JPH0977806A - Continuous polymerization method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce polymers free from extraneous material, quality deterioration of appearance and deposit on a reactor wall of gas phase by spray feeding the supplying liquid comprising monovinyl monomer and solvent into the gas phase space of the polymerization reactor. SOLUTION: In the continuous bulk or continuous solution polymerization of a monovinyl monomer by continuously supplying the mixture of a monomer and a solvent into the continuous polymerization reactor 1 under forced agitation, the supplying liquid is sprayed and supplied into the upper gas phase space 12 of the reactor 1 so as to allow the upper gas phase space wall to be wet with the mixture. The produced polymer solution is continuously taken out and the vapors of monomer, etc., in the reactor are condensed through the pipe opening at the upper gas phase space 12 and the condenser 5 and the condensate is made to return to the reactor 1 through the pipe 8 allowing to control the polymerization temperature by removing the generated heat of polymerization by taking out the latent heat of evaporation.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a styrene-acrylonitrile copolymer (AS), polystyrene (PS),
The present invention relates to an improvement in a continuous bulk or solution polymerization method of a monovinyl compound monomer or a mixture thereof for producing a homopolymer or a copolymer such as polymethylmethacrylate (PMMA).

[0002]

2. Description of the Related Art Various polymerization methods such as emulsion polymerization, suspension polymerization, bulk polymerization and solution polymerization have been developed as polymerization methods for obtaining (co) polymers such as AS, PS and PMMA. . Recently, many continuous bulk polymerization methods or continuous solution polymerization methods have been proposed in order to cope with water pollution prevention, economy, and sophistication of quality requirements in the market. Generation heat such as reaction heat and heat of stirring is removed by utilizing latent heat of vaporization of monomers and the like. Specifically, JP-A-48-17584 and JP-A-49-7393 disclose methods for removing reaction heat and the like by latent heat of vaporization of monomers and added water. Furthermore, when the AS resin is produced by continuous bulk or solution polymerization, the heat of reaction is removed by the latent heat of evaporation of the monomer, and a polymer having a constant acrylonitrile (AN) / styrene (St) composition ratio is obtained. Are disclosed in JP-A-58-29807.

The method for producing a polymer disclosed in this Japanese Patent Laid-Open No. 58-29807 discloses that a preliminarily polymerized St and AN polymerization liquid is supplied to a horizontal continuous polymerization vessel from one longitudinal end thereof. While taking out as a high polymer from the other end and continuously performing bulk or solution polymerization, a predetermined flow rate of St is added to each of the polymerization liquids from a plurality of locations in the lower portion in the longitudinal direction of the polymerization vessel to obtain a polymer composition. Is adjusted, and a predetermined flow rate of AN is sprayed and evaporated on the surface of the polymerization liquid from a plurality of locations on the upper side in the longitudinal direction of the polymerization vessel to remove heat. This method includes AN / in polymer
There are improvements such as keeping the St composition constant.

[0004]

However, the above-mentioned polymerization method requires a pre-polymerization vessel and an addition control facility for each of AN and St at a plurality of locations in the horizontal type polymerization vessel, which is a problem in operation. , There is a technical problem. Further, the polymer produced by this method has quality problems in the following two points.

(A) A white to blackish brown polymer is produced, grows and drops on the wall surface of the upper gas phase of the polymerization vessel to become foreign matters and black spots in the obtained polymer, which causes remarkable deterioration of appearance quality. . (B) In the method of spraying AN on the surface of the polymerization liquid in the polymerization vessel, the content of AN in the upper part of the polymerization liquid is large, and the content of AN in the produced polymer is also large. Unevenness occurs in the composition inside. If the AS resin has uneven composition, the transparency of the obtained polymer is impaired.

