Polymer devolatilization method, steam stripping devolatilization device and polymer devolatilization system

Abstract

The invention relates to a polymer devolatilization method, a steam stripping devolatilization device and a polymer devolatilization system. The polymer devolatilization method is used for removing volatile components in a to-be-purified polymer system so as to improve the purity of a target polymer product, the to-be-purified polymer system comprises the target polymer product, a solvent and impurities, and the polymer devolatilization method comprises the following steps: by taking the to-be-purified polymer system as a raw material, performing countercurrent contact on the raw material and saturated steam, carrying out devolatilization treatment on the raw materials in a solvent steam stripping manner, and removing volatile components in the to-be-purified polymer system to obtain a devolatilization product; the saturated steam is formed by heating a stripping medium, and the stripping medium comprises a solvent. According to the method, devolatilization is carried out in a solvent stripping mode, vaporization of the solvent in the raw materials is greatly reduced, the fluidity of the raw materials in the devolatilization process is guaranteed, and the technical problem that in the prior art, the removal effect of small molecule compounds is affected due to the fact that the viscosity of a polymer system is increased along with removal of the solvent in the polymer system can be solved.

Description

Technical Field

[0001] The invention belongs to the technical field of chemical industry, and in particular relates to a polymer devolatilization method, a steam stripping devolatilizer and a polymerization devolatilization system. Background Art

[0002] Polymer devolatilization is an important step in the polymer production process. During the polymer synthesis process, affected by the process conditions, the product contains volatile components such as unreacted monomers, solvents, additives, by-products and oligomers. These volatile components will affect the polymer processing technology, the quality of the processed products, the performance of the products, and have an adverse effect on the environment. Generally speaking, the volatile organic matter content in the system entering the devolatilization stage from the polymerization production stage is as high as 10%-80%, and the quality requirements of polymer products usually require the content of volatile organic matter to be reduced to thousands of mg / kg or even tens of mg / kg. Therefore, it is necessary to remove the volatile components in the polymer. The process of removing volatile components is the devolatilization process.

[0003] Generally, devolatilization requires three processes: the small molecular volatile components in the polymer system are transferred to the gas-liquid interface through diffusion, aggregation and foaming processes; then, these small molecular volatile components are converted into gaseous state due to the gasification process at the gas-liquid interface, and then the volatile components are removed under the action of vacuum.

[0004] However, the existing devolatilization process has a poor effect on the removal of small molecular compounds. Summary of the invention

[0005] In view of this, the object of the present invention is to provide a polymer devolatilization method, a steam stripping devolatilizer and a polymer devolatilization system to solve the technical problems such as poor removal effect of small molecular compounds when using existing devolatilization processes.

[0006] The inventors discovered during the research process that the existing devolatilization method is to remove impurities and solvents in volatile small molecule compounds in the polymer system during the devolatilization process. However, as the devolatilization process continues, the viscosity of the system continues to increase (even by several orders of magnitude). As the viscosity of the system increases, other small molecule compounds in the polymer system except the solvent are difficult to separate from the system, resulting in poor removal effect of other small molecule compounds in the polymer system except the solvent.

[0007] To achieve the above object, the technical solution of the present invention is as follows:

[0008] In a first aspect, the present invention provides a polymer devolatilization method, which is used to remove volatile components in a polymer system to be purified to improve the purity of a target polymer product, wherein the polymer system to be purified comprises a target polymer product, a solvent and impurities, and is characterized in that the polymer devolatilization method comprises: using the polymer system to be purified as a raw material, contacting the raw material with saturated steam in countercurrent, performing a devolatilization treatment on the raw material by solvent stripping, removing volatile components in the polymer system to be purified, and obtaining a devolatilization product;

[0009] The saturated steam is formed by heating a stripping medium, and the stripping medium includes the solvent.

[0010] Optionally, the solvent content in the devolatilization product is greater than or equal to the solvent content in the polymer system to be purified.

[0011] Optionally, the devolatilization temperature is less than or equal to the saturated steam temperature.

[0012] Optionally, during the devolatilization process, a heat exchange medium is used for heating, and the heat exchange medium flows in the opposite direction to the raw material.

[0013] Optionally, the stripping medium is the solvent.

[0014] In a second aspect, the present invention provides a stripping devolatilizer, the stripping devolatilizer comprising a shell, the shell being provided with a saturated steam inlet.

