JPH08239420A - Method for purifying polymerization product - Google Patents

Abstract

PURPOSE: To purify a soln.-polymn. product mainly comprising a methacrylate polymer, etc., efficiently without causing the degradation in qualities by removing volatile components such as an unreacted monomer and a solvent with an extruder having vent holes under specified conditions. CONSTITUTION: A polymn. product contg. volatile components such as an unreacted monomer, a by-product, and a solvent (e.g. methanol or acetone) is heated to 120-270 deg.C and fed into an extruder having vent holes and having the barrel temp. kept at 170-280 deg.C to separate and recover most of the volatile components through the first vent hole kept under a pressure of 0.3-3atm. The remaining volatile components are removed through the downstream-side vent holes kept under a pressure of 1-400Torr to reduce the volatile content to 1wt.% or lower. An esp. suitable solvent for the polymn. is methanol. The vented extruder used kneads a thermally molten polymer with a screw rorating in a high-temp. cylinder and extrudes the polymer through a die.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for purifying a polymerization reaction product containing a volatile component. More specifically, in a solution polymerization process, the reaction product after the polymerization step is efficiently and economically unreacted. The present invention relates to a method for removing volatile components such as monomers and solvents.

[0002]

2. Description of the Related Art In recent years, methacrylate-based polymers having particularly excellent properties in transparency, weather resistance and surface gloss have been used in recent years.
It is widely used in many applications such as lighting for automobiles, light electric parts and optical materials, signs, displays. Conventionally, a suspension polymerization method which is generally used as a method for producing a methacrylate resin molding material is accompanied by problems such as contamination of the polymer with a suspending agent, complexity of the washing and wastewater treatment steps,
In recent years, the solution polymerization method has attracted attention as an excellent process in terms of economy and product quality. In this solution polymerization method, a devolatilization step of removing volatile components such as unreacted monomers or solvents remaining in the polymerization liquid after the completion of polymerization is indispensable. As a method of removing the volatile components from such a polymerization reaction product, it is generally performed to heat the polymerization reaction product to a high temperature and guide it under a reduced pressure atmosphere to evaporate and separate the volatile components. It is suitable for mass production on a commercial scale because it can process a large amount of polymerization reaction products.

As an example of this method, Japanese Examined Patent Publication (Kokoku) No. 48-297.
In Japanese Patent Publication No. 97, there is reported a method in which a polymer solution is heated using a multi-tube heat exchanger and flashed in a devolatilization tank which is decompressed while foaming and the like to remove volatile components. In this devolatilization method, it is necessary to previously heat the polymerization reaction product to a sufficiently high temperature in order to reduce the concentration of residual volatile components in the obtained polymer. Also, the polymerization reaction product flushed in the devolatilization tank foams due to evaporation of volatile components, is cooled by the heat absorption at this time and increases in viscosity, and separation of the volatile components is likely to be insufficient, so that the volatile components are not recycled again in the devolatilization tank. The polymer is continuously discharged by a gear pump or the like at the bottom while heating to maintain fluidity. This polymer is usually supplied as it is to a vent extruder or the like, and finally produced as a product through devolatilization and mixing of additives and the like.

In solution polymerization of a methacrylate polymer, alkylbenzene such as toluene is generally used as a solvent in many cases, as shown in JP-A-1-172401, but in such a solvent system, a devolatilization tank is used. About 1
Unless kept at an absolute pressure of 50 mmHg or less, it is difficult to remove volatile components from the polymerization reaction product after polymerization. This is because the polymerization reaction product is not very volatile and contains only volatile components having an affinity for the polymer. In order to maintain this degree of pressure reduction, it is necessary to rapidly evaporate the vaporized and separated volatile components from the devolatilization tank, and to condense low-pressure volatile components vapor from this exhaust gas with a heat exchanger for efficient recovery. However, the load on the vacuum device and the refrigerating equipment increases, which is economically disadvantageous.

In order to solve the drawbacks of such a flash tank type devolatilization apparatus, Japanese Patent Laid-Open No. 3-281504 uses a devolatilization tank equipped with a discharge gear pump of a specific shape.
By controlling the rotation speed and supplying the polymerization reaction product to the meshing part of the gear, we are aiming for an efficient volatilization operation, but in order to process a large amount of polymerization reaction product, a large special A gear pump is required, equipment costs increase, and the liquid contact area and retention area increase, so the effects of contamination and heat deterioration cannot be ignored.

In the above flash operation and discharge operation, a part of the polymer is inevitably scattered and adhered to the wall surface of the devolatilization tank or stays at the bottom of the devolatilization tank, and the polymer is exposed to high temperature for a long time. In addition to being easily deteriorated due to heat, contamination from dust from liquid contact parts such as a gear pump and oil for mechanical seal is also a problem. In particular, in the case of a resin such as a methacrylate polymer, which is required to have high quality due to its transparency, even a slight deterioration or deterioration may cause deterioration in quality due to coloring or the like.

In order to solve this problem, an intermediate devolatilization device typified by a flash tank is omitted, and the polymerization reaction product is heated and then directly supplied to a vent extruder or the like for devolatilization, additive mixing, and activation. A process for collectively processing a series of post-processing steps such as shapes has been proposed. The following method has been reported as an example of such a devolatilization method, and according to this method, the processing time of the polymerization reaction product is shortened and the thermal history received by the polymer and the contamination caused by the contact with the equipment are reduced. Therefore, it is possible to devolatilize without compromising quality by a simple process.

In Japanese Patent Publication No. 52-17555 and Japanese Patent Publication No. 51-29914, a methyl methacrylate polymer composition produced by a bulk polymerization method or a solution polymerization method is heated to a high temperature to vapor pressure of volatile components. The pressure is increased to the above pressure, and is sprayed directly onto the feed section screw of the devolatilizing extruder maintained at an atmospheric pressure or less through the pores to separate and recover most of the volatile matter, and the remaining volatile matter is 250 to 290.
A method of separating with a vent at a temperature of 50 ° C and a vacuum degree of 50 mmHg or less has been reported. Further, in Japanese Patent Application Laid-Open No. 05-17516, a polymer solution is introduced into a heating device having an outlet directly connected to an extruder, and heated at a heating temperature under a pressure lower than a vapor pressure of the polymer solution to remove volatile components. Immediately after vaporizing the part, the polymer is scraped off immediately with a screw at the outlet of the heating device, and at the same time volatile components are removed from the pressure reducing vent port of the extruder. Methods for removing volatiles have been reported. Further, in JP-A-62-89710, a methacrylate-based polymerization reaction product is heated to a high temperature and cast into a devolatilization tank having a space above to remove volatile components and then supplied to a vent extruder. A method for reducing the residual volatile content to 1% by weight or less is shown.

