JP2005112870A - Manufacturing apparatus of (meth)acrylic polymer and manufacturing method of (meth)acrylic polymer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing apparatus and a manufacturing method of a (meth)acrylic polymer which can stably manufacture the (meth)acrylic polymer containing a small amount of volatile components. <P>SOLUTION: The manufacturing apparatus of the (meth)acrylic polymer comprises a polymerization tank, a devolatilizing extrusion apparatus, a connecting part for connecting the polymerization tank to the devolatilizing extrusion apparatus, and a mechanical back-pressure valve provided at the connecting part. The manufacturing method of the (meth)acrylic polymer comprises a step for continuously feeding a raw material composition comprising (meth)acrylic monomers, a radical polymerization initiator and a chain transfer agent to the polymerization tank, a step for causing at least a part of the (meth)acrylic monomers to polymerize in the polymerization tank to form a reaction mixture, a step for continuously drawing out the reaction mixture from the polymerization tank, a step for adjusting the pressure of the reaction mixture by the mechanical back-pressure valve, and a step for subjecting the reaction mixture with its pressure adjusted to the devolatilization treatment to obtain the (meth)acrylic polymer. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an apparatus and a method for producing a (meth) acrylic polymer by a continuous polymerization method.

  (Meth) acrylic polymers such as polymethyl methacrylate (PMMA) produced by polymerizing (meth) acrylic monomers such as methyl methacrylate are excellent in transparency, weather resistance, and appearance. It is used in many fields such as lighting, signage, and vehicles. It is also widely applied to optical applications such as optical lenses, disk substrates, and plastic optical fibers.

  As a method for producing a (meth) acrylic polymer, a suspension polymerization method is generally used, but an auxiliary agent such as a suspension dispersant to be used is mixed in the (meth) acrylic polymer. Its transparency was lowered and it was not suitable for optical applications. In addition, complicated processes such as filtration, washing, and drying were required, and productivity was poor.

  As a method for producing a (meth) acrylic polymer, a bulk polymerization method and a solution polymerization method are known in addition to the suspension polymerization method described above. According to these methods, it is possible to produce a (meth) acrylic polymer having excellent characteristics without lowering transparency. More recently, attention has been drawn to a continuous polymerization method in which productivity is increased by continuously performing a bulk polymerization method or a solution polymerization method containing a small amount of a solvent. However, in the production of (meth) acrylic polymers by these techniques, it is known that when the polymer content increases, a phenomenon in which the polymerization reaction rate rapidly accelerates due to the so-called “gel effect” occurs. . That is, it is very difficult to control so as to cause a stable polymerization reaction with a high polymer content.

  Therefore, in order to realize a stable polymerization reaction, the polymerization reaction is often terminated at a stage where the polymer content is low. The obtained (meth) acrylic polymer and a reaction mixture containing a volatile component mainly composed of an unreacted (meth) acrylic monomer are extracted from the polymerization kettle, heated and pressurized, and vented. Is introduced into a devolatilizing extrusion apparatus. The volatile component contained in the reaction mixture is removed by a devolatilization extrusion apparatus, and the desired (meth) acrylic polymer can be obtained.

For example, the obtained reaction mixture is pressurized to 20 kg / cm ² or more and heated to 210 to 270 ° C., and introduced into the supply unit of the devolatilization extrusion apparatus adjusted to a pressure of 50 torr or more and atmospheric pressure, A method for producing a (meth) acrylic polymer having a low volatile component content is known by adjusting the pressure of the water to 50 torr or less and the temperature to 250 to 290 ° C. (Patent Document 1). However, if long-term production is carried out continuously, the pressure of the reaction mixture introduced into the devolatilization extruder gradually shifts, resulting in an increase in the content of volatile components in the resulting (meth) acrylic polymer. There was a problem of causing a vent-up.
Japanese Patent Laid-Open No. 50-40688

  This invention is made | formed in view of the said situation, and provides the manufacturing apparatus and manufacturing method of a (meth) acrylic-type polymer which can manufacture stably the (meth) acrylic-type polymer with little volatile component content. The purpose is to do.

The present invention
In a production apparatus for a (meth) acrylic polymer, comprising a polymerization kettle, a devolatilization extrusion apparatus, and a connecting portion for coupling the polymerization kettle and the devolatilization extrusion apparatus
An apparatus for producing a (meth) acrylic polymer, wherein the connecting portion has a mechanical back pressure valve. According to such a (meth) acrylic polymer production apparatus, a (meth) acrylic polymer having a small volatile component content can be produced stably.

