Process for increasing the permeability of plastic membrane
US4430278A · kind A · utility
Inventor
Key dates
| Filing date | Feb 1, 1982 |
| Grant date | Feb 7, 1984 |
| Priority date | — |
| Expiry date | Feb 1, 2002 |
Classification
- Technology area (CPC B)Performing Operations; Transporting
- CPC primaryB26F1/26
- WIPO fieldChemical engineering
- WIPO sectorChemistry
Abstract
The regulated permeability of a thermoplastic membrane is modified by subjecting the thin membrane sheeting to warm to hot water, increasing the absorption of water in the membrane. The membrane is then rapidly heated with microwave radiation energy, typically at the 2450 MHz frequency absorbed by water, or heated in hot air. The water molecules absorbed in the membrane are explosively boiled out of the membrane, increasing the porosity of the membrane to water and also to other small molecules dissolved in water. The permeability of the plastic membrane is controlled by varying the concentration of water molecules initially absorbed in the hot membrane. Several types of plastic membrane having a relatively higher water absorption can be treated. The thin plastic membrane can be manufactured by extruding a small diameter, thick wall plastic tubing into hot water, and expanding the tubing with a hot water stream pumped into the inside of the tubing. The thin plastic sheet membrane can also be prepared by stretching a thicker plastic membrane in hot water. The hot water in which the plastic membrane is immersed can also contain small volatile, water-soluble molecules, such as methano…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.