However, in any of the above methods, a polymerization reaction product containing only a volatile component having a low volatility such as a monomer or an alkylbenzene and having an affinity for a polymer in a high concentration is directly added. For processing, an extruder having a multi-stage vent and a large devolatilization capacity is required as compared with the one used in usual extrusion molding. Further, in order to reduce the concentration of residual volatile components in the product, it is necessary to preheat the polymerization reaction product to a high temperature of 200 ° C. or higher and to maintain the vent part of the extruder at a high temperature and a high vacuum. The cause of the thermal deterioration of the polymer is not removed from such an operating environment, and there is a concern that the facility cost may increase in the case of commercial mass production.

[0010]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for economically and efficiently removing volatile components from a polymer composition without causing deterioration by deterioration such as coloring.

[0011]

By heating a polymerization reaction product containing a specific low boiling point solvent and then discharging it onto a screw of an extruder from a feed port kept under a constant pressure, As a result, a high surface area liquid film is formed in the vicinity of the first vent port of the extruder and a large evaporation area is secured, so that most of the volatile components in the polymer composition can be efficiently removed and It was found that a high-quality polymer usable as a molding material can be produced without causing deterioration such as coloring by removing the remaining volatile components by a vent and extruding the present invention, and thus the present invention has been accomplished.

That is, the present invention separates and removes volatile components from a polymerization reaction product containing an unreacted monomer, a reaction by-product, and a volatile component composed of at least one solvent selected from methanol and acetone. In the method for purifying a polymerization reaction product, (A) a plurality of vent ports in which the polymerization reaction product is heated to a temperature of 120 to 270 ° C and (B) the polymerization reaction product is barrel temperature 170 to 280 ° C. Is supplied to an extruder having, and first, most of the volatile components are separated and recovered from the first vent held at 0.3 to 3 atm,
(C) Then, the residual volatile content of the polymer composition is reduced to 1% by weight or less by removing the remaining volatile components with at least one rear vent set to a vent pressure of 1 to 400 Torr. The present invention relates to a method for purifying a characteristic polymerization reaction product. The first vent is the vent farthest from the die of the extruder and closest to the feed port thereof, and the rear vent is another vent closer to the die than the first vent.

In the present invention, the solvent contained in the polymerization reaction product may be methanol or acetone,
Particularly preferred is methanol. These alone
Alternatively, two types can be used in combination. Since these solvents have the following characteristics, it is possible to efficiently separate volatile components. (1) It has a low boiling point and is apt to evaporate. By heating, the polymerization reaction product is maintained at a high pressure to promote foaming at the time of discharge. (2) Since a low boiling point mixture such as an azeotropic mixture is formed with respect to the methacrylate-based and acrylate-based monomers, the evaporation of these monomer components is particularly promoted. (3) The polymer exhibits sufficient solubility when heated to maintain the uniformity of the polymerization reaction product in a wide concentration range. In addition, it is known from Japanese Examined Patent Publication No. S50-34071 that methanol has the following additional features. (4) When the polymerization reaction product containing the solvent is cooled, the solubility of the volatile component in the polymer is drastically lowered, so that it is easy to separate from the polymer, and the viscosity of the polymerization reaction product is lowered, so that the polymer can Difficult to adhere to the inner wall of the pipe.

The extruder to be used may be any apparatus which is equipped with a vent port for exhausting volatile components, plasticizes while heating and melting a polymer melted and kneaded by a screw rotating in a high temperature cylinder, and then extrudes from a die. Generally, a general molding vent extruder is selected. For example, a single-screw or twin-screw vent extruder is suitable, but an extrusion molding with a kneader or multistage front vents or rear vents is selected according to the purpose. Machines and the like are also used. In order to reduce the concentration of residual volatiles in the polymer as much as possible, L / D 20 to 4 provided with at least one rear vent in addition to the first vent
An extruder of about 0 is preferable. It is also possible to use a raw material supply port (hopper) of an ordinary extruder as a first vent and install a nozzle inside to discharge the volatile matter while flushing the polymerization reaction product toward the screw.

The temperature of each part of the extruder is set to a temperature suitable for shaping depending on the type and brand of the polymer to be produced, but the temperature of the rear vent other than the first vent and the barrel is usually 170.
The temperature is maintained at 280 ° C, preferably 150 ° C to 250 ° C.
The pressure of the rear vents other than the first vent is 1 to 400.
Torr, particularly 50 to 200 Torr is preferable. Most of the volatile components are separated and removed in the first vent, so there is no need to maintain a high vacuum in the rear vent. The screw rotation speed is determined so that the residence time of the polymer composition in the vent extruder is 1 to 30 minutes, preferably 5 to 15 minutes. At the same time, it is possible to prepare additives such as an ultraviolet absorber, a lubricant, a stabilizer, a coloring agent or a bluing agent in the polymer by using this extruder. The polymer extruded in this manner is chopped by a pelletizer, a hot-cut pelletizer, or the like, and the residual volatile content is 1% by weight or less, usually 0.
5% by weight or less of a polymer usable as a molding material is obtained.

The polymerization reaction product is introduced into the extruder so that the inside of the first vent of the extruder is maintained at an atmospheric pressure in the range of 0.3 to 3 atm, preferably 0.5 to 1.5 atm. Supplied. In a pressurized atmosphere of more than 3 atm, the evaporation rate of volatile components such as methacrylate monomers and solvents contained in the polymerization reaction product is low and separation is insufficient, and in a reduced pressure atmosphere of less than 0.3 atm, low boiling point volatilization occurs. It is not economical because a large-scale vacuum device or refrigerator is required to recover the components and maintain the degree of reduced pressure of the first vent. In order to avoid deterioration or deterioration of the polymer, an atmosphere composed of an inert gas such as nitrogen gas and / or a vapor of a volatile component constituting the polymerization reaction product is desirable, and it is not preferable for the purpose of promoting the emission of the volatile component vapor. An active gas may be introduced into the first vent and distributed.
In this case, an inert gas such as nitrogen or carbon dioxide is used, but nitrogen is particularly preferable. The volatile component evaporated and separated from the polymerization reaction product can be usually exhausted from the first vent by an exhaust device such as an ejector, a blower or a vacuum pump, introduced into a condenser, cooled, condensed and recovered.