[0015] Optionally, a material distributor and a steam screen plate are sequentially arranged in the shell from top to bottom.

[0016] Optionally, a heating component is provided outside the shell.

[0017] Optionally, the heating component uses a heat exchange tube, and the heat exchange tube includes a heat exchange medium inlet tube and a heat exchange medium outlet tube, and the heat exchange medium inlet tube and the heat exchange medium outlet tube are respectively arranged on the lower side and the upper side of the shell exterior.

[0018] In a third aspect, the present invention provides a polymer devolatilization system for removing volatile components in a polymer system to be purified to improve the purity of a target polymer product, wherein the polymer system to be purified comprises a target polymer product, a solvent and impurities, and is characterized in that the polymer devolatilization system comprises the stripping devolatilizer as described above, and further comprises a heater, wherein the heater is used to heat a stripping medium to form saturated steam, wherein the stripping medium comprises the solvent; and a saturated steam outlet is provided on the heater, and the saturated steam outlet is connected to the saturated steam inlet.

[0019] As described above, the devolatilization method, polymer production method and system of the present invention have the following beneficial effects:

[0020] The present invention uses saturated steam formed by heating a substance that is the same as the solvent contained in the polymer system to be purified as a stripping medium, that is, a solvent stripping method is used for devolatilization. Since the solvent steam in the devolatilizer is in a saturated state, the vaporization of the solvent in the raw material is greatly reduced, and the fluidity of the raw material during the devolatilization process is guaranteed. The technical problem that the viscosity of the polymer system increases during the devolatilization process of the traditional polymer system due to the removal of the solvent, thereby affecting the removal effect of small molecular compounds other than the solvent, is solved, and the removal effect of the small molecular compounds is improved.

[0021] In the present invention, by setting the ambient temperature in the stripping devolatilizer to be the same as the temperature of saturated steam (ie, the stripping medium), the removal effect of small molecular compounds can be further improved while ensuring the purity of the product.

[0022] In the present invention, the heating mode of the stripping devolatilizer is adjusted from internal heating to external heating, and the heating component of the gas devolatilizer is configured to adopt a heat exchange tube, the heat exchange tube includes a heat exchange medium inlet tube and a heat exchange medium outlet tube, and the heat exchange medium inlet tube and the heat exchange medium outlet tube are respectively arranged at the lower part and the upper part of the shell, that is, the heat exchange medium can adopt a bottom-in and top-out method, which can further improve the removal effect of small molecular compounds. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 Schematic diagram of the structure of the devolatilization system of Example 1.

[0024] Description of reference numerals:

[0025] 1- Heater;

[0026] 2-devolatilizer, 21-material distributor, 22-steam sieve plate, 23-heat exchange medium outlet pipe, 24-heat exchange medium inlet pipe. DETAILED DESCRIPTION

[0027] The present invention is further described below through specific examples, but it should be pointed out that the specific material ratios, process conditions and results described in the embodiments of the present invention are only used to illustrate the present invention and cannot be used to limit the scope of protection of the present invention. All equivalent changes or modifications made according to the spirit of the present invention should be included in the scope of protection of the present invention.

[0028] An embodiment of the present invention provides a polymer devolatilization method, which is used to remove volatile components in a polymer system to be purified to improve the purity of a target polymer product. The polymer system to be purified includes a target polymer product, a solvent and impurities. The polymer devolatilization method includes: using the polymer system to be purified as a raw material, contacting the raw material with saturated steam in countercurrent, performing devolatilization treatment on the raw material by solvent stripping, removing volatile components in the polymer system to be purified, and obtaining a devolatilization product. The devolatilization temperature is less than or equal to the saturated steam temperature. During the devolatilization process, a heat exchange medium is used for heating, and the heat exchange medium flows in the opposite direction to the raw material. The solvent content in the devolatilization product is greater than or equal to the solvent content in the polymer system to be purified.

[0029] Saturated steam is formed by heating a stripping medium, which includes a solvent.

[0030] In one embodiment of the present invention, the stripping medium is a solvent.

[0031] Another embodiment of the present invention provides a stripping devolatilizer, which includes a shell, the shell is provided with a saturated steam inlet, a material distributor and a steam sieve plate are arranged in sequence from top to bottom in the shell, and a heat exchange medium inlet pipe and a heat exchange medium outlet pipe are respectively arranged on the lower side and the upper side of the shell outside.

