Method of making media of controlled porosity and product thereof
OwnerHassan Bodaghiinventor
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Abstract
A method of making a non-woven fibrous media, combining high vapor permeability and low liquid permeability, includes the steps of providing a non-woven fabric formed from fibers that are prematurely crystallized during fabric formation and have a wide heat of fusion range distribution, and calendering the fabric to soften the small polymer crystals therein of low heats of fusion, but not the relatively larger polymer crystals therein of relatively higher heats of fusion, thereby to retain high vapor permeability while providing low liquid permeability. The polymer is preferably isotactic polypropylene.
Claims41
A method of making a fibrous media combining high vapor permeability and low liquid permeability, the method comprising the steps of:
- (A) providing a non-woven fabric formed from fibers that are prematurely crystallized during fabric formation to form small polymer crystals therein having low heats of fusion and relatively larger polymer crystals therein of relatively higher heats of fusion;
- and
- (B) calendering the fabric to soften the small polymer crystals therein of low heats of fusion, but not the relatively larger polymer crystals therein of relatively higher heats of fusion, thereby to retain high vapor permeability while providing low liquid permeability.
A method of making a non-woven fibrous media combining vapor permeability and low liquid impermeability, the method comprising the steps of:
- (A) providing a non-woven meltblown fabric formed of a polymer of isotactic polypropylene prematurely crystallized by quenching thereof prior to completion of fabric formation to form small polymer crystals therein having low heats of fusion and relatively larger polymer crystals therein of relatively higher heats of fusion;
- and
- (B) calendering the fabric to soften the small polymer crystals therein of low heats of fusion, but not the relatively larger polymer crystals therein of relatively higher heats of fusion, thereby to retain vapor permeability while providing liquid impermeability through fiber shrinkage and contraction in the fibrous media, the temperature, pressure and roll speed of the calendering operation being selected to soften the small polymer crystals but not the relatively larger polymer crystals.
A non-woven fibrous media combining high vapor permeability and low liquid permeability, comprising:
- a non-woven meltblown fabric formed from fibers that are drawn and then prematurely crystallized during fiber formation by premature quenching with a stream of cold quench air immediately after drawing to form small polymer crystals therein having low heats of fusion and relatively larger polymer crystals therein of relatively higher heats of fusion, said fabric being calendered to soften said small polymer crystals, but not said relatively larger polymer crystals, thereby to retain high vapor permeability while providing low liquid permeability, through compaction, fiber shrinkage and contraction in the fibrous media.
A non-woven fibrous media formed from fibers that are prematurely crystallized during fabric formation and then calendered to yield a moisture vapor transmission rate greater than about 1,200 g/m2 @24h and a hydrohead of at least about 10 millibars.
A composite non-woven fabric formed from at least two non-woven layers, said composite having a MVTR of at least about 2,000 g/m2 @24 h and a hydrohead of at least about 20 millibars.
A composite non-woven fabric formed from at least two non-woven layers, including:
- (A) as a first layer, a first non-woven fibrous media combining high vapor permeability and low liquid permeability, comprising:
- a non-woven meltblown fabric formed from fibers that are drawn and then prematurely crystallized during fiber formation by premature quenching with a stream of cold quench air immediately after drawing to form small polymer crystals therein having low heats of fusion and relatively larger polymer crystals therein of relatively higher heats of fusion, said fabric being calendered to soften said small polymer crystals, but not said relatively larger polymer crystals, thereby to retain high vapor permeability while providing low liquid permeability, through compaction, fiber shrinkage and contraction in the fibrous media;
- and
- (B) as a second layer, a second non-woven fibrous media.
A composite non-woven fabric formed from at least two non-woven layers, said composite having a MVTR of at least about 2,000 g/m2 @24 h and a hydrohead of at least about 20 millibars, said at least two non-woven layers including:
- (A) as one layer, a non-woven fibrous media combining high vapor permeability and low liquid permeability, comprising:
- a non-woven meltblown fabric formed from fibers that are drawn and then prematurely crystallized during fiber formation by premature quenching with a stream of cold quench air immediately after drawing to form small polymer crystals therein having low heats of fusion and relatively larger polymer crystals therein of relatively higher heats of fusion, said fabric being calendered to soften said small polymer crystals, but not said relatively larger polymer crystals, thereby to retain high vapor permeability while providing low liquid permeability, through compaction, fiber shrinkage and contraction in the fibrous media;
- and
- (B) as another layer, another non-woven fibrous media.
Dependencies are inferred from the claim text.