The polymerization reaction product can be discharged directly from the outlet of the heater onto the screw of the extruder, but normally a nozzle or the like is installed at the supply port. As this nozzle, various valves and dies used in molding machines are used.
For example, the valve includes various valves such as a needle valve, a stop valve, a control valve, a vent plug, a purge valve and a die head valve used for discharging a polymer, and the die includes a strand die for granulation. To be These may be used alone or in combination of two kinds. These nozzles maintain a pressure inside the heater by creating a pressure difference from the heater side to the extruder side, and prevent rapid foaming devolatilization to reach the inside of the heater to prevent heat exchange in the heater. It enhances the capacity and expands the surface area of the released polymerization reaction product to promote the evaporative separation of volatile components.

Further, the polymerization reaction product discharged from these nozzles is kept at a constant flow rate and shaped into a constant cross-sectional shape, which enables stable supply to the extruder. When using a strand die or valves, the opening diameter of the pores or orifices is selected in the range of 0.5 to 15 mm, preferably 1 to 10 mm. If the opening diameter is too small, a pressure difference that exceeds the pressure limit of the heater will occur, which is dangerous, and if the opening diameter is too large, foaming devolatilization will reach the inside of the heater, making stable flash operation difficult. Become. Furthermore, by using a control valve as the nozzle, it is possible to control the internal pressure of the heater and the amount of the polymerization reaction product released, and to carry out the treatment economically while maintaining the optimum devolatilization effect.

The nozzle or the supply port may be installed at any position inside the first vent of the extruder or in the barrel in the vicinity thereof, but the nozzle or the supply port is installed as close as possible to the outlet of the heater to keep a sufficient temperature. Needs to be done. When it is installed inside the first vent, it is possible to feed the flashed polymerization reaction product while directly approaching the screw of the extruder and spraying it. When it is installed in the barrel near the first vent, it may be located at the front, the same position, or the rear of the first vent. When installed in front of the first vent, the first vent is a rear vent,
When installed behind the first vent, the first vent serves as an exhaust port for volatile components separated as a front vent. In that case, the polymerization reaction product can be supplied to the extruder barrel from any direction from the upper part to the lower part.

When a polymerization reaction product containing a specific solvent and heated to a temperature having sufficient pressure and fluidity is discharged into an atmosphere near atmospheric pressure through a nozzle or the like, the solvent in the polymerization reaction product is first discharged. The polymer rapidly evaporates near the outlet, and the polymer blows while foaming. At this time, by ensuring a large evaporation area, other volatile components in the polymerization reaction product,
Mainly the monomers are also evaporated at the same time and can be effectively separated and removed.
In particular, the pressurization inside the heater has a great influence on the separation of volatile components during flash, and the pressure at the feed port of the heater is 3 to 6
By maintaining at 0 Kg / cm ² , preferably 7 to 40 Kg / cm ² , the polymerization reaction product is efficiently devolatilized.

The polymer composition discharged into the extruder is cooled by the heat absorption due to the evaporation of the volatile components and becomes a highly viscous state while foaming. At this time, the temperature in the vicinity of the supply port of the extruder and in the first vent is 50 to 270 ° C., preferably 80 to 270 ° C.
Maintained in the range of 250 ° C. At a temperature of 50 ° C or lower, the foamed polymer rapidly solidifies and the volatile components are difficult to separate, and the separated volatile components condense in the first vent and are difficult to remove. At 270 ° C or higher, the polymer is Thermal deterioration is likely to occur. The polymer can take various forms from the solid state to the molten state in the extruder depending on its properties and heating temperature, but the supply of the polymerization reaction product to the extruder and the exhaust of volatile matter from the first vent are stable. If possible, any form will do. At this time, the residual volatile content concentration of the polymer composition near the first vent port is 1 to 10% by weight, preferably 1 to
It is maintained at 6% by weight.

In the heater, the polymerization reaction product is heated to a temperature at which an optimum devolatilizing effect is obtained depending on the composition of volatile components and the heat of vaporization. This heating temperature is generally 120 to 2
The temperature is selected in the range of 70 ° C, and is preferably 150 to 250 ° C, more preferably 170 to 250 ° C in consideration of the viscosity and thermal stability of the polymerization reaction product. The pressure in the heater depends on the composition of volatile components in the polymerization reaction product, the heating temperature and supply rate of the polymerization reaction product, the pressure loss due to the heater and the nozzle, and the pressure resistance of the heater, die and piping. It does not matter if the limit is not exceeded.

A heat exchanger is generally used as a heater for the polymerization reaction product, and a multi-tube heat exchanger, a plate fin type heat exchanger, a static mixer type heat exchanger and the like are preferable. A stirring tank or a horizontal reactor equipped with a screw and a stirrer may be used. In order to avoid thermal denaturation of the polymerization reaction product, it is necessary to uniformly raise the temperature to a predetermined temperature in the shortest possible time, and a structure capable of efficient heat exchange is desirable. It is desirable that the heater is installed as close to the feed port of the extruder as possible so that the heated polymerization reaction product is promptly discharged into the extruder.

According to the method of the present invention, after the polymerization reaction product is discharged into a high temperature flash tank and devolatilized as described above,
Compared with the process of supplying to a vent extruder in a molten state and finally treating, the equipment is simplified, the heat history of the polymer is mitigated, and the contact area with the equipment that causes pollution is reduced. Furthermore, compared with a conventional process of heating a polymerization reaction product containing a solvent such as a monomer or an alkylbenzene and then directly supplying it to a vent extruder to perform a devolatilization treatment, a vent extruder having a low devolatilization performance or a treatment capacity, For example, an ordinary single-screw extruder can be used, and the operating conditions such as the temperature of the vent portion and the degree of pressure reduction are alleviated.

Therefore, the energy consumption for collecting the volatile components under reduced pressure, maintaining the vacuum in the flash tank, and maintaining the fluidity of the polymerization reaction product is reduced, and the equipment capacity of the vacuum device, the condenser, the extruder, etc. is low. In addition, there is an advantage that even a polymer which is particularly susceptible to heat deterioration and contamination can be treated without suppressing the coloring and impairing the appearance. As a result, the utility unit and equipment costs are reduced, and it becomes possible to economically advantageously produce a high-quality polymer.

