Poly(vinyl alcohol)을 이용한 poly(vinyl acetate-co-ethylene) 에멀젼 중합에 관한 연구

Abstract

The objective of this study was to examine various physical proper- ties of a poly(vinyl acetate-co-ethylene)(VAE) emulsion, which is used widely used as an adhesive, a coating agent, and a felt binder, as well as the multiple phenomena generated during polymerization. For these purposes, the following areas were examined: changes in the viscosity of VAE emulsions depending on the types of poly(vinyl alcohol)(PVA) protective colloid used as an emulsifier in polymerization; changes in the physical properties generated by the graft as a result of the polymerization of VAE products; the impact of the agitation conditions, such as the structure of the impellers and the speed of agitation during polymerization, on the particles of the VAE emulsion; and the impact of plasticizers that are used widely in the present industry. Although PVA affects the final viscosity of the emulsion that uses PVA as a protective colloid, there has been no clear investigation of the physical properties and viscosity of the VAE emulsions. This study was investigated looked at the influence of PVA on the physical properties of the final emulsion in oxidation-reduction polymerization using VAc and ethylene as the main monomers. The lower viscosity products were obtained from PVA with a low molecular weight; whereas higher viscosity products were obtained from PVA with a high molecular weight. In addition, the viscosity and swelling were also changed by graft and PVA property modifications due to pH changes in VAE emulsion polymerization. As a result, the rate of the graft reaction increased with increasing pH and the viscosity decreased awith increasing molecular weight. The VAE polymerization using PVA as an emulsifier generates a graft reaction between the mutual chains during polymerization. This has also been studied using 13C-NMR. The frequent transfer of chains occurred between the growing VAE and free radicals during VAE polymerization. The graft reactions between PVA and VAc opccur in three stages: 1) chain transfer between the growing molecules; 2) chain transfer between the growing molecule and the monomer; and 3) growth by the continuous addition of monomers on the terminal double bond. Therefore, the graft reaction was initiated by PVA. The H+ proton was separated due to the sulfate ion radical and it created a free radical of the VAc monomer to generate PVA-g-VAE. PVAs with different molecular weights were used to calculate the rate of the graft reaction of the VAc by measuring the particle distribution. When the ratio of the VAc monomer to PVA in water was low, it exhibited a gel effect and the particles were distributed widely. In addition, gel particles and precipitates created nuclei continuously. This is contradictory to the general notion that there is a close relationship between the final number of particles and the ratio of monomers. This indicates that the graft reaction, which is generated in a broad range of areas by PVA, takes place in wide regions. Different types of agitators were used to study the impact of the agitation conditions on the VAE emulsion polymerization. The emulsion polymerization of the VAc, ethylene and N-methylol acrylamide was performed with a wide range of agitation speeds using a flat Rushton impeller under high pressure. The particles during the reaction were measured through capillary hydrodynamic fractionation (CHDF) and the number of particles was calculated by CHDF. As a result, the size of the particles grew consistently due to the monomers being provided consistently. The process of coagulum formation during the reaction was also examined. The formation of coagulum increased at a conversion rate of more than 20 %. The formation of the coagulum was influenced by the types of impellers and agitation speeds, which were varied based on the operation and reaction conditions. Di-butyl phthalate, which is used commonly as a plasticizer to regulate the physical properties (e.g. Tg) when used in a VAE emulsion, was integrated to study the changes in the physical properties according to the quantity of plasticizer added. The glass transition temperature (Tg) of the dried film was measured by differential scanning calorimetry. The Tg was decreased with the addition of DBP, whereas the viscosity of the emulsion was increased with increasing quantity of plasticizer. In dry films, the plasticizers inhibited a mutual reaction inbetween the high molecule chains, decreasing the Tg. In the emulsion phase, the plasticizer permeated into the chains and caused the emulsified particles to swell, increasing the size of the particles and the viscosity. The mechanical properties were decreased with increasing quantity of plasticizer however, the water resistance was increased with plasticizer.