CN113877498A - Device and method for preparing SAN resin with stable composition and low volatile component - Google Patents
Device and method for preparing SAN resin with stable composition and low volatile component Download PDFInfo
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Abstract
The invention provides a device and a method for preparing SAN resin with stable composition and low volatile component, belonging to the field of preparation methods of high polymer materials. The method adopts thermal initiation free radical continuous bulk polymerization to prepare SAN resin, and controls acrylonitrile steam to instantaneously condense and flow back to the reaction kettle to participate in polymerization through a built-in condensing coil pipe at the top of the polymerization reaction kettle, so that the composition of styrene, acrylonitrile monomer and the final SAN resin in a reaction system is stable. The method optimizes the two-stage devolatilization mode of two static flash tanks in series in the prior SAN resin preparation process into the dynamic devolatilization mode of a primary flash tank static devolatilization series two-stage double-screw devolatilization extruder, effectively reduces the thermal degradation risk of the SAN resin at the high temperature of a secondary devolatilizer, and improves the mechanical property, transparency and appearance quality of the SAN resin. Meanwhile, compared with the devolatilization effect of a two-stage serial static flash tank, the SAN resin obtained by the process has lower volatile content which can reach 600-700 ppm.
Description
Technical Field
The invention belongs to the field of preparation methods of high polymer materials, and particularly relates to a device and a method for preparing SAN resin with stable composition and low volatile component.
Background
SAN resin is a binary random copolymer of styrene and acrylonitrile, and has excellent transparency, higher mechanical strength and good heat resistance and chemical properties. SAN resin is mainly used for transparent structural materials or as a matrix material of ABS resin, and has very wide application in the fields of electronic appliances, automobiles, building materials, furniture, sports and entertainment products, machinery, instrument industry and the like.
SAN resin can be prepared by emulsion polymerization, suspension polymerization and bulk polymerization methods based on the principle of free radical initiated copolymerization. At present, SAN dominant synthesis technology in industrial production is a thermal initiation continuous bulk polymerization process, and the technology has the advantages of high polymerization controllability, short process flow, low investment cost, good product quality, few environmental pollution problems and the like, and is a synthesis method which is most used in the industrial field. The technological process of preparing SAN resin by using a thermal initiation continuous bulk polymerization method mainly comprises the following steps: preparing a monomer/an auxiliary agent; carrying out monomer copolymerization reaction in a reactor; devolatilizing the unreacted monomer and the solvent; condensing and recovering volatile components; granulating and drying to obtain the SAN resin.
The synthesis of SAN resins with excellent properties using a thermally initiated continuous bulk process requires two key issues to be addressed:
(1) stability of SAN resin composition. The continuous bulk polymerization reactor has high viscosity, large reaction heat release and difficult temperature control, and the evaporation of reaction monomers is a common heat removal mode. However, since the boiling point of acrylonitrile monomer (77.35 ℃) is significantly lower than that of styrene (145.16 ℃), the concentration of acrylonitrile in the vaporized vapor is high, and the composition of styrene and acrylonitrile in the polymerization reactor changes, which results in unstable composition of the SAN copolymer formed. The literature reports that the compatibility among SAN copolymers with different composition distributions is poor, the mechanical property of the resin is deteriorated, the haze is improved, and the transparency is reduced due to the change of the content of acrylonitrile in the SAN resin. Therefore, the difference of acrylonitrile content of SAN copolymer of different components in SAN resin needs to be controlled within 4%.
In order to control the stability of styrene/acrylonitrile monomer composition in a reactor, the patent CN106188374A divides the introduction of styrene monomer into two paths, wherein one path is added into an evaporative condenser to be mixed with high-concentration acrylonitrile, and the concentration of the acrylonitrile in the condenser and the reactor is controlled to be close to the same by adjusting the dosage of the styrene; patent CN104628925B provides a method for producing SAN resin by two-kettle series polymerization, wherein fresh monomer mixture and devolatilized condensate are introduced into the second polymerization kettle, so that the viscosity of the SAN resin is not significantly increased in the second kettle, and the uniformity of the proportion of the reaction monomers is ensured by the supplement of fresh monomers and the shorter residence time of the second kettle, which is very important for preparing SAN resin with high acrylonitrile content.
