Synthesis And Study Of Aqueous Acrylate Resins Used For Enteric Drugs Coating

With the development of medical technology, polymer coating material hasreceived widespread attention, especially acrylic resin coating material. Acrylic resinsas the most commonly used polymer coating materials, the advantage is that they aresafe and nontoxic, their film are very good, they are not absorbed by the body. Andnow they were prepared normally by the methods of emulsion polymerization usingwater as the solvent instead of solution polymerization using organic solvent asmedium. The trend is also adapted to the requirements of sustainable development; theresearch of aqueous acrylate resins is getting more and more attention by the people.The preparation method and influencing factors of aqueous enteric acrylic resinsfilming materials were detailed studied in this paper. The optimum synthetic processesof the polymerization reaction were as follows. The volume ratio of water phase andoil phase was3:7, the molar ratio of methacrylic acid and ethyl acrylate was1:2, thedropping time of two uniformLy mixed monomers was not less than2h. Thepotassium persulfate was used as initiator, and its dosage was0.5%of the total qualityof mixed monomers. The Emulsifiers were mixture of sodium dodecyl sulfate (SDS)and OP-10, their mass ratio was1:3, and their dosage was1.5%of the total quality ofmixed monomers. The selected molecular weight modifier was linear α-methyl styrenedimer, which accounted for0.3%by the total amount of the monomer mixture. The pHbuffer is sodium bicarbonate, and its total amount was0.2%of the total amount of themonomer mixture. The polymerization reaction temperature was controlled between78to80oC, stirring speed is200to300rpm. The synthetic acrylic resins werecharacterized by infrared spectrum (IR), scanning electron microscopy (SEM), gelpermeation chromatography (GPC) and differential scanning calorimeter (DSC). Theresults showed that the two monomers almost all participated in the polymerization,the particle size of latex was uniform, the molecular weight distribution was narrowand they were suitable used for drug coating materials.The acrylic copolymer emulsions which there were differential content ofhydrophilic monomer, methacrylic acid, were also prepared in this paper. Thedistribution of carboxyl groups in followed three phases, in the water phase, thesurface of latex particles and the interior latex particles was determined. The resultsshowed that with the increasing of the content of hydrophilic monomer methacrylic acid, the contents of carboxyl groups in water phase, latex particle surface andembedding in the latex particles were all increased, but the increasing percent weredifferent. The carboxyl content in the water phase increased more obviously than thatin the latex particle surface and interior because the hydrophilic monomers preferentialentered into the aqueous phase in the synthetic procedure. It was also found that thecontent of the hydrophilic monomers had little effect to the molecular weight and itsdistribution of the obtained polymers.High solid content of acrylate emulsions were synthesized by every kinds ofmethods, such as using protective colloid as assistant in the emulsion polymerization,core-shell emulsion polymerization, and the seed emulsion polymerization. But thesystemic studying researches in this field are not enough. The experiments water stillneed to be improved and perfected latterly.