[0006]

DISCLOSURE OF THE INVENTION The inventors of the present invention have made diligent studies to solve the inconveniences (a) and (b) at the same time, and as a result, found that the following problems can be solved by the following method. The present invention has been completed. That is, the present invention provides: A feed liquid consisting of a mixture of a monovinyl compound monomer and a solvent is continuously fed into a continuous polymerization vessel under forced agitation for polymerization, and a polymer solution is continuously taken out, Polymerization temperature by removing the heat generated by condensing monomer and other vapors in the vessel through a condenser that opens from the gas phase space through the condenser, and by removing the latent heat of vaporization by returning the condensate to the reactor In the continuous bulk or solution polymerization method for controlling, a continuous bulk or solution polymerization method, characterized in that the supply liquid is sprayed and supplied to the upper vapor phase space of the polymerization vessel to wet the upper vapor phase space part vessel wall,

[0007] 2. Using a vertical continuous polymerization vessel,
From a supply pipe installed in a ring shape in the vapor phase space above the polymerization vessel, sprayed using a spray nozzle to the wall surface of the upper end plate portion inside the polymerization vessel, which is the gas phase portion, and was sprayed from the spray nozzle. 2. The polymerization method according to 1, wherein the wall surface is completely wetted by the supply liquid.

3. A feed solution consisting of a mixture of two or more kinds of monovinyl compound monomers and a solvent is continuously fed into a continuous polymerization vessel under forced agitation to polymerize, and the polymer is continuously polymerized. Taking out the solution, condensing vapor such as monomer in the vessel through a condenser from a pipe opening to a gas phase space above the polymerization vessel, and further returning the condensate into the reactor to remove latent heat of vaporization. In a continuous bulk or solution polymerization method in which the generated heat is removed by controlling the polymerization temperature by means of, the feed liquid is divided into two, and one is supplied by being sprayed so as to wet the upper gas phase space wall of the polymerization vessel. 3. On the other hand, the continuous bulk or solution polymerization method characterized in that the other is mixed with the condensate and supplied from the bottom of the polymerization vessel. 4. The method according to 3, wherein the polymer solution in the polymerization vessel is stirred at a stirring strength of 2 KW / M ³ or more.

The present invention is intended for a continuous bulk or solution polymerization method carried out in a reactor having a gas phase part, and (a) at least a part of reaction heat of a high viscosity polymerization system is a monomer contained in the reaction system. In the method of removing heat by evaporation latent heat removal method of solvent, a part of the monomer liquid supplied to the polymerization vessel is sprayed on the gas phase wall surface of the polymerization vessel, and the wall surface is wet with the monomer solution. By setting the state, it is possible to prevent the adhesion growth of the polymer on the wall surface of the gas phase portion,

(B) In the polymerization vessel for producing the copolymer, the vapor condensate taken out from the gas phase contains a large amount of low-boiling monomers, and the proportion of the low-boiling monomers is in this. A small amount of the monomer and other liquids fed to the polymerization vessel are mixed in an appropriate amount to bring the proportion of the monomer close to that in the polymerization vessel and return to the lower liquid phase section of the polymerization vessel. Then, the difference in the monomer ratio between the upper and lower liquid phase parts in the polymerization vessel is eliminated, the composition unevenness of the polymer is eliminated, and the transparency of the obtained polymer is improved. (C) A copolymer is produced. in the polymerization vessel to the interior of the polymer solution 2KW / M ³ or more, preferably 4KW / M ³
Stirring with a stirring strength of 10 to 10 KW / M ³ has the advantage of eliminating uneven monomer composition remaining in the polymerization system, which causes uneven composition of the polymer.

In the present invention, examples of the monovinyl compound monomer used include aromatic vinyl monomers such as styrene and α-methylstyrene, vinyl cyanide monomers such as acrylonitrile and methacrylonitrile, and maleic anhydride. Unsaturated dicarboxylic acid anhydrides, methacrylic acid esters such as methyl methacrylate, methyl allylate, and allyl acid n
A single or a mixture of two or more selected from acrylates such as butyl, methacrylic acid, acrylic acid, phenylmaleimide and the like.