(2) Low volatility of SAN resin. The SAN reaction solution after polymerization needs to remove unreacted monomers and solvent. Higher volatile components can cause yellowing, reduced transparency, and poor mechanical properties of the SAN resin during heating. Industrial devolatilization apparatuses are classified into two types, static type and dynamic type: static devolatilization equipment does not have mechanical stirring such as a flash tank and a stripping devolatilizer, is suitable for devolatilization of materials with higher volatile content, but often cannot meet the requirement of extremely low residual amount of volatile. Dynamic devolatilization equipment such as an exhaust screw extruder, a wiped film evaporator and the like use mechanical stirring to provide large-scale surface updating, so that the separation effect of volatile components from polymers is remarkably improved, very low volatile component residue is achieved, and the method is suitable for devolatilization of materials with low volatile component content.
In the continuous bulk polymerization process of thermally initiated free radicals, the exothermic heat in the polymerization vessel is mainly controlled by three ways: introducing low-temperature reaction materials, removing heat by cooling media in a jacket of the reactor, and evaporating and condensing monomers and solvents in a reaction system to transfer heat by phase change. At present, in the industrial SAN resin preparation process, the heat removal application by utilizing the evaporation and condensation of low molecular substances is the most extensive.
In a polymerization reaction kettle, compared with a styrene monomer and a solvent toluene, an acrylonitrile monomer has low boiling point and is volatile, and acrylonitrile is greatly evaporated and takes away heat in the polymerization process, so that the method has positive effects on controlling the temperature in the reaction kettle and ensuring the polymerization safety. In the current SAN polymerization process, a condenser for evaporating gas is usually disposed outside the reaction vessel, and there are two types of removal of condensate: (1) conveying the materials back to the charging process for utilization; (2) and the mixture is refluxed into the reaction kettle to continuously participate in the polymerization reaction. In the first mode, the high-concentration acrylonitrile in the condensate returns to the feeding process, so that the ratio of styrene to acrylonitrile monomer in the reactor is changed, the composition of the SAN resin obtained by polymerization is unstable, and the performance of the SAN resin is deteriorated due to the change of the polymer composition distribution; in the second mode, the condensation path and the reflux time are too long due to the external arrangement of the condenser, although the acrylonitrile monomer is not polymerized in a steam state, the condensate in the condenser is polymerized at a high temperature to form a copolymer insoluble gel with polyacrylonitrile or extremely high acrylonitrile content, the difference with the acrylonitrile content of the SAN resin in the kettle is very large, the incompatibility is caused, the mechanical property and the chromaticity of the SAN resin are reduced, and the problem is more serious particularly when the SAN resin with high acrylonitrile content is synthesized.
Devolatilization, which can meet health and environmental requirements while improving polymer properties, has become one of the necessary unit operations in a polymer production process. The generation of an interface, the mass transfer of the interface and the updating of the interface in the polymer devolatilization process have a decisive influence on the devolatilization effect. At present, a two-stage devolatilization mode with two flash tanks connected in series is usually adopted in the production process of SAN resin. However, as a static devolatilizer, the interface mass transfer capacity and the update capacity are poor in the devolatilization process, and a large amount of energy is required to be input for achieving an ideal devolatilization effect. The devolatilization mode of the two-stage serial flash tanks cannot ensure the low volatile component concentration of the SAN resin, so that the SAN resin obtained by the process cannot meet the application requirement in the field with low VOC content requirement.
In recent years, the devolatilization technology of a dynamic twin-screw devolatilization extruder is rapidly developed, an interface is generated through the formation of a film and the growth of bubbles, mass transfer is carried out through diffusion and bubble breakage, and the interface is updated through convection mixing, so that the devolatilization purpose can be achieved with the least energy, the retention time of a polymer in a devolatilization device can be reduced, the thermal degradation and aging of materials are reduced, and the devolatilization technology is the most advanced process of polymer devolatilization at present. On the other hand, in the devolatilization process of the twin-screw extruder, the residence time provided by the twin-screw extruder is short due to the structural characteristics of full-meshing self-cleaning, so that the twin-screw extruder is only suitable for treating materials with high solid content.
