CS224879B1 - Preparation method of water dispersions of macromolecular substances and equipment for execution of the method - Google Patents

Description

The invention relates to a process for semi-continuous emulsion polymerization of unsaturated monomers in an aqueous medium and to a device for carrying out it.

The preparation of macromolecular aqueous dispersions by emulsion polymerization of monomers containing one or two double bonds by a semi-continuous process is described in a number of publications and descriptions of inventions (eg, Kolloid Z. 227. 1968, No. 1-2, p. 92; <J. Polymer Sci. , C 1969, No. 27, p. 77, Chemical Industry £ 2, 1975, p. 86, British Pat. No. 1,150,513, US Pat., No. 3,914,196, US Pat. 555,874, European Pat. No. 6,697). In particular, the advantages of the semi-continuous process are mentioned. However, there are a number of other works in which some of the negative phenomena of this process are solved, namely the elimination of sticking on the reactor walls and the stirrer and further reducing the formation of so-called coagulate, ie particles several orders of magnitude larger than U.S. Pat. No. 4,142,033, U.S. Pat. No. 2,930,757, Pet. USSR No. 762,109, European Pat. No. 87,999).

In this work, this problem is solved primarily by forming protective hydrophilic films on the reactor walls prior to polymerization and then modifying the surfactant assembly used in the manufacturing regulations, mainly by strengthening the non-ionic component. The method of supplying all necessary raw materials to the rector and their homogenization and the influence of this method on the quality of the final dispersion are not discussed in detail,

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224 879 for contamination of the roctor wall, contamination of the stirrer and for heat transfer during synthesis.

From these publications and from the knowledge of the present dispersion processes, it is apparent that the feedstocks are brought to the surface of a gradually increasing liquid content in the reactor, using a low-speed anchor or frame type stirrer for mixing the reactor contents. ,

In particular, the dispersions produced by this process contain a large undesirable amount of coagulate, i.e. particles which by several orders of magnitude exceed the particle size of the dispersion, which are in the range of 0.1 to 2 [mu] m. Furthermore, the contamination of the stirrer, the walls and the reactor reactor by the film resulting from the synthesis of the dispersions increases rapidly in this process. This is mainly due to the fact that the reactants are fed to the level of the reaction mixture in the reactor, which is then the site of an intense uncontrolled reaction, with the impossibility of thermal control and always with a large evaporation of monomers into the steam space of the reactor. After condensing, these vapors then polymerize on the exposed reactor walls, particularly on the reactor lid. In order to counteract these negative phenomena, it is recommended in some of the above-mentioned works to cool the lid, which is a considerable complication to the equipment.

The present invention is directed to a process for the preparation of aqueous dispersions of macromolecular substances by semi-continuous emulsion polymerization of unsaturated monomers in an aqueous atmosphere under an inert atmosphere under the action of redox initiators by separately feeding solutions of the individual components of the redox system. and a device for carrying out the process, comprising a vertical cylindrical reactor, a vertical stirrer, a feed line and other conventional emulsion polymerization equipment. The principle of the method is that the reactants and the auxiliaries and optionally modifiers used are fed to the stirred reaction medium below the level of the reaction mixture into an area with a maximum mixing intensity, which is the lower part of the reaction mixture up to 0.3 times its final height. wherein it is preferably cooled below 40 ° C and / or mixed with each other prior to entering said environment. The principle of the apparatus is that the supply lines of the reactants and auxiliary and modifying substances, optionally provided with a jacket for the passage of the cooling medium, are connected via a flange to the wall and / or bottom of the reactor and into the reactor Preferably, the orifice is located at a distance of 0.05 to 0.3 times the internal diameter of the reactor from the internal surface of the reactor, optionally connected to the mixing section before termination.

In the above-mentioned arrangement of feed to the reactor, it is advantageous to use a multi-stage agitator with oblique or arrow blades and a baffle in the boiler. A further advantage of the proposed process for the preparation of dispersions is that said feed line supplies additional raw materials such as neutralization solutions, dispersion viscosity adjusters, defoamers and other auxiliary liquids after the emulsion polymerization is completed.

