Opaque polymer particles with encapsulated air voids were produced by sequential emulsion polymerization. Methyl methacrylate and methacrylic acid were used as basic monomers. In order to have sufficient opacity, the core and shell have to comprise at least about 2owt % and 5wt % acid monomer to the total amount of monomers, respectively. The shell polymer has to be neutralized with an equivalent amount of ammonium hydroxide and heated to 95℃ for three hours.
Methyl methacrylate, methacrylic acid를 기본 단량체로 사용하고 sequential emulsion 중합에 의해 입자내 void가 포함된 opaque polymer 입자를 합성하였다. 충분한 불투명성을 갖기 위해서 core는 전체 단량체중 20wt%이상의 acid 단량체가 포함되어야 하며, shell은 전체 단량체중 5wt%이상의 acid 단량체가 포함되어야 한다. 또한 shell polymer는 암모니아수로 95℃에서 3시간 이상 팽윤시켜야 한다.
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