By combining the devolatilization characteristics of two different types of devolatilizers, the ideal devolatilization effect cannot be achieved by a single flash tank, and a two-stage devolatilization mode with two flash tanks connected in series is usually adopted. The operating temperature of the primary flash tank is 110-120 ℃, and unreacted acrylonitrile monomers are mainly removed; the operating temperature of the secondary flash tank is 220-260 ℃, and unreacted styrene monomers and solvents are mainly removed. The volatile content of SAN resin prepared by adopting a two-stage flash tank series devolatilization mode at present is still about 1000ppm, and the devolatilization process needs to be further optimized to reduce the volatile content.
Disclosure of Invention
The invention aims to solve the problems of wide component distribution of monomer materials in a reaction kettle and high concentration of unreacted monomers and solvents after devolatilization in the existing SAN thermal initiation free radical continuous bulk polymerization process, and provides a device and a method for preparing SAN resin with stable components and low volatile components.
In order to solve the technical problems, the technical scheme of the invention is as follows:
the present invention first provides an apparatus for preparing SAN resin with stable composition and low volatile component, which comprises:
a charging tank, a reaction kettle, a flash tank devolatilization device and a devolatilization extruder;
the feeding tank is connected with the reaction kettle, a feeding pump is arranged between the feeding tank and the reaction kettle, and raw materials enter the reaction kettle to carry out polymerization reaction after being fed in the feeding tank;
a stirrer and a cooling coil are arranged in the reaction kettle, the cooling coil is arranged at the top end of the reaction kettle, the bottom end of the stirrer penetrates through the cooling coil and extends into the reaction kettle to stir materials, and the top end of the stirrer extends out of the reaction kettle and is connected with a motor;
the reaction kettle is connected with the flash tank devolatilizer, a discharging gear pump is arranged between the reaction kettle and the flash tank devolatilizer, a heat exchanger is connected above the flash tank devolatilizer, and the flash tank devolatilizer carries out primary devolatilization on a reaction mixture in the reaction kettle;
the flash tank devolatilization device is connected with the double-screw devolatilization extruder, a melt pump is arranged between the flash tank devolatilization device and the double-screw devolatilization extruder, the double-screw devolatilization extruder carries out secondary devolatilization on devolatilization products of the flash tank devolatilization device, secondary devolatilization gas enters the recovery through an exhaust port, and the secondary devolatilization products enter a water tank through an opening die to be cooled and then are cut into particles and dried.
The invention also provides a method for preparing SAN resin with stable composition and low volatile component based on the device, which comprises the following steps:
the method comprises the following steps: uniformly mixing raw materials of styrene, an acrylonitrile monomer, a solvent and a chain transfer agent in a feeding tank to obtain a mixed solution, continuously injecting the mixed solution into a reaction kettle through a feeding pump, carrying out polymerization reaction for 1.5-3 hours at 130-180 ℃ to obtain a reaction mixture, and controlling an acrylonitrile steam to be instantly condensed at the top of the reaction kettle and flow back to the reaction kettle to participate in polymerization by a cooling coil pipe in the reaction kettle;
step two: starting a discharging gear pump, a flash tank devolatilization device and a double-screw devolatilization extruder, starting a feeding pump at the same time, adjusting the speed of the feeding pump and the discharging gear pump, keeping the feeding speed consistent with the discharging speed, feeding the reaction mixture obtained in the step one into the flash tank devolatilization device through the discharging gear pump for primary devolatilization to obtain primary devolatilized gas and a primary devolatilized product, and recovering the primary devolatilized gas through a heat exchanger to generate condensate;
step three: and (3) feeding the primary devolatilization product into a double-screw devolatilization extruder through a melt pump for secondary devolatilization to obtain secondary devolatilization gas and a secondary devolatilization product, recovering the secondary devolatilization gas through an exhaust port, and feeding the secondary devolatilization product into a water tank through an orifice die for cooling, granulating and drying to obtain the SAN resin.
