CN112142880A - Continuous purification method of polymer polyol - Google Patents
Continuous purification method of polymer polyol Download PDFInfo
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- C08F6/00—Post-polymerisation treatments
- C08F6/001—Removal of residual monomers by physical means
Abstract
The invention relates to a continuous purification method of polymer polyol, which mainly solves the problems of high residual content of styrene monomers and acrylonitrile monomers in the polymer polyol, large odor and high VOC (volatile organic compounds) of the polymer polyol in the prior art. The present invention provides a continuous purification method of polymer polyol, which comprises the following steps: continuously, sequentially passing polymer polyol I containing 1.50-2.5% of acrylonitrile monomer and 1.85-2.5% of styrene monomer through a first-stage flash tank, a second-stage flash tank, a third-stage flash tank, a vibrating screen and a stripping tower in percentage by mass, and continuously obtaining polymer polyol II with the styrene content less than or equal to 5ppm and the acrylonitrile content less than or equal to 2 ppm.
Description
Technical Field
The present invention relates to a continuous purification method of polymer polyol.
Background
Polymer polyols are prepared on the basis of polyether polyols by grafting vinyl monomers onto the basic polyether polyol by free radical in situ polymerization. Polymer polyols are mainly used in the production of flexible polyurethane foams, and are widely used in life.
In the conventional process for preparing polymer polyol, styrene is introduced into vinyl monomers, so that the bearing capacity of a foam product is increased, and the appearance of the product is improved. In recent years, with environmental protection factors and requirements of downstream customers, polyurethane polyol products with excellent performance are increasingly demanded and are more and more strict, and polymer polyols with low odor, low VOC and low monomer residue are more and more favored.
In order to reduce the content of the residual monomers in the POP product, the treatment temperature generally needs to be increased or the treatment time needs to be prolonged; or by bubbling an inert gas. In the above process, although the residual monomer content of the POP product can be reduced, other problems are introduced. Such as raising the temperature or prolonging the treatment time, the acrylonitrile block gathered by the polymer is subjected to side reaction, and the product turns yellow and dark; and the load of a vacuum unit is increased by adopting an inert gas bubbling mode, the energy consumption and the cost are higher, and the aldehyde content in the POP product is increased more when steam stripping is adopted.
Chinese patent CN101333288 discloses a method for purifying polymer polyol by stripping using a packed column, but for polymer polyol, POP particles or residual monomers are easily scaled on the inner surface of the column and even block the pipeline under heated conditions, thereby affecting heat transfer efficiency and removal effect, and increasing the difficulty of operating and treating the equipment.
Chinese patent CN106866893A discloses a preparation method of polymer polyol with high solid content and low VOC, and step III discloses that the product of step II passes through a multi-stage thin film evaporator and a multi-stage removal tank, inert gas is introduced under the high vacuum state, and vaporized vinyl monomers, solvents and other small molecular substances are removed. The invention prepares the polymer polyol with low VOC by changing the preparation method, and meanwhile, the post-treatment part has no specific operation steps and operation conditions.
The prior art odor detection method is to place the sample in a glass container and evaluate the odor by the tester under room temperature conditions. The number of people to be evaluated is at least 3, the difference between the scores given by each person cannot be larger than 2, if the difference is larger than 2, the evaluation is carried out again, and the number of people is 5. The odor test standard can be evaluated according to VDA 270-; among them, the 3.0 grade is "noticeable but not much obstructive", the 4.0 grade is "noticeable and offensive", and the 5.0 grade is "strong offensive smell and strong irritation".
Disclosure of Invention
The invention aims to solve the technical problems of high residual quantity of styrene and acrylonitrile monomers, large odor and high VOC in polymer polyol in the prior art, and provides a novel purification method of the polymer polyol.
