CS261550B1 - A method of producing an aqueous latex from polystyrene waste - Google Patents

Abstract

The proposed procedure belongs to the field of chemistry. Its essence lies in the fact that an aqueous solution of two emulsifiers is added to a solution of polystyrene in an organic solvent that is immiscible with water and whose boiling point, or the boiling point of its azeotrope, is lower than the boiling point of water at atmospheric pressure. After intensive mixing of this mixture, an emulsion is formed having water as a continuous phase. The organic solvent is evaporated from the emulsion with constant stirring at a temperature of 70 °C for 2.5 hours. The aqueous latex produced by the proposed method can be used for the production of dispersion film-forming coatings, adhesives and binders that are harmless to health.

Description

SUMMARY OF THE INVENTION The object of the present invention is to treat waste foamed polystyrene to waterlatex which can be used as a feedstock for the production of, for example, dispersion film-forming coatings, adhesives and binders.

The solid dispersions of polymers are becoming increasingly important in the world, especially in the paints and adhesives industry, which is reflected in our annual increase in production of about 50% over the past 10 years. health, as and] the possibility of achieving improved, respectively. complete new properties of paints, leases and adhesives, as opposed to conventional products based on solution polymers in organic solvents.Therefore, aqueous dispersions from polymers that are directly synthesized directly in the world are now produced in the world. polymerization water monomer emulsions, either by direct disintegration of the polymer in colloidal guf or triple mills of the presence of water and emulsifier, or by dissolution in a water-immiscible organic solvent, emulsification of this polymeric bed in water with the presence of an emulsifier by mechanical stirrer and vaporizing the solvent from the emulsion to form an aqueous polymer dispersion. The second method is to produce solid dispersions such as polyisoprene, polybutadiene, ethylene-propylene rubber and some other polymers.

In the production of foamable polystyrene backing plates, which are mainly used for the production of various pre-molded protective covers with excellent damping properties, about 30% by weight of the foil web is produced. However, this post-ground foamed polystyrene waste cannot be recycled, as is commonly done in plastic technology, as it contains about 50 times as much air as the polymer, due to its large relative volume.

The extremely low density of waste (about 20grams / dm 3) causes problems in the preparatory manufacturing operations of the production of polystyrene dishes, such as the mixing of the raw materials in the rotary drum mixer and the countercurrent air dryer, as well as in the extruding state, which makes it impossible to recycle even parts of the pelletized. grit. (In large-scale production of polystyrene plates, the problem of waste is solved by using a special degassing extruder that separates unwanted air from the polymer melt based on the large melt-air viscosity difference with the aid of the product. The product is a non-susceptible polystyrene granulate. However, this technology for the production of polystyrene bowls requires a separate introduction of blowing agent and extruded polystyrene, which corresponds to another type of extruder with expensive non-flame retardant (freon) and complicated pressure technology. The present invention provides the preferred processing of the polystyrene waste, which consists in the production of a latex by adding an aqueous solution of an emulsifier to a solution of polystyrene in an organic solvent which is immiscible with water and whose temperature or boiling point of the azeotrope is more than the boiling point of water. who is pressure, whereby an emulsion having water and a continuous phase and a solution of polystyrene and discontinuum are produced by intensive mixing. Under continuous stirring at an elevated temperature, the organic solvent will evaporate to form a latex containing relatively few non-colloidal particles, which can be used to produce dispersion film-forming coatings, adhesives or inserts, wherein the vaporized organic solvent is formed. can recycle.

The term organic solvent polystyrene refers to a solvent which does not mix with water or only negligibly in the liquid state, having a boiling point lower than water under atmospheric pressure, or which forms azeotropic mixtures with water whose temperature is boiling is lower than water at atmospheric pressure. Solvents including, for example, C 5 to C 7 cyclic hydrocarbons such as cyclohexane, methylcyclohexane, C 6 to C 8 aromatic hydrocarbons and less recommended halosubstituted C 1 to C 8 hydrocarbon solvents and, if desired, a combination of two or more organic solvents of the aforementioned groups .

Preference is given to such solvents having a boiling point higher than water but their azeotropic mixtures with water have a lower boiling point than water. This particularly relates to aromatic solvents including toluene, xylene, ethylbenzene, cumene.

