METHOD OF PRODUCING FINE POWDERED POLYETHYL METHACRYLATE FOR DENTAL PROSTHETICS Russian patent published in 2023 - IPC C08F20/06 C08F265/06 A61C13/00 

FIELD: dental prosthetics.

SUBSTANCE: invention relates to the field of producing high-molecular compounds, namely to a method of producing fine powdered polyethyl methacrylate used in dental prosthetics. Fine powdered polyethyl methacrylate for dental prosthetics is produced on the basis of water-microemulsion polymerization of ethyl methacrylate in a glass polymerizer reactor. The polymerization mixture contains an initiator, benzoyl peroxide, dissolved in ethyl methacrylate and a plasticizer, dibutyl phthalate. The initiator content in the mixture is 1.25 wt.% of the original ethyl methacrylate monomer, and the plasticizer content is 1.0 wt.% of the original ethyl methacrylate monomer. Ethyl methacrylate is taken on the basis that its concentration in the aqueous microemulsion should be 16.5±1 wt.%. Then the resulting polymerization mixture is introduced into an aqueous microemulsion heated to 85±1°C. An aqueous microemulsion is prepared in a glass polymerization reactor with stirring at a glass stirrer speed of 200 rpm at a temperature of 85± 1°C by adding polyvinyl alcohol to water in an amount of 4.0 wt.% of the original ethyl methacrylate monomer and in 10 minutes a 8 wt.% suspension of potato starch in an amount of 3.5 wt.% of the original ethyl methacrylate monomer is gradually added while stirring continues until a gel is formed. After introducing the polymerization mixture into the reactor, the speed of the glass stirrer is increased to 350 rpm and at a temperature of 85± 1°C an induction process is carried out, which turns into an exothermic polymerization reaction carried out for 20–25 minutes maintaining a polymerization temperature of 87± 1°C, by periodically adding cold purified water into the reactor through a reflux glass refrigerator in portions of 50–100 ml. To complete the polymerization process, a stable temperature of 87±1°C is maintained in the reactor for an hour and then the resulting aqueous suspension of polyethyl methacrylate is cooled to a temperature of 62±2°C. After which it is drained and mixed for 3 minutes with water heated to 45°C, then it is left to stabilize for 4 hours. 10–20 minutes before decanting, the top layer is stirred for 1 minute. After decanting, the elutriated polymer is washed on a suction filter through belting filter material with water heated to 40–50°C until the wash water becomes transparent and free of opalescence. Residual water is sucked out by connecting the suction filter to a vacuum for 2–3 minutes – residual pressure 0.1 atm, and dried at a temperature of 40±2°C for 6 hours. The proposed invention makes it possible to obtain finely dispersed polymethyl methacrylate powder, white, odorless and free of foreign inclusions with particle sizes of 50–110 microns. This material is suitable for use in dentistry due to its technological properties.

EFFECT: method presented in the invention is simple and does not require the use of complex equipment or toxic substances.

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