  In the apparatus for producing a (meth) acrylic polymer of the present invention as described above, the mechanical back pressure valve is preferably a spring type. Moreover, it is preferable that the said mechanical back pressure valve can be adjusted to the pressure of the range of 1-3 MPa.

The present invention also provides:
(A) a step of continuously supplying a raw material composition containing a (meth) acrylic monomer, a radical polymerization initiator, and a chain transfer agent to the polymerization kettle;
(B) A (meth) acrylic polymer obtained by polymerizing at least a part of the (meth) acrylic monomer in the polymerization vessel and polymerizing at least a part of the (meth) acrylic monomer. Comprising a reaction mixture comprising:
(C) continuously extracting the reaction mixture from the polymerization kettle;
(D) adjusting the pressure of the reaction mixture continuously extracted from the polymerization kettle with a mechanical back pressure valve;
(E) introducing the reaction mixture whose pressure has been adjusted into a devolatilizing extrusion apparatus and performing a devolatilization process to obtain the (meth) acrylic polymer. It is a manufacturing method of a polymer. According to such a method for producing a (meth) acrylic polymer, a (meth) acrylic polymer having a small volatile component content can be stably produced.

  In the method for producing a (meth) acrylic polymer of the present invention as described above, it is preferable that the mechanical back pressure valve is a spring type. Moreover, it is preferable to adjust the pressure of the reaction mixture to 1 to 3 MPa in the step (D).

  According to the (meth) acrylic polymer production apparatus and production method of the present invention, a (meth) acrylic polymer having a low volatile component content can be produced stably.

  The (meth) acrylic polymer production apparatus of the present invention is a (meth) acrylic polymer production apparatus having a polymerization kettle, a devolatilization extrusion apparatus, and a connecting portion for connecting the polymerization kettle and the devolatilization extrusion apparatus. And it has the feature that it has a mechanical back pressure valve in a connection part.

  The polymerization kettle used in the present invention can use a tank reactor equipped with a raw material composition supply port, a reaction mixture discharge port, and a stirrer, and the stirrer preferably has mixing performance over the entire polymerization kettle. . Further, it is preferable to have a mechanism for removing heat or controlling to a predetermined polymerization temperature by heating as necessary. A known mechanism can be used as the mechanism for temperature control. For example, a mechanism using a jacket installed around the polymerization kettle, a mechanism for circulating a heat medium to a draft tube or coil installed in the polymerization kettle, a mechanism for temperature control by adjusting the temperature of the raw material composition, etc. it can.

  For the devolatilization treatment used in the present invention, for example, a vent estruder-type devolatilization extrusion apparatus such as ME-150 (trade name) manufactured by Mitsubishi Heavy Industries, Ltd. or TEX (trade name) manufactured by Nippon Steel Works may be used. it can. Various types of devolatilizing and extruding devices are known that differ in size, screw configuration, vent installation position and number, etc., but are used in the (meth) acrylic polymer production apparatus of the present invention. There are no restrictions on the devolatilization extrusion equipment. From the viewpoint of devolatilization efficiency and operating cost, a devolatilization extrusion apparatus having 2 to 4 vents is suitable in the present invention.

  In the present invention, the polymerization kettle and the devolatilizing and extruding device are connected by a connecting portion having a mechanical back pressure valve. Although it does not specifically limit as a mechanical back pressure valve and a well-known thing can be used, A spring-type mechanical back pressure valve is used preferably.

  FIG. 2 shows a cross-sectional view of an example of a spring-type mechanical back pressure valve that can be used in the (meth) acrylic polymer of the present invention. This mechanical back pressure valve has an inlet 71 and an outlet 72, and discharges the liquid introduced from the inlet 71 from the outlet 72 in a state where the pressure is stabilized. Inside the valve body 52, the spring receiver 53 and the valve rod 54 are integrally movable valve 60, a spring 56 installed between the spring receiver 53 and the spring retainer 55, and the lowest point of the valve 60. The valve seat 51 that can come into contact with the valve body 52 is arranged as shown in FIG. When the supply pressure of the liquid supplied from the supply port 71 is weak, the valve 60 cannot be pushed up and the valve body 52 and the valve seat 51 are in contact with each other, so that the liquid is not discharged to the discharge port 72. When the supply pressure of the liquid increases, the valve 60 is pushed upward in FIG. 2 until the supply pressure and the pressure due to the repulsive force of the spring 56 are balanced, and the liquid flows to the discharge port 72. Even if the supply pressure of the liquid changes, the valve 60 moves up and down accordingly, so that the pressure of the liquid discharged from the discharge port 72 becomes stable. Further, the pressure value to be stabilized can be changed by moving the adjustment bolt 57 up and down by turning the cap 58. With such a mechanism, the mechanical back pressure valve can discharge the liquid in a state where the pressure is stable.