The polymer of the present invention means a copolymer formed by polymerization of methyl methacrylate alone or a monomer mixture of the following monomers copolymerizable with methyl methacrylate and methyl methacrylate. The polymerization reaction product contains 5 to 55% by weight of an unreacted monomer component with respect to 90 to 30% of the polymer. Examples of the monomer copolymerized with methyl methacrylate include methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, ethyl methacrylate, n-propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, cyclohexyl methacrylate, styrene, N-phenyl. Maleimide and the like can be mentioned, but among them, combinations of methyl methacrylate and methyl acrylate, methyl methacrylate and n-butyl acrylate, and methyl methacrylate and styrene are particularly preferable.

In order not to impair the resin characteristics such as transparency and weather resistance which are the characteristics of the methacrylate polymer, methyl methacrylate is 50% or more, particularly 75 to 100% by weight.
Although a polymer containing it is preferable, the copolymer of methyl methacrylate and styrene may be a polymer composed of 5 to 74% by weight of methyl methacrylate and 26 to 95% by weight of styrene.

The method for removing volatile components of the present invention can be applied as a polymer separation step to a polymer production process by a continuous solution polymerization method or a bulk polymerization method. Examples of the continuous preparation method include (1) continuous solution polymerization of a mixture of a monomer component containing methyl methacrylate and the solvent such as methanol in the presence of a polymerization initiator and a chain transfer agent, and (2) Continuous bulk polymerization of methyl methacrylate alone or a mixture of methyl methacrylate and a monomer component for copolymerization in the presence of a polymerization initiator and a chain transfer agent is carried out, and the reaction product is subjected to the above-mentioned methanol or the like. A method of adding and mixing the solvent may be considered.

A polymer can be produced by any of the methods, but the optimum composition and method may be selected in consideration of the physicochemical properties of the monomer component and the polymer to be produced and the process advantages. Further, the present method can be applied to the treatment of polymerization reaction products obtained by various other methods.

The polymerization reaction product in the present invention is a polymer,
It includes a monomer component and a solvent as main components, and a component derived from a polymerization initiator, a chain transfer agent and an additive added at the time of polymerization.
Further, the polymerization solution of the solution polymerization method using the above-mentioned methanol as a solvent may be treated as it is, or may be prepared by adding a solvent such as methanol to the polymerization solution of the bulk polymerization method or the solution polymerization method. Good. The polymer composition is 30 to 90% by weight, and when the amount of the polymer exceeds 90% by weight, the polymerization reaction product has a high viscosity, which makes it difficult to move and distribute it in a pipe or a heater. Further, if the polymer concentration is less than 30% by weight, the residual volatile content in the obtained polymer will increase and the production efficiency will decrease, which is not practical. The polymerization reaction product contains the monomer component in an amount of 5 to 55% by weight, preferably 10 to 40% by weight.

It is practically difficult to obtain a polymer composition containing less than 5% by weight of the monomer component, and when the amount of the monomer component exceeds 55% by weight, the residual amount in the obtained polymer increases. Not practical. Further, the solvent is 5 to 65 in the polymerization reaction product.
It should be contained in the range of, preferably 6 to 35% by weight. When the amount of the solvent is less than 5% by weight, the residual volatile content in the polymer also increases, and when the concentration of the solvent exceeds 65% by weight, the productivity is lowered and it is inefficient. Further, this polymerization reaction product needs to be maintained at a temperature at which it has a uniform and fluid viscosity, and it is preferable to maintain it near the polymerization temperature particularly when carrying out solution polymerization using methanol or the like.

In the present invention, the polymerization reaction product must have a weight ratio of the monomer component to the solvent of 0.3 to 8, and preferably 0.5 to 4. When the weight ratio of the monomer component to the solvent exceeds 4, problems such as insufficient removal of volatile components and a large amount of residual volatile components in the polymer occur.

The present invention will be more specifically illustrated, but the present invention is not limited thereto. FIG. 1 is a schematic flow sheet of the apparatus used to carry out the method of the present invention. The polymerization reaction product is prepared in the stirring tank 1, supplied to the heater 3 at a predetermined flow rate by the metering pump 2, and heated to a predetermined temperature.
The outlet of the heater is directly connected to the supply port 5 installed in the lower barrel of the first vent 6 of the vent extruder 9 via the control valve 4. The polymerization reaction product is injected into the vent extruder 9 through the supply port 5 while adjusting the heater internal pressure and the discharge flow rate by the control valve 4. At this time, nitrogen gas is introduced through the inlet 7 on the side surface of the first vent and circulated so that the inside of the first vent 6 is maintained at a predetermined pressure.

The injected polymer composition is heated and melted while being transferred by a screw. Finally die 13
Are continuously extruded through the pelletizer 14 and processed into pellets suitable for use in various molding machines by the pelletizer 14. Volatile components evaporated at the time of injection are discharged together with nitrogen gas from the first vent 6, condensed in the condenser 10 and collected in the receiver 11. The volatile components separated after the first vent 6 are exhausted from the second vent 8 by the exhaust device, the high boiling point components are removed by the distillation tower 12, and the monomer components are recovered by the condenser and sent to the exhaust device.

FIG. 2 is a schematic flow sheet of a devolatilizer for flushing the polymerization reaction product through the nozzle 15 installed inside the first vent of the vent extruder 9. In this case, the polymerization reaction product prepared in the stirring tank 1 is supplied to the heater 3 and heated to a predetermined temperature, and then installed on the side surface of the first vent 6 of the vent extruder 9 via the control valve 4. Flush from the supply port 5 through the nozzle 15 toward the screw of the vent extruder 9. The inside of the first vent 6 is maintained at a predetermined pressure, and the flashed polymer is heated and melted while being transferred by a screw as in FIG. 1, and is continuously extruded. Volatile components evaporated during the flash are discharged from the first vent 6, condensed in the condenser 10 and collected in the receiver 11. The volatile components separated after the first vent 6 are exhausted from the second vent 8, the high boiling point components are removed by the distillation tower 12, and the monomer components are recovered by the condenser.

