DESCRIPTION

The present invention relates to a polymeric composition comprising functionalized polyetheretherketone (PEEK) of formula (II), in admixture with a co-polymer having a melting point lower than the melting point of not functionalized PEEK. The invention also relates to the use of the PEEK of formula (II) for the preparation of fibers and yarns having antibacterial, decontaminating and self-cleaning properties and which are useful, for example, for making sanitary garments, such as sanitary coats and masks, and for making filters for ventilation systems and for kitchen hoods.

Prior art

As is known in the literature, photocatalysis is a process that enables the generation of radicals and is used to obtain materials endowed with self-cleaning, antibacterial, decontaminating and UV-protective properties.

This process is promoted by the action of a photoactive agent (or photosensitizing agent) capable of being excited by irradiation, for example with UV light, and leading to the consequent formation of radicals. For the formation of garments or fabrics having photocatalytic properties, the chosen photoactive agent is generally dispersed in a polymer matrix which then undergoes spinning. However, one of the problems is tied to the spinning properties, or spinnability, of the polymer admixture comprising the photosensitizing agent.

To date, the photoactive compound that is most used and studied is the titanium dioxide (Ti0 ₂ ) owing to its properties of photostability and activation on exposure to UV radiation (Bouquet-Somrani et al. Appl. Catal. B: Environ, Vol.8, 1996, pp101 -106)). However, the presence of Ti0 ₂ can lead to a progressive degradation of the substrate it is anchored to, generating a consequent deterioration of the latter over time.

As an alternative to nanoparticles of Ti0 ₂ , the use of benzophenone, or compounds containing benzophenone groups, as the photosensitizing agent is known, owing to its ability to be excited by UV radiation. This excitement leads to an electronic transition of the η-π* type, and to the consequent formation of the benzophenone radical (see, for example, Gilbert et al.CRC Press: Boca Raton, 1991 , Chapters 5 and 7). Among the polymeric derivatives which include benzophenone functionalities, PEEK (polyetheretherketone or poly(oxy-1 ,4- phenyleneoxy-1 ,4-phenylenecarbonyl-1 ,4-phenylene)) is a semi-crystalline thermoplastic polymer of formula (I):

(I)- PEEK

wherein n is a number comprised between 10 and 1 ,000,000,

used in processes and applications that require excellent properties of thermal stability, mechanical strength and chemical resistance.

It has a melting point of around 350° C and a glass transition temperature of about 150° C. Owing to its physicochemical characteristics, PEEK is used above all in the mechanical, aeronautic and biomedical industries.

PEEK can be easily converted into fibers (and thus fabrics) by spinning. However, PEEK is not capable of generating radicals via UV irradiation, and thus cannot be used, for example, to prepare fibers or yarns with photochemical properties. There remains the need, therefore, to find a polymeric derivative which is endowed with good spinnability and capable of generating benzophenone radicals by photo- irradiation, so as to be usable for making yarns with antibacterial, decontaminating and self-cleaning properties, particularly appreciated in sanitary environments such as hospitals and the like.

The applicants have now found that when the PEEK of formula (I) is selectively functionalized with sulfonic, nitric or amino acid residues, and is mixed with a suitable co-polymer, the resulting polymeric composition is capable not only of being spun, but also of generating antibacterial, decontaminating and self-cleaning benzophenone radicals by UV irradiation, and thus of expressing the desiderate antibacterial, decontaminating and self-cleaning properties. Moreover, depending on the co-polymer used, it is possible to obtain fibers with an extremely fine diameter (even on the scale of nanometres), suitable for making photocatalytic materials in the form, for example, of yarns, meshes or fabrics or also nonwoven fabrics. Summary of the invention

In a first aspect, the invention relates to a polymer composition (or admixture) comprising functionalized PEEK of formula (II),

(II)

wherein:

X is selected from: -S0 ₃ H, -N0 ₂ and -NH ₂ , and

n is an integer comprised between 10 and 1 ,000,000

in admixture with a co-polymer having a lower melting point than non- functionalized PEEK, i.e. less than about 350° C.

In a further aspect, the invention relates to a polymer fiber obtained by spinning the above-described composition, preferably in the form of a micro- or nanofiber. In an additional aspect, the invention relates to a material made with the polymer fiber of the invention, preferably in the form of a yarn, mesh, fabric or nonwoven fabric.

In a further aspect, the invention relates to a garment made with the polymer fiber, preferably selected from: sanitary coats and sanitary uniforms in general, masks, gloves, and a component made with the polymer fiber, preferably selected from: air filters (for example, for ventilation systems or for kitchen hoods), air and water purification devices and roofing for buildings.