[0032] Another embodiment of the present invention provides a polymer devolatilization system for removing volatile components in a polymer system to be purified to improve the purity of a target polymer product. The polymer system to be purified includes a target polymer product, a solvent and impurities. The polymer devolatilization system includes the stripping devolatilizer as described above, and also includes a heater, which is used to heat a stripping medium to form saturated steam, and the stripping medium includes a solvent; a saturated steam outlet is provided on the heater, and the saturated steam outlet is connected to a saturated steam inlet.

[0033] It should be noted that all directional indications in the embodiments of the present invention (such as up, down, top, bottom, inside, outside...) are only used to explain the relative position relationship, movement status, etc. between the components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0034] In the present invention, unless otherwise clearly specified and limited, the terms "connected", "fixed", etc. should be understood in a broad sense. For example, "fixed" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0035] In addition, the meaning of "and / or" appearing in the full text includes three parallel solutions. Taking "A and / or B" as an example, it includes solution A, solution B, or a solution that satisfies both A and B. In addition, the technical solutions between the various embodiments can be combined with each other, but it must be based on the fact that ordinary technicians in the field can implement it. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the protection scope required by the present invention.

[0036] The present invention is described in detail below by specific examples. It should also be understood that the following examples are only used to specifically illustrate the present invention and cannot be understood as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the above content of the present invention belong to the scope of protection of the present invention. The specific process parameters and the like in the following examples are also only examples within a suitable range, that is, those skilled in the art can make a selection within a suitable range through the description herein, and are not limited to the specific values ​​​​exemplified below.

[0037] Example 1

[0038] See also Figure 1 , Figure 1 The present invention is a schematic structural diagram of a polymer devolatilization system according to an exemplary embodiment of the present invention, wherein the polymer devolatilization system is used to remove volatile components in a polymer system to be purified to improve the purity of a target polymer product, wherein the polymer system to be purified includes a target polymer product, a solvent, and impurities. The polymer devolatilization system includes a heater 1 and a stripping devolatilizer 2.

[0039] like Figure 1 As shown, the heater 1 is a place for heating the stripping medium to form saturated steam from the stripping medium, and the stripping medium includes a solvent; a saturated steam outlet is provided at the top of the heater 1, and a solvent inlet is provided at the bottom of the heater 1, the solvent inlet is the inlet for the solvent to enter the heater 1, and the saturated steam outlet is the outlet for the saturated steam to discharge from the heater 1. The heater 1 can be an electric heater, an infrared heater, a heat exchanger, etc.

[0040] Please continue reading Figure 1The stripping devolatilizer 2 is a place for devolatilizing the polymer system to be purified (i.e., removing volatile components such as unreacted monomers, by-products and oligomers). The stripping devolatilizer 2 includes a shell, a gas outlet is provided at the top of the shell, a feed inlet is provided at the upper part of the shell, a material outlet is provided at the lower part of the shell, a saturated steam inlet is provided at the lower part and / or the bottom of the shell, and the saturated steam inlet is connected to the saturated steam outlet of the heater 1. The upper and lower parts of the shell are respectively connected to a heat exchange medium outlet pipe 23 and a heat exchange medium inlet pipe 24, and the heat exchange medium can be water vapor, heat transfer oil, etc. The feed inlet is the inlet for the polymer system to be purified to enter the stripping devolatilizer 2, the material outlet is the outlet for the polymer after devolatilization, the saturated steam inlet is the inlet for the saturated steam to enter the stripping devolatilizer 2, and the gas outlet is the outlet for the small molecular volatile components separated from the polymer system to be purified to discharge the stripping devolatilizer 2. A material distributor 21 and a steam sieve plate 22 are arranged in sequence from top to bottom in the shell between the feed inlet and the material outlet. The material distributor 21 is located at the upper part of the shell and is arranged in the horizontal direction. The material distributor 21 is provided with a plurality of distribution holes. The material distributor 21 is used to make the polymer system to be purified uniformly distributed along the cross section in the shell. The steam sieve plate 22 is located below the material distributor 21 and is arranged in the horizontal direction. The steam sieve plate 22 is provided with a plurality of sieve holes. The steam sieve plate 22 is used to make the saturated steam uniformly distributed along the cross section in the shell, so that the saturated steam can countercurrently contact with the purified polymer system flowing from top to bottom and divided into a plurality of thin streams by the material distributor 21 during the process of flowing from bottom to top, thereby improving the heat exchange efficiency of the two and further improving the devolatilization efficiency. At the same time, the sieve holes on the steam sieve plate 22 can also serve as a channel for the small molecular impurities after devolatilization to flow from bottom to top.