  Here, even if a pressure regulating valve is installed instead of the mechanical back pressure valve, in principle, the pressure of the liquid can be adjusted, but in this case, the operation and management of pressure regulation by manually operating the pressure regulating valve are not possible. It is necessary separately, and the pressure adjustment accuracy is not good due to manual operation, and in some cases, pressure adjustment may be delayed. Although it is possible to automatically adjust the pressure of the liquid by installing a pressure gauge type pressure regulating valve instead of the mechanical back pressure valve, the pressure gauge actually detects the pressure change and opens the valve based on the signal. Since the degree is adjusted, a time lag occurs, and the pressure stability is not so good as compared with the mechanical back pressure valve. Also, if the pressure gauge and the pressure regulating valve are installed at different positions, accurate pressure adjustment is not possible. In contrast, mechanical back pressure valves do not require separate work and management, have high adjustment accuracy, no pressure regulation delay (time lag), good pressure stability, accurate pressure, etc. There are benefits. Therefore, it is possible to prevent vent-up that is likely to occur during the production of the (meth) acrylic polymer, and it is possible to stably produce a (meth) acrylic polymer having a low volatile component content.

  The mechanical back pressure valve in the present invention is preferably one that can be adjusted to a pressure in the range of 1 to 3 MPa from the viewpoint of use in the production of a (meth) acrylic polymer. More preferably, it is 1.5-2.5 MPa. In the present invention, “Pa” such as the pressure of the mechanical back pressure valve and the vent pressure are all expressed in gauge pressure.

  The connecting portion in the present invention is required to have the mechanical back pressure valve as described above, but if necessary, a pipe type equipped with a pump for liquid feeding, a heater for liquid heating, and a static mixer. A reactor or the like may be provided.

  In FIG. 1, the example of 1 structure of the manufacturing apparatus of the (meth) acrylic-type polymer of this invention is shown. A polymerization vessel 10 equipped with a stirring device 11 is provided with a raw material composition inlet 12 and a reaction mixture outlet 13. The reaction mixture discharge port 13 is connected to the reaction mixture supply port 41 of the devolatilization extrusion apparatus 40 by the connecting unit 20. The pump 21, the heater 22, and the mechanical back pressure valve 30 are disposed in the connecting portion, and are connected by pipes 23 to 26, respectively. The devolatilization extrusion apparatus 40 is provided with vents 42 and 43 and a polymer discharge port 44.

  According to the apparatus for producing a (meth) acrylic polymer as described above, a (meth) acrylic polymer having a small volatile component content can be stably produced.

  Next, the manufacturing method of the (meth) acrylic-type polymer of this invention is demonstrated.

The method for producing the (meth) acrylic polymer of the present invention is as follows.
(A) a step of continuously supplying a raw material composition containing a (meth) acrylic monomer, a radical polymerization initiator, and a chain transfer agent to the polymerization kettle;
(B) A (meth) acrylic polymer obtained by polymerizing at least a part of the (meth) acrylic monomer in the polymerization vessel and polymerizing at least a part of the (meth) acrylic monomer. Comprising a reaction mixture comprising:
(C) continuously extracting the reaction mixture from the polymerization kettle;
(D) adjusting the pressure of the reaction mixture continuously extracted from the polymerization kettle with a mechanical back pressure valve;
(E) introducing the reaction mixture whose pressure has been adjusted into a devolatilizing extrusion apparatus and performing a devolatilization process to obtain the (meth) acrylic polymer.