Description of the figures

Figure 1 : electron paramagnetic resonance (EPR) spectrum of the SPEEK/PE mixtures, with a content by weight of SPEEK equal to: 2%, 4% and 6%.

Figure 2: EPR spectrum of the SPEEK/PVA mixture, with a content by weight of SPEEK equal to: 100%, 50%, 30%, 15% and 5%. Figure 3: EPR spectrum of SPEEK/PP fiber obtained by melt spinning at temperatures of 180° C, 200° C and 220° C.

Detailed description

The term "percentage by weight" means the % by weight of a component relative to the total weight of the composition.

"Spinnability" is meant to indicate the ability of a polymeric material to be converted into fiber.

The term "fiber" is meant to indicate the material obtained by spinning the polymer admixture, while the term "yarn" indicates a set of fibers held together by twisting them to form a thread.

The term "co-polymer" means a polymer used in admixture with the functionalized PEEK of formula of (II), used to make the present composition or polymer admixture.

As mentioned above, the non-functionalized PEEK of formula (I) does not show any photocatalytic property under UV irradiation, since it is not capable of generating benzophenone radicals following exposure to UV radiation. In contrast, the functionalized PEEK (II) of the invention, thanks to the presence of a sulfate, nitric or amino group on the hydroquinone part, is capable of generating benzophenyl ketyl radicals by UV photo-irradiation. Furthermore, by mixing it with a co-polymer having a melting point lower than the melting point of the PEEK of formula (I), (i.e. lower than about 350° C), one obtains a polymer admixture endowed not only with excellent spinnability, but also with improved photocatalytic properties. Associating the functionalized PEEK (II) with a suitable co-polymer, in fact, increases its capability of electron excitation (which leads to the formation of the benzophenone radicals), also enabling it to be spun, which would otherwise not be achievable using the PEEK polymer (II) alone, not mixed.

In one embodiment of the invention, the functionalized PEEK has a formula (II) wherein X is a sulfonic group -SO3H (sulfonated PEEK or SPEEK).

This functionalization can be obtained using aromatic substrate sulfonation processes known in the art, for example via a reaction with concentrated sulfuric acid. In an equally preferred embodiment, the functionalized PEEK has a formula (II) wherein X is a nitro group-N0 ₃ (nitrated PEEK or NPEEK). NPEEK can be obtained by nitration of the PEEK of formula (I), for example via a reaction with a sulfo-nitric mixture (HN0 ₃ and H ₂ S0 ₄ ), according to methods known in the art. In this case, it is possible to obtain NPEEK with a different degree of functionalization, in particular NPEEK with a high degree of nitration (i.e. up to about 6 nitro units per monomer unit) or NPEEK with a low degree of nitration (i.e. up to about 2 nitro units per monomer unit) as indicated in the experimental part. Finally, in a further embodiment, the PEEK is functionalized with an amino acid residue (formula (II) wherein X is -NH ₂ ) to yield amino PEEK or NH-PEEK for example via a reduction reaction of NPEEK with Na ₂ S ₂ 0 ₄ in DMF, according to methods known in the art.

The electron paramagnetic resonance (EPR) analysis carried out shows that the PEEK of the invention of formula (II) possesses good photocatalytic properties due to its ability to form benzophenyl ketyl radicals on exposure to UV radiation.

By way of example, after 15 minutes' irradiation of a SPEEK film, one observes the formation of a free radical, attributable to the phenyl ketyl radical, characterized by an EPR signal of 9.86 GHz with a g value of 2.0033 (where g is a tensor that is characteristic for different radical species, known to the person skilled in the art), typical of the benzophenone radicals (for general reference see Yoshida et al. Bull. Chem Soc. Jpn, 1971 , 44, 2950).

As mentioned above, in order to obtain a polymeric composition with photocatalytic properties capable of being effectively spun, the functionalized PEEK of the invention is mixed with a co-polymer having a melting point lower than the melting point of the non-functionalized PEEK. In this regard, it was noted that co-polymers with a higher melting point than PEEK can negatively impact the spinning of the resulting admixture.

For example, when the co-polymer is unmodified PEEK of formula (I), the resulting SPEEK/PEEK polymer admixture has poor spinnability, such as to compromise the use of the admixture in the preparation of yarns.

Moreover, since associating the functionalized PEEK (II) with a co-polymer leads to a decrease in the viscosity of the resulting admixture relative to the initial viscosity of the individual components, it is preferable to choose a co-polymer endowed with high viscosity. In this regard, preferred co-polymers are those having a melting point below 350° C and a shear viscosity between 100 and 20000 Pa.s.

In a particularly preferred embodiment, the co-polymer is selected from: polypropylene (PP), polyvinyl alcohol (PVA), polyester (PE), polyamide (PA) and polyacrylate, PP, PE and PVA being particularly preferred. Even more preferably, the co-polymer is PP or PVA.

