DE1495145B2 - PROCESS FOR DISCHARGE THE HEAT OF REACTION DURING POLYMERIZATION IN DISPERSION OR SOLUTION - Google Patents

Description

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The polymerization in dispersion or monomers and thus the boiling pressure of the liquid

Heat of reaction occurring in solution is in tech phase. The will change accordingly

on a technical scale, mostly via the boiler wall or the polymerization temperature. For example, increases with

Good heat conducting internals, e.g. B. cooling coils, the polymerization of vinyl acetate the polymer

discharged. The dispersion or solution is in this case 5 sation level of initially 72 ⁰ C to about 95 ⁰ C

stirred vigorously to ensure good heat transfer at the end of the polymerization. Such big ones

the heat exchange surfaces is guaranteed. Temperature changes are in the majority of the

If one wants the polymerization to be unsustainable for economic reasons.

Carry out founding in larger boilers, so it is also possible with evaporative cooling the dissipation of the heat of polymerization is always not a given, different from a polymer more difficult problem. This is because the molecular weights to be achieved because the molecular ratio from boiler volume to boiler surface weight is known to depend very much on the polymer and thus depends on the heat exchange surface with increasing temperature. The production is decisive Kettle size is becoming more and more unfavorable, so that ter different molecular weights often required one has to increase the polymerization time. For 15 a large variation in the polymerization temperature, the polymerization time, however, there are certain upper limits. It has now been found that the reaction limits which one must not exceed if heat is polymerizable during the polymerization ^ clubs certain quality of the product can be achieved bonds in dispersion or solution by Versoll, vaporize one or more in the dispersion or

Although various proposals have been made, 20 liquids contained in the solution condense the

in order to overcome these difficulties, vapors could be stored in a cooler and

the problem of heat dissipation is not yet particularly advantageous in condensed vapors in the reactor.

be resolved in a satisfactory manner. Increased stickiness can be dissipated if you are in a closed place

In general, stirring does not bring any progress, the system works and by regulating the condensate

especially with highly viscous dispersions, the rate of polymerization in the cooler

by the heat transport from the inside of the boiler to the temperature in the reactor keeps constant, whereby the

Wall not accelerated significantly. In addition, change in the condensation conditions by a

In addition, the increased agitation intensity is controlled by the polymerization

dissipate additional heat brought into the system. temperature in the reactor is controlled.

In addition, if the stirring power is higher, the number 30 will usually come for the process according to the invention

Polymerization interrupted or significantly inhibited. for example the following polymerizable compounds

Another suggestion to better dissipate the heat: Ethylene, propylene, butadiene, styrene,

lead, which consists in adding vinyl chloride, vinylidene chloride, vinyl formate, vinyl

Cooling surface through appropriate fixtures to create acetate, vinyl propionate, acrylic acid, methacrylic acid,

in many emulsions and suspensions 35 the esters of acrylic acid, methacrylic acid, maleic

of polymerizing compounds, especially acid or fumaric acid having 1 to 4 carbon atoms

for emulsions and suspensions that are still viscous, in the alcohol chain, acrylonitrile, acrylamide, meth-

because of the increased tendency to coagulate on acrylamide and mixtures of the mono-

the interfaces not passable. The purification of these. Possible coolants are

like internals, which are mainly done manually, 40 z. B. the above monomers, insofar as they

is awkward. The proportion of coagulate increases with - under the given conditions and vaporizable

increasing polymerization time. are condensable, alone, in a mixture with one another

Attempts have also been made to solve the problem of the other or mixed with dispersing or solution

Dissipate heat in a fundamentally different way, use a medium, such as water, methanol, acetone, methyl-

by using the so-called formate, ethyl acetate, aliphatic hydrocarbons,

called evaporative cooling dissipates. Here is a for benzene. Toluene.

the polymerization temperature under atmospheric- The composition of the vapor will change

pressure boiling substance, e.g. B. the monomer that evaporates generally change in the course of the polymerization,

and the steam outside the reactor in a temperature in the reactor, d. H. the poly

Condenser condenses, from where it merisation temperature as condensate 5 °, is with the help of a control

returned to the reactor. With this kept constant, which works so that with one

Arrangement one is in the choice of the ratio deviation of the polymerization temperature from the sol

depending on the cooling surface of the cooler for the reactor value, the condensation in the cooler corresponds accordingly

volume completely free and can therefore be changed into practical. The operating pressure in the closed

vessels of any size in the shortest possible time.

Dissipate heat, regardless of viscosity, flexible boiling pressure adapted to the coolant,

of the polymerization approach. This method of It can be both positive and negative pressure

Evaporative cooling can only be used if the equipment is used.

the component serving as the cooling liquid, e.g. B. Inert gases produced during the reaction, the monomer or its azeotrope with water, are removed from the system _{in 6 ° j e as required.} For this purpose, they will boil close to the polymerization temperature. A they first cooled in gas coolers, so that the well-known example is the polymerization of vinyl condensable vapors largely withheld acetate (cf. Bios report 1161). will. The exhaust gas can be discharged either by hand or by means of suitable regulating devices: Since you are generally at a constant 65. The regulation can, for example, be based on a pressure and constant monomer feed polymer exhaust gas temperature measurement in an auxiliary cooler or based, the polymerization rate is not based on a physical-chemical analysis of the constant, the concentration of the gases change, with the discharge of the inert

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Gases autonomous and independent of the regulation and percentages are weight units. Parts by weight

the internal temperature can take place. relate to parts of volume like kilograms

The monomer feed can be used to maintain liters.

of a certain monomer level is constant. B e i s d i e 1 1

hold or via the internal pressure of the reactor 5

be controlled. The feed of the catalyst can be placed in a vessel with a capacity of 1000 parts by volume

take place continuously or discontinuously, for example, a highly viscous polyvinyl propionate dispersion in

is controlled wisely by the internal pressure of the reactor. 1 to 1.5 hours at a polymerization temperature

The figure shows an example of an apparatus temperature of 82 ° C polymerized without this

for carrying out the method according to the invention. OK temperature is exceeded even for a short time.

