METHOD FOR RECYCLING FILTERING FACEPIECE RESPIRATORS

Abstract

The invention relates to a method for recycling respiratory protection masks comprising a plurality of layers manufactured from a single thermoplastic polymer chosen from polypropylene, polyethylene terephthalate, polylactic acid, homopolymers and copolymers of polyamide 6 (PA6) and long-chain polyamides such as PA11 or PA12, and comprising a filtration layer made of polyvinylidene fluoride.

Claims

1. A method for recycling respiratory protection masks containing from 98.5% to 99.5% by weight of a predominant thermoplastic polymer chosen from polypropylene, polyethylene terephthalate, polylactic acid, homopolymers and copolymers of polyamide 6 (PA6) and long-chain polyamides, and from 0.05% to 1.5% of poly(vinylidene fluoride) or PVDF in the form of nanofibers, said method comprising a step of grinding the masks leading to the obtaining of flakes, and a step of granulating said flakes, leading to the obtaining of a masterbatch in the form of granules.

2. The recycling method as claimed in claim 1, wherein the mask employed consists of a body and of retaining straps, said body being composed of at least two layers, including a layer of PVDF filtering material, said retaining straps being fixed to the body of the mask without addition of material.

3. The recycling method as claimed in claim 1, wherein said mask comprises a nonwoven inner layer having a grammage of between 20 and 100 g/m.sup.2 and made of thermoplastic polymer having a melt flow rate of 34 g/10 min at 230° C. under 2.16 kg.

4. The recycling method as claimed in claim 1, wherein said mask comprises a central layer comprising a nonwoven substrate with a grammage of between 20 and 100 g/m.sup.2 and having a permeability of between 500 and 2500 l/m.sup.2/s measured at 100 Pa.

5. The recycling method as claimed in claim 4, wherein said substrate is manufactured by blow molding or spun-bonding from a thermoplastic polymer that has a melt flow rate of 34 g/10 min at 230° C. and 2.16 kg.

6. The recycling method as claimed in claim 4, wherein said central layer comprises an electrospun layer of PVDF nanofibers.

7. The recycling method as claimed in claim 1, wherein said PVDF comprises at least one of a PVDF homopolymer; a mixture of two PVDF homopolymers; a copolymer comprising vinylidene difluoride (VDF) units and one or more types of units of comonomers compatible with vinylidene difluoride; a mixture of a PVDF homopolymer and of a VDF copolymer; or a mixture of two VDF copolymers.

8. The recycling method as claimed in claim 1, wherein said PVDF nanofibers have a mean fiber diameter D50 of between 30 and 500 nm.

9. The recycling method as claimed in claim 1, wherein the mean thickness of said layer of PVDF nanofibers is from 0.1 μm to 100 μm.

10. The recycling method as claimed in claim 1, wherein said mask comprises a nonwoven outer layer having a grammage of between 20 and 100 g/m.sup.2 and made of thermoplastic polymer having a melt flow rate of 34 g/10 min at 230° C. under 2.16 kg.

11. The recycling method as claimed in claim 2, wherein said retaining straps are adjustable loops produced by injection molding or 3D printing or elastic bands, manufactured from said predominant thermoplastic polymer.

12. (canceled)

13. A method of extruding comprising adding the master batch obtained from the method of claim 1 to the predominant thermoplastic polymer of claim 1 and extruding the combination.

Description

EXAMPLES

[0074] The following examples illustrate the invention without limiting it.

Example 1: Production of Electrospun Fibers on 18 g/m.SUP.2 .Spunbonded Polypropylene (Spunbond PP)

[0075] A mixture of VF2 homopolymer (Kynar®761A) and copolymer (Kynar®2801-00) is dissolved with stirring for 2 hours at 55° C. and according to the composition indicated in table 1.

TABLE-US-00001 TABLE 1 Electrospinning solution composition DMAC (wt %) 62.6 Acetone (wt %) 25 K761A (wt %) 8.05 K2801 (wt %) 3.45 Pluronic F127 (wt %) 0.4 Triton X-100 (wt %) 0.5

[0076] This solution is then supplied to an electrospinning process on a 18 g/m.sup.2 PP spunbond support. Such nonwovens are sold for example by Mogul. A filtration membrane based on electrospun fibers is thus produced with a width of 480 mm using the conditions indicated in table 2.