In order to solve the technical problems, the technical scheme adopted by the invention is as follows: a process for the continuous purification of a polymer polyol comprising the steps of:
1) according to the mass percentage, polymer polyol I containing 1.50-2.5% of acrylonitrile monomer and 1.85-2.5% of styrene monomer continuously passes through a first-stage flash tank, and nitrogen is simultaneously introduced into the first-stage flash tank for bubbling to continuously obtain a material I;
2) continuously introducing the material I into a second-stage flash tank, and simultaneously introducing nitrogen into the second-stage flash tank for bubbling to continuously obtain a material II;
3) continuously introducing the material II into a third-stage flash tank, and continuously obtaining a material III by combining nitrogen bubbling and steam bubbling in the third-stage flash tank;
4) and continuously passing the material III through a vibrating screen and then introducing into a stripping tower, and stripping by adopting medium-pressure steam in the stripping tower to continuously obtain the polymer polyol II with the styrene content of less than or equal to 5ppm and the acrylonitrile content of less than or equal to 2 ppm.
In the above technical scheme, preferably, the polymer polyol entering the first flash tank contains, by mass, 1.50-2.0% of acrylonitrile and 1.85-2.0% of styrene.
In the technical scheme, preferably, after the first-stage flash tank is filled with nitrogen and bubbled, the pressure is controlled to be-0.075 to-0.090 Mpa, the temperature in the first-stage flash tank is not less than 145 ℃ and less than 165 ℃, and the retention time of the polymer polyol I in the first flash tank is 1 to 1.8 hours; and after nitrogen is introduced into the second-stage flash tank for bubbling, the pressure is controlled to be-0.075 to-0.090 Mpa, the temperature in the second-stage flash tank is more than or equal to 155 ℃ and less than 165 ℃, and the retention time of the material I in the second flash tank is 0.8 to 1.5 hours.
In the technical scheme, preferably, after the material II enters the third-stage flash tank, the pressure in the tank is-0.08 to-0.10 Mpa when bubbling of nitrogen and steam is carried out, the mass ratio of the nitrogen flow to the steam flow is 2:5 to 5:5, and the steam flow is 80 to 120m3H; the retention time of the material II in the third-stage flash tank is 1-1.5 h, and the temperature in the third-stage flash tank is 165-170 ℃.
In the technical scheme, preferably, the material III is subjected to medium-pressure steam stripping after entering the stripping tower, the medium-pressure steam pressure is 1.1-1.3 Mpa, and the medium-pressure steam flow is 110-130 m3H; the pressure at the upper end of the stripping tower is-0.07 to-0.1 Mpa, and the pressure at the lower end of the stripping tower is 0.8 to 1.0 Mpa; the retention time of the material III in the stripping tower is 2-10 min, and the stripping temperature is 170-175 ℃.
In the above technical scheme, preferably, the styrene content of the obtained polymer polyol II is less than or equal to 3.5ppm, and the acrylonitrile content is 0 ppm.
In the above technical scheme, preferably, an internal spraying system is adopted in the first, second and third flash tanks, that is, a stainless steel coil is arranged at the top inside the flash tank, a plurality of openings are arranged on the lower surface of the coil, and a material inlet is arranged on the stainless steel coil; the bottom of the flash tank is provided with a gas distribution coil pipe, the gas distribution coil pipe is evenly provided with open pores, and nitrogen or steam is bubbled through the materials in the open pores.
After entering from the feed inlet, the material flows into the tank bottom in a spraying state through the opening of the upper coil pipe; after nitrogen and steam bubbles enter the tank through the pipeline, the materials at the bottom of the tank are bubbled in a spraying state through the opening of the bottom coil pipe.
The invention provides a new continuous purification method of polymer polyol, which adopts nitrogen bubbling, steam bubbling or single stripping in the prior art, and often cannot achieve the effect of low residual monomer; meanwhile, the materials pass through the oscillating screen before entering the stripping tower, so that particles in the materials are effectively separated, the materials are prevented from scaling on the inner surface of the stripping tower and even blocking a pipeline, and the stripping effect is improved; finally, the purified polymer polyol can achieve excellent demonomerization effect (styrene is less than or equal to 3.5ppm, acrylonitrile is 0ppm), no yellowing is generated, the aldehyde content (the sum of formaldehyde, acetaldehyde and acrolein) is less than 3 mug/g, and good technical effect is achieved with low odor grade (less than or equal to 3.0 grade).