Polystyrene dispersions are not produced by polymerizing the styrene emulsion in the water in the presence of an initiator. The disadvantage of this process is the relatively high cost of monomeric styrene, as well as the complexity of process polymerization. A preferred method of producing a polystyrene dispersion is described in the present invention, wherein a mixture of 30 parts of polystyrene foam and 85 parts of toluene is stirred at room temperature for about 1.5 hours with vigorous stirring. adding 85 parts of an aqueous emulsifier solution containing 2 to 10 wt. % of incompletely hydrolyzed polyvinyl alcohol and 0.05 to 3 wt. naphthalenesulfonic acid condensate with formaldehyde. From the emulsion thus prepared, toluene is evaporated under intensive stirring at 70 ° C for about 2.5 hours.

The subject matter of the invention is not dependent on the use of a particular water

2 G 1 5 5 O

With a soluble emulsifier or combination of emulsifiers. It may be practiced by several types of emulsifiers or combinations thereof used for emulsion polymerization of some monomers such as styrene, vinyl chloride, vinyl acetate and others. Emulsifiers capable of forming stably aqueous polymer dispersions can be divided into the following groups: a) one or more anionic emulsifiers b) one or more nonionic emulsifiers c) combinations of anionic and nonionic emulsifiers.

Anionic and nonionic water-soluble emulsifiers usually contain from 8 to 22 carbon atoms per molecule, provided that they do not carry polymer. Polymer colloidal stabilizers are most commonly used in combination with low molecular weight emulsifiers. The use of 0.4 to 20 wt. emulsifying material with respect to the ipolymer, which is dissolved in the organic solvent, is sufficient in all instances, where 1 to 10% by weight of emulsifier is sufficient for the majority of the experiments, since the proposed aqueous latex production process minimizes the the desired emulsifier.

Anionic emulsifiers include, but are not limited to, alkali metal salts such as oil and sodium stearate, also aryl sulfates, e.g., sodium lauryl sulfate (tradename Syntapol L), alkyl arylsulfonates (Abescn Na, Dubarol M 20) and water-soluble low molecular weight emulsifiers having the formula R (OCH 2 CH 2) nOSO 3X, wherein R is an aliphatic, aromatic, aliphatic or cyclic radical, n is 1-9 and X is a monovalent metal or ammonium radical (Etoxone EPA, Eton AF-5 - all produced, Association for Metallurgical and Chemical Production).

Nonionic emulsifiers may be selected from the group of emulsifiers that represent alkylpolyoxyethylene ethers and alcohols or polyethylene ethers or alcohols. These include, in principle, polymeric emulsifiers comprising water soluble polyelectrolytes, made synthetically or isolated from natural materials, having an average molecular weight of at least 10,000 g / mol, which readily adsorb to the polymer / water interface such as polyvinyl alcohol (PVA), methylcellulose (MC ) and polyvinylpyrrolidone (PVP).

It has been shown that the use of incompletely hydrolysed PVA containing 10 to 20% mol. The 8 acetate groups in the macromolecule, which are likely to be blocked, the higher the hydrophobicity of the respective molecule and hence its ability to adsorb the surface of the oil phase, is very advantageous. The hydrophilic portion of the macromolecule surfactant "shakes" free into the water phase together with the other non-adsorbed moieties of the macromolecular chains, protect the polymeric particle emulsions.

The protective-colloidal properties of the partially acetylated polyvinylalkobols have little dependence on molecular weight in the range of 11,000 to 69,000, with the most stable dispersion of dispersion, and about 6% of the polymer solution in the water. A similar colloidal system is the emulsion of the PS solution in toluene / in the present invention, as it is also substantially stabilized by polyvinyl alcohol (SloviolR 16, CHZWP Novaky), which degree of hydrolysis is 88-90% and its molecular weight is 30,000 to 40%. 000- g / mol.

Polyvinyl alcohol forms complexes with some α-anionic and nonionic surfactants that improve its protective-colloidal properties, e.g., in the synthesis of polyvinyl acetate, PVA is used together with polyoxyethylene - (10) - nonylphenyl ether and sodium dodecylbenzenesulfonate as well as with sodium salts of sulfated fatty alcohols, which can reduce the polymer PAL concentration by about half.

The naphthalenesulfonic acid / formaldehyde condensate (KortamolNNO - Association for Metallurgical and Chemical Production) has very good adsorption and dispersing properties, which has been confirmed by the invention that the emulsifying amount of PVA to Vi has been reduced, thereby significantly reducing stability as · also the amount of foam formed by the evaporation of toluene from the emulsion which inhibits the evaporation intensity of the organic solvent, while also facilitating the transition of the V / O type to O / V type due to a reduction in its viscosity and thereby improving the oil phase integration of the emulsion. the PS: PVA: Cortort NNO ratio in the subject invention is 1200: 80: 1.