Preferably, the mixed solution of the first step includes, in parts by weight: 60-90 parts of styrene monomer, 10-40 parts of acrylonitrile monomer, 10-50 parts of solvent and 0-10 multiplied by 10 parts of chain transfer agent-4And (4) portions are obtained.
Preferably, the solvent in the first step is toluene and has a boiling point of 110.6 ℃.
Preferably, the chain transfer agent in the first step is selected from one of n-butyl mercaptan, i-butyl mercaptan, n-dodecyl mercaptan or t-dodecyl mercaptan.
Preferably, the first-stage devolatilization temperature in the second step is 105-110 ℃, and the absolute pressure is 30-50 kPaA.
Preferably, the twin-screw devolatilization extruder in the third step is used for six-stage devolatilization, the temperature of the first two stages is 170-180 ℃, the temperature of the middle two stages is 190-200 ℃, and the temperature of the tail two stages is 200-210 ℃.
The invention has the advantages of
Compared with the prior art, the device and the method for preparing SAN resin with stable composition and low volatile component provided by the invention have the main advantages that:
the invention adjusts the external arrangement mode of the condenser in the prior SAN polymerization process into that the cooling coil is arranged in the top of the inner kettle of the reaction kettle, and water is used as a cooling medium. Three key problems are solved in this way: (1) the steam is condensed, refluxed and removed of heat at the top end in the reaction kettle, so that the controllability of a polymerization system is ensured; (2) acrylonitrile steam is instantaneously condensed at the top of the kettle and flows back to the reaction kettle to participate in polymerization, so that the composition change of styrene and acrylonitrile monomers in a reaction system is very small, and the composition of SAN resin obtained by polymerization is stable; (3) the cooling coil is positioned at the top of the kettle, so that the problem that the evaporated acrylonitrile monomer is subjected to homopolymerization or copolymerization reaction at the top of the kettle to form insoluble gel is avoided, and the product quality of the SAN resin is improved.
In addition, the invention optimizes the devolatilization mode of the existing SAN secondary series flash tank into the static devolatilization mode of a primary flash tank and the dynamic devolatilization mode of a secondary double-screw devolatilization extruder. The devolatilization temperature of the primary flash tank is 105-110 ℃, unreacted acrylonitrile monomers are mainly removed, and the viscosity of the devolatilized material is increased to completely meet the viscosity requirement of the devolatilization process of the secondary extruder; the temperature of the secondary double-screw devolatilization extruder is controlled at 170-210 ℃, and unreacted styrene monomers, solvents and a small amount of acrylonitrile monomers are mainly removed. Compared with the secondary flash tank 240-260 ℃ in the prior art, the devolatilization temperature of the invention is obviously reduced, the thermal degradation risk of SAN resin at high temperature is effectively reduced, and the mechanical property, transparency and appearance quality of the SAN resin are improved. Meanwhile, compared with the devolatilization effect of a two-stage serial flash tank, the SAN resin obtained in the process has lower volatile content which can reach 600-700 ppm, the VOC content of the resin is obviously reduced, and the application field of the SAN resin is widened.
Finally, the purpose of effectively regulating the molecular weight of the SAN resin can be achieved by regulating and controlling the temperature and the chain transfer concentration of a polymerization reaction system in the process of thermally-initiated free radical continuous bulk polymerization; the monomer conversion rate is usually between 60 and 80 percent in the polymerization process, and the volatile component concentration of the final product of the SAN resin is reduced by devolatilization treatment; the acrylonitrile content in the SAN resin prepared by the invention can be controlled within the range of 20-40%, and the requirements of different applications are met.
Drawings
FIG. 1 is a schematic diagram of the structure of an apparatus for preparing a SAN resin with stable composition and low volatility;
in the figure, 1, a feeding tank, 2, a high-pressure metering pump, 3, a motor, 4, a cooling coil, 5, a reaction kettle, 6, a flash tank devolatilizer, 7, a melt pump, 8, an exhaust port, 9, a port die, 10, a devolatilization extruder, 11, a discharge gear pump, 12, a stirrer, 13, a heat exchanger, 14 and a base.