[0041] The principle of the devolatilization system of this embodiment is: by connecting the saturated steam inlet of the stripping devolatilizer 2 to the saturated steam outlet of the heater 1, the stripping medium (the stripping medium agent includes the solvent) can be heated by the heater 1 to form saturated steam, and the saturated steam is allowed to enter the stripping devolatilizer 2, so as to avoid the technical problem in the prior art that the viscosity of the polymer system increases with the removal of the solvent in the polymer system, affecting the removal effect of other small molecular compounds, thereby improving the removal effect of small molecular compounds other than the solvent.

[0042] Example 2

[0043] The polymer devolatilization system of Example 1 is used to devolatilize a polystyrene system containing dimethylformamide solvent, and the specific steps are as follows:

[0044] Dimethylformamide is preheated to 185° C. by the heater 1 to form a saturated steam state, and enters the stripping devolatilizer 2 through a connecting pipe between the saturated steam outlet of the heater 1 and the saturated steam inlet of the stripping devolatilizer 2;

[0045] The ambient temperature in the stripping devolatilizer 2 is controlled to be 185° C. by controlling the temperature of the heat exchange medium in the heat exchange medium inlet pipe 24, and the polystyrene system is fed into the stripping devolatilizer 2 from the feed port. The polystyrene system enters the material distributor 21 and is countercurrently contacted with the saturated steam of dimethylformamide (i.e., the stripping medium) entering the stripping devolatilizer 2 from the saturated steam inlet. During the countercurrent contact process, the saturated steam of dimethylformamide exchanges heat with the polystyrene system, thereby heating the polystyrene system, and removing small molecular impurities in the polystyrene system by stripping. The small molecular impurity gas separated from the polystyrene system is discharged through the gas outlet at the top of the stripping devolatilizer 2, and the devolatilized polystyrene is discharged from the material outlet.

[0046] Comparative Example 1

[0047] The difference between this comparative example and Example 2 is that the stripping devolatilizer 2 is not connected to the heater 1. The stripping devolatilizer of this comparative example is used to devolatilize the polystyrene system with the same source as that of Example 2. The specific steps are as follows:

[0048] The ambient temperature in the stripping devolatilizer 2 is controlled to be 185° C. by controlling the temperature of the heat exchange medium in the heat exchange medium inlet pipe 24, and the polystyrene system is fed into the stripping devolatilizer 2 from the feed port, and the polystyrene system enters the material distributor 21. The heat exchange medium entering from the heat exchange medium inlet pipe 24 exchanges heat with the polystyrene system, thereby heating the polystyrene system and removing small molecular impurities in the polystyrene system. The small molecular impurity gas separated from the polystyrene system is discharged through the gas outlet at the top of the devolatilizer, and the devolatilized polystyrene is discharged from the material outlet.

[0049] Content detection

[0050] Sampling analysis was performed to detect the polystyrene content in the raw materials used in Example 2, the polystyrene discharged from the material outlet of Example 2 and Comparative Example 1, and the dimethylformamide content in the polystyrene. The results are shown in Table 1, and the small molecule impurity content in the polystyrene was calculated according to the following formula:

[0051] ω 小分子1 =1-ω 聚苯乙烯 -ω 二甲基甲酰胺1 ;

[0052] In the formula, ω 小分子1 It refers to the mass percentage of small molecular impurities in polystyrene, in wt%; ω 聚苯乙烯 It refers to the mass percentage of polystyrene in polystyrene, in wt%; ω 二甲基甲酰胺1 It refers to the mass percentage of dimethylformamide in polystyrene, in wt%.

