| 摘要 |
In a pressure operated dispensing container (12) commonly called an aerosol container, a floating piston (10) is provided to separate the propellant chamber (14) from the product chamber (16). To provide combined properties such as impermeability and neutrality to the absorption and adsorption of water, the piston provided is thermoformed from a multi-ply sheet material (Figure 2) having an impermeable centre layer (22) of nitrile polymer sandwiched between two shielding layers (20, 21) of polypropylene. The thermoformed piston has thin side walls (105) providing a close fit to the can wall, conformance to out of round conditions, and minimum swelling. The thermoforming of the piston makes it possible among other things to employ a simple, less expensive fabricating technique that required less material than does injection moulding. |
