CS236237B1 - Process for emulsion polymerization or copolymerization of unsaturated monomers - Google Patents

Abstract

An increase in the polymerization rate and an increase in the conversion of monomers in the preparation of aqueous dispersions by emulsion polymerization of unsaturated monomers is achieved by first subjecting the mixture of monomers, water and surfactants or an emulsion prepared from these components to intensive mixing in an inert gas atmosphere with a specified energy input intensity and at a specified shear stress, then, with constant stirring at a significantly lower intensity, a solution of the initiator and, if applicable, an accelerator or a regulator of the molecular weight of the final polymer or copolymers is added to the resulting emulsion and the reaction mixture is heated to a temperature of 25 to 97 °C, at which it is maintained for 1 to 5 hours.

Description

The present invention relates to a process for carrying out emulsion polymerization and copolymerization of unsaturated monomers in an aqueous medium.

Presently, two major methods are used to prepare aqueous dispersions, redox and reflux. The different procedures differ from each other in initiation systems, emulsifying systems, temperature regime, pH of polymerization mixture, etc.

These processes can be further subdivided into batch one- or multi-step olocontinuous or continuous processes. For a summary, examples of individual process variants are given in the monograph Sňupárek J., Formánek L. Most processes for emulsion polymerization and copolymerization of unsaturated monomers are the subject of a number of patents, batch processes, eg brit. U.S. Pat. 573 333, semicontinuous MS. U.S. Pat. 145,658 to " continuous " e.g. In addition, there are numerous publications showing the results of monitoring the polymerization process itself in an aqueous emulsion of monomers, such as emulsion particle size at different agitation intensities (Durdil P., Ludvík M., Šteidl H .: Dynamics emulsification in the presence of non-ionic emulsifiers, CHISA, Mar. Lázně, 1982), particle growth in discontinuous emulsion polymerization (Lichti G., Gilbert RG, Napper DH: J. Polymer Sci. (PCHE) 19, 1981, No. 4, p.

925 - 958) and the like. A common disadvantage of these processes is the relatively low polymerization rate and the resulting long polymerization time required to conduct the reaction up to 100% conversion.

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This problem is solved by the present invention, which relates to a process for emulsion polymerization or copolymerization of unsaturated monomers in water containing active substances, preferably aqueous emulsions prepared by mixing a mixture of monomers, water and surfactants with an intensity of 5 · 10 10 ^ ^ až 1.1OO ”” ^2. kW.nf ^ .s “** at a shear stress of 1 · 10 to 5 · 1θ Nm, in the presence of polymerization initiators and optionally substances affecting the final product properties · The essence of the invention is that a mixture of monomers, water and surfactants or an emulsion prepared from these constituents is first subjected to an intensive stirring at an energy input intensity of 1.0 to 3.10 kW.m · s ”for 0.1 to 300 s in an inert gas atmosphere and at a zz shear stress of 10 to 100 Nm · of continuous stirring, with an intensity below 1.10 kW.m, add to this emulsion a solution of an initiator and optionally an accelerator or mole regulator. weight of the final polymer or copolymer and the reaction mixture is heated to a temperature of 25 to 97 ° C, where it is maintained for 1 to 5 h.

The advantage of the process according to the invention is, in particular, an increase in the polymerization rate of the system up to twice as much as the previously known polymerization processes. This can be used in both the discontinuous and semi-continuous or continuous processes for preparing dispersions. In the semi-continuous process of conducting emulsion polymerization, a conversion of 10 to 20% higher than that of the prior art processes at the same component feed rate and polymerization temperature conditions is achieved. In addition, in a thermally insulated system, with a continuous polymerization run and a suitable monomer / water ratio, nearly 100% can be achieved. Conversion of monomers without the need for an initial increase in system temperature from external sources and without additional heating of the dispersion before the polymerization is complete, typically to a temperature of 80 to 95 ° C. These advantages also apply to polymerization in flow-through stirred reactors.

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All unsaturated compounds with vinyl double bond, especially styrene and its derivatives, acrylic and methacrylic acid and their commonly used derivatives such as esters, hydroxyesters, amides, N-substituted amides, nitriles can be processed as monomers by emulsion polymerization or copolymerization according to the process of the invention. and the like, vinylagatate, alkyl vinyl ethers, optionally other vinyl monomers, maleic acid, fumaric acid and derivatives thereof, etc.

The obtained aqueous dispersions of synthetic polymers and copolymers are used for the preparation of water-based paints, adhesives, sealants and leveling materials, synthetic plasters and polymer-cement mortars, as binders for the treatment of textile materials, carpets, mineral fibers, paper, leather and many others fields.