Detailed Description
The present invention firstly provides an apparatus for preparing SAN resin with stable composition and low volatile component, as shown in FIG. 1, the apparatus comprising:
a charging tank 1, a reaction kettle 5, a flash tank devolatilization device 6 and a devolatilization extruder 10;
the feeding tank 1 is connected with the reaction kettle 5, a feeding pump 2 is arranged between the feeding tank 1 and the reaction kettle 5, and raw materials enter the reaction kettle 5 for polymerization reaction after being fed in the feeding tank 1;
a stirrer 12 and a cooling coil 4 are arranged in the reaction kettle 5, the cooling coil 4 is arranged at the top end of the reaction kettle 5, the bottom end of the stirrer 12 penetrates through the cooling coil 4 and extends into the reaction kettle 5 to stir the materials, and the top end extends out of the reaction kettle 5 and is connected with a motor 3;
the reaction kettle 5 is connected with the flash tank devolatilizer 6, a discharging gear pump is arranged between the reaction kettle 5 and the flash tank devolatilizer 6, a heat exchanger 13 is connected above the flash tank devolatilizer 6 and used for recovering the devolatilized gas to form condensate, and the flash tank devolatilizer 6 carries out primary devolatilization on the reaction mixture in the reaction kettle 5;
the flash tank devolatilization device 6 is connected with a double-screw devolatilization extruder 10, the double-screw devolatilization extruder 10 is arranged above a base 14, a melt pump 7 is arranged between the flash tank devolatilization device 6 and the double-screw devolatilization extruder 10, the double-screw devolatilization extruder 10 carries out secondary devolatilization on devolatilization products of the flash tank devolatilization device 6, secondary devolatilization gas enters and is recovered through an exhaust port 8, and the secondary devolatilization products enter a water tank through an orifice die 9 to be cooled and then are granulated, dried and packaged.
The invention also provides a method for preparing SAN resin with stable composition and low volatile component based on the device, which comprises the following steps:
the method comprises the following steps: uniformly mixing raw materials of styrene, an acrylonitrile monomer, a solvent and a chain transfer agent in a feeding tank 1 to obtain a mixed solution, continuously injecting the mixed solution into a reaction kettle 5 through a feeding pump 2, carrying out polymerization reaction for 1.5-3 hours at 130-180 ℃ to obtain a reaction mixture, and controlling acrylonitrile steam to instantaneously condense and reflux at the kettle top in the reaction kettle 5 by a cooling coil 4 to participate in polymerization so as to ensure that the styrene, the acrylonitrile monomer and the final SAN resin in a reaction system are stable;
the mixed solution preferably comprises the following components in parts by weight: 60-90 parts of styrene monomer, 10-40 parts of acrylonitrile monomer, 10-50 parts of solvent and 0-10 multiplied by 10 parts of chain transfer agent-4And (4) portions are obtained.
The solvent in the first step is preferably toluene, the boiling point of the solvent is 110.6 ℃, and the removal of acrylonitrile in the first-stage devolatilization process is facilitated;
the chain transfer agent in the first step is preferably one selected from n-butylmercaptan, isobutylmercaptan, n-dodecylmercaptan or tert-dodecylmercaptan;
step two: starting a discharging gear pump 11, a flash tank devolatilization device 6 and a double-screw devolatilization extruder 10, starting a feeding pump 2 at the same time, adjusting the speeds of the feeding pump 2 and the discharging gear pump 11, keeping the feeding speed consistent with the discharging speed, feeding the reaction mixture obtained in the step one into the flash tank devolatilization device 6 through the discharging gear pump 11 for primary devolatilization to obtain primary devolatilization gas and a primary devolatilization product, and recovering the primary devolatilization gas through a heat exchanger 13 to generate condensate; the first-stage devolatilization gas mainly takes acrylonitrile as a main component; the first-stage devolatilization temperature is preferably 105-110 ℃, and the absolute pressure is preferably 30-50 kPaA; the temperature of the first-stage devolatilization is strictly controlled, when the temperature is lower than 105 ℃, the devolatilization efficiency is reduced, so that the energy consumption is increased, and when the temperature is higher than 110 ℃, AN self-aggregation can be caused, so that the SAN yellow index is increased.
