JPH0150241B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for stopping polymerization in an addition polymerization reaction, and more specifically, in the case of an abnormality such as a power outage or a failure of a stirrer during an addition polymerization reaction, a polymerization inhibitor is introduced into the reaction system, This is a method of effectively stopping a polymerization reaction by intermittently evaporating and boiling a monomer and/or a non-polymerizable compound (hereinafter referred to as a monomer, etc.) having a higher vapor pressure than the monomer.

In general, polymerization reactions of polymers are exothermic reactions and are often carried out at high pressure.In the event of an abnormality such as a power outage, a failure of the stirrer, or a stoppage of cooling water supply, it becomes difficult to remove the reaction heat, and the temperature and pressure gradually decrease. When the pressure rises and the reaction eventually goes out of control, and the set pressure is exceeded, a large amount of unreacted monomer gas will be ejected from the safety device such as the safety valve or laptia disc, and the ejected gas may cause secondary disasters such as explosions. In addition, there are many environmentally undesirable materials such as vinyl chloride monomers.

Conventionally, as a safety measure of this kind, a method was taken to stop polymerization by adding a polymerization inhibitor such as phenol, quinone, or amine (Japanese Patent Application Laid-Open No. 51-90381, Japanese Patent Application Laid-open No. 51-61591, etc.). There is. However, if stirring is not possible, simply adding an inhibitor will not have much of an inhibitory effect. In addition, as in DT2428705, by flowing cooling water by gravity from a cooling water storage tank installed at a high place to a condenser connected to the reactor in the event of an abnormality such as a power outage, the reactants can be collected in the condenser. There is a method in which the monomer is condensed and the heat of reaction is removed using the latent heat of vaporization, but this method requires large-scale equipment and is not economically preferred.

The present invention involves intermittently releasing monomers, etc. to the atmosphere after adding a polymerization inhibitor in a reaction system where a stirrer is not possible.
Alternatively, the polymer can be evaporated intermittently by degassing the monomer etc. from the reactor to recovery equipment, or by intermittently condensing the monomer etc. by introducing it to a condenser connected to the reactor. This provides a method for effectively stopping polymerization by boiling.

Polymerization methods used in the present invention include bulk polymerization, suspension polymerization, emulsion polymerization, and solution polymerization.
Particularly preferred are polymerization systems in aqueous media such as suspension and emulsion polymerizations.

Polymerization monomers include olefin monomers such as ethylene and propylene; vinyl halides and vinylidene halides such as vinyl chloride, vinyl bromide, and vinylidene chloride; acrylic esters such as methyl acrylate and ethyl acrylate. Vinylidene monomers having at least one unterminated _CH2 =C< group such as; vinyl acetate; methacrylic acid esters such as methyl methacrylate and butyl methacrylate; styrene and styrene derivatives such as a-methylstyrene and vinyltoluene; Examples include vinylnaphthalene; diolefins such as butadiene, isoprene, and chloroprene; arbitrary mixtures of the above-mentioned various monomers, and mixtures with other monomers copolymerizable with them. In addition, in the polymerization reaction of monomers with low vapor pressure such as styrene and vinyl acetate, certain non-polymerizable compounds that have a higher vapor pressure than monomers such as propane and butane and have less influence on the reaction are used. By making the compound exist in advance, a method can be adopted that utilizes the evaporative boiling effect of the compound.

Examples of polymerization inhibitors include phenols such as hydroquinone, tertiary butylcatechol, and butylhydroxyanisole; quinones such as parabenzoquinone; amines such as nitrohydroxyamine and phenylenediamine; and sulfur compounds such as mercaptan and dithiocarbamate. There is no particular limitation as long as it is a substance that has the ability to inhibit polymerization.

The amount of the inhibitor added is in the range of 0.0001 to 1.0 parts by weight, preferably 0.01 to 0.5 parts by weight, based on 100 parts of the monomer.

Methods for adding the inhibitor include dissolving the inhibitor in water or a solvent, storing it in a specific tank, equalizing the pressure between the reactor and the tank, and then adding it, or pressurizing it with high-pressure gas such as nitrogen gas. is used.

A method for intermittent evaporation and boiling is as follows: ○B. Open the atmosphere release valve attached to the reactor for a certain period of time to release monomers, etc. to the atmosphere and evaporate and boil the reactants, then continue for a certain period of time. Close the valve and stop boiling. A method of intermittently evaporating and boiling the polymer by repeating this operation of evaporating and boiling and stopping the boiling twice or more at least several times. A method of intermittently evaporating and boiling the polymer by opening and closing the valve in the same manner as in ○A. Methods such as evaporating and boiling can be adopted.

The advantages of the intermittent boiling method, which is a feature of the present invention, are as follows:
Compared to continuous evaporation and boiling,
In addition, by evaporating and boiling off a small amount of monomer, etc., it is possible to mix the inhibitor and unreacted monomer, and it is possible to effectively stop the polymerization. It is possible to reduce the amount of monomer released in cases ○B and ○C, and in the case of ○B and ○C, it is possible to stop the polymerization without releasing the monomer etc. into the atmosphere using small-scale equipment. Furthermore, by automating the valve opening and closing operations for intermittent boiling, from the injection of these inhibitors, using a control computer or sequencer, it becomes possible to reliably stop the reaction even in the event of an abnormality such as a total power outage in the factory, thereby increasing safety. It is also preferable from an environmental standpoint.

The present invention will be explained below with reference to Examples.