[0053] Table 1 Test results of Example 2 and Comparative Example 1

[0054] Group Polystyrene content Dimethylformamide content Small molecule impurity content raw material 40.14wt% 54.81wt% 5.05wt% Example 2 42.21wt% 57.63wt% 0.16wt% Comparative Example 1 92.51wt% 3.84wt% 3.65wt%

[0055] As can be seen from Table 1, compared with Comparative Example 1, the content of small molecule impurities in the product after devolatilization in Example 2 is reduced to a greater extent. This result shows that the present invention uses saturated steam formed by heating the same substance as the solvent contained in the polymer system to be purified as the stripping medium, that is, the solvent stripping method is used for devolatilization. Since the solvent vapor in the devolatilizer is in a saturated state, the vaporization of the solvent in the raw material is greatly reduced, and the fluidity of the raw material during the devolatilization process is ensured. The technical problem in the prior art that the viscosity of the polymer system increases with the removal of the solvent in the polymer system affects the removal effect of other small molecule compounds can be avoided, and the removal effect of small molecule compounds is improved.

[0056] Example 3

[0057] The polymer devolatilization system of Example 1 is used to devolatilize a nylon-6 (i.e., polyamide 6) system containing a formic acid solvent, and the specific steps are as follows:

[0058] The formic acid is preheated to 110° C. by the heater 1 and forms a saturated steam state, and enters the stripping devolatilizer 2 through a connecting pipe between the saturated steam outlet of the heater 1 and the saturated steam inlet of the stripping devolatilizer 2;

[0059] The ambient temperature in the stripping devolatilizer 2 is controlled to be 110° C. by controlling the temperature of the heat exchange medium in the heat exchange medium inlet pipe 24, and the nylon-6 (i.e., polyamide 6) system is fed into the stripping devolatilizer 2 from the feed port. The nylon-6 (i.e., polyamide 6) system enters the material distributor 21, and is countercurrently contacted with the saturated formic acid steam (i.e., stripping medium) entering the stripping devolatilizer 2 from the saturated steam inlet. During the countercurrent contact process, the saturated formic acid steam exchanges heat with the nylon-6 (i.e., polyamide 6) system, thereby heating the nylon-6 (i.e., polyamide 6) system, and removing small molecular impurities in the nylon-6 (i.e., polyamide 6) system by stripping. The small molecular impurity gas separated from the nylon-6 (i.e., polyamide 6) system is discharged through the gas outlet at the top of the devolatilizer, and the devolatilized nylon-6 (i.e., polyamide 6) is discharged from the material outlet.

[0060] Comparative Example 2

[0061] The difference between this comparative example and Example 3 is that:

[0062] The ambient temperature in the stripping devolatilizer 2 is controlled to be 180° C. by controlling the temperature of the heat exchange medium in the heat exchange medium inlet pipe 24 .

[0063] Comparative Example 3

[0064] The ambient temperature in the stripping devolatilizer 2 is controlled to be 70° C. by controlling the temperature of the heat exchange medium in the heat exchange medium inlet pipe 24 .

[0065] Content detection

[0066] Sampling analysis was performed to detect the nylon-6 content in the raw materials used in Example 3, Example 3, Comparative Example 2, and the nylon-6 (i.e., polyamide 6) discharged from the material outlet of Comparative Example 3, and the formic acid content in nylon-6 (i.e., polyamide 6), and the small molecular impurity content in nylon-6 (i.e., polyamide 6) was calculated according to the following formula:

[0067] ω 小分子2 =1-ω 尼龙-6 -ω 甲酸 ;

[0068] In the formula, ω 小分子2 It refers to the mass percentage of small molecular impurities in nylon-6, in wt%; ω 尼龙-6 It refers to the mass percentage of polynylon-6 in nylon-6, in wt%; ω 甲酸 It refers to the mass percentage of formic acid in nylon-6, in wt%. The results are shown in Table 2.

[0069] Table 2 Test results of Example 3, Comparative Example 2 and Comparative Example 3

[0070] Group Nylon-6 content Formic acid content Small molecule impurity content raw material 55.20wt% 41.67wt% 3.13wt% Example 3 57.83wt% 42.11wt% 0.06wt% Comparative Example 2 78.51wt% 20.30wt% 0.12wt% Comparative Example 3 46.24wt% 53.69wt% 0.07wt%

