US Patent 7470639 Production of wetlaid-spunbond laminate membrane support

Nonwoven fabric laminates suitable for use as semipermeable membrane supports are produced by forming a spunbond nonwoven fabric first layer of continuous thermoplastic polymer filaments; forming a wet-laid nonwoven fabric second layer of discrete length thermoplastic polymer fibers; and bonding the first and second layers in opposing face-to-face relationship to form a composite support, where the first and second layers define first and second outer surfaces of the composite support. The resulting semipermeable membrane supports provide an advantageous balance of properties, including smoothness, porosity, interlaminar adhesion, and flux properties.