METHOD FOR THE ADHESION OF PARTICLES TO AN INERT SUBSTRATE

Abstract

The present invention relates to a method for adhering particles with exceptional functional properties, such as hydrophobia, to an inert substrate. The present invention falls within the area of nanotechnology, specifically in the sector where it is necessary to modify the surface properties of a material or substance, such as the food, pharmaceutical, biomedical or energy sector.

Claims

1. A method for adhering particles to an inert substrate, characterized in that it comprises the following steps: a) deposit adhesive fibers on an inert substrate by means of an electro-hydrodynamic or aero-hydrodynamic process or a combination of both processes; b) optionally, thermally treat the deposit obtained in (a) at a temperature lower than the melting or degradation temperature of the adhesive fibers for a period of time between 0.1 s and 1 h; c) homogeneously distribute particles of a size between 0.001 nm and 100 m on the adhesive fibers obtained in step (a) or (b) by means of deposition; and d) thermally treat the deposit obtained in (c) at a temperature lower than the melting or degradation temperature of the adhesive fibers for a period of time between 0.1 s and 1 h.

2. The method according to claim 1, characterized in that it comprises the following steps: a) deposit adhesive fibers on an inert substrate by means of an electro-hydrodynamic or aero-hydrodynamic process or a combination of both processes; b) thermally treat the deposit obtained in (a) at a temperature lower than the melting or degradation temperature of the adhesive fibers for a period of time between 0.1 s and 1 h; c) homogeneously distribute particles of a size between 0.001 nm and 100 m on the adhesive fibers obtained in step (a) or (b) by means of deposition; and d) thermally treat the deposit obtained in (c) at a temperature lower than the melting or degradation temperature of the adhesive fibers used in step (a) for a period of time between 0.1 s and 1 h.

3. The method according to any of claim 1 or 2, characterized in that the inert substrate is a thermoplastic, thermostable or elastomer plastic or a biopolymer.

4. The method according claim 3, characterized in that the inert substrate is selected from the list comprising polyolefins, polyesters, polyamides, polimides, polyketones, polyisocyanates, polysulphones, styrenic plastics, phenolic resins, amide resins, urea resins, melamine resins, polyester resins, epoxide resins, polycarbonates, polyvinylpyrrolidones, epoxy resins, polyacrylates, rubbers, polyurethanes, silicones, aramides, polybutadiene, polyisoprenes, polyacrylonitriles, polyvinylidene fluoride, polyvinyl acetate, polyvinyl alcohol, ethylene vinyl alcohol copolymer, ethylene-vinyl-alcohol, polyvinyl chloride, polyvinylidene chloride and a combination thereof.

5. The method according to claim 3, wherein the substrate is a biopolymer selected from among proteins, polysaccharides, lipids, polyesters and a combination thereof.

6. The method according to any of claims 1 to 5, characterized in that the adhesive fibers of step (a) are comprised of polycaprolactone; polyamides, ethylene vinyl alcohol (EVOH) copolymers and derivatives thereof; or biopolymers.

7. The method according to claim 6, characterized in that the biopolymers are selected from among peptides and natural or synthetic proteins obtained chemically or by genetic modification of microorganisms or plants and natural elements; synthetic polysaccharides obtained chemically or by genetic modification of microorganisms or plants; polypeptides, nucleic acids and synthetic nucleic acid polymers obtained chemically or by genetic modification of microorganisms or plants; biodegradable polyesters such as polylactic acid, polylactic-glycolic acid, adipic acid and derivatives thereof, and polyhydroxyalkanoates, polyhydroxybutyrate and its copolymers with valerate; and biomedical materials, such as hydroxyapatites, of the group of synthetic and natural (plant or animal) polysaccharides, such as cellulose and derivatives; carrageenans and derivatives; alginates, dextran, gum arabic and chitosan or any of the natural and synthetic derivatives thereof; and corn proteins (zein); gluten derivatives, such as gluten or the gliadin and glutenin fractions thereof; gelatin, casein and soy proteins and derivatives thereof; as well as natural or synthetic peptides preferably of the elastin type obtained chemically or by genetic modification of microorganisms or plants and mixtures thereof.

8. The method according to claim 7, characterized in that the biopolymers are biodegradable polyesters.

9. The method according to any of claims 1 to 8, characterized in that the adhesive fibers of step (a) have a diameter smaller than 5 m.

10. The method according to any of claims 1 to 9, characterized in that the deposit obtained after step (a) has a thickness between 10 nm and 100 m.

11. The method according to any of claims 1 to 10, characterized in that step (a) is carried out by means of an electro-hydrodynamic process with electrospinning.

12. The method according to any of claims 1 to 10, characterized in that step (a) is carried out by means of an aero-hydrodynamic process with blow spinning.