Detailed Description
Example 1
1) Continuously introducing polymer polyol (CHP-2045D) I with styrene content of 1.69% and acrylonitrile content of 1.86% into a first-stage flash tank, wherein the capacity of the first-stage flash tank is 20T, the liquid level of the polymer polyol I in the first-stage flash tank is controlled to be 35%, the flow of the polymer polyol I is 6T/h, and the retention time of the polymer polyol I in the first-stage flash tank is 1.17 h; introducing nitrogen into the first-stage flash tank for bubbling at the same time, wherein the nitrogen flow is 150m3H, controlling the pressure in the kettle to be-0.080 Mpa and the temperature in the tank to be 155 ℃, and continuously obtaining a material I;
2) continuously introducing the material I into a second-stage flash tank, wherein the capacity of the first-stage flash tank is 16T, controlling the liquid level of the material I in the second-stage flash tank to be 40%, and controlling the flow of the material I to be 6T/h, so that the retention time of the material I in the second-stage flash tank is 1.07 h; the second-stage flash tank is simultaneously filled with nitrogenBubbling with a nitrogen flow of 150m3H, controlling the pressure in the kettle to be-0.080 Mpa and the temperature in the tank to be 160 ℃, and continuously obtaining a material II;
3) continuously introducing the material II into a third-stage flash tank, wherein the capacity of the third-stage flash tank is 16T, controlling the liquid level of the material II in the third-stage flash tank to be 40%, and controlling the flow of the material II to be 6T/h, so that the retention time of the material II in the third-stage flash tank is 1.07 h; in the third stage flash tank, the nitrogen bubbling and the medium pressure steam bubbling are combined for demonomerization, and the nitrogen flow is 80m3H; steam flow rate of 100m3H; controlling the pressure in the kettle to be-0.10 Mpa and the temperature in the tank to be 165 ℃, and continuously obtaining a material III;
4) and continuously enabling the material III to pass through the oscillating screen and then enter the stripping tower, feeding the material III from the upper part of the stripping tower, arranging a liquid distribution pipe above the stripping tower, and feeding medium-pressure steam at the bottom of the stripping tower. The packing in the tower is a loose pile plastic pall ring with specification phi of 25mm and specific surface area of 213m2/m3Void fraction: 91% of bulk weight 85kg/m3Dry packing factor 285/m; stripping with 1.2Mpa medium pressure steam at 120m3H; the feeding flow rate of the material III is 6t/h, and the retention time is 2 min; controlling the pressure at the upper end of the stripping tower to be-0.1 Mpa; the pressure at the lower end of the stripping tower is 1.0 Mpa; the temperature of the stripping tower is set to be 175 ℃, and polymer polyol (CHP-2045D) II is continuously obtained; the performance test data are shown in Table 1.