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The process of the present invention ensures their perfect mixing with the dispersion in the reactor and avoiding the formation of further coagulated particles that are generated when these liquids are brought to the surface of the reactor. Furthermore, there is no spraying of said resonance components on the reactor walls and lid and on the non-wetted part of the stirrer, where the polymer layer has grown in earlier processes. A further advantage of the process according to the invention is that the raw materials coming into the reactor are intensely homogenized, reacted immediately and the local overheating of the reactor contents is reduced. These advantages are particularly advantageous when compared to the aforementioned known processes in which the reaction components are brought to the level of the liquid in the reactor.

The feed line may be cooled by a fluid passing through the jacket, which is usually cooling water or nitrogen, which is also used to maintain an inert atmosphere in the reactor. If the feed line is then routed outside the reactor and connected through the flange to the reactor, it need not be cooled. Advantageously, in this method of feeding the raw materials to the reactor, they are used to mix them in a mixing section into which all the feed lines terminate before all components enter the reactor. A further advantageous arrangement of this feed line to the reactor is that its orifice in the reactor is led to a vigorous liquid mixing point, which is at a distance of 0.05 to 0.3 times the internal diameter of the reactor from the internal surface of the reactor body.

Example 1

A 26.4 wt.% Monomer emulsion in water was fed to a 120 mm diameter 31a reactor through a feed line passing through the reactor lid and being jacketed with a nitrogen tube. % methyl methacrylate, 27.5 wt. 2 parts by weight of ethyl acrylate; parts of methacrylamide, 3.6 wt. 4 parts by weight of N-methylolacrylamide; parts by weight of the surfactant PAL-SUS 87 (sodium sulfosuccinate based on higher fatty alcohols) and 36.3 wt. % of demineralized water at a rate of 0.105 times the weight of the final amount of dispersion in the reactor per minute. A solution of 10 wt. parts by weight of ammonium persulfate and 90 wt. parts of water at a rate of 2.2. IO ⁴ times the weight of the final amount of dispersion in the reactor per minute by a solution of the composition 7.4 wt. % of sodium bisulfite and 93 wt. parts of water at a rate of 2.1. 10 * ⁴ times the weight of the final amount of dispersion in the reactor per minute. At the beginning of the reaction, a solution containing 14.5 wt. % of surfactant PAL-SUS 87, 84 wt. parts of water, 0.64 wt. % of ammonium persulfate and 0.64 wt. % of sodium bisulfite in an amount of 0.1 times the weight of the final amount of dispersion in the reactor. The inlet ducts are terminated at 0.1 times the final reactor level from the bottom and at a distance of 0.1 times the internal diameter. reactor from the wall. The stirrer in the reactor is vane with a blade pitch of 45 °. The polymerization was conducted at 80 ° C and terminated after 120 min. After this time, the temperature was raised to 80 ° C for 1 hour. Then with the supply line for the emulsion

224,879 monomers are supplied with ammonium hydroxide of 25 wt. parts of ammonia and 75 wt. parts of water at a rate of 0.05 times the weight of the final amount of dispersion in the reactor per minute for 30 minutes. The reactor contents were then cooled to 30 ° C and discharged.

The aqueous copolymer dispersion obtained contains 0.01 wt. % coegulate (mean of 4 experiments). The dispersion prepared by the same procedure on the same reactor, except that all components are fed to the level of the reaction mixture in the reactor during the reactor, contains 0.18 wt. % coagulate (average of 7 experiments).