FIG. 3 is a schematic flow sheet of a polymer production process by a continuous solution polymerization method to which the method of the present invention is applied. In this case, after the monomer components, the solvent such as methanol, the polymerization initiator, the chain transfer agent, and the like are mixed in the mixing tank 17 to prepare the raw material liquid, the constant mixing pump 18 is used to prepare a constant mixing flow rate for the complete mixing polymerization reactor 16 And continuously polymerize. This polymerization liquid is taken out by a metering pump 2 and introduced into a heater 3 to be treated in the same manner as in FIG. 1 to continuously produce a polymer.

FIG. 4 shows an example in which the above-mentioned solvent such as methanol is additionally added to and mixed with the polymerization liquid extracted in the polymer production process by the continuous bulk polymerization method. In this case, as in FIG. 2, the raw material liquid is prepared by mixing the monomer components, the polymerization initiator, the chain transfer agent, etc. in the preparation tank 17, and then the constant mixing pump 18 supplies the mixture to the complete mixing polymerization reactor 16 at a constant flow rate. Supply and polymerize. This polymerization liquid was extracted by the metering pump 2, the solvent such as methanol was continuously added additionally through the injection port 20, uniformly mixed by the mixer 19, and then introduced into the heater 3 and the same as in FIG. 1 below. To continuously produce a polymer. The temperature and pressure of each part can be changed by an external heating device or a pressure control valve, and the temperature and pressure of the polymerization reaction product and the volatile component in each part are measured. The flow rate and composition of the supplied polymerization reaction product can be arbitrarily changed.

[0038]

EXAMPLES Next, more detailed description will be given with reference to Examples.
The invention is not limited to the examples. All "parts" and "%" described herein indicate parts by weight and% by weight.
In the following examples, the physical properties of polymers were measured by the following methods.

(1) Volatile components contained in the polymer were analyzed by gas chromatography to quantify the content. (2) The total light transmittance (%) of the molded product is ASTD1003
It was measured by the method. The specifications of the main equipment used are as follows. Stirring tank and polymerization tank: Capacity 6 liters, heat medium circulation jacket, equipped with stirrer Heater: Static mixer with jacket Control valve: Venturi throat type angle control valve, 3 / 4B, Cv = 0.01 flash nozzle: Single hole strand die, open Caliber 2.
5mm × L10mm Extruder: Single screw, screw diameter φ40mm, L
/D=32.2 With vent

The polymerization reaction product was supplied to the extruder by the following method. Method of directly injecting the polymerization reaction product into the vent extruder from the supply port inside the barrel Method of flushing the polymerization reaction product toward the screw through the nozzle installed inside the first vent

The abbreviations used in Tables 1 to 4 are as follows. MMA: Methyl methacrylate MA: Methyl acrylate EA: Ethyl acrylate BA: n-Butyl acrylate Me: Methanol AC: Acetone ST: Styrene TOL: Toluene ND: Detection limit of gas chromatography (0.01
%) Indicates the following

Example 1 Using the apparatus of FIG. 1, polymethylmethacrylate 60.0
Part, 25.6 parts of methyl methacrylate, 1.1 parts of methyl acrylate, and 5 kg of a methacrylate-based polymerization reaction product containing 13.3 parts of methanol were heated to 150 ° C. in the stirring tank 1 and uniformly stirred and mixed. This polymerization reaction product was supplied to the heater 3 at a flow rate of 1 kg / h by the metering pump 2, heated to 190 ° C., and then injected into the vent extruder 9 from the supply port 5 at the lower part of the barrel of the first vent 6. . At this time, the pressure in the heater introduction part is controlled by the control valve 4.
It was maintained at 5 kg / cm ² . The generated volatile component vapor was discharged from the first vent 6, and the volatile component condensed through the condenser 10 was collected in the storage tank 11. Volatiles were recovered at 0.37 kg / h, 93% of theory, containing 61.0% methyl methacrylate, 2.6% methyl acrylate and 36.4% methanol. Also, the first vent port 6
The internal pressure was maintained at 0.9 to 1.1 atm.

Immediately after being devolatilized by the first vent 6, methyl methacrylate 4.2 as residual volatile components in the polymer.
%, Methyl acrylate 0.12% and methanol 0.
05% was included. This polymer was heated and melted while maintaining the barrel temperature at 230 ° C., and the volatile matter was further removed by the second vent 8 set at a vacuum degree of 150 Torr. The polymer was continuously extruded through a die 13 and pelletized by a pelletizer 14. The volatile component vapor exhausted from the second vent 8 of the vent extruder 9 was introduced into the distillation column 15 to separate and remove the high boiling point component, and the monomer component was recovered by the condenser. The remaining volatile components in the obtained polymer are 0.33% methyl methacrylate and 0.01% methyl acrylate.
And methanol were below the detection limit, and the total volatile matter concentration was 0.34%. The total light transmittance was 93%, which was colorless and transparent and had a good appearance.

Examples 2 to 6 Polymerization reaction products having the same composition as in Example 1 were prepared and devolatilized under various conditions by the same method to obtain pelletized polymers. Table 1 shows the composition of the polymerization reaction product, the heating temperature and supply rate, the devolatilization / extrusion processing conditions, the remaining volatile components of the obtained polymer, and the total light transmittance.

Example 7 A polymerization reaction product having the same composition as in Example 1 was prepared by using the apparatus shown in FIG. 2 and keeping it at 150 ° C., and was supplied to the heater 3 at a flow rate of 1 kg / h and heated to 190 ° C. After that, when flushed toward the screw through the nozzle 15 installed inside the first vent of the vent extruder, the polymer separated into foamed strands having an outer diameter of about 4 mm was fed as it was into the extruder. Immediately after flushing, the polymer contained 4.1% methyl methacrylate, 0.12% methyl acrylate and 0.04% methanol as residual volatiles.

After that, the polymer was heated and melted at a barrel temperature of 230 ° C. as in Example 1, and further volatile components were removed by the second vent 8 set to a vacuum degree of 150 Torr and then extruded. The remaining volatile components in the obtained polymer were methyl methacrylate 0.33% and methyl acrylate 0.0.
1% and methanol were below the detection limit, and the total volatile matter concentration was 0.34%. The total light transmittance was 93%, which was colorless and transparent and had a good appearance.