The present invention is illustrated by the following non-limiting example. Said parts and percentages are by weight of the unit. Example 100 parts of a 30% solution of polystyrene in toluene are poured into an emulsifying and evaporating flask and 20 parts of a 5% solution of polyvinyl alcohol in water are added with stirring. After 15 minutes of vigorous stirring, 10 parts of ordinary water are added and after 30 minutes of total stirring an additional 10 parts of water. Viscous emulsion

Claims (1)

Ί 8 2S1550 type V / 0 is allowed to stir for one hour, warming to about 50 ° C, leading to its inversion to the 45 minute total mixing time, resulting in a fine creamy O / emulsion This is further stirred for another 30 minutes with 20 parts of 5% (polyvinyl alcohol) and 5 parts of a 0.5% aqueous solution of naphthalenesulfonic acid / formaldehyde condensate. After the addition of the last portion of the water - 20 drops - the viscosity of the emulsion is significantly reduced with the concomitant growth of the stirrer wobble, which must be reduced in order to avoid undesirable spraying of the emulsion to the vessel walls. the organic solvent can be expelled by raising the temperature to 70 [deg.] C. and the external aqueous heating of the flask as well as cooling the apparatus for about 2.5 hours while the stirrer is in operation. The product is a coagulation stable 40-45% polystyrene latex of several months. The amount of coagulated polystyrene retained on the stirrer and the walls of the flask is less than 1%. The amount of condensed toluene is 85 to 95 percent of the flood amount, which means that the resulting polystyrene dispersion is partially softened with an organic solvent. The dispersion must be kept closed to prevent the formation of the skin by smoothing the latex. The production apparatus for carrying out the present invention should be transparent, made of glass, since the process of emulsifying the PS solution in toluene into the water with a stirrer, as well as mixing the emulsion while evaporating the organic solvent in the distillation apparatus, must be followed. The emulsification as well as the evaporation of the toluene is carried out in a fixed, ball-shaped spherical flask with continuous rotor rotation control, which is further provided with an external water heater, thermometer and inlet and outlet openings. The cooking vessel is connected to a flow-through condenser and a closed condensation vessel, in which the condensed organic solvent is collected as well as the phase-separated water from both the azeo-tropical mixture and the emulsion. Its amount depends, indeed, on the desired degree of concentration of the final polystyrenelatex. The unification of the emulsification and evaporation process into one apparatus has the advantage that it prevents the leakage of toluene to the collagen during emulsification, as well as removing residual coagulum of the polymer deposited on the walls of the flask formed during the discharge. urging toluene from the emulsion to increase the temperature where the colloidal system is subjected to high mechanical and thermal loading. An advantage of the present process for the production of polystyrene latex is the advantageous processing of the secondary raw material - foam polystyrene waste which is otherwise not worked. Further, the proposed process is relatively simple compared to the styrene polymerization, due to some of the preferred properties of polystyrene crumb. In particular, it is a relatively low molecular weight polystyrene in the range of 180,000 to 200,000 g / mole, which gives relatively low-viscosity polymer solutions in the organic solvent, e.g., a solution of 20 to 30% by weight. polystyrene has a viscosity in the range of 250 to 1100 mPas, which is a precondition for the dispersion system used, i.e. the accelerator. In the case of higher viscosities of the polystyrene solution, a colloid mill or homogenizer is used which is used for emulsifying the organic phase having a viscosity of up to 10,000 mPas. However, these devices are expensive and have relatively low performance, giving a homogeneous dispersion of particles, causing a rapid increase in viscosity of the resulting dispersion at a relatively low non-volatile phase. The use of a foamed polymer has the advantage that it is completely dissolved in the organic solvent for 10 minutes at room temperature. In the case of rigid polystyrene, this time is many times longer, which is probably due to the much smaller contact surface between the phases. SUBSTANCE A method for producing an aqueous foam polystyrene waste latex having a homogeneous solution consisting of 30 parts by weight of polystyrene waste. polystyrene and 85 parts by weight. of toluene with vigorous stirring for 1.5 hours at room temperature, adds 85 parts by weight of toluene. % of an aqueous emulsion flow comprising 2 to 10 wt. % of incompletely hydrolyzed polyvinyl alcohol and 0.05 to 3 wt. of condensate-naphthalenesulfonic acid with formaldehyde, and from the resulting emulsion was toluene evaporated under stirring at 70 dC for 2.5 hours. Severojjrafia, n. P. 7, Most Price 2,40 Kís