TABLE-US-00002 TABLE 2 Electrospinning PP 1 Emitter-collector distance (mm) 150 Emitter voltage (kV) +42 Collector voltage (kV) −45 Airflow in the chamber (m.sup.3/h) 600 Chamber air temperature (° C.) 25 Chamber air relative humidity (%) 25 Rotational speed of electrospinning 18500 heads (rpm) Polymer solution flow rate (ml/min) 15 Conveyor speed m/min 5 Oven temperature (° C.) 45 Material penetration according to 6 EN149 + A1 (%) Permeability l/m.sup.2/s (100 Pa) 97

Example 2: Production of Electrospun Fibers on 28 g/m.SUP.2 .Spunbonded Polyester (Spunbond PET)

[0077] The electrospinning solution prepared as described in example 1 is supplied to an electrospinning process on a 28 g/m.sup.2 PET spunbond support. Such nonwovens are sold for example by Mogul under the name Buffalo. A filtration membrane based on electrospun fibers is thus produced with a width of 480 mm using the conditions indicated in table 3.

TABLE-US-00003 TABLE 3 Electrospinning PET 1 Emitter-collector distance (mm) 150 Emitter voltage (kV) +42 Collector voltage (kV) −45 Airflow in the chamber (m.sup.3/h) 600 Chamber air temperature (° C.) 25 Chamber air relative humidity (%) 25 Rotational speed of electrospinning 18500 heads (rpm) Polymer solution flow rate (ml/min) 15 Conveyor speed m/min 5 Oven temperature (° C.) 45 Material penetration according to 5 EN149 + A1 (%) Permeability l/m.sup.2/s (100 Pa) 101

Example 3: Nose Bridge Production

[0078] The nasal support bridge is formed of a rod 1.5 mm in diameter and 10 cm in length. This rod is obtained by mixing/extrusion, at 230° C. in a single-screw extruder, of a 50/50 by mass mixture of PVDF homopolymer having a melt flow rate of 32 g/10 min at 230° C. under 2.16 kg and of polypropylene with a melt flow rate of 35 g/10 min at 230° C. under 2.16 kg.

Example 4: Assembly of the Mask from the Elements Produced in Examples 1 to 3

[0079] A mask is produced using the elements obtained in the preceding examples with the following structure: spunbond PP 1—Espun PP membrane 1—spunbond PP 2. The “spunbond PP 1” nonwoven (40 g/m.sup.2) forms the outer layer and improves the mechanical strength of the mask body. The “Espun PP 1” intermediate layer provides for aerosol filtration. Lastly, the “spunbond 2” nonwoven (18 g/m.sup.2) placed inside the mask is intended to be in contact with the face of the user, and it protects the filtration layer from possible degradation. The elastic bands are round strands of polypropylene, such products being sold for example by Liasa.

[0080] The assembly follows the steps described below: [0081] Cohesion between the layers of nonwovens is obtained by lamination. [0082] The nose bridge produced in example 3 is inserted into a space created by folding the nonwoven material over a width of 5±2 mm close to the periphery of the mask. The bridge is retained by spot welds placed regularly along the length of the fold. [0083] The elastic bands are fixed on each side of the mask so as to form a loop and are fixed without addition of material by ultrasonic welding.

Example 6: Grinding/Granulation and Extrusion of the Recycled Material

[0084] After decontamination by passing through an oven at 70° C. for one hour, the masks are ground in a knife mill. The flakes obtained are fed into a BUSS-type twin-screw extruder at 230° C. in order to produce granules.

[0085] The granules obtained are composed of about 0.9 wt % of PVDF and are used as a masterbatch to achieve a concentration of 500 ppm of PVDF in the PP, and then used in a process for manufacturing multi-filaments by extrusion spinning.

[0086] The pressure reached at the extruder head during the production of PP multi-filaments in the presence of 500 ppm of PVDF is of the order of 4.8 MPa, i.e. approximately 20% lower than that conventionally obtained during the processing of PP alone. Also, the impact of the presence of PVDF is visually observed by less fouling of the dies after several hours of extrusion.