Examples 8 to 10 Polymerization reaction products having the same composition as in Example 1 were prepared and devolatilized under various conditions in the same manner as in Example 7 to obtain pelletized polymers. The results are also shown in Table 2.

Examples 11 to 14 Polymerization reaction products having different concentrations of the polymer, methyl methacrylate, methyl acrylate and solvent were prepared and subjected to volatilization treatment in the same manner as in Example 1 to obtain a pelletized polymer. did. The results are also shown in Tables 2 and 3.

Example 15 A polymerization reaction product was prepared by using acetone as a solvent,
A devolatilization treatment was carried out in the same manner as in Example 1 to obtain a polymer in pellet form. The results are also shown in Table 3.

Examples 16 to 17 Polymerization reaction products were prepared using ethyl acrylate and n-butyl acrylate as comonomers, and Example 1
A devolatilization treatment was carried out in the same manner as in 1. to obtain a pelletized polymer. The results are also shown in Table 3.

Examples 18 to 19 Polymerization reaction products were prepared by using styrene as a comonomer, and volatilized by the same method as in Example 1 to obtain pelletized polymers. The results are also shown in Tables 3-4.

Comparative Example 1 A polymerization reaction product containing 60 parts of polymethyl methacrylate, 25.6 parts of methyl methacrylate, 1.1 parts of methyl acrylate and 13.3 parts of toluene was prepared by using the apparatus shown in FIG. did. 1 k of this polymerization reaction product
After supplying to the heater 3 at a flow rate of g / h and raising the temperature to 190 ° C., it was devolatilized under the same conditions as in Example 1, but the internal pressure of the heater 3 at this time was 8 kg / cm ² . First vent 6
Immediately after being devolatilized by, the polymer contained 9.5% of methyl methacrylate, 0.28% of methyl acrylate and 4.93% of toluene as residual volatile components. A pellet-like polymer obtained by further removing volatile components from this polymer by a second vent 8 by the same method and then extruding the polymer contained 1.16% of methyl methacrylate, 0.03% of methyl acrylate and 0.60% of toluene. Including, the total volatile matter concentration was 1.79%.

Comparative Example 2 A polymerization reaction product containing 71 parts of polymethyl methacrylate, 27.8 parts of methyl methacrylate and 1.2 parts of methyl acrylate was prepared by using the apparatus shown in FIG. This polymerization reaction product was supplied to the heater 3 at a flow rate of 1 kg / h, heated to 190 ° C., and then devolatilized under the same conditions as in Example 1, but the internal pressure of the heater 3 at this time was 7 kg.
Was / cm ² . Immediately after being devolatilized by the first vent 6, the polymer contained 9.7% of methyl methacrylate and 0.28% of methyl acrylate as residual volatile components. The pellet-like polymer obtained by further removing the volatile matter from this polymer by the second vent 8 by the same method and then extruding, contained 1.18% of methyl methacrylate and 0.03% of methyl acrylate as residual volatile components, The total volatile matter concentration was 1.21%.

Reference Example 1 Continuous solution polymerization was carried out using the apparatus shown in FIG. 83.2 parts of methyl methacrylate, 3.5 parts of methyl acrylate,
13.3 parts of methanol, 0.01 part of di-tert-amyl peroxide and 0.23 part of n-dodecyl mercaptan are mixed in a blending tank 17 under a nitrogen atmosphere to prepare a raw material liquid. 4.6 kg of this raw material liquid was added to the polymerization tank 16 in advance and the mixture was sealed, and the temperature was raised to 150 ° C. to polymerize until the monomer conversion rate reached 69% and the polymer concentration reached 60%. It is continuously supplied to the polymerization tank 16 at a flow rate of 1 kg / h.
By setting the reaction temperature in the polymerization tank 16 to 150 ° C. and the average residence time to 4.6 hours, 60 parts of a polymethylmethacrylate polymer having a weight average molecular weight of about 100,000, 25.6 parts of methyl methacrylate, and 1.1 parts of methyl acrylate. And a polymerization reaction product containing 13.3 parts of methanol was produced.

Example 20 Using the apparatus shown in FIG. 3, the polymerization reaction product produced in Reference Example 1 was continuously fed to the heater 3 at a flow rate of 1 kg / h by the metering pump 2 and heated to 190 ° C. After that, like the first embodiment, it was injected into the vent extruder 9 from the supply port 5 at the bottom of the barrel of the first vent 6. At this time, the internal pressure of the heater 3 was maintained at 25 kg / cm ² by the control valve 4. Methyl methacrylate as a residual volatile component in the polymer immediately after being devolatilized by the first vent 6.
1%, methyl acrylate 0.12% and methanol 0.04% were included. The residual volatile components in the pellets obtained by extruding this polymer after removing the volatile components by the second vent 8 in the same manner as in Example 1 contained 0.33% of methyl methacrylate and 0.01% of methyl acrylate. And the total volatile content was 0.34%.
Methanol was below the detection limit. The total light transmittance was 93%, which was colorless and transparent and had a good appearance.

Reference Example 2 Continuous bulk polymerization was carried out using the apparatus shown in FIG. Methyl methacrylate 96 parts, methyl acrylate 4 parts, di-tert-
0.018 parts of butyl peroxide and 0.2 parts of n-dodecyl mercaptan are mixed in a mixing tank 17 under a nitrogen atmosphere to prepare a raw material liquid. This raw material liquid (4.6 kg) was added to the polymerization tank 17 in advance and sealed, and the temperature was raised to 150 ° C. to polymerize until the monomer conversion rate reached 60%, and then the raw material liquid was flowed at a flow rate of 1 kg / h. It is continuously supplied to the polymerization tank 16.
By setting the reaction temperature in the polymerization tank 16 to 150 ° C. and the average residence time to about 3 hours, 60 parts of a polymethylmethacrylate polymer having a weight average molecular weight of about 100,000, 38.4 parts of methyl methacrylate and 1.6 parts of methyl acrylate. A polymerization reaction product containing was produced.

