JPH0618601B2 - Automatically controlled distillation method for distillable substances - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION "Industrial field" The present invention provides viscous properties, such as when recovering unreacted monomer in a polymer latex or suspension containing unreacted monomer. A method of distilling distillable substances from a mixture of

"Prior art" For example, as a method for removing unreacted monomers from a polymer latex or suspension containing unreacted monomers (hereinafter referred to as a polymerization solution) and separating and recovering, heating under reduced pressure or normal pressure is performed. A method is used in which a substance that evaporates is cooled and liquefied by a condenser and then distilled off.

However, when the polymerization liquid has a viscous property because the reaction product does not have a viscous property, particularly in the latter half of the distillation, bubbles are easily generated. That is, the monomer or solvent dissolved or adsorbed in the polymerization solution is rapidly vaporized to form bubbles. As a result, bubbles and splashes of bubbles reach the condenser through the distillation port of unreacted monomer vapor, causing clogging of the condenser due to solidification of the polymer and oligomer and a decrease in purity of the recovered monomer. .

Therefore, this foaming must be prevented, but in the past, a person manually confirmed the foaming phenomenon, added an antifoaming agent, and closed the distillation port, which was a manual operation.

However, this manual operation requires a long time for the recovery operation, which causes a delay in the polymerization cycle, a decrease in productivity, and an adverse effect on the product due to the excessive addition of the defoaming agent.

"Problems to be solved by the invention" In view of the above-mentioned drawbacks of the conventional techniques, the present invention enables distillation while automatically preventing the foaming phenomenon that occurs when distilling a distillable substance from a viscous mixture. It seeks to provide a method of distilling material.

"Means for solving the problem" That is, the present invention, in the step of distilling the distillable substance from the viscous mixture, to detect the height of the bubble surface in the tank,
This is an automatic control-type distillation method for distillable substances, characterized by controlling the addition amount of the defoaming agent and controlling the opening and closing of the distillation port.

Hereinafter, the method of the present invention will be described in detail with reference to the drawings. Although FIG. 1 shows preferable schematic steps for carrying out the method of the present invention, it is not limited as long as it does not violate the essence of the present invention, and may be appropriately changed.

The present invention is not particularly limited as long as it is a viscous mixture containing a distillable substance, and examples thereof include aromatic vinyl compounds such as styrene, vinyltoluene, divinylbenzene and α-methylstyrene, and methacryl. Polymerization liquid of at least one polymer consisting of acrylic acid ester such as methyl acrylate and butyl acrylate, ethylenically unsaturated nitrile such as acrylonitrile, or a polymerization solution of a copolymer consisting of two or more kinds, and removing volatile components that need to be removed. It includes.

Examples of volatile substances are unreacted monomers, oligomers, catalysts, molecular weight regulators and solvents mentioned above.

First, the above-mentioned monomers are polymerized in the polymerization reactor 1 according to a usual emulsion polymerization or suspension polymerization method. Polymerization initiator, emulsifier, used for this polymerization
The dispersant and other additives such as a chain transfer agent, which are added as necessary, may be those conventionally used according to the type of the monomer used, and there is no particular limitation.

After the completion of the polymerization, the operation of removing the polymerization liquid containing the unreacted monomer in the polymerization reactor 1 is performed by injecting hot water or steam into the jacket 11 provided outside the polymerization reactor 1 to heat it. Method. The rotation of the stirrer during this operation is preferably a rotation speed at which the dispersion of the polymerization solution can be kept uniform. In the case of a conventionally known method such as a visual manual operation, when a sudden bubbling phenomenon of the polymerization liquid occurs, the recovery of the unreacted monomer is hindered due to the delay of the response for the manual operation. In some cases, this demonomerization operation is easily carried out without the above-mentioned troubles. Polymerization liquid is 80 ° C after completion of polymerization
Heat to ~ 130 ° C. With this heating, the unreacted monomer adsorbed and dissolved in the polymerization liquid is vaporized and a foaming phenomenon occurs on the liquid surface. Along with the bubbles, oligomers, polymers, catalysts, molecular weight modifiers, solvents and the like appear on the upper surface of the polymerization liquid. In the case of the conventional manual operation method, a person visually confirms this foaming phenomenon and controls the opening and closing of the valve at the distillation port, and at the same time, adds an antifoaming agent to the polymerization reactor in order to suppress foaming. .