  The method for producing a (meth) acrylic polymer of the present invention is suitably applied to bulk polymerization or solution polymerization of (meth) acrylic monomers. It does not specifically limit as a (meth) acrylic-type monomer, For example, the (meth) acrylic-acid alkylester which has a C1-C18 alkyl group can be used. Specifically, methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, n-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, (meth) acrylic Examples include dodecyl acid, stearyl (meth) acrylate. These (meth) acrylic monomers can be used alone or in combination of two or more. In addition, the expression “(meth) acrylic acid” means methacrylic acid or acrylic acid (the same applies hereinafter).

  The present invention is suitable for producing a (meth) acrylic polymer containing 80% by mass or more of methyl methacrylate units and further containing (meth) acrylic acid alkyl ester units other than methyl methacrylate units. At this time, since methyl methacrylate and (meth) acrylic acid alkyl esters other than methyl methacrylate are generally different in polymerization activity, in order to obtain the (meth) acrylic polymer as described above, It is preferable to select the composition of the acrylic monomer appropriately depending on the polymerization activity. For example, the composition of the (meth) acrylic monomer in the case of producing a (meth) acrylic polymer having 80% by mass of methyl methacrylate units and 20% by mass of methyl acrylate units or ethyl acrylate units. Is different depending on conditions such as the type of radical polymerization initiator and polymerization temperature, but is preferably about 75% by mass of methyl methacrylate and about 25% by mass of methyl acrylate or ethyl acrylate.

  The radical polymerization initiator in this invention is not specifically limited, Well-known radical polymerization initiators, such as an organic peroxide or an azo compound, can be used individually or in combination of 2 or more types. Preferably, it is a radical polymerization initiator having a half-life at the polymerization temperature in the polymerization vessel of 10 seconds to 1 hour. In the case of a radical initiator having a too short half-life, the uniformity of the reaction may be lowered, and in the case of a radical initiator having a too long half-life, a polymer lump is easily generated in the polymerization vessel, and the operation can be stably performed. It can be difficult. More preferably, it is a radical polymerization initiator having a half-life at a polymerization temperature in a polymerization vessel of 120 seconds to 30 minutes. In addition, the value of “half-life” of the above radical polymerization initiator was a value described in a known product catalog such as Nippon Oil & Fats Co., Ltd. or Wako Pure Chemical Industries, Ltd.

  Examples of such radical initiators include tert-butyl peroxy-3,5,5-trimethylhexanate, tert-butyl peroxylaurate, tert-butyl peroxyisopropyl monocarbonate, tert-hexyl peroxyisopropyl. Monocarbonate, tert-butylperoxyacetate, 1,1-bis (tert-butylperoxy) 3,3,5-trimethylcyclohexane, 1,1-bis (tert-butylperoxy) cyclohexane, tert-butylperoxy 2-ethyl hexanate, tert-butyl peroxyisobutyrate, tert-hexyl peroxy 2-ethyl hexanate, di-tert-butyl peroxide, 2,5-dimethyl-2,5-bis (tert-butyl peroxy) Xyl) organic peroxides such as hexane; 2- (carbamoylazo) -isobutyronitrile, 1,1′-azobis (1-cyclohexanecarbonitrile), 2,2′-azobisisobutyronitrile, 2, 2'-azobis (2-methylbutyronitrile), dimethyl 2,2'-azobisisobutyrate, 2,2'-azobis (2,4,4-trimethylpentane), 2,2'-azobis (2 -Azo compounds such as methylpropane).

The amount of the radical polymerization initiator used may be appropriately selected in consideration of the polymerization temperature and productivity. For example, 5.0 × 10 ⁻⁶ to 5.0 with respect to 1 mol of the (meth) acrylic monomer. An amount of about × 10 ^-5 mol can be used.

  The chain transfer agent in this invention is not specifically limited, Well-known chain transfer agents, such as a chlorine containing compound, an alkylbenzene compound, a mercaptan compound, can be used individually or in combination of 2 or more types. A mercaptan compound is preferred because the efficiency of the chain transfer agent is high and the (meth) acrylic polymer to be produced is excellent in thermal decomposition resistance.

  As a mercaptan compound, n-butyl mercaptan, isobutyl mercaptan, n-octyl mercaptan, n-dodecyl mercaptan, sec-butyl mercaptan, sec-dodecyl mercaptan, tert-butyl mercaptan and the like have a primary alkyl group or a substituted alkyl group. , Secondary and tertiary mercaptan compounds; aromatic mercaptan compounds such as phenyl mercaptan, thiocresol, 4-tert-butyl-o-thiocresol; thioglycolic acid and esters thereof; 3 to 3 carbon atoms such as ethylenethioglycol 18 mercaptan compounds and the like. Among these mercaptan compounds, tert-butyl mercaptan, n-butyl mercaptan, n-octyl mercaptan, and n-dodecyl mercaptan are particularly suitable.