Example 2
1) Continuously introducing polymer polyol (CHP-H45) I with styrene content of 1.80% and acrylonitrile content of 1.95% into a first-stage flash tank, wherein the capacity of the first-stage flash tank is 20T, controlling the liquid level of the polymer polyol I in the first-stage flash tank to be 50%, and controlling the flow of the polymer polyol I to be 8T/H, so that the retention time of the polymer polyol I in the first-stage flash tank is 1.25H; the first-stage flash tank is simultaneously filled with nitrogen for bubbling, and the nitrogen flow is 200m3H, controlling the pressure in the kettle to be-0.075 Mpa and the temperature in the tank to be 160 ℃ to continuously obtain a material I;
2) continuously introducing the material I into a second-stage flash tank, controlling the capacity of the first-stage flash tank to be 16T, and controlling the material I to be inThe liquid level of the second-stage flash tank is 50%, the flow of the material I is 6t/h, and the retention time of the material I in the second-stage flash tank is 1.33 h; introducing nitrogen into the second-stage flash tank for bubbling at the same time, wherein the nitrogen flow is 200m3H, controlling the pressure in the kettle to be-0.085 Mpa and the temperature in the kettle to be 163 ℃ to continuously obtain a material II;
3) continuously introducing the material II into a third-stage flash tank, wherein the capacity of the third-stage flash tank is 16T, the liquid level of the material II in the third-stage flash tank is controlled to be 50%, the flow of the material II is 6T/h, and the retention time of the material II in the third-stage flash tank is 1.33 h; in the third stage flash tank, the nitrogen bubbling and the medium pressure steam bubbling are combined for demonomerization, and the nitrogen flow is 40m3H; steam flow is 80m3H; controlling the pressure in the kettle to be-0.09 Mpa and the temperature in the kettle to be 168 ℃ to continuously obtain polymer polyol (CHP-H45) II;
4) and continuously introducing a material III into the oscillating screen and then passing through the stripping tower, feeding the material III from the upper part of the stripping tower, arranging a liquid distribution pipe above the stripping tower, and feeding medium-pressure steam at the bottom of the stripping tower. The packing in the tower is a loose pile plastic pall ring with specification phi of 25mm and specific surface area of 213m2/m3Void fraction: 91% of bulk weight 85kg/m3Dry packing factor 285/m; stripping with 1.2Mpa medium pressure steam at 120m3H; the feeding flow rate of the material III is 2t/h, and the retention time is 10 min; controlling the pressure at the upper end of the stripping tower to be-0.07 Mpa; the pressure at the lower end of the stripping tower is 0.8 Mpa; the temperature of the stripping tower is set to be 175 ℃, and polymer polyol (CHP-2045D) II is continuously obtained; the performance test data are shown in Table 1.
Comparative example 1
1) Continuously introducing polymer polyol (CHP-H45) I with styrene content of 1.80% and acrylonitrile content of 1.95% into a first-stage flash tank, wherein the capacity of the first-stage flash tank is 20T, controlling the liquid level of the polymer polyol I in the first-stage flash tank to be 50%, and controlling the flow of the polymer polyol I to be 8T/H, so that the retention time of the polymer polyol I in the first-stage flash tank is 1.25H; the first-stage flash tank is simultaneously filled with nitrogen for bubbling, and the nitrogen flow is 200m3H, controlling the pressure in the kettle to be-0.075 Mpa and the temperature in the tankContinuously obtaining a material I at the temperature of 155 ℃;
2) continuously introducing the material I into a second-stage flash tank, wherein the capacity of the first-stage flash tank is 16T, controlling the liquid level of the material I in the second-stage flash tank to be 50%, and controlling the flow of the material I to be 6T/h, so that the retention time of the material I in the second-stage flash tank is 1.33 h; introducing nitrogen into the second-stage flash tank for bubbling at the same time, wherein the nitrogen flow is 200m3H, controlling the pressure in the kettle to be-0.080 Mpa and the temperature in the tank to be 155 ℃, and continuously obtaining a material II;
3) continuously enabling the material II to pass through a third-stage flash tank, wherein the capacity of the third-stage flash tank is 16T, controlling the liquid level of the material II in the third-stage flash tank to be 50%, and controlling the flow of the material II to be 6T/h, so that the retention time of the material II in the third-stage flash tank is 1.33 h; the third-stage flash tank is simultaneously filled with nitrogen for bubbling, and the nitrogen flow is 200m3H, controlling the pressure in the kettle to be-0.085 Mpa and the temperature in the tank to be 160 ℃, and continuously obtaining a material III;
4) continuously passing the material III through a fourth-stage flash tank, wherein the capacity of the fourth-stage flash tank is 16T, controlling the liquid level of the material II in the third-stage flash tank to be 50%, and controlling the flow of the material II to be 6T/h, so that the retention time of the material II in the third-stage flash tank is 1.33 h; the third-stage flash tank is simultaneously filled with nitrogen for bubbling, and the nitrogen flow is 200m3H, controlling the pressure in the kettle to be-0.085 Mpa and the temperature in the kettle to be 165 ℃, and continuously obtaining polymer polyol II (CHP-H45); the performance test data are shown in Table 1.