Step three: and (3) allowing the primary devolatilization product to enter a double-screw devolatilization extruder 10 through a melt pump 7 for secondary devolatilization to obtain secondary devolatilization gas and a secondary devolatilization product, recovering the secondary devolatilization gas through an exhaust port 8, allowing the secondary devolatilization product to enter a water tank through an orifice die 9 for cooling, and then granulating and drying to obtain the SAN resin. The secondary devolatilization gas mainly comprises styrene and a solvent; the twin-screw devolatilization extruder in the third step is used for six-stage devolatilization, the temperature of the first two stages is 170-180 ℃, the temperature of the middle two stages is 190-200 ℃, and the temperature of the tail two stages is 200-210 ℃. The temperature of the secondary devolatilization is strictly controlled, the temperature has influence on the volatile content and the product color, when the temperature is lower than 170 ℃, the devolatilization effect is reduced, the volatile content is high, and when the temperature is higher than 210 ℃, the yellow index of the SAN product is increased.
The present invention is further illustrated by reference to the following specific examples, in which the starting materials are all commercially available.
Example 1
Uniformly mixing 75 parts by weight of styrene monomer, 25 parts by weight of acrylonitrile monomer, toluene accounting for 25% of the monomers by weight and chain transfer agent n-dodecyl mercaptan accounting for 0.15% of the monomers by weight in a feeding tank, continuously injecting the mixture into a reaction kettle through a feeding pump, and carrying out polymerization reaction for 3 hours at 150 ℃ to obtain a reaction mixture; a cooling coil arranged in the reaction kettle controls acrylonitrile steam to be instantly condensed and refluxed to the reaction kettle at the top of the reaction kettle to participate in polymerization, so that the composition of styrene, an acrylonitrile monomer and the final SAN resin in a reaction system is stable;
starting a discharging gear pump, a flash tank devolatilization device and a double-screw devolatilization extruder for devolatilization, simultaneously starting a feeding pump, adjusting the speed of the feeding pump and the discharging gear pump, and keeping the feeding speed consistent with the discharging speed. Feeding the reaction mixture into a flash tank devolatilizer through a discharge gear pump for primary devolatilization to obtain primary devolatilized gas and a primary devolatilized product, and recovering the primary devolatilized gas through a heat exchanger to generate condensate (mainly taking acrylonitrile as a main component); the first-stage devolatilization temperature is 110 ℃, and the absolute pressure is 35 kPaA;
and (3) feeding the primary devolatilization product into a double-screw devolatilization extruder through a melt pump for secondary devolatilization to obtain secondary devolatilization gas and a secondary devolatilization product, recovering the secondary devolatilization gas (mainly comprising styrene and a solvent) through an exhaust port, and feeding the secondary devolatilization product into a water tank through a neck mold for cooling, granulating and drying to obtain the SAN resin. The twin-screw devolatilization extruder has six sections of devolatilization, wherein the temperature of the first section is 170 ℃, the temperature of the second section is 180 ℃, the temperature of the third section is 190 ℃, the temperature of the fourth section is 200 ℃, the temperature of the fifth section is 200 ℃ and the temperature of the sixth section is 210 ℃. The results of the product performance tests are shown in table 1.
Example 2
75 parts by weight of styrene monomer, 25 parts by weight of acrylonitrile monomer, toluene accounting for 25 percent of the weight of the monomers and chain transfer agent n-dodecyl mercaptan accounting for 0.15 percent of the weight of the monomers are uniformly mixed in a batching tank and then are continuously injected into a reaction kettle through a charging pump, and the polymerization reaction is carried out for 2.5 hours at 160 ℃. The other procedures were the same as in example 1. The results of the product performance tests are shown in table 1.