  The amount of chain transfer agent used may be appropriately selected in consideration of the physical properties of the target (meth) acrylic polymer. For example, the weight average molecular weight (standard polystyrene equivalent value) of the (meth) acrylic polymer is The amount used is preferably in the range of 70000-150,000. Specifically, it is 0.01 to 1.0 mol, preferably 0.05 to 0.5 mol, per 100 mol of the (meth) acrylic monomer. If the amount is too large, the degree of polymerization of the (meth) acrylic polymer may be lowered, and the product strength may be lowered. If the amount is too small, the heat decomposability of the (meth) acrylic polymer may be lowered.

  In the present invention, a raw material composition containing the components as described above is continuously supplied to the polymerization vessel, and at least a part of the (meth) acrylic monomer is polymerized in the polymerization vessel, thereby producing a (meth) acrylic type. A reaction mixture containing a (meth) acrylic polymer in which at least a part of the monomer is polymerized is used. The form of polymerizing at least a part of the (meth) acrylic monomer may be bulk polymerization without using an inert solvent or solution polymerization using an inert solvent. Particularly preferred is bulk polymerization. Even in the case of solution polymerization, if the inert solvent to be used is less than 5% by mass of the entire reaction mixture, it is possible to efficiently increase the polymerization rate with a small amount of radical polymerization initiator as in the case of bulk polymerization. A (meth) acrylic polymer having excellent thermal decomposition resistance is preferable because it can be produced with high productivity. In a solution polymerization system in which the inert solvent used is 5% by mass or more, it is necessary to use a large amount of radical polymerization initiator, which makes it difficult to control the polymerization reaction. As the inert solvent, known organic solvents such as methanol, ethanol, toluene, xylene, acetone, methyl isobutyl ketone, ethylbenzene, methyl ethyl ketone, and butyl acetate can be used. Methanol, toluene, ethylbenzene, and butyl acetate are particularly preferred. The inert solvent can be used by being added to a raw material composition containing the (meth) acrylic monomer as described above, a radical polymerization initiator, and a chain transfer agent.

  What is necessary is just to select suitably the temperature at the time of superposing | polymerizing at least one part of a (meth) acrylic-type monomer with a polymerization kettle from the kind of raw material to be used, a compounding ratio, etc. The temperature control can be performed by a known method. For example, methods such as temperature control by a jacket, temperature control by circulation of a heat medium to a draft tube or a coil installed in the polymerization kettle, temperature control by temperature adjustment of the raw material composition, and the like can be employed.

  In this invention, it has the process of extracting continuously the reaction mixture containing the (meth) acrylic-type polymer which at least one part of the (meth) acrylic-type monomer superposed | polymerized from the polymerization kettle. The average residence time of the reaction mixture in the polymerization kettle is preferably 1 to 6 hours. By making it within this range, the polymerization control can be stabilized and a (meth) acrylic polymer excellent in molding processability can be produced. If the residence time is too short, it is necessary to increase the amount of radical initiator used, and it is difficult to control the polymerization reaction due to the increase in radical initiator, and the amount of terminal double bonds in the (meth) acrylic polymer increases. Therefore, a polymer excellent in heat decomposability cannot be obtained. More preferably, it is 2 hours or more. On the other hand, if the average residence time is too long, the productivity is lowered and the production of dimers of (meth) acrylic monomers is increased, which is not preferable. More preferably, it is 5 hours or less.

  The reaction mixture withdrawn from the polymerization kettle preferably has a polymer content of 35 to 65% by mass. If the polymer content is too high, mixing and heat transfer efficiency may be reduced and stability may be deteriorated. If the polymer content is too low, it will be difficult to separate volatiles mainly composed of unreacted (meth) acrylic monomers.

  In this invention, it has the process of adjusting the pressure of the reaction mixture extracted from the superposition | polymerization kettle with a mechanical back pressure valve. Although it does not specifically limit as a mechanical back pressure valve and a well-known thing can be used, A spring-type mechanical back pressure valve is used preferably. When the reaction mixture is introduced into the mechanical back pressure valve, as mentioned above, the valve moves up and down immediately in response to the supply pressure of the introduced reaction mixture, so that the reaction mixture discharged from the discharge port is discharged to a desired pressure. It is possible to keep it stable.

