The Covid-19 pandemic has triggered the high demand of masks and investment in meltblown nonwovens equipment. In a webinar broadcast held recently, member companies of the VDMA Textile Machinery Association introduced the advanced production and quality control technologies for the sector.

In-line production with high uniformity and versatility

Oerlikon Nonwoven meltblown technology is one of the efficient methods of producing high separation filter media from plastic fibers.
Oerlikon Nonwoven meltblown technology can be used to produce nonwovens for masks efficiently, with over 70 stand-alone production lines already installed worldwide.

Oerlikon meltblown lines emphasize uniformity, specifically in terms of fluid and air management, as well as versatile polymer usage. They can accommodate a wide range of polymers, including PP, PET, PE, PA, PLA, PPS, etc.

The one-step process facilitates in-line production, eliminating the need of semi-product stores and providing full control over the whole value chain. It offers low OPEX (Operational Expenditures): few operators, high capacity, low energy consumption, low waste rate.

The fully automated production lines have high-end spinning design. The air around the spinning area for quenching is controlled at temperatures of between 7-40°C and at pressures of between 5-20 mbar.

The spinning throughput can achieve up to 200kg per hour/meter for PP and 70kg per hour/meter for PET/PBT, with production speed up to 200m per minute, although typical operational speed is about 100m per minute.

Oerlikon meltblown lines also have the CE and UL certified integrated ecuTEC unit for in-line high power corona charging. This allows high charging density (up to 6 mA/m) to be applied to either or both sides of the meltblown web to be charged.

The products of the production lines are of high performance at low basis weight to meet the high market requirements. The payback time of plant investment is approx. 3-4 years.

Basis weight and air permeability the key parameters

Accordind to Mahlo, a key supplier of inline quality control systems, the two key quality control parameters for masks are basis weight and air permeability.

The basis weight ensures the correct protection level is being provided by the masks, while the air permeability ensures the masks are comfortable to wear and do not restrict breathing.

The company’s Qualiscan QMS-12 scanners measure basis weight by either beta transmission or x-ray. With beta transmission sensors, the radiation is damped by the web mass and the loss of radiation signals the basis weight. The possible drawback for this system is radiation safety requirements have to be satisfied.

With the x-ray alternative, no license and radiation safety are required if the system is operating below 5kV. However, costs are increased due to the need for air or water cooling for long life time.

Meanwhile, the Airporo APM sensors on the Qualiscan QMS-12 scanners are designed to measure a wide range of air permeability by drawing air through the web using precisely sized orifices. A test pressure of 200 Pa is maintained by a differential pressure sensor controlling a variable speed vacuum pump.

As achieving the lowest possible tolerance on basis weight results in significant material savings, the payback time for Qualiscan QMS-12 scanners is less than a year.
A new Spinbeam 1,600mm line from Nanoval has been sold to China.
An alternative process to conventional methods

Berlin-based Nanoval, founded in 1987, developed the Nanoval process as an alternative to conventional meltblown technologies.

The Nanoval process uses a Laval nozzle to atomize over 1,000 different alloys to finest metal powders crucible or crucible-free up to almost 3500°C. It can be applied to create continuous filaments in a range from 3 µm down to the submicron scale.

In addition, a filament distribution of 1-30 µm can be achieved in a similar nonwoven by a specific variation of the nozzle’s geometry.

The company sold its first Spinbeam to China, which was designed for the production of bacteria filters, but the commissioning of that 1,600mm line is on hold due to the pandemic.

The Nanoval process is not widely applied in the market so far, and the company will increase its market share step by step.