Example 21 The polymerization reaction product produced in Reference Example 2 was continuously withdrawn by the metering pump 2 at a flow rate of 1 kg / h using the apparatus shown in FIG. 153 kg
Polymerization reaction product containing 52.0 parts of polymethyl methacrylate, 33.3 parts of methyl methacrylate, 1.4 parts of methyl acrylate, and 13.3 parts of methanol, which was additionally added at a flow rate of 1 / h and uniformly mixed by the mixer 19. Was prepared.
This polymerization reaction product was continuously supplied to the heater 3 at a flow rate of 1.153 kg / h to raise the temperature to 190 ° C., and thereafter, as in Example 1, the supply port 5 at the bottom of the barrel of the first vent 6 was used. Was injected into the vent extruder 9. At this time, the internal pressure of the heater 3 is 24 kg / c by the control valve 4.
It was maintained at m ² . Immediately after being devolatilized by the first vent 6, 4.2% of methyl methacrylate, 0.12% of methyl acrylate and 0.05% of methanol were contained as residual volatile components in the polymer. The residual volatile components in the pellets obtained by treating this polymer with a vent extruder under the same conditions as in Example 1 contained 0.33% methyl methacrylate and 0.01% methyl acrylate, and the total volatile content concentration was 0. It was 0.34%. Methanol was below the detection limit. The total light transmittance was 93%, which was colorless and transparent and had a good appearance.

[0058]

According to the present invention, the polymerization reaction product containing a predetermined solvent such as methanol is heated and pressurized and directly supplied to the vent extruder, whereby the polymer is taken out while the volatile components are separated. Further, the polymer can be easily separated and purified, and a high quality polymer can be produced without causing deterioration such as coloring. It is possible to improve degassing efficiency and operate the equipment stably for a long time with low equipment cost.

[0059]

Table 1 Example No. 1 2 3 4 5 6 Comonomers used MA MA MA MA MA MA MA MA Composition in polymer (%) 4 4 4 4 4 4 Solvent used Me Me Me Me Me Me Me Polymerization reaction composition (%) ) Polymer 60.0 60.0 60.0 60.0 60.0 60.0 MMA 25.6 25.6 25.6 25.6 25.6 25.6 Comonomer 1.1 1.1 1.1 1.1 1.1 1.1 Solvent 13.3 13.3 13.3 13.3 13.3 13.3 Supply of polymerization reaction product Supply temperature (℃) 150 150 150 150 150 150 Supply rate ( kg / hr) 1.0 1.0 1.0 1.0 1.0 1.0 Heater outlet temperature (℃) 190 190 190 190 170 210 Heater inlet internal pressure (kg / cm2) 25 35 25 20 15 30 Vent extruder supply method (A) (A) ) (A) (A) (A) (A) First vent internal pressure (atmospheric pressure) 1.0 1.0 1.4 0.6 1.0 1.0 Residual volatile components (%) immediately after flushing MMA 4.20 4.70 4.90 2.40 5.60 3.00 Comonomers 0.12 0.14 0.14 0.07 0.16 0.09 Solvent 0.05 0.04 0.05 0.04 0.05 0.04 Extruder barrel temperature (℃) 230 230 230 230 230 230 Second vent vacuum degree (Torr) 150 150 150 150 150 150 150 Residual volatile components in extruded pellets (%) MMA 0.33 0.36 0.37 0.23 0.41 0.27 Comonomers 0.01 0.01 0.01 0.01 0.01 0.01 Solvent ND ND ND ND ND ND Total light transmittance (%) 93 93 93 93 93 93

[0060]

Table 2 Example No. 7 8 9 10 11 12 Comonomers Used Composition in polymer (%) MA MA MA MA MA MA MA Used solvent 4 4 4 4 4 4 Composition of polymerization reaction product (%) Me Me Me Me Me Me Me Polymer 60.0 60.0 60.0 60.0 50.0 70.0 MMA 25.6 25.6 25.6 25.6 35.2 20.5 Comonomer 1.1 1.1 1.1 1.1 1.5 0.9 Solvent 13.3 13.3 13.3 13.3 13.3 8.6 Supply of Polymerization Reaction Product Supply Temperature (℃) 150 150 150 150 150 150 Supply Rate ( kg / hr) 1.0 1.0 1.0 1.0 1.0 1.0 Heater outlet temperature (℃) 190 190 190 200 190 190 Heater inlet internal pressure (kg / cm2) 25 35 20 25 27 15 Vent extruder supply method (B) (B) ) (B) (B) (A) (A) First vent internal pressure (atmospheric pressure) 1.0 1.0 0.6 1.0 1.0 1.0 Remaining volatile components (%) immediately after flushing MMA 4.10 4.60 2.30 3.60 5.20 2.10 Comonomers 0.12 0.13 0.07 0.11 0.15 0.06 Solvent 0.04 0.05 0.04 0.05 0.04 0.05 extruder barrel temperature (℃) 230 230 230 230 230 230 second vent Check the degree (Torr) 150 150 150 150 150 150 residual volatiles extrusion pellet (%) MMA 0.33 0.36 0.23 0.30 0.39 0.22 comonomer 0.01 0.01 0.01 0.01 0.01 0.01 solvent ND ND ND ND ND ND Total light transmittance (%) 93 93 93 93 93 93

[0061]

[Table 3] Example No. 13 14 15 16 17 18 18 Comonomer used MA MA MA MA EA BA ST Composition in polymer (%) 4 9 4 4 4 20 Solvent used Me Me AC Me Me Me Polymerization reaction composition (%) ) Polymer 40.6 60.0 60.0 60.0 60.0 69.4 MMA 28.2 24.3 25.6 25.6 25.6 13.9 Comonomer 1.2 2.4 1.1 1.1 1.1 3.5 Solvent 30.0 13.3 13.3 13.3 13.3 13.3 Supply of polymerization reaction product Supply temperature (℃) 150 150 150 150 150 150 Supply rate ( kg / hr) 1.0 1.0 1.0 1.0 1.0 1.0 Heater outlet temperature (℃) 190 190 190 190 190 190 Inside pressure of heater inlet (kg / cm2) 30 25 20 25 25 25 Vent extruder supply method (A) (A) ) (A) (A) (A) (A) First vent internal pressure (atmospheric pressure) 1.0 1.0 1.0 1.0 1.0 1.0 Residual volatile components after flash (%) MMA 1.50 3.40 3.60 4.10 4.20 2.31 Comonomer 0.04 0.24 0.11 0.14 0.18 0.64 Solvent 0.04 0.05 0.04 0.04 0.05 0.04 extruder barrel temperature (℃) 230 230 230 230 230 220 second base Doo vacuum (Torr) 200 150 150 150 150 150 residual volatiles extrusion pellet (%) MMA 0.18 0.29 0.40 0.33 0.33 0.23 comonomer 0.01 0.02 0.01 0.01 0.01 0.06 solvent ND ND ND ND ND ND Total light transmittance (%) 93 93 93 93 93 92