In the present invention, the solvent is a single solvent selected from ethylbenzene, toluene, methyl ethyl ketone, methyl isobutyl ketone, propanol, butyl alcohol and pentanol, or a mixture of two or more thereof. Alternatively, a mixture of two or more kinds may be formed at a desired ratio between 0 ° C. and 60 ° C. to form a homogeneous phase, and the mixture of the unreacted monomer, the solvent and the produced polymer in the polymerization vessel may be the polymerization temperature or the polymerization vessel. It is a liquid compound that forms a homogeneous phase in its composition.

In the present invention, the liquid supplied to the polymerization vessel is 0 ° C.
It is necessary to supply at a temperature in the range of -60 ° C, preferably 10 ° C-40 ° C. Since the feed liquid is sprayed in the vapor generated from the polymer solution in the polymerization vessel, heat exchange occurs between the feed liquid and the vapor, and when the feed liquid adheres to the wall surface, it rises above the feed liquid temperature. are doing. Therefore, the temperature of the supply liquid is sufficiently lower than the polymerization temperature,
The temperature of the supply liquid attached to the wall surface of the gas phase portion is set to 20 ° C. higher than the temperature of the polymerization liquid by controlling the temperature to be in the range of 10 ° C., preferably 10 ° C. to 40 ° C.
C. is lower than 30.degree. C., more preferably 30.degree. C. or lower, and it becomes possible to prevent the formation of polymer on the wall surface by wetting the wall surface with the supply liquid.

In the present invention, the polymer solution leaving the polymerizer is used as a product by removing the unreacted monomer and the solvent from the polymer solution in the subsequent process. At this time, in order to remove the unreacted monomers and the solvent from the polymer solution, a method of using a heater and a volatilization tank under reduced pressure, a method of using an extruder having a reduced pressure vent, and these are used together There are ways. The polymerizer is composed of a part called a mirror plate obtained by splitting a spheroid into two parts and a cylindrical part connecting the two parts.In the case of the vertical polymerizer of the present invention, a spray is applied to the upper mirror plate part. It is necessary for the supply liquid sprayed from the nozzle to directly hit the nozzle without leakage.

In the present invention, the spray nozzle is not limited to any type as long as it can spray the liquid only by the pressure of the supply liquid and the spray liquid can reach the wall surface of the gas phase portion. The spray liquid from the spray nozzle exchanges heat and mass with the vapor in the vapor phase when it is scattered toward the wall in the vapor phase space, and when it reaches the wall, it becomes a composition different from the supplied liquid composition. In some cases, it is enough if the spray liquid can reach the wall surface.

In the present invention, paddle blades, pitched paddle blades, helical blades, double helical blades, Maxblend blades, full zone blades, etc. are used as the stirring blades of the stirrer. The stirring power obtained by dividing the stirring power (unit: KW) measured from the torque meter attached to the stirring shaft and the number of rotations by the volume of the liquid (unit: M ³ ) in the polymerization vessel subjected to stirring is 2 kW / M ³ or more, preferably 4 KW / M ^{3 to} 10 KW
By stirring with / M ³ , non-uniformity in the reaction solution can be prevented.

The present invention will be described in more detail below with reference to the drawings. FIG. 1 is a conceptual diagram showing an example of a polymerization vessel (vertical type) and its accessories used for carrying out the present invention. Reference numeral 1 is a vertical polymerization vessel, which may have a baffle on its wall surface in order to suppress vortices by a stirring blade, 2 is an inlet pipe for a feed solution which is a mixed solution of a monomer and a solvent, and 3 is a polymerization apparatus A spray for spraying the supply liquid to the upper wall of the gas phase part, 4 is a vapor withdrawal amount control valve, keeps the pressure inside the polymerization vessel constant, and as a result keeps the polymerization temperature constant, 5 is a vapor condenser , To condense the steam withdrawn from the polymerizer, 6 is a pipe for adding a part of the feed liquid to the condensate, 7 is a pump for returning the condensate liquid and the added feed liquid to the polymerizer, 8 is a bottom Supply piping to
9 is a stirring blade of a stirrer, 10 is a stirrer motor, 11 is a polymerization solution outlet pipe, 12 is a gas phase part, 13 is a polymerization solution, and 14 is a polymerization solution level.