Example 2

An emulsion of 31 wt.% Monomers in water was fed to the reactor into a 80 L reactor and a 350 mm diameter reactor via a three feed line outside the reactor and through a flange attached to the bottom of the reactor. parts of styrene, 28 wt. parts of ethyl acrylate, wt. parts by weight of methacrylic acid, 5 wt. parts by weight of Disponil PES 77 (sodium fatty alcohol ether sulfate) surfactant and 35 wt. parts of demineralized water at a rate of 6.3. 10 ^- ^ times the weight of the final amount of dispersion in the reactor per minute, second solution composed of 5.6 wt. % of ammonium persulfate and 94.4 wt. % water at a rate of 3.8-10 times the weight of the final amount of dispersion in the reactor per minute; parts by weight of sodium bisulfite and 97.4 wt. of water at a rate of 3.8. 10 times the weight of the final amount of dispersion in the reactor per minute. This triple feed line is connected to the mixing section before being connected to the reactor. An anchor agitator is used to stir the reaction mixture in the reactor. At the beginning of the dispersion preparation, a 10 wt. parts of Disponil FES 77 surfactant, 0.3 wt. % of ammonium persulfate and 0.15 wt. % of sodium bisulfite in 89 wt. parts of water in an amount of 0.09 times the weight of the final dispersion content in the reactor and the ee reaction was conducted at 80 ° C. After 120 min. The feed in the reactor is increased to 90 ° C for 1 h and then a 25 wt.% solution is metered through the line for monomer emulsion feed into the reactor. parts of ammonia and 75 wt. parts of water at 4.7. 10 times the weight of the final amount of dispersion in the reactor per minute.

5 experiments were performed with the following results:

Experiment no. 1 2 3 4 5 Weight % coagulate in the final dispersion 0.001 0.0009 0,0012 0.0015 0.0001 Gloss of coating film (visual evaluation according to ČSN 67 3063), scale 1 to 5 1 2 2 1 1

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There were no stickers on the walls of the apparatus and on the agitator after these five attempts to be removed.

With the same composition of the reaction mixture, five experiments were carried out on the same apparatus except that the feedstocks were fed through the reactor lid to the liquid level in the reactor. The results of these experiments are as follows:

Experiment no. 1 2 3 4 5 Weight % coagulate in the final dispersion 0.0056 0.005 0,0026 0,002 0.01 Shine of the paint film (visual assessment according to ISN 67 3063), scale 1 to 5 2 3 1 3 3

In these five experiments, significant increases in the polymerized film were observed, mainly on the stirrer and on the reactor lid.

Example 3

With the same composition of the reaction mixture as in Example 2 and the same procedure, a dispersion was prepared in a 250 L reactor and a 700 mm diameter reactor. The supply piping is connected so that the bundle of three piping with cooling water and nitrogen casing reaches the bottom of the reactor, where the piping is terminated at 0.15 times the final level of the reaction mixture in the reactor from the bottom and at a distance of 0.2 times diameter of the reactor from its wall. A three-stage paddle stirrer with arrow blades and reactor stops are used for mixing. An ammonium hydroxide solution is metered in at the end of the polymerization through the aqueous monomer emulsion feed line. The amount of coagulate in the final dispersion is 0.0012 by weight of the total dispersion content.

By the same procedure, a dispersion was prepared in the same reactor except that the solutions and emulsions used were brought to the level of the reaction mixture. The coagulate content of this dispersion was 5 to 10 times higher and the reactor walls and the stirrer were greatly contaminated with the polymer film after preparation.

Claims (2)

Process for the preparation of aqueous dispersions of macromolecular substances by semi-continuous emulsion polymerization of unsaturated monomers in an aqueous atmosphere under an inert atmosphere under the action of oxidation-reducing initiators by separately feeding solutions of the individual components of the oxidation-reducing system. ingredients and auxiliaries and, optionally modifying agents are introduced into a stirred reaction medium under the surface of the reaction mixture in a maximum mixing intensity, which is the lower part of the reaction mixture up to 0.3 times the final height of its surface, before entering into the environment _of the preferably cooled below 40 ° C and / or mixed with each other. 2. Apparatus for carrying out the process according to claim 1, comprising a vertical cylindrical reactor, a vertical stirrer, feed lines and other emulsion polymerization accessories, characterized in that the feed lines of the reactants and the auxiliary and modifying agents, optionally provided with a jacket for the coolant passage. are connected via a flange to the wall and / or bottom of the reactor and exit into the reactor in the space between the bottom of the reactor and 0.3 times the final level of the reaction mixture, preferably so that the pipe orifice is spaced from 0.05 to 0.3 times the internal diameter of the reactor from the internal surface of the reactor, and are optionally connected to a mixing section before termination.