Method for preparing PMMA (Polymethyl Methacrylate) microsphere with core-shell structure through soap-free emulsion polymerization

Abstract

The invention provides a method for preparing a PMMA (Polymethyl Methacrylate) microsphere with a core-shell structure through soap-free emulsion polymerization, and belongs to the technical field of high polymer chemistry. The method comprises the following steps of: carrying out reduced pressure distillation on an MMA (Methyl Methacrylate) monomer to obtain a fresh monomer; uniformly mixing the MMA monomer and water, heating in a water bath, then, adding a water-soluble initiator, and reacting while stirring under the condition of the water bath to obtain a colloid emulsion; filtering to remove impurities and conglobated macromolecular substances in the colloid emulsion; then, carrying out centrifugal separation, and drying the obtained solid product at constant temperature to obtain the PMMA microsphere with the core-shell structure. By using a soap-free emulsion, the affect from a micromolecular emulsifying agent is eliminated, and the physical-chemical, mechanical and adhesive properties of a polymer are improved; a defoaming agent is not used basically in the preparation process, so that the pollution of the emulsifying agent to the environment is eliminated; the microsphere with monodispersity and a clean surface can be prepared, and the microsphere is uniform in particle size and has the core-shell structure.

Description

technical field [0001] The invention relates to a method for synthesizing organic polymer PMMA microsphere particles, belonging to the technical field of polymer chemistry. Background technique [0002] With the application of emulsion polymerization technology in many fields of industry today, emulsion polymerization has become one of the main methods for the production of synthetic rubber, synthetic resins, coatings, adhesives, etc. Every year, tens of millions of polymers are produced by emulsion polymerization in the world ton meter. Although the emulsifier is used in a small amount in the emulsion polymerization system, it plays an important role. The emulsifier stabilizes the emulsion before and after polymerization, guides monomers to polymerize according to the micellar mechanism during polymerization, and affects the polymerization rate, number of latex particles, particle size, and distribution. However, after polymerization, the emulsifier adsorbed on the surfac...

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Problems solved by technology

However, after polymerization, the emulsifier adsorbed on the surface of the latex particles will desorb in many cases, resulting in multiple defects: (1) under the action of high shear force, it is easy to produce gel; (2) the freeze-thaw stability of latex (3) When adding components such as pigments to the emulsion, the emulsifier will compete with the pigment dispersant for adsorption at the two interfaces of the emulsion particle and water, and the pigment and water, thereby affecting the rheological properties and stability of the emulsion (4) When the solid product is prepared by the gel method, the emulsifier will remain in the water phase, causing environmental pollution; (5) The emulsifier will migrate during film formation, or be enriched at the interface between the film and the air, Affect the gloss and other surface properties of the film; or be enriched at the interface between the film and the substrate, affecting the bonding performance of the film; (6) The residual emulsifier will also cause slow film formation rate and reduce the water resistance of the film

In addition, the stability of the soap-free emulsion is related to the polarity of the polymer. The increase of the polarity of the polymer leads to the enhancement of the interfacial interaction of the water phase, which can reduce the surface energy and improve the aggregation stability of the latex. On the contrary, the hydrophobicity increases and the stability decreased sex

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