TABLE 1 data for performance testing of examples and comparative examples
As can be seen from table 1, the residence time was controlled by using a purification system in which three flash tanks and a stripping column were used in combination, and bubbling nitrogen and steam simultaneously in the third flash tank, and the first, second, and third flash tanks used internal spraying systems; the polymer polyol with low styrene residual monomer, low acrylonitrile residual monomer, low VOC and low odor is prepared by the technical scheme that the material is purified by the oscillating screen and then enters the stripping tower, and a good technical effect is achieved.
Claims (6)
1. A process for the continuous purification of a polymer polyol comprising the steps of:
1) continuously passing polymer polyol I containing 1.50-2.5% of acrylonitrile monomer and 1.85-2.5% of styrene monomer through a first-stage flash tank in percentage by mass, and introducing nitrogen into the first-stage flash tank for bubbling at the same time to continuously obtain a material I;
2) continuously introducing the material I into a second-stage flash tank, and simultaneously introducing nitrogen into the second-stage flash tank for bubbling to continuously obtain a material II;
3) continuously introducing the material II into a third-stage flash tank, and continuously obtaining a material III by combining nitrogen bubbling and steam bubbling in the third-stage flash tank;
4) and continuously passing the material III through a vibrating screen and then introducing into a stripping tower, and stripping by adopting medium-pressure steam in the stripping tower to continuously obtain the polymer polyol II with the styrene content of less than or equal to 5ppm and the acrylonitrile content of less than or equal to 2 ppm.
2. The continuous purification method of polymer polyol according to claim 1, wherein the polymer polyol introduced into the first flash tank contains 1.50 to 2.0% by mass of acrylonitrile and 1.85 to 2.0% by mass of styrene.
3. The continuous purification method of polymer polyol according to claim 1, wherein after the first-stage flash tank is filled with nitrogen gas and bubbled, the pressure is controlled to be-0.075-0.090 MPa, the temperature in the first-stage flash tank is more than or equal to 145 ℃ and less than 165 ℃, and the retention time of the polymer polyol I in the first flash tank is 1-1.8 h; and after nitrogen is introduced into the second-stage flash tank for bubbling, the pressure is controlled to be-0.075 to-0.090 Mpa, the temperature in the second-stage flash tank is more than or equal to 155 ℃ and less than 165 ℃, and the retention time of the material I in the second flash tank is 0.8 to 1.5 hours.
4. The continuous purification method of polymer polyol according to claim 1, wherein the pressure in the third-stage flash tank is-0.08 to-0.10 MPa when bubbling nitrogen and steam is performed on the material II, the mass ratio of the nitrogen flow to the steam flow is 2:5 to 5:5, and the steam flow is 80 to 120m3H; the retention time of the material II in the third-stage flash tank is 1-1.5 h, and the temperature in the third-stage flash tank is 165-170 ℃.
5. The continuous purification method of polymer polyol as claimed in claim 1, wherein the material III is subjected to medium pressure steam stripping after entering the stripping tower, the medium pressure steam pressure is 1.1-1.3 Mpa, and the medium pressure steam flow is 110-130 m3H; the pressure at the upper end of the stripping tower is-0.07 to-0.1 Mpa, and the pressure at the lower end of the stripping tower is 0.8 to 1.0 Mpa; the retention time of the material III in the stripping tower is 2-10 min, and the stripping temperature is 170-175 ℃.
6. The continuous purification process of polymer polyol according to claim 1, wherein the obtained polymer polyol II has a styrene content of 3.5ppm or less and an acrylonitrile content of 0 ppm.
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN113318468A (en) * | 2021-05-14 | 2021-08-31 | 安徽实华工程技术股份有限公司 | Production system for removing VOC (volatile organic compounds) from polyether polyol |
| CN115043990A (en) * | 2022-07-26 | 2022-09-13 | 上海华谊（集团）公司 | Production process of low-VOC polymer polyol |
| WO2023166120A1 (en) | 2022-03-03 | 2023-09-07 | Ineos Styrolution Group Gmbh | Continuous method of manufacturing acrylonitrile-containing copolymers with reduced content of propionitrile |
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