[0062]

[Table 4] Example, Comparative Example No. 19 Actual 20 Actual 21 Ratio 1 Ratio 2 Comonomers used Composition in polymer (%) ST MA MA MA MA Solvent used 40 4 4 4 4 Composition of polymerization reaction product (%) Polymer without Me Me Me TOL 69.4 60.0 60.0 60.0 71.0 MMA 10.4 25.6 25.6 25.6 27.8 Comonomer 6.9 1.1 1.1 1.1 1.2 Solvent 13.3 13.3 13.3 13.3 0.0 Polymerization reaction product Supply temperature (℃) 150 150 150 150 150 Supply rate (kg / hr) ) 1.0 1.0 1.0 1.0 1.0 Heater outlet temperature (℃) 190 190 190 190 190 Heater inlet internal pressure (kg / cm2) 25 25 24 8 7 Vent Extruder supply method (A) (A) (A) (A) ) (A) Internal pressure of first vent (atmospheric pressure) 1.0 1.0 1.0 1.0 1.0 Remaining volatile components after flushing (° C) MMA 1.73 4.10 4.20 9.50 9.70 Comonomer 1.27 0.12 0.12 0.28 0.28 Solvent 0.05 0.04 0.05 4.93 0.00 Extruder barrel temperature (° C) 220 230 230 230 230 second vent vacuum degree (Torr) residual of 150 150 150 150 150 extrusion pellets Volatile component (%) MMA 0.20 0.33 0.33 1.16 1.18 comonomer 0.14 0.01 0.01 0.03 0.03 solvent ND ND ND 0.60 0.00 Total light transmittance (%) 92 93 93 93 93

[Brief description of drawings]

FIG. 1 is a conceptual diagram of a flow of an apparatus used in Examples 1 to 6, Examples 11 to 19 and Comparative Examples 1 and 2.

FIG. 2 is a conceptual diagram of a flow of the apparatus used in Examples 7 to 10.

FIG. 3 is a conceptual diagram of a flow of the apparatus used in Example 20.

FIG. 4 is a conceptual diagram of a flow of Example 21 in which the method of the present invention is applied by additionally adding and mixing the solvent to the polymerization liquid in the polymer production process by the bulk or solution polymerization method.

[Explanation of symbols]

1: Stirring tank 11: Receiver 2: Metering pump 12: Distillation tower 3: Heater 13: Extruder die 4: Control valve 14: Pelletizer 5: Extruder supply port 15: Flash nozzle 6: Extruder first vent 16 : Complete mixing polymerization reactor 7: Nitrogen inlet 17: Mixing tank 8: Extruder second vent 18: Metering pump 9: Vent extruder 19: Mixer 10: Condenser (condenser) 20: Inlet

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shinichi Hinagata 5-6-2 Higashihachiman, Hiratsuka-shi, Kanagawa Sanryo Gas Chemical Co., Ltd. Hiratsuka Laboratory

Claims (12)

[Claims] 1. An unreacted monomer, a reaction by-product, and
In a method for purifying a polymerization reaction product by separating and removing the volatile component from a polymerization reaction product containing a volatile component consisting of at least one solvent selected from methanol and acetone, (A) temperature of the polymerization reaction product 120-270 ° C
And (B) the polymerization reaction product at a barrel temperature of 170.
The mixture is supplied to an extruder having a plurality of vent ports at 280 ° C, and most of the volatile components are separated and recovered from the first vent held at 0.3 to 3 atm, and (C) then the vent part. A polymerization reaction product characterized in that the residual volatile content of the polymer composition is reduced to 1% by weight or less by removing the remaining volatile components with at least one rear vent set to a pressure of 1 to 400 Torr. Purification method. 2. The supply port of the polymerization reaction product to the extruder is
The method for purifying a polymerization reaction product according to claim 1, which is a supply port installed in a barrel near the first vent. 3. The purification of the polymerization reaction product according to claim 1, wherein the supply of the polymerization reaction product to the extruder is a supply for flushing toward the screw of the extruder through a nozzle installed inside the first vent. Method. 4. An unreacted monomer, a reaction by-product, and
A polymerization reaction product containing a volatile component composed of at least one solvent selected from methanol and acetone is used at a temperature of 1
Discharge to the screw of the extruder from a supply port installed in the barrel inside or near the first vent of the extruder which is heated to 50 to 250 ° C. and kept at 0.5 to 1.5 atm. 1. The method for purifying a polymerization reaction product according to 1. 5. The polymerization according to claim 1, wherein the extruder is a single-screw extruder capable of extruding from a die after kneading and plasticizing the polymer heated and melted by a screw rotating in a high temperature cylinder. A method for purifying a reaction product. 6. The polymerization according to claim 1, wherein the extruder is a twin-screw extruder capable of extruding from a die after kneading and plasticizing a polymer heated and melted by a screw rotating in a high temperature cylinder. A method for purifying a reaction product. 7. A nozzle is used for discharging the polymerization reaction product onto a screw of an extruder, and the nozzle is selected from a needle valve, a control valve, a vent plug and a strand die. 5. The method for purifying a polymerization reaction product according to item 5. 8. The method for purifying a polymerization reaction product according to claim 1, wherein the solvent contained in the polymerization reaction product is methanol. 9. The polymerization reaction product comprises unreacted monomers 5 to 55.
The method for purifying a polymerization reaction product according to claim 1, wherein the method comprises 5% by weight and 5 to 65% by weight of a solvent. 10. The polymer in the polymerization reaction product is 75 to
The method for purifying a polymerization reaction product according to claim 1, which is a polymer obtained by polymerizing a monomer component composed of 100% by weight of methyl methacrylate and 0 to 25% of acrylic acid ester. 11. The polymer in the polymerization reaction product is 5 to 7
The method for purifying a polymerization reaction product according to claim 1, which is a polymer obtained by polymerizing a monomer component composed of 4% by weight of methyl methacrylate and 26 to 95% by weight of styrene. 12. The method for purifying a polymerization reaction product according to claim 1, wherein the polymerization reaction product is prepared by adding and mixing a solvent to the product obtained by the bulk polymerization method or the solution polymerization method. .