The reactor 1 (polymerization kettle, autoclave) The steam consists mainly of vinyl propionate

is equipped with a stirrer motor and an anchor stirrer and contains very little water. There is in the boiler

fitted. The reactor jacket is at a cooling sustained negative pressure.

Medium circuit 2 is connected, which is used for heating or cooling with jacket cooling in the same boiler. The internal temperature of the reactor 15 and, for the same approach, 4 hours for the poly or the polymerization temperature is required by a merisatibn. If you use the method Thermometer 3 measured. The vapor of the cooling liquid also enters the cooler 4 when the highly viscous dispersion is cooled. The temperature decreases, so the time for the steam to cool down is measured at point 5. The of 8O ⁰ C to 4O ⁰ C 80 minutes to 20 minutes cooler 4 is appropriate to a coolant circuit 6 20 poise at a viscosity of 30 measured in closed, the temperature measured at 7 and Epprecht viscometer (measuring body C, Geschwindigdurch Additions of heat or coolant (WM or ability level 1).
KM) from the measuring point of the polymerization temperature- Example 2
ratur 3 ago via a cascade circuit 8, 9 can be changed. The condensate runs out of the 25. In a kettle of 1000 parts by volume, the cooler 4 is returned to the reactor 1 via the filter 10 and a flow-through 15% aqueous solution of a mixture of knife 11 at 12. 90% mono- 90% acrylamide and 10% acrylic acid, based on mers and catalyst, are polymerized from the storage tank 13, the mixture, and further, not shown, in one hour below 40 ° C. The polymerization temperature is never exceeded during this time, separately via flow regulators 14 in 30. The steam reactor 1 passed. Above the cooler 4 there is a predominantly water,
Small cooler 15 is attached, through which the same polymerization in the same kettle coolant constantly flows. It is used to separate exhaust gas using jacket cooling, and steam. At 16 on his head, the temperature rises sharply, which analyzes the exhaust gas. The analyzer 17 also independently controls an undesired reduction in the poly of the exhaust gas valve 18. Before the flue gas causes the degree of merization,
Leaving the apparatus, it becomes an exhaust gas. .
cooler 19 freed from further amounts of steam. Another example 5
Condensed steam reaches the reactor 1 via the likewise cooled downcomer line 20, which has a capacity of 1000 parts by volume. The amount of exhaust gas can be determined with the aid of vinyl chloride and 50 parts of vinyl propionate with a flow meter 21 and a gas meter 22. Polymerization temperature of 82 ° C in just under 3 hours

The new process succeeds in fully polymerizing the reactants. Be with jacket cooling

tion heat during the polymerization ethylenically un- for the same batch 6 to 7 hours for the poly-

saturated compounds in dispersion or solution 45 merization is required.

dissipated much faster than this according to the previous The steam consists in the longest polymerization usual Process, e.g. with jacket cooling, possibly 95% vinyl chloride. Depending on the loan was. So you can use a much larger ratio of polymerization rate to boilers polymerize and the polymerization run speed is a pressure of 4 to reduce. 5 ° 7 atm. When the dispersion is cooled, the

The dispersion produced by the new process steam over the dispersion only from water. For sions or solutions of polymers to show cooling, only the set temperature of the boiler is required. B. when measuring the adhesive strength to be reduced inside finish. The cooling time effect, the viscosity or the coagulum content is reduced to 25 minutes using the new method compared to better or more uniformly good values than the dispersions produced by known methods according to 55 over the method with jacket cooling or 75 minutes. Solutions emerge. The scatter of the values from batch to a viscosity of the product of about 50 poise, batch decreases to about ± 5% compared to measured in the Epprecht viscometer (measuring body C, about ± 20% at speed level 1 produced with jacket cooling).
Dispersions or solutions. 60 The present example shows that the procedure

Further advantages are that the polymerization not only takes place in the area of the saturation vapor pressure,

speed by measuring the value from the cooler, which in the present case is 9 atmospheres, but rather

returning steam condensate is then applicable in a simple manner. if not a clear one

can be measured that the coagulum approach to the reactor relationship between the polymerization temperature

wall is lower and that certain desired 65 and pressure in the subsaturation area at pressures

Molecular weights can be set by being given from 4 to 6 atmospheres. The absolute pressure in

Polymerization temperature is selected in a suitable manner. the apparatus plays no role in the regulation.

The parts mentioned in the following examples can, however, be used to

to get an approximate indication of the ratio of monomers to polymers. That however only works if the monomer determines the pressure.

Claims (2)

Patent claims: 1. A method for removing the heat of reaction in the polymerization of polymerizable Compounds in dispersion or solution by evaporation of one or more in the dispersion or solution containing liquids, condensation of the vapors in a cooler and recirculation of the condensed vapors in the reactor, characterized in that one firstly works in a closed system and secondly, by regulating the rate of condensation in the cooler, the polymerization temperature in the reactor is kept constant, with the The condensation ratios are changed by means of a control system that controls the polymerization temperature is controlled in the reactor. 2. The method according to claim 1, characterized in that non-condensable gases be removed from the closed system before and or or during the polymerization. 1 sheet of drawings