Biodegradable composite filter media for air filters and manufacturing method thereof

A biodegradable composite filter media for an air filter of a facial mask, comprising:

• a thermally bonded biodegradable filter support comprising a dry nonwoven fabric composed of single or multiple layers and made of sheath-core type polyester-based biodegradable thermal bonding composite fibers, each having a fiber length of 38 to 64 mm and a fiber fineness of 1.5 to 4.0 denier;
• and
• an electrospun nanofiber layer comprising a nanofiber having a diameter of 70 to 500 nm, the nanofiber layer being formed by electrospinning a polymer resin onto one or both surfaces of the thermally bonded biodegradable filter support,
• wherein the nanofiber layer is formed in an attachment amount of 0.3 to 1.0 g/m2 on any one surface of the thermally bonded biodegradable filter support,
• wherein the dry nonwoven fabric is formed by thermally bonding the polyester-based biodegradable composite fibers to each other, and has a basis weight of 20 to 80 g/m2 and a thickness of 0.05 to 0.40 mm,
• wherein each of the sheath-core type polyester-based biodegradable thermal bonding composite fiber comprises:
• a core portion comprising a biodegradable polyester resin having a melting point of 220 to 260° C.;
• and a sheath portion comprising a biodegradable thermal bonding polyester resin having a melting point of 100 to 180° C., which is lower than the melting or softening point of the core portion,
• wherein the difference in the melting point between the sheath portion and the core portion is 80° C. or more, and the sheath portion and the core portion have a weight ratio of 6.0:4.0 to 4.5:5.5,
• wherein the biodegradable polyester resin of the core portion is a biodegradable polyethylene terephthalate resin containing 0.5 to 3.0 wt % of a biodegradant,
• wherein the biodegradable thermal bonding polyester resin of the sheath portion comprises a low-melting-point polyester resin formed of an acidic component containing terephthalic acid;
• and a diol component,
• wherein the diol component comprises 20 to 50 mol % of 2-methyl-1,3-propanediol, 0.1 to 2 mol % of 2-methyl-1,3-pentanediol, and the balance of ethylene glycol up to 100 mol %,
• wherein the low-melting-point polyester resin comprises 0.5 to 3.0 wt % of a biodegradant, and
• wherein the thermally bonded biodegradable filter support has an air permeability of 200 to 500 ccs, a tensile strength of 3 kgf/5 cm or more, and a tensile strength retention of 90% or more, determined by the following equation 1:
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• wherein A is an initial tensile strength of the biodegradable filter support, measured in the machine direction (MD), and B is an MD tensile strength of the biodegradable filter support, measured after being left to stand for 180 days under the conditions of a temperature of 25 (±10)° C. and a relative humidity of 55 (±15) %.