Example 1

Weigh 281 g of styrene, 15 g of acrylic acid, 587 g of water, 27 g of sodium monooctylsulfosuccinate (Disponil SUS 87, 30% by weight of the active substance) and 2 g of hydroxymethylcellulose into a 1 L reaction flask. This mixture is stirred at 120C with a turbine mixer with a specific power input to the system of 9.6 kW.m.s and a shear stress on the stirrer rotor of 65 N.m · Inert gas (nitrogen) is introduced into the flask. Upon completion of this emulsion preparation, the emulsion is heated to 30 DEG C. and 10 ml of a 1.1% by weight ammonium persulphate solution are added to the reaction flask. and 10 ml of 5.6% sodium pyrosulfite solution. The reaction flask was thermally insulated and stirred with an intensity of 1.5 * 10 < 6 > kW / sec. The reaction temperature rises with time. The course of the monomer conversion is shown in Figure 2 by the curve A, the course of the reaction rate is shown in Figure 3 by the curve A.

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For comparison, the same experiment is carried out, but the monomer emulsions are prepared in a conventional manner, i.e. using a propeller mixer with a total energy input of 6.10 ** ^ kW.m ^ .s' at a shear stress of 9.10 Nm. Fig. 1, 2, 3 of curve B.

Example 2

400 parts by weight of water are weighed into a first container equipped with a propeller stirrer and an inert gas inlet,

12.5 wt. 32 parts by weight of sodium alkyl polyethylene glycol ether sulfate (Etoxone EPA, 34% by weight of active ingredient); parts of the condensation product of 1 mole of nonylphenol with 9 moles of ethylene oxide,

380 wt. parts of styrene, 345 wt. parts of butyl acrylate and 24 wt.

parts of acrylic acid. The agitator is then operated, which is operated at a rate of 4.10 kW.m.s for 10 min., To prepare the so-called / mmzeX ^e ^, which is then dispensed by the pump within 60 consecutive minutes. it pumped through a continuous stirred second tank equipped with a turbine mixer with a total power input to the system of 2.5.10 kW.m.s, operating at a shear stress of 20 Nm, with an average residence time of eraulsion in this tank of 10 s to the polymerization reactor. This second container is also provided with an inert gas supply. Pre-weighed 140 wt.% Into a polymerization reactor equipped with a reflux condenser and an inert gas inlet. parts of water, 2.3 wt. 4 parts by weight of the aforementioned anionic emulsifier; parts of sodium pyrosulfite. The contents of this reactor are heated to a temperature of 70 ° C and maintained during emulsion dosing. Simultaneously with the emulsion dosing, a 4 wt. parts of ammonium persulfate in 36 wt. parts of water. During this dosing, the mixture is stirred with a low-speed stirrer. After completion of the emulsion addition, i.e. 60 min. from the start of dosing, the contents of the reactor are heated to 95 ° C and left at this temperature for 1 hour. Then it is cooled to a temperature of 30 to 40 ° C. The course of the monomer conversion during this polymerization is shown in Figure 4 by curve A.

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Compared to this process, the same experiment is performed except that the emulsion pump is dosed directly into the polymerization reactor. The course of the monomer conversion under these conditions is shown in Figure 4 by curve B.

Example 3

An untreated emulsion of Example 2 is used which is injected into the emulsifier nozzle by a high-pressure pump (20 MPa pressure) where a modified emulsion is produced at a tangential stress of 100 Nm, and further processed in the same manner as in Example 2. The copolymerization is shown in Figure 4, curve C.

Claims (1)

SUBJECT OF THE INVENTION 236 237 A method of emulsion polymerization or copolymerization of unsaturated monomers in water containing the active substances, preferably aqueous emulsions prepared by stirring a mixture of monomers, water and surfactant with an intensity of 5 · 10 to 1.10 ~ ^ ^"2 kW.ní \ s at a shear stress of 1.10 to 5 * 10 Nm, in the presence of polymerization initiators and optionally substances affecting the final properties of the product, characterized in that the mixture of monomers, water, and surfactants or emulsion prepared from these components is first subjected to an inert atmosphere for 0.1 to 300 s gas at intensive stirring at power input / 3.10 ^ kW.m \ s ~ ^ and at shear stress of 10 to •• 2 100 .mu.m, then with stirring at an intensity below -2-3-3 1.10 kW.m.s add to this emulsion a solution of the initiator and optionally the accelerator or the mol. % by weight of the final polymer or copolymer; and the reaction mixture is heated to a temperature of 25 to 97 ° C, where it is maintained for 1 to 5 hours.