A part of the monomer is sprayed from the spray 3 through the pipe 2 toward the gas phase wall surface of the polymerization vessel, and drops while wetting the wall surface of the vessel. In order to obtain a polymer having a target molecular weight in the polymerization vessel at a target monomer conversion rate, the copolymerization monomer composition, the amount of the molecular weight modifier, the amount of the polymerization initiator, the polymerization temperature is determined, It is adjusted based on the measurement results of molecular weight and conversion rate. In order to adjust the polymerization temperature in real time, the internal pressure of the polymerization vessel is adjusted.
It is performed by extracting a desired amount of vapor in the vapor phase portion of the polymerizer by adjusting the control valve 4. The extracted vapor is condensed in the condenser 5, mixed with the monomer from the pipe 6, and supplied from the bottom of the pipe through the pipe 8. The monomer is polymerized with stirring in the vessel, and the polymerization liquid is continuously withdrawn from the pipe 11.

In the polymerization vessel used in the practice of the present invention, it is desirable that the stirring is driven downward so that spraying to the gas phase of the upper portion of the polymerization vessel is effective. In the present invention, when the target product is a homopolymer, the condensate is the same as the monomer, so there is no need to particularly supply the condensate or monomer from the bottom of the polymerization vessel, and the total amount of gas in the top of the polymerization vessel is not required. You can spray from the spray of the phase toward the vessel wall. When the target product is a copolymer, especially when the boiling points of the copolymerized monomers are significantly different, the composition of the condensate and the monomer mixture are different. It is necessary to supply from.

Specifically, in the case of PS, only the upper spray is required, but in the case of PMMA, since a small amount of the second component monomer is actually used, the condensate and the monomer are not used. It is advisable to feed the mixture from the bottom. In the case of AS, the bottom feed liquid is such that the amount of the monomer mixture is 0.5 parts by weight or more, preferably 1.0 parts by weight or more, relative to 1 part by weight of the condensate. If it is less than 0.5 part by weight, A
If the N content is too high, compositional unevenness will occur and the polymer molded product will fog.

[0021]

EXAMPLES Examples and comparative examples are shown below, but the present invention is not limited to these examples. The haze (intensity of transmitted scattered light) of the polymer molded product in the examples was measured by SM-3 manufactured by Suga Test Instruments Co., Ltd.
(Trade name) was used and a 3 mm-thick injection-molded flat plate was used as a sample according to ASTM D1746.

(Example 1) Polymer composition (weight ratio) St / AN = 70/30 Polymerizer capacity 190 l Polymerization liquid effective capacity 100 l Polymerization temperature 150 ° C. (2 kg / c finely adjusted by the pressure inside the polymerization reactor-temperature)
m ² ) Agitation power 0.4 kW (Agitation strength 4 kW / M
³ ) (Agitating blade is Maxblend blade) Condensate amount 10l / hr Monomer supply amount 40l / hr Solvent amount in feed liquid (ethylbenzene) 20wt% Gas phase wall spray amount 30l / hr Branch amount to the lower part ( Mixing with condensate) 10 l / hr Continuous bulk copolymerization was carried out under the above conditions. Even after being carried out for 150 days, there was no white or black foreign matter in the obtained polymer, and no deposit was found on the wall surface of the gas phase part of the polymerizer in the open inspection of the polymerizer. Also, the transparency of the polymer molded product was good at Haze = 2%.

(Comparative Example 1) Continuous bulk copolymerization was carried out under the same conditions as in Example 1 except that the total amount of the condensate and the monomers were fed from the bottom. In 30 days of practice, from the 10th day, the brown polymer was found to be mixed in the obtained polymer.
In the inspection of the inside of the polymerization reactor after the production was carried out for 30 days, in the inspection of the inside of the gas phase portion, an icicle of black-brown polymer adhered to the entire wall surface of the gas phase portion.

