| 摘要 |
A semi-continuous, multi-stage polymerization process is provided for synthesizing a heat-sealable multi-layered composite particle latex. The multi-layered composite latex particles of this invention provide excellent oxygen and vapor barrier properties without hindering the desired surface properties, including high heat-sealing strength, low minimal seal temperature, excellent machinability, i.e. low blocking and low coefficient of friction. The latex particles of the present invention are formed as three-layered composite particles having an acrylic ester seed layer composed of a copolymer of methyl methacrylate and methyl acrylate. The latex particles have an intermediate core layer composed of a terpolymer having a high vinylidene chloride concentration, the other comonomers of the core layer include methyl acrylate and methacrylic acid. The latex particles also include an outer skin layer composed of a terpolymer having a low vinylidene chloride concentration, the other comonomers of the outer skin layer also include methyl acrylate and methacrylic acid. An aqueous latex of these particles is coated when wet onto substrates, such as thermoplastic films, i.e. oriented polypropylene or polyethylene films. After drying, the coated film exhibits superior oxygen and vapor barrier properties, excellent surface properties including good machinability and sealability. The coated film also exhibits excellent heat-seal strength and low minimum sealing temperature.
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