Process for producing a steam-sterilizable porous polyolefin membrane and polyethylene membrane steam-sterlizable at 134.degree. C.
AssigneeDsm N.V.
InventorsHenricus M. Fortuin, Petrus H.M. Stokman
Life of this patent
Estimating the term…
Abstract
Process for producing a steam-sterilizable porous polyolefin membrane with a porosity of at least 20% and a shrinkage of 4% at most in every direction in the plane of the membrane in steam sterilization by subjecting a porous stretched film to a shrink treatment at a temperature equalling at least the sterilization temperature, but below the melting point of the polyolefin, in which treatment the permitted shrinkage is at least 95% of the critical shrink factor of the film in every direction in the plane of the film and a membrane of polyethylene with an intrinsic viscosity of at least 5 dl/g, steam-sterilizable at 134.degree. C.
Claims18
A process for producing a steam-sterilizable porous polyethylene membrane having a porosity of at least 20% and an intrinsic viscosity of at least 5 dl/g, said process comprising the steps of:
- a) preparing a porous polyethylene film from a solution of polyethylene;
- b) stretching the porous polyethylene film in at least one direction;
- and
- c) subjecting the stretched polyethylene film to a heat treatment wherein said heat treatment comprises:
- a shrink treatment in which the stretched polyethylene film while in a gaseous atmosphere, is exposed to a temperature of between at least 134.degree. C. and not more than the melting temperature of the polyethylene, wherein the amount of shrinkage resulting from exposure to said temperature is at least 95% of a critical shrink factor in the relevant direction, wherein the critical shrink factor is defined by (l.sub.0 -l.sub.1)/l.sub.0 !(100%), wherein l.sub.0 is the linear dimension of the film in said relevant direction before shrinking, and l.sub.1 is the residual length in said relevant direction after exposing the film at the temperature in said gaseous atmosphere, whereby the thus obtained membrane shows a shrinkage of at most 4% in every direction in the plane membrane upon exposure to steam having a temperature of 134.degree. C. for 10 minutes.
Dependencies are inferred from the claim text.