(Comparative Example 2) Continuous bulk copolymerization was carried out under the same conditions as in Example 1 except that the entire amount of the condensate and the monomer was sprayed onto the wall surface of the gas phase part. The obtained polymer molded article had low transparency and Haze = 30%.

(Comparative Example 3) Example 1 was repeated except that the stirring strength was lowered to the point where the power for stirring place was 0.1 kW.
Continuous bulk copolymerization was carried out under the same conditions as above. The obtained polymer molded article had low transparency and Haze = 20%.

[0026]

EFFECTS OF THE INVENTION According to the method of the present invention, deposits are not formed on the wall surface of the gas phase part of the polymerization vessel, and therefore, the obtained polymer does not contain foreign matters generated in those polymerization vessels. In addition, even in the case of copolymerization production, a uniform and highly transparent copolymer was obtained without causing composition unevenness.

[Brief description of drawings]

FIG. 1 is a conceptual diagram showing an example of a vertical continuous polymerization vessel used for carrying out the present invention and its accessories and the like.

[Explanation of symbols]

 1: Vertical polymerization vessel 2: Inlet piping for feed solution which is a mixture of monomer and solvent 3: Spray for spraying the feed solution on the wall of the gas phase part above the polymerization vessel 4: Steam withdrawal control valve 5: Steam Condenser 6: Pipe for adding a part of the feed liquid to the condensate 7: Pump for returning the condensate and the added feed liquid to the polymerization vessel 8: Pipe for supplying to the bottom 9: Stirrer blade of a stirrer 10 : Stirrer motor 11: Polymerization liquid outlet pipe 12: Gas phase portion 13: Polymerization liquid 14: Polymerization liquid surface

Claims (4)

[Claims] 1. A feed solution comprising a mixture of a monovinyl compound monomer and a solvent is continuously fed into a continuous polymerization vessel in which forced agitation is carried out for polymerization, and a polymer solution is continuously taken out, Condensing monomer vapor in the vessel through a condenser from a pipe opening to a gas phase space above the polymerization vessel,
Further, in the continuous bulk or solution polymerization method in which the generated heat is removed by removing the latent heat of vaporization by returning the condensate into the reactor to control the polymerization temperature, the feed liquid is fed to the upper gas phase space of the polymerizer. A continuous bulk or solution polymerization method, characterized in that it is sprayed and supplied to wet the upper gas phase space vessel wall. 2. A vertical continuous polymerization vessel is used to feed the feed liquid from a feed pipe arranged in a ring shape in a vapor phase space above the polymerization vessel to a wall surface of an upper end plate portion in the polymerization vessel which is a vapor phase portion. On the other hand, the polymerization method according to claim 1, wherein spraying is performed using a spray nozzle, and the wall surface is directly wetted by the supply liquid sprayed from the spray nozzle. 3. A continuous supply of a feed liquid comprising a mixture of two or more monovinyl compound monomers and a solvent into a continuous polymerization vessel under forced agitation for polymerization to continuously polymerize the polymer. Taking out the solution, condensing vapor such as monomer in the vessel through a condenser from a pipe opening to a gas phase space above the polymerization vessel, and further returning the condensate into the reactor to remove latent heat of vaporization. In a continuous bulk or solution polymerization method in which the generated heat is removed by controlling the polymerization temperature by means of, the feed liquid is divided into two, and one is supplied by being sprayed so as to wet the upper gas phase space wall of the polymerization vessel. And the other is mixed with the condensate and supplied from the bottom of the polymerization vessel, which is a continuous bulk or solution polymerization method. 4. The polymer solution in the polymerization vessel is 2 KW / M ³
The polymerization method according to claim 3, wherein the stirring is performed with the above stirring strength.