| CN102126910A (en) * | 2010-12-15 | 2011-07-20 | 兰州大洋化学有限责任公司 | Butadiene polymerization inhibitor used in separation system of ethylene unit |
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