The ratio between functionalized PEEK (II) and co-polymer is generally chosen according to the type of co-polymer used. Preferably, the polymeric composition of the invention comprises functionalized PEEK (II) and co-polymer in a percentage ratio by weight comprised between 50/50 and 5/95, preferably between 35/65 and 5/95, even more preferably between 10/90 and 5/95. Higher percentages of functionalized PEEK could lead to a disadvantageous lowering of viscosity, such as to compromise the spinnability of the resulting composition.

In one embodiment, the polymer admixture of the invention, useful for preparing fibers or yarns with antibacterial and self-cleaning properties, comprises PEEK of formula (II), preferably SPEEK, and the co-polymer PP or PE, even more preferably in a percentage ratio by weight comprised between 10/90 and 5/95. These admixtures can be conveniently used in the preparation of a fiber having a diameter on a micron scale and endowed with excellent antibacterial and mechanical properties, as described below in detail.

In particular, Figure 1 shows the electron paramagnetic resonance (EPR) spectra of a SPEEK/PE admixture with different percentages of the two components. As can be noted, and as mentioned above, the addition of the co-polymer, besides enabling the composition to be spun, increases the ability the PEEK polymer (II) to generate radicals of. In fact, the intensity of the signal of the benzophenyl radical increases with increasing concentrations of SPEEK, in the range of 2-6%.

In a further embodiment, the polymer admixture of the invention comprises PEEK of formula (II) and the co-polymer polyvinyl alcohol (PVA). Preferably, the polymer admixture comprises functionalized PEEK and PVA in a percentage ratio by weight comprised between 5/95 and 50/50%, more preferably between 15/85 and In particular, from the EPR spectra of Figure 2 it may be deduced that the 30/70 ratio between SPEEK and PVA enables the largest amount of benzophenone ketyl radicals to be obtained.

As mentioned above, the functionalized PEEK of the invention (capable of generating benzophenone radicals on exposure to UV light), when mixed with a suitable co-polymer, enables a polymeric composition to be obtained which is endowed with good spinnability and can thus be used to prepare fibers endowed with photochemical properties. Therefore, in a further aspect, the invention relates to a polymer fiber obtained by spinning the present composition.

Said fibers can in turn be conveniently used to make photochemical materials with antibacterial and self-cleaning properties, in the form, for example, of yarns, meshes, fabrics or also nonwoven fabrics.

The fibers can be obtained by means of spinning techniques known in the art, such as, for example: wet spinning, dry spinning, melt spinning, electrospinning or gel spinning, melt spinning and electrospinning be preferred. As is well known, the melt-spinning technique consists in bringing the polymer admixture to its melting temperature prior to the spinning process, and of cooling the yarn during spinning, causing the solidification thereof (see, for example, Ziabicki et al. Fundamentals of Fiber Formation, Wiley-lnterscience 1976).

The electrospinning procedure, on the other hand, is a process enabling continuous filaments of polymeric materials with a diameter of even less than a micron to be obtained.

The spinning temperature is generally comprised between 170 and 250° C depending on the technique used and/or the thermal stability of the functionalized PEEK. Preferably, the spinning temperature of the present polymeric composition is comprised between 180 and 220° C.

In particular, Figure 3 shows the electron paramagnetic resonance (EPR) spectra of a fiber obtained from the SPEEK/PP admixture at three different spinning temperatures, i.e. 220° C, 200° C and 180° C. In particular, the stability of the functional compound (SPEEK) is not influenced by increases in the process temperature. Advantageously, thanks to the versatility of the present composition, it is possible to obtain polymer fibers having a linear density comprised between 15 and 700 dtex, preferably comprised between 50 dtex and 250 dtex, and a diameter comprised between a micron and a nanometer. In particular, in this regard, the fibers have a diameter preferably comprised between 25 pm and 1 mm, more preferably between 25 and 200 pm.

In one embodiment, the invention relates to a nanofiber obtained by spinning the present polymer admixture, preferably comprising PEEK of formula (II) and PVA. The polymer admixture is generally spun in a solution or suspension with a solvent commonly used in this technique.

It was noted, in fact, that the functionalized PEEK admixture, preferably SPEEK, and PVA, has a spinnability that makes it particularly well-suited to spinning techniques like electrospinning, for the production of nanofibers.

Said nanofibers can have a diameter comprised between 100 nm and 900 nm, even more preferably between 200 and 500 nm. The possibility of obtaining nanofibers is particularly convenient for preparing nonwoven fabrics, which can be used, for example, as air filters or for producing air or water purification devices. Therefore, in a further aspect, the invention relates to a nonwoven fabric obtained from the fibers of the present invention, preferably nanofibers.

