Back to results
US 5,308,691 AGranted
Controlled-porosity, calendered spunbonded/melt blown laminates
AssigneeE. I. Du Pont de Nemours and Company
InventorsHyun S. Lim, Hyunkook Shin
Life of this patent
Estimating the term…
Loading patent…
Loading patent…
AssigneeE. I. Du Pont de Nemours and Company
InventorsHyun S. Lim, Hyunkook Shin
Estimating the term…
Controlled porosity composite sheets comprising a melt-blown polypropylene fiber web having a spunbonded polypropylene fiber sheet laminated to at least one side thereof are made by calendering an assembly of the component webs in such a manner that, when a two-layer composite sheet is made, the web of melt-blown fibers is in contact with a metal roll heated to 140.degree.-170.degree. C. operating against an unheated resilient roll; and, when a three-layer composite sheet is made, the spunbonded web in contact with the heated metal roll has a dtex per fiber value of less than 6. These composite sheets have a Gurley-Hill porosity of about 5-75 seconds, excellent mechanical and tear strengths, high water vapor penetration rate, and low liquid water permeability. They are particularly suitable for making housewrap sheets and sheets for sterile packaging. In the sterile packaging field, they are significantly better than medical paper used for the same purpose.
A high-strength, tear-resistant, calendered, composite sheet having an opacity, as determined by TAPPI test T-519 om-86, of at least 75%, having low air permeability expressed as Gurley-Hill porosity of 5-75 seconds, high water vapor transmission rate of at least 500 g/m.sup.2 in 24 hours according to ASTM standard E96, method B, low liquid water permeability expressed by a hydrostatic head pressure of at least 0.75 m according to AATCC standard 127-1985, and barrier properties against bacteria that are significantly better than those of medical paper used for sterile packaging, which sheet comprises one melt-blown polypropylene fiber web and a spunbonded polypropylene fiber sheet laminated to at least one side thereof, the melt-blown fibers having an average diameter of 1-10 .mu.m, the melt-blown fiber web itself having an average weight of about 17-40.7 g/m.sup.2, and the fibers of the spunbonded sheet having an average diameter of at least 20 .mu.m, the spunbonded sheet itself having an average weight of about 17-100 g/m.sup.2.
A process for forming a composite sheet by calendering an assembly consisting of a melt-blown polypropylene fiber web and a spunbonded polypropylene fiber sheet laminated to at least one side thereof, the melt-blown fibers having an average diameter of 1-10 .mu.m, the melt-blown fiber web itself having an average weight of about 17-40.7 g/m.sup.2, and the fibers of the spunbonded sheet having an average diameter of at least 20 .mu.m, the spunbonded sheet itself having an average weight of about 17-100 g/m.sup.2, in a calender comprising a smooth metal roll heated to a temperature of 140.degree.-170.degree. C., operating against an unheated, resilient roll having a Shore D hardness of 75-85, at a nip loading of about 1.75.times.10.sup.-5 -3.5.times.10.sup.-5 N/m;
Dependencies are inferred from the claim text.