[0071] As shown in Table 2, compared with Comparative Examples 2 and 3, the content of small molecule impurities in the product after devolatilization in Example 3 is significantly reduced. The results show that when the saturated steam in the heater 1 enters the stripping devolatilizer 2 with a higher ambient temperature, the solvent vapor (i.e., the stripping medium) is no longer saturated, so that the solvent in the polymer system to be purified is vaporized, resulting in a decrease in the fluidity of the polymer system to be purified (i.e., the raw material); when the saturated steam in the heater 1 enters the stripping devolatilizer 2 with a lower ambient temperature, the solvent vapor (i.e., the stripping medium) is supersaturated, and the gas phase solvent (i.e., the stripping medium) is liquefied into the polymer system to be purified (i.e., the raw material), resulting in an increase in the fluidity of the polymer system to be purified (i.e., the raw material), and a reduction in the devolatilization time of the polymer system to be purified (i.e., the raw material). Obviously, the present invention can further improve the removal effect of small molecule compounds while ensuring the purity of the product by setting the ambient temperature in the stripping devolatilizer 2 to the same as the temperature of the saturated steam (i.e., the stripping medium).

[0072] Example 4

[0073] The polymer devolatilization system of Example 1 (the devolatilizer height is 6.5 m) is used to devolatilize the polyacrylonitrile (i.e., polyamide 6) system containing dimethylformamide solvent, and the specific steps are as follows:

[0074] Dimethylformamide is preheated to 185° C. by the heater 1 to form a saturated steam state, and enters the stripping devolatilizer 2 through a connecting pipe between the saturated steam outlet of the heater 1 and the saturated steam inlet of the stripping devolatilizer 2;

[0075] The ambient temperature in the stripping devolatilizer 2 is controlled to be 185° C. by controlling the temperature of the heat exchange medium in the heat exchange medium inlet pipe 24 (specifically, the temperature of the heat exchange medium in the heat exchange medium inlet pipe 24 is controlled to be 185° C., and the temperature of the heat exchange medium in the heat exchange medium outlet pipe 23 is measured to be 173° C., i.e., the heat exchange medium adopts a bottom-in-top-out method), the polyacrylonitrile system is fed into the stripping devolatilizer 2 from the feed port, the polyacrylonitrile system enters the material distributor 21, and is countercurrently contacted with the saturated steam of dimethylformamide (i.e., the stripping medium) entering the stripping devolatilizer 2 from the saturated steam inlet. During the countercurrent contact process, the saturated steam of dimethylformamide exchanges heat with the polyacrylonitrile system, thereby heating the polyacrylonitrile system, and removing small molecular impurities in the polyacrylonitrile system by stripping. The small molecular impurity gas separated from the polyacrylonitrile system is discharged through the gas outlet at the top of the devolatilizer, and the devolatilized polyacrylonitrile is discharged from the material outlet.

[0076] Comparative Example 4

[0077] The difference between this comparative example and Example 4 is that the upper and lower parts of the stripping devolatilizer 2 are respectively connected with a heat exchange medium inlet pipe 24 and a heat exchange medium outlet pipe 23, and the ambient temperature in the stripping devolatilizer 2 is controlled to be 185°C by controlling the temperature of the heat exchange medium in the heat exchange medium inlet pipe 24 (specifically, the temperature of the heat exchange medium in the heat exchange medium inlet pipe 23 is controlled to be 185°C, and the temperature of the heat exchange medium in the heat exchange medium outlet pipe 23 is measured to be 173°C, that is, the heat exchange medium adopts a top-in and bottom-out method).

[0078] Content detection

[0079] Sampling analysis was performed to detect the polyacrylonitrile-6 content in the raw materials used in Example 4, the polyacrylonitrile discharged from the material outlet of Example 4 and Comparative Example 4, and the dimethylformamide content in the polyacrylonitrile, and the small molecular impurity content in the polyacrylonitrile was calculated according to the following formula:

[0080] ω 小分子3 =1-ω 聚丙烯腈 -ω 二甲基甲酰胺2 ;

[0081] In the formula, ω 小分子3 It refers to the mass percentage of small molecular impurities in polyacrylonitrile, in wt%; ω 聚丙烯腈 It refers to the mass percentage of polyacrylonitrile in polyacrylonitrile, in wt%; ω 二甲基甲酰胺2It refers to the mass percentage of dimethylformamide in polyacrylonitrile-6, in wt%. The results are shown in Table 3.