In another embodiment, the invention relates to a microfiber obtained by spinning the present admixture, preferably SPEEK, of formula (II) and PP or PE. The microfibers can have a diameter comprised between 25 and 1000 microns, preferably between 25 and 200 microns. Known techniques in the field of polymers, such as, for example, melt spinning and the like, can be used to produce them from the molten composition, at a temperature preferably comprised between 180° C and 200° C. The microfibers of the present invention are particularly well-suited for preparing fabrics which are useful, for example, as air filters (for example for ventilation systems or kitchen hoods), roofing and personal protective equipment. Therefore, in a further aspect, the invention relates to a fabric obtained from the present fibers, preferably microfibers.

As thoroughly described in detail, the polymeric composition of the invention comprising functionalized PEEK (II) and a co-polymer having a lower melting point than non-functionalized PEEK (i.e. about 350° C) possesses excellent characteristics in terms of spinnability, associated with effective photochemical properties. In fact, the presence of functionalized PEEK with sulfonic, nitric or amino groups enables the generation of benzyl ketyl radicals, which are useful for imparting the desired antibacterial, self-cleaning, decontaminant and UV-protective properties to the admixture. The association with the chosen co-polymer, moreover, enables the production of fibers or yarns that can be used to make garments or materials in the form of a fabric or nonwoven fabric, usable in sanitary environments, for example hospitals. By virtue of their photochemical properties, the fibers of the invention lend themselves well to the manufacture of garments suitable for sanitary use, such as sanitary coats, gloves, masks and the like, also ensuring excellent mechanical properties and wearability.

EXPERIMENTAL PART

Example 1 : Preparation of functionalized PEEK of formula (II)

(II)

Example 1.1 : preparation of SPEEK (X=-S0 ₃ H).

Sulfonation of PEEK in powder form was carried out in a reactor in an air atmosphere at a constant temperature of 45 ° C. 5% p/v of PEEK was added to a solution of concentrated sulphuric acid (H ₂ S0 ₄ 98%) and the solution was stirred for a period of 3 hours.

The SPEEK product obtained was then precipitated by dropwise addition of a 500 ml solution of cold distilled water. The precipitate was washed to remove the excess acid and dried in an oven at 70 ° C for 12 hours.

Mass spectrometry and IR analyses confirmed that the sulfonated PEEK has a single sulfonic acid group per monomeric unit.

Example 1.2: preparation of NPEEK (X=-N0 ₃ ). Example 1.2a: preparation of NPEEK with a high degree of nitration (up to about 600%).

The nitration of PEEK in powder form was carried out in a reactor in an air atmosphere at room temperature. 12.5% p/v of PEEK was slowly dispersed in a solution of concentrated sulfuric acid (H ₂ S04 98%) and the solution was stirred for a period of about 30 minutes. Subsequently, nitric acid (HN0 ₃ 65%) was added in two portions of equal volume.

The solution becomes yellowish and one notes the formation of the product as a precipitate. After separation by means of suction filtration, the product was washed twice with deionized water and dried in an oven at 70° C.

Example 1.2b: preparation of NPEEK with a low high degree of nitration (up to about 200%).

A stirred suspension of 8% PEEK in powder form in a solution of nitric acid/sulfuric acid (4:1 v/v) was heated under constant stirring at a temperature of about 60° C for 1 hour. The product was filtered and washed with water until reaching a pH=7, and with ethanol and dried in an oven at 70 ⁰ C.

Example 2: preparation of PP/SPEEK microfibers

PP (grade PPH 4050) was mixed with SPEEK using a microcompounder. The optimal SPEEK concentration was 5% by weight. This admixture was then spun using a melt-spinning process at a temperature of about 200° C, with a capillarity of 30/1 mm and a spinning length of 5 cm. Fibers having the characteristics shown in the table are obtained, including ones having a diameter of 45 microns and filaments with a fineness 15 dtex.

Sample Linear

Diameter Strength Elongation

(spinning density

[Mm] [kg] [%]

temperature) [dtex]

PP/SPEEK

250 687 23.40 3.05 240.00 58.31

(220° C)

PP/SPEEK

120 158 58.00 16.60 388.00 37.01

(200° C)

PP/SPEEK

55 33 78.80 4.21 438.00 60.99

(180° C) PP/SPEEK

45 15

(200° C)

The yarns show excellent photocatalytic properties, as demonstrated by the electron paramagnetic resonance (EPR) spectra in Figure 3.

The yarns show excellent photocatalytic properties, as demonstrated by the electron paramagnetic resonance (EPR) spectra in Figure 2.