  In the present invention, it is preferable to adjust the pressure of the reaction mixture extracted from the polymerization kettle to 1 to 3 MPa using a mechanical back pressure valve. When the pressure is too low, it may be difficult to separate the (meth) acrylic polymer from the volatile component containing the unreacted (meth) acrylic monomer as a main component in the devolatilization process described later. If it is too high, the flow of the reaction mixture may become slow and productivity may deteriorate. More preferably, it is 1.5-2.5 MPa. Moreover, it is preferable that the reaction mixture extracted from the polymerization kettle is heated to 180 to 250 ° C.

  In this invention, it has the process of introduce | transducing the said reaction mixture in which the pressure was adjusted into a devolatilization extrusion apparatus, carrying out a devolatilization process, and obtaining the said (meth) acrylic-type polymer. In the devolatilization treatment, when the reaction mixture that is continuously sent is treated with reduced pressure (for example, in a devolatilization extrusion apparatus having two vents, the upstream vent pressure is -0.01 to -0.04 MPa hour. The downstream vent pressure is adjusted to about -0.09 to -0.1 MPa), and heated to 200 to 290 ° C. under the unreacted (meth) acrylic monomer as a main component. It can be carried out by continuously separating and removing most of the volatile components. It is preferable that the (meth) acrylic monomer dimer remaining in the resulting (meth) acrylic polymer is 1000 ppm or less and the (meth) acrylic monomer is 3000 ppm or less. Thereby, it becomes a (meth) acrylic polymer having a high heat distortion temperature and excellent moldability. Further, the remaining chain transfer agent is preferably 50 ppm or less. Thereby, the coloring by the heating at the time of the shaping | molding process of a (meth) acrylic-type polymer can be suppressed. These can be achieved by appropriately setting the pressure and temperature conditions for the devolatilization treatment.

  Simultaneously with or after the above devolatilization treatment, if necessary, lubricants such as higher alcohols and higher fatty acid esters, UV absorbers, heat stabilizers, colorants, antistatic agents, etc. It can be added to the polymer.

  The (meth) acrylic polymer obtained by the production method and production apparatus of the present invention can be used in many fields such as lighting, signboards, vehicles and the like by taking advantage of its excellent transparency and weather resistance. It can also be applied to optical applications such as optical lenses, disk substrates, and plastic optical fibers. Furthermore, it is also suitable for large molded products in which the holding time in the cylinder becomes long during injection molding and thin molded products in which the resin temperature is set high.

  Hereinafter, the present invention will be described in detail by way of examples.

Example 1
A (meth) acrylic polymer was produced using a (meth) acrylic polymer production apparatus having a mechanical back pressure valve having the configuration shown in FIG.

  First, a raw material composition having the following mixing ratio is supplied to a tank reactor (polymerization kettle) equipped with a stirrer, and the polymerization temperature is set to 135 ° C. and the average residence time is 3 hours. A polymerization reaction was performed.

<Raw material composition>
-Methyl methacrylate (MMA) 98.0 parts by mass-Methyl acrylate (MA) 2.0 parts by mass-n-octyl mercaptan 0.25 parts by mass-tert-butylperoxy-3,5,5-trimethylhexano Eate
70 mass ppm (based on the total amount of MMA and MA)
The reaction mixture extracted from the tank reactor was heated to 220 ° C. with a heater composed of a multi-tubular heat exchanger, and the uniaxial devolatilizing extruder (φ150 mm, screw: L / D28). The (meth) acrylic polymer is produced by introducing through the mechanical back pressure valve 30 and performing devolatilization treatment (260 ° C., pressure of the vent 42 −0.02 MPa, pressure of the vent 43 −0.097 MPa). did. As the mechanical back pressure valve, R-F-93703-3-1 (trade name, 40 × 40 back pressure valve for high pressure) manufactured by Kishikawa Special Valve Co., Ltd. is used, and the initial pressure setting of the mechanical back pressure valve is 2 It was set to 1 MPa. The polymer content of the reaction mixture withdrawn from the tank reactor at the initial stage when the polymerization reaction was stable was 51% by mass, and the (meth) acrylic remaining in the obtained (meth) acrylic polymer. The system monomer was 2400 ppm, the weight average molecular weight (standard polystyrene conversion value) was 98000, and the mass ratio of the MMA unit to the MA unit was 98.5: 1.5.