Example 3
75 parts by weight of styrene monomer, 25 parts by weight of acrylonitrile monomer, toluene accounting for 25 percent of the weight of the monomers and chain transfer agent n-dodecyl mercaptan accounting for 0.15 percent of the weight of the monomers are uniformly mixed in a batching tank and then are continuously injected into a reaction kettle through a charging pump, and the polymerization reaction is carried out for 2 hours at the temperature of 170 ℃. The other procedures were the same as in example 1. The results of the product performance tests are shown in table 1.
Example 4
Uniformly mixing 70 parts by weight of styrene monomer, 30 parts by weight of acrylonitrile monomer, toluene accounting for 25% of the weight of the monomers and chain transfer agent n-dodecyl mercaptan accounting for 0.15% of the weight of the monomers in a batching tank, continuously injecting the mixture into a reaction kettle through a charging pump, and carrying out polymerization reaction for 2.5 hours at 160 ℃ to obtain a reaction mixture. The other procedures were the same as in example 1. The results of the product performance tests are shown in table 1.
Example 5
65 parts by weight of styrene monomer, 35 parts by weight of acrylonitrile monomer, 25% by weight of toluene and 0.15% by weight of chain transfer agent n-dodecyl mercaptan are uniformly mixed in a batching tank, and then continuously injected into a reaction kettle through a charging pump, and a polymerization reaction is carried out for 2.5 hours at 160 ℃ to obtain a reaction mixture. The other procedures were the same as in example 1. The results of the product performance tests are shown in table 1.
Comparative example 1
75 parts by weight of styrene monomer, 25 parts by weight of acrylonitrile monomer, toluene accounting for 25 percent of the weight of the monomers and chain transfer agent n-dodecyl mercaptan accounting for 0.15 percent of the weight of the monomers are uniformly mixed in a batching tank and then are continuously injected into a reaction kettle through a charging pump, and the polymerization reaction is carried out for 2.5 hours at 160 ℃. In the polymerization process, a condenser is externally arranged in a reaction kettle for evaporation, condensation and heat removal, and the condensate flows back to the reaction kettle. The other procedures were the same as in example 1. The results of the product performance tests are shown in table 1.
Comparative example 2
75 parts by weight of styrene monomer, 25 parts by weight of acrylonitrile monomer, toluene accounting for 25 percent of the weight of the monomers and chain transfer agent n-dodecyl mercaptan accounting for 0.15 percent of the weight of the monomers are uniformly mixed in a batching tank and then are continuously injected into a reaction kettle through a charging pump, and the polymerization reaction is carried out for 2.5 hours at 160 ℃. In the devolatilization process, a two-stage devolatilization mode with two flash tanks connected in series is adopted, wherein the devolatilization temperature of a first-stage flash tank is 110 ℃, and the absolute pressure is 35 kPaA; the devolatilization temperature of the secondary flash tank is 240 ℃ and the absolute pressure is 3 kPaA. The other procedures were the same as in example 1. The results of the product performance tests are shown in table 1.
TABLE 1 SAN resin test results prepared in examples and comparative examples
Table 1 shows the SAN resin test results of the examples of the present invention and the comparative examples, and the comparison shows that the SAN resin prepared by the optimized process route of the present invention has more stable composition, lower volatile content and better appearance color. According to the method, the SAN resin with high purity and excellent performance can be stably prepared.
The above description is only a preferred embodiment of the present application and is not intended to limit the present application, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, improvement and the like made within the spirit and principle of the present application shall be included in the protection scope of the present application.
