| 摘要 |
Water-soluble, biodegradable containers are made by (a) using a polyvinyl alcohol (PVA) contg. /} 0.5 wt.% of Na acetate and with 80-92% deg. of hydrolysis, (b) forming an intermediate thermoplastic compsn. by addn. of 13-20 wt.% of a plasticiser, (c) homogenising this compsn. by application of energy of /- 0.5 kW/h/kg, at < 230 deg C, to give a uniform compsn. with Karl Fischer moisture /} 0.5% at 200 deg C and /} 0.1% at 120 deg C, and contg. infusible particles in amt. such that, in a film 100 mu thick, 10m<2> contains < 9 particles of size 150-200 mu , and no particles of size > 200 mu , and (d) using the uniform compsn. to form the containers. Pref. (a) The Na acetate content of the PVA is not /} 0.3 wt.%. (b) The amt. of plasticiser is 15-17%, or /-10% of glycerol, or /-3% of triethylene glycol or of polyethylene glycol with mol. wt. 200-400. (c) Homogenisation is /} 220 deg C, using 0.5-1.2 kW/h/kg of energy, and partic. in a double-screw extruder with an internal temp. profile of 140-230 (160-220) deg C. The compsn. is claimed. Esp. (i) for prodn. of containers by extrusion-blowing, the melt flow index (MFI) of the homogenised compsn. is 1-10 g/10 mins. (at 230 deg C and 2.16 kg load), and the PVA has viscosity 8-40 (8-26) mPa.s at 20 deg C, or (ii) for injection-moulding, the MFI of the homogenised compsn. is 10-30 g/10 mins. (at 190 deg C and 2.16 kg load), and the PVA has viscosity 3-8 (3-5) mPa.s. The container may have an internal envelope formed of the homogenised compsn., and an outer envelope. If the contents are used as an aq. soln., suspension or dispersion, the emptied container may be immersed in the water.
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