A patent by Mermet, France, proposes a method for producing highly flame retardant composite polymer fibres, using PIN fire safety, with a multi-filament core and a two-layer polymer sheath. In particular, 150 – 500 µm diameter yarns can be produced using only non-halogenated materials and PIN flame retardants.
The patent method uses a single deposition step for the two outer polymer layers, using miscible molten polymers containing PIN flame retardants. Applications targeted include textiles for sun protection and properties achievable include fire resistance, UV resistance, weathering and high and low temperature resistance. Flameproofing conform to French NFP92507 M1 or German DIN 4102 B1 can be achieved.
US patent US 2017 / 0044694, F-X. Damour, Mermet, France, “Novel process for manufacturing flame-retardant yarns”, published Feb. 2017 http://www.freepatentsonline.com/y2017/0044694.html