13. The method according to any of claims 1 to 12, characterized in that step (b) is carried out by applying pressure between 0.1 bar and 100 bar.

14. The method according to claim 13, wherein step (b) is carried out by applying pressure below 30 bar.

15. The method according to any of claims 1 to 14, characterized in that the particles of step (c) have hydrophobic, hydrophilic, oleophobic, oleophilic, amphiphobic, amphiphilic or amphipathic, self-cleaning, antioxidant, antimicrobial, self-curing, UV light absorbent or flame retardant properties, or serve as a barrier towards gases and vapors.

16. The method according to any of claims 1 to 15, characterized in that the particles of step (c) are selected from among cellulose nanocrystals, cellulose microfibers, kenaf nanofibers, keratin nanofibers, nanoclays, carbon nanotubes, carbon nanofibers, carbon nanosheets, metal oxides, metal hydroxides, nanosilica, silicon nanodioxide, metal nanoparticles, titanium nanodioxide with or without organic modification and a combination thereof.

17. The method according to claim 16, characterized in that the particles of step (c) are selected from among nanosilica, silicon nanodioxide, titanium nanodioxide with or without organic modification and a combination thereof.

18. The method according to any of claims 1 to 15, characterized in that the particles of step (c) are selected from among polytetrafluoroethylene and polystyrene.

19. The method according to any of claims 1 to 15, characterized in that the particles of step (c) are selected from among hydroxyapatites and phosphates of organic salts, optionally modified with quaternary ammonium salts and/or organosilanes.

20. The method according to any of claims 1 to 19, characterized in that step (c) is carried out by means of electro-hydrodynamic deposition, aero-hydrodynamic deposition or a combination of both techniques.

21. The method according to any of claims 1 to 19, characterized in that step (c) is carried out by means of electro-spraying, blow-spraying or gravimetric dusting.

22. The method according to claim 21, characterized in that the blow-spraying technique is selected from among pneumatic, piezo-electric or ultrasonic nebulization.

23. The method according to any of claims 1 to 22, characterized in that step (d) is carried out by applying pressure between 0.1 bar and 100 bar.

24. The method according to claim 23, characterized in that step (d) is carried out by applying pressure below 30 bar.

25. The method according to any of claims 1 to 24, wherein step (d) is carried out by means of a heated press, a calender, an oven or an ultraviolet or infrared lamp.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0062] FIG. 1 shows a diagram of the process of the present invention.

[0063] FIG. 2 shows images of the measurement of the contact angle of the PET films coated with PLA nanofibers.

[0064] FIG. 3 shows images of the measurement of the contact angle of the PET films coated with a layer of PLA nanofibers and another layer of organo-modified nanoparticles of SiO.sub.2.

[0065] FIG. 4 shows images of the measurement of the contact angle of the PE films coated with a layer of PCL nanofibers and another layer of organo-modified nanoparticles of SiO.sub.2.

[0066] FIG. 5 shows images of the measurement of the contact angle of the PE films coated with a layer of PCL nanofibers and another layer of PTFE nanoparticles.

[0067] FIG. 6 shows images of the measurement of the contact angle with water (left) and olive oil (right) of the PE films coated with a layer of PCL nanofibers and another layer of PTFE nanoparticles.

[0068] FIG. 7 shows images of the contact angle with water on the PET/PLA-NF/SiO.sub.2 NPs and PET/PLA+TiO.sub.2/SiO.sub.2 NPs surfaces before (left column) and after (right column) the thermal treatment at 150 C. for 3 s.

[0069] FIG. 8 shows images of PET films: (A) PET without film; (B) PET/PLA processed at 50 C. for 3 s; (C) PET/PLA processed at 50 C. for 60 s; (D) PET/PLA processed at 60 C. for 3 s; (E) PET/PLA processed at 60 C. for 60 s and (F) PET/PLA processed at 70 C. for 3 s.

EXAMPLES

[0070] The invention is illustrated below by means of assays carried out by the inventors which reveal the effectiveness of the product of the invention.

[0071] FIG. 1 shows the diagram of the method of the invention.

Example 1

[0072] Deposition of polylactic acid (PLA) nanofibers obtained by means of electrospinning on polyethylene terephthalate (PET).

[0073] A solution of PLA at 15% by weight was prepared in a mixture of dimethylformamide (DMF) and acetone (1:1). Said mixture was electrospun on a PET sheet under the following conditions: [0074] electrical voltage: 17 kV, [0075] rate of injection: 1 mL/h [0076] and distance to the collector: 15 cm.

[0077] The sheets coated with the nanofibers were placed between two plates at 50 C. for 3 s to promote adhesion between the sheets.

[0078] The PET films coated with PLA nanofibers showed contact angles of around 120, characteristic of hydrophobic surfaces (See FIG. 2). It is observed that the porous morphology created during electrospinning favors hydrophobicity.