Example 1 540Kg of pure water, 2,2'azobis-2,4dimethylvaleronitrile (ABVN) in 1000 reactor
68g, partially saponified polyvinyl alcohol (PVA)
After charging 216g and ordinary additives such as antioxidants and scale inhibitors, the inside of the reactor was degassed while stirring, and 340Kg of vinyl chloride (VCM) was charged, and the temperature was raised to 58℃.
Polymerization was carried out at a pressure of 8.9 kg/cm ² G.
Five hours after the start of polymerization, stirring of the reactor and supply of cooling water to the jacket were stopped, and a 5% toluene solution 3 of parabenzoquinone was added. 5 from stirring stop
As a result of repeating the operation of collecting VCM for 2 minutes and stopping collection for 2 minutes three times from the minute, the pressure was 8.5Kg/cm ² G
After that, collection was stopped for 30 minutes and the temperature and pressure inside the can were observed, but no increase was observed in either temperature or pressure.

Example 2 Polymerization was started in the same manner as in Example 1, stirring and jacket cooling water supply were stopped at the second hour, and a 5% toluene solution 4 of tertiary butylcatechol (TBC) was added. From 5 minutes after the stirring was stopped, the operation of collecting for 3 minutes and stopping for 3 minutes was repeated three times, and as a result, the pressure decreased to 8.4 Kg/cm ² G.
After that, collection was stopped and observed for 30 minutes, but no increase in pressure was observed.

Example 3 After charging 540 kg of pure water, 78 g of ABVN, 324 g of partially saponified PVA, and additives such as ordinary antioxidants and scale inhibitors into a 1,000-liter reactor, the inside of the reactor was degassed while stirring, and 320 kg of VCM and Charge 20 kg of vinyl acetate (VAC), raise the temperature to 61.5℃, and pressure 9.5
The polymerization was carried out at Kg/cm ² G. Five hours after the start of polymerization, stirring of the reactor and supply of cooling water to the jacket were stopped, and a 5% solution of TBC in toluene 4 was introduced.
As a result of repeating the operation of collecting for 2 minutes and stopping collection for 1 minute 5 times from 6 minutes after stopping stirring, the pressure was 8.8 kg/
cm ² G. After that, collection was stopped and observed for 30 minutes, but no increase in pressure was observed.

Example 4 30 kg of pure water, 4.5 g of ABVN, 90 g of dodecylbenzenesulfonate, and cecil alcohol in a 50 reactor
After replacing the air with nitrogen gas, 15 kg of VCM was charged while stirring, and after dispersing and homogenizing it through a homogenizer for 2 hours, the system was heated to 58°C and polymerized at a pressure of 8.9 kg/cm ² G. . After polymerization starts, 5
At the hour, stop stirring and jacket cooling water supply.
0.2 of a 5% solution of TBC in toluene was added. After the stirring was stopped, the operation of collecting VCM for 2 minutes and stopping the collection for 2 minutes was repeated 4 times from the 7th minute, and the pressure was 8.6.
It decreased to Kg/cm ² G. After that, collection was stopped and 30
Although observed for several minutes, no increase in pressure was observed.

Example 5 10.8Kg of pure water and potassium persulfate in 25 reactors
18g, n-dodecyl mercaptan 30g, tertiary potassium phosphate 12g and sodium fatty acid 15% aqueous solution 2 were charged, and after replacing the air with nitrogen gas, 1.8kg of styrene and 4.2kg of butadiene were charged while stirring.
The temperature was raised to 50°C and polymerization was carried out at a pressure of 4 kg/cm ² G. Six hours after the start of polymerization, stirring and the supply of cooling water to the jacket were stopped, and 150 c.c. of a 4% aqueous solution of potassium dimethyldithiocarbamate was added. After stopping stirring, 5
As a result of repeating the operation of releasing the air to the atmosphere for 1 minute and stopping the release for 1 minute five times from the minute, the pressure decreased to 3.8 Kg/cm ² G. After that, the discharge was stopped and observed for 30 minutes, but no increase in pressure was observed.

Example 6 11 kg of pure water, 40 g of benzoyl peroxide, and 12 g of tertiary calcium phosphate were charged into a 25 reactor.
After replacing the air with nitrogen gas, add 10 kg of styrene while stirring.
and 2.5 kg of butane were charged, the temperature was raised to 90°C, and polymerization was carried out at a pressure of 3.5 kg/cm ² G. After the start of polymerization, stirring and jacket cooling water supply were stopped at 1 hour.
200 c.c. of a 5% solution of TBC in toluene was charged. After the stirring was stopped, the temperature rose to 94°C 10 minutes later,
As a result of repeating the operation of releasing the air into the atmosphere for 1 minute and stopping the release for 1 minute three times, the temperature decreased to 89°C. After that,
As a result of observation for 30 minutes, no increase in temperature was observed.

Comparative Example 1 Polymerization was started in the same manner as in Example 1, stirring and jacket cooling water supply were stopped at 5 hours, and 5% toluene solution 4 of parabenzoquinone was added. After the stirring was stopped, the pressure reached 15 Kg/cm ² G at 25 minutes, and there was a risk that the reaction would run out of control, so VCM was collected.

Comparative Example 2 Polymerization was started in the same manner as in Example 1, stirring and jacket cooling water supply were stopped at 5 hours, and 5% toluene solution 4 of parabenzoquinone was added. After collecting VCM continuously for 10 minutes from 5 minutes after stopping stirring, the collection was stopped and observed. As a result, the pressure gradually increased, and the pressure reached 15 minutes after stopping the collection.
Kg/cm ² G was reached and there was a risk of runaway reaction, so VCM was collected.

Claims (1)

[Scope of Claims] 1. A method for emergency termination of a polymerization reaction, which comprises adding a polymerization inhibitor to the polymerization reaction and intermittently evaporating and boiling the monomer. 2. The method for emergency termination of a polymerization reaction according to claim 1, wherein a non-polymerizable compound having a vapor pressure higher than that of the monomer is allowed to coexist in advance in the polymerization system.