PROCESS OF LOW-TEMPERATURE DEEP ALKALI HYDROLYSIS OF POLYETHYLENE TEREPHTHALATE Russian patent published in 2007 - IPC C08F8/12 

FIELD: industrial organic synthesis.

SUBSTANCE: low-temperature deep alkali hydrolysis of polyethylene terephthalate is accomplished with sodium or potassium hydroxide solutions having initial concentrations 5-12 g-equ/kg at 40-85°C in vertical-type bead mill provided with high-speed blade stirrer and glass beads as grinding agent at weight ratio to charge (2-3):1. Alkali solution and distilled water and dry sodium (potassium) hydroxide is charged into reactor wherein glass beads and previously non-reacted polymer are already comprised. External heating is supplied, mechanical stirring is started, temperature of contents is adjusted to working value within a range 40 to 85°C, temperature is stabilized and polymer preliminarily reduced into powder with particle size 0.5 mm and less s added in such an amount that its total amount with preliminarily charged non-reacted polymer is in 10-20% excess over its stoichiometrically required amount. Stirring is continued while alkali consumption is controlled. When 95% of alkali is consumed stirring is continued under the same conditions for further 5-10 min. Thereafter, distilled water preheated to working temperature or slightly higher is added in amount calculated such as to ensure solubility of terephthalic acid salt in thus diluted alkali solution and virtually all the suspended terephthalate salt is transferred into solution. The latter is separated from beads and unreacted polymer and routed to recover terephthalic acid and ethylene glycol or to another type of processing. Unreacted solid polymer is rinsed to remove salt and re-introduced into process.

EFFECT: enhanced process efficiency at low temperature.

2 cl, 1 tbl, 11 ex