Claims (7)
1. An apparatus for preparing a compositionally stable, low volatile SAN resin, comprising:
a charging tank, a reaction kettle, a flash tank devolatilization device and a devolatilization extruder;
the feeding tank is connected with the reaction kettle, a feeding pump is arranged between the feeding tank and the reaction kettle, and raw materials enter the reaction kettle to carry out polymerization reaction after being fed in the feeding tank;
a stirrer and a cooling coil are arranged in the reaction kettle, the cooling coil is arranged at the top end of the reaction kettle, the bottom end of the stirrer penetrates through the cooling coil and extends into the reaction kettle to stir materials, and the top end of the stirrer extends out of the reaction kettle and is connected with a motor;
the reaction kettle is connected with the flash tank devolatilizer, a discharging gear pump is arranged between the reaction kettle and the flash tank devolatilizer, a heat exchanger is connected above the flash tank devolatilizer, and the flash tank devolatilizer carries out primary devolatilization on a reaction mixture in the reaction kettle;
the flash tank devolatilization device is connected with the double-screw devolatilization extruder, a melt pump is arranged between the flash tank devolatilization device and the double-screw devolatilization extruder, the double-screw devolatilization extruder carries out secondary devolatilization on devolatilization products of the flash tank devolatilization device, secondary devolatilization gas enters the recovery through an exhaust port, and the secondary devolatilization products enter a water tank through an opening die to be cooled and then are granulated and dried.
2. A method for preparing a compositionally stable, low volatile SAN resin based on the apparatus of claim 1, the method comprising:
the method comprises the following steps: uniformly mixing raw materials of styrene, an acrylonitrile monomer, a solvent and a chain transfer agent in a feeding tank to obtain a mixed solution, continuously injecting the mixed solution into a reaction kettle through a feeding pump, carrying out polymerization reaction for 1.5-3 hours at 130-180 ℃ to obtain a reaction mixture, and controlling an acrylonitrile steam to be instantly condensed at the top of the reaction kettle and flow back to the reaction kettle to participate in polymerization by a cooling coil pipe in the reaction kettle;
step two: starting a discharging gear pump, a flash tank devolatilization device and a double-screw devolatilization extruder, starting a feeding pump at the same time, adjusting the speed of the feeding pump and the discharging gear pump, keeping the feeding speed consistent with the discharging speed, feeding the reaction mixture obtained in the step one into the flash tank devolatilization device through the discharging gear pump for primary devolatilization to obtain primary devolatilized gas and a primary devolatilized product, and recovering the primary devolatilized gas through a heat exchanger to generate condensate;
step three: and (3) feeding the primary devolatilization product into a double-screw devolatilization extruder through a melt pump for secondary devolatilization to obtain secondary devolatilization gas and a secondary devolatilization product, recovering the secondary devolatilization gas through an exhaust port, and feeding the secondary devolatilization product into a water tank through an orifice die for cooling, granulating and drying to obtain the SAN resin.
3. The method for preparing SAN resin with stable composition and low volatility as claimed in claim 2, wherein the mixed solution of the first step comprises the following components in parts by weight: 60-90 parts of styrene monomer, 10-40 parts of acrylonitrile monomer, 10-50 parts of solvent and 0-10 multiplied by 10 parts of chain transfer agent-4And (4) portions are obtained.
4. The method for preparing a composition-stable low-volatile SAN resin according to claim 2, wherein the solvent in the first step is toluene and has a boiling point of 110.6 ℃.
5. The method for preparing SAN resin with composition stability and low volatility according to claim 2, wherein the chain transfer agent in step one is selected from the group consisting of n-butylmercaptan, isobutylmercaptan, n-dodecylmercaptan and t-dodecylmercaptan.
6. The method for preparing SAN resin with stable composition and low volatility as claimed in claim 2, wherein the first devolatilization temperature in the second step is 105 to 110 ℃ and the absolute pressure is 30 to 50 kPaA.
7. The method for preparing SAN resin with stable composition and low volatility as claimed in claim 2, wherein the twin screw devolatilization extruder in the third step is a six-stage devolatilization extruder, the temperature of the first two stages is 170-180 ℃, the temperature of the middle two stages is 190-200 ℃, and the temperature of the end two stages is 200-210 ℃.
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| CN114984892A (en) * | 2022-06-30 | 2022-09-02 | 广东石油化工学院 | Device for producing graphite foamable polystyrene by using body method |
| CN115090245A (en) * | 2022-06-30 | 2022-09-23 | 广东石油化工学院 | Device for producing flame-retardant expandable polystyrene by using body method |
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