Example 2

[0079] Deposition of modified silicon oxide nanoparticles (HDK H18 by Wacker) on the deposit obtained in Example 1.

[0080] PET films coated with PLA nanofibers were manufactured by using the method indicated in Example 1. A suspension of organo-modified silicon oxide particles (HDK H18 by Wacker) (1% w/v in DMF) was deposited on these samples under the following conditions: [0081] electrical voltage: 10 kV, [0082] rate of injection: 0.3 mL/h and [0083] distance to the collector: 15 cm.

[0084] The coated PET films showed contact angles of around 130, characteristic of hydrophobic surfaces (See FIG. 3). It is observed that the addition of the layer of organo-modified SiO.sub.2 nanoparticles on the polymer layer improves the hydrophobic properties of the surface.

Example 3

[0085] Deposition of polycaprolactone (PCL) nanofibers obtained by means of electrospinning on polyethylene (PE).

[0086] PE films coated with PCL nanofibers were manufactured by using the method indicated in Example 1.

Example 4

[0087] Deposition of organo-modified silicon oxide nanoparticles on the deposit obtained in Example 3 and subsequent thermal treatment.

[0088] A suspension of organo-modified silicon oxide particles (HDK H18 by Wacker) (1% w/v in butanol) was deposited on these samples under the following conditions: [0089] electrical voltage: 10 kV, [0090] rate of injection: 1 mL/h and [0091] distance to the collector: 15 cm.

[0092] Next, a thermal treatment was carried out at 50 C. for 3 minutes. The coated PE films showed contact angles of around 160, characteristic of superhydrophobic surfaces (See FIG. 4). It is observed that the addition of the layer of organo-modified SiO.sub.2 nanoparticles (HDK H18 by Wacker) on the polymer layer improves the hydrophobic properties of the surface.

Example 5

[0093] Deposition of micronized polytetrafluoroethylene (PTFE) powder on the deposit obtained in Example 4 and subsequent thermal treatment.

[0094] PE films coated with PCL nanofibers were manufactured by using the method indicated in Example 1.

[0095] A micronized PTFE powder was deposited on these samples, followed by a thermal treatment at 50 C. for 3 minutes. The coated PE films showed contact angles greater than 160, characteristic of superhydrophobic surfaces (See FIG. 5). It is observed that the addition of the layer of PTFE microparticles on the polymer layer improves the hydrophobic properties of the surface.

Example 6

[0096] Deposition of polycaprolactone (PCL) nanofibers obtained by means of electrospinning on polyethylene (PE) and subsequent thermal treatment.

[0097] PE films coated with PCL nanofibers were manufactured by using the method indicated in Example 1.

[0098] Next, a thermal pre-treatment was applied at 50 C. for 1 minute with the aim of generating a flat film and favoring the oleophobic nature of the film.

Example 7

[0099] Deposition of micronized PTFE powder on the deposit obtained in Example 6 and subsequent thermal treatment.

[0100] A micronized PTFE powder was deposited on these samples, followed by a thermal treatment at 50 C. for 3 minutes.

[0101] The coated PE films showed contact angles with the water close to 160, characteristic of superhydrophobic surfaces, and contact angles with oils close to 70 (See FIG. 6), characteristic of hydrophobic surfaces. This methodology enables amphiphobic or amphiphilic, also called amphipathic, films to be created according to that which is described.

Example 8

[0102] Deposition of SiO.sub.2 and SiO.sub.2/TiO.sub.2 nanoparticles on the deposit obtained in Example 1 and subsequent thermal treatment.

[0103] Two PET sheets coated in PLA were manufactured according to Example 1. SiO.sub.2 and SiO.sub.2/TiO.sub.2 nanoparticles were deposited, respectively. Thermal post-treatment was applied to these sheets at a temperature of 150 C. for 3 s with the aim of transforming the morphology of PLA nanofibers into a flat film with few hydrophobic properties. FIG. 7 (right column) shows how the contact angle is reduced drastically after treatment at a high temperature.

[0104] Table 1 shows the effect of temperature and time on the final contact angle. It is observed how the thermal treatment improves the adhesion of the nanoparticles, keeping some properties intact, such as hydrophobicity.

TABLE-US-00001 TABLE 1 Effect of temperature and time on the contact angle of a water droplet. Sample Temperature ( C.) Time (s) Contact angle () A 50 3 122 B 60 90 C 60 3 134 D 60 114 E 70 3 133 F 60 nd

[0105] Another property of the film that is kept intact is transparency. FIG. 8 shows different films treated according to the different conditions defined in Table 1, covering printed letters on a paper. At first glance, it is observed how the different post-treatment conditions affect the the transparency of the film.