On the other hand, in the case of the present invention, the height of the bubble surface on the polymerization liquid surface which appears when the polymerization liquid is heated is detected by the liquid level detector 6, and a signal is sent through the liquid level controller 7 to the defoamer flow rate. Sent to the controller 8, the antifoaming agent flow rate control valve 9 and the automatic distillation port valve 10,
Transmits the opening and closing of the valve. In the defoaming agent flow control valve 9, a predetermined amount of defoaming agent is added to the polymerization reactor from the defoaming agent adjusting tank 3 according to the signal opening / closing command. The distillation port automatic valve 10 is an automatic valve of a recovery line when the vaporized unreacted monomer generated on the liquid surface is guided to a condenser to recover the unreacted monomer that is distilled off. A signal of an opening / closing command according to the height of the bubble surface detected by the liquid level detector 6 is set in the automatic valve 10 to allow oligomers other than unreacted monomers to accompany the bubbles, polymers, catalysts, molecular weight regulators, etc. Control of the distillation automatic valve 10 to prevent the purity of the recovered monomer from decreasing due to the introduction into the condenser and the decrease in productivity due to clogging in the condenser due to solidification of the oligomer and polymer. Can be carried out.

As the liquid level detector used in this step, there are a capacitance type, an ultrasonic type, a microwave type and the like, and each can be used, but the capacitance type is preferable. The defoaming agent is not particularly limited as long as it is usually used in emulsion polymerization or suspension polymerization.

[Examples] Hereinafter, the present invention will be further described with reference to Examples.

Example In the apparatus shown in FIG. 1, 120 parts by weight of water, 30 parts by weight of acrylonitrile, 70 parts by weight of styrene, 0.3 part by weight of lauryl peroxide, 0.025 part by weight of t-butylperoxybenzoate, and 0.5 part by weight of tricalcium phosphate were added. Polymerization was carried out for 8 hours. After the completion of the weight, the unreacted monomer in the dispersion polymerization liquid in which the composition of the acrylonitrile-styrene copolymer was about 30/70 weight ratio was recovered.

The jacket temperature was heated by steam to adjust the temperature of the dispersion polymerization liquid to 120 ° C. Although foaming occurred remarkably, the liquid level detector installed in the polymerization reactor detects the height of the foaming surface and at the same time the defoaming agent flow control valve in the defoaming agent addition line opens and the polyether fatty acid ester defoaming agent Simultaneously with the addition, the distillation port automatic valve of the unreacted monomer recovery line was closed and the automatic control was operating smoothly.

The time required to recover 900 kg of unreacted monomer per 36 m ^{3 of the} dispersed polymerization liquid (content of copolymer: 46% by weight) was 3.5 hours. No solid was found in the condenser. The amount of defoaming agent used was 0.2 kg per ton of copolymer. The recovered monomer was polymerized again under the same conditions, and as a result, the copolymer content after the polymerization for 8 hours was 46% by weight.

Comparative Example In the Examples, liquid level detector, liquid level controller, flow rate controller,
The same procedure as in Example was carried out except that neither the flow control valve nor the automatic valve was used. After the polymerization was completed, the foaming phenomenon that occurred during heating in the unreacted monomer recovery step was visually checked to determine the foam surface level, and the manual valve was manually opened and closed. 5.5 to recover 900 kg of unreacted monomer per 36 m ^{3 of} dispersed polymer solution.
It took time. Further, it was necessary to frequently stop the collection operation due to clogging due to solidification of the oligomer and polymer in the condenser. The amount of defoamer used was 0.4 kg per ton of copolymer.

As a result of carrying out the polymerization again under the same conditions using the recovered monomer, the copolymer content after the polymerization for 8 hours was 40% by weight.

"Effects of the Invention" As described above, the present invention greatly improves the drawbacks of the conventional manual operation. That is, the response is improved by automatically detecting the foaming in the unreacted monomer recovery operation step by the liquid level detector. As a result of the improvement, the polymerization cycle is prevented from being delayed and the productivity is improved. , The solidification of the polymer causes clogging of the condenser, and the addition of an excessive amount of the defoaming agent which adversely affects the performance of the product is brought about.

[Brief description of drawings]

FIG. 1 is a process schematic diagram showing one embodiment of the method for automatically distilling a distillable substance according to the present invention. 1 ... Polymerization reactor, 2 ... Condenser, 3 ... Defoaming agent adjusting tank,
4 ... Defoaming agent feed pump, 5 ... Recovery tank, 6 ... Liquid level (foam level) detector, 7 ... Liquid level controller, 8 ... Defoaming agent flow rate controller, 9 ... Defoaming agent flow rate control valve, 10 … Automatic distillation valve, 11
…Jacket.

Claims (3)

[Claims] 1. In the step of distilling a distillable substance from a viscous mixture, the height of the bubble surface in the tank is detected to control the addition amount of the defoaming agent and to open / close the distilling port. A method for automatically distilling distillable substances, which is characterized by controlling 2. A method for automatically distilling a distillable substance according to claim 1, wherein the mixture is obtained by a polymer polymerization reaction and the distillable substance is an unreacted monomer. . 3. The liquid level detector detects the height of the bubble surface in the tank and sends a signal to the controller of the defoaming agent inflow control valve to control the amount of defoaming agent added and to distill off. The method for automatically distilling a distillable substance according to claim 1 or 2, wherein the opening / closing of the distillation port is controlled by sending a signal to a controller of the port opening / closing valve.