[0082] Table 3 Test results of Example 4 and Comparative Example 4

[0083] Group Polyacrylonitrile content Dimethylformamide content Small molecule impurity content raw material 30.48wt% 63.19wt% 6.33wt% Example 4 34.66wt% 65.31wt% 0.03wt% Comparative Example 4 35.82wt% 64.08wt% 0.10wt%

[0084] As shown in Table 3, compared with Comparative Example 4, the content of small molecule impurities in the product after devolatilization in Example 4 is significantly reduced. The results show that when the stripping medium is heat exchanged in the stripping devolatilizer 2 in a top-in-bottom-out manner, the stripping medium enters the bottom to become supersaturated steam, and the solvent gas (i.e., the stripping medium) is liquefied and directly enters the product. In the process of gradual rise of the steam, the temperature rises, and the solvent in the polymer system to be purified (i.e., the raw material) will continue to vaporize, resulting in a slight decrease in the fluidity of the purified polymer system (i.e., the raw material); when the stripping medium is heat exchanged in the stripping devolatilizer 2 in a bottom-in-top-out manner, the solvent vapor (i.e., the stripping medium) enters the bottom and gradually rises, the temperature decreases, the gas phase solvent (i.e., the stripping medium) continues to liquefy, and the liquid phase solvent (i.e., the stripping medium) is partially integrated into the purified polymer system (i.e., the raw material) that is flowing and devolatilizing, and partially directly enters the product. Obviously, the present invention adjusts the internal heating mode of the stripping devolatilizer to an external heating mode, and configures the heating component of the gas devolatilizer to adopt a heat exchange tube, the heat exchange tube includes a heat exchange medium inlet pipe and a heat exchange medium outlet pipe, and the heat exchange medium inlet pipe and the heat exchange medium outlet pipe are respectively arranged at the lower part and the upper part of the shell, that is, the heat exchange medium can adopt a bottom-in and top-out mode, which can further improve the removal effect of small molecule compounds.

[0085] The above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Anyone familiar with the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by a person of ordinary skill in the art without departing from the spirit and technical concept disclosed by the present invention shall still be covered by the claims of the present invention.

Claims

1. A polymer devolatilization method for removing volatile components in a polymer system to be purified to improve the purity of a target polymer product, wherein the polymer system to be purified comprises a target polymer product, a solvent and impurities, characterized in that: The polymer devolatilization method comprises: taking the polymer system to be purified as a raw material, contacting the raw material with saturated steam in countercurrent, and performing a devolatilization treatment on the raw material by solvent stripping to remove volatile components in the polymer system to be purified, thereby obtaining a devolatilization product; The saturated steam is formed by heating a stripping medium, and the stripping medium includes the solvent.

2. The polymer devolatilization method according to claim 1, characterized in that: The solvent content in the devolatilization product is greater than or equal to the solvent content in the polymer system to be purified.

3. The polymer devolatilization method according to claim 1, characterized in that: The devolatilization temperature is less than or equal to the saturated steam temperature.

4. The polymer devolatilization method according to claim 1, characterized in that: During the devolatilization process, a heat exchange medium is used for heating, and the heat exchange medium flows in the opposite direction to the raw material.

5. The polymer devolatilization method according to claim 1, characterized in that: The stripping medium is the solvent.

6. A stripping devolatilizer, characterized in that: The stripping devolatilizer comprises a shell provided with a saturated steam inlet.

7. The stripping devolatilizer according to claim 6, characterized in that A material distributor and a steam screen plate are arranged in sequence from top to bottom in the shell.

8. The stripping devolatilizer according to claim 6, characterized in that A heating component is arranged outside the shell.

9. The stripping devolatilizer according to claim 8, characterized in that The heating component adopts a heat exchange tube, and the heat exchange tube includes a heat exchange medium inlet tube and a heat exchange medium outlet tube. The heat exchange medium inlet tube and the heat exchange medium outlet tube are respectively arranged at the lower part and the upper part of the shell.

10. A polymer devolatilization system for removing volatile components from a polymer system to be purified to improve the purity of a target polymer product, wherein the polymer system to be purified comprises a target polymer product, a solvent and impurities, characterized in that: The polymer devolatilization system comprises the stripping devolatilizer as described in any one of claims 6 to 9, and also comprises a heater, wherein the heater is used to heat the stripping medium to form saturated steam, wherein the stripping medium comprises the solvent; and a saturated steam outlet is provided on the heater, and the saturated steam outlet is connected to the saturated steam inlet.

Images