Recently, there have been a number of incorrect reports by the media on the origins of N95 and other masks.
There are two technologies that led to the development of today’s N95 and surgical masks. The first was the meltblowing technology which can produce small fibers compared to other processes. Two structure attributes are critical for filtration. These are solidity (1 – porosity) and fiber size. Meltblowing is a very economical, large-scale process that creates fibers that can be mostly sub-micron, and smaller fibers are essential for particle capture.
The second critical technology was the development of electrostatic charging which enhances the particle capture efficiency of filters and leads to significantly lower pressure drops. Other critical technologies that were developed focused on ensuring that the charge density is high and more importantly, stable.
The first key patent was due to 3M in 1980 when a meltblown structure was electrostatically charged to form a high-efficiency, electret filter. And, in 1985, 3M developed the first molded respirator.
The meltblowing technology extends back to 1941 when the process was invented. The key events are outlined below:
|1951||Key Patent by Naval Research Laboratory|
|1965||First Melt Blowing line (Exxon) – the so-called Exxon Die – technology licensed to 6 companies|
|1971||First Commercial Line – U.S.|
|1972||First US Manufacturing (Accurate Products)|
|1973-5||First Seven Practitioners – U.S.|
|1974||First Japanese Practitioner (Tonen)|
|1989||First REICOFIL MB Line|
The first mask was in 1967, while the first respirator was patented in 1976. A key development was the application of electrostatic charge to meltblown webs in 1980. The key patents leading to the current charged N95 respirators soon followed. Some of the early key inventions are listed below:
|3,333,585||1967||Robert J Barghini, Walter M Westberg, Patrick H Carey Jr, “Cold weather face mask”, assigned to 3M|
|3,971,373A||1976||David L. Braun, “Particle-loaded microfiber sheet product and respirators made therefrom”, assigned to 3M Co|
|4,215,682A||1980||Donald A. Kubik & Charles I. Davis, “Melt-blown fibrous electrets”, assigned to 3M Co|
|4,536,440A||1985||Harvey J. Berg, “Molded fibrous filtration products”, published 1985-08-20, issued 1985-08-20, assigned to 3M|
|4,807,619||1989||James F. Dyrud, Harvey J. Berg, Alice C. Murray, “Resilient shape-retaining fibrous filtration face mask”, assigned to 3M|
|4,850,347||1989||Martin R. Skov, “Face mask”, assigned to Moldex Metric Inc|
|4,856,509||1989||Jerome H. Lemelson, “Face mask and method”|
|5,307,796A||1994||Joseph P. Kronzer, Roger J. Stumo, James F. Dyrud, Harvey J. Berg, “Methods of forming fibrous filtration face masks”, assigned to 3M|
The top inventors in this field are:
|Inventor||No. of Patents|