  The operation was continued for 5 days, and the (meth) acrylic monomer remaining in the obtained (meth) acrylic polymer was measured every 12 hours (twice / day). The result was 2300-2500 ppm. The range was very small. Further, the outlet pressure of the pump 21 changed gradually and sometimes suddenly in the range of 2.75 to 3.10 MPa, but vent-up did not occur during the operation period.

(Comparative Example 1)
Similar to Example 1 except that the pressure regulating valve (manual) is provided at the same position instead of the mechanical back pressure valve 30, using the (meth) acrylic polymer production apparatus having the configuration shown in FIG. The (meth) acrylic polymer was produced under the conditions described above. The initial outlet pressure of the pressure regulating valve was adjusted to 2.1 MPa. The polymer content of the reaction mixture withdrawn from the tank reactor at the initial stage when the polymerization reaction was stable was 51% by mass, and the (meth) acrylic remaining in the obtained (meth) acrylic polymer. The system monomer was 2400 ppm, the weight average molecular weight (standard polystyrene conversion value) was 98000, and the mass ratio of the MMA unit to the MA unit was 98.5: 1.5.

  The operation was continued for 5 days, and the (meth) acrylic monomer remaining in the obtained (meth) acrylic polymer was measured every 12 hours (twice / day). The result was 2200-2700 ppm. The range was wide and the runout was large. Further, since the outlet pressure of the pump 21 changed gradually and sometimes suddenly in the range of 2.75 to 3.10 MPa, the outlet pressure of the pressure regulating valve was adjusted as much as possible to 2.1 MPa each time. However, vent up occurred in the upstream vent during the operation period, and the (meth) acrylic polymer discharged from the devolatilizing extruder was colored, so it was necessary to stop the devolatilizing extruder and clean the vent. Occurred.

It is a figure which shows the structure of the manufacturing apparatus of the (meth) acrylic-type polymer which is one Example of this invention. It is sectional drawing of an example of the mechanical back pressure valve used by this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Polymerization pot 11 Stirring apparatus 12 Raw material composition inlet 13 Reaction mixture outlet 20 Connection part 21 Pump 22 Heater 23-26 Piping 30 Mechanical back pressure valve 40 Devolatilization extrusion apparatus 41 Reaction mixture supply port 42, 43 Vent 44 Heavy Combined discharge port 51 Valve seat 52 Valve body 53 Spring receiver 54 Valve rod 55 Spring presser 56 Spring 57 Adjustment bolt 58 Cap 60 Valve 71 Inlet 72 Discharge port

Claims (6)

In a production apparatus for a (meth) acrylic polymer, comprising a polymerization kettle, a devolatilization extrusion apparatus, and a connecting portion for coupling the polymerization kettle and the devolatilization extrusion apparatus
An apparatus for producing a (meth) acrylic polymer, wherein the connecting portion has a mechanical back pressure valve.   The apparatus for producing a (meth) acrylic polymer according to claim 1, wherein the mechanical back pressure valve is a spring type.   The apparatus for producing a (meth) acrylic polymer according to claim 1 or 2, wherein the mechanical back pressure valve can be adjusted to a pressure in a range of 1 to 3 MPa. (A) a step of continuously supplying a raw material composition containing a (meth) acrylic monomer, a radical polymerization initiator, and a chain transfer agent to the polymerization kettle;
(B) A (meth) acrylic polymer obtained by polymerizing at least a part of the (meth) acrylic monomer in the polymerization vessel and polymerizing at least a part of the (meth) acrylic monomer. Comprising a reaction mixture comprising:
(C) continuously extracting the reaction mixture from the polymerization kettle;
(D) adjusting the pressure of the reaction mixture continuously extracted from the polymerization kettle with a mechanical back pressure valve;
(E) introducing the reaction mixture whose pressure has been adjusted into a devolatilizing extrusion apparatus and performing a devolatilization process to obtain the (meth) acrylic polymer. A method for producing a polymer.   The method for producing a (meth) acrylic polymer according to claim 4, wherein the mechanical back pressure valve is a spring type.   The method for producing a (meth) acrylic polymer according to claim 4 or 5, wherein the pressure of the reaction mixture is